GUI DANCE ADDENDUM

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Office ofSolid Waste andEmergency Response

Directive No. 9355.0-49FSERA 540-F-93-035PB 93-963339September 1993

Presumptive Remedy for „CERCLA Municipal LandfillSites

Office of Emergency and Remedial ResponseHazardous Site Control Division 5203G

Quick Reference Fact Sheet

Since Superfund's inception in 1980, the remedial and removal programs have found that certain categories of sites havesimilar characteristics, such as types of contaminants present, types of disposal practices, or how environmental mediaate affected. Based on information acquired from evaluating and cleaning op these sites, the Superfund program isunderrating an initiative to develop presumptive remedies to accelerate future cleanups at these types of sites. Thepresumptive remedy approach is one tool of acceleration within the Superftutd Acceknted Cleanup Model (SACM).

Presumptive remedies are preferred technologies for common categories of sites, based on historical patterns of remedyselection and EPA's scientific and engineering evaluation of performance data 00 technology imptementatioo. Theobjective of the presumptive remedies initiative is to use the program's past experience to streamline site investigationand speed op selection of cleanup actions. Over time presumptive remedies are expected to ensure consistency in remedyselection and reduce the cost and time required to clean up similar types of sites. Presumptive remedies are expected tobe used at all appropriate sites except under unusual site-specific circumstances.

This directive establishes coarta<uuu**ts the presumptive remedy fothe presumptive remedy for these sites is presented in a streamlining manual entitled Conducting Remedial Investiga-tions/Feasibility Studies for CERCIA Municipal Landfill Sites, February 1991 (OSWER Directive 9355. 3-11). Thisdirective highlights and emphasizes the iniportaiice of certain stramlina^stages of me remedial mverigatkxi/foribiiity study (RI/FS) that were identified in the manual The directive alsoprovides clarification of and additional guidance in the following areas: (1) the level of detail appropriate for riskassessment of source areas at municipal landfills and (2) the characterization of not spots.

BACKGROUND

Supertund has conducted pilot projects at four municipallandfill sties1 on die National Priorities List (NPL) toevaluate the effectiveness of the manual Conducting

Municipal LanayiU Sites (hereafter referred to as "themanual") as a stteamlininf tool and as die framework forthe mooictpaJ landfill presumptive remedy* Consistent

CootingencyHao(orh«>),EPA*sexpeaitic« was thatconn^nnCTipchniiioglesgcneraitywouldtefor municipal landfill waste because the volume andheterogeneity of the waste generally make treatmentimpracticable. The results of the pilots support thisexpectation and demonstrate that the manual is aneffective tool for streamJioing die RI/FS process formunicipal landfills.

dOU stettypioritymunici|Mi ntf 10 a leacr extent hi

Since the manual's development, the expectation tocontain wastes at municipal landfills has evolved into apresumptive remedy for these sites.1 bnt ementationof

four pilot sites helped to highlight issues requiringfurther clarification, such as die degree to which riskassessments can be streamlined for source areas and thecharacterization and remediation of hot spots. Thepilots also demonstrated the value of focusingstreamlining efforts at the scoping stage, recognizingthat the biggest savings in time and money can beream^ ifstreainlinuigbuxocporateda^of die RI/FS process. Accordingly, this directiveaddresses those issues kkntified during the pilots andhighKjhn m^mlmmg n|ipnrt»i>itiM rn he consideredduring the scoping component of the RI/FS.

'See EPA PubttctttaB 9203.1-021, SACM Buttetiai. PresvnpavetrmtHttfirMimie+QlLMjm fifrf. April t992, Vot I. Na. 1. mafefamry 1993. VoL 2. No.l, «xJ SACM Bdktin Prtnmpav*RrmtAtr, AigiM 1992. Volt. No. 3.

Finally, while ihe primary focus of the municipal tadfillmanual is on streamlining the RI/FS, Superfmd's goalunttoSACMistoaccctoate ihe entire ckan-up process.Other guidance issued under the municipal landfillpresumptive remedy initiative identifies design data thatmaybe coUecied during the RI/FS to stKanhne theoverall response process for these sites (see PublicationNo. 9355.3-18FS, Presumptive Remedies: CERCLALandfill Caps Data Collection Guide, to be published inOctober 1993).

CONTAINMENT AS A PRESUMPTIVEREMEDY

Section 300.430(aXui)(B) of the NO> contains theexpectation that engineering controls, such ascootaiimient,wmbeused£orwas»thatpo8esareteivelylow long-term thieator where treatment is impcactiafcfe.

as a type of site where treatment of die waste may beimpracticable because of the size and heterogeneity ofthecontents(55FR8704). Waste in CERCLA landfillsusually is present in large volumes andisaheterogeoeousmixture of municipal waste frequently co-disposedwith industrial and/or hazardous waste. Becausetreatment usually is impracticable. EPA generallyconsiders containment to be the appropriate responseaction, or the "presumptive remedy," for the sourceareas of municipal landfill sues.

The presumptive remedy for CERCLA municipallandfill sues relates primarily to containment of thelandfill mass and collection and/or treatment of landfillgas. In addition, measures to control landfill feachate,affected ground water at the perimeter of the landfill,and/or upgradiemgn3und-water that iscausingsaturaoonof the landfill mass may be implemented as part of thepresumptive remedy.

The presumptive remedy does not address exposurepathways outside the source area (landfill), nor does itinclude the long-term ground-water response action.Additional RI/FS activities, including arisk assessment,will need to be performed, as appropriate, to addressthose exposure pathways outside the source area. It isexpected that RI/FS activities addressing exposurepaihwtysootskte the source genaaUywiBbeconductedconcurrently with the streamlined RI/FS forthektttdfillsource presumptive remedy. A response action forexposure pathways outside the source (if any) may beselectt* together witothepreawq^developing a comprehensive site response), or as anoperable unit separate from the presumptive remedy.

Highlight 1 identifies thecompoqents of the presumptiveremedy. Response actions selected for individual siteswill include only most components mat are necessary,based on site-specific conditions.

Highlight 1: Components ofthe Presumptive Remedy:Source Containment

Landfill cap;Source area ground-water controlto contain plume:Leachate collection and treatment;Landfill gas collection andtreatment; anoVorInstituttonalcontroteto supplementengineering controls.

The EPA (or State) sue manager will make the initialdecision of whether a panscolar municipal landfill siteis suitable for the presumptive remedy or whether ammcompreheaaveRVrcisieqaired. Generally, thisdetermination willdependon whether the site is suitablefor a stteamfaied risk evaluation as described on page4. The community, state, and potentially responsiblepvties (PRPs) should be notified that a presumptiveremedy is being considered for the site before work onthe RI/FS work plan is initialed. Tlie notification maytatethefonnofa£ttsheet,ai)ot»cemak)caloewsp4>er.andfer a public meeting.

Use of the presumptive remedy etiminates the need forthe initial identification and screening of alterativesduriagthefeasilMikysuidy(FS). Section 300i430(eXl)of the NCP states that/... the lead agency shall includean alternatives screening step, when needed, (emphasisadded) to select a reasonable number of alternatives fordetailed analysis."

EPA conducted an analysis of potentially availabletechnologies for municipal landfills and found thatcertain technologies ate routinely and appropriatelyscreened out on the basis of effectiveness, feasflii^om(NCP Section 300.430(e)(7)). (See Appendix A tothis directive and "Feasibility Study Analysis forCERCLA Municipal Landfills/ September 1993available at EPA Headquarters and Regional Offices.)Based on this analysis* the universe of alteratives thatwill be analyzed in detail may be limited to thecoaaponenu of the containment remedy identified inHighlight 1, unless site-specific conditions dictateotherwise or attentive* are considered tat were notaddressed in the FSwalysis, TheFS snalystsdocoment,together with this directive, must be included in theadministrative record for each municipal landfillpresumptive remedy sue to support elimination of theinitial identification and screening of site-specificalternatives. Further detailed and comprehensive

supporting materials (e.g., FS reports included inanalysts, technical reports) can be provided byHeadquarters, as needed.

While the universe of alternatives to address the landfillsource will be limited to those components identified inHighlight I. potential alionatives that may exist for eachcomponent or combinations of components may beevaluated in the detailed analysis. For example, onecomponent of the presumptive remedy is source areaground-water control. If appropriate, this componentmay be accomplished in a number of ways, includingpump and treat, slurry walls, etc. These potentialalteniattvesmaythenbecombinedwithothercomponentsof the presumptive remedy to develop a range ofcontainment alternatives suitable for site-specificconditions. Response alternatives must then be evaluatedin detail against the nine criteria identified in Section300.430(eXg) of the NCP. Tne detailed analysis willidentify site-specific ARARs and develop costs on thebasis of the particular size and volume of the landfill

EARLY ACTION AT MUNICIPALLANDFILLS

EPA has identified the presumptive remedy site categoriesas good candidates for early action under SACM. Atmunicipal landfills, the upfront knowledge that the sourcearea will be contained may facilitate such eariy actions asinstallationofalaixlfUicaporagroivKl-waiercontainrnentsystem. Depending on the circumstances, eariy actionsmay be accomplished using either removal authority(e.g., non-time-critical removal actions) or remedialauthority. In some cases, it may be appropriate for anEngineering Evaluation/Cost Analysis to replace pan orall of the Rl/FS if the source control component will be anon-time-critical removal action. Some factors may affectwhether a specific response action would be betteraccomplished as a removal or remedial action includingthe size of the action, the associated state cost share, and/or the scope of OAM. A discussion of these factors iscontained in Early Action and Long-term Action UnderSACM • Interim Guidance. Publication No. 9203.1-051,December 1992.

SCOPING A STREAMLINED RL/FSUNDER THE PRESUMPTIVE REMEDYFRAMEWORK

The goal of an Rl/FS is to provide the informationnecessary to: (1) adequately characterize the site; (2)define site dynamics; (3) define risks; and (4) develop theresponse action. As discussed in the following sections,the process for achieving each of these goals can bestreamlined forCERCLA municipal landfill sites becauseof the upfirom presumption that landQII contents will becontained The strategy for streamlining each of these

areas should be developed early (i.e.,during the scopingphase of the RI/FS).

1. Characterizing the Site

The use of existing data is especially important inconducting a streamlined Rl/FS for municipal landfills.Characterization of a landfill's contents is not necessaryor appropriate for selecting a response action for thesesites except in limited cases; rather, existing data are usedto determine whether the containment presumption isappropriate. Subsequent sampling efforts should focuson characterizing areas where contaminant migration issuspected, such as kachate discharge areas or areaswhere surface water runoff has caused erosion. It isimportant to note that the decision to characterize hotspots should also be based on existing information, suchasreliabkanecdoulirifonnation.documematk^physical evidence (see page 6).

In those limited cases where no information is availablefor a site, it may not be advisable to initiate use of thepresumptive remedy until some data are collected. Forexample, if there is extensive migration of contaminantsfrom a site located in an area with several sources, it willbe necessary to have some informanon about the landfillsource in order to make an association between on-siteand off-site contamination.

Sources of information of particular interest duringscoping include records of previous ownership, stalefiles, closure plans, etc., which may help to determinetypes and sources of hazardous materials present Inaddition, a site visit is appropriate for several reasons,inchitogtheverificaikmofexistib^^of existing site remediation systems, and to visuallycharacterize wastes (e.g., teachaie seeps). Specificinformation to be collected is provided in Sections 2.1through 2.4 of the municipal landfill manual

2. Defining Site Dynamics

The collected data are used to develop a conceptual sitemodel, which is the key component of a streamlinedRVFS. The conceptual site model is an effective tool fordefining the site dynamics, streamlining the riskevaluation, aixldevetofiiiig trie resr^ime action. Highlight2 presents * generic conceptual site model f or municipallandfills. The model is developed before any RI fieldactivities are conducted, and its purpose is to aid inunderstanding and describing the site and ID presenthypotheses regarding:

• The suspected sources and types ofcontaminants present;Contaminant release and transportmechanisms;

Highlight 2: Generic Conceptual Site Model

Rateofcontaminamreleaseandtransport(where possible);Affected media;Known and potential routes of migration;andKnown and potential human anden vironmental receptors.

After the data are evaluated and a site visit is completed,ttecontamiiiantreteaseand transport mechanisn^to the site should be determined. The key element indeveloping the conceptual she model is to identify thoseaspects of the model thai require more information tomake a decision about response measues. Becausecontainment of the landfill's conlents is the presumed

3. Defining Risks

The municipal landfill manual stales thata streamlined orlimited baseline risk assessment will be sufficient toinitiate response action on the most obvious problems ata municipal landfill (e.g.. ground water, leachafc, landfillcontents* and landfill gas). One method for establishingrisk using a streamlined approach is to comparecontanwuntconcentrabon fcveh(if available) ID standardsthat are patentialchenucal-specific applicable or relevantand appropriate requirements (ARARs) for the action.The manual states that where established standards forone or more contaminants in a given mediini are clearlyfturcrdfd. remedial action generally is warranted.5

use in identifying areas beyond the landfill source itselfthat will require further study, thereby focusing sitecharacterization away from the source area and on areasof potential contaminant migration (c^ ground water orcontaminated sediments).

It is important to note, however, that based on site-specific conditions, an active response is nottBBUffltifground-water contaminant concentrations exceedchemical-specific standards but the sifts risk is within theAgency's acceptable risk range (10* to 10*)- Forexample, if it is determined that the release of

'Sec also OSWER Directive 9355.0-30. RoUofttu JAM/M* XiitAntimni w 5ifw/H«tf JtaMdy StbctuM OccttMM. April 22.1991 . which itttcs ihatif MCU or non-aero MCLGi M* exceeded, (arctponte) •ctkn generally it wirnmod.

contaminants from a particular landfill is declining, andconcentrations of one or more ground- water contaminantsare at or barely exceed chemical-specific standards, theAgency may decide not to implement an active response.S uch a deciskm might be based on the understanding thatthe landfill is no longer acting as a source of ground- watercontamination, and that the landfill does not present anunacceptable risk from any other exposure pathway.

A site generally will not be eligible for a streamlined riskevaluation if ground-water contaminant concentrationsdo not clearly exceed chemical-specific standards or theAgency's accepted level of risk, or other conditions donot exist that provide a clear justification for action (e.g.,dircacontaa with lardfiD contents resultslopes). Under these circumstances, a quantitative riskassessment that addresses all exposure pathways will benecessary to determine whether action is needed

Ultimately, it is necessary to demonstrate that the finalremedy addresses all pathways and contaminants ofconcern, not just those that triggered the remedial action.As described in the following sections, the conceptualsite model is an effective tool for identifying thosepathways and illustrating that they have been addressedby (he containment remedy.

Streamlined Risk Evaluation Of The LandfillSource . »Experience from the presumptive remedy pikxs supportsthe usefulness of a streamlined risk evaluation to initiatean early response action under certain circumstances. Asa matter of policy, for the source area of municipallandfills, a quantitative risk assessment that considers allchemicals, their potential additive effects* etc, is notnecessary to establish a basis for action if ground-waterdauareavailabtetodenwnsoaietriatcowanunantsexceed established standards or if other conditions existthat provide a clear justification for action.

A quantitative risk assessment also is not necessary toevaluate whether the containment remedy addresses allpathways and contaminants of concern associated withthe source. Ratrta.aUpotentialexposurcpathwayscanbeidentified using the r^rqmtyl das p™rfel and comparedtn the pathw^**W«Wbvihecf«^remedy. Highlights iUusowestrtatthecontainmemrefnedyaddresses all exposure pathways associated with thesource at municipal landfill sites.

Finally, a quantitative risk assessment is not required todetermine clean-up levels because the type of cap will bedetermined by closure ARARs, and ground waw that isextracted asacomponent of the presumptive remedy willbe required to meet discharge limits, or other standards forits disposal Calculation of clean-up levels for ground-water contamination that has migrated away from thesource will not be accomplished under the presumptive

Highlight3:Source ContaminantExposure Pathways Addressedby Presumptive Remedy

1. Direct contact with soil and/ordebris prevented by landfill cap;

2. Exposure to contaminated groundwater within the landfill areaprevented by ground-watercontrol;

3. Exposure to contaminatedleachate prevented by leachatecollection and treatment; and

4. Exposure to landfill gasaddressed by gas collection andtreatment, as appropriate.

remedy, since such contamination will require aconventional investigation and a risk assessment.

Streamlining the risk assessment of the source areaeliminates the need for sampling and analysis to support

wiih direct contact, his important to note that because thecontinued effectiveness of the containment remedydepends on the integrity of the containment system, it islikely that institutional controls will be necessary torcstfttftmirc activities at a CERCI^munku^after construction of the cap and associated sysmns. EPAhas thus determined that it is not appropriate or necessaryto estimate the risk associated with future residential useof the landfill source, as such use would be incompatiblewith the need to maintain the integrity of the containmentsystem. (Long-term waste management areas, such asmunicipal landfills, may be appropriate, however, forrecreational or other limited uses on a site-specific basis.)The availability and efficacy of institutional controlsshould be evaluated in the PS. Decision documentsshould include measures such as institutional controls IDensure thecontinued integrity of such containmentsystemswhenever possible.

Areas of Contaminant MigrationAlmost every iminic^laralfUlsittrrcthat may require additional study, such as leachatedischarge toa wetland or significant svface water run-offcaused by drainage proWems, These migrantas well as ground- water contamination that has migratedaway from the source, generally will require

to determine whether action is warranted beyond thesource area and, if so, the type of action that is appropriate.

While future residential use of the landfill source areaitself is not considered appropriate, the land adjacent to

landfills is frequently used for residential purposes.Therefore, based on site-specific circumstances, iimay beappropriate to consider future residential use for groundwater and other exposure pathways when assessing nskfrom areas of contaminant migration.

4. Developing the Response Action

As a first step in developing containment alternatives,response action objectives should be developed on thebasis of the pathways identified for action in theconceptual site model. Typically, the primary responseaction objectives for municipal landfill sites include:

P";ininUK|ve Remedy

Preventing direct contact with landfillconcents;Minimizing infiltration and resultingcontaminant leaching to ground water.Controlling surface water runoff anderosion;

Collecting and treating contaminatedground water and leachate to containthe contaminant plume and preventfurther migration from source area;andControlling and treating landfill gas.

Non-Presumptive Remedy

Remediating ground water.Remediating contaminated surfacewater and sediments; andRemediating contaminated wetlandareas.

As discussed in Section 3. "Defining Risks," thecontainment presumptive remedy accomplishes all butthe last three of these objectives by addressing allpathways associated with the source. Therefore, thefocus of the RI/FS can be shifted to characterizing themedia addressed in the last three objectives(contaminated ground water, surface water andsediments, and wetland areas) and on collecting data 10support design of the containment remedy.

Treatment of Hot Spots

The decision to characterize and/or treat hot spots is asite-specific judgement that should be based on theconsideration of a standard set of factors. Highlight 4lists questions that should be answered before making

the decision to characterize and/or treat hot spots. Theoverriding question is whether the combination of thewaste's physical and chemical characteristics and volumeis such that the integrity of (he new containment systemwill be threatened if the waste is left in place. Thisquestion should be answered on the basis of what isknown about a site (e.g.. from operating records or otherreliable information). An answer in the affirmative to allof the questions listed in Highlight4 would indicate thatit is likely that the integrity of the containment systemwould be threatened, or thatexcavaiionand treatment ofhot spots would be practicable, and that a significantreduction in risk at the site would occur as a result oftreating hot spots. EPA expects that few CERCLAmunicipal landfills will fall into this category; rather,based on the Agency's experience, the majority of sitesare expected to be suitable for containment only, basedon the heterogeneity of the waste, the lack of reliableinformation concerning disposal history, and theproblems associated with excavating through refuse.

The volume of industrial and/or hazardous waste co-disposed with municipal waste at CERCLA municipallandfills varies from site to site, as does the amount ofinformation available concerning disposal history. It isimpossible to fully characterize, excavate, and/or treatthe source area of municipal landfills, so uncertaintyabout the landfill contents is expected. Uncertainty byitself does not call into question the containmentapproach. However, containment remedies must bedesigned to take into account the possibility that hotspots are present in addition to those that have beenidentified and characterized. The presumptive remedymust be relied upon to contain landfill contents andprevemmigrationofcontaminanis, Tmsisaccomplishedby a combination of measures, such as a landfill capcombined withateachatecoUection system. Monitoringwill further ensure the continued effectiveness of theremedy.

The following examples illustrate site-specific decisionmaking and show how these factors affect the decisionwhether to characterize and/or treat hot spots.

Examples of Site-Specific Decision MakingConcerning Hot Spot Characterization/Treatment

SiteA

There is anecdotal information that approximately 200drunjs of hazardous waste were disposed of at this 70-acre former municipal landfill, but their location andcontents are unknown. The remedy includes a landfill capand ground-water and landfill gas treatment

A search for and diaraoerizaoon of hot spots is notsupported at Site A based on the questions listed in

Highlight 4: Characterizationof Hot Spots

If all of the following questions can beanswered in the affirmative, it is likelythat characterization anoVor treatmentof hot spots is warranted:

1. Does evidence exist to indicatethe presence and approximatelocation of waste?

2. Is the hot spot known to beprincipal threat waste?*

3. Is the waste in a discrete,accessible part of the landfill?

4. Is the hot spot known to be largeenough that its remediation willreduce the threat posed by theoverall srte but small enough thatit is reasonable to considerremoval (e.g.. 100.000 cubicyards or less)?

A Guide to Principal Threat and LowThreat Wastes. November 1991.

Suptrfund Publication No. 9380.3-06FS.

Highlight 4: (l)no reliable information exists to indicatethe location of the waste: (2) the determination of whetherthe waste is principal threat waste cannot be made sincethe phyacal/themical characteristics of the wastes areunknown; (3) since the location of (he waste is unknown.the determination of whether the waste is in a discreteaccessible location cannot be made; (4) in this case, theprcsMiceof200dnimsina70-acrelandfiU^to significantly affect the threat posed by the overall site.Rather, the containment system will include measures toensure its CQ|UinuedciTccavcrKss(e.g.. monitoring and/orleachate collection) given the uncertainty associated withthe landfill contents and suspected drums.

SiteB

Approxinutdy3SXXX)diums,inanycontaining hazardouswastes, were disposed of in two drum disposal units at thisprivately owned 80-acrc inactive landfill, which waslicensed to receive general refuse. The site is divided intotwooperable units. The remedy for Operable Unit 1 (OU1) is incineration of drummed wastes in the two drumdisposal units. The remedy for OU 2 consists of treatmentof contaminated ground water and leachate andcontainment of treatment residuals (from OU 1) and

remaining landfill contents, including passive gascollection and flaring.

Treatment of landfill contents is supported at Site Bbecause all of thequesuons in Highlighi4can be answeredin the affirmative: (1) existing evidence from previousinvestigations and sampling conducted by the state (priorto the RI) indicated the presence andapproximate locationof wastes; (2) the wastes were considered principal threatwastes because they were liquids and (based on sampling)were believed to contain contaminants of concern; (3) thewaste is located in discrete accessible pans of the landfill:and (4) the waste volume is large enough that itsremediation will significantly reduce the threat posedby the overall site.

CLOSURE REQUIREMENTS

Subtitle D

In the absence of Federal Subtitle D closure regulations,State Subtitle D closure requirements generally havegoverned CERClJV response actkjnsatmuiucipal landfillsas applicable or relevant and appropriate requirements(ARARs). New Federal Subtitle D closure and post-closure care regulations will be in effect on October 9,1993 (56 FR 50978 and 40 CFR 258)* State closurerequirements that are ARARs and that are more stringentthan the Federal requirements must be attained or waived.

Thcr>ewFc<toalret>ilaiM)nscc<itamto construction and maintenance of the final cover, andleachate collection, ground-water nxniioring, and gasmonitoring systems. The final cover reguiadoM will beapplicable requirements for landfills that receivedhousehold waste after October 9,1991. EPA expects thatthe final cover requirements will be applicable to few. ifany, CERCLA municipal landfills, since the receipt ofhousehold wastes ceased at most CERCLA landfillsbeforcOciober 1991. Rather.thesubstaruivereo^nanentsof the new Subtitle D regulations generally will beconsidered relevant and aumuuiiaie requirements forCERa re^onseaowratriatoccurata

Subtitle C

RCRA SubtiilcC closure requirements may beappucabkor relevant and appropriate in certain circumstances.RCRA Subtitle C is applicable if the landfill receivedwaste that is a listed or characteristic waste underRCRA. and:

1. The waste was disposedof after November 19,1980(effective date of RCRA), or

'An extension of the effective date has been proposed buc notfinalued M Uttf time.

2. The new response action constitutes disposal underRCR A (i.e.. disposal back into the original landfill).*

The decision about whether a Subtitle C closurerequirement is relevant and juyntHiate is based on avariety of factors, including the nature of the waste and itshazardous properties, the date on which it was disposed,and the nature of the requirement itself. For moreinformation on RCRA Subtitle C closure requirements,see RCRA ARARs: Focus on Closure Requirements,Directive No. 9234.2-04FS, October 1989.

'Note thai dispoui of only mud! qaamity kaiankMi wane andhousehold huwdotu waste doet not make Subtitle C qipUcaMe.

Notice:

Trie policies set out in this document are intended solely as guidance tq the U.S.Protection Agency (ERA) personnel; they are not final EPA actions and do not constitute rutemaking.These policies are not intended, nor can they be relied upoft. to create any rigltoef orceable^^p*in ttfgation with the United States. EPA officials may decide to follow the guidance provided m tWsdocument, or to act at variance with the guidance, based on an analysis of spedrte site circumstances.EPA also reserves the right to change the guidance at any time without pubic notice.

APPENDIX ATECHNICAL BASIS FOR PRESUMPTIVE REMEDIES

This Appendix summarizes the analysis that EPA conducted of feasibility study (FS) and Recordof Decision (ROD) data from CERCLA municipal landfill sites which led to the establishment ofcontainment as the presumptive remedy lorthese sites. The objectiveo! the study was to identify thosetechnologies that are consistently included in the remedies selected, those that are consistentlyscreened out. and to identify the basis for their elimination. Results of this analysis support the decisionto eliminate the initial technology identification and screening steps on a site-specific basis for this sitetype. The technical review found that certain technologies are appropriately screened out based oneffectiveness, implementability, or excessive costs.

The methodology for this analysis entailed reviewing the technology identification and screeningcomponents of the remedy selection process for a representative sample of municipal landfill sites. Thenumber of times each technology was either screened out or selected in each remedy was compiled.A detailed discussion of the methodology used is provided below.

METHODOLOGY

Identification of Sites for Feasibility Study Analysis

Of the 230 municipal landfill sites on the N PL, 149 sites have had a remedy selected for at leastone operable unit. Of the 149 sites. 30 were selected for this study on a random basis, or slightly greaterthan 20 percent. The sites range in size from 8.5 acres to over 200 acres and are located primarily inRegions 1,2,3. and 5. This geographical distribution approximates the distribution of municipal landfillson the NPL.

Technology Screening and Remedial Alternative Analysis

The FS analysis involved a review of the technology identification and screening phase.including any pre-screemng steps, followed by a review of the detailed analysis and comparativeanalysis phases. Informationderivedfrom e ach re view was documented on site-specHic data collecttonforms, which are available for evaluation as part of the Administrative Record for this presumptiveremedy directive. The review focused on the landfill source contamination only; ground-watertechnologies and alternatives were not included in the analysis.

For the screening phase, the full range of technologies considered was listed on the datacollection forms, along with the key reasons given for eliminating technologies from further consider-ation. These reasons were categorized according to the screening criteria: cost, effectiveness, orimplementability. The frequency with which specific reasons were given for eliminating a technologyfrom further consideration was then tallied and compiled into a screening phase summary table.

For the detailed analysis and comparative analysis, information on the relative performance ofeach technology/alternative with respect to the seven NCP criteria was documented on the site-specificdata collection forms. The advantages and disadvantages associated with each ctean-up option werehighlighted. In some cases, a technology was combined with one or more technologies into oneor morealternatives. The disadvantages of a technology/alternative were then compiled into a detailedanalysis/comparative analysis summary table, under the assumption that these disadvantagescontributed to non-selection. All summary tables are available for review as part of the AdministrativeRecord.

APPENDIX ATECHNICAL BASIS FOR PRESUMPTIVE REMEDIES (continued)

RESULTS

The information from the technology screening and remedial alternative analyses is providedin Table 1. It demonstrates that containment (the presumptive remedy), was chosen as a componentof the selected remedy at all thirty of the sites analyzed. No other technologies or treatments wereconsistently selected as a remedy or retained for consideration in a remedial alternative. However, ateight of the thirty sites, there were circumstances where technologies were included in the selectedremedy to address a site-specific concern, such as principal threat wastes. These technologies areincluded in the column entitled Tech. Not Primary Component of Alternative" in Table 1 and includeincineration at two sites, waste removal and off-site disposal at two sites, soil vapor extraction at twosites, and bioredamation at one site.

Leachate collection and gas collection systems were also tracked as part of the detailedanalysis and comparison of remedial alternatives. These types of systems generally were notconsidered as remediation technologies during the screening phases. At fifteen sites, leachatecollection was selected as part of the overall containment remedy. At seventeen sites, gas collectionsystems were selected as part of the overall containment remedy.

This analysis supports the decision to eliminate the initial technology identification andscreening step for municipal landfill sites. On a site-specific basis, consideration of remediationtechnologies may be retained as needed.

1 This column title is used for record-keeping purposes only and is not meant to imply that these treatmenttechnologies are not considered important components ot the selected remedies.

10

TABLE 1* SUMMARY OF SCREENING AND DETAILED ANALYSIS FOR LANDFILLS '

TECHNOLOGY2

O tftiWfcmrtorimCMiMbiMV^ SjaS* &S ** » i IHOTMIVHI* >r_. VA. I RODs WHERE CAICMCM CovamauTEO TO NON-SELECTION

MuM-tayarCap 21 25

ClayCap

Cap 17 17 14

Cone/anCap 17 17 14

SoilCowar 16

SyntwkCap 13 10 10

ChwrocilSaal '" 6

SlurryWal 22 14

GutCurtain 18 IS

ShattPinfl 17 16 13

GaulIr clon

Block

BottxnSaaNng

TABLE 1 • SUMMARYOF SCREENING AND DETAILED ANALYSIS FOR LANDFILLS (Continued)

/ I ROOs WHERE CMVRION CONTMBUTEO TO NON-SELECTION

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UMTS

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Often LandH(urepMittd)OnsiitNonhazardousUndlifl

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BuftmMtation(ufttfMdted) 13 13 13

10 10

Ifttiu IS 14 13

DMhtofWzaftorfAPEQ

QridriorfRefaction 12 12

TABLE 1 • SUMMARY OF SCREENING AND DETAILED ANALYSIS FOR LANDFILLS (Continued)1

TECHNOLOGY 2i RODs WHERE CMTOION CONTRIBUTED TO NON-SELECTION

Nwtnliuion

ThwrmlOMVuetion

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TABLE 1 • SUMMARY OF SCREENING AND DETAILED ANALYSIS FOR LANDFILLS (Continued)1

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