United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPAIRODIR08-921062
December 1991
PB93-964402
&EPA
Superfund
Record of Decision:
Denver Radium (Operable
Unit 9), CO
EPA Report Collection
Information Resource Center
US EPA Region 3
Philadelphia. PA 19107
, ,
~~~~~f.
if.J$EPA. Reglon~ce Center
Phladelphla~ PA 19107
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NOTICE
The appendices listed In the index that are not found In this document have been removed at the request of
the issuing agency. They contain material which supplement. but adds no further applicable information to
. the content of the document. All supptemental material is, hoWeIIer. comained In the adn*Iistrattve record
for this site.
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REPORTDOCUMENTA~ON T 1. REPORT NO. I ~ a. A8dp1enC'. ~ No.
PAGE EPA/ROD/R08-92/062
4. 1118"''''''' L AIport 08t8
SUPERFUND RECORD OF DECISION 12/23/91
Denver Radium (Operable Unit 9), CO I.
Eiahth Remedial Action - Subseauent to follow
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U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
111. "..' .-...., No-
PB93-964402
11. Ab8nct (LImIt: 2110 WOId8) -
The Denver Radium site is a former radioactive mining site located in Denver, Denver
County, Colorado. The site includes a 17-acre former brick plant, a parking lot, and
a large amount of exposed soil. Land use in the area is predominantly commercial and
industrial, with a residential area located several blocks east of the site. The
South Platte River lies 1,000 feet from the former brick plant. Industrial activities
commenced at the site in 1886 with the construction of the Bailey Smelter. In 1890,
the Gold and Silver Extraction Company began a cyanide leaching operation onsite. In
1901, the Bailey Smelter burned down. By 1903, the Colorado Zinc Company had
constructed a mill on the site of the Bailey Smelter, and zinc milling operations
continued until 1910. From 1914 to 1917, the U.S. Bureau of Mines operated a radium
processing facility onsite, known as the National Radium Institute (NRI). Other
onsite industrial activities included minerals recovery, manufacturing and servicing
of storage batteries, treating and sacking of metallic ore insulation, oil
reclamation, and landfilling. Robinson Brick Company (Robco) acquired 13.5 acres of
the site in 1941 and a contiguous 3.5-acre parcel in 1951. Robco, the present owner
(See Attached Page)
17. DoaIm8nt An8Iye18 L DncrIpton
Record of Decision - Denver Radium (Operable Unit 9), CO
Eighth Remedial Action - Subsequent to follow
Contaminated Medium: soil
Key Contaminants: Metals (arsenic, lead, zinc)
b. Id8ntlfi8r8/Op8n-End8d T-
c. COSA 11 A8IdIGrCM41
18. Avlil.bllly Statement 18. Sec:I8'IIy CI... (l'hl. Report) 21. No. 01 P.ge.
None 48
20. Sec:I8'IIy CI... (l'hl. Page) n PrIce
Nnnp
~ (4.77)
S0272 101
(See ANSl-Z3t.1S)
See Inalrucliona on flew-
IForrnetIy NTlS-35)
Departnwnt 01 Commerce
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EPA/ROD/R08-92/062
Denver Radium(Operable Unit 9), CO
Eighth Remedial Action - Subsequent to follow
Abstract (Continued)
of the site, utilized the site until 1980 to manufacture bricks. In 1983, EPA discovered
that 30 properties, including the Robco property, contained radiologic contamination in
the soil attributable to prior NRI operations. In 1988, the U.S. Bureau of Mines.
initiated excavation of the radiologically contaminated material. In the course of the
radium cleanup, metals contamination, resulting from mining wastes disposed of and used
as fill from the mid-1880's to the early 1920's, was discovered onsite. Excavation of
the radiologically contaminated materials was completed in 1991 as part of OUs 4 and 5.
This ROD addresses approximately 16,500 cubic yards of metal-contaminated soil as OU9,
the 9th of 11 OUs planned for the site. The primary contaminants of concern affecting
the soil are metals, including arsenic, lead, and zinc.
The selected remedial action for the site includes constructing a 3.7-acre multi-media
cap over onsite contaminated soil with metal concentrations exceeding action levels;
utilizing the existing concrete floor of the brick plant and asphalt parking lot in
concert with the backfilled soil cap; providing inspection and repair of the concrete
floor, as necessary; upgrading the asphalt with geotextile fabric and an additional
6-inch layer of asphalt; monitoring downgradient ground water; long-term monitoring to
ensure effectiveness of the cap; and implementing institutional controls including deed
restrictions to limit the ground water use and to maintain the integrity of the cap. The
estimated present worth cost for this remedial action is $1,702,000.
PERFORMANCE STANDARDS OR GOALS: Design of the cap will comply with RCRA and state
requirements. Chemical-specific soil remediation goals, which are based on health
criteria, include prevention of exposure and direct contact with action level
concentrations exceeding arsenic 79 ug/l; lead 1,000 ug/l; and zinc 17,000 ug/l.
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\1111111
204481 .
Denver Radium, Operable Unit 9
Robinson Brick Company Property
Declaration for the Record of Decision
ADMINJSTRA TIVE
RECORD
401
Site Name and Location
Denver Radium Site, Operable Unit 9
Denver, Colorado
Statement of Basis and Purpose
This decision document presents the selected remedial action
for the Denver Radium Site, Operable Unit 9, in Denver, Colorado,
which was chosen in accordance with the requirements of the
Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA) and, to the extent
practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision document explains the
basis and purpose of the selected remedy for this Site.
The State of Colorado concurs on the selected remedy. The
information supporting this remedial action decision is contained
in the administrative record for 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 danger to public health, welfare, and
the environment.
Description of the Remedy
The Denver Radium Site consists of eleven operable units
throughout the City and County of Denver which were contaminated
as a result of several minerals processing operations. The
Operable Unit (OU) 9 property, located at 500 South Santa Fe
Drive, has previously been remediated for radiological
contamination. The selected remedy presented in this ROD
addresses metals contamination in the soils. Direct contact
with, or inhalation or ingestion of metals-contaminated soils
have been determined to pose the principal threat to human
health. The function of th~s final response action at the OU is
to permanently reduce the risks associated with metals
contamination in the soils by creating a barrier between
contaminated soils and any potential human receptors. No
environmental receptors were identified.
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The major components of the remedy in€lude:
- Capping the metals-contaminated soils;
- Conducting environmental monitoring to ensure the
effectiveness of the remedial action; and
- Implementing institutional controls to 1) limit use of
groundwater at the Site, and 2) maintain the integrity of
the cap.
Declaration
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. This remedy utilizes
permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable for this
Site. However, because treatment of the principal threats at the
Site was not found to be practicable, this remedy does. not
satisfy the statutory preference for treatment. While treatment
would reduce the mobility of the contaminants, there would be no
significant increase in protectiveness to human health and the
environment over the selected capping remedy.
Because this remedy will result in hazardous substances
remaining on-site above health-based levels, a review of the
remediation will be conducted within five years after
commencement of remedial action to ensure that the remedy
continues to provide adequate protection of human health and the
environment.
/2 lor 1/
Administrator
Protection Agency
Jame
Regi
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Denver Radium, Operable Unit 9
Robinson Brick Company Property
Decision Summary for the Record of Decision
I.
Site Name, Location and Description
Operable Unit (OU) 9 of the Denver Radium Site is located in
the south-central part of Denver, Colorado at 500 South Santa Fe
Drive, near the intersection of West Alameda Avenue and
Interstate 25. The 17 acre OU, referred to in this document as
the "Site", consists of the Robinson Brick Company (Robco)
property. It is bounded on the west by a frontage road adjacent
to Interstate 25, on the east by the main north/south rail
corridor owned by the Denver & Rio Grande Western Railroad, and
on the south by the U.S. Welding Company property. To the
northwest is a vacant Regional Transportation District (RTD)
facility. (See Figure 1-1.)
The abandoned brick plant and a few small structures are
presently standing at the Site. An asphalt parking lot is
located adjacent to the brick plant. However, the Site is mostly
undeveloped. Commercial and industrial land uses dominate the
area surrounding the Site. The nearest residential population is
located several blocks east of the Site.
The Site slopes gently to the West toward the South Platte
River which is about 1000 feet from the Robinson Brick Company
property boundary. The Site does not lie within a flood plain.
Ground water at the Site is found in the alluvium at depths of 10
to 20 feet below ground surface. There is no current use of
ground water at the Site.
II.
Site History and Enforcement Activities
History of Operations
Industrial activity at the Site began in 1886 with the
construction of the Bailey Smelter. The Bailey Smelter appears
to have operated only sporadically in the late 1880's. In 1890,
the Gold & Silver Extraction Company began a cyanide leaching
operation at the Site using the McArthur Forrest Chemical Cyanide
Process. In 1901, the Bailey Smelter burned down. By 1903, the
Colorado Zinc Company had constructed a mill on the Site of the
old Bailey Smelter. Zinc milling operations continued until
about 1910. From 1914 to 1917, the U.S. Bureau of Mines operated
a Radium processing facility (the National Radium Institute) on
Site. Other industrial activities at the Site have included
minerals recovery, manufacturing and servicing of storage
batteries, treating and sacking of metallic ore insulation, oil
reclamation, and landfilling. In 1941, the Robinson Brick
Company acquired 13.5 acres of the Site and in 1951 acquired an
3
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FIGURE 1 . 1
Location Map of Operable Uait ,
W. BAYAUD AVE.
,..:
ell
;:::
c
...
...
vi
SEC. 15
N
1000
1500
I
o
I
500
I
W. Al.AMEDA AVE.
,..:
ell
W. NEVADA PL
g
z
! W. DAKOTA AVE.
vi
W. ALASKA PL
W. VIRGINIA AVE.
OBINSON BRICK
COMPANY PROPERTY
W. ..mDlE CT.
SEC. 15
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additional 3.5 contiguous acres and manufactured bricks on the
Site until 1980. The Robinson Brick Company is the present owner
of the Site.
Past Site Investigations and Superfund Activities
In 1979, research by EPA led to the rediscovery of the
former National Radium Institute (NRI). By 1983, thirty
properties, including the Robco property, were found to have
radiologic contaminants in the soils and were placed on the
National Priorities List for Superfund cleanup. Due to their
association with the NRI, the U.S. Bureau of Mines was named as a
responsible party for the radiologic contamination at OU 9 and
the Bureau has agreed, pursuant to a Memorandum of Understanding,
to pay for the radiologic clean up at the Site. In May 1988,
excavation of the radiologically contaminated soils at OU 9
began. In September of that year, during the courSe of the
radium cleanup, metals contamination was discovered on Site. An
investigation to characterize the nature and extent of metals
contamination was conducted in 1989 and 1990. The investigation
resulted in a feasibility study (July 1991)- outlining a number of
alternatives for the cleanup of approximately 16,540 cubic yards
of metals-contaminated soils remaining in place on the Site.
(Excavation of the radiologically contaminated materials was
completed in March 1991 as part of operable units 4 and 5.)
III.
Highlights of Community Participation
- .
The Focused Feasibility Study (FFS) and the Proposed Plan
for Operable Unit 9 of the Denver Radium Site were released to
the public for comment on August 2, 1991. These two documents
were made available to the public in the Administrative Record
maintained at the Central Branch of the Denver Public Library and
at the EPA Region VIII Superfund Records Center in Denver,
Colorado. The notice of availability for the Focused Feasibility
Study, the Proposed Plan, and other documents in the
Administrative Record was published in the Denver Post on August
2, 1991. The initial public comment period was held from August
2, 1991 to September 3, 1991. Upon timely request, the public
comment period was extended for 30 days to October 3, 1991. A
public meeting was held in Denver on August 14, 1991 to allow the
public an opportunity to provide comments on the Proposed Plan
and to ask questions of representatives of EPA and the Colorado
Department of Health about the Site and the remedial alternatives
under consideration. A response to the comments received during
the public comment period is included in the Responsiveness
Summary, which is part of this Record of Decision.
This decision document presents the selected remedial action
for Operable Unit 9 of the Denver Radium Site, in Denver,
Colorado chosen in accordance with the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA)
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as amended by the SupErfund Amendments and
(SARA) and, to the extent practicable, the
Plan. The decision for this Site is based
Record.
Reauthorization Act
National Contingency
on the Administrative
IV.
Scope and Role of Operable Unit Within Site Strategy
Operable Unit 9 is one of eleven operable units which
comprise the Denver Radium Site. The Denver Radium Site was
divided into separate units since the contaminated material was
found in discrete locations within the City and County of Denver.
The Robco property and adjacent railroad right-of-way property
have already been remediated for radiologic contamination as part
of operable units 4 and 5. This Record of Decision, for OU 9,
addresses metals contamination on the Robco property. Records of
Decision have been signed for each of the other OUs of the Denver
Radium Site with the exception of OU 8.
V. Summary of Site Characteristics
Source and Nature of Contamination
In the Site characterization program, forty-nine boreholes
were driven on the Site to sample the soils. The data from the
borehole samples shows that contamination of the soils by
arsenic, lead, and zinc is largely confined to the fill material.
The data also shows that no metals contamination for arsenic,
lead or zinc extends into the bedrock or the soils below the
water table. Two conclusions were drawn from this data. First,
the fill material is the source of the metals contamination on
the Site. Based on the history of industrial operations at the
Site, EPA determined that. the metals contamination resulted from
mining wastes disposed and used as fill from the mid-1880s to the
early 1920s. The second conclusion reached by EPA is that the
metals contamination is not migrating significantly from the
contaminated fill material into the alluvium or the bedrock.
Groundwater is encountered at ten to twenty feet below the
surface. Cadmium, lead, and zinc concentrations, in excess of
the Federal drinking water standards, have been found associated
with isolated pockets of low pH groundwater found on the. Site.
These isolated areas are probably the result of early minerals
processing operations on the Site. The distribution of the
contaminants indicates that they are not extremely mobile in the
alluvial aquifer ground water. Based on the available
hydrological data, it was concluded, in the characterization
study, that the contaminant concentrations appear to be
controlled locally by the ground water pH. Where pH values are
low, contaminant concentrations are elevated. As contaminated
ground water migrates away from areas of low pH on the Site
toward areas of higher pH, the reaction causes the contaminants
to come out of solution.
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Extent of Contamination
Distribution of the metals of concern on-site is described below:
Arsenic generally occurs at the Site in high concentrations
along with lead. Background concentration of arsenic in the
subsurface is approximately 2 parts per million (ppm). The
maximum value for arsenic in soil samples analyzed is 490
ppm.
Lead is generally elevated in samples from fill material
across the Site. Background concentration of lead in the
subsurface is approximately 30 ppm. The maximum value for
lead in soil samples analyzed is 35,800 ppm.
Zinc is also generally elevated in samples from fill
material. Elevated concentrations are seen in some samples
that do not have high cadmium and lead concentrations.
Background concentration of zinc in the subsurface is
approximately 50 ppm. The maximum value for zinc in soil
samples analyzed is 32,050 ppm.
Based on the risk assessment, action levels were defined for
each metal of concern. Concentrations of metals which exceed
these levels would pose an unacceptable health risk. Based on
the available data, an estimated 16,540 cubic yards of soils are
contaminated with metals above the action levels. The affected
area was determined to be approximately 4.8 acres.
The areal extent of the fill material contamination is
illustrated in Figure 5-1, "Areal Distribution of Metals
Contamination at OU 9". The contaminated areas are presented as
a large central body with four small isolated outliers. The
large central area can be divided into three separate subareas:
1. Contaminated Area under Brick Plant 27,000 square feet 13%
2. Contaminated Area under Parking Lot 45,000 square feet 22%
3. Contaminated Area of Exposed Soil 130,000 square feet 63%
Total Contaminated Area 202,000 square feet 98%
The remaining 5,000 square feet or 2 percent is accounted
for by the four outliers. The four small isolated outliers
represent single detections above the action level and can be
divided into two groups. Two of the outliers are to the north of
the main body of contaminated soil along the western boundary of
the Site and represent surface contamination. The other two
isolated outliers are south of the main body of contaminated
soil. These last two outliers are each based on a single
detection of metal contamination at four and fourteen feet below
clean soils.
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FIGtJD 5 . 1
Anal DiatribatioD of Meta18 CoDtuaiD8tioD at au 9
z
s$ -
.
SURFAa: EXPRESSION OF CONT,w"A1ED
SOLS FROIII AU. DEPtHS
[XPUMATDI
/
/
.
RTD
-~
~ ---..
W:::.A ~ 1 r --
1
. I us
01
I
1
~I
WELD INC
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Potential routes of contaminant migration and. population and
environmental areas that could be affected by the contaminants
are described in Section VI.
VI.
Summary of Site Risks
As part of the Characterization of Selected Metals study,
EPAprepared a Baseline Risk Assessment for the Robco Site in
July 1990. This risk assessment was conducted to characterize,
in the absence of remedial action (i.e., the "no-action"
alternative), the current and potential threats to human health
and the environment that may be posed by contaminants at the
Site.
HUMAN HEALTH RISKS
Contaminants and Site Media
Exposure pathways were identified and analyzed for ground
water, surface water, soils, and air media at the Site. It was
concluded in the risk assessment that only direct contact with,
or inhalation or ingestion of soils, could result in significant
health risks. Of the contaminants studied in the Baseline Risk
Assessment, the following metals were determined to be the
primary contaminants of concern in the soils:
Arsenic due to potential carcinogenic and non-
carcinogenic health effects in humans;
Lead due to potential non-carcinogenic and carcinogenic
health effects in humans; and
Zinc due to potential environmental effects and non-
carcinogenic health effects in humans.
Other metals (chromium, cadmium, copper,
detected on the Site were not present in
would pose any significant environmental
threats.
and selenium) that were
concentrations which
or public health
Exposure Assessment
The major exposure routes that lead to public health threats
are inhalation of dusts, incidental ingestion of soils and dusts,
and direct skin contact with soils and dusts. Ingestion of
contaminated ground water is not a significant exposure route due
to past, present, and likely future land use (highways, railroad
rights-of-way and industrial properties), the availability of
municipal water supplies, and the low potential for migration of
the contaminants from the Site.
To analyze potential risks to human health, the baseline
risk assessment evaluated various scenarios to establish
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potential risks associated with alternate uses of the Site.
current and three future land-use scenarios were considered.
the four scenarios considered, EPA concluded that metals
contamination could pose a health risk in the following three
scenarios:
One
Of
Current land-use scenario:
; )
Children trespassing onto the Site.
Future land-use scenarios:
2 )
Construction workers involved in a short duration
construction project. New construction would require
cleaning, scraping, and shallow excavating at the Site.
Laborers are the construction workers closest to the
metals-contaminated soil.
3 )
Children residing in a subdivision constructed on Site.
This scenario examines potential health effects on
children who have spent five years (i.e., between the
ages of one and six) in the subdivision.
The fourth scenario, industrial workers, was not evaluated
further since the associated carcinogenic and non-carcinogenic
health risks were determined to be negligible. EPA determined
that the scenario involving children residing in a subdivision
constructed on the Site would not be considered further due to
the current and potential future use of the Site. Given the long
industrial history at the ROBCO Site and its location between
Interstate 25 and a major rail corridor, it is unlikely that the
property would ever be converted to residential use. Therefore,
only the first two scenarios were considered in determining
action levels for metals in soil.
Current Risks
The baseline risk assessment shows that children trespassing
on the Site could be at risk for unacceptable non-carcinogenic
health threats due to arsenic and zinc. In particular,
dermatoxic effects may result due to combined ingestion and
direct contact with arsenic-contaminated soils. Skin irritation
resulting from direct contact with acidic salts of zinc is also
possible. The risk assessment indicates that blood lead levels
in children could become elevated.
Future Potential Risks
According to the risk assessment, construction workers
involved in a short duration (1 year) construction project could
be at risk for both carcinogenic and non-carcinogenic health
threats due to arsenic exposure. Dermatoxic effects may result
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. .
from cumulative exposure to arsenic via the ingestion and direct
contact routes.
Toxicity Assessment
The toxicity of chemicals is evaluated in terms of
carcinogenicity and other, non-carcinogenic effects. Cancer
potency factors for carcinogenic chemicals and reference doses
for non-carcinogenic chemicals are used to evaluate risks posed
by the exposure to chemicals. (Table 5.5 of the Baseline Risk
Assessment summarizes the cancer potency factors and the.
reference doses for contaminants of concern.)
The cancer potency factor for a given compound is multiplied
by the estimated dose to obtain the carcinogenic risk estimate.
The individual risks from each compound in a particular exposure
pathway are then summed to obtain an estimate of the overall
carcinogenic risk posed. (At this Site, carcinogenic risk is
posed only through the inhalation pathway.) The acceptable
carcinogenic risk range is between 1E-04 and 1E-06. The baseline
risk assessment shows that the cumulative carcinogenic risk at
the Site for the current land-use scenario is 3.8E-07. For the
future land-use scenario, the cumulative carcinogenic risk is
2.6E-~4. The carcinogenic risk associated with this scenario is
just above the upper threshold that would justify a response
action. While lead has been identified as a probable human
carcinogen, no potency factors have been established. Until a
potency factor has been developed and approved, the interim
guidance on soil lead cleanup has set an action level in the
range of 500 to 1000 parts per million (ppm). EPA selected an
action level of 1000 ppm for the Robco property given the
industrial nature of the area. (See the Interim Guidance on
Establishing Soil Lead Cleanup Levels at Superfund Sites, OSWER
Directive 9355.4-02, September 7, 1989.)
Reference doses (RfDs) indicate the potential for adverse
health effects caused by exposure to contaminants exhibiting non-
carcinogenic effects. The RfD for a given compound is divided
into the estimated dose to obtain the hazard quotient (8Q). The
HQs for each compound in a particular pathway are then summed to
obtain a hazard index (HI), which is the estimate of the overall
non-carcinogenic risk. A reference dose has not been determined
for lead, although guidance suggests that acceptable levels for
lead in soils are between 500 and 1000 parts per million (ppm).
Risk Characterization
The non-carcinogenic risks for all contaminants associated
with children trespassing on Site are presented in Table 6-1.
The risks presented are based on levels of contamination with no
remediation. For arsenic, the HI is 2.7, for zinc the HI is 1.2.
An HI over 1.0 indicates that there may be a risk posed by the
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exposure to non-carcinogenic compounds. As indicated above,
there is no RfD for lead and thus no HI ~an be calculated.
Table 6-1 also shows the non-carcinogenic risks associated
with an on-site construction' worker population. For this
scenario, the HI for arsenic is 1.4 indicating that there may be
a risk posed by exposure to arsenic.
TABLE 6-1
Noncarcinogenic Hazard Evaluation
Cumulative HI
Arsenic Zinc
5.7E-01 3.2E-01
2. 1 9.0E-01
'1 . 5 E-1 0 1.8E-07
2.7 1 .2
Children Trespassing
Ingestion HI
Direct Contact HI
(soils)
Direct Contact HI
(runoff)
Construction Worker
Ingestion HI
Direct Contact HI
(soils)
5.3E-01
8.2E-01
3.0E-01
3.6E-01
Cumulative HI
1 .4
6.6E-01
. Based on the exposure pathway analysis, .the estimated dose
of metals that persons could receive, and the toxicity of each of
the metals, action levels for each metal were calculated. These
action levels define the concentrations above which the health
risks are unacceptable. The additive risks of arsenic and zinc
were taken into consideration in setting the action levels. The
cleanup goal for arsenic will serve to reduce the estimated
incremental risk of cancer for the construction worker to
acceptable levels. Table 6-2 summarizes the action levels.
Table 6-2
Action Levels for Metals of Concern at Robco OU 9
Metal
Value (ppm)
Arsenic
Lead
Zinc
79
1000
17,000
'0
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ENVIRONMENTAL RISKS
The ecological effects due to contamination at this Site are
not expected to be significant since this industrialized area
does not provide- a habitat for wildlife, and ground water
modeling shows that contaminated ground water on the Site would
have no adverse impact on the water quality in the nearby South
Platte River. None of the modeled mixing zone predictions are
above the ambient water quality criteria and data suggests that
ground water contamination is limited to local ground water cells
that have low pH.
CONCLUSION
Actual or threatened releases of hazardous substances from
this Site, 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. The
hazardous nature of this Site is illustrated by the values
presented in Table 6-1. Risks are associated with inhalation,
ingestion, and/or direct contact with contaminated soils at the
Site for the potential exposure pathways identified in the
Baseline Risk Assessment. Elevated lead levels are also of
concern at the Site since lead has been identified as a probable
human carcinogen and lead could result in adverse noncarcinogenic
toxic effects. Remediation of the Site by capping metals-
contaminated soils with at least two feet of clean soil as
described in this ROD will result in risks which are within the
acceptable range as established by the NCP. Non-carcinogenic
risks will be reduced so that the Hazard Index is no greater than
1, and carcinogenic risks will be reduced to a range no greater
than 1E-04 to 1E-06.
VII.
Description of Alternatives
The Focused Feasibility Study was conducted to develop and
evaluate alternatives for metals-contaminated soils at the Site.
Remedial action objectives were first identified on the basis of
the Site characterization results and the risk assessment. Next,
a range of response actions were assembled from remedial
technology process options to meet these objectives. The
response actions and technologies were screened based on
effectiveness, implementability, and cost. Those which passed
the initial screening were then combined into remedial action
alternatives. Finally, the remedial action alternatives were
screened in detail using the nine criteria required by the NCP.
Following the detailed screening, five remedial alternatives
remain. These alternatives include no action, as required by the
NCP, two containment options, excavation with off-site disposal,
and an on-site treatment and disposal alternative.
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The alternatives presented in the Focused Feasibility Study
report are .summarized below:
Alternative 1 - No Action
The no action alternative provides the bapeline for
comparing other alternatives. This alternative would not involve
any removal, containment or treatment of the contaminated soils.
The Site would be left in the same condition as it presently
exists. However, it would include periodic ground water
monitoring. .
Because this alternative would result in contaminants
remaining on Site, CERCLA would require that the Site be reviewed
every five years. The 30-year present worth for Alternative 1 is
$174,300. Implementation time for this remedy would be
negligible.
Alternative 2 - Cappinq with Clay, S9ils, Existinq Structures and
Institutional Controls (clay cap)
This alternative is conceived as a multi-media cap utilizing
the existing concrete floor of the brick plant and the asphalt
parking lot in concert with an engineered clay and soil cap. Of
the 4.8 acres of contaminated 50115 on the Site, 3.7 acres would
be capped with clay and soil; the remaining area would be covered
by the existing structures. The concrete floor of the plant
would be inspected and repaired, if necessary, for long-term
stability and to minimize maintenance costs. The asphalt parking
lot would be upgraded to minimize future maintenance costs by
using geotextile fabric and an additional six-inch layer of
asphalt. Fill material would be used to backfill the pit created
by previous remedial activities. For those portions of the Site
that are not covered by concrete or asphalt, a combination clay
and soil cap would be built over the areas that are contaminated
above the action levels. The two outliers to the north of the
main area of contamination would be left in place and capped with
clay and soil. The two outliers to the south of the main area of
contamination are already covered by at least four feet of clean
material and would be left in place without additional capping.
The ground would be graded to provide appropriate drainage of
precipitation and compacted to form the foundation for the cap.
A two-foot thick layer of clay would be laid down in several
lifts and compacted to design specifications.
Upon completion of the clay layer, an additional two-foot
layer of clean fill would be added. The final step in completing
the cap would be re-vegetating the area to provide long-term
stability.
Certain State and Federal technical requirements (including
RCRA) concerning grading, fill, compaction, and completion of a
1 2
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A"
cap were identified as applicable or relevant and appropriate
requirements. The cap would be designed to meet all of these
ARARs. During the construction phase, appropriate measures would
be taken to control fugitive dust to assure compliance with the
provisions of the Colorado Air Quality Control Act identified as
ARARs. .
Following construction of the cap, long-term maintenance,
ground water monitoring, and institutional controls would be
instituted. The long-term maintenance would consist of a plan
for periodic inspections to assure the integrity of the cap with
contingencies for repair, if needed. Ground water down-gradient
of the Site would be periodically monitored to verify that
contamination does not reach the South Platte River in
detr~mental concentrations. The institutional controls would
consist of tpe placement of deed restrictions on the Site to
prevent use of the Site for non-industrial/commercial purposes
and to prevent uses of the capped area that could compromise the
integrity of the cap. .
As extra precautionary measures, EPA would require deed
restrictions to prohibit placement of any wells on the Site for
the purpose of supplying drinking water and would present to the
City and County of Denver a proposal to zone the Site to control
uses of the capped portions of .the Site. If a zoning proposal
can be agreed upon, presented to the City Council, and approved,
such zoning m~y be used in concert with the deed restrictions or
if EPA determines that the zoning is adequate and effective, EPA
may allow the deed restrictions to be removed.
Any contaminated soils that were excavated as the result of
future development of the Site would be disposed at a RCRA
Subtitle C permitted facility. This disposal method would be
used to insure overall protectiveness.
Because this alternative would result in contaminants
remaining on-site, CERCLA would require that the Site be reviewed
every five years. The 30-year present worth value for
Alternative 2 is $2,656,000. It would take approximately 6 weeks
to implement this remedy. .
Alternative 3 - Cappinq with Soil, Existinq Structures
and Institutional Controls (soil cap)
Alternative 3, the preferred alternative, is designed to
make use of the existing concrete floor of the brick plant,
asphalt parking lot and a cap of backfilled soil. As in
Alternative 2, the concrete floor would be inspected and
repaired, if required, and the asphalt would be upgraded to
ensure long-term stability. Fill material would be used to
backfill the pit created by previous remedial action. The soil
cap would cover approximately 3.7 acres of the Site (where metals
1 3
"
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ccntamination in the soil exceeds action levels) with a minimum
of two feet of fill including six inches of soil which is
adequate to support shallow rooted plants. The outliers to the
north of the large area of contamination would remain in place
and be covered with at least two feet of clean soil. The
outliers to the south of the large area 6f contamination are
already covered with over two feet of clean soil and would remain
in place without additional cover. The design specifications
prepared during the remedial design phase would be met.
As in Alternative 2, certain State and Federal technical
requirements for caps were identified as ARARs. .All
construction and related activities would be conducted so as to
meet these ARARs. Appropriate measures would be implemented
during construction to control fugitive dusts to assure
compliance with the provisions of the Colorado Air Quality
Control Act identified as ARARs.
Long-term maintenance and institutional controls, including
the extra precautionary measures, would be identical to those
described for Alternative 2. Any contaminated soils that were
excavated as the result of future development of the Site would
be disposed at a RCRA Subtitle C permitted facility. This
disposal method would be used to insure overall protectiveness.
Because this alternative would result in contaminants
remaining in place, CERCLA would require that the Site be
reviewed every five years. The 30-year present worth for
Alternative 3 is $1,702,000. The estimated implementation
is three weeks.
time
Alternative 4 - Excavation, Off-Site Disposal and Limited
Institutional Controls (excavation with off-site
disposal)
This alternative would achieve a complete removal of all the
contaminated soils above the action levels by excavating the
soils and transporting them to an off-site disposal site. After
demolition of the small buildings and partial demolition of the
other structures, the remedy would remove approximately 16,540
cubic yards of contaminated soil which would be loaded into bulk
hauling trucks. The soil would then be taken to the nearest RCRA
Subtitle C permitted facility for disposal. Other d~bris would
be disposed at a local permitted landfill. Approximately 50,000
cubic yards of clean overburden would be moved and stockpiled on
uncontaminated areas of the Site to allow access to the metals-
contaminated soils. The clean overburden would later be used as
fill to regrade the Site. Approximately 30,000 cubic yards of
additional fill would be needed to complete the re-grading.
Although the contaminated soi1s are not regulated under RCRA
because they are classified as mining wastes which are exempted
1 4
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A'
by th~ mining waste exclusion, the remedy would include disposal
at a RCRA Subtitle C permitted facility. This disposal method
would be used to insure overall protectiveness. In addition, a
determination of acceptability under EPA's off-site policy (OSWER
Directive 9834.11, November 13, 1987) would have to be secured
prior to shipment of contaminated material off-site.
Following completion of the excavation and shipment of the
contaminated soils and regrading of the Site, appropriate
institutional controls would be initiated. No contaminated soils
would be left on-site. Therefore, deed restrictions and/or city
zoning. provisions on use of the Site and inspection and
maintenance actions would not be included in this alternative.
.Five-year reviews, as required by CERCLA, would be included
because contaminants would be present in the ground water above
health based levels. Periodic ground water monitoring would be
conducted to measure attenuation of any contamination in the
ground water. A prohibition against installation of wells for
drinking water supply would also be included until the water
quality was shown to meet all primary maximum contaminant levels
(MCLs).
The thirty-year present worth of this alternative is
estimated at $10,392,200 with an implementation time of
approximately 12 weeks.
Alternative 5 - Excavation, Solidification/Stabilization,
On-Site Disposal and Institutional Controls
(solidification)
This alternative would utilize a treatment technology to
immobilize the metals in the soils by mixing the soils with
fixation agents such as fly ash or concrete to form a solid mass.
Limited demolition of existing structures would be required to
gain access to the contaminated soils. The alternative would
require the excavation of about 16,540 cubic yards of
contaminated soils that would then be mixed with water and
fixation agents. The resultant product would be poured into two-
foot by two-foot by four-foot forms. Once the material was
solidified, the solid blocks would be removed from the forms and
allowed to cure. After the blocks had cured, they would be
placed in the excavated areas and covered with soil. Because the
treatment process would increase the volume of the waste by
adding water and fixative agents, additional areas of the Site
would be excavated for deposition of the blocks, All disposal
cells would be designed to meet the Colorado requirements for
solid waste landfills. After the treated materials had been
disposed and covered with soil as in Alternative 2, the area
would be revegetated. .
During the excavation of soils, operation of the treatment
. facility, and placement of the treated materials, appropriate
, 5
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measur~s would be taken to assure that fugitive dusts were
controlled to comply with the provisions of the Colorado Air
Quality Control Act.
Following completion of treatment and disposal, long-term
maintenance, ground water monitoring, and institutional controls
would be instituted as described in Alternative 2. The estimated
total present worth of the construction, treatment costs and the
associated O&M for this alternative is $9,912,000 with an
implementation time of 8 to 12 weeks.
VIII.
Comparative Analysis of Alternatives
The remedial alternatives developed in the FFS were analyzed
in detail using the "nine evaluation criteria required by the NCP.
These criteria are: 1) overall protection of human health and the
environment; 2) compliance with applicable or relevant and
appropriate requirements (ARARs); 3) reduction of toxicity,
mobility, or volume through treatment; 4) long-term ef.fectiveness
and permanence; 5) short-term effectiveness; 6) imp1ementabi1ity;
7) cost; 8) state acceptance, and 9) community acceptance.
Criteria 1 and 2 are threshold criteria which must be met by the
selected remedial action alternative. Criteria 3, 4, 5, 6 and 7
are balancing criteria. The final two criteria are modifying
criteria used to evaluate the alternatives based on State and
local concerns.
The strengths and weaknesses of the alternatives were
weighed to identify the alternative providing the best balance
among the nine criteria. A discussion of the comparative
analysis of alternatives is discussed below.
Overall Protection of Human Health and the Environment
Overall protection of human health and the environment
addresses whether a remedy provides adequate protection and
describes how risks posed through each pathway are eliminated,
reduced, or controlled through treatment, engineering controls,
or institutional controls.
All of the alternatives analyzed (with the exception of No
Action) would provide overall protection of human health and the
environment by controlling, or eliminating the risks posed by
direct contact with, or inhalation or ingestion of metals-
contaminated soils. Alternatives 2 and 3 (capping) would control
or eliminate Site risks by using a combination of engineering
controls, capping, and institutional controls. Alternative 4
(off-site disposal) would eliminate the Site risks by excavation
and off-site disposal of the contaminated soils at a RCRA
Subtitle C permitted landfill. Alternative 5 (solidification)
would control or eliminate Site risks by the same means as
Alternatives 2 and 3 but would add a treatment component which
16
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.. .
may serve to reduce the mobility of the contaminants. The No
Action alternative is not considered further in this analysis
since it would not satisfy this threshold criteria. .
Compliance with ARARs
Compliance with ARARs addresses whether a remedy will meet
all applicable or relevant and appropriate Federal and State
environmental laws and/or provide a basis for a waiver from any
of these laws. These ARARs are divided into chemical specific,
action specific, and location specific requirements.
Two specific determinations by EPA had a significant effect
on the ARARs chosen for this Site. In characterizing the Site
and identifying ARARs, EPA determined that the sources of
contamination were mining wastes which are exempt from Resource
Conservation and Recovery Act (RCRA) Subtitle C regulation under
the RCRA "mining waste exclusion." The exclusion exempts from
regulation "... solid waste from the extraction, beneficiation,
and processing of ores and minerals...." 42U.S.C. i .
3001(b)(3)(A)(ii).
Over the last 100 years, industrial operations at the Site
which have produced mining wastes include smelting, cyanide
leaching, and milling. The first such operation on the Site, the
Bailey smelter, began operation sometime in ;886. In 1890, the
Gold and Silver Extraction Company established a mill and
laboratory at the Site to process ore by the McArthur Forrest
chemicai cyanide extraction process, a cyanide leaching process.
The Bailey smelter appears to have been converted for use by the
Gold and Silver Extraction Company. In 1901, the Bailey smelter
burned down. In 1902, the Colorado Zinc Company constructed a
mill on the Site, which operated through 1911. In 1913, the
National Radium Institute began milling operations at the Site
which continued through 1918. Each of these ore and mineral
processing operations generated mining wastes which may have been
disposed at the Site and which in turn may have contributed to
the metals contamination now found at the Site.
Mining wastes from the milling operations conducted on the
Site are "beneficiation wastes", as defined at 40 C.F.R. !
261.4(b)(7), and therefore, fall within the mining waste
exclusion. The wastes from the cyanide leaching process also
fall within the definition of beneficiation wastes and are
excluded from RCRA regulation, see 51 FR 24496, July 3, 1986 and
54 FR 36592, 36616, note 1, September 1, 1989.
Smelter wastes at the Site fall under the definition of
"mineral processing wastes" and are only excluded from RCRA
regulation if the wastes .fall within certain specific categories.
EPA has determined that the process used by the Bailey smelter
was most likely primary lead smelting. Waste slag from primary
17
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lead smelting is still excluded from RCRA regulation under the
mining waste exclusion, see 55 FR 2322, January 23, 1990.
While RCRA has been determined not to be applicable, certain
RCRA provisions concerning construction and maintenance of caps
and closure of landfills were found to be relevant and
appropriate due to the contaminated material at the Site being
sufficiently similar to RCRA wastes and due to the similarity
between activities contemplated at the Site and activities
regulated by RCRA.
EPA also determined that the alluvial aquifer under the Site
was not a potential drinking water source. The alluvial aquifer
is not presently used as a drinking water source and is unlikely
to be used as a drinking water source due to poor natural quality
(i.e., high total dissolved solids), low yield, and its location
(i.e., in an industrial area between a major rail corridor and an
interstate highway). Though the aquifer is not a potential
drinking water source, there is the concern that, due to the
Site's proximity to the South Platte River, the aquifer has a
connection with the river. Nevertheless, modeling has predicted
that it is unlikely that contaminants from the Site would reach
the river in detrimental concentrations.
Because the aquifer was determined not to be a potential
drinking'water source and it is unlikely that contaminants from
the Site would affect the South Platte River, EPA determined that
the Safe Drinking Water Act (SDWA) Maximum Contaminant Levels
(MCLs) and the Clean Water Act (CWA) water quality criteria were
neither applicable nor relevant and appropriate to activities at
the Site. Nonetheless, EPA identified ground water monitoring to
verify the modeling predictions as a remedial action objective
for the Site. Thus, ground water monitoring would be included
for each alternative.
Each of the alternatives would comply with all applicable or
relevant and appropriate requirements (ARARs). No chemical- or
location-specific ARARs were identified for the Site. Certain
provisions of the State Solid Waste Act and specific technical
provisions of RCRA pertaining to closure of landfills and
construction and maintenance of caps were identified as action-
specific ARARs.
Alternatives 2 and 3, capping, would have to be constructed
and maintained to comply with 40 CFR !! 264.310(a)(2),(3),(4) and
(b)(1 ),(4) and '264.117(c). These RCRA landfill closure and
general closure regulations require design and construction of
the cap to promote drainage, to minimize erosion ar abrasion of
the cap, and to accommodate settling and subsidence. In
addition, measures to maintain cap integrity and prevent
incompatible uses of the cap must, be taken.
1 8
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. .
Alternative 5, solidification, would have to meet all the
same ARARs as the capping alternatives. In addition, excavation,
treatment, and redisposal of the contaminated soils would have to
be done in accordance with 'State solid waste regulations found at
6 CCR 1007-2 S 6. ,These regulations establish minimum standards,
closure requirements, site standards, and engineering design
standards for waste impoundments used to store or dispose solid
waste.
Discharge of air pollutants during implementation of any of
the alternatives would be controlled to comply with the State Air
Pollution requirements identified as ARARs. An evaluation of all
State and Federal ARARs identified for the Site is found in Table
7-1.
Reduction of Toxicity, Mobility, or Volume Through Treatment
Reduction of toxicity, mobility, or volume through treatment
refers to the preference for a remedy that uses treatment to
reduce health hazards, contaminant migration, or the quantity of
contaminants at the Site.
, Alternative 5, Stabilization, would be the only alternative
that would provide any reduction in toxicity, mobility, or volume
through treatment. Treatment in Alternative 5 may reduce the
mobility of the contaminants. The degree of mobility reduction
would be determined by treatability studies conducted during
remedial design. However, the volume would increase and there
would be no change in toxicity.
Long-Term Effectiveness
Long-term effectiveness and permanence refers to the ability
of a remedy to maintain reliable protection of human health and
the environment over time. This criterion includes the
consideration of residual risk and the adequacy and reliability
of institutional controls.
Each alternative would be expected to provide similar
degrees of long-term effectiveness and permanence. Alternative
5, solidification, is the only alternative that involves
treatment. Solidification may reduce the mobility of the metals,
but would not reduce the toxicity and would increase the volume.
The long-term effectiveness of this alternative would be
dependent on the long-term integrity of the cap and preventing
incompatible uses of the capped area. Therefore, maintenance of
the cap and institutional controls as described for Alternatives
2 and 3 would be part of this, alternative.
Alternative 4, excavation with off-site disposal, would
remove all contaminated soils to a RCRA Subtitle C permitted
landfill, thereby eliminating the long-term risks at the Site.
19
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However, the long-term effectiveness of this alternative would be
dependent on the reliability and operation of the landfill where
the contaminated material would be disposed. While Alternative 4
would eliminate on-site risks, off-site disposal without
treatment is the least preferred option under CERCLA.
Alternatives 2 and 3 would use capping and institutional
controls to control or eliminate the risks at .the Site. As long
as the cap was maintained, the risks identified for the Site -
direct contact with, and inhalation or ingestion of contaminated
soils - would be eliminated. Long-term maintenance of the cap
would be required. Institutional controls to prevent uses of the
capped area which would be inconsistent with maintaining the
integrity of the- barrier would also be .required.
Each of the alternatives' long-term effectiveness would be
dependent on long-term maintenance of the remedy. For
Alternatives 2, 3, and 5, an on-site operation and maintenance
program would be required. For Alternative 4, operation and
maintenance would be performed by the disposal facility. Thus,
there would be no appreciable difference in the long-term
effectiveness of any of the alternatives.
Short-Term Effectiveness
Short-term effectiveness refers to the period of time needed
to complete the remedy and any adverse impacts on human health
and the environment that may be posed during the construction and
implementation of the remedy. .
Short-term effectiveness would be provided by each of the
alternatives. Alternative 3, soil cap, would provide the
greatest degree of short-term effectiveness. This alternative
would take the least time to implement and involve the least
disturbance of the contaminated materials, therefore resulting in
the least risk to on-site workers and the surrounding
communities. Alternative 2, clay cap, would be only slightly
less effective than Alternative 3 due to a slightly longer
implementation time for the clay and soil cap. Alternative 4,
excavation with off-site disposal, would provide the least degree
of short-term effectiveness because all the contaminated material
would be disturbed, loaded on trucks, and transported for off-
site disposal. Alternative 5, solidification, would be somewhat
more effective than excavation with off-site disposal in the
short-term due to the fact that no transportation would be
involved. Also, Alternatives 4 and 5 would each require a longer
time to implement than either of the capping alternatives.
Implementability
Implementability refers to the technical and administrative
feasibility of a remedy, in~luding the availability of materials
20
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. .
and services needed to implement the chosen solution. It also
includes coordination of Federal, State, and local governments to
clean up the site.
Each of the alternatives, except Alternative 5,
solidification, utilizes standard technologies and equipment, and
would be readily technically implementable. Solidification,
while a proven technology, would require additional study during
the design of the remedy to maximize its implementability.
Implementation of deed restrictions for Alternatives 2, 3,
and 5 would require the cooperation and approval of the owners of
the Site. The owners of the Site have indicated they would
cooperate in establishing deed restrictions.
Implementation of zoning for the Site pursuant to the City
and County of Denver ordinances, which may be made part of
Alternatives 2, 3, and 5 as an extra precautionary measure,
presents uncertainty in implementation. If a change in zoning
would be necessary, this would require a public process, with
public notice and comment, and. City Council approval.
Cost
This criterion examines costs
For comparison, capital and annual
calculate a present worth cost for
are as follows:
for each remedial alternative.
O&M costs are used to
each alternativ~. The costs
Alternative 5
- No Action
- Clay Cap
- Soil Cap
- Excavation with
OLf-Site Disposal
- Solidification
$ 174,300
$ 2,656,000
$ 1,701,900
Alternative 1
Alternative 2
Alternative 3
Alternative 4
$10,392,200
$ 9,912,000
State Acceptance
The State of Colorado, through the Colorado Department of
Health (CDH), has had an active role in the Focused Feasibility
Study (FFS), selection of ARARs, and the remedy selection
process. CDR was provided the opportunity to comment on the FFS
document and the proposed plan, and attended the public meeting
held to inform the public of the proposed plan. The State has
concurred on EPA's selection of Alternative 3, soil cap.
Community Acceptance
Community input on the alternatives for remedial action at
OU 9 was solicited by EPA during the public comment period from
August 2, 1991 to October 3, 1991. Comments were received from
the property owner, a vicinity property owner, and the City and
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County of Denver. The property owner generally showed support
for the soil cap remedy, while the vicinity property owner and
the City and County of Denver supported Alternative 4, excavation
with off-site disposal. Responses to all comments are found in
the attached Responsiveness Summary. .
IX.
SELECTED REMEDY
After consideration of the statutory requirements of CERCLA,
the detailed analysis of alternatives, and public comments, EPA
has selected capping the contamination with a protective soil
cover and existing structures, and implementation of
institutional actions (Alternative 3) as the remedy for OU 9 of
the Denver Radium Site. This remedy is made up of the following
components:
The cap will be a multi-media cap utilizing the existing
concrete floor of the brick plant and the asphalt parking lot in
concert with a backfilled soil cap. The concrete floor will be
inspected and repaired, if necessary. The asphalt parking lot
will be upgraded to minimize future maintenance costs by using
geotextile fabric and an additional six-inch layer of asphalt.
The third component of the cap is the backfilled soil cap to be
placed over the contaminated 50il not already covered by the
concrete floor or asphalt parking lot. Before the soil cap can
be placed the pit created by the remedial action for OU 4 and 5
will be backfilled with soil from off-site. The ground will then
be graded and contoured to provide appropriate drainage to
minimize erosion and compacted to form the foundation for. the
cap. Contaminated soils will not be moved or used during the
grading and contouring.
Of the 4.8 acres of soils with contamination above the
action levels, the soil cap will cover approximately 3.7 acres.
The soil cap will include a minimum of two feet of fill including
six inches of soil which is adequate to support shallow rooted
plants. The outliers to the north of the large area of
contamination will remain in place and be covered with at least
two feet of clean soil. The outliers to the south of the large
area of contamination are already covered by at least two feet of
clean soil and will remain in place without additional cover.
The cap will be designed and constructed so as to comply
with the specific requirements of RCRA and the State Solid waste
Act which were found to be relevant and ~ppropriate, as shown in
Table 10-1. In particular, the cap will be designed and
constructed to function with minimum maintenance, to promote
drainage, to accommodate .settling and subsidence so that the
cover's integrity is maintained, to minimize erosion or abrasion
of the cover, and to provide a two foot final cover over any
contaminated soils.
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80
In addition, appropriate measures will be implemented during
construction of the cap to control fugitive dusts to assure
compliance with the provisions of the Colorado Air Quality
Control Act identified as ARARs.
Following construction of the cap, long-term maintenance,
ground water monitoring and institutional controls will be
instituted. The long-term maintenance will consist of a plan for
periodic inspections to assure the integrity of the cap with
contingencies for repair if needed. These inspections will also
be used to assure that the institutional controls are effectively
controlling uses of the capped areas.
Monitoring of ground water down-gradient of the Site will be
conducted periodically to verify that contamination does not
reach the South Platte River in detrimental concentrations. The
monitoring program will be developed during remedial design.
Institutional controls will consist, at a minimum, of the
placement of deed restrictions on the Site to prevent use of the
Site for non-industrial/commercial purposes and to prevent uses
of the capped area that could compromise the integrity of the
cap. EPA will allow the capped area to be used as long as that
use does not threaten the integrity of the cap. EPA will also
allow the cap to be dug into, such as for a foundation, as long
as proper precautions were taken and the integrity of the cap was
restored. Any soils removed from the cap or from under the cap
will need to be sampled. If sampling shows that such soils are
RCRA characteristic, EPA will require that such soils be taken
off-site and disposed in a RCRA Subtitle C facility. The deed
restrictions will be established such that subsequent purchasers
of the Site are bound by the provisions of the restrictions. The
Site owners have indicated they will cooperate with the EPA on
placement of deed restrictions on the Site.
As extra precautionary measures, EPA will require the deed
restrictions to include a prohibition on placement of any wells
on the Site for the purpose of supplying drinking water and will
present to the City and County of Denver a proposal to zone the
Site to control uses of the capped portions of the Site. EPA is
presently working, and will continue to work with the City and
County of Denver and the Site owners on developing a proposal to
zone the Site under present City ordinances. The intent of such
a proposal will be to establish a formalized procedure whereby
proposed uses of the capped area which could threaten the
integrity of the cap will be reported to the City and/or EPA,
and/or the State for review. The exact details of this proposal
and the roles of the City, EPA, the owners of the Site, and the
State are yet to be determined. If a zoning proposal can be
agreed upon, presented to the City Council, and approved, such
zoning may be used in concert with the deed restrictions, or, if
EPA determines that the zoning is adequate and effective, EPA may
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allow the deed restrictions to be remOved.
Because this alternative will result in contaminants
remaining on Site, CERCLA requires that the Site be reviewed at
least every five years to assure the protectiveness of the
remedy. The estimated implementation time for construction of
the cap is three weeks. EPA's selection of this alternative
assumes that deed restrictions and/or zoning will effectively and
reliably control uses of the cap. EPA will closely monitor the
Site to verify that these assumptions are true. >.Should
experience show that the institutional controls are not effective
and reliable, EPA will reconsider the remedy.
Some modifications or refinements may be made to the
remedy during remedial design and construction. Such
modifications or refinements, in general, would reflect results
of the engineering design process. The estimated cost for the
selected remedy is $1,701,900. Table 9-1 shows the detailed cost
summary for the selected remedy.
Based on the findings in the Baseline Risk Assessment, the
remedial action objectives for this Site are the following:
1 )
Prevent inhalation or ,ingestion of, and direct contact
with soils having concentrations of arsenic, lead, and
zinc in excess of the action levels, i.e., 79 ppm,
1,000 ppm, and 17,000 ppm, respectively; and
2 )
Ground water down gradient from the Site will be
monitored to verify the modeling predictions that
contaminants from the Site will not degrade the South
Platte River.
Attainment of these remedial action goals will provide
protectiveness of human health and the environment.
x.
STATUTORY DETERMINATIONS
The selected remedy meets the statutory requirements of
Section 121 of CERCLA. The statute requires that remedial
actions undertaken at Superfund sites be protective of human
health and the environment. The statute also mandates that the
selected remedy ~omply with applicable or relevant and
appropriate environmental standards established under Federal and
State environmental laws unless a statutory waiver is }ustified.
In addition, the selected remedy must be cost-effective and
utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable. The statute also includes a preference for
remedies that employ treatment that permanently and significantly
reduces the volume, toxicity, or mobility of hazardous substances
as their principal element. The following sections describe how
24
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..
TABLE 9 - 1
Capping with Asphalt, Conaete and SoU
Coaatructicm Co8.. (1991 Start)
=':=B
Semi-annual Groundwater Monitoring
3.
Laboratory Analyses
Report
2 S35.00Ihr
.
1 $100.OOIday
4 S4OO.OOIea
1 S6S.00Ihr
5" $5,OOOIWell
1.
Inspection and Water Sampling
Health & Safety Monitoring
2.
4.
Well Maintenance
Cap and Site
1.
Inspection
1
S80.00Ihr
2.
airs
511t
5"
$1,036,800
Contingency
Total Annual O&M cost
Present Worth of O&M Cosr
Five-Year Reviews
Present Worth of Five-Year Reviews
5
$8,OOOIea
TOTAL CONSTRtJcrION COST
...
TOTAL ALTERNATIVE PRESENT VALVE
1 Rounded to the nearest $100
:I Present worth analysis for 30 years at present warth discount rate of 511t
"
-------
TABLE 9 . 1 (continued)
Cappins with Aapbalt, Coacnte and Soil
Ccmatnaction C.... (1991 Start)
-- ;;}:~*;;:::;'.:::i\;~:B..~~.tlftl.i:8\~:;}i:::::~:;::J ::!\~1;:~~1~!1~.:
::...:'~:1i::::::::::':::::~<;::::':;:;:::::: :j:::;::t1WeJUDiia:i:;;: ::::::,::~g?
Site Preparation
Parking Area 500 yds. :& 510.00Iyd.:& $5,000
Equipment Storage Area 500 yds.:& 510.00Iyd. :& $5,000
Air Monitoring Stations 3 510,000 eL S30,000
Support Facilities
Office Trailers 2 510,000 ea. 520,000
Decontamination trailer 1 $25,000 eL $25,000
Capping
Site Oearing 3.7 acres 51,3OO1acre $4,800
S~de Preparation 15,000 yds. :& 515.00Iyds. :&
Geotextile . Material & Install 5,000 yds. :& $25.00 S125,000
Asphalt 1,000 yds. :& 515.OOIyds. :& 515,000
Fill 30,000 yds. s S8.501yds. 1 5255,000
Top Soil Layer 2,000 yds. s S30.OOIyds~S 560,000
Layering, Grading, Compacting 40 Ms. S3OO.OOIhr. s 512,000
Revegetation 3.7 acres 511,OOOIacre $40,700
Total Direct Construction Costs (IDCe) 5597,500
TOTAL CONSTRUCI'ION COSTS II. ..
1 Rounded to the nearest 5100
-------
."
the selected remedy addresses these statutory provisions.
Protection of Human Health and the Environment
The remedy selected for metals-contaminated soils at the
Robco Site protects human health and the environment by capping
the contaminated soils, monitoring ground water down-gradient
from the Site, and using deed restrictions to limit access to and
uses of the capped area. Capping and deed restrictions will
control or eliminate the risks from direct contact with, or
inhalation or ingestion of the contaminated soils. Ground water
monitoring will, serve to verify the modeling predictions that no
contaminated groundwater from the Site will reach the South
Platte River in detrimental concentrations.
As extra precautionary measures, institutional controls to
limit future use of groundwater will be instituted and the use of
the City and County of Denver's zoning authority will be pursued
to prevent uses of the Site that would threaten the integrity of
the capped area.
Implementation of the selected remedy will not pose any
unacceptable short-term risks or cross-media impacts.
Compliance with ARARs
Under Section 121(d)(1) of CERCLA, remedial actions must
attain standards, requirements, limitations, or criteria that are
"applicable or relevant and appropriate" under the circumstances
of the release at the Site. All ARARs would be met upon
completion of the selected remedy at the Robco Site.
No chemical- or location-specific ARARs were identified for
the Site. Certain provisions of the State Solid Waste Act and
specific technical provisions of RCRA pertaining to closure of
landfills were identified as action-specific ARARs. These
action-specific ARARs will be met in the design and
implementation of the remedy. Table 10-1 iists Federal and State
ARARs for the selected remedy.
Cost-Effectiveness
The selected remedy is cost-effective in mitigating the
risks posed at the Site by metals-contaminated soils. Section
300.430(f)(ii)(D) of the NCP requires EPA to evaluate cost-
effectiveness by comparing all the alternatives which meet the
threshold criteria: protection of human health and the
environment and attainment of ARARs, against three additional
balancing criteria: long-term effectiveness and permanence;
reduction of toxicity, mobility, or volume through treatment; and
short-term effectiveness. Overall effectiveness is then compared
to cost to ensure that the remedy is cost effective.
25
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TABLE 10-1
Applicable or Relevant and Appropriate Requirements (ARARs)
Federal
Action Specific
Standard. Requirement. Criteria.
or Lim; tat I on
CLEAN AIR ACT.
42 use !~ 7401-7642
National Ambient Air Quality
Standards. 40 CrR 50.
Oescrlotlon
Establishes afr quality
standards for regulated air
po II utants.
State
Action Specific ARARs
Standard. Requirement. Criteria.
or limitation
Colorado Air Quality Control Act
Regulation 1
Stationary. 5 CCR. 1001-3
Reg. I. ~ 111-02 Subparts a.b.c.
e.f .S.h. and I.
Colorado Air Quality Control Act
Regulation 1
Stat i onal'Y. 5 CCR. 1001-10
Reg. 8. ~ VI.
Colorado Air Quality Control Act
Regulation 3
5 CCR 1001-5. Reg. 3. ! IV. 0
Colorado Air Quality Control Act
Regulation 12
5 CCR 1001-14. Reg. 12
Oescriotlon
Regulates stationary sources.
Sets forth e.lsslon control
standards for hazardous air
po II utents.
Stat I onary etn I ss I on source
cannot interfere with attainment
and maintenance of any National
or State AAQS.
Controls on emissions from
diesel vehicles.
Appl fceble?!
Re I event and
Aooroor I ate?
Appf Icable
Applicable?!
Re I event end
Aooroorlete?
Applicable
Appl fcable
Applicable
Appl icable
Comment
HAAQS would be eppllcebte to the extent that
the Imple.entatlon of the chosen alternative
would Impact the IIIIIbtent air quality.
.
COIIIIIent
Applicable to construction activities to
Implement the capping remedy.
Appl icBble to construction activities to
Implement the capping remedy,
Applicable to construction activities to
Implement the capping remedy.
Applicable to construction activities to
implement the capping remedy.
-------
Standard. Requirement. Criteria.
or Limi tat I on
Ha2ardous Waste Regulation.
Capping. 6 COR 1007-3
i 264.310(a)(2).(3).(4) and
(b)(I).(4). Landfill cl03ure
with waste in place.
H~2ardous Waste Regulations.
Capping. 6 CCR 1007-3
~ 264.117(c). Closure.
Ha2ardous Waste Disposal Siting
Requirements. 6 CCR 1007-2
Par"t 2. ~~ 2.4.1-2.4.5.
Ha2ardous Waste DI~posal Siting
Requir'ements. 6 ':CR 1007-2
Part 2. !! 2.4.9-2.4.10.
Ha2ardous Waste Disposal Siting
Requirement. 6 CCR 1007-2
Part 2. ~ 2.4.8.
Ha2ardous Waste Disposal Siting
Requirements. 6 CCR 1007-3
~ 264.IB(b).
Solid Waste Regulations
Standards for new facll itles.
6 CCR 1007-2 ~ 4. I. I.
Sol id Waste Regulations
Standards for new faci I ities.
6 CCR 1007-2 ~ 4.1.5.
Solid Wa$te R~gulations
St~ndards fnr new faci I ities.
b CCR 1007-2 ~ 4.2.2.
Table 10-1(Cont;)
ARARS
Description
Des I 9" and cOMtruct cap to
prOlllOte drainage. to .Inlmln
erosion or IIbreslon of the cap.
accOlllllOdate sett II ng and
subs I dence. and ma I nta I n cap
Integrity.
Restrict post-closure use of
property as necessary to prevent
damage to cap.
.
Design facility to prevent
adverse effects on ground water.
surface water. air qual ity.
public health. and the
environment.
"on I tor ground water. 5Urface
water. and prov I de qua II ty
control during construction.
Close facility to assure
prevention of long-term adverse
eHects.
Construct Run-on and Run-off
control systems capable of
handling peak discharge of a
100-year storm.
Site tOpography shall miniml2e
climatic Influence upon the
faci Iity.
Faci I Itles wi II make use of
favorable geologic conditions to
isolate waste. .
Permanent surface water
diversion structures.
Applicable?!
Re I evant and
Appropriate?
Relevant and
Appropriate
Re I evant and
Appropr I ate
Relevent and
Appropriate
Re I evant and
Appropr I ate
Relevant and
Appropr i ate
Re I evant and
Appropriate
Re I evant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
."
Comment
Contaminated soils to be capped are similar
to RCRA wastes and capping Is s!lnllar to
capping a RCRA landfill.
Contaminated soils to be capped are similar
to RORA wastes and capping is similar to
capping a RCRA landfill.
Conta.inated soils are si.llar to RCRA wastes
and the facility Is similar to a landfill
wnere wastes are to be left In-place.
Contaminated soils are similar to RCRA wa3te~
ana the facility Is similar to a landfill
where wastes are to be left in-place.
Contaminated soils are similar to RCRA wastes
and the facll ity Is simi lar to a landfi II
where wastes are to be left in-place.
Conta.lnated sol Is are similar to RCRA wastes
and the facll ity Is slmi lar to a landfi II
where wastes are to be left In-place.
Contaminated soils are solid wastes but this
Is not a new facility.
Contaminated soi Is are solid waste~ but this
is not a new faci I ity.
Contaminated soi Is are 501 Id wastes but this
is not a new facil ity.
-------
Standard, Requlretllel1t, Crlterill"
or LI.ltlltlon
SOlid Wastll Reguilltions
Standards for new fee III ties,
6 CCR 1007-2 I 4.2.3,
So II d IIIISte Regii lilt I ons
Standards for new fee III ties,
6 CCR 1007-2 I 4.2.4.
Solid Waste Reguilltions
Standards for new feel II ties.
6 CCR 1007-2 ! 4.2.6.
Solid WMte Regulatlons-
Standarlb for new feel II ties.
6 CCR 1007-2 ! 4.2.7. .
Solid Weste Regulations
"Inl- standards for new end
existing facilites,
Surfeee water control,
6 CCR 1007-2 ! 2.1.4.
Table 10-1(Cont.)
AltARS
Oeser lilt I on
Geo I og I c Hazards Shill I not
prevent cOlllp II ance.
Groundwater lIOII1 tor I ng wall s
des i gned to code.
Two foot final cover.
Water aVllllable .to 'prevent sol Is.
frOll blowing.
.
Provide surface drainage to
prevent pondlng. erosion. water
and al r po II ut Ion. COIIIpeeted
fill 88terllll will be provided
as we II as adequate cover to
minimize nuisance con~itlons.
Applicable?!
Re I event and
Allllrollr I ate?
Re I event and
Approprillte
Relevant and
Appropriate
Relevant and
Appropriate
Ae I eV8I1t8l1d .
Appr opr i lite
Appl icBble
COIIIIII!I1t
Cont.lnlltect soils ar8 solid wastes but this
Is not II new 'feeility. .
Contll8lnllted soils ere solid wastes but this
Is not II new feeility.
..
Cont.ineted soils are solid wastes but this
is not II new'feeillty.
. ,
.'
".
Cont. i nllted 50 i Is are 50.11 d wastes but th i s
is not a new feeillty.
Contmlineted soils are solid wastes.
-------
.
The selected remedy provides the best overall effectiveness
of all alternatives considered proportional to its cost. All
the alternatives meet the threshold criteria of protecting human
health and the environment and attaining ARARs. The preferred
alternative will be the most effective alternative in the short-
term. Each of the alternatives are similar in terms of long-term
effectiveness. Only Alternative 5, solidification, involves any
. treatment. Solidification is expected to reduce the mobility of
the contaminants in the soil. However, in terms of cost-
effectiveness, solidification would cost $9.9 million, when the
selected alternative, soil capping, would' provide similar
protectiveness for $1.7 million, the lowest cost of all th~
alternatives except no-action, and one-fifth of the cost of
solidification. Therefore, while treatment is not a component of
the preferred alternative, the selected remedy provides the best
overall effectiveness of all alternatives considered proportional
to its cost.
utilization of Permanent Solutions and Alternative Treatment
Technologies (or Resource Recovery Techniques) to the Maximum
Extent Practicable
EPA has determined that'the selected remedy
represents the maximum extent to which permanent
technologies can be utilized in a cost-effective
remediate metals-contaminated soils at the Site.
for OU 9
solutions and
manner to
Of those alternatives that are protective of human health
and the environment and comply with ARARs, the selected remedy
will provide the best balance in terms of the five primary
balancing criteria and the two modifying criteria. The selected
remedy is the lowest in cost, provides the best short-term
effectiveness, and is the remedy preferred by the State and the
owners of the Site. Each of the alternatives provides a similar
degree of long-term effectiveness and implementability.
Alternative 4, excavation with off-site disposal, is preferred by
the City and County of Denver and a vicinity land owner.
However, off-site disposal without treatment is the least
preferred option under CERCLA. Alternative 5, solidification, is
the only alternative that uses treatment to reduce toxicity,
mobility, or volume of the contaminants. However, this treatment
will only reduce mobility, will not change toxicity, will
increase the volume of contaminated soil and will cost 5 times
more than the preferred option. Alternative 2, clay cap, is
similar to the preferred option. However, the clay cap will cost
approximately $1.0 million more to install and provide no more
protectiveness considering the risks at the Site.
The State of Colorado concurs with the selected remedy. The
Proposed Plan for the Robco Site was released for public comment
in August 1991. The Proposed Plan identified Alternative 3, soil
26
,
-------
cap, as the preferred-remedy. EPA reviewed all written and
verbal comments submitted during the public comment period. Upon
review of these comments, EPA determined that no significant
change to the remedy originally identified in the Proposed Plan
was necessary.
Preference for Treatment as a Principal Element
Treatment of the principal threats at the Site is not a
component of the selected remedy. Therefore, this remedy does
not satisfy the statutory preference for treatment. While
treatment may reduce the mobility of the contaminants, there
would be no significant increase in protectiveness to human
health and the environment over the selected capping remedy.
- -
27
-------
.
Denver Radium Site, Operable Unit 9
Denver, Colorado
Responsiveness Summary
A.
OVERVIEW
When the Proposed Plan was issued, Alternative 3, a soil cap
with institutional controls was presented as the preferred
alternative for Operable Unit 9 (OU 9) of the Denver Radium
Superfund site. The Proposed Plan also solicited comments on
four other alternatives. The Record of Decision selects
Alternative 3, a soil cap with institutional controls, as the
remedy for contaminated soils at the site.
Judging by comments received during the public comment
period, the City and County of Denver and an adjacent property
owner, the Regional Transportation District (RTD), favor an
excavation with off-site disposal remedy. The property owner,
Robinson Brick Company ~Robco), generally supports EPA's Proposed
Plan for remediation of metals contamination with the
implementation of appropriate institutional controls. The
Colorado Department of Bealth (CDB) worked closely with EPA in
developing the Focused Feasibility Study (FFS) and Proposed Plan.
As a result, CDB did not submit formal comments during the public
comment period.
These sections follow:
* Background of Community Involvement
* Summary of Comments Received during Public Comment
Period and Agency Responses
B.
BACKGROUND ON COMMUNITY INVOLVEMENT
Sections 113(k)(2)(B)(i-v) and 117 of the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA)
require that the U.S. Environmental Protection Agency (EPA) keep
the community informed and encourage them to participate in the
decision-making process in selecting a remedy for a Superfund
site. At a minimum, CERCLA requires (1) notice to potentially
affected persons and the public, (2) a reasonable opportunity to
comment, (3) an opportunity for a public hearing, (4) a response
to each significant category of comment submitted, and (5) a
statement of the basis and purpose of the selected action.
This section describes the specific community participation
activities that occurred in the process of selecting a remedy for
OU 9. This responsiveness summary fulfills one of the key public
participation requirements of CERCLA by incorporating a response
to each comment submitted by the public.
-------
In September of 1988, during the course of the radium
cleanup at the .site, metals contamination was discovered. The
community was informed of this development in a March 1989 Denver
Radium Information Update. An investigation to characterize the
nature and extent of the metals contamination was conducted in
1989 and 1990. That investigation resulted in the FFS which
outlines a number of alternatives for the cleanup of the metals-
contaminated soils at the site.
The FFS and the Proposed Plan for OU 9 were released to the
public .for comment on August 2, 1991. These.two documents were
made available to the public in the Administrative Record
maintained at the Central Branch of the Denver Public Library and
at the EPA Region VIII Superfund Records Center in Denver,
Colorado. The notice of availability for the FFS, the Proposed
Plan, and other documents in the Administrative Record was
published in the Denver Post on August 2, 1991. A public meeting
was held in Denver on August 14, 199". At this meeting, the
public was invited to ask questions of EPA and CDH
representatives concerning the site and the remedial actions
under consideration. A transcript of the meeting was prepared
and placed in the Administrative Record.
C.
SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD
Comments raised during the OU 9 public comment period, on
the draft FFS and Proposed Plan, are summarized briefly below.
The comment period was held from August 2, 1991 to October 3,
1991.' The comments are categorized by relevant topics.
Focused Feasibility Study
Robco had several comments on the Focused Feasibility Study.
Those comments and EPA's responses are summarized below:
1 )
It was recommended that some of the information in the
Site History section of the FFS, especially regarding
the procedures of past operations and the activities of
the National Radium Institute (NRI), be deleted as
unnecessary.
EPA Response: The metals contamination found at the
Site may have resulted from any of the mineral
processing operations known to have occurred on the
Site. Therefore, EPA chose to include as much
information about past operations and activities at the.
site as possible to give a complete picture of the site
history.
2
-------
'.
2 )
Several concerns were raised about the section of the
FFS regarding the Nature and Extent of Contamination.
Generally it was recommended that the information be
reorganized and more clearly integrated with
information in other sections of the FFS.
EPA Response: Extensive revisions were made to
section prior to finalization of the FFS. The
revisions addressed the concerns raised by the
commentor. .
this
3 )
Containment was identified as a general response action
and capping was identified as a remedial technology
type that should have been included in Table 2-2.
EPA Response: Containment and capping were both
included in Table 2-2 in the final version of the FFS.
4 )
It was recommended that the discussion on institutional
controls be reorganized within the text. Also, the
details of specific institutional con~rols and how they
would meet the goals and objectives of the remedial
action should be discussed.
EPA Response: The discussion on institutional controls
was reorganized within the text of the report. The FFS
was not modified to include details on institutional
controls. However, the'Record of Decision for OU 9
(ROD) identifies deed restrictions as the primary
institutional control to be used at the Site. EPA will
also continue to work with the City and County of
Denver, the State, and Robco to identify and implement
other institutional controls at the Site, such as
zoning under City ordinance. The specific details of
the deed restrictions and any other potential
institutional control will be determined during
remedial design in cooperation with the State, City and
County of Denver, and Robco, as appropriate.
5 )
Since ground water was not established as a pathway of
concern, it was recommended that the FFS be modified to
indicate that the potential migration of contaminants
in ground water is not an issue which should affect the
Record of Decision.
EPA Response: EPA determined that ground water was not
a pathway of concern, in part, based on the modeling
predictions that contaminated ground water from the
Site would not reach the South Platte River in
detrimental concentrations. In order for the remedy to
be protective, EPA determined that monitoring of the
ground water downgradient of the Site should be done to
3
-------
verify the modeling predictions. If monitoring shows
that contamination is migrating to the River in
detrimental concentrations, EPA will reconsider its
determination that the ground water is not a pathway of
concern and may reconsider the remedy.
Applicable or Relevant and Appropriate Requirements
Robco also had several comments on the Applicable or Relevant and
Appropriate Requirements (ARARs) for the site. The comments and
EPA's responses are summarized below.
1 )
The assertion that 6 CCR 1007-2 SS 2.4.1 - 2.4.5 are
relevant and appropriate is incorrect since ground
water has not been identified as a pathway of concern;
the only water quality issue is degradation of the
Platte River; and, the impact on the highway property
is irrelevant.
2 )
EPA Response: The standards in 6 CCR 1007-2 88 2.4.1-
2.4.5 are general standards for the closure of solid
waste sites and facilities. EPA determined that these
standards would be ARARs for any alternative which
involved the disposal of solid wastes. In particular,
EPA felt that the proposal to dispose the treated waste
under the solidification alternative would involve the
disposal of solid waste and therefore these standards
would be ARARs for that proposal. These standards were
not identified as ARARs for the. selected remedy.
6 CCR 1007-2 Part 2 88 2.4.9 - 2.4.10 and Part 2 8
2.4.8 were each identified as relevant and appropriate.
The property owner was unable to find these citations
and therefore can't comment on their designation as
relevant and appropriate.
EPA Response: These regulations provide general
narrative standards for the design, construction, and
closure of a hazardous waste disposal site and
facility. These standards are similar to the RCRA
requirements which were found to be relevant and
appropriate to activities at the Site.
3 )
The owner of the property found troubling the
determination that 6 CCR 1007-3 8s264.117 (c) is
relevant and appropriate. The property owner will not
accept a regulation requiring permission from EPA or
any other agency to develop the property for an
appropriate use and a regulatory determination that any
incursion into a cap is 'necessary'.
4
-------
.
4 )
EPA Response: This regulation requires post-closure
use of the property to be restricted as necessary to
prevent damage to the cap. In order for the selected
remedy to be operational, functional, and protective,
non-industrial/commercial uses of the Site must be
prevented and the integrity of the cap must be
maintained. EPA will work with Robco to design
restrictions for the Site which are protective of the
remedy and meet Robco's needs. If such restrictions
cannot be agreed upon, EPA may have to ,reconsider the
selected remedy.
The property owner understands that any capping
alternative 'will impact the -manner in which future
constructiQn activities occur on the property in two
respects: (1) compliance with 29 CFR Part 1910 will be
necessary, and (2) at the completion of any
construction, the cap will have to be repaired or
replaced to the extent it was disturbed by the
construction activities. No additional constraints
beyond those that would apply in any case are necessary
to protect public health or the environment. Any'
additional constraint would be deemed an impermissible
and compensable taking.
EPA Response: EPA, determines which remedial activities
to conduct at a Site based on whether such activity is
necessary to protect human health and the environment.
Any such determination would not rise to the level of a
taking. However, EPA will work with Robco to reduce
the impact of any restrictions to the extent possible.
In addition to the comments of Robco, RTD, a vicinity
property owner, had several comments on ARARs. Those comments
and EPA's responses are summarized below.
1 )
It was suggested that the preferred alternative,
capping of contaminated soils, is inconsistent with
ARARs chosen for Operable Units (OUs) IV/V since a cap
would prevent the excavation and off-site disposal of
identified radiological contaminants. The vicinity
property owner states, "There is still Radium-226
contaminated soil that exceeds the UMTRAP standard
along with Thorium-230 contaminated soil that exceeds
the established UNC removal criteria at the site. The
proposed remedial action of leaving the metals
contamination on site and capping the area will not
fulfill the ROD for au's IV/V."
EPA ResDonse: Radium and thorium deposits which occur
below the water table were left in place. The decision
to leave this material in place is consistent with the
5
'\
-------
Department of Energy's (DOE) Protocol for Excavation of
Thorium-230. (See the Generic Protocol for Excavation
of Thorium-230, DOE, January 25, 1989.) The decision
is also consistent with the criteria for applying
supplemental standards, set forth in 40 CFR 192.21(c).
The regulation states that remedial action will
generally not be necessary where residual radioactive
materials have been placed semi-permanently in a
location where site-specific factors limit their hazard
and from which they are costly to remove, or where only
minor quantities of residual radioactive materials are
involved. To the degree that leaving these radium
deposits in place constitutes a significant change in
the remedy for OU 4 and 5, EPA will publish an
explanation of significant differences.
2 )
The Record of Decision for the remediation of
radiologic contamination at this site identified 40 CFR
192 as an ARAR. It was suggested that 40 CFR 192.32,
Subpart D, and the ground water protection standards
contained therein, be identified as an ARAR for OU 9.
EPA Response: The standards for uranium and thorium
mill tailings, 40 CFR 192, were identified as relevant
and appropriate for operable units 4 and 5 of the
Denver Radium Site. The basis for this determination
was that radium is similar to uranium and thorium and
that radium processing sites were similar to the
uranium and thorium processing sites covered by 40 CFR
192. The contaminants at OU 9 are not similar to
uranium and thorium and the source of the OU 9
contaminants mayor may not be the radium processing
which occurred at the Site. As a result, the
requirements in 40 CFR 192 are not relevant and
appropriate to activities conducted under OU 9.
3 )
RTD disagrees with EPA's determination that the metals-
contaminated soils at the site are exempt from RCRA
regulations under the mining waste exclusion. Research
revealed that some of the waste at the site resulted
from gold and silver extraction by use of the McArthur
Forrest cyanide process. RTD asserts that the use of
this process renders the mining waste exclusion
inapplicable.
EPA Response: EPA has specifically determined that
wastes from cyanide leaching processes fall within the
definition of beneficiation wastes and are exempt from
RCRA under the mining waste exemption, see 51 FR 24496
(July 3, 1986) and 54 FR 36592, 36616, note 1
(September 1, 1989). Therefore, the fact that wastes
found on-site may have come from a cyanide leaching
6
-------
.
process does not change EPA's determination that all
mining wastes found at the Site are RCRA exempt under
the mining waste exclusion.
4 )
It is suggested that the State Groundwater Human
Health, Secondary Drinking Water, and Agricultural
Standards are relevant and appropriate since the
standards will be applicable when the aquifer is
classified.
EPA Response: Until a regulation is promulgated, -it is
not considered to be either applicable or relevant and
appropriate. At most, the State Groundwater Human
Health, Secondary Drinking Water, and Agricultural
Standards are regulations to be considered (TBCs).
Given that the ground water at the Site has not been
identified as a pathway of concern, EPA did not
consider these regulations.
5 )
The Record of Decision for OU IV/V stated that ground
water remedial actions would be conducted to be
consistent with the proposed requirements of the ground
water protection provisions of 40 CFR 192, Part B. The
comment or identified two on-site wells and two off-site
wells where these standards are not met. Further, the
comment or states that the standards will not be met
since radionuclides remaining in the soils on site will
continue to degrade ground water quality.
EPA Response: 105,555 tons of radiologically-
contaminated materials were excavated from OU IV/V for
off-site disposal. The radionuclides remaining in the
soils on site are below the ground water table
consistent with the DOE protocol. It is anticipated
that with the source of the radiological contamination
removed, contamination in the ground water will
naturally attenuate. The wells where contamination has
been identified will continue to be monitored to verify
attenuation of the contaminants. Ground water at and
down-gradient from the site will also continue to be
monitored to verify that any migration of contaminated
ground water will not degrade water quality in the
South Platte River.
6 )
It is suggested that MCLs be identified as ARARs on the
site.
EPA Response: Because the aquifer was determined not
to be a potential drinking water source and it is
unlikely that contaminants from the Site would affect
the South Platte River, EPA determined that the Safe
Drinking Water Act (SDWA) Maximum Contaminant Levels
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(HCLs) and the Clean Water Act (CWA) water quality
criteria were neither applicable nor relevant and
appropriate to activities at the Site. Nonetheless,
EPA will require, as an additional protective measure,
and to verify modeling predictions, that the selected
remedy include ground water monitoring.
Ground Water
EPA received several comments concerning ground water from
both RTD and the City and County of Denver. The comments of RTD
and EPA's responses are summarized below.
1 )
The commentor states that, "The results of the vas
instantaneous mixing predictions for cadmium; the
groundwater analysis obtained off-site; the fact that
the contaminants are leachable; the fact that cadmium
can accumulate in sediments; and that the un-
characterized paleochannel provides a preferred pathway
for migration, all mandate that the groundwater and
source soils must be addressed in the remedy
selection."
EPA Response: Ground water modeling indicates that it
is unlikely that any migration of ground water will
degrade the water quality of the South Platte River.
Modeling data shows that the site is presently
contributing little to the metals load carried by the
South Platte River. None of the mixing zone
predictions are above the ambient criteria and most are
significantly lower. Cadmium migrating from the site
has the potential to contribute to highly localized
exceedances of the chronic criterion for protection of
aquatic biota in the instantaneous mixing zone. Ground
water monitoring will be used to verify the modeling
predictions that contamination is not reaching the
River in detrimental concentrations. If monitoring
shows that contamination is migrating to the River in
detrimental concentrations, EPA will reconsider the
remedy.
2 )
The commentor has also suggested that off-site ground
water contamination has not been completely
investigated.
EPA Response: During the remedial design process,
following the Record of Decision, EPA will develop a
sampling and analysis plan for ground water monitoring.
At that time, additional ground water monitoring wells
will be developed, as needed, to better characterize
ground water down-gradient from the Site.
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The comments of the City and County of Denver concerning
groundwater and EPAis responses are summarized below.
3 )
1 )
The City and County of Denver suggests that sampling
the Platte River would be useful to validate EPA's
modeling which shows that metals contaminated ground
water from the site will not have an adverse impact on
the water quality in the river.
EPA Response: EPA will consider including sampling of
the South Platte River in developing the ground water
sampling and analysis plan.
2 )
It is suggested that if there is no identifiable trend
of decrease in metals contamination in the ground water
after five years, remediation of the property should be
readdressed.
EPA Response: The metals contaminated ground water
only becomes a risk concern if this ground water moves
to the South Platte River in concentrations which would
degrade the Platte. EPA will reconsider the selected
remedy if it is shown that ground water contamination
is degrading the water quality of the South Platte
River.
Since the preferred alternative does not reduce the
toxicity, mobility, or volume of the metals
contaminated soils, it is suggested that monitoring of
the ground water will be required in perpetuity or
until contamination levels decline.
EPA Response: EPA will require ground water monitoring
as long as is necessary to assure that the remedy is
protective.
Institutional Controls
Issues regarding the implementation of institutional
controls were raised by the property owner, the City and County
of Denver, and at the public meeting. Comments made by the City
and County of Denver and EPA's responses are summarized below.
1 )
The City and County of Denver commented that there is
no permanent and effective management control mechanism
which would assure no public contact with metals
contaminated material in the future.
EPA Response: Institutional Controls are an integral
part of the selected remedy. EPA is working with Robco
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()
to establish deed restrictions on the Site to prevent
use of the Site for non-industrial/commercial purposes,
to prevent uses of the capped portions of the Site that
could compromise the integrity of the cap, and to
prohibit the placement of any wells on the Site for the
purpose of supplying drinking water. As an extra
precautionary measure, EPA is working with the State,
City and County of Denver, and .Robco to develop and
present to the City and County of Denver a proposal to
zone the Site to control uses of the capped portions of
the Site.
In addition, EPA will be critically reviewing the
. reliability and effectiveness of any controls used at
the Site as part of its duty to assure that the remedy
remains protective. If this review shows that controls
are not reliable and effective, EPA will reconsider the
remedy.
2)
The City and County also questioned who would have
long-term management responsibility for the site if the
property is abandoned or property taxes are not paid.
EPA Response: When wastes are left on-site, EPA is
required to review conditions at the Site at least
every five years to assure that the remedy remains
protective. In. addition, the State and EPA will be
responsible for assuring that the remedy is operated
and maintained.
3 )
The comment was made that Special Construction Zone
criteria and how such criteria would be administered
were not established in the Proposed Plan. Rezoning of
the site as a Special Construction Zone would require
public notice and City Council approval. Since it is
not known that such approval would be forthcoming, the
Special Construction Zone should not be relied upon in
the Record of Decision. The City also raised the
concern that there would be ongoing costs associated
with administering a Special Construction Zone and that
these costs should not be passed on to local
governments.
EPA Response: EPA acknowledged in the proposed plan
and in the ROD that there are uncertainties in the
implementation of any zoning or rezoning on the Site.
The ROD makes it clear that EPA is not relying on
zoning of the Site as part of the remedy. Instead, EPA
is proposing zoning as an extra precautionary measure
for the remedy. EPA recognizes that additional costs
may be associated with administering a Special
Construction Zone. EPA will assist the City and County
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.
of Denver with any such additional costs to the exterit
allowed by law.
Comments concerning institutional controls made by Robco and
EPA's responses are summarized below.
1 )
Robco commented that they are amenable to deed
restrictions to memorialize requisite constraints on
development of the property. Robco further commented
, that implementation of a Special Construction Zone may
ha ve mer i.t .
EPA Response: If a zoning proposal can be agreed upon,
presented to the 'City Council, and approved, such
zoning may be used in concert with deed restrictions.
If EPA determines that the zoning is adequate and
effective, EPA may allow the deed restrictions to be
removed.
Two questions, raised by a representative of Robco, were
addressed to EPA during the public meeting. EPA's responses to
those questions are summarized below.
1 )
The comment or questioned exactly how ground water use
at the site would be limited.
EPA Response: EPA replied that limiting the use of
ground water would require the cooperation of the
property owner to put a deed restricti.on on the
property to ensure t~at no drinking-water supply wells
would be established on the Site.
2 )
The commentor also questioned if the Special
Construction Zone was being considered as part of the
remedy.
EPA Response: At the time of the public meeting, EPA
responded that it would be working with the City and
County of Denver to determine if establishment of a
Special Construction Zone would be an implementable
institutional control. Since that meeting, EPA has met
several times with representatives of the City and
County of Denver on this issue. EPA will continue to
work with Denver and the other parties at the Site to
try to establish the most effective combination of
institutional controls to assure that the remedy
remains protective.
Remedy Selection
Each of the interested parties - Robco, RTD, and the City
and County of Denver had comments on the selection of the remedy
1 1
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at the site. The comments of Robco and EPA's responses are
summarized below.
1 }
Robco commented that the proposed plan does not take
into account the additional costs which may be
associated with the removal of underground petroleum
storage tanks at the site. Additional costs could be
incurred if removal of the tanks also required the
excavation and subsequent disposal of any metals-
contaminated soils.
EPA Response: The removal of any underground storage
tanks at the site and the costs associated with such
removal is the responsibility of the property owner.
2 }
Robco also suggested that future incremental costs
associated with construction activities in the metals
contaminated soil or with repair of the cap when'
incursions occur should be included as part of the
remedial action response cost.
EPA Response: Any incremental costs associated with
construction activities in the metals-contaminated soi1
is the responsibility of the property owner and/or the
developer of 'the property.
RTD also commented on remedy selection at the site.
comments and EPA's responses are summarized below.
Their
1 }
The commentor states that the EPA-preferred remedy does
not meet the threshold criteria of complying with ARARs
or protecting the environment. Nor does the preferred
alternative reduce toxicity, mobility, or volume.
EPA Response: The selected remedy is protective of the
environment and complies with all applicable or
relevant and appropriate regulations. The
environmental threat at the site comes from the
potential for contaminants to migrate via ground water
to the South Platte river. EPA's modeling shows that
contaminants will not migrate from the Site to the
South Platte in detrimental concentrations. EPA has
included ground water monitoring as part of the
selected remedy specifically to verify that the
modeling predictions are correct. If the monitoring
shows that the modeling predictions were incorrect, EPA
will reconsider the remedy.
CERCLA and the National Contingency Plan contain a
preference for remedies that use treatment to reduce
the toxicity, mobility, or volume of the contaminants
where practicable. In this case, treatment, i.e.,
1 2
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a
2)
solidification, was determined to be no more effective,
yet five times more costly than the selected remedy.
For that reason, the treatment alternative was
determined not to be practicable for this Site.
RTD supports the excavation with off-site disposal
alternative stating that the mobility of the
contaminants would be reduced, there would be greater
long-term effectiveness and permanence, and the ARARs
relating to ground water would most likely be met since
the source material would be removed.
EPA Response: Excavation with off-site disposal
remove all contaminated soils to a RCRA Subtitle
permitted landfill. The inherent risks presented
these contaminants would not change. Therefore,
alternative would not reduce mobility of the
contaminants. The risk would just be transferred to
'the off-site facility and the long-term effectiveness
of this alternative would be dependent on the
reliability and operation of the off-site facility.
While excavation with off-site disposal would eliminate
on-site risks, off-site disposal without, treatment is
the least,preferred option under CERCLA.
The City and County of Denver's comments regarding remedy
selection and EPA's responses are summarized below.
would
C
by
this
1 )
The City and County expressed concern about the
inclusion of an ex~sting structure ,as part of the cap
for the contaminated soils. They commented that, "It
is essential that existing, abandoned structures be
removed because they represent an attraction to
children, transients and homeless people."
EPA Response: EPA's response authority is limited by
CERCLA. EPA has no authority to spend trust money
demolishing the structures unless necessary to
remediate a risk posed by the hazardous substances, or
by pollutants or contaminants which may present an
imminent and substantial danger to the public health or
welfare.
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