DSHW-2008-025202 - 0901a068801e21f1

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

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

Dear Mr. Gosen:

The Division of Solid and Hazardous Waste has completed its review of the response to comments and subsequent information that ATK submitted to this office on June 2, 2008 and July 30,
2008. Based on the information submitted in July, additional model runs were completed and convergence of the model was achieved using an additional solver (MOC). This information
addresses our comments (numbers one and three) regarding the stability and grid spacing of the flow model.

With this letter, the Groundwater Flow and Contaminant Transport Models for the ATK Promontory facility are hereby approved. Please be reminded that, in accordance with Post-Closure
Permit Conditions V.A.2. and V.A.3, ATK is required to submit a human-health risk assessment to the Executive Secretary within 180 days of approval of the models. The deadline for submittal
of the human-health risk assessment is March 2, 2009. An ecological risk assessment also needs to be submitted by ATK no later than one year from the approval date of the models.
The deadline for submittal of the ecological risk assessment is September 2, 2009.

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

Sincerely,

ORIGINAL DOCUMENT SIGNED BY DENNIS R. DOWNS ON 9/9/08
Dennis R. Downs, Executive Secretary
Utah Solid and Hazardous Waste Control Board

DRD\JV\tjm

c: Paul Hancock, ATK Launch Systems
Nancy Morlock, USEPA Region VIII

File to: ATK Launch Systems – Promontory

September 9, 2008
Page 2
TN200800743

September 9, 2008

288 North 1460 West • Salt Lake City, UT
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TN200800743 Printed on 100% recycled paper

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