i UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
? WASHINGTON, D.C. 20460
OFFICE OF
SOLID WASTE AND EMERGENCY
RESPONSE
JUL192005
OSWER 9200.4-39
MEMORANDUM
SUBJECT: Use of Alternate Concentration Limits (CLs) in Superfund Cleanups
FROM- Michael D. Uook, Uirecjf
Office of Superfund ReJietiik^flri^W'lecKioiu'tol Innovation
TO: Superfund National Policy Managers, Regions 1-10
Purpose
The purpose of this memorandum is to present EPA policy regarding use of Alternate
Concentration Limits (ACLs) in remedies selected under the authority of the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (CERCLA). CERCLA
section 121 provides authority to use ACLs under certain circumstances.1 CERCLA section 121
also requires that all Superfund remedies selected, including those based on ACLs, be protective
of human health and the environment. Regions are requested to consult with the Office of
Superfund Remediation and Technology Innovation (OSRTI) prior to selecting a remedy that
includes CERCLA ACLs.
If the Agency, in its discretion, decides an ACL might be appropriate based on site-
specific circumstances, CERCLA section 121 sets forth a number of specific requirements that
must be met. This memorandum, which is designed to assist Regions in evaluating the potential
of ACLs at Superfund sites, is not a regulation itself, nor does it change or substitute for any
regulations. It describes national policy and does not impose legally binding requirements on
EPA, states, or the regulated community. This policy does not confer legal rights or impose legal
obligations upon any member of the public. Interested parties are free to raise questions and
objections about the substance of this memorandum and the appropriateness of the application of
this policy to a particular situation. EPA and other decision makers retain the discretion to adopt
approaches on a case-by-case basis that differ from those described in this memorandum, and may
change this policy in the future.
'The term CERCLA ACLs is used in this memorandum to distinguish this term from alternate concentration
limits used in other programs (e.g., RCR ACLs, provided for in 40 CFR Part 264, or state ACLs), Only CERCLA ACLs
are addressed in this memoradum.
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Background
CERCLA section 121 establishes certain requirements for the Superfund cleanup process.
Section 121(b)(l) requires that remedial actions be protective of human health and the
environment. In addition to that independent requirement, Section 121(d) generally provides that
remedial actions shall meet applicable or relevant and appropriate requirements (ARARs), unless
those requirements are waived pursuant to section §121(d)(4) under appropriate site-specific
circumstances.2 Section 121(d)(2)(B)(ii) also addresses ACLs and limitations concerning their
use, as follows:
(ii) For the purposes of this section, a process for establishing alternate concentration
limits to those otherwise applicable for hazardous constituents in groundwater under
subparagraph (A) may not be used to establish applicable standards under this paragraph
if the process assumes a point of human exposure beyond the boundary of the facility, as
defined at the conclusion of the remedial investigation and feasibility study, except
where-
(I) there are known and projected points of entry of such groundwater into surface
water; and
(II) on the basis of measurements or projections, there is or will be no statistically
significant increase of such constituents from such groundwater in such surface
water at the point of entry or at any point where there is reason to believe
accumulation of constituents may occur downstream; and
(III) the remedial action includes enforceable measures that will preclude human
exposure to the contaminated groundwater at any point between the facility
boundary and all known and projected points of entry of such groundwater into
surface water then the assumed point of human exposure may be at such known
and projected points of entry.
The CERCLA ACL provision is directed at standards that are "otherwise applicable for
hazardous constituents in groundwater." Examples of such standards may include state
requirements to clean up ground water to background levels (e.g., some state antidegradation
requirements) or state requirements for ground water cleanup. Such standards must otherwise
qualify as an applicable standard pursuant to section 121(d)(2)(A) (e.g., must be properly
promulgated, enforceable, consistently applied).3
ARAR waivers are also discussed in §300.430(f)(l)(ii)(C) of the!990 National Oil and Hazardous
Substances Pollution Contingency Plan (the NCP).
Federal or state Maximum Contaminant Levels (MCLs) or non-zero Maximum Contaminant Level Goals
(MCLGs) established under the Safe Drinking Water Act generally are not "applicable" requirements but are
considered to be "relevant and appropriate" requirements for aquifers that are current or potential future sources of
drinking water, (see. CERCLA section 121(d)(2)(A)(i); and §300.430(e)(2)(i)(B) ofthe NCP). Similarly, water
quality criteria under the Clean Water Act also may be "relevant and appropriate" standards for specific
contaminants where a plume discharges to (or threatens) surface water (see. CERCLA section 121(d)(2)(A)(i) and
(B)(i); and §300.430(e)(2)(i)(E) ofthe NCP). Further information concerning environmental standards that may be
either applicable or relevant and appropriate to a Superfund cleanup action is available from the EPA web site:
http://www.epa.gov/superfund/action/guidance/remedv/arars.htm
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This provision of the statute also contains several site-specific conditions which must be
met in order to establish CERCLA ACLs. Regions have broad discretion under the statute when
evaluating whether a CERCLA ACL might be appropriate under site-specific circumstances.
Generally, in satisfying the statutory requirements in section 121(d)(2)(B)(ii), Regions should
consider a number of factors, including:
1. whether contaminated ground water discharges to surface water;
2. whether all plumes of contaminated ground water are discharging to surface water (e.g., are
contaminants present in a deeper aquifer that does not discharge to surface water?);
3. whether significant degradation of the aquifer might occur prior to discharge to surface water
(e.g., could the plume spread to uncontaminated portions of the aquifer or to other aquifers that
are interconnected?);
4. whether "known and projected" points of entry of the plume (or plumes) into a surface water
body have been, or can be, specifically identified;
5. whether the discharge of ground water to surface water would lead to a "statistically
significant" increase of contaminant concentrations in the surface water body at those points of
entry, at points downstream, or at any point at which contaminants might be expected to
accumulate (including accumulation of contaminants that might occur in sediments at or below
those points of entry);
6. whether ground water can be restored (e.g., can the program goal of restoring contaminated
ground water to its beneficial uses be met in a reasonable time frame?);
7. whether there is the potential for degradation products, particularly those that could represent
more of a risk than the parent compounds (e.g., trichloroethene (TCE) can degrade into the more
toxic compound, vinyl chloride), within the zone between the source and the points of entry;
8. whether the ACL will lead to a "statistically significant" increase in the concentration of
degradation compounds in the surface water, and whether the assessed risk from any potential
degradation products in the surface water is within EPA's acceptable risk range;
9. whether enforceable measures can be implemented to preclude human consumption of the
contaminated ground water, and ensure that there would be no exposure to contaminants in the
ground water above health-based levels (e.g., is it possible to reliably prevent human exposure to
the contaminated ground water through the use of institutional controls?); and
10. whether a Total Maximum Daily Load (TMDL) pursuant to Clean Water Act section 303(d)
has been (or is being) established for the surface water, and whether an ACL could result in
exceedence of a TMDL even though there would be no "statistically significant" increase in the
concentration of the contaminant in the surface water body.
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Implementation
In general, Regions should consider the factors discussed in this guidance in evaluating
whether use of CERCLA ACLs may be appropriate under site-specific circumstances. Where
CERCLA ACLs are established as part of a remedy, the Superfund Record of Decision (ROD)
should identify the applicable standards for which the CERCLA ACLs have been substituted, and
should document specifically how the site meets the specific conditions required by the statute
(e.g., point of entry, no statistically significant increase of constituents, enforceable measures that
will preclude human exposure). The ROD also should explain the process used to establish the
CERCLA ACLs and their numeric values. Finally, the ROD should explain how the ACL meets
the independent requirement in CERCLA section 121 that CERCLA response actions be
protective of human health and the environment (e.g., selected engineering measures;
institutional controls).
For sites not meeting the statutory conditions for use of CERCLA ACLs, Regions should
consider other flexibilities provided for in CERCLA and the NCP that may be appropriate.
ARAR waivers are an example of the flexibility provided in CERCLA and the NCP (section
§121(d)(4) and part §300.430(f)(l)(ii)(C), respectively).4
This memorandum provides EPA policy related to the use of CERCLA ACLs in
Superfund cleanups and supersedes any previous guidance on this matter. Where the Region
contemplates using an ACL, and for questions regarding program flexibilities that may be
appropriate to ground water cleanup, including CERCLA ACLs, please have your staff contact
Kenneth Lovelace of OSRTI, at (703) 603-8787. For question regarding ARARs compliance,
please have your staff contact Robin M. Anderson of OSRTI at (703) 603-8747.
cc: OSRTI Managers
Ed Chu, Land Revitalization Staff
Debbie Deitrich, OEM
Linda Garczynski, OBCR
Matt Hale, OSW
Jim Woolford, FFRRO
Cliff Rothenstein, OUST
Susan Bromm, OSRE
Dave Kling, FFEO
Scott Sherman, OGC
Eric Steinhaus, Superfund Lead Region Coordinator, US EPA Region 8
NARPM Co-Chairs
Joanna Gibson, OSRTI Documents Coordinator
Also, EPA guidance on factors to consider when evaluating the technical impracticability of ground water
restoration can be found at: http://www.epa.gov/superfund/resources/gwdocs/tec imp.htm .
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