ASTM E2531-06(2020)
(Guide)Standard Guide for Development of Conceptual Site Models and Remediation Strategies for Light Nonaqueous-Phase Liquids Released to the Subsurface
Standard Guide for Development of Conceptual Site Models and Remediation Strategies for Light Nonaqueous-Phase Liquids Released to the Subsurface
SIGNIFICANCE AND USE
5.1 This guide will help users answer simple and fundamental questions about the LNAPL occurrence and behavior in the subsurface. It will help users to identify specific risk-based drivers and non-risk factors for action at a site and prioritize resources consistent with these drivers and factors.
5.2 The site management decision process described in this guide includes several features that are only examples of standardized approaches to addressing the objectives of the particular activity. For example, Table 1 provides example indicators of the presence of LNAPL. Table 1 should be customized by the user with a modified list of LNAPL indicators as technically appropriate for the site or group of sites being addressed.
5.3 This guide advocates use of simple analyses and available data for the LCSM in Tier 1 to make use of existing data and to interpret existing data potentially in new ways. The Tier 1 LCSM is designed to identify where additional data may be needed and where decisions can be made using existing data and bounding estimates.
5.4 This guide expands the LCSM in Tier 2 and Tier 3 to a detailed, dynamic description that considers three-dimensional plume geometry, chemistry, and fluxes associated with the LNAPL that are both chemical- and location-specific.
5.5 This guide fosters effective use of existing site data, while recognizing that information may be only indirectly related to the LNAPL body conditions. This guide also provides a framework for collecting additional data and defining the value of improving the LCSM for remedial decisions.
5.6 By defining the key components of the LCSM, this guide helps identify the framework for understanding LNAPL occurrence and behavior at a site. This guide recommends that specific LNAPL site objectives be identified by the user and stakeholders and remediation metrics be based on the LNAPL site objectives. The LNAPL site objectives should be based on a variety of issues, including:
5.6.1 Potenti...
SCOPE
1.1 This guide applies to sites with LNAPL present as residual, free, or mobile phases, and anywhere that LNAPL is a source for impacts in soil, ground water, and soil vapor. Use of this guide may show LNAPL to be present where it was previously unrecognized. Information about LNAPL phases and methods for evaluating its potential presence are included in 4.3, guide terminology is in Section 3, and technical glossaries are in Appendix X7 and Appendix X8. Fig. 1 is a flowchart that summarizes the procedures of this guide.
1.2 This guide is intended to supplement the conceptual site model developed in the RBCA process (Guides E1739 and E2081) and in the conceptual site model standard (Guide E1689) by considering LNAPL conditions in sufficient detail to evaluate risks and remedial action options.
1.3 Federal, state, and local regulatory policies and statutes should be followed and form the basis of determining the remedial objectives, whether risk-based or otherwise. Fig. 1 illustrates the interaction between this guide and other related guidance and references.
1.4 Petroleum and other chemical LNAPLs are the primary focus of this guide. Certain technical aspects apply to dense NAPL (DNAPL), but this guide does not address the additional complexities of DNAPLs.
1.5 The composite chemical and physical properties of an LNAPL are a function of the individual chemicals that make-up an LNAPL. The properties of the LNAPL and the subsurface conditions in which it may be present vary widely from site to site. The complexity and level of detail needed in the LCSM varies depending on the exposure pathways and risks and the scope and extent of the remedial actions that are needed. The LCSM follows a tiered development of sufficient detail for risk assessment and remedial action decisions to be made. Additional data collection or technical analysis is typically needed when fundamental questions about the LNAPL cannot be answ...
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2531 − 06 (Reapproved 2020)
Standard Guide for
Development of Conceptual Site Models and Remediation
Strategies for Light Nonaqueous-Phase Liquids Released to
the Subsurface
This standard is issued under the fixed designation E2531; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This 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, subsurface
LNAPL 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 to
poor remedial strategies. By using this guide, the user will be able to perform a more appropriate
assessment 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 site
complexity and site-specific information required for the decision-making process.The RBCAguides
apply to LNAPL and to dissolved and vapor phases. This guide supplements the RBCA guides by
providing more information about identifying LNAPL, linking the LCSM to the RBCAprocess, and
describing 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 in
identifying site objectives, determining risk-based drivers and non-risk factors, defining remediation
metrics, evaluating remedial strategies, and preparing a site for closure. If the processes in this guide
are adequately followed for sites with LNAPL, it is expected that more efficient, consistent,
economical, and environmentally protective decisions will be made.
1. Scope E1689)byconsideringLNAPLconditionsinsufficientdetailto
evaluate risks and remedial action options.
1.1 This guide applies to sites with LNAPL present as
residual, free, or mobile phases, and anywhere that LNAPL is
1.3 Federal, state, and local regulatory policies and statutes
a source for impacts in soil, ground water, and soil vapor. Use
should be followed and form the basis of determining the
of this guide may show LNAPL to be present where it was
remedial objectives, whether risk-based or otherwise. Fig.1
previously unrecognized. Information about LNAPL phases
illustrates the interaction between this guide and other related
and methods for evaluating its potential presence are included
guidance and references.
in 4.3, guide terminology is in Section 3, and technical
1.4 Petroleum and other chemical LNAPLs are the primary
glossaries are in Appendix X7 and Appendix X8. Fig.1 is a
focus of this guide. Certain technical aspects apply to dense
flowchart that summarizes the procedures of this guide.
NAPL(DNAPL),butthisguidedoesnotaddresstheadditional
1.2 Thisguideisintendedtosupplementtheconceptualsite
complexities of DNAPLs.
model developed in the RBCA process (Guides E1739 and
1.5 The composite chemical and physical properties of an
E2081) and in the conceptual site model standard (Guide
LNAPL are a function of the individual chemicals that
make-up an LNAPL. The properties of the LNAPL and the
subsurface conditions in which it may be present vary widely
ThisguideisunderthejurisdictionofASTMCommitteeE50onEnvironmental
Assessment, Risk Management and CorrectiveAction and is the direct responsibil-
from site to site. The complexity and level of detail needed in
ity of Subcommittee E50.04 on Corrective Action.
the LCSM varies depending on the exposure pathways and
Current edition approved Nov. 1, 2020. Published November 2020. Originally
risks and the scope and extent of the remedial actions that are
approvedin2006.Lastpreviouseditionapprovedin2014asE2531–06(2014).DOI:
10.1520/E2531-06R20. needed. The LCSM follows a tiered development of sufficient
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2531 − 06 (2020)
detail for risk assessment and remedial action decisions to be 1.14.2 Remedial actions taken should be protective of
made. Additional data collection or technical analysis is human health and the environment now and in the future.
typically needed when fundamental questions about the
1.14.3 Remedial actions should have a reasonable probabil-
LNAPL cannot be answered with existing information. ity of meeting the LNAPL site objectives.
1.14.4 Remedial actions implemented should not result in
1.6 This guide does not develop new risk assessment
greater site risk than existed before taking actions.
protocols.Itisintendedtobeusedinconjunctionwithexisting
1.14.5 Applicable federal, state, and local regulations
risk-based corrective action guidance (for example, Guides
should be followed (for example, waste management
E1739 and E2081) and regulatory agency requirements (for
requirements, ground water designations, worker protection).
example, USEPA 1989, 1991, 1992, 1996, 1997).
1.15 This guide is organized as follows:
1.7 ThisguideassiststheuserindevelopinganLCSMupon
1.15.1 Section 2 lists associated and pertinentASTM docu-
which a decision framework is applied to assist the user in
ments.
selecting remedial action options.
1.15.2 Section 3 defines terminology used in this guide.
1.8 The goal of this guide is to provide sound technical
1.15.3 Section 4 includes a summary of this guide.
underpinning to LNAPL corrective action using appropriately
1.15.4 Section 5 provides the significance and use of this
scaled, site-specific knowledge of the physical and chemical
guide.
processes controlling LNAPL and the associated plumes in
1.15.5 Section 6 presents the components of the LCSM.
ground water and soil vapor.
1.15.6 Section 7 offers step-by-step procedures.
1.9 This guide provides flexibility and assists the user in 1.15.7 Nonmandatory appendices are supplied for the fol-
developing general LNAPL site objectives based on the
lowing additional information:
LCSM. This guide recognizes LNAPL site objectives are
1.15.7.1 Appendix X1 provides additional LNAPLreading.
determined by regulatory, business, regional, social, and other
1.15.7.2 Appendix X2 provides an overview of multiphase
site-specific factors. Within the context of the Guide E2081
modeling.
RBCA process, these factors are called the technical policy
1.15.7.3 Appendix X3 provides example screening level
decisions.
calculations pertaining to the LCSM.
1.15.7.4 Appendix X4 provides information about data
1.10 Remediation metrics are defined based on the site
collection techniques.
objectives and are measurable attributes of a remedial action.
1.15.7.5 Appendix X5 provides example remediation met-
Remediationmetricsmayincludeenvironmentalbenefits,such
rics.
asfluxcontrol,riskreduction,orchemicallongevityreduction.
1.15.7.6 Appendix X6 provides two simplified examples of
Remediation metrics may also include costs, such as installa-
the use of the LNAPL guide.
tioncosts,energyuse,businessimpairments,wastegeneration,
1.15.7.7 Appendix X7 and Appendix X8 are glossaries of
waterdisposal,andothers.Remediationmetricsareusedinthe
technical terminology relevant for LNAPL decision-making.
decision analysis for remedial options and in tracking the
performance of implemented remedial action alternatives. 1.15.8 A reference list is included at the end of the docu-
ment.
1.11 This guide does not provide procedures for selecting
one type of remedial technology over another. Rather, it 1.16 Theappendicesareprovidedforadditionalinformation
and are not included as mandatory sections of this guide.
recommends that technology selection decisions be based on
the LCSM, sound professional judgment, and the LNAPL site
1.17 This standard does not purport to address all of the
objectives. These facets are complex and interdisciplinary.
safety concerns, if any, associated with its use. It is the
Appropriateuserknowledge,skills,andjudgmentarerequired.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.12 This guide is not a detailed procedure for engineering
mine the applicability of regulatory limitations prior to use.
analysisanddesignofremedialactionsystems.Itisintendedto
1.18 This guide offers an organized collection of informa-
be used by qualified professionals to develop a remediation
tion or a series of options and does not recommend a specific
strategythatisbasedonthescientificandtechnicalinformation
course of action. This document cannot replace education or
contained in the LCSM. The remediation strategy should be
experienceandshouldbeusedinconjunctionwithprofessional
consistent with the site objectives. Supporting engineering
judgment. Not all aspects of this guide may be applicable in all
analysis and design should be conducted in accordance with
circumstances. This ASTM standard is not intended to repre-
relevant professional engineering standards, codes, and re-
sent or replace the standard of care by which the adequacy of
quirements.
a given professional service must be judged, nor should this
1.13 ASTM standards are not federal or state regulations;
document be applied without consideration of a project’s many
they are voluntary consensus standards.
unique aspects. The word “Standard” in the title of this
1.14 The following principles should be followed when
document means only that the document has been approved
using this guide: through the ASTM consensus process.
1.14.1 Data and information collected should be relevant to 1.19 This international standard was developed in accor-
and of sufficient quantity and quality to develop a technically- dance with internationally recognized principles on standard-
sound LCSM. ization established in the Decision on Principles for the
E2531 − 06 (2020)
Development of International Standards, Guides and Recom- time due to processes such as diffusion, dispersion, sorption,
mendations issued by the World Trade Organization Technical chemical degradation, and biodegradation.
Barriers to Trade (TBT) Committee.
3.1.3 chemicals of concern, n—specific chemicals that are
identified for evaluation in the corrective action process that
2. Referenced Documents
may be associated with a given LNAPL release and are a
2.1 ASTM Standards:
concern because of potential risk or aesthetic issues.
D653Terminology Relating to Soil, Rock, and Contained
3.1.3.1 Discussion—Identification can be based on their
Fluids
historical and current use at a site, detected concentrations in
D6235Practice for Expedited Site Characterization of Va-
environmental media and their mobility, toxicity, and persis-
dose Zone and Groundwater Contamination at Hazardous
tence in the environment. Because chemicals of concern may
Waste Contaminated Sites
be identified at many points in the corrective action process,
D5717Guide for Design of Ground-Water Monitoring Sys-
includingbeforeanydeterminationthattheyposeanunaccept-
tems in Karst and Fractured-Rock Aquifers (Withdrawn
able risk to human health or the environment, the term should
2005)
not automatically be construed to be associated with increased
E1689Guide for Developing Conceptual Site Models for
or unacceptable risk.
Contaminated Sites
3.1.4 conceptual model, n—integration of site information
E1739Guide for Risk-Based Corrective Action Applied at
and interpretations generally including facets pertaining to the
Petroleum Release Sites
physical,chemical,transport,andreceptorcharacteristicspres-
E1903Practice for Environmental Site Assessments: Phase
ent at a specific site.
II Environmental Site Assessment Process
3.1.4.1 Discussion—Aconceptual model is used to describe
E1912Guide forAccelerated Site Characterization for Con-
comprehensively the sources and chemicals of concern in
firmed or Suspected Petroleum Releases (Withdrawn
environmental media and the associated risks for particular
2013)
locations, both now and in the future, as appropriate, at a site.
E1943Guide for Remediation of Ground Water by Natural
3.1.5 corrective action, n—sequence of actions taken to
Attenuation at Petroleum Release Sites
address LNAPL releases, protect receptors, and meet other
E2081Guide for Risk-Based Corrective Action
environmental goals.
E2091Guide for Use of Activity and Use Limitations,
3.1.5.1 Discussion—Corrective actions may include site
Including Institutional and Engineering Controls
assessment and investigation, risk assessment, response
E2205Guide for Risk-Based Corrective Action for Protec-
actions,interimremedialaction,remedialaction,operationand
tion of Ecological Resources
maintenance of equipment, monitoring of progress, making
E2348Guide for Framework for a Consensus-based Envi-
no-further-action determinations, and termination of the reme-
ronmental Decision-making Process
dial action.
2.2 EPA Standard:
3.1.6 dense nonaqueous phase liquids (DNAPL),
EPAMethod 8021BAromatic and Halogenated Volatiles by
n—nonaqueousphaseliquidwithaspecificgravitygreaterthan
Gas Chromatography Using Photoionization and/or Elec-
one (for example, a chlorinated solvent, creosote, polychlori-
trolytic Conductivity Detectors
nated biphenyls).
3. Terminology
3.1.7 engineering controls, n—physical modifications to a
site or facility (for example, slurry walls, capping, and point-
3.1 Definitions—Definitions of terms specific to this stan-
of-use water treatment) to reduce or eliminate the potential for
dard are included in this section, with additional technical
exposure to LNAPLor chemicals of concern in environmental
terminology provided for reference in Appendix X7 and
media.
Appendix X8.
3.1.1 active remediation, n—actions taken to reduce or
3.1.8 entrapped LNAPL, n—residual LNAPLin the form of
control LNAPLsource flux or the concentrations of chemicals discontinuous blobs in the void space of a porous medium in a
of concern in dissolved- or vapor-phase plumes. Active reme-
submerged portion of a smear zone resulting from the upward
diation could be implemented when the no-further-action and movement of the water table into an LNAPL body.
passive remediation courses of action are not appropriate
...
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