I
United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EP A/ROD/R08-91 /045
June 1991
~>I
rrB Cf 2. -16~ t/-Or
ft
oEPA
Superfund
Record of Decision:.
Chemical Sales
(New Location)
(Operable Unit 1), CO
u . S. Environmental Protection AgetfCf
Region III Hazardous Waste
Technical Information Center
841 Chestnut Street, 9th Floor -..
Philadelphia. PA 19107
HazardouS Waste CoUection
information Resource Center
US EPA RegIon 3
Philadelphia, PA 19107
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50272-101
I REPORT DOCUMENTATION \1. REPORT NO.
PAGE EPA/ROD/R08-91/045
I ~
3. RecIpient. AccetI8Ion No.
4. 11tIe and Subtitle
SUPERFUND RECORD OF DECISION
Chemical Sales (New Location)
First Remedial Action
7. AuItIor(.)
5. Report O.te
06/27/91
(Operable Unit 1), CO
6.
8. Perfonning Org8l\iza1Ion RepI. No.
8. Perfonnlng Org81niza1lon Name and Acldre..
10. ProjectlT.8klWork Uni1 No.
11. ContrIIct(C) or Gr8nt(G) No.
(C)
(G)
12. Spon8orIng Organization Name and Addre88
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report & Period Cowrecl
Agency
800/000
14.
15. Supplement8ly No'"
16. Ab8lr8ct (Umlt: 200 _ni.)
The Chemical Sales (New Location) (Operable Unit 1) site is an active chemical sales
and storage facility in Commerce City, Adams and Denver Counties, Colorado. Land use
in the area is predominantly industrial, and there are six residences located on the
northern portion of the site. The site is bounded by Sand Creek to the north and lies
within the 100-year floodplain of the creek. An estimated 30,000 people who reside
near the site use the alluvial aquifer as the principal source of drinking water.
Since 1976, Chemical Sales (CS) has used the site to store and sell organic chemicals
and acids. Site features include a warehouse and tank farm including an associated
system of above-ground and underground storage tanks and pipelines. Between 1985 and
1990, three onsite chemical releases of hazardous substances into the soil and ground
water' from the CS facility were reported. In 1985, approximately 200 gallons of
methylene chloride were spilled into onsite soil during a chemical transfer. The
second release was in 1986 when rain water contaminated with several VOCs was
discharged into a nearby drainage ditch. The third release occurred in 1990, when
approximately 3,700 gallons of methanol were spilled on the ground surface near the CS
tank farm. Several EPA investigations confirmed the release of hazardous substances
(See Attached Page)
17. ~t An8IyaI. L Oe8cripIDrs
Record of Decision - Chemical Sales (New Location)
First Remedial Action
Contaminated Media: soil, gw
Key Contaminants: VOCs (PCE, TCE)
(Operable Unit 1), CO
b. Idontifler8lOpen-Ended Terma
c. COSA 11 FieIdIGrlq)
18. Avlil8bl1ty Statement
19. Security CI... (Thi. Report)
None
:zoo Security CI... (Thi. Page)
Nnno
_.*.... ...
21. No. of P.gea
187
I
n Price
(See ANSl-Z39.18)
See InslrUClJons on Reverse
272 (4-77) .
(Forrnetty NTl5-35)
Deper1ment of Commerce
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EPA/ROD/R08-91/045
Chemical Sales (New Location)
First Remedial Action
(Operable Unit 1), CO
Abstract (Continued)
into the ground water from the CS Property. The site has been divided into three
operable units for remediation. This Record of Decision (ROD) addresses remediation of
soil and ground water contamination south of Sand Creek, as OUI. Future RODs will
address other site contamination including the ground water plume and associated
contamination (OU2), and residential exposure to contaminated wells and domestic water
from the municipal water supply (OU3). The primary contaminants of concern affecting
the soil and ground water are VOCs including PCE and TCE.
The selected remedial action for this site includes treating contaminated onsite soil
using vapor extraction; treating air emissions with catalytic oxidation; recirculating
exhaust from the catalytic oxidation system into the contaminated soil; pumping and
onsite treatment of ground water in the source area and plume area using air stripping,
followed by reinjecting the treated water from the source area wells and reinfiltrating
treated water from the plume area through onsite discharge; monitoring ground water,
treated water, and air; providing public notice of potential health threat from
contamination ground water; and implementing institutional controls including ground
water use restrictions. The estimated cost for this remedial action is $2,081,000. No
O&M costs were provided for this remedial action.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific soil cleanup goals are based on an
acceptable concentration of leachate multiplied by the partitioning coefficient for ,the
soil, and include PCE 0.150 mg/l and TCE 0.115 mg/l. Chemical-specific ground water
cleanup goals are based on SDWA MCLS, and include PCE 0.005 mg/l and TCE 0.005 mg/l.
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RECORD 01' DECISIO)f
CBEKICAL SALES COMPANY SUPERPUHD SITB
OPERABLB UNIT 1 - LEYDEN STREET LOCATION
JUNE 28, 1991
PART 1 - DECLARATION STATEMENT
SITE NAME AND LOCATIO)f
Chemical Sales Company site
4661 Monaco Pkwy., Denver, Colorado
Operable unit 1 - Leyden Street Location
STATEMENT 01' BASIS AND PURPOSB
This decision document presents the selected Remedial Action (RA)
for Operable Unit 1 - Leyden street Location (OU1) of the
Chemical Sales Company (CSC) Superfund site located in the
counties of Denver and Adams, State of Colorado. The remedy was
chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA, as
amended by the Superfund Amendments and Re-authorization Act of
1986) and the National contingency Plan.
This decision document explains the basis for
remedy for OU1 of this Site. The information
basis of this RA decision is contained in the
Record for this site and is summarized in the
summary.
selecting the
that forms the
Administrative
attached decision
The State of Colorado concurs with the selected remedy for OU1.
ASSESSMENT OF THE SITB
Actual or threatened releases of hazardous substances from OU1 of
this site, if not addressed by implementing the response action
selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare,
or the environment.
DESCRIPTION OF SELECTED REMEDY
The CSC Superfund site has been divided into three OUs. OU1
addresses the source area located in the vicinity of the CSC
property and groundwater contamination south of Sand Creek~ OU2
addresses the groundwater plume emanating from OU1 and other
groundwater contamination located north of Sand Creek. OU3
addresses residential exposure to contaminated alluvial
groundwater through use of domestic private wells and domestic
water supplied by the SACWSD. The selected remedy presented in
this ROD addresses soil and groundwater contamination within the
boundaries of OU1. It describes remediation intended to reduce
levels of contaminants in groundwater south of Sand Creek that
ACS1/BSPM/062691
. ".",
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o
v
were released from the CSC facility. OU2 addresses downgradient
residual groundwater contamination north of Sand Creek associated
with the CSC OU1 site and another identified plume of groundwater
contamination, referred to as the "PCE Plume." OU3 addresses
residential exposure to contaminated groundwater through use of
private alluvial wells.
The Remedial Action (RA) selected by the Environmental Protection
Agency (EPA) for OU1 includes a system for extraction and
treatment of contaminated soils and groundwater identified for
this operable unit. Contaminated soils have been detected on and
directly adjacent to the CSC property. A contaminated
groundwater plume emanates from CSC OU1. The major components of
the selected action include:
ACS1/BSPM/062691
*
Monitoring of groundwater, discharged treated water and
air;
*
Notification of potential health risks associated with
use of contaminated groundwater upon request for an
alluvial well permit within the OU1 area;
*
High volume (i.e., 1000 gallons per minute (gpm» and
pulsed pumping of groundwater exceeding groundwater
remediation levels in the source area (area south of
East 48th Avenue);
High volume (i.e., 1000 gpm) groundwater extraction
within the CSC plume area (area north of East 48th
Avenue and south of Sand Creek);
*
*
Treatment of contaminated groundwater with two air
stripping towers for both source and plume areas; the
source area air stripping tower would be located on CSC
property; the plume area air stripper would be located
near East 52nd Avenue;
*
Re-injection and re-infiltration of treated
groundwater; aquifer re-injection by wells for treated
water from the source area; re-infiltration through
discharge into a trench or existing gravel pit for
treated water from the plume area;
*
Soil vapor extraction of contaminated soils exc~eding
soil remediation levels;
*
catalytic oxidation of air emissions from the soil
vapor extraction system and source area air stripping
unit; recirculation of exhaust from catalytic oxidation
system into the contaminated soil.
,
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DBCLARATXOH OF STATUTORY DBTBRMXNATXOHS
The selected remedy is protective of human health and the
environment, complies with Federal and state requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost effective. This remedy utilizes
permanent solutions and alternative treatment technologies to the
maximum extent practicable.
Because this remedy may result in hazardous substances remaining
on site above health based levels, and based on EPA policy
(structure and Components of 5-Year Reviews, May 29, 1991), a
review of the remediation will be conducted within five years
after commencement of the RA to ensure that the remedy continues
to provide adequate protection of human health and the
environment.
~-S~h2!r~
Regional Administrator
EPA Region VIII
~ .;J.. 7, Ii" "71
pjte .
ACS1/BSPM/062691
,
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ACS1/BSPM/062691
()
()
RECORD OF DECISION
CHEMICAL SALES COMPANY SUPERFUND SITE
OPERABLE UNIT 1 - LEYDEN STREET LOCATION
PART 2 - DECISION SUMMARY
,
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I.
II.
Decision Summary
TABLB 01' COH'l'EH'l'S
SITE NAME, LOCATION AND DESCRIPTION
. . . . .
. . . . .
SITE HISTORY AND ENFORCEMENT ACTIVITIES
. . .
. . . . .
III. HIGHLIGHTS OF COMMUNITY INVOLVEMENT
SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY. .
IV.
V.
VI.
. . . .
. . . . . .
SITE CHARACTERISTICS.
. . .
.........
. . . . .
SUMMARY OF SITE RISKS
. . . . .
. . .
. . . . . .
. . .
VII. DESCRIPTION OF ALTERNATIVES
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
. . .
VIII.
IX.
X.
XI.
. . . . .
. . .
. . . . . .
SELECTED REMEDY
. . . . . .
. . .
. . . .
. . .
. . . .
STATUTORY DETERMINATIONS.
. . .
. . . .
........
DOCUMENTATION OF SIGNIFICANT CHANGES
. . . .
. . . . . .
ACS1/BSPM/06Z691
,
\)
J
1
7
12
13
14
37
53
64
70
80
85
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LIST OF FIGURES
FIGURE 1. Operable units 1 and 2
. . . .
.......
FIGURE 2. Map of Groundwater Plumes.
FIGURE 3. OUl site Layout
. . . . .
.......
. . . . .
.......
. . . . . .
FIGURE 4. Elements of the Leyden street site
. . .
. . . . .
FIGURE 5. Configuration of Bedrock Surface
. . . .
. . . . .
FIGURE 6. Saturated Thickness of Unconsolidated Deposits,
September 1990 . . . . . . . . . . . . . . . . . .
FIGURE 7. Water Table Configuration, September 1990 . . . . .
FIGURE 8. Regions of contamination Above Field GC Soil
Headspace Action Levels. . . . . . . . . . .
. . .
FIGURE 9. Thickness of Soil Above Water Table Exceeding
Field GC Headspace Action Levels. . . . . .
FIGURE 10.Areal Extent of Soil Contamination Exceeding
Action Levels Based on Laboratory Results.
. . .
. . . .
FIGURE 11.Storage Tank Locations
. . . . .
. . .
. . . . . .
FIGURE 12.Distribution of Tetrachloroethene (PCE) in
Ground Water. . . . . . . . . . . . . . .
. . . .
FIGURE 13.Distribution of Trichloroethene (TCE) in
Ground Water. . . . . . . . . . .
. . . . .
FIGURE 14.Passive Pumping system, OUl . . .
FIGURE 15.Active Pumping system, CUl
. . . .
. . . . .
. . . . . . .
. . . . .
ACS1/BSPM/062691
,
2
3
5
8
16
17
18
21
22
23
27
35
36
56
61
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TABLE 1.
TABLE 2.
TABLE 3.
TABLE 4.
TABLE 5.
ACS1/BSPM/062691
LIST OF TABLES
Summary of Underground and Aboveground Tank Data
Laboratory Grounq Water Quality Summary Table for
Target Volatile Organic compounds. . . . . . .
Summary of Cancer Risks by Pathway for Potential
Receptors at the Chem Sales OU1 Site. . . . . . .
Summary of Non-carcinogenic Risks (Hazard Indices)
by Pathway for Potential Receptors at the Chem
Sales OU1 site. . . . . . . . . . . . . . . . . .
Groundwater Remediation Level. . . .
. . .
. . . .
,
"
()
25-26
30-33
44
45
50
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I.
SITB HAKB, LOCATIO. AND DESCRIPTIO.
The Chemical Sales Company (CSC) superfund site is located in
Commerce City, Colorado and in the northern portion of Denver,
Colorado, approximately five miles northeast of downtown Denver.
The site is divided into three operable units.
OU1: This operable unit (OU) includes the CSC property and
addresses soil and groundwater contamination south of
Sand Creek. It is approximately bounded by Forest
street to the west; I-70 to the south; Monaco Parkway
to the east; and Sand Creek to the north as shown in
Figure 1. This OU is also referred to in this ROD as
the Leyden street Location and/or Leyden Street site.
OU2: This OU addresses groundwater contamination generally
downgradient of OU1. It is approximately bounded by
Quebec Street to the east; Holly Street to the west;
Sand Creek to the south; and East 86th Avenue to the
north (see Figure 1). The boundaries for OUl and OU2
are defined by the approximate extent of groundwater
contamination (Figure 2). If contaminants within the
groundwater continue to migrate, the boundaries of CSC
OU1 and OU2 will correspondingly expand.
OU3: This OU covers the same area as OU2 but addresses
residential exposure to contaminants through domestic
use of alluvial groundwater.
ACS1/BSPM/062691
1
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CSC SITE oUt RlIFS STUDY
OPERABLE UNITS 1 & 2
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01/'061" FIGURE 1 --
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CSC OU2
SAC-47
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SAC-21
SAC-18
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TREATMENT PLANT
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"
CSC OUt,
1-70 -'.j
!II PCE PLUME
~ > 50 ug/L PCE
SAC-'S SACWSD ALLUVIAL
o MUNICIPAL WELL
FIGURE 2
MAP OF GROUND-WATER PLUMES
3
,
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The subject of this Record of Decision (ROD) is CSC OU1. This OU
includes the CSC property located at 4661 Monaco Parkway in
Denver, Colorado. The topography within OU1 slopes northward
toward Sand Creek. Elevations range from 5,200 feet near Sand
Creek to 5,265 feet Above Mean Sea Level (AMSL) in the
southeastern corner of OUI. Natural topographic features have
been extensively modified by construction and earthwork. A
relatively abrupt change in the natural topography occurs as a
terrace in the vicinity of East 48th Avenue, where there is as
much as a 50 foot change in elevation to the north. This slope
roughly parallels East 48th Avenue from Leyden Street, and then
parallels the Chicago, Rock Island & Pacific Railroad (Figure 3) .
The northern portion of OU1 lies within the Sand Creek
floodplain. Sand Creek, which forms the northern boundary of
OU1, is the primary discharge point for drainage ditches in OU1.
Approximately three miles downstream (northwest of OU1), Sand
Creek enters the South Platte River.
Two drainage ditches were identified in the southern portion of
OU1. The drainage ditch near the CSC site (located on the
northern portion of CSC property) drains the CSC property north
of the CSC warehouse and tank farm. The other ditch originates
at a culvert beneath the Chicago Rock Island & Pacific Railroad
and terminates at a culvert at the intersection of Monaco Parkway
and East 48th Avenue.
The property located adjacent to the western boundary of the CSC
property is owned by the Interstate Distribution Center
Associates (IDCA), LTD. The Trammell Crow Company acts a~ an
agent for IDCA. The figures of this ROD text refer to the
building constructed on the IDCA property as the "Trammell Crow"
building. Prior to the preparation and construction of this
building at 4650 Leyden st., a drainage swale existed which
provided surface drainage from the CSC property. This drainage
ACS1/BSPM/062691
4
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OU1 SITE LAYOUT
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OPERABLE UNIT 1
DENVER. COLORADO
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. .
swale extended from just south of the CSC tank farm across what
is now the IDeA property.
Groundwater within CSC OUI flows northward into CSC OU2.
Groundwater in the csc OU2 area is the principal source of
domestic drinking water for the South Adams County Water and
Sanitation District (SACWSD). SACWSD supplies water to
approximately 30,000 customers. The majority of the SACWSD
municipal water supply is derived from the alluvial aquifer. A
total of six alluvial aquifer production wells are currently in
use within OU2.
The land use within OUI is largely industrial. Six residences
are located in the northern portion of OUI. One residence is
located on East 50th Avenue and the others are located on East
52nd Avenue. All of the residences within OUI are connected to
the SACWSD system.
Railroad spurs located to the north and south of the CSC
warehouse service the CSC. Chemicals are transported in bulk to
the CSC facility by train and are unloaded along these railroad
spurs.
Most of the OUI population consists of workers who commute from
outside OUI to jobs in the office and warehouse buildings. Other
than the few residences in the northern portion of OUl, the
predominant land use consists of commercial offices and
warehouses, with a gravel mining operation along Sand Creek in
the northernmost portion of OUI.
Past and present surface and subsurface storage units and other
structures on the CSC OU 1 property include several underground
and above ground chemical storage tanks and drums. The size of
these tanks ranges from 5,000 to 15,000 gallons, and they contain
a variety of organic chemicals and acids. Several underground
ACS1/BSPM/062691
6
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tanks have been removed from the CSC property. The CSC storage
tanks are located along the western boundary of the CSC property
(Figure 4).
II.
SITB HISTORY AND BHPORCEXENT ACTIVITIBS
Initial Inv8stiqation8
In 1981, the Environmental Protection Agency (EPA) conducted a
random national survey of drinking water systems. During this
survey, several organic chemicals were detected in SACWSD
alluvial municipal water supply wells. Additional sampling in
1982 and 1985 confirmed these results. As a result of these
findings, EPA began a RI/FS for an area named the "Off-Post Rocky
Mountain Arsenal (RMA) OU 1" (Off-Post RMA OU1). This area
extended from Sand Creek to the south: East 80th Avenue to the
north: the South Platte River to the west: and the western border
of the RMA to the east. The RI/FS was completed in December
1986. The RI results consistently indicated widespread
contamination by chlorinated volatile organic compounds in
groundwater along the eastern portion of the study area. The
selected alternative was a permanent water treatment system for
SACWSD water. A Record of Decision was signed in June 1987 which
implemented the construction of the Klein Treatment Plant, which
began operating in October 1989. In addition, approximately 400
residents within the CSC OU2 site were connected to SACWSD.
The adjacent RMA was suspected as one of the sources of
groundwater contaminants in the former Off-Post study area
because of the history of waste disposal on that site. Further
investigation by EPA indicated that additional source areas were
potentially contributing to contamination detected within the
study area.
ACS1/BSPM/062691
7
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ELEMENTS OF THE
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER. COLORADO
Source: EngIne8m8 Sdenc8. 1881
,
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In April 1986, the EPA Field Investigation Team (FIT) conducted a
soil gas survey of a 65-acre area near East 48th Avenue.
Elevated trichloroethene (TCE) values were discovered on the
north side of the rail spur in the northern portion of the CSC
property. In August 1986, EPA's FIT installed monitoring wells
in the area where elevated soil gas TCE values were observed.
These wells were sampled by the FIT in late August and early
september 1986. A full description of these field investigation
activities and a summary of the data obtained through these
efforts are provided in the following reports:
*
South Adams Soil
I-270 and Quebec
E. 48th Ave. and
1986c)
E. 50th Ave. and Ivy Street (E&E 1986d)
E. 56th Ave. and Magnolia (E&E 1987).
Gas Survey (E&E 1986a)
Street (E&E 1986b)
Leyden Street (E&E
*
*
*
*
The results of these studies indicated the release of hazardous
substances into groundwater from the CSC property. As a result
of this finding and subsequent scoring of the site based on the
Hazard Ranking System (HRS), EPA proposed the CSC site for the
National Priorities List (NPL) in June 1988. This listing w~s
finalized in August 1990.
EPA issued the CSC a Special Notice Letter in August 1988,
requesting that CSC conduct a RIfFS for the CSC site. CSC
notified EPA that the company would not undertake the RIfFS for
the entire CSC site. In June 1989, EPA subdivided the
groundwater RIfFS activities into two separate OUs for the CSC
site (OU1 and OU2) and requested that CSC conduct a RIfFS for
OU1. In August 1989, CSC submitted a good faith offer to EPA to
conduct the RIjFS for OU1. In September 1989, EPA and CSC
entered into an Administrative Order (AO) on Consent (Docket No.
ACS1/BSPM/062691
9
,
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CERCLA-VIII-90-03) requiring CSC to conduct a RIjFS for CSC OU1.
As a result of site characterization activities conducted during
the OU1 RIjFS, hazardous substances in the form of chlorinated
volatile organic compounds were detected in soils within the IDeA
property boundaries at 4650 Leyden street (noted as "Trammell
Crow" on figures). As a result of this finding, EPA issued
general notice to IDeA in October 1990 notifying IDCA that it was
considered a Potentially Responsible Party (PRP) for the CSC
Superfund site.
Chemical Sales Company Operations
In 1962, a warehouse was constructed at 4661 Monaco Parkway.
Between 1962 and 1976, the warehouse was occupied by Samsonite,
and then by Gates Rubber Company. These companies reportedly
used the facility solely as a product warehouse. CSC purchased
and occupied the facility in October 1976. All existing surface
and underground storage tanks, pipelines, and appurtenances were
installed between October 1976 and February 1977.
There have been three reported chemical releases of hazardous
substances into the soil and groundwater at the site from the CSC
facility. The first occurred on August 21, 1985, when
approximately 200 gallons of methylene chloride were released as
a result of a spigot breaking off during chemical transfer
(Colorado Department of Health, 1986a). The second release
occurred on March 28, 1986, when contaminated rainwater in the
transfer pipe gallery was discharged into a nearby drainage ditch
(Colorado Department of Health 1986b). Sampling conducted by the
Colorado Department of Health indicated that methylene chloride,
chloroform, and 1,1,1-trichloroethane (l,l,l-TCA) were present in
the discharge. The third release was a methanol spill which
occurred on May 9, 1990, when approximately 3,700 gallons of
ACS1/BSPM/062691
10
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methanol were spilled on the ground surface in the area of the
CSC tank farm (Foster, 1990).
Remedial IDv.stiqatioD/~.asibility study
As stated previously, on September 29, 1989, an AO on Consent was
issued to the CSC requiring the company to conduct a RIfFS to
characteri~e the nature and extent of contamination and identify
and evaluate alternatives to address the identified
contamination. The remedial investigation included geophysical
surveys, drilling and sampling 45 soil borings, installing and
sampling 22 groundwater monitoring wells, and collecting six
surface water samples.
The RIfFS report, completed in February 1991, indicates that
hazardous substances are present in soils and groundwater in
portions of OU1. The'contaminated aquifer of concern is a
shallow, unconsolidated aquifer which is not presently used as a
drinking water source within aUl. This alluvial aquifer,
however, supplies drinking water for approximately 30,000 people
further downgradient in the CSC OU2 area. The source areas
contributing to the observed groundwater contamination have been
identified as contaminated soils within the properties owned by
CSC (4661 Monaco Parkway) and IDeA (4650 Leyden st).
As part of the RIfFS, EPA prepared a Baseline Risk Assessment
(RA) in October 1989 to estimate potential health and
environmental risks which could result if no action were taken in
csc OU1. The RA indicated that exposure to groundwater and soil
contaminants at the CSC OUl site could result in significant
unacceptable risks to public health. Details of the RA are
summarized in section VI of this ROD.
ACS1/BSPM/062691
11
,
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1\
, \
III. HIGHLIGHTS O~ OOKKUHITY IBVOLVBKBHT
Community interest in the groundwater contamination in South
Adams County was very intense in 1985 and early 1986 when the
problem first became public. The initial blame was placed on the
Rocky Mountain Arsenal, which was adjacent to the contaminated
public water supply area and already receiving significant media
attention. Local citizens formed a very vocal group Citizens
Against Contamination (CAC), which held a number of well attended
public meetings (over 600 people attended the March 6, 1986
meeting). CAC kept the issue in the press and in the attention
of local, State, and federal politicians. EPA and the Army
responded to numerous public and media inquiries, issued press
releases for new developments, and attended the public meetings.
Community relations activities were coordinated among the EPA,
the Army, and the south Adams County Water and Sanitation
District (SACWSD). The State conducted a separate program.
Public interest subsided in mid-1986 after a temporary water
treatment system funded by the Army and the EPA came into
operation at SACWSD and was made available to the affected
residences. In the fall of 1986, EPA named the Chemical Sales
site as a source of groundwater contamination. EPA has since
issued a number of fact sheets discussing the progress of the
investigation and activities at the site. The Chemical Sales
site was also included in joint community relations activities
with several other south Adams County superfund sites.
The Proposed Plan for QU2 was issued to the public concurrently
with proposed plans for QU1 and QU3 on February 25, 1991. The
proposed plan and RI/FS reports were made available to the public
in the Administrative Record maintained at the EPA Region VIII
Superfund Records Center in Denver, Colorado. A notice of
availability for these documents was published in the Denver Post
ACS1/BSPM/062691
12
,
-------
"
and Rocky Mountain News on February 28, 1991; in the Commerce
City Beacon February 27, 1991; and in the Commerce City Express
on March 5, 1991. The public comment period was open from
February 28 to April 1, 1991. The public meeting was held March
14, 1991 at the Commerce City Recreation Center. A transcript of
the public meeting is included in the Administrative Record. At
this meeting, EPA representatives answered questions about the
site and discussed the remedial alternatives under consideration.
Responses to comments received during the public comment period
on the proposed plan are presented in the Responsiveness Summary
section of this ROD.
xv.
SCOPB AND ROLB OF OPERABLB UNXT WXTBIH SITB STRATEGY
The CSC Superfund site has been divided into three OUs. OUl
addresses the source area located in the vicinity of the CSC
property and groundwater contamination south of Sand Creek. OU2
addresses the groundwater plume emanating from aUl and other
groundwater contamination located north of Sand Creek. OU3
addresses residential exposure to contaminated alluvial
groundwater through use of domestic private wells and domestic
water supplied by the SACWSD.
The remedy selected in this ROD is for OU1. This remedy
addresses the contaminated soil on the CSC and IDeA property and
contaminated groundwater south of Sand Creek emanating from these
properties. The groundwater poses an unacceptable risk to human
health and the environment due to ingestion, and inhalation
during showering, of contaminants in groundwater above existing
or proposed Maximum Contaminant Levels (MCLs) as established by
the Safe Drinking Water Act or exceeding the 10"6 risk level.
Due to high concentrations of PCE, and other solvents, there is a
strong possibility that pools and pockets of liquid PCE or other
solvents are present at the site. These contaminants in their
liquid form are called dense non-aqueous phase liquids (DNAPLs).
ACS1/BSPM/062691
13
,
-------
v
If detected, they will present a source of groundwater
contamination and thus a "principal threat" to public health and
the environment.
"
Contaminated groundwater in CSC OU1 migrates northward into OU2.
A reduction in the mass of contaminants within OU1 will result in
a subsequent reduction in concentration of contaminants in
groundwater within the OU2 area.
In addition, surficial soils pose an unacceptable risk through
ingestion and inhalation of contaminants associated with
contaminated soils.
v.
SITE CHARACTERISTICS
site Geology and Hydrology
The northern portion of OU1 (north of East 48th Avenue) lies
within the Sand Creek flood plain, which is part of the South
Platte River System. The topography, distribution of surficial
deposits, and the materials encountered during drilling suggest
that the southern portion of OUI (south of 48th Avenue) is a
terrace comprised of Slocum Alluvium beneath eolian sand, silt
and clay. The terrace was most likely formed by renewed
downcuttinq of the Sand Creek tributary of the South Platte
River.
The alluvial aquifer below OU1 is generally composed of fine to
coarse, poorly sorted sands and occasional gravels containing
silt and clay. North of East 48th Avenue, the aquifer appears to
be composed of coarser grained sand and gravel compared to the
area south of East 48th Avenue.
The alluvial aquifer is underlain by shale, siltstone, and
sandstone of the Denver Formation. The bedrock surface of the
ACS1/BSPM/062691
14
,
-------
Denver Formation reflects the erosional development of the South
Platte River Valley, and is characterized by isolated bedrock
highs and paleochannels. In general, the bedrock surface
exhibits a regional northward slope, with maximum elevations
occurring in the southern portion of QU1 and minimum elevations
in the northern portion of QU1 (Figure 5). As illustrated in
Figure 5, a paleochannel may be present within QU1, trending
north-northwestward toward Sand Creek.
Depths to groundwater beneath QU1 generally decrease from south
to north toward Sand Creek. The decreased depth to water toward
the north corresponds to an increase in saturated thickness.
Figure 6 illustrates the saturated thickness of the alluvial
aquifer.
The water table shown in Figure 7 indicates that the alluvial
groundwater flows in a northerly to northwesterly flow direction.
Because of the increase in the presence of coarser-grained sand
and gravel from south to north, the alluvial groundwater velocity
increases three-fold north of East 48th Avenue. South of East
48th Avenue, the groundwater flow velocity is estimated to be
approximately 1 ft/day. North of East 48th Avenue, the
groundwater flow velocity is estimated to be approximately 10
ft/day.
Sand Creek does not act as a barrier to northward groundwater
migration. This determination is based on the (1) detection of
contaminants in groundwater north of Sand Creek, (2) lack of
detection of contaminants in Sand Creek (based on data collected
for the Sand Creek Industrial RI (1988» and (3) the occurrence
of unnatural perennial discharges associated with the Aurora
Wastewater Treatment Plant located upstream. The artificial
flows probably exceed Sand Creek's base flow during most of the
year, and thus some portion of its flow infiltrates to the
ACS1/BSPM/062691
15
,
-------
"
~. IrG
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LECEND
£P" WQl. N\AI8£It
IC)ItOOC SURfACE EL£VA'1\CN
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o IEDltOOC SUltf'ACE EUV"'1\ON
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FIgure I
CONFIGURA 11 ON OF
BEDROCK SURFACE
~
~
S'TAP\£TON ORl~ NOR1H
LEYDEN SlREET SliE
OPERABLE UNIT 1
DENVER. COLORADO
Source: EngIneeq Scl~ 1881
-.. .
16
,
-------
UHE (6 EQUAl SA1\JRA Tm '1HIao.ESS
- 20 - OASHED ..EM INF'ERR£'D
CONTCUIt t'1[RVAL - 5 n
I csc I CHGlICAL. SALES C:OWP AllY WAR£);OUSE
v
,
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LEGEND
IP A 'lIEU. NUYlOt
SA 1UItA TED 1HIa
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"to 0'10.1', .,77.8
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LEGEND
£PI. .u. ~
ClROUHD WAlO L£\'n ElEiAl10N
(n. AlO'tt WSQ t..ESS 5.000 n: 201."5201.1
£PI. WELl. POINT NUWI£It
GROUND WA1ER I.E'fU ELEVAl10N
(n. ABO'tt WSl) LESS 5.000 n= 180.5005180.5
<)
1ft! SA
. '10.7
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. GROUND WI. 10 \EtIn El.£VA lION
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1M or EQUAL WAD l£\tI. E1.[VAlION
-S115--(FT. AIIO'tt WSt). DASHED YiHERE INF'ERRED
CONTOuR IH1ERVAL - 5 n
I csc I OIEWICAL $AL£S COWPAHY WAR£HOusE
NOTE: WAD l£\tl FOR LSS-WWS WAS W£ASUR£D
ON OCT08E1t 5. 1t90. mE ~ WAS IWPAC1tD
IV 1HE TANK REWOVALS.
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figure 7
WATER TABLE
CONFIGURA -nON
SEPTEMBER 1990
LE'roEN STREET SITE
OPERABLE UNIT 1
DENVER, COLORADO
;
~
ST AP\.£TON 0ftS\'E NOR1H
Source: Enp~ ScIence, 1"1
-.,a
18
,
-------
"
underlying aquifer resulting in dilution of the contaminant
plume.
Additional efforts to determine groundwater/surface water
interactions in this portion of Sand Creek have included gauging
and installation of piezometer nests, but the results of those
studies were inconclusive.
Nature and Extent of contamination
The RI for CSC OU1 included an investigation of the groundwater,
soils, surface water and air media. Based on data collected
during these investigations, the surface water medium was
determined not to be of concern with regard to contaminant
pathways at the site.
The RI investigatory activities were divided into three separate
phases (Phases I - III). During Phase I, a soil gas survey and
geophysical survey were conducted to identify potentially
contaminated areas requiring further characterization. Soil
borings and monitoring wells were installed during Phase II to
determine the areal extent of soil and groundwater contamination.
Additional soil borings and monitoring wells were installed in
Phase III. Ambient air data were also collected during this
phase.
soil contamination. Forty-five (45) soil borings were installed
during the RI to characterize the nature and extent of soil
contamination. Soil headspace measurements were taken for soils
at 5-foot depth intervals. Measurements were based on readings
of soil headspace made with a field gas chromatograph (GC). Gas
chromatograph readings of the soil headspace were initially
conducted as a preliminary screen to determine the presence or
absence of contaminants in the soil. During Phase II soil
sampling, approximately 30 percent of soil samples displaying
ACS1/BSPM/062691
19
- -.-
,
-------
soil gas detections were submitted for laboratory analysis. Due
to analytical discrepancies and difficulties associated with both
soil field GC headspace analysis and laboratory analysis of soil,
all samples registering soil headspace detections were submitted
for laboratory analysis during the Phase III investigation.
RI investigations indicated the presence of hazardous substances
in the soil media in the vicinity and within the properties owned
by CSC and IDeA. The areal extent of soil contamination based on
soil headspace GC measurements is presented in Figure 8. The
vertical extent of the soil contamination based on measurements
is presented in Figure 9. Contamination is present in the soils
and capillary fringe areas. (The capillary fringe is located
between the water table and vadose zone). Soil contamination
indicated by the laboratory analyses is presented in Figure 10.
The contaminated areas outlined in these figures represent the.
soil zones contributing to groundwater contamination.
Discrepancies between soil and soil headspace data can be
attributed to: (1) lack of adequate laboratory confirmation by
laboratory analysis of soil samples during Phase II sampling; (2)
loss of volatiles prior to laboratory analysis of soils during
Phase II sampling; and (3) difficulties in comparing
concentrations of contaminants detected in the soil vapor and of
contaminants bonded to the soil (through a process referred to as
adsorption); and (4) lack of precision and accuracy of soil
headspace data.
EPA has determined that the extent of soil contamination
requiring remediation should be based on the field GC head space
data as depicted in Figure 8. Field GC head space data for CSC
CUl are more comprehensive than laboratory data collected for the
site. In addition, the potential for loss of volatiles prior to
laboratory analysis was minimized for the GC head space analyses
since samples were analyzed immediately following sampling.
ACS1/BSPM/062691
20
,
-------
..,: Ot.fW24 Ot.lW18
II)
z ,
'"" F9nI
~
~ REGIONS OF CONTAMINA 11 ON
ABOVE FIElD GC SOIL
-N- HEADS? ACE ACll0N LEVELS
I
LEYDEN STREET St1C:
OPERABLE UNIT 1
200 400 DENVER. COLQ~AP.O
FEET Source: engineering Sdenc8. ,",
?1
,
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t.f~4
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@
@
~85 @
00..0.... :1
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LE:CEND
l£YOEN STREET SI'Tt; WEU. NUMBER
L£'tt)EN SiREET S1'Tt; SOIL BORINC NUMBER
SOIL CONT~INA T10N EXCEEDS ACT10N L.£\nS
ABOVE T1-IE CAPIu.ARY FRINGE
SOIL CONT~INA T10N EXCEEDS ACT10N LEVUS
BElOW T1-IE CAPtLl..ARY FRINGE
SOIL CONT~INAT1ON EXCEEDS ACT10N LEVUS
ABOVE AND BELOW 'THE CAPILL.ARY FRINGE
.
..
CHDiICAL
SALES
COYPANY
-------
/
o
/
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h't
\ J
5 x~. \
5 ~l-
LEGEND
A "'W17 L£'tt)Df STREET Sl1E WELL NU\oIBER
5 'T1iICKNESS OF SOIL EXCEEDING
AC110N ~ (FEET)
lEtt>E:N mEET Sl1E SOIl 80RING NUMBER
'THICKNESS OF SOIL EXCEEDING
AC110N LE'vUS (FEEi)
- -15 - UNE OF EQUAl SOIL 11iICKNESS EXCEEDING
AC110N l£'itLS (FEET)
OASHED 'M-4ERE INFERRED
CONTOUR IN1[RVAl-10 FEET
X SB7
15
EAST 48th AVE
~DfICAL
SALES
COt.tPANY
..,:
en
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w
~
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Ct.AW24
o
OMW18
o
00.04-17
. ,
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200
FEET
400
FIgure .
THICKNESS OF SOIL
ABOVE WATER TABLE
EXCEEDING FJELD GC
HEAOSP ACE ACll0N lEVELS
LEYDEN STREET SITE
OPERABL£ UNIT 1
DENVER. COL9~~DO
Source: engineering ScIence. 1881
22
,
-------
..~
(300 ~r' ... fJI ".U) \
\ ~W1J
1500.
, 0
S817
V
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SS17
+
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~ ....... -
::;0 ---- - - - -
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BUILDING
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13
CHEMICAL SALES WAREHOUSE
LEGEND
o LEYDEN StREET SITE ~ NUMBER
MM.
)( PHASE /I LEYDEN StREET SITE
SB1 SOIL BORING NUMBER
PHASE III lEWEN STREET SITE
SOIL BORING NUMBER
PHASE III LEYDEN StREET SITE
SHAllOW SOIL BORING NUMBER
CHEMICAl SAlES COMPANY
CONCENTRAl1ON. ug,A(g (VALUE
REPRESf:NTS HIGHEST CONCENTRA nON
Of PCE
- - - AC110N LINE (DEfiNED BY AC110N lEVEl
ISOPLETH fOR PCE
DASHED WH£RE INFERRED
PC[ WAS OETECTED IN THE CAPILLARY
rRINGE OR AT 111F.: WA lER TABLE ONL Yt-
OETECflON MAY BE ATTRIBUTED TO
CONTAMINATED GROUND WATER
;E
~
lL
~
~
t-
o
(I)
o
x
S81
~11
+
SS10
)(
S89 CSC
210. J J10
~~~ --
S88/
/
/
( /
+SS14 II
OM'f7 J
480"""'-
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+ SS13
.
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1
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r...
-t
100
~
o 25 50
<--- -
rEEf
FIguN 10
AREAL EXTENT Of SOIL
CONT AMINA 11 ON EXCEEDING
ACTlON LEVELS BASED ON
LABORATORY RESULTS
LEYDEN SmEET SITE
OPERABLE UNIT 1
DENVER, C9LORADO
80ur08: ~. 1011008, ''''
-------
con~aminants were detected in the surficial soil, throughout the
soil column, and in the capillary fringe area. This
contamination is the principal source of alluvial groundwater
contamination within OU1. Potential sources of the observed soil
contamination include: (1) organic solvents stored at CSC tank
farm; (2) surface drainage from the CSC property; (3) leaks and
spills from rail cars during unloading operations; and, (4)
releases during CSC operations. The following chemicals of
concern (COCs) were detected in the soil:
Tetrachloroethylene (PCE),
Trichloroethylene (TCE),
1,1-Dichloroethylene (DCE),
cis-1,2-Dichloroethylene (cis-1,2-DCE),
1,1,1-Trichloroethane (TCA),
1,1 Dichloroethane (DCA), and
Methylene chloride.
A description of each of the four source areas is provided below.
CSC Tank Farm. The CSC tank farm is located within the
western boundary of the CSC property. CSC has stored
various acids and organic solvents in this area (See Figure
11 and Table 1). The tank contents reported in Table 1 were
current as of the date of the final RI report (Engineering
Science, 1991). High concentrations of the COCs have been
detected in soil and groundwater immediately northwest of
this area. High soil-gas detections of the compounds PCE,
TCE, and 1,1,1-TCA were also observed in the southern ~
portion of the CSC tank farm. PCE has been and is currently
being stored aboveground in the northwestern portion of the
CSC surface tank farm (presently stored in Tank T-17, Figure
11).
ACS1/BSPM/062691
24
,
-------
TABLE' I (Culllillucd)
SUMMARY OF UNDEItGROUND AND AnOVEGROUNDTANK DATA
LBYDEN STREET sim
Ol8EltAULE UNIT I
DENVEI{, COLORADO
Dale Size Dimensions Tank
Tank 10 Installed (ganons) (feet) Contents Remarks
Aboyeground Tanks
5-1 1977 1,500 NA Hmply
5-2 1977 1,500 NA Hmply
5-J 1977 1,500 NA Empty
5-4 1977 1,500 NA Empty
5-8 1977 3,000 NA Odorless Mineral Spirits
N S-9 1977 5,000 NA Stoddard8 Solvent Petroleum Distillate
c..n
S-IO 1977 4,000 NA 140 Solvent Petroleum Distillate
T-13 1977 1 0, ()()() NA Methylene Chloride
T-14 1977 1 5,000 NA Empty
T-15 1977 15,000 NA Chlorothene SM 1,1,1- Trichloroet hane
T-16 1977 1 5, ()()() NA Chemtrex Petroleum Distillate
T-17 1977 20,000 NA Dowper Tetrachloroethylene
T-18 1977 15,000 NA Ilydrochioric Acid Ilazardous Substance
I
... T-19
1977 13, ()()() NA Ilydrochioric Acid Hazardous Substance
T-20 1977 5,000 NA Sulfuric Acid Hazardous Substance
T-2J 1977 5,000 NA N ilric Acid J-Iazardous Substance
T-22 1977 4,000 NA Stoddard8 Solvent
al NA - in(urm8liun not available.
-------
TABLE I
SUMMARV OF lJNOERGROtlNO AND AnOVEGROUND TANK DATA
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER, COLORADO
Date Size Dimensions Tank
Tank 10 Installed (gallons) (feet) Contents
Underground Tanks
T-l 1976 10,000 9 x 21 Empty
T-2 1976 5,000 R x 16 DUlyl Cellosolve
T-3 1916 10,000 9 x 21 Xylene
~
1\ T-4 1976 10,000 9 x 21 Isopropyl Alcohol (95%)
T-S 1976 15,000 11 x 21 Toluene
T-6 1976 15,000 11 x 21 Melhyl Ethyl Ketone
T-7 1916 15,000 11 x 21 Xylene
T-8 1916 15,000 11 x 21 Acetone
T-9 1976 15,000 11 x 21 Methanol
T-IO 1976 15,000 11 x 21 Isopropyl Alcohol (99%)
.. T-l1 I 1916 15,000 11 x 21 Dow Frost
T-12 : 1916 15,000 11 x 21 VM &. P Naptha
#13 NA8' 6,000 NA Unleaded Gasoline
#14 NA 10,000 NA Diesel Fuel
Remarks
Underground Tanks T-l through T-12 removed
as of June 1990 .
2-butoxyethanol
Hazardous Substance
Isopropanol
Hazardous Substance
Hazardous Substance
Hazardous Substance
Hazardous Substance
Isopropanol
Propylene Glycol
Dates of tank installation and dimensions
for #13 and #14 are unknown; tanks .were
already installed when Chemical Sales
Company purchased the property.
-------
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CHEMICAL SALES
COMPANY
WAREHOUSE
,
-N-
I
40
FEET
STORAGE TANK LOCA TlONS
CHEMICAL SALES COMPANY
LEYDEN STREET SITE .
OPERABLE UNIT 1
DENVER, COLORADO
Source: ~Ineemg ScIenc8. 1"1
27
,
-. ~. .
-------
Surface Drainaae of the CSC ProDerty. Prior to site
preparation for the IDeA building (4661 Leyden st.), a
drainage swale extended from just south of the CSC tank farm
across what is now the IDeA property (Legal Memorandum on
the Defenses to Liability of IDCA, 1991). This swale
potentially provided a pathway for releases of hazardous
substances on the CSC property. The railroad spur, north of
the tank farm, may potentially have caused ponding of
surface drainage from the CSC property. Soil contamination
has been detected in close proximity to the swale and
suspected ponding area.
Railroad SDur. Another potential primary source for the
identified soil and groundwater contamination is the
railroad spur immediately north of the tank farm. Chemicals
are delivered to CSC via the rail spur, and have been stored
in rail cars parked on the spur. Leaks and spills during
unloading operations could have contributed to the
contamination at that location. PCE, 1,1,1-TCA, and other
chemicals are transferred directly from rail cars into the
surface tanks via fill pipes and hoses. Soil and
groundwater contamination has been detected in the vicinity
of the railroad spur north of the CSC tank farm.
Releases During CSC Operations. Several documented releases
of hazardous substances have been reported resulting from
CSC operations. On August 21, 1985, approximately 200
gallons of methylene chloride were released. On
March 28, 1986, contaminated rainwater in the transfer pipe
gallery was discharged into a nearby drainage ditch.
Additionally, on May 9, 1990, 3700 gallons of methanol were
spilled on the ground surface in the area of the CSC tank
farm. Several releases of acid fumes have also been
reported. On February 13, 1990, the Denver Fire Department
ACS1/BSPM/062691
28
'-~.._.. _....
,
-------
responded to an acid release reported fro. CSC property.
The fire department evacuated workers from nearby buildings,
including 4650 Leyden, and treated several workers for the
inhalation of acid fumes. Three additional releases of
acid fumes have been reported and investigated by the Denver
Fire Department. These releases occurred on the following
dates: August 2, 1990; September 11, 1990; and
February 16, 1991.
Groundwater Contamination. During the Remedial Investigation, 36
groundwater monitoring wells were sampled and analyzed for
volatile organic compounds, semi-volatile organic compounds,
total and dissolved metals, and anions. As a result of this
effort, a groundwater contaminant plume was identified in the
alluvial aquifer, emanating from the CSC and IDCA properties.
The direction of contaminant migration is to the north-northwest.
The following COCs have been identified for the groundwater
medium:
PCE,
TCE,
l,l,l-TCA,
1,1-OCE,
l,l-DCA,
cis-l,2-DCE,
Vinyl chloride,
Methylene chloride, and
Carbon tetrachloride.
Groundwater data collected for the COCs during the RI are
provided in Table 2. The data indicate the presence of high
concentrations of volatile organic compounds (VOCs) in the
groundwater beneath the CSC and IDCA properties and in an area
approximately three hundred feet northwest of the CSC tank farm.
PCE has been detected at concentrations as high as 30 parts per
ACS1/BSPM/062691
29
,
-------
TABLE. 2
LABORATORY OROUND WATER QUALITY SUMMARY TABLE
fOR TAJlOET VOLATILE ORGANIC COMPOUNDS
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER. COLORADO
Dile ViAy! M..,I.. I.I-Dichloro- ..:-DidUoro- uua-1.2- C:&tOoG
Sampled DF II 010" CbIorid8 cbIM chac(T oaI) Di~orocUlcnc Tc::raclliorido:
SAMPLE It) "lit. bI ",/L. ,.aIL. IIIIt. IIIIt. 111'1.
US WElJ..S SAMPLED DU'RINO PHASES D AND m
US-~I 02-23-90 100 0.51 15.000 500 SOO U cI 50C UM dI 500 l.!
LSS-M'VQ7-
-------
(;
. TABLE 2 (CoatiDued)
LABOIlATOIlY CiROUND WATEIl QUALITY SUM MAllY TABLE
fOil TARCiET VOLATILE OROANTC COMPOUNDS
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER,COLOIlADO
DII8 ViAyt Mchyl.... 1.I-Dicb1oro- 1.2-Dicb1oro- tnIU-I.Z- C4rbon
Sampled DF II Chloride C1I1orid8 UCD8 crhcnc(ToW) Dichloroahcu T -"t~!IIor:dc
SAMPLE II) jla/l bI 1Ia/l jI&lL jI&lL I'1/t. "" 1-
WELU SAMPLED IN SEPTEMBEJlI990
FIT-MWO 1 <,01 ~-90 1 10 U 5 U 5 U 5 US 5 U S u
FIT -M\\ '0: <,0 1 0H6-90 10.1000 100 U 5 &I 410 190 5 2 J 50 U
m-~'C3-002 09-07 -90 1.10 10 U 5 U 51 13 S 5 U 61
FIT-MWt5A-IQ tI 1.0 I.: 1.: I,;
US-M'\t6 11~-19 5(1. \.IU 11.~36 593 NQ 1.0 U 1.21.:
FIT-~'03 11-03-89 1 I.' U 1.0 U 49 NQ 1.0 U I.: U
FIT-M'Io~ 11..JJa-19 1 1.1 U 2.0 U UU NQ 1.0 U 1.: U
FIT-M\\"C5 11..03-19 1 I.S U 2.0 U 42 NQ 1.0 U 1.: U
FIT-M'\\'07 11..07-59 1 \.S U 2.0 U UU NQ 1.0 U 1.: 1,;
FIT -M\\"CS 11-02-89 1 I.S U 2.0 U 19 NQ 1.0 U 1.: t.:
FIT-W?-)1 1I~19 1 \.1 U 2.0 U UU SQ 1.0 U 1.: U
31
,
-------
TABLE' -2 Continued
LABORATORY CiROv"ND WATER QUALITY SUMMARY TABt.E
FOR TARCiET VOLATILE ORCiANIC COMPOUNDS
L.EYDEN STREET SITE
OPERABLE UNIT 1
DENVER, COLORADO
D8CI ~il-I.l-Oi- I.I-Dichlora- 1.2-0idlJoro- I.I.I-Tn- TrichJor~ Tcnc!l1oro-
Sampled DF &I cAloroct1caa er.hue cI\ue cA1orocr.haAa cdIc4. cUlcne
SAMPLE II) "IlL "IlL "IlL ,.IIL ,.elL "liL
US WE1.U SAMPLED DUJUNO PHASES D ANt) m
US-MWQ$-OOl 02-23-90 100 SOO UM 290 1" SOOU 120 I.~ 6.700
US-MW01-OO1 01-29-90 10.100 no M 50 U SOU 160 910 -.300 0 rl
US-MWOIA-001 02-1:-90 I .5 UM .s U .5 U 140 IS s.a
US-MWOIS-001 02-12-90 1 5 UM 5 U .5 U 160 19 91
US-MWIQ-OOI 02-20-90 20 100 UM 100 U 100 U 1.300 15\1 1.700
LSS-MWU-001 02-2HO 20 100 UM 100 U 100 U 461) .5.000 1.300
L.SS-MWI2-OO1 03-23-90 1.100 3JO E.'f 35 5 U 1.200 0 ~. 700 D 10.000 0
US-MWI 3-00 I ~-o2-90 1.1 00.500 S UM 190 25 12.000 0 5.900 0 17.000 D
US-MWI-Hj() I ()4~-90 1.100 6 M S U 5 U 1.300 0 370 E 2.100 0
L.SS-MWU-ciO I 0:-13-90 1.100 130 M 6 5 U 1.300 0 2.100 D -.300 D
L.SS-MWI6-Ci01 ~~;o 1.100 120 1M S U 5 U 3.0&00 0 5.500 D 10.000 0
US-MWI7-OO1 ~-J3~ 10.50.500 ~M 50 U sou 7.200 0 9.500 D ~.ooo 0
US-MWll-001 03-30-90 1 . 5 t:M S U S U 5 U 5 U 3 1
US-M\\':OA-ci01 03-:~ 1 31 M 12 5 U 5 U 3; "
US-MW20B-ciO I 03-3
-------
~
T ABLE 2~ (CoatiDucd)
LABORATORY GROUND WATER QUALrrV SUMMARY TABLE
fOR TARGET VOLATILE ORGANIC COMPOUNDS
LEYDEN STREET SITE
OPERABLE UN11' 1
DENVER,COLORADO
D.. cis-1.1-Di- 1.I-Oidlloro- 1.2-0idtJoro- I.I.I-Tri- Trich1ol'O- T Cra.:t\Joro-
Sampled OF II c:!I1orocthcM crAu8 ccII.u8 c:!I1or0cd\aA8 QCZl8 aAme
SAMPLE ID 1'1'1. l'aIL /laIL -1'1- /11'1- I','t.
WE1.U SAMPLED IN SEPTEMBEJlI990
m-MWOI-<301 ()9-q7-90 I .5 U .5 U .5 U .5 U I 1 13
FIT-MWOl-<301 ~ 10.1000 190 11 J SOU 7.200 0 2.000 .5.500 0
FIT -MW03-
FIT-~\.5A-<30\ 09-04-90 I S 6 S U 16 n 56
m-MW\5B-<301 09~ I oW II S U .5 U 31 26
SC~"GC)1 ~ 1.50 260 D I S U .520 0 no 0 1.100 0
m-wP04-001 09~5-90 I 60 29 I 1 17 24 16
U-B \3-ao1 09-12-90 I .5 U .5 U .5 U 11 6 IS
R,J.-iU.HJOl 09-12-90 1.20 190 :3 1 J l.sea 0 9400 3.100 0
u'-B 14-<30\(r.du~) 09-1%-90 1.10.100 150 0 17 S U :.300 0 1.000 0 ute 0
WELU SAMPLED IN SOVEMBEJlI989
US-MWOl 114-19 1 SA V 0.1 U 0.3 U 0.3 U 1.1 t.: 19
US-~fW06 11~-89 50 SA ~ 0.3 t.: 13.169 9..~5O 1~.SOO
FIT-~fW03 11-03-&9 1 NA 4 0.3 U 29.5 1.1'12 626
m-MW04 11.J)1-19 1 !'fA 0.1 U 0.3 U 0.3 U 1.2 U 0.3 U
FIT-MWOS 11-03-19 1 !'fA 9 0.3 U 116 60 ~1
FIT -MW01 1l~7-19 1 SA 30 0.3 U 0.3 U 11 19
m-MWCI 11~-19 1 !'fA 9 0.3 U 15 161 31
m-wp-ol 11 ~19 1 NA 0.7 U 0.3 U 100 69 ~7
Ii OF . dillWOA facton. DIU ... dcnvod irom multiple sample dilll1iOIl resu1ca.
bI /1'11.. . aUcrolrama per :i&8r.
" U . ~mpowsd wu ualyz.ed Cor. but aoc dcteCed.
dI M . val\18 wu derived from masa rpoc:tr'IIm ~.
II J . com~ is ptaCIIIlI & ~ Wow eM sample qu&DtilaCiOft limit.
r: D . Compowsd wu iclcDtJied 1& & JOCOIIcIary dilllllon (actor.
&! McchylCZ18 Cbloridc resulta b.avc boaa conec:zod (or auocialed method bLuUt ~OWI:WWioli.
bi E . CoXICCDQ'Uion of the compouad uc:ceded the c:a1ibnLioA tUll. of lAC ~mCAt.
iJ (r.~up) . F'tdd dupli'*c of p~iD, s&1II~1..
ji S . Value wu derived from 1M SUmm&nOli of valli a (or cis-1.2 di~oroe&Acnc &Ad traIU-1.2 dichlorocthcnc.
kI NQ . QO( <\lI&IWtlAbl..
V SA . ftGC ualyzed.
33
,
-------
;,
million (Well LSS-MW17). The highest TCE concentrations detected
were 9.5 parts per million (Well LSS-MW17).
The concentrations of groundwater contaminants decrease
significantly, and the width of the groundwater plume increases,
toward the northern portion of OU1. Concentrations of
contaminants in the groundwater decrease by an order of magnitude
immediately north of Sand Creek. This is most likely a result of
dilution due to groundwater recharge from the Creek. Figures 12
and 13 depict the areal extent of groundwater contamination due
to PCE and TCE, respectively. The areal distribution of these
two chemicals is representative of the distribution of all CSC
OU1 groundwater COCs with respect to areal extent of
contamination and physical and chemical behavior.
In the liquid phase, all of the COCs, with the exception of vinyl
chloride, are heavier than water and tend to sink in an aquifer.
Contaminants which are heavier than water are called dense non
aqueous-phase liquids (DNAPLs). DNAPLs have greater mobility as
a separate phase than lighter-than-water non aqueous-phase
liquids (referred to as LNAPLs) due to their relatively low
solubility, high density and low viscosity. Because of their low
solubility, DNAPLs do not readily mix with water. If a small
volume is spilled, it flows downward under gravity until reaching'
a residual saturation in the vadose zone. It can partition into
the vapor phase, with dense vapors sinking to the capillary
fringe. Infiltrating waters can dissolve residual constituents,
including vapors, and carry them to the groundwater.
If a large volume of a DNAPL is spilled, the liquid may penetrate
into the aquifer as a separate phase liquid and pool above an
impermeable barrier. In the aquifer, the liquid will remain
until dissolved by the groundwater. Groundwater contaminant
concentrations in excess of 10 percent of the chemical's
solubility limit may indicate the presence of a pure DNAPL source
ACS1/BSPM/062691
34
,
-------
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FIgure '2
DISTRIBUTION OF
TETRACHLOROETHENE (PCE)
IN GROUND WATER
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER, CO~9.~~DO
Source: fnglneemg Sca.nce. ,",
I
-------
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LEGEND
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DASHED ~ERE INF'ERREO;
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NOTE: Itl£ASE SEE TA8l£ 4.11 ,~ OATES
WtU.S 'tIO£ SAA8UD
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COWPOUNO WAS HOT D£itC'ItD:
'THE ACCOIoIP AH~C MAl8ER IS 'THE
PRACTICAL QUAH11T"TlON UWIT
COWPOUNO PIt£SEHT AT A
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SAWPU: QUAH'I1TATION LIMIT
VALUt OITAIHED F'ROW SECONOARY
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FIgure 13
DISTRIBUTION OF'
TRICHLOROETHENE (rCE)
IN GROUND WA 'fER
LEYDEN STREET SITE
OPERABLE UNIT 1
DENVER, COLORADO
Source: EngIneer".8g Sdence. '"'
,
-------
..
in the aquifer. PeE has been detected at levels approaching 20
percent of its solubility limit in the suspected source areas of
OU1, indicating a pure PeE residual may exist as a long-term
source of contamination. However, the RI did not locate such a
source.
Once dissolved, the COCs are transported in the direction of the
groundwater flow, and travel at a rate somewhat lower than the
rate of groundwater movement. All of the COCs are relatively
mobile in groundwater. The estimated rate of groundwater
migration is about one foot per day (south of East 48th Avenue)
and about 10 feet per day (north of East 48th Avenue).
The COCs (except vinyl chloride) for OU1 can be degraded by
aerobic and anaerobic bacteria. The compounds are degraded
through dehalogenation. Anaerobic biodegradation of the COCs may
generate vinyl chloride, which is more toxic than its precursors.
Vinyl chloride was detected in groundwater from 8 monitoring
wells. The highest vinyl chloride concentration was observed at
30 parts per billion. Three of the vinyl chloride detections
were observed north of East 48th Avenue (Wells FIT-SC4, FIT-WP4,
and LSS-MW21A). These detections are most likely the result of
the biodegradation of COCs. Subsequent biodegradation of the
vinyl chloride is not a significant process under normal
environmental conditions.
VI.
SUMMARY OF SITB RISKS
Actual or threatened releases of hazardous substances from this
OU, if not addressed by implementing the response action selected
in this ROD, may present an imminent and substantial endangerment
to public health, welfare, or the environment.
CERCLA mandates that EPA select remedies that protect human
health and the environment from current and potential exposures
ACS1/BSPM/062691
37
,
-------
to hazardous substances. Therefore, EPA has conducted a Baseline
RA to evaluate the risk posed by the presence of contaminants at
CSC OUl. The risk analysis resulting from EPA's Baseline RA was
used for the CSC FS and for this ROD. This risk assessment was
carried out to characterize the current and potential threats to
human health and environment which exist at this OU in the
absence of any remedial action.
For a risk to exist, three components must be present: (l) a
source of contamination; (2) a pathway for contaminants to reach
humans, plants or animals; and (3) a population that could
potentially be exposed. If any of the three components is
missing, no risk can exist.
The key component of any health risk assessment is the amount of
chemical reaching the population. This is know as the dose. For
any given dose, there are two general types of toxic responses:
non-carcinogenic and carcinogenic (cancer-causing).
Non-carcinogenic risks are calculated by assuming that there is a
dose below which no adverse health effects will occur. These
calculations are usually based on results of animal studies and
include a number of additional conservative assumptions to take
into account what the estimated risk is to humans. For such
chemicals, exposures less than this dose (referred to as the
"reference dose" (RFD}) will result in no toxic effects.
Potential concern for non-carcinogenic effects of a single
contaminant in a single medium is expressed as the hazard
quotient (HQ) or the ratio of the estimated intake derived from
the contaminant concentration in a given media referred to as the
chronic daily intake (CDI) to the reference dose (RFD). By
adding the HQs for all contaminants within a medium or across all
media to which a given population may be reasonably be exposed,
the Hazard Index can be generated. The HI provides a useful
reference point for gauging the potential significance of
ACS1/BSPM/062691
38
_..... ....
,
-------
u
multiple contaminant exposures within a single medium or across
media.
For carcinogens, it appears that there is no safe dose. Instead,
the risk of cancer becomes smaller and smaller as the dose
. decreases. Cancer potency factors (CPFs) are used for estimating
excess lifetime cancer risks associated with exposure to
potentially carcinogenic chemicals. Excess lifetime cancer risks
are determined by multiplying the intake level with the cancer
potency factor. These risks are probabilities that are generally
expressed in scientific notation (i.e., 1 x 10.6 or lE-6). An
excess lifetime cancer risk of 1 x 10.6 indicates that an
individual has a one in one million chance of developing cancer
as a result of site-related exposure to a carcinogen over a 70-
year lifetime under the specific exposure conditions at the site.
A risk in the range of 10~ to 10.6 is considered to be
acceptable. EPA generally uses 10.6 as a goal in evaluating
cleanup alternatives. However, other factors, such as exposure,
availability of chemical-specifics ARARs, technical limitations,
background concentrations, and uncertainties may result in the
setting of a different goal.
Contaminants and Toxicity Assessment
CSC RI results indicate contamination in the soil, groundwater,
and air media. In order to characterize site risk at CSC QU1,
the RA identified nine CQCs for the groundwater and soil media at
the CSC QUl. These chemicals were identified based on the
concentrations at the site, frequency of detection, toxicity,
physical/chemical properties that affect mobility, and
prevalence/persistence in these media. A listing of these
chemicals is presented in Section V. They were determined to
represent the total potential health and environmental risks at
the Site.
ACS1/BSPM/062691
39
,
-------
u
The COCs for OUl are a diverse group of volatile chlorinated
hydrocarbon solvents. Most of the chemicals are central nervous
system depressants and either liver or kidney toxins at high
doses. six of the COCs are carcinogenic (PCE, TCE, Methylene
Chloride, Carbon Tetrachloride, 1, i-DCA, and 1,2 DeE). The
carcinogenic potency of a compound is represented by its cancer
potency factor (CPF). The CPFs for OUl COCs are presented in
Appendix A. DeE and PCE are generally the carcinogens present at
the highest concentrations in the groundwater, soil and soil gas.
The potential for the COCs identified for OUl to cause
noncarcinogenic health effects varies widely. The RFDs for the
COCs are presented in Tables 1-11, 1-12, 1-13 and 1-14 of
Appendix A.
Land Use
Land use within OUl was assessed based on a survey conducted by
the Tri-County Health Department of Colorado. The land use
within OUl is largely industrial. The OUl population is
comprised mostly of workers who commute from outside OUl to jobs
in the office and warehouse buildings within the site. Six
residences are located in the northern portion of OU1. One
residence is located on East 50th Avenue and the others are
located on East 52nd Avenue. All of the residences within OUl
are connected to the SACWSD system. The alluvial groundwater
within OU1, however, is considered to be a potential future
drinking water source for OUl residences. In addition,
contaminated groundwater within the CSC OU1 area flows northward
into the CSC OU2 area. Alluvial groundwater within the OU2 area
is the principal source of water for domestic uses in Co~erce
City.
Based on an analysis of current and future land use,
calculations have been performed for three different
that could be exposed to contaminants present at the
risk
populations
OU1 area:
ACS1/BSPM/062691
40
,
-------
(,
industrial workers, current residents and hypothetical future on-
site residents. Based on the current land use, industrial land use
(i.e., occupational exposure) exists for the area south of East
48th Avenue. This area is currently zoned for industrial and
commercial uses. Risks for a "current resident" were assessed
based on residential land use north of East 48th Avenue.
Residential land use exists in the area north of East 48th Avenue.
In order to assess future residential exposure for a "hypothetical
future resident" at the site, potential risk associated with
residential land use in the area south of East 48th Avenue was
evaluated. Because this area is currently zoned for industrial and
commercial uses, it is unlikely that residential land use will
exist in this area within the next few years. There is a
possibility, however, that future residential development may occur
within the current industrial area during the time period required
to implement the remedial alternatives evaluated in this ROD.
There are no endangered species at the CSC OU1 area. Potential
environmental receptors include aquatic habitat, wildlife and
vegetation within the Sand Creek floodplain. The alluvial aquifer
is a Class I aquifer as described in EPAs Groundwater Protection
Strategy.
Exposure Assessment
The results of site investigations conducted under the CSC RI
indicated the presence of contaminants in the soil, 'groundwater,
and air media. Based on these results and the evaluation of land
use at the site, the following potential exposure pathways were
quantitatively evaluated:
1.
Ingestion of groundwater contaminants in drinking water
and inhalation of volatilized contaminants through
showering (industrial, current and future residential
ACS1/SSPM/062691
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u
2.
land uses). No site residents within OU1 are currently
exposed to contaminated groundwater.
Dermal contact with COCs during showering (industrial,
existing and future residential land uses).
In addition, the following existinq exposure pathways were
quantitatively evaluated:
1.
Direct contact and incidental ingestion of contaminated
soil (industrial and future residential land uses).
2.
Inhalation of onsite ambient air (industrial). For
future residents, a potential pathway exists
regarding inhalation of vapors from soil and
groundwater contaminants in basements. Due to the
high degree of uncertainty associated with
quantitatively assessing risk from this pathway
through use of the Garbesi and Sextro model (1989),
risks for this pathway are presented qualitatively.
Basement VOC exposure is not evaluated for this
reason since a validated basement exposure model was
not available at the time the risk assessment was
prepared. Such potential risks will be reevaluated
during the 5 year review to ensure the remedies
selected are protective.
Since only undetectable amounts of groundwater contaminants
discharge into Sand Creek, it was determined that a complete
pathway does not exist for the environmental receptors withinOU1.
Concentrations of contaminants used to estimate current and
potential risk were based on the 95 percentile confidence limit of
the geometric mean of data collected for the groundwater, soil and
air media. These concentrations are presented in Appendix A.
ACS1/BSPM/062691
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Exposure assumptions used to determine the average amount of
chemical in contact with a particular individual are also presented
in Appendix A. These estimates represent Reasonable Maximum
Exposure scenarios.
The highest exposure potential is associated with current 'workers
and future residents. This represents potential exposure based on
current and future use of the area south of East 48th Avenue. This
risk potential represents both existing and potential pathways. In
the case of current workers, there is no indication that
groundwater is used for any domestic or commercial purpose in the
area. The future resident scenario would require conversion of the
current industrial area (south of East 48th Avenue) to residential
use.
Risk Characterization
The baseline risk assessment quantitatively estimated potential
noncarcinogenic and carcinogenic risks posed by the COCs in various
media at C5C QU1. As stated previously, noncarcinogenic risk is
presented as the fraction of the daily dose of a given chemical
which is estimated to result in no adverse health effects.
Carcinogenic risk is presented as a probability value (i.e., the
chance of developing cancer over a lifetime). These risk estimates
are conservative and many overestimate the actual risk due to
exposure. A summary of noncarcinogenic and carcinogenic risk at
CSC QU1 is presented in Tables 3 and 4. A description of these
risk is presented below.
Industrial Land Use. Noncarcinoqenic Risk. High
concentrations of contaminants in groundwater pose a large
noncarcinogenic aggregate risk of 75 due to ingestion (HI of
62) and inhalation (HI of 13) of contaminants during drinking
and showering with contaminated groundwater. Soil contam-
ination does not pose a significant noncarcinogenic risk.
ACS1/BSPM/062691
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..
(
4
oj TABLE 3
SUMMARY OF CANCER RISKS BY PATIiWA Y FOR
POTENTIAL RECEPTORS AT THE CHEM SALES OUI SITE
Current Current Future Future
Exposure Pathway Workers Residents Residents Children
Groundwater Pathways
Ingestion of ground water 4 1 10-2 3 1 1O~ 1 1 10-1 NE
Inhalation of VOCs during 2 x 10-2 4 1 10~ 9 X 10-2 NE
showering
Direct contact witb VOCs 3 x 10~ 1 X 10"7 8 x 10~ NE
during showering
Total Risk for 6 x 10-4 71 l~ 1 1 10"1 NE
Groundwater Pathways
SoiJ Pathways
Direct contact with surface 2 x 10~ NE 6 x 10~ 1 x 1O~
soil (dermal absorption)
Incidental ingestion of 7 1 10-7 NE 7 X 10"7 9 x 10-5
surface soil
Total Risk for Soil 2x 1~ NE 6 x 10-4 1 x 1O~
Pathways
Inhalation of VOCs in 5 1 10"5 NE NE 4 1 10-5
ou tdoor ambient air
Total Risk for Air 5 1 10"5 NE NE 4 1 10-3
Pathways
TOTAL RISK 6 x 10-2 7 x 1O~ 2 1 10-1 3 x 10~
NE = Not Evaluated
44
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,
.
TABLE 4
SUMMARY OF NONCARCINOGENIC RISKS (HAZARD INDICES) BY PATIiWA Y
FOR POTENTIAL RECEPTORS AT THE CHEM SALES OUI SITE
Current Current Future Future
Exposure Pathway Workers Residents Residents Chi 1 dren
Groundwater Pathways
Ingestion of ground water 62 0.3 84 NE
Inhalation of VOCS during 13 0.2 26 NE
showering
Direct contact with VOCs 0.006 0.00005 .01 NE
during showering
Total Risk for 75 0.5 110 NE
Groundwater Pathway
Soil Pathways
Direct contact with surface 0.0001 NE 0.3 3.9
soil (dermal absorption)
Incidental ingestion of 0.003 NE .003 0.02
surface soil
Total Risk for Soil 0.003 NE 0.3 3.9
Pathway
Inhalation of VOCS in 0.007 NE NE 0.01
outdoor ambient air
Total Risk for Air 0.007 NE NE 0.01
Pathway
TOTAL HAZARD 75 0.5 110 4.0
INDEX
NE = Not Evaluated
45
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o
Industrial Land Use. Carcinoaenic Risk. High concentrations
of contaminants in groundwater present a high potential
cancer risk (5.4 X 10.2) due primarily to ingestion and
inhalation of contaminants during drinking and showering
with contaminated groundwater. In addition, inhalation of
COCs in outdoor ambient air and dermal absorption of
contaminants through direct contact with soil contamination
exceeds EPA's 10-6 acceptable risk point of departure. The
risk posed through inhalation of ambient air is estimated at
5 X 10.5. The risk posed through dermal contact of
contaminated soils is 2 X 10.6. The total cancer risk posed
to this population (workers) is 6 X 10.2. The chemicals
contributing the largest potential risk are DCE and PCE.
Existina Residential Land Use. Noncarcinogenic Risk.
Concentrations of contaminants in the groundwater decrease
significantly north of East 48th Avenue. Due to this
factor, a hazard index of less than 1.0 was determined for
the groundwater pathway. soil contamination has not been
detected in the existing residential area.
Existina Residential Land Use. Carcinoaenic Risk. Potential
carcinogenic risk posed to current site residents is based
solely on the groundwater media. Due to the decrease in
concentration of groundwater contamination in the existing
residential area (north of East 48th Avenue), potential
carcinogenic risk posed through ingestion and inhalation of
contaminants during drinking and showering with contaminated
groundwater is much less than either the worker or future
resident exposure scenarios. This risk is estimated at~7 X
10.4. This potential risk, however, still exceeds EPA's
-4 -6
acceptable risk range of 10 to 10 .
ACS1/BSPM/062691
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Future Residential Land Use. Noncarcinoaenic Risk.
Potential noncarcinogenic risks posed to future site
residents are associated with the groundwater and soil
media. Noncarcinogenic risk at the Site are the highest for
this population because this scenario assumes residential
habitation in the most highly contaminated areas. CDI
estimates are higher for residents than workers due to a
higher frequency and duration of exposure. The estimated
potential noncarcinogenic aggregate risk associated with the
groundwater media is 110.
Future Residential Land Use. Carcinogenic Risk. Potential
carcinogenic risks posed to future site residents are
associated with contamination detected in the groundwater
and soil media. Children were identified as the most
sensitive group of this population. Potential carcinogenic
risks associated with the groundwater media is 1 X 10.'.
Potential carcinogenic risk for children through exposure to
contaminated surficial soils is 2 X 10.4 due to direct
contact, incidental ingestion and inhalation. Inhalation of
contaminants in basements constructed in areas of high
concentration of soil and groundwater contaminants would
most likely present unacceptable carcinogenic and
noncarcinogenic risk.
Results
The results of the CSC OU1 RA indicate that contaminants detected
within this OU pose an unacceptable potential risk to site
workers and current and future site residents. Risks posed to
these populations exceed the 10.4 risk level. These risks
represent hypothetical exposure since groundwater is not
currently used for domestic indoor uses and no basements exist
within OU1.
ACS1/BSPM/062691
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u
Based on the results of the RA, two actual or existing pathways
pose unacceptable risks to public health at CSC OU1. These
pathways relate to soil contamination at the Site. Carcinogenic
risk posed through inhalation of volatile COCs in the ambient air
by site workers is estimated at 5 x 10.5 risk, and posed through
dermal contact with surficial soils is estimated at 2 x 10'6
. -6 .
risk. These r~sks exceed EPA's 10 po~nt of departure.
Groundwater Remediation Levels
Federal regulations require that maximum contaminant level goals
(HCLGs) established under the Safe Drinking Water Act, and that
are set at levels above zero, shall be attained by remedial
actions for ground or surface waters that are current or
potential sources of drinking water, where the HCLGs are relevant
and appropriate under the circumstances of the release based on
the factors in 40 CFR ~300.400(g) (2). If an HCLG is determined
not to be relevant and appropriate, the corresponding maximum
contaminant level (HCL) shall be attained where relevant and
appropriate to the circumstances of the release.
Where the HCLG for a contaminant has been set at a level of zero,
the HCL promulgated for that contaminant under the Safe Drinking
Water Act shall be attained by remedial actions for ground or
surface waters that are current or potential sources of drinking
water, where the HCL is relevant and appropriate under the
circumstances of the release based on the factors in 40 CFR
~ 300.400(g) (2).
In cases involving multiple contaminants or pathways where
attainment of chemical-specific ARARs will result in cumulative
risk in excess of 10.', other criteria in paragraph (e) (2) (i) (A)
of 40 CFR Part 300.400 cleanup level to be attained.
ACS1/BSPM/062691
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Maximum Contaminant Level Goals (MCLGs) exist for some of the CSC
OU1 COCs. All of these MCLGs are set at zero and therefore are
not considered in establishing groundwater remediation levels.
MCLs for CSC OU1 are available for TCE, 1,1-DCE, Cis-1,2-DCE,
vinyl chloride and carbon tetrachloride. The cumulative risk
associated with exposure to groundwater contamination at the MCLs
for these compounds is 1 x 10-4 based on the ingestion and
inhalation of contaminants.
MCLs are drinking water standards for specific chemicals that are
enforceable for public drinking water systems. These standards
are "relevant and appropriate" requirements for establishing
acceptable groundwater remediation levels of contaminants in
groundwater. Proposed MCLs are "To Be Considered" (TBCs) for
establishing acceptable groundwater remediation levels in the
groundwater for those chemicals without a promulgated Federal or
State standard. For those chemicals without a promulgated MCL,
State standard, or proposed MCL, acceptable groundwater
remediation levels have been derived based on a 10-6 cancer risk
and practical quantitation levels. Practical quantitation levels
represent the lowest concentration that a laboratory can
"practically" detect. Residential use exposure assumptions were
used in the development of these values. Attainment of these
groundwater remediation levels will assure that risk associated
with exposure to contaminated groundwater will fall within the
. -4-6
acceptable r1sk range of 10 to 10 .
Acceptable groundwater remediation levels as determined by
chemical-specific ARARs and TBCs for OU1 COCs are presented in
Table 5.
Based on the evaluation conducted in the CSC OU1 Baseline RA,
evaluation of chemical-specific ARARs and TBCs, and EPA policy,
ACS1/BSPM/062691
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'..)
Chemical
DCA
DCE
TCA
PCE
TCE
1,2 DCE
VC
Carbon
Tetrachloride
Methylene
Chloride
ACS1/BSPM/062691
TABLE 5
GROUNDWATER REMEDIATION LEVEL
standard (ma/1) Comment
.005
10 -6 Risk Level,
.007
MCL (40 CFR 141)
MCL (40 CFR 141)
.200
.005
MCL, (56 FR No. 20,
1/30/91)
MCL (40 CFR 141)
.005
.070
Colorado Basic Standard
for Groundwater,
Effective
September 30, 1989
.002
MCL (40 CFR 141)
.005
MCL (40 CFR 141)
.010
10'6 Risk Level
50
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the following remedial action objectives have been established
for QUI groundwater.
3.
1.
Prevent ingestion and inhalation of groundwater 1)
with carcinogens in excess of remediation levels
identified in Table 5 and, 2) which presents a
total carcinogenic risk range greater than
1 x 10-6 - 1 x 10-4.
2.
Protect uncontaminated groundwater
future use by preventing migration
excess of remediation levels.
for current and
of contaminants in
Restore contaminated groundwater to 1) remediation
levels specified Table 5, and 2) concentrations
which present a total carcinogenic risk of 1 x
10 -4 - 1 x 10-6.
Soil Remediation Levels
Appropriate soil remediation levels were determined based upon
leaching of soil contaminants into the underlying groundwater.
Levels are based on restoring the groundwater to its most
beneficial use which is drinking water~ (see Table 5). Based on
exposure calculations, performed during the RA, these levels are
also protective for the incidental soil ingestion, inhalation and
direct contact pathways.
Soil remediation levels are based on the groundwater remediation
levels, aquifer dilution, the physical and chemical properties of
the contaminant, and the ability of the soil to retard leaching
of the contaminant due to adsorption. Soil remediation levels
were calculated by multiplying the acceptable concentration of
leachate from the soil by the partitioning coefficient (Kd) for
the soil. The Kd represents the mobility of a particular
ACS1/BSPM/062691
51
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G
'--,
contaminant within the soil at the CSC property. They were
developed based on site-specific batch and column adsorption
studies conducted for CSC OU2.
The acceptable concentration of leachate represents the amount of
contaminants in the soil that will be allowed to migrate into the
groundwater. For CSC OUl, this value was derived by multiplying
the groundwater remediation levels (i.e., MCLs) by a
Dilution/Attenuation Factor. A Dilution/Attenuation Factor of
100 was used for these calculations. This factor assumes that
leachate concentrations will be reduced by a factor of 100 due to
aquifer dilution and soil attenuation in the soil above the
aquifer. This value has been determined to be protective and
appropriate based on evaluations and studies documented in the
Toxicity Characteristic Rule, 40 CFR 261.
Soil Remediation Levels and Kd values for the COCs in the soil
medium are as follows:
Compound Groundwater KD x 100 = Soil Remediation
Remediation Level Level (ppm)
PCE 0.005 0.30 0.150
TCE 0.005 0.23 0.115
1,1,1-TCA 0.200 0.22 4.400
1,1-DCE 0.070 0.15 0.105
DCA 0.005 0.18 0.090
Vinyl Chloride 0.002 0.06 0.012
Methylene Chloride 0.010 0.14 0.140
Soil remediation levels are based on
the RI/FS and on the assumption that
contaminated. These levels will only
data are collected pertaining to the
soil data collected during
the soil column is uniformly
be revised if additional
mobility of contaminants
ACS1/BSPM/062691
52
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(i.e., if column and batch flushing tests are conducted). These
data may be collected during Remedial Design/Remedial Action
(RD/RA). Any revised soil remediation levels derived from
additional data must be protective of groundwater based on the
groundwater remediation levels cited in Table 5.
VII.
DBSCRIPTIO. OF ALTBRNATIVES
An FS was conducted to develop and evaluate remedial alternatives
for OU1 at the Chemical Sales Superfund site. Remedial
alternatives were assembled from applicable remedial technology
process options and were initially evaluated for effectiveness,
imp1ementabi1ity, and cost. As a result of this screening, three
alternatives were considered for detailed evaluation. These
three alternatives (1, 3, and 5) were then evaluated and compared
to the nine criteria required by the NCP. Alternative 1, the "no
action" alternative, is required by the NCP to be retained for
detailed evaluation. The no action alternative serves as a
baseline point of comparison for other alternatives.
A batch flushing groundwater model was used to estimate the time
required to clean up the contaminated groundwater (USEPA, 1988c).
This model predicts the volume of water that would be required to
be removed and treated to reduce existing concentration levels to
groundwater remediation levels. Because the model cannot
simulate actual conditions in the aquifer, a great deal of
uncertainty is associated with estimates of aquifer restoration
time frames.
As stated previously, the groundwater remediation levels are
based on MCLs, proposed MCLs and 10-6 risk. Attainment of these
levels will be protective of human health and the environment.
EPA recently studied the effectiveness of groundwater extraction
systems in achieving specified goals and found that it is often
difficult to predict the ultimate concentration to which
ACS1/BSPM/062691
53
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contaminants in the groundwater may be reduced. The
effectiveness of groundwater extraction may be further inhibited
if DNAPLs are present. The study did find that groundwater
extraction is an effective remediation measure to prohibit
further migration of contaminants and can achieve significant
mass removal of contaminants. Two of the remedial alternatives
described in this section include groundwater extraction systems
and assume that it is technically feasible to achieve the
groundwater remediation levels cited in this ROD.
Except for the "no action" alternative, which
groundwater monitoring only, each alternative
following two common elements:
includes
includes the
Groundwater Monitoring. Existing and future groundwater
monitoring wells would be sampled and analyzed periodically
throughout OU1 to assess the effectiveness of ongoing remedial
activities. Monitoring points are anticipated to be located
upgradient of the plume (to detect contamination from other
sources), within the plume (to track the plume movement during
remediation), and downgradient from the OU (to detect plume
migration and remediation effectiveness).
Notification of potential Health Threat. Upon request for a well
permit within the OU1 area, the applicant would be notified by
the Colorado state Engineers Office of the potential health risk
associated with the contaminated groundwater until groundwater is
cleaned up to groundwater remediation levels.
Alternative 1. No action with groundwater .onitorinq.
Under this alternative, EPA would take no further action to
control or remediate contamination detected within OU1.
Groundwater monitoring would continue on an annual basis at
approximately 12 monitoring wells. Measured contaminant
ACS1/BSPM/062691
54
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concentrations would be used to update the prediction of the
groundwater contaminant migration patterns and impacts on
downgradient water supply wells. Contaminated groundwater
originating from OU1 would be treated by the SACWSD Klein
Treatment facility for 30 years, the expected operating life of
the facility. Residents within the area would continue to be
provided with water from SACWSD. Because this alternative would
result in contaminants remaining onsite, CERCLA requires that the
site be reviewed every five years. If indicated by the review,
remedial actions would be implemented at that time to remove or
treat the wastes.
Results of groundwater modeling indicated that at a minimum,
approximately 50 years would be required to remediate the
contaminated groundwater to groundwater remediation levels based
on Alternative 1. This estimate does not take into considerat~on
the potential presence of DNAPLs or account for leaching of soil
contaminants into groundwater.
The present worth cost for Alterative 1 would be $301,000. Since
the alternative requires "no action", there would be no capital
cost. Annual operation and maintenance (O&M) costs are estimated
to be $19,600 for groundwater monitoring.
Alternative 3. Thermally Bnhanced Soil Vapor Bxtraction, Lov
Volume Groundwater Interception in Source and Plume Areas, Air
strippinq, catalytic oxidation in Source Area, Reinfiltration of
Treated Water.
This remedial alternative would entail the installation of two
lines of groundwater extraction wells or drain systems, one south
of East 48th Avenue and another along East 52nd Avenue, (Figure
14). One or more aquifer tests would be required to obtain
appropriate data for design of these systems. Estimates of the
number of wells and specific locations of wells would be refined
ACS1/BSPM/062691
55
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r-
"
.,.,.------..............".------............
/ /, ,
,. " "
,." "
/ , ,
/ " '\
1\\
~ I \ \
>- f \ \
~ I \ I
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, I ,
\ I I
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"" ,.
'..c../ ,,/ E.50th
E.52nd
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II
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STAPLETON DRIVE NORTH
N
A
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o
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300
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600
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LEGEND
.
COLLECTION WELLS
/ ..... COLLECTION WELLS
\ J F'lADIUS OF INFLUENCE
-
o CHEMICAL SALES
U C::JMPANV WAF'lEHOUSE
FIGURE 14
PASSIVE
PUMPING
SYSTEM,OUI
Adapted from Engineering Science, 1991
56
,
-------
during remedial design
groundwater monitoring
information.
based on aquifer test data, additional
data and other relevant site and design
The objective of the East 48th Avenue system would be to collect
contaminated groundwater from the contaminant source area for
treatment. Approximately 20 extraction wells located along an
1,800-foot-1ong pumping line south of East 48th Avenue would be
used to contain and collect the more highly contaminated
groundwater in the source area. This pumping line would produce
approximately 100 gpm. The extracted groundwater would be
transported to a central air stripping unit. VOc emissions from
the air stripping unit would be treated through catalytic
oxidation. This process would result in the destruction of
approximately 97 to 99 percent of the VOCs emitted from the air
stripping unit.
The objective of the East 52nd Avenue system would be to prevent
northward migration and reduce the impact from this groundwater
plume on the SACWSD water supply wells. Groundwater collection
would be accomplished using two high-volume extraction wells.
These wells would be located approximately 400 feet south of East
52nd Avenue to collect groundwater in the Sand Creek area and
would pump approximately 420 gpm each. The combined flow of 840
gpm would be treated in a 6- to 8-foot diameter air stripping
tower. The total VOC emissions from this tower are estimated to
be less than six pounds per day. Air emissions resulting from
air stripping operations at the East 52nd Avenue system would be
sampled as necessary to assure compliance with State of Colorado
Air Quality Standards and Regulations as promulgated under the
Colorado Air Quality Control Act and EPA policy. The CSC site is
located in an ozone non-attainment area.
Colorado Air Quality Regulations Nos. 1, 2, 3, 7, and 8 are
applicable requirements for actions involving air stripping.
The
ACS1/BSPM/062691
57
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specific citations of these regulations and their purpose are as
follows: (a) 5 CCR 1001-5, Reg. 3, requires air pollution
emission notices (APENs), air impact analyses for toxic
pollutants, and the attainment and maintenance of state
standards; (b) 5 CCR 1001-5 Sec. IVD, Reg. 3, regulates the
attainment and maintenance of any National Ambient Air Quality
Standards (NAAQS); (c) 5 CCR 1001-9, Reg. 7, regulates emissions
of volatile compounds; (d) 5 CCR 1001-10, Reg. 8, regulates vinyl
chloride and benzene emissions: (e) 5 CCR 1001-4, Reg. 2,
requires that the design provide for odor-free operations: and
(f) 5 CCR 1001-3, Reg. 1, requires that particulate emissions be
minimized, opacity limitations be observed, and a particulate
emission control plan be filed. Federal ARARs pertaining to air
stripping include National Emission Standards for Hazardous Air
Pollutants for regulating vinyl chloride emissions (40 CFR 61).
In addition, EPA has established a policy (OSWER Directive
9355.0-28, Control of Air Emission from Superfund Air Strippers
at Superfund Groundwater sites) regarding the control of air
emissions from air stripping units at Superfund sites located
within ozone non-attainment areas. This policy recommends
controls for air emissions exceeding 3 pounds per hour, 15 pounds
per day and 10 tons per year. The estimated maximum VOC air
emissions from the East 52nd Avenue system is less than six
pounds per day (based on 840 gpm). It is anticipated that this
emission rate will drop substantially throughout the
implementation of this action. Estimated risk associated with
this action is less than 1 x 10-6.
Treated groundwater would be discharged to the aquifer through
downgradient infiltration trenches for the East 48th Avenue
system, and discharged into gravel-filled infiltration beds
located near Sand Creek for the East 52nd Avenue system.
ACS1/BSPM/062691
58
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The treated groundwater would be sampled as necessary to
sUbstantively comply with Underground Injection Control (UIC)
requirements (40 CFR 144, 146, and 147), EPA RCRA requirement
section 3020 and Colorado Regulations 5 CCR 1002-2, Sec. 6.1.0: 5
CCR 1002-3 sec. 10.1.0 and 6 CCR 1007-3 section 100.21(b). Under
these requirements, reinjected groundwater must be treated to
health-based levels (i.e., MCLs or proposed MCLs).
contaminated soils contributing to groundwater contamination,
would be treated through the installation and operation of a
thermally enhanced soil vapor extraction system. Extracted
vapors from both the soil vapor extraction system and air
stripping unit would be treated through catalytic oxidation. The
hot combustion gases from the catalytic oxidation unit would be
recycled to the soil to enhance extraction of the soil
contaminants.
On June 28 - July 2, 1990, soil vapor extraction pilot tests were
conducted at CSC OU1. pilot test results indicated that a vapor
extraction rate of 100 cubic feet per minute (CFM) would remove
contaminants within a 75 to 100-foot radius. Contaminant removal
rates for these tests ranged from 7.0 to 9.6 pounds per hour. In
addition, similar vacuum readings were observed at various
pressure monitoring points screened at the same depth and same
distance from the extraction wells, indicating that soils within
the test area are relatively homogeneous. Based on the high VOC
removal rates, large radius of influence and homogeneous nature
of the soil, the results of these tests indicate that this type
of technology is extremely effective in removing soil
contaminants at the CSC site. It is anticipated that 10 soil
vapor extraction wells, spaced 150 feet apart, with a total
extraction of 1000 CFM (100 CFM per well) would be installed
under this alternative. Based on this conceptual design, it is
estimated that soil remediation levels would be attained within
150 days. Laboratory analysis of soil would be conducted upon
ACS1/BSPM/062691
59
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completion of the soil vapor extraction activities to verify
compliance with soil remediation levels. A full summary of the
soil vapor extraction pilot test is presented in Appendix J of
the CSC QUl RIfFS report.
It is estimated that approximately 7 years would be required to
clean up the groundwater plume area (between East 48th Avenue and
Sand Creek) and approximately 34 years would be required to
attain groundwater remediation levels for the source area (south
of East 48th Avenue). Capital costs for Alternative No.3 would
be approximately $733,000, with an annual 0 , M cost of $96,000
for years 1-7 and $66,000 for years 8-34. The present worth cost
would be approximately $1,922,000.
Alternative 5. Thermally Bnhanced Vapor Bxtraction, High
Groundwater Bxtraction in Source Area and Plume Area, Air
stripping, catalytic Oxidation in Source Area, Aquifer
Reinjection ot Treated Water.
Volume
This alternative is similar to Alternative NO.3, except that a
more aggressive groundwater extraction system would be
implemented (Figure 15). Soil contamination would be treated
through soil vapor extraction as described in Alternative No.3.
It is anticipated that 150 days would be required to attain soil
remediation levels for CSC QU1.
Contaminated groundwater located near the source (south of East
48th Avenue) would be removed through a pulsed pumping operation
with upgradient reinjection of treated groundwater to improve
flushing efficiency and contaminant recovery. A grid of
approximately 65 extraction wells is estimated for this
alternative. Each well would be equipped with a submersible pump
and recharge line so that any problem well could be used for
either extraction or reinfiltration. The anticipated pumping and
recycle rate for this alternative is approximately 250 gpm. To
ACS1/BSPM/062691
60
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STAPLETON DRIVE NORTH
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I
SCALE
300
I
FEET
600
I
LEGEND
.
COLLECTION NELLS
I --. COLLECTION WEllS
\ - ) ~ADIUS OF INFLUENCE
o
EXTRACTION WELLS
EXTRACTION WELLS
A~EA OF INFLUENCE
D CHEMICAL SALES
U COMPANY WA~EHOUS~..
FIGURE 15
ACTIVE
PUMPING
SYSTEM, OUt
Adapted from Engineering Science, 1991
61
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"
minimize pumping volumes, operation of extraction wells and
reinjection wells would be alternated. The groundwater
extraction system would also lower the water table and expose the
capillary fringe area and improve vapor extraction from this
highly contaminated region.
If DNAPLs are present at the Site, this alternative would be able
to effectively extract and treat these liquids due to a large
volume of pumping and number of wells. If DNAPLs are detected,
separate pumping of the DNAPLs and the contaminated groundwater
would possibly be required. Additionally, if DNAPLs are
detected, investigations may be required to delineate the pockets
of DNAPLs. These activities include the installation of
additional soil borings and monitoring wells.
Similarly to Alternative No.3, air stripping would be used to
treat contaminated groundwater in the source area. Groundwater
would be required to be treated to groundwater remediation
levels. Due to the high groundwater contaminant concentrations
in the source area, emissions from the air stripping operation at
the source area would be treated by catalytic oxidation. Exhaust
from the catalytic oxidation system would be recirculated to the
soil. Treated groundwater would be sampled as necessary to
comply with Federal UIC requirements (40 CFR Parts 144, 146, and
147 and State of Colorado Regulations 5 CCR 1002-2, Sec. 6.1.0
and 5 CCR 1002-3, sec. 10.1.0). Concentrations of reinjected
groundwater must be below health based levels as stipulated under
these requirements.
Extraction of groundwater in the plume area (between East 48th
Avenue and East 52nd Avenue) would also be similar to Alternative
No.3, with the exception of the addition of two extraction wells
in the southern portion of the plume area. These two additional
extraction wells would be located in the more heavily
contaminated area between 48th Avenue and East 50th Avenue. The
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extraction rate of these wells would be approximately 150 qpm.
The extraction rate of the two extraction wells located between
East 50th Avenue and East 52nd Avenue would be approximately 350
gpm compared to 420 gpm under Alternative No.3. The estimated
combined groundwater extraction rate for the plume area would be
1000 gpm. Use of the additional extraction wells would more
rapidly. remove contaminated groundwater in the plume area and
would reduce plume area remediation time to approximately 6
years.
The additional water generated by these wells would be combined
with water collected at the two high-volume wells at East 52nd
Avenue and treated in a central 6- to 8-foot diameter air
stripping tower. The total VOC emissions from this tower are
estimated to be six pounds per day. The treated water would then
be discharged into infiltration beds or trenches or an existing
gravel pit located in the Sand Creek area. The treated
groundwater would be sampled as necessary to comply with UIC
requirements. Air emissions resulting from air stripping
operations at the East 52nd Avenue system would be sampled as
necessary to comply with the State of Colorado regulations
promulgated under the Colorado Air Quality Control Act, Federal
requirements, and EPA pOlicy. The State and Federal ARARs
pertaining to air stripping emissions for this alternative are
identical to the ARARs cited for Alternative No.3 (CCR 1001-5,
Reg. 3; 5 CCR 1001-5 Sec. IVD, Reg. 3, 5 CCR 1001-9, Reg. 7, 5
CCR 1001-10, Reg. 8; 5 CCR 1001-4, Reg. 2; 5 CCR 1001-3, Reg. 1;
and 40 eFR 261). A summary of these ARARs is provided in the
Alternative No.3 description and in Appendix B.
The treated plume area groundwater would be sampled as necessary
to comply with Federal UIC requirements (40 CFR 144, 146, and
147), RCRA requirements (section 3020) and State of Colorado
Regulations (5 CCR 1002-2, Sec. 6.1.0, 5 CCR 1002-3, sec. 10.1.0,
and 6 CCR 10Q7-3 Sec. 100.21(b». After treatment, water would
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"
be discharged into reinfiltration trenches or into an existing
gravel pit along Sand Creek.
It is estimated that approximately six years would be required to
attain EPA groundwater remediation levels in the plume area and
approximately 13 years would be required to attain EPA
groundwater remediation levels in the source area.
capital cost for Alterative No.5 would be approximately
$989,000. Annual 0 & M cost are estimated at $135,000 for years
1-6 and $95,000 for years 7-13. The present worth cost would be
approximately $2,081,000.
VIII.
SUMMARY OP COMPARATIVE ANALYSIS OP ALTERNATIVES
The remedial alternatives developed in the CSC OUl FS were
analyzed in detail using nine evaluation criteria. The resulting
strengths and weaknesses of the alternatives were then weighed to
identify alternatives providing the best balance among the nine
criteria. These criteria are (1) overall protection of human
health and the environment: (2) compliance with applicable or
relevant and appropriate requirements (ARARs), (3) reduction of
toxicity, mobility, or volume through treatment, (4) long term
effectiveness and permanence; (5) short-term effectiveness: (6)
implementability; (7) cost; (8)state acceptance; and (9)
community acceptance. Each of these criteria is described below.
Criterion 1:
Protection of Human Health and Environment
Overall protection of human health and the environment addresses
whether a remedy provides adequate protection and describes how
risks posed through each pathway are eliminated, reduced, or
controlled through treatment, engineering controls, or
institutional controls.
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The "no action" alternative (Alternative NO.1) is not protective
of the environment because it would not eliminate or reduce risk
through the treatment of contaminants in soil and groundwater.
Due to the observed soil contamination, an unacceptable risk
would exist under Alternative No.1 through direct contact with
contaminated soil (industrial exposure). CUrrent risk associated
with inhalation of volatile contaminants in ambient air
(industrial exposure) is outside the acceptable risk range. In
addition, with regard to potential pathways associated with
groundwater use, this alternative is not protective of public
health and the environment (aggregate risks of 6 X 10-2 current
workers; 7 X 10-4 current residents; and 2 X 10-1 future
and does not reduce potential risks associated these
residents)
pathways.
Alternative Nos. 3 and 5 are protective of public health and the
environment. All the treatment technologies employed by these
alternatives are protective of human health and the environment
by eliminating or reducing risk through the treatment of
contaminants in soils and groundwater. Alternative NO.5,
however, would reduce risks associated with groundwater in less
than one third of the time required by Alternative NO.3, thereby
reducing the period of potential exposure by two thirds.
Criterion 2:
Compliance with Applicable Relevant and Appropriate
Requirements lARARs).
Applicable requirements are those cleanup standards, standards of
control, and other substantive requirements, criteria, or
limitations promulgated under Federal or state environmental or
facility siting law that specifically address a hazardous
substance, pollutant, contaminant, remedial action, location, or
other circumstance at a CERCLA site. Relevant and appropriate
requirements are those cleanup standards, standards of control,
and other substantive requirements, criteria, or limitations
ACS1/BSPM/062691
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promulgated under Federal or state environmental siting law that
while not "applicable" to a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance at
a CERCLA site, address problems or situations sufficiently
similar to those encountered at the CERCLA site that their use is
well suited to the particular site.
Compliance with ARARs addresses whether a remedy will meet all
federal and state environmental laws and/or provide basis for a
waiver from any of these laws. These ARARs are divided into
chemical specific, action specific, and location specific groups.
Alternative Nos. 3 and 5 would comply with all ARARs".
Alternative No. 1 would not comply with chemical-specific ARARs
for alluvial groundwater. The alluvial groundwater would not be
cleaned up to Federal and state standards within a reasonable
time frame (i.e., less than 50 years). Because the no action
alternative does not satisfy the requirements of the threshold
criteria (protection of public health and attainment of ARARs),
it will not be discussed under the evaluation of the other seven
criteria. An evaluation of ARARs for CSC QUI is provided in
Appendix B.
Criterion 3:
Lonq-term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a
remedy to maintain reliable protection of human health and the
environment over time. This criterion includes the consideration
of residual risk and the adequacy and reliability of controls.
Alternative No.5 would result in minimal residual risks. Under
this alternative, soil and groundwater contaminants would be
reduced to acceptable levels through treatment. It is
anticipated that Alternative No.3 would also result in minimal
risk unless DNAPLs are present. If pockets of DNAPLs are
ACS1/BSPM/062691
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detected to be present, this alternative would not be effective
at removing these liquids. These liquids would continue to act
as a source of contamination to the alluvial groundwater. Due to
the long period of time required to implement Alternative NO.3,
this alternative would not be effective in controlling risk
during the period of implementation.
criterion 4:
Treatment
Reduction of Toxicitv. Mobilitv. or Volume throuqh
Reduction of toxicity, mobility, or volume through treatment
refers to the preference for a remedy that uses treatment to
reduce health hazards, contaminant migration, or the quantity of
contaminants at the site. All the alternatives employ an
irreversible treatment as a primary element to address the
principal threat of contamination. Both Alternative Nos. 3 and 5
reduce toxicity, mobility, and volume of contaminants in soil and
groundwater in the source area through catalytic oxidation. with
regard to treatment of groundwater in the plume area, these
alternatives indirectly reduce toxicity and volume through
photodegradation of contaminants. Alternative No.3 will not
meet EPA's statutory preference for treatment of a principal
threat of contamination to the maximum extent practicable, if
DNAPLs are present.
criterion 5:
Short-term Effectiveness
Short-term effectiveness refers to the period of time needed to
complete the remedy and any adverse impacts on human health and
the environment that may be posed during construction and
implementation of the remedy.
Due to a larger extraction volume, greater number of wells, and
construction design, Alternative No.5 would achieve groundwater
remediation levels in one third the time required under
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Alternative No.3. These alternatives are not expected to pose
any appreciable short-term risks to the community and workers
during construction and implementation.
Alternatives Nos. 3 and 5 release emissions to the atmosphere,
but at negligible levels and minimal risk (i.e., less than 1 x
10.6). Additional controls for these two alternatives include
monitoring to ensure compliance with state of Colorado air
quality standards, and a Reasonable Available Control Technology
analysis to ensure emissions are minimized.
Criterion 6:
ImDlementability
Implementability refers to the technical and administrative
feasibility of the remedy, including the availability of
materials and services needed to implement the chosen solution.
It also includes coordination of Federal, state and local
governments to clean up the site.
Both Alternative Nos. 3 and 5 are technically and
administratively feasible. Alternative No.3 would be slightly
more easy to implement than Alternative No.5 because of the
technical complexities associated with a pulsed pumping system.
In Alternative NO.5, catalyst would be required to be replaced
more frequently and access would be required to be obtained from
a significant number of property owners. These concerns are
considered to be minor and technically and administratively
feasible.
Both alternatives require air and groundwater monitoring. Air
monitoring activities would be coordinated with EPA and the state
of Colorado.
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Criterion 7:
Cost
This criterion examines the estimated costs for each remedial
alternative. For comparison, capital and annual 0 & M costs are
used to calculate a present worth cost for each alternative.
Alternative No.3 has lower 0 & M and capital costs than
Alternative No.5. The present worth costs of Alternative No.3
and Alternative No.5 are relatively equivalent ($1,922,000 and
$2,081,000 respectively); however, Alternative No.5 would be
completed in a much shorter time.
Criterion 8:
state Acceptance
This criterion pertains to the state of Colorado's opposition,
support, or comment regarding the remedial alternatives proposed
for CSC OU1. The state of Colorado has been actively involved
throughout the RI/FS and remedy selection process. The state of
Colorado was provided the opportunity to comment on the RI/FS
document and proposed plan, and took part in the public meeting
held to inform the public on the proposed plan. written comments
from the state of Colorado received during the public comment
period indicate that the state concurs with EPA's identification
of Alternative 5 as the preferred remedy for CSC OU1. The state
of Colorado indicated, however, that several state requirements
were ignored in the FS and noted concerns regarding exposure
calculation conducted to assess public health impacts resulting
from air stripping. The state of Colorado's comments are further
addressed in the attached Responsiveness Summary.
Criterion 9:
Community Acceptance
Community acceptance includes determining which components of the
alternatives interested persons in the community support, have
reservations about, or oppose. EPA solicited input from the
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community on the clean up methods proposed for CSC OU1. Although
public comment indicated no opposition to the preferred
alternative, many CSC site residents raised concerns at the
public meeting over cumulative public health impacts resulting
from air stripping operations either proposed or in operation at
CSC OU1, CSC OU2, and the Rocky Mountain Arsenal.
IX.
SELECTED REMEDY
EPA has selected Alternative No.5 as the remedy for the CSC site
OU No.1. This remedy is comprised of the following components:
ACS1/BSPM/062691
*
Monitoring groundwater, discharged treated water
and air; monitoring will include determination of
the presence or absence of DNAPLs;
*
Notification by the Colorado state Engineers
Office of the potential health risks associated
with use of contaminated groundwater upon request
for an alluvial well permit within the OU1 area;
*
High volume (1000 qpm) and pulsed pumping of
groundwater exceeding groundwater remediation
levels (i.e., MCLs and proposed MCLs) in the
source area (area south of East 48th Avenue);
*
High volume (1000 gpm) groundwater extraction
within the CSC plume area (area north of East
Avenue and south of Sand Creek);
48th
~-
*
Treatment of contaminated groundwater with two air
stripping towers for both source and plume areas;
The source area air stripping tower would be
located on the CSC property. The plume area air
stripper would be located near East 52nd Avenue;
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*
Reinjection and reinfi1tration of treated
groundwater. Aquifer reinjection by wells for
treated water from the source area.
Reinfi1tration through discharge into a trench or
gravel pit for treated water from the plume area;
*
soil vapor extraction of contaminated soils
exceeding soil remediation levels;
*
catalytic oxidation of air emissions from the soil
vapor extraction system and source area air
stripping unit. Recirculation of exhaust from the
catalytic oxidation system into the contaminated
soil.
The remedial design will specify the appropriate number and
locations of wells and monitoring points, and system parameters
such as flow rates for the source and plume area systems. The
presence or absence of DNAPLs will be monitored during RA. How
this monitoring will be conducted will be determined during RD.
Some modifications or refinements may be made to the remedy
during remedial design and construction. Such modifications or
refinements, in general would reflect results of the engineering
design process. Estimated cost for the selected remedy is
$2,081,000.
The selection of this remedy is based upon the comparative
analysis of alternatives presented in section VIII, and provides
the best balance of tradeoffs with respect to the nine evaluation
criteria. ARARs for the selected remedy are provided in Appendix
B. Short term effectiveness was critical in selecting
Alternative No.5. This alternative will clean up the
groundwater in approximately one third less time and at
relatively the same cost as Alternative No.3. The selected
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remedy will also effectively remove and treat DNAPL's if detected
during RD/RA.
Remediation Goals and Performance Standards for Ground Water and
~
Remedial Action Obiectives
Remedial Action Objectives for this site are presented in Section
VI.
Ground Water
Area of Attainment. The area of attainment for the ground water
remediation shall be the entire CSC OU1 plume exceeding ground
water remediation levels for all COCs. This includes ground
water exceeding remediation levels within CSC QUI, irrespective
of CSC and IDCA property boundaries. The estimated area
requiring remediation is shown on Figure 12. PCE is an indicator
compound for the volatile organic plume. The plume area shown in
Figure 12 currently includes all areas where other COCs exceed
their respective remediation levels. This area may be revised
based on water quality sampling during RD/RA.
Restoration Time Frame. The restoration time frame for this
remedial action is estimated to be approximately six years in the
source area (south of East 48th Avenue) and approximately 13
years in the plume area (between Sand Creek and East 48th
Avenue) .
Performance Standards. Specific performance standards, used to
ensure attainment of the remedial action objectives for ground
water are:
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ACS1/BSPM/062691
1)
Reduce contaminant
within the area of
specified in Table
total carcinogenic
concentrations in ground water
attainment to the remediation levels
5 and to levels which present a
risk of 10.4 to 10"6.
2)
Ensure capture of the plume within the area of
attainment. Verify that plume movement is being
controlled by measuring hydraulic gradient within and
outside of the plume, and demonstrating that the
gradient is inward toward the pumping wells.
3)
Meet all ARARs identified in this ROD for the
remediation of ground water,
air emissions monitoring and
reinjection of ground water.
including requirements for
UIe requirements for
4)
The remedial action shall be considered complete after
the remediation levels have been maintained in all
compliance monitoring wells for four years.
The extraction system shall continue to operate until
remediation levels have been maintained in all
compliance monitoring wells for four consecutive
quarters of sampling.
After that time, ground water extraction may be
terminated upon approval by EPA. The remediation
levels must then be met for three additional years
(with a sampling frequency to be determined during
RD/RA, but expected to be quarterly), after whi~h the
remedial action may be considered complete. After the
remedial action is complete, there may be additional
monitoring required by EPA, at EPA's sole discretion.
If any excedence of the performance standards occurs in
any of the compliance monitoring wells during this
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ACS1/BSPM/062691
three-year period, the extraction and treatment system
shall be restarted and operated until performance
standard are again attained in all compliance
monitoring wells. This cycle shall continue until
quarterly monitoring for one year demonstrates no
excedence of performance standards in the compliance
monitoring wells.
The wells to be used for compliance monitoring for
water quality and water levels will be approved by EPA
during review of the 60% RD completion report, and
will, at a minimum, include wells upgradient of the
plume, within the plume, around the plume, and
downgradient of the plume. Any statistical methods to
average well concentrations shall be specified during
RD/RA.
The third remedial action objective, stated above, is
to restore ground water to its beneficial use as a
drinking water aquifer. Based on information obtained
during the Remedial Investigation and a careful
analysis of all remedial alternatives, EPA and the
state of Colorado believe that the selected remedy will
achieve this objective. It ~ay become apparent,
however, during implementation or operation of the
ground water extraction system and its modifications,
that contaminant levels have ceased to decline or are
remaining constant at levels higher than the
remediation goal over some portion of the contaminated
plume. In such a case, the system's performance
standards and/or the remedy may be reevaluated. If new
extraction or remediation technologies become available
in the future which would significantly improve the
remediation process (allow attainment of remediation
levels which were not previously attainable, or
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ACS1/BSPM/062691
expedite the cleanup), the remedy will be reevaluateQ
in light of the new information.
The sele9ted remedy will include ground water
extraction for an estimated period of six years in the
source area and 13 years in the plume area, during
which time the system's performance will be carefully
monitored on a regular basis and adjusted as warranted
by the performance data collected during operation.
Modifications may include any or all of the following:
a)
at individual wells where cleanup goals have been
attained, pumping may be discontinued:
b)
alternating pumping at wells to eliminate stagnation
points:
c)
pulse pumping to allow aquifer equilibration and to
allow adsorbed contaminants to partition into ground
water: and
d)
installing additional extraction wells to facilitate or
accelerate cleanup of the contaminant plume.
To ensure that remediation levels are maintained at
those wells where pumping has ceased, those wells will
be monitored every year following discontinuation of
groundwater extraction, until the remedial action is
completed.
5)
Best efforts shall be used to remediate the plume in a
timely manner. "Best efforts" shall include
implementation of the remedy in compliance with the
ROD, Consent Decree and SOW, to maximize performance of
the remedial action to achieve the performance
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,
/
standards as quickly as possible.
Performance and ComDliance SamDlina Proaram. A sampling program
for monitoring the remedial action performance and for
determining compliance with the performance standards shall be
implemented during the remedial action. This program will be
developed during remedial design and shall include, at a minimum,
the following: locations of performance and compliance
monitoring wells for water quality sampling, frequency of
monitoring of performance and compliance wells, analytical
parameters (focusing on COCs with possible use of indicator
chemicals), sampling field methods, water level measurement
frequency, analytical methods for chemical analysis (with
possible use of non-CLP analysis), locations and methods for
water level measurement, and statistical methods for evaluating
data. The performance and compliance sampling program will be
specified in the RA Workplan and may be modified during the RA.
The performance monitoring system will be designed to provide
information that can be used to evaluate the effectiveness of the
remedial action with respect to the following:
horizontal and vertical extent of the plume and
contaminant concentration gradients, including a
balance calculation, if possible
mass
rate and direction of contaminant migration
changes in contaminant concentrations or distribution
over time
effects of any modifications to the original remedial
action.
other items to be specified in the performance monitoring plan
ACS1/BSPM/062691
76
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y,
include:
monitoring of concentrations of influent and effluent
to the air stripper and catalytic oxidation units
(influent water concentration, and effluent water and.
air concentrations) so as to meet air emission
standards
concentrations of contaminants in ground water to be
reinjected, so as to comply with UIC requirements for
reinjected ground water.
Soils
Area of Attainment. The area of attainment for the soil
remediation shall be the entire area within CSC OUI with soil
concentrations exceeding the remediation levels cited in Section
VI, irrespective of CSC and IDeA property boundaries. The entire
vertical soil column will be used to determine where remediation
is required. The estimated area requiring remediation is shown in
Figure 8. This area may be revised based on soil sampling during
RD/RA.
Restoration Time Frame. The restoration time frame for this
remedial action is estimated to be approximately 150 days.
Performance Standards. Specific performance standards, used to
ensure attainment of the remedial action objectives for soil,
are:
1)
Reduce contaminant concentrations in soil within the
area of attainment to the soil remediation levels
specified in Section VI.
2)
Meet all ARARs identified in this ROD for the
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ACS1/BSPM/062691
remediation of soil, including requirements for air
emissions monitoring.
3)
The remedial action shall be considered complete after
the soil remediation levels have been attained in all
compliance soil borings and surface soil samples.
Attainment of the remedial action objectives for the
incidental ingestion and direct contact pathways must
be verified through chemical analysis of the upper six
inches of soil. Attainment of the remedial action
objectives for the pathway of migration of soil
contaminants into ground water must be verified by
sampling the soil concentrations area11y (from a number
of boreholes) and vertically (from a number of samples
collected from a single borehole). The extraction
system shall continue to operate until remediation
levels have been reached in all compliance soil borings
and surface soil samples (upper six inches of soil).
Attainment of the soil remediation levels will be
verified by chemical analysis of soil samples, not by
soil headspace analysis. After the remedial action is
complete, there may be additional monitoring required
by EPA, at EPA's sole discretion.
The soil borings and surface soil samples to be used
for compliance monitoring for soil will be specified
during Remedial Design, and will, at a minimum, include
borings and samples within and surrounding the area of
attainment. The borings shall be drilled to the water
table, at a minimum, as approved by EPA during RD. Any
statistical methods to average soil concentration
areally or vertically within a borehole shall be
specified during RD/RA. The EPA guidance document
entitled "Methods for Evaluating the Attainment of
Cleanup Standards--Volume 1: Soils and Solid Media"
78
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(EPA 230/02-89-042) will be consulted when establishing
the Performance and Compliance Sampling Program,
described in the following subsection.
It may become apparent during implementation or
operation of the soil remediation system that
contaminant levels have ceased to decline or are
remaining constant at levels higher than the
remediation level. In such a case, the system's
performance standards and or the remedy may be
reevaluated. If new extraction or remediation
technologies become available in the future which would
significantly improve the remediation process (allow
attainment of remediation levels which were not
previously attainable, or expedite the cleanup), the
remedy will be reevaluated in light of the new
information.
The soil remediation system's performance will be
carefully monitored on a regular basis and adjusted as
warranted by the performance data collected during
operation.
4)
The PRP shall use best efforts to remediate the soil in
a timely manner. "Best efforts" shall include
implementation of the remedy in compliance with the
ROD, Consent Decree and SOW, to maximize performance of
the remedial action to achieve the performance
standards as quickly as possible.
Performance and ComDliance SamDling Proqram. A sampling program
for monitoring the remedial action performance and for
determining compliance with the performance standards shall be
implemented during the remedial action. This program will be
developed during remedial design and shall include, at a minimum,
ACS1/BSPM/062691
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the following: locations of performance monitoring points within
the soil vapor extraction system; locations of compliance
monitoring boreholes to be drilled after remediation is believed
to be complete, to confirm that remediation levels have been
reached; frequency of monitoring of the performance of the SVE
system, analytical parameters (focusing on COCs, with possible
use of indicator chemicals), analytical methods for laboratory
and field chemical analysis (with possible use of non-CLP
analysis), field sampling methods, and statistical methods for
evaluating data. The performance and compliance sampling program
will be specified in the RA Workplan, and may be modified during
the RA.
other items to be specified in the performance monitoring plan
include:
monitoring of concentrations of influent and effluent
air into and out of the catalytic oxidation unit.
x.
STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select
Remedial Actions that are protective of human health and the
environment. CERCLA also requires that the selected remedial
action for a site comply with applicable or relevant and
appropriate environmental standards established under Federal and
State environmental laws, unless a waiver is granted. The
selected remedy must also be cost-effective and utilize permanent
treatment technologies or resource recovery technologies to the
maximum extent practicable. The statute also contains a
preference for remedies that include treatment as a principal
element. The following sections discuss how the selected remedy
for the CSC OUl site meets these statutory requirements.
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Protection of auaan aealth and Bnvironaent
In order to meet the remedial objectives outlined previously, the
risk associated with exposure to the contaminated soil and
groundwater must fall within the acceptable risk for carcinogens.
Attainment of soil and groundwater remediation levels described
previously in Section VI will assure that site risk falls within
this range. EPA expects that contaminants will be reduced to
acceptable levels in 150 days for the soil, 6 years for
groundwater in the plume area (between Sand Creek and East 48th
Avenue) and 13 years for groundwater in the source area. (south of
East 48th Avenue). Of all the alternatives evaluated for CSC
OU1, the selected alterative provides the best protection to
human health in the least amount of time. No unacceptable short-
term risks or cross-media impacts would result through
implementation of this remedy.
Attainment of Applicable or Relevant and Appropriate Requirements
of Bnvironmental Laws
All ARARs would be met by the selected remedy.
Chemical-Specific ARARs. The selected remedy would achieve
compliance with chemical-specific ARARs related to the alluvial
groundwater within the CSC OU1 area. The relevant and appropriate
requirements include Federal and State primary drinking water
standards established by the Safe Drinking Water Act. Some
contaminants of concern identified for CSC OU1 have MCLs. MCLs
have been proposed for the majority of the remaining contaminants
of concern identified for this ROD as TBCs. Concentration of
COCs at the CSC OU1 site would be reduced below MCLs or proposed
MCLs by implementation of Alternative 5.
Vinyl Chloride emissions from the air stripping treatment system
will be monitored and if required, controls would be implemented
ACS1/BSPM/062691
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I -
o
to ensure compliance with National Emission standards for
Hazardous Air Pollutants (40 CFR PART 61.60). At present it is
not expected that constituents for which standards have been
established for the Colorado Air Quality Control Act (CRS-25-7-
101-2) will be emitted. In the unlikely event that these
constituents are produced, the necessary controls would be
implemented in order for the emissions to comply with the
regulations. Predicted air emission concentrations for the plume
area in the OU1 FS are within acceptable levels based on an
assessment conducted in the FS. These estimates are based on
generalized assumptions which cannot be verified until the final
location of the air stripping unit is identified. Risks
associated with air stripping operations for the plume area will
be reevaluated based on the identification of a specific location
for the air stripping unit during remedial design.
Implementation of air emission controls and/or emission
limitations may be required pending that assessment.
Action-Specific
action-specific
the groundwater
CCR 1002-3 sec.
Sec. 100.21(b),
3020.
ARARs. The selected remedy would comply with
ARARs for injection of treated water back into
as set forth in state of Colorado Regulations 5
10.1.0, 5 CCR 1002-2, Sec. 6.1.0 and 6 CCR 1007-3
Federal UIC Program 40 CFR 144-147 and RCRA Sec.
EPA policy (Applicability of Land Disposal Restrictions to RCRA
and CERCLA Groundwater Treatment Injection Superfund Management
Review: Recommendation No. 26 OSWER Directive No. 9234.1-06,
December 27, 1989) is that UIC rules take precedence over LDRs
for injection of hazardous waste into the groundwater.
Therefore, for injection of the treated water, the LDRs are not
relevant and appropriate. However, as noted previously, UIC
regulations are applicable to this action.
ACS1/BSPM/062691
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II
As discussed above, land disposal restrictions are not applicable
to the groundwater injection aspects of the selected remedy.
Instead, RCRA section 3020 applies to reinjection of treated
groundwater into Class IV injection wells during CERCLA response
actions. Since the goal is to clean up groundwater to drinking
water levels, health based drinking water standards (MCLs),
rather than land disposal restrictions, are relevant and
appropriate clean up standards.
Federal and State of Colorado requirements pertaining to air
emissions will be met with regard to air stripping operations.
These include Colorado Air Quality Regulations 1,2, 3 and 8 (for
vinyl chloride). The specific actions regulated and the specific
regulatory citations are presented in Appendix B.
Location Specific ARARs. The selected remedy would address and
comply with all location-specific ARARs for preservation and
protection of the Sand Creek River floodplain according to
requirement of 40 CFR 6.3022 and protection of site wetlands
within the CSC OU1 area.
Cost Bffectivenes8
EPA believes the selected remedy is cost-effective in mitigating
the principal risk posed by contaminated groundwater within a
reasonable period of time. Section 300.430(f) (ii) (D) of the NCP
requires EPA to evaluate cost-effectiveness by comparing all the
alternatives which meet the threshold criteria: Protection of
human health and the environment and the attainment of ARARs,
against three additional balancing criteria: long-term
effectiveness and permanence; reduction of toxicity, mobility or
volume through treatment; and short-term effectiveness. The
selected remedy meets these criteria and provides for overall
effectiveness in proportion to its costs. The selected remedy is
approximately the same cost as Alternative No.3, however, it
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will achieve groundwater remediation levels in approximately one
third the time required for Alternative No.3.
Therefore, the selected remedy is cost-effective as defined in
the NCP. The estimated cost for the selected remedy is
approximately $2,081,000.
utilization of Permanent
Technologies or Resource
Extent Practicable
solutions and Alternative Treatment
Recovery Technologie. to the xaximua
EPA believes the selected remedy represents the maximum extent to
which permanent solutions and treatment technologies can be
utilized in a cost-effective manner for CSC OUi. Of those
alternatives that are protective of human health and the
environment and comply with ARARs, EPA has determined that the
selected remedy provides the best balance of trade-offs in terms
of long-term effectiveness and permanence, reduction in toxicity,
mobility or volume achieved through treatment; short-term
effectiveness; implementability; and cost, and also considering
the statutory preference for treatment as a principal element and
considering state and community acceptance.
Of the two alternatives which meet the threshold criteria
(Alternative Nos. 3 and 5), the selected remedy (Alternative No.
5) reduces toxicity, mobility and volume of the contaminants in
the groundwater and soil equally as well as Alternative No.3.
Short term effectiveness was critical in choosing Alternative No.
5 due to the much shorter remediation time frame.
~
Preference for Treatment &s & Principal Blement
The selected remedy satisfies the statutory preference for
treatment as a principal element. If pools and pockets of
are detected, they will be treated through extraction, air
DNAPL
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stripping and catalytic oxidation. Treatment ot DNAPLs may
require that the DNAPL be diluted prior to treatment.
Surficially contaminated soils do not pose a sufficient risk to
be considered a "principal threat".
XI.
DOCUMENTATION OF SIGNIFICANT CHANGBS
50 Siqniticant Chanqe.
The proposed plan for OUl of the Chemical Sales Company site was
released for public comment on February 28, 1991. The proposed
plan identified Alternative 5 as the preferred alternative. EPA
reviewed all written and verbal comments submitted during the
public comment period. Upon review of these comments, it was
determined that no significant changes to the remedy, as it was
originally identified in the Proposed Plan, were necessary.
ACS1/BSPM/062691
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REFERENCES
CDM FEDERAL PROGRAMS CORPORATION, 1991. Final Feasibility Study
Report, Chemical Sales Company site, Operable unit 2.
Document No.: 7760-004-FS-BPPY.
Camp, Dresser & McKee, Inc. 1988. Remedial Investigation Site
Characterization Report, Sand Creek Industrial Site;
Commerce City, Colorado. Submitted to U.S. Environmental
Protection Agency, Report No. 203-RI1-RT-ESDW-1, Contract
No. 68-01-6939.
Colorado Department of Health. 1986a. Colorado Department of
Health Waste Management Division Hazardous Waste Inspection
Report. Inspection of Chemical Sales Company Property
Conducted on March 18, 1986.
Colorado Department of Health. 1986b. Colorado Department of
Health Waste Management Division Hazardous Waste Inspection
Report. Inspection of Chemical Sales Company Property
Conducted on April 1, 1986.
Ecology and Environment (E and E). 1987. Analytical Results
from E. 56th Ave. and Magnolia Street, Denver, CO; TDD F08-
8701-01 submitted September 1, 1987.
1986a. South Adams County Soil Gas Survey
Interpretive Report, South Adams County, CO; TDD R8-8603-07,
submitted June 24, 1986.
1986b. Final Results Report for I-270 and Quebec
Street, Commerce City; TDD R8-8609-05, resubmitted November
18, 1986.
1986c. Analytical Results~from E. 48th Ave. and
Leyden Street, Denver, CO: TDD R8-8609-04. Submitted
December 15, 1986.
1986d. Analytical Results Report, E. 50th Ave. and
Ivy Street, Commerce City, CO; TDD R8-8609-03 and TDD R8-
8604-03, submitted December 17, 1986.
Engineering-Science, Inc. 1991. Remedial Investigation/
Feasibility Study - Leyden Street Site, Operable unit 1.
Foster, D. 1990. Personal Communication.
Company, Denver, Colorado.
Chemical Sales
u.S. Environmental Protection Agency. 1988c. Guidance on
Remedial Actions for Contaminated Groundwater at Superfund
Sites. EPA/540/G-88/003.
ACS1/BSPM/062691
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References, cont.
. 1989. Control of Air Emissions from Superfund Air
Strippers at Superfund Groundwater Sites (OSWER Directive
9355.0-28).
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ACS1/BSPM/062691
APPENDIX A
SUHKARY OP BASELINE RISK ASSESSKEH'l'
,
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SUXNARY O~ ASSUXPTIOBS USBD TO BSTIMATB CHROBIC DAILY IBTAKB
01' CBBKICALB O~ COBCBRII AT TBB CHBJIICAL SALlIS COKPABY OU1 SITB
Exposure assumptions used in the CDr estimates for the exposure
pathways evaluated in the Chemical Sales Company OU1 site risk
assessment are discussed in this appendix. Many of the exposure
assumptions are based on values that are recommended by EPA in
Risk Assessment Guidance for Superfund (RAGS) (EPA 1989a).
Additional values were obtained from the Exposure Factors
Handbook (EPA 1989b) or are age-specific and site-specific values
that are considered appropriate for the Chemical Sales Company
OU1 site.
Several of the exposure assumptions such as exposure duration,
body weight and averaging time are used in all of the exposure
pathway calculations and are the same for all pathways. The
average adult body weight is 70 kg and is recommended by EPA
(1989a, 1989b). The average body weight for a child ages one
through six is 16 kg and was obtained from the Exposure Factors
Handbook (EPA 1989b). The exposure duration for workers and
residents is 30 years and is based on the national upper-bound
time (90th percentile) at one residence, and is also recommended
by EPA (1989a). The averaging times for carcinogens and
noncarcinogens are pathway-specific periods of exposure and are
recommended by EPA (l989a). These exposure values have been
revised downward (e.g. exposure duration for workers = 25 years,
soil ingestion 50 mg) in the SupDlemental Guidance "Standard
Default EXDosure Factors" (OSWER Directive 9285.6-3) dated March
25, 1991.
Since the exposure factors utilized in this risk assessment
result in a more protective remedy than would be prescribed if
the new exposure factors were used, EPA has decided to maintain
the risk assessment as originally prepared. Exposure point
concentrations are upper 95th confidence intervals of the
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,}
arithmetic mean for groundwater. Maximum detected concentrations
in soil and air were used as exposure point concentrations due to
lack of sufficient data to calculate an arithmetic mean. Tables
1-1 through 1-8 of Appendix A present the exposure point
concentrations, cancer ~otency factors (CPF) and reference doses
(RfD) for each chemical as well as the cancer risk and hazard
index for each pathway and each chemical of concern.
The remaining exposure assumptions for individual pathways will
be discussed below. Table 1-1 presents exposure assumptions for
ingestion of groundwater. Frequency of exposure for residents is
based on the likelihood of groundwater being ingested every day
of the year. For workers, the exposure frequency of 245
days/year was based on exposure occurring 5 days a week and
considers that a worker will have 2 weeks of vacation, 96 days of
weekends and 10 days of holidays. The ingestion rate of 2 L/day
is the 90th percentile water ingestion rate for adults (EPA
1989d) and is recommended by EPA (1989a).
Table 1-2 presents assumptions used to estimate exposure via
inhalation of volatiles while showering. The frequency of
exposure for residents assumes that a resident may take a shower
every day while for a worker it is assumed that they may shower
three times a week. The ventilation rate of 15 L/minute is
recommended by Foster and Chrostowski (1987) and is used in their
model to evaluate exposure to volatiles while showering. The
exposure duration of 20 minutes assumes 15 minutes is spent
showering and 5 minutes is for after showering activities as
volatiles may still be present in the room after showering. A
~~
shower time of 15 minutes is recommended by EPA (1989a).
Table 1-3 presents exposure
groundwater via showering.
assumed that a resident may
worker may shower only three
assumptions for dermal contact with
As previously discussed above, it is
shower every day of the year while a
times a week out of a possible 245
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v
TABLE 1-1
EXPOSURE ASSUMPTIONS USED TO ESTIMATE CHRONIC DAILY INTAKE OF
CHEMICALS OF CONCERN VIA INGESTION OF GROUNDWATER
CDI = Intake (aq/kq-day) = CW z IR z BP z BD
BW z AT
Parameter
Exposure
Chemical concentration in water (CW)
mg/L(a)
Frequency of Exposure (EF)
Residents (current and future)
Workers
365 d/yr (b)
245 d/yr (c)
30 yr (d)
Exposure Duration (ED)
Ingestion Rate (IR)
2 L/day (d)
Average Body Weight (BW)
70 kg (d)
Averaging Time (AT)
carcinogens
Noncarcinogens
365 d/yr x 70 yr
(d)
365 d/yr x 30 yr
(d)
(a) Concentration is the upper 95th confidence interval of the
arithmetic mean.
(b) Based on exposure occurring 7 days a week.
(c) Based on exposure occurring 5 days a week and takes
account that a worker will have 2 weeks of vacation, 96
of weekends and 10 days of holidays (365 - 2(7) - 10 -
245) .
(d) USEPA (1989a)
into
days
96 =
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TABLE 1-2
EXPOSURE ASSUMPTIONS USED TO ESTIMATE CHRONIC DAILY INTAKE OF
CHEMICALS OF CONCERN VIA INHALATION OF VOLATILES WHILE SHOWERING
CDI = Intake Caq/kq/4ay) = CV z va z liT z EF z ED
BW z AT
Parameter
Exposure
Chemical Concentration in
Vapor (CV)
3
mg/m (d)
Frequency of
(EF)
Workers
Residents
future)
Exposure
147 d/yr (b)
365 d/yr (a)
{current and
Exposure Duration (ED)
30 yr (c)
15 L/min (d)
Ventilation Rate (VR)
Exposure Time (ET)
20 min (c,d)
Average Body Weight (BW)
70 kg (c)
Averaging Time (AT):
Noncarcinogens
Carcinogens
365 d/yr x 30
yr ( c)
365 d/yr x 70
yr ( c)
(a)
(b)
Based on exposure occurring 7 days a week.
Based on exposure occurring 3 times a week and takes
account that a worker will have 2 weeks of vacation,
of weekends and 10 days of holidays (365 - 2(7) - 10
245; 3/5 x 245 = 147.
USEPA (1989a)
Based on shower model by Foster and Chrostowski {1987~
into
96 days
- 96 =
(c)
(d)
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L
TABLE 1-3
EXPOSURE ASSUMPTIONS USED TO ESTIMATE
CHRONIC DAILY INTAKE OF CHEMICALS OF CONCERN VIA DERMAL
CONTACT WITH GROUNDWATER
CDI - Absorbed OoS8 (aq/kq/day) = cw z SA Z PC Z BT z IF z ID z CI'
BW z Aif
Parameter
Exposure
Chemical Concentration in
Water (CW)
mg/L (a)
Conversion Factor (CF)
-6
10 kg/mg
Frequency of Exposure (EF)
Residents (current and
future)
Workers
365 d/yr (b)
147 d/yr (c)
Exposure Duration (ED)
30 yr (d)
Skin Surface Area (SA)
2
18,200 cm (d,e)
Exposure Time (ET)
0.25 hr/day
(d,f)
Permeability Constant (PC)
70 kg (d)
8 x 10.4 cm/hr
(d,g)
Average Body Weight (BW)
Averaging Time (AT):
Noncarcinogens
Carcinogens
365 d/yr x 30 yr
(d)
365 d/yr x 70 yr
(d)
(a)
(b)
(c)
Concentration is the upper 95th confidence limit of arithmetic mean.
Based on exposure occurring seven days a week.
Based on exposure occurring 3 times a week and takes into account that
a worker will have 2 weeks of vacation, 96 days of weekends and 10
days of holidays (365 - 2(7) - 10 - 96 = 245; 3/5 x 245 = 147).
(d) USEPA (1989a)
(e) USEPA (1989a). 50th percentile body surface area values for an adult
are used (average of males and females).
(f) USEPA (1989a). Assumes a shower/bath time of 15 minutes.
(g) USEPA (1989a). Permeability constant for water is used as a default
value.
ACS1/BSPM/062691
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days/year. The skin surface area of 18,200 6m2 is the 50th
percentile body surface area value for adult males and females.
The 50th percentile value is recommended by EPA (1989a).
Exposure time is 15 minutes and is also recommended by EPA
(1989a). The permeability constant of 8 x 10.' cm/hr is that for
water and reflects the movement of the chemical across the skin
to the stratum corneum and into the bloodstream. This value is
recommended by EPA (1989a) in the absence of chemical specific
data.
Table 1-4 presents the assumptions used to calculate exposure via
inhalation of VOCs in ambient air. Workers are assumed to be
exposed all working days of the year. The inhalation rate of 20
m3/day assumed for workers is the average inhalation rate for
adults and is recommended by EPA (EPA 1989a, b). The inhalation
rate assumed for children was 30 m3/day and was obtained from the
Exposure Factors Handbook (EPA 1989d). This is the average
inhalation rate for a child ages one through six at moderate
activity.
Table 1-5 presents exposure assumptions used to estimate exposure
via ingestion of surface soil. Climatological data from the
National Weather Service (1990) indicate that the ground may be
covered with snow or frozen for the months of December through
March, therefore leaving the months of April through November
available for exposure. Based on this information, exposure
frequencies were calculated as follows. For workers, exposure
was assumed to occur two times a week during the months of April
and November and 3 times a week during May through October. This
results in 98 days/yr of potential exposure for workers.
Children are assumed to be exposed to surface soil all year round
due to exposure to wind-entrained soil particles present in
household dust. This frequency of exposure (365 days/yr) for
children is recommended by EPA (1989a). Soil ingestion rates of
100 mg for adults and 200 mg for children are recommended by EPA
and are based on Interim Final Guidance for Soil Ing~~~~on Rates
from the Office of Solid Waste and Emergency Response (EPA 1989a,
ACS1/BSPM/062691
A-6
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,/
(a)
(b)
(c)
(d)
(e)
( f)
TABLE 1-4
EXPOSURE ASSUMPTIONS USED TO ESTIMATE CHRONIC DAILY INTAKE OF
CHEMICALS OF CONCERN VIA INHALATION OF VOCS IN AMBIENT AIR
CDI = Intake (aq/kq-day) = CA z IR z BT z BP z BD
BW z AT
Parameter
Exposure
Chemical Concentration
in Air (CA)
3
mg/m (a)
Frequency of Exposure
(EF)
Workers
Children (future)
245 d/yr (b)
365 d/yr (c)
Exposure Duration (ED)
Workers
Children
30 yr (c)
6 yr (c)
Inhalation Rate (IR)
Workers
Children
3
20 m /day
(c,d1e)
30 m /day
(c,d,e)
Average Body
(BW)
Workers
Children
Weight
70 kg (c, f)
16 kg ( c , f)
Averaging Time (AT):
Noncarcinogens
Carcinogens
365 d/yr x 30
yr (c)
365 d/yr x 70
yr (c)
Concentration is the maximum detected value.
Based on exposure occurring 5 days a weeks and takes~.into
account that a worker will have 2 weeks of vacation, 96 days
of weekends and 10 days of holidays (365 - 2(7) - 10 - 96 -
245).
USEPA (1989a).
USEPfa (1989c).
20 m/day is the average inhalation rate for an adult, 30
mylday is the average inhalation rate for a child ages 1
through 6 at moderate activity.
70 kg is the average adult body weight, 16 kg is the average
body weight for a child ages 1 through 6.
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TABLE 1-5
EXPOSURE ASSUMPTIONS USED TO ESTIMATE CHRONIC DAILY INTAKE OF
CHEMICALS OF CONCERN VIA INGESTION OF SURFACE SOn..
cm = Intake (mg/kg-day) = CS x IR x CF x n x EF x ED
BW x AT
Parameters Exposure
Conversion Factor (CF) 10~ kg,Img
Chemical Concentration in Soil (CS) m.g/kg (a)
Frequency of Exposure (EF)
Workers 98 d/yr (b)
Children 365 d/yr (c)
Exposure Duration (ED)
Workers 30 yr (c)
Children 6 yr (c)
Ingestion Rate (IR)
Workers 100 mg/ day (c,d,e)
Children 200 mg/day (c,d,e)
Average Body Weight (BW)
Workers 70 kg (c,f)
Children 16 kg (c,f)
Averaging Time (AT):
Noncarcinogens 365 d/yr x 30 yr (c)
Carcinogens 365 d/yr x 70 yr (c)
Fraction Ingested (PI) 1 (c)
(a)
(b)
Concentration is the maximum detected value.
Based on exposure occurring 3 times a week for the months of May through October and 2 times
a week for the months of April and November. Climatological data indicates the ground may be
covered or frozen for the month of December through March (NationaJ Weather Service, 1990).
USEPA (1989a).
USEPA (1989c). Interim rmaJ Guidance for Soil In~estion Rates. Office of Solid Waste and
Emergency Response. (OSWER Directive 9850.4).
Current EP A suggests soil ingestion rates.
70 kg is the average adult body weight, 16 kg is the average body weight for a child ages 1 through
6 (EPA, 1989b).
(c)
(d)
(e)
(f)
ACS1/BSPM/062691
A-8
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c). The fraction ingested accounts for the fraction of soil
contacted that is presumed to be contaminated. Due to the
extensive soil contamination at this site, all soil contacted was
presumed to be contaminated resulting in a fraction ingested
value of one.
Table 1-6 presents assumptions used to estimate exposure via
dermal contact with surface soil. The frequency of exposure for
workers and children are 98 and 365 days/year respectively and
have been previously described for the soil ingestion pathway.
The exposed skin surface area for workers considers exposure to
forearms and hands and is 3,120 cm2. The exposed skin surface
area for children considers exposure to forearms, hands and legs
and is 7,070 cm2. Skin surface areas are 50th percentile body
surface areas as recommended by EPA (1989a). A skin adherence
factor for Kaolin clay was used due to lack of site-specific soil
data. This value is a conservative estimate and is presented in
RAGS (EPA 1989a, 1989d, 1988b). An absorption factor of one was
used due to lack of chemical specific data and is a conservative
estimate. In the absence of chemical specific data a
conservative estimate is recommended by EPA (1989a). The soil
matrix factor used is 0.15 and represents the percentage of
chemical that is available for absorption due to soil binding and
the small amount of chemical that is in actual contact with the
skin. This value is based on a study by Poiger and Schlatter
(1979). This value was recommended by EPA Region VIII (Weis,
1990).
Tables 1-7 through 1-14 present exposure point concentrations,
chronic daily intakes, cancer potency factors or reference doses
and carcinogenic or non-carcinogenic risks for all pathways and
receptors considered.
ACS1/BSPM/062691
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TABLE 1-6
EXPOSURE ASSUMPTIONS USED TO ESTIMATE CHRONIC DAILY INTAKE OF
CHEMICALS OF CONCERN VIA DERMAL CONTACT WITH SURFACE SOIL
CDI = Absorbed Dos. (aq/Jtq-day) = CS :II: CP :II: SA :II: All' :II: ABS :II: BP :II:
BD J: SM
BW :II: AT
Parameter
Exposure
Chemical Concentration in
Soil (CS)
mg/kg (a)
Conversion Factor (CF)
-6
10 kg/mg
Frequency of
Workers
Children
Exposure (EF)
98 d/yr (b)
365 d/yr (c)
Exposure Duration (ED)
Workers
Children
30 yr (c)
6 yr (c)
Skin Surface Area (SA)
Workers
Children
3,120 cm2 (d)
7,070 cm2 (d)
Average Body Weight (BW)
Workers
Children
70 kg (c,e)
16 kg (c,e)
Averaging Time (AT):
Noncarcinogens
Carcinogens
365 d/yr x 30 yr
(c)
365 d/yr x
(c)
70 yr
Soil Matrix Factor (SM)
0.15 (g)
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(f)
(g)
Skin Adherence Factor (AF)
2.77 mg/cm2
(c,f)
Absorption Factor (ABS)
1 (c)
(a)
(b)
Concentration is the maximum detected value.
Based on exposure occurring 3 times a week for the months of
May through October and 2 times a week for the months of
April and November. Climatological data indicates the
ground may be covered or frozen for the months of December
through March (National Weather Service, 1990).
USEPA (1989a)
USEPA (1989a). 50th percentile body surface area values for
adult forearms and hands were used for workers, and
forearms, hands, and legs were used for children ages 1
through 6.
USEPA (1989a). 70 kg is the average adult body weight, 16
kg is the average body weight for a child ages 1 through 6.
USEPA (1989a). Adherence factor is for Kaolin clay.
Soil matrix factor is based on a study by Poiger and
Schlatter (1979) and recommended by EPA (Weis, 1990).
(c)
(d)
(e)
ACS1/BSPM/062691
A-11
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TASLE 1-7
TOTAL CANCER RISKS FOR WORKERS AT THE CHEMICAl.. SALES CJ:)tIP/tHV SITE OU 1 AA'EA
Cone. CDI CanCCl Upper Bound Total CaDCCI Wei,,"..,i
in Medium (m&lkg/day) potency Excess Ufetime Pathway PoteDCY EvidcDce
Chemical (e) Factor Cancer Rjsk Risk Source .(1)
Exposure Pathway. Ingestion of Ifound water
Methylene O1loride I.3E +04 1.IE~1 7.SE~3 7.9E.04 ATSDR (d) B2
1.1-Dichlorocthene 5.1£+03 4.6E-02 6.0E~1 2.8E-02 HEA(a) C
1.1.Dichlorocthane 2.6E +02 2.2E-03 9. 1 E-02 2.0E.04 HEA C
Chloroform 2.4E +02 2.0E-03 6. 1 E-03 1.1£-05 HEA(a) B2
Carbon Tetrachloride 8.5E+Ol 7.0E.04 I.3E~1 - 9.1E-05 HEA(a) B2
cis-l,3-Dichtoropropene 1.4E+02 1.IE-03 1.8E~1 2.0E.04 HEA B2
Trichlorocthene 5.3E+03 4.3E-02 1. 1 E-02 4.8E.04 HEA B2
Tetrachloroctbene 1.4E+04 1.1E-Ol 5.1E-02 5.8E-03 HEA B2
Vinyl Oloride 1.4E+00 1.1E-05 2.3E+00 2.6E-05 3.5E-02 HEA A
Exposure PathWay. Inhalation of volatile organics while showerin&
Methylene O1Ioride 4.5E-02 4.4E.a3 1.4E-02 6.1 E-05 ATSDR(d) B2
Carbon Tetrachloride 2.0E-03 1.9E.04 I.3E~1 2.5E-OS HEA(a) B2
Chloroform 6.0E-03 5.8E-04 8.1E-02 4.1£-05 HEA(a) B2
ds-l,3-Dichtoropropene 3.4E-03 3.3E.04 I.3E~1 4.3E-OS HEA B2
1.1-Dichloroctheoe 1.6E-Ol 1.6E-02 1.2E+00 1.9E-02 HEA(a) C
TrichloretheDe 1.3&01 I.3E-02 1.1£-02 UE.04 HEA 82
Tetrachlorocthene 3.2E-Ol 3.1 E-02 3.3E~3 1.0E.04 HEA 82
Vioyl Otloride S.2E-OS 5.0E-06 3.0E~1 I.5E-06 1.9E-02 MEA
Exposure Pathway: Dermal exposure to organics while showcriog (bot)
Methylene Chloride I.3E+04 4.8E-06 I.5E-02 1.2E-08 NA NA
Carbon Tetrachloride 8.5E+Ol 3.2E-08 2.6E~1 8.3E.09 NA I"A
1.1-Dicbloroctheoe 5.1£+03 2.1E-06 1.2E+00 2.SE-06 NA NA
1.I-Dichlorocthane 2.6E+02 9.9E-08 l.8E~1 1.8E-08 NA I"A
Chloroform 2.4E+02 8.9E-08 I.2E-02 1.1E.09 NA I"A
. Trichloroclhcae 5.3E +03 2.0E-06 2.2£-02 4.4E-08 NA NA
Tclrachlorocthcoe 1.4E+04 5.2E-06 1.0E~1 5.2E-m NA NA
Vinyl Otloride 1.4E+00 5.2E-I0 4.6E +00 2.4E-09 3.2E-06 NA NA
Exposure Pathway. Dermal exposure 10 surface soil (b.c:).
Trichloroctbene 9.5E-Ol 2.6E-m 2.2E-02 6.0E-09 NA NJ
Tetrachlorocthene 8.0E+Ol 2.0E-05 1.0E~1 2.0E-06 2.0E-06 NA NJ
Exposure Pathway: Incidental ingestion of surface soil
Tri<:hloroclhene 9.5£.01 1.6E-07 1.1 E-02 1.1£-09 HEA B
Tet rachlorocthene 8.0£+01 1.3£-05 5.1E-02 6.1E-m 6.7£-07 HEA B
Exposure Patbway. Inhalation of Voc.s present in ambient air
Mctb lene Chloride 1.4E.ol 3.7E-03 1.4E-02 5.2E-OS 5.2£-OS ATSDR d E
TOTAL CANCER RISK TO WORKERS 5.5E-02
A-12
I
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TABLE 1-8
TOTAL CANCER RISKS FOR CtR£NT RESIDENTS AT n£ Q£MICAL SALES COMPANY SITE 001 MEA
. .. - .- .
Cone. CDI Cancer Upper Bound Total CaDCCr Wcicht of
in Medium (mJlk&lday) PotcDC:J E.ttcss Ufctime Pathway Potcocy EvideDcc
Chemical (e) Factor CaDcer Risk Risk(f) Source '00
Exposurc Pathway: Ingestion or gound water 1.6E~ 7.5£-03
Methylcnc Chloride I.3E+02 t.2E-OS A TSDR (d) 82
1.I-DicbloroctheDC 1.4E+02 1. 7E.04 6.0E.ol 1.0E.04 HEA(a) C
1.I-Dichlorocthanc 1.2E +02 1.5E.04 9.1 E-02 I.3E-OS HEA C
Trichlorocthcnc 6.0E +02 7.4E.o3 1.1 E-02 8.1E-OS HEA 82
Tetracbloroethcnc 5.0E +01 6.1E.04 5.lE-02 3.1 E-OS HEA 82
Vinyl Chloride 3.4E+00 4.1 E-05 2.3E+00 9.5E-OS 3.3E~ HEA A
Exposure Pathway: Inhalation or volatile or&anics while showering
Methylenc Chloride 3.6E.03 1.5E-03 1.4E-02 2.2E-OS ATSDR(d) 82
1.1.DicblorocthcDC 4.0E.04 1. 7E-04 1.2E+00 2.1E~ HEA
-------
TABlE 1-8
TOTAL CANCER RISKS FOR FUTURE RESIDENTS AT THE CHEMICAl SALES COWPNN Sm: 001 MEA
CoDe. CDt ~ncer Upper Bound Total CaDCCl' Wei&-
in Medium (mglkg/cSay) Potency Eacess Uretime Patbway PotcDC)' Evide~
Chcmical (c) Factor ~DClCr Risk Rist(f) Source (I)
Exposure Pathway: Ingcstion or gfound water
Methylene Chloride I.3E+04 1.6E-Ol 7.5E-03 1.2E-03 ATSDR(d) 82
Chloroform 2.4E+02 6.8E-03 6.1E.Q3 4.1E.QS HEA
-------
TABLE 1-10
TOW. CANCER RISKS FOR FUT\JRE CHLDREN AT TIE O£MICAL. SALES COMPAHY SITE 001 MEA
CoDe. CDI ~ncer Upper Bound Total CAncer Wei&ht 4
in Medium (m&lk&lday) Potency EJ.:ocss Uletime Pathway Potency Evideoc
Oemical (e) Factor CAncer Risk Risk(O Source (&)
Exposure Pathway: Incidental ingestion or surrace soil
Tetrach1oroetbene 9.5E-Ol 8.6E-OS S.IE~ 4.4E-«t HEA 82
Trich1oroethene 8.0E+Ol 1.0E-«t 1.1 E~ 1.1 E~ 8.7E~S HEA 82
Exposure Pathway: Dermal contact with surface soil (b.c)
Tricblorethene 9.5E-Ol 9.9E-OS 2.2E~ 3.3E.07 HEA 82
Tetracbloroethene . 8.0E+Ol 8.4E-03 1.0E-Ol 1.3E-04 l.3E-04 HEA B2
Exposure Pathway: Inhalation or ambient air
Methylene Chloride
1.4E-Ol
3.0E-03
1.4E~
4.1E-OS
4.1E-OS ATSDR (d)
82
TOTAL CARCINOGENIC RISK TO FUfURE CHILDREN:
2.6E-04
A-IS
,
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~ 1-11
TOTAL NONCARCINOGENIC RISKS FOR WORKERS A.T 11iE Q£MlCAL. SALES ~ SITE 001 MEA
CoDe. CDI Rcf~r~nce Hazard Tow R.fD
in Medium (mglkyday) Dose Index Palhway Source
Ch~mic:al (e) (IUD) (HI) HI
-Exposur~ PathwaY. Ingestion of ground water.
Acetone 3.6E+04 6.9E~1 1.0E~1 6.9E +00 HEA(a)
Chloro(orm 2.4£+02 4.6E.o3 1.0E-02 4.6E~1 HEA(a)
Carbon T~trachlorid~ 8.5£+01 1.6E~3 7.0E-04 2.3E +00 HEA(a)
cis-l,3- DichloropropcM 1.4£ +02 2.6E-03 3.0E-04 8.8E+00 HEA
1,1- Dichloroethcne 5.7E+03 1.IE~1 9.0E-03 1.2£ +01 HEA(b)
1,1- Dichloroethane 2.6£ +02 S.OE~3 1.0E~1 5.0E-02 HEA(b)
1,2-Dichlroethene 2.0£ +02 3.9E.o3 2.0E.02 1.9E~1 HEA(a)
Eth)'lbGnz.ene 9.1£+01 1.8£-03 1.0E~1 I.8E.02 HEA(a}
Methylene Chloride 1.3£ +04 2.5E~1 6.0E-02 4.1E+00 ATSDR(d)
Tetrachloroethene 1.4£+04 2.6E~1 1.0E-02 2.6E +01 HEA(a}
1,1,1- Trichloroetbane 5.9£+03 1.IE~1 9.0E-02 I.3E+OO HEA(a}
Toluene 1.2£+03 2.3£-02 3.0E~1 7.8E.02 HEA(a}
X lenes total 3.5£ +02 6.7E~3 2.0E+00 3.3E.03 6.2E +01 HEAl
Exposurc Pathway: Inhalation o( volatik or&anics while sbowerinC
Acetone 2.2E-Ol 4.9E-02 1.0E-Ol 4.9E~1 HEA
1,I-Dich1oroetbane 7.3E-03 1.6E~1 1.0E-Ol 1.6E+00 HEA
l,l-Dichloroethene l.6E-Ol 3.6E-02 9.0E~3 4.0E+00 HEA
1,2- Dichtoroethene 5.7E-03 I.3E-03 2.0E-Ol 6.4E.03 HEA
Etby1benzene 2.5E-03 5.6E-04 1.0E.ol 5.6E-03 HEA
Metbylene Chloride 4.5E-02 1.0E-02 9.0E~1 1.1E-02 ATSDR(d}
Tetraehloroethene 3.2E.ol 7.1E-02 1.0E-m 7.1E+00 HEA(d)
1 ,1 ,I-Trichloroethane I.5E-Ol 3.3E-02 3.0E~1 1.1E~1 HEA
Toluene 3.3E.02 7.3E~3 5.0E~1 1.5£-02 HEA(I}
X lenes total 9.5E-03 2.1E.m 9.0E-m 24E-02 I.3E +01 HEAa
Exposure Pathway: Dermal absorptioD of chemicals white showering(b,c).
Acetone 3.6£+04 3.1E-05 5.0E-02 6.3E-04 HEA
Qloro(orm 2.4£+02 2.1E~ 5.0E.m 4~ MEA
Carbon Tetracbloride 8.5E+Ol 7.5£-08 3.5£-04 2.1E-04 HEA
cis-l,)- Dich1oropropcDC 1.4E +02 1.2E~ 1.5£-04 8.0E-04 MEA
1,1- Dicbloroethane 2.6E+02 2.3E.07 S.OE.m 4.6E~ MEA
l,l-Dich loroc:thene 5.1£+03 S.OE~ 4.5E.o3 1.IE-03 HEA
1,2-Dichloroethene 2.0£+02 I.8E~ 1.0E-m 1.8£~ HEA
Methylene Chloride 1.3£+04 1.1 E-05 3.0E-02 3.7E-04 HEA
Tetracbloroethene 1.4E+04 1.2E-05 5.0E-03 2.4E-03 HEA
1,1,1- Trichloroethane 5..9E+03 5.2E~ 4.5E-02 1.1 E..()4 HEA
Toluene 1.2£+03 1.1E~ 1.5~1 7.1 E..06 HEA
Etby1benz.ene 9.1E+Ol 8.0£-08 5.0E-02 1.6E..06 HEA
Xyknes (total) 3.5£ +02 3.1E~ 1.0E+00 3.1£~ 5.7£.03 MEA
A-16
,
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TASLE 1-11 (cent.)
Exposure Pathway: Dermal contact with surface soil (b,C).
Tetnchloroethene 8.0E +01 4.0E~ S.OE4) 2.0E~ MEA
1,1, I-Trichloroethane 1.0E+OO S.OE-06 4.sE.02 1.0E~ 1.0E-04 HEA
Exposure Pathway: Incidental ingcstion or surface soiL
Tetrachloroethene 8.0E +01 3.1 E-OS 1.0E.02 3.1E~ HEA
1,1, I-Trichloroethane 1.0E+OO 3.8E~ 9.0E.02 4.3E-06 3.1 E-03 HEA(a)
Exposure Pathway: Inhalation or VOCs present in ambieDt air.
Methylene Chloride 1.4E~1 3.SE-03 9.0E-Ol 3.9E~3 ATSDR(d)
1,1,1- Trichloroethane 2.8E +02 9.6E-04 3.0E-Ol 3.2E~ 7.1 E~3 HEA(a)
TOTAL HAZARD INDEX 7.6E+Ol
,
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TABLE 1-12
TOTAL NONCARCINOGENIC RISKS FOR CURRENT RESIDENTS AT "THE Q£MtCAL SALES COtIff¥'Nf SITE 001 MEA
CoDe. CDI Rderence Hazard Total
in Medium (mg/kyday) Dose Indc:l Patbway IUD
C1\cmical (e) (RID) (HI) HI Source
Exposure Pathway: Ingestion of ground water.
Acetone 2.3E+Ol 6.6E-04 1.0E-Ol 6.6E.Q3 HEA(a)
l,l-Dichtoroethene 1.4E+Ol 4.0E-04 9.0E~ 4.4E.02 HEA(b)
l,2-Dicblroethene 2.8E+Ol 8.0E-04 2.0E-02 4.0E-02 HEA(a)
Methylene C1\loride l.3E+02 3.7E-OO 6.0E-02 6.2E-02 _ATSDR(c)
Tctrachlorocthene S.OE+Ol 1.4E-OO 1.0E-02 1.4E-Ol HEA(a)
l,I,l-Trichloroethane 1.1E+Ol 3.1 E-04 9.0E-02 3.5E-03 3.0E-Ol HEAl
Exposure Patbway: Inbalation of volaule organics while sbowering
Acetone 1.4E-04 1.4E-04 1.0E-Ol 1.4E-03 HEA
1,1- DichloroetheDe 4.0E-04 4.0E-04 9.0E-03 4.4E.02 HEA
1,l-Dichloroethanc 3.3E-04 3.3E-04 1.0E.en 3.3E-03 HEA(a)
1,2-Dichloroethcne 7.8E-04 7.8E-04 2.0E-02 3.9E-02 HEA
Tctrachloroethene 1.2E-03 1.2E-03 1.0E-02 I.2E-Ol HEA
1,1,1- Trichloroethane 2.8E-04 2.8E-04 3.0E-Ol 9.2E-04 HEA(a)
Meth lenc Q\loride 3.6E-03 3.6E-03 9.0E-Ol 4.0E-03 2.1 E-Ol HEA
Exposure Pathway: Dermal absorption or chemicals wlule showering (b,c).
Acetone 2.3E+Ol S.OE~ S.OE.02- 1.0E~ HEA
l,l-Dichloroethanc 1.2E+Ol 2.6E~ 5.0E-02 5.2E.(J7 HEA
1.1-Dichlorocthcne 1.4E +01 3.1E~ 4.sE.03 6.8E~ HEA
1.2-Dichloroethcne 2.8E+Ol 6.1E-08 1.0E-02 6.1E~ HEA
Methylene Chloride l.3E+02 2.8E-07 3.0E-02 9.4E~ HEA
Tetrach1oroetbene S.OE +01 1.IE.(J7 5.0E-03 2.2E~ HEA
l,l,t-Trichlorethanc 1.1E+Ol 2.4E-08 4.5E-02 S.3E.(J7 4.6E-OS HEA
TOTAL~DINDEX: 5.1E-Ol
A-17
,
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TABLE 1-13
TOTAL NONCARONOGENIC RISKS FOR FUT\JRE RESIDENTS /a THE Q£MICAI.. SALES ~ snE OU1 AAEA
CoDe. CDI Reference Hazard Total RID
in Medium (m&'kg/day) Dose Indcz Pathway Source
Chemical (e) (RID) (HI) . HI
Exposure Pathway: Ingestion or gound Wlter
Acetone 3.6E+04 1.0E +00 1.0E~1 1.0E+00 HEA
Chloroform 2.4E+02 6.8E-03 1.0E-62 6.8E-Ol HEA
-------
"
Exposure Pathway: Dermal exposure 10 surface soil (b,t).
,
TABLE 1-13 (coni.)
I, I, I - Trichloroetbaoc 1.0E +00 t.8E~ 4.5E~ 4.0E~ HEA(a)
TctracbJoroethenc 8.0E+Ol l.SE-03 S.OE~3 3.0E-01 3.0E-01 HEA(a)
Exposure Patbway: Incidental ingestion or surface soiL
1,1,1- TricbJoroetbaDc 1.0E+OO 3.8E-07 9.0E~ 4.3E.Q6 HEA(a)
TetrachJoroethenc 8.0E+Ol llE-OS 1.0E~ 3.1 E-03 3.1 E-03 HEA(a)
TOTAL HAZARD INDEX I.1E+02
-
,
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TASlE 1-14
u
TOTAL NONCARCINOGENIC RISKS FOR FUTURE CHLDREN AT 11£ CHEMICAL SALES COfIPANf SITE 001 AREA
Cone:. CDI Reference Hazard Total RID
in Medium (mllk&lday) Dose Index Pathwa)' Source
Chemical (e) (RID) (HI) HI
Exposure Pathway: Direct contact with surface soiL
TetracbloroetheDe 8.0E +01 2.0E-02 S.OE-OJ 3.9E+00 HEA(d)
t.t.t-trichloroethane 1.0E+00 2.SE~ 4.SE-02 S.4E~ 3.9E+00 HEA(a)
Exposure Pathway: Incidental ingestion of surface soil.
TetrachloroethcDe 8.OE+Ol 2.0E-04 1.0E~2 2.0E-02 HEA(a)
t.l.l-trichloroethane 1.0E+00 2.SE~ 9.0E~2 2.8E~ 2.0E.{)2 HEA(a)
Exposure Pathway: Inhalation of ambient air.
Methylene Chloride 2.8E.{)2 6.9E~3 9.0E~1 7.6E-03 A TSDR(d)
1.1.1- Trichloroethane 1.4E-Ol 1.9E-03 3.0E~1 6.2E~ 1.4E.{)2 HEA(a)
TOTAL HAZARD INDEX: 4.0E+00
A-19
,
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FOOTNOTES FOR TA8LES 1-7 TO 1-14
(a) Verified and on IRIS, but under review.
(b) Note: The dermal absorption pathway exposure assessment is associated with a great deal of uncertainty
due to the fact tbat ~ncer Potency Factor (CPF) and Reference Dose (RID) values are currently
unavailable for chemicals for the dermal patbway.
(c) RID was adjusted for dermal absorption as foUows:
Oral RID X 0.50 = RID for dermal absorption (assumes 50% absorption of chemical).
Cancer Potency Factors were adjusted for dermal absorption as fonows:
Oral CPFIO.5O = Dermal CPF (assumes SO% absorption)
(d) A TSDR (Agency for Toxic Substanc:a and Disease Registry) (1989)
(e) Concentration is the upper 95th percentile of the arithmetic mean for ground water and the maximum detected
detected concentrations for soil and air.
(f) Concentrations for shower pathway are mt/kglshower.
HEA = Health Effects Assessment (1990).
NA - Not applicable as dermal absorption potency factors were estimated using oral potency factors.
(g) EPA Weight-of-Evidence aassification System for Carcinogenicity
A - Human Carcinogen
B - Probable Human Carcinogen
C - Possible Human Carcinogen .
D - Not Classifiable as to human carc:iDogenicity
E - Evidence of noncarcinogenicity for humans
Note: Notation should be interpreted as foUows: 1.3E+04 is equivalent to 13,c:xn
,
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UHCBRTAINTIBS A8SOCIATBD WITH DB CHBXICAL SALBS COKPAHY SIT.
OUl RISK A8SBSSXBB!
There are several sources of uncertainty associated with the
Chemical Sales Company site OUl site risk assessment. Some are
generic to the risk assessment process and include uncertainty
related to extrapolation of experimental animal study results to
humans, dose-response relationships at high and low doses, and
sensitivity of subgroups within the human population to chemicals
and mixtures of chemicals. other sources of uncertainty include
uncertainty regarding the validity of models used to estimate
exposure, such as the shower model, toxicity information
available, and extent of environmental sampling.
In general, for each scenario there are several uncertainties in
determining the exposure parameters that go into the scenario and
that are ultimately combined with toxicological information to
assess risk. For example, a number of uncertainties are
associated with estimates of how often, if at all, an individual
would come into contact with the chemicals of concern and the
period of time over which such exposure would occur. It is
likely that these time estimates in this risk assessment will
overestimate the estimated risks associated with exposure to
contamination in the various areas.
Risks resulting from dermal exposure to soil and groundwater are
difficult to assess due to the fact that dermal Cancer Potency
Factors and Reference Doses are currently not available for most
chemicals. Therefore, oral toxicity values for the chemicals of
concern were adjusted in order to assess these pathways.
However, this adjustment results in further uncertainty with risk
characterization for exposure to chemicals via dermal absorption.
Several items should be noted when considering risks calculated
based on ingestion of groundwater and inhalation of dust and
volatiles by future residents. First, it should be noted that it
was assumed that concentrations of chemicals of potential concern
ACS1/BSPM/062691
A-20
,
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will not increase or decrease in the future, but rather
concentrations currently detected in the groundwater would remain
constant over a 70-year lifetime. This assumption may lead to
overestimates or underestimates of the risks calculated for these
scenarios. In addition, estimates of contaminant concentrations
in air conservatively assume that all dust at the facility is
composed of particulates from surface soils from the facility.
Dose-response information is a potential source of error in risk
assessment in general. There can be major uncertainties in
extrapolating both from animals to humans and from high to low
doses. There are important species differences in uptake,
metabolism, and organ distribution of carcinogens, as well as
species and strain differences in target site susceptibility.
Human populations are variable with respect to genetic
construction, diet, occupational and home environment, activity
patterns and other cultural factors.
There is also a great deal of uncertainty in assessing the
toxicity of a mixture of chemicals. In this assessment, the
effects of exposure to each of the contaminants present in the
environmental media have initially been considered separately.
However, these substances occur together at the site, and
individuals may be exposed to mixtures of the chemicals.
Suitable data are not currently available to rigorously
characterize the effects of chemical mixtures similar to those
present at the CSC QU1 site. Consequently, as recommended by
EPA, chemicals present at the CSC QUl site were assumed to act
additively, and potential health risks were evaluated by summing
risks.
In addition,
this site is
restrictions
industrial.
it should be noted that the potential future use of
somewhat uncertain based on current zoning
which indicate that the site may remain mostly
Based on this information, the future residential
would be unlikely to occur.
use scenario
ACS1/BSPM/062691
A-21
,
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As a result of the uncertainties described above, this risk
assessment should not be construed as presenting an absolute
estimate of risks to human or environmental populations. Rather,
it is a generally conservative analysis intended to provide a
preliminary indication of the potential for adverse impacts to
occur under the exposure conditions assumed.
-
ACS1/BSPM/062691
A-22
,
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SOKHARY 01' RISD A'!' '1'JIB CBBXICAL SALlIS COXPUY OU1 SI'1'.
The objective of the RA for CSC OUl is to evaluate potential
health risks to local residents and workers from exposure to
contaminated groundwater, surface soil, and ambient air. The
scope of the RA includes both cancer and noncancer health risks
which may be associated with long-term exposure (30 years) to
chemicals present in these media. Chronic health risk estimates
are based on concentrations of chemicals of potential concern
(COCs) in groundwater, surface soil, and ambient air measured in
the spring and fall of 1990 and assume no change in
concentrations will occur over the exposure interval.
The magnitude of potential health risks from inhalation, dermal
absorption and ingestion of contaminants in air, soil and
groundwater at OUl are discussed below. Carcinogenic and
noncarcinogenic risks will be discussed by exposure pathway for
each exposure scenario.
CARCINOGENIC RISKS
Ingestion of Groundwater
For current workers, the upper bound excess lifetime cancer risk
associated with ingestion of groundwater is approximately
4 x 10.2. For current residents, the upper bound excess lifetime
cancer risk associated with ingestion of groundwater is
approximately 3 x 10.4. For future residents, the risk estimate
. -, .
1S 1 xlO. In each exposure scenar1o, the largest components of
the risk estimate are the contaminants DeE and PCE.
Inhalation of Volatiles Baitted During a Shower
For current workers at the Chemical Sales Company OUl site, the
upper bound excess lifetime cancer risk associated with
inhalation of volatiles during showering is approximately
ACS1/BSPM/062691
A-23
,
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-2 . .
2 x 10 , pr1mar1ly from DeE. For current residents, the upper
bound excess lifetime cancer risk associated with inhalation of
volatiles emitted during a shower is approximately 4 x 10-4, due
primarily to DeE and TCE. For future residents, the upper bound
excess lifetime cancer risk associated with inhalation of
volatiles during showering is approximately 9 x 10.2, primarily
from DeE.
Dermal Absorption ot Chemicals while Showering
For workers at the Chemical Sales Company OU1 site, the upper
bound excess lifetime cancer risk associated with dermal
absorption of chemicals while showering is approximately 3 x 10.6
with most of the risk estimate derived from DeE and PCE. The
upper bound excess lifetime cancer risk for current residents
resulting from exposure to contaminants via dermal absorption is
approximately 1 x 10.7. For future residents, the upper bound
excess lifetime cancer risk associated with this pathway is
approximately 8 x 10'6. For all three populations, most of the
risk is attributable to DeE and PCE.
Dermal Contact with surtace soil
For dermal contact with soil, as well as the incidental ingestion
pathway described below, the risk estimates are driven
exclusively by the extraordinarily high soil levels of PCE. For
current workers, the upperbound excess lifetime cancer risk for
exposure to VOCs by direct contact with surface soil is
approximately 2 x 10.6. For future residents the upper bound
excess lifetime cancer risk that results from direct contact with
chemicals in surface soil is approximately 6 x 10'6. For future
children at the site, the upper bound excess lifetime cancer
risk, resulting from this exposure pathway is approximately 1 x
10.4.
ACS1/BSPM/062691
A-24
,
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Incidental Inqe.tion of Surface Soil
The upper bound excess lifetime cancer risk that results from
incidental ingestion of surface soil is approximately 7 x 10.7
for both workers and future residents. For future children,
incidental ingestion of surface soil results in an upper bound
excess lifetime cancer risk of approximately 9 x 10'5. Risks for
all populations are due to the presence of tetrach10roethene.
Inhalation of Ambient Air
The estimated risks for this pathway are due to a single
chemical, methylene chloride. For current workers, inhalation of
ambient air results in an upper bound excess lifetime cancer risk
-5 .
of approximately 5 x 10. For future ch~ldren, the upper bound
excess lifetime cancer risk is approximately 4 x 10-5 for
inhalation of ambient air.
NONCARCINOGENIC RISKS
Ingestion of Groundwater
The combined hazard index for all COCs evaluated in this exposure
pathway is approximately 60 for workers. The hazard index for
current residents is 0.3 for water ingestion, due mostly to PCE.
The hazard index for future residents is approximately 80. DeE
and PCE are the largest components of the hazard index for all
populations evaluated.
~.'
Inhalation of Volatile. Baitted Durinq a Shower
The combined hazard index for all COCs evaluated in this exposure
pathway is approximately 10 for workers. DeE, DCA and PCE are
the largest components of the hazard index. The hazard index for
current residents is 0.2 for inhalation of volatiles while
- - -.. ,,~...
ACS1/BSPM/062691
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showering, due mostly to PCE.
residents is approximately 25.
The hazard index for future
Dermal Absorption of Chemicals while Showering
The hazard index associated with dermal absorption of
contaminants while showering is considerably less than one for
workers, future and current on-site residents. In each case, PCE
is the main component of these risk estimates.
Direct contact with Surface 80i1
As previously stated for carcinogenic risks, PCE is the COC upon
which the hazard index is based for both dermal contact and
incidental ingestion for soil. The hazard indices for current
workers and future residents are considerably less than one for
the dermal absorption pathway. For children the hazard index is
approximately 4.0 with most of the risk due to tetrachloroethane.
Incidental Ingestion of Surface soil
The hazard index for current workers and future residents,
including children, is approximately 0.02 - 0.003 for incidental
ingestion of surface soil.
Inhalation of Ambient Air
The hazard index for inhalation of ambient air for workers is
0.007. The hazard index for inhalation of ambient air by future
children is 0.01.
INTEGRATION OF EXPOSURE PATHWAYS
It is reasonable to combine exposure pathways within each of the
exposure scenarios because the pathways represent normal everyday
activities and would be expected to occur regularly~. Total risk
estimates for carcinogens and noncarcinogens under each of the
ACS1/BSPM/062691
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three exposure sc~narios evaluated in this RA are discussed
below.
CUrrent Worker Bxposure Scenario
Combination of upper bound cancer risk estimates for all seven
exposure pathways results in a total upper bound cancer risk
. . .2
est1mate of approx1mately 5 x 10 for the current worker
exposure scenario. The COCs which contribute the largest
component of this risk estimate are DeE and PCE.
Combination of hazard indices for all seven exposure pathways
results in a total hazard index of 75. DCE and PCE are the COCs
with the heaviest overall contribution to the total hazard index.
Ingestion of groundwater is the major exposure pathway.
Current Residents Bxposure Pathway
Combination of upper bound cancer risk estimates for the three
exposure pathways evaluated in this exposure scenario results in
a total upper bound cancer risk estimate of 7 x 10.' for the
current residents exposure scenario. The COCs which contribute
the largest component of this risk estimate are DeE, TCE and PCE.
Ingestion of groundwater is the highest exposure pathway.
Combination of hazard 'indices for these pathways results in a
total hazard index of 0.5. PCE is the COC with the heaviest
overall contribution to the total hazard index. Ingestion of
groundwater and inhalation of volatiles while showering are the
major exposure pathways.
Future Residents Bxposure Pathway
Combination of upper bound cancer risk estimates for all seven
exposure pathways results in a total upper bound cancer risk
. -1
estimate of approx1mately 2 x 10 for the future residents
exposure scenario. The COCs which contribute the largest
ACS1/BSPM/062691
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component of this risk estimate are DCE and PCE. A subset of
risks associated with children playing in contaminated soil in
the south part of the site is calculated at 3 x 10.4.
Combination of hazard indices for all seven exposure pathways
results in a total hazard index of 110 for future residents. DCE
and PCE are the COCs with the heaviest overall contribution to
the total hazard index. Ingestion of groundwater is the major
exposure pathway. For future children, the hazard indices for
the three soil pathways evaluated is 4.0 with most of the risk
due to dermal absorption of TCE in soil.
ACS1/BSPM/062691
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RBI'BU)JCBS I'OR APPB)IJ)IX A
Poiger, H. and C. Schlatter. 1979. Influence of Solvents and
Adsorbents on Dermal and Intestinal Absorption of TCDD.
Food Cosmet. Toxicol., 18(5): 477-487.
u.S. Environmental Protection Agency (U.S. EPA).
Assessment Guidance for Superfund, Volume I,
Evaluation Manual (Part A). Interim Final.
891002. December 1989.
1989a. Risk
Human Health
EPA/5401/1-
1989b. Exposure Factors Handbook. Office of Health
and Environmental Assessment. EPA/600/8-89-043.
1989c. Interim Final Guidance for Soil Ingestion
Rates. Office of Solid Waste and Emergency Response (OSWER
Directive 9850.4).
Weis, Chris. 1990.
Toxicologist.
Personal Communication.
EPA Region VIII
ACS1/BSPM/062691
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APPENDIX B
ARARs
ACS1/BSPM/062691
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CHEMICAL SPBCIPIC ARARs1/(1)
Citation Requirement Evaluation
Groundwater - Volatile Organic Compounds (TCE, Carbon tetrachloride, 1,2-
DCE, 1,1,1-TCA, 1,1-DCE, VinYl Chloride)
42 U.S.C. ~300g Safe Drinking Water Act
40 CFR 141 National Primary Drinking The alluvial aquifer is
5 CCR 1003-1 Water Standards - used a public drinking
establishes health-based water source. Regulation
standards for public is applicable.
water systems [maximum
contaminants levels
(MCLs)] and Colorado
Primary Drinking Water
Requlations.
Pub.L. No. 94-580 Resource Conservation and
as amended Recovery Act (RCRA)
40 CFR Class IV Injection Wells: Land disposal restriction
144.13(c) addresses waste injection may be waived if the
as pa~ of RCRA and reinjected water is
CERCLAI remediation treated to substantially
reduce hazardous
constituents and is
protective of human
health and the
environment. Regulation
is applicable.
5 CCR 1002-8 Colorado Groundwater The alluvial aquifer is
Sec. 3.11.0 Standards: establishes used as a public drinking
water quality standards water source, therefore
to protect existing and the regulation is
potential beneficial applicable.
qroundwater users.
ACS1/BSPM/062691
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( )
CBBXICAL 8PBCIPIC ARAR.w
(continued)
Citation Requirement Evaluation
Soil - Volatile Orqanic Compounds (PCE, TCE. 1.1-DCE)
40 CFR 148 Land Disposal Variance can be
Restrictions: prohibits granted on site-
land disposal of certain specific basis.
contaminated soil and Regulation is relevant
debris. and applicable to
contaminated soils.
40 CFR 261 Identification and Regulation is relevant
Listing of Hazardous and appropriate,
Waste: specifies establishing maximum
Toxicity Characteristic soil concentrations of
Leaching Procedure (TCLP) leachable compounds to
and establishes meet MCLs.
regulatory levels for
orqanic chemicals.
CRS-2S-7-101-S12 Colorado Air Quality Regulation is
control Act: sets applicable to vapor
ambient air standards and extraction and
air emissions volatile emissions.
requlations.
5 CCR 1001-14 Colorado Ambient Air Applicable to vapor
Quality Standards extraction and
volatile emissions.
CRS-30-20-101 through Colorado Solid Waste Applicable to any non-
118 Disposal Act: regulates hazardous solid waste
the management of solid regulated under this
waste. act. Regulation is
relevant and
appropriate to
management of all
solid waste.
40 CFR Part 60, Performance standards Regulation is relevant
Subpart Kb and appropriate to
volatile liquids
storage.
Air
5 CCR 1001-10 Hazardous Air pollutants: These requirements are
Reg. 8 Regulate emission of applicable to vinyl
seven specific chemicals. chloride.
ACS1/BSPM/062691
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',)
I ACTIO. SPBCIPIC ARAR.u .
Citation Requirement Evaluation
29 U.S.C. Occupational safety and Applicable to
~~651-678 Health Act: regulates worker response actions.
health and safety.
49 CFR 107, 171-177 Hazardous Materials These requirements
Transportation: regulates are applicable to any
transportation of hazardous transportation of
materials. hazardous materials.
40 CFR 260-270 Resource Conservation and These requirements
Recovery 'Act: regulates are relevant and
generation, treatment, appropriate to
storage and disposal of disposal of soil or
hazardous waste. treatment residue.
S CCR 1002-2 Regulation for state Sets forth applicable
discharge permit regulations for land
treatment and
disposal
40 CFR 144-147 Underground Injection Control These requirements
Program: regulates are applicable to
underground injection wells. reinjection of
treated qroundwater.
, CCR 723-18, HMT 1-9 Rules and Regulations These requirements
Governing the Transportation are applicable to the
of Hazardous Materials Within transport of
Colorado: establishes hazardous waste.
specific requirements for the
transportation of hazardous
materials within the state.
6 CCR 1007-3 Colorado Hazardous Waste These requirements
~260 and 270 Regulations: regulates are applicable to
dis~osal of hazardous waste, onsite disposal of
TSD/ facilities, and treatment residue,
treatment of residue. and may apply to
offsite disposal.
S CCR 1002-8 Colorado Water Quality These requirements
~3.1.0-3.1.11, Control Act: regulates are rele~~nt and
3.11. 0 discharge to state waters. appropriate to
discharges to surface
water.
ACS1/BSPM/062691
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ACTIO. SPBCIPIC ARARaw I
(continued)
Citation Requirement Evaluation
~25-12-103, C.R.S. Colorado Noise Abatement: These requirements apply
establishes standards for to construction
controlling noise. activities.
37-91-104, 106, 110 Water Well Construction These requirements apply
C.R.S. and Pump Installation: to well construction and
Regulates water wells, groundwater withdrawal.
test holes, and pump
installation.
33 U.S.C ~1251-1376 Clean Water Act
40 CFR 230, 231, Dredge or Fill (Section A small area may be a
33 CFR 323 404): Requires permit to wetland. A permit will
discharge dredged or fill not be required pursuant
material into navigable to Section 121(e) of
waters or wetlands. CERCLA, but the
substantive requirements
may be appropriate for
activities involving
dredge and fill.
Executive Order No. Protection of Wetlands: Regulations may be
11990, 40 CFR 6.302(b) requires action to avoid relevant and appropriate
adverse effects, minimize to a small wetland area.
potential harm and
preserve and enhance
wetlands.
5 CCR 1001-5 Colorado Air Pollution CERCLA Section 121(e)
Reg. 3 Control Regulations: exempts onsite response
requires air pollution actions from obtaining
emission notices (APEN) permits, but requires
and permits. compliance with
substantive provisions
and filing of APEN.
Regulations are
applicable.
ACS1/BSPM/062691
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u
,
5 CCR 1001-9
Reg. 7
LOCATIO. SPBCIFIC ARAR.w
Volatile Organic
Compounds: regulates
emissions of volatile
compounds.
5 CCR 1001-3
Reg. 1
Fugitive Dust Emissions:
regulates fugitive dust
emissions and opacity
limitations. Requires
that particulate emissions
be minimized, that opacity
limitations be observed,
and that a particulate
emission control plan be
filed.
Discharge of effluent to
qroundwater
5 CCR 1002-3, ~ 10.1.0
5 CCR 1001-5
Sec. IVD, Reg. 3
Stationary Emissions:
regulates attainment and
mainte~ance of any
NAAQS. I Also requires
air impact analyses for
toxic pollutants, and the
attainment and maintenance
of State standards.
Odor-Free Operation:
requires design action to
provide odor-free
operation.
5 CCR 1001-4
Reg. 2
aJ ARARa = Applicable or Relevant and Appropriate Requirements.
bl CERCLA '" Comprehensive Environmental Response, Compensation, and
Uability Act.
1;1 TSO '" Treatment. storage, and disposal.
dl NMQS = National ambient air quality standards.
el RACT = Reasonable, available control technique.
(1) Remediation levels are presented in Table 5, pg 53 of the ROO teJCt.
ACS1/BSPM/062691
8-5
RACTe/ is appl icable and
is required to control
emissions in ozone non-
attainment area.
These regulations would
apply to construction,
excavation and haul
roads.
Applicable to treated
water discharqe.
The Operable Unit is in
a non-attainment area.
The regulations are
applicable.
These are applicable in
order to limit nuisance
conditions from emission
sources.
I
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DEPARTMENT
OF A H EA LTH
ROY ROMER
Goyornor
JOEL KOlIN
lolorim Executiye Director
Graad JuDClioo RC£ioDAI Office
222 S. 6th Street. Room 232
Graad JuDCIioo. Colorado 81501.2768
Telcfu Number.
(303) 248.7198
@) priNtd on m:ycltd (1<11'"
June 25, 1991
Mr. James P. Scherer
Regional Administrator
U.S. Environmental Protection
Region VIII
One Denver Place
999 18th Street, Suite 500
Denver, Colorado 80202-2405
Agency
State of Colorado Concurrence on Chemical Sales,
Operable Unit 1 - Record of Decision
.
Dear K~herer:
The state of Colorado concurs with the Record of Decision for
Operable Unit 1 of Chemical Sales, with the understandings noted
below. We would like to congratulate EPA for the speedy and
competent manner in which the RIfFS and ROD for the site were
developed. We look forward to a continued good working
relationship with EPA during the Remedial Design and Remedial
Action phases for the cleanup of this source of pollution to the
alluvial aquifer.
Re:
An additional issue has been raised by the State Engineer's Office
that may apply to the project. A ground water augmentation plan
may be required for water 10ss due to evaporation from the air
stripping operation. This issue will need to be pursued during
the Remedial Design phase.
The State of Colorado concurs with the Record of Decision for
Operable Unit 1 of Chemical Sales, with the understanding that
although not specifically stated in the ROD, the cumulative risks
for the multiple contaminants and multiple pathways present at the
site have been assessed and determined to be within EPA's
acceptable risk range for the chosen remediation.
Also, we note that although chloroform was not designated as a
chemical of concern, it will be removed during the soil vapor
extraction and air stripping operations.
Sincerely,
<--./ i.£
1~?1'1 ~~"7-
Thomas P. LOO~
Assistant Director for Health and
Environmental Protection
Colorado Department of Health
TPL:nr
cc:
Ron Cattany
Dave Shelton
John Leary
Charlotte Robinson
Robert Eber
Vickie Peters
Hal Simpson
Nancy Chick
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ACS1/BSPM/062691
RECORD OF DECISION
CHEMICAL SALES COMPANY SUPERFUND SITE
OPERABLE UNIT 1 - LEYDEN STREET LOCATION
PART 3 - RESPONSIVENESS SUMMARY
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BACKGROUND 01' COJOltnfITY IHVOLVBJI1DI'1' ACTIVITIB8
Community interest in the groundwater contamination in south
Adams County was very intense in 1985 and 1986 when the problem
first became known, and persisted until the permanent water
treatment plant started operation in October 1989. The initial
blame was placed on the Rocky Mountain Arsenal, which was
adjacent to the contaminated public water supply area and already
receiving significant media attention. The EPA and the Army
responded to numerous public and media inquiries, issued press
releases for new developments, and attended public meetings.
Community relations activities were coordinated between the EPA,
the Army, and the SACWSD. The state conducted a separate
program.
In 1984 and 1985, local newspapers were printing stories almost
daily concerning the Arsenal cleanup process and groundwater
contamination. In the spring and summer of 1985, several local
newspapers reported the detection of low levels of
trichloroethylene (TCE) in SACWSD supply wells west of the
Arsenal. The press quickly built up momentum on the new issue,
and collectively published at least 10 articles in July of 1985.
EPA personnel responded to numerous questions from reporters and
the public, and supplied them with the~ata.
In response to the press coverage, citizens Against Contamination
(CAC), a local citizen's group, formed and arranged a meeting
that was held September 3, 1985. One hundred to 200 people
attended, including EPA, Colorado Department of Health (CDH) , the
Army, SACWSD officials, and local poli~icians. The meeting was
covered by at least KUSA TV, Channel 9.
On November 13, 1985, the Army issued a press release announcing
the detection of TCE in wells on the Arsenal property. The
Denver Post responded with an article. A public meeting was held
on November 25, 1985, in which the Army reported the results of
the sampling. The Army stated that they planned to locate the
ACS1/BSPM/062691
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source of the TCE found in the Arsenal wells and discussed the
next steps. They maintained that the available information was
not sufficient to determine if the Arsenal was a source of the
TCE found in the SACWSD wells.
On December 19, 1985, the EPA issued a press release stating that
they were seeking Superfund money for cleanup of the south Adams
County water. At least 22 articles appeared in the Denver Post
and the Rocky Mountain News in December 1985 and January 1986.
The articles focused on EPA's attempts to obtain funding and on
the Arsenal as a suspected source. Congresswoman Pat Schroeder
was pressuring the Army to pay for treating the water. Robert
Duprey of the EPA did a live interview on KDEN radio. On January
24, 1986, Mr. Duprey and others met with CAC and promised to
answer their questions, implement suggestions, and provide copies
of documents.
CAC arranged a public meeting on February 13, 1986 with speakers
from the EPA, the Army, SACWSD, and CDH. The Army offered
technical assistance and funding for an interim solution. The
EPA passed out a fact sheet listing contacts for information on
various topics. There were at least 15 newspaper articles in
February concerning the citizens fears and the Army's role.
One predominant issue in the press was that Governor Lamm blamed
the Arsenal for the contamination and that the State was ready to
sue the Army. The Army issued a press release on February 6,
1986, stating that CDH had agreed to withdraw the State suit.
This was followed by an article in the Denver Post.
The CDH issued a health advisory on February 27, 1986,
recommending that residents using shallow private wells in a
specified area boil their drinking water or use bottled water
(the advisory was updated by a second release on March 4, 1986,
clarifying the boundaries of the affected area). The advisory
resulted in a flurry of newspaper articles (including a headline
in the Denver Post) expressing citizen concerns. The-agencies
ACS1/BSPM/062691
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were again flooded with calls from the public, the press, and
politicians. A major concern was access to bottled water for
children at school. Both the EPA and Senator Gary Hart requested
that the Army supply bottled water for the schools. The Army
agreed, and the water was delivered in March. Coors also donated
bottled water.
The EPA held a press conference on March 4, 1986, and issued a
press release on March 5, 1986, reporting levels of TCE in three
private wells that were much higher than levels found in water
provided by SACWSD. The EPA issued an additional press release
on March 5, 1986, stating that the EPA and the Army had agreed in
concept to enter into an agreement to transfer funds from the
Army to the EPA to pay for water treatment. A number of
newspaper articles followed.
CAC held another public meeting on March 6, 1986, which was
attended by over 600 people, including representatives of the
EPA, the Army, CDH, Tri-County Health (TCH) and SACWSD. There
were no formal presentations; just questions and answers.
Questions centered on the health effects and the advisory. The
CDH passed out a summary of the health advisory with
clarifications. Residents using contaminated private wells were
urged to connect to the public water system. The EPA stated that
their goal was to have an interim water treatment system in place
in four to twelve months (this was reiterated by SACWSD). The
EPA also hoped to have an agreement with the Army and SACWSD to
transfer funds from the Army to SACWSD for the interim system.
The Army passed out a letter explaining that the evidence was
still insufficient to substantiate the Arsenal as a contributor
or the sole source of the TCE contamination.
Heavy newspaper coverage continued following the meeting. A
press release issued March 20, 1986, announced an agreement to
transfer $1 million from the Army to the EPA. On April 7, 1986,
the Army, the EPA, the State, and SACWSD signed a cooperative
agreement to provide funding for the water treatment. The
ACS1/BSPM/062691
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agreement transferred the funds to SACWSD.
followed.
Press coverage
On April 23, 1986, the EPA presented an External Award to CAC for
steadfast pursuit of safe drinking water and the cleanup of
hazardous waste contamination. Also in the spring of 1986, the
EPA prepared and widely distributed a videotape that answered
common questions residents had regarding the TCE in their water.
On May 1, 1986, EPA issued a press release reporting new data on
private wells. The new data gave a clearer .indication that
sources of TCE in addition to the Arsenal were involved. In May
of 1986, six Colorado members of Congress wrote Lee Thomas, EPA
Administrator, requesting he make funds available for the
cleanup.
CAC held another public meeting on May 22, 1986, at which CAC,
the Army, and the EPA presented updates. The EPA passed out a
statement describing progress. The EPA was ready to fund the
connection of private wells to SACWSD. The meeting was attended
by a number of state, local and Federal politicians.
The Summer 1986 issue of SACWSD's newsletter "The Waterspout"
announced the installation of the temporary carbon filtration
system (May 30, 1986) and urged residents with shallow wells in
the area to apply for free hookups. The EPA issued a press
release offering the free hookups. A questionnaire was also sent
to individual well owners.
Media and public interest subsided in the fall of 1986 after the
safe drinking water issue had effectively been addressed via
about 200 private well hookups and the start of the temporary
water treatment system. EPA issued a fact sheet in August of
1986 containing information about the site (referred to as EPA's
Rocky Mountain Arsenal Off-Post Study Area) and a summary of
activities in progress. A press release September 11, 1986,
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announced that the Army had transferred $6 million to the EPA to
fund a permanent treatment facility.
In the fall of 1986, results of an
and Leyden streets were brought to
October 23, 1986 press conference,
Chemical Sales site as a source of
south Adams County.
EPA study in the area of 48th
public attention. In an
EPA specifically named the
groundwater contamination in
In December of 1986, the EPA issued another fact sheet discussing
the findings of an initial remedial investigation in the EPA Off-
Post Arsenal study Area. Remedial alternatives were presented
and a public comment period from December 12, 1986, to January 7,
1987, was announced. Notice of the opportunity to comment was
also published in the newspaper on December 10, 1986. Comments
were received from CAC, CDH, SACWSD (and consultant), TCH, the
City of Commerce City, the Adams County Commission, Adams County
School District No. 14, Holme Roberts and Owen, the Army (and
contractor), and a number of residents. The majority of
commentors supported EPA's preferred alternative, a granular
activated carbon filtration system.
In June of 1987, the EPA issued a ROD for the selected remedial
alternative, a permanent water treatment plant (the Klein Plant)
with a granular activated carbon filtration system. In October
of 1987, the Army and the EPA agreed to pay to construct the
plant and operate it for 25 years.
The EPA issued a fact sheet for EPA's Off-Post Arsenal Study Area
in April of 1988 announcing further field activities for
investigation of the contamination. The EPA prepared a Community
Relations Plan for the Chemical Sales Site in December of 1988.
In August of 1989, the EPA issued a fact sheet stating that the
Chemical Sales site had been proposed for inclusion on the
National Priorities List (NPL).
ACS1/BSPM/062691
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The Klein Water Treatment Plant opened on November 17, 1989.
EPA, Army, and state officials were honored at both the ground-
breaking and opening ceremonies for the Klein Plant. According
to SACWSD's newsletter "The Waterspout", a capacity crowd
attended the opening ceremonies.
The EPA issued a fact sheet in April of 1990 concerning TCE
contamination in the Commerce City Area. The fact sheet
discussed the background and the status of the site. In May of
1990, the EPA issued an additional fact sheet covering the status
of four south Adams County Superfund Sites, including Chemical
Sales.
On May 22, 1990, EPA gave two presentations to brief City and
County officials on the Superfund process and sites in south
Adams County. Also in May of 1990, the EPA Community Relations
Coordinator took approximately 40 EPA management personnel and
officials on a tour of the south Adams County Superfund sites.
EPA mailed out Proposed Plans for the three Operable Units at the
Chemical Sales Site on February 28, 1991. The Proposed Plans
discussed remedial action alternatives for the source and the
groundwater contamination, and announced the public comment
period. Notice of the public comment period also appeared in
four local newspapers between February 27, 1991, and March 5,
1991. A public meeting held March 14, 1991, was attended by 50
to 75 people.
ACS1/BSPM/062691
6
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RECORD OF DECISION
CHEMICAL SALES COMPANY SUPERFUND SITE
OPERABLE UNIT 1 - LEYDEN STREET LOCATION
Written comments on the Chemical Sales Company (CSC) OUl RI/FS
were received from Adrian Brown Consultants, Inc. (for Interstate
Distribution Center Associates, Ltd., IDCA); the Colorado
Department of Health; Parcel, Mauro, Hultin & Spaanstra, P.C.
(for CSC); and Department of the Army. Responses to the comments
have been prepared and are presented in this section of the ROD.
The comments have been grouped by topic and, in some cases, have
been combined if they address a common concern. The actual text
of the comments has been paraphrased for the purposes of this
section, and the complete text is attached to this part of the
ROD as Exhibit 1.
1.
Department of the Army, Appendix H, Batch Flushing Kodel,
Comments 1-5
A set of comments pertaining to the appropriateness of using
a batch flushing model were raised, including concerns of
how the model did not account for spatial variability of
parameters, assumed clean inflow of water, lacked a
sensitivity analysis, and presented inconsistent units.
EPA Response. The batch flushing model represents a
simplified means to estimate time required to restore the
alluvial aquifer to groundwater remediation levels within
OUl for the various alternatives evaluated in the detailed
analysis phase. Due to technical, time and budgetary
constraints, it was impracticable to simulate all variations
within the CSC OUl groundwater system. Thus, many
generalized assumptions were used in the development of this
model.
The simplifying assumptions included (a) that the mass of
the contaminant is in chemical equilibrium between the solid
(soil) and the liquid phases, (b) the soil-water
partitioning isotherm (Kd) is linear and reversible, (c) the
concentration of the contaminant in water used to flush the
model aquifer is zero, and constant at that value, (d) no
other chemical reactions occur that interfere with the
adsorption/desorption process, (e) the units cubic
centimeter (cc) and milliliters (ml) can be used as
equivalent units for water, (f) the bulk density, porosity,
distribution coefficient and contaminant concentration are
all constant values throughout the model aquifer, and (g)
that aquifer flushing estimates are conservatively evaluated
under this method by using PCE as the contaminant. Since
each evaluated alternative incorporated the same aquifer
restoration time estimates based on the aquifer flushing
model, the model served as a useful tool for co~p~~ing the
effectiveness of one alternative with another.
ACS1/BSPM/062691
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Because the model cannot simulate actual variations in the
groundwater system, the time frames presented in the OUl FS
are estimated, and are valid only as a relative comparison
of time frames amongst alternatives. The uncertainty
associated with these estimates are therefore acceptable for
the purposes the CSC OUl FS. If the model accounted for
spatial variability and conducted a sensitivity analysis,
the relative effectiveness of the various alternatives would
remain unchanged. Additional modeling may be considered
during the remedial design to optimize well locations and
pumping rates, and during remedial action to evaluate the
effectiveness of the system. EPA has evaluated the model
for consistency of units and, given the assumption above,
requests further clarification on this concern.
2. Adrian Brown Consultants, Inc., General Co..ent, paq. 1,
paraqraph 1.
Reference to Trammell Crow as the owner of the land and
buildings adjacent to the CSC property to the west is
incorrect and should be changed to clearly identify
Interstate Distribution Center Associates, Ltd. (IDCA) as
the owner of this property.
EPA Response. EPA acknowledges this concern. All future
references pertaining to the ownership of the 4650 Leyden
st. property, including the CSC QUl Record of Decision, will
identify the Interstate Distribution Center Associates, Ltd.
as the current owner.
3.
Adrian Brown Consultants, Inc., General Comment, page 16,
paraqraph 3.
Throughout most of the document, Trammell Crow is
misspelled. All references to Trammell Crow should be
replaced with IDeA, the owner of the property to the west of "
ese.
EPA Response. It is recognized that Trammell Crow is
misspelled and also that IDeA is the owner of this property.
4.
Adrian Brown Consultants, Inc., General Comment, Page 1,
paraqraph 2.
Potentially contaminated rinsate waters were disposed on the
IDCA property in violation of the General Sampling and
Analysis Plan.
EPA Response.
The comment is noted.
5.
Adrian Brown Consultants, Inc., General Comment, Page 16,
paragraph 1.
Reports from the Denver Fire Department and the Colorado
Department of Health indicate that on March 28,--1986, ese
ACS1/BSPM/062691
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was found discharging chemical wastes onto the ground to the
north of the CSC property. Given this incident and the
possibility of additional such discharges, it does not
appear that the RI sampling and analysis has been adequate
to characterize the contamination resulting from such
discharges.
EPA ResDonse. A comprehensive soil gas survey was conducted
during Phase I of the CSC aUl RI. The objective of the
survey was to focus and streamline data collection
activities. Areas exhibiting soil gas detections were
further characterized during Phase II and Phase III
activities. Soil and soil gas data was collected from the
area north of the CSC property during all three phases.
These activities are considered to be sufficient to
characterize resulting contamination from this release.
6.
Adrian Brown Consultants, Inc., site History Comment, Page
16.
IDCA strongly objects to the inclusion of unsubstantiated
claims of historic uncontrolled waste disposal as in
paragraph 2 on page 2-1. IDeA also objects to the inclusion
of the statement that strong fumes were reported while
excavating for the construction of the Trammell Crow
building (paragraph 3, page 2-1). This statement is no
longer in the RI/FS. EPA has been provided with affidavits
stating that the only similar incident that IDeA is aware,
was a release from a tanker unloading at CSC.
EPA ResDonse. The affidavits submitted to EPA by IDeA which
document that no fumes were reported as a result of building
excavation have been incorporated into the EPA
Administrative Record of the CSC site. Historical
uncontrolled waste disposal was proposed as one of the
several possibilities resulting in the observed soil and
groundwater contamination. Data collected during the Phase
II and Phase III RI, do not confirm the existence of an
uncontrolled waste dump on the IDCA property.
7.
Adrian Brown Consultants, Inc., site History Comment, Page
1, paragraph 1.
The RI/FS claims that a very large area which includes QUl
was historically used for uncontrolled dumping. This claim
in unsubstantiated in the RI/FS. Nor does the RI/FS
identify any disposal activities that coincide with the
sources of contamination identified in the RI/FS.
EPA ResDonse. Since the 4650 Leyden st. property was vacant
until the early 1970s, and uncontrolled dumping activities
have been identified throughout this area, the
identification of this type of potential source-is 'deemed
ACS1/BSPM/062691
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~
appropriate for recognizance purposes. Data collected
during the CSC OUl FS have not confirmed the presence of
uncontrolled dump sites as sources to the observed soil and
groundwater contamination.
8.
Adrian Brown Consultants, Inc., sit. Hiatory Comment, paq.
2, paraqraph 3.
Five other spills are noted and requested for inclusion.
EPA Response. The EPA will include this additional
information in the CSC OUl Administrative Record. These
spills have also been identified in the CSC OUl ROD.
9.
Department of the Army, Remedial Inv..tiqation, Specific
Comment 2.
The site history indicates that there were several other
potential sources of contamination that were not addressed
in the report, such as the landfill and the airfield.
EPA Response. Although there is evidence to indicate that
landfill and airfield operations may have occurred within a
large area indicated in Figure 3-1, a more detailed survey
of historical aerial photographs has not shown those
activities to have taken place on the CSC property. While
these activities could potentially be sources of
contamination, the CSC RIfFS was not intended to identify
sources beyond the boundaries of the operable unit.
10. Adrian Brown Consultants, Inc., Source of Contamination
Comments, paqes 12 and 13.
The RIfFS does not accurately address the potential sources
of contamination at the site. Aerial photographs indicate
the storage of CSC materials on what is now the IDCA
property. These same photographs do not support the RIfFS's
claim that uncontrolled dumping occurred on the IDeA
property.
EPA Response. EPA has included 1978 and 1979 aerial
photographs of the CSC and IDCA properties in the CSC
Administrative Record. EPA notes IDCA's contention that
drums were stored on what is now IDeA property. Assuming
these drums may have leaked in the past, EPA is unclear why
IDCA so vehemently denies any source materials being on this
portion of its property.
11.
Adrian Brown Consultants, Inc., Adequacy of Remedial
Investiqation Comment, paqe 6.
The RIfFS may not have fully identified all significant
sources of contamination upgradient of OUl.
ACS1/BSPM/062691
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EPA ResDonse. The identification of 87 ppb of TCE, 15 ppb
of PCE, 9 ppb of 1,1,1 TCA and 5 ppb of 1,1 DeE in
upqradient Well MW 24, indicates that a potential source may
exist upgradient of the IDeA and CSC properties. This well
only has been sampled once and will be sampled during
remedial design to verify these results. The saturated
thickness observed in well MW 24, however, is less than one
foot, indicating that the total potential mass of
contaminants migrating from upqradient onto the IDCA and CSC
facility is extremely small. It should be noted that
upgradient well MW 1, located on the southeast corner of the
CSC property has not detected contamination in three
separate sampling rounds. EPA will sample Well MW 1 during
the remedial design. A final determination of the presence
of upqradient sources will not be made until these results
are analyzed. The CSC site will not be extended if
upgradient sources are identified.
Adrian Brown consultants, Inc., Groundwater Contamination
Comment, Pages 11 and 12.
12.
Based on water quality data from well MW-13, it appears that
there is a source of contamination upgradient of the IDeA
property. However, the RI/FS implies that the potential
sources of contamination are near well MW-12.
EPA ResDonse. Although the contamination could have
originated from groundwater flowing from upgradient
locations, the possibility that a localized source or
sources not encountered in the soil borings cannot be
completely ruled out. The text does offer other hypotheses.
The text also correctly describes the contaminant
distributions.
13. Adrian Brown Consultants, Inc., s~te History Comment, Page
2, paragraph 5, 6.
It is unclear which tank farm is shown to have
in the 1954 photographs. It is also incorrect
the fill material used during pad construction
buildings was imported.
been expanded
to state that
for IDCA
EPA ResDonse. The description of the construction of the
pads for the IDeA building in the CSC QUl ROD have been
revised.
14. Adrian Brown Consultants, Inc., Soil Gas Survey Results
Comment, Page 3.
A lengthy comment was made questioning the usefulness of
identifying specific sources using soil gas methods,
including the ability of the method to distinguish between
soil sources and soil that has become contaminated by
volatilization from contaminated groundwater.
ACS1/BSPM/062691
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~
15.
16.
17.
BPA ResDonse. The reviewer is apparently confused by the
manner in which soil gas results were collected and the
purpose of their intended uses. Two sets of data containing
soil gas results are presented in the report. The first is
presented in Section 4.2.3, Soil Gas Survey Results. This
application was intended to serve as a screening tool to
delineate approximate areas within OU1 which warranted
further investigation. The TCE map (Figure 4.13) delineates
an areal distribution of soil gas and provided the basis for
hypothesizing several different potential source areas. The
second soil gas application, in Section 4.3.1, utilized soil
gas as derived from headspace from soil samples collected at
approximately 5 foot depth intervals within the designated
boreholes. This second application was used to
qualitatively discern the vertical and areal distribution of
contaminants and delineate those areas in which only soil
was contaminated compared to those areas in which soil and
groundwater were contaminated.
Adrian Brown Consultants, Inc., Soil Gas Survey Results
Comment, Page 4, paragraph 1.
A point was made regarding the apparently incorrect
distribution of PCE soil gas results near the CSC tank farm
and the IDeA building.
BPA ResDonse. Closer examination of the data indicates that
the narrative description and the referenced figure for PCE
soil gas concentrations are correct as given.
Adrian Brown Consultants, Inc., Quality of Soil Gas Analyses
Comment, Page 24, paragraph 1.
Concern was raised over the apparent lack of soil gas daily
calibration in the Phase III RI.
EPA Response. The text indicating daily calibration refers
to the soil gas survey. The Phase III RI involved no such
survey, hence the reference is inappropriate.
Department of the Army, Remedial Investigation, Specific
Comment, Page 4-33
The presence of soil gas slightly upgradient (with respect
to groundwater flow) of a groundwater source does not
preclude groundwater as the source of the observed soil gas
concentrations. Soil gas flow is not governed by
groundwater gradients.
EPA ResDonse. The EPA agrees that soil gas flow is not
governed by groundwater gradients. The distribution of soil
gas, however, often mirrors that of the VOC's in groundwater
when contaminated groundwater is the source of the
contamination detected in the soil gas. Low levels of VOC's
ACS1/BSPM/062691
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were recently detected in the CSC upgradient monitoring
well. It is possible that this "upgradient" contamination
may be at least part of the source of the upqradient soil
gas that has been recorded.
18.
Adrian Brown consultants, Inc., Quality of soi~ Gas Analyses
Comment, Page 24, paragraph 2.
Concern was raised regarding the depiction of duplicate
results as being generally well matched. The argument was
made that the duplicate results are poorly matched when the
duplicates for which the compound was (a) not detected and
(b) exceeded 10,000 are not included in the evaluation.
EPA ResDonse. The EPA feels it is appropriate to include
both ND and >10,000 values in the evaluation of duplicate
similarity. With these sets of results included, as they are
in the RIfFS report, the duplicate values are indeed well
matched.
19.
Adrian Brown Consultants, Inc., Quality of Soil Gas Analyses
Comment, Page 25, paragraph 1.
The data from instrument and syringe blanks was not included
in the report.
EPA ResDonse. Data from instrument and syringe blanks were
not deemed necessary for inclusion in the CSC QU1 RIfFS. The
Gas Chromatograph sampling methodology and field analysis as
provided in the CSC Sampling and Analysis Plan is
appropriate for DQO Level II data.
20. Adrian Brown Consultants, Inc., Blectrical Resistivity
Survey Results Comment, Page 4.
Adrian Brown Consultants, Inc., Magnetic Survey Results
Comment, Page 5, paragraph 2.
The manner in which hypotheses were offered regarding
interpretation of the resistivity and magnetic survey
results include the possibility of uncontrolled dumping even
though there is no data to substantiate the claim that
uncontrolled dumping has ever occurred on the IDeA property.
EPA ResDonse. Uncontrolled dumping was identified as one of
the several possibilities, (including natural conductivity
contrasts), to explain the distributions obtained from the
surveys. Since this survey was used as a screening tool to
focus data collection activities, the identification of
several possibilities contributing to the observed results
is appropriate.
---.... .....
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21.
22.
23.
24.
Adrian Brown Conaultanta, Inc., Xaqnetic survey a.aulta
Comm.nt, Page 5, paragraph 1.
Concern was expressed over the statement in the report
relating the lateral extent of an anomaly to the area
reportedly used for filling operations.
EPA ResDonse.
The EPA agrees with this comment.
Adrian Brown Consultants, Inc., Pield Gas Chromatograph 80il
Beadspace Interpretations Comment, Page 5.
The discussion of results did not include factors which
could affect the concentrations detected in the headspace
gases.
EPA Response. Many factors such as temperature, type of
vadose zone material and heterogeneity of vadose zone
material, effect the magnitude of detected soil gas
concentrations. Soil gas, however, was used to the
determine the presence or absence of contaminants in the
soil. Since this data is used qualitatively (000 Level II),
the identification of factors effecting quantitative
analysis is unnecessary.
Department of the Army, General Comment 5
Department of the Army, specific Comment, Risk Assessment,
Page 1-3
No corresponding sediment samples were collected along with
the surface water samples. The rationale for not collecting
the sediment samples was not presented.
EPA ReSDonse. Sediment sampling was not deemed to be
necessary based on the circumstances at the site. The data
indicates that the streams and ditches of concern are losing
streams, thus water would be moving from the stream into the
groundwater, not vice versa. Since the contaminants of
concern are all volatile organic compounds with fairly low
sorptive capabilities, stream and ditch sediments are not
considered to be likely sites for contaminant concentration.
Adrian Brown Consultants, Inc., Assessment of contamination
from Known Releases Comment, Page 6.
Department of the Army, Specific Comment, Page 1-3.
Because no contaminants were found in Sand Creek surface
water, the potential for surface water contamination was
dismissed. No sediment sampling was discussed in the
report. The investigation of the contribution to surface
water by contaminated groundwater would be aided by the
inclusion of sediment sampling results, if available.
ACS1/BSPM/062691
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EPA ResDonse. Sediment sampling of Sand Creek was not
conducted because it is not expected that volatile organic
compounds (VOCs) would be present in sediment. Volatile
organic compounds do not readily absorb to sediment
particles in a surface water environment. Since no VOCs
were detected in surface water in the wetlands from which
the ditch empties, it is unlikely that residual VOCs will be
detected in the ditch sediments.
25.
Adrian Brown consultants, Inc., Soils Contaaination Comment,
Pages '-8.
Concern was raised regarding the depth of soil contamination
detected in boring SB-10 and SB-14, located on the IDCA
property, and why leaching of contaminants to the water
table at these locations is unlikely.
EPA ResDonse. The EPA does not rule out the hypothesis that
the absence of detectable contamination below about 20 feet
could be due to the low adsorptive capacity of the soils and
thus that contaminants could have leached to the
groundwater. The arguments given to rule out this
hypothesis are weak and unclear. A very low Kd of the sandy
soils could easily result in adsorbed VOC concentrations
being low enough to be below soil analytical detection
limits. Also, the mass balance argument presented does not
consider that contaminants may have leached through the
vadose zone and into the aquifer in the past.
2'.
Adrian Brown Consultants, Inc., Soils Contamination Comment,
Page 9, paragraph 1.
Compounds identified in groundwater below the IDCA property
have not been identified in the soils at the property.
These compounds include methylene chloride, cis-1,2-
dichloroethene, 1,1-dichloroethane, 1,2-dichloroethane, and
vinyl chloride.
EPA ResDonse. With the exception of methylene chloride, the
other compounds listed in the comment could and likely are
breakdown products of perchloroethene, trichloroethene
and/or trichloroethane.
27.
Adrian Brown Consultants, Inc., Soil Contamination Comment,
Page 9, paragraph 3.
The mass:mass ratios for PCE to TCE in soils is much higher
than the ratios for groundwater under the IDeA property.
EPA ResDonse. The EPA considers the ratios to suggest th .~
a source of PCE exists in soils on the IDeA property. Tr:
ratio would tend to decrease as biodegradation ensues and
dehalogenation occurs, leading to lower concentrations of
the more chlorinated compounds and higher concentrations of
ACS1/BSPM/062691
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I,'
the less chlorinated compounds. An additional difference in
the soil and groundwater ratios probably relates to the
groundwater under the IDCA property being affected by flow
from upgradient locations which may have a different mix of
compounds.
28. Adrian Brown Consultants, Inc., Direction of Groundwater
Plow Comment, Page 10.
The piezometric map (Figure 3.9) misrepresents the bulk of
the information pertaining to groundwater flow direction and
the RI provides incorrect information by omitting MW-S.
EPA Response. The piezometric surface map shown on the
figure is very similar to the piezometric surfaces of other
months, and indicates that groundwater flows in a north to
northwest direction. The associated text is similarly
accurate and correct. The comment was unable to state that
a localized westerly flow component apparently existed in
the vicinity of the CSC underground tank farm based on
measurements collected in March and June, 1990, but not in
september 1990. As clearly indicated in a note on the
figure, well ES-MW-S was damaged and unavailable for
measurement during" the month for which the piezometric
surface on the figure portrays. At IDeA's request, water
level information from well ES-MW-5 was collected the
following month and included in the figure. Because an
annual cycle of water level measurements had not been
collected and there had been disturbance associated with
excavation of the underground storage tanks on the CSC
property, it is not known if the highly localized westward
component of flow as shown on the March and June piezometric
surface maps exists seasonally, is due to measurement
errors, or is real.
29.
Adrian Brown Consultants, Inc., Risk Assessment Hydrogeology
Comment, Page 17.
The groundwater flow direction would be more accurately
described as flowing generally to the north but also slowing
to the west and northwest in the southern portion of OU1.
EPA Response. The summary of groundwater flow directions
presented in the Risk Assessment is for general information
purposes and does not supersede the detailed information on
piezometric surface configuration presented the RI.
Adrian Brown Consultants, Inc., soil Action Levels Comments,
Page 14 and 15.
30.
The approach used in the RI/FS, using MCLs and a
dilution/attenuation factor (DAF) appears to be based on a
misunderstanding of both the DAF and the physical chemistry
of the sorption and leaching.
ACS1/BSPM/062691
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EPA ResDonse. Some confusion apparently exists over how the
soil action levels were established. The goal ot setting
soil remediation levels is to have the leachate derived from
the soils at low enough concentrations such that, after
dilution in the aquifer, the resultant groundwater
concentrations are at or below groundwater remediation
levels. Soil remediation levels were back calculated from
groundwater remediation levels. Groundwater remediation
levels were multiplied by a dilution factor of 100. This
value represents the acceptable leachate concentration for a
particular compound. Soil remediation levels were derived
by multiplying the acceptable leachate concentrations by the
partitioning coefficient for soil contaminants at the ese
facility. Partitioning coefficients were based on site
specific studies conducted during the OU2 RI. These values
are considered acceptable for establishing soil remediation
levels for OUI. The model assumed that the soil column was
uniformly contaminated
Partitioning coefficients derived from column or batch
studies conducted on the ese facility would provide more
accurate partitioning coefficient values. Since many
conservative assumptions were used in the derivation of ese
OUI soil remediation levels, EPA considers the soil
remediation levels presented in this ROD as protective to
human health and the environment and does not find it
necessary to require the performance of these additional
studies. EPA, however, does not want to impede IDeA from
conducting these tests. If additional batch or column test
are conducted, EPA will revise the soil remediation levels
based on data acquired during these studies.
31.
Adrian Brown Consultants, Inc., Risk Assessment General
Comment, Page 1'.
A concern was raised regarding inadequacy of the RI sampling
due to discharges of chemical wastes onto the ground north
of the ese property.
EPA Response. CSC conducted an initial soil gas survey to
evaluate the extent of voe contamination and designed its
soil boring and well installation program around the survey
results and review of areal photographs. In addition, ese
sampled the marsh located north of the ese property. It is
likely that VOC contamination discharged north of the
property would have been detected in the soil gas survey,
marsh sampling or the groundwater sampling results if the
discharge was significant.
32. Adrian Brown Consultants, Inc., Effectiveness of Soil Vapor
Extraction Systea Comment, Page 22.
The comment maintains that the pilot SVE test did not
address the ability of system to decrease voe
ACS1/BSPM/062691
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concentrations, but simply tested the air-flow hydraulics of
the system.
EPA ResDonse. The EPA directs the reviewer to the text
again, to read the section on the calculated mass removal
that approached several pounds per hour during the test.
is very clear, at least to the EPA, that such mass removal
indicates that VOC concentrations in the vadose zone soils
have been reduced accordingly. Given the large number of
field and laboratory factors that can affect soil VOC
concentrations, in addition to the costs to collect and
analyze such samples, it is not considered appropriate to
have measured soil mass loss during the pilot test in the
manner suggested.
It
33. Adrian Brown Consultants, Inc., Data Quality Comments, Pages
23 and 24.
It is requested that DQOs for the field Gas Chromatograph
data collection portion of the investigation be included,
and that the QA/QC section be revised per previous EPA
comments.
EPA ResDonse. The data quality objective for Gas
Chromatograph data are to qualitatively (1) determine the
vertical areal extent of 60il contamination within CSC QUl
and (2) determine the nature of contaminants (i.e. type of
compound) .
Adrian Brown Consultants, Inc., Data comparability Comment,
Page 24.
34.
The reviewer notes that the headspace results were
significantly higher than the GC/MS results.
EPA ResDonse. The EPA notes the comment, and questions if
the higher headspace results may indicate that fewer VOC
losses occur with the headspace method compared to the GC/MS
method, leading to the conclusion that the headspace results
may yield a more accurate depiction of actual site VOC
conditions.
35.
Adrian Brown Consultants, Inc., Quality of Pield GC Analyses
Comment, Page 25-26. .;.
A concern is raised over the high variance associated with
the calibration standards and with the check standards.
EPA ResDonse. The comments are noted. The variance
associated with the procedure may be acceptable for the DQO
level associated with the field Gas Chromatograph analyses.
The EPA does not agree with the assertions made regarding
the check standards. Except for standards results on two
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days, the RPDs are within 20 percent, which is adequate f9r
the purposes of the field method.
Adrian Brown Consultants, Inc., aeadspace Data comparability
Comment, paqe 27-28.
36.
While there is a stronq correlation between the laboratory
GC/MS and the field headspace analyses for all compounds but
Ta.
EPA ReSDonse. The EPA notes IDa's concurrence on page 27
that there is apparently a moderately strong relationship
between the field headspace results and the laboratory GC/MS
results for PCE and TCE. . The relationship for Ta is not as
strong, but EPA feels that it is sufficient for the
screening application for which it was used.
37. Adrian Brown Consultants, Inc., Pield GC Calibration
Comment, paqe 28, paraqraph 1.
The basis for the statement regarding great variation in
RSDs due to column degradation is requested.
EPA ReSDonse. The variation of RSDs related to a comparison
of RSDs between compounds. It is known through laboratory
studies conducted at Stanford and elsewhere that the
different VOC's have different degradation rates.
Degradation is expected to occur through a variety of
factors in the laboratory, thus it is not surprising that
different amounts of degradation would occur to the
different compounds.
38. Adrian Brown Consultants, Inc., Pield GC Calibration
Comment, paqe 28, paraqraph 2.
A question arose regarding the classification scheme for the
RPD results.
EPA Response. As the text clearly indicates, the good, fair
and poor classifications are "for the purposes of this
discussion" and are clearly defined in the text.
39. Adrian Brown Consultants, Inc. Pie14 GC Calibration Comment,
paqe 29.
The number of samples used to calculate the RPDs is
requested for inclusion.
EPA Response. Approximately 5 samples were used to calculate
RPDs.
ACS1/BSPM/062691
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40. Adrian Brown consultant., Inc., US. of .i.ld QC a.adspac.
Data Comment, paq. 2'.
Concern was raised that the Field Gas Chromatograph
headspace results are not a valid method to determine soil
contamination.
EPA Response. Since Gas Chromatograph Headspace sampling
was more comprehensive and did not allow for loss of
volatiles during sampling, the CSC OUl FS used field Gas
Chromatograph Headspace data to qualitatively assess
vertical and areal extent of soil VOC contamination. The
use of DQO Level II data in determining the extent of
contamination is consistent with EPA guidance, Data Quality
Objectives for Remedial Response Activities, 1987.
Confirmation of the attainment of soil remediation levels,
however, will based on laboratory analytical results (DQO
Level IV).
41. Adrian Brown Consultants, Inc., Use of Field GC Beadspace
Data Comment, paqe 30 through 32.
A lengthy presentation of concerns was made again regarding
the method used to determine soil action levels, including
the conversion of soil headspace to soil solid matrix
concentrations.
EPA ResDonse. The FS converted soil headspace levels to
laboratory analytical levels in order to approximate the
areas requiring remediation of contaminated soils. As
stated previously, DQO Level II data is of sufficient
quality to qualitatively identify the extent of soil
contamination. Laboratory analytical data will be required
to confirm the attainment of soil remediation levels
presented in this ROD upon completion of remedial action.
The EPA also notes IDCA's concurrence on page 32 that the
field Gas Chromatograph can appropriately be used in
outlining the area of soils requiring remediation.
42.
Department of the Army, specific Comment, Page 1-4.
Based on exposure point concentrations, the future resident
scenario did not include residents on site, but did include
residents adjacent to the site. It would be useful to
include a discussion of the rationale for these scenarios.
Only 1990 data were used, arbitrarily limiting the data base
upon which remedial determinations were made. It would be
useful to discuss the rationale for this approach.
EPA ResDonse. This comment is incorrect. The future
residential scenario is based on current on-site analytical
data. Exposure to groundwater is based on concentrations
presented in Table 5-2 and exposure to soil is based on
ACS1/BSPM/062691
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43.
concentrations presented in Table 5-5. These concentrations
represent current on-site contamination.
As discussed on page 4-1 of the Chemical Sales Company OU1
Risk Assessment (CDM 1990a), the most current sampling data
were used in the risk assessment in order to obtain exposure
estimates that reflect current contamination at the site.
The use of the most current sampling data is also consistent
with risk assessment procedures followed for the Chemical
Sales Company OU2 site (CDM 1990b) as well as current EPA
guidance (U.S. EPA 1989). The use of previously collected
sample data for purposes of risk assessment would not give
exposure estimates that reflect current conditions at the
site. Since much of the previously collected data had not
been validated, it was determined that this data was not of
sufficient quality to be used in the OU1 Risk Assessment.
EPA Data Quality Objective Guidance recommends that data.
used in risk assessment be validated.
Department of the Army, Risk Assessment, specific
page 4-7.
Comment,
It appears that soil gas concentrations were obtained from
the headspace of monitoring wells (see Table 4-4). The RI
indicates soil probes were used. If monitoring well
headspace was used, the concentrations obtained are not
equivalent to soil gas that could enter basements and do not
appear to be appropriate in assessing inhalation of
volatiles in the basement pathway. It would be useful to
clarify this section.
EPA ReSDonse. There appears to be some misinterpretation of
what type of soil headspace was used for the basement
scenario. Headspace data used to evaluate exposure to soil
gas in a basement was that obtained from soil borings, not
headspace of monitoring wells as stated in the comment
above. At the time of the risk assessment was written
(June-July 1990), validated data from the vapor extraction
analysis was not available. Therefore, the soil headspace
data were considered adequate for evaluation of the basement
inhalation pathway. A recent comparison of the soil
headspace data to the vapor extraction data indicates that
the soil headspace values compare favorably to the vapor
extraction values (i.e., within an order of magnitude).
44.
Department of the Army, specific Comment, Page 5-1.
No environmental assessment was included in 40 CFR section
300.430(e) (2) (i) (G). This document provides guidance for
conducting environmental evaluations to assess threats to
the environment, especially sensitive habitats and critical
habitats to species protected under the Endangered Species
Act.
ACS1/BSPM/062691
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46.
45.
EPA ResDonse. There are no known endangered species in the
Chemical Sales Company OU1 area. The area is zoned as
highly industrial and is currently occupied by several
industries and storage facilities making it uninhabitable by
most wildlife. Sand Creek is potentially capable of
supporting aquatic wildlife, however, and considered a
wildlife corridor. An environmental assessment of this
corridor is provided in the Chemical Sales Company OU2 Risk
Assessment (CDM 1990b).
Department of the Army, Specific Comm.nt, Page 5-8.
The method of calculating basement exposures seems
incompletely presented, making any verification of the
calculation difficult if not impossible.
EPA Response. Using the assumpti9ns described in the text
and a soil permeability of 3 x 10. em/see, Garbesi and Sextro
(1989) used a two dimensional, steady-state finite element
flow model to simulate the flow of soil gas into a basement.
T~eir results indicated an entry rate of soil gas of 2.5
m/hr. Coupling this entry rate with the mean VOC
concentrations in Table 5-4 provided the fluxes for use in
the mass balance model. The mass balance model was used to
estimate the VOC concentration which would result in the
basement under the assumptions described in the text. The
mass balance equation used was:
CA = VOC Concentration in basement air (mg/m3)
F = VOX flux into basement (mg/hr)
T = Time for basement air3exchange (hr)
V = Volume of basement (m)
The value of CA was then used in the intake equation shown
in the text.
Due to the large amount of uncertainty associated with
quantitative risk estimates from the basement pathway using
this model, risk via the basement pathway are presented
qualitatively in the CSC ROD. Protectiveness of the remedy,
including consideration of updated models, will be examined
through the 5-year reviews.
Department of the Army, Specific Comment, Table 7-1.
It would be valuable to include explanations for why the
future children scenario contains only three pathways.
It appears that the future residents scenario should contain
inhalation of ambient air as an exposure pathway.
While chloroform and cis-l,3-dichloropropene contribute to
the calculated cancer risk, they were deleted from the FS as
chemicals of concern and do not have any remedial action
ACS1/BSPM/062691
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levels assigned to them. An explanation of the rationale
for this decision should be included.
Inappropriate slope factors may have been used since very
high cancer risks were observed. It would be useful to
clarify this relative to EPA's Integrated Risk Information
System instructions.
EPA ResDonse. Due to the significant differences between
children and adults for the soil exposure pathways, future
children were evaluated separately for the soil pathways
only. For purposes of this risk assessment, it is difficult
to assess the location of a future residential receptor.
The risk assessment was based on Phase I and II data.
Original evaluation of these data indicated that chloroform
and cis-1,3-dichloropropene should be considered as COCs
based on frequency of detection and toxicity. However, upon
receipt of Phase III data, it was determined that, based on
frequency of detection, these chemicals may be omitted as
COCs.
Chloroform and cis-1,3-dichloropropene were omitted from the
FS based on low frequencies of detection and low
concentrations at which they were detected. Chloroform was
detected in three out of 36 samples (8%) at concentrations
of 2J (estimated), 720D (diluted) and 37 ~q/L. Two of these
values are associated with some uncertainty as indicated by
their qualifiers. Cis-1,3-Dichloropropene was detected in
only one of 36 (3%) samples at a concentration of 330(D)
~g/L. Superfund guidance states that if a chemical is
detected in 5% of samples obtained or more, it should be
retained as a chemical of concern. For this reason
chloroform was retained as a COC in the risk assessment.
However, upon consideration of the uncertainty associated
with the concentrations detected, it was omitted as a COC in
the FS. Cis-1,3-Dichloropropene was only detected in 1% of
the samples, and accordingly was dropped in the risk
assessment.
Because dermal slope factors are not available for
chemicals, dermal slope factors were extrapolated from oral
slope factors according to EPA guidance. These slope
factors are most likely conservative estimates. Oral and.
inhalation slope factors were obtained from the HEAST
(Second Quarter, 1990) tables and are correct.
47.
Department of the Army, Specific Comment, Page 7-4.
All non-carcinogens were grouped together for computation of
the hazard index. While RAGS indicates that this may be
done for a screening analysis, it appears more aEpr?priate
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to group hazard indices by mechanism and target organ
system.
EPA Response. In general, the target organs for the COCs
are the liver and kidney. All of the COCs are considered to
have similar adverse health effects and mechanisms of
action. Therefore, it is appropriate to add hazard indices
as recommended by EPA guidance (1989).
48. Adrian Brown consultants, Inc., General Comment, Page 16,
paragraph 2.
During recent months, CSC operations have resulted in at
least four hazardous chemical releases extending beyond CSC
property: February 2, 1990, August 3, 1990, August 7, 1990,
and September 11, 1990, and February 16, 1991. In the
February incident, the Denver Fire Department responded,
evacuated a number of workers from nearby businesses and
administered first aid to several of these workers. During
the September incident, the Denver Fire Department forced
the tenants of the IDeA building to evacuate. The risk
assessment should address the potential health consequences
of continuing releases from CSC. Since the risk assessment
can only address information presented in the RIfFS, these
releases need to be discussed in the RIfFS.
EPA Response. A qualitative statement discussing these
releases may have been warranted. However, it is not the
intent of the RA to speculate on future releases. The
quantitative evaluation of contamination and resultant
exposures can only be based on validated data obtained from
the RI report. In addition, the purpose of the RA is to
estimate risks associated with chronic exposure to
contaminants present at the site, not acute exposure.
49. Adrian Brown Consultants, Inc., Hydrogeology Comment, Page
17.
The risk assessment contains a statement that groundwater
flows in a northerly direction (paragraph 3, page 3-1). It
would be more accurate to state that the groundwater flow is
generally to the north but also flows to the west and
northwest in the southern portion of OU1 (see Figures 5 and
6, enclosed). ~
EPA Response. EPA does not agree with this interpretation.
Groundwater near the CSC property flows in a general north
to northwest direction. This is based on water table
elevations and migration of groundwater contamination.
50. Adrian Brown Consultants, Inc., Data Evaluation Comment,
Page 17, paragraph 1.
This section should include a discussion of th~.indoor air
monitoring data from the IDCA building.
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EPA ResDonse. Indoor air monitoring data collected at the
IDeA property were never considered in the scope of the RI
or RA. The RA is based on data presented in the RI only per
EPA guidance (U.S. EPA 1989). These data are, however,
discussed on page 7-9.
Adrian Brown Consultant., Inc., Data avaluation Comment,
Page 17, paragraph 2.
51.
Will data from the Phase II of the RI be included in the
final risk assessment?
EPA ReSDonse. The baseline risks calculated for pathways
associated with the groundwater, surficial soils and soil
gas media did not include data collected during the Phase
III sampling effort. Results of sampling for these media
during Phase III were comparable to results from data
collected during Phase II. Risks associated the air media
were re-evaluated based on air monitoring conducted
subsequent to the release of the QUI RA.
52. Adrian Brown Consultants, Inc., Data Validation Comment,
Page 17, paragraph 3.
The Risk Assessment mentions, but does not include, the
results of the field validation procedure used to evaluate
the reliability of the field gas chromatography paragraph 1,
page 4-2).
EPA Response. Field validation results were not available
at the time the risk assessment was written.
53.
Adrian Brown Consultants, Inc., Summary of Sampling Data
Comment, Page 17.
A section should be included on the indoor air monitoring
data from the IDeA building.
EPA ReSDonse. Indoor monitoring data collected at the IDeA
building were not incorporated into the RI or the RA as
those data were not considered in the scope of the RI
process. They are, however, discussed on page 7-9 and have
been included in EPA's Administrative Record for CSC QUI.
54.
-
Adrian Brown Consultants, Inc., Identification of Exposure
pathways Comment, Page 17, para 1.
The Risk Assessment should address the potential health
consequences of continuing releases from CSC.
EPA Response. As stated previously, it is not the goal or
purpose of a risk assessment to speculate on future releases
of contamination at a site.
ACS1/BSPM/062691
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55. Adrian Brown Con8ultant., Inc., Identification of Bxpo8ure
Pathway. Comment, paqe 17, paraqraph 2.
Use of the highest measure concentration of PCE in surface
soils (80,000 ~g/kg at SSB-10) dramatically overstates the
risks for OU1. The concentration of PCE at SSB-10 certainly
is not typical. The next highest PCE concentration is 1,900
~g/kg or 42 times less than the SSB-10 value. The
arithmetic average of the concentration of PCE in the
surface soils, excluding the one high value and the one NO,
is 373 ~g/kg or 214 times less than the SSB-10 value. Thus,
to use the concentration of PCE at this one "hot spot" for
the OUl risk estimate seems to exceed the "reasonable
maximum exposure" expected to occur at OU1.
EPA ResDonse. The use of the maximum detected concentration
is in accordance with Superfund Guidance (U.S. EPA 1989)
which states that when the upper 95th percentile of the mean
exceeds the maximum detected concentration, the maximum
detected concentration should be used instead.
56. Adrian Brown Consultants, Inc., Quantitative Evaluation of
Pathways Comment, paqe 17.
There does not appear to be a section specifying the
assumptions used in calculating the risks from inhalation of
indoor air at the IDCA building.
EPA ResDonse. Table 5-10 (COM 1990a) presents exposure
assumptions used to calculate inhalation of indoor air in a
basement.
57. Adrian Brown Consultants, Inc., Inhalation of Volatiles in a
Basement Comment, paqe 18, paragraph 1.
Because the soil gas data used to calculate basement
concentrations are from an unknown mass of soil in a VOA
vial with an unknown headspace volume, it is not known how
these data relate to the quantities of volatiles that could
infiltrate into a basement (paragraph 2, page 5-8).
EPA ResDonse. It is acknowledged that the soil gas data is
only of screening level quality. However, it is reasonable
to use these data as estimates of soil gas concentrations
for the purposes of this RA. Due to many factors including
data quality, the risks via the basement pathway are
evaluated qualitatively in the CSC OUl ROD.
58. Adrian Brown Consultants, Inc., Inhalation of Volatiles in a
Basement Comment, paqe 18, paraqraph 2.
The assumed ventilation rate of one air exchange every 6
hours seems unusually low. Our experience is that an air
exchange occurs every 1-2 hours (paragraph 2, p~g~ 5-8).
ACS1/BSPM/062691
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EPA Response.
exchange.
59. Adrian Brown Consultants, Inc., Direct Contact with Surface
Soil comment, Page 18, paragraph 1.
This value was selected as a conservative air
The assumption that indoor dust with windblown contaminants
contains the same concentration of volatiles as soil
overstates the risks from this pathway since most volatiles
in soil will certainly be volatilized if windblown
(paragraph 1, page 5-11).
EPA Response. The assumption that indoor dust is the same
concentration as soil is, most likely, conservative,
however, EPA guidance recommends that one should assume 80%
(U.S. EPA 1991) of indoor dust is contaminated by windblown
soil. Therefore, the use of 100% as an assumption would not
result in a significant overestimate of exposure relative to
EPA recommendations.
60. Adrian Brown Consultants, Inc., Direct Contact with Surface
Soil Comment, Page 18, paragraph 2.
The assumption that every time children play outside their
legs become covered with soil overstates the risks from this
pathway (paragraph 1, page 5-11). Use of the skin adherence
factor for kaolin clay (the highest such factor recommended
by RAGS) overstates the risks from this pathway since the
geologic data show that the surface soils in QU1 are
predominantly sandy, with a lower skin adherence factor
(paragraph 1, page 5-11).
EPA Response. The assumption that a child's legs may be
covered with soil is conservative. However, it is not
unlikely that dermal exposure to soils on a child's legs or
potentially more of their skin surface area may occur as a
result of playing outdoors.
Site-specific soil data were not available, therefore, a
conservative adherence factor was used. The soil adherence
factors provided by EPA in the Risk Ass,ssment Guidance for
Superfund (U.S~ EPA 1989) are 1.4 mg/cm for potting soil
and 2.77 mg/cm for kaolin clay. The difference in these
two values is unlikely to have a significant effect on~.the
exposure estimations. Page 5-16 recognizes the
conservativeness of this assumption.
61.
Adrian Brown Consultants, Inc., Direct contact with Surface
Soil Comment, Page 18, paragraph 3.
The Risk Assessment uses a skin absorption factor of 1.
This again overstates the risks from this pathway as a
significant portion of the volatiles in contact with the
skin will volatilize rather than be absorbed through the
skin (Table 5-12).
ACS1/BSPM/062691
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EPA ResDonse. The use of 1 as a dermal absorption factor is
a conservative assumption. However, due to lack of chemical
specific data, this value was used in order to avoid
underestimation of exposures.
62. Adrian Brown Consultants, Inc., neraal Contact with Surfac.
soil Comment, paq. 18.
The risks from dermal contact (and incidental ingestion) of
surface soils in OU1 are dramatically overstated. Use of
the one "extraordinarily high" PCE soil value to
characterize all of OU1 results in unrealistically high risk
estimates.
EPA ResDonse. The risks from these pathways may be
overestimated for some areas of the site. However, based on
the limited soil data set, it cannot be concluded that other
hot spots on the site do not exist. As previously stated,
the use of the highest concentration is recommended by EPA
(1989) in cases where the upper 95th percentile exceed the
maximum detected value. This was the case for the soils
data, therefore, the highest value for PCE was used to
evaluate exposures to soils.
63.
Adrian Brown Consultants, Inc., Inteqration of Bxposure
Pathways Comment, paqe 18, paraqraph 1.
IDeA is very concerned that the summary statements on risk
may be taken out of context. We do not disagree with the
technical findings. However, we feel that additional
explanation is essential to clarify that the risks (in the
southern portion of OU1) relating to groundwater use and
inhalation of volatiles in basements are Dotential risks to
which current populations are believed not to be exposed.
EPA ResDonse.
This is discussed in Section 7.6.
64.
Adrian Brown Consultants, Inc., Inteqration of Bxposure
Pathways Comment, paqe 18, paraqraph 1.
IDCA strongly recommends that every time risk estimates are
given for such Dotential risks that a footnote or text be
included explaining that these risks could result if
groundwater would be used or if basements would be
constructed; and that current populations are not subject to
such exposures because groundwater is not in use and there
are no basements. It is also important to note in each
instance where indoor inhalation of volatiles is mentioned,
that indoor monitoring (at the IDCA building) has found
insignificant levels of chemicals to be present. Following
are locations in the Risk Assessment where such
clarification is needed:
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7.4.lparagraphs 1 and 2, page 7-6
7.4.2paragraph 3, page 7-6
7.4.3paragraph 5, page 7-6
7.7
paragraphs 3 and 4, page 7-10
paragraph 5, page 8-3; paragraphs 2, 4 and 5, page 8-4
8.5
EPA ResDonse. EPA agrees that these pathways represent
Dotential risks. This analysis is discussed in Sections 5.5
and 7.6 and in the CSC OU1 ROD.
'5. Adrian Brown consultants, Inc., Uncertainti.. in Risk
Characterization Comment, Page 19.
As discussed in the Data Quality section of these comments,
IDCA has substantial concerns with the quality of some of
the data used in the Risk Assessment. The Risk Assessment
notes that the field soil gas (and we would add field head
space) data do not meet Data Quality Objective Level IV
(paragraph 4, page 4-1). It is recommended that all risk
estimates using these data should be so noted (paragraph 4,
page 5-4; and Table 5-4).
This discussion should be expanded to summarize the nature
and extent of uncertainty associated with the models used to
estimate exposure, such as the basement inhalation and
dermal absorption models, and the extent of environmental
sampling, particularly regarding the concentration of PCE in
surface soils.
EPA ResDonse. Uncertainties associated with risk
calculations conducted are discussed on page 7-8 of the CSC
OU1 RA and in Appendix A in the CSC OU1 ROD.
". Adrian Brown Consultants, Inc., Discussion of Risk
Characterization Comment, Page 1', paragraph 1.
The Risk Assessment should mention that the very low
concentrations of VOCs measured in the indoor air at the
IDCA building could come from common building materials and
nearby sources, including CSC (paragraph 2, page 7-9).
EPA ResDonse. Page 7-9 discusses the results of indoor air
sampling. There is not enough data to speculate on the
source of these chemicals.
ACS1/BSPM/062691
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',-
67. Adrian Brown Consultants, Inc., Discussion of Risk
Characterisation Co..ent, Page 1', paragraph 2.
The detection limit for the indoor air analyses in the IDCA
building was from sub ppb to low ppb range (paragraph 3,
page 7-9).
EPA Response. The RA states "detection limit was low ppb
range for all COCs".
68. Adrian Brown Consultants, Inc., Summary of Potential Health
Risks Comment, Page 20, paragraph 1.
It is important that the presentations of the summary
information distinguish between actual exposures and
potential exposures (if groundwater is used and if basements
were to be constructed) for current and potential future
land uses.
EPA Response. The distinction between potential and actual
exposures is made frequently throughout the risk assessment
document (page 7-7).
6'. Adrian Brown Consultants, Inc., Summary of Potential Health
Risks Comment, Page 20, paragraph 2.
The Risk Assessment should note that the cancer risks to
"current" workers are based upon exposure to groundwater,
and that this exposure currently does not occur (paragraph
3, page 7-10).
EPA Response. This distinction is mentioned throughout the
RA document (page 7-7).
70. Adrian Brown Consultants, Inc., summary of Potential Health
Risks Comment, Page 20, paragraph 3.
The Risk Assessment should note that the cancer risks to
"current" workers from the inhalation of volatiles present
in basements are potential risks since no employees
currently work in basements in OU1. It also should be noted
that indoor monitoring (at the IDCA building) has found
insignificant levels of chemicals to be present (paragraph
4, page 7-10).
EPA Response. Page 7-9 states the low concentrations of
chemicals detected inside IDCA building. Page 7-7 states
that basements are not currently used at OUl and that the
basement pathway is incomplete.
71. Adrian Brown Consultants, Inc., Summary of Potential Health
Risks Comment, Page 20, paragraph 4.
It should be noted that the majority of the noncancer risks
to "current" workers are from the use of groundwater and
ACS1/BSPM/062691
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working in basements, neither of which condition currently
exists in OUI.
>
EPA ReSDonse.
statements are made on page 7-7.
72.
Adrian Brown consultants, Inc., sumaary of Potential Health
Risks Comment, Page 20, paragraph 5.
The Risk Assessment contains a statement that the indoor air
at the IDeA building does not appear to be associated with
non-carcinogenic adverse health effects (paragraph 3, page
7-11). The discussion on carcinogenic risks should contain
a statement that indoor air at the IDCA building represents
low risks (page 7-10).
73.
EPA ResDonse. This is not the case. Cancer risks foros
workers inhaling VOCs inside of Trammell Crow are 7x10 .
Adrian Brown Consultants, Inc., (Summary) Potential
Chemicals of Concern Comment, Page 20.
This section should include a discussion of the indoor air
monitoring in the IDCA building.
EPA ResDonse. Only data presented in the RI were used for
evaluation of COCs. These data are discussed in page 7-9.
74.
Adrian Brown Consultants, Inc., (Summary) Risk
Characterization Comment, Page 20, paragraph 1.
The discussion of CUrrent Land Use - Cancer risks should
more clearly state that the high risks are based upon
potential exposures that do not now occur (paragraph 5, page
8-3).
EPA ResDonse. EPA identified that the highest risk at the
CSC OUI are from Dotential pathways on page 7-7.
75. Adrian Brown Consultants, Inc., (Summary) Risk
Characterization comment, Page 20, paragraph 2.
The discussion of Current Land use - Noncancer Health Risks
should clearly state that the high risks are based upon
potential exposures that do not now occur (paragraph 2, page
8-4).
EPA ResDonse. This request is discussed on page 5-1 and
page 7-7 of the OUI RA.
76. Adrian Brown Consultants, Inc., (summary) Risk
Characterization Comment, Page 20, paragraph 3.
The discussion of Future Land Use - Cancer Risks and
Noncancer Health Risks should clearly state that the high
risks to residents are based upon an assumption-that OUI
ACS1/BSPM/062691
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78.
79.
would be residential, although it is expected to remain
nearly exclusively industrial (paragraphs 4 and 5, page 8-
4) .
EPA Response. It is likely that the Chemical Sales Company
OU1 site will remain mostly industrial for the area south of
East 48th Avenue.
77.
Departaent of the Aray, General Comment 1
Department of the Aray, specific Comment, Remedial
Investigation, Piqures 1.1 and 1.2
The area investigated by the RI is less than the total area
of Operable Unit 1. It is unclear why only a portion of the
operable unit was investigated.
EPA ResDonse. The areal extent of groundwater contamination
was delineated by the 1986-1987 sampling results as shown on
sheet 4-5 of the OU2 RIfFS. The western boundary of OU1 has
been moved to the east to Forest Street in this ROD to
reflect this data. Subsequent sampling at the OU1 site
focused on depiction of the source area and heaviest zone of
contamination of groundwater.
Department of the Army, General Comment 2.
The depth at which surficial soils were collected may not be
representative of surficial soil contamination, particularly
in regards to dermal contact with contaminated soils.
Instead of the 0 - 6 inches or 0 - 12 inches depths that
were sampled, a more representative sampling interval would
be the 0 - 2 inches interval.
EPA ResDonse. EPA does not agree that a sampling depth of 2
inches is appropriate at this site. Since the contaminants
of concern are volatile compounds, the contaminants will
volatilize and not be found in the top two inches.
Consequently, the greatest concentrations of contaminants in
the surficial soils will occur at depths greater than two
inches. As an industrial site, the greatest risk of
exposure to contaminated soils will occur during any type of
excavation or intrusive activities, which generally exceed 2
inches in depth, that disturb the upper soils. Therefore
the EPA has determined that it would be more protective of
human health if the surficial soils were considered to .
include soils to depths greater than 2 inches at this site.
Department of the
Department of the
Department of the
Comment Page 8-3.
Army, General Comment 3
Army, General Comment 10
Army, Remedial Investigation, Specific
The vertical extent of contamination has not been fully
characterized, particularly in regard to the p~~s~nce of
Dense Non-Aqueous Phase Liquids (DNAPL) at the site. Due to
ACS1/BSPM/062691
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the concentrations found dissolved in the groundwater, it is
possible that DNAPL could be present at the site.
Therefore, assuming that DNAPLs do exist at the site, a
standard 'pump-and-treat' system will not effectively remove
the DNAPLs. Remediation could take longer than the time
calculated.
~
EPA ResDonse. EPA recognizes that there are some data gaps
remaining, particularly in regards to the existence of
DNAPLs at the site. DNAPLs are quite elusive and difficult
to identify at any given site. Due to EPA's preference for
remedial activities to begin as soon as it is practical to
do so, EPA has determined that sufficient information is
presently available to begin remediation of the groundwater.
The number of wells that will be installed during the
remediation will greatly increase EPA's ability to determine
if DNAPLs are present. A careful review of the RI/FS shows
that two alternatives are carried into the detailed analysis
phase. These two alternatives differ primarily in their
assumptions regarding the presence or absence of DNAPLs.
Alternative 3 assumes that there is little of no DNAPL
present, and Alternative 5 assumes that there are pockets of
DNAPLs in the saturated zone which will require remediation.
The differences in the remediation time are also included in
these two different alternatives. If, during the design or
implementation phases of the remedial alternative, it is
determined that DNAPLs are found to be present, then EPA
will modify the remedial design as necessary to address the
DNAPLs.
80.
Department of the Army, General Comment 4
In-situ hydraulic conductivities (K) have not been
determined at the site. Only contaminant migration rates
and literature values have been used to estimate K values.
It is difficult to determine the actual hydraulic
characteristics of the aquifer from these data. The
influence of Denver Fm./alluvial aquifer interactions,
ground-/surface-water interactions, and anisotropy cannot be
evaluated.
EPA ResDonse. Hydraulic conductivity values were needed
primarily for the purposes of evaluating relative costs of
the various remedial alternatives which involved pump and
treat systems. Since similar well field configurations were
used in sets of alternatives and each used the same K
values, the values used were deemed accurate enough for the
level of cost comparisons required for the alternative
evaluation. Furthermore, the K estimates derived from
evaluation of a methylene chloride spill corroborates with
the K values selected for use in the conceptual well field
designs presented in the FS portion of the report. Finally,
the document acknowledges the need to obtain more accurate
values of K obtained from on-site aquifer pumpiD.g ~ests
prior to actually implementing the selected alternative.
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81.
Departaent of the Aray, General Co...nt ,
The rationale for why only three polychlorinated biphenyl
(PCB) analyses were conducted at the site should be
presented.
EPA ResDonse. PCBs were never suspected as being a
contaminant of concern at CSC OUI based on the nature of the
operations at the site and Chemical Sales Company's records
of the types chemicals used. Therefore, it was not
considered necessary to look for PCBs at this site.
However, in an effort to be as thorough as possible in
determining the potential threats to human health and the
environment, EPA's toxicologists recommended that samples
for PCBs be collected in areas where PCBs would most likely
be found, such as near transformers. An initial screening
of three samples were collected to evaluate this potential
threat. The results of this sampling indicated that PCBs,
as suspected, were not a contaminant at CSC OUI and any
further sampling for PCBs was not warranted.
82.
Department of the Army, General Comment 7
There are a limited number of background samples collected
upon which to base the background criteria for metals in the
soils at the site.
EPA ResDonse. Metals were not determined to be COCs for CSC
OUI. Concentrations of metals in soils were analyzed for
all soil samples submitted to the laboratory during Phase
II. This included soil samples taken from MW 18 which is
upgradient from the site. No tested metal exceeded the
maximum concentration recorded for that metal in soil in the
western U.S., and most were at t~e low end of the reported
range. Based on a survey of CSC waste handling and storage
procedures during the RI/FS scoping, heavy metal soil
contamination was not identified as a concern. Thus, one
location upgradient of the facility and comparison to
Western U.S. data was deemed appropriate for the
determination of background concentration for metals.
For all identified COCs at the CSC OUI site, any detection
of soil contaminants were considered to exceed background.
83.
Department of the Army, General Comment 8
Department of the Army, Specific Comment, Remedial
Investigation, Section 7.2.4
The National Contingency Plan (NCP) states that the 10.6 risk
level shall be used as the point of departure if ARARs are
not available or they are not sUfficiently protective due to
the presence of multiple contaminants. The FS ~$e~ MCLs or
proposed MCLs which does appear to be consistent with the
ACS1/BSPM/062691
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'>-
NCP. A clarification of the use of MCta for a site with
multiple contaminants and pathways would be helpful.
EPA Response, EPA's policy on the use of MCLs in
establishinq qroundwater remediation levels (General Policy
RCRA, CWA, SDWA Superfund Fact Sheet, 1, OERR 9234-2-01FS)
states that qenerally, MCLs should be used to set
remediation levels when available, provided the MCLs are
cumulatively within the risk ranqe. CUmulative risks from
the ingestion and inhalation of contaminants associated with
contaminated groundwater for CSC OU1 COCs is calculated to
be 1 X 10(-4) which is within the protective risk ranqe.
Thus, MCLs have been used at the CSC OU1 site to establish
groundwater remediation levels.
84. Department of the Army, General Comment 8
Department of the Army, Feasibility study, Specific Comment,
Table 7-1
Department of the Army, Feasibility study, Specific Comment,
Page 7-'
Department of the Army, Risk Assessment, Specific Comment,
Table 7-1
Chloroform and cis-1,2,-dichloropropene, which are
carcinogens, have been deleted from the remedial action
objectives. Please explain the rationale for not includinq
these chemicals.
EPA Response. Chloroform and cis-1,3-dichloropropene were
deleted from the remedial action objectives because they
were deleted from the list of COCs for CSC OU1. Chloroform
and cis-1,3-dichloropropene were omitted from the FS based
on low frequencies of detection and low concentrations at
which they were detected. Chloroform was detected in three
out of 36 samples (8%) at concentrations of 2J (estimated
value), 720 D (sample was diluted for analysis), and 37 ppb.
Two of these values are associated with some uncertainty as
indicated by their qualifiers. Cis-1,3-dichloropropene was
detected in only one of 36 (3%) samples at a concentration
of 330D ppb. Superfund guidance states that if a chemical
is detected in 5% of samples obtained or more: it should be
retained as a chemical of concern. For this reason
chloroform was retained as a COC in the risk assessment.
However upon consideration of the uncertainty associated.
with the concentrations detected, it was omitted as a COC in
the FS. Cis-1,2-dichloropropene was detected in only 3% of
the samples.
85.
Departaent of the Army, General Comment 8
The estimated ~isk.for groundwater inges~lo~ was calcu~ated
to be 1.2 x 10 wh~ch exceeds the 1 x 10 r~sk stated ~n the
remedial action objectives.
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~
EPA ResDons~. The estimated risk associated with
groundwater concentration levels for CSC OU1 COCs at their
MCL is estimated to be 1 X 10(-4) based on the ingestion and
inhalation during showering pathways.
86.
Department of the Army, General Comment 8
Proportionally extending the risk reduction which was
calculated from groundwater ingestion to other groundwater
pathwa~s and soil gas leaves a risk of approximately
6 x 10 .
EPA ResDonse. Due to the uncertainty associated with the
basement model used in the CSc OUl RA, this pathway is
evaluated qualitatively in the CSC OUl ROD. EPA will
continue to review the protectiveness of the remedy,
including consideration of updated models, through the five
year review.
87.
Department of the Army, General Comment'
Emission controls for the air strippers have not been
included to remove volatile organic compounds from the
exhaust gasses for the source area.
EPA ResDonse. All remedial alternatives retained for
detailed analysis included the use catalytic oxidation to
destroy contaminants removed from contaminated soil and
groundwater in the source area (i.e. south of East 48th
Avenue) during air stripping and soil vapor extraction
operations.
88.
Department of the Army, Remedial Investigation, Specific
Comment, Page 3-23
Wells in the alluvial aquifer do
amplitude fluctuation than those
as evidenced by the much greater
versus FIT-WP4.
not show a greater
wells located farther south
amplitude in well LSS-MWl1
EFA ResDonse. It is correct to state that the amplitude in
well LSS-MW11 was greater than in FIT-WP4. However, when
all of the wells in the CSC OUl area are considered, ~here
is a trend to greater amplitude in the northernmost wells as
compared to the southern wells. The average water level
fluctuation north of E. 50th Avenue is 0.73 feet, while the
average fluctuation south of E. 50th Avenue is 0.41 feet.
The cause of the large fluctuation that occurred in LSS-MWll
is believed to be in response to the July 9, 1990
precipitation event. It is possible that LSS-MWll's
proximity to the disturbed ground at the underground tank
storage area may possibly have contributed to a higher
influx of surface water than normally occurs at-the rest of
the site.
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.,.
Oepartaent of the Aray, Rea.dial Inve.tiqation, Specific
Comment, Section 4.2.2
The detailed lithologic interpretations that are presented
do not seem to be supported by the resistivity sounding
profiles.
EPA ResDonse. The resistivity soundings should not be taken
to be the final determination of the lithology present.
Geophysical techniques are not known to be 100% precise.
They only give an indication of the lithology at any given
site.
90.
Department of the Army, Feasibility Study, Specific Comment,
Table 9-4
Voluntary controls are recommended for the drilling of new
wells. The state Engineer is currently limiting water use
from new wells in much of this area to domestic use only
because of over-appropriation. It may be prudent to
consider passing an ordinance restricting drilling of new
wells for domestic purposes. A similar ordinance was passed
in Aurora for wells near the Lowry Landfill.
EPA ResDonse. Due to the complexity of water rights law,
limiting access to groundwater for which water rights are
owned by an individual is very difficult to accomplish. The
vast majority of the water users in the area are connected
to the municipal water supply, which is treated at the Klein
Water Treatment Facility. There are only a very few
domestic well users located within in the CSC operable
units. These well users are to be hooked up to the
municipal water system under the ROD for CSC OU3.
Therefore, it is questionable how much benefit, if any,
would be gained from the massive effort required to pass an
ordinance regarding domestic well use.
'1.
Department of the Army, Groundwater Collection, Specific
Comment 2.
Department of the Army, Groundwater Collection, Specific
Comment 3.
Department of the Army, Groundwater Collection, Specific
Comment 4.
The analysis of the well field arrays does not demonstrate
that the contaminated groundwater is captured. Nor does it
demonstrate how the well field will maintain capture in the
event of one or more of the wells going "off-line". The
analysis would be more useful if it addressed these
capabilities were demonstrated. The analysis should also
include a sensitivity analysis in order to provide an
estimate of the number of wells, pumping rates, and capture
zones at the site~
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92.
EPA ResDonse. The information requested in this comment is
very valuable and is necessary to the design of an
extraction system. It is EPA's intent to provide this
information during the design phase of the remediation
proqram.
Department of the Ar8y, Remedial Investigation, Specific
Comment Page 9-34
It appears that all soil excavation and aboveground
treatment options were screened out based on volatilization
during excavation and handling. Aboveground treatment would
be technically implementable with proper emissions controls.
This alternative should be carried through the initial
screening of alternatives.
EPA ResDonse. EPA disagrees that above ground treatment
alternatives should be further considered given the current
structures and operations on site and the difficulties
associated with maintaining proper air emission controls
during excavation and handling. The potential risks
associated with possible air emissions made the use of above
ground treatment alternatives less desirable than in-situ
methods, under these circumstances.
93.
Department of the Army, Remedial Inveatiqation, Specific
Comment, Page 10-7
What is the estimated temperature rise in the soil matrix
from the injection of hot gases? Is there enough thermal
energy produced to enhance volatilization over 30 years?
EPA ResDonse. For the purposes of this FS, it was not
deemed necessary to calculate the exact temperature rise.
An estimated temperature rise of 10°F in 3-4 weeks is
anticipated based on past experience with thermal
enhancement in similar situations with similar contaminants.
94.
Department of the Army, Remedial Investigation, Specific
Comment, Groundwater Collection 1.
It would be useful to present the assumptions associated
with the analytical equation utilized to predict aquifer
response to pumping. The results should be discussed i.n
light of the assumptions in order to understand the
limitations of the analytical results.
EPA ResDonse. The assumptions associated with the aquifer
extraction alternatives are presented in Appendix H of the
RIfFS. The following assumptions were used in the
calculations:
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98.
99.
Saturated thickness (H) =
Hydraulic conductivity (K) =
Drawdown
Saturated thickness
during pumping (h..)
Well radius (r..)
3 !\
10 mlsec
2 m
..
=
3.6 ft
= . 33ft
95.
stat. of Colorado, Department of Law, Co..ent 1.
The effluent limitations set forth in 5 CCR 1002-3, sec.
10.1.0 are applicable to any potential discharge to
groundwater.
EPA Response.
EPA concurs with this comment.
96.
state of Colorado, Department of Law, Comment 2.
All State groundwater standards apply the groundwater at
this site, even though most of the standards are not a
problem at the site.
EPA Response.
EPA concurs with this comment.
97.
state of Colorado, Department of Law, Comment 3.
The Solid Waste Disposal Act is applicable to any management
of solid wastes and may be relevant and appropriate to the
management of all solid wastes. Also, sections 2.2.5,
2.2.6, 2.4.4, 2.4.5 and all other groundwater provisions in
the solid waste regulations are applicable at the site.
EPA Response.
EPA concurs with this comment.
state of Colorado, Department of Law, Comment 4.
The new source performance standards for volatile organic
liquids storage in 40 CFR Part 60, Subpart Kb are relevant
and appropriate.
EPA Response.
EPA concurs with this comment.
..;.~
state of Colorado, Department of Law, Comment 5.
Regulation 5 CCR 1002-2, 6.1.0 sets forth requirements
regarding land treatment and land disposal. This regulation
must be incorporated as applicable.
EPA Response.
EPA concurs with this comment.
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100.
stat. of Colorado, Department of La., Co...nt ,.
Colorado Hazardous Waste Regulation 5 CCR 1007-3, sections
260-270 is applicable to generation, treatment, storage, and
disposal of hazardous waste, and may be relevant and
appropriate to the management of solid wastes.
EPA Response.
EPA concurs with this comment.
101.
state of Colorado, Department of La., Comment 7.
The narrative standard in 5 CCR 1002-8, section 3.11.0 as
well as the numerical standards, are applicable to the
groundwater at the site.
EPA Response.
EPA concurs with this comment.
102.
state of Colorado, Department of La., Comment 8.
Colorado Air Pollution Control Regulation 7 should be
identified as applicable rather than relevant and
appropriate.
EPA Response.
EPA concurs with this comment.
103.
Colorado Department of Bealth (CDB), Air Pollution
Control Division (APeD) (Comment. 1-2, and 4-8)
CDH APCD stated that the risk assessment point for
residential exposure should not be nearest residence, but
the maximum impact as modelled on or outside the Chemical
Sales' property boundary. In addition, various exposure
factors were used which are not consistent with Risk
Assessment Guidance for Superfund. Volume 1. Part A
(EPA/540/1-89/02), including the use of .6 m2/hr instead of
20m3/day.
EPA Response: For purposes of the FS, the air stripping
unit for the plume area does not appear to require controls
based on existing land use. This determination will be
verified during remedial design.
The location of the air stripping unit for treatment of the
plume area is tentatively planned for the area pproximately
located 550 meters northwest of the CSC building in an open
field. Although this location was identified for purposes
of the CSC OU1 FS, the use of this land will be confirmed
during remedial design. This location may not be
appropriate due to access unavailability and final design of
system. EPA will require, however, during remedial design
that an assessment of risk from uncontrolled emissions for
the plume area air stripping unit, be conducted upon final
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104.
identification of the specific location tor the air
stripping unit. EPA will consult with the CDB APCD
regarding the adequacy of this assessment, compliance with
action specific ARARs for air stripping and the need for air
emission limitations and/or controls. EPA will require
controls and or emission limitation if this assessment
concludes that a risk of greater than 1 x 10 (-6) exists due
to this treatment system. EPA will also require extensive
monitoring, during the implementation of the remedial action
to ensure compliance.
EPA agrees that 20 m3/hr should be used instead of the .6
m3/hr. This difference, however, does not substantially
change the overall risk to site residents and workers. It
is important to note, that the assessment assumed that
concentrations would remain constant over the 6 year period.
This is an extremely conservative assumption since it is
anticipated that groundwater concentrations will decrease by
close to two orders of magnitude during remedial action.
CDS APCD Comment '3.
The risk assessment did not include the 250 gpm air
stripping tower, or the soil vapor extraction system.
EPA ResDonse: EPA did not require that a risk assessment be
conducted for these units because no emissions will result
from the proposed system. Catalytic oxidation will be used
to destroy over 97% of VOC emissions. The hot exhaust from
.the catalytic oxidation u nit will be recirculated to the
soi1 in order to raise the temperature within the vadose
zone.
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~,
Referenc.. for Responsivene.. suaa&ry
Camp Dress' McKee, Inc. (CDM). 1990a. Remedial Planning
Activities at Uncontrolled Hazardous Substance Disposal
sites in A Zone for EPA Regions VI, VII, and VIII, Risk
Assessment, Chemical Sales Site, Operable Unit 1. Submitted
to U.S. EPA, Document No. 7760-008-RA-BLXP, Contract No. 68-
W9-0021.
1990b. Remedial Planning Activities at Selected
Uncontrolled Hazardous Substance Disposal Sites in A Zone
for EPA Regions VI, VII, and VIII, Risk Assessment, Chemical
Sales Company Site, Operable Unit 2, Chlorinated Hydrocarbon
Groundwater Plume. Submitted to U.S. EPA, Document No.
7760-004-RT-BHNS, Contract No. 68-W9-0021.
Engineering-Science, Inc. 1991. Remedial Investigation/
Feasibility Study - Leyden Street site, Operable Unit 1.
Garbesi, K. and R.G. Sextro. 1989. Modeling and Field Evidence
of Pressure-driven Entry of Soil Gas into a House Through
Permeable Below-Grade Walls. Env. Sci. Tech. 23, p. 1481-
1487.
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