DSHW-2007-008773 - 0901a06880163129

David P. Gosen, P.E.
Director, Environmental Services
ATK Launch Systems – Promontory
P.O. Box 707
Brigham City, UT 84302-0707

RE: Promontory Groundwater Flow and Contaminant Transport Models
ATK Launch Systems – Promontory Facility, EPA I.D. #UTD009081357

Dear Mr. Gosen:

Based on the results of the Promontory groundwater flow and transport modeling, which were presented and discussed at a meeting on September 13, 2007, at the EarthFax, Salt Lake City,
Utah office, between the Division of Solid and Hazardous Waste, ATK, and EarthFax, we would like to inform you with this letter that we support the future utilization of the “new” groundwater
flow model.

We understand that the “new” model incorporates some important subsurface features (among them a perched aquifer along a portion of the eastern boundary of the model domain), and that,
in addition, even without a full recalibration of the flow model, the TCE contaminant transport run yields a lower root mean of squared residual errors (RMS), as well as a lower mean
of absolute residual errors (MA).

Please use this “new” model to complete the remaining contaminant transport scenarios, and submit the final groundwater model report to the Division by December 7, 2007.

Thank you for your professional cooperation. If you have any questions, please contact Jeff Vandel of my staff at 538-6170.

Sincerely,

ORIGINAL DOCUMENT SIGNED BY DENNIS R. DOWNS ON 9/19/07
Dennis R. Downs, Executive Secretary
Utah Solid and Hazardous Waste Control Board

DRD\JV\tjm

c: Paul Hancock, ATK Launch Systems
Richard White, EarthFax Engineering, Inc.

September 19, 2007

TN200701070
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

Richard W. Sprott
Executive Director

DIVISION OF SOLID AND HAZARDOUS WASTE

Dennis R. Downs
Director

JON M. HUNTSMAN, JR.
Governor

GARY HERBERT
Lieutenant Governor