United States
Environmental Protection
Agency
Office 01
Emergency and
Remedial Response
EPAIROD/ROS-89/116
September 1989
8EPA
Superfund InfolJ.~ t.~1i
Record of Decision: rrtJlJtiofJ Hioo~:~/f!
~enter
Windom Dump, MN
Hazardous Waste Collection
Information Resource Center
US EP A Region 3
Philadelphia, PA 19107
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50272.101
REPORT DOCUMENTATION 11. REPORTHO. 12.
PAGE EPA/ROD/R05-89/116
3. Rec:ipient'8 Acceuion No.
4. Tille end Sublille
SUPERFUND RECORD OF DECISION
Windom Dump, MN
First Remedial Action - Final
7. AUlhOf(e)
5. RepOf1 Date
09/29/89
a.
8. Perfonnlng Or"enlzatlon Rept. No.
8. Perfonnlng Or"elnlzallon Heme end Add-
10. ProjectlTeeklWorII Unit No.
11. Contrect(C) or Grent(G) No.
(C)
(G)
12. Sponeoring Or"enizatlon Heme end Addre..
U.S. Environmental Protection
401 M Street, S.W.
washington, D.C. 20460
13. Type 01 Report & Period Covered
Agency
800/000
14.
15. Supplomentery No...
16. Ab8trect (Urn/t: 200 _rde)
The 11-acre Windom Dump site is a former municipal landfill in Windom, Cottonwood
County, Minnesota. Land use in the vicinity of the site includes residential areas and
commercial, industrial, and agricultural operations. City water supply wells northwest
of the site lie downgradient of the landfill. Landfilling operations began in the 1930s
and continued until 1974. During this period paint sludges from a large manufacturing
operation were disposed of along with municipal refuse resulting in low levels of toxic
substances contaminating an underlying aquifer, which is used as a water supply. The
primary contaminants of concern affecting the ground water are VOCs including benzene,
PCE, and TCE; metals including arsenic; and other in organics.
The selected remedial action for this site includes grading and capping the fill area
with a 2 foot clay cap overlain by one foot of granular material, topsoil, and new
vegetation; modifying the existing municipal water plant by installing additional
aeration nozzles and structure venting; and ground water monitoring. In the event that
allowable contaminant limits are exceeded in the monitoring wells, a contingency plan
including a ground water pump and treatment system will be implemented. The estimated
present worth cost for this remedial action is $865,000, which includes an annual O&M
cost of $5,700 for 30 years.
17. Document An8Jy818 L DHcrIpto18
Record of Decision - Windom Dump, MN
First Remedial Action - Final
Contaminated Medium: gw
Key Contaminants: VOCs (TCE, PCE, benzene), metals (arsenic), other inorganics
b. Idenlifler8lOpen.Enc8d T-
c. COSA TI Fl8ld/Group
18. Avellebllty--
11. SecurIty CIa88 (ThI8 Report)
None
211. SecurIty CIa88 (ThI8 Page)
Non~
21. No. of Pegee
50
I
22. PrIce
(See ANSl-Z38.1')
See IMInICfI- on Re-
(4-71)
(Fornwrty NTlS-35)
D8partment 01 Commerce
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DECLARATION STATEMENT
RECORD OF DECISION
SITE NAME AND LOCATION
Windom Municipal Dump
Windom, Minnesota
STATEMENT OF BAsIS AND PURPoSE
This decision document serves as United States Environmental
Protection Agency's (U.S.EPA) concurrence with and adoption of
the remedial' action decision for the Windom Municipal Dump site,
as selected by the Minnesota Pollution Control Agency (MPCA), and
pursuant to section 117 of the Comprehensive Environmental
Response, Compensation and Liability Act (CERCLA). MPCA approved
this remedial action in conformance with the Minnesota
Environmental Response and Liability Act; and it has provided
U.S.EPA with documentation to demonstrate that the State's
selectio~ of the remedy generally conforms with the requirements
of CERCLA, as amended by the Superfund Amendments and~
Reauthorization Act (SARA). and the National Contingency Plan, to
the extent practicable.
The State has undertaken response action at the Windom Municipal
Dump and has sought U.S.EPA concurrence in a~option of the
remedy which has been selected. The U.S.EPA's concurrence with
the State's selected remedy is based upon the items listed in the
Attachment, and the adequacy and completeness of those documents
as represented by the State.
DESCRIPTION OF REMEDIAL ACTION
The selected remedy provides for final cleanup requirements
related to the Windom Municipal Dump site, as provided below:
* Close the landfill in accordance with MPCA Solid Waste
Rules, which require gradinq and cappinq the site, in order
to minimize leachate generation;
* Modify the existing water treatment plant by installing
additional. aeration nozzles and structure venting to protect
the public drinkinq water supply and;
* No action will be taken to actively control contaminant
migration. Groundwater monitoring will be conducted; and if
established intervention limits are exceeded, a groundwater
pump and treatment system will be installed.
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1-)""I( PRO"{~V
UNtTED, STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 5
230 SOUTH DEARBORN ST.
CHICAGO, ILLINOIS 60604
REPLY TO THE" TTE"''TION OF:
2 9 SEP 1989
5RA-14
Mr. Gerald L. Willet
Commissioner
Minnesota Pollution
520 Lafayette Road
st. Paul, Minnesota
Control Agency
55155
Dear Mr. Willet:
Enclosed is the u.s. Environmental Protection Agency's (U.S.
EPA's) Declaration Statement which concurs and adopts the Record
of Decision'(ROD), completed by Minnesota Pollution Control
Agency (MPCA) for the Windom Municipal Dump Site.
Our concurrence with and aQpption of the ROD are based on the
remedial action plan outlined within the ROD. It is the Agency's
understanding that subsequent to your signing the ROD, the
monitoring program at Windom Dump has detected higher
concentrations of contaminants and further movement of the
contaminant plume toward the city well field. Additional actions
that are being considered include using the city well #7 as an
extraction well and installation of an air stripper. The U.S.
EPA recommends that the public be informed of continuing
developments in this remedial action and request that the Agency
is kept abreast of progress or developments in the remedial
action.
Further, it is and will continue to be U.S. EPA's policy to
utilize a 10-6 cumulative carcinogenic risk level as its point of
departure. The Agency feels, however, that MPCA's adopted level
of 10-5 may also be appropriate for the particular circumstances
presented at this site.
We 100 forward to our
Munic' al Dump S' e.
Sine pjJ~ytrs
Valdas V. Ada us
Regional Admi istrator
continuing involvement on the Windom
Enclosure
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DECLARATION
aased on the information described above, U.S.EPA adopts and
concurs with the remedy selected by the MPCA for the Windom
Municipal Dump site. The selected remedy is protective of human
health and the environment, attains Federal and state
requirements that are applicable or relevant and appropriate for
this remedial action, and is cost-effective. The ROD states that
state solid waste management rules, which were in effect at the
time Windom Landfill ceased operation in 1974, are applicable to
this. site. Further, requirements of Resource Conservation and
Recovery Act (RCRA), 40 CFR Part 264, are considered by the state
to be met. Subtitle G landfill closure requirements, however,
are not deemed appropriate by U.S.EPA for the following reasons:
a.
The majority of total wastes deposited was general
municipal garbage.
Only low levels of toxic substances have been detected.
An endangerment assessment performed for the site
concluded that it does not pose a significant threat to
human health. ..
b.
c.
Finally, in addressing landfills specifically, the preamble of
the draft National Contingency Plan (NCP) suggests that RCRA
closure may not be appropriate where waste is of low toxicity and
contamination is dispersed over a wide area that bears little
resemblance to the discrete units regulated under subtitle C.
This remedy satisfies the statutory preference for remedies that
employ treatment that reduces toxicity, mobility, or volume as a
principal element and utilizes permanent solutions and alter-
native treatment technologies to the maximum extent practicable.
Because this remedy will result in hazardous substances remaining
on-site, the State is expected to supply information such that
the U.S.EPA can conduct a review, no less than 5 years after
commencement of remedial action, to ensure that the remedy
continues to provide adequate protection of human health and the
environment. Also, the MPCA will inform the u.s. EPA if the
intervention limits, which trigger the implementation of the
groundwater pump and treat system, are exceeded.
U.S.EPA reserves the right to take enforcement actions under
Sections 10,6 and 107 of the CERCLA against the Responsible
Parties to assure that the remedy, as well as any necessary
additional future work, is undertaken.
". If
-Jrr. J# ,~/qKr
Dat
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FORMER WINIX>M MUNICIPAL LANDFILL
WINIX>M, MINNESaI'A
RECORD OF DECISION
1.
SITE NAME, I.O:ATION, AND DESCRIPI'ION
The City of Windan operated a municipal landfill iran the 1930's to 1974.
As shown on Figure 1, the landfill is located south of Thirteenth Street and
east of Lakeview Avenue on the east side of the city.
The site is located in an abandoned sand/gravel pit covering an area of
approximately 11.4 acres. Access to the site is off of Thirteenth Street with
gates located at the northwest and northeast corners of the landfill.
The site
is secured to the north by a fence.
To the east, the landfill is oordered by
the Cottonwood County storage area which extends nearly 300 feet beyond the fill
area and is secured by a fence. Residential lots along Lakeview Avenue are
approximately 350 feet west of the fill area and are separated fJXll\ the landfill
by a fence.
Several other single family residences are located about 400 feet
to the northeast and east of the site outside of the city limits.
The area surrounding the foDter Windan Municipal Landfill is canprised of
residential, ccmnercial-industrial, and agriculture land. Beyond the county
storage area to the east lies agricultural land used for gr<:Ming hay and
livestock grazing.
'!he Windan Ready Mix plant and gravel pit operates 500 feet
north of the landfill site. A recreational softball field and bicycle race
course are lpcated approximately 600 feet to the northwest of the site. A
canetery is located approximately 1,000 feet to the southwest. Historically,
the land in the vicinity of the site had been used for agriculture, sand and
gravel mining/canent tile works, and flax pile storage for the Kimberly-Clark
Crnpany .
A pond, surrcnmded by sparsely wooded grasslands, is located 100 feet
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-----:-~--~
--
~ c,"'
NOV.
1986
SITE
LOCATION
MAP
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south of the landfill.
Other nearby surface waters include Cottonwood Lake,
approximately 1,100 feet to the nOrth, the Des MJines River, 3,500 feet to the
southwest, Wolf Lake, :3,000 feet to the southeast, and Perkins Creek, 4,000 feet
to the northwest.
II.
SITE HIS'roRY AND ENFORCEMENr ACrIVITIES
A.
History
Prior to the beginning of refuse disposal, the landfill site was
quarried for sand and gravel. The actual depth of excavation is not known.
The
elevation of Thirteenth Street, however, is approximately 1,400 feet (N:;VD) and
the ground water elevation is nearly 1,355 feet (N;VD).
It is believed that a
maximum 40 to 45 feet of sand and gravel were ratDVed prior to landfilling.
Hence, refuse was placed near, b.1t above, the ground water table.
The depth of
excavation and waste disposal was conf.i.med to be above the ground water ~able
during the Remedial Investigation (RI, Hickok and Associates, 1987).
A 1981 engineering rep:Jrt indicated that municipal refuse was placed
in the landfill beginning in the 1930's (Bonestroo, 1981). No specific
infonnation is available regarding landfill operations for the tine period iran
the 1930's to 1951. The Toro Carpany began operations in the City of Windcm in
the late 1940' s. 'n1e Toro plant primarily manufactured lawrmJWers and
snowblO'.-Jers and disposed of cardboard, wooden pallets, plastic casings, and
paint sludge in the landfill.
Prior to 1971, all refuse was burned.
It is believed that IIDst of
the paint sludges disposed of by Toro were 00rned. During the period 1971 to
1973, b.1rning operations were ceased and the nunicipal refuse was placed along
the westem 00undary of the disposal area. Toro discontinued its disposal
operations in 1974 when the landfill was closed. The facility was operated as
an Unpennitted dispOsal area.
-. '"F . .'F' ...'.,.. --"--"'."._n.___._.-...............-....-..........---...-------.u.-----..
'.-."........ ---.-------_. ----... .-* .
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The Cottorrwood. County storage area east of the site was used as a
gravel source by the County beginnihg in 1955 through 1958.
Since 1965, the pit
on the County propertY has been used to store new and used metal and concrete
culverts, various item> suc;:h as scrap iron, old plows, barrels, discarded fuel
tanks, wood, tires and related materials camonly used by the County Highway
Department.
The County has stated that it has not stored or disposed of
hazardous substances, Pollutants, and contaminants at the storage site.
An MPCA
insPection, including sampling, detennined that the county storage site is not a
source of contamination.
B.
Enforcanent
In response to a canplaint received by the Minnesota Pollution
Control Agency (MPCA) in December 1980, the MPCA initiated an investigation of
the fonter Windan Municipal Landfill.
The canplaint alleged that hazardo~s
wastes may have been disposed of at the site. MPCA expressed concern that these
hazardous wastes and other wastes disposed of at the facility may be a source of
pollutants to the area surface water and ground water.
In a correspondence dated April 2, 1981, MPCA fonnally requested
that the city prepare an investigation plan for the site.
The City sul:mitted a
report in Novanber 1981, in response to the MPCA request. The c:Iocumant was
entitled "Report on Groundwater M::mitoring Plan - City~" (Bonestroo, 1981).
As presented in the plan, six ncnitoring wells/piezareters were installed near
the per.ineter of the landfill to deteJ:mine the ground water flCM clirection and
ground water quality.
In Decanber 1983, the MPCA and the u. S. Enviromental Protection
Agercy (EPA) :reviewed the available data and catpleted a preliminary assessment
for the site.
Based on their :review of the data, the agencies calculated a
Hazard Ranking System score of 38 for inclusion of the site on the State
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Superfund Pennanent List of Priorities (PLP) and Federal Superfund National
Priorities List (NFL)~.
Early in 1986, E. A. Hickok and Associates, Inc. (EAR) was retained
by the City to independently assess the envirollltEntal conditions at the site
throUgh a review of existing data.
This review was presented in a document
entitled "PreliminaJ:y Assessmant" which was sulmitted to the MPCA on April 4,
.1987, (EAH, 1986). Limited field activities, including ITOnitoring of ground
water elevations, ~loptent and s~ling of existing ITOnitor wells, and
s~1ing' of near.by residential and municipal water supply wells were also
conducted February through August 1986.
The MPCA issued a Request for raredial action (RFRA) to the City of
Windon and the Tore Ca11pany on June 24, 1986, requiring the naned Responsible
Parties (City of Windon anct Tore Canpany) to conduct a Remedial Investigation
(RI) of the site. At the time of RFRA issuance, the City was alI:eady
investigating the site.
A series of RI plans and reports were prepared by EAH and subnitted
to the MPCA in November 1986.
Documants were revised in February 1987, to
include MPCA requests for additional infoDnation and to incorporate changes in
occupational safety and health regulations. Fonnal MPCA approval was granted on
April 23, 1987. The RI docurrents subnitted include:
"Evaluation Report for the Ra1e:lial Investigation,"
l'bIaIiJer 1986.
n Identification of General raredial action AI teJ:nati vas
for the Windcm Landfill," Novanber 1986.
"Work Plan for the RalEdial Investigation," l'bIaIiJer 1986;
revised February 1987.
"Quality Assurance Project Plan for the Remedial
Investigation" l'bIaIiJer 1986; revised February 1986.
"Site Safety Plan for the Ranedia1 Investigation,"
l'bIaIiJer 1986; revised February 1987.
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"Site Security Plan for the Raredial Investigation,"
November 1986.
The site RI was initiated at the landfill in May 1987.
Investigation
activities included:
canpleting eleven soil borings to detennine on-site
geology; constructing and developing twelve additional Ironitoring wells to
better define ground water flow; canpleting eight refuse borings and saITI>ling of
. soils to characterize .the waste disposed at the site; conducting two rounds of
water quality sampling at new and existing m:mitoring wells, municipal wells,
and darestic wells to better define ground water quality; and ground water flow
m:x:ieling to estimate aquifer characteristics and the influence of municipal well
field pumping on ground water flow/contaminant transport in the area of the
landfill site.
The site investigation activities were canpleted in Septanber
1987.
In Septanber 1988 a report entitled "Feasibility Study - Fonner WindOO1
Municipal Landfill, Windan, Minnesota" was prepared by Wenck Associates, Inc .
and sulmitted to the MPCA in fulfil1nent of the Request for Response l\ct.ion
(RFRA) issued June 24, 1986.
The Alternatives Report and Detailed Analysis
Report required by the RFRA (Section VI, Exhibit A, Tasks A and C) were canbined
into this single docunent as read upon by MPCA and City of Windan
representatives on July 1, 1988.
This report identified and evaluated several
remedial action alternatives for the Site in context of specific remedial action
objectives. Alternatives which passed an initial screening process and a Irore
detailed evaluation were rec':'llIl::nded for implenentation.
III.
CCJ1MUNITY REIATIOOS
A pililic catIIe1t pericxi for the Feasibility Study (FS) and the
recQlllended al ternati ve was open fran January 10, 1989, to February 8, 1989.
Copies of the RI and FS Reports, and a Fact Sheet detailing the al ternati ves
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-6-
evaluated and the recamendedalternative, were rrade available to lhe coomunity
at that time.
The Windan City Hall seLVeS as the infoDnation rep::>sitbry for the
ciocunents .
MPCA issued a news release and placed a notice in the Windcrn
newspaper aJ1I1OW1Cing the J;cl>lic cament period and outlining the al teJ:T1a.ti ves
evaluated and the rE!C.'Q111~nded alternative. A public nEeting was held at Windan
City Hall on January 17, 1989.
No J;cl>lic ccmnents were made at the January
. J;cl>lic nEeting or received during the J;cl>lic coomant period.
IV.
SCOPE OF rate:tial actio~
The selected ratEdy represents the final remedial action for the Windan
site.
In addition, long-tenn- ground water m:>nitoring and a contingency plan for
protecting the municipal water supply will be included in the Final rem:d.ial
action Plan.
As a result of this rate:tial action the principal threat at the
site, ground water contamination, will be mitigated.
v.
SITE aJARAC'I'ERISTICS
The following discussion sunmarizes the findings of the RI.
A.
Ground Water
Ground water at the Site is located in glacial outwash dep::>sits
consisting primarily of sand and gravel.
'!his aquifer is underlain by a thick
clay layer which serves as a natural barrier to water flow and protects deeper
aquifers fran contamination.
The saturated thickness of the sand and gravel
deposit ranges fran 50 to 150 feet.
Depth to the water table about 50 feet fran
the ground surface.
The general ground water flow direction at the site is in a
nOrthwesterly cW:ection.
The ground water flow velocity in the vicinity of the
landfill is estimated to range between 90 to 700 feet per year.
Water quality I1Dnitoring at the site has indicated that no surface
water impacts have occurred; however, elevated concentrations of several
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-7-
inorganic and volatile organic canpounds have been detected in the ground water
near the fill area.
Volatile organic canpounds found in the Irost significant
concentrations near the fill area are the chlorinated ethylene canpounds;
1,1,2,2-tetrachloroethylene (PCE); 1,1,2-trichloroethylene ('ICE),
cis-1,2-dichloroethylene (1,2-0CE); and vinyl chloride (Irooochloroethylene).
Various inorganic indicators have been detected slightly above
. background at various downgradient site perinEter wells.
A notable exception is
nitrate detected at. as high as 15 mg/l. However, no clear trends in the data
are evident at this time which would be indicative of leachate migration fran
the fill area.
B.
City Well Field
City Water Supply Well 7 is located approximately 500 feet northwest
of the landfill site screened at a depth of approximately 150 feet into the
glacial aquifer.
Catplter flow m:x:ieling anployed to simulate hydraulic
conditions of the aquifer indicated that the radius of influence from pumping
City Well 7 probably extends under the landfill site.
Pumping of City well 7
generally induces a cone of depression with ground water flow noving radially
toward the well.
However, since the natural flow direction at the site is to
the northwest, pumping of City Well 7 does not greatly alter ground water flow
at the site.
1,2-OCE and vinyl .chloride have been detected. in untreated water at
City Well 7 on several cx:casions. However, it is not clear whether or not the
detections can be directly attributed to the landfill because Ironitoring well
data, to date, indicate ground water impacts are limited to the iJmediate fill
area.
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Well 7 at levels ~ to 2.1 micrograms per liter (ug/l).
1,2-OCE concentrations have been detected in untreated water at City
The RecOOTrended
Allowable Limit (RAL)'for 1,2-DCE is 70 micrograms per liter (ug/l).
On several occasions vinyl chloride levels in untreated water has
equaled or exceeded the Maximum Contaminant level (M:L) drinking water standard
of 2 ug/l. However, vinyl chloride has not been detected in treated water in
the City's distribution system although trace BI1DWlts of 1,2-OCE have been
found below drinking water criteria. As a precaution, the City has installed
enhanced aeration spray nozzles at its water treat.nent plant to rarove volatile
organic canpounds through volatilization.
C.
Soil/Refuse
Refuse borings conducted at the landfill site in the buried refuse
area indicated the subsurface naterial to be a dark loamy organic soil that was
mixed with chunks of concrete and rubble. No soil staining was observed below
the refuse in the burned refuse area.
Borings conducted on the edge of burned
areas and unOOrned areas indicated soil staining to depths 8 to 15 feet below
the refuse.
Chanical analysis of soils collected below the refuse indicated
metals to be present in concentrations slightly above background at nonhazardous
levels.
No EPA organic priority pollutants were detected in soil samples,
except for di-n-b.1tylphthalate, ranging in concentrations fran 330 to 1,600
milligrams per kilogram (mg/kg). Di-n-b.1tylphthalate is a widely used
plasticizer catp)Und in the nanufacturing of plastics, textiles, cosmetics,
insecticides, arx:t coatings/adhesives.
D.
Air Quality
Air quality IIDnitoring was also conducted during the RI.
M:>nitoring
did not indicate any extended releases of organic vapors or methane above
---- -------....--
._'--""'-'----~_.n....._.._..._~.. .... ... --..-.- .....- .
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background at ~;-,c s.:.t.e which may have been hazardous to on-site workers.
No
. ,
detectable vapors or ne,thane was detected at the perineter of the site.
SUMMARY OF RISKS
VI.
The landfill has been identified as a source of inorganic and organic
contaminants in the local ground water beneath the landfill site. Other
possible sources of contaminants to the ground water in the vicinity of the
'landfill have not been 'verified as actual sources.
The concentrations of contaminants found in nonitoring wells in the fill
area and untreated water f:ran one municipal well (City Well 7) have exceeded
State Applicable or Relevant and Appropriate Requi.I:ements (ARARs) as shown in
Table 1.
The RI conducted during May through Septa11ber 1987 has deteDnined that
the only significantly affected nedia at the site is the gJ:OUnd water of the
glacial drift aquifer. No contamination of the ambient air or local surface
waters have been found and only insignificant levels of contaminants were found
in the soils below the refuse. Hence, the only nechanism for transport of
chemicals f:ran the site is the ground water of the glacial drift aquifer.
It is
believed that deeper aquifers are protected due to the presence of a thick clay
layer underlying the site. This thick clay would be expected to be a confining
layer to both ground water flow and contaminant transport.
As previously discussed, the ground water of the glacial drift aquifer is
used in the vicinity of the landfill for a variety of purposes. The primary use
is for water supply. Thus, the only pathway of concern for I1urtan exposure to
the contaminants would be f:ran ingestion of the ground water.
Several :resideoces east and south of the Site :rely on datestic wells for
hmnan consunption. Water quality analysis indicates that these wells are
unaffected by contaminated ground water under the landfill.
Residences west of
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be used only for nonhuman consumption ptlqX>ses.
the Site are supplied with city water and any associated wells are believed to
five wells and is loc~ted downgradient of the fill area, with the cit.y water
The city well field consists of
supply well 7 located nearest to the site.
This well field supplies the entire
p:>pulation of the City of Windon, approximately 5,900 people, with p::>table
water (approximately 12 to 24 million gallons per ITDnth).
Several inorg~c and organic constituents have been identified in the
ground water beneath the fill area.
above background include amronia, nitrate and arsenic.
The inorganic canpounds which have been detected at levels significantly
Amronia is not a concern
for this health assessnent because as amronia migrates fratl the reducing
conditions beneath the fill to a ITDre oxidizing envirornnent away fratl the fill,
amronia transfonns into nitrate.
Hence, before arrncnia reaches a p::>int of
exposure, it would ITDst likely be in the fom of nitrate.
Thus, the health risk
assessnent for nitrogen cCl1pJunds focuses on nitrate.
to 2.6 ng/I.
The nitrate concentrations have been detectable within the fill area up
At the per.ineter wells nitrate concentrations have generally
ranged as high as 4.6 ng/l.
Concentrations above 10 ng/l drinking water
standard at per.ineter wells have been found on two occasions but have not been
conf.inted by recent sanpling.
Samples and water supply sanples do not indicate
the presence of nitrate.
Thus, the exposure dose to humans due to nitrate was
found to be insignificant.
Arsenic concentrations at the fill area did on a few occasions exceed the
50 ug/l drinking water standard. Arsenic has been designated by EPA as a human
carc;inogen.
However, arsenic was not detected at the perineter wells or at City
Well 7.
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Arsenic would not be expected to migrate away fran the fill area due to
near neutral pH q:mditions of the ground water.
Neutral pH conditions are
generally not conduciVe to m::>bilizing heavy rretals in ground water.
Hence, the
exposure dose to populations fran arsenic through consumption of drinking water
was found to be insignificant.
Volatile organic c~ (VOC' s) have also been detected at elevated
concentrations near the fill area.
The VOC' s that have been identified in
significant concentrations which may have toxic or carcinogenic effects fran
exposure include PCE, 'I\:E, 1,2-0CE, vinyl chloride and benzene.
A sunmary of
-
concentrations detected are presented in Table 1.
These catp:>unds, particularly
1,2-OCE and vinyl chloride, have exceeded drinking water standards or criteria
on many occasions at m::>nitoring wells in the fill area.
site.
Only trace amJuntS of 1,2-OCE have been detected at the perineter of the
This suggests that volatile organic canpounds have not migrated CMay fran
the landfill.
Migration is probably being attenuated through various natural
processes .
Even though it does not appear that contaminants are presently migrating
beyond the fill area, untreated water fran City Well 7 has shown the presence of
two volatile organic canpounds, 1,2-OCE and vinyl chloride.
Concentrations in
untreated water sanples fran City Well 7 have been detected up to 2. 1 and 5
ug/l, respectively, for 1,2-OCE and vinyl chloride.
Vinyl chloride on several
occasions has equaled or exceeded the Maximum Contaminant level of 2 ug/l in
untreated water.
1,2-OCE has ranained well belCM the Rec.-c.llIl::!nded Allowable
Limit (RAL) of 70 ug/l.
See Table 1.
Although these two canpounds have been detected, the likelihocxi of human
exposure is negligible. The 1, 2-OCE concentrations are well belCM established
drinking water criteria.' Vinyl chloride has been detected at or slightly above
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the federal drinking water standards on several occasions in untreated water.
Vinyl chloride ha~ been designated by EPA as a carcinogen.
The presence of vinyl chloride and 1,2-OCE at the observed concentrations
in untreated water at City Well 7 does not pose a significant threat to human
heal th at this time for several reasons:
1.
Health risks associated with vinyl chloride occur over an
. extended period of time (i.e. lifetime exposure of 70 years).
Based on the
m:mitoring period of record, there does not appear to be a long history of vinyl
chloride being present at City Well 7.
2.
-
City Well 7 is used only 7 to 10 days each Ironth.
Thus there
was a very limited exposure to the cClt1pO\md over an annual period, if any
exposure was, in fact, occurring.
3.
Vinyl chloride and 1,2-0CE, due to their high volatility, are
probably stripped and further diluted to safe levels as it passes through the
filtration and distribution systen. To date, vinyl chloride has not been
detected in treated water in public distribution systen.
4.
Volatile organic canpounds which reach Well 7 are further
raroved by the m:x:li.fied treatment systen (aeration nozzles) prior to reaching
the distribution systen.
5.
If vinyl chloride and l,2-OCE begins to consistently appear in
City Well 7 and the present water treatment systen is not successful in treating
these levels in the distribution systen, additional action will be taken such as
closing down the well or inproving the water treatment systan to prevent vinyl
chloride fran reaching the public.
Drinking water criteria for VO:'s has not been exceeded in treated water
in the distribution systan. Thus, the estimated exposure to humans fran VCX::'s
was found to be insignificant.
~.;
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Al though elevated concentrations of inorganic and organic contaminants
have been detected in ground water beneath the landfill, the contaminants
leaching fran the fill' do not appear to have migrated to any human exposure
point.
funitoring well data does not indicate that contaminants are migrating
off-site.
Hence the present risk to human health associated with the landfill
itself is negligible.
If contaminants are observed to be migrating in
. significant concentrations fran the fill area in the future, the risk to hLm1a115
would increase because the city water supply wells are located downgraclient of
the landfill.
VII.
IXX:UMENrATIoo OF SIGNIFlCANI' CHAN::;ES
No significant changes have been made since the publication of the FS and
Proposed Plan.
VIII.
DESCRIPl'IOO OF ALTERNATIVES
The main objective for rate:lial actions is to abate or minimize ground
water contamination and prevent migration of volatile organic catpounds fran the
Site and thereby protect the aquifer and the city of Winda1\'s water supply.
Feasibility Study report prepared by Wenck Associates (dated September 1988)
The
assessed fourteen technologies as p:>ssible rate:tial action al ternati ves ( see
Table 2).
These ranedial action technologies are categorized under three main
objectives; 1) protect the municipal water supply, 2) minimize leachate
generation, and 3) control contaminant migration.
IX.
INITIAL SCREENIN:; OF AL'reRNATIVES
,
After fourteen rate:lial action technologies for the three objectives were
identified, the rate:tial action alternatives weI:e then assessed and screened.
Table 3 is a sUl'll11ary of the initial screening which briefly states the
advantages or disadvantages of each al ternati ve ranedial action.
associated with various rate:lial actions are given by Table 4.
Costs
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x.
FINAL SCREENING OF ALTERNATIVES AND SUMMARy OF CCl-!PARATIVE ANALYSIS
Table 5 p~sents the results of the final alternative screening process
and the reasons for rejecting or retaining the rareclial action alternatives
under consideration.
Alternatives were further evaluated using the following criteria based on
u. S. EPA guidance for Records of Decision (ROD):
* Reduction of Toxicity, M:>bility, and Volmne - 'nUs criterion evaluates
the anticipated perfoDMnCe of trea1:nent al temati ves.
* IDng-Tem Effectiveness - This criterion evaluates the long-tenn
protection of human health and the environmant at the canpletion of
I:aTedial action. It is assessed in the magnitude of residual risks,
adequacy of controls in achieving cleanup criteria, and reliability of
controls against possible failure.
* Short-'l'eDn Effectiveness - The effectiveness of alternatives in
protecting hmnan health and the envi.roment during implanentation of
I:aTedial action is evaluated by this criterion. Short-tenn
effectiveness is assessed by protection of the ccmnunity, protection
of "-Urkers, environmantal impacts, and time until protection is'
achieved.
* Implanentability - This assessnent evaluates the teclmical and
administrative feasibility of alternatives and the availability of
services and materials.
* Overall Protection of Human Health and the Envirorrnent - This
assessnent draws on the results of the above evaluations to describe
whether, and l'1ow, each alternative provides protection of human health
and the envi.roment.
* Carpliance with ARARs - The assessnent against this criterion
describes l'1ow the alternative CCI'Iplies with ARMs, or if a waiver is
required and l'1ow it is justified.
* Cost - '!be estimated capital, annual maint:enaoce and IIDnitoring, and
present "-Urth value costs are evaluated by this criterion. Present
"-Urth costs are calculated using a ten percent discount rate over a
30-year period of operation. Cost estnnate sumnaries of al ternati ve
I:aTedial actions are given in Table 4.
* State kceptance - The State of Minnesota (MPCA) is the lead agency
for the site.
* Carmunity Acceptance - Carmunity acceptance to the alternatives is
included in this Record of Decision (ROO).
. -.--..-. -.
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The reredial action alternatives which passed the initial screening
process were evaluated in depth using the criteria described above in a
comparative analysis.
The results of this process are surnnarized in Table 6.
In sum, this process gave the highest ratings to the following three reccmrended
ranedial actions; protect the municipal water supply by ITDCtifying the existing
water treatnent plant, minimize leachate generation by site capping, and control
. contaminant migration by groW1d water plUTq:> out and leachate treatnent (Table, 6
alternatives lB, 2B. and 3B, respectively).
The following discussion evaluates
the three recamended ranedial actions.
A.
Protect Municipal Water Supply by M:x:lifying the Existing Water
TreatJrEnt Plant -
Reduction of Toxicity, M:>bility, and Volune ('lMV) -
As stated in the description of this alternative, the two
contaminants foW1Ci in City Well 7 (vinyl chloride and 1,2-0CE) are highly
volatile.
Pressw::e spraY,nozzles will break the raw water into fine droplets,
thereby increasing the surface area of the water for greater water-air contact.
In addition to the spray nozzles, power ventilators will increase the rate of
airflow through the systan and provide greater air-water contact.
The
canhination of these two maasw::es have been shown to effectively ratDVe volatile
catq:X)UI1ds including vinyl chloride and 1,2-0CE.
Effectiveness will be
da1Dnstrated through perfonnance ItDnitoring.
Should contaminant drinking water
criteria be exceeded in the distribution systan, IRXlification of the existing
treatnent systan or ~larentation of an additional treatnent systan will be
required. .
Short and IDnq-Tenn Effectiveness -
, . '
As part of the overall water treatnent systan, the
ITDCtifications would be useful for an indefinite period of time.
Individual
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canponents such as spray nozzles, vents, or blowers may need to be replaced
pericxtically, but the.overall effectiveness of the treatment would not be
altered.
Implanantability-
The proposed m:x:lifications are relatively simple and would
require parts that can be readily obtained through equipnent vendors.
Operation
of the systan would only require additional electrical supply to power the
ventilators.
The operation of the m:x:lifications would be considered very
reliable.
Infrequent replacanant of individual ccrrp:>nents may be required, but
these parts can easily be obtained thereby minimizing maintenance downtime.
The m:x:lifications employ the sane technologies utilized in
spray irrigation systems and air stripping systems which have successfully been
used for ground water cleanup at other sites.
Implanantation of the proposed m:x:lifications would result in
the release of lCM concentrations of volatile organic canpounds to the
atm:>sphere .
No adverse envirormental impacts are expected as a result of the
m:x:lifications given the low concentrations involved.
During inplanantation and maintenance of the treatment system,
the flCM of water would temporarily be shut off.
Hence the risk of workers
being exposed to the volatile organic caTIpOUnds would be minimal.
'!be power
ventilators would release the volatile organic caTIpOUnds to the at:nDsphere
thereby minimizing the risk of worker exposure during routine operation.
Given
the lCM concentrations of volatile organic caTIpOUnds currently observed in the
water supply, no adverse effects are expected.
Calculations derronstrating the
lCM"risk of exposure are presented below.
No fire or explosion threats are
anticipated.
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Water leaving the treatment plant must not exceed the water
'\
quality standards . set forth in Minn. Rules ch. 7050 and the U.S. Primary
Drinking Water Standards (40 CFR, Part 141).
Protection of HlDTIall Health and the Environrrent -
By .iJ1q:>latenting the proposed mxlifications, vex:' s ~uld be
reroved fran the city water suWly thereby minimizing the risk of exposure
, through ingestion. Volatile organic canpounds rencved fran the water ~ld be
vented to the atm::>sphere.
However, given the low concentrations of VCX::'s in the
water, concentrations in the atm::>sphere are not expected to present a
significant health risk, as discussed in the following section.
Furthenrore ,
the water tI:eatm:mt plant is located in a relatively undeveloped area (Le.; no
residential hcmas or businesses); therefore, the exposure risk ~ld be
minimized. Any air anissions as a result of the mxlification ~ld be below
relevant requirements. MJnitoring of the distribution system will continue and
a contingency plan to roodify or enhance the treatrnent system will be iroplatented
if drinking water criteria are exceeded.
Ccmpliance with ARMs -
Safe Drinking Water Act (SWDA); 40 ern Parts 141-146.
The SrMA
sets forth maxinn.Jm contaminant levels for contaminants in public drinking water
supplies.
The Windcm Municipal Well Field is downgradient of the landfill.
However, no M::L, have been exceeded within the distribution system.
FurtheIJn:>re, the city has installed several additional spray nozzles which will
increase volatilization of volatile organic canpounds in the event they should
reach the water sUWly well.
Bel~ is a CCI1paIison of potential air anission concentrations to Threshold
Limit Values (TIN's) for 1,2-OCE and vinyl chloride.
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Assume volat. .,Ie organic CaT1pOunds canpletely volatilize fran
water. Assu.'€ design air:water ratio is 20:1.
Maximum cis-l-,2-dichloroethene concentration detected at City
Well.7 is 2.1 ug/l, to date.
2.1 ug/l x 1,000 11m3 x 1 mg/1,000 ug = 2.1 mg/m3.
2. 1 mg/m3 120: 1 dilution factor in air = O. 11 mg/m3 in exhaust
air.
Threshold Limit Value for 1,2-dichlo:rethene is 790 mg/m3 in air
for eight-hour tine-weighted average (ACGIH, 1988).
'I11e:refo:re, the theo:retical max.iJIun 1, 2-dichloroethene
concentration in air exhaust is about 7,000 tines belav-' the
acceptance max.imum air concentration not taking into account
dispersion i!l the a1:nDsphere.
Maximum vinyl chloride concentration detected at City Well 7 is
5 ug/l, to date.
5 ug/l x 1,000 11m3 x 1 mg/l,OOO ug = 5 mg/m3.
5 mg/m3 120: 1 dilution factor in air = 0.25 mg/m3 in exhaust
air.
Threshold Limit Value for vinyl chloride is 10 mg/m3 in air for
eight-hour tine-weighted average (ACGIH, 1988).
The:refo:re, the theo:retical max.imum vinyl chloride concentration
in air exhaust is about 40 tines below the acceptable maximum
air concentration not taking into account dispersion in the
a1:nDsphere.
'Ihe aOOve calculations may need updating if VOC levels
increase. Treat:nent of VOCs in the vapor phase may also be
requ.i:red in the futu:re.
Costs -
-
Costs for mxfifying the water treatm:mt plant are S\DtI1\aI'ized in
Table 4. Costs for inplE!1enting the m:xlifications are relatively small. M:>st
of the operation and maintenance costs are associated with ItDnitoring to
dem:>nstrate treat:nent efficiency.
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State Acceptance -
For protection of the municipal water suWly, the MPCA staff
has selected the alternative consisting of a m:xiification of the existing water
tI:eatmant plant. This alternative has already been voluntarily implarented at
the plant by the city of Windan.
Carmunity Acceptance -
A public cament period for the Feasibility Study (FS) and the
recarrrended alternative began on JanuaIy 10, 1989. Copies of the RI and FS
Reports, the Fact Sheet detailing the al ternati ves evaluated and the reccmnended
alternative, were made available to the ccmnuni.ty at that tine. The Windan City
Hall serves as the infonnation repJsitory for the ciocurtents. MPCA issued a news
release and placed a notice in the Windan newspaper announcing the public
ccmnent period and outlining the alternatives ~aluated and the recamended
alternative. A public neeting was held on January 17, 1989, at W.indan City
Hall.
No public camentswere received during the 30 day public cament period.
B.
Minimize Leachate Generation by Site Capping -
Reduction of Toxicity, M::>bility, and Volmne -
Capping the site is interrled to minimize infiltration of
precipitation with use of low-penneability catq::>acted clay. The effectiveness of
the cap will be enhanced through grading of the site to a mi.nim..mt slope of two
percent to praoote surface water run-off. The site will be revegetated thereby
increasing the effectiveness of the cap through proper stabilization of the
cover and erosion control.
Short and IDng-TeDn Effectiveness -
The useful life of a cap is uncertain, however, the anticipated
design life is estimated to be greater than 30 years. The useful life of the
cap will be maintained through proper long-tenn postclosure care of the site.
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infil tration of Precipitation into wastes.
Dmplementability -
Capping is known to be a reliable technology. for preventing
to be canpleted at landfills under MPCA Solid Waste Managem:mt Rules (Minn.
Rules pt. 7035.2815), and thus is considered !to be the best practical technology
Closure which includes capping is
for minimizing leachate generation.
Grading and capping of the site can be easily implatented. Site
capping activities can be perfoDTed using heavy equiptent which is readily
available such as graders, bulldozers, and rollers.
The soil materials such as
native clay for the cap and sand and gravel for drainage layers are also readily
available nearby.
Postclosure care is necessary to ensure proper function of the
cap.
The cap must be inspected pericxlically to check for settlatent, erosion,
pending of Precipitation, and breaching.
nine ItDnths.
It is estimated that the tinE to implatent this option would be
This pericx:i would include tinE for topographic surveying of
plans and specifications and bidding docurrents, soliciting bids, selecting a
existing site conditions, preparing a grading plan, designing the cap, preparing
contractor, and actual construction.
Minn. Rules pt. 7035.2815. AR;>roval fran the county or township may also be
needed dependent upon the location of the borrow area for clay or other soil
Closure activities of the site will be in confonnance with the
materials.
health by minimizing further ground water impacts fran the site.
Protection of Human Health and the Enviroment -
Capping of the site would have beneficial inpacts to public
During
construction, no significant safety conceD1S are expected.
Physical hazards for
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workers will exist due to moving equipment on-site.
Fugitive dust emissions
will occur during' grading, ,ha.Yever, these emissions will be controlled as
necessary by watering the site.
No chemical hazards are expected since wastes
are not expected to be disturbed during the grading of the site.
~r, the
site safety plan for construction will need to address any contingencies in the
event of chanical hazards being encountered.
Capping the site would also be beneficial to the environment by
having p:>sitive impacts on local water quality.
Closure would improve the
aesthetic appearance of the site.
During grading, neasures such as placarent of
silt fences should be taken to prevent run-off of sedi.nEnt into surface waters
until the vegetative cover is established.
Cat1pliance with ARM's -
Installing a designed cap in accordance with Minn. Rules pt.
7035.2815 will minimize leachate generation and reduce ground water
contamination.
subpart 6.C of this rule calls for a 2 foot canpacted clay
barrier layer overlain by a 1 foot layer of granular material and topsoil.
Costs -
4.
Costs for grading and capping the site are sumnarized in Table
Grading costs will be highly dependent upon the final grading design and the
. anuunt of earthwork required.
Costs for the cap are highly dependent upon the
proximity of the clay borrow area to the site.
Proper grading and establishnEnt
of a vegetative cover should also minimize annual operational and maintenance
costs to repair the cap.
State Acceptance -
'l11e MPCA staff has selected the installation of a clay cap, in
accordance with Minn. Rules pt. 7035.2815 as the ratedial altemative for
reducing leachate generation.
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Ccmnuni ty Acceptance -
A. public ccmnent period for the Feasibility Study (FS) and the
recoornended alternative began on January 10, 1989.
Copies of the recamended
alternative, were made available to the Ccmnunity at that time.
The windan City
Hall. serves as the infonnation repository for the documants.
MPCA issued a news
release and placed a notice in the Windan newspaper announcing the recamended
al te.rnati ve. A public' neeting was held on January 17, 1989, at Windan City
Hall. No public caments were received during the 30 day public CCJmEnt period.
C. Control Contaminant Migration by Ground Water Pump Out And
Treatnent -
Reduction of Toxicity, M:>bility, and Volume -
If intervention limits in ITDnitoring wells are exceeded in the
future, a ground water pump out/treatnent systan would be installed between the
well field and the landfill to intercept contaminants migrating fran the
landfill. Purrq:> tests show that wells can be designed and constructed so that
the cone of depression 'NOUld intercept contaminants migrating fran the landfill.
'IMV of the contaminants would be reduced by a treatment systan which would be
designed to handle the pump out water.
Continued ITDnitoring for intervention limits (Table 7) in
ITDnitoring wells and residential wells around the perineter of the Site is
sufficient at this time to assure that further rate:lial action would be
inplemmted in a timely fashion, if the ground water resource or mmicipal well
field are inpacted by future contaminant releases fran the Site..
Short and IDng-Tem Effectiveness -
If inplarented the life of the ground water pump out system
would be designed based upon the time necessary to renediate the ground water to
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acceptable levels.
This v.'": :.lId be dependent upon the extent and magnitude of
contamination at 17he t.i1te of .iJT1planentation.
Controlling contaminant migration through ground water pump out
and treatment has been shown to be effective at many sites across the United
States. One such site is the Washington County Sanitary Landfill No. 1 in lake
ElIro, Minnesota. At that site a gradient control well systan was .iJrplanented to
. capture contaminated ground water found to be m:wing in the direction of a
residential area which used the aquifer for water supply.
The effectiveness of any such systan would be daoonstrated
-
through pilot testing as well as ongoing m:>nitoring of ground water and
treatment systan discharges.
Inq:>lanentability -
Operation and maintenance requiren'ents would include
winterizing the systan, to prevent freeze-up of pumping, piping, or treatment
facilities in order to ensure year-round operation, nonnal maintenance and
replacanent of parts such as pumps may be necessary periodically to ensure
maximum operation efficiency.
If an on-site treatIrent scheme is used such as
spray irrigation, then maintenance of the treatmant area soils \tJOUld be needed
periodically to ensure proper infiltration.
A ground water pump out and treatIrent systan can be easily
inplanented. Materials are readily available fran vendors and drillers for
installing ~ing wells and treatmmt facilities.
No special problan \tJOUld be
anticipated with constructing such a systan at this site.
An estimated four IIDnths \tJOUld be needed to inplanent such a
system fran the time a ground water control system is dcatled necessary.
'l11is
would include time for studies, system design, construction, as well as
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peDILiLLillY.
\...untinued ground. water rroni toring would .be necessary to deteDTline
the length of time to operate the systatl.
Regulatory approval fran the MPCA would be needed to implarent
the systatl as ~ll as Minnesota Department of Health for construction of ~lls
and. the Minnesota Departm:mt of Natural Resources for appropriation of the
ground water.
Protection of Human Health and the Environment -
Irnplarentation of a ground water pump out systatl, if
inte:rvention limits are exceeded, would benefit public health.
The. pump out
systatl would control the ItDVanent of contaminants, thereby preventing migration
to points of use. l-bnitoring of volatile organics in the air would also need to
be conducted, dependent upon the treat:nent systatl used, in order to ensure no
exposure of the public to air-borne contaminants.
No significant safety concerns are anticipated with
construction.
A rareclial action site safety plan would address the need for
proper personal protective equiptEnt during drilling of pump out ~lls.
Ground water pump out would .benefit the environment by raroving
contaminants and controling contaminant migration, and thus protect the ground
water resource. No significant negative impacts to the environment are
anticipated fran this type of systan. Water levels would need to be Jronitored
in the area to ensure private .~lls are not affected by ground .water drawdown at
the punping ~lls.
Influence on other production wells in the area would be
addressed during the design phase of such a systan.
Canpliance with MAR's -
In order to protect public health and the environment fran
contaminant migration in the future, the intervention limits and standards as
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set forth in Minn. Rules pt. 7035.2815, Subp. 4.F shall apply.
Table 7 presents
a partial listing. of intervention limits for cClTIpOunds of major concern at the
Site.
Minn. Rules pt. 7050.0220 requires that discharges to ground
water which will be used for consumption attain M:Ls and RALs for drinking
water. '!he ground water pLm1p out systan, if implemanted, would not discharge to
the ground water. However, contaminants would be drawn fran the landfill
leachate into the ground water. Any contaminants however, would be treated by
the plm1p out systan, thus the ARM would be attained.
Any discharge of pLm1p out water to surface waters shall be
required to neet the provisions of Minn. Rules pt. 7070 and a National Pollutant
Discharge Elimination .Systan (NPDES) peDnit shall be obtained.
Costs -
Costs for this alternative are sumnarized in Table 4.
Construction costs are highly dependent upon the number of wells and the type of
treatment systan. These factors would be deteIJni.ned precisely during a design
phase.
It is anticipated that the least expensive treatmant scenario for both
capital and annual operation and maintenance costs would be spray irrigation, as
opposed to treat:nent and ctischarge to the stonn or sanitaJ:y sewer systan.
State Acceptance -
'!he MPCA staf.f has selected the ground water pump out systan
1:eIIWYas the selected ~I-=dy if in the future it is detennined that such a
systan should be installed.
Camtunity Acceptance -
A public carmant period for the Feasibility Study (FS) and the
recamended alternative began on January 10 I 1989. Copies of the RI and FS
Reports I the Fact Sheet detailing the al ternati ves evaluated and the recamencled
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alternative, were !MOO available to the Ccmnunity at that time.
The Windan City
Hall serves as the. infonnation repository for the documents.
MPCA issued a fle'.NS
release and placed a notice in the Windan fle'.NSpaper annoW1Cing the public
carment period and outlining the al ternati ves evaluated and the recarmended
alternative. A public neeting was held January 17, 1989, at Windan City Hall.
No public caments were received during the public carment period.
XI.
SELECTED ALTERNATIVES
Based on the. screening process, and the detailed review in consideration
of the evaluation criteria (Table 6), the MPCA staff selects the recarmended
. alternatives as the nost appropriate final raoady for the Windan Landfill Site.
This ralr::=Jy is divided into three al ternati ve ranedial action objectives as
discussed below.
Objective 1)
Protect Municipal Water Supply -
This alternative called for m:xlifications to the existing water
treatm:mt plant as previously described.
These m::xtifications have already been
inplem:mted.
'n1e m:xlifications enhance volatile organic CCITp)UI1d raroval during
the water treatment process.
Raw and treated water were tested m:>nthly for
three consecutive IIDnths for the presence of volatile organic catp)Unds after
inplatentation of the m::xtifications.
These tests have dem::>nstrated the raroval
efficier1cy of t~c ~-i.fi~ '..:ater treatnent process is successful in Ireeting
drinking water starrlards.
Quarterly testing is now perfoDDed and the systan
will continue to be evaluated as part of the Rene::lial J\ct.ion Plan/Closure Plan
(RAP/CP) .
'n1e RAP/cp will provide any further rec:cAlllendations to be perfonned
if necessary to achieve greater efficiency, or reculllt:=nded actions to pursue
another alternative to protect the municipal water sUWly if results of the
m::xtifications are not effective.
_. ...,- ...
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Objective 2)
Minimize Leachate Generation -
It is recatTlEnded that the site be closed in accordance' with MPCA
Solid Waste Rules, which reCp.ire grading and capping the site.
Implarentation
of this alteD1ative may eli.minate the need for iJrplarenting ground water pump
out and treatment systems in the future. The grading plan, cap and cover
design, as well as nethods for construction and tinetable will be presented as
part of the RAP/cp.
Objective 3) Control Contaminant Miqration -
At this tine it is recatTlEndedthat no action be taken with regard
to active control of ground water at the site. Currently, no significant ground
v.'ater impacts are appa...--ent at the Site perineter wells.
Thus no significant
benefits would be gained with regard to iJrprovatent of ground water quality at
the Site for the arrount of cost incurred.
However, the RAP/CP will include a contingency plan which would be
implemented if, in the future, any single intervention limit is exceeded at any
Site perineter well or nonitored residential well. Table 7 presents a list of
intervention limits for canrxmnds of major concern.
The contingency plan shall
require quarterly sanpling of the perineter and nearby residential wells. After
every quarterly sanpling event of these wells, the analytical results shall be
canpared to the intervention limits.
If subsequent sanpling results indicate
that any single intervention limit is exceeded for the sane paraneter at the
sane well during the next two quarterly sanpling events (exceedence for a total
of three consecutive. quarters), a ~rk Plan for a ground water pump out system
shall be subnitted to the MPCA within sixty (60) calendar days of such
deteDnination. The ~rk Plan shall include an iJrplarentation schedule for the
pump out systan. Grow1d water pump out and treatmant shall continue for the
duration specified in the approved ~rk Plan.
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-28-
XII.
S'rATUroRY DETERMINATIONS
A.
Protection of Human Health and Environment
The selected J::'E!TEdy is Protective of human health and the
environment, attains federal and state requirenents that are applicable or
relevant and appropriate to this I:'E!IEdial action, and is cost-effective.
The
selected rE!1I1::rly protects public health by mxlification of the municipal water
treatnent system to ratDve any volatile organic canpotmd which ffi3Y be contained
in the ground water. supply. The treatmant system will maintain, at a minimum, a
risk no .greater than 10~5 cumulative lifet.ine excess cancer risk and
concentrations less than the K:L. The risk of exposure to contaminants
volatized by the treatmant system is less than 10-5 risk criteria. This system
will ranain effective as long as proper maintenance and JOOnitoring occur.
The
landfill capping raredy ,is
Protective of human health and the environment.
Capping will reduce Wil tration and thereby reduce the risk of grotmd water
contamination. This reu-=uy satisfies the statutoJ:Y preference for ratedies that
anploy treatmant that reduces toxicity, JOObility or volUIIE as a principal
elanent and utilizes peImanent solutions and al te.mati ve treatmant technologies
to the maximum extent practicable.
B. Attainment of ARAR' s
The selected alternatives will neet the follCMing federal and state
ARAR's:
1. Resow:t:e Conservation and Recovery Act (RCRA); 40 CFR Part 264.
RCRA (40 CRF Part 264) requires the :rem::wal of all waste residues and soil
contaminated with hazardous waste. However, RCRA has not defined the level of
decontamination required. EPA guidance requires that any contaminants left in
subsoils will not inpact any envi.romental nedia.
The cap will further reduce
and --. control any minor ancunts of VO::s ranaining in the subsoils that ffi3Y mJve
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-29-
downward through the soil column and enter the shallow ground water beneath the
Site.
A ground water punp ?ut/treatment alternative has been prepared for
irnplerentation in case shallow ground water becc:mes contaminated.
2.
Clean Water:Act (CWA); 40 CFR Parts 122 and 125.
Treated ground water will be utilized by the municipal water supply.
is planned for discharge to surface waters at this time.
No water
3.
Safe Drinking Water Act (SrMA); 40 CPR Parts 141-146.
The SOOA specifies M:Ls for contaminants at plblic drinking water supplies.
The
ground water beneath the Site is near the capture zone of the Windan City Well
7, however, a treatnent systan is already in place for the water supply.
Windan water supply is currently neeting M:Ls.
The
4.
Minn. Rules pt. 7035.2815.
State solid waste managarent rules are applicable to this Site.
These
regulations became effective in 1970 and were revised in 1973.
They were in
effect at the tirne the windan landfill ceased operation in 1974.
New solid
waste managenent rules pranulgated in 1987 and amended in 1988, have interim
requirerrents for landfills closed within 18 m:>nths of the effective date (Le.,
before May 15, 1990).
It is anticipated the interim requirements will be
applicable for the rena:li.al actions at this Site.
Closure of the foDreI' Windan M.mi.cipal Landfill is expected to be
canpleted by Septenber 1989.
The final cover to be installed and closure
certification of the Site is designed to be in confoDnanCe with those rules.
The awlication of the ground water inte:rvention limits and standards
set by Subpart 4.F. will protect the enviroment and is consistent with the
State ground water protection strategy based on the goal of nondegradation of
ground water resources.
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-30-
5. Minn. Stats. 115 and 116 and Minn. Rules chs. 7001 and Minn.
Rules pt. 7050.021.
There is no discharge 'to surface water in the al ternati ves being ilrplatented at
this tine.
6. Minn. Rules pt. 7050.0220.
This rule requires that discharges to ground water which will be used for
. consurtption attain M:Ls and RALs for drinking water.
The selected alternative
will not discharge to ground water, however as stated previously, minor anounts
of va:s may nove c:icMnward through the soil to the ground water within the
capture zone of the pump out system where they will be raroved and treated.
7. Minn. Stat. S 116.07, subd. 4.A.
The operation of the aeration nozzles (air stripper) will not require. an air
quality peDnit W1der this statute, which regul~tes air anissions of toxic
pollutants. The emissions have calculated and are well below, the adverse ilrpact
level and therefore do not require additional control neasures.
Where State ARARs are m:>re stringent than Federal ARARs, the State
requi.ranents will be met at the canp1etion of the remedial action.
C.
Cost-Effectiveness
All costs have and will be borne by the Responsible Parties under tenns of the
existing RFRA.
D.
Utilization of Pennanent Solutions and Alten1ative Treatment
Technologies to the Maximum Extent Practicable
The MPCA has deteDnined that the selected .Lt::Il~ is the m:>st appropriate
solution for neeting the remedial action goals at the Windan Dump Site. The
selected .rell-=dy provides the best balance ancng the evaluation criteria (Table
6) .
The selected ratedy is a pennanent solution that uses al ternati ve treatment
technologies to the maximLmt extent practicable.
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-31-
E.
Preference for Treatment as a Principal Element
The statutory preference for remedies that employ treatnent which pennanentl y
and significantly rec.h.ice the toxicity, Jrobility, or volune 'of hazardous
substances as a principal element is satisfied since the contaminants
transferred to the air will be degraded by naturally occurring processes.
XIII.
SQiEDULE
The ratedial action for the Site is expected to be inplatented in
accordance with the. following schedule:
- Execute RCD and approve FS
- Approve remadial action Plan
April 1989
April 1989
- Implatent remadial action
May 1989
Septanber 1989
- Site Closure Certification
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TABLE 1
SUMMARY OF CON::ENI'RATI~ DETECTED
FOR ASSESSIH; HEAL'IH RISK
FORMER WINJX'M MUNICIPAL U\NDFILL
Ca1pJund ARAR* Background Fill Area Perimater City ~ll 7
(untreated )
Nitrate-Nitrogen (ng/l) 10.0 <0.05 <0.05-2.6' <0.05-15? <0.05
Arsenic (ug/l) 50 <5 <1-75 <5 <5
1,1,2,2-Tetrachloroethylene (PCE) (ug/l) (6.6) <1.0 <1.0-48 <1.0-5.6? <1.0
1, 1, 2-Tr ichloroethy lene ('R:E) (ug/l) 5 <1.0 <1.0-35? <1.0 <1.0
1,2 cis Dichloroethylene (OCE) (ug/l) (70) <1.0 <1.0-730 <1. 0-1.2 <1.0-2.1 .
Vinyl Chloride (ug/l) 2 <1.0 <1. 0-210 <1.0 <1.0-5
Benzene (ug/l) 5 <1.0 <1.0-21? <1.0-32? <1.0
Note: levels of all listed canpounds in treated water in the Fcl>lic distribution
system after treat:mant have not been detected above ARAR' s .
*ARAR's .include Maxirm.nn Contaminant levels, M:L, and Recrnmanded Allowable
Limits, RAL. RAL' s are denoted by parentheses.
. .
Background = ~ll nest MW-7
< = less than
Fill Area = lfi-5, SA, and 6
? = High range of data unconfiDred .
by ~ent sanpling
Perimater = lfi-1,2 and well nests MW-8, 9, and 10
Based on data available as of March 1989.
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TABLE 2
REMEDIAL ACrION ALTERNATIVES
FORMER WINIXX-1 MUNICIPAL lANDFILL
GENERAL REMEDIAL ACrION
OBJECTIVE 1: ~ MUNICIPAL WATER SUPPLY
'I'ECHr-JJIffiIES
No Action
-1vbnitoring
Water Trea1:ItEnt
-MOdifications to existing
plant
Alternate Water Supply
-Packed tower air stripper
-Abandon water supply well/
Construct new well
OBJECTIVE 2: MINIMIZE LEACHATE GENERATION
No Action
-M:>ni toring
Source Control
-Site capping
-Removal and off-site disposal
-In-situ solidification/
stabilization
-Removal and on-site disposal
OBJECTIVE 3: CCNl'ROL CXNrAMlNAm' MIGRATION
No Action
-M::>ni toring
Plmping
-Ground water
~ out/tIea1:ItEnt
In-situ Treatment
-Bioreclamation
Subsurface Barriers
-Slurry walls/Grout
curtains/Sheet piling
Subsurface Drains
-Interceptor systans
Based on: "Feasibility Study - Fonner Windan Municipal Landfill, Windan,
Minnesota," Wenck Associates, Inc., Septanber 1988.
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TABLE 3
()
ALTERNATIVE REMEDIAL ACTION
, INITIAL SCREENIN3 SUMMARY
FORMER WINOCM MUNICIPAL LANDFIIL "
REMEDIAL ACTION ALTERNATIVE
ADVANrAGES/DISADVANl'AGES
OBJECTIVE 1: PROl'ECT MUNICIPAL WATER SUPPLY
No Action
Potential exposure to contaminants.
MJdifications to-Water TreatItent
Plant
Easily and quickly irnplanented at a
low cost ($l1K). Effectiveness needs
to be daronstrated through ItDnitoring.
Proven technology and easily
implarented rot at a much higher cost
( $84K) . Additional operation and
maintenance costs to be incurred.
Air Striwer Unit
Relocate New Well
Additional subsurface geologic,
hydrogeologic, and chanical testing
and studies necessary to site well.
Capital costs similar to an air-
stripper unit but much lower operation
and maintenance costs.
OBJECTIVE 2: MINIMIZE IEACHATE GENERATION
~
No Action
Continued generation of leachate and
impacts to ground water.
Effective proven technology. Site
grading necessary. lDwest cost
alternative ($300-800K).
Site Capping
RenDVal and Off-Site Disposal
Effective in controlling source.
Potential impacts to air quality
during excavation (fugitive dusts and
vapors) . Strict following of MPCA,
RCRA, oor and mIA regulations
requiIed. Adequate and willing
disposal facility to be located.
IDng-teDn liability incurred for
wastes at another facility. High
transport and disposal costs.
Effective technology. Potential
impacts to air quality during
excavation (fugitive dusts and.
vapors) . IBngthy and detailed
penni tting process. High costs for
construction of facility - 1 to 2
oIders of magnitude greater than site
capping.
.RenDVal and On-Site Disposal
-------
TABLE 3 (continued)
REMEDIAL ACTIOO ALTERNATIVE
INITIAL SCREENIn:; SUMMARy
FORMER WINI::X:M MUNICIPAL LANDFILL
REMEDIAL ACTIOO ALTERNATIVE
~/DI5ADVANrAGEs
On-Site Stabilization/Solidification
Extensive testing required prior to
implementation to test feasibility.
High costs of 1 to 2 orders of
magnitude greater than site capping.
OaJECTIVE 3: CCWl'ROL CONrAMINANr MIGRATIOO
No Action
Potential increase in magnitude and
extent of ground water impacts.
Ground Water PurrqJout and Treatment
Effective and proven technology.
PeJ::mi.ts needed for disposal of ground
water dependent upon disposal
alternative. LDng-tenn operation and
maintenance costs.
In-situ Treatment
Not effective for all types of organic
canpounds such as chlorinated
canpounds. Feasibility would need to
be tested through pilot testing.
Effective and proven technology for
shallow applications. ~uld need to
be implemented in conjunction with
other ranedi.al action such as pumpout
systan or drains. Potential
incanpatibility of chanicals with
barrier materials.
Subsurface Barriers
Subsurface Drains
Effective for shallow contamination
problans in lCM-hydraulic COnductivity
aquifers. Generally used in
conjunction with subsurface barriers.
Based on: "Feasibility Study - FODtEr Windan Municipal Landfill, Windan,
Mirmesota," Wenck Associates, Inc., Septanber 1988.
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TABLE 4
.u
COSTS OF ALTERNATIVE RESPONSE ACTIONS
MODIFICATIONS TO WATER TREATMENT PLANT
Construction Costs
. Equipment and Materials
Labor for Installation
$
5,000
4.000
9,000
1,000
1.000
Subtotal
Contingency (10%)
Engineering (10%)
ESTIMATED CAPITAL CONSTRUCTION COST
$ 11,000
Annual Operation and Maifltenance Costs
Labor for Increased Cleaning
Electrical Power
Monitoring
$
600
500
1.600
ESTIMATED ANNUAL COST
2,700
PRESENT WORTH OF ANNUAL COST.
$ 25,000
Summary of Present Worth Costs
Total Estimated Capital Construction Cost
Total Estimated Annual Present Worth Cost.
$ 11,000
25.000
TOTAL ESTIMATED COST
$ 36,000
*Based on a 10 percent discount rate for a 30-year operation
period
-------
TABLE 4 (CONTINUED)
COSTS OF ALTERNATIVE RESPONSE ACTIONS
PACKED TOWER AIR STRIPPER UNIT
Construction Costs
Treatment Unit & Installation
Contingency (10%>
Engineering (10%>
ESTIMATED CAPITAL CONSTRUCTION COST
$ 70,000
7,000
7.000
$ 84,000
Annual ODeration and Ma~ntenance Costs
. .
Labor/Materials
Monitoring
Electrical Power
$
1,000
2,000
6.000
9,000
ESTIMATED ANNUAL COST
PRESENT WORTH OF ANNUAL COST*
$ 85,000
Summary of Present Worth Costs
Total Estimated Capital Construction Cost
Total Estimated Annual Present Worth Cost*
TOTAL ESTIMATED COST
$ 84,000
85.000
$169,000
*Based on a 10 percent discount rate for a 30-year operation
period
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TABLE 4 (CONTINUED)
COSTS OF ALTERNATIVE RESPONSE ACTIONS
CONSTRUCTION OF NEW WATER SUPPLY WELL
Construction Costs
Permanently Abandon City Well 7
Site Selection. Studies and Tests
Construct New Well
Connect New Well to Distribution System
Subtotal
$ 6,000
15,000
17,000
38.000
$ 76,000
Contingency (10%)
Engineering (10%)
8,000
8.000
. ESTIMATED CAPITAL CONSTRUCTION COST
$ 92,000
Annual Operation and Maintenance Costs
1-
2.
Labor/Materials
Monitoring
$
.500
1.000
1,500
ESTIMATED ANNUAL COST
PRESENT WORTH OF ANNUAL COST*
$ 14,000
Summary of Present worth Costs
Total Estimated Capital Construction Cost
Total Estimated Annual Present worth Cost*
$ 92,000
14.000
TOTAL ESTIMATED COST
$106,000
*Based on a 10 percent discount rate for a 30-year operation
period
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TABLE 4 (CONTINUED)
COSTS OF 'ALTERNATIVE RESPONSE ACTIONS
SITE CAPPING
Construction Costs
Site Preparation and Grading
Clay Cap (18,000 CY compacted)
Cover and Top Soil
Seeding
Con~ingency (1~%)
Engineering (10%)
Subtotal
$140,000
250,000
250,000
20.000
660,000
70,000
70.000
$800,000
-
ESTIMATED CAPITAL CONSTRUCTION COST
Annual ODeration and Maintenance Costs
Inspections
Cover Maintenance (Repairs)
ESTIMATED ANNUAL COST
$
1,000
2.000
3,000
PRESENT WORTH OF ANNUAL COST*
$ 29,000
Summarv of Present Worth Costs
Total Estimated Capital Construction Cost
Total Estimated Annual Present Worth Cost*
TOTAL ESTIMATED COST
$800,000
29.000
$829,000
*Based on a 10 percent discount rate for a 30-year operation
period
-------
TABLE 4 (CONTINUED)
. COSTS OF ALTERNATIVE RESPONSE ACTIONS
GROUNDWATER PUMPOUT AND TREATMENT
Construction Costs
Drill Wells (2 wells @ 140' deep)
. Pumps (15 hp)
Hardware (piping, flow meters, housing, spray
irrigation)
Aquifer Testing
Per:nli tting
Contingency (10%)
Engineering (10%)
$ 25,000
6,000
Subtotal
10,000
10,000
10.000
61,000
6', 000
6.000
ESTIMATED CAPITAL CONSTRUCTION COST
$ 73,000
Annual ODeration and Maintenance Costs
Electrical Power'
Labor/Materials
Monitoring
Reporting
ESTIMATED ANNUAL COST
$ 15,000
2,000
15,000
10.000
42,000
PRESENT WORTH OF ANNUAL COST*
$396,000
Summary of Costs
Total Estimated Capital Construction Cost
Total Estimated Annual Present Worth Cost*
TOTAL ESTIMATED COST
$ 73,000
396.000
$469,000
*Based on a 10 percent discount rate for a 30-year operation
period
From:
"Feasibility Study - Former Windom Municipal Landfill,
Windom, Minnesota, It Wenck Associates Inc., September 1988.
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TABLE 5
REMEDIAL ACl'IOO ALTERNATIVES
FINAL SCREENIN:; RESULTS
FORMER WINIX>M MUNICIPAL lANDFILL
Alternative
Screening Result
Reason
OBJECI'IVE 1:
PROI'ECT MUNICIPAL WATER SUPPLY
lA No Action
Eliminated
!:bes not neet objective
1B Modifications to
Treatment Plant
Retained
Low cost, potentially effective
lC Air Stripper
ID Relocate New Well
Eliminated
Cost is prohibitive
Cost is prohibitive
-
Eliminated
OBJEcrIVE 2: MINIMIZE LEACHATE GENERATION
2A No Action
Eliminated
!:bes not neet objective
2B Site Capping
Retained
Effective and relatively
inexpensive
2C Removal/Off-site
Eliminated
Additional long-teDTl disposal
liability and high cost
2D Removal/On-site
Disposal
Eliminated
Pennitting concern, t.i.Jre to
inplarent and high costs
Site-specific feasibility
uncertain and high cost
2E On-Site Stabilization/
Solidification
Eliminated
OBJECTIVE 3: CON1'ROL CONrAMINANr MIGRATION
3A No Action
Eliminated
If impacts appear downgradient
of landfill, then it does not
meet objective
Effective technology
3B Ground Water Pmnpout/
Treatment
Retained
3C In-situ Treatment
Eliminated
Site-specific feasibility
uncertain
3D Subsurface Barriers
Eliminated
Cost prohibitive at depths
required for this site
Ineffective for this site
3E Subsurface Drains
Eliminated
-- -~ _-..n - ..-- - ..
-------
'rABLE 6 "
FORMER MUNICIPAL LANDFilL
WINIX:.:M, MINNESarA
OUTERIA EVAUlATIoo
ALTERNATIvEs GRaJPED BY OBm:TIVE
(1) (2) (3)
Protect Water Supply Minimize leachate Control Migration
Evaluation Criteria 1A 1B lC 10 2A 2B 2C 2D 2E 3A 3B 3C 3D 3E
Shoct-Tenn Effectiveness
Protection of Cannunity + + + + + + + +
Protection of ~rkers + + + + + + + + + -
Envirol1l'lental Impacts + + +
Tine
IDn;J-Tenn Effectiveness
Magnitude of Residual Risks + + + + + + + ~
Adequacy of Controls + + + + + +
R3liability of Controls + + + + + +
Reduction of Toxicity, MJbility, + + + + + + +
V::>lmne
Implementability
T3ChniCal Feasibility + + + + +
Administrative Feasibility + + + + +
Availability of Se:rvices arrl + + + + +
Materials
Cos: + +
Can )liance with ARARs + + + + + +
Ove :-all Protection of Human + + + + + + +
H ~ th and Environnent
Sta :e Acceptance + + +
Can nuni ty Acceptance + + +
ror \L -14 +14 +8 +7 -9 +9 +2 -3 -11 -14 +13 -11 -15 -15
Not ~s : + = generally favorable in carrparison to other al ternati ves
- = general 1 y unfavorable in carrparison to other al temati ves
blank space = neither favorable nor unfavorable
-------
TABLE 6 . (CONI'INUED)
REMEDIAL ACI'ION CRITERIA EVALUATION
FORMER WINro1 MUNICIPAL LANDFILL
KEY FOR ALTERNATIVES
OBJECl'IVE 1. . PRal'ECT MUNICIPAL WATER SUPPLY
1A No .Action
1B M:xiification of existing water treat:m3nt plant
1C Packed tower air strir.per
lD Abandon water supply well/construct new well
OBJECl'IVE 2. MINIMIZE LEACHATE GENERATIOO
2A No .Action
2B Site capping
2C Removal and off-site disposal
2D Removal and on-site disposal
2E In-situ solidification/stabilization
OPJECTIVE 3. CCNrnOL COOl'AMINANI' MIGRATIOO
3A No .Action
3B Ground water pump out/treat:m3nt
3C In-situ treatment
3D Subsurface barriers
3E Subsurface drains
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"
TABLE 7
CONrINGEOCY PU\N
PARI'IAL LIST OF INI'ERVENrION LIMITS
FOR ~I'IDRING WELLS
FORMER WINIXM MUNICIPAL LANDFILL
C~ of. Major Concern
Nitrate - Nitrogen (mg/l)
Intervention Limit*
Arsenic (ug/l)
2.5
12.5
1,1,2,2-Tetrachloroethylene (PCE) (ug/l)
1.7
1,1,2 Trichloroethylene ('ICE) (ug/l)
1,2 cis Dichloroethylene (DCE) (ug/l)
7.8
17
Vinyl Chloride (ug/l)
0.037
Benzene (ug/l)
3
*Intervention limits for catIpOUnds not found on this list are found in Minnesota
Solid Waste Managenent Rules Part 7035.2815, Subp. 4. F .
..-.. - . ... .... -.. _h
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i)
,
~' I
" DECLARATION
SITE NAME AND I1X:ATION
FODTEr Windan Municipal Landfill Contamination Site
Windan, Minnesota
STATEMENr OF BASIS AND PURPOSE
This decision c:iocurrent presents the selected ratEdial action for the FODTEr
Windan, Municipal Lahdfill Contamination site developed in accordance with the
Catq;>rehensive EnvirollDEntal_Response, Canpensation, and Liability Act of 1980
(CERCIA), as emended by the Superfund Amendm:!nts and Reauthorization 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
Fonner Windan Municipal Landfill Contamination Site.
DESCRIPI'ION OF 'IHE SELECl'ED REMEDY
The final ground water r€llt=dy for the site was developed to protect public
heal th and the envirollDEnt by min.irnizing migration of contaminants fran the
landfill to the ground water.
-------
~
-"" - .
~
The major canponents of ~ selected rattedy are as follows:
Installation of "an aeration systan at the Windan municipal water
treatment plant;
Capping the landfill with a cover systan consisting of a 2 foot, '".
",;.', .' .
catpa.cted clay barrier layer, overlain by a .5 foot sandy drainage
layer, a 45 foot layer of topsoil;
lDng-tenn ground water nonitoring; and
Installation of a ground water pump out/treatment systan in the event
that intezvention limits are exceeded in nonitoring wells.
DECIJ\RATION
The selected Lt:211::=lly is protective of human health and the environment, attains
federal and state requiIatents that are applicable or :relevant and appropriate
for this ranedial action, and is cost effective.
The l:eu-=uy utilizes pennanent
solutions and alternatives or :resource recovery technologies to the maximum
extent practicable for the clay cap and municipal water aeration treatment
systan. A ground water pump out/treatment systan is not needed at this time but
will be installed if inteI:Vel1tion limits are exceeded in ItDnitoring wells.
f/:' ", ~,
~ I .. '" I. ,
.... . .:/ j i"~
);t.~ j; / j lAjgf
Gerald L.: Willet
Ccmnissioner
Minnesota Pollution Control Ageocy
11/'7
Date/
7
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