SEPA
United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R05-90/136
September 1990
Superfund
Record of Decision:
Naval Industrial Reserve
Ordnance Plant, MN
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REPORT DOCUMENTATION
PAGE
1. R&ORTNQ.
EPA/ROD/R05-90/136
4. THbMdSubMi
SUPERFUND RECORD OF DECISION
Naval Industrial Reserve Ordnance Plant, MN
First Remedial Action
09/28/90
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The 82.6-acre Naval Industrial Reserve Ordnance Plant (NIROP) site is a weapons system
manufacturing facility in Fridley, Minnesota, which began operations in 1940. The site
is a government-owned, contractor-operated, plant located just north of the FMC Corp.
Superfund site. NIROP is located approximately 30 feet above and 700 feet east of the
Mississippi River and less than one mile upstream from the city of Minneapolis drinking
water supply intake. During the 1970s, paint sludge and chlorinated solvents were
disposed of onsite in pits and trenches. In 1981, State investigations identified TCE
in onsite water supply wells drawing from the Prairie DuChien/Jordan aquifer, and the
wells were shut down. In 1983, EPA found drummed waste in the trenches or pits at the
northern portion of the site, and as a result, during 1983 and 1984, the Navy authorized
an installation restoration program, during which approximately 1,200 cubic yards of
contaminated soil and 42 drums were excavated and landfilled offsite. In 1987, TCE use
at the site was discontinued, but the principal threat posed by the site is the
continued migration of TCE via ground water to the Mississippi River. This Record of
Decision (ROD) addresses the remediation of a shallow ground water operable unit. The
(See Attached Page)
17. Documwil Amlyita *. DMCriptora
Record of Decision - Naval Industrial Reserve Ordnance Plant, MN
First Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (PCE, TCE, toluene, xylene)
Ix IdMilHbn/OpwvEndtd Term
c. COSAT1 FMd/Oroup
18. AvriKMIty SUtwntnl
It. Stcurity CtaM (Thto Report)
None
20.
None
21.
52
22. MM
(SM ANSJ-Z39.18)
SM frufrucltorM on fltwtw
OPTIONAL FORM 272 (4-77)
(Fonmfty KT1S46)
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EPA/ROD/R05-90/136
Naval Industrial Reserve Ordnance Plant, MN
First Remedial Action
Abstract (Continued)
need for a second operable unit to treat potential contamination sources will be
determined pending the results of additional investigations. The primary
contaminants of concern affecting the ground water are VOCs including PCE, TCE,
toluene, and xylene.
The selected remedial action for the site is a two-phased approach. Phase I includes
ground water pumping and pre-treatment, as necessary, before disposal to a local
publicly owned treatment works (POTW) via an existing sanitary sewer system; and
testing the recovered water to assist in the design of Phase II treatment facilities/-
Phase II includes treating the recovered ground water by either a two-stage air
stripping process, followed by vapor-phase granular activated carbon (GAC) to treat
air emissions, or treating ground water using aqueous-phase GAC, depending on Phase 1
test results; and discharging treated ground water into the Mississippi River. Both
options include disposal of the treated effluent offsite and regenerating the spent
carbon at an offsite facility. The estimated present worth cost for this remedial
action is $4,100,000 for the GAC-only option. O&M costs were not provided.
PERFORMANCE STANDARDS OR GOALS: Ground water quality in the unconsolidated aquifer-
at the site will be restored to MCLs or State recommended allowable limits, if more
restrictive. Because TCE was found with the greatest frequency and in the highest
concentrations at the site than any other VOC, TCE 5.0 ug/1 (MCL) was established as
the target cleanup goal for ground water in the aquifer. Cleanup levels for
recovered ground water discharged to the local POTW must not exceed 10 mg/1 and
individual VOC levels must be less than 3 mg/1 (local POTW standards). Contaminants
in any uncaptured portion of the aquifer are expected to dissipate by natural means
ove r t ime.
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I '
DECLARATION
SITE NAME AND LOCATION
Naval Industrial Reserve Ordnance Plant
Fridley, Minnesota
STATEMENT OF BASIS AND PURPOSE
This decision document presents a selected remedial action which will provide
hydraulic containment and recovery of ground water (operable unit) at the Naval Industrial
Reserve Ordnance Plant (NIROP) site in Fridley, Minnesota. This decision document was
developed in accordance with CERCLA, as amended by SARA, and, to the extent practicable,
the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). Through this
document, the Navy plans to remedy the threat to human health, welfare, or the environment j
posed by VOC-contaminated ground water by hydraulic containment, recovery, and treatment!
This decision document is based on the administrative record for this site.
The Minnesota Pollution Control Agency (MPCA) and United States Environmental
Protection Agency (USEPA) concur with the selected remedy.
On-going work at the NIROP is defining the extent of soils contamination. A
subsequent Record of Decision (ROD) may be issued in the future for a soils operable unit.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from the NIROP, if not
addressed by implementing the response action selected in this Record of Decision, may
present a threat to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
This action addresses the principal threat posed by the NIROP by preventing
endangerment of public health, welfare, or the environment by implementation of this Record
1
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TABLE OF CONTENTS
•
RESPONSIVENESS SUMMARY 48
OVERVIEW 48
BACKGROUND OF COMMUNITY INVOLVEMENT 48
SUMMARY OF COMMENTS RECEIVED DURING PUBLIC COMMENT PERIOD 48
List of Tables
Table 1 - Range of VOCs in Ground Water 18
Table 2 - Potential Risks Associated with VOCs in Ground Water Downgradient of the
NIROP 23
Table 3 - Action-Specific ARARs 31
List of Figures
Figure 1 - Location Map j 6
Figure 2 - Site Plan | 7
Figure 3 - Typical East-West Cross Section .'9
Figure 4 - Extent of TCE in Upper Zone of Unconsolidated Aquifer 19
Figure 5 - Extent of TCE in Lower Zone of Unconsolidated Aquifer 20
Figure 6 - Zone of Capture for Containment and Recovery of Ground Water 36
Figure 7 - Preferred Alternative: Ground Water Pumpout, Treatment, and Disposal -
Process Flow Diagram 39
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TABLE OF CONTENTS
Title Page
DECLARATION . 1
SITE NAME AND LOCATION 1
STATEMENT OF BASIS AND PURPOSE 1
ASSESSMENT OF THE SITE 1
DESCRIPTION OF THE SELECTED REMEDY 1
STATUTORY DETERMINATIONS 3
DECISION SUMMARY 5
1. SITE NAME, LOCATION. AND DESCRIPTION 5
2. SITE HISTORY AND ENFORCEMENT ACTIVITIES 11
3. COMMUNITY RELATIONS HISTORY |4
4. SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY 15
5. SUMMARY OF SITE CHARACTERISTICS 16
6. SUMMARY OF SITE RISKS 21
7. DESCRIPTION OF ALTERNATIVES 25
8. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 29
8.1 Overall Protection of Human Health and the Environment 29
8.2 Compliance with Applicable or Relevant and Appropriate Requirements
(ARARs) 29
8.3 Long-Term Effectiveness and Permanence 30
8.4 Reduction of Toxicity, Mobility, and Volume 30
8.5 Short-Term Effectiveness 32
8.6 Implementability 32
8.7 Costs 33
8.8 Agency Acceptance 34
8.9 Community Acceptance 34
9. THE SELECTED REMEDY 35
10. STATUTORY DETERMINATIONS 42
10.1 Protection of Human Health and the Environment 42
10.2 Compliance with ARARs 42
10.3 Cost-Effectiveness 46
10.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies 47
10.5 Preference for Treatment as a Principal Element 47
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RECORD OF DECISION
FOR
GROUND WATER REMEDIATION
NAVAL INDUSTRIAL RESERVE ORDNANCE PLANT
FRIDLEY, MINNESOTA
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of Decision through hydraulic containment and recovery of all future migration of contaminated
ground wateMrom the NIROP and by recovery, to the extent feasible, of contamination
downgradient of the NIROP.
The selected remedy includes installation and operation of ground water containment
and recovery wells, with a two-phased plan for disposal of the ground water from the well
system.
Under Phase I, the contaminated ground water from the containment and recovery
well system will be discharged directly to the existing sanitary sewer system, for treatment at
the local wastewater treatment facility. Pretreatment will be provided if necessary to meet local
discharge requirements. Phase I activities will also include field testing of the recovered
ground water, followed by design of a ground water treatment plant at the NIROP. Prior to
start-up of the ground water containment system, the Navy will submit a ground water j
monitoring program for approval by the USEPA and MPCA, to confirm that containment of tie
ground water plume is effective.
During the first 90 days of recovery system operation, the Navy will collect data to
determine whether hydraulic containment is being effectively achieved. This determination will
be summarized in a document which will be sent to the USEPA and MPCA for review and
approval at the end of the 90-day period. The USEPA and MPCA will provide written approval
of, or comments on, the determination document within 30 days after its receipt. If the USEPA
and MPCA do not approve the determination document, the Navy will submit a revised
determination document to the USEPA and MPCA within 60 days after the Navy is notified of
specific deficiencies in the document. If the determination document, after its approval by the
USEPA and MPCA, indicates that effective hydraulic containment is not being provided by the
ground water recovery system, the Navy will prepare and submit to USEPA and MPCA a
written plan for upgrading the recovery system to assure that the performance objectives of
the containment system are met, and the Navy will implement the finally approved plan.
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Under Phase II, within 365 days after the USEPA and MPCA approve the determination
that the ground water containment and recovery system is effective, design documents for a
ground water treatment system will be completed by the Navy and approved by the USEPA
and MPCA. Treated ground water will be discharged to the Mississippi River via a National
Pollutant Discharge Elimination System (NPDES) storm sewer discharge.
A portion of the aquifer within the Anoka County Parkland closest to the Mississippi
River may not fall within the zone of capture of the ground water recovery system. However,
should this occur, contaminants in any uncaptured portion of the aquifer are expected to
dissipate by natural means over time to levels that are protective of human health and the
environment. Should the City of Minneapolis or another community decide in the future to
develop a supplemental water supply well system in the Anoka County Parkland, the Navy will
control the health risk within acceptable levels by implementation of a ground water treatmerjt
system or other measures as approved by the MPCA and the USEPA. |
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 alternative
treatment (or resource recovery) 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. Because this remedy may result in hazardous substances
remaining in on-site ground water above health-based cleanup levels, a review will be
conducted by the Navy, the USEPA, and the MPCA within 5 years after start-up of the ground
water containment and recovery well system to ensure that the remedy continues to provide
adequate protection of human health and the environment. This review will be conducted at
least every 5 years as long as hazardous substances remain in ground water on-site above
health-based cleanup levels.
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United States Navy
Date/
(Title)
Minnesota Pollution Control Agency
Date
(Title)
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DECISION SUMMARY
1. SITE NAME, LOCATION, AND DESCRIPTION
The Naval Industrial Reserve Ordnance Plant (NIROP) is located in the northern
portion of the Minneapolis/St. Paul Metropolitan Area within the city limits of Fridley, Minnesota
(Figure 1). Advanced naval weapons systems are designed and manufactured at the NIROP.
The northern portion of the plant is government-owned and operated by a private contractor
(PMC Corporation • Naval Systems Division), and the remainder of the plant is owned
independently by FMC (Figure 2). The government-owned portion of the plant constitutes
what is referred to within this document as the NIROP.' The word 'site,' wherever used in this
document, includes the NIROP as well as the area! extent of contamination and all suitable
areas in very close proximity to the contamination necessary for implementation of the
response action. '
The NIROP comprises approximately 82.6 acres, most of which are covered with -
buildings or pavement. The NIROP is situated on a broad, flat outwash terrace which is
approximately 30 feet above and 700 feet east of the Mississippi River.
Adjacent land use consists of the following:
To the north - Commercial and light industrial
To the south - Industrial
To the west - Recreational
To the east - Railyards and commercial/light industrial
Natural resource use in the area consists of recreational activities in the Anoka County
Parkland, which is directly across East River Road from the NIROP, and on the Mississippi
River. Use of these resources does not result in access to the NIROP itself, which is highly
restricted by the Department of Defense. There are no federal or state fresh-water wetlands
located within 1 mile of the site. No critical habitats of endangered species or national wildlife
refuges have been identified in the vicinity of the site.
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MISSISSIPPI
RIVER
IN CITIES
/r ARSENAL
NEW
BRIGHTON
COLUMBIA
HEIGHTS
SCALE: r-2.5 MILES
MINNESOTA
I
I
North
Dakota
MINNEAPOLIS
South MINNEAPOLIS^. Wisconsin
Dakota [
MISSISSIPPI
RIVER
LOCATION MAP
FIGURE 1
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1 Q F RIDLEY WELL
APPRQx.
TRENCH
AREA
NIROP FACILITY
FUTURE QROUNOWATER
TREATMENT PLANT
(APPROXIMATE)
EXISTING STORM
SEWER
ANOKA COUNTY
PARK
FMC FACILITY
WATER INTAKE
(APPROX
LEGEND
— NIROP PROPERTY BOUNDARY
— — FMC FACILITY BOUNDARY
0 PROPOSED GROUNDWATER
RECOVERY WELL (APPROXIMATE
LOCATIONS. FINAL LOCATIONS BASED
ON UPCOMING PUMP TESTS.)
1- SOO
FIGURE 2
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The City of Minneapolis water supply treatment plant withdraws water from the
Mississippi River less than 1 mile downstream from the NIROP. The population of the area
served by the City of Minneapolis Water Supply treatment plant is approximately 500,000
people.
Ground water use in the vicinity of the NIROP consists primarily of high-capacity
industrial production wells which draw water from the Prairie du Chien/Jordan (PCJ) aquifer
system. The City of Fridley maintains a backup potable water supply well (Fridley well 13 -
Figure 2) which also draws water from the PCJ immediately north of the NIROP. During peak
demand periods, Fridley Well 13 is used to supplement the current water supply system. The
total population served by ground water within a 3-mile radius is 29,000 residents.
Contamination has not been found above detection levels in Fridley Well 13. There are no
ground water wells or users downgradient of the NIROP between the NIROP and the (
Mississippi River. !
An aquifer within unconsolidated sediments overlies the PCJ in the vicinity of the
NIROP. The thickness of the unconsolidated aquifer ranges from 100 feet to 140 feet under
the NIROP. Except for an area at the southern end of the NIROP where the St. Peter
Sandstone has been eroded, the unconsolidated aquifer is hydraulically separated from the
PCJ by a silty to shaly layer of the St. Peter Sandstone, which acts as an aquitard. The
unconsolidated aquifer is in contact and hydraulically connected with the PCJ in the eroded
area, at the southern side of the NIROP. A conceptual representation of the aquifer and
geology beneath the NIROP is shown on Figure 3.
The location of nearby populations is limited to a residential neighborhood
approximately 200 feet east of the adjacent railyards.
There are presently no known major underground structures at the NIROP with the
exception of typical industrial and utility piping. Previously disposed drums have been
excavated and removed, as discussed in Section 2.
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COUNTY
PARK
PROPERTY UNC
PROPERTY LINE
NAVAL INDUSTRIAL RESERVE ORDNANCE PLANT
no
_ /-UKUUND WATER TABLE
MISSISSIPPI
RIVER
. BURLINGTON
{ NORTHERN
! RAILROAD
SAND
UNCONSOUDATED DEPOSITS
790
740
710
TILL
LAYER
CROUNDWATER FLOW
TILL LAYER
7M
740
TOO
PRAIRIE du CHIEN/JORDAN DOLOMITE
720
700
CROUNDWATER FLOW
TYPICAL EAST-WEST CROSS SECTION
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The FMC facility to the south of the NIROP has been the subject of separate response
actions underCERCLA. A Record of Decision signed by the United States Environmental
Protection Agency Regional Administrator on September 30, 1987, selected a site remedy
consisting of ground water extraction to control a plume of contaminated ground water. The
origins, migration, and remediation of the FMC plume are distinct from those at the NIROP.
FMC has also excavated approximately 38,600 cubic yards of contaminated soil on the FMC
facility to the south of the NIROP which were placed in an on-srte storage vault served by a
ground water monitoring system. The excavated area was capped with a multi-layer cover
and revegetated.
10
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2. SITE HISTORY AND ENFORCEMENT ACTIVITIES
A chronological summary of significant events and activities at the NIROP leading to
the current remedial action is as follows:
1940 -1941 Naval ordnance manufacturing facility was
constructed; owned by the government and
Northern Pump Company.
1942-1964
1964
Early 1970s
December 1980
March and April 1981
April 24, 1981
December 31, 1981
Northern Ordnance, Inc., a subsidiary of
Northern Pump Company, operated the naval
ordnance manufacturing complex.
FMC Corporation purchased the southern
portion of the manufacturing facility property
from Northern Pump Company, and has
remained the operating contractor to the U.S.
Navy for the entire facility from 1964 to the
present.
Limited disposal at the NIROP of paint sludge!
and chlorinated solvents in pits and trenches.
was performed. |
Anonymous telephone call to the Minnesota
Pollution Control Agency (MPCA) concerning
past waste disposal practices at the NIROP.
Trichloroethylene (TCE) identified at 0.035 to
0.200 mg/L in NIROP water supply wells No. 2
and 3 and FMC Well No. 1.
NIROP water supply wells shut down.
First quantifiable concentrations of TCE
identified at the Minneapolis water treatment
plant intake (0.0012 mg/L).
In response to these events, the following investigations, remedial actions, and
CERCLA enforcement activities have taken place:
September 1980
March 1982
May 1983
U.S. Navy implemented the Navy Assessment
and Control of Installation Pollutants (NACIP)
program.
The NACIP program was implemented at the
NIROP.
U.S. Navy authorized the current Installation
Restoration (IR) program.
11
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1983
November 1983 - March 1984
May 22, 1984
June 1986
March 1987
June 1987
November 1987 - February 1988
July 1988
August 1988
February 8, 1989
April 13, 1989
May 22, 1989
June 15, 1989
July 14, 1989
Initial Assessment Study (IAS) at the NIROP
was performed under NACIP. The IAS
identified that drummed waste was disposed in
the northern portion of the NIROP in 8- to 10-
foot-deep trenches or pits. Ground water
monitoring wells were installed and sampling
began.
Approximately 1,200 cubic yards of
contaminated soil and 43 drums were
excavated and disposed off-site in a USEPA-
approved landfill.
The MPCA issued a Request for Response
Action at the site to the U.S. Navy and FMC
Corporation.
A remedial investigation (Rl) and feasibility
study (FS) was initiated by the U.S. Army
Corps of Engineers, for the U.S. Navy.
All use of trichloroethylene at the NIROP was j
discontinued. 1,1,1 -trichloroethane was put •
into use in place of trichloroethylene. j
Final Rl report was issued. Additional
investigations recommended.
Additional investigations were performed at the
NIROP.
FS report and an Addendum to the Rl report
were issued.
Addendum to the FS report was issued.
The U.S. Navy establishes the Technical
Review Committee (TRC) for the project and
convenes the first meeting. TRC membership
includes the following: USEPA, MPCA, U.S.
Navy, Corps of Engineers, Anoka County, City
of Fridley, FMC Corp., Metropolitan Waste
Control Commission, Minnesota Department of
Natural Resources, and RMT, Inc.
TRC meeting #2 held.
Public meeting to present the RI/FS held in
Fridley, Minnesota.
TRC meeting #3 held.
NIROP listed as a proposed site on the NPL by
the USEPA.
12
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September 13, 1989
November 21, 1989
February 7,1990
May 1, 1990
May 9, 1990
May 9, 1990
May 1, 1990 - May 30, 1990
May 22, 1990
TRC meeting #4 held.
NIROP listed as a final site on the NPL by the
USEPA.
TRC Meeting #5 held.
U.S. Navy issues final Proposed Plan for
ground water remediation after review by the
MPCA and USEPA.
TRC Meeting #6 held.
Public meeting to present the Proposed Plan
held in Fridley, Minnesota.
Public comment period for the proposed
ground water remedial action.
Special Notice letter from USEPA received at
the NIROP.
13
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3. COMMUNITY RELATIONS HISTORY
A statement of the basis and purpose of the selected action can be found on page 1
of this document. The RI/FS documents and Proposed Plan were made available to the public
in both the Administrative Record and information repositories maintained at the USEPA
Region V Docket Room in Chicago and the Anoka County Library in Fridley. The notice of
availability of these documents and a notice for the public meeting were published in various
local and area newspapers. Fact sheets explaining the Proposed Plan were mailed to
approximately 400 residents prior to the public meeting. Copies of the Proposed Plan were
mailed to TRC members and other interested local officials.
The public comment period occurred from May 1 to May 30, 1990. A public meeting
was held on May 9, 1990, at the Fridley Community Education Center. At this meeting,
representatives from the U.S. Navy, USEPA, and the Minnesota Pollution Control Agency (
(MPCA) answered questions about the NIROP and the Proposed Plan. Responses to verbal}
as well as written, public comments are contained in the Responsiveness Summary included
in this Record of Decision.
Prior to the public comment period in May 1990, there was limited community
involvement in activities at the NIROP. In May 1989, newspaper announcements were placed
for a public meeting presented by the U.S. Navy and other members of the Technical Review
Committee in Fridley on May 22, 1989, to discuss the results of the RI/FS. There was no
attendance at this meeting.
Local input to the selection of the preferred remedy has come predominantly through
the Technical Review Committee (TRC) established by the U.S. Navy in February 1989. TRC
membership has included the USEPA, the MPCA, the U.S. Navy, the Corps of Engineers,
Anoka County, the City of Fridley, FMC Corp., the Metropolitan Waste Control Commission, the
Minnesota Department of Natural Resources (MDNR), and RMT, Inc. Subsequent meetings
have been held in April, June, and September 1989, and in February and May 1990.
Involvement through the TRC has facilitated remedial planning and has alerted local groups to
the proposed activities.
14
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4. SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
Prior to the RI/FS work for this site, the Navy had conducted a removal action in 1983
and 1984 to address the immediate threat of hazardous substances posed by past waste
disposal practices. Approximately 1,200 cubic yards of contaminated soil and 43 drums were
excavated and disposed off-site in a USEPA-approved landfill.
The RI/FS work for this site addressed both the soil and ground water media. During
the evaluation of alternatives, it was determined that the available data were not sufficient to
determine an appropriate response, if any was required, for contaminated soil. Additional
investigative work concerning the source of the contamination was requested by the USEPA
and MPCA and is presently being organized by the U.S. Navy.
This ROD addresses the remedial action planned for a ground water operable unit at
the site. The principal threat posed by the site is the continuing migration of TCE via grou
water to the Mississippi River. This remedial action addresses the principal threat by providing
total hydraulic containment to prevent migration of all contaminated ground water off the
NIROP, and by recovering, to the extent feasible, contaminated ground water beneath the
Anoka County Parkland. The need for future action, possibly as a separate operable unit, to
address potential contamination sources at the NIROP will be addressed pending the results
of the upcoming investigative work.
The Navy believes that the combination of source remediation, if any subsequent
RI/FS concerning the source indicates such remediation is necessary, and ground water
remediation should address all contamination at the site. By remediation of contaminated
soils, if found to be present, contaminant loading to ground water and risks posed by the
contaminated soils at the NIROP would be reduced. By remediation of contaminated ground
water, the Navy believes that present and future risks posed by migration of contaminated
ground water will be reduced. This remedial action for hydraulic containment and recovery of
ground water at the NIROP, and to the extent feasible, ground water downgradient of the
NIROP, will stop future migration of contaminated ground water from the NIROP and will
provide protection to the City of Minneapolis water supply intake.
15
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5. SUMMARY OF SITE CHARACTERISTICS
The first phase of the remedial investigation began in June 1986, and an Rl report was
submitted in June 1987. Based on the initial Rl work, a follow-up investigation was performed
between November 1987 and February 1988. An Rl addendum report was submitted in
July 1988.
Analysis of information gathered during the two phases of the remedial investigation
indicates the site characteristics listed below.
TCE Usage and Potential Source Areas
All use of TCE at the NIROP was discontinued by April 1, 1987. Plant
operations which previously used TCE now use 1,1,1-trichloroethane. A
solvent management program is currently in place at the NIROP, and disposal
of solvents is in accordance with state and federal regulations.
Elevated concentrations of TCE and dichloroethylene were found in soil pore I
gas near the former pit/trench disposal area, near a concrete pad in the nortrj
storage yard area, and at several locations near the north property boundary;
The former pit/trench disposal area (and immediate vicinity) in the northern
region of the NIROP is considered an on-site source area. Findings from the
soil pore gas survey and on-going occurrence of TCE in the ground water
suggest that it is likely that some VOC residuals and/or VOC-contaminated soil
still exist in this area. Investigations showed TCE at the intermediate depth of
the uriconsolidated aquifer in the southeast corner of the NIROP.
Unidentified sources are suspected at the NIROP near the eastern NIROP
property boundary, and east and northeast of the NIROP property.
Because TCE is present in upgradient wells, upgradient sources may also be
contributing to ground water contamination originating at the NIROP.
The NIROP includes controlled access to plant grounds and buildings.
TCE is a probable human carcinogen. Remediation of TCE will concurrently
address risks posed by other constituents.
Hydrogeology
Site hydrogeology consists of an unconsolidated sand and gravel aquifer
overlying a bedrock aquifer. The unconsolidated aquifer consists of 85 feet of
saturated thickness. The water table is 20 to 25 feet below the surface. A
discontinuous till layer is present at approximately 50 to 80 feet (Figure 3).
16
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The underlying bedrock consists of the Prairie du Chien/Jordan (PCJ)
dolomite. The St. Peter Sandstone overlies the PCJ across the northern
portion of the NIROP. The St. Peter Sandstone acts as a confining layer
where it is present; where it is absent, the unconsolidated aquifer is
hydraulically connected to the PCJ.
Ground water flow in the unconsolidated aquifer is generally from the
northeast to the southwest across the NIROP. The aquifer discharges to the
Mississippi River, and is the predominant migration pathway.
There are currently no ground water users downgradient of the NIROP in the
Anoka County parklands. The United States Geological Survey (USGS) has
studied the parklands for potential development of a supplemental water
supply system for the City of Minneapolis. No decision has been made to
date on whether any community in the area will install wells in the future for a
water supply in Anoka County Park land downgradient of the NIROP.
Extent of Migration via Ground Water
Ground water in the unconsolidated aquifer beneath the NIROP contains
volatile organic compounds (VOCs), including the following: TCE,
1,1,1-trichloroethane, 1,2-dichloroethylene, tetrachloroethylene, {
1,1-dichloroethane, toluene, xylene, and ethylbenzene. Concentrations of »
these constituents are listed in Table 1. !
TCE was found more frequently and at higher concentrations than any other
VOC, and is therefore the best indicator chemical. The approximate extent of
TCE in ground water is illustrated on Figures 4 and 5.
Concentrations of TCE in ground water reaching the Mississippi River are
probably on the order of 1 to 10 mg/L This range of TCE concentrations can
be expected to continue if no remedial action is taken, given the TCE levels
detected at the southwest corner of the NIROP.
The investigations show concentrations of VOCs below drinking water
standards in the Prairie du Chien bedrock aquifer.
Extent of Migration via Storm Sewers
One round of samples was collected from storm sewers serving the NIROP.
No VOCs were found.
17
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TABLE 1
RANGE OF VOCs IN GROUND WATER (mg/L) ,
CONSTITUENT
Trlchloroethylene
1.1,1-Trichloroethane
1 ,2-Dichloroethylene
Tetrachloroethylene
1,1-Dichloroethane
Toluene
Xylene
Elhylbenzene
MCL
0.005
0.20
NP
0.005
NP
NP
NP
NP
UPGRADIENT WELLS
SHALLOW
< 0.005-0.17
< 0.005 - 0.002
< 0.005
< 0.005 • 0.001
< 0.005
< 0.005
< 0.005
< 0.005
DEEP*
< 0.005 - 0.004
< 0.005
< 0.005
< 0.005
< 0.005 - < 0.010
< 0.005
< 0.005
< 0.005
ON-SfTE WELLS
SHALLOW
< 0.005 - 28.0
< 0.005 • 0.39
< 0.005 - 0.31
< 0.005 - 0.22
< 0.005 - 0.066
< 0.005 -0.010
< 0.005
< 0.005 - 0.037
DEEP*
< 0.005 - 37.0
< 0.005 - 0.287
< 0.005-1.41
< 0.005 -0.141
< 0.005 - 0.106
< 0.005 - 0.012
< 0.005 - 0.036
< 0.005 - 0.21
DOWNGRADIENT WELLS
SHALLOW
< 0.005 - 12.7
< 0.005
< 0.005 - 2.44
< 0.005 - 0.021
< 0.005 - 0.009
< 0.005
< 0.005
< 0.005
DEEP*
< 0.005 - 10.8
< 0.005 - 0.0086
< 0.005 - 0.092
< 0.005
< 0.005 - 0.003
< 0.005 - 0.0082
< 0.005
< 0.005
• D««p wells Include piezometers Installed at various depths In the unconsolidated aquifer. VOCs were not detected In bedrock wells
above MCLs.
NP - No MCL Promulgated.
Values listed which are below the detection limit (0.005 mg/L) are estimated values (M* qualifiers).
-------
APPROX
PIT TRENCH
AREA
NIROP FACILITY
FMC FACILITY
EXTENT OF TCE IN UPPER ZONE
OF UNCONSOLIDATED AQUIFER
— 1.0 — ISO-CONCENTRATION LINE, mg/L TCE
(DASHED WHERE INFERRED)
FIGURE 4
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APPROX.
PIT TRENCH
AREA
NIROP FACILITY
^
^
EXTENT OF TCE IN LOWER ZONE
OF UNCONSOLIDATED AQUIFER
UEQEND
— 1.0 — I80-CQMCINTMATION LINE, mf/L TCE
(DASHED WHERE INFERRED*
>eo'
i" • 300'
FIGIIRP
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6. SUMMARY OF SITE RISKS
Actual Human Risks
The primary concern resulting from contamination from the NIROP is human ingestion
of VOC contaminants in ground water, either directly or via the Minneapolis water treatment
plant intake on the Mississippi River. Concern is focused on trichloroethylene (TCE) since it
represents the predominant constituent at the NIROP and has been widely detected in
concentrations above the drinking water standards Maximum Contaminant Level (MCL) in
ground water. Of the highest observed VOC concentrations in shallow and deep wells
downgradient of the NIROP, TCE accounts for over 90 percent of the total VOCs. Other
constituents pose considerably lower risks in comparison to TCE; therefore, TCE provides a
good indicator of total risk. In addition, remediation designed to recover TCE will concurrently
address other constituents. .
In the short term, the only potential point of significant human exposure is via
ingestion of drinking water from the Minneapolis water treatment plant. The intake for the
plant is located on the Mississippi River approximately 1,500 feet south of the NIROP, and
could potentially be affected by ground water entering the river near the NIROP. Based on Rl
data, it was estimated that ground water entering the river would mix with from 10 to 100
percent of the total river flow before reaching the city water treatment plant intake farther
downstream. It was assumed that there would be no volatilization or other losses of TCE
within the river or during the treatment process within the city water treatment plant.
TCE is a probable human carcinogen. As a result, the excess lifetime cancer risk to
the exposed population would be approximately 2 x 10'5 and 2 x 10* respectively, under 10-
and 100-percent mixing estimates using the 7-day, 10-year low river flow and a typical TCE
concentration in the ground water discharge of 10 mg/L These risk estimates are based on
the assumed presence of TCE in the city water treatment plant intake. No TCE has been
found in samples collected annually by FMC at the intake for the past 3 years, at a detection
21
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limit of 5 \ig/L Therefore, if an exposed population does not exist, the actual risk is zero.
TCE had been previously detected in 26 of 40 samples collected by the MPCA from 1981 to
1983 at the city water treatment plant intake, at concentrations less than 5 jig/L
Potentlal Human Risks
Possible future effects on public health would vary depending on whether the
concentration of TCE in ground water discharging to the river increases or decreases. In the
long term, possible future effects may also include the creation of a completely new exposure
pathway. At the present time, there is no consumption of ground water or surface water
between the NIROP property line and the city water treatment plant intake on the Mississippi
River approximately 1,500 feet south of the NIROP. The installation of a new water supply well
downgradient of the NIROP, before ground water enters the river, would create a new j
exposure pathway. The United States Geological Survey (USGS) has investigated the !
suitability of this area for supplemental water supply purposes for the City of Minneapolis.
Although no decisions have yet been made on whether or not to use ground water from this
area, the existing contamination is one factor that would influence the selection of this
potential water source area. Since ground water in this location contains higher
concentrations of VOCs than would exist at the city intake, the risk level would increase under
such an exposure scenario.
Maximum and typical ground water VOC concentrations in downgradient wells are
listed in Table 2 with the corresponding potential risk. These risks represent the risks
associated with ingestion of ground water. Since the exact exposure point concentration is
not known, and may change in the future, the range of typical values reported in Table 2
represents typical concentrations encountered in ground water which may be recovered under
the future use scenario. TCE accounts for the majority of risk in comparison to other
carcinogens.
22
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TABLE 2
POTENTIAL RISKS ASSOCIATED WITH VOCs IN GROUND WATER
DOWNGRADIENT OF THE NIROP
Carcinogen
Trichloroethylene
Tetrachloroethylene
1-1-Dichloroethane
Concentration (mg/L)
Maximum
12.7
0.21
0.009
Typical
1-10
< 0.003
< 0.005
CDI01 (mg/kg-d)
Maximum
0.363
0.0006
0.0003
Typical
0.028-0.28
< 0.00014
< 0.00014
CSF121
(mg/kg-d)1
1.1 E*
5.1 E2
9.1 E2
TOTAL
Potential Risk
Maximum
4E*
3E*
2E9
4E3
Typical '
3 E* - 3 £•*
<7E«
< 1E9
3 E* - 3 E 3
01 GDI = Chronic Daily Intake
0 Source: USEPA, January/April 1990. Health effects assessment summary tables: First/second quarter 1990. OERR 9200.6 -
303(90-1/2). CSF = Cancer Slope Factor
-------
s
The land between the NIROP property and the Mississippi River currently serves as a
park owned by Anoka County. Access to existing potable water supplies provided along East
River Road is available, which would eliminate the necessity for installation of any new water
supply well in the parkland immediately downgradient of the NIROP. However, if ground water
in the narrow strip of parkland between the NIROP and the Mississippi River is used in the
future for potable water supplies, the Navy will control the hearth risk within acceptable levels
by implementation of a ground water treatment system or other measures as approved by the
MPCA and the USEPA. (This alternative was evaluated during the FS.)
Actual or Potential Environmental Risks
Potential environmental risks resulting from present conditions at the site consist of
ingestion or uptake of TCE and other VOCs by aquatic organisms in the Mississippi River, j
Since VOCs readily evaporate from surface waters and since they typically do not !
bioaccumulate, the risk to aquatic organisms is not believed to be significant. The acute and
chronic Ambient Water Quality Criteria for TCE are 45.0 and 21.9 mg/L, respectively. The
typical range of TCE in the plume migrating to the river is 1 to 10 mg/L (maximum value =
12.7 mg/L), indicating that these criteria will not be exceeded.
24
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7. DESCRIPTION OF ALTERNATIVES
The Feasibility Study developed a total of eight remedial alternatives to respond to the
conditions defined during the remedial investigation. These alternatives addressed both soil
and ground water at the NIROP, although the preferred alternative presently addresses only
the ground water operable unit, pending additional investigation of soil at the NIROP.
No-Action Alternative
The Superfund program requires that the 'no-action* alternative be considered at every
site. Under this alternative, no specific action would be taken to prevent exposure to soil or
ground water at the NIROP. A long-term ground water monitoring program would be
developed and implemented using previously installed monitoring wells to further assess
present and future conditions. !
Alternative A: Capping
This alternative consists of the construction of a 6,000-square-foot concrete cap over a
potential source area of ground water contamination at the NIROP. The contamination source
addressed by this alternative is the residual concentrations of VOCs contained in soil in the
vicinity of the previous pit/trench disposal area located at the north end of the NIROP. This
alternative would reduce infiltration and subsequent contaminant loading to ground water.
The area would be graded to promote surface water drainage away from the cap.
Precipitation which accumulates on the cap would be drained via modifications to the facility's
storm water collection system. A long-term ground water monitoring program would also be
implemented.
25
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Alternative B1: Soil Excavation and Disposal in an Off-site Landfill
This alternative consists of the excavation of approximately 300 cubic yards of soil
containing residual concentrations of VOCs, and disposal in an off-site RCRA Subtitle C
landfill. Excavation would be centered around the trench locations originally excavated in
1983. This alternative would reduce contaminant loading to the ground water. The excavation
would be backfilled with clean soil. A long-term ground water monitoring program would be
implemented.
Alternative B2: Soil Excavation and Disposal in a Landfill at the NIROP
This alternative is analogous to alternative B1 with the exception that disposal would
be in a newly constructed RCRA-permitted landfill at the NIROP.
i
Alternative C: Soil Excavation Treatment and Disposal I
This alternative would consist of the aeration of approximately 300 cubic yards of
excavated soil at the NIROP prior to backfilling in the original excavation. VOCs would be
removed down to an established treatment performance level.
Alternative D: Soil Treatment Using In-situ Vacuum Extraction
This alternative involves treatment of soil in the vicinity of the former disposal pits and
trenches. In-situ vacuum extraction technology would be used to remove residual
concentrations of VOCs by inducing a negative pressure on the unsaturated soil. Enhanced
airflow through the soil would volatilize adsorbed constituents, and the recovered air would be
vented to the atmosphere. If necessary, the system would be equipped with air treatment
equipment to meet local air emission requirements. A long-term ground water monitoring
program would be implemented.
26
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Alternative £: Ground Water Pumping and Disposal
•
This alternative consists of ground water recovery using a series of pumping wells and
direct discharge to the Metropolitan Waste Control Commission sanitary sewer system. An
option to discharge directly to local storm sewers was also considered.
Alternative F: Ground Water Pumping Treatment and Disposal
This alternative involves the pumping of ground water from source areas and
downgradient locations. For evaluation purposes, it was assumed that five hydraulic
containment and recovery wells would operate at a combined flow rate of up to 650 gpm.
Although various disposal options were considered, the base-line alternative specified a
phased ground water remediation plan. Under Phase I, recovered ground water would be .
discharged to the Metropolitan Waste Control Commission (MWCC) sanitary sewer system, .
where tt would be treated at the Pig's Eye Wastewater Treatment Plant. Pre-treatment would
be used, if necessary, to meet MWCC requirements.
During Phase II, one of two treatment process options would be incorporated into the
pumping program, pending the results of testing on recovered water during Phase I:
Option A: Treatment of ground water at the NIROP by two-stage air stripping,
with disposal through an existing NPOES-permitted storm sewer
outfall, and treatment of air emissions using vapor-phase granular
activated carbon. Spent activated carbon would be regenerated at a
permitted off-site facility.
Option B: Treatment of ground water at the NIROP using aqueous-phase
granular activated carbon, with disposal through an existing NPDES-
permitted storm sewer outfall. Spent activated carbon would be
regenerated at a permitted off-site facility.
Two additional alternatives were presented in the Feasibility Study to address the
possibility that the City of Minneapolis may decide to develop a supplemental water supply
well system downgradient of the NIROP, located within the TCE plume. One of these
alternatives included a 'point of use' ground water treatment system utilizing granular
27
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activated carbon, to be installed at the location of the potential well field. Spent activated
carbon from (he treatment system would be regenerated at a permitted off-site facility. The
second additional alternative considered the possibility of relocating the proposed water
supply well system, and providing additional piping and construction easements, as
necessary. The alternatives would be available if future decision-making called for
development of a supplemental water supply system in the Anoka County Parkland.
28
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8. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
8.1 Overall Protection of Human Health and the Environment
The No-Action alternative would not provide increased protection of human health or
the environment above existing conditions.
Alternative A would reduce potential contaminant loadings to ground water over the
long term, but would not reduce potential exposures from existing conditions.
Similarly, Alternatives B1, B2, C, and D would remove a long-term source of
contaminant loading by excavation and/or treatment. However, Alternative B1 would result in
re-disposal of NIROP materials at an off-site disposal facility, which could result in possible
future migration from the off-site facility. None of these alternatives address the more
immediate potential exposures resulting from constituent migration via ground water.
Alternatives E and F would provide a high degree of overall protection by reducing '
potential ingestion of VOCs in ground water affected by the NIROP, and by mitigating '
continued discharge of VOCs to the Mississippi River. Alternative F would be implemented
with state and focal discharge approvals that specify protective levels for air and water
emissions.
8.2 Compliance with Applicable or Relevant and Appropriate Requirements (ARARs)
For soil, chemical-specific ARARs have not been identified. Certain remedial
alternatives would be subject to action-specific ARARs under the Resource Conservation and
Recovery Act (RCRA) for source area capping (Alternative A) and soil disposal (Alternatives B1
and B2). RCRA treatment standards may also be ARARs for soil treatment under
Alternative C. Off-site disposal would be subject to RCRA land disposal restrictions.
For ground water, the Maximum Contaminant Level (MCL) for TCE has been
identified as relevant and appropriate as a ground water cleanup target at the site.
Alternatives E and F would seek to meet this ARAR by hydraulic containment and direct
29
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ground water removal. Alternatives A, B1, B2, C, and D would provide source control, but
would not directly meet the MCL ARARs for ground water.
Discharges of ground water under Alternatives E and F would meet local and state
requirements. Air emissions under Alternatives D and F (and possibly C) would be subject to
state air emission requirements.
A summary of major ARARs for each alternative is provided in Table 3.
8.3 Long-Term Effectiveness and Permanence
The No-Action alternative would provide no long-term effectiveness or permanence.
The remaining alternatives would provide long-term effectiveness in varying ways.
Alternatives E and F would provide long-term migration control and permanent contaminant
removal from the saturated zone, but not the unsaturated zone. Alternatives A, B1, B2. C, I
and 0 would permanently remove contaminant sources in the unsaturated zone, with the likely
result of a gradual improvement in ground water quality over time.
8.4 Reduction of Toxlcltv. Mobility, and Volume
The No-Action alternative would not reduce the toxicity, mobility, or volume of
contaminants in soil or ground water.
Alternative A would reduce future mobility of contaminants from unsaturated soil to
ground water by limiting the infiltration of precipitation, but would not reduce toxicity or
volume.
Alternatives B1, B2, C, and D would reduce mobility, toxicity, and volume by removing
a contaminant source. Alternative B1 would provide the highest degree of reduction by
disposal of excavated soil off-site. Alternatives C and 0 would transfer contaminants from a
solid matrix to the air matrix, with possible recovery and destruction of contaminants from the
air matrix under Alternative D.
30
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TABLES
ACTION-SPECIFIC ARARS
No Action
A. Capping
B1. Soil Excavation and Disposal in an Off-Site Landfill
B2. Soil Excavation and Disposal in a Landfill at the NIROP
C. Soil Excavation, Treatment, and Disposal
D. Soil Treatment Using In-Situ Vacuum Extraction
E. Ground Water Pumping and Disposal
F. Ground Water Pumping, Treatment, and Disposal
Option A: Air Stripping
Option B: Aqueous Granular Activated Carbon
RCRA Subtitle C, Subpart F, Ground Water Monitoring
RCRA Subtitle C, Subpart F and Capping Requirements
i
RCRA Subtitle C, Subpart F; DOT Transport Requirements; Land
Disposal Restrictions
RCRA, Subtitle C, Subpart F, TSD Requirements, Closure and
Minimum Technology Requirements
RCRA Subtitle C, Subpart F, TSD Requirements, Closure and
Minimum Technology Requirements; CAA - NAAQs for VOCs
RCRA Subtitle C, Subpart F, TSD Requirements; CAA - NAAQs for
VOCs
RCRA Subtitle C, Subpart F; MWCC Pretreatment Requirements;
NPDES Permit for Storm Sewer Discharge
RCRA Subtitle C, Subpart F, TSD Requirements; CAA - NAAO's for
VOCs; CWA - NPDES for VOCs; WQS - MCLs; Land Disposal
Restrictions and DOT Requirements for Spent Activated Carbon.
RCRA Subtitle C, Subpart F, TSD Requirements; CWA - NPDES for
VOCs; WQS - MCLs; Land Disposal Restrictions and DOT
Requirements for Spent Activated Carbon.
-------
Alternatives E and F provide direct reductions in the toxicity, mobility, and volume of
contaminantsjn ground water. Emissions of contaminants via air or water discharges would
be within state limits.
8.5 Short-Term Effectiveness
The No-Action alternative would provide no short-term effectiveness.
Alternatives E and F would provide the highest degree of effectiveness in the short
term by directly mitigating the movement of constituents via ground water to the Mississippi
River and potential subsequent receptors.
Alternatives A, B1, B2, C, and D would provide limited short-term effectiveness
because they primarily address constituents only in the unsaturated zone. They would not
provide immediate migration control. j
I
8.6 Implementabllltv
All of the alternatives are implementable. Alternative A is the most straightforward from
an engineering standpoint, and would involve simple construction methods. Alternative 61 is
also straightforward, but implementation would require off-site disposal approval.
Alternatives B2, C, and D would involve either more sophisticated construction
techniques or a form of soil treatment. Although more complex, they are readily
implementable.
Alternatives E and F would involve a relatively higher degree of uncertainty due to the
complexities of ground water flow and recovery technology. This can be overcome by a
program of effectiveness monitoring and treatment monitoring, with system adjustments as
needed. Discharge approvals would be required.
32
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8.7 Costs
The estimated capital and total present worth costs for each alternative are
summarized below.
Alternative
No Action
A Capping B
B1 Excavation and Off-Site
Disposal "'
B2 Excavation and Disposal at
the NIROP (1)
C Excavation, Treatment, and
Disposal '"
D jn Situ Vacuum Extraction m
E Pump and Dispose of
Ground Water (1)
F Pump, Treat, and Dispose of
Ground Water w
Option 1 : Air Stripper
Option 2: GAG
Estimated Costs ($ 1,000s)
Capital
40
210
170
370
150
1,000
320
1,100
800
Total Present Worth'
490
310
170
530
150
1,000
7,300
3,700
4,100
GA - Granular Activated Carbon
- Present worth based on 30-year period and 1 0% interest rate.
Note: For Alternative E, a substantial portion of the estimated present worth is
due to an estimated publicly owned treatment works (POTW) discharge
fee at $1.08 per 1,000 gallons of water.
Source:
01 RMT, Inc. 1988. Feasibility Study Report.
B RMT, Inc. 1988. Feasibility Study Addendum Report.
33
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8.8 Agency Acceptance
The MPCA and the USEPA have provided comments on the Rl and FS. The MPCA
and the USEPA agree with the recommended remedial action for a ground water operable
unit.
8.9 Community Acceptance
The community has not been strongly for or against any one of the alternatives.
Several questions have been raised over whether implementation of Alternative F would
deplete a ground water resource which may have otherwise had beneficial uses. The
hydrogeologic setting at the site has been reviewed, and it has been determined that pumping
of shallow ground water at the NIROP will not adversely affect other potential users. These
questions have also been addressed in the Responsiveness Summary. '
34
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9. THE SELECTED REMEDY
The selected remedial alternative to address the presence and migration of TCE and
other constituents in ground water at the NIROP is Alternative F: Ground Water Pumping,
Treatment, and Disposal. The objective of this alternative is to address the principal threat
posed by the site by providing hydraulic containment to prevent further migration of
contaminated ground water off the NIROP and by recovering, to the extent feasible,
contaminated ground water beneath the Anoka County Parkland. Based on the results of the
RI/FS, this alternative provides the best balance among the alternatives with respect to the
nine evaluation criteria specified under the National Contingency Plan.
The selected remedy will provide long-term effectiveness in satisfying the objective of
reducing future exposures to VOCs in ground water. The alternative provides a high degree
of permanence by recovering contaminated ground water at the site and treating f
contaminated ground water using approved and proven methods. Future migration and |
potential exposure to ground water beneath the Anoka County Parkland will be mitigated. In
this manner, both the mobility and volume of VOCs migrating to the Mississippi River are
reduced.
The initial goal of the selected alternative is to contain and recover contaminated
ground water from both the NIROP and, to the extent feasible, the Anoka County Parklands.
The targeted capture zone is illustrated on Figure 6. The ultimate goal is to restore ground
water quality in the unconsolidated aquifer at the site to Maximum Contaminant Levels (MCLs).
These goals comply with all identified Applicable or Relevant and Appropriate Requirements
(ARARs).
A portion of the aquifer within the Anoka County Parkland closest to the Mississippi
River may not fall within the zone of capture of the ground water recovery system. However,
should this occur, contaminants in any uncaptured portion of the aquifer are expected to
dissipate by natural means over time to levels that are protective of human health and the
35
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FRIDLEY WELL 13
APPROX.
PIT/TRENCH
LEGEND
^••^••^••B
— • —• NIROP PROPERTY BOUNDARY
FMC FACILITY BOUNDARY
© PROPOSED GROUNOWATER
RECOVERY WELL (APPROXIMATE
LOCATIONS. FINAL LOCATIONS BASED
ON UPCOMING PUMP TESTS.)
-~——• TARGETED ZONE OF CAPTURE
ZONE OF CAPTORE FOR
CONTAINMENT AND RECOVERY
OF GROUNDWATER
500
1"- 500'
FIGMRF
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environment. Should the City of Minneapolis or another community decide in the future to
develop a supplemental water supply well system in the Anoka County Parkland, the Navy will
control the health risk within acceptable levels by implementation of a ground water treatment
system or other measures as approved by the MPCA and the USEPA.
37
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Components of the Selected Remedy
The design concepts for the selected remedy as developed in the Feasibility Study
(FS) are illustrated on Figure 7, and include the following:
Phase I
Installation and operation of five ground water recovery wells at a
combined design flow rate of up to 650 gpm. Two wells will be installed at
source locations to capture the ground water plume containing higher
concentrations of TCE. The three remaining wells will be installed at the
downgradient side of the NIROP to control migration and recover ground water
which has already moved off the NIROP to the fullest extent possible.
Discharge of ground water to the local sanitary sewer. The discharge will
meet local regulations, and the water will be treated at the Metropolitan Waste
Control Commission (MWCC) Pig's Eye Wastewater Treatment Facility. If
necessary to meet MWCC requirements, pretreatment will be provided.
Testing and design of a treatment system located at the NIROP. During
Phase I, testing will be performed on pumped ground water to establish j
design parameters for the full-scale treatment system. The phased approach*
to the ground water remediation will allow the start-up of ground water |
recovery operations while testing, remedial design, and construction of the
treatment system proceed.
Phase II
Construction and operation of a ground water treatment system, with
discharge of treated ground water through an NPDES-permrtted outfall to
the Mississippi River. The unit operations for the treatment system as
described in the FS include two-stage air stripping with treatment of the off-
gas using granular activated carbon. The final unit operations will be
determined during remedial design based on the discharge requirements
established by the state during the NPDES submittal review process, and
based on the results of treatability testing performed during Phase I.
Long-term monitoring of ground water quality changes and capture
effectiveness. A network of monitoring wells will be established and sampled
to determine ground water quality changes during remediation and the
effectiveness of ground water capture. Based on determinations of capture
effectiveness, the pumping rates for individual wells will be adjusted as needed.
to optimize recovery. If necessary to achieve hydraulic control, additional wells
will Deinstalled.
Operations and Effectiveness Monitoring
The ground water recovery and treatment systems will be monitored for proper
operation during the course of the remediation. This will include the following activities:
38
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BS
=1
si
$*
|8
il
SI
if
O
i
AT-1
AT-X
AT-:
r-3
PHASE
|_ NECESSMTV ,
ATMOSPHERE
APPROVED
DISCHARGE TO
SANITARY SEWER
AND TREATMENT
IN POTW
VAPOR PHASE
GRANULAR
ACTIVATED
CARBON
SPENT ACTIVATED
CARBON TO OFF-SITE
REGENERATION FACILITY
PHASE 2
EXTRACTION
WELLS
EQUALIZATION
TANK
NPDES PERMITTED
DISCHARGE TO
EXISTING STORM
SEWER
EFFLUENT
COLLECTION
TANK
AIR BLOWER
PREFERRED ALTERNATIVE^ GROUND WATER
PUMPOUT, TREATMErTT AND DISPOSAL
PROCESC FLOW DIAGRAM
-------
Collection of combined flow water samples prior to discharge to the MWCC
Pig's Eye Wastewater Treatment Facility.
*
Hydraulic evaluation of the capture effectiveness of the recovery well network.
The initial evaluation will occur within 90 days after start-up and will be
submitted to the USEPA and the MPCA by the U.S. Navy.
Periodic inspection of the ground water pumps, piping, and controls, and
routine maintenance as required.
Recording flow rates from individual wells and computing cumulative recovery
volumes for payment of sewer use charges.
Collection of individual well head samples for analysis of VOCs and other
indicator constituents.
Periodic inspection of pumps, blowers, piping, and other mechanical
components of the treatment system, and routine maintenance as required.
Collection and analysis of effluent samples from the ground water treatment
plant to demonstrate compliance with approved discharge limits.
i
A ground water monitoring program will be implemented to determine the j
effectiveness of the remediation. This will include the following:
Measurement of water levels in local monitoring wells to calculate the effective
ground water capture zone. Additional wells will be added, if necessary.
Adjustment of pumping rates as necessary to optimize ground water capture.
Collection of ground water samples and analysis for VOCs and other indicator
constituents.
Calculation methods for determining if MCLs have been reached in the aquifer,
and whether or not Alternative Concentration Limits (ACLs) are necessary.
A detailed operation, maintenance, and monitoring plan will be developed by the U.S.
Navy during the remedial design phase. The plan will document specific operations and
effectiveness monitoring techniques. The plan will be submitted for USEPA and MPCA review
and approval prior to implementation.
During the first 90 days of recovery system operation, the Navy will collect data to
determine whether hydraulic containment is being effectively achieved. This determination will
be summarized in a document which will be sent to the USEPA and MPCA for review and
40
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approval at the end of the 90-day period. The USEPA and MPCA will provide written approval
of, or commerjts on, the determination document within 30 days after its receipt. If the USEPA
and MPCA do not approve the determination document, the Navy will submit a revised
determination document to the USEPA and MPCA within 60 days after the Navy is notified of
specific deficiencies in the document. If the determination document, after its approval by the
USEPA and MPCA, indicates that effective hydraulic containment is not being provided by the
ground water recovery system, the Navy will prepare and submit to USEPA and MPCA a
written plan for upgrading the recovery system to assure that the performance objectives of
the containment system are met, and will implement the finally approved plan.
In addition, if it is determined by the Navy that pretreatment of water during the
Phase I discharge is necessary to meet MWCC requirements, the Navy will submit an
implementation plan to the USEPA and the MPCA within 30 days after this determination is f
made, which when approved by the USEPA and MPCA will be implemented by the Navy. I
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10. STATUTORY DETERMINATIONS
10.1 Protection of Human Health and the Environment
The selected remedy protects human health and the environment through hydraulic
containment, recovery, and treatment of TCE-contaminated ground water. TCE and other
VOCs will be permanently removed from the ground water by air-stripping or another
appropriate treatment technology. Air emissions from this treatment will be set at protective
levels established by the MPCA.
Recovery of the VOC-contaminated ground water will also eliminate the threat of
exposure from ingestion of VOCs via ground water or surface water. The present potential
carcinogenic risk of 2 x 105 to 2 x 10"8 will be reduced even further by hydraulically limiting the
migration of TCE-contaminated ground water to the Mississippi River. The future potential
carcinogenic risk of 3 x 10'3 to 3 x 10" will be reduced to a protective level based on the MCj.
for TCE, which will be the target cleanup level for the site (see discussion below). |
There are no short-term threats associated with the selected remedy that would weigh
against the long-term protection. No adverse cross media impacts are expected.
10.2 Compliance with ARARs
Chemical-Specific ARARs
Because of the potential for the placement of a supplemental well field in the
contaminated ground water downgradient of the NIROP to provide additional drinking water to
the city of Minneapolis, and questions regarding the permanence of existing prohibitions on
placement of private wells in the parkland, federal and state health-based standards for
drinking water were considered in determining the cleanup level required for the contaminated
ground water aquifer. These include standards established under the Federal Safe Drinking
Water Act (SDWA) and the State of Minnesota Recommended Allowable Limits (RALS) for
drinking water.
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The SOWA established Maximum Contaminant Levels (MCLs) and Maximum
Contaminant Level Goals (MCLGs) for specific contaminants to ensure the quality of drinking
water supplies. MCLGs are non-enforceable health goals, set at levels where no known or
anticipated adverse health effects will occur in exposed people and which allow for a margin
of safety. Technical feasibility or cost are not taken into account. MCLs are enforceable limits
for the concentration of certain contaminants in public water supplies. They are required to be
at levels as close to MCLGs as feasible, taking into account use of the best available treatment
technologies, costs to public water systems, and analytical limits of detection. The MCLG for
TCE is 0. The promulgated MCL for TCE is 5.0 jig/L
The MCLs and MCLGs apply at the tap to 'public water systems,' which are water
systems having at least 15 service connections or which regularly serve at least 25 individuals.
They would thus be applicable to water supplied to users of the Minneapolis public water j
supply. They would be applicable to ground water in the aquifers at the Anoka County Park I
the aquifers were used directly for public drinking water. At this time, there are no wells
downgradient of the NIROP supplying public drinking water. The Minneapolis water treatment
plant intake receives some portion of the ground water, but this is diluted with river water, and
the water is treated before delivery to users. The SDWA standards would apply after such
dilution and treatment at the tap.
The SOWA standards are 'relevant* cleanup standards for the remediated ground
water, however, because the ground water may in the future be accessed through wells for a
drinking water supply, and because it may be drawn into the Minneapolis public water supply
intake in the Mississippi River downstream of the NIROP. The USEPA has determined that
MCLs are relevant and appropriate standards for ground water that may be used for drinking
water unless, under the circumstances at a site, more stringent standards must be applied to
ensure protection of public health or the environment.
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The Minnesota Department of Health's Recommended Allowable Limits (RALs) for
drinking water may also be considered in establishing target ground water cleanup levels.
Although these recommended contaminant levels are not promulgated state standards, and
therefore are not ARARs, such nonpromulgated federal or state advisory levels may be
considered in determining target cleanup levels. Similar to MCLs, these levels are in the 10"*
to 10"* cancer risk range, which the USEPA has determined to be acceptable for carcinogens.
The RAL for TCE is 31 jig/L However, since the MCL is more protective, and since state
guidance specifies that RALs should not be used in place of MCLs, the MCL for TCE (5 ppb)
will serve as the target cleanup goal for ground water for the site.
*
Attainment of Cleanup Targets
The achievable concentration of any constituent in ground water from a pumping '
program cannot be predicted with certainty. At this site, there is a medium to high uncertainty
that cleanup targets can be achieved within a reasonable time frame. Despite extensive
recovery efforts, very low concentrations of TCE may persist in the aquifer above the target
cleanup level. If at some time in the future, the Navy believes that achieving the target
cleanup level (MCL) is technically impracticable, at that time the Navy will apply for an
Alternate Concentration Limit (ACL) in accordance with guidance for implementation of ACLs.
The Navy plans to use a mathematical formula to determine if concentrations have dropped to
an asymptotic level. This asymptotic level will be used to show technical impracticability.
The procedures to be used to determine whether an asymptotic level has been
reached, and when it has been reached, will be included in the ground water monitoring
program plan to be submitted to the USEPA and the MPCA for review and approval prior to
start-up of the ground water recovery system. In addition, if it is shown, based on the facts at
the time, that upgradient sources are contributing VOCs to the ground water, the U.S. Navy
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will request approval of an alternate cleanup target level or approval to terminate ground water
recovery operations.
Action-Specific ARARs
The contaminated ground water extracted by pumping will be discharged under
Phase I to the sanitary sewer for treatment at the Pig's Eye Wastewater Treatment Facility, a
publicly owned treatment works (POTW). Section 307(b) of the Clean Water Act, 33 U.S.C.
§1317(b), and regulations promulgated thereunder (40 CFR 403), require POTWs to develop
and enforce pretreatment standards (specific effluent limitations regulating the amounts of
pollutants that may be discharged to the POTW) to prevent interference with operation of the
POTW and pass-through of pollutants through the wastewater treatment system to surface
water. These requirements are applicable to this remedial action because, during Phase I, thje
contaminated ground water will be discharged to a POTW. The MWCC has established a j
discharge limit for total VOCs of 10 mg/L, and 3 mg/L for any single VOC to be met at the
point of discharge to the existing sanitary sewer prior to mixing with any other wastewater. If
necessary, pretreatment equipment will be installed to meet MWCC limits. During the
discharge period, periodic monitoring will be conducted to demonstrate the effectiveness of
hydraulic containment.
Under Phase II, the discharge of treated ground water to the Mississippi River will be
subject to state NPDES requirements. The MPCA will set numerical limits for contaminant
concentrations in the treated ground water. These limits will form the basis for final design of
the ground water treatment plant at the NIROP.
Location-Specific ARARs
No location-specific ARARs have been identified.
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Other Requirements
In addition to the regulations described above, the U.S. Navy will be responsible for
obtaining all other federal, state, and local approvals which are necessary for performance of
the ground water remedial action. The following requirements have been discussed with the
USEPA and the MPCA for the remedial action at the NIROP:
Minnesota Department of Health approval for all ground water recovery well
installations.
Minnesota Department of Natural Resources approval for ground water
resource appropriation.
Minnesota Pollution Control Agency agreement with respect to the state
nondegradation policy for surface water discharges.
Minnesota Pollution Control Agency approval for a point-source air discharge
from the air stripping columns in the ground water treatment facility.
Metropolitan Waste Control Commission, Anoka County, and City of Fridley .
approvals for access to and construction of sewer tie-ins as needed. |
The U.S. Navy has also obtained approval from FMC for placement of recovery and monitoring
wells on FMC property.
The MPCA, MWCC, Anoka County, and the City of Fridley have been active in TRC
meetings and are aware of the proposed remedial action. This prior knowledge and
participation in project planning should facilitate the approval process.
10.3 Cost-Effectiveness
The selected remedy is cost effective because it provides a degree of protection
commensurate with its cost. The present-worth cost estimate for the selected alternative
(Alternative F) is $3,700,000. Of the two alternatives providing direct ground water recovery
(Alternatives E and F), the selected remedy is the less costly.
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10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
The selected remedy represents the maximum extent to which permanent solutions
and treatment technologies can be utilized in a cost-effective manner. Treatment is a principal
element of the remedy as it will be applied to the recovered ground water. The remedy is
permanent because it results in removal of TCE and other constituents from the aquifer.
The remedy represents the best balance among the nine criteria used in the
alternatives evaluation. Of the available alternatives evaluated, it provides the highest degree
of protection in reducing potential present and future exposure to TCE. The remedy will
comply with ARARs by meeting the MCL for TCE as the target cleanup level for the site. The
alternative will reduce the toxicity, mobility, and volume of TCE in the aquifer. By meeting the
MCL for TCE, other VOCs will also be reduced proportionately. The alternative is
implementable and is effective in both the short-term and long-term. The MPCA and the '
USEPA concur with the remedy.
10.5 Preference for Treatment as a Principal Element
Ground water will be treated during the initial Phase I period at the Pig's Eye
Wastewater Treatment Plant and during the long-term Phase II period at a treatment plant at
the NIROP specifically designed and constructed for that purpose. Therefore, the statutory
preference for remedies that employ treatment as a principal element is satisfied.
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RESPONSIVENESS SUMMARY
OVERVIEW
At the time of the public comment period, the U.S. Navy had selected a preferred
remedy to address ground water contamination at the NIROP. This preferred remedy was
selected in coordination with the USEPA and the MPCA. Other members of the Technical
Review Committee (TRC) for this project were also involved in discussions and planning of the
ground water recovery and treatment alternative. Technical details of the alternative have
been discussed, and no fundamental objections to its selection have been raised.
The sections below describe the background of community involvement on the project
and the U.S. Navy's responses to verbal and written comments received during the public
comment period. I
BACKGROUND OF COMMUNITY INVOLVEMENT '
Prior to the public comment period in May 1990, there was limited community
involvement in activities at the NIROP. In May 1989, newspaper announcements were placed
for a public meeting presented by the U.S. Navy in Fridley to discuss the results of the RI/FS.
There was no attendance at this meeting.
Local input to the selection of the preferred remedy has come predominantly through
the TRC, established by the U.S. Navy. Meetings held approximately quarterly since early
1989 have brought together local representatives of the water and wastewater utilities, and the
city and county. This involvement has facilitated remedial planning by the U.S. Navy and has
alerted affected local groups to the proposed activities.
SUMMARY OF COMMENTS RECEIVED DURING PUBLIC COMMENT PERIOD
During the public comment period, two letters were received. At the public meeting
on May 9, 1990, several questions and comments were raised.
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The written and verbal comments can be divided into two broad categories: those
related to the-protectiveness of the preferred remedy and those related to effects on the local
and regional aquifer system. Specific comments are addressed below:
Protectlveness of the Preferred Remedy
1. Comment (verbal): Is the activity at NIROP related to that at FMC?
Response: The ground water cleanup planned for the NIROP is distinct
from that at FMC. Although the contamination and remedies
at the two locations have similarities, the projects are
implemented, managed, and monitored separately.
2. Comment (verbal):
Response:
The 'no-action* alternative is not a reasonable alternative.
The U.S. Navy agrees.
Comment (verbal):
Response:
Comment (verbal):
Response:
Comment (verbal):
Response:
Do VOCs pose a fire potential? .
In concentrated form, VOCs may pose a flammable or j
explosive hazard. In dilute concentrations in ground water, '
such as would be recovered from the NIROP, no such hazard
would exist.
Since TCE is heavier than water, how does it migrate into the
Mississippi River?
In its pure form, TCE is heavier than water and would tend to
settle to the bottom of an aquifer. However, when it is
dissolved in water at relatively low concentrations such as
found at the NIROP, it is free to migrate along with ground
water flow. Ground water at the NIROP enters the Mississippi
River and carries dissolved TCE with it.
During a flood event, could the ground water pumpout and
discharge system be shut down to avoid additional flow in the
river?
Yes. Although it is desirable to maintain continuous operation
over a long period of time, the system can be shut off, as
needed, under any emergency situation. The ground water
discharge would also be very small in comparison to the river
flow.
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6. Comment (verbal):
Response:
7. Comment (verbal):
Response:
8. Comment (verbal):
Response:
9. Comment (verbal):
Response:
10. Comment (verbal):
Response:
Is there a potential for leakage from the sewers which receive
ground water from the pumpout system?
Sewers are typically not completely watertight. The NIROP
intends to temporarily discharge untreated ground water into a
96-inch-diameter sanitary interceptor sewer. Ground water will
be diluted with industrial and municipal wastewater flowing into
the sewer. The effect of ground water on the overall quality of
wastewater in the sewer is expected to be negligible. If leaks
occurred, the effect of contaminants from the temporary
contribution of NIROP ground water versus contaminants
contributed from the other wastewater sources would not be
significant.
Does the Pig's Eye Wastewater Treatment Plant have the
capacity to accept the volume of water from the NIROP?
Approval for the ground water discharge will be obtained from
the Metropolitan Waste Control Commission (MWCC). In initial
discussions, the MWCC has not indicated that the expected
flow from the NIROP will be a problem.
The Pig's Eye Plant is a secondary treatment plant which is {
not equipped to remove chemicals from the wastewater. >
It is true that the Pig's Eye Plant does not provide a tertiary
level of treatment specifically for synthetic chemicals.
However, the aeration and biological treatment provided by the
plant will serve to reduce volatile organics, such as TCE. Also,
the quality of the plant's treated water discharge is established
by a state permit which is based on protection of the receiving
water body.
What will the quality of water be after on-site treatment?
The quality of treated ground water will be' set by the MPCA for
discharge to the Mississippi River. The allowable limits will be
based on protection of the river environment and downstream
users.
Will packed tower aeration be considered as a treatment
technology? Can the water be treated by distillation?
Packed tower aeration (air stripping) will likely be part of the
treatment process. Other options, either singly or in
combination with air stripping, will be reviewed during final
system design to determine the best way to meet the ground
water treatment objectives. Distillation is appropriate to
recover solvents such as TCE from concentrated liquids, but
not from the dilute concentrations found in the ground water.
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11. Comment (verbal):
Response:
Chlorine gas would be produced from regeneration of
activated carbon used to treat the ground water.
Activated carbon, if used for ground water treatment at the
NIROP, would be regenerated at an off-site facility designed to
perform that function. Air emissions from the regeneration
process would be regulated by state air permits, which would
establish emission limits protective of the local area
Effects on the Local Ground Water Resource
12. Comment (verbal):
Response:
13. Comment (written):
Response:
14. Comment (written):
Response:
15. Comment (verbal):
Response:
What is the origin of ground water beneath the NIROP?
Ground water beneath the NIROP originates as rain and
snowmelt that infiltrates through the soil to the aquifer. The
area over which this infiltration takes place extends to the
north and east of the NIROP.
What effect will the pumpout system have on shallow, private
wells in the area?
No shallow, private wells have been identified in the immediati
vicinity of the NIROP. The calculations completed for the j
radius of influence of the capture wells indicate that the off-site
effect of the pumping will extend only into the Anoka County
Park, west of the NIROP.
What effect will pumping have on the moisture content of clay
layers (and subsequent strength relative to settlement)
beneath the Horizon Circle and Crown Road area?
The pumpout system will not affect the hydraulic head in the
vicinity of Horizon Circle and Crown Road. The calculation of
the radius of influence indicates that the effect of the pumping
will be limited to the immediate vicinity of the pumpout system
wells.
The City of Fridley draws water from the Prairie du Chien
formation where water levels have been dropping. Will the
pumpout system deplete the amount of water in the aquifer
available to communities?
The pumpout system will not deplete the amount of water
available to local communities. The pumpout system will be
constructed in an aquifer that overlies the Prairie du Chien
formation. The hydrogeologic data obtained during the Rl
indicate that there is little interconnection between the Prairie
du Chien and the overlying aquifer in the vicinity of the NIROP.
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16.
Comment (verbal):
Response:
17.
18.
19.
Comment (written):
Response:
Comment (written):
Response:
Comment (verbal):
Response:
To alleviate demand on city supplies, can pumped ground
water be used beneficially as cooling water in the plant?
FMC considered this option when designing their ground water
pumpout program, but found it to be infeasible from an
engineering perspective. However, the U.S. Navy will consider
this option during final design of its system to determine if it is
viable.
The water should be cleaned and used in Fridley.
The U.S. Navy agrees that the water resource should not be
wasted. It will consider options for beneficial re-use if plans or
proposals are developed and forwarded by the City or others.
Will the discharge to the MWCC be metered so that Fridley will
not be charged for the water usage?
Yes. The U.S. Navy will pay the MWCC for discharges from its
system.
Will the diversion of this amount of ground water, which ,
currently enters the river, cause more severe problems with i
low river flow if the recent drought conditions were to
continue?
I
The ground water will only be diverted from eventual discharge
into the river during the Phase I pumpout period, when the
ground water will be discharged to the local sanitary sewer.
Phase I is planned to last no more than 3 years. When the on-
site ground water treatment system is started up under Phase
II, the treated ground water will be discharged to the river near
the NIROP, thus maintaining the same ground water flow to
the river as under present conditions. The slightly reduced
river flow resulting from ground water discharge of up to 650
gallons per minute to the sanitary sewer during Phase I is not
expected to have an adverse impact during potential drought
conditions, due to the substantial volume of river flow
compared to the volume of pumped ground water flow even
under the drought conditions. (For example, even during the
drought period of 1988, the lowest river flow was
approximately 400,000 gallons per minute.)
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