&EPA
              United States
              Environmental Protection
              Agency
            Office of
            Solid Waste and " '
            Emergency Response
DIRECTIVE NUMBER:

TITLEi"Waiver from Double Liner Requirements Pursuant to
    Section 3015 (b)(l) and 40 CFR Section 265.301 (c)"
    for CECOS International, Inc., Williamsburg, Ohio,
    Landfill Cell NO. 9 <
APPROVAL DATE: 11/14/85,

EFFECTIVE DATE:

ORIGINATING OFFICE: osw

D FINAL

m DRAFT

 STATUS: C - For regional review and comment



REFERENCE (other documents):
  OS WER      OS WER      OS WER
/E   DIRECTIVE   DIRECTIVE   D.

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                                                                          a-n
  vvEPA
             Unueti Slates cri.'iror.menid. Pictection Agency
                    Washington. DC 20460

      OSWER Directive Initiation Request
                                                                      interim Directive Numoer
                                     Originator Information
Name o( Contact Person
 Kent  Anderson
               Mail Code
               WH-565E
                                                          Telephone Number
                                                             382-4654
Lead Office

   D OERR

   Q OSW
D OUST

CD OWPE

LJ AA-OSWER
                                                    Approved for Review
               Signature of Office Director
                                                                      Qate
Title
      "Waiver  from  Double  Liner  Requirements  Pursuant to  Section  3015(b)(1)
       and 40  CFR Section  265.301(c)"  for CECOS International,  Inc.,
       Williamsburg,  Ohio,  Landfill Cell No.  9.
Summary of Directive
     /    CECOS International,  Inc.,  in a letter  to EPA  of May  30, .1985,
      formally requested  a waiver,  as  provided for in Section 3004 (o) (2)
      of the  Solid Waste  Disposal Act,  as amended,  from the double liner
      requirements of Section 3004 (o) (1)  .for  their previously constructed
      Cell No. 9.                              i  .:••
                                               XI I «•'
                                            /"
           The attached transmittal memorandum, Waiver, Fact Sheet, and
      Evaluation Report resulted in a /finding that the CECOS Cell No.  9
      design  and operation can  be considered  to be as effective  as
      the interim statutory design of  Section 3004 (o) (5) (B) and  40 CFR
      Section 265. 301 (a)  under  the conditions stated in the Waiver.
Type of Directive /Manual. Policy Directive. Announcement, etc.)
                                            Status
      Waiver   .
                                                 Draft

                                              LJ Final
                                                                        I
                                                                           tLJ New

                                                                           LJ Revision
Does this Directive Supersede Previous Directive(s)?  |  | Yes

If "Yes" to Either Question. What Directive (number, title)
                             No   Does it Supplement Previous Directive^)?
                                                                             yes
Review Plan

  LJ AA-OSWER

  D OERR

  S OSW
D OUST

[HI OWPE

S Regions (V
D OECM

D OGC

   OPPE
                                            D
                                Other /Specify!
This Request Meets OSWER Directives System Format
Sigrature of Lead Office Directives Officer
Signature of OSWER Directives Officer
                                                       i Date
                                                       I Date

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                              DRAFT
.».u,M>ftKTniiM                               OSWER Directive
MEMORANDUM
SUBJECT:  CECOS International, Inc., Williamsburg, Ohio, Landfill
          Cell No. 9 — Waiver from Double Liner Requirements

FROM:     Marcia Williams, Director
          Office of Solid-Waste (WH-562)

TO:       Basil Constantelos ,  Director
          Waste Management Division, Region V


     CECOS International Inc., in a letter to John Skinner

dated May 30, 1985, requested a waiver from the minimum techno-

logical requirements of Section 3004(o)(l) of the Solid Waste

Disposal Act, as amended (SWDA), for Landfill Cell No. 9 at

CECOS' Aber Road Facility, Clermont County, Ohio.

     The general authority to grant waivers for hazardous waste

disposal facilities, such as this request, has been delegated to

the Regional Administrator.  Because this was the first request

for a waiver from the minimum technological requirements and

because we have not developed detailed guidance on evaluating

such waiver requests, our office, in conjunction with Ohio EPA

and the U.S. EPA Offices of Region V, the Office of Research and

Development - Cincinnati, the Office of General Counsel, the Office

of^Waste Programs Enforcement, and the Office of Enforcement and

Compliance Monitoring, has developed the attached draft Waiver

from Double Liner Requirements Pursuant to Section 3015(b)(l)

and 40 CFR §265.301(c) .

     As we have discussed with your staff, we are turning the

draft waiver over to your office for completion of the waiver

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 determination process.  This will include the public notice and

 public hearing requirements of 40 CFR Part 124 for the draft

 waiver and the issuance  (or denial) of the final waiver.  Because

 of  the public interest in  the general vicinity of the CECOS

 facility, a public hearing would be advisable.  In the interest

 of  concluding the Agency's action on this waiver request as

 quickly  as possible,  I believe it is appropriate to announce the

 time  and place of the public hearing concurrent with the request

 for public comments.  I  understand that CECOS is also interested

 in  a  final determination in this case as soon as possible.

      The package of  materials that I am attaching for the purpose
_-~-
 of  assembling an administrative record regarding this waiver

 request  include:

      - Draft Waiver  from Double Liner Requirements Pursuant to
       Section 3015(b)(l)  and 40 CFR §265.301(c)

      - Fact Sheet

      - Correspondence between CECOS and EPA on Cell No. 9

      - Memoranda documenting meetings between CECOS and EPA

      - CECOS1 evaluation report entitled  "Evaluation of Leachate
       Collection and Liner System Performance, Facility No. 9
       CECOS  International, Clermont, Ohio", May, 1985.

      - CECOS  International, Clermont County, Ohio, Secured Chemical
       Management Facility No. 9, AS BUILT drawings  sheets  1 to 10,
       January  31,  1985.

      - US EPA's  evaluation report  entitled  "Waiver Evaluation
        for CECOS  International Aber  Road  Facility Secure  Chemical
        Management Facility No.  9,  Clermont  County,  Ohio",
        October,  1985.

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     - Draft Minimum Technology Guidance on Double Liner Systems
       for Landfills and Surface Impoundments — Design,  Construction,
       and Operation.  December 19,  1984.

     - Draft Guidance on Implementation of Minimum Technology
       Requirements of HSWA of 1984.   January 31, 1985.

     - Draft Guidance on Implementation of the Minimum Technological
       Requirements of HSWA of 1984,  Respecting Liners and Leachate
       Collection Systems, Reauthorization Statutory Interpretation
       #5D, EPA/530-SW-85-012, May 24, 1985.

     - Draft Minimum Technology Guidance on Double Liner Systems
       for Landfills and Surface Impoundments — Design,  Construction,
       and Operation, EPA/530-SW-85-014, May 24, 1985.

     - Construction Quality Assurance for Hazardous Waste Land
       Disposal Facilities, EPA/530-SW-85-021, October,  1985.

     -'Federal Register, Vol. 50, No. 135, July 15, 1985.

     - CECOS International "SCMF No.  9: Summary Geotechnical
       Report", January 1985  (This report is not attached but
       is already in the Regional Office).

     - CECOS International "SCMF No.  9:  Field and Laboratory
       Quality Control Data of HOPE Liner Construction",
       February 1985 (This report is not attached but is already
       in the Regional Office).

     - CECOS International "SCMF No.  9:  Field Quality Control
       Data of Compacted Soil Liner Construction," January 1985
       (This report is not attached but is already in the Regional
       Office).
Attachments

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                              DRAFT

              Waiver from Double Liner Requirements
      Pursuant to Section 3015(b)(l)  and 40 CFR §265.301(c)


     Section 3015(b)(l) of the Solid Waste Disposal Act (SWDA),

as amended, requires that new landfill units,  that qualify to

operate under interim status, comply with the minimum technological

requirements of Section 3004(o), including the requirements of

Sections 3004(o)(l) (codified at 40 CFR §265.301(a)) and 3004(o)(2)

(codified at 40 CFR §265.301(c)), with respect to waste received

on or after May 8, 1985.  Section 3004(o)(l) requires that the

owner or operator of a landfill install two or more liners and

leachate collection systems  above and between such liners for

each new unit.  These requirements apply to CECOS International,

Aber Road Facility Secure Chemical Management Facility Cell No.9,

Clermont County, Ohio.

     Section 3004(o)(2) of the SWDA and 40 CFR §265.301(c) provide

that the above minimum technological requirements do not apply

where the Regional Administrator finds for such landfill that

alternative design and operating practices, together with location

characteristics, will prevent migration of hazardous constituents

to .ground water and surface  water at least*, as effectively as

such liners and leachate collection systems.  The Regional

Administrator for Region 5 here finds that Cell Number 9 qualifies

under the standards set out  in Section 3004(o)(2) of the SWDA and

40 CFR  §265.301(c) for a waiver  from the minimum technological

requirements to the extent specified below, upon the specific

condition that CECOS incorporate the alternative design  features

and observe the alternative  operating practices described below.

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     The design of CECOS'  Cell Number 9 deviates from the


requirements of Section 3004(o)(l)  of the SWDA and 40 CFR §265.301(a)


by the failure to have a secondary leachate collection system


that covers all areas of the landfill between the top and bottom


liners.  This deficiency is compensated for, as documented by


the CECOS AS-BUILT drawing, sheet number 7, dated January 31,


1985, by the inclusion of a primary sidewall contingency leachate
 ./

collection system and a thicker compacted lower soil liner than


is provided for in the interim statutory design contained in


Section 3004(o)(5)(B) of the SWDA and 40 CFR §265.301(a).

    /
   / To continue to qualify for this waiver, the alternative


design and operation of the primary leachate collection system


(including the contingency sidewall collection and removal system)


must include:


Design - The leachate collection system must have:


     1) A primary  leachate collection sump  conveyance system


        capable of automatic and continuous functioning.


     2) A primary  leachate collection system on the cell's


        sidewall  consisting of the following components  (see


        CECOS1 AS-BUILT drawing, January 31, 1985, sheet No. 7)
                                         *.

        above the  top liner:


             0  6-ounce protective geotextile


             0  1-foot sidewall washed sand  blanket with a


                hydraulic conductivity of 1X10"^ cm/sec or


                more

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        0 Contingency leachate collection  piping consisting




          of 6-inch ABS schedule 80  pipe up the  sidewall  at  8



          locations (at approximately 70-foot  spacing).   The



          pipes extend 5 feet into the primary leachate




          collection and removal system at the bottom of  the



          cell.  This 5-foot section is perforated  and




          functions as a contingency leachate  collection



          system (see CECOS' AS-BUILT drawing,  January 31,



          1985, sheet No. 9).



        0 16-ounce geotextile drainage media




        0 Leachate collection pumps.



3) The ability to monitor leachate head levels within the



   landfill at the sidewalls during  the active life and the



   post-closure care period.



4) Been designed as specified in EPA regulations and guidance



   (e.g., 40 CFR §264.301 and "Permit Applicants Guidance



   Manual for Hazardous Waste Land Treatment,  Storage, and



   Disposal Facilities," EPA/530-SW-84-004) so as to withstand



   the stresses and disturbances from overlying wastes,



   waste cover materials, and equipment operation.



5) Been designed as specified in EPA regulations and guidance



   (e.g., 40 CFR §264.301 and "Permit Applicants Guidance




   Manual for  Hazardous Waste Land Treatment,  Storage, and




   Disposal Facilities," EPA/530-SW-84-004) so  as to withstand



   to  function without  clogging through the active  life and




   post-closure care  period.

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 Construction  -  Components  must be properly installed to assure

 that  the  specified performance of the  leachate collection system

 is  achieved.  Future construction of the sidewall primary leachate

 collection  system must  be  documented by a construction quality

 assurance (CQA)  program prior to operation of that portion of the

 unit.   The  CQA  program,  as specified in EPA  draft guidance

 documents entitled  "Draft  Minimum Technology Guidance on

 Double Liner  Systems  for Landfills  and Surface Impoundments—

 Design, Construction,  and  Operation",  EPA/530-SW-85-014, May 24,

 1985  and  "Construction Quality Assurance  for Hazardous Waste
?•'
 Land  Disposal Facilities", EPA/530-SW-85-021, October, 1985,

 must  be used  to monitor and document the  quality of  materials

 (e.g., liner, drainage, piping)  used and  the conditions and

 manner of their placement.  The  program must be  developed,

 administered, and  documented by  a  registered professional engineer.

 The documentation  must include a report containing a summary of

 construction  activities, observations, test  data sheets, deviations,

 and as-built  drawings.   The documentation for the CQA program

 must  be kept  available for review.

 Operation - The following  operational  procedures must be  followed:

      1) The primary leachate removal  system must be  operated

         automatically and  continuously during  the active  life

         and post-closure care period  whenever  leachate  is  present

         in the sumps (leachate standpipes)  and  must  remove  accumulated

         leachate at the earliest practicable time to minimize   (produce

         very low or no) head of leachate on the top liner.   The

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   leachate depth above the top  liner  shall  not  exceed  one




   foot except temporarily (for  a few  days)  after  major




   storms during the active life of the unit.  ..



2) The contingency sidewall primary leachate removal system




   must be operated daily during the active  life and




   post-closure care period whenever leachate is present in




   the pipe and must remove accumulated leachate at the



   earliest practicable time to minimize the leachate head



   on the liner to a very low level.  Even a very low leachate



   depth shall not be present in the contingency leachate



   collection pipes, except temporarily after major storms.



3) Inspect for proper operation of the primary leachate



   (including contingency sidewall) collection and removal



   system, and  for the presence of  leachate in the removal



   sumps and  the  contingency leachate collection pipes



   daily during the operating period and monthly during




   closure and  the post-closure care period.  A record of



   inspections  and findings must be kept available for



   review.



4) Repair  of  damaged primary leachate  collection and contingency



   sidewall system components as soon  as practicable during the



   operating  period.



5) During  the active  life and post-closure  care period,



   notification of the Regional  Administrator,  in  writing:




         a) within 7 days of the  presence  of a removable



           quantity of leachate, except temporarily

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                (i.e.,  a few days)  after  major storms  during  the

                active  life, in the contingency sidewall  leachate

                collection and removal  system;

             b)  within  7 days of the presence  of a  leachate

                depth of one foot or more above the top liner;

             c)  within  15 days of known damage to the  primary

                leachate collection and contingency sidewall

                system  components;  the  notification should

                outline procedures planned to  repair the  damage

                and a projected schedule.

     6) Collected leachate must be removed to  a storage,  treatment,

        or disposal facility that is permitted under 40 CFR

        Part 264 or operating under interim status  pursuant  to

        40 CFR Part 265.

     Any modifications  to plans and specifications  following

waiver approval must be approved in writing by the  Regional

Administrator prior to construction and operation.
Date:
                                 Regional Administrator
                                 US .EPA, Region V

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                            FACT SHEET
                               for
                     Waiver from Double Liner
                      Requirements Pursuant
                    to Section 3015(b)(l) and
           40 CFR i265.301(c) for CECOS International,
                Aber Road Facility Secure Chemical
                    Management Facility No. 9
                      Clermont County, Ohio


A.  Background:  On May 30, 1985, CECOS International, Inc.,

    requested a formal review of the design of their hazardous

    waste, landfill Cell No. 9 at CECOS1 Aber Road Facility near

    Williamsburg, Ohio, for compliance with Section 3015(b)(l)

    of the Solid Waste Disposal Act (SWDA) as amended regarding
  /
    double liners and leachate collection and removal systems.

    In EPA correspondence to CECOS on June 25, 1985, EPA stated

    that this unit is a "new unit" (because no waste had been

    placed in the unit as of November 8, 1984) and therefore is

    required under Section 3015(b)(l) of the SWDA to comply with

    the minimum technological requirements in Section 3004(o)(l)

    or (2).  But because Cell No. 9 does not meet the requirements

    of Section 3004(o)(l) (as U.S. EPA Region V notified CECOS

    on May 3, 1985),  EPA regards the CECOS letter of May 30,

    1985, as a formal request for a waiver under standards

    set out in Section 3004(o)(2) of the SWDA.  On July 15, 1985

    EPA codified the SWDA Section 3004(o)(l) and (2) into 40 CFR

    §265.301(a) and (c).

B.  Legal basis for waiver including reference to statutes,

    regulations, and supporting references:

         The Hazardous and Solid Waste Amendments to the Solid

Waste Disposal Act were signed into law on November 8, 1984.

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These amendments, under Section 3004(o)(2), provide a provision

for a waiver from Section 3004(o)(1)(A)(i), which requires the

installation of two or more liners and  a  leachate collection

system above and between such liners for  certain landfills seeking

permits.  Section 3015(b)'(l) of the SWDA made the requirements

of Section 3004(o) applicable to  certain  interim status landfills,

including "new units" such as CECOS' Cell No. 9.  On July 15,
 ./
1985, EPA codified the requirements of  Sections 3004(o)(1)(A)(i),

(o)(2), and 3015(b)(l) of the SWDA in 40 CFR §§264.301(c) and

265.301(a) and (c).  The waiver of Section 3004(o)(2) and 40 CFR

§265.301(c) is applicable to owners and operators of landfills

'that demonstrate that alternative design  and operating practices,

together with location characteristics, will prevent the migration

of any hazardous constituents into the  ground water or surface

water at least as effectively as  the liners and leachate collection

systems, specified in Section 3004(o)(1)(A)(i) and 40 CFR §265.301(a).

Section 3004(o)(5)(B), 40 CFR §265.301(a), and 40 CFR §264.301(c)

provide an interim statutory design that  can be used to satisfy

the liner and leachate collection system  requirements of Section

3004(o)(l)(A)(i) and 40 CFR §265.301(a).  EPA determined that
                                         i,
the CECOS Cell No. 9 does not meet the  design called for in

Section 3004(o)(l) because of the lack  of a secondary leachate

collection and removal system in  all areas between the liners,

and therefore CECOS would have to seek  a waiver under

Section 3004(o)(2); i.e. 40 CFR §264.301(c).

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     CECOS'  Cell No. 9 was primarily constructed in advance of




EPA's draft Minimum Technology Guidance that specifies the use



of an extensive construction quality assurance (CQA} program to



ensure that the unit is constructed in conformance to the design.



While CECOS'  CQA program did not completely conform to that




in EPA's draft guidance,  it was considered at that time to



constitute very high CQA standards.  Units constructed since



issuance of the May 24, 1985, draft guidance should undergo a much



more rigorous testing and construction quality assurance plan.



C.  Reasons requested waiver appears justified:



     CECOS conducted a comparative evaluation of the design of



Cell No. 9 vs a "preferred regulatory design" (from EPA's draft



liner guidance dated December 19, 1984) that differs somewhat




from the interim statutory design of Section 3004(o)(5)(B) of




SWDA and 40 CFR §2G5.301(a).  The interim statutory design has a



lower liner that consists of three feet of low permeability



recompacted natural material while the "preferred regulatory



design" used by CECOS in their evaluation has a composite lower



liner consisting of a synthetic liner as the upper-most component




of the composite and a lower component consisting of two feet of



low permeability recompacted natural material.  The CECOS comparative



evaluation is documented in a report entitled "Evaluation of



Leachate Collection and Liner System Performance, Facility No. 9,



CECOS International, Clermont County, Ohio".  The report, prepared



by the consulting engineering firm of STS D'Appolonia Ltd. and




dated May 1985, concludes that the performance of the leachate



collection and liner systems of the Cell No. 9 design should

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exceed the capabilities of the preferred regulatory design in


mitigating leakage.



     U.S. EPA conducted its own evaluation of the CECOS Cell


No. 9 landfill design and operation and compared its ability to


prevent migration of any hazardous constituents into the ground



water or surface water to that of the interim statutory design


of Section 3004(o)(5)(B) and 40 CFR §265.301(a).  The EPA
 ./

evaluation compared the CECOS design to the interim statutory


design, rather than the "preferred regulatory design," since


this is the design that meets the requirements of the statute.


EPA's evaluation is fully documented in the report entitled


"Waiver Evaluation for CECOS International Aber Road Facility


Secure Chemical Management Facility No. 9, Clermont County,


Ohio," October 1985.  The result of this study is that the


CECOS Cell No.  9 design and operation can be considered to be


as effective as the interim statutory design of Section 3004(o)(5)(B)


and 40 CFR §265.301(a) only under the conditions stated in the


"Waiver from Double Liner Requirements Pursuant to Section


3015(b)(l) and 40 CFR §265.301(c)" for CECOS Cell No. 9.


D.  Description of procedures for reaching a final decision:

 f-   -                            •••.-•

     The draft Waiver will be made available for public comment,


including a public hearing in a location convenient to the public


living near the facility.  The public comment" period will be for


45 days.  Public notice of the draft Waiver and of the public


hearing will be given at least 30 days before the hearing.


Applicable methods outlined in the Code of Federal Regulations,


40 CFR §124.10, for making the notice public will be followed.

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     The beginning and end dates of the public comment period

are November 	 1985 [DATE OF PUBLIC NOTICE] to
1985 [DATE 45 DAYS AFTER DATE OF PUBLIC NOTICE] .   After the

close of the public comment period, the Regional Administrator

will issue a final Waiver decision.

E.  The following person may be contacted for additional information

  ,  regarding this request for waiver:

         Bruce Sypniewski
         U.'S. EPA, Region V
         230 South Dearborn Street
         Chicago, Illinois 60604
         (312) 886-6189

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          WAIVER EVALUATION FOR
  CECOS INTERNATIONAL ABER ROAD FACILITY
SECURE CHEMICAL MANAGEMENT FACILITY NO.  9
          CLEFMONT COUNTY, OHIO
               OCTOBER 1985

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                        ACKNOWLEDGEMENT
The analysis for this report was conducted by Battelle Columbus
   Laboratories for the U.S. Environmental Protection Agency
                 under Contract No. 68-03-3248.

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                               TABLE OF CONTENTS






      Tables 	  ill


      Figures	..	   iv


1.0   Introduction	    1


2.0   General Description of the  Landfill Designs  	    2


      2.1  Interim Statutory Design 	    2


      2.2  CEOOS Cell No. 9 Design 	    2


3.0   Evaluation Approach 	    4



      3.1  Performance Criteria	    4
      /'

      3.2  Failure Scenarios  	    5



      3.3  Hydraulic Modeling Methodology	    6


      3.4  Model Simulation	    8



4.0  Model Results	     9


5.0  Conclusions  	    17


6.0  Findings and Recommendations  	    17


     References	    19
                                        ii

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                              TABLES


1.   Hydraulic Conductivities of Materials 	.-	   8

2.   Summary of Model Input Data	   10

3.   Flow Distribution Within the Sidewall Region 	   11

4.   Drainage Time Factor, Volume Exiting Sidewall Djring
      Drainage Time, and Breakthrough Time	   12
                               iii

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                             FIGURES






1.  Schematic of Interim Statutory Design	    3



2.  Schematic of CECOS Cell No.  9 Design	    3




3.  Max imam Release Rate Comparison	   13



4.  Drainage Time Comparison  	   14



5.  Breakthrough Time Comparison  	   15
                                        iv

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                               WAIVER EVALUATION FOR
                       CECOS INTERNATIONAL ABER ROAD FACILITY
                     SECURE CHEMICAL MANAGEMENT FACILITY NO.  9
                               CLERMONT COUNTY, OHIO
                                    OCTOBER 1985
1.0  INTRODUCTION

     The Hazardous and Solid Waste Amendments (HSWA) of 1984,  amends Section 3004
of RCRA by adding a new paragraph (o) imposing minimum technological requirements
on owners and operators of certain landfills and surface impoundments seeking
permits.  HSWA also adds a new Section 3015 to RCRA imposing the minimum technological
requirements set out in Section 3004(o) on certain interim status landfills and
surface impoundments.  Specifically, Section 3004(o)(1)(A) requires that affected
units must install two or more liners, a leachate collection system above (in the
case of a landfill) and between the liners, and ground water monitoring.  Section
3004(o)(5)(B) allows the use of a particular type of liner design pending the
issuance of EPA regulations implementing the double liner requirements.   Section
3004(o)(2) provides for an exemption from the Section 3004(o)(1)(A) standards for
liners and leachate collection systems if alternative design and operating practices,
together with location characteristics will prevent the migration of hazardous
constituents as effectively as systems under Section 3004(o)(1)(A).

     The Section 3015 requirements are applicable to the CECOS International Aber
Road Facility, Secure Chemical Management Facility No. 9 (hereafter referred to as
CECOS Cell No. 9) in Clermont County, Ohio.  The main issue with the CECOS Cell
No. 9 design is that a secondary leachate collection system does not cover all
areas of the landfill between the upper and lower liners.  CECOS International
has requested a waiver for Cell No. 9 from EPA.  The purpose of this report is to
document the hydraulic evaluation of CECOS Cell No. 9.  This evaluation compares
the performance of CECOS Cell No. 9 with the interim statutory design contained in
Section 3004(o)(5)(B) per Section 3004(o)(2) (hereafter referred to as the interim
statutory design) which allows alternative designs under certain circumstances.

     In enacting HSWA, Congress has mandated the use of two or more liners and a
leachate collection system above (in the case of a landfill) and between such
liners.  The need for this system is based on the experience that some existing,
single lined landfills and surface impoundments have failed.  The Congress intends
that, for general protection of human health and the environment, hazardous waste
facilities provide means to minimize the risk of waste migration out of the unit.
The statutory design for landfills in Section 3004(o)(l) provides for liners and
leachate collection systems covering all areas of the unit that are in contact
with the wastes (See Federal Register, Vol. 50 No. 135, July 15, 1985, p.28,709).
This means that the unit must have a leachate collection system above the top
liner, two or more liners, and a secondary leachate collection and removal system
between the liners on the landfill bottom and side walls.

     The evaluation of the CECOS Cell No. 9 landfill design and operation was
performed to conpare its relative ability to prevent migration of any hazardous
constituents into the ground water or surface water at least as effectively as the
interim statutory design.  In doing so, the evaluation focuses on conditions where
the lower liner and secondary leachate collection systems are required,  i.e.,
various failures of the upper liner and primary leachate collection system.

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 2.0  GENERAL DESCRIPTION OF THE LANDFILL DESIGNS

     This evaluation conpares the CEOOS Cell No. 9 design to that of the interim
 statutory design contained in Section 3004(o)(5)(B) which satisfies the require-
 ments of Section 3004(o).  The general features of the interim statutory design
 and the CECOS Cell No. 9 design are provided in the following sections.  Details
 for the interim statutory design are based on the design presented in Section
 3004(o)(5)(B) of HSWA.  Details for CECOS Cell No. 9 design are based on the AS-BUILT
 specifications (dated January 31, 1985) provided by CECOS International.

 2.1  INTERIM STATUTORY DESIGN

     The interim statutory design consists, at a minimum, of a primary leachate
 collection and removal system.  The top liner consists of a liner designed, operated,
 and constructed to prevent the migration of any constituent into such liner during
 the active life and post-closure care period (i.e., flexible membrane liner (FML)).
 A secondary leachate collection system is between the two liners on the bottom and
 sidewalls to detect, collect, and remove liquids entering the collection system.
 The lower liner consists of a liner designed, operated, and constructed to prevent
 the migration of any constituent through such liner during such period.  HSWA
 specifies that the bottom (lower) liner be deemed to satisfy this requirement if
 it is constructed of at least a 3-foot thick layer of recompacted clay or other
 natural material with a permeability of no more, than 1 x 10  cm/sec.   Figure 1
 is a schematic of the interim statutory design.

 2.2  CECOS r-FTl. NO.  9 DESIGN

     A schematic representation of the CECOS Cell No.  9 is shown in Figure 2.   The
 sidewall liner system consists of,  from top to bottom, a protective soil layer, a
 geotextile,  1-foot of sand (leachate collection layer), a geotextile,  the FML, and
 7.5-feet compacted soil liner (bottom or lower liner).  The sidewall slope is 2:1
 (horizontal to vertical).  Eight 6-inch pipes,  spaced approximately equally around
 the facility,  are located in the sand layer on the sidewalls and extend 5 ft.
 into the primary leachate collection and removal layer at the bottom of the cell.
These pipes are perforated in the bottom layer and function as a contingency leachate
 collection and removal system.   This contingency leachate collection system is a
 very important element of Cell No.  9 because it is designed to provide additional
and backup capability to remove liquids from the sidewall area.

     The cell bottom liner system,  from top to bottom, consists of a protective
 soil layer,  a geotextile, 1-foot of sand (primary leachate collection and removal
 system),  the FML,  4-feet of compacted clay,  1-foot of sand (secondary leachate
 collection and removal system), and 2.5-feet of compacted clay (secondary liner).
The secondary leachate collection system is located below the 4-feet of compacted
 clay except near the sidewall/bottom interface and under a center berm.  An
 additional leachate monitoring system is located below the 2.5-feet of clay layer
 as a requirement under TSCA (not shown in Figure 2).  For specific details of the
 design see AS-BUILT Drawing.

     Cell No.  9 is located within a zone of saturation.  To help maintain slope
 stability,  a dewatering system is operated outside the unit until the cell becomes
 sufficiently full to offset the hydrostatic pressure.   Because of the presence of
  1  AS-BUILT Drawing, sheet 7 of 10 by Soil and Material Engineers, Cincinnati,  Ohio,
    dated January 31,  1985.

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            Figure 1.  Schematic of Interim Statutory Design


Protective Soil or Cover
                                                                              3 ft miniouB Lev Permeability
                                                                              Kacoapacted Natural Material
   Secondary  Leachate
   Collection and  Removal
   System
                      Primary Leachate
                      Collection and  Removal
                      System
                                                                                        Native Soil Foundation
                                                                                            (Not to Scale)
               Figure 2.  Schematic of CECOS Cell No. 9 Design.
             Ceotextile
                     7.S ft Recompacted
                     Soil Liner
                                               tlngency Leach
                                            Collection System
                                            (at approx. 70 ft spaclng>
                                            Native Foundation
                                            Material
                                                                                     Secondary Leachate
                                                                                     Collection and Removal
                                                                                     System
                                                                               (Not to Scale)

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ground water, the point of comparison for the CBCOS Cell No. 9 facility and
the interim statutory design is at the interface between the compacted soil
liner on the sidewalls (or the compacted clay liner on the bottom) and the
native material.

3.0  EVALUATION APPROACH

     The evaluation approach was based on hydraulic modeling of the CECOS Cell
No. 9 design and the interim statutory design.  Performance criteria and failure
scenarios were developed to characterize the ability of each design to prevent
or minimize migration of hazardous constituents into the ground water and surface
waters under conditions where the secondary leachate collection and liner systems
woulcj be needed.  The performance criteria selected are (1) liner systems breakthrough
times, (2) maximum leakage release rates, and (3) a drainage time factor related
to the length of time a release could occur.  The failure scenarios include various
situations where primary design components are assumed to fail and secondary systems
become necessary to minimize releases to the environment.  The performance criteria,
failure scenarios, and hydraulic modeling methodology are described in more detail
in the next sections.

3.1  PERFORMANCE CRITERIA

     The legislative history to the waiver provision indicates that alternative
designs should not only assure equivalent containment, but also provide for
equivalent leachate removal or other means of controlling the volume of hazardous
leachate.  (Senate Report No. 284, 98th Congress, 1st Session, pp. 27-28, 1983.)

     The performance criteria that were selected for this evaluation represent the
factors affecting migration:  (1) when breakthrough will occur,  (2) the maximum rate
of leakage, and (3) the duration of a release from the unit.  The first two factors
consider the ability of the design to contain wastes within the  unit while the
third criterion primarily evaluates the efficiency of the leachate collection and
removal system.

     The three performance criteria were developed to establish  a quantifiable
definition of "effectiveness" for each design.  The CECOS Cell No. 9 design and
operation has to be at least as effective as the interim statutory design in terms
of these three performance criteria.  The three performance criteria taken together
are conservative and will allow comparisons and ensure that the  goals  of the legis-
lation and regulations, primarily section 3004(o)(5)(B), are met.

     Criteria I — Breakthrough Time:  This is a measure of the  time required for
leachate or hazardous constituents to migrate through the bottom (lower) liner,
following a failure of the primary (top) liner system.  In the case of CECOS Cell
No. 9, the facility is located within a zone of saturation and,  therefore, any
migration beyond the secondary liner is  a release to the ground  water.  A section
3004(o)(2) waiver would require that this breakthrough time for  the alternative
design and operating condition be equivalent to or greater than  the breakthrough
time  for the interim statutory design.

     Criteria II — Maximum Leakage Release Rate:  The maximum leakage release  rate
is the maximum  daily rate that liquids are  released  from the bottom (lower) liner
on the sidewall.  This maximum rate is based  on  the  "worst-case" condition where

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the  facility has developed a very large hydraulic head above the liner systems.
This worst-case condition could occur if the primary leachate collection system
became severely clogged  (or was not operated) and the final cover system failed to
prevent  infiltration of water into the unit (i.e., the "bath tub" effect).  A
section  3004(o)(2) waiver requires that the alternative design along with operating
practices has a maximum leakage release rate less than or equal to the interim
statutory design.

     Criteria III — Duration of a Release From the Unit:  This is a measure
of the time required to empty from the unit the volume of leachate being modeled,
utilizing the secondary leachate collection systems.  In this analysis the
volume of leachate was assumed to be one pore volume (i.e.,  the landfill waste
is saturated with leachate).  While this analysis results in a measure of time,
it is also a measure of the effectiveness of the design to collect and ranove
leachate, which is dependent on the rejection efficiency of the liner.  The
rejection efficiency is a measure of the liner's ability to prevent migration
into the liner.  In this analysis, the primary leachate collection and removal
system was assumed to be nan-functioning.  This criterion is a drainage time factor
calculated by dividing the volume of liquids stored in the unit by the removal
rate of the secondary leachate collection systems for the interim statutory design.
For the CECOS design, the volume of liquid is divided by the removal rate of
both the secondary leachate collection system on the bottom of the unit and the
contingency leachate collection and removal system on the sidewalls.  Therefore,
the drainage time factor is an evaluation of the efficiency of the drainage
system to remove a given volume of liquid.  The greater the efficiency of the
leachate collection system, the greater the quantity of liquids that will be
removed versus being absorbed into the liner.   As a result,  the drainage time
factor is the period of time that liquids are potentially available for release
into the liner.  Even if an alternative design and operating practice has a
longer breakthrough time (Criteria I) and a smaller rate of release than the
interim statutory design (Criteria II), a larger total volume of hazardous constituents
could be released to the environment unless this third criterion is also considered.
If the alternative design along with operating practices has an equal or smaller
value for this third criterion when compared to the interim statutory design and
meets the other two performance criteria,  it would provide an equivalent or
better level of environmental protection.                                               •

3.2 FAILURE SCENARIOS

   Failure scenarios were developed to provide conditions where the secondary
systems would be needed.  Since the main issue with CECOS Cell No. 9 is the
sidewall, the failure scenarios focused on conditions in which liquids, hydraulic
head driving forces, and leaks through the top FML are present at the sidewalls.
The first failure assumption is that the primary leachate collection system on
the bottom of the cell does not function.   The second assumption is that infiltra-
tion into the waste cell results in the unit filling with liquids.  These two
assumptions allow liquids (hydraulic head) to build up in the facility.  The
third assumption is that the top liner, an FML, does not prevent migration.
Three permeation rates (represented as effective hydraulic conductivities) are
assumed for the FML on the sidewalls: 1 x 10~9 cm/sec,  1 x 10~7 cm/sec, and
1 x 10~4 cm/sec,  which represent increasingly severe failures to the FML on
the sidewall.  The hydraulic conductivity of the FML on the bottom of the unit
is assumed to have a very low hydraulic conductivity of 1 x 10"10 cm/sec.

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     An operational assumption in the failure scenarios  is  that the  secondary
leachate collection systems are functional and operated  at  design capacity
for both the CECOS and interim statutory designs.   Corrective measures are triggered
by some circumstance, such as the presence of leachate in the secondary  leachate
collection systems, detection of leachate in the monitoring wells, or observation
of high head levels within the waste cell.  In the event that corrective measures
have not been triggered and the secondary leachate collection systems are not
operated, then the CEOOS Cell No. 9 design would have a  slightly smaller release
rate due to the thicker liner on the sidewall (assuming  that the interim statutory
design has the same  as-built soil liner properties as the CECOS Cell No. 9 soil
liner).  An operational assumption for the CECOS Cell No. 9 includes cases with
and without the operation of the contingency leachate collection system above
the top  liner on the sidewall of the cell.

     Worst-case assumptions were established for the hydraulic head for the
failure  scenarios.   The head was held at  50 feet above the bottom of the secondary
clay liner.  A 50  foot head was  selected  since this is the approximate depth of
the landfill cell.   While the head is held at 50 feet, this head would not be
transmitted through  the secondary drainage layer because of the greater hydraulic
conductivity of the  drainage  layer as compared to  that of the waste.  Therefore,
in the case of the interim statutory design, the bottom  liner is not subjected
to the full head.  However,  for  the  CECOS design,  if the contingency side wall
collection system  is not operated, the  bottom  liner on the sidewalls will be
subjected to the hydraulic head  from the leachate  in the landfill.  The water
table  was generally assumed  to be  10 feet below  the bottom of the secondary clay
liner  except for one case  where  it was  assumed to  be  5  feet above the bottom of
the secondary clay liner.

     These two cases (i.e., water table 10  feet  below and  5 feet above  the
bottom of the secondary clay liner)  relate to CECOS Cell No. 9  (i.e., location
characteristics as required  under Section 3004(o)(a)).   During most of  the active
life of the  unit,  the ground water  is held below the  unit  by a dewatering system
operated outside  the unit  (i.e.,  the need to evaluate the  design with the water
table  10 feet below the bottom of the  secondary  clay  liner).  After the unit
becomes sufficiently full  to offset  the hydrostatic pressure on the sidewalls,
 the operation of the dewatering system will be stopped  and the ground water will
 be allowed to rise  outside of the unit (i.e.,  the case  where the water table
 is 5 feet above the bottom of the secondary clay liner).  The second case,  where
 the ground water is assumed to be above the bottom of the unit was used to
 demonstrate that the most critical period is while the ground water is at or
 below the unit.

   3.3  HYDRAULIC MODELING METHODOLOGY

        The performance of the CECOS Cell No. 9 and the interim statutory designs
 can be  effectively  evaluated using  two-dimensional (cross-section), saturated
 ground-water flow,  model  analyses.  Conceptually, each  design is represented as
 a saturated system, somewhat like a full bath tub with  the same amount of water
 flowing in as  flowing out of the drain.  The methodology  and modeling  approach
  are discussed below.

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     Engineered landfill facilities and failure scenarios  are evaluated with CFEST
(Gupta et al., 1982), a saturated ground-water flow model.  CFEST is one of nany
ground water models that could be used to conduct this study.  It was selected
because it was documented and has been tested.  The authors also have experience
with the application of CFEST.  The failure scenarios can be conservatively evaluated
using steady-state saturated flow analysis because the maximum amount of liquid
will be forced through the system under saturated conditions.  Under unsaturated
conditions, hydraulic conductivities of the lower liner (including the sidewalls)
could be an order-of-magnitude smaller, therefore, allowing less flow through the
system.  The landfill designs modeled all contain a lower liner that extends up
the sidewall that is compacted with hydraulic conductivities of 1 x 10   on/sec
or 1 x 10   cm/sec.  The materials overlying the  lower liner are more permeable
with'the exception of the FML.  The relatively  "tight" lower soil liner, in contrast
to the "native material," that underlies it, down to the water table, provides an
over-drained condition; therefore, the soil liner is the rate-limiting material at
the base of the engineered facilities.  The failure scenarios assume a consant
saturated  level in the waste cell.  All failure scenarios presume some degree of
leakage through the  top FML and  initial and steady-state  saturated conditions.

     The modeling analysis uses  steady-state assumptions  for material properties
and  constant  head conditions  to  determine how much  flow will go to the operating
collection systems and how much  flow will  leak through the bottom soil  liner.  A
constant head condition (i.e., the landfill remains filled with  leachate)  is used
because there is an  unlimited source  of liquids to the overall system,  so  the
resulting  release rates and  leachate  collection rates  are essentially the  worst-case
values.  This methodology is conservative in  that it will generally underestimate
the efficiency of each design because unsaturated flow analysis would have large
decreases  in hydraulic conductivities of the  various layers above the sidewall and
 bottom soil liner.   More detail flow analyses could be conducted, such as  unsaturated
 flow analysis or transient saturated flew analysis, however, those modeling approaches
 are nuch more susceptible to unknown errors in the determination of basic parameters
  (e.g., unsaturated moisture characteristic curves).

      Breakthrough times are calculated with the  Green-Ampt eqauation.  The Green-Arrpt
  (Green and Ampt, 1911) equation can be used to estimate  the time for a wetting
  front to  advance in a soil column.   In this  study, the Green-Ampt equation was
  used  to provide relative time estiinates  for  water to pass through the bottom
  soil liner on the sidewall.

       This equation approximates the wetting front as a square wave to which
  saturated Darcy flow analysis is applied.  The equation captures the dynamics of
  a wetting front and is a conservative method for estimating breakthrough times
  (EPA,  1984).  Heads above and below the soil liner on the sidewall (h^ and h-D)
  for this  equation are determined from the CFEST model runs.

       The  Green-Ampt equation can be written  as:
  t =
       es - ei
          K
Z - (ftp - he ) In
                                        + Z -
                    hp -

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                                        8
where

     t  =  time for the wetting front to advanoa through the liner;

     es = saturated moisture content of the liner material (above
          the wetting front);

     e^ = initial moisture content of the liner material (below
          the wetting front);

     K =  hydraulic conductivity of the liner material at some
          average moisture content (i.e., between es and ej_);

    ' Z =  liner thickness

     hji = head at the top of the liner; and

     hg = head at the base of the liner.

3.4  MODEL SIMULATION

     The CFEST finite-element ground-water code was used to simulate CECOS Cell
 No.  9 and the interim statutory design under various  failure  scenarios.  A finite
 element grid was  set up to represent each layer within each design case.  For
 all cases,  the head at the top of the landfill was held at 50 feet above  the
 bottom of the secondary liner which corresponds to a worst-case hydraulic head
 condition.   By doing so, liquids are always available at the top to replace
 liquids that are removed by the leachate collection systems.   The water table at
 the bottom of the region was held at either 10 feet below the secondary liner or
 5 feet above the secondary liner, depending on the failure scenarios.   Liquids
 flow from a higher to a lower head (i.e., from 50 feet to 5 feet or to -10  feet
 relative to the bottom of the  secondary liner).  The hydraulic conductivity  (K)
 for all the materials siirulated are shown in Table 1.

             Table 1.  Hydraulic Conductivities  of the Materials

             Material                                  K  (on/sec)

             Waste                                       1 x 10~5
                                                                *\
              Sand (Leachate Collection Layers)           1  x 10~z

              Compacted Soil*                       1  x 10~6 and 1 x 10~7

              FML  (Sidewall)**                      1  x 10~4, 1 x 10~7,  and 1  x 10"9

              FML  (Bottom)**                              1 x 10~10

              Native Material                            1  x 10~3

             *CBCOS  Cell No.  9  is  evaluated with both  K values
             **EML's leaks are simulated using equivalent K values

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     Two values of hydraulic conductivity for CECOS Cell No. 9 compacted soil
liner were used because of uncertainty in the as-built field hydraulic conductivity.
However, the soil utilized on the sidewalls  is  a  silty till material that has
laboratory K values less than 1 x 10~7 cm/sec.  In the construction of Cell No. 9,
CECOS used what was considered at the time to be  good quality control to assure
that the unit was constructed as designed (i.e.,  hydraulic conductivity of less
than 1 x 10""' on/sec).  A complete description  of the model input'data in each
case is shown in Table 2.

     Five failure scenarios were evaluated for  the interim statutory design and
two versions of CECOS cell No. 9 design,  version  A with a soil liner K of 1 x 10~°
cm/sec and version B with a soil liner K of  1 x 10~7  cm/sec.  A description of
each case is as follows:

     Case 1 -  Severe failure of the sidewall FML (K  = 1 x 10"4 cm/sec).
               Water table below the cell.

     Case 2 -  Moderate failure of the sidewall FML (K = 1 x  10" 7  cm/sec).  Water
               table below the cell.

     Case 3 -  Severe failure of the sidewall FML (K  = 1 x 10"4 on/sec).
               Water table above the cell bottom.

     Case 4 -  Severe failure of the sidewall FML (K = 1  x 10"4 cm/sec).
               Water  table below the cell.  Contingency leachate collection
               system operating in CECOS Cell No. 9.

      Case 5  - Minor  failure of the sidewall FML (K = 1 x 10~9 cm/sec).  Water
               table  below the cell.

      In all  cases the primary leachate collection system on the bottom unit
 is not operating, the secondary leachate collection  systan is operating, and the
 hydraulic head in the waste is held at 50 feet above the bottom of the cell.
 The letter A designates CECOS Cell No. 9 with  a  sidewall soil liner K of 1 x 10~6
 cm/sec,  the  letter B  designates CECOS  Cell  No. 9 with a sidewall soil liner K of
 1 x 10   on/sec,  and  the letter S  designated the interim statutory design with a
 sidewall soil liner K of 1  x 10~7  cm/sec.

      Case 1,  2,  and 5 demonstrate the effects  of different leakage rates through
 the top liner (FML).   Case 1 versus Case 3  demonstrates the effect of different
 assumptions of the location of the water table under the worst-case FML failure
 condition.  Case 1 versus Case 4 demonstrates  the effect of operating the contingency
 leachate collection systan in CECOS Cell No. 9 under the vorst case FML failure
 condition.  Case 1 and 4 represent the most severe cases.

 4.0  MODEL RESULTS

      The model results are presented in Tables 3 and 4.  Graphical comparisons of
 the three performance criteria for the failure scenarios are  also presented  in
 Figures 3, 4, and 5.   Table 3 shows the distribution of flow within the sidewall
 region.  Flow rates are expressed in units of ft /day/ft  (rate of flow in  cubic

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                                        10
Table 2. Summary of Model Input Data
Design
Case

1A
IB
IS
2A
2B
2S
3A
3B
3S
4A
43
4S
5A
53
5S
Sidewall Compacted Water Table*
FML K Soil K Elevation
(cm/sec) (on/sec) (ft)

1 x 10"4 1 x lO"6 -10.0
1 x 10"7
ii M n
1 x 10~7 1 x ID"6
1 x 10~7
n M n
1 x 10~4 1 x 10~6 5.0
1 x 10~7
M M ii
1 x 10~4 1 x 10"6 -10.0
1 x 10~7
n n • ii
1 x 10~9 1 x 10"6
1 x 10~7
II M II
Contingency Leachate
Collection System

Not Operated
„
N/A
Not Operated
ll ll
N/A
Not Operated
„
N/A .
Operated
'•
N/A
Not Operated
' „
N/A
Cases 1A-5A and IB-SB are CECOS Cell No. 9 simulations




Cases 1S-5S are Interim Statutory Design simulations



*  Relative to the bottom of the secondary liner.

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                                        11
Table 3.   Flow Distribution Within the Sidewall Region
           (all values are in units of ft3/d/ft)*


Design      Maximum Release Rate    Flow Rate Through       Flow Rate Through
Case         Through Sidewall       Secondary Leachate     Contingency Leachate
                                    Collection System        Collection System
1A                1.91                    0.54                  N/A
IB                0.23                    0.07                  N/A
IS  "             0.07                    4.98                  N/A

2A                1.79                    0.41                  N/A
2B                0.23                    0.07                  N/A
2S                0.07                    3.67                  N/A

3A                1.33                    0.53                  N/A
3B                0.16                    0.07                  N/A
3S                0.06                    2.76                  N/A

4A                0.43                    -0-  .                 9.73
4B                0.05                    -0-                  10.03
4S                0.07                    4.98                  N/A

5A                0.16                    0.02                  N/A
5B                0.10                    0.01                  N/A
5S                0.004                   0.178                 N/A
   Rate of flow in cubic feet per day from a one-foot slice of the landfill
   sidewall from top to bottom.

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                                        12
Table 4.
Design
Case
Drainage Time Factor  (Volume of Liquids in the Landfill
Divided by Leachate Collection Rate),  Volume Exiting Sidewall
During Drainage Time, and Breaktlirough Tims
       Drainage Time
         (days)
Volume Exiting
Sidewall During
 Drainage Time
    (ft3/ft)
Breakthrough
   Time
  (days)
1A
IB
IS

2A
2B
2S

3A
3B
3S

4A
4B
4S

5A
5B
5S
          876
        7,045
          390

          974
        7,158
          525

        1,151
        9,231
          700

          211
          213
          390

       12,596
       19,391
       10,808
    1,672
    1,637
       27

    1,744
    1,640
       37

    1,535
    1,509
       42

       91
       10
       27

    1,950
    1,894
       43
     19
    157
    253

     20
    170
    312

     25
    204
    372

     98
    947
    253

     81
    234
    899

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to
>>
p
E
pg

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      Figure 5.   Breakthrough Times (days)
P
•p

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                                        16
feet per day from a one-foot slice of the landfill sidewall frcn top to bottom)       (
because the CFEST model analysis is based on a cross-section of each design.
Flows at or near the sidewall are either released through the sidewall (i.e.,
maximum release rate through sidewall) or collected by the secondary or contingency
leachate collection systems.  These rates are maximum values because of the high
constant head conditions assumed in this analysis.  Because CEOOS1  Cell No. 9
only has a secondary leachate collection system on the bottom of the cell (i.e.,
no sidewall secondary leachate collection systsn), very little flow from the
sidewall reaches the secondary leachate collection system.

     The drainage times presented in Table 4 and Figure 4 are calculated by
dividing the total amount of liquids within each design by the flow rate through
the secondary and/or contingency leachate collection systems.  The drainage time
factor relates directly to the length of time a release could occur given that
the secondary or contingency leachate collection systems were being operated to
remove all liquids from the landfill.  Remember, however, that this analysis  has
a constant head, while under normal field conditions, the head would be declining
eventually to zero if all liquid input into the cell were eliminated.  Table 4
also contains the volume exiting the sidewall during the drainage time.  These
values are determined by multiplying the maximum release rates by the drainage
time.  These volumes are another measure of the effectiveness of each design.
The physical significance of these volumes is that while  liquids are being removed
by  the secondary or contingency leachate collection systems,  releases through
 the sidewall will  occur;  thus,  more effective collection systems will  reduce  the
 volume of liquids  release to the environment.

      Breakthrough  times are presented in Table 4  and Figure 5.  Breakthrough
 times represent another measure of performance of each design but  because of the
 drastic head conditions and conservative breakthrough equation, these values  have
 little resemblance to breakthrough times that would occur under less severe conditions
 (i.e., normal field conditions).  The relative relationship between breakthrough
 times for various designs and operating conditions should, however, be similar
 with the smaller heads that are more likely to occur in an actual landfill.

      The results generally indicate that the interim statutory design is not
 significantly affected by  various failure scenarios.  Cases  1S-4S all have almost
 identical maximum release rates through the  sidewall.   This  result is  due to the
  secondary leachate collection system's ability to reduce the head on the sidewall
  soil liner to a very small value.   Case 5S has a much smaller release rate because
  the moderate failure of the sidewall FML still significantly reduces the flow of
  liquids into the secondary collection system.   The drainage time  factor, and
  breakthrough times are also similar for each statutory case (except case 5S).

       A comparison of A and B cases shows that different .assumed hydraulic
  conductivity values for the sidewall in Cell No. 9 have a major effect on
  performance of this design.  Maximum release rates are about  a factor of 8 higher
  in Cases 1A-4A than Cases 1B-4B while drainage times and breakthrough times are
  about a factor of 8 lower for Cases 1A-4A than Cases 1B-4B.   Cases 5A and 5B are
  not as different because  flew rates are restricted by  the top FML.

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                                        17
     Cases 1A,  IB,  and IS versus 3A,  3B,  and 3S indicate  the  effects of water
table location.  Because the location of the water table  affects the net head
gradient on the sidewall, a lower water table gives more  conservative  results
(i.e., a worst case).  CEODS Cell No. 9,  after completion,  will have water table
located above the cell bottom along the sidewall, so Cases  3A,  3B,  and 3S  are  more
representative of this situation.  However, a lower water table assumption, such
as during the construction of Cell No. 9, gives more conservative results.  The
lower water table assumption was preferred in the modeling analysis because a
snail amount of liquid could enter the secondary leachate collection systems from
outside of the cell  (i.e., ground water) in several cases.   This ground water
could not be distinguished  from liquids  entering the collection system from within
the  cell  (i.e., leachates)  by this modeling analysis.

     K. comparison of Cases  1B-3B and 5B  with Cases 1S-3S and 5S illustrate that
CECOS Cell No. 9 is  not  equivalent to the  interim  statutory  design when the
contingency leadhate collection system is  not  operated.  Maximum release rates
are  about a factor of 3  higher  in Cases  IB-SB  as compared to 1S-3S and a  factor
of 25 higher  in Cases 5B than interim statutory case 5S.  Drainage times and
volumes  exiting the  sidewall during drainage times are drastically higher in  the
gECOS Cases 1-3  and 5 versus the interim statutory design  cases 1-3 and 5.

      Cases  4A and 43 illustrate the effect of operating  the  contingency leachate
 collection system.   Case 4B demonstrates that the  CECOS  Cell No. 9 is more
 effective, by all three  criteria, than the interim statutory design when  the
contingency leachate collection system is  operated and the sidewall soil  liner
hydraulic conductivity is at least 1 x 10    cm/sec.  The maximum release  rate
 through the sidewall is 0.05 ft3/day/ft for Case 4B versus 0.07 ft3/day/ft for
 Case 4S.   The drainage time and volume exiting the sidewall  during the drainage
 time are smaller for Case 4B than Case 4S.  The breakthrough time is  larger for
 Case 4B than Case 4S.

      Since the CECOS Cell No.  9 design and operation (Case 4B) is batter  than the
 interim statutory design under catastrophic failure conditions for all three
 performance criteria (i.e., breakthrough time, maximum release rate through
 sidewall, and drainage time),  the CECOS Cell No. 9 design and operation will  be
 more effective than the interim statutory design for the other failure conditions.
 For example,  under  a moderate failure mode of the FML, the CECOS design would
 exceed the performance of Case 5S if the contingency leachate collection system
 is operated.
L     i-                                     •
 5.0  CONCLUSION

      The result of  Section 4 demonstrate that the CECOS Cell No. 9 design and
 operation can be considered to be as effective as the interim statutory design
 ONLY WITH THE OPERATION OF THE  CONTINGENCY LEACHATE COLLECTION SYSTEM.

 6.0 FINDINGS AND RECOMMENDATIONS

      The modeling evaluation was based  on properties  of various materials as
 reported by CECOS.   They implemented a  construction quality assurance program
 to  assure that the  compacted soil  liner was  constructed as  designed. EPA

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used the 1 x 10   an/sec hydraulic conductivity value for the sidewall  comparison
based on the demonstration by CEQOS that they complied with regulations and
guidance available at the time of construction.

     If CEOOS Cell No. 9 is given a waiver, it is strongly recommended, based
on this analysis, that leachate heads within the cell be keep to"an absolute
minimum at all times by operating the primary  leachate collection system and the
contingency  leachate collection system to keep leachate away from the  sidewalls.
Future placement of the one-foot sand layer above the top liner on the sidewalls
should be inspected during placement in accordance with  current  EPA guidance.
During the post-closure  care period the head  levels  should be monitored very
frequently on the sidewalls.   The permit should have provisions  for immediate
response to  any head build-up in the cell.

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REFERENCES

Green, W.H. and G.A. Anpt.  Studies in Soil Physics I:   The Flow of Air
  and Water Through Soils, Journal of Agricultural Science 4,  1911.

Gupta, S.K., C.T. Kincaid, P.R. Meyer, C.A. Newbill, and C.R. Cole.  A
  Multi-Dimensional Finite-Element Code for the Analysis of Coupled Fluid
  Energy and Solute Transport  (CFEST), PISL-426, Pacific Northwest.
  Laboratories,  Richland, WA,  1982.

U.S.EPA, Procedures for Modeling Flow Through Clay Liners  to Determine
   Required Liner Thickness,  EPA/530-SW-34-002, OSW, Washington,  D.C.

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