DSHW-2005-002242 - 0901a0688013c756

ATK
ALLIANT TECHSYSTEMS
6 December 2005
8200-FY06-032
Mr. Dennis R. Downs, Executive Secretary
State of Utah
Department of Environmental Quality
Division of Solid and Hazardous Waste
288 N. 1460 W.
P.O. Box 144880
Salt Lake City, Utah 84114-4880
ATK Thiokol Inc.
P.O. Box 707
Brigham City, UT 84302-0707
Tel [phone]
Fax [phone]
RECEIVED
DEC - 9 2005
UTAH DIVISION OF
SOLID & HAZARDOUS WASTE
Dear Mr. Downs
ATTENTION: Jeff Vandel
Subject: ATK Response to Division Comments Related to the Groundwater Risk
Assessment Work Plan, ATK Thiokol - Promontory Facility, EPA ID
#009081357
The Division of Solid and Hazardous Waste sent comments on the ATK Groundwater Risk
Assessment Work Plan in a September 21, 2005 letter. The letter requested that we respond to
comments one, two and six. Attached, please find responses to these comments.
We appreciate your understanding in our delay in responding to these comments due to the death
of John Holladay who was working this project.
If you have any questions regarding these responses, please direct them to myself at (435) 863-
3344.
Sincerely
Paul V Hancock, Manager
. Environmental Remediation
REPONSE TO SELECTED STATE COMMENTS:
ATK THIOKOL PROMONTORY GROUNDWATER RISK ASSESSMENT
WORK PLAN
6 December 2005
1. Comment: Please include a schedule that identifies when the sampling will be completed,
when the data will be available, and when the assessment will be submitted.
Response: Additional sampling specifically related to the human-health risk assessment
is not anticipated under this work plan. It is, however, currently anticipated that
ecological evaluations of areas of potential exposure will be completed within 6 to 12
months of work plan approval. The precise schedule will depend on the timing of work
plan approval relative to the season when such evaluations should be conducted. For
example, if the work plan is approved in December, a 4 or 5 month waiting period may
be needed before ecological evaluations could effectively be started. The results of
ecological evaluations should be available within 3 moths of completing the field
evaluations. A draft of the human and ecological risk assessment should be available
within 6 months of approval by the State of the ecological evaluation report.
2. Comment: Chapter 1, Introduction. How does Thiokol propose to use the results of the
groundwater flow and contaminant transport models in the human health and ecological
risk assessments?
Response: The risk assessments will identify risk-based concentrations for contaminants
of potential concem at points of human and ecological exposure to groundwater. The
groundwater modeling effort will be used to predict future concentrations at those same
points of potential exposure. Hence, the models will assist in delineating long-term
concentrations (and, hence, risk) and will allow future remediation efforts, if required, to
concentrate on areas of highest risk.
6. Comment: Section 2.3.1, Screening-Level Ecological Risk Assessment. "These data will
be combined with the contaminant fate and transport concepts discussed previously to
identify potential mechanisms of ecotoxicity associated with the contaminants and their
potential receptors." This statement is unclear and should be clarified. For instance,
where are the fate and transport discussions? Mechanism of ecotoxicity refers to how a
chemical causes adverse health effects. This information is part of the derivation of
toxicity values for ecological receptors but the link with fate and transport characteristics
is unclear.
Response: ATK agrees that the sentence, as written, is unclear. The paragraph in which
this sentence occurs will be re-written as follows:
Using the data evaluated in the human health risk assessment, contaminants of potential
ecological concem and their maximum detected concentrations will be tabulated.
Groundwater pathways by which these contaminants may reach exposure points will be
identified using the groundwater flow and contaminant transport models currently being
developed for the site. These models will also be used to predict future concentrations of
the contaminants of potential concem at those exposure points, thereby allowing an
estimation of whether future concentrations will exceed historic concentrations.
Maximum historic or predicted concentrations will be documented for each contaminant
of potential concem. Potential mechanisms of ecotoxicity will be determined, for those
contaminants with a complete exposure pathway, based on a review of published
literature.