Unii&J States Off ice of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R09-93/099
September 1993
c/EPA Superfund
Record of Decision:
Fresno Sanitary Landfill, CA
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, 50272.101
REPORT DOCUMENTATION 11. REPOATNO. . 2. 3. Recipient's AccenIon No.
PAGE. EPA/ROD/R09-93!099
4. TItle and Subthle 5. Report Data
SUPERFUND RECORD OF DECISION 09/30/93
Fresno Sanitary Landfill, CA 6.
First Remedial Action
7. Author(s) 8. Performing Organization Rept. No.
9. Performing Organization Name and Addn18S r 10 Project TukIWork Unit No.
.'.
11. . Contl'8ct(C) or Grent(G) No.
(C)
(G)
12. Sponsoring Organization Name and Addraa 13. Type of Report & Period Covsr8d
U.S. Environmental Protection Agency
401 M Street, S.W. 800/800
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Washington, D.C. 20460 14.
15. Supplementary Not..
PB94-964519
.
16.' Abstract (Umlt: 2OO,worda)
The 145-acre Fresno Sanitary Landfill site is an active municipal landfill located in
Fresno County, California. Land use in the area is predominantly agricultural, with
several residences adjacent to the north and south. An estimated 350,000 people use
eight municipal wells situated within 3 miles of the site to obtain their drinking
water supply. From 1937 to 1989, the City of Fresno owned and operated the landfill,
which is the oldest compartmentalized landfill in the western United States. The trash
prism, which. is the source of contamination, contains approximately 79 million yd3 of
trash.' . Waste was dumped in trenches, which then were covered with soil excavated from
the next trench to be used, but the landfill was never lined. In 1981 and 1984,
respectively, EPA and the State conducted studies that revealed off site migration of
methane. In 1988, at the direction of the City, two methane b~rriers wereinstalled'to
prevent the exposure of nearby residents to migrating landfill gas. In 1990, EPA
ordered the City to apply an active vacuum system and to install, a landfill gas
extraction system to the methane barriers to improve their gas capture performance.
However, the systems did not produce acceptable results and, again, EPA directed the
City, to implement a monitoring program to ensure that nearby residents, not protected
by the methane barriers, were not being exposed to vinyl chloride. In 1991, sampling
(See Attached Page)
17. Document Analysis .. Descriptors
Record of Decision - Fresno Sanitary Landfill, CA
First ~emedial Action
Contaminated Media: soil, debris, gas
Key Contaminants: VOCs (PCE, TCE), other organics
b. IdentifieralOpen-Endad T.ms
, ,
c. COSATI FleldIGroup
18. Availability Sta'ement 19. Security Cia.. (ThIs Report) 2~. No. of Pages
'None 22
20. Security Class (This Page) 22. Price
, None
(See ANSI.Z39.18)
See Instructions on ReV81'SB
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
o.partlMnt of Commen:e
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EPA/ROD/R09-93/099
Fresno Sanitary Landfill, CA
First Remedial Action ~
Abstract (Continued)
performed by the City revealed that vinyl chloride and other landfill gas contaminants
were present in the soil gas in areas supposedly protected by the methane barriers and in
soil gas near homes 700 feet from the landfill. Former landfill practices, including
landfilling without liners, have allowed landfill contaminants to migrate into and
contaminate the surrounding atmosphere, soil, and ground water. This ROD addresses an
interim remedy for the landfill and landfill gas, as OU1. Future RODs will address
contaminated soil, ground water,- and other ancillary issues at the site. The primary
contaminants of concern affecting the soil, debris, and gas are VOCs, including PCE and
TCE; and other organics.
The selected remedial action for this site includes capping the landfill soil and debris
using a low-permeability synthetic membrane; managing the storm water. using drains,
basins',' and other structures; venting the landfill by installing a landfill gas collection
and conveyance system to convey landfill gas to a gas treatment system; treating landfill
gas onsite by flaring; collecting gas condensate using the piping system, storing the
residual onsite, and transporting the condensate offsite for treatment; providing a
contingent remedy, including a- leachate collection system consisting of liquid extraction
pumps placed in the bottom of extraction wells, piping to convey the leachate, temporarily
storing leachate onsite, and transporting the leachate offsite for treatment, if EPA
determines that liquid levels found in gas wells area threat to ground water; and
monitoring landfill gas migration. The estimated present worth cost for this remedial
action is $23,195,000, which includes an O&M cost of $5,279,000 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
Chemical-specific landfill emissions cleanup goals were based on health-based levels, to
ensure that the emissions would not exceed a 10~6 excess cancer risk, and Solid Waste
Disposal Sites-Draft Rule 46-42, which states that organic compounds measured as methane
at any point on the landfill surface shall not exceed 1,000 ppm.
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RECORD OF DECISION
Fresno Sanitary Landfill Superfund site
Fresno, California
EPA 1D# CAD980636914
PART I - DECLARATION
statement of Basis and PurDose
This Record of Decision ("ROD") presents the selected
interim remedial action for the Fresno Sanitary Landfill
Superfund site (lithe Site") in Fresno, California. This document
was developed in accordance with the Comprehensive Environmental
Response, Compensation and Liability Act of 1980, ("CERCLA"), as
amended by the Superfund Amendments and Reauthorization Act of
1986 ("SARAn), 42 U.S.C. SS 9601 et seq, and, to the extent
practicable, in accordance with the National oil and Hazardous
Substances Pollution Contingency Plan ("NCpll), 40 C.F.R. Part
300, and the laws of the State of California. The State of
California concurs with this remedy. This decision is based on
the administrative record for the Site which identifies the
documents upon which the selection of the remedial action is
based.
Assessment of the site
. Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response action
selected in this ROD, may present an 'imminent and substantial
endangerment to public health, welfare, or the environment.
Description of the Remedv
The Fresno Sanitary Landfill (FSL) accepted waste from 1937
to 1989. The landfill is approximately 145 acres, is unlined and
has a soil cover and no landfill gas (LFG) control system in
place. This remedy is a source control operable unit (SCOU), and
is an interim remedy. There will be a second and final operable
unit ROD for the groundwater, off-site vadose soils and any
ancillary issues. This selected remedy is an interim remedy
because there is still subsequent remedial action to be
undertaken at the site, but the SCOU ROD contains certain final
ARARs for this portion of the cleanup.
The selected remedy cQnsists of the following major components:
Landfill gas collection and conveyance system consisting of
interior gas extraction wells, perimeter gas extraction
wells, a blowersyste~, and a piping system for conveyance
of collected LFG to a gas treatment system.
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Landfill gas treatment sy~tem consisting of on-site
combustion of landfill gas in landfill gas flares.
Gas condensate collection system consisting of piping and
storage vessels to manage the condensate generated during
the operation of the gas control system.
A contingency leachate collection system consisting of
liquid extraction pumps placed in the bottoms of gas.
extrac~ion wells, piping to convey the leachate and storage
vessels to manage the collected leachate. The collected
leachate will be trucked off-site for treatment. This
contingency will be implemented if EPA determines that
liquid levels found in a gas well are a threat to .
groundwater.
Landfill gas migration monitoring system consisting of a
series of'monitoring probes placed along the landfill
perimeter.
Landfill cover consisting of a series of functional layers
that together minimize the infiltration of water into
underlying refuse by using a synthetic membrane as the low
permeability layer, provide erosion control, and contribute
to effective operation of the gas control system by
providing a barrier to fugitive surface emissions and to
ambient air entering the waste pile under vacuum conditions.
Storm water management consisting of perimeter dr~ins,
retention basins, and associated structures.
statutory Determinations
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost effective. This remedy utilizes
permanent solutions and alternative treatment or resource
recovery technologies, to the maximum extent practicable, and
satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a
principal element.
Because this remedy will result in hazardous substances
remaining on-site, a review will be conducted within five years
after the commencement of remedial action to ensure that the
remedy continues to provide adequate protection of human health
and the environment.
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John ~ C. IN--
Acting Regional Administrator
'7.30.~
Date
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PART II - DECISION SUMMARY
Fresno Sanitary Landfill Superfund site
Fresno, California
Analysis of the selected remedial action for the Fresno
Sanitary Landfill Site is contained in' the Proposed Plan
published by EPA on March 30, 1993. The Site information
summarized below is discussed fully in the Revised Final
Technical Memorandum Fresno sanitary Landfill Source Control
Operable Unit (FTM) prepared for the City.of Fresno by Camp
Dresser and McKee dated January 20, 1993. After considering
public comments, EPA has adopted the Proposed Plan, with minimal
. change, as the selected'remedy~ The State of California concurs
with EPA's selected remedy.
1. Site Name. Location. and Description.
The Fresno sanitary Landfill is located four miles southwest
of the city of Fresno in Fresno County, California. The landfill'
consists of approximately 145 acres and is bounded on the north
by Jensen Avenue, on the east by West Avenue, on the south by
North Avenue and the west. by agricultural fields. The landfill
stands approximately 60. feet above the surrounding flat grade and
extends approximately 3q feet below the surrounding grade. The
area surrounding the landfill is primarily agricultural with
several residences adjacent to the north and. south boundaries.
The landfill is surrounded by a fence. Eight municipal wells are
located within 3 'miles of the site~ Water from these wells is
blended into a system serving 350,000 people. The site receives
an annual average precipitation of 10.? inches usually during a
several month. wet season from November to April.
2. site History and Enforcement Activities. .
The FSL was owned and'operated solely by the City of Fresno.
, from 1937 to 1989, and is reported'to be the oldest
compartmentalized landfill in the Western United States.
Operations began in the north section in 1937 as short trenches
were dug to a depth of 3 feet (eventually increased'to 25 feet).
Waste was then dumped into the trench by collection trucks and
. the pile was leveled off and compacted,.- A second trench was dug
adjacent to the first trench, and the dirt from the second trench
was used to cover the waste fill. The landfill was never lined.
At the time of its inception, the landfill was located north
of Annadale Avenue. The City expanded the landfill to the south
of Annadale Avenue in 1945. Prior to this expansion, an
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irrigation canal extended in an east-west direction through
is now the south portion of the landfill. After expansion,
canal was replaced with a pipeline 'that is currently in use
is covered by landfill material.
what
this
and
The FSL was first evaluated by EPA pursuant to a CERCLA
Section 103(c) notification by the City of Fresno Solid Waste
Management Division filed on May 27, 1981. The California
Department of Toxic Substances Control (DTSC) (formerly,
California Department of Health Services) conducted a preliminary
inspection of the site in June 1984 in response to complaint
letters from nearby residents. The state inspectors found,off-
site migration of methane and also reviewed the documentation of.
volatile organic compound (VOC) contamination of groundwater.
In 1988 the City retained Laidlaw,Gas Recovery Systems to
design a landfill gas (LFG) extraction and energy recovery ,system
for'the FSL. Also, in 1988 two methane barriers were installed,
on the north and south sides of the landfill, by the City to
prevent the exposure of nearby residents to migrating LFG. The~e
barriers were designed and installed independent of any
environmental agency involvement or oversight. The methane
barriers are 26 foot deep trenches backfilled with gravel and a
membrane liner on the landfill side of the barrier. The trenches
have two perforated horizontal collection pipes at 12 and 19 feet
in depth which are 'passively vented to the surface.
, , '
The Fresno sanitary Landfill was finalized on the National
, Priorities List on October 4, 1989. EPA sent the City of Fresno
a General Notice of liability for the FSL Superfund Site on April
5, 1990. On June 22, 1990 EPA sent the City a Special Notice
letter inviting the City to submit a good faith offer to EPA to
conduct the remedial investigation and feasibility study (RIfFS)
for the FSL. On September 21, 1990 EPA and the City signed an
Administrative Consent Order (U.S. EPA Docket No. 90-22) wherein
the City of Fresno agreed to conduct the RIfFS.
In the'summer of 1990, EPA held discussions with the City
regarding the problem of migrating LFG and the possibility of
installing a landfill cover and energy recovery facility on-site.
Subsequently, with the consent of the city, EPA issued a
Unilateral Order (U.S. EPA Docket No. 90-19) to the City on
September 19, 1990. This order. directed the City to: 1) apply an
.active vacuum system to the methane barriers to improve their gas
LFG capture performance and 2), to install a landfill gas
extraction system in the body of the landfill. Subsequently, the
City's contractor, Laidlaw Gas Recovery Systems, withdrew from
the gas extraction and energy recovery facility project. EPA
then issued a second Unilateral' Order to modify the original
Order. The direction to install a vacuum system 'on the methane
barriers was retained but because overall LFG control was not
possible in the near future, the second Unilateral Order (U.S.
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EPA Docket No. 90-23) directed the City to implement a monitoring
program to ensure that residents near the landfill, not protected
by the methane barriers, were not being exposed to vinyl chloride
(a potent carcinogen in the migrating LFG) in their homes.
From,September 1990 to August' 1991, the City proceeded to
install a vacuum system on the methane barriers. The discharge
from the vacuum system was to be passed through an ~ctivated
carbon system to remove harmful VOCs. During start-up of the
vacuum system the City discovered that the barriers were in
direct contact with trash. Consequently the vacuum system
collected some gas from the resiqents' side of the barrier but
also collected gas from the refuse prism. The constant supply of
LPG from the trash prism overwhelmed the activated carbon system.
Without effective treatment, vacuum system operation would have,
necessitated discharge of the extracted LFG directly to the
atmosphere. ' ,
Also in the summer of 1991, the City prepared a sampling
plan to sample the soil gas between the 'landfill and homes not
protected by the methane barriers. This sampling, which the City
of Fresno conducted in September and October of 1991, revealed
that not only was there vinyl chloride and other LFG contaminants
in the soil gas near homes not protected by the barriers, but
that homes supposedly protected by the barriers also had
dangerous levels of vinyl chloride nearby in the soil gas. These
homes were up to 700 feet from the landfill. In November 1991,
the City sampled the in-home air of seven potentially affected
residences. No vinyl chloride was detected in any of the homes
on three different occasions (November 1991, March 1992 and
November 1992). "
EPA then determined that operation of the methane barrier
vacuum system would not be appropriate. This, was because; 1) the
methane barriers had allowed LFG to migrate 700 feet directly
past the barriers, 2) the vacuum system discharge would have,to
be released untreated and 3) the in-home air sampling showed no
apparent immediate exposure to LFG under .or near the homes.
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These response efforts were performed concurrent with the
RI, and were temporary and partial measures in response to the
principle threat of migrating landfill gas. The source control
operable unit should control migrating landfill gas and obviate
any further temporary or partial measures.
3. Hiqhlights of Community Participation.
Five fact sheets have been released describing activities at
the site. In March, 1993 EPA released a proposed plan for the
site. site documents were made available at the EPA offices and
at a. local repository, and a public notice was published allowing
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30 days for public comment on the Proposed Plan. A 30 day
extension to the public comment period was requested and granted.
A public meeting was held on March 39, 1993 to describe the
proposed remedy and receive comments. Four members of the pUblic
asked questions or made co~ents during the public meeting, and
two written comment letters were received from the potentially
responsible party (PRP) community. EPA has responded to all
comments r~ceived during this period in the attached "Analysis of
Public Comments. II '
4. Scope and Role of Remedial Actions.'
The selected remedy is a source control operable unit and an
. interim remedy. The trash prism is the source of contamination
at the FSL site with landfill gas and leachate acting as the
primary relea~e mechanisms. Surface runoff/erosion is considered
a secondary release mechanism. This remedy will address only on-
site control of contaminants. This will be by confinement, and
by extraction and tre~tment of landfill gas, LFG condensate and
leachate.
The SCOU systems in the remedy are intended to: (1) collect
and control the release of LFG through the surface of the '
landfill and in the 'subsurface, (2) control the infiltration of
storm water into the trash which would result in leachate
percolation ~nto.the underlying groundwater, (3) collect and
truck off-site for treatment leachate encountered ,in the gas
extraction wells or' LFG condensate encountered in the gas
collection system, (4) control the intrusion of oxygen into the
trash which woul~ happen if a vacuum system were installed
without a landfill cover, ('5) control erosi6n and off-site
transport of contaminated soils, (6) collect and manage the.
incident storm water, (7) treat the collected LFG to destroy any
harmful contaminants in the LFG stream.
, There will be a second and final operable unit ROD for the
site. This second OU ROD will address groundwater, off-site
vadose soils and any ancillary issues. This selected remedy is
an interim remedy because there is still subsequent remedial
action to be undertaken at the site, however the SCOU ROD
contains certain final ARARs for this portion of the cleanup.
5. Site Characteristics.
The trash prism, which is, the source of contamination,
contain~ approximately 4.7 million tons (7.9 million cubic yards)
of trash. The City has conducted site investigations which have
included sampling and analysis of ambient air, indoor residential
air, soil gas, landfill well groundwater, residential well
groundwater and, surface and subsurface soils. The City has also
conducted' a hydrogeologic investigation. While EPA had planned a
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.".
leachate investigation it was not executed because of the health
an~ safety issues of drilling through the refuse prism and the
high expense of this investigation relative to the potential of
. . locating leachate. and the value of that information. The City
has completed field investigations for a remedial investigation
(RI) report, and a preliminary draft RIreport has been
submitted. .
Ambient Air: Six air sampling stations were used where 24
hour composite samples were collected over two separate 24 hour
periods. Samples were taken with Summa canisters under vacuum
using control flow orifices. . Samples were analyzed for benzene,
carbon tetrachloride, chloroform, 1,2-dichloroethane, 1,2-
dichloromethane, methylene chloride, tetrachloroethane (PCE),
1,1,1-trichloroethane, trichloroethene (TCE), vinyl chloride and
dichlorodifluoromethane (Freon-12). Vinyl chloride is typically'
the only contaminant which can be uniquely attributed to a
landfill. Vinyl chloride results showed non-detect for all
upwind ambient air samples while downwind samples were as high as
1 part per billion by volume (ppbv). Resul~s for PCE and TCE
were also non-detect for upwind samples and were as high as 1.8
ppbv and 0.64 ppbv respectively in the downwind ambient air.
Residential Air: Indoor air samples were taken at three
different times spanning 1 year at seven residences where
temporary soil gas probe results indic~ted the potential for
exposure of residents to vinyl chloride. Samples were taken with
Summa canisters as 24 hour composite samples and were analyzed
for the same contaminants as the ambient samples. vinyl chloride
was never detected in any indoor air samples.
Soil Gas: All soil gas samples were analyzed for the same
contaminants as the ambient air samples plus methane except as
noted. Samples which were taken with Summa canisters provided
the only reliable data on vinyl chloride contamination. Summa
canister samples were analyzed at a fixed base laboratory with a
sophisticated cryogenic sample preconcentration step and a GC-
mass spectrophotometer. other sample analysis techniques had
vinyl chloride reliability problems due to interference by other
light chlorinated VOCs. All .sampling and analysis has provided
reliable data on other LFG vadose contaminants.
Soil gas sampling comprised: (1) 199 temporary soil gas
monitoring probe samples taken at a depth of 15 feet and analyzed
with an on-site GC, (2) 48 temporary soil gas ,monitoring probe
samples taken at a depth of 15 feet using a Summa canister and
analyzed at a fixed base laboratory with a GC-mass
spectrophotometer, (3) 26 samples taken with Summa canisters from
permanent multidepth landfill perimeter gas monitoring wells, (4)
21 samples taken from permanent multidepth landfill-perimeter gas
moriitoring wells analyzed with a hand held instrument for only
methane, (5) 12 samples taken with Summa canisters from permanent
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off-site multidepth gas monitoring wells. The temporary soil gas
probe samples were configured as columns 400 feet apart moving
out from the landfill perimeter at. 100 foot intervals. The
permanent multidepth landfill perimeter gas monitoring wells are
spaced 1000 feet apart along the pe~imeter of the landfill.
Results from the soil gas investigation show extensive off-
site LFG vadose contamination. Landfill gas was detected up to
700 feet from the landfill on the north, south and east sides,
and up to 1000 feet from the landfill on the southwest side.
Some maximum contaminant concentrations detected off-site in the
vadose were: vinyl chloride - 9,000 ppbv, PCE - 25,665 ppbv, TCE
- 3,753 ppbv, Freon 12 - 870,730 ppbv (8.7%, on the northwest
side of the landfill) and methane - 57,256,858 ppbv (57%).
Results from the permanent multidepth landfill perimeter gas
monitoring wells show maximum contaminant concentrations of:
vinyl chloride - 39,000 ppbv, PCE - 10,000 ppbv, TCE - 7,100 ppbv
and methane - 58%. .
Landfill Groundwater Monitorinq Wells: Various
investigations have identified three general hydrostratigraphic
units: shallow (60-80 feet BGS), intermediate (110 - 140 BGS) and
deep (180 - 235 BGS). These units appear to correspond to
aquifer zones of more permeable sand units. These units were
selected for well completion to vertically characterize a
somewhat interconnected- aquifer system. Any aquifer
interconnection may be due to the natural stratigraphy and in
part to the numerous irrigation and domestic wells in the area
that are often screened or open across multiple permeable layers.
Off-site groundwater wells were installed and completed at up to
three discrete depths for a given location. A total of 43 wells
were sampled at 26 locations. Water samples ~ere analyzed for
VOCs, semi-volatiles also known as base, neutral, acids (BNAs),
pesticides/PCBs, herbicides, dioxins, metals and water quality
parameters.
The results from the groundwater wells, in the three of five
planned rounds of year long sampling have shown no pesticides,
herbicides or dioxins. VOC contamination above health based
acceptable levels includes vinyl chloride - 12 ppb (maximum
contaminant level or MCL=0.5), PCE - 140 ppb (MCL=5), TCE - 140
ppb (MCL=5) and trans 1,2 DCE - 15 ppb (MCL=10).
VOC contamination appears to be most significant in the
. shallow aquifer zone. There is slight VOC contamination of the
intermediate zone and VOCs were not detected in the deep zone in
this investigation. In addition, VOC contamination was detected
in an irrigation well proximal to the landfill that has an
unknown screen interval and may be open to a depth of several
hundred feet.
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The horizontal extent of VOC contamination in groundwater,
varies between 400 and 700 feet to .the east, between 700 and 1500
feet to the south, between 1200 to 1,500 feet to the west and at
least 1300 feet to the south.
Residential Groundwater Wells: There ,were' 13 residential
private drinking water wells sampled ~ear the landfill (7 on the
south and 6 on the north of the landfill). The samples were'
analyzed for VOCs, BNAs, pesticides/PCBs, herbicides, dioxins,'
metals and water quality parameters! Six of the 13 wells showed.
VOC contamination (1 on the north side and Son the south of the
landfill). Residential well contaminants included PCE - 2.9 ppb,
methylene chloride - 2.0 ppb, 1,2-dichloropropane - .53 ppb and
trichloroflouromethane - 2.6 ppb. The City of Fresno has
provided a number of the residences near the landfill with
bottled drinking water or the City has installed activated carbon
filters on their private domestic water systems.
Surface and Subsurface Soils: Surface soil samples were
collected at 7 sites around the landfill. Samples were analyzed
for volatile and semi volatile organics, pesticides, herbicides,
PCBs, dioxins and metals. Xylenes (VOC) were detected in one
sample on the east side of the landfill at .03 parts per million
(ppm). The pesticide/PCB analysis showed one surface sample with
several endosulfans and DDE'.(a degradation product of the
pesticide DDT) at low levels. ~ll of the surface soi1 samples
(except one) showed a variety of dioxin contamination at levels
below a health based 'concern. .
Subsurface soil samples were collected at various depths
during the installation of seven landfill perimeter LFG
monitoring wells. Samples ,were analyzed for volatile and semi
volatile organics, pesticides, herbicides, PCBs, dioxins and
metals. Analysis showed 1,4-dichlorobenzene - ,.04 ppm, xylenes -
.03 ppm and chloromethane - .1 ppm all on t~e east side of the
landfill at depths between 3.5 and 6.5 feet. No pesticides,
herbicides or BNAs were detected in these samples. Various
dioxins were detected on the east side of the landfill at depths
between 1 and 6.5 feet at levels below health based concern.
During the installation of off-site groundwater monitoring wells
,pilot borings were sampled at, depths ranging from 79 to 235 feet.
These samples were analyzed for ,VOCs and total organic carbon.
Methylene chloride and chloromethane were detected in three
samples at low levels (0.4 and 0.03 ppm respectively.
6. Summary of Site Risks.
A final risk assessment for the site will be incorporated
into the final operable unit ROD. An ecological assessment has
not been performed but may be incorporated into the final risk
, assessment if EPA determines a need for such a study. EPA has
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determined that the landfill cover and gas control systems are
necessary to stabilize the.site, prevent further degradation of
groundwater and achieve significant risk reduction quickly. A
landfill cover and gas control system are necessary in order for
any remedial action for off-site groundwater and vadose cleanup
to be effective.
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the selected remedy,
may present an imminent and substantial endangerment to public
health, welfare, or, the environment.
The site is currently fenced and unoccupied: There is no
surface cover other than several inches to several feet of local
soil. A potential risk exists from inhalation of air
contaminated by landfill gas seeping through the existing cover
and mixing with the ambient air. There is also a potential risk
that air in nearby residences could be contaminated from
subsurface LFG migration, followed by gas transport into the
living space. All monitoring performed to date, however has
shown no LFG migration into homes~ These potential inhalation
risks are important because the LFGcontaminant vinyl chloride is
an especially potent carcinogen for young children. Until the
landfill gas is collected and treated these potential risks will
remain. The performance criteria for the gas collection and
, treatment system will ensure that these risks are minimized.
Possible ingestion of contaminants can occur if landfill gas
.comes into contact with and contaminates groundwater which is a
drinking source. There are several private drinking water wells
which have been contaminated by landfill contaminants. This risk
is minimized with the control of the subsurface migration o~
l~ndfill gas. Collection and treatment 'components of the
selected remedy. will provide this control. '
Groundwater contamination can also occur as leachate
generated in the refuse prism comes in contact with groundwater
underlying the site. The impact of this contaminant transport
mechanism will be limited by the construction of the landfill
cover and drainage system. By preventing ponding of storm water
and subsequent infiltration into the refuse, leachate generation
is minimized. . .
7. Description of Alternatives.
Alternatives' were analyzed to address ~ontaminant source
control at the site. The primary contaminant transport
mechanisms addressed are LPG and leachate. A summary of the
alternatives is presented below~ Each alternative is described
in detail in the Source Control Operable Unit Final Technical
Memorandum found in the Administrative Record. With the
exception of the no action alternative the various remedial
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alternatives'are some combination of a landfill cover and on-site
or off-site LFG treatment. ,The different landfill covers are the
same except for the ,low permeability layer.
Alternative 0 - No Action:
, ,
. As required, by the NCP, a no-action al ternati ve was
considered as a baseline for comparison. This'alternative wquld
leave the landfill as it is with no further effort to clean up
the problems associated with the landfill. Landfill gas.
monitoring would be conducted, however, to determine the impacts
associated with no cleanup action. The costs associated with
this alternative are due to the regular gas monitoring -and the
maintenance of the monitoring wells. The annual cost of
Alternative 1 is $24,000, and the thirty year present worth cost
is approximately $369,000.
Containment Component
Landfill Cover: The landfill cover will have different layers.
Starting from the bottom, they are a foundation laver, a low
permeability layer, a,drainaqe laver, a filter laver and a
landscaped layer. There are several alternatives for the. low '
permeability laver of the landfill cover, which is the most
important feature of the cover. This layer will prevent storm
water from infiltrating into the' landfill and will prevent gas
from escaping from the landfill. The other layers in the cover
will remain the same regardless of which low permeability layer
is used. The low permeability layer alternatives which were
considered are given below with the capital costs for the entire
coyer using that particular low permeability layer.
Alternative (1) a one foot thick low permeability clay layer,
cost - $18,893,000
Alternative (2) a two foot thick layer of more permeable local
clay, cost - $14,406,000
Alternative (3) a synthetic membrane similar to a thick plastic
sheet, cost - $12,621,000 and
Alternative (4) a composite of one foot of low permeability clay
'under a synthetic membrane, cost - $21,766,000.
Treatment Components
Landfill Gas Treatment: The two landfill gas treatment
alternatives are on-site LFG flaring which is alternative
off-site LFG combustion to generate electricity which is
alternative 6. The off-site energy recovery alternative
a conveyance pipeline to the Power Generation Facility.
5 or
r~quires
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Alternatives 5 and 6 have several components in common.
Both alternative 5 and 6 include:. (1) a landfill gas collection
and conveyance system consisting of interior gas extraction
wells, perimeter gas extraction wells, a blower system, and a
. piping system for conveyance of collected gas; (2) a gas
condensate collection system consisting of piping and storage
vessels to manage the condensate generated during the operation
of the gas control system (collected condensate will be trucked
off-site for treatment); (3) a storm water management component
consisting of perimeter drains, retention basins, and associated
structures; (4) a landfill gas migration monitoring system.
consisting of a series of monitoring probes placed along the
landfill perimeter; and (5) a contingency leachate collection
system consisting of liquid extraction pumps placed in the
bottoms of gas extraction wells, piping to convey the leachate
and storage vessels to manage the collected leachate. The
collected leachate will be trucked off-site for treatment. This
.leachate contingency will be implemented if EPA determines that
liquid levels found in a gas well are a.threat to groundwater.
.. .
The performance criteria for the flare station operation
will include a minimum combustion temperature and flow rate
restrictions which will maintain a minimum residence time. These
requirements together will achieve a destruction efficiency for
VOCs. Periodic emission monitoring will be carried out to assess
the effectiveness of the system in meeting the destruction
efficiency. The specific destruction efficiency necessary will
be determined by EPA during the design of the system pursuant to
the 10-6maximum excess cancer risk performance criteria.
Alternative (5) - On-site Landfill Combustion In A Landfill Gas
Flare: The on-site LFG treatment facility will consist of two
landfill gas flares of the same or similar size. One will be
used to combust gas collected from the interior gas control
system and one will combust gas collected from the perimeter
system. The two flares of same or similar size will allow for
some redundancy within the system and flexibility in the way the
total facility is operated (e.g., blending of all gases, if
appropriate). Flares and accessory equipment, piping, and
valving will be designed so th~t various operational scenarios
can be used. Blowers will pe installed to withdraw the gas by
placing a vacuum on the header lines. A spare blower will be
i~stalled at the treatment facility for redundancy in cas~ one
blower should fail.
The capital cost of alternative (5), independent of the
.landfill cover 1s $5,295,000, and the present wdrth cost of
. thirty years operation and maintenance (O&M) is $5,27~;000.
total present worth cost is $10,574,000. .
The
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Alternative (6) - Off-site Landfill Gas Combustion For Energy '
Recovery; . The off-site LFG combustion, alternative (6) is
similar to the on-site LFG combustion, alternative (5) except
that one flare is eliminated and the high methane content LFG
collected from the interior control system would be transported
by conveyance pipeline, three miles west, to the City of Fresno
Regional Wastewater Facility (RWWF) for combustion and energy
recovery in a Power Generation Facility (PGF). Landfill gas
collected from the perimeter extraction system would be combusted
using a LFG flare system located on-site. This system will have
one flare and two blowers. There will be a primary blower and a
back-up blower in case of a primary blower failure.
The capital cost for alternative (6) without the landfill
cap is $9,835,000 and the present worth of the operation and
.maintenance for thirty years is $6,041,000. The total present
worth cost is $17,876,000. These costs do not include any
credits for the electricity savings at the treatment plant. It
is difficult to accurately calculate the present worth of the
electricity savings, but it is likely that the net cost of this
alternative would be lower than alternative (5) if the
electricity savings were included.
8. Summary of Comparative Analysis of Alternatives.
Overall Protection of Human Health and the Environment
Alternative 0 (no action) will not be protective of human
health and the environment.
Containment Component: Alternatives 1,2,3 and 4 equally and
adequately will control landfill gas surface emissions,
subsurface LFG migration, enhance LFG extraction well efficiency
and control odors. Alternatives 1,3 and 4 will control
infiltration of stormwater into the trash thereby protecting the
underlying groundwater. Alternative 2 is less likely than
Alternatives 1, 3 and 4 to adequately control stormwater
infiltration and protect groundwater.
Treatment Component: Alternatives 5 and 6 equally and
adequately will treat the collected LFG by thermally destroying
hazardous contaminants in the LFG stream.
Compliance with ARARs and Performance Standards
Containment Component: Alternatives 1,3 and 4 will achieve
the action specific ARAR of a maximum 10~6cm/sec water
permeability landfill cover. Alternative 2 is not likely to
comply with this action specific ARAR.
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Alternatives 1,2,3 and 4 will achieve the 'chemical specific
performance standard for surface emission contro~ of 1000 parts
per million methane maximum at any point on the landfill surface.
Alternatives 1,2,3 and 4 will achieve the chemical specific ARAR,
Section 17783 of Title 14 of the California Code of Regulations,
for subsurface migration co~trol of less than 5% methane at the
boundary. '
Treatment Component: Alternatives 5 and 6 will achieve the
action specific performance standard of 10-6excess cancer risk
from the landfill gas treatment facility emissions, and the
action specific threshold minimum of 98% destruction efficiency
for any reactive organic except methane.
Long-term Effectiveness and Permanence
containment Component: A quantitative residual risk
calculation has not been performed for this operable unit.
Alternative 2 may have a higher residual risk'due to a greater
water permeability and 'consequently a greater threat to
groundwater. Alternatives 3 arid 4 have a greater likelihood of
long-term effectiveness during differential settlement. A clay
low permeability layer will crack during differential settlement
of the trash whereas a synthetic membrane will tend to deform but
remain effective during differential settlement. Alternatives
1,2 and 4, which use clay as part or all of the low permeability
layer will require water to be applied to keep the cover moist.
If the cover is not kept moist it will desiccate and crack in the
arid Fresno climate, which will render the cover ineffective.
Alternative 3 will not require such a watering system and will
not crack due to desiccation, and therefore satisfies the
requireme~t of long-term effectiveness and permanence.
Treatment Component: Alternatives 5 and 6 will'have
equivalent and adequate long-term effectiveness and permanence.
Reduction of Toxicity, Mobility, or Volume Through Treatment
Containment Component: Alternatives 1,2,3 and 4 equally and
adequately will improve the efficiency of the LFG collection and
treatment alternatives.
Treatment Component: Alternatives 5 and 6 will achieve'
adequate treatment of the collected LFG stream. Generally, LFG
flares (Alternative 5) achieve a greater destruction and removal
efficiency of hazardous contaminants than energy recovery units
(Alternative 6) because flares can achieve higher operating
temperatures.
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i','
, .~ j' ..,';
Short-Term Effectiveness
C9ntainment Component: Short term risks to the community
posed by construction may exist, but will be mitigated by proper
controls. Environmental impacts which may include noise, LFG
emissions, erosion, odors and dust during construction will.
require engineering controls. Alternatives 1,2,3.and 4 will have
equal and adequat~ short-term effectiveness.
Treatment Component: Alternatives 5 and 6 will have equal
and adequate short~term effectiveness.
Implementability
Containment Component: Alternative 1 is the most
administratively implementable because it is the prescriptive
landfill cover alternative. Alternatives 2,3 and 4 will require
. administrative approval by' EPA as engineered alternatives to the
prescriptive landfill cover. Alternative 3 is the most.
administratively implementable engineered alternative because EPA
has selected the RWQCB proof criteria for this Alternative.
Alternative 3 has the gre?test technical implementability
because a synthetic membrane can be easily anchored to the top of
the landfill and will be less likely to slip on the steep slopes
on, the east side of the landfill. Alternatives 1, 2 and 4, which
call for clay covers, would not be as easily implementable or
stable.
Alternative 3 can be implemented with a variety of services
and materials, however Alternatives 1 and 4 will require clay,
which may not be as easily available. Alternative 2 would use a
clay like material which is locally available.
Treatment Component: Alternative'5 is administratively and
technically implementable. Alternative 6 is technically
implementable and will require construction of a conveyance
pipeline and energy recovery units in addition to the LFG flare
facilities required in Alternative 5. Alternative 6 is not as
administratively implementable because it will require various
off-site permits and local agency involvement beyond that
required .for Alternative 5. Alternative 6 will also require
integration with another existing facility.
Alternative 5 can be implemented with readily available
services 'and materials. For Alternative 6, the emissions
standards established to operate the energy recovery units' on
landfill gas will impact the availability of this equipment. The
LFG contaminants may limit the numbe~ of vendors with established
track records able to offer the engines and turbines capable of
meeting the emissions standards.
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'Cost
Each alternative was formulated in sufficient detail to
develop' capital and operating costs within a range of -30% and
+50%. A present worth analysis was used to evaluate annual
operations and maintenance (O&M) costs, and a discount rate of 5%
was applied for analysis. Capital costs for each containment
alternative are provided and the present worth costs for the
treatment alternatives are provided. The treatment present worth
cost includes a lump sum annual O&M cost for the containment
alternatives.
containment Components: All containment components are the same
except for the low permeability layer.
Alternative (1) a 1 foot thick 10-6cm/sec permeability clay
layer,
cost - $18,893,000
Alternative (2) ~ two foot thick laye~ of more permeable local
clay (approximately 10-6cm/sec),
cost - $14,406,000
Alternative (3) a synthetic memDrane
cost - $12,621,000 and'
Alternative (4) a composite of one foot of 10-Gcm/see
permeability clay under a synthetic membrane,
cost - $21,766,000.
Treatment Component:
Alternative (5), on-site LFG flare.
The capital cost of alternative (5), independent of the
landfill cover is $5,295,000, and the present worth cost of
thirty years operation and. maintenance (O&M) is $5,279,000.
total present worth cost is $10,574,000.
Alternative (G), off-site LFG combustion for energy recovery. .
The capital cost for alternative (G) without the landfill
cap is $9,835,000 and the present worth of the operation and
maintenance for thirty years is $6,041,000. The total present
worth cost is $17,876,000. These costs do not include any
credits for the electricity savings at the treatment plant. It
is difficult to accurately calculate the present worth of the
electricity savings, but it is likely that the net cost of this
alternative would be lower than alternative (5) if the
electricity savings were included.
The
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state Acceptance
EPA is the lead agency and is responsible for overseeing the
remedy selection for the site and this interim remedy operable
unit. The California Department of Toxic Substances Control is
the lead state agency coordinating state response and interaction
for the Site. After considering comments from the public,
potentially responsible parties, and other state agencies, all of
which are included in the attached Response to Public Comment
Summary, EPA is finalizing its selection of this interim remedial
action for the Site in this ROD. The Department of Toxic
Substances Control as the representative for the State of
California concurs with the choice of .remedy. .
community Acceptance
A public meeting to discuss and receive comment on the
proposed remedy was held on March 30, 1~93. community members
appeared satisfied with agency responses to questions and with
the selected remedy. Residents and nearby community members have
long supported a landfill cover and gas extraction system for
protection of their health, protection of their property values.
and for aesthetic reasons. Specific responses to public comments
are included in the attached Response to Comments, which is
incorporated' as part of the Administrative Record for this
decision.
9. Selected Remedy.
EPA's Selected Material For The Low Permeability Layer Of The
Landfill Cap:
The synthetic membrane (Alternative 3) is the. selected low
permeability layer in the cover. This. alternative has several
important advantages over the others (Alternative 1,2,4). It'is
the least maintenance intensive, and it will not require water to
be applied to keep it moist. If a clay cap is allowed to dry it
will crack (Alternatives 1,2). A synthetic membrane will also be
effective as portions of the landfill settle. Differential.
settling may crack a clay cap (Alternatives 1,2). The synthetic
membrane (Alternative 3) will deform, slightly without failure as
the landfill settles. On the steep slopes on the. east side of .
the landfill a synthetic membrane can be anchored to the top
easily and would be less likely to slip on .the slope which could
be a problem for a clay cap (Alternatives 1,2,4). A synthetic
membrane (Alternative 3) is also the'least costly of the various
alternatives. .
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EPA/s Selected Landfill Gas Treatment Remedy;
The selected alternative for landfill gas treatment is
Alternative 5, on-site landfill gas combustion in a landfill gas
flare. This is because it is protective of human health and the
environment; meets ARARs, and it can be implemented immediately.
The off-site landfill gas combustion for energy recovery,
alternative 6, has a number of issues which presently jeopardize
its implementability. Also, most of the components of
Alternative 5, the on-site landfill gas flare alternative will be
required as backup facilities if Alternative 6, the off-site
energy recovery alternative is ever implemented. Furthermore,
EPA would like to encourage the use of Alternative 6, the off-
site energy recovery, if the City of Fresno determines that it is
advantageous. EPA would allow implementation of the off-site
energy recovery alternative through a modification to this ROD if
and when the City of Fresno is prepared to design and construct
this alternative.
«
The control of storm water infiltration will be effective as
soon as the landfill cover construction is complete. While
leachate generation will be reduced, leachate may still pose some
reduced threat to groundwater.
The major components of the selected remedy include;
Landfill gas collection and conveyance system consisting of
interior gas extraction wells, perimeter gas extraction
wells, a blower system, and a piping system for conveyance
of collected gas to an on-site gas treatment system.
- Landfill gas migration monitoring system consisting of a
series of monitoring probes placed along the landfill
perimeter.
Landfill gas treatment system consisting of on-site
combustion of landfill gas in landfill gas flares.
Gas condensate collection system consisting of piping and
storage vessels to manage the condensate generated during
the operation of the gas control system. Collected
condensate will be trucked off-site for treatment.
A contingency leachate collection system consisting of
liquid extraction pumps placed in the bottoms of gas
extraction wells, piping to convey the leachate and storage
vessels to manage the collected leachate. The collected
leachate will be trucked off-site for treatment. This
' leachate contingency will be implemented if EPA determines
that liquid levels found in a gas well are a threat to
groundwater.
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I," 'I." :
. I
,
.' "
. .,
...
, .
Landfill cover consisting of a series of functional layers
that together minimize the infiltration of water into
under~ying refuse by using a synthetic membrane as the low
permeability layer, provide erosion control, and contribute
to effective operation of the gas control system by
providing a barrier to fugitive surface emissions and to
ambient air entering the waste pile under vacuum conditions.
storm water management consisting of perimeter drains,
retention basins, and associated structures. .
10. Statutory Determinations
Protection of BumanBealth and the Environment
The selected remedy protects human health and the
environment ~hrough extraction and thermal destruction of
landfill gas and installation of landfill cover. The thermal
destruction will permanently remove harmful contaminants in the
LFG such that the excess cancer risk from ambient air exposure to
LFG treatment facility effluent will not be greater 10-6. The
landfill' cover will be designed to reduce surface emissions and
odors; prevent oxygen intrusion into the refuse, which will allow
the gas control system to work effectively; prevent surface water
infiltration which. will assist in leachate management; and
promote erosion control. . .
Short-term risks associated with the selected remedy can be
easily controlled. In addition, no adverse cross-media impacts
are expected from this remedy.
Applicable or Relevant and Appropriate Requirements (ARARS)
The selected remedy for the source control operable unit
will be designed to attain the following ARARs. These ARARs were
identified from federal, and more stringent promulgated state and
local environmental and public health l~ws.
The California Regional Water Quality Control Board -
Central Valley Region (CR~QCB-CVR) has identified sections of
Title 23, Chapter 15 of the California Code of Regulations as
ARARs. The sections EPA selects as ARARs are; Section 2510(a),
2510(b), 2510(c) and.2510(d) of Chapter 15, which pertain to
applicability of chapter 15 and to engineered altern~tives to the
prescriptive standard for final cover at a waste management unit;
Section 2580 of Chapter 15, which pertains to general closure
requirements; Section 2581 of Chapter 15, pertaining to landfill
closure requirements; Section .2540 of Chapter 15, which pertains
to general construction standards for containment structures;
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"
Section 2541 of Chapter 15, which pertains to general design and
construction requirements for containment structures; Section'
2546 of Chapter 15, which pertains to the design, construction
and maintenance of drainage, collection and holding facilities
for waste management units; Section 2547 of Chapter 15, which
pertains to design and construction of landfill structures to
withstand seism~c events; Section 2596 of Chapter 15, which
pertains to the information required in the design reports and
operations plan for containment structures, precipitation and
drainage control facilities and ancillary facilities.
The California Integrated Waste Management Board (CIWMB) has
identified Sections of Title 14, California Code of Regulations
as ARARs. The Sections which EPA ,selects as ARARs are; Section
17705 of Title 14, which pertains to gas control; Section 17774
of Title 14, which pertains to construction. quality assurance;
section 17783 of Title 14, which pertains to gas monitoring and
control during closure and post-closure; Section 17783.9 of Title
14, which pertains to monitored parameters; section 17783.11 of
Title 14, which pertains to monitoring frequency; Section 17773
of Title 14, which pertains to final cover; section 17777 of
Title 14, which pertains to final site face; Section 17778 of
Title 14, which pertains to final drainage; Section 17779 of
Title 14, which pertains to slope protection and erosion control;
section 17778.5 of Title 14, which pertains to perimeter
monitoring network; Section 17783.:7 of Title 14, which pertains
to structure monitoring; Section 17776 of Title 14, which
pertains to final grading; section 17783.15 of Title 14, which
pertains to gas control; Section 17788 of Title 14, which
=pertains to post-closure maintenance; Section 17792 of Title 14,
which pertains to change of ownership during closure and post-
closure maintenance; Section 17796 of Title 14, which pertains to
post-closure land use.
I
Additional Performance Requirement~
EPA selects the following as performance criteria for the
selected 'interim remedy. Ambient air concentrations of landfill
gas, contaminants or landfill gas treatment facility contaminant
emissions shall not exceed a level,' as determined by EPA, which
would cause a 10-6excess cancer 'risk as determined pursuant to
the California Air Pollution Control Officers Association
(CAPCOA) Air Toxics "Hot spots" Proqram Risk Assessment
Guidelines (January 19~1). .
At a threshold minimum, 'the remedy must meet the
requirements of. the Solid Waste Disposal Sites - Draft Rule 46-
42, which (1) establishes a reactive organic destruction.
efficiency of 98% for any reactive organic except methane, (2)
requires that flares designed as part of the landfill gas control
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system be enclosed in a shroud, and (3) requires that the maximum
concentration of organic compounds measured as methane, measured
at any point on the surface of the landfill, shall not exceed
1000 ppm.
(Note: Section 4.2.1.6 of Rule 2201 of the Rules and Regulations
of the San Joaquin Valley Unified Air Pollution Control District
(SJVUAPCD) exempts the selected interim remedy from the "offset"
requirements which would otherwise be applied to the flare
effluent, including oxides of nitrogen under the Rule.)
The landfill gas extraction system will be operated until
LFG production has declined to the extent that the compliance
points LFG monitoring (at the surface an organic compound maximum
of 1000 ppm measured as methane and at the perimeter monitoring
wells a maximum of 5% methane) requirements can be met without
active LFG extraction. The LFG flares shall be operated as long
as the LFG extraction system is in operation.
Cost-Effectiveness
The selected remedy is the most cost effective remedy which
is protective of human health and the environment, complies with
ARARs. The selected remedy is also the most cost effective
remedy which has the greatest likelihood of long-term
effectiveness, reducing toxicity, mobility, or volume through
treatment, short-term effectiveness and implementability. The
present worth cost of the proposed synthetic membrane landfill
cover, LFG control system with on-site LFG treatment and other
ancillary systems will be approximately $23,195,000.
Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum
Extent Practicable
EPA believes the selected remedy represents the maximum
extent to which permanent solutions and treatment technologies
can be used for this operable unit at the Fresno Sanitary
Landfill. Of those alternatives that are protective of human
health and the environment and comply with ARARs, EPA has
determined the selected remedy provides the best balance in terms
of long-term effectiveness and permanence, reduction in toxicity,
mobility and volume through treatment, short-term effectiveness,
.implementability, and cost while considering the statutory
preference for treatment as a principal element as well as
community input.
The combination of alternatives 3 and 5 reduces the
toxicity, mobility, and volume of the contaminants in the
landfill gas, complies with ARARs, provides short-term
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effectiveness, and protects human health and the environment more
effectively 'and more rapidly than any of the other alternatives
considered. The selected remedy is more reliable and can be
implemented with less difficulty than the other landfill, cover
alternatives or off-site gas combustion for energy recovery, and
is therefore determined to be the most appropriate and cost-
effective remedy for this operable unit at the Fresno Sanitary
. Landfill site. ' .
Preference For Treatment As A Principal Element
By treating the landfill gas using thermal destruction, the
selected remedy satisfies the statutory preference for remedies
that employ treatment of the principal threat which permanently
and significantly reduces toxicity, mobility, or volume of
hazardous substances as a principal element. The landfill cover
further increases the efficiency of the gas control system by
reducing surface emissions and preventing oxygen intrusion into
the refuse. The selected interim remedy also uses treatment for
the collected LFG and leachate which will be trucked off-site for
treatment. The NCP (55 FR 8846, March 8, 1990) indicates that
liEPA' expects to use treatment to address the principal threat
posed by a site, whenever practicable" and "...to use engineering
controls, such as containment, for waste that poses a relatively
low long term threat or where treatment is impracticable." The
selected remedy for hazardous substances remaining on-site meets
theNCP expectation for engineering controls rather than
treatment of wastes where treatment is impracticable, because it
would be impracticable to remove and treat the estimated 4.7 '
million tons (7.9 million cubic yards) of trash in the landfill
due to severe implementability problems, the potential for
significant short-term risks and prohibitive costs.
11. Documentation of Sianificant Chanqes:
The synthetic membrane landfill cover and on-site landfill
gas combustion in a landfill gas flare were presented in the
proposed plan as the preferred alternative. No significant
changes have been made to t~ese alternatives,. although a
contingency has been added to the selected remedy which includes
a leachate collection system in any gas extraction wells ,which
are found to contain levels of leachate which may pose a threat
to groundwater. Any collected leachate may. be added to the'
landfill gas condensate collection system and will be trucked
off-site for treatment. This leachate collection contingency,
even if implemented in each gas well, will not significantly'
affect the cost ,of the selected remedy. The use of this
contingency in every gas well may increase the total remedy
by $1 to $2 million~ Since the cost of the proposed remedy
estimated to be $23,195,000, with an accuracy range of -30%
+50%, the cost of,the remedy is not significantly affected.
costs
is
to
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