UrtadStUM
Emkonranal Prattctfon
Aotnoy
OfflMof
EPA/ROO/H05-«a074
Sept«mber 1988
5.EPA
Superfund
Record of Decision;
Oak Grove Landfill, MN
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REPORT DOCUMENTATION
PAGE
1U REPORT NO.
EPA/ROD/R05-88/074
S. Redptanr. Accasaton No.
4. TNta and Subtitle
SUPBRPUMD RECORD OF DECISION
~^k Grove Landfill/ MNi
cat Remedial Action
1 "W/W/88
/. Author**)
t. Performing Organization Rapt. No:
». Performing Organization Name and Address;
ia ProJoct/Task/WOrk UnK No.
11. ContracMO or QranMO) No.
(O
(G)
12. Sponsoring Organization Nama and Addrass
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 204f>0
13. Tyoa of Report * Parted Covarad
800/000
14.
IS. Supplamantary NotM
1C Abatraet (Limit 200 wond)
The Oak Grove Sanitary Landfill covers 45 to 50 acres in Oak Grove Township, Anoka
County, Minnesota, approximately 38 miles northwest of
St. Paul. There are 249 people that live within 1 mile of the site and 6,786- reside
within 4 miles. The majority of these residents depend on water from wells drawn
primarily from the lower aquifer, or surface water sources. Surface runoff from the
landfill empties into a wetland to the south. A creek flows through this wetland,
\scharging to Rum River two to three miles'southwest of the site. The landfill
jceived 200,000 to 300,000 cubic yards of waste per year from 1976 until it reached its
permitted capacity in late 1983. Most of this waste consists of household trash and
garbage. In addition, waste consisting of oil sludge from an oil recycling process,
paint and solvent wastes, foundry wastes, metal sludges, organic compounds from
pesticide manufacturing, cutting oils and lubricants, cleaning solvents, and inks are
reported to have been buried near the center of the landfill but their exact location is
unknown. Minnesota Pollution Control Agency (MPCA) and Anoka County records indicate a
number of violations and operational problems throughout the active history of the
site. MPCA discovered a ground water contamination problem from monitoring well samples
obtained at the site in 1984. The primary contaminants of concern affecting ground
water and surface water are VOCs including ethyl benzene, toluene and xylenes.
Attached Sheet)
17. Dominant Analyaia a. Descriptors
Record of Decision
Oak Grove Landfill, MN
First Remedial Action
Contaminated Media: gw, sw
(ethyl benzene, toluene, xylenes)
e. COSATI Plaid/Group
IS.'Availability Statamant
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
63
22. Price
(See ANSI-Z39.18)
See Instruction* on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R05-88/074
\k Grove Landfill, MN
icst Remedial Action
16. ABSTRACT (continued)
The selected remedial action for this site includes: installation of a security
fence; capping with a final cover system consisting of a gas control layer, a barrier
layer of low permeable material or a flexible membrane and a drainage layer; topsoil
cover and vegetation; deed restrictions; consideration of treatment options .for air
emissions from gas vents after construction of the final cover; consideration during
design of the need for extra protection for frost damage without significantly
increasing cost or likelihood of failure; and air and ground water monitoring. The
second remedial action will address the ground water contamination and possible
remediation of the downgradient plume. The estimated present worth cost for this
remedial action is $6,300,000 to $11,100,000 if a clay barrier is installed, or
$5,500,000 to &9,300,000 if a synthetic membrane barrier is installed, with annual O&M
of $42,000 or $40,000.
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RECORD OF DECISION
SITE NAME AND LOCATION
Oak Grove Sanitary Landfill Site '
Oak Grove Township, Anoka County, Minnesota
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected source control operable unit
remedial action for the Oak Grove Sanitary Landfill Site, 1n Oak Grove
Township, Anoka County, Minnesota, developed in accordance With the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthor1zat1on Act of
1986 (SARA), and to the extent practicable, consistent with the National Oil
and Hazardous Substances Pollution Contingency Plan (40 CFR Part 300). This
decision is based upon the contents of the administrative record for the Oak
Grove Sanitary Landfill site. The attached index identifies the Items which
comprise the administrative record. The Minnesota Pollution Control Agency's
decision is based in accordance with the Minnesota Environmental Response and
Liability Act of 1983.
The State of Minnesota and the U.S. Environmental Protection Agency'(-USEPA),
each and independently, concur and adopt the selected remedy.
DESCRIPTION OF THE SELECTED REMEDY
This operable unit Is the first of two operable units for the site. The first
operable unit addresses the source of the contamination by containing the on-
site wastes and contaminated soil. The function of this operable unit is to
provide a final cover for the Oak Grove Sanitary Landfill which will prevent-*
or minimize ground water contamination andTisks associated with exposure to
the contaminated materials. The remedy does not fully address the principal
threats at the site because it is not appropriate to address the ground water
contamination at this time. The second operable unit will address the ground
water contamination and possible remediation of the downgradient plume.
r . . -
r .
The major components of the selected remedy include:
* Installing a security fence around the landfill site;
* Capping with a final cover system consisting of a gas control layer, a
barrier layer of low permeable material or a flexible membrane, and a
drainage 'layer;
* Topsoil cover and vegetation;
* Site deed restrictions limiting further use of the site;
;:*:
* Treatment options for air emissions from gas vents will be considered
after construction of the final cover;
* Consideration during design, of tiie need for =;
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* Air and ground water monitoring to ensure the effectiveness of the remedial
action will be implemented after construction of the final cover.
The barrier layer component of the final cover system will be evaluated during
the remedial design to determine whether low permeability material (clay) or a
flexible synthetic liner is best suited for use.
This action will require operation and maintenance activities to ensure
continued effectiveness of the remedial alternative. The action being taken is
consistent with Section 121 of CERCLA as amended by SARA, 42 U.S.C. S 9621.
DECLARATION
The selected remedy is protective of human health and the environment, attains
Federal and State requirements that are applicable or relevant and appropriate,
and is cost-effective. This remedy utilizes permanent solutions and alternative
treatment technologies to the maximum extent practicable for this site. The
size of the landfill plus the fact that there are no on-site hot spots that
represent the major sources of contamination preclude a remedy in which
contaminants could effectively be excavated and treated.
Because this remedy will result in hazardous substances remaining on-site above
health-based levels, a review will be conducted within five years after
commencement of remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environmen
Date Valdas V. Adamkus
Regional Administrator
U.S. EPA, Region V
Date ' ' /Gerald L. Willet
T^^comiissioner
1} Minnesota Pollution Control Agency
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SUMMARY OF REMEDIAL ALTERNATIVE SELfcX.'1'lON
Oak Grove Sanitary
Oak Grove Township, Anoka County, Minnesota
I. SITE NAME, LOCATION, AND DESCRIPTION
Location
The Oak Grove Sanitary landfill (OGSLF)is located in Oak Grove Township,
Anoka County, Minnesota (figure 1) near the intersection of Eidelweiss
Street and County Road 22 (Viking Boulevard) as shown in Figure 2. The
OGSLF is approximately 38 miles northwest of St. Paul, the state capital.
Site Description
The OGSLF :Ls located in the eastern portion of the Small Lake Section of
the Central Lowland Physiographic Province. The Small Lake Section is a
plain of huimucky moraines of Wisconsin till with the «>nyt-*»rn portion
divided into a number of areas. The OGSLF is located in the Anoka
Sandplain Area, which is characterized as a broad sandplain formed largely
from glacial drainage. The topography of the area consists of low regions
of uplands and sand dunes interspersed among numerous lakes and wetlands.
Elevations vary from approximately 900 feet above mean sea level (MSL) to
approximately 870 MSL. The site is located on an east-west trending
upland.
The nearby developed land consists of agricultural and residential uses.
The western and northern edges of the OGSLF border single family _
residences. An estimated 249 people reside within one mile of the
landfill and 6,786 people reside within four miles of the landfill. These
population estimates were taken from the 1980 population census. It is
estimated that the majority of nouses in the vicinity of the OGSLF Draw
their water from wells or surface water sources.
«
A wetland is located adjacent "to and south of the landfill and receives
surface runoff from the landfill. Cedar Creek flows through the wetland
and discharges to the Rum River which is about two to three miles
southwest of the site.
The site hydrogeology consists of two shallow ground water units beneath
the landfill. The upper unit is ccmposed of surficial outwash sand while
the lower unit is a confined aquifer ccmposed of valley train deposits. A
till deposit is present between the two aquifer units and may function as
an aquitard. The till unit is composed of three facies, a gray till
facies, a red fir.e-grair.ed facies and a red coarse-grained facies. Ground
water levels in ircnitcriiig -.veils indicate that flow from both of the units
is predominately south from the landfill. Residential wells around the
site generally do ncc use the surficial aquifer for drinking water. Most
wells in the area draw from the lower aquifer.
:%;-^y-y:.. :-;~;~"*-:&-v;;r^av^
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II. SITE HISTOKY . ;
A solid waste landfill permit was issued to the owner of the site in 1971
by the Minnesota Pollution Control Agency (MFCA). In 1976, landfill
operations were assumed by a consortium of refuse haulers. The i*nHfm
reached its permitted capacity in late 1983 and was not allowed to receive
additional waste. The MPCA tried unsuccessfully to enforce the permit
requirement that final cover be installed at the site. The MPCA. allowed
lime sludge to be applied as a base material for final cover in an attempt
to obtain proper closure of the site under conditions of the permit.
Initially, lime sludge was being spread over the landfill by the operator.
However, subsequent inspections by the MPCA and Anoka County staff
discovered that the lime sludge was being stockpiled on top of the
landfill and near the borrow pit. Also, the lime sludge spread over the
landfill was not properly applied and was causing ponding of water instead
of allowing it to run off over the sides. Therefore, in order to halt the
improper application and stockpiling of lime sludge at the OGSLF, the MPCA
issued a Cease and Desist Order in 1985.
Ground water contamination was discovered in the monitoring wells at the
OGSLF in 1984 and the MPCA issued a Request for Response Action (RFRA) to
the owners and operators of the OGSLF on August 28, 1984. The RFRA was
issued for the purpose of completing closure activities and initiating a
Remedial Investigation/Feasibility Study (RI/FS) at the site to determine
the extent and magnitude of ground water contamination. When the owners
and operators of the OGSLF failed to respond to the RFRA, a Determination^
of Inadequate Response was issued and the MPCA entered into a Multi-Site *
Cooperative Agreement (MSCA) with U.S. Environmental Protection Agency
(USEPA) for implementing a RI/FS at the site. The OGSLF was listed on the
National Priorities List in October 1984, with a Hazard Ranking System
score of 43. USEPA is the lead agency for the enforcement portion of the
project. ;
t '
The landfill received an estimated 200,000 to 300,000 cubic yards of waste
per year. The fill area of the site covers approximately 45-50 acres.
Most of the waste present in the landfill is municipal trash and garbage.
However, a small documented quantity of industrial, chemical and hazardous
wastes are believed to be buried in the landfill. These wastes are
reported to nave been placed near the center of the fill area but their
exact location is unknown. The wastes included oil sludge from an oil
recycling process, paint and solvent wastes, foundry wastes, metal
sludges, chlorinated and other organic conpcunds from pesticide
manufacturing, cutting oils and lubricants, cleaning solvents, and inks.
Currently, there is an estimated 2.5 million^ cubic yards of waste in the
landfill. -X
MFCA and Anoka County records shew a number of violations and operational
problems that occurred over the operational history of the site. The
records indicate that the landfill %-as not iterated properly and that
filling took place L: ; rsr.itT, iashicn ins-.i2c:. of in phases as the permit
specified.
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III. ENFORCEMENT ACTIVITIES
IV. SUMMARY OF SITE QiARACTERISTICS
RI activilu.es were initiated at the OGSLF in 1986 and are cur.ieiit.ly
ongoing. The activities and results obtained to date will be briefly
summarized in this section. However, it should be noted that the data and
hydrogeological results presented here are preliminary and will be
subjected to further refinement during the migration management operable
unit RI/FS.
Throughout various phases of field work, 19 monitoring wells were
installed at various depths at twelve locations (figure 3), and water
samples were collected twice from each well for chemical analysis.
analytical results are presented in Table la. Surface water and sediment
samples were collected from seven locations as shown in Figure 4. Sample
results are listed in Tables Ib and Ic. Figure 5 shows the location of
the five leachate sample collection points and Table Id presents- the
analytical result from these samples. In addition, slug tests were
performed and 48 subsurface soil samples were taken for geotechnical
analysis to help assist in the hydrogeological investigation.
Residential wells near the OGSLF were sampled by MPCA staff on seven
separate occasions. The samples were analyzed for volatile organic
compounds (VOCs) by the Minnesota Department of Health. None of the
residential wells sampled are known to be contaminated. _- {
Hydrogeoloqy
The geology can be generally divided into three unconsolidated layers in
descending order: a surficial outwash sand, a till layer, and a deeper
sand and gravel layer. A peat layer exists in the wetland area south. of
the site (see Figure 2). '
The surficial sand aquifer is thought to be continuous throughout the site
and ranges in thickness from five to 60 feet. The minimum thickness
occurs in the wetland area* Hydraulic conductivities range from
1 x 10~ on/sec to 4 x 10~* cm/sec and ground water flows in a southerly
direction ( see Figure 6 ) .
The till unit ranges ir. cclor and composition from gray fine-grained
facies with traces of =and and gravel, to red fine-grained facies and red
coarse-grained facies. The thickness of the till unit ranges from 40 to
70 feet. The grey isci? is discontinuous- ^nd occurs mainly in the
eastern and southern portions of the site. The red till facies (fine- and
coarse-griained ) exist throughout the site in varying thicknesses, relative
positions, and later;! extent. Through the interfingering and wedging of
these red till faci=£ iich ;cui-_ =:aand vertically frpn the overlying
cutwash to the underlvi.-.T "t'lr" train derrsiis.
^^^zn^y?3ff35?t^^
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-4-
The till unit may act as an aguitazd since hydraulic .conductivities of the
gray till facies are extremely lew and range iron 2 x 10 to 4 x 10
on/sec. Hydraulic conductivities in the red till facies were unobtainable
due to difficulties in acquiring an adequate sample. However, based on
the grain size distribution curves of each facies, the red fine- and
coarse-grained facies are assumed to have higher hydraulic conductivities
than the gray till facies.
The deep sand and gravel layer is located within a bedrock valley that
transects the site in a north to south direction (see Figure 7). The
thickness of this layer is approximately 175 feet as shown in Figures 8 .
and 9 and hydraulic conductivities range from 4 x 10 cm/sec to 5 x 10
on/sec. Ground water in this aquifer also flows in a southerly direction
(Figure 6).
Depth to water table ranges from zero feet in the wetland to about 20-40
feet throughout the rest of the site. Vertical gradients indicate that
the surficial and deeper aquifers tend to discharge into the wetland area
at the southern portion of the site. Vertical gradients also indicate
that a downward gradient may exist throughout a portion of the fill area
fron the surficial to the deeper aquifer.
Runoff generated from the southern one-half of the site drains directly to
the wetland by overland flow and erosional gullies created on the side
slopes. Runoff from the northern one-half of the OGSLF flows to low lying
drainage ditches that partially discharge into the wetland or into a
borrow fill area located off the northeast corner of the site. The rest - f
of the site drains directly to the wetland which lies approximately twenty
feet from the southern edge of the fill area. The wetland discharges into
a small unnamed stream located approximately 1,000 feet from the landfill
which then flows into Cedar Creek.
Extent of Contamination ;>,
i * .
Results fron the analyses of samples collected during the RI document the
presence of a variety of compounds. The most common of these compounds
are acetone, methylene chloride, toluene, ethyl benzene, and total
xylenes. Further investigation is ongoing and is required in order to
characterize the extent and magnitude of the ground water contamination at
the OGSLF site, especially in the deeper aquifer. As described in section
VI, the migraticr. managsrrrent operable unit will address this portion of
the project. A draft ?.I report has been prepared and will be put into
final form upon completion of additional ground water sampling and
hydrogeolccicai studias.
vv
Many organic and inorganic compounds were detected in ground water,
surface water, soil ar.a ieachate samples collected during the RI conducted
at the OGSLF. Tr.e ciacning zone was monitored during drilling activities
using a photoioniz^_i:r. Tatar. This instrjn-.ent was also used to detect
possible hot spots ^- -/.e iardilll. Table I-presents on-site contaminant
information and the :-._i---vi.-.r j^ragraphs ur~"i^3 a brief summary of the
results of samoiir/: -.:: care
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Ground Water
Ground water contamination was detected in three monitoring well nests
screened in the surficial outwash sand unit iirmediately south
(downgradient) of the landfill. There were 63 occurrences of Hazardous
Substance List (HSL) organic compounds in these wells compared to one
occurrence in all other surficial aquifer wells and four occurrences in
confined aquifer wells. Total xylenes were detected at 108 ug/1 and
arsenic was detected at 141 ug/1 and was the highest level of ground water
contamination found. Results from downgradient wells in the wetland area
presently .indicate that the extent of lateral muvaifcaiL of contamination in
the shallow ground water is less than 1,000 feet.
Four organic compounds were reported in ground water samples from two
downgradient wells screened within the lower confined aquifer. These
results indicate possible vertical migration of the contaminants into the
lower confined aquifer.
Surface Water -^
Surface water samples were collected from the wetland immediately south of
the landfill and from Cedar Creek. Seven organic compounds were detected
in samples of the standing water in the wetland adjacent to the landfill:
chloroethane, methylene chloride, acetone, 1,1-dichloroethane,
4-methyl-2-pentanone, 4-methylphenol, and benzoic acid. Acetone was the
compound with the highest level of contamination (3500 ug/1). Chromium,
barium, vanadium, and cyanide (among others) were among the inorganic - \
constituents detected in these samples. Of the constituents found in the
wetland surface water samples, chloroethane, methylene chloride, and
1,1-dichloroethane were detected in downstream surface water samples.
Trichloroethene and trans, 1-2 -dichloroethene were found in downstream
samples but not in wetland samples. Inorganic constituents detected in
downstream samples were comparable to levels detected in the upstream .
background sample.
Soil
Subsurface soil samples were collected from beneath landfill leachate
sesps. The samples taken from south of the landfill contained methylene
chloride, acetone, chloroform, and xylene. The highest level of
contamination detected -.vas 16,000 ug/1 for the compound 2-butanone.
Samples taken frcm north of the landfill were not measurably contaminated.
Because of methyiene chloride and acetone occurrence in most of the
laboratory blanks for the soil samples, the RI, at this stage, has not
been able tc ccncluis v.T.sther these contamVi^nts were site related.
Leachate
As 'dcuid be expected, isachats samples collected frcm erosional gullies on
the sides of the landfill 9;i:L:icecl the hichsst concentrations and number
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of HSL organic compounds. The most prevalent compounds,.In terms of
distribution, were acetone, nethylene chloride, and toluene. The highest
level of contamination detected was acetone at 19,000 ug/1. Other
organics found at high concentrations were 2-butanone (methyl ethyl
ketone), 4-methyl-2-pentanone, 4-methylphenol, and benzoic acid. DDT was
also reported at low concentration in one sample. One leachate sampling
location exhibited inorganic contamination at levels significantly higher
than the background surface water sample. The metals detected included
aluminum, chromium, iron, mercury and zinc.
Residential Wells
Residential wells near the OGSLF were sampled for 53 VOCs on seven
occasions as follows:
10 residential wells May 1985
8 residential wells June 1985
5 residential wells July 1985 ._
7 residential wells February 1986
9 residential wells September 1986
10 residential wells June 1987
10 residential wells June 1988
During the June 1985 sampling event, low levels of VOCs were detected in
samples taken from three of the eight residential wells sampled. These
wells were resampled during the July 1985 sampling event and showed no
contamination. Subsequent sampling events have not confirmed the presence,
of contamination in these residential wells.
Air
Readings taken from the breathing zone during drilling activities at the
site with a photoionization meter did not indicate the presence of organic
vapors. A soil gas survey did", however, detect organic vapors beneath'the
existing lime sludge cover. Most of these readings also taken with a
photoionization meter are apparently the result of methane accumulations,
although three points beneath the lime sludge cover did indicate the
presence of nonmethane organic compounds. Cover soil samples taken from
these locations indicated the presence of methylene chloride, acetone, and
toluene at concentrations less than 40 ug/kg. There was little indication
of organic vapor accumulation beneath the vegetative cover on the western
cr.e-third of the landfill.
Source of Ccntaminaticr.
xv
There is no discrete source of contamination other than mixed municipal
waste at the CG3LF. Most of the waste present at the landfill is
hcusehold trash and garbage. A small quantity of industrial, chemical,
and hazardous waste. .-.cv.-sver, Lz believed to be buried near the center of
"he landfill. The -.vu^-as ircluda oil sludcs from an oil recycling
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process, paint and solvent wastes, foundry wastes, metal .sludges,
chlorinated and other organic compounds from pesticide manufacturing,
cutting oils and lubricants, cleaning solvents, and inks. As mentioned
earlier, the former active landfill area covers about 45-50 acres. Most
of the waste was placed above grade, to a maximum height of approximately
50 feet. 'Die waste does not appear to be in contact with the water table.
V. SUMMARY OF RISKS
A preliminary endangezment assessment (EA) was prepared and was based on
information presently available from the RI. Since the RI will be
completed after further site characterization Is performed, the EA will
also be completed at that time. These activities will be performed during
the second operable unit portion of the project.
,«
The preliminary EA identified potential exposure pathways which will be
mitigated by the source control operable unit. The potential exposure
pathways are: exposure to air emissions from the landfill, exposure to
contaminated soils, exposure to contaminated surface water, and exposure
to contaminated ground water.
Current exposure to air emissions from the site appears to be minimal, and
not significant from a public health viewpoint. However, a short-term
increase in emissions would be expected during construction of any
remedial action which disturbs the existing cover. There are
approximately 35 single family residences located within 10,000 feet of
the site. Based on meteorological data cited in the preliminary EA, these
areas would be exposed to airborne contaminants approximately 17 percent *
of the time. The duration of exposure would depend on the duration and
type of construction activities.
Contaminated soils are not expected to pose a public health concern.
Contamination of cropland and. ingestion of contaminated food is unlikely,
since the identified volatile' Constituents are present at low
concentration and do not tend to bioconcentrate in the food chain.
Contaminated surface water is a potential pathway for exposure. Surface
water in the wetland area immediately south of the landfill receives
surface runoff from the landfill. This runoff carries contaminated
leachate from surface seeps and potentially contaminated particulate
material from the s-.irface of the landfill. This runoff could be
responsible for plant damage which is evident in the wetland along the
.south edge; of the landfill. The wetland provides a pathway for
contaminants tc enter Cedar Creek. The preliminary EA report indicated
that there: are no s-rrf?.c3 water withdrawal points on Cedar Creek for
potable, agricultural, cr industrial use downstream of the site.
Ground water represenc-s another potential exposure pathway for
contaminants. Ground water is in irrportant source of water in the area,
and shareware a number of dc-e=-io wells in ;lose proximity to the site.
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However, these wells are all upgradient or crossgradient, of the landfill
and are completed to depths of 150 to 200 feet. The nearest downgradiefit
well identified in the EA is approximately 5,000 feet from the landfill
and is located on the south side of Cedar Creek. The RI data, to date,
indicates there may be a potential for interconnections between the
surficial aquifer and the deeper aquifer. This poses the greatest concern
as a pathway of exposure. Further investigation will more clearly
delineate the magnitude of the threat posed by contaminants reaching or
presently existing in the deeper aquifer.
Implementation of the selected remedy as presented by this operable unit
for source control, will eliminate exposure to contaminated soils, contiml
air emissions, minimize rodent burrowing and prevent further contamination
of surface water by controlling runoff from the landfill and minimize or
prevent contamination to the deeper aquifer. Subsurface migration of gas
has not been detected and appears to be an unlikely pathway for migration
of 'contaminants.
VT. SCOPE AND ROLE OF OPERABLE UNIT -~
Since further work is needed to complete the RI/FS for the ground water
contamination, which was started in October 1986, the USEPA and MPCA
agreed to divide the project into two operable units in order to
facilitate progress toward remedial action at this site. The two operable
units are for source control and migration management. The first operah&e
unit will address the source of the contamination by containing the
on-site wastes and contaminated soils. The second operable unit will . w
involve further study of the ground water contamination and will addressK
remediation of the downgradient contaminant plume. The role of each
operable unit will be further explained below.
Source Control Operable Unit
The MPCA in conjunction with the USEPA decided to proceed with a FS to
determine what type of final cover would be suitable for the site. The
OGSLF never received final cover when the landfill was closed. Therefarav.
an operable unit which will address the containment of wastes and
contaminated soil at the site, can occur prior to the completion of the
ground water remediation because construction of a suitable final cover
will prevent further infiltration of precipitation which will reduce
resulting leachate production.
Migration Manaqanent Operable Unit
This operable uni- will '.-'= a continuation Q£ the RI/FS which began in
1986. The preliminary results of the RI indicate the presence of
contamination in the upper aquifer, but further work is necessary to
determine the ccmcstsncy of the confining layer that lies between the
^ upper and lower aquii'-sr. ar.cl to determine if t^.e Ic-.ver aquifer is being
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contaminated by the OGSLF. Some of the remaining tasks to be performed
include installation of additional monitoring wells, performance of a
series of slug tests, collection and analysis of additional water samples,
and preparation of the final RI report. Die FS will be initiated after
completion of these RI activities.
VII. COMMUNITY RELBTIONS
The source control alternatives evaluated in the FS were presented in the
interested community in a manner consistent with the Superfund law and EPA
guidelines on connunity relations at the conclusion of a FS.
A public comment period on the alternatives began on September 2, 1988,
and ended on September 23, 1988. The MPCA published a notice in the
September 2, 1988 edition of the Anoka County Union, the local newspaper,
and also provided a news release to the paper. The notice included
information on the availability of the FS and proposed plan at the Oak
Grove Township Hall, the dates of the public comment period and_public
meeting, and a description of the alternatives and the proposed -
alternatives. In addition, on August 30, 1988, the MPCA mailed a copy of
the notice and news release, which explained in more detail the proposed
alternative, to the Oak Grove site mailing list. This mm ling list
includes interested residents, township and county officials, elected
officials, and site owners and operators. The Oak Grove Township Hall
served as the information repository for the Administrative Record, the FS
and the proposed plan.
A public meeting was held on September 14, 1988, in the Oak Grove Township
Hall. The attached Responsiveness Summary lists the comments received at
the meeting and during the Garment period, as well as the MPCA's response
to those cements.
VIII. DOCUMENTATION OF SIGNIFICANT .CHANGES
»
No significant changes have been made since the publication of the FS and
proposed plan.
IX. DESCRIPTION OF ALTERNATIVES
The alternatives under consideration for source control were developed by
examining a number of possible remedial technologies, and compliance of
these alternatives with applicable or relevant and appropriate
requirements (ARARs) of federal and state environmental statutes.
excavation of the landfill (with destruction of the wastes by
incineration, disposal off-sits in a secure commercial landfill, or
redisposal on-site in a lined landfill) was"'eliminated in the initial
screening process. The criteria used for elimination of excavation were
short-term iiroacts on human health due to air anissicns and excessive
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-10-
cost. In-place closure of the landfilled waste, consisting of alternative
cover systems, consistent with the state and federal regulations,
including the Resource Conservation and Recovery Act (RCRA.) for landfill
closure and Minnesota proposed rules pts. 7035.2525 and specifically pt.
7035.2815 were developed for detailed evaluation.
The source control alternatives are:
* Alternative 1; No Action
* Alternative 2a: Cover system satisfying interim minnesota rules for
municipal landfill closure with clay barrier layer.
* Alternative 2b; Cover system satisfying interim minnesota rules for
municipal landfill closure with synthetic membrane harrier layer.
* Alternative 3a; Cover system satisfying minnesota rules for municipal
landfill closure with clay barrier layer. ._
* Alternative 3b; Cover system satisfying minnesota rules for municipal
landfill closure with synthetic membrane barrier layer.
* Alternative 4a; RCRA equivalent cover system for hazardous waste
facility closure.
* Alternative 4b: RCRA cover system for hazardous waste facility
closure. . *
All alternatives except "no action" would include capping the former
disposal area with varying layers and thicknesses of soil and/or synthetic
materials which in combination would comprise a cover system for the
landfill. Each alternative cover system described below includes a
foundation layer overlying existing materials to support the cover system
and a continuous coarse-grained soil layer in conjunction with gas vents
which will be utilized to control gas migration. The differences in the
alternative cover systems consist of varying thicknesses of cover soil,
the presence and thickness of a lateral drainage layer and the type of
barrier layer utilized to minimize percolation of surface water. The
cover systems would provide varying degrees of control of contaminant
migration into ground water and surface water by minimizing percolation of
rainfall and snow melt thrcugh the landfill contents.
Alternative 1; No Acticn
Construction Cost: 390,000-3110,000
Annual Operation and Maintenance (O&M) Costs: None
Months to Implement: 1
Comprehensive Environmental Response, Compensation, and Liability Act of
1980 (CERCLA) requires that the "r.c action" alternative be considered at
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-11-
evezy site. Under this alternative, MPCA would .fence the site to
direct human contact with landfilled wastes, but take no' further action to
control the ability of contaminants to migrate.
Alternative 2A; Interim Minnesota rules for municipal landfill-clay
barrier.
Construction Cost: $3,900,000-$?,300,000
Annual O&M Costs: $38,000
Months to Implement: 18-24
This remedy would include the installation of a minimum 42-inch cover
system (Figure 10) over the landfill area. The barrier to downward
percolation of infiltrating surface water is provided by a 24-inch
(.impacted clay layer. Additional quantities of soil fill are required to
construct a minimum two percent slope to facilitate surface water runoff.
The Alternative 2A soil cap complies with state regulations for a landfill
which will no longer receive waste and will be closed within 18 months of
the effective date of Pts. 7035.2525 to 7035.2815 of the Minnesota
proposed rules.
Alternative 2B; Interim Minnesota rules for municipal landfill-synthetic
membrane barrier.
Construction Cost: $3,100,000-$5,400,000
Annual O&M Costs: $37,000
Months to Implement: 18-24
This alternative is similar to Alternative 2A, except a high density
polyethylene (HDPE) membrane is substituted for the 24-inch clay barrier
(Figure 10). The 30-mil thick HDPE membrane complies with state
regulations for closure of a municipal landfill.
<
Alternative 3A; Minnesota rules for municipal landfill-clay barrier;1
Construction Cost: $5,900,000-$10,700,000
Annual O&M Costs: $42,000
Months to Implement: 18-24
Under this alternative, the landfill area is capped by a minimum 60-inch
cover system (Figure 10). A 24-inch compacted clay layer provides the
barrier to downward migration to contaminants due to percolation of
surface precipitation. In comparison to Alternatives 2A and 2B,
Alternative 3A provides si:: inches of additional cover material for
promotion of vegetation, irainage and protection of the barrier layer.
The minimum percent slope is increased to Vnree percent and a 12-inch
thick lateral drainage layer is added to intercept surface water
percolating into the ccv-ir systan. This alternative complies with state
regulations for a landfill -.vhich w-.H receive --vastes 18 months after the
effective date of Pts. 7f;:3.2525 -- 7025.2815 of the Minnesota proposed
rules.
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-12-
Alternative 3B; Minnesota rules for municipal landfill-synthetic membrane
barrier.
Construction Cost: $5,100,000-$8,900,000
Annual O&M Costs: $40,000
Months to Implement: 18-24
This alternative is similar to Alternative 3A, except an HOPE synthetic
membrane is substituted for the 24-inch clay barrier layer (Figure 10).
The 30-mil thick HOPE liner system also complies with state regulations
for closure of a municipal landfill.
Alternative 4A; RCRA equivalent for hazardous waste facility.
Construction Cost: $7,400,000-$13,400,000
Annual O&M Costs: $45,000
Months to Implement: 18-24
A minimum 78-inch soil cap is included with this alternative (Figure 10).
A composite barrier to downward percolation is provided by an HOPE liner
overlying a 12-inch clay layer. The cover soil is 30 inches thicker than
in Alternatives 3A and 3B. This alternative is in substantive compliance
with RCRA regulations for closure of a hazardous waste facility, but
varies from federal design guidance in the thickness of the clay layer.
Alternative 4B; RCRA closure for hazardous waste facility.
Construction Cost: $8,000,000-$14,600,000
Annual O&M Costs: $46,000
Months to Implement: 18-24
Alternative 4B differs from alternative 4A in that the thickness of the
clay layer is increased from: 12 inches to 24 inches (Figure 10). This
alternative is in compliance with RCRA hazardous waste regulations and
federal design guidance.
X. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The National Contingency Plan and Section 121 of Superfund Amendments and
Reauthcrization Act of 1986 (SARA) form the regulatory basis for the nine
evaluation criteria to cs utilized in determining the appropriate remedial
action at a CERCLA. sita. Specifically, Section 121 of SARA requires that
the selected remedy is tc be protective of human health and the
environment, cost-effective.. =md use permanent solutions and alternative
treatment technologies rr vsscurcs recovery*technologies to the maximum
extent practicable.
Alternatives were evaluated using current USEPA guidance, including
"Interim Guidance on S'-r-rrfunc 5i=i<=cticn of Renscv" dated December 24,
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-13-
1986, and "Additional Interim Guidance for FY 87 Records of Decision"
dated July 24, 1987. In the July 24, 1987, guidance; the following nine
evaluation criteria are referenced;
* Long-Teem Effectiveness - This criterion evaluates the long-term
protection of human health and the environment at the completion of
remedial action. It is assessed in the magnitude of residual risks,
adequacy of controls in achieving cleanup criteria, and reliability
of controls against possible failure.
* Reduction of Toxicity, Mobility, and Volume - This criterion evaluates
the anticipated performance of treatment alternatives. It is not
applicable to the containment alternatives evaluated for the OGSLF
site.
* Short-Term Effectiveness - The effectiveness of alternatives in
protecting human health and the environment during implementation of
remedial action is evaluated by this criterion. Short-term _
effectiveness is assessed by protection of the community, protection of
workers, environmental impacts, and time until protection is achieved.
* Implementability - This assessment evaluates the technical and
administrative feasibility of alternatives and the availability of
services and materials.
* Cost - The estimated capital, annual maintenance and monitoring, and
present worth value costs are evaluated by this criterion. Present . ,
worth costs are calculated using a ten percent discount rate over a ~*
50-year period of operation. Cost estimate summaries of alternative
cover systems are given in Appendix B.
* Overall Protection of Human Health and the Environment - This
assessment draws on the results of the above evaluations to describe
whether, and how, each alternative provides protection of human health
and the environment.
* Compliance with ARARs - The assessment against this criterion describes
how the alternative complies with ARARs, or if a waiver is required and
how it is justified.
* Ccrminity Acceptance - Community acceptance to the alternatives is
presented in the responsiveness summary, included in this Record of
Decision (ROD) as an attachment.
* State Accsptar.ce - Tlvr S'-.ate of Minnesota^ MPCA) is the lead agency for
the site.
This sectd.cn provides a .5-.^rrary of che relative performance of the
alternatives with respsc.: -.:: each jf -he nine criteria. Tables 2 through
8 present a comparison cf rns nir.3 criteria for ^ach alternative-
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-14-
Overall Protection of Human Health and the Environment. 'All of the
alternatives, with the exception of the no action alternative, would
provide, with varying degrees of efficiency, an increased protection of
human health and the environment with respect to existing conditions. The
increased protection is achieved by reducing percolation of surface
precipitation through the landfilled wastes and thereby controlling
leachate production and contaminant migration into ground water and
surface water. The cover systems would also reduce the risk of direct
contact with the contaminants remaining at the site.
Compliance with ARARs. Alternatives 4A and 4B meet or exceed all ARARs of
federal and state municipal landfill and hazardous waste facility closure
regulations. Alternatives 3A and 3B meet state and federal ARARs for
municipal landfill closure. Alternatives 2A and 2B comply only with
interim state ARARs for municipal landfill closure and the no action
alternative does not comply with state or federal regulations for landfill
closure.
Long-Term Effectiveness and Permanence. Long-term effectiveness for this
operable unit is evaluated in terms of the reduction of leachate
generation with respect to present conditions, and potential for failure
of the cover system. A ground water monitoring system will be included in
the migration management operable unit work phase for control of movement
of contamination through ground water. The future ground water monitoring
system will be used to verify the effectiveness of the containment unit.
- «
Leachate generation was estimated using the HELP computer model developed.
by the U.S. Army Corps of Engineers and average weather data for nearby
St. Cloud, Minnesota. The simulated percolation reaching the base of the
landfill, expressed as a percentage of total precipitation falling on the
landfill surface, is as follows:
Alternative ' ] Percentage
1 39.0
2A 11.5
2B 12.0
3A 6.5
3B 5.7
4A 0.0
4B 0.0
The above values are estimates only and represent conditions assumed to
exist inmediately following construction ofc^the cover system. It is
ijnportant to note that =1 the ugh the actual-.percentage of precipitation
which will percolate from the base of the landfill under Alternatives 4A
and 4E can potentially be 'quite lew, it will never achieve the zero
percent indicated by the HELP ncdei simulation. The simulation does 'not
take into account the decrease in effectiveness due to poor installation,
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-15-
naterial defects, and physical abrasion and degradation, j Alternatives 2A,
2B and no action do not comply with the State of Minnesota requirement
that a cover system be able to reject or contain at least 90 percent of
the surface precipitation. Alternatives 3A, 3B, 4A and 4B do, however,
exceed this requirement.
Possible failure modes for cover systems include differential settling of
landfill contents and subsequent breaching of the barrier layer,
penetration of the barrier layer by erosion, burrowing animals, vegetative
growth, damage to the barrier layer by freezing/thawing, and improper
construction and installation. Insufficient information concerning the
potential for differential settlement at the landfill makes it difficult
to adequately evaluate whether a clay or a synthetic membrane barrier is
more appropriate for the site. Alternative 2A and 2B, which include only
12 inches of cover soil and no lateral drainage layer, have the greatest
potential for failure due to penetration or freeze/thaw damage of the
carrier layer. Alternatives 4A and 4B provide the greatest long-term
protection against failure.
Reduction of Toxicity, Mobility, or Volume of the Contaminants. This
evaluation criterion is not applicable to the OGSLF site because none of
the alternatives includes treatment of the contaminants.
Short-Tenn Effectiveness. All cover system alternatives will have minimal
potential impact on human health because construction activities will not
disturb in-place wastes. The major impact on the nearby residents will be
temporarily increased truck traffic required to transport the large _ ,
quantities of soil comprising the cover system components. The cover " "
system will require 18 to 24 months to design and construct, depending on
seasonal weather conditions. Alternatives 4A and 4B will probably require
a slightly longer construction period than Alternatives 2A, 2B, 3A and 3B.
Implementability. The equipment, materials, and skilled workers needed to
construct the cover system alternatives are readily available in the Twin
Cities area. The plans and specifications for the alternative cover
system are likely to attract construction bids from local and regional
contractors. The manufacturers and suppliers of the synthetic membrane
are likely to be companies operating nationally.
Cost. Alternative 1 has minimal estimated construction costs. The
estimated construction costs for each of the remaining alternatives are as
fellows:
* Alternative 2A - $3,900,000 - $7,300,000
* Alternative 2E - 33,100,000 - $5,4-.C$,000
* Alternative 3A - $5,900,000 - $10,70*0,000
* Alternative 3E - 35,100,000 - $8,900,000
* Alternative 4A - .57,400,000 - $13,400,000
* Alternative 4E - £3,000,000 - $14,600,000
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-16-
The estimated construction costs are sensitive to the unit costs of the
soils and/or synthetic membrane comprising the cover system alternatives.
The availability of the various soil types comprising the cover systems
cannot be determined with respect to quantity, quality or unit cost until
further detailed engineering investigations are initiated.
The annual operation and maintenance costs for each cover system
{Alternatives 2A through 4B) are estimated as follows:
* Alternative 2A - $38,000
* Alternative 2B - $37,000
* Alternative 3A - $42,000
* Alternative 3B - $40,000
* Alternative 4A - $45,000
* Alternative 4B - $46,000
State Acceptance. The State of Minnesota supports the preferred
alternative.
Community Acceptance. Community acceptance of the preferred alternatives
will be evaluated after the public eminent period has ended and is
described in the Responsiveness Summary.
SPT.BCTED ALTERNATIVE
Based on current information, the USEPA and MPCA select Alternative 3
(Figure 11) as the most appropriate alternative for the final cover at the
OGSLF site. This alternative provides the best balance among the nine
criteria that USEPA uses to evaluate the remedial alternatives.
Alternative 3 contains two variations of barrier layer materials. At the
present time, there is insufficient information regarding the available
quantity, quality and cost of the materials comprising the barrier layer.
Therefore, the final selection will be made during the early stages of the
remedial design. During the remedial design, an evaluation will be '
conducted to determine:
1. Whether low permeability soil (compacted clay) or a synthetic membrane
will withstand settlement of the refuse and freeze/thaw damage; and
2. Cost and availability of both barrier layer materials.
Beth variations of Alternative 3 use containment techniques and will
minimize future contaminant migration by reducing the volume of
precipitation which percolates through the landfilled wastes. Alternative
3 was also selected because Lt meets ARARs.';Cpnsistent with the State of
Minnesota proposed rules for closure of a municipal landfill and is cost
effective. The effectiveness of the selected cover system in protecting
ground water quality will be verified by a monitoring net-.vork installed as
part of the migration mar.cigs^ent operable unit phase of work.
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-17-
Gonsideration will be given to extra protection from frost damage during
the design stages of the project. Air quality monitoring will also be
considered.
XI . STATUTORY DETERMINATIONS
A. Protection of Human Health and the Environment
selected remedy will reduce the generation of leachate by
infiltration, thereby reducing the release and subsequent harm or
potential harm to public health, welfare and the environment. A
release of contaminants has been documented in the surficial aquifer
at toxicologically significant concentrations. Although the surficial
aquifer is unlikely to be used as a drinking water source, migration
of contaminants from the surficial aquifer into the deeper aquifer is
possible. The selected remedy will decrease the likelihood for
degradation of the deeper aquifer which is currently used for
individual potable water supplies in the vicinity of the site and is
capable of yielding larger quantities of water for commercial and
public uses where necessary.
Additional RI activities are necessary to determine if the deeper
aquifer is contaminated or if it is vulnerable to contamination. The
selected remedy will not address the release of contaminants via
lateral movement of ground water through source material at the
southwest corner of the fill area nor the continued production of
leachate through infiltration subsequent to placement of the cover. *
This release as well as an appropriate remedy for the deeper aquifer'
will be addressed through another FS and ROD after the RI activities
are completed.
B. Attainment of Applicable or Relevant and Appropriate Requirements
(ARARs) ' (
i .-
Conpliiance with ARARs
SARA requires that remedial actions meet legally applicable or
relevant and appropriate requirements of other environmental laws.
These laws may include: the Toxic Substances Control Act, the Safe
Drinking Water Act, the Clean Air Act, the Clean Water Act, the Solid
Waste Disposal Act (RCRA), and any state law which has stricter
requinaments than the corresponding federal law.
Applicable requirements are cleanup standards, standards of control,
and ether substantive environment?.! protection requirements, criteria
or limitations promulgated under federaVor state law that
specifically address a hazardous substance, pollutant, contaminant,
remedial action, location or o-cher circumstance at a site. A
requirenent is "applicable" if the remedial action or circumstances at
the site satisfy all of the jurisciicticnal crerequisitss of the
requirsrent.
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-18-
Relevant and appropriate requirements are cleanup standards, standards
of control, and other environmental protection 'TR'jiiix'ntfn1^T criteria
or limitations promulgated under federal or state law that, while not
legally "applicable" to a hazardous substance, pollutant, contaminant,
remedial action, location or other circumstance at a site, address
problems or situations sufficiently similar to those encountered at
the site that their use is well suited to that site.
"A requirement that is judged to be relevant and appropriate must be
complied with to the same degree as if it were applicable. However,
there is more discretion in this determination: it is possible for
only part of a requirement to be considered relevant and appropriate,
the rest being dismissed if judged not to be relevant and appropriate
in a given case" (Interim Guidance on Compliance with Applicable or
Relevant and Appropriate Requirements, 52 FR 32496, August 27, 1987).
Closure Requirements
The RCRA regulations which govern Hazardous Waste Treatment^. Storage
and Disposal facilities (40 CFR Parts 264 and 265) apply to landfill
facilities that received hazardous waste after November 19, 1980. The
USEPA has not documented, at present, that any hazardous waste was
disposed of at OGSLF following November 19, 1980. The RCRA., Subtitle
C requirements for hazardous waste landfill closure are not known to
be "applicable" at this site.
The USEPA has documented the disposal of a small quantity of hazardous
waste at OGSLF; therefore, Subtitle C is a "relevant" requirement.
The USEP arrived at its conclusion that a Subtitle C cap/cover was not
appropriate at OGSLF based "on the following analysis.
OGSLF was a sanitary landfill which received a small documented
quantity of hazardous waste. The presently documented proportion of
hazardous waste is based
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-19-
RCRA Subtitle D regulations have been delegated to the State of
Minnesota. The Minnesota regulations incorporating RCRA's Subtitle D
requixenents are applicable, relevant, and appropriate. While
recognizing that Subtitle D is an "applicable, relevant and
appropriate requirement" for OGSLF, it is not deemed protective. As
discussed earlier, this alternative is highly susceptible to frost and
structural damage. Moreover, some hazardous waste, albeit a small
quantity, has been documented to exist in the landfill. Thus, the
USEPA .is compelled to increase the protectiveness afforded by a
Subtitle D cover, and believes it is obtained by Alternative 3.
In view of the small documented quantity of hazardous waste and the
potential wide dispersion of the waste in a 45-acre sanitary 1flnrifi.11,
there does not seem to be sufficient similarity between the OGSLF site
and the type of circumstances Subtitle C requirements are intended to
address. Thus Subtitle C, though "relevant" is not "appropriate".
C. Cost Effectiveness
The selected remedy will be consistent with the overall site strategy
for restoring the ground water and soils to acceptable cleanup levels.
The selected remedy is the least expensive of the alternatives which
meet site cleanup goals.
D. Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum Extent
Practicable/Preference for Treatment . .
Since the purpose of this source control operable unit was to provide
a suitable final cover for the OGSLF which would satisfy all ARARs
while minimizing the potential risk to human health, welfare and the
environment, no treatment of any kind has been addressed as part of
this operable unit. Another operable unit, for the migration
management portion of this project, will address possible remediation
of the ground water and will consider treatment as a principal element
of the overall site strategy.
-------
Figure 1. Location map.
\f^tn- ~rt
i I I I
. t-u-l
; u*s» I !
Oak Grove Sanitary Landfill
-------
N
=z
2000
SCALE IN FEH7
JOOO
Figure 2.
r»f Site location.
Oak Grove Sanitary Landfill
'£r CEDAR. MINNESOTA 'JSGS T.S
SE^r^*:S*kr^.^>Ir^^jr««^^
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Figure 3. Monitoring well locations.
-------
APPfl'oxiirATE\"is
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T - SED
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LEGEND
L -. LEACHA7E SEEP SAMPLES
T SEDIMENT SAMPLES
LEACH ATE SEE? AND
SEDIMENT SAMPLE LOCATIONS
OAK GROVE LANDFILL RI/RS
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s
-------
800
MILES
BEDROCK SURFACE CONTOURS
CONTOUR INTERVAL 50 F==T
Figure 7.
REGIONAL BEDROCK
TOPOGRAPHY
''OAK GROVE LANDFILL Rl/FS
n==: MINNESOTA GEOLOGiCAL SUPVEV VHSC2LLANEOL1;
MA? SERIES M-55. PLATE z OF z.
-------
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D INTC A SHAU.OW WATE«
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Figure 8.
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SURFICIAL GEOLOGY
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=: AN SVAJ.ULTION Oc SU=":
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-------
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800
700
600-
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BOO
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Cross section of site geology.
SCALE IN FEET
0
i
2500
5000
HORIZONTAL SCALE
100
200
i
VERTICAL SCALE
VERTICAL EXAGGERATION - 2Sx
LEGEND
A! - ARTIRCAL FILL
Oc* - OUTWASH DEPOSITS
21 GLACIAL TILL
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Figure 8.
CROSS-SECTION A-A1
GENERAL NE - SW
CROSS-SECTION
OAK GROVE LANDFILL RI/FS
RECENT AND OUATE°SAPV .j=CJ.CGv ADAFTE^ AND GENERALIZED
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t HAIUMAL son NAIUHAL SOL NAIUHAL SOL
'in.- nn ama stcnnn K PCR PBOPO-»O SIAIT ^nn MASH Rtnis. ' ' unit: IMS CROSS stcnoN is rtn CCNTRAL U.SC.P.A. OINOAMCC win: i»#* CMOSS stcno* is PCM CTMRAI U.S.I.P.A. OWAMX
j UIWHSOIA RIRIS PAMI '()» 181). VIBPARI . ItlU 0.
1 i ,
ALtEmiAflVE COVER SYS1EM 3O ALTtRM^BVE j:QVCR SYSTEU 4A ALTERNATIVE COVER SYSTEM 48
OAK GROVE PROPOSED PLAN
MINNFSOTA POLLUTION CONIROL AGCNCY
Figure 10.
ALTERNATIVE COVER SYSTEMS
-
-------
PROPOSED FINAL SURFACE. GOOD VEGETATION
VEGETATIVE LAYER
TOPSOIL
COVER SOIL
DRAINAGE LAYER
BARRIER LAYER
LOW PERMEABILITY MATERIAL
(2x10~6cm/sec)
OR FLEXIBLE MEMBRANE
GAS CONTROL LAYER
FOUNDATION LAYER
EXISTING COVER SOIL
AND PROPOSED PILL
REFUSE
0.5 FT.
1.0 FT.
1.0 FT.
2.0 FT.
0.5 FT.
1.0-10.0 FT.
0-40.0 FT.
-\
NATURAL SOIL
NOTE: THIS CROSS SECTION IS PER PROPOSED STATE SOLID WASTE RULES.
MINNESOTA RULES =ART 7C25.2815, SUSP ART 6, ITEM D.
-------
Table It
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Table 1a (cont.)
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-------
Table -. (cont.)
SUWW OF GRtUNDUnitR
OW ERM RI/TS
K9LT9 IN «|/l
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Table 1b. ^ -
SIHVIRV tr SURWX uniERS
DTK r,lwt di/rs < - * --
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Tal ic.
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-------
TABLE 2
OAK GROVE SANITARY LANDFILL
ALTERNATIVE 1 ANALYSIS " . .-"
ALTERNATIVE 1 - NO ACTION
Description: The No Action alternative consists of leaving the present cover
in place and fencing the site to minimize future access.
Assessment:
Overall Protection of Human Health and the Environment
o Not protective of the environment. Contaminants will continue to
leach into ground water and surface water.
o Unknown impact on human health. Future contaminant concentrations
in ground water and surface water may or may not exceed drinking
water and other health-based standards.
Compliance with ARARs:
o Does not comply with State or Federal landfill closure regulations.
Long-Tenn Effectiveness:
o Wastes remain on-site.
o Present landfill cover is inadequate to prevent contaminant
transport to ground water.
o Future impacts on ground water quality are likely.
Reduction of Toxicity, Mobility, or Volume: -
o Not applicable because no treatment is involved.
Short-Term Effectiveness:
o Not applicable because no remedial construction is included.
Implementability:
o Technical feasibility ' not applicable because no remedial - con-
struction is included.
o Not administratively feasible. No action inconsistent, with State
and federal landfill closure guidelines.
o Availability of services and materials not applicable because no
remedial construction -is included.
Cost:
o Capital Cost: $80,000 - illC.OOO
o Annual Maintenance and Mcr.-itsring Cost: SO
o Estimated Present Wcrtr.: :£::,000 - S110.COO
;.».
State Acssotanca:
o Not apD"iic3blr beci'jiS :r.:: Is a State-lead sits.
Community Accsctancs:
o NG acf.cn :: likely t; oi ;::::;:.
-------
..., .v ''"'The"long-term a'dequacy of land disposal 3s'unknown.- ...... __r. ..
^x o Minima"! potential ~for barrier layer failure/^ue to Differential ?.-:
settling of landfill contents. " .-:.:--:.-..-;-.-. _T.....
:>-- o The minimal thickness ;<12") of the. cover.sot! makes the clay barrier ^
susceptible to damage by burrowing animals, shallow to deep:rooted
vegetation and erosion, with a subsequent decrease in effectiveness.
; o Very susceptible'to frost damage and significant decrease 1n effec-
tiveness"; -*>:-- :: -.- r.~. "~^-'~'~; -~*. .*.*.- >--......
o Future increases in the water table elevation may bring ground water
into contact with landfill contents.
o Lack of drainage can destroy vegetation increasing percolation and
leachate production (lower effectiveness).
o Lack of drainage can increase slope instability of the cover soil.
Reduction of Toxicity, Mobility, Or Volume:
o Not applicable because no treatments involved.
Short-Term Effectiveness:
o Minimal risk to the community during cover system construction.
-------
3a
o Potential risk to workers during construction due to emissions of
volatile .organic compounds or methane. Requires air monitoring and'
possible'respiratory protection. ...-.--
o Possible environmental impacts due to participateemissions. Re-
quires dust control during remedial construction. ,
o Engineering and construction will require 1 to 2 years. Protection
against infiltration will be achieved immediately, although the
effect on ground water quality will not be observed until a later
time when percolation of previous infiltration is complete.
Implementability:
o Technically feasible. Minimal technical problems during design and
construction.
o Administratively feasible. Requires agency coordination to assess
the appropriateness of a municipal waste closure action.
o Services and materials are available.
Cost:
o Capital Cost: $3,900,000 - $7,300,000
o Annual Maintenance and Monitoring Cost: $38,000
o Estimated Present Worth: $4,300,000 - $7,700,000
State Acceptance:
o Not applicable because this is a State-lead site.
Community Acceptance:
o All containment alternatives may be opposed.
-------
TABLE 4
..OAK GROVE SANITARY LANDFILL
ALTERNATIVE 2B ANALYSIS : -
ALTERNATIVE 28 - MINNESOTA RULES FOR INTERIM MUNICIPAL LANDFILL WITH SYNTHETIC
MEMBRANE BARRIER
Description: The Alternative 2B cover system consists of grading and soil
fill to construct a foundation layer with minimum 2 percent slope, a gas
control layer of 6 inches of sand, a synthetic flexible membrane, and a 12
inch vegetated cover layer.
Assessment:
Overall Protection of Human Health and the Environment
o Lowest protection of the alternatives. Allows about 12.0 percent of
surface precipitation to infiltrate landfill. Some leaching of
contaminants into ground water and surface water.
Compliance with ARARs:
o Complies with State closure regulations for an existing municipal
solid waste facility which will not receive additional wastes within
18 months of the enactment of the Minnesota proposed rules.
o Does not comply with ARAR of at least 90S containment of rejection
of surface precipitation.
Long-Term Effectiveness:
o Wastes remain on-site.
o Cover system allows percolation of 12.0 percent of surface prectpJ-
tation.
o The long-term adequacy of land disposal is unknown.
o Minimal potential for barrier layer failure due to differential
settling of landfill contents.
o The thickness of cover soil (12") provides the synthetic membrane
with only minimal protection from physical damage from burrowing
animals, vegetation, erosion and surface traffic, thereby resulting
in a decreased effectiveness.
o Damage to single synthetic membrane could result in significant
decrease in effectiveness.
o Future increases in the water table elevation may bring ground water
into contact with landfill contents.
o Ljck of drainage can destroy vegetation, increasing percolation and
"eicnate production.
o Lack of drainage may increase slope failure of the cover soil.
Seduction of Toxicity, Mobility, 0" VoV.-s:
o Not applicable because no treatment's involved.
inert-Term Effectiveness:
c Mir.imc! r^sk to the coiwnu-.-'; d-rir,c cover systerr, construction.
-------
4a
o Potential risk to workers during construction due to emissions of
volatile organic compounds or methane. Requires air monitoring and
possible respiratory protection. -": :
o Possible environmental impacts due to particulate emissions. Re-
quires dust control during remedial construction.
o Engineering and construction will require 1 to 2 years. Protection
against infiltration will be achieved immediately, although the
effect on ground water quality will not be observed until a later
time when percolation of previous infiltration is complete.
Implementability:
o Technically feasible. Minimal technical problems during design and
construction.
o Administratively feasible. Requires agency coordination to assess
the appropriateness of a municipal waste closure action.
o Services and materials are available.
»
Cost:
o Capital Cost: $3,100,000 - $5,400,000
o Annual Maintenance and Monitoring Cost: $37,000
o Estimated Present Worth: $3,500,000 - $5,800,000
State Acceptance:
o Not applicable because this is a State-lead site.
.*>
Community Acceptance:
o All containment alternatives may be opposed.
- *
'^SiiiMi^/^^j^ ^C^WcE;Gv-V.;
-------
TABLE 5
..-. .OAK GROVE SANI1ARY 1ANUFILL
ALTERNATIVE 3A ANALYSIS : '
ALTERNATIVE 3A - MINNESOTA RULES FOR ACTIVE MUNICIPAL LANDFILL, CLAY BARRIER
LAYER
Description: The Alternative 3A cover system consfsts of grading and soil
fill to construct a foundation layer with minimum 3 percent slope, a gas
control layer of 6 inches of sand, a barrier layer of 24 Inches of clay, a 12
inch sand lateral drainage layer, and an 18 inch vegetated cover layer.
Assessment:
Overall Protection of Human Health and the Environment
o Intermediate protection. Allows about 6.5 percent of surface pre-
cipitation to infiltrate landfill. Some leaching of contaminants
into ground water and surface water.
Compliance with ARARs:
o Complies with State closure regulations for an active municipal
solid waste facility which will not close within IB months of the
enactment of the Minnesota proposed rules.
Long-Term Effectiveness:
o Wastes remain on-site.
o Cover system allows percolation of 6.5 percent of surface precipita-
tion. m
o The long-term adequacy of land disposal is unknown.
o Minimal potential for barrier layer failure due to differential
settling of landfill contents.
o Burrowing animals and vegetation can disturb upper thickness of
barrier without significant reduction in effectiveness.
o Lateral drainage layer, minimizes potential frost damage.
o Future increases in the water table elevation may bring ground water
into contact with landfill contents.
Reduction of Toxicity, Mobility, or Volume:
o Not applicable because no treatment is involved.
Short-Terr, Effectiveness:
o Minimal risk to the community curing cover system construction.
o Potential risk to workers curing ccr.structicn due to emissions of
volatile organic compounds or rcethane. Requires air monitoring and
pcssible respiratory project:or..
o Possible environmental ir.pact: due. ta parficulate emissions. Re-
quires dust control during rexaiial construction.
o Engineering and construction will rsquire 1 to 2 years. Protection
against infiltration wi":": : = acrr.'ec1 immediately, although the
effect on ground water cuc~'ty w'l"; net 35 otse-ved until-a later
time wher, percolation o~ orsv'-o'js :rv.-':~-ration '.- ::rr,Dlete.
-------
5a
Implementability: . ' *
o Technically feasible. Minimal technical problems during design and
-construction. -:.. - -v.v.'"*.' ' . -
o Administratively feasible. Requires agency coordination to assess
the appropriateness of a municipal waste closure action.
o Services and materials are available.
Cost:
o Capital Cost: $5,900,000 - $10,700,000
o Annual Maintenance and Monitoring Cost: $42,000
o Estimated Present Worth: $6,300,000 - $11,100,000
State Acceptance:
o Not applicable because this is a State-lead site.
Community Acceptance:
o All containment alternatives may be opposed.
-------
TABLE 6
. ;;_v -.- ... . OAK GROVE SANITARY LANDFILL
ALTERNATIVE 3B ANALYSIS ; :
ALTERNATIVE 3B - MINNESOTA RULES FOR ACTIVE MUNICIPAL LANDFILL, MEMBRANE LINER
BARRIER LAYER
Description: The Alternative 3B cover system consists of grading and soil
fill to construct a foundation layer with minimum 3 percent slope, a gas
control layer of 6 inches of sand, a barrier layer of 30 mil thickness high
density polyethylene liner, a 12 inch sand lateral drainage layer, and an 18
inch vegetated cover layer.
Assessment:
Overall Protection of Human Health and the Environment
o Intermediate protection. Adequate short-term barrier to leachate
generation with about 5.7 percent of precipitation infiltrating
landfill. However, failure may occur due to differential settling
or penetration by burrowing animals and/or vegetation.
Compliance with ARARs:
o Complies with "State closure regulations for an existing municipal
solid waste facility which will not close within 18 months of the
enactment of the Minnesota proposed rules.
Long-Term Effectiveness:
o Wastes remain on-site. . *
o Cover system allows percolation of 5.7 percent of surface precipita-
tion.
o The long-term adequacy of land disposal is unknown.
o Increased potential for membrane failure due to differential set-
tling of landfill contents.
o Potential for membrane, failure due to abrasion or other disturbances
if cover thickness is 'decreased by erosion.
o Potential for membrane failure due to inadequate quality control
during installation.
o If penetrated, the effectiveness of the synthetic membrane may be
significantly reduced.
o Burrowing animals or vegetation may penetrate entire thickness cf
barrier thus reducing ths effectiveness of the barrier.
o Future increases in the wctsr tacle elevation may bring ground water
into contact with landf:"". c:n:=r,ts.
Reduction of Toxicity, Mobility, or .'?:'j~=:
o Not applicable because no f.-=i;~cr^;is involved.
Short-Term Effectiveness:
c Minimal risk to tne csmrr.u.-.:-.> :urir.g c:ver system construction.
-------
6a
o Potential risk to workers during construction due to emissions of
volatile organic compounds or methane. Requires air monitoring and
possible respiratory protection. - . "- - " "
o Possible environmental impacts due to particulate emissions. Re-
quires dust control during remedial construction.
o Engineering and construction will require 1 to 2 years. Protection
against infiltration will be achieved immediately, although the
effect on ground water quality will not be observed until a later
time when percolation of previous infiltration is complete.
Implementability: ^
o Technically feasible. Minimal technical problems during design and
construction.
o Administratively feasible. Requires agency coordination to assess
the appropriateness of a municipal waste closure action.
ot Services and materials are available.
Cost:
o Capital Cost: $5,100,000 - 58,900,000
o Annual Maintenance and Monitoring Cost: $40,000
o Estimated Present Worth: $5,500,000 - $9,300,000
State Acceptance:
o Not applicable because this is a State-lead site.
^
Community Acceptance:
o All containment alternatives may be opposed.
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TABLE 7
... OAK GROVE SANITARY LANDFILL
ALTERNATIVE 4A ANALYSIS ; v
ALTERNATIVE 4A - RCRA EQUIVALENT COVER SYSTEM FOR HAZARDOUS WASTE CLOSURE
Description: The Alternative 4A cover system consists of grading and soil
fill to construct a foundation layer with minimum 3 percent slope, a gas
control layer of 6 inches of sand, a barrier layer of 30 mil thickness high
density polyethylene liner and 12 inches of clay, a 12 inch sand lateral
drainage layer, and a 48 inch vegetated cover layer.
Assessment:
Overall Protection of Human Health and the Environment
o Protective. Virtually eliminates leachate generation due to infil-
tration of precipitation.
Compliance with ARARs:
o May achieve compliance with RCRA closure regulations for a hazardous
waste cover system. Achieves desired barrier performance criteria
with 12 inches of clay rather than the 24 inches recommended in
guidance documents.
Long-Term Effectiveness:
o Wastes remain on-site.
o Cover system essentially eliminates percolation of surface precipi-
tation, initial efficiency of 100 percent.
o The long-term adequacy of land disposal is unknown. --/
o Synthetic membrane and lateral drainage layer minimizes frost damage
to the clay barrier.
o Minimal potential for cover system failure.
o Future increases in the water table elevation may bring ground water
into contact with landfill contents.
f
i _.
Reduction of Toxicity, Mobility, or Volume:
o Not; applicable because no treatment is involved.
Short-Term Effectiveness:
o Minimal risk to the community during cover system construction.
o Potential risk to workers curing construction due to emissions of
voUtl'-e organic compounds or metnane. Recuires air monitoring and
possible respiratory protection.
o Possible environmental impacts cue to particulate emissions. Re-
cu'rcs dust control during rsnedla" construction.
o Engineering and construction «-;*.", ..-squire 1 to 2 years. Protection
against infiltration will be acKVeved immediately, although the
effect on ground water aus"."ty wi'l net be observed until a later
tine when percolation of prsvirus infiltration to the ground water
tab:3 is ccmoiete.
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7a
Implementability: -.-..'.
o Technically feasible. Minimal technical problems during design and
construction. ~ - - --. ---'
o Administratively feasible. Requires agency approval of Interpreta-
tion of RCRA performance criteria.
o Services and materials are available. High costs for clay transport
may cause bentonite/soil mixture to be a cost-effective alternative.
Cost:
o Capital Cost: $7,400,000 - $13,400,000
o Annual Maintenance and Monitoring Cost: $45,000
o Estimated Present Worth: $7,900,000 - $13,900,000
State Acceptance:
o Not applicable because this is a State-lead site.
Community Acceptance:
o All containment alternatives may be opposed, but possible lesser
opposition due to the second barrier layer provided.
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TABLE 8
OAK GROVE SANITARY LANDFILL
ALTERNATIVE 4B ANALYSIS
«M^^^M^^MM^«i^^M^^«^^^MM^BMWM^^^HIM . % _
ALTERNATIVE 4B - RCRA COVER SYSTEM FOR HAZARDOUS WASTE CLOSURE
Description: The Alternative 4B cover system consists of grading and soil
fill to construct a foundation layer with minimum 3 percent slope, a gas
control layer of 6 inches of sand, a barrier layer of 30 mil thickness Wfh
density polyethylene liner and 24 inches of clay, a 12 inch sand lateral
drainage layer, and a 48 inch vegetated cover layer.
Assessment:
Overall Protection of Human Health and the Environment
o Protective. Virtually eliminates leachate generation due to infil-
tration of precipitation.
Compliance with ARARs:
o Compliance with RCRA closure regulations and design guidance docu-
ments for a hazardous waste cover system.
Long-Term Effectiveness:
o- Wastes remain on-site.
o Cover system virtually eliminates percolation of surface precipita-
tion, initial efficiency of 100 percent.
o The long-term adequacy of land disposal is unknown.
o Synthetic membrane and lateral drainage layer minimizes frost damage
to the clay barrier. -*
o Minimal potential, for cover system failure.
o Future increases in the water table elevation may bring ground, water
into contact with landfill contents.
Reduction of Toxicity, Mobility, or Volume:
o Not applicable because' no treatment is involved.
i
Short-Term Effectiveness:
o Minimal risk to the community during cover system construction.
o Potential risk to workers during construction due to emissions of
volatile organic compounds or methane. Requires air monitoring and
possible respiratory protection.
o Possible environmental impacts due to particulate emissions. Re-
quires dust control during remecial construction.
o Er.cinee'-'rig and construction wi"" require i to 2 years. Protection
against infiltration will be achieved immediately, although the
effect on ground water qual'~y *"«" not De observed until a later
time when percolation of prsvic-L-s infiltration is complete.
-------
8a
Implementability:
o Technically feasible. Minimal technical problems during design and
construction. - . -" "
o Administratively feasible. Requires agency coordination to assess
the appropriateness of a hazardous waste closure action.
o Services and materials are available. High costs for clay transport
may cause bentonite/soil mixture to be a cost-effective alternative.
Cost:
o Capital Cost: $8,000,000 - $14,600,000
o Annual Maintenance and Monitoring Cost: $46,000
o Estimated Present Worth: $8,500,000 - $15,100,000
State Acceptance:
o Not applicable because this is a State-lead site.
Community Acceptance:
o All containment alternatives may be opposed, but possible lesser
opposition due to the second barrier layer provided.
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ENFORCEMENT
Prior to implementation of the RI/FS, U.S. EPA issued notice letters to the
owners and operators of the Oak Grove Sanitary Landfill. --._. ..-:-
During the RI/FS, numerous information request letters pursuant to CERCLA
104(e) were sent in an effort to identify additional PRPs. Consequently,
five generators and one transporter were identified as PRPs.
Section 122(a) of SARA give the President the authority to enter into
agreements with PRPs to perform response actions if he determines the
actions will be done properly. If the President determines that it is
Inappropriate to enter into an agreement or to initiate negotiations, the
responsible parties will be notified of this decision and the reasons
behind it. Nine PRPs were sent a letter in September 1988 notifying them
of the decision not to enter into negotiation with them consistent with
this requirement of Section 122(a).
PRPs identified to date were generally not considered viable candidates to
implement remedial action. U.S. EPA is also planning to issue
approximately 50 additional information requests. Should U.S. EPA Identify
viable PRPs as a result, U.S. EPA will initiate the special notice^
moratorium under SARA 122(e).
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05.-13 88 02:46 MPCA MO.G0b 002
OAK GROVE LANDFILL, OAK GROVE TOWNSHIP, MINNESOTA _
SOURCE CONTROL FEASIBILITY STUDY - -
RESPONSIVENESS SUMMARY
This community responsiveness summary has been developed to document community
Involvement and concerns durlno the source control operable unit phase of the
project, and to respond to public comments received during the public comment
period. Also Included, as Attachment A, 1s a sunroary of the community relations
activities conducted by the Minnesota Pollution Control Agency (MPCA) since the
Remedial Investigation and Feasibility Study was funded, under a cooperative
agreement with the U.S.,Environmental Protection Agency (EPA). EPA hereby
adopts the MPCA responses for the purpose of Section 117 of CERCLA.
A. OVERVIEW
The recommended alternative for a landfill cover at the Oak Grove site was
announced to the community through an advertisement 1n the local newspaper and a
news release. These Items were also mailed to names on the Oak Grove- site
mailing 11st. The recommended alternative 1s a landfill cover which Includes a
3 to 20 percent slope, a gas control layer, a barrier layer of either two feet
of clay or a 30-m1l high density polyethylene membrane, a drainage layer, cover
soil and vegetated topsoll.
Anoka County and several residents living near the site supported the MPCA's
recommendation for a landfill cover. Comments were also received from a few
residents and the landfill owners and operators (the potentially responsible
parties) adamantly opposing the MPCA's alternative and supporting the no-action
alternative.
This responsiveness summary contains the following sections:
o Background on Community Involvement
i "
o Summary of Comments Received and Agency Responses
o Remaining Issues
o Attachment: Community Relations Activities at Oak Grove Landfill
B. BACKGROUND CN COMMUNITY INVOLVEMENT
A high level of community interest in the Oak Grcvs Landfill site had existed
during the time that the landfill was operating and has continued at relatively
the same level following closure of the landfill, ^r.c throughout the Superfund
project to this point. The primary focus of rodents' concerns since the land-
fill closed has been the ground water contamination from the site and its poten-
tial effect on nearby residential wells.
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- 2 -
The MPCA conducted the community relations activities for the Superfund project.
In November 1985, residents were provided with information on plans for the pro-
ject through a news release, fact sheet and public meeting. . A second public
meeting was held and fact sheet provided in December 1986, following approval of
the work plan and start of the field work. Letters to update interested persons
on the progress of the ground water investigations were mailed to names on the
Oak Grove site mailing list in February and June 1988. These letters also
included information on the MPCA's decision to conduct a source control
feasibility study and the purpose of the study.
The MPCA announced a 21-day public comment period (September 2 - September 23,
1988) on the alternatives for the landfill cover through an advertisement in the
Anoka County paper and a news release. Copies of the advertisement and news
release were also mailed to persons on the mailing list. A public meeting was
held midway in the public comment period, on September 14, and fact sheets were
distributed at the meeting and made available at the township hall.
C. SUMMARY OF PUBLIC COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND
MPCA RESPONSES
Comments received during the public comment period on the Source Control
Feasibility Study and Proposed Plan are summarized below:
Comment:
MPCA Response:
Residents living near the site expressed support for the, MPCA's
recommendation for a landfill cover.
The MPCA agrees that a landfill cover is needed and is the best
source control alternative for the site. The MPCA proposed - *
alternative 3 because it is appropriate for a solid waste land- *
fill and is the most cost-effective alternative.
Comment:
Anoka County supported the proposed alternative, noted it was
long-overdue and recommended it be undertaken quickly. The
County also:
- requested that the existing lime sludge be graded before the
fill is placed
- questioned whether gas venting v/ould be provided
- questioned how surface runoff .rill be controlled
- requested that the quality of t.~ -jpcer 13 inches of soil
meet county requirements
- questioned .-/nether the :JS= :f ".;= synthetic barrier is
realistic because of trie -~: \~vty of rapair after cover
soils are placed
- requested that consideration ';-: given to additional cover
soils for frcst protection
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- 3 -
MPCA Response:
Gas venting will be provided as part of the landfill cover. The
existing lime sludge will be graded before the fill is placed.
During the remedial design phase, specific plans for surface
water runoff control will be developed and specifications for
the topsoil and cover soils determined. Throughout the design
phase, the MPCA will periodically meet with and update county
staff to keep them informed of the plans for the landfill cover.
County concerns about runoff control and topsoil and cover soil
quality will be considered as design specifications are
developed.
The MPCA considers either barrier layer material clay or
synthetic membrane equivalent and appropriate for the cover.
The MPCA also recognizes, however, the difficulties in repairing
the synthetic membrane after placement of cover soils. The
choice of barrier material will be made early in the design
stage, after the MPCA receives more site-specific information on
the availability and cost of the materials.
Frost control is not required for cover under Minnesota-1 s pro-
posed solid waste rules. The MPCA believes that the drainage
layer in the cover system will remove a sufficient amount of
moisture from the cover to prevent frost damage.
Comment:
MPCA Comment:
One resident objected to "big government spending" and indicated
interest in bidding on the project. The resident also objected.
to the landfill owner's loss of development rights for the land-
fill property.
The proposed alternative was evaluated on how well it met the
nine criteria developed by EPA for evaluation of remedial action
alternatives under the federal Superfund program. The nine.
criteria are: protection of human health and the environment";
compliance with health and environmental regulations; reduction
of toxicity, mobility or volume of the contaminants; short-term
effectiveness; long-term effectiveness; implementability; public
acceptability; state acceptability; and cost. The proposed
alternative represents the best balance among the nine criteria.
While the estimated cost is higher than the MPCA expected, the
agency believes that through the competitive bidding process,
the cover will be constructed at the 1c\/ast cost possible.
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- 4 -
Under state competitive bidding procedures, any qualified
contractor has an opportunity to bid on state contracts.
Relative to the property development issue, the reason that the
property cannot be developed in the future is the need to keep
the cover intact, and added weight placed on the cover could
result in additional settling of the landfill. In addition,
future use of the property in some manner could restrict
operation of the gas venting system. Although the construction
of the cover will prevent future use of the property, the pro-
perty owners should realize that, even without the use restric-
tions of the cover, it is unlikely that the landfill property
would be of interest to potential developers.
Comment:
MPCA Response:
Another resident supported the no-action alternative, citing the
high cost to taxpayers as the primary objection. The resident
also noted that two nearby landfills, Anoka Municipal and Waste
Disposal Engineering, are not being covered and that, given the
information available on the ground water contami nation-at the
Oak Grove site, the existing lime sludge cover would be ade-
quate.
The MPCA's response to the cost issue is contained in the
response to the previous commenter. In addition, the MPCA notes
that little if any Superfund monies would probably have been
required for the cover had the owners and operators agreed to
participate in timely design and construction of an appropriate
final cover for the landfill, as was requested by the MPCA.
Both the Anoka County Landfill in Ramsey and the Waste Disposal
Engineering Landfill in Andover will have covers that are equal
to or more stringent than the proposed cover for Oak Grove.
Landfill covers are .designed not only to reduce the generation
and movement of leachate into the ground water. They are also
designed to: control the release of methane and other gases
forming in the buried wastes, prevent erosion and control runoff
from the surface of the landfill, provide adequate drainage,
prevent rodents from burrowing into the landfill and prevent
direct contact with the wastes. The existing lime sludge on the
landfill is not designed to accomplish this, and is, therefore,
not an adequate cover.
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- 5 -
Comment:
The attorney for the owners and operators of the landfill, who
are responsible parties, and several of the landfill owners
objected to the proposed alternative, supported'the no-action
alternative, and provided the specific comments (1 - 5) listed
below.
For clarity, the MPCA's response follows each comment.
1. The landfill should be left uncovered the no-action
alternative -- because of the lack of demonstrated harm. The
MPCA's draft report on the extent of contamination, has not
shown the landfill poses a problem, a potential threat to the
public or an effect on drinking water. Ground water con-
tamination detected in the study is not severe and is being
treated as it is discharged to the wetland.
MPCA Response:
The MPCA's study of the contamination at the landfill is not
complete and it is too early to characterize the severity of
contamination at the landfill. .
Under Minnesota Proposed Rules 7035.2815, Subpart 6, every sani-
tary landfill in Minnesota will be required to have a final
cover that meets new specifications, whether or not there is
ground water contamination present. All covers are required to
control and prevent a variety of potential problems, besides
reducing production of leachate and movement of leachate into
the ground water. Landfill covers are also required to control
erosion, runoff from the surface, and access to the site, . j
control the release of methane and other gases from the buried
waste, provide adequate drainage, and prevent rodents from
burrowing into the landfill, and prevent direct contact with the
waste.
Comment:
MPCA Response:
2. The landfill has been uncovered for many years without
causing a problem. The MPCA is moving too quickly in making
this decision ahead of completing its investigation.
The MPCA is continuing its remedial investigation at the land-
fill. Sines the cover will be required -~cr the landfill no
matter v/hat the investigation finds >no it will not interfere
/nth any -]!':und .;ater remedies thai -?. 'je needed, the MPCA has
cnosan to tocaed .viuh the co^er -11 :=rr:3t;. ve prior to the
completion of the investigation.
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- 6 -
Comment: 3. The cost of the alternative is excessive compared to the
seriousness of the threat from the landfil.-l-.and .responsible par-
ties will face legal action and potential economic ruin. EPA
has indicated they have suspended negotiations with the respon-
sible parties and the responsible parties do not understand this
and need more facts. '
MPCA Response: The MPCA's response to the cost issue is contained in the
response to a commenter above. . The federal and state Superfund
laws, enacted by Congress and the Minnesota Legislature, give
the EPA and MPCA the authority to recover costs for remedial
actions from responsible parties, in this case the owners and
operators of the landfill.
At this site, EPA is the lead agency for enforcement actions and
will negotiate with responsible parties for cost recovery.
Under EPA procedures, a moratorium is placed on these nego-
tiations until after the Record of Decision is signed.
Following this action, EPA re-opens the negotiation process for
a specified period of time.
Comment:
MPCA Response:
4. Public officials and area residents were not in attendance
at the meeting and should have been.
The MPCA sent a notice of the meeting to all persons on the
Oak Grove mailing list, which includes residents and government
and elected officials. The MPCA also published the meeting
announcement in the Anoka County Union.
Comment:
MPCA Response:
5. Some of the background information in the Feasibility
Study relating to the estimated amount of hazardous waste in the
landfill is inaccurate.
The estimated amount-of hazardous waste disposed of in the ..
landfill was provided primarily for background purposes and Was
an amount included in the draft report on the ground water
investigation prepared by the MPCA's previous consultant. The
amount listed is the documented amount of hazardous waste
disposed of at the landfill. The MPCA and EPA believe that
additional amounts of hazardous waste ^ay have been disposed of
at the site.
Relative to tlie questioned percentage -3- hazardous waste to
total waste volume, the MPCA's consultant agrees that the figure
shoulc have been .12 oercent, and ~.'.">3 '-'P'~* has notad this .OS
2ercent error. .'»
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- 7 -
D. REMAINING ISSUES
The MPCA was unable to specify which barrier layer for the cover" clay or a
high density polyethylene membrane would be the final choice. This decision
will be made during the early stages of remedial design, after the MPCA receives
more site-specific information on the availability and cost of both barrier
materials. The MPCA considers either barrier layer material equivalent and
appropriate for the cover as both have been designed to divert water from
entering the fill! .material and infiltrating through the buried wastes.
In addition, some of the comments received from Anoka County will be addressed
during the remedial design. County concerns relating to the quality of the top-
soil and cover soils and questions about surface water runoff will be considered
during this phase of the project. Through periodic meetings and updates, the
MPCA will work with the county on these issues and keep them informed on the
progress of the design.
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ATTACHMENT A
COMMUNITY RELATIONS ACTIVITIES CONDUCTED AT THE OAK GROVE LANDFILL SITE
The MPCA has conducted the following community relations activities for the
Oak Grove Landfill to date:
November 6, 1985 - Public meeting held to discuss future federal Superfund
project at the landfill. Fact sheet provided to meeting
attendees and township.
December 1985 - Community relations interviews conducted and information
repository established at the Oak Grove Township Hall.
Spring 1985 - Community relations plan written and approved by EPA.
November 17, 1986 - News release announcing meeting in Oak Grove Township on
beginning of Superfund project field work.
December 3, 1986 - Meeting held in Oak Grove Township; fact sheet provided to
residents and township; project work plan placed "in infor-
mation repository.
February and - Letters sent to persons on mailing list to provide updated
June 1988 information on the status of the ground water investigation
and indicating that the MPCA was proceeding with a source
control feasibility study while continuing investigation at
the landfill.
August 30, 1988 - News release announcing completion of feasibility study foi*
cover; announcing public comment period and date of public
meeting.
September 2, 1988 - Ad published in Anoka County Union announcing same infor-
mation as news;release. Feasibility Study and Proposed
Plan placed in information repository.
September 14, 1988 - Public meeting held, fact sheet provided and comments
accepted from public.
September 23, 1988 - Public comment period ended; responsiveness summary written
and attached to Record of Decision.
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03'23/88
02:50
MPCfl
NO.005
009
COUNTY OF
COMMUNITY HEALTH & SOCIAL SERVICES DEPARTMENT ^
_~^;-_. --- FOURTH FLOOR -r-.i: -^i-:^r^-v
COURTHOUSE ANOKA, MINNESOTA 55303 .- 612-422-7000
tartly * CMtfrwft ftwvtett
voiuntMr tome**
Oa*tiapm«ntti AcMtxmmt
19, 1988
Minnesota Pollution Control.Agency
c/o Wayne Sarappo
520 North Lafayette Road '^^±-^----
St. Paul, MN ., ^. ;
Dear Mr. Sarappo: :.. : ^ ^ -
Reference Is made to the Source Control Operable Unit Proposed Plan for the
Oak Grove Sanitary Landfill which was submitted to us on September 2, '1988.
The work proposed In this plan Is long overdue and needs to be undertaken as
soon as possible. -_. ._,.._,.._ . -..,:: ^......
. .
Our review of the proposed plan has Identified several Items needing
clarification which we'd like to bring to your attention. These Items are as
follows: ..---;- ---- - -...-. -- - - .
1.
The quality of the upper 18 Inches of soil has not been specified. We
would request that the quality of the upper 18 Inches of final cover
soil meet the criteria specified 1n the County's Solid Waste Ordinance
for such soils. I hjv; enclosed a copy of tha dsflnitlofi of final covtr
which Indicates the soil quality requirements for the upper 18 inches of
soils. 'v-''Vas_--., ...-_--... ':.....-.:.. . ..... .--.,-.,
3.
4.
It was not clear 1n the plan whether or not the existing lime sludge on
the top Phase II area would be graded before fill placement. Care
should be taken to grade the existing lime sludge so that there are no
pockets to pond water after placement of the fill soils necessary for
establishing the final grade.
Both cover plans, 3A and 3B, provide for 2J feet of cover over the
Impervious material (low permeable soils or flexible membrane). Two and
a half feet of cover may not provide sufficient protection of these
materials from damage caused by freeze/thaw cycles. Consideration
should be given to additional protective cdvier soils.
Is the use of a membrane cap a realistic alternative? Membrane caps
are, at best, extremely difficult to repair if damaged after cover soil
placement.
5. Hill gas venting be provided?
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0S.'28/eS 02:51 MFCS 1C. 0Q6 010
Nlnntsota Pollution Control Agency
c/o Wayne Sarappo ------ -.,-.. -.-. -
September 19/1988 -
Page 2 ...
5. W111 gas venting be provided?
6. How will surface run off water be controlled and managed to get 1t off
__.. of the fill without damaging the cover?
I look forward to your favorable consideration of the foregoing comments. If
you have any questions concerning this matter, please feel free to call me.
Yours very trull/,
Robert H. Hutchison
Director, Environmental Services
RMH:kk
* *
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* -sn.., .f. . -
09/28/88 02:5.1 MPCA NO. 005 011 -^
| lubeectlon 13. Tranafer Station" la defined ea en Intermediate aolld waste dleposal
facility In which solid waste collected from any eouree Is temporarily deposited to await
* transportation to the final disposal alta or facility. \
.-*"'*
~^Li,,-...'..^.: Subsection 1*. "Incineration" la defined M the process by which aolld wastes ere V-^
.-.,----.--..-.- burned for tha purpose of volume and weight reduction In facilities designed for such we. _ i^.
^^^r ^-"".-^ - ": Subaaction 13. "Site" and Taelllly" are defined ea all real and personal property which ''':::^
-"-'-'- ------ |, QT may 5, mtd fyr (* Intermediate disposal or final-disposal of aolld waata and ""^'
which requires e lleenee under the provisions of this ordinance. . -,>-. - "-'
Subsection 1C. "Shoreland" la defined aa land located within the following distances ~I
from the ordinary high water elevation of public watarst (a) land within 1,000 feet from tha
normal high watermark of a lake, pond, reservoir, Impoundment, or flowagei end Ob) lend '--
within 300 feat of a river or stream or tha landward side of flood plain delineated by
ordinance on such a river or streem, whichever la greater.
Subsection 17. "Waste Tire" la defined es aolld waste which consists of the rubber or .J.
other resilient material product which la wad on a vehicle or other equipment wheel to 2±
provide tread which la discarded or which cannot be uaad for Its original Intended purpose V
because It Is used, damaged or defective.
Subaaction 18. "Intermediate Disposal" Is daflnad as the preliminary or Incomplete ^i.-,
disposal of solid waste Including, but not limited to, transfer station operationa, open ^~
burning, incomplata land disposal, Incineration, composting, reduction, shredding, '
compression, recycling, processing, resource recovery, and any other management or .-"
handling of waste short of flnel disposal. ^tf
Subsection'!?, "final Disposal" is defined as tha complete and ultimate disposal of
uolid waste by placement In or on the lend. ' ^.
Subsection 20. Termlnetion" Is defined as all af those sotlvltles anddutles relating to
Itha closing of waste site or facility whether performed prior to or after operation of tha
olta or facility has ceased, and tha maintenance, monitoring and long-term cere of the alta " '
nr facility after the site or facility has ceased to accept wastaa. .-' - .";
Subsection 21. "Closure" is defined ee that phase of alto or facility termination in
which tha site or facility Is prepared for post-closure care. :
Subsection 22. "Post.elesure" is defined as that phase of site or facility termination ~~"
during which tha long-term cere, maintenance and monitoring of the site or facility takes
place. ^..
Subsection 23. "Gate Yerd of Waste" ie defined es e cubic yard of waete measured In -":,.
the hauling vehicle as received et the site or facility before It le processed or prepared for
disposal.
Subsection 24. "Adequate Turf" Is defined es a live ground cover mat of native
perennlol grosses or other suiteble vegetation free of noxious weeds which.-provides
sufficient ground cover to effectively prevent loss of fine! cover by wind or water erosion.
The edequacy of the turf mey not be determined until at least one year after seeding.
Subsection 23. "Flnel Cover" Is defined as the cover pieced on a finished area of e site
or facility after the eree h»s reached the approved development elevation or operations in
the area have ceased, and shall consist of three horizons! a lower Impervious cap, e middle
earthen raver materiel, and an upper topioil. The lower Impervious csp shall consist of at
least twelve (12) Inches of e soil or other approved material having e permeability no
([Tester than 10'6 cm/»»c. The middle earthern cover msterlal shall consist of at lesst
twelve (12) inches of soil classified ss aondy clay loam, sandy loam, clay loam, loam, silty
Clay los/ri, loamy tsnd, or silt loam. The upper top soil shell consist of at least six (6) inches
of soil classified as loam, sandy loam, gilt loam, stlty clay loam, clay loam, or sandy cley
loam. Tor sites or facilities Initially licensed prior to October 1, 1983, the middle end upper
soil horizon* may consist of a soil manufactured on site which Is uniformly mixed, contains
between five (346) end ten (10%) per cent organic material, less then eighty (60%) par cent
silt, less than fifty (50%) per cant clay, less than seventy (70%) per cent send, end has a
moisture retention capacity of at least 0.2 Inches moisture per Inch of soil.
Subsection 26. "Mixed municipal solid weste" is defined es garbage, refuse,'end other
solid waste from resldentlel, commercial, Industrial, and community activities which Is
generated and collected In aggregate, but does not Include auto hulks, street sweepings, ssh,
-~- I
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