DSHW-2024-005503

DSHW-2024-005503 195 North 1950 West • Salt Lake City, UT
Mailing Address: P.O. Box 144880 • Salt Lake City, UT 84114-4880
Telephone [phone] • Fax [phone] • T.D.D. 711
www.deq.utah.gov
Printed on 100% recycled paper
State of Utah

SPENCER J. COX
Governor

DEIDRE HENDERSON
Lieutenant Governor
Department of
Environmental Quality

Kimberly D. Shelley
Executive Director

DIVISION OF WASTE MANAGEMENT
AND RADIATION CONTROL

Douglas J. Hansen
Director

March 29, 2024

Kris Blauer, Manager Environmental Services
Northrop Grumman Systems Corporation
P.O. Box 707
Brigham City, UT 84302-0707

RE: Soil Vapor Probe Installation and Sampling Report
Post-Closure Permit
ATK Launch Systems LLC. – Promontory
Northrop Grumman Systems Corporation
EPA ID UTD009081357

Dear Mr. Blauer:

The Division of Waste Management and Radiation Control (Division) has completed a review of the
Soil Vapor Probe Installation and Sampling Report (Report) dated December 21, 2023, and prepared by
Geosyntec Consultants for the ATK Launch Systems LLC. – Promontory Facility. Soil vapor probe
installation and sampling activities were conducted in accordance with the work plan approved by the
Division to evaluate vapor intrusion modeling and to support the groundwater human health risk
assessment (HHRA) for the site.

The Report includes a summary of field investigation activities, soil vapor sampling, laboratory analysis,
and data validation. The Report also includes vapor intrusion modeling results using the United States
Environmental Protection Agency (U.S. EPA) Johnson and Ettinger (J&E) model. The model calculates
trichloroethene soil vapor concentrations vs depth for comparison with measured data. The Report
concludes that the U.S. EPA J&E modeling results provide conservative estimates of vapor migrations
in the subsurface and further support conservative risk estimates in the groundwater HHRA at the site.

Based on the Division’s review, the Report appears to be acceptable and is hereby approved.

(Over)

If you have any questions, please call Hao Zhu at 801-558-9833 or Karen Wallner at 385-499-0218.

Sincerely,

Douglas J. Hansen, Director
Division of Waste Management and Radiation Control

DJH/HZ/wa

c: Dorothy Adams, Interim Director, Salt Lake County Health Dept.
Ron Lund, Environmental Health Director, Salt Lake County Health Dept.
Eric Peterson, Environmental Health Deputy Director, Salt Lake County Health Dept.
Jesse Newland, U.S. EPA, Region VIII
Brian Smith, Geosyntec Consultants (Email)
Blair Palmer, Northrop Grumman Systems Corporation (Email)
Tim Jimenez, Northrop Grumman Systems Corporation (Email)
Kris Blauer, Northrop Grumman Systems Corporation (Email and Hard Copy)
Karen Wallner, Division of Waste Management and Radiation Control, UDEQ