DSHW-2006-008875 - 0901a06880161e1e

Paul Hancock, Manager
Environmental Remediation
ATK Thiokol Inc. – Promontory
P.O. Box 707
Brigham City, UT 84302-0707

RE: Groundwater Risk Assessment Work Plan
ATK Thiokol – Promontory Facility
EPA ID #009081357

Dear Mr. Hancock:

The Division of Solid and Hazardous Waste has reviewed ATK Thiokol’s response to our comments on the Groundwater Risk Assessment Work Plan that was submitted on December 9, 2005. Your
correspondence included responses to comment numbers one, two and six as requested by the Division. Based on the review of the original work plan and Thiokol’s response to our comments,
the work plan is hereby approved contingent on the implementation of the following two changes, both regarding comment number one.

First, additional sampling specifically related to the human-health risk assessment may be required. The conceptual site model must be developed, as discussed in more detail under comment
number four in our original review of the work plan, before it is determined that additional samples are not needed. It should not be assumed that additional sampling will not be required
before a rigorous conceptual site model is developed to assess possible exposure pathways.

Second, the groundwater risk assessment needs to be submitted to the Division sooner than the schedule proposed in your response to our comments. The Groundwater Flow and Contaminant
Transport Model submitted by ATK Thiokol is currently under review by the Division. Information generated by the model is necessary to completing the groundwater risk assessment. ATK
Thiokol needs to submit the human-health risk assessment within six months of the approval date of the model and the ecological risk assessment within one year of the approval date of
the model. In order to complete the human-health risk assessment in this shorter period of time, the Division recommends that the human-health and ecological risk assessments be submitted
separately.

A response to these two comments is not requested. ATK Thiokol may begin work on components of the risk assessment while the review of the groundwater model is completed. If you have
any questions, please contact Jeff Vandel at 538-6170.

Sincerely,

ORIGINAL DOCUMENT SIGNED DENNIS R. DOWNS ON 4/12/06
Dennis R. Downs, Executive Secretary
Utah Solid and Hazardous Waste Control Board

DRD\JV\tm

c: Lloyd C. Berentzen, M.B.A., Health Officer/Director, Bear River Health Dept.
Nancy Morlock, USEPA Region VIII
Chris Bittner, DSHW

File to: ATK Thiokol Inc. - Promontory

April 12, 2006
Page 2

April 12, 2006

TN200600318.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