PB98-963139
                              EPA 541-R98-151
                              March 1999
EPA Supei fund
      Explanation of Significant Difference
      for the Record of Decision:
      Tri-County Landfill/
      Waste Management Illinois
      South Elgin, IL
      4/23/1998

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               UNITED STATES  ENVIRONMENTAL PROTECTION AGENCY
        \                              REGIONS
        8                    77 WEST JACKSON BOULEVARD
                                 CHICAGO, IL 60604-3590
                                                       REPLY TO THE ATTENTION OF

                 EXPLANATION OF SIGNIFICANT DIFFERENCES

                 TRI-COUNTY-ELGIN LANDFILLS SUPERFUND SITE
                             KANE COUNTY, ILLINOIS

I.     INTRODUCTION
The Tri-County/Elgin Landfill Superfund Site (TCLF) encompasses both the Tri-County and
Elgin Landfills. The site is located in northeastern Illinois on the east side of Kane County near
the triple junction of Kane, Cook, and DuPage Counties.  The Tri-County Landfill, an inactive
landfill of approximately 46 acres, and the 20-acre Elgin Landfill, are located 2/3 of a mile
southeast of the Village of South Elgin. The land to the west of the site is occupied by the
Woodland Landfill, an active sanitary landfill which has accepted municipal and selected special
wastes since 1976.

Response actions at the site are being taken under the authority of the Comprehensive
Environmental Response,  Compensation, and Liability Act (CERCLA) as amended by the
Superfund Amendments and Reauthorization Act (SARA) and the National Contingency Plan
(NCP).  The lead and support regulatory agencies for the TCLF site are the United States
Environmental Protection Agency (EPA) and the Illinois Environmental Protection Agency
(ffiPA), respectively.

Section  117(c) of CERCLA and Section 300.43 5(cK2)(i) of the NCP establish procedures for
explaining, documenting, and informing the public of significant changes to the remedy that occur
after the Record of Decision (ROD) is signed. Significant changes to a component of a remedy
generally are incremental changes to the management approach selected for the site (e.g., a
change in timing, cost, materials, etc.).  Significant changes do not fundamentally alter the overall
approach intended by the remedy. When such changes are necessary, EPA publishes an
Explanation of Significant Differences (ESD). Generally, an ESD is prompted when significant
new information becomes available during or after the public comment period for the ROD.  In
the case of the TCLF site, this information was developed during the Remedial Design (RD)
process. The RD was conducted by two potentially responsible parties (PRP) under an
Administrative Order on Consent. The purpose of this ESD is to explain why the design for the-
landfill cap component of the remedy differs from that set forth in the ROD and to address the
cost differentials associated with the change.

This Explanation of Significant Differences and supporting documents are a part of the
Administrative Record file which is available for viewing at the Gail Borden Public Library, Elgin,
Illinois,  and the EPA Regional Offices at 77 West Jackson Boulevard in Chicago, Illinois, during
normal business hours. Notice of availability of this ESD and supporting documents will be
             Ftocyclad/RacycUble • Printed with VeoetaWe Oil Baaod Inks on 50% Recycled Paper (2O% Postconsumer)

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published in a local newspaper of general circulation.  The public is encouraged to review the
updated Administrative Record to better understand EPA's rationale for modifying the selected
remedy.

H.  BACKGROUND
The Tri-County Landfill property was part of a gravel mining operation prior to the 1940s.
Disposal of industrial, commercial, and household waste began in April 1968 and continued until
December 1976, under a series of disposal permits and owners/operators.  The existing landfill
cover was installed in early 1981.  The Elgin Landfill property was also the site of a sand and
gravel mining business that was operated until the late 1950s.  Waste disposal operations began in
1961 with the landfill accepting a variety of residential and commercial wastes, as well as
construction and demolition refuse. The property has recently been used for disposal of
construction and landscaping material.  Several commercial enterprises operate out of buildings
on top of the landfill. Immediately to the north of the site is a State of Illinois conservation area.
Northwest is agricultural land and wetland, and to the south are undeveloped upland and wetland
areas.

The Site was placed on the National Priorities List (NPL) of Superfund sites in March 1989.
EPA conducted a Remedial Investigation and Feasibility Study (RTFS) from 1988 to 1992 to
define the  nature and extent of contamination and evaluate alternatives for Site cleanup.  The RI
identified contamination in soil, sediment, and ground water, and determined that a primary
pathway for the contaminants to migrate off-site is through rain and snowmelt infiltrating through
the inadequate landfill cover, leaching contaminants from the landfilled materials, and transporting
them to ground  water and surface water by surface and subsurface flow. On September 30,  1992,
EPA signed a Record of Decision (ROD) selecting a remedy for the Site with the concurrence of
the Illinois Environmental  Protection Agency (IEPA).   The major components of the 1992 ROD
include:

       excavation and consolidation under the landfill cap of contaminated sediments that exceed
       background levels;
       construction of a landfill cap in compliance with Title 35, section 807.305, Illinois Solid
       and Special Waste Management Regulations, and RCRA Subtitle D cover requirements,
       as  applicable. These regulations  require a low permeability clay barrier layer a minimum of
       24 inches thick, with a minimum of eight inches of topsoil as a vegetated erosion layer;
       collection, treatment, and disposal of leachate and contaminated groundwater at the
       landfill perimeter, with natural attenuation of off-site, low-level ground water
       contamination, to ultimately comply with drinking water or health-based standards for all
       ground water outside of the waste boundaries;
       active collection and treatment of landfill gases;
       comprehensive monitoring program to ensure the effectiveness of the remedy;
       institutional controls to limit land and groundwater use;
       provisions for contingency measures to address new information or previously unknown
       problems, and flexibility on type and timing of the ground water response component; and
       remedy  cost estimate of $12,624,000.

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EPA entered into an Administrative Order on Consent (AOC) for RD on February 2,  1994, with
Waste Management of Illinois, Inc. (WMI) and Browning-Ferris Industries of Illinois, Inc. (BFI).
In order to ensure that the final remedy would meet the performance standards in the ROD and
the statutory requirement for long-term effectiveness of the remedy, the AOC established
functional design specifications for each remedy component set forth in the ROD.

With regards to the landfill cap, the ROD specified low permeability as the qualitative
performance standard for the clay barrier layer.  This performance standard relates to the rate at
which water will infiltrate through the barrier layer, potentially leaching contaminants  from the
underlying waste and transporting them to ground water. The AOC implemented the ROD
requirement by establishing the following design specifications and associated performance
standards for the landfill cap: 1) a two-foot thick clay barrier layer, buried below maximum frost
depth, with a hydraulic conductivity (infiltration rate)  of not more than 1 x 10"7 cm/sec and 2) a
one-foot thick drainage layer, with a hydraulic conductivity of not less than 1  x 10~3 cm/sec.  The
AOC also provided some design flexibility to meet these performance standards, allowing for use
of alternative materials for the barrier layer.

In a 1996 ESD, EPA deferred implementation of the ground water component of the remedy to
allow for a monitoring period to determine how effective the other remedy components alone
would be in reducing migration of ground water contamination from the landfill. EPA's decision
to issue the ESD was primarily based on the results of a pre-design investigation (PDI), where
EPA used a computer-aided  infiltration model to study the rate of water infiltration through the
landfill surface. Infiltration rates through the current,  inadequately capped, landfill surface ranged
from 3 to 56 inches per year. The model predicted a reduced infiltration rate of 0.85 inches per
year, assuming the landfill was covered by a cap designed to maintain the low permeability of the
barrier layer over the life of the remedy. A design analysis predicted that the reduced leachate
generation alone could result in a 60 to 80 percent reduction in off-site contaminant
concentrations within the first five years of remedy operation.  EPA issued the 1996 ESD because
it believed that the landfill cap, if designed and constructed pursuant to the terms of the 1994
AOC for RD, would significantly reduce the migration of contaminants into the ground water.
EPA will make future decisions on ground water response actions based on long-term ground
water monitoring results.

On September 30, 1997, EPA approved the final Remedial Design submitted by WMI and BFI.
The RD included a landfill cap with different design specifications than those set forth in the ROD
or AOC. The RD specifies the use of synthetic materials for the cap,  namely, a 40 mil
geomembrane for the barrier layer, a geonet drainage  layer, a geotextile to protect the drainage
layer, and approximately 18  inches of soil cover. The following discussion explains EPA's
rationale for approving the modified landfill cap design and explains the associated cost
differences.

ffl.    BASIS FOR AND DESCRIPTION OF  SIGNIFICANT DIFFERENCES
EPA has determined that the modified landfill cap design, as approved in the RD, is the best
approach for this site in meeting the performance  standards in  the ROD and AOC for low
permeability of the barrier layer.  The changes will more  effectively satisfy the evaluation criteria

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in the NCP for long-term effectiveness and permanence, short-term effectiveness, and
implementability of the remedy. The reduced infiltration rates may also result in a lowering of the
water levels within, the waste mass, allowing more contaminants to be removed by the gas
collection system.

The ROD required the construction of a low-permeability clay barrier layer a minimum of 24
inches thick, covered with a layer of topsoil at least 8 inches thick. The AOC required the barrier
layer to be buried below the maximum frost depth in Kane County.  The purpose of the frost
depth requirement was to protect the barrier layer from-the damaging effects of freeze-thaw
cycles, which are known to cause significant, permanent increases in hydraulic conductivity in
compacted clay covers.  Research has demonstrated that the hydraulic conductivity of an
unprotected clay layer can increase by one to three orders of magnitude within three to five
freeze-thaw cycles. The resulting barrier layer would then fail to meet the low-permeability
performance standard specified in the ROD over the life of the remedy.

The AOC also required the construction of a one-foot thick drainage layer directly above the clay
barrier layer. The purpose of the drainage layer is to minimize the thickness of standing water
(the "hydraulic head") in the saturated soil over the barrier layer, in order to eliminate as much
infiltration of precipitation as possible from reaching the waste and leaching additional
contaminants to ground water. Because the barrier layer requires a very thick layer of soil cover
to protect it from freezing, this increases the thickness of the hydraulic head.  Without a lateral
outlet for the water through the drainage layer, the hydraulic head would create a steady
downward pressure on the barrier layer and contribute to increased infiltration.

The design options in the AOC for the barrier layer were either to 1) add a frost-protective soil
layer approximately 42 inches thick over the 24-inch barrier layer; or 2) use alternative barrier
materials that are not subject to frost damage,  and therefore do not require a thick protective
layer. The former approach would require trucking in over 600,000 cubic yards of soil, or
approximately 15,000 truck trips. With regard to short-term effectiveness, this could be
unnecessarily disruptive to the local area.  In addition, because the waste goes right up to the
property boundaries, the cover would not meet maximum side slope requirements without
extending well into a highway right-of-way and conservation areas.  This would pose
implementability problems.  Accordingly, EPA determined that it was appropriate to substitute an
alternative material - a 40 mil low density polyethylene (LDPE) geomembrane - in place of the
clay layer.  Geomembranes are not subject to frost damage and therefore need not be buried
below maximum frost depth. In addition, they have lower permeability than clay and require
fewer truck trips to deliver the materials.  The end result is a lower overall thickness for the cap
system.

EPA also determined that a "geonet" synthetic drainage layer should be substituted for a sand or
gravel drainage layer because of its superior performance, comparable cost, and compatibility with
the geomembrane.

As a result of information gathered after the issuance of the ROD and the modifications to the
landfill cap design, EPA has adjusted its original ROD cost estimate and is presenting a revised

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cost estimate based on the RD. The estimated present worth of the ROD remedy in 1992 was
$12,624,000. The ROD calls for a ground water treatment and discharge system as pan of the
remedy, but certain costs for this component were omitted from the ROD estimate. Through this
ESD, EPA is correcting the 1992 ROD estimate and setting forth a revised estimate of
$14,309,500*

The 1992 ROD cost estimate also did not include a figure for retaining commercial uses at the
Site. Several commercial enterprises currently operate out of buildings on the landfill and
immediately adjacent to the waste boundaries. The ROD states that the impacts to these
businesses shall be considered during the design process. EPA determined that there is no risk-
related basis for requiring the businesses to relocate, and that the remedy can be designed to
accommodate the existing buildings and commercial activities. Under several different cost
estimating scenarios (primarily associated with differing quantities or unit costs for materials), the
cost of retaining commercial use appears to be between  1.7 and 2 million dollars. While the ROD
does not require that commercial uses of the site be retained, the ROD gives EPA the discretion
to accommodate such uses. Accordingly, EPA approved the RD, which provides for the retention
of the existing business at the Site.

EPA has estimated that the modified remedy set forth in the RD, including a figure for retention
of commercial uses, will cost approximately $16,650,000. EPA developed this estimate using
currently available unit costs for materials and services.  This estimate does not include a figure
for the groundwater component of the remedy, as that has been deferred by the 1996 ESD.
Because of the reduction in leachate generation and contaminant concentrations that will be
achieved through the synthetic cap, it is very likely that EPA would not require the construction
of the ground water component of the remedy after the period of observation. By comparison, the
cost of the remedy set forth in the 1992 ROD, using currently available unit costs for materials
and services, would be approximately $18,600,000.  This estimate includes figures for the ground
water component and retention of commercial use at the Site.

The approved modifications to the remedy, through this ESD, are as follows:
       1    Appendix E of the FS estimated the costs for all components of the selected remedy to
be approximately $9,544,000 for capital costs and $310,000 for annual operation and maintenance
(O&M) over 30 years.  In preparing this ESD,  EPA found that, through an oversight, the ROD
omitted costs  for the ground water treatment and discharge systems.  Appendix E estimated the
combined capital costs for those systems at approximately $910,000, and the annual O&M costs at
$64,400.  Taking these additional costs into account results in a corrected 1992 ROD cost estimate
of $14,309,500.

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 Cap profile:
         Eight inches of topsoil
     24 inches of low-permeability clay
 Cost estimate for entire remedy:
  -in 1992: $14,309,500
  -in 1998: $18,600,000
Cap profile:
            Six inches of topsoil
   12 inches general soil fill (protective layer)
    Geotextile to protect the drainage layer
           Geonet drainage layer
        40 mil LLDPE geomembrane
   6-inch bedding layer for the geomembrane
Cost estimate for entire remedy:
    $16,650,000
IV.   SIGNIFICANCE OF THE CHANGE
The significance of a change in the remedy determines how EPA must document and
communicate that change to the public.  EPA has determined in this case that the change is
significant, but not fundamental. The landfill cap design in the final RD was modified in order to
ensure the long-term effectiveness and performance of the remedy, and improve short-term
effectiveness and implementability. The cost of the remedy changed as a result of the
modifications, and EPA estimates the cost of the remedy to be $16,650,000. All other remedy
components remain unchanged. The fundamental objectives of the remedy also remains the same:
to contain contamination within the vertical boundaries of the landfill, prevent direct contact with
waste materials, and prevent infiltration of precipitation from carrying contamination to ground
water. The changes to the remedy will allow these objectives to be met more efficiently and
effectively, from both a cost and technical perspective.

V.    SUPPORT AGENCY COMMENTS
The Illinois Environmental Protection Agency (IEPA) supports the change.

VL   AFFIRMATION OF STATUTORY DETERMINATIONS
The statutory determinations in the ROD are reaffirmed, in light of the changes made in this ESD.
U.S. EPA has determined that the revised landfill cap profile, in conjunction with the other
remedy components, is protective of human health and the environment, complies with applicable
or relevant and appropriate requirements (ARARs), and meets the objectives of the remedy.
William E. Muno, Director
Superfund Division
             Date

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                                                                                  AR.
                        U.S. ENVIRONMENTAL PROTECTION AGENCY
                                   REMEDIAL ACTION

                               ADMINISTRATIVE RECORD
                                        FOR
                           TRI-COUNTY/ELGIN LANDFILLS SITE
                            ELGIN, KANE COUNTY, ILLINOIS

                                      UPDATE  #3
                                   MARCH 26,  1998
NO.   DATE

 1    09/30/92
AUTHOR

U.S. EPA
                                    RECIPIENT
Public
TITLE/DESCRIPTION       PAGES

Record of Decision for    136
Tri-County/Elgin Land-
fills Site
 2    02/02/94
U.S. EPA
Respondents
 3    08/00/95
 4    03/00/96
 5    04/00/96
 6    06/25/96
 7    07/00/96
U.S. EPA/
NRMRL
U.S. EPA
U.S. DOI/
Bureau of
Reclamation
and U.S. EPA/
NRMRL
Montgomery
Watson
U.S. EPA
U.S. EPA
Public
Bartz, L.,
Earth  Tech
Ballard, W.
U.S. EPA
Administrative Order       80
on Consent re: Predesign
and Remedial Design
for the Tri-County/
Elgin Landfills Site

Project Summary: Effect   161
of Freeze-Thaw on the
Hydraulic Conductivity
of Barrier Materials:
Laboratory and Field
Evaluation (EPA/600/
SR-95/118)

Report: Freeze-Thaw       128
Cycling and Cold Temp-
erature Effects on
Geomembrane Sheets and
Seams  (U.S. DOI Report:
R-96-03)

Remedial Design Work      118
Plan for the Tri-County/
Elgin Landfills Site

Explanation of Signifi-      8
cant Differences for the
Tri-County/Elgin Land-
fills Site

FAX Transmission             4
Forwarding 30%  and  60%
Remedial Design Final
Cover Detail  Drawings

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HO.   DATE

 8    11/12/96
            AUTHOR

            Ballard,  W.,
            U.S.  EPA
                  RECIPIENT

                  Leibrock,  M.,
                  Haste Manage-
                  ment ,  Inc./
                  Midwest
                            Tri-County/Elgin AR
                                      Update #3
                                         Page 2

                  TITLE/DESCRIPTION       PAGES

                  Letter re: U.S. EPA's       2
                  Comments on WMI'S
                  Responses to U.S. EPA
                  30% Design Comments for
                  the Tri-County/Elgin
                  Landfill Site
      11/21/96    U.S. EPA
                              File
                                    60% Design Meeting
                                    Submittals
10
11/25/96
11
11/25/96
12    11/26/96
13
12/09/96
14
12/12/96
Benson,  C.;
University
of Wisconsin/
Madison

Moses,  D. and
D.  Taylor;
U.S. Army
Corps of
Engineers/
Omaha District
            Ballard,  W.,
            U.S. EPA
Leibrock, M.,
Waste Manage-
ment ,  Inc./
Midwest

Leibrock, M.,
Waste Manage-
ment ,  Inc.
Ballard, W.,
U.S. EPA
Ballard, W.,
U.S. EPA
                  Leibrock,  M.,
                  Waste Manage-
                  ment, Inc./
Ballard, W.,
U.S. EPA
Ballard, 'W. ,
U.S. EPA
Memorandum re:  Clay
Barriers Used in Liners
and Covers
FAX Transmission
Forwarding Attached
Journal Article: Effects
of Freezing on Hydraulic
Conductivity of Compacted
Clay (Kim, W., et al;
Journal of Geotechnical
Engineering/July 1992)

Letter re: U.S. EPA's
Disapproval of Design
for the Tri-County/
Elgin Landfills Site

Letter re: Notification
of Dispute Resolution
Letter re: Resubmittal
of 60% Remedial Design
w/Montgomery Watson's
Attachments and Plan
Set
                                                                                  97
15    12/16/96    Ballard, W.,
                  U.S. EPA
                              Leibrock, M.,
                              Waste Manage-
                              ment ,  Inc./
                              Midwest
                                    Letter re-. U.S. EPA's
                                    Disapproval of  the
                                    Re-Submitted  60% Design
                                    for the Tri-County/
                                    Elgin Landfills Site

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NO.   DATS

16    12/18/96
            ADTHOR

            Moses,  D.,
            U.S.  Army
            Corps of
            Engineers/
            Omaha District
RECIPIENT

Ballard, W.,
U.S. EPA
          Tri-County/Klgin AR
                    Update #3
                       Page 3

TITLB/DB3CRIPTION       PAGHS

FAX Transmission:           6
Supporting the Need for
Frost Protection and
Drainage Layer
17    12/23/96
18    12/31/96
            Leibrock,  M.,
            Was te Manage-
            ment,  Inc.
            Ballard,  W.,
            U.S.  EPA
Ballard, W.,.
U.S. EPA
Leibrock, M.,
Waste Manage-
19
01/01/97
                  Benson, C. ,-
                  University
                  of Wisconsin/
                  Madison
Letter re: Re-Submittal
of 60% Design Drawings
w/Drawings and Calcula-
tions Submitted Under
Separate Cover

Letter re: U.S. EPA's
Written Response to
Notice of Dispute w/
Attached  (1)  Excerpts
from May 1991 U.S. EPA
Seminar Publication:
Design and Construction
Of RCRA/CERCLA Final
Covers/ (2) Excerpts
from July 1989 U.S. EPA
Technical Guidance
Document: Final Covers
on Hazardous Waste Land-
fills and Surface
Impoundments;  (3) August
1991 U.S. EPA Project
Summary: Factors
Controlling Minimum
Soil Liner Thickness;
and  (4) Excerpts from
the March 12, 1992
Scope of  Work, August
1993 Pre-Design Report,
March 1994 RD/RA Work
Plan and November  1994
30t Remedial Design  for
the Hunts Disposal  Land-
fill  (WI) Site

Report: A Review of
Alternative  Landfill
Cover Demonstrations
 (Executive Summary and
Conclusions)  [Environ-
mental  Geotechnics
Report  No. 97-1)
13
                                                                           23

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NO.   DATE

20    01/07/97
21    01/08/97
22
01/09/97
            AUTHOR

            Ballard,  W.,
            U.S.  EPA
            U.S.  EPA
                  Moses,  D.,
                  U.S.  Army
                  Corps of
                  Engineers/
                  Omaha District
                  RECIPIENT

                  Leibrock,  M.,
                  Waste Manage-
                  ment , Inc./
                  Midwest
                  File
                  Leibrock,  M.,
                  Waste Manage-
                  ment ,  Inc.
                                                                Tri-County/Blgin AR
                                                                          Update #3
                                                                             Page 4
                  TITLE/DESCRIPTION
                                          PAGES
                  Letter re: U.S. EPA's
                  Clarification of State-
                  ments Made in U.S. EPA's
                  December 31, 1996 Written
                  Response to Notice of
                  Dispute

                  Agenda and Handout
                  Material from the
                  January 8, 1997 Dispute
                  Resolution Meeting re:
                  the Tri-County/Elgin
                  Landfills Site

                  FAX Transmission
                  Forwarding Examples of
                  Synthetic Cap Profiles
                           10
23
01/15/97
24
01/27/97
25
01/30/97
26
02/04/97
Leibrock, M.,
Waste Manage-
ment ,  Inc.
Ballard, W.,
U.S. EPA   •
                  Leibrock,  M.,
                  Waste Manage-
                  ment ,  Inc./
                  Midwest
                  Honegger, S.,
                  Lathrop & Gage/
                  M. Flowers,
                  Waste Manage-
                  ment , Inc.
Ballard, W.,
U.S. EPA
Leibrock, M.,
Waste Manage-
ment ,  Inc./
Midwest

Ballard, W.,
U.S. EPA
                  Kallos, C.,
                  U.S. EPA
Letter re: WMI's
Response to U.S. EPA's
December 31, 1996
Written Response to
Notice of Dispute

Letter re: U.S. EPA's
Surreply to WMI's •
January 15, 1997 Letter
Letter re: WMI's
Response to U.S. EPA's
Proposal to Consider
an Alternative Design
Cover

Letter re: Response to
U.S. EPA's January 29,
1997 Letter Concerning
the Administrative
Record for Dispute for
the Tri-County/Elgin
Landfills Site
                                                                                 11

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HO.   DATS

27    02/05/97
28    02/14/97
            AUTHOR

            Kallos,  C.,
            U.S. EPA
            Mayka,  J.,
            U.S.  EPA
                  RECIPIENT

                  M. Flowers,
                  Waste Manage-
                  ment , Inc./
                  S. Honegger,
                  Lathrop & Gage

                  Leibrock, M.,
                  Haste Manage-
                  ment , Inc./
                  Midwest
                            Tri-County/Elgin AR
                                      Update #3
                                         Pag* 5

                  TITLE/DESCRIPTION       PAGES

                  Letter re:  Disputed         5
                  Issues and the Alterna-
                  tive Cap Design for the
                  Tri-County/Elgin Land-
                  fills Site

                  Letter re:  U.S. EPA's       4
                  Written Notification of
                  Resolution of Dispute
                  Concerning the Predesign
                  and Remedial Design
                  for the Tri-County/Elgin
                  Landfills Site
29
09/00/97
30
09/00/97
31
09/23/97
32
09/30/97
Montgomery
Watson
U.S. EPA
                  Montgomery
                  Watson
Leibrock, M.,
Waste Manage-
ment , Inc.
Ballard, W.,
U.S. EPA
                  U.S. EPA
Ballard, W.,
U.S. EPA
Leibrock, M.,
Waste Manage-
ment , Inc./
Midwest
Final  (100%) Remedial     100
Design Report: Volume 1
of 2  (Text, Tables and
Figures) [Revised August
1997 Report]

Final  (100%) Remedial     440
Design Report: Volume 2
of 2  (Appendices A-K)
[Revised August 1997
Report]

Letter re: Modifications    7
to the Final Remedial
Design for the Tri-County/
Elgin Landfills Site w/
Attached Revised Pages

Letter re: U.S. EPA's       2
Approval with Modifica-
tions and Exception  for
the Final Remedial Design
for the Tri-County/Elgin
Landfills Site
33    10/01/97    Ballard, W.,
                  U.S. EPA
                              Leibrock, M.,
                              Waste Manage-
                              ment , Inc./
                              Midwest
                                     Letter re:  Revision to
                                     September 30,  1997
                                     Remedial Design Approval
                                     Letter
34    01/15/98    Ballard,  W.,
                  U.S. EPA
                               Leibrock, M.,
                               Waste Manage-
                               ment , Inc./
                               Midwest
                                     Letter re:  Cost Esti-
                                     mates for the Remedial
                                     Action at the Tri-County/
                                     Elgin Landfills Site w/
                                     Attached Tables
                                              12

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NO.   DATS

35    02/16/98
36
03/24/98
AUTHOR

Prattke, M.,
Waste Manage-
ment and
M. Miller,
Browning
Ferris
Industries

Ballard, W.,
U.S. EPA
                              RECIPIENT

                              Ballard,  W.,
                              U.S.  EPA
File
                            Tri-County/Klgin AR
                                      Update #3
                                         Page 6

                  TITLB/DB8CRIPTIOH       PAGRS

                  Letter re: WM/BFI's        59
                  Responses to U.S. EPA's
                  Review of Cost Estimates
                  for the Tri-County/Elgin
                  Landfills Site w/
                  Attachments
Memorandum re: Cost        21
Estimates for Remedial
Action at the Tri-County/
Elgin Landfills Site

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                        U.S. ENVIRONMENTAL PROTECTION AGENCY
                                   REMEDIAL ACTION

                               ADMINISTRATIVE RECORD
                                         FOR
                           TRI-COUNTY/ELGIN LANDFILLS SITE
                            ELGIN, KANE COUNTY, ILLINOIS

                                      UPDATE #4
                                   APRIL 23, 1998
NO.   DATE

 1    02/00/97
AUTHOR

Melchior, S.
                  RECIPIENT
                  TITLE/DESCRIPTION
                        PAGES
      12/00/97
Chamberlain,
E., et al.
U.S. Army
Corps of
Engineers
Journal Article: In-Situ
Studies on the Perform-
ance of Landfill Caps
(Compacted Soil Liners,
Geomembranes, Geosyn-
thetic Clay Liners,
Capillary Barriers)
[Proceedings of the
International Containment
Technology Conference,
February 1997]

Report: Frost Resistance
of Cover and Liner
Materials for Landfills
and Hazardous Waste
Sites  (Special Report
97-29)
32
      01/15/98
      03/30/98
Muno,  W.,
U.S. EPA
Ballard, W.,
U.S. EPA
Pingel, B.,
St. Charles
Resident
Potentially
Responsible
Parties
Letter re: U.S. EPA's
Response to Citizen's
Concerns About Property
Which is Part of the
Tri-County/Elgin Landfills
Site

Cover Letter with Draft
Explanation of Signifi-
cant Differences and the
Administrative Record
Index for  Update #3 for
the Tri-County/Elgin
Landfills  Site Attached
13
      04/14/98
Mayka, J.  and
W. Carney;
U.S. EPA
U.S. EPA/
Superfund
RPMs
Memorandum  re:  Findings
and Recommendations
of the  Working  Group
Reviewing Landfill Cover
Requirements and Decision
Making  by Region 5
Superfund Program
 25

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NO.   DATE

 6    04/14/98
 7    04/23/98
 8    04/23/98
AUTHOR

Miller, M.,
Browning-
Ferris
Industries
of Illinois

Ballard, W.,
U.S. EPA
RECIPIENT

Ballard,  W.,
U.S. EPA
File
U.S. EPA
Public
          Tri-County/Elgin AR
                    Update #4
                       Pag* 2

TITLE/DESCRIPTION       PAGES

Letter from BFILL on the    5
Draft Explanation of
Significant Differences
for the Tri-County/Elgin
Landfills Site

Memorandum: U.S. EPA's      4
Response to Input on the
Draft Explanation of
Significant Differences
for the Tri-County/Elgin
Landfills Site

Explanation of Signifi-    14
cant Differences for the
Tri-County/Elgin Landfills
Site

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