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ED 241 770 CE 038 574
AUTHOR Brush, Richard E.TITLE Wells Construction. Hand Dug and Hand Drilled.
Appropriate Technologies for Development. ManualM-9.
INSTITUTION Peace Corps, Washington, DC. Information Collectionand Exchange Div.
PUB DATE Sep 82. NOTE 294p.
PUB TYPE Guides - Classroom Use - Guides (For Teachers) (052)
EDRS.PRICE. MF01/PC12 Plus Postage.DESCRIPTORS *Construction (Process); *Construction Materials;
Developing Nations; *Extension Education; Guidelines;Hand Tools; Machine Tools; Planning; PostsecondaryEducation; *Rural Development; Rural Education; SiteDevelopment; Tables (Data); Trade and IndustrialEducation; Volunteers; Volunteer Training; *WaterResources
IDENTIFIERS *Wells
ABSTRACTThis manual is intended for use by development
workers involved in the construction of wells to supply water to alocal population for personal consumption. Discussed first are thebasic points to consider when planning a well. Various aspects ofconstructing hand-dug wells are explained, including well design,supplies, the lowering and-raising of workers and equipment, digging,lining techniques, construction,of the middle section of a well, andconstruction of the bottom of a well. Addressed in the chapter ondrilled wells are drilling and casing techniques; the hand rotary,hand percussion, sludger, and driven and jetted methods of wellconstruction; and the bottom section of a drilled well. Appendixes tothe marvial include conversion factors and tables as well asdiscussions of.the use of vegetation as an index of ground water, theuses of dynamite in hand-dug wells, cement, leveling and plumbing amold, pipe, pumps, water treatment in wells, and rope strength.(MN)
***************************************4******************************** Reproductions supplied by EDRS are the best that can be made
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INFORIATION COLLECTION & OCCHANGE
Peace Corps' Information Collection & EXchange (ICE) wasestablished so that the strategies apd technologies devel-oped by Peace Corps VOlunteers, their co-workers, and theircounterparts could be made available to the wide range ofdevelopment organizations and individual workers who mightfind them useful. Training guidei, curricula, lesson plans,project reports, manuals and other Peace COrps-generatedmaterials developed in the field are oollected and reviewed.Some are reprinted "as is"; others provide a' source of fieldbased information for the production of manuals or for re-search in particular program areas. Materials that you sub-mit to the Information Collection & Exchange thus becomepart of the Peace Corps' larger contribution to development.
Information about ICE publications and services is availablethrough:
Peace CorpsInformation Collection & ExchangeOffice of Program Development806 Connecticut Avenue, N.W.Washington, D.C. 20526
Add your experience to the ICE Resource Center. Send ma-terials thattyou've prepared so that we can share themwith others forking in the development field. Your tech-nical insights serve as the basis for the generation ofICE manuals, reprints and resource packets, and alsoensure that ICE is providing the Trost updated, innovativeproblem - solving' techniques and information available toyou and your fellow development workers.
Peace Corps3
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WELLS CONSTRUCTIONHand Dug and Hand Drilled
written by
Richard E. Brush
Illustrated by
Laura KP . Gould
edited by
Eugene EccliSandy Eccli tDavid Tyler
t
Peace CorpsInformation Collection and Exchange
Manual M-9September 1982
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ACTION Pamphlet 4200.35 (8/79)
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INTRODUCTION
Purpose
This manual is intended for use by developmentworkers involved in the construction of wells tosupply water to a local population for personal con-sumption. It has been designed to help field workerswith little*or no construction experience to assistscommunities in
%planning and designing a well, or wells,
appropriate to the needs of the local population;
assessing the advantages or disadvantages oflocally available construction materials;
deciding on the most appropriate construct'.techniques;
constructing a well, or wells, capable ofmeeting the community's needs.
Most of the materials, tools, and methods coveredin this manual are applicable throughout the world in'avariety of local situations. The techniques are designedto be useful in the rural areas of most developingcountries. Step-by-step plans outline constructionmaterials and techniques to be used where skills may bearitted, Although all potential situations cannot becovered, this manual provides enough background to allowworkers to assess unusual situations, and determine whatavailable techniques might be useful.,
organization of This Manual
The manual is organized into three sections.Section One, Planning, introduces the knowledge neededfor wells planning and discusses those aspects of waterdevelopment and wells construction that should beconsidered before a wells project is begun. It alsopresehts an outline of the different methods of con-structing wells. These are covered in greater detailin the next two sections. Section One will give you somebasic ideas about the kind of well that might be mostappropriate in your situation.
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Section Two, Hand Dug Wells, provides informationon wells that can, or must, be dug by band:
a detailed= outline of the tasks involved in wellsconstruction;
a discussion of the top, middle and bottomsections of a hand dug well, their parts, and methodsused in constructing them;
the tools, equipment and materials needed:
if tools and supplies can safely be loweredinto and out of the well;
the operations that must take place in thehole;
details of the construction of the middlesection;
details of the construction of the bottom section.
Section Three, Drilled Wells, provides informationon drilling techniques that can be used in certainsituations:
the basccomponents and procedures used indrilling for water;
the different possible sinking methods;
a detailed description of equipment andprocedures used in a variety of hand-drilling methods;
how the bottom section of a drilled well isconstructed and finished for use.
on:Several appendices follow, giving useful information
101Metric-English measurement conversion;
vegetation as a possible indicator of water;
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use of dynamite;
use of cement;
techniques Of levelling and plumbing molds;
piping;
pumps.
Following these, the two figures (A and B) Which aappear inside the front and back covers are.reproducedat the beginnings of Section Two and Section Three re-spectively. The manual concludes with a glossary and anannotated bibliography.
How the Manual Can Be Used
You can use this manual:
as a text to teach and train people about wellsand their use;
to locate the information necessary to constructa well; D
to stimulate thinking about possible usefulmodifications of presently used techniques;
to.,loc4te other sources of information.
ACKNOWLEDGEMENTS
Many thanks are due to F. Eugene McJunkin for his technicalrovi(,w or the material in Wells Construction. Thanks to Sam1\unkle 1411,; wrote Appendix IT,,Vegetation as an Index of GroundWater.
Thanks also to the many people who helped in the preparationof this manual, especially Craig Hafner, Howard Ebenstein, BrendaGates, Francis Luzzatto, Laurel Druben, Sde Chappelear,-Pascal Pittman, Mary Ernsberger, Vic Wehman, Vicki Fries,Vernell Womack, and Teri Barila.
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TABLE OP CONTENTS
SECTION ONE: PLANNING
Chapter 1: Introduction to Wells Planning 1
SECTION TWO: HAND DUG WELLS
Chapter 2: Introduction to Hand Dug Wells 19
Chapter 3: Well Design 23
Chapter 4: Supplies 37
Chapter 5: Lowering and Raising Workersand Equipment 43
4.--1 Chapter 6: Digging
Chapter 7: The Middle Section: Overviewof Lining Techniques.. .
Chapter 8: Construction of the MiddleSection
57
63
77
Chapter 9: Construction of the BottomSection. 99
SECTION AAREE:
Chapter 10:
'-----Chapter 11:
Chapter 12:
Chapter 13:
Chapter 14:
Chapter 15:
DRILLED WELLS
Introduction to Drilled Wells 117
Drilling and Casing Techniques 129
Construction: Hand Rotary andHand Percussion Methdds 147
Construction: Sludger Method 165
Construction: Driven and Jetted . . . 173
The Bottom Section 191
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APPENDICES
Appendix I: Conversion Factors and Tables . . . .209
Appendix II: Vegetation as an Index ofGround Water 211
Appendix III: Uses of Dynamite inHand Dug Wells ~ -213
Appendix IV: Cement 221
Appendix V: Leveling and Plumbing the Mold . . .239
Appendix VI: Pipe 243
Appendix VII:' Pumps 249
Appendix VIII: Water Treatment in Wells 261
Appendix IX: Rope Strength 267
Glossary of Terms 269
Annotated Bibliography 273
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Section 1:
PLANNING
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Chapter 1
INTRODUCTION TO WELLS PLANNING
A. Overview
There is water at some depth almost everywhere beneaththe earth's surface. A well is a dug ordrilled hole thatextends deep enough into the ground to reach water. Wellsare usually circular and walled with stone, concrete or pipeeb prevent the hole from cyailng in. They are gunk bydigging or drilling through one or, more layerp of soil androck to reach a layer that is at least partially full ofwater called an aquifer. The top of the aquifer, or thelevel beneath whic ground is saturated with water, iscalled the water table: In some areas there is more thanone aquifer-Beneath the water table. Deep wells, such asthose sunk by large motorized equipment, can reach and pullwater from more than one aquifer at the same time.. However,this manual will only discuss sinking wells-to the firstusable'aquifer with hand-powered equipment.
,10 B. The Need for Adequate Water Supply
A new properly built well can provide people with moreand better water. But the new well itself may have littleor no impact on the surrounding community's health if thewell users do not know how to make effective use of thewatcr.
It is important to leant the water needs of 'a localpopulatipn in order to construct an appropriate water source.In all locales an adequate supply of clean water is essentialfor 'maintaining and improVing health. Many ofthe most com-mon and serious diseases in developing countries are closelyrelated to the amount and quality of water people use. With-,out an adquate supply of clean water/ little can be done tocontrol diseases that spread through contaminated watersupplies.
In order to ascertain` ocal needs, you must consider_two limiting aspects to the provision of water: 1) thequality of the water and 21 .he quantity of water available16cally.
Good quality water does not contain chemicals andbacteria which are hazards to health and life. The qualityof water can be assured by:
locating the site to avoid possible -watercontamination;
proper construction of the well 7r any other,water source, to protept'the water supply fromcontamination;
initial and periodic water treatment, usuallywith chlorine, to kill dangerous bacteria (see'Appendix VIII, Water Treatment);
education of the local users so that they can main-tain the purity, or at least prevent the gross con-tamination of their water.
The quantity of water is often more difficult toensure. Especially in a rural setting, access (distance)to water will often limit the amount thAlt can be used byeach indivjdual, because of the time needed to convey it.Quantity, however, has a direct bearing on health.
-Five liters per person per day is considered .theminimum consumption level, although desert' dwellersexist on less. Mote than 50 liters per person per day,it has been estimated, gains no further health benefits.Twenty-fiVe liters per person per day may become anacceptable goal in places where piped connections toindividual'houses are not feasible. Wherever-possible,water use beyond minimum-level consumption should be'en-couraged. consumptiori will rise under the fallowing cir-cumstances!
new well construction to provide a water sourcecloser to a group of people, who will thenpresumably be able to gather more water in thesame amcunt of time that they previously wereable to elo;
education of local users toward a greater use ofwater, especially for hygienic purposes (bathing,washing clothes and cooking utensils).7
The quantity of.water needed may also be signifi-cantly affected by.the number of livestock that requirewater and by whether the water is to be used for gardenirrigation.
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C. Involving the Local Community-
The degree of community 'participation and controlmay be the most important factors in determining thesuccess of any wells construction project. The idealsituation is. that the entire project be completely con-trolled and run by the local people. This, however, isoften not possible. It therefore becomes the task ofthe development worker to see that a community in needof a better water. supply is encoukaged to realize thatneed and act to meet it.
It is usually best to use the decision-making systeMithat have already been established and accepted by thecommunity. These systems vary between open town meeting-type forums where everyone who wishes to can speak, and arelatively closed council or other politically establishedgroup or person. In all cases, each of the vari &s possi-bilitis for well construction should be fairly. presentedso that whatever decisions are made realistically reflectthe needs and concerns .of the decision-making unit.
Some kind of organized educational campaign shouldbe an integral part of every water supply improvementproject. The benefits to be gained from using largerquantities of clean water are not often understood by thelocal users. Unless they can be convinced of the benefitsclean water can bring to themand their children, they arenot likely to make effectivegse of a newly developed watersource. In societies wherechange is often very slow, suchan attitude change will taketime. Only when the peoplebecome willing to act on theirunderstanding of the importanceof clein water and what needsto be done to keep it clean canany water supply improvementproject be truly successful.
This educational effortis probably one of the mostimportant and difficult as--poets_ of-water-sulopment. Even with a massiveeducation campaign, realchange may take many years.But without it, a supply of-clean water-may-mean nothing.
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Such a campaign Of education is especially importantfor the future maintenance of the well. If people oan seeclean water as being vital to them, they will be willing tooccasionally spend a little time or money to keep theirwatee supply safe. However, where people are not involvedin planning and, to some extent, construction from the be-ginningino amount of general education later will beeffective.
D. Selecting the Most Appropriate Water Source
When the community has decided that more and betterwater is needed, ,it will be necessary for them to decidewhat kind of source is passible and will best suit theirneeds. A well is not always the most appropriate watersource in a particular locale. Their goal is to find thecheapest, most reliable way to provide the needed amountof clean water.
Here are the chief potential sources of water listedin their approximate order of preference based on cost,quality of water, need for equipment and supplies:
Springs - If there areyear-round springs nearby,they can usually be devel-oped to supply cleanwater. This water canoften be conveyed throughpipes without the expenseof pumps or water treat-ment. Springs can mostoften be found in hillyor mountainous regions(see Fig. 1-1);
Wells - Because th4rWntswater at some depth al-most everywhere beneaththe earth' -s surface, awell can be sunk (usingthe approOtiate tech- RtG. i -I. SPRING LOCATIONnique), almost anywhere.The water that comes into the bottom of a well has
_filtered down from the surface and is, in mostcases, cleaner -thaw-water-that-Is-exposed on_theopen ground;
SANG,
WATER IASI-6
--- Rainwater - and storage of rainwatermay provide -anot:ii-eia--eu-r-t-e=wirere=s_ur-1-_ag.e marl
underground water supplies are limited or diffi-cult to reach. Normally, except in the rainiestregions,_ rainwater will not supply all the water
can be collected from roofs or protected ground-run-off ..areds,-.-and stored in covered cisterns toprevent.cmtamination.--4
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Surface water - Streams, rivers, and lakes are allcommonly used as sources of water. Although noconstruction is needed to enable them to supplywater, the quality of the water is almost alwayspoor. Only clear mountain streams flowing fromprotected watersheds could be considered as fitfor human consumption.
E. Site Choice
Locating the site for a well should be based on thefollowing guidelines:
The well should be located at a site that is:
water bearing;
acceptable to the local community;
suitable to the sinking methods available;
not likely to be easily contaminated.
It is not always possible for a site to meet all ofthese guidelines. Therefore, a site will need to be chosenwhich best approximates the guidelines, with particularemphasis on the likelihood of reaching water (see Fig. 1-2).Where there is an equal chance of reaching water at severaldifferent locations, the one closest to-the users is pref-erable.
Where is water likely to be found?
A development worker can assist the community'seffort to locate a likely site by.collectingavailable infUYMAtion on local-ground. water. Inmany countries, some information is available throughappropriate ministries, water agencies, and inter-national development organizations.
Choosing the site for a well can be difficult,because easily available and abundant water cannever be guaranteed. Even profesiibnals, beforea'well is sunk, rarely know where they will reach
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water and how much-wtrl-be-avallabIeTHowever,there are a number of guidelines which can bevery useful in providing information about pos-sibly successful well sites.
or present water source. By doing so, you are likelytaraacil water at approximately the same depth as the
Where possible, a well can be located near a past
other source.1
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If no other sources exist or have ever been de-veloped nearby, you must be more cautious inchoosing a well site. Unless you have the bene-fit of detailed geological information, it isbest simply to look for the lowest spot nearby.Both surface and ground water are likely tocollect here. In some cases, plants can beindicators of the presence of ground water(see Appendix, Vegetation as an Indicator ofGround Water). However, be careful not to buildin a place so low that the well would be susceptibleto flooding in heavy rain.
PIG. I - Z. POSSIBLE. wii.k. VMS
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a) Limited water would be available at this site,because the impermeable rock layer is close tothe ground_surface, allowing slight fluctuationsin the water table to drastically-4 fect_wateravailability.
CO Closest site to village and therefore the bestsite if it is possible to dig down far enoughto reach water.
0 At this site, there would be a better chance ofreaching more water that at 2. but the site isfurther from
6) This is the site where water is most likely toreached_by.a well although it is some distancefrom the village. Be-ddifse-±t-is-in-the-absolutPbottoi of-the valley, it may belsubject to
ceding _ _
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Is the site acceptable to'the local community?
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The community must accept the final: site choiceand be willing to use the well when it is completed.Only then will it benefit local residents.
Is the site suitable to the available sinking methods?
If the most likely site would require that the wellpenetrate a layer of rock, and if there are no toolsavailable to do so,difficult a job, the site is.notan appropriate one..
Is the well likely to be easily contaminated?
The most important consideration here is that thewell not be located within 15 meters of a latrineor other sewage source. This would also includenot placing the well where it might be damaged orinundated by a.flood or heavy rain.
F. Preventing Water Contamination
What is the optimum well design for the prevention ofcontamination?
The only way to design a well to prevent water con-tamination,is to seal it so that water can enter onlythrough the bottom section. Dug wells need to be coveredwith a:permanent cover through which a pump is installedto draw water. All wells should have a platform aroundthem that is at least 1 meter wide, one which water willnot penetrate. This platform ought to be sloped in sucha way that any spilled water runs off away from the well.(See Figs. A and B on inside of front and back.manualcovers.)
These and other measures are described in more detail111 the design section for the different types. of wells(pp. 23 and 124).
G. 'Types of Wells
In general, there are two types of wells: dug wellsand drilled wells. -The obvious-difference.between_the_twois the size of the holes. (See Figs. A and B).
Dug wells are sunk by people working down in th-d-hOleto loosen and remove the soil. They zieed to be at.,,least1 meter wide'to give people room to work:
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Drilled wells, on*the other hand, are punk by usingspecial tools which are lowered into the ground'and workedfrom the surface. These wells are normally less than30 centimeters (cm) in diameter, and for the purpose ofthis manual, will usually be less than 15 cm. The reasonfor this is the difficulty of drilling larger holes withhand-powered tools.
ea&
In both categories, there are many different specificsinking techniques which will be discussed in more detail _
later.
H. Well Sections
'Every well, whether drilled or dug, has three sections:top, middle, and bottom. Each of.these sections varies inconstruction, because each nnrt function differently. (SeeFigs. A and B.)
Top section - That part of the well at or abovethe ground surface level. It should be designedto allow people to get water as easily as possible,and, at the same time, to prevent water, dirt, andother contaminants from entering.
Middle section - That part of the well which isbetween the ground surface and the water. Thissection is usually a circular hole. It is rein-forced with some kind of lining to prevent thewall's from caving in.
NOTE: Lining and casing refer to the same part ofthe well (see Figs. A and B). Lining is used torefer to that part of the dug well, while casingrefers to the pipe used to reinforce a drilled well.
Bottom section - That part of the well that extendsbeneath the water table into the aquifer. It shouldbe designed to allow as much water as possible toenter, and yet prevent the entrance of any soil fromthe aquifer. Its lining will have holes, slots, oropen spaces, allowing water to pass through.
I. Materials
/. Availability of Materials
Even as you are beginning site selection andcommunity awareness activities, you should deter-mine the availability of construction materials andthe difficulty in obtaining them. Later you willneed to assess in greater detail the specific toolsand supplies needed, and the quantities of,wh.
First of all, can you get cement or.pipe?NTfcement is available, it should be fresh and powdery,and not congealed in hard clumps. Cemebt, sand,gravel, and water can be mixed to make concrete whichwhen it hardens is very strong and long lasting es-pecially when reinforced with steel reinforcing rod(rerod). If neither cement nor pipe is available, youwill need to find a local material that can serve asthe lining. (See p. 38.)
Metal, plastic, or concrete pipe can be used.Metal pipe, usually galvanized iron or steel. is moredurable for well sinking but is subject to corrosionand rusting over time. Plastic pipe, on the otherhand, has less strength and is not easy to use in thesinking process. Nevertheless, it A virtually unaf-fected by ground water quality. Large diameter con-crete pipe can be used to line dug wells.
If you can get these basic materialt',-you willprobably be able to find the other related tools,equipment, or adapt local equipment. A localmetal worker (welder or blacksmith) can probablymake any special tools you may need. For a list ofthese, see page 37 of the next section.
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2. Use of Local Materials
Construction of a well is cheaper, more easilyunderstood, and more likely to be incorporated intothe culture if the builders uae local materials when-ever possible.
The materials required to construct the bottomsection, lining,. -well head, and pump (see Figs. A andB) should be sufficiently strong to withstand the stressof installation and the wear and tear of daily use.They should also be able to support the weight of thecolumn where necessary and not contaminate the water,as a result of natural wear, during the lifespan ofthe well.
In emergency situations, when the best wateravailable is immediately needed, a number of substitutematerials and techniques can be used. For example,wood lining can be used instead of cement. Wells builtwith wood or other substitute materials and techniqueswill supply acceptable water for'a short period of time.However, they cannot now or in the future be convertedinto permanent sources of clean water without rebuildingmajor portions of the structure.
3. Materials for Well Parts
The two most important sections of the well are thelining for casing), and the bottom (or intake) section.While it is not necessary that both be built of thesame material, it is often cheaper and more convenientto do so. Almost all modern well linings_gre- made ofeither concrete or pipe (metal or plastic).
Nowadays, concrete is used most often in the liningof hand dug wells. It can be easily mixed and oast,,inplace in the well. Reinforcing bars can be added toN.either mortar or concrete to make a much stronger andmore durable lining. (See Appendix IV, Concrete.)
Metal pipe is normally used in the construction ofdrilled wells. It can easily be shaped to make. thenecessary tools with which to sink the well.and canalso serve as the permanent casing and bottom section.
Plastic pipe is too soft to use during drillingbut is in many situations a better casing than metalpipe, because it will not rustor corrode.
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Cement and pipe are available in most countriesand usually in all but the most remote regions. Whenboth materials are available, consider such factors astransportation, type Of well, depth, ease of construc-tion, and adaptability to local practices beforedeciding which is the more appropriate.
J. Tools and Equipment
The choice of tools and equipment will depend on the.construction material and its use. Many basic tools can beused to perform a number of different functions. However,a job is more easily and quickly done with the tool designedfor that job. The following are the tools and equipmentrecommended for wells construction: hammer, nails, wood,saw, hacksaw, chisel, mason's trowel, level, shovel, mixing
,.hoe, pick, ruler, plumb-bob, buckets, heavy rope, pulley,square, pliers, crow-bar, wrenches, pipe wrenches, screw-driver, file, mason's hammer, tie,wire, sheet metal, pipecutter. tripod, and pipe 'threader. For specifics, see thechapters on sinking methods in the sections on Dug Wells(Chapters 7-8) and Drilled Wells (Chapters 12-14).
K. Sinking Method
A sinking method is a specific way of sinking a well.Wells may be dug by hand, drilled. with hand tools, ordrilled with motorized equipment. Many methods and tech-niques are used. The particular choice depends on theavailable materials and equipment, the expected'groundconditions at the well site, and your familiarity witleaspecific sinking technique.
Motorized drilling techniques are summarized in thesection on Drilled Wells, but are not described in detailbecause of the high level of technical expertise necessaryin the use of the equipment.
The following are general descriptions of hand-dugand hand-drilled sinking methods. For more details, seethe manual sections on Band-Dug Wells and Drilled Wells.
1. Hand-dug wells are sunk by digging a hole asdeep as is necessary to reach water. Once the water-bearing-l-ayer is reached, it should be penetrated. asfar as possible. This process is always basicallythe same, with only minor variations because of theparticular tools and equipment available and thevariety of ground conditions (see Fig. 1-3).
21
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Advantages
This procedure is a very flexible one. It canbe easily adapted with a minimum of equipment toa variety of soil conditions, as long as cementis available.
Because the resulting well is wide-mouthed, itis easily adaptable to simple water-lifting tech-niques, if pumps are not available or appropriate.
It provides a reservoir which is useful foraccumulating water from ground formations whichyield water slowly. .
F16. 3.DIGGING A WSL-1.-
Disadvantages_
A hand-dug well takes longer to constructth..n a drilled well.
It is usually more expensive than a hand-drilled well.
It cannot easily be made into a permanent watersource without the use of cement.
Hand-digging cannot easily penetrate hard groundand rock.
22
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It may be difficult to penetrate deeply enoughinto the aquifer so that the well will not dryup in the dry season.
2. Drilled wells are sunk by using a special tool,called a bit, which acts to loosen whtitever.soil orrock is at the bottom of the hole. It is connectedto a shaft or line which extends to the ground surfaceand above. The part of the shaft or line extendingabove the ground can then be moved to operate thebit (see Fig. 1-4).
.F16. TitiL Ltt4G A WELLAdvantages
'It is fast.
Where cement is not available, wells can besunk with locally made drilling equipment andlined with local materials.
23
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While not easy, it is possible to penetrate hareground and rock formations that would be verydifficult to dig through.
Drilling usually requires fewer people thanhand-digging.
It is especially suitable for u6 in loose_sandwith a shallow'water table.
Disadvantages
There are a number of different hand-drillingtechniques that are suitable for a wide rangeof ground conditions. However, each repuiresspecial equipment.
Pumps almost always have to be used becausebuckets are too 'large to be lowered intothe well:
Limited depth can be reached with hand-powereddrilling equipment. .
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Suitability of Well Construction Methodsto Different Geological Conditions
Characteristics
Types of WellsJ.:
. ,
1
Dug.
i
HandDrilled
MachineDrilled
Range of practicaldepths (generalorder of magnitude)
Diameter
Type of geologicalformation:ClaySiltSandGravelCemented gravelBoulders
Sandstone,Limestone
Dense igneous rock
.
0-30meters
1- 6meters
YesYesYesYesYesYes
Yes ifsoft and/or frac-tured
No
0-30meters
0.05-0,30'meters
YesYesYes ,
Yes.NoYes, if Lessthan welldiameterYes, ifsoft-and/or frac-tured
No
0-300meters
0.1-0.5meters
YesYesYesYesYesYes, whenin firmbeddingYes
Not
25r.
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L. Preparation for Construction
Once you have decided how to silk the well and whatmaterials to use, you need to organi;:e and prepare for theconstruction.
1. Workers
It 'is best if local laborers perform as much ofthe work as they are capable of performing withoutspending too much time in training. Thkt will allow
-.them to better understand the well, its construction,and later maintenance needs.
With any laborers it should be very clearlyestablished before construction begins who is expectedto do what, how long is should take, and what qualitythe end product should be. Any later misunderstandingscan be more easily cleared up if'an initial under-standing was agreed to by all parties.
Consider the following questions concerning theworkers:
What skills are required?
Will the workers require training?
If so, how much training? .
How many workers are needed?
How long will their services be needed?
Will they volunteer their work or will they be paid?
NOTE: While yOu can be of assistance, it isimportant to let the community set their owngoals.
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2. Material's :Before the construction begins, it is helpful to
have at the well site as many of the tools,, equipment,and supplies as,you think will be necessary to complete;the job. This-prior organization will facilitate theday-to-day operation. If large quantities of supplies
I 26.
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Suitability Of Well Construction Methodsto Different Geological Conditions
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.,
Types of Wells
Characteristics
DugHandDrilled ,
MachineDrilled
Range of practicaldepths (general 0-30 0-30 0-300order of magnitude) meters meters meters
Diameter 1- 6 0.05-0.30 0.1-0.5meters meters meters
Type of geologicalformation: .
Clay Yes Yes1
Yessilt Yes Yes YesSand Yes Yes YesGravel ,Cemented gravel
YesYes
YesNo
YesYes
Boulders Yes Yes, if lessthan welldiameter
Yes, whenin firmbedding
Sandstone, . Yes, if Yes, if YesLimestone soft and/ soft and/
- or frac- or frac-tured tured
.
Dense igneous rock.
No No No- i.
4)9
p
lb
01,
.L. Preparation for Construction
Once you have decided how to sink the well and whatmaterials to use, you need to organize and prepare for theconstruction.
1. Workers
It is best if local laborers perform as much ofthe work as they are capable of performing withoutspending too much time in training. This will allowthem to better understand the well, its construction,and later maintenance needs.
With any laborers it should be very clearlyestablished before construction begins who is expectedto do what, how long is should take, and what quality",the end product should be. Any later misunderstandingscan be more easily cleared up if an initial under-standing was agreed to by all parties.
Consider the following questions concerning theworkers:
What skills are required?
Will the workers require training?
If so, how-much training?
How many workers are needed?
How long will their services be needed?
Will they volunteer their work or will they be paid?
NOTE: While you can be of assistance, it isimportant to let the community set their owngoals.
2. Materials
Before the construction begins., it is helpful tohave at the well site as many of the tools, equipment,and supplies as you think will be necessary to completethe job. This prior organization will facilitate theday-to-day operation. If large quantities of supplies
28
17
will need to be stored at the site (such as the sandand gravel for concrete) , the storage site should bedecided on beforehand so as not to interfere withlater work. If theft is a serious problem, workersmay have to take turns guarding the construction siteat night.
M. planning
Planning the construction of a well can be complicated.There is the necessity to find the appropriate material,, theinitial decision as to which sinking method will be used,and the complexity in assessing the ground conditions ofthe well site. These factors are difficult ones to.evaluate,especially when information about local conditions is in-complete. Because situations change, the feasibilitystudies and planning may have to-be repeated and updatedbefore well construction begins..,
To help you to plan effectively, the following isan outline of the wells construction process.
"1/4)
Overview of Well Construction
Initial feasibility questions
Is there a need -for water?
Is a well the most appropriate water sourceto build?
Are construction materials available?
Community involvement
How will the community participate?
What training is needed?
How will they be organized?
Technical questions
Where will the well be sunk?
How will the well be sunk?
How will the well be designed to best preventwater contamination?
29
18
ro,
Construction of the middle section
Initial site preparation.
Sinking the hole.
Lining (casing) the hole.
Construction of the bottom section
Testing the quality and quantity ofwater available.
Sinking and lining below the water table.
Constructing the bottom plug or filter.'
Construction of the top section
Building the he.4d wall.
Constructing the platform.
Installing the pump.
Well disinfection beforeinitial use
Maintenance - The question ofwho will maintain the well andpump after their constructionshould be realistically re-solved before construction.
After you have read the rest of the manual and havedecided how you can best sink a well, you should use thisoverview as a checklist to make sure that you have consideredall the necessary aspects of wells construction.
30
Section 2:
HAND DUG WELLS
31
.
I
I:I
1
ti
1
II
Chapter 2
INTRODUCTION TO HAND-DUG WELLS
A. Overview
Rural communities have frequently employed hand-dugwells to increase the supply of water available for indi-vidual use. Using'simple construction techniques andsuitable materials, hand-dug wells can provide reliablesources of water and offer the following advantagess
Because the community can be involved inthe actual construction, it is "their" well,which they are more likely to maintain.
The equipment needed is light and simple andthus suitable for use in remote areas.
The construct -ion techniques are easily taughtto unskilled workers, thus cutting supervisiontime..
With the exceptions of cement and reinforcingrods, the necessary materials are usually locallyavailable,' making it one of the cheapest methodsof wells construction in a rural community.
A completed well provides a reservoir at the sourcewhich will accumulate and store water from aquifersthat would otherwise be too weak to use.
On the other hand,'hand-dug wells present certainlimitations:
60 meters is usually the practical limit to thedepth that can b3 reached, although most dug wellsare less than 20 meters deep.
Construction is slow.
Extracting large quantities of water withmotorized, pumps is not feasible.
Hard rock is very difficult to penetrate and oftencan only be accomplished by blasting, which isslow, hard work.
Because it is difficult to penetrate very farinto the aquifer, slight fluctuations in thewater table often make hand-dug wells unpredic-table and unreliable.
33
19
20
The hand-dug well is the only method of well con-struction where people actually go into the well to work.An educational campaign to demonstrate and explain whateach part of the well is and how it works. might helpvillagers understand and then want to work with and main-tain it more. In so doing, proper maintenance necessaryin keeping the well functioning might be better carried out,particularly in communities using a well or an improvedwater source for the first time.
For sanitation reasons a.pumpis desirable. If installed ona hand-dug well with a fullcover,a pump will help reducechances of contamination sig-nificantly. In'rural areaswhere pump, maintenance andrepair can be a real problem,large diameter wells are oftenthe best solution to watersupply problems. Pumps can beinstalled while leaving anaccessway through which watercan be drawn by rope and bucketif the pump should break down.(See Pumps Appendix).
Compared to other-well sinking methods, digging a wellby hand takes a longtime. An organized and experiencedconstruction team consisting of five workers plus enoughpeople to lower and raise loads in the well can dig andline 1 meter per day in relativ'ly loose soil that doesnot cave in. However, the bottom section is likely totake 2 or 3 days per meter because of the difficulty inworking while water continually enters the well. Depending.on how you plan to develop the well, the top section cantake anywhere from a day or two to several weeks. Anexperienced team sinking a 20 meter well and installingpulleys on the top structure could easily take 5 weeks,including occasional days off (this, of course, assumesno major delays). A new or inexperienced group would beexpected to take twice that time.
Hand-dug wells should be dug during the dry seasonwhen the water table is likely to be at or near its lowestpoint. The well can be sunk deeper with less interferencefrom water flowing into it. The greater depth should alsoensure a year-round supply of water.
If the well cannot be dug during the dry season, planto go back to it at the end of the dry season to deepen it.
34
21
B. Work Outline
Outlined below are tlie major steps involved in digginga well. The appropriate Community leaders, health committee,public-works committee, atd others who are interested shouldbe involved in all the planning decisions.
Begin community education and awareness activitiesto enable the people to understand what is happeningand how they can benefit.
Choose a well site, based on geological factors,user preference, sanitary conditions, andaccessibility.
s Determine available expertise - people (includingyourself) with well,or general construction ex-perience.
Assess materials available - tools, cement,reinforcement rods fre-rods), sand, gravel,wood. .
Select methods of construction that are mostsuitable for the use and available materials,considering shape, size, depth, lining, bottom,and top.
Plan and begin any braining that will be necessaryfor workers.
Before construction begins, put down in writingthe workplan for the construction of the entirewell.
Gather all equipment and materials needed forconstruction of the well at the well site.Arrange these at the site so as to facilitateconstruction as much as possible..
If concrete lining rings are to be used, peginconstructing them.in advance. Each ring mustbe cured for at least 4 days before it is putin place at the well head.
Lay out the hole with provisions for checkingdiameter and plumb (see p. 53).
Arrange for people and materials to get in andout of the well.
22
Dig and line the middle section.
Continue the digging and lining procedure until
(1) you reach water, or
(2) some obstruction causes you to
(a) change digging/lining procedure(b) abandon this well and pick a new site.
Dig and line the bottom section as far as possibleinto the aquifer. The method used to dig and linethe bottom section will often be different fromthe digging and lining method used in the middlesection. This may be necessary because you are not,only concerned with digging, lining, and possiblehole collapse (as in the middle section), but alsowith removing enough water from the well to permitwork to continue.
Install a simple sand and gravel filter or porousconcrete plug across the bottom of hole.
Extend the lining up above ground to form thehead wall.
Build and install the well cover.4
Install the pump in the cover on the well.
Disinfect the well.
Build the apron (platform) around the head wallto channel the run-off to one particular place.
Build a drainage pit or other device for removalof standing water.*
Build an animal trough.*
Build a wash-basin platform.*
*These items are not always necessary but should be considered.
368
Chapter 3
WELL DESIGN
Q
.23'
A. Introduction
To design a well, it is necessary to decide whatmaterials will be used and how they will be put together.This includes determining:
the size and shape of the hole;
which digging and lining methods will befollowed;
how much water needs to be available, and, there-fore, how deep the bottom section should go intothe aquifer;
how the top section should be constructed to bestprotect the well from contamination, while allowingeasy access to water by those who will use the well;
the anticipated well depth.
This chapter discusses the decisions that must bemade and presents options for consideration.
B. Well Shape
The shape of the well is what it would look like ifyou were looking straight down into it.
C. Well Size
The size of the well is a measure of how wide it is.Some holes are very large, and some are very small. Thesize will be largely determined by: (1) the way it is
1excavated, (2) the materials used to line it, and (3) thepurpose of the well.
The size of the round hole is usually expressed byits diameter, a measurement from one edge of the hole .
through the midpoint of the well to the other side ofthe circle. (See Figs. 3-2 and 3-3.)
Although wells can be dug in any shape, ilmost'allwells are round. The reason for this is that a round wellproduces the greatest amount of water for the least amount
37
24
1
4
ae
'
r
of work. Also,,a round lining is the strongest that canbe built for the smallest quantity of materials. Thus,while other well shapes have been used without problems,a round shape enables the builder to get the most fromavailable time, money, and materials.
Square or rectangular wellsFIG.3-1 SQUARE WEL L.
are usually dug where materials'to be used in lining the wellnecessitate such a shape. Thisis most often the case when flatwood boards, are the only liningmaterials available. Wood,however, is not recommended forseveral reasons which will bediscussed later. (See p. 74.)-
1. Well Size-Diameter
X
Before the actual digging work begins, the exactdiameter of the hole must be decided (see Pigs. 3-2and 3-3).
3- 2. IbumoWas.
J
38
NO
NpNO
NO
F16.3-3. DIAMETER IS TIMirbi4ge5r MEASUREMENTAtaces 1461-6-
Many factors could determine which diametershould be used.
If there is a government-sponsored organiza-tion or agency which does wells constructionusing a standard diameter, you should considerusing the same diameter. Doing so will makethe eventual incorporation of the well intocommunity and government planning and develop-ment much easier.
. If forms or pre-cast lining sections areavailable, you might consider using them.It would necessitate choosing an appropriatediameter for the particular equipment youhave. However, if the former situation(mentioned above) also exists, it should inmost cases receive priority.
Generally, the choice of diameter will bebased on two considerations. The well shouldhave (a) the smallest diameter which still provides(b) a comfortable working space for the number of
.people that will be working in the well at one time.,
a. The smaller the diameter of the well, theless soil and rock will have to be dug and theless materials will be required to line the well.Remember, if you double the diameter of the well,you increase the amount of soil and rock thatmust be dug by four times. For example, as in-dicated in the table below, a 1.0-meter diameterwell 20 meters deep requires removal of 15,.7 cubicmeters (m3) of material while a 2.0-meter diameterwell 20 meters deep will require the removal of62.8 m3.
Diameter x Diameter x 0.7854 = Area.Area x Depth = Volume -
r
Diameter Area Depth Volume.
1.0 m 0.79 m2 20 m 15.7 m31.1 0.95 20 19.01.2 1.13 20 22.61.3 . 1.33 20 26.61.4 ].54 20 30.81.5 1.77 20 35.41.6 2.01 20 40.21.7 2.21 '20 45.41.8 2.54 20 50.'81.9 2.84 20 56.82.0 3.14 20 _62.8 it
33
25' .--
.4.
' 26
b. The workers wirlneed enough space So'that they are not ham-pered in' their work.There must be enoughspace for them to usetheir tools and for thebucket which will removeexcavated materials frOMthe well. Without enoughspace, they will continu-_ally bump into each otherand the wall. Duringstages of its construc=tion, a well may havetwo or sometimes threediffereht diameters (see,Fig. 3-4).'
kik
(1), The l'Oleis dugto the diameter de-cided upon.
(2) When a liningis installed, the di-ameter is further re-duced along with theavailable workingspace.
(3) You may be in-stalling the bottomsection lining in-side the existinglining. This willfurther reduce thediameter.
MOLE
LINING
UNINQ RINGS
(TET:critea0
.fatio'g`c)""14,114,
ICI
siDE: view3r. LI. THREE. FFEReisrDiAmeTE.R.s USED
C4-.1
LINING RII445 (BOTTOM SECTION)
Ey/40.
.27
D. Ground Conditions and Lining
, It is very difficult to anticipite what the finaldepth of a well will be before it is begun. However, ifthere are other wells in the area, it is possible to getan idea of the approximate depth of the water table. Thiscan be a great help when gathering supplies needed forlining construction, because it will enable you to stock-pile approximately enough materials to complete the well.
All wells, except those drilled through rock, can beexpected to cave in with time unless a lining is installedto support the well. The lining thus helps to keep thewell open. There are certain acts of nature, such as earth-quakes or even gradual ground shifts, which will break eventhe strongest linings, but these"cannot be planned for oranticipated. Occasionally, slight ground shifts can putpressure on linings causing them to split and separate ifnot strongly built. -Geologists can usually predict whefesuch shifts are likely to occur. If no such informationis available, it is recommended that you build the liningstrongly enough to withstand normal earth stresses.
Depending on ground" conditions, you may or may not beable to dig the complete hole and then line it. In veryloose sandy soil, for example, the sand from the walls ofthe hole will frequently cave into the hole, seriouslyhampering efforts to deepen the hole. There are oftenrelatively simple Methods of dealing with such problems(see p. 58) .
Designing the lining for the middle section islargely a matter of assessing the ground conditions andmaterials availability to determine the lining materialsand method most appropriate for the situation.
1. Ground Conditions
Very loose soil (example: dry sand)as wide as the hole is deep becausetinually collapse and cave in (Fig.
Loose soil (example: damp sand) - ashallow (1 to 5 meters) hole can beits sides may cave in Fig. 3-5b.
Firm soil (example: compacted clay and sand mix) -a hole can be dug to the water table with minimaldanger of collapse and cave in Fig. 3-5c.
- the hole isits sides con-
relativelydug before
28
Ct.
ID.
C.
61;ZOUND COADITIONS
Unless you have had substantial experiencedigging in the area and this particular type of soil,or have been trained in the idehtification of soilsand their properties, do not leaVe the hole unlinedfor more than 5 meters.
The only possible advantage to digging the entirehole first is that you can then be certain that watercan be reached before you start using your often ex-pensive materials to line the well. However, if thereis any question about the safety of working in an un-lined section of the well, it is not worth the gambleto leave it unlined.
2. Dill and line options
pig a short section and line
One source has suggested that for safety reasons,no more than 5 meters of a well shoul,d be dug andleft unlined. More commonly, this cautious methodis used in loose soil. This means of constructionis also recommended in all soils when workers areinexperienced. Using this method, wells are dugin 0.5 to 5 meter sections, and then lined.
29
No Or
Dijto water table and line
This method is commonly used in firm soil, especiallywhere the water table is not very deep. It has thepreviously mentimed advantage of not using, any ex-pensive materials in a well until a good supply of .water can be assured. However, this method shouldnot be attempted by workers inexperienced with wellwork.
Dig complete well and then line
This method is not recommended because of thedanger of cave -ins beneath the water table whichwould undermine the entire well shaft. The onlysituation in which this method might be justifiedis where the middle section lining must rest onthe bottom section lining for support, but thereare many ways of avoiding that necessity.
E. Design: The Bottom Section
There are two basic methods for constructing thebottom section - sink lining and dig-and-line.
1. Sirik lining into place. Advantages include:
The method protects workers from cave-insduring sinking;
workers in the well can put all their effortinto removing soil and water, presumablyallowing greater well penetration into theaquifer.
A disadvantage is the possibility that workers mayhave difficulty in firmly attaching the rings to-gether. (See lining rings, Fig. A.)
2. Dig and then line. Advantages include:
The method requires less special preparation;
The bottom section lining attaches directly tothe lower part of the middle section lining, thusproducing a stronger, continuous structure.
43
30
The disadvantages include:
Workers probably cannot get as far into the aqui - tfer as in the other method because of the nedessityfor workers to remove soil and water and place re-inforcing rod and concrete at the same time;
There is greater possibility of cave-ins because ofa need to work beneath concrete that has not hadtime to completely set;
The method may require special fast-Setting cementso as not to be washed away by water entering thewell.
The purpose of the bottom section is to allow as muchwater as possible into the well without permitting any ofthe fine soil particles from the surrounding aquifer toenter the well.
There are three commonly used methods of allowingwater to enter the well. (See Fig. 3-6.)
Through porous concretelining - Lining ringssunk into the bottomsection can be made ofporous concrete whichacts as a filter toprevent soil particlesfrom entering the well.
Through angled holes inthe lining - Holes canbe punched in a freshlypoured concrete ring,which, when cured, canbe sunk into the bottomsection. These holesare more effective atpreventing soil entryif they are slanted uptoward the middle ofthe well.
Through the bottom -The bottom of the wellshould always be con-structed to allow waterto come up through itOften the bottom issimply left open anduncovered but it is
. preferable '-to- preventsoil entry and thegradual filling up ofthe. well. FIG.3-6. wATeR. ENTRY Imo way-.
31
F. Design: Top Section
The purpose of the top section is to provide safe andeasy access to well water and to prevent as much contami-nated surface materials as possible from entering the well.
The design of the top. section is strongly influenced bytwo aspects of well usage: (1) access to water or how wateris drawn from the well, and (2) preventing, as much as pos-sible, surface contaminants from entering the water. Thesetwo functions are not always compatible. It is often neces-sary to compromise sanitation for the sake of water accessand community acceptance. Obviously you want to do this aslittle as possible but not to the point of jeopardizingsupport from the local community or goverAment.
A top section, in fact, is not absolutely necessary forthe function of a well. However, the different design ofthe parts of the top section is intended to make the wellsafer, cleaner, and more convenient for users.
Here are the major components of the top section:
Head wall;
Drainage apron (platform);
Cover;
Animal trough;
Wash basin.
1. Head wall
A head wall should be built on all wells whichwill not be fitted with a permanent cover and apump as a simple inexpensive safety feature whichwill prevent people and animals from accidentallyfalling in.
This is simply a wall which extends above thesurface of the ground far enough to prevent mostaccidental entry of people, particularly children,and animals. Its external dimension is dependenton how thick you want the head wall to be. A headwall that is unnecessarily thick will encouragepeople to stand on it to draw their water, creatingan unsafe situation. The easiest and best way toconstruct the head wall is as an extension of thelining. In most cases it will be convenient tobuild the head wall as an extension of the lining
32
above ground. You will already have the equipMent andsupplies on site with which to do this. The head wall.should extend 80 to 100 cm above the ground surfaceor apron, if there is one (see Fig. 3-7) .
FIG. 3-7. TOP SEC.TioN
2. Drainage apron (platform) (See Fig. A.)
A drainage apron is most often a reinforced con-crete slab 1 to 2 meters-Vide which surrounds a welland, because of its slight slope, channels surfacewater away from the well. Wire mesh reinforcing maybe used if it is available.
By forcing water to flow away from the well, theapron serves two functiolis:
It prevents contaminated .surface vater from fol-lowing the outside of the lint end flowing backdown into the well before it i ..ad a chance tobe sufficiently filtered by the earth.
It prevents the formation of a mucky area immedi-ately around the well which can be a breedingground for disease and a source of contaminants,to the well water.
46
33
A sloping platform,(Fig. 3-8) will simply movethe mucky area from directcontact with the head wallto the edge of the platform.It will still be an eyesoreand health hazard, althoughnot so much as if it wereright next to the well.
By installing a shallowchannel (Fig. 3-9) or veryshort wall (Fig: 3-10) aroundthe edge of the platform, thewater can be funnelled off toone specific area away fromthe well where people andanimals will not have totrack through it to get tothe well.
FieN3'"'9.51.102u.LOWCMANNSOLL.
IG.. 3 "' 10. SST Wil1/4 t. I-
,.,
.,
The apron should be strongly and carefully constructedas it will receive a lot of wear, and any cracks or chipswhich develop will decrease the effectiveness of the apron.
4 7
34.
An apron can be built of stone with mortared jointsif cement is in short supply. If for some reason it isnot feasible to build an apron, dirt should be built uparound the well so that water spilled will tend to runoff away from the well rather than collect around it.
3. Cover
A cover can improve the sanitary quality of thewater in the well by preventing the dust and dirtnormally carried in the air from entering and contami-nating the water. It also prevents people fromdropping things into the well.
There are two basic variations of well covers-temporary (removable) and permanent (fixedin place).
A temporary cover would be one that covers the wellbetween the timesit is being used,but must beremoved to pull water from the well. Forexample,a temporary cover would be a wooden cover that restson top of the well but must be removed to throw abucket, tied to a rope, into the well. This is alimited step toward protecting the well water fromsurface contamination.
A permanent cover is usually made of reinforcedconcrete. It can be poured in place on the wellor pre-cast in one or more pieces and later setover the well. (See Fig. 9-9.) Pump mountingbolts and an access door can be cast into theconcrete. Pre-casting the cover in one or twopieces may be easier because of the difficultyof building a form which is both strong enoughto support the weight of the concrete over theopen well and which can then be removed afterthe concrete has set.
4. Drainage pit
In some areas it may be necessary to constructa special drainage pit to allow spilled and run-offwater to soak into the ground. This may be usedwhere other measures cannot feasibly prevent the build-up of standing water. If such a pit is deemed neces-sary, make surethat it is at least 10 meters from thewell. The pit can simply be a hole dug in the groundwhich is then filled with loose rock and gravel.
48
35
NOTE: Where the water table is less than 3 meters fromthe surface, ,a drainage pit should not be dug becauseof the danger of directly contaminating the water supply.
5. Animal trough
If an animal trough is necessary, it should bebuilt far enough from the well so that neither theanimals nor their dung will collect around-the welland this contaminate the water.
6. Wash basinflo
It may be useful to build a wash basin ifclothes washing is done at the w911. It is impor-tant to prevent wash water from pouring back intothe well and thus contaminating it. The basinshould, therefore, be watertight and built at anelevation below the mouth of the well. Where thereis no place to build a basin below the level of thewell, it can be located 10 meters from the well.
49
Chapter 4
SUPPLIES
A. Introduction
Supplies include the materials, tools, andequipment necessary for construction of, the well.
The following supplies will be needed for con-struction of any hand dug well:
digging tools - shovel, pick, mattock;
equipment to lower ..and lift people and suppliesin and out of the well;
37
construction material and the tools needed towork with it.
Tools that may be used with the various materialsinclude the following:
reinforced concrete - cement, sand, gravel,forms, reinforcing-rod, tie wire, re-rodcutter, re-rod bender, wire cutters, pliers,buckets, 1 trowel (2 would be better), mixinghoes, aggregate gauge box;
concrete - cement, sand, brick or rock, mixingarea, buckets, trowel, mixing hoes, aggregategauge box;
wood - wood, saw, nails, hammer.
B. Tools and Equipment
lowering equipment - tripod, headframe orpulley'support with pulley;
cable or rope - 12 mm steel or 25 mm hemp;
buckets - 1 large, 2 small;
square nosed shovel (mixing);
50
38
round nosed shovel Jdigging);
hammers
hard hat for each worker in weal:
spare shovel and hammer hand -lest
plumb bob and plumb line;
level.
C. Materials
1. Cement
Most of the lining methods discussed here relythe use of Cement in one form or another, including con-crete, mortar, and porous concrete. Pkor the constructionof permanent, sanitary hand-dug wells; cement compoundsare the only materials in common use'around the world.There is no other material so readily available worldwidethat combines .the strength,'workability, and adaptabilityof cement compounds. 'Without cement it will be very dif-ficult to build a permanent, sanitary water source.(See Cement Appendix, p. 221.)
on
a. Limited amount of cement available
Where there is a limitecUsupply of cement avail-able which will not permit yogi. to pour linings or buildmasonry, you might consider bluilding a loose rock orbrick wall. Simply mortar the inside layer to preventit from falling into the well. This should only beattempted in very stable ground not subject to collapse.
In some areas only the top 3 metersof the wellneeds to be lined. This reinforces the area of thewell which is most likely to cave-in and uses a mini-mum of material, and it cdn'be attempted only where amortar or concrete lining is built in place in a well'which is being sunk in firm. soil.
Wells lined like this are rarely more than 10meters deep.
b. Cement Substitutes
Cement substitutes a e sometimes cmmerciallyavailable or can be manuf ctured locally. Lime,for example, can be mixed with sand and water to
5i
39
form a mortar-like paste which can be used in layingbrick or rock walls. Like other cement substitutes, itdoes not have anywhere near the bonding strength ofcement mortar.
2. Other Materials
If you cannot get cement in a reasonable length oftime and at a reasonable cost, you should consider build-ing the well with other materials such as wood or unmor-tared rock. These other materials will not last as longas cement but they will enable you to make water availablewhere it is needed now.
Unmortared brick or rock
Many wells have been built of unmprtared rock and. have lasted for hundreds of years. This, however, id-
only where highly skilled stone masons and suitablerock are both available.,
Normally unmortared brick or rock is only atemporary solution which will collapse in time.Where the ground is very stable, you might con-sider such a lining, although the well may standunharmed without'a lining for a long time in thiscase.
Wood
This also is only a temporary solution. It will
rot soon (in 1-3 years), tainting the water and allow-ing cave -ins.
D. Organization of supplies at the well site
In your planning consider:
the space needed for each operation;
the arrangement of supplies within each operationspace;
, which operations must be performed at the sametime so that their respective spaces do not con-
.
flict or cross;
that a different lining method may be used for thebottom section which will require spabe for-work-
ing and materials.
52
.40
4
There are 3 different types of operations which must beperformed duting the sinking of a_well:
removing'excavated soil and rock and dumping it;
lowering and lifting people and supplies in andout of the well;
preparation and placement of lining materials.
The puipose of organizing the supplies around thewell is to provide comfdrtable working spaces for eachof these operatiollp wheri they will not conflict witheach other but are still close enough to be coordinatedand efficient. (See Fig. 4-13
ST0M.AGE.foRCEMENT AND
OTHER SUPPLIES
1111
[MIXINGAREA
Ors.:5E-
GRAVEL
SAND
F 1 G . 8-I -a.LAYOUT of MATeltiALS AkiVo SUPPLIES
1. Removing excavated soil and rock and dumping it.
A great deal of time will be spent performing thissame basic operation over and over again. As a resultworkers will be tempted to do the least amount of work
53
necessary to get by. It is important .that the dumpingarea be:
far enough a$iay frothe well to not subject thewell to danger of caving in;
not so far away as to slow well sinking becauseexcavated material is not being dumped fastenough;
located so that rain will not wash material backinto the well;
located in order that:water pulled from the wellfor sinking the bottom' section will run off andnot collect near the well;
large enough to hold all the material taken fromthe well.
' 2. Lowering and lifting eoleandstpiesinandoutofthe well.
This operation is critical for the whole well sink-ing process but is also so flexible in its placement thattoo often it is simply assumed that space can be foundafter everything is set up. Unnecessary delays and pos-sibly dangerous situations can be avoided in later workby simply arranging the supplies so that nothing ever ob-structs the lane the pullerOmust use to raise and lowersupplies in th.! well. Also avoid placing supplies so thatthey must cross the pulling lane to be used.
3. The preparation and placement of lining materials.
Most hand dug wells need spade to store and latermix sand, water, gravel, and cement to form concrete.The actual nliVng area should be close to the well andnext. to the pulling lane to permit easy movement of con-crete into the well. The materials necessary for con-
. 'rete should be stored near the mixing area but far enoughfrom the well to prevent danger of cave-ins.
Sand and gravel storage will take up a large amountof .space, which should preferably be easily a...cessiblefrom the mixing area and from the oppositd side to allowfor replenishment if necessary., Also, if you plan to usepre-cast lining rings, you will have to allow space fortheir construction.
The importance 'a few minutes worth of planning,can have is demonstrated in the following example.
54
$
42
Assume that we have a well with a 1.3m interior finishdiameter, a 7.5cm thick reinforced concrete lining, and adepth of 20m--an average sized well. This well will re-quire about fifty 50kg bags of cement for construction ofthe middle and bottom section. If only complete bags of
,cement are mixed at a time that will require:
50 trips to and from the cement storage area;
50 wheelbarrow trips of sand;
100 wheelbarrow trips\-of gravel:,
some multiple of 50 trips to and from the watersupply;
about 500 trips with concrete from the mixingarea to the well, depending on the sizeof theconcrete buckets. /
Obviously the shorter all these trips can be, theless time and energy will be consumed by them. Remembezztoo that as you take sand and gravel from the near sideof the storage piles you have to walk farther and farther.
55
..t
Chapter 5
LOWERING AND RAISING WORKERS AND EQUIPMENT
A. Introduction
At some point most materials and equipment in-volved in hand dug wells construction will be lowered in-to or pulled out of the well. This raising/loweringoperation is so basic to wells construction that it willbe discussed here in some detail. (See Fig. 5-1.)
The raising and lowering operation will eventuallybecome routine because itmust be performed so often.Before the real well sinking work is begun, you should tryto plan that routine by considering what equipment will beused and how the workers should be organized to use theequipment safely.
FIG.. -I. RAIGING AND LOwERIMG OPSRKrioa
JP
44
B. Safety
Most major accidents or injuries that happenduring the construction of a well result from f.ultyraising and lowering procedures. Accidents usuallyoccur becr.ase someone forgot, didn't understand, orwasn't ready to perform his/her part. of the operation.Remember that people's lives depend on how carefullythis operation is performed.-
There are many tools, pieces of equipment anditems of knowledge that can help in this operationby making it easier and safer. They include:
tripod, headframe;
pulleys;
winch;
rope-knots;
buckets.
Everyone coming in contact with this raising/lowering operation should be thoroughly familiarwith it. It is a good idea to do a couple of prac-tice runs so that everyone understands exactly whatis involved.. Switch people around to help them under-stand what is happening at different points in theoperation. It is also useful to have well workerslowered in and out of the well to help resist anylater tendencies for joking while pulling on therope. That way, everyone understands the realityof being suspended on a rope with no way to helpyourself if a problem occurs.
Certain safety features should be followed:
All workers in the well should wear hard hats;
People are most safely raised or lowered inthe well on a bosun's chair made of a board, logor other appropriately strong seat firmly tied toa rope (see Fig. 5-2).
Nothing should ever be left lyingnear the'opening of the hole. Insituation, people can easily tripknocking loose materials into the
on the grounda workingand fall,well.
4f
_-111
FIG. S-2.-rwo 5t)G6ESTIM>DESIGNS FOR. A 150.-suP4t5c.4-1Aire.
45
It is also necessary to beconcerned with the safetyof people other than the wellworkers. Passersby have anatural curiosity and wishto find out what is happening.Before construction is begun,it is very useful to estab-lish some kind of perimeter,or even a fence, which is tobe crossed only by those actu-ally involved in construction.This may be difficult enoughto enforce during workinghours but becomes more impor-tant and more difficult atnight and on non-workingdays. It may then be nec-essary to use a.guard toremind passershy that theyare not supposed to be inthe area. The guard canalso make sure that toolsand supplies are not takenfrom the site.
It is very helpful to have a set of signals tocontrol raising and lowering. These should be voicecommands as well as hand signals. Four simplesignals will usually cover most of your needs (seeFig. 5-3).
raise;
lower;
stop;
slower.-
C. Lowering Supports, Tripod, Headframe
Some type of lowering support is necessary whendigging, except in very shallow wells. It, provides amuch safer and easier way to lower tools and materialsfor use in the well and remove the soil and rock dugup in the hole. Such a structure usually has 1 or2 pulleys which can be suspended over the center ofthe hole or offset. The offset arrangement is ofteneasier to work with.
Choose the type of lowering support post suitablefor the kind of work you expect to be doing and thematerials you have available. (See Figs. 5-4, 5-5,and 5-60
47
Woos LOWEXIMCG sUPPoe.T5
60
49
If they will not obstruct other operationsethe low-ering supports can be erected before you begin digging.Or, more often, erect them after you have dug a meter ortwo and passing buckets by hand in and out of the well be-gins to get difficult.
It is the operation of this unit which will largelydetermine the safety of the workers in the hole. Empha-size this major point to all workers and visitors at thewell site. Also, observe these six points on safety:
1) Lowering and raising materials and people shouldalways be done with enough people on the rope.It is dangerous to rely on one or two strong in-dividuals. Using several people assures controlof the load even when a hauler trips or is other-wise unable to continue supporting the load, whenpeople are in the well, or when someone is on therope being raised or lowered in the well.
2) Someone should always be posted at the well edge,watching the load being worked within the well.In case of a problem this person can alert thehaulers or other workers. The same individualcould also hook and unhook buckets, loads, andpeople from the rope and ease them into and outof the well.
3) When pulling large buckets full of soil, rockand water from the wellftwo people may be neededto pull the heavy bucket out of the well andplace it on the ground next to the well for la-ter dumping.
4) There should be an established setof signalswhich the person at the well head will use todirect those hauling on the rope. (SeeFig. 5-3) These signals should be taken veryseriously and are to be used only when necessary,but with no hesitation when they are necessary.Practice in using and understanding the signalsis advisable.
5) Throughout the well sinking process be especiallycareful that nothing falls into the well. Evena small pebble unknowingly knocked into the wellcan cause serious injury to a worker at the bot-tom if it falls from a distance. Take preventivemeasures. Be careful how You work around the edgeof the well.
62
.
50
6) Always leave a safety line hanging in the hole.This is a rope tied off at the ground surfacewhich can be,used in an emergency as an exitfrom the well.
D. Other Raising/Lowering Arrangements
While lowering supports have been found tcl be theeasiest and safest form of entry and exit, many othermethods have been used. In these other methods tools andmaterials are lowered by rope by people standing next tothe hole. People may be raised and lowered in this waybut it is usually easier for individuals to make their ownway in and out of the hole by climbing up and down:
an anchored stationary rope which may be knottedat regular intervals;
a rope ladder; or
a regular wooden ladder which may be constructedin stages for use in deeper wells and anchored tothe walls. of the hole.
E. Common Raising /Lowering Problems
Lack of tools or materials from which to makethe equipment necessary for the raising lowering'operation
This is rarely a real problem because some waycan always be found to raise and lower peopleand supplies if you and the local people arecommitted to constructing the well.
Equipment breakage'
This is usually due to misuse by overstressing .
or old age. Misuse can be prevented by carefulwork habits and frequent inspection of the equip-ment.
Equipment will gradually wear out with time.While this cannot be prevented, it can be anti-cipated, so that old equipment is replacedbefore it becomes dangerous.
51
Lack of sufficient people to perform raising/.lowering operation
This too is more of a perceived problem thana real one. If there are enough people in anarea to warrent digging a new well, then thereshould be enough available to help with thisaspect of the work.
If vehicles are available they can be morereliable pullers than people. Workers canalso easily raise and lower themselves wherenecessary.(Figs. 5-7 and 5-8)
FIO, 5- 7. wHeas- RIM CAPSTAN
0.. IIIM.
i
Fqb 6-8. tiCwERitogRAISIM6 'ROPE ATTACHED TO VEH1 ci.E.
64
,
52
F. Useful Equipment
1. Ropes
The liver of you and your workers will depend onthe ropes you us., so be very careful in selecting rope.
Make sure that the rope you use is strong enoughfor the loads you will impose on it. (See Rope StrengthAppendix, p. 267.) It should be inspected regularly forflaws and traying. If possible, use new rope. As ropeages it loses up to half its strength. You should takethis into consideration during selection and use.
Hemp rope is usually available and is very suitablefor wells construction, although contact with cements willspeed its natural aging and deterioration.
Nylon rope is often available and suitable, al-though it will stretch as a load is put on it.
Wire rope is excellent, combining strength andsmall size although it is really only suitable for usewith a winch. Wire rope should notibe pulled by handwithout the use of gloves as it tends to frgr, leavingends sticking out which easily cut the skin.
2. Knots
A few basic knots, when used properly, can helpmake the work easier and safer.
bowline - This knot can be tied to form a loopof whatever size you need that will not slip orcome loose.
0 Its most common use is in rescue operationswhere people have to be hauled or lifted out ofdangerous situations. (Fig. 5-9)
r16.6-1. eOWLINE_
65
PULL
LOOP
square knot - This knot is used to join tworopes together. (Fig. 5-10)
Vi. 5-10.SQUARE KNOT
53
half hitch - This is very commonly used toattach a rope around a solid object. Once tied,it is difficult to tighten the rope although theknot itself will only become tighter if the ropeis pulled. (Fig. 5-11)
F16. 5-11.HALF (-1 fTCNE.S
66
54
3. Buckets
The use of two or threedifferent kinds of buckets isoften convenient for work inh well.
To avoid the possi-bility of tipping over whilebeing lowered or raised inthe well buckets should havetwo features (Fig. 5-12). .
.handles attached to/
the bucket along its'upperrim. Any weight in the bucketwill tend to keep it upright.
buckets should bedeeper than wide, which con-centrates the weight furtherdown making the buckets evenharder to tip over.
-HOOK GThHHELPWIE.NT
TIPPING
Air1,
NAN WAAl TACHeirlb UPPERRIM
FIG. 6" 12.Etuc..KET
V1:,*
Buckets, like ropes, should be checked regularlyfor defects. Particularly look for:
a weak bottom;
a worn handle/bucket junction;
cracks or broken places;
worn handle.
Discard rejected 15utckets, if possible,,to)avoidpossible future confusion and unsafe use in the well'.
Buckets may be used for different operations andtheir desired features will vary accordingly. Buckets usedin excavation, such as.removing soil and rock frowthe holeshould haver
handles that connect to the bucket rim;.
greater depth than width;
reinforced bottoms;.'
,67c
r.
is
.
4i 55
handle safety latches; and
hooks in the middle of the. handles.-
Buckets used for cementing (lowering cement intothe well) should have:
handles connecting to the rim. of the bucket;
wide rims for. pouring.
Buckets used for lowering and raising tools shouldhave:
handles connecting to the rim of thebucket;.1'
greater depth than width.
4. pulley
The use of a pulleywill greatlyfacilitatewell construction work.If unavailable, arrange across piece with a smoothsurface over which you canpull the rope.. It is farmore preferable to pullthe rope over a pulleythan try to stand at thewell edge 'and pdll the.rope straight up hand overhand. Ropes will wear ,
much faster when pulledaver even a relativelysmooth surface than whena pulley is used andshould thereforevbechecked frequently.
Al sulleys.are.of7.ten available as a unit'with a*hdok. (. ig. 5-13)
i. iulleys can alsobe built with shaft ends.(Fig: 5-14)
d
Pulleyi may ,bemounted in hard woodblocks anchored to solidframe. _ (Fig. 5-15)
Pto1.L.v1 %%vim MOLHATIMGIUDOK
RG.5-1s1. Jea.EYera A SHAFT
FOG. 5- Ak.i.ENgaterea-MS
56
5. Brake Post
The brake post is a log set in the ground 4 to5 m from the well which, when the raising/loweringrope is wrapped around it several times, acts as afriction brake. This can help, especially whenlowering heavy objects into the well, by allowingmuch easier control of the lowering speed.. Aperson standing behind the brake post controls thelowering speed by the amount of tension he/she keepson the rope as it feeds around the post -and on tothe well.
A brake post should be:
located 4 to 5 m from the well straight outfrom the pulley (See Fig. 5-1.);
about 25 cm in diameter, round, and smooth;
set in concrete 1 m into the ground;
set at an angle of about 600 from the well.
57
Chapter
DIGGING
A. Introduction
Hand dug wells are sunk working down inside the holeto loosen the sub-soil which is then lifted to ground leveland dumped. How one actually digs and then lifts out theloose dirt and rock depends largely on personal preference,based on the available equipment and safety procedures onewishes to follow.
B. Tools
The tools you need depend on the soil conditions.Shoyels, pickst mining bars, hoes, jack hammers, and handshave all been used. Anything that will loosen the dirt androck so that you can then load it into containers and haulit to the surface will work.
NOTE: By shortening the normally long handles of shovelsin particular, you can reduce the possibility of injuriesand make them easier to use in the confined space at thebottom of a well
C. Digging'
Digging a hole that reaches water and becomes a wellis slightly different from just digging a hole. Pay atten-tion to the diameter of the hole, how smooth and even thewalls are, and whether the hole is straight up and down.
Many people have found it convenient to followthese steps when using a sinking technique where the holeis first dug, and lined afterward.
Dig down and remove a layer from 10 to 40cmthick that comes to within 5 or 10cm of thedesired diameter (see Fig. 6 -lb);
Continue removing layers of soil until you havereached a depth of about a meter (see Fig. 6 -lc);
70
58
FIG. G Smrs To robeiNG Noug.
0.. b. C. 41.
Now go back and trim out this section to thedesired diameter, making sure that the holewalls continue to be plumb (see Fig. 6-1d);
Continue this process, which may be brokenup by periods of lining the hole, until youreach the desired depth of the hole.
While digging a well, you are likely to encounterseveral different types of soils which range betweenvery loose and very'hard. It can be difficult to sinka hole into either extreme. Digging} in loose, drysand can present some serious problems because of itstendency to fall back in. Dry sand acts like a verythick liquid.' Unless you cap stop the sand from con-tinually flowing back, your well will end up V-shapedbut even wider at the top than the hole is deep. Insuch a situation you can sometimes stop the sand bydigging 10 to 15 cm and then splashing a mixture ofcement and water on the wall. This will dry inminutes to form a thin hard layer. If that fails,pour 200 liters of water into the hole before diggingthe next meter. This saturates the sand,to make itmore stable. If this fails, you should considersinking the lining through the sand.
D. Hard Rock
Digging down and reaching a hard rock layer abovean aquifer is one of the most discouraging things thatcan happen to a well digger, who must then either tryto continue sinking the well into and through the rocklayer by whatever means possible, or abandon the holeand try again someplace else.
In order to proceed correctly you need to researchand analyze existing information on water accessibilityand rock layers. Often there will be only minimal docu-mentation available. Wells project workers may have to
71
59
reach conclusions on the basis of incomplete information..Here is a series of questions, the answers to which willassist well workers in developing such information:
Has this or a similar rock layer been encounteredbefore in other attempts to sink wells?
Where were the wells attempted?
At what depth was rock encountered?
Is this a situation that local peopleknow about?
Is this a general long slope of the groundsurface in a certain direction?
What do you think happens to this rock layerin that direction?
Is there another source of water that could befurther developed to supply additional water?
How important is it that these people' havea well to supply them with water?
E. Plumb
An object is plumbif it is straight up anddown (perfectly vertical).Wells should be as plumbas possible for conveni-ence and to avoid manyother possible complica-tions. This is particu-larly important in sinkingpre-cast lining sections.Structurally, a well thatis plumb is generallystronger than one thatis not.
dp4
Plumb can be checkedt#
with simply a string with 1a weight tied to the bottomof it (see Fig. 6-2).-Plumb-
*P'
bobs can be purchased com- .
mercially and are relatively .cheap. For-convenience sake .
..
4 PLU BOB\one, especially if there isit may be useful to purchase M'S
a sliding piece for the top..
which is exactly the same .
width as the plumb-bob itselfso that you can easily get rit;. 6-2. "Ps-um6 - Boos BE 1 ".16exact measures. '7 ell vsepino CHEL.K.1:1-10413 of Ht71...e
i 4
60
F. Diameter
It will be necessary to regularly check the diameterof the well for many reasons. The hole you dig should havethe exact diameter that you have designed for it.
If the hole diameter is less than planned, the pie-cast lining may not fit or poured concrete walls, will bethin and weak. This can be easily fixed by trimming thehole to the desired diameter.
If, on the ether hand, you have dug' the hole too wide,it probably won't affect the final condition of the well,but you will have spent unnecessary extra time,diggingand it will take more time, and perhaps materials, to fillthe well back in to the desired diameter. Excessive widthis especially serious when pouring concrete walls inplace in the well. The diameter of the forms is set andfilling in behind them will require a great deal moreconcrete.
G. Methods of Checking the Diameter
1. Drop Bar
Preparation
Bend 6mm re-rod into a circle which conforms to de-sired circumference of the well.
Continue bending the re-rod around a second time tomake double bar and tie the two together.
Check roundness by rotating a straight bar the samelength as the diameter within the circle drop bar.
During Digging
Dig one meter and be careful not to displace thedrop bar or excessively dig outward at the wall. Afteryou have dug one meter, you are ready to use the drop-bar.
For right-handers, plcace your left hand lightly Onthe bar. Hold the trowel sideways under your left fore-arm. Using the upper back corner of the trowel, work to-wards your body and scrape away the dirt below the bar.
73
O
Work along the circumference, scraping away justenough dirt to allow the bar to drop. Continue in thismanner, working around the hole until the bar is at thebottom of the hole. (See Fig. 6-3
If you constantly look at the bar and keep itlevel, the bore of the well will be straight and consis-tent.
If you now plan to pour the lining'in theyell,dig a bit with the trowel until the bar is-belowthe floor of the first dig and cover it with sand.
Do not smooth the wall.
FIG- 6-3
Fi G.
74
61
62
2. Other Methods
This next Aethod can be used to check both thediameter and plumb and can also be used to center formsused in;ttie yell.
This method involves hanging a measuring bar fromthe center of a centering boars which fits across the topof the well and is located by a stake on eithei side ofthe well. (See Fig. 6-44 .
Dig anchoring holes for re-rod stakes, one oneither side of the location of the well and about 30cmback from what will be the edge of the hole.
Cement stakes in place and place tops of bothstakes through holes already drilled in centering boardbefore the cement sets, to exactly locate stakes.
Locate a hook or hole in the center of the board
Draw a circle of the desired hole size in theground centered at the hook. This exactly locates thehole to be dug.
As each meter is dug, hang the measuring bar froma line board over the hook. The bar should pivot freely,just touching the edge of the hole with both ends to in-dicated that the hole is both plumb and the proper size.
A variation of this would be to use a plumb-bob tolocate the center and gauge the radius of the well fromthere. (See Fig. 6-5) Hang a plumb-bob from the hook tolocate the center of the hole.
with a re-rod measuring piece cut to the exactradius of the hole, check the diameter as shown inFig. 6-5. The measuring piece should just fit betweenthe plumbline and the wall.
A person could also stand in the hole with a rodwhich is the exact diameter as the hole in order to trimthe hole down to the desired size. (SeeFig.
75
1
Chapter 7
THE MIDDLE SECTION: OVERVIEW OF LINING TECHNIQUES
A. Introduction
The middle section of the well is the first part tobe built. It involves digging and lining the hole fromthe ground surface to the water table.
B. Lining: Purposes
The lining is a circular wall made of a strong, per-manent material placed or built adjacent to the walls ofthe hole.
The lining has three purposes:
it retains the walls after completion; it keepsthe hole from caving in;
it acts as a seal to prevent polluted surfacewater from entering the well;
it serves as foundation and support for the welltop.
Wells should be lined if possible. Without linings,wellsare'subject to damaging cave-ins.
Only in hard rock formations are-linings not neces-csary because rock is not liable to cave -in. Liningsshould be4built of permanent materials which will not rot, .
deCay or otherwise lose their strength in a relativelyshort period of time.
In some places wells are lined, meter by meter,'onlydown to adepth of about 3 meters. From there down thewalls are left unlined. Such a limited lining reinforceswhat is normally the most unstable part of the well. Ifcaving in is not a prOblem, this amount of wall reinforce-ment may enable the development of a semi-permanent watersource. It requires a minimum amount of materials but isnot really suitable for development as a sanitary watersource.
76
63
64
It would be tempting to think of this kind of wellas an appropriate temporary solution which could laterbe easily up-graded to meet the need for a permanentsanitary water source. However, consider that although
. the partly-lined well meets the current water needs, itmay be difficult to motivate local inhabitants to donatetime and money to later improve a source that alreadymeets their felt needs.
O
C. Lining: Methods
There are two basicmethods of lining a hand-dugwell.
Dig and line
The hole or a portionof the hole is first dug andthen lined. /This is a veryflexible method and is there-fore suitable for use in manydifferent ground conditions.
sink lining
Pre-made lining sec-tions are put in place andsunk by digging soil outfrom inside the bottom liningsection. This method is usedprimarily in loose, dry sands /where dig-and-line methodswill not work bicause holewalls cave in too quickly.(Fig. 7-14 SiNg.
1. Dig and Line
This method, which has been traditionally used forwell sinking in all parts of the worldohas many variationsthat make it suitable for many different construction ma-terials and ground conditions.
In this method the hole is always dug first and thenlined.
,I
LININGRUNGS
CUTTINGRING
77
65
Commonly used variations of this method arei
dig-a-meter, pour-a-meter (see Fig. 7-2);
dig-and-line-in-short-sections(see Fig. 7-3);
dig a hole to water and line;
dig a hole as far into water as possible and line.
The advantages of a dig-and-line.method are that:
it enables you to dig as deep as you can beforecommitting expensive materials to lining the hole;
it is capable of penetrating anything except hardrock (hard rock can sometimes even be penetratedfor short distances);
the lining can be built in place in the wellor built on the surface and lowered into thecompleted hole;
the lining curbs (see p. 69) can be built into increase lining stability.
Its disadvantages include:
possible dangers from cave-ins if the hole is dugWO far without lining;
requiring more work in the well than "sink-lining."
2. Sink Lining (Caissoning)
This method is most suitable for use in loose fluidsoils.
The lining is assembled at the surface before it issunk. It can be made of.pre-cast reinforced concreterings which are set inplace at the ground surface one byone as the others are sunk, or brick or circular rock wallswhich are built up at the surface layer by layer as thecolumn sinks.
The lining is sunk by workers standing inside thelining co/Umn and digging out soil. As more supportingsoil is removed the lining will gradually sink under itsown weight.
The sinking proceeds. by digging out soil until the top
(continued on p. 68):
66 F G. /- Z. DIG-A-msTaRIP6012- A M OMR
a. The hole is dug andtrimmed to the exactdiameter and depthrequired.
c. The hole has been dugbeneath the flerst pourto-a depth slightlygreater than the heightof the form to allowspace for concrete to bepoured into the secondlined section.
b. The concrete lining forthe first meter has beenpoured in place in thewell between the formand the hole wall. Endsof the vertical rein-forcing rod have beenpushed into the groundbeneath the poured con-crete section so thatthey can later be con-nected with the follow-ing pour.
d. The second meter has.beenreinforced and poured asin the first meter.Vertical re -rods of thefirst pour were tied tothe vertical re-rods ofthe second pour beforeconcrete was placed be-hind the mold for thesecond meter.
e. The hole has again beendug down beneath the lastPoured lining section toa depth slightly more thanthe height of the mold.The-gap between the firstand second pours can nowbe filled in with mortarto give a smooth contin-uous lining.
79
.
41
F16.1-3. DIG-AND- LINE-IN- SHORT- SECTIONS
a.The hole has been dug asdeep as five meters andtrimmed to the properdiameter. Verticalreinforcing has been putin place over the entiredug section. The secondpour has just been com-pleted on top of thefirst pour. Each suc-cessive poured liningsection will be poured ontop of the previouslypoured section until the,hole is completely lined.
1
b. The final poured sectionhas been completed forthis short section ofthe well.
!
t "I
II
'..-,
c. The hole is now extendedas deep as five metersbeneath the first shortsection. It will thenbedined as in the pre-vious short section andconnected to it with thevertical re-rod that wasleft beneath the firstpour of the first shortsection:
80
1
a
67
W..
68
3
of the lining sinks almdst to ground level and adding an-other lining seceton, ,digging, and sinking that sectkon 'tothe ground levet,\and sO onuntil the lining is sunk asfar into the water as possible.
As a well sinking method to be used fromithe groundsurfaceoit is useful for.shallow wellsiand those wellswith larger than normal diameters wher the ground Isfree from boulders and other huge obs7rActions. .
This method has these advantages:
the equipment is simpler tVan that required fordig and line;"
a headframe is not essential;, .
6, not as much re-rod is required;
most construction work is carried out on the sur-face;
adyance preparation of Xining can.. significantlyspeed the sinking. process.
. \The disadvantAges include the following:
it is difficult to keep shaft vertical;
boulders or even large stones in the ground cancause the column to tilt;
the stability of the completed lining depends en-tircly on the-friction between the lining and thehole wall and since this'As irregular, stressesare set up which may cause slipping, jamming oropening construction joints;
as t he depth of the well increases, a tendencydevelops for sections to "hang", causing tensionfailure, or to buckle or crush under the weightof the column of rings;
the aquifer may become contaminated by seepagefrom the surface down, the outside of the liningring because it is not sufficiently form-fittedto the hole wall.
81
etc,. 7-14. LIMN& cvite,
D. The Curb ,
:The curb is an elbow-,
shapediCut'made in the wallthat is 'poured full of con-crete and acts as an-anchorto prevent the lining fromsliding down through theground,. The.bottom.of thecut is flat, 40 cm into thewall, and the top; is cit 40cm higher than the bottomcut, and allows concrete toflow to all part of the ,
curb. The're-rod should be lameo:MOLDSk
attached.to each vertical(as "'Shown in Fig. 7 -4). It will -
obviously take -more concretefor a pour that includes a :
curb.
6.9
Cv415 HomiZoNTALRV' ROD
There is no commonly accepted standard regardinga recommended distance between curbs. In'fact, somesources question whether they are even necessary wherea concrete lining is poured in pl&ce. Other sourcesrecommend curbs every 5-meters to 10 meters. It isrecommended here that'curbs be installed every 10meters.
It is always a good idea to install a curb at or'nearthe bottom of the middle section lining, just above thewater table.
E. Cast-in-Place Versus Pre-Cast
1. Definitions
Cast-in-Place
The lining is built in place right up against thewalls of the hole.
Pre-Cast
Sections of the lining are built above ground andlater lowered or sunk into place in the well.
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2. Decide Whether to Pre-Cast or Cast in Place
The decision to pre-cast or cast in-place the middleszction lining usually depends on such factors as size of
the project, lining materials, equipment available, ground
conditions, and personal preference.
Generally, a lining that is built in place is betterthan one that is built ahead of time and then installed in
the well. By building it in place, especially if usingreinforced concrete or mortar, the lining conforms tothewalls better, providing' greater adhesion, stability, andsealing,*as well as preventing 'the entry of contaminated
surface water.
Car4-in-Place
generally preferable--strong, waterproof.permanent;
bonds well with ex-cavation walls;
limited working spacein the well.
Pre-Cast
forms helpful butnot required;
pre-made concretesections available;
provides more timeand space to builda stronger lining;
may not bond wellwith the hole wall;
requires heavy low-ering equipment.
To prevent tools and materials from being ac-cidentally knocked into the well and the possible collapseof the Looser surface soil into the well you may wish toinstap. a lining in the top meter of the well as soon as
it is dug. This can be either a temporary or permanentlining depending on what materials you have available andthe lining method you plan to use.
When in place, this lining should reach at least 10cm,above the ground surface to prevent tools, materials,
and other articles from falling into the well.0
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An inside lining mold canbe used as a temporary lining.(See.Fig. 7-5.) There must beenough room for people andsupplies to move in and out ofthe hole. The ;mold should becarefully packed in place toprevent it from slipping downwhile the hole is being exca-vated beneath it. Rememberthat, once in place, this tem-porary lining cannot be moveduntil the construction is com-plete. It is, therefore,necessary to plan on makingor purchasing 'this in additionto all lining molds neededfor the construction of thepermanent lining.
If you build a perma-nent lining, pour it inplace possibly with an anchorabove ground.
As you sink the well be-yond this top support, taperthe inside hole walls out tothe desired hole diameterabout 30-40cm below bottomof top support. This willhelp support it while diggingcontinues below it.
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/ -3(.4y
PIG. 7 5LINING MOLD ASitmADRARY LIMING
if you decide not to put a top support in you shouldmake some effort to ensure that workers in the well aresafe from ground surface collapse and accidental entry ofanything into the well. For example, four boards may belaid in a square around the hole and used to accomplishthis.
Such a construction will help to distribute weightnear the edge of the hole and act as a constant reminderto well workers and others to be careful.
Many wells have been dug without the use of anymeasures to prevent accidents except to warn everyoneabout the consequences. Well workers will all be sensi-tive to the need for safety but local villagers often arenot.
In some cases wells projects have established rulesthat no one, including village elders and children, cancome within 2 meters of the well until it is completed.This may be hard to enforce but is nevertheless a veryuseful procedure.
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NOTE: Hole diameter and lining thickness: As a,generalrule the lining thickness should be about 1/20 of thehole diameter but never less than 7 cm.
Finish well diameter = interior lining form diameter =9/10 hole diameter (for wells Whole diam. 1.40m)
F. Lining: Materials
The availability of materials largely determines howyou line the well. Here are the most frequently used lin-ing materials in order of preference.
This order is generally applicable to most localesalthough there may be minor changes due to limitations ofgeological conditions. Such limitations are almost alwaysdue to the fact that soil conditions will not permit youto dig down to the water table without first reinforcingthe walls. The installation of temporary reinforcing issometimes an appropriate solution, but that involves alarge added expe:ise for temporary lining which is beyondthe scope of this manual.
Reinforced concrete
This is probably the best material now commonlyavailable for large-diameter well lining. Whenproperly cured it is very strong. Depending onits ingredients it can be virtually waterproof orquite porous. Re-rod is available in most coun-tries, although it is sometimes difficult totransport to the well site. Concrete can be pre-cast into appropriately sized sections and thenlowered into the hole or it can be poured andcured in place inside the well. Depending onwhat other equipment and materials are availablefor use with it,,it is the most-adaptable materialfor many of the situations which may be encounter-ed in wells construction.
Reinforced mortar
This material has all the.same advantages anduses as reinforced concrete. The difference isthat only sand is added to cement to make mortarwhile sand and gravel are added to cement to makeconcrete. Gravel acts as a stretcher to make theconcrete go further so mortar is more expensivefor the same volume of final (product. Mortar isa more "workable" mixture and in some cases maybe more suitable than concrete.
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Concrete
Concrete without re-rod is not as strong as rein-forced concrete.
Mortar
This has the same qualities as concrete but ismore expensive.
Brick
Brick should be solid rather than hollow. It isbest suited for digging to the water table andthen lining the complete well. It can be used toline in short sections although it is difficult to'Support a lined section while digging beneath it.Mortared brick makes a strong.lining but does notadhere very well to the hole wall.
Rock
Rock is very similar to brick in that it is bestsuited for lining a hole that has been completelydug. Mortared rock walls can be quite strong al-though because of their irregular shapes andstrengths they will often contain weak spots andbe subject to cracking.
Unm6rtared rock walls can also be very strong ifbuiltproperly, but require proper materialsand a degree of expertise which cannot be adequatelycovered in thiS manual.
=lefr
ty4V711;IPF,.._
Pk;. 7-4", ViCc.K. WALL.
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Timber (wood)
The only advantages of wood are that it has beengenerally available; moderately strong and cheap.In' many areas of the world wood is no longergenerally available or cheap, and its disadvantagesare such as t9, prevent any serious considerationof wood as a lining material for a permanent potablewater source. It is liable to rot, taint the waterand harbor insects. It is impossible to make thelining watertight and so prevent re-entry ofcontaminated surface water.
G., Possible Digging/Lining Methods for Each Material
1. Reinforced concrete cast in 'place:
Dig to water and line;
Di9-a-meter, pour-a-meter;
Dig and line in short section's.
2. Reinforced concrete pre-cast:
This requires header capacity lowering equipment.
DiV to water Aid line;
Sink lining.
3. Reinforced mortar thrown in place:
Dig to water and line;
Dig-a-meter, pour-a-meter;
Dig and line short sections.
4. Reinforced mortar pre-cast:
Dig to water and line;
Sink lining.
5. Uni'einforced concrete or mortar cast in place_:
This has very little tensile strength..
Dig to water and line;
Dig-a-meter, pour-a-meter;
Dig and line in short sections.
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6. Unreinforced concrete or mortar pre-cast:
Its low tensile strength makes lowering it intothe well difficult.
Dig to water and line;
Sink lining.
7. Brick or,rock:
These materials also have relatively low tensilestrength:
Sink lining (on cutting ring);
Dig to water and line;
Dig and line in short sections withanchoring curbs.
8- Wood (timber or split bamboo):
Employ verticals with horizontal supportsall anchored to walls;
Use any sinking method but try to avoidthe use of wood in the first place, forreasons discuSsed above.
I NOTE: Efficient use of cement
Cement is probably the most expensive materialof all so it should be used as efficiently aspossible.
Of all cement compounds, reinforced concreterequires the least amount of cement per volume ofbuilding material (either mortar or concrete) pro-duced.
On one wells construction project where 50 cmrock walls were built, 15 cm reinforced concrete wastried instead.
The results were a 1/3 reduction in cement used,walls were more waterproof, and the construction timewas significantly reduced. The initial cost wasgreater bedause of the need for forming materiAs,but forms can be re- used. By prorating the cost. offorms over a number of wells and figuring'the reducedlabor costs the tonal of each well went downcost_about 25%.
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Chapter 8
CONSTRUCTION OF THE MIDDLE SECTION
A. Introduction
,'77
This chapter first presents a step-by-step descrip-tion of the use of reinforced concrete inthe constructionof the middle section by three methods: 1) dig-a-meter,pour-a-meter; 2) digand-line-in-short-sections; and 3) dig-to-the-water table-and-line. It then describes the use ofthe same material in building lining rings and concludeswith a discussion of the use of alternative materials,mortar and mortared brick or stone.
B. Sinking Depth and Lining
How deep you sink the hole before you begin lining itis a quesc.ion you must answer for yourself/liven thelocal conditions. Major concerns are the ground condi-tions, the lining material to be used and personal prefer-ence.
gt:ound_condktions
. In loose soil, dig to whatever depth can be conven-iently dug -and lined without the hole walls caving in;1/2 meter is the usual minimum.
in firm soil, the maximum recommended depth withoutlining is 5 meters. This is usually a safedepth and mayprevent or at least limit the damage resulting from. cave-,ins.
..
Many experienced well diggers will simply dig as far asthey can until either .1) walls show signs' of loosening-andpossible cave-intor 2) they reach the water table. Thisis, however, not recommended for beginning well diggerswho have little or no experience estimating the strength ofvarious ground formations.
NOTE: In some locales:where the soil is fi'm all the waydown to the water table, entire wells have been dug beforeany lining was constructed. Where necessary and whereground conditions permit, wells can still be dug that way.
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C. Dig-a-Meter, Pour-a-Meter
One meter is the height of the circular forms,sometimes called molds, which will be placed in the welland around which concrete will be poured. Circular liningforms do not have to be one meter high and where they arenot the general procedure for this digging/lining methodcan s.ill be followed. Another name for this method couldbe one mold height and then line one mold height.
Outliner of Work
1. Dig the hole to the specified. depth.
- Check the diameter and plumb. (See pp. 59-62.)
2. Assemble the re-rod cage in place.(See Fig. 8-1.)
25 to 30 cm of each vertical re-rod should ex-tend into the soil below the bottom of thispour.
- Evenly spas.-1 the horizontal .re -rods along theheight of the pour and tie them to the verticals.
a. The hole has been dug to therequired depth and rerod verticalsstuck into the ground. The rerodhorizontals are then tied to theverticals.
FIG.8-1. REINFORCED CONCRETE.&ALT l#1 PI..ACS
o
.\b.I The inside fining mold has'been centered and leveled. Con-crete can now be poured around'the.rerod between the liningmold and the side of the hole.Also see Fig. 8-3.
3. Lower and assemble the mold.
- Wvel and center the mold. This is very importantfor the first section.
4. Pour concrete behind the mold (see Fig. 8-1b) andon all sides of mold to evenly distribute andnot displace the mold. Gently tap around moldwith a hammer to settle the concrete and preventhoneycombing.
5. Leave the mold of first pour in place.
- Dig beneath it to a depth of a mold plus 10 cm(8-15cm) (If 1 m mold, dig 1.1 m; if 1/2 m mold,dig 60cm)
- Check diameter and plumb.
6. Assemble the re-rod ir place.
- Tie the top of the vertical piece to the bottomsof the pieces extending out below the previouspour.
7. Lower and assemble the mold (another one, or thedrop mold used in the first section)
- Level and center the mold.
Therk will be a 10 cm gap between the top of themold and the bottom of the previous pour throughwhich !-o pour the concrete.
8. Mix a. i pour the concrete behind the mold.
9. continue as in second meter.
After the mold is placed for the third pour, plas-ter the joint between the first and second pourswith mortar for a smooth continued surface.
A more specific 'work plan for each of thesesteps is given in the next section.
91.
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Dig-a-Meter, Pour-a-Meter: Work Plan
1. Dig hole to desired depth
- Check diameter and plumb. (See pp. 59-62.)
- Determine depth of hole, as follows.
When you dig the'hole for the first one metersection to be poured, the actual depth of the holewill depend on 1) how much of a headwall you wishto include as part of the first-pour, and 2) howyou can best leave 25 cm to 30 cm of each verticalre-rod beneath the pour in such a way that theywill not be embedded in the concretb. This willlater be connected to the next lower pour.
Here are various headwall options for your consisleration:
- No headwall
The depth of the hope is the height of the moldso that the pour will be flush with the groundsu-face. (See Fig. 8 -2)
(3- 2. NO N E.AD WA
- 10cm headwall
The depth will be 10cm less than the height ofthe mold.
501t headwall
You will need an optional 50cm exterior headwallmold. The depth will be 50cm less than the height,f the mold. For a 50cm headwall the mold should
lm high. Assemble the normal ltt re-rod cage in
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place. The cage will extend almost 50cm aboveground. Place, level and center the interior andexterior molds., The tops of both molds should beapproximately even with the top of the re-rodslightly (3cm) 'below that. The width of the head-wall is determined in the same way as the hole dia-meter.
2. Assemble re-rod cage in place.
The total height of the vertical re-rods should be(mold height) + 20(re-rod diameter)+ 10cm (forspace to pour concrete between pours) + 10cm (forone 5 cm hook on each end of the rod).
For example: When using a one meter mold and 8mmre-Tod verticals will be 1 meter (mold height) plus0.16m (20x8mm re-rod diameter) also .10m (forconcrete pouring gap) plus .10m (2-5cm hooks).The verticals will be 1.36 meters long.
- Normally use about 15 vertical pieces although.youmay need up.to 30 pieces in very loose unstablesoil.
- Bend over a 5cm hook on one end of each verticalre-rod.
- Space re-rods evenly around the hole. 'ush theunbent end of each re-rod about 30cm into theground or-until the top of the hooked end is about3cm below the top of this poured section of lining.
-'These re-rods should'all be pushed into the groundwhere. hey will be approximately in the middle ofthe lining thickness. (See Fig. 8-3)
*An C AL R.E RODLINING MOLD
1 OgADwALL 11 Ei 6H T
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,
17
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81
HORIZONTAL RE-Robe
FIG e - 3. PLAcem Ekir of t>Mt> F000-4 IN Ho e-
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- If tne ground is too hard to push SWre-rodstraight dowA, then dig down far enough to providespace for the bottom ends and fill the hole backin to.the desired depth. However, this may wastetime,and effort that could be used more economicallyby digging the hole deeper before you line it..(See an alternative sinking technique on p.
-`03u will normally need 3horizontil reinforcingrods per meter, althodgh in loose soil 4 horizontalre-rods are better. These will be circles of re-rod with a diameter slightly less than the hole,they are usually placed on the outside of the ver-ticals.
- To compute the length of re-rod which will need tobe bent into the proper size circle for use as ahorizontal reinforcing rod, used the followingformula. The complete lengths of the re-rod willbe the distance around the circle at the pointwhere the re-rod will be placed, plus the lengthof the re-rod overlap, plus the length of the hookon each end of the re-rod.
E( hole diameter)-(lining thickness)] x 3.1416 +20(re-rod diameter) + 2(5cm end hooks = length ofhorizontal. re -rod
Example: For a well with a hole Jiameter of 1.5meters with a lining thickness of 7.5cm (.075m)usiug 6mm (.006m) re-rod, the computation wouldlook like tzis.
i(1.5) - (.075)] x 3.1416 + 20 (.006) 2 (.05)11.425] x 3.1416 +0.12 + 0.10
4.48 + 0.12 +'0.10 = 4.7 meters.
Vorizontals should be evenly spaced in each r_ter;fur example, if there are three horizontals. oneis placed in the middle of each meter;the othertwo are placed 37cm away on either side. (SeeFig. 8-3) Be sure to include the 10cm or 15cm gapbetween successive poured sections if appficablein the computation of the length over which thehorizontal re-rods should be evenly-spaced. Tieall intersections of horizontal and verticals;make sure the re-rod is no closer than 3cm to thehole wall. Put pieces of stone or dried concretebetween the re-rod and the hole wall where it isnecessary to ensure spacing.
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NOTE: Instead of using a certain number of horizontalpieces, you can also use a continuous spiral re-rodwhich circles the hole 3 or 4 times per meter dependingon how strong the lining musebe. .
3. Lower and assemble the mold.
- Lower the mold sections into the welland assemblethem in place.
- It is also possible to assemble the mold above theground and lower it into place.
- Center the mold in the hole making sure that itis level and that the distance between the moldand the hole wall is the same all the way aroundthe hole. (See Fig. 8-4.)
./' , ."'J
FIG. 8- Ll. MOLD LEVE LEP AND CENTE-RF-17
- It is very important that the mold be correctlycentered and leveled for this first section be-cause all of the other pours must line up and beattached to it. If the first poured section is notaligned properly all subsequent sections, if fol-lowed from the first one, could mgnify that errorand cause the well shaft to curve or angle out ofplumb as it is sunk.
- Especially with the first meter it is often a goodidea to check the level and centering again,.just-before the concrete is poured, tc make sure that ithas not been disturbed.
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4. Pour concrete behind mold.
- Concrete is mixed on the surface (See CementAppendix, p. 221.) and lowered in buckets down,to workers in the well who will pour the concretebehind the mold.
- When pouring concrete. behind the mold, do so fromalternating opposite sides of the mold. If youcontinually pour the concrete into one spot or un-knowingly concentrate on one side of the concrete,it will soon build up enough weight that it willmove the m-ad off center or out of line. Once thathappens it i,s virtually impossible to move the moldback its intended position. :See Fig. 8-5.)
Orlc the concrete is poured, gently tap around theinfF.de of the mold with a hammer. This slightlyvi*ates tne concrete so it settles into any voidsth,:t may have been left while pouring. After the.c ncrete has set in an hour or two, you car. begih....A-king on the second pour.
FiG.8-5. PourZING CONCRETE EVE/41-Y IN PLACA AROLNICA /4401-0
5. hole Deneath the first poured section
Thu depth of this dig £hould be the mold heialtplus 10 cm for a gap between the bottom of thefirst poured section and the top of the second'pourthroujh which ot. will pour concrete. (See Fi9, 8-6.1
to -m, keciziu"11
. ,
F16. 45-6p. PROPgR NoLE 10 cmDEPTH 5ENEATH AN yA LRE-Apy roome CoLIN IP-iG ZEC.T K"./.4
6. Assemble reinforcing rod in place
- Bend a 5 cm hook on the bottom ends of the re-rodextending down from the previously poured section.
- Place the horizontal pieces in the well; pull thehorizontal pieces up into place and tie all inter-sections with horizontals.
- Assemble the same number of vertical pieces as inthe first pour.
- Bend a 5 cm hook on one end; stick the unhooked endinto the ground 25-31) cm directly beneath the ver-ticals of the previously poured section and insidethe horizontals lying on the ground.
- Connect the verticals to the previous verticalswith sufficient overlap, twenty times the diameterof the re-rod, and a 5 cm hook at either end of theoverlap.
- Place the horizontals as in the first pour. Makesure the re-rod is no closer than 3 cm to the holewall.
7. Lower mold into place
- If you have only one mold, remove and lower it fromthe previously poured section.
- This way it is possible to dig and line about 1meter each day in soil that is easily dug. A singlemold should be cleaned and oiled at least once every3 meters.
- During the one day that each poured concrete sectionsits while the following section is dug, it will zetsufficiently to enable the mold to be carefully re-
,
moved. (See Cement Appendix, p. 221.)
- If you have more than one mold you may leave themin place until needed for constructing subsequentsections.
- Center and leii61
8. Mix and pour Tpncrete behind mold
Don't forget to alternate sides for pouringeach successive bucket to allow the concrete tosettle evenly.
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1.
9. Successive 'pours
- Continue as in second pour;
- Fill gaps between pours with mortar when the moldshave been removed from both sections.
D. Dig and- Line -in- Short - Sections
This lining method involves-digging the hole to someconvenient depth and then lining it. Once the lining forthat section is complete and is anchored in place,. con-tinue digging the hole beneath the already lined sections.These sections are dug and lined until the water table isreached. The depth of each section can be whatever youfeel comfortable with both from the point of view of safe-ty and work convenience.
1. Dig hole to certain depth
Dig a hole until you reach a depth Where youfeel it might be unsafe to continue, or until you havesunk the hole a maximum of 5 meters. Depending onwhether you want a headwall and, if so, on the heightyou want it to be, you may want to slightly change thehole depth so that the top of the mold will be at the'desired top of the headwall after a number of pouredlining sections are completed.
2. Assemble -te-rod cage in placeA
- Where possible, use single long pieces of re-rod forverticals. These can be anchored to the hole wallwith short pieces of re-rod bent into hooks andpounded into the hole wall around the verticals.
- Put horizontals in place, beginning at the bottom andworking up.
- Tie each horizontal in place temporarily with enoughties to hold it in place. This allows for any ad-justments that might be necessary later.
- Before the mold is put in place for each pour, secure-ly tie all of the intersections of horizontals_ andverticals.
3. Lower and assemble mold
- LeVel and center the mold in the bottom of the hole.
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4. Pour concrete behind mold
- Leave the top surface rough for a good bond to thenext pour.
5. Lower and assemble another mold
- Set it directly on top of previous mold;
- Pour concrete behind mold;
- Repeat this step until you reach the ground surfaceor bottom of the previous set of pours.
6. Repeat steps 1 through 5
- Repeat, these steps until water is reached. The bot-tom of the lining should be constructed with a curbjust above the water table.
NOTE: If you are digging and lining beneath a previouslift be careful to leave enough room between the top ofthis lift'and the bottom of the previous lift throughwhich you can pour concrete (See Fig. 8-6.)
E. Dig-down-to-Water-Table-and-Line
This method is recommended only where the water tableis within a few meters of the earth's surface and theground is firm. It is included here to demonstrate thatthe same operations must always be performed although, de-pending on tne depth, they may be donein a slightly dif-ferent crier:
O
I. The hole is dug down to just slightly above thewater table.
Dig out a curb at the bottom of the hole.
3. Assemble the re-rod in plade.
4. Set the form in place. Remember to carefullycenter and level the form.
5. Mix and pour the concrete into the form.
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6. Continue lowering molds on top of previous moldsand pouring concrete behind them until you reachthe ground surface.
99
Pre-cast reinforced concrete rings are often used toline wells. They are poured and cured above ground to belowered into the well later. There are two basic methodsfor installing rings:
lowering and stacking them in an already dug well:(See Fig. 8-7.)
setting them in position at the ground surfaceand sinking them into place. (See Fig. 8-10.)
P
Rings should be made so that they:
can be easily,stacked or attached one on top ofanother;
can form a watertight joint where they meet;
are strong enough to support weight of a longcolumn ofarings;
will not rot, corrode, rust or otherwise loseany of the above qualities;
a.
will not react with water to make the water lessdesirable for consumption.
This method is more useful in a large project whererings can be centrally manufactured and then transportedto the well site for use.
Making your own rings will require the use of inner,outer, top and bottom forms. The inner, outer and topforms can be carefully removed after the concrete has.just started to set, usually in an hour or two, making itpossible to make several rings each day if enough bottomforms are available. Where a number of forms are avail -able, it is better to leave them in place to allow theconcrete to cure better.
You can,l) make yourown reinforced concrete ringsor 2) sometime's obtain them on the local market as cul-vert pipe or a similar item. /BUth are suitable,.
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Determining how two ringsfit together is a majorconcern when lining a well with concrete rings. Fre-quently flat edges have simply been mortared and stackedon. flat edges. (See Fig. 8-8a.) This provides Ihrylittle resistance if an unequal sideways force is exerted.A tapered or flared fit is better. (See^ Fig. 8-8b and c.)These will resist sideways forces better and should bearranged so that water flowing down the otitside of thelining will tend to flow away from and not into the well.Where possible,'the two ringeshould be firmly attachedtogether. This is most often done with nuts and boltsthrough steel fittings cast into the rings. This type ofconnection is especially useful when the lining will besunk into place but may not be necessary when stackingrings in an already open hole.
FIG. 8- a. CoNCizare LINING RING Jouwrs
a..
As with most other concrebacasting-iechniques, theconcrete in the rings can either be made watertight orporous. Porous concrete rings can be especially usefulwhen sinking the lining into the bottom section of thewell.
1. Stackel in open hole: Work Plan
- Dig curb slightly above water level;
- Reinforce the curb and pour it around a form in sucha_way fhatd_liningringwill sit on top of it. (SeeFig. 8-9.)
Lower ring into place on top of curb.2.
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- The major problem with lining a well this way is thatthere is vary little adhesion between the lining andsurrounding soil.
3. Continue lowering rings and filling in around themuntil you reach the grdund surface.
NOTE: It may be useful to install curbs or some othertype of anchoring to help hold the column in place.
F16. 0-9. LIMING 1Qµ64 LoweIZED. ;OW rk..ACe. ON ANCHORING CURES
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2. Sunk from ground surface: Work Plan
This involves stacking rings as necessary on acutting ring while the whole column is sunk by diggingout soil from inside and underneath the bottom ofthe column. Because of its complete protection fromcaving this method is used in very loRse soils thatwould be difficult to keep the column going out ofplumb, especially in loose soils. The problem is com-.pounded by the fact that once the'column begins sink-
. inn askew it is very difficult and sometimes impossibleto get it straight again.
A cutting ring-is a :special ring that providesa cutting edge to help sink the column and also helpsto funnel soil directly. underneath it into the middleof the hole for removal. (See Fig. 8-10a.)
1. Set 1 or 2 lining rings on top of the cutting ring.The more rings you can stack, the more weight thecolumn will have and the easier it will be to sink.However, the rings are .very heavy and it willusually be verydifficult to lift the rings anyhighet than 1 meter with locally made equipment.
2. Workers will stand inside the ring and dig to re-move soil and permit column to sink. (SeeFig.. 8-10b.)
3. Digging should be done especially carefully to tryto remove soil evenly from around the bottom ofthe hole so that the column will sink plumb.
4. Add more rings when the existing column sinks downto where another ring can easily be added (usuallyabout ground level or just above). (SeeFig. 8-10c.)
5. Continue sinking the column and adding rings asfar as possible into the water table. (SeeChapter 9, p. 99.)
_NOTE.: __Because of the strong possibility_ofaskew and the uneven forces that will often have to beapplied to the column in order to get it straight again,it is a good idea to have the rings firmly attached toone another.
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* Often in looie soil, mostly sands, the rings sinkaskew, which causes problems, especially when the thicknessof the loose layeeis about 4 m or more. In less thicklayers (about 2 m) the best way to sink the column-rela-tively plumb is to continue'digging as-fast as possibleuntil firmer layers are struck. Even if the rings areastanding askew, they maybe put in an upright positionagain as follows.
If the rings are.askew, asin Fig. 8-11a., work inside thecolumn of rings to remove thesoil from beneath the lowestedge of.the bottom ring asshown. The hole you dig should ^extend underneath and beyondthe outside edge of the ring.When this is completed, care-fully dig the soil away frombeneath the opposite side ofthe column but, on this sidetry not to dig any further outbeneath the ring than absolutelynecessary. (See Fig. 8-11b.)As the column sinks from thispoint, it should graduallyease over toward the side thatwas first dug out. (SeePig. 8-11c.)
FIG. 13 -Is. STRAge+ITEits NGA COLUMN HASBEEN Su Not OUT OFPLUME>
pi& HEIM
G. Mortar (Elaster)
1. Cast in place.
Reinforced mortar is used much like reinfordedconcrete. The major advantage of this method is tlatno forms are required because the mntar is thrownonto the wall in place.
This variation evolved in Senegal. It wasdifficult to transport heavy steel molds to the wellsites, so the masons miuld "throw" the concrete ontothe walls. But concrete is not'very workable son themasons began leaving out the gravel and using justmortar.
Walls are normally plastered meter-by-meter asthe well is dug. This 'is a variation 'of the "dig-a-meter-pour-a-meter" method used with reinforced con-crete.
This process is as follows:
1. Dig the hole about 1.1 m deep.
2. Check the hole diameter and plumb.
3. Cut and shape as much re-rod as possiblebeforehand because the next steps must bedone quiCkly.
4. Splash the mixture (1:4, cement: water)on all surfaces to be plastered. If thesurface dries too quickly, wet it again im-mediately. before plastering.
5. Apply a 3cm thick layer of mortar with atrowel.
6'. Place the re-rod.
7. Apply second 3cm coat of mortar while the'/ first is still wet.
8. A third, thinner layer may be applied toMake the walls as smooth as possib.J.e.
.107
95
96
2. Pre-Cast
Mortar can also be used to pre-cast rings evenwhere forms are not available.
1. Dig a round hole with the desired outside diameterof the ring. (See Fit?. 8-12a.)
- The hole's depth will determine the height of thering.
2. The hole is then plastered and reinforced just asit would be in the well. (See Fig. 8-12b and c.)
3. After ..t has cured for several days it can ibe dugup and later installed in the well. (SeeFig.. 8-12d.)
This type of ring' should be allowed to harden forat least one week before it is placed in the well.
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H. Mortared brick or stone (masonry)
Rock has been used toconstruct linings in wells forcenturies. Construction of awell using rock usually involvesdigging the hole as far as -,
possible into the water tablebefore the lining is built.Once the foundation underwater is established, the wallsare usually built up in adouble layer about 50 cm. thick.Rock walls are very weak intension so they can be easilycrackedif any uneven stressesare put on them.
.
This type of well can pro-, vide acceptable quality well
water if precautions are takento prevent contamination fromsurface water seepage throughthe lining. 'A 5 cm. thick layerof concrete-or mortar around the
97
V
top 3 m. of the rifling can pre- Fle.8-15. ROCK LINEpteaLL-Sns.Vent the seepage of contaminated °F eol`lcRara Ow MeMrAPP.. sEA1-, te 'n, Peavet.43- CONTA th.t IS_AT1014surface watei back into the well. _ _
In fact, the surface waterseepage may eventually reach thewater table and find its wayback, into the well", but ifthis seepage has been filteredthrough at least 3 m of soil,the potehtially harmful con-taminants will have beenremoved. (See Fig. 8-13.)
Brick or stone masonrycan be used in most of thedifferent digging and liningmethods but, because of itstendency to crack understress, it is not normallyused except to build thelining from the bottom ofthe well-tp, in one continuousoperation.
A brick or rock wall canbe built up on a cutting ringand sunk into the ground (See.Fig. 8-14.) but any caving
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98
around the outside couldcrack or topple the wall.If such a column were to sinkaskew it could be very dif=ficult to get it upright againwithout exerting some kind ofsideways force on the columnwhich could crack or destroythe column.
It is possible to usereinforcing rod to help holda brick lining together. Thisis sometimes used in sinkingthe bottom section of a well.It is not normally used.forconstruction of the middlesection because in most casesa reinforced concrete or mor-tar wall could also be builtwith the same materials, andprovide a stronger lining.(See Fig. 8-15.)
It 'is also possible to usemasonry to line the wall insections. When a lining isneeded after having dug-downa number of meters, a curbcan be installed and thelining built up on the curb.
_The curb serves as a base onwhich the lining can be builtup and as a solid anchoringpiece which can be supportedto allow digging to continuebeneath and through it. Asa safety precaution, the curbshould be supported by longpieces of wood, or whateverelse is available, which canbe wedged between the bottomof the hole and the curb.(See Fig. 8-16.)
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Chapter 9
CONSTRUCTION OF THE BOTTOM SECTION
A. Introduction
This chapter provides detailed information to assistwells workers to construct the bottom section of the well.Describing the unique features of that section, it alsoraises such special concerns as'the choice of sinking/lining methods, selection of materials, keeping water outof the well to allow diggers to dig deeper, and facilita-ting water entry. V
The bottom section is that portion of a well belowthe water table. Its purpose is to allow as much water aspossible to enter the well while blocking fine soil parti-cles from the surrounding aquifer. This is accomplishedby digging a hole and extending an appropriate lining asfar beneath the water table into the aquifer as possible.
As the bottom section is being sunk, using what-ever method, water will have to be removed to allowcontinued sinking. This can be done by simply fillingthe buckets normally used to remove excavated materialand emptying them at the ground surface, or by using apump. Pumps fare generally easier to use because theyallow water to be removed from the well faster; awell can be dug deeper than if buckets were used. Thiswill be especially important if the bottom section isbeing constructed when the water table is above itslowest level and the well is being finished at any othertime than the end of the dry season. (See Fig. 9-1.)
The construction of the bottom section consists ofthe same two operations digging and liningoas the middlesection. However, because water is entering the wellwhile the digging is proceeding and the lining is beinginstalled, the whole process becomes more complicated.
These two situations will limit your ability to dig deeper:
water flowing into the well
As you begin to get int, the water layer therewill probably be little water entering the well.As you go further down, water will enter the well
111
100
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faster until 1) it is coming in so fast that you canno longer remove enough of it to be able to continuedigging or 2) you reach the bottom of the waterbearing layer. If you reach the bottom of the waterbearing layer you will have to evaluate whether thesupply of water is sufficient for the needs of thelocal'users. Again there are two possibilities: a) thewater flows very slowlypor b) this is an isolatedsmall pocket of water that is limited and willbe quickly used up.
112
In a), the well will always have water in it butthere may be very little and people's water consumptionmay be limited. It might be possible to dig other wellswhich could each supply a limited amount of water butwhich combined with the rest would allow for an increasein water consumption.
In b), the decision will have to be made whetherto try to continue sinking this well or start anotherwell in a different location.
walls collapsing as you dig
This is likely to be aproblem in all wells, butit will be much more seriousin wells which reach aqui-fers composed of loose,usually sandy soil. Thedeeper the hole is sunkinto the aquifer, themore serious the problemwill become. The collaps-ing of the walls is causedmainly by the flow ofwater coming into thewell. The water, as it
exerts pressUre on theaquifer particles aroundwhich it must pass. Thefaster the water entersthe well, the more pres-sure it exerts and there-fore the more likely thewalls are to collapse.By sinking the bottomsection lining ring intoplace, the possible hin-drance and danger ofcollapsing hole wallscan be prevented. (SeeFig. 9-2.)
101.
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113
3.02
B. Sinking/Lining Methods
1. Sink Lining
To sink the lining into the bottom section the ringsmust be made just small enough to fit inside the middlesection lining. When using reinforced concrete a differ-ent set of forms from those used for the middle sectionlining will be needed. A well can probably be sunk alittle deeper using this method rather than othersobe-cause it allows workers to spend all their time removingsoil and water from the bottom of the hole, thus deepeningit.
2. Dig-to-Bottom-and-Line
This method is limited to sites where ground condi-tions permit digging below the water tabl.e. This can onlybe done where aquifers are made up of relatively consoli-dated material and is not recommended where the aquiferconsists of loose materials that tend to'cave-in.
NOTE: Wells have been sunk into loose, Unconsolidatedaquifers byusing temporary lining to reinforce the wallsand prevent cave -ins: -In-most cases -todayotime-and moneythat-would_before have been spent on temporary lining cannow be more usefully and saieiy-elpitiorking-with-perma---nent cement linings installed as the hole is dug eitherby sinking the lining or digging and lining in shortsections.
3. Dig-and-Line-Short-Sections
It may be possible in slightly caving formations todig and line several short 1/2 m sections before reachinga point where water enters the hole fast enough to slowlyerode the eaith-walls or wash away wet concrete or mortarfrom inside a form. At this point the lining can no longerbe built in complete rings but will have to be continuedby completing each 1/2 meter ring in several sections oneat a time. The use of quick drying Cement will signifi-cantly aid this work.
114-
3.03
Some have used this technique because it requireiless preparation than sinking a lining which requirespre-casting lining rings. it requires less equipment andmay produce a structurally superior well although thestructural continuity achieved here may not be of sig-nifies advantage in the overall functioning of a well.On the other hand, for shallow wells that reach a limitedsupply of water, expenditure in time and money on a moreelaborate well structure probably will not be worth-while. Also, the actual work required is somewhat com-plicated, requiring well diggers to perform varioustasks simultaneously and with great competence.
C. Water- Entry
The bottom section should be constructed so that thewater comes in through the bottom, and perhaps lining,depending on the bottom lining procedure and the groundconditions. (See Fig. 9-3.)
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FIG.9-3. WATE-12. emrRy INTO Tervom Stc.TION
Lining Procedure:
sink lining._ bottom, and perhaps liningdig-to-bottom-and-line -bottom, and perhaps lining
-dig- and -Line- short - sections - .bottom
Water entry through:
It is best to construct the bottom section so thatwater will come through the lining as well as the bottom.The more area you have open for water to enter the fasterthe well will recharge and the less strain there will beon those areas where water comes through. However, animpermeable lining is recommended where the aquifer islikely to be very fine sand that will clog or comethrough even porous concrete. 115
104
1. Water Entry through Lining
There are two methodsused predominantly for con-structing lining sections that will permit water to flowthrough. In both cases it is better to construct thelining sections on the surface where their constructioncan be more easily controlled before they are sunk intothe bottom.
a.Leave holes in lining sections
1) Concrete
Forms should have holes through which you can-
stick re-rod to make the holes in the concrete.
holes should be sloped up and to the middleto prevent aquifer particles from entering thewell. The holes could be perfectly horizontalwhere aquifer particles are larger than theholes.
Holes can also be poked in the bottom of thewell, although this has xarely been attempted.
2) Brick or Rock
Dig to the bottom of the well and stack unmottaredbrick or rock. The open spaces between the stacked brickor rock allow water to enter.
Many successful wells have traditionally been builtthis way but it can be difficult to do, is sometimesdangerous, and cannot usually penetrate an aquifer as faras other lining methods.
b. Use porous concrete (cement and giavel withlittle or no sand)
Use porous concrete to make lining rings.Simply substitute porous concrete for regularconcrete when casting lining sections. Somehave suggested using regular concrete for 10 cmof top and bottom edges to strengthen these.Porous concrete is not as strong as regular.
Use porous concrete to make blocks which canbe set on a cutting ring and sunk or built upfrom the bottom.
116
2. Water Entry through the Bottom
105
The bottom of the well should normally permitwater to come up through it. However, in unconsolidated(loose) aquifers the water will tend to carry particlesof the aquifer along with it up into the well to com-pletely fill and clog it.
Where the well is sunk into a relatively conso-lidated (firm) aquifer, water coming in through the bot-tom tends to act similarly but the aquifer particles areusually too big.and heavy to be moved by water. In bothcases it is advisable to put a filter or plug across thebottom of the hole.
When the aquifer is composed of very'fine sand,this sand tends ,to act as a liquid and follow the waterup through the bottom filter. The filter, if properlyconstructed, will prevent the sand from doing this butmust, at the same .time, be able to withstand the pres-sure of the sand and water. Rather than coming upthrough the filter the sand and water can possibl,y exertsufficient pressure to push.the whole filter layer up in-to the well and clog it. This is admittedly an ex-treme case but one that must be carefully guarded against.
D. Construction of the Boti.om Sectionob
1., Sink Lining Method
a. Lining Rings:
are manufactured on the ground surface forlater sinking into the the bottom section of thewell;
should allow for water to enter the well, asdiscussed previously;
should have the capacity to be firmly attachedtogether;
should have an outside diameter 10cm less thanthe inside diameter of the lined middle sectionof the well;
can be very heavy and awkward to move and soNNmay require a special lowering device;Nmare most commonly made of reinforced concrete
or mortar which should be cured at least 3 days
117
106
after pouring before being lowered into the well(see Cement Appendix, p. 221.)
are usually set on a cutting ring which canalso be poured at the ground surface although itwill require a different form.
NOTE: A cutting ring may not be a necessity in loosesandy aquifers but is useful. The cutting edge couldalso be cast on to the bottom lining ring. A flat edgewill tend to be caught more easily, preventing furthersinking/as opposed to a cutting edge which will tend tocut through loose material and funnel it toward the cen-ter for easier removal from the well.(See Fig. 9-4.)
FIG. 9 - 4.
CUTTING RtmCa
b. Construction Procedure
1) The general construction procedure to be followedwhen all materials are assembled and ready for use is asfollows.
stack several (usually 2 to 4) lining rings on ,top of a cutting ring which has been centered andlevelled in the bottom of the hole.
This initial column should be 2 to 3 metershigh whether it is composed of 1/2 meter highrings or 1 meter high rings. If holes have beenmade in the rings to allow water entry, make surethat the holes slant up toward the middle of thehole. Firmly attach rings together by whatevermeans you have chosen.
118
Unstable ground can make the initial leveling/plumbing of rings very difficult. Where you cananticipate this, place a layer of gravel on thebottom before lowering the cutting ring into thehole. .
after the liningrings have been stacked onthe cutting ring in the hole,well diggers will fill in thespace between the liningand the middle section liningwith gravel. (See Fig. 9-5.)Instead, some have placedseveral boards vertically inthat space to act as a guideto help the column sinkstraight. (See Fig. 9-6.)Gravel is easier and betterto use because it will tendto fill in around the ringsas they are sunk, filling upany voids that might becreated by over-pumping.Gravel-is also -a convenientfiller that is normally usedto fill that space once thebottom section is sunk.
FIG.41 -ea.130Aaos vseD10 6u.DESiNicio6 R11.165
FIG. 9.5. GRAVEL,USED "Ttr3 6u10a.SOW KING 'Fa p...16S
119
107
108
Remove soil,and water from inside the cuttingring thus causing the column to sink. Begindigging in the middle and gradually'work out tothe edges of the column being careful to removesoil evenly so as not to encourage the column tosink out of alignment with the rest of:the hole.(See Pig. 9-7.)
Add more rings as necessary as the 'columnsinks. It is always necessary to have some over-lap of the sinking column and the middle section,and helpful to have up to 2 meters of overlap toprovide extra weight which will aid sinking andhelp to guide the column down.
Plan to add more rings when it won't interruptthe sinking process. If it requires many peopleto lower the rings, lower as many as you need inone or two sessions to avoid the need to regather
- and reinstruct a large group of people.
Continue digging and sinking until water canno longer be removed from the hole fast-enoughto allow further sinking. This will occur whenwell workers are digging in as such as 1 meter ofwater. Remember,the farther this'column is sunkinto the water bearing layer without going be-yond it, the more water will be available fromthat well. In commonly-found loose sand aquifers,the column of rings is usually sunk between 2 and4 meters beneath the bottom of the middlaksectionlining. In more consolidated aquifers, where watergenerally enters the well more slowly, a greaterdepthcan and should be reached.
When sinking is stoppel it is necessary tohave some overlap between the respective liningsof the middle and bottom sections.. If the wellhas been completed in other than the end of thedry season, it may be useful to leave several ex-tra ring sections stacked up into the middlesection lining. If necessary, the well can thenbe easily deepened at the end of the dry seasonwhen the water table°is at its lowest level.This will help to provide a permanent supply ofwater.
120
4
FIG. c) 7
Digging stees,while sinking lining
a. Dig a cone-shaped hole downto a convenient depth.
b. At four evenly spaced pointsin this cone - shaped hole,widen the hole so that itreaches the width of thecutting ring.
c. Widen the hole at fourmore places between theareas already widened.
d. Continue enlarging andwidening the hole untilthe column of rings sinks.
121
gmb
109
110
2. Dig-to-Bottom-and-Line
It is likely that this method will only be consideredwhen:
The middle section of the well has been dugbut not lined because there is little danger ofsoil collapse. (A temporary lining could be usedtoTeinforce,the section or help prevent caving.).
The water bearing soil is firm enough to per-mit digging and removing water without greatdanger of collapse.
Under these conditionsan °per. -hole can be "dug downinto the aquifer.' Even so,digging beneath the watertable mustbe done verycarefully and can only reacha limited depth because'bfthe increased danger ofcave-ins and collapse as thehole reaches deeper and,deeper into the aquifer.The hole should be dug asdeep as.is safely possible.
In the traditional wellthe lining is begun bystacking rounded stones to aheight of between .5 and lm.(See Fig.9-8.) A rock orbrick masonry wall is thenbuilt on top of the loose rockwall. Alternately, pre-castrings can be'lowered inplace or the linihg couldpossibly be poured in place.If, however, one has theequipment and supplies tocast concrete walls, it isusually possible to sink thelining into-place. This ismuch safer_and can reach agreater depth where there isai.y danger of cave-ins.Whctever lining method isuse.i is then continued up_to the ground surface andthe section of the wellconstructed.
122
FIG . 9- 8. 77:riiirso Tso tit A1.-WE I- 150:51-1-00.
111
3. Df.g- and - Line -Short Sections
This particular method of digging into the watertable is a variation of the "dig -a- meter, pour-a-meter"method sometimes used to line the middle section. Thebottom section is dug"and lined, ustally 1/2 meter at atime. As the aquifer is penetrated increasing amountsof water will enter the well as the depth increases.Eventually-a depth will be reached where.the water iscoming into the well so fast that 1) it will wash awaythe mortar or concrete before it has a chance to set, or2) it will wash the walls in before there is time to seta form, re-rod, and pour. From this point, use the fol-lowing procedure to extend the well as far into the aqui-fer as possible.
Make sure that the vertical re-rods extend beneaththe bottom of the last pour so that the subsequentsections can be attached to the existing lining.
Dig in tha center of the hole to form an invertedcone which is about 40 cm deep andsloped,out to thebottom of the previous plastered section. (SeeFig. 9-9a.) This tapered hole keeps'sand fromwashing out from behind the sections already lined.
Quickly dig a short section on one side down toabout 30 cm. (See Fig. 9-9b.)
Roughly plumb and smooth the newly dug short section.
Throw handfuls of dry quick-setting cement mixonto the moist slowly collapsing sand.
Moisten small quantities of the mix and quicklyplaster the short section. The mortar should set(ir about 5 minutes) before the water flow causesit to collapse. (See Fig. 9-9c.)
Continue digging and plastering short sections30 cm deep around the hole until one complete 30 cmdeep section is plastered. (See Fig. 9-9d.)
Place re-rod; leave extensions below plasterlimit for connection to next pour.
NOTE: A quick-setting mortar mix consists of 1 part quick-setting cement, 2 parts ordinary cement, and 1 part sand.
Plaster over re -rod with same quick-setting mix.
Continue digging and plastering short sections
123
112
F16 9.Ole Al4DCarrom sEcnoks
a. Dig a 40 cm deepinverted cone-shapedhole.
c. Immediately cover the30 cm deep section witha layer of mortar.
b. On one side, quickly digand plumb a 30 cm deepsection.
d. Continue mortaring shortsections until the holeis lined all the wayaround, then attach re-rod and put another lhyerof mortar over the re-rod.
124
until 1) the water flowing into the well preventsfurther plastering. or 2) you have reached the deiireddepth into the water table. Do not leave any re-rodexposed to water. If necessary bend it up and plas-ter, ^r cut it off and plaster.
NOTE: Special bricks may be made for covering placeswhere water is coming through the sand too quickly to per-mit plastering. These bricks are made outside the well byspreading a 1 1/2 cm. layer of mortar on a .flat surface,and then cUtting it into 15 cm.x 15 cm. squares with theedge of trowel before the mortar dries. Whenever a spotis found where the water flow is so rapid that it erodeseven the rapid setting mix, one of these square mortarbricks can be used as a stopper. Throw dry cement mixfreely on the place where the water is entefng and slapa flat brick over it. Hold the brick in place until thecement sets. It can then be plastered over An the samemanner as the rest of the short section being lined.
E. Bottom Plug or Filter
Most hand dug wells need a filter over the bottomof the well that will allow only water and no fine parti-cles of soil to enter the well. It is especially criti-cal where the aquifer is very fine. sand. Only wherewells are sunk into hard rock is this not a consideration.
There are two different materials that can be usedseparately or together: a gravel filter or a porous con-crete plug.
1. Gravel Filter.
A layer of gravel across the bottom of the well canserve as the filter.
A minimum depth of 20 cm is suggested. 'The filtercan be made more effective by using 2 or more differentsizes of gravel in separate layers with the smallest sizegravel on the bottom and the largest size gravel on top.
2. Concrete Plu2
a. This is a slab of porous concrete which fitsclosely to the inside diameter of the bottom lining. Theslab can be cast in sections on the surface and laterlowered and placed in the well. It is placed in the wellon top of a shallow (10 - 15 cm) layer of gravel.
The slab)should be made porous either by makingholes in a regular concrete slab or using a concrete
125
113
mixture with very little sand as described in the CementAppendix. It can easily be cast on the surface digging amold out of the ground.
b. Making a bottom plug with the ground as the form
Choose a fairly flat section of ground that canbe dug and will hold its shape.
Draw a circle with a diameter a few centimetersless than the inside diameter of the bottom section.
Dig out the circle to a depth of 6 cm and make thebottom surface fairly even and square with the sides.(See Fig. 9-10.)
Put a divider across the center of the circle sothat you will then pour two halves of the slab whichcan be more:easily lowered and placed. The dividershould be at least 6 cm high and be made from somesuitable form material. (Alternately where a divi-der is not available or appropriate, two circles canbe drawn but then only half of each dug out to formthe two halves of the slab.) (See Fig. 9-10.)
Place re-rod in each half of the form. Leavehandles or lowering hooks. When using 10 mm re-rodit can be placed 20 cm apart or with 8 mm re-rodleave 15 cm between re-rods.
Pour concrete either standard or porous mix.If using non-porous concrete, make holes through theslab with a piece of re-rod when the concrete beginsto set.
Cure for about a week.
place in well on 10 to 15 cm of gravel.
FIG. -la CAST IL143 11410, 5eTTIDM PI-Vey
a. Dig a 6 cm deep hole to the desired size.
b. Pour concrete in theform after the re-rodhas been placed.
--
c. After the concrete hasset and cured for aweek, it may be dug upand placed in the well.
115
c
) Section 3:
DRILLED WELLS
128
Chapter 10
INTRODUCTION TO DRILLED WELLS
A. Overview of Small Diameter Wells
1. Basic Features
117
Small diameter wells usually have diameters of lessthan 50 cm and can be as small as 2.5 cm. For the pur-poses of this manual, all wells. that are sunk by usingtools from the ground. surface, and therefore do not re-quire that people go down and work in the well to sinkthem, are small diameter wells. They are also called"drilled" wells, "tube" wells, or "boreholes."
Small diameter wells normally require a pump to sup-ply water on demand at the surface. These wells areusually small enough so that a bucket used to lift waterfrom a large diameter well will not Lit into the well. Aspecial water lifting device must then be built and in-stalled in the well to allow people to draw water.
There are many different kinds of water lifting de-vices that may be used, ranging fiom a modified bucketarrangement that will fit in the well to a motor-poweredturbine pump capable of delivering thousands of litersper minute.- This manual emphasizes pumps that will com-fortably supply enough water to meet the minimal needs'of the local population.
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118
Every small diameter well is sunk by using the samearrangement of equipment. At the ground surface is apower unit which supplies the necessary motion to sinkthe hole.
At the bottom of thehole is a cutting tool(drill bit) which, whenmovedin a certain way,loosens whatdver soil orrock is beneath it in thehole. (See Fig.10-14
Between the. powir unitand the bit is a connectingmechanism that transmits the,motion of the power unit tothe cutting tool.
ria. IQ- I. PeILL 6irs
131
.
2. Drilling Motions
Because of the size andshape of small diameter wellsand the equipment required tosink them, there are only twodifferent kinds of drillingmotion that are used (Fig. 10-2 ):
a. up and down - calledpercussion
b. around and around - calledrotary
FIG. io-Z. DRiLLINGNOrIONS
a. b.
All well sinking equipment isintended to use one of these twodifferent motions. However, allsuch equipment is designed to useone of the motions predominantly andoften the other motion in somesecondary capacity. Thus, tools thatuse an up-and-down motion are referredto as "percussion" tools because theyrely on their downward fall to stikeand loosen ground materials. Toolsthat must be'turned to gouge and scrapeground materials are referred to asrotary" tools for obvious reasons.
Both of the different types ofequipment can be adapted for use inmost ground conditions. However, whenusing simple hand powered variationsof either of these techniques there arecertain limitations which will benoted later.
3. Removal of Drill Cuttings from the Hole
In order for the\cutting tool or drill bit to
effectively do its job.of loosening the soil at thebottom of the hole, the soil and rock that it hasalready loosened or chipped away must be removed soas not to hinder the bit's continued operation.There are several different techniques and tools thatcan be used.
A special tool can be lowered into the well toremove the drill cuttings. For example, a bailer,which is essentially a hollow tube with a valve at
132A
119
120
the bottom end, can be lowered to the bottom ofthe hole and then dropped, topick up the drillcuttings. When the bailer is dropped onto apile of drill cuttings, the cuttings force thevalve open as the bailer falls down around thecuttings. When the bailer is lifted, the valvecloses, allowing the bailer with the cuttingsinside it to be lifted to the surface and emptied.(Fig. 10-3)
The cutting tool itself can be used to removedrill cuttings from the hole. For example,auger bits which are screwed into the groundremove soil by either accumulating the loosenedsoil inside the bit (see Fig. 10-4a) which willhave to be emptied regularly, or by forcing thesoil upwards as the bit is rotated. (See Fig.10-4b.)
A fluid can be used to continually pick updrill cuttings and carry them to the surface.Fluid is normally pumped down through the drillrod and out of holes in the bit where it picksup drill cuttings and carries them back up throughthe hole.
F& 10 -3. BAILER
133
AuGER. BITS.
121
4. Equipment and Materials
Here are the equipment and materials that areusually employed (see Fig. B for illustration cfMaterials):
hole sinking equipment: Choose equipment whichis appropriate to the particular ground-conditions.
hand tools: Each sinking method will require aspecific set of hand tools. Example of toolsthat are often needed include pipe wrenches,screwdrivers, tape measures, and hack saws.
lifting/lowering equipment: This equipment isalways useful but the particular sinkingtechnique chosen and the depth of the well willdetermine whether it is necessary.
casing: This pipe is used to hold the hole per-manently open to' allow the use of pumps.
well screen: This allows water entry and`preventsthe entrance of aquifer material.
water lifting device (see Pumps): This pulls waterout of the narrow casing pipe.
material to build platform around well head(cement preferred).
5. Casing
A pipe is installed in a well to prevent the hole wallsfrom caving in and provide a conduit through which watercan be brought to the surface.
If a well is sunk through anything other than con-solidated rock, it will need to be cased to assure apermanent hole.
The casing extends from just above the ground surfaceto the top of the well screen which is at the bottom ofthe well.
Commercially drilled wells are usually cased withsteel pipe which is either welded together or coupled,".using specially threaded couplings. Although plasticsare being used increasingly because they will not rust oicorrode, nevertheless they cannot be driven into the
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hole as required by some drilling techniques and groundconditions. Basically, any cylindrical product which canbe installed in the hole to prevent its collapse will work.For small diameter shallow wells, galvanized iron pipe,clay tile, bamboo and even hollowed logs have been used,although the last two are, for obvious reasons, not recom-mended.
NOTE: Before using steel or even galvaniz'ed iron casing,test the water to obtain some kind of measure of itscorrosive properties. In Libgria, wells with steel casinghad life spans of as'little as six months due to corrosion.
6. Well Screen
This is the water intake section at the bottbm ofthe well. it is about the same diameter ass the casingand is made as long as is necessary a) for the depth ofaquifer and 2) to produce the amount of water needed.
The screen itself acts both as a filtei and as amedium through which the soil particles immediately sur-rounding.the screen can be rearranged to permit easierand better water flow into the well, a process known asowell development. Wells' are usually developed by rapidlyforcing water in arid out of the well screen. This re-moves the fine soil'particles,from right next to the screenleaving only larger soil particles witti larger spaces be-tween them,thus perMitting more and easier water movement,into the well. (Fig. 10-5)
The different kinds of screens are discussed in de-tail in Chapter 15.
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B. Design of Drilled Wells
The basic objective of well design is to achieve thebest combinatiOn of materials, techniques, and cost toproduce a well which is useful to a local community. Againsta background of scarce material and financial resources,the design of wells for small rural communities in thedeveloping countries requires a flexible approach to in-dividual water supply needs that involves comprohises onthe allocations of community resources.
1. Design Problems
Two major problems in all water improvement projects:a) system maintenance and b) water testing and:treatmentshould be considered in the design and planning of thewell.
Maintenance is 'the major prOblem in water develop-ment. A system cannot last anywhere nearly aslong as expected unless regular maintenance isperformed on the system and the usual minorproblems are fixed as they happen.
Water testing and treatment:
Water is rarely tested to determine itschemical and bacteriological characteristics.Chemical testing is necessary to determinepossible appropriate materials for intakeand pumping equipment, as well as potability.Bacteriological testing is needed to detectpossible disease-carrying organisms. Manysimple, inexpensive,'and.relatively effectivemethods of treatment are available and couldeasily be used to help ensure water potabilityand to lower disease rates. (See Appendix VIII.)
2. Diameter
Where large supplies of water are needed, the normalprocedure for determining the well diameter is to:
determine the quantity of water needed;
find the size of the pump needed to deliver acertain quantity of water per unit of time whichis lifted a certain distance (head);
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choose casing that is slightly larger than thepumping equipment;
excavate a hole whose diameter can accommodatethe required casing- (See p. 145.)This presumes finding one or more aquifers thatcan deliver the quantity of water needed.
For small wells, the same general considerationsapply, although based on the selection of the most ap-propriate equipment available. The casings in most ofthese wells will be between 5 cm and 10 cm in diameter.
3. Depth
Where it is possible to get any idea of whatthe depth of the well will be, a sinking methodmust be chosen that is capable of reaching thatdepth.
Where small water supplies are being developed,the usual Practice is to develop the first majoraquifer, reached by sinking the intake sec-tion as far into the aquifer as possible withthe given equipment, until a sufficient sup-ply to meet local needs is assured.
The possible depth of the well snnk with hand-powered drilling techniques is usually about 20meters except where a.fluid is used to removedrill cuttings, in which case wells can often besunk deeper.
4. Choice of Pump (Also see Pump Appendix.)
The largest commonly manufactured hand pumpcylinder will fit in a 14 cm hole.'
The deeper a well is, the smaller(the diameter ofthe pump cylinder used.
It may be difficult to introduce hand pumpson previously open wells where the depth isgreater than 30 meters. The reason is thatpeople who probably had been using animalsto draw their water will be required to dothe pumping themselves.
If the well i's properly developed, most smalldiameter wells. cannot be pumped dry with a handpump.
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C. Planning
Overview4
Here is an overview of planning which presents majorchoices and their determining factors. Use it as a check-list in your planning activities.
a. How you sink the hole depends on:
ground conditions: What ground conditions doyou expect? Are you prepared to go throughrock? HOW much rock must be penetrated?
sinking methods: What sinking methods canyou use in these ground conditions?
equipment: What equipment do you have? Howaccessible is it? Which equipment is suitablefor the ground condition's you expect? (See
Small Equipment and Drilling Techniques, p. 137.)
b. How,you case- the well (reinforce the hole walls)will depend on
material: What material will the casing bemade of? What casing material would be suit-able for the chemical and bacteriologicalcharacteristics of the water to be tapped?
ground conditions: If loose, caving forma-tions are encountered, it may be necessary tosink the casing along with Vie excavation tokeep the hole/open and thus allow continuedsinking. It is not necessary to case a holethat is sunk into solid rock, although if thehole continues on through the rock into anotherunconsolidated formation, the entire hole shouldbe cased.
sinking methods: The casing can be loweredinto the hole after the hole is excavated ordriven along with the excavation process.
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c. How the intake section is constructed will dependon:
materials: What kinds of screens can be builtlocally or. are commercially available? Whateffect will different possible choices ofscreens have on well production?
ground conditions: The aquifer depth andparticle size will determine the optimumlength and opening size. of the intake section.
sinking methods: The method used to sink theintake section can determine the type of wellscreen that will be used.
casing: Whetlier the casing is sunk along-withdrilling or lowered into the completed holewill determine the type of screen connectionto the casing.
d. HOW the top section is constructed will dependon: 1) the degree of sanitary protection thatis felt necessary and 2) users'preferences for aparticular method of water delivery.
e. The maintenance performed on the well depends on:
the arrangements made forregular maintenance.
the community involvement and interest in thewell throughout the construction process.
the understanding of the connection betweenimproved water supplies and better health.
D. Werk Outline,
Here is an outline of the essential constructionactivities, in working order:
Community awareness and education activities shouldbe in progress so that actual construction canserve to illustrate,ideas that have already beenpresented.
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Gather and arrange supplies at the well site.Planning the placement and use of supplies aroundthe well can make work more efficient and easier.
Excavate hole (sink hole, dig or drill hole).The hole is sunk as near to the desired depth aspossible. This will often include sinking thehole as far as necessary into the aquifer, asground conditions permit.
Case hole (line and reinforce walls). (Seep. 145.) In all wells except those sunkthrough hard rock, a casing must be installedto prevent possible collapse of hole walls.For small diameter wells, the casing is usuallypipe.
Excavate bottom section. If the bottom sectioncannot be sunk by whatever method was used toexcavate the middle section, then another sinkingmethod' which is more appropriate to the groundconditions will have to be used.
Install a well screen. (See p. 122.) A wellscreen is a filter which enables the develop-ment of the surrounding aquifer to allow asmuch water and as few aquifer particles aspossible to enter the well. The well screencan be attached to the casing and installedwith it. Or it can be installed separatelyafter the casing is in place.
Seal top 3 m of casing. Grout around the casingdown to at least 3 m below the ground surface,to help prevent surface contamination from en-tering the well.
construct a platform around the hole which, bygently sloping away fromthe hole (1:40 slope),allows water to run off,, preventing accumulationand possible well'contamination from surface waterseeping in around the pump.
Install a pump or water lifting device which con-forms as much as possible with local watergathering customs and practice.
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CHAPTER 11
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DRILLING AND CASING TECHNIQUES
A. Introduction
Small diameter well sinking techniques include:
techniques that require large, expensive equipment;
techniques that need only small equipment.
Large scale techniques are covered here in enough de-tail to understand their basic operating principles. Thesemethods use large, expensive, complicated machinery whosedetailed operation can be adequately understood only-witifthe benefits of hands-on training. However, the basicdrilling techniques used with these larger rigs are, inmany cases, the same as those which can be used withsmaller equipment and may serve to better illustrate thepossitle variations of each technique.
Small scale techniques are covered later in enoughdetail to enable interested persons to perform them.
B. Drilling Techniques with Large Scale Equipment
1. Types of Rigs
These techniques all use a specially made unit knownas a "rig" which includes all of the different powersystems needed to operate one or a variety of types ofdrilling tools. The cost of these rigs ranges fromabout $20,000 to $500,000 and up. Depending on the typeof rig and the drilling method, holes can be sunk withdiameters ranging from 4 cm to 1.4 m. (See Fig. 11-1.)
There are two basic types of large drilling rigs,percussion rigs which give an up-and-down motion to thetools and rotary rigs which turn the drilling-tools.
By far the most common type of percussion rig is thecable tool. Drilling tools are suspended on a cable whichis alternately pulled and released to create the up-and-down motion of he tools. When drill cuttings haveaccumulated to the point that they impede the action ofthe bit, it is removed from the hole and a bailer islowered, usually on a second cable, to pick up the cuttings.This is One of the two most common methods of well dril-ling and is known as cable tool percussion. Cable tool
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rigs are also adaptable to other forms of percussiondrilling such as hydraulic percussion and jet percussion.These other percussion techniques are not, however,commonly practiced.
Unlike percussion, there are several different relativelycommon types of rotary rigs. The biggest of these, andperhaps the most complicated of all well drilling machinery,is the rig capable of hydraulic rotary drilling and itsvariants. This and the cable tool are the two mostcommonly used water well drilling rigs.
Other types of rotary rigs are those that use augersand core drills. Auger rigs are designed to drill rela-tively large diameter holes to a relatively shallow depthin non-caving formations. Core drills are designed todrill. very small diameter holes to great depths andrecover samples of all the materials drilled through. Bothof these kinds of rotary drills have been used to drillwater wells, although both have limitations for such use.
NOTE: When considering using this equipment, carefullycheck the manufacturer's size specifications. Therehas been much confusion and delay resulting from the fact.that tools and equipment are commonly manufactured in bothEnglish and Metric sizes, which are not generally compati-ble. To compound the problem there are many differentkinds of thread patterns in use which can be cut on eitherEnglish or Metric pipe sizes.
2. Drilling Variations
T11,rk a number of possible drilling variationsgiven the two basic methods, percussion and rotary, depend-in on whother or not a fluid is used and which way it iscir2ulatcd.
..ccossion only - cable tool percussion.(See Fig. 11-.2a.)This is commonly used to sink wells through allkinds of formations.
prcussion and regular fluid circulation - jetnn'115,,sion.(See Fiq.11-20
is meth,Jd it; no longer frequently used butwhere wells are jetted from the surface it isusually a fowof jet percussion.
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percussion and reverse fluid circulation - hydraulicpercussion. (See Fig. 11 -2c.)This method is not commonly used with largemachines, although the small scale version,known as the sludger technique, has beenextensively used in some areas.
rotary only - auger. (see Fig. 11-2d.)Augering or boring is commonly used to drillrelatively shallow holes for wells and manyother uses.
rotary and regular fluid circulation - hydraulicrotary. (See Fig. 11 --2e.)
Phi method is commonly used to drill wellsthrough all kinds of formations.
rotary and reverse fluid circulation - reversecirculation. (See Ffg.11-2f.)
Reverse circulation drilling has the same usesas hydraulic rotary and is sometimes perferred.
rotary and air as drilling fluid - air rotaryor down-the-hole hammer.This is a relatively new technique which usescompressed air as the drilling fluid and is mostsuitable for drilling through rock.
The following two techniques are not really primarydrilling techniques since they are not often used withlarge drilling equipment to sink wells from the groundsurface. They are, however, frequently used in welldrilling operations to sink the well screen and casinginto place in the aquifer after a hole has been drilleddown to the water table by any of the above techniques.For more information, see Chapter 14.
regular fluid circulation only - jetting or washing.(See Fig. 11-20The fluid itself loosens the soil at thebottom of the hole and also carries the loosenedsoil to the surface.
no fluid circulation - driven; (See Fig. 11-2h.)With this technique the casing and well screenare simply pounded into the ground.
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aY b. c.
I
uP AND DOWN Tom reoriot4
I Toot.3 ARE POUNOED ORPUSHED 150wr4
DtAECTION OF FLUID FLOW
sir Is weitse.c. im-ou MOLE. TO 1.00SEN SOIL
FIG. 1 I Z.DRILLANG METHODS.THE CHOICE. OF DRILLINGMETHOD DEPamtn MAINLYON WHAT MATERIALSARE AvAiL.A13L.E.,.
a e.
9.
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3. Drilling Depth
Assuming that the rig and tools are appropriate forthe particular ground formation being penetrated, thedepth that can be drilled is limited only by the abilityof the rig to lift the tools from the hole.
For example, one particular manufacturer provides thefollowing suggested depth capabilities for their top-of-the-line hydraulic rotary drilling rig fitted out withvarious drilling tools.
drilling method hole diameter depth
augercontinuous flight augerreverse circulationair rotary
900 mm300 mm600 mm170 mm
12 m15 m150 m450 m
The same company's core drilling rig is capable ofdrilling a 48 mm diameter hole to 1400 meters..
C. Overview of Small -Scale Techniques
1. Introduction
The small -scale techniques,given here have beenadapted for use with a minimum amount of equipmentand expense. These techniques may require only handtools, pipe, and a great deal of labor, or they mayrequire a tripod, a motor pump, drilling pipe, anddrill bit plus whatever material will be permanentlyinstalled in the well. Wells workers may select froma variety of equipment varying in cost and technicaldifficulty, all of which are less expensive and lesscomplicated than a drilling rig.
These sinking methods may be used in largelyconsolidated ground formations (see Glossary). Thesuitability of the different methods varies with thedegree of caving expected and whether rock will beencountered.
It is common practice to use more than onemethod to sink the complete hole. With adequatefinances and equipment, it is helpful to use theparticular technique most suited to the (1) groundcon.jlitions, (2) expected depth of water, and(3) the section of well being worked on.
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Each individual small equipment sinking techniqueis generally limited to use in a certain type of soil.Where the soil layers to be penettated are similar,using one appropriate sinking technique will be mostefficient. However, it is much more likely'that youwill encounter several different soils, requiring theuse of variations on a single sinking technique, oreven different techniques, When evaluating the varioussinking techniques, choose the one most appropriate toa particular situation. You may also want to considerwhat other equipment might be needed in differentground conditions.
In many cases, ground conditions will vary betweenthe middle and bottom sections of the well. The sametype of soil may surround the complete well, but wherethat soil is saturated with water (bottom section), itsdrilling characteristics will'usually be different. Forexample, a sand or combination of sand and gravel aqui-fer will usually be subject to caving, making it impos-sible to 'excavate a hole down into the aquifer withoutsinking a casing with the drilling tools.. Sand that isonly damp, on the other hand, will tend to stick to-gether and not cave in.
However; if rock is struck, the well must bemoved to a different site where rock might not beencountered, or the workers must switch to drillingtools appropriate for rock. Hand-powered tools com-monly used in unconsolidated formations generallygouge and slice through soil to loosen it. This isnot suitable for rock, which must be sittashed andchipped or broken into smaller pieces in order tobe removed from the hole.
2. Sinking Methods and Ground Conditions
There are then three basic, types of ground conditionsthat can be encountere4 while drilling.
Grpund Condition Suitable Sinking Technique
Rock '
Loose, non-caving
Loose, caving
percussion ,
rotary, percussion or sludger
driven, jetted
Where all three ground conditions are likely to beencountered you should be equipped with the types of toolsappropriate to each 148
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3. 'Level 0 Complexity and Common Uses of Small ScaleTechniques
a. techniques that require the least equipment andexpertise
driven - Variations of this technique are usedin almost all methods. By itself it can onlyreach a limited depth in relatively loose4soil.
sludger - This is a specific., adaptation of aperLassion technique which uses a drillingfluid but does not require a pump during dril-ling. The technique is quick and there aregood possibilities where the ground permits.
b. techniques that require a minimum of manufacturedequipment but require that materials and semi-skilled labor be available to produce the.necessaryequipment.
hand percussion - This excavation techniqueworks in the widest range of soil conditions.
iHowever, it is slow and requires considerablehard labor. Although it is simple, there aremany possible minor variations which couldaffect drilling but which require someexper-ience to use effectively.
hand auger - This is one of the simplest andmoss easily understood methods for simple fieldwork. It is limited to non-caving formationwithout rocks bigger than the auger. It isalso slow and can only reach a limited depth.
techniques that require at least local manufactureof the necessary equipment and pumps.
jetted - This technique will only work in thesame places that the sludger method will andit requires more equipment and expertise. Itwill, however, usually be faster and requireless work than sludger.
D. Small Equipment and Drilling Techniques
Here is basic informationon small equipment drillingtechniques, which provides the following information oneach method:
materials required;
quick description of method;
suitability of ground conditions;
cost;
work;
depth.
1. Rotary hand augerO
e. Materials required - auger, drill stems to connectthe auger bit with the handle, and a handle.
The particular operation will depend onthe exactbit being used. Mast often,the bit is turned inthe hole until it is full of drill cuttings. Itis then brought to the surface,, emptied, andreturned to the hole.. This process is continueduntil the desired depth is reached or ground con-ditions change causing this method to be unusable.(See Fig. 11-3S
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FIG.11-3. HAND AUGIERAN;Suitability to ground conditions - This method canbe used in clay, silt, and sand formations notsubject to caving. In caving formations a casingslightly larger than the bit can be driven down asthe hole is sunk. Where rock is reached thissinking method will have to be disbontinued.
.Cost - The U.S. cost of a 10 cm diameter auger,drill stem, and handle in the spring of 1978 was$16.50. ,
Work - Unskilled workers can easily be taught to usethis method to sink and finish wells up to 20 m deepin five days.
Depth -e20 m is the usual maximum depth.
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2. Hand percussion
Materials required - Youwill need a chopping hit(see Fig. 11-4), bailer(see Fig. 11-5), eitherdrill shafts or rope, anda tripod and pulley toassist in lifting anddropping the drillingtools. ,
The bit is lifted and droppeduntil it has loosened so muchmaterial in the bottom of thehole that its progress isstopped. The bit is then re-moved and the bailer is droppedinto the hole to pick up thecuttings. The bailer is workedto pick up as much as it canand then removed from the welland emptied. The bit can thenbe lowered back into the holeand worked as before. Thissequence is continued untilwater is reached or the groundconditions change to necessi-tate a change in sinkingtechnique.
Suitability of ground conditionsThis sinking technique can be
used to sink wells in all kindsof ground conditions althoughit can be very slow in hardrock.
Cost - The cost of hand percus-sion tools will depend on thesophistication and quality de-sired but, compared to mostother methods, these tools arecheap an4 easily made.
Work-- Unskilled workers caneasily be taught to use thismethod although semi-skilledsupervision will be necessary foroptimum performance.
P
139
Fl&.CHOPPING Btr
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'I.
Depth - Great depths arepossible in optimum groundconditions but as the holegets deeper more and moretime will be spent switchingback and forth between thebit and the bailer becauseof the greater distance theymust be raised and lowered.
This method is best suited fordrilling through soft rock and wellpacked, non-caving soils. It canbe used in hard rock althoughprogress will be slow and.drillingbits will need to be sharpenedfrequently. It can also be usedin caving soils if the casing isdriven in as the hole is sunk.
3. Hand percussion and fluid(s lodger)
Materials required - Youwill need metal pipe andcouplings, a cutting bitwhich can be made from acoupling, pipe wrenches,and a tripod or,. leverstructure with which tolift and drop the metalpipe.
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Ft6. 11- bAi Lag_.
)\..*;
141
FIG. II -4. SWOCIER.-raci-INIQua
The pipe string equipped with a one-way valve is liftedand dropped into the hole which is full of drilling fluid(usually water). The one-way valve permits fluid andcuttings to flow up through the pipe but not down. Theup-and-down action of the pipe, acting with the valve,allows the tool string to act as a pump removing fluidand cuttings from the well. The fluid can be recircu-lated if cuttings are allowed to settle out. (SeeFig. 11-6-.)
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Suitability to groundconditions - This method canbe used in fine or sandysoils as long as rocks areno larger than medium-sizedgravel.
Cost - Obviously the costwill vary from place to place,but to give an example, wellsusing this technique drilledwith 1.5" G.I. and finishedwith plastic 'casing costl2 to l6 per ft. in Nepalin 1976.
Work - Six relatively unskilledmen can build a 4 cm diameter60 m deep well in four days.
Depth - Maximum 80 m.
4. Driven
Materials required includea drive point, a casing pipe,a drive cap to protect cas-ing pipe when driven, and aheavy weight to strike thecap.
Driven wells are sunk bypounding a special type ofwell screen called a drivepoint (well point) into theground. The drive point-isattached to the casing pipe andmore casing pipe is added'asnecessary as the whole stringof casing pipe and drive pointis driven down. (See Fig. 11-7.).
Suitability to ground condi-tions - This method isgenerally used and easiestto drive in loose, cavingformations. It will notgo through rock and sinks.through clay only withdifficulty.
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F16.11t.Dltiveto
'e
Cost - As of August 1976, a-91 cm long, 5 cm diameter,stainless steel, continuousslot drive point cost 480.14and a 305 cm length of 5 cmdiameter seemless, ungal-vapized (black), steel
. casing pipe cost $43.65 inthe U.S These are manu-facturers'prices and aregiven here merely asexamples.. Acceptablesubstitutes for both ofthese can usually be loc,%.lymanufactured.
Work - The majority of thework involVed in Sinking.awell with this method fs]ifting and dropping a heavy -
weight to drive the pipe.into the around.
Depth - WelIt can usually not bedriVen more 'than 10 m by hand or20 m be machine because of thefriction between the casing, pipeand-the soil.
S. jetted
Materiai. = required inclUde.a pump, hoses, a watertightconnection of the .hose tothe top ,_)k the drillingstring, ,a hollow drill pipe,a hbist, and a jetting bit.
Jetted wells.are sunk byPumping drilling kluid(usually water) down throu nthe drill pipe and, out aSpecie jetting bit. Thisworks..)n.the same prir-Apleas.a flowing garden osethat can be pushed into theground. The.was ng actionof a stream of later alonecan used t
andsmall
diameter pi and wellscreens i sandy formation,;.(See Fig 11-8.)-
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144
PIG. II- a...15-rrai) WELL
Suitability to groundconditions - Jetting withpercussion can be used togo through all but hardrock formations. It iscommonly used to sink smalldiameter well screens inwater bearing sand.
Cost - Because of theequipment necessary,this sinking method ismore expensive than theother techniques coveredhere. Its actual costis difficult to estimatebecause of the wide rangeof equipment possibilitiesthat can be used. A simplehand-operated diaphragmpump can he used to sinkone long pre-assembledlength of casing intoplace at a cost compara-ble to other methodsdiscussed.
Depth - Jet percussionbuilds wells 8 to 10 cmin diameter up to 60 m.With simple equipment, awell can be jetted to adepth of about 20, m.
Work - This method requiressome technical skill, ex-perience, and judgment,although all of these arestraightforward and easilyunderstood by people withmodest technical back-grounds.
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E. Casing Installation
1. Overview'of Casing Techniques
145
Now the casing is installed in the well depends onsuch factors as casing materials, and ground conditions.
Before the casing is set into place it is very im-portant that you also consider how the well screen willbe attached to it. (See p. 192.) If the casing aboveis set in place the well screen must later be telescopedinto place. Special tools and materials are then re-quired to seal the well screen to the casing.
The same three methods of installing the casing arepossible whether or not the well screen is attached.
Lowering the casing into the hole - Where the drilledhole will remain open without caving for a long enoughperiod of time, the casing can simply be lowered intothe completed hole. Normally, the casing is loweredas far as possible into the hole, after which it canbe sunk further by one of the following methods.
Driving the casing - This method can only be usedwhere heavy metal pipe, which will not: deform as itis driven, is used as the casing. It ean be used inall but very hard formations although it is most oftenused in loose caving formations. (Seep. 163.)
The casing can be driven into place either after thehole has been sunk as far as possible or as the dril-ling proceeds. The latter is used primarily withpercussion techniques where a bailer can be workedinside the casing to remove loose, caving types ofsoil as the casing is driven in to reinforce and main-tain the hole. In this instance special drive clampsmust be attached around the casing pipe so that it canbe driven while the bailer is inside it.
When the casing will be driven into place ,b4fore thewell screen is attached, a sharpened coupling can bescrewed on to the bottom of the casing to facilitatesinking. (See Fig. 11-9.)
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F1&. 11 -9.SHARPENEDWu Pl. sNO
Washing the casing into place - This method usesthe process of pumping a fluid down through thepipe to remove loosened soil particles from the holeand allow the casing to sink. The only differencebetween this and the jetting process described onpage 176 is that a special jetting bit whichdirects a high velocity fluid stream at the bottomof the hole is not used. Because this method re-quires that the Pipe -joints be watertight. itgenerally is used only with manufactured pipe.It also requires the use cif a pump, to force waterdown through the casing, and a watertight connection'at the top of the casing through which the water canbe pumped. (See p. 239.)
2. Sealing the Casing
Once the casing is set in its final position in thewell any space around the casing should be filled in.The top three meters of this space should be filled'with mortar or concrete to seal the casing to theground formation and thus prevent possible contaminantsfrom easily flowing down along the outside of thecasing pipe.
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Chapter 12,
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CONSTRUCTION: HAND ROTARY AND HANDPERCUSSION METHODS
A. The Hand Rotary Method--
1. Overview of Method
This method of well sinking has been commonlyreferred to as borin . Sometimes percussion tech-niques are included under the general title of boredwells. Because of theelimited soil conditions inwhich simple rotary methods are effective, it isoften useful to have percussion tools available.However, for clear explanation, simple rotary.andpercussion techniques are discussed separately here.
Where sophisticated drilling methods are availablefor well sinkjng, hand augering is used only for takingsoil samples at relatively shallow depths. It is cheapand provides very accurate soil samples, but requirestime and effort and is limited to unconsolidated/non-caving formations.
An auger, which functions as a drill bit, isattached to the bottom of a length of drilling rod andturned ip}ith the handle, which is attached to the top ofthe drilling rod. (Fig. 12-1.)
The auger serves first to loosen soil at the bottomof the hole and second to remove it. As the auger isturned, the loosened soil accumuldtes in or on the auger.
When the auger is full, it is lifted to the surfaceand emptied and then returned to the hole to continuesinking. Lengths of drilling rod are added to the toolstring as the hole is deepened. It has been estimatedthat 70 to 80% of the time required for this sinkingmethod is taken up by raising and lowering the toolstring.
2. Advantages and Disadvantages
There are severJ:1 Advantages to this method.
The equipment is simple, light, portable and easyto make froir i..vtAlable materials.
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It provides excellent samples of soil layerspenetrated for future reference.
The technique is simple and easily !taught.
It is easily combined with simple percussiontechniques to make the combination method suitableeven where some rock exists.
It has, however, certain disadvantages.
It is limited to unconsolidated, non-caving groundformations.
Well depth is limited to 15 or 20 meters maximumbecause of the physical difficulty of operatinga tool string any longer than that.
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3. Equipment
Excavating equipment includes:
mier - An auger works at the bottom end of a tool p
string to excavate soil. There are two generaltypes of augers each of which has variationswhich are suitable for use in different groundconditions:
a. cylindrical bucket type - different variationsused for hand or power drive. (See Fig.12-2.)
b. open blade type - used mainly with-powerequipment (continuous spiral) although someare available with hand drive.(See Fig. 12-3.)
FIG. 12 -Z. BUCKET AUGERS
162aS
150 to.
A
FIG.12-3. OPEN 'BLADE AUGERS
drill shaft (drill stems, drill rod) Thedrill shaft is made up of 1 to 5 meter sectionswhich are connected together between the augerand the handle. It is most 'often fairly smalldiameter hollow metal pipe. This size and shapehelp to reduce the weight of the tool string aswell as provide the appropriate motion andstrength necessary to transmit the drillingmotion from the handle to the bit. Because somuch time is spent removing and lowering thebit, the shaft connections should be quick,easy, and sure. It is necessary that all ofthe equipment use the same type of drill shaftconnection.
The following are examples of types of connec-tions that have been used.
- Threaded pipe aid coupling is probably themost freqUently used connection because itis so readily available.
163
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A
- Another opnnection involves slipping the twoconnecting endsof the drill shaft into a.slightly larger piece of pipe and boltingthem in place. Only one bolt needs to bereMovedto disconnect the two shaft sections.That can usually be easily done because ithas been found that the bolts need only befinger'tight. An alternative to using aregular nut and bolt could be to use atoggle type bolt.
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Rock hammer - This is a percussion tool which canbe dropped or thrown down the hole to chip or breakrocks which are too large to be removed by the auger.
v
Sand bailer - This can be used to remove sand fromloose caving formations.
Casing - Some type of casing must be installed inthe well to reinforce the walls. In caving forma-tions, a sand bailer can be operated inside thecasing to sink the hold and the casing. The insidediameter of the casing will need to be slightlylarger than the outside diameter ofothe sand bailer.
Tripod - This can hold a pulley to aid in liftingthe tool string and also support the upper end ofthe drill stems when drilling through harder layers,such as laterite'(see Glossary). The support is tohold drill stems plumb while drilling" with extra .
weight on the stems to enable penetration of thehard formations.
Fishing tool - This is used for retrieving toolsand equipment that have come disponnected fromworking pipe string or have dropped into the hole.(See Fig. 12-4.)
NOTE: A magnet can be a fishing tool for smallitems dropped into the hole.
Plumb bob and level - These may be used to checkwhether a. hole is perfectly straight and vertical.
Handle - The handle attaches to the drill shaft'enabling the auger to be turned by people at, theground surface. it can either be attached to thetop end of drill stems to form a T.or be a crosspiece that clamps to the drill stem wherever itis needed.
1R4
151
152
4. The Sinking Process
Arrange and set up all tools, equipment andsupplies; clear the area immediately around wellsite of all unnecessary tools. Set up and locatea tripod or headframe if it is necessary to pro-vide support for the upper end of the drill stem.Locate it directly over the hole so that the drillstem will be plumb.
Assemble the auger, drill stems and handle.
Begin boring by forcing the auger blades down intothe soil while turning the tool. Digging a 3 to50 cm deep hole of sufficient diameter to allowintroduction of the auger usually helps to get thedrilling started.
Turn the bit until it is full of loosened soil.It is only necessary to turn the bit just enoughto fill it. The number of turns required to fillthe bit is determined by the soil hardness, andmay be only two or three turns. Be careful withsome augers not to screw them too tightly intothe ground. In hard formations, it may be neces-sary to push down as well as turn the tool. (SeeFig. 12-5.).
165AtiPCP m.seics-lr kuscessAtty -ro FE toirrizAre 1.04.1Q45 Gebvpags.
Remove loosened soil from the hole. Lift theauger from the hole and empty the soil accumulatedon or in it. By systematically depositing thecomponents of the auger in short ridges, eachcontaining the soil from 1/2 or 1 meter of welldepth, you can keep a record of the soil layerspenetrated.' Keep the samples far enough away .
from the well so as not to hinder the well sink-ing operations.
Return the auger into the hole and contin2e sink-ing.
Continue turning the auger, removing the augerfrom hole when full, emptying and returning theauger to the hole to be turned more. As the holeis sunk deeper and deeper, more and more drillstem sections will need to be added.
Continue sinking the hole by the same processuntil a) you have reached a sufficient depth intothe water table or b) you can no longer sink thehole any deeper by this process. If (a) is thecase, see Chapter 15, p. 191. If (b) is the case,you were probably stopped for one of the follow-sing reasons: the auger encountered,rock,the holecontinues to came in permitting you to go nodeeper, or the tool string is not longenough to go further.
If the auger encountersrock you still have severaloptions. Try to remove theentire rock from the holewith a ram's horn (spiral
FIG. )2 -(a.auger} . (See Fig. 12-6.) SPIRAL- /MAMA.This will work only if therock is smaller than thehole.
Although a spiral augeris a piece of equipment -
listed- in the literature forremoving rocks from augeredholes, field experience hasfound that percussion tech--niques work better. (See HandPercussion', p. 155.)A percussion rock bit
166
153
I
s.
154
would be attached to a rope and dropped in thehole or attached to the end of the drill shaftsjust as the auger is. Abandon the hole and trysome other place if you have no equipment topenetrate a rdck layer or if it is too thick orhard to be penetrated by whatever tools you have.
If the hole continues to' cave in permitting youto go no deeper, you have two options. If youhave hit water at the same time, see "BottomSection." If the hole is still dry, however,you must evaluate your situation to decide whetheryou want to continue sinking this hole. The holewill usually be caving because the earth is loosesand. To go deeper you will need to sink a casingto hold the walls in place. Determine how muchdeeper you can go and whether it is worthwhile. '
If the tool string is not long enough to gofurther, abandon this hole and try another .
location.
5. Time Saving Suggestions
Disconnect as few of the drill shaft connectionsas possible. Simply remove and replace shaftsections in lengths as long as you can comfortablyhandle.
Leave disconnected shaft lengths standing uprightright next to the well. A scaffold could'be builtagainst which long shaft sections could be leanedwhile waiting to be reconnected and go back intothe hole.
Use an auger with a long central cavity in whichto accumulate drill cuttings.
Leave an opening in the auger which will enablethe cuttings to be quickly,and easily poked out.
B. The Hand Percussion Method,
1. Introduction
155
This method has usually been classified as a variationor useful addition to hand augering. It makes use of thesame methods that are used on a larger scale in cable-tool percussion drilling with large rigs.
The basis of this method is the up and down motionused to sink a hole. The tool string is lifted by anappropriate means and dropped, causing the bit at thebottom of the string to come into sudden, forceful con-tact with the bottom of the hole. The heavier the toolstring, the harder it will strike the bottom of the hole.
It is usually useful to have several different bitssuitable for varying ground formations. All of thesebits are operated by dropping them onto the bottom of thehole. It will often be useful to turn the bit in thehole, either with a wrench or with a handle, that can beattached similar to an auger handle to make drillingeasier band help ensure a round hole.
Cuttings can be removed from the hole in severaldifferent ways depending on the particular bit beingused. Hard rock cuttings and very loose, cavingmaterial is usually removed with a bailer. (SeeFig. 1240.) Non-caving soil can usually be packedinto a hollow bit. (See Fig. 12-9.)
2. Advantages and Disadvantages
The hand percussion method is suitable for usein a wide range of ground conditions, and may beeffective where an auger is not.
This method can be slow, especially in hardformations.
168
156
3. Equipment Overview
Cutting bits. There areseveral different kindsof bits that are commonlyused depending on thecharacteristics of theformation being pene-trated.
A cutting bit is neededfor hard formations.(See Figs. 12-7 and12-8.) Heavy bits withsharp hard edges areused to smash and chiprock. The bit actioncuts and mixes the dr'cuttings with a smalamount of water ad d tohole to form a pa ate whichcan be easily reMoved withthe bailer (too much waterwill slow drilling). Whilea solid piece of regularsteel can be used to makethe rock bit, it is a goodidea toiface or fit thecutting/edges of hardsteel. This can be doneby building up the tip withwelding steel;. and grindingit down to the desiredshape. The bit will re-quire less frequent shar-pening and will last longer.The bit can be wor%ed eitherhanging by rope or cable,
-dr connected to drill shafts.
Roe or cable will tend towear and may break duringthe drilling process. Ifthis happens, the bit willhave to be "fished" fromthe hold. (p. 163.)Although rope wears faster,it does have one advantageover cable. When rope sud-
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170
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denly-reaches the endof its fall, it gives aquick little turningmotion to the bit whichhelps prevent the bitsticking in the hole.For the very heavy (80kg) bits which are-moreeffective in harder rock,rope or cable seems '
far more suitable.than drill shafts.-With an 80 kg bit, fiveto seven people areneeded and they requirefrequent rests (every SOto 100 strokes). Thebest action with a rockbit can be achieved withshort (SO cm) rapid
;strokes.
A hollow rod bitcan be easily madelocally from apiece of heavymetal pipe. (SeeFig. 12-9.) Galvanizediron pipe is suf-ficient. It canbe made with eithera sharpened straightbottom edge as in thefigure or a jaggedbottom edge. Thestraight edge issimply sharpened witha file while thejagged edge can becut with a hack saw.The opposiLe end ofthe bit should befitted so that itcan connect to a
SiAT ef4Flitte0 NPR
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PIG. 12-9. HOLLOWROD err
NOTE: If you reach rock, it is usually advisable to con-tinue drilling for three to five days to get an idea' ofwhether this is an isolated boulder; a thin, easily pen-etrable rock layer; or a virtually impenetrable thickrock layer. After about SO cm penetration into rook, itis normally possible to identify a boulder, because aboulder will usually break up.
1 71
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drill shaft or rope.It will probably bebetter with thistype of bit to at-"tech it to a drillshaft so that thebit can be forciblyturned or pushed downas-necessary. Itwill be very usefulto leave or cut anarrow slot almostthe entire length ofthe bit so that drillcuttings'that havebee.. packed up into thebit can be removed byprying with a piece ofre-rod or somethingsimilar.
Fl. 12- laZokit_e1a...
A bailer is the most commonly used tool in loosesoils. It is a long cylindrical tube with avalve in the bottom end which permits materialto be forced up into the tube but will not per-mit it to fall back out (See Fig.12-10.) Bailersused with hand equipment are most often equippedwith flap valves. The bailer is lowered to 'thebottom of the hole. Lift it 1 to 2 meters anddrop it. The impact of the bailer on the bottomof the hdle willforce some of the loose soil upinto the hollow core. Continue lifting anddropping until the bailer is full or until it haspicked up as much of the loose material as it can.Experience will show how long to continue liftingand dropping the bailer to-get the maximum usage.When the bailer is full, pull it up to the sur-face and empty it away from the well.
A bailer has several uses in different situations.It removes rock pieces loosened by rock bit; itremoves sand in caving formations from insidethe casing; it functions to remove loose materialthat cannot be packed or retain its shape.
172
159
3.60
Drill shaft. The shaftlengths connect the bit tothe lifting apparatus.Connections between therods need to be ,strong; towithstand constant liftingand dropping, and quick be-cause of the frequentnecessity to disconnect andreconnect rods when raisingand lowering bit to emptyit {see details on drillrod}.
Turning handle. This isnot necessary, but it canbe useful to turn the toolstring to facilitate sink-ing and help ensure a roundhole.
Lifting apparatus. A lift-ing apparatus can be madefrom whatever materialsare locally available.
"Fishing" tool. Afishing tool is use-ful for retrievingtools that have be-come disconnected inthe hole.
Casing. Casing isnecessary for perma-nent well constructionand ,can be used toreinforce the holewhen sinking through,caving formations.
A plumb-bob or levelis needed to check theverticality of thehole especially whenthe hole is started.
Hand tools. Very fewhand tools are absolute-ly necessary althoughmany will be found use-ful by those who knowhow to use them.
pope is always usefulfor a variety of pur-poses.
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4. The Sinking Process
Arrange and set up all tools, equipment andsupplies. Clear the area immediately around the
,well. Locate a tripod or other lifting apparatusdirectly above hole site. It should be anchoredwell to prevent the legs moving when a heavyweight is supported by the tripod. The exacthole location can be found by hanging a plumb-bob
173
from,the drill shaft guide or fromithe liftingpoint of the tripod or frame. This will helpensure a vertical hole.
Dig a shallow starting hole before beginning thesinking process with tool string.
Assemble the tool string and set it in place. Itis very useful at this point and also during thesinking process to have a guide for that part ofthe drill shaft which will extend above groundlevel. This will help to ensure that the hole isperfectly vertical, especially when starting thehole. However, do not depend on the shaft guidealone to ensure a plumb hole.
Frequently and carefully check'to see that thetool string continues to be plumb, especiallywhen the hole begins to guide the tools. At adepth of about 50 cm, the hole itself willprobably have more of a guiding effect thanany above-ground tool string guide.
Begin the sinking process by lifting and droppingthe tool string; the lifting and dropping toolsmay be connected to a rope. The rope comes fromthe bit or tool string over a pulley and back toa solid post or tree around which it can be wrappedor tied at a convenient height so that workers caneasily reach it. Workers can then raise the bitby lining up along the rope and pressing down.From there it is quickly released to allow thebit to fall in the hole. You can also use a rear carwheel as shown in Figs. 5-7 and 5-8.
5. Sinking Variations
There are three variations of this sinking processthat can be used depending on the ground conditionsencountered.
In hard, compacted formations; a club typdbit has been found most effective. (See Fig.127.) When dropped, the bit smashes and chipsthe hard formation to break away small pieces ata time. As the bit continues to be lifted anddropped, the small drill cuttings will graduallyaccumulate in the hole until they prevent thebit from coming in contact with the bottom ofthe hole. The driller should continually watchthe progress of the bit so that he can stop thedrilling and remove the accumulated cuttingswhenever the progress of the bit is slowedsignificantly." Determining when to stop and re-move the cuttings is a matter of judgment andexperience. After the bit hasillan lifted from
161
the hole, the cuttings are removed by loweringa bailer into the hole and lifting and droppingit until it has accumulated as much of thecuttings as possible. Adding a small amount ofwater to the hole sometimes aids the bit in:.pulverizing rock and producing a slurry that caneasily be removed by a bailer.
In loose, non-caving formations, a hollow rodbit can sometimes be used effectivelY, (SeeFig. l2-9.)When this bit is dropped in this typeof ground, it does.two things: 1) the circularbottom edge of the bit cuts out a plug of materialthat it has sunk into and 2) this plug forces,material already picked up in the'hollow innercore of the bit farther up in the bit and packsit in so that it cannot fall out when the bit islifted again. It is this packing 014 the loosened,cut-away material into the bit that allows thematerial to be removed from the hole by liftingthe bit to the surface and prying out the packedin mater *al.
Here are some comments and suggestions that mayhelp. It,may be necessary to add water to thehole to facilitate sinking because either toomuch or n6t enough soil is sticking to the bit.Rotating the bit in the hole is sometimes usefulto loosen the bit after it has been dropped andto help maintain a round hole. Leaning the toolstring against the rod sipport or tripod toempty the bit, as opposed to laying it down,saves time and energy. Where the handle isneeded to turn the bit, it will be most usefulif it can simply be clamped into the tool stringwherever .desired. This can be long hard workbut a system of alternating work and rest periodsfor teams of workers has proved efficient.
4 As the bit fills with the loosened soil, it picksup less and less with each stroke until it becomesso packed that it can no longer loosen and pickup any soil. Because different soils pack dif-ferently, the bit may be as little as one thirdfull when it must be removed and emptied. Withexperience, one quickly gains a feel for whenthe bit needs to be emptied.
175
gi
In loose, caving formations like saturated sand,a bailer can be operated inside the casing tosink the hole as the casing is sunk or driven.,(See Fig. 12-10.) The outside diameter of the,bailer should te slightly less than the insidediameter of the casing being installed.
If the casing will sink by itself, the bailer issimply worked up and down inside the casing pipeto pick up loose ground material. As the bailerpicks up the material from the bottom of the hole,the casing should sink under its own weight.(If the casing does not sink, it can be driven.)When the bailer fills up, it, will need to be re-moved from the hole and emptied.
The casing can be driven at the same time that thebailer is being worked or it can be driven downabout .5 m and then bailed. This particularprocess of driving and bailing is very commonlyused to penetrate loose caving formations.
6. Problems in Sinking
e If th4 bit becomes stuck in the bottom of thewell, it may be freed by attaching to the ropeor shaft a long pole which pivots over a rockor log next to the hole.to lever up the bit.(See Fig. 14-10.)'
Fishing - When a rope becomes worn, it maybreak, especially under the added strain of try-ing to retrieve a stuck bit. It may be possibleto fit a hook onto the end of the drill shaft,hook the bit, and pull it up. A solid drill shaftis much easier to control and manuever in thehole than rope or cable.
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163
Chapter 13
CONSTRUCTION: SLUDGER METHOD
A. Hand Percussion and Fluid (Sludger)
1. The Method /A sinking method that has been used quite successful-
ly in India and Pakistan is called the "sludger" method.It is an adaptation of the "hollow rod" technique whidhhas been used with large drill rigs to sink wells. It ismore formally referred to as the "hydraulic percussion"method; "hydraulic" because drilling fluid is used and"percussion" because the motion of the tools is up-and-down.
The tool string consists simply of a bit, a checkvalve, and lengths of hollow drill pipe. The tool stringis lifted and dropped in the hole which is full of drillingfluid (usually water). The check valve in the tool stringallows drilling fluid and the drill cuttings which aresuspended in the fluid to pass through the valve on thedownstroke of the pipe. These are not permitted to flow backout on the upstroke of the pipe. With the next downstrokemore fluid and cuttings are forced up through the valve,thereby forcing the first mass further up the pipe. Thiscontinued up-and-down motion of the tool string thencauses it to function as an inertia pump which acts toremove the drill cuttings from the hole. (See Fig. 13-1.)
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. FIG.13-1. SLUGGER. I:STA! L.,
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a As the pipe is lifted, there is room for more fluid to flowown into the hole. f...
b. Dropping or pushing the pipe down forces fluid and cuttingso come up through the valve into the pipe and, after several
0ttrokes, out the top.
.When the pipe strikes the bottom of the hole as you drill,
e valve closes, preventing the fluid in the pipe from floT;iingback down into the hole.
178 .4,
The cutting action isperformed by a bit attachedtc the lower end of the toolstring. This can be simply asharpened or jagged edgedcoupling that is screwed onto the bottom length of pipe.The bit strikes the bottom ofthe hole at the end of thedown-stroke and acts to loosenthe material which can thenbe picked up by the drillingfluid to be removed from thehole. (See Fig. 13-2.)
Several variations ofthis technique have been usedeffcctivply. Wells have beensunk using standard pipe andcoupling as the bit while aperson uses his/her hand toact as the check valve by co-vering and uncovering the topend of the pipe. Hollow drillpipe with a swivel joint at-tached on the top has a7.so beenused. (See Fig. 13-3.)
Where a motorized liftIngapparatus is not available,more and more labor will berequired to lift and drop thedrill string as it gets longerand heavier.
This particular sinkingmethod.is the.only one thatuses drilling fluid to removedrill cuttings from the holebat does not need a specialpump. Normally the pump isrequired to move the fluid sothat it will pick up thedrill cuttings but with thistechnique the drill string it-self acts as the fluid plimp.
FIG. i3-2.SHAT PEt4e counikNL-,
179
167
2. Advantages and Disadvantages
Here are the major advantages of using this tech-nique:
very few tools are required;
the work is completed quickly;
the subsurface conditions are easily determinedfrom 1) cutting samples taken from the drillingfluid issuing from the top of the drill pipe and2) the rate of descent of the tools.
The major disadvantages are:
the method requires that water be available;
rocks larger than medium sized gravel cannot bepenetrated.
3. Equipment
Cutting bit: A regular pipe coupling can work asa cutting bit if the edges are sharpened. Fileor grind only the inside edge of the coupling toavoid narrowing the diameter. (See Figure 13-2.)
Check valve: A valve prevents the downward flow ofliquid in the drill pipe. Ball valves are commonlyused. Where materials are scarce a well workercould use his/her hand to cover the top of thepipe when it is lifted, lifting the hand as thepipe is dropped. (See Fig. 11-6.)
Drill pipe: Metal pipe which can be coupled to-gether in suitable lengths as needed to providenecessary drill string height is usually used.
Swivel hose connection to top of drill pipe: Awater discharge piece is not absolutely necessary,althougti'it is useful in helping to channel thewater to a specific location rather than having itcome directly out of the top of the drill pipe.(See Fig.13-3.) 'Depending on the lifting appa-ratus used, a flexible hose could even be connect-ed directly to the top of the drill pipe althoughit may become damaged with the continual up anddown motion adding stress to it.
18,1 .4
169
170
t
Lifting mechanism: This can be made of local ma-terials and be whatever you think appropriate.Some options are:
- a tripod with pulley and rope and some wayto pull and release the rope;
- a springpole; C
c
- a capstan made of an empty rear car wheel;
- a lever type assembly attached directly to the.
pipe by means of a rope or.chain. (See Fig. 11-6.)
Hand tools
An assortment of hand tools is always handy at awell site. When using metal pipe,pipe wrencheswill be almost indispensable.
4. Sinking Process
Po-range and set up all tools, equipment and sup -p -Les. Leave the area immediately around the wellclear of materials that do not have to be there.Set up the lifting device and locate it appropri-ately. A tripod should have the pulley centeredover the hole. A lever type arrangement shouldhave the end of the lever adjacent to"the hole.
Start the hole in non-caving formations by sinkinga hole as far as possible with a post hole diggeror spade. In caving formations drive a section ofpipe down so that the top end is slightly belowground level.
Dig out a settling pit appropriate to the waterdischarge piece. With a swivel type dischargehead or where water can be channeled to one loca-tion, dig a settling pit on one side of well witha small channel feed fdr water from. the pit tothe hole. With no discharge piece, the only alter-native is to *Ake the settling pit a circularshape around the hole. The problem with that ar-rangement is that it allows too many cuttings tofall back into the hole.
Fill the settling pit and hole with water.(See Fig. 13-4.)
182
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Assemble the tool string,which consists of a bit,check valve, drill pipe and discharge piece. Setthe tool string upright in the hole, and attachit to the lifting device. .
Begin the drilling operation by raising and drop-ping the tool string. The harde the 'material '-eingcirilled,the more rapid and shorter the strokesshould be for the best results. Up to 120 strokesper minute may be desirable for shales, sandstone,and limestone. The softer the material beingdrilled,the slower the stroka should be, from 30to 60 strokes per minute in clays, loose sand, andgravel. In extremely soft material take carenot to let the bit sink too far into,the formation,thus plugging the bit or valve, and making removaldifficult. The best and safest method is to allowthe bit to cut and mix the cuttings so that nochunks latge enough to clog it are passed up thepipe.' When threaded pipe is used in the toolstring, it should be continually rotated in aclockwise direction to help ensure that the con-nections stay tight -and a straight round hole isbeing drilled.
Add more drill pipe when necessary as the hole isdeepened. As'the string becomes heavier'it willrequire more and more power to lift it.
It is also necessary to add water as the hole isbeing sunk to keep the hole full. The settlingpit may need to be cleaned out to prevent excava-ted material from flowing back into the hole withthe drilling fluid.
When a good water-bearing layer is reached thereis usually a noticable drop in drilling fluid le-vel.
usuallypumping action will produce'roduce Water
and if sufficient quantity of water is produced.drilling can be stopped. Drilling fluid will alsonoticably drop when some dry sand, or gravel for-mations are.reached. In this case it will benecessary to increase the weight (thickness) of the.drilling fluid with additional clay, to help seal
183
172
the hole and prevent fluid loss. '(In this situa-tion the casing could also be driven in to rein-force the walls.) Rice hulls, wheat chaff, cow
}dung or other material can also be added to thefluid but the more and coarser the sealing materi-al used the more difficult it Will be to developand clear up the well later. Excessive use of hullsdr. straw-loaded material may later plug the wellscreen and render the well useless.
Casing - As in most other sinking methods, thecasing can either be installed after the hole issunk or driven down as the hole is sunk.
Casing -thole after it is completed ,mss usuallypossible because drilling mud will tend to rein-force hole walls to prevent them from caving. Re-move the drilling tool string and start the firstsection of casing pipe. It will usually have to be .driven. Use a drive shoe (sharpened coupling)"onthe bottom of the casing to protect it. Add moresections of casing pipe as necessary. After thecasing is driven it will be necessary to remove thematerial that will have accumulated inside the cas-ing. This will not be difficult because the accumu-lated cuttings will be loose.
- Casing the hole while drilling proceeds is onlynecessary where the hole caves in, hampering dril-ling efforts. The casing is driven down as drillingproceeds so that the bottom of the casing is at thesame ley as where the tool is working. Water willthen have to be introduced into the casing pipe,probably by hand because the casing will be stick-ing up above ground level, preventing drilling fluid_from entering the hole. When this happens, theefficiency of the "pumping* process through thedrill pipe may not permit water to be pumped uphigh.enouch above the static water level in thecasing pipe (which will go down as pumped) to comeout of the discharge piece.
The hole is drilled. and cased to the maximum depthpossible, to the bottoM of-the aquifer, or untilthe water-bearing'layer has been penetrated farenough to produce the desired amount of water.
Sink and develop the bottom section of the well.Most often the casing and well point are driveninto aquifer.
NOTE: Where a single well is being sunk, the drill pipecould also be used as the casing if it isIsealed tight toprevent water seepage down around the casing.
4
181
3
Chapter 14
CONSTRUCTION: DRIVEN AND JETTED
tI
A. Introduction
, The driven and jetted sinking methods aredifferent from the others in that they can sinkthe entire casing and well screen into the groundat the same time that the hole is being, excavated.They are used primarily to sink the casing anwell screen into final position in holes that havealready been sunk down to the water table where theaquifer is composed of loose; caving soil. Theycan also be used to sink wells from the groundsurface, although the conditions which would allowthem to be used economically are very specific andrelatively uncommon.
t. Driven
1. The method
Techniques used, in thesinking of driven wells are mostcommonly used not to drive wellpoints and casing from theground surface as the methoddescribes but to drive casingsdown into place and well pointsand attached casing in from thetop of the aquifer. It is amethod that is used primarilyalong with and as a part ofother methods. sionem
173
PIPIE comma:1)1am.41-
F16.14-.1. CONTINUOUS SLOT ORM!. POINT'
This is a single pieceof wire wrapped around andwelded to a supportingframe attached to a steelpoint at one end and tothe connecting pipe atthe other. A cross-section of a bamboovariation'of this typeof.screen.is shown in itE5Figure 15-4.
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174
.
7
. Make use. of these varioustechniques when caving condi-tions prohibit the excavation ofthe complete hole for latercasing.
1
This well sinking method ismost effectively used in con-junction with hand augeringwhere the aquifer is loose sandor gravel and the soil above itis non-caving. Hand-augering ismore effective and faster innon-caving formations throughwhich it would be difficult todrive a well point. Driving is-.then used in the lower water-bearing formation which will notsupport a hand-augered hole.
2. Advantages and Disadvantages
These wells are easilydriven, pulled out and put downelsewhere. In time and moneyexpended to'reach water, drivenwells may be cheapest.
The limitations of a drivenwell include the following:
Supplies are often un-available. Drive points almostalways have to be purchased becauseof the necessary high quality.Metal pipe and pumps areavailable inmost countries, but notoften in rural areas.
Drive points will notpenetrate hard rock and willpenetrate clay only with greatdifficulty.
A drive point can rarelybe driven.deer than 15 meters.
3. Equipment
The following equipment is
F16. 14.2. BRASS -JACKET °Am% POINT
A steel point attachedto a pipe With holes in it,wrapped with a brass meshpreventing small-soilparticles from enteringwith the water.
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required for constructing drivenwells:
Drive well point. These arewell screens with sharp steelpoints on their bottom ends sothat they can be easily poundedinto the ground. Because of the comiva,stresses put on them while they COUPLINGare being driven, drive pointsare invariably made of strongmetal. It is possible to makea well point from a piece ofiron,or steel pipe by cuttingand bending one end into apoint, but commercially manu-factured well points can with-stand much greater stress.Above the pointed tip, allwell points have a length ofwell screen through whichwater will enter the well.(See Figs. 14-1 and 14-2.)
Metal pipe. Metal pipeis attached to the drive pointand driven into the ground'where it will act as the casing.Only metal pipe is' trongenough to withstand the stressesput on it during the driving,process.
Drive couplings. Theseare special couplings in whichpipe ends actually meet.(Questions have come up about,the usefulness of this type ofcoupling because when driven,the connection loosens some-what and cannot be tightenedagain because pipe ends areflush with each otheralready:)' (See Fig. 14-3.)
FIG. 14-3.PI PE COUPLINGS
187
REGULAR COUPLING
a
175
176
Drive cap. This is installedon the pipe being driven to protect it.There are two kinds of drive caps: fe-male drive caps (see Fig. 14-4a) whichscrew directly onto the threads or thetop of the pipe and male drive caps (seeFig. 14-4b.) which screw into a drivecoupling which screws onto the top ofthe pipe.
41 Drive weight. This will be usedto strike drive cap to drive it into theground.
Lifting device. This is an ap-paratus to lift drive weight to then letit fall on drive cap.-,
A plumb bob or level is needed tocheck that the pipe being driven is goingstraight down.
A water lifting device will beneeded for final installation to allowpeople to get water from well.
i 1.1Mom. CAPS 00TOOL. STiz-t kb&E,
18
outsve CAP
OReva
Gt.
Comilsuote SIATDftwa roster
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4. Tools
Here are the major tools that are neecied:
Two pipe wrenches are needed to tighten metalpipti sections together.
A pipe cutter or hack saw is needed to cut themetal pipe off at the desired level when it has beendriven as far as desired.
A metal file is needed to remove rough or sharpedges from the pipe after it is cut. This is notabsolutely necessary, put it is always a handy tool tohave around.
Pipe threader. You will usually need to threadthe metal pipe once it is cut so that you can attach thepump base plate to it. (Most commercial pumps have ascrewed connection to the drop pipe.) Make sure that thepipe threader will work on the short section of pipe thatis sticking outof the ground.
Pipe dop'd or sealer should be put on metal pipethreads to make them watertight before the pipe is screwedinto a coupling.
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5. Driving Methods and Equipment
Following are five.differentmethods and the equipment thatcan be used to drive wells.
Use a sledge hammer tostrike the drive cap directly.The equipment required includesa drive cap and a sledge hammerweighing 5-10 kilograms. Takecare to hit the drive cap squarelybecause glancingblows may damagethe pipe. Only a limited depth ispossible because of the limiteddriving force. This method isphysically very hard. (SeeFig. 14-5.)
Use a sledge to strike adriver which fits over the, ivecap. The equipment required in-cludes the drive cap, a sledgehammer, and a driver. A driverhelps prevent damage from_glancing blows.
Use a weighted driverwhich fits over the drive cap.The driver is lifted and thrownor dropped to strike the drivecap. The equipment required.in-eludes a driver and drive cap.A driver can be fitted withhandles to help in lifting andthrowing, thus permitting twopeople to use it and enablingthem to apply more force.(See Fig. 14-6.)
1 0
PIG. 14-S. SLEDS.HAmmeR WED 1.tDRivE WEt.L
c4\
.
Use a steel driving bar iiALINGattached to a rope which is RINGO
lowered into the pipe to strikedirectly on the driving point.(See Fig. 14-7.)The equipment .re-quired includes a driving bar,rope, tripod, and pulley. Thisis one' of the safest methods ofdriving because it does not weakenthe pipe.
1
FiG.144-7.*EEL DRIVING MR ARRANGEMENT
;
A drive point can beriven down through the
casing by a heavy weightwhich is lifted and droppedonto a reinforced headattached to the top of thedrive point., The rein-forced head shown herealso has two sealingrings to seal it to the -xsing.
This drive point isriven into p13,7e by along heavy bar which,when dropped, strikes theback side of the steel
4 point on the'drive point.A special packing mustthen be wedged intoplace to seal the drivepoint to the casing.
a
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A m1
179
.
i!
180
A 15-20 kg driving weightis used to strike a) a drive capor b) a drive clamp attached tothe pipe. The equipment requiredincludes ja.Ndrive cap or driveclamp, au'driving weight, rope,pulley(s), and a tripod.These are all variations of thebasic idea that a guided heavyweight strikes an instrument onthe pipe to drive it,.
a. The driving weightcan have a bar extending downfrom it which slides through ahole in the drive cap. (SeeFig. 14-8a.)
b. The driving weightcan slide up and down the metalpipe to strike a set of driveclamps attached to pipe. (SeeFig. 14-8b.)
FIG. 04-9. HEAVYDItiviNe WEIGHTS
6. The Sinking Process: From the Water Table
Here is a de, pled description of the sinking processwhere a hole has already been sunk to the top of an aquiferfrom which it is desirable to ?raw water:
Before removing the in5.tial holesinking tools from well., it wouldbe useful if possible tc try to sinkthe tools some distance into theaquifer to get an idea how deep it is.Only attempt this if your initial
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181.
sinking tools are such that once sunkinto the aquifer you are able removethem.
Arrange and set up all tools, equipment andsupplies. Make an effort to maintain anorderly well site as you proceed, to ensure.the safety and convenience of further work.
Attach the well point and extensions ifneeded, to the first pipe length. Pipe jointsmust be made up carefully both to insure awatertight joint and to prevent thread break-age. Attach a coupling to the top end of thefirst pipe length. Attach a pipe clamp justbelow the coupling on the top end of firstpipe length. Lower the assembled pipe andscreen into the hole, setting both ends ofthe pipe clamp on raised flat surfaces, such aswooden blocks on either side of the hole .
Screw the coupling into one end of anotherpipe section and attach another pipe clampbelow it as was done for first pipe section.
Screw this second pipe section into thecoupling on top of first pipe section now in thehole.
Taking the weight of the pipe string on thepipe clamp on top of the second pipe section,lift the pipe string up just enough so thatthe first pipe clamp is not resting on theblocks.
Remove the first pipe clamp and lower thepipe string until the second pipe clamp restson the blocks.
Continue adding pipe sections and loweringthe pipe string until the well point restson the bottom of the previously sunk hole.
Plumb the pipe and drive it into the aquifer.Plumbing the pipe will be much easier than ifdriving had been started from the ground sur-face, but you must still be 'careful that thepipe string is being sunk plumb. To tightenthe joint,give. the uppermost pipe a fractionof a turn with each glow until it is permanentlyset.
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Once you have driven the pipe as far as you canor want to into the water layer, you will needto develop the well. (See p. 202.)
Before the pump is installed and any surfaceplatform'work is done, the gap between thepipe and the sides of the hole must be filled.This can,be done with any material pulled outof the well up to a:point three meters belowthe ground surface. The top three metersshould be sealed with either mortar or puddiledclay to prevent surface contamination fromentering the water source.
7. The Sinking Piocess: From the Ground Surface
Driving the entire well from the ground surface ismost commonly used for extracting water from sands, espe-cially those underlying beds of intermittent streams, andmaking use of the natural filtering properties of sandybeds of perennial rivers. Here is a detailed descriptionof the major activities involved in sinking from theground surface:
Arrange and set up all tools, equipment and supplies.Clear the area immediately around the well site of all un-necessary tools. If a tripod is to be used, set it up andlocate it so that the weight will be centered directly over11631e. *(It is easier to keep the pipe perfectly plumb ifthe weight is properly centered.)
Place the well point in place and begin to drive it(p. 178). It is a good idea to dig or auger a shallow(50-80 cm) nole in which to start the well point. Especiallyat the beginning, pipe plumb must be frequently,checked.Later, when several lengths of pipe have been sunk, the wholelength will be supported by the ground and will require in-frequent checks of plumb. A support for the upper end ofthe pipe will initially help to hold it plumb and may laterassist in aligning new sections of pipe so they can bescrewed intc couplings.
Drive the pipe and a.dd more pipe as needed. When thepipe has been driven so far that driving can no longer beaccomplished, add another section of pipe.
- Remove the drive cap and screw a couplingin its place. Install a drive cap on topof the new pipe section. Screw the newpipe section into the coupling on top ofthe pipe set in ground. (See Fig. 14-9.)
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DRovECApWhere drive clamps are being used insteadof a drive cap, a slightly different pro-cedure is followed. To begin driving placeclamps no more than 50 cm above ground cnpipe for at the bottom of a pipe sectionif the well screen sticks above the groundmore than 50 cm). It is easier to keep the
New pipes plumb if the point of impact is closerto the grourid surface. When the screen and
sec:nom pipe have been driven down to a point wherethe drive clamps almost touch the groundsurface, move the clamps up 30 to 50 cm.Reset them on the pipe and drive them downagain. As more and more pipe is driven intothe ground and the danger of driving the pipestring out of plumb decreases, the clamps canbe moved. When the driving weight can nolonger be raised far enough to provide suf-ficient striking force to drive the pipestring, a new length of pipe will need to beadded. Screw a coupling onto the top of the
Courum pipe being driven and screw a new section ofpipe into the top of the coupling. Make surethe weight can be raised above the coupling
Ple.14-9.before the coupling is screwed on the pipe.
UnALLOUG NEW You may want to slip new pipe through theftoricw driving weight before attaching it to the
coupling.
To determine whether water has been reached,the plumb line can be lowered into the pipe.If the line comes up wet, you have hit water..By comparing the depth the line reaches to'the known depth of the pipe, you can also getan idea about whether earth or sand has toany significant degree entered the screen.
You can also learn what kind of soil or for-mation you are, driving through by the reactionsof the pipe anti driving weight when the pipeis struck by the weight.
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RELATION; OF DRIVING TO SOIL CONDITIONS
Type offormation
Drivingconditions
Rate ofdescent
Soundof blow
Rebound Resistance torotation
Soft moist clay Easy driving Rapid Dull None Slight but continuous
"Tough hardened clay Difficult driving Slow but steady None 7requent rebounding Considerable
Fine sand Difficult driving Varied None Frequent rebounding Slight " c'
Coarse sand Easy driving Unsteady irregular Dull None Ra4tion is easy and
(especially whensaturated with
penetration forsuccessive blows
, accompanied by agritty sound
'water).
Gravel Easy driving Unsteady irregularpenetration forsuccessive blows
Dull None Rotation is irregularand accompanied bya gritty sound
Boulder and rock Almost impossible
%
Little or none Loud Sometimes of both I Dependent on type of
hammer and pipe formation previous-ly passed throughby pipe
(From: Well Drilling Operations, TMS-297/AFM 85-23, Army/Air Force Technical Manual, p.24.)
196 197
1
185
e When you reach water, drive the pipe as far intothe water layer as, possible. The bottom of the well pointshould just touch the top,of the impermeable layer on top ofwhich the water sits. To be useful and not put too muchstress on the well screen, the aquifer should be deeper thanthe height of the well screen. (See Well Screens, p. 193.)If you can driverthe'point six or seven meters into an aquiferwithout reaching the bottom, you have assured a very largesupply of water and there may be no point in driving any further.
If you don't reach water or have lor some reasondriven beyond the water bearing formation, you may want tolift the.pipe string just a little or remove it completely fromthe hole. 1) You can sometimes lever the pipe up by usingpipe clamps and crowbar or a stout stick. (See Fig. 14-10.)2) You can use two jacks and pipe. clamps to jack it out. (SeeFig. 14-11.) After it has been raised a few feet, the rest can bedone by hand. Rotating the pipe clockwise will assist its removal.
Once you have driven the pipe as far as you can or wantto into the water layer, you will need to develop the well.(See p. 202.) You may wish to prepare the top end of thepipe for connection or use with the particular water liftingdevice you are using before developing till well.
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4.
186
C. Jetted
1. The method
Jetted wells are sunk through the action of a fluidunder pressure directed to the bottom of the hole toloosen soil particles and carry them to the surface.
Variations of this technique have been used in manydifferent wells construction situations. A major use isto wash the casing into a loose or slightly caving for-matioby pumping water down through the casing'and outthe open bottom of the casing or well screen. Wells con-tinue to be jetted from the ground surface only in areaswhere rock is not likely to be found and the largerdrilling equipment is not available or too expensive.
In jetted techniques, drilling fluid is pumped downthrough the hollow drill rod and out through a hole inthe jetting bit. (See Fig. 11-2g.) The faster and morepowerful the spray, the better cutting action it will have.After the fluid has been directed at the bottom of the'hole, it flows back up the hole carrying with it thesoil that has loosened from the bottom of the hole.Once the fluid reaches the top of the hole, it is channeled through a small ditch into a large settling pit.The fluid stands in the settling pit long enough toallow drill cuttings to settle out of the fluid, beforeit is pumped back down the drill rod.
The volume of the settling pit should be at least threetimes the volume of the hole being drilled. .It should berelatively shallow (0.7-1.0 meter is usually sufficient)and about twice as long in the direction of flow, as it iswide and deep. Por examplee a settling pit two meterslong, one meter wide and one meter deep could be used whendrilling a 10 cmcdiameter well 85 meters, deep.
The drilling fluid is usually a mixture of clay andwater. The clay is needed to make a fluid of such con-sistency that it will tend to reinforce the hole walls byforming a kind of "mud cake" along them. Fluid with toomuch clay and accumulated drill cuttings will be thickand difficult to pump. The thickness of the fluid mayneed to be adjusted during drilling by adding more waterand/or removing some of the accumulated cuttings fromthe settling pit. Water alone will often act effec-tively as a drilling fluid, especially as it thickensafter accumulating some of the finer drill cuttings.
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2. Advantages and Disadvantages
Here are the major advantages of using this technique:
Loose, caving formations are easily penetrated.
Few people are needed to operate the eqUipmer.t.
The major disadvantages are:
The method requires more special equipment thanothers.
A large quantity of water is required for drilling.
Hard clay and boulders may slow and stop drilling.
3. Equipment
Jetting bit: A shortened percussion type bit withwater passages is helpful in loosening material atbottom of the hole. (See Fig. 14-12.)
'WATER.; UNDER
PRESSURE COMESour HOLAC IDLOOSEN AMR RENove
4.- SOIL.
Curr ING EDGE
FIG. 12. SETT$MG 'BITS
Drill rod: Hollow drill rod is necessary to trans-. mit the drilling fluid to the bottom of the hole.The'smaller the diameter of the rod the lighter itwill'be.
Swivel hose connection to top of drill rod: It isnot absolutely necessary to have a swivel connectionalthough some type of connection is needed through
'U
187 .%
188
&IL
I
A
which fluid can be pumped into and down the drillrod. A swivel connection allows the tool string to
' be turned during jetting, thus helping to assure astraight, plumb hole and helping to loosen soil atthe bottom of the hole.
Flexible hose: This is needed to connect thepump with the connection on the top of the drillrod, allowinv fluid to be pumped through the drillrod.' A length is also needed between thepump andthe setting pit from where the fluid is pumped
Pump: A pump is needed to move the drilling fluidthrough the drill rod and out the bit, where itcan loosen and remove soil from the bottom of thehole. Large capacity hand pumps have been success-fully used although motor pumps are easier and pro-vide better jetting action. Diaphragm pump areprobably best suited to this kind of work becauseof their ability to move relatively large soilparticles without damaging the pump.
Tripod or other overhead support: Some type ofoverhead support is needed from which the toolstring can be suspended and lifted or lowered whennecessary.
Hand tools: A number of hand tools can be used toconnect and disconnect hoses and drill rod whennecessary. Pipe wrenches, screwdrivers, and regularwrenches may be particularly handy, although shovels,rope and pulley will also be needed.
4. Sinking Process
Arrange and set up all tools, equipment and supplies.Leave the area around the well clear of materialsthat do not have to be there. Set up the overheadtool string support and locate it directly over theproposed site. (See Fig.14-13.)
Dig out a settling pit as needed for thethole diameterand expected depth. A shallow channel should connectthe settling pit and the hole so thatidrilling fluidcoming up out of the hole will flow into the sett1ingpit.
Statt the hole by digging as far as possible witha shovel or post-hole digger.
Fill the settling pit and hole with drilling fluid orwater.
FIG. ILI -13.
TETT' PG EG)UsPME4-Sr
Assemble the tool string and suspend it from theoverhead support. Attach the hoses between thedrill rod and the pump and between the pump andthe settling pit.
'do Start the pump to begin the drilling operation.Begin by pumping slowly to allow time to care-fully plumb the tool string as it sinks the firstmeter or two. As the drilling proceeds, morepressure may be necessary to get the needed cuttingaction with the heavier drilling fluid. A slightup and down percussion action may help. to speed thedrilling.
202
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190
r
ff
Add more drill rod when necessdry as the hole isdeepenel. The fluid circulation will have to bestopped to permit another length of drill rod tobe addd\into.the tool string. 'It may then bedifficult to get the fluid circulgtion startedagain because the heavier soil particlesterrd to set-tle in the hole, clogging the bottom: Where theaquifer depth is known, it is possible to avoid t44?problem by assembling the entire casing and openbottom well screen above the hole, supported by alarge scaffolding, o that it can all be sunk in
-.one continuous operation., 6
It may be necessary to add more fluid and cleansome of the accumulated cuttings:from the settling--pit at some point during the drilling process sothat drilling can proceed effectively.
When a good water-bearing layer is reached, thereis usually a noticable drop in the drilling fluidlevel and-often a significant increase in the speedwith which the hole is being sunk. The hole shouldbe sunk as far as possible into the aquifer.
Because the jetting operation tehds to reinforcethe hole walls with the drilling fluid, it may be,possible to pull the drilling tools completely outof the well and then set the assembled casing andwell screen into the bottom of the hole. Keep anaccurate record of the depths at which water was
. first reached and where the drilling was stopped sothat you can determine how much well screen shouldbe installed and whether the easing and well screenhave been lowered to the actual bottom of 'the hole:If the complete casing cannot be lowered intoplace it will have to be driven or washed down.You will want to jet the well to_its final depth.It is possible that the-well may begin to cave inas the tools are being pulled out, but if it hasbeen jetted' to the final depth, it will be mucheasier to drive or wash the casing and well screeninto place than if the well has not been completelysunk.
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e r
Chapter 15/
THE BOTTOM SECTION
A. Introduction
, ..
191
..he bottom 'section of a small diameter well usuallyconsists of. part of the casing pipe and a well screenwhich acts as the int&ze section. (See Fig: B.) Inorder for the well screen to fundtion effectively, theaquifer material that surrounds' the screen must be re-arranged to allow as much water as possible to flowthrough it. This rearrangin% process is known as develop-ment.
For wells that are sunk into solid rock, the intakesection could simply be the open bottom of the casingpipe but this is not a normal occurrence in relatively
...-shallow wells.
The intake section or well screen is a continuationof the casing in that it reinforces the walls to keep thehole open. Simple screens can be made by making holes inthe casing. However, commercially available well screens:Jay incorpiate useful features that cannot be obtainedfrom homemade screens. (See Well Screen, p. 193.)
. B. 'Considerations in the Construction of the Bottom Section
)
Thereare several considerations to bear in mindbefore beginning work on the bottom section:
I
choosing the appropriate screen. One must consi-der the cost,. material, local manufacture, open-ing size, diameter, length, and strength
properly placing the screen in the water bearing.;layer so that it can produce as much water asnecessary;
developing the aquifer material surrounding thescreen to obtain the most efficient production.
204
1
192
.
e-
e
p
C. Construction Procedure Outline
In general, there are only two steps involved in theconstruction of the bottom section:
setting the screen in the desired place in thehole;
developing the well.
Both of these stepsmust be done carefully and pre-cisely in order to make full use of the rest of the workthat has gone and will go into building the well. Theamount of water that can be drawn from the well is almost
. completely controlled by how this section is built. .Hereare the activities involved in the two steps:
1. Set the screen in its designated place in the hole.Two general procedures can be followed, dependingon the size of the well screen in relation to thecasing pipe.
a. A pipe-size screen i attached directly to thebottom of the casing pipe and lowered'into placein the hole. Usually the hole has been at leastpartially sunk and the screen and casing havepenetrated to the desired depth 1y being drivenor washed down. Where drilling fluid has beenused in the sinking procets, it may reinforcethe hole enough to prevent its caving, thus perl.mitting the screen and casing to be simply low-ered into place.
b. A telescoping-size screen is lowered into placethrough casing.
1) The most popular professional method is forthe hole to be drilled to the desired depthand cased. The screen is then set in placeon the bottom of the hole inside the casingand then the casing is pulled up to exposethe screen. A special packing piece is nextwedged into place between the screen and thecasing'to prevent the entry of unwantedaquifer material.
,,do'''i
i
2) The screen can also be washed down into theaquifer froM the.bottom of the permanentlypraced:.casing./
05,
,,
4
.NOTE: Telescoping screens into place may be difficultwith locally made materials because of the difficulty ofsealing the screen to the casing pipe once both have beenset in their permanent places. Normally this is donewith a special packing piece that is wedged into place.
2. Develop the Well
This is the process of using any one of a number oftools or methods to quickly move water in and out ofthe well screen, thereby removing the fine particlesfrom the aquifer in the vicinity of the screen. Itusually requires an average of 6 to 10 hours to com-plete.
D. Materials and Equipment
L.
The following types of materials and'equipment willhe required for construction of the bottom section:
Sinking equipment: The different sinking methodsand ground conditions in which they are appropri-ate have been covered in detail in "Middle Section,Sinking Methods." Because people do not have towork in this kind of well in order to sink it, --
sinking methods need not change between the middleand bottom sections. The only difference betweenthe two is tnat ground conditions beneath thewater table are liable to be loose and caving.
well screen intake section: This refers to anyportion of the casing that has holes in it whichare intended to allow water to enter the well.(See Otction E on Well Screens, below.)
Developing the well: For the equipment necessaryto develop the well, see the section on Develop-
,. ment, p. 202.
Well Screens
A well screen is a special section of casing withholes in it which is placed in the water bearing layer to'allow water to enter the well. It should be strong enough'
206
193
194
to withstand stress while it is being installed as wellas caving pressure in the hole. It should be made ofmaterial appropriate to the chemical and bacteriologicalcharacteristics of the local ground water, neither easilycorroding nor rotting. The greater the open area of holescontained in the screen, the more efficiently it willwork by' letting in more water.
Well screens can eitherbe commercially or locallymade. The cost of com-mercially made screens andthe time required for deliveryto the well site usually makethem unsuitable for isolatedwells whose object is tosupply only a few thousandliters of water per dayto the local inhabitants.However, commerciallymanufactured screens offeradvantages in quality.They can often be moreeasily installed andprovide more water ofbetter quality for alonger time than locallymade screens. (See Fig.15-1.)
Locally made screens areusually produced from thecasing materials that will beused in the normal small dia-meter well sinking operation.There are some limitations%;oncerninq which materialscan be used in various kinds of
207
LOUVER.TYPO-
GoNTINuoUSSt.oT
F16.15-1 MANUFACTURED SCEEENS
ground formations, b t anappropriate solutio can almostalways be found. T e cost ofa locally made screen willsimply be the cost of puttingholes in a section of casingwhich has already been pur-chased for installa- .
tion in the well. Perhaps theirbiggest disadvantage is thedifficulty of producing thesmall opening sizes which maybe necessary in fine sands.(See Fig. 15-2.)
A new method has beendeveloped which would enablethe local manufacture ofcontinuous slot well screensout of specially made plasticpipe. This pipe is extrudedto prOvide lengthwise reinforcingridges along its inside surface.A lathe equipped with a highspeed grinder on which thegrinding wheel is replaced bya small circular saw thedesired slot width is used tocut a continuous slot.For more information seethe article by Sternberg(Sternberg 1978) cited in thebibliography.
Manufacturers will pro-vide well screen informationon request. However, becauseshipping and cost considera-tions may prohibit the use ofcommercially produced wellscreen, the remainder of thediscussion will relate tolocally producable screens.
F. Design
195.
S
FICA. 15 - . LOCALLY 14A0aSLOTTED ?LAST' c, PIPE
Designing the bottom section of'a small diameterwell involves deciding 1) what the screen will be made of,2) how long it will be, 3) what the diameter of thescreen should be, 4) how big the openings are, 5) theopening shape, 6) the arrangement of the openings, and7) exactly where this will be placed in the water-bearing formation.
In sinking with locally available hand poweredequipment, certain limitations will influence how youdesign the bottom section.
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-196
1. Screen Material
Materials that are suit-able for use as casing canall be modified ,for use aswell screens by making holes.in them.
Commonly used materialssuch as steel or galvanizedsteel are suitable and oftenavailable, and can be driveninto place where necessary:-The quality of the water shouldbe carefully checked for thepossibility of corrosion orincrustation. Note that gal-vanized steel is only coatedon the outside, so that onceholes are made in it it isnolonger protected from rusting.This is a serious considerationbecause well life spans havebeen as little as three monthsin areas where steel casing wasused in highly corrosive water.
Plastic such as PVCand ABS is very useful forscreen production where driv-ing is not necessary. Or,alternately, the casing andthe screen can be bailed downunder constant downward pres-sure.- Holes are asily .cut-into plastic, the material isso lightweight that it may bepossible to lower it by hand.It will not corrode and isusually significantly cheaperthan steel.
Clay is another pos-sibility.. Clay pipe locallymade and fired should be madewith socket and joint fittingsto enable certain location andprevent unwanted surface waterentry. They are most success-fully used where the hole iscompleted all the way Lo thebottom before the screen ariacasing installation.(See Fig. 15-3.)
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P16.15-3.CA-A1, Pi PaGAS MI6 AMP SGRENNI
Mh
Wood has been used insome temporary. wells. Inthese cases, long straightsections of tree trunks havebeen used for casing and forscreens`. If you must forsome reason use wood, cut thescreen openings lengthwisewith the grain for greaterstrength.
Bamboo, where it isavailable, has been used forcasing and screens in wellswhose life expectancy is onlya few years. With the innersections punched out, it canbe made into a servicable.pipe.Screens can be made n two ways.Long pieces of bamboo can besplit lengthwise, arranged aroundcircular spacers and wrapped withrope, (See Fig. 15.4) or narrowlengthwise slits can be cut witha circular saw in a sold pieceof bamboo. As the bamboo getswet, these slits will betomesmaller, an advantage in awell screen.
All of the materialsmentioned above have some limi-tation which makes them inappro-priate in certain situations.Stgl -..is easily corroded: -Plasticwill deform under too much stress.Clay is easily broken. Bamboo andwood will rot and taint the water.some materials, such as stainlesssteel, can be used in almost anysituation but they are usuallyexpensive.
2. Screen Length
ll
FIG. 15-4.8AMSOO
s cote eAs
Most small capacity well screens are between oneand three meters long. The determining factor is theamount of open area the area of all the holes added to-gether) that will permit water to enter. Two or threemeters of locally made well screen will usually be suf-ficient while one meter of commercially produced con-tinuous slot well screen is more than sufficient for usewith a, hand pump.
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197
To check whether your screen is long enough:
Determine the total amount of hole space in thescreen. Assuming the holes are all approximatelythe same size and shape, you can figure out thearea of.one hole and multiply that figure by thenumber of holes.
Next,estimate the maximum short term demand forwater. To do that, answer the question: How fastcan someone possibly removeswater'f;om the well?That will be expressed in liters perNminute or.gallons per minute.
Divide the firat figure by the second figure.The screen should have at least 5.5 cm2 for eachliter of water per minute, or 3.23 in2 for eachgallon per minute, that can be taken from thewell. These are absolute minimum figures. Agreater area will be much better for well screensmade of locally available materials.
3. Screen Diameter
When the screen is made of the same material as thecasing, it will be the same diameter as the casing. It issimply a normal section of casing with hOlei.
It would be possible to make the screen a larger orsmaller diameter than the casing and still firmly attachit to the casing by using reducing couplings or bushings,but there appears to be no advantage in doing so. If in-creasing the diameter would increase the amount of waterthat would flow into the'well, it might be useful, but the
--increase in water flow with all increased diameter_ is sosmall as to make it insignificant.
4. Opening.Size
This is probably the most difficult technical aspectto deal with because it is often just not possible tomake your own screen openings as small as they should be.
Ideally, the openings should be big enough to allowthe smaller particles of the surrounding soil through andyet hold out the larger soil particles.
211
5. Opening Shape
Generally the mosteffective opening shape is along thin slit, easily madewith a saw. This providesthe greatest amount of openarea in a small spa:be and is
\ not easily. clogged. Small\round or square holes., on theether hand, are more easilyclogged and require moreconstruction time. Depth andcross-sectional shape can alsobe itrtant but can only beeffectively dealt with incommerally manufacturedscreens (See Fig. 15-5.)
6. Arrangement ofOpenings
Make anq arrange thescreen holes \both to main-tain material\strength andalso to permit the greatestflow of water.
PUNCTURED METALCASING USED AS wal.t. scer.40
7. Location\of the Screen in a Water Bearing Formation
Ideally, the screen should rest on the bottom of thewater bearing layers and extend up from ther-6:- Often,however, it is not possible to sink the well that deepwith hand- powered equipment-:---In that- case; -the screen-should be placed as far into the water bearing layer aspossible. Some well Construction specialists suggest that6 to 7 meters is deep enough beneath the water table toassure adequate.year-round yield. However, this willvary depending on several factors that are not easy toevaluate, such as aquifer permeability and surface recharge.(See Glossary.)
In some cases, the allifer will be made up of layers ofdifferent kinds of soil. If sufficiently deep into theaquifer, the coarsestilayer\will produce the most water and,therefore, that should be where the screen is set.
G. Installation of Well Screen
There are two different general techniques forsetting the screen in place, in the hole. In the first,the screen is attached tothe bottom of the casing and
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200
lowered into place with casing. In the second, the screenis telescoped through a casing that is already in place.Telescoping screens into place is a difficult procedureto complete successfully with only locally availablematerials: (See Fig. 15-6.)
Here are four possible approaches to setting a wellscreen and casing in place.
1. The casing and the screen can be lowered into a holethat is already sunk to the finish depth in theaquifer. This is only possible where the hole willstay open long enough to allow the screen and casingto be lowered into place, i.e., non - caving formationsor where drilling mud has been used. In cases whereminor caving will occur, it may be possible to drillthe hole a little deeper than necessary so that.cavingmaterial will accumulate below the level of the screenand not interfere with its installation. Where thiswill not work, another method of screen and casinginstallation must be used. Any appropriate casingmaterial can be used because no particular strain isput on,the casing while lowering it into place. Withsections of clay pipe, for example, where one endfits inside the end of the next sections, the sectionscan even be lowered and placed one at a time.(See Fig.= 15-7.)
2. The casing and the bottom screen can be sunk into theirfinal position'by operating a bailer inside the casingand screen to remove soil and allow the casing to sink.This,method can be used to loosen caving soils whichwill not permit the.hole to remain open. It is alsoemployed in harder clay type soils although it willquldkiy-reAch.a-poiht.where-the-da-gin4-WirI-riti-Idifigersink because of too much friction with the surroundingground material. It is useful where the casing ismade of a material such as plastic that cannot bedriven but can be helped along by adding weight tothe top of the casing. When the desired depth isreached, the open screen bottom must be plugged.(See Fig. 15-8.)
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3. The casing and thescreen can be driven into finalposition by any of the previouslyoutlined driving techniques(See p. 178.) This method canbe used in any unconsolidatedformation whether it is caving ornot, but is more useful in cavingformations. In this method, anopen bottom screen is alternatelydriven and bailed out as in theprevious. technique, but becausethe casing can be driven, it isnot as likely to become jammedin the hole jn harder layers. Ahard casing and screening materialmust be used that will not easilydeform when struck. When thedesired depth is reached, theopen screen bottom must be plugged.(See Fig. 15-9.)
4. Where pumps are available,the casing andscreen may be washed inby pumping wader down throughthe casing and out the bottom ofthe screen where it will pick upand carry soil particles back upto the surface between the casingand the hole walls. Some water willgo out the screen openings but mostwill go out the bottom. This methodcan be used only where the casing isa continuous waterproof string.(See Fig. 15-10.)
H. Development
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1. Basic Features
To develop a well is to remove the very small soilparticles from the water - bearing formation-which immediate-ly surrounds the well screen. This increases the yield ofthe well and forms a graded filter around the screen. Thefilter prevents the entry of small soil particles whichcould eventually clog the well or damage the pumpingmechanism.
A well can be developed once the screen and casingare in their permanent positions in the hole. By usingthe tools and methods described below, water is forced in
216
203
and out of holes in the well screen. This in and out watermotion tends to loosen the adjacent soil and carry. withit through the screen openings all particles which aresmall enough to fit through them. Only the largest soilparticles are left, deposited next to the outside of thescreen. Farther from the screen, the predominant soilparticles become smaller and smaller. (See Fig.10-5.)When development-is complete, a graded soil filter surroundsthe screen, which both prevents the entry of small'soilparticles into the well and allows the water to flow asfreely as possible toward the screen. This is possiblebecause there are gradually more open spaces for the waterto flow through as it gets closer to the. screen.
The time required for development depends on thenature of the water bearing layer, the opening size ofthe well screen as.related to aquifer particle sizetandthe type of equipment and degree of development desired.
2. Methods
a. Overpumping
This is probably the simplest method of removingthenfines"from the water-bearing formations. Thewell is pumped at a faster rate than normal until nomore fine aquifer particles are removed with the water.While this does, not really agitate the soil enough tocreate a real filter around the screen, overpumpingis a useful technique. If a well will support over-pumping, it should certainly operate at a capacityless than that with no problems.
It is strongly recommended that if,a well'is tobe developed by overpumping, a'separate pump shouldbe used for the development-process. Fine soilparticles to be removed during development can causean abnormally high rate of wear on the pump resultingin early pump failure.
b. Backwashial9
This, too, is a relatively simple method 'of de-velopment which requires a water lifting device anda container in which water can be stored and thenfrom which it will be allowed to flow easily back intothe well. This involves pumping water to the surfaceand then letting it flow back into the well many times.The process prolAdes a rack and forth motion that canmore effectively develop a water-bearing formationthan overpumping. However, in many cases,' the motionmay not be strong enough to obtain maximum development.
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Backwashing is more difficult to accomplish thanmight be expected. The water lifting device used to'pull water to the surface may have to be completelyremoved from the hole to permit water to flow backdown. Water will not flow back down a pump riser pipebecause there is a foot valve at the bottom designedto prevent that. It must then flow down between thepump pipe and the casing. An exception is a turbinepump which will pump water without a foot valve, butthese are expensive. Note, however, that even a-little backwashing is better than none.
c. Surging
Surging is the most common_method of well develop-ment. It involves forcefully moving water back andforth, in and out of the well screen, to remove thefine soil particles. The surging action is causedby a tool being lowered into the well casing to somedepth beneath the water level where it is then movedup and down, causing the water to move back and forth.The closer the tool seals to the well casing, themore forceful the surging action can be.
There are a variety of tools that have been usedto give this surging action.
Bailer: If an open bottom screen is sunk intothe water-bearing layer by bailing, the bailer'sup and down motion also causes a surging actionwhich will develop the area around the screen.The heavier the baiter is, the better it is,because it then has more force to push waterback out of the screen. A bailer may operatemore effectively for this purpose if it hasaccumulated soil, making it heavier and in somecases preventing water from coming,up throughthe casing. A bailer can also be used todevelop a formation once the, well screen isalready in place. Because baiters cannot formtight seals with the inside casing walls, theydo not usually develop a formation as well as asurge block. (See below.)
'Swab: A swab isl,simply a series of rags care-fully tied around a pipe and built up untilthey will fill the casing pipe. This is thenlowered down into the water and operated in muchthe same way as a bailer.
217
.
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,
'7
Surge block: A surge block is basically a flatseal that closely fits the casing interior and"is operated like a plunger beneath the water 4
level. Becatse'it seals closely to the casing,it has a very direct positive action on themovement in the well. There are two basic typesof surge plungers, solid and valve type.- Bothcan be easily made from fairly readily availablelocal materials. (See Fig. 15-11.)
FoG.15-$1.sowt, Type. surto& TLIANSFrit
- 205
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'A valve type surge plunger ismade the same way as a solid typeplunger but wish two additions,Before assembly, several holes aredrilled through the wood pieces and .
the sealing rings in such a way thatthey will all line up when theplunger is assembled. During theassembly a flexible' sealing flap,with the same diameter as the wood,is added between the top woodpiece and the metal washer. Thisacts as a flap valve over the holesthat have been drilled through therest of the plunger. (See Fig. 15-12.)
The action on the down strokeof a valve type plunger is milderthan that of a solid plunger becausesome water will pass up throughthe holes in the plunger and maypossibly be pumped to the surfaceby the up and down plunger actionif the plunger seals well with thecasing.
Surging Operation
.Arrange and install necessary tools 4nd equip-ment in an appropriate place. A plunger orswab will need to be beneath the water level.
o Apply an up and down motion, repeatedly raisingand dropping the plunger 60 to 100 cm. Theplunger should drop rapidly on the downstrokeeither as a result of being forced down orbecause of the weight of the connecting shaft.
Surge for several minutes, then remove theplunger and use a bailer or sandpump to removethe accumulated fine particles. Be careful notto surge too long. If you do,',the screen willfill up with so much fine material that only ,
the upper portion of the screen,can be developed.
219
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A solid type surge plunger can be made from the samematerials. Leave out the flexible sealing flap and donot drill holes through the woodemports and sealing rings.
440
207
208
e 'Continue surging and bailing until no morefine particles are removed with the water.The up and down motion of the plunger shouldat first be relatively slow and continue that 1
way until the amount of fine material drawninto the well' begins to decrease. The speedshould thed begradually increased and eachsurging session should become longer andlonger.
Exactly how long and how fast surging takes place willdepend on how much material is being brought into thewell, the ease with which it is brought up, and thekind of equipment you have.
Adding some kind of weight to the plunger or theconnecting shaft will probably make jst easier to workfor a longer period of time, especially if you canuse a rope and pulley to lift and then drop it inthe well. If you can add some weight it is best toadd it as close above the plunger as possible.
NOTE: It is a good idea to make the operating shaftlong enough so that if it is dropped down into thewell some of the shaft will still stick up above thecasing to help in its removal.
22i
APPENDICES
222
0
0.
209
Appendix I
CONVERSION FACTORS AND TABLES
Length
Inch (in.) = 2.54 am.Foot (ft) = 12 in. = 30.48 cmYard (yd) = 3 ft = 0.9144 mMile = 5280 ft = 1.609 kmCentimeter (cm) = 0.3937 in. = 0.01 mMetei (m) = 100 cm = 3.281 ft = 1.0936 ydKilometer (km) = 1000 m = 0.6214 mile
Area
Square inch (sq. in) = 6.452 cm2Square foot (sq. ft) = 144 sq. in. = 929.0 cm
2
Acre (43 560 sq. ft.) = 0.4047 haSquare mile (sq. = 640 acres = 2.590 km2Squake centimeter- Acm4) = 0.155 sq. inSquare meter (m2) = 10 000 cm2 = 10.764 sq. ftHectare (ha) = 10 000 m2 = 2.471 acresSquare kilometer (km2) = 100 ha = 0.3861 sq. mile
Volume and Capacity_
Cubic inch (cu. in.) = 16.387 cm3 or mlCubic foot (cu. ft) = 1729 Cu. in. = 28.316 1 = 6.229 Imp.
gal = 7.481 US galCubic yard (cu. yd) = 27 cu. ft = 0.7646 m3Fluid ounce (British)(fl. oz.) = 28.41 ml
(US)(US fl. oz.) = 29.57 mlPint (British) (pt) = 20 fl. oz. = 0.5682 1
(US)(US pt) = 16 US fl. oz. = 0.4732 1Quart (British) (qt) = 2 pt = 1.1365 1
( US)(US qt) = 2 US pt = '0.9463 1Imperial gallon (British)(Imp. gal.) = 277.42 cu.US gal. = 4.546 1
US gallon (US gal.) = 231.0 cu. in. = 0.8327 Imp.Acre-foot = 1233.5 m3Cubic centermeter(cm3) = 0.999972 ml =0.06102 cu.
in. =
gal =
in.
1.20
3.785 1
Mililiter (ml) = 1.000028 cm3 = 0.03520 fl. oz.Liter (1) = 1000 ml = 0.2200 Imp. gal. = 0.2642 US gal.
= 0.035316 cu. ftCubic meter (m3) = 1000.028 1 = 1.3080 cu. yd = 220.0 Imp. gal -
= 264.2 US gal = 0.0008107 acre-foot
223
"210
Weight
Grain .3. 0.06480 gOunce (oz.) = 437.5 grains = 28.35 gPound (lb.) = 16 oz. = 0.45359 kgStone = 14 lb. = 6.350 kgHundredweight (cwt) (British) =.112 lb. = 50.802 kg
(Us) = 100 lb. = 45.359 kg(Long) ton (British) = 2240 lb. = 1.01605 tShort ton (US) = 2000 lb. = (90718 tGram (g) = 15.432 grainsKilogram (kg) = 1000 g = 2.2046 lb.Metric ton (t) = 1000 kg = 0.9842 long ton = 1.1023 short tonsft3 water = 62.4 lbs.1 liter water = 1 kg
Pressure
Pound per square inch (R.s.i.) = 0.06805 atm. =,0.07031 kg/cm2= 0.7031 m of water = 2.307 ft of water
Standard atmosphere (atm.) = 14.696 p.s.i. = 1.0332 kg/c.1Metric atmosphere (kg/cm2) = 14.223 p.s.i. = 0.9678 atm.
Flow rate
Cubic foot per second (cu. ft/sec) = 0.5382 mgd(Imp.) =0.6463 mgd(US)
Cubic foot per minute (du.ft/min) = 0.4719 1/secImperial gallon per minute (Igpm) = 0.7577 1/sec = 0.2728 m3/hUS gallon per minute (9pm) = 0.06309 1/sec = 0.2271 m3/hMillion gallons per day (mgd)(Imperial) = 52.615 1/sec
(US) = 43.811 1/secLiter per second (1/sec) = 3.001 m3/h = 13.20 Igpm = 15.85 gpm= 0.019006 mgd (Imp.) = 0.022825 mgd (US)
Cubic meter per hour (m3/h) = 0.2778 1/sec = 3.666 Igpm= .4.403 gpm
Filtration rate
Million Imperial gallons per acre per day (mgad,Imp.) =1.1234 m3/m2/day
Million US gallons per acre per day (mgad) = 0.9354 m3/m2/dayCubic meter per square meter per day (m3/m2/day) = 0.8902 mgad, Imp
= 1.0691 mgad
Miscellaneous
Horsepower (h.p.) = 33 000 foot-pounds per minute = 0.746 kW= 1.0139 CV
Kilowatt (kW) = 1.36 CV = 1.34 h.p.Cheval-vapeur (CV) = 0.9863 h.p. = 0.736 kWOne liter of water weighs one kilogram (at 4°C)One cubic foot of water weighs 63.43 poundsOne US gallon of water weighs 8.345 pounds
224
Appendix II
211
VEGETATION AS AN INDEX OF GROUND WATER
The presence of certain species of vegetation can be auseful indication that ground water or soil moisture liesrelatively close to the land surface. These plant indicatorsare most obvious in arid parts of the world, where greenvegetation stands out, but the principle of using plantspecies as an index to locate ground water near the Surfaceis equally useful in humid countries. The best relationshipsare found between certain groups of plants (called plantassociations) and the depth of ground water or the salinityof water. In North Africa, for example, research has identi-fied various plant associations (usually three to four mainspecies per association) and their relationship to groundwater depth and salt content of the water. The presence ofcertain trees and shrubs, for example the "salt cedar" typetrees (Tamarix species), indicates salty water. Similarly,in the arid western U.S., Tamarix species, cottonwood trees,willows an other plants are associated with shallow groundwater tables.
Planet whose roots actually tap the ground water arecalled "phreatophytes." Due to their high transpirationrates in arid zones, the phreatophytes can "pump out" a smallstream or lower the level of a well. This transpiration loss-could be of ,concern if, for example, many trees or other deep-rooted plants are planted around a well for shade or tostabilize sand in a dry, windy setting. High transpirationby the plants also can increase the salt concentration in thewell water.
In arid zones, the perennial plants, especially treesand shrubs, are the most useful indicators of ground water.Annual plants, mainly legumes and grasses, are generallynot good indicators since they come and go depending on rainsand the season of the year.
Generally surveys of vegetation to help find shallowground water are most effective if carried out in the dryseason.
It would be useful at this point to present a table ofplant species and plant associations, country by'country.Unfortunately this information is not available for mostcountries, at least not in published form. Even if feasible,
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212
a list of all the plant species would be much too large.Finally, most people would need plant pictures and descrip-tions to accompany the names. You will therefore have tomake the effort locally to determine the local plants whichare good indicators of ground water. Sources of possibleinformation include experienced well diggers or drillers inthe area; water resource engineers; in rare cases, published,reports (,e.g., old FAO reports); and research station oruniversity botanists. In many cases the necessary information.can come only from interviews with these loyal sources ofinformation.
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213
Appendix III
USES OF DYNAMITE IN HAND DUG WELLS
This article by Christopher Henney was written as anoverview of the uses of dynamite in the Peace Corp/Togo wellsconstruction program.
It is reprinted from'the Action/Peace Corps P&T Programand Training Journal /Special Issue: Wells Manual) publishedby the Peace Corps in 1974.
PART I: Obtal.ring it
When to. use d nesite
When and if you encounter a hard rock layer and there is NO OTHER WAY tobreak it in order to attain the aquifer,then dynamite is in order. Ofcourse, you could move the well site, but in same regions this probablywould not make much difference. Never 004 dynamite before It is absolutelynecessary as villagers will immediately start to rely on it as soon as the
going gets rough. It is very difficult to stop using it once you havestarted. Dynamite in an, old well -or using dig-a-meter-pour-a-meter method.Start with small charges and deep blast holes and try to leave 50 an betweencaissons and rock.
Haw to get it
Because it is an extremely dahgerous substance and can be used for sabotageor other crimes,most governments are very cautious aboutvhaa they givepermission to use dynamiter thus one's procedure. for obtaining it shouldalways be through all necessary officials channels. InTogn this generallymeans:
2) Chef-Cir2) Travaux Publics
or Assainissement3) Interior Ministry4) An authorized dealer
First you get your Chef -Ci r to address a "demand* de permission d'achat",;emission to 'buy request to the Minister of Interior. Thdr will statequantity and type of dynamite plus quantity and type of detonators. Whatpurpose it is to be used for and where: where it will be kept, and by whom.Attached to this should be an agreement of your local boss: in my case theEngineer of Assainissement, Sokode. This letter will then be transmittedto Lame (the capital) and will be returned as a letter of permission to thebureau of the Chef-Cir. Ne,will give it to you. -Remember this permissionexpires after six months, so use it immediately. With this letter you then
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214
go to Lome and order the dynamite and detonators from Brossetto et Valor-(an authorized dealer). This could take time as it must come from Prance.So plan 6 months ahead.
Another option is to have Travaux Publics-Service Eydraulique order it foryou when they order theirs. Especially if you only want one or two cases.This is because Nrossette require* a minimum order of three cases unlessyou want to wait until it can be attached to someone else's order. Thisalso has the advantage of free transport up-country. It is not alwayseasy to get a transporter to carry high explosives.
MEAT TO ORDER:
The Dynamite
There are a number of kinds of dynamite or explosives adaptable to wells.And the choice islrobably made with expert help. Service Eydrauliqueis your best bet or Service des Mines. After usingthree different typesand talking to a number of people. I decided on the type known as "Gamma A"Tolamite. This is a redgelatimmussubstance rolled into 30 grms. packagesby means of wax paper. It is waterproof and maleable. The gases it releasesupon ignition are non-toxic (although they may irritate lungs. but I willget to that later) and the stuff won't go off if bumped,- smashed. dropped,etc. The maleability is important as sometime you want to squpqze it intoa crack like toothpaste. I generally figure quantities on thMrscale:
1 charge Am 50 or 100 gram. dynamite
Metersdepth of Diameter Number of
rock of well Quantities blast holes.
Z METER 1 meter f 12 charges 3
1 METER 1 meter 25 0 10 charges 5
1 METER 1 meter 40 f 24 charges 6
1 METER 1 meter 80 f 28 charges -------- 7
This should be more than adequate; usually it takes two 'rounds of explosionsto do a Irter although this depends on the depth of the blast holes and thehardness of the rock. Normally your local water bureau or Travaux Publicswill be able to tell you how deep you will have to blast. One case ofdynamite weighs about 25-30 kg.
The Detonators
For each three charges. you will need two detonators. This will insure'an
adequate supply. Make sure they are electrical firing detonators. Fuses are
dangerous and should not be used. The best kinds are type 866 low intensity,
total resistance 1.5-3 ohms, medium 2'ohms. Make sure the wires are 2 m long.
215
In general both dynamite and detonators have an expiration date. So makesure you don't get an old batch, because it may be unstable and thereforeDANGEROUS.
Where to Store and Row
The storage of dynamite is most important for your own health and that ofothers. Don't keep it at home as you may have kids or other curious peoplearound. personally. I prefer to keep it at the local gendarmerie, policeor travaux publics. This has a number of advantages:
a) You cannot be accused of sabotage for politica: reasons
b) If you work on weekends, you can get it at the first two places
c) If there is an accident, you are not around or responsible
Keep detonators away from dynamitelif possible at the other side of alocked room and in a case. Never let dynamite and detonators come intocontact until you are ready to use them. Remember a good shock can setoff the detonators, and detonators can blow your hand off. Keep tabs onhow much you have and how much has been used. If you cannot keep it atthe above mentioned locations, make sure you have a good store room withlock and the only key in your possession.
Row to Carry to your Site (If You Must)
If you don't want to keep at the site because there is no adequate storeroom or you have many sites and prefer to bring it in when needed from acentral store, then you must decide how it will be carried. I personallydon't like this as there is a small amount of risk involved; but I did itfor over six months. Anyway, if you follow certain simple rules, youshould be all right.
1) Keep detonators and dynamite in separate waterproof sealed cans -- Thedetonators preferably in a plastic one.
2) Keep the batteries or exploder somewhere else in your pack and separatefrom the detonators. This will insure you except if you get hit bylightning or squashed by a truck, both of which are very real dangers.
A normal crash because of sand, etc., should cause you no problems. (I hadtwo).
PART II: Row to Use
Rules for Use in a Well
The use of dynamite follows a couple of rules of thumb:
a) Use common senseb) Don't.use more than needed to get the job donec) Make sure the site is cleared of people
9
21-6
d) Keep children away from site at all timese) Get someone else to trigger itf) Don't let anyone else handle dynamite or detonators0) Keep the batteries in your pocket or jack until you are out of
the well and the site is clearedh) Check whether all charges went off (see Part 221)1) Never send someone else to get dynamite or detonators from the
store room''j) Never go down in a well containing unfired charges unless you
have secured the batteriesA) Place the charges yourself.
Rules a, b, c, d, g, j are constants, but e, f, 1, k are changeable if youhave trained a competent person to do the job. But no, matter what happens,
//
you will always be held responsible.
Tools You Need
Assuming you are working on a village level and you don't have a jackhammer (compressor), you will need:
1) Mining bar2) 75 meters of extension cord flex3) I roll of insulation tape4) 1 flat file (to sharpen mining bar)
5) 5 flash light ;3 volt cell batteries, size D6) Dynamite and detonators7) One 2-meter spoon
Now to Place Charges
As 1' have said before, the number of Charges is in proportton to the depthof the blast holes and the diameter of the well. A good rule of thumb istwo charges per hole (blast hole) and:
3 holes for 1 m 05holesfor1m25cmO6 holes for 1 m 40 cm 07 holes for 1 m 80 cm f
but depending on the rock,you may have three cha es Per hole' (or one).Never blast if your holes are not deep enough. ilaso/aiamite.The blast holes should be at least the length o a man's arm, 80 cm andpreferably more. The deeper the better. Dias holes should always be inthe most protruding places.
131AsT Soles \,./figure A.
wt. 1.041
Axle. totiv
30
r
Here is a good diagram of where to place them in general:
\:.
1 change
4 charges
7 charges
*..
2 charges
5 charges
3 charges
6 charges
The charges toward the outside walli of the well should slope out as inFigure A and in the case of 4 - 1 charges.
How to Make up Charges
There are two methods that I use: placing side by side, or one on top ofthe other.
Figure B.
-2:eroudehx.
IINAttrie
lerceATeg.
I prefer the side by side method where the hole is large enough. This isdone by unwrapping the wax paper around the dynamite and sticking the twocharges together, then rewrapping. The detonator is then inserted untilcompletely inside the dynamite. This method has the advantage of neverhaving only one charge go off because the other got ooveree by mud andseparated from the first charge as in the one on top of the other method.But in really hard rock it is sometimes not always possible to make theblast hole wide enough. The one on top method is also better for reallydeep holes as you can pet 3-4 chaiges in'with no difficulty. I might alsomention that the tighter the fit of the dynamite, the better blast you aregoing to get. Once the dynamite is in the hole with the detonator securelyin the dynamite. pack the hole with damp sand.. And pack, the sand with astick so it is well in and well packed.
fikekeeOM( .
231,
217
218
3
Figure C.
Don't pussy-foot but don't pound as if-you were driving railroad spikes.This insures that the dynamite has something to Push off on and thatthe gas does not escape out the open hole. Never fill your hole up to thetop with dynamite. This pet is.a solo waste.
If you have more than one charge as you will moot .of the time, you musthook them up in series.' Each detonator has two wires, on one will be a flag.
Now in order to hook up.a-seriesp'you must hook flag to non flag of anothercharge:
This leaves you with one flag and one, non flag which is then attached to theextension cord that goes above ground. Next collect your ends and tie themto the extension cord:
.4Jr you have four detdhators, there should be five joints left out of .the
TI:'to and so on..)falcs sure these are separated so as not to cause a short
rcizit.r:
A%Also make sure that this knot is above the water levelPreferably as highas possible without pulling the detonators out - and that is easier thanimagined even when the charges are packed in sand. Then get out of yourwell, being careful not to pull on the extension cord.
Lelat-
Mow to Dig the Blast Roles-
Using the blade' end of the mining bar, pound the rock. This must be donewhile continually rotating the blade so as to make a nice neat round hole.At intervals, add water to make a slurry - this is messy but necessary.After a bit, use the 2 meter long spoon to gii out the dust and dirt madefrom pulverized rock: or if the hole is wide enough, use your hand. Nevermake holes wider than your hand (fist) as this is just wasteful of dynamite.
232.
a
The sand will be blown out and little rock will be blasted. .Thii.ishard work and can take several days.
Ignition
To set off the dynamite, place the four or five batteries end to end andtouch the two ends with the two ends of the cord. Bake sureyou do this firmly and keep the. ord touching until you havecounted five (even though the explosions will happen spon- of staneously). This could save you many hours of looking forlive charges that did not go off. For 1-3 charges, fourbatteries. Add one battery for every additional charge; i.e.for 5 charges, 6 batteries; for 6 charges, 7 batteries, andfor 7 charges, 8 batteries.
'Before you fire, clear the site. Let no one stand hearer than 50'meters tothe well. Let a Togolese do'thefiring. There are two reasons for this. Ifsomeone gets hurt you did not pull the trigger, and Togolese-American relationswill not be upset. Also, you are needed to keep a sharp look out for fallingrocks, impulsive children, or new arrivals. But if anything does happen, youwill still be responsible for the site and though not legally, you will beheld responsible in the eyes of. the people you are working with.
Once the explosion has gone off wait a minute. You will often be surprisedhow long it takes rock to fall back to earth. Then pull up the extensioncord and count the number of detonator wires. If all have gone. off great, butif one is:severed half way up, there is a chance it is still alive. Also, ifthere is/ anything holding the .lord dowt yank it up. This could well be thewire that did not fire, and by following it you will easily find the unfiredcharge instead of digging all over to find it. Now wait 15 minutes - half anhour until the smoke clears. You can choke to death by smoke inhalation even
219
if the smoke is not toxin per se.
What to Do if a Charge does not go off
First, climb down and check your detonator wires. If one stays stuck, digaround it reasonably carefully. ,(rf an explosion could not set the chargeoff, you would really have to try). There is not too muc danger if youare careful. When you reach sand, pull the, detonator out slowly, then digout the charge. The charge is now harmlesi. Or you can also rewire thedetonator, climb out, and fire it. If this does not work and you cannotextract the charge, put a new one in on top of it and fire that. This wayyour well is clean. Then send workers down but.NOT until you have at leastextracted the detonator(s).
The causes of unfired charges are:
1) A short circuit2) A set of old batteries (no power)3) old detonators
233
/4.
Alter each explosion& check out your cable and patch or out. jhen placebatteries at one end and the two vireo on your tongue at the other and;if it tingles, all is well. Coil and put away. If not*find the short.Always do this after each explosion. It saves eMbaraesment when nothinggoes off. You can work in up to 1 meter of water.
Recap of Procedure Rules
1) Only use dynamite where nothing.glse works.2) Never use before it is absolutely needed, even when the work is hard.3) Follow all official procedures in obtaining it.4) Make sure it is not outdated stuff.5) Never use fuses, always electric detonators.6) Don't keep it at home, store safely.7) Never send an inexperienced person-to get it out of storage. Go yourself.8) Xeep dynrinite.separate from detonators and detonators separate from
batteries.9) use coaraonsense (take all the risks that need, taking yourself).10) Don't use more than you have to.11) Make sure the site is cleared of people.121 Keep children away from site.13) Get someone else to fire it while you watch.14) Don't let others handle dynamite or detonators or batteries.15) When you are in well, keep batteries. in your pocket. This is your
only insurance.16) After explosion, check for unfired charges.17) Never go after unfired charges unless you have secured the batteries.18) Place all charges yourself.19) Always pack some sand on top of a charge..20) -Make sure your detonators are wired properly and that the jointed ends
don't touch.21) Tie the wires to the cord.221 Make sure knot is above water.23) Don't'pull on cord. You might extract detonators by accident.24) Let no one stand closer than 50 m when you blast.25) Touch batteries firmly. Count to five.26) Check for dead charges yourself.27) Wait for smoke to clear.28) Check extension cable after each explosion.29) Xeep tools in good repair.30) Remember you are responsible for your life and other lives.
PLEASE NOM: Under no circumstance should dynamite be used unless anexhaustive study concerning its use has been conducted by experts who areknowledyeablein the use of dynamite.
GOOD LUCK AND TAix CARE.
g3 4
221
Appendix IV
CEMENT
A. Introduction to Cement
Cement is one of the Most useful materials in wellsconstruction. It can easily be mixed with sand and waterto make mortar or with gravel, sand and water to make con-crete. Both mortar and concrete are among the strangestand most durable materials used for all types a construc-tion around the world. Mortar is normally used as the-bonding agent bdtween bricks or rocks while concrete is-normally reinforced with steel bars and molded to thedesired size and shape.
For well work, mortar or'concrete is usually thebest material for the lining, headwall, platform andcover of dug wells,and the platform and seal aroundthe top three meters of casing in drilled wells.
Cement is available in almost every country in theworld and sand and gravel are usually available locally..Occasionally it will be difficult to get cement for wellsconstruction either because there are other higher priori-ty demands for the cement or becauie it just costs toomuch. It is impossible here to say how or even whethercement can be obtained in such a circumstance.
.0f the two cement compounds, mortar and concrete,concrete is the stronger. This is because the rock thatmakes up the gravel itself is stronger than the concreteand so contributes to its strength. Sometimes the twocan be used interchangeably where lack of materials or
'working conditions demand it. Remember that concrete isthe stronger product and should be used where possible.
NOTE: The rest of the discussion in this appendix willdeal specifically with concrete. The same procedures canand should be followed if mortar is used instead.
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222
B. Ingredients of Concrete
Concrete is made from cement, sand, gravel and water.These ingredients are combined in certain proportions toachieve the desired strength., The'smount of water used tomix these ingredients is by far the most important factorin determining the final strength of the concrete. Use theleast amount of water that will still give you 4 workablemix. Sand and gravel, which are sometimes referred,to asfine and coarse aggregate respectively, should be clean andproperly graded. Cement and water form a paste which, whenmixed, acts as a glue' to bind the aggregates together ina strong hard mass.
1. Proportions:
There are four major ingredients in concrete:cement, sand, gravel, water.
Dry ingredients are normally mixed in certainproportions and then water is added. Propor-tions are expressed as follows: 1:2:4, whichmeans that to one part cement you add two partssand and four parts gravel. A "part" usuallyrefers to a unit of volume. Example: A 1:2A4concrete mix could be obtained by mixing 1 bucketfull of cement with 2 buckets of sand and 4buckets of gravel.
Proportions are almost always expressed as cement:.sand:gravel, and they are usually labelled thatway.
There are many minor variations in the propor-tions used for mixing concrete. The most commonlyused are 1:2:4,.1:2:3, 1:2.5:5. For our purposesall work equally well.
NOTE: ,A 1:2:4 mix will go a little farther than the 1:2:3mix and allows a little more room for using not the bestsand or gravel than a 1:2.5:5 mix.
Normal range for amount of water used to mixeach 50 kg bag of cement is between 20 liters and30 liters (94 lb. bag of cement is between 4.5gal. and 7 gal.)
236
o.
223
The water-tightness of concrete depends primarilyon the water-cement ratio and the length of moistcuring. This is similar to concrete strength inthat less water and longer moist curing promotewater-tightness.
2. Choice of ingredients
cement: The descriptions and properties givenWinire specifically of Portland cement. Thisis the type most commonly used and what we thinkof when we say cement.
When used, it should be dry, powdery and free oflumps. When storing cement try to avoid all pos-sible contact with moisture. Store it away fromexterior walls, off damp floors, and stackedclose together to reduce air circulation. If itcould be kept completely dry it could be storedindefinitely. Even exposed to air it will gra-dually draw moisture, thus limiting even thecovered storage time to between 6 months and Iyear depending on conditions.
water: In general, water fit for drinking issuitable for mixing concrete. Impurities in thewater may affect concrete, setting time, strength,shrinkage or promote corrosion of reinforce-ment.
aggregates: Fine and coarse aggregates togetheroccupy 60 to 80% of concrete volume.
- fine aggregate: Sind should range in size fromless than .25 mm to 6.3 mm. Sand from sea shores,dunes or river banks is usually too fine fornormal mixes. (You can sometimes scrape about30 cm of fine surface sand off and find coarser,more suitable sand beneath it.)
large aggregate: Within the recommended sizelimits mentioned later, the larger the gravelyou use the stronger and more economical theconcrete will be.
The larger the size of the gravel the less waterand cement will be required to get the samestrength concrete.
23 7
224
The maximum gravel size should not exceed
- one-fifth the minimum dimension of themember;
- three-fourths the clear space between rein-forcing bars or between reinforcement andforms. (Optimum aggregate size in manysituations is about 2.0 cm.)
The shape and surface texture of aggregates affectproperties of freshly mixed concrete more than theyaffect hardened concrete. Rough textured or flat andelongated particles require more_water to produce workableconcrete than do rounded or cubical aggregates and morewater reduces the final strength of the concrete.
It is extremely important to have the graveland sand clean. Silt, clay, or, bits of organic matter ineven low concentrations will ruin concrete. A verysimple test for cleanliness makes use of a clear wide-mouth jar. Fill the jar about half full of the sandand small aggregate to be tested, and cover with water.Shake the mixture vigorously, and then allow it to standfor three hours. In almost every case there will be adistinct line dividing the fine sand suitable for con-crete and that which is too fine. If the very fine mater-ial amounts to more than 10% of the suitable material,then the concrete made from it will be weak.
This means that other fine material should be sought,or the available material should be washed to remove thematerial that is too fine. This can be done by puttingthe sand (and gravel if necessary) in some con-tainer such as a drum. Cover the aggregate with water,stir thoroughly, and let stand fora minute, and pour offthe liquid. One or two such treatments will remove mostof the very fine material and organic matter.
Another point to consider in the selection of aggre- -gate is its strength. About the only simple test is tobreak some of the stones with a hammer. If the effortrequired to break the majority of aggregate stones isgreater than the effort required to break a similar sippiece of concrete, then the aggregate will make strongconcrete. If the stone breaks easily, then you can ex-pect that the concrete made of these stones will only beas strong'as the stones themselves.
In very dry climates several precautions must be taken.If the sand is perfectly dry, it packs into a smallerspace. If you put 20 buckets of bone dry sand in a pile and
238
stirred in two buckets of water, you could carry awayabout 27 buckets of damp sand. If your sand is completelydry,. add some water to it or else me'sure by weightinstead of volume. The surface of the curing concreteshould be kept damp. This is because water evaporatingfrom the surface will remove some of the water needed tomake it cure properly. Cover the concrete with buildingpaper, burlap, straw, or anything that will hold moistureand keep the direct sun and wind from the concrete sur-face. Keep the concrete moist by sprinkling as oftenas necessary; this may be as often as three times per day.After the first week of curing, it is not necessary tokeep the surface damp continuously. (See p. 236.)
3. Making Quick-Setting Concrete
TO produce quick-setting concrete with high ini-tial strength, calcium chloride can be added to themixture.
This will not affect the estimation of materialsneeded because the calcium chloride will be dissolvedin the water used to mix the concrete.
Quick-setting cement is often useful for example,.when repeated castings are needed from the same mold.A concrete mixture which contains calcium chloride asan accelerator will set about twice as fast as a mix-ture which does not. The mixed batch must be put intothe forms faster, but since quick-setting batches areusually small, this is not a problem. Calcium chloridedoes not lessen the strength of fully-cured concrete.
No more than 1 kg (2 pounds) of calcium chlorideshould be used per sack of cement. It should be usedOnly if it is in its original containers, which shouldbe moisture-proof bags or sacks, or air-tight steeldrums.
The best way to add the calcium chloride is tomix up a solution containing 1/2kg per liter (1 poundper quart) of water. Use this solution as part of themixing water at a ratio of 2 liteta (2 quarts) persack of cement
4. Estimating quantities of materials needed
1. Calculate the volume of concrete needed.
2. Multiply the volume of concrete needed by 3/2(1.5) to get the total volume of dry loose
239
226
material needed. The cement and sand do littleto add to the volume of the concrete becausethey fill in the air spaces between the gravel.
3. Add 10% (1/10) for losses due to handling.
4. Add the numbers in the volumetric proportionthat you will use to get a relative total.This will allow you later to compute fractionsof the total needed for each ingredient.(1:2:3=6)
5. Determine the amount of cement needed bymultiplying the volume of dry material needed(from step 2) by the proportional amount of thetotal mix (amount cement needed) = 1/6 x (volumedry materials).
6. Divide by the unit volume per bag, 33.2 litersper 50 kg bag cement or 1 cubic foot per 94 lb.bag cement. When figuring the number of cementbags round up to nearest whole number.
NOTE: This calculation, even with the 10% addition forhandling losses, rarely leaves any extra concrete,particularly for small jobs requiring less than 5 handmixed bags of cement.
24
ti
Here is an example:
the volume of a cylinder=1fr2h=(3.1416)(radius)2(height)= (3.1416)(radius)(radius)(height)
the'volume of concrete needed to build the liningand platform of the pictured well could becomputed as follows (See Fig..IV-1).
the volume of thethe volume of the0.7m radius minuscylinder with a 0
V =[ x(.7)2(20.8)]'[(3.1416)(.49)(=32.0-23.5-8.5m3
lining and headwall would be20.8m high cylinder with athe volume of the 20.8m high.6m radius.
20.6)[-6[(3.1416)(.36) (20.8)]
FIG. ne-1 .C*O$5 S WNW op TvpicALcon 010tuCtot.Aroom oF Couluterg.
knotsthe volume of the platform would be the volume ofthe .08m high cylinder with a 2m radius minusthe volume of the .08m high cylinder with a.7m radius.
- V= [ (3.1416) (2)1(.08)]-](3.1416) (.7)2(.08)]
[(3.1416)(4)(.08)]-[(3.1416)(.49)(.08)1
1 0.1=0.9 m3
241
227
0
228
Following the steps outlined above the volume\of materialsnecessary to construct the well would be computked asfollows:
1. total volume = 8.5 + .9 = 9.4 m3
2. (9.4)(1.5) = 14.1 m3 dry material estimatec
3. 14.1 x 1.1 = 15.5 m3 dry material necessary 14caute oflosses in transport.
4. 1:2:4 cement:sand:gravel 1+2+4=7
5. 15.5 x 1/7 = 2.2m3 cement15.5 x 2/7 =4.4m3 sand15.5 x 4.7 = 8.9m3 gravel
6. 2:20 cement = 2,200 .liters (1.) of cement
2,200 1. cement 1-33.2 1. per 50 kg bag cement =66.26 bags of cement
67 bags of cement will be needed.
C. Construction with Concrete
1. outline of Concrete Work:.
build form;
place rerod;
mix concrete;
pour concrete;
finish surface;
cure concrete;
remove forms.
242
2. Interior Well Forms
a. .Introduction
An interior well form or-mold is circular with asmooth exterior surface which will form the inside sur-face of the lining. This form can be used either on thesurface with other forms to make lining ringt or in thewell to form a lining that is poured in place. (See Fig.IV-2.)
HORIZONTAL. RE-RODS
FIG. IV- Z.INmseAvet losamNs'Fosi4
Freshly mixed concrete is heavy and plastic. Formsfor holding it in place until it hardens must te wellbraced and should have-a smooth inside surface. Cracks,knots, or other imperfections in the forms may be per-manently reproduced in the concrete surface.
Forms should be easy to fill with concrete and easyto remove once the concrete has hardened. Be sure that'the 'fastenersused to hold the form together are bothaccessible and easy' to unfasten.
NOTE: When using nails to hold a wood form together,do not drive them all the way in. Leave them stickingup just enough so that they can easily be pulled whennecessary to remove the form.
243
229
230
b. Materials for Forms
The following materials are used to construct in-terior forms:
steel: forms made of steel range in height from1/2 m to 1 m. They are heavy, awkward, and expensivebut last for a long time.
sheet metal: with a simple triangular interiorsuRport, forms made of sheet metal have provedtoe successful. They are lighter and moremaneuverable' than steel forms but arenot as strong and durable.
wood: this material is commonly used because itis lightweight and strong. It must be carefullybent, waterproofed, and reinforced.
By using boards as wide as possible, form con-struction will be easier and quicker. It willalso reduce the number of lines on the concretesurface that form at the junction of two boards.Plywood is excellent, especially if it has aspecial high density overlay surface. This allows,for a smoother concrete finish, easier form re-moval and less wear on the forms.
If unsurfaced wood is used for forms, oil orgrease the inside surface to make removal of theforms easier and to prevent the wood from drawingtoo much water from the concrete. Do not oil orgrease the wood if the concrete surface will bepainted or stuccoed.
earth: Any earth that can be dug into and stillWord-its shape can also be used as a form. Care-fully dig out the desired shape and fill it withconcrete. Once the concrete has set and curedit can be dug up and used where needed. A newform will have to be dug Out for each piece ofconcrete poured. (See Figs. 8-12 and 9-10.)
other materials: Plastics and fiberglass arealso occasionally used and continue to be ex-perimented with as form materials. .Fiberglass ismuch lighter than steel and, if taken Proper careof, should last for a long time. Its cost andavailability in developing nations seem to be theonly factors limiting more widespread trials.
231
ti
3. Concrete Reinforcement
Reinforcing concrete will allowr much greater loads tobe carried. Design of reinforced concrete structures thatare large or must carry high loads can become too compli-cated for a person without special training.
Condrete alone has great compression strength butlittle tension strength. Concrete is very difficult tosqueeze (compression), but breaks relatively easily whenstretched (put in tension). Reinforcing steel has exactlythe opposite properties; it is strong in tension and weakin compression. Combining the two results in a material(rdinforcedconcrete) which is strong in both compressionand tension and therefore useful in a large number ofsituations.
Concrete is best reinforced, with specially madesteel-rods which can be imbedded in the concrete. 'Bamboohas also been used to reinforce concrete with some successalthough it is liable to deteriorate in time.
Reinforced concrete sections should be at least7.5 cm thick and 10 cm is much better.
. The reinforcing rod (rerod) usually comes in longsections of a given diameter.
The range of different diameter sizes commonlymanufactured is usually measurd'in millimeters;for example, 4 mm, 6 mm, 8 mm, 10 mm, and 12 mm.
Exactly how much rerod is needed in a particularpour will depend on the load it will have to sup-port. For most concrete work, including every-thing discussed in this manual, rerod should 'takeup 0.5% to 1% of the cross - sectional. area.
Reinforcing rods should also have clean surfaces freeof loose scale and rust. Rods in poor conditionshould be brushed thoroughly with a stiff wire brush.-
When placing rerod in a form before the concreteis poured it should be located:
- at least 2.5 cm from the form everywhere..
- in a plane approximately two-thirds of the wayinto the thickness of the pour from the side
245
ti
4
232
Cs
which will have, a weight or force pressing onthe concrete. (See Fig. IV-3.)
2/3Tour-saaSSVSTomW40MEEEEEEE
SeSs.8040*avawbvAL
WM-4-.101,01.ft,
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RS Roo TI-ATPcsamPAGEOles4T
W W. 4ED .Mw
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.
- in a grid so that there is never more than3 times the final concrete thickness hetweenadjacent rods:
- no closer than 3 cm to a parallel rod.
ems.cmVhAmmtur
Rerod strength is approximately additive accordingto cross-sectional area. Four 4 mm rods will beabout as strong as one 8 mm rod. The cross -sectional area of four 4 mm.rods equals the cross-sectional area of one 8 mm rod.
tt.
The r9d should begrid-type patternalong the longest
All intersectionswith thin wire.
arranged in an evenly spaced-with more and/or thicker roddimension of the pour.
where rods cross should be tied
When tying one rod on to another to increase thelength of the rods, they should overlap 20 timesthe diameter of the rod and be tied twice with wire.(See Fig. IV-4.)
Rod size Overlap,
6 mm 12 cm = 120 mm8 mm 16 crim rg 16010 mm, 20 cm == 200.12 mm 24 cm = 240
246
4.
diameter $2)::4_ x (diargefer) 4
\)<Xso.US6NS<>1.20 x diasteier
PIG. IV-. 4. ityrittO ova.
diameter
Larger sizes of rod often have raised patternson them which are designed to allow them to beheld firmly. in place by the concrete. Smallersizes of rod are generally smooth. When usingsmooth rod always make a small hook at the endof each piece that will be in the concrete.Without the hook, temperature changes mayeventually loosen the concrete from the rod there-by losing much of its reinforcing effect.
Rerod should be carefully prepared so that the rodis straight and square where it should be.Sloppy rod work will result in weaker concrete andwastes rod.
For particularly strong pieces or where smallirregular shapes are being formed, the rerod canbe put together in a cage-like arrangement. Usesmall rod for the cross-sections and lariii rodfor the length. This system is used to reinforcepieces like a cutting ring, with its irregularshape, or perhaps a well cover,which may have many.people 'standing on it at one time.
Where possible, it is usually best to assemble re-rod inside the form so that it will fit exactly.
The proper distance from the bottom of tht pourin a slab can be achieved by setting the rod ona few small stones before the concrete is pouredor simply pulling the rerod grid a couple ofcentimeters up into the concrete after some con-crete'has been spread over the whole pour.
247
,233
234
4. Mixing Concrete By Machineor By Hand
a. Mixing by Machine
Concrete must- be thoroughlymixed to yield the strongest pro-duct. For machine mix, allow5 or 6 minutes after all the mat-erials are in the drum. First,put about 10% of the mixingwater in the drum. Then add, iiO4#4water uniformly with the drymaterials, leaving another 10%to be added after the dry mater-ials are in the drum. Goo.vo41 zgo
Omar 144044-.b. Mixing by Hand
On many self-help projects,the amount of concrete neededMay be small or it may be diffi-cult to get a mechanical mixer.Concrete can be mixed by hand;if a few precautions are taken,it can be as strong as concretemixed in a machine.
The first requirement formixing by hand is a mixing areawhich is both clean and water-tight. This can be a wood andmetal mixing trough (Fig. IV-51
or a simple round concretefloor (Fig. 1V-6 ) .
,LAgAN
Flo. iv-5 tIONGveou614
1411
eAiss noreig Vao cM
FIG. %V -6. M MINGPLATFORM
Use the following procedure:
I) Spread the fine aggregate evenly over the mixingarea.
2) Spread the cement evenly over the fine aggregate andmix these materials by turning them with a shovel un-til the color is uniform.
3) Spread this mixtureaggregate on it andmaterials should; beadded.
out evenly and spread the coarsemix thoroughly again. All drythoroughly mixed before water is
/7
24?
235
When work is finished for the day, be sure to rinseconcrete from the mixing area and the tools to keep themfrom rusting and to prevent cement from caking bn them.Smooth shiny tools and mixing boat surfaces make mixingsurprisingly easier. The tools will also last much longer.Try to keep from getting wet concrete on your skin becauseit is caustic.
A workable mix should be smooth and plastic -- neitherso wet that it will run nor so stiff that it will crumble.
If the mix is too wet, add small amounts of sand andgravel, in the proper proportion, until the mix is work-able.
If the mix is too stiff, add small amounts of waterand cement, maintaining the proper water-cement ratio,until the mix is workable.
Note the amounts of materials added so that you willhave the correct proportions for subsequent batches.
If a concrete mix is too stiff, it will be difficultto place in the forms. 'If it is not stiff enough, themix probably does not have enough aggregate, thus makingit an uneconomical use of cement.
5. Pouring Concrete into Form
To make strong concrete structures, it is important toplace fresh concrete in the forms correctly.
The wet. concrete mix should not be handled roughly whenit is being carried and put in the forms. .It -is very easy,through joggling or throwing, to separate the fine aggregatefrom the coarse aggregate. Do not let the concrete dropfreely for a distance greater than 90 to 120 cm. Concreteis strongest when the various sizes of aggregates and cementpaste are well mixed.
Properly propoitioned concrete will have to be workedinto place in the form. Concrete that would on its own flowout to completely fill in a form would be too wet and there-fore weak.
When pouring concrete structures that are over 120cmhigh, leave holes in the forms at intervals of less than120cm through which concrete can be poured and which canlater be covered to permit pouring above that level. Alter-natively, a slide could be used through which concrete couldflow down to the bottom of the form without separating.
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236
Any "u"-shaped trough wide enough to facilitate pouring con-crete into it, narrow enough to fit inside the form, andlong enough so that the concrete can slide down the chutewithout separating will work.
As the'concrete is being placed it should be compactedso that no air holes, which would leave weak spots in theconcrete, are left. This can be done by tamping the con-crete with some long thin tool or vibrating the concrete inone of several ways. Tamping can be accomplished with athin (2 cm) iron rod, a wooden pole or a shovel.
On large commercial jobs concrete is compacted with aspecial vibrator usually powered by an air compreisor whichis submerged in the concrete immediately after it is poured.The concrete will be compacted to some extent as it is movedinto its final position in the form. However, specialattention must be paid to the edges of the pour to make surethat the concrete has completely filled in the form up tothe edges. If the forms are strong enough they' can be struckwith a hammer on the outside to vibrate the concrete justenough to allow it to settle completely in against the forms.Too much tamping can force most of the large aggregate towardthe bottom of the pout, thus reducing the overall strengthof the concrete.
6. Finishing
Once the concrete is poured into the forms, its surfaceshould be worked to an even finish. The smoothness of thefinish will depend on what the surface will be used for. Wheremore concrete or mortar will later be placed on this pour,the area should be left relatively rough to facilitate bond-ing. Where the surface will later be walked on, as forexample the cover of a well on which a pump will be mounted,it should be somewhat rough. to prevent people from slippingon the concrete when its surface is wet. This somewhatrough texture can be achieved by finishing with a wooden floator by also lightly brushing the surface to give it a texture.A very smooth finish can be made with a metal trowel.Over-finishing (repeated finishing) can lead to powdering anderosion of the surface.
7. Curing Concrete
After the forms are filled, the concrete must be curedOPuntil it reaches therequiredstrength. Curing involveskeeping the concrete damp so that the chemical reaction thatcauses the concrete to harden will continue for as long asis necessary to achieve the desired strength. Once the con-crete is allowed to dry the chemical hardening action will
250
A
gradually taper off and cease.
.The early stage of curing is extremely critical. Specialster4 should be taken to keep the concrete wet. Once the con-crete dries it will stop hardening; after this happens itcannot be re-wetted in the field to re-start the hardeningprocess.
Covering the exposed concrete surfaces is usuallyeasier than. continuously sprinkling or frequently dous-ing the'concrete with water which would otherwise benecessary to prevent the concrete surface from becomingdry to the touch. Protective covers often used includecanvas, empty cement bags, burlap, plastic, palm leaves,straw and wet sand. The covering should also be keptwet so that it will not absorb water from .the concrete.
Concrete is strong enough for light loads after 7 days.In most cases, forms can be removed from standing structureslike bridges and walls after 4 or 5 days, but if they areleft in place they will help to keep the concrete fromdrying out. Where concrete structures are being cast on theground, the forms can be removed as soon as the concrete setsenough to hold its own shape (3 to 6 hours) if there is noload on the structure and measures are taken to ensure propercuring.
The concrete's final strength will result in Dart fromhow long it is moist cured. As can be seen from thegraph, concrete will eventually reach about 60% of its de-sign strength if not moist cured at all, 80% if moist curedfor 3 days, and almost 100% if moist cured for =7 days. Ifconcrete is kept moist it will continue to harden indefinitely.
You will also notice from the graph that even though theconcrete may be cured for 7 days, at that point it will onlyhave gained-about 60% of the strength it will ultimately haveand that it will be another 3 weeks before it reaches 90%of its ultimate'strength: Practically,this means that whenpouring a concrete ring which will later be put in the welleven after curing has stopped, the ring,should be left alonefor at least another week (and preferably longer) before itis installed in the well. It will during that time hardento reach about 75% of its final strength.
251
237 .
150
0rn
00 125
to
N 100044
0
75
b.
of
4-1 4)50
IA -0a)
of w> u
to o 25m ua)
roO 4
WO 0u a 0 -I
3
GRAPH: STRENGTH OF CONCRETE AFTER DAYS OF MOIST-CURING
/I
moist-curedentire
in air after 7 days- .... 42. .11 ift Mr
in air after 31.4au
in air entire timeMP
7
Age, days
28
252
90 180
239
Appendix V
LEVELING AND PLUMBING THE MOLD
When you check the level of the mold you also takea measure of whether or not the sides of the mold are per-fmtly plumb. If they are perfectly plumb the shaft willgo straight down. A well does not have to have a shaftthat goes straight down; it could just as easily curve orgo down at an angle. Plumb is easy to measure, however,and there are many reasons why it is desirable to keep thewell plumb.
1) A plumb well shaft and lining is a strongerstructure than one that is not plumb.
2) Sinking the hole straight down requires lessexcavation work than an angled or a curved hole.
3) Fewer materials are required to construct a liningthat will support the well.
4) If a pump is to be installed, the pipe that reach-es to water should be perfectly plumb. If it isnot plumb, there will be greater stress on thepipe and pumping components will wear out muchsooner than they should.
1. Tools
Use a commercial level (see Fig. V-3 ) or a clearplastic hose with water in it. (See Fig. V-4.)
For the purpose of demonstration, level the interiorlining mold in the well with a commercial level (spiritlevel, or water level). The normal ordinary level hasa clear glass or plastic tube which is 'slightly curvedand full of liquid with one air bubblevthere will alsobe two marks on the tube, one on either'side of thecenter of the tube. To read the level set it, with thetube side up, on whatever you want to check; the ob-ject will be level when the air bubble in the tube is
253
240
exactly centered between the two marks on the tube.(See Fig. V-1.)
FIG. V I. eUiseLe eerwsSm mAtaits INDICATING olsaacT
If the object is not level the bubble will be off-center toward the side which is highest. (See Fig. V-2.)
F I do V 2 . 8U St3L E. CA). 1416HER st De of UM-t.EvEk. oalecT
2. Care of the level
Levels are sensitive and exact instruments whicharrive adjusted from the factory. Great care should betaken never to drop a level or otherwise damage itsedges. Many levels also come with insets for checkingverticality (plumb) and 45° angles. (See Fig. V-3.)
FI6. V. s. ccm M Par.IAL t.Y MAsuFACTURA-P Levt_t_
254
If a level is not commercially available, yoll can easilymake your own level with a clear plastic hose and water.(See Fig. V-4.)
WATS.. Wk.
f145.1V-.14.COAALictsa,AwowATERIJSBOAS uevoL.
If the surface of the water in the hose is evenwith the edge of the mold on one side, then when theedge of mold on the opposite side of the hole is evenwith the surface of the water in the other end of thehose, the mold is level in that direction.
Water in two ends of the same tube will always be atthe same height no matter what the tube does betweenthe two ends.
NOTE: If the diameter of the clear plastic hose issmall, a "meniscus" (U- shaped surface due tocapillary action) may form. All level readings shouldbe made at the same point of the meniscus, preferablyat the center.
3. Checking the level of a horizontal object.
Always cheOk the level in two opposite directionsbefore declaring that an object is level.
For a flat plate, see Fig. V-5.
A6.V-5. L.evet. CHU.ice IN Two.virtecnor4s ot.3 fi-AT SidgFIVGE
255
241
242
1
For a lining mold, see'Fig. V-6.
Fla.. V-4). LEVEL. 414Er...KOD 114 Ivo
rilrorcnoess ON 1..1ink3& 0401-1>
To check two objects not connected with each other,find a straight object (a board, a shaft etc.) that canbe laid down between the two objects to be leveled.(See hig. V-7.)
Or
USING A sTmAIGHT 130A120 To cliedg. Levet.. Aceces mea-o
Check the straightness of the board by looking alongits edges from one end.
256
Appendix VI
PIPE
A. Introduction
243
Water is often needed in locations where none isavailable. Pipe can help to meet this need if there issome force available to move water through it. Gravity-and pumps can exert the necessary force on water to causeit to flow through a pipe. But pipe can be expensive andmay not be appropriate for use4n some situations. Wherewater needs to be transported from one place to anotheracross the surface of the earth,' a simple trough arrange-ment might work and be more easily repaired when damaged.
Generally speaking, however, pipe is superior toother water transportation devices.; It is readily avail-able and it can be used for a number of purposes, besidestransporting water. It is commonly 'used in the casingfor drilled wells and in the drop. pipe for pumps. De-pending on the material from which it,was made,'it canbe used to make many handy tools or simple equipment.
NOTE: For pipes laid in the ground, aways maintain suf-ficient pressure in a completed line of pipe so thatwater will leak out of any holes. If pressure around thepipe is greater than that inside it, contaminents fromthe ground will be forced into the pipe.
When evaluating possible pipe choices, .a number offactors should be considered. They include:
cost;
accessibility/availability;
pressure. Where necessary, can the pipe with-stand the pressure of the water that will becarried inside it? Computing the actual pressureis beyond the scope of this manual.
It is sufficient to say here that the pressureof the water is directly related to the verticalhdight of the water column above that point'.
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244
pipe connections. Can the pipe connections bemade completely watertight, to prevent unpecessaryloss of water and the entrance of possible con-taminpnts?
weight. Will you need special equipmelit to raiseor lower the needed length of pipe?
possibility of decay or corrosion. Is the pipesuitable for the ground and water conditions inwhich you intend to use it?
B. Pipe Materials
1. Bamboo
Although an appealing idea considering the wide'-spread availability of bamboo, in fact bamboo is seldomused as water pipe. This is due to the fact that it isessentially a temporary solution, requiring considerableupkeep to keep,a well from being contaminated by therotting of the bamboo segments.
Bamboo can take the pressure from a column ofwater 20m in height, or about 2 atmospheres.
Preserve bamboo for use as water pipe with oilbased paint or varnish to seal it on the outside,or soak in 5% boric acid and water solution.
NOTE: Boric acid can give water an unpleasant smell forabout three weeks.
Chisel or drill to break inner membranes' ofbamboo.
Join pieces by three possible methods:
1) sliding one pie-,e into the next, and thenwrapping the joint with tar-soaked rope;
2) using extra bamboo as interior or exteriorcoupling and then wrapping the joint withtar-soaked rope;
3) wrapping cow-hide tightly twice around the /joint and sealing it iith two pieces of wire:
There will be a three to four year life expectancyif the pipe is carefully installed.
If chlorine is used to disinfect the, water be-fore it flows through the pipe, alld sufficientcontact time for chlorine to act before the waterenters the pipe.
r258
.1..411k
245
2. Iron or Steel-commonly referred to as "black" pipe
Iron or steel is frequently used for water pipeeven though it is sometimes subject to rust andcorrosion from the water.
These materiall; are commonly used as casing pipefor drilled wells. where the water is not corro-sive.
Iron and steel are galvanized to help preventrust and corrosion. (See'next entry.)
3. Galvanized Iron or Galvanized. Steel ,
Regular iron or steel, pipe is simply coated witha thin layer' of zinc when galvanized. This helpsreduce rust and corrosion normal to iron and steel.
The piping is joined by threaded connections.The threading process cuts through the zinc layer.Thus, threads are paticularly susceptible torusting and corrosion.
Galvanized iron or steel is .commonly manufacturedin metric and English sizes.,,
Because this material is strong, the pipe is alsoparticularAy useful in manufacturing many smalltools and pieces of equipment to suit a specificjob an location.
4. Plastic - ABS (Acrilonitrilelatadiene-Styrene)
ABS plastic has_excellent impact resistance, evenat low temperatures.
ABS has heat resistance up to 160°F.
It has pressure ratings of 1,000; 1,250 and1,600 pounds per square inch (p.s.i.); dependingon composition and thickness.
It posesses excellent corrosion and chemicd1resistance to non-oxidizing chemicals.
It can be joined by solvent cementing or by pipethreads where wall thickness is adequate.
259
.0
ABS plastic ilso presents certain Problems:
It is subject to attack from organic solvents.
Direct exposure to the ultraviolet rays of thesun reduces its strength and elongation pro-'perties. This is a gradual process which islikely to significantly affect the pipestrength only afteli months of exposure.
Plastic -.PE (Polyethylene)
There are three types of plastics, varying fromsoft to hard. _Their rigidity, tensile strength,surface hardness, softening temperature andchemical resistance increase with density andmolecular weight.
They have p.s.i. ratings of 80, 100, 125, and160, according to composition and thickness,.
They are extremely resistant to chemicals.
This kind of plastic can be-joined by flaring,using insert fittings, or by heat fusion.
They are low cost, lightweight and flexible,long lengths can be coiled.
PE plastic also presents -certain problen;s:
It has low design stress and poor rigidity.
The temperature limit:varies from 100 to 180 °F.depending on density.
PE plastic is sensitive to light but can beleft in the open for a month or more
It is flammable, although easily extinguished'.
American and European polyethylenes have differentdensity ratings.
Plastic - PVC (Polyvinyl Chloride)
j
PVC plastic h&s excellent strength and rigidity.
Its p.s.i. ratings are comparable to those of 4PE and ABS.
260.1
It is extremely resistant to chemicals and oils.
It can be joined by heat fusion, by solvent ce-ment, or by various kinds of mechanical joints.
It is readily threaded if there is sufficientwall thickness.
PVC plastic also presents certain problems:
It is readily softened by ether, ketones andchlorinated hydrocarbons.
It is heavier than PE and ABS.
Its temperature limit is 150 °F.
However, its many advantages make it widely usedas plastic pipe.
5. Concrete
Concrete is usually used to make large culvert-type pipe.
It can be used as well casing or lining if careis taken to seal successive sections from eachother.
6. Fired Clay
Clay is usually used to make four inch to sixinch drainage tile.
Unless it is manufactured with spedial end fittings,usually a bell and socket, it is not easily adaptedto water transport.
It is relatively weak and easily broken...
261
249
Appendix VII
PUMPS
A. Introduction
There are many different kinds of pumps in usearound the world. This discussion is limited to anoverview of the most commonly used pumps.
Fla. VU -I. PUMP Aetiot4
e As the piston goes down, the check valve in it opensallowing the water to come through. The check' valve atthe base of the cylinder remains closed holding the waterin th'e cylinder.
Ai the piston moves up,the check valve in it closesallowing the water above the piston to be lifted. Therising piston also pulls more water up into the cylinder
rough the valve at its base.c and9 The continued down and up motion of the pistoninside he cylinder and the opening and closing of thedifferent valves enables water to be moved up and out ofthe pump.
262
250
The most common type ofhand pump uses a smoothcylinder against which apiston (plunger) slides upand down. The up and downmotion of the piston, coupledwith the concurrent actionof two valves, causes waterto move through the cylinder.(See Fig. VII-1.)
While there are othertypes of pumping mechanismswhich will be mentioned later,this type of pump is by farthe most common.
B. Piston Pump Variations
1. Shallow/deep well _pumps
Although the basic opera-tion of cylinder pumps is alwaysthe same, there are, two dif-ferent ,arrangements of thecomponents depending on the dis-tance between the pump and thewater surface. For the pump towork the cylinder must be within6.5 m of the water surface in thewell.
Shallow well pump: If thiwater level in the well is within6.5 m of where the bottom ofwhere the pump will be placed,the cylinder can be incorporatedinto the pump body. (See
Fig. VII-2.)
Deep well pump: If thewater level in the well is morethan 6.5 m from.the bottom ofthe pump at any time, thecylinder will have to be insidethe well. (See Fig. VII-3.)
Because the working partsof the pump are all above groundin the shallow well pump, thispump is much easier to repair.Deep well pumps, however, aremore common because water is notoften found within 6.5 m of theground surface.
PIG.
470i7A7
Vil-.2.11.4ALLOW WIT PUMP
Moo. rIpe.
.m.. .PUMP
CVLoadfiere
.11
aucenek$11)+PIL
VII - 3. IMPusu. tor P.m?263
251
NOTE: Contrary to popular opinion, pumps do not 'lift'water up from the source. Instead, the pump reduces the --atmospheric pressure on the water in the suction pipeand the atmospheric pressure on the water outside of thesuction pipe pushes the water up and into the pump. Theprinciple is the same as that of drawing water through astraw or filling a syringe.
Theoretically a pump should be able to raise water10.4 m up to the cylinder. However, because seals andvalves can never function perfectly, the absolute limitis 6.7 meters. Where pumps are locally made, tolerancesare usually greater so that the practical limit is 6.5 mor even slightly less.
Elevation above sea level also plays a part indetermining the practical limit of pumping height becausethe higher above sea level the less atmospheric pressurethere is to push the water up. (See Chart.)
There is no theoretical limit to how far a cylindercan push water up above itself if the pump parts arestrong enough. Practically, however, hand pumping overdistances greater than about 30 in becomes difficult becauseof the pressure exerted by the 30 m column of water. Toreduce this pressure, most pump manufacturers useprogressively smaller cylinders at increasing depths.This reduces the surface area of the piston and thereforethe pressure, but it also reduces the output of thepump. In and hard rock regions where other waterlifting techniques are not feasible, hand pumps have beenused at depths greater than 50 m.
2 64
252
MAXIMUM SUCTION HEAD OF RECIPROCATING HAND PUMPS
AT DIFFERENT ALTITUDES FOR WATER AT 600F (15.60C)
r
I
Altitude-Above
Mean Sea Level
Barometric Pressure1
Practical Suction Head
of PumpAir
4
EquivalentHead of Water
Feet Meters Psi Feet Meters Feet Meters
0 01000 3052000 6103000 9144000 12196000 18298000 2438
10000 3048
'14.714.213.713.212.711.810.910.1
34.0 10.3632.8 10.0031.5 9.6030.4 9.2729.2 8.9027.2 8.2925.2 7.6823.4 7.13
22.6 6.9121.9 6.6721.0 6.4020.3 6.1819.5 5.9318.1 5.5316.8 5.1215.6 4.75
2. Lift pumps /lift and force pumps
If you plan to use the pump to force the waterabove the level of the pump spout, you will need a "liftand force" pump. The only difference between this andthe simple lift pump is that the lift and force pump hasa stuffing box around the pump rod at the top of thepump body to prevent water from flowing out that way.(See Figs. VII-3 and VII-4.)
If you are considering ordering a deep well pump, youwill also have to decide whether the pump should have anextractable or non-extractable cylinder. (See Figs.VII-5and VII-6.)
An open or extractable cylinder is connected toa drop pipe which is slightly larger than thepiston assembly in the cylinder. This allowsthe piston to be removed by simply pulling thepump rod up. The large diameter drop pipe ismore expensive, heavier, and more difficult towork with.
A closed or non - extractable cylinder is connectedto a smaller diameter drop pipe which will not
265
.1.
o
ZI
FIG. sits It SHALuctow
vsliw..1 I. iPT ANI, POitc111.PUMP
CY t. II t4 Dn.*.
FIG. VII S.
NON exritikc.TAIN-6.c.yi. embafte-
vAt.vE.
Pi ST'or4
CUP SEALS
4
FOOT VAL VE.
266
Fla vii - 4.exrce,AcTA6t.e-
c.lf to IN 0E42
253
254/
permit removing the piston assembly by itself.Instead the whole length of pipe must be removedfrom the well and the cylinder disconnected topermit access to the piston assembly.
The cup seals in the piston assembly need to bechanged every three months to three years, depending on
- how much use. the pump gets, the cylinder material, andthe, quality of the water. In cast iron cylinders thefirst cup seals tend to wear faster than later seals,perhaps due to an initial honing action. For a closedcylinder changing cup seals will require some kind ofheavy lifting device to be able to remove.all,the pipeand gain access to the cylinder and the piston assemblywith its cup seals. The same operation performed onan open cylinder will simply involve disconnectingthe pump from the pipe and pulling up the pump rodwith the piston assembly attached to its botton end.
C. Difficulties with Piston Pumps.
- All piston pumps present certain difficulties inpractical, everyday use.
The cylinder will be seriously damaged if sandis pumped with water. Sand scratches thecylinder wall and wears out the cup seals.
There is the problem of'cup seal wear. Thesmoothness of the cylinder wall largely, deter-mines the wear rate of seals. Brass is com-monly used because it has a smoother finishthan cast iron or steel and will not corrodebut cast iron is probably the most commonlyused cylinder, aterial. Steel cylinders arerare. Experiments are now underway withplastics and resin cylinders, cylinder linersand cup seals. The initial results are promising.
The pump rod and handle can present problems.Most handle arrangements do not pull the rod'straight up and down but allow some lateral move-ment. This back and forth movement adds to thewear on both the pump rod and the cup seals. Fora regular handle arrangement to come close tostraight up and down motion, -there must be threepivot points which add to the maintenance. How-ever, a new arrangement developmed in India, theJalna-type pump, has one pivot point and pullsthe rod straight up and down. (See Fig. VII-7 andVII-8.) The "Mark II" is the latest Indian devel-opment in Jaina-type pumps and is being used inUNICEF assisted projects in India and in someAfrican countries.
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256
D. Other Types of Pumps
There are too many other types of water pumps tomention all of them here, but a few should be brieflynoted.
1. Diaphragm Pumps
Diaphragm pumps operate similarly to piston pumpswith the diaphragm going up and down causing water to moVbthrough the pump as two valves alternately open and close.(See Fig. VII-9.)
They offer several advantages:
There is no sliding friction of a seal rubbingagainst a cylinder wall as in a piston pump.
Particles as big as the valve openings can bepumped, with little or no damage to the pump.
A small capacity pump of this type could be easilymanufactured by a local machine shop.
There is also one chief disadvantage:
An uneven stress is exerted on the diaphragmcausing it to wear more quickly around thepiston.
Po svbt1
DIAPHRAGM1> I 5C 84A ILG.G
FI.AP VALveR
Ili..."bole.,-.,mIalr./*
IIAIWAIWWWAVA VIP 4 rirM/IP
AL,11111010WS.101WWIII7WWWWWwwwikwamal, t aFa WA IA /4 'AralV/ I rA IA I.
1141.2.1- FLAPVALVE-
FIG.V11-9. DirPHRAGt4 Pume69
2. Helical Rotor Pumps
This is a modern typeof pump with a spiral-shaped interior designwhich is preferred inseveral developingcountries because of theextremely limited amountof maintenance that is re-quired despite the pump'shigh cost. It will pumpalmost anything that iscapable of being forcedthrough its pumping unitwith little or no damageto it.
DRIVE SHAFT
Two handles are used ttErAt... GASTiNG-
to drive the gear whichturns the shaft with therotor, on its bottom end,which turns inside a rub--ber stator to move waterupward. (See Fig. VII-10.)The pump is designed insuch a way that the weightof the water is supportedon a set of bearings, asopposed to piston pumpswhich Support the weightof the water through thepump rod and pump handle.Unlike standard rotarypumps, the height to whichwater can be pumped with ahelical rotor is not deter-mined by the speed of. thepump.
it6,V1I-i0. 1-IEL1C.AL ROTOR_Pumpikg, UNIT
270
25.
258
c
3.Bucket pumps
A series of bucketsattached to a chain orrope pick up water anddump it into the spoutas the handle is turned.This type of pump can beeasily made from locallyavailable materials. -
(See Fig. VII-ll.)
1
4
4
FiG. VIl2, CI4A1I4 PUMP
n
FIG,V11-11. 'BUCKET PUMP
4. Chajn Pumps
LWather or rubberdiscs usually attachedto a chain trap water inthe pipe and push it upthrough the pipe to 'thespout as the handle isturned to move the chain.This type of pump can bereadily modified to makeit suitable for localmanufacture. (See Fig.VII-12.)
271.1
5. Motorized pumps
Motorized pumps are normally not appropriate forrural water supplies where a.limited amount of watet isneeded. The energy required to power these pumps isusually expensive, not readily available or both.
The motorized pumps most commonly used for pumpingwater are:
Centrifugal pumpswhich rely on auoutside power sourceto turn a rotorfast enough to bothlift and forcewater. (See Fig. VII-13.)
FIG. VII- 14. Tuagime PUMP
B-
A- r.mpaiXeRs
B STAGESC-514^FTD- STRAINER..
FIG. VII -13. GENrili Fv&At- MAW
Turbine pumps whichalso rely on an out-side power source. toturn a rotor fastenough to move thewater. The turbinerotors must be sub- -
merged. (See Fig. VII-14.)
2720
259.
"it
260'
741
6. Hydraulic Rams
Hydraulic rams cannot be used to lift water froma well, but in the proper situation can be very usefulin pumping water from one location to another. Ramsare most often utilized to move
of water above, the ram to/a storage tank or cis -water from an open
/ tern which is higher than the-level of the open bodyof water.
Et. Manufacturing aPump
Another approach to the installation of pumps whichhas been successful in some areas is to purchase onlythat part of the complete pumping unit which needs to becarefully machined. The rest of the.pump can be assembledfrom locally available materials, withthe obvious ad-vantages of familiarity and availability;
The most widely ,used pump of this type is composedof a cylinder assemblytpurchasea from a manufacturer,attached to locally available galvanized drop pipe. Thepump stand, handle and spout can be assembled from woodand pipe. (See Fig
. ff6. V 5 . WICALLY MAG.&4 PUMP HEAP
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261
Appendix VIII
WATER TREATMENT IN WELLS
A. Well Disinfection
After a well is built, the whole structure should becarefully disinfected. Disinfection is needed to killany possibly harmful bacteria that could be transferredfrom the pipe or concrete lining to the water and thenon to the people who consume the water.
The wall can be disinfected by adding enough chlorineto the well water to produce a strong chlorine solution;This solution can then be used tc rinse off the rest ofthe well and so disinfect it.
1. First, the volume of the water in the well willhave to be determined.
NOTE: The volume of water in a circular well canbe easiliucomputed by measuring the depth of the waterand the diameter of the well. Multiply (water depth) x(1/2 diameter) x .(1/2 diameter) x (5.1416). Expresgedanother way this becomes: Volume = (depth)(radius)4(3.1416).
2. From Table VIII-1 find the amount of chlorine thatwill have to be added to the computed volume of water toproduce a strong chlorine solution.
3. Dissolve the required amount of the chemical ina bucket of water before adding it to the well.' Add nomore than 100 g of bleaching powder or calcium hypo-chlorite to each bucket of water.
4. Pour the solution into the well. it is best toagitate the water to insure that the chlorine is evenlymixed.
5. The strong chlorine solution should be left inthe well for at least 12 hours and preferably for 24.It must be stressed that this strong chlorine solutionis not suitable for humans or animals.
6. After the 12 to 24 hour contact time, thestrongly chlorinated water should be pumped from the welluntil the residual chlorine level is below 0.7 mg perliter of water. (See belpw.) The pumping equipment tobe installed on the well can be disinfected by using it
274
262
to remove the excess chlorine. Choose a disposal placefor the chlorine solution where it will have as littlecontact with plant and animal life as possible
B. Water Disinfection
Water can be easily disinfected by adding to it oneof several commonly available chemicals which containchlorine. The most common type of household bleach isa mild chlorine solution which can be used to disinfectwater.
The amount of chemical or solution needed to dis-infect water will depend on the degree of contaminationof the water and the amount of chlorine present in thechemical. However, in most cases where the water isclear with no suspends. solid particles, the followingdisinfection procedure can be used.
1. Determine the volume of water to be disinfected.
2. Find the amount of chlorine compound that will5e needed to disinfect that volume of water. (SeeTable VIII-2.)
3. Dissolve the requiied amount of chemical in abucket of water before adding it to the water to bedisinfected. Add no more than 100 9 of bleaching powderor calcium hypochlorite to each bucket of water.
4. Pour the bucket of chlorine solution into thewater to be disinfected. Agitate the water to ensuregood mixing.
5. when the chlorine residual (See below.) inthe water drops below 0.2 mg per liter, this disinfectionprocedure should be repeated.
C. 'Chlorine Residual
The chlorine residual is the amount of chlorine thatis left in treated water. Chlorine is used up as itdisinfects. Add enough chlorine to the water so thatthere is a little left over (the residual) after thechlorine has had at least 30 minutes to react with andkill all the living-organisms in the water. This assuresthat all the disease causing bacteria have been destroyedand that there is still some chlorine available to killother contaminants which might enter the water at a latertime.
2 75
The recommended chlorine residual is 0.5 mg perliter. A higher residual will cause an obvious chlorinetaste in the water. Above 3.0 mg per liter chlorineconcentration can cause diarrhea.
Chlorine residual is easily checked with any of thecommercially available color comparators. Most of theseuse an "orthotolidine solution", which turns progressivelymore yellow at higher chlorine residuals.
1
276
263
264
TABLE VIII -1
AMOUNTS OF CHEMICALS REQUIRED FOR ASTRONG CHLORINE SOLUTION CAPABLE OF
DISINFECTING WELLS AFTER THEIR CONSTRUCTION*
Water(m3)
Bleaching powder(25-35%)(g)
High strengthcalcium hypochlorite
(70%)(g)
Liquid bleach(5% sodium
hypochlorite)(ml)
0.10.120.150.2
10121520
4.35.26.58.6
607290
1200.25 25 11 1500.3 30 13 1800.4 40 17 2400.5 50 22 3000.6 60 26 3600.7 70 30 4200.8 80 34 48G1 100 43 6001.2 120 52 7201.5 150 65 9002 200 86 1 2002.5 250 110 1 5003 300 130 1 8004 400 170 2 4005 500 220 3 0006 600 260 3 6007 700 300 4 2008 800 340 4 800'
10 1 000 430 .6 00012 1 200 520 7 20015 1 500 650 9 00020 2 000 860 12 00030 3 000 1 300 18 00040 4 000 1 700 24 00350 5 000 2 200 30 00060 6 000 2 60070 7 000 3 00080 8 000 3 400
100 10 000 4 300120 12 000 5 200 -
150 15 000 6 500200 20 000 8 600.250 25 000 11 000300 30 000 13 000400 40 000 17 000500 50 000 22 000
,* This produces a chlorine concentration of approximately
30 mg/1 flipmY. This water should not be .drunk by peopleofanimals.
277
TABLE Ian -2
AMOUNTS OF CHEMICALS NEEDED TODISINFECT A KNOWN QUANTITY OF
WATER FOR DRINKING*
Water-(re)
Bleaching powder(25-35%)(g)
High strengthcalcium hypochlorite
(70%)(g)
Liquid bleach(5% sodium
,hypochlorite)(m1)
11.21.52
2.5
2.33
3.556
11.21.52
2.5
1417212835
3 7 .3 424 9 4 565 1.2 5 70
' 6 14 6 847 16 7 988 19 8 110
10 23 10 14012 28 12 17015 35 15 21020 50 20 28030 70 30 42040 90 40, 56050 120 50 70060 140 60 84070 160 70 98080 190 80 1 100
100 230 100 1 400120 280 120 1 700150 350 150 2 100200 470 200 2 800250 580 250 3 500300 700' 300 4 200400 940 400 5 600.500 1 170 500 7 000
Approximate dose = 0.7 mg of applied chlorine per litre ofwater.
278
265
J.
267
Appendix IX
ROPE STRENGTH
Nominal Diameter Circumference RopeWeight
Safe Working Capacitymetric tons
, kg.inches cm cm per No. 1 Manila Sisal
. m
1/4 .64 .2.01 .03 06 .053/8 .97 '3.05 .06 .15 .12-1/2 1.27 3.99 .11 .29 .235/8 1.60 5.03 .20 .49 .393/4 1.91 6.00 .25.. .60 .487/8 2.24 7.04 .28 .86 .69.
1 2.54 7.98 '.40 1.01 ,811-1/8 Z.87 9.02 .53 1.35 1.081-1/4 3.18 9.99 1.52 1.211-1/2 3.81 11.97,4. . 11 2.08 1.661-3/4 4.45 .13.98 1.32 2.98 2.382 5.08. 15.96,' 1.60 3.48 2.792-1/2 6.35 19.95 2.00 5.23 4.18
7.62 23.94 3.58 7.20 5.76
This chart is based on a similar chart found, in EngineerField 'Data (1969) FM5-34, Headquarters Department of theArmy, 554 pp., The original chart was given in English unitswhich have here been converted to metric units.
The safe loads listed are for new rope used underfavorable conditions. These have been calculated by diVidingthe breaking strength of the rope by 4. As rope ages ordeteriorates, progressively_ reduce safe loads to one-half ofthe values given.
Here is an example. of-how the chart can be used.
A 1 meter high lining ring 10 cm thick with a 1.2minterior diameter contains 0.41 m3 of concrete. Since con-crete normally weighs about 2300 kg. per m3 the lining ringweighs about 943. kg. or 0.943 tons. A new manila rope witha diameter of at least 2.54 cm and a circumference of 7.98cm will be needed to safely handle the lining ring.
279
269
GLOSSARY.
apron - A slightly sloped concrete pad which surroundsthe well and helps prevent contaminated surface waterfrom finding its way back into the well.
aquifer - A, water-bearing laver (stratum) of permeablerock, sand, or gravel.
artesian well - A:well that reaches water which, frominternal pressure, flows up like a fountain.
bit - The piece which operates at the bottom end of thetool string to loosen the soil or rock to deepen thehole.
bottom plug - A concrete slab across the bottom of a wellwhich can act to prevent anything from entering thewell or allow only water to enter.
bottom section - That part of the well that extends be-neath the water table.
brake post - An anchored cylindrical object which can actas a friction brake for rope wrapped around it.
casing - Metal pipe used to reinforce a drilled well.
cement - A gray powder used as an ingredient in mortarand concrte.
concrete - A hard strong building material made by mixingcement, sand and gravel with sufficient waterto causethe cement to set and bind the entire mass.
consolidated ground formation - Any of the various kinds ofrock: hard rock; examples: granite.
contaminate -,To make impure or unclean.
curb - A part of the well lining that extends out frOm thelining into the surrounding soil, helps to hold it inplace and, prevents it from sliding down.
cutting ring - A sharp edged ring used on the bottom of alining that is being sunk into place to'make sinkingeasier.
280
development - See well development.
drive cap - A strong protectivd covering, screwed onto the top of a metal casing pipe and then struckto drive t'ae pipe into the ground.
drop pipe - That section of pipe in a deep well pumpassembly which extends between the pump cylinder andthe pump body.
foot valve -.A valve at the'bottom of the suction pipewhich prevents the water pulled up into it by thecylinder frod flowing back into the well.
form - The structure or material around or in which con-crete will exactly conform to.
ground water - Water deep enough in the ground so thatit cannot be drawn off by plants or evaporated outthrough the ground surface; accumulates in quantityin aquifers from which it can be drawn out of theground through weirs.
grout seal - Mortar or concrete used to fill in a spaceto snake it waterproof.
head wall - A short wall which extends above the groundlevel around a well.
hydrologic cycle - Continual natural cycle through whichwater moves from oceans tOaclouds to ground and ul-timately back to oceans.
impermeable - A su5s4.ance through which water cannotpenetrate.
intake section - That part of the bottom section throughwhich water enters the well.
laterite - A residual product of rock decay that is red incolor; prevalent inAfrica; difficult to penetrate buthas little strength for construction purposes.
level -.(Adj.) perfectly horizontal; (noun) a deviceused to establish a perfectly horizontal line.
lining - Masonry wall bUilt to reinforce dug well holewalls.
lining ring - A hollow circular column, usually made ofconcrete, which is used to reinforcega dug well.
271
middle section - That part of the well between the groundsurface and the water table.
mold - Form used in the construction of linings and liningrings.
percussion - The act of tapping sharply.
permeability - The speed which water can move through acertain type of soil or rock. Water will move muchfaster through sand than it will through clay so thesand is said to bemore permeable.,
platform,- See apron.
plumb - Perfectly straight down or up.
pump cylinder - That part of the pump in which the pistonand cup seals slide to move water,.
sinking method - Any technique used to di, or drill a well.
stable ground - Firm soil; not likely to cave in.
suction pipe - That part of the pump assembly which extendsbeneath the cylinder into water.
surface recharge - The amount of water that soaks down throughthe ground to reach an aquifer in a certain length of time.
surface water - Water that is found on the ground surfieein puddles, streams, rivers, lakes or oceans.
surge plunger - A device that can be inserted into thecasing pipe and is moved up and down to develop the well.
swivel connection - A device used tlo connect two pipes orhoses and which permits one or both to turn freely.
tool string - The entire length of equipment and connec-tions operated in the hole to sink a drilled well.,
top section - That part of the well above the ground sur-face.
transpiration - The passage of water vapor from .plants intothe atmosphere.
unconsolidated ground formation - any type of soil other thanhard rock;. examples: sand, gravel, clay.
282
.11
272
valve - A structure that permits the movement of fluid inone direction only.
water source - Any place where people could possibly cometo gather water; for example a well, spring, river,lake, reservoir, public tap, private home faucet.
water table - The upper limit, of that portion of theground which is wholly saturated with water.
watertight seal - An impermeable material used to preventwater from moving from one area to another.
well development - The process of rearranging the soilparticles around the intake section of a well to permiteasier and better water flow into the well.
t
283
ANNOTATED BIBLIOGRAPHY
Abramo, V.J., ed. Peace Corps Wells Manual for Volunteers(1972). ACTION/Peace Corps. Information Collectionand Exchange, Washington, D. C. 20525, U.S.A.(Book, 135 pp.)
This is essentially,a conference reportyritten after a meetingof PCV's working on wells projects in W. Adrica. General,coverage of organization and techniques. Much good infor-mation, but sometimes difficult to locate. The scope islimited and occasionally omits variables that might applyin*special cases. Now out of print.
Allesbrook, J.C.P. "Driven Tubewells", in AppropriateTechnology (Vol. 4, No. 4, Feb 1978). Intermediate.Technology Publications Ltd., 9 King Street, LondonWC2E 8HN, England. ('Periodical Article, 2 pp.)
Short quick description of driven wells with an interes ingmethod presented for making a drive point out of a pie e ofmetal pipe.
. "Where Shall We Dig the Well?" inAppropriate Technology (Vol. 4, No. 1, May 1977).Intermediate Technology Publications Ltd., 9 KingStreet, London WC2E 8HN, England. (PeriodicalArticle, 3 pp.)
An overview of various geological situations and where oneis likely to find water in them. Unfortunately, the articleis helpful only if you know the geological conditions ina given area.
Anderson, Keith E. Water Well Handbook (197V. MissouriWater Well and Pump Contractors Assn., Inc., P.O. Box250, Rolla, MO 65401, U.S.A. (Book, 281 pp.)
Intended as a reference book to supply all charts, tablesand other data commonly needed by drillers, engineers andgeologists working with water wells. Topics include math-matical formulas and conversion tables, water data, qualityof Water, cable tool drilling, rotary drilling, air rotarydrilling, pipe and casing, pumps, electrical data, flowmeasurement, geology and hydraulics of wells, water supplyand equipment. Because the book is meant for use in U.S.,all sizes and measurements are in American terms, withlimited use in developing countries. Although there areno "how-to" explanations, many of the tables are very infor-mative.
284
273
274
Annual Report (1976). WHO, International Reference Centrefor Community Water Supply, P.O. Box 140, 2260 Leid-schendam, Netherlands. (Booklet, 48 pp.)
A description of activi ies of the IRC. They leave unclear
ijust exactly who is to receive their efforts and what '
specific services they'ave to offer.
Assignment Children (April-Jun 1976). UNICEF, Carnets del'enfance/Assignment Children, Palais Wilson, Casepostale 11, 1211 Geneve 14, Suisse. (Quarterly Review,131 pp.)
Several articles in a variety of languages about reals needsand planning of water supply development in small communities.Interesting and useful discussion of successful approachesto the problem.
Chad Wells 1977 (1977). "Chad PCV Report.", (Report, 27 pp.)A short history of the Peace Corps /Chad -well drilling pro-gram up to-1977. Details are given on pump development. Agood quick overview f methods and materials used, butreaders must unders nd.the technology. Fine drawings ofan example well, an some of the equipment, plus lists ofmaterials suppliers and references.
Community Water Supply and Excreta Disposal Situation in theDeveloping Countries; A Commentary (1970). World'Health Organization, Distribution and Sales Service, 1211Geneva 27, Switzerland. (Booklet, 11 pp.)
Comments and analysis of 1970 WHO survey to determine "watersupply and excreta disposal conditions ant needs in 75developing countries." The booklet concludes that "It ishard to find a successful rural community water supplyprogramme that did not'involve active community participation."
Darrow': Ken and Rick Pam. Appropriate Technology Sourcebook(Nov 1976). AT Project, Volunteers in Asia, Box 4543,Stanford, CA 94305,U.S.A. (Book, 304 pp.)
A guide to practical plans and books for village and smallcommunity technology. Publications were chosen that provideenough practical information to be of significant helpinunderstanding principles and in actually building the designsincluded. Highly recommended.
46enis, A. and N. Fernando. "Low Cost Tube Wells", inAppropriate Technology (Vol. 2, No. 4, Feb 1976).Intermediate Technology Publications Ltd., 9 King Street,London WC2E 8HN, England. (Periodical Article, 2 pp.)
This brief article lists Simple drilling equipment, outlineof procedures, and comparison of locally available materialsfor use as casing in a small diameter well. Be aware thatthe bamboo procedure outlined here was tried unsuccessfullyaccording to Bruce Eaton, The Chief Driller's Report on JJCIP(q.v.).
285
Design and Control of Concrete Mixtures (July, 1978). 11th-edition. Portland Cement Association, Old Orchard Rd.,Skokie, Illinois 60076, U.S.A. (Report, 121 pp.)
Everything a reader would want to know about the propertiesand variables of concrete, telling everything about what you:can and cannot do with concrete. Much of this information isnot specifically useful for simple concrete work in developingcountries, although it could be a source for design ideas.
Dulansey, Maryanne. Water Resource Development (March 1977).American Council of Voluntary Agencies for ForeignService, Inc., Technical Asifisteence Information ClearingHouse (TAICH), 200 Park Avenue South, New York, N. Y.10003, U.S.A. (Booklet, 23 pp. plus appendices.)
Offers a summary of the experience of U.S. non-profit orga-nizations: their programs, results and recommendations. Itwas quickly put together for water conference, citing thelarge amount of work done by NGO's and recommending that theybe coordinated for future efforts.
Eaton, Bruce. The Chiet Driller's Report on JCCIP (June1976). Agricultural Development Agencies in Bangladesh,549F, Road 14, Dhanmandi, Dacca-5, Bangladesh. (Book-let, 29 pp.)
A comparison of 20 wells completed with different kinds ofequipment and using different techniques. The bookletemphasiiei that when propellor pumps are installed directlyin a PVC casing, the casing acts as a riser pipe and doesnot work very well for a number of reasons. Booklet offersa comparison of several different drilling and developingmethods, and it is recommended for appropriate drillingprojects.
Freedman,'Ben. Handbook (1%77) 4th edition.Peerless.Publishing Co., P.O. Box 30187, New Orleans,Louisiana 70130, U.S.A.
Gives Ou everything you need to know about sanitation.Mostly geared to U.S., but a wealth of good basic informa-tion, including 180 pages on water. It is highly technical,and the non - specialist cah get most of the informationelsewhere.
Gibson, U.P. and R.16." Singer. Water Wells Manual (Jan 1969).Premier Press, Box 4438, Berkeley, CA 94704, U.S':A.(Booklet, 156 pp.)
This booklet (formerly Small Wells Manual, published byUSAID), covers exploration and deVelopment of ground-watersupplies. Discusses wells up to 4 inches in diameter, 100feet deep, with yields up to 50 U.S. gal./min. Much ofthe technical information on drilling is taken from GroundWater and Wells (q.v.), plus descriptions of some lesstechnical drilling methods. Requires a good knowledge olioEnglish and a technical orientation. 1
J 286 .
275
276
Gordon, R.W. Water Well Drilling with Cable Tools (1958).Bucyrus-Erie Company, 1100 Milwaukee Ave., SouthMilwaukee, Wisconsin 53172,*:U.S.A. (Book, 230 pp.)
Excellent book, describing cable-tool drilling equipment andprocedures, but it is needed only by people working withan actual rig they must become familiar with.
Ground Water and Wells: A Reference Book for The Water-Well-----inaustry (1975). UOZT.Johnson, Universal Oil Products,
Johnson Division, St. Paul, MN 55165, U.S.A. (Book, 440 pp.)An excellent book for anyone working with wells, specificallywith drilled wells. Generally acknowledged as the basicreference work on drilled wells.
Guidelines and Criteria for COmmunity Water Supplies in theDeveloping Countries (1969). USAI and USPHS, Devel-opment Information Center, DS/DIU DI, Room 105, SA 18,Agency for'International Developm nt, Washington, D. C.20523, U.S.A. (Book, 101 pp.)
Offers data on water supply-programs in 12 c.,,weloping coun-tries in various parts of the world, although Africa isexcluded. Makes recommendations for development and planningof large water supply programs. Sometimes written in ahard-to-read format, but ten years ago this study came toconclusions that were ahead of its time and have stillnot been effectuated. The book concludes that deiign of.water supply systems must take into account the people whowill'be using. them and that what works in a developed country .
is often not appropriate in a developing country.
Huiman, L. and W. Wood. Slow Sand Filtration (1974).World Health Organization, Distribution and Sales Service,1211 Geneva 27, Switzerland. (Booklet, 11 pp.)
Intended as a defense of slow-sand filtration for largetreatment systems. Chiefly a discussion of large-scaleslow-sand filtration, useful and appropriate in many areas.Offers excellent basics on'slow-sand filtration. Tells howit works and how to build slow-sand filter, although nosimple plans are given for a small scale filter, probablybecause the authors feel that such filtration can be moreefficiently and effectively done on a large scale.
Karr, William V. Ground Water: ''Methods of Extraction andConstruction ("69). International Underground WaterInstitute. Contact: Ranney Water Systems, Inc.,1134 Corrugated Way, Columbus, OH 43201, U.S.A.(Book, 95 pp.)
Academic presentation of radial collection-well techniquespfor those who might possibly use one for large water supplies.Covers large diameter caissons sunk an average of 30 m, with18 to 24 inch thick walls.
-287
6
Kear, D. and B.L. Wood. The Geology and Hydrology of WesternSamoa (1959). New ZeaIandrGeologicafiturvey. GeologicalSurvey Division, Department of Scientific and IndustrialResearch, Private Bag, Wellington, Neil Zealand, Attention:Publications. (Book., 92 pp. plus mats.)
An excellent, moderate -level presentation and discussion onthe availability of fresh water,on islands.' To quote from-the book, "The basic theoretical factord in the general areaof underground water are described; the possible sources ofwater in Samoa are listed and described; the technical,administrative, and educational requirements of Samoan watersupply,are discussed; the present supply position is reviewed;and the suggested sources of supply are given for-most of theTerritory." This may not' be available.
Leopold, Luna and Walter B. Langbeir. A Primer on Water(1960, 1966). Geological Survey, airailabIe from Super-intendent of Documents, U.S. Government Printing Office,Washington, D.C.20402, U.S..41 for $0.35. (Booklet, e
50 pp.)An introduction to water and where it comes from, intendedfor use by the average American citizen who has never hadto think about:water because it always comes from_the faucet:
mann, H.T. and D. Williamson. Water Treatment and Sanitation(Jan 19763. Revised edition. .Intermediate TechnologyPublications Ltd., 9 King Street, London WC2E BaN,England. (Booklet, 90 pp.)
Mostly an overview of basics, but the booklet offers 21pages do water testing and treatment, with emphasis on sandfiltration. It also includes information on measuring waterflow, pumps, latrines, sewage treatment, and final disposalof waste, but a field worker could not treat water usingthis manual alone.
Manual c ndividual Water $upply S stems (1975). USEPAU.S. Environmental Protection Agency, Water.
Supply Division, Washington, D.C. 20460, U.S.A.(Book, 155 pp.)
This book offers basic information, primarily on drilled wells,to a homeowner wishing to understand more about his or herwater system. It emphasizes sanitary protection of watersources, and isan into:;. sting overview of the differentsystems one could build. It is not meant to be a "how-to"manual.
Matthias, A: J. and E. ,Smith. How to Design and InstallPlumbing. (1967). 4th edition, .revifea. Ame-rttfarTechnical Society, 5608 S. Stony Island Ave., Chicagc,Illinois 60637, U.S.A. (Book, 446 pp.)
Overview of what to look for and roughly how t9 plan plumbinJsystems in virious situations. Does not offer "how-to"descriptions of the actual work involved to cut, thread, orotherwise connect pipe, and assumes availability of manufac-tured pipe and joints.
288
277
278
McJunkin, F. Hand Pumps for Use in Drinking Water Suppliesin Developing Countries (19771. WHO, InternationalReference Centre !Zi-Community Water Supply, P.O. Box140, 2260 Leidschendam, Netherlands. (Book, 230 pp.)
This book is an excellent introduction and analysis ofthe technical aspects of hand pumps, including quite a bitof detail. Offers the state-of-the-art on manufacturedhand pumps and some mention of locally made pumps. Gives agood idea of what is available, how it is designed, and whydesigns are as they are. Free if requested from developingcountries; r:therwise, $8.00.
McJunkin, F.E. Surveillance of Drinking Water Quality (1976).World Health Organization, Distribution and SalesService, 1211 Geneva 27, Switzerland. (Book, 135 pp.)
This book offers ". . . information and guidelines forplanning, organizing, and operating programmes for surveil-lance of drinking-water quality at the national or regionallevel in developing countries." It is more oriented towardorganizing a national water quality program, although thereis some good detailed information on relatively simplemethods of water testing and what it means, the significanceof large planning and some good "how-to" methodology. Youwill learn that disinfection, usually with chlorine, isrelatively simple, easy to monitor, and the single mosteffective water treatment technique.
McJunkin, F.E. and C.S. Pineo. The Role of Plastic Pipe inDeveloping Countries (1969). USAID. DevelopmentInformation Center, DS/DIU/DI, Room 105, SA 18, Agencyfor International. Development, Washington, D. C. 20523,U.S.A. (Book, 150 pp.)
The premise of this book is that because pipe is the singlemajor component of most water supply systems, the cost of,construction of these systems could be reduced if the pipewere manufactured in the country. Book is intended as anawareness piece for decision makers and engineers and "shouldenable the reader to (1) weigh the merits of plastic as apipe material, (2) quickly acquire an awareness of the stateof the art, (3) prepare design criteria and standards andspecifications for manufacture, testing and installation ofplastic pipe, (4) organize a testing program, and (5)undertake preliminary feasibility studies of manufactureand marketing of plastic pipe." It has limited use as afield document.
Miller, Arthur P. Water and Man's Health (Jul 1967). USAIDreprint. Development Information Center, DS/DIU/DI,Room 105, SA 18, Agency for International Development,Washington, D. C. 20523, U.S.A. (Book, 92 pp.)
279
Now out of print but many copies are still around in PeaceCorps or AID offices. An excellent presentation of back-ground information on specific water-related diseases;water's relatedness to disease; the seriousness of watertransmitted disease; method of transmission; the historyof discovery of causative agents; human susceptibility towater-borne disease; and methods of control. Offers infor-mation on chemical pollutants as a likely source of watercontamination, theresulting physice conditions from over-doses, and recommended maximum concentrations in drinkingwater. This book is now being rewritten by F.E. McJunkinand is expected to be available by late 1980.
More Water for Arid Lands (1974). National Academy ofSciences, 2101 Constitution Ave., Washington, D.C.20418, U.S.A. (Book, 153 pp.)
Report of an ad-hoc panel of the Advisory Committee onTechnical Innovation, Board on Science and Technology forInternational Development, Commission on International Rela-tions. Discusses "little known buti_promising technologiesfor the use and conservation of scarce water supplies inarid areas . . . The technologies discussed should, atpresent, be seen as supplements to, not substitutes for,standard large-scale water supply and management methods."A most useful overview of techniques that can be used forwater supply and water conservation 'in arid areas, butoffering no real "how-to" information. A good bibliographyfor readings in selected areas, and a French edition isavailable.
Okun, D.A. and G. Ponghis. Community Wastewater Collectionand Disposal (1975). World Health Organization,.Distribution and Sales Service, 1211 Geneva 27,Switzerland. (Book, .285 pp.)
A description of large-scale sewage treatment plant designand construction. Good information on hydraulics, flayingpipe, and water treatment.
Pacey, Arnold. Hand-Pump Maintenance in the Context ofCommunity Well Projects (1978). Intermediate Techno-logy Publications Ltd., 9 King Street, London WC2E 8HN,England. (Booklet, 38 pp.)
This presents the basics of a hand-pump installation programneeded for a supply of clean water from wells, offering achoice between three different levels of technology andtheir concurrent levels of local community involvement.Probably the best introduction to pumps, since it deals withcommunity aspects and not just with technology. Highlyrecommended.
290
280
Rajagopalan, S. and M.A. Shiffman. Guide to Simple SanitaryMeasures for the Control of Enteric Diseases (1974).World Health Organization Distribution and Sales Service,1211 Geneva 27, Switzerland. (Booklet, 103 pp.)
Good, practical plans and things to look for in constructingand maintaining sanitary water sources, concentrating onmethods of simple disinfection with chlorine.
Shallow Wells, Shenyanga Region, Third Progress Report (1976).Governments of Tanzania and Netherlands. (Booklet, 55 pp.)
A description of a wells project in the Shenyanga region ofTanzania. Interesting quick discussion of a large projectwhich dug wells, lined them with pre-cast concrete rings,and installed a locally manufactured hand pump. Offersgood plans and detailed descriptions of equipment and work.
Sternberg, Y. and R. Knight. Development of PVC Well Screensfor Local Fabrication in Developing Countries (1918).Public Utilities Report No. RES14. International Bankfor Reconstruction and Development, 1018 H St., N.W.,Washington, D.C. 20006, U.S.A. (Working Paper, 8 pp.)
This paper describes the development and manufacture of acontinuously slotted well screen made of specially reinforcedPVC pipe. Where PVC is extruded and where motorized lathesare used, these well screens might be produced at low cost.This may be a new breakthrough in well screen manufacture,and it is now being field tested.
Wagner, E.G. and J.N. Lanoix. Water Supply for Rural Areasand Small Communities (1959). World Health Organiza-tion, Distribution and Sales Service, 1211 Geneva 27,Switzerland. (Book, 337 pp.)
The book is old, rapidly becoming outdated... It is expensiveand oriented to larger pumps and distribution systems, butstill probably serves as the basic' reference book on thesubject. Almost everything in the book is covered betterand in more detail by some other book, but no other referencehas all of the basics together and'easily accessible in oneplace.
Walton, William C. Groundwater Resource Evaluation (1970).McGraw-Hill Press, 1221 Avenue of the Americas, NewYork, N.Y. 10020, U.S.A. (Book, 664 pp.)
This book offers equations and methods used to quantitativelyappraise the hydrogeologic parameters affecting the water-yielding capacity of wells and aquifers, and those used "toquantitatively appraise the response of wells and aquifersto heavy pumping." A college-level engineering text.
29i
281
Water Purification, Distribution, and Sewage Disvosal forPeace Corps Volunteers (19691. Volunteers in TechnicalAssistance (VITA), 3706 Rhode Island Ave., Mt. Ranier,Maryland 20822, U.S.A. (Book, 243 pp.)
An early attempt at an appropriate technology manual onthese subjects. The book answers most technical questions,but concentrates on a technical point of view withoutinformation on using locally available materials. There ismuch useful material, organized with lesson plans, but thebook also includes some irrelevant material.
Water Resources Development-2 (1974). Action for FoodProduction (AETRO), C-52, N.D.S.E. Part XI, New Delhi -110049, India. (Booklet, 72 pp.)
This. booklet offers some "how-to" plans for several differentwater sources, including drilling wells by hollow rodsystem, a multiple-well scheme for irrigation, lined dugwells, and blasting procedures. The material is good,relatively simple, and geared to locally available materialin India.
Water Well Journal. National Water Well Association, 500 W.Wilson Bridge Rd., Suite 130, Columbis, Ohio 43085 U.S.A.(Monthly periodical.)
Intended for commercial well drillers and water well equip-ment suppliers in the U.S. The magazine annually publishesa buyers' guide and a directory of manufacturers as well asoffering interesting articles on new and old techniques andequipment, business and industry practices.
'Watt, S. and W.E. Wood. Hand Dug Wells and Their Construction(1976). Intermediate Technology Publications Ltd.,9 King Street, London WC2E,810, England. (Book, 234 pp.)
The best book on hand dug wells 'available. Emphasis on onespecific kind of dug well construction with concrete, butconsiderable description of alternative methods. Manyuseful pictures and drawings.
Well Drilling Operations (1965). Departments of the Armyand the AEr Force, TM-5-297/AFM85-23. Superintendent ofDocuments, U.S. Government Printing Office, Washington,D.C. 20402, U.S.A. (Book, 249 pp.)
This book offers about 50 pages of introductory discussionand material on hand-dug, bored, jetted, and driven wells.The rest is primarily a good basic discussion of cable tool'and rotary rigs.
292
282
White, Anne U. and Chri$ Seviour. Rural Water SUp 1 andSanitation in Less-Developed County es 1 . Inter-national Development Research Centre, Box 8500, Ottawa,Canada K1G 3H9. (Booklet, 81 pp., with annotatedBibliography.)
This booklet provides a good overview of the subject withperhaps more emphasis on the design and planning of projectsthan on actual "how-to" methods. It offers an excellent5 page introduction on the history and development of watersupply, and current trends.
Winter, G. and A.H. Nelson. Design of Concrete Structures(1973). McGraw-Hill Press, 1221 Avenue of the Americas,New York, N.Y. 10020, U.S.A. (Book, 615 pp.)
The text for a basic college level course in design withconcrete. There is a lot of higher math in this book, butanyone with mechanical or engineering background canpersist to figure out the exact design requirements ofany concrete structure. Not recommended to those withoutsolid technical education.
To avoid sending to Europe for publications from the Inter-mediate Technology Development Group or the World HealthOrganization, U.S. readers may order ITDG and WHO publicationsfrom the distributors indicated below:
ITDG distributors are:
International Scholarly Book Services, Inc.P. O. Box 555
, Forest Grove, Oregon 97116
WHO distributors are:
"GPO soa.sso
World Health Publication Center49 Sheridan AvenueAlbany, New York 12210
293
+.)
Since 1961 when tMe Peace Corps was created, more than 80,000 U.S. citizens have servedas volunteers'in developing countries, living and working arcing the people of the ThirdWorld as colleagues and co-workers. Ttday 6000 PCVs are involved. in programs designedto help strengthen local capacity to address such fundamental concerns as foodproduction, water supply, energy development, nutrition and health education andreforestation.-
Loret Miller Ruppe, DirectorEdward Currah:.Deputy Director DesignateRichard B. Abell, Director, Office of Program Developrentl_
Peace Corps overseas offices:
HELIZF FIJIP.O. Box 487 P.O. Box 1094Belize City ,Suva
BENINBPCotonou _
BOTSWANA-P.O. Box93Gaborone
-CAMI-ROuN
BPYaounoe
CENTRAL AFRICANRE-PUBLIC
We 1080Bangui
CuSTA RICAkartado Postal1266San Jose
DOMINICAN RLPUBEICApartano Postal.
1414
Santo Doringo
LASTERN CARRIBBEANIncluding: AntiguaBarbados, -Grenada,Montserrat,St. Kitts - Nevis,
St.Lucia,St.Vincent, Dominica'Erin Court"Bishops Court hillP.O. Box 696-CBridgetown, Barbados
ECUADORCasilla 635-AQuito
GABONBP 2u98Libreville
GAMBIA, TheP.O. Box 582Banjul
GB. Aft%
P.O. Box 5796Accra (North)
GUATEMALAba Avenida 1-46Zona 2Guatemala
HONFCRASApartado PostalC-51Tegucigalpa
JAMAICA9 Musgrove AvenueKingston 1U
KENYAP.O. Box'30518Nairobi
LESOTHOP.O. Box 554Maseru
LIBERIABox 707monrovia
MALAWIBox 208Lilongwe
MALAYSIA-177 Jalan Raja MudaKuala Lumpur
MALIBP 85Bamako
MAURITANIAWP 222Nouakchott
MICRONESIAP.O. Box 336Saipan, MarianaIslands
MORuCOO1, Zanquat PenzerteRabat
NEPALP.O. Box 613Kathmandu.
NIGERBP 10537Niamey
OMANP.O., Box 966muscat
PAPUA NEW GUINEAP.., Box 1790Boroko 6
:PARAGUAYc/o Arerican Embassy
TunisAsuncion
SIERRA LEONEPtivate Mail BagFreetown
SOLOMON ISLANESP.O. Box 547honiara
SWAZILANDP.O. Box 362Mbabane
TANZANIASox 9123Dar es Salaam
THAILAND42 Sol Somprasong 2Petchhuri RoadBangkok 4
TOGOSP 3194 -
Lome
TONGAPP 147Nuku'Alofa
TUNISIA,B.P. 96'1002 Tunis - Belvedere
PHILIPPINESPLO. Box 7013Manila
RWANEA s
.c/to Arerican ErnassyKigali
SENEGALBP 2534Dakar
294
SEYCHELLESaox-,564
Victoria
UPPER VOLTABP 537 -Samandin
Ouagadougou
WESTERN SAMOAP.O. Box FPOApia
YEMENP.O. Pox 1151Sana'a
ZAIRE-
BP 697Kinshasa
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