Construction Documents - University of Washingtoncourses.be.washington.edu/larch/498/2013/Readings/17...222 Construction Documents Soil Specification Axioms * Planting soil compaction

C H A P T E R FIVE

Construction Documents

Construction documents are the basis for the successful execution of aproject. The specifications required for the planting soils are extremelyimportant because the plant palette can be changed more easily than

the soil. Once an incorrect soil is installed, it is very expensive and difficult toremediate, and often it will require replacement. Replacement is somethingthat no client would wish to do. If the planting soil is not adequately designed,specified, and installed, the whole realization of the design and the long-termcare and health of the plants are in jeopardy. Soil installation is a perfect exam-ple of making sure something is done correctly the first time. With these itemsin mind, the planting soil specifications must be clear, concise, and detailedenough for the landscape contractor to follow.

The Need for Detailed Soil Specifications

Soils, by their very nature, are complex entities with a host of physical andchemical properties that vary both spatially and vertically. Providing a soil thatallows plants to flourish is not rocket science, it is an exercise in common sense.There are several axioms concerning soil specifications for planting soils.

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222 Construction Documents

Soil Specification Axioms

* Planting soil compaction is a plant killer.• A compacted urban soil has a low water-holding capacity, decreased

ability to allow roots to penetrate, and an interrupted nutrient cycle.If the roots cannot penetrate into the soil, there is less volume forthe roots to uptake water and nutrients. The plant's eventual growthis limited by these restrictions of the soil. Any and all attempts toreduce compaction when placing the planting soil are absolutelyrequired. Soils that are subjected to after-placement compaction,such as soils for playing fields, streetside trees, or courtyard designs,need to be designed to resist further compaction.

• Using nature as a guide, high-productivity agricultural soils have abulk density (BD) of around 1.0 after tillage and compact to around1.3 during the growing season. The BD of the planting soil shouldfollow the same progression.

4 Excessive coarse fragments (rocks, stones, gravels, pebbles) reduce root-ing volume.• Planting soils with large amounts of coarse fragments (e.g., stone,

brick, and concrete) have a low-water holding capacity and a lowernutrient-holding capacity. The roots may penetrate the coarser soilmaterial, but the stones do not have the same ability as soil to holdwater and exchange available nutrients.

• In the USDA soil texture schema, particles larger than 5 millimeters(about 0.2 inch) are not considered soil; they are considered soiltexture modifiers and are called coarse fragments. Soils consistingof 35 to 90 percent coarse fragments are classified in soil taxonomyas "skeletal," and soils with a coarse fragment volumetric percentage90 percent or greater are classified as "fragmental" material, not soil(Soil Survey Staff 1998). The authors consider a percentage of coarsefragments over 35 percent detrimental to most planting soils formost design elements. The only exception is for on-structure appli-cations that will have additional irrigation and maintenance as partof the entire long-term plan of the landscape.

• The type of coarse fragments also can influence the soil. If the frag-ments are limestone or concrete, they will try to raise the soil's pHto their level of 8.3. This can be a problem if one is trying to growan acid-loving plant species such as azaleas. Brick can make the soilacidic. When asphalt weathers, it releases hydrocarbons toxic toplant roots. These types of fragments need to be removed.

Soil Specification Axioms 223

Organic matter should be in the surface 6 inches of the soil. It is wastedelsewhere.• Organic matter is critical to sustaining the carbon cycle and nutri-

ent cycling in the soil. Organic matter usually has twice as manyexchange sites that can hold plant available nutrients as clay has(Brady 1974, Sparks 1995). According to the laboratory characteri-zation data from the National Soil Survey Laboratory in Lincoln,Nebraska, most natural agricultural soils only have about 1 to 5 per-cent organic matter (OM) by dry weight within the surface horizon(topsoil). However, some forested soils may have as high as 15 per-cent OM in their 1- to 2-inch thick "A" horizon. Natural soils alsotypically have less than 1 percent OM within the subsoil. Use natureas a guide.

• Organic matter below the biologically active surface layers does notadd much in the way of nutrients because the microbes require oxy-gen to break down organic matter. Generally, the organics will com-press, causing settlement, and remain in their current form forthousands of years.

• Adding over 10 percent organic matter by weight to a soil allows thesoil to become too loose and fluffy like a pillow, and within twoyears all that organic matter in the biologically active zone will begone due to decomposition if no additional OM is added, and thesoil will settle.

Proper installation procedures and scheduling reduce work and soilcompaction.• It is crucial to describe the soil installation so that the number of

passes with equipment, foot traffic, and extraneous construction traf-fic is minimized. Once the site is turned over to the landscape con-tractor, all other traffic must be eliminated. It is the responsibility ofthe landscape contractor to install barricades and keep the plantingarea free of other contactors' equipment and debris. The landscapearchitect must review the staging and clearly specify the work pro-gression, soil installation procedures, and subsequent planting areaprotection.

Soil submittals are key to quality soils.• The review and approval of the planting soil materials require testing

and sample inspection by the landscape architect or soils consultant.The procedure for reviewing test results and approval of the variousplanting soils is called soil submittals. Submittals are a multistepprocess that help the landscape architect and landscape contractor

224 Construction Documents Planting Soil Specifications 225

monitor the planting soil from specification to installation. Soil sub-mittals are primarily for the protection of the landscape design, butalso for the landscape architect as well as the landscape contractor toensure that the specified planting soil is being installed. Improperplanting soils and installation cause the majority of landscape designfailures.

* Landscape contractor concurrence with the soil specifications leads tosuccess.• Landscape contractors unfamiliar with complex designed planting

soil requirements can get confused when reviewing the specifica-tions. Contractors bidding on the project may also inflate their costsbecause ten pages of soil specifications are not the usual two and ahalf paragraphs normally seen. Specifications written for plantingare quite detailed; soil specifications should be the same. Time mustbe taken to get client and landscape contractor acceptance andunderstanding of the planting soil specifications. Clients are startingto become more demanding of the landscapes surrounding theirbuildings; therefore, planting soils must be more specific in order tomeet clients' goals concerning their landscapes.

To fully ensure that these axioms are incorporated into the constructiondocuments, detailed instructions are required so that everyone understandsthe materials and procedures. The landscape architect also needs to educatethe landscape contractor in sustainable landscapes. This text is not only forlandscape architects, but landscape contractors as well. In addition, the liti-gious nature of our society requires that everything be spelled out in nause-ating detail, not only for the protection of the landscape architect but thelandscape contractor as well. No longer can two paragraphs of planting soilspecifications suffice for successful, defendable soil installations.

Planting Soil Specifications -Jj,

The planting soil specifications are typically placed in the "Planting" area of thetechnical specifications. The proper title should be "Planting Soils" or "Manu-factured Planting Soils," and the section usually is made up of three writtenparts, in association with detail drawings contained in the Landscape sectionof the construction drawings. These parts are:

1. PART 1—GENERAL

This is where the scope of work, definitions, submittals, and testingprocedures are included. This section is for setting up the review

procedures and stating the acceptable testing authorities, facilities,and approval conditions.

2. PART 2—PRODUCTS

The Products section of the specifications states exactly what materialswill be acceptable for the landscape project. Descriptions of materialsand the various soil profiles to be used in each landscape planting ele-ment are given here.

3. PART 3—EXECUTION

The submittal approvals, installation procedures, and pre- and post-construction maintenance are discussed within the Execution portionof the "Planting Soil" specifications.

PART I — G E N E R A L

The General part of the planting soils specification contains RELATED DOC-UMENTS, SCOPE OF WORK, and RELATED WORK, which is typically pre-written material, in the form and style consistent with the firm's standards.Items that should be expanded are QUALITY ASSURANCE/DEFINITIONS;SUBMITTALS AND TESTING; DELIVERY, STORAGE, AND HANDLING;and ACCEPTANCE AND MAINTENANCE.

Quality Assurance/Definitions

There are professional organizations that deal with soils, and they have stan-dards for testing and reporting results. The Soil Science Society of Americahas a tome of testing standards for various soil chemical, physical, and biolog-ical properties. Methods of Soil Analysis is a four-volume compilation of peer-reviewed scientifically derived testing procedures for soils. The AmericanSociety of Testing Materials also has several standardized tests for soil physicalproperties. The National Cooperative Soil Survey provides on-site soil investi-gation and laboratory standards for the mapping and classifying of soils so thatthe public can properly make informed land-use decisions. The Association ofOfficial Agricultural Chemists is a group of scientists who deal with standard-izing laboratory procedures to promote confidence in analytical results. TheAssociation of Official Agricultural Chemists accredits soil-testing laboratoriesas meeting those procedural standards.

The analysis and testing of soil submittals must follow these standards inorder to provide trustworthy test results. Failure to follow standardized proce-dures can lead to erroneous results, and decisions based on those results canhave long-term financial impacts on the project due to delays and incorrectdesign specifications.


Additional items that need to be covered within this part of the specifi-cations are the various contractor qualifications. Contractor qualifications willvary depending on the complexity of the project. If the design requires soilmixing or a soil supplier, then those contractor qualifications must be added.

Testing laboratory qualifications are also necessary due to the widebreadth of testing required. One would not employ an engineering testing labto accomplish soil nutrient testing for agronomic purposes; conversely, onewould not employ an agricultural testing service for proctor density results.Within this section, the landscape architect can specify a particular lab thatthey are familiar with, and/or require the landscape contractor to submit thename of the testing labs for the landscape architect's approval. Not all labs per-form all the tests that may be needed; therefore, there might be as many asthree labs testing soil mix materials.

The following are some examples of specification verbiage that can beused for this purpose.

Analysis and Testing of Materials. For each type of packaged material required forthe work of this section, provide manufacturer's certified analysis. For all othermaterials, provide complete analysis by a recognized laboratory made in strictcompliance with the standards and procedures of the following:

4 American Society of Testing Materials (ASTM)

4 American Society of Agronomy (ASA)

« Soil Science Society of America (SSSA)

4 Association of Official Agricultural Chemists (AOAC)

4 International Society of Arboriculture (ISA)

4 Environmental Protection Agency (EPA)

Installer Qualifications. A qualified landscape installer whose work has resulted insuccessful installation of planting soils and the establishment of exterior plants.

4 Require Installer to maintain an experienced full-time supervisor onproject site when installing soils and when exterior planting is inprogress.

4 The Landscape Contractor shall have experience in the proper andsafe transportation and installation of soil material.

4 The Landscape Contractor shall prepare and present to the landscapearchitect required soil submittals, and their associated specified testresults, six months prior to the scheduled soil and plant installationfor proper lead time for material location, initial soil mix testing, andapproval.

4 The Landscape Contractor shall have between three and five yearsexperience in installing designed soil mixes.

Soil Mixing Contractor Qualifications:

4 The Soil Mixing Contractor shall be able to provide soil mixes thatmeet the specifications within tolerances assigned.

4 The Soil Mixing Contractor shall be able to produce enough consis-tently uniform soil material for the project to meet the scheduleddemands.

4 The soil mixing contractor shall be engaged at least six months priorto scheduled soil installation, to allow for sufficient time for materialsearches and initial planting mix approval.

Testing Laboratory Qualifications. An independent laboratory, recognized by thestate Department of Agriculture. The testing laboratory must specialize in,have experience with, and be capable of conducting the testing indicated.

* Employ a qualified independent testing and inspection laboratoryacceptable to the Landscape Architect and Owner to perform testsand certifications indicated. It is the responsibility of the LandscapeContractor, in conjunction with the Soil Supplier, to submit materialfor the soil and compost tests. Tests shall be made in strict compliancewith the standards of the Association of Official Analytical Chemistsand follow standards from ASTM, EPA, and/or Methods of Soil Analy-sis, SSSA.

The incorporation of these items allows the landscape architect to spec-ify the qualifications of the contractors, and provide the scientific basis for thetest results required to bring a project to its successful conclusion. Other itemsthat may be included within this section are specific laboratories, requiredcertificates of materials, and who is responsible for employing the testing lab-oratories.

Submittals and Testing

To ensure the quality of the soils to be installed for a specific project, the soilsubmittal shall be the device to determine if the soils meet the specifications.Initial soil submittals must be presented in a timely manner. It is suggestedthat initial soil submittals be delivered at least four months prior to soil instal-lation. This will allow time for the landscape architects to review and make cor-rections to the soil mix. Time must be built into the initial approval process toallow for soil mixes to be made, tested, and reviewed. One must consider that


the laboratory turnaround time for the required soil tests is usually seven toten working days. The full submittal process from mixing a sample to reviewwill take a minimum of three weeks.

Items that need to be reviewed for the products that will be used for thedesign are the planting soil chemical (nutrients, pH) and physical properties(particle-size distribution, infiltration, bulk density, clay types), type of stone,mulch, and organic amendments such as compost. There are specific tests thatshould be used to determine the acceptability of the materials that will be usedas planting soils and other materials that will affect the planting soils. Thesetests will be detailed later in this chapter.

Compost, organic mulch, and organic matter amendments must betested for maturity, maximum particle size, nutrient content, heavy metals,and reaction. Compost and other organic soil amendments must be mature,well-cured material. Immature compost (carbon/nitrogen ratios larger than30:1) actually cause nitrogen immobilization and increased amounts of ammo-nia that are toxic to plants (Landschoot 1996). Compost must also have someavailable nutrients to help start plant growth. Heavy metals cause a problemwhen adsorbed into plant tissue, which will then get incorporated into thefood chain. Heavy metals can also be toxic to plants at certain levels (Craul1992). The pH of the compost becomes extremely important when it is to beapplied to areas where pH-dependent plant species will be planted.

Quality assurance (QA) is needed to determine if subsequent soil mixbatches are meeting the planting soil specifications. The amount of QA testingis determined by the complexity of the project. Greater numbers of differentsoil mixes will require more monitoring. Projects with over 10,000 cu yd of soilneed more samples than a project with 1,000 cu yd of soil material. In addi-tion, planting soils that are from natural sources will require more testingbecause of the possible variability within stockpiles, stockpile sources, and thenatural variability of soils. The authors recommend QA testing at the followingintervals:

4 Test every soil mix batch made, or every 500 cu yd of individual soil-layer soil for large projects.

4 Test every 150 cu yd of individual soil layers, for smaller projects.

4 For projects that use less than 100 cu yd per soil layer, just one QA testshould be sufficient to maintain planting soil quality.

Testing should not be viewed as a burden, but as a means for the land-scape architect and contractor to ensure that they are getting the soil materialthey pay for.

A mixed planting soil's homogeneity can be manually controlled at themixing plant, allowing for fewer tests; however, close supervision of the end

Planting Soil Specifications 229

product must still be enforced. For example, one test per mixed planting soilbatch will suffice, instead of every 250 cu yd of natural soil material. The cor-rect place to list the QA testing should be within the "Submittal and Testing"part, so that all testing requirements are located together for easy reference.

The format for testing requirements needs to be separated into individ-ual sections, so that sampling intervals and exact tests are specified clearly.Therefore, it is necessary to have a distinct section pertaining to the samplinginterval. An example of a testing interval specification follows:

Testing Intervals for Organic Amendments, Planting Soil Mixes, Topsoil, and Subgrade.

Testing is required at the following intervals:

4 Testing of the organic compost material: Test certificates required forproducers of composts or biosolids are described in the planting soilspecification, Part 1, "Submittals and Testing," and shall follow criterialisted in the planting soil specification, Part 2, "Products."

4 After test results for the composted organic material have beenaccepted, the Contractor shall create sample soil mixes for each of thesoil layers for the planting soil mix and perform tests described in theplanting soil specification, Part 1. If the Landscape Architect or SoilScientist deems it necessary to adjust the planting soil mixes, retestnew mixes until test results are accepted.

NOTE: If the soil supplier requires help in adjusting the soil mix,it is recommended that the soils consultant get particle-size tests ofthe soil ingredients prior to mixing. The final planting soil mixratio can then be calculated based on the soil mix ingredients thatare currently on hand at the soil supplier. This can reduce the timeneeded to test, review, and adjust planting soil mixes, saving moneyand time.

4 Testing of specified topsoil sources for approval shall be performedusing criteria listed in Part 1, following criteria listed in Part 2 of thisSection. The Soil Scientist and Landscape Architect may deem it nec-essary for clarification to request additional testing of the topsoilbased on anomalous test results.

4 Permeability of the subgrade shall be tested, for at least three loca-tions within each defined planting area. The Soil Scientist or Land-scape Architect shall specify locations and numbers of tests based onthe complexity of each planting area.

4 During the placement of planting soils, test every XXX cubic yards (orone test for every defined planting area) of planting soil mix delivered


to the job site. Tests shall be for soil mix quality assurance to maintainadherence to particle size distribution, pH, organic matter, salts, andammonium. Report organic matter content on a percent by weightbasis. Testing applies to all soil layers of the Soil Profile. Testing pro-cedures are described in Part 1 of this section.

4 Soil moisture content testing shall be accomplished on all soils to beplaced at least two days prior to installation by a qualified testing agency.

4 In-place density tests for soils prescribed under sidewalks shall be con-ducted for at least one test of surface soil density per 20 feet of linearplanting areas.

The following is an example of specifications for a project that containsblended designed soils; natural soils and organic amendments should haveheadings for each component, with specified tests under each. Separate test-ing parameters for each planting soil element provide clarity, and often spe-cific tests that work well for one type of planting soil will not give correctresults for another.

Test Procedures and Reporting. Submit certified reports for each test required.

4 Soil testing shall be performed and reported for particle size, requir-ing percent of gravel (>2.Omm), very coarse sand (2.0-1 .Omm), coarsesand (1.0-0.5 mm), medium sand (0.5-0.25 mm), fine sand (0.25-0.10 mm), very fine sand (0.10-0.05 mm), silt (0.05-0.002 mm), andclay (<0.002 mm). Saturated conductivity, bulk density, pH, total poros-ity, salt content, ammonium content, and organic matter percentageon a dry weight basis shall also be tested.

4 The soil mix for initial approval shall be tested using the followingprocedures:• Particle-size distribution by ASTM Fl 632-03 for all soil layers. The

ASTM F1632 test is acceptable for the loamy sand soil specified.Fines passing the #270 sieve are to be measured using the hydrome-ter method, as outlined in ASTM F1632.

• Saturated hydraulic conductivity, total porosity, and bulk density byASTM F1815-97 for all soil layers.

• Organic matter content by ASTM F 1647-02a.• Salts and ammonium test using the Woods End Research Labora-

tory procedures #104 "Soluble Ion Test" or approved equivalent.• Soil moisture testing required prior to soil placement shall be by

gravimetric oven dry method, as described in Soil Science Society ofAmerica, Methods of Soil Analysis, Part 1, 1986.

Planting Soil Specifications 23 I

4 Specified topsoil testing for initial approval shall be tested using thefollowing procedures.• Particle-size distribution by the Pipet method, as outlined in Methods

of Soil Analysis, Part 1, 1986. This includes the removal of organicmatter and carbonates with hydrogen peroxide. ASTM F 1632 is notacceptable for the natural topsoil specified.

• Saturated hydraulic conductivity, total porosity, and bulk density byASTM F1815-97 or equivalent Methods of Soil Analysis determinationfor the tested sample.

• Organic matter content by ASTM F 1647-02a.• Salts and ammonium test using Woods End Research Laboratory

#104 "Soluble Ion Test" or approved equivalent.• Soil chemical and nutrient analysis shall be tested using Methods of

Soil Analysis, Parts 1 and 3, 1986 and 1996, or approved equivalent.• Soil moisture testing required prior to soil placement shall be by

gravimetric oven dry method, as described in Soil Science Society ofAmerica, Methods of Soil Analysis, Part 1, 1986.

4 Subgrade permeability is to be tested using a single ring infiltrometerthat consists of a cylinder approximately 6 to 10 inches in diameterand 10 to 12 inches high that is driven into the scarified subgrade sothat it is embedded several inches into the subgrade. Pack soil aroundthe outside of the ring to seal the cylinder into the subgrade. Fill thecylinder once with water and let stand until the water has infiltratedfor at least 4 hours. Refill the cylinder with water and time the amountof water drop over a period of at least 60 minutes, or the time thewater drops 1 inch.

4 In-place designed soil testing for sidewalk construction areas:• The surface that is to support sidewalk construction is to be tested.• In-place soil density testing shall be conducted using ASTM D1556

"Standard Test Method for Density and Unit Weight of Soil in Placeby the Sand-Cone Method."

4 Analyses of composted organic materials, including composted sewagesludge, are required prior to initial soil mix acceptance. Analyses shallinclude all tests for criteria specified in Part 2 of this section.

Review of Tests

Not all soil tests are created equal. Certain tests are adequate for certain soilproperties, while others will provide erroneous data if not used correctly. Thisis most apparent with the soil particle-size analysis. For sandy loams andcoarser soil textures, ASTM F1632 is adequate, but for soils with finer textures,


and especially soils that are derived from topsoil, this test will provide differ-ent results than the Method of Soil Analysis Pipet Method. The reason forthis is the soil's ability to "flocculate," or bind together in clumps because ofthe attraction between small organic and soil particles with large surfaceareas, such as clay (Klute 1986). The sample must be deflocculated, and theorganic material must be removed through the use of hydrogen peroxide.ASTM D422 and ASTM F1632 both deflocculate using sodium hexameta-phosphate, but they do not burn off organic matter or calcium carbonate.Both these items may cause the silt and clay contents to be underestimatedbecause of their binding properties on soil particles (Klute 1986). ASTM F1632follows USDA particle-size breaks, which are based on soil productivity andagronomic soil physics, not on the soil mechanics that engineers are most con-cerned about. The following tests are reviewed for each soil property requiringtesting.

NOTE: The hydrometer method is considered less accuratebecause every time the hydrometer is removed, it stirs the soil sus-pension. The pipet method does not disturb the soil suspension asmuch. The hydrometer also can have particles acting on the bul-bous float in all directions, so that the soil dispersion is pushing thehydrometer down when it should be causing the hydrometer tofloat higher in the more dense soil suspension (Klute 1986, Gee andBauder 1979). Walter et al. (1978) compared pipet and hydrometermethods and found the difference within 5 percent using glacialtill soils. Glacial till soils typically contain more sand than residualor wind-deposited Midwestern soils. High clay content soils mightbe best measured with the pipet method (Table 5.1).

Soil pH is critical for plant growth. The standard for running pH is the1:1 in water method. This test is commonly referred to as the soil paste pHmethod. With all soil tests, there are several variations on the 1:1 water method.For mineral soils, the 1:1 method measured with a calibrated electrode isacceptable. National Cooperative Soil Survey methods use a different methodfor determining taxonomic classification of acidic organic soils, a 1:1 1M potas-sium chloride method. This gives a better measurement of organic soils thatusually have pH ranges below 4.0. Table 5.2 provides the pros and cons of eachof the tests.

Determination of soil nutrients has many different tests. Some must beused together with other tests to provide results for each nutrient and deter-mine the validity of the results. The examples below are used in conjunctionto give the total soluble cations as well as those cations located in exchange-able sites on the soil particles. Standard agricultural testing laboratories use

Soil Particle-Size Analysis

ASTM F1632

ASTM D422

Methods of SoilAnalysis, Part 1(hydrometermethod)

Methods of SoilAnalysis, Part 1(pipet method)

Pros

• Standard for golf greens

• Designed usingagronomic sieve cluster

• Disperses fines

• Standard for soilengineering

• Sieve cluster is designedto provide information forstructural support

• Disperses fines

* Standard for soilresearch

• Uses various dispersiontechniques based on soilmorphology

• Standard for soilresearch

• Uses various dispersion

techniques based on soilmorphology

• Considered moreaccurate than hydrometermethod

Cons

• Does not removeorganic matter orcalcium carbonates

• Uses a hydrometer forparticles less than0.05 mm in dia.

• Does not removeorganic matter orcalcium carbonates


• Does not use sievecluster needed foragronomic results


• More expensive inmost cases than ASTMtests to run properly

• Most expensive in mostcases to run properly

• Few laboratory facilitiesoffer this method

• Only state Land GrantAgricultural TestingServices will provide thistest (check withlaboratory)

Notes

This test is adequatefor testing a sandyloam or coarser soiltexture with less than10 percent clay.

This test should not beused for planting soils.It does not provideenough coverage inthe soil particle-sizebreaks commonly usedin the USDA textures.

This test is acceptablefor coarse-texturedsoils with high contentsof highly oxidizedclays, amorphous clays(volcanic ash), andhigh calcium andorganic contents.

This test is preferredfor fine-textured soilswith high contents ofhighly oxidized clays,amorphous clays(volcanic ash), andhigh calcium and/ororganic contents.

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^H»


Soil Reaction

Methods of Soil

Analysis, Part 3(1:1 watermethod)

Methods of SoilAnalysis, Part 3(1:1 1M potassiumchloride method)

Methods of SoilAnalysis, Part 3(colorimetricmethod)

Notes

This test is the standardfor mineral soils.

This test is preferred foracidic organics.

This test should only beused as a generalmeasurement techniqueto determine if die soilis acidic, neutral, oralkaline in nature.

Pros Cons

• Standard for • Does not work well withsoil research soils of high salt contents

• Standard for * More expensive in mostsoil research cases to run properly

• National • Results agree so closelyCooperative Soil with 1:1 water method thatSurvey uses this this procedure might not bemethod for worth the effort for mineral

acidic organics soils

• Standard for • Not as accurate assoil field use electrode measurement

• Easy to use • Reagents have a short shelflife and can go bad withoutthe scientist's knowledge

• Results can be greatlyinfluenced by reagenttemperature, salt content,and free iron ions

the NH4Oac extraction to give the available calcium, magnesium, sodium, andpotassium. The Bray P-l is used to determine phosphorous, and nitrogen can-not be readily determined without very expensive detailed tests that can givevery wide results. Nitrogen cannot be tested accurately because it has manyforms that can be easily transformed and/or volatized off as a gas (ammoniaand anhydrous ammonia, to name a few). Testing for soil organisms is alsovery expensive and difficult to obtain accurate representative results becauseof the dynamic nature of populations. Erwin Schrodinger, an Austrian Physi-cist, developed the idea that the very act of measuring the location of electronschanges the measurement. It is the same with nitrogen and soil organisms.The very act of removing the soil from its ecosystem and placing it in a sealedbag changes its environment. Nitrogen can change its form, and soil organismpopulation changes to meet the changes in their habitat. We do not suggestmeasuring for nitrogen or soil organisms because of their variability. It is morepractical and cheaper to measure the properties of the ecosystem they inhabit.

Soil Nutrients Pros

NH4Oacextraction


Saturationextraction


Bray P-l • Standard for soilresearch

• Widely acceptedstandard

Cons

• Does not work well withsoils of high salt contents

• Only determinescalcium, magnesium,sodium, and potassium

• Does not work well withsoils of high salt contents

• Only determinescalcium, magnesium,sodium, and potassium

• Only determinesphosphorus

Notes

This test determines theexchangeable bases. Best touse to determine Ca, Mg,Na, and K availability.

This test determines solublecations.

This test determinesavailable soil phosphorus.

We know what acceptable soil properties support healthy soil organisms whichin turn supports an active carbon / nitrogen cycle. The following tests are rec-ommended for determination of available nutrients (Table 5.3).

Delivery, Storage, and Handling

This section should be the place where the site-staging plan should be dis-cussed. If there is not room on-site to stockpile soil material, then it must bestated here. The need to limit compaction on the site during installation alsorequires a statement to the effect that vehicle access is to be limited to certainpaths, weather conditions, and sequence deliveries, as the soil material isneeded.

Planting soils are quite fragile, being susceptible to compaction, andshould be handled at certain moisture contents. Engineers achieve high peaksoil densities at the optimum water content. For most naturally occurring soils,this is typically at a moisture content between 12 and 18 percent by weight(Holtz and Kovacs 1981). Therefore, it is recommended to cover the plantingsoil stockpiles several weeks prior to installation to limit additional soil mois-ture acquired from precipitation.

The drawback of covering planting soil stockpiles is that, because of lim-ited space, they are usually piled high to limit the area needed for tarps. Piling


soil in large stockpiles can cause the interior of the pile to become anaerobic.Anaerobic soils produce gases such as methane, hydrogen sulfide, and ammo-nia that are highly toxic to upland plant species (Craul 1992). The extent ofthe reversion from aerobic to anaerobic soil conditions is related to theamount of organic matter within the soil. Subsoil with less than 0.1 percentorganic matter will produce less toxic gas than a stockpile of topsoil with 5 per-cent organic matter, and topsoil will produce less gas than an organic compostpile. It is imperative to monitor ammonium (easiest to test for) as an indicatorfor soil stockpiles that have started to go anaerobic, or "cook." Temperature isanother way of testing the interior of stockpiles. Stockpile interior tempera-tures that are well above the ambient surface temperature are an indicationfor breaking the pile down to smaller piles to allow the decomposition processto halt. This is the main reason that long-term storage of soil and compostshould be in piles no higher than 6 feet, and that turning them every coupleof weeks to maintain oxygen within the pile is required.

The following items need to be added to the delivery, storage, and han-dling part of the planting soil specifications:

4 Soil that is to be stockpiled longer than two weeks, whether on- or off-site, shall not be placed in mounds greater than 6 feet high. If soilstockpiles greater than 6 feet high are to be stored for more than twoweeks, the contractor shall break down and disperse soil so thatmounds do not exceed the 6-foot height restriction, or thoroughlymix the stockpile once a month.

4 Vehicular access to the site is restricted. Prior to construction, the Con-tractor shall submit for approval a plan showing proposed routing fordeliveries and site access, which shall include, but not be limited to,equipment movements and staging locations.

4 Soil materials shall be covered at least two weeks prior to installation,to prevent excess moisture from saturating the soil stockpile. Test forthe moisture content of the planting soil using the gravimetric ovendry method, as described in Soil Science Society of America, Methodsof Soil Analysis, Part 1, 1986, at least two days prior to soil installation.

4 Soil materials shall not be handled or hauled, placed, or compactedwhen it is wet, as after a heavy rain, nor when frozen. Soil shall be han-dled only when the moisture content is between the specified rangesin percent water by volume.

NOTE: Optimum moisture contents for working soils vary withtheir texture. For example, well-graded loamy sand at 8 percentmoisture is at the optimum moisture content for maximum com-paction. Silty clay at 17 percent moisture is optimum for maximum

compaction. Therefore, review Figure 4-22 and reference Holtz andKovacs (1981) for other examples of moisture contents for somesoil texture examples.

Acceptance and Maintenance

It must be spelled out who is responsible for the acceptance of the plantingsoil installation. It may fall to the landscape architect to review the placementof the planting soils. Statements to that effect are needed, to allow time for thereviewer to get to the site and make a determination. The acceptance is thequality assurance for the planting soils, but the quality control (QC) must restfirmly on the shoulders of the landscape contractor.

The initial planting soil submittal is not adequate to maintain QC forthe landscape architect. Additional interval soil submittals related to the com-plexity of the design are required to provide a timeline of quality that thefinal acceptance is based on. For this reason, the timely submittal of QC testresults is imperative to a timely partial or final acceptance of the planting soilinstallation.

Here is an example of what could be placed in the "Acceptance andMaintenance" part:

4 Soil installation acceptance: Notify the Soil Scientist or Landscape Archi-tect at least 10 days in advance of date of soil placement. Inspection ofthe soil installation shall take place during placement of the drainagelayer, while some of the subgrade is visible, and another inspectionshall take place during the placement of the planting soil layers, beforeplacement of the subbase for sidewalk construction or topsoil layerinstallation.

4 Partial acceptance: Acceptance of partial areas or portions of the totalwork may be granted at the option of the Landscape Architect only ifthe area to be inspected for acceptance is large, well defined, and eas-ily described. The Landscape Architect is not obligated to provide par-tial acceptance of the work.

PART 2 —PRODUCTS

The products portion of the planting soil specifications is where the individualproperties of the materials to be used for the planting soil are stated. Thisincludes the ingredients of the soil mix, natural soil properties, and compostintended for organic amendment of the soils. Additional items that should becontained within this part are reiterations of the acceptance procedures involv-ing the soil materials, and if necessary, preferred suppliers of materials.

^WWH


Submittal testing is very critical for the approval of planting soil andmust be reviewed at each step of the way. This is the only way that the land-scape architect and contractor can be assured that they received the specifiedsoil. Failure of the soil submittal to meet specifications means that certainaspects of the soil mixes or materials should be reexamined to determine howthe soil can be corrected. Failure to meet the planting soil specifications mayhappen through errors or omissions on the part of the landscape contractoror testing laboratory. It is essential to catch soil problems at the mixing stagebefore installation. Removal or remediation of installed soils is just too expen-sive and time-consuming, when an ounce of prevention can save the budgetand schedule. If improper planting soils are received, the landscape architectand contractor have every right to reject the shipment and ask for what is spec-ified. This is the stage where the consulting soil scientist can help both theproject's success and the landscape contractor. By working together, the land-scape contractor and soils consultant can provide the best planting soil locallyavailable.

A general portion of this part would be the preferred place to restate theacceptance procedures, as well as procedures for dealing with planting soilsthat do not meet the specifications. It is up to the landscape contractor or soilsupplier to provide acceptable materials. If the landscape architect is workingwith competent contractors and suppliers, this job is easy and quite rewarding.The landscape architect is ultimately responsible for reviewing and correctingthe planting soils and soil installation procedures to make sure that the clientis getting what is being paid for.

General

All plant mix material shall fulfill the requirements as specified and betested to confirm the specified characteristics.

Samples of individual components of plant mixes in addition toblended plant mixes including mulch materials shall be submitted bythe Contractor for testing and analysis to the approved testing labora-tory. Include verification testing of on-site subsoils. Comply with spe-cific materials requirements specified.• No base component material or soil components for plant mixes

shall be used until certified test reports by an approved agriculturalchemist have been received and approved by the Landscape Archi-tect and Soil Scientist.

• As necessary, make any and all soil mix amendments and resubmittest reports indicating amendments until approved.

+ The Landscape Architect and Soil Scientist may request additionaltesting by the Contractor for confirmation of mix quality and/or soilmix amendments at any time until completion.

Soil suppliers that regularly deal with soil mixing are available. However,they're mostly located around large metropolitan areas. The best way to findthese suppliers and soil mixing specialists is through searching the Internetusing key words such as "Topsoil Suppliers," "Manufactured Soils," and "SoilSuppliers." It is imperative that qualified soil suppliers be located prior to con-struction, and a list of suppliers within the specifications may be helpful tostart a landscape contractor in the search. A simple Web search of related busi-nesses within the project area will provide contact information. Contact eachsupplier within a reasonable trucking distance and ask two major questions:"Have you ever mixed soils to a specification?" and "Have you ever providedsoil blends for the golf course or athletic field industry?" If they answer "yes"to both questions, they should know the procedures involved to provide adesigned planting soil mix as well as quality natural soils. If they have answered"yes" to only one question, they may need closer supervision on the part of thelandscape architect and contractor. A "no" answer to both questions may leadto major handholding, costly delays, and numerous problems with providingquality soils based on a specification.

The landscape contractor, during initial review of the soil suppliers,should confirm that they can provide the needed quantities and quality ofmaterials. This statement should be included within the specifications atthis time:

In the event that any of the materials are not available from thesupplier or are not in compliance with specifications herein, theContractor shall obtain material from other suppliers and conducttests specified herein to provide materials in compliance with thesespecifications. If the cited suppliers cannot provide the specifiedmaterial, no additional compensation shall be paid to the contrac-tor to locate acceptable suppliers.

Soil Mixes

The actual specifications of the soil mixes should be placed next within theProducts portion of the Planting Soils section. The best way to state the soil'sphysical parameters is in table format with the correct sieve cluster breaks usedin the soil particle-size tests specified. See Table 5.4 for an example.

Additional soil properties should be stated in table format or listed in aparagraph. The following is an example of the paragraph format:

^Wi

240 Construction Documents Planting Soil Specifications 24 I

Soil Layer Particle-Size Distribution

Particle Size Class Passing Sieve No.

Fine gravel 10

Very coarse sand 18

Coarse sand 35

Medium sand 60

Fine sand 140

Very fine sand 270

Silt*

Clay*

Organic Matter

OM%

*Determined by hydrometer method in ASTM F1632-03.

Range in Percent PassingASTM F1632-03

10090-100

70-85

44-60

25-35

18-2512-185-12

Percent Range by WeightASTMFI647-02a

4-8

Planting Topsoil: A sandy loam modified with organic componentto have at least 4% organic matter but not more than 8% organicmatter, dry weight basis, a compacted minimum infiltration rate of2.5 cm/hour, pH range of 5.5 to 6.5, and no coarse fragments over2.5 cm in size.

The preinstallation testing of available macronutrients of a mixed soil isnot really necessary at this time. The reason for this is the addition of compostto the mix to raise the total organic matter to the specified levels. There areinherent nutrients within the compost that should be sufficient to start theplants for one growing season. Soil nutrient samples should be taken of onlythe surface 6 inches of the planting soil. Then the amount of chemical fertil-izer required as a starter is reduced, allowing a cost savings. It is recommendedthat soil tests be taken after planting soil installation and before the next grow-ing season, then lime and fertilize according to the soil tests. For turf applica-tions, follow the standard recommended fertilizer and lime requirements ofthe species and locale. Fertilization of trees is not recommended within thefirst year. The roots have not grown out of the rootball yet; therefore, the treecannot take up nutrients.

Natural Soils

Natural topsoil that is to be trucked in to the site can have its specifications abit broader. Most state highway departments have a specification for topsoil;however, they are typically quite broad in scope. The Department of Trans-portation topsoil specifications are adequate for roadside grass and coarseslope-stabilizing plant materials, but they are not defined enough for a richsustainable landscape design that contains trees and shrubs as well as grasses.

The availability of local sources for topsoil needs to be determined. Tobetter estimate the quality of useful topsoil within the project area, certainproperties need to be considered. The National Cooperative Soil Survey hasbeen mapping soils and reporting natural soil properties within the UnitedStates since 1899. There usually is a published soil survey for most countieswithin the lower 48 states. To find out the availability of this resource, visit theUnited States Department of Agriculture, Natural Resources ConservationService's soil Web site at http://soils.usda.gov/. (See Chapter 4 for details.)

Contained within each soil survey are tables indicating tested and pre-dicted soil properties for the soil survey area. The main table to review for theproject area is "Source of Reclamation Material, Roadfill, and Topsoil." Not allareas will have suitable natural soils for importation; therefore, an alternativedesigned soil may be the only option. This table provides listings of the soilseries that are acceptable for use in topsoil (Table 5.5).

This table was developed from the National Soil Survey Information Sys-tem (NASIS) that resides at Fort Collins, Colorado. The database contains allthe data collected and developed for all the published soil surveys for theentire country. All the field soil scientists inputting data into the database asthey make determinations in the field keep the soils data up to date. Thedirect URL link to this Web site is http://soildatamart.nrcs.usda.gov/, but itcan also be reached through the national soils Web site. Select your state, thenyour county, then click on Generate Reports.

This table is interpreted by means of the soil map unit located on the left.These three or four alphanumeric symbols are used to label the soil delin-eations on the spatial maps of the survey. The name listed below is the soilseries name. Soil mapping units are not just one named soil series; they are asuite of soils that occur on the delineated soil/landscape. There can be severalsoil series within a mapping unit; therefore, the percent noted is the percentof the soil mapping unit that is the named series. The soil rating for topsoil isat the far right. The limitations stated are soil property problems that limit theusefulness of the soil for use as topsoil. The most limiting factor is stated first.The "value" numbers adjacent to the listed limitations are "fuzzy values" from0 to 1 that indicate the importance of the limitation on the soil's use. Thesmaller the number, the more effect the restriction has on the interpretation.

Source of Reclamation Material, Roadfill, and Topsoil

Centre County, Pennsylvania

[The information in this table indicates the dominant soil condition but does not eliminate the need for onsite investigation. The numbers in the valuecolumns range from 0.00 to 0.99. The smaller the value, the greater the limitation]

Map symboland soil name

Pet.of

mapunit

Potential as a source ofreclamation material

Rating class andlimiting features

Value

Potential as a source of roadfill


Value

Potential as a source of topsoil


LIB:

Leetonia 90 Poor Fair Poor

Value

Leetonia 90

LvB:

Leetonia 90

LvC:

Leetonia 90

Lx:

Lindside 90

MaB:

Markes 85

MeB:

Meckesville 90

US DA Natural Resources§0̂ 1 Conservation Service

242

Poor

DroughtyOrganic matter

content lowToo sandyToo acidCobble content

Poor

Wind erosionDroughtyToo sandyOrganic matter

content lowToo acid

Poor

Wind erosionDroughtyToo sandyOrganic matter

content lowToo acid

Fair

Organic mattercontent low

Water erosion

Fair

DroughtyOrganic matter

content lowDepth to bedrockToo acid

Fair

Too acidOrganic matter

content lowDroughty

00.01

0.07

0.50.95

000

0.13

0.5

000

0.13

0.5

0.13

0.99

0.09

0.13

0.54

0.54

0.12

0.13

0.47

Fair

Cobble content 0.05Depth to bedrock 0.58

Good

Good

Poor

Low strength 0Depth to saturated 0.76

zone

Poor

Depth to bedrock 0Depth to saturated 0

zone

Fair

Depth to saturated 0.78zone

This report shows only thi

Tabular Data Version: 3

Tabular Data Version Date: 08/12/2005

Poor

Rock fragmentsHard to reclaim (rock

fragments)Too sandyToo acid

Poor

Too sandyToo acidRock fragmentsHard to reclaim (rock

fragments)

Poor

Too sandyToo acidSlopeRock fragmentsHard to reclaim (rock

fragments)

Fair

Depth to saturatedzone

Poor

Depth to saturatedzone

Rock fragmentsDepth to bedrockToo acid

Fair

Too acidRock fragmentsDepth to saturated

zone

00

0.07

0.32

00.32

0.88

0.88

00.32

0.37

0.88

0.88

0.76

0

00.54

0.98

0.59

0.76

0.78

e major soils in each map unit. Others may exist

Page 1 of 1


Another table that should accompany the "Source of ReclamationMaterial, Roadfill, and Topsoil" table is "Acreage and Proportionate Extent ofthe Soils." This table lists the soil map units contained within the soil surveyarea. Table 5.6 is an example of a portion of the legend for Centre County,Pennsylvania.

The review of the local soil survey data helps the landscape architect andcontractor to evaluate the soils on the project site, if the site is a conversion ofnatural or agricultural area to a landscape design, or to evaluate prospectivesources of topsoil. An example of how to incorporate this data is a specifica-tion that was written to import topsoil for a project in Cedar Rapids, Iowa:

Preferred soil series for sources for topsoil are Aredale, Bertrand,Fayette, Richwood, Tell, or Whittier, as described by the Soil Surveyof Linn County, Iowa, United States Department of Agriculture,Natural Resources Conservation Service.

There should be additional caveats associated with the above statement.The soil is made up of horizons, and the correct definition of "topsoil" inNational Cooperative Soil Survey terms is the "A" or "Ap" horizon. The plant-ing soil should be from this layer, and not from the typically more clayey sub-soil, or "B" or "C" horizons.

NOTE: The natural soil is made up of several horizons that aredesignated by capital letters. These letters are sorted from "A" to"R," ranging from the top of the soil profile to hard bedrock. For areview of soil horizons, see Chapter 1.

Another item that is necessary to specify is that the internal drainage ofthe natural soil must be moderately well or well drained. It should not be mot-tled with what soil scientists call redoximorphic features. These features are inthe form of depletions (removal of iron, gray soils) or concentrations (accu-mulation of iron, rusty-colored soils). A good reference for further reading ondefinitions of redoximorphic features can be found on the Soil Science Soci-ety of America's Web page at http://www.soils.org/sssagloss/. For these rea-sons, an additional statement is necessary to make sure that the planting soilsare not wet or of material that is low in biologic activity.

The topsoil specification shall consist of an acceptable agricultural,homogenous, silt loam, or loam "Ap" horizon, as designated by theNational Cooperative Soil Survey. High clay content subsoil or soilswith redoximorphic features (mottled) are not acceptable.

It is recommended that a particle-size distribution table also be includedin the same format as for a designed soil mix, in order to maintain continuity.


Mapsymbol

AbB

AbC

AcB

AcC

AIB

AnB

AnC

AoB

AoC

ArA

ArB

At

Ba

BkB

BkC

BkD

BID

BMP

BrA

BrB

BrC

BsB

BtB

BuB

BuC

BxB

BxD

CA

CdA

CdB

Ch

CkA

CkB

CIB

CIC

CvB

CvD

Total

Acreage and Proportionate Extent of the Soils

Centre County, Pennsylvania

Map unit name

Albrights silt loam, 3 to 8 percent slopes

Albrights silt loam, 8 to 15 percent slopes

Albrights very stony silt loam, 0 to 8 percent slopes

Albrights very stony silt loam, 8 to 15 percent slopes

Allegheny silt loam, 2 to 8 percent slopes

Andover channery silt loam, 0 to 8 percent slopes

Andover channery silt loam, 8 to 15 percent slopes

Andover very stony loam, 0 to 8 percent slopes

Andover very stony loam, 8 to 15 percent slopes

Armagh silt loam, 0 to 3 percent slopes

Armagh silt loam, 3 to 8 percent slopes

Atkins silt loam

Basher loam

Berks shaly silt loam, 3 to 8 percent slopes



Berks very stony silt loam, 8 to 25 percent slopes

Berks and Weikert soils, steep

Brinkerton silt loam, 0 to 3 percent slopes

Brinkerton silt loam, 3 to 8 percent slopes

Brinkerton silt loam, 8 to 1 5 percent slopes

Brinkerton very stony silt loam, 0 to 8 percent slopes

Buchanan loam, 2 to 8 percent slopes

Buchanan channery loam, 3 to 8 percent slopes

Buchanan channery loam, 8 to 15 percent slopes

Buchanan extremely stony loam, 0 to 8 percent slopes

Buchanan extremely stony loam, 8 to 25 percent slopes

Carlisle muck

Cavode silt loam, 0 to 3 percent slopes

Cavode silt loam, 3 to 8 percent slopes

Chagrin soils

Clarksburg silt loam, 0 to 3 percent slopes

Clarksburg silt loam, 3 to 8 percent slopes

Clymer sandy loam, 3 to 8 percent slopes

Clymer sandy loam, 8 to 1 5 percent slopes

Clymer very stony sandy loam, 0 to 8 percent slopes

Clymer very stony sandy loam, 8 to 25 percent slopes

Acres Percent

1,710 0.2

1 ,240 0.2

820 0.1

1,820 0.3

500

7,900 1.1

4,340 0.6

8,670 1.2

12,780 1.8

770 0.1

1,810 0.3

4,260 0.6

3,270 0.5

1 ,500 0.2

7,110 1.0

10,310 1.4

1,140 0.2

27,200 3.8

490

3,670 0.5

2,230 0.3

540

1 ,780 0.3

3,270 0.5

2,600 0.4

14,830 2.1

13,920 2.0

680

350

4,320 0.6

2,030 0.3

420

1 ,270 0.2

2,720 0.4

860 0.1

26,510 3.7

10,400 1.5

190,040 26.7

* Less than 0.1 percent.

USDA Natural Resources2&^H Conservation Service

244

Topsoil Particle-Size Distribution

Particle-Size Class

Fine gravelVery coarse sandCoarse sandMedium sandFine sandVery fine sandSilt*Clay*

Organic Matter

OM%

*Determined by hydrometer method in ASTM F1632-03.

Passing Sieve No.

10183560

140270

Range in Percent PassingMethods of Soil Analysis,

Part I

10090-10070-8544-6025-3518-2512-185-12

Percent Range by WeightASTMFI647-02a

4-8

Here is an example of particle-size distribution determined for acceptable soilseries mentioned in the Soil Survey of Linn County, Iowa (Table 5.7).

If natural topsoil is to be used without compost amendment, the nutri-ent requirements must be tested. Table 5.8 lists what is considered a reason-able starting point for planting soils. It is still a good idea to test any natural

Tabular Data Version: 3

Tabular Data Version Date: 08/12/2005

Property

pHPhosphorus (Strong Bray method)PotassiumCalciumSodiumCation exchange capacity (CEC)Soluble saltsSodium adsorption ratio (SAR)

Acceptable Range

5.5-7.020-40 ppm

200-600 ppm1500-6000 ppm

<250 ppm20-100 cmol/kg

<1.5 dS/M<5

Page 1 of 1


soil prior to installation, to determine what physical and chemical propertiesthere are to work with, even if organic compost is to be added. This is consid-ered backup data to determine the acceptability of the highly variable naturalsoil. Of course the full range of soil submittals should be planned for naturalsoils as well; however, quality assurance testing should be done on just aboutevery other truckload of planting soil, unless it has been screened in largebatches, in which case, sampling of each screened batch should be sufficient.

Soil reaction (pH) will need to be adjusted based on the species selec-tion, but the rest of the macronutrients can remain as listed above. The cationexchange capacity (CEC) is a measure of available ion exchange sites. Cationsare nitrogen, phosphorus, potassium, calcium, sodium, magnesium, and otherpositively charged atoms. In simpler terms, CEC is how many macronutrientatoms the soil can hold. If a soil has low CEC, it means that the available nutri-ents held in the soil will be limited, and so will the resulting plant growth. Sol-uble salts become a soil problem in desert areas of the Southwest, the greatvalley in California, and beaches and tidal marshes of the coastlines. Too muchsalt in the soil prevents plant growth because (1) the soil has larger conductiv-ity than the roots, and (2) the osmotic potential has water and nutrients flow-ing from the plant to the soil, instead of the other way around (Brady 1990).

Composted Organic Amendments

Compost is a fine-textured mass of decomposed organic material such as grassclippings, food wastes, mushroom substrate, brewer's waste, sewage sludge, live-stock manures, and tree trimmings. The composting procedure involves "cook-ing" the organic matter to break down the large organic particles to smallerones so that they can be readily incorporated into the soil's organic cycle. Thefinished product is a useful amendment for soils to rebuild the soil structureso necessary for high water infiltration, root extension, nutrient uptake, andgas exchange within the surface of the soil (Brady 1990).

Addition of compost to a soil should only be used in the surface; organicmatter incorporated too deep within the soil profile will only cause settlementof the entire soil due to compression and decomposition. This is to be avoided.An example of incorporating too much organic matter within the soil profilewas Dan Kiley's North Carolina National Bank Plaza in Tampa, Florida (Hazel-rigg 2004). The soil volume was more than adequate for the plants, but the soilwas not designed to also support the pavers placed on the surface. The trees ofthat site grew quite well, but the addition of too much organic matter withinthe profile caused uneven settlement of the pavers (Urban 2004). The ideathat more organic matter is better is not correct. Most natural mineral, agricul-tural soils only have between 1 and 5 percent organic matter within the surface

and almost none below 6 inches (Sparks 1995). In design and construction,follow nature's example.

The compost must be well cured and free of heavy metals, salts andnonorganic debris. A representative sample of the specification for organicamendments should state everything in the following excerpt of a planting soilspecification.

Organic Amendment

Composted organic matter shall have the following criteria:

4 Type. The organic material may be brewer's waste, composted sewagesludge without excessive content of large wood chips, triple-groundcomposted leaf mulch, or aged composted mushroom substrate.Livestock manures are also acceptable. Composted municipal waste(chipped, shredded, and screened wood, leaves, bark, etc.) alone isnot acceptable unless it meets all of the criteria noted in compostcriteria.

4 Carbon/nitrogen ratio. This ratio shall be between 11/1 and 22/1.

4 Degree of maturity. Maturity shall be between Grades IV and V, "curingcompost" and "very stable compost," as measured in a colorimetric-based maturity test (Woods End Research Laboratory, or equivalent).The compost shall be considered "stable" and not subject to continu-ing biologic or chemical processes.

4 Odor. The composted material shall not produce any unpleasant resid-ual odor such as hydrogen sulfide, ammonia, or others.

4 Mineral/organic content and fineness (particle size). The organic materialshall contain at least 40% organic matter (dry basis) and shall have100% passing a /^-inch or smaller screen. Debris particles such as metal,glass, plastic, wood, asphalt, or masonry shall not exceed 10 mm insize, and shall not total more than 2% dry weight.

4 Reaction (pH). The pH shall be within the range of 5.5 to 8.0 (CaClmethod).

4 Salinity. Total salinity shall not exceed 2 grams of salt per liter (ex-pressed as sodium chloride, NaCl) or <1.5 mS/cm.

4 Ammonium content. Ammonium shall be less than 400 ppm on a dryweight basis.

4 Nutrient contents. The material shall contain some nitrogen, phosphorus,potassium, calcium, magnesium, sodium, and micronutrients includ-ing iron, copper, boron, manganese, and molybdenum, so that heavy


applications of fertilizer are not required to sustain plant growth. Alsothe nutrients shall be present in appropriate agricultural and horti-cultural proportions to prevent ion antagonism.

4 Heavy metals. Concentrations of zinc, mercury, cadmium, lead, nickelchromium, and copper must be below EPA and project's state envi-ronmental protection agency standards for applications to soils withhuman activity.

It is recommended that organic amendments be added to the surfacesof all soils installed, especially when using imported "topsoil." The organicamendments will even out a lot of variability of the soils installed. They willalso mitigate some of the compaction caused by soil installation. The idea isto provide a higher content of natural organic matter within the surface sothat plant nutrient uptake roots and soil organisms have a favorable environ-ment to propagate in. Procedures for incorporating organic matter into thesurface layer of the soil are described in the EXECUTION portion of thespecifications.

Soil Profiles

Written descriptions of the soil profiles to be used within the project should bestated here. This portion of the "Products" part of the specifications will haveto reference the drawings. Cross-sections of the soil profiles will need to beadded to the details of the drawings. Simple drawings showing the depths ofeach horizon, overall planting soil depth, and any underdrainage requiredshould be detailed (see Chapter 4). The detailed verbal descriptions should ofcourse match the detail drawings.

Nature is a good guide for developing soil profiles. The typical highlyproductive agricultural soil consists of three main horizons. The topsoil, or"A" horizon, is usually 6 to 8 inches thick, with a "B" horizon that provides thewater-holding and structural stability. The "B" horizon can be from 18 to70 inches thick. The "C" horizon is the parent material of the soil and providesthe basis for future soil development through the five soil-forming factorsdescribed in Chapter 1. The "C" horizon is quite variable in thickness, so anyreal definition of a range is difficult. The designed soil should follow thesesimple guides by nature. The topsoil, or SI layer, should be between 6 and8 inches thick. The "B" horizon, or S2 layer, can range from 6 to 24 inchesthick, depending on the landscape design element selected. The 24-inch S2layer should be used when medium to large trees are being planted, whilethinner layers can be used for shrubs and turf. Of course, the turf can have thethinnest "B" horizon. The "C" horizon can be the drainage layer, or S3 layer, ifthe subgrade is very dense and impervious; otherwise, the subgrade can con-stitute the lowest soil horizon.

The wisdom of using various layers is to eliminate the unnecessary or-ganic matter, nutrients, and more expensive soil below the topsoil. Developinga soil profile will also help the soil to more quickly develop its own structureand equilibrium with the surrounding environment. A homogeneous soil mixwill have to develop its own profile and environmental equilibrium at animmature level. This could result in more settlement, and chemical or bioloe-

o

ical instability.

Streetside So/7 Profile within Pavement

Here is an example of a streetside soil profile for a designed soil. The trees willbe planted within a trench following the length of the frontage of this project.Sidewalks will then be constructed over the trench, with pit openings for thetrees that are to be planted later.

* The Streetside soil profile: The planting soil profile consists of three soilhorizons (see Soil Profile Detail Drawings). The A horizon (SI layer)of 6 inches (only within the tree pit and in open planting beds), the Bhorizon (S2 layer) of a maximum of 24 inches, and the drainage layer(S3 layer) of 6 inches. The basis for the SI and S2 layers is the sandyloam specified in Part 2. The drainage layer (S3) is sand specified inPart 2 of this section.• Streetside tree profiles shall include a 6-inch S3 drainage layer. The

S2 layer shall be a maximum thickness of 24 inches, except wheresubsurface structures encroach on the depth of the profile. The S2layer shall be thinned where subsurface structures limit the overall36-inch depth, while the S3 layer shall remain 6 inches. It is pre-ferred that the overall soil profile depth for street trees be a total of36 inches.

• The SI layer is to be placed only within the open portion of the side-walk for trees within paving.

• The SI shall be a minimum of 6 inches in all open planting beds.• In cases where the overall depth of the planting area fill is deeper

than the 36 inch designed profile depth, subgrade in situ soil mate-rial can make up the 36 inch depth.0 The placed subgrade shall have a permeability of not less than 0.5

inches/hour. Determine permeability7 of the subgrade using a sin-gle ring infiltrometer method.

0 The subgrade shall be scarified prior to the permeability testing.

* The S3 drainage layer is placed first to a depth of 6 inches. The S2 isthen placed to the level below the gravel subgrade for the concretesidewalk and compacted to specifications noted in the Concrete sec-tion and not to exceed 95 percent of peak density. Compaction of the

250 Construction Documents Planting Soil Specifications 25 I

S2 layer shall only be accomplished on the final surface. Compactionshall not be attempted prior to the placement of the final lift. Do notcompact the S2 layer under sidewalks over 95 percent of peak density.The gravel and concrete is then constructed on top of the S3 and S2material.

Rooftop Profiles

To provide a variation in elevations on a rooftop application without addi-tional soil weight, void form foam blocking is often used to reduce roof loads.The soil depths will need to be maintained at a thickness at which the depth tofoam will not cause growth limitations in the plant materials. Shallow soils arevery droughty and in dry seasons will show as water stress reducing the overallhealth of the plants.

Specifications for the soil depths will need to be quite detailed to main-tain proper soil depths and horizonation. Designed soils should always be usedin rooftop designs due to the very limited weight loading and the needed soiluniformity in particle size. The following example is of an on-structure designthat incorporates both a turf design and tree-lined walkways. Notice that theengineering compaction for the sidewalks is only done on the final lift anddirectly under the sidewalk.

* Tree planting soil profile: The tree planting soil profile consists of threesoil horizons (see Soil Profile Detail Drawings). The A horizon (SIlayer) of 6 inches, the B horizon (S2 layer) of a maximum of 24 inches,and the drainage layer (S3 layer) of 6 inches. The basis for the SI andS2 layers is the loamy sand specified in the planting soil specifications.The drainage layer (S3) is a sand specified in Section 2.01.• All profiles shall include a 6-inch S3 drainage layer. The S2 layer

shall be a maximum thickness of 24 inches, unless subsurface struc-tures encroach on the depth of the profile. The S2 layer will bethinned where subsurface structures limit the overall 36-inch depth,while the SI and S3 layers will remain 6 inches.

• In cases where the overall depth of the planting area is greater thanthe 36-inch soil depth, void foam blocking will be needed to reduceweight and bring the subgrade up to the 36-inch depth. Refer to theEarthwork specifications.

• Sidewalk installation: The S3 drainage layer is placed first to a depthof 6 inches. The S2 is then placed to the level below the gravel sub-grade for the concrete sidewalk and compacted to specificationsnoted in the Concrete section. Compaction of the S2 layer shallonly be accomplished on the final surface. Compaction shall not beattempted prior to the placement of the final lift. Do not compact

the S2 layer under sidewalks to over 95 percent of peak density (Proc-tor) . The gravel base and concrete are then constructed on top ofthe S3 and S2 material.

* Turf planting soil profile: The planting soil profile consists of three soilhorizons (see Soil Profile Detail Drawings). The A horizon (SI layer) of6 inches, the B horizon (S2 layer) of 6 inches, and the drainage layer(S3 layer) of 6 inches. The basis for the SI and S2 layers is the loamysand specified in the planting soil specifications. The drainage layer(S3) is a sand specified in Section 2.01.• All profiles shall include a 6-inch S3 drainage layer. The S2 layer

shall be a maximum thickness of 6 inches, unless subsurface struc-tures encroach on the depth of the profile. The S2 layer will bethinned where subsurface structures limit the overall 18-inch depth,while the SI and S3 layers will remain 6 inches.

• In cases where the overall depth of the planting area is greater thanthe 18-inch soil depth, void foam blocking will be needed to reduceweight and bring the subgrade up to the 18-inch depth.

4 Sidewalk installation: The S3 drainage layer is placed first to a depth of6 inches. The S2 is then placed to the elevation required to be belowthe gravel subgrade for the concrete sidewalk and compacted to spec-ifications noted in the Concrete section. Compaction of the S2 layershall only be accomplished on the final surface. Compaction shall notbe attempted prior to the placement of the final lift. Do not compactthe S2 layer under sidewalks over 95 percent of peak density. The graveland concrete are then constructed on top of the S3 and S2 material.

Compost-Amended Topsoil for Turf

For projects that wall not have heavy use, such as residential lawns or protectedturf areas, a more inexpensive solution can be used. The soil typically used forthis design can be natural topsoil imported from local or near-local sources.There should be care in specifying the topsoil, because not all topsoil is really"topsoil." Review Chapters 2 and 4 for how to determine usable topsoil.

The following example uses specified topsoil 8 inches deep over sub-grade currently on the site. Care must be taken to make sure the properties ofthe topsoil are similar to those of the subgrade, in order to eliminate chancesof severe interfaces that would impede root growth, slope stability, water hold-ing, and infiltration into the subgrade.

4 Turf planting areas: The turf planting areas that contain trees and turfsurrounding the building shall have the subgrade established to a min-imum of 8 inches below final grade.


• The subgrade shall be filled with approved fill material free of con-struction debris, and rock fragments shall not be larger than 3 inchesin diameter. Rock fragments between 0.5 and 3 inches in diametershall not constitute more than 15 percent of the soil by volume.

• The soil profile shall consist of a minimum of 8 inches of approvedtopsoil that has been amended with approved compost.

A verbal description of the soil profiles is helpful to reinforce the properprocedures and complement the drawings. Any additional or specialty soilprofiles should also be included here. Transition cross-sections from designedsoils to in situ soils and slope stabilization procedures such as terracing thesubgrade or adding of geofibers to the soil for stabilization should also bementioned here.

Soil Profile Details

Drawing details for soil profiles will need to be included within the bid pack-age to reinforce the verbal description. Cross-sections of areas will also berequired in complex situations where the soil profile will differ depending onplanting options. See Chapter 4 under "Tree Pit Designs" for standard tree pit,soil profile, and within-pavement tree pit details.

Specialty details are needed when the soil design requires transitions,shallow portions, or other complex installation aspects. When it is complex, apicture is worth a thousand words. Review Chapter 4 for particular details thatshould be incorporated into the drawing details.

Transition Details

Transition details are required when a highly permeable designed soil essen-tial for compaction resistance is joined to a denser in situ soil. The permeabil-ity of the in situ soil is most often much less than that of the sandy designedsoil. Therefore, there will be a need to remove water at the bottom of the slopeand feather in the two soils to diffuse the transition line between the designedand the in situ soil.

Steep Slope Soil Profile Details

Steep slopes are another site condition that is best shown in the detail draw-ings. The way the subgrade is graded and scarified, and the procedure usedfor placing the planting soil, make all the difference for slope stabilization.Most landscape designs will have slopes. Problems arise when the slopes getsteeper than 4:1, or 25 percent (14 degrees). It is strongly suggested that thereshould not be any slopes greater than 3:1, or 33 percent (18.5 degrees). Mostsoils have an internal angle of friction between 25 and 30 percent (Holtz andKovacs 1981, Bowles 1996). This means that slopes greater than these angles


are unstable and will slip. The other item that will also cause slope slippage isthe subgrade. If the subgrade is smooth, water running along the interfacebetween the dense subgrade and the more porous planting soil will causehydraulic lubrication that will cause a slide.

The scarification must be accomplished on the contour of the slope. Thiswill produce ridges parallel to the contour of the slope that will intersect sub-surface water flow and also provide "teeth" for the planting soil to adhere to.

Streetside Tree Pit Details

Planting within pavement raises a host of problems for the successful growthof the plant. The constricting nature of the site limits the size of plant and themethods for creating openings. The pavement opening size for the trees isspecies-dependent. Try not to include grates or pavers within the pit openingbecause too often the follow-up maintenance is not done when the tree out-grows the opening. Trees should have a big enough opening for their maturestate, not for when they are little; therefore, an elm will have a bigger initialopening than a medium-sized tree such as a flowering pear or crab apple. Ifthere is enough room, raised beds are preferred. This is especially true in thenorthern climates, where the road salts can accumulate within the tree pit.Raised linear beds for trees also protect them during snow removal—and fromincidents with car doors.

Another aspect of Streetside trees is that it might be wise to limit theirgrowth rate so that they do not try to expand past the tree pit structure tooquickly.

All these aspects can be generated within the detail drawings: rootingvolume, opening size, underdrainage, linear trench, and irrigation/aerationprocedures. Review Chapter 4 for in-depth discussions on what form of street-side planting is proper for the project.

PART 3 —EXECUTION

The execution portion of the specifications describes the procedures forinstalling the planting soil. Proper execution of the soil installation is manda-tory. The best designed soil will still need to be installed correctly, or thedesign will fail. All aspects of mitigating the inherent soil compaction associ-ated with placement of soils will be discussed at length. Slope stabilization pro-cedures will also be discussed, along with rooftop installation.

Coordination

Coordination between other construction contractors and the soil installa-tion contractor is crucial to limiting excessive traffic over installed soils. Com-


paction and construction debris on the installed soil are among the main rea-sons for planting soil removal.

The landscape contractor is responsible for determining the acceptabil-ity of the landscaper's starting point on the project. If there are deficientitems, such as subgrade that is not at the proposed starting elevations of thecontract, the landscape contractor must note deficiencies and receive com-pensation from the contractor responsible for that portion of the project, orrequest additional funding from the client to complete the work. All startingpoints of the project must be clearly stated within the contracts as well as thespecifications and drawings. The following excepts can be used for the sectionunder "Coordination."

* Preinstallation Examination Required: The Contractor shall examine pre-vious work, related work, and conditions under which this work is tobe performed and shall notify the Owner in writing of all deficienciesand conditions detrimental to the proper completion of this work.Beginning work means that the Contractor accepts substrates, previ-ous work, and conditions. The Contractor shall not place any plantingsoil until all work in adjacent areas is complete and approved by theOwner.

* Planting Soil Preparation: Examine soil and remove foreign materials,stones over 1 inch, and organic debris over 2 inches in length. Mix inamendments as required by tests and as approved by the Owner. Allpreparation and mixing shall be accomplished when the soil moisturecontent is less than 10 percent by volume.

* Coordinate activities with other project contractors so that there is nosoil disturbance from traffic or other construction activities subsequentto placement.

Excavation and Scarification

Scarification is the tool that we use to control overcompaction of the plantingsoil and to prevent interfaces between placement lifts. The scarification mustalso be used on the subgrade to increase its infiltration and provide adherenceof the placed planting soil to the subgrade. This is especially important forplanting soils being placed on slopes. There is one piece of equipment thatshould not be anywhere near the soil installation (Figure 5-1).

There are several pieces of equipment that can be used for scarification.Each type of equipment is specific, however, and should be employed accord-ing to its limitations. Some equipment only scratches the upper 1 to 2 inches,while other types do not work in soils with rock fragments larger than 2 inchesin diameter. Other machines built for excavation can be used to loosen or


5-1 Roller used incompaction of sub-roadbeds, notplanting soils

scratch the subgrade. The best scarification equipment is agricultural tillagetools such as chisel-plows, disks, and spring-tooth harrows. Unfortunately, thesetillage implements are too large for most design areas.

Spade-tooth Tiller. This piece of equipment mounts on the three-point hitchof a small tractor. The tiller is powered by the "power take off (PTO) (Fig-ure 5-2). The shovel-shaped tillers are thrust into the soil, and then they arepried to the rear, chipping the soil out of the ground (Figure 5-3). The maindrawback of this implement is that, if any of the spades hit a stone larger than2 inches in diameter, the tiller will jump out of the ground and possibly dam-age the equipment. The more rock fragments within the surface, the lesseffective the spade-tooth tiller is.

Rototiller. The rototiller comes in different sizes, from walk-behind types to 12-foot-wide agricultural models (Figures 5-4 and 5-5). The tiller has heavy steelblades that are parallel to the soil surface; when they rotate, they chop the soil.Rototillers work very well in soils without rock fragments. They are slightly bet-ter than a spade-tooth tiller at working soil with rock fragments; however, therototiller only penetrates below the surface based on the size and torque of theequipment. Of course, the more stones within the soil, the shallower the tillercan work effectively. Hanging onto a walk-behind rototiller can be very hard on

5-2 Spade tillerused for

scarification5-4 Walk-behindrototiller

5-3 Operating endof the Spade tiller

256

5-5 Tractormounted rototiller

257


the operator, when the soil contains large amounts of stones. Towed equipmentin stony soils can be easily broken, and it is also not as effective with greater stonepercentages.

Disks. The agricultural disk slices into the soil, throwing the furrow to oneside, and the trailing offset series of disks breaks up that furrow and throws itto the opposite side (Figure 5-6). It is very useful for scarification of crustedsoils and is often used for the preliminary cultivation prior to final fitting ofthe planting surface. Disking forms parallel ridges that, if run parallel to thecontour, reduce soil erosion on sloping surfaces (Figure 5-7). One of the draw-backs of the use of the disk in landscaping projects is that a lot of space isneeded to operate a disk at the proper speed. Agricultural disks are recom-mended for large areas needing scarification, such as large lawns or otherlarge planting areas. Another drawback is that one pass of the disk will onlyscarify about 4 inches deep, and it commonly leaves a compacted zone belowthe depth of the disk cut. The compacted zone is caused by the disk scrapingacross the soil at the depth of tillage (Figure 5-8).

Backhoe Teeth. Track-hoes or backhoes can be used to scarify within tight areasand are typically in abundance around construction sites. All the operatorneeds to do is fully extend the bucket so the teeth are pointed down. Thendrag the teeth along the surface of the subgrade. The subgrade should looksomething like the cross-section in Figure 5-9.

Hand Tools. Hand tools such as rakes or soil forks work well for scarification

5-7 The effect ofdisk tillage

5-6 An agriculturaloffset disk

Compacted Zone

A AgriculturalDisk

5-8 CompactedZone under tillageequipment

259


6"

5-9 A cross-section of scarified

subgrade anddesigned soil

18"

ScarifiedInterface

Subgrade

between soil lifts. The compacted areas that are left from the soil installationor foot traffic can easily be broken up using the rake to scratch the surface tomitigate the compaction. Of course, this requires manual labor and should belimited to very tight areas that equipment cannot maneuver in.

Deep Loosening. Track-hoes or backhoes can be used to loosen the soil to the

5-10 Deeploosening withsmall backhoe

Planting Soil Specifications 26 I

depth of the bucket (Figure 5-10). The hoe operator digs a one-bucket depthand then dumps the excavated soil back into the hole (Rolf 1986). The roughsurface is regraded with light equipment that will seat the soil, compacting itenough to minimize excessive settling. This works well with very dense sub-grades and heavily compacted soils prior to placing the topsoil or designedsoil on top.

Excavation and scarification specifications that deal with excavationdepths, underdrainage installation, irrigation installation, size and type ofequipment, slope stabilization procedures for the subgrade, and describingparticular scarification procedures for special areas should be included here.Here are some examples of specifications:

Final Excavation Depths

4 Excavation of the subsoil for street planting areas shall be accom-plished to a depth of 30 inches below the level of the subbase for thesidewalk, for areas noted for designed soil placement. All constructiondebris shall be removed from the planting areas prior to placement ofthe soil layers. Care shall be taken to avoid working the soil when it has10 percent moisture content or above.

4 Subgrade for the planting area shall be accomplished using approvedmaterials and compacted to standard subgrade compaction ranges.

4 After the specified engineering compaction for all subgrades is accom-plished and the trees within the terrace area are planted, scarify thecompacted surface of the subgrade following final rough grade to adepth of 4 to 6 inches prior to the soil placement. The subgrade shallhave a permeability of not less than 0.5 inches/hour. Determine per-meability of the subgrade using a single ring infiltrometer methodafter it has been scarified. If infiltration of the subgrade is below0.5 in/hr, scarify perpendicular to previous scarification to a depth of6 to 8 inches and retest for infiltration.

Removal of Topsoil prior to New Grading

4 Clear and grub entire turf area in conformance to the Planting andSeeding section of the specifications.

4 Remove topsoil in conformance to the Planting and Seeding sectionof the specifications and Part 3 of this section.

Equipment Limitations

4 Small tracked equipment shall be used to grade and move the soils, tolimit the amount of soil compaction occurring during grading.

4 Back-blading the topsoil will orient soil particles, causing overcom-paction. Back-blading is prohibited.


Specialty Scarification Areas

4 Specific grading procedures for the designated areas. Follow procedures forstockpiling the topsoil in the general portion of this section. Soil usedas fill that is not from the site or does not meet the Additional SoilMaterial specifications noted in the Products portion of this sectionwill not be accepted. Grade the surface as pertaining to the EarthworkSpecifications section, with the following exceptions:• Area A: If cutting the soil greater than 6 inches after the 2-inch top-

soil removal within this area, the cut shall extend an additional 6inches so as to allow replacement of the clay loam subsoil with themixed loam stockpiled topsoil.

• Area B: There are no exceptions for soil installation within this areaother than noted elsewhere within this section.

• Area C: This area contains highly disturbed soil. Locations withinthis area that are not filled to a depth greater than 6 inches willrequire the deep loosening procedure outlined in the Executionportion of this section. The highly disturbed and compacted in situsoil must be loosened if it occurs within the rooting zone of the turfor planted trees (6-10 inches for turf, 12-18 inches for trees).

Mixing of Designed Soil

* The planting soil shall be mixed in a ball mill or tub mill fitted withproper screening and paddles. Windrowing the materials is not accept-able, as it does not produce uniform mixing of the components.

* Mixing of the compost for the SI layer (topsoil) shall be accomplishedin the same manner as the other mixing procedures. The compostshall be moist, but not so wet that water can be squeezed out by handor so dry as to be easily blown by wind.

4 Incorporation of organic matter compost amendment to the turfareas shall be accomplished by spreading 1 inch of compost to the sur-face, and incorporated using a rototiller or renovator. Add an addi-tional 1-inch layer of compost and incorporate perpendicular to thefirst tillage operation.

Placement of Soil Layers (Horizons)

Soil installation is extremely variable, depending on what the soils design callsfor. There may be differing depths of soil for trees, shrubs, and turf. Streetsidetree pits need to incorporate engineering compaction parameters for soilsunder pavement and still provide a viable rooting volume. Rooftop soils may

need lightening using foam blocking or lightweight soil additives. Compostamendments can be incorporated as the soil is mixed or by surface incorpo-ration. As it stands, there are many possible soil profiles to meet the needs ofthe planting design.

It is recommended to reemphasize the procedures for starting soil place-ment. The soil installation is not the only thing that the landscape contractorwill need to do. Prior to soil installation, the subgrade will need to be reviewed,scarified, and tested before any planting soil is placed. The following is anexample of the preliminary steps required before soil installation.

* Soil placement preparation:• Verify that the underdrainage and/or irrigation systems have been

installed and accepted, if applicable.• Verify that the subgrade passes the minimum water infiltration

requirement.• Determine that the subgrade is free of debris.• Verify that the subgrade meets a soil density requirement of 95 per-

cent of peak density and is the proper depth.• Verify that the soil mix and topsoil are below 10 percent moisture at

least two days prior to soil placement.• Notify the Owner of soil placement operations at least 10 calendar

days prior to the beginning of work.

4 Examination of subgrade: The subgrade shall be examined by the Con-tractor prior to the start of soil placement and planting. Any defi-ciencies shall be noted and related to the Owner in writing prior toacceptance of the subgrade by the Landscape Contractor. Deficienciesinclude, but shall not be limited to, the following:• Construction debris is present within the planting areas.• The subgrade is at incorrect depths for installing the designed soil

profile.• There is incomplete irrigation and/or subsurface drainage instal-

lation.• The subgrade is not at 95 percent of peak density. The Contractor

shall use the owner's testing agency for determining if subgradedensity meets the requirements.

There are three main soil profiles that can be used that should handlemost of what the Landscape Architect and Contractor wish to accomplish:(1) the placement of 6 inches of topsoil and its surface amendment of com-post, (2) within-pavement tree plantings, and (3) a planter soil profile. Thefollowing statements are for the more typical applications.


Placement of the Open-Turf Planting Soil

Note that the trees and shrubs are planted before the topsoil is installed.Through other various projects, it has been determined that filling the surfacesoil layer in and around the plants reduces a large amount of compaction thattypically occurs with the final soil layer placement. It also eliminates the needto drive over the soil to plant the trees. In very tight planting areas, this proce-dure may not be economically feasible. This soil profile was used with a speci-fied natural soil of certain properties.

4 Plant individual trees in locations noted on the drawing at this time,using the dished tree detail described in the planting soil specifica-tions and noted in the Drawings. Scarify the sides of the tree pit. Back-fill the tree pit and lightly tamp in and around the rootball.

* Place the approved topsoil in one 6-inch lift in and around treesand planting areas. Back-blading the topsoil will orient soil parti-cles and cause overcompaction. Back-blading is prohibited. Smalltracked equipment is required for planting soil placement. Submitrequest for approval from the Landscape Architect on equipmentsize and type.

4 Organic matter compost amendment shall be incorporated by spread-ing 1 inch of compost to the surface and incorporate the compostusing a rototiller or renovator. Compost-amendment application rateshall be 3 cu yds/1,000 sq ft.

* Seed and plant according to the turf establishment specification.

Placement of Streetside Planting Soil

The following streetside designed soil example is a continuous trench underthe majority of the sidewalk that contains the manufactured soil. In this soilprofile, the sidewalk paving is completed before tree planting, after the S2layer has been installed. This allows the soils directly under the pavement to becompacted to the engineering specifications while the tree planting is accom-plished within the opening, loosening the soil directly around the rootball.This soil profile was for a designed soil.

* Scarify the subgrade and test the subgrade's infiltration rate. Each areashall have at least three infiltration tests per planting area. The street-side planting area shall be defined by limits of hardscape for treetrench. Locations are noted on the Drawings.

* Place the S3 drainage layer in one 6-inch lift. Compaction of this liftshall consist of light tamping by the installer's foot traffic. No mechan-ical compaction shall be allowed.

4 Place 24 inches of the S2 layer where the soil installation shall notexceed 6-inch lifts. Light foot traffic is allowable for placing the nextlift and as needed to seat the soil layers within the profile, thus reduc-ing overall subsidence. A light scarification with hand tools is requiredto break up any compacted surface and eliminate any interface. Addi-tional compaction is prohibited.

* Care shall be taken to maintain the separation between the designedsoil layers. Do not mix the SI, S2, or S3 with adjacent layers.

* Reducing the amount of compaction to the soils can be accomplishedby beginning the work in corners, against walls, or at the center of iso-lated beds, and progressing outwards. This limits the amount of trafficon the placed soil during installation.

+ Planting soils shall never be moved or worked when wet or frozen.

4 The Contractor shall place barricades as required to prevent anyunnecessary compaction of planting soil from vehicles, equipment, orpedestrian traffic.

NOTE: It is wise to repeat the basic compaction, handling, andtraffic restriction mantra so that the landscape contractor knowsthat this is important. To limit repetition, a General Proceduresportion of the Execution section could be developed that strictlystates that these procedures are to be followed in all planting soilinstallations.

4 After sidewalk construction is complete, the S2 layer shall be exca-vated for tree planting following Section 02900 of the specifications.• The excavation shall be such that care is taken not to damage the

concrete.• The depth of the excavation shall be the depth of the rootball less

7 inches. Compact only the very bottom of the excavation with ahand tamper to form a dense pedestal of at least 95 percent of peakdensity to support the tree rootball.

• The root collar of the tree shall be set to the level shown on theDrawings.

• Place the SI soil layer in and around the rootball to a depth of notless than 6 inches. Fill the remaining volume to the top of the root-ball but below the plant's root collar.

Placement of Planter Planting Soil

This example of a planter soil profile used a designed soil within a cylindricalplanter with geotextile-covered drain holes at the bottom.


* Place the S3 drainage layer in one 6-inch lift.

4 Place the S2 layer in 6-inch lifts to a level of 7 to 8 inches below the topof the planter. This will allow the final grade to be at least 1 inch belowthe top of the planter. Light tamping is allowable for seating the lift,reducing overall subsidence. A light scarification with hand tools isrequired to break up any compacted surface and eliminate any inter-face. Additional compaction is prohibited.

4 Excavate a hole within the S2 material for the tree rootball. The depthof the excavation shall be the depth of the rootball less 7 inches. Com-pact only the very bottom of the excavation with a hand tamper to forma dense pedestal to support the tree rootball. The root collar of thetree shall be approximately 1 to 2 inches above the level of the 6-inchSI layer, to allow for mulch placement.

4 Backfill around the rootball with S2 material. Place 6 inches of theSI material on the scarified S2 surface and slightly pack around therootball.

4 Finish with 2 inches of specified mulch, keeping mulch below the rootcollar of the tree.

Placement of Soils on Steep Slopes

There are several ways to deal with slope within the specifications. Here is anexcept of a specification that was written to stabilize a slope around 28 percent(3.5:1). Notice that a roller is used to compact the S3 and lower lifts of the S2into the scarified subgrade to "seat" the soil to limit future slippage.

4 The soil shall be placed in lifts not to exceed 6 inches in thickness andonly hand-tamped avoiding mechanical tamping and excessive trafficwith the following exceptions:• For areas steeper than 4:1 grades, the following compaction proce-

dure will be followed to increase soil stability. The S3 drainage layerwill be placed on the prepared subgrade and compacted with a smallroller weighing about 100 Ibs per foot-width of the roller and passedover the area once. The first 6-inch lift of the S2 will be compacted withthe same weighted roller for one pass over the surface. The second6-inch S2 lift shall be compacted with a 50 Ibs per foot-width rollerpassed over the surface once. Any additional compaction must beavoided. The final 6-inch S2 lift will not be compacted with the handroller and only moderately hand-tamped. The tree and shrubs shouldbe planted in the S2 at this time, and the SI layer shall be placedaround them by working from one end of the area to the other, elim-inating the possibility of compaction due to foot and vehicle traffic.


In those cases where the final soil profile depth exceeds the heightof the plant rootball, the entire soil depth beneath the rootball shallbe compacted to 95% Proctor to create a firm pedestal and preventsettlement of the rootball.

Protection and Repairs

Often some jobs are not completed within one season, or there is significantdamage to the soil due to severe weather during construction. Sometimesother construction is delayed, and hardscape contractors need to revisit thesite and may cause damage to the installed soils. Of course, it would be up tothat contractor to pay the landscape contractor for fixing their damage. Donot let anyone other than the landscape contractor fix any soil damage. Prob-lems will arise because other contractors deal with constructing structures onsoils and are not familiar with working soils to make plants grow.

Specifications should state exactly who is responsible for fixing damage.It makes sense that the landscape contractor is supposed to do this job, butfinger pointing later will be quickly solved if the responsibility is defined inwriting. To ensure that everyone understands their responsibilities, thesestatements are needed in other portions of the specifications, such as SitePreparation, Paving, and even Planting.

4 The Landscape Contractor shall protect newly graded areas fromtraffic and erosion. Keep them free of trash, debris, or constructionmaterials.

4 All contractors shall be prohibited access to the restricted areas andkeep the established planting soil free of construction debris.

4 Within the installation warranty period, repair and reestablish gradesto specified tolerances where completed or partially completed sur-faces become eroded, rutted, settled, or compacted due to subsequentconstruction operations or weather conditions.• Repair areas so that they smoothly blend with established areas.

Repairs shall meet original specifications and standards.• If additional excavation is required for correcting underground util-

ities, the following procedure must be followed: Scarify or removeand replace material to a depth as directed by the Owner; reshapeand recompact by hand-tamping only, at the prescribed moisturecontent.

4 Where settling occurs, before sidewalk construction and final soil in-stallation acceptance, backfill with additional approved material, com-pact to specified rates, and restore any disturbed areas to a conditionacceptable to the Owner.


Postinstallation Maintenance

Once a project is completed, the client will be required to maintain the site.There are several ways to realize this. One way is to develop a separate docu-ment that the client will need to follow for a sustainable landscape design.Another way is to add a section to the specifications to make sure that the clienthas documents with specialized postinstallation maintenance procedures.This may also help the client get a bid price for postproject maintenance.

Any necessary annual or biannual fertilization and soil pH adjustmentsshould be included within this section, along with irrigation requirements,maintenance of pavers or tree grates around pavement trees, and any otherspecialty maintenance functions. This part of the specifications should have aheading paragraph stating who is responsible for the maintenance.

The following items are the responsibility of the Owner after theguarantee period, to ensure the sustainability of the designed soiland plants for the life of the site.

Fertilization and pH Adjustment

Quite often, fertilization is overdone. Fertilization and liming should only be forthe upper 6 inches of the soil. This is where almost all of the nutrient uptake forthe plants occurs. The very fine root hairs are the "mouths" of the plants. Roothairs are almost always within the upper 2 to 4 inches of the soil. Fertilizationbelow this level is a waste of time and money. Frequently, fertilization is accom-plished based on what has worked elsewhere, and not on a scientific basis. Theplanting soil installed at one job site is not always the same as that of the previ-ous one. It is better to "know" than to "guess." The owner should develop asoil-sampling program to monitor soil nutrients for determining fertilizerapplication rates. Fertilizer and liming procedures stated within the specifica-tions can assist the owner in developing a comprehensive maintenance plan.

In the case of trying to lower pH, the application of sulfur compoundscan be incorporated within the soil profile. In most cases, this is required toactively lower the pH enough. Further applications will of course be needed,but the sulfur applications and their effect are limited to the surface. Again,the owner should test the soil to determine the exact rates of applicationbefore "guessing."

* Fertilization of turf planting areas shall be handled after establish-ment, as noted in Section 02900.

4 After one year, collect soil samples of the surface 6 inches in each ofthe various soil areas, and submit them for laboratory testing for fer-tilizer and liming recommendations. Take samples of each "area" atseveral locations and mix into a bucket. Collect a subsample from the

bucket as the soil test submittal. The local land grant university coop-erative extension office can assist with the sampling procedure andlocate testing facilities.

* Each "type" of soil and planting area must be sampled separately, butsimilar areas can be grouped. For example, areas of soil in turf areasversus planting beds (flower and shrub) need to be sampled and testedseparately. Fertilization and liming need to be tailored to each area formaximum effect, to reduce overfertilizing and overliming that lead topossible contamination of groundwater and runoff.

4 Repeat soil sampling for these areas every two years after first sam-pling, and fertilize and lime to test recommendations.

Turf Maintenance

Turf maintenance is quite different from tree maintenance. Grasses usuallyrequire more nutrient inputs to provide the aesthetic appearance most peopledesire from their turf. Most golf courses require four annual fertilizations, inthe spring, midsummer, late summer, and late fall. High-intensity residentialareas also suggest this interval of fertilization. However, soil testing is stillrequired to regulate the levels of usable nutrients, so as not to overfertilize.

When turf is first seeded or sodded, it requires some establishment time.In the case of seeded grasses, one full growing season is required for properestablishment, at the very least. The grasses selected for seeding should deter-mine the length of the establishment period.

The following list should be included within the maintenance portion ofthe specifications. These procedures are specific to turf maintenance.

* Restrict all traffic on renovated areas with fenced-in enclosures untilthe turf is fully established. At least one growing season is recom-mended. Two seasons are better.

* Aerate yearly, using a plug method or other method to loosen the soiland provide gas exchange paths for the established lawn. Avoid theareas under trees for a distance from the trunk of at least 1.5 times thetree's height.

For the Boston Commons project (Sasaki Associates), the seeded turf areaswere closed to pedestrians for two full growing seasons. For Ohio State Uni-versity's Oval Restoration project (Michael Van Valkenburgh Associates),the turf establishment period will be one growing season.

270 Construction Documents Value Engineering 27 I

4 For areas that receive heavy use, amend the compacted areas by firstloosening the soil surface to a depth of 3 to 4 inches, then grade andreseed. Keep traffic off the area until grass is firmly established.

4 Repeat soil sampling for these areas every two years after the firstsampling, and fertilize and lime to test recommendations.

IrrigationIrrigation is required for dry environments that have succulent plants, verysandy soils, soils that will have high traffic during the summer months, plant-ing areas within courtyards with south-facing highly reflective facades andpavement, and planting areas with limited rooting volumes. Planting speciesof plants meant for the more humid temperate regions of the U.S.—KentuckyBluegrass, for example—will require more water than some environments canprovide. The coarser sandy soil does not have the water-holding capacity of asilt loam soil of similar volume. High-traffic areas during the summer needperiodic rest from heavy use and more water to offset the crushing effects ofpedestrian traffic. The reflective heat of the facades and pavement will causeincreased evapotranspiration, resulting in heat stress for plants, which onlymore water can alleviate. Planting areas that have very low rooting volumes,such as planters, contained raised beds, and shallow planting areas, will needmore water to offset the limited water available from smaller soil volumes.

4 Tailor irrigation requirements to the evapotranspiration needs of thetrees and shrubs separately. Close supervision of irrigation needs isrequired.

4 Irrigation should be balanced with natural precipitation.

4 Use precipitation sensors on irrigation systems to prevent overwater-ing during periods of rain.

Tree Maintenance

Trees require maintenance throughout their lives. Trees in the urban envi-ronment are treated like billboards, Christmas trees, bike racks, get banged byopening car doors, and even garbage cans. The very harsh urban environmentabuses them to extremes. The urban environment is too hot in the summer, toocold in the winter, too windy, too wet, and too dry. To reduce some of the trees'stress, people have to take a proactive roll in their survival. As a tree grows, thevery landscape design will have to be altered to provide adequate room for it.These items should be part the Postinstallation Maintenance section.

4 Maintain the brick pavers so that there is ample room for the treetrunk to expand. After several years, the openings within the paversshall be expanded to allow growth.

4 Do not wrap wire or lights tightly around tree limbs. If attachmentof designer lighting is attempted, readjust any attachments yearly toaccommodate tree growth. Do not use wire for attachments; widerplastic ties are recommended.

4 Maintain the cast-iron grates so that there is ample room for the treetrunk to expand. After several years, the openings within the gratesshall be expanded to allow growth.

Future Soil Excavations

The specifications for planting soils were written to provide a surrogate soilprofile that will eventually become a soil in equilibrium with its environment,providing support to plants in both the structural and nutritional aspect. Dis-turbance of this equilibrium with future excavations, for whatever reason, willdisrupt the soil's ability to support plant growth. This is the reason behind thefollowing statements incorporated into the Postinstallation Maintenance por-tion of the planting soils specifications.

4 If the designed soil is to be excavated in the future, the soil needs to beplaced back in the specified profile, as originally placed.

4 Any postinstallation changes or amendments to previously approvedsoils without the landscape architect or soil scientist's consent are theresponsibility of the owner.

Value Engineering ^̂ ^

The landscaping budget is often the first budget cut because it is the lastelement of any construction project. When buildings and hardscape con-struction costs exceed their budget, the landscape architect is pressured tovalue-engineer the landscape to look for savings. Because planting soils canbe somewhat expensive, they tend to be a target for cost savings. If the qualityof the planting soils is reduced, this puts an undue burden on the sustainabil-ity of any landscape design. This problem is compounded when a building hasalready been designed and is under construction, and a landscape architect isthen engaged to develop a landscape design with a budget that cannot allowfor even the slightest consideration to the soils that need to sustain even thesimplest planting design. This is a recipe for certain failure of the plants.

Structural engineers will not allow the thinning of major support beamsbecause of safety concerns. Landscape architects and contractors should takethe same approach to safety as engineers. For example, if a tree for some mirac-ulous reason grows to a large size, and the hardscape structures have limitedthe tree's ability to grow sturdy framework roots, then the tree can fall over—

272 Construction Documents Planting Soil Construction Document Checklist 273

5-11 Example ofwhat may happen

with poorlystabilized

framework roots(Photo courtesy

Dr. J.C. Patterson)

perhaps injuring someone or damaging property (Figure 5-11). The owner ofthe property is then liable, and will turn to the contractor and landscape archi-tect for compensation for a problem that should have been resolved duringconstruction.

All landscape projects will be under budgetary pressures, but the land-scape architect, landscape contractor, and owner will have to work together tofind solutions without destroying the design. In the end, the client must bemade to understand that proper planting soil is required for sustainable land-scapes and protects the design intent.

The following checklist can be helpful when reviewing or developing the con-struction documentation for the planting soils. These are the items the CraulLand Scientists use in the determination of acceptable specifications.

Are the related documents correctly numbered and not contrary to theobjectives of the planting soil specifications? You will have to reviewother specifications to make sure there are no conflicts between them.

Are the testing qualifications using agronomic-based testing standards,and not engineering standards? Certain aspects of the project, such assoil peak density, fill, and subbase standards, may use engineering test-ing, but this should be restricted to those aspects of the project. Is thesoil submittal testing giving the proper information to the landscapearchitect? Are the correct tests specified?

Are the installers' and soil-mixing contractors' qualifications reason-able for this project? A small simple project will not require as muchexperience as a large complex job.

Are the submittal testing and submission procedures sufficient to main-tain quality control of the planting soil? Make sure there is enough leadtime to allow testing and review. Initial approval submittals should bedone six months before construction. The perfect time to work outthe soil mixes is during the winter, well before the planting season.

Can the specified sources of materials supply what is specificallyneeded for the project? Call them and make sure.

Is the control of the planting soil submittal approval process in thecorrect hands? It should be with the landscape architect, and not withthe contractor or general project manager. Specify which labs areacceptable to the landscape architect, or at least get approval of testingagencies prior to the submittals.

Is there enough control over the Delivery, Storage and Handling of theplanting soil? Is it being handled when dry and nonfrozen? Is the stag-ing such that other construction trades on the project will not compro-mise the planting soil? Who is responsible for fixing a damaged plantingsoil installation?

Are there adequate specifications of protection for the installed plant-ing soils?

Is the authority to accept the planting soil installation given to thelandscape architect or soils consultant?

GENERAL PRODUCTS

Is the Scope of Work section correctly stated in an abbreviated formthat covers all that the contractor will have to accomplish? Just coverthe basic steps of the work.

Is there a stipulation that all planting soil materials shall meet thespecifications and that additional testing may be required to ensurecompliance?


G Are the specifications clear as to what planting soil properties will betested and reviewed? The landscape contractor will need to know whatthey will be required to provide.D Are the planting soil particle-size breaks using the USDA texture

sieve cluster? Specifying ASTM F1632 should be sufficient forensuring the proper sieve cluster.

D Is the pH requirement meeting the needs of the plant species, andare there soils within the area that can match the pH range?

D Are there plants that require special soil nutrients to facilitate ger-mination or recovery from transplanting?

G Is the organic matter content specified to be below 10 percent withinthe surface layer only? Organic matter below the surface 6 inches is awaste of material and could lead to settlement of the soil profile.

G Are the specifications for organic matter complete? Review the speci-fication example above for compost specifications.

G Is the mixing procedure in a ball or tub mill? If not, work with the land-scape contractor to ensure a homogenous planting soil mix. If there isto be surface amendment with compost, make sure the compost is fineenough to be incorporated completely (about /^-inch to M-inch diame-ter material; larger material will be raked off during final fitting, so itwill be wasted).

G Are all the planting soil profiles defined, and do they have correspond-ing details in the drawings?

G If there are multiple soil profiles, is there a plan view showing wherethe various soil profiles will be used?

G Do the soil profile detail drawings match the terminology used in thespecifications?

EXECUTION

G Is there coordination between the various construction trades? Makesure that the irrigation, hardscape, and landscape contractors worktogether to ensure a smooth installation without causing damage toanyone's installation.

| | Are there statements specifying cleanup of the subgrade before plant-ing soil installation? There should be detailed descriptions of whatconstitutes a clean, prepared subgrade.

G Are the subgrade testing procedures and schedule listed?

Planting Soil Construction Document Checklist 275

G Do the specifications clearly define when, which, and how subgrade isto be scarified?

G Are there cautionary notes on the proper planting soil moisture con-tent for installation? Planting soils should not be placed when they areat moisture contents that allow peak density compactions (betweenabout 8 and 15 percent moisture contents) (Holtz and Kovacs 1981).

G Are there cautionary notes not to place the planting soil when it isfrozen or saturated?

G Are the procedures for placing the planting soil concise and logical?Review examples of planting soil installation procedures above. If thereare several soil profiles used, there should be soil installation proce-dures specific to each profile.

G Are the statements pertaining to the protection and repairs of theinstalled planting soils complete? Additional specifications should benoted on how to fix damaged planting soils. One cannot foresee everycrisis, but the simple application of common sense pertaining to thesoil properties should suffice.

G Is there a need for mentioning Post Installation Maintenance? In mostcases, this section should be employed to provide the client and land-scape contractor with procedures to maintain the project efficiently.

G Most fertilization for turf should follow the standard procedures typi-cal for the species and area. Suggested fertilization times are earlyspring, just as the turf is starting to grow; midsummer, but not duringa drought; and fall, around late October or early November. Some turfexperts suggest fertilization four times a year. It is still recommendedto fertilize based on soil nutrient testing, so as not to overfertilize andcause leaching and runoff into pristine waters. A prime example ofexcessive nutrient loading on ecosystems is the degradation of theChesapeake Bay.

G For tree and shrub fertilization, follow ANSI A300, Part 2 (Tree CareIndustry Association), which recommends not to fertilize trees andshrubs during the first year until the roots extend beyond the rootball.