United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
E PA/ROO/R08-90/028
March 1990
Superfund
Record of Decision;
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50272.101
REPORT DOCUMENTATION 1'. REPORTNO. 12.
PAGE EPA/ROD/R08-90/028
3. Redpien1'a Acceaalon No.
4. TlUe and SubIlUe
.UPERFUND RECORD OF DECISION
rhitewood Creek, SD
First Remedial Action - Final
7. AlI1IIor(a)
5. Report Gate
3/30/90
6.
8. Performing Organlzallon Rep!. No.
II. Performing Orgalnlzallon Name and AdeI",..
10. ProjectlTaalllWork Unit No.
11. Cant/'aCl(C) or Grant(G) No.
(C)
(G)
12. Sp_oring Organization Name and AdcIreaa
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report. PerIod Covered
Agency
800/000
14.
15. Supplemenwy Nolea
16. Abatract (Umlt: 200 worda)
The Whitewood Creek site is a mine tailings deposit area near the town of Whitewood
in Lawrence, Mead, and Butte counties, South Dakota. Situated along 18 miles of
Whitewood Creek, the 2,018-acre site consists of woodlands, farmland, and residential
homes. From 1877 to 1977, arsenic-rich tailings from gold and ore mining and milling
iperations, conducted by the Homestake Mining Company, were discharged directly into
~nitewood Creek. The tailings, which consist of finely ground rock, residual metallic
and non-metallic compounds not extracted from the ore, and trace compounds used during
the extraction process, were deposited downstream from the mine. The largest tailings
deposits at the site are found along the floodplains of Whitewood Creek and the Belle
Fouche and Cheyenne Rivers. Since 1977, however, material from the ore milling process
has been treated prior to backfilling residual material into the mine, and process
water also has been treated prior to discharge into Whitewood Creek. The tailings are
the major source of contamination at the site affecting onsite residential soil and
continue to leach metals to surface and subsurface waters. A 1989 remedial
investigation revealed that some residential properties contain arsenic levels that
present health risks. Residential soil contains arsenic contamination as a result of a
(See Attached Sheet)
17. Document Analyala .. Deacrtpto..
Record of Decision - Whitewood Creek, SD
First Remedial Action - Final
Contaminated Medium: soil
Key Contaminants: metals (arsenic)
b. IdenlilieralOpen-EndecI Tenna
c. COSA TI ReIdlGr4M4'
-.. vailablUty Statement
111. Security Cia.. (Thla Report)
None
20. Security Cia.. (Thla Page)
None
21. No. of Pagea
78
22. PrIce
See ANSl-Z3II.18
See Instructions on Reverse
(Formelly NTlS-35)
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EPA/ROD/R08-90/028
Whitewood Creek, SD
First Remedial Action - Final
building in the tailings area, windblown tailings, and the use of arsenic-contaminated
soil as a soil conditioner and a driveway base. Approximately 12 residences are
estimated to have arsenic-contaminated soil exceeding 100 mg/kg. The total number of
affected residences, however, will be determined during the remedial design phase. This
Record of Decision (ROD) addresses the arsenic-contaminated soil in the residential
areas. The primary contaminant of concern affecting the soil is arsenic.
The selected remedial action for this site includes removing and/or covering frequently
used areas with clean surface soil (arsenic <20 mg/kg) in residential areas with arsenic
levels above 100 mg/kg followed by disposal of the arsenic-contaminated soil, if approved
by EPA, and revegetation of the remediated area; soil sampling at all remediated areas to
confirm that arsenic levels are below 100 mg/kg; implementing institutional controls
including land and access restrictions; conducting an annual education program to inform
site residents of the potential health hazards associated with exposure to tailings,
soil, and downgradient ground water; refining knowledge of the extent of the
contamination and delineating the 100-year floodplain of Whitewood Creek; and surface
water monitoring. EPA is invoking ARAR waivers based on the technical impracticability
of remediating contaminated ground and surface waters. The estimated present worth cost
for this remedial action is $882,813, which includes an annual O&M cost of $12,000 for
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RECORD OF DECISION
MARCH 30, 1990
DECLARATION STATEMENT
SITE NAME AND LOCATION
Whitewood Creek Site ..
Lawrence, Meade, and Butte Counties, South Dakota
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the
Whitewood Creek site in Lawrence, Meade, and Butte Counties, South
Dakota. This document was developed in accordance with the
Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA), and the National Contingency
Plan (NCP) (40 CFR Part 300).
This decision document explains the factual and legal basis for selecting
the remedy for this site. The information supporting this remedial action
decision is contained in the administrative record for this site and is
summarized in the attached decision summary. This decision is based on
the administrative record for this site.
The State of South Dakota concurs with the selected remedy. The State,
however, does not concur on the boundaries of the site.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if
not addressed by implementing the response action selected in this
Record of Decision {ROD), may present an imminent and substantial
endangerment to public health, welfare, or the environment.
DESCRIPTION OF SELECTED REMEDY
The remedial action selected by EPA for the Whitewood Creek
Superfund site consists of covering and/or removal of contaminated soils
at existing residential properties and establishment of institutional
controls to restrict access to tailings deposits. Implementation of these
measures will reduce the risk to public health presented by residential
.soils, ~ailings deposits and alluvial groundwater contaminated with
arseruc.
The major components of the selected remedy include:
. Cover and/or remove soils in the existing residential areas containing
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. Restrict future development in the lOO-year floodplain and tailings
deposits as provided through county ordinance.
. Prohibit excavation of tailings deposits for other uses and prohibit
excavation of remediated areas through county ordinance, however,
mining would be allowed subject to the regulations of the State of
South Dakota.
. Refine knowledge of the extent of contamination and delineate the
IOO-year floodplain. Provide detailed maps to define site boundaries
and specify activities to support county ordinances.
. Set up an educational program to inform people about hazards
presented at the site and ways to decrease their personal exposure.
. Continue enforcement of the ban on installation of water supply wells
with the lOO-year floodplain (this is already prohibited by a state
regulation).
. Continue monitoring the surface waters of Whitewood Creek for
significant releases of hazardous substances.
. Resample remediated residential areas after major flood events.
DECLARATION OF STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment,
complies with most Federal and State requirements that are legally
applicable or relevant and appropriate to the remedial action, and is cost
effective. A waiver is invoked for complying with maximum contaminant
levels for arsenic under the Safe Drinking Water Act and the water
quality criteria for protection of human health by consumption of fish
because of the technical impracticability of meeting these requirements.
This remedy utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable for this site. However,
because treatment of the principal threats posed by the site was not
found to be practicable, this remedy does not satisfy the statutory
preference for treatment as a principal element. Treatment is
Impracticable because of the large volume of contaminated soils and
tailings deposits, the lack of appropriate treatment technologies, and the
potential for adverse environmental impact.
Because this remedy will result in hazardous substances remaining on
site above health-based levels, reviews of the remedial action will be
conducted no less often than each five years after initiation of the
remedial action, to ensure that human health and the environment are
being protected by the remedial action being implemented.
~. ~..
J a es . Sch~rerf'
RegIOnal Administrator
EP A Region VIII
.2r. "<-..L. ~'" dfo
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RECORD OF DECISION
ATTACHMENT A
WHITEWOOD CREEK SUPERFUND SITE
DECISION SUMMARY
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III.
IV.
VII.
VIII.
IX.
x.
RECORD OF DECISION
ATTACHMENT A
WHITEWOOD CREEK SUPERFUND SITE
DECISION SUMMARY
Table of Contents
Page
I.
II.
SITE NAME AND LOCA TI 0 N --------------------------------------------------m______- 1
SITE HISTORY AND ENFORCEMENT ACTIVITIES ---------------------------- 3
HI GHLIGHTS OF COMMUNITY PAR TICIP jJ,TION ---------------------------- 7
SITE CHARACfERISTI CS----------------------------------------------------------------- 9
V.
SUMMARY OF SITE RISKS --------------------------_m_____------------------------18
D ESCRIPTI 0 N 0 F ALTERNATIVES ----------------------------------------------_m 26
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES ------34
THE SELECfED REMED Y ------------------------------------------------------40
ST A TUTOR Y DETERMINATIONS ----------------------------------------------42
DOCUMENTATION OF SIGNIFICANT CHANGES---------------------------45
Appendices
Appendix A Intake Assumption EP A's EA
Appendix B Health Based Soil Action Level for Arsenic
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RECORD OF DECISION
ATTACHMENT A
WHITEWOOD CREEK SUPERFUND SITE
DECISION SUMMARY
I. SITE NAME AND LOCATION
The Whitewood Creek Superfund site, a National Priorities List site, is located in
Lawrence, Meade and Butte Counties, South Dakota (Figure A-1). The site is situated in
west central South Dakota on the northern perimeter of the Black Hills, 40 miles northwest
of Rapid City on Interstate 90. The site lies within portions of Township 6, 7 and 8 North,
Range 4, 5 and 6 East and is mapped on the Rapid City (1:250,000) quadrangle at a
latitude of 44°-450N and longitude lOZo-104oW.
The Whitewood Creek site, a mine tailings contaminated site, encompasses approximately
2,018 acres along 18 miles of Whitewood Creek floodplain from the Crook City Bridge to
the confluence with the Belle Fourche River. From the 1870s to 1977, tailings were
discharged into Whitewood Creek from upstream gold mining and milling operations.
These tailings were deposited along the floodplains of Whitewood Creek and the Belle
Fourche and Cheyenne Rivers.
The primary concerns for potential harm to human health and the environment presented
by the site are exposure to arsenic-rich tailings deposits, and alluvial soil, residential soil,
and alluvial groundwater contaminat'ed with arsenic.
The dominant land use within the site is woodlands. The remaining land within the site is
used for agriculture and residences. The agricultural lands are located in somewhat
discontinuous sections along the edge of the floodplain in areas adjoining and occasionally
overlapping the tailings deposit areas.
The residences are scattered along both sides of Whitewood Creek. Based on 1988 data,
22 households and five vacant residential properties are situated within or in close
proximity to the site with a population totaling 85 (63 adults and 22 children). Eighty
households, with a population of 283, are within a mile of the site on either side of the
creek and 168 households, with a population of 647, exist within three miles of the site.
The Town of Whitewood, located about one mile west of the site, has a population of 821.
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SOUTH
DAKOTA
Butte County
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~I Meade County
g.
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B.
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~I
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Figure A-1
Whitewood Creek Site Location
Approximate distribution of tailings deposits
within the 1 OO-year floodplain of Whitewood
Creek.
~Mttt}}H TAILINGS
ROADS
- - - COUNTY LINE
WHITEWOOD CREEK
CROOK CITY
BRIDGE
Nl
o
.
2
. MLES
APPROXIMATE SCALE
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II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
History of Operations
1877 to 1977. The Homestake Mining Company, located in Lead, South Dakota, began
gold mining operations in the Whitewood Creek watershed in the late 1870s, following
development of gold deposits discovered prior to 1850. Mining operations over the last
century have produced about one billion tons of ore from both open pit and subsurface
shafts which currently extend to a depth exceeding 8,000 feet below the surface. The
processing of the ores has changed over the years, resulting in changes in the characteristics
of the waste stream. Methods have become progressively more efficient, so that earlier
tailings were coarser and contained more metal than those resulting from present
operations.
The first milling methods were primitive and non-mechanized. Gold was recovered by
gravity or by amalgamation with mercury. By 1880, the early crude methods of milling
were replaced with more than 1,000 stamp mills which crushed the ore to a coarse sand
size. The tailings were then discharged to Whitewood Creek or its tributaries. Prior to the
turn of the century, much of the ore consisted of red-colored minerals which were the near
surface residual oxidation products of the original unoxidized ore bodies.
After the turn of the century, the black and green-colored reduced ores from deeper in the
mine, below the zone of oxidation, were the focus of mining activity. The use of ball and
rod mills, brought into service in the 1920s, created finer-grained tailings referred to as
"slimes." After 1935, much of the sand-sized portion of the tailings was returned to the
mine to backfill mined areas. The "slimes" as well as some coarse-grained sands continued
to be discharged directly into Whitewood Creek until 1977, with the exception of five years
during World War II when the mine was closed. Mercury amalgamation was discontinued
in 1970.
Tailings, consisting of finely ground rock, residual metallic and nonmetallic compounds not
extracted from the ore, and trace compounds used in the extractive processes, were
transported away from the mine by the water of Whitewood Creek. These tailings were
deposited downstream from the mine with the largest deposits along the banks of
Whitewood Creek between the Crook City Bridge and the confluence with the Belle
Fourche River. The tailings remain along much of this reach of Whitewood Creek and
continue to leach metals to surface and subsurface waters.
] 977 to Present. Presently ore is milJed in crushers and rod and ball mills. The material
from the milling process is separated into two size fractions, sand and slimes. These
fractions are treated separately by cyanide leach and carbon filter methods. Residual sand
material is used to backfill within the mine. Residual slimes and process waters are piped
to the Grizzly Gulch tailings impoundment in the upper reaches of the Whitewood Creek
watershed.
A wastewater treatment plant now treats water from the tailings impoundment and the
mine. This plant utilizes rotating biological contactors to remove cyanide and ammonia;
iron precipitation and sorption to remove metals; and sand filtration to remove suspended
solids. Solids are returned to the tailings pond. Water enters Gold Run Creek which
discharges into Whitewood Creek between the towns of Lead and Deadwood. This
discharge is monitored to meet requirements of the Clean Water Act.
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History of Site Investigations
The first systematic studies of the Whitewood Creek area were undertaken by the South
Dakota Department of Health in 1960. This work quantified the solids and cyanide loading
to Whitewood Creek, recommended further study, and reported that a comprehensive
water pollution control program was needed, if any beneficial use was to be made of
Whitewood Creek. A study by the South Dakota Department of Game, Fish and Parks in
1965 determined that aquatic bottom organisms were not present in Whitewood Creek
downstream from the waste discharges. In 1970-71, a series of studies by the U.S.
Environmental Protection Agency (EP A) and the U.S. Food and Drug Administration
(FDA) were undertaken to document and characterize the discharge of tailings to
Whitewood Creek and to determine the magnitude and extent of the resultant pollution.
These studies, together with one prepared by the University of South Dakota, focused on
the possible serious environmental hazard created by mercury contamination. In
December 1970? results of these studies led to the discontinuance of mercury in gold
recovery operatIons.
In the winter of 1974-75, about 50 Holstein cattle that were part of a dairy operation
located adjacent to Whitewood Creek, died of unknown causes. Later, a study by the South
Dakota State University Department of Veterinary Science concluded that the .cattle had
died of arsenic toxicosis due to consumption of corn silage that had been contaminated by
the accidental incorporation of mining wastes with fodder during silo-filling operations. A
joint study, conducted by the. South Dakota Geological Survey and Water Resources
Division between May 1975 and July 1978, investigated the presence of arsenic in surface
and groundwaters along Whitewood Creek and the Belle Fourche River and portions of
the Cheyenne River. This study, published in 1978, found arsenic concentrations ranging
from 2.5 to 1,530 ug/L in groundwater from areas with large tailings deposits.
One common conclusion of all these pollution investigations was that Whitewood Creek
would remain highly contaminated until the discharge of tailings was discontinued. To
comply with new environmental laws, including the Ore Mining and Dressing Effluent
Guidelines, Homestake Mining Company implemented the Grizzly Gulch Tailings
Disposal project, an impoundment area for tailings storage. The tailings disposal system
became operational on December 1, 1977, and no discharge of tailings to Whitewood
Creek has occurred since then.
In 1981, at the request of the governor of South Dakota, the Whitewood Creek site was
placed on the "Interim National Priorities List." Subsequently, on September 8, 1983, the
site was placed on the National Priorities List (NPL).
Following the initial placement of the site on the Interim National Priorities List, EP A, the
South Dakota Department of Water and Natural Resources (DWNR), and Homestake
Mining Company (Homestake) entered into a three-party study agreement in 1982 to
conduct a comprehensive study of the site. The study, funded by Homestake and
conducted by Fox Consultants, Inc. of Denver, Colorado, was supervised by a project
advisory committee composed of representatives of each of the three parties. The Fox
study investigated the quality of surface waters, groundwaters, soils, sediments aquatic life
and vegetation in the study area, on an 18 mile segment of the floodplain of Whitewood
Creek above its confluence with the Belle Fourche River. The study used 14 target
substances as indicators of potential public health and environmental threat. The
conclusions, published in a multi-volume report in December 1984, indicated that arsenic
was the contaminant of most significant environmental concern throughout the media
under evaluation.
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The report also indicated that, although mercury and cyanide had originally been
contaminants of concern in tailings discharged from Homestake Mine, concentrations of
these contaminants at the Whitewood Creek Superfund site were near background levels
and therefore not of environmental concern at this time.
Simultaneously with the Fox study, two related studies were conducted. Homestake
assembled a group of consultants led by J.A. Cherry to assist the project advisory
committee. These consultants studied the hydrogeochemistry of the site and prepared a
report completed in 1985. This report, titled "Hydrogeochemistry of sulfide and arsenic-
rich tailings and alluvium along Whitewood Creek, South Dakota" was published in 1986 in
Mineral and Energy Resources. The second study, an extensive investigation of the surface
water in Whitewood Creek, was initiated in 1982 by hydrologists from the U.S. Geological
Survey. The U.S. Geological Survey published a draft report in 1985. Subsequent
published reports and unpublished data are currently available from the U.S. Geological
Survey.
Homestake and the State of South Dakota submitted a request to EP A in 1983 to initiate
proceedings to delete Whitewood Creek from the NPL, and resubmitted the request in
1985. This request was supported by a human health exposure assessment performed by
Homestake's contractor, Environ Corporation, which concluded that the site posed no risk
to human health. EP A, believing that it was premature to discuss deletion until the studies
were completed, did not pursue delisting further.
Homestake also funded several additional studies which included: 1) an evaluation by
Industrial Waste Management Inc. of the water quality sampling results collected by the
U.S. Geological Survey in Whitewood Creek before and after the installation of the
wastewater treatment system upstream from the CERCLA site; 2) an analysis of the age of
trees growing on the tailings deposits along Whitewood Creek (for the purpose of dating
these deposits) conducted by Pope and Talbot, Land Forester; 3) an assessment of the
sources, occurrences and mobility of selenium in the \\~.itewood Creek Basin and a re-
analysis of the selenium concentrations in existing waLe supply wells along Whitewood
Creek, both performed by Geochemical Engin€ering Inc. Another study by Geochemical
Engineering Inc. in October 1988, incorporated additional groundwater quality data and
soil characterization data. Forthis study, the population residing within the site was
interviewed regarding their habits with respect to the intake of drinking water and locally
grown food crops. The study included testmg of water supply wells.
In December 1988, an Administrative Order on Consent was signed by EP A and the
Homestake Mining Co. This order concluded that the Fox study constituted the functional
equivalent of a remedial investigation, as prescribed by the NatIonal Contingency Plan.
The order required that Homestake conduct a feasibility study (FS) in order to identify and
evaluate alternatives for the appropriate extent of remedial action to prevent or mitigate
the migration, release or threatened release of hazardous substances, pollutants or
contaminants from the site.
In 1989, an FS was conducted by ICF Technology Inc. on behalf of Homestake. Soil data
collected in May, June and July 1989 by Homestake and analyzed by Geochemical
Engineering Inc. was incorporated into this study, along with a report prepared by
Morrison Knudsen Engineers, on the feasibility of removing tailings.
Remedial action objectives for the FS were based on EP A's endangerment assessment.
EP A contracted with Battelle Pacific Northwest Laboratory to perform an endangerment
assessment. The first draft was released in January 1988 and comments were provided by
Homestake in April 1988. A second draft was released by EPA in March 1989 and
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commented on by Homestake in June 1989. In July 1989, EP A, with the assistance of
Jacobs Engineenng, released a final endangerment assessment for the site.
The conclusions of the RI/FS and the EA were that 1) although the tailings deposits
contained high concentrations of arsenic, so lon~ as the site resident does not spend
significant amounts of time in the tailings deposIts areas, the risk to that individual from
the tailings is minimal. Some residential areas and irrigated cropland do contain
concentrations of arsenic which present health risks to people living and working in these
areas because of the large amount of time the individuals are exposed to arsenic over their
lifetime, 2) ingestion of contaminated groundwater could present a risk to human health,
but that this risk could be eliminated if consumption of contaminated groundwater were
not allowed, 3) the surface water of Whitewood Creek is being impacted by the tailings
deposits but, although the concentration of arsenic in the stream occasionally exceeds some
appropriate standards, it is within the ranges specified by applicable standards.
History of Enforcement Actions
EP A sent a notice letter to Homestake in 1981 notifying them of potential liability at
Whitewood Creek and requesting information about their activities. Early in 1982, EPA,
the State and Homestake began negotiations for Homestake to perform necessary studies.
On August 11, 1982, EP A, South Dakota and Homestake completed these negotiations and
signed a memorandum of understanding among the three partIes to conduct a study of the
Whitewood Creek area. .
In September 1988, a Special Notice Letter was sent to the Homestake Mining Company
. and to Goldstake Explorations, Inc., informing them that both companies were potentially
responsible parties for cleanup of the site. The notice letter gave both parties the
opportunity to conduct the feasibility study. Goldstake elected not to panicipate in the FS
studies. As mentioned above, an Administrative Order on Consent was signed in
December 1988 by EP A and Homestake requiring Homestake to conduct an FS for this
site.
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III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
Based upon nomination by the State of South Dakota, the Whitewood Creek site was
proposed for listing on the National Priorities Ust (NPL) of hazardous waste sites in 1981
and finalized on September 8, 1983. In August and October 1985, EP A conducted
interviews with representatives from the DWNR, the Sierra Club, the Rapid City Journal,
Homestake and concerned citizens, in order to gain an understanding of the public's
concerns and attitudes about the site. Based on these interviews, concern about the site
was determined to be fairly low. This low concern was attributed to: a) Homestake having
invested time and money towards resolving contamination issues and having made
substantial progress in cleaning up the creek; b) the return of fish to Whitewood Creek, a
once-dead stream; and c) local perception that the site's problems were minor compared to
other Superfund sites across the country.
The results of these interviews were used by EP A to develop a community relations plan
for the site. Also in December 1985, EP A prepared a mailing list and sent letters to
property owners located near monitoring wells along the creek, informing them of EP A
community relations policies and requesting their input into the development of the
community relations plan. The plan was completed in April 1986 and placed in four
repositories established in Rapid City, Brookings, Deadwood and Pierre, South Dakota. In
May 1986, EP A prepared and distributed to persons on the site mailing list, a fact sheet
describing the Superfund program and how it relates to the Whitewood Creek site.
During 1988 and 1989, EP A held several meetings with property owners, elected officials
and governmental agencies. In May and September 1988, EP A met with property owners
living at or near the site and with the Centennial Valley mayor's association, In order to
discuss the status of site activities and to hear any concerns about the site. The property
owners expressed concern about the health of their children and livestock and about the
use of croplands near the site. In addition to these concerns, the mayor's association
expressed concern about the effect of the Superfund status of this site on the mining
industry, since the local economy is somewhat dependent on this industry.
In November 1988, EPA met with state legislators in Pierre, South Dakota to discuss
community concerns in the Whitewood area. The major concern expressed during these
meetings was the effect of the site on the mining industry in the state.
In September 1989, EP A met with officials from local municipalities and from the counties
of Lawrence, Butte and Meade, whose jurisdiction overlapped the site area. These
meetings were held to discuss the possibility of implementing regulatory controls such as
zoning restrictions as part of the remedy at the site.
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Following completion of the feasibility study, a proposed plan for cleanup of contamination
at the site was prepared by EPA The administrative record was established on January 5,
1990 and copies placed on file at the information center for the site, the Lawrence County
Registry of Deeds Office in Lead, South Dakota. The proposed plan fact sheet was
distributed to persons on the mailing list on January 10, 1990. Public notices, published in
the Rapid City Journal on January 8 and January 14 and the Black Hills News on January 10
announced the conclusion of the RIfFS and availability of the proposed plan for the site;
established a public comment period (from January 10 to February 9, 1990) for submitting
comment on the proposed plan; announced the upcoming public meeting to describe the
findings of the RIfFS and discuss the proposed plan; and announced the availability of the
site Administrative Record for public reVIew. The public meeting to discuss the proposed
plan was held in Whitewood, South Dakota on January 25,1990. A response to comments
received during the public comment period is included in the Responsiveness Summary,
Attachment B of this record of decision.
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IV. SITE CHARACTERISTICS
Geology and Hydrology
This section provides general information about the Whitewood Creek drainage basin and
sets the stage for the detailed discussion of contaminant migration and affected media
which follows on page 14. Figures A-2 and A-3 are schematic representations of the
geologic and hydrologic conditions and contaminated media at the Whitewood Creek
Superfund site.
The headwaters of Whitewood Creek originate in the Black Hills, which are predominantly
Precambrian granite and schist. The schist is the host rock for the gold ore at the
Homestake Mine. The gold is found in veins composed of quartz and 'iron and arsenic
sulfide minerals. The Homestake mine is in Lead, South Dakota, about six miles upstream
from the Whitewood Creek Superfund site. North of the town of Lead, the bedrock
lithology changes to thick-bedded limestone of Paleozoic age. Whitewood Creek passes
over these limestone beds and across Mesozoic sedimentary rocks containing shale and
gypsum, with some thin sandstOne and limestone beds.
Whitewood Creek was originally a small meandering stream with insufficient capacity to
transport the large quantities of tailings discharged into it by various mining and milling
operations prior to the turn of the century. The deposited tailings and some alluvial
material subsequently filled in the meanders of the creek, and thereby straightening its
channel and increasing its gradient. This, in turn, caused the creek to downcut its channel
- to the resistant shale bedrock which today forms the channel bottom for most of the length
of the eighteen-mile stretch of the Superfund site.
Although some tailings deposits exist above and below the site, the largest deposits occur
within the Superfund site, which is from the Crook City Bridge where the stream gradient
decreases at the edge of the Black Hills, to the confluence of Whitewood Creek with the
Belle Fourche River. The tailings deposits at the site range in thickness from less than one
foot to 15 feet and cover an area from 50 to 300 feet wide on either side of the creek across
the Superfund site.
Reddish-brown tailings from ore mined prior to the turn of the century make up the
majority of the deposit. Grayish-green tailings from ore mined later are also present. Both
types of tailings may be interbedded with the natural alluvium. The natural alluvium
consists of sandy to sandy silt materials with variable amounts of intermixed tailings. The
alluvium generally is less than 30 feet thick, and increases in thickness and lateral extent
downstream through the study area. Upland alluvial terraces away from the creek bed are
the site of most residences and agricultural land. Some tailings material has been
deposited on these terraces by floodwaters and wind action. There are also oral reports
that tailings have been imported to some residential areas for use as road paving material
or garden soil conditioners.
The major aquifers in the area of Whitewood Creek are the shallow alluvial aquifer, and
two deep bedrock aquifers, the Mesozoic Dakota sandstone and the Paleozoic Minnelusa
limestone.
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FIGURE A-2
Schematic Map View Diagram
of Contamination at Whitewood Creek Site
A schematic representation of potentially contaminated media at Whitewood creek.
During remedial design activities, detailed maps will be developed that show the
1 OO-year floodplain and limits of tailings deposits and alluvial and fringe areas where
arsenic concentrations are above 100 mglkg.
5
KEY
FRINGE
4~
5D
6-
100-YEAR FlOODPLAIN (UNCONTAMINATED)
UPLAND AREAS (UNCONTAMINATED)
RESIDENCES
18
2 t:.:.:~~
3-
ALLUVIUM
TAILINGS
-.-
LIMIT OF 100- YEAR FLOODPLAIN
-
ROAD
-------
" . . .. .
Irrigated
Soils
Driveways - -
&
t Gardens
~-':$
Whitewood
Creek
-----
---------
-------------
. . ....... . '" . . , . . . . . . .. .
~ . . . . .. , . ,
, , . , . . J , . . J . . . . J ~
. .. 4' J J .
.. "....."~.,.
FIGUBE A.3
Schematic Diagram of Contamination
at the Whitewood Creek Site
Illustrates the relationship of tailings deposits and alluvial materials to
Whitewood Creek and groundwater units 1 thru 4 (see text). The horizontal
scale on this figure is exaggerated and only some 01 the irrigated cropland
and residences within the site are contaminated with high levels 01 arsenic
and other metals.
: :: Tailings
G) WATER TABLE IN TAILINGS DEPOSITS
@ DOWNGRADIENT ALLUVIAL AQUIFER
CID UPGRADIENT ALLUVIAL AQUIFER
@ UPLAND ALLUVIAL AQUIFER
- -. Alluvial Materials
':':': and Soil
-: -: -: Shale bedrock
- Water Table
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The shallow groundwater at the site appears in four units which act as a single aquifer. It is
useful to describe the four units separately in order to understand the movement of
contaminants within the various media.
Tailings deposits are generally coarse-grained material, with some fine layers (Unit
1 in Figure A-3).
Alluvial aquifer materials underneath the tailings, which are most directly
influenced by water moving through the tailings, are referred to as the downgradient
aquifer (Unit 2 in Figure A-3).
Alluvial aquifer materials and shallow bedrock shale within the floodplain outside
the immediate influence of the tailings are referred to as the upgradient aquifer
(Unit 3 in Figure A-3).
Upland alluvial aquifer terrace deposits are upland away from the tailings and
floodplain alluvial materials (Unit 4 in Figure A-3).
The water table along Whitewood Creek occurs mainly in the natural alluvium underlying
and adjacent to the tailings. During wet periods of the year, the water table may rise into
the tailings. Some recharge of the shallow aquifer may occur then, as precipitation
infiltrates through the terrace materials and tailings deposits. .
In general, the water table slopes toward the floodplain, and during most of the year, there
is a net flow of groundwater from the alluvium into the creek. During high creek flow,
-lasting from two to eight weeks each spring, the flow is reversed and water flows from the
creek as far as 200 meters into the alluvium.
Migration of contaminants from the tailings to the alluvium and groundwater occurs at a
slow rate because of the chemistry of the contaminants and tailings deposits (see page 14).
The upgradient alluvial aquifer and upland alluvial aquifer appear to be uncontaminated
by tailings materials. Groundwater in the tailings deposits and the downgradient alluvial
aquifer are of greatest concern to human health.
The bedrock aquifers are separated from the shallow aquifer by up to 1,000 feet of
relatively low permeability shale. The thickness of the shale and the lack of continuous
porous zones In the shale both serve to limit the connection between the alluvial and
bedrock aquifers. Water supply wells in the bedrock aquifers tested in the RI did not
contain contaminants from tailings deposits materials.
Sources and Types of Contaminants
The initial RI studies completed by Fox in 1984 identified the tailings deposits as the
source of contamination in the study area. Fourteen target substances were investigated as
indicators of potential public health and environmental threat (Table A-I). Arsenic was
considered to be the contaminant of most significant environmental concern throughout
the media under evaluation. Cadmium, copper and manganese were detected at
concentrations above background levels but too low to be of concern to human health. The
remaining substances were either determined to be naturally occurring (sulfate, selenium)
or present at concentrations near background levels (chromium, silver, nickel, iron,
mercury, lead, zinc and cyanide).
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'.
TABLE A-I
MAXIMUM CONCENTRATIONS OF CONTAMINANTS IN AFFECTED MEDIA
WHITEWOOD CREEK, SOUTH DAKOTA
.
.
TAILINGS
MG/KG
ALLUVIUM
MG/KG
IRRIGATED
SOILS
MG/KG
ReSIDENTIAL
SOILS
MG/KG
GROUND
WATER
MG/L
SURFACE
WATER
MG/L
NATURAL
VEGETATION
MG/KG
IRRIGATED
CROPS
MG/KG
Arsenic 42,500 700 600 2,400 0.780 0.200 240 1.8
Cadmium 180 14 7.4 1.2 0.029 0.010 3.7 16
Chromium 41 22 48 NM 0.019 0.020 58 8.2
, Copper 246 104 660 NM 0.032 0.060 30 22
Iron 136,000 75,000 58,000 NM 316 0.850 9,250 438
lead 48 24 25 NM 0.10 0.002 NO NO
Manganese 8,000 5,030 1,450 NM 29 0.310 1,500 68
Mercury 5.9 1.5 0.14 0.138 NO 0.0003 0.105 0.075
Ni cke 1 2,050 33 44 NM 0.330 NM 32 22
Selenium 10 2 NO NO 0.079 0.003 1.2 0.5
Silver 2.2 4.9 0.7 NM 0.004 0.001 1.3 0.21
Sulfate 145,000 3,800 8,400 NM 4,800 NM NM NM
Zinc 136 116 159 NM 2.20 0.140 313 52
Cyanide NM NM NM NM 0.050 0.030 NM NM
NO ::: Not detected
NM ::: Not measured
Source: Whitewood Creek Study, 1984, Fox Consultants, Inc.
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Affected Media
The RI/FS documented that hazardous substances are present in a variety of media at the
site including: .
Tailings deposits;
Alluvial materials underlying tailings deposits;
Surface soils in some of the irrigated lands adjoining tailings deposits;
Surface soils in residential yards, gardens, and driveways;
Alluvial groundwater under the tailings deposits
Surface water; and
Vegetation.
Potential health impacts and risk assessments are presented in Chapter V. Th~ media
posing the greatest potential risk to human health and the environment are listed below.
The potential for contaminants migrating between the media as demonstrated by remedial
investigations, especially the Cherry study, is also summarized below.
Surface Soils in the Tailings Deposit and Fringe Areas
Tailings Deposits (Medium 2, Figure A-2). It is estimated that 21.6 million tons of tailings
exist within the site. The tailings deposits contain concentrations of arsenic (maximum
42,500 milligrams per kilogram or mg/kg) and cadmium (maximum 180 mg/kg) which are
significantly above levels in uncontaminated alluvial soils at the reference site on the Belle
Fourche River above the confluence with Whitewood Creek (12 mg/kg and 1.5 mg/kg,
respectively).
"
The tailings have been determined to be the major source of the contamination found in
other affected media. The ore body from which the tailings are derived is a metamorphic
iron magnesium carbonate. The gold is found in veins along with quartz, calcite, iron and
arsenic sulfides and other minor metals.
Oxidation of the iron and arsenic sulfides in the tailings produces a weak sulfuric acid. In
most cases, this acid is buffered by calcium in the carbonates in the ore and from the
exposed sedimentary rocks. In this buffered environment, the contaminants are relatively
immobile. Isolated pockets having an acid environment occur within the tailings and
alluvium, where some arsenic may be mobilized.
Most of the substances are transported in their solid form, rather than in solution. At
present, the contaminants contained in the tailings deposits are being released very slowly
mto the alluvial aquifers. Small amounts are being transported into the underlying
alluvium. It is anticipated that these contaminants will continue to be released through
both chemical and physical processes at these slow rates for many years.
In all but a few locations (estimated at 25% of the area for purposes of estimating costs of
potential remedial action), the tailings deposits support vegetation including grasses, shrubs
and trees. Most unvegetated areas have a thin gypsum crust at the surface. This cover
provides some stability for these deposits. The tailings exhibit some instability at the creek
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bank edges and where cover is absent. Some of the tailings with their contaminants are
released to the surface waters of Whitewood Creek. It is estimated that 7,000 kg of arsenic
may be added to the surface waters from normal erosion, hea~ rainfall and seepage during
a normal year. Periodic flooding events may introduce an additional 35,000 kg m a single
event.
The potential risk to human health through inadvertent ingestion of tailings was evaluated
as part of the soil exposure pathway.
Alluvial Materials Underlying Tailings Deposits (Medium l;Figure A-2). It is estimated
that at least 10 million tons of alluvium underlie the tailings deposits within the site. The
alluvium underlying the tailings deposits consistently exhibits elevated levels of arsenic
(maximum 700 mg/kg).
While the contaminants within the alluvium are relatively immobile, they are being
released very slowly to alluvial aquifers, and transported in small amounts to the surface
waters of Whitewood Creek. There may be some scouring of alluvial materials from the
bank into the creek during high river flows. In most instances, the alluvium is covered by
tailings and the contaminants within it are insulated from, and not available to,. surface
transport processes, such as erosion or runoff. Because of the covering tailings deposits, no
human health exposure pathways exist.
Irrigated Soils (Media 3, 4, and 5, Figure A-2). Approximately 83 acres of irrigated
cropland are located within the site. About one-fourth of the water used for irrigation
comes from upgradient alluvial or bedrock aquifers, one-fourth from Whitewood Creek
and one-half from the Belle Fourche River. Only some portions of the total irrigated
croplands are contaminated by arsenic. Overbank floodmg and windblown tailings
materials probably contributed most of the contamination, although Whitewood Creek
surface water may have contributed small amounts of arsenic to the soil where it is used for
irrigation.
Arsenic levels are elevated in samples of irrigated soils taken at different locations
throughout the site (maximum 600 mg/kg). There is no indication that contaminants in the
irrigated soils are migrating into the alluvial groundwaters because of the relative
immobility and low concentrations of arsenic in these soils. Contaminant uptake by crops
occurs to varying degrees, depending on the contaminant. The potential risk to human
health through inadvertent ingestion of contaminated soil was evaluated as part of the soil
exposure pathway. The potential risk due to ingestion of crops is discussed below in the
section on vegetation.
Surface Soils in Residential Yards. Gardens and Driveways (Medium 6, Figure A-2). The
contamination in the residential areas is from windblown tailings materials and from
tailings materials inadvertently transported in by dirty work boots etc. or imported for use
as a soil conditioner and driveway base. Three residential properties within the site have
been found to have surface soil arsenic contamination (maximums: lawn 520 mg/kg, garden
540 mg/kg, driveway 2400 mg/kg). In these samples, maximum concentrations were
reported in the 0-6" samples. Concentrations of arsenic in the 18" and 24" depth samples
were above background for the area but less than 100 m:: ':'g. Other residential properties
within the site have not been sampled. Approximately L . ~'sidences were estimated in the
feasibility study to have arsenic concentratIons greater than 100 mg/kg. The total number
of affected residences and amount of contaminated material will be determined during the
remedial design phase of the Superfund work.
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There is no indication that contaminants contained in these soils are migrating into the
alluvial groundwaters because of the relative immobility and low concentration of arsenic
in these soils.
The potential risk to human health through inadvertent ingestion of contaminated soil was
evaluated as part of the soil exposure pathway. .
Downgradient Alluvial Groundwater. The water from the downgradient alluvial aquifer
(Unit 2, Figure A-3) is the only groundwater to exhibit elevated levels of contaminants.
Concentrations of arsenic (maximum: 0.78 mg/l) are detected above background levels.
These concentrations exceed primary drinking water standards and the South Dakota
Drinking Water Standards.
The water table along Whitewood Creek occurs mainly in the natural alluvium underlying
the tailings. During wet periods of the year, the water table may rise into the tailings.
Some recharge of the shallow alluvial aquifer may occur then, through infiltration of
precipitation moving through the terrace deposits and the tailings deposits. In general, the
water table slopes toward the floodplain and, during most of the year, there is a net flow of
groundwater from the alluvium into the creek. During high creek flow, lasting from two to
eight weeks each year, this flow is reversed. The effect of recharge from the stream may be
seen as much as 200 meters ftom the stream. In the areas where the tailings deposits are
fine-grained with low permeability, localized perched zones produce small seeps and
springs along the bank of the creek. Gypsum crusts form in places at the surface of the
tailings and at the seeps.
Three mechanisms appear to act in movement of arsenic from the tailings to the
groundwater: 1) dissolution of arsenic during those times of the year when the water table
is in the tailings, 2) dissolution of arsenic when preci?itation infiltrates downward through
the tailings and 3) incorporation of tailings particles mto the alluvium, which probably
occurred as the tailings were being deposited. Movement of contaminants presently
continues at a slow rate, and could continue for thousands of years.
The potential risk to human health occurs through ingestion of contaminated groundwater.
Surface Waters of Whitewood Creek. The concentrations of contaminants (Table A-I) in
surface waters of Whitewood Creek comply with water quality standards established by
South Dakota for Whitewood Creek and EP A water quality criteria for chronic toxicity to
aquatic life. Concentrations of arsenic at the U.S. Geological Survey Vale sampling station,
downstream of the site, occasionally exceed the water quality critena for the protection of
human health from the consumption of fish. These exceedances are due in part to .
upstream sources and to the additional contributions from the tailings deposits along the
creek within the site.
The upstream sources include minor unquantified discharges of municipal and industrial
wastewaters from the communities of Lead, Deadwood and Whitewood. Minor additional
contamination may be attributed to the few tailings deposits between the Homestake Mine
and the beginning of the Whitewood Creek Superfund site at the Crook City Bridge.
Homestake mine discharge also contributes to the upstream loading. Prior to the
installation of the Grizzly Gulch Tailings Impoundment and Homestake's wastewater
treatment plant, the surface water in Whitewood Creek below the mine was substantially
degraded and incapable of supporting aquatic life. Following completion of the treatment
plant, Homestake has been dIscharging to Whitewood Creek under a draft permit from the
State of South Dakota. The allowable discharge concentrations for arsenic (0.184 mg/L,
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daily maximum; 0.105 mg/L, daily average) in the treatment plant effluent "were developed
to be protective of a cold water fishery usage of Whitewood Creek between Lead and the
Superfund site using ambient water quality above the discharge, and wasteload allocation
calculations. The present arsenic concentrations in the effluent at the discharge point
located near the town of Lead average 0.03 mg/L with maximums of 0.06 mg/L.
The water quality of Whitewood Creek is different as it leaves the site from that entering
the site. Groundwater seeping through the tailings and alluvium into the creek adds an
average of 365 kg/year of arsenic to the creek. Normal erosion of tailings along"
Whitewood Creek contributes on the average of 300 kg/year of arsenic and heavy rains
may contribute another 6,000 kg/year. During periodic flood events up to 35,000 kg of
arsenic is added to Whitewood Creek from the erosion of the tailings. This added load of
contaminants to the" surface water across the site results in an increase of arsenic
concentrations which varies with the amount of flow in the creek and time of year.
The levels of dissolved arsenic at the downstream end of the site exceed water quality
criteria for the protection of human health from the consumption of fish. The levels also
periodically exceed the National Primary Drinking Water Standards for arsenic of 0.05
mg/L and have approached the criteria established by the EP A for chronic toxicity to
aquatic life of 0.190 mg/L. The observed changes in water quality are related 10 the
uncontrolled releases from the site throughout the year as well as the processes which lead
to removal of contaminants from the water column to the sediment of the stream bed.
Consequently, the range of observed percent change in arsenic concentrations in
Whitewood Creek reported between 1985 and 1987 was from a loss of 80 percent in
September 1985 to an increase of 490 percent in July 1985.
Preliminary calculations in the RI/FS indicated that the potential risk to human health of
ingesting contaminated water is too low to be of concern, in part because there is no
current or anticipated future use of Whitewood Creek surface water for drinking. The
National Primary Drinking Water Standards for arsenic are therefore neither applicable,
relevant or appropriate as a requirement for Whitewood Creek. There are no applicable
standards for toxicants in the reach of Whitewood Creek within the site. However, the
EP A, 1986 Quality Criteria for Water document established arsenic levels for preventing
chronic toxicity of 0.190 mg/L which may be considered as a relevant and appropriate level
for protection of the semi-permanent warmwater fishery designated by the State for
Whitewood Creek within the site. Due to the potential for exceedances of the national
chronic toxicity criteria, coupled with the uncertain future rates of release of arsenic from
the tailings deposits, EP A has determined that continued monitoring of Whitewood Creek
water quality is needed. .
Vegetation. Certain native plants growing on the tailings deposit areas contain
concentrations of arsenic (maximum 240 mg/kg, Table A-I) above that of vegetation from
the reference area. Some cultivated crops (alfalfa, for example) contained concentrations
of arsenic elevated above background, but below levels cited as producing reduction in
crop productivity or causing toxic effects in livestock. Arsenic levels were not elevated in
crops for direct human consumption. During the endangerment assessment, consumption
of vegetation was not considered as a transport pathway, because of the low arsenic levels
and because arsenic does not accumulate in tissue or increase in concentration as it
progresses up the food chain.
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v. SUMMARY OF SITE RISKS
Actual or threatened releases of hazardous. substances from this she, if not addressed by
implementing the response action selected in this ROD, may present an imminent and
substantial endangerment to public health, welfare, or the environment.
CERCLA mandates that EP A select remedies that protect human health and the
environment from current and potential exposures to hazardous substances. Therefore
EP A has conducted endangerment assessments (EA) to evaluate the risks posed by the'
presence of contaminants at the Whitewood Creek site; These studies are listed in Section
II of this document. The risk analyses resulting from EP A's summary document were used
for the feasibility study and for this Record of Decision.
For a risk to exist, three components must be present: 1) a source of contamination; 2) a
pathway for contaminants to reach humans, plants or amma1s; and 3) a population that
could potentially be exposed. If any of the three components is missing, no risk can exist.
The key component of any health risk assessment is the amount of chemical reaching the
population. This is known as the dose. For any given dose, there are two general types of
toxic responses: non-carcinogenic and carcinogenic (cancer-causing).
Non-carcinogenic risks are calculated by assuming that there is a dose below which no
adverse health effects will occur. These calculations are usually based on results of animal
studies and include a number of additional conservative assumptions to take into account
that the estimated risk is to humans. For such chemicals, exposures less than this dose
(referred to as the "reference dose") will result in no toxic effects. Many of the 14 metal
contaminants found at Whitewood Creek Superfund site have an effect on multiple organ
systems. Therefore, the method of adding all the contaminant-specific risk estimates was
considered appropriate for estimating actual risks. Potential concern for non-carcinogenic
effects of a smgle contaminant in a single medium is expressed as the hazard quotient
(HQ) (or the ratio of the estimated intake derived from the contaminant concentration in a
given medium to the contaminant's reference dose). By adding the HQs for all .
contaminants within a medium or across all media to which a given population may
reasonably be exposed, the Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of multiple contaminant exposures
within a single medium or across media.
For carcinogens, it appears that there is no safe dose. Instead, the risk of cancer becomes
smaller and smaller as the dose decreases. Cancer potency factors (CPFs) are used for
estimating excess lifetime cancer risks associated With exposure to potentially carcinogenic
chemicals. Excess lifetime cancer risks are determined by multiplying the intake level with
the cancer potency factor. These risks are probabilities that are generally expressed in
scientific notation (e.g., 1 x 10-6 or 1E-6). An excess lifetime cancer risk of 1 x 10-6
indicates that an individual has a one in one million chance of developing cancer as a result
of site-related exposure to a carcinogen over a 70-year lifetime under the specific exposure
conditions at a site. A risk in the range of 10-4 to 10-6 is considered to be acceptable. EP A
generally uses 10-6 as a goal in evaluating cleanup alternatives. However, other factors,
such as exposure, technical limitations, background concentrations, and uncertainties may
result in the setting of a different goal.
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Contaminants
The media most contaminated by arsenic and cadmium, the contaminants of greatest
concern for this site, are the downgradient alluvial aquifer, tailings deposits, irrigated
cropland soils and residential soils. Each of these media contribute a portion of the dose
ingested by the exposed population depending upon the concentrations of conlaminants in
the media and the individuals exposure to the media. Section V discusses the volume and
mobility of contaminants in these media in greater detail. See Table A-2 for average
concentrations of all substances assessed in the EA The discussion which follows outlines
assumed exposure patterns for a variety of exposure scenarios.
Pathways
There are a number of pathways by which contaminants from the tailings deposits may
reach individuals living within or visiting the site. EP A's EA for the site concluded that the
pathways which present the highest risk are ingestion of groundwater and ingestion of
contaminated soil media (tailings deposits, irrigated cropland soils and residential soils).
The existing ranches and potential ranch sites in the Whitewood Creek area could be
expected to utilize groundwater from the upgradient alluvial aquifer. Ranches .could also
hypothetically use the downgradient. alluvial aquifer in the future (See Figure A-2 and A-3).
Some of tbe ranches exist near tailings deposits and/or contaminated irrigated soils.
Inadvertent soil ingestion could occur at tbese ranches during an individual's lifetime from
such activities as playing, hunting, fishing, cutting wood, gardening, and working in the
yards and fields. Furthermore, household dust might contain arsenic blown in or
mechanically transported (e.g., dirty work boots) from tailings and cropland soils. Most
large dust particles which are breathed into the lungs are removed from the lungs by the
lung's self cleaning action. Contaminants can become incorporated into mucus and
swallowed, in a pathway referred to as incidental soil ingestIOn.
Additional pathways were also considered, but risk calculations were not developed. Risks
for the consumption of homegrown foodstuffs, the air pathway (through inhalation of
respirable partIcles) and the surface water pathway were not calculated in the
endangerment assessment becauselreliminary calculations in the RI/FS indicated
concentrations of contaminants an the potential for exposure through these pathways
were too low to be of concern.
Population Exposure Scenarios
The expOsure to the potential carcinogen, arsenic (Table A-2), and non-carcinogenic
metals in soil and groundwater via ingestion was evaluated for four exposure scenarios.
These include 1) a representative adult site resident, 2) a representative child site :esident,
3) a recreational visitor, and 4) a hypothetical future (maximum exposed) site resi.::ent.
Assumptions for ingestion rates are included in Appendix A
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TABLE A-2
AVERAGE CONCENTRATIONS OF
CONTAMINANTS IN VARIOUS MEDIA
Groundwater (mq/L)
Contaminant
Upgradient
oowngradient
Irrigated
Cropland
Soil (mq/kq)
Residence
(yard)
Tailings
Arsenic 0.009 0.21 99 2,116 166
~ Cadmium 0.004 0.003 2.1 14 0.90
:;)
Chromium 0.008 0.005 26 29 26
Copper 0.11 0.002 48 49 48
Lead 0.019 0.025 19 37 19
Manganese 0.015 1.6 575 1,816 575
Mercury 0.0003 0.0004 0.065 1.63 0.084
N i c ke 1 0'.01 0.01 26 23 26
Source:
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.Representative Resident (Adult and Child~ This scenario was examined to assess the
potential risk to a current representative site resident. Using the exposure assumptions
outlined in the para~raphs which follow, it was determined that the carginogenic risks to
the representatIve sIte resident are 1 X 10-4 through exposure to groundwater, and 2.4 X
10-4 through exposure to all soils with a total risk of 4.3 X 10-4. The representative adult
site resident is not considered to be exposed to excessive non-carcinogenic risk because the
hazard index for groundwater was 0.54 and for soil 0.14, a total hazard index of 0.7 (less
than 1). The representative child site resident was considered to be exposed to excessive
non-carcinogeruc risk from ingestion of soil because the hazard index calculated was 1.0
(equal to 1).
The representative site resident carcinogenic risk scenario considers exposures which a
person living and working on site would encounter during six years as a child and thirty
years as an adult. For adult non-carcinogenic risk, only exposure levels due to adult
activities are assumed. Adults are assumed to be exposed to soils from the contaminated
residential, irrigated cropland, and tailings areas, and water from the upgradient alluvial
aquifer. The upgradient aquifer was chosen as representative of present conditions,
because downgradient wells are presently banned by the State.of South Dakota and there
are no users of this aquifer. .
The fraction of daily soils ingestion from differing areas on site is assumed to be
proportional to time spent at that area. It is also assumed that soil is too frozen to be
mgested for 33 percent of the year. For the adult, 16 hours per day is assumed to be spent
at or near the residence. It was estimated that residents are exposed 260 hours per year to
tailings deposits soils while engaged in activities such as woodcutting, hunting, and various
minor agncultural activities. It was also estimated that the resident would be working at
irrigated cropland soil locations for approximately 3.4 hours per 8 hour work day per 5 day
work week.
Children in this scenario are assumed to be exposed only to residential soil on site and also
to upgradient alluvial aquifer groundwater. The average resident child (age group 1-6
years) is assumed to be exposed to mobile (not frozen) contaminated soils at residential
areas 90% (21.6 hours) of the average day.
Recreational Visitor. The recreational visitor scenario was examined to assess the
potential risk associated with the use of Whitewood Creek area for recreational purposes
by persons who do not live within the site. Assuming that the recreational visitor would
only be exposed to tailings deposit soils as detailed in the following par~raph, it was
determined that. this person would incur a carcinogenic risk of 8.2 X 10- . The recreational
visitor would not incur an unacceptable non-carcinogenic risk from soil ingestion because
the hazard index calculated was .05 (less than 1).
The recreational visitor scenario assumes that a person hunting and fishing at the site could
be exposed to contaminants through incidental ingestion of tailings deposit soils. This
person is estimated to be exposed to soils at the tailings areas approximately once per week
for 6 months per year for a period of 20 years (a total of 520 occurrences. of exposure ). For
this scenario, it is also assumed that incidental ingestion and dermal absorption of
Whitewood Creek surface water represents insignificant human exposure pathways.
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Maximum Exposed Resident. The maximum exposed resident scenario was examined to
assess the risk associated with a person who may have the maximum exposure to site
contaminants, based on reasonable assumptions. Using the exposure assumptions outlined
in the paragraphs which follow, it was determined that the carginogenic risks to the
maximum exposed site resident are 4.4 X 10-4 through exposure to groundwater, and 2.6 X
10-3 through exposure to all soils with a total risk of 7.0 X 10-3. The maximum exposed site
resident is consIdered to be exposed to excessive non-carcino~enic risk because the hazard
index for groundwater was 3.8 and for soil 1.1, a total hazard mdex of 4.9 (greater than 1).
The maximum exposed resident scenario is a hypothetical e~osure scenario which assumes
that future development occurs on site, resulting in the buildmg of residences on the
tailin~s soils and also resulting in the use of downgradient alluvial aquifer water for
drinking purposes. The scenario considers exposures that a resident would incur by simply
living on site. For carcinogenic risk, 30 years of adult exposure and an additional 6 years of
exposure as a child have been assumed. For adult non-carcinogenic risks, only adult
exposure levels are assumed.
Adults are assumed to be exposed to tailings deposit soils for approximately two-thirds of
each day, and that tailings are frozen 33 percent of the year. In this scenario, it is assumed
that the average child resident will spend 90 percent of the average day in the tailings
areas, which are frozen 33 percent of the year.
Risk Characterization
The results of EP A's EA indicated that arsenic is the contaminant of concern for non-
carcinogenic and carginogenic risks associated with site exposure. Concentrations of
arsenic exceed background levels and result in an unacceptable risk to current and future
site residents. EP A has determined that an excess upper bound cancer risk of less than 1 X
10-4 is acceptable for the site. .
The background concentration of arsenic corresponds a~proximately to 2XlO-4 risk
through ingestion of groundwater and 1 XlO-5 to 5 XlO- through ingestion of soils (based
on site information and EPA 1983, Hazardous Waste Land Treatment, SW-874 (28a».
EP A requires that acceptable e}q)osur~ levels represent an exces~ upper bound cancer risk
of 10-4 to 10-6. EP A uses 10-6 as a "pomt of departure" for selectIng acceptable levels of
protectiveness. Because the risk associated with exposure to background concentrations
exceed the 10-5 risk level, EP A has selected 10-4 as an acceptable level of protectiveness for
the .Whitewood Creek site. 10-4 was used by EP A as the target risk for the selection of an
action level for site remediation.
As a result of the assessment of site risk in the EA, EP A has determined that ingestion of
downgradient aquifer groundwater (4 X 10-3) and tailings deposit soils (2.3 X 10-3) as
defined in the maximum exposed resident provides an unacceptable risk to future residents.
In addition, exposure through the ingestion of all soils (2.4 X 10-4) as defined in the
representative rural resident scenario for existing residents is determined to not be
protective of public health. Risk associated with the exposure as described in the
recreation visitor scenario is within the acceptable risk range for the site.
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The greatest non-carcinogenic risks are to the maximum exposed site resident and
representative child resident (Table A-4) from ingestion of downgradient alluvial
groundwater and tailings deposit soils. Recreational visitors and representative site
residents are not considered to be exposed to excessive non-carcinogenic risks. In all
scenarios, arsenic is the metal of greatest concern.
Based on the findings of the EA, response objectives for the soils and alluvial groundwater
were identified. The response objectives for soil remediation at Whitewood Creek are to
control exposure through ingestion of contaminated tailings deposit soils, alluvial soils and
residential soils, or downgradient alluvial groundwater. Target cleanup objectives for
groundwater are the Maximum Contaminant Levels. Target clean-up objectives for soils
were developed based on soil concentrations which correspond to carcinogenic health risks
of 1 x 10.4. Acceptable contaminant levels for the chemical of concern (arsenic) in
residential soils are 100 mg/kg, based on the 1 x 10-4 target risk levels derived in the
endangerment assessment. This action level would also reduce non-carcinogenic risk to an
acceptable level. A summary of these calculations is provided in Appendix B of this
document.
Environr ~ntal Risks
Surface Water: Remedial investigation studies completed prior to installation of
Homestake's wastewater treatment plant indicate that enVlI'onmental populations of
recreational or commercial significance were not at risk at or near the site. The Fox study,
for example, re?orted 16 non-game species of fish and a varie::, of invertebrates in the
. waters prior to Installation of Homestake's wastewater treatment plant. The FS assumed
that the improved quality of the treated water observed following the installation of tbe
plant resulted in an improved habitat in Whitewood Creek.
High discharge events in the past ten years have resulted in some increase in arsenic
loading to the stream from erosion of cutbanks and exposed tailings materials. In most
areas, however, the stream bed currently has incised bdow the level of the tailings,
decreasing the erosional capacity of normal stream flow. It is anticipated that annual flood
events might have a temporary effect on the quality of the stream. In addition, infrequent
larger flood events probably would result in the redistribution of some tailings deposIt
materials, but the volumes of material most likely would not be large.
Whitewood Creek below the Crook City Bridge is designated by the State of South Dakota
as a warmwater, semi-permanent fishery, and meets the State criteria for this use (few toxic
contaminants are included in the criteria). The levels of dissolved arsenic at the
downstream end of the site have approached the criteria established by the EP A for
chronic toxicity to aquatic life of 0.190 mg/L. EPA water quality criteria and the criteria
for the State of South Dakota are based on protectiveness to the aquatic habitat. Since
these levels are not exceeded, it is assumed that the aquatic habitat is currently not
threatened or endangered. However, because the current release of arsenic into the
surface water is uncontrolled, there is a possibility of exceedances of these criteria in the
future. Monitoring c - surface water quality is therefore part of EP A's selected remedy for
this site.
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Table A-3
Potential Lifetime Cancer Risk for Exposure to Arsenic
Via The Soil and Groundwater Ingestion Pathways
Groundwater1
Arsenic Risk
Soil2
Scenario
Representative Site Resident
Maximum Exposed Site Resident
1.9 X 10-4
4.4 X 10-3
2.4 X 10-4
2.6 X 10-3
8.2 X 10-5
Total
4.3 X 10-4
7.0 X 10-3
8.2 X 10-5
Recreational Visitor
Table A-4
Hazard Indices Due to Exposure to Contaminants of Concern
Via the Soil and Groundwater Ingestion Pathways
Total Hazard Index
Groundwater1
SoiIZ
Total
Scenario
Representative Site Resident 0.54 0.14 0.7
Maximum Exposed Site Resident 3.8 1.1 4.9
Recreational Visitor N/A 0.05 0.05
Representative Child Resident N/A 1.0 1.0
1 Upgradient and downgradienl groundwater ingeslion rates vary by scenario. See text and Appendi.x A for
explanation. .
2 Tailings deposit soils, irrigaled cropland soil and residential soil ingestion rates vary by scenario. See text
and Appendix A for explanalion .
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Vegetation: Two major types of riparian plant communities are present along Whitewood
Creek. The southern portion is dominated by bur oak, while the northern portion, with
shallower gradient and wider floodplain, is dominated by cottonwood and willow.
Although some of the tailings deposits remain barren, an abundant plant community with
limited diversity has gradually colonized the tailings over the years. The succession appears
to begin when grasses take root in leaf litter trapped in depressions in the surface of the
tailings. Some trees in the tailings deposits have been dated at over 100 years old.
Some native plants growing on the tailings deposit areas contain concentrations of arsenic
above that of vegetation from the reference area. It appears however, that arsenic is only
one of the limiting factors for establishing a normal plant community on the tailings
deposits. Other factors such as the presence of other minerals, clay content, soil pH and
permeability may act independently in restricting growth, or may control the phytotoxicity
of arsenic in this environment.
Other Species: An informal survey of site residents indicates that deer, turkey, grouse and
other wildlife are common in the area. A field survey for threatened or endangered species
is presently underway.
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VI. DESCRIPTION OF ALTERNATIVES
Nine remedial alternatives (see Table A-5) were initially identified in the FS to address the
public health risk at the Whitewood Creek Superfund site documented in the EA
The remedial action objectives identified by EP A Region VIII are:
Prevent ingestion by site residents of surface soils of the tailings deposit areas that
would pose a potential excess lifetime cancer risk from the intake of arsenic which
when combined with the potential excess lifetime cancer risks posed by arsenic'
intake from the ingestion of surface soils from other areas within the Site, would
exceed 1 X 10-4. As noted in the EA, ~iven the uncertainties inherent in
determining the fractions of tailings sojl ingested by individuals livin~ at the site, this
remedial action objective should mitigate the incidental tailings soil mgestion to
justify use of smaller intake fractions for tailing soils in post remediation risk
calcula tions.
Prevent ingestion, by residents of the Site, of residential surface soils having an
average arsenic concentration that exceeds 100 mg/kg. .
Prevent ingestion, by residents of the 'Site, of drinking water drawn from the
downgradient alluvial ground waters having an average concentration of any
inorganic constituent other than selenium that exceeds the maximum contaminant
level for that constituent specified in 40 CFR 141.11 (b) of the National Primary
Drinking Water Regulations.
Continue monitoring the water quality and flow of Whitewood Creek at the
sampling stations near Whitewood and Vale.
These alternatives were evaluated and screened based on three criteria: 1) effectiveness to
achieve the remedial action objective, 2) implementability, and 3) cost. As a result of this
screening, six alternatives were considered for detailed evaluation. These six alternatives
(1,4, 4a, 5, 7 and 9) are described below. .'
For all cases, except the "No Action" alternative, it would be necessary to refine knowledge
of the extent of the 100-year floodplain of Whitewood Creek and determine the extent of
tailings deposits and areas where surface soil (up to 2 feet below surface) contain greater
than 100 mg/kg of arsenic. The adoption of institutional controls, designed to minimize
exposure of site residents to surface soils at the site containing elevated arsenic
concentrations, are an integral part of all alternatives but the "No Action" alternative. All
alternatives would rely on the continuance of the State regulation prohibiting the
installation of water supply wells in the alluvial aquifer within the 100-year floodplain in
order to prevent exposure of site residents to contaminated groundwater. All options
except Alternative 9 would require that a public health and environmental evaluation be
conducted every five years.
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TABLE A-5
REMEDIAL ALTERNATIVES FOR WHITEWOOD CREEK
Alternative 1:
Alternative 2:
Alternative 3:
Alternative 4:
Alternative 5:
Alternative 6:
Alternative 7:
Alternative 8:
Alternative 9:
No action
Institutional controls
Institutional controls with fencing of tailings deposit areas
Institutional controls with covering and/or removal of surface soils
of exist:' 6 residential properties a
Institutional controls with fencing of tailings deposit areas and
covering and/or removal of surface soils of existing residential
properties a
Institutional controls with full soil cover of tailings deposit areas
and covering and/or removal of surface soils of existing residential
properties
Institutional controls with partial soil cover of tailings deposit areas
and covering and/or removal of surface soils of existing residential
properties a
Institutional controls with removal of tailings deposit areas, on-site
disposal of tailings and covering and/or removal of surface soils of
existing residential properties
Institutional controls with removal of tailings deposit and alluvial
tailings from tailings deposit areas, on-site disposal of tailings and
covering and/or removal of surface soils of existing residential
properties
a
During the detailed analysis, a sub-alternative (allowing for future development) to
these alternatives was added.
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.....
Alternative 1: No Action
The No Action alternative would consist of no remedial activities.
The current State of South Dakota ban on construction of water supply wells within the
100-year floodplain of Whitewood Creek between the Crook City Bridge and the
confluence with the Belle Fourche River would continue to be enforced (South Dakota
Water Rights Rules, Section 74:02:04:26). This regulation prohibits construction of wells
that supply water to the public or supply water for household domestic use or for
agricultural purposes. A variance is also provided for in this regulation which may be
granted, if it is shown that a well in this location will not be contaminated from tailings
deposits and will not cause groundwater pollution. A public health and environmental
evaluation would be conducted every five years.
Alternative 4: Institutional Controls with Covering and/or Removing Surface Soils at
Residential Properties (Including the Restriction of Future Development)
Two activities required to refine knowledge of the extent of site contamination and define
site boundaries would be completed during remedial design. A survey would be conducted
to define the limits of the 100-year floodplain. Soil would be sampled both at the surface
and at depth to define the tailing deposit areas and parcels of land with surface soils
arsenic concentrations greater than 100 mg/kg. Maps compiled during these activities will
be used to support the county ordinances regardin~ use of tailings deposits and fringe
areas. All residential properties within the site whIch potentially contain soils with arsenic
concentrations greater than 100 mg/kg as defined by this initial sampling of soils would
also be sampled.
To define the boundaries of the tailings deposit areas on both sides of the creek, transect
lines perpendicular to and at selected intervals along a baseline connecting the Crook City
Bridge to the point where Whitewood Creek joins the Belle Fourche River would be laid
out on a map and in the field. Parallel baselines may be utilized as needed to .
accommodate local obstructions. Surface soil measurements of, or samples for the analysis
of, total arsenic would be taken along each of these transect lines near the approximate
boundaries of the tailings deposit areas on either side of the creek and at intervals as
required to identify the extent of soils with arsenic concentrations greater than 100 mg/kg.
The sample locations and associated analytical results would be plotted on a map to define
the boundaries of the tailings deposit areas.
Tailings deposits will be identified by a statistically significant change in the physical and
chemical characteristics of the surface solids. These parameters may include, but not be
limhed to, color, particle size, grain size distribution and arsenic concentration.
To define the locations and boundaries of those parcels of land .outside and on the fringes
of the tailings deposit areas that have surface soils arsenic concentrations greater than 100
mg/kg, sample measurements or samples of the top one inch and at six inches below the
surface of soils would be taken along (or parallel to) each of the transect lines described in
the previous subsection. These arsenic measurements or soil samples would be taken at
intervals beyond the apparent boundary of the tailings deposit areas until arsenic
concentrations at or below 100 mg/kg were detected.
The survey to define the limits of the 100-year floodplain would start with ground truthing
of existing aerial photographs and maps including Federal Emergency Management
Authority (FEMA) maps. The objectIve of this task is to analyze the potential for
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redistribution of existing tailin~s deposits during major flood events by identifying segments
where flood events may result m significant erosion and/or deposition. .
Areas around the residential properties with greatest potential exposure to arsenic
concentrations exceeding 100 mg/kg in the surface soils would be remediated as
subsequently described. If the arsenic level exceeds 100 mg/kg within a defined parcel
around each of the potentially affected residences, the property would be subjected to
remediation as described below.
The parcel around each of the residences will be based on the most actively used portion of
the property including the immediate yard (non-garden) around the residence, the
driveway and garden areas. The boundaries of each of the residential parcels and the
subareas within each parcel would be determined during RD/RA, and must be
coordinated with the current resident(s). These areas would be detailed on a residential
site map as part of the site plan for each property. It is assumed that the residential parcels
will be approximately two acres, and that gardens will be approximately 90 feet by 180 feet.
If use patterns exceed this area, then up to 8 acres and 2 acres respectively will be
remediated. If the residential property is less than two acres, the entire parcel, regardless
of size, would be remediated if the arsenic levels as determined from the sampling exceed
100 mg/kg. .
A limited number of random samples would be collected from driveways and residential
soils at any of the twenty-two residences which were within the RI study area but are
outside the 100 mg/kg isopleth. If any sample contains surface soil concentrations greater
than 100 mg/kg arsenic, then a residential parcel would be selected for sampling as
outlined above and remediated as required.
At the residential parcel subject to potential remediation, a garden area designated for
food production would be identified on the residential site map along with driveways,
buildmgs and other physical features. The residential area would be divided into a grid
with the line spacings set at 30 feet. Each of the 900 square foot areas defined by the grid
lines would be sampled to determine the arsenic level at the surface and the six inch depth.
The two samples for analysis from each 900 square foot area (surface and subsurface)
would be a composite of the less than 2 mm size fraction from each of the four quadrants
of the area. If any of the samples from the surface or subsurface exceed the 100 mg/kg
arsenic level, then that 900 square foot area would be subjected to remediation.
Samples collected during the RI/FS indicate that where residential soils are contaminateo,
arsenic concentrations are above 100 mg/kg in the top twelve inches of soil. Samples taken
from eighteen and twenty-four inch depths were at background levels. It is assumed th...t in
the non-garden areas where no invasive activities occur, twelve inches of cover will provide
sufficient protection for the residents.
The remediation of those non-garden yard areas which exceed the 100 mg/kg arsenic level
therefore would involve some combination of the following actions to minimize exposure of
the residents to contaminated surface soils. 1) If topography, building foundation level
and resident permit, 12 inches of soil cover would be placed. 2) If it is possible to maintain
topography consistent with immediately adjacent areas, or if the resident requests, the
removal of twelve inches of soil and replacement with twelve inches of clean soil may be
required. 3) If surface soil arsenic concentrations of less than 100 mg/kg can be achieved
by removing 6 inches or less of existing soil, this would be done, and sufficient clean soils
(20 mg/kg arsenic) would be placed on the excavated areas. In any of these cases, the
areas would be restored to their former vegetated conditions. As noted below, excavation
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below areas remediated would be prohibited by county ordinance, unless the soil is
demonstrated to contain less than 100 mg/kg arsenic.
In garden areas, the invasive and mixing activities associated with gardening could result in
elevated levels of arsenic below that found in the adjacent soils. Twenty-four inches of soil
would therefore be removed and replaced with clean soil from off-site sources ( < 20 mg/kg
arsenic).
Roadways and driveways at existing residential properties are paved with gravel or other.
non-asphaltic, non-cement materials. Where the surface soil arsenic concentrations exceed
100 mg/kg, these gravels would be cleaned up. Six inches of existing gravel would be
removed and replaced with clean imported gravel or road base « 20 mg/kg arsenic).
Contaminated soil and gravel will be disposed of at an off-site facility approved by EP A,
such as the Grizzly Gulch tailings impoundment near Lead, South Dakota. Under section
121(cf)(3) of CERCLA, any off-site dIsposal facility used must be operating in compliance
with all applicable Federal law and State requirements. The disposal will be undertaken in
compliance with EP A policy and/or regulations governing off-site disposal of CERCLA
waste.
Following removal and/or covering activities, composite soil samples would be 'taken at
one inch and at one-half the depth of soil or gravel cover from all remediated areas in the
manner previously described, and analyzed for total arsenic concentrations. Sampling
density will be similiar to that required for pre-remediation sampling. This confirmation
sampling would confirm that arsenic levels have been brought to below 100 mg/kg.
SimIlar sampling and analysis would also be performed after any flood event that resulted
in inundation of any residential property within the site.
The arsenic analysis of soils and other material at the site may be performed using an EP A-
approved laboratory or by a combination of laboratory and field analysis using a portable
X-ray fluorescence (XRF) instrument. The use of field-portable instruments will be
acceptable after development of EPA-acceptable quality assurance/quality control and
calibration at an acceptable detection limit for the concentrations bemg analyzed. If
samples are analyzed by XRF in the field, 15 percem of the initial characterization and
confirmational samples will be split and sent to an EP A-approved analytical laboratory to
confirm the field results and, for confirmational samples, that the arsenic levels are less
than 100 mg/kg.
The three counties involved, Meade, Butte and Lawrence, have all expressed a willingness
to enact controls similar to those outlined in Appendix D of the Feasibility Study. These
institutional controls would include:
County zoning and building permit regulations would be adopted prohibiting
residential and commercial development within the tailings deposIt areas and
prohibiting residential development of properties that exhibit surface soil arsenic
concentrations exceeding 100 mg/kg.
County regulations would be adopted prohibitin~ the removal and use of tailings
soils from the tailings deposit areas and prohibitmg disturbing remediated areas
below the depth of soil removal/cover unless the soil is demonstrated to contain less
than 100 mg/kg arsenic. Mining of the tailings deposits would be allowed subject to
pertinent regulations of the State of South Dakota.
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Excavation below areas remediated would be prohibited, unless the soil is
demonstrated to contain less than 100 mg/kg arsenic.
An education program would be conducted annually to acquaint site residents with
the potential health hazards associated with exposure to the tailings soils and
downgradient alluvial groundwaters within tht site. This education would also
include methods residents can use to minimize incidental ingestion of contaminated
materials. A mechanism to inform potential property owners of the potential health
hazards will also be included in the education program.
In the event of a flood where contaminated materials potentially were redistributed, the
flooded areas would be resampled. Action would be taken to return any newly
contaminated or re-contaminated areas to post-remediation conditions.
The surface water quality of Whitewood Creek would be monitored at the U.S. Geological
Survey sampling stations near Whitewood and Vale four times a year. These sampling
events would be conducted in late winter before major snow-melt runoff; during peak
runoff in spring; during the low flow period in late summer; and once immediately
following a major precipitation event. Continued monitoring of Whitewood Creek water
qualitY. is needed to evaluate the effect of uncenain future rates of release of arsenic from
the. taIlings deposits on the environment. These data will be reviewed during the five-year
reVIew.
The rules of the Occupational Safety and Health Act would apply to the construction-oe .
activities carried out to remove and/or cover contaminated soils. It is estimated that l'L .
would take 9 to 18 months to implement the covering and/or removal component of this
alternative.
~
A review of site conditions (five-year review) would be required every five years to ensure
that human health and the environment are being protected by the remedial action being
implemented. This would include, but not be limited to:
Verification sampling within the remediated residential areas.
A review of development activity within the site. If development has taken place
which is inconsistent with specifications as described in EP A's ROD, these
k~b.rties would be required to be remediated in a manner consistent with the
A review of the effectiveness of the education program in alening present and
potential property owners to concerns related to the contamination which remains
on site.
A review of compliance with the monitoring well ban in the floodplain.
A review of the surface water quality data collected from Whitewood Creek to
assure that levels protective of human health and aquatic life are being maintained.
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Alternative 4a: Institutional Controls with Covering and/or "Removing of Surface Soils
Existing Residential Properties (Allowing Future Development)
This alternative would involve the same activities as Alternative 4, but would allow future
development within the contaminated fringe areas of the 100-year floodplain outside of the
tailings areas, following remediation to provide conditions protective of human health.
The county ordinances to be enacted as additional institutional controls would allow for a
variance in which an approval of plan for cover and/or removal of soils of greater than 100
mg/kg would be required by the South Dakota Department of Natural Resources prior to
development of the land.
A variance procedure allowing development on lands within the site (but outside the
tailings deposit areas), following appropriate remediation, would be adopted. A
variance procedure allowing public works developments on land inside the tailings
deposit areas, following appropriate remediation, would also be adopted.
A potential developer must sample the surface soils of any parcel in the fringe area
determined to contain contaminated soils. The sampling program would be similar
to that outlined for residential remediation in Alternative 4 to identify which
portions of the parcel contain concentrations of arsenic greater than 100 mg/kg.
The developer then would submit sample results and a remedial plan to the South
Dakota Department of Natural Resources. This remedial plan would describe
removal, cover or other procedures for brin~ing all surface soils to 100 mg/kg and
would include plans for confirmatory samplmg.
After approval of the plan, the developer may perform the work and confirmatory
sampling. The developer would also assume the obligation of complying with a
county regulation prohibiting the removal or impairment of any covers placed on
the parcel under the plan unless pre-approved by the State.
Alternative 5: Institutional Controls with Fencing of Tailings Deposit Areas and Covering
and/or Removing of Surface Soils of Existing Residential Properties
This alternative would involve the same activities as Alternative 4 with the addition of
installation of fencing around the perimeter of the tailings deposit areas. A three-strand
barbed wire fence, or equivalent, would be installed, using eXisting fencing where available.
The purpose of the fence would be to reduce current exposures of site residents to the
elevated surface soil arsenic concentrations by discouraging access to the tailings deposit
areas. ARARs would be the same as for Alternative 4.
Alternative 7: Institutional Controls with Partial Soil Cover of Tailings Deposit Areas and
Covering and/or Removing of Surface Soils of Existing Contaminated Residential
Properties
This alternative would involve the same activities as Alternative 4 with the addition of
placement of soil cover over barren areas (i.e., devoid of vegetation) in the tailings deposit
areas. Barren areas would be identified based on field observations and review of aerial
photographs. In the places where these bare areas form steep banks along the creek, these
banks would be peeled back to create banks having slopes of no more than 1 horizontal to
3 vertical. The peeled-back tailings materials would be placed in layers on the adjoining
tailings deposits before placement of the soil cover. Six to 12 inches of native soils
imported from off-site sources would be spread over the barren and/or stabilized tailings
deposits. This cover would be vegetated with native grasses to stabilize it and minimize
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erosion. It is estimated that approximately 700 acres (25%) of the tailings deposits are
candidates for partial soil cover.
Partial cover activities would be designed and implemented to comply with the
Occupational Safety and Health regulations.
Alternative 9: Institutional Controls with Removal of Tailings Deposits Areas, and
Alluvial Tailings From Tailings Deposit Areas, On-site Disposal of Tailings, and Covering
. and/or Removing of Surface Soils of Existing Residential Properties
This alternative would involve the same activities as Alternative 4 with the addition of
removal of alluvial tailings and on-site disposal of these tailings. The site would be divided
into eight blocks (segments) for logistical purposes. At each block, the tailings deposits
would be removed using a front-end loader and two trucks. The excavated materIals would
be stodq)iled prior to feeding through a screen plant. The screen plant would separate
material into three size categories: -24 mesh (assumed to be all tailings), -10 to +24 mesh
(assumed to be mixed tailings and alluvium) and + 10 mesh (assumed to be alluvium).
Alluvium-sized material would be washed and returned to the stream bed. Tailings and
mixed material would be hydraulically transported to an on-site tailings impoundment. Six
inches of native soils brought in from areas off the site would be placed over the excavated
areas, and grass would be planted to stabilize the soils and minimize erosion. .
The removal of tailings materials from the tailings deposit areas would require compliance
with the Occupational Safety and Health Act. Construction, use and post-closure
maintenance of the tailings deposit facility that would be employed to inter the tailings
would require compliance with the South Dakota Solid Waste Rules.
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VII. SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
This section presents a comparison of alternatives using nine component criteria. These
criteria, which are listed below, are derived from requirements contained in Section 300.68
(h)(2) of the National Contingency Plan and CERCLA sections 121(a) and (b). Table A-6
contains a summary of the comparative analysis.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Protection of human health and the environment;
Compliance with ARARs;
Reduction of toxicity, mobility, or volume;
Long-term effectiveness and permanence;
Short-term effectiveness;
Implementability;
Cost;
State acceptance; and
Community acceptance.
Criterion 1: Protection of Human Health and the Environment
All of the action alternatives would provide some protection of the health of siie residents.
The ban on use of the alluvial aquifer, if continued, would protect the health of residents
from the impacts of ingesting these groundwaters. Removmg and/or covering soils of
existing residential properties that have surface soil concentrations greater than 100 mg/kg
arsenic would reduce the exposures of the residents of these properties to acceptable levels. .
Alternative 9 would provide the greatest amount of overall protectiveness because, in
addition to the protection from elevated residential soil arsenic concentrations, it would
also remove the tailings deposits providing protection from contact with these materials in
the future and allowing for eventual restoration of groundwater ~uality. Alternatives 7 and
9 would allow for protection of the environment by removing tailmgs deposits from along
Whitewood Creek. This would decrease the loading rates of contaminants into the surface
water, erosion potential, migration and mobility of the contaminants and the chance of
redepositing the tailings into the environment. How.ever, this alternative would result in a
massive envi~onmental disturbance along eighteen miles of Whitewood Creek, which is
currently a relatively stable ecosystem. Removal of the contaminated alluvium would also
destroy the downgradient alluvial aquifer.
. .
Alternative 7 would be somewhat less effective than Alternative 9; but somewhat more
effective than Alternatives 4, 4a and 5 because bare tailings which may potentially be
ingested by site residents would be covered. The addition of fencing in Alternative 5 would
not be more effective in protecting residents from the tailings deposits. Removal of
additional contaminated material for future development in Alternative 4a could result in a
small incremental loss of exposure to residents.
Under the No Action alternative, no remediation would take place other than continued
enforcement of the current state regulation prohibiting the installation of water supply
wells in the 100-year floodplain of Whitewood Creek. Based on the characteristics of the
contaminants present, the risks to human health and the environment would remain at the
unacceptable level described in the endangerment assessment.
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TABLE A-6
EPA Evaluation of Cleanup Alternatives
Whitewood Creek Site, South Dakota
Criteria a
Remedial
Alternatives b
Protection of
Human Health
and the
Environment
Compliance
with
ARARs
Reduction of
Toxicity,
Mobility or
Volume
Long-term
Etfediveness
and
Permanence
Short-term
Effectiveness Implementabifity
Cost C
1 0 e 0 0 0 $26,000
4 e ~ ~ ~ ~ ~ $638,392
4a e ~ ~ ~ ~ ~ $882,813
5 ~ ~ ~. e ~ ~ $1,345,841
7 e e e ~ ~ e $5,605,254
9 ~ ~ ~ ~ ~ ~ $75,054,925
8 Better
10
o Worse
a The criteria of state and community acceptances were evaluated during the public comment period and discussed in the text.
b EPA prefers Alternative 4a.
C Includes capital and operation and maintenance (0 & M) ~sts; discounted at 5% over 30 years.
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Current EP A guidance requires that a public health and environmental evaluation be
conducted every five years for any alternatives in which hazardous substances, pollutants or
contaminants remain on-site. The five-year public health and environmental evaluations
would therefore be required for all alternatives except Alternative 9, and would allow
assessment of whether future action or remediation would be required. Any problems with
protectiveness identified in the five-year reviews will be addressed at that time.
Criterion 2: Compliance with Applicable or Relevant and Appropriate Requirements
(ARARs) .
Due to nature and extent of contamination, it is unlikely that any alternative would achieve
compliance with the following chemical-specific ARARs for the downgradient alluvial
groundwaters: the National Primary Drinking Water Standards and the state of South
Dakota Drinking Water Standards with respect to arsenic and occasionally cadmium and
selenium.
As discussed in Section IV the surface water of Whitewood Creek would not achieve
compliance with the water quality criteria for the protection of human health from the
consumption of fish with respect to arsenic followmg implementation of these alternatives
because upstream surface water exceeds this criterion. However, Whitewood Creek
entering the site meets the aquatic life criteria established by the State for this section of
the creek and the water quality criteria for chronic toxicity to aquatic life.
For all action alternatives, during the removal and/or covering of residential soils Or
tailings deposits, compliance must be maintained with the National Primary and Secondary
Ambient Air Quality Standards and the South Dakota Ambient Air Quality Standards.
The rules of the Occupational Safety and Health Act would apply to the on-site activities
carried out during remedial design and remedial action. Continued enforcement of the
rule prohibiting the installation of water supply wells within the Site would continue to
achieve compliance with the South Dakota Water Rights Rules.
The Archaeological and Historic Preservation Act; National Historic Preservation Act;
Historic Sites, Buildings and Antiquities Act; Fish and Wildlife Coordination Act;
Endangered Species Act; Floodplain Management; and Protection of Wetlands are all
potentially applicable for Alternatives 7 and 9. A definitive determination of the potential
Impacts of implementing these alternatives will be made in the design of this remedial
action and necessary steps taken to achieve compliance.
Criterion 3: Reduction of Toxicity, Mobility, or Volume
Alternative 9 would achieve the most significant reduction in mobility of arsenic from
tailings deposits and contaminated alluvium from along Whitewood Creek by the removal
of these materials to an impoundment. No reduction in toxicity or volume would be
accomplished, however. There would also be limited reduction in mobility and volume of
arsenic in soils adjacent to residential areas. Alternative 7 would achieve limited reduction
of the mobility and volume of arsenic in soils adjacent to residential areas. It would, in
addition, achieve some reduction in mobility of arsenic from the tailings by covering the
bare areas of these deposits.
-------
Alternatives 4, 4a and 5 would achieve limited reduction of the mobility and volume of
arsenic from soils adjacent to residential areas by moving the contaminated material to a
secure storage area. The majority of arsenic at the site is contained in tailings deposits
which would not incur any reduction in toxicity, mobility, or volume under these
alternatives.
Under the No Action alternative, no reduction of toxicity, mobility, or volume of the
tailings constituents on site would occur.
Criterion 4: Long-term Effectiveness and Permanence
The greatest reduction in risk would be achieved by Alternative 9 through removal of the
tailings deposits from along Whitewood Creek. The on-site disposal of tailings deposits
would be considered the most effective remedy, but not a permanent remedy because the
potential exists for disposal facility failure. Partial cover of exposed tailings in Alternative
7 would provide some reduction of risk but would not be considered a permanent remedy
because the potential exists for cover failure.
The removal/covering of residential soils in all action alternatives would achieve a risk
reduction from exposure to these soils. This would not be considered a permanent remedy
for residential soil contamination if any contamination is allowed to remain. .
The institutional controls portion of Alternatives 4, 4a, 5 and 7 would allow a reduction of
risk to site residents by limiting exposure to tailings deposits. The long term effectiveness
would be dependent on the local government's ability to enact, implement and enforce
- these controls. Unforseen future community pressure to allow unrestricted development in
the area may result in the lack of enforcement or revocation of the proposed zoning
controls.
The addition of a development variance would slightly increase the effectiveness and
permanence of Alternative 4a when new areas are cleaned up prior to development. The
addition of fencing in Alternative 5 is not believed to add to the long term effectiveness or
permanence of this alternative.
The No Action alternative would not be effective, as no action is being taken to reduce the
major risk pathways. The restriction on use of the water supply has been enforced since
1985 and is likely to remain an enforceable regulation.
Criterion 5: Short-term Effectiveness
The institutional controls portion of the action alternatives would provide short-term
effectiveness in that it is anticipated that institutional controls would be immediately
enacted, implemented aDd enforced. No contaminated material would be disturbed in this
process, therefore there. !ould be no need to protect the community, the workers or the
environment during implementation.
The removal/cover portion of these alternatives would also be implemented in a short
period of time since contaminated materials in the residential areas available for direct
exposure would be excavated and/or covered within a few months from beginning of
activity. Minor impacts to the site residents, workers and the environment are anticipated
while excavation and covering are underway. It is anticipated that these effects can be
mitigated by proper planning and use of personal protective equipment according to
OSHA regulations.
-------
Implementation of Alternative 7 would begin immediately, but it is anticipated that it will
take three years to fully implement. This alternative could result in some short-term
adverse environmental impacts due to physical disturbances while implementing the
remedy. Alternative 9 would take up to fifteen years to fully implement. Although it would
provide additional protection by removing and containing the tailings, it could result in
significant short term adverse environmental impacts due to the extensive physical
disturbance that would be involved in the excavation process to implement the remedy.
Tbe No Action alternative is not effective because this alternative does nothing to reduce
the major risk pathways at the site. The State regulation restricting construction of water
supply wells in the site is already in place, and because no implementation activities would
be mvolved, this alternative would be immediately implemented.
Criterion 6: Implementability
The State regulation prohibiting the installation of water supply wells within the site is
currently being implemented. The No Action alternative includes no other implementation
actions, thus this alternative is implementable.
During the Public Comment period the local governments expressed the willingness and
ability to enact, implement and enforce institutional controls as recommended. Lawrence
County presently has an ordinance in place restricting the use of tailings deposit soils. The
institutional controls portion of all action alternatives is therefore implementable. The
skilled workers and construction equipment needed to implement clean up activities in the
action alternatives are readily available since removal, transport and disposal techniques
are commonly used in nearby mining operations. Alternative 5 includes fencing, which,
where possible, would include the use of existing fences. Obtaining right-of-way for
construction of new fences may present a problem with implementing this remedy.
Alternatives 7 and 9 can be readily implemented from a technical standpoint. These
alternatives have the potential for a short-term impact on the environment due to physical
disturbance in the excavation process. Construction activities therefore would require an
extensive coordination effort to control adverse impact to the environment.
Criterion 7: Cost
The cost of the No Action alternative would be $26,000, the cost estimated for the five-year
public health and environmental evaluation. Alternative 4 is the least costly, and
Alternative 9 the most costly. All action alternatives except 5 have an estimated high
capital cost and low operation and maintenance (O&M) cost. Estimated operation and
maintenance on the fence over a thirty year period are approximately equal to estimated
cost of original installation.
Estimated net present value costs, total capital costs and annual O&M costs for each
alternative follow. For some options, certain capital costs are assumed to be incurred over
the course of the thirty year period. Not all annual O&M costs are incurred every year of
the thirty year period.
-------
The estimated cost for Alternative 4 to remove/cover contaminated soils at existing
residences is $638,392 ($581,000 capital costs, $11,000 annual O&M cost). Alternative 4a
adds testing and removal/cover at 15 additional residences. . Costs are estimated to be
$882,813 ($1,028,000 capital costs and $12,000 annual O&M cost). Alternative 5, which is
similar to 4 with the addition of fencing, is estimated at $1,345,841 ($981,000 capital costs
and $31,000 annual O&M cost). Alternative 7, which is alternative 4 with the addition of a
partial soil cover, is estimated at $5,605,254 ($5,471,000 capital costs and $16,000 annual
O&M cost). Alternative 9 is estimated at $75,054,923 ($107,575,000 capital costs and
$36,000 annual O&M costs).
Criterion 8: State Acceptance
The State of South Dakota concurs with the selection of Alternative 4a.
Criterion 9: Community Acceptance
Public comments that were received indicated that there is no concensus on what presents
the best remedial alternative for the arsenic-contaminated mill tailings along Whitewood
Creek. Some citizens expressed the opinion that the tailings appeared to present no health
hazard and that the No Action alternative was the best solution. An equal number felt that
the tailings pose a hazard to human health and the environment that can only be mitigated
by complete removal (Alternative 9). Other people were in favor of the remedy proposed
by EP A, with reservations about the potential effect of the remedy on the economics of the
community.
-------
VIII. THE SELECTED REMEDY
Alternative 4a: Institutional Controls with Covering and/or Removing of Surface Soils of
Existing Residential Properties (Allowing Future Development).
Based upon a review of information contained in the site Administrative Record, EP A has
decided that the most appropriate remedy for the Whitewood Creek Superfund site is to
remove and/or cover contaminated residential soils and restrict access to contaminated
tailings and ~roundwater by use of institutional controls. As described in Section IX below
this remedy IS the most protective alternative which would not have adverse effects to the"
environment. It also provides the greatest protection in the most cost-effective manner.
It is estimated that it would take approximately 18 months to implement institutional
controls and remove/cover surface soils of existing residential properties. It is also
estimated that 15 additional properties will be developed through variance from county
ordinance over the thirty year period.
The estimated net present worth for the selected remedy is $882,813 (Table A-7). Capital
costs total $1,028,000, $581,000 of which will be spent during start-up, $447,000 which will
be incurred over the thirty year period. Annual O&M costs are estimated to be $12,000.
At existing residences exhibiting greater than 100 mg/kg arsenic in surface soils, these soils
would be removed and/or covered in garden, non-garden and roadway areas. All material
removed would be placed in a disposal facility approved by the State and EP A which is
designed and constructed to hold wastes that are similar in nature and concentration of
contaminants. Soil sampling would be conducted both on the surface and at depth
following this remedial action to confirm that remedial action goals have been met. Any
properties developed under variance would be sampled and remediated in a similar
fashion. If remediated areas should be flooded these areas would be resampled and
appropriate action taken to return any contaminated areas to post-remediation
contaminant levels. A five-year review would be performed five years after remediation is
completed. South Dakota Water Rights Rules (Section 74:02:06:26) ban on water wells in
the Whitewood Creek 100-year floodplain would also be continued.
The scope and performance of the remedy selected in this ROD are consistent with the
remedy proposed at the start of public comment because the elements of remedial action
to be implemented are the same. In response to comments received from citizens during
the public comment period, EP A has decided warning signs and notice in deed are not
necessary because the proposed educational program is deemed to be sufficient.
Response Objectives
The response objectives for soil remediation at Whitewood Creek are to control exposure
through ingestion of contaminated tailings deposit soils, alluvial soils and residential soils,
or downgradient alluvial groundwater. Target cleanup objectives for groundwater are the
Maximum Contaminant Levels. Target clean-u:p objectives for soils were developed based
on soil concentrations which correspond to carcInogenic health risks of 1 x 10-4.
Acceptable contaminant levels for the chemical of concern (arsenic) in residential soils are
100 mg/kg, based on the 1 x 10-4 target risk levels derived in the endangerment assessment.
This action level would also reduce non-carcinogenic risk to an acceptable level. A
summary of these calculations are provided in Appendix A of this document.
-------
TABLEA-7
ESTIMATED COSTS FOR THE SELECTED REMEDY
INSTITUTIONAL CONTROLS WITH COVERING AND/OR REMOVAL OF
SURFACE SOILS OF EXISTING RESIDENTIAL PROPERTIES
(ALLOWING FOR FUTURE DEVELOPMENT)
ITEM
COST
Capital Costs:
Delineation of floodplain
and extent of contamination
$175,000
Pre-implementation sampling of
twelve existing and fifteen future
residential properties
Removal, soil covering and confirmation
sampling of residential properties
. 199,000
604,000
Assisting the counties in adopting land
use and tailings use regulations
Performing the initial education program
30,000
20,000
Remediate properties under variance
Total Capital Costs
447.000
1,028,000
Operation and Maintenance Costs
Re-sample existing residential properties
in the fifth year after removal and soil
covering at these properties ($26,000
distributed over five years)
Annual Costs
Maintenance of the educational program
Annual monitoring of Whitewood Creek
5,000
2,000
5,000
Total Annual O&M Costs
Year 1 - 5
Year 6 - 30
12,000
6,000
Total Costs (Net present value calculated
using discount of 5% and 30 year O&M period) ~
-------
IX. STATUTORY DETERMINATIONS
EP A's primary responsibility at Superfund sites is to select remedial actions that are
protective of human health and the environment. In addition, section 121 of CERCLA
provides several of the following statutory requirements and preferences. CERCLA also
requires that the selected remedial action for the site must comply with applicable or
relevant and appropriate environmental standards established under federal and state
environmental laws, unless a waiver is granted. The selected remedy must also be cost-
effective and utilize permanent treatment technologies or resource recovery technologies
to the maximum extent practicable. The statute also contains a preference for remedIes
that permanently or significantly reduce the volume, toxicity, or mobility of hazardous
substances. The following sections discuss how the selected remedy for contaminated soils
at Whitewood Creek meet these statutory requirements.
Protection of Human Health and the Environment
The selected remedy protects human health and the environment through restricting access
to, and use of, the tailings and contaminated groundwater by implementation of
ordinances. This remedy would permanently eliminate the ingestion threat currently posed
to residents from contaminated residential soils. It would further limit, but not.elimiriate,
exp'?sure to t,,:ilings deposits. The cancer risks associated with the residential soils and
taIlmgs deposIts areas would therefore be reduced to an acceptable level of 1.0 x 10-4.
There are some short-term risks associated with the selected remedy during removal of
contaminated soils from residential properties, but these can be minimized with protective
and preventative measures. Of all the alternatives, the selected remedy provides the best
protection to human health, without significant adverse impact to the environment.
Attainment of ARARs
CERCLA Section 121 requires selection of a remedial action that is protective of human
health and the environment. The determination of protectiveness is based on compliance
of the selected remedy with applicable or relevant and appropriate requirements
(ARARS). Appendix C is a hst of the ARARs identified for this site which apply to the
selected remedy.
Applicable requirements are those cleanup standards, standards of control, and other
substantive requirements, criteria, or limitations promulgated under Federal or State
environmental or facility siting law that specifically address a hazardous substance,
pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA site.
Relevant and appropriate requirements are those cleanup standards, standards of control,
and other substantive requirements, criteria, or limitations promulgated under Federal or
State environmental siting law that, while not "applicable" to a hazardous substance,
pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA site,
address problems or situations sufficiently similar to those encountered at the CERCLA
site that their use is well suited to the particular site.
As discussed in Section VII, the selected remedy would not achieve compliance with some
chemical-specific ARARs related to the downgradient groundwater and surface water of
Whitewood Creek. For the groundwater, the relevant and appropriate requirements
include primary drinking water standards (40 CFR 141) and the Drinking Water Standards
for the State of South Dakota (ARSD:74:04:05). As these would not be attained, a waiver
is invoked under CERCLA Section 121(d)(4)(C) because remediation of the groundwater
would be technically impracticable as discussed in Section VII. The continuing
-------
enforcement of South Dakota regulations (ARSD 74:02:06:26) prohibiting use of the
downgradient aquifer would provide adequate protection of human health and the
environment.
The selected remedy will also not attain the surface water ARARs including ambient water
quality criteria (40 CFR 131) for the consumption offish. As these would not be attained,
a waiver is invoked under CERCLA Section 121(d)(4)(C) because cleanup of the surface
water is technically impracticable because the water entering the site does not meet this
criterion and because of exceedances allowed under South Dakota regulations (ARSD
74:03).
The selected remedy would address and comply with all location- and action-specific
ARARs for worker protection, onsite dust emissions, protection of historic and natural
resources and other criteria listed in Appendix A
Cost Effectiveness
EP A believes the selected remedy is cost-effective in mitigating the risk posed by
contaminated residential soils and tailings deposits within a reasonable period of time. The
selected remedy effectively redu :es exposure to contamination to acceptable levels while
remaining cost-effective. Present net worth costs associated with Alternative 4a are
approximately $882,813.
Utilization of Permanent Solutions and Alternative Treatment Technologies or Resource
Recovery Technologies to the Maximum Extent Practicable
EP A analyzed the alternatives to determine which would utilize treatment technologies to
the maximum extent practicable. The selected remedy would achieve the response
objectives of preventmg ingestion of surface soils of the tailings deposits areas, in~estion of
contaminated residential soils, and ingestion of contaminated downgradient alluVIal
groundwaters. Permanent solutions or alternative treatment technologies are not feasible
or practical for the wastes at this site. .
This remedy utilizes permanent solutions and alternative treatment technologies to the
maximum extent practicable for this site. However, because treatment of the principal
threats posed by the site was not found to be practicable, this remedy does not satisty the
statutory preference for treatment as a principal element. Treatment is impracticable
because of the large volume of contaminated soils and tailings deposits, the lack of
appropriate treatment technologies, and the potential for adverse environmental impact.
Preference for Treatment as a Principal Element
The selected remedy does not satisfy this statutory preference. The principal threat to
human health is from arsenic-contaminated tailings deposits and alluvial groundwater.
There are no demonstrated and available processes for the treatment or removal of arsenic
from contaminated soils. Withdrawal and treatment of ~roundwater for removal of arsenic
is also a largely untested method and probably will reqUIre an unacceptably long time to
reach desirable levels of contaminants. See Section 4.0 above for further discussion.
-------
5.
x. DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for the Whitewood Creek site was released for public comment on
January 10, 1990. . The Proposed Plan identified Alternative 4a, institutional controls and
removalj covering of residential soils, as the Preferred Alternative. EP A reviewed all
written and verbal comments submitted during the public comment period. Based upon
public comments received, the following changes have been made to the Preferred
Alternative:
1.
The definition of the site has been clarified from that published in the proposed
plan. The site's southern boundary is the Crook City Bridge, not Interstate Hi~hway
90. The characteristics of this two-mile stretch of Whitewood Creek included In
remedial investigation studies are similar to Whitewood Creek downstream of 1-90
in gradient and volume of tailings deposits. The area also corresponds to the area
of the alluvial water well ban in South Dakota rules ARSD 74:02.
2.
The allowance for a public works variance to allow construction in the tailings
deposit areas has been added, in response to letters received from the State of
South Dakota and concerned citizens.
3.
Warning signs have been removed from the planned educational program, because
EP A concurred with comments at the public meeting that these SIgns would not
significantly lower risk to site residents. .
Notice in deed restrictions will not be required. An alternative method of educating.
potential property owners will be included in the education program.
4.
The area of land per residence to be tested for contamination and clean-up if
necessary was estImated in the proposed plan to be two acres. Land use patterns
will be used to select the appropriate area, which is expected to be two acres per
residence, but may include up to eight acres if required to be protective of the
health of the site residents.
-------
APPENDIX A
Intake Assumptions for EPAs Endangerment Assessment
Consideration of the differing physical characteristics and behavior patterns of children and
adults results in separate intake rate estimates for these two age groups. The establishment
of separate intake rates allows calculation of risks expected for the specific scenarios
described in Section V. For instance, the estimation of chronic non-carcinogenic risks can
be achieved for both children and adults using the intake rates specific to each
subpopulation. Alternatively, carcinogenic risks, which are calculated usin~ the average
contaminant intake over a 70 year lifetime, can be estimated by consideratmg that an
individual living onsite could experience both the child and the adult intake rates during a
lifetime. .
The discussion in this section focuses upon the significant revisions to the soil contaminant
intake equations which have been incorporated in this report. For the rural residential
scenarios, it is assumed that site soils are available for ingestion during times when the
ground is not frozen. The factor 0.667 corresponds to the average fraction of a year in
which soils in the Northwestern U.S. are not frozen. Also for the soil ingestion pathways, it
is assumed that the absorption efficiency of arsenic from soils is equivalent to its absorption
efficiency from foods. The soil ingestion rates for children and adults are 200 mgj day and
100 mgjday, respectively. Intake parameters and equations for the soil and groundwater
-------
A
q =
Cr =
c; =
Cw =
F-
1
Fra =
Frc =
Ft
Fy =
Ia =
Ic =
Iw =
Nv =
NI =
Wa =
Wc =
TABLE 1(A)
INTAKE PARAMETERS FOR
SOIL AND GROUNDWATER PATHWAYS
=
Absorption factor for contaminant in soil (0.80 for arsenic, 1.0 for other indicator
contaminants)
Average concentration of contaminant in irrigated cropland soil
Average concentration of contaminant in soil at the residences
Average concentration of contaminant in tailing soils
Average concentration of contaminant in groundwater
=
Fraction of ingested soil derived from irrigated cropland soils (0.1)
Fraction of ingested soil for adults derived from soils at residence (same as average time
spent at residence) (0.65)
Fraction of ingested soil for children derived from soils at residence (same as average time
spent at residence) (0.90)
Fraction of ingested soil derived from tailings soil (0.03)
Fraction of year for which soils are available for ingestion (0.667)
Soil ingestion rate for adults (100 mg/day)
Soil ingestion rate for children up to 6 years (200 mg/day)
Groundwater ingestion rate (1.075l/day) .
Number of visits for a recreational visitor per lifetime (500)
Number of days per 70 year lifetime (25550)
Average body weight for adults (70 kg)
Average body weight for children up to 6 years
-------
TABLE 2(A)
INTAKE EQUATIONS FOR THE
SOIL AND GROUNDWATER PATHWAYS
ReDresentatlve Rural Resident
Age group: 6-70 vears
Intake (soil) = (A. Fy. IafWa) . (Ft. c; + Fra. Cr + Fi. CD
Intake (groundwater) = (lw. Cw)fW a
Age group: 0-6 vears
Intake (soil) = A. Fy . Ie . Fre . CrfW e
Intake (groundwater) = (lw. Cw) fW e
Recreational Visitor
Intake (soil) = (A. Nv. Ia. CtJ/(VVa. Nt)
Maximum EXDosed Rural Resident
At!e group: 6-70 vears
Intake (soil) = (A. Fy . Ia . Fra . CtJfW a
Intake (groundwater) = (lw. Cw)fW a
Age group: 0-6 vears
Intake (soil) = (A. Fy . Ie. Fre . Ct)/We
-------
APPENDIX B
Health Based Soil Action Level for Arsenic at the Residences
A health based soil action level may be derived for arsenic in the driveway and yard soils at
the residences of the Whitewood Creek site by assuming that remedial action efforts aimed
at groundwater and the tailings area are in place. An action level derived under these
conditions would be based upon an acceptable incremental risk that individuals may incur
by living at a site residence for a specified number years out of a 70 year life-time.
The usual levels of regulatory concern span the range of 10-4 to 10-7 (USEPA 1986).
However, naturally occurring arsenic concentrations found in soils and water result in a risk
level of 10-4. Furthermore, regulations pertaining to arsenic result in 10-3 risk as an
acceptable target risk (e.g. a risk level of 10-3 results from the arsenic MCL of 0.05 mg/l).
~ acce.ptable risk level for a!s:nic intake via driveway and yard soil ingestion could be 10-
4 If the nsk due to total arseruc mtake does not exceed the 10-3 level.
The following equation, based upon the representative rural resident soil intake equations
(Table 2(A) of this report) and the representative adult rural resident exposure scenario
(Section V of this r:;port), has been used to calculate an action level for arsenic under the
assumption that 10 represents an acceptable incremental arsenic risk incurred by an
individual living onsite:
c=
Tr
CPF * A * Fy [(Da * Ia * Fra)/Wa + (Dc * Ic * Frc)/Wc]
where:
CPF = Carcinogenic Potency Factor (1.75 [mg/kg-dayfl);
Dc = Exposure duration fraction for individuals up to 6 years assuming 6 years of
exposure during a 70 year lifetime (0.0857);
Da = Exposure duration fraction for individuals from 6-70 years assuming 9 to 30
years of exposure during a 70 year lifetime (0.13 or 0.43);
Tr = Target risk of 10-4
and where the rest of the intake parameters are given in Appendix A, Table 1 of this
report. .
Two values have been chosen for D~ the exposure duration fraction for adults, based upon
the estimated variation in values of va across the nation (Schaum 1989). This results in a
range of target concentrations. It should be noted that the inherent variability of the other
parameters in this equations can also add to the range of variability that would be expected
m the calculation of arsenic action levels at the site.
Substituting the input parameters and solving the equation for both values of Da gives a
-------
APPENDIX C
APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS FOR WHITEWOOD CREEK SUPERFUND SITE
Federal and state requirements, which are either applicable or relevant and appropriate to the
Whitewood Creek Superfund site and to remedial actions recommended at this site In the Record of
Decision, are listed below. These requirements are also discussed In relationship to site conditions
anticipated following remedial actlvites.
STANDARD, REQUIREMENT
CRITERIA OR GUIDELINE
ARAR?
'ilij11111~i~11ijij!!iiil_~i~p~~li!~:!~,~ijl~~:~::!:::~:!il
[[[',"""'0"':"""""""""""""
National Primary Drinking Water Standards, 40 CFR
Part 141; establishes Maximum Contaminant Levels for
community water supply systems.
Yes
'W Quality Criteria, 40 CFR Part 131: establishes
c for the protection of aquatic life and the
protection of human health through the consumptiOD of
fish and water.
Yes
National Primary and Secondary Ambient Air Quality
Standards, 40 CFR Part 50: establishes standards for
ambient air quality to protect human health and welfare.
Yes
C -1
COMMENTS
Although these standards are not applicable because
they apply to community water supply systems, they
are deemed to be relevant and appropriate to the
downgradient alluvial groundwaters of Whitewood
Creek. If these waters are ever used for water
supply, it is unlikely that they would be treated
before use. These ARARs would not be met for
groundwater following implementation of the
selected remedy. A waiver is necessary because of
the potential for increase in risk to public health and
because of the technical impracticality of meeting
this ARAR (see Section VII).
These criteria are not applicable to surface water
because they are not enforceable standards.
However, they may be relevant and appropriate
under CERClA Section U1(d)(2)(A). The criteria
for the protection of human health from the
consumption of fish is relevant and appropriate as .
Whitewood Creek is designated for use as a fIshery
in the South Dakota Water Quality Standards. The
criteria for the protection of aquatic life are relevant
and appropriate except for the criteria included in
South Dakota Water Quality Standards. These
ARARs would not be met as the water entering the
site does not meet these criteria.
These standards are applicable. There is no known
exceedance of these standards at this time. These
standards may not be attained during brief times
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APPENDIX C
APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS FOR WHITEWOOD CREEK SUPERFUND SITE
STANDARD, REQUIREMENT
CRITERIA OR GUIDELINE
1~!~i!!!!!!!j!!!!!I!~!~!1~j~!!~~!1!11!11~~~:!:i:~.~!!11)!::1!:::::!1
Groundwater Quality Standards, ARSD 74:03:15:
establishes maximum concentration limits for
groundwaters.
Surface Water Quality Standards, ARSD 74:03:02:
establishes water quality standards for Whitewood
Creek.
Ambient Air Quality Standards, ARSD 74:26:02:04 and
ARSD 74:26:02:35: establishes ambient air quality
standards for particulate matter.
Drinking Water Standards, ARSD 74:04:05 establishes
MCLs for public water systems.
11::!:~i~:j!:!~1:1~!:~:!::li~~~I!~B~lg::t:~iI11!!j:::::::::::::1
Archaeological and Historic Preservation Act, 40 CFR
Section 6.301(c): establishes procedure to provide for
preservation of historical and archaeological data which
might be destroyed through alteration of terrain.
National Historic Preservation Act, 40 CFR Section
6.301(b): requires consideration of the effect on any
district, site, building, structure or object that is included
in or eligible for inclusion in the national register of
historic places.
Historic Sites, Buildings and Antiquities Act, 40 CFR
Section 6.301(a): requires consideration of the existence
and location of landmarks on the national registry of
natural landmarks to avoid undesirable impacts on such
landmarks.
ARAR?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
C-2
COMMENTS
These standards are applicable.
These standards are applicable.
These standards are applicable.
These standards are as stringent as National Primary
Drinking Water Standards. They are relevant and
appropriate to ground water for reasons discussed
under National Drinking Water Standards.
This requirement might be applicable to those
remedial actions (such as the removal of tailings
from the tailings deposit areas) which would involve
the alteration of terrain. Determination of its
applicability will be made in the design of remedial
actions.
Same as above.
-------
APPENDIX C
APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS FOR WHITEWOOD CREEK SUPERFUND SITE
STANDARD, REQUIREMENT
CRITERIA OR GUIDELINE
Fish and Wildlife Coordination Act, 40 CFR Section
6.302(g): requires consultation with the Fish and
Wildlife Service for the modification of any stream or
other water body and adequate provision for protection
of fish and wildlife resources.
Endangered Species Act, 40 CFR Section 6.302(h):
requires protection of any threatened or endangered
species and their critical habitat.
Floodplain Management, 40 CFR Part 6, Appendix A,
Executive Order No. 11,988: requires an evaluation of
the potential effects of actions taken in a floodplain in
order to avoid, to the maximum extent possible, the
a~erse impacts associated with direct and indirect
IOpment of the floodplain.
Protection of Wetlands, 40 CFR Part 6, Appendix A,
Executive Order No. 11,990: requires the avoidance of
adverse impacts associated with the destruction or loss
of wetlands.
I:::::::::::::~:i'!:!:(::::!:i:i:i:t::::i:::::::::::t::t!:i?:;::ti:r:::'!":::::::::::::::::::::!:::::::::!:::::::::::::::(::1
/::::::::ff:::::::}'ffigm~ffimfmrrreM~F:f::::::::::
Occupational Safety and Health Act, 29 U.S.c. Sections
651 - 678: establishes regulations to protect the safety
and health of workers.
~:I!I:~I!!!::I:I:1:::::!!!:::!111:!tr,~~~!:~~!I!t:li:!i~~~~:!!:::!!:::1:::1::!!:11
Water Right Rules, ARSD 74:02: establishes regulations
governing the use of groundwaters, including regulations
biting the installation of water supply wells within
te.
ARAR?
Yes
Yes
Yes
Yes
Yes
Yes
C - 3
.
COMMENTS
This requirement might be applicable to those
remedial actions (such as the removal of tailings
. from the tailings deposit areas) which would involve
modification of Whitewood Creek. Determination of
its applicability will be made in the design of
remedial actions.
This requirement might be applicable to those
remedial actions (such as the removal of tailings
from the tailings deposit areas) which would impact
endangered species or their habitat. Determination
of its applicability will be made in the design of
remedial actions.
This requirement might be applicable to those
remedial actions (such as the removal of tailings
from the tailings deposit areas) which might impact
the floodplain. Determination of its applicability will
be made in the design of remedial actions.
This requirement might be applicable to those
remedial actions (such as the removal of tailings
from the tailings deposit areas) which might
adversely impact wetlands along Whitewood Creek.
Determination of its applicability will be made in the
design of remedial actions.
This requirement might be applicable to those
remedial actions (such as the removal of tailings
from the tailings deposit areas) that encompass
occupational activities subject to these regulations.
Determination of their applicability will be made in
the design of remedial actions.
These regulations would be applicable to the
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RECORD OF DECISION
ATTACHMENT B
WHITEWOOD CREEK SUPERFUND SITE
RESPONSIVENESS SUMMARY
-------
RESPONSIVENESS SUMMARY - ATTACHMENT B
WHITEWOOD CREEK SUPERFUND SITE
DECISION SUMMARY
TABLE OF CONTENTS
PAGE
I. OVER VIEW -------------------------------------------------------------------------------------------------1
n. BACKGROUND ON COMMUNITY INVOLVEMENT -------------------------------------2
m. SUMMARY OF PUBUC COMMENTS AND AGENCY RESPONSES-----------------3
A Summary of Comments Received During the Public Meeting --------------------------3
B. SummaI)' of Written Public Comments ------------------------------------------------------ 10
C. SummaI)' of Homestake Comments on the Preferred Alternative -------------------14
-------
.'
I. OVERVIEW
During the public comment period, the U.S. Environmental Protection Agency (EP A)
presented its preferred alternative for cleanup of the Whitewood Creek Superfund site in
Lawrence, Meade and Butte Counties, South Dakota, in a Proposed Plan which was mailed
to individuals on the site mailing list and presented at a public meeting in Whitewood,
South Dakota. EP A's preferred alternative addressed the tailings deposits, contaminated
residential soils and alluvial groundwater. The preferred alternative specified in the
Proposed Plan involved covering and/or removal of soils adjacent to residences which
contain over 100 milligram per kilogram (m~/kg) arsenic and continued monitoring of the
surface water of Whitewood Creek. InstitutIonal controls, including continuation of the
South Dakota ban on water wells in the 100-year floodplain, zoning regulations to prohibit
development within the tailings deposits areas and provisions for development with
variance in the tailings impacted areas, deed restrictions, posting of warning signs, and an
educational program to inform the public of site hazards were also included.
Based upon comments received by the EP A during the public comment period, all
concerned parties (the residents of the site, the commissioners of the three counties
involved, the State of South Dakota and Homestake Mining Co.) supported continuation of
the ban on water wells, institution of zoning regulations to pr'Jhibit development within the
tailings deposits areas, and an educational program. Homestake believed that the 100
mg/kg actIOn level is overly protective and protested the necessity of covering/removing
soils in the residential areas. The deed restrictions and posting of warning signs were felt
by many to be unnecessary. The site residents were confused about the risk to human
health because of the lack of visible effects over the past 100 years. Some expressed doubt
over st'~')orting the covering/removal of soils. Others expressed the opinion that all of the
tailing . ~posits should be removed.
After ';:view of all comments received during the public comment period and as part of the
reCOL )f decision (ROD), EP A selected a remedy similar to the preferred alternative.
The selected remedy includes covering and/or removal of soils adjacent to residences
which contain over 100 milligram per kilogram (mg/kg) arsenic, continued monitoring of
the surface water of Whitewood Creek, and institutional com:ols. These controls consis )f
continuation of the South Dakota ban on water wells in the 100-year floodplain, zoning
regulations to prohibit development within the tailings deposits areas and provisions for
develo:pment with variance in the tailings impacted areas, and an educational program
consistmg of distribution to the public of brochures containing site information and
notification to future buyers of properties within the site.
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II. BACKGROUND ON COMMUNITY INVOLVEMENT
Prior to the issuance of EP A's Proposed Plan for the Whitewood Creek Superfund Site,
there had not been strong community interest in the site. Prior to, and concurrent with, the
listing of the site on the National Priorities List (NPL) of hazardous waste sites, and as a
result of mandatory com~lianc~ wit~ EP A S~rface 'Yater Quality and Discharge Standards,
Homestake has made major stndes m returmng WhItewood Creek to a clear running
stream with a viable aquatic population. Vegetation now established on the tailings
deposits area supports a wildlife population.
Homestake has entered into a joint venture with Goldstake Explorations Inc. to mine the
tailings on the site for gold, for which most site residents will receive royalties on their
mineral rights. Homestake has been actively communicating with site residents for several
years. Homestake has informed the citizens that activities related to minin~ of the
Whitewood Creek tailings, such as a request for mine permits, cannot be imtiated until
EP A has made a decision regarding cleanup of the site. Homestake sponsored a meeting
in Whitewood on January 24, 1990, to discuss potential impacts of EP A's preferred remedy
on future mining activities. Site residents and interested parties, as well as EP A
representatives, were invited. Most concerns expressed by site residents at this meeting
were reiterated at EP A's public meeting on January 25, 1990. .
Over the past few years, EP A has been involved in the process of developing an
Endangerment Assessment for the Whitewood Creek Superfund Site. In thIS assessment,
EP A concludes that the risk posed to the site residents through incidental ingestion of
arsenic-contaminated soil is significant enough to require remediation of soils around
residential properties. Homestake does not agree with EP A's assessment of risk posed to
site residents through incidental ingestion of arsenic-contaminated soil. Homestake has
expressed this view to site residents, along with Homestake's concern that excessive
expenditures on remedial action will limit the economic viability of the mining venture.
Because of the strong reliance on institutional controls in the selected remedy, EP A has
actively solicited input from the state and counties involved as these entities will have
principal control over adoption and enforcement of the controls outlined in the selected
remedy. Meetings with these agencies are discussed in greater detail in Section III of this
document, which is the Decision Summary Attachment B to the Record of Decision
(ROD) for the Whitewood Creek Superfund site. These recent activities, and a growing
interest in the area regarding environmental concerns, have led to an increase in
community involvement.
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III. SUMMARY OF PUBLIC COMMENTS AND AGENCY RESPONSES
A. Summary of Comments Received During the Public Meeting
Comments raised during the Whitewood Creek public meeting are summarized briefly
below. The public meeting was held on January 25, 1990. The comments are categonzed
by relevant topics.
Public Participation Process
Comment #1:
EPA Response:
Comment #2:
EP A Response:
One resident suggested that EP A has not held enough public
meetings.
EP A has had an active community involvement program at the site.
EP A has conducted interviews with site residents, county officials and
state legislators. Al5 a result of these conversations, EP A determined
that it would not be productive to hold a public meeting before a
specific remedial action plan could be discussed. Because. of the
increased level of public interest expressed during the public meeting,
the Agency will schedule additional meetings during the remedial
design and remedial action process.
Two residents expressed concern because they were not aware of the
program under which the public could obtain technical assistance
grants. They asked for an explanation of the program.
The Technical Al5sistance Grant program provides grants of up to
$50,000 to citizens' groups to obtain assistance in interpreting
information related to cleanups at sites on, or proposed for, the NPL.
These grants are to be used by citizens' groups to hire technical
advisors to help them understand site-related technical information
for the duration of site response activities.
An applicant is eligible to receive a technical assistance grant if that
applicant is a group of individuals that may be affected by a release or
threatened release of a hazardous substance at a Superfund Site. The
applicant is ineligible if it is a potentially responsible party, or
represents a governmental office of any kind or an academic
institution. The following are examples of activities suitable for
technical advisors: (1) reviewing and interpreting site-related
documents, whether produced by EP A or others, (2) meeting with the
recipient group to explain techmcal information, (3) providing
assistance to the recipient group in communicating the group's site-
related concerns, and (4) traveling to meetings, hearings, etc., directly
related to the situation at the site.
-------
Cost/Funding Issues
Comment # 1:
EP A Response:
Two residents inquired about the cost of the selected remedial action.
The residents wanted to know where the $882,813 will come from, a
breakdown of how it will be spent and the percenta~e of
administrative costs on the total $882,813. One resIdent also asked if
the money for wa~es will be spent primarily for EP A staff or for local
workers. One resIdent su~ested that it would be cost-effective to
have EP A inspectors on sIte during the entire time of remediation to
assure that the work is done correctly and will not have to be
repeated.
The breakdown of estimated costs for Alternative 4a is as follows:
Capital Costs
Delineation of floodplain
and extent of contamination
$175,000
Pre-implementation sampling of
twelve existing and fifteen future
residential properties
Soil covering, removal and
confirmation sampling of residential
properties
199,000
604,000
Labor related to county assistance
in developing land use ordinances
Education program (includes design
and printing of brochures and
notification of buyers of site.
properties)
30,000
20,000
Estimation for remediation of future
residential properties
447,000
Operation and Maintenance Costs (Annual)
Re-sample existin~ residential
propertIes in the fIfth year after
coverin~ and/or removing soil these at
propertIes ($26,000 distributed over five
years)
5,000
Maintenance of the education program
Annual monitoring of Whitewood Creek
2,000
5,000
The total capital cost is estimated to be $1,028,000. Annual operation
and maintenance (O&M) costs are estimated to be $12,000 per year
in the first five years and $6,000 per year in the remaining 25 years.
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Comment #2:
EPA Response:
Decision Process
Comment #1:
EPA Response:
The net present value calculated using a discount rate of 5% over the'
30 year O&M period is $882,813.
If Homestake or another potentially responsible party performs the
work, EP A costs will be associated with overseeing the work
performed by the potentially responsible party. If the work is
lIDplemented according to the specifications of EP A's ROD and the
Remedial Design Plans without any significant problems, EP A's costs
are minimized. If the work is done improperly, EP A's oversight costs
can escalate significantly. Usually, EP A's oversight is substantial
during initial remedial action activities. Once EP A is satisfied that
the work is being conducted properly, the level of oversight may
decrease to periodic visits. Tbe potentially responsible party would be
responsible for reimbursement of EP A's oversIght costs.
Upon issuance of the ROD for the Whitewood Creek Site, EP A will
issue to Homestake or any other potentially responsible party a
special notice letter offering an opportunity to conduct the remedial
action outlined in EP A's ROD. If Homestake or any other potential1y
responsible party refuses to conduct this work, EP A would either
order one or more potentially responsible party(ies) to conduct the
work or may opt to conduct the work itself. EP A would then attempt
to recover from the potentially responsible party, any costs incurred
while conducting this work.
One resident asked about the cost to the County government to
implement ordinances.
EP A disagrees with certain assumptions made by Homestake in the
feasibility study, one of which is the assumption that certain costs
would be borne by the local counties. Because of the cost burden to
the counties, EP A does not ,feel that this assumption is proper and
encouraged specific input from Butte, Meade and Lawrence Counties
on their abilities to contribute to remedial costs. EPA expects any
cost incurred by the counties to be funded by the potential1y
responsible party (ies) for the site.
One resident questioned the procedure to be taken if the counties do
not agree with the recommendations of the ROD to implement
ordinances.
At the Public Meeting, EP A requested formal responses from the
counties about their willingness to implement specific ordinances.
EP A also stated at that time that if the counties did not wish to .
cooperate, that EP A might choose another alternative. During t:ie
public comment period, EP A received formal responses from Butte,
Meade and Lawrence counties. Each county has expressed a
willingness to enact ordinances described in Alternative 4a.
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Technical Questions/Concerns Regarding Remedial Altern~tives
Comment # 1:
EP A Response:
Comment #2:
EPA Response:
Comment #3:
EPA Response:
Comment #4:
EP A Response:
One resident asked where the tailings will be taken, if they are
removed.
Under the preferred alternative, the tailings piles will not be removed.
Arsenic-contaminated soils removed only from residential areas
would be disposed of at a disposal facility or location approved by
EP A and the state, such as the Grizzly Gulch tailings impoundment in
Lead.
Two residents questioned how EP A will delineate the Whitewood
Creek floodplam and why there isn't already a floodplain map upon
which the residents may comment.
Current delineation of the 100-year floodplain is based on Federal
Emergency Management Authority (FEMA) maps. The scale of
these maps is one inch to 2,000 feet. Since this scale is not sufficient
for remedial design, this information will be augmented by additional
surveys to delineate the 100-year floodplain during the remedial
design phase.
One resident asked how much soil cover would be put over residential
soils. A second concern expressed was the effect that various kinds of
plants growing on the clean soil will have in transporting arsenic from
the lower contaminated area to the clean surface.
The parcel around each residence will be based on the most actively
used portion of the property. For purposes of the Feasibility Study,
EP A estimated that a residential property consists of a an eIght acre
area with up to two acres for vegetable gardens. EP A is proposing to
cover non-garden areas with 12 inches of non-contaminated soil, or to
remove soil to a depth of 12 inches and replace with one foot of clean
cover as necessary to maintain the local topography. Garden areas
would be excavated to two feet and backfilled With clean soil.
Driveway areas would be replenished with six inches of gravel.
These depths have been determined to be sufficient to eliminate
ingestion of contamination by site residents durinS invasive activities
(gardening, etc.) and to elirmnate uptake of arsemc in the vegetation.
One resident was concerned about the emphasis on arsenic, when
other contaminants, such as cyanide and mercury, are also present.
As part of EP A's final endangerment assessment, EP A assessed the
potential risk from inorganic contaminant constituents associated with
the tailings, including cyanide and mercury. Each potential
contaminant was considered with its appropriate pathway. After this
evaluation, arsenic remained the only constituent of concern. The
other contaminants were not present in sufficient concentration to
pose a substantial public health risk.
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Comment #5:
BPA Response:
Comment #6:
EPA Response:
Comment #7:
EP A Response:
Comment #8:
EPA Response:
Comment #9:
Two residents were concerned about the potential for re-
contamination of remediated areas by flooding.
If flooding occurs, then the flooded area will need to be resampled. If
. the concentrations exceed the 100 mgjkg action level, then additional
remedial action will be necessary. The ROD contains a provision for
post-flood sampling and, if necessary, reclamation of property.
Two residents questioned the size of the study area.
The FS study area encompasses land within the Whitewood Creek
100-year floodplain bounded to the south by 1-90 and to the north by
the Belle Fourche River confluence. The FS study area does not
correspond with site boundaries. EP A has defined the boundaries of
the Whitewood Creek Superfund Site as the area within the 100-year
floodplain. The southern boundary of tbe site is the Crook City
Bridge. The northern boundary of the site is at the Whitewood Creek
and Belle Fourche River confluence.
Two residents asked for clarification on what EP A considered to be a
residential property. One resident said that soil sample surveys
showed greater than 600 mgjkg arsenic within 200 feet of the house
and requested to know the area requiring remediation.
A residential property is defined as the area used for a residence or
domicile. The parcel around each of the residences will be based on
the most actively used portion of the property including the
. immediate yard (non garden) around the resIdence, and the driveway
and garden areas. EP A has estimated that the size of a residential
property within the site is up to eight acres. Remediation will be
conducted in coordination with property owners on only those soils
exhibiting arsenic concentration of greater than 100 mgjkg.
One resident said he has notic~d a reduction in wildlife, such as bi':" .1;;
and rabbits, in areas of contamination. He questioned the effect on
wildlife from remedial action.
EP A is not aware of a reduction of wildlife in the study area. EP A is
concerned, however, that removal of the tailings will result in an
adverse short-term impact on the ecological habitat alqng Whitewood
Creek. In addition, there is a potential of release of tailings material
into Whitewood Creek as a result of removal of tr~ tailings. The
selected remedy will not adversely affect the ecolof1cal hab~tat of the
Whitewood Creek area in the short term.
Two residents asked for clarification on the potential for excavation
(mining) of the tailings. The questions deal with who would have
jurisdiction over the mining activity, and what kind of mining
restrictions are there to prevent contamination from future mining
activities.
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EP A Response:
Comment # 1 0:
EPA Response:
Comment #11:
EP A Response:
Under the Superfund program, EP A is charged by Congress with
protecting the public health and the environment. The objective of
EP A's selected remedy is to reduce the exposure of arsenic in the
downgradient groundwater, residential soils, and tailings to acceptable
risk levels. Mining of Whitewood Creek is considered to be an
economic venture which will be permitted and regulated under the
jurisdiction of the State of South Dakota Mining Regulations. Any
mining activities and their effects on public health and the
environment would be closely monitored by the State of South Dakota
and any adverse effects would be evaluated -by EP A in its 5-year
review of the Superfund site to ensure protectiveness of human health
and the environment.
Several questions were raised about the risk assessment. One resident
was confused about the real potential for cancer development, since
apparently the local populatiOn is generally healthy and the creek is
reclaiming itself. Homestake expressed its concern that the cost of
remedial action may not be justified, based on risk potential. Another
resident was confused about how the need to cover the soils around
residential areas was related to reducing the cancer risk to one out of
10,000.
EP A has determined that unacce:ptable public health risk is posed
through incidental lifetime ingestIon of residential soils with arsenic
concentration exceeding 100 m~/kg. The 100 mg/kg action level is a
level that corresponds to reduCIng the health risk at the site from the
ingestion of arsenic to an acceptable level. This risk level corresponds
to the chance of one additional person out of 10,000 contracting
cancer as result of site conditions. EP A's selected remedy entails
covering contaminated soils with clean soils so that the risk from soil
ingestion is reduced to an acceptable level.
Several questions involved the .use of institutional controls. Many of
the residents did not think it would be possible to keep signs up for
any length of time. One resident was against deed restrictions and
warning signs because of the potential negative effect on land values.
The purpose of warning signs proposed as part of the preferred
remedy was to discourage extended and frequent activity within the
tailings area. As a result of expressed community concern regarding
the posting of warning signs in the tailings area and the reality that
they would likely not have much effect SInce the occasional recreation
user is not at unacceptable risk according to .EP A's endangerment
assessment, EP A has decided not to incorporate this element as part
of its selected remedy.
EP A has also not incorporated deed restrictions as part of the
selected site remedy as stated in the ROD due to community
opposition. EP A requires, however, that as part of the educational
program, prospective buyers of property within the site be informed of
potential hazards associated with the site.
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Comment # 12:
EP A Response:
The issue of future development was discussed. One resident did not
feel that future development in the floodplain was desirable and that
there was probably an ordinance covering this. Another resident
questioned what development would be allowed or disallowed.
Although EP A does not believe it is wise to develop within the
Whitewood Creek lOO-year floodplain and EP A discourages such
activities, the selected remedy allows for such development if the .
appropriate cleanup actions are taken. Development restrictions
within the site are currently in place for Lawrence County. The EP A-
selected remedy entails the implementation of additional restrictions
within the site for Lawrence, Butte and Meade counties. EP A has met
with the Commissioners of Lawrence, Butte and Meade counties to
assess the willingness of the counties to support land use ordinances to
restrict development. Each of these counties expressed a willingness
to cooperate.
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B. Summary of Written Public Comments
Letters received from the public indicated concern about the effect deed restrictions and
warning signs would have on property values. Statements were made both in support of
EP A's risk assessment and in question of its validity. One of the major concerns was that
development variances be allowed so that a water treatment system for the City of
Whitewood can be installed.
Cost/Funding Issues
Comment #1:
EP A Response:
A resident expressed concern that many of the studies to date,
including the Feasibility Study, were paid for by Homestake and done
by their consultants. While he understands that funding is a problem
for EP A, the resident would "feel much better and have much more
faith in the project" if EP A had conducted the studies and recovered
the expenses from the responsible parties.
At the public meeting on January 25, 1990, Mr. Levene of EPA stated
that Homestake would be required to monitor site conditions for 5
years. For Superfund cleanups and investigations, EPA is required by
Congress to offer the potentially responsible parties the opportunity
to conduct the proposed work. It is the intent of Congress that those
parties who are responsible for the contamination should be obligated
to clean up the contamination. This work is conducted under the
extensive oversight of EP A. If a potentially responsible party refuses
to implement selected remedies outlined in the ROD, EP A would
either order the potentially responsible party to conduct the work or
opt to implement the selected remedy itself. EP A would then attempt
to recover from the potentially responsible party any cost incurred.
Technical Questions Concerning Remedial Alternatives
Comment #1:
EP A Response:
Several residents expressed concern about the need for posting signs
and erecting fences on their property when EP A and Homestake say
that it is safe for residents to live there and carry on normal activities
and for sportsmen to visit. Fencing their winter pasture, which is
along Whitewood Creek, would create a problem of access to water
and shelter; this access has been used for the past 50 years. Other
concerns were that signs would be ineffective and not worth the cost
of administering and that this program would be an extra burden on
the local County governments, which are already financially strapped.
In response to concerns of private citizens and Homestake, EP A
agrees that the possible benefits of signs and fences would be
outweighed by disadvantages. Signs and fences have not been
included in the selected remedy.
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..
Comment #2:
EPA Response:
Commentn:
EP A Response:
Comment #4:
EPA Response:
Commentj[j:
EPA Response:
Three residents wrote on the subject of deed restrictions. The major
concern is that if the site is completely cleaned up, then deed
restrictions are unnecessary. If contamination is left and deed
restrictions are placed on their property, then the restrictions may
affect the property value. Any remedial program should increase the
land's value, not decrease it.
In response to this concern, EP A has not incorporated deed
restriction as part of its selected remedy. EP A requires, however, that
prospective buyers of property within the site be informed of potential
hazards as part of the educational program for the site.
Several parties addressed the issue of development restrictions from
different view points. There was concurrence that residential building
should be prohibited on the tailings areas. It was stated that because
every ranch along Whitewood Creek is dependent upon some kind of
livestock operation for its success, any development restrictions that
would have a negative impact on the livestock industry would be
objectionable.
EP A's remedy does not restrict grazing of cattle on the tailings area.
Commercial (e.g., feedlot, industrial property) and residential
development, however, will not be allowed in the tailings area.
Commercial development will be allowed within the lOO-year
floodplain but outside the tailings area if appropriate actions are
taken. EP A will allow a variance for public works projects within the
lOO-year floodplain and tailings area.
Meade and Lawrence county officials expressed willingness to
cooperate with the EP A in matters of public health. The counties will
consult with the state concerning the proposed ordinances. They
request a formal letter from EP A defining specific health hazards,
including specific maps of the ~ected areas and desired county
actions.
EP A has documented the presence of a public health risk in the EP A
Final Endangerment Assessment.
Officials of the state and the City of Whitewood, as well as site
residents, requested that a public works variance be allowed.
Specifically, a variance is requested for the proposed lagoon and
artificial wetlands to be built north of the Whitewood Valley Road on
Homestake property.
EP A does not see a health threat from this proposed action and
therefore would not object to this proposal.
-------
Comment~:
EP A Response:
Comment #7:
EP A Response:
Comment #8:
EP A Response:
Several citizens think that the estimate of endangerment to human
health is unrealistic. One woman wrote that between 1951 and 1971
. ,
she and her late husband owned land in Butte County where
Whitewood Creek runs into the Belle Fourche River. They had a
herd of cows and calves there for 20 years and did not observe any ill
effects from the cyanide in the water. Now that it has all been cleaned
up, she wonders why EP A is asking for further clean-up.
Due to arsenic contamination in the residential soils, tailings and
groundwater which still remaj.ns despite other clean-up efforts, EP A
has determined that further action IS required at the site to protect
the public health of site residents. .
One resident believes that EP A is taking the wron~ approach to
remedy the concern about residences located on hIghly contaminated
soils. This resident estimated, using EP A's cost projections, that it
would cost approximately $65,000 per residence to excavate and refill
with new soil. He recommended that EP A should consider moving
the "residences" to an uncontaminated area and eliminating the
hazard entirely which he believed may be a more economical and
satisfactory solution.
Because there is no acute public health threat to the site residents that
cannot be remediated without moving residents, EP A has determined
that relocation of the residents is umyarranted.
One concerned citizen advocated the implementation of Alternative
9. His argument was that over the past 100 years of Homestake's
involvement in the State of South Dakota, Homestake has reaped.
profits far in excess of the $109 million dollar cost estimated in the
proposed plan for Alternative 9. He felt that Homestake's profits
were at the expense of the environment, since EP A has identified
Homestake as the potentially responsible party. He questioned why
EP A preferred Alternative 4a, because if cost was not a factor (and
should not be), then the benefits of Alternative 9 were better than
those of Alternative 4a.
This citizen pointed out that South Dakota's Governor advocates
economic development as the key to the State's future. Implementing
Alternative 9 would put more money back into the State's economy
and would more thoroughly clean up Whitewood Creek at the same
time. In short, this citizen believed that the benefits of Alternative 9
justify its selection over Alternative 4a, even considering the higher
cost.
Under the Superfund process, cost is one of the nine criteria used to
evaluate alternatives and the selection of the preferred and selected
remedy. EP A did not select Alternative 9 (removal of the tailings)
due to the high cost of the alternative and the potential for adverse
impacts on the Whitewood Creek ecosystem. EP A's selected remedy
(similar to the preferred alternative) provides only a slightly less
degree of protectiveness to public health than Alternative 9, at a much
lower cost.
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Mining
Comment #1:
EP A Response:
Several residents wrote to endorse the removal and mining of tailings
along Whitewood Creek, as long as it is under the supervision of the
State of South Dakota.
Other citizens were concerned about Homestake's proposed project to
mine the tailings. They feel there is a lack of concern on the part of
the Company for the long-term reclamation of the land. This concern,
as expressed by one person, is based on mining companies' past record
in the lack of long-range reclamation planning and input from
"officials" with whom he has spoken on this issue. It was felt that
mining could be viable if: 1) there were strict regulation and
enforcement by Federal a~encies (the state and local governments
would not be able to proVIde the same strength as the Federal
government); 2) there is environmental protection of soil, water and
air while the project was underway; and 3) there is a definite and
detailed plan for reclamation of the land (Homes take should make a
sufficient profit from the mining operation to pay for planting native
species of trees, shrubs and ground cover). .
Mining activities at the site will be regulated under the jurisdiction of
the State of South Dakota Mining Regulations. EP A, as the lead
federal environmental agency administering environmental statutes;
has the authority to stop mining operations at the site if the public
health or environment 15 threatened as a result of related activities.
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C. Summary of Homestake Comments on the Preferred Alternative
Homestake submitted comments on EP A's preferred alternative on February 7, 1990
durin~ the public comment period. Prior to this public comment period, Homestake
subnutted comments on EPA's Final Endangerment Assessment on October 6, 1989. The
Endangerment Assessment bears directly on EPA's preferred and selected remedy. Most
of these comments were reiterated in their official comments to the preferred alternative
submitted on February 7, 1990. Letters of comment were also subnutted by Gary Dietrich,
ICF Technologies, Homestake's contractor, on January 30, 1990 and February 9, 1990.
EPA notes at the outset that Homestake's comments included several issues on which
Homestake is in agreement with EP A's preferred remedy. The areas of agreement include:
(1)
. Implementation of institutional controls to restrict access to and use of the tailings
deposits areas
Implementation of an educational program to educate site residents of risk posed by
the site
(2)
(3)
Continuance of the State of South Dakota ban on installation of water wells within
the Whitewood Creek 100-year floodplain
Inclusion of waiver for compliance with Maximum Concentration Levels (MCLs) in
groundwater
(4)
(5)
Regulation of mining within site under the jurisdiction of the State of South Dakota
This discussion will not address these areas of agreement in detail, but rather will focus on
areas where Homestake's position differs from EPA's position.
Homestake's main concern was that EPA's proposed plan is based upon EPA's
Endangerment Assessment which overstates the risks at the site. Homestake supports this
contention by providing comments on (1) the ingestion rate of soil, (2) cancer potency
factor for arsenic, (3.) detoxification of arsenic, and 4) assessment of future land use. Other
comments relate to details of the preferred alternative, especially as related to the action
level. Comments are also provided on specific points where public input was requested by
EP A in the Proposed Plan.
Comment #1:
Homestake stated that the relevant population of concern for
purposes of estimating exposure include only those people living in
the floodplain area. They contend that the one-mile and three-mile
populations should be excluded, as should the town of Whitewood.
They indicate that the Proposed Plan incorrectly stated the one- and
three-mile populations.
Homestake also stated that the past and present use of the tailings
deposits and fringe areas for native woodlands and limited agriculture
are unlikely to change in the foreseeable future.
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EP A Response:
Comment #2:
EPA Response:
Comment #3:
EPA Response:
Comment #4:
The one-mile and three-mile populations were reported incorrectly in
EP A's Proposed Plan. The correct figures, from the FS, are 283 and
647 respectively, with an additional population of 821 in the town of
Whitewood. This error does not affect EP A's assessment of risk at the
site.
EP A is required by Superfund regulations to consider a reasonable
maximum exposure scenario for the site. This scenario assumed
habitation of the tailin~s area. Although currently no residents have
built on the tailings, this scenario seems very plausible, as represented
by the close proximity of present homes to the tailings, and the
possibility of future pressure to increase development in the area. As
a result of assessing this scenario, EP A proposes to have the counties
enact ordinances to restrict development in the tailings area. This
portion of the remedy is supported by Homestake.
Homestake stated that because of the very substantial buffering
capability which occurs naturally by virtue of the presence of
carbonate material through the site, there will not be substantial
arsenic releases from the arsenopyrite and other arsenic minerals in
the tailings.
EP A agrees that in relation to substantial amount of arsenic in the
tailings, the rate of release of arsenic to the surface water and
groundwater is relatively slow. This release is significant, however,
because it is does result in an exceedance of EP A's Maximum
Concentration Level of arsenic for drinking water in the groundwater.
Despite the fact that there are no indications of significant surface
water quality degradation of Whitewood Creek, EP A remains
concerned about potential for future degradation of the surface water.
This concern is supported by the estimation that 30,000 to 35,000
kilograms of arsenic are releas~d into surface water during high flow
events. As a result of this concern, EP A is requiring additional
surface water monitoring as part of the selected remedy for the site.
Homestake stated that the exposure assessment conducted by Joseph
Rodericks, Environ CorporatIon, titled Assessment of Exposure and
~~s:ble E:Cts °kn l:umar SHe~~t~ o~ ~old Mi~~ ~ailingslln the
- i ewoo ~ ea 0 ou a 0 a, cons i u es a fu y
satisfactory endangerment assessment.
The remedial action objectives for the site were based on EP A's Final
Endangerment Assessment. These objectives were based on pathways
such as incidental soil ingestion and ingestion of downgradient alluvial
groundwater which were not examined in the above referenced
report. The pathways assessed in EP A's endangerment assessment
and the methodology for calculating endangerment at the site are fully
consistent with EP A guidance and the National Contingency Plan.
Homestake commented that "despite over a century of environmental
and human residential exposure to tailings, if the tailings posed any
threat to human health, surely their effects would be in evidence."
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EP A Response:
Comment #5:
EP A Response:
~
The population along Whitewood Creek is not of sufficient size to
display ongoing cancer problems as a result of the exposures
predicted. The EP A's endangerment assessment does predict that
such problems may arise intermittently as a result of exposure to the
tailings along Whitewood Creek. Since data to determme past
problems is missing, it is impossible to assess historical site-related
health problems.
Homestake disputed soil ingestion rates used by EPA (100 mg/day for
adults, 200 mg{ day for children). Homestake recommended the use
of lower rates (10 mg/day for adults, 50 mg/day for children).
The soil ingestion rate estimates suggested by Homestake represent
central tendency calculations (median) from a sin~le study (Calabrese
et al., 1989). These estimates are inaccurate and mappropnate for
several reasons:
(a)
The Calabrese study was conducted on a nonrandom
population.
Parents of children used in the study were highly
educated, of higher than average income, and married.
All of the above have a strong potential for skewing the
study results toward lower ingestion rates.
(b)
(c)
The study was conducted on a population which was
under constant daycare supernsion. This is in clear
contrast to the agricultural setting and behavior of the
population along Whitewood Creek.
Since the data represented in the Calabrese report are
log normally distributed, the best measure of central
tendency is the g~ometric mean and not the median.
Tabulated below are the geometric mean, median, and
95 percentile of the Calabrese data:
(d)
Mean Median
Tracer (mg/d) (mg/ d) 95%
Al 153 29 223
Si 154 40 276
Y 85 9 106
As is evident from the difference between the median and geometric
mean values presented above, Homestake is suggesting a soil
ingestion rate which may seriously underestimate the exposure at the
Whitewood Creek Superfund site. Further, it is EP A policy to protect
for more than half the population. EP A Risk Assessment Guidance
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Comment #6:
EP A Response:
Comment #7:
EP A Response:
for Superfund (dated July, 1989) clearly suggests the use of the 95
percent upper confidence limit on the data. It is clear that the
estimate for soil ingestion used by the Agency in the endangerment
assessment is neither unreasonable nor "unscientific" as suggested by
Homestake. The above discussion does not account for the child
exhibiting pica who would be expected to occupy the extreme tail of a
skewed distribution and hence be at greatly increased risk.
HOIDIstake commented that the cancer potency factor (1.75 mgjkg-
day r used by EP A in their endangerment assessment is based on
epidemiological data from a study of Taiwanese populations. The
Science Advisory Board is reviewing the Taiwanese study in
comparison with studies in the United States populations and suggests
other models might be more appropriate. Homestake stated that use
of this factor grossly overestimates risk of cancer from arsenic at the
Whitewood Creek site.
The results of the Taiwanese study have been both confirmed and
duplicated in studies conducted in Chile, Argentina, and Mexico
(Borgono and Greiber, 1972; Bergoglio, 1964; Cerbrian et al., 1983).
The studies conducted in the United States do not in any way
contradict the evidence obtained in the Taiwanese study (Morton et
al., 197~; Southwick et al., 1981). Sample size of the U.S. studies were
of insufficient statistical power to use for extrapolation. Further, the
tremendous size and stability of the cohort used in the Taiwanese
study provide for some of the strongest evidence of human
carcinogenicity used by EP A
Arsenic is regarded as an "A" known human carcinogen. This
classification follows com:prehensive review of the quality of the
evidence for carcinogenicity and reflects the reviewers' confidence in
the overall data used to derive the slope factor for arsenic.
EPA used a 70-year lifetime as. the total exposure time for residential
scenarios in their endangerment assessment. Homestake commented
that use of numbers from EPA's Exposure Factors Handbook (1989)
would present a "reasonable worst case" assumption. This handbook
states that nine years is the average length of time that a person
resides at one location during a lifetime and thirty years is the
reasonable worst case.
It appears that the Homestake reviewer misinterpreted the total
exposure time used in EP A's EA calculations. The value for duration
of exposure used in EP A's Endangement Assessment for Whitewood
Creek was in fact 30 years. This value represents the 90th percentile
for time spent at one residence in the U.S. (EPA, 1989). In the .
calculation of carcinogenic risks, the duration of exposure was divided
by a value representing a 70 year (average) life:ir.1e. This procedure
results in a value for average lifetime exposure Dased upon a 30 year
duration of exposure. For non-carcinogenic effects, we are interested
in evaluating health effects due to chronic, but not necessarily lifetime
exposures (EP A considers a chronic exposure to be an exposure
lasting> 7 years and u:p to a lifetime (70 years». Therefore in the
case of the HI calculatIOn, the exposure occunng over 30 years which
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Comment #8:
EP A Response:
Comment #9:
EP A Response:
.,
is considered to be a chronic exposure, is not "averaged out" over a 70-
year lifetime.
Homestake commented that EP A used an absorption rate of 80% in
their endangerment assessment. Homestake proposes that this is
based on a form of arsenic not like that found at Whitewood Creek.
Homestake proposed additional studies.
Estimates of arsenic absorption are based on studies conducted by
Vahter and Norin (1980) and Tam et al. (1979). These studies show
nearly complete absorption of tri- and pentavalent arsenic.
Homestake supports the use of preliminary leachin~ studies which
indicate that soil arsenic at the Whitewood Creek sIte is "tightly
bound" and hence less bioavailable. EP A recognizes the possibility
that forms of arsenic found at the site may differ slightly from those
used in the above cited studies. The Agency would support a
comprehensive absorption study funded by Homestake to determine
the bioavailability of soil arsenic at the Whitewood Creek Site. Such a
study must be designed to define the absorption and excretion kinetics
of soil arsenic found in particulates less than 150 urn in diameter. The
study must be conducted in an animal species whose digestive
anatomy and physiology is comparable to humans and provide for
adequate mass balance determmation. Such a study would be most
useful if designed in cooperation with an EP A toxicologist.
EP A will not accept preliminary benchtop geochemistry experiments
as adequate for determination of bioavailability in lieu of peer
reviewed, widely accepted literature which strongly suggests
otherwise.
Homestake commented that EP A ignored findings by its own Science
Advisory Board that humans effectively detoxify and excrete arsenic
that is ingested at or below the .rate of 250 micrograms per day.
Homestake stated that EP A did not consider detoxification of arsenic
by the human body in their endangerment assessment. Homestake
contends some studies show that at a low dose (less than 250 ug/day),
. 80 to 90% of ingested and absorbed arsenic is detoxified and excreted.
Homestake feels an 80% factor should be incorporated into the dose
calculations. .
Official EP A policy regarding arsenic is clearly defined in the
document titled Special Report of Inorganic Arsenic: Skin Cancer:
Nutritional Essentiality (1987) prepared by the Risk Assessment
Forum..This report has been reviewed and approved by the Science
Advisory Board. Homestake has apparently mistaken the
subcommittee letter (September 28, 1989) for official Agency policy.
The argument posed by Homestake that EP A did not consider
"detoxification" of arsenic in EP A's endangerment assessment is ill-
founded. The assumption that methylation of arsenic constitutes
detoxification remains unproven. The Drinking Water Subcommittee
of the Science Advisory Board identified methylation as a possible
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.
,
Comment # 10:
EP A Response:
Comment #11:
EP A Response:
Comment # 12:
EP A Response:
Comment # 13:
EP A Response:
Comment #14:
EPA Response:
detoxification mechanism. Indeed, methylation of arsenic may
constitute activation. Since there is no animal model with which to
test the hypothesis that the methylated derivative of arsenic is more or
less carcinogenic than any other form of arsenic, the carcinogenic
potential of arsenic is best estimated from the abundance of human
evidence now available.
Homestake commented that the surface water of Whitewood Creek is
not presently used for drinking water, and does not pose a threat to
human health or the environment. Therefore, there is no need for
further sampling of the creek. Their conclusions are based on U.S.
Geolo~ical Survey monitoring data, the Cherry report and proposed
remedIal actions.
EP A is requiring additional surface water monitoring in Whitewood
Creek due to the concern over potential for future water quality
degradation as a result of erosion of the tailings resulting from high
precipitation events and changes in the course of the stream (see
response to Homestake Comment No.2).
Homestake questioned the effectiveness of warning signs In restricting
access to the tailings area.
As discussed earlier, EP A has re-evaluated its position based on
comments by Homestake and site residents at the public meeting. In
response to these concerns, warning signs have not been incorporated
in EPA's selected remedy.
Homestake commented that the property owners should be
responsible for remediation of areas where future development is
allowed.
EP A accepts this comment for consideration during the remedial
design/remedial action negotiation phase of this project.
Homestake commented that commercial development should be
allowed within the IOO-year floodplain but outside the tailings area.
EP A concurs with this comment unless concentrations within this area
exceed the level of arsenic in soils associated with public health risk.
Homestake recommended that both pre-implementation and
verification sampling be confined to the surface. They further stated
that soil sampling is not necessary to define the limits of the lOO-year
floodplain.
It is EP A's position that any surface soil (up to the depth of
disturbance by plant or animal mechanisms) with arsenic
concentrations above the action level poses potential risk to site
residents. As a result, EP A is requiring 12 inches of cover in the
residential areas and 24 inches in garden areas. In order to assure
that sufficient cover has been added and the cover has not been
significantly disturbed subsequent to remediation, it is EP A's position
that sampling at depth is required.. .
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Comment # 15
EPA Response:
1
.
EPA requires that further delineation of the ,Whitewood Creek 100-
year floodplain be conducted to specifically document the areas
regulated under the proposed county ordinances.
Homestake commented that based on EP A's endangerment
assessment, the Environ report and the Intake Survey by Geochemical
Engineering Inc., there does not appear to be sufficient indication of
substantial arsenic uptake through the food chain to warrant further
investigation.
Based on current information, EP A concurs with this comment.
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'I'
I,
References:
Bergoglio, R.M. (1964) Mortality from cancer in regions of arsenical waters of the province
of Cordoba Argentine Republic. Prensa Med. Argent. 51:994-998.
Borgono, J.M. and R. Greiber. (1972) Epidemiological study of arsenicism in the City of
Antofagasta. In: Trace Substances m Environmental Health-V. Proceed. 5th Annual
Conference, University of Missouri, Columbia, MO, June 29-July 1, 1971. D.C.
Hemphill, Ed., University of Missouri, Columbia, MO p. 13-24.
Calabrese, EJ. Barnes, R., Stanek III, EJ., Pastides, H., Gilbert, C.E., Veneman, P., Wang,
. X., Lasztity, A and Kostecki P.T. (1989) How much soil do young children ingest: an
epidemiologic study, Reg. Tox. and Pharmaeol. 10:123-137.
Cerbrian, M.E., Albomes, A, Aguilar, M., and Blakely, E. (1983) Chronic arsenic
poisoning in the north of Mexico. Human Toxieo! 2:121-133.
EPA, 1989. Risk Assessment Guidance for Superfund, Part A EPA, July 1989.
Morton, W., Starr, G., Pogl, D., Stoner, J., Wagner, S. and Wesig, P. (1976) Skin Cancer
and water arsenic in Lane County, Oregon. Cancer 37:2523-2523. .
Southwick, J., Western, A, Beck, M., Whitley, T., Isaacs, R., Petafan, J., and Hansen, C.
(1981) Community health associated with arsenic in drinking water in Millard County,
Utah. Health Effects Research Laboratory, Cincinnati, OH, EPA-600jl-81-064.
Tam, G.K., Charbonn71~' S.M., Bryce, F., Pomroy, C., and Sandi, E. (1979) Metabolism of
inorganic arsenic ( As) in humans following oral ingestion. ToxieoL AppL Pharmaeol.,
50:319-322.
Tseng, W.P. (1977) Effects and dose-response relationships of skin cancer and blackfoot
disease with arsenic. Environ. Health Perspeet. 19:109-119. .
Vahter, M. and Norin, H. (1980) Metabolism 74 As-I~belled trivalent and pentavalent
iniorganic arsenic in mice. Environ. Res. 21: 446-457.
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