United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R07-91/048
September 1991
Superfund
Record of Decision:
Hastings Ground Water
Contamination (OU1), NE
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50272-101
REPORT DOCUMENTATION 11. REPORTNO.
PAGE EPA/ROD/R07-91/048
1 ~
3. ReclpIenI'. Acce88lon No.
4. TItle and SW1I1Ie
SUPERFUND RECORD OF DECISION
Hastings Groundwater Contamination
Second Remedial Action
7. AUlhor(.)
5. Report Date
09/30/91
(Operable Unit 1), NE
6.
8. Perfonnlng Organllllllon Rept. No.
8. Perfonnlng OI'galnllllllon Name and Acldre..
10. ProjectlTalklWortI Unit No.
11. ContnIct(C) or Grant(O) No.
(C)
(0)
1 ~ Sponsoring Organization Name and Addre..
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report " Perfod Covered
Agency
800/000
14.
15. Supplementary Note.
16. Abatrect (Utnlt: 200 words)
The Hastings Groundwater Contamination site consists of localized areas where the
aquifer is contaminated with industrial chemicals, primarily VOCs, in the City of
Hastings, Adams County, Nebraska. This ROD addresses part of the Colorado Avenue
subsite, which is one of several Hasting Groundwater Contamination subsites. This
subsite consists of contaminated soil at three industrial properties, which was
addressed in a 1988 ROD as OU9, and a ground water contaminant plume approximately
1 mile long, which is the subject of this ROD and referred to as OU1. Land use in
the area is residential and industrial. The West Fork Big River lies to the north of
the site, and the site is characterized by a nearly flat ground surface with a gentle
slope to the southeast. The estimated 23,000 residents of Hastings obtain their
drinking water from a municipal system that taps into the underlying sole-source
aquifer. From 1967 to 1982, Dravo Corporation, the former owner of one of the
industrial properties, manufactured heating and air conditioning equipment on~ite and
discharged chlorinated solvents from its vapor degreasing process into sanitary and
storm sewers. Leaky sewer joints and discharge of storm drains to open ditches have
resulted in seepage of chlorinated compounds into the soil, and eventually into the
(See Attached Page)
17. Document Analysis L Descrlptora
Record of Decision - Hastings
Second Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (DCE,
Groundwater Contamination (Operable Unit 1), NE
PCE, TCE)
b. identifiers/Open-Ended Terms
c. CO&A 11 field/Group
18. AvailsbiHty Statement
18. Security Cis.. (ThIs Report)
None
20. Sea81ty Cia.. (ThIs Page)
None
21. No. of Page.
39
n PrIce
(See ANSl-Z38.18)
See Instructions on Reve-
I 212 (4.n)
(Formelty NTl5-35)
Department of Commerce
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EPA/ROD/R07-91/048
Hastings Groundwater Contamination (Operable Unit 1), NE
Second Remedial Action
Abstract (Continued)
aquifer. In 1983, after 30 years of nonuse, Hastings municipal well #18 was put back
online to pump ground water, but complaints from citizens about the odor and taste of
the water prompted the city to remove the well from service. In 1985, EPA investigated
onsite ground water contamination, including well #18, and identified onsite TCA, TCE,
and PCE contamination. Monitoring wells showed that the contaminant plume extended
about 1 mile eastward in the direction of ground water flow. The source of this
contamination was traced to Dravo's industrial facility. All affected wells were
subsequently shut down. A 1988 ROD addressed the soil component of the Colorado Avenue
subsite as OU9 and identified treatment using soil vapor and vacuum extraction
technologies, followed by treatment of extracted vapor using an activated carbon
system, and monitoring soil, ground water, and air. This ROD addresses the ground
water contamination component as OU1. Future RODs may address additional source
control measures, subsurface monitoring, ground water extraction and treatment,
wellhead protection and treatment, and provide institutional controls. The primary
contaminants of concern affecting the ground water are VOCs including DCE, PCE, and
TCE.
The selected remedial action for this interim remedy includes managing the contaminant
plume by pumping a number of pore volumes (5,550,000 gallons) of VOC-contaminated
ground water, treating the extracted ground water onsite using granular activated
carbon (with a contingency to use air stripping and emissions treatment, or UV
oxidation), and reusing or reinjecting the treated ground water; regenerating spent
carbon offsite; and monitoring ground water quality to measure effectiveness of the
interim action. The estimated present worth cost for this remedial action is
$6,061,000, which includes an annual O&M cost ranging from $269,000 to $767,000 for
10 years. EPA has increased the estimated remedial action timeframe for this interim
action to 15 years. The total present worth cost of the remedial action will increase
from the 10-year estimate primarily due to a longer period of O&M.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific ground water clean-up goals are
based on State and Federal MCLs, and include PCE 0.005 mg/l and TCE 0.005 mg/l.
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1.
. a
INTERIM ACTION RECORD OP DECIS~ON
DECLARATION
SITE NAME AND LOCATION
(Colorado Avenue Subsite)
Hastings Ground Water Contamination Site
Hastings, Nebraska
D.~.J
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim action for
the Colorado Avenue subsite, Hastings Ground Water contamination
site, Hastings, Nebraska, which was chosen in accordance with the
Comprehensive Environmental Response, Compensation and Liability
Act of 1980 (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA), and, to the extent
practicable, the National oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the
administrative record for this subsite. .
The state of Nebraska concurs with the selected remedy as an
interim action for this subsite.
ASSESSMENT OF THE SI~
Actual or threatened releases of hazardous substances from this
subsite, if not addressed'by implementing the response int~rim
action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, ,
or the environment.
DESCRIPTION OF THE SELECTED INTERIM REMEDY
This interim action Record of Decision (ROD) addresses
remediation of the ground water operable unit through extraction
and treatment of the contaminated ground water. This interim
action relates to the ground water operable unit and will reduce
the ~isk posed by the ground water contamination at the subsite. '
The Colorado Avenue subsite includes a ground water operable unit
(OU 1) and a source control operable unit (OU 9). Source control
remediation was addressed in a Record of Decision issued in
September 1988 which called for extraction of volatile
contaminants from the silt and sand unsaturated zones; monitoring
contaminants in the soils above the'aquifer; and monitoring of
ground water contamination at the subsite.
The major components of the selected interim remedy include:
.
Extraction of contaminated ground water to
achieve contaminant mass removal and plume
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.
t
.
containment, . .
Treatment of contaminated ground water by
granular activated carbon with contingencies
for air stripping and air emissions treatment
or use of ultraviolet oxidation,
Reinjection and/or use of the treated ground
water, and
.
.
Ground water monitoring to measure interim action
effectiveness.
STATUTORY DETERMINATIONS
This interim action is protective of' public health, welfare
and the environment, complies with action-specific and chemical-
specific Federal and state applicable or relevant and appropriate
requirements for this limited-scope action and is cost-effective.
As explained in the attached Decision Summary, the selected
interim action (remedy) and all contingency actions defined by
this Record of Decision will satisfy the statutory requirements
of CE~CLA. Although this interim action is not intended to fully
address the statutory mandate for permanence and treatment to the
maximum extent practicable, this interim action utilizes
. treatment and thus is in furtherance of that statutory mandate.
Because this action does not constitute a final remedy for the
subsite, the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as.a
principal element, although partially addressed in this remedy,
will be addressed by the final response action. Subsequent
actions are planned to address fully the threats posed by the
conditions at this subsite. Because this remedy will result in
hazardous substances remaining on site above health-based levels,
a review will be conducted to ensure that the remedy continues to
provide adequate protection of human health and the environment
within five (5) years after commencement of the remedial action.
Review of this subsite and of this remedy will be ongoing as EPA
continues to develop final remedial alternatives for the Colorado
Avenue subsite.
fj-30-CfI
Date
~/ I~:;J--
~~ i :'ay .
Regional Administrator
Region VII
Attachments:
Decision Summary
Responsiveness Summary
Administrative Record Index
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INTERIM ACTION RECORD OP DECISION
DECISION SUMMARY
HASTINGS GROUND WATER CONTAMINATION SITE
COLORADO AVENUE SUBSITB
HASTINGS, NEBRASKA
Prepared by:
o.s. Environmental Protection Agency
Region VII
Kansas City, Kansas
September 30, 1991
. - .
-
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Section
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
Interim Action Record of Decision
Decision Summary
Contents
Site Description
site History
. . . . . . . . .
. . . . . . .
. . .
. . . .
. . . . . . .
. . . .
Enforcement History. .
Community Relations
. . . . . . e. . .
. . . .
. . . . .
. . .
. . . .
. . .
Scope and Role of Operable Unit.
site Characteristics
. . . .
. . . .
. . . . .
. . . .
. . . . .
Summary of Site Risks.
. . . . .
. . . . .
. . .
Description of Alternatives.
. . . . .
. . . . .
Summary of Comparative Analysis of Alternatives.
Selected Remedy. . . . . . .
Statutory Determinations
. . . .
. . . . . .
. . . . . . .
. . . . .
Documentation of Significant Changes
. . . . . .
Figures:
1.
2.
3.
Tables:
4.
Site Location Map. . . . . . . . . . . . .
Colorado Avenue Subsite ..........
Total VOC Concentrations,
.september 1990 . . . . . . . . . . . . . . .
PI ume Map. . . . . . . . . . . . . . . . .
1.
Colorado Avenue Interim Action ~arget
Concentrations for Ground Water. . . . . .
Volatile organic Compounds. . . . . . . . .
Description of Alternatives. . . . . . . .
Comparative Analysis of Alternatives. .'. .
Action Specific State of Nebraska ARARs ..
Cost Summary for the Selected Remedy. . . .
2.
3.
4.
5.
6.
~
1
1
5
6
7
11
13
17
21
29
33
, 34
2
3
8
14
10
12
19
22-23
26
29
i
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, DECISION StJKHARy
COLORADO AVENUE St1BSITB,
BASTINGS GROUND WATER CONTAMINATION SITE
SITE DESCRIPTION
The Colorado Avenue subsite consists of contaminated soils
and a ground water contaminant plume of approximately one mile in
length and is one of several subsites that make up the larger
Hastings Ground W3ter Contamination Site in Hastings, Nebraska
(Figure 1). The subsite is part of the Central Industrial Area,
which contains commercial and industrial properties situated
along the Burlington-Northern Railroad right-of-way. The'
Colorado Avenue plume is moving eastward in Hastings and has
forced the City of Hastings to remove several contaminated wells
from service.
Soil contamination was found at three industrial properties
within the subsite. Dravo Corporation, former owner of one of the
industrial properties, discharged waste solvents from its vapor
degre~sing process into sewer lines at the Colorado Avenue
subsite. Residential properties are located immediately south
and east of the subsite. There are no wetlands.~r natural'
resources located within the subsite area.
The population within the City of Hastings is approximately
23,000. The City obtains all of its drinking water supply from
the municipal system which taps the Pleistocene-age ground water
aquifer. The contamination problems addressed by this interim
ROD pertain to this aquifer.
The City of Hastings and the surrounding area 'are
characterized by a nearly flat ground surface with a gentle slope
to the southeast. This topography is typical of the loess plains
that are present in south-central Nebraska. The majority of the
site region is uplands with narrow floodplains located along the
streams. Most of the area drains via tributaries to the West,
Fork Big Blue River. The areas east and south of the city limits
drain to the Little Blue River. This region of Nebraska is
blanketed by loess that is underlain by unconsolidated soils,
primarily sands and gravels, deposited during the Pleistocene and
Pliocene epochs. The soil deposits -range in thickness from 100
to 250 feet. ' '
SITE HISTORY
The ground water contamination addressed by this ROD ,was
discovered in 1983 when the City of Hastings attempted to put
Municipal Well M-18 back into servi~e. Well 18 is one half mile
east of the former Dravo facility on Colorado Avenue. The well
had not been used for approximately 30 years. Following startup,
1
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~ .\
LOCA TlON OF HASTINGS RECION
WITHIN THE STATE or NEBRASKA
17111 SIr..1
HASIINCS
R(QONAI.
«Nltlt
LEGEND
N_X
IIUIIIOPIIL
M8'CIItT
210.5-
COLORADO AVE.
SUBSITE
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- MAJOR H'QlWAY
f"'" "/;-W APPROXIMATE AREA OF SUBSlTE
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8
FIGURE 1
SITE LOCATION
MAP
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the city received complaints from citizens of a. foul taste and
odor from the water. The city promptly removed the well from
service. The Nebraska Department of Health (NDOH) and the
Nebraska Department of Environmental Control (NDEC) analyzed
samples collected from M-18 in 1983 and 1984 and detected
elevated levels of the compounds l,l,l-trichloroethane (TCA),
trichloroethene (TCE), and tetrachloroethene (PCE). These
compounds belong to a general class of compounds referred to as
volatile organic compounds (VOCs). VOCs are those chemicals that
tend t~ evaporate when exposed to air. The NDOH and NDEC a180
detected elevated levels of these and other VOCs in three other
municipal wells in Hastings. These wells, M-3, M-10, and M-12,
were taken out of service.
Due to risks posed by the ground water contamination in the
Hastings area, EPA identified the area as a proposed Superfund
site in 1984 and placed it on the National Priorities List (NPL)
in 1986. The NPL is a nationwide list of hazardous waste sites
that are eligible for investigation and remediation under the
Superfund program.
In 1985, EPA began an investigation of the contamination
detected in Municipal Well M-18 as part of a larger overall
investigation of ground water contamination problems in the
Hastings area. Evidence collected during the investigation
indicates that the TCA, TCE, and PCE contamination in Well M-18
originated in the general vicinity of the former Dravo
Corporation industrial facility located at 108 South Colorado
Avenue. This facility is now owned by Marshalltown Instruments
Company. Evidence indicates that the chlorinated solvents- (TCE,
TCA, and PCE) were used at the industrial facility located at 108
S. Colorado Avenue and disposed of in sanitary and storm sewers -
during the 1960s and 1970s when Dravo occupied the facility. Due
to leakage from joints in the sewers and the discharge of the
storm sewer to an open ditch, the contaminants seeped through the-
soil and reached the Pleistocene-age aquifer underlying the
Colorado Avenue subsite.
The EPA installed ground water monitoring wells at the
subsite (Figure 2). Since 1985, many water quality sampling
everits have occurred. Existing wells and E~A-installed wells
have bee~ sampled. The EPA analyzed samples of soil collected
from the areas around -the suspected leaking sewers. These soil
samples showed elevated levels of volatile organic chemicals
including the chlorinated solvents named above. Due to these
findings, EPA designated the ground water contamination and soil
contamination at the subsite as two projects or operable units.
In September 1988, EPA signed a Record of Decision which
addressed the soil contamination at the subsite. The EPA issued
a Unilateral Administrative Order to Dravo Corporation and
Marshalltown Instruments in 1990. The order requires the
respondents to proceed with the soils cleanup project.
3
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.LEGEND
EPA MONITORING WEll
MUNICIPAL WEll
STATE MONITORING WEll
FIGURE 2
COLORADO AVENUE
SUBSITE
o p,o' JOf"
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~
ENFORCEMENT HISTORY
In September 1985, general notice letters were issued to
potentially responsible parties (PRPs) connected with the
Hastings Ground Water Contamination site. PRPs are those
individuals or businesses potentially responsible for the
contamination at a site. The first meeting held with PRPs
for the Hastings Ground Water contamination site was held in
October, 1985, at which time the PRPs were asked to perform a
Remedial Investigation/Feasibility Study (RI/FS) for the entire
Hastings site. No. proposals to undertake the RI/FS wpre made by ,
the PRPs. The.EPA proceeded with the remedial investigations at
selected subsites, including the Colorado Avenue subsite.
In December 1986, EPA issued general notice letters which
notified Dravo Corporation and.Marshalltown Instruments of their
potential liability at the Colorado Avenue subsite. In January
1987, EPA held a PRP meeting to review EPA's findings to date.
Dravo Corporation and Marshalltown Instruments were asked to
complete the RI/FS investigations. Neither party made an offer.
During meetings held with the PRPs in 1987, EPA requested that
the needed removal interim actions be done by the PRPs. The PRPs
refused to complete the RI/FS and did not agree to undertake any
removal actions. The first offer made to EPA was by Cravo
Corporation following the issuance of a special notice letter on
August 25, 1987, and the 60-day moratorium which followed.
Pursuant to Section 122(e) of CERCLA, the special notice letter
granted a period of negotiation in an attempt to "facilitate an
agreement" with Dravo to expedite remedial action. section
122(e) (2) (B) of the statute allows 60 days for the liable party
to make a good faith offer to perform the needed work as outlined.
by EPA. Instead of offering to perform the work, Dravo asked to
be considered for a de minimis settlement as defined in CERCLA,
section 122. section 122(g) statutorily authorizes de minimis
settlements to efficiently resolve cases in which the PRP
contributed small amounts of hazardous substances with minimal
toxicity to the site or the PRP is the site owner but did not
introduce the hazardous substances or contribute to the release.
The Agency informed Dravo that it could not accept its offer as
it did not meet the requisite statutory criteria for such a
settlement., Dravo did not counter-offer after receiving the.
Agency's response. Dravo and Marshalltown were requested to sign
an order pursuant to Section 106 of .CERCLA in .1988 which would
have required them, among other things, to implement a source
control response action. In April 1988, Marshalltown requested
its status as a liable party be reviewed and it submitted.
documents to support its position that it had not disposed of TCA
at its facility. The Agency reviewed Marshalltown's status
pursuant to this request and determined that Marshalltown was not
eligible for a CERCLA Section 107(b) (3) defense which states that
there is no l~ability for persons who can prove the release or
5
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\
threat of release of hazardous substances resulted from specific
occurrences caused by an act of God, an act of war, or an act or
omission of a third party under certain conditions. Marshalltown
had an indirect contractual relationship with one (another party)
who had disposed of TCA at the subsite and Marshalltown had
reason to know of the disposal, as that term is defined under
CERCLA, when it purchased the property. .
In April 1988, the PRPs for the Hastings subsites formed a
steering committee to work with EPA in developing the most
. efficient and cost-effective remedial actions. On April 13,
1988, the Hastings PRPs met with EPA and offered to undertake a
pilot study of soil vapor extraction (SVE), the preferred
alternative to remediate soil 'contamination at the subsite. The
Agency requested that the PRPs submit a proposal. On June 8,
June 28, and July 22, 1988, EPA met with the PRPs to discuss
pilot scale testing for source control at the Colorado Avenue
subsite. A draft proposal by EPA concerning Colorado Avenue was
discussed on July 22, 1988, and negotiations continued in August
1988. The source control ROD was issued by EPA in September
1988. A pilot study of the SVE process was carried out by the
PRPs pursuant to an order issued under section 106 of CERCLA.
The pilot study, which began in August 1989 and ended in December
1989, was successful in removing VOCs from the soil at the
subsite. Data from the pilot study are providing the basis for
designing a full-scale SVE remedial action project at the
subsite. The EPA asked the PRPs to undertake the full-scale SVE
project, but Dravo and Marshalltown failed to submit a good faith
offer as requested. In September 1990, EPA issued a Unilateral
Administrative Order pursuant to section 106 of CERCLA ordering
them to implement the SVE remedial action at the Colorado Avenue
subsite. Design work pursuant to the Unilateral Administrative
Order is currently proceeding.
In December 1990 following continued dialogue with the Dravo
and Marshalltown, EPA sent the PRPs a notice letter requesting
that they undertake a Feasibility Study (FS) for the ground water
operable unit. Dravo and Marshalltown declined to undertake the
FS. The EPA completed the FS in June 1991.
.
COMMUNITY RELATIONS
Community relations activities for the Hastings Ground Water
Contamination site were initiated by EPA in 1984. Early
community relations activities included meeting with City and
state officials to discuss the site (December 1984), conducting,
interviews with local officials and interested residents
(February 1985), establishing an information repository (February
1985), and preparing a Community Relations Plan (October 1985).
Since December 1984, EPA has conducted periodic meetings with
6
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.
.
Hastings officials to update them regarding site work and
findings. The Community Relations Plan was revised and updated
in January 1988 and in January 1990 to reflect new community
concerns and site activities.
Information'on the Colorado Avenue subsite has been mailed
to all parties on the mailing list for the Hastings Ground Water
Contamination site. Specific community relations activities that
have been conducted regarding the subsite include distributing
fact sheets updating citizens on subsite activities, announcing
and conducting public meetings, and summarizing preferred
alternatives. Public meetings at which information regarding the
Colorado Avenue subsite has been made available include the
following:
On November 22, 1985, a public meeting was held to
present site information and plans for the RI/FS and
to respond to citizens' questions 1
On March 5, 1988, a public meeting was held to discuss
the preferred alternatives for source control and to .
receive citizens' comments and questions1 and
On July 18, 1991, a public meeting was held to'discuss
the preferred alternatives for ground water
remediation and to receive citizens' comments and
questions.
Following release of the Engineering Evaluation/Cost
Analysis (EE/CA) in February 1988 for source control at the
Colorado Avenue subsite, EPA held a public. comment period from
February 3 to April 30, 1988. Agency responses to public
comments were included in the Responsiveness Summary portion of
the Record of Decision issued in september 1988 for soil cleanup'
at the subsite.' .
.
.
'0 .
. The EPA also held a public comment period from June 25 to
August 23, 1991, following the release of the Proposed Plan which
identified measures to mitigate the ground water contamination at
the COlorado Avenue subsite. Agency responses to these comments
are included in the Responsiveness Summary portion of this Record
of Decision. ."
SCOPE AND ROLE OF OPERABLE UNIT
. ,
This interim action will involve pumping the contaminated
ground water out of the contaminated area in the aquifer and
treating the water to remove the contaminants. This' will provide
for. reduction in risk to human health from potential exposure to
the contaminants, and prevent environmental degradation due to
further spread of the highly contaminated portion of the plume.
The reduction in risk will be achieved by removal of contaminant
mass, thereby reducing the concentrations of the chemicals in
ground water (area shown in Figure 3). The Colorado Avenue'
7
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.. .....,.............. .. . I' .......-....... .........,. ...... ... ...-..-.-.-.-- ..- '..."""" . ................
I I
! .....! 1
J... .... ~~ ;~ .J_J
! TCA 145 .
; onos 1 79
TOTAl 4400
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; TCA 5 U ~' Duncon PeE 5 U
OTHERS 50 Fleld TCA 5 U
; TO'IAl 12 . .,.-.....- .-1 -"-imOS 10.
..-3; ." '''''''''''''!:~;~ J :';~~~ .~ ~ i g tOTAl ~
~ ~~ J.................. .~ ~ ~.......... . 0ntE~ ~= ~ 0:1=.-. --_......~
"";cA " J ~ 120 ; roTAl 24000"-- --Ha,m --13
O1MERS 50 TOTAl 8640 i . TeE 217 ~
TOTAl 218 ,.; Po'" PeE . "
. . I TCA H
. . cmos !IO
I TO'IAl 280
NOTE:
-If e UNDETECTED AT NOTED
CONCENTRATION
-.r = ESTIMATED VAlUE
, .
, .
141" ~I'I!..I:
.. i . . .'...
I
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'J'd 51,....1'
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"
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a.li...............,......
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,
..
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\ ! PeE 5 U: ! OW-&!!
........; ..... ....~~ ;, U"'''''I '''''..m. . TCE 38 J
! TOTAl 58 ,; . PeE 5 U
TCA 5 U
7"d_~.I,.,:~I~._._._..J OW-liD m;~ ~
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...I.... ..... . ...... ............_....~ : U
i
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... ! '..!II. SI,....I:
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cmIERS 50
. .._..~~.~.'.~........ I...
" I
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"'.,
,
'.'.-..--.. ..... .J
.-2
TeE 1'1:)00 ..
PeE 900 J
TCA 71::<1 J
OTHERS -"I'" i
TO'IAL ~''OO'''r'''''''!'
i
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IA SI'..el ;
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\: 9 51,....1 I ......... .......... ......... .-.....-... ""1"" '"''
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;!' ~"l" "':''''''''''-1'' """'"'''''' ; T'''-' j 11. .! I
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;j ! ..m J'" ..,.. 0 I u; ! X I 1.1 ;
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.
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LEGEND
EPA MONITORING' WELL ~ CONCENTRATIONS ARE
MUNICIPAL WELL POSTED IN IJ.g/1
STATE MONITORING WELL,
o 1 ';0' "00'
I . .
~;(;AI.I.
fino'
I
......, ......,.
.
i
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crf-4S
TC[D
- PCE5U
TCA5U
O'JH£RS 50
TOTAl 11
.;
>
0(
E
Q"-'''''''''''''''''''''''''''-'
"-""-"""''''''
Burlington
Northe,n
RR
......................... ""'.-$0"'-- '--'(ri-:1iS-'
TeE 5 U TeE 5 U fi'\
. PeE5U PeE5U \V
~. TCA5U TCA5U
0( .1' O'JH£RS so: .; cmos 50
.~ . TOTAl !!8;",,,,,,,,,-,~, '''''1OtAl III.....
~i ! l. ,-~
- ,U L..- -- ...~ -----.--- \/-~:1---
r.'-"'"''
C=. .....-....-..
FIGURE 3
TOTAL VOC CONCENTRATIONS
SEPTEMBER, 1990
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.
.
.
.
subsite includes a source control operable unit (OU 9) and a
ground water operable unit (OU 1). Source control remediation
was addressed in a Record of Decision issued in September 1988
which called for extraction of volatile contaminants from the
silt and sand unsaturated zoneS1 monitoring contaminants in the
soils above the aquifer1 and monitoring of ground water
contamination at the subsite. The EPA issued a Unilateral
Administrative Order to the liable parties for the source control
cleanup and testing of the soils, and proceeded with data
collection for the ground water operable unit.
This ROD is consistent, to the extent practicable, with the
National oil and Hazardous Substances Pollution Contingency Plan
(NCP), an EPA regulation which establishes procedures for the
selection of response actions. According to the NCP, an interim
action is appropriate where a contamination problem will become
worse if left unaddressed, and the interim action will not be
inconsistent with any final remedial action. Because a final
remedial action will follow, the interim action need not meet all
federal and state standards for clean up of the aquifer, nor must
it provide a permanent solution to the contamination problems.
In accordance with the NCP, the interim ~ction for the Colorado
Avenue subsite will complement and be consistent with the final
remedy for the subsite because the interim action and the final
action must be permanent, effective and employ treatment to the
extent possible. This is explained further in EPA's FS. The
final remedy may include additional source control measures,
subsurface monitoring, ground water extraction and treatment
options, well head protection and treatment and institutional
controls. Any future actions will be considered and selected
based on the requirements of the NCP and remedy selection process
as described herein. .
This interim action is fully consistent with all anticipated
future site work. This statement is based on the fact that
pumping and treatment is the only technology currently available
which has been implemented at enough sites to be considered
applicable to the conditions at the Hastings site.
The subsite interim actions will have an interim goal to
achieve containment of the plume and reduct!on of c9ntaminant
concentrations within the plume at levels corresponding to no
more than an estimated one cancer case in a population of 10,000
based on an assumed 30-year exposure period due to any of the
.contaminants present (for further explanation of excess cancer
risks, see "Summary of site Risks"). The contaminant levels
which correspond to one in 10,000 (also known as 1 x 10-4) cancer
risk due to exposure to the contaminants of concern at the
subsite are shown in Table 1. Also shown are the Maximum
Contaminant Levels (MCLs) for the contaminants which will be the
goal for any final remedy. The EPA will ensure that any final
remedial action will be protective of human health and the.
9
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. -
Colorado
Table 1
Avenue Interim Action Target Concentrations for ~round Water
Health-Baaed Riak Le..la and Chemical-Specific ARAR8 (MCLe)
Of Compounda Detected in Gro~d Water
10-4 Cancer Safe Drinking
Water Act
Risk (SDWA)
Due to 30- Haximum
Year Contaminant
Contaminant Exposure- Level (HCL) Nebraska HCL SDWA MCLG"
mg/1 mg/1 mg/1 mg/1
1,1-Dichloroethene (DeE) 0.005 0.007 0.007 0.007
Tetrachloroethene (PCE) 0.150 0.005 0.005 0
1, 1, l-Trichloroethane N/A 0.200 0.200 0.200
(TCA)
Trichloroethene (TCE) 0.290 0.005 0.005 0
1,2-Dichloroethane 0.045 0.005 0.005 0
(1, 2-:-DCA)
DichloromethaneO 0.900 0.005 0.005 0
-Reference: Colorado Avenue Ground Water Interim Action Operable Unit Feasibility Study, June 1991.
~aximum Contaminant Level Goal.
eAlso known as Methylene Chloride
Note: All value~ above are shown in ppm, 1 ppm - 1 milligram per. liter -.1 mg/l
(l.mg/l - 1,000 micrograms per liter (ug/l) where 1 ug/l is equivalent to 1 ppb)
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,
environment relative to contamination emanating from the Colorado
Avenue subsite. currently, contaminants in the ground water are
not being consumed by humans since affected municipal wells are
out of service. No private domestic water supply wells are
currently in use within the city. Testing results from samples
collected during EPA's on-going investigations are supplied to
the City and Nebraska Department of Health (NDOH). If future
sampling indicates the chemicals have migrated to other supply
wells, the NDOH is authorized under the Safe Drinking Water Act
to respond to this problem in order to ensure continued public
access to safe drinking water supplies. However, their options
~re limited considering the extent of the plume. '
SITE CHARACTERISTICS
Ground water in the Pleistocene-age ground water aquifer,
located underneath the subsite, is generally encountered at a
depth of approximately 120 feet. This aquifer is the sole source
of drinking water for the Hastings area and is used extensively
for industrial and irrigation purposes.
Regional ground water flows east-southeast with local
deviations where ground water intersects streams and pumping
wells. The ground water flow rate is approximately one foot per
day. The only places in south-central Nebraska where natural
ground water discharge occurs are the stretches of stream valleys
incised below the water table. The largest of these streams are
the Platte, Big Blue, Little Blue, and Republican Rivers. . High-
yield municipal and irrigation wells and lower yield private
wells account for most of the balance of the discharge in the
area.
Since 1985, EPA has installed ground water monitoring wells
at several of the subsites which make up the Hastings Ground
Water contamination Site. The EPA has conducted quarterly ground
water sampling. EPA installed ground water monitoring wells at
the Colorado Avenue subsite from 1986 to 1989 (Figure 2). Table
2 shows the chemicals detected in the vicinity of the subsite,
the lifetime or 30-year incremental cancer risks associated with'
exposure to these chemicals and their frequency of detection. As
indicated, 'EPA has detected elevated levels.of a number of VOCs
in the ground water including trichloroethene (TCE), and 1,1,1-
trichloroethane (TCA), tetrachloroethene (PCE), and 1,1-
dichloroethene (DCE). At the subsite, TCE, TCA, and PCE have
been detected in the greatest number of ground water monitoring
wells, and at the highest levels. Also present in the ground'
water are 1,1-dichloroethene and 1,1 and 1,2-dichloroethane,
which form when TCE, TCA, and PCE break down. ~he apparent
original source of these VOCs was Dravo's industrial facility on
Colorado Avenue.
~
11
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~a!>le 2
Volatile Orqanic Compo~ Detected iA G~oUDd .ate~
Colo~ado AYeDue Sub.ite
1.85 to lJJO
ComPound
Balogenate4 Volatil..
2'arqet
Concentration
for 1 a 10"
Cancer Risk
(uc:r/l)
2'richloroethene
l,l,l-Trichloroethane
Tetrachloroethene
l,1,2,2-Tetrachloroethane
290
150
l,l-Dichloroethene
1,2-Dichloroethene
l,l-Dichloroethane
1,2-Dichloroethane
Chloroform
Chloroethane
Bromodichloromethane
Methylene Chloride
5
(total)
45
94
31
900
31
Carbon Tetrachloride
Highest
Concentration
(uc:r/l)
Location of
Highest Detected
Concentration
55,000
3,000 J
1,300
530
400 J
630 J
400 J
42
MW-2
MW-22
. MW-2
MM-2
MM-22
MM-22
MM-22
MW-22
26
14J
0.7 J
2,200
100
MW-4
MW-22
MW-IO
MW-2
MW-IO
Volatile Aromatic. - F~om Nearby Secon4 Street Sub.ite
Toluene
Benzene
Acetone
Xylenes (total
Ethyl Benzene
Styrene
140
260
Notes:
15,000 J
15,000 J
8,000
5,200 J
3,200
7,800 J
MW-9
MW-9
MW-9
MW-9
MW-9
MW-9
2 Database of wells (Table B-1 of FS) depicted on Figure 2.
2 Risk numbers listed only for potential carcinogens.
Source: Colorado Avenue Feasibility Study Report.
J J - estimated concentration
. Carbon tetrachloride is not attributable to Colorado Avenue.
I Volatile aromatic compounds .~re not attributable to Colorado Avenue.
Number of
Locations
Detected
19
15
13
2
9
9
7
3
3
2
1
B
8
14
8
9
7
6
2
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.
VOCs remaining in the unsaturated zone above the water table
provide a continuing source of ground water contamination. Vapor
phase contaminants migrate through the soil pore spaces downward
to the ground water since the contaminant vapors are heavier than
air. Control of this source area was addressed by the 1988 ROD
for the soils operable unit.
The EPA also detected elevated levels of benzene in a
monitoring well north of the subsite, away from the direction of
ground water flow, and concluded that the benzene contamination
was coming from a source other than the Colorado Avenue property.
After identifying the source area north of the Burlinqton- '
Northern Railroad tracks, EPA designated that area as the Second
Street subsite. The EPA has conducted soil sampling to further
characterize the aromatic chemical contamination found at the
Second Street subsite.
Based on the results from the September 1990 sampling
(Figures 3 and 4), consideration of seasonal trends of
concentrations of the various constituents in the ground water,
and the concentrations corresponding to the 1 x 10 -4 cancer risk
for the chemicals of concern, EPA has determined that the ground
water requires a response action. The volume of ground water to
be addressed by the interim action based on preliminary estimates
is approximately 550 million gallons, and contains approximately
18,800 pounds of TCE.
SUMMARY OF SITE RISKS
The Superfund law requires EPA to seek permanent solutions
to protect human health and the environment from hazardous
chemicals. "These solutions provide for removal, treatment, or
containment of dangerous chemicals so that any remaining
contamination does not pose a health risk to anyone who might
come into contact with it. The EPA has determined that an
interim action is needed at the Colorado Avenue subsite based on
its evaluation of the contamination in the ground water.
The EPA has evaluated potential risks to human health posed
by exposure to ground water contamination ifno'remedial action
were taken. This approach attempts to answer the question of
what could occur if no action were taken at a site. This
evaluation is known as a baseline-risk assessment. The Baseline
Risk Assessment, which is a portion of the FS, is based on the
results of statistical analysis of water samples taken at the
subsite from 1985 to 1990 and evaluates potential carcinogenic
and noncarcinogenic risks which exist at the site. The results
presented here apply to the 1991 Base~ine Risk ~ssessment ,study,
as it was based on a more complete set of ground water monitoring
results than the 1987 study appearing in "Report of
Investigation, Hastings Ground Water contamination Site, Colorado
Avenue Subs~te", 1987.
13
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I
. I
.......14Ih ~I~~~.I..;........... M.wli'2''''''.. ......,...-.............. ...............
I I -! I I
........>,~d.. .~I 'eel :..............~... .-.. ...-.. .. ......... ... .........1............: .
i . I
I ,
I I
..t...........
,
o.
>
go m,
.. ....... .............
u
~ iii:
'u ~:
o ..;
n O'
c I"""'''''''''.'''''''..
.~ !
~
........ "n,-...
""'u.. ,..........
1--- ---.-
. . ..... ................j............. "...."'"'1"'..."'-"-"". ...............................-...-...:...... .....................:.....................
I! .
I' ~
! ore .
~ ....-...:............. ."''''''''''--''. ..-...................
.~...._..._....__...........- "'----.....
i
(................-.
I
,
"""""-'-""""'0'
~
',....n...'"''''''''
I :
, ,
! I
i . J
;2nd SI,eel:
; i
ihl SI,eell
!... ..... -...in..
;
,
I
......t...........
!
I
......\ ......................
Burlin910n
Northe.n
RR
. .;
........,.-.- ..........._~
0(
/'"..-........
(
..--..../
( ,............-......-.
-......--.
.,"""""'''''''''.. \
l . r.."':...
I .
'.........:'
.............- ..........._, ""''''',,.,,'''''-'_.., '.""".l""'.. """'..'.'"
. ..., i
. """'"
"
-
.*
...
-220-
--70--
FIGURE 4
PLUME MAP
DATA FROM SEPTEMBER, 1990
o 150' .JOO'
I . .
SCALE
600'
I
NOTE:
8lf' = NOT DETECTED AT NOTED
CONCENTRATION
. 8 J' = ESTIMATED VALUE
8 A8 = DEPTH - AVERAGED VALUE
,.
l'r(M 1\ '.
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. .'
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In preparing the Baseline Risk Assessment, EPA,first
determined the most likely ways in which community members might
come into contact with site-related chemicals. "The EPA
determined that residents living near the Colorado Avenue subsite
might be exposed to contaminants in ground water if they drink
ground water, come into direct contact with the ground water
while bathing, or if they inhale ground water vapors while
cooking or showering. The EPA concluded that three chemicals in
the ground water were the principle concern at the Colorado
Avenue subsite and might pose a health risk of concern to
resid6nts who'use the ground water. These chemicals are DCE,
PCE, and TCE. The interim action will focus on reducing risks to
human health and the environment resulting from exposure to these
chemicals. '
The EPA considers that exposure to a chemical presents an
unacceptable cancer risk if it leads to more than one additional
case of cancer for every 10,000 people exposed to it over a 30-
year period. The term cancer risk sometimes is referred to as
"excess cancer risk" because it is the number of additional cases
above the average number of cases that are expected to occur ~n
the general population if the chemicals are not present. The
EPA's assessment of the Colorado Avenue subsite determined that
the single exposure to the DCE concentrations detected might lead
to 10 additional cancer cases per 10,000 people; exposure to the
PCE concentrations detected might lead to two additional cancer
cases for every 10,000 people exposed; and exposure to the TCE
concentrations detected might lead to 100 additional cancer cases
per 10,000 people over a 30-year period. These cancer risks are
additive for the chemicals presenting an exposure potential. In
addition to estimating potential carcinogenic health effects, the
Baseline Risk Assessment evaluated potential non-carcinogenic
health effects caused by site-related chemicals. The EPA
determined that TCE is the primary chemical detected in the
ground water that might cause harmful non-carcinogenic health
effects to nearby residents using the ground water. The fact
that these risk levels are found at the subsite prompted EPA to
evaluate plume management alternatives for an interim action.
The interim action is needed to achieve significant risk
reduction while a final remedial solution is being developed.
.As a result of releases of hazardous substances from the
Colorado Avenue subsite into the ,environment, these four
chemicals below are found in the ground water at concentrations
which far exceed human health-based criteria. The EPA's
description of health effects inclu4ing classification for
'15
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. .
.
"
varying levels of carcinogenicity are provided below for the
principal contaminants of concern:' .
..
.
Trichloroethene (TCE) is categorized as group B-2,
Probable Human Carcinogen for both inhalation and oral
intake routes, based upon sufficient evidence of
carcinogenicity in animals, but inadequate evidence of
carcinogenicity in humans. Acute exposure to TCE may
cause headaches, vertigo, visual disturbance, tremors,
nausea, vomiting, eye irritation, dermatitis, cardiac
arrhythmias, and paresthesia. Chronic exposure may
irreversibly damage the respiratory system, heart,
liver, kidneys, and central nervous system.
1,1,1-Trichloroethane (TCA) is categorized as group D,
Not Classified, based upon inadequate evidence of
carcinogenicity in animals. TCA is still unclassified
in the Integrated Risk Information System (IRIS) as of
June 1991. Acute exposure to TCA may cause headaches,
lassitude, central nervous system depression, poor
equilibrium, eye irritation, dermatitis, and cardiac
arrhythmias. . Chronic exposure may cause irreversible
damage to the central nervous system, cardiovascular
system, and eyes.
.
.
Tetrachloroethene (PCE) is categorized as group B-2,
Probable Human Carcinogen for both the inhalation and
oral intake routes, based upon sufficient evidence of
carcinogenicity in animals, but inadequate evidence of
carcinogenicity in humans. Acute exposure to PCE may
cause irritation to the eyes, nose, and throat: finger
tremors: flushed face and neck: vertigo, dizziness:
skin erythema: liver damage: and mental confusion.
Chronic exposure may lead to irreversible damage of
the liver, kidneys, eyes, upper respiratory system,
and central nervous system.
.
l,l-Dichloroethene (DCE) is categorized as group C,
possible Human Carcinogen for both inhalation and oral
intake routes, based upon limited evidence of
carcinogenicity in animals. Acute exposure to DCE may
cause irritation to the skin and ~ucous membranes, .
headaches, and liver and kidney damage. Chronic
exposure may lead to irreversible damage of the liver
and kidneys. It is considered an experimental
. mutagen.
~Reference: EPA Weight-of-Evidence Categories fo~ Potential
Carcinogens. (Exhibit B-2). "Superfund Public Health Evaluation
Manual."
16
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"
The interim action will reduce contaminant concentrations in
the aquifer to a level at or below that which will present a
cancer risk of 1 x 10-', (or a risk of less than one cancer case
in 10,000 due to exposure to contamination) by removing
'contaminants from the ground water. This will provide a
significant level of protectiveness to human health. In addition
to risk reduction, the interim action will prevent furthe~
degradation of the environment by plume containment. Pumping
wells will be installed to capture contaminants before they
migrate further eastward with the flow of ~e ground water.
DESCRIPTION OF ALTERNATIVES.
Remedial alternatives for ground water interim actions Mere
developed in order to mitigate further degradation and to meet
. the objectives of CERCLA and, to the extent practicable, the NCP.
The process used to evaluate alternatives for the Colorado Avenue
subsite is discussed in the FS. CERCLA and the NCP require that
each alternative developed, including the no-action alternative,
be evaluated first with respect to two threshold criteria:
overall protection of human health and the environment1 and
compliance with applicable or relevant and appropriate
environmental requirements (ARARs). Seven additional criteria
are considered as a means to compare the alternatives. These
include: long-term effectiveness; reduction of toxicity,
mobility or volume1 short-term effectiveness: implementability:
cost1 state acceptance1 and community acceptance.
The remedial alternatives described in the Feasibility study
fall into three general categories. These are no action,
institutional' controls, and plume management. Each plume
,m~nagement alternative includes mass removal of contaminated
ground water and containment of the contaminant plume. Capital
and Operation & Maintenance (O&M) cost estimates are presented in
Table 6. The following summary will focus on significant
evaluation criteria as they relate to the alternatives developed
for the Colorado Avenue subsite. '
No Action
The NCP requires that the no action alternative be carried
forward for detailed analysis and serve as ~ basis against which
the other remedial alternatives can.be compared. Under the no
action alternative, the subsite would remain in its present
condition. The potential for exposure of the community to
contaminant levels exceeding health standards still would exist. .
The no action alternative fails to meet ARARs, or satisfy
remedial action goals for the subsite.to rapidly ,reduce human
health risk. The alternative does not,prevent further degradation
of ground water or reduce risks.associated with exposure to
ground water. ~
17
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. '
Institutional Control.
Institutional controls are actions which lower the risk or
exposure to contamination through physical and/or legal means.
For areas affected by the Colorado Avenue plume, institutional
controls would include'access restrictions to limit future
development and water well installation. Institutional controls
can be effective in preventing City residents from ingesting,
contaminated water from onsite wells. Ground water monitoring
could be used as a means primarily to warn potential future users
of the aquifer. Institutional con~rols have been implemented in
the City of Hastings since 1984 to prevent pumping 'of
contaminated water into the city water distribution system. Four
City of Hastings wells have been removed from service because of
ground water contamination. City ordinances are in place that
prohibit private parties from drilling drinking water wells in
the city. ,Although institutional controls have been effective in
preventing public exposure to contaminated ground water, this
alternative will not attain ARARs, satisfy the remedial action
objectives established, or compare favorably with the plume
management alternatives when evaluated in terms of the nine
criteria evaluation.
Plume Management Alternatives
The plume management alternatives differ by ground water
treatment process and the treated water discharge options. Each
plume management alternative includes mass removal and
containment of the contaminated ground water to prevent
contaminant plume migration and further contamination of the area
ground water. The ground water treatment processes considered
were air stripping with granular activated carbon (GAC) with
either on- or off-site regeneration of the carbon liquid phase
GAC, and ultraviolet (UV) photooxidation. The treated water
discharge options considered were surface discharge, reinjection,
and pumping to the city (or industrial) water supply. Each of
these processes is described in Table 3.
. _In order to compare mass removal and containment
alternatives on a common cost basis, an estimate was made of the
ground water pumping rate that would have tQ be used to achieve.
the target concentration (less than 290 ug/l for TCE for a 1 x
10-' risk level) in a 10-year period., Preliminary analyses
indicated that the affected volume of ground water, approximately
550 million gallons, could be circulated eight times through the
aquifer over 10 years at a flow rate of 1,000 gallons per minute,
and that this would be sufficient to reach the interim action
cleanup level. This flow rate and duration was considered in an
effort to estimate costs of the ground water alternatives. other.
pumping rates are possible. A low rate t~at would only control
the spread of 'ground water but not aggressively remove
18
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"
!'ab18 3
.De.crlptlOD of Alt8rnatl...
EPA's selected remedy for the Colorado Avenue aubsite appears below in bold-italic
typeface. EPA identified optional components which are indicated by asterisks.
PLUME MAN~
"... ~val and Conta1nm&at
2'be contaminated ground water 1. pumped to tbe .urface .to prevent tbe contam1.nant
1'1&l.1l:I8 from .preading and furtber contam1.nating tbe ground water. Well. would be
l.n.ta.1.1ed l.n tbe contaminant plume and ground water would be pWllpffd to tbe .urfaee
and treated. 2'be PUlDpl.ng proce.. Jonr. tbe ground vater le9'8l J.n tbe area. n,t.
force. ground water from tbe .urroundJ.ng ana to flow l.nto tbe ar.a w1t..b tbe Jonncf.
water Je1'81.. 2'be l.ncoml.ng water dJ..place. tbe contam1.nant pllllD8 and reduce.
contam1.nant concentraU=-.
GROUND WATER. TREATM!:N'.r
Z,1qu1d 'ba.e Granular AcUvated Carboa (GAe)
W.1tb l1qu1d pba.e GAe, tbe ground water 1. pa..ed O9'8r a bed of granular act1".ted
carbon to remove conta.m1nant.. 2'be carbon t..ben would be tran.port.ed off-.1te and
tbe cbem1cal. remo1'8d from 1t u.1ng an DA-appro1'8d tecbn1que .0 tbat t..be carbon
could be u.ed agal.n. .
.Air Stripping
An air stripper transports the contaminated ground water through.a pipeline to the
top of "the air stripper tower where the water is released. As the water falls down
over a group of loosely-packed plastic balls, a fan blows air up through the water.
The blowing air forces organic comp9unds in the water to evaporate. Before being
released to the atmosphere, the evaporated chemicals would be treated by vapor phase
granulated carbon.
Vapor Phase Granular Activated Carbon (GAC) with On- or Off-Site Regeneration
This process involves passing the contaminated ai-r over a bed of specially-
treated carbon, to which the evaporated chemicals cling. The treated air would
be released to the atmosphere, and the carbon is transported off-site and treated
to remove the chemicals clinging to it. On-site regeneration would include
heating the carbon to force the chemicals to evaporate into steam. The steam
would be cooled to water, which then would be treated to remove the chemicals.
The chemicals would be disposed of or destroyed in an environmentally safe
manner. After the chemicals are removed from the carbon in the regeneration
process, the carbon can be used again.
.Ultraviolet Photooxidation
UV photooxidation requires a treatment tank and involves adding certain chemicals
to the contaminated ground water and exposing the water to ultraviolet light. This
process converts the contaminants into harmless compounds, carbon dioxide, inorganic
chloride, and water. '.
TREATED 'WATER. nISCHARGE
Re1nject1on ';
f'r.ated ground water 1. re1njected througb a p1peHne and 1njecUon .,..1.1. l.nto tbe
aqu.1fer we.t of tbe .ub.1te, up.tre&lll of tbe contaminant plume or ot..ber appr01'8d
JocaUon. .
Surface nischarge - .
The. treated ground water would be discharged by pipeline either to Pawnee Creek,
south of Hastings, or to a tributary of the West Fork of the Big Blue River.
.City Water Supply
Treated water would ~ sent by pipeline to the City of Hastings water distribution
system.
..
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'.
contaminants would require a much longer duration for operation.
A higher rate than considered for cost analysis could remove
contaminants in a lesser amount of time.
As was noted in the FS, final design of the pumping rate and
distribution within the plume, might be contingent upon further
remedial design functions, including a subsite-specific pump test
and more sophisticated ground water modeling. .
All of the ground water treatment processes under
consideration are protective of human health and the environment
and comply with appropriate ARARs. In addition, the processes
will have long-term effectiveness and permanence because the
plume management alternatives all provide for removal of 90t or
more of the contaminant mass from the aquifer. Each of the
processes reduce the toxicity, mobility and volume through
treatment and destruction of the contaminants. The capital costs
of the plume management alternatives ranged from $2.8 to $3.8
million. Annual operations and maintenance costs for a 10-year
period ranged from $270 to $770 thousand.
The specific plume management alternatives discussed in the
FS are identified below. The first four alternatives differ by
ground water treatment process, but include surface discharge as
the common water discharge option. The next four alternatives
listed also differ by treatment process, but include reinjection
of treated ground water into the aquifer as the common water
discharge option. The last alternative is the only alternative
in which pumping to the City water supply is the discharge
option. . All treatment processes were conceptually designed and
cost-estimated based on meeting EPA Drinking Water Standards and
the State of Nebraska Ground Water Quality Standards for the
discharge. Treatment processes were evaluated based on
literature review, vendor information, and prior experience at
other sites.
.
Mass Removal and Containment; Air Stripping; Vapor
Phase Granulated Activated Carbon (Off-site
Regeneration); Surface Discharge
Mass Removal and Containment;Air.stripping;'Vapor~
Phase GAC (On-site Regeneration); Surface Discharge
.' .
.
Mass Removal 'and containment; Liquid Phase GAC;
Surface Discharge
Mass Removal and Containment; Ultraviolet
Photooxidation; Surface Dis,charge '
.
.
Mass Removal and Containment; Air Stripping; Vapor
Phase GAC (Off-site Regeneration); Reinjection'
20
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"
.
Mass Removal and containment: Air stripping: Vapor
Phase GAC (On-site Regeneration): Reinjection
Mass Removal and Containme~t; Liquid Phase GAC: .
Reinjection
.
.
Mass Removal and Containment; Ultraviolet (UV)
Photooxidation: Reinjection
Mass Removal and Containment: Liquid Phase GAC: City
Water Supply
.
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The NCP sets forth nine evaluation criteria which serve as a
basis for comparing the remedial alternatives for final actions.
Interim actions, such as those proposed, may not achieve final
cleanup levels for the ground water although they are effective
in the short term in preventing further degradation and
initiating reduction in toxicity, mobility or volume. Nine
evaluation criteria were developed by EPA to serve as a basis for
comparing the remedial alternatives for final actions. Interim
actions, such as those proposed, may not fulfill the requirements
of all nine criteria.
The nine criteria are divided into three categories:
Threshold Criteria, Primary Balancing Criteria, and Modifying
criteria. If any remedial alternatives identified during the
Feasibility Study do not meet the Threshold criteria (Criteria 1
and 2), EPA will not consider them as possible final remedies.
If the alternatives satisfy the Threshold Criteria, they then are
evaluated against the next five criteria, called the Primary
Balancing Criteria. These criteria are used to compare the
remedial alternatives against each other in terms of
effectiveness, degree of difficulty involved, and cost. The
final two criteria, state acceptance and community acceptance,
are called Modifying criteria. The alternatives are compared
against the Modifying Criteria after the state and the community
have reviewed and commented on the Proposed Plan and the other
alternatives considered by EPA.
Table 4 presents a comparative analysis of how the 11
remedial alternatives satisfy the Threshold and Primary Balancing
Criteria. Evaluation of compliance with the remaining Modifying
criteria is included in the following discussion. The following
is a discussion of the nine criteria used by EPA for remedy
selection and how the alternatives meet the criteria.
21
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'IIIU81IOt.D CIUftIUA
0ftIIALI. nora:i'row or IIUMaII 8Uliftl ~1N1C8
at.ftllllAnft8 AND ftE DWlJIOI84Dtr WID UAIUII .
1. No Action None None
Z. In.tltutlonel Control. Have been effective In preventlnq Inqe.tion of IIone
contaminated water from on-.ite veil.
J. Ha.. Removal end Contein88nt, Air Strlpplnq, Te., v111 prevent further deqradetion of 9round 'e.'
Vapor Phale Crenulated Activated Carbon ICAC' 10ff- water
.ite R~generatlon', Surface Di.charge
.. ~I' Removal .nd Cont.ln-.nt, Air Stripping' Te., v111 prevent further deqredetion of 9round 'e.'
Vapor Phale CAC (On-.lte Reqeneretion), Surface vater
Dhchltrge
-
S. ~.. R-e1 end Contel-nU CAC, Surfece Te., viII prevent further degredation of 9round ,...
Dhcharge ..ater
5. ~.. Removel .nd Contelnment, U1trevlolet Te., ..111 prevent further deqradetlon of 9round ,...
Photooaidation, Surface Di.charge "liter
1. Me.. Remov.1 .nd Contelnment, Air Stripping, Te., ..111 prevent further deqredatlon of 9round ,..1
Vapor Pha.e CAC (Off-Site Reqeneretion), ..ater
Rein,ec:tIon
8. ~.. Removal end Contal~ent' Air Strlpplnq, Te., ..Ill prevent further deqradatlon of 9round ,..'
Vllpor Pha.e CAe (On-Site Reqeneretlon), ..ater
R..an,ec:t1on
t. ~88 R8IIId.e1 .nd Containment, Liquid 'ha.. CAC, Te., v111 prevent further deqredatlon of qroand ,..'
Rein'..c:tIon "liter
10. Me88 R_v81 and Cont.l_nt, ,UV 'hotoo8Idatlon, - Te., v111 prevent further deqredatlon of ground "e.'
Rein'ec:t1on wllter
11. Me88 RetII_81 .nd conteln88nU tLlquld 'hue CAe, Te., w111 prevent further deqradatlon of 9round ,...'
City Water supply wllter
TABU 4 - COMPARATIVE ANALYSIS OF ALTERNATIVES
8.
1.
4 ~_leal-.pee1f1e ARAKI ara .hown In Tabl. 1.
~ctlon lpeelfle AltAR. ere .hown in Table S.
Treeted wet.r w111 _t MCLS.
2.
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TABLI: 4 -- COMPARATIVE ANALYSIS or ALTERNATIVES
(COH'1'INtJED)
aALMCI181: CUftlUA
LCMC-ftIIIN 8lIOII2-'1.-. D'rIrC7JftIIU. "u:DOIC:'I'l~ or 'J01rIctn. DftDmrD81101ft CIOft
&rncT1VDlR88 MOIIILITY NIl) VOUNr ftIIOUCII ~M4 18
AND 'E~ TIU:A'IMEIf'I' t.1Ioa.1I1Id8)
I. Non. None None Ye. -- alternatl.. Co.t e.t188te. not
required by NCP prepared
I. None None None Ye. Capital Co.t, '110,
Annual O'M: '54,
Pre.ent Net North,
85Jt
3. Ye. Ye., howe..r. Ie.. YOlat lie Ye.. conta.lnant. cIe.troyed Ye., panelta for 811' ceplt81 CO.t. '3.01"
eanpound. ~ay not be r~.ed through treatment ..I.. Ion and .urfaee Annuel O'M, '303-""
effectl.el, and ..y enter water dlacherge will be Pre.ent Net North,
.urface water. . needed II.UI
.. Y.. .,.., howe..r. I... Y01etUe Ye.. eont..lnant. de.troyed .,.., .url.ee ..ter ceplt.81 Co.t.. .J.1,.
~und. 1118' not be rlllllo.ed through treat~ent dl.charqe penelt -Ill be Annual O'M, '311-'35'
effectl..I, and ~a, enter needed Pre.ent Net North,
.urface water. . ".2'0
5. Ye. Y.. Ye.. conta.lnant. de.troyed Ye., .urleee weter ceplt81 Coat. .J.IJ'
through treat~ent dl.charge penelt -Ill be Annual O'M, "11-"00
needed Pre.ent Net North,
U.353
I. 'e. Cont.-Inent. would be de.troyed Ye., conta.lnant. would be May ha.e .tart-up cepltel co.t.. '3.051
on-.lte, howe..r. treatment de.troyed, hove.er. ozone and probl... due to newne.. Annuel O'M. .3.0-.3"
proce.. I. .tl1l new .nd there paro.lde u.ed In tre.t~ent .re of technology, .urlee. Pre..nt Net North,
I. uncertainty with It. highly to. Ie and would ha.. to water dl.charqe penelt ",0"
effect I..ne.. be handled and .tored .Ith wl1l be needed
care
1. Ye. y.., there could be e low le..l Technology de.troy. Ye., .pent CAe require. cepltel Coet. ",1"-
rl.t for Ie.. yolatile conta.lnant., ma, not de.tro, treat.ent, atoray:' and Annual O'M, ""-'115
~nd. not .ffectl.el, MCLa If Influent cont..lnant dl.po.al, In'ect on .re.ent Net North.
r-o.ed to r_nter the ,round concentration I. high, liquid penelt w111 be needed 85,13'
I pha.. carbon eay be needed a.
e .eeondar, .y.t..
.. ,.. y.., 1... YOletlle C08pOUnd. Ye., eont..lnant. de.troyed Y.. Capltel t08t. .3,.1.
.., not be r880.ed effeetl..ly through treat.ent Annual O'M: .303-..,J
and eould enter'.urface water. - Pre.ent Net North:
85,'"
,. Ye. 'e., ..rJ' effecthe treetll8nt 'e. Ye., In'ectlon penelt. cepltel CO.t. ",,.,
proee.. .111 be needed Annual O'M: ""-"1'
Pre.ent Net North.
..,051
10. 'e. Conte.ln.nt. would be de.troyed Y.., eont..l~ant. cIe.troyed Pilot te.t required, cepltal co.t. '2,'11
on-.lte, howe.er, treat..nt through treataent In'eetlon perelt need8d Annual O'M, '312-8.IJ
proee.. 1. .tlll n.. and there .re.ent Net North,
I. uncertelnty with It. 85,164
effect I..ne..
II. 'e. Ye. Reduce. YOl~ end 8Obllltr' Require. NDOR perelttlnt ceplt.t co.t, '3,011
.a, not achieve reduction of and eonltorlnq, Annual O'M: n15-813'
conta.lnant le.el. to MCL. treat..nt procea. . .re.ent Net North:
requlr.. chlorination ..,422
~
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. .: .
Threshold Criteria:
Overall Protection of Buman Bealth and the" Environment
The EPAassesses the degree to which the alternatives
would eliminate, reduce, or control threats to public
health and the environment through removal,
containment, and/or institutional controls. An
alternative is normally considered to be protective of
human health if the excess cancer risk is reduced to a
range from 1 in 10,000 to 1 in 10 million and do not
pose noncarcinogenic health ris~s.
The no action alternative and the institutional
controls alternative will not provide overall
protection to human health and the environment in the
future. They will be eliminated from further"
discussion in this comparative analysis. All of the
plume management alternatives are protective of human
health and the environment because they will reduce
concentrations of chemicals and prevent their
migration, and will be the focus of discussion in this
ROD.
Compliance with all stat. and Federal Environmental
Regulations
The EPA assesses whether the remedial alternatives
being evaluated will comply with all applicable or
relevant and appropriate requirements, called ARARs,
established by the state and federal governments. As
this is an interim action, the NCP allows full
compliance with ARARs to be delayed until
implementation of the final action. ARARs as referred
to here are regulations controlling exposure of humans
to ground water with contaminants at levels above the
maximum contaminant levels (HCLs). The interim action
will provide for treatment of extracted pumped water
to HCLs prior to discharge or reinjection.
There are three (3) types of ARARs to be addressed, -i.e.,
chemical-specific, action-specific and location-specific.
.
Chemical-specific ARARs are requirements that set
final concentrations of chemicals of concern in the
contaminated material (e.q., ground water, soil) which
must be achieved by the remedial action. This interim
remedial action will not attain chemical-specific
ARARs (referenced in the state of Nebraska's Title 118
for non-degradation of ground water standards) in the
ground water plume as the target concentrations of
ground water that would be contained coincide with a
24
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. .
~
.
10.' risk level which, for the primary compounds of
concern at the Colorado Avenue subsite exceed MCLs.
Chemical-specific ARARs will be attained for
discharged ground water after treatment. All of the
plume management alternatives will comply with MCLs
for the disposition of treated ground water. ,
Action-specific ARARs are those requirements that set
standards for the treatment and discharge components
of the remedial action. Action-specific ARARs will
apply to the int~rim and final remedial action and
were considered in the Feasibility study. The use of
air stripping, with no emission controls, would result
in the discharge of VOCs into the atmosphere. NDEC's
Title 129 limits discharges of VOCs to 2.5 tons/year.
Air emissions will comply with all ARARs.
Technologies considered for the ground water operable
unit meet these ARARs.
.
Location-specific ARARs are requirements that might
apply to a remedial action due to the site's unique
cultural, archaeological, historical or physical
setting (e.g., wetlands). Location-specific ARARs .
will not apply to the ground water interim or final
remedial action at the Colorado Avenue subsite because
there are no such features in the subsite area.
,
All plume management alternatives will comply with the
following Federal laws.
Clean Water Act
Safe Drinking Water Act
Clean Air Act
Occupational Safety & Health
Act
Solid Waste Disposal Act,
Subtitle C, as amended by
the Resource Conservation
and Recovery Act of
1976. (RCRA)
33 U.S.C. SS1251-1387
42 U.S.C. SS300f-300j-26
42 U.S.C. SS7401-7642
29 U.S.C. SS651-678
42 U.S.C.SS6901-6992k
In addition, State of Nebraska ARARs for the Plume Management
Alternatives appear in Table 5.
Primary Balancing criteria:
Long-Term Effectiveness and Permanence
-0<
The alternatives are evaluated based on their ability
to maintain reliable protection of human health and
the environment after the ~emedial action is
completed. This criterion also focuses on the
2S
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.'
8fab18 5
Action-Specific Itate of .&bra.t. &RAa8
Action-Specific State ARARs
I.
Nebraska Environmental Protection Act
Rules and Regulations Goveming
the Nebraska Pretreatment Program
Effluent Guidelines and Standards
Rules and Regulations Pertaining to the
Issuance of Pe~ts Under the National
Pollutant Discharge Elimination System
Rules and Regulations for Underground
Injection and Mineral Production Wells
Air Pollution Control Rules and Regulations
Nebraska Surface Water Quality Standards
Ground Water Quality Standards and Use
Classification
Rules and Regulations Pertaining to
Solid Waste Management
Rules and Regulations Governing Hazardous
Waste Management in Nebraska
II .
Rules and Regulations Pertaining to the
Management of Wastes
Water Well Standards and Contractors'
Licensing Act
III.
Regulations Governing Licensure of Water
Well and Pump Installation Contractors
and Certification of Water Well Drilling
and Pump Installation Supervisors
Nebraska Safe Drinking Water Act
IV.
Regulations Governing Public Water
Supply Systems
Statutes Relating to Disposal Sites
V.
Statutes Relating to Ground Water
Citation
Neb. Rev. Stat.
Ch. 81, ~icle 15
Neb. Adm. Rules , Regs
,-itle 121
Neb. Adm. Rules , Regs
,-itle 121
Neb. Adm. Rule. , Regs
,-itle 119
Neb. Adm. Rules , Regs
Title 122
Neb. Adm. Rules , Regs
Title 129
Neb. Adm. Rules , Regs
,-itle 117
Neb. Adm. Rules , Regs
Title 118
Neb. Adm. Rules' Regs
Title 132
Neb. Adm. Rules , Regs
Title 128
Neb. Adm. Rules , Regs
Title 126
Neb.' Rev. Stat.
Ch. 46, Article 12
Neb. Adm. Rules' Regs
Title 118
Neb. Rev. Stat.
Ch. 11, Article 53
Neb. Adm. Rules' Regs
Title 119
Neb. Rev. Stat.
Ch. 19, Article 21 , 4
Neb. Rev. Stat.
Ch. 46, Article 5
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. .
. .
magnitude of health and environmental risks remaining
after the remedial action is completed.
Because this is an interim action and not a final
remedy, EPA evaluates the alternatives only on the
basis of those wastes which are treated. However, EPA
will evaluate the effectiveness of the remedy within
the first two years of implementation to determine
what additional action will be needed as a complement
to the selected remedy. Also, as mandated by
CERCLAjSARA, EPA will conduct five-year reviews at the
site as long as hazardous chemicals remain at the
subsite above health-based criteria~
Reduction of Toxicity, Mobility, or Volume Through Treatment
This criterion focuses on the amount and types of
hazardous materials that will be destroyed or treated,
whether the' results of the remedial action are
reversible, and whether the alternative includes a
treatment process, a remedial action component which
is favored by EPA. EPA evaluates each alternative
based on how its treatment methods reduce the harmf~l
nature of the contaminants, the ability of the
contaminants to move, and the amount of contamination
remaining after the remedial action is completed.
All of the plume management alternatives employ
treatment. Treatment options including air stripping
with air emission control and UV oxidation that can
satisfy the goals of the selected remedy may be .
contaminant reduction goals will be evaluated further
during design (as provided by requirements found in
the Selected Remedy section of this ROD).
Short-Term Effectiveness
The length of time needed to implement each segment of
the alternative is considered, and EPA considers the
risks that conducting a particular activ~ty may pose
to site workers, nearby residents, or the local
environment.
All of the plume management alternatives will utilize
techniques to minimize risks to human health and the
environment during implementation. The UV technology
may require greater implementation time if employed
because of the uncertainty of its performance and
required air emissions testing. In addition, careful
handling and storage of highly toxic chemicals used in
the UV process will ensure protection during
implementation.
27
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'. -. ,.
Implementability
The EPA considers the technical (e.g., how difficult
the alternative is to construct and operate) and
administrative (e.g., how other government agencies
and EPA will coordinate monitoring programs)
feasibility of a remedy, including the availability of
goods and services and personnel (e.g., disposal
services, storage capacity) needed to implement and
manage the alternative.
All of the plume management options will be
implementable, but there is a higher degree of
uncertainty of the implementability of UV because it
has been implemented at fewer sites.
Cost
The EPA considers capital costs, operation and
maintenance costs, and present net worth, which is the
cost, expressed in terms of a lump sum at today's
dollar value, of the activities that will take place
until the remedial action is completed. Capital costs
apply to needed equipment and materials and activities
such as construction, land and site development, and
disposal of waste materials. Annual operation and
maintenance costs are spent on activities such as on-
going operation of equipment, insurance, and periodic
site reviews. Based on cost estimates, all of the
plume management options are cost effective. Cost for
comparison of the interim action alternatives was
based on an extraction rate of 1,000 gallons per
minute and duration of ten years (Table 6).
Modifying criteria:
.
state Acceptance
The state concurs with the selected remedy as an
interim action for the ground water operable unit.
Community Acceptance
The EPA held a public comment period to allow the
community to comment on the preferred alternative and
the other alternatives considered. Comments were made
regarding the scope of costs and plume management
. options, and treatment technologies described in' the
Proposed Plan. The EPA reviewed these comm~nts before
making a final decision on the interim action remedy.
28
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"
..
~ab1e ,
aatimated Coata of the Selected R8m8dy
Color.do A~ue SUb.ite
(ba.ed OD &PA'a re..1bi1ity Study, JUDe 1'81)
Capital Costs:
Treatment Component
Estimated Cost
$ 1,076,000
$ 1,.513,000
$ 357.000
Mass Removal
Treatment
Discharge
$ 2,946,000
Annual Operation and Maintenance:
Mass Removal
TreatmentJ
Discharge'
$
$
$
$
120,000
125,000 to $ 548,000
24,000 to $ 99,000
269,000 to $ 767,000
Present Worth:'
Mass Removal
TreatmentJ
Discharge'
$ 2,012,000
$ 3,443,000
$ 606,00'0
$ 6,061,000
JA;substantial decrease in cost is expected after year one.
'Dependant on quantity reinjected.
)Present Worth based on weighted average O&M costs as in the FS.
-------
. . ., ..
EPA's responses to these comments are included in the
Responsiveness summary section of th1s document.
SELECTED REMEDY
The EPA selected "Mass Removal and Containment with Liquid
Phase Granular Activated Carbon Treatment and Ground Water
Reinjection" as the remedy for protecting human health and the
environment from ground water contamination. The selected remedy
provides the best balance among other interim action alternatives
with respect to the evaluation criteria detailed above. This
remedy, as previously stated, is protective, .implementable, and
effective in reducing the toxicity, mobility, and volume of
contamination present at the subsite. The NCP does not require
that all ARARs be met for an interim action that is consistent
with the final remedy.
The selected remedy calls for the design and implementation
of this interim remedial action to protect human health and the
environment. The goals of this remedial action are to halt the
spread of a contaminant plume, remove contaminant mass, and to
collect data on aquifer. and contaminant response to remediation
measures. The ultimate level of remediation to be attained will
be determined in a final remedial action for this subsite. This
remedial action will be monitored carefully to determine the
feasibility of aChieving remediation goals with this method and
to ensure that hydraulic control of the contaminated plume is
maintained. A final action ROD for the ground water which
specifies the ultimate subsite goal, remedy and anticipated
timeframe will be prepared after a period of time as determined
by EPA. Upon completion of the RIfFS for the final action, this.
interim action may be incorporated into the design of the site'
remedy specified in the final action ROD.
The major components of the selected remedy include the
following:
.
The selected remedy will provide for contaminant mass
removal and ~ontainment of ground water.
Approximately S50 million gallons of ground. water in
the underlying aquifer is contaminated. The selected' .
remedy provides that this volume of ground water will
be displaced approximately eight times in a lS-year
period. Optimization of the locations and withdrawal
rates of the extraction wells may produce pumping
efficiencies such that the removal of eight pore
volumes will not be necessary throughout the. plume are
shown in Figure 4.
30
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.
. .. .
.
The specific ground water extraction rate will be
based on an aquifer pump test at the Colorado Avenue
subsite. CUrrent information indicates that an
extraction system capable of removing one thousand.
gallon.s per minute from the aquifer will be needed in
the initial stages of pumping, and this ~emedy
provides for an evaluation of pumping rates based on
the pump test results and system operational data.
The selected remedy will provide for treatment of
extracted ground water with granular activated carbon.
(GAC). Alternative treatment technologies (air
stripping with air emissions treatment, UV, or
combinations which may include GAC) may be implemented
based on four criteria -- cost, short-term
effectiveness (air emissions), ability to meet
contaminant mass removal goals, and implementability.
The EPA will issue an explanation of significant
differences which includes a public notice, should a
treatment alternative other than GAC ~e approved for
implementation.
.
..
The target concentrations for chemicals in the ground
water shall be those corresponding to the 1 x 10.4
cancer risk levels due to 30-year exposure, as defined
in Table 1, for TCE, DCE, PCE, 1,2-DCA and Methylene
Chloride. The performance standards for treated
ground water for this interim action shall be the
MCLs, shown in Table 1, for TCE, TCA, DCE, PCE, 1,2-
DCA and Methylene Chloride. .
Tne selected remedy will provide for reinjection
and/or use of the treated ground water.
.
.
The selected remedy will provide for monitoring of the
effectiveness of the interim ~emedy, including an
assessment of the interim action two years subsequent
to implementation of the remedial action.
other components of the selected remedy .include:
.
.
Installation of monitoring wells to obtain water
quality data to refine EPA's preliminary estimate of
the pore volume for the interim action:
Installation of a monitoring well network tor long-
term compliance ~onitoring downgradient from the
location of the containment/extractio~.well network:
.
..
31
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. : "
.
Installation of monitoring wells as needed and
recording of water level measurements at prescribed
frequencies" to verify that the system hydraulically
responds as required;
Monitoring of extraction well influent contaminant
levels; and
.
Monitoring treated water effluent quality for VOCs
utilizing laboratory methods prescribed by SDWA having
detection levels which will assure MCLs are not
exceeded.
The remedy provides an approach to containing and removing
contaminant mass from the ground water plume. The remedy will
rapidly reduce contaminant concentrations and be consistent with
the final remedy. The containment area required by this interim
action will provide a significant level of protectiveness to
human health for both carcinogenic and non-carcinogenic potential
health effects. '
.
The specific elements of the initial extraction system will
be determined during the Remedial Design. Subsequent
modifications will be based on the review of data generated
during initial operations. Extraction parameters to be
determined include well location, depth of withdrawal within the
aquifer and pumping rate. The ground water contaminant
parameters of concern shown in Table 2 will be monitored
frequently before and during system operation. Continual
evaluation of monitoring data will ensure that hydraulic control
of contaminated ground water is maintained. All collected data
will be evaluated to determine the final remedial action goals
for ground water.
The pumped ground water will be treated with granular
activated carbon and then reinjected into the aqUifer. The
treated ground water will be injected into the aquifer upstream
of the contaminant plume. Other locations for reinjection may be
considered pending approval by the appropriate regulatory
agencies. All extracted ground water will be treated to drin~ing
water' "quality standards (MCLs) prior to disc.harge, and all action, ,
specific ARARs will be met. The ARARs are shown in Tables 1 and
s.
Granular activated carbon (GAC) is a proven technology that
has been used successfully at a number of Superfund sites. This
alternative is easily implemented. Operationally, GAC treatment
has several distinct advantages. There are no air emissions
associated with the process, it is effective in removing a wide
range of VOCs and other organics, and is also effective over a
wide range of influent concentrations. All of these factors
reduce the risk of human exposure during operation.
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Additionally, GAC is a relatively low maintenance system. The
system requires frequent monitoring, but little. in the way of
maintenance. Monitoring and carbon changeouts would become less
frequent with time as experience is gained and influent
concentrations decrease. . . .
Operationally, the GAC treatment plant would consist of a
10,000 gallon influent tank to provide surge capacity and
equalization of flow into the carbon columns. contaminant
removal should be nearly 100 percent. Series operation, that is,
water flowing through two carbon beds in sequence, gives GAC ~e
additional advantage over the other considered processes of
having a reserve treatment capacity at all times. By monitoring
the treated water effluent from the first colUmn in series,
contaminant breakthrough would be detected well before the second
column in series were significantly loaded.
The EPA has considered costs due to carbon usage. Carbon
consumption is directly proportional to the amount of
contamination removed from the ground water. Because of this,
the process is very sensitive to influent contaminant
concentrations. Costs can increase if the actual contaminant
loading rate were to be higher than estimated in the FS.
Ground water reinjection has been identified as the
preferred method of water discharge because of its ability to
return ground water to the aquifer for beneficial use. .
Reinjection was considered preferable to surface water discharge
because the latter would not result in beneficial use of the
pumped ground water. Options for use of the pumped ground water
will be considered upon request.
The total cost of the remedy, in 1991 dollars, based on
operating costs for a 10-year life, was estimated to be $6.06
million. These costs are explained in Table 6. Based on
considerations by EPA and comments received during the public
comment period, EPA has increased the estimated remedial action
timeframe for this interim action to 15 years. The total present
value cost of the remedy under this circumstance will increase
from the 10-year estimate primarily due to a longer period of
O&M. .
STATUTORY DETERMINATIONS
The selected remedy will achieve substantial reduction in
risks by initiating the reduction of the toxicity, mobility and
volume of ground water contaminants, by limiting ground water
contaminant migration and by reducing environmental risks
associated with the contaminated ground water. .
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The selected remedy meets ARARs for the treatment of the
extracted ground water, the disposal of spen~ carbon and
control of air emissions from treatment processes. This
determination is based on the remedy's compliance with the
following federal standards and state of Nebraska standards
listed in Table 5. Federal ARARs are the Safe Drinking Water
Act, the Clean Air Act, the Resource Conservation and Recovery
Act, Occupational Safety and Health Act and Clean Water Act.
The selected remedy will protect human health and the
environment, prevent further environmental degradation, .and will
achieve significant risk reduction while a final remedial action-
is being prepared. The selected remedy is protective of human
health because the interim action will reduce contaminant
concentrations in the aquifer to a level that will achieve a
significant reduction in risk. This level will be at or below
the 1 x 10-' cancer risk level, or a risk of less then one case
in 10,000 due to exposure to contamination. This will provide a
significant level of protectiveness to human health for both
carcinogenic and non-carcinogenic potential health effects. In
addition to risk reduction, the interim action will stabilize the
ground water contaminant migration and prevent further
degr~dation of the environment by mass removal and plume control.
The overall effectiveness of this remedy is proportional to the
projected costs and provides the best balance among the
alternatives with respect to the evaluation criteria.
The implementation of either air stripping, GAC or UV or a
combination, will be based on four criteria -- cost, short-term
effectiveness (air emissions), ability to meet mass contaminant
removal goals, and implementability. .
Because this remedy will result in hazardous substances
remaining onsite above health-based levels, a review will be
conducted to ensure that the remedy continues to provide' adequate
protection of human health and the environment within five (5)
years after commencement of the remedial action. Review of the
subsite source control and ground water remedies will be ongoing
as EPA continues to develop final remedial alternatives for the
Colorado Avenue subsite.
DOCUMENTATION OF SIGNIFICANT CHANGES
EPA has selected an interim ~emedy consisting of mass
removal and containment. The selected remedy provides that the
ground' water will be treated using granular activated carbon.
However, air stripping with air emissions treatment .or
ultraviolet oxidation may be considered as an a4ternative to
liquid phase carbon treatment. The selected remedy specifies
that the treated water must be either reinjected or made
available to others for use in orde~ to minimize depletion of the
ground water resources.
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. --
. ..
The changes to the interim acti~n reflected in this ROD
compared to the Proposed Plan were made after careful
consideration of public and PRP comments. The differences that
exist between EPA's proposed plan and the selected remedy relate
to the time frames for implementation. The EPA has reevaluated
the proposed ten year period of active pumping outlined in the
proposed plan. To provide more flexibility for the project
designers, the timeframe for the active pumping phase has been
extended to lS years. This will allow pumping and treating of
the ground water concurrent with field testing and various design
and installation activities. In summary, to promote site cleanup
in a timely manner, pumping and treating of ground water can be
initiated after the installation of extraction wells and
completion of the aquifer pump test.
The EPA will evaluate information gained during the first
two years of remedial action to assess the decline in the
concentration of ground water contamination and mass of
contaminants removed. This evaluation will be conducted two
years after implementation of the interim action and include a
review of ground water pump rates and number of extraction wells.
. ,
The selected interim remedy also includes monitoring of
ground water quality both during and after completion of the
active pumping phase of the project. The selected interim remedy
requires ground water monitoring during the lS-year active
pumping phase and for a period of ten years after completion of
the active pumping phase of the interim action. The data
collected will be used to assure that the interim action has
effectively reduced the concentration of contaminants in the
aquifer to the health-based target levels defined by this Record
of Decision.
"
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