1、Designation: E2531 06 (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
2、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
3、 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
4、 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.Th
5、e 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 RBCAguidesapply to
6、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
7、 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 expec
8、ted 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
9、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 th
10、e 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
11、.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 LN
12、APLs 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 proper
13、ties 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 d
14、evelopment 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. Originall
15、yapproved 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 States1detail for risk assessment and remedial action decisions to bemade. Additional data collect
16、ion 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,
17、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 is to provide s
18、ound technicalunderpinning to LNAPL corrective action using appropriatelyscaled, site-specific knowledge of the physical and chemicalprocesses controlling LNAPL and the associated plumes inground water and soil vapor.1.9 This guide provides flexibility and assists the user indeveloping general LNAPL
19、 site objectives based on theLCSM. This guide recognizes LNAPL site objectives aredetermined by regulatory, business, regional, social, and othersite-specific factors. Within the context of the Guide E2081RBCA process, these factors are called the technical policydecisions.1.10 Remediation metrics a
20、re defined based on the siteobjectives and are measurable attributes of a remedial action.Remediation metrics may include environmental benefits, suchas flux control, risk reduction, or chemical longevity reduction.Remediation metrics may also include costs, such as installa-tion costs, energy use,
21、business impairments, waste generation,water disposal, and others. Remediation metrics are used in thedecision analysis for remedial options and in tracking theperformance of implemented remedial action alternatives.1.11 This guide does not provide procedures for selectingone type of remedial techno
22、logy over another. Rather, itrecommends that technology selection decisions be based onthe LCSM, sound professional judgment, and the LNAPL siteobjectives. These facets are complex and interdisciplinary.Appropriate user knowledge, skills, and judgment are required.1.12 This guide is not a detailed p
23、rocedure for engineeringanalysis and design of remedial action systems. It is intended tobe used by qualified professionals to develop a remediationstrategy that is based on the scientific and technical informationcontained in the LCSM. The remediation strategy should beconsistent with the site obje
24、ctives. Supporting engineeringanalysis and design should be conducted in accordance withrelevant professional engineering standards, codes, and re-quirements.1.13 ASTM standards are not federal or state regulations;they are voluntary consensus standards.1.14 The following principles should be follow
25、ed whenusing this guide:1.14.1 Data and information collected should be relevant toand of sufficient quantity and quality to develop a technically-sound LCSM.1.14.2 Remedial actions taken should be protective ofhuman health and the environment now and in the future.1.14.3 Remedial actions should hav
26、e a reasonable probabil-ity of meeting the LNAPL site objectives.1.14.4 Remedial actions implemented should not result ingreater site risk than existed before taking actions.1.14.5 Applicable federal, state, and local regulationsshould be followed (for example, waste managementrequirements, ground w
27、ater designations, worker protection).1.15 This guide is organized as follows:1.15.1 Section 2 lists associated and pertinent ASTM docu-ments.1.15.2 Section 3 defines terminology used in this guide.1.15.3 Section 4 includes a summary of this guide.1.15.4 Section 5 provides the significance and use o
28、f thisguide.1.15.5 Section 6 presents the components of the LCSM.1.15.6 Section 7 offers step-by-step procedures.1.15.7 Nonmandatory appendices are supplied for the fol-lowing additional information:1.15.7.1 Appendix X1 provides additional LNAPL reading.1.15.7.2 Appendix X2 provides an overview of m
29、ultiphasemodeling.1.15.7.3 Appendix X3 provides example screening levelcalculations pertaining to the LCSM.1.15.7.4 Appendix X4 provides information about datacollection techniques.1.15.7.5 Appendix X5 provides example remediation met-rics.1.15.7.6 Appendix X6 provides two simplified examples ofthe
30、use of the LNAPL guide.1.15.7.7 Appendix X7 and Appendix X8 are glossaries oftechnical terminology relevant for LNAPL decision-making.1.15.8 A reference list is included at the end of the docu-ment.1.16 The appendices are provided for additional informationand are not included as mandatory sections
31、of this guide.1.17 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
32、1.18 This guide offers an organized collection of informa-tion or a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in
33、 allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a projects manyunique aspects. The word “Standard” in the title of this
34、document means only that the document has been approvedthrough the ASTM consensus process.E2531 06 (2014)22. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD6235 Practice for Expedited Site Characterization of Va-dose Zone and Groundwater Contamin
35、ation at HazardousWaste Contaminated SitesD5717 Guide for Design of Ground-Water Monitoring Sys-tems in Karst and Fractured-Rock Aquifers (Withdrawn2005)3E1689 Guide for Developing Conceptual Site Models forContaminated SitesE1739 Guide for Risk-Based Corrective Action Applied atPetroleum Release Si
36、tesE1903 Practice for Environmental Site Assessments: PhaseII Environmental Site Assessment ProcessE1912 Guide for Accelerated Site Characterization for Con-firmed or Suspected Petroleum Releases (Withdrawn2013)3E1943 Guide for Remediation of Ground Water by NaturalAttenuation at Petroleum Release S
37、itesE2081 Guide for Risk-Based Corrective ActionE2091 Guide for Use of Activity and Use Limitations,Including Institutional and Engineering ControlsE2205 Guide for Risk-Based Corrective Action for Protec-tion of Ecological ResourcesE2348 Guide for Framework for a Consensus-based Envi-ronmental Decis
38、ion-making Process2.2 EPA Standard:4EPA Method 8021B Aromatic and Halogenated Volatiles byGas Chromatography Using Photoionization and/or Elec-trolytic Conductivity Detectors3. Terminology3.1 DefinitionsDefinitions of terms specific to this stan-dard are included in this section, with additional tec
39、hnicalterminology provided for reference in Appendix X7 andAppendix X8.3.1.1 active remediation, nactions taken to reduce orcontrol LNAPL source flux or the concentrations of chemicalsof concern in dissolved- or vapor-phase plumes. Active reme-diation could be implemented when the no-further-action
40、andpassive remediation courses of action are not appropriate.3.1.2 attenuation, nthe reduction in concentrations ofchemicals of concern in the environment with distance andtime due to processes such as diffusion, dispersion, sorption,chemical degradation, and biodegradation.3.1.3 chemicals of concer
41、n, nspecific chemicals that areidentified for evaluation in the corrective action process thatmay be associated with a given LNAPL release and are aconcern because of potential risk or aesthetic issues.3.1.3.1 DiscussionIdentification can be based on theirhistorical and current use at a site, detect
42、ed concentrations inenvironmental media and their mobility, toxicity, and persis-tence in the environment. Because chemicals of concern maybe identified at many points in the corrective action process,including before any determination that they pose an unaccept-able risk to human health or the envi
43、ronment, the term shouldnot automatically be construed to be associated with increasedor unacceptable risk.3.1.4 conceptual model, nintegration of site informationand interpretations generally including facets pertaining to thephysical, chemical, transport, and receptor characteristics pres-ent at a
44、 specific site.3.1.4.1 DiscussionA conceptual model is used to describecomprehensively the sources and chemicals of concern inenvironmental media and the associated risks for particularlocations, both now and in the future, as appropriate, at a site.3.1.5 corrective action, nsequence of actions take
45、n toaddress LNAPL releases, protect receptors, and meet otherenvironmental goals.3.1.5.1 DiscussionCorrective actions may include siteassessment and investigation, risk assessment, responseactions, interim remedial action, remedial action, operation andmaintenance of equipment, monitoring of progres
46、s, makingno-further-action determinations, and termination of the reme-dial action.3.1.6 dense nonaqueous phase liquids (DNAPL),nnonaqueous phase liquid with a specific gravity greater thanone (for example, a chlorinated solvent, creosote, polychlori-nated biphenyls).3.1.7 engineering controls, nphy
47、sical modifications to asite or facility (for example, slurry walls, capping, and point-of-use water treatment) to reduce or eliminate the potential forexposure to LNAPL or chemicals of concern in environmentalmedia.3.1.8 entrapped LNAPL, nresidual LNAPL in the form ofdiscontinuous blobs in the void
48、 space of a porous medium in asubmerged portion of a smear zone resulting from the upwardmovement of the water table into an LNAPL body.3.1.8.1 DiscussionAt a residual condition, however, atransient fall of the water table can result in local arearedistribution of LNAPL that is no longer in a residu
49、alcondition.3.1.9 exposure pathway, ncourse a chemical of concerntakes from the source area to a receptor or relevant ecologicalreceptor and habitat.3.1.9.1 DiscussionAn exposure pathway describes themechanism by which an individual or population is exposed toa chemical of concern originating from a site. Each exposurepathway includes a source or release from a source (forexample, LNAPL released from a tank or pipeline), a point ofexposure, an exposure route, and the potential receptors orrelevant ecological receptors and habitats. If the exposure pointis not at the so
