United States
Environmental Protection
Agency
Off ice of
Emergency and
Remedial Response
EPA/ROD/R09-90/055
September 1990
&EPA
Superfund
Record of Decision
Operating Industries
(Amendment), CA
-------
50272-101
1 REPORT DOCUMENTATION 1. REPORT NO. 2.
I PAGE EPA/ROD/R09-90/055
I Tin* and SubtMe
I SUPERFUND RECORD OF DECISION
I Operating Industries, CA
I Third Remedial Action - (Amendment)
1 7. Author(»)
1 ». Performing Organization Name and Addmu
1 12. Sponsoring Organization Name and Addre**
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3. Recipient* Aece**ion No.
S. Report Daw
09/28/90
c.
8. Performing Organization Rept No.
10. Pro|ecVTaak/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
13. Type of Report & Period Covered
800/000
14.
IS. Supplementary Note*
16. Abetract (Umit: 200 word*)
The 190-acre Operating Industries site is an inactive municipal landfill in Monteray
Park, California. Surrounding land use is primarily industrial, however, 53,000
residences are located within three miles of the site. Onsite disposal activities began
in 1948, and continued until 1984. Wastes accepted at the landfill included household
^nd organic refuse, scrap metal, non-decomposable inert solids, and liquid wastes. The
Randfill was capped with a soil cover after operations ceased. Two 1987 Records of
Decision (RODs) addressed site control, monitoring, and leachate management. A third
ROD, signed in 1988, addressed landfill gas migration control and documented the
implementation of an active landfill gas collection and treatment system. Since that
time, continued settling of onsite landfill wastes and the occurrence of subsurface
fires have decreased the integrity of the existing landfill cap. As a result, oxygen
and precipitation have intruded landfill wastes. This ROD amends the original 1988
landfill gas-migration control ROD to include the addition of an upgraded landfill cap.
(See Attached PageX
17. Document Anaiy*i* a. Descriptor*
Record of Decision - Operating Industries, CA
Third Remedial Action - (Amendment)
Contaminated Medium: air
Key Contaminants: VOCs (benzene, PCE, TCE, toluene)
b. Mentfflen/Open-Ended Term*
c. COSATI Held/Group
1 18. Aveilabilty Statement
19. Security da** (Thi* Report)
None
20. Security Claw (Thi* Page)
None
21. No. of Page*
30
22. Price
(See ANSI-Z39.1S)
See Instruction* on ftevente
OPTIONAL FORM 272 (4*77)
(Formerly NTIS-3S)
Department of Commerce
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EPA/ROD/R09-90/055
Operating Industries, CA
Third Remedial Action - (Amendment)
Abstract (Continued)
A final comprehensive site remedy will be addressed in a subsequent ROD. The primary
contaminants of concern affecting the air are VOCs including benzene, PCE, TCE, and
toluene.
The amended selected remedial action includes capping the landfill to reduce surface
gas emissions, to prevent oxygen intrusion and surface water infiltration, and to
provide for erosion control; installing landfill gas extraction wells around the
perimeter and on the top of the cap; collecting and treating landfill gas by
incineration; and dewatering saturated landfill zones. The estimated present worth
cost for this amended remedial action ranges from $125,300,000 to $181,300,000 (based
on the range of costs for the gas control system and landfill cover), which includes
an annual O&M cost of $3,700,000 to $4,100,000 for 30 years.
PERFORMANCE STANDARDS OR GOAIjS: A destruction and removal efficiency of 99.99% for
each organic landfill gas component will be achieved in accordance with RCRA
requirements.
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DECLARATION
SITE NAME AND LOCATION
Operating Industries, Inc. (Oil)
Monterey Park, California
STATEMENT OP BASIS AND PURPOSE
This decision document presents an amendment to the remedial
action selected on September 30, 1988 for the Gas Migration
Control Operable Unit at the Operating Industries, Inc. site in
Monterey Park, California. The amended remedy was chosen in
accordance with CERCLA, as amended by SARA, and, to the extent
practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision to amend the previously
selected remedial action is based on the administrative record
for this site operable unit.
The State of California concurs with the amended selected remedy.
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 amended Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare,
or the environment.
DESCRIPTION OP THE AMENDED SELECTED REMEDY
The amended Gas Migration Control ROD at the Oil site
addresses the landfill gas (LFG) migration control and landfill
cover. The major component of this amendment is the addition of
landfill cover to the previously selected gas migration control
remedy.
The major components of the Gas Migration Control ROD as
amended include:
o Landfill cover designed to: (1) reduce surface gas
emissions and odors; (2) prevent oxygen intrusion into
the refuse; (3) prevent surface water infiltration; (4)
provide erosion control; and (5) improve site
aesthetics;
Page 1
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o Perimeter LFG extraction wells, with placement focused
on minimizing off-site LFG migration;
o LFG extraction wells on the top deck of the landfill,
with placement focused on maximizing source control of
LFG;
o Shallow and deep slope wells with placement focused on
reducing surface emissions and controlling intermediate
to deep subsurface migration at the perimeter;
o Integrated above-grade LFG headers and condensate
sumps;
o LFG monitoring wells at the site boundary;
o Upgraded thermal destruction facility for landfill gas;
and
o Pumps in appropriate gas wells, with above-grade
collection sumps, to de-water saturated zones.
The amended gas control remedial action will be integrated
with the two additional operable units, Site Control and
Monitoring, and Leachate Management now being implemented.
STATUTORY DETERMINATION
The amended remedy selected is protective of human health
and the environment, is designed to comply with Federal and State
requirements that are legally applicable or relevant and
appropriate to the remedial action, or a waiver is justified, and
is cost-effective. This remedy uses permanent solutions and
alternative treatment technologies, to the maximum extent
practicable. The gas control and landfill cover remedy selected
by the amended decision document satisfies the statutory
preference for remedies that employ treatment that reduces
toxicity, mobility, or volume as a principal element.
As this remedy will result in hazardous substances remaining
on-site above health-based levels, a review will be conducted
each fiv« years after the commencement of the final remedial
action to ensure that the remedy continues to provide adequate
protection of human health and the environment.
DanielM/. McGovern «^tv Date
Regional Administrator
EPA, Region IX
Page 2
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AMENDMENT TO DECISION SUMMARY
OPERATING INDUSTRIES, INC.
GAS MIGRATION CONTROL OPERABLE UNIT
RECORD 0? DECISION
SCOPE AND ROLE OP OPERABLE UNIT
The Gas Migration Control Operable Unit Record of Decision
(hereinafter referred to as the "original gas ROD") at the
Operating Industries, Inc. (Oil) Superfund site in Monterey Park,
California, is being amended to include the design and
construction of landfill cover. EPA signed the original gas ROD
for this operable unit on September 30, 1988. A copy of the
original gas ROD is attached. EPA is addressing the problem of
landfill gas (LFG) as an operable unit to expedite the LFG and
cover remedial action prior to the selection and implementation
of the overall final remedial action for the site.
Integration of the gas control remedy with landfill cover is
preferred due to technical and economic advantages resulting from
concurrent design and construction, and because an integrated
approach will provide for protection of public health and the
environment in a shorter time period. Landfill cover is required
to: (1) reduce gaseous surface emissions and associated odor; (2)
minimize oxygen intrusion into the refuse; (3) reduce surface -
water infiltration and the subsequent formation of leachate; (4)
minimize slope erosion; and (5) improve site aesthetics.
The amended remedy retains the primary components of the
original gas ROD; however, the addition of a landfill cover may
affect certain elements of the design. For example, it is
possible that a different number of wells than that specified in
the original gas ROD will be necessary to control landfill gas.
Similarly, factors such as well spacing, depth and type will be
impacted by the addition of cover and will be reevaluated at the
time of design.
The original gas ROD states that the decision to place
landfill cover was deferred due to a lack of site-specific
knowledge. Additional information about the existing landfill
cover and refuse characteristics is now available as a result of
the ongoing Remedial Investigation and EPA's experience from
operation and maintenance of the landfill systems over the past
three years (as part of the Site Control and Monitoring operable
unit remedial action).
The addition of landfill cover is an amendment to the remedy
selected for the third operable unit, Gas Migration Control, at
the Oil site. Two previous RODs for Site Control and Monitoring
and Leachate Management were signed on July 31, 1987 and November
16, 1987, respectively. The ongoing Remedial Investigation
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Feasibility Study (RI/FS) for the overall site remedy is
currently scheduled for completion in 1993.
SITE DESCRIPTION
A site description is included in the original gas ROD. The
following additional information is pertinent to the selection of
landfill cover and its design.
More than 50 years of continuous rainfall data exist from
two Los Angeles County Flood Control District (LACFCD) weather
stations near the site. The average annual rainfall is
approximately 16 inches, with a maximum annual rainfall of
approximately 37 inches in 1982-3. Approximately 90 percent of
the annual rainfall occurs during the 6-month period of November
through April. The estimated probable maximum precipitation
(PMP) is estimated to be about 21 inches for a 24-hour storm and
35 inches for a 72-hour storm (Bureau of Reclamation, 1974).
EPA estimates that the Oil landfill settlement rates ranged
from 3 to more than 4 feet per year between 1974 and 1983.
Settlement rates observed from December 1987 to December 1988
were slightly greater than 2 feet per year. Additionally, the
upper 10 to 30 feet of existing cover and refuse appear to be
undergoing downslope creep at a rate of 2 to 9 inches per year.
Geotechnical monitoring using inclinometers, piezometers, surface
monuments, and seismic monitoring stations at various locations
around the landfill provides additional information regarding the
static and dynamic properties of the refuse prism and existing
cover.
SITE HISTORY AND ENFORCEMENT ACTIVITIES
The original gas ROD contains a chronology of site
enforcement activities through 1988. EPA has undertaken the
following enforcement activities since September 1988:
*v
May 1989 A Partial Consent Decree (CD) between the
United States, the State of California, and
approximately 120 Potentially Responsible
Parties (PRPs) was entered in the District
Court for the Central District of California,
United States, et al v. Chevron Chemical, et
al. The Partial Consent Decree resolved
claims for some State and Federal past costs,
EPA oversight costs, and the implementation
of the first two operable units, Site Control
and Monitoring and Leachate Management.
July 1989 EPA sent General Notice letters to
approximately 91 additional PRPs representing
an additional five percent by volume of the
Page 2
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manifested liquid wastes.
The generators noticed to date represent
approximately 85% by volume of the manifested
liquid waste.
March 1990 EPA extended an offer to the 91 PRPs noticed
in July 1989 and to previous nonsettlors for
settlement of the same issues as the first CO
(past costs to June 1, 1988, liability for
the first two operable units, and EPA
oversight cost for the two OUs). The offer
closed August 3, 1990. The settlement will
result in a Second Partial Consent Decree.
COMMUNITY PARTICIPATION
Pursuant to the requirements for public participation set
forth in Sections 113 (k) (2) (B) (i-v) and 117 of CERCLA, EPA
conducted the following activities for the ROD amendment:
o EPA mailed the amended Proposed Plan (dated December
1989), to approximately 1600 interested parties. The
amended Proposed Plan presented the preferred
alternative of addition of landfill cover to the
previously selected gas control remedy.
o A notice of the release and mailing of the Proposed
Plan, the time and place of the public meeting, and the
dates for the public comment period was published in
the Los Angeles Times. San Gabriel edition, on December
15, 1989.
o The public comment period opened on December 11, 1989
and closed on January 12, 1990. Documents from the
Administrative Record were placed in the site
information repositories for public review during the
comment period.
o On January 4, 1990, EPA held a public meeting at a high
school near the site to discuss the alternatives
evaluated, to present the amended preferred
alternative, and to provide an opportunity for public
comment. During this meeting EPA solicited written and
verbal comments and provided responses to the comments.
A transcript of the public meeting, including comments
and responses, is part of the Responsiveness Summary
for the ROD Amendment.
o EPA received two sets of written comments during the
public comment period and addresses these comments in
the attached Responsiveness Summary for the ROD
Page 3
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Amendment.
SUMMARY OF SITE CHARACTERISTICS
A summary of the site characteristics relating to the
landfill gas control system is included in the original gas ROD.
An additional discussion of site characteristics relating to
landfill cover is presented below.
The Oil landfill is divided by the Pomona Freeway into two
areas, a south parcel and a north parcel. The south parcel is
approximately 145 acres in size and is characterized by 43 acres
of relatively flat top deck and 102 acres of sloped areas. The
slopes have two to three intermediate bench roads, 10 to 12 feet
wide, to allow access and slope maintenance. Total slope heights
vary from 100 to 200 feet with average slope angles ranging from
less than 4H:1V (Horizontal:Vertical) to as steep as 1.5H:1V.
Locally, slopes do exceed 1.5H.-1V in steepness. The majority of
the 145-acre south parcel was used for waste disposal whereas
approximately 15 acres of the western area of the north parcel
were used for waste disposal.
The 145-acre south parcel of the landfill is bounded by the
Pomona Freeway to the north, business and residential areas to
the west and south, and an oil field to the east. The majority
of the perimeter of the landfill abuts the freeway or residential
areas which severely limits any expansion of the landfill
boundaries to decrease the steepness of the slopes.
The maximum vertical thickness of the landfill on the south
parcel is approximately 330 feet. The top of the landfill ranges
from 70 to 225 feet above the adjacent ground surface with the
elevation of the top deck averaging approximately 620 to 640 feet
above mean sea level (msl). The lowest elevation of the bottom
of the landfill is estimated to be approximately 300 feet above
msl.
N
The landfill is currently covered by a soil layer of
variable thickness which ranges from nearly 0 feet to 25 feet.
The cover tends to be thicker on the top deck and thinner on the
slopes and consists of varying amounts of clay, sand, and silt.
The engineering characteristics of the cover are highly variable
and, generally, are not adequate for landfill closure. Surface
cracking, depressions, and evidence of erosion exist at many
locations around the landfill. The primary deficiencies of the
existing cover are that it does not: (1) prevent gaseous surface
emissions; (2) prevent oxygen intrusion into the refuse; (3)
limit infiltration of surface water; or (4) provide for adequate
erosion control and stormwater management.
Landfill gas that is not adequately controlled by the gas
control system or by the landfill cover currently in place is
Page 4
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released by venting through the landfill cover, resulting in
unacceptable surface emissions of landfill gas on- and off-site.
Excessive surface emissions have been documented by grid survey
data from the landfill surface. On-site areas with the highest
levels of surface emissions have historically been on the slopes.
The slopes have a thinner existing cover and have experienced
significant erosion which further increases the amount of gaseous
surface emissions. As the landfill refuse settles, the resulting
cracks and fissures also-act as a preferential pathway for
surface emissions.
Historically, subsurface fires have been a recurring problem
at the Oil landfill. These fires have resulted from oxygen
intrusion in combination with the high temperatures created
during anaerobic decomposition of the refuse. The negative
pressure (vacuum) necessary for the operation of gas extraction
wells draws oxygen through the surface of the landfill, providing
a source of oxygen within the refuse. Another major source of
oxygen is supplied by an air dike injection system on the western
border of the landfill, designed by Oil to inject a curtain of
compressed air into the ground to create a barrier to subsurface
LFG migration.
Evidence of subsurface fires (e.g., elevated gas well
temperatures) has existed for several years in some areas of the
landfill. These fires can produce voids within the landfill
that, upon collapse, may result in surface settlement depressions
and the release of landfill gas. The reduction of oxygen
intrusion requires the replacement of the air dike system with
gas extraction wells and/or a decrease of the gas extraction
system vacuum. Merely decreasing the system vacuum, given the
current inadequacy of the existing gas extraction system, would
result in a significant and unacceptable increase in off-site gas
migration.
Oxygen intrusion into the refuse has also lowered the
percent combustibles of the gas stream in the landfill gas
extraction system, which could subsequently reduce the
destruction efficiency during incineration. In existing areas of
thin cover, the vacuum system applied to the gas extraction wells
has been decreased or shut off due to elevated temperatures or
poor gas quality, thus reducing the radius of influence of the
well and the volume of gas extracted. The placement of landfill
cover facilitates the extraction of high-quality LFG and will
allow the system to operate with maximum efficiency.
The existing landfill cover is highly variable in its
thickness and permeability and in its ability to prevent surface
water infiltration. The lack of adequate cover allows surface
water from rainfall and site irrigation to percolate through the
thin cover, cracks, or fissures into the refuse prism. Left
uncontrolled, the liquids percolate through the refuse and
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increase the amount of leachate in the landfill.
In addition to providing a physical barrier for gaseous
surface emissions, oxygen intrusion, and surface water
infiltration, the landfill cover forms the physical base for the
stormwater management and erosion control systems at the
landfill. The site drainage system currently consists of
concrete-lined or clay-lined ditches along the toe of the
intermediate slopes and on the top deck which drain to asphalt
inlet and drop structures. Surface drainage is conveyed off-site
in approximately ten locations around the south parcel.
Substantial amounts of surface water are conveyed along the
shoulder of access roads. Poor control of surface runoff has
resulted in significant erosion of cover soil on slopes and
access roads.
The existing drainage system is inadequate to prevent slope
erosion and off-site sediment transport. An hydrologic analysis
is being conducted as part of the Site Control and Monitoring
(SCM) remedial action to assist in the design of a comprehensive
stormwater management system. Improvements to the site drainage
system conducted as part of SCM will be incorporated into the
design and construction of the stormwater management system
component of landfill cover.
SUMMARY OP SITE RISKS
A discussion of site risks is included in the original gas
ROD. The Preliminary Risk Assessment for this operable unit
demonstrated the need for landfill gas migration control and
landfill cover to stabilize the site, to minimize further
contaminant migration, and to quickly achieve significant risk
reduction. The Preliminary Risk Assessment is found in Volume l
Text. Public Comment Draft. Operable Unit Feasibility Study for
Landfill Gas Migration Control, at page 4-10.
DESCRIPTION OF ALTERNATIVES
This amendment presents an additional alternative, .
Alternative 11, for evaluation and comparison with Alternatives 1
through 10 presented in the original gas ROD. The addition of
this alternative is the result of public comment on the original
gas ROD and additional site-specific knowledge now available to
EPA as a result of its presence on-site performing a RI and
conducting SCM for the last three years.
Alternative 11 consists of the landfill gas control remedy
previously selected in the original gas ROD with the addition of
design and construction of landfill cover. The Operable Unit
Feasibility Study for Landfill Gas Migration Control, in
conjunction with the "Technical Memorandum of Cost Estimates for
Landfill Cover Concepts RI/FS," provides a thorough discussion of
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the integrated gas control and landfill cover alternative. A
summary of the components for Alternative 11 is included below.
TREATMENT COMPONENTS
Alternative n includes the treatment components specified
for Alternatives 9 and 10 which were presented in the original
gas ROD. Alternative 11 provides for the extraction and thermal
destruction of an estimated 90 percent of the landfill gas
produced by the landfill (original gas ROD, page 37). This
represents a 78 percent reduction in the volume of methane gas
currently being released from the site. The thermal destruction
facility for the landfill gas will meet the 99.99 percent
destruction efficiency as required by the Resource Conservation
and Recovery Act (RCRA). Liquids (e.g., leachate and condensate)
collected by the gas control system will be collected and treated
in an on-site treatment plant currently being designed and
constructed under the Leachate Management Operable Unit.
CONTAINMENT COMPONENTS
Alternative 11 amends the gas control remedy previously
selected by adding the design and construction of landfill cover.
The installation of landfill cover will further enhance the
collection efficiency of the gas control system, thus reducing
the potential for contaminant migration. The cover will be
designed to meet applicable or relevant and appropriate
requirements (ARARs) for landfill closure, including those under
the Resource Conservation and Recovery Act (RCRA), 42 U.S.C.
§ 6901, et seq. which defines general cover system performance
standards, as well as more stringent promulgated State landfill
cover requirements. The specific components for the cover will
be developed during the remedial design stage.
Generally, the cover is designed to: (1) reduce gaseous
surface emissions and associated odor; (2) minimize oxygen
intrusion "into the refuse; (3) reduce surface water infiltration
and the subsequent formation of leachate; (4) minimize slope
erosion; and (5) improve site aesthetics. Cover design options
include characteristic components such as:
1) A base layer placed on the existing cover which acts as
a foundation for the cover system;
2) A drainage layer (e.g., gravel, synthetic geogrid) to
collect gas or liquids migrating to the surface of the
landfill;
3) A barrier layer (e.g., clay, synthetic flexible
membrane liner) to prevent gaseous surface emissions
and surface water infiltration; and
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4) A soil or synthetic layer to control erosion, prevent
off-site sediment transport, and improve site
aesthetics.
Test cover plots are currently being developed as part of
the SCM activities. Information obtained as a result of the
construction, operation, and maintenance of the test plots will
facilitate the design and construction of a landfill cover which
will effectively meet the RCRA cover system performance
standards.
The 30-year present worth cost for the gas control system of
$62,900,000 was presented in the original gas ROD. Capital
costs, operation and maintenance costs, and present worth costs
for the landfill cover are estimated in the "Technical
Memorandum—Cost Estimates for Landfill Cover Concepts RI/FS,"
dated December 11, 1989. A range of potential cover designs were
identified and evaluated in the Technical Memorandum. Based on
the range of cost estimates for the gas control system plus the
landfill cover, the 30-year present worth cost, discounted at 5%,
for the gas control system and landfill cover is estimated at
$125,300,000 to $181,300,000. Significant efficiencies should
result from the integrated design and construction of the
landfill gas collection system and cover, resulting in a
reduction in capital and life-cycle costs.
SUMMARY OF COMPARATIVE ANALYSIS OP ALTERNATIVES
Tables 1 and 2 provide a summary of the relative performance
of the alternatives, comparing present worth costs,
effectiveness, and compliance with ARARs. Table 3 presents a
more detailed evaluation of the effectiveness of the
alternatives.
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Table 1
ALTERNATIVES COMPARISON SUMMARY
OH LFG MIGRATION CONTROL
Effectiveness
Cost Estimate (a)
/,
Alternative
No.
0.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
II.
Description
No Action
Status Quo
Improved Status Quo
Minimal Gas Extraction with LFG Flaring
Intermediate Gas Extraction with LFG Flaring
Maximum Gas Extraction with LFG Raring
Maximum Gas Extraction with LFG Boiler and Steam Power Generation
Replacement Gas Extraction with LFG Flaring
Replacement Gas Extraction with LFG Boiler and Steam Power Generatior
Modified Replacement Gas Extraction with LFG Flaring
North Parcel System
Alternatives 9 and 10 with Landfill Cover
Innovative or
Resource Recovery
Technology
No
No
No
No
No
No
Yes
No
Yes
No
No
No
Estimated
Additional LFG
Collection (b)
-
0%
0%
0%
20%
45%
70%
70%
70%
70%
70%
70% +
Probability of
Meeting or
Exceeding ARARs
No
No
No
Partially
Possibly
High Probability
High Probability
High Probability
High Probability
High Probability
High Probability
High Probability
Capital
Investment
($ Million)
0
0
5.8
15.5
23.3
32.1
46.6
45.3
59.8
27.0
0.4
68.4-118.3
Operation &
Maintenance (c)
($ Million)
0
1.6
1.5
2.0
2.5
3.0
3.4(d) / 3.0(e)
2.6
l.0(d)/2.6(e)
2.3
0.038
3.7-4.1
Notes:
(a)
(b)
(c)
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TABLE 2
Amended to Include Alternative 11
NET PRESENT WORTH OF ALTERNATIVES
Present Worth Rates ($ in millions)
Alternative Project Life ' @ 3% (S?5% <@10%_(intere_stl
1 30 years
45 years
60 years
2 30 years
45 years
60 years
3 30 years
45 years
60 years
4 30 years
45 years
60 years
5 30 years
45 years
60 years
6 30 years
45 years
60 years
7 30 years
\ 4-5 years
60 years
8 30 years
45 years
60 years
9 30 years
45 years
60 years
10 30 years
45 years
60 years
11 30 years
45 years
60 years
31.1
37.5
41.4
35.3
41.6
45.5
54.1
62.3
67.6
71.5
82.1
88.8
90.0
103.0
111.2
94.0
107.0
115.3
96.1
107.6
114.9
100.2
111.6
119.0
71.6
81.5
87.9
1.1
1.2
1.2
140.9-198.7
159.1-218.8
170.8-231.8
24.4
27.2
28.3
29.0
31.7
32.9
45.7
49.4
51.1
61.1
65.9
68.1
77.5
83.5
86.2
82.2
88.8
91.5
85.2
90.4
92.9
90.5
95.8
98.0
61.9
66.5
68.6
1.0
1.0
1.0
125.3-181.3
134.2-191.1
138.4-195.9
15.0
15.1
14.9
20.0
20.2
20.2
34.0
34.3
34.3
46.5
46.9
46.9
60.0
60.6
60.6
67.7
68.4
68.4
69.8
70.3
70.3
77.5
78.1
78.1
48.4
48.8
48.9
0.8
0.7
0.7
103.3- 157.0
104.9-158.7
105.3-159.2
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Table 3*
EFFECTIVENESS EVALUATION OF ALTERNATIVES
/. Overall Protection of Human Health and the Environment
Effectiveness Criteria
How Alternative Provides Human Health
and Environmental Protection
Alternative 11
• Landfill Gas normally released as surface
emissions and subsurface migration will be
reduced.
• Greater reduction than Alternatives 9/10
through addition of landfill cover.
• Cover enhances extraction well efficiency.
2. Compliance with ARARs
Effectiveness Criteria
Compliance with Chemical-Specific
ARARs
Compliance with Action Specific ARARs
Compliance with Location-Specific ARARs
Alternative 11
• Surface emissions control (less than 50
ppm average of methane; 500 ppm
maximum at any point): Greater likelihood
of compliance with addition of landfill
cover than with Alternatives 9/10.
• Subsurface migration control (less than 5
percent methane at boundary:): Greater
likelihood of compliance by enhancing
extraction system efficiency than with
Alternatives 9/10.
• Odor control: High potential for control
of odorous surface emissions with
maximum well coverage and landfill cover
installation.
• Thermal destruction facility will achieve a
destruction and removal efficiency of
99.99%
No location-specific ARARs apply
3. Long-term Effectiveness and Permanence
Effectiveness Criteria
Alternative 11
Magnitude of Residual Risk
A quantitative residual risk calculation has
not been performed for this operable unit.
However, due to greater control of
emissions and enhanced gas collection
associated with Alternative 11, residual risk
is less than that potentially posed by
Alternatives 9/10. A quantitative residual
risk analysis will be done as part of the
final site remedy.
Please see the attached ROD (9/30/88) for a complete evaluation of Alternatives 1-10.
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4. Reduction ofToxicity. Mobility, or Volume Through Treatment
Effectiveness Criteria
Alternative 11
Degree of Expected Reduction in Toxicity,
Mobility, and Volume
Placement of cover will allow the other
components of the remedy outlined in
Alternatives 9/10, (including the treatment
component discussed in the original ROD)
to work more efficiently. High potential for
reduction due to maximum well coverage
plus landfill cover.
5. Short-Term Effectiveness
Effectiveness Criteria
Alternative 11
Protection of Community During Remedial
Actions
Short term risks posed by construction
and/or surface emissions may exist, but
will be mitigated by proper controls.
Environmental Impacts
Noise, LFG emissions, erosion, odors,
and dust during construction will require
engineering controls.
Protection of Workers during Remedial
Actions
• Potential contact with hazardous
substances may exist, and will require
appropriate health and safety procedures.
• Physical hazards may exist due to on-
slope construction of gas/cover
components
Time Until Remedial Action Objectives are
Achieved
• Integrating gas/cover systems gains
efficiencies in ease and time of design and
construction. Remedial action objectives
should be met sooner than with Alternative
9/10.
• Without integration, cover would require
difficult retrofitting to gas system (e.g.
extension of extraction wells).
• Time required to implement integrated
gas/cover will be longer than implementing
gas exclusively but less than implementing
gas plus a retrofitted cover.
6. Implementability
Effectiveness Criteria
Alternative 11
Ability to Construct and Operate the
Technology
Integrated gas/cover systems are widely
used for control of releases at landfills.
Broad range of technologies available,
both proven and innovative, for system
design. Slope steepness will impact the
ease with which the cover will be installed;
however, this issue will be addressed by
considering a variety of cover systems for
different portions of the landfill.
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Reliability of Technology
Ability to Monitor Effectiveness of Remedy
Ability to Obtain Approvals from Other
Agencies
Integrated LFG/cover system is a
demonstrated and widely-used landfill
technology. A broad range of equipment
and materials are available, have been used
on other landfills, and will be evaluated
during system design.
Same as Alternatives 9 and 10.
Same as Alternatives 9 and 10
7. Cost
Effectiveness Criteria
Capital Cost
Operating and Maintenance Cost
Present Worth Costs
Alternative 11
Higher than Alternatives 9/10.
Because the landfill cover will be installed
together with the gas control components in
Alternatives 9/10, it is likely there will be
efficiencies gained in both operation and
maintenance. Moreover, the original ROD
contemplated a cover for the site, and O/M
costs would be required for final remedy.
Higher than Alternatives 9/10.
& State Acceptance
Effectiveness Criteria
Alternative 11
Features of the Alternative the State
Supports
State concurs with choice of remedy, and
has not identified any features about which
it has reservations.
9. Community Acceptance
Effectiveness Criteria
Alternative 11
Features of the Alternative the Community
Supports
Community concurs with choice of
remedy, and has not identified any features
about which it has reservations.
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STATE ACCEPTANCE
EPA and the State of California, Department of Health
Services, agree on the preferred alternative. Both Agencies have
been involved in the technical review and the development of the
Proposed Plan. The Department of Health Services issued a
Negative Declaration on April 9, 1990 for the Gas Migration
Control with Landfill Cover Operable Unit in compliance with the
requirements of the California Environmental Quality Act (CEQA).
COMMUNITY ACCEPTANCE
During the public comment period, EPA received two sets of
written comments from the community.
1) A local community group Homeowners to Eliminate
Landfill Problems (H.E.L.P.) concurs with the preferred
alternative to amend the ROD to add landfill cover to
the gas remedy.
2) The Oil Steering Committee, a group of potentially
responsible parties involved at Oil, supports the
consideration of integration of the cover component of
the site remedy with the gas control remedy, but
expressed concern about the lack of specificity
regarding the exact type of cover design to be
implemented. Detailed responses to the issues raised
by the Oil Steering Committee are included in the
Responsiveness Summary section of the ROD.
A transcript of the public meeting, including public statements
made during the meeting, is also included in the Responsiveness
Summary.
SELECTED REMEDY/STATUTORY DETERMINATIONS
*v-
The selected remedy, Alternative 11, for this ROD amendment
integrates the design and construction of landfill cover with the
landfill gas control remedy previously selected in the original
gas ROD. The major components of the amended landfill gas
control and cover remedy include:
o Landfill cover designed to: (1) reduce surface gas
emissions and odors; (2) prevent oxygen intrusion into
the refuse; (3) prevent surface water infiltration; (4)
provide erosion control; and (5) to improve site
aesthetics;
o Perimeter LFG extraction wells, with placement focused
on minimizing off-site LFG migration;
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o LFG extraction wells on the top deck of the landfill,
with placement focused on maximizing source control of
LFG;
o Shallow and deep slope wells with placement focused on
reducing surface emissions and controlling intermediate
to deep subsurface migration at the perimeter;
o Integrated above-grade LFG headers and condensate
sumps;
o LFG monitoring wells at the site boundary;
o Upgraded thermal destruction facility for landfill gas;
and
o Pumps in appropriate gas wells, with above-grade
collection sumps, to de-water saturated zones.
The addition of landfill cover to this operable unit
significantly increases the protection of human health and the
environment and will be designed to attain ARARs or a waiver is
justified.
PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy protects human health and the
environment through extraction and thermal destruction of
landfill gas and installation of landfill cover. The thermal
destruction will permanently remove 99.99 percent of the
contaminants in the landfill gas. The landfill cover will be
designed to reduce surface gas emissions and odors; prevent
oxygen intrusion into the refuse, which will allow the gas
systems to work more effectively; prevent surface water
infiltration, which will assist in leachate management; and
promote erosion control.
N
Short-term risks associated with the selected remedy, as
addressed in the original gas ROD (at page 31), can be readily
controlled. In addition, no adverse cross-media impacts are
expected from the remedy.
COMPLIANCE WITH ARARS
The selected amended remedy for the landfill gas migration
control and landfill cover operable unit will be designed to
attain the following applicable or relevant and appropriate re-
quirements (ARARs), in addition to the ARARs identified in the
original gas ROD. These ARARs were identified from Federal, and
more stringent promulgated state and local environmental and
public health laws.
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The amended remedy is an operable unit which only addresses
landfill gas migration control and landfill cover. While certain
closure and post-closure requirements are applicable, this
remedial action does not address all closure and post-closure
ARARs. Upon conclusion of the Remedial Investigation and
Feasibility Study, additional remedial actions may be selected.
EPA currently expects that further actions, including groundwater
remediation, may be required. The ARARs for such remedial
actions will be identified and addressed at that time.
Federal Requirements
1. Resource Conservation and Recovery Act (RCRA)
The Resource Conservation and Recovery Act (RCRA), Subtitle
C, sets forth several applicable requirements for the amended
remedy at 40 C.F.R. Part 265, Interim Status Standards for Owners
and Operators of Hazardous Waste Treatment, Storage, and Disposal
Facilities, and several relevant and appropriate requirements in
40 CFR part 264, Standards for Owners and Operators of Hazardous
Waste Treatment, Strorage and Disposal Facilities.
The Land Disposal Restrictions of RCRA are neither
applicable, nor relevant and appropriate to this remedial action.
Generally, any movement of hazardous waste will be within the
same area of contamination. There will be no residuals from the
thermal destruction facility to be redeposited, and any
condensate or leachate will be treated on site at the treatment
plant currently being designed and constructed under the Leachate
Management operable unit.
A. Part 265f Subpart 6: Closure and Post-Closure
40 C.P.R. s 265.117; Pest-closure care and use cf property
Post-closure care requirements must begin after closure of
the unit and continue for 30 years after that date. These re-
quirements include (c): post-closure use of the property on or in
which hazardous wastes remain after partial or final closure must
never be allowed to disturb the integrity of the cover.
B. Part 265, Subpart N: Landfills
40 C.F.R. S 265.310 - closure and Post-Closure Care
The final landfill cover must be designed and constructed
to: (1) provide long-term minimization of migration of liquids
through the closed landfill; (2) function with minimum
maintenance; (3) promote drainage and minimize erosion or
abrasion of the cover; (4) accommodate settling and subsidence so
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that the cover's integrity is maintained; and (5) have a
permeability less than or equal to any bottom liner system or
natural subsoils present.
The 30 year post-closure care of the cover must include:
(1) maintenance of the integrity and effectiveness of the cover,
including repairs to the cover as necessary to correct the
effects of settling, subsidence, erosion or other events; (2)
prevention of run-on and run-off from eroding or otherwise
damaging the cover; and (3) protection and maintenance of
surveyed benchmarks.
C. Part 264, Subpart O: Incinerators
Several of the sections of this subpart are relevant and
appropriate requirements for the thermal destruction facility,
which meets the RCRA definition of an "incinerator," namely an
enclosed device using controlled flame combustion to incinerate
hazardous waste.
40 C.F.R S 264.343 - Performance standards
The remedy will be designed to attain the standards required
by this section. The thermal destruction facility must be
designed, constructed and maintained to meet the following
performance standards:
(1) the facility must achieve a destruction and removal
efficiency of 99.99 percent for each principal organic hazardous
constituent in the waste feed;
(2) the facility must reduce hydrogen chloride emissions to
1.8 kg/kr or 1 percent of the HC1 in the stack gasses before
entering any pollution control devices; and
(3) the facility must not release particulate in excess of
180 mg/dscm corrected for the amount of oxygen in stack gas.
40 C.F.R S 264.345 - Operating Requirements
The thermal destruction facility will be operated to meet
the following requirements of this section: (1) monitoring of
various parameters during operation, including, combustion
temperature, waste feed rate, an indicator of combustion gas
velocity, and carbon monoxide; (2) control of fugitive emissions
by (a) keeping the combustion zone totally sealed against
fugitive emission, (b) maintaining combustion-zone pressure lower
than atmospheric pressure, or (c) controlling via an alternate
means to provide fugitive emissions control equivalent to
maintenance of combustion zone pressure lower than atmospheric
pressure; and (3) utilization of an automatic cutoff system to
stop waste feed when operating conditions deviate.
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2. Clean Water Act (CWA)
Clean Water Act National Pollutant Discharge Elimination
System (NPDES): 40 C.F.R. Part 125 sets forth requirements for
permits for the discharge of pollutants from any point source
into waters of the United States. Minimization of the off-site
transport of materials and debris to meet the substantive portion
of the NPDES permit requirements will be addressed during the
Remedial Design phase in the development of the landfill cover
grading plan and the design of the site stormwater management and
drainage structures.
State Requirements
The State of California has timely identified several ARARs
which are applicable to the amended selected remedy in addition
to the ARARs identified in the original gas ROD. Moreover, the
selected remedy will meet ARARs, as noted below, for which
interim waivers were invoked in the original gas ROD pending the
addition of landfill cover.
1. South Coast Air Quality Management District, Rules and
Regulations (administered by the South Coast Air Quality
Management District, as delegated by the California Air Resources
Board).
Rule 402 - Nuisance. This rule prohibits the discharge of
any material (including odorous compounds) that cause injury,
detriment, nuisance, or annoyance to the public, businesses, or
property or endangers human health, comfort, repose or safety.
The selected amended remedy will be designed to attain this
ARAR, waived in the original gas ROD.
Rule 432.1 - A typographical error in the original ROD
identified this Rule as 431.1.
\
Regulation XX - Source Specific Standards - 1150.2
The original gas ROD identified Rule 1150.1, Control of
Gaseous Emissions from Active Landfills, as an ARAR for the
selected remedy and waived this requirement pending selection of
landfill cover. The cover selected by this amended remedy will
be designed to meet Rule 1150.2, Control of Gaseous Emissions
from Inactive Landfills, which is an applicable state
requirement.
Rule 1150.2 - Control of Gaseous Emissions from Inactive
Landfills, requires perimeter landfill gas monitoring probes to
evaluate off-site migration and limits concentration to total
organic compounds to 50 ppm over a representative area of the
landfill and maximum concentration of organic compounds (measured
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(1) The concentration of methane gas must not exceed
1.25% by volume in air within on-site structures;
(2) The concentration of methane gas migrating from the
landfill must not exceed 5% by volume in the air at the facility
property boundary or an alternative boundary in accordance with
Section 17783.5.
(3) Trace gases shall be controlled to prevent adverse
acute and chronic exposure to toxic and/or carcinogenic
compounds .
Subsection (b) sets forth the period during which monitoring
should continue and subsection (d) provides that the monitoring
and control systems shall be modified, during the closure and
postclosure maintenance period to reflect changing on-site and
adjacent land uses. Postclosure land use at the site shall not
interfere with the function of gas monitoring or control systems.
b. section 17783.3 - Monitoring
This section requires that the gas monitoring system shall
be designed to meet with the specified site characteristics, and
potential migration pathways or barriers, including, but not
limited to: (1) local soil and rock conditions; (2) hydrogeolo-
gical conditions at the facility; (3) locations of buildings and
structures relative to the waste deposit area; (4) adjacent land
use, and inhabitable structures within 1000 feet of the landfill
property boundary; (5) man-made pathways, such as underground
construction; and (6) the nature and age of waste and its poten-
tial to generate landfill gas.
c. Section 17783.5 - Perimeter Monitoring Network
This section sets forth specific requirements for the loca-
tion (subsection a) , spacing (subsection b) , depth (subsection c)
and construction (subsection d) of the monitoring wells.
d . Section 17783.7 - Structure Monitoring
This section requires that the design of the monitoring sys-
tem include provisions for monitoring on-site structures, iden-
tifies some methods for monitoring such structures, and requires
that structures located on top of the waste deposit area be
monitored on a continuous basis.
e. section 17783.9 ** Monitoring
This section requires that all monitoring probes and on-site
structures be sampled for methane and for specified trace gases,
when there is a possibility of acute or chronic exposure due to
carcinogenic or toxic compounds.
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as methane) to 500 ppm, at any point on the surface of the
landfill.
2. Solid Waste Management and Resource Recovery Act of
1972 (administered by the California Integrated Waste Management
Board). The following titles of this act are applicable to the
landfill cover component of the selected amended remedy.
A. Title 14. California code of Regulations. Division 7
The following sections of Chapter 3, Minimum Standards of Solid
Waste Handling and Disposal, Article 7.8, Disposal Site Closure
and Postclosure, are applicable to landfill cover.
1. Section 17773 - Final Cover
The regulation is applicable and the cover will be
constructed to meet its requirements. This regulation requires
that a minimum thickness and quality of cover be placed over the
entire surface of the final lift which meets the standards of
Title 23, CCR, Subchapter 15, Section 2581 or that meet the
standards set forth for an engineered alternative. The
prescriptive standard must be not feasible and the alternative
must be consistent with the performance goals of subsection (e)
and afford equivalent protection against water quality
impairment. Subsection (d) provides the basis for showing
compliance with this standard is not feasible.
Subsection (e) sets forth the following minimum performance
goals for the thickness and quality of cover: (1) a need to
limit infiltration of water, to the greatest extent possible; (2)
a need to control landfill gas emissions; (3) the future reuse of
the site; and (4) a need to protect the low permeability layer
from desiccation, penetration by rodents, and heavy equipment
damage.
^2. Section 17783 - 17783.15
These sections are applicable to the amended selected
remedy, and it will be designed to attain these requirements.
These regulations became effective August 1989 and were not
promulgated at the time the gas ROD was originally signed.
However, the remedy both as originally selected and as amended,
will meet these ARARs.
a. Section 17783 - Gas Monitoring and Control Purina
Closure and Postclosure
During periods of closure and postclosure maintenance,
landfill gases generated at the facility must be controlled as
follows:
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f. Section 17783. 11 - Monitoring Frequency
This section requires a minimum of quarterly monitoring with
more frequent monitoring required if results indicate the
landfill gas is migrating or accumulating in structures.
g. Section 17783.15 - Control
Subsection (a)(1) requires that all immediate steps be taken
when the results of gas monitoring indicate levels of methane in
excess of the compliance levels required by Section 17783(a).
Subsection (b) requires that the gas control system be
designed to: (1) prevent methane accumulation in on-site struc-
tures; (2) reduce methane concentrations at monitored property
boundaries to below compliance levels; (3) reduce trace gas con-
centrations; (4) provide for the collection and treatment and/or
disposal of landfill gas condensate at the surface.
Subsection (c) indicates that the gas control systems may
include, but are not limited to, the control systems enumerated
in subsections (c)(1), (2) and (3).
Subsection (d) provides steps to be taken in the event on-
site structure methane levels exceed that specified in Section
17783(a).
Subsection (e) requires that the operator provide for system
monitoring and adjustment to ensure that the gas control system
is operating at optimum efficiency.
3. Section 17796 - Poatclosure Land Use
This regulation sets forth requirements concerning
postclosure land use. Subsections (c), (d) and (e) are
applicable to this remedial action. Subsection (c) requires that
construction improvements on the site shall maintain the
integrity of the final cover and the function of the monitoring
system(s). Subsection (d) sets forth conditions to be met for
construction of structural improvements on top of landfilled
areas during the post-closure period. Subsection (e) sets forth
building conditions pertaining to on-site structures constructed
within 1,000 feet of the waste holding area.
B. Title 22. California Code of Regulations
Article 18: General Facility standards
Section 67108: Seismic and Precipitation Design
standards
This section is applicable to the landfill cover component
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and requires the design of cover systems and drainage control to
function without failure when subjected to capacity, hydrostatic
and hydrodynamic loads resulting from a 24-hour probable maximum
precipitation storm. Additionally, all covers and cover systems
which will remain after closure must be designed, constructed and
maintained to withstand the maximum credible earthquake without
the level of public health and environmental protection afforded
by the original design being decreased.
Article 23 - Closure and Post-closure for Interim
Status and Permitted Facilities
Section 67211 - Closure Performance standard
Subsection (b) of this section is applicable to the selected
amended remedy and requires that the facility be closed in a man-
ner which controls, minimizes, or eliminates, to the extent
necessary to protect human health and the environment, post-
closure escape of hazardous waste, hazardous waste constituents,
leachate, contaminated rainfall, or waste decomposition products
to the ground or surface waters or to the atmosphere. As noted
above, this operable unit does not address all aspects of
closure; to the extent not addressed by this or earlier operable
units, these will be addressed by subsequent remedial actions.
Article 29 - Landfills at Both Interim Status and
Permitted Facilities
Section 67418 - Closure and Post-Closure Care of
Landfills at Interim status Landfills
This section requires the design and construction of final
cover to meet certain standards which are equivalent to those set
forth under RCRA. More stringent, applicable requirements in-
clude, subsection (1) which requires the prevention of downward
entry of water into the closed landfill throughout a period of at
least 100 years, and subsection (5) which requires that the cover
be designed and constructed to accommodate lateral and vertical
shear forces generated by earthquakes so that the integrity of
the cover is maintained.
C. Title 23. California Code of Regulations
Chapter 3, State Water Resources Control Board
Subchapter 15 - Discharges to Land
Three sections of this subchapter are applicable. For the
purposes of applying these regulations, the Oil Site is con-
sidered to be a Class I facility. (See Section 2531(a)(2) of
this Title.)
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1. flection 2546; Precipitation and Drainage Controls
Subsection (a) requires that the cover shall be designed and
constructed to limit, to the greatest extent possible, ponding,
infiltration, inundation, erosion, slope failure, washout and
overtopping under probable maximum precipitation conditions.
Subsection (c) requires diversion and drainage facilities to
be designed and constructed to accommodate the anticipated volume
of precipitation and peak flows from surface run-off under prob-
able maximum precipitation conditions.
Subsection (d) requires collection and holding facilities
associated with precipitation and drainage control systems to be
emptied immediately following each storm or otherwise managed to
maintain the design capacity of the system.
Subsection (e) requires surface and subsurface drainage from
outside of a waste management unit to be diverted from the waste
management unit.
Subsection (f) requires cover materials to be graded to
divert precipitation from the waste unit, to prevent ponding of
surface water over wastes, and to resist erosion as a result of
precipitation with the return frequency specified in Table 4.1.
2. Section 2547; Seismic Design
This section requires structures which control surface
drainage, erosion or gas shall be designed to withstand the maxi-
mum credible earthquake without damage.
3. Section 2581; Landfill Closure Requirements
The requirements of subsection (a) for cover are applicable.
This section requires at least two feet of appropriate materials,
(primarily soil-type materials) as a foundation layer and an
additional one foot of soil on top of this foundation layer.
These requirements will not be met by the selected remedy, and
are being waived pursuant to Section 121(d)(4)(B), (C) and (D),
42 U.S.C. § 9621 (d)(4)(B), (C) and (D). Due to the
configurations of the Oil site, including its steep slopes and
direct proximity to both homes and the Pomona freeway, a cover
constructed of soil-type materials and with the thickness
required by this subsection would result in a greater risk to
human health and the environment than the selected remedy.
Construction for such a cover is technically impracticable from
an engineering perspective; far greater flexibility in types of
materials and cover design is required by this site. The remedy
selected will attain a standard of performance that is equivalent
to that required by this section through an alternative approach
which provides for a variety of cover materials.
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The landfill cover component will be designed to attain the
requirements of Sections 2581(b) and (c). Subsection (b) sets
forth grading requirements which provide that closed landfills
will be graded and maintained to prevent ponding and sets forth
conditions specific to the steepness of slopes. Subsection (c)
requires that the surface water be monitored in accordance with
Article 5 of this Section.
COST-EFFECTIVENESS
Of the alternatives evaluated, the selected remedy provides
the highest level of protection of human health and the
environment in a cost-effective manner. Significant technical
and economic efficiencies will be gained from the integrated
design and construction of the landfill gas collection system and
landfill cover.
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 Oil site. 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,
effectiveness, and reduction in volume achieved through
treatment, short term effectiveness, implementability, and cost
while considering the statutory preference for treatment as a
principal element as well as community input.
Alternative 11 reduces the toxicity, mobility, and volume of
the contaminants in the landfill gas, complies with ARARs, or a
waiver is justified, provides short-term 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 implementation of gas control and landfill cover
separately, and is therefore determined to be the most
appropriate and cost-effective remedy for this operable unit at
the Oil 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 addition of
landfill cover will further increase the efficiency of the gas
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control system by reducing surface emissions and preventing
oxygen intrusion into the refuse. Complete treatment of the
refuse at this landfill is impracticable due to severe
implementability problems, the potential for significant short-
term risks, and prohibitive costs.
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