HomeMy WebLinkAboutDSHW-2005-009764 - 0901a068801660d3
Paul Hancock, Manager
Environmental Remediation
ATK Thiokol Inc. – Promontory
P.O. Box 707
Brigham City, UT 84302-0707
RE: Review of the Groundwater Risk Assessment Work Plan, ATK Thiokol – Promontory Facility, EPA ID #009081357
Dear Mr. Hancock:
The Division of Solid and Hazardous Waste has reviewed the Groundwater Risk Assessment Work Plan (Work Plan) that was prepared by EarthFax Engineering, Inc. and submitted to our office
on May 23, 2005. The Division requested the Work Plan because it is generally more efficient to reach agreement on the various details of the risk assessment prior to completing risk
calculations. If details or factors used in risk assessment calculations need to be changed, the calculations may need to be redone.
The Work Plan that was submitted included very little detail on the technical aspects of how the risk assessments will be conducted. Consequently, most of the comments that are enclosed
are general in nature. The enclosed list of comments was compiled from the individual comments of Chris Bittner and Jeff Vandel of my staff and Chris Cline, Contaminants Biologist,
U.S. Fish and Wildlife Service, Utah Ecological Services Field Office. As you are aware, Ms. Cline has been participating in the Technical Advisory Group that was formed to work on
the Fat-whorled Pondsnail Conservation Plan. This conservation plan was generated in an effort to protect the Fat-whorled Pondsnail population that exists in springs along the southern
border of the ATK Thiokol facility.
Although most of the comments are general in nature, and are meant to assist you in the preparation of the risk assessment, there are some comments for which the Division requests a
response to from ATK Thiokol. Please submit a written response to comments number one, two, and six within 30 days of the date of this letter. The Division is not requesting that ATK
Thiokol revise the Work Plan; however, we urge ATK Thiokol to contact Jeff Vandel or Chris Bittner at 538-6170 if you have any questions regarding the preparation of the risk assessment
or this correspondence.
Sincerely,
ORIGINAL DOCUMENT SIGNED BY DENNIS R. DOWNS ON 9/21/05
Dennis R. Downs, Executive Secretary
Utah Solid and Hazardous Waste Control Board
DRD\JV\ts
c: Lloyd C. Berentzen, M.B.A., Health Officer/Director, Bear River Health Dept.
Nancy Morlock, USEPA Region VIII
Chris Cline, Contaminants Biologist, U.S. Fish and Wildlife Service, Utah Ecological Services Field Office
Richard B. White, P.E., President, EarthFax Engineering, Inc.
File to: ATK Thiokol Inc. - Promontory
ATK Thiokol Groundwater Risk Assessment Work Plan
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.
Chapter 1, Introduction. How does ATK Thiokol propose to use the results of the groundwater flow and contaminant transport models in the human health and ecological risk assessments?
Section 2.2 Human Health Risk Assessment. The work plan proposes to select chemicals of potential concern using comparisons with risk-based concentrations. The risk-based concentrations
must be documented to comply with the requirements of R315-101. For instance, USEPA Region 9 Preliminary Remediation Goals do not meet the requirements of R315-101 because neither cumulative
exposures to multiple chemicals or vapor intrusion are considered. Chemicals lacking data to calculate risk-based concentrations should be included as chemicals of potential concern.
Section 2.2 Human Health Risk Assessment. It is stated in this section of the Work Plan that “potential receptors and exposure pathways will be identified through development of a conceptual
site model. Only exposure to groundwater, groundwater-impacted soil, and groundwater-impacted domesticated animals will be included in this human health risk assessment.”
The sources of potential exposure that will be assessed shouldn’t be identified before the conceptual site model is developed. For example, game birds have been raised on private property
south of the Thiokol facility using surface water that originates at contaminated springs. Perchlorate has been detected in the stream on the private property. If game birds are raised
on water that has been impacted with COCs and the birds are shot and then consumed, this is a potential exposure pathway that needs to be assessed. Are surface water or groundwater-impacted
crops a potential source of exposure? Is the inhalation of indoor air that has been impacted by organic COCs volatilizing from contaminated groundwater a potential exposure pathway?
It is essential to develop a thorough conceptual site model (CSM) so these kinds of questions can be answered and the appropriate exposure pathways are assessed. The CSM should detail
contaminant sources, fate and transport mechanisms, and pathways through environmental media to potential receptors, both human and ecological. The objective of the CSM is to ensure
that all appropriate receptor types and pathways are identified and evaluated, and conversely, to eliminate inapplicable pathways from further consideration. In addition, the CSM will
help identify what data is needed so that these exposure pathways may be assessed.
Section 2.3.1, Screening-Level Ecological Risk Assessment. The samples collected for the human health risk assessment (HHRA) may not be adequate for characterizing risks to ecological
receptors. The exposure to aquatic, sediment-dwelling, and terrestrial (both soil-dwelling and free-ranging) ecological receptors by pathways that exist should be discussed in the ecological
component of the CSM. If mobilization costs for sampling are significant, ATK Thiokol should consider attempting to identify data needs prior to preparing the risk assessment.
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.
The components of a good Screening-Level Ecological Risk Assessment (S-ERA) are:
1) A good CSM that ensures that all relevant ecological exposure pathways and receptors are evaluated.
2) A demonstration that datasets used in the S ERA are adequate to assess exposure to those receptors along those pathways. In the case of a S ERA, the facility should be able to demonstrate
that maximum likely exposure concentrations have been identified and characterized for each pathway/receptor/constituent class.
3) A good identification and selection of conservative benchmark concentrations for all relevant media and receptor classes (e.g., aquatic wildlife, sediment dwelling wildlife, terrestrial
wildlife).
Using these guidelines, if a pathway/receptor/constituent class is screened out, the facility, regulators, and public can have maximal confidence that the risk associated with that unit
is below levels of concern, and that there is good reason to continue analysis (at a baseline level) for pathway/receptor/constituent classes that remain after the screening
step. These three components of a good S-ERA are discussed in more detail below:
1) As mentioned above, start the S-ERA out with a good CSM . This is especially appropriate for a S ERA because it forms the “universe” that both the S ERA and any future baseline ecological
risk assessment (B ERA) will be based upon. For the screening-level problem formulation, the risk assessor develops a CSM for the site that addresses five issues (Ecological Risk Assessment
Guidance for Superfund USEPA, 1997):
Environmental setting and contaminants known or suspected to exist at the site;
Contaminant fate and transport mechanisms that might exist at the site;
The mechanisms of ecotoxicity associated with contaminants and likely categories of receptors that could be affected;
What complete exposure pathways might exist at the site (a complete exposure pathway is one in which the chemical can be traced or expected to travel from the source to a receptor that
can be affected by the chemical); and
Selection of endpoints to screen for ecological risk.
The work plan attempts to identify the appropriate exposure pathways and toxicity values without identifying the other components of the CSM. The adequacy of the exposure pathways proposed
in the work plan cannot be determined based on the information provided.
2) As stated above, a common short coming of ecological risk assessments (ERA) is that in sharing data used for the HHRA, oftentimes sampling points and datasets that are appropriate
for HHRA are not complete with respect to an ERA. As part of the problem formulation phase of the S-ERA, ATK Thiokol should evaluate and describe whether the existing environmental
media dataset is complete and appropriate for performing the
B-ERA. A good way to do this is to evaluate the CSM by “likely” pathway/receptor/constituent class, and make a determination for each of those classes as to whether there is adequate
data to assess its ecological risk. If the answer is “no” for any CSM component, that may be cause for moving that class on to further evaluation in a B-ERA, collecting additional data
to fill that gap (in consultation with regulators), or at the very least, covering that unit in a qualitative risk and uncertainty assessment (realizing that this may still mean that
the "unit" is moved on to a B ERA).
The ability to perform this kind of systematic analysis is another good reason to have a good CSM. With respect to ecological receptors, particular attention should be paid to likely
ecological exposure routes: surface water, soils and sediments.
3) Be sure that ecological benchmark selection is appropriate for a S-ERA, and that appropriate benchmarks are selected for all pathways and receptors. If NOAELs are to be used, how
will ATK Thiokol ensure that they are adequately conservative, particularly for constituents where there may be a minimum amount of toxicological information (e.g., perchlorate)? Benchmark
selection should be consistent with EPA guidance. Common sources are: soil USEPA Ecological Soil Screening Levels (ESSLs); sediment Ingersoll McDonald Consensus Sediment Quality Screening
Concentrations; water National Ambient Water Quality Criteria concentrations (protective of aquatic life under chronic exposure conditions). There may be other databases of screening
concentrations available (e.g., Oak Ridge, EPA Region 5, etc.).
The S ERA should include a table of Benchmark concentrations used, their source, and justification for their selection. If benchmarks cannot be identified for a particular pathway/receptor/constituent
class, that class is (by definition in the EPA S ERA guidance) moved on to the B-ERA.
September 21, 2005
Page 2
September 21, 2005
TN200501189.doc
288 North 1460 West • PO Box 144880 • Salt Lake City, UT 84114-4880 • phone (801) 538-6170 • fax (801) 538-6715
T.D.D. (801) 536-4414 • www.deq.utah.gov
State of Utah
Department of Environmental Quality
Dianne R. Nielson, Ph.D.
Executive Director
DIVISION OF SOLID AND HAZARDOUS WASTE
Dennis R. Downs
Director
JON M. HUNTSMAN, JR.
Governor
GARY HERBERT
Lieutenant Governor