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Basic information The Guide for Industrial Waste Management, its corresponding CD-ROM, and thePartners user's guide and technical background documents for the Industrial Waste

Management Evaluation Model (IWEM) and Industrial Waste Air Model (IWAIR)Guide for industrial models can be ordered quickly and free of charge from EPA's National Service

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2. When you install IWEM from the CD-ROM, you must launch theIWEM tool from the IWEM icon on your desktop. IWEM will not launchfrom the "Already Installed" button; it must be launched from thedesktop icon.

• Industrial Waste Management Evaluation Model (IWEM) TechnicalBackground Document, EPA530-R-02-012

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Basic information Chapter SummariesPartnersGuide for Industrial ^ne Guide for Industrial Waste Management contains 11 chapters divided into 5

Waste Management maJ°r sections. Click on the links below to view a summary of each of the chaptersand access the portable document version of the entire chapter. You will need

Tools Adobe Acrobat to view the chapter in this format.Frequent Questions

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Individuals Involved in Creating the Guide

Part I - Getting Started

• Chapter 1: Understanding Risk and Building Partnerships• Chapter 2: Characterizing Waste• Chapter 3: Integrating Pollution Prevention• Chapter 4: Considering the Site

Part II - Protecting Air Quality

• Chapter 5: Protecting Air

Part III - Protecting Surface Water

• Chapter 6: Protecting Surface Water

Part IV - Protecting Ground water Quality

• Chapter 7 - Section A: Assessing Risk• Chapter 7 - Section B: Designing and Installing Liners: Technical

Considerations for Surface Impoundments, Landfills, and Waste Piles• Chapter 7 - Section C: Designing a Land Application Program

Part V - Ensuring Long-Term Protection

• Chapter 8: Operating the Waste Management System• Chapter 9: Monitoring Performance• Chapter 10: Taking Corrective Action• Chapter 11: Performing Closure and Post-Closure Care

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Basic information Chapter 11: Performing Closure and Post-Closure CarePartners

Guide for Industrial Adobe PDF (40 pages, 412KB)Waste Management

To0is This chapter explains how closure and post-closure care is an integral part of aunit's overall design and operation. It describes various closure options and

Frequent Questions demonstrates how facilities can provide long-term environmental protection byIn the News reducing or eliminating potential threats and mitigating the need for future

corrective action at the site. Furthermore, this chapter describes why adequateOrder CD/ Publications funding should be set aside to cover the planned costs of closure and post-closure

care.

This chapter helps to answer the following questions:

• How do I develop a closure plan?• What factors should I consider when choosing a closure method?• What are the components of a final cover?• What costs are associated with post-closure care?

Refer to the Resources page for additional information on topics discussed in thischapter.

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Part VEnsuring Long-Term Protection

Chapter 11

Performing Closure and Post-Closure Care

•ofo&v

Contents

I Closure Plans 11-1

II Selecting a Closure Method 1L- 3

III Closuie b) Use of Final Cover Systems 11-4

A Purpose and Goal of Final Co\er Systems 11-4

B Technical Considerations for Selecting Covei Materials 11-5

C Components of a Final Cover 11-8

D Capillary-Bieak Final Covers 11- 16

E The Hydrologic Evaluation of Landfill Peifoimance (.HELP) Model II- 17

F Recommended Cover Systems 11-18

IV Closure by Waste Removal 11-21

A Establishing Baseline Conditions 11-22

B Removal Piocedures 11-22

C Disposal of Removed Wastes 11- 23

D Final Sampling and Analysis , 11-23

V Post-Closure Care Consideiations When Final Co\ei Is Used 11-24

A Maintenance 11-24

B Monitoring During Post Closure Caie 11- 25

C Recommended Length of the Post-Closuic Care Penod , 11-25

D Closuie and Post-Closure Cost Considerations 11- 26

Peifoimmg Closure and Post-Closure Caie Activity List 11- 34

Resouices 11-35

Tables

Table 1 T>pes of Layeis in Final Cover Systems 11-9

Table 2 Types of Recommended Final Co\ei Systems 11-18

Table 3 Example Closure/Post-Closure Cost Estimate Form 11-27

Table 4 Sample Summaiy Cost Estimating Wot ksheet 11-29

Table 5 Estimated Closuie and Post Closuie Care Costs 11- 31

Figures

Figure 1 Regional Depth of Fiost Penetiation in Inches 11-6

Figure 2 Diamage Layer Configuration 11-11

Contents (cont.)

Figme 3 Geonet \\ith Geotextile Filter Design for Drainage Layer 11-12

Figuie 4 Passixe Gas Venting System 11-15

Figure 5 Active Gas Venting System 11-15

Figure 6 Example of a Capillaiy-Bieak Final Cover System 11-17

Figure 7 Recommended Final Cover System Foi a Unit With a Double Lmei 01 a Composite Liner 11-19

Figuie 8 Recommended Final Covei System Foi a Unit With a Single Clay Lmei 11-19

Figuie 9 Recommended Final Covet S>stem For a Unit With a Single Cla) Lmei in an Arid Atea 11-20

Figuie 10 Recommended Final Cover System Foi a Unit With a Single Synthetic Liner 11 20

Figure 11 Recommended Final Cover System For a Unit With a Natutal Soil Liner 11-21

Ensuring Long-Term Protection—PLrfoimmg Closure and Post-Cloiua Can

Performing Closure and Post-Closure CareThis chapter will help you

• Provide closure and post-closure care as an integral part of a

unit's overall design and operation

• Provide long term environmental protection by reducing or elimi-

nating potential threats and the need for potential corrective

action at the site

• Plan and accomplish the goals of closure and post-closure care by

requiring that adequate funding be set aside to cover the

planned costs of closure and post-closure care

The ovetal l goal of closure is tominimize or eliminate potentialthi eats to human health and theenviionment and the need forfuture collective action at the site

If removing the wastes containment devices,and any contaminated subsoils from a unit,the unit should be returned to an acceptablerisk level so that it is not a cunent 01 futuicthicat If wastes will be left in place at clo-suie, the unit should be closed in a mannerthat also leduces and contiols current 01future threats Steps should also be taken toavoid future disruptions to final covei sys-tems and monuoimg devices

This chapter will help address the follow-ing questions

• How do 1 develop a closure plan7

• What factors should 1 considei whenchoosing a closure method7

• What are the components of a finalcovei7

• What costs are associated with post-closure care7

Foi post-closuie caie the overall goal is tominimize the infiltiation of watei into a unitb> piovidmg maintenance ol the final coveiMaintenance should be continued until suchtime as it is determined that caie is no longernecessary Also during post closuie caie,closed units should be monitored to vtnf)and document that no unacceptable releasesaic occunmg

I. Closure PlansA well-conceived closuie plan is the pn-

mary tesource document foi the final stage inthe life of a waste management unit The puipose of a closuie plan is to considei allaspects of the closuie scenario It should becomptehensne so that staff v\ho will imple-ment it yeais aftei its w i l t i ng will clearlyunderstand the activities it specihes It alsoneeds to proucle enough detail to allow cal-culation of closure and post-closure care costsfoi detei mining how much funding needs tobe set aside foi those activities

11 1

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

What should be considered when

developing a closure plan ?

You should tailor a closure plan to accountfor the unique characteristics of the unit, thewaste managed in the unit, and anticipated ,future land use. Each unit will have differentclosure activities. Closing a surface impound-ment, for example, involves removal ofremaining liquids and solidifying sludgesprior 10 placing a final cover on the unit.

The following information is important to'consider when developing a closure plan: ,'

• Overall goals and objectives of closure.

• Future land use.

• Type of waste management unit.

• Types, amount, and physical state ofwaste in the unit.

• Constituents associated with the wastes.

• Whether wastes will be remoyed orleft in place at closure.

• Schedule (overall and interim). ,:.

• Costs to implement closure.

• Steps to monitor progress of closureactions, including inspections, mainte-nance, and monitoring (e.g., ground-water and leachate monitoring).

• Health and safety plans, as necessary.

• Contingency plans.

• Description of waste treatment or sta-bilization (if applicable).

• Final cover information (if applicable).

• Vegetation management.

• Run-on and runoff controls.

• Closure operations and maintenance.

• Erosion prevention and repair.

• Waste removal information (if applica-ble).

• Parameters to assess performance ofthe unit throughout the post-closureperiod.

The plan should address the types of wastethat have been or are expected to be depositedin the management unit and the constituentsthat can reasonably be associated with thosewastes. The types of expected wastes willaffect both the design of the final cover andthe types of activities that should be undertak-en during the post-closure care period.Biodegradable waste, for example, can cause afinal cover to subside due to decompositionand can also require gas management.

The closure plan should provide otherinformation that will address the closure strat-egy. If, for instance, a final cover is planned,then the closure plan should consider season-al precipitation that could influence the per-formance of both the cover and themonitoring system. Information concerningfreeze cycles and the depth of frost perme-ation will provide supporting informationwith which to assess the adequacy of thecover design. Similarly, arid conditions shouldbe addressed to support a decision to use aparticular cover material, such as cobbles.

The closure plan should address the closureschedule, stating when closure is expected tobegin, and when closure is expected to be com-pleted. You should consider starting closurewhen the unit has reached capacity or hasreceived the last expected waste for disposal.For units containing inorganic wastes, youshould complete closure as soon as possibleafter the last expected waste has been received.A period of 180 days is a good general guidefor completing closure, but the actual timeframe will be dictated by site-specific condi-tions. For units receiving organic wastes, moretime might be needed for the wastes to stabilize

11-2

Ensuring Long-Term Protection—Pcrfoi mmg Closure and Post-Closure Care

pnor to completing closure Similarly, othersite-specific conditions, such as pi capitationor winter weather, can also cause delay incompleting closure For these situations, youshould complete closure as soon as feasibleYou should also consult with the state agencyto determine if any requnements exist for clo-sure schedules

Even within a waste management unit,some areas will be closed on different sched-ules, with ceitain areas in paitial closuie,while other areas continue to opeiate Theschedules and partial closure activities (suchas intermediate cover) should be consideredin the closure plan Although the processesfor closing such areas might not be diffeientthan those for closing the unit as a whole, itis still more efficient to integrate paitial clo-sure activities into the closuie plan

If the closuie plan calls foi the stabiliza-tion, solidification, or other neatment olwastes in the unit before the installation of afinal cover, the plan should describe thoseactivities in detail Waste stabilization, solidi-fication, 01 other tieatment has fom goals

• Removing liquids, which aie ill-suil-ed to supporting the final cover

• Decreasing the sui face area ovetwhich the transfer or escape of conta-minants can occui

• Limiting the solubility of leachableconstituents in the waste

• Reducing toxicity of the waste

For closure strategies that will use engi-neering conn ols, such as final covers, the planshould provide detailed specifications Thisincludes descnptions of the cover materials ineach layer and their permeability as well asany drainage and/or gas migration controlmeasures included in the opeiation of thefinal cover Also the plan should identify mea-sures to veiify the continued integrity of the

final cover and the propei operation of the gasmigration and/or drainage control strategies

If wastes will be removed at closure, the clo-sure plan should estimate volumes of waste andcontaminated subsoil and the extent of contam-inated devices to be removed during closure Itshould furthei state waste removal procedures,establish peiformance goals, and address anystate or local requnements foi closuie by wasteremoval The plan should identify numericclean-up standaids and existing backgioundconcentrations of constituents It also shoulddiscuss the sampling plan foi determining theeffectiveness of closuie activities Finally, itshould descnbe the provisions made for the dis-posal of removed wastes and other materials

The closuie plan should also provide adetailed descnplion of the monitoring thatwill be conducted to assess the units perloi-mance thioughout the post-closuie peiiodThese measurements include monitoringleachate volume and charactetistics to ensurethat a cover is minimizing inf i l t ia t ion It isimportant to include appiopnate ground-water quality standards with which to com-pare ground-water moniloung icports Youshould develop the performance measuiessection of the plan pnor to completing clo-suie This section establishes the paiametersthat will describe successful closure of theunit If limits on these parameters are exceed-ed, it will prov ide an early warning that thefinal cover system is not functioning asdesigned and that measures should be undei-taken to identify and coi rect problems

II. Selecting aClosure Method

Factors to consider in deciding whether toperfoim closure by means of waste removalor thiough the use of a final cover include thefollowing

11-3


• Feasibility. Is closure by wasteremoval feasible? For example, if thewaste volumes are large and underlyingsoil and ground water are contaminat-ed, closure by total waste removal •might not be possible. If the unit iscontaminated, consult Chapter10-Taking Corrective Action to identifyactivities to address the contamination.In some cases partial removal of thewaste might be useful to remove thesource of ground-water contamination.

• Cost-effectiveness. Compare the costof removing waste, containmentdevices, and contaminated soils, plussubsequent disposal costs at anotherfacility, to the cost of installing a finalcover and providing post-closure care.

• Long-term protection. Will the finalcover control, minimize, or eliminatepost-closure escape of waste con-stituents or contaminated runoff toground or surface waters to the extentnecessary to protect human health andthe environment?

• Availability of alternate site. Is analternate site available for final dispos-al or treatment of removed waste? Youshould consult with the state agencyto determine whether alternate dispos-al sites are appropriate.

Sections III and V address closure by use offinal cover systems and associated post-closurecare considerations. Alternatively, Section IVaddresses closure by waste removal.

III. Closure by Useof Final CoverSystems

You might elect to close a waste manage-ment unit by means of a final cover system.

This approach is common for landfill units andsome surface impoundment units where somewaste is left in place. The choice of final covermaterials and design should be the result of acareful review and consideration of all site-spe-cific conditions that will affect the performanceof the cover system. If you are not knowledge-able about the engineering properties of covermaterials, you should seek the advice of profes-sionals or representatives of state and localenvironmental protection agencies.

This section addresses the more importanttechnical issues that should be consideredwhen selecting cover materials and designing acover system. It discusses the various potentialcomponents of final cover systems, includingthe types of materials that can be used in theirdesign and some of the advantages and disad-vantages of each. This section also examinesthe interaction between the various compo-nents as they function within the system.

A. Purpose and Goal ofFinal Cover Systems

The principal goals of final cover systemsare to:

• Provide long-term environmental pro-tection of human health and the envi-ronment, by reducing or eliminatingpotential risk of contaminant release.

• Minimize infiltration of precipitationinto the waste management unit tominimize generation of leachates with-in the unit by promoting surfacedrainage and maximizing runoff.

• Minimize risk by controlling gas migra-tion (as applicable), and by providingphysical separation between waste andhumans, plants, and animals.

• Minimize long-term maintenance needs.'

The final cover should be designed to pro-vide long-term protection and minimization of

11-4

Ensuring Long-Term Protection—Per/bun ing Closure and Post-Closure Care

leachate formation Final cover systems canbe inspected, managed, and lepaired to main-tain long-term protection Foi optimal peifot-mance, the final cover system should bedesigned to minimize mfiltiation, suifaceponding, and the erosion of covei materialTo avoid the accumulation of leachale withina unit, the cover system should be no morepeimeable than the hnei system For exam-ple, if a unit's bottom liner system is com-posed of a low-permeability material, such ascompacted clay or a geomembiane, then thecovei should also be composed of a lovv-pei-meabihty mateiial unless an evaluation ofsite-specific conditions shows an equn alentreduction in infiltration If the covei system ismote permeable than the liner leachate willaccumulate in the unit This buildup of liq-uids within a unit is often leferred to as the'bathtub effect" In addition, since manyunits can potentially genet ate gas, covet sys-tems should be designed to conliol gasmigiation Propel quality assurance and qual-ity contiol duung consliuction and installa-tion of the final covei aic essential in oiclei toensute that the final cover performs in accoi-dance with its design For geneial informa-tion on quality assuiance duung consliuctionof the final covei, refer back to the construc-tion quality assurance section of Chapter 7,Section B—Designing and Installing LmeisRecommendations foi the type of final coversystem to use will depend on the type of hneiand the gas and liquids management sti ategyemployed in a unit

B. Technical Considerationsfor Selecting CoverMaterials

Several environmental and engmeenng con-cerns can affect cover materials and should beconsidered in the choice of those materials

How can climate affect a finalcover?

Freeze and thaw effects can lead to thedevelopment of microfiactures in low perme-ability soil layers These effects also can causethe realignment of interstitial Fines (silts andclays), thereby incieasmg the hydraulic con-ductivity of the final cover As a result, youshould deteimme the maximum depth offiosl peneliation at a site and design coversaccordingly In other woids, barnei layersshould be below the maximum host penetra-tion depth Infotmation tegaiding the maxi-mum frost penetiation depth for a parliculaiaiea can be obtained fiom the NaturalResouice Conservation Service with the U SDepailment of Agriculture, local utilities,construction companies, local universities, orstate agencies Figuie 1 illustrates the regionaldepth of frost penetration You should ensurethat vegetation layeis are thick enough thatlow permeability soil layeis in the final coverare placed below the maximum frost penetra-tion depth

How can settlement and subsi-dence affect a final cover?

When w aste decomposes and consolidates,settlement and subsidence can tesultExcessive settlement and subsidence can sig-nificantly unpaii the integrity of the finalcovei system by causing ponding of water onthe suiface, fiacturmg of low permeabilitymfiltiation layers, and failuie of geomem-branes The degree and i ate of waste settle-ment ate difficult to estimate, but they shouldbe considered during design and developmentof closuie plans Waste settlement should alsobe considei ed when determining the liming ofclosut e Steps should be taken to minimizethe degiee of settlement that will occur afteithe final covei system has been installed

11-5


Figure 1. Regional Depth of Frost Penetration in Inches

Source: U.S. EPA. 1989a

How can erosion affect the per-

formance of a final cover? ,.

Erosion can adversely affect the perfor-mance of the final cover of a unit by causingrills that require maintenance and repair.Extreme erosion can lead to the exposure ofthe infiltration layer, initiate or contribute tosliding failures, or expose the waste.Anticipated erosion due to surface-water •runoff for a given design criteria can beapproximated using the USDA Universal SoilLoss Equation1 (U.S. EPA, 1989a). By evaluat-ing erosion loss, you might be able to opti-mize the final cover design to reducemaintenance through selection of the bestavailable soil materials. A vegetative cover hotonly improves the appearance of a unit, but italso controls erosion of the final cover.

The vegetation components of the erosionlayer should have the following characteristics:

• Locally adapted perennial plants thatare resistant to various climaticchanges reasonably expected to occurat the site.

• Roots that will not disrupt the low-permeability layer.

• The ability to thrive in low-nutrientsoil with minimum nutrient addition.

• The ability to survive and functionwith little or no maintenance.

Why are interfacial and internalfriction properties for cover com-ponents important?

Adequate friction between cover compo-nents, such as geomembrane barrier layersand soil drainage layers, as well as betweenany geosynthetic components, is needed toprevent extensive slippage or interfacial shear.Water and ice can affect the potential for

11-6

USDA Universal Soil Loss Equation: X = RKLSCP where: X = Soil loss (tons/acre/year); R = Rainfall ero-sion index; K = Soil credibility index; L = Slope length factor; S = Slope gradient facior; C = Crop man-agement factor; P = Erosion control practice. For minimal long-term care X < 2.0 tons/acre/year.

Ensuring Long-Term Protection—Pcrfomnng Closure aiul Post-Closure Cart-

cover components to slip Sudden sliding cantear geomembranes or cause sloughing ofearthen materials Internal shear can also be aconcern for composite or geosynthetic clayliner materials Measures to improve stabilityinclude using flatter slopes or texturedgeosynthetic membranes, geognds designedto resist slipping forces, otherwise remfoicmgthe cover soil, and providing drainage

Can dry soil materials affect a

final cover?

Desiccation, the natural drying of soilmaterials, can have an adverse affect on thesoil layers compromising the final coveiAlthough this process is most commonlyassociated with layers of low permeabilitysoil, such as clay, it can cause problems withother soil types as well Desiccation causescracks in the soil surface extending down-waid Covei layers are not very thick, andtherefore these cracks can extend through anentire layer, radically changing its hydraulicconductivity or permeability Care should betaken to detect desiccation at an early stage intime to mitigate its damage Also, the tenden-cy for final covers to become dry makes rootpenetration even more of a problem in thatplants respond to drought by extending theirroot systems downward

Can plants and animals have aneffect on a final cover?

When selecting the plant species toinclude in the vegetative cover of a wastemanagement unit, you should considei thepotential for root systems to grow throughsurface cover layers and penetrate underlyingdrainage and barrier layers Such penetrationwill form preferential pathways foi waterinfiltration and compromise the integrity ofthe final cover system Similarly, the presenceof burrowing animals should be foreseenwhen designing the final cover system Suchanimals can burrow in the sut face layers and

can potentially breach the underlying barneilayer Strategies for mitigating the effectsdescribed here are discussed below in thecontext of protection layers composed ofgravel or cobbles

Is it necessary to stabilize wastes?

Before installing a final cover, liquid 01semi-liquid wastes might need to be stabi-lized or solidified Stabilization 01 solidifica-tion might be necessary to allow equipmenton the unit to install the final cover or toensure adequate suppoit, or bearing capacity,for the final cover With proper bulk coveitechnique, it might be feasible to place thecover over a homogeneous, gel-like, semi-liq-uid waste When selecting a stabilization orsolidification process, it is impoitant to con-sider the effectiveness of the process and itscompatibility with the wastes Performancespecifications foi stabilization or solidificationprocesses include Icachabihty, Irce-hquid con-lent, physical stability, bearing capacity, reac-livity, ignitability, biodegradabihty, strength,permeability, and durability of the stabilizedand solidified wasie You should considerseeking professional assistance to properlystabilize or solidify waste pnor to closure

Where solidification is not practical, youshould consider reinforcement and construc-tion of a specialized lighter weight cover sys-tem over unstable wastes This involves usingcombinations of geognds, geotextiles,gconets, geosynthetic clay liners, andgeomembranes For more detail on this prac-tice, consult Deferences such as the paper by-Robert P Grefe, Closure ofPapcrmill SludgeLagoons Using Gcosynthetics and SubsequentPerfoimancc, and the Geosynthetic ResearchInstitute pioceedmgs. Landfill Closings-Geosynthetics Interface Fnction and NewDevelopments, cited in the Resources section

11-7


How can wastes be stabilized?

Many stabilization and solidificationprocesses require the mixing of waste withother materials, such as clay, lime, and ash.These processes include either sorbents orencapsulating agents. Sorbents are nonreac-tive and nonbiodegradable materials that soakup free liquids to form a solid or near-solidmass. Encapsulating agents enclose wastes toform an impermeable mass. The following areexamples of some commonly used types ofwaste stabilization and solidification methods.

• Cement-based techniques. Portlandcement can use moisture from thewaste (sludge) for cement hydration.The end product has high strength,good durability, and retains wasteeffectively.

• Fly ash or lime techniques. A com-bination of pozzolanic fly ash, lime,and moisture can form compoundsthat have cement-like properties.

• Thermoplastic techniques. Asphalt,tar, polyolefins, and epoxies can bemixed with waste, forming a semi-rigid solid after cooling.

• Organic polymer processes. Thistechnique involves adding and mixingmonomer with a sludge, followed byadding a polymerizing catalyst. Thistechnique entraps the solid particles.

After evaluating and selecting a stabilizationor solidification process, you should conductpilot-scale tests to address issues such as safe-ly, mix ratios, mix times, and pumping prob-lems. Testing will help assess the potential foran increase in waste volume. It will also helpto plan the production phase, train operators,and devise construction specifications.

When conducting full-scale treatmentoperations, options exist for adding and mix-ing materials. These options might include in

situ mixing and mobile plant mixing. In situmixing is the simplest technique, using com-mon construction equipment, such as back-hoes, excavators, and dump trucks. In situmixing is most suitable where large amountsof materials are added to stabilize or solidifythe waste. The existing waste management'area, such as a surface impoundment, can beused as the mixing area. The in situ mixingprocess is open to the atmosphere, so envi-ronmental and safety issues, such as odor,dust, and vapor generation, should be takeninto consideration. For mobile plant mixing,wastes are removed from the unit, mechani-cally mixed with treatment materials in aportable processing vessel, and depositedback into the unit. Mobile plant mixing isgenerally used for treating sludges and otherwastes with a high liquid content.

C. Components of a FinalCover

Cover systems can be designed in a varietyof ways to accomplish closure goals. Thisflexibility allows a final cover design systemto integrate site-specific technical considera-tions that can affect performance. This sectiondiscusses the potential components or layersof a final cover system, their functions, andappropriate materials for each layer. Since thematerials used in cover systems are the sameas those used in liner systems, refer toChapter 7, Section B-Designing andInstalling Liners for a more detailed discus-sion of the engineering properties of the vari-ous materials.

Table 1 presents the types of layers andtypical materials that might exist in a finalcover. The minimum appropriate thicknessesof each of the five types of layers dependsupon many factors including site drainage,erosion potential, slopes, types of vegetativecover, type of soil, and climate.

11-8

Ensuring Long-Term Protection—Pcrfoimmg Closure and Post-Closure Care

Table 1Types of Layers in Final Cover Systems

Layer Type of Layer Typical Materials

1

2

3

4

5

Surface (Etosion, Vegetative Cover)Layer

Protection Layer

Drainage Layet

Barnei (.Infiltration) Layei

Foundation/Gas Collection La)ci

Topsotl Gcosynthelic Erosion Contiol Layei,Cobbles

Soil, Recycled or Reused Waste Materials, Cobbles

Sand and/oi Gtavel, Geonet or Geocomposite,Chipped or Shiedded Titcs

Compacted Clay, Geomembrane, Gcosynthetic ClayLmei

Sand or Gravel, Soil, Geonet 01 Geotextile.Recycled ot Reused Waste Matcml

Source Jestonek et al, 1995

What function does the surfacelayer serve?

The role of the surface layer in the final coversystem is to promote the growth of native, non-woody plant species, minimize erosion, restorethe aesthetics of the site, and protect the bameilayer The surface layrer should be thick enoughso that the root systems of the plants do notpenetrate the underlying barrier layei The vege-tation on the surface layer should be resistant todrought and temperature extremes, able to sur-vive and function with little maintenance, andalso be able to maximize evapotianspiration,which will limit water infiltration to the barrierlayer It is recommended that you consult w ithagncultuie or soil conservation expeits concern-ing appropnate cover vegetation Finally, thesurface layer should be thick enough to with-stand long-term erosion and to prevent desicca-tion and freeze/thaw effects of the bamer layeiThe recommended minimum thickness for thesurface layer is at least 12 inches The stateagency can help to determine the appropnateminimum thickness in cold climates to protectagainst freezc-thavv effects

What types of materials can beused in the surface layer?

Topsoil has been by far the most common-ly used material for suiface layers The princi-pal advantages of using topsoil in the suifacelayer include us general availability and itssuitability for sustaining vegetation When top-soil is used as a suiface layer, the roots ofplants will remfoice the soil, reduce the rate oferosion, decrease runoff, and remove waterfrom the soil through evapotranspiration Toachieve these benefits, however, the soilshould have sufficient watei-holding capacityto sustain plant growth There are some con-cerns with regard to using topsoil For exam-ple, topsoil requires ongoing maintenance,especially during periods of drought or heavylamfall Prolonged drought can lead to crack-ing in the soil, cieating preferential pathwaysfor water infiltration Heavy rainfall-can lead toerosion causing rills or gullies, especially onnewly-seeded or steeply sloping covers If thetopsoil does not have sufficient water holdingcapacity, it can not adequately support surfaceplant growth, and evapotranspiration can

11-9


excessively dry the soils. In this case, irrigationwill be required to restore the water balancewithin the soil structure. Topsoil is also vulner-able to penetration by burrowing animals.

Geosynthetic erosion control material canbe used as a cover above die topsoil to limit -erosion prior to the establishment of a maturevegetative cover. The geosynlhetic material caninclude embedded seeds to promote plantgrowth, and can be anchored or reinforced toadd stability on steeply sloped areas.Geosynthetic material, however, does notenhance the water-holding capacity of the sqil..In arid or semi-arid areas, therefore, the soil 'might still be prone to wind and water erosionif its water-holding capacity is insufficient.

Cobbles can be a suitable material for thesurface layer in arid areas or on steep slope'swhich might hinder the establishment of veg-etation. If they are large enough they willprovide protection from wind and water crd-sion without washout. Cobbles can also pro-tect the underlying barrier layer fromintrusion by burrowing animals, but cobblesmight not be available locally, and their usedoes not protect the underlying barrier layerfrom water infiltration. Because cobbles createa porous surface through which water canpercolate, they do noi ordinarily support veg-etation. Wind-blown soil material can fillvoids between cobbles, and plants can estab-lish themselves in these materials. This plantmaterial should be removed, as its rools arelikely to extend into the underlying barrierlayer in search of water.

What function does the protec-tion or biotic barrier layer serve?

A protection or biotic barrier layer can beadded below the surface layer, but above thedrainage layer, to protect the latter from ,

intrusion by plant roots or burrowing ani-mals. This layer adds depth to the surfacelayer, increasing its water storage capacityand protecting underlying layers from freez-ing and erosion. In many cases, the protec-tion layer and the surface layer arc combinedto form a single cover layer.

What types of materials can beused in the protection layer?

Soil will generally be the most suitablematerial for this layer, except in cases wherespecial design requirements exist for the pro-tection layer. The advantages and disadvan-tages of using soil in the protection layer arethe same as those stated above in the discus-sion of the surface layer topsoil. Factorsimpacting the thickness and type of soil to useas a protection layer include freeze and thawproperties and the interaction between the soiland drainage layers. Other types of materialsthat can be used in the protection layerinclude cobbles with a geotextile filler, graveland rock, and recycled or reused waste.

Cobbles with a geotextile filter can forma good barrier against penetration by plantroois and burrowing animals in arid sites.The primary disadvantage is that cobbleshave no water storage capacity and allowwater percolation into underlying layers.

Gravel and rock are similar to cobblessince they can form a good barrier againstpenetration by plant roots and burrowing ani-mals. Again, this use is usually only consid-ered for arid sites, because gravel and rockshave no water storage capacity and allowwater percolation into underlying layers.

Recycled or reused waste materials suchas fly ash and bottom ash can be used in theprotection layer, when available. Check withthe state agency to verify that use of these

11-10


materials is allowable. The advantages ofusing these materials in the protection layerare that they store water that has infiltratedpast the surface layer, which can then bereturned to the surface through evapotrans-piration, and that they offer protectionagainst burrowing animals and penetration byroots. If planning to use waste material in theprotection layer, consider its impact on sur-face runoff at the unit's perimeter. Designcontrols to ensure runoff does not contributeto surface-water contamination. ConsultChapter 6-Protecting Surface Water for moredetails on designing runoff controls.

What function does the drainagelayer serve?

A drainage layer can be placed below thesurface layer, but above the barrier layer, to •direct infiltrating water to drainage systems atthe toe of the cover (see Figure 2) or to inter-mittent benches on long steep slopes. For

drainage layers, the thickness will depend onthe level of performance being designed andthe properties of available materials. Forexample, some geonet composites, with athickness of less than 1 inch, have a transmis-sivity equal to a much thicker layer of aggre-gate or sand. The recommended thickness ofihe high permeability soil drainage layer is 12inches with at least a 3 percent slope at thebottom of the layer. Based on standard prac-tice, the drainage layer should have ahydraulic conductivity in the range of 10~- to10 ' cm/sec. Water infiltration control througha drainage layer improves slope stability byreducing the duration of surface and protec-tion layer saturation. In this role, the drainagelayer works with vegetation to remove infil-trating water from the cover and protect theunderlying barrier layer. If this layer drainsthe overlying soils loo well, it could lead tothe need for irrigation of the surface layer toavoid desiccation.

Figure 2. Drainage Layer Configuration

. "df tlnag* layirt

Source: U.S. EPA, 1991.

11-11


Another consideration for design ofdrainage layers is that the water should dis-charge freely from the toe of the cover or inter-mittent benches. If outlets become plugged orare not of adequate capacity, the toe of theslope can become saturated and potentiallyunstable. In addition, when designing thedrainage layer, you should consider using flex-ible corrugated piping in conjunction witheither the sand and gravel or the gravel withgeotextile filter material to facilitate the move-ment of water to the unit perimeter.

What materials can be used inthe drainage layer?

Sand and gravel are a common set ofmaterials used in the drainage layer. Theprincipal consideration in their use is thehydraulic conductivity required by the overalldesign. There can be cases in which thedesign requires the drainage of a largeamount of water from the surface layer, andthe hydraulic properties of the sand and grav-el layer might be insufficient to meet theserequirements. The advantages of using sandand gravel in the drainage layer include theability to protect the underlying barrier layerfrom intrusion, puncture, and temperatureextremes. The principal disadvantage to thesematerials is that they are subject to intrusionsfrom the overlying protective layer that canalter their hydraulic conductivity. Similarly,fines in the sand and gravel can migratedownslope, undermining the stability of thecover slope. A graded filter or a geotextile fil-ter can be used to separate and protect thesand and gravel from intrusions by the over-lying protection layer.

Gravel with a geotextile filter is also awidely-used design, whose applicability canbe limited by the local availability of materi-als. The gravel promotes drainage of waterfrom the overlying layers, while the geotextilefilter prevents the clogging of granular

drainage layers. Again, be aware of the possi-bility that a gravel drainage layer might drainoverlying soils so well that irrigation of thesurface layer might become necessary. Theprincipal advantage to a gravel/geotextiledrainage layer is the engineering community'sconsiderable body of knowledge regardingtheir use as drainage materials. Other advan-tages include their ability to protect underly-ing layers from intrusion, puncture,temperature extremes, and their commonavailability. The geotextile filter provides acushion layer between the gravel and theoverlying protection layer.

Figure 3.Geonet with Geotextile Filter Design

for Drainage Layer

COVER SiSUB-SO.

3nes or GeocamoesiioQaamarebrane

Source: U.S. EPA, 1991.

Geonet and geotextile filter materials canbe used to form an effective drainage layerdirectly above a compacted clay or geomem-brane liner (see Figure 3). They are a suitablealternative especially in cases where othermaterials, such as sand and gravel, ire notlocally available. The principal advantage isthat lightweight equipment can be usedduring installation, reducing the risk of dam-aging the underlying barrier layer.

The disadvantages associated with geonetand geotextile materials are that they providelittle protection for the barrier layer againstextreme temperature changes, and there canbe slippage between the interfaces betweenthe geomembrane, geotextile, and low perme-

11-12

Ensuring Long-Term Protection—Perfoimmg Closure and Post-Closure Care

ability soil barrier matenals The use of tex-tured materials can be considered to addressslippage Furthermore, problems can arise inthe honzontal seaming of the geotextiledrainage layei on long slopes

Chipped or shredded tires are an addi-tional option for drainage layer matenalsChipped or shredded tires have been used foibottom diamage layers m the past and mightbe suitable for cover drainage layers as wellOne caution concerning the use of chipped01 shiedded tires is possible metal contami-nants, or pieces of metal that could damage ageomembiane liner You should consult withthe state agency to determine whether thisoption is an acceptable piactice

What function does the barrierlayer serve ?

The bai ner layer is the most critical com-ponent of the cover system because it pre-vents water infiltration into the waste It alsoindirectly promotes the storage and drainageof water from the ovei lying protection andsurface layeis, and it pi events the upwaidmovement of gases This layer will be the leastpermeable component of the final cover sys-tem Typically, the hydiaulic conductivity of abarrier layer is between 10" to 10 cm/sec

What types of matenals can beused in the barrier layer?

Single compacted clay liners (CCLs) aiethe most common material used as baineilayers in final cover systems CCL popularity-arises largely because of the local availabilityof materials and the engineering community'sextensive experience w ith their use Dryingand subsidence are the pnmary difficultiesposed by CCLs When the clay dnes, cracksappeal and provide prefeiential pathwaysalong which water can entei the waste, pro-moting leachate formation, waste decomposi-tion, and gas formation (when methane

producing waste is present) Diy waste mater-ial and gas formation within the unit con-tribute to diymg from below, while a range ofclimatological conditions, including drought,can affect CCLs from above Even withextremely thick surface and protection layers,CCLs can still undergo some desiccation

Clay liners are also vulneiable to subsi-dence within the waste unit This problemcan fust manifest itself dining liner construc-tion As the clay is compacted with machin-ery, the waste might not provide a stable,even foundation foi the compaction processThis will make it difficult to create the evenlymeasured lifts compnsing the liner As wastesettles ovei time, depressions can fonn alongthe top of the CCL These depiessions puidiffeiential stresses on the liner, causingcracks which compromise its integnty Forinstance, a depression of only 5 lo 11 inchesacioss a 6-foot area can be sufficient to ciackthe hnei matenals

Single geomembrane liners are sheets ofa plastic polymei combined wi th olhei ingre-dients to foim an effective barriei to watermfiltiation Such liners are simple andstraighlfoiwaid lo install, but they are rela-tively fi agile and can be easily punctureddining installation or by movement in suifacelayer materials The pnncipal advantage of ageomembrane is that it provides a lelativelyimpermeable barriei with materials that aregenerally available It is not damaged by tem-peratuie extremes and therefoie does notlequire a thick surface layer The geomem-brane is more flexible than clay and not asvulnerable to cracking as a result of subsi-dence within the unit The principal disad-vantage is that it provides a point of potentialslippage at the interface with the cover soilsSuch slippage can tear the geomembrane,even if it is anchored

Single geosynthetic clay liners (GCLs)aie composed of bentomte clay supported by

11-13


geotextiles or geomembranes held togetherwith stitching or adhesiveS. These liners arerelatively easy to install and have some self-healing capacity for minor punctures. Theyare easily repaired by patching. The main dis-advantages include low shear strength, lowbearing capacity, vulnerability to puncturedue to relative thinness, and potential forslippage at interfaces with under- and overly-ing soil materials. When dry, their penneabil-ity to gas makes GCLs unsuitable as a barrierlayer for wastes that produce gas, unless theclay will be maintained in a wet state for the *entire post-closure period.

Geomembrane with compacted clay lin-ers (CCLs) can be used to mitigate the short-comings of each material when used alone. Inthis composite liner, the geomembrane acts toprotect the clay from desiccation, while pro-viding increased tolerance to differential set-tlement within the waste. The clay acts toprotect the geomembrane from punctures andtearing. Both components act as an effectivebarrier to water infiltration. The principal dis-advantage is slippage between the geomem-brane and surface layer materials.

Geomembrane with geosynthetic clay lin-ers (GCLs) can also be used as a barrier layer.As with geomembrane and CCL combinations,each componeni serves to mitigate the weak-ness of the other. The geosynthetic material is'less vulnerable than its clay-counterpart tocracking and has a moderate capacity to self-heal. The geomembrane combined with the 'GCL is a more flexible cover and is less vulner-able to differential stresses from waste settle-ment. Neither component is readily affected byextreme temperature changes, and both worktogether to form an effective barrier layer. Formore information on the properties of geosyn-thetic clay liners, including their hydrationafter installation, refer to Chapter 7, Section •B-Designing and Installing Liners. The poten-tial disadvantage is slippage between the upperand lower surfaces of the geomembrane and

some types of GCL and other surface layermaterials. The geomembrane is still vulnerableto puncture, so placement of cover soils isimportant to minimize such damage.

Textured geomembranes can be used toincrease the stability of cap side slopes.Textured geomembranes are nearly identicalto standard "smooth" geomembranes differingonly in the rough or textured surface that hasbeen added. This textured surface increasesthe friction between the liner and soils andother geosynthetics used in the cap, and canhelp prevent sliding failures. In general, tex-tured geomembranes are more expensive thancomparable "smooth" geomembranes.

Using textured geomembranes allows capdesigners to employ steeper slopes which canincrease the available airspace in a wastemanagement unit, and therefore increase itscapacity. Textured geomembranes also help'keep cover soil in place improving overallliner stability on steep slopes. The degree to

" which textured geomembranes will improvefactional resistance (friction coefficients/fric-

'. tion angles) will vary from sile-to-sitedepending upon the type of soil at the siteand its condition (e.g., moisture content).

Textured geomembranes are manufacturedby two primary methods. Some texturedgeomembranes have a friction coating layeradded to standard "smooth" geomembranesthrough a secondary process. Others are tex-tured during the initial production process,meaning textured layers are coextruded aspart of the liner itself. Textured geomem-branes can be textured on one or both sides.

Textured geomembranes are seam-weldedby the same technologies as standardgeomembranes. Due lo their textured surface,however, seam welds can be less uniformwith textured liners than with normal liners.Some textured geomembranes have smooth

• edges on the top and bottom of the sheet to'allow for more uniform seam welding.

11-14

Ensuring Long-Term Protection—Ptrfonmng Closure and Post-Closure Care

soilvent

What function does the gas col-

lection layer serve?

The role of the gas collection layei is tocontrol the migration of gases to collectionvents This collection layei is a peimeablelayei that is placed above the foundationlayei It is often used in cases wheie the foun-dation layer itself is noi the gas collectionlayei Foi moie information on Clean Air Actrequirements foi managing gas from landfillsand othei wasie managemeni units, refei toChapter 5-ProtectingAn Quality Figure

Gas control systemsgeneially include mech-anisms designed to con-trol gas mtgiation andto help vent gas emis-sions into the atmo-spheie Systems usingnatural pressuie andconvection mechanismsare refeired to as passivegas contiol systems (seeFiguie 4) Examples ofpassive gas conliol sys-tem elements includeditches, tienches, ventwalls, perforaied pipessuriounded by coaisesoil, synthetic mem-branes, and high mois-ture, fine-grained soilSystems using mechani-cal means to lemove gasfrom the unit areleferred to as active gascontiol systems Figure5 illustrates an activegas system Gas contiolsystems can also beused as pan of coriec-tive action measuiesshould the concent la-

tion of methane use to dangeious levels Aswith all aspects of a waste containment sys-tem, construction quality assuiance plays acnlical role in the success of a gas manage-ment system

Gas extraction wells aie an example ofactive gas contiol systems For deep wells,the number, location, and extent of the pipeperfoiattons aie important Also, the depth ofthe well must be Kept safely above the linersystem beneath the waste Foi continuous gas

4 Passive Gas Venting System

gas vent

• • • • L l B •'••

gas flare

t T i1 TW • • m'm mmlmmmk

Source Robinson W , c d 1986 Tin iolid Waste Handbook APiad\udGuide Rcprmied by permission of John Wiley & Sons, Inc

Figure 5 Active Gas Venting System

gas monitoring probeinstalled in refuseI

monitoringprobe

installedin surrounding

ground

Souice Robinson W, ed 1986 The Solid Waste Handbook A PiatticalGuide Repnnted by permission of John ^ ilcy & Sons, Inc

11-15


collection layers beneath the barrier layer,continuity is important for both soils andgeosynthetics.

Knowing the rate of gas generation isessential to determining the quantity of gasthat can be extracted from the site. Pumpingan individual well at a greater vacuum willgive it a wider zone of influence, which isacceptable, but obviously there are points ofdiminishing marginal returns. Larger suctionpressures influence a larger region butinvolve more energy expended in the pump-ing. Pumping at greater vacuum also increas-es the potential for drawing in atmosphericair if the pumping rate is set too high.Significant air intrusion into the unit canresult in elevated temperatures and evenunderground fires. You should perform rou-tine checks of gas generation rates to betterensure that oplimal pumping rates are used.

The performance of gas extraction systemsis affected by the following parameters,which should be considered when designingand operating gas systems:

• Daily cover, which inhibits freemovement of gas.

• Sludge or liquid wastes, which affectthe ease at which gas will move.

• Shallow depth of unit, which makesit difficult to extract the gas, becauseatmospheric air will be drawn induring the pumping.

• Permeability of the final cover, whichaffects the ability of atmospheric airto penneate the wastes in the unit.

What types of materials can beused in the gas collection layer?

Sand and gravel are the most commonmaterials used for gas collection layers. Withthese materials, a filter might be needed toprevent infiltration of materials from the bar-

rier layer. Geotextile and geosyntheticdrainage composites also can make suitablegas collection layers. In many cases, these canbe the most cost-effective alternatives. Thesame disadvantages exist with these materialsin the gas collection layer as in other layers,such as slippage and continuity of flow.

With a geomembrane in the final coverbarrier system, uplift pressures will be exert-ed unless the gas is quickly and efficientlyconveyed to the wells, vents, or collectiontrenches. If this is not properly managed,uplift pressure will either cause bubbles tooccur, displacing the coyer soil and appear-ing at the surface, or decrease the normalstress between the geomembrane and itsunderlying material. This problem has led toslippage of the geomembrane and all overly-ing materials creating high tensile stressesevidenced by folding at the toe of the slopeand tension cracks near the top.

D. Capillary-Break FinalCovers

The capillary-break (CB) approach is analternative design for a final cover system(see Figure 6). This system relies on the factlhat for adjacent layers of fine- and coarse-textured material to be in water-potentialequilibrium, the coarse-grained material(such as crushed stone) will tend to have amuch lower water content than the fine-grained material (such as sand). Because theconductivity of water through a soil decreasesexponentially with its water content, as a soilbecomes more dry, its tendency to stay dryincreases. Therefore, as long as the strata in acapillary break remain unsaturated (remainabove the water table), the overlying fine-tex-tured soil will retain nearly all the water andthe coarse soil will behave as a barrier towater percolation due to its dryness. Sincethis phenomenon breaks down if the coarselayer becomes saturated, this alternative

11-16


cover system is most appropriate for semiandand desert environments.

What types of materials are usedin capillary-break covers?

The CB cover system typically consists offive layers: surface, storage, capillary-break,barrier, and foundation. The surface, barrier,and foundation layers play the same role inthe cover system as described above. Thestorage layer consists of fine material, such assilly sand. The capillary-break, or coarse,layer consisls of granular malerials, such asgravel and coarse sand. A fabric filter is oftenplaced between the coarse and fine layers.

E. The HydrologicEvaluation of LandfillPerformance (HELP)Model

The relative performance of various coverdesigns can be evaluated with the HydrologicEvaluation of Landfill Performance (HELP)model, developed by the U.S. Army Corps ofEngineers Waterway Experiment Station forEPA. The HELP model was designed specifi-cally to support permit writers and engineersin evaluating alternative landfill designs, butit can also be used to evaluate various finalcover designs.

The HELP model integrates runoff, perco-lation, and subsurface-water flow actions intoone model. The model can be used to esti-mate the flow of water across and through afinal cover. To achieve this, the HELP modeluses precipitation and other climatologicalinformation to partition rainfall and snowmelt into surface runoff, evaporation, anddownward infiltration through the barrierlayer to the waste.

The HELP model essentially divides awaste management unit into layers, each

Figure 6. Example of a Capillary-Break Final

Cover System

I ' i { I4u(*r *&r*f'&A ^hk-^p-^t

'Wmjj?:- -Adapted from <www.hanford.gov/eis/hraeis/eisdoc/graphics/fige-1 .gif>

defined in terms of soil type, which is relatedto ihe hydraulic conduclivily of each. Usersfill in data collection sheets that request spe-cific information on the layers and climate,and this information is input to the model. Inperforming its calculations, the model willlake inlo account ihe reported engineeringproperties of each layer, such as slope,hydraulic conductivity, and rates of evapo-transpiration, to estimate the amount of pre-cipitation thai can cnier ihe wasie uniithrough the final cover. To use the HELPmodel properly, refer to the HELP ModelUser's Guide and docutnentaiion (U.S. EPA,1994b; U.S. EPA, 1994c). The model itself,ihe User's Guide, and supporting documenta-tion can be obtained from the U.S. ArmyCorps of Engineers Web site at<www. wes .army .mil/el/elmodels>.

11-17


F. Recommended CoverSystems

The recommended final cover systems cor-respond to a waste management unit's bot-tom liner system. A unit with a single

geomembrane bottom liner system, for exam-ple, should include, at a minimum, a singlegeomembrane in its final cover system unlessan evaluation of site-specific conditions canshow an equivalent reduction in infiltration.Table 2 summarizes the minium recommend-

Table 2: Minimum Recommended Final Cover Systems*

Type of Bottom Liner Recommended Cover System Thickness Hydraulic Conductivity 1Layers (From top layer down)' (In inches) (In cm/sec) 1

Double Liner

Composite Liner

Single Clay Liner

Single Clay Liner inan And Area

Single Synthetic Liner

Natural Soil Liner

Surface LayerDrainage Layer

Geomembrane

Clay Layer

Surface LayerDrainage LayerGeomembrane

Clay Layer

Surface LayerDrainage LayerClay Layer

Cobble LayerDrainage LayerClay Layer

Surface LayerDrainage LayerGeomembrane

Clay Layer

Earthen Material

^^^^MBBMBMi H^BMM^HiMH

1212"

30mil(PVC)60m.il (HOPE)

18

1212"

30 mil (PVC)60 mil (HOPE)

18

1212"18

2-412"18

1212"

30 mil (PVC)60 mil (HOPE)

18

24-

not applicable1x10' lo 1x10 !

less than 1x10''

not applicablelx lO J to 1x10 '

less than 1x10'

not applicableI x I O - ' t o 1x10'less than 1x10"

not applicable1x10-' to 1x10'less than 1x10'

not applicablelxlO-2to 1x10'

less than 1x10'

No more permeable thanbase soil

Please consult with your state regulatory agency pnor to constructing a final cover.

The final selection of geomembrane type, thickness^ and drainage layer requirements For a final covershould be design-based and consultation with your state agency is recommended.

This recommended thickness is For high permeability soil material with at least a 3 percent slope al thebottom oF ihe layer. Some geonei composites, with a minimal thickness oF less than 1 inch, have atransmissivity equal to a much thicker layer oF aggregate or sand.

Thickness might need lo be increased lo address Freeze/thaw condilions.

11-18


ed final cover systems based on die units bol- addilion, you should consider whether totorn liner system. While the recommended include a protection layer or a gas collectionminimum final cover systems include closure layer. Figures 7 through 11 display recom-layer component thicknesses and hydraulic mended minimum final cover systems,conductivity, the cover systems can be modi-fied to address site-specific conditions. In

Figure 7 Recommended Final Cover System for a Unit With a Double or Composite Liner

Figure 8. Recommended Final Cover System for a Unit With a Single Clay Liner

-irch Surface

12-Inch Drainage Layer53 ! < id'r CB

t $-inc?i Clay Bamer Layer(maxmum * < K

11-19

Ensuring Long-Term Protection—Pcifaiming Closure and Post-Closure Caie

Figure 9 Recommended Final Cover System for a Unit With a Single Clay Liner in an And Area

S-CSllt-WS *&" 'S

Live?;

emmac a i « 10 ' :

13-irwh C'ay Ba^nw Layer.rnuxlmum i * lO-'errvwcl

Figure 10 Recommended Final Cover System for a Unit With a Single Synthetic Liner

11-20

Paul Cassidy/DC/USEPA/US To -Steve Wall/R9/USEPA/US@EPA

05/26/2005 12:03 PM Cc

bcc

Subject Re: Question on publish date of Industrial WasteManagement guideQ

February 2003 - it was announced by the AA in March/April of 2003

Paul CassidyIndustrial and Extractive Waste BranchOffice of Solid Waste

Steve Wall/R9/USEPA/US

Steve Wall/R9/USEPA/US05/26/2005 02:34 PM To Pa"' Cassidy/DC/USEPA/US@EPA

John Sager/DC/USEPA/US@EPA, RichardCC Kinch/DC/USEPA/US@EPA

0 .. . Question on publish date of Industrial Waste ManagementSubject ..

guide

Question on publish date of Industrial Waste Management guide....

Looking at the web site for this, I can't find the date for when the guide was issued/published...can you tell me please

thanks!

Steve WallOffice of Pollution Prevention and Solid Waste (WST-7)US EPA Region 975 Hawthorne StreetSan Francisco, CA94105415-972-3381 phone/415-947-3530 fax

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