PB94-964402
EPA/ROD/R08-94/081
July 1994
EPA Superfund
Record of Decision:
Sand Creek Industrial Site,
Commerce City, CO
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RECORD OF DECISION
DECLARATION STATEMENT
SITE NAME AND LOCATION
Site-wide groundwater, Operable Unit 4 (OU4), Sand Creek Industrial Superfund Site,
Commerce City, Colorado.
OF BASIS AND PURPOSE
This decision document presents the selected remedy for Operable Unit 4 (OU4), Site-wide
groundwater at the Sand Creek Industrial Superfund Site in Commerce City, Colorado. This
remedy has been developed in accordance with the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 (CERQLA) as amended by the Superfund Amendments
and Reauthorization Act of 1986 (SARA), applicable state laws, and the National Oil and
Hazardous Substances Pollution'Contingency-Plan (the National Contingency Plan (NCP), Title
40 Code of Federal Regulations Part 300). This decision is based on the administrative record
for OU4.
The State of Colorado is expected to concur with the selected remedy.
ASSESSMENT OF THE SITE
The Sand Creek Industrial Superfund Site has an extensive history of industrial use, including.
pesticide manufacturing, petroleum refining, acidic waste disposal, municipal landfilling, and
chemical storage and distribution. OU4 addresses groundwater underlying the Site and is
contaminated with volatile organic compounds (VOCs), semi-volatile organic compounds
(SVOCs), pesticides, and metals. OU4 also includes a plume of light non-aqueous phase liquid
(LNAPL) floating on the water table beneath the northwest portion of the Site. The migration
of groundwater contaminants tends to be impeded by the presence of impermeable clayey
materials.
Although groundwater in the area is classified as a potential drinking-water supply by the State
of Colorado, there is no unacceptable current health-risk due to ingestion, inhalation, or skin
contact with contaminated groundwater since water for residential use is provided through
treated water from either the Denver Water Department or the South Adams County Water and
Sanitation District However, risks associated with potential future use of groundwater for
domestic purposes are unacceptable. Actual or threatened releases of hazardous substances
from OU4, if not addressed by implementing the response action selected in this Record of
Decision (ROD), may present an imminent and substantial endangerment to public health,
welfare, or the environment.
DESCRIPTION OF THE REMEDY
The remedy selected for OU4 will minimize direct contact with and ingestion of groundwater
underlying the Site and prevents further offsite migration of contaminants in excess of federal
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.
Implementation of institutional controls that will minimize exposure to
contaminated groundwater at OU4 by limiting groundwater usage to non-
domestic purposes and preventing any usage of highly contaminated
groundwater.'
.
Quarterly groundwater and surface water monitoring to evaluate contaminant
, migration and changes in site conditions.,
.
Removal of the recoverable portion of the LNAPL plume located in the
northwest portion of the Site with a dual vapor extraction (DYE) system.
Recovered LNAPLwill be transported off site to a recycling facility.
.
Onsite infiltration of treated groundwater removed incidentally by operation of
the DYE system. '
.,
, Five-year site reviews will be conducted at OU4 and additional remedial action
will be taken if warranted by a change in site conditions.
STATUTORY DETERMINA nONS
. The selected remedy provides protection to human health by limiting exposure to and
preventing ingestion of contaminated groundwater through institutional corttrols. This
alternative protects the environment by requiring groundwater and surface water monitoring
to ensure that OU4 contamination does not impact Sand Creek or downgradient aquifers at
some futUre date. Removal'of the recoverable portion of the LNAPL plume will effectively
eliminate a source of groundwater contariuriationat OU4.' , ,,'
, ,
The selected remedy is protective of human health and the environment, complies with federal
and state requirements that are legally applicab~e or relevant and appropriate to the remedial
action, and is cost-effective. This remedy utilizes permanent solutions and alternative
treatment technologies to the maximum extent practicable for this site, but because treatment
of the principal threats of OU4was not found to be feasible, this remedy does not satisfy the
statutory preference for treatment as a principal element. However, many of the principal
threats at the Site are being 'addressed under other
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Section
TABLE OF CONTENTS
Page
DECLARATION STATEMENT. . . . . . . . . . . . . ~ . : . . . . . . . . . . . . . ~ . . . . . . . . . ~ .. i
SITE NAME, LOCATION, AND DESCRIPTION. . . . . . . . . . . . ... . . . . . . . . . . 1
SITE HISTORY AND ENFORCEMENT ACI1VITIES . . . . .'. . . . . . . . . . . . . . . . . 3
I.
n.
ID.
ffiGI-lllGHTS OF COMMUNITY PARTIaPATION ...................... 5
IV.
SCOPE AND ROLE OF RESPONSE ACTION. . . . . . . . . . . . . . . . . . . . . . . . . ~ 6
v.
. .
SUMMARY OF SITE CHARAcrERISTICS . . .. . . . . . . . . . . . .'. . . . . . . . . . . . . 8
A.
B.
C.
D.
E.
. VI.
Topography. . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Geology. . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Hydrogeology. . . . . . . . . . . . . . . . . . . . . . . .. ~ . . . . . . . . . . . . . . . . . . 9
Water Diversions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
Nature and Extent of Contamination. . . . . . . . . . . . . .'. . . . . . . ... . .. 12
SUMMARY OF SITE RISKS. . . . . . . . . . . . .. . . . . .. . . . . .'. .. . . ~ . . . . . . . ... . 16 .
A.
B.
C.
ContaDrinants of Concern. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . .. 17
Exposure Assessment. . . . . . . . . . . . . . ... . . . . . . . . .. . . . . . . . . . . .. 20
Risk Otaracterization ................................. ~ . .. 21
1. Cmrent Human Health Risks. . . . . . . . . . . . . . . . . . . .. 21
2. Future Hum~ Health Risks. . ; . . . . . . . . . . . . . . . . . .. 22
3. Environmental Risks. . . . . . . . . . . . . . . . . . . . ... . . . . . . 24
. VIT.. DESCRIPTION OF ALTERNATIVES .. . . . . . . . . . . . . . . . . . . . . . . . : .. . . ~ .. 24 .
. ,
Alternative 1: No Action. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ .. 25
Alternative 2: Monitoring and Institutional Controls. . . . . . . . . . . . . .. 25
Alternative 3: Monitoring and Institutional Controls
with LNAPL Removal. . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. 26
Alternative 4: Limited Con~ent of LNAPL using a Cutoff Wall .... 26
Alternative 5: Localized Pump and Treat with LNAPL
Containment and Groundwater Treatment by GAC and Air Stripping. .. 29
Alternative 6: Localized Pump and Treat with LNAPL
Removal and Groundwater Treatment by GAC and Air Stripping. . . . .. 29
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VIn.
, F.
DC
x.
Alternative 7: Localized Pump and Treat with LNAPL
Containment and Groundwater Treatment by UV Oxidation. . . . . . . . .. 30
Alternative 8: Localized Pump' and Treat with LNAPL
Removal and Groundwater Treatment by UV Oxidation.... . . . . . '. . . . . 31
Alternative 9: Site-Wide Pump and Treat for Total Groundwater
Restoration with LNAPL Containment. . . . . . . . . . . . . . . . . . . . . . . .. 31
Alternative 10: Site-Wide Pump and Treat for Total Groundwater
Restoration with LNAPL Removal. . . . . . . . . . . . . '. . . . . . . . . ... . . .. 32
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES. . . . . . . . . .. 32'
A.
Overall Protection of Human Health and the Environment. . . . . . . . . ... 33 ,
B.
Compliance with ARARs .................................. 33
C.
Long-Term Effectiveness and Permanence. . . . . . . . . . . . . . . . . . . . . .. 37
D.
Reduction of Toxicity, Mobility, or Volume Through Treatment. . . . . . .. 37,
Short-Term Effectiveness. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. 38
E.
Implementibility .....'..'....,...... ~ . . .. . . . . .' . . . . . . . :'. . . . '. 38
G.
Cost. . . . . . . . . . . . . .'. . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . .. 39
H.
State Acceptance' . . . . . . . . . . . . . . . . . . . . . ~ . . . ',' . . . . . . . . . . . .. 41
I.
Community Acceptance. . . . . . . . . . . . . .'. . . . . . . . . . . . . . . . . . . .. 41
SELECTED RElVfEDY ............................ ~ . . . . . . . . . ',' .. 41
STA11JTORY DETERMINATIONS. . . . . . ~ . . . '. . . . . . . . . . . . . . . . . . . . . .. 47
A.
Protection of Human Health and the Enwonment . . . . . . . . . . . . . . . .. 47
B.
Compliance with ARARs """"".......,...............:. 48
c.
Cost Effectiveness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
D.
Utilization of Permanent'Solutions and Alternative Treatment
"Technologies (or Resource Recovery Technologies) to the
Maximum Extent Practicable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50
E.
Preference for Treatment as a Principal Element. . . . . . . . . . . . . . . . .. 51
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Appendix A. RESPONSIVENESS SUMMARY. . . . . . . . .. . . . . . . . . . . . . . . . . . .. A-I
LIST OF FIGURES
1.
2.
3.
4.
5.
6.
7.
Location of Sand Creek Superfund Site and Study Area. . . . . . . . . . . . . . . . . . . '2
Conceptual Cross-Section of Alluvial Aquifers. . . . . . . . . . . . . . . . . . . . . . . .. 10
Extent of Aquifers 0, 1, and 2 .................................... 11
. Occurrence of Trichloroethene in Groundwater. . . . . . . . . . . . . . . . . . . . .. .. 13
Occurrence of Tetrachloroethenein Groundwater. . . . . . . . . . . . . . . . . . . . .. 14
Occurrence of Benzene in Groundwater. . . . . '.' . . . . . . . . . . . '.' . . . . . . . .. 15
Localized and Site-Wide Extent of Remediation and Proposed
Vibrating Beam ~all Location. . . '. . . .. . . . . . . . . . . . . . . . . .~ . . . . . . .. . . '. . 27
Detail of Localized Exte~t. of Remediation and Proposed' . .
Vibrating Beam Wall Location. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .'. .. 28
Dual Vapor Extraction (DYE) System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 44
8.
9.
LIST OF TABLES
1.
2.
O\emicals of Concern for Groundwater and LNAPL at OU4 . . . . . . . . . . . . . .. 18
. Total Carcinogenic.and NoncarcinogenIc Risks Calculated for
Potential Future Exposure to OU4 Contamination'. . . . . . . . . . . .' . . ~ . '.'. . . .. 23
Selected Potential ARARs and TBCs for Operable Unit 4, . .
Sand Creek Industrial Superfund Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
Costs Associated With Alternatives Developed for OU4 (1994 Dollars) ........ 40
Institutional Controls Available for OU4 ...................:......... 43
Regulatory Standards for Clemicals of Concern at OU4 .................. 46
3.
4.
5.
6.
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Sand Creek Industrial Superfund Site
Operable Unit 4
Commerce City, Colorado
Record of Decision
I.
SITE NAME, LOCATION, AND DESCRIPTION
The Sand Creek Industrial Superfund Site (Site) occupies about 300 acres within portions of
both Commerce City in Adams County, Colorado and the' City and County of Denver ~ The Site
is bounded on the north by Interstate 270, on the south by East 48th Avenue, and on the east
by Ivy Street and the eastern extent of the 48th and Holly Landfill. The western boundary is
approximated by Colorado Boulevard, Vasquez Boulevard, and Dahlia Street (Figure 1). Four
known sources of ,contamination are present at the Site and all are currently inactive: the
Colorado Organic Chemical Company (COCC) pr.operty, the 48th and Holly Land.6ll, the, L.e.
Corporation (Lcq property, and the Oriental Refinery property. Operable Unit 4 (OU4) of the
Sand Creek Industrial Superfund Site addresses groundwater affected by these four sources
and is the focus of this Record of Decision (ROD).
Land use near the Site is primarily industrial and includes trucking firms, petroleum refining
operations, chemical productio~ and supply companies, warehouses, and small businesses. '
Several other Superfund sites are also located in the area, including the Rocky Mountain
Arsenal, O1emical Sales Company, and Woodbury O1emical sites. Properties 'adjacent to the
Site are zon~ for light ~d heavy industrial 'uses, industrial park, industrial park storage, and
agricultUral uses.' Fifteen residences housing appro~ate1y 25 people are located Within a on~
mile radius of the Site. The daytime population reaches several hundred due to local'
businesses and the industrial nature of the area. '
The Denver portion of the Site is located south of East 52nd A venue west of Forest Street and
south of East 48th Avenue to the east of Forest Street. This area is zoned for heavy industrial
use. No changes in zoning are anticipated by the City and County of Denver Planning
Administration (CCDP A) in the near future. CCDP A indicates that long-range land-use plans
,will dep~nd on the fate of Stapleton International Airport following completion of the new
, Denver International Ahport. The Comriterce' City portion of the Site is zoned for agricultural '
and heavy industrial use. Commerce City's ComprehensIve Plan for 1985 to 2010 indicates that'" '
future land use. of this area will be primarily industrial with a recreation/open space designation
for the Sand Creek floodplain.
Municipal water for the area surrounding OU4 is supplied by the South Adams County Water
and Sanitation District (SACWSD) and the Denver Water Department (DWD). Groundwater
produced from alluvial and bedrock wells ,located north of 1-270 is a major source of water
supplied by SACWSD. Water supplied by the DWD is obtained primarily from surfac~water,
sources lOCated outside of the Site area. Residents near the OU4 area are not currently using
contaminated groundwater for domestic purposes. '
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Arsenal
OU4
STUDY AREA
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Intematlonal
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CHE~ICAL .
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USEPA n
Sand Creek Industrial Superfund Sitc ~
OU4 Record of Decision , II
Figure 1
Location of Sand Creek Superfund Site
and Study Area
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II.
SITE mSTORY AND ENFORCEMENT ACTMTIES
During the 1970s and early 19805 a variety of environmental contamination was discovered and
identified at the Site by EPA's Field Investigation Team (FIT). This contamination has resulted
from at least four sources: The COCC facility; the LCC property; the Oriental Refinery site;
and the 48th and Holly Landfill. Although the ownership and the operations on these
properties were distinct, they were included together as the Sand Creek Industrial Superfund
Site and placed on the National Priorities List (NFL) in 1982 for cleanup under the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA),
as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA). Under
the Superfund law, the Environmental Protection Agency (EPA) is charged with the
responsibility of developing and implementing cleanup. remedies that protect human health
and the environment.
. .
. .
Oriental Refinery Property. The Oriental Refinery was located on the northwest comer of
52nd and Dahlia and was gutted by a fire in 1955. As a result of the fire, approximately 48,000
gallons of refined petroleum products may have been released from storage tanks. Plant
operations and the fire have resulted in groundwater contamination. The Tri-County Health
pepartment (TCHD) sampled the soils at the old refinery site and found hydrocarbon
con~ated soi1~ to a depth of 28 feet. The EP A Field Investigation Team (FfI) investigated
the Site in 1980 and found diesel fuel contamination in several groundwater monitoring wells.
Colorado Organic Chemical Company Property.. The eoee plant originally manufactured
pesticid~ in the 19605 ~nder the name of Tun,es CheInical. The COCC site ~as been the scene
of two fires, both of which occurred when the facility was operated by Colorado Irlternational
. Corporation (aq. In 1968 a fire destroyed three buildings. In December 1977 a fire destroyed
the manufacturing equipment within the facility. Eight hundred people were evacuated and
at least 26 people were treated for the inhalation of toxic parathion fumes. Fll"efighters sprayed
more than 350,000 gallons of water on the blaze and subsequently washed the pesticide-
contaminated water downhill toward Dahlia Street. After. these fires several health agenc;ies
found unacceptable conditions at the plant, including: unsatisfactory waste management
practices; unsatisfactory worker safety conditions; violations in storage and handling of
. flammable liquids; c:m~ soil containing high levels of thermally alte~ed pesticides and other
chemiails. .. .... . .
Immediately after the December 1.977 fire, the Colorado Department. of Health (CDH) issued
an Emergency Cease and. Desist order to ae, Western United Resources, Globe CheInical,
Chicago, Rock Island and Pacific Railroad, and Mr. Phillip Mozer. This order stated that the
operations on the Site must be halted, the area contaminated by the fire must be isolated, and
among other tasks, the fire-damaged material must be left intact. Although Western United
Resources was named in the Order, documentation has not been found to indicate that they
participated in any operations relevant to the Site.
..
A March 1984 report described the COCC facility as an unfenced site consisting of six
structures, ten large above-ground tanks (ranging in size from 2000 to 20,000 gallons), and an
uncovered drum storage area. The six structures contained, among other items, approximately
50 dr:mns and an uncertain quantity of pesticide bags. Of the approximately 1()()'125 total
drums observed both in the open storage area and in the buildings on site, most were
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Unlabeled and many were rusted, corroded, bulging, stressed, and leaking. Later in 1984,
eoee removed waste drums and contaminated soil, and constructed a fence around the area
in response to an order froJ;n EP A.
Between 1985 and 19.90, Remedial InvestigationlFeasibility Study (RIfFS) activities occurred at
the eocc property as part of the Sand Creek Superfund Site studies. Treatability studies were
also performed to evaluate the effectiveness of soil washing and bioremediation technologies
in cleaning up soil contamination attributable to the COCC facility. During 1991 and 1992,
approximately 2,000 cubic yards of debris, including four buildings, four rail cars, two concrete
tanks, and 13 steel tanks were removed by a licensed hauler and disposed of in permitted
landfills. Soil vapor extraction (SVE) operations, designed to remove volatile organic
compounds from subsurface soil, began at the eoce property during the summer of 1993..
This remedial action is d~ented in the Explanation of Significant Differences (ESD, 1992)
to ~e Operable Unit 1 (OUl) ROD (1989). Low Temperature Thermal TteatInent (L1TT) was
selected as the method for cle~g up soils contaminated with pesticides and metals at eoc~ .
in' the Operable Unit S (OUS) ROD Amendment (1993). Remediation of OUI and OUS is
. expected to be completed in 1994.
L.C. Corporation Property. The LCe property has been a part of Commerce Oty industry .
since 1948. Between 1948 and 1958, part of the property was used as a gravel quarry. In 1968,
Shell Chemical 'Company contracted with LCe for the disposal of spent acidic wastes from'
Shell's. chemical plant 'at the Rocky Mountain Arsenal.. . LCe was to line .its disposal
impoundments with an ethylene propylene copolymer film before disposing of any acidic.
wastes. A.Hner was installed, however, it was breached after acidic wastes'were deposit~ in .
the pits. Approximately 7,810 tons of sulfuric acid were'disposed of m the LeC pits.' .
In November 1974, Tam investigated a complaint involving severe chemical burns to livestock
that had strayed ontt;) the LCC 'property. TOID found pools of liquids in lined pits on the
property. LCe agreed to' clean up the liquid after analysis showed that it was a 30% sulfuric
acid solution with a highly acidic pH of 0.75.
In July 1975, TOID employees discovered a seep discharging acidic liquid into Sand Creek.
Analyses of the seep liquid and water from Sand Creek in 1976 indicated that both con~ed .
a sulfone 'believed to be ait'intermediate by-product from Shell's manufacture of the herbiCide
Planavin.
In 1980, at the request of CDH, LCC used lime to neutralize the pits and filled them with clean
backfill. Sampling indicates that the lime was effective in neutralizing the acid pits, and that
the pits do not pose an unacceptable risk to public health, as documented in the Operable Unit
2 (OU2) ROD (1993). .
48th and Holly Landfill. Waste disposal operations were conducted from 1968 to 1975 at the
48th and Holly Landfill (Landfill). The Landfill accepted both demolition and domestic refuse,
and although known hazardous and pathological wastes were reported to be excluded from
disposal, the method of exclusion and the consistency of its application are unknown.
In 1977, two explosions of combustible gas were traced to the migration of methane gas from
the Landfill. Two passive methane gas venting s~stems, which proved to be ineffective, were
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installed at the Landfill in 1978 and 1980. In 1991, the passive systems were replaced with an
active landfill gas extraction system (LFGES) as part of the Sand Creek Superfund Site activities
at Operable Units 3 and 6 (OU3/0U6). The landfill-gascollected by the LFGES is burned using
. an enclosed flare to destroy contaminants and eliminate odors. Condensate produced within
the system is collected, treated, and discharged'to a sanitary sewer.
After the Landfill ceased operation in 1975, the site was covered with between 1 to 10 feet of
sandy soil, and re-vegetated. In response to erosion, ponding due to differential compaction
within the refuse, and areas laclcingwe1l established vegetative cover, several site improvement
activities were undertaken in 1992. These site improvements included fill placement, erosion
control, and reclamation.
. ,
Site-Wide Groundwater" The groundwater underlying the Sand Creek Industrial Superfund
. Site!:tas been contaminated from the four onsite sources (theCOCC facility; the LCC 'property; . .
the Oriental. Refinery site; and the 48th and Holly Landfill). In addition, some contaminated
groundwater is moving on site from the Chemical Sales Company Superfund site and
unidentified upgradient source(s). The site-wide groundwater is addressed under this QU4
ROD.
Residuals and breakdown products of chemicals contaminating the soils at the COCC facility
have been found in the groundwater. The soils' at the Oriental Refinery have been'
contaminated with hydrocarbons and petroleum contamination has been found in monitoring
wells. The a,~d wastes disposed of in pits on' the LCC property impacted both groundwater
. and surface. water. in .Sand Creek. Contamination from the 'Landfill . haS impacted the.
groundwater at the Site. At the present time no known contamination is. entering the surface
water of Sand Creek from the Site. .
m.
IHGHLIGHTS OF COMMUNITY PARTICIPATION
Community interest in OU4, specifically, and the Sand Creek Industrial Superfund Site, in
general, has been limited. EP A has undertaken several community relations activities as part
of the recent site history.
Community involvement activities for the' Site began ~ April 1985. ~ A . distributed an .
introductory fact sheet to area residents, businesses, and agencies. The fact sheet provided
background information about the Site and an explanation of the Superfund process. EP A also
attended a public meeting organized by the Citizens Against Contamination, a local group from
the area, and compiled a list of property owners for the entire site.
EPA mailed a second fact sheet for the Site in November 1985. This fact sheet provided
additional information on investigation and clean-up activities associated with the Site. During
. the same month, EPA provided a groundwater contamination .briefing at a second . public
meeting held by the Citizens Against Contamination.
In January 1986, EP A contacted property owners and Commerce City officials to inform them
of activities at the Site. In April 1987 , EP A surveyed area reside~ts about their water use habits
to determine future outreach efforts.
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An RI report describing the nature and extent of contamination at the Sand Creek Industrial
Superfund Site was released for public review in March 1988. In May 1988, EP A contacted
owners for permission to sample soils on their property. In October 1988, EPA met with
Commerce City officials to brief them and solicit their reaction to cleanup plans for the site.
On three occasions in 1990, EP A held public meetings addressing all of the Superfund sites in
South Adams County, excluding the Rocky Mountain Arsenal. In the fall of 1991, community
interviews were conducted to update the site Community Relations Plan (CRP) originally
issued in December 1984. The CRP outlines community concerns, £PA's strategy for
implementing the plan, and establishes information repositories. A list of contacts and .
~terested parties throughout government and the local community are also provided. The
revised CRP was released in DeCember of 1991. In ac;idition to meeting directly with the public,
. EPA and the CDH have met with the TCHD, SACWSD, Rocky Mountain Arsenal personnel,
Commerce City/Adams County officials, Metro. Waste Water officials, and Representative
Patr:icia S~peders staff to update them on activities.
EP A issued the Proposed Plan for OU4 on February 14, 1994. The Proposed Plan and RI
reports were made available to the public through the Administrative Record maintained at the
EP A Region vm Supe#Und Records Center in Denver and at the information repository at the
Adams County Library. A notice of availability of these documents and notification of the
public meetirig were published in The Rocky Mountain News on February 14, 1994 and in The
Commerce City Express on February 15, 1994.
The public comment period was open from February 14 to March 16, 1994. . The public'meeting
was held on March 1, 1994 at the Commerce Gty Recreation Center. . EPA explained the
alternatives and responded to questions. A transcript of the public meeting has been entered
into the Administrative Record. A Responsiveness Summary, prepared by EP A to address
public comments, is included as Appendix A of this ROD.
IV.
SCOPE AND ROLE OF RESPONSE ACTION
Due to the complex nature of the Sand Creek Industrial Superfund Site, EP A has divided it into
six operable. units. (OUs),or study areas, in order to more effectively address specific
cC;>ntamination problems. The OUs were established based on the types of contaminants.
present, the tYPe of media' affected, and physical characteristics. As discussed above, this
ROD for OU4 addresses the .principal potential threats to humans and the environment
resulting' from exposure to contaminated groundwater throughout the Site. The six operable
units at the Site are defined as follows:
.
Operable Unit 1: OUI addresses contaminated buildings, soil contamination
greater than 1000 parts per million (ppm), and volatile organic compounds
(VOCs) in the subsurface soils. The OUI area i;ncludes approximately.IS acres
of the site, including the COCC plant property, the land between COCC and
LCC, and the northern portion of the Oriental Refinery site. The Explanation
of Significant Differences (E5D; 1992) to the OUI ROD (1989) selected SVE as the
method for removing VOCs from soils ranging in depth from 8 to 20 feet at
OU1. The purpose of the OUI ROD and ESD was to address the principal
threat of contact with contaminated soils by the public and Site workers, and to
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protect surface water and groundwater resources. The OU1 ROD and ESD
called for a cleanup of chloroform, methylene chloride, tetrachloroethene, and
, trichloroethene in the subsurface soils. In addition, demolition and removal of
contaminated tanks and buildings located in the area was included in the
selected remedy.
.
Operable Unit 2: This OU addresses the acid waste disposal pits on the LCC
property, just north of the COCC facility. The pits located there were used for
disposal of acid waste from various chemical manufacturing activities occurring
both off and on site. The OU2 ROD (1993) selected a No Further Action
alternative for the acid pits.
.
, ' ,
Operable Unit 3: This OU comprises the 48th and Holly Landfill and specifically
includes contaminated surface water, groundwater, sediment, soil, and air in its
vicinity. 'The OU3/0U6 ROD (1993) ,selected a remedial al~ernative for ,the
Landfill. The ROD called for both engineering and institutional controls.
Engineering controls included the continued operation and maintenance of the
landfill gas extraction system (LFGES). The ROD also dictated that the landfill
cover system be maintained, and groundwater in the vicinity of the Landfill be
monitored for potential releases of contaminants from the Landfill. In ad~tion,
the OU3/0U6 ROD provides that if it is determined by EP A, in consultation
with CDH, that the Landfill is responsible for a contaminant release to
groundwater outside the boundary of OU3, such release(s) will be addressed
, under OU3'. . , , '
.
Operable Unit 4: This study area is the focus of this ROD and consists of
contaminated groundwater underlying the Sand Creek Industrial Superfund Site.
However, groundwater beneath the 48th and Holly Landfill and groundwater
directly related to the Landfill is being addressed under the OU3/0U6, ROD.
OU4 also includes the light non-aqueous, phase liquid (LNAPL) plume floating
on the water table beneath a Dortion of the Site. Petroleum contamination is
6 .
generally excluded from CERCLA investigations due to the Petroleum Exclusion.
,However, EP A included LNAPL in OU4 because the product i~ mixed with
hazardous substances; the presence of hydrocarbons in the subsurface adversely
affects SVE remediatio~ at aU1, and the LNAPL provides a continuous source
of dissolved-phase contaminants to groundwater. Contaminants detected in the
groundwater include volatile organic compounds (VOCs), s,emi-volatile organic
compounds (SVOCs)~ pesticides, metals, and sulfones.
Operable Unit 5: OUS includes the same area as OU1 but addresses pesticides
and heavy metals in shallow soils to a dep'th of S feet. ,These soils have
, contaminant concentrations greater than action leyels and less than or equal to
" 1,000 ppm of halogenated organic compounds (HOCs). The remedy selected in
the OUS ROD (1990) called for soils at the COCC property with concentrations
above action levels to be excavated and treated on site using a soil washing
process. Subsequent to the OUS ROD, EP A analyzed additional samples of the
contaminated soils, performed soil washing treatability studies, and investigated
other cleanup technologies. As a result of this additional work, EP A selected
.
-------
the use of Low Temperature Thermal Treatment (LTIT) in the OU5 ROD
Amendment (1993) as the method for cleaning up contaminated soils. It is
estimated that approximately 8,000 cubic yards of contaminated soil will require
treatment at OUS.
.
Qperable Unit 6: This OU addresses the gaseous emissions at the 48th and
Holly Landfill. The remedy for OU6 was selected in the OU3/0U6 ROD (see
OU3 above) and called for continued operation of the LFGES installed as part of
a removal action in 1991. .
v.
SUMMARY OF SITE CHARACI'ERlSTICS
The Sand Creek Industrial Superfund Site is located in an urban environment that has been
extensively modified by industrial dev~opment over the past 50 years. The Site lies in an .area .
of low relief within the Sand Creek floodplain, which is part of the South 'Platte River System.
The on-site drainage represents less than one-half of one percent of the total drainage to S~d
Creek. The only surface-water feature within the Site is a I-acre wetland that is fed by a
subsurface drain system and is located immediately north of the Landfill.
This Site is in an area classified as mid-latitude semiarid, indicating an area of high summer
temperatures, cold winters; and sparse rainfall. The average annual precipitation is
. approximately 15 inches.
A..
Topography
Topography in the area rises gently to the south, with elevations ranging from
approximately 5,180 feet abov~ mean sea level (MSL) in th~ northwestern corner of the
Site to approximately 5,250 feet MSL in the southeastern comer. Interpretation of
natural features is complicated by the extensive amount of fill that has been brought
into the area. Between 2 and 10 feet of soil capping material currently covers the refuse
at the Landfill and similar thicknesses of fill. materials OCcur locally in other parts of the
Site. Natur~ drainage paths have also been altered by development in much of 'the
. area. .
B.
Geology
The subsurface geology ~ the vicinity of the Site consists of Quaternary alluvial
deposits and Tertiary bedrock. A,lluvial deposits range in thickness from less than 20
feet to more than 100 feet and consist of sand, silt, and clay of the Piney Creek
Alluvium, eolian deposits of silt and clay, and sand and gravel of the Broadway
Alluvium. Oayand gravel sediments of the Slocum Alluvium are also .locally present.
Bedrock in the area is made up of claystone, shale, siltstone, and sandstone of the
Denver Formation.' In the central portion of the Site, a paleochannel is eroded in the
becUock surface and may influence the occurrence and movement of groundwater in the
area. The Denver Formation is underlain by the Arapahoe Formation, Laramie
Formation, and Fox Hills Sandstone. Outcrops of bedrock are not visible at the Site.
-------
c.
Hydrogeology
Three discrete alluvial aquifers (Aquifers 0, 1, and 2) have been identified within the
unconsolidated sediment overlying bedrock in the area. Borehole logs taken from
'investigations in the vicinity of the Site show .that alluvial deposits are composed of
relatively high permeability sands and gravels interbedded with low permeability clayey
and silty material. The extensive amount of clay material present in the subsurface at
the Site tends inhibit groundwater flow and contaminant migration. A generalized
cross-section of the aquifer sys.tem at the Site is provided in ~gurE! 2.
. In the southeastern portion of the Site, Aquifer 0 is the only alluvial aquifer present
(Figure 3), and it directly overlies bedrock or fine-grained alluvial sediments overlying
bedrock. In the central part of the Site, Aquifer 0 exists under perched conditions above
Aquifer 2. The lateral extent of Aquifer 0 is limited to the northwest.. Aquifer 0 is
unconfined thr01,1ghout its extent and is underlain by a low permeability clayey layer
(Aquitard A), which inhibits downward'movement of groundwater. Within Aquifer 0, .
groundwater £low is generally toward the north to northwest. Slug test data from
Aquifer 0 wells indicate that the horizontal hydraulic conductivity typically ranges from
0.6 to 1.0 foot per day (ftld), but was measured to be as high as 354 ftld at one well.
The hydraulic gradient of Aquifer 0 ranges from 0.004 to 0.06 foot per foot (ftlft). Using
an estimated effective porosity of 20%, average £low velocities calculated by Darcy's Law
range from 0.03 to 17.7 ftId for Aquifer O.
Aquifer 0 receives reCharge from upgradient of the Site and disch~ges to Aq~er .2
. where the confining unit '(Aquitard A) separating these aquifers pinches out in the'
northwest portion of the 48th and Holly Landfill. It is believed that Aquifer 0 also
discharges to the spring located north of the Landfill via a finger. drain syst~. The .
direction of groundwater flow in Aquifers 0 and 2 is generally consistent with the
regional £low direction of the alluvial system (i.e., northerly toward Sand Creek).
Aquifer 1 is present in the northwestern portion of the Site and northwest of the Site
(Figure 3). Aquifer 1 exists under unconfined conditions and is separated from Aquifer
. 2 by a clayey impermeable unit (Aquitard B). Groundwater flow within Aquife,r 1 is
generally' toward the. .east/northeast. Groundwater. may discharge from Aquifer 1 to
Aquifer 2 in the' area where the confining unit separating these aquifers pinches out,
in the vicinity of the northern boundary of the Landfill: Data from slug tests performed
on Aquifer 1 wells indicate the horizontal hydraulic conductivity ranges from 0.7 to 273
ftld. The average hydraulic gradient of Aquifer 1 is 0.006 ftlft. Using an estimated
effective porosity of 20%, average £low velocities ::alcu1ated by Darcy's Law range from
0.02 to 8.2 ftld for Aquifer 1.
Aquifer 2 is present over the western po~on of the Site (Figure.3). Aquifer 2 underlies
Aquif~ 0 and Aquifer 1. in areas where present and also overlies fine-grained alluvial
.sediments overlying bedrock. The extent of hydraulic communication between Aquifer
2 and Aquifers 0 and 1 is not known, but it is believed that some leakage occurs across
the aquitards (A and B) that separate these aquifers. In addition, the limited extent of
the aquitards allows groundwater from Aquifers 0 and 1 to discharge to Aquifer 2 where
the aquitards pinch out. Downward vertical £low velocities from Aquifer 1 to Aquifer
-------
NORTHWEST
ORIENTAL REFINERY
-1t .C.O.C.;. .;
CHEMlCAL SAlES
48TH & HOLLY LANDFILL
.. ...;
.,
~~
GROUND SURFACE
.,
.~
~:
...
...
LEGEND
)
<
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of
.'
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'V POTENT!OMETRIC SURFACE
~ BEDROCK ~ FREE PHASE PRODUCT
[}] CONFINING BED
. 0 . 500 1000
1 -2000' .HORtZ. .
1"-&0' VERT. 0 IS JO
2000
.
80
SOUTHEAST
..
USEPA n
Sand Creek Industrial Superfund Site .. --.
OU4 Record of DecIsion ~ r
Figure 2
Conceptual Cross- Section
01 Alluvial A,!ull8rl-
-------
...........
.,. .
...
?
LEGEND
-;
~
iii
.!!
:c
o
o
[d
OJ
EJ
AOUIFER 0
AOUIFER 1
--
AOUIFEA 2
,.,..
USEPA n
Sand Creek Industrial Superfw1d Site ..........
. OU4 Remrd ofDedsion "
i
FJgWe 3
Extent of
AqWfers 0,1 and 2
o """ -
b.....d
.-
SCAlE: 1.. 1000'
J
II»
(~-
iii
.2:-
C5
:z:
iii
l'
-------
2 are calculated to range from 0.0009 to 20 ftld. Aquifer 2 exists under confined
conditions to the west and northwest portion of the Site but is unconfined beneath the
Landfill and south of the Site. Groundwater flow within Aquifer 2 is generally toward
the north. Slug test data from Aquifer 2 wells indicate, the horizontal hydraulic
conductivity'ranges from 0.2 to 409 ftId. The average hydraulic gradient of Aquifer 2
is 0.003 ft/ft. Using an estimated effective porosity of 20%, average flow velocities
calculated. by Darcy's Law range from 0.003 to 6.1 ftld for Aquifer 2.
D.
Water Diversions
The rights for surface-water diversion from Sand Creek exist at' two separate locations
downstream of the Site. The first diversion point is the proposed Henrylyn Sand Creek
Diversion, which is approximately 1.5 miles downstream of the Site. Diversions from
this location could reach 250 cubic feet per second of water for direct irriga~on and.
stm:age in existing and pl~ed reservoirs. The second diversion point is appro~tely
2 miles downstream of the Site where the Burlington Ditch intersects Sand Creek. A
maximum of 250 cubic feet per second of water is appropriated for irrigation, and
domestic use at this location. According to a representative of the Burlington Ditch
Company, water rights along the proposed Henrylyn Sand Creek Diversion or the
existing Burlington Ditch have not been exercised to date.
E.
Nature and Extent of Contamination
Eleva:ted, levels of organic and inorganic contaminants have been detected throughpu~
OU4 ~ AqUifers 0, 1 .and 2. Except for the eastern portion of OU4 near the Chemical
Sales Company Superfund.Site (see Figure 1), low levels of organic contaminants have
been detected in upgradient wells used to define backgroUnd water quality. These
include chlorinated VOCS and benzene in Aquifer 0; benzene, toluene, ethylbenzene,
and xylene (Le., BTEX), acetone and chlorobenzene in Aquifer 1 and benzene, toluene,
ketones and chlorinated VOCs in Aquifer 2. High levels of chlorinated VOCs are
present upgradient from the eastern portion of the OU4 stUdy area. These occurrences
are believed to be largely the result of releases from past ~dustrial activities at the .
O1.emical Sales Company Superfund Site' located upgradient of the OU4 study area. .
Groundwater'remediation at OUt of the Chemical. Sales. Company Superfund Site is
scheduled to begin during the summer of 1994 and will address thIs source of VOC
contamination. The Occurrence of trichloroethene (fCE), tetrachloroethene (PCE), and
benzene are representative of the extent of VOC and BTEX in groundwater at OU4.
Figures 4, 5, and 6 indicate the extent of TCE, PCE, and benzene contamination at the
Site, respectively.
Groundwater in Aquifer 0 contains VOCs; phenols; naphthalene; 1,4-dichlorobenzene;
herbicides and elevated levels of antim~>ny, barium, iron, lead, manganese and. .
vanadium, as compared to background concentrations. Most of the organic
contaDrinants such as chlorinated VOCs, ketones, toluene, ethylbenzene, xylene,
phenols, 2-methylnaphthalene and naphthalene were detected primarily in the
southeastern portion of OU4. Benzene and phthalates were detected throughout
Aquifer O. Elevated levels of styrene, antimony, bariUm, iron, lead and manganese
were detected within and/or down gradient of the 48th and Holly Landfill.
-------
USEPA
Sand Creek Industrial Superfund Site
OU4 Record of Decision
Figure 4
Occurrence of Tridiloroethene
in Ground water
Cotorodo
Organic
Chtmicol Componv
-— OU4 Boundary
AquHw 0 montorin9 •<•
48»n AND Hoar
LANDFILt
Aotliftri 0*2
touiltn 1 If 2
-------
USEPA f\
Sand Creek Industrial Supofund Site ^tt^
OlM Record of Decision
Figures
Occurrence of Tetrachloroethene
In Ground water
Concrct*
/ Culvert
4Uonitarina w«V screened across
AoXm 1 en* 2
DilKbon obao ua oT S ppb
AoV'w 0
*o>l*r I
4B'> AND HOLLY
LANOntL
0*2
AqnH«n t ft 2
Contaminant Plm*!' trtffil teyontf OU4
boundary it ne<
-------
'-~":;~t~:tt":",:,...~;. -;-.
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, \ "-':~" "'" ..:;~:~~~.;,;;~:: -'" ~ -, (II ~,-,- n, ., - ,
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j~ o.toctJon 0""'" lAC\. 01. S ppb
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!:~ ~ AqviI~ I .. 2
ill ' c-tomi_t -' ."ent be)oond 00'
, -', ; ....-.y it 110\ .-... .
i I " ~'"
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. .. Slott JfO'ldard 01 11'f1i1 ,..,.
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/1 :-'7"
-------
Contaminants detected in Aquifer 1 include chlorinated VOCS, ketones, BTEX, styrene,
phenols, polyaromatic hydrocarbons (P AHs), chlorinated benzene, pesticides,
herbicides, aluminum, iron, magnesium, manganese, and sulfate. Elevated levels of
organic and inorganic constituents have been detected throughout Aquifer 1, except in
the northern and western portions of the aquifer where there are no Aquifer 1 wells.
Generally, the highest concentrations of contaIniIUmts were detected on the COCC and
northern Oriental Refinery properties. Pesticide contamination in groundwater appears
to be limited to the same area, which coincides with pesticide contamination in soil at
OUS.
Aquifer 2 groundwater contains chlorinated VOCs, ketones, BTEX compounds, phenols,
P AHs and elevated levels of antimony, barium, iron, sulfate, lead and manganese.
Concentrations of, organic containinants are greatest in two areas: the' eastern and
southeastern portions of OU4, ,which are primarily affected by chlorinated VOCS; and
th~ COCC, Oriental Refinery, and LCC prop~es. '
The bedrock aquifers underlying the Site, with the exception of the weathered surface
of the Denver Formation, do not appear to have been impacted by groun~water
contaminants. The low-permeability nature of the claystone at the top of the Denver
Formation in conjUnction with its, depth provides protection for the underlying units
from dissolved-phase contaminants. The weathered surface at the top of the Denver
Formation is characterized by extensive fracturing along bedding planes and behaves
hydrologically as, part of the overlying alluvial aquifer system.
A plume of LNAPL is present on the groundwater surface beneath the ~OCC and LCC
properties. The LNAPL is located in Aquifer 2 and overlying clay layers, and the
thickness of the plume ranges from 1.7 to 4.7 feet. Migration of the LNAPL plume is
impeded by the presence of thick, clayey materials. It is estimated that approximately
190,000 gallons of LNAPL occurs as mobile product and another 170,000 gallons of
residual LNAPL is present in fine-grained materials. Fingerprinting analysis conducted
in 1992 of the LNAPL concluded that it is comprised of two hydrocarbon products: a
light naphtha solvent and a diesel-like f:uel oil, which increases in age from south to
north (along the Aquifer 2 hydraulic gradient). In contrast, hydrocarbon-contaminated
'soil in the ~orthem portion of th~ QrientaI Refinery property and groundwater '
northeast of the Site and north of Sand Creek was found to contain only the solvent,'
while soil in the southern portions of the Oriental Refinery and LCC properties
contained only the fuel oil product. The data indicate the presence of at least two
l.NAPL sources and the northward migration of the LNAPL plume to its current
location. Dissolved-phase groundwater contamination associated with the LNAPL
includes BTEX, and a .plume of tetraethyllead (TEL).
VI.
SYMMARY OF SITE RISKS
CERa.A mandates that EP A protect human health and the erivironment from current and
potential exposures to hazardous substances. Groundwater underlying OU4 was evaluated for
potential human health and environmental risks posed by contaminants in several
inyestigations at the Site. These evaluations were baseline assessments and evaluate potential
-------
risks associated with exposures to cUrrent levels of contamination in the absence of any
remedial action at the Site. The following documents describe these risk evaluations:
.
1988 Preliminary Endangerment Assessment (EA) for the Sand Creek Industrial
Site, Colorado: This document described a site-wide risk assessment that
, evaluated risks from contaminated soils, groundwater, surface water, and air at
the Site.
.
1993 48th and Holly Street Landfill (OU3) Risk Assessment (RA): This document
updated and supplemented the 19a8 EA by incorporating new data presented
in the OU3 RI. The two media evaluated in this RA were groundwater in the
vicinity of the Landfill and landfill gas.
.
1993. Health Evaluation Update: This document was prepared as part of the
OU4 'RIlFS. It.updated and supplemented the 1988 EA by incorporating 1:'\ew
data collected during the OU4 RIlFS as well as data collected for the 1993 OU3
RA. Groundwater and the LNAPL plume were the subjects of this evaluation~
Results were compared with the previous EA study.
A.
Contaminants of Concern
The potential human health and environmental hazards 'associated with OU4 result
from exposure to: contaminated groundwater, the LNAPLplume, ~d contaminated
. surface water .that could result from the discharge of groundwater to Sand ~~. The
LNAPL plume does not appear to be mobile due to its presence within a clay layer that.
thickens to the north. The LNAPL plume, however, provides a continuous source of
mobile, dissolved-phase contaminants such as BTEX and TEL.
. .
The chemicals of concern (COCS) for OU4 include VOCs, SVOCs, pesticides, and
metals. All detected contaminants classified as carcinogens are included in this list.
The COCS also include the contaminants likely to present the greatest hazard to human
health and the environment based on potential noncarcinogenic adverse effects. EP A
co.mbined and eValuated the 37 COCs previo~sly -identified in the 1988 site-wide RI,
data from. the OU~ Fr~Phase Plume Investigation, and'the cots identified in the 1993' ".
OU3 RA to determine if it was necessary to continue to use all 37 COCs, or if it was
reasonable to retain only a portion of the total number of COCS for the development of
a site remedy. For example, some of the 37 COCs were detected in only a few samples,
some COCs were present at concentrations at or below normal health-based risk levels,
and some COCs had similar properties, such that one coe could be used to represent
other COCS. All COCs were evaluated and 18 were identified as key contributors to
risk at the site based on concentratioJ\s and toxicity. In addition, 2,4-D and 4,4'-DDT,
soil contaminants that are prompting remediation at OUt and OUS, were included at
the' request of EP A. The compound chlorophenylmethylsulfone (CPMSO) was also ,
added to the list of COCs at CDH's request after it was detected in urine samples from
residents living near the Rocky Mountain Arsenal, located north (downgradient) of
OU4. CPMSO was detected in soil and groundwater on the LCC property. Table t1ists
all of the COCS evaluated for OU4 and identifies the 21 key COCS selected for
development of remedial alternatives in the OU4 FS. '
-------
TABLE 1
CHEMICALS OF CONCERN FOR GROUNDWATER AND LNAPL AT OU4
"..i .i. .. .
.... ..' .
LNAPv:rr,>:: m-
...,... . .. '" ...
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. .....,... ........'... ... .... ......
::;:;:;:;:;:::::::::::;..::::;::;::::::;:::':::.::::.::':::;:',:::;:::::::::::
..,".... ....... n. ..', . '.'
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.." . ,.' ...
.... .. ...'
... . .
Volatile Organic Compounds
Acetone x
Benzene x x x
Calorobellzene x
ChJoiofoIm x x
l,l-DIchlcnoethene x x
l,2-Dic:h1oroethene (total) x x
Ethy1beftzene x x
Methylene Calorlde x x.
Styftne x x
Tetnchloroethene x x
Toluene x
1,1,1-Trichlqroethane x
Trichlcnoethene x x
trans-l,2-DichlOJOethene x x
Vmyl O11oride x x
XyJenes x
Semi-Volatile Organic Compounds
Acmaphthene x
bis(2-ethylhexyl)phthalate x
Dibenzofuran x
1,2-Dichlmobenzene x
1,4-Dichlombenzene x
Fluonnthene x
Flucuene x
2-Methylnaphtha1ene x
Naphthalene x x x
Phenanthrene x
PyJene x
-------
TABLE 1
CHEMICALS OF CONCERN FOR GROUNDWATER AND LNAPL AT OU4
1..,i~ff0~ii~I~~~li&.
. .
d Herbicides
alpha-BHC
Dieldrin
2,4-D'"
4,4' -DDT"
gamma-BHC (Lindane)
Metals
x x
x x
x x
x x
x x
Antimony
Arsenic
Cadmium
x
x
x
x
x
Manganese
Selenium
Zinc
x
x
x
x
Other
CPM5C)8
Tetraethyl Lead
x
x
x
x
"2,4-0 and 4,4' -DDT, soil contaminants that are prompdng remediation at OUI and OUS, were included at the request
of EPA. CPMSO (p-chlorophenylmethylsulfone) was added at the request of CDH. .
-------
B.
Exposure Assessment
Exposure pathways and receptors were identified for OU4 in a conceptual model
developed for the Site. Potential release mechanisms associated with OU4 are discharge
of groundwater to surface water and pumping groundwater for residential, agricultural,
or industrial use.
A 1990 report prepared by TCHD for EP A and CDH contains the most current
information on OU4 area water use. The report summarizes the findings of a door-to-
door well inventory and information survey. The survey encompassed an area bounded
by Sand Creek on the north, Interstate 70 on the south, Quebec Street on the east, and
Colorado Boulevard on the west. (This survey area extends beyond the boundaries of
OU4.) .The survey supported CDH and EPA efforts to identify potential receptors of
groundwater contaminated by several sources, including sources at the Site. TCHD
cpntacted property owners to determine the number, location, depth,construction.
details, and current use of wells in the survey area. . .. .
TCHD obtained information on water use from 419 of the 420 properties in the survey
area. SACWSD and DWB serve most of the water users in the survey area. fiowever,
the. survey identified 23 private wells, with nine completed in the shallow alluvium.
Data regarding the depth of nine wells were unavailable. Four wells identified as deep
ranged from 560 to 1600 feet depth and, thus, are not in the shallow alluvial aquifers.
Two of the deep wells provided water for drinking. No contamination of the deep
bedrpck aquifers a~ the Site h~s been ' observed in the studies performed to q,ate.. .
Of the wells completed in the shallow alluvium, only five are in use. Three are used
for irrigation and one as a seasonal water supply for livestock. The remaining well,
located at a business on Oriental Refinery property, provides water for a sanitary waste
system. The.potential for human exposure to groundwater contaminants resulting from
these uses is unknown. These wells will be sampled and evaluated as p~ of the OU4
monitoring program to determine the need for future action. EP A and CDH will notify
and provide recommendations to the users if contamination is detected.
Since current use of .shallow alluvial groundwater is limited to agricultural and.
wastewater uses, exposures for the. current scenano were not quantified. Domestic use
of contaminated groundwater and exposure to the LNAPL, however, were evaluated
for potential future exposure scenarios. Exposure pathways evaluated quantitatively
were ingestion of groundwater, and inhalation of volatile contaminants during
showering. Dermal exposure to contaminants in groundwater during showering, and
exposure to surface water contaminants for aquatic biota were evaluated qualitatively.
Estimated exposures were evaluated for the average case and the reasonable maximum
ca,se. The arithmetic mean concentration of contaminants in groundwater was used for
the average case. Maximum contaminant concentrations detected in groundwater were
used for the reasonable maximum case. A resident weighing 70 kilograms was
assumed to ingest 2 liters of water per day for 70 years. The 70 kilogram resident was
also assumed to be exposed to contaminants volatilized from a lO-minute shower and
to remain in the shower room for 5 minutes longer' for a total exposure time of 15
-------
minutes. A volatilization model developed by Foster and Chrostowski was used to
estimate air concentrations. These were the same basic assumptions used in the 1988
EA, and were developed before current guidance regarding the use of reasonable
maximum exposures (RMEs) was issued. Results from the 1988 report provide a
conservative estimate of risks that are essentially equiv~ent to risks calculated with
current. guidance.
c.
Risk Characterization
Potential health risks to humans are expressed in two ways: carcinogenic (cancer
causing) and noncarcinogenic. For carcinogens, it is assumed that there is no safe dose,
. but that the risk of cancer is reduced as the dose is decreased. Slope factors (SF) are
used to estimate excess lifetime cancer risks associated with exposure to potentially
carcinogenic chemicals. Excess lifetime cancer risk is determined by multiplying the
intake by the~. These risks are probabilities and are generally expressed as exc~ss
cancer risks. An excess lifetime cancer risk indicates the chance; over and above the .
background average risk (approximately one in four), that an individual will develop
cancer as a result of exposure to a carcinogen over a 7o-yearlifetime under specific
exposure conditions. In determining the need for remedial action at Superfund sites,
EP A guidance states that the total excess cancer risk for all contaminants must fall
below the range of 1 chance in 10,000 (lE-Q4) to 1 chance in 1 million (lE-Q6).
Noncarcinogenic risks are calculated by assuming there is a dose below which no
adv~ health effects ~ occur. This level is called ~e reference dose (RID) and is
qsed to estimate the hazard quo~ent (HQ) associated with the potential exposUre to '
noncarcinogens. HQs are determined by calculating the ratio of the estimated intake
level to the RID. A hazard index (HI) can be generated by adding the HQs for all
chemicals with similar target organs or critical effects within a medium, and by adding
HQs across all media to which a population may reasonably be expected to be expose~i.
The HI provides a useful reference point for evaluating the potential significance of
multiple contaminant exposures within a single medium or across media. An ill of 1
is identified in the NCP as a Superfund site remediation goal.
Risks es~ted for. OU4 indicate that actual or threatened releases of hazardous
substance~from OU4 groUndwater~ if not addressed by iInplementing the response
action selected in this ROD, may present an imminent and substantial endangerment
to public health, welfare, or, the environment. Current and potential future human
health risks as well as environmental risks attributable to OU4 are discussed below:
1.
Current Human Health Risks
Currently, shallow alluvial groundwater is not used for domestic purposes..
There are five wellS completed in the shallow alluyjum in the OU4 vicinity and
.they are used for agricultural or sanitary waste purposes. Estimates of current
risks were not calculated due to the lack of sampling data for these wells and the
absence of completed exposure pathways. As mentioned previously, these wells
will be sampled and evaluated as part of the OU4 groundwater monitoring
-------
program, and EP A and CDH will.notify and provide recommendations to the
users if contamination is detected.
2.
Future Human Health Risks
The contaminants of concemand exposure factors used to calculate risks for the ,
1993 OU3 RA and 1993 Health Evaluation Update were identical to those used
in the 1988 site-wide RI and, therefore, the risk values generated in these three
evaluations can therefore be directly compared. This comparison illuminates
differences and similarities in the contaminant and risk profile for ,shallow
alluvial groundwater in 1988, 1991, and 1992. However, there were significant
differences in sample size for each aquifer and each investigation, which
potentially affects the results (i.e., fewer samples and fewer wells sampled may
result in data that do not represent aquifer contamination). In addition, only
. some of the samples collected in 1991 were analyzed for pesticides, and the 1992 ,
. investigation, did not include analysis for metals. The. i992 Aquifer O,data are . .
considered inadequate for risk evaluation because of the small sample size.
Similarly, the data collected in 1991 are considered inadequate to evaluate the
risks associated with Aquifer 1.
The calculated total risks for individual aquifers and specific data bases are
presented in Table 2 and are an based on the maximum detected concentration
from the sample data for each aquifer, rather than on an average concentration.
Gen~y, the 1991 and 1992 data indicate risks siIiri1ar to those caltUlated from
. data collected for the 1988 site-wide. RI. The risk values' indicate that'
groundwater in all three aquifers, and the LNAPL plume h8ve' total excess
cancer risks (ranging from 1E-02 to 1E-03) that are above EP A's acceptable risk
range.
The greatest risks are associated with ingestion of groundwater. However,
inhalation of VOCS during showering contributes significantly to risk in several
cases. The primary contaminants contributing to cancer risk in groundwater are
arsenic, benzene, and vinyl chloride, all classified as known human, or "Oass
. . A"., carcinogenS. For the LNAPL, benzene alone contributes the total cancer risk
of greater than 1 iri .100 (1E-02) when ingestion is conSidered. The, high
concentrations of contaminants in the LNAPL make ingestion unlikely due to
odor, bad taste, and visible contamination. The LNAPL is likely to be acutely
,toxic. It should be noted that the difference in risks calculated for the individual
aquifers versus the OU4 collective data is primarily attributable to the exclusion
of benzene and other petroleum-related compounds from the aquifer-by-aquifer
analysis in the 1988 EA.
. The primary contributors to noncarcinogenic risk in groundwater are t;he
.' chlorinated solvents tetrachloroethene and 1,2-diChloroethene (critical effects:
liver and kidney damage), the metals manganese (critical effect: neurological
disorders) and arsenic (critical effect: skin lesions), the polyaromatic hydrocarbon
naphthalene (critical effect: interference with developmental weight gain), and
the insecticide dieldrin (critical effect: liver damage). Tetraethyllead (critical
-------
TABLE 2
TOTAL CARCINOGENIC AND NONCARCNOGENIC RISKS CALCULATED FOR POTENTIAL
FUI1JRE EXPOSURE TO OU4 CONTAMINATION.
mil '::.,:,;, " ' " .'.::;";':".:':'.' ,':," ..': ,:. "
. ",. . ..... . ,',
":0~~~?:~,::::::::::::;::':.,:" "" .", '.", .....
,,;',j,::I':'''''!:!',~~~0!1::~::;'!':;''}'':'';::: :1=~~0:;;'\~'::::::':,::,,: I,.:::::A~~~~:,:~:.:.,
:,::, ..
" .. '.', , .. "... ,'....
.... ,:,1991:::,::,: '1992,;:, 1988:,:,:::,: ...,". " '1991"',::':" :,.1992::::"::,,
:..::198&:",:,: .. :)991~:,' ':'l99Z;:,,;:; 1988::,:,' .:1991::;:;:,. 1991,:",
Inpstion of Gromadwa.
- Total Cancer Risk 4E-3 4E-3 - 9E-3 - 3£-5 2£-3 SE-4 3E-3 3E-2 >1E-2
- Hazud Index 2 3 - 5 - 0.06 4 4 1 44 3
Inhalation of Volatile cOCa in Cromadwater WldJe Showerins
- Total Cancer Risk ,9E-4 3E-3 - 7E-4 - SE-1 4E-4 lE-3 4E-4 - -
- Hazard Index - 0.9 - 1 - 0.03 0.4 0.05 0.4 - -
Note: The year indicated refers to a values reported in a specific risk assessment report or values calculated from .
specific data base. 1988 8 Risks calculated using 1986 and 1981 RI data and reported in the 1988 Preliminary
Endangerment Assessment. 1991 and 1992 8, Risks calculated using groundwater data collected in 1991 and 1992.
Data collected in 1991 and 1992 are considered to b~ too limited to evaluate risks associated with Aquifer 1 and Aquifer
0, respectively.
-------
effect liver damage and central nervous system disorders) is the primary contributor to
noncarcinogenic risk for the LNAPL.
3.
Environmental Risks
, .
The potential hazards to environmental receptors were qualitatively evaluated
in the 1988 EA and the 1993 OU3 RA. Terrestrial and aquatic habitats present
at the Site were described and individual species known to occur in the vicinity
were identified. No federal or state ~eatened or endangered plant or animal
species are known to be present on the Site. .
The likelihood of exposure of terrestrial receptors to COCs in groundwater is
considered remote beCause groundwater is not accessible except at the point of
discharge into a marsh near the landfill. The maximum concentrations of COCS
in surface water' colleCted at the marsh were compared to federal ambient water
quality criteria. (AWQq and state water quality standards for protection of
aquatic life. Maximum surface water concentrations at the marsh were lower
than A WQC and state standards for all COCS having an established standard.
These results agreed with previous similar comparisons for the 1988 EA.
Because of the IQw potential for exposure to groundwater contaminants for
terrestrial receptors and the low concentrations of contaminants found in surface
water, enviro~ental risks are currently expected to be minimal.
,VD.
PES~ON OF ALn;RNATIVES
In the OU4 FS, a x:ange of options were developed for addressing groundwater and LNAPL
contamination at OU4. Ten remedial alternatives were retained for OU4 following the
development, screening, ~d detailed analysis of alternatives in the FS. EP A decided to
include alternatives involving containment or full-scale treatment of the LNAPL plume because:
(1) the LNAPL plume poses a potential threat to human health or the environment through
discharge to Sand Creek, the Denver Metro sanitary sewer lines, and downgradient wells; (2)
the LNAPL plume represents a continual source of contaminants and therefore affects
groundwat~ trea~ent options; and (3) the presence of the LNAPL interferes with operation
of the soil vapor extraction (SVE) system constrUcted.for r~mediation of"OU1. As discussed
previously, petroleum contamination is generally excluded from CERCLA investigations due
to the Petroleum Exclusion, which exempts pure product from CERCLA response actions.
However, EPA has response authority to address the LNAPL at OU4 because the product is
mixed with hazardous substances. Removal of the recoverable portion of the LNAPL plume
beneath the COCC property would occur under OUI remedial action, but it is considered to
be a component of the alternatives developed for OU4 since many of the treatment options for
OU4 would contain or treat the LNAPL as well as dissolved-phase groundwater contamination.
Five-year site reviews ~ould be' conducted for all alternatives developed for OU4. Except for
the "No-Action" alternative, each alternative also includes the following common elements:
Groundwater and Surface Water Monitorine - Existing and future groundwater
monitoring wells (approximately 16) would be'sampled and analyzed periodically
throughout OU4 to assess the effectiveness, of the selected alternative and changes in
-------
natural conditions. Monitoring points would be located upgradient of the Site (to detect
contamination entering the Site), within the LNAPL plume (to track movement of the
LNAPL), downgradient. from OU4 (to detect. dissolved-phase and LNAPL plume
migration off site), within Sand Creek (to assess the possible discharge of contaminated
groundwater to surface water), and iDimediately north of Sand .Creek (to detect any
migration of contaminants under the creek). Samples will initially be collected
quarterly, but may be collected less frequently if data indicate that site conditions are
not changing significantly on a quarterly basis. In addition, the !ive private wells that
are completed in the shallow alluvium in the vicinity of. OU4 will be sampled and
evaluated as part of the OU4 gro~ndwater monitoring pro~. EP A and CDH will
notify and provide recommendations to the users if contamination is detected. .
Institutional Controls - EP A and CDH will coordinate with local officials and property
. owners, and will.request the use and implementation Qf institutional controls at the .
Site. Zoning restrictions, .including r~ommendations against well usage for doinestic
purposes, will be proposed in order to minimize potential future human exposure to
contaminated groundwater underlying the site. These objectives are already achieved
in part through state advisories. against the construction of water wells in areas with
known contamination. Additional institutional controls .that may be impleinented as
necessary include subdivision regulations, building permits, recording requirements,
state statutes, local ordinances, and deed restrictions and notices implemented by
current property owners.
Alternative 1: No Action.
The Superfund program requires that the "N~Action" alternative be considered at every site..
The No Action alternative establishes a baseline for comparison of other alternatives. Under
this alternative, EP A would not remove, treat, or contain the LNAPL plume or contaminated
groundwater. However, groundwater contamination levels may be reduced over the long-term
through natural attenuation. EP A could set specific action levels and take remedial action at
OU4 in the future if warranted by a change in site conditions. .
. Alternative 2: Monitoring and Institutional Controls
As with Alternative 1, EP A would take no action to remove, treat, or contain the LNAPL plume
or contaminated groundwater. However, steps would be taken to limit human exposure to
. contaminated groundwater through the. implementation of local institutional controls. In
addition, monitoring of groundwater and surface water at the Site would be performed to
evaluate changes in site conditions. Natural attenuation processes would reduce contaminant
concentrations in groundwater over the long-term. As with Alternative 1, EP A could set
specific action levels and implement remedial action in the future if warranted by a change in
site conditions. .
-------
Alternative 3: Monitoring and Institutional Controls with LNAPL Removal
Alternative 3 is similar to Alternative 2, with the addition of removal of the LNAPL plume.
The principal elements of this alternative are:
.'
Dual vapor extraction (DVE) wells would be installed in the LNAPL plume area.
LNAPL vapors and liquids removed from the subsurface would pass through an
airlliquid separator, and the resulting liquid stream would flow through an
oil/water separator to recover free-phase LNAPL. Recovered LNAPL would be
transported off site to a recycling facility. Water from the oilIwater separator
would be' transported to an on-site groundwater treatment' facility. LNAPL
vapors from the airlliquid separator would be transported by pipeline to the soil
vapor extraction (SVE) system in operatio~ at OUI for treatment by the existing
catalytic oxidation unit.
Water received at the treatment facility from the DVE syStem oilIwater separator
would first be pre-treated for metals removal using chemical precipitation
followed by sedimentation. Groundwater pretreatment for metals is necessary
to prevent potential fouling and clogging of the air stripper. The water would
then pass through an air stripper where volatile contaminants would be
removed. In particular, air stripping would remove vinyl chloride and
methylene chloride, which would tend to pass through the granular activated
carbon (GAq unit. Treatment of the off-gas from the air stripper may be
, required depending upon the level of emissions. Uquid phaseGAC would
follow as the final treatment prOCess, however, a detailed engineering evaluation
could result in a re-sequencing of the air stripping and GAC treatment
processes. Spent GAC would be regenerated off site.
.
.
Treated groundwater would be injected on site, upgradient of the extraction
wells. EP A permitting (SDW A mc Oass 5 permit) and testing prior to injecti.on
would occur as necessary. .
Alternative 4: Limite~ Containment of LNAPL using a ,Cutoff Wall ,
, ,
, ,
Alternative 4 is similar to Alternative 3 with the exception that the LNAPL plume would be
contained, rather than removed. The principal elements of this alterI).ative are:
.
A vibrating beam wall would be constructed along the northern and eastern
edges of the LNAPL plume (Figures 7 and 8) to contain and prevent further
migration of the ,LNAPL plume and associated dissolved-phase groundwater
contamination, and therefore prevent further degradation of the groUndwater.
A serieS of extraction wells woUld be constructed up gradient and adjacent to the
Vibrating beam wall. Groundwater would be pumped, only as necessary, to
reduce the pressure and prevent flow around the wall.
.'
.
Extracted groundwater would be transported by pipeline to an on-site treatment
facility.
-------
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"'..... "::~>.. ">..;,.(iJ -. Figure 1
"" '~':::~~':>."'" '. e -.. Localized and Site - Wide Extent of Remediation
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-------
USEPA f\
Sand Creek Industrial Suponind Site **r
OU4 Record of Decision
Figures
Detail of Localized Extent of Remediation and
Proposed Vibrating Wall Location
Colorado
Organic
Chemical Company/
LEGEND
CfUM ol
Fra«-P>>OM (UWL)
VlbraVfif B««m Wai lor
£ Aquifer 1 menJIenn^ *•!
• Aquifer 2 monftcwmfl w«l
.£. UwtHonnf *rf •erc*n«4
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A T«At«tfvt CvtrKtton Wtl Ue«r«n
Jl
-------
.
Groundwater would be treated to reduce concentrations of metals and organic
compounds, as described under Alternative 3. Any LNAPL withdrawn with the
groundwater would be separated out with an oi1Jwater separator prior to
groun~water treatment and be transported off site to a recycling center.
.
Treated groundwater would be injected on site, downgradient of the vibrating
beam wall. EPA permitting (Safe Drinking Water Act (SDWA) Underground'
Injection Control (UIq Gass 5 permit) and testing prior to injection would occur
as necessary. . .
No additional removal, treatment or containment of the groundwater would
occur except for the removal and treatment necessary to maintain the integrity
arid effectiveness of the containment system.
Alternative. 5: Localized Pump. and Treat with LNAP~ Contaiiunent and Groundwater
Treatment by GAC and Air Stripping .
.
In this alternative, as well as the following alternatives, dissolved phase contaminants in
groundwater are specifically targeted for remediation. The LNAPL plume is contained as
described in Alternative 4. The major ele;ments of this alternative are:
.
A series of extraction wells would be constructed within the localized extent of
groundwater remediation area defined on Figures 7 and 8.
.
. .
. .
Umited containment of the LNAPL plume (vibrating beam wall), as described.
in Alternative 4, would be implemented in conjunction with the pump and treat
system. .
.
Groundwater would be pumped and transported by pipeline tp an on-site
treatment facility. The contaminated groundwater would be treated to reduce
~eve1s of metals and organic compounds, as described under Alternative 3.
.
. .
Treated groundwater woul.d. be injected downgradient of the vibrating beam .
wall. EP A permitting (SDW A mc Class 5 'permit) and testing prior to injection
would occur B:s necessary. . .
Alternative 6: Localized Pump and Treat with LNAPL Removal and Groundwater Treatment
by GAC and Air Stripping
Alternative 6 is identical to Alternative 5 with the exception that .the LNAPL plume would be
removed, rather than contained. The major components of this alternative are:
.
.. A series of extraction wells would be constructed within the localized area
defined on Figure 7. Groundwater would be pumped and transported by
pipeline to an on-site treatment facility, where it would be treated to reduce
concentrations of metals and organic compounds, as described under Alternative
3. .
-------
.
DYE wells would be installed in the LNAPL plume area. LNAPL vapors and
liquids removed by the DVE wells would pass through an air/liquid separator,
and the resulting liquids stream would flow through an oil/water separator to
recover free-phase LNAPL. Recovered LNAPL would be transported off site to
. a recycling facility. Water from the oil/water separator would be transported to
an on-site groundwater treatment facility where it would be treated with
groundwater removed by the localized extraction system. LNAPL vapors from
the airlliquid separator would be transported by pipeline for treatment by the
catalytic oxidation unit in operation at the OUl SVE system.
.
Treated groundwater would be injected back into the shallow aquifer. EPA
permitting (SDW A UIC Class 5 permit) and testing prior to injection would
occur as necessary. . .
. .
Alternative 7:. Localized Pump and Treat with LNAPL Containment and Groundwater'
Treatment by UV Oxidation
Alternative 7 is similar to Alternative 5 with the primary difference being the groundwater
treatment method. This alternative would use UV oxidation, rather than air stripping and GAC
. filtr~tion for treatment of contaminated groundwater. Since UV oxidation is an innovative and
unproven technology, a treatability study would be performed prior to implementation of
Alternative 7 to verify the effectiveness of the treatment process at OU4. The principal
components, of Alternative 7 are:
.
. .
, . .
. ,
. A series of extraction wells would be constructed within the localized extent of
groundwater remediation area defined on Figures 7 and 8.
.
Limited containment of the LNAPL plume (vibrating beam wall), as descri1?eci
in Alternative 4, would be implemented in conjunction with the pump and treat
system. .
.
Groundwater would be pumped and transported by pipeline to an on-site
~ea~ent facility. . .
.
Any LNAPL withdrawn with the groundwater would be separated out with an
oil/water separator and transported off site to a recycling center. The
groundwater treatment process would consist of pre-treatment for metals using
chemical precipitation followed by sedimentation. The water would then pass
through a UV oxidation unit to remove VOCs. H ozone is used in the treatment
process, off-gas from the t:;reatment process would pass through an ozone
decomposer before air venting.
.
.' Treated groundwater would be injected downgradient of the vibrating beam
wall. EP A permitting (SDW A UlC Class 5 permit) and testing prior to injection
would occur as necessary.
-------
Alternative 8: Localized Pump and Treat with LNAPL Removal and Groundwater Treatment
by UV Oxidation
This alternative is similar to Alternative 7 in that it includes a localized pump and treat system
and the use of UV oxidation in treating contaminated groundw~ter. The main difference is that
Alternative 8 provides for removal of the LNAPL plume, rather than containment. As with .
Alternative 7, a treatability study would need to be performed prior to implementation of the
alternative to verify the effectiveness of UV oxidation in treating contaminated groundwater at
OU4. The prinuiry elements of this alternative include:
.
A series of extraction wells would be constructed within the localized area
defined on Figures 7 and 8. Groundwater would be pumped and transported
by pipeline to an on-site treatment facility. .
A DYE s~tem. 'w~uld be installed in the LNAPL plume area and operated as . .
described under Alternative 3. .
,
.
Water received at the treatment facility from both the groundwater extraction
system and the dual vapor extraction system would treated as described under
Alternative 7.
.
Treated groundwater would be injected back into the shallow aquifer. EPA
permitting (SDW A mc Gass .s permit) and testing prior to inj~on would
. occur as necessary. . .
Alternative 9:. Site-Wide Pump and Treat for Total Groundwater Restoration with LNAPL
Containment .
Alternative 9 consists of the same basic elements as Alternative .s except that the scope of the
remedial action is more comprehensive. In this alternative C! site-wide groundwater extraction
system would be constructed, rather than focusing only on the most highly contaminated area
near the COCC and LCe properties.
...
. .
A series of extraction wells would be constructed throughout the entire site (see
site-wide extent of groundwater remediation on Figure 7).
.
limited containment of the LNAPL plume (vibrating beam wall), as described
in Alternative 4, would be implemented in conjunction with the pump and treat
system.
.
Groundwater would be pumped and transported by a conveyance system
. (pipelines) to an on-site treatment facility. Groundwater treatment for metals
..and organic compounds would occur as described in Alternative 3.' .
.
Treated groundwater would be injected downgradient of the vibrating beam
wall. EP A permitting (SDW A UIC Gass 5 permit) and testing prior to injection
would occur as necessary.
-------
Alternative 10: Site-Wide Pump and Treat for Total Groundwater Restoration with LNAPt
Removal
This alternative is similar to Alternative 9 in that sit~wide .remediation would occur, but the
LNAPL plume would be removed rather than contained. Following completion of the remedial
action, the Site would be available for unrestricted commercial andlor industrial use. The
principal components of this alternative are:
.
A series of extraction wells would be constructed throughout the entire Site, as
indicated in Figure 7. Groundwater would be pumped and transported by
pipeline to an on-site treatment facility. . .
.
A DVE system would be installed in the LNAPL plume area, as described in
Alternative 3.
.
Contanrlnated water received at the treatme~t facility from both the groundwater
extraction system and the dual vapor extraction system would treated for metals
and organic compounds as described under. Alternative 3. .
.
Treated groundwater wo~d be injected back into the shallow aquifer. EPA
permitting (SDW A UIC Gass 5 permit) and testing prior to injection would
occur as necessary.
VIn. SUMMARY O~ COMPARATIvE ANALYSIS. OF ALTERNATIVES.. .
In this section, alternatives developed for OU4 are evaluated and compared to each other using
the nine evaluation criteria required by the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP; 40 CFR ~ 300.430) to identify the alternative that provides the best
balance among the criteria. The relative performance of the alternatives is sununarized by
highlighting the key differences among the alternatives in relation to the following criteria:
1. Overall Protection of Human Health and the Environment; .
2. Compliance with Applicable, or Relevant and Appropriate Requirements'(ARARs); ,
3. Long-Term Effectiveness and Permanence; .
4. Reduction of Toxi~ty, Mobility, or Volume Through Treatment;
5. Short-Term Effectiveness;
6. Implementability;
7. Cost;
8. State Acceptance; and
9. Community Acceptance.
The NCP defines the first two criteria as threshold criteria which must be met by the. '
alternative. .The succeeding five criteria, termed balancing criteria, form the primary criteria
on which the detailed analysis of alternatives is based. The last two criteria are modifying
criteria 'and were evaluated after public comment on the Proposed Plan is received.
-------
A.
Overall Protection of Human Health and the Environment
This criterion assesses the protection afforded by each alternative, considering the
magnitude of the residual risk remaining at the Site after the remedial action has been
completed. Protectiveness is determined by evaluating how site risks from each
exposure route are eliminated, reduced, or' controlled by the specific alternative~ The
evaluation also takes into account short-term or cross-media impacts that result from
implementation of the alternative remedial activity.
Although groundwater in the'area is classified as a potential drinking water supply by
the State of Colorado~ there is no 'unacceptable curi'ent health-risk due to ingestion,
inhalation, or skin contact with contaminated groundwater because water for residential
use is provided through treated water from either the DWD or SACWSD.
, Alternative 10 is the ,most protective of huma.n h~alth and the environment and would,
allow future commercial/industrial use 'of the Site without engineering or institutional
controls and without limitations on the exposures for human and environmental
receptors. Alternative 1 provides the least protection to human health and the
environment of the ten alternatives. Contaminant levels would only be, reduced
through natural attenuation under Alternatives 1 and 2, arid the LNAPL and dissolved
contaminant plumes are not contained or treated. Remedial action could be taken
under Alternatives 1 and 2, however, if future information' indicates ,that the
contamination migrates to either Sand Creek or the underlying aquifers. Alternatives
2 through 10 would, provide overall protection to human heal~ through the use. 'of
instirotiortal controls which would limit human exposure to 'con~ted 'media.
Migration of the LNAPL plume which could potentially threaten Sand Creek, Metro
sanitary sewer lines, or downgradient wells is prevented by the installation of a
vibrating beam wall in Alternatives 4,5, 7, and 9. However, Alternatives 3, 6,8, and
10 would provide relatively greater protection from potential effects from exposure to
the LNAPL by removing the recoverable LNAPL from the Site, rather than containing
it. Site-wide groundwater remediation included in Alternatives 9 and 10 would provide
relatively greater protection of human health and the environm,ent at OU4 than the
localized groundwater ,remediation proposed under Altemati,ves 5 through '8.
B.
Compliance with ARARs
Section 121(d) of SARA mandates that for all remedial' actions conducted under
CERCLA, cleanup activities, must be conducted in a manner that complies with ARARs,
or if.ARARs cannot be attained a justifiable waiver must be obtained. The NCP and
SARA have defined applicable requirements and relevant and appropriate requirements
as follows:
'.
Appli~able reqUirements are'those federal imd state r~eIrients that would be '
"legally applicable, either directly, or as incorporated by a federally authorized
state program.
.
Relevant and appropriate requirements are those federal and state requirements
that, while not legally "applicable," are designed to apply to problems
-------
.
sufficiently similar to those encountered at CERCLA sites that their application
, is appropriate. Requirements may be relevant and appropriate if they would
otherwise be "applicable," except for jurisdictional restrictions associated with
. the requirement.
Other requirements to be considered are federal and state non-regulatory
requirements, such as guidance documents or criteria. Advisories or guidance
documents do not have the status of potential ARARs. However, where there
are no specific ARARs for a chemical or situation, or where such ARARs are not
sufficient to be protective, guidance or advisories should be identified and used
to ensure that a remedy is protective.
Federal and state ARARs which must be considered include those that are: chemical-
specific, location-specific, and action-specific. Chemical-specific ARARs govern t:l}e
'extent of site cleanup in terms of actual treatment . levels. Location-specific, ARARs
govern natural features such as wetlands and floodplains, and man-made features such
as archeological and historic areas. Action-specific ARARs are technology- or activity-
based requirements that set restrictions on particular kinds of actions at CERCLA sites.
Table 3 summarizes the potential ARARs and guidance, advisories, and criteria to be
considered (TBCs) for OU4. All alternatives would likely comply with pertinent
chemical-, action- and location-specific ARARs. Alternatives which involve withdrawal,
, ' treatment, and injection of groundwater (Alternatives 3 through 10) will be requirec:t to
. achieve Safe Drinking Water Act Maximum Contaminant Levels (SDW A MCLs) an4lor
state standards prior to groundwater injection. Contaminated groundwater attributable'
to the Site would also be required to meet SDW A MCLs and/or state groundwater
standards at the downgradient (i.e., northern) Site boundary. There are no chemical-
specific ARARs for Alternative 1 since no activity would occur.
Wells installed for monitoring andlor extraction and injection systems in Alternatives ,
2 through 10 would be subject to the requirements of the Colorado Departmept of
Natural Resources, State Engineer's Office. . Additional action-specific ARARs that
. Alternatives 3 thro~gh 10 must comply with include: state air regulations ,for emissions
from the LNAPL and groundwater' treatment systems; the Hazardous Materials
Transportation Act (HMTA) and the Resource Conservation and Recovery Act (RCRA)
for the off.site transport of treatment residuals; and RCRA for waste disposal, reuse,
, and recycling. There are no action-specific ARARs for Alternati'!'e 1 since no activity
would occur. .
Compliance with location-specific ARARs for alternatives that include the vibrating
beam wall, extraction and injection systems, or treatment facilities (Le., Alternatives 3
through 10) would depend on the location of these components. Howev~, no
prot~ properties have been identified in the immedi8.te vicinity of OU4.
Guidance regarding ambient air levels of toxic air pollutants (National Ambient Air
Quality Standards, NMQSs) should be considered for designing air pollution controls
for the Site. The EP A Reference Concentrations and Slope Factors would be used to
calculate the hazar~ indices and the risk levels. The State of Colorado considers the
-------
TABLE 3
SELECTED POTENTIAL ARARs AND TBCs FOR
OPERABLE UNIT 4, SAND CREEK INDUSTRIAL SUPERFUND SITE
RenJation atation Comments
ARAR.8
Resource Conservation and Recovery 42 USC S 6901 ARAR if Remedial Action
Act 40 a:R Parts 260-268 involves hazanious waste or
suffic::ientlv similar material.
Safe Drinking Water Act - 42 USC S 300 (g) ARAR if Remedial Action
Underground Injection Control 40 a:R Parts 144 - 147 ~~ injection of
Re2ulations water. .
Primary Drinking Water Regulations 42 USC S 300 (f) Indudes final maximum
40 a:R Part 141 contlUninant levels (MCLs)
and Ma goals (MaGs)
greater than zero. May serve
as treatment level prior to .
iniection.
Colorado Classification and Water S CCR 1002-8 May serve as dean-up and/or
Quality Control Act treatment levels. Contains
allowance for variance at
CERa.A sites.
Colorado Basic Standards for S CCR 1002-8 May serve as dean-up and/or
Groundwater treatment levels. Contains
allowance for variance at
CERa.A sites.
Hazardous Materials Transportation 49 S 1801 !tt:. ~ ARAR if hazardous materials
Act 49 a:R Parts 107. 171, 172 are trans'OOrted off site.
Cean'Air Act 42 USC S 7412 ~
. NSPS 40 a:R Part 60 ARAR if Remedial Action
involves regulated new
source(s).
. PSD requirementS ' 40 a:R Part 52 ARAR if RA involves major
new source(s) of 501 or N01.
. NESHAPs 40 a:R Part 61 ARAR if RA involves emission
of a regulated pollutant &om
a re2Ulated 'source.
. Colorado Air Pollution Control ., S CCR 1001-1 ~
Regulations ..
. Regulation 1 SCCR 1001-3 Regulates emission of SO~
particulates and smoke.
. Regulation 2 S CCR 1001-4 Regulates odorous emissions
&om a single source.
. Regulation 3 S CCR 1001-5 Sets permitting requirements,
only substantive requirements
may be ARARs.
. Regulation 6 S CCR 1001-8 Sets perfonnance standards
for new emissions sources.
. Re2u1a.tion 7 S CCR 1001-9 Re2Ulates VOC emissions.
Colorado Revised and Amended Rules 2 CCR 402-2 ARAR for groundwater
and Regulations of the Board of monitoring weD installation
Examiners of Water Well Construction and abandonment activities.
and Puntn Installation Contractors
. Executive Order on Floodplain Executive Order 11988 ARAR if designated floodplain
. Manasr:ement 40 a:R Part 6:302lb\ . is affected.
Executive Order on Protection of Executive Order 11990 ARAR if designated wetland
Wetlands 40 a:R Part 6.302 (a) is affected.
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TABLE 3
SELECTED POTENTIAL ARARs AND TBCs FOR
OPERABLE UNIT 4, SAND CREEK INDUSTRIAL SUPERFUND SITE
I Regulation I atation I Comments I
I TBCa I
Oean Air Act - 42 use 5 7401 ARAR if more than 250
National Ambient Air Quality 40 a:R Part 50 tonslyear of SO, or NO, or
Standalds (NAAQS) 100 tonslyear of PM-IO, CO or
0) are emitted &om RA
treatment facilitv.
Massachusetts Allowable Code of MaSsachusetts Regulations The State of Colorado
Ambient Levels Title 310 5 6.04 considers these air quality
standards a TBC.
Safe Drinking Water Act National 42 USC 5 300 (f) May serve as clean-up level
Primary Drinking Water Standards - 40 a:R Parts 141.11 and 141.16 ' for treating groundwater prior
PropOsed, to injection.
Colorado Interim Organic Pollutant 5 CCR 1002-8 May serve as clean-up level
Standalds for treating groundwater prior
to iniection.
Superfund LDR Guide 15 ,EPA OSWER Directive 9347.3-0SFS Guidance for on-site disposal
of hazardous waste.
" Superfund LDR Guide 17 EPA OSWER Directive 9347.3-08FS Guidance for on-site disposal
of hazardous waste. .
EPA Guidance Document EPA OSWER Directive 9355.0-28 Guidance for control of
'emjssions &om air strippers at
S~nd sites. ,"
CERaA Petroleum Exclusion Cause 42 USC 5 101 (4) Limits CERaA authority and
42 USC 5 104 (a) funding for removal and
treatment of petrolewn
oroduct.
Adams County Zoning Regulations - May affect institutional
controls.
-------
Massachusetts Ambient Air Level standards as important guidance. EP A has issued
a policy statement regarding air emission controls for air strippers located in ozone non-
attainment areas and believes that this policy is a TEC because Denver is an ozone non-
attainment area (OSWER Directive 9355.0-28). Other TECs identified for OU4 are the
CERa.A Petroleum Exclusion, and EP A guidance .regarding land disposal restrictions.
C.
Long-Term Effectiveness and Permanence
The focus of this criterion is to determine the effectiveness of each alternative with
respect to the risk posed by treatment of residuals and/or untreated wastes .after the
cleanup criteria have been achieved. Several components were addressed in making
the determinations, including:
.
. Magnitude of residual risk from the alternative;
Likelihood. that the alternative will meet process efficiencies and performance
specifications;
.
.
Adequacy and reliability of long-term management controls providing continued
protection from residuals; and
.
Associated risks in the event the technology or permanent facilities must be
replaced. .
. .
Alternative 10 would provide the greatest .degree of .long-t~ effectiveness since
contaminants would be permanently removed flom the Site and no residual risks would
remain. Alternatives 2 through 9 would be effective at limiting contact with and
ingestion of contaminated groundwater in the long term provided that institutional
controls are effective. The No-Action alternative would not provide long-term
effectiveness. Alternatives 3 through 10 effectively prevent the spread of the LNAPL
plume and a portion of the dissolved contaminant plumes in the long term provided
the integrity of the vibrating beam wallis maintained or the dual extraction system
operates satisfactorily. The long-term effectiveness of groundwater remediation in
.Alternatives 5 ~ough 10depends upon continual remediation since re-contaIIliruition .
of the site would occUr due to upgradient sources once the OU4 pump and treat system ". .
was shut down.
D.
Reduction of Toxicity; Mobility, or Volume Through Treatment
This criterion evaluates the ability of the alternatives to significantly achieve reduction
of the toxicity, mobility, or volume ~f the contaminants or wastes at the site through
treatment. The criterion is a principal statutory requirement of CERa.A. This analysis
evaluates the quantity of contaminants treated and destroyed, the degree of expected .
reduction in toxicity, mobility, or volume measured as a percentage of reduction, the .
degree to which the treatment will be irreversible, the type and quantity of residuals
produced, and the manner in which the principal threat will be addressed through
treatment. The risk posed by residuals is considered in determining the adequacy of
reduced toxicity and mobility achieved by each alternative. .
-------
Alternative 10, followed by Alternative 9, provide the greatest reduction in toxicity,
mobility and volume of contamination through total restoration of groundwater (versus
localized groundwater remediation under Alternatives 5 through 8) at the Site. Removal
of the LNAPL plume in Alternatives 3, 6, 8, and 10 would reduce the volume of
LNAPL, rather than simply reduce its mobility as would be accomplished with the
. vibrating beam wall in Altematives4, 5,7, and 9. No reduction in contaminant toxicity,
mobility, or volume, other than by natural processes, would occur under Alternatives
1 and 2. Alternative 4 reduces the mobility of the LNAPL plume, but would provide
only a minimal reduction in contaminant toxicity and volume by treatment only of
groundwater extracted to maintain the integrity of the vibrating beam wall. Upgradient
sources would provide a continuous source of. contaminants (LNAPL and VOCS) to the
OU4 area under all the alternatives.
E.
Short-Term Effectiveness
, The short-term effectiveness of each alternative was assessed based on the risk
associated with the implementation of the remedial action to the community, workers,
and environment and the time required to achieve the response objectives. Measures
to mitigate releases and provide protection are central to this determination.
All of the alternatives except for Alternative 1 would provide a similar degree of short-
term effectiveness by protecting the community, workers, and environment through
adequate preventative measures. These preventative measures include items such as
. estab~hing .exclusion zones during. remedial activities, use of personal protective
.' equipment for onsite workers, and dust control practices. The greater scope of
construction activities associated with site-wide groundwater remediation in
AlternativeS 9 and 10 would result in slightly higher short-term risks as compared with
the localized treatment or containment actions included in the other alternatives.
However, standard engineering controls and adherence to standard health and safety
practices would minimize potential adverse short-term impacts. Alternative 1 would
provide the least amount of short-term effectiveness. The time until the response
objectives are achieved for Alternatives 5 through 10 is unknown because the duration
of re~ediation at 0I!4 is largely dependant on removing 1:lpgradient sources of
. contamination' (LNAPL and 'upgradient .contaminated groundwater).. For cos~g
purposes, it was assumed that at least 30 years would be necessary.
F.
Implementability
This criterion analyzes technical and administrative feasibility, and the availability of
services and materials. Technical feasibility assesses the difficulty of construction or
operation of a particular alternative and uncertainties associat~ with process
technologies. The reliability of the technologies based on the likelihood of technical
problems that would lead to proj~ delays is critical in this determination. . The ability
to monitor the effectiveness of the alternative is also considered.
Administrative feasibility assesses the ease or difficulty of obtaining permits or rights-of-
way for construction. Availability of services and materials evaluates the need for off-
site treatment, storage, or disposal services, and. the availability of such services.
-------
Necessary equipment, specialists, and additional resources are also evaluated in
determining the ease by which these needs could be fulfilled.
All of the alternatives under consideration, except those involving site-wide remediation
(Alternatives 9 and 10), are both technically and administratively feasible, although
implementation of Alternative 1 is unlikely from an administrative standpoint. It is
doubtful that regulatory agencies or the public would accept a No Action alternative for
OU4. Alternative 2 is the easiest to implement because relatively little construction
would be involved. Alternatives 3 through 6, 9 and 10 involve the utilization of readily
available, proven technologies. Alternatives 7 and 8 woul4 be more difficult to
implement because they incorporate an innovative, unproven technology (i.e., UV
oxidation) requiring a treatability study. The larger scope of the remedial effort under
Alternatives 9 and 10 and the presence of upgradient contaminant sources would make
implementation of these alternatives much more difficult than that associated with
. alternatives invol~g localized or no groundwater remediation. .
G.
Cost
Alternatives are evaluated for cost in terms of both capital costs and long-term O&M
costs necessary to ensure continued effectiveness of the alternatives. Capital costs
include the sum of the direct capital costs (materials, equipment, labor, land purchases)
and indirect capital costs (engineering, licenses, or permits). Long-term O&M costs
include labor, materials, energy, equipment replacement, disposal, and sampling
nec~ssary to imp~ement the alternative. ~e objective of the cost analysis is to ~te
those alternatives that (1) do not provide measurably greater.protection of human h~alth
and the environment, and (2) include costs that are substantially greater than those of .
other alternatives.
The present worth analysis is used to evaluate expenditures that would occur during
different time periods. By discounting all costs to a common base year (Le., 1994), the
costs can be compared on the basis of a single figure for each alternative. Total present.
worth costs were calculated by multiplying the capital and O&M cost incurred during
each year by the present wor:th factor. 'An interest rate of 5% and a project duration of
30'years w~s.used in accordance with.EPA guidance.
The estimated costs associated with each alternative are shown in Table 4. The total
present worth costs range from $22,300 for Alternative 1 to $ 22,312,400 for Alternative
10. Alternatives that include site-wide groundwater treatment bave high capital and
O&M costs, whereas alternatives that address localized contamination have medium
capital and O&M costs. However it should be noted that the 3O-year estimate for
project duration may not be accurate for those alternatives involv:mg groundwater
treatment. It is not expected that groundwater up gradient of OU4 will attain MCLs in
'the foteseeablefuture, nor is it known if the groundwater pump and treat component
of Alternatives 5 through 10 will be capable of removing all groundwater contamination
in a 3O-year period. Therefore, costs associated with Alternatives may be significantly
higher than estimates provided in Table 4. Alternatives that incorporate removal of the
LNAPL plume, rather than containment of the plume, have relatively lower present
worth costs. Cost savings in those alternatives that include LNAPL
-------
TABLE 4
COSTS ASSOCIATED WITH ALTERNATIVES DEVELOPED FOR OU4
(1994 DOLLARS) .
.. " .. '"
.. ..... '"
... ...... . . . ..... .. . ,,,,,,",.
:;::~~~~~.:j:....:;:;=~~::i:.-!:!..;.:.:::::;!.j:i!ji:i!::.;.::~t5;i~:;:;:;:::~::.:.: ..~~=~:~i..:I:.
1 $0 $ 8,000 $ 22,300
2 $ 37,300 $ 186,200 $ 2,799,000
,
:3 $ 256,200 $ 241,400 $ 3,866,500.
4 $ 2,683~2oo $ 359,000 $ 8,101,300
5 $ 2,847,600 $ 392,700 $ 8,783,700
6 $ 448,600 $ 250,700 $ 4,201,900
7 $ 3,146,600 $ 567,200 $ 11,765,200
8 $ 1,435,800 $ 484,300 $ 8,780,000
9 $ 5,158,500 $1,117,500 $ 22,236,600
..
10 $ 5,202,100 $ 1,119;600 $22,312,400
-------
removal (Alternatives 3, 6, 8, and 10) are anticipated by utilizing the existing OUI SVE
system and treatment facilities as well as associated O&M activities, as opposed to
building and operating new facilities.
H.
State Acceptance
This criterion evaluates technical and administrative issues that may be raised by the
State. EP A has involved CDH throughout the RIlFS and remedy selection process. The
State of Colorado concurs with EPA's selected alternative, as presented in Section IX.
I.
Community Acceptance
This criterion evaluates questions and comments on the Proposed Plan received from
members of the community. Few comments were received on the OU4 Proposed Plan,
and it appears that community accepts EPA's selected remedy, as presented in Section
~. EP A's responses to oral and written comments are provj,ded in the Responsiveness,
Summary of this ROD (Appendix A).
SELECTED REMEDY
IX.
EP A has selected Alternative 3 as the remedy for OU4. The remedial action selected for OU4
will restrict direct contact with and ingestion 'of groundwater underlying the Site' and will
protect currently uncontaminated groundwater. Five-year reviews of the Site will be required
because contaminants will remain at OU4 following completion of the remedial action. This
remedy ,is comprised of the following compon~nts~ '
Groundwater and Surface Water MonitorinS - Existing and future groundwater
monitoring wells (a total of approximately 16) will be sampled and analyzed periodically
throughout OU4 to assess the effectiveness of ongoing remedial activities or changes
in natural conditions. Samples will be analyzed for the presence ofVOCs, semi-volatile
compounds, pesticides, and metals. Monitoring poInts will be located upgradient of,the
Site (to detect contamination from other sources), downgradient of the LNAPL plume
(to track potential plume movement), downgradient from OU4 (to detect contaminant
migration off, site), within Sand Creek (to assess the iIt'\pacts of contaminated.
groundwater possibly discharging 'to surface' water) and imme~tely north of Sand
Creek (to detect any potential migration of contaminants under the creek). Samples will
initially be collected quarterly for at least one year but may be, collected less frequently
(i.e., semi annually or annually) if data indicate that site conditions are not changing
significantly on a quarterly basis. For costing purposes, it was assumed that quarterly
monitoring would be conducted for a period of 30 years. However, actual monitoring
will continue for as long as contaminant concentrations in groundwater at the Site
boundary exceed SDW A MCLs or state groundwater standards. In addition, the five
private wells that are ~ompleted in the shallow alluvium u,. the vicinity of OU4 will be
sampl~ once and evaluated as part of the OU4 groundwater monitoring program. EP A
and CDH will notify and provide recommendations to the users if contamination is
detected.
-------
Institutional Controls - EPA and CDH will coordinate with local officials and property
owners, and will request the implementation of institutional controls at the Site.
Zoning restrictions, including recommendations against well usage for domestic
purposes, willbe implemented to the extent possible to prevent future human exposure
to contaminated groundwater underlying the site. These objectives are already achieved
in part through state advisories against the construction of water wells in areas with
known contamination. Additional institutional controls that may be implemented as
necessary include subdi~ion regulations, building permits, recording requirements,
" state statutes, local ordinances, and deed restrictions and notices implemented by
current property owners. Table 5 provides additional information on the Institutional
controls available for OU4.
LNAPL Removal - A DVE system (Figure 9) will be used to remove both LNAPL vapors
and liquids from the "su~urface. Vapors will be extracted by applying" a vaoium to the "
well, as in SVE. The applied vacuum will also create a hydraulic gradient toward the"
well, causing LNAPL and groundwater to flow to the extraction well. LNAPL can then
be recovered without creating a drawdown of the water table.
Higher overcill removal rates can be achieved using a DVE system, as opposed to
pumping liquids only. The greater removal efficiency is achieved by extracting vapors"
from the LNAPL plume as well as liquids. In addition, drawing cUr through the
subsurface enhances biodegradation of additional LNAPL in situ, further expediting
r~ediation. By combining liquids extraction, volatilization, and biodegra~tion, a DVE :
. system is considered to be significantly. more effective than a liquids only extraCtion
system. It is expected that the eXcess capacity of the catalytic oxidation unit in
operation at the OUt SVE system can be used for treating vapors removed by the DVE
wells,. thereby. reducing construction time and costs.
Approximately twenty DVE wells will be installed in the center of the LNAPL plume
area shown in Figures 7 and 8. The location of the wells will be restricted based on .
planned OUS excavation activities. INAPL vapors and liquid removed from the
subsurface will pass through an airlliquid separator, and the ~esulting liquid$ stream
. will flow .through" an oil/water separator to recover free-phase LNAPL. Recovered
LNAPL will be transported off site to a recycling facility. Water from the oil/water
separator will be piped to an on-site groundwater treatment facility. LNAPL vapors
from the airlliquids separator will be transported by pipeline to the SVE system in
operation at OUt for treatment by the existing catalytic oxidation. unit.
Water received at the treatment facility from the DVE oil/water separator will first be
pre-treated for metals removal uSing chemical precipitation followed by sedimentation.
Groundwater pretreatment for metals is necessary to prevent potential fouling and
clogging of-the air stripper. The water will then pass through the air stripper where
volatile contaminants will be removed. In particular, air stripping will remove vinyl
chloride and methylene chloride which would tend to pass through the GAC unit
Treatment of the off-gas from the air stripper with a thermal or catalytic oxidation unit
may be required depending upon the level of emissions. liquid phase GAC will follow
as the final treatment process. However, a detailed epgineering evaluation could result
in a re-sequencing of the air stripping and GAC treatment processes. Spent GAC will
-------
TABLE 5
INSTITUTIONAL CONTROLS A, V AILABLE FOR OU4
:::'r!!!'::..:!':::::::::i:.'\;'.:' ;:.:~~~~'i?:'::(:"\:\'(\\::::'i.;:':!.:::\:.:.::::::::::::'. .....
Zoning and
Deed
Restrictions
,c:..
w
Municipal
Water Supply
Limit. or prohibit certain uses of
the property (deed restrictions.
easements, covenanls).
Alert potential future buyers of
property to site risks (deed
notice).
Control the development of site
land (zoning, permits).
Minimize the use of OU4
groundwater as a
domestlclpotable water source.
~~:;.~~e~.
.'::. "~:~:'''f'¥~lft!'::'!r:~~~~!:r;rf!r~J:t::::::..:.:::.:j:::::i:::::!!::::.::::\:\\!!;:::.;:ig:!!!r!rr,::!t:M.1;::I~:~.'~.r.~r:i!?:.
Deed restrictions,
deed notices,
easements,
covenanls,
permits.
Require use of
existing municipal
.water supply.
The OU4 site area faUs within an area already zoned
for Industrial use under the existing Commerce Oty .
Zoning Ordinance. Existing laws prohibit resldendal
development In those portions of the site designated
as 1.2 or 1-3. Colorado Rev. Statute 30-38.114 gives
the Adams County Commissioner authority to . .
enforce zoning by Issuing flnes and Imprls~nment for
violators. County zoning. however, could be revised
to change the cunent zoning of the OU4 sUe area In
the future.
Existing Commerce City Subdivision Regulations
allow.the city councU to prohibit. control or restrict
subdivision/development of property that could place
present or future Inhabitants of the area at risk. The
regulations also require a title check that should
disclose any reCorded Information relating to past site
use and hazards.
EPA could negotlate'a settlement with the PRPs.
which Includes attaching a deed notice or restrictloJ1
to property owned by the PRPs.
Existing zoning laws contribute to prevention of use
of OU4 groundwater for domestic purposes. (OU4
groundwater Is cunently not being used for domestic
pU!poses).
Existing Commerce Oty subdivision regulations
require the collection and anslyses of water samples
prior to subdivision or development of the property
for both residential and non-residential development.
Any such.sampllng at OU4 would disclose the
contaminated state of the groundwater and prevent,
by law, a developer from using the groundwater (or
drlnldng purposes If the proposed development site
Is underlain by contamlnsted groundwater,
Commerce CIty would require an agreement from
SACWSD, or the Denver Water Department If .
applicable regarding the supply of municipal water to
the new development. . .
EPA could negotiate a CERCLA
Section 122 Consent Decree with
OU4 potentially responsible parties
(pRPs) restricting OU4 land use.
EPA may Include In Section 122
Consent Decrees penalty
provisions for violation of the
decree.
EPA could petition the Colorado
Land Use CommissIon to require a
hearing to decide If OU4 should be
designated as an "Area of Interest*
under the Land Use Act. Such a
designation would require any
potential developer to obtain a
permit prior to the development of
any portion of the site.
Persuade the record owners of
OUt property by deed to create an
Easement In Gross to restrict
development of theIr property.
EPA could negotiate a CERaA
122 Consent Decree with OU4
PRPs restrIcting groundw~ter use.
EPA could petition the Colorado
State Engineer to advise against
the drilling of new wells In the
OU4 site area.
The City Council of Commerce
Oty haa the authority under
Colorado Rev. Statute 31-15-708 (1)
(c) to enact an ordinance
prohibiting the drilling or use of
wells In areas In which the
groundwater 15 deemed Injurious
to health. Commerce City has the
'authorlty under Colorado Rev.
Statute 31-16-101 to enforce
ordinances such a8 wen restriction
ordinances with fines and
-------
Estracted liquJd
\---
. _J_--,
-~,
. 1 VeporIUquid'.1 ,
: ~'I
L-_-----_..J
To
A1Irt DlIlh8re
t
Vacuum
Em8dIon
Una
. Vepar
T,na-I08nt
S,......
-'....,
,
_1
,
"
~---r
Dual V8f1«
Eztr8ctkm
Wel"
ODIW8Iar
SepcatDr
~ LNAP;~ "
-1 Tr8=m "
Figure 9. Dual Vapor Extraction (DVE) System
-------
be regenerated off site. Treated groundwater will be injected upgradient of the
extraction wells. EP A permitting (SDW A UIC Oass 5 permit) and testing prior to
injection will occur as necessary.
Remediation Goals and Performance Standards. Remedial action objectives (RAas) developed
for aU4 are:
.
Prevent direct contact with and ingestion of groundwater; and
.
Protect uncontaminated groundwater for current and future use by preventing further
migration of contaminants (both LNAPL and dissolved phase) ~ excess of federal and
state drinking-water standards.
The DVE system will be designed to remove the mobile portion of the LNAPL plUIne located
. near ~e cacc and Lce properties in the northwest pOrtion of aU4. The current estimated
extent of this plume is indicated in Figures 7 and 8. Approximately 50% (190,000 gallons) of
the total LNAPL volume at aU4 is estimated to be mobile under normal fluid flow, but a
.
greater amount of LNAPL recovery is expected due to the addition of residual LNAPL removal
through volatilization by the DVE system. The initial vapor-phase LNAPL removal rate is
expected to be equivalent to approximately 200 gallons per day. The initial liquid-phase
LNAPL removal rate ~ more difficult to estimate due to the lack of sufficient pUInp test data
and uncertainties regarding the actual LNAPL plume thickness. However, an estimated
removal rate of approximately 25 to 75 gallons per day of liquid LNAPL appears reasonable
based on the limited data. ' , .
Completion of removing, the recoverable LNAPL will be determined based on monitoring o(
vapor emissions from the DVE system. Sampling of vapors will ocair under equilibrium
conditions and will be conducted on a monthly basis. Oeanup of the recoverable LNAPL will
be considered completed when the LNAPL vapor removal rate of the DVE system becomes
asymptotic. The specific criteria that must'be met for completion of LNAPL removal are: (1)
a greater than 90% reduction from initial vapor concentrations must be achieved, and (2) the
. ~A;PL removal rate must be less than 10% per month for a three consecutive mOI,\th period.
Groundwater and surface' 'water monitoring at aU4 'will be performed indefinitely Until
concentrations of contaminants meet applicable or relevant and appropriate federal and state
standards. The duration of the aU4 monitoring program will be largely dependant on
remediation of up gradient ground~ater contamination. Remedial action at the Chemical Sales
Company Superfund Site, located immediately southeast of the 48th and Holly Landfill, is
expected to begin during the sununer of 1994 and will address a source of the vac
contamination present in the eastern portion of aU4. '
The points of compliance at aU4 will be groundwater and surface water at Sand Creek along'
the northern' (downgradient) boundary of the Site, and at the groundwater injection wells.
Contaminated groundwater attributable to the Site will be required to meet SDW A MCLs and
more stringent state groundwater standards at the points of compliance. Contaminant levels
in groundwater monitoring wells at the Site will be evaluated and compared with upgradient
(i.e., background) contamination. Table 6 presents the action levels for those caCs at aU4
that have an established federal or state drinking-water standard. The groundwater standard
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TABLE 6
REGULATORY STANDARDS FOR CHEMICALS OF CONCERN AT OU4
'!::~i\!~!:::!~:::::I:lli::_iIlJ!llI_:;:iiii~:ii~iii::::I::it"'_~II:::!~:iil~li~ig-
Benzene 0.005 OOPS
OUorobenzene 0.100 OOPS
OUoroform 0.006 OOPS
CPMSO 0.02 EPA
2,4-D 0.07 SDWA MCL
4.4-DDT 0.0001 OOPS
1 ,2~Dichlorobenzene 0.6 SDWA MCL
1,4-Dichlorobenzene 0.075 SDWA MCL
1,1-Dichloroethene 0.007 SDWA MCL
trans-1,2-Dichloroethene 0.1 SDWA MCL
Dieldrin 0.000002 OOPS
Ethvlbenzene 0.680 OOPS
Methvlene Chloride 0.005 SDWA .MCL
lindane -BHa 0.0002 SDWA MCL
Styrene 0.1 SDWA MCL
T etrachloroethene 0.005 SDWA MCL
Toluene 1 SDWA MCL
1 1.1- Trichloroethane 0.2 SDWA MCL
T richloroethene 0.005 SDWA MCL
Vinyl OUoride 0.002 SDWA MCL
Xvlenes (total) 10 SDWA MCL
Antimonv 0.006 SDWA MCL
Arsenic 0.05 SDWA MCL
Selenium 0.01 OOPS
COPS
SDWA'Ma.
EPA
Colondo Interim Organic Pollutants Standards
Safe Drin1cing Water Act Maximum Contaminant Level
EPA Memonndum on Toxicity of p-OtlolOphenylmethyl Sulfide and its Oxidation Products; &om
Robert Benson. Ph.D.. Toxicologist to Lury Diede OaltUal)' 21.1994).
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for CPMSO was established based on a toxicological study performed by EP A. Concentrations
of COCS that do not have a federal or state drinking-water standard will also be monitored,
and potential risks associated with detected concentrations of these contaminants will be
evaluated. '
x.
STATUtORY DETERMINATIONS
EP A's primary responsibility at Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment. In addition, CERCLA ~ 121
establiShes several other statutory requirements' and preferences. These specify. that when
complete, the selected remedial action for a site must comply with applicable or relevant and
appropriate environmental standards established under federal and state environmental laws
unless a statutory waiver is justified. The selected remedy must also be cost effective and '
utilize permanent solutions and alternative treatment technologies or r~ource, recovery
, technologies to the maximum extent:practicable. Fmally, the statute includes a preference for '
, remedies that employ treatments that permanently and significantly reduce the volUme,'
toxicity, or mobility of hazardous wastes as their principal element. The following discussion
addresses how the selected remedy meets these statutory requirements.
A.
Protection of Human Health and the Environment
EP A/s Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA
(1988) indicates that' protectiveness may be achieved. by reducing exposure through
actio,ns such as co~tainment, limiting access, ot providing an alternative water supply. :
, A contaihment system does not appear to be necessary at OU4 at this time because the
LNAPL and dissolved-phase contaminant plumes are not migrating significantly. This
is due to a relatively flat hydraulic gradient at the Site and the presence of impermeable
clays that inhibit con~t transport. '
Since groundwater is not currently used for drinking water or other domestic uses,
there is presently not a significant health risk at OU4 because of a lack of completed .
exposure pathways. The risks associated with potential future exposure scenarios are
. adeq~ately address~d in the selected remedy by the implementation of LNAPL Ie~oval,
inStitutional controls, and monitoring', Removal o( the' recoverable LNAPL 'will
minimize potential discharges to Sand Creek, the Metro Waste Water sanitary sewer
system, downgradient water supply wells, and will eliminate a potential source of
groundwater contamination. Groundwater and surface-water monitoring will allow for
evaluating the performance of the selected remedy and the need for additional action.
The monitoring program conducted for the 48th and Holly Street Landfill under the
OU3 Unilateral Order will also provide information on changes in groundwater quality
at OU4.
Short-term 'and cross media impacts due to implementation of the selected remedy are
expec'ted to be minimal. Potential risks to human health and environment through
exposure to contaminated groundwater and soil during well installation and
construction of the DVE system will be minimized by the use of appropriate
preventative and protective measures. Potential cross media impacts will be minimized
by proper well construction methods. '
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Due to the presence of upgradient contamination, including petroleum product which
is exempt from remediation under CERCLA, and the residual LNAPL contamination
that is likely to remain at the Site, institutional controls must be used at OU4. The
institutional ~ontrols will minimize risks associated with potential future use' of
contaminated groundwater. Although CERCLA favors active remediation, institutional
controls may be implemented under CERCLA in appropriate circumstances. As
provided by the Preamble to the NCP (55 Federal Register 8666-8706 [March 8, 1990]):
Examples of institutional controls, which generally ~t hUman activities at or
near facilities where hcizard~us substances, pQllutants, or contaminants exist or
will remain onsite, include land and resource use and deed restrictions, well
drilling prohibitions, building permits, and well use advisories and deed notices.
EP A believes... that institutional controls have a valid role in remediation and
are allowed under CERCLA (e.g., Section 121(d)(2)(B)(ii) appears to contemplate
such controls).. Institutional co~trols are.a necessary supplement 'when some
waste is left in place, as it is in most response actions. Also, in some instances
where the balancing of tradeoffs among alternatives during selection of remedy
process indicates no practicable way to actively remediate a site, institutional
controls such as deed restrictions or well-drilling prohibitions are the only means
available to provide protection of human health. .
B.
Compliance with ARARs
The selected remedy will comply with all federal. and state ARARs, ~ which must'
. be considered include those that are chemical-, action-, and location-specific. Potentiai
ARARs identified for OU4 were described in Table 3 and are listed below for the.
selected alternative:
Chemical-specific: For compliance with pertinent chemical-specific ARARs,
contaminated groundwater attributable to the Site will be required to meet applicable
SDW A MCLs (40 CFR Part 141) and applicable state groundwater standards such as the
Colorado Oassmcation and Water Quality Control Act and the Colorado Basic
. Standards for Groundwater (5 CCR 1002-8) at the downgradient Site' Pound~.
Contaminant levels in groundwater monitoring wells at the Site will be evaluated and
compared with upgradient (i.e., background) con~tconcentrations. Groundwater
that is removed incidentally by the DYE system and subsequently treated will also need
to meet these groundwater standards prior to injection. The groundwater treatment
facility included in the selected remedy will be capable of achieving these applicable
regulatory standards. .
Action-specific: Treatment residuals ttom the LNAPL removal system will be
transported off site in. compliance with HMTA (applicable) and RCRA (applicable)
requirements if the residuals are considered to be haZardous. Disposal of any
hazardous treatment residuals. will occur off site at a RCRA Subtitle C treatment,
storage, or disposal (TSD) facility. Wells installed for the OU4 monitoring program and
the abandonment of existing unneeded wells will be subject to th~ Colorado Revised
and Amended Rules and Regulations of the Board of Examiners of Water Well
Construction and Pump Installation Contractors (2 CCR 402-2). EP A permitting (SDW A
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Underground Injection Control Regulations, Gass 5 permit) and testing prior to
injection of groundwater will occur as necessary.
Most of the air ARARs depend on emission sources and, therefore, are action specific.
Because there are no major sources of emissions at OU4, . these ARARs pertain to
activities associated with the selected remedy, rather than to existing conditions. The
selected remedy will comply with the following air ARARs:
.
.
.
National Ambient Air Quality Standards (NAAQS) - Particulate emissions will
be controlled during construction activities, and VOC emissions, which act as
a precursor to ozone formation, will be managed during remedial action. The
selected remedy will not cause or contribute to violations of the NAAQS.
Colorado Ambient Air.Quality Standards - The selected remedy will comply with
state-specificstandards for lead and total suspended particulate matter.
.
Regulation 1 - The selected remedy will comply with provisions
regarding opacity limitations and control of particulate emissions that
apply to construction activities.
.
Regulation 2 - All actions taken at OU4 will be in compliance with state
odor regulations.
RegUlation 3 - Air Polluti~n Emission Notices (APENs) ~ be filed for.
. each stage of activity; including construcnon, and operation of the DYE
system and water treatment equipment. . .
.
.
Regulation 6 and Federal New Source Performance Standards - 40 CFR
Part 60, Subpart FF contains provisions relating to VOC emissions from
petroleum refinery wastewater systems. The selected remedy will meet
relevant and appropriate portions of Regulation 6 and the . New Source
Performance Standards.
.
Regulation 7 - Reasonably A vciilable Control Technology (RACY) for VOC
sources within Colorado will be applied to the .selected remedy.
Colorado Regulation 8 - Limitations on beryllium and lead emissions will
be met during construction if contaminated soils are disturbed. Relevant
and appropriate limitations on mercury emissions will be attained if
water treatment system sludge is dried. Relevant and appropriate
provisions involving vinyl chloride emissions from. specific types of
equipment will also be met.
..
National Emissions Standards for a Hazardous Air Pollutants (NESHAPs) - The
selected remedy will meet relevant and appropriate portions of the NESHAPs
(i.e., Subpart FF of 40 CFR Part 61).
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Location-specific: Location-specific ARARs include the Executive Orders on Floodplain
Management and Protection of Wetlands. Only a relatively small portion of the Site is
located within the Sand Creek floodplain. Cpmpliance with location-specific ARARs
depends on .the location of the treatment facility, monitoring wells, DYE wells, and
groundwater injection wells. No protected properties have been identified.in the
immediate vicinity of OU4 and, the selected remedy will comply with location-specific
ARARs.
Other Guidance. Criteria. or Advisories to be Considered rmCs): 'Guidance regarding
ambient air levels of toxic air pollutants (National Ambient Air Quality Standards,
NAAQSs) will be considered for designing a.jr pollution controls for the Site. The State
of Colorado considers the Massachusetts Ambient Ajr Level standards as important
guidance. EP A 'has issued a policy statement regarding air emission controls for air
strippers at Superfund sites,located in ozone non-attainme~t areas and considers thi$'
policy a TBC because Denver is an ozone non-attainment area (OSWER Directive 9355.0-
28). The CERCLA Petroleum Exclusion which limits CERCLA authority and funding
for removal and treatment of petroleum product is also identified as a TBC for the
selected remedy.
C.
Cost Effectiveness
The selected remedy has been determiited to provide overall effectiveness proportional
to i~ costs and is therefore considered 'cost effective. The OU4 monitoring program. will . .
allow asse~sment of groundwater contamination attributable to the Site~ The analysis
of sampling data collected will provide information necessary for making cost-effective
decisions regarding the need for futufe action at the Site. . The alternative selected
includes removal of the recoverable LNAPL which is less expensive than containment
and provides' a relatively greater degree of protectiveness. Total capital, annual O&M,
and present worth costs for the selected remedy are $256,200; $241,400; and $3,866,500;
respectively. The selected alternative is the third least expensive option of the ten
alternatives developed for OU4. ,'.
D.
Utiliza~on of Permanent So~utions and Alternative TreatDtent Technologies (or'
Resource Recovery Technologies) to the Maximum Extent :practicable'
The selected remedy utilizes permanent solutions and treatment technologies to the
maximum extent practicable at OU4. Site-wide remediation of OU4 was found not to
be feasible because groundwater is not currently being used for domestic purposes, the
existence of upgradient contaminant source(s), the inability of a groundwater pump and
treat system to extract all of the residual contamination, 'and high cost of treating all
groundwater beneath the Site. Removal of the recoverable LNAPL will permanently
eliininate a potential source of groundwater contamination to OU4. Implemeritation. '
and continued enforcement of institutional controls will minimize the potential for
exposure to contaminated groundwater. However, the effectiveness of institutional
controls. is largely dependant on the continued cooperation of property owners,
municipalities, and other governmental entities. The. OU4 groundwater monitoring
program will allow for evaluation of changes in groundwater quality, the detection of
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any offsite migration of contaminated groundwater.. and the need for further action at
the Site.
Of the alternatives that are protective of human health and the environment and comply
with ARARs, EP A believes that the selected remedy provides the best balance in terms
of long-term effectiveness and permanence; reduction in toxicity, mobility, or volume
achieved through treatment; short-term effectiveness; implementability; and cost.
Overall protection of human health and the environment; and cost were the most
decisive criteria in selecting Alternative 3 as the preferred remedy.
E.
Preference for Treatment as a Principal Element
Treatment of the principal threats at OU4 was found not to be attainable due to the
Presence of up gradient contaminant sources and limitations in EP A's response authority
due to the Petrole~ Exclusion., Therefore, the selected remedy does not satisfy the
statutory preference for treatment as a principal element. However, many of th~
principal threats at the Site are being addressed under remedial actions occurring at
other OUs and ultimately will eliminate or control sources of groundwater contaminants
affecting the Site. LNAPL vapors removed by the DVE system will be permanently
destroyed by a thermal or catalytic oxidation unit, and groundwater removed during'
operation of the DVE system will treated to SDW A MCLs or more stringent state
drinking-water standards.
. BecauSe the sel~ed remedy will result. iI1 hazardous substances remaining 'on site, a
reView will be conducted every five years after commencement' of remedial action to
ensure that the remedy continues to provide adequate prot~tion of human health and
the environment.
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APPENDIX A
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RESPONSIVENESS SUMMARY
SAND CREEK INDUSTRIAL SUPERFUND SITE, OPERABLE UNIT 4
COMMERCE CITY, COLORADO
1.
OVERVIEW
The U.S. Environmental Protection Agency (EP A) established a public comment period from
February 14, 1994 through March 16, ,1994 for interested parties to comment on the Feasibility
Study (FS) report and the Proposed Plan for Operable Unit 4 (OU~) of the Sand Creek
Industrial Superfund Site in Commerce City, Colorado. EP A also held a public meeting at 5:30
p.m. on March 1, 1994 at ~e Commerce City Recreation Center to outline the proposed remedy
for OU4. The preferred alternative includes monitoring and institutional cC;>ntrols with light
~on-aqueous phase liqUid (LNAPL) removal. ' . , .
The Responsiveness Summary, required by the NCP (40 CFR Part 300.430(f)(3)(i)(F), provides
a sUJIUl)al'y of comments received from the community during the public comment period, as
well as EP A's responses to public concerns. All comments received during the public coIIUIient
period were considered in EPA's final selection of a remedial alternative for OU4.
2.
BACKGROUND ON COMMUNITY INVOLVEMENT
Mos~ of the community involvement at the Sand Creek Site 'Industrial Site has stemmed from
local officials and neighboring businesses. In the past, concern' about liability . and prop~
values has been high in this community.. Site-specific concerns identified through recent
community interviews include credibility of the government, publicity and ,economic issues,
the Superfund process, remedial activities, and health effects~ '
The following discussions identify the general nature of the concerns expressed by the
community and indicate specific concerns where appropriate.
Credibility of the Government: Reportedly, a distrust of local, 'state~ and federal government,
persists in this conun.unity. This distrust ,is attributed to contradictory'statements made by ,
government representatives and what some people feel is a historical cover.:up of
environmental problems. In addition, the tremendous amount of environmental contamination
that has occurred in this community has made residents of ,Commerce City and the
surrounding area feel like "governmental and scientific guinea pigs," according to one resident.
On one occasion, some individuals who work near the Sand Creek site requested information
from the EP A about water and soil quality in the area. According to those interviewed, the
EP A response was that the water was fine but there was a problem with soils at the Sand
'Creek Superfund Site. Because these individuals,worked uphill, from the Site, they, were told,
that they were not at risk. The workers did not believe the EP A and have feelings of distrust
toward the Agency.
Publicity and Economic Concerns: Residents of Commerce qty feel that bad publicity has
stifled the economy of the community and destroyed the area's ability to attract new business.
A primary concern of local officials is that contamination in the area has been associated solely
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with Commerce City although area Superfund sites are also located in Denver and
. unincorporated Adams County.
Residents and business owners in the area are very concerned about property values. One
local business owner said that he is unable to use his land for collateral and the property is
virtually unsalable. Homeowners feel that a decline in property values can be attributed to the
presence of Superfund sites in the area. Liability under Superfund has been a major concern
during the history of the Sand Creek Site, but the issue has not been raised by the community
~~~. .
The Superfund Process: Local officials, residents, and business owners expressed concern
about the amount of time it takes to cleanup a site. Specifically, one individual said that by the
time a remedy is about to be implemented, the treatment or dispos.al alternative that was
. selected in the ROD may not be appropriate for the site. Another concern is that
contamination. may l1ave an opportunity to migrate. while studies are being conducted and a .
remedy is being designed. . . .
Several interviewees felt that the Superfund process was inefficient. One individual said that
the Superfund process has become ineffective because a substantial portion of the Superfund
. money has been spent on. legal fees.
Remedial Activities: Lack of information about environmental sampling, remedial activities,
and protective clothing tends to intimidate and frighten people who work near the Site area.
In addition, 19Cal employees expressed a desire to know the schedule of sampling and remedial.
activities in advance. Dusts generated <;hllingdeanup are. a primary concern associated with
remedial activity. The people want to be assured that the proper preventative measures are
. taken to limit the generation of dust, and that air quality near the Site is monitored adequately
during cleanup work.
Health Effects: Some of the individuals interviewed associate personal physical problems with
contamination in the area. The risks to pregnant women who work near the Site are of
particular concern to local employees. The community is also concerned about the overall air,
wat~, and soil quality in the area.
EP A General R~sponse: The. CommunitY Relations Program fo~ the Sand Creek Industrial
Superfund Site is improving the community's understanding of the data and the potential
hazards associated with the site, as .well as the Superfund process. The community has been
kept informed of ongoirig activities conducted at the Sand Creek site through mailings,
riewspaper announcements, and public meetings. A notice of availability of the OU4 Proposed
Plan, RI, and FS reports and notification of the public meeting were published in The Rocky
Mountain News on February 14, 1994 and in The Commerce City Express on February 15, 1994.
The publi~ comment period for the OU4 Proposed Plan was open from February 14 to March
16, 1994,.and the public meeting was held on March 1, 1994 at the Commerce City Recreation
Center. EPA'explained the alternatives developed for OU4, presented its preferred remedy,
and responded to questions. In addition, EP A has established an information repository at the
Adams County. Ubrary and the EP A Superfund Records Center in Denver, Colorado where
materials relevant to the community's concerns and interests may be reviewed. Documents
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4
pertaining to OU4 which are stored at the repository include: the RIlFS reports, risk
assessments, and related documents; and the Proposed Plan.
Because remedial actions for contaminated groundwater at Superfund sites often use similar
technologies and approaches, EP A has developed guidelines designed specifically for
addressing contaminated groundwater at these sites (EP AI54O/G-88/003). This focused
approach was adopted in conducting the RIlFS for OU4. Use of these guidelines helPed to
expedite the RIlFS and center the remedy selection on proven and widely used technologies,
which ultimately resulted in a more efficient use of time and resources. By streamlining the
RIlFS process EPA: (1) improves the efficiency and effectiveness of decision making at these
sites; (2) provides consistency among the EP A Regions in their approach to conducting an RIlFS
and selecting a remedy; and (3) facilitates more effective remedial designs.
The Comprehensive Environmental Response, -Compensation, and Liability Act (CERCLA)
mandates that EP A pro~ human health and the environment from CUlTent and potential",
exposures to hazardous subStances. Groundwater "underlying bU4 was evaluated for potential
human health and environmental risks posed by contaminants in several investigations at the
Site. These studies evaluated baseline risks and potential future risks associated with
exposures to CUlTent levels of contamination at OU4. The following documents describe risk
evaluations performed at the Site: "
.
1988 Preliminary Endangerment Assessment (EA) for the Sand Creek Industrial
Site, Colorado: This document described a site-wide risk assessment that
evaluated risks from contaminated soils, groundwater, surface water, and air ~t
" the Site." . "" "
.
1993 48th and Holly Street Landfill (OU3) Risk Assessment: This document
updated and supplemented the 1988 EA by incorporating new data presented
in the OU3 RI. The two media evaluated in this risk assessment were
groundwater in the vicinity of the Landfill and landfill gas.
.
1993 Health Evaluation Update: This document was prepared as part of Ute
OU4 RIlFS. It updated and supplemented the 1988 EA by incorporating new
data collected during the OU4 RIlFS as well as data collected for the 1993 OU3
risk assessment. Groundwater and the LNAPL plume were the subjects of this "
evaluation. Results wez:e compared with the previous EA study. "
Protection of the community during remedial action is a primary conc~ of EP A. The
preferred remedy for OU4 will meet all applicable or relevant and appropriate federal and state
requirements. Monitoring will be performed during construction activities to evaluate the air
quality, adequate controls will be used to suppress dust generation, and appropriate measures
will be taken to protect workers and residents during remedial action. "
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3.
SUMMARY OF COMMENTS RECEIVED DURING PUBUC COMMENT PERIOD
AND EPA RESPONSES
EP A solicited written and oral comments from the C01JUI\unity on the OU4 Proposed Plan
during the public comment period and at the public meeting. 'A summary of comments
received and EPA's responses are provided below:
Comment: One participant at the public meeting wanted to know how many wells are
in the Sand Creek Superfund site area, regardless of whether they wer~ used for
drinking water or agricultural purposes. He also wanted to know if the wells had been
tested over a period of time. ' .
, EPA Response:' A 1990 report prepared by Tri-County Health Department (raID; 1990)
for EPA and the ColQrado Department .of Health .(CDH) contains the most current
information on OU4 area water. use. The report summarizes the findings of a door-to-
door well inventOry and information survey. The survey encompassed an area bounded
by Sand Creek on the north, Interstate 70 on the south, Quebec Street on the east, and
Colorado Boulevard on the west. (This survey area extends beyond the boundaries of
OU4.) The survey supported CDH and EPA efforts to identify potential receptors of
groundwater contaminated by several sources, including sources at the Site. TaID'
contacted property owners to determine the number, location, depth, construction
details, and current use of wells in the survey area.
. TCHD'obtained information on water U5~ £rom 419 of the 420 properties in the survey
area.' South Adams County Water and Sairitation DiStrict and Denver Water Board
serve most of the water users in the survey area. However, the survey identified 23
private wells, with nine completed in the shallow alluvium., Data regarding the depth
of nine wells were unavailable. Four wells identified as deep ranged from 560 to 1600
feet depth, and thus are not in the shallow OU4 aquifers. Two of the deep wells
provided water for drinking.
Of the wells completed in the shallow alluvium, five are in' use~ Three are used for
itrigation and one as a seasonal water supply for livestock. The remaining well, located '
. at a business on Oriental Refinery property, proVides water for a sanitary waste system.... .
These ~ells have not been sampled by EP A in the past, but will be included in the OU4
monitoring program.
Within the OU4 site boundary, there are approximately 80 groundwater monitoring
wells. EP A intends to permanently abandon those monitoring wells that will not be
sampled in the OU4 and OU3 groundwater monitoring programs.
Co~ent: A city council member at the public meeting felt that the proposed remedy'
for OU4 was primarily a monitoring function and was not sufficient because it
addressed only a limited geographic area. He believed that this has a direct effect on
the marketability and economics of the area, the willingness of the people to invest in
the area, and establishing permanent ~ommercial and industrial use of the land.
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.
I
EP A Response: Groundwater underlying the Sand Creek site does not appear to be
migrating due to the nature of the aquifer system and the presence of clays. EP A
believes that monitoring is an appropriate response for the conditions at the Site. The
proposed remedy for OU4 also includes the implementation of institutional controls
which will minimize potential exposure to contaminated groundwater. The dual vapor
extraction (DVE) system will be used for removing LNAPL, a potential source of
groundwater contamination. The groundwater monitoring component of the preferred
alternative will not interfere with industry in the area and will provide protection by
detecting any offsite migration of contaminants and the need for further action at the
Site. "
Remedial action is underway at other nearby Superfund sites, and collectively these
activities will reduce risks associated with contamination in the area. By cleaning up
. these sites, the potential environmental liability associated with the affected properties
is reduced, the property values increase~ and the marketability of the area is enhanced~
Comment: A community member at the public meeting wanted to know what would
be done with the groundwater that will be removed during operation of the DVE
system.
EP A ReSJ'onse: Contaminated groundwater that is extracted along with the LNAPL by
the bYE system will be" treated at the site for the removal of organic and metal
contariUnants and will be returned to the alluvial aquifer system by onsite ground':Vater
" re-injection or infiltration." Specific engineering det3ns of the groundwaier treatment
and re-injection system will be developed during the remedial design phase of the
project. It is currently estimated the groundwater removal rate during operatio~ of the'
DYE system will be approximately 20 gallons per minute (gpm).
Comment: A written comment was received" indicating concern that groundwater
issues that have been evaluated and addressed under OU3 are not explicitly excluded
from coverage" under OU4in the Proposed Plan. The author asked EPA to cl~.in the
OU4 ROD that groundwater in the vi
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~
actions provide reliable controls for future management of untreated materials and
thereby reduce the residual risk associated with the Sand Creek Superfund Site.
EP A Re5J'onse: Compared with the other alternatives developed for OU4, Alternative
2 provides the second lowest degree of long-term effectiveness and permanence.
Alternative 2 is largely dependant on the willingness of property owners and local
governments to implement and enforce institutional controls. EP A has little authority
with respect to establishing and enforcing institutional controls. However, the
proposed remedy for OU. (Alternative '3) combines LNAPL removal with institutional
controls and groundwater monitoring and, therefore, provides a greater degree of long-
term effectiveness and permanence.
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