DSHW-2006-008873 - 0901a06880161e1c

April 12, 2006

Paul Hancock, Manager
Environmental Remediation
ATK Thiokol
P.O. Box 707
Brigham City, Utah 84302-0707

Subject: Post-Excavation Sampling at M-39 and M-636
(Final Closure Certification Report)
Response to Comments
ATK Thiokol – Promontory EPA ID #009081357

Dear Mr. Hancock:

This letter provides Division responses to ATK response comments regarding closure of M-39 and M-636. Unless noted below, the responses to other comments were acceptable. The response
comments follow:

Section 2.3. Ecological Risk. The methodology deviates from the Ecological Risk Assessment Guidance for Superfund (USEPA, 1997) (ERAGS) and UAC R315-101. No information is provided
on the potential receptors and habitats at the site. No discussion of assessment endpoints, measures of exposure, or measures of effects were provided. The evaluation of cadmium is
acceptable because the USEPA has integrated most of these factors into the development of the soil screening levels. ATK should duplicate the ecological soil screening levels methodology
for silver or evaluate silver consistent with ERAGS. Some toxicity values for silver are available in the literature (e.g., Los Alamos National Laboratory Ecorisk Database). ATK should
evaluate chemicals without toxicity values as uncertainties. The uncertainty evaluation should focus on determining if site management decisions would be affected if toxicity values
were available. If adequate toxicity values are unavailable, a risk assessment to determine appropriate site management may not be possible. An alternative is to clean the site to
background levels.

Please explain why perchlorate was selected as a chemical of potential concern for the risk assessment. As shown in Table 3-1 and 3-2, perchlorate was not detected in soil and would
not be a chemical of potential concern unless the analytical reporting limits exceed risk-based concentrations.

While the Division does not understand why perchlorate was selected as a chemical of potential concern, we also find the provided rationale for not evaluating perchlorate in the risk
assessment unacceptable. ATK states that perchlorate was not evaluated because the USEPA has not formally released its evaluation. An uncertainty evaluation may be adequate if the
absence of toxicity values is unlikely to impact site management decisions.

Please provide a written response to each comment and a revised document or change pages within 45 days of the date of this letter. Thank you for your continued cooperation. If you
have any questions, please contact Chris Bittner or David Larsen of my staff at 538-6710.

Sincerely,

Original Document signed by Dennis R. Downs on 4/12/06

Dennis R. Downs, Executive Secretary
Utah Solid and Hazardous Waste Control Board

DRD/DCL/kk

c: Chris Bittner, DSHW
Lloyd C Berentzen, M.B.A., Health Officer, Bear River Health Department
Mike Gansecki, USEPA Region VIII

April 12, 2006
Page 2

TN200600310.doc
288 North 1460 West • PO Box 144880 • Salt Lake City, UT 84114-4880 • phone [phone] • fax [phone]
T.D.D. [phone] • www.deq.utah.gov

State of Utah

Department of Environmental Quality

Dianne R. Nielson, Ph.D.
Executive Director

DIVISION OF SOLID AND HAZARDOUS WASTE
Dennis R. Downs
Director

JON M. HUNTSMAN, JR.
Governor

GARY HERBERT
Lieutenant Governor