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6 JUL 2008
• REPLY TO THE ATTENTION OF
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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REGION 5
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Alisa Liu, P.E.
Environmental Scientist
Illinois Pollution Control Board
James R. Thompson Center
100 W. Randolph, Suite 11-500
Chicago, Illinois 60601
Dear
Ms.
Liu:
Thank you for your inquiry regarding the Delisting Risk Assessment Software (DRAS)
and
its
use in evaluating delisting petitions. Please note that this response is confined to the
questions posed to Todd Ramaly of my staff and does not constitute an opinion on the delisting.
You indicated that Region 6 has elected to base proposed rules to grant delistings on the results
of the
beta
version of DRAS version 3, which is not in general release to the public at this time.
DRAS version 3 includes several updates to the modeling methodology, but requires a number of
workaround adjustments in order to obtain reproducible results. DRAS version 3 is intended to
replace DRAS version 2. You wanted to know which version should be used.
Let me begin by pointing out that the DRAS is a tool we use in order to evaluate the
potential risk posed by delisted wastes when disposed of in a subtitle D landfill or surface
impoundment. DRAS is designed to conduct this evaluation based on the criteria for listing a
hazardous waste (40 C.F.R. § 261.11(a)(3)). Although this evaluation is a requirement of the
regulations governing delistings (40 C.F.R. § 260.22), the specific use of DRAS and its
methodologies are not. As such, there is no regulatory requirement to use DRAS (or any specific
version of DRAS).
Furthermore, the authority to evaluate and conduct delistings is delegated to each U.S.
Environmental Protection Agency Region. Thus, the approach to delisting may differ from
Region to Region. In your case, the State of Illinois has been authorized to conduct delistings for
wastes disposed of within Illinois and is free to evaluate the waste and the criterion in
40 C.F.R. § 261.11(a)(3) using DRAS or any other appropriate assessment approach.
At this time, EPA Region 5 is using DRAS version 2 with modifications for projects
which have already been proposed by EPA for approval. DRAS version 3 is under active repair
and
a
version suitable for release to the general public should be available this summer. EPA
Region 5 intends to use this repaired version of DRAS 3 for new delisting determinations
immediately upon its release.
Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Recycled Paper (50% Postconsuicer)
Sincerely,
We are also responding to a separate inquiry made regarding potential corrections to the
DRAS version 2 surface impoundment groundwater pathway for a proposal currently before the
board. Mike Maxwell of Weaver Booz, Inc. noted corrections to landfill dilution attenuation
factors (DAFs) in previous DRAS user-alerts, explaining that there should not be any DAFs
equal to zero. He asked if the same applies to surface impoundment DAFs, as several indeed
have a value of zero. The effect of the zero DAF is to cancel the pathway for evaluation.
Upon consulting with the original modeler for DRAS version 2 DAFs, we realized that
the minimum base (before volume adjustment) surface impoundment DAFs for carcinogens
should be 5.3 and for noncarcinogens 3.92. All the surface impoundment DAFs with zero values
or values less than those quoted above should be modified in Steps 4 and 5 for the DRAS.
Parameters, such as the DAFs, can be changed by scrolling across the database, typing the new
value, then saving the updates. The change to the default value is site-specific and must be done
each time DRAS is used for a new evaluation. Documentation of the change can be obtained by
selecting to print the DRAS report
List of COCs with Altered Chemical Properties.
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Please feel free to contact Todd Ramaly of my staff at (312) 353-791/or at the address
above with questions or comments.
Dale Meyer
Chief
RCRA Programs Section
cc: M.
Crites, IEPA
M. Maxwell, Weaver Booz, Inc.
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