STATE OF DELAWAREUNIVERSITY OF DELAWARE

DELAWARE GEOLOGICAL SURVEY

OPEN FILE REPORT NO. 29

SOURCES OF GROUND-WATER CONTAMINATION IN DELAWARE

BY

JOHN H. TALLEY

NEWARK. DELAWARE

JUNE 1985

Reprinted

6-95

SOURCES OF GROUND-WATER CONTAMINATION IN DELAWARE

John H. Talley

INTRODUCTION

Ground water is Delaware's most important naturalresource. Our aquifers, which are present everywhere inDelaware, provide more than 75 million gallons each day forall uses. Nearly all of the water used in Delaware south ofthe Chesapeake and Delaware Canal is obtained from aquifers,both water-table and artesian. An appreciable quantity ofwater is also obtained from aquifers in northern New CastleCounty. Ground water has generally been of good quality,been used with little or no treatment, and has beenreadily available at low cost.

Natural discharge of ground water provides base flow(dry weather flow) to streams and supports fish andwildlife. Approximately three-quarters of the annualstreamflow is provided through natural discharge of groundwater (Johnston, 1976).

More than half of the ground water used in Delaware iswithdrawn from the Columbia Formation and Group, a regionalwater-table aquifer. This aquifer consists of sands andgravels that occur as channel fill deposits in northernDe'laware and as a broad sheet across central and southernDelaware. Approximately seventy-five percent (1500 sq. milof the State's area is underlain by saturated sections ofthe regional water-table aquifer that are at least 25 feetthick (Johnston, 1973). This near-surface aquifer, whichnaturally receives its water from infiltration ofprecipitation, is protected only by a relatively thin soilzone that acts as a filtering mechanism. The hydrologiccharacteristics and the position of this aquifer withrespect to land surface render it particularly susceptibleto contamination. In many areas, the soil has limitedcapacity for removal of potential contaminants (low cationexchange capacity, low organic matter). Activities such asremoval of borrow for construction purposes have resultednot only in removal of soil but have also createddepressions or holes that have been used for disposal ofgarbage and chemicals.

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Confined or artesian aquifers in Delaware occur atgreater depths than the water-table aquifer. These aquifersare bounded top and bottom by relatively impermeablematerial referred to as confining beds and are usually notas susceptible to contamination as unconfined aquifers.However, such aquifers may· be subj ect to contamination intheir recharge areas. For example, aquifers in the PotomacFormation in northern New Castle County have been exposed tocontaminants through removal of the overlying sands andgravels of the Columbia and placement of contaminant­generating materials on the surface of the Potomac.Pollutants have entered the aquifer and have migrated intoits artesian portion toward existing water supply wellfields (Weston, 1973). Other mechanisms responsible forcontamination include slow leakage through confining beds,improperly constructed or abandoned wells, and salt waterintrusion.

Extensive ground-water pumpage in Delaware's coastalareas (Delaware River and Bay, Inland Bays, and AtlanticOcean) has in some areas resulted in a reversal of thenatural hydraulic gradient causing the migration of saltwater to several wells.

Ground-water contamination can be defined as theaddition of materials (man-made or natural) such aselements, compounds, and/or organisms to water which alterits composition thereby reducing or preventing the use ofwater· for normal purposes (Pye and Kelley, 1984). Suchcontamination may not be easily observed and the effects maynot be noticed until damage has occurred. Remedial actionsto correct problems are usually very costly, time consuming,and are not always successful. In some instances the damageis irreversible.

Once in the ground water, contaminants become part ofthe ground-water system and may be transported away from thesite of contamination, resulting in widespread pollution.Once contaminated, aquifers generally remain so at least fordecades. Surface waters may also be polluted throughnatural discharge of contaminated ground waters.

The amount of contaminated ground water in Delaware isthought to be relatively small at this time. However,during the past 10-12 years incidents of ground-watercontamination are occurring and/or being detected withgreater frequency (Comprehensive Water Resources ManagementCommittee, 1983b; Boller and Young, 1984). Contaminationhas resulted in local and regional problems. Generally, themost severe ground-water contamination problems occur inareas where both the present demand for ground water isgreat and the greatest future demand is expected to occur.

2

SOURCES OF CONTAMINATION

The varied sources of ground-water contamination inDelaware may be classified according to several methods.For example, one method is based on the severity of problemscreated regardless of sources of contamination: (1) maj orproblems; (2) intermediate problems; and (3) minor problems.Another method classifies sources according to types ofpollutants: (1) wastes that are oxygen-demanding such asdomestic wastes and animal manure; (2) disease-causingwastes which contain parasites, viruses, and bacteria(pathogens); (3) toxic metals such as lead, cadmium, andarsenic; (4) synthetic organic compounds including petroleumproducts, cleaning solvents, pesticides, herbicides, andseptic tank cleaners; (5) fertilizers containing nitratesand phosphates; and (6) radioactive materials (Miller,1985) •

The method used in this report is consistent with thatused in "Groundwater Quality Management" prepared by theGroundwater Quality Subcommittee of the DelawareComprehensive Water Resources Management ·Committee (1983b).Contaminants are classified into four categories accordingto methods of disposal. A list of categories and associatedsources of contamination that are presented in this reportare included in Table 1.

Category I

This category includes activi ties purposely designedto discharge wastes or wastewater onto the surface or into

. the shallow subsurface (Figure 1).

On-Site Waste Water Disposal Systems(Septic Systems)

One of the major causes of ground-water contaminationof the water-table aquifer in Delaware is effluent fromseptic systems. Studies during the past 13 years haveindicated that nitrate contamination from septic systems ismuch more widespread than previously thought (Miller, 1972;Robertson, 1977; Ritter and Chirnside, 1982). Isolatedinstances of such contamination had been consideredrelatively insignificant before 1972. However, because ofthe growing number of homes utilizing septic systems andshallow wells in rural Delaware (areas not served bymunicipal or privately-owned package sewage systems) ,ground-water contamination from septic systems isincreasing and problem areas are becoming regional.· Suchproblems are especially common in areas underlain by

3

Table 1.

SOURCES OF GROUND-WATER CONTAMINATION IN DELAWARE

Category I.

Category II.

Activities purposely designed to dischargewastes or wastewater onto the surface orinto the shallow subsurface.

A. On-Site Waste Water Disposal Systems(Septic Systems)

B. Land Application of Waste Water andSludge

Activities which may unintentionally resultin the discharge of wastes or wastewaters tothe land surface or into ground water

A. Landfills and DumpsB. Surface Impoundments (waste-holding

ponds, pits, and lagoons)C. Agricultural Activities (animal feed­

lots, manure storage, and stockpiles)D. Leaking Sanitary Sewer Lines

Category III. Facilities and activities which may result inthe accidental discharge of materials not'considered waste onto the surface or into thesubsurface.

A. Leaking Buried Storage Tanks andPipelines

B. Chemical and Mineral StockpilesC. Highway De-Icing SaltsD. Accidental Spills of MaterialsE. Proper/Excessive Application of Manure,

Fertilizers, and Pesticides

Category IV. Processes or activities not associated withwaste handling or processing butunintentionally become a way by which fresh­water resources are degraded.

A. Salt-Water IntrusionB. Improperly Constructed and Abandoned

Wells

(Modified from Comprehensive Water Resources ManagementCommittee, 1983b)

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impermeable soils and rocks in which renovation andinfiltration of effluent cannot occur (bacteriologicalcontamination) and in highly permeable soils and rocks whichlack the capacity for removing nitrates and organic cleaningsolvents from effluent.

Increased concentrations of nitrates, chlorides,dissolved solids, detergents, and/or bacteria are usuallyindicative of ground-water quality degradation by septicsystems. Most of the health hazards resulting from suchcontamination are caused by the recycling of domesticeffluent containing undesirable materials and disease­causing organisms from septic systems to nearby wells usedfor drinking water.

Problems caused by both malfunctioning and properlyoperating septic systems can be reduced through properdesign, site evaluation, siting density, installation,operation, and maintenance. The Delaware Department ofNatural Resources and Environmental Control (DNREC),Division of Environmental Control has revised the"Regulations Governing the Design, Installation, andOperation of On-Site Wastewater Treatment and DisposalSystems" to address the problems stated above. The newregulations were put into effect on January 4, 1985 and" .•• include what are considered to be the best engineereddesign standards for on-site systems, as determined byresearch and practical experience" (Department of NaturalResources and Environmental Control, 1985, p. iii).

Land Application Of Waste Water and Sludge

Land application of wastes includes spray irrigation,infiltration-percolation basins, and sludge. Sprayirrigation of animal wastes and brine-containing wastewaterfrom food processing operations and textile dying operationshave resulted in several incidents of ground-water pollution(Comprehensive Water Resources Management Committee, 1983biRi tter and Chirnside, 1982). Such practices have causedelevated levels of both nitrates and sodium.

Problems associated with land application of wastewatercan be reduced by thorough investigation of soils andgeologic and hydrologic conditions, both on site and innearby areas likely to be affected. Utilization of bestmanagement practices including irrigation scheduling,systems designed to apply wastewater at proper rates, andmatching application rates to plant nutrient needs willreduce and possibly alleviate ground-water qualitydegradation and increase crop yields. At this time, permitsfrom the DNREC are required prior to applying wastewater andsludge onto the land surface.

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other activities that can cause ground-watercontamination, but which are not used in Delaware at thistime, include injection of untreated wastewater and brines.Injection of untreated wastewaters and brines arespecifically banned as stated in Section 3.04(e) of theRegulations Governing the Control of Water Pollution(Department of Natural Resources and Environmental Control,1983) •

Category II

This categoryunintentionally resultwastewaters to the land2 ) •

includes activities which mayin the discharge of wastes or

surface or into ground-water (Figure

Landfills and Dumps

There are at least 80 known landfills in Delaware(Spoljaric and Talley, 1982; Department of Natural Resourcesand Environmental Control, 1984). Several existing butpreviously unknown landfills and dumps are identified eachyear in Delaware. Preliminary assessments of the newlydiscovered sites are made through, the ERRIS program(Emergency and Remedial Response Information System) whichis operated by the Department of Natural Resources andEnvironmental Control. Preliminary assessments are followedby recommendations for future action such as site specificinvestigations.

Evidence obtained through ground-water qualitymoni toring at 12 landfills indicates that ground water isbeing contaminated beneath most of these sites. Based onthe results of monitoring at these 12 sites (ComprehensiveWater Resources Management Committee, 1983b), and ourunderstanding of the geology and hydrology in Delaware, onecan anticipate that contamination is probably occurringbeneath most of the other landfills. Exceptions would bethe two properly designed landfills in Kent and Sussexcounties operated by the Delaware Solid Waste Authority.The Department of Natural Resources and EnvironmentalControl and the Delaware Solid Waste Authority have closedmunicipal landfills except those that are "properlydesigned" (Matthew P. Brill, DNREC, personnel communi­cation) .

Landfills placed in operation before 1980 are locatedboth on top of the ground and in the ground, usually in oldborrow pits with no evident thought of control of pollution.The borrow pit itself does not cause contamination; rather,it provides a convenient location in a permeable mediumwhere improper disposal can readily damage ground water. Inmany instances the landfills contain all types of material

7

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ranging from municipal garbage, chemicals, industrial waste,and pesticides to relatively inert substances such asconstruction debris. Past practice involved covering thelandfill material with soil or rock (sand, silt, clay) atthe end of each day. Closing of landfills may have involvedfinal covering and abandonment. Problems developed asleachate formed and migrated offsite.

Leachate is a liquid high in dissolved solids and inchemical and biochemical oxygen demand. Leachate in wetclimates is generated by water entering the waste,percolating through it, and picking up many solublematerials and the products of chemical and biologicalreactions. Water can enter a landfill from precipitation,springs, surface runoff, ground water, or flooding.Improperly designed landfills situated in areas with highwater tables and abundant precipitation will almostcertainly eventually pollute ground and surface water. Suchpollution can exist for· many years and even for decadesafter landfills are closed.

Because of the ground-water quality problems caused byimproperly designed, operated, and abandoned landfills andin response to potential large scale ground-watercontamination problems associated with existing landfills,new methods of disposing of wastes have been developed andare being employed. New criteria for siting, designing,operating, and monitoring landfills and ground-water qualityshould ensure that future landfills will pose minimal dangerto the environment. State of the art landfills are inoperation in Kent and Sussex counties and similar facilitiesare being constructed in New Castle County (N. C. Vasuki,Delaware Solid Waste Authority, personnel communication).

Another potential source of ground-water contaminationassociated with Category II is the illegal dumping ofmaterial such as garbage and chemicals into abandoned gravelpits.

Surface Impoundments

(Waste-Holding Ponds, Pits, and Lagoons)

Surface impoundments are used for the storage,processing, and treatment of wastes, both hazardous andnon-hazardous, and to a lesser degree for the final disposalof such wastes. Waste-holding lagoons in Delaware are usedby the food processing industry to store and treat poultryand other animal wastes prior to disposing of them throughspray irrigation. Lagoons are also used to store and treatoil and municipal and industrial wastes.

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Unlined waste lagoons and ponds, which were prevalentthroughout Delaware prior to development and implementationof regulations· banning them, have created several ground­water pollution problems. The most significant problemshave resulted from industrial wastes. In one instance, anaquifer used for public water supply was contaminated withhigh concentrations of sulfate, iron, and manganese whichresulted in abandonment of the aquifer (Comprehensive WaterResources Management Committee, 1983b).

Even though methods for recovering wastes, especiallyindustrial wastes, are being developed, aquiferscontaminated with such materials are usually renderedunusable for decades and perhaps centuries.

Ground-water problems associated with surface impound­ments can be minimized through proper site evaluation,impoundment designs that include use of impermeable liners,and proper operatio~ and subsurface monitoring.

Agricultural Activities

(Animal Feedlots, Manure storage, and Stockpiles)

Confined animal feedlots may bewater contamination. Precipitationbacteria, and organic compounds fromcan infiltrate into the subsurface.

a source of ground­may leach nitrates,the manure pack that

The storage of manure in large stockpiles awaitingfinal disposal can result in the generation of leachate richin nitrates and bacteria that may flow into surface waterbodies or infiltrate into the subsurface. Ritter andChirnside (1982) reported that stockpiling and applicationof poultry manure in Kent and Sussex counties were "maj or"causes of ground-water contamination. They sampled 482wells and concluded that high nitrate concentrationsoccurred in intensive poultry or intensive crop productionareas underlain by excessively drained soils. The highestconcentrations of nitrate appear to be associated withpoultry manure.

Best management practices are being developed to limitthe amount of time that manure is stockpiled in particularareas. Such practices include use of manure to supply theplant nutrients instead of commercial fertilizers, thusreducing stockpile storage time. Impermeable covers arebeing used to prevent infiltration of precipitation andleaching of nitrates to ground water.

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Leaking Sanitary Sewer Lines

Improperly constructed or damaged sanitary sewers canresult in the contamination of ground water. untreatedeffluent may leak through joints and cracks and migrate intothe subsurface. Areas underlain by porous and permeablerocks such as coarse sand and gravel and' weathered marbleare especially susceptible to this type of contamination.,In such areas, lines are usually up to five feet below landsurface.

Proper selection of materials and application ofappropriate const'ruction techniques sui table to particularengineering, geologic, and hydrologic conditions willminimize the potential for ground-water contaminationresulting from leaking sewer lines.

Category 'III

This category includes facilities and activities whichmay result in the accidental discharge of materials notconsidered waste onto the surface or into the subsurface(Figure 3).

Leaking Buried Storage Tanks and Pipelines

Leaking underground storage tanks and buried pipelineshave resulted in tens of documented cases of ground-watercontamination in Delaware. Boller and Young (1984) reportedthat leaks and spills from, underground storage tanks aloneare occurring at an accelerating rate. Because of thenumbers of underground tanks and pipelines and thesusceptibility to corrosion of materials of which they areconstructed, one can expect leaks to occur far into thefuture, thereby providing, perhaps, serious risk to healthand environment.

Most materials stored in such facilities are fairlytoxic (gasoline and other petroleum products). Because thefacilities are underground, leaks are very difficult todetect. Usually by the time they have been detectedsignificant quantities of fluid have been discharged intothe subsurface. Detection of leaking tanks and pipelinesoften results from the appearance of the fluids at thesurface as seeps or springs, or the presence of fumes inbasements. By the time such leaks are detected, fluids havenormally migrated large distances, rendering ground waternon-potable. In addition, fumes derived from leakage offlammable products may create an explosion hazard.

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Problems resulting from tanks and pipelines can beminimized through the incorporation of properly designedtank foundations, application of advances in tankconstruction materials and in associated monitoringfacilities. A special State committee (Ad Hoc LeakingUnderground Storage Tank Committee) has been convened toreview the problems resulting from leaking undergroundstorage tanks and to develop a comprehensive plan for thedetection, control, and ultimately the prevention of leaksfrom underground tanks.

Chemical and Minerals Stockpiles

Stockpiles include salt, mineral, and chemical storage.Historically these stockpiles have not been covered and,therefore, have been exposed to precipitation. Fluidsgenerated (leachate) when the material -reacts withprecipitation and flow of such fluids into surface water orinfiltration into the ground causes both surface andground-water quality degradation. Most documented cases ofsuch pollution have been those resulting from salt storagepiles.

Manyeliminateleachate.

stockpiles have been enclosedcontact with precipitation and

Highway De-Icing Salts

or coveredgeneration

toof

The utilization of salt for de-icing"highways in wintercoincides with the beginning of greatest recharge to theground-water system in Delaware. Salt is soluble in waterand in areas where salt is concentrated the possibility forboth surface and ground-water contamination exists.Contamination has been documented in Delaware in areaswhere runoff from roads and bridges is concentrated.

Proper application of salt or usematerials in areas susceptible to rapidsurface water high in salt contentcontamination of potable ground water.

of alternativeinfiltration of

will prevent

Accidental Spills of Materials

Accidental spills of materials, often hazardous, havebeen and will continue to be a threat to both our surfaceand ground-water resources. Many instances involvingaccidental spills have been documented in Delaware; however,quick response to such incidents in recent years by SERT(State Emergency Response Team) has alleviated manypotential problems. The primary function of SERT is to

13

respond to spills, conduct preliminary assessments, andrequest additional expertise as required. Other instanceshave resulted in ground-water contamination, particularlynear industrial complexes.

Proper/Excessive Application ofManure, Fertilizers, and Pesticides

Many documented instances of nitrate contamination ofshallow, potable ground water in Delaware have resulted fromboth proper and excessive application of fertilizers,including manure spreading (Ritter and Chirnside, 1982) •Robertson (1977, p. 56) in a report on ground-water qualityin eastern Sussex County concluded that " ••• leaching offertilizers may be the single largest volume contributor ofni trate for the area as a whole ••• " Ground-water qualitydegradation may also occur as a result of infiltration ofherbicides and pesticides. Contaminants enter the ground­water system in late winter and spring when rates ofrecharge are at a maximum and nitrogen-utilizing plantgrowth is at a minimum. Best management practices,including manure, fertilizer, and pesticide management, arebeing used to reduce problems associated with theseagricultural activities.

Category IV

The fourth category includes processes or activitiesnot associated with waste handling or processing butunintentionally become a way by which fresh-water resourcesare degraded (Figure 4).

Salt Water Intrusion

Salt-water intrusion is generally restricted to areasalong the Delaware Estuary and Bay, Atlantic Coast, andInland Bays. Lowering of the hydrostatic head as a resultof pumping water from the subsurface can lead to migrationof salt water towards wells. In several areas alongDelaware's Atlantic Coast and Inland Bays wells have beenabandoned as a result of salt-water . intrusion. New wellshave been drilled farther inland to avoid the problem.

An understanding of ground-water systems in coastalareas together with proper management of ground-waterresources should alleviate problems of salt-water intrusion.

Contamination of ground water (high concentrations ofsalt and dissolved solids) can also occur in inland areas asa result of pumping. Water having a salinity of 500 mg/l isfound as shallow as 500 to 700 feet beneath the Coastal

14

Pumping Wells

, UNINTENTIONAL

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15

Plain of Delaware, including New Castle County (Groot,1983). The presence of this brackish water establishes thatthe potential exists for this water to migrate bothvertically upward and laterally updip in response to head(water-level) changes resulting from high rates of ground­wa ter pumpage (see Figure 4). Care must be exercised inlocating wells and establishing pumping rates to preventreversals in ground-water flow directions and possible saltwater migration to well fields.

Improperly Constructed and Abandoned Wells

Improperly sealed or grouted wells can provide pathsfor contaminated surface waters or subsurface waters toenter wells through the space between the drill hole and thewell casing. Ground water in the vicinity of improperlyconstructed dug wells is especially susceptible tocontamination.

Improperly abandoned wells, uncapped wells, wells inwhich the casing has been partially removed, and old wellswith deteriorating casing may provide access forcontaminates to enter aquifers from the surface or from thesubsurface. When aquifers are connected, migration of poorquality water to uncontaminated aquifers can occur.

statewide regulations governing the installation anduse of water wells have existed since 1969 (Water and AirResources Commission, 1969) • Al though these regulationsprovide guidelines pertaining to the installation,operation, and abandonment of water wells, changingconditions, both environmental and technical, resulted in adecision to review the existing regulations for accuracy andcompleteness. These regulations are currently being revisedto incorporate up-to-date design, construction,disinfection, and abandonment criteria based on research andpractical experience.

CONCLUSIONS

The extent and severity of ground-water contaminationproblems in Delaware have not been adequately quantified atthis time. Instances exist that have rendered ground wateruseless in areas ranging in size from less than one acre totens of acres and have resulted in alteration of establishedsurface land use and associated ground-water development.New cases are being reported to State officials with everincreasing frequency. Nevertheless, contaminated groundwater in Delaware, which has been classified as not fit forconsumption, constitutes a small, but critical fraction ofDelaware's total ground-water supply.

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Ground-water contamination is a very complex problemthat requires special attention if we are to be successfulin mitigating existing problems, locating potentialproblems, and preventing future problems.

Because a relatively small percentage of ground waterhas been adversely affected, adequate time remains toaddress the land and water management practices which haveresulted in problems. The state is expending considerableeffort to develop strategies, regulations, and bestmanagement practices to protect our ground water. Publicawareness through education, advances in technology,recycling of wastes, application of state of the artmethods, and a commitment at all levels of government willbe required to protect our ground-water resources. Advancesin technology will not only have to be used to adequatelyaddress practices which could lead to ground-water qualitydegradation, but will also be required to mitigate existingproblems.

The most effective means of precluding ground-watercontamination are those involving adequate preventivemeasures. The successful implementation of programsdesigned to prevent or minimize ground-water contaminationis dependent to a large degree on an understanding of thehydrogeologic environment.

Most of the regulatory functions pertaining directly toground-water quality protection reside with DNREC. Otheragencies having regulatory functions include the Division ofPublic Health and the Department of Agriculture.

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SELECTED REFERENCES

Boller, M. and Young, S., 1984, Leaking underground storagetanks, in Delaware hazardous waste update: Departmentof Natural Resources and Environmental Control, 4 p.

Comprehensive Water Resources ManagementThe management of water resources inreport: Department of NaturalEnvironmental Control, 41 p.

Committee, 1983a,Delaware, summary

Resources and

______~, 1983b, The management of water resources inDelaware, groundwater quality management: Department ofNatural Resources and Environmental Control, 86 p.

Department of Natural Resources and Environmental Control,1983, Regulations Governing the Control of WaterPollution.

_______, 1984, Delaware hazardous waste update, 4 p.

_______, 1985, Regulations governing the design,tion, and operation of on-site wastewaterand disposal systems, 118 p.

installa­treatment

Geophysics Study Committee, 1984, "Overview andrecommendations", in Studies in geophysics, groundwatercontamination: National Academy Press, Washington,D. C., p. 3-22.

Groot, J. J., 1983, Salinity distribution and ground-watercirculation beneath the Coastal Plain of Delaware andthe adjacent Continental Shelf: Delaware GeologicalSurvey Open File Report No. 26, 24 p.

Johnston, R. H., 1973, Hydrology(Pleistocene) deposits of Delaware:gical Survey Bulletin 14, 78 p.

of the ColumbiaDelaware Geolo-

______~_1976, Relation of ground water to surface water infour small basins of the Delaware Coastal Plain:Delaware Geological Survey Report of Investigations No.24, 56 p.

Lehr, J. H., Gass, T. E., Pettyjohn, W.1980, Domestic water treatment:Company, 264 p.

A. and DeMarre, J.,McGraw-Hill Book

Miller, G. T., Jr., 1985, Living in the environment:Wadsworth Publishing Co., p. 374-378.

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Miller, J. C., 1972, Nitrate contamination of the water­table aquifer in Delaware: Delaware Geological SurveyReport of Investigations No. 20, 30 p.

Pye, V. I. and Patrick, R., 1983, Ground water contaminationin the United States: Science, v. 221, p. 713-718.

Pye, V. I. and Kelley, J., 1984, The extent of groundwatercontamination in the United States, in Studies ingeophysics, groundwater contamination: ~ationalAcademy Press, Washington, D. C., p. 23-33.

Ritter, W. F. and Chirnside, A. E. M., 1982, Ground-waterquality in selected areas of Kent and Sussex counties,Delaware: Agricultural Experiment Station, Universityof Delaware, 229 p.

Robertson, F. W., 1977, The quality and potential problemsof ground water in coastal Sussex County, Delaware:Water Resources Center, University of Delaware, 58 p.

Spoljaric, N. and Talley, J. H.,hydrologic aspects of . landfills:Survey Open File Report No. 16, 22

1982, Geologic andDelaware Geologicalp.

U. S. Environmental Protection Agency, 1977, Waste disposalpractices and their effects in ground water, Report toCongress: Office of Water Supply, U. S. EPA,Washington, DC, 521 p.

Water and Air Resources Commission, 1969,governing the use of water resourcessubaqueous lands: State of Delaware, 27 p.

Regulationsand public

Weston, Roy F., Inc., 1973, Ground water contaminationassociated with the Llangollen Landfill, New CastleCounty, Delaware, 13 p.

19

Aquifer.yieldingsprings.

GLOSSARY

A water-bearing body of permeable rock capable ofusable quantities of ground water to wells and

Artesian (Confined)permeable rock whichbelow it. The wa teratmospheric.

Aquifer. A water-bearing body ofhas a confining bed both above andin it is under pressure greater than

Base Flowstream fromsprings.

The sustained or fair weather flow of anatural discharge of ground water from seeps and

Confining Bed. A body of rock that is not permeable enoughto yield usable quantities of water to wells and springs.

Effluent. A liquid discharged as a waste, such ascontaminated water from a septic tank or from a factory.

Ground Water. Water in the saturated zone under ground.

Injection. The pumping, under pressure, of liquid wastesinto the ground through wells.

Renovation. The process of removing undesirable materialsfrom effluent.

Water Table. The surface between the zone of saturation andthe zone of aeration; the upper boundary of the saturatedzone at which water pressure is atmospheric.

Water-Table (Unconfined) Aquifer. A water-bearing body ofpermeable rock whose upper boundary is at the water table.

20