DSHW-2018-010622 - 0901a0688091c31b

DSHW-2018-010622 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. [phone]
www.deq.utah.gov Printed on 100% recycled paper
State of Utah
GARY R. HERBERT Governor SPENCER J. COX
Lieutenant Governor
Department of
Environmental Quality
Alan Matheson Executive Director DIVISION OF WASTE MANAGEMENT AND RADIATION CONTROL Scott T. Anderson Director
November 8, 2018

Kris Blauer, Manager Environmental Services ATK Launch Systems – Promontory P.O. Box 707
Brigham City, Utah 84302-0707
RE: Review of the Updated Groundwater Flow and Contaminant Transport Model UTD009081357
Dear Mr. Blauer:
The Division of Waste Management and Radiation Control has completed its review of ATK’s Updated Groundwater Flow and Contaminant Transport Model. The following comments are provided for your response:

1) Separate Aquifers, p.3: The text states, “The agency has recently indicated that they are now comfortable with the model showing separate aquifers if needed to provide better predictive results. This current model update was
performed with the separate aquifers in mind.” Please explain how the separate aquifers are set up in the
six-layer model. Was the flow model modified? Is a specific layer set up to represent the perched aquifer everywhere in the model domain, followed by a low conductivity zone to represent an aquitard? Does its thickness vary over the model domain? Please elaborate.
2) Groundwater Contaminant Transport Calibration, p.5:
The text states that calibration targets for the mean average error, normalized root mean square error, and mass balance error were all achieved. Is it possible to supply calibration charts for the flow model (e.g., observed vs. modeled heads) and the transport model (e.g., observed vs. modeled TCE and
perchlorate concentrations)? These charts seem to be missing in the appendices. What is the rationale
for performing linear interpolation from measured values in model cells to estimating perchlorate mass concentrations, as concentration data can be non-linear? Please elaborate.

3) Alternatives Recommendation, p. 6: The text states that two alternatives were considered: Alternative 1: Full and instantaneous remediation of all source areas.
Alternative 2: No remediation of or continued contaminant input at any source area.
It is unclear which alternative is recommended, or if there is any alternative in between these two bounds which is preferred. Were the predictions in both cases run without any perchlorate emanating from M-136-associated source areas entering the model domain? Please elaborate.

Please provide your responses to the Division at your earliest convenience. If you have any questions, please call Helge Gabert at [phone]. Sincerely,

Scott T. Anderson, Director Division of Waste Management and Radiation Control

STA/JV/kl c: Lloyd Berentzen, MBA, Health Officer, Bear River Health Department Grant Koford, EHS, Environmental Health Director, Bear River Health Department
Amy Hensley, USEPA, Region 8
Paul Hancock, ATK Launch Systems