1、Designation: E 2531 06Standard Guide forDevelopment of Conceptual Site Models and RemediationStrategies for Light Nonaqueous-Phase Liquids Released tothe Subsurface1This standard is issued under the fixed designation E 2531; the number immediately following the designation indicates the year oforigi
2、nal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis guide provides a framework for developing a light nonaqueo
3、us 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 wel
4、ls.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 thi
5、s guide is a “tiered” approach, similar to the risk-based corrective action (RBCA)process (Guides E 1739 and E 2081), 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
6、 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
7、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 mor
8、e 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 LNA
9、PL 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
10、 of this guide.1.2 This guide is intended to supplement the conceptual sitemodel developed in the RBCA process (Guides E 1739 andE 2081) and in the conceptual site model standard (GuideE 1689) by considering LNAPL conditions in sufficient detailto evaluate risks and remedial action options.1.3 Feder
11、al, 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
12、 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
13、 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 developm
14、ent 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, 2006. Published February 2007.1Copyright ASTM I
15、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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
16、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, GuidesE 1739 and E 2081) and regulatory agency requirements (forexample, USEPA 1989, 1991, 1992, 1996, 1997).1.
17、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 sound technicalunderpinning to LNAPL corrective action using appropriatelyscaled, site-specific knowledge of t
18、he 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 site objectives based on theLCSM. This guide recognizes LNAPL site objectives aredetermined by regulatory, b
19、usiness, regional, social, and othersite-specific factors. Within the context of the Guide E 2081RBCA process, these factors are called the technical policydecisions.1.10 Remediation metrics are defined based on the siteobjectives and are measurable attributes of a remedial action.Remediation metric
20、s 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, business impairments, waste generation,water disposal, and others. Remediation metrics are used in thedecisi
21、on 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 technology over another. Rather, itrecommends that technology selection decisions be based onthe LCSM, sound profe
22、ssional 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 procedure for engineeringanalysis and design of remedial action systems. It is intended tobe used by qualifie
23、d 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 objectives. Supporting engineeringanalysis and design should be conducted in accordance withrelevant professiona
24、l 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 followed whenusing this guide:1.14.1 Data and information collected should be relevant toand of sufficient quantit
25、y 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 have a reasonable probabil-ity of meeting the LNAPL site objectives.1.14.4 Remedial actions implemented should
26、not result ingreater site risk than existed before taking actions.1.14.5 Applicable federal, state, and local regulationsshould be followed (for example, waste management require-ments, ground water designations, worker protection).1.15 This guide is organized as follows:1.15.1 Section 2 lists assoc
27、iated 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 of thisguide.1.15.5 Section 6 presents the components of the LCSM.1.15.6 Section 7 offers step-by-step proc
28、edures.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 multiphasemodeling.1.15.7.3 Appendix X3 provides example screening levelcalculations pertaining to the LCSM
29、.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 use of the LNAPL guide.1.15.7.7 Appendix X7 and Appendix X8 are glossaries oftechnical terminology relevan
30、t 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 of this guide.1.17 This standard does not purport to address all of thesafety concerns, if any, associated
31、 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.1.18 This guide offers an organized collection of informa-tion or a series of options and does not recomme
32、nd 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 allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by whi
33、ch 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 thisdocument means only that the document has been approvedthrough the ASTM consensus process.E25310622. Refer
34、enced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 6235 Practice for Expedited Site Characterization ofVadose Zone and Ground Water Contamination at Hazard-ous Waste Contaminated SitesD 5717 Guide for Design of Ground-Water MonitoringSystems in Karst an
35、d Fractured-Rock Aquifers3E 1689 Guide for Developing Conceptual Site Models forContaminated SitesE 1739 Guide for Risk-Based Corrective Action Applied atPetroleum Release SitesE 1903 Guide for Environmental SiteAssessments: Phase IIEnvironmental Site Assessment ProcessE 1912 Guide for Accelerated S
36、ite Characterization forConfirmed or Suspected Petroleum ReleasesE 1943 Guide for Remediation of Ground Water by NaturalAttenuation at Petroleum Release SitesE 2081 Guide for Risk-Based Corrective ActionE 2091 Guide for Use of Activity and Use Limitations,Including Institutional and Engineering Cont
37、rolsE 2205 Guide for Risk-Based Corrective Action for Protec-tion of Ecological ResourcesE 2348 Guide for Framework for a Consensus-based Envi-ronmental Decision-making Process2.2 EPA Standard:4EPAMethod 8021B Aromatic and Halogenated Volatiles byGas Chromatography Using Photoionization and/or Elec-
38、trolytic Conductivity Detectors3. Terminology3.1 DefinitionsDefinitions of terms specific to this stan-dard are included in this section, with additional technicalterminology provided for reference in Appendix X7 andAppendix X8.3.1.1 active remediation, nactions taken to reduce orcontrol LNAPL sourc
39、e flux or the concentrations of chemicalsof concern in dissolved- or vapor-phase plumes. Active reme-diation could be implemented when the no-further-action andpassive remediation courses of action are not appropriate.3.1.2 attenuation, nthe reduction in concentrations ofchemicals of concern in the
40、environment with distance andtime due to processes such as diffusion, dispersion, sorption,chemical degradation, and biodegradation.3.1.3 chemicals of concern, nspecific chemicals that areidentified for evaluation in the corrective action process thatmay be associated with a given LNAPL release and
41、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, detected concentrations inenvironmental media and their mobility, toxicity, and persis-tence in the environment. Because chemicals of concern maybe i
42、dentified at many points in the corrective action process,including before any determination that they pose an unaccept-able risk to human health or the environment, the term shouldnot automatically be construed to be associated with increasedor unacceptable risk.3.1.4 conceptual model, nintegration
43、 of site informationand interpretations generally including facets pertaining to thephysical, chemical, transport, and receptor characteristicspresent at a specific site.3.1.4.1 DiscussionA conceptual model is used to describecomprehensively the sources and chemicals of concern inenvironmental media
44、 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 taken toaddress LNAPL releases, protect receptors, and meet otherenvironmental goals.3.1.5.1 DiscussionCorrective actions may include siteassessment
45、and investigation, risk assessment, response ac-tions, interim remedial action, remedial action, operation andmaintenance of equipment, monitoring of progress, makingno-further-action determinations, and termination of the reme-dial action.3.1.6 dense nonaqueous phase liquids (DNAPL),nnonaqueous pha
46、se liquid with a specific gravity greaterthan one (for example, a chlorinated solvent, creosote, poly-chlorinated biphenyls).3.1.7 engineering controls, nphysical modifications to asite or facility (for example, slurry walls, capping, and point-of-use water treatment) to reduce or eliminate the pote
47、ntial forexposure to LNAPL or chemicals of concern in environmentalmedia.3.1.8 entrapped LNAPL, nresidual LNAPL in the form ofdiscontinuous blobs in the void 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
48、 DiscussionAt a residual condition, however, atransient fall of the water table can result in local arearedistribution of LNAPL that is no longer in a residualcondition.3.1.9 exposure pathway, ncourse a chemical of concerntakes from the source area to a receptor or relevant ecologicalreceptor and ha
49、bitat.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 source, a transport or exposure medium (forexample, air), or both, are also included.3.1.10 facility, nproperty containing the source of theLNAPL or
