o
PB94-964140
EP A/ROD/R05-941267
April 1995
EPA
Superfund
. Record of Decision:
Mac Gillis & Gibbs Co./Bell Lumber &
Pole Co.
(O.U. 3), New Brighto.n, MN
9/22/1994
o
EP A Report Collection
Information Resource Center -
US EP A Region 3
Philadelphia, PA 19107
Hazardous Waste Collection
Information Resource Cehter
US EPA Region 3
Philadelphia, PA 19107
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DECLARATION FOR THE RECORD OF
t . -'. ,,:1
-
o /0\ \\?
DECISION ~ Lf
SITE NAME AND ~OCATION
MacGillis & Gibbs Co./Bell Lumber & Pole Co.
New Brighton, Minnesota
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial
action for Operable Unit 3 (OU3) of the MacGillis & Gibbs Co.
portion of the site in New Brighton, Minnesota. This action 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, with the National Oil
and Hazardous Substances Contingency Plan (NCP). The decisions
contained herein are based on information contained in the
administrative record for this site.
The State of Minnesota concurs with the selected remedy.
ASSESSMENT OF THE SITB
Actual or threatened releases of hazardous substances from OU 3
of the MacGillis & Gibbs portion' of the site, if not addressed by
implementing the. response action selected in this Record of
Decision (ROD), may present an imminent and substantial
endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE SBLECTED REMEDY
The objectives of the response actions approved for the OU 3 are
to protect public health, welfare and the environment and to
comply with applicable federal and state laws.-
The MacGillis and Gibbs portion of the Site is separated into
three operable units, the first designated for state-lead.
activities, the second two for federal-lead activities. Operable
Unit 1 (DPA-QU) is defined as the waste material, debris,
contaminated soils and sediments in the disposal pit area.
Operable Un1t 2 consists of abandoned pentachlorophenol (PCP)
process/storage tanks and the light non-aqueous phase liquid
(LNAPL) plume beneath the former PCP process area. Operable Unit
3 consists of the-soils, surface water and ground water beneath
the Site which are not included in Operable Units 1 or 2.
This remedy addresses only Operable Unit 3. The remedy will
eliminate the spread of PCP, polynuclear aromatic hydrocarbons
(PAHs) , dioxins/furans, chromium and arsenic into the ground
water from the contaminated soils in Operable Unit 3. In
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addition, removal of the surface soils will eliminate any direct
contact threat to site workers. The remedy will also restore
groundwater t~its beneficial uses which include both domestic
and auxiliary (non-drinking water) uses.
The major components of the selected remedy include:
1.) Soil excavation;
2.) On-site incineration of organics contaminated soils with on-
site backfilling of bottom ash and off-site disposal of fly
ash;
3.) On-site solidification/stabilization
soils with subsequent disposal in an
4.) Removal and off-site disposal and/or
tanks and vaults;
S.) Groundwater extraction and treatment of the contaminated
groundwater in the New Brighton Aquifer in an on-site
biological wastewater treatment facility;
6.) Discharge of effluent water from the on-site wastewater
treatment facility to a Publicly Owned Treatment Works
POTW) for final treatment and discharge in accordance with
National Pollutant Discharge Elimination System (NPDES)
pretreatment limits;
6.) Institutional controls, including deed restrictions limiting
use of groundwater in contaminated areas and if necessary,
future abandonment of residential wells impacted by
contamination;
7.) Long term groundwater monitoring in the New Brighton and
Hillside Aquifers and;
8.) Long term monitoring of selected ecosystems adjacent to the
site.
of metals contaminated
off-site landfill;
recycling of underground
It is the intent of the groundwater portion of the
.restore groundwater in the New Brighton Aquifer to
uses. However, if it is determined that the remedy
restoration, the contingency measures specified in
this ROD will be implemented.
remedy to
its beneficial
cannot achieve
Sect"fon IX of
STA'l'tJTORY DBTBRMINATIONS
The selected remedy is protective of human health and the
environment~complies with Federal and State applicable or
relevant and appropriate requirements that are legally applicable
or relevant and appropriate to the remedial action, and is cost-
effective. This remedy utilizes permanent solutions and"
alternative treatment technologies, to the maximum extent
practicable, and satisfies the statutqry preference for treatment
that reduces toxicity, mobility, or volume as a principal
element. "
Because this remedy will result in hazardous substances remaining
on site at levels preventing unlimited exposure and unrestricted
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use while remedial action is taking place, the five-year review
requirement applies to this action.
..
9/2 ~ l Y-
i Date
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t((..4,.,,{, I - t ' LL
I Valdas V. Adamkus
~ Regional Administrator
t Region V
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DECISION SUMMARY FOR THE RECORD OF DECISION
MacGILLIS & GIBBS CO./BELL LUMBER & POLB CO.
OPERABLE UNIT 3
~
I. SITE NAME, LOCATION, AND DESCRIPTION
The MacGillis & Gibbs (M & G) and Bell Lumber & Pole (Bell)
National Priority List (NPL) Site consists of two adjacently
located wood preserving facilities. The facilities are located in
a mixed residential and commercial area within the corporate
limits of the City of New Brighton, Ramsey County, Minnesota.
The site is bordered on the south by First Street NW, on the west
by Eighth Avenue NW, on the north partly by 5th Street NW and on
the east by Fifth Avenue NW. The Bell facility is located on the
western port~on of the site ~nd the M & G facility is located on
the east. See figures 1 and 2 for site location and layout.
The elevation of the site is between 900 to 920 feet above mean
sea level. Surface drainage at the site is to the northeast
toward 5th Avenue and to the southwest toward the Minnesota
Transfer Railroad tracks and the pond in the disposal area of the
site. The site is surrounded by a combination of residential,
commercial and industrial development. Residences lie to the
north and northeast of the M & G facility and to the north,
northwest and southwest of the Bell facili~y. Commercial and
industrial properties are to the east and south of the M&G
facility and to the north of the Bell facility.
A number of surface water bodies including lakes, streams and
wetlands are within 2 miles of the site. Several of the lakes in
the area are used for recreational purposes. There are no other
known uses of surface water in the vicinity of the site. Wetland
areas are located northeast of the M & G facility and northwest
of the Bell facility. These areas have some limited recreational
use. They are also ecological habitats for ~igratory and native
animal and plant species. .
Groundwater is used as a drinking water source in the site area. .
The City of New Brighton has a municipal water system which.
supplies drinking water to the area. This system consists of ten
drinking water wells which are drawing water at a depth of 400 to
900 feet from the deep bedrock aquifers in the area. The
municipal wells are located 1/2 mile or more to the north, west
and south of the M & G facility.
The M & G portion of the site has been divided into three
operable units, as follows:
Operable Unit 1 (OU 1): Contaminated soils and debris in a former
disposal pit area on the west edge of the M & G facility.
Operable Unit 2 (OU 2): Light Nonaqueous Phase Plume (LNAPL) in
the PCP process area and residuals and sludges contained in
abandoned aboveground and belowground storage and process tanks.
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Removal and disposal of the above ground tanks and associated
piping would also be included as part of Operable Unit 2.
.
Operable Unit 3 (OU 3): Contaminated soils (other than those
addressed in Operable Unit 1), removal and disposal of
underground tanks and vaults, and groundwater contamination.
Contamination which has moved off-site to the surrounding area,
including small lakes, wetlands and a stream, is also addressed
in Operable Unit 3.
U.S. EPA and MPCA have already selected remedies for Operable
Units 1 and 2. Both of these ,operable units are currently in the
design phase, which means that engineers are developing the
detailed plans to implement the remedies.
This ROD will discuss the selected remedial action for Operable
Unit 3 of the M&G facility. The objective for Operable Unit 3 is
to clean up the groundwater and also the contaminated soils which
are the major source of the groundwater contamination.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
Site History
Each of these'facilities has been involved in wood preserving
activities since the 1920's and is still active today. The M&G
and Bell facilities were included as one site on the NPL because
of their adjacent locations and similarities of processes and
contaminants.
M&G began wood preserving treating operations in the '1920's and
has changed its processes several times over the years.
Pentachlorophenol (PCP), creosote and chromated copper arsenate
were used for the wood preserving proces~ at various times.
In 1979 the initial investigation at M&G was conducted after a
spill of 4000 to 5000 gallons of chromated copper arsenate (CCA).
A number of studies were conducted from 1981-1987 by both the
MacGillis & Gibbs Company and the MPCA to define the extent of
contamination and to propose cleanup activities. Significant
contamination of the disposal pit area was found as
well as c~ntamination around the CCA process area and in the
groundwater-beneath the site.
The MacGillis & Gibbs/Bell Lumber & Pole site was included on the
National priorities List (NPL) in 1984. This is a list of sites
throughout the country that are eligible for study and cleanup,
if necessary, under the Superfund Program. In 1988 U.S. EPA
monitored some initial cleanup activities being performed by the
MacGillis & Gibbs Company. Approximately 200 deteriorated drums
of pentachlorophenol process wastes were stabilized in overpack
drums and placed in a newly constructed storage facility. A
Lighter than Water Nonaqueous Phase Liquid (LNAPL) plume was also
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detected and a pump out well was installed to begin the removal
of this plume.
~
In 1990 a Focused Feasibility Study was conducted by U.S. EFA.
This study found contamination of soils in the PCP and CCA
process areas and PCP wastes were also found in abandoned tanks
on site. Significant contamination of the groundwater under the
site in the upper aquifer was detected. The contaminant
groundwater plume was also found to be moving off-site.
Additional study was proposed to further delineate the extent of
contamination.
While additional study was being performed, U.S. EFA issued an
Interim Action Record'of Decision for Operable Unit 2 to control
the spread of contamination from identified source areas into
soils and groundwater. The Operable Unit 2 remedy included
actions to accelerate the removal of the LNAPL plume and also to
remove the wastes in the abandoned aboveground and belowground
storage and process tanks.
A Focused Feasibility Study was conducted in 1992 by the MPCA
on Operable Unit 1 which includes contaminated soils and wood
debris, sediments and a pond in the disposal area of the site.
The MPCA and U.S.,EPA subsequently issued a Record of Decision
for Operable Unit 1 which included incineration of wood debris
, and soil washing of soils and sediments. The residuals from the
soil washing process would then be treated by either
bioremediation, incineration, or solidification/stabilization.
The ROD for Operable Unit 1 required that treatability studies be
performed on the soil treatment technologies to determine their
effectiveness. The ROD indicated that if these technologies prove
to be ineffective for soils, a contingency remedy will be
incineration~ '
The MPCA, as lead agency for Operable Unit 1, has decided to
select incineration as the remedy for contaminated soils and
sediments for the disposal area of the site. Incineration was the
contingency remedy in the December 1992 ROD for Operable Unit 1.
Incineration-costs have significantly decreased since'the time of
the ROD. Incineration has been selected as the cleanup remedy
because of cost and implementability. An Explanation of
Significant Diff~rences document will be prepared to reflect this
change from the original ROD.
During 1993, U.S. EPA removed 700 drums of process wastes and
also contaminated oils from the LNAPL plume pump out activities
from the site. ' .
u.S. EPA completed its Remedial Investigation CRI) and
Feasibility Study (FS) for OU 3 in 1994. The RI sampling
determined that there were about 30,000 cubic yards of organics-
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contaminated (PCP, creosote, and small amounts of dioxins and
furans) soils ~n and around the PCP process area and
approximately 19,000 cubic yards of metals-contaminated soils
(chromium and arsenic) in and around the CCA process area.
The New Brighton Aquifer, which is the shallow aquifer beneath
the site, was found to be contaminated with both organics and
metals. The contaminant plume was found to have moved off-site to
the northeast in the New Brighton Aquifer. Ecosystems (small
lakes, wetlands, and a stream) near the site were also found to
be contaminated.
Enforcement Activities
Bell entered into an agreement with MPCA under the Minnesota
Environmental Response and Liability Act (MERLA) in 1985 to
perform an investigation and cleanup of its facility. MacGillis &
Gibbs did not enter into a similar agreement. Current
investigations at the M&G site are being conducted with funds
from the Superfund p~ogram.
On October 23, 1992 and March 26, 1993, U.S. EPA notified
MacGillis & Gibbs that pursuant to Section 122 (a~ of CERCLA, the
Agency would not be using the special notice and negotiation
procedures for the remedial actions at Operable Units 1 and 2.
:I:I:I. H:IGHL:IGBTS OP COMNtJN:ITY :INVOLVEMEN'T
Various community relations activities were conducted to solicit
public comment on the Proposed Plan for this OU 3 Remedial
Action. A fact sheet for the Proposed Plan was mailed out on
June 14, 1994. A notice of availability of the Proposed Plan and
announcement of the public comment period was published in
the Minneapolis Star Tribune newspaper on June 8, 1994. The
Proposed Plan was released to the public on June 9, 1994
outlining remedial alternatives and informing residents that the
Feasibility Study and all other documents comprising the
Administrative Record for the site were available at the Arden
Hills Public_Library. The public comment period extended from
June 9 through July 8, 1994 and a public meeting was held June
23, 1994. ~estions were asked during the meeting, however, no
formal public comments were made. Written comments were received
from two commenters subsequent to the public meeting. Responses
to these comments are contained in the Responsiveness Summary
portion of this Record of Decision.
:IV. SCOPE AND ROLE OP OPERABLE tJN:IT W:ITB:IH S:In STRATEGY
As previously indicated in the ROD, remedial actions have already
been selected for OU 1 and OU 2 in Records of Decision issued
December 31, 1992 and September 30, 1991, respectively. These
RODs selected remedies for discrete portions of the site which
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could be studied separately and on a more rapid schedule. In the
case of OU 2, the abandoned tanks and LNAPL plume were obvious
source areas Which were significantly contributing to groundwater
contamination and thus an interim action ROD was issued to begin
to remediate these problems while other portions of the site were
being studied.
Operable Unit 3 includes all contaminants and sources of
contamination on the MacGillis & Gibbs portion of the site that
were not specifically addressed in the previous operable units.
This includes contaminated soils (other than those addressed in
OU 1), underground tanks and vaults, and groundwater
contamination. Contamination which has moved off-site to the
surrounding area; including ecological habitats, is also included
in Operable Unit 3.
The buildings and underlying soils in the CCA process area will
require further investigation. If, after further investigation,
additional contamination is found, the remedial action selected
herein will address that contamination.
The remedial action objectives of Operable Unit 3 are to clean up
the groundwater contamination at the site and also the remaining
soil contamination which is contributing to the groundwater"
contamination. Cleaning up the contaminated soils will "also
eliminate the potential of site workers being exposed to risks
from the soils. The groundwater and soil contamination being
addressed by OU 3 are principal threats posed by the conditions
at the site. It is anticipated that au 3 will be the final
operable unit for the site.
v. SUMMARY OP SZTB CHARACTERISTICS
Wood preserving operations at the facility have resulted in
discharge of contaminants to the soils. Potential contaminant
sources from past operations include spills and leakage from
waste PCP materials remaining in the abandoned PCP
process/storage tanks and process piping. Spilled solution from
the current chromated copper arsenic treatment process and the
dripping of solution from staged lumber remain as potential
contaminant sources from present operations. The disposal area is
another source of contamination. The disposal area was filled
with wood chips, debris, and spent treatment solutions from the
PCP process. A drain line from the PCP process area discharges
water collected in piping vaults to the pond in the disposal
area. It is likely that some of the process water from the PCP
wood treating operations was also discharged via this line. Drum
shells which had formerly contained copper chromium arsenic
solution were also reportedly placed in the disposal area. PCP
solution was also reportedly used as an herbicide for weed
control at the facility from 1940 to 1974.
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Groundwater i~ used as the source of drinking water in the site
area. The City of New Brighton has ten wells which supply
drinking water to the ,area. These municipal wells draw water from
the deeper aquifers including the Prairie du Chien formation,
Jordan Sandstone, Mt. Simon Sandstone, and the Hinkley Sandstone.
These 'wells are between 400 to 900 feet deep. Seven of the
municipal wells are located within 1 1/2 miles of the site, to
the northwest, west and south. The majority of the residences' in
the area are served by the municipal wells; however, there are a
limited number of private residential wells. A residential well
survey was performed of residences within a half mile of the
M & G site. Based on the survey responses and previous
residential well sampling, 8 residential wells were identified.
Four of these wells are used as a source of drinking water, and
the remaining four wells are used for ,auxiliary purposes such as
filling swimming pools, watering lawns and gardens or washing
cars.
The fate of contaminants at the site is dependent in part on the.
geology underlying the site.. The near surface geology consists'
of approximately 167 to 335 feet of unconsolidated glacial
deposits overlying bedrock. These unconsolidated deposits can be
divided into three distinct formations. In descending order,
these formations are the New Brighton Formation, the Twin Cities
Formation, and the Hillside Sand Formation. The New Brighton
Formation contains two distinct layers. The uppermost layer is a
fine-to-medium sand, and the lower is a silty clay to clayey silt
. layer. Below the New Brighton Formation is a silty and sandy clay
representing the Twin City Formation. Underlying this clay till
is a fine-to-coarse sand comprising the Hillside Sand Formation.
The hydrogeology at the site is characterized by a two-aquifer
system within the glacial overburden. The uppermost aquifer con-
sists of the unconfined New Brighton Sands and the lower aquifer
consists of the Hillside Sands, which is confined by the Twin
Cities Till Formation. Based on information gathered during the
RI for au 3, it appears that an aquitard separating these two
aquifers is continuous acrross the site. Groundwater flow
direction in these aquifers has been approximated based on
several investigations in which groundwater elevations were
taken. Groundwater elevations measured in monitoring wells in the
New Brighton Aquifer indicate that there is a groundwater divide
which trends east to west in the vicinity of the disposal pond.
Under average climatic conditions, groundwater north and
northeast of the disposal pond flows to the northeast,
groundwater to the west flows to the west, and groundwater south
of the pond flows to the south~ During heavy rainfall, however,
recharge from the disposal pond creates a radial groundwater flow
effect around the pond. In the confined Hillside Aquifer,
groundwater elevation measurements indicate the groundwater flow
direction is to the north.
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Nature and Extent of Contamination
u.s. EPA bega~the first phase of a Remedial Investigation/
Feasibility (RI/FS) in October 1990. The purpose of an RI is to
define the nature and extent of contamination at the site and to
describe the extent of the threat that contaminants pose to human
health and the environment. The purpose of an FS is to develop a
set of alternatives for addressing the contamination problems at
the site.
The sampling in the Phase 1 RI was used in defining the problem
and determining the remedial 'action for OU 2. At the conclusion
of the Phase 1 RI, it was determined that additional sampling was
required to fully define the extent of the contamination at the
site. Therefore, a Phase 2 RI was initiated in July 1992 to
further study the site. .
The Phase 1 and 2 RI field work included the sampling of waste
materials in the abandoned process tanks, surface soils (both on-
site and off-site), subsurface soils, groundwater and residential
wells. Ecological sampling of surface water, sediments and fish:
was also performed.
These media w~re analyzed for the contaminants of concern
identified in previous studies which are pentachlorophenol (PCP),
polynuclear aromatic hydrocarbons (PAHs), metals, including
arsenic and chromium, and dioxins/furans (PCDDs/PCDFS). In
addition, samples were also analyzed for other semivolatile
organics, volatile organics and pesticides/polychlorinated
biphenyls to identify other potential contaminants of concern. A
summary of the results of the RI sampling is described below.
Waste/Contaminant Source Characterization
Waste samples were collected from abandoned process/storage tanks
in the PCP process area and the oil recovery well TCT-3D which
was installed by the M & G site owner .to begin recovery of the
LNAPL plume. PCP was detected in the highest concentration in all
the waste samples collected. The maximum concentration of PCP
found was 60;100 mg/kg (parts per million) in the sample taken
from the LNAPL pumping well.
PCDDs/PCDFs were also detected in the waste samples. PCDDs/PCDFs
are known byproduc~s from the manufacturing of pentachlorophenol.
For risk assessment purposes, the many PCDF/PCDD isomers are
often expressed in terms of 2,3,7,8 tetrachlorodibenzodioxin
(TCDD) equivalents. The 2,3,7,8 TCDD isomer is the most toxic and
carcinogenic PCDD/PCDF isomer. The 2,3,7,8 TCDD equivalent for
theLNAPL pumping well sample was 79.95 ug/kg (parts per
billion). The maximum 2,3,7,8 TCDD equivalent collected from the
abandoned tanks was 37.40 ug/kg.
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On-sit. Surface Soils Characterization
Surface soil samples were collected from 53 on-site and off-site
locations. For on-site samples, PCP was detected at a range of
140 to 23,000 ug/kg. PAHs were detected at a range of 23 ug/kg to
1300 ug/kg for benzo(b)fluoranthene and 38 ug/kg to 1000 ug/kg
for benzo(a)pyrene. The maximum concentrations of arsenic,
chromium and copper were 159 mg/kg, 272 mg/kg and 128. mg/kg,
respectively. While PCP, PAHs and metals were widespread across
the facility, the surface soil sampling confirmed that
concentrations of PCP and metals contamination were generally
higher in the disposal area (OU1) , the PCP process area and the
CCA process area.
The PCDD/PCDF sampling results indicated that of 20 on-site
surface soil samples analyzed for PCDDs/PCDFs, all of the samples
contained at least one PCDD/PCDF isomer. The highest
concentrations of the PCDD/PCDF isomers were detected in samples
collected from areas close to OUl and from the PCP process area.
Two of the samples, which are located in the PCP process area,
had TCDD Equivalent concentrations greater than the Agency for
Toxic Substances and Disease Registry (ATSDR) cleanup goal of 1
~g/kg; the remaining 18 surface soil samples contained TEF
concentrations below this cleanup goal. Total TCDD Equivalent
. concentrations in the on-site surface soil samples ranged from
0.1 ~g/kg to 4.0 ~g/kg.
Volatile organic compounds (VOCs) were analyzed to support the
air pathway analysis in determining whether vapors are being
emitted directly from the surface soils. Two VOCs were detected
in the on-site surface soils (methylene chloride and toluene) .
Methylene chloride was detected in two samples, but it is a
common laboratory artifact, and, typically, values up to 10 times
the blank concentration can be considered laboratory
cont~mination. Toluene was detected in 13 samples at concen-
trations ranging from 5 ~g/kg to 39 ~g/kg.
The pesticide/PCB analytical results indicated the presence of 15
pesticides in the on-site surface soil samples. Most of the
samples collected contained concentrations of 4,4'-DDT above the
detection limits, with a maximum concentration of 6.2 ~g/kg. The
highest con~ntration of six pesticides was detected in a sample
collected near t~e center of the PCP process area. The frequency
of detection and distribution of these compounds suggest that the
pesticides detected in the on-site surface soil samples may be
attributable to spraying for pest control. PCBs were not
detected in any of the on-site surface soil samples.
Off-.it. Surfac. Soil Sampl..
Twelve off-site surface soil samples were collected from
residential properties, public parks, roadway dust, and
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background locations in the study area. Two samples of roadway
dust samples were collected to the east of the site on 5th Avenue
Northwest. Three soil sample locations were selected to represent
background conditions in the study area. These samples were
collected from undeveloped lots and a public park to the east and
southeast of the site.
Additional samples were collected from locations to the north and
northeast of the M & G facility. Because the predominant wind
direction during the summer months (when dust generation at the
M & G facility would be higher than during other seasons) is from
the southwest; these sample locations were selected to evaluate
the most reasonable migration pathway for particulates from the
facility.
The highest concentrations of PCP detected in the off-site
surface soil samples were 150 ~g/kg and 220 ~g/kg. These
concentrations were detected in samples collected from road dust
near the entrance to the M & G facility, and from surface soil at
a residential property to the northeast of the PCP process area. .
Seven cPAHs were detected in the off-site samples, with the
highest concentration being 460 ~g/kg of benzo(b)fluoranthene in
a road dust sample. Dioxin and furan isomers were .detected at low
concentrations, with a maximum TCDD Equivalent value of 0.054
~g/kg.
Arsenic and chromium were detected in all of the off-site surface
samples at concentrations ranging from 0.9 mg/kg to 55.9 mg/kg
and 4.7 mg/kg to 21.1 mg/kg, respectively. The off-site
background soil sample in which 55.9 mg/kg of arsenic was
detected is not considered to be representative of background
conditions in that the other 2 background samples contained less
than 5 mg/kg of arsenic.
The surface sampling suggests that contaminants have migrated
off-site to the northeast. The area to the northeast is directly
downwind from the source locations on the facility. Dust caused
by work activities and vehicular traffic is likely to be
contributing to the contamination in the off-site samples.
SUb.urfac8 8011 Sampl..
A total of 38 borings were performed during the Phase 1 and Phase
2 RI to determine the extent of subsurface contamination. PCP
concentrations ranged from 61.9 ug/kg to 1,500,000 ug/kg with the
maximum concentration being located in the disposal area. PCP
contamination was found from just below the ground surface to a
depth of about 35.feet. The highest concentration of PCP found
outside of the disposal area was 1,100,000 ug/kg in a boring in
the PCP process area. Elevated concentrations of carcinogenic
PAHs were found, including chrysene (190 ug/kg to 41,000 ug/kg) I
benzo(a)pyrene (200 ug/kg to 5,800 ug/kg), benzo(a)anthracene
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(130 ug/kg to 20,000 ug/kg) and benzo(b)fluoranthene (220 ug/kg
to 11,000 ug/kg). PCDDs/PCDFs were also found with a maximum
concentration of 10.866 ug/kg TCDD Equivalent found in a boring 2
to 4 feet below ground in the PCP process area. .
The metals of concern, arsenic and chromium, were detected at
maximum concentrations of 221 mg/kg and 171 mg/kg at 0 to 2 feet
below the ground surface in the CCA process area. Similar to
surface soil results, the subsurface soil samples collected
indicate significantly higher concentrations of the chemicals of
concern in the disposal area, PCP process area and the CCA area
than those found in other areas of the M & G facility.
Two soil borings (one in the disposal area and the other in the
PCP process area) also revealed visual evidence of a Dense
Nonaqueous Phase Liquid (DNAPL). The DNAPL material which was
observed is PCP contained in a dense carrier oil. Since the DNAPL
is denser than water, it travels downward by gravity .through both
saturated and unsaturated soils. As DNAPLs move through soils,
large quantities of the material are trapped in the soil pores.
DNAPLS persist for long periods of time while releasing large.
concentrations of contaminants. The difficulty of removing DNAPL
from the saturated soils is an important concern in groundwater
cleanup plans.
Groundwater Characterization
New Briahton Aauifer
A total of 67 groundwater samples were collected from the New
Brighton Aquifer during the Phase 1 and 2 RI. Approximately half
of the monitoring wells which were sampled were screened to
intercept the water table, while the other half were screened at
the base of the aquifer at the interface of the silty clay
confining layer. .
PCP concentrations ranged from .02 to 96,000 ug/l with the
highest concentrations of PCP detected about 7S feet northeast of
the disposal pond. The maximum off-site concentration of PCP was
5,250 ug/l and was found in a monitoring well northeast of the
site. Several other wells to the northeast of the site also
contained stgnificant concentrations of PCP which demonstrates
that PCP has mov~d off-site in the direction of groundwater flow.
. .
PCDDs/PCDFs were detected at TCDD Equivalent concentrations of
1.9 to 2249 pg/l (parts per quadrillion). The maximum.
concentration of 42 pg/l of the 2,3,7, 8 TCDD isomer was detected
in a monitoring well just south of the. disposal pond.
Carcinogenic PAHs were detected in about one fourth of the wells
that were sampled. The maximum carcinogenic PAH concentrations
detected on-site were 15 ug/l for chrysene and 11 ug/l of
benzo(a) anthracene. The maximum off-site concentration of 2.06
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11
ug/l was found northeast of the site.
Chromium and a~senic concentrations detected in groundwater
samples indicated two primary impacted areas resulting-from
sources on the M & G facility. The maximum chromium
concentration, 23,800 ~g/L, was detected in a sample from a water
table monitoring w~ll near the drip pad in the CCA process area.
The chromium groundwater contamination is effectively tracked off
site in a plume that appears to follow a similar path as the PCP
contaminant plume. The groundwater samples from off-site basal
monitoring wells contained chromium concentrations of 1,150 ~g/L
and 2,770 ~g/L, respectively. These concentrations are well above
the Maximum Contaminant Level (MCL) drinking water standard of
100 ~g/L. Arsenic was detected at concentrations exceeding the
MCL of 50 ~g/L in only two groundwater samples collected from on-
site monitoring wells. Arsenic was not detected at
concentrations exceeding the MCL in any off-site groundwater
samples..
The groundwater sampling of the New Brighton Aquifer indicate.
that the primary sources of PCP and chromium contamination exist.
in the disposal area and the CCA process area, respectively.
These contaminants are also migrating off of the M&G facility
towards the northeast.
Hillside Aauifer
Phase 1 RI groundwater sampling results from Hillside Aquifer
monitoring wells indicated PCP concentrations of .84 ug/l to 6.22
ug/l. However, PCP was also detected in field and laboratory
blanks at a concentration of .228 ug/l. Phase 2 RI groundwater
sampling showed PCP in all 6 samples taken. However, 3 of the.
samples contained concentrations below those found in the field
blank samples. The other 3 samples indicated 1.6, 2.4 and 40 ug/l
of PCP. . .,
The maximum PAR concentration was .8 ug/l of pyrene. There were
no concentrations of carcinogenic PAHs detected in the samples.
The only Hillside monitoring well sampled for PCDDs/PCDPs had a
TCDD Equivalent concentration of 5.48 pg/l. Of the metals of
concern, arsenic was detected at concentrations ranging from 3.5
ug/l to 42.rug/l. The maximum concentration of arsenic was found
in a monitoring well north of the disposal area. Chromium was
detected in one 's~mple at a concentration of 9.3 ug/l.
As described above, PCP and arsenic were detected in several
samples from monitoring wells in the Hillside Aquifer, however,
the contaminants were also found in the field blank samples.
Except for the monitoring well (MW 1H) sample in which 40 ug/l of
PCP was detected, all of the laboratory analyses for PCP were
either below or slightly above the MCL for PCP which is 1 ug/l.
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12
The MW 1H sample indicates that PCP could be of concern in the
Hillside Aquifer. However, the MW 1H sample which had a
concentration of 40 ug/l in Phase 2, had a lower concentration of
PCP in Phase 1 by an order of magnitude (3.1 ug/l). During Phase
1, MW 1H was randomly selected to have a duplicate analysis
performed. The original and duplicate analysis in Phase 1
detected 6.22 ug/l and .146 ug/l, respectively. The sample
analyses were averaged and recorded as 3.1 ug/l.
MW 1H is located in the southern portion of the site and is
upgradient of the process area and thus would not be expected to
be si~ificantly contaminated by the site. It is possible that
there may be an off-site source that may be contributing to
contamination in this well.
The contamination of field blank samples, the inconclusive
results between the Phase 1 and 2 laboratory samples for MW 1H,
and the presence of a clay confining layer which appears to be
continuous across the study area make it difficult to assess the
extent and source of PCP contamination. The majority of the.
samples do not show PCP contamination significantly above the MCL
for PCP in the Hillside Aquifer. .
Residential Well Samoles
Four residential wells were sampled during the Phase II field
investigation. . The selection of the wells sampled was based on
the proximity, availability, and location of the wells with
respect to the M & G facility. Two of the residential wells
sampled (RW6 and RW8) are located to the northeast of the M & G
facility, and are completed in the New Brighton Aquifer. The
other two residential well samples (RW9 and RW5) are Hillside
aquifer wells located east of Highway 35W to the northeast and
southeast, respectively, of the M & G facility. . .
Three VOCs, carbon tetrachloride, trichloroethene, and methylene
chloride were detected in the residential well samples; carbon
disulfide was detected in RW9 at 0.6 ~g/L, carbon tetrachloride
was detected-in RW6 (averaged duplicate) and RW8 at
concentrations of 2 ~g/L and 3 ~g/L, respectively, and
trichloroet~ne was detected in RW6, RW8, and RW9 at
concentrations o~ 1 ~g/L, 1 ~g/L, and 2 ~g/L, respectively.
PCP was detected in all four residential wells sampled. The
results for two of the wells were not greater than five times the
field blank concentration of .3 ~g/L, and therefore would not be
of concern. Samples RW6 and RW8 contained PCP at concentrations
of 14 ~g/L and 24 .~g/L, respectively.
Nine' PCDD/PCDF isomers were detected in the groundwater sample
from RW6. Total TCDD Equivalent concentrations ranged from 0.445
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. 13
pg/L to 4.421 pg/L for the residential well samples collected.
Of the metals of concern at the M & G facility, only arsenic was
detected in the Phase 2 residential well samples. Arsenic was
detected in the field blank and the sample results were not
greater than 5 times the field blank contamination, or 5.5 ~g/L.
Arsenic was found in a residential well southwest of the site
during Phase 1 sampling at a concentration of 42.4 ug/l. This
well was located in the Hillside Aquifer. The well has since been
abandoned by the owner and plugged with cement. Chromium was also
detected at a concentration of 18.6 ug/l in RW 6 during Phase 1
RI sampling, however, it was not detected in this well during the
Phase 2 RI.
Eco1oQica1 SAmnlinq Results
Surface water and sediment samples were collected from storm
drains and off-site ecosystems ih the vicinity of the M & G/Bell
site to characterize the nature and extent of contamination
identified during the Phase I RI, and to evaluate the potential.
risks posed by the site contaminants to ecological receptors in .
the habitats investigated. See figure 3 for the location of the
adjacent ecosystems. In addition, toxicity tests were performed
on bulk sediment samples to evaluate the potential impacts to
benthic organisms, and samples were collected to assess potential
bioaccumulation of PCP in fish.
Slightly elevated PCP concentrations were detected in surface
water samples from Farrel's Lake to the northeast of the site and
Hanson's Wetland to the west. PAHs were not detected in any of
the surface water samples collected from the three ecosystems
investigated.
PCP was detected at a concentration of 14 ~g/kg in a sediment
sample collected from Farrel's Lake. A concentration of 1400
ug/kg of PCP was detected in sediment in Schmidt's Pond, which
was selected as the background habitat for the Phase II
ecological assessment. Six carcinogenic PARs were detected at
five off-site sediment sample locations, with total cPAH
concentratiorts in the four sediment samples collected from
Hanson's Wetland ranging from 1,764 ~g/kg to 25,900 ~g/kg.
PCDDs/PCDFs~ere also detected at low concentrations in the
Hanson's Wetland sediment samples. The maximum TCDD Equivalent.
value detected was .012 ug/kg.
Tetrachlorophenol (TCP) was detected in eight of the 12 fish
samples from Farrel's Lake at concentrations ranging from 17
~g/kg to 1,370 ~g/kg. PCP was detected in three samples, with a
maximum concentration of 172 ~g/kg. TCP and PCP were detected in
up to 11 of the 12 fish samples from Schmidt's Pond at maximum
concentrations of 1,090 ~g/kg and 431 ~g/kg, respectively.
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14
Six storm drain sediment samples were collected during the Phase
II field investigation. PCP was detected in only one sample at a
concentration of 150 ~g/kg. Up to six cPAHs were detected in the
storm drain samples, with a maximum concentration of 320 ~g/kg
for benzo(a) anthracene in a sample collected from a catch basin
located to the immediate south of the M & G/Bell site. Arsenic
and chromium were detected in all six storm drain sediment
samples, with maximum concentrations of 2.3 mg/kg and 11.5 mg/kg,
respectively. PCDD/PCDF isomers were detected in 4 of the storm
drain sediment samples, with a maximum TCDD Equivalent
concentration of.31 ug/kg.
Whole sediment toxicity tests, using Hyalella azteca and
Chironomus riparious (benthic invertebrates), were performed on
bulk sediment samples collected from Hanson's Wetland and
Schmidt's Pond. Low survival rates were reported for all of the
samples tested, including the laboratory control, which had
average survival rates as low as 70% for H. azteca and as low as
0% for C. riparious. The laboratory control is a reference test
using sediment from a clean habitat. The laboratory control
provides a basis for interpreting data obtained from the test
sediments with respect to the health and relative quality of the
test organisms.
Due to the low laboratory control survival rates for
C. riparious, no conclusions could be drawn concerning the
effects of the sediments on this species. However, while the
s.urvival rate data appeared to be inconsistent, the mean dry
weight and mean length reported for survivors in the test
populations indicated some adverse impact in the Hanson's Wetland
survivors.
The Phase II EA sampling results indicate the presence of
M & G/Bell site contaminants in all of the off-site ecosystems
investigated. Given the areal extent of the New Brighton Aquifer
and the hydraulic head data for the surrounding lakes and
wetlands, it appears that groundwater from the site discharges,
at least in part, to the surrounding, adjacent lakes and
wetlands.
Sediment samples collected from the storm water drainage network
contained erevated levels of several PAHs and PCDDs/PCDFs. The
maximum concentrations of these compounds were detected in
samples collected .from storm drains near the M & G facility which
are the most likely to receive storm water runoff from the
facility. In addition, a sample which was collected from a catch
basin immediately south of the M & G/Bell site was the only storm
drain sediment sample that contained PCP. These results indicate
that the storm water drainage network in the vicinity of the M &
G/Bell site may be a migration pathway for the contamination
detected in Farrel's Lake and Hanson's Wetland sediments.
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15
Preliminary surface water and sediment sampling conducted during
the Phase I RI identified the presence of site contaminants in
Farrel's Lake and Hanson's Wetland. T~e Phase II analytical data
confirmed these results, with PCP and PARs being the primary
contaminants in sediment samples from Farrel's Lake and Hanson's
Wetland, respectively. However, sediment samples and biological
samples collected from Schmidt's Pond, which was selected as a
background location, also contained elevated concentrations of
PCP. .
Schmidt's Pond is located approximately 1 mile southeast of the
M & G facility, and is upstream of any storm water drainage
outfalls that may be impacted from the facility. In addition,
potential contamination of Schmidt's Pond via airborne dispersion
of contaminants from the site is unlikely due to its distance
from the M & G facility and the relatively high contaminant
levels detected in the sediment samples. Significant deposition
of contaminated soils from the site to Schmidt's Pond is unlikely
because the predominant wind direction during the spring and
summer seasons, when dust generation and migration would be
expected to be higher than during other seasons, is from the
southwest. In addition, the PCP concentrations detected in
sediment samples collected from Schmidt's Pond are much higher
than those detected in surface soil s~mples collected from off-
site locations to the northeast of the M & G facility, which
would be expected to be high depositional areas.
Because no plausible pathway exists for M & GIBell site
contaminants to migrate to Schmidt's Pond, the source of the PCP
contamination detected in this habitat is unknown. The presence
of the contaminants in Schmidt's Pond suggests that another
contaminant source may exist in the area.
Potential ExDosure Pathways
The contaminants detected in the abandoned tanks, soils,
groundwater and in ecosystems have the potential to adversely
affect both human and ecological receptors. On-site workers and
off-site residents would have the potential to ingest, dermally
contact or inhale contaminated soils. Off-site residents with
private residential wells have tLe potential to ingest, inhale
and have de~l exposure to contaminated groundwater through
normal domestic uses such as drinking, cooking and showering or
auxiliary uses such as swimming pool usage or lawn and garden
watering. Recreational users of surrounding lakes and wetland
areas such as waders and fishermen would have potential ingestion
and dermal contact exposure to contaminated surface water,
sediments and fish. In the affected eco~ystems, benthic
invertebrates, fish, amphibians, reptiles and mammals may all
have potential exposure to contaminated surface water and
sediments.
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. 16
The RI has identified contamination in all of these pathways and
receptors exist to make all of the pathways potentially complete.
The actual risKs to these receptors is evaluated in the Summary
of Site Risk section which follows.
VI. SUMMARY OF SITE RISKS
The RI report for Operable Unit 3 includes a Baseline Risk
Assessment (BRA). The BRA consists of two parts, the human health
risk assessment and the ecological risk assessment. The BRA
examines the potential effects of site-derived contaminants on
both human and envirorimental receptors. For this purpose, data
from both Phase I and Phase II were used to evaluate potential
risks; .
HUMAN HEALTH RIS~ ASSESSMENT
A Baseline Human Health Risk Assessment (HHRA) focuses on
existing and potential risks posed by site-derived contaminants
to both on-site and off-site human receptors. The HHRA supports.
decisions regarding whether site remediation may be necessary and
to what extent remediation should be performed, and then aids in
the selection and development of the remedial technique(s) used.
The objectives of the HRRA for the M & G facility are to identify
site-related contaminants of potential concern (COPCs); to
identify potential pathways of exposure for human receptors; to
quantitatively estimate the exposures that could occur; and to
estimate the potential risks to human health associated with
these exposures. The HHRA is composed of four components:
identification of COPCs, exposure assessment, toxicity assessment.
and risk characterization.
Identification of COPCs
COPCs were selected from validated EPA Contract Laboratory
Program data. After evaluating the effects of data qualifiers,
blank contamination, and background concentrations .on the
analytical results, 32 organic compounds and 7 metals were
selected as COPCs. Among these compounds, PCP, PARs, arsenic and
chromium and PCDDs/PCDFs were determined to present the greatest
risk.
As previously noted, analytical data was gathered in a two phase
RI field investigation process. The Phase I and Phase II
groundwater data represent two rounds of sampling of the
available wells. The two rounds are comparable, in terms of
methodology and detection limits, and equally representative;
therefore, the groundwater data from both phases were used in the
risk assessment. .
In contrast, the Phase II soil data are from randomly selected
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17
locations and are therefore statistically representative, while
the Phase I samples are from locations selected in a planned
fashion to inv~stigate specific features of the site. They were
not randomly selected and are not statistically representative.
In addition, the site is repeatedly regraded, so the Phase I
samples may no longer represent the locations where they were
collected. For these reasons, only the Phase II soil samples were
used in the risk assessment.
EXDosure Assessment
The M & G site is an active 24-acre facility located in a mixed
commercial, light industrial, residential area in the City of New
Brighton, Minnesota. The Land Use Plan from the City's
Comprehensive Plan identifies the future use of the site as
"limited industrial" use.
The majority of residents in the area are served by public water
supplies which draw water from deeper, uncontaminated aquifers,
and thus the majority of residents are not at risk from domestic,
use. of this contaminated groundwater. There are a limited number
of residential wells in the area. A few are used for drinking
and general domestic purposes and several others are used for
auxiliary purposes such as watering lawns and gardens or washing
cars. The most sensitive ,use of groundwater for these auxiliary
purposes would be for use in swimming pools.
. The potentially complete exposure pathways identified in the HHRA
are listed below:
1.) On-site worker exposure to soils.
2.) Residential groundwater exposure. (Domestic Use)
3.) Auxiliary use of'groundwater (swimming exposure).
4.) Off-site residential exposure to surface soil.
5.) Off~site residential exposure to airborne contaminants.
6.) Recreational use of wetlands (surface water and
sediments exposure) .
7.) Recreational fishing exposure.
8.) Future residential groundwater usage.
9.) Future residential on-site surface soil exposure.
Concentrations of contaminants used in the exposure assessment
calculations were derived for the applicable media (soils,
"
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18
groundwater etc.). In accordance with u.s. EPA guidance, for each
media source, the 95 percent upper confidence limit (UCL) of the
arithmetic mean of observed concentrations was used to estimate
the exposure point concentrations for both the reasonable maximum
exposure (RME) case and also the typical exposure case. RME is
the highest exposure that would reasonably be expected to occur
at a site and represents exposure levels well above the average
case.
Exposure point concentrations for on-site soils were calculated
from the 20 surface soil samples collected during the Phase 2 RI.
For off-site soils, exposure point concentrations were based on
the off-site samples taken. Air exposure point concentrations on-
site and off-site were calculated using surface soil samples in
conjunction with air emission/dispersion models.
The exposure point concentration for current groundwater usage
was based on the concentrations detected in the nearest
residential well downgradient from site source areas. For future
groundwater usage, monitoring well data from both the New
Brighton and Hillside aquifers were used separately because
current residential wells are known to exist in both aquifers.
The maximum surface water concentration or near shore sediment
concentration was used to evaluate exposure point concentrations
because of the small number of samples analyzed for each
ecosystem. Fish samples were analyzed for PCP and .
tetrachlorophenol. The maximum detected concentrations of these
chemicals detected in fish greater than 4 inches in length was
used as the exposure point concentration. A concentration of
arsenic in the fish was also estimated using a bioaccumulation
factor.
Exposure estimates combine the exposure point concentrations
described above with several other factors which include: 1.)
Estimates of contact rate and the frequency and duration of
exposure that receptor populations are likely to experience; and
2.) Estimates of various physiological parameters( e.g.,
breathing rate, body weight, and average life expectancy) .
- .
Toxicitv A....sment
The HHRA identified 39 total compounds which were COPCs for the
site. The toxicity of the contaminants that pose the most
significant risk are discussed below.
Arsenic
Arsenic is a naturally occurring element and is usually found
combined with one or more elements, such as oxygen, chlorine, or
sulfur. All people are exposed to low levels of arsenic because
it is naturally occurring, and low levels are present in food,
n
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19
water, soil, and air. Workers in several industries (nonferrous
smelting, wood preservation, arsenical pesticides) may be exposed
to significantiy higher levels.
Chronic arsenic overexposure may cause many health effects
including body weight changes, changes in the blood, and liver
and kidney damage. The critical or most sensitive effects, based
on chronic oral exposure to humans, are hyperpigmentation,
keratosis, and possible vascular complications.
u.s. EPA considers arsenic a Group A human carcinogen.
Epidemiologic studies and case reports have found evidence that
arsenic exposure is associated with increased risk of cancer of
the skin, lungs, bladder, and kidneys. In workers exposed by the
inhalation pathway, increas€~ risk of lung cancer is the major
carcinogenic effect. If humans are exposed by the oral route, the
major carcinogenic effect is an increased risk of skin cancer.
Chromium
Chromium is a naturally occurring element used industrially in
the manufacture of steel and other alloys. Exposure to chromium
can result from inhalation of air containing chromium-bearing
particles and ingestion of contaminated water or food. Chromium
is considered an essential nutrient that helps to maintain normal
glucose, cholesterol, and fat metabo~ism. The minimum daily
requirement of chromium for optimal health has not been
established, but ingestion of 20 to 500 ~g/day has been estimated
to be safe and adequate. .
There are two major forms of chromium, which differ in their
potential adverse health effects, found in the environment. One
form, chromium VI (chromium 6+), is irritating; short-term,
high-level exposure can result in adverse effects at the site of
contact, causing ulcers of the skin, irritation and perforation
of the nasal mucosa, and irritation of the gastrointestinal
tract. Minor to severe damage to the mucous membranes of the
respiratory tract and to the skin have resulted from occupational
exposure to as little as 0.1 mg/m3 chromium VI compounds.
Chromium VI may also cause adverse effects in the kidney and
liver. Long-term occupational exposure to low levels of chromium
VI compounds-has been associated with lung cancer in humans.
Chromium VI is classified by EPA as a Group A known human
carcinogen based: on evidence from epidemiological studies.
The second form, chromium III (chromium 3+), does not result in
these effects and is the form thought to be an essential
nutrient. The only effect observed in toxicological studies of
chromium III was a decrease in liver and spleen weights in rats.
This effect was used as the basis for the RfD.
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20
Pentachlorophenol (PCP)
PCP is one of ~he most widely used pesticides in the United
States. The principal use of PCP is for wood preservation, with
80% of the domestic use accounted for in the treatment of utility
poles. PCP does not occur naturally.
PCP can easily enter the body through the
pollutant, through the digestive tract as
or food, or through the skin. In general,
routes of exposure are through inhalation
lungs as an air
a contaminant of water
the most significant
arid dermal absorption.
Brief human exposure to high levels of PCP may result in adverse
effects to organ systems, including the liver, kidneys, skin,
blood, lungs, central nervous system, and gastrointestinal tract.
Such poisoning may also result in death. Long-term exposure to
lower levels of PCP can cause damage to the liver, blood, and the
central nervous system. .
Animals that. have been exposed to PCP in scientific experiments.
have also shown adverse effects; similar to those seen following'
accidental exposure of humans, in many organ systems. The
critical or most sensitive noncarcinogenic effect.of exposure to
PCP seen in animal studies is pigmentation of the liver and
kidneys. Birth defects have not been found in animals unless the
PCP dosage was high enough to cause maternal toxicity. In
addition, an increased risk of cancer, primarily of the liver,
kidney, and spleen, has been demonstrated in animals exposed to
. PCP. Epidemiological studies have resulted in no convincing
evidence that PCP produces cancer in humans. Based on the animal
studies and lack of Supporting human data, EPA has classified PCP.
as a Group B2 probable human carcinogen.
Polychlorinated Dibenzodioxins and Polychlorinated Dibenzofurans
(PCDDs/PCDPs)
PCDDs/PCDFs are two classes of related chemicals. There are 75
different forms of PCDD and 135 forms of PCDF. Most studies,
therefore, focus on 2,3,7,8-TCDD, commonly called dioxin, which.
is the most ~oxic member of this family of chemicals.
2,3,7,8-TCDDris a colorless and odorless compound. The compound
does not dissolve in water and can persist in the environment for
a long time. Neither PCDDs nor PCDFs are known to occur
naturally, nor were they deliberately produced or released to the
environment. Rather, they are unwanted trace contaminants formed
during the manufacture or burning of certain chlorinated
chemicals. These compounds are present in certain pesticides and
automobile exhaust, and are formed during the incineration of
municipal waste.
Workers in the chemical industry, at municipal and industrial
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21
incinerators, and at hazardous waste sites can be exposed to
2,3,7,S-TCDD. The general public can be exposed to 2,3,7,8-TCDD
by skin contacc with contaminated soil; by consuming contaminated
fish, meat, milk, or root vegetables grown in contaminated soil.
It is unlikely that significant amounts of 2,3,7,S-TCDD are
carried by drinking water or contaminated air; however, an
exception is presented by the inhalation of small particles of
contaminated fly ash, which could be a major source of exposure
for populations near an incinerator.
In humans, overexposure to 2,3,7,8-TCDD has caused chloracne, a
severe skin lesion. There is limited evidence to suggest that
2,3,7,'S-TCDD causes liver damage, loss of appetite, weight loss,
and digestive disorders in humans.
Animal studies have shown many different adverse effects of
2,3,7,S-TCDD. The severity and type of adverse effects varies
with species. Animal studies have demonstrated severe liver
damage, severe weight loss followed by death, toxicity to the
immune system, spontaneous abortions, and malformations in
offspring ,whose mothers were exposed to the chemical during
pregnancy. In addition, 2,3,7,S-TCDD has been demonstrated to
cause cancer in rats and mice. 2,3,7,S-TCDD is classified as a
Group B2 probable human carcinogen by EPA.
Polynuclear Aromatic Hydrocarbons (PABs)
PAHs contain only carbon and hydrogen and consist of two or more
fused benzene rings in linear, angular, or cluster arrangements.
PAHs are formed during the incomplete burning of fossil fuel,
garbage, or any organic matter. PAHs produced by burning may be
carried into the air on dust particles and distributed into water
and soil. In general, PAHs do not evaporate easily and do not
dissolve in water. '
Exposure
drinking
PAHs. In
food are
to PAHs may occur by inhaling airborne particles,
water, or accidentally ingesting soil or dust containing
addition, smoking tobacco or eating charcoal-broiled
common routes of exposure to PARs.
Some PAHs are known carcinogens, and potential health effects
caused by PARs are usually discussed in terms of an individual
PAH compound's carcinogenic or non-carcinogenic effects. Little
attention has been paid to noncarcinogenic effects of PAHs.,
Rapidly growing tissues, such as the intestinal lining, bone
marrow, lymphoid organs, blood cells, and testes seem to be
especially susceptible targets to non-carcinogenic effects.
Concentrations of 150 mg/kg or more administered to laboratory
animals have been shown to inhibit body growth.
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, 22
Risk Characterization
The risk characterization portion of the HHRA combines the
information developed in the exposure and toxicity assessment to
obtain the estimates of risk to human health.
As discussed in the toxicity assessment, chemicals are
categorized as either carcinogenic (cancer causing)
or noncarcinogenic, although some chemicals may exhibit both
carcinogenic and noncarcinogenic effects. u.s. EPA has
established the policy that acceptable exposure levels are those
that represent an excess lifetime cancer risk to an individual of
between 1 x 10-4 (1 in 10,000) to 1 X 10-6 (1 in 1,000,000). It
should be noted that these risks are in addition to the normal
risk of cancer posed by everyday life.
Arsenic is a known human carcinogen while PCP, a number of the
PAH compounds, and the PCDD/PCDF isomer are probable human
carcinogens. For noncarcinogens, risk is determined by
calculating a hazard index which is the ratio of' estimated
exposure to the acceptable daily intake. A hazard index greater'
than 1 indicates that adverse effects may be possible while a
value less than 1 means that adverse effects would not be
expected. The five principle contaminants of concern all exhibit
non-carcinogenic effects.. .
Several exposure pathways potentially complete under existing
site conditions had estimated cancer risks greater than the 10-6
risk level. Under existing site conditions the highest estimated
exceSs cancer risk from potentially site-related contamination
(1.2 x 10-4) was associated with adult residential exposure to
cOPCs in groundwater used for general domestic purposes. The
bulk of this estimated risk is due to ingestion of arsenic as
well as dermal contact with pentachlorophenol and PCDDs/PCDFs
detected in the groundwater in RW06. Although the New Brighton
Aquifer is used for domestic water supply purposes at some
locations, RW06, the maximally impacted well, is reportedly used
only for watering lawns. Therefore, there are no residents known
to be exposed to these contaminant levels in their drinking
water. The potential risks associated with the most sensitive
auxiliary use of groundwater, filling swimming pools, were 2.3 x
10-5 for adults and 2.0 x 10-5 for young children for the RME
case. These risks were due mainly to potential dermal absorption
of pentachlorophenol and PCDDs/PCDFs.
The potential risks to nearby residents exposed to surface soil
also exceed 10-6 for the RME case (4.6 x 10-5 for adults and 3.0
x 10-5 for children) due primarily to qirect contact with
PCDDs/PCDFs and arsenic found in the soil. Estimated cancer risks
associated with inhalation of airborne soil particles were less
than 1% of the total risk to off-site residents. Under the
typical exposure case, the estimated risks to nearby residents
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23
from soil exposure is 5.3 x 10-7 for adults and 1.0 X 10-5 for
children.
~
Another current e~osure pathway with estimated cancer risks
exceeding the 10-6 level was worker exposure to surface soil, 8.5
x 10-5 for the RME case. The bulk of this risk (74%) is due to
direct exposure to PCDDs/PCDFs in soil. Most of the remainder is
due to exposure to arsenic.
Under current conditions, the total hazard indices for each
pathway are less than 1. Using RME assumptions, a total hazard.
index slightly greater than 1 (1.3) could be possible for a child
using well water as a domestic supply, HI=0.74, exposed to soil
in a residential yard, HI=O.22, and eating fish, HI=O.3S.
Virtually all of the noncarcinogenic risk is associated with
ingestion of arsenic. However, under the typical exposure case,
the total HI is only 0.8.
For future residential scenario exposures, the estimated.total
cancer risks to both adults and children under RME conditions
exceeded 10-4 for general domestic use of groundwater in both the
New Brighton and Hillside aquifers (3.S x 10-2 and 3.8 x 10-4,
respectively, for an adult receptor) .
The future auxiliary use of groundwater is more likely than. the
future use of groundwater for all domestic purposes. Under the
RME case, cancer risks from swimming in water from the New
Brighton aquifer are estimated to be .1.6 x 10-2 and 1.3 X 10-2
for adults and children, respectively. For the Hillside aquifer,
risks are estimated to be 3.6 x 10-5 for adults and 3.2 x 10-5
for children. The vast majority of the risks to swimmers (99%
for the New Brighton aquifer and 96% for the Hillside aquifer)
are due to dermal absorption of pentachlorophenol and
PCDDs/PCDFs. .
. .
Exposure of hypothetical future residents to on-site surface
soils also had estimated total cancer risks greater than 10-4 for
both adult and child receptors under the RME case. However, as .
previously indicated, this exposure scenario is not likely to
occur since t~e future land use is expected to remain industrial
The inhalation of airborne soil particles is estimated to account
for <1% of rhe cancer risk to adult receptors.
Hazard indices fo~ noncarcinogenic effects exceeded 1 for both
adults and children exposed to COPCs in groundwater under the
hypothetical future domestic use scenario. The hazard indices for
children, assuming RME conditions, were 43 for the New Brighton
aquifer and 4.0 for the Hillside aquifer. For the New Brighton
aquifer, the bulk of the risk is due to PCP, which had a hazard
index of 31; the remainder is due to chromium (HI=S.7), antimony
(HI=3.9), and arsenic (HI=2.9). Arsenic, with a HI of 3.2, is
responsible for most of the potential noncancer risk from the
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,"
24
Hillside aquifer, for children under RME conditions.
The hazard indices for exposure of hypothetical child receptors
to on-site soil also exceeded 1. The bulk of the risk is due to
arsenic. The percentage of the noncancer risk due to the
inhalation of airborne soil particulates was <1% for both adults
and children. Incidental ingestion accounted for approximately
99% of the risk to children.
Tables 6-34 and 6-36 from the HHRA summarize the risks for all
exposure pathways evaluated and are attached to this ROD. These
tables indicate both the carcinogenic and noncarcinogenic risks
for the RME case.
ECOLOGICAL RISK ASSESSMENT
The second portion of the Baseline Risk Assessment that was
conducted for the site was the Ecological Risk Assessment.
Similar to the Human Health Risk Assessment, contaminants of
concern were identified. The contaminants of potential
environmental concern (CPEC) included the primary site
contaminants PCP, PAHs, arsenic, chromium and PCDDs/PCDFs, as
well as other organics and metals detected in the ecosystems.
The Phase 1 RI identified Farrel's Lake and Hanson's Wetland as
the ecosystems most impacted by site contamination. Phase 2 RI
sampling activities were directed at further determining the
extent of contamination in these ecosystems. Schmidt's Pond was
chosen as a background ecosystem to compare against the impacted
ecosystems. The risks posed by the contaminants in the three
ecosystems is discussed below.
Hanson's Wetland Risk Characterization
The risk generated by CPECs can be estimated by a method called
the Toxicity Quotient (TQ) method. The TQ method compares the
exposure point concentration found to an appropriate
environmental benchmark. The ratio of these values is calculated
to determine the TO. TO values approximately 1 or greater suggest
a risk for t~at CPEC in the ecosystem being evaluated.
PCP and TCP~re the only CPECs detected in Hanson's Wetland
surface waters. The TO value for PCP is 1.0. Based on the PCP TO
value, there may be a potential for impairment of liver function
and growth rates of water column biota (fish) and semiaquatic
biota (amphibians, reptiles, and mammals). An additional risk may
also be posed to biota through bioaccumulation of PCP and TCP.
PCP can accumulate in fish tissue via 4irect uptake from water,
and presumably, TCP may pose a risk via the same route.
Bioaccummulation of PCP and TCP could pose a problem to
Blanding's turtle (E. blandingii), a state threatened species,
which may be present in the area. However, this species was not
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. 25
observed in Hanson's Wetland, during either the Phase I or Phase
II sampling activities.
~
Hanson's Wetland sediments contained six inorganic CPECs and 13
organic CPECs. Of the inorganic CPECs, the TQ for arsenic (0.97)
and for chromium (0.95) approach 1.0. The TQ values for the 12
PAR detected in sediment samples are all well above 1; with some
values exceeding 100 and some exceeding 1,000 (Table 6-21).
Additionally, the TQ value for 2,3,7,8-TCDD and equivalents is
8.45. These values indicate a potential for chronic impacts from
exposure to these sediments.
Farrel's Lake Risk Characterization
As with Hanson's Wetland, PCP and TCP are the only CPECs detected
in surface water samples from Farrel's Lake. The TQ value for
PCP (3.27) indicates that there is a potential risk to biota that
inhabit Farrel's Lake. As discussed above, PCP readily
bioaccumulates in fish tissue. Analytical results of the fish
tissue analysis indicate that bioaccumulation of PCP and TCP has.
occurred. Six replicate samples of two size classes of fish « 4 .
inches and> 4 inches) from Farrel's Lake were analyzed for PCP
and TCP.
Only one fish in the> 4 inch group had measurable TCP and PCP
concentrations (1,370 ~g/kg and 172 ~g/kg, respectively). All of
the < 4 inch'group samples had tissue TCP concentrations and two
had tissue PCP concentrations. The New York State Department of
Environmental Conservation (NYDEC) set fish flesh criteria for
piscivorous (fish-eating) wildlife (NYDEC 1987). Only one fish
> 4 inches with a TCP concentration of 1370 ug/kg exceeded the
TCP criterion. None of the fish analyzed had PCP levels exceeding
the PCP criterion. These results indicate that there is some
limited potential for non-carcinogenic effects to occur in
pisc1vorous (fish-eating) wildlife. '
Concentrations of the inorganic CPECs detected in, sediments in
Farrel's Lake are generally equal to or higher than those
detected in Hanson's Wetland. The corresponding TQ values are
generally higner as well, indicating that there is a potential
risk to benthic invertebrates from exposure to the sediments in
the lake. ASrin Hanson's Wetland, 11 PABs were detected in
concentrations yielding TQ values greater than 1.0. This, along
with the 2,3,7,8~TCDD Equivalents TQ value of 4.47, indicates
that there is a moderate potential for adverse impacts to benthos
in the lake. The TQ value for PCP in Farrel's Lake sediments is
less than 1.0, indicating the concentrations of PCP seen in the
lake sediments may not be bioavailable to benthic organisms.
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26
Schmidt's Pond Risk Characterization
Schmidt's pond.was sampled and intended to be a representative
background habitat. Upon receipt of the analytical data, it was
found that pond sediments had CPECs at concentrations that
exceeded benchmark criteria. No plausible migration pathway
exists for contamination from the M & G facility to reach this
ecosystem. Therefore, the source of these contaminants remains
unclear.
There were no CPECs detected in surface water samples from
Schmidt's Pond at concentrations exceeding benchmark criteria.
There were however, both inorganic and organic CPECs detected in
sediments. Arsenic (6.28), cadmium (6.50), copper (7.00), lead
(3.87) and zinc (1.38), all had TQ values greater than one,
indicating a potential risk to benthos in the pond.
Although sediment PCP concentrations yielded a toxicity value
less than one, and neither PCP nor TCP were detected in surface
waters from the pond, every fish sample (except one < 4 inch
sample) collected from the pond contained detectable levels of
both PCP and TCP. This indicates that both PCP and TCP may be
bioaccumulated from sediments as well as water. The levels of PCP
found in the fish tissue also may be indicative of previously-
higher surface water PCP concentrati~ns.Schmidt's pond
sediments generally had higher concentrations of PCP and TCP than
Farrel's Lake sediments.
Conclusions
It appears, based on the characterization of the risks presented
above, that the aquatic habitats discussed above may have the.
potential to be impacted from site-derived contaminants. The
habitats of primary concern to be at potential risk from site-
related contaminants are Hanson's Wetland and Farrel's Lake and
Wetland. Based on the Phase 1 sampling, County Ditch 2, and the
Storage Wetland may also be at some risk. The background habitat,
Schmidts Pond, as well as other background habitats sampled
during the Phase 1 RI (Little Lake Johanna, Johanna's Stream, and
Johanna's Marsh), may also be at risk, but the source of the
contaminants in these habitats is unclear.
There appears to be viable pathways for the CPECs to migrate
the site to the habitats of concern. The two most probable
pathways is the surface water (storm drain) pathway and the
groundwater to surface water pathway.
Benthic invertebrates, fish, amphibians, and reptiles (especially
Blanding's turtle) all have a potential to be at risk from
exposure to the CEPCs detected in sediments in the habitats of
concern. Potential risks to higher-order consumers are not
expected to be significant because the CPECs identified in the'
from
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27
habitats of concern do not generally bioaccumulate and/or
biomagnify up the food chain.
~
Based upon the surface water analytical results and the results
of the fish tissue analyses, there is a potential risk to fish
living jn these habitats. Amphibians, reptiles, semiaquatic
mammals (muskrats, beaver, etc.), and terrestrial wildlife that
drink from the waters of these habitats may also be subject to a
lesser risk from long-term exposures to surface waters in these
habitats.
VII. DESCRIPTION OP ALTERNATIVES
The FS identified and evaluated alternatives that could be used
to remediate threats and/or potential threats posed by the site
to human health and the environment. The alternatives have been
divided into two categories, one for soil remediation and one for
groundwater remediation.
SOIL ALTERNATIVES
The alternatives evaluated for addressing the soils contamination
problem are:.
SOIL ALTERNATIVE 1 -No Action
* Estimated Cost: $0
* Estimated Timeframe: Immediate
This alternative involves no cleanup action for the contaminated
soils. This alternative would not effectively reduce the threats
to human health and the environment ~t the site. The inclusion of
the no action alternative is required by Section 300.430(e) (6) of
the NCP to give U.S.EPA a basis of comparison.
SOIL ALTBRNATIVE 2- Institutional Controls; Cap Installation and
Surface Runoff Controls; Removal and Off-site Disposal and/or.
Recycling of~nderground Tanks/Vaults; On-site Incineration of
Excavated Soils from Tank/Vault Removal
* Estimated Costs: Capital Costs: $ 3,689,000
Operation and Maintenance Costs: $ 3800/year
Present Worth Cost: $ 4,296,000
* Estimated Timeframe: 10 to 12 months
This alternative is intended to contain contaminated soil through
the placement of a cap over contaminated areas. The approximate
extent of organics and metals contaminated soils that require
remediation. are shown in the Attached Figure 2-1 from the FS.
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28
Organics contamination is principally located in the PCP process
area while metals contamination is principally located in the CCA
process area. ~
The cap would limit the amount of direct human exposure to
contaminated soil and would prevent precipitation from
percolating through the soil and carrying contaminants to the
groundwater below. The cap would be constructed in accordance
with the Resource Conservation Recovery Act (RCRA) requirements
for Subtitle C landfill closures, 40 C.F.R. ~~ 264.110-264.120;
264.310. Because contaminated soils would remain on site, this
alternative would include institutional controls in the form of
access and deed restrictions to limit the possibility for human
exposure.
The abandoned tanks and vaults in the PCP process area would
limit the effectiveness of the cap and would have to be removed.
The removal of the tanks and vaults would also necessitate the
excavation of soil immediately surrounding these structures.
Because this soil is expected to be heavily contaminated, it wil~
have to be treated before being placed back on site. Due to the.
high level of contamination of these soils, it is assumed that
the soil would be incinerated on-site.
Incineration of the soils under this alternative and also
Alternatives 3 and 4 would be subject to RCRA and Clean Air Act
requirements governing technical standards for hazardous waste
incineration at 40 C.F.R. ~S 264.340-264.999 and Parts 60 and 61
or any State requirements which are more. stringent. Incinerated
soil which is placed back on-site would be subject to RCRA
regulations directed to land disposal of treated wastes at 40
C.F.R. Part 268.
Under this alternative, and the remaining soil alternatives,
the tanks and vaults would be dismantled/demolished for
transportation off-site. Any reclaimable material from the tanks
would be recycled and the remaining materials (e.g. concrete)
would be decontaminated and disposed of in a landfill. Rinse
water from decontamination activities would be treated in the
on-site trea~ment plant with final effluent discharge to the
Publicly Owned Treatment Works (POTW). If the concrete and other
debris are SUfficiently decontaminated, these materials can be
disposed of in a non-hazardous RCRA Subtitle D landfill. If the
debris cannot be decontaminated, the materials would have to be
sent to an approved RCRA Subtitle C hazardous waste landfill.
SOXL ALTBRNATIVE 3- Soil Excavation; Soil Washing; On-Site
Incineration and Backfilling; On-site Stabilization and Off-site
Disposal; and Removal and Off-Site Disposal and or Recycling of
Underground Tanks/Vaults
* Estimated Cost: $ 14,200,000
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29
* Estimated Timeframe: 12 to 14 months
It is estimate5 that there are 30,000 cubic yards of organics-
contaminated soils located predominately in the PCP process area.
Under this alternative organics-contaminated soils would be
excavated and treated in a soil washing process which removes
contaminants from the coarser portion of the soil using a liquid
washing solution. The coarser washed soils could then be plac~d
back on-site if cleanup goals are achieved. Clean soils would
then be used to cover treated soils placed back on-site. The
finer fractions of the , washed soil that retain contamination, as
well as high concentration soils that cannot be treated by soil
washing, will be incinerated on-site. Alternative 4 below
discusses the effectiveness of incineration, including the
necessary monitoring and testing requirements to ensure proper
operation.
A pilot scale demonstration of soil washing conducted on the
M & G site by Biotrol, Inc. reported 87 to 89 % removal of PCP.
The lowest PCP concentration achieved in washed soil in this
study was 14 mg/kg, which slightly exceeds the 10 mg/kg cleanup'
level for PCP. Laboratory scale studies have shown that PCP and
PAHs can potentially be reduced to concentrations below site
cleanup levels using'soi,l washing. A treatability study would
need to be performed for the soil washing process to determine
whether the necessary removal levels can be achieved.
. Wastewater from the soil washing process would be discharged to
the Metropolitan Waste Control Commission publicly owned
treatment works (POTW) which has a National Pollutant Discharge
Elimination System (NPDES) permit under the Clean Water Act, 33
U.S.C. ~ 1251, to ensure proper treatment of the contaminated
water. '
Metals contaminated soil will be stabilized/solidified on-site
which will neutralize the contaminants and reduce their mobility.
It is estimated that there are 'approximately 20,000 cubic yards'
of metals contaminated soils located predominately in the CCA
process area. The solidified soil will then be landfilled off-
site. -
SOIL ALTBRHA~IVB 4- Soil Excavation; On-Site ~ncineration
and Backfilling; On-site Stabilization and Off-site Disposal; and
Removal and Off-site Disposal and/or Recycling of Underground
Tanks/vaults
* Estimated Cost: $ 15,700,000
* Estimated Timeframe 10 to 12 months
Alternative 4 differs from Alternative 3 in that soil washing
would not be utilized to reduce the volume of organics-
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30
contaminated soils prior to incineration. All organics-
contaminated soils would be incinerated.
~
Incineration destruction and removal efficiencies of 99.99% for
chlorinated organic compounds such as those found at the M & G
site have been well demonstrated by incineration systems. PCP and
PARs would be reduced to concentrations well below the site
cleanup levels. Assuming an incineration process rate of 10 cubic
yards per hour, around the clock operation, and 20 % downtime,
the incineration of the 30,000 cubic yards of organics-
contaminated soils would take three and a half months.
The remainder of the 10 to 12 month remediation time would be
required to mobilize/demobilize the incinerator and to perform
the test burn. There currently exists an incinerator on the Bell
portion of the site which is owned by Bell Lumber & Pole. If the
Bell incinerator were to be used, mobilization/demobilization of
a mobile incinerator would not be required.
Emission control equipment on the incinerator and air monitoring
would be utilized to ensure no significant emissions are released
during incineration. Ash that meets cleanup goals will be .
backfilled on-site while ash that does not meet cleanup goals
will be landfilled off site. Based on a review of analytical data
from a test burn for OU 1 soils, bottom ash should be able to be
backfilled on-site. rhe fly ash, however, did not meet site
cleanup levels and would require solidification/stabilization
prior to disposal in an off-site landfill.
A test burn of the incinerator will be performed to ensure that
the incinerator would comply with all appropriate requirements
referenced above. In addition to ensuring that organic
contaminants will be effectively destroyed, the test burn will
also ensure that any arsenic present in the soils will not be
volatilize4 and emitted at unacceptable concentrations. The
volatilization of metals is not expected to present a problem
because significant concentrations of metals have not been
detected in the PCP process area, the primary area of organic
contamination. Also, to assure the safety of area residents, a
risk assessment will be performed evaluating both direct and
indirect exposure from the incinerator emissions. Performance of
this risk assessment is in accord~nce with EPA's guidance
entitled liEPA's Draft Waste Minimization and Combustion Strategy
and Its Implications for Superfund".
ALTERNATZVE 5- Soil Excavation; On-Site High Temperature Thermal
Desorption/Backfilling; On-site Stabilization and Off-site
Landfilling/Disposal; and Removal and Disposal and/or Recycling
of Underground Tanks/Vaults
Estimated Costs: $ 14,900,000
Estimated Timeframe: 10 to 12 months
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31
Alternative 5 differs from Alternatives 3 and 4 in that soil
washing would not be used to reduce the volume of organics
contaminated soils and the thermal desorption process would be
used instead of incineration to treat organics contaminated
soils. As was the case with Alternatives 2, 3, and 4, treated
soils which are placed back on-site would be governed by RCRA
Land Disposal Restrictions at 40 C.F.R. Part 268.
Thermal desorption uses relatively low temperatures to remove
volatile and semivolatile contaminants from soils. The
contaminants which have been transferred to a gas stream are
further treated by either carbon filters, high temperature
incineration or a condensation process.
then
Thermal desorption units can be either high or low temperature. A
high temperature unit would be needed at M&G to achieve proper
removal and destruction of the site contaminants. Thermal
desorption would achieve a somewhat lesser degree of contaminant
destruction than incineration, although site cleanup levels would
be met. Similar to incineration, at a feed rate of 10 cubic yard~
of soil per hour, this alternative would take about three and a .
half months. The remainder of the 10 to 12 month remediation time
would be required to mobilize/demobilize the thermal desorption
uni t and to perform the test burn. .
Thermal desorption must be performed in accordance with RCRA
regulations for miscellaneous units, Part 264, Subpart X..A
treatability study would need to be performed to ensure that the
thermal desorption unit would comply with all appropriate
requirements.
GROUNDWATER ALTERNATXVES
The alternatives considered .for addressing the groundwater
contamination at the site are as follows:
GROUNDWATER ALTERNATXVB 1- No Action
* Estimated Cost: $0
This alternative would not control the migration of contaminated
groundwater-~rom the site. The inclusion of the no-action
alternative is required by Section 300.430(e) (6) of the NCP to
give U ..S. EPA a basis of comparison.
Common Elements of Alternatives 2.3. and 4
The remaining groundwater alternatives are intended to actively
remediate the portions of the New Brighton Aquifer that have been
contaminated by the site. Remediation would consist of
institutional controls, monitoring activities and the extraction
and treatment of groundwater. .
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32
Institutional controls would include deed restrictions limiting
use of groundwater in contaminated areas and possibly future
abandonment of~wells impacted by contamination. Monitoring
activities would incluQe groundwater monitoring and ecological
monitoring. .
Groundwater monitoring of the New Brighton Aquifer will be
performed on a long term basis to determine whether the
contaminant plume is being captured by the groundwater extraction
wells and also whether contaminant concentrations are being
reduced by the remedia~ion action.
Groundwater monitoring of the deeper Hillside Aquifer will also
be conducted. Although contaminants were found beneath the site
in this aquifer, active remediation is not planned at this time.
It is anticipated that remediation of contaminated soils on site
and groundwater in the upper New Brighton Aquifer would remove
any potential contaminant sources and that active remediation of
the Hillside Aquifer may not be necessary. If contaminant
concentrations increase or begin to move off site towards ,
regidential wells, active remedial action would be considered for
the Hillside Aquifer. An initial round of groundwater sampling of
the Hillside wells will be conducted during the design phase of
au 3. This initial round of sampling will be compared to the two
previous rounds of sampling to better evaluate the extent of
contamination in the Hillside Aquifer.
As previously indicated, the ecological risk assessment 'found
. that several of the habitats (Hanson's Wetland, County Ditch 2,
Farrel's Lake and Wetland, and the Storage Wetland) are
potentially at risk from site derived contaminants. However,
several background habitats were also found to be potentially at
risk from the same contaminants. Evidence presently available
, does not conclusively establish a link between the site and the
background habitats. Further, a relatively small amount of data
was used in determining the risk estimate for the various
habitats. '
u.S. EPA has determined that disturbance of the ecosystems
through a remediation process such as dredging could be
irreversible and pose a serious threat to the ecosystem's health.
U.S.EPA pre~rs, for these reasons, to remove the contaminant
source at the M&G facility and to monitor natural decomposition
of the contaminants in the ecosystems. Ecological monitoring will
consist of sediment, surface water and biota sampling to
determine whether contaminant concentrations are declining
through natural degradation processes.
Monitoring will consist of sediment and surface water sampling
from four habitats (Hanson's Wetland, Farrel's Lake, Schmidt's
Pond and a background location). Biota sampling will be conducted
at three habitats (Farrel's Lake, Schmidt's Pond and a background
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33
location). The ecological sampling will be performed on an annual
basis for five years and then every five years until EPA
determines that no further monitoring is warranted.
Under all of the remaining groundwater alternatives, a
groundwater extraction system will be constructed consisting of
four or more extraction wells and associated pumps. It is
anticipated that groundwater extraction and treatment in the New
Brighton Aquifer will have to be conducted for a long period of
time (approximately 30 years) before cleanup levels can be
achieved. The approximate extent of groundwater contamination in
the New Brighton Aquifer is shown in Figure 2-2 from the FS which
is attached to this ROD. Contamination was detected in both water
table and basal wells and the extraction system will be designed
to remediate both the water table and the deeper basal
contamination. In order to properly design the groundwater
extraction system, further characterization of the extent of the
DNAPL contamination will be performed during the design phase.
Groundwater will be treated on-site to meet the pretreatment
standards for final discharge to the Metropolitan Waste Control
Commission treatment facilities.
Although a different primary treatment process for organic
contaminants will be evaluated for each of the groundwater
alternatives, there will be several shared components for all of
the alternatives. These are: an oil/water separator for oil
removal, a metals precipitation process for metals removal and
housing for all on-site treatment facilities.
All of the alternatives will utilize on-site treatment with
discharge to a POTW, and thus would be subject to Section 307 of
the Clean Water Act to ensure pretreatment requirements are
achieved prio~ to discharge to the POTW.
GROUNDMATER ALTERNATIVE 2- Groundwater Extraction and Carbon
Treatment
Capital Cost: $554,875
Annual O&M Costs: $177,130
Present Worth Costs: $2,464,000
Alternative-~ uses carbon columns to adsorb the organic
contaminants in the groundwater onto the large internal pore
space of the carbon. When the pore space of the carbon cannot
adsorb any more contamination, the carbon is replaced. The used
carbon must either be disposed of as a hazardous waste or sent to
appropriate facilities to be regenerated for reuse.
GROUNDMATER ALTERNATIVE 3- Groundwater Extraction and Biological
Treatment
Capital Costs: $524,400
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34
Annual O&M Costs: $169,130
Present Worth Costs: $2,320,000
..
Alternative 3 differs from Alternative 2 in that the primary
treatment for organic contaminants is biological treatment rather
than carbon adsorption. The contaminated groundwater is treated
in a bioreactor in which the water is trickled over a fixed film
of biomass and contaminant removal is achieved through biological
action. It may be necessary to use a small carbon adsorption unit
following the bioreactor to assure removal of dioxin/furans are
removed and the MWCC's pretreatment limits are achieved.
GROUNDWATER ALTERNATIVE 4- Groundwater Extraction and Oxidation
Capital Costs: $552,575
Annual O&M Costs:, $202,110
Present Worth Costs: $2,189,000
Under Alternative 4 the organic contaminants would be broken down
using chemical oxidation possibly enhanced with ultraviolet ligh~
and/or ozone. The organic contaminants are eventually reduced to .
carbon dioxide and water.
Off gases may need to be collected and treated. In addition,
groundwater may have to be pretreated before entering the
oxidation unit, as suspended solids in the groundwater may reduce
the effectiveness of the process.
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF THE ALTERNATIVES
The National Contingency Plan (NCP) 40 CFR 300.430(e) (9) (iii)
requires that the alternatives be evaluated on the basis of the
nine criteria presented below.
1. Overall Protection of Human Health and the Environment
This evaluation criterion addresses whether or not a remedy is
adequately protective of human health. It describes how risks
posed through each pathway are eliminated, reduced, or controlled
through treacment, engineering controls, or institutional
controls.
2. Compliance with Applicable or Relevant and Appropriate
Requirements (ARARS)
This evaluation criterion is used to determine whether each
alternative will meet all Federal and State environmental
statutes (as defined in CERCLA Section 121) and/or provide
grounds for issuing a waiver.
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" 35
3 .
Long Term Effectiveness and Permanence
This criterion~is used to evaluate the amount of risk remaining
at a site after completion of the remedial action, and the
ability of the remedy to maintain reliable protection of human
health and the environment over time once cleanup goals have been
met.
4.
Reduction of Toxicity, Mobility, and Volume
This evaluation criterion addresses the statutory preference for
selecting remedial actions that employ treatment technologies
that permanently and significantly reduce the toxicity, mobility,
and volume of hazardous substances as a principal element.
5 .
Short Term Effectiveness
This evaluation criterion addresses the speed with which the
remedy achieves protection, as well as the remedy's potential to
create adverse impacts on human health and the environment that
may result during the construction and implementation period.
6 .
Implementability
This criterion addresses the technical and administrative
feasibility of implementing an alternative and the availability
of various services and material required during its
implementation.
7.
Cost
The estimated capital, annual maintenance and monitoring, and
present worth value costs are evaluated under this criterion.
Present worth is "the total cost of an alternative in terms of
today's dollars.
8 .
Support Agency Acceptance
This evaluation criteria evaluates whether the support
agency concurs with, opposes, or has no comment on the
recommended" alternative.
9 .
Community Support
This criterion refers to the community's comments on the remedial
alternatives under consideration. These comments are presented
in the Responsiveness Summary which is included as an attachment
to this Record of "Decision.
The first two evaluation criteria are threshold criteria that all
alternatives must meet. Criteria 3 through 7 are balancing
criteria that are used to compare the alternatives against each
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36
other and determine which alternative provides the best balance
of the evaluation criteria. The remaining two criteria are
modifying criteria. The input from the community and the support
agency will be considered by the lead agency in making its final
decision.
The comparative analysis of soil and groundwater alternatives
against the nine evaluation criteria is shown below.
Soil Alternatives
Threshold Criteria
~. Overall Protection of Human Health and the Environment
Alternative 1 provides no protection to human health or the
environment, and would not achieve the risk-based soil cleanup
levels. Alternative 2 is protective (in conjunction with a
groundwater remedial action) in that it limits the potential for
contaminants to migrate. However, the soil cleanup levels would.
not be met. The soil cleanup levels are discussed in Section IX .
of this ROD and are also shown in the attached Table 2-1.
Alternatives 3 through 5 would meet the cleanup levels, and will
effectively remove sources of further soil and groundwater
contamination by excavating and treating contaminated soil and
removing the underground tanks, vaults, and related structures.
2.
Compliance With ARARs
Alternative 1 would result in the continued presence of
uncontrolled hazardous waste on site. Under Alternative 2, a cap
would be designed and constructed in accordance with RCRA cap
requirements. Alternatives 2 through 5 would be required to
comply with action-specific ARARs for soil and tank/vault
removal, treatment, and disposal. The treatment technologies
included under Alternatives 2 through 5 should be capable of
meeting their respective ARARs. Waste streams generated by the
treatment processes would require treatment and/or disposal in
compliance with land disposal requirements and/or haza~dous waste
treatment requirements. The laws governing these actions include,
but are not limited to: the Resource Conservation and Recovery
Act, the Cle~n Air Act, the Clean Water Act and any State laws
that have more stringent requirements than the corresponding
federal laws.
Modifvina Criteria
3.
Long-term Bffectiveness and Permanence
Alternative 1 would provide no long-term effectiveness.
Alternative 2 would utilize capping to reduce contaminant
migration, but would not reduce contaminant concentrations, with
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37
the exception of soil removed and subsequently treated as part of
the tank/vault removal, and would not provide a permanent remedy.
Remaining cont~minants would continue to pose potential threats
to human health and the environment over a long time period.
Alternatives 3 through 5 would be equally effective in the long
term as. they all include removal and treatment of contaminated
soil. Both incineration and thermal desorption processes (with
subsequent treatment of desorbed contaminants for thermal
desorption) would result in the permanent destruction of organic
contaminants. Solidification/stabilization of metals under
Alternatives 3 through 5 would immobilize the metals,
significantly reducing the potential of the metals to migrate.
The stabilized metals-contaminated soil would be landfilled in a
permitted facility which would be required to have a leachate
collection systems.
In addition, by removing contaminated soils and mitigating
potential physical hazards associated with the tanks and vaults
under alternatives 3 through 5, future land uses of the property.
would not be as restricted as they would be if the tanks and .
vaults were to remain in place or if contaminated soils were
capped and left in place.
4. Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternative 1 would provide no reduction of toxicity, mobility,
or volume of contaminants, as no treatment would be implemented.
Alternative 2 would physically reduce the mobility of
contaminants by limiting the flow of water through contaminated
areas, but would not chemically treat contaminants to limit the
potential of contaminants to migrate. Alternative 2 would'
provide a reduction in the toxicity and volume of contaminants in
only a small portion of the contaminated' soils at the site (i.e.,
the soils removed with the abandoned tanks/vaults that is
subsequently incinerated).
Alternatives 3 through 5 would sat.isfy the statutory preference
for treatment as a principal element of the remedial action.
Alternatives-3 through 5 all provide for the reduction of
toxicity by removing/destroying organic soil contaminants.
Because of the uncertainties in predicting contaminant
concentration levels in the soils, .there is less confidence that
. Alternative 3 will be as effective in reducing the toxicity,
mobility and volume as Alternatives 4 and 5. It is estimated that
25% of the soils are too contaminated for soil washing to be
effective. If the' actual amount of heavily contaminated soil
significantly exceeds this estimate, soil washing would not be
effective.
Thermal desorption of contaminants, followed by treatment of
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desorbed contaminants and other waste residuals, would result in
the permanent destruction of the desorbed organic contaminants.
Incineration ot organic contaminants would provide the greatest
reduction in contaminant concentrations that is achievable using
currently available technologies. Therefore, the ash generated
under Alternative 4 would contain lower residual organic
contaminant concentrations than would the washed soil under
Alternative 3 or the thermally desorbed soil under Alternative 5.
The treatment of metals-contaminated soils under Alternatives 3,
4, and 5, utilizing stabilization/solidification techniques,
would significantly reduce the mobility of the metals. This
process physically encases contaminants, trapping the
contaminants in a solidified mass and reducing the potential for
water to come in contact with contaminants and leach the metals
from the treated soil. This process also limits mobility of
metals by creating an alkaline chemical environment in which
metals will be much less likely to form water-soluble compounds
and would therefore stay in a solid, non-mobile form.
5. Short-term Effectiveness
In terms of potential hazards that would be posed.by the actual
implementation of alternatives, Alternative 1 involves no action
and would therefore pose no such haza~ds. Impacts caused by
increased truck traffic and noise from heavy equipment operation
would be similar under Alternatives 2, 3, 4, and 5. The
implementation of Alternative 2, because less contaminated soil
would be disturbed, would pose slightly less of a potential
hazard through dust generation than would Alternatives 3, 4, and
5, all of which would involve significant excavation and soil
handling. Alternative 3 would potentially generate more dust than
would Alternative 4 or 5 because two treatment steps would be
required for the organics-contaminated soil. Appropriate dust
control measures would minimize the amount of dust generated
under any alternative.
Air emissions from incineration or thermal desorption would also
potentially pose a threat, but any such threat would be minimized
by proper emission control equipment. If a system upset were to
occur, incineration would be less likely to release contaminants
(including any PCDDs/PCDFs generated during thermal treatment) to
the atmosphere than would thermal desorption, since the high
temperatures in the secondary combustion chamber in an
incinerator would destroy the contaminants even if emission
control equipment failed. However, both incineration and thermal
desorption have been implemented at a number of hazardous waste
sites in compliance with all air emission standards, and
emissions under these alternatives are not expected to pose
significant threats to the surrounding human population or
environment. Monitoring of surrounding air and close control of
treatment process operating parameters would be utilized to
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39
ensure emissions will not have a significant impact.
In terms of minimizing existing threats posed to human health and
the environment by contamination presently on site, Alternative 1
would not mitigate these threats at all in the short term.
Alternative 2 would provide limited short-term protection through
the removal and treatment of site soils immediately surrounding
the abandoned tanks and vaults, but would leave significant
contamination in place. The more significant short-term benefits
that would be provided by Alternative 2 would be restricting
direct exposure to soil and reducing migration of contaminants
from soil to groundwater. Alternatives 3, 4, and 5, within a
relat~vely short time frame, would achieve the site RAOs,
minimize the .chemical threats posed by contaminated soil on site,
and eliminate the physical hazards posed by abandoned process
tanks, vaults, and other structures. Therefore, Alternatives 3,
4, and 5 would provide the greatest short-term protection.
6. Xmplementability
Alternative 1 poses no technical implementation difficulties, but
would not be acceptable from a regulatory standpoint. In terms
of remedial construction activities, Alternative 2 would be
implemented more quickly and more simply than Alternatives 3, 4,
and 5, since less soil would be excavated and treated (e.g., no
stabilization/solidification would be required since none of the
metals-contaminated soil would be excavated).
Alternatives 3, 4 and 5 are fairly complex. All of the
alternatives except Alternative 1 would require treatability
tests and/or test burns prior to remediation. Alternatives 2, 3,
4, and 5 would require excavation of tanks, vaults, and soil; on-
site operation of treatment systems; and backfilling or off-site
disposal of treated soil and residual wastes. These alternatives
would therefore. require design and monitoring of construction
activities and would require at least four months to implement.
Excavation of soil to the depth of the water table would require.
sloping or construction supports to avoid caving.
Process equipment for Alternatives 2, 3, 4, and 5 is available
from a number of vendors. The reliability of incineration would
be somewhat-bigher than that for soil washing or thermal
desorption, based on the proven performance of incineration under
a variety of operating conditions. Operation of a soil washing
system would involve screening of the soil prior to washing to
facilitate the process, and treatment of wastewater generated by
the process, but these factors should not significantly impact
the implementability of soil washing. Under Alternative 5, the
possible presence of PCDDs/PCDFs in residual waste streams (e.g.,
organic liquid waste streams) may require special treatment prior
to disposal. -
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The space required for soil excavation and staging activities
would occupy a significant portion of the site. Additional soace
would be required for the operation of on-site treatment systems.
Alternative 3 would require the most space (for soil washing,
incineration, and soil stabilization operations), and may require
more space than is available on site, especially considering that
a groundwater treatment system associated with OU2 or aU3 also
may be in operation and occupy a portion of the site.
Alternative 2 would require less space than Alternative 3, 4, or
5. If the Bell incinerator were to be used for Alternatives 2, 3,
or 4, less space would be required than if an incinerator were
mobilized to and constructed' on the M & G property.
Because the MPCA has decided to implement an incineration remedy
for the contaminated soils in OU1, it is anticipated that the
incineration of contaminated soils in Operable Units 1 and 3 can
be combined into one remedial construction contract. This would
allow greater implementability through having a single design and
bidding effort. Less coordination in areas such as space concerns
would be required between the operable units during the .
remediation. If separate construction contracts were undertaken,'
there is also the possibility that two different incineration
contractors could be on-site at the same time which could lead to
implementation problems for the remedial action as well as
heightened concerns by nearby residents. In terms of coordination
with remediation activities in OU1, Alternative 4 would be more
implementable than Alternatives 3 and 5.
Although Alternatives 2, 3, 4, and 5 would all impact wood-
treating operations currently being conducted at the site,
Alternative 2 would have less of an impact. Wood-treating
operations would have to be halted at least temporarily under any
of these alternatives. .
7. Cost
If the no action alternative were implemented at the site, no
costs would be incurred. Alternative 2, estimated to cost
approximately $4.3 million, would be much less costly than
Alternative 3, 4, or 5, since it would incur much lower
excavation, treatment, and disposal costs. Alternatives 3, 4, and
5, estimat~d to cost approximately $14.2. million, $15.7 million,
and $14.9 million, respectively, would be fairly similar in cost.
See attached tables 4-1 through 4-4 from the FS for a detailed
breakdown of soil remediation costs.
Because the unit cost for soil washing is less than the unit cost
for incineration, Alternative 3 .is estimated to be less expensive
than Alternative 4. However, this would only hold true if a
majority of the organics-contaminated soil at the site is
amenable to soil washing. Alternatives 5 is slightly less
expensive than Alternative 4, primarily because thermal
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desorption would require less energy than incineration.
Because MPCA will be implementing incineration as the remedy for
Operable Unit 1, it is anticipated that all of the organics
contaminated soils from both Operable Units 1 and 3 can be
treated under one remedial construction contract. The current
cost estimate for Alternative 4 does not reflect the potential
cost savings of combining OUs 1 and 3 into one construction
contract. Cost savings would be realized as only a single design
and bidding effort would be required. Cost savings are also
normally obtained when larger quantities of materials are
remediated~ Therefore, costs for Alternative 4 are likely to be
equal to or less than the costs for Alternatives 3 and 5.
Modifvinq Criteria
8. State Acceptance
The State of Minnesota supports the selection of the selected
alternative, that is, Soil Alternative 4.
9. Community Acceptance
Comments received at the public meeting and subsequent written
comments were generally supportive of the remedy. Written.
comments on behalf of the City of New Brighton requested that
additional areas of soil on the site be addressed, possible
contamination in the area of the currently operating facilities
and buildings be addressed and that more stringent cleanup levels
be used for arsenic cleanup. All written comments received are
addressed in the Responsiveness Summary portion of the ROD.
Groundwater Alternatives
Threshold Criteria
1.
Overall Protection of Human Health and the Environment
Alternative ~ provides no protection to human health or the
environment. If no action is taken, contaminant plumes from the
M & GIBell Site will continue to migrate, impacting downgradient
portions of the aquifer and possibly impacting ecological
habitats. The human health threats posed by groundwater
contamination would continue, and possibly increase as
contaminant plumes spread through the aquifer.
Protection of human health and the environment would be provided
under Alternatives 2, 3, and 4, by treating the groundwater in
the New Brighton Aquifer to levels which would be safe. to use for
general domestic purposes. Alternatives 2, 3, and 4 all provide a
similar level of protection to human health and the environment.
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Active remediation of contamination in the Hillside aquifer will
not be undertaKen at this time. Although some of the wells
currently exceed the MCL for PCP, the contamination is confined
to the site and no residential wells are contaminated above MCLs.
It is anticipated that with remediation of soils and also
groundwater in the New Brighton Aquifer which are a potential
source, active remediation may not be necessary. Monitoring of
this aquifer will be conducted to evaluate future changes in
contaminant concentrations. If future monitoring shows that the
Hillside aquifer is significantly impacted by site contamination,
further remedial action would be considered at that time.
2.
Compliance with ARARs
Under Alternative 1, contaminants would be allowed to migrate,
uncontrolled, off site; therefore, this alternative would not
comply with state and federal corrective action requirements for
contaminated groundwater. Groundwater extraction under
Alternatives 2, 3, and 4 would treat contaminated water in the.
New Brighton Aquifer to the Maximum Contaminant Levels specified
in the Safe Drinking Water Act. For arsenic and dioxin/furans,
the cleanup levels are more stringent than MCLs in drder to
provide a 10-4 risk level for these contaminants. Residual waste
streams generated under Alternatives 2, 3, and 4 would have to be
disposed of, and treated if necessary, in compliance with action-
specific ARARs. The laws governing these actions would include
but are not limited to: the Safe Drinking Water Act, the Clean
Water Act, RCRA and any State laws that have more stringent
requirements than the corresponding federal laws.
Balancinq Criteria
3..
Long-ter.m Effectiveness and Per.manence
Alternative 1 provides no long-term permanence; contaminants
would continue to migrate off site with groundwater flow over a
long time period. Alternatives 2, 3, and 4, would reduce
contaminant concentrations to levels safe for general domestic
use, which would provide long-term protection to downgradient
receptors. Contaminants removed from collected groundwater would
be treated and disposed of, and would no longer pose a threat to
human health or the environment.
4.
ReductioD of Toxicity, Mobility, or Volume Through Treatment
Alternative 1 incorporates no treatment, and therefore would not
actively reduce the toxicity, mobility, or volume of
contaminants. The groundwater extraction component of
Alternatives 2, 3, and 4 would reduce the volume and mobility of
contaminated groundwater remaining in the New Brighton aquifer
beneath and downgradient from the site. The treatment components
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of Alternatives 2, 3, and 4 would reduce the toxicity of organic
contaminants (through carbon adsorption and subsequent treatment
of the carbon,~through biological degradation, or through
chemical oxidation, respectively) and would reduce the mobility
of metals through precipitation and subsequent
treatment/disposal.
s.
Short-ter.m Effectiveness
The actual implementation of Alternative 1 would not cause any
negative impacts, but if no action is taken there would be no
protection from existing human health and environmental risks
within the immediate future.
The actual implementation of Alternatives 2, 3, and 4 (i.e.,
construction and operation of extraction wells and treatment
systems) should not have an adverse impact on human health or the
environment as long as proper health and safety procedures are
observed during implementation. Under Alternatives 2, 3, and 4,
th~ institution~l actions, p~rticularly possible future .
abandonment of existing private wells and restrictions on future
well installation in impacted areas, would provide protection of
human health from the most significant threats within a short
time frame. .
6.
~lementability
. There are no technical limitations to implementing Alternative 1.
However, from an administrative standpoint, the no action
alternative will not be acceptable.
The materials, equipment, and labor necessary to implement
Alternatives 2, 3, and 4 are readily available. The extraction
. and treatment systems considered under these alternatives are all
fairly standard systems. Property access may be required for
installation of extraction wel~s and piping, but should not pose
a major difficulty. A permit to discharge to the POTW would need
to be secured, as well as disposal facilities for sludges from
the treatment systems, spent carbon (under Alternative 2), and
the oil phase waste.
Treatabilit~testing would be required to ensure the
effectiveness of the treatment systems and to optimize the
eventual full-scale operating conditions. However, since
biological treatment will be utilized to treat groundwater
collected under the interim action to address OU2 at the site,
fur~her treatability testing may not be required. In addition,
the biological treatment system for OU2 may be able to be
utilized to treat groundwater extracted under OU3, or may be able
to be expanded to treat a higher flow rate of water.
The presence of PCDDs/PCDFs may pose difficulties for disposing
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of residuals generated by the different treatment processes.
Many of the PCDDs/PCDFs would be expected to be retained in the
oil separation~phase. PCDDs/PCDFs may also accumulate in sludges
generated by the biological (Alternative 3) and metals
precipitation (Alternatives 2, 3, and 4) treatment systems and in
spent carbon (Alternative 2). Treatability testing would be
required to determine whether or not the PCDDs/PCDFs would pose
significant difficulties.
Under Alternative 2, oil which is not captured by the oil/water
separator could accumulate on the carbon, reducing its
effectiveness in adsorbing contaminants, and thereby increasing
the amount of carbon used to meet effluent limits. Under
Alternative 4, suspended solids in extracted groundwater may
reduce the effectiveness of chemical oxidation, and additional
pretreatment steps, therefore, may be required. The biological
process under Alternative 3 would be less likely to be affected
by the oil and suspended solids interferences than Alternatives 2
and 4.
Alternative 2 will generate large quantities of spent carbon
which will require frequent changes and off-site disposal in a
landfill or regeneration of the carbon in a permitted facility.
Alternative 3 will generate significantly less residual biomass
which will require d~sposal.
Each of the alternatives would be technically implementable.
However, Alternative 3 would likely be the most readily
implemented because of the planned use of biological treatment
for groundwater under OU2 and the other technical considerations
discussed above.
7.
Cost
. . .
Alternative 1 would incur no costs, while Alternatives 2, 3, and
4 would incur capital costs of approximately $555,000, $524,000,
and $553,000, respectively. Alternatives 2, 3, and 4 would incur
annual O&M costs of $204,000, $195,000, and $232,000,
respectively. The present worth estimated for Alternatives 2, 3,
and 4 would De $2.5 million, $2.3 million, and $2.8 million,
respectively. See attached Tables 4-6 through 4-8 from the FS for
a detailed ~eakdown of groundwater remediation costs. If oil-
phase contaminants lessen the effectiveness of carbon adsorption
under Alternative .2, the O&M costs for that alternative could
increase significantly. The differences in cost between
Alternatives 2, 3, and 4 are not significant, however,
Alternative 3 is estimated to be less expensive than Alternatives
2 and 4. Typically, biological treatment is less expensive than
other organic treatment technologies.
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Modifvinq Criteria
8. State Accep~ance
The State of Minnesota supports the selection of the selected
alternative, that is Groundwater Alternative 3.
9,. Communi ty Acceptance
Comments received at the public meeting were generally supportive
of the remedy. Written comments received on behalf of, the City of
New Brighton questioned some elements of the groundwater remedy.
, All written comments received are addressed in the Responsiveness
Summary of the ROD.
IX. SELECTED REMEDY
Based on the information collected and developed in the RI/FS
'process, and using the comparative analysis of alternatives
described above, U.S. EPA in consultation with MPCA, have
selected Soil Alternative 4 and Groundwater Alternative 3 as the
most appropriate remedial actions for soil and groundwater
contamination in Operable Unit 3. Soil Alternatives 4 and 5 were
similar in all of .the evaluation criteria. Alternative 4 was
chosen because of potential advantages in the cost and
implementability criteria if OU 3 soils are incinerated with the
MPCA's OU 1 soils. Groundwater Alternative 3 was also chosen
because of its advantages under the implementability criterion.
This remedy is made up of the following components:
1.) Soil excavation:
Approximately 30,000 cubit yards of organics-contaminated
soils from the PCP process area and 20,000 cubic yards of
metals-contaminated soils from the CCA process area will be
excavated to the water table which is approximately 12 feet
deep. Several other areas on the site will also be excavated
to a depth of 2 feet.
2. )
On-site incineration and on-site backfillinq of orqanics
contaminated soils:
Incineration conducted on-site will achieve a destruction
efficiency of 99.99% as required by RCRA. This destruction
efficiency will ensure that organic contaminants are treated
to well below the site cleanup levels. Emission control
equipment on the incinerator and air monitoring would be
utilized to ensure no significant emissions are released
during incineration. Ash that meets cleanup goals will be
backfilled on-site while ash that does not meet cleanup
goals will be landfilled off site. A test burn will be
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performed for the incinerator prior to full-scale operations
to ensure that appropriate emission levels are met.
or
3 . )
On-site solidification/stabilization of metals contaminated
soils with subseauent disDosal in an off-site landfill:
Metals contaminated soil will be stabilized/solidified on-
site which will neutralize the contaminants and reduce their
mobility. The solidified soils will then be disposed of in
an off-site landfill.
4. )
Removal and off-site disDosal and/or recyclinq of
underqround tanks and vaults:
The-tanks and vaults would be dismantled/demolished for
transportation off-site. Any reclaimable material from the
tanks would be recycled and the remaining materials (e.g.
. concrete) would be decontaminated and disposed of in a
landfill. If the concrete and other debris are sufficiently
decontaminated, these materials can be disposed of in a non--
hazardous RCRA Subtitle D landfill. If the debris cannot be
decontaminated, the materials would have to be sent to an
approved RCRA Subtitle C hazardous waste landfill.
5. )
Groundwater extraction and treatment of the contaminated
qroundwater in an on-site bioloqical wstewater treatment
facility:
A groundwater pumping system will be used to extract the
contaminated groundwater in the New Brighton Aquifer.
Groundwater will be treated to site cleanup levels in order
to restore groundwater to its beneficial uses. The extracted
groundwater will be treated by an on-site treatment plant.
The primary component of the on-site t~eatment facilities
will be a fixed-film bioreac~or. An oil/water separator for
oil removal and a metals precipitation unit for metals
removal will also be employed. It may be necessary to use a
carbon adsorption unit following the bioreactor to assure
removal of dioxin/furans to the pretreatment level required
by the MWCC.
6. )
Discharqe of effluent water from the on-site -
wastewatertreatment facility to a Publicly Owned Treatment
Works (POTW)- for final treatment and discharqe in accordance
with National Pollutant Discharqe Elimination System (NPDES)
cretreatment limits:
The on-site treatment facility will be discharging to the
Metropolitan Waste Control Commission (MWCC), which is the
local POTW. The discharge of effluent to the MWCC facility
will be in compliance with the pretreatment requirements of
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7. )
40 CFR 403 as well as MWCC's pretreatment requirements.
Institutional controls. includina deed restrictions limitinq
use of aroundwater in contaminated areas and if necessary.
future abandonment of residential wells impacted by
contar.1ination:
Deed restrictions may be implemented to limit future
installation of water supply wells in contaminated areas and
limit future use of contaminated areas. Existing City of New
Brighton ordinances will also be examined to see if the City
has sufficient legal authority to prohibit activities in the
contaminated areas. Future abandonment of residential wells
will be necessary if co~taminant levels exceed cleanup
levels in'residential wells used for domestic purposes or
risk based contaminant levels in residential wells used for
nondomestic purposes. U. S. EPA will consult with the MPCA
and the Minnesota Department of Health if future
abandonment of residential wells is considered.
8. )
Lona term qroundwater monitoring in the New Briahton and
Hillside Aauifers:
Groundwater monitoring of the New Brighton Aquifer will be
performed on a long-term basis to determine whether the
contaminant plume is being captured by the groundwater
extraction wells and also whether contaminant concentrations
are being reduced by the remediation action. Groundwater
monitoring of the deeper Hillside Aquifer will also be
conducted. Active remediation of the Hillside Aquifer is not
planned at this time. Groundwater monitoring of
contamination in the Hillside Aquifer shall be conducted. If
contaminant levels exceed MCLs at monitoring wells at the
M & G property boundaries, active remediation of the
Hillside Aquifer will be considered. ' .
Monitoring of both aquifers will consist of analysis of
groundwater samples from monitoring wells and, residential
wells. An estimated ten wells will be sampled on an annual
basis for metals, semivolatiles and PCDDs/PCDFs. It may be
determined that additional wells should be installed and
monitored during the final design of the groundwater
extraction system.
9.) Lona-term monitorina of selected ecosystems ad;acent to the
site.
Active remediation of the adjacent ecosystems will not be
conducted at this time. Monitoring will be conducted to
determine whether remedial actions at the site will reduce
. ,the degree of contaminant effects on the ecosystems.
Monitoring will consist of sediment and surface water
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sampling from four habitats (Hanson's Wetland, Farrel's
Lake, Schmidt's Pond and a background location). Biota
sampling will be conducted at three habitats (Farrel's Lake,
Schmidt's Pond and a background location). The ecological
sampling will be performed on an annual basis for five years
after the groundwater remedy has been implemented and then
every five years thereafter. Monitoring must be conducted
for a minimum of ten years. If after ten years, U.S. EPA
determines that the level of contamination in an individual
ecosystem has decreased or stabilized, monitoring may cease.
Cleanu1) Levels
As part of the FS, cleanup levels were established for the soils
and groundwater to be remediated. The cleanup levels were based
on ARARs, regulatory guidance and criteria referred to as To Be
Considered (TBCs), and also risk-based values.
As previously discussed, U.S. EPA has established an acceptable
risk range of 10-4 to 10 -6 for potential excess cancer risks. The.
State of Minnesota generally establishes its cleanup goals at the
10 -s level. The risk assessment showed that several exposure
routes exceeded the 10 -s risk level. These pathways are as
follows:
.
Ingestion of, and dermal contact with, soil by
site workers - due to arsenic and PCDDs/PCDFs;
.
Domestic use of groundwater from private
wells by nearby residents - due to ingestion
of, and dermal contact with, arsenic, PCP,
and PCDDs/PCDFsi
.
Future (hypothetical) domestic and auxiliary
use of groundwater from private wells by
nearby residents - due to ingestion of, and
dermal contact with, PCP and PCDDs/PCDFs
(and, to a lesser extent, arsenic and PARs);
and
.
Auxiliary use of groundwater from private'
wells by nearby residents - due to ingestion
of, and dermal contact with, PCP and
PCDDs/PCDFs.
The cleanup levels that have been developed for the site focus on
eliminating or reducing the potential for exposure through these
pathways. Cleanup levels for the site were calculated with a goal
of a 10 -s risk level. This was not achievable for soils because
of the u.S. EPA policy cleanup level for PCDDs/PCDFs. However, a
total cleanup level for soils of 10-4 has been established, which
is within u.s. EPA guidelines. For groundwater, a cleanup level
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of between 10 -4 and 10 -5 has been established. A summary of the
cleanup levels for both soils and groundwater is shown on Tables
2-1 and 2-2 from the FS. The basis for the individual contaminant
cleanup levels is discussed below.
Soil Cleanup Levels
General objectives for contaminated soil at the M&G/Bell Site
include:
-Minimizing potential for human exposure to contaminants
eliminating significant exposure routes and/or reducing
contaminant concentrations in soil; and
by
- Minimizing further degradation of soil and groundwater by
restricting contaminant migration to unaffected areas.
In order to establish the cleanup levels to accomplish the above
objectives, several factors were considered. The risk assessment
determined that dioxin/furans and arsenic in surface soils posed.
significant health risks. Although PCP, cPAHs and chromium do not
pose as significant a risk in surface soils, significant
concentrations were found in subsurface soils and groundwater.
This subsurface soil contamination is suspected 6f contributing
to groundwater contamination. Exposure to groundwater represents
the greatest potential risk at the site. Both the MPCA and u.s.
EPA have established methods to calculate soil cleanup levels
that would be protective of groun4water. Therefore, cleanup goals
have been established for PCP, cPAHs and chromium, in addition to
arsenic and PCDDs/PCDFs. The individual contaminant cleanup
levels are as follows: .
PCDDs/PCDFs
For PCDDs/PCDFs, the cleanup level is 1 ug/kg. This cleanup level
was developed by the Agency for Toxic Substances and Disease
Registry (ATSDR) and has been established as EPA policy. This
concentration is also the practical detection limit for
laboratory analysis of PCDDs/PCDFs in soil. The 1 ug/kg cleanup
level does exceed the 10 -5 risk level that MPCA uses as a goal.
However, the remaining cleanup levels for other site contaminants
have been ca~culated so that total risk from all contaminants at
the site will not exceed 10-4 which is within u.s. EPA's
acceptable risk range.
PCP
The cleanup level for PCP is 10 mg/kg. This value is consistent
with the cleanup level previously used at the Bell Lumber portion
of the site. This number is significantly lower than the risk-
based concentration of 290 mg/kg and would be protective of hum~n
health. Although this number is slightly in excess of the
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calculated groundwater-protective level, it is still expected to
be protective of groundwater.
PARs
The cleanup level for the sum of cPAHs is 5 mg/kg which is the
groundwater protec~ive value. The cleanup level is lower than the
risk-based concentration of 8 mg/kg in soils and thus would be
protective of human health. No cleanup level for non-carcinogenic
PARs was established because these PAHs pose less risk than cPAHs
and cleanup actions that meet the cleanup level for cPAHs and PCP
will also address risks from non-carcinogenic PAHs.
Chromium
The cleanup level for chromium is 400 mg/kg. This applies to
total chromium concentrations which includes hexavalent chromium,
Cr (VI). This value is consistent with the RCRA Corrective Action
value TBC and is significantly below the human health risk-based
concentration of 17,500 mg/kg.
Arsenic
The cleanup level for arsenic is 55 mg/kg. This value was
considered because of the presence of sigpificant volumes
(estimated at 30,000 cubic yards) of surface soil at the site
that contain between 31 and 55 mg/kg arsenic. The 55 mg/kg
concentration is only slightly above 31 mg/kg, which represents
. the 1 x 10-5 risk level for arsenic, and the cost of removing and
treating/disposing of this soil would be significant (greater
than $2.5 million), while not necessarily accomplishing a
significapt decrease in risks posed by the site.
.This approach of establishing 55 mg/kg as a cleanup level for
arsenic was also undertaken because of the uncertainties involved
with the risk estimation process and the inherent .
conservativeness of the estimates. The margin of safety built
into the risk assessment process should still provide sufficient.
protection to allow a cleanup level of 55 mg/kg.
The 55 mg/kg value is higher than the 10-5 risk-based
concentration of 31 mg/kg for arsenic as an individual
contaminant, but takes into consideration the fact that at an
arsenic concentration of 50 mg/kg, the total site cleanup level
will represent a risk of 10-4, which is at the upper end of the
risk range acceptable to EPA. Assuming a background concentration
of 5 mg/kg for arsenic, 5 mg/kg should be added to the cleanup
level which is based upon risk considerations, resulting in a
cleanup level of 55 mg/kg.
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Groundwater Cleanup Levels
General object1ves for contaminated groundwater at the M & G/Bell
Site include:
.
Minimizing potential for human exposure to
contaminants by eliminating significant
exposure routes and/or reducing contaminant
concentrations in groundwater; and
.
Minimizing further, degradation of soil and
groundwater by restricting contaminant
migration from groundwater to unaffected
areas.
U.S. EPA's Maximum Contaminant Levels (MCLs), State of Minnesota
Recommended Allowable Limits (RALs) , RCRA action levels, and
risk-based concentrations were considered for establishing
specific numerical cleanup levels for site groundwater. In
addition, standard quantitation limits were considered to ensure,
that it would be technically feasible to verify cleanup following
remedial action.
The Safe Drinking Water Act established MCLs, which represent the
maximum concentrations of contaminants allowed in public water
supply syst~ms. The State of Minnesota RALs were also considered.
RALs are advisory levels rather than promulgated. standards.
The New Brighton Aquifer is considered to be a Class II Aquifer
under the "Guidelines for Groundwater Classification Under the
EPA Groundwater Protection Strategy" because it is a potential
drinking water source. The Hillside Aquifer is considered as a
Class II Aquifer because several residential wells currently use
it for drinking water. .
MCLs for PCP, cPAHs and chromium are being used as cleanup
levels. Although risk-based concentrations for these
contaminants were lower than MCLs, they were also lower'than
standard quantitation limits and thus contamination could not be
quantified at these concentrations. MCLs pose risks below the
10-4 level for site carcinogens, with the exception of arsenic
and PCDDs/PCDFs. Since MCLs for PCP, cPAHs, and chromium fall
within the acceptable risk range of 10-4 to 10-6, and are
technically achievable with regard to quanti tat ion limits, they
are being set as cleanup levels. '
For arsenic and PCDDs/PCDFs, concentrations at which 1 x 10-4
excess cancer risks potentially would be posed were selected as
cleanup ievels rather than MCLsto provide added protection to
human health.
The following are the groundwater cleanup levels:
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.
PCP - 1 ~g/Lt
Sum of cPAHs - 0.2 ~g/Lt
.
.
Chromium - 100 ~g/Lt
Arsenic - 5 ~g/Lt and
.
.
TCDD Equivalent - 12 pg/L.
All cleanup levels are at or below MCLs and represent a risk of
10 -4 or less. The MCL for arsenic, presently 50 ~g/L, is
currently under review by EPA. If the MCL is revised to a value
below the site cleanup level of5 ~g/L, the cleanup level for
arsenic will need to be reevaluated.
Achievability of Groundwater Cleanup Levels
The goal of this remedial action is to restore the groundwater in
the New Brighton Aquifer to its beneficial use, which is, at thi$
site, both auxiliary and potential domestic use. Based on
information obtained during the RI and the analysis of remedial
alternatives, U.S. EPA believes that the selected. remedy may be
able to achieve this goal. Groundwater contamination, however,.
may be particularly persistent in the immediate vicinity of the
contaminant's source where DNAPL materials have been observed and
concentrations are high.
The ability to. achieve cleanup levels at all points throughout
the area of attainment, or plume, cannot be determined until the
groundwater extraction system has been implemented/modified as
necessary and plume response monitored over time.
If the selected remedy cannot meet the specified remediation
levels. at all of the monitoring points during implementation, the
contingency measures and objectives described in this section may
replace the selected remedy and remediation levels for these
portions of the plume. Such contingency measures at a minimum
shall include containment of contaminated groundwater and
institutional controls. These measures are considered to protect
human health and the environment, and are technically
practicable~
The selected remedy will include groundwater extraction for an
estimated period of thirty years, during which the system's
performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during
the operation. Modifications may include any or all of the
following:
- Discontinued pumping at individual wells where cleanup goals
have been attained
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- Alternating pumping wells to eliminate stagnation points
- Pulse pumpiITg to allow aquifer equilibriation and to allow
adsorbed contaminants to partition into groundwater
- Installing additional extraction wells to facilitate or
accelerate cleanup pf the contaminant plume
- Remedial technologies to enhance removal of possible DNAPL
materials.
To ensure that cleanup levels are maintained at those wells where
pumping has ceased, the aquifer shall be monitored in accordance
with the detailed groundwater monitoring plan which will be
developed during design. The detailed monitoring plan will be
modified as necessary during the monitoring stage as conditions
require.
If it is determined, on the basis of the preceding criteria and
the system performance data, that certain portions of the aquifer
cannot be restored to their beneficial use, all of the following
measures involving long-term management may occur, for an
indefinite period of time, as a modification of the existing
system:
- Engineering controls, such as long-term gradient control
provided by low level pumping, will be implemented as containment
measures.
- Chemical specific ARARs will be waiveQ for the cleanup of those
portions of the aquifer based on the technical impracticability
of achieving further contaminant reduction.
-Institutional control will be provided and maintained to
restrict access to those portions of the aquifer that remaip
above remediation levels.
-Monitoring of specified wells will continue.
-Remedial technologies for groundwater restoration will be
reevaluated periodically.
x.
STATUTORY DBTBRKINATIONS
u.s. EPA's primary responsibility at Superfund sites is to select
remedial actions that protect human health and the environment.
Section 121(d) (2) of CERCLA also requi~es that the selected
remedial action for the site comply with applicable or relevant
and appropriate environmental standards established under state
and federal environmental laws with respect to contaminants
remaining on site at completion of the remedy unless a waiver is
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54
granted. With respect to ongoing work at the Site, it is U.S.
EPA's policy to comply with state and federal environmental laws.
The selected ~emedy must also be cost-effective and utilize
permanent treatment technologies to the maximum extent
practicable. The statute also contains a preference for remedies
that include treatment as a principle element. The following
section discusses how the selected remedies for soils and
groundwater contamination at aU3 meet these statutory
requirements.
Protection of Human Health and the Environment
The selected remedial action will be effective in removing the
source materials in the soils that are contributing to the
continued contamination of the groundwater in the New Brighton
and Hillside Aquifers, and in controlling and reducing the
groundwater contamination that has already occurred.
Remediation of soils contaminated with organic compounds and
metals through incineration and stabilization/solidification is
expected to eliminate the risk of human exposure via the
identified pathways, which are: dermal contact with current and
future workers on the site property; to off-site residents of the
adjacent area through contact with contaminated soils; and to
offsite residents o~ the adjacent area through contact with
airborne contaminants.
, ,
The groundwater component of the remedy likewise is determined to
be protective of human health and the environment. The
alternative is expected to achieve restoration of the upper
aquifer and reach health-based levels at the facility boundary
and beyond. Continued monitoring of groundwater in the vicinity
of the PCP process area, where there is evidence of a DNAPL
.plume, will be conducted to ensure that health-based levels are
met on site. The selected alternative thus presents th~,best
available technological alternative for protecting human health
and the environment.
The identified pathways for human exposure are: the present and
future use ot groundwater for domestic and auxiliary purposes;
recreational use of nearby surface waters; and fish consumption.
Additionally, three sensitive aquatic areas near the site are
potentially at risk to exposure from site-derived contaminants,
via a storm drain or the migration of contaminants through
groundwater to the surface waters in the affected habitats.' By
extraction and treatment, through a combination of oil/water
separation, metals precipitation and bioreaction, the groundwater
component of the selected remedy will vastly reduce and control
the risk of continued human exposure via these pathways.
Continued monitoring and, if necessary, modification, of the
pumping scheme will maximize contaminant extraction from the
groundwater. Application of institutional controls is expected
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further to reduce or eliminate the risk to human health.
Continued monitoring of the affected aquatic habitats, combined
with removal o! the contaminant sources, is expected to reduce or
eliminate the risk to these sensitive areas.
Through implementation of the remedy, the site risk is expected
to be reduced to within the 1 X 10-4 range for carcinogens in the
soils and to within the 1 X 10-4 to 1 X 10-5 range for
groundwater, and the Hazard Indices for non-carcinogens will be
less than one. The combined effect of the two selected
components of the remeqy thus will be to achieve comprehensive
protection of human health and the environment from the
contamination that resulted from historical waste disposal
practices at the Site. Finally, implementation of the remedy
will not cause unacceptable short-term risks or cross-media
impacts to the site, the workers or the community.
Compliance with ARARs
The selected remedial action is expected to meet all identified
applicable or relevant and appropriate Federal, and more
stringent State, requirements. ARARs for the selected remedy are
listed below. It is noted that MCLGs are listed as ARAR, but as
was indicated in the Feasibility Study Report (Ecology &
Environment, Inc., April; ~994), the MCLGs for the contaminants
of concern (PCP, cPAHs, chromium, arsenic and TCDD) were either
zero or the same level for the corresponding MCL. Thus,
. consistent with Section 300.430(e) (2) (i) (B) and (C) of the NCP,
the MCL values for the contaminants of concern were used in
evaluating the remedial alternatives.
A.
Chemical SDecific ARARs
1.
RCRA Definition and Identification of Hazardous waste
(40 CFR Part 261); Minnesota Hazardous waste rule
7045.0020-7045.0135 (4) (f) (Minnesota equivalent
regulation) '.
2.
RCRA Toxicity Characteristic Rule regarding
classification for soils containing arsenic, chromium
and PCP (40 CFR 261.24) .
3.
Safe Drinking Water Act Maximum Contaminant Levels
(MCLs) and Maximum Contaminant Level Goals (40 CFR 141
Subparts B and F)
B.
Action SDecific ARARs
1.
RCRA Standards for Generators of Hazardous Waste (40
CFR Part 262); Minnesota Hazardous waste rule
7045.0211-7045.0304 (Minnesota equivalent regulation)
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56
2.
RCRA Standards for Owners and Operators of Hazardous
Waste Treatment Facilities (40 CFR Part 264); Minnesota
Hazardous waste rule 7045.0552-7045.0642 (Minnesota
equivalent regulation)
3 .
RCRA Standards for Transporters of Hazardous Waste (40
CFR Part 263);
4.
RCRA Land Disposal Restrictions (40 CFR Part 268)
5 .
RCRA Boilers and Industrial Furnaces Rule -- Metals
Emissions from Boilers and Industrial Furnaces (40 CFR
266.106)
6.
RCRA Boilers and Industrial Furnaces Rule -- Hydrogen
Chloride (HCl) Emissions from Boilers and Industrial
Furnaces (40 CFR 266.107)
Clean Air Act National Ambient Air Standards (40 CFR
Part 50)
Clean Water Act Standards for Discharge to Publicly-
Owned Treatment Works (40 CFR Part 403)
C.
Location SDecific ARARs
1.
2.
RCRA Location Standards for Hazardous Waste Treatment
Units (40.CFR 264.18)
EPA Wetlands Protection; Floodplain Management (40 CFR
6.302, Appendix A)
In addition, u.S. EPA's .cERCLA Off-Site Policy" (OSWER Dir".
9834.11, November 1987) will govern discharges of CERCLA
wastewaters to the POTW and landfill disposal of metals- . .
contaminated soils, non recyclable debris, and any in~ineratbr fly
ash that does not meet cleanup standards.
Finally, in implementing the selected remedy, u.S. EPA and the
State have ~reed to consider several procedures that are not
legally binding. These include the draft guidance on combustion,
u.S. EPA Waste Minimization and Combustion Strategy (Draft
Guidance May, 1993), and the imposition of institutional controls
to be enforced by the local government to ensure that human
health is protected while remedial action is in progress.
As indicated above, the presence of the DNAPL plume at the former
PCP process area is not expected to prevent u.S. EPA from
attaining MCLs within the facility boundary through the process
of groundwater extraction. Nonetheless, u.S. EPA recognizes the
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57
possibility that information may emerge from the operation of the
selected system suggesting that contamination cannot be
completely removed and containment will be necessary. In view of
the selected remedy's effectiveness in meeting MCLs at the
facility boundary and off-site, U.S. EPA determines that it is
approp~iate to proceed with remedial construction and to continue
to monitor groundwater in the PCP process area and, if necessary,
to implement containment measures in this area at a future date.
Cost Effectiveness
U.S. EPA determines that the selected remedy is cost-effective in
removing sources of groundwater contamination from the site and
restoring groundwater, within a reasonable period of time.
Section 300.430(f) (1) (ii) (D) of the NCP requires U.S. EPA to
evaluate cost-effectiveness by comparing all the alternatives
that meet the threshold criteria (protection of human health and
the environment and compliance with ARARs) against three
balancing criteria (long-term effectiveness and permanence,
reduction of toxicity, mobility or volume through treatment, and.
short-term effectiveness). The selected remedies meet these
criteria, and provide for overall effectiveness in proportion to
their cost, as set forth in the Feasibility Study Report (Ecology
& Environment, Inc., April, 1994) at pp. 4-16 -- 4-18; 4-35 -- 4-
38. The estimated present worth value of the groundwater
component of the selected remedy is $2,300,000 and the capital
cost thereof is approximately $524,000; the estimated cost of the
soils component is $15,700,000.
Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum
Extent Practicable
U.S. EPA determines that the selected remedy represents the
maximum extent to which permanent solutions and treatment
technologies can be used in a cost-effective manner for the
M&G/Bell Site. Of those alternatives that are protective of
human health and the environment and comply with ARARs, U.S. EPA
has determined that the two selected components provide the best
balance of trade-offs with respect to long-term effectiveness and
permanence; reduction in toxicity, mobility or volume achieved
through trea~ment; short-term effectiveness; implementabilitYi
and cost, also considering the statutory preference for treatment
and State and community acceptance.
Soils Alternative 4 complies with the ARARs identified above, and
reduces the toxicity, mobility and volume of contaminants in the
soil. Soils Alternative 4 will reduce contaminant concentrations
and meet cleanup goals, unlike Soils Alternatives 1 and 2, and
thereby contemplates a permanent solution that enables future
beneficial use of the facility property. While Soils
Alternatives 3 through 5 would be expected to be equally
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58
effective in reducing metals contaminant concentrations in the
long term, the greatest reduction in organic contaminant
concentrations~can be expected to be achieved through
incineration. Additionally, unlike Soils Alternative 5, Soils
Alternative 4 does not present the possibility of PCDDs/PCDFs
requiring further treatment in the residual waste stream. As
with Soils Alternatives 3 and 5, Alternative 4 would result in
more disturbance of contaminated soil, and would take somewhat
more time to implement, than Soils Alternative 2, but this
detriment to short-term effectiveness is offset by Soils
Alternative 4's capacity to achieve Remedial Action Objectives
and eliminate the physical threats posed by contaminated soils
and abandoned tanks and vaults within a relatively short period.
Soils Alternative 4 is expected to occupy less physical space
than Alternative 3 and thus interfere less with response other
activities at the site, rendering it superior in terms of
implementability. Soils Alternative 4 costs are higher than
those that would be incurred in implementing any of the other
four Alternatives but, on balance, these are justified by the
expected effectiveness of organic contaminant reduction.
Groundwater Alternative 3 likewise represents the best balance of
factors among the array of protective remedial alternatives. No
available technology would be expected completely to eliminate
contaminant concentrations throughout the New Brighton aquifer,
but Groundwater Alternative 3, like Groundwater Alternatives 2
and 4, contemplates continued pumping to control migration of any
residual contamination, and modification of the extraction
system, if necessary, to provide the most efficient capture of
contaminants. Alternatives 2, 3 and 4 are expected to comply
with ARARs and achieve control of the contaminant plume within a
short period of time, and each employs equipment that is readily
available. Groundwater Alternative, 3's advantage over
A~ternatives 2 and 4 lies in its superiQr implementability and
effectiveness: the carbon adsorption unit of Alternative 2 may
accumulate oil not removed by the oil/water separation unit, ,
thereby reducing its effectiveness in removing organic,
contaminants and resulting in an excess of spent carboni and
suspended solids in the extracted groundwater may affect the
effectiveness of the chemical oxidation phase of Alternative 4,
thereby requiring further treatment before discharge to the POTW.
Finally, Gr~undwater Alternative 3 offers a cost savings over the
other two active alternatives.
The State of Minnesota concurs in the selected alternatives. A
Proposed Plan describing the selected remedial alternatives and
,the others discussed in this Record of Decision was made
available to the public, and a public meeting on the Plan was
held on June 23, 1994, to ensure' local awareness and acceptance
of the alternatives. u.S. EPA has received written comments from
two sources, and has addressed them in the Responsiveness Summary
to this Record of Decision.
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Preference for Treatment as a Principal Element
Both the soils~and groundwater components of the selected remedy
satisfy the preference for treatment as a principal element. The
selected alternative for soils contemplates treatment through on-
site incineration of soils contaminated primarily with organic
compounds (PCP, PAHs) , with further treatment and off-site
disposal, if necessary, of fly ash. It also calls for on-site
stabilization/solidification of soils contaminated w1th metals
before disposal off-site, thereby ensuring a reduction in
contaminant mobility. Finally, contaminated groundwater
extracted from the New Brighton Aquifer will be treated via an
oil/water separator, a precipitation unit for metals removal, and
a bioreactor employing a trickling film process for removal of
organic contaminants. Carbon adsorption may follow the
biological treatment process to ensure pretreatment standards are
met. On-site treatment will be followed by discharge to a POTW
for further treatment. Thus, the statutory preference for
remedies employing treatment as a principal element is satisfied
here.
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