ASTM E2531-06

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Designation: E 2531 – 06
Standard Guide for
Development of Conceptual Site Models and Remediation
Strategies for Light Nonaqueous-Phase Liquids Released to
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the Subsurface
This standard is issued under the fixed designation E 2531; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number 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 E 1739 and E 2081), 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 RBCA process, 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 E 1689) by considering LNAPL conditions in sufficient detail
to evaluate risks and remedial action options.
1.1 This guide applies to sites with LNAPL present as
1.3 Federal, state, and local regulatory policies and statutes
residual, free, or mobile phases, and anywhere that LNAPL is
should be followed and form the basis of determining the
a source for impacts in soil, ground water, and soil vapor. Use
remedial objectives, whether risk-based or otherwise. Fig. 1
of this guide may show LNAPL to be present where it was
illustrates the interaction between this guide and other related
previously unrecognized. Information about LNAPL phases
guidance and references.
and methods for evaluating its potential presence are included
1.4 Petroleum and other chemical LNAPLs are the primary
in 4.3, guide terminology is in Section 3, and technical
focus of this guide. Certain technical aspects apply to dense
glossaries are in Appendix X7 and Appendix X8. Fig. 1 is a
NAPL(DNAPL),butthisguidedoesnotaddresstheadditional
flowchart that summarizes the procedures of this guide.
complexities of DNAPLs.
1.2 This guide is intended to supplement the conceptual site
1.5 The composite chemical and physical properties of an
model developed in the RBCA process (Guides E 1739 and
LNAPL are a function of the individual chemicals that
E 2081) and in the conceptual site model standard (Guide
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
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ThisguideisunderthejurisdictionofASTMCommitteeE50onEnvironmental
the LCSM varies depending on the exposure pathways and
Assessment, Risk Management and CorrectiveAction and is the direct responsibil-
risks and the scope and extent of the remedial actions that are
ity of Subcommittee E50.04 on Corrective Action.
Current edition approved Nov. 1, 2006. Published February 2007. needed. The LCSM follows a tiered development of sufficient
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E2531–06
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
...