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;~esource Center
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, PA 19107
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United States
Environmental Protection
Agency
Office 01
Emergency and
Remedial Response
EP AIRODIR08-90/032
September 1990
~I
~ 11- ,Z.''l-Io
Superfund
Record of Decision:
Ogden Defense Depot
(Operable Unit 2), UT
EPA Report Collection
Information Resource Center
US EPA R~ion 3
Philadelphia, PA 19107
-------
~J
REPORT DOCUMENTATION 11. REPORT NO. 1 2. 3. Reclpien'" Acceaaion No.
PAGE EPA/ROD/R08-90/032
I. Title and Subtitle 5. Report Date
SUPERFUND RECORD OF DECISION 09/27/90
Ogden Defense Depot (Operable Unit 2), UT
6.
First Remedial Action
7. Author(a) 8. Perfonnlng Organization Rep1. No.
II. P8rf0nnlng Orgalnlzallon Name and Addre.. 10. ProjecVT aaklWork Unit No.
11. Conltacl(C) or Grant(G) No.
(C)
(G)
12. SponaorIng Organization Name and Addte.. 13. Type 01 Report & Period Covered
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
washington, D.C. 20460 14.
15. Supplementary Notea
16. Abatract (Limit: 200 worda)
The 1,100-acre Ogden Defense Depot site is an active military facility in Ogden, Weber
County, Utah. Land use in the surrounding area is mixed residential and commercial.
The site overlies a shallow unconsolidated lacustrine and alluvial aquifer, which is a
potential source of drinking water. In the past, both liquid and solid wastes have been
l1sposed of at the site. Oily liquid materials and combustible solvents were burned in
onsite pits, and solid materials were buried onsite. In fact, six different
contaminated disposal areas have been identified and divided into four Operable Units
(OUs) for remediation. This Record of Decision (ROD) addresses OU2, which is comprised
of a french drain area, a building used for pesticide storage (B5l), and a parade ground
area. From the early 197 Os until 1985, the 8.5 by 20-foot french drain area, which is
comprised of a 2.5 to 4-foot deep gravel-filled excavation, was used as a loading and
mixing area for pesticides and herbicides, and for rinsing the empty containers.
Rinsate from this activity was allowed to percolate through the french drain directly
into the ground. The onsite storage building was used to mix and store pesticides,
herbicides, and paint, although no contamination resulting from B51 activities has been
detected to date. In addition, two onsite oil and solvent burning pits were previously
(See Attached Page)
17. Document Ana/yala L Deacrlptora
Record of Decision - Odgen Defense Depot (Operable Unit 2), UT
First Remedial Action
Contaminated Media: soil, gw
Key Contaminants: VOCs (benzene, PCE, TCE) , other organics (pesticides)
b. IcIentifiera/Open.Ended Terma
c. CooA T1 Reid/Group
18. Avallabl8ty Statement 19. Security Clua (Thia Reporl) 21. No. 01 Pagea
None 50
I 20. Security Clua (Thla Page) 22. Price
N()np
272 (4-77
(See II NSI.Z39.18)
5H In.trucuon. on Rev."",
(Formerty NT\S-:~)
Depertment 01 Commerce
50272-101
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EPA/ROD/R08-90/032
Odgen Defense Depot (Operable Unit 2), UT
~irst Remedial Action
Abstract (Continued)
utilized on or near the onsite parade ground area. Site investigations in 1979, 1981,
and from 1985 to 1986, determined that improper waste disposal practices were used at the
site, and discovered ground water contaminated by VOCs and pesticides near the french
drain area. Subsequent investigations from 1988 to 1990, further characterized the
ground water contamination, and also identified onsite soil contamination, including high
pesticide levels in the french drain area. This ROD addresses soil at the french drain
area and onsite ground water contamination. Subsequent RODs will address the remaining
three OUs and will involve continued investigations and possible remediation of other
onsite areas and media, including buried wastes, a mustard gas storage area, and the oil
burning pit area. The primary contaminants of concern affecting the soil and ground
water are VOCs including benzene, PCE, and TCE; and other organics including pesticides
and herbicides. .
The selected remedial action for this site includes excavating approximately 40 cubic
yards of pesticide- contaminated soil from the french drain area, followed by offsite
incineration and disposal at a hazardous waste treatment facility; backfilling the
excavated area with clean soil and revegetating the area; pumping and treatment of
approximately 28 million gallons of contaminated ground water using air stripping and
liquid phase carbon adsorption, if contaminants are not adequately removed in the air
stripping process; reinjecting or infiltrating treated ground water onsite; and ground
water monitoring. The estimated present worth cost for this remedial action is $676,000,
which includes an annual O&M cost of $75,000 to $103,000 for five years.
'ERFORMANCE STANDARDS OR GOALS: The excavation level for soil has been set at
consistently detected concentration level including pesticides/herbicides
(chlordane/bromacil) 1 mg/kg. Ground water cleanup goals are Federal MCLs and
TCE 5 ug/l (MCL) and chlordane 2 ug/l (MCL).
the lowest
include
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DRAFf FINAL RECORD OF DECISION
AND
RESPONSIVENESS SUMMARY
FOR OPERABLE UNIT 2
DEFENSE DEPOT OGDEN, UTAH
This is a primary document of the DDOU RIfFS. It will be available in the Administrative
Record, which is maintained at the:
Weber County Library
2464 Jefferson Avenue
Ogden, Utah
Hours:
10 am - 9 pm (Monday-Thursday)
10 am - 6 pm (Friday and Saturday)
FFASubmittBlDate: September 14, 1990
Actual Submittal Date: September 14, 1990
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DDOU OPERABLE UNIT 2
DECLARATION
FOR THE
RECORD OF DECISION
Site Name and Location
Defense Depot Ogden, Utah
Ogden, Weber County, Utah
Operable Unit 2 - French Drain and Parade Ground Areas
Statement of Basis and Purpose
This decision document presents the remedial action for Defense Depot Ogden, Utah
(DDOU) Operable Unit 2 (OU 2) selected in accordance with the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as
amended by the Sup.erfund Amendments and Reauthorization Act of 1986 (SARA), and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This
decision is based upon the administrative record for DDOU OU 2.
The State of Utah and the U.S. Environmental Protection Agency (EPA) concur on the
selected remedy.
Assessment of the Site
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and
substantial endangennent to public health, welfare, and the environment.
Description of the Selected Remedy
DDOU Operable Unit 2 is composed of the French Drain Area, the fonner Pesticide Storage
Building, and the Parade Ground Area. OU 2 is one of four operable units at the DDOU
National Priority List (NPL) site, and the first one for which a remedy has been selected.
The other three operable units will require continued study and possible remediation of
other contaminant media. The French Drain Area consists of an 8.5 foot by 20 foot area
which was excavated to a depth of 2.5 to 4 feet, filled with gravel, and used as a mixing and
loading area for pesticides and herbicides. The former Pesticide Storage Building
(Building 51) was used in the past for storing and mixing pesticides. The Parade Ground
is a grassy area south of the French Drain, where two oil burning pits were identified in
DDOU records. The exact locations of these pits are not known. However, soil-gas and
ground-water analyses revealed evidence of possible waste disposal sites in this area.
In general, the only contaminants detected in the soil at OU 2 were pesticides found in the
localized area of the French Drain. Analysis of ground-water samples indicates that there
has been limited migration of the pesticide chlordane through the soil into the ground
water. The major source of volatile organic compounds (VOCs) in the shallow ground
water underlying OU 2 appears to be centered in the northern part of the Parade Ground
Area. No soil or ground-water contamination due to pesticides has been detected in the
vicinity of Building 51. Thus, the major threats at OU 2 are exposure to pesticides in the
soil at the French Drain and the potential for future exposure to VOCs and pesticides in
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ground water. The remedy will remove these potential threats by incinerating the
contaminated soil and removing the ground-water contaminants through treatment.
The selected remedy for DDOU au 2 consists of the following:
.
Extraction of contaminated ground water, treatment by air stripping and
carbon adsorption, if necessary, and repli,cf:ment in the aC!uifer.
.
Excavation and transport of contaminated soil off site for incineration and
disposal in a commercial landfill.
.
Conducting ground-water monitoring to ensure the effectiveness of the ground-
water treatment alternative.
This alternative will control potential future exposures and risks associated with
contaminated shallow ground water.
Statutory Determinations
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
treatment technologies to the maximum extent practicable and satisfies the statUtory
preference for remedies that employ treatment that reduces toxicity, mobility, or volume as
a principal element. In order to ensure that the ground-water treatment continues to
provide adequate protection of human health and the environment, a review will be
conducted by DDOU within five years after commencemen! ':)! !~e !'2~2~E::1 :::t:~:~.
-2-
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eXITED STATES ENVIRON~tENTAL
PROTECTION AGE~CY
By:
Ck._.~,
L/ J ame; . Scherer
REGION VIII AD:-"UNISTRATOR
-3-
Date:
4.-r- ' ~ 7, I -; '7 u
;' .
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STATE OF UTAH
DEPART~tE:\T OF) HEALTH
~1/~ 1Ir:~/~
-Kenneth L. Alkema
DIRECTOR. L"TAH DIVISIO:-; OF
E:-;VIRO~~lE:\TAL HEALTH
By:
-4-
Date: C;~~:k/~~zr:., Icj?d
I ./
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DEFEtlSE DEPOT OGDEN
8y:
Date:
-5-
~j/f()
.
v
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TABLE OF CONTENTS
1.0 - SITE NAME, LOCATION, AND DESCRIPTION
2.0 - SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 History
2.1.1 French Drain Area
2.1.2 Former Pesticide Storage Building
2.1.3 Parade Ground Area
2.2 Enforcement History
2.3 Investigation History
2.4 Community Relations History
2.5 Scope and Role of Operable Units
3.0 - SITE CHARACTERIZATION
3.1 Nature and Extent of Contamination
3.2 Public Health and Environmental Impacts
3.2.1 Contaminant Identification
3.2.2 Exposure Assessment
3.2.3 Toxicity Assessment
3.2.4 Risk Characterization
3.2.5 Uncertainties
3.2.6 Summary of Site Risks
4.0 - ALTERNATIVES EVALUATION
4.1 Development of Preliminary Alternatives
4.2 Initial Screening of Preliminary Alternatives
4.3 Description of Alternatives
4.3.1 Alternative 1 - No Action
4.3.2 Alternative 2 - Institutional Action
4.3.3 Alternative 4 - Off-Site Soil Incineration
4.3.4 Alternative 6 - On-Site Ground-Water Treatment and
Off-Site Soil Incineration
4.3.5 Alternative 7 - Off-Site Ground-Water Treatment and
Soil Incineration
4.3.6 Alternative 12 - Enhanced Ground-Water Treatment and
Off-Site Soil Incineration
4.4 Comparative Analysis of Alternatives
4.4.1 Alternative 1 - No Action
4.4.2 Alternative 2 - Institutional Action
4.4.3 Alternative 4 - Off-Site Soil Incineration
4.4.4 Alternative 6 - On-Site Ground-Water Treatment and
Off-Site Soil Incineration
4.4.5 Alternative 7 - Off-Site Ground-Water Treatment and
Soil Incineration
4.4.6 Alternative 12 - Enhanced Ground-Water Treatment and
Off-Site Soil Incineration
4.5 Comparison of Alternatives
PAGE
1
2
2
2
2
2
2
3
4
4
4
4
5
6
6
6
14
17
17
17
17
19
19
19
21
21
21
21
21
22
Z3
24
24
25
21)
27
27
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Table of Contents
5.0 - SELECTED REMEDY
5.1 Description of the Selected Remedy
5.1.1 Remediation Goals
5.1.2 Costs
5.2 Statutory Determinations
5.2.1 Protection of Human Health and the Environment
5.2.2 Compliance with Applicable or Relevant and
Appropriate Requirements
5.3 Cost Effectiveness
5.4 Utilization of Permanent Solutions
5.5 Preference for Treatment as a Principal Element
5.6 Documentation of No Significant Changes
LIST OF TABLES
TABLE
NO.
TITLE
1
2
3
4
5
Selection of Indicator Chemicals for Carcinogenic Effects
Selection of Indicator Chemicals for Noncarcinogenic Effects
Current Potential Exposure Pathways for au 2
Future Potential Exposure Pathways for au 2
Estimated Carcinogenic and Chronic Risks From Contaminants
Present at au 2
Screening Summary
Alternative 6 - Ground-Water Treatment & Soil Disposal
Identification of Federal Contaminant-Specific ARARs
Identification of State Contaminant-Specific ARARs
Identification of Federal Action-Specific ARARs
Identification of State Action-Specific ARARs
6
7
8
9
10
11
LIST OF FIGURES
FIGURE
NO.
TITLE
28
28
29
29
29
29
31
39
39
40
40
PAGE
7
8
9-10
11-13
15-16
a:>
30
33-34
35
36-37
38
FOLLOWING
PAGE NO.
1
2
3
DDau Location Map .
Isoconcentration Map for TCE in Ground-Water at au 2
Possible Configuration for Ground-Water Extraction and Reinjection, au 2
11
1
5
29
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DDOU OPERABLE UNIT 2
DECISION SUMMARY
FOR THE
RECORD OF DECISION
1.0 SITE NAME. LOCATION. AND DESCRIPTION
'"
DDOU is located at 1200 South Street and Tomlinson Road along the original right-of-way
of the Central Pacific Railroad in the northern reaches of the City of Ogden, Weber County,
Utah (see Figure 1). The Utah General Depot was originally activated on September 15,
1941, and later renamed the Defense Depot Ogden, Utah.
The Depot is situated in a semi-rural setting with the small communities of Harrisville
(population 2,500) located 1.5 miles to the north, Farr West (population 1,750) located 3 miles
to the northwest, and numerous small ranches and a few small businesses located to the
west, east, and south. The Walquist Junior High School is located approximately 1.5 miles
to the northwest. DDOU covers approximately 1,100 acres in a topographically flat area
within the Great Salt Lake Valley. It is drained by Mill and Four-Mile Creeks, both of
which traverse the installation from east to west. A DDOU residential area is located
approximately 200 feet west of the Parade Ground Area and about 800 feet south of the
French Drain Area. However, no one currently uses the shallow ground water at the Depot.
The nearest off-Base residence is located about one-quarter mile to the northeast.
The Depot is underlain by unconsolidated lacustrine and alluvial deposits of Quaternary
and Rp.r.p.nt age. A shallow water table aquifer, ranging in thickness from 5 to :30 !0et,
underlies the site at depths ranging from 6 to 12 feet below the ground surface. The shallow
aquifer is classified by the State of Utah as a Class II aquifer, a potential future source of
drinking water. Ground-water flow in the shallow aquifer underlying OU 2 is toward the
northwest. A deeper, confined aquifer has been encountered at a depth of approximately 125
feet below the ground surface in the northern part of DDOU. Where encountered, this
aquifer exhibits artesian conditions with water levels in the wells rising above the ground
surface. Regional studies indicate that there may be some hydrologic communication
between the shallow and deep aquifers. The strong upward gradient which currently exists
could potentially change in the future as a result of excessive pumping of ground water
from the deeper aquifers.
In the past, both liquid and solid materials have been disposed of at DDOU. Oily liquid
materials and combustible solvents were burned in pits, and solid materials were buried,
burned, or taken off site for disposal. Several waste disposal areas have been identified on
property currently or formerly controlled by DDOU. The six different waste disposal areas
at DDOU have been divided into four operable units. Under the National Contingency
Plan (NCP), "an operable unit is a discrete part of a remedial action that can function
independently as a unit and contributes to preventing or minimizing a release or threat of
a release." This Record of Decision (ROD) addresses Operable Unit 2, the first of the
DDOU OUs to complete.the Remedial Investigation/Feasibility Study (RI/FS) process.
Operable Unit 2, which is located in the southeast part of DDOU (see Figure 1), is composed
of the French Drain Area and the former Pesticide Storage Building (Building 51), as well
as the Parade Ground Area, although there is no discrete boundary. Analyses of soil
samples revealed that the soil in the French Drain has been contaminated with the
-1-
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Source: USGS 7.5 minute quadrangles -
Plain City, Plain City SW, No. Ogden, and Ogden
DDOU LOCATION MAP
FIGURE 1
-------
insecticide chlordane and the herbicide bromaci1. Analysis of one ground water sample
from a well immediately adjacent to the French Drain indicated concentrations of
chlordane above the EPA drinking water standards. Ground water in the shallow aquifer
underlying the Parade Ground is contaminated with volatile organic compounds (VOCs)
including trichloroethene (TCE) and cis-1,2-dichloroethene (cis-1,2-DCE).
2.0 SITE mSTORY AND ENFORCEMENT ACTIVITIES
2.1 HISTORY
As discussed in the previous section, OU 2 is composed of the French Drain Area and the
former Pesticide Storage Building (Building 51), as well as the Parade Ground Area. The
locations of the areas within OU 2 are shown in Figure 1.
2.1.1 French Drain Area
The French Drain is located in the southeast portion of the Depot next to Building 23. It
consists of an 8.5-foot by 20-foot area which has been excavated to a depth of approximately
2.5 to 4 feet and filled with grave1. The drain was covered by a series of railroad rails
(removed during the Phase II site characterization activities) spaced about three inches
apart. It was surrounded by an asphalt parking and storage area. According to DDOlJ
personnel, the French Drain Area was used as a mixing and loading area for pesticides
and herbicides from the early 1970s until as late as 1985. It has also been reported that
empty pesticide and herbicide containers were rinsed, and the rinsate was discharged into
the French Drain. Since the French Drain is not tied to any sewer lines, the rinsate
percolated into the ground.
2.1.2 Former Pesticide Storal!e Buildinl!
The former Pesticide Storage Building (Building 51) is located approximately 800 feet
southwest of the French Drain. The building was used for storing and mixing pesticides
until January of 1984. The building is presently used to store paint products. A new
pesticide facility (Building 21) was constructed and put into service in January of 1984 and
has been in use since that time for pesticide storage and mixing. No contaminants
associated with this site have been detected in the two ground water or three soil samples
collected from the well and soil boring located adjacent to this building.
2.1.3 Parade Ground Area
The Parade Ground is a grassy lawn area located south of the French Drain. Two oil
burning pits measuring approximately 6 feet by 9 feet at the Parade Ground Area were
identified from DDOU records during an early investigation. Although the exact location
of these burning pits is not known, elevated TCE soil gas measurements taken in the
Parade Ground Area, as well as elevated TCE and other VOCs in the ground water
sampled from wells downgradient, confirmed the presence of contamination in this area.
2.2 ENFORCEMENT mSTORY
In 1979, a records search was performed to determine past waste management practices at
the facility. The study identified locations on DDOU where hazardous materials might
have been used, stored, treated, or disposed of. Three DDOU locations were recommended
for further study, including the French Drain Area which is part of OU 2.
-2-
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In 1984, DDOU was proposed for inclusion on the National Priorities List (NPL) and the
decision was finalized in July of 1987. As a result, the Defense Logistics Agency WLA) was
directed to conduct a study to determine the location of any past disposal sites and the
potential for ground-water contamination resulting from those sites.
On June 30, 1986, DDOU entered into a Memorandum of Agreement with the State of Utah
Department of Health (UDOH) and the U.S. F.n\rironmental Protection Agency to undertake
an RIfFS under the Installation Restoration .frogL'am. A technical review committee
composed of DDOU, EPA, UDOH, and local officials was established in 1987.
In November of 1989, DDOU entered into a Federal Facility Agreement between DDOLJ,
EPA, and UDOH. The purpose of the agreement was to establish a procedural framework
and schedule for developing, implementing, and monitoring appropriate response actions
at DDOU in accordance with existing regulations. The FF A requires the submittal of
several primary and secondary documents for each of the four operable units at DDOLJ.
This ROD concludes all of the RIfFS requirements for OU 2.
2.3 INVESTIGATION HISTORY
In 1981, ten shallow monitoring wells were installed at DDOU, including four wells in the
vicinity of OU 2. Analysis of the ground water sampled from these wells indicated the
presence of pesticides and VOCs.
In 1985 and 1986, an investigation and evaluation of the hydrogeology of the various DDOU
sites was conducted. Five additional monitoring wells were installed in the vicinity of OU
2. Analysis of the ground water sampled from both sets of wells indicated the presence of
pesticides in samples from wells in the immediate vicinity of the French Drain.
During the summer and fall of 1988, Phase I of the RI site characterization activities was
conducted. These activities included a soil-gas investigation, drilling and sampling of
shallow and deep soil borings, installation of shallow monitoring wells, and sampling and
analysis of all monitoring wens installed at DDOU. Three monitoring wens were
installed in the OU 2 area and two soil borings were drilled and sampled. Phase I also
included a water well survey and development of a list of potential human, floral, and
faunal receptors which was used in the preparation of an endangerment assessment. In
general, results of the Phase I site characterization activities indicated that no
contaminants were present in the soil samples analyzed and low concentrations of VOCs
were present in the soil gas and ground water underlying the site.
The Phase II RI site characterization activities, conducted during November and December
of 1989 and January of 1990, included excavation and sampling of test pits, drilling and
sampling of additional shallow soil borings, installation and sampling of additional
shan ow monitoring wens, surface soil sampling and analysis, and installation and
sampling of deep monitoring wells. During Phase II, five shallow monitoring wells were
installed in the vicinity of OU 2. In addition, a test pit was excavated and six soil borings
were drilled and sampled. Results of the Phase II site characterization activities confirmed
the presence of VOCs in the shallow ground water underlying OU 2 in concentrations which
exceeded maximum contaminant levels (MCLs) in samples from five wells. In addition,
relatively high concentrations of the pesticide chlordane (450 mglkg) and the herbicide
bromacil (3700 mglkg) were detected in soil samples from the French Drain.
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2.4 COMMUNITY RELATIONS mSTORY
The Phase II RI Report, the OU 2 Feasibility Study Report, and the Proposed Plan for DDOU
OU 2 were released to the public on June 15, 1990. These documents were made available to
the public in both the Administrative Record and an infonnation repository maintained at
the Weber County Library. The notice of availability for these two documents was
published in the Salt Lake Tribune, the Deseret News, and the Ogden Standard Examiner
on June 15, 16, and 17, 1990. A public comment period was held from June 15, 1990 through
July 14, 1990. In addition, a public meeting was held on July 2, 1990. At this meeting,
representatives from DDOU, EPA, and the State of Utah answered questions about problems
at the site and the remedial alternatives under consideration. A court reporter prepared a
transcript of the meeting. A copy of the transcript and all written comments received
during the comment period have been placed in the Administrative Record. In addition,
copies of the transcript were sent to all of the meeting attendees who requested one. A
response to the comments received during this period is included in the Responsiveness
Summary, which is part of this Record of Decision. This decision document presents the
selected remedial action for DDOU OU 2, chosen in accordance with CERCLA, as amended
by SARA and, to the extent practicable, the National Contingency Plan. The decision for
this site is based on the Administrative Record.
2.5 SCOPE AND ROLE OF OPERABLE UNITS
DDOU, with concurrence from the State of Utah and EPA, has elected to divide the site into
four operable units. They are:
.
Operable Unit 1: Burial Sites 1, 3-B, and 3-C
.
Operable Unit 2: French Drain Area, Former Pesticide Storage Building, and
the Parade Ground Area
.
Operable Unit 3: Burial Site 3-A and the World War II Mustard Gas Storage
Area
.
Operable Unit 4: Burial Sites 4-A through 4-E, the Oil Burning Pit Area, and the
backfilled Plain City Canal
The remedial actions planned for these units are independent of one another. This Record
of Decision addresses the remedial action for Operable Unit 2, which is the first of the
DDOU operable units to complete the RI/FS process.
3.0 SITE CHARACTERIZATION
3.1 NATURE AND EXTENT OF CONTAMINATION
There is no evidence of areal1y extensive contamination in the ground water beneath or
down gradient from the French Drain. This confinns reports that the French Drain was
used only for occasional overflow and rinsing and not for frequent disposal of pesticides,
herbicides, or other contaminants. No soil or ground-water contamination related to
Building 51 was detected.
The only contaminants detected in the soil at OU 2 are located in the French Drain.
Although relatively high concentrations of the insecticide chlordane (450 mg/kg) and the
herbicide bromacil (3700 mg/kg) were found in localized "hot spots" in the soil near the
-4-
-------
surface, the contaminants were not detected below a depth of 2.5 feet. Chlordane was
detected in one sample from a well located immediately adjacent to the French Drain at a
concentration of 4.6 /lg/l which is over twice its proposed MCL of 2 /lg/1. Chlordane has
never been detected in any other ground-water samples at OU 2. The detection of several
VOCs in the test pit soil samples collected from the French Drain indicate that it may be a
source of VOCs in the ground water underlying au 2. It should be noted that vinyl ch londe
was analyzed for but never detected in the OU 2 ground-water samples.
The major source of VOCs in the shal10w ground water underlying OU 2 appears to be
centered around the northwest corner of the Parade Ground, where the highest
concentration of TCE was measured at 25 /lg/1 during the Phase II sampling activities.
Five /lg!1 is the maximum contaminant level (MCL) for TCE al10wed in a public water
supply. Figure 2 shows the distribution of TCE contaminant concentrations in the ground
water beneath au 2. The zone of elevated TCE concentrations (defined as greater than 1
/lg!1) extends downgradient for approximately 4,000 feet. The total areal extent of the zone
underlain by concentrations of TCE above the MCL of 5 /lg/1 is on the order of 14 acres,
although this area could increase in size before remediation begins. The total volume of
ground water containing TCE at concentrations above 5 /lg/l is estimated to be
approximately 28 million gallons. This estimate is based on the assumption that the
contaminant concentration remains constant throughout the entire thickness of the
shal10w aquifer. It should be noted, however, that the current size of the area inside the 5
/lg/1 contour may increase before remedies actually begin at au 2.
Speculation that the VOCs present in the ground water beneath the Parade Ground may be
migrating from the oil burning pits reportedly located at the south end of the Parade
Ground are unfounded, based on results of ground-water and soil samples analyzed from
wells in!:tal1ed at the south end of the Parade Ground which indicate th~~ ~c '.'OC:> :;.:-:
present in either medium in that area. Thus, the reported locations of the oil burning pits
appear to be incorrect. Based on data obtained during Phase II, the actual source of TCE in
the ground water appears to be located in the immediate vicinity of the northwest corner of
the Parade Ground. In any event, given the concentrations of VOCs present in the au 2
ground-water samples, the source is very small.
3.2 PUBLIC HEALTH AND ENVIRONMENTAL IMPACTS
A baseline risk assessment was conducted for au 2 fol1owing completion of the Phase II
site characterization activities. The purpose of the assessment was to determine the most
significant contaminants present at au 2, the different ways by which people or plants and
animals potentially would come into contact with the contaminants, and the probability of
any harmful effects occurring as a result of that contact. Based on the data collected and
results of the risk assessment, the media of concern for au 2 were determined to be soil and
ground water in the French Drain Area, ground water downgradient of the Parade
Ground, and contaminated vapors emanating from the ground-water surface. Other
forms of airborne contamination, such as dust emissions, are not present at OU 2. l\lost of
the surfaces at au 2 are either paved or landscaped with grass which prevents dust from
being generated. Volatile contaminants were not found in significant concentrations in
the soil from the French Drain or Parade Ground. Surface water was not considered a
medium of concern for au 2 because the only surface water in the vicinity is upgradient
from the au 2 sites. In addition, contaminant concentrations were at or below detection
limits in surface water samples. Results of the baseline risk assessment indicated that
contaminant concentrations in the soil and ground water at au 2 pose no significant
current risks to human health or the environment. However, there is a potential for
significant future risks if land use changes at au 2. In particular, in the unlikely event
-5-
-------
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-------
TABLE 1
SELECTION 01<' INDICATOR CHEMICALS FOR CAltClNOGENIC EFFECTS
Compmmd
Maximum
Concentmtion
Measured (I)
Inhalation SF
(mglkg/day.1 )(2)
Numher of
Positives Out of
48 Samples
Weight of
Evidence
Classification (3)
Carcinogenic
Index
(Cone. x Oml
SF + 35)
IngCl..tion SF
(mglkg/day(-l»
GROUNDWATER
Benzene
Bromoform
ChIorofonn
1,1-Dichloroethane
1,1-Dichloroethene
Dichloromethane
Tetrachloroethene
TrichIoroethene
Chlordane
DDD
.
-:J
,
SOIL
Chlordane
2.0 x 10-4 2 2.9 x 10-2 2.9 x 10-2 A 1.7 x 10-7
5.h 10-3 3 7.9 x 10-3 NA B2 1.2 x 10-6
9.4 x 10-3 10(5) 6.1 x 10-3 8.1 x 10-2 B2 1.6 x 10-6
1.7 x 10-3 3 9.1 x 10-2 NA B2 4.4 x 10-6
4.0 x 10-4 2 6.0 x 10-1 1.2 x 100 C 6.9 x 10-6
6.1 x 10-3 1 7.5 x 10-3 1.6 x 10-3 B2 1.3 x 10-6
7.8 x 10-3 13 5.1 x 10-2 3.3 x 10-3 B2 1.1 x 10-6
2.5 x 10-2 19 1.1 x 10-2 1.3 x 10-2 B2 7.9 x 10-6
4.6 x 10-3 2(4) 1.3 >I 100 1.3 x 100 B2 1.7 x 10-4
2.0 x 10-5 1(4) 2.4 x 10-1 NA B2 1.4 x 10-7
4.5 x 102
NA
1.3 >I 100
1.3 x 100
B2
5.9 x 102
Note:
(1)
(2)
(3)
(4)
(5)
(6)
Ni\
Compounds in bold selected as indicator chemicals.
In units of mgll for ground-water samples and mglkg for soil samples.
Not used for calculation of carcinogenic index. Included for calculating the '::ancer risks in Table 5.
A - Human Carcinogen
B2 - Probable Human Carcinogen
C - Possible Human Carcinogen
Number of positives out of 32 samples.
Chloroform was detected in six blanks.
Calculated as concentration times slope factor. Not directly comparable to b'fOund-water indices.
Not available.
-------
TABI.I~ 2
SELEGrION OF INDlCATOn t:IIEl\1ICALS FOn NONCAHCIN()(;ENIC IIEALTII EFFECTS
Compound
Maximum
Concentration
Measured()
Number of Positives
Out of
48 Samples
Ingestion
RID
(mglkg/day)
Inhalation
Ro>(2)
(mg/kg/day)
Noncarcinogenic
Index
(Cone. xl/Oral nn>;. 35)
GROUNDWATER
,
00
,
llenzene
llromoform
Carbon disulfide
Chloroform
l,l-Dichloroethane
l,l-Dichloroethene
trans-l,2-Dichloroethene
cis-l,2-Dichloroethene
Dichloromethane
Tetrach]oroethene
l,l,l-Trichloroethane
Trichloroethene
Chlordane
DDD
Delta-BHC
Endosulfan I
2.0 x 10-4 2 7.0x lO-4 NA H.:.! x 10-:1
5.4 x 10-3 3 2.0 x 10-2 NA 7.7 x 10-3
2.0 x 10-4 3 LOx 10-1 NA fi.7 x 1O-fi
9.4 x 10-3 10(3) 1.0 x 10-2 NA 2.7 x 10-2
1.7 x 10-3 3 1.0 x 10-1 NA 5.0 x 10-4
4.0 x 10-4 2 9.0 x 10-3 NA 1.3 x 10-3
1.8 x 10-3 6 2.0 x 10-2 NA 2.6 x 10-3
2.0 x 10-1 ~) 2.0 x 10-2 NA 2.9 x 10-1
6.1 x 10-3 1 6.0 x 10-2 8.6 x 10-1 2.9 x 10-3
7.8 x 10-3 13 1.0 x 10-2 NA 2.2 x 10-2
2.1 x 10-3 3(3) 9.0 x 10-2 3.0 x 10-1 7.0 x 10-4
2.5 x 10-2 19 7.0 x 10-3 7.0 x 10-3 1.0 x 10-1
4.6 x 10-3 2(4) 6.0 x 10-5 NA 2.3 x 10-1
2.0 x 10-5 1(4) NA NA NC
1.2 x 10-2 4(4) 3.0 x 10-4 NA 1.1 x IOO
1.3 x 10-5 2(4) 1.3 x 10.5 NA 7.4 x 10-3
SOIL
Benzoic Acid
Bromacll
Chlordane
6.0 x 10-1
3.7 x }()3
4.5 x 102
NA
NA
NA
4.0 x 100
1.3 x 10-2
6.0 x W-fi
NA
NA
NA
1.5 x 10-1(:;)
2.H x }(r')(")
7.5 x WH(G,
Note:
Compounds in bold selected a8 indicator chemicals.
(1)
(2)
(3)
(4)
(5)
In units of mg/l for ground-water sample!! and mg/kg for soil samples.
Not used for calculation of noncarcinogenic index. Included for calculating the hazurd quotients in Tahle 5.
Chloroform was detected in six blanks and l,l,l-Trichloroethane was detected in two hlanks.
Number of positives out of 32 samples.
Calculated as maximum conccnlration divicled hy rcfprcncc dose.
Not direct Iy com para hie to ground-water indices.
NA = Not Availahle or Not Applicahle
Nt: = Nott :alculatecl
Hfl) = Heferencc !lose
-------
TABLE 3
CURRENT POTENTIAI, EXPOSURE PATIIW A YS FOR OU 2
Environmental
Media
Potential
Receptors
Potential Exposure Route
GROUND WATER 1
Potentially Significant Pathway?
Shal10w Aquifer
,
!D
,
Deep Aquifer
SURFACE SOIL
Nearby residents,
Base personnel
Nearby residents
Nearby residents,
Base personnel
Nearby residents,
Base personnel
Base personnel
Ingestion, inhalation, and dermal
contact with potable water.
Consumption of produce irrigated wi th
water from the shal10w aquifer,
consumption of beef or dairy products
from cattle that drink this water.
Ingestion, inhalation, and dermal
contact with potable water.
Consumption of produce irrigated with
water from this aquifer; consumption of
beef or dairy products from cattle that
drink this water.
Ingestion of contaminated soil or dust.
No. Shal10w aquifer flows downgradient
from OU 2 beneath DDOU property. The
VOC contaminant plume extends to DDOU's
western boundary where VOCs are present at
concentrations significantly below their
MCLs. DDOU and nearby residents are
served by city water.
No. Shallow aquifer flows doWnb>Tadient
from OU 2 beneath DDOU property. The
VOC contaminant plume extends to DDOU's
western boundary where VOCs are present at
concentrations significantly below their
respective MCLs. DDOU and nearby
residents are served by city water.
No. Deep aquifer has not been shown to be
contaminated. DDOU and nearby residents
are served by the city water system.
No. Deep aquifer has not been shown to be
contaminated. DDOU and nearby residents
are served by the city water system.
No. The site is generally covered by
pavement. Test pit samples from the French
Drain show high concentrations of
chlordane and bromaciJ. However, this
area is now covered with plastic and 2 feet of
compacted clay. The site is controlled by
DDOU.
1 Ground-wateJ: contamination a]50 includes contaminants which may leach from contaminated soil.
-------
TABLE 3
CUlffiENT POTENTIAL EXPOSURE PATIIWAYS FOIl OU 2
(CONTINUED)
Environmental
Media
Potential
Receptors
Potential Exposure Route
Potentially Significant Pathway?
SURFACE SOIL
(cont.)
Nearby residents,
. Base personnel
Deep Soil
Nearby residents,
Base personnel
AIR
Deep Soil
Nearby residents,
Base personnel
,
~
o
,
Ground Water
Base personnel
Base personnel
Consumption of produce, beef or dairy
products grown on contaminated soil.
Diffusion upward, adsorption of volatiles to
surface soil, ingestion of soil.
Diffusion upward to surface followed by
dispersion toward houses or Base
buildings, where it is inhaled.
Diffusion of VOCs upward to surface
followed by dispersion toward houses or
Base buildings where they are inhaled.
Diffusion ofVOCs into the basement of a
building where workers or residents inhale
the VOCs.
No. OU 2 lands are not used for agricultural
purposes.
No. OU 2 VOC contaminant concentrations
are low.2
No evidence of significant contamination of
deep soils.
Yes. Residents living in buildings west of
the Parade Ground could inhale TCE
volatilizing into the atmosphere. The
presence of TCE in soil gas measurements
is an indication that TCE my be volatilizing
into the atmosphere in spite of the fact that it
was detected only once in soil.
No. Contaminant plume does not currently
underlie any buildings with basements.
2 Soil gas concentrations at OU 2 are low at a 3-foot depth and they will decrease further bef«re diffusing to the surface. Soil boring data
also did not show evidence of significant subsurface contamination. Test pit samples from the French Drain indicate the presence of
chlordane and bromacil at a 6-inch depth. Neither of these compounds are volatile. Analysis of samples showed most VOC
concentrations to be below detection limits. No VOCs were present in concentrations exceeding 1 mglkg.
-------
TABLE 4
FUrUItE POTENTIAL EXPOSURE PATHWAYS FOn OU 2
Environmental
Media
Potential
Receptors
GROUND WATER
Potential Exposure Route
Potentially Significant Pathwl'.Y'!
Shallow Aquifer
,
......
......
,
Nearby residents,
base personnel
Nearby residents
Nearby residents
Future residents
on base
Construction
workers
Ingestion, inhalation, and dermal
contact with potable water on OU 2.
Ingestion, inhalation, and dermal
contact with potable water which has
migrated northwest.
Consumption of crops, beef, or dairy
products from crops or cattle exposed
to currently contaminated water or
water which has migrated
northwest.
Ingestion, inhalation, and dermal
contact with potable water from
domestic wells.
Inhalation of VOCs in exposed
groundwater.
No. The DDOU controls the on-base property and it is
served by city water.
Yes. The contaminants in the existing plumes which
are currently on base could eventually reach the wells of
nearby residents to the northwest. Bromacil and
chlordane could migrate from soil into the ground water
and then travel off base to the northwest.
VOCs - No. Pesticides - Yes. VOCs are not significantly
accumulated by crops and animals. Pesticides are only
expected to be present in low concentrations, but will
accumulate in soil over time. This scenario is treated
qualitatively.
Yes. Contaminants could persist to occur in the shallow
aquifer on base. Bromaci\ and chlordane could continue
to migrate into this aquifer and increase their
concentrations. Incidental inhalation of VOCs during
lawn or crop irrigation is possible, but will be small
compared to ingestion or shower inhalation.
Yes. If contaminated groundwater were exposed during
excavation, workers could inhale VOCs. Scenario is
treated qualitatively.
-------
TABl.E 4
FUTUllE POTENTIAI~ EXPOSURE PATHWAYS FOn OU 2
-------
TABLE 4
FUTURE POTENI'IAL EXPOSURE PATHWAYS FOR OU 2
(CONTINUED)
Environmental
Media
Potential
Receptor's
Potential Exposure Route
SURFACE SOn.
Potentially Significant Pathway?
I
.....
c.,)
I
AIR
Nearby residents
Construction
workers on base
Nearby residents,
base personnel
and residents on
base
Consumption of produce, beef or
dairy products grown on
contaminated soil.
Dermal contact and inhalation of
fugitive dust during construction
period.
Inhalation of VOCs in soil air
diffusing into basements and into
the air.
No. There is no evidence of significant soil
contamination except that detected in the French Drain
test pit, which consists of a small area. Potential
exposure is small compared to other sources.
No. There is no evidence of significant soil
contamination except in the French Drain test pit. This
area is sman and the contaminated zone is thin, so the
overa1J exposure of any worker would be small.
Outdoor Air - No. Basements - Yes. There is evidence
that contaminant concentrations in soil air could
increase over time, based on the trend of increasing
ground-water concentrations. Estimated current
concentrations of contaminants in outdoor air are very
low, so that even some moderate future increase in air
concentrations would not matter. However, there is a
possibility that a complete pathway could be formed by a
plume moving under a building or by a building being
built over the plume, where VOCs volatilizing into a
basement could be inhaled. However, there are too many
uncertainties to quantify this pathway.
-------
Reference doses (RIDs) have been developed for indicating the potential for adverse health
effects from exposure to chemicals exhibiting noncarcinogenic effects. RIDs, which are
expressed in units of mg/kg-day, are estimates of allowable lifetime daily exposure levels
for humans, including sensitive individuals. Estimated chronic intakes of chemicals
from environmental media (e.g., the amount of a chemical ingested from contaminated
drinking water) can be compared to the RID. RfDs are derived from human
epidemiological studies or animal studies t{) which uncertainty factors have been applied
(e.g., to account for the use of animal data to predict effects on humans). These uncertainty
factors help ensure that the RIDs wi11 not underestimate the potential for adverse
noncarcinogenic effects to occur.
3.2.4 Ri"k Characterization
c
Excess lifetime cancer risks (sometimes referred to as carcinogenic risks) are
determined by multiplying the intake level by the cancer slope factor. These risks are
probabilities that are generally expressed in scientific notation (e.g., 1 x 10-6). An excess
lifetime cancer risk of 1 x 10-6 indicates that, as a plausible upper bound, an individual has
a one in a million chance of developing cancer as a result of chronic site-related exposure
to carcinogens over a 70-year lifetime under the specific exposure conditions at the site.
According to the National Contingency Plan, the target risk level for a site is 1 x 10-6,
although a value in the range of 1 x 10-4 to 1 x 10-6 is acceptable.
Potential concern for noncarcinogenic effects of a single contaminant in a single
medium is expressed as the hazard quotient (HQ). The HQ is the ratio of the estimated
intake derived from the contaminant concentration in a given medium to the
contaminant's reference dose. By adding the HQs for all contaminants within a medium
and across all media to which a given population may reasonably be exposed, a hazard
index (HI) can be generated. A total hazard index greater than 1 indicates that there may
be a concern for potential health effects, while a total hazard index less than 1 indicates that
the concern for potential health effects is quite low.
The carcinogenic risk to DDaU residents associated with the current inhalation exposure
pathway is on the order of 2 x 10-9, which is insignificant. The potential carcinogenic risk
to future off-site residents who use the shal10w ground water at the western boundary is on
the order of 1 x 10-8, which is also insignificant. The total hazard index for
noncarcinogenic effects to future off-site residents is on the order of 5 x 10-4. The estimated
carcinogenic risk to potential future on-site residents is on the order of 8 x 10-5, and the
total hazard index is estimated to equal 2. These values could increase in the future if
chlordane and bromacil continue to leach into the ground water. If that occurs, the
carcinogenic risk is estimated to equal 3 x 10-4 and the hazard index would be on the order
of 200. A list of the carcinogenic and noncarcinogenic risks for each of the scenarios from
contaminants present at au 2 is presented in Table 5.
There do not appear to be any significant environmental threats associated with au 2. The
only area where ecological receptors could possibly come into contact with contaminants is
through the water and sediments of Mill Creek. However, because Mill Creek only flows
part of the year, and it is a small area, it is not a critical habitat for wildlife in the area.
There are no known threatened or endangered species in the vicinity. Finally, because
concentrations of metals (the most significant class of compounds detected) are similar
upstream and downstream from au 2, it appears that contaminants present at au 2 have no
impact on Mi11 Creek.
-14-
-------
TABLEr.
ESTIMATED CAHCINOGENIC AND ClffiONIC RISK.", FROM
CONTAMINANTS PRESENT AT OU 2
Ingestion Inhalation
'('ot..1 Tot.al
Dose Cancer Ilazard Dose Cancer Hazard Cancer Hazard
Contaminant (mglkg/day) RiskO) Quotient (mglkglday) Risk(I) Quotient Risk Index
CURRENT RISKS
Trichloroethene NI NI NI 3.5 x 10-7 2 x 10-9 5 x 10-5 2 x 10.9 5 x 10-5
FUTURE RISKS
Off.Base
Benzene 1.2 x 10-10 2 x 10-12 C 2.1 x 10-10 2 x 10-12 C 4 x 10-12 C
Chloroform 1.9 x 10-9 5 x 10-12 C 2.7 x 10-9 9 x 10-11 C 1 x 10-10 C
cis-l,2-Dichloroethene 1.8 x 10-7 NC 9 x 1O-u 2.8 x 10-7 NC C NC 9 x 1O-u
' Tetrachloroethene 8.7 x 10-9 2 x 10-10 C 1.1 x 10-8 2 x 10-11 C 2 x 10-10
~ C
C1I
' Trichloroethene 9.1 x 10-7 4 x 10-9 1 x 10-4 1.3 x 10-6 7 x 10-9 2 x 104 1 x 10-8 3 x 104
Bromacil 1.9 x 10-6 NC 2 x 10-4 NV NV NV NC 2 x 104
Ch lorclane(2) 3.6 x 10-11 2 x 10-11 6 x 10-7 NV NV NV 2 x 10.11 6 x 10-7
Delta-BHC 8.7 x 10-11 NC 3 x 10-7 NV NV NV NC 3 x 10-7
On.Base: Parade Ground
cis-l,2-Dichloroethene 5.7 x 10-3 NC 3 x 10-1 8.8 x 10-3 NC C NC a x 10-1
Trichloroethene 7.1 x 104 3 x 1O-U 1 x 10.1 9.9 '( 104 6 x 1O~ 1 x 10-1 9 x 1O-u 2 x 10-1
On-Base Current Groundwater
Concentrations: French Drain
Benzene 2.6 x 10-5 3 x 10-7 4 x 10-2 4.3 K 10-5 5 x 10-7 C 8 K 10-7 4 x 10-2
Chloroform 2.7 x 104 7 x 10-7 3 x 10,2 3.9 x 104 1 x 10-5 C 1 x 10-5 3 x 10,2
cis-l,2-Dichloroethene 1.0 x 104 NC 5 x 10-3 1.6 K 104 NC C NC 5 x 10-3
Tctrachloroethcne 3.7 x 10-5 H x 10-7 4 x 10-3 4.7 x 10,5 7 x 1O~ C 9 x 10,7 4 x 1O~1
Trichloroethcnc 2.3 x 10-5 1 x 10-7 3 x 10-3 3.2 :< 10-5 2 x 10,7 5 x 10-3 3 x 10-7 8 x 10-3
Bromacil 0.0 NC 0.0 NV NV NV NC 0
Ch lord a nc(2J 1.1 x 104 G x 10-5 2 NV NV NV 6 x 10-5 2
Dclta-BHC 1.4 x 10-7 NC 5 x (()-4 NV NV NV NC :; x ]0-1
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c
o
TABLE 5
ESTIMATE() CAHCINOGENIC AN()l'HHONIC HISKS FHOM
CONTAMINANTS PRESE.'lT AT OU:l
(CONTINUEI):
Ingestion Inhalation
Total 'foUl'
Doee Cancer Hazard nose Cancer Hazard Cancer Hazard
Contaminant (mglkg/day) RiskU) Quotient (mg/kg/day) RiskO) Quotient Hisk Index
On-Base Future Groundwater
Concentrntions: French .Drain
Benzene 2.6 x 10-5 3 x 10-7 4 x 10-2 4.3 x 10-5 5 x 10-7 C 2 x 10-1, 4 x 10-2
Chloroform 2.7 x 10-4 7 x 10-7 3 x 10-2 3.9 x 10-4 1 x 10-5 C 3 x 10-5 3 x 10-2
cis-l.2-Dichloroethene 1.0 x 10-4 NC 5 x 10-3 1.6 x 10-4 NC C NC 5 x 1O~1
Tetrachloroethene 3.7 x 10-5 8 x 10-7 4 x 10-3 4.7 x 10-5 7 x 10-8 C 1 x 10-6 4 x 10-3
Trichloroethene 2.3 x 10-5 1 x 10-7 3 x 10-3 3.2 x 10-5 2 x 10-7 5 x 10-3 5 x 10-7 8 x )0-3
Bromacil 3.1 x 100 NC 2 x 102 NY NY NY NC 2 x 102
Ch lorda neW 4.6 x 10-4 3 x 10-4 8 x 100 NY NV NV 7 x 10-4 8 x Id>
. Delta-BHC 1.4 x 10-7 NC 5 x 10-4 NY NY NY NC 5 x 10-4
to-'
0)
. 2 x 10-9 5xl0.o 2 x 10-D 5xl0.o
Total Current Risks NI NI
Total Off-Base Future Risks 5 x 10-9 3 x 104 7 x 10-9 2 x 10'4 1 x 10-8 5 x 10-4
Total On-Base Future Risks: Parade Ground 3 x 10-6 4 x 10-1 6 x 10-6 1 x 10-1 9 x 10-6 5 x 10-1
Total On-Base Future Risks, Cu'lT'Cnt 6 x 10.0 2xl00 1 x 10-5 5 x 10-3 8 x 10.0 2 x 1(p
Groundwater Condition: French Drain
Total On-Base Future Risks, Future 3 x 10-4 2 x 102 1 x 10-5 5]1 10-3 3 x 104 2 x 1(~
Groundwater Conditions: French Drain
Notes:
1
Calculated as Dose x SF x (30/70), where the factor of 30170 represents 30 years of exposure out of a 70 yellr lifetime.
2
The dose given is from chlordane leaching into groundwater from soil and then migrating to the receptor. This dose is used instead of the dose
based on current groundwater contamination as it is ahout a factor of three hi!,'her.
C No hazard index h.jven because compound is only a carcino~enic in,licutor ch'!mical or no rl'ference dmlC is nvailahlc.
NC Compound is a noncarcinogen or no cancer potency factor is
-------
3.2.5 Uncertaintie!o;
The primary uncertainty associated with the exposure pathway of greatest concern,
ingestion of ground water by future on-site residents, is whether or not the pathway will
become complete. The yield of the shallow aquifer is very low, while more prolific aquifers
are present at reasonable depths. All of the estimates of the total hazard index for exposure
through ground water are incomplete, and therefore, low, due to a lack of reference doses
for some compounds. An analytical ground-water model was used to estimate future off-
base concentrations of contaminants. This model has elements which are not
conservative, although with a cancer risk estimate of 1 x 10-8, any underestimate of
exposure is probably insignificant. What may be more important is certain exposure
pathways whose risks were not quantified. These include volatiles from ground water
diffusing into the basement of a home built on top of the contaminant plume at a later date
and inhalation and ingestion of pesticides in the surface soil of the French Drain.
3.2.6 SnmmJlJ"V of Site Ri!o;k!o;
There are no current, significant risks to human health and the environment. No
significant risks are. likely to develop in the future, as long as the Depot remains in
existence. However, if the Depot is demilitarized and residential housing were built in OU
2, the potential exists for someone to install a private well in the contaminated plume of the
shallow aquifer and use the ground water for all domestic purposes. This scenario would
create a significant potential for both carcinogenic and non-carcinogenic health effects to
occur. Consequently, actual or threatened releases of hazardous substances from this site,
if not addressed by implementing the response action selected in this ROD, may present an
imminent and substantial danger to public health, welfare, or the environment.
4.0 ALTERNATIVES EVALUATION
As part of the DDOU OU 2 Feasibility Study, 12 remedial alternatives were developed.
Under Section 121 of SARA, the selected remedial action must be protective of human health
and the environment, cost effective, and attain Federal and State applicable or relevant
and appropriate requirements (ARARs). The selected alternative must also use
permanent solutions and alternative treatment or resource recovery technologies to the
maximum extent practicable. EPA guidance documents establish a preference for
remedies that employ treatment which permanently and significantly reduces the
mobility, toxicity, or volume of hazardous substances as their principal element. This
section summarizes how the remedy selection process for OU 2 addressed these
requirements.
4.1 DEVELOPMENT OF PRELIMINARY ALTERNATIVES
A preliminary set of alternatives was assembled to illustrate the range of approaches
available for remediation of au 2. The most important objective in choosing the
preliminary alternatives was that they adequately represent the range of available
remediation options. With this in mind, a set of alternatives was developed starting with
the no action alternative, and each subsequent alternative represented an increased degree
of complexity. Each alternative contained different processes and extent of remediation
for ground water and soil.
The preliminary alternatives chosen include excavation and treatment of soils, with or
without ground-water treatment. Both in-situ and direct treatment processes were
incorporated into the alternatives, along with on-site and off-site disposal options. Two
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alternatives employed extraction and treatment of soil vapors to enhance the remediation
of ground water.
Twelve preliminary alternatives were developed for DDOU OU 2. The main features of
these alternatives were:
1.
2.
3.
No Action - Ground water monitoring would be continued (this is an
element common to all alternatives), but no active remedial actions would
be taken to reduce the levels of contamination.
Institutional Action - Legal and administrative actions would be taken as
necessary to limit potential exposures under both the current and future use
scenarios. For example, steps would be taken to block out water rights for
down gradient areas to prevent the possible future use of ground water.
Containment - Contaminant migration potential would be reduced by
controlling infiltration through installation of caps on the French Drain
and Parade Ground source areas, and by use of subsurface barriers in the
Parade Ground Area.
4.
Off-Site Soil Incineration - Contaminated soil would be excavated and
transported off site for incineration and disposal at a commercial facility.
Institutional actions would be employed as necessary to control potential
future exposures to contaminated ground water.
5.
On-Site Soil Treatment - Contaminated soil would be excavated and treated
on site using biological methods and then be returned to the excavation.
Institutional actions would be employed as necessary to control potential
future exposures to contaminated ground water.
6.
On-Site Ground-Water Treatment and Off-Site Soil Incineration-
Contaminated ground water would be extracted through wells, treated by air
stripping and possibly with liquid phase carbon adsorption, and reinjected
into the aquifer. Contaminated soils in the French Drain area would be
excavated and transported off site for incineration and disposal at a
commercial facility.
7.
Off-Site Ground-Water Treatment and Soil Incineration - Contaminated
ground water would be extracted through wells and transported off site for
treatment and disposal at a publicly owned treatment works (POTW).
Contaminated soil would be excavated and transported off site for
incineration and disposal at a commercial facility.
8.
On-Site Ground-Water Treatment and On-Site Soil Treatment-
Contaminated ground water would be removed by wells and treated by air
stripping and possibly liquid phase carbon adsorption, followed by
reinjection into the aquifer. Contaminated soil would be excavated and
treated using fixation/stabilization before being returned to the excavation.
9.
In-Situ Soil and Ground-Water Treatment - Contaminated ground water
would be treated in place using steam stripping techniques. Soil would be
treated in place using biological methods.
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10.
Biolo~cal Ground-Water Treatment and Soil Treatment - Contaminated
ground water would be removed by wells and would be treated by biological
methods before discharge to a surface drainage. Contaminated soils would
be excavated and treated using fixation/stabilization before being returned
to the excavation.
11.
Ground-Water Extraction and Off-Site Soil Incineration - Extraction wells
and vents would be used to remove ground water and vapors for surface or
spray evaporation. Soil would be excavated and transported off site for
incineration and disposal at a commercial facility.
12.
Enhanced Ground-Water Treatment and Off-Site Soil Incineration - A
combination of wells and vents would be used to extract ground water and
vapors, with ground water being reinjected after treatment by carbon
adsorption. Soils would be excavated and transported off site for
incineration and disposal at a commercial facility.
4.2 INITIAL SCREENING OF PRELIMINARY ALTERNATIVES
In accordance with current RI/FS Guidance under SARA, the preliminary alternatives
were screened using three broad criteria: effectiveness, implementabi1ity, and cost.
Because the purpose of this screening was to reduce the number of alternatives that require
detailed analysis, screening was limited to a level of detail sufficient to distinguish
among alternatives. Comparisons were made among those alternatives which offered
similar functions or extent of remediation. The most promising of each group was carried
forward for detailed analysis. Table 6 indicates how each alternative compared with the
three major criteria.
The end result of the screening process was a shortened list of alternatives which were
recommended for detailed analysis. The intent of this selection was to retain those
alternatives which appeared more effective, easier to implement, and less costly than other
options offering a similar level of protection or extent of remediation. In making
selections, it was important to preserve the original range of alternatives as much as
possible. This allowed the more quantitative information developed in the detailed
evaluation to be applied to those alternatives which offered a range of protectiveness.
As shown in Table 6, six alternatives were selected for detailed analysis; all six share
continued monitoring of ground-water quality as a common element. These alternatives
were:
1.
2.
4.
6.
7.
12.
No Action
Institutional Action
Off-Site Soil Incineration
On-Site Ground-Water Treatment and Off-Site Soil Incineration
Off-Site Ground-Water Treatment and Soil Incineration
Enhanced Ground-Water Treatment and Off-Site Soil Incineration
4.3 DESCRIPrION OF ALTERNATIVES
4.3.1. Alternative 1 . No action
The only activities that would occur under the no-action alternative are monitoring
ground water contaminant levels. Ground-water samples would be collected annually
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TABLE 6
SCREENING SUMMARY
AItemative Effectiveness lmplementability Cost Selected for Conunents
Detailed
Analysie
1. No Action Fair Excellent Excellent Yes Represents baseline case for comparison.
2. Institutional Action Fair ('.ood "~xcellent Yes Affords non-invasive exposure control.
May be required based on future land use.
3. Containment Fair Good Poor No Technically difficult and costly compared to equally effective
options.
Offers little increase in protection over no action.
4. Off-Site Soil Incineration Good Good Excellent Yes Eliminlltes a potential source.
Takes advantage of natural attenuation in ground water.
5. On-Site Soil Treatment Good "'air Good No Requires substantial treatability efforts to treat limited soil volume.
Ability to lower concentration may be limited.
~ 6. On-Site Ground-Water Excellent Good Good Yes Uses proven technology for ground water and soil.
? Treatment and Off-Site Provides short-term reduction in MTV for both mewa of concern.
Soil Incineration
7. Off-Site Ground-Water Excellent "'air Poor Yes Provides ground-water treatment using existing facilities.
Treatment and Soil Limits liability associated with oIT-site disposal.
Incineration
8. On-Site Ground-Water Fair Poor Poor No Unproven technologies do not offer significant protection
Treatment and On-Site advantages.
Soil Treatment Permanent solutions for soil are available at similar costs.
9. In-Situ Soil and Ground- Fair Poor Poor No Unproven technologies do not offer significant protection
Water Treatment advantages.
10. Biological Ground-Water Excellent Fair Fair No Requires substantial treatability efforts to treat limited soil volume.
Treatment and Soil Discharge of treated water constitutes consumptive use
Treatment
11. Ground-Water Extraction Excellent Good "'air No "~vaporation constitutes consumptive use.
and Off-Site Soil Soil incineration does not substantially increase protectiveness.
Incineration
12. Enhanced Ground-Water Excellent Fair "'air Yes Hepresents alternative eliminating need for further acUon.
Treatment and Off-Site Provides recharge to aquifer to limit consumptive use.
Soil Incineration
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from 20 wells at au 2 and analyzed for volatile organic compounds and pesticides. These
analyses were selected because TCE and chlordane are the principal ground-water
contaminants at au 2. The purpose of this alternative is to serve as a basis for comparing
the other alternatives described below.
4.3.2. Alternative 2 - Institutional Action
This alternative is limited to legal and administrative actions to limit potentia] exposures
under the current and future use scenarios. Actions taken would include an appropriate
combination of access and use restrictions for the present. Future actions might include
deed restrictions, prohibition of basements and shallow ground water use, or fencing. It
may also involve limitations on the pumping rate of municipal wells in order to prevent
migration of contaminants from the shallow portion of the aquifer to the deep aquifer.
Ground water monitoring as described for Alternative 1 is also included in Alternative 2.
4.3.3. Alternative 4 - Off.Site Soil Incineration
Under this alternative, contaminated soil from within the French Drain area would be
excavated and transported off site for incineration and disposal at a commercia] facility.
Institutional actions would be employed as necessary (as in A]ternative 2) to control
potential future exposures and risks associated with contaminated shallow ground water.
Phase II RI results indicate removal of the approximately 40 cubic yards of soil currently
held under temporary containment at the French Drain would alleviate pesticide
(ch]ordane) contamination in this area. The material removed would require
incineration to remove the chlordane contaminants, after which the soil would be
considered suitable for land disposal at a pennitted hazardous waste disposal facility. The
excavation would then be refilled with clean soil, regraded, and revegetated.
4.3.4. Alternative 6 - On-Site Ground Water Treatment and Off.Site Soil Incineration
This alternative incorporates extraction of contaminated ground water with wells,
followed by treatment with air stripping and possibly the use of liquid phase carbon
adsorption, and reinjection into the aquifer. A required treatment rate of about 100 gallons
per minute (gpm) or about 50 million gallons per year was estimated to extract the entire
volume of TCE-contaminated ground water in six months.
4.3.5. Alternative 7 - Off-Site Ground.Water Treatment and Soil Incineration
Description. Under this approach, contaminated ground water would be removed by wells
and transported off site for treatment and disposal at a paTW (Central Weber Sewer
Improvement District) through connections with the existing DDOU wastewater col1ection
system. Conversations with the local POTW have provided a clear indication that the
ground water removed can be permitted and combined with other wastewater flows from
DDOU. The discharge must be monitored and a separate discharge permit applied for
before the ground water can be pumped. French Drain area soil would be excavated and
transported off site to be incinerated and disposed of in commercial facilities.
4.8.6. Alternative 12 - Enhanced Ground-Water Treatment and Off-Site Soil Incineration
Description. This alternative would employ a combination of wells and vents to extract
ground water and vapors. Contaminated ground water would be treated by activated
carbon to reduce residual organic concentrations. Reinjection of treated effluent would be
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used to enhance flushing of the aquifer. Soil would be excavated and taken off site for
commercial incineration.
4.4 COMPARATIVE ANALYSIS OF ALTERNATIVES
The detailed analysis of alternatives presented the relevant information needed to select a
site remedy. During the detailed analysis for DDOU au 2, each alternative was assessed
against nine evaluation criteria. The results of this assessment were arrayed to compare
the alternatives and identify the key tradeoffs among them. This approach to analyzing
alternatives was designed to provide sufficient information to adequately compare the
alternatives, select an appropriate site remedy, and satisfy other CERCLA remedy
se lection requirements.
Under CERCLA, nine evaluation criteria have been developed to address the technical and
policy considerations that have proven important for selecting among remedial
alternatives. These evaluation criteria serve as the basis for the detailed analysis and the
subsequent selection of an appropriate remedial action. In assessing alternatives, all
must meet Criteria numbers 1 and 2, which are the threshold criteria. Those alternatives
satisfying the threshold criteria are compared using the balancing criteria. The final two
modifying criteria can change the preferred alternative selected as a result of applying the
balancing criteria. The evaluation criteria are:
Threc:;hold Criteria
1.
Overall Protection of Human Health and the Environment - The
assessment against this criterion describes how the alternative, as a whole,
achieves and maintains protection of human health and the environment.
2.
Compliance with ARARs - The assessment against this criterion describes
how the alternative complies with ARARs or, if a waiver is required, how it
is justified. The assessment also addresses other information from
advisories, criteria, and the guidance that the parties have agreed is "to be
considered. "
Balancin~ Criteria
3.
Long-term Effectiveness and Permanence - The assessment of
alternatives against this criterion evaluates the long-term effectiveness of
each alternative in protecting human health and the environment after the
response objectives have been met.
4.
Reduction of Mobility, Toxicity, and Volume Through Treatment - The
assessment against this criterion evaluates the anticipated performance of
the specific treatment technologies an alternative may employ.
5.
Short-term Effectiveness - The assessment against this criterion examines
the effectiveness of alternatives in protecting human health and the
environment during the construction and implementation of a remedy and
until the response objectives have been met.
6.
Implementability - The assessment against this criterion evaluates the
technical and administrative feasibility of the alternatives and the
availability of the goods and services needed to implement them.
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7.
Cost - The assessment against this criterion evaluates the capital, indirect,
and operation and maintenance costs of each alternative. Cost can only be
a deciding factor for alternatives equally protective of human health and
the environment.
Modifvine- Criteria
8.
State Acceptance - This criterion reflects the state's preferences among or
concerns about alternatives.
9.
Community Acceptance - This criterion reflects the community's
preferences among or concerns about alternatives. Community acceptance
is implicitly analyzed for the selected remedy in the Responsiveness
Summary at the end of this document.
The following discussion summarizes the evaluation of alternatives presented in the
Feasibility Study. Each of the alternatives was compared against the threshold and
balancing criteria. Those alternatives which did not meet with State acceptance are noted
in the discussion. .Community acceptance of the alternatives is discussed in the
Responsiveness Summary.
4.4.1 Alternative 1 . No Action
Threshold Criteria. Under Alternative 1, the no-action alternative, the current health
risk, as described in the baseline risk assessment, would continue to exist at OU 2 until
land use changes. Under current land use, there is no exposure to contaminated ground
water, and the risks are insignificant. If shallow ground water is subsequently used as a
water supply, then the risks may exceed 10-4 due to the existing contaminants plus
chlordane leaching from soil beneath the French Drain. Chlordane is highly
carcinogenic, and it dominates the cancer risks through the ingestion pathway.
Environmental risks, as opposed to human health risks, are not expected to change in the
future. Therefore, Alternative 1 protects human health and the environment unless
shallow ground water is used as a water supply in the future. Most contaminant
concentrations at au 2 currently meet ARARs, and it is expected that, except for chlordane,
these concentrations will decline through natural attenuation. The maximum TCE
concentration is expected to decline to less than the MCL of 5 !lg!1 in about five years. In
contrast, chlordane in the soil beneath the French Drain Area may slowly leach into
shallow ground water where it will maintain high concentrations for several hundred
years. Other contaminant concentrations are expected to decline similarly to TCE due to
natural attenuation. Therefore, Alternative 1 meets chemical-specific ARARs with the
exception of chlordane. However, Alternative 1 does not meet the action-specific ARARs
under RCRA. Leaving chlordane-contaminated soil beneath the French Drain appears to
violate RCRA closure regulations.
Balancing Criteria. Alternative 1 provides for long-term effectiveness and permanence
for all contaminants except chlordane. Other contaminant concentrations will decline
through natural attenuation, but chlordane in the ground water will remain at relatively
high concentrations for several hundred years according to the screening model presented
in the Phase II RI Report. This alternative would not result in a reduction of mobility and
there may be an increase in the volume of contaminants. The alternative would be
effective in the short tenn, as there is no significant health threat under current land use.
Implementation would obviously be readily accomplished.
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Only the costs associated with ground-water monitoring will be incurred by no action. It is
estimated that collecting and analyzing a ground-water sample each year from each of 20
wells at OU 2 will cost $1,000 per well or $20,000 per year. Other costs have been added for
preparing a report of the results and a five year review of the monitoring plan, for a total of
$25,000 per year. It is anticipated that monitoring will continue for 20 years because most of
the contaminant concentrations will be well below the ARARs by then. If chlordane
concentrations persist, or if land use changes, then monitoring may continue beyond 20
years. The present worth cost of Alternative 1 is estimated at $323,000. A detailed cost
analysis for each alternative is presented in Appendix C of the OU 2 FS Report.
4.4.2 Alternative 2 . Institutional Action
Threshold Criteria. Alternative 2 provides institutional mechanisms to prevent land uses
that are incompatible with the presence of shallow, contaminated ground water. With these
controls in place, the estimated health risks are insignificant, and there are no threats to
the environment. It is anticipated that concentrations of all contaminants except
chlordane will quickly decline to below their ARARs through natural attenuation.
Chlordane concentrations may persist above its ARAR for many years.
Balancing Criteria. In the long term, this alternative would provide a permanent remedy
for ground water, and all risks and potential exposures would be controlled. However, it
does not provide a permanent remedy for chlordane in soil. In addition, there will not be a
reduction in mobility and there may be an increase in the volume of contaminated soil and
ground water. In the short term, this alternative would consist of restrictions instituted by
DDOU on activities at OU 2. Restrictions could be placed on subsurface construction
activities, such as trenching and excavation for foundations. Limiting access to the
French Drain area wi1l minimize contact with any harmful contaminants. These actions
should result in good short-term effectiveness. Implementing restrictions within DDOU's
or DLA's jurisdiction would present no serious obstacles, but ground-water restrictions or
zoning changes would require working with State, County, or City government entities. If
the land use changes or DLA no longer controls the property, many other institutional
restrictions would be needed.
Costs include annual ground-water monitoring for 20 years as described under
Alternative 1 and estimated costs associated with setting up restrictions and obtaining
water rights, etc. The present worth cost of Alternative 2 is estimated at $435,000.
4.4.3 Alternative 4 - Off.Site Soil Incineration
Threshold Criteria. Removal of the soil provides a slight increase in protectiveness
compared to the previous alternatives by removing a potential source of contamination and
eliminating any possibility of pesticide-contaminated soils contributing to future ground-
water contamination. Contaminants remaining in shallow ground water are expected to
quickly decrease with time. Institutional controls as described for Alternative 2 would be
enacted to control potential exposures until ground-water monitoring indicates that
shallow ground water is useable. The cancer risk due to using shallow ground water
decreases to less than 10-6, which is the target level, in about 15 years. Therefore,
Alternative 4 protects human health and the environment through declining contaminant
concentrations and institutional controls. The removal and land disposal of the
chlordane-contaminated soil would meet the intent of RCRA closure requirements, but
would likely violate the land disposal standards. Because some of the soil contains greater
than the land disposal standard of 0.13 mg/kg chlordane, the soil will need to be
incinerated. For ground water, it is anticipated that with this alternative the
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concentrations of all contaminants, including chlordane, will decline to levels below their
ARARs through natural attenuation.
Balancing Criteria. Removing and incinerating the soil would provide an effective,
long-term solution to the problem in the French Drain area, and would effectively
eliminate any possibility of future problems resulting from contaminants leaching out of
the soil and entering the ground water. In that regard, reduction in potential residual risk
to ground-water receptors is accomplished. Since this alternative does not include an
active response to ground water, only a gradual change would be effected in the reduction of
mobility, toxicity, and volume of contaminants in the ground water. A substantial
reduction in mobility, toxicity, and volume of contaminants present is expected to occur as
a result of the soil incineration process. The hazardous materials in the soil would
effectively be destroyed, removing any toxicity present, ending mobility, and reducing the
volume of the contaminants. In the short term, soil removal will present some risk of
increased exposure to the removal workers and perhaps to persons working nearby. These
potential risks would result from increased dust generation due to disturbance of the
contaminated soil. These risks can be easily controlled with reasonable caution in
excavation procedures and the use of appropriate respiratory protection measures for
removal workers. There should be no significant adverse environmental impacts as a
result of this action. Remedial action objectives for soil can be achieved in a matter of a
few days by removing the soil and regrading the site. Natural processes will be relied on to
alleviate ground water contamination which is estimated to take up to 15 years.
Implementation of this action will be straightforward. The equipment is readily available
and has proven reliability. The necessary permits should be obtainable.
The present worth cost of this alternative is estimated to be $543,000. Continued monitoring
over the period required for natural degradation and attenuation of ground-water
contaminants represents the major part of this financial obligation. Capital costs are the
charges for removal, transportation, incineration, and disposal of 40 cubic yards of soil at
a site presumed to be in Texas, while operation and maintenance required after the
removal is limited to maintenance of the restored site.
4.4.4 Alternative 6 - On-Site Ground-Water Treatment and Off-Site Soil Incineration
Threshold Criteria. Alternative 6 protects human health and the environment by
removing contaminated soil from beneath the French Drain as described by Alternative 4
and by extracting and treating contaminated shallow ground water. Cancer risks would
be reduced to about 10-6 in an estimated two and one-half years. Institutional controls
described in Alternative 2 would be enacted to restrict potential exposure to shallow ground
water during the remediation period. This alternative meets ARARs .for both soil and
ground water. The soil removal can attain RCRA ARARs as described by Alternative 4,
and contaminant concentrations in shallow ground water are expected to meet ARARs
within two and one-half years, if the treatment rate estimate of 100 gpm is verified. The air
stripper vapor emissions are expected to be low enough to attain Utah ARARs for air
emissions.
Balancing Criteria.. This alternative provides long-term effectiveness and permanence
for remediation at the OU 2 site. The extraction and air stripping process will reduce the
volume of contaminants present in the ground water in what is an irreversible process.
The ability of this approach to achieve very low residuals «5 J..LWI) in ground water in some
geochemical environments is, however, limited as evidenced by experience with other
sites. Remaining ground-water contaminants will be attenuated or reduced by natural
biological processes. Contamination in the soil will be greatly reduced by incineration
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and the soil will be disposed of in a permanent facility where the residual contaminants
will be less mobile. The short-term effectiveness will be immediate for the soil removal.
The ground water is expected to meet ARARs in about 2 and one-half years. However,
because of the inherent uncertainties associated with ground-water cleanup, the estimated
time frame may change. In the short term, some increase in exposures can be expected due
to the release of vapors to the atmosphere, but these emission rates can be controlled through
proper process design. The effectiveness of this alternative, in terms of reduced
concentrations in ground water, can be monitored as part of the ongoing monitoring
program and should, over time, provide a check on the degree of cleanup obtained per
volume of water treated. Monitoring will continue for at least two years after remediation
is completed, or until five years after the initiation of remedial activities, whichever is
later. If chlordane, bromaci1, or TCE are detected in the effluent at concentrations above
the health-based levels and it appears that the air stripping system is not capable of
reducing concentrations below these levels, liquid phase carbon adsorption win be added to
the affected air strippers. This ground-water treatment system can be easily implemented
using readily available equipment with proven field reliability. Excavation and soil
removal, incineration, and disposal can be accomplished by conventional means.
Necessary permit approvals should be obtainable. However, permit approvals may require
additional equipment, such as vapor-phase treatment on the air stripper outlet.
Costs associated with this alternative include those for soil excavation, incineration and
disposal, a ground-water extraction system, an air stripper system, and ground water
monitoring. The present worth cost for this alternative is estimated at $676,000. This cost
also includes a potential cost of $138,000 for a liquid phase carbon adsorption system.
4.4.5 Alternative 7 - Off.Site Ground-Water Treatment and Soil Incineration
Threshold Criteria. Alternative 7 can reduce the cancer risk to 10-6 in an estimated 13
years. All contaminants could be removed from the site. This alternative can attain the
RCRA ARARs for soil excavation and off site disposal, and contaminant concentrations
will fall below the ARARs within about 13 years. Pretreatment standards for the POTW
are considered ARARs. Issuance of an NPDES permit for the point of discharge into the
DDOU sanitary sewer system will allow the POTW to monitor the ground water before
dilution with other DDOU existing discharges. Sludges are landfilled by the POTW on-
site. Treating the ground water off site may constitute consumptive use in which case
compliance with Utah State Engineer requirements for water rights would be necessary. It
is likely that sufficient water rights could be obtained because few water rights were found
in the vicinity for shallow ground water and because many of the existing water rights are
unused because of the availability of municipal drinking water.
Balancing Criteria. In terms of protectiveness, this alternative is similar to Alternative
6. It would provide a permanent solution to the ground-water and soil contamination
problems in OU 2 by reducing the amounts of contaminants found in both media and
disposing of treated materials off site. Destruction of the pesticides in soil by incineration
would be essentially complete, while contaminant removal in the shallow aquifer would
leave very low residuals of contaminants at concentrations less than their respective
MCLs. This alternative offers a resulting reduction in mobility, toxicity, and volume, and
it would be fairly effective in the short term, but will result in moderate consumptive use of
ground water. Potential exposures may increase slightly during soil removal. This
alternative avoids the need for transporting and installing treatment equipment on the site
and would thus be easy to implement, assuming necessary agreements can be worked out
with the receiving authority for wastewater. Consumptive use of the ground water will
need to be reviewed with respect to ARARs.
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Costs for this alternative include a ground-water extraction system, monitoring, connection
to a POTW, and soil disposal options. Present worth cost for this alternative is estimated to
be $799,000.
4.4.6 Alternative 12 - Enhanced Ground-Water Treatment and Off'"L';Hte Soil Incineration
Threshold Criteria. The addition of soil vents to Alternative 12 will accelerate to some
degree the rate of ground-water cleanup of VOCs. The vents will be a closed system to
prevent health effects during remediation.
Balancing Criteria. The incineration of soil is the same remedy as for Alternatives 6 and
7, and thus offers the same short and long-term effectiveness, and reduction of mobility,
toxicity, and volume. It is expected that Alternative 12 would reduce cancer risk to 10-6
within five years. The volatiles removed from the ground water will be transferred to
activated carbon and then burned during the carbon regeneration process. Alternative 12
will reduce the volume of contaminants present in soil and ground water through a
comprehensive treatment program. As with all extraction-treatment systems, removal will
be limited by geochemical and physical factors, but the combination of vapor removal and
recirculation of treated water will be employed to maximize removal efficiencies.
Organics removed from the ground water will be collected on activated carbon and wi11 be
incinerated during the carbon regeneration process. Some increase in potential exposure
can be expected during remediation due to disturbance of the contaminated soils. Water
from the ground-water treatment and gas from the soil venting systems win pass through
carbon systems to prevent volatiles from being discharged to the atmosphere. The
effectiveness of the action in terms of reduced ground-water concentrations can be
monitored as part of the ongoing program, providing means of tracking the degree of
cleanup obtained per volume of water treated over time. This treatment system can be
implemented using readily available equipment with proven reliability. The necessary
permits should be obtainable.
Costs include a ground-water extraction system, liquid phase carbon treatment, a
reinjection system, ground-water monitoring, a soil vapor extraction system, and off site
incinerator for contaminated soils. The present worth cost of this system is estimated to be
$761,000.
4.5 COMPARISON OF ALTERNATIVES
Alternative 1, the no action alternative, is the least protective alternative, both in the short-
term and in the long-term. Along with Alternative 2, which uses institutional controls, it
fails to achieve a permanent remedy for chlordane. Neither alternative reduces the
mobility or volume of contaminants. Alternative 1 does have the advantage of being the
easiest to implement of all of the alternatives, and Alternatives 1 and 2 are the two least
expensive alternatives. Alternative 4, which adds off-site soil incineration to the
institutional controls of Alternative 2, is more protective than Alternatives 1 and 2. By
eliminating surface-soil contamination, some routes of exposure which were not quantified
in the risk assessment will be eliminated. By removing the source of chlordane from the
soil, risks associated with ground-water exposure pathways will be reduced much more
rapidly, thus assuring a more permanent solution. The mobility, toxicity, and volume of the
soil contaminants would be greatly reduced for Alternative 4 versus Alternatives 1 and 2,
and no major implementation problems would be expected. The additional cost of
Alternative 4 versus the first two is not an issue since it is a more protective treatment.
Alternatives 6 and 7 build on Alternative 4 by adding ground-water treatment. All three
alternatives are equally protective in the short term. Long-term protectiveness and the
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reduction in contaminant toxicity, mobility, and volume are better for Alternatives 6 and 7
than Alternative 4 as a result of actively treating the ground water rather than permitting
natural attenuation of contaminants to occur. The advantages of Alternative 6 over
Alternative 7 are that: 1) treatment time is shorter, 2) it is easier to implement from the
perspective of not neeeting to coordinate with a POTW, and 3) it is less expensive by at least
15 percent. Alternative 7 has the advantages of: 1) providing a more proven method of
reducing pesticide concentrations, and 2) being more easi!y implemented from the
perspective of transporting and installing equipment on-site. Alternative 12 builds on
Alternative 6 by adding carbon adsorption to the air stripping system from the beginning
and by adding a soil venting system. This remedy is as protective in the short term as
Alternative 6 and is slightly more effective in the long term by reducing the time to complete
remediation. The reduction in toxicity, mobility, and volume of the contaminants is about
the same as that for Alternative 6. This alternative would be slightly more difficult to
implement than Alternative 6, due to the additional apparatus involved. The main
difference between Alternatives 6 and 12 is cost. The estimated $85,000 difference between
the two, should be regarded as a minimum, since the $676,000 cost estimate for Alternative 6
includes $138,000 for a carbon adsorption system which may not be necessary.
5.0 SF.T .F.CTED REMF.DV
The selected remedy for DDOU Operable Unit 2 is Alternative 6, on-site ground-water
treatment and off-site soil incineration. This remedy was the preferred alternative in the
Proposed Plan. A detailed description of the selected alternative including the remediation
goals, corresponding risk levels to be attained, and the costs associated with each component
of the remedy is presented in the following discussion.
5.1 DESCRIPTION OF THE SELECTED REMEDY
Under Alternative 6, contaminated soil from within the French Drain would be excavated
and transported off site for incineration at a hazardous waste treatment facility. The
excavation would then be refilled with clean soil, regraded and revegetated. It is estimated
that removing approximately 40 cubic yards of soil from the French Drain will eliminate
pesticide contamination in this area, and that soil remediation will be completed within one
year after the start of remedial activities. Removal of the soil will protect people by
removing the potential for contact with pesticideslherbicides and eliminating any
possibility of the pesticide contaminated soils contributing to future ground-water
contamination.
Ground-water extraction and treatment would be employed to control potential future
exposures and risks associated with consumption of contaminated ground water. Ground-
water extraction and treatment would last an estimated two and one-half years, although
this estimate obviously has some uncertainty associated with it. The monitoring wi\1 be
conducted for at least two years on a quarterly basis after remediation is completed or five
years after the initiation of remedial activities, whichever is later. If chlordane, bromacil,
or TCE are detected in the effluent at concentrations above health-based levels, and it
appears that the air stripping system is not capable of reducing concentrations below these
levels, the liquid phase carbon adsorption will be added to the system. During the treatment
period, the contaminated portion of the shallow aquifer wi11 be flushed about five times,
which should allow attainment of the ARARs. This estimate was tested using a Theis
analytical model with 10 extraction wells surrounded by 10 reinjection wells. Based on this
preliminary evaluation, the aquifer should be capable of yielding up to about 10 gallons per
minute (gpm) to each extraction well with a maximum drawdown of about 8 feet. The
assumed transmissivity was 3,000 gpdlft, the approximate arithmetic mean of the available
slug test data. One possible configuration for the system using these preliminary design
-28-
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values is shown in Figure 3. Prior to completing the detaiJed design, several pump tests \\-;11
need to be conducted in the plume area using we]]s installed at a few of the anticipated
extraction locations. In addition, the adsorption and desorption processes which are
occurring in the aquifer wiJI have to be evaluated to properly estimate the period of extraction
necessary to remediate the aquifer. Exhaust air from the air stripper would be vented to the
atmosphere, while treated water would be used to recharge the aquifer using injection wells
or infiltration gaJ1eries. The process components of this alternative and pertinent
n,(onnation and assumptions on sizing, concentrations, flow rates, etc., are presenteci 10
Table 7. It should be noted that some changes may be made to this remedy as a result of
remedial design and construction processes.
"
5.1.1. Remediation Goals
The point of compliance for soil wi]] be removal and treatment of aJI soil containing at least
1 mg/kg of bromacil or chlordane. This is the lowest concentration that can be consistently
detected. Ground water will be treated until contaminant concentrations are below their
MCLs and contaminants without MCLs pose less than one in a miHion excess cancer risk.
A one in a miHion excess cancer risk means that no individual wiJI have more than a one
in a miHion chance of developing cancer as a result of living or working near OU 2. The
point of compliance for ground-water cleanup is the point of maximum contaminant
concentrations in the ground water. Thus, contaminant concentrations would have to be
reduced to levels below MCLs in aJI OU 2 ground-water samples. When these goals are met,
the shaJIow ground water wi]] be available for beneficial uses.
5.1.2. .c..om
The costs associated with remediation of OU 2 using Alternative 6 are shown in Table 7.
Ihe totai capital cost of the project is estimated at $305,000. This includes costs of insta]]jng
a ground-water extraction and injection system, storage tank, an air stripping system
equipped with a liquid-phase carbon adsorption system, ground-water monitoring,
excavation, and commercial incineration of contaminated soil. Indirect costs for
administration, engineering, and design services were estimated to be approximately
$63,000, while annual operation and maintenance costs are estimated at $103,000. The
present worth cost of the project, using a five percent discount value, is estimated at $676,000.
This does not include any costs associated with additional monitoring that must be
perfonned as a result of the EPA five year review.
5.2 STATUTORY DETERMINATIONS
The selected remedy for DDOU Operable Unit 2 meets the statutory requirements of Section
121 of CERCLA as amended by SARA. These statutory requirements include protection of
human health and the environment, compliance with ARARs, cost effectiveness, utilization
of pennanent solutions and alternative treatment technologies to the maximum extent
practicable, and preference for treatment as a principal element. The manner in which the
selected remedy for DDOU OU 2 meets each of these requirements is presented in the
following discussion.
5.2.1 Protection ofHurnan Health and the Environment
The selected remedy for DDOU OU 2 protects human health and the environment through the
fo]]owing engineering controls:
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EXPLANATION
@
Dewatoring well
.
Injection well
1~ Contours 01 drawdown
- (inleet)
~ Area where TCE
V exceeds its MCL 01
5 fig/I
~
o 200
I""'-"'~
Scale in Feel
400
I
POSSIBLE
CONFIGURATION FOR
GROUND-WATER
EXTRACTION AND
REINJECTION
OU2
FIGURE 3
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TABLE 7
ALTERNATIVE 6 - GROUND.WATER TREATMENT & SOIL DISPOSAL
Ground Water
Soil
Exposure Control
Exposure Control
Eliminate exposure pathways through remediation
Eliminate exposure pathways by removing contaminated soil
Extraction - Extraction Wells
Extraction - Excavation
System of 10 wells, each 40-feet deep, 4-inch diameter
Individual well flow rates = 10 gpm
432,000 gallon storage pond
Excavate 40 cubic yards of contaminated soil
Transport contaminated soil ofT-site to commercial incinerator
Refill excavation with clean soil
Regrade and revegatate excavation site
Treatment - Air Stripping
Treatment - Commercial Incineration
c..,
o
I
Flow rate =100 gpm
Surge Tank = 5,000 gallons
Influent water temperature = 50° F
Influent TCE concentration = 25 ~g/J
. Effluent TCE concentration < 5 ~g/J
Influent cis-l,2-DCE concentration = 200 ~gl\
Effluent cis-1,2-DCE concentration < 70 J.1g1\
Vapor phase controls = None
Aqueous phase carbon to control chlordane
Deep Rock, Texas Incineration
Disposal - Off-site
Soil DisposaVfreatment Costs - Commercial Incinenltion
Indirect = $25,000
Capital = $123,000
Annual O&M = $5,000
Disposal - Reinjection into Aquifer
Indirect costs include soil analysis necessary for landfill disposal
System of 10 injection wells, each 40-feet deep, 4-inch diameter
Individual well flow rates == 10 gpm
Capital costs include excavation/transportJdisposal
O&M costs cover site restoration for two years
Ground-Water Treatment Costs (Includes Air Stripping and Carbon
Adsorption) .
Indirect = $38,000
Capital = $182,000
Annual O&M = $75,000
Indirect costs include administration, engineering, design and
perm i tti ng
O&M costs include monitoring program costs
Total Co~is:
Indirect =
$6.1,000
Capital =
$:J05,()(X)
Annual O&M
$10:1,000
Present Worth Co~i = $67f),OOO
-------
.
Excavation and incineration of all soil containing at least 1 mg/kg of bromacil
or chlordane from the French Drain;
.
Extraction and treatment of all ground water until contaminant
concentrations are below their MCLs, or the potential health risks are less than
1 x 10-6 for contaminants without MCLs.
Removal and incineration of the soil at au 2 will eliminate the source of pesticide and
herbicide contamination in the ground water as well as removing the potential for contact
with these contaminants in soil, and thus this will no longer be a complete pathway.
Treatment of contaminated ground water at au 2 to a level below the MCLs will result in
less than a 1 x 10-6 cancer risk to potential future ground-water users. Currently, the
contaminants in the ground water do not pose a risk to anyone because there is no complete
pathway to a ground-water user. However, there is a potential for a cancer risk of 3 x 10-4
and a hazard index of 200 if someone were to become a ground-water user at a later date.
The remedy will not eliminate the potential for a ground-water pathway, but it will reduce
contaminant concentrations to levels which would not present a significant risk. The
selected remedy for soil and ground water at au 2 will not pose an unacceptable short-term
risk and will have the effect of minimizing cross-media impacts.
5.2.2 Comn1innce with Annlica.ble or Relevsnt nnd Annl"Onriate Reouirements
Section 121Cd)(1) of CERCLA as amended by SARA, requires that remedial actions must
attain a degree of cleanup which assures protection of human health and the environment.
In addition, remedial action that leaves any hazardous substances, pollutants, or
contaminants on site must, upon their completion, meet a level or standard which at least
attains legally applicable or relevant and appropriate standards, requirements,
limitations, or criteria that are "applicable or relevant and appropriate requirements"
(ARARs) under the circumstances of the release. ARARs include federal standards,
requirements, criteria, and limitations and any promulgated standards, requirements,
criteria or limitations under State environmental or facility siting regulations and that
are more stringent than federal standards.
"Applicable" requirements are those cleanup standards, standards of control, and other
substantive environmental protection requirements, criteria, or limitations promulgated
under Federal or State law that specifically address a hazardous substance, pollutant or
contaminant, remedial action, location, or other circumstance at a remedial action site.
"Relevant and appropriate" requirements are cleanup standards, standards of control,
and other substantive environmental protection requirements, criteria, or limitations
promulgated under Federal or State law that, while not "applicable" to a hazardous
substance, pollutant or contaminant, remedial action, location, or other circumstance at a
remedial action site, address problems or situations sufficiently similar to those
encountered at the site that their use is well-suited to the particular site.
In determining which requirements are relevant and appropriate, the criteria differ
depending on the type of requirement under consideration, i.e., chemical-specific,
location-specific, or action-specific. According to the NCP, chemical-specific ARARs are
usually health or risk-based numerical values which establish the acceptable amount or
concentration of a chemical that may remain in, or be discharged to, the ambient
environment. Location-specific ARARs generally are restrictions placed upon the
concentration of hazardous substances or the conduct of activities solely because they are in
special locations. Some examples of special locations include floodplains, wetlands,
historic places, and sensitive ecosystems or habitats. Action-specific ARARs are usually
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technology- or activity-based requirements or limitations on actions taken with respect to
hazardous wastes, or requirements to conduct certain actions to address particular
circumstances at a site. Remedial alternatives which involve, for example, closure or
discharge of dredged or fill material may be subject to ARARs of RCRA and the Clean
Water Act.
The remedial action proposed, the hazardous substances present at the site, as well as the
physical characteristics of the site and the potential receptor population, were all
considered when determining which requirements are applicable or relevant and
appropriate to the selected remedy for DDOU OU 2. Federal and State laws, standards,
requirements, criteria, and limitations were reviewed for possible applicability to the
DDOU OU 2 site. A complete list of the potentially relevant Federal and State ARARs is
presented in Appendix A of the OU 2 Feasibility Study Report.
Through careful review of the ARARs, it has been determined that the remedy selected for
OU 2 will meet all applicable or relevant and appropriate public health and environmental
requirements of Federal or State laws. Therefore, no SARA Section 121(d)(4) waiver will
be necessary. A brief discussion of how the selected remedy for OU 2 satisfies the principal
ARARs associated with the site is presented below.
Chemical-Specific Requirements. In general, the chemical-specific ARARs set health- or
risk-based concentration limits in various environmental media. Ground-water quality
ARARs for DDOU OU 2 are based on the Safe Drinking Water Act maximum contaminant
levels (MCLs), the maximum permissible levels .of a contaminant in water which is
delivered to any user of a public water system. MCLs are generally relevant and
appropriate as cleanup standards for contaminated ground water that is or may be used for
drinking. Other applicable requirements include the Clean Air Act, the Occupational
Safety and Health Administration
-------
-
TABl.ES
IDENTIFICATION OF FEDERAL CONTAMINANT. SPECIFIC ARABS
Applicable!
Relevant
Standard, Requirement, and
Criterion, or Limitation Citation Description Appropriate Comments
Solid Waste Disposal Act 42 USC Sec. 6901-6987
Standards Applicable to 40 CFR Part 263 Establishes standards N o/Y e s Transportation of soil off site.
Transporters of which apply to persons
Hazardous Waste transporting hazardous
waste within the U.S. if the
transportation requires a
W manifest under 40 CFR
C>J Part 262.
.
Standards for Owners 40 CFR Part 264 Establishes minimum N o/Y e s Ground-water treatment
and Operators of national standards which system.
Hazardous Waste define the acceptable
Treatment, Storage, and management of
Disposal Facilities hazardous waste for
owners and operators of
facilities which treat,
store, or dispose of
hazardous waste.
D.O.T. Hazardous Material 40 CFR Parts 107, 171-177 Regulates transportation Yes/Yes Transportation of soil ofT site.
Transportation Regulations of hazardous materials.
Occupational Safety and 20 USC Sec. 651-678 Regulates worker health Yes/--- All people involved in
Health Act and safety. implementing the remedy;
includes exposure limits to
chemicals.
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TABLE 8
IDENTIFICATION OJ<' FEDERAL CONfAMINANT - SPI<:CIFIC AltARS
(CONTINUED)
Applicable/
Relevant
Standard, Requirement, and
Criteriion, or Liinitation Citation Description Appropriate Comments
EPA Ground-Water EPA Guidance Establishes a ground- No/Yes Contributes to the National
Protection Strategy water classification Primary Drinking Water
system for protection of Standards (MCLs) being
ground-waters based on remedial action objectives.
their value to society, use,
c., and vulnerability.
~ Safe Drinking Water 42 USC Sec. 300g
I
National Primary 40 CFR Part 141 Establishes health-based No/Yes Remedial action objectives:
Drinking Water standards for public water Benzene - 5 J.lg/l Ch loroform -
Standards systems (maximum 100 J.lg/l Trichloroethene - 5 J.lglI
contaminant levels)
Clean Air Act 42 USC Sec. 7401-7642
National Primary Air 40 CFR Part 50 Establishes standards for Ye sl - n DDOU is in Weber County,
Quality Standards ambient air quality to which is a nonattainment area
protect public health and for carbon monoxide. The
welfare. selected remedy will generate
carbon monoxide.
c>
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"
TABLE 9
IDENTIFICATION OF STATE CONTAMINANT - SPECIFIC ARARs
Applicable/
Relevant
Standard, Requirement, and
Criterion, or Limitation Citation Description Appropriate Comments
Utah Public Drinking Water Sections 3.1.1. and 3.1.2. Establishes maximum N o/Y e s Values identical to
Regulations contaminant levels for Federal MCLs for all
inorganic and organic compounds present at
chemicals. site.
Utah Public Drinking Water Section 3.2 Establishes secondary N o/Y e s Requirements are
c., Regulations, Pesticides drinking water relevant and appropriate
t11 standards. to the DDOV Site.
I
Utah Groundwater Quality Utah Adm. Code R448-6 Establishes ground-water Yes/Yes Contributes to the
Protection Regulations quality standards for the National Primary
different ground-water Drinking Water
aquifer classes. Standards (MCLs) being
remedial action
objectives.
Bureau of Solid and Title 26, Chapter 11, Corrective Action Clean- Yes/Yes Lists general criteria to
Hazardous Waste, Division V.C.A., V.A.C. 450-101 up Standards Policy - be considered in
of Environmental Health, RCRA, VST, and establishing clean-up
Department of Health CERCLA sites. standards.
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TABLE 10
IDENTIFICATION OF FEDERAL ACTION - SPEClI<'lC ARARS
Applicable/
Relevant
Stan~ Requirement, and
Criterion, or Limitation Citation Description Appropriate Comments
Solid Waste Disposal Act 42 USC Sec. 6901-6987
Standards Applicable to 40 CFR Part 263 Establishes standards No/Yes Transportation of soil
Transporters of which apply to persons off si te.
Hazardous Waste transporting hazardous
waste within the U.S. if the
transportation requires a
c., manifest under 40 CFR
0') Part 262.
,
Standards for Owners 40 CFR Part 264 Establishes minimum No/Yes Soil incineration
and Operators of national standards which system - Subpart O. Also
Hazardous Waste define the acceptable see especially Subpart G
Treatment, Storage, and management of - Closure and Post-
Disposal Facilities hazardous waste for Closure for the ground-
owners and operators of water treatment system.
facilities which treat,
store, or dispose of
hazardous waste.
Land Disposal 40 CFR Part 268 Regulate disposal of Y es/ --- Affected selection of
Restrictions untreated waste on land. remedy for soil
contaminants.
D.O.T. Hazardous 40 CFR Parts 107,171-177 Regulates transportation Y es/ --- Transportation of soil
Material Transportation of hazardous materials. off si te.
Regulations
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TABLE 10
IDENfIFICATlON OF FEDERAL AcrION - SPECIFIC ARARS
(CONrINUED)
Applicable'
Relevant
Standard, Requirement, and
Criterion, or Limitation Citation Description ApJropiate Comments
Occupational Safety and 20USC Sec. 651-678 Regulates worker health Ye s/ --- Defines training for
Health Act and safety. workers involved in
implementing the
remedy.
Underground Injection 40 CFR Part 146 Subpart F Standards for Class V Yes/--- Applicable to reinjection
c.., Control Program underground injection of treated ground water.
-:J wells.
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TABLE 11
IDENTIFICATION OF STATE ACTION - SPECIFIC AREAS
Department. Division
or Commission
8atute
Description
Applicable!
Relevant
and
Appropriate
Department of Agriculture
Comments
Industrial Commission
I
CiJ
CIO
I
Bureau of Solid and Hazardous
Waste, Division of
Environmental Health,
Department of Health
Bureau of Water Pol1ution
Control, Division of
Environmental Health,
Department of Health
State Engineer, Department of
Natural Resources
Bureau of Air Quality, Division
of Environmental Health,
Department of Heal th
TitJe 4, Chapter 14, Utah
Code Annotated
(U.C.A.), U.A.C. R68-07
Title 35, Chapter 9,
U.C.A., U.A.C. R500
Title 26, Chapter 11,
U.C.A., U.A.C. R450
Title 26, Chapter 11,
U.C.A., U.A.C. R448-7
73-3-5, U.C.A., U.A.C.
R625-4
Title 26, Chapter 13,
U.C.A., U.A.C. R446
Pesticide control--safe
and approprjate use of
pesticides.
Utah Occupational Safety
and Health Standards.
Solid and Hazardous
Waste.
Underground injection
con trol.
Well drilling standards -
standards for drilling
and abandonment of
wells.
Utah Air Conservation
Rules.
Yes/---
Yes/---
Yes/---
Yes/---
Yes/---
Yes/---
See particularly R68-07-10, U.A.C.,
regarding storage, transport and
disposal, and R68-07-11, U.A.C.,
regarding other unlawful acts.
These rules are identical to federal
OSHA regulations.
R450-0, regarding spill reporting
requirements, has no corresponding
federal provisions.
See particularly R448-7-9 specifying
technical requirements.
Indudes such requirements as
performance standards for casing
joints, requirements for abandoning a
well.
Important requirements include a limit
of 1.5 tons of annual emissions of VOCs
without obtaining a permit, fugitive
dust emission standards, application of
BACT to any source, and visible
emission standards.
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To Be Considered Requirements. In implementing the selected remedy for OU 2. DDOC
has agreed to consider a number of requirements that are not legally binding. TBC
requirements include the fo11owing proposed MCLs: chlordane (2 Ilg/lJ: cis-1.2-
dichloroethene (70 Ilg/1); trans-1,2-dichlorethene (100 1lg!1); and tetrachloroethene (5 IlgJ1J.
5.3 COST EFFECI'IVENESS
Overa11 cost-effectIveness can be defined as the reduction jn threat to public health and the
environment per do11ars expended on a remedy. The selected remedy for DDOU OU 2 is
the most cost-effective alternative because it provides the maximum effectiveness
proportional to cost of any of the alternatives analyzed.
5.4 urILIZATION OF PERMANENT SOLUTIONS
.:;
This section briefly describes the rationale for the selected rem€dy and explains how the
remedy provides the best balance of tradeoffs among a11 the alternatives with respect to the
five summary balancing criteria, which include:
1.
Long-term effectiveness and permanence
2.
Reduction of toxicity, mobility, or volume through treatment
3.
Short-term effectiveness
4.
Imp lementabi lity
5.
Cost
Other criteria include state and community acceptance. A detaped comparative analysis
of a11 the alternatives is presented in the worksheets provided in Appendix B of the OU 2 FS
Report .
Of the six alternatives selected for detailed analysis (Alternatives 1, 2, 4, 6, 7, and 12),
alternatives 6, 7, and 12 rate comparably with respect to the five primary balancing criteria
and are superior to Alternatives 1, 2, and 4. However, Alternative 7 (off-site ground-water
treatment and soH incineration) rated slightly lower than Alternative 6 (on-site ground-
water and off-site soil incineration) and Alternative 12 (enhanced on-site ground-water
t.reatment and off-site soil incineration) with respect to implementability and cost.
Because Alternative 7 would require consumptive use of ground water, it was not
considered acceptable by the State of Utah. Alternative 6 was chosen over Alternative 12
because it has a lower cost, and rated higher with respect to implementability.
The selected remedy for DDOU OU 2 utilizes permanent solutions and treatment
technologies to the maximum extent practicable. It is estimated that remediation of soil
and ground water will be complete when the 5-year review is conducted by DDOU. In order
to ensure the effectiveness of the remedy, monitoring and management of the site will be
required for at least two years on a quarterly basis after remediation is completed or until
five years after the star't of remediation, whichever is later. The contaminant volume in
the ground water wi11 be reduced through air stripping approximately 50 mi11ion ga110ns of
contaminated ground water for removal of organics. Contaminated soils will be
incinerated and sent to a landfi11 to reduce mobility.
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5.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The selected remedy uses treatment to the mwdmum extent practical. Contaminated soils
will be incinerated, eliminating the potential for contact with contaminants in the soils
and eliminating the source of pesticide contamination in the ground water. The other
potential threat is ingestion and inhalation of contaminants in ground water. The
selected remedy treats the ground water through an air stripping system that may include
liquid phase carbon adsorption.
5.6 DOCUMENTATION OF NO SIGNIFICANT CHANGES
The Proposed Plan for DDOU OU 2 was released for public comment in June 1990. The
Proposed Plan identified Alternative 6, On-Site Ground-Water Treatment and Off-Site
Soil Incineration, as the preferred alternative. All written and verbal comments
submitted during the comment period were reviewed. The conclusion of this review was
that no significant changes to the remedy, as identified in the Proposed Plan, were
necessary.
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DDOU OPERABLE UNIT 2
,RESPONSrvENESSS~Y
FOR THE
RECORD OF DECISION
1.0 OVERVIEW
~
"
This responsiveness summary serves two purposes: first, it provides regulators with
information about the views of the community with regard to the proposed remedial action
for DDOU Operable Unit 2. Second, it documents how public comments have been
considered during the decision-making process and provides answers to significant
comments.
The Phase II Remedial Investigation Report and the OU 2 Feasibility Study Report and
Proposed Plan were made available to the public for comment from June 15 through July 14,
1990. A public meeting was held at the Weber County Library on July 2, 1990. As presented
in the Proposed Plan, the preferred alternative for DDOU Operable Unit 2 was Alternative
6, on-site groundwater treatment and off-site soil incineration.
Only one comment was received from the public during the public comment period and the
public meeting. That comment was a request for information on the proposed schedule for
remediation of all of the DDOU operable units. Thus, apparently the residents and
officials located in the vicinity of DDOU have no objections to the proposed remedial
alternative for OU 2.
2.0 BACKGROUND ON COMMUNITY INVOLVEMENT
A Community Relations Plan for DDOU is currently under review by the regulatory
agencies. As part of the Community Relation Plan (CRP), interviews were conducted with
local residents and leaders and county and state officials during the period from July 5
through July 18, 1990. The purpose of the interviews was to determine how DDOU could best
provide information to the community and the nature of community concerns regarding
the DDOU site. Other community activities include a press release and public meeting
associated with the DDOU OU 2 FS. Based on the public interviews and comments received
during the public comment period, community interest in the cleanup of DDOU has been
very low, with few community concerns expressed.
3.0 SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC
COMMENr PERIOD AND nDOU RESPONSE
Only one comment was received during the public meeting and response period. That
comment is summarized below.
3.1 LOCAL COMMUNITY COMMENTS
1.
At the public meeting a representative of the Ogden Nature Center which is
located adjacent to DDOU to the south, requested information on the
proposed length of time for complete cleanup of OU 2 and whether or not
complete cleanup would occur at OU 2 before the cleanup process at other
operable units was to begin.
-1-
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Dnou Resnonse. DDaU responded that they would be working on all four
operable units concurrently. The predicted time for remediation of au 2 is
approximately 3 years, although the time required for remediation is very
hard to predict at this stage.
3.2 TECHNICAL COMMENI'S
The only technical comments received were the EPA Comments on the Draft Final
Feasibility Study Report for au 2. A response to those comments is presented below.
1.
Page 2-2. Section 2.2.1.3. The FS does not discuss a reversal of the vertical
gradient in a future use scenario. This possibility remains a concern.
DDOU Resnonse. While a gradient reversal is a possibility, the possibility is
extremely remote during the time-frame in which the selected remedy is projected
to be completed. However, the potential for a gradient reversal is mentioned in
Section 1.0 of the Decision Summary. In addition, limitations on pumping rates of
municipal wells has been included as a possible institutional control in
Section 4.3.2.
2.
Page 2-9 (now 2.10), Section 2.3.1.6. No change was made in the statement
regarding the extent of trichloroethene (TCE) contamination. Given the lack of a
clear downward trend in the ground water concentration levels at au 2, the FS
should acknowledge that the current 5 IJ.g/l plume may increase in size before
remedies begin.
DDOU Response. This has been acknowledged in Section 3.1 of the Decision
Summary.
3.
Page 207, Sections 2.2.2.3. and 2.2.2.7. (now Sections 2.2.4.3. and 2.2.5.3.) The text
was reorganized, but the concern about chlordane migration into the ground water
was not addressed. The only chemical factor mentioned was a laboratory-based
partition coefficient.
Response. The term "immobile" was used in a relative sense, rather than the
absolute sense which has been interpreted by the reviewer. In other words,
chlordane can be expected to move at an extremely slow rate. This is not
contradicted by the presence of chlordane in ground water. The organic carbon
partition coefficient CKoc) value cited is the best indication, on a qualitative basis,
of how slowly chlordane will move toward ground water. The Koc value of 140,000
indicates that it sorbs very strongly to soi~ with any organic component. This may
not have been true in the past if spills in the pesticide mixing area introduced
chlordane with an organic carrier solvent.
-2-
Hazardous I
Informatio~
US EPA Re~
Philadelph}
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