1、Designation: E 1689 95 (Reapproved 2003)e1Standard Guide forDeveloping Conceptual Site Models for Contaminated Sites1This standard is issued under the fixed designation E 1689; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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.e1NOTESection 3.1.2 was editorially revised in July 2003.1. Scope1.1 This guide is intended to assist in the development of
3、conceptual site models to be used for the following: (1)integration of technical information from various sources, (2)support the selection of sample locations for establishingbackground concentrations of substances, (3) identify dataneeds and guide data collection activities, and (4) evaluate theri
4、sk to human health and the environment posed by a contami-nated site. This guide generally describes the major compo-nents of conceptual site models, provides an outline fordeveloping models, and presents an example of the parts of amodel. This guide does not provide a detailed description of asite-
5、specific conceptual site model because conditions at con-taminated sites can vary greatly from one site to another.1.2 The values stated in either inch-pound or SI units are tobe regarded as the standard. The values given in parenthesesare for information only.1.3 This guide is intended to apply to
6、any contaminated site.1.4 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
7、to use.2. Referenced Documents2.1 ASTM Standards:2D 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and Rock2.2 EPA Documents:3Guidance for Data Useability in Risk Assessment (Part A)Final, Publication 9285.7-09A, PB 92-963356, April1992Guidance for Data Useability i
8、n Risk Assessment (Part B),OSWER Directive 9285.7-09B, May 1992Guidance for Conducting Remedial Investigations and Fea-sibility Studies Under CERCLA, OSWER Directive9355.3-01, October 19883. Terminology3.1 Definitions:3.1.1 background concentration, nthe concentration of asubstance in ground water,
9、surface water, air, sediment, or soilat a source(s) or nearby reference location, and not attributableto the source(s) under consideration. Background samples maybe contaminated, either by naturally occurring or manmadesources, but not by the source(s) in question.3.1.2 conceptual site model, nfor t
10、he purpose of thisguide, a written or pictorial representation of an environmentalsystem and the biological, physical, and chemical processesthat determine the transport of contaminants from sourcesthrough environmental media to environmental receptorswithin the system.3.1.3 contaminant, nany substa
11、nce, including any radio-logical material, that is potentially hazardous to human healthor the environment and is present in the environment atconcentrations above its background concentration.3.1.4 contaminant release, nmovement of a substancefrom a source into an environmental medium, for example,
12、 aleak, spill, volatilization, runoff, fugitive dust emission, orleaching.3.1.5 environmental receptor, nhumans and other livingorganisms potentially exposed to and adversely affected bycontaminants because they are present at the source(s) or alongcontaminant migration pathways.3.1.6 environmental
13、transport, nmovement of a chemicalor physical agent in the environment after it has been releasedfrom a source to an environmental medium, for example,movement through the air, surface water, ground water, soil,sediment, or food chain.3.1.7 exposure route, nthe process by which a contami-nant or phy
14、sical agent in the environment comes into directcontact with the body, tissues, or exchange boundaries of anenvironmental receptor organism, for example, ingestion, in-halation, dermal absorption, root uptake, and gill uptake.1This guide is under the jurisdiction of ASTM Committee E47 on BiologicalE
15、ffects and Environmental Fate and is the direct responsibility of SubcommitteeE47.05 on Risk Assessment, Communication, and Management.Current edition approved March 15, 1995. Published May 1995.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
16、serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, Bldg 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright ASTM International, 100 B
17、arr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.8 migration pathway, nthe course through whichcontaminants in the environment may move away from thesource(s) to potential environmental receptors.3.1.9 source, nthe location from which a contaminant(s)has entered or
18、may enter a physical system. A primary source,such as a location at which drums have leaked onto surfacesoils, may produce a secondary source, such as contaminatedsoils; sources may hence be primary or secondary.4. Summary of Guide4.1 The six basic activities associated with developing aconceptual s
19、ite model (not necessarily listed in the order inwhich they should be addressed) are as follows: (1) identifi-cation of potential contaminants; (2) identification and charac-terization of the source(s) of contaminants; (3) delineation ofpotential migration pathways through environmental media,such a
20、s ground water, surface water, soils, sediment, biota, andair; (4) establishment of background areas of contaminants foreach contaminated medium; (5) identification and character-ization of potential environmental receptors (human and eco-logical); and (6) determination of the limits of the study ar
21、ea orsystem boundaries.4.2 The complexity of a conceptual site model should beconsistent with the complexity of the site and available data.The development of a conceptual site model will usually beiterative. Model development should start as early in the siteinvestigation process as possible. The m
22、odel should be refinedand revised throughout the site investigation process to incor-porate additional site data. The final model should containsufficient information to support the development of currentand future exposure scenarios.4.3 The concerns of ecological risk assessment are differentfrom t
23、hose of human-health risk assessment, for example,important migration pathways, exposure routes, and environ-mental receptors. These differences are usually sufficient towarrant separate descriptions and representations of the con-ceptual site model in the human health and ecological riskassessment
24、reports. There will be elements of the conceptualsite model that are common to both representations, however,and the risk assessors should develop these together to ensureconsistency.5. Significance and Use5.1 The information gained through the site investigation isused to characterize the physical,
25、 biological, and chemicalsystems existing at a site. The processes that determinecontaminant releases, contaminant migration, and environmen-tal receptor exposure to contaminants are described and inte-grated in a conceptual site model.5.2 Development of this model is critical for determiningpotenti
26、al exposure routes (for example, ingestion and inhala-tion) and for suggesting possible effects of the contaminants onhuman health and the environment. Uncertainties associatedwith the conceptual site model need to be identified clearly sothat efforts can be taken to reduce these uncertainties toacc
27、eptable levels. Early versions of the model, which areusually based on limited or incomplete information, willidentify and emphasize the uncertainties that should be ad-dressed.5.3 The conceptual site model is used to integrate all siteinformation and to determine whether information includingdata a
28、re missing (data gaps) and whether additional informa-tion needs to be collected at the site. The model is usedfurthermore to facilitate the selection of remedial alternativesand to evaluate the effectiveness of remedial actions in reduc-ing the exposure of environmental receptors to contaminants.5.
29、4 This guide is not meant to replace regulatory require-ments for conducting environmental site characterizations atcontaminated (including radiologically contaminated) sites. Itshould supplement existing guidance and promote a uniformapproach to developing conceptual site models.5.5 This guide is m
30、eant to be used by all those involved indeveloping conceptual site models. This should ideally includerepresentatives from all phases of the investigative and reme-dial process, for example, preliminary assessment, remedialinvestigation, baseline human health and ecological risk as-sessments, and fe
31、asibility study. The conceptual site modelshould be used to enable experts from all disciplines tocommunicate effectively with one another, resolve issuesconcerning the site, and facilitate the decision-making process.5.6 The steps in the procedure for developing conceptualsite models include elemen
32、ts sometimes referred to collectivelyas site characterization. Although not within the scope of thisguide, the conceptual site model can be used during siteremediation.6. Procedure6.1 Assembling InformationAssemble historical and cur-rent site-related information from maps, aerial images, crosssecti
33、ons, environmental data, records, reports, studies, andother information sources. A visit(s) to the site by thosepreparing the conceptual site model is recommended highly.The quality of the information being assembled should beevaluated, preferably including quantitative methods, and thedecision to
34、use the information should be based on the datasmeeting objective qualitative and quantitative criteria. Formore information on assessing the quality and accuracy ofdata, see Guidance for Data Useability in Risk Assessment(Part A) and Guidance for Data Useability in Risk Assessment(Part B). Methods
35、used for obtaining analytical data should bedescribed, and sources of information should be referenced. Aconceptual site model should be developed for every site unlessthere are multiple sites in proximity to one another such that itis not possible to determine the individual source or sources ofcon
36、tamination. Sites may be aggregated in that case. Aconceptual model should then be developed for the aggregate.6.2 Identifying ContaminantsIdentify contaminants in theground water, surface water, soils, sediments, biota, and air. Ifno contaminants are found, the conceptual site model should beused t
37、o help document this finding.6.3 Establishing Background Concentrations ofContaminantsBackground samples serve three major func-tions: (1) to establish the range of concentrations of an analyteattributable to natural occurrence at the site; (2) to establish therange of concentrations of an analyte a
38、ttributable to source(s)other than the source(s) under consideration; and (3) to helpestablish the extent to which contamination exceeds back-ground levels.E 1689 95 (2003)e126.3.1 The conceptual site model should include the naturallyoccurring concentrations of all contaminants found at the site.Th
39、e number and location of samples needed to establishbackground concentrations in each medium will vary withspecific site conditions and requirements. The model shouldinclude sufficient background samples to distinguish contami-nation attributable to the source(s) under consideration fromnaturally oc
40、curring or nearby anthropogenic contamination.The procedures mentioned in 6.2 and 6.3 are sometimesgrouped under the general heading of contaminant assessmentand may be performed as a separate activity prior to thedevelopment of a conceptual site model.6.4 Characterizing SourcesAt a minimum, the fol
41、lowingsource characteristics should be measured or estimated for asite:6.4.1 Source location(s), boundaries, and volume(s).Sources should be located accurately on site maps. Mapsshould include a scale and direction indicator (for example,north arrow). They should furthermore show where thesource(s)
42、is located in relationship to the property boundaries.6.4.2 The potentially hazardous constituents and their con-centrations in media at the source.6.4.3 The time of initiation, duration, and rate of contami-nant release from the source.6.5 Identifying Migration PathwaysPotential migrationpathways t
43、hrough ground water, surface water, air, soils,sediments, and biota should be identified for each source.Complete exposure pathways should be identified and distin-guished from incomplete pathways. An exposure pathway isincomplete if any of the following elements are missing: (1)amechanism of contam
44、inant release from primary or secondarysources, (2) a transport medium if potential environmentalreceptors are not located at the source, and (3) a point ofpotential contact of environmental receptors with the contami-nated medium. The potential for both current and futurereleases and migration of t
45、he contaminants along the completepathways to the environmental receptors should be determined.A diagram (similar to that in Fig. X1.4) of exposure pathwaysfor all source types at a site should be constructed. Thisinformation should be consistent with the narrative portion andtables in the exposure
46、assessment section of an exposure or riskassessment. Tracking contaminant migration from sources toenvironmental receptors is one of the most important uses ofthe conceptual site model.6.5.1 Ground Water PathwayThis pathway should beconsidered when hazardous solids or liquids have or may havecome in
47、to contact with the surface or subsurface soil or rock.The following should be considered further in that case:vertical distance to the saturated zone; subsurface flow rates;presence and proximity of downgradient seeps, springs, orcaves; fractures or other preferred flow paths; artesian condi-tions;
48、 presence of wells, especially those for irrigation ordrinking water; and, in general, the underlying geology andhydrology of the site. Other fate and transport phenomena thatshould be considered include hydrodynamic dispersion, inter-phase transfers of contaminants, and retardation. Movementthrough
49、 the vadose zone should be considered.6.5.2 Surface Water and Sediment PathwayThis pathwayshould always be investigated in the following situations: (1)aperennial body of water (river, lake, continuous stream, drain-age ditch, etc.) is in direct contact with, or is potentiallycontaminated by a source or contaminated area, (2) an unin-terrupted pathway exists from a source or contaminated area tothe surface water, (3) sampling and analysis of the surfacewater body or sediments indicate contaminant concentrationssubstantially above background, (4) contaminated ground wa
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