ASTM_E_2531_-_06_2014.pdf

Designation:E253106(Reapproved 2014)Standard Guide forDevelopment of Conceptual Site Models and RemediationStrategies for Light Nonaqueous-Phase Liquids Released tothe Subsurface1This standard is issued under the fixed designation E2531;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis guide provides a framework for developing a light nonaqueous phase liquid(LNAPL)conceptual site model(LCSM)and for using that LCSM in a corrective action decision framework.LNAPLs are most commonly petroleum or petroleum products liquids.Historically,subsurfaceLNAPL distribution has been conceptualized based on the thickness observed in monitoring wells.However,these conceptualizations often result in an insufficient risk analysis and frequently lead topoor remedial strategies.By using this guide,the user will be able to perform a more appropriateassessment and develop an LCSM from which better remedial decisions can be made.The design of this guide is a“tiered”approach,similar to the risk-based corrective action(RBCA)process(Guides E1739 and E2081),where an increase in tiers results from an increase in the sitecomplexity and site-specific information required for the decision-making process.The RBCA guidesapply to LNAPL and to dissolved and vapor phases.This guide supplements the RBCA guides byproviding more information about identifying LNAPL,linking the LCSM to the RBCA process,anddescribing how the presence of LNAPL impacts corrective action at sites.In addition to developing the LCSM,the components of this guide will support the user inidentifying site objectives,determining risk-based drivers and non-risk factors,defining remediationmetrics,evaluating remedial strategies,and preparing a site for closure.If the processes in this guideare adequately followed for sites with LNAPL,it is expected that more efficient,consistent,economical,and environmentally protective decisions will be made.1.Scope1.1 This guide applies to sites with LNAPL present asresidual,free,or mobile phases,and anywhere that LNAPL isa source for impacts in soil,ground water,and soil vapor.Useof this guide may show LNAPL to be present where it waspreviously unrecognized.Information about LNAPL phasesand methods for evaluating its potential presence are includedin 4.3,guide terminology is in Section 3,and technicalglossaries are in Appendix X7 and Appendix X8.Fig.1 is aflowchart that summarizes the procedures of this guide.1.2 This guide is intended to supplement the conceptual sitemodel developed in the RBCA process(Guides E1739 andE2081)and in the conceptual site model standard(GuideE1689)by considering LNAPLconditions in sufficient detail toevaluate risks and remedial action options.1.3 Federal,state,and local regulatory policies and statutesshould be followed and form the basis of determining theremedial objectives,whether risk-based or otherwise.Fig.1illustrates the interaction between this guide and other relatedguidance and references.1.4 Petroleum and other chemical LNAPLs are the primaryfocus of this guide.Certain technical aspects apply to denseNAPL(DNAPL),but this guide does not address the additionalcomplexities of DNAPLs.1.5 The composite chemical and physical properties of anLNAPL are a function of the individual chemicals thatmake-up an LNAPL.The properties of the LNAPL and thesubsurface conditions in which it may be present vary widelyfrom site to site.The complexity and level of detail needed inthe LCSM varies depending on the exposure pathways andrisks and the scope and extent of the remedial actions that areneeded.The LCSM follows a tiered development of sufficient1This guide is under the jurisdiction ofASTM Committee E50 on EnvironmentalAssessment,Risk Management and Corrective Action and is the direct responsibil-ity of Subcommittee E50.04 on Corrective Action.Current edition approved Nov.1,2014.Published December 2014.Originallyapproved in 2006.Last previous edition approved in 2006 as E2531061.DOI:10.1520/E2531-06R14.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 detail for risk assessment and remedial action decisions to bemade.Additional data collection or technical analysis istypically needed when fundamental questions about theLNAPL cannot be answered with existing information.1.6 This guide does not develop new risk assessmentprotocols.It is intended to be used in conjunction with existingrisk-based corrective action guidance(for example,GuidesE1739 and E2081)and regulatory agency requirements(forexample,USEPA 1989,1991,1992,1996,1997).1.7 This guide assists the user in developing an LCSM uponwhich a decision framework is applied to assist the user inselecting remedial action options.1.8 The goal of this guide