DSHW-2002-001690 - 0901a06880132596

ATK
ALLIANT TECHSYSTEMS
DECEIVED
Michael S. Robbinson
Vice President
Environmental Safety & Security
5060 Uncoln Drive
Edina, MN 56436
Phone: [phone]
E-mail: [e-mail]
lAY 0 3 2002
C?:L. 0/5~00
DWSiOBof Solid & Haiardous Waste
'•flU ffftnsrtmBnt nf Fnvironmental QHaHf
April 30, 2002
Kipp and Christian, P.C.
Attention: Gregofy J. Sanders
10 Exchange Place
Fourth Floor
Salt Lake City, Utah 84111
Dennis R. Downs, Executive Secretary
State of Utah
Department of Environmental Quality
Division of Solid and Hazardous Waste
288 N. 1460 W.
P.O. 80x144880
Salt Lake City, Utah 84114-4880
Subject: Response to Comments on the Draft Screening Level Endangerment Assessment
(SLEA) of the Promontory Facility
Dear Mr. Sanders and Mr. Downs,
ATK, as well as the ATK Thiokol Propulsion facility thank you for your comments on the Draft ofthe
Screening Level Endangerment Assessment (SLEA) perfonned on the Promontory facility. Many of
the comments provided are being used in the preparation of the final SLEA document by Walsh. We
anticipate the document will be completed, and a copy delivered to you by approximately May 3,
2002.
Walsh has presented ATK with their responses to your comments. They are enclosed for you here,
along with this transmittal letter which seeks to provide an overall framework for the comments from
ATK's perspective, as well as a path we see going forwanj.
As you recall, ATK acquired the Thiokol Propulsion facility from Alcoa as a part of its acquisition of
Cordant Technologies in April 2001. Due diligence review of the facility's environmental condition
was accomplished priorto the acquisition, resulting in the determination that while there was a
substantial amount of remediation yet to be accomplished at the site, considerable work had been
accomplished in evaluating, and in some cases remediating, the site for historical contamination
from past practices.
Upon the notice of a pending RCRA Citizens Suit, and the subsequent meeting with Connor Cattle
Company and Utah Department of Environmental Quality (UDEQ) representatives, ATK proposed
conducting an SLEA of the Promontory facility in an attempt to determine if there were significant
off-site exposures currently occurring from the facility. The SLEA would also serve the purpose of
identifying any areas where insufficient data existed to make a determination as to whether
significant off-site exposures were or may be occurring. ATK commissioned Walsh Environmental in
September 2001 to conduct this SLEA with the purpose of getting the answers it could within a fairiy
short amount of time.
1
ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
Walsh Response to Comments
From Utah Department of Environmental QuaUty (January 30,2002)
Comments on the PreUminary Draft Screening Level Endangerment
Assessment for the Thiokol Propulsion Promontory Facility
Note: Comments are in plain text, responses are in italics.
Executive Summarv
1. Are any ofthe approximately 30 compounds that represent data gaps potentially
significant constituents that could be released to the environment at Thiokol?
• The SLEA will be amended to more clearly document data gaps for pathways of
concem, including the 30 referenced compounds, however further evaluation of those
data gaps is not in the scope ofthe SLEA.
Section 1 - Goals and Objectives
1. It is stated in this section that "this SLEA does not address dioxin and related
compounds, which may be emissions sources from open buming as these are being
separately assessed by Thiokol and UDEQ."
Dioxin-like (those with a USEPA 2,3,7,8 - tetrachlorodibenzo(p) dioxin toxic
equivalency factor) chemicals have been observed in bang box emissions from
buming plastics and other duimage or reactive chemicals with perchlorate. The health
risk associated with dioxins and related compounds generated by open buming will
be evaluated through the risk assessment that is required as part of the permit
appUcation. Any otiier potential sources of dioxins and related compounds would not
be assessed through this process.
The SLEA should therefore consider whether other potential sources of dioxin exist
which would create a data gap that requires additional analysis.
Finally, the Division does not expect to conduct an independent analysis of dioxin
emission, but will be overseeing Thiokol's evaluation. As cunentiy written, the
statement quoted above may be accurate.
• The SLEA will be amended to clarify that potential dioxin and related compound
impacts to off-site receptors from current open burning/open detonation processes
are being evaluated by Thiokol and reviewed by UDEQ as part ofa RCRA permit
application.
• The SLEA will be amended to state that Walsh is not aware of any other current
facility processes (aside from open burning/open detonation) which have the potential
to generate dioxin and related compounds that may impact off-site receptors.
thiokol.slea.responses.udeq.043002.docPage I of 5 4/30/2002
ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
Section 2 - Source Characterization
1. Off-site soils should be considered potential receptors of on-site sources as was done
for off-site springs and smface water.
• The SLEA will be amended to clarify that off-site soils are potential receptors of on-
site sources, however there are very few off-site soils data and consequently this will
be discussed as a data gap.
2.2.1 -Reported Hazardous Air Pollutants
1. The EPA Screening model SCREEN3 only evaluates air expostu-es (no deposition
to soil, etc.) but it is conservative for assessing inhalation exposiu-es.
• The SLEA is being amended to better define the assumptions used in the SCREEN3
model for Hazardous Air Pollutant, and the Uncertainty section is being modified to
better justify why this model is believed to produce conservative (health protective)
results.
• The SLEA is being amended to clarify that deposition to off-site soil is a potential
pathway for on-site air emissions.
2.2.2 -Open Buming Emissions
1. A list ofthe waste streams that were included in the emissions calculations, as they
appear on waste profile sheets, should be included in the report so it can be seen
which ones were included.
• The draft SLEA will be revised to provide a list ofthe waste streams, as they appear
on waste profile sheets, which were included in the emissions calculations.
2. It is stated in this section that "the chemical constituent air emissions from these open
buming operations were calculated using the emission factors for 1.3 propellants."
Were emission factors for 1.1 propellants not included in the calculations?
• The SLEA will be amended to explain that emissions from 1.3 propellants were
modeled because they are burned in much larger quantities than I.I propellants and
because I.I propellants do not contain any contaminants that are not already being
evaluated using 1.3 propellant assumptions.
3. The Division made a number of comments on the open buming modeling that was
performed for the RCRA Part B permit application that was submitted in 1991. These
comments are included in the Notice of Deficiency that the Division provided
Thiokol in November, 1993. It is understood that conservative assumptions were used
when predicting emission concentrations fi-om open buming, however, it is not
known how the concems identified in 1993 impact the results obtained by Walsh.
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
Walsh Response to Comments
From Connor Cattle (February 26,2002)
Regarding PreUminary Draft Screening Level
Endangerment Assessment
Note: Comments are in plain text, responses are in italics
The comments provided below address the Preliminary Draft Screening Level
Endangerment Assessment ("SLEA"), prepared by Walsh Environmental Scientists &
Engineers/Ecology & Environment ("Walsh"), dated December 20, 2001. The SLEA has
been prepared to address the ATK Thiokol Propulsion ("Thiokol") Promontory Facility
("Site") in northem Utah.
General Comments
1. It appears that the SLEA document has been prepared, as much as possible, to
circumvent or prevent any potential liability on Thiokol's part. For instance, it
does no appear that any soil testing or off-site soil sampling has been conducted,
when such testing is clearly warranted. It seems that is may be helpful for the
Holmgren's property and other off-site properties to have been sampled,
particularly for those contaminants that have akeady been identified in certain on-
site disposal areas.
• The SLEA was prepared to address the Goals and Objectives presented in
Section 1 (page I). While it may be useful to conduct additional soil testing or
additional off-site soil sampling for other purposes at the site, such testing
and sampling were beyond the scope and time limitations ofthe SLEA.
• The SLEA will be amended to clearly indicate that sampling was not
conducted.
2. It seems that all efforts at evaluating risk are associated with or focused on the
current on-site contamination, rather than cunent consequences of past
contamination. In other words, it seems that the Endangerment Assessment is
intended to address off-site or associated problems that originate with or derive
fi-om current on-site conditions, once or after those on-site conditions become
subject to the Resource Conservation and Recovery Act ("RCRA") or major
federal and state environmental statutes (see e.g., the document's reference to
review of databases under RCRA, Toxic Release Inventory ["TRI"], etc.).
• The SLEA presents a comprehensive evaluation of on-site contamination
(focused on the site boundary) from current operations.
• The SLEA also presents a partial evaluation of on-site contamination from
previous operations, based on two approaches. First, current analyses of
contamination (such as soils or groundwater) are indicative of contaminants
from previous operations which are persistent and have not been transported
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
off-site. Second, contaminants of concern were in part identified (for
example, see Table I under "Groundwater-Suspected") by reviewing permits
and monitoring requirements and reports that themselves are partially based
on information going back to the 1970s (e.g., the Remedial Facility
Investigation and the Comprehensive Groundwater Monitoring Evaluation).
• The SLEA presents a partial evaluation of off-site contamination where data
or modeling estimates were available (e.g., off-site surface water data are
described in Section 2.6 and off-site air emissions are described in Section
2.2).
• The SLEA will be amended to clearly indicate the completeness or limitations
of current and historical data and information, both on- and off-site.
3. Estimation of concentrations of Potential Contaminants of Concem ("PCOC") at
or beyond the Site perimeter was apparently attempted for air exposures, but no
estimations are provided for concentrations of PCOC in groimdwater or surface
water. In fact, the off-site concentrations are inappropriately assumed to be
essentially the same as "fence line" concentrations.
• "Fence line" groundwater concentrations were estimated using both on-site
and selected off-site wells, where data were available (see off-site wells EW-6,
BC-2, and G-3 on Figure 1 Site Map). The estimated Upper Confidence Level
of these "fence line" concentrations is greater than any other off-site wells for
selected parameters (for example, the "fence line" Perchlorate UCL
estimated for groundwater is 32,800 pg/l and the highest detection at any
other off-site well is 8.2 pg/l at Adams North Well).
• "Fence line" surface water concentrations were also estimated using both on-
site and off-site sampling locations, where data were available (see off-site
locations such as Meyers, Quaky, Powerline, Fork, and various Holmgren
springs on Figure I Site Map). The SLEA uses the maximum concentration
detected from these on- and off-site locations (for example, the "fence line"
Perchlorate in surface water is the maximum detected level of 147 pg/l from
Pipe Springs).
• The SLEA will be amended to clearly indicate how "fence line"
concentrations were derived.
4. It is premature and inappropriate for the SLEA to define which PCOC are "likely,
unlikely or uncertain" to cause short- or long-term effects on human health or the
environment. The absurdity of this categorization is obvious given that
molybdenum for example, is included in the list of PCOC that are "Uncertain, as
to whether off-site impairment is caused", and yet, the scientific data clearly
demonstrate short- and long-term impacts from molybdenum to on-site and off-
site receptors and the environment. This mis-categorization calls into question the
classification of the other PCOC, in addition to molybdenum. It would be more
appropriate for the SLEA to simply identify all of the PCOC and identify those
data gaps and investigations needed to resolve whether inclusion of those
contaminants is appropriate in the future, once the needed data has been collected.
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
• The terms "likely, unlikely, or uncertain " are used in the SLEA in a relative
and qualitative manner and are not derived using any scientific protocol. The
terms were intended to assist the layperson in evaluating which contaminants
may be of greater or lesser concem. This SLEA will be amended to clarify
this distinction.
• While on-site molybdenum concentrations may have contributed to the
impairment of cattle grazing on-site, the SLEA focuses on potential off-site
impairment. Off-site concentrations of molybdenum in vegetation are shown
in the Figure 1 Site Map, and since some of those concentrations exceeded the
2 ppm screening level for vegetation shown on Table 25, this parameter was
listed as a Preliminary Contaminant of Concem for vegetation. The authors
are unaware of any benchmark value for wildlife that definitively demonstrate
off-site impairment to ecological receptors due to molybdenum. Figure I Site
Map will be amended to show the location of six dead cows; however these
cattle were all located in on-site leased grazing areas.
• The SLEA will be amended to more clearly identify data gaps. The scope of
the SLEA did not include recommendations for future investigations.
5. The document presupposes, perhaps through the total absence of discussion, that
the existing exposure pathways and land use will not change in the future. This is
likely not the case, and certainly not an appropriate assumption on which to base
an analysis over the next 70 or more years. The SLEA should be conducted with
the most sensitive land use and exposure scenarios in mind. The SLEA should
also evaluate sensitive populations, including children.
• The SLEA did not presuppose any land use. Both acute (short-term) and
chronic (lifetime) criteria for contaminants are presented and compared to the
levels detected. The sources for these criteria are presented in the Human
Health and Ecological Assessment portions ofthe SLEA. However, the SLEA
will be amended to more clearly document the assumptions (duration,
exposure scenarios, etc.) that form the basis for these criteria, including
whether they are intended for evaluating impairment to adults or children.
6. It is apparent that some from of medical monitoring may be appropriate,
especially given the potential historical exposures that long-time residents may
have - and possibly continue to experience. Off-site residents, ranchers in
particular, may have experienced the cumulative effects from inhalation, dermal
exposure and ingestion of surface water, groundwater and soil from their youth
through adulthood. With their historical access to leased lands, these potential
rancher receptors may have experienced exposures as both off-site residents as
well as on-site workers.
• Walsh believes that medical monitoring at this point would be premature. If
risk calculations derived using conservative but reasonable assumptions
indicate potential adverse effects on human health, taking site-specific
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
exposure scenarios into account, a focused medical monitoring program
could be considered at that time.
Perchlorate is an important PCOC at this site. At the time the SLEA was written
the United States Environmental Protection Agency's ("EPA") action level was
18 fAg/L defined from risk assessments that were available in 1997. Since the
issuance of the SLEA, calculations based on EPA's recently released draft
reference dose' ("RfD") suggest protective concentrations of 1 and 0.3 jxg/L for
the adult and child respectively. The estimated No Adverse Effect Level
("NOAEL") of 0.001 mg/kg/day (Lowest Observed Effect Level ["LOAEL"] of
0.01 mg/kg/day divided by 10) conesponds to a drinking water concenfration of
70 ng/L for the adult and 10 p,g/L for the child. Based on this evaluation by EPA,
state organizations, specifically the Califomia Department of Health Services
("DHS") has concluded that its action level needed to be revised downward.
Accordingly, DHS has reduced the perchlorate action level to 4 ^g/L, the same
level as the lower ofthe 4-to 18-|xg/L range that provided the prior action level.
The 4-|xg/L Action Level also conesponds to the current detection limit for
purposes of reporting ("DLR"). The DLR is the level at which EPA is confident
in the quantitation of the contaminant in drinking water. If analytical methods
improve and the DLR can be lowered, the regulatory agencies may reduce the
action level further until development of a perchlorate Maximum Contaminant
Level ("MCL") in drinking water.
In other words, the action level for risk characterization for perchlorate has been
substantially lowered recently, highlighting the significance of evaluating the
exposure of this chemical to on-site and off-site workers and residents near the
Site. See Table 1 below.
Table 1. Comparison of US EPA's evaluation of perchlorate.
Parameter
No or low/est observed adverse effect level
(NOAEL or LOAEL) Units = mg/kg/day
Uncertainty Factor (UF) (product ofthe following
factors, e.g., 10x10x1)
Factor to account for intrahuman
variability within people
Factor to account for a study of short
duration, instead of a long-term "chronic"
study
USEPA
(1992)
0.14
1,000
10
10
USEPA
(1995)
0.14
300-1,000
10
10
USEPA
(1998) draft
0.1
100
3
1
USEPA
(2002) draft
0.01
300
3
3
' us EPA, 2002, Perciilorate Environmental Contamination: Toxicological Review and Risk
Characterization, Extemal Review Draft, NCEA-1-0503, January 16, 2002.
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
Factor to account for deficiencies in data
available on the effects of perchlorate
• Factor to account for interspecies
extrapolation
• Factor for use of minimal LOAEL rather
than NOAEL
"Provisional" Reference Dose (RfD) = NOAEL/UF,
or LOAEL/UF Units = mg/kg/day
Corresponding drinking water concentration;
assumptions = 2 liters/day and 70-kg body weight
for adult.
Corresponding drinking water concentration;
assumptions = 1 liters/day and 10-kg body weight
for child.
10
1
-
0.0001
4 Mg/L
1 pg/L
. ..
3-10
1
-
0.0001-
0.0005
4-18 Mg/L
1-5 pg/L
3
3
3
0.0009
32 Mg/L
10 Mg/L
3
3
10
0.00003
1 Mg/L
0.3 Mg/L
• The EPA published Draft perchlorate NOAEL and RfD levels shortly after the
SLEA was completed. These levels were identified as not to be quoted, and
subject to extemal peer review. The SLEA will be revised to refer to these
Draft levels.
8. The SLEA relies heavily on a number of historical modeUng studies. These
studies were presumably not scoped or conducted with the goals and objectives of
an endangerment assessment in mind. Consequently, these studies may or not be
appropriate for this SLEA. These studies may or may not be sufficiently
conservative, and may or may not be outdated. ModeUng has its limitations, as
we all know, and can readily be manipulated in favor of or against a particular
proposition. It is important that the modeling studies be summarized in this
document and the pertinent assumptions and results provided in appendices to the
SLEA. It is important that the limitations and assumptions be addressed in the
"Uncertainty" sections ofthe document.
• The SLEA describes the limitations of some ofthe models (see Section 2.2.2);
however these will be more clearly summarized in the Uncertainty section of
the amended document.
9. Throughout the text, in assessing impacts to ambient air from open buming, the
point is made repeatedly that the modeled values for 90 days were used because
they were more health protective than the 150-day bum day models. This point is
not intuitively obvious and should be explained for the uninitiated reader.
10.
• The amended SLEA will describe the assumptions that make the calculated 90
day duration of bums more health protective than the 150 day duration.
The SLEA should be expanded to include a history of site activities, including a
chronology of land use (specifying agriculture, industry, recreation, waste
deposition, and residential development).
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
• Documenting a history of site activities was beyond the scope of this SLEA,
although many ofthe references cited contain portions of such a history.
11. The SLEA should document the key site characteristics, including, geology,
hydrogeology and meteorological parameters. The SLEA should also evaluate all
possible contaminant sources, media, exposure pathways, land uses and receptor
populations (including sensitive populations). The document should include a
human health toxicity assessment section, much like the eco-toxicity section and
should be certain to select toxicity values consistent with EPA's Integrated Risk
Information System ("IRIS").
• Documenting site characteristics was beyond the scope ofthis SLEA, although
many ofthe references cited contain portions of such a history.
• The SLEA will be amended to clearly indicate any issues not covered,
including specific contaminant sources, media, exposure pathways, land uses,
and receptor populations (including sensitive populations).
• The SLEA will be amended to include a summary table stating human health
effects from selected contaminants, based on IRIS information. In addition,
the SLEA will explain that human health toxicity data and information are
separately available in a more comprehensive form from the ACGIH and
OSHA and were not reproduced in the document.
• The SLEA adopted toxicity levels which are promulgated in Utah Rule R307-
410, therefore the SLEA will be amended to clarify that these levels may be
different from those in the EPA IRIS database. A literature article (Williams,
et. al, 1994) will be cited which compares IRIS and ACGIH or PEL values.
Specific Comments
Executive Summary
Please note that a number of comments and suggestions are provided regarding the
Executive Summary, as this section of the document allowed for the first infroduction of
many of the tables by the authors. All of the comments provided below regarding the
Executive Summary pertain as well to each of the detailed sections that follow.
Comments regarding the Executive Summary have not been repeated, unless additional
detail was needed for clarification.
1. On page v, the "Goals" state that Thiokol retained Walsh to "evaluate whether
discharges from ongoing and/or existing soil/groundwater contamination from the
facility may be causing short- or long-term effects on human health or the
environment at sunounding off-site locations". This singular goal for the SLEA
is nanowly defined and should be broadened to address instead any and all
contamination that is the result of past and/or on-going operations from the
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
facility that may be causing, or could cause in the future, acute or chronic effects
on human health or the environment at both on-site and off-site locations.
• As addressed in the response to General Comment #2, the SLEA evaluates
past contamination by including data (such as current soils and groundwater)
that are indicators of past operations and parameters identified in reports,
such as the RCRA Facility Investigation, that were derived based on past
operations.
• We believe the SLEA provides a comprehensive assessment of current
operations and contamination.
• The SLEA does not address future potential operations or future potential
contamination that might migrate from on-site to off-site receptors if not
otherwise mitigated. This exclusion will be clarified in the amended SLEA.
• The SLEA excluded potential on-site impairment from the scope of work,
although some on-site data were used to evaluate potential off-site impacts
where no data were available. This exclusion will be clarified in the amended
SLEA.
1. On page v, the objective of "Identification of pathways which may fransport
chemicals from on-site sources to off-site human health and/or aquatic or
tenestrial ecological receptors" is overly limited in scope. The defmition of the
on-site area and off-site areas is especially important. Some of the area on-site
may be leased or otherwise used by potential off-site receptors.
• The scope ofthe SLEA did not include consideration of on-site exposures due
to leases or other activities. The SLEA will be amended to clarify that these
on-site pathways were not addressed.
3. On page v, the "Characterization of potential exposure to PCOC for off-site
human health and ecological receptors" should be expanded to include potential
exposures to on-site receptors.
• As noted in response #2, above, the scope of the SLEA did not include
potential on-site exposures.
4. On page vi, the SLEA states that "A wide variety of data and information was
requested and received from Thiokol, including: published and unpublished
reports, permits and monitoring data, underlying raw data which was used to
develop selected reports and monitoring, results of unpublished and published
modeling...". This information, should be referenced and cited in the report, the
source documents should be included in the Refer-ences and Citations section in
the report. To the extent that the SLEA relied upon this information for its
interpretations or conclusions, those documents should be included as appendixes.
• The amended SLEA will include references and citations to all sources of data
used in the report.
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
• Due to the volume of referenced sources, these materials are not included as
appendices in the SLEA but can be viewed separately in the project files
maintained by Walsh.
5. On page vi, the report states that "Walsh retains the responsibility and authority to
approve or reject solicited comments for the purposes of this SLEA". The
Executive Summary should describe whether this is a document for Thiokol's
intemal use or whether it will be made available to the public. If comments from
"the sunoxmding property owners, the State of Utah and Thiokol" may be
approved or rejected by Walsh, will the entirety of those organizations' comments
be made available along with the final document?
• The SLEA will be amended to show the distribution ofthe document.
• The comments received from Connor Cattle and the State of Utah will be
included as appendices in the amended SLEA, along with the responses from
Walsh.
6. On page vii, the SLEA lists the "Pathways for Further Evaluation". The list of
pathways provided is incomplete; if certain pathways have been screened out or
eliminated, the process and methodology for doing so should be provided.
Ingestion of surface water and groundwater by off-site workers and residents, for
example, should be retained for consideration and evaluated.
• The amended SLEA will clarify which pathways were excluded or screened
out of consideration. For example, ingestion of surface water and
groundwater by off-site workers and residents was excluded in the SLEA.
7. The Executive Summary should include a section on cunent and fiiture land use.
By omitting an analysis of future land use the SLEA process may arbitrarily
eliminate potential pathways for exposure to potential receptors.
• The SLEA will be amended to clarify assumptions made about current land
use and how that affected the pathways evaluated.
• The amended SLEA will clarify that it did not include evaluation of possible
future changes in land use.
8. On page vii, additional discussion is wananted regarding the definition of
"assumed", "suspected", and "analyzed" contaminants. The text states that
"assumed contaminants are those actually measured and cunentiy reported by
Thiokol", while "suspected contaminants include compounds neither reported or
analyzed by Thiokol, but which were identified as either previous or cunent
contaminants in specific conespondence by the Department of Environmental
Quality (UDEQ), or by Walsh in review of Waste Profiles and other operations
information". Additionally the text states that "Analyzed contaminants were
those parameters for which data were reviewed in this assessment". This
discussion, taken together with the table on page viii, implies that Thiokol has
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ATK/Thiokol Propulsion/SLEA Walsh Response to Comments
never measured, nor does it cunentiy report contaminant information in any
media, other than in air from stack testing, open buming or static rocket testing.
Altematively, contaminant information for other media may not have been
available to Walsh; which ever is the case the text should be clarified.
• The text and tables of the SLEA will be amended to clarify whether
contaminants are estimated, suspected, analyzed, or reported.
9. Similarly, the table on page vii implies that numerous PCOC were identified
through data reviewed for the SLEA, which are not cunentiy reported on by
Thiokol nor identified as previous or cturent contaminants in conespondence with
UDEQ. This implication should be revisited and verified for accuracy and the
text revised accordingly.
• The SLEA will be amended to clarify which contaminants are not currently
reported on by Thiokol or identified as previous or current contaminants in
correspondence with UDEQ.
10. On page ix, the SLEA states that groundwater concenfrations were documented
from monitoring well data collected by Thiokol. This discussion appears to
conflict with the discussion and table provided on page viii. Further, it was
conveyed in a recent meeting/conference calP to review the SLEA that the
groundwater concentrations were taken from monitoring wells located at the site
boundary; the text should be modified to accurately describe the source locations
of the groundwater data. The text indicates that groundwater PCOC
concentrations were evaluated and documented from 25 off-site and boundary
monitoring wells. There are many more wells on the faciUty than this; all of the
available data from the monitoring wells should be taken into consideration and
evaluated for screening PCOC. The tables should also be footnoted to identify the
monitoring well locations with the highest PCOC concentrations.
• The SLEA will be amended to clarify that only data from off-site and
boundary wells were evaluated. The tables will be modified to indicate the
wells with the highest PCOC concentrations.
11. Utilizing historic or recent groundwater concentration data to identify PCOC is
likely not sufficient for the Thiokol site. A recent report'^ from the UDEQ shows
a significant trichloroethene ("TCE") plume in groundwater. This plume will
likely continue to expand off-site and increase groundwater and surface water
concentrations of TCE above cunent levels. Estimates of future groundwater and
surface water concentrations of TCE (and other contaminants) should be modeled
before PCOC are eliminated in the SLEA. This is especially important to aquifer
^ Meeting on January 11, 2001 with personnel from Thiokol, Walsh, Connor Cattle Company and UDEQ.
^ Comprehensive Groundwater Monitoring Evaluation, October 27, 2000, prepared by the Utah Department
of Environmental Quality, Division ofSolid and Hazardous Waste, Hazardous Waste Branch, Hazardous
Waste Facility Section.
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systems that exhibit transmissivities ranging from 50 to 18,000 ft /day as this site
does.
• The SLEA will he amended to clarify that potential future groundwater and
surface water concentrations ofPCOCs were not modeled and were excluded
from the scope of work ofthis SLEA.
12. On page ix, the text states; "No sediment data were available and no estimates
were made". This is not adequate. Samples should be collected from nearby
surface water bodies receiving discharge from the Site. Samples are needed at a
sufficient number of sampling points to characterize exposure pathways, and at
discharge points to the water body to detennine if the site is contributing to
surface water / sediment contamination.
• The SLEA will be amended to clarify that it did not include collection and
analysis of sediment samples.
13. Page x ofthe SLEA provides a table captioned "Summary of Screening Results".
This table indicates 20 total PCOC exceeding benchmark criteria for the various
pathways of concem. The table should be modified to actually specify the
contaminants of concem and not just the number of them.
• The table "Summary of Screening Results" will be modified to list the
PCOCs.
14. The Conclusions section on page xi should be modified to list the compoimds that
could impair human health or the envfronment both on-site and off-site. The
thirty compounds that represent data gaps, in that they were not sampled, or
represent compounds that were sampled at different times or locations than
desired for the SLEA should also be listed. Recommendations should be
provided as to the process and analyses needed to remove the cunent data gaps.
To the extent that a chemical was not sampled at the appropriate time or location,
it should be retained as a PCOC that is categorized as "uncertain as to whether
off-site impairment is caused". The approximately 20 compounds that are listed
PCOC need not be subdivided further, as the "most likely", "less likely" and
"uncertain" categories are arbitrary at best.
• The Conclusions section ofthe SLEA will be revised to list the compounds that
could impair human health or the environment at off-site locations.
Evaluation of possible on-site endangerment was not part ofthe scope ofthe
SLEA.
• The SLEA will be amended to clarify what data gaps apply to which pathways,
including the thirty compounds previously identified by the UDEQ.
Section 1.0 - Goals and Objectives
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1. In addition to the goals and objectives the purpose of the document needs to be
described on page 1.
• The SLEA will be amended to clarify the purpose ofthe document.
2. On page 1, the SLEA states that it is not intended to be a "Comprehensive
Environmental Response, Compensation, and Liability Act ("CERCLA") or
RCRA Baseline Risk Assessment, but does draw on procedures and protocols
embedded in these other evaluations. The document should describe which
procedures and protocols were adopted and which were neglected and why?
• The SLEA can be amended to reference CERCLA or RCRA procedures that
were used. However, a comprehensive documentation of all potential
CERCLA or RCRA procedures that were not used is beyond the scope ofthis
project.
3. Page 2 ofthe document states that the SLEA does not address dioxin and related
compounds, but are separately being assessed by Thiokol and UDEQ. Please
elaborate on how the risk associated with these highly toxic compoimds is being
addressed.
• The SLEA will be amended to reflect that Dioxin (and related compounds) risk
is being evaluated through an OB/OD risk assessment required by the Utah
DSHW for permitting of open burning activities. The model required by the
State of Utah requires highly conservative (health protective) assumptions for
exposure scenarios and contamination levels.
• The SLEA will be amended to state that Walsh is not aware of any other
current facility processes (aside from open buming/open detonation) which
have the potential to generate dioxin and related compounds that may impact
off-site receptors.
4. Pages 1 through 3 provide no additional detail than in the Executive Summary.
• Pages I through 3 and the Executive Summary were intended to present the
same Goals and Objectives.
Section 2.0 - Source Characterization
1. Page 4 states "the short-term (acute) and long-term (chronic) concentrations of
those contaminants at, near or beyond the property boundary were either
documented from sampling results or estimated using models. The text, tables
and figures should clearly describe which contaminants were documented
from sampling results and those that required modeling.
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• The SLEA text and tables will be amended to more clearly document
which data are from sampling results and which are from modeling.
Section 2.2 - Air Emissions
2. On page 5, the SLEA indicates that all ofthe sources of actual data utilized in
characterizing the air emissions sources are from Calendar Year ("CY") 1998
and 2000. The sources of information listed with earlier dates would Ukely
not provide chemical concentration information. That being the case, the air
emissions information reflects only current conditions, or conditions
representative ofthe last few years. This information would likely not allow
the identification of historical exposures and the identification of PCOC that
presumably could have and may still, impact human health and the
environment.
• The SLEA will be amended to clarify the time periods (1991, 1994, 1998-
2000, etc.) that form the basis for emissions estimates.
• The SLEA will be amended to clarify that historical exposures were
indirectly evaluated by presenting soils and vegetation data (see Table 9
for buming area M225 and Table 16 for buming area Ml36) that are
expected to reflect current conditions because of the persistence and
immobility ofthe metals PCOCs.
3. On page 5, a svunmary of SCREEN3 modeUng conditions, including stack
height, diameter, and emission exit velocity and emission temperature inputs
should be provided in an appendix.
• The SLEA will be amended to include SCREEN3 model assumptions.
4. On page 6, the text states that air emissions were calculated from open
buming operations using factors for "1.3 propellants". Why were not
emissions calculated for 1.1 propellants?
• The SLEA will be amended to explain that emissions from 1.3 propellants
were modeled because they are bumed in much larger quantities than I.I
propellants and because I.I propellants do not contain any contaminants
that are not already being evaluated using 1.3 propellant assumptions.
5. As indicated on page 6, the "Open Buming" pollutant concenfrations derived
from the modeling should be updated through the use ofa model acceptable to
the State of Utah. In the interim, as indicated the SLEA, the reader should
place little confidence in the concentrations predicted by the modeling.
However, some discussion outlining UDEQ's objections to the model used to
determine pollutant concentrations from open buming and static testing would
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be helpful. For example, did UDEQ comment on the modeling that was
previously performed, and what issues did the UDEQ raise at that time?
• The SLEA will be amended to summarize issues raised by the UDEQ
conceming the PCAD modeling for the Subpart X open buming permit
submittal. The comments essentially were questions and requests for
additional data as follows: Specifics on how the model was validated,
why it was selected; were there any specific monitoring or other data for
use in model calibration and modeling assumptions; amounts of
propellant modeled. Questions on how pan shape and size and total area
affect the plume rise. Requests for modeling during inversions and worst
case scenarios; mass balances for model inputs and outputs, additional
information regarding the INPUFF model. Specifics on how PCAD works
and a summary ofthe input file and out put file for the model runs
reported.
Section 2.3 - Wastewater Discharges
1. Contrary to the text on page 7, Tables 10 «&; 11 do not provide the results for
the 72 parameters monitored at the NPDES outfalls.
• The amended SLEA will clarify that the 72 parameters monitored in
wastewater appear on Table I, however Tables 10 & II (and Table 6) may
be summarized by parameter group (for example, VOCs are shown as one
average on Table II and are shown as 48 individual parameters on Table
If
2. The text on page 7 states, "Basic statistics were performed on these data,
including the median and 80 percentile, for use in subsequent models. The
median has been used because the data set has a high frequency of non-
detects, and is probably not normally distributed". The text is not clear,
whether values were assigned to the non-detects prior to calculating the mean
or the 80**^ percentile; it would not be appropriate to use zero values non-
detects. The environmental analytical chemistry literature offers a number of
acceptable altematives to computing the mean, and other statistics, for data
sets having a large number of non-detect values, whether the data is normally
• distributed or log-normally distributed. Notwithstanding the treatment of
values below the detection limit, the data populations should be plotted to
determine whether or not they are normally distributed. Further, the SLEA
should not arbitrarily select the mean, or 80"^ percentile, as neither value is
necessarily conservative or consistent with typical regulatory agency
approaches. The 95 percentile should be selected, consistent with most EPA
protocols and guidance.
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• The SLEA will be amended to clarify that performing detailed statistics on
the wastewater data was beyond the scope of work. The level of effort was
aimed at developing representative levels for comparison to chronic and
acute criteria.
• The SLEA will be amended to clarify that the 8(f percentile was used per
discussion with the Water Quality Division ofthe UDEQ. That discussion
indicated that the 8(f percentile of the end-of-pipe discharge (high
loading) should be combined with the 2(f percentile of the stream (low
flow), in order that the cumulative effect would give the UDEQ a high
degree of confidence that acute conditions were being evaluated.
3. On page 7 regarding wastewater discharges, "Insfream concenfrations for
outfall 002 ... were calculated assuming no backgroimd concentration of site
related contaminants in Blue Creek". This approach is not the most
conservative approach, and unfortunately is not consistent with regulatory
agency guidance. The concentrations of contaminants in the outfall should be
added to background for purposes of evaluating whether PCOC exceed the
benchmarks. Regulatory guidance seldom allows risk to be calculated on an
incremental basis. The purpose of the SLEA is to determine the total risk to
the various receptors; here again ifthe purpose is otherwise, it should be made
abundantly clear in an introductory section ofthe document.
• The SLEA will be amended to clarify that Tables 10 & II are intended to
present an evaluation of incremental risk from the facility to Blue Creek,
not the total risk in Blue Creek including background.
• The SLEA will be amended to clarify that Table 12 presents data from
upstream background in Blue Creek.
• The SLEA will be amended to clarify that conclusions have been drawn
separately for the incremental risk and background risk, but that a
detailed evaluation of total (cumulative) risk was beyond the scope of
work.
Section 2.4 - Storm Water Discharges
1. On page 8, the text describing Thiokol's practice for reporting metals
concenfrations in storm water and surface water as total dissolved metals is
confiising. If the intent of the text were to indicate a level of conservatism, in
that Thiokol is measuring total metals, while indicating that the requirement is
only dissolved metals, this would be inconect. When considering surface
water or groundwater as a drinking water source, agency guidance would
encourage the use of total metals for the determination of potential risk.
• The SLEA will be amended to clarify that Table 14 provides storm water
data collected by Thiokol, the majority of which show Total Metals but for
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which one sample shows Dissolved Metals. The criteria shown on Table
14 are from the UDEQ and represent Dissolved Metals criteria.
• As noted in the response to Comment #6, Executive Summary, surface
water was not evaluated as a pathway for a drinking water receptor.
Section 2.5 - Groundwater Discharge
1. As regards the discussion pertaining to "Groundwater Discharges" on page 8,
again, it is not appropriate to "focus on evaluation of groundwater monitoring
wells at and near the perimeter of the Site". As standard risk assessment
methods for non-cancer and cancer endpoints, and typical exposure
assumptions are based on a 2-liter per day ingestion rate, a 70-kilogram adult
body weight and a 70-year lifetime, it is absolutely necessary to be able to
estimate maximum concenfrations for exposure over a 70-year period. While
this evaluation may not be possible for the SLEA, given that this document is
being used to screen PCOC, it would be pmdent to use the maximum
concenfrations of contaminants in groimdwater whether on-site or off-site to
conduct the initial screening of contaminants. The presence of "occasional
high detection limits" or and "probable outliers" are not reason enough to
select the 95*'' percentile for each parameter; suspect data should be eliminated
through the use of quality assurance and quality control samples.
• The SLEA will be amended to clarify that the 95' percentile was used
because a detailed statistical analysis and outlier analysis was not part of
the scope of work ofthe SLEA.
• As noted in other responses, on-site data were generally not considered to
be representative of "fence line" conditions and were therefore not
included in the SLEA.
2. Concentrations in groundwater should also me modeled over time to assess
the concentrations expected in the fiiture at possible exposure points. It is not
reasonable to assume that contaminant concenfrations at current exposure
points will not increase in the fiiture given the location, geometry and
movement of at least the TCE plume, and likely plumes of other
contaminants. Have any other groimd water contaminant plumes been
mapped, other than TCE?
• • As noted in other responses, no modeling of future plume movement was
part ofthe scope of work for the SLEA.
• The SLEA will be amended to clarify where maps of plumes, such as for
molybdenum in Figure 1, were relied upon.
Section 2.6 - Off-Site Springs and Associated Surface Waters
1. On page 8, the text is not clear as to whether Table 15 represents the results
from all sampling or results from just CY 2001.
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• The SLEA will be amended to clarify that Table 15 shows detected values
of VOCs from 1997-2001, and detected values of metals and perchlorate,
and some TDS data from only 2001.
Section 2.7 - Soils and Vegetation
1. The SLEA does not clearly identify which sampling results were used to
identify PCOC. The text seems to indicate that only results from CY 1999 or
later were used in the evaluation. Ignoring the data earlier sampling rounds
would be inappropriate.
• The SLEA will be amended to clarify the dates for soils and vegetation
data presented in Tables 9 and 16. Thiokol has provided Walsh with
additional soils and vegetation data since the SLEA was published, and
these will be summarized and referenced in the Final SLEA.
2. On page 9, the SLEA indicates that the results of the August 2001 soil-
sampling program at buming site Ml36 show "no molybdenum" was detected
in the area. These results should be reevaluated. It would be highly unusual
for all 12-soil samples to show results below background level concentrations
for molybdenum in soil. Altematively this impUes that the soil backgroimd
level for molybdenum is zero.
• The SLEA will be amended to clarify the reporting limits for molybdenum
in the text and Table 16.
Section 3.0 - Human Health Assessment
1. Please clarify whether the population of receptors described as "non-Thiokol
workers near the site" includes on-site workers or a subset of them including
ranchers and others having access to current or previously leased lands? This
population of receptor appears to have been overlooked.
• The SLEA will be amended to clarify that "Non-Thiokol workers near the
site " would include ranchers or other workers engaged in current off-site
activities. This term would not include any current or previous workers
engaged in activities on-site.
2. Why is there no human health toxicity section?
• As noted in a separate response, the SLEA will be amended to explain that
the most comprehensive human health toxicity data and information are
separately available from the ACGIH and OSHA and were not reproduced
in the document. The revised SLEA will include a carcinogen and non-
carcinogen summary table derived from the USEPA IRIS database,
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however as noted in other responses the IRIS database is not as complete
as the ACGIH and OSHA databases for the potential contaminants of
concem at Thiokol.
Section 3.3 - Problem Statement
1. The exposure pathways should be expanded to include on-site workers. The
exposure pathways should also be expanded to include dermal exposure to
soils, and ingestion of surface water and groundwater. The fact that
groundwater is not thought to be a potable source of water for residents and
workers in the area, is not a reason to eliminate this exposure pathway.
Groundwater was used as a drinking water source in the past, and may again
in the future. Groundwater may be used for human consumption or
agricultural use in the future.
• As noted in a separate response, the SLEA will be amended to clarify that
evaluation of on-site workers was not part ofthe scope of work.
• The SLEA will be amended to clarify that no off-site soils data were
available from which conclusions could be drawn regarding dermal
exposure.
• As noted in a separate response, the SLEA will be amended to clarify that
groundwater was not evaluated as a pathway for off-site human drinking
water receptors. However, groundwater was considered as a pathway to
surface water for potential ecological receptors, including agriculture, as
shown in Table 24 and described in Section 4.7.
2. The SLEA should identify all previous domestic weUs in the vicinity of the
site, and should verify that groundwater is not being used for domestic
purposes even now.
• As noted in separate responses, this SLEA did not evaluate groundwater
as a potential pathway for off-site drinking water receptors.
3. The exposure pathways should be expanded to include dermal exposure to
soils and surface water, ingestion of surface water and groundwater, and
ingestion agricultural products including vegetables, crops and livestock.
These exposure pathways should be assessed for both on-site and off-site
workers, as well as residents and recreators.
• The SLEA will be amended to clarify that it did not include exposure
pathways for dermal exposure to soils, ingestion of surface water and
groundwater for human receptors, and human ingestion of agricultural
products including vegetables, crops and livestock.
• The SLEA did include dermal exposure to surface water by recreators, and
ingestion of surface water and groundwater by ecological receptors.
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• As noted in other responses to comments, the SLEA did not address on-site
receptors.
Section 3.5 - Screening Methodology
1. The EPA publishes the IRIS database, which includes toxicity information for
both cancer causing and non-cancer causing contaminants. Why was the
information this standard reference for toxicity assessment not used for the
SLEA?
• As noted in a separate response, the SLEA adopted toxicity criteria
promulgated in Utah Rule R307-410. Therefore, the SLEA will be
amended to clarify that these levels may be different from those in the EPA
IRIS database. As a practical matter, the IRIS database has no
information on a substantial percentage of the potential contaminants of
concem at the site, therefore the more comprehensive ACGIH and OSHA
databases were used in conjunction with the Utah Rule R307-410. A
literature article (Williams, et. al., 1994) will be cited which compares
IRIS and ACGIH or PEL values.
2. On page 13, the text should state which compounds had sunogates selected
for them for determination of occupational standards, and which compoimds
did not have an appropriate surrogate identified and why.
• The SLEA will be amended to clarify that the surrogates appear in
parenthesis next to the compound in each of the tables and to indicate
compounds that could not be evaluated due to lack of an appropriate
surrogate.
Section 3.5.3 - Surface Water: Recreators Near the Site
1. The second paragraph of this section seems to be under the wrong subheading
as it discusses inhalation of contaminants. Notwithstanding its location, the
paragraph states that an acute exposure is any exposure lasting less than one
hour and that open bums last approximately on hour. The estimate of
exposure via inhalation, to a receptor, acute or chronic, needs to account not
for the duration of the bum, but for the actual duration of exposure. This
exposure may last for an extended duration, depending on climatic conditions,
but is much longer than the duration ofthe actual bum itself
• The SLEA will be amended to correct the misplacement of the second
paragraph of Section 3.5.3.
• The SLEA will be amended to clarify the estimated duration of exposures
based on the different models utilized. These durations will be compared
to the correct criterion. For example, ifthe duration is an instantaneous
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maximum, this exposure would be compared to the acute exposure
duration, which UDEQ defines as one hour or less.
Section 3.6 - Results
1. The text on page 15 discusses nine contaminants that exceeded the Utah Rule
R307-410 value calculated for acute exposure. Please identify the acmal
chemicals in the text.
• The SLEA will be amended to clarify the names ofthe nine contaminants
exceeded Utah Rule R307-4I0 concentrations.
Section 3.7 - Exposure and Uncertainty Discussion
2. The Exposure and Uncertainty Discussion addresses almost exclusively air
emissions exposure. This section of the SLEA defends the document's
reliance on modeling studies performed previously, for example, based on the
fact that the air modeling "included a number of simplifying assumptions that
may have over-estimated the actual concenfrations to which ... receptors were
exposed". Yet the document never elaborates on the specifics of the
parameters, which were reportedly conservatively estimated. The document
also indicates that the off-site receptors were assumed exposed to fence-line
contamination levels as opposed to concenfrations further down gradient.
Taken together, these assumptions cause the authors to conclude that the afr
concenfrations of contaminants are "likely over-estimated". It is possible that
the highest concenfrations of contaminants occur beyond the fence line. It is
also possible that the simplifying assumptions are not appropriate to an
endangerment assessment. Please verify these assertions. Please also
describe whether the models were ever field validated.
• The SLEA will be amended to clarify where the modeled concentrations
are estimated to occur, which in some cases is beyond the fence line.
• The SLEA will be amended to clarify what modeling assumptions, if
available, were made and how they relate to an endangerment assessment.
3. Overall the Exposure and Uncertainty Discussion does not adequately
characterize the uncertainty.
It is afready known that for most environmental risk assessments the
uncertainty about the numerical results can be large. Consequently, it is
especially important to identify the critical site related variables and
assumptions that contribute the most uncertainty. There are several categories
of uncertainty associated with screening level risk assessments. One is the
initial selection of the contaminants of concem, based on sampling data and
available toxicity information. Other sources are inherent in the toxicity
values for each chemical selected to characterize risk. Additional
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uncertainties are inherent in the exposure pathways or exposure assessment
for individual chemicals and individual exposures. These uncertainties are
usually driven by uncertainty in the site monitoring data and the models used
to estimate exposure concentrations in the absence of actual monitoring
information.
• The SLEA will be amended to clarify the relative uncertainties involved in
this endangerment assessment related to sampling, toxicity, pathways, and
exposure data and assumptions.
4. This section should address, 1 the difficulties in quantifying risks for
individual substances (carcinogens and non-carcinogens), 2 the aggregate
risks from exposure to multiple contaminants, 3 the combining of risks across
exposure pathways, and 4 a discussion of site-specific uncertainty factors.
• As noted above, the SLEA will be amended to clarify the uncertainties in
quantifying risks for individual substances and due to site-specific
uncertainty factors.
• The SLEA will be amended to clarify that it excluded aggregate risks, as
well as the combining of risks across exposure pathways.
5. As indicated in other comments, it is most important that this section include
an evaluation of site-specific uncertainty factors. This discussion should
discuss uncertainty associated with the physical setting of the site and the site
conceptual model; it should address past, cunent and future land uses, past,
current and fiiture exposure pathways, and the selection of substances as
PCOC. This section should address the likelihood of exposure pathways and
land uses occurring in the future (perhaps for the next 50 to 70 plus years).
• As noted in previous responses, the SLEA did not include an evaluation of
past or future exposure or land uses.
• The SLEA will be amended to clarify uncertainties associated with
selection of PCOCs and the conceptual model.
6. In addition, the Exposure and Uncertainty Discussion should address the
uncertainty of chemicals not being included in the PCOC as a consequence of
missing information on health effects or lack ofquantitation in the analysis of
a contaminant. If chemicals with known health effects were elirhinated from
the risk assessment, for example on the basis of concentration or frequency of
detection, or substances detected at the site but not included in the PCOC were
eliminated because of data limitations, this section of the report should
address the possible consequences of exclusion on the determination of risk.
• As noted above, the SLEA will be amended to clarify the uncertainties
associated with data quality, data gaps, and health effects information.
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Section 4.0 - Ecological Assessment
1. The Introduction states "the assessment considers environmental media and
exposure pathway that could result in a potential risk and adverse effects to
ecological receptors now or in the foreseeable future". The assessment should
address adverse effects historically as well as the future.
• As noted previously, the evaluation of "adverse effects historically" was
not in the scope of the SLEA, and we believe that such an evaluation
would be exceedingly difficult from an ecological perspective. Identifying
historic impacts would require an intensive comparison of community
composition in potentially affected areas with mutually agreed-upon
"reference" areas, which is inherently difficult given the wide range of
biotic and abiotic variables that can confound the community-level data.
Even if such an evaluation were practicable, it cannot be known whether
current conditions reflect "historic" conditions because ofthe ability of
populations to adapt to environmental stressors through time.
2. The Introduction states "the focus of this preliminary assessment is to: ...
Highlight existing data gaps to assess the presence of PCOC in off-site
locations". It is important to identify data gaps, which impact the assessment
of PCOC both on-site and off-site. Why were the data gaps not identified in
the Human Health Assessment section as well?
• The SLEA will be amended to identify data gaps that occurred in the
Human Health Assessment.
• As noted previously, the scope ofthe SLEA did not include on-site issues.
Section 4.2 - Problem Formulation
1. This section identifies potential conclusions that may be drawn from the
SLEA. However, it seems that at least one potential conclusion may have
been omitted. Why not explore the conclusion that 'Concentrations of
contaminants are sufficiently elevated to impose ecological risk and have
impacted the survival, growth or reproduction of receptors'.
• This potential conclusion was intended to be captured by the third bullet
under Problem Formulation: "A potential for ecological effects is present
based on available benchmarks." The major disparity between the
proposed statement and the statement used in the SLEA concems the issue
of whether "elevated" contaminants "have" affected ecological receptors,
as opposed to having the potential to do so (implying that they may
already have done so). See the response to Comment #1 of this section
conceming the difficulty of reconstructing historical impacts—except
where the degree of impact is extremely severe. The revised SLEA will
clarify this issue.
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Section 4.5 - Potential Ecological Receptors
1. Pheasants are missing as potential receptors.
• Specific bird species were not addressed by the SLEA because the brief site
visit conducted by WALSH personnel did not allow for a detailed bird survey.
However, all birds that are reported for the site vicinity are considered as
potential receptors, including the ring-necked pheasant. This non-native
gamebird would be considered an omnivorous species, which is one of the
receptor groups specified in the SLEA.
Section 4.6 - Conceptual Site Model
1. On page 23, the text states "A dispersion modeling effort is beyond the scope
of this project, however factors present at the Site indicate that exposure to
receptors through dfrect contact with air, or addition of contaminants in the afr
into other primary source media may be an issue". Please explain the
meaning of this sentence. What factors are the authors referring to
specifically? What other media are an issue?
• The factors referenced are the practices at the site that may be introducing
contaminants into the soil via dispersion of airbome PCOCs. For
example, some contaminants may be deposited onto on-site soils and
subsequently re-entrained and transported off-site as suspended
particulates. Off-site transport of these re-entrained contaminants would
be in addition to other airbome contaminants. The revised SLEA will
clarify this point.
2. On page 23, the fate of soil contaminants is addressed, but does not include a
discussion of bioaccumulation of contaminants in plant media.
Bioaccumulation is an important factor, which potentially increases the
exposure to both humans and ecological receptors.
• The SLEA authors recognize that contaminants may be accumulated in
plant tissues at concentrations greater than in soil, and that some
contaminants may be preferentially accumulated in some plant tissues.
The SLEA will be revised to clarify this point.
3. On page 24, the text references table 23 as identifying potential receptors and
exposure pathways ... and considers all sources of contamination, potential
receptors, and exposure pathways within the project area". However, many
exposure pathways and receptors are missing from the table. The table and
text should be amended to include additional media and receptors. For
example, surface water should be included as an exposure pathway for
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mammals and birds. Why weren't inhalation and/or dermal contact included
for other potential receptors? Shouldn't the table include domestic animals as
potential receptors as well?
• The SLEA will be amended to clarify which pathways were included and
which were excluded, and why. Inhalation and/or dermal exposure routes
were not considered for ecological receptors and livestock, consistent with
EPA (1997) guidance that recognizes the generally much larger data set
available on the ingestion pathway for terrestrial animals. However, the
authors recognize that these other routes may be relevant for some species
groups (e.g., burrowing rodents). Accordingly, the revised SLEA will
address these, and other, additional pathways to the extent practicable
based on available information.
4. Regarding Table 23, what is the meaning of the footnote "Groundwater plume
will be amended to indicate the potential for irrigation and drinking water in
selected areas of the site"? This note seems to recognize that groundwater is
an important drinking water source both on-site and off-site from an exposure
perspective. This note seems also to recognize the importance of evaluating
agricultural exposures as well, which could include crops, vegetables,
domestic Uvestock, and human exposures in tum via combined pathways.
• The SLEA will be amended to clarify that groundwater is a potential
pathway for off-site drinking water, but that it was not evaluated in this
SLEA.
• Screening Level Ecological criteria do address agricultural exposure
since screening criteria are intended to evaluate the primary pathways of
exposure from source to receptor. This would include surface water
impacts on crops and vegetables and impacts to livestock from other
media including soil and uptake into plants that may be part of their diet.
Screening level criteria are often developed using a much more sensitive
species such as less tolerant plants and small invertebrates to create a
"screening value" that can be used to extrapolate to larger species and
evaluate their potential risk.
Section 4.7 - Selection of Ecological Contaminants of Concem
1. The text states, "HAPS data was not included since none ofthe analyses in the
HAPS list exceeded human health inhalation criteria and human health criteria
are generally more stringent than ecological criteria". Was this assessment
actually performed for all the contaminants and potential receptors?
• All HAPS data were considered under this type of screening, based on the
stringent nature of human health inhalation criteria. Additionally,
ecological inhalation criteria were not available for these contaminants.
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All other data were screened according to accepted eco-risk assessment
practices. The revised SLEA will clarify that HAPS modeling estimated
that 66 of 69 contaminants are below all human health criteria, and that
three contaminants are above some criteria using some assumptions.
Section 4.8 - Potential Receptors and PCOC Ecotoxicity
1. The exposure profiles on page 25 and 26 do not match those given on table
23. As well, injection of groundwater/surface water is missing for a number
of receptors.
• The SLEA will be amended to correct the differences in the text on pages
25 and 26 compared to Table 23. We assume that the comment was
intended to reference "ingestion " of groundwater/surface water.
2. On page 26, the concenfration of 1,1-dichloroethene ("DCE") inducing acute
and chronic effects in fish appear to be reversed.
• The SLEA will be amended to correct discrepancies for DCE in the text
and tables.
Section 4.10 - Exposure Pathways and Assessment
1. The Exposure Pathways described for the various receptors beginning on page
29, are more encompassing than described previously in the text or in the
conesponding tables.
• This discussion is presented as a general description of significant
pathways based on the ecological niches and trophic levels ofthe various
receptors. This information is not necessarily relevant to the specific
receptors used in the conceptual model. The revised SLEA will clarify this
point and more clearly indicate which exposure pathways are potentially
complete, which are known to be complete or incomplete, and which are
not evaluated in the SLEA.
Section 4.12 - Risk Characterization / Effects Evaluation
1. On page 32, the SLEA properly indicates the data gaps associated with soil,
surface water and vegetation sampling in the vicinity of M225. However, are
there no historical data for the PCOC in these media around M225 bum area?
• Since the SLEA was prepared, Thiokol has pi-ovided Walsh with additional
historical soils and vegetation data for the M225 burn area. These data
will be summarized and referenced in the Final SLEA. I
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2. Regarding the Risk from PCOCs in Surface Water, it is not reasonable to
conclude at this stage in a screening level assessment that because the HQ
values are "only slightly over 1.0" and the maximum concentrations are "not
more than an order of magnitude over the toxic effects concentration" that the
"ecological effects from volatiles in surface water are minimal". See in
addition the comments regarding uncertainty.
• The wording ofthe quoted phrase will be revisited in the amended SLEA.
Note that both the Conclusions and Executive Summary sections of the
SLEA clearly indicate that three volatile organic compounds
(trichloroethene, 1,1-DCE, and 1,1,1-TCA) are considered contaminants
of concem.
Section 5.0 - Conclusions
1. Throughout this section, contaminants exceeding the benchmark criteria are
described in terms of the number of chemicals. It would be helpful if the text
focused more on describing the actual chemicals exceeding particular
benchmarks.
• The SLEA will be amended to include lists of contaminants of concem in
the text, in addition to the listings in tables.
2. On page 37 and 38, the upgradient surface waters in Blue Creek are described
as being impacted by runoff from off-site soils potentially impacted by afr
emissions from open buming at area Ml36. Earlier in the document, the up
gradient concenfrations are referred to as background only.
• The SLEA will be amended to clarify that upgradient surface waters are
potentially impacted from site-related activities, and that a background
evaluation would need to be conducted to draw firm conclusions, but that
such an evaluation was beyond the scope of work ofthe SLEA.
On page 39, the text states that total metals concentrations exceeded dissolved
metals criteria by a factor of two for selenium. Given the complexing of
selenium in aqueous solutions, it may not be appropriate to assume that
dissolved metals concentrations are much less than total metals
concentrations. This assessment needs to be made on a metal-by-metal basis,
based on the geochemistry of the contaminant. Perhaps selenium should be
retained as a PCOC?
• As noted above, an off-site background evaluation would need to be
conducted to draw firm conclusions, and such an evaluation was beyond the
scope of work of the SLEA. It should also be noted that Table 6 estimates the
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contribution of selenium from end-of-pipe discharges to be about IOO times less
than surface water criteria.
4. Twelve samples are probably not sufficient to draw the conclusion that metal
concenfrations "noticeably decrease" with distance from the Ml36 bum site.
At the M225 bum site, metals concentrations decrease moving away from the
bum area and then increase again at some distance away from the bum site.
The SLEA will be amended to indicate the basis for this conclusion for the
Ml36 bum area, and will make comparisons to the M225 burn area for
locations farther downwind than those sampled.
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