United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPAIROD/R08-86/008
September 1986
3EPA
Superfund
Record of Decision:
?t3 ~ 7 ~ f ~ Cj JJ '<.
C;oste Collection
~esource Center
ion 3
1, PA 19107
Marshall Landfill, CO
,_.
U.S. Enviranmental ProtQ~lhm Aaaocy
Region III Informati~~ ~Qsource
Center (3PM52) .r .
841 Chestnut street v '~'':''.:;'t~
Philadelphia, fA 191Q1 ?a~
\
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TECHNICAL REPORT DATA
(Pftall rtad 'flSlfUCIIOflS Ofl Iht rtVt"t ~rtXt co,""ftllflll
1. "'1'OIilT NO. I~' 3. I'IICIPIENT'S ACCESSION NO.
EPA/ROD/R08-86/008
.. TITLE AND 5UITITLI 5. I'IEPOAT DATE
SUPERFUND RECORD OF DECISION C:;",nl-"'mber ?*' 1986
Marshall Landfill, CO e. PEIII"Ol'lMING OAGANIZATION CODE
7. AuTHOACSI 8. PEIII"Ol'lMING Ol'lGANIZATION I'IIPOI'IT NO
t. PERIIOAMING OIilGANIZATION NAME AND ADORE55 10. PAOGRAM EL.EMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME ANO AOORESS 13. TYPE 0" I'IEPOAT ANO PEI'IIOO COVEREO
U.S. Environmental Protection Agency F;n~' ROD -
401 M Street, S.w. 1.. SPONSORING AGENCY COOE
washington, D.C. 20460 --. 800/00
1'. SUPPI..EMINTAAY NOTES
18. ABSTAACT
The Marshall Landfill, located three miles southeast of Boulder, Boulder County, CO,
consists of two parcels: an 80-acre active County landfill and an 80-acre inactive
landfill due north. Between 1965 and 1974, the inactive landfill accepted unstabilized
sewage sludge and many unidentified and potentially hazardous wastes. Septic wastes anc
possibly liquid industrial wastes were also disposed off site in two, now closed, septic
ponds. Since 1974, the active landfill has accepted sewage sludge and municipal waste.
(Industrial waste may have been accepted during the early years of operation.) Since
1975 the active landfill has been operated by Landfill Inc. (LI), a wholl y-owned
subsidiary of BrOwning-Ferris Industries (BFI). Prior to 1978, County inspectors
observed landfill leachate seepage into Community Ditch, a conveyor of potable water
from nearby Marshall Lake to the City of Louisville and irrigation water for the Farmer
Reservoir and Irrigation Co. Two remediation actions have been taken subsequent to the
July 1982 EPA proposal for inclusion on the NPL: a mid-1983 Cooperative Agreement to
which LI agreed to install a pipeline to convey water from Marshall Lake across the
inactive landfill and conduct an RI/FS: and an October 1983 order by EPA to LI to
install the above mentioned pipeline, and to submit to EPA data and reports prepared
pursuant to the Cooperative Agreement. The primary contaminants of concern include:
VOCs including TCE, PCE, DCE, and benzene, and heavy metals including cadmium and lead.
(See Attached Sheet)
17. I(EY WOAOS ANO OOCUMENT ANAL.YSIS
a. OISCI".'TOIilS b.IOENTIFIERS/OPEN ENOEO TERMS C. COSA Ti F leldlG/ouP
. .
Record of Decision
Marshall Landfill, CO
contaminated Media: gw, sw
Key contaminants: VOCs, TCE, PCE, DCE,
lead, cadmium, heavy metals
1.. DISTIIII,UTION STATEMENT 19. SECURITY CLASS, Tills RtpO'1! ~1. NO. OF PAGES
None 54
~O. SECURITY CL.ASS ITI.II paltl 22. PRICE
None
"
el'. ,.,'" 2220-1 (ltn. .-77)
IO"'CYIOUI IOITIO" II 08101.ITI
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EPA/ROD/R08-86/008
Marshall Landfill. CO
a
16.
ABSTRACT (continued)
The selected remedial action includes: installation of a subsurface
collection system using natural ground water gradients to collect all
contaminated ground water leaving the Marshall Landfill site; treatment of
contaminated ground water by sedimentation, air stripping, and off-gas
carbon adsorption; landfill improvements, including regrading, revegetation,
perimeter ditches, and fences,-to minimize future environmental and public
health impacts from the site; and ground and surface water monitoring. The
estimated capital cost for this remedy is $1,819,000 with annual O&M costs
of $1,152,000.
~-
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UN;TED STATES ENVIROW.1ENTAL PROTECTION AGENCY
REGION VIII
ONE DENVER PLACE -- 999 18TH STREET - SUITE 1300
DENVER, COLORADO 80202-2413
RECOre of Dfcision
Remedial klternative Selection
Site
~arshall Landfill
Boulder County, Colorado
Dccuments Revie~ed
.-,
I ar!1 b:!sing my decision prinarily 0" the follo\'/ir.g documents describing
the analysis of tne cost and effectiveness of remedial alternatives for the
r"lar~hall Landfill:
, - ~:arshall Landfill Remedial Investigation, January 1985, prepared by
Landfill, Inc., a re~ponsiole party.
- r,iarshall Landfill Feasibility Study, prepared by Landfill, Inc., a
responsible party.
- Task I: Initial screening of Remedial Technologies and
Development of Alternatives, July 1985.
- Task II:
Detai led Eval uation of Remedi al Al ternatives, r4ay 1986.
- Final Responsiveness Summary for Marshall Landfill Site, April 1986,
prepared for EPA Region VIII by Camp, Dresser & McKee (attached)
- Memorandum dated June 16, 1986, from James Baker to Liz Evans
pertaining to a toxicological evaluation of the Marshall Feasibility
Study.
- Memorandum dated June 12, 1986, from Acting Director, Office of Health
Assessment, Agency for Toxic Substances and Disease Registry,
Department of Health and Human Services, to ~ichael A. McGeehin,
Public Health Advisor, EPA Region VIII, pertaining to a health
assessment of the Marshall Landfill.
- Draft Risk Assessment, Marshall Landfill, August 1985, prepared for EPA
Region VIII by PRe Engineering.
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- 2 -
- Report of Sampling Activities at the Deep Well Adjacent to Marshall
Landfill, October 1984, prepared for EPA Region VIII by Ecology and
Envi ronment.
- National Oil ar.d Hazardous Substances Pollution Contingency Plan,
40 CFR Pa rt 300.
- Sumnlary of Remedial Alternative Selection, EPA Re~ion VIII,
September 15, 1986 (attached).
Description of Selected Remedy
'~.....
The EPA preferred alternative for Marshall Landfill includes final
destruction of tt,e contamination emanating from the site. As required by
40 C.F.R. section 300.68(f), this alternative attains or exceeds applicable or
relevant and appropriate Federal public health or environmental standards that
havt; bee,n identified. By attaining these standards, this alternative
effectively minimizes the release of hazardous substances into the environment
so that they do not migrate to cause substantial danger to present or future
public health, welfare; or the environment (40 C.F.R. 300.68 (a)(l)). The
preferred alternative'entails:
- a subsurface collection system using natural ground-water gradients
to collect all contaminated ground water leaving the ~arshall
Landfill site;
- treatment of contaminated ground water by sedimentation, air
stripping, and off-gas carbon adsorption to meet clean-up criteria
established in the "Summary of Remedial Alternative Selection"; and
- landfill improvements, including regrading, revegetation, perimeter
ditches, and fences, to'minimize future environmental and pUblic
health impacts from the site.
Operation and maintenance requirements are an integral fart of the EPA
preferred alternative. An extensive network of environmenta monitoring
points, including surface water, ground water, and treatment system influent
and effluent, has been developed to assure that EPA has adequate knowledge of
the performance of the preferred alternative and of the ultimate environmental
remediation. The contamination treatment system will remain in operation
until monitoring shows that off-site ground-water standards are achieved.
The EPA preferred alternative thus provides for final destruction of the
contamination .t the Marshall Landfill site utilizing proven and effective
engineering and geotechnical practices.
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- 3 -
The preferred alternative includes off-site monitoring to establish
whether or not off-site sources of contamination exist ana are d~gradin9 the
environ~ent. These monitoring data will be used to determine if further
response actions will be necessary. If so, this will be addressed in a
subsequent decision document.
Declarations
Consistent with the Comprehensive Environmental Response, Compensation,
and Liability Act of 1980 (CERCLA), 42 U.S.C. section 9601 et ~., and the
National Contingency Plan (40 C.F.R. Part 300), I have determinea that the
selected remedy at the Marshall landfill is cost-effective and consistent with
a permanent remedy that provides adequate protection of public health,
welfare, and the environment. The State of Colorado has been consulted and
agrees with the approved'"-remedy. In addition, the action will require future
operation and maintenance activities to ensure the continued effectiveness of
the remecy. These activities will be considered part of the approved action.
EPA has not reached agreement with the responsible parties at the site to
implement the selected remedy.
Pote'ntial off-site sources of contamination will be monitored.
Subsequent response action will be considered if the monitoring shows
contamination above the.clean-up criteria.
I also have determined that the action being taken is a cost-effective
alternQtive when compared to the other remedial options reviewed.
~~~~J~ h. f",.:~
John G. Well es r-
Regional Administrator
EPA Reg; on V II I
~r~
Date
tf4 )7f~
I
.
Attachments
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ROD ISSUES ABSTRACT
Site:
Marshall Landfill, Boulder County, Colorado
Region:
VIII
Briefing for Regional Administrator:
September 10, 1986
Site Description
The Marshall Landfill, located southeast of Boulder in Boulder
County, consists of an active designated County landfill and an
inactive landfill due north. The inactive landfill and the active
landfill accepted municipal waste, sewage sludges, and possibly
industrial solvent wastes. Alluvial and deep bedrock ground
waters are the principal contaminant migration pathways that
could lead to public exposure to the contaminants. Consumption
of alluvial ground water on-gite or adjacent to the site would
result in a greater than 10- incremental cancer risk or other
non-carqinogenic health effects. The active landfill is operated
by Landfill Inc. (LI), a wholly-owned subsidiary of Browning-
Ferris Industries (BFI).
Selected Alternative
The cost-effective remedial alternative selected for this site
includes: fencing, regrading, and revegetating the site to res-
trict access and minimize infiltration; collection of contami-
nated ground water by a series of drains partially surrounding
the site to eliminate off-site transport of contaminants via
alluvial ground water; treatment of the ground water by air
stripping with off-gas carbon adsorption to reduce the concentra-
tions of the volatile organics in the ground water to the most
conservative of the applicable or relevant and appropriate stan-
dards and criteria (and prevent the escape of volatile organics
to the atmosphere); ground water and surface water monitoring to
assess the effectiveness of the proposed remedial alternative.
The total present worth cost of the selected alternative is
$3,259,000 which includes $152,800 per year of operation and
maintenance cost for thirty years.
.ISSUES AND RESOLUTIONS
KEY WORDS
1.
LI states in the FS that the slurry
wall will provide minimal benefit in
dewatering the site. The Agency's
position is that the analysis lacks
an adequate data base. The selected
alternative includes additional
field testing and analysis to assess
the slurry wall potential to reduce
o
o
Slurry Wall
Source Control
1
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contaminant sources, long term oper-
ation and maintenance costs, and the
potential for deep aquifer contami-
nation. A favorable assessment would
lead to modification of the selected
alternative to include the slurry
wall.
2 .
Effluent from the treatment facility
will meet the most conservative of
the applicable or relevant and ap-
propriate water quality standards
and criteria.
3 .
Capping of the landfill in accord-
ance with RCRA closure requirements
was rejected as a remediation option
because infil~ration is a minor
component of the water balance at
the site, the proposed regrading and
revegetation of the site will fur-
ther minimize infiltration, the
gro~nd water collection system will
prevent contaminants from migrating
beyond the RCRA compliance point,
and the installation cost of the cap
is high.
4.
The alternative selected represents
a technology that destroys hazardous
wastes in that the off-gas carbon
once saturated with contam~nants is
thermally regenerated.
The selected remedial action addres-
ses prevention of off-site con-
taminant migration from the inactive
and active landfill. Because off-
site contamination exists at this
time and off-site sources are sus-
pected, a monitorinq proqram will be
implemented to assess ground water
quality changes off-site and thus
provide data to determine if further
corrective action will be appro-
priate. If a problem exists, EPA
will consider further response ac-
tion.
5.
2
,/
o
Ambient Water
Quality Criteria
Cleanup Criteria
Drinking Water
Standards
o
o
o
o
Capping
RCRA Closure
Requirements
o
Air Stripping
o
Deferred
Decisions
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SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
Marshall Landfill
Boulder County, Colorado
SITE LOCATION AND DESCRIPTION
Marshall Landfill is in the western quadrant of Section 23,
Township 1S, Range 70W in Boulder County, Colorado (Figures 1 and
2). Although the original Marshall Landfill designation spanned
the entire north half of Section 23 (320 acres), only SO-acres in
the western portion of the designation were intensively
landfilled. This SO-acre portion is called the "inactive site".
An additional SO-acres were added to the landfill in 1974. This
area is in the westarn half of the southwest quadrant of Section
23, directly south of the SO-acre inactive site. The land added
in 1974 is still being landfilled and is called the "active
site". Together these two parcels comprise the 160-acre site
which has been the focus of the remedial investigation/feasibili-
ty study.
Both the active and inactive landfills were designated County
landfills under private operation. The various operators at the
site are discussed in the following section, ~it!_~istoI~
Property interest at the site is discussed in the Enforcement
section. -----------
The inactive landfill is in Cowdrey Drainage which conveys
surface water from Cowdrey Reservoir No.2 to South Boulder
Creek. Community Ditch is also within the drainage and conveys
potable water at various times of the year from Marshall Lake to
the City of Louisville and irrigation water for the Farmers
Reservoir and Irrigation Company. Additionally, two small
lagoons, dug by Boulder County in an attempt to collect and
contain landfill leachate, are on the inactive SO-acres.
With three exceptions, the area surrounding Marshall Landfill is
used primarily for livestock grazing. These exceptions are: 1)
a storage facility for the National Center for Atmospheric
Research adjacent to the site on the east side of South 66th
Street: 2) Marshall Lake, an irrigation and municipal drinking
water reservoir, to the west; and 3) a small non-food warehouse
building .to the northeast that has been leased for a variety of
storage uses.
The major population centers surrounding the site include the
town of Marshall (1.5 miles west), the town of Superior (2 miles
east), the city of Boulder (3 miles northwest), and the city of
Louisville (3.5 miles northeast). The area within a one mile
radius of the site is sparsely populated.
1
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"
,-
" \. '-
r'\.
N
SCALE:
I : 24.000
'IGU... 1 '
MAASHA'LL LAN9FILL LOCATION MAP
REF: TASK 1
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.
.\ TO THE LOUISVILlE
. D~RSION"
4- TO SOC1TH BOUU>ER CREEK
. COWDREY
~. RESERVOIR.
NO.2
x
MARSHALL LAKE
ACTIVE
LANDFILL
APPROXIMATE SCALE:
1 . . 1000.
22 23
+
27126
'IGURa .
MARSHALL LANDFILL SITE DETAIL
3
...,: TASK I ADDENDUM "IIFS
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SITE HISTORY
Landfill operations began at the Marshall site in 1965. The
Richland Company of Colorado Springs leased the property from the
COwdrey Corporation, and under contract with the County Commis-
sioners conducted the first official solid waste management oper-
ation from 1965 to 1969. The operations specified by the con-
tract were the composting of solid waste. However, the company
continuously lost money. resUlting in a poorly run operation with
relatively little actual composting conducted during this period
(less than 20%, the balance landfilled). In 1969, Salvage Inc.
of St. Louis purchased the operation from Richland for the ex-
press purpose of landfilling, and soon thereafter entered into a
joint venture with local investors and was renamed Urban Waste
Resources (UWR). UWR operated the now inactive landfill from
1970 to 1974 under certification by Boulder County. In 1974, UWR
in conjuction with Mesa Sand and Gravel expanded the operation to
the south and aband'Oned the now" inactive" landfill. The com-
bined sand and gravel excavation and landfilling to the south was
operated under a Special Use Permit for which the first opera-
tions and monitoring plan was developed. In 1975, Landfill Inc.
(LI) a wholly-owned subsidiary of Browning-Ferris Industries
(BFI), purchased the operation and has operated the landfill ever
since. .
The inactive landfill accepted unstabilized sewage sludge and
many unidentified and potentially hazardous wastes during its
operation from 1965-1974. Prior to 1970, these wastes also were
disposed in Cowdrey Drainage on the east side of South 66th St.
between Community Ditch and Cowdrey Drainage. Septic wastes and
possibly liquid industrial wastes also were disposed in the now
closed septic ponds located east of South 66th St. and south of
Community Ditch. The septic ponds were operated by the landfill
operator.
Since 1974, the active landfill has accepted sewage sludge and
municipal waste. Industrial waste may have been accepted during
its early years of operation.
Investigations by EPA, the State, and the County have shown
extensive contamination at the Marshall Landfill. As shown in
Table 1, sampling and analysis of seeps, the leachate collection
lagoons, a French drain along a segment of the western boundary,
and alluvial ground-water monitoring wells within and adjacent to
the 160-acre site indicate contamination in the alluvial aquifer.
This contamination includes numerous volatile organics and heavy
metals. The Remedial Investigation, conducted by LI also indi-
cates trace organic contamination in the Laramie-Foxhills aqui-
fer, a bedrock aquifer beneath the site. Surface water on the
site, in Cowdrey Reservoir and the leachate lagoons is contami-
nated with heavy metals and organics (see Table 1).
Prior to 1978, County inspectors observed landfill leachate seep-
ing into Community Ditch. In 1978, the Boulder County Commis-
sioners established a "sinking fund" through a rate increase at
4
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Table'
MAXIMUM CONTAMINANT CONCENTRATIONS OBSERVED AT THE
BOULDER/MARSHALL LANDFILLS
Backgronj Sh8110w Deep
. Surf.:e Alluvial O'\-site orr-site Bedrock Bedrock
PI.-ter1 ..ter 2 Ground Water Ground Water Ground lIIIater Grunt ..ter Ground Water
1058 1U' "5 U2(I) .2O 26)7 1770
CI- 5.c) 15 900 26 , 1
SO.- 92 107 7900 100 , 2)
...,. 57 120 0.1 0.) 0.'
r. '10 110 58700 " 190 1\00
.... 580 )9 6500 '10 160 220
81 J60 no 2(D) 600 120 16P
In )1 80 250 97 2' ,
At 50
at )) 18
fib 60 15
58 90
"II 1.1 1., 0..
VI Cr 19 8 9
"'-'018 19 2650 5
l,l-olchlo~ 250 15 (n) 15 ,
T.... 1.2-olchloroet~1- 5:JO " 9
1.l,l-Trlchloroethlne .9 - (550)
T r1chlol'08t.., lene " 6 (1'9)
Tet nchloroet"'lene ~ 7) (98)
Olch1oroet~lene - (1'9)
Et"'l BeNene n
Toluene 1250
Benzene .,
1 Y8lues listed .n 10 ug/1 except for - IIIh1ch Indlcltes Y81ues 10 119/1
Not Detected
Y81ues for Manltorlng Well NA-9 10 ..notheses
2 All ..ter ~It, Y81ues In besed an eIIt. obtained by the EPA's f'1J Contractor (E 6 E.
or ellta obtained IiIrlng the Al (fox ConaIltants, Inc., 198'. 198. a, b, 6 c)
198' and 1985)
REF: TASK 2 FS
-------
a
the landfill to finance clean-up at the landfill.
still in place.
This fund is
In July 1982, EPA proposed Marshall Landfill for inclusion on the
National Priorities List (NPL). At the time of the proposed
listing, the site was the State of Colorado's highest priority
for remediation under CERc.LA. In September 1983, Marshall
Landfill was included on the first NPL. The hazard ranking
system (HRS) score for the site when listed was 46.52.
Subsequently, two actions were taken to initiate remediation at
the site. First, in mid-1983, LI, Boulder County, the Colorado
Department of Health (CDH) , the City of Louisville, and the
Farmers Reservoir and Irrigation Company signed a Cooperative
Agreement. The Cooperative Agreement was entered into pursuant
to beginning negotiations with EPA for the RI/FS and also a CDH
notice of violatio~.issued to LI under authority of the State
Solid Waste Disposal Sites and Facilities Act, Title 30-20, Part
1, C.R.S. 1973 (as amended). LI agreed to implement remedial
measures to protect Community Ditch water and conduct a remedial
investigation and feasibility study (RI/FS). Community Ditch was
to be protected by installation of a 60-inch pipeline to convey
the water from Marshall Lake across the inactive landfill.
Second, in October 1983 EPA issued a unilateral CERCLA 106 Order
to LI when negotiations broke down. The Order required LI to
install the Community Ditch pipeline by April 1, 1984, and to
submit to EPA all data generated and all reports prepared pur-
suant to the Cooperative Agreement.
CURRENT SITE STATUS
Results of the Remedial Investigation
Several reports prepared pursuant to the Cooperative Agreement
comprise the Remedial Investigation for the site. The reports
are:
Task 1:
Task 2:
Task 2:
Task 3:
Task 3:
Evaluation of Water Quality and Water Quality
Monitorinq at the Boulder Landfill, Boulder,
Colorado, April 1983
Geologic and Hydrologic Data Collection at the
Boulder Landfill, Boulder, Colorado, November
1983.
Addendum: Results of Additional Field and
Laboratory Investigations Conducted April-August,
1984.
Site Characterization and Contaminant Migration
Report for the Active Boulder and Inactive
Marshall Landfills, Boulder County, Colorado,
December 1983.
Addendum: Responses to Comments and Evaluation of
1984 Field and Laboratory Results, January 1985.
6
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In addition, quarterly monitoring data collected over a period of
1 1/2 years were part of the Remedial Investigation.
Site Geology and Hydrology
This section is the site conditions summary of the FS prepared by
Landf ill, Inc.
The Marshall Landfill is between the crest of Lake Mesa and a
small bedrock ridge along the north side of Marshall Lake (see
Figure 1). Lake Mesa is a broad, upland pediment surface, con-
sisting of a gravel capped bedrock erosional surface along the
crest, a series of colluvial and terrace deposits along the
flanks, and colluvial and weathered soil along Cowdrey Drainage.
Refuse in the active landfill was placed across the top of Lake
Mesa. Refuse within the inactive landfill was placed along the
bedrock slope north~of Cowdrey Drainage, down into Cowdrey Drain-
age, and up along the flank of Lake Mesa.
The bedrock geology of the area consists of a faulted sequence of
Laramie Foundation and Fox Hills Sandstone. The continuity of
the beQrock formations in this area has been severely disrupted
by a series of northeast-trending, high-angle normal and reverse
faults. The most prominent of these is the Crown Davidson Mesa
fault which bisects the inactive landfill, dividing the landfill
area into two distinct tracts. The first tract, located north of
the fault and consisting of the northern portion of the inactive
landfill, is interpreted to be underlain by a thick sequence of
Laramie shale. The second fault block, which consists of the
southern and central portion of the inactive landfill and the
entire active landfill area, is interpreted to be up-thrown
relative to the northern fault block and to be underlain by a-
thin sequence of Laramie Formation shales and coal measure rocks,
the basal A and B sandstones of the Laramie Formation, and the
Milliken Sandstone of the upper portion of the Fox Hills
Sandstone (see Figure 3).
The surface water in the area of the landfill is dominated by
Marshall Lake, a 240-acre irrigation and municipal water supply
reservoir. The flow into Marshall Lake is derived primarily from
Community Ditch, which collects surface water from South Boulder
Creek approximately 4 miles west of the landfill. Outflow from
the lake is dominated by flow within Community Ditch, which
conveys. water from the reservoir across the southern portion of
the inactive landfill, along the northwest flank of Lake Mesa,
and out onto the eastern plains of Colorado for agricultural uses
and to the City of Louisville for municipal supply. Cowdrey
Reservoir No.2 is supplied primarily by seepage beneath Marshall
Dam with a lesser contribution due to runoff from the surrounding
ISO-acre area and seepage and leachate discharge from the
landfill itself. Outflow from Cowdrey Reservoir No.2 occurs
primarily as surface flow in Cowdrey Drainage. This drainage
traverses the northern portion of the inactive landfill, across
South 66th Street, and through the area of uncontrolled dumping
7
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VI.. L...I.. Soath Fro. Actlv. L..4I1I1I
EM'
5100
"..
00
",,*'
~f
.*
".~
.
fl..
.-
"00
"'0
L..dlm Ar..
w...
R.lu..
R.cha,.. Zon..
5700
Uacon.olldat.d
Depo.lt.
'1
5650
~.~,
.,..~
"
~\\....
,,'" ~
\0.
.~
ff.'
fO~
.". \\\-
fO.
. .~
~99
5600
\0.
.~
C"
fO.
.".\-0.-
fO.
~.~
,,0
FIGURE 3
Horl.ontal Sc.le
5550
I
O.
2lo.
Interpretive East. West Cross Section. Lake Mesa Fault Block. Boulder/Harshall Landfill
REF: TASK 3 ADDE"'''''""
'}
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on the east side of South 66th Street, where it reverses course
back to the west to join South Boulder Creek 3 miles from the
landfill area.
The uppermost hydrogeologic unit at the Marshall Landfill is an
alluvial aquifer consisting of sands, gravels, and clays mantling
the top and flank of Lake Mesa;, colluvial material along the base
of Lake Mesa; weathered bedrock in the low areas around Cowdrey
Reservoir; alluvium along Cowdrey Drainage: and refuse that has
been placed within the landfill area. Flow within the alluvial
aquifer is generally to the north and northwest in the immediate
vicinity of the landfill up to Cowdrey Drainage and to the south
and southeast along the flank of the small ridge on the north
side of Cowdrey Drainage (see Figure 4).
Bedrock aquifers beneath the site are dominated by the regional
Laramie-Fox Hills aquifer of the Denver Basin. Beneath the
southern portion of~--the inactive landfill and the entire active
landfill, four distinct hydrostratigraphic units have been
identified within the regional Laramie-Fox Hills aquifer. These
consist of an upper shallow bedrock aquifer, the B sand of the
Laramie Formation, the A sand of the Laramie Formation, and the
Milliken member of the Fox Hills Formation. With the exception
of the Milliken Sandstone, all of these units are inferred to
outcrop beneath the landfill area. Each of these aquifers is
separated by thin-shale and shale and coal measure aquitards.
These aquitards result in a complex pattern of vertical flow
gradients. Beneath the eastern portion of the active landfill,
flow is interpreted to be vertically downward through all four
units. Beneath the western portion of the active landfill, flow
is interpreted to be vertically upward from the A sand of the
Laramie Formation. Beneath the southern portion of the inactive
landfill, flow is interpreted to be vertically upward from the B
sand of the Laramie Formation.
Site Contamination
Surface water and ground water on-site and ground water off-site
at Marshall Landfill are contaminated (see Table 1). Contami-
nated surface water and ground water are characterized by ele-
vated concentrations of major ions, heavy metals, and by the
presence ot priority pollutant volatile organic compounds. The
maximum contaminant concentrations in on-site alluvial ground
water are above water quality standards and guidelines (See Table
7) .
Figure 5, from the RI prepared by LI, shows the known extent 0 f
alluvial ground water contamination. Several items are
noteworthy here. The alluvial ground water of the southern
sector of the inactive landfill has the most degraded water
quality. Contamination occurs off-site to the east despite
the fact that groundwater gradients are to the north-northwest
(see Site Geology and Hydrology Section). Two potential off-site
sources of contamination east of South 66th Street are suggested:
9
-------
FIGURE 4
WATER TABLE MAP OF ALLUVIAL AQUIFER
------.---
- ------..-
~
o
"
,
.
.
"'J
(I) ) I
, I . ..JI' .
\ ~- J ;
.
,
\
. .;;,...,
, .
. I..... ".'-'." . ''''''0 '- '~""""I I.. ,.,
...1..,.
... - ..,-.... _.... ~....- ......, ,- ''''''''''10. I... . I.'
- 1........-... .-.
" ,..... "."...-,..........,1."_"""'11 .... ....
.. 'II. . 0' _.'"
"1 .'1 _".1 ,"1._..-, ....... II '- ,''-,,,,,,,,, I... ...
I:~J' .--... '0_-
. ........,..-.... """. '-"" '...-.............. ,.,
,""_'''',''',''''','' ,...
,. I I
. .-J.
...' .,..1 t..
,'. to-....... ,..t....... -' -. '.' ...... 0-.1''''0'' ...-,
,..1... .... ...
., . ..'... ". .. .. . 110,'" ............... I",
.. '..., .... .'<. -'-". "_'0"""''''''--
'. . "'. "-'" ,. "0"'.'" .-............-
.;0 t..-.o. ''''''-'0 ."-'''' -''''''''''''''''''.'-
""""''''''''''''''-''''''''''''''-..''.''
.\ .-.'t......, ...,-
~-
" ...- - ., .'., -"" ...... I "'u... '-,_...
,.. . .
.. . ..~. ""'.. ".. ",., -. -" ..~....... ,...
'" ... '.' -.,. "'" ...' .""~'" I... .- '.,
-------'---.-.. .----
REF: TASK
111M RUf8
-------
~. ~\~l.
" \ 1 ..r;p..,A.\~,A.q,f. . \
,,~po. -0 .
",c, . #~~ \
,r /". --" . . TO mE lOUISVlllE
/ DIVERSION ~
15 14
+
22 23 EPA- 1
INACTIVE 6/
. ,...1
/ NA-11/
/.
~ TO SOtTTH 8OUU>ER CREEK
COWDREY
RESERVOIR
NO.2
.
CDH-11
I
LANDFILL I'
~~"$ FX-3
6----~
FX-20
I
I
I
I
LANDFILL I
I
FX-10'
SBW- 1ul
DBW-1~
I
..NA-'
MARSHALL LAKE
ACTIVE
APPROXIMATE SCALE:
1.~1000'
22 + 2J FX-8
27/26
+ BELOW DETECTION LIMITS
~ LESS THAN 100ug/l
o 100 ug/l - 500 ug/l
. 500 ug/l - 1000 ug/l
. )1000 ug/l
+NA-IO
. NA-9
OEPA-IO
;;:A NA-l
c:c
~ N.C.A.R.
= F AC I LI TV
...
..0
-0
6. NA - 7
X
. NA-e
+ EPA-5
FIGURE 5
MAXIMUM TOTAL VOLA TILE ORGANIC CONCENTRATIONS
11
-------
of ~onitor ~ell NA-6.
:: ~.:: 3.: ~.~~? .--.": ',',' - : ~ ': .;:.~:: j
~-.....-. .....
-- - '- -- ..... '-
..- - -. j-
.... -..-...:
.3. :-. .j ~ :--, e
----...::.- '....., -_. -. ..., ~'-"
--....-- ....... '---..--
Piezometric head data indicate a potential for contaminatei
recharge of the sandstone aquifers in the east-southeast portion
c, : t :. ~ :\ C t i '/ e 1 and f i 11 , and pet e n t i a 1 f :) r ~ e c h a, r J e c: t :'1 ~
landfill refuse and alluvium ~rorn the Laramie sandstones in the
~~he~ a~e3S of the landfilr. Monitoring data for the shal1o~
cedroc~ ~el~ (SBW-I) and the deep bedrock well (DBW-I) located in
the east-sc~theast sector of the active landfill (see Figure 5)
i;;d,:::;,?te trace levels of 1,1.-dichloroethar.e. This ::Jay C~
evidence of bedrock aquifer contamination resulting fro~
conta::Jinated alluvial ground water recharge of these units.
There is no apparent threat to users of surface water originating
in Marshall Lake and passing through the site as contaminants
were not detected in the waters leaving the site via Cowdrey
Drainage or CommunI-ty Ditch during the conduct of the Remedial
Investigation. After completion of the Remedial Investigation,
the Fall 1985 sampling and analysis indicated 5u9/1 of 1,1-
dichloroethane in Cowdrey Drainage surface water where it crosses
the section line to the northeast. This concentration is the
method ,detection limit and is the first occurrence of priority
pollutant contamination in Cowdrey Drainage surface water off the
160-acre site.
Migration Pathways and Potential Receptors
LI prepared a pUblic health evaluation in accordance with EPA
guidance for performing feasibility studies. LI selected indica-
tor parameters based upon whether they met 3 or more of the 4
following criteria: frequently detected, present in more than one -
hydrologic media, occurrence at concentrations above standards or
proposed health advisories, and availability of toxicity data.
The selected parameters were benzene, trichloroethylene (TCE),
tetrachloroethylene (PCE), 1,2- dichloroethylene (1, 2-DCE), cad-
mium, and lead.
There are documented human health effects resulting from exposure
to benzene either by inhalation, ingestion, or skin contact. The
most notable health effect resulting from exposure to benzene is
its carcinogenic potential. Benzene is classified as a positive
human carcinogen based upon epidemiological data from occupa-
tional exposure. Benzene occurs in alluvial ground water on-site
at concentrations in excess of lhe Clean Water Act (CWA) water
quality criterion based on a 10- incremental cancer risk.
Human exposure to TCE can occur by either inhalation, ingestion,
or skin contact. Prolonged or repeated skin contact to TCE can
result in dermatitis. Although numerous non-carcinogenic health
effects can result from inhalation or ingestion of TCE, the
primary concern with respect to TCE is its carcinogenicity. EPA
has classified TCE as a suspected human carcinogen. TCE is
present in alluvial ground water within or adjacent to the site
12
-------
3:' :::-:..:e::::-.:l:..:...:r.3 1;1 excess::: t~e C~";A
based ~n a lO-~ incremental cancer risk.
-. -::.....=;-
... ,.... '- - -
q 'j a 1 i : ::~
, ,
\:~.;..~~~:'.::-.
The primary human exposure route for PCE is inhalation or inges-
tion. Similar to TCE, PCE exposure can result in many non-
c3rci~cgenic health effects. The ~ost noted ccncern is the fact
that it is a suspected animal ~arcinogen. EPA considers it to be
a pote:1~ial huma~ teratogen. - PCE occurs in allu'J'ial ground ',Vater
i/ithin and adjacent to -the site at concentrations above the 10-6
i~cre~ental cancer risk criterion.
Sleepiness and hallucinations can result from inhalation of 1,2-
DCE. There is no information on health effects resulting from
oral exposure. 1,2-DCE occurs in alluvial ground water within
the site at concentrations in excess of the Recommended Maximum
Contaminant Level (RMCL).
The primary human exposure route for cadmium is ingestion. Non-
carcinogenic health effects from cadmium exposure include renal
tubular dysfunction, bone damage, hypertension, anemia, sensory
loss, endocrine alterations, and immunosuppression. Cadmium is a
suspected carcinogen and a known animal teratogen. Cadmium 'is
present in on-site alluvial ground water at concentrations in
excess of the primary drinking water standard.
The primary human-exposure route for lead is also ingestion.
Lead is known to have toxic effects on the hematopoietic system
and nervous system. Lead exposure to children and pregnant women
has been linked to decreased learning ability of the affected
child. Lead can also be an animal carcinogen and teratogen, in
certain forms. Lead occurs in on-site alluvial ground water in
concentrations in excess of the drinking water standard.
There are four communities near the landfill. These are the
towns of Superior (1.5 miles east of the landfill), Marshall (1.5
miles west), Louisville (3.5 miles northeast), and the City of
Boulder (3 miles northwest). The estimated 1985 populations and
projected populations for the year 2000 for these communities are
as follows (Boulder County Planning Commission, 1985):
Community
1985 Population
(estimated)
96,500
9,500
500
250
2000 Population
(projected)
122,200
17,000
1,000
500
Boulder
Louisville
Superior
Marshall
In addition to the residents of the area around the landfill, a
number of people travel to the immediate vicinity of the landfill
for recreational or business purposes. Primarily, these include
recreational users of the Louisville Rod & Gun Club, who use
property near Marshall Lake; employees of the National Center for
Atmospheric Research (NCAR); workers engaged in cattle management
in the area; and those employees of Farmer's Reservoir and
13
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:~rig3tic~ Cc~panl.
Community Ditch.
i~volved in the ope~a~icn
c~ ~arshall Da~ ~~:
The LI FS estimates that there are 558 established wells within a
3-mile radius of the landfill, 96% of which are used for domestic
~urposes only and 4% of which are used for commercial or munici-
pal purposes (see Figure 6). - Of the 558 wells, 251 are alluvial
~ells. The rest are completed in the underlying Laramie Fox
Hills aquifer.
The first potential pathway of contaminant transport is alluvial
ground water. The LI FS states that the alluvial wells within a
]-mile radius of the landfill are isolated from the contamination
bearing alluvial ground waters associated with the site (see
Figure 6). While there are no alluvial wells in Cowdrey Drainage
registered with the Colorado State Engineers office, the extent
of off-site contamination along Cowdrey Drainage is unknown and,
therefore, care must be taken with this potential pathway. Life-
time consumption of alluvial ground water on site and a~ong the
boundaries of the site would result in a greater than 10- incre-
mental cancer risk due to ingestion of benzene, trichloroethy-
lene, and tetrachloroethylene, and could produce non-carcinogenic
health effects from ingestion of lead, cadmium, trans-dichloro-
ethylene, trichloroethylene, and tetrachloroethylene whose con-
centrations exceed -either the primary drinking water standards,
ambient water quality criteria, health advisories, and/or ad-
justed acceptable daily intakes (see Tables 1 and 7). Provisions
for further monitoring of this pathway are included in the pre-
ferred alternative.
A second potential pathway of contaminant transport is the
bedrock groundwater beneath the landfill. As stated in the LI
RI/FS, trace levels of volatile organic compounds have been
detected in the shallow and deep bedrock aquifers beneath the
site. These are 1,1-dichloroethane and trans 1, 2-dichloro-
ethylene (see Table 1). The shallow and deep bedrock aquifers
described in the RI/FS are part of the Laramie Fox Hills Aquifer.
The Laramie-Fox Hills Aquifer is used for drinking water
purposes. Within a 3-mile radius of Marshall Landfill, 307 wells
are completed in the Laramie-Fox Hills Aquifer. The risks from
this potential pathway are not quantified because the contaminant
concentrations are below water quality standards.
A third pptential pathway of contaminant transport is the surface
water leaving the site via Cowdrey Drainage and Community Ditch.
Water from Community Ditch is used as a drinking water source by
the City of Louisville. Although Community Ditch was replaced
with a pressurized pipeline where it traverses Marshall Landfill,
ground water continues to seep into Community Ditch east of the
landfill. The LI RI/FS monitoring data show trace levels below
clean-up criteria of hazardous substances, pOllutants, and con-
taminants in Cowdrey Drainage. Cowdrey Drainage, tributary to
South Boulder Creek, is a water body subject to stream standards
for South Boulder Creek imposed by the State of Colorado. South
Boulder Creek is classified by the State of Colorado as Class I
14
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R 70 'tV
R 69 'N
~ t I ~ ! 1 3 l' I"" I I i : ; 2 , J ;231 0 : 5 i 41 I ! I i
~ I I ' I -
212, i 1 i I ' I I i " I 1 i , I ! t ! 7 i 1 1 I i I I
I
2 i 2 i I 1 I I, I . I I I I 1 I I i I 111 i a : 5 , I I
I ! i I
I 1 I I 1 I I ! 1 I 2 i ; 1 I 2: i 2: Isal14j a 146 2\ I I
I
I I i I I i I I I 1! 1 is: 2 1231 3 i 5 i 5 ' I i 2 I
I
I 12 i I I ! I I 2 I 4! 14 I 51 41 5 I I I
I I I I I I 1 I 7 I I 7 I 91 1 I 1 I I I
I I ! I I I 2 21 I, I 2 al41 I I
I 12 I 't' I , I I I 13 21 I 21 I I 1
I 1'1 II' I I I 2 !....... """ I I I 1 I I
I 12 ~ 2/21 I lJ.-1 "I I 21 ) 13 I 31 2' 2
I 1 I I 1 111"1 5 I ~ , I I I 1 I I 3) "3 1 I 2 I 5 I I I
1 'I I 3/1 I 6 I 2 3\ I ~11 II I I 6 21 I I a
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21~151 "'-, I I~ ~}:11 I I I I I I,
51 6 I I I I N I i I~' ! , I I I I I
I 1 !
1! I I I I I I" ! i ~ I ! \'1 I I 'I I I I
, Marshat! Landfill I
I I I I ! I I I I .1 i I I I I I I I i I 1
I I I I I I I I I I I I I I I I
I I I I I I I I I I I I I I I I I I I
I I I I I I I I I I I I I I
I I I
I I I I
I
T
1
S
T
2
S
EXPLANATION
\ lound8ry of Allu„181 ...In Cont81nlne
\.... 118""811 L8ndtln
,~ 118"'''811 Landfill
(A fte, St8te Entlnee,. Office a HLA Field In8pectlon8)
FIGURE 8
REF: FINAL FS
DISTItIIUTION City Querte, SeellOft) OF EXISTING WILLS WITHIN
3-1I1L1 ItADIU. 0' IIAIt.HALL LANDFILL
l~
-------
recreational (primary contact, i.e. swimming), Class I cold water
aquatic life, water supply (domestic use) and agriculture.
The Agency for Toxic Substances and Disease Registry (ATSDR)
reviewed the sampling data from the site and has proposed
recommendations for further investigation. These recommendations
include sampling off-site wells used for drinking water,
determining ground water users'near the site that may be impacted
by the site, confirming the extent of alluvial and deep bedrock
contamination, assuring the remediation system intercepts the
plume, assuring that metal contamination is adequately addressed
in the proposed ground water treatment system, soil sampling in
areas of exposed refuse, air sampling to assess volatile organic
concentrations in the air, and estimating the impact on air
quality of air stripping of volatile organics. The ATSDR agrees
that collection of ground water along the eastern boundary of the
site with subsequent treatment will minimize exposure of the
nearby populationt~,the contaminants.
ENFORCEMENT - see Enforcement Confidential Attachment
ALTERNATIVES EVALUATION
LI designed the FS ,to evaluate remedial action alternatives that
met the following' four objectives as outlined in the in the
"Feasibility Study, Task 1 Initial Screening of Remedial Tech-
nologies and Development of Alternatives":
1.
Assure that all surface water discharge from the land-
fills does not adversely impact the current or planned
future beneficial uses of the surface waters in this area
or any other waters that it may contact;
Control the generation of contaminated ground water at the
landfills;
2.
3.
Assure that any off-site contaminated ground water origi-
nating at the landfills does not adversely impact the
possible beneficial uses of the ground waters in this
area or any other surface waters and ground waters it may
contact;
4.
~liminate or control the impacts resulting from leachate
seepage in the landfills.
LI developed numerous remedial technologies potentially appli-
cable to the response actions that address these objectives. In
accordance with the National Contingency Plan (NCP) at 40 CFR
300.68 (f), remedial action alternatives that address the overall
problem were developed by combining appropriate remedial technol-
ogies. In the development of the alternatives, consideration was
given to meeting all the objectives and providing alternatives
16
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that fall into the five categories outlined at 40 CFR 300.68 (f),
Le., alternatives that consider offsite disposal at an EPA
approved facil i ty, attainment of appl icable or relevant and
appropriate federal public health and environmental requirements,
exceedance of applicable or relevent and appropriate require-
ments, non-attainment of applicable or relevant and appropriate
requirements but reduction of the threat from hazardous substance
release, and no action. Tables 2 and 3 present the 16 alterna-
tives that were dev~loped and how they address the above stated
factors.
In accordance with 40 CFR 300.68 (f) and (g), these alternatives
were screened to narrow the list of alternatives to those that
most closely met the NCP requirements and the site objectives.
The screening process also eliminated alternatives offering simi-
lar levels of protection but were otherwise more difficlult to
implement, more exp~nsive, or posed significant adverse impacts.
Four organizations;-' EPA, LI, CDH, and the Boulder County Heal th
Department (BCHD) actively participated in the screening.
Alternative 2 was eliminated because of its high cost relative to
Alternatives 6, 7, 9, 12, and 15, the latter alternatives of-
fering .similar benefits. Alternative 3 was eliminated because it
only addressed one of the proposed response objectives, i.e.,
source control. Alternatives 4, 11, 13, and 14 were eliminated
because they do not address existing ground water contamination.
Alternative 8 and 10 differ only by the inclusion in Alternative
10 of surface water collection. Surface water collection via
perimeter ditches would help reduce runon and thus infiltration
at a low cost, therefore, Alternative 8 was eliminated on this
basis. Alternatives 9 and 16 are similar to Alternative 15.
However, unlike Alternative 15, Alternative 9 does not include-
surface water collection and treatment which would provide addi-
tional benefit at a low cost. It was therefore eliminated. Al-
ternative 16 includes leachate collection which adds cost and
increased exposure of workers to the contaminants relative to
Alternative 15. Because leachate collection does not provide
significantly greater benefits relative to Alternative 15, it was
eliminated. Alternatives 6, 7, and 12 all include ground water
collection and treatment. Because Alternative 7 also includes
both surface water and leachate collection as opposed to Alterna-
tives 6 and 12 which simply include one or the other, Alterna-
tives 6 and 12 were eliminated from further consideration.
In summary, the alternatives retained for further evaluation are
as follows:
Alternative 1
Alternative 5
- No action,
- Surface water and ground water collection and
discharge,
- Surface water, ground water, and leachate
collection, treatment, and discharge,
- ground-water barrier with surface water and
ground water collection and discharge,
Alternative 7
Alternative 10
17
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Tabl. 2
APPLICATION OF PROPOSED REMEDIAL ALTERNATIVES TO
PROPOSED REMEDIAL RESPONSE OBJECTIVES
Response Db tec::t! ves
Off -Site
Sur face Ground- Leac::hate
Water Source Water Seepage
Remedial Alternatives. Control Control Control Control
1. ~ Action
2. Excavation X x
3. Ground-Water Barrier X
4. Surface-Water Diversion,
Collection, and Discharge
and Ground-Water Barrier X X
5. Surface- and Groun~~Water
Collection and Diversion X X X
6. Surface- and Ground-Water
Collection and Treatment X X X
7. Surface-Water, Ground-Water,
and Leachate Collection and
Treatment X X X X
8. Ground-Water Collection
and Ground-Water-Barrier X X
9. Ground-water Barrier and
Ground-Water Collection
and Treatment X X
10. Surface- and Ground-Water
Collection and Discharge with
Ground-Water Barrier X X X
11. Surface-water and Leachate
Collection and Discharge
with Ground-Water Barrier X X x
12. Ground-Water and leachate
Collection and Treatment X X x
13. Ground-Water Barrier and
Leachate Collection and
Treatment X X
14. Partial Excavation and
Ground-Water Barrier X X
15. Ground-Water Barrier with
Surface-Water and Ground-
~ater Collection,
Treatment and Discharge X X X
16. Ground-water Barrier with
Surface-water, Ground-
water, and Leachate
Collection and Treatment X X X X
. Regrading and revegetating is to be considered a part of all alternatives.
18
"IF: TAlK 1 FI
-------
Tobie 3
APPLICATION OF PROPOSED REMEDIAL ALTERNATIVES TO
NCP-REQUIRED ALTERNATIVES
Propose~ Alternative-
1. ~ ktion"
2. Excavation
3. Ground-water Barrier
4. Surface-Water Diversion,
Collection, and Discharge
a~d Ground-Water Bar-rier--
5. Surface- and Ground-Water
Collection and Diversion..
6. Su;face- and Ground-Water
Collection and Treatment-.
7. Surf~ce-Water, Ground-
~ater, and Leachate
Collection and Treatment--
8. Ground-Water Collection
a,j Ground-Water Barrier"
9. Ground-Water Barrier
a,d Ground-Water
Collection and Treatment..
10. Surface- and Ground-water
Collection and Discharge
-ith Ground-Water Barrier" -
11. Surface-Water and Leachate
Collection and Discharge
with Cround-Water Barrier
12. Ground-Water and Leachate
Collection and Treatment..
13. Ground-water Barrier ,and
Leachate Collection and
Treatment-
Off-Site NCP Required Alternative
Treatmentl Attain Exceed Reduce No
Oisposal Standards Standards Threat Action
x
x
x
x
X
x
X
X
X
X
X
X
. Re;rading and revegetating of the landfill cover is to be considered a
part of all alternatives.
-. Potentially applicable to both source control and management of
migration; all others apply to source control only.
19
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Table 3 (continued)
Proposed Alternative-
Off-SIte NCP RequIred AlternatIve
Treatment/ Attain Exceed Reduce No
Disposal Standards Standards Threat Action
14. Partial Excavation ~nd
Ground-Water Barrier
15. Ground-Water Barrier with
Surface-Water and Ground-
Water Collection,
Treatment and DiSCharge"
16. Ground-Water Barrier with
Surface-Water, Ground-
Water, and Leachate
Collection and Treatment--
x
x
x
- Regrading and revegetating of the landfill cover is to be considered a
part of all alternatives.
.- Potentially applIcable to both source control and management of
migration; all others apply to source control only.
REF: TASK 1 FS
~
20
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Alternative 15 - ground-water barrier with surface water and
ground water collection, treatment and dis-
charge.
These alternatives fall as appropriate into several of the
categories specified at 300.68 (f):
(i) attain requirements and (ii) exceed requirements: Al-
ternatives 7 and 15 attain and may exceed water quality
criteria. The LI FS did not include RCRA standards with
respect to treatment facility design, closure, and Sub-
part F ground water protection standards in the develop-
ment of any of the alternatives;
(iii)
do not attain requirements: Alternatives 1, 5, and 10
significantly reduce the release of hazardous substances
but may not attain applicable or relevant and appro-
priate water quality criteria; and
(iv)
no action:
alternative.
Alternative 1 represents the no action
Although off-site disposal is a category specified at 300.68 (f),
excavation of the refuse with off-site disposal at a RCRA facil-
ity was eliminateq on the basis of excessive cost without a
corresponding significant improvement in benefits relative to the
other alternatives considered.
The alternatives listed above were renumbered alternatives 1-5 in
the document "Feasibility Study - Task II: Detailed Evaluation of
Remedial Alternatives Boulder/Marshall Landfills, Boulder, Color-
ado". Table 4 presents the renumbered alternatives with asso-
ciated capital, operation and maintenance, and present worth
costs. A description of each of these alternatives is in this
section.
In addition to these five alternatives, EPA developed a sixth
alternative which is also described in this section. Table 4 also
shows the capital, operation and maintenance, and present worth
costs of this alternative.
EPA policy and NCP guidance require examination of innovative
technologies that destroy hazardous substances as an alternative
to land.disposal. This is consistent with EPA policy to seek
permanent solutions to environmental contamination as opposed to
on-site or off-site disposal of hazardous materials. The EPA
preferred alternative is designed to capture all contaminated
ground water leaving the site. The contaminated ground water
will then be treated by air stripping and carbon adsorption of
the off-gases. The contaminants captured in the off-gasses will
ultimately be destroyed during thermal regeneration of the car-
bon.
LI conducted the detailed analysis of the alternatives in accor-
dance with the NCP, 40 CFR 300.68 (h). The full discussion is in
21
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Tabl. 4
SUMMARY OF COST ESTIMATES FOR THE FIVE
EXAMPLE REMEDIAL ALTERNATIVES
Cap! tal Cos ts 0 , M Costs. Present Value**
Remed! al A1 ternative (1000'5 of S) (1000 's of S) (1000'5 of S)
1. MJ Action 0 38 358
2. Sur raO! water Cl"\d GrolS'ld
Water Collection Cl"\d Dis-
c:tIarge --.
a) drains CJ'\ly 2,036 72 2,715
b) wells CJ'\ly 1,104 152 2,537
3. SJr raO! Water, GrOJnd Water
and LeaChate Collection,
Treatment and DisCharge
a) dr ains CJ'\ly
(l) aeration basin 3,668 98 4,592
(2) air stripr;;ing 3,750 120 4.881
b) wells a'11y
(l) aeration basin 1 ,402 201 3,297
(2) air stripping . 1,529 222 3,622
4. Slurry Wall Wi tn Sur face
Water and Ground Water
Collection and DisCharge
.) drains CI'11y 3,131 72 3,810
b) wells only 2,199 152 3,632
s. Slurry Wall Wi th ~r'ace
Water end Croc.nd Water
Collection and Treatment
a) dr ajn5 CI'11 y
(1) aeration basin 3,162 94 II ,048
(2) air stripplng 3,289 116 4,383
b) wells CI'11y
(1-) aeration basin 2 ,230 174 3,870
(2) air stripping 2,357 196 4,205
6. EPA Alternative 1,819 153 3.259
* Annual Cost
** Capital cost plus the present value of the 0 & M cost assuming a 10%
interest rate and 30 year planning period.
22
REF: TA8K 2 F8
-------
the "Feasibility study - Task II: Detailed Evaluation of Remedial
Alternatives".
LI refined the description of the alternatives in detail, with an
emphasis on the use of established technologies; detailed cost
estimates; evaluation of engineering implementation, reliability,
and constructibility; and assessment of the extent to which each
alternative is expected to prevent, mitigate, or minimize threats
to, and provide adequate protection of, public health, welfare,
and the environment.
The five LI alternatives and the one EPA alternative are as
follows:
Alternativ~ the no action alternative, consists of the
previously instal~ed 60-inch pressurized pipeline, continued
maintenance of~the pipeline, and environmental monitoring.
The environmental monitoring will consist of semi-annual
sampling of the surface water monitoring stations and ground-
water wells shown in Figure 7 and sample analyses for the
parameters shown in Table 5. The no action alternative is
not recommended because it does not prevent offsite migration
of, contaminants and thus does not reduce the potential
damages to public health, welfare, and the environment.
Alternative 2, 'includes the following operable units:
Surface Water Collection
- perimeter ditches around the landfill to convey runoff
to Cowdrey drainage
- collection of the Cowdrey Drainage flow
Ground Water Collection
- east boundary drain or well array
- west boundary drain or well array
~ off-site drain or well array south of Community Ditch
- Cowdrey drainage drain or well array (north of east
boundary drain)
Landfill Improvements
- regradinq and revegetation of the inactive
promote runoff and minimize infiltration
- perimeter fencing
landfill to
'Environmental Monitoring
- surface water and ground water monitoring as described
for Alternative 1
Treatment
- passive via collection of surface and ground water in a
system of sedimentation/equalization basins
Figure 8 is a schematic representation of Alternative 2.
Whether subsurface drains or wells are employed, the landfill
will be sUbstantially isolated from the surrounding alluvial
23
-------
INACTIVE'
./'~ COO
,./" 'NA-4
CRO MARSHALL I
," ..'. ..'" f' cOPO
I 8EPA- 3
I
I
I
- -- --1 8NA-l
I
I
I N.C.A.R.
I~
I:
I~
I
J
I
I
I
15 14
1-
22 23
~ To South Boulder Creek
.~.
. ...' .......,... "'. ~......
60'INCH
PRESSURIZED
PIPELINE
MARSHAL/.
I.AKE
ACTIVE
BOULDER
LANDFILL
FX-1
S8W-1
D8W-1
EXPLANATION
22 23
+
27 26FX-8
I
S.?? : Suoerior Pa~er Products
N.C.AR. : Notional Canter for Atmosoneric: Research
o
I
FIGURE 7
ALTERNATIVE 1 - NO ACTION:
ENVIRONMENTAL MONITORING NETWORK
24
l.1
\
To tne
Louisville -'
Diversion
8 NA-9
8
NA-7
8
NA-6 t
N
8 EPA-S
1000
2000 f..,
REF: FINAL FS
-------
Table 5
fJATSR QC~.LITY P,4.RA11ETERS TO BE EVALCATED CNDER TEE
~O ACTION ALTERNATIVE
F:.~:C P'3r3~e':~:s
ce~th t~ water (~e~ls only)
fl~w rat~ (surfac~ water only)
f:H
Gereral Analytical Para~et:rs
phenols
total dissolved solids
total suspended solidS (s~rface water only)
!norcanic Parameters
sodium
potassil.lm,
ca.lcit.,;m
rr.a,;nesium
ochlor ice
~e':3l P3Z':r~et==s
a :1..;m::~I...r.1
a:~er;.:c
oaril...m
c3cii1ium
cnromium
copper
iron
Volatile OrQanics
benzene
bis(Chloromethyl)ether
bromoForm
carbon tetrachloride
chlorobenzene
2-chloroethyl vinylether
chlorofor~
dichlorobromomethane
aichloroaifluoromethane
l,l-aichloroethane
1,2-diChloroethane
l,l-dichloroethylene
l,2-oichloropropane
25
specific canductar.c~
temcer3tur~
fluor ide
sulfate
ammonia as N
total alkalinity as CaC03
nitrate + nitrits, as N
leac
mar.t;ar.ese
mercury
selenium
silver
zinc
1,3-dichloropropylene
ethylbenzene
methylbromide
methylchlorlde
methylene chloride
1,1,2,2-tetrachloroethane
toluene
trans-l,2-dichloroethylene
l,l,l-trichloroethane
l,l,2-trichloroethane
trichloroethylene
trichlorofluoromethane
vinyl chloride
.,: '.AL"
-------
l.1
~
To Ine
LouIsvIlle ~
DiverSion
15 14
...
22 23
~ To Souln Boulder Creek
INACT I V E
--.
60.. I~c~q \
PRESSURIZ:D J
PIPELINE
---
N.C.A.~.
,WAR SHALL
lAKE
';
11
'-
ACTIVE
BOULDER
LANOFILL
=
-0
-0
~
"3
~
(
N
SP.P. :I Superior'apw Producu
N.C.A.R. = N~tion~1 Center fnr Atmospheric ReseMch
@ ..\pproxim~te Alignment of Subsurf~ce Collection Or~ins (Dot Represenu Loc~tion of
Collection Sumps if Required) or Pumping Well Amys
Surface.Water Collection Point
Small MixinliSedimentation Basin
22 23
27/26
eXPLANATION
.
~
A
System Oisch~rge Point
New Perimeter. Surface-Wacer O~i
e System
o
I
1000
I
2000 f..,
I
---
Fivur. 8
ALTERNATIVE 2 - SURFACE WATER AND GROUND WATER
COLLECTION Aff DISCHARGE
REF: 'II8AL F8
-------
grGund ~3~er. The drains or wells would be completed to t~e
base of the alluvium. with this alternative, contaminants
may still migrate to the east via the subsurface drain
beneath the pressurized pipeline and possibly to the north of
the Cowdrey drain. Under this alternative, the source of
contaminants will not be eliminated because the refuse will
not be significantly dewatered. LI reports that this is a
result of upflow from th~ bedrock aquifers and the low trans-
missivities of the alluvium. The location and effectiveness
of the off-site drain is questionable because the extent and
nature of off-site contamination is unknown.
The combined surface water and ground water flows collected
will be passively treated by passage through a sedimentation
and equalization basin resulting in some nominal reductions
in contaminant concentrations. Based o~ the predicted qual-
ity of the effluent, a greater than 10- incremental cancer
risk would be pgsed through lifetime ingestion of benzene,
trichloroethylene, and tetrachloroethylene in the water. LI
predicts the effluent concentrations to be as follows:
Compound
Benzene
Trichloroethylene
Tetrachloroethylene
CRL (ppb)*
0.67
2.80
0.88.
Effluent
Concentration
1
7
27
(ppb )
*CRL - Cancer Risk Limit for 10-6 incremental cancer risk
from consumption of water only (ppb).
Alternative 3, shown in Figure 9, is similar to Alternative 2
with the addition of two components. A subsurface drain would-
be installed in the southern portion of the inactive landfill
to collect leachate, and the combined surface water, ground-
water, and leachate flows would be actively treated before
discharge. Although the leachate collection drain will de-
water some of the refuse in the southern section of the
inactive landfill, it does not provide any further contain-
ment of contaminants relative to Alternative 2. Both dif-
fused aeration (assumed VOC reduction of 70') and air strip-
ping (assumed VOC reduction of 99') were evaluated under thi~
alternative. Only air stripping results in less than 10-
incremental cancer risks with respect to lifetime ingestion
of the effluent due to the presence of benzene and tetra-
chloroethylene. The effluent concentrations are shown below:
Compound
Benzene
Trichloroethylene
Tetrachloroethylene
CRL (ppb)*
0.67
2.80
0.88
Effluent
Concentration
2 to <1
3 to <1
11 to <1
(ppb)
Note: Range reflects effluent concentrations from diffused
aeration and air stripping respectively.
27
-------
15 14
..
22 f23
To rhe
Louis,,, i Ie
D. . -"
''''er~lon
~ To South Boulder C:eek
INACTIVE
.-.
--- .' tANDFlll I
lAGOON I
---
N.C.A.R.
MA,;J_~HAI.I.
lAK~
ii
»
...
-
ACTIVE
BOULDER
lANDFill
t
N
I
eXPLANATION
S.P.? = Superior PaD.r Products
N.C.AR. : National C."tet For Atmoson,ric Researcn
@ Approximate Alignment of Subsurface Collecrion Drains (Dot Recres.nts
Location of Co Ilection Sumps if Required) or Pymping Well Arrays
Surface Water Coll,ctian Points
Treatment Facility
2 23
27/26
.
~
A
System Discharge Point
New Perimeter Surface Water Draina;. System
o
I
1000
2000 f..,
I
---
Fig ure cr
nF: FINAL F~
ALTERNATIVE 3 - SURFACE WATER, GROUND WATER, AND
LEACHATE COLLECTION, TREATMENT, AND DISCHARGE
28
-------
~
Alternati~e J also includes landfill improvements and
ronmental monitoring as described for Alternative 2.
envi-
Al~~rnativ~!L (see Figure 10) is similar to Alternative 2
but includes a slurry wall around the perimeter of the land-
fill, and the draining and treatment of the contents of the
lagoons. The lagoons would be subsequently backfilled and
regraded to prevent future seeps of leachate. The French
drain flow presently discharging to lagoon #1 would be routed
to the sedimentation/equalization basin. Under this alterna-
tive the FS states that there would be no significantly
increased drawdown of alluvial water within the bounds of the
slurry wall, and thus no significantly increased dewatering
of the refuse relative to Alternative 2 (no slurry wall).
Removing the lagoons would eliminate possible direct exposure
of the public to the contaminants contained therein. As with
Alternative 2, passive treatment will not reduce the concen-
trations of bel1~ene, tri~~lc:>roethYlene, or tetra.chlor?e~hy-
lene to less than the 10 1ncremental cancer r1sk l1m1ts.
Alternative 4 also includes landfill improvements and envi-
ronmental monitoring as described for Alternative 2.
Alternative 5, (see Figure 10) is equivalent to Alternative 3
with the addition of a perimeter slurry wall. As discussed
under Alternative 4, the slurry wall is not expected to
increase signi~icantly the dewatering of the refuse. As with
Alternative 3,. sedimentation basins and air stripping are
likely to achieve an effluent meeting all applicable or
relevant and appropriate standards or criteria. Alternative
5 also includes landfill improvements and environmental moni-
toring described for Alternative 2.
Table 6 summarizes the five alternatives of the LI FS with
respect to performance, reliability, and implementability.
In addition to the five alternatives that LI developed in the FS,
EPA identified another alternative. This alternative is made up
of elements of the other five, successfully meets the objectives
of the FS, and is consistent with the NCP, 40 CFR 300.68 (i).
Alternative 6, (see Figure 11) includes the following com-
ponents:
Ground-Water Collection
- east boundary drain
- Cowdrey Drain
- south boundary drain
Treatment of Contaminated Ground Water
- sedimentation basins
- air stripper
- air stripper off-gas carbon adsorption
Environmental Monitoring
- surface water, ground water, and the treatment system
29
-------
S.P.~. a Suo.rior Paoe, Products
N.C.A~. : National Canter ~or Atmolcneric ~.secrch
~ AgorOJlimate Alic;nmen' of Subsurface Col'.ction Drains (Dot ~epr.sents
Location of Collection Sumos if Required) 0' Pumpin9 Well Arrays
. Surface Warer Collection Points
~ Small MiainglSedimentarion Basin (Alternative 4) or Treerment Facility (Alternative 5)
. System Discharge Pain' 0 1000
- - - New Perimerer Surface Warer Drainage S."rem I '
//////// AcoroJlimare Location of p~,.ime'er Siu Wall and Oo'ia"al In'erior Drain 5 srem 0' Pum
15...14
22 23
i 0 rh e
Louls...lle --
Ci"otr5lon
~ To South Sou/der Cree"
INACTIVE
--.
6~"~C~\
P~ESSURIZ:J -
?IPE!.INE
N.C.A..q.
(
N
I
EXPLANATION
2000 r..,
Fi9url 10
ALTERNATIVES 4&5 - GROUND WATER BARRIER WITH SURFACE WATER
& GROUND WATER COLLECTION TREATMENT (Alternative 5), AND DISCHARGE
30
MF: FINAL F.
-------
(S)
Rf]fEI)lAL ALTERHATIVES
Relied ia I
Alternative
(1)
(2)
Ho Action
su , OW Collection
, Dbcharae
I.tJ
-
(3)
su. OW , Leachate
Collection Treataent
(4)
OW 8arrier vI
su , CW Collection
, Di.charle
CW Barrier vI
SW , CW Collection
Treat.nt
Dbcharle
(6) EPA Alternative
Operable
Unit
Honitorinl
(g)
(g)
(h)
(b)
(c)
South
(h)
(a)
(b)
Cc)
Cd)
(e)
(f)
(I)
(h)
West Drain
East Drain
Covdrey Drain
Off-site Drain
Surface Water Control
Sed./Equal 8a81ns
Ca through f)
Leachate Drain
Air.trippinl Tower
(a through f)
Slurry Wall
(8 through f)
Drain
Tobie 6
CRITERION
Source
Control
None
EFFECTIVENESS
Site
Containment
I
None
Hinor Effect
HaJor Effect
No Effect
No Effect
Minor Effect
None
Hlnor Effect
Major Effect
Hinor Effect
No Effect
Major Effect
None
(as above)
Major Effect Minor Effect
None None
PERFORMANCE
WQ
Improvement
Uone
Moderate Effect
Major EHec t
MInor Effect
Minor Effect
MInor Effect
Major Effect
Major Effect
Hajor Effect
(as above under Alternative 2)
Hinor Effect Major Effect None
(as above under alternative 2)
(a8 above under Alternative 4)
(a8 above under Alternative )
USEFUL LIFE
Indefinite
10-30 years
10-30 years
10-30 years
10-30 years
10-30 years
30 years
(88 above)
10-30 years
30 years
(as above unde!
Alternative 2;
30 years or mol
Major Effect Major Effect Major Effect 10- ]11 ,,", .II'S
Major Effect Major Effec t Maju.- Eff~ct I!J- J( J .,' \ '. I 1 :-)
Minor Effect Minor Effect Minor Effect I ()-'II) ", . . I '" ~-.
None None Maj or Effect J() )"','1:,
-------
Table
6
(cont.)
1Da!Dua. Al.1DIIAf"!S
IELWILIn
o , " .equ1re~nta
1-4i.1 O,er.bl.
Altern.tlv. Unit C018plu J t ~ frequency
(1) .. AcU- 11081&01'18& 51.ple Quart.rI,
(2) .&GII (a) VeaC Dl'ala HOder.tel, eo.pl.. S-IO ye.n
(It) Ea.c Oral. to "
(c) CoWre,. Oral. .. "
(eI) Off-8ite DI'818 to .. "
(e) Surface Vacel' Control S18ple 2-5 y.an
.
(I) .... .IEquel 'a81..8 518pl. 1-2 yun
W
N
U)
SII. GII , Leachate
Collectlo. Tl'e.t..ac
(a throu,h f)
Leachata Drdn
Ail'acrlppla, T0M81'
5-10 yun
Dal1y or lleekl,
(.. above)
Hoder.tely CO.ple.
HOder.tely Coaplex
(.)
(h)
(6) GV "l'I'lel' -/ (a throu.h I)
IV , GII CoUecU- (,) Slurry 11011
& Dloch.I',.
'
.
U) GII 'arrler -I (0 throu,h f)
III , GII Coll.ctloa <,)
11'_'-' ... Dla- (h)
.......
(6) EPA Alternative (b)
(c)
South Drain
(h)
(.. r.qulr.d under Alt.rnativ. 2~
Hon. Required
(.a .bove under Altern.tlve 2)
(.. .bove under Alternatlv. 4)
(.. .bove under Alternatlv. ])
Modt!rdlely Complex 5-10 years
II " "
II " II
II " Daily or weekly
'o'.lble f.llure Hode.
Off-.lt. .I,r.tlon b.tveen 8OO1torloi
.t.tlon.
-CloSIJnl"lulllnl of dr'ln Ot 'uap
-'u.p hllure
-freellnl of tr.n.fer plplol
It
..
to
-ch.nnel' ero.lon/8edl8ent.tlon
-F.llure of ,u.p pu8p
-£ro.lon .round .nd b,-p"8Inl of 'U8p
-In.uffJclent retention t188 tor co.pl.t.
.edl.ent re8O..1
-In.ufflclent '1It.tlon for .ISnlf1cent
reduction In vol.tll. orlenlc.
-Contr..t bet~een qule.eent .nd turbulent
condition. required for .edlaent
v.. YOC control
(.. .bove)
-Pover f.llure
-PIUlllnl of p.cklnl ..terl.1 b, .edJ-
.ent or preclplt.te.
-che.lc.l ch.nlea (I.e.. pH)
-Inco.plete re8Ov.1 of orl.nle.
-('8 .bove)
-Che.lc.1 breakthroulh b, IDcoapatJbla
leachate.
-Underflow bene.th 'Iurry vall
(I.... found.tloD f'llure)
-Cluggillg,
II
fa i lu ["I" ,
II
pump
11'"l'l.iIlB
II
"
-I'uwer failur~'. plllggiI1f-'"
changes
-Ilicomplele remuv,"
, 1,,'JII'1.-d]
,'""I i,"s
~
-------
1DC!DU1. AJ.TDNATIVU
....4t81
Alcar.act"a
(1) .. AcU-
(2)
.Ieu
w
w
" (])
sv.eu , LeachaCe
Collecet- T~e.t88ne
(4) eu "rrt.~ ./
IV , eu Coll.cct..
I Dtac"'~,.
(') GU "rrte~ -/
IV I ell CeUecU..
T~a.C_.C 8841
Dtac"'~,.
(6) EPA Alternative
Ope r" 1.
Unit
IlDalcodna
(a) "..e Dratn
(II)
Ia.e Dret.
(c) Cowdre, Dr.ln
(4) Off-.tce Dr.18
(e)
(I)
Surf.ce Vacer Concrol
Se4.IE,ual I..lna
(a chrou.h f)
(I) Leachace Drala
(h) AJr.ert"tnl Tover
(I)
(a chrouh,h f)
Slun, Val1
(I)
(h)
(a throulh f)
(b)
(c)
South Drain
(h)
Tobie 6 (cont.)
CIUrU(OH
(onu rue t ab IIlty
Syate. alread, in place
St rallht forvard
Difficult olon, aouthern
portion due to tha
deprh to bedrock
StralShtforvard
Kajar difficult, due to the
depth to bedrock
Stra I"ht forvard
Stullhtfol"Vord
(AI above)
StulshtfoI"Vard
StutshtfoI"Vard
Caa above under Alternative 2)
KaJor dlfftcultlel anttclpated
due to 11.lted apaca available
and lack of aultable foundation
-te..1818
Caa above under Alternative 2)
Caa above under Alternattve 4)
Caa above unde.. Alternattve )
DifflLlilt along
portiun
Straightforward
IHfficlilt along
purtion
Straightforward
~
IHPLI'JIDfTAI f L1 TT
lli!
~I 80nth
12 80ntha
15 80DCha
16 -ntha
Southern 15 months
Eastern
15 months
15 months
15 months
Safety Conslderatlona
None
-Sidewall Itability
-f.poaure to conta.lnated OW
-Severe Itdewall atabillt, proble..
-E.posure to conta.tnated OW
-Traffic con,eatlon alonl S. 66th St.
-E.poaure" to cont..tnated OW
-Severe al~evall atabillt, probl...
-EKpolure to cont..lnated OW
None
-(aa above)
-[.poaure to .,ery cont&81nated leachate
-I.pact of air ..I..10n. OD aurrouDdlDS
area
-Cal above under Alternatlv. 2)
-Traffic con,eltlon olon, S. 66th St.
See (2) abovt;'
"
"
Nune
REF: TASK 2 FS
-------
'5 14
22 + 23
INACTive
~ To Sou,h Bouldtf Creek
"'.'
LANDFILL
.. "'.10"."'.
MANSHAU
LAKE
60. INCH ~i
PRESSURIZED:
PIPE ~INE I
I
I
I
I
I
I
I
I
,
I
I
I
,
I
,
22 3---
27/21,Fx.e
FX.1
SBW.1 ,
DeW.) ,
I
---'
ACTIve
BOULDER
LANDFill
EXPLANATION
s. p. P. . Suo.rior PO"' "odue,.
N.C.A.R. J No"OftOI un'., for AtmosC)heric Research
MONITORING LOCA TIONI
. WILL
. SU"FACE WATIR
- IU.SURFACE DRAIN
----NRIIiETIR I""'ACI WATER DRAINAGE IVSnll
,
. FIGURE 11
ALTERNATIVE 8 - E'A ALTERNATIVE
~4
"
.A.-1S
l.)
To the
louisvi lie
Di~ers'on -'
,
I
I
I
I
I
I
I 8NA.1
I
I
I N.C.A.R.
I
I ..
I ~ .
! i :p~~A~: t
I N
,
8EP4-21 I
.
NA-]
. EPA.
1000
I
2000 1M,
I
-------
<.>
~ill be monitored
Landfill Improvements
- perimeter ditches around the landfill
- drain the lagoon
- regrade and revegetate the inactive landfill
mote runoff and minimize infiltration
- perimeter fenci~g,
This alternativ~ is expected to capture the contaminated
ground water migrating from the site and treat it by means of
sedimentation and air stripping so that the effluent will
attain all applicable or relevant and appropriate water qual-
ity standards or criteria. Under this alternative, the
source of contaminants (the refuse) will not be eliminated
because the refuse will not be significantly dewatered.
How~ver, according to the LI FS, dewatering the landfill may
not be practicaple due to the upflow from the bedrock aqui-
fers and the low"transmissivities of the alluvium.
to pro-
Under this alternative, surface water leaving the site will
not be collected or treated. During the RI, analyses of
surface water at the site boundary showed no contamination.
To meet other appropriate environmental laws (RCRA for this
site), design for elements of this alternative - the draining
of the lagoons, sedimentation basins, treatment system,
associated piping, and off-site ground water will take into
account the RCRA requirements. This will be discussed more
fully in the section fon~!sten£y_~it~othe!_Enviro!!!!!en!~l
Laws.
Table 6 also summarizes the EPA alternative with respect to
performance, reliability, and implementability.
COMMUNITY RELATIONS
EPA placed the RI/FS report submitted by LI in six information
repositories in metropolitan Denver and Boulder County. The three
week public comment period started on February 25, 1986, and
culminated with a public hearing held on March 18, 1986 to
receive questions, position statements, and comments from the
public on the draft RI/FS.
The majority of the comments on the RI/FS came from the CDH,
aCHD, and the Boulder County Public Works Department (BCPWD).
CDH commented on the need for: 1) an expanded and improved moni-
toring system; 2) treatment facility in compliance with RCRA
design standards; 3) air stripping as opposed to aeration as the
primary treatment process; 4) reevaluation of the slurry wall;
and 5) completion of the public health evaluation. The BCHD also
commented on the need for expanded monitoring, air stripping, and
reevaluation of the slurry wall. The BCPWD emphasized the terms
of the Cooperative Agreement especially as it related to LI's
35
-------
responsibility in the financing of remedial action at the site.
The CDH and BCHD technical comments have been addressed in the
Agency's preferred alternative. Two private citizens expressed
the opinion that the objectives of the FS do not address the
potential for contamination of the bedrock aquifers. Also a
private citizen questioned the validity of the calibration period
for the ground water model _which is the primary tool used by LI
to evaluate technically the effectiveness of the various alterna-
tives.. .
Following the public comment period, EPA prepared a responsive-
ness summary for the comments received. Both the responsiveness
summary and a transcript of the public meeting were placed in all
six repositories.
EPA shares the concerns expressed by the private citizens and
local and state gov~~nments. These concerns are addressed in the
Recommended Alternative section. Note especially the discussion
of additional field testing and analysis pertaining to the slurry
wall.
CONSISTENCY WITH OTHER ENVIRONMENTAL REQUIREMENTS
Section 300.68(j) of the NCP requires that the lead agency select
a cost-effective remedy that effectively mitigates and minimizes
threats to and that provides adequate protection of public
health, welfare and the environment. This requires selection of
a remedy that attains or exceeds applicable or relevant and
appropriate Federal public health and environmental requirements
identified for each specific site. EPA has determined that the
following applicable or relevant and appropriate standards apply
to the Marshall Landfill site:
Safe Drinking Water Act: Maximum Contaminant Levels (MCLs),
Recommended Maximum Contaminant Levels (RMCLs)-
Clean Water Act: point source control; water quality standards
Clean Air Act: stationary source of volatile orqanics
Resource Conservation and Recovery Act (RCRA): ground-water
monitoring and corrective action; site access restrictions:
runon/runoff controls, secondary containment and leak detection
for surface impoundments and tanks and associated piping.
In evaluating the alternatives, EPA has determined that the
recommended alternative would comply with these standards as
follows: .
Safe Drinking Water Act: MCLs and RMCLs are among the cri-
teria used to establish the effluent standards for both the
treatment facility and the target off-site ground-water qual-
ity concentrations.
36
-------
Clean Water Act: EPA met with representatives of CDH Water
Quality Division at which time EPA was made aware of CDH's
requirement for a Colorado Pollution Discharge Elimination
System (CPOES) permit for the treatment facility. The State
intends to require that LI obtain a CPOES permit. The
facility effluent will have to comply with Colorado stream
standards for the mainstem of South Boulder Creek and other
water quality standards as' determined by COH for toxic pollu-
tants. '
Clean Air Act: COH determines the need and thus the
requirement for emission controls for the release of toxic,
hazardous, or odiferous compounds on the basis of:
1) odors at the site boundary;
2) maximum ground level concentrations greater than the
Threshold Limit Value (TLV) divided by 420 (a factor
currently used by the state of Massachussetts and
under consideration by CDH);
3) the existence of reasonable available control tech-
nology (RACT);
4) the economic burden of installing RACT.
Until CDH is notified of the expected emission and has
analyzed the emission data, the requirement for emission
controls cannot be determined.' The proposed off-gas carbon
system represents RACT and is included in the recommended
alternative to prevent transferring hazardous substances from
one environmental medium to another. EPA has met with CDH
and informed them that an air stripper tower is being
considered at the Marshall Landfill.
Resource Conservation and Recovery Act: The boundary of the
site will be considered the compliance point for ground water
monitoring and corrective action. The surface impoundments
and piping will have secondary containment which also will
provide for leak detection. The perimeter ditches will
provide runon/runoff controls. The facility will meet 40 CFR
264 Subpart B General Facility Standards, Subpart C
Preparedness and Prevention, Subpart D Contingency Plan and
Emergency Procedures, and Subpart E Manifest System,
Recordkeeping, and Reporting. Spent off-gas carbon and
sludges dredged from the sedimentation ponds will be handled
and treated/disposed as hazardous waste.
RECOMMENDED ALTERNATIVE
Section 300.68 (i) of the NCP (40 CFR Part 300), states that the
appropriate extent of remedy shall be determined by the lead
agency's selection of a cost effective remedial alternative that
effectively mitigates and minimizes damage to and provides
adequate protection of public health and welfare and the
environment. Except for reasons of fund-balancing difficulties,
technical impracticality, or unacceptable environmental impacts,
37
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"
"
this will require selection of a remedy that attains or exceeds
applicable or relevant and appropriate Federal public health and
environmental requirements.
EPA's recommended alternative consists of selected operable units
that comprise the five alternatives evaluated by LI. This
alternative is consistent with 40 CFR 300.68 (i).
Ground Water Collection
To eliminate offsite transport of contaminants via alluvial
ground water, a drain or series of drains will be constructed
along the entire eastern and southern boundaries of the 160-acre
site. These two directions were chosen because of the migration
patterns identified by the RI. EPA did not include a west drain
in the recommende~, alternative because it would not improve
source control relative to the performance of the combined south
and east drains. EPA did not include a north drain because
ground water moving north eventually intersects Cowdrey Drainage.
Cowdrey Drainage underflow will be collected by the east drain.
The drain will consist of 3 to 5 foot wide trenches excavated one
foot into bedrock and containing drain pipe and gravel.
As shown in Figure' 12, a 6-inch layer of fine gravel in the base
of the trench will provide the bedding for the 6-inch perforated
(or slotted) drain pipe. The trench will then be backfilled with
three-quarter inch gravel to approximately the maximum water
table level. If deemed necessary during the remedial design
phase, the trench will be lined or the drain pipe wrapped with
filter fabric to reduce blinding of the collection system. The
remainder of the trench will be backfilled with compacted fill
originally removed during the excavation. The drain will follow
the natural grade of the bedrock. Sumps will be installed where
required for gravity collection of ground water.
The sumps will be constructed from 6-foot sections of 60-inch
steel reinforced concrete sewer pipe, installed vertically with a
6-inch thick concrete floor. An alternatinq duplex pump system
will be installed in each sump to remove collected ground water.
The pumps will operate intermittently in response to signals from
float type level controls within the sump. Ground water will
then be pumped to the onsite treatment facility via 4-inch buried
PVC pipe.
EPA and LI's estimates for a drain system show it to be more
costly than a well array desiqned to serve the same pUrpose. The
drain is still preferred. The drain will require significantly
less maintenance. If well spacing to achieve flow convergence
has been overestimated in the FS, then the cost of the well array
system could increase significantly. Also, a lower discount rate
or longer planning horizon would tend to narrow the difference in
the present value of each option. At this time, the lower
operation and maintenance costs associated with the drain system
38
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<.
.., J
GROUND SURFACE
MINIMUM SLOPE ANGLE
REQUIRED TO MAINTAIN
SIDEWALL STABILITY
10' -1.5' DEPENDING
ON SATURATED
THICKNESS
COMPACTED COMMON FILL
''''-,
.2.. APPROXIMATE
== MAXIMUM
WATER TABLE
LEVEL
BEDROCK
.\: :::":;. ~: ,:<."i :;;: ::;: :.:,:',:~, ':: ~}}i:t:} .,..,
... :.:: G~AVEt BACKFILL:. ::~
:". >";(3ii.QRAI~)6c~('
; :. 8.:' "0 " .: :. '.:.. ~.I.:'
~ I" ::.' ::" .',: .:'.':'.'
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-------
.)
Treatment of Contaminated Water
Contaminated water collected at the Marshall site will be treated
to achieve an effluent quality that meets all applicable or
relevant and appropriate standards and criteria. These include
Recommended Maximum Contaminant Levels (RMCLs), Maximum Contami-
nant Levels (MCLs), Clean Water Act Water Quality'Criteria,
Suggested No Adverse Respons~ Limits (SNARLs), Adjusted Accepted
Daily Intakes (AADIs), .and Colorado Stream Standards. These
standards and criteria are presented in Table 7 along with the
effluent standard which represents the most conservative of the
criteria.
The effluent standard will be achieved by treating collected
ground water in a facility consisting of equalization/sedimenta-
tion basins, air stripper, and air stripper off-gas carbon
adsorption. The facility will be located on Cowdrey property
east of South 66th S~'reet. Effluent will be discharged to Cow-
drey Drainage. The effluent will meet CPDES permit requirements
to be set by the State of Colorado. The facility will meet
applicable RCRA standards identified at 40 CFR 264.
The surface impoundments will consist of a 10 foot by 10 foot
catch basin to receive ground water from the collection system
followed by a 25 foot by 25 foot equalization/sedimentation
basin. The basins will be 4 feet deep, and double lined with a
leak detection system between the liners. The liner material
will be compatible with the constituents of t~e ground water.
All underground piping will be double piped for leak containment
and leak detection.
The air stripper will be designed and operated to achieve the
effluent standards for the volatile organics. The discharge from
the off-gas carbon system will contain non-detectable
concentrations of the volatile organics. The off-gas discharge
will be monitored to demonstrate attainment of this standard and
to verify adequate maintenance of the off-gas system in
accordance with manufacturer recommendation. Spent carbon from
the air stripper will be thermally regenerated to destroy the
adsorbed hazardous constituents.
The effluent standards for inorganic parameters are largely set
by the South Boulder Creek instream water quality standards. It
is likely the influent inorganic quality to the treatment system
will comply with these standards. One possible exception may be
iron (predicted effluent concentration = 1.2 mg/l), in which case
chemical addition may be required to facilitate additional pre-
cipitation in the equalization/sedimentation basins.
The treatment system will be operated until the effluent
standards specified in Table 7 are met by the collected ground
water or until such time that EPA determines that the collected
ground water no longer adversely affects water quality.
41
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TABLB 1
APPLICABLI OR RBLEVANT AND APPROPRIATE WATER QUALITY STANDARDS AND CRITIiRIA
Treat....nt 1
PlCl.2 RPlCl.3 4 SNARl.5 AADI6 errlu..nt
Strea. I WQC Standard.
Standard.
Tolal Di..ohed 500 .1l/1 500 18./1
Solid.
Chlori.... 250 ../1 250 .11./1 ~50 .../1
Sul,..t.. 250 .,/1 2:.U .1l11 250 0111./1
A..oni. 20 20
Nltr..t.. 10 ..11 10 ../1 10 ..11 f'- 10 .11/1 , to.n"
Ar8ttna... 50 50 5u 010.0025'88 100 0
Bari... 1000 150U 11100 1000
Cad.I... 0.6 10 5 10 18 0.'6
Chro.i... 50 1251' (50 I' 120 .
(50 I' 110 25
Copper 1 1300 1000 1300 1
Iron 300 300
Lealt 4 50 20 50 4
"an,.ne..e 50 50
~ ".rcury 0.05 2 3 10 5 0.05
N Nlckfll 50 15.4 15.4
S.Ieni... 10 10 45 10 106 10
81 her 0.1 50 50 0.1
Zinc 50 5000 50
Ph.nola 3500 350V..
I,I-Dlchloro.thane ...
10.941 0
tran. 1,2-Dlchloroethylene 10 350 10
I,I,I-Trlchloroethane' 200 19,000 1000 200
Tetrachloroethylene 010.88'" 20 0'"
Dlchloroeth,lene 0(0.033'" 70 0'"
Ithylbenz.ne 680 2400 3400 680
Toluen. 2000 15,000 340 10, 100 340
B.nzene 0 0(0.61}88 10 0'"
Trichloroethylene 0 OC 2 .11'" 75 0'"
(Table 7 continued)
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s:-
I".)
Table
7
(continued)
'<
G
Colorado
.alnale.
Dr.lna,e
Slrea. Slandard. are .el
of Soulh Boulder Creek fro.
~hich i. a lribulary lo Soulh
for ap~ciflc bodle. of water. The .landard. .hown here
the h~ad waler. lo Soulh Boulder Rd. The.e .l.ndard. apply
Buulder Creek
are
to
for the
Cowdrey
2
"..:~I.u. Conlo.lna"l Level. 1 HCLIO I Wp.re foraulated under lhe Safe Drinkln. "'ater Act a. the allowable le"..I. In
pllbllo water ,,"ppllea. The levela '..nrr..Il)' ...."..dder..d Ilfetl..e e"poeure fro. a nu..ber of aoure..a, ..,cludln,
air. waler. and food, when calculal'o« Ihe allowahle I....el. for drlnkin, waler. The.e le..ela con.ldered
h...lth f.clora .nd lhe econo.lc feaalbililr of re8l0..ln, each conta"'n.nt fro. lhe drlnkln, ~ater.
:8
"",'o..rnded Ha." .u. Conl..1 n.nl L....e I.. - The EPA ha.. d.."elop"d and propolled Reco...ended
1,.,,',-1. purauant 10 the Safe Dri"klll' Wit,.." A"I. Th..)' are ,uldelinee for drinkin, ..aler
a.andarda. and arp. L..lld enlirelr 00 he.lth conNid"rotione.
Cont....lnllnt
r.lhf~r than
~ax'.u.
qual i I)'
.
"'a l.. r QuaJll, Criteria - The Clean "'a'er Ac' IC"'AI Water Oualll)' Crit~l. were developed under Sectlnn 303c of
Ihr r"'A to prot.....1 the beneficial II~"" of . water hod)'. The crllerla '.hpwn here are non-e~forceable but are
I"telldl'd a. 'uldellne. for the pro'ertloll of hu.an health fro. Ilfetl." e"po.ure of drinkin, the wa'er.
5
""1\111. Ad"i.orie. (SNARLS I - The H..olth A,h'laorlea or SU«'..,,'ed No Ad,'rr.e Re..ponse Llmlt8 (SNARI.SI are
'"Idelln.-. dr"elnprd b, the Offl,'" of IIrl"kln. "'.ler. The)' were formulated t.o pro"lde .uidance Ie"," 8 fur
........i...I". root rout Ineh' found '0 water ""Pld iea. The ,uldellne. "lied here are for Jon, ler. e"pollur.. '.n terma
of ...,u,ka or .onlhal In a I-)'ear-old Inf,,,,l. "aaf,,')' mar.ln h.. be..n In,'orporaled Into the le"et.., The SNARI.S
dn unt 'n'~orpnrn'f~ cbrr.ah
-------
~
~
All con~enlrallon. are expre..ed In u~/l unl.... Indicaled olherise
S'~~cl~'r1t '.)r hexavalenl chro.i".
10 'nere-a.p',1 C8nCftr raak "or ~r,,,k in" w"ler only
Thr Muggeale~ cleanup alandard. are 0 because lhl. co.pound I. a carcinogen.
CI..anup will be a..u...d co....I"... wilh respecl lo lh..a.. co..pounda when lh"y
li.lt defined by lhe EPA Conlracl Laboralory Pro.re..
Thi. standard I.. for 1,2 - dichloroeth..ne and r..preaenl. lhe
only. Thl. alandard ia ua"~ for 1,1 - dichloraelhane becauae
an~ the lack 0' .paclflc ~rileria for 1,1 - dichloraelhane.
Table
7
(continued)
NOn,:;
. .
. ..
. '",.
are below the
....lhod
deleclion
10-8 Incre..ed cancer riak for drinking waler
of lhe che.ical al..tlarlly of lhe lwo co.pound.
"
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v
/>.) .)
Monitoring
An environmental monitoring program will be implemented to verify
the effectiveness of the remedial action and to assure protection
of public health. The monitoring program will provide data to
evaluate the performance of the treatment and collection systems
and the sources and movement of contamination east of South 66th
Street. The monitoring netwQrk will include at the minimum the
ground water.wells and surface water locations shown in Figure
11. The rationale for selection of these stations is as follows:
7.
8.
1.
Operational Monitoring
a. ground water drawdown and quality adjacent to the
east drain
- NA-4, EPA-19, EPA-3, NA-1, EPA-20, EPA-21, FX-1,
b. flow and water quality influent to the equaliza-
tion/sedimentation basins (not shown in Figure 11)
c. flow anc'l.water quality influent to the air stripper
(not shown in Figure 11)
d. flow and water quality of the effluent from the
treatment facility (not shown in Figure 11)
2.
Surface Water Quality in Cowdrey Drainage
. - CRO, CDO, CD@SPP, CD@S66
3 .
Surface Water Quality in Community Ditch
- CDPO, CDDG
4.
Ground water Quality and Potentiometric Surface Along
Community Ditch
- EPA-18
5.
Ground water Quality and Potentiometric Surface in Cow-
drey Drainage Alluvium
- FPZ-J, NA-4, EPA-14, EPA-15, EPA-16, EPA-17
6.
Ground water Quality and Potentiometric Surface East of
Active and Inactive Landfills
- NA-6, NA-7, NA-9, NA-10
Ground water Quality and Potentiometric Surfaces for the
Alluvium, Shallow Bedrock Aquifer, and Deep Bedrock Aqui-
fer
- FX-l, SBW-I, DBW-l
Background Ground water Quality
- EPA-5, FX-8
Monitoring will be on a frequency consistent with the objectives
of the monitoring program. Initially ground water levels will be
measured monthly until levels reach equilibrium; subsequent mea-
surements will coincide with the sampling of ground water wells
and surface waters. The wells and surface water sampling loca-
tions will be sampled quarterly for one year, and semi-annually
in subsequent years. Operational monitoring with respect to the
45
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treatment system will be conducted weekly until data indicate a
lower frequency would be adequate. Samples will be analyzed for
the parameters identified in Table 5.
A thirty year planning horizon is used here as the time period
for estimating monitoring expenses. The actual aquifer clean-up
ultimately will dictate whether monitoring can cease within the
thirty year planning horizon or 'will need to continue longer.
The off-site monitoring well data will be used to determine if
additional response actions are necessary to protect public
health, welfare and the environment. Such a determination will
be made as appropriate in a subsequent decision document.
As shown in Table 8, the estimated capital cost for the recom-
mended alternative is $1,819,000. The cost takes into considera-
tion all elements of the landfill improvements, ground water
collection system, g~ound water treatment system, and monitoring
program. O&M costs are estimates for the initial years.
Reduction of environmental monitoring in subsequent years will
reduce this figure.
Landfill Improvements
The perimeter of the site will be fenced with a three strand
barbed wire fence approximately four feet in height. The fence
will keep cattle off the site and restrict public access to the
site. Signs which are legible from a distance of 25 feet will be
posted in sufficient numbers around the site to be seen from any
approach to the site. The signs will state "Danger--Unauthorized
Personnel Keep Out". All signs will be printed in English and
Spanish.
The existing leachate collection lagoons will be drained and the
lagoon liquid contents transferred to the on-site treatment
system. Should the quality of the lagoon contents be considered
unacceptable for on-site treatment, necessary approvals for final
disposition of the lagoon water will be secured. The lagoons
will then be backfilled and the area regraded to achieve a final
slope of 13%. Should leachate surface after regrading the area,
additional grading or other actions as might be necessary will be
performed to eliminate completely surface seeps of contamination.
The lagoons will be closed in compliance with the standards
specified" in RCRA, 40 CFR 264.228. The ground water collection
system and off-site environmental monitoring will provide addi-
tional assurance to the closure of these lagoons.
The French drain discharge that is currently received by lagoon
#1 will be redirected to the treatment facility.
Surface water in Cowdrey Drainage will otherwise not be collected
and treated. Further corrective actions will be considered in an
additional decision document if hazardous substances, pollutants,
46
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V N 0
TABLE 8
ESTIMATED COSTS OF RECOMMENDED ALTERNATIVE
Capital Annual Present
Operable Unit Costs O&M Costs Value *
$ $ $
1. Perimeter Ditches 35,000 1,500 49,000
2. Ground water Collection
Drain 1,372,000 5,000 1,419,000
3. Equalization Basins 50,000 15,100 192,000
4. Regrading & Revegetation 190,000 0 190,000
5. Perimeter Fencing 7,000 0 7,000
6. Environmental Monitoring 7,000 87,500** 832,000
7. Air Stripping 158,000 43,700 570,000
TOTALS 1,819,000 152,800 3,259,000
--.
* Present value equals the capital cost plus the present value
of the annual operation and maintenance cost calculated based on
a 10% interest rate and 30 year planning horizon.
** 27 surface water, and ground water, sampling stations X 2
analyses/yr X $7 SO/analysis = $40,500. Labor estimated at
$20,000. First year environmental monitoring will require twice
this expenditure as. quarterly monitoring is required. For cost
estimating purposes, operational monitoring with respect to the
treatment facility is assumed to be conducted on a frequency of
once per month; 3 sampling locations X 12 analyses/yr X
$750/analysis = $27,000.
47
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'.'
or contaminants are subsequently detected during environmental
monitoring of the surface water leaving the 160-acre site.
The entire 160-acre site will be regraded and seeded to promote
runoff and thus minumize infiltration. Regrading will include
elimination of depressions where water can accumulate, and the
application of at least six inches of soil to the regraded sur-
face. The soil will be subsequently seeded with native grass.
Perimeter ditches will be installed along the landfill south of
Cowdrey Drainage. .
As the Marshall Landfill is still in operation, a cap is not
included in the preferred alternative. However, the objectives
of the cap, as stated in RCRA, 40 CFR 264.310 will be met:
1.
Minimization of migration of liquids through the landfill
will be achieved by final cover, regrading, revegetation,
the perimete~,ditches, and the subsurface drain.
The regrading and revegetation along with perimeter
fencing will minimize maintenance costs.
2.
3.
Drainage will be promoted by regrading; revegetation and
'regrading will minimize surficial erosion.
4.
Annual maintenance will assure the integrity of the final
cover.
5.
Infiltration is a minor component of the water balance as
discussed in the Task 3 Addendum of the RI.
OPERATION AND MAINTENANCE
The preferred alte~native will require on a routine basis envi-
ronmental monitoring, maintenance of the ground water collection
system and operation and maintenance of the ground water treat-
ment facility. The environmental monitoring has been previously
described and consists of operational monitoring and monitoring
to evaluate the effectiveness of the remedial action and the
protection of public heal tho A thirty year time frame for these
activities has been used for estimating purposes. However, the
actual time period for operation and maintenance depends on the
site conditions. The ground water collection system will require
periodic inspection and cleaning when necessary. The ground
water tre.atment system will require regular attendance for
operations and maintenance. Maintenance will include periodic
removal of the packing material in the air stripper or in-place
cleaning of the packing. The off-gas carbon system will require
routine monitoring and replacement of the carbon as necessary to
maintain performance. The equalization/sedimentation basins will
require periodic dredging to remove accumulated solids. The
annual cost for operation and maintenance is estimated at
$152,800. The present value of this cost over 30 years is
$1,440,000.
48
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(..> ~ u
SCHEDULE
4Q FY 86
X
x +
x +
x +
x +
1 month
10 months
12 months
25 months
Regional Administrator signs EDD
- Resolution of Enforcement Activity
- Start Design
- Complete Design
- Start Construction
- Complete Construction
FUTURE ACTIONS
Results of monitoring off-site ground water may indicate that
further response actions are needed. As stated in the recom-
mended alternative, if significant improvement of off-site
ground water quality is not observed in three years after imple-
mentation of the selected remedial action, than further action
will be considered as necessary.
49
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