&EPA
                   Unirad Suit*
                   Environmental Pro(«cnon
                   Agency
 0cv
     9476,00-9
DIRECTIVE NUMBER
	                    >
TITLE: part 265 Land Treatment Closure/Post Closure
      Guidance

APPROVAL DATE:  4/14/87

EFFECTIVE DATE:  4/14/87

ORIGINATING OFFICE: Osw

O FINAL
                    D DRAFT

                      STATUS:
  I
[  ]
[  )
                     A- Pending OMB approval
                     B- Pending AA-OSWER approval
                  ]   C- For review &/or comment
                [  ]   D- In development or circulating

REFERENCE (other document*):         headquarters
1. Guidance Manual on Unsaturated Zone Monitoring for
  Hazardous Waste Land Treatment Units

2. Permit Guidance Manual  on Hazardous Waste Land
  Treatment Demonstrations
'E     DIRECTIVE     DIRECTIVE     L

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                   United SU(««
                   Environmental Protection
Office of
Solid vvuta end
Emergency Retoonte
                    DIRECTIVE NUMBER:
                                          9476.00-9
                    TITLE: part 265 Land Treatment Closure/Post Closure
                           Guidance

                    APPROVAL DATE:  4/14/87

                    EFFECTIVE DATE:  4/14/87

                    ORIGINATING OFFICE:  OSw

                    O FINAL
                    D DRAFT

                      STATUS:
  I
                      A- Pending OMB approval
                      B- Pending AA-OSWER approval
                [  ]   C- For review &/or comment
                [  ]   D- In development or circulating

REFERENCE (other document*):        headquarters
1. Guidance Manual on Unsaturated Zone Monitoring for
  Hazardous Waste Land Treatment Units

2. Permit Guidance Manual on Hazardous Waste Land
  Treatment Demonstrations
'E     DIRECTIVE     DIRECTIVE     L

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&EPA
Wasnmgion uC 2W60
OSWER Directive Initiation Reauest
rf T 0 it c „ '„*
9476.00-9
Name ol Contact Person
Jon Perry
Leac Office Q 0UST
D OERR Q OWPE
GO OSW Q AA-OSWER
WH-565E T?DB e'e°n0n?382-4654
Aoorov-ed »jr Sev.ew
Signature of Office 0 rector Qat9
i
                                              Or q rater
T.tie
          Part  265 Land Treatment Closure/Post  Closure Guidance
Summary of Directive
         Manual-Addresses Closure  and  Post-Closure of  Hazardous  Waste  Land  Treatment
         (HWLT) Units Under  40 CFR Part 265  Subpart G  and  Section 265.280 of Subpart  M
Key Words:
             Land Treatment, Closure,  Refinery  Waste
Type ot Oneuive tManual Policy Directive. Announcement etc i
          Guidance Manual
                                                                        Status
                                                                       1    Li Draft
                                                                       !   IS Final
                                \    I—i  New
                                                                                             D
                                                                                                Revision
                                            \\
Ooe» tnis Directive Supersede Previous Direcnweis,'   |  | Yes   |X| No   Does It Supplement Previous Directweisi'
If Yes to Either Question What Directive tnumber nttel
                                                                                               Yes
                                                                                                        No
Review Plan
   D AA OSWER   U OUST
   D OERR        O OWPE
   LJ OSW        LJ Regions
                                    U OECM
                                    D OGC
                                    D OPPE
                                                      D
Other Specify/
This Request Meets OSWER Directives Svstem Format
Signature of Lead Office Directives Officer
                                                                                      Date
Signature of OSWER Directives Officer
                                                                                      Date

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     r
      \         UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

\ VNl/^L 5                     WASHINGTON DC  20460
 \    ~  UA^^ ^
                Office ot Solid Waste      I

     TO:        Hazardous »vaste Management Division Directors
                Regions I-X


          To assist permit writers and owners/operators of those land
     treatment, units that' may be closing, ObW is  issuing the Guidance
     Manual on hazardous y>aste Land Treatment Clobure/ Post-Closure ;
     40 CFR Part 2b5 .   A copy of the manual is attacned.  This guidance
     manual aadresses  closure and post-closure of uazaraous waste  land
     treatment (n'^LT)  units unaer 40 CFR Part 265 Subpart G and Section
     2oD.2dO ot Subpart M.  Th& guidance is not intended to be a detailed
     technical document, but rather a document tuat provides general
     guidance to owners and operators of HWLT units and permit writers on
     implementing Part 265 closure regulations.   I want to emphasize that
     the methods described in the manual are for guidance only and are
     neitner requirements nor regulations.  An applicant may use alter-
     native methods, provided that these methods comply with applicable
     regulatory requirements.

         This manual specifically addresses five areas,:

     (1) general information on HVvLT and methods of closure,  (2) objec-
     tives of closure  and post-closure, (3) factors affecting closure and
     post-closure,  (4; methods for addressing closure and post-closure
     based on migration potential, and (5) management during closure and
     post-closure.

          Finally,  I want to stress that completion of a successful land
     treatment closure .vould provide valuable information that should be
     shared among Regions.   Therefore,  when such  information becomes
     available,  I would appreciate your efforts to irirorm the appropriate
     Headquarters Permit Assistance Team members.

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     If your staff has questions regarding this  jUi^ri'ice,
contact Jon Perry, on ts-3a2-4654 in the Land ui^^osdl  Branca for
further information.

Attachment

cc with Attachmenti
RCRA Branch Chiefs, Regions I-X
Permit Section Chiets, Region I-X
Joe Carra
Susan 3romm
Sylvia Lowrance

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                                                        9476.00-9
                GUIDANCE MANUAL ON

HAZARDOUS WASTE LAND TREATMENT CLOSURE/POST-CLOSURE

                  40 CFR PART  265



                   INTERIM  FINAL
                   Prepared for
               Office of  Solid  Waste
       U.S. Environmental Protection Agency
              Washington, D.C.  20460
 Department  of  Civil  and  Environmental Engineering
               Utah  State University
                 Logan, Utah 84322
                    April,  1987

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                              TABLE  OF  CONTENTS


                                                                          Page

1.0 Considerations for Closure and Post-closure of Hazardous Waste
      Waste- Land Treatment Units Under 40 CFR Part 265	     1
    1.1 Purpose of manual	     1
    1.2 Overview of manual   	     1
    1.3 Approach to closure and post-closure   	     1
    1.4 General information on hazardous waste land treatment ....     7

2.0 Factors in Addressing Closure and Post-closure   	     9

    2.1 Introduction   	     9
    2.2 History of waste application  	     9
    2.3 Mobilfty and migration potential 	     9
    2.4 Environmental site conditions 	    11
    2.5 Waste residue characterization in the unsaturated zone   ...    11

3.0 Methods for Addressing Closure Based on Mobility and
      Migration Potential 	  ~~ 18

    3.1 Suggested closure methods  	    18
    3.2 Factors, to be considered in the selection of a closure
        method  " . ~	    18
    3.3 Removal of contaminated soil as a closure method	    21
    3.4" Establishment of a fi'nal cover as a closure method	    22
    3.5 Continued groundwater monitoring 	    28
    3.6 In-place treatment as a closure method 	    28

4.0 Management During Closure   	
    4.1 Introduction	    31
    4.2 Unsaturated zone monitoring   	    31
    4.3 Run-on and run-off control 	    32
    4.4 Control of dispersal  of particulates   	    32

5.0 Management during Post-closure 	    33
    5.1 Post-closure requirements  	    33
    5.2 Duration of post-closure care	    33

References	    35

Appendix A .  -	    38

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                                  Chapter 1

        CONSIDERATIONS  FOR CLOSURE AND POST-CLOSURE OF HAZARDOUS WASTE
                  LAND  TREATMENT  UNITS UNDER 40 CFR PART 265
L.I  PURPOSE OF MANUAL

     This  guidance  manual  addresses  closure and  post-closure  of  hazardous
waste land treatment (HWLT) units under 40 CFR Part 265 Subpart G  and  Section
265.280 of Subpart M.   The guidance  provided  is  not  intended  to be a detailed
technical document,  but rather a document  that  provides  general   guidance  to
owners and operators of HWLT  units and  permit  writers  on  implementing  Section
265 closure regulations.   The guidance  contains  a discussion of options  that
may.be pursued in implementing closure and post-closure requirements.

1.2  OVERVIEW OF MANUAL

     This  manual  specifically addresses  five  areas  including:   (1)  general
information  on  HWLT  and  methods   of  closure,  (2)  objectives  of
closure/post-closure,  (3)  factors  affecting closure  and  post-closure,  (4)
methods for addressing  closure and post-closure  based  on  migration  potential,
and  (5)  management  during  closure and  post-closure.   This  guidance  also
summarizes relevant  information from  additional  U.S.  Environmental  Protection
Agency  (EPA  or  Agency) publications  and  refers  the user to  EPA publications
,for background  and  for additional  information supporting  approaches for  site
characterization, chemical analyses,  establishment  of  cover, etc.

1.3  APPROACH TO CLOSURE AND POST-CLOSURE

     The  owner  or  operator  of a  hazardous waste management  facility  must
submit  a  closure plan  to the EPA Regional  Administrator at  least 180  days
prior to  the  date  on which closure is expected  to begin  at the first  unit  at
the facility.  Owners or operators  with  approved  closure plans must notify the
Regional Administrator  in  writing at  least 60  days  prior  to the date on  which
closure is expected  to  begin  at a  HWLT  unit  at  the facility  (Section  265.112
(d) (1)).

     Within 30 days after receiving the  known final  volume of  hazardous waste,
the owner  or  operator of  the HWLT  unit must  commence closure  in  accordance
with the  approved  closure plan (Section  265.112 (d)  (2)).   The closure  plan
should  identify steps  necessary to completely or partially close the facility
at  anytime  during  the facility's intended operating  life,  and to  completely
close  the  facility  at  the  end  of  ics  operating  life.   At  a  minimum,  the
closure plan must include  (Section  265.112(b)(!)-(?)):

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     (1)  a description of how each waste management unit at the facility will
be closed  in accordance  with  the  performance  standards  given  in  Section
265.111;

     (2)  a description of how final closure of the facility will be conducted
in accordance with  Section  265.111,  including  a  description of  the maximum
extent of  the operation  that will be unclosed during the  active  life of the
facility;

     (3)  an estimate of  the  maximum  inventory  of  hazardous wastes in storage
or treatment at  the  facility  during its operating  life;

     (4)  a description  of methods  to be used during partial and final closure,
including, but not  limited  to  methods for  removing,  transporting,  treating,
storing,  or  disposing  of all  hazardous  waste, and  identification  of and the
type(s) of  off-site hazardous  waste management  unit(s)  to  be  used,  if
applicable;

     (&)   a  description  of methods for decontamination  of  system  components,
equipment, and structures,  including  criteria  for determining  the  extent  of
decontamination  necessary to  satisfy the closure performance standard (Section
265.111);

     (6)   a  description  of other  activities necessary for  closure,   including
run-on  and  run-off  control  systems,  groundwater monitoring  and  other
monitoring systems;

     (7)  a  schedule  of  closure  for each hazardous  waste  management unit and
for final  closure of the  facility,  including specific periodic reporting dates
to monitor progress;  and

     (8)  an est.imate of  the expected year of final" closure for facilities that
use  trust  funds   to  demonstrate  financial   assurance (Sections  265.143  or
265.145)  and whose remaining  operating life  is less than 20 years.

     The  owner or operator may amend the closure plan at any time prior to the
notification of   partial  or  final  closure  of the  facility  in  accordance with
Section 265.112  (c).   The closure  plan must  be amended if there are changes in
operating  plans  or facility design  that will affect the closure plan, if there
is a change  in the expected year of closure, or if  during  the performance  of
partial or final  closure activities, unexpected events require a modification
of the closure plan  (Section  265.112 (c) (1) (i), (ii), and (iii)).

     Financial  responsibility requirements  to  ensure that  owners or operators
of hazardous  waste  management facilities  have adequate  funds  to  implement
closure  and  post-closure plans  are given  in  Subpart H  of Part  265.   In
general,   the  regulations require  that  the owner  or operator  have  written
estimates  of the  cost of closing  the  facility  and  the annual  cost  of a post-
closure monitoring and maintenance program.  The owner  or  operator  must also
adopt one of the  financial  instruments provided by  the  regulations to assure
financial  responsibility.

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     Additional  specific requirements  that  must  be addressed in the  closure
plan for a HWLT unit are given in Section 265.280.   The goal  of closure of a
unit is  to  control,  minimize  or  eliminate any potential for damage to human
health  and  the  environment  (Section  265.111).   Closure of the  HWLT unit  is
therefore  concerned with  the  extent  of  degradation, transformation,  and
immobilization  of  constituents within  a  defined  treatment  zone, and  the
control  of  pathways  of migration  of hazardous  waste  and  hazardous waste
constituents into  the  environment,   including  groundwater,  surface  water,
atmosphere,  and food-chain crops  grown on site  (Section  265.280(a)  (l)-(4)).
The effectiveness  of  previous  treatment of hazardous waste and hazardous waste
constituents in  the  treatment zone  soil  (Section   265.280(b)(l),(2),(6)  and
(7)) is  determined from  a  site  reconnaissance  study   and  from historical
records of waste application  and  site sampling.   Information  requirements for
site-characterization are specified in Section 265.280(b)(3),(4)  and (5).

     The guidance  provided  in this  manual  for  approaches and  criteria for
utilizing appropriate methods  for closure  and  post-closure, including but not
limited to  those  identified in Section 265.280(c), i.e.,  (1) soil removal, (2)
cover  or  cap placement,  and/or  (3)  groundwater  monitoring,  is   based  on
site-specific   information.   This  information  includes  waste   type  and
constituents,   soil  type(s),   climate,   and  extent  of degradation,
transformation,  and immobilization  of hazardous  waste  and  hazardous waste
constituents within  a  defined treatment  zone.   The information is used to
predict potential  pathways of migration of hazardous waste and hazardous waste
constituents into  the  environment.   Closure  by soil  removal  may  limit  or
eliminate  the  potential  for future  migration by  eliminating  or reducing
contamination at the source,  while  closure  by cover placement  may limit or
eliminate direct  contact  and  jnhalation exposure  and/or  limit  or  eliminate
leachate production by minimizing infiltration.

     Continued  in-place  treatment of applied  hazardous wastes  is  also a method
recommended  for  use  during  the  closure  period  at  a HWLT unit.    In-place
treatment  may  consist  of  a  continuation  of the  operating and   management
practices utilized during  the  active  life of  the  facility,  or  use  of
additional  amendments or  techniques for enhancing degradation,  transformation,
and/or  immobilization.

     Another approach presented   in this guidance combines  the  use  of  two or
more of  the  recommended  closure  methods  to  achieve  control  of  migration of
hazardous wastes  and hazardous waste constituents  from  the  HWLT  unit.   For
example,  partial  removal  of  more  highly contaminated soil may be followed by
covering  the  unit,   or  by continued in-place  treatment  followed  by
establishment or  placement of  a cover.

     The closure  plan submitted by the owner  or operator  must  include a method
for evaluation  of  the  potential  migration of  residual  waste  constituents to
environmental  media,  including  groundwater,  surface water,  and   atmosphere
(Sections 265.111  and 265.280  (b)  (2)).  An  evaluation of potential  migration
pathways  of concern  requires  site-specific  information  concerning waste
residues and site/soil  characteristics  and may involve  the use of  laboratory
studies  and/or mathematical  models  for predicting  the rate and  amount  of
migration of constituents  into   the  environment.  Levels of  constituents  in

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leachates  or  emissions  may be  determined  by the  use of  soil  leaching  or
volatilization  tests  or  estimated  based  on  known  characteristics  of  the  waste
constituents  and  soil  characteristics  (e.g.,  solubility and  partitioning
coefficients).   The mathematical model presented in the Permit  Guidance Manual
on  Hazardous  Waste  Land  Treatment Demonstrations  (U.S.EPA 1986a)wa?
developed by  Short[1985)specifically  for  evaluation of  degradation  and
immobilization  of individual organic  waste  constituents  in a  land  treatment
unit, and for assessment of  the potential migration of individual  constituents
to  groundwater  and  to atmosphere.  The  model  can be used  on  IBM-compatible
personal  computers  (PCs).  The  model  can be  used  to predict  the  fate  and
relative  concentration of  hazardous constituents at point(s)  of exposure,  thus
indicating potential  migration  pathways  of  concern that should  be controlled.
A  detailed  description  of the model  program, including   capabilities,
assumptions,  and limitations, rationales for selected  input criteria,  methods,
and information for  using  the model  is given  in the  Permit Guidance  Manual  on
Hazardous Waste Land  Treatment  Demonstrations  (U.S. EPA 1986a).A method for
evaluation of the potential  for migration of metal constituents to groundwater
for hazardous waste/soil residues  using sequential desorption,  adsorption, and
column  leaching  tests  is  presented  in  Protection  of  Groundwater  by
Immobilization  of Heavy Metals  in  Industrial Waste Impacted Soil Systems  (Sims
and McLean 1986). The geochemical model  MINTEQ may also be  used  to  determine
estimates  of  metals  species  distributions  that  can  be used to predict
migration potential of metals (Felmy et al. 1984).

     The  time required for closure will be a function  of the method chosen for
closure.  If the wastes are left in place for continued treatment, the  length
of  time  required for closure will  be related to the  time required for the
degradation of hazardous  waste  and hazardous  waste constituents to achievable
levels  protective  of  human  health and  the  environment.   While Section
265.113(b)  requires  that  closure  be  completed  within  180 days  after  receiving
the final known volume of  hazardous wastes at the  HWLT unit,  caution  should be
taken  not  to  close  a unit"  before  satisfactory  levels are  achieved.    The
Regional  Administrator may approve an extension to the closure period if the
owner or operator demonstrates  that closure activities will take  longer  than
180 days  to complete (Section 265.113(b)(l)(i)).   Closures  by  soil removal  or
by  clay or synthetic capping are expected to require the  least time, usually
within  the  180 day  period given  in Section 265.113(b),  while closure  by
vegetative cover  or   a  combination  of  approaches  requires time  periods
dependent  upon  biological  processes   and  can  also be  anticipated  to  be
seasonally dependent.  Therefore,  closure activities  at a HWLT  unit may  often
be  expected to continue longer than 180  days.  Also,  if a  vegetative  cover is
used  as  part  of a closure  method utilizing continued treatment, sufficient
time must be  allowed  for degradation and detoxification of  soil/waste  residues
so  that a vegetative  cover can be  established and  maintained.  A demonstration
of  the ability of the site to support vegetation  is  also recommended  prior to
the completion  of closure

     Any  unit  that  closes after  January 26,  1983  is subject   to obtaining a
post-closure  permit  under Part  264  (Section 270.1 (c)).   While the   scope  of
Section  265.280 requirements  is  currently  limited  to hazardous  waste  and
hazardous waste constituents  (i.e., those listed in Appendix VII of Part  261),
the  post-closure  permit  must address  hazardous  constituents  (i.e.,   those

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listed in Appendix VIII of Part 261)  (Section 264.280).  Since evaluation of only
hazardous waste and "hazardous waste constituents under Section  265.280 pay allow
significant and potentially harmful levels of hazardous constituents to remain in
HWLT units, it is recommended that owners/operators consider the performance of
analysis and control of these constituents from the viewpoint of protection of
public health and the environment, as required by Section 264.280.  If approved
by the permit writer, the hazardous constituents for wastes handled at a facility
that are from an identified process (e.g.,) petroleum refinery processes) for
which analysis is required may include only tiiose hazardous constituents that are
"reasonably expected to be in , or derived from, the wastes to be land treated"
(Section 270.20 (b)  (4).  A list of Appendix VIII constituents commonly found
in petroleum refinery wastes is included1 in .Appendix A.  For facilities other
than petroleum refineries, guidance for determining hazardous constituents for
which a facility should test could follow the guidelines given to facilities
for preparation of petitions to delist hazardous waste (U.S. EPA 1985b).  The
permit writer and applicant should agree in writing on the specific subset of
Appendix VIII constituents for which analysis will be required.

    The closure performance standard given in Section 265.111 states that post-
closure escape of hazardous waste, hazardous constituents, leachate, contaminated
run-off, or hazardous waste deconposition products must be controlled,  minimized
or eliminated.  The permit writer should use health-based acceptable concentrations,
as described below, or remove constituents to background levels,  or to levels
achievable by the use of selected closure technology at the specific HWLT unit
when Agency approved health-based levels are not available.  These criteria should
be used to assess risk due to direct contact with the unit soils (i.e., soil
inqestion), exposure to ground water at the unit boundary, and surface water quality
impacted by ground water discharge or surface runoff.

    Concentration levels for Appendix VIII constituents for each potential route
of exposure are based upon the most appropriate Agenc/-established health-based
levels.  The following levels should be used for setting closure target levels
in each medium:

    (1)  for all routes of exposure involving a drinking water scenario, use
Maximum Contaminant Levels (MCLs) established as drinking water standards under
the Safe Drinking Water Act (3CWA).  The Agency is in the process of proposing
and 'finalizino additional MCLs and will continue to do so over the next several
years;

    (2)  where no VCLs currently exist,  however,  the closure target levels
involving a drinking water scenario should be based on Reference Doses (Rfi?s)
for threshold contaminants, and Pisk Specific Doses (PSDs) for non-threshold
contaminants,  assuming a risk level of 1/1,000,000 for Class A and E carcino-
gens and 1/100,000 for Class C carcinogens;

    (3)  for routes of exposure involving direct contact with the soil surface
and direct soil ingestion,  closure target levels should be based on RfDs and
F5Ds,  as described above;

    (4)  for routes of exposure involving inhalation of chemical contaminants
or particulate natter,  the closure target level should be based on National
Ambient Air Quality Standards (^CVAOS)  where they exist; where no NAAQS exist,

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target levels based  on  RfDs  and RSDs should  be  used,  assuming an inhalation
route of exposure;

     (5)  closure target levels for  any  medium (soil,  air,  or water)  could be
based on  adverse effects  on  environmental  systems  or species;  where  such
environmental  effects are  potentially significant,  the closure target levels
should be  based on  Federally-approved  State  Water Quality  Criteria  (for
protection of aquatic species); the  assumption  is  made that a contaminant in
air, soil, or groundwater  in  addition  to surface water could  affect aquatic
organisms;

     (6)  under  certain  circumstances,  the  closure  target levels  based  on
Agency-established  human health standards (i.e., MCLs, RfDs, RSDs,  etc.)  may
be lowered.   Such circumstances  include:

         (a)  where  a mixture of  contaminants is  present  in  any  one medium
     resulting  in exposure to multiple  contaminants that could cause adverse
     effects  on  the  same human organs;

          (b) where  an  unusual exposure  scenario or  a vulnerable population at
     the site requires  a more  stringent  target  level;

          (c)  where levels necessary to  protect  an  aquatic  organism  or  other
     environmental  species or  system are  appropriate.

The Agency will  prepare additional  guidance  in the near future  to provide a
more precise  description of these and other  circumstances that would warrant a
lowering of  the  closure  target  levels.

     If reduction of  concentrations of   constituents to background  levels  is
used  as  a goal   to  be  achieved during  closure and post-closure  care,  these
levels  may  not be  appropriate for  conservative  metal  constituents.   If
immobilization  of metals is successful  in the treatment zone, then background
levels will  not  be achievable.   An alternative approach  may  be  to  use  the
suggested maximum concentrations  of  metals  that may be added safely  to  soils
that are given  in Tables 6.46  and 6.47 in Hazardous Waste Land Treatment  (U.S.
EPA  1983).   The concentrations,  based   on  literature  and  experience,   were
developed  using   microbial  and  plant  toxicity limits,  animal  health
considerations,  and  soil chemical properties that reflect the ability the soil
to immobilize metals.   Other pathways of exposure such as  ingestion,  however,
were not considered.

     Within  60 days  after completion  of closure, the  owner or operator must
submit to the Regional  Administrator  a  certification   that   the HWLT  unit  has
been closed in  accordance  with the approved  closure plan.   This certification
must  be  signed  by  the owner or  operator and by either an  independent
registered professional  engineer or  by an independent qualified soil scientist
(Sections 265.115  and  265.280(e)).  Within  60 days  after   certification  of
closure, the  owner  or operator must  also submit to  the local zoning authority
or to the authority  with jurisdiction over local land use,  and  to the Regional
Administrator,  a  record  of  the  type,   location,  and  quantity  of hazardous
wastes disposed of  at the unit (Section   265.119 (a)).   The  owner or  operator

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must  record,   in  accordance  with  state  law,  a  notation on  the  deed to  the
facility  property,  or  on  some  other  instrument that  is normally  examined
during  title  search,  that will  notify  any  potential  purchaser  of  the  property
that  the  land has been  used  to manage  hazardous  waste  and  that  its use  is
restricted under Subpart G regulations (Section 265.119  (b)).

      A  post-closure  permit will  be required  for  all  units that closed  after
January 26,  1983,  except where  a  unit satisfies the requirements of  Section
264.280  (e),'  i.e.,  no  hazardous  constituents have  migrated  beyond  the
treatment zone during  the active life  of  the unit,  and  there  are no hazardous
constituents  in  the  treatment  zone above background  levels   at  the  time  of
closure. Certification of completion of post-closure care must  be submitted to
the Regional Administrator within 60 days of the completion of the established
post-closure  care  period,  according to  the requirements given  in  Section
265.120.

1.4   GENERAL  INFORMATION ON HAZARDOUS WASTE LAND TREATMENT

      Land treatment is characterized in 40 CFR Section  265.272  (a) as  follows:
"Hazardous waste must  not be placed in or  on a land treatment  facility unless
the  waste can  be  made  less  hazardous   or   non-hazardous  by degradation,
transformation,  or  immobilization  processes  occurring  in or  on  the soil."
Degradation  of organic  hazardous  waste,  hazardous  waste constituents,  and
hazardous  constituents as defined  in 40  CFR Part  261  (i.e., Appendix  VIII
hazardous  constituents),  describes  the  loss of  parent  compounds  through
chemical  and  biological  reactions   within  the soil/waste  matrix.  The rate  of
degradation may be  established  by  measuring  the loss of  parent compound  with
time.   Degradation   and  detoxification  represent  primary mechanisms  for
assimilation  of organic  waste  constituents in a soil system.   Transformation
refers  to  the formation of intermediates  during  the process  of degradation.
Immobil zation refers  -~ the extent of retardation  of the downward transport,
or  leaching  potential, and  upward   transport,  or volatilization potential,  of
waste constituents.   Immobilization  is the primary  mechanism for treatment of
.hazardous  metals  in  soil- systems.    Immobilization of  organic  waste
constituents  allows for time for degradation processes  to occur.  The  mobility
potential  for waste constituents to  transport  from the waste to water,  air,
and soil  phases is  affected by  the relative  affinity of  the constituents  for
each  phase.    The  evaluation  of  soil treatment requires integration of  the
results of degradation, transformation, and immobilization processes for  waste
constituents of concern.

      At  a  HWLT unit, waste  is  generally  applied  to  the  surface and/or
incorporated  into  the soil. At  some HWLT  units, the  waste is  injected  below
the  surface  using  subsurface  injection techniques.  The zone of incorporation
(ZOI) represents the area and  depth over  which waste is  applied; generally the
ZOI  is  15-20 cm (6-8  in.) in depth.  The  treatment zone  includes the ZOI  and
the unsaturated soil  below the  ZOI  where treatment  is  achieved.  (In  Section
264.271  (c),  the  maximum depth of  the treatment zone  is  defined  as  1.5 m  (5
ft.)).   Loading rate  (amount  of waste  added per  volume of  land),  and  the
frequency  of waste  application  vary for each HWLT   unit, and are generally
functions of  the waste degradation  rate,  waste production rate, and climate.

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     Unlike  other  land  disposal  options  ,  including  landfills,  surface
impoundments,  and waste  piles,  where  wastes   are  contained  or  stored
indefinitely   or  for  future  disposal,  HWLT  units  are designed to accomplish
simultaneous  treatment  and ultimate disposal.  The objective of HWLT achieves
safe assimilation of  wastes  by  the treatment soil  through  the  processes of
degradation,  transformation,  and  immobilization.    Additional  information
concerning  the objectives,  functions,  and processes  operating  within  an HWLT
unit are provided  in Hazardous Waste Land Treatment (U.S. EPA 1983) and  in the
Permit  Guidance Manual  on  Hazardous Waste Land Treatment Demonstrations (U.S.
EPA 1986a).
                                     8

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                                 Chapter 2

               FACTORS IN ADDRESSING CLOSURE AND  POST-CLOSURE
2.1 INTRODUCTION

     To  achieve  the  objectives of  closure  and  post-closure,  the owner or
operator must provide  information  concerning  the type  and  amount  of hazardous
wastes  applied  to  the  HWLT  unit during  the   active life  of the  facility,
migration potential  of the hazardous  wastes and  hazardous  waste  constituents,
environmental  site conditions,  and waste  residue  characterization  in  the
unsaturated zone.

2.2  HISTORY OF  WASTE APPLICATION

     The owner  or operator of  a  HWLT  unit  should provide,  as  required in
Section 265.280  (b)  (1),  information  concerning  past  waste  management
practices.    Table 2.1  lists  suggested  important  waste  management data  and
records.  These records include available  history of  waste application  (i.e.,
application rates,  timing,  and  location)  and available history  of  hazardous
waste quality.                                                 	  .

2.3  MOBILITY AND  MIGRATION  POTENTIAL

     An assessment of  mobility and  migration  potential of  the  hazardous  waste
and hazardous waste constituents  at  the unit into environmental pathways of
exposure is necessary  to  address the objectives  of closure,  i.e.,  control of
migration of constituents  (Section 265.280(b)(2)).  Assessment  of  mobility and
migration  potential  is  also  necessary  in selecting  an   appropriate closure
method.

     The extent of  treatment  and  migration of  constituents from wastes  that
have  been  applied  to  the  HWLT  unit  may  be  assessed during  a  site
reconnaissance investigation as part of closure activities. Determination of
the potential  for future migration  of  constituents requires  information
concerning the  extent  of  immobilization and rate  of  degradation of
constituents as  affected  by  site/soil conditions.

     Migration  potential for  organic  and  inorganic  constituents  may be
evaluated  and  predicted  using  reconnaissance data  supplemented  as required
with  a combination  of  treatability  studies,  predictions  based on   known
characteristics  of  the  soil  and waste  constituents,  and  modeling using  the
approach  presented in  the Permit  Guidance  Manual on Hazardous Waste  Land
Treatment  Demonstrations  (U.S~!  EPA   1986a).    Refer  to  the Permit Guidance
Manual  on Hazardous  Waste Land  Treatment Demonstrations  (U.S.  EPA  1986a)  for

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            TABLE 2.1   USEFUL WASTE MANAGEMENT DATA AND RECORDS
Category
 Item
Specific Information
History of Waste
 Application
Years in service
 and annual  quan-
 tity of waste land
 treated

Placement of wastes
 on land treatment
 plots
History of Waste
 Quality
Waste Analyses
   Records of measured or
    estimated annual  waste
    quantity treated  over
    the 1ife of the unit.

   Records of quantity, date,
    and location of each waste
    application for each land-
    treated waste over the
    life of the HWLT  unit,
    including management
    practices used

   Analyses of each land-
    treated hazardous waste
    applied during the
    operating life of the
    unit.  (Non-hazardous
    waste analyses are also
    necessary if these
    wastes were land
    treated in the same
    plots as hazardous
    wastes.)
                                      10

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detailed information for  determining  migration  potential.   Prediction  of the
migration potential  of organo-metallic complexes present in waste residues at
closure  is  a difficult  aspect  of closure  to  evaluate at  the  present  time.
This  difficulty  is  directly  related  to  changes  in physical,  chemical,  and
biological  properties that  occur  as  a result of  the complexation  of organic
constituents with metal  species.   The resulting  organo-metal1ic  complex may
not have properties  that  are identified  with either  the  organic  fraction or
the metal  fraction.   It  is  important to  know  the structure of  the organo-
metal lie complex  in  order  to  predict  and/or  evaluate the  degradation  and
mobility potential.   Changes  in  either  the  organic  or  metal  fraction  may
result in drastic changes  in  toxicity,  persistence,  and/or mobility.

2.4  ENVIRONMENTAL SITE  CONDITIONS

     Sections  265.280  (b)  (3),  (4),  and (5)  require  the  evaluation  of
environmental site conditions of the HWLT  unit  as  they relate to  the control
of migration and transport of hazardous waste constituents to groundwater and
surface  water  and to  the control of the  release  of   airborne particulate
contaminants.    Specifically,  the   regulations  require  that  the following
factors must be evaluated:

     (1)  site  location,  topography, and  surrounding land use;

     (2)  climate,  including  amount, frequency,  and  pH  of precipitation;

     (3)  geological  and  soil  profiles;

     (4)  surface and  subsurface hydrology of the  s  ,e;

     (5)   soil  characteristics,  including  cation exchange  capacity,  total
organic carbon,  and  pH.

     Additional  soil  properties  that  are  important  in waste  treatment  and
mobility, at  HWLT units and.  should be assessed  include  soil  texture,  soil
mineralogy,  bulk  density,   particle density,  available  water  capacity,
porosity,  saturated  hydraulic  conductivity,  aeration status,  nutrients,
electrical  conductivity, - and  buffering  capacity.  Data concerning  any  other
soil  and site  conditions  that may be  required  as  input  to  the mathematical
model  for  land  treatment  systems  should also  be collected  if  predictive
modelling  is  used to  evaluate  migration  potential   and/or  to  choose  an
appropriate closure method.

     Guidance concerning  the use of site  data for prediction of transport of
hazardous waste constituents  from the  HWLT unit  may be  found  in Chapter  3 of
Hazardous Waste Land  Treatment,  (U.S.  EPA 1983), in Contaminated Surface  Soil
In-Pi ace Treatment Techniques  (Sims   et  al.  1986),  in the  Permit  Guidance
Manual on Hazardous Waste  Land Treatment  Demonstrations  (U.S. EPA 1986a).

2.5  WASTE  RESIDUE CHARACTERIZATION IN  THE  UNSATURATED  ZONE

     The purpose of waste residue characterization in the  unsaturated zone at
the HWLT unit  (Section  265.280  (b)  (6)   and  (7))  is  to  detect and  predict

                                     11

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migration of  hazardous  wastes and  hazardous  waste constituents  in  order  to
determine the effectiveness of  land  treatment during the  active  life of  the
facility and to  choose and  implement  appropriate closure methods.   Information
from waste residue characterization  may  also be used  in the mathematical model
for land treatment to assess potential migration  of residual  hazardous wastes
and hazardous waste constituents  (Section  265.280  (b)  (2)).

     Since  wastes  at  the  HWLT unit  do  not  exist  separately from  the
environmental matrix,  measurement of  waste characteristics must be  assessed  as
part of the soil  matrix,  and in  the  soil pore  liquid,  groundwater,  and surface
runoff.  Thus analysis  techniques will  usually  include  collection of samples
from the HWLT unit,  extraction/digestion  procedures  to  separate constituents
from the environmental matrix, and chemical  analyses  of the constituents. The
types of waste residue  analyses  recommended have  been categorized into three
groups, as shown  in Table 2.2.

     The analysis  of  specific characteristics or  constituents  to be measured
in  the  waste residue/soil   matrix should  provide  information  concerning the
potential   treatability of  a hazardous  waste  in a  soil  system  (e.g.,  pH,
nutrients,  electrical  conductivity),  and should include analyses that are  used
to  optimize the  performance  of  other  analytical  procedures   (e.g.,  oil  and
grease  content  affects  the extraction  and  analysis  of samples  for specific
organic constituents).   These analyses  have  been  designated  Type I analyses
(Table 2.2).

     Type II and  Type  III analyses (Table  2.2) are  concerned with  analysis for
specific hazardous waste constituents (i.e.,   the waste constituents for which
the waste was listed)  and  hazardous   constituents (i.e.,  additional Appendix
VIII constituents other than those for which  the  waste  was listed as hazard-
ous) in the waste residue/soil matrix. Since  EPA believes "it  is necessary  to
include  all  hazardous constituents   ...  to  ensure that all  contamination  is
adequately  addressed  at   closure"  (51  FR  16425),  it  is  recommended   that
hazardous constituents  be  analyzed   as well  as  hazardous  waste constituents
(see page 5 of this manual).  If  approved  by the permit writer, EPA may accept
analyses for a subset  of Appendix VIII compounds that  are "reasonably expected
to be  in, or derived  from,  the wastes to  be land treated"  (Section 270.20 (b)
(4)), when the wastes  handled  at  a facility  are from  an identified  process.  A
list  of Appendix VIII  constituents commonly found  in  petroleum  wastes  is
included in Appendix  A.  Similar  lists may be developed for  other industrial
waste processes  but should  be  approved by  the  permit writer and/or  EPA.

     Type II  analyses are  designed   to detect and monitor levels  of organic
constituents on  a routine basis  using sample extraction preparation techniques
and  gas chromatography  (GC)  and/or  high  performance  liquid  chromatography
(HPLC)  for  detection  of organic  constituents.   These analyses  are  used for
known constituents such as  those  for which a waste was listed as hazardous  or
those   listed  in  an  approved   subset  of Appendix  VIII  constituents for  a
specific waste type. The use of  Type II  analyses  allows  for the processing  of
larger numbers of samples at lower costs than  Type  III analyses.
                                     12

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                                                TABLE 2.2
                                    SUGGESTED ANALYTICAL  INFORMATION
                                              (U.S. EPA  1987)
Typo of
Ana I ys i s
PHI pose
                               Const ituenta
Media  to be Sampled
                                                         Soil
                                                           Zone of
                                                         Incorporat ion
                                                         Treatment
           Below
Soil-  Ground-
                                                         Zone Below  Treatment   Pore
                                                          Zone of      Zone    Liquid*
                                                       Incorporation
                              water
Type I. To provide infor-
I mat ion concerning
th<" Inni! trent-
ab i 1 i ty of a waste

* 2. To optimize other
.inn lyt ica I pro-
cedures





Oil and grease i
Total organic
carbon
Extractable
hydrocarbons* *
Total dissolved
solids or
electrical con-
ductivity (EC)
PH
Nutrients (nitro-
gen, phocphoruA,
potassium)
X

X

X



X
X


X
X

X

X



X
X



X

X

X



X
X



X

X

X X



X X
X X




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                   TABLE 2.2  CONTINUED

Type o
Analys
Type
H
f Purpose Constituents
is
To detect, monitor, Metals***
and quantify selected
constituents Constituents that
Media to be
Soil
i Zone of Treatment
lucorpornt ion Zone Below
1 Zone of
Incorporat ion
X X
Sampled

Below
Treatment
Zone
X

Soil-
Pore
Liquid *
X

Ground-
wdter*
X
 exceed  the  maximum
 concentration  listed
 in Table  1  of  40 CFR
 261.24  that  cause a
 waste to  exhibit EP
 toxicity  (Required)

Constituents  that
 caused  the  wastes to
 be listed as a hazard-
 ous waste (Required)

Appendix VIII organic
 constituents (40 CFR
 270.20) that are reason-
 ably expected  to be in,
 or derived  from waste
 placed  in or on the treat-
 ment  zone of a land treat-
 ment  unit (Recommended)

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                                          TABLE  2.2  CONTINUED

Type of Purpose
An n lysis




Type To identify and
lit quantify Appendix
V 1 [ t organic con-
«t 1 1 uetU s

Const ituents



-

Appendix V[[[
organic con-
st ituents and
intermediate de-
gradation products
Media to be
Soil
Zone of Treatment
Incorporation Zone Below
Zone of
Incorporat ion



X X

Sampled

Below Soil-
Treatment Pore
Zone Liquid




X X



Ground-
water





X

If selected sites have previously installed samplers.
If used as an indicator of amount of wastes applied.
Total concentrations and not EP toxicity data; if food chain crops are grown, analysis of arsenic, cadnum,  lead
and mercury required; analysis of all Appendix V11I metals reccrrrrended.

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     Type  II  analyses  also  include  the  detection of  metals  in  the waste
residue/soil  matrix by the use of  inductively  coupled  plasma (ICP)  or atomic
absorption (AA).

     Type III analyses are designed  to  identify and  quantify organic constitu-
ents using sample  clean-up and extraction  techniques  and gas chromatography/
mass  spectrometry  (GC/MS)  for  identification  and  quantification.   These
analyses  are  usually performed when  the  identity  and  levels  of  hazardous
constituents  are not  known.   They  are  also  used  periodically in conjunction
with Type II  analyses to  confirm the accuracy of Type II  techniques.

     All procedures used  to measure  constituents  should  be  those approved by
EPA or  should  be recognized standard methods.   Methods that may  be used for
analysis of  constituents  are  described in  Test Methods  for  Evaluating Solid
Waste,  Physical/Chemical  Methods,  SW-846 (U.S.  EPA 1987), in  the Guidance for
the Analysis  of Refinery Wastes (U.S. EPA 1985a),  in Standard Methods for the
Examination  of  Water  and Wastewater  (APHA 1985), Tri  Methods  for  Organic
Chemical Analysis of  Municipal and  Industrial Wastewater  (U.S.  EPA  1979), HT"
Characterization  of Hazardous  Waste   Sites,  A  Methods  Manual.    Volume 3:
Available Laboratory Analytical  Methods (Plumb 1984),and  in  Methods  of Soil
Analysis, Parts 1  and 2,  Second EditTon (Klute  1986,  Page 1982~TAdditional
information concerning specifically  the  analysis of  waste constituents at HWLT
units may  be  found  in  the Permit  Guidance Manual  on Hazardous Waste  Land
Treatment Demonstrations  (U.S. EPA 1986a).

     Unsaturated  zone monitoring,  including sampling  of soil core  and  soil
pore liquid,  is used to accomplish waste residue  characterization in the soil
system.

     Soil core  sampling   is used  to determine  the  type,  concentration,  and
depth of migration  of hazardous waste constituents in  the soil as compared to
background concentrations, as  required  in  Section  265.280  (b)(7).   Guidance
concerning soil core  sampling,  including  procedures and equipment,  depth of
sampling, area! distribution of sampling,  analysis of  soil  core sampling, and
interpretation  of  soil  core  sample data is  given  in  the Guidance  Manual  on
Unsaturated Zone  Monitoring for Hazardous Waste Land Treatment Units (U.S. ETA
1986b),the  Permit  Guidance Manual   on   Hazardous  Waste  Land  Treatment
Demonstrations  (U.S.EPA 1986a),in Preparation  of Soil  Sampling  Protocol:
Techniques and  Strategies  (Mason 1983),  and  in Soil  Sampling Qua!ity Assurance
User's  Guide  (Barth and Mason  1984).

     Soil-pore liquid  monitoring   is  intended  to  detect  rapid  pulses  of
constituents  that occur  immediately  after  significant  additions of liquids to
the  HWLT  unit.    Therefore,  the  timing  of soil-pore liquid  sampling  is
essential to  the  usefulness of this  technique (i.e., scheduled sampling cannot
be  planned on  a preset  date,  but  must be coordinated with  precipitation,
irrigation, etc.).   The use of several   types of soil-pore  liquid samplers is
recommended to enhance the  likelihood  of  obtaining samples.   Discussions  of
soil-pore  liquid  sampling are presented  in the   Permit Guidance  Manual  on
Hazardous Haste Land  Treatment Demonstrations (U.S. EPA  1986a)  and  in Permit
Guidance Manual  on  Unsaturated  Zone Monitoring  for  Hazardous Waste  Land
Treatment Units (U.S.  EPA 1986b).

                                     16

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     Information  collected  as  required  for  waste  residue  characterization
should be  representative of  the  waste residue/soil system.  Sampling  designs
should  provide  information of  maximum  reliability.    Statistical  plans
including knowledge  of the  expected  variability  and confidence  limits  of  both
the  analytical methods  used and  the sampling  designs  employed   should be
incorporated in the  closure plan.    It  is  recommended  that  the owner or
operator  secure the  services of  a  statistician  familiar  with  the design of
sampling  and monitoring studies to prepare the sampling plan
                                    17

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                                  Chapter 3

              METHODS FOR ADDRESSING CLOSURE BASED ON MOBILITY
                           AND  MIGRATION POTENTIAL
3.1  SUGGESTED CLOSURE METHODS

     In order to address the goal  of  closure and post-closure of controlling
the migration  of  hazardous waste  and  hazardous  waste constituents  from the
HWLT  unit  to the  environment  (Section 265.280  (a)),  Section  265.280 (c)
requires  that  at least  three  methods be  considered and  discussed by the
owner/operator in  the  closure plan.  These approaches include:

     (1)  removal  of contaminated soil  from  the land  treatment unit;

     (2)  placement  of a final  cover over the unit, such as a vegetative  cover
or a clay or synthetic cap;  and

     (3)  continued  groundwater monitoring.

     An additional method is also suggested  for. use-:..

     (4)  continued treatment  of  the waste residue  in the  soil  system, with
the use of treatment amendments and enhancements  as required.

     A combination  of  these'methods may also be considered.   Examples of such
combinations include:

     (a)   partial  removal  of contaminated  soil  (e.g., the  ZOI  soil) and
placement of a vegetative cover or  a cap  of  clay  or synthetic material;

     (b)   partial  removal   of  contaminated  soil, continuation  of treatment,
possibly using amendments to enhance  treatment,  and  placement of a vegetative
cover or cap; or

     (c)   no  soil  removal,  continuation of  treatment,  possibly  using
amendments,  and placement of a  vegetative cover.

     Additional  options not presented  here  may also  be used  if the control of
migration of constituents of concern can  be  achieved.

3.2  FACTORS TO BE CONSIDERED IN THE SELECTION OF A CLOSURE METHOD

     The selection  of  one of the four  options presented  in  this  guidance for
use  in  closure  requires  the evaluation  of  several  potential  sources  of

                                     18

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information,  including  information  collected from  the  reconnaissance
investigation of  the  unit,  environmental site  and soil conditions, laboratory
studies,  and/or  mathematical  modeTing  to  predict  potential  pathways  and
extent of migration.  The factors presented for consideration  in the following
sections  are not meant  to  be exhaustive  but  are indicative  of  the  types  of
information that  may  be  used  in  the choice of an appropriate closure method.

3.2.1  Selection  of Removal of Contaminated Soil as  a Closure  Method

     The  use of  soil  removal  should  be considered   if information concerning
mobility  and migration potential indicates that:

     (1)    unsatisfactory migration of  constituents  of concern  from  the unit
has occurred;

     (2)    environmental  site  and  soil  conditions (e.g.,  high precipitation,
low  evapotranspiration,   soils  of  high  permeability and/or  low  sorptive
capacity,  high  runoff  potential,  soil  considerations)   indicate  a high
potential for migration;

     (3)   the characteristics of residual  constituents (e.g.,  high volatility,
high  degree  of water  solubility,  high  concentrations)  indicate  a  high
potential for migration;

     (4)   the degree  of  hazard presented by the residual constituents suggests
that  the   contamination   should   be  removed  (direct  exposure
opportunity/potential effect on  post-closure);  and/or

     (5)   the results of the  use of the mathematical  model for land treatment
indicate  a high potential for migration.

     P'artval  removal"  of  contaminated soil  should be considered if constituents
with higher potential for migration and/or higher toxicity are concentrated  in
the upper- soil 1-ayers,  e.g., the ZOI.  Additional closure  activities  may  be
necessary to stabilize the new soil surface and control migration of remaining
constituents.

3.2.2  Selection  of a Cover Over the Unit  as a  Closure Method

     Two  types of covers, which act  to control  migration  in  different ways,
are  suggested  for  use.  In  general,  factors to be  considered in the  use  of
either type of cover, i.e., vegetative cover or capping, include:

     (1)    unsatisfactory  migration  of constituents  from  the  unit has  not
occurred;

     (2)    environmental  site  and  soil  conditions  (e.g.,   moderate  to  low
precipitation  and high  evapotranspiration,  soils   with  moderate  to  high
sorptive  capacity)  indicate a moderate to  low potential for migration from the
unit; and
                                    19

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     (3)   residual  waste constituents  are  at low  to  medium concentrations,
exhibit moderate  potential  for  transport  in percolating  water  or  in  air,
and/or are of low residual  toxicity;

     Specific  factors  that  should  also  be  considered  in  the  selection  of
vegetation as a cover include:

     (1)  a lower potential for migration to  groundwater exists such  that  the
primary purpose of  the cover would be  to minimize  direct  contact   and
inhalation of residual  constituents  and  to control erosion  and run-off; and

     (2)   there  may be potential  for continued  in-place  treatment of waste
residuals  in the-soil system during  the  post-closure period.

     The use of capping with clay  or synthetic materials should be evaluated
using the  following factors:

     (1)  migration of constituents  in percolating water  would be minimized or
eliminated if infiltration  were controlled;

     (2)   migration  of constituents to the  atmosphere  would be minimized or
eliminated  if  a cap were  used that  reduced  vapor  transport  or  particulate
windborne  erosion;

     (3)  the type of constituents present would  not present a greater threat
to human health and the environment under the anaerobic conditions  that would
likely develop  below  a clay  or synthetic cap (e.g.,  if cessation of further
treatment,  greater  mobility,  and/or  higher  toxicity  might result,  and/or
methane migration might occur);  and

     (4) waste(s)  and  waste(s)  constituents  would  be  isolated  from a direct
contact pathway.

3.2.3  Selection of the Use of  Continued Groundwater Monitoring
       as  a Closure Method

     The  use  of continued monitoring of the HWLT  unit  as it was operated
during the  active  life  of  the  facility  without  additional  closure  activities
should be  considered according  to  the following factors:

     (1)  no migration of constituents of concern has  occurred  from the HWLT
unit;

     (2)  there is  little or no potential for  future migration of constituents
from  the  unit,  as  indicated  by  site and soil   conditions, residual  waste
characteristics, laboratory studies,  and/or predictive mathematical modelling;
and

     (3)  there is  no danger from  direct contact with waste residuals.
                                     20

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3.2.4  Selection of Continued In-Pi ace Treatment  as  a  Closure Method

     Factors that should be considered in the selection  of  the use of  in-place
treatment as a closure method include:

     (1)  waste residues are capable  of  further  treatment  in the soil system;
and

     (2)  potential migration of waste residuals during the closure period is
low.

3.3  REMOVAL OF CONTAMINATED SOIL  AS  A CLOSURE  METHOD

     Complete or partial removal of contaminated  soils at the HWLT unit may be
used to eliminate or reduce the  source of contamination  at  the unit.

3.3.1  Description of Excavation and  Disposal

     Excavation  is  a common technique  used  in  earth-moving projects  and is
widely  used  to  move  solid and   thickened  sludge materials.  Excavation is
achieved  by  mechanical  means.   Typical  excavation equipment   includes
draglines,  backhoes,  earthmovers,  and  bulldozers.   The  hazardous  waste
contaminated soil  excavated from  an  HWLT unit  must  be  disposed  of  in  a
RCRA-approved hazardous waste facility.  Arrangements for disposal must be made
as part of the closure plan.

     Technical  guidance concerning excavation  technology and costs associated
with excavation, transportation  and disposal  are  presented  in the Handbook for
Remedial Action  at~Waste Disposal Sites  (U.S. EPA 1982a)   and  in  Liners for
Sanitary Landfills and  Chemical and  Hazardous  Waste  Disposal  Sites  (U.S. EPA
1978).

3.3.2  Advantages and Disadvantages of Excavation and Disposal
       to Completely Remove Contaminated  Soil

     The use of excavation  and  disposal  is  not  recommended  as the sole closure
method   for  HWLT  units  unless  there   is  a  severe potential for  migration of
hazardous waste constituents from  the  unit  or potential  for direct exposure to
toxic levels of hazardous waste(s) or constituents  following  closure.   Waste
residues left in the soil at HWLT  units may be  subject to further treatment in
the soil, however, to render them  less or  non-hazardous.   The availability of
space  in  another RCRA-approved facility for  the  large quantities  of  soils
associated with an HWLT unit may be limited and difficult to locate.

     However,  an advantage  to the  use of excavation and  disposal  as  a closure
method  is  that  if the  unit has  been  excavated to  such  a depth  so  as  to
completely remove the source of contamination,  it should therefore  present no
threat   to  human health and  the  environment,   and  activities  associated  with
post-closure care  may be  limited  under Section  265.118  (f).    However,  a
post-closure  permit  will   be  required unless  the  requirements of  Section
264.280 (e)  are met.

                                     21

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     Partial  removal  of  contaminated  soils  may reduce  the major  source of
constituents  with  a higher potential  for  migration from  the  unit  and/or a
higher degree of hazard from  direct  contact.   Additional  closure methods may
then  be  implemented to further  control expected  pathways of  migration of
remaining constituents.

3.4  ESTABLISHMENT  OF  A FINAL  COVER AS  A CLOSURE METHOD

     Two types  of covers  should be considered:   vegetative covers and clay or
synthetic caps.  Covers  are used to minimize  or  eliminate infiltration  into
the soil and to stabilize  the  soil surface.

3.4.1  The Use of Vegetation as a Final Cover

     The use  of vegetation  as  the  final  surface cover is highly recommended at
the  HWLT  unit  to  prevent  water  and  wind  borne  erosion  and  transport of
soil/waste materials,  to provide  infiltration  control  into the  soil,  and to
allow continued treatment  of hazardous  constituents.

     The vegetative cover  should  be  established at such  time  that the cover
will  not  impede  the  treatment of hazardous  constituents.    Since  certain
operating  practices to accomplish  and enhance  treatment,  such  as  tilling,
cannot be performed without damaging or destroying  the  vegetative cover, the
owner or operator  should  postpone establishing  the  vegetative  cover until
satisfactory  treatment has occurred following the  last  application of waste.
Results from unsaturated  zone monitoring,  treatment zone  soil  analyses, and
run-off monitoring  should  be  used  to  determine  the  degree  of treatment
achieved^..    Once  the  cover   is  established,  operating  practices  that are
inconsistent  (e.g., tilling)   with  establishment  and maintenance of  the
vegetative cover  should be  discontinued  (U.S. EPA 1983).  Long-term vegetative
stabilization generally  involves  the planting of grasses, legumes,  and shrubs.

     Technical  guidance  concerning the  establishment of  a  vegetative cover at
HWLT-  units may be   found  in Hazardous  Waste Land Treatment  (U.S.  EPA 1983),
Handbook for  Remedial  Action at Waste Disposal  Sites (U.S.  EPA 1982a), and in
Evaluating Cover  Systems for Solid and  Hazardous Vlaste (Lutton 1982).

3.4.1.L  Description of Vegetative Cover--

      In order to establish  egetation  at an  HWLT  unit,  the following factors
should be addressed in the  closure plan  (U.S. EPA 1983):

      (1)  Selection of species  adapted  for the site

      (2)  Seedbed preparation

      (3)  Seeding/planting

      (4)  Management practices  for cover maintenance
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     3.4.1.1.1  Selection of Species--

     The selection of suitable plant species for vegetating a closed HWLT unit
depends on cover  soil  characteristics and site  and  plant  characteristics,  as
shown in Table 3.1.

     Perennial grasses such as fescue that have dense root  systems that anchor
soil  and  enhance  infiltration  provide  a  quick  and lasting  ground  cover.
Legumes (e.g..., lespedeza,  vetch,  clover) fix nitrogen from  the  atmosphere  in
their roots,  enhancing soil  fertility and  assisting  the  growth of  grasses.
Shrubs  also  can  provide  a dense   surface cover.   A  mixture of plants  will
allow more efficient  use of  soil  moisture  and  nutrients  at various  depths.
Trees are generally planted in the later stages of revegetation,  after  legumes
and  grasses  have established  a  stable  ground  cover.   They help  to  provide
long-term protective  cover and build  up a stable,  fertile  layer of  decaying
leaves/branches.
     TABLE 3.1.  FACTORS FOR SELECTION OF PLANT SPECIES (U.S.  EPA 1982a,
                                U.S. EPA  1983)
        Site/Soil Characteristics
Plant Characteristics
          Texture
          Organic content
          Nutrient and pH levels
          Soil water content
          Climate
          Site hydrology (slope
           steepness and drainage
           characteristics)
 Ease of establishment
 Sensitivity to resi-
  dual waste constitu-_
  ents
 Tolerance to soil
  characteristics
 Ability to control
  erosion
 Productivity
 Ability to withstand
  competition with
  undesirable
  plants
 Availability of seed
  at reasonable cost
 Ease of maintenance
 Resistance to dis-
  eases and insect
  damage
 Water tolerance
 Suitability for
  future land use
 Desirable species
  (not noxious or
  poisonous)
                                      23

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     Information concerning  the  suitability of  specific  plant  species  for
revegetation of  HWLT units  are  presented in Table  3.5  in  the Handbook  for
Remedial Action  at  Waste Disposal  Sites  (U.S.  EPA 1982a),  in  Tabie 8.11  in
Hazardous Waste  Land Treatment (U.S.  EPA  1983),  and  in Tables  11, 12,  and  13
in Evaluating Cover  Systems  for Solid  and  Hazardous Waste  (Lutton  1982).

     Other  sources  of  information  are  highway cut  revegetation  standards
available from  most state  highway  departments  and  recommendations  from  the
Soil- Conservation  Serv-ice,  state  agricultural  extension  services,  and/or
agronomy departments at  universities.   In  some cases, plant  species may  be
used in  climatic zones  other than those recommended  if  special conditions
unique  to  the  HWLT unit  would  permit their  use,   e.g.,  when the  use  of
irrigation provides  additional moisture.

     The  use of food-chain  crops  for vegetating  an  HWLT  requires special
considerations,   as  given in  Section  265.276.   These  regulations must  be
followed  if  food-chain  crops are  to  be  grown.    Before  growing  food   chain
crops,  the owner or  operator  must  demonstrate,  based  on  field  testing,  that
any arsenic,  lead,  mercury,  or any constituent  that caused the  waste   to  be
listed  as a hazardous waste  will not be  transferred to  the food  portion  of the
crop by plant uptake or direct contact,  and will not be  ingested by food  chain
animals.  The owner or operator also must demonstrate that  these  constituents
will not occur in greater concentrations  in  crops grown on  the  HWLT  unit than
in  the  same  crops  grown  on untreated  soils  under  similar  conditions  in  the
same region.  If the wastes applied to the HWLT unit contain cadmium, special
requirements concerning  annual and  cumulative applications of cadmium must  be
met, as given in  Sections 265.276 (c).

     Selection  of suitable  plant  species for  HWLT  units that  have had  oily
wastes  applied may  be  difficult  because  at  this  time  there are  little  data
available on the revegetation of  these sites with perennial  plants.  Streebin
et al.(1984) prepared a literature review  on  the effects of  oily wastes  on the
growth  of  plants.    Problems  identified  for  plant growth  include phytotoxic
waste constituents  and   impaired water,  air, and  nutrient  relations.    The
authors recommended  that  research  be conducted to  identify and  develop  plants
that are tolerant to oily wastes.

     Because of possible  impacts that wastes  at  an HWLT unit may have on the
growth   of  vegetation,  the  use  of  a  demonstration  study  of selected  plant
species or  potential species  is  recommended.  The study  may be conducted  in
field plots  at the  site,  or a greenhouse simulation  study  may  be performed.
Possible protocols  for  conducting  these  types  of studies  are  presented  in
Field and  Laboratory Evaluation  of Petroleum Land Treatment  System Closure
(Overcash et al.  1985)."~

     3.4.1.1.2   Seedbed Preparation--

     Seedbed preparation   is  necessary to create a favorable environment for
the rapid germination and growth  of the planted  species.  The characteristics
of an adequate  seedbed  include:

     (1)  appropriate pH  level

                                    24

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     (2)  adequate nutrients

     (3)  freedom from live vegetation

     (4)  firm soil  below  seeding depth

     (5)  adequate  amounts of mulch,  plant  residues,  or chemical  stabilizers
on the soil  surface

     Applications  of lime  are  used  to  neutralize  acidic soils,  while
acidifying agents may be  added  to  soils  with  too high  pH levels.   Fertilizers
are  added  to provide essential  plant nutrients.   The  amount  of lime  or
acidifying  agents  and  fertilizers  required  should  be  determined from
site-specific  soil  tests-.

     Plowing  is  the  most  common  method  of  preparing  a seedbed  to  destroy
existing vegetation and to create  a  favorable soil  density.   Mulches or plant
residues are  added  to  the  soil  to  conserve  soil moisture,  dissipate raindrop
energy,  moderate soil  temperatures, prevent  crusting,  increase  infiltration,
and control  wind and water erosion.   Mulches may also  be used as  a seedbed  to
protect  seeds  from  injury from  volatile and  dissolved constituents  during
germination  and early growth.

     3.4.1.1.3  Seeding/Planting Program--

     The development  of  a successful  vegetative stand  also  depends  on   an
effective  seeding/planting program.  Elements of a seeding program  include:

     (1)  seeding/planting method

     (2)  seeding/planting rate

     (3)  seeding depth

     (4)  timing  of seeding/planting

     Seeding  should be  performed   as soon  as  possible  after  seedbed
preparation.   The most common methods  of  seeding   are  broadcasting and
drilling.   Drilling is usually preferred, since  seed/soil contact  is  important
for successful stand establishment.  The effectiveness of broadcasting  may  be
enhanced by following seeding  with  harrowing  or  discing to  increase  seed/soil
contact.  Hydroseeders may also  be  used, which  spray seed,  fertilizer,  mulch,
and lime at one  time.   However, phytotoxicity  of residual  waste constituents
may cause difficulty in  germination and  may require  the  use  of  mulches   to
protect seeds  and  developing  seedlings  from  toxic  constituents  in the
waste/soil  matrix.

     Hand  planting  may be required  for  trees  and  shrubs.   Until  trees have
recovered  from the initial  shock that planting causes their root systems, they
should  not  be  exposed to  oil  contaminated soils (Streebin  et al.  1984).   In
order to buffer  roots  from treated  soil  and  to  give trees time to  establish
themselves  oefore the roots  come into  contact with  contaminated soil,  a large

                                     25

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hole about twice the  size  normally  used  to  plant  the tree should be used and
filled in with uncontaminated  soil.

     The use  of a proper  seeding  rate  is  also critical to the establishment of
a vegetative  stand.    The  quantity of  seed applied depends  on  the  plant
species, the  method of seeding, and  waste/soil characteristics.

     Optimum  seeding depth  depends  on  seed size,  quantity of stored energy in
the seeds, and texture of  the  surface soil (U.S.  EPA  1983).    If  seeds are
planted too deep,  there may not  be  enough stored energy  to allow developing
seedlings  to  reach  the soil  surface.   Too shallow  seeding  may  result  in
desiccation of the seed.  Seed may be  planted deeper  in lighter-textured soils
than in heavier textured  soils.

     The optimum time for  seeding  is  dependent on  the  local  climate and the
requirements   of  the  individual   plant species.    Seeding/planting should  be
performed  under favorable temperatures and  soil  moisture  conditions.  For
perennial species,  early  fall  seeding  is  usually recommended (U.S. EPA 1982a).
Annuals are usually best  seeded  in  spring and early summer, although they can
be  planted whenever  soil  is  damp  and warm.    In mild climates  (e.g.,
southeastern   United  States)  the  planting of both  summer  and  winter grasses
will extend the period of time of active  growth at the site.

     3.4.1.1.4. Management  Program--

     A  management  program  of periodic  maintenance  should  be  established  to
ensure  the long-term  establishment  and functioning  of the vegetative  cover.
Periodic reliming and  fertilization may be  necessary  to maintain optimum
growth.  Soils with poor buffering capacity may  require  frequent  liming  to
maintain suitable pH  levels.   Periodic  fertilization  using appropriate
fertilizer formulations,  time of application, and method  of application will
also aid in revegetation- efforts.   Mowing and  the judicious use of selective
herbicides will  help control  undesirable weed  and  brush species.    Grass
sodding  and  remulching  or  planting new  shrubs  and  trees  is  recommended for
sparsely covered areas.

3.4.1.2  Advantages and Disadvantages  of  Vegetative Cover—

     An advantage of closing the  HWLT  unit by establishing a vegetative cover
is that  the wastes are left in place  and  continued treatment of  any remaining
constituents   can  occur in  the  soil  system.   Vegetation  will   also help  to
reduce  the potential  for transport of  hazardous  constituents from  the HWLT
unit by control of wind and water erosion and by evapotranspiration, which by
decreasing the amount of  percolating water, may  decrease the  transport  of
hazardous constituents to the  groundwater.

     However,   since the wastes are  left  in  place,  there  exists potential for
migration  into  the  environment.   There  also exists potential  for  uptake  by
plants and biomagmfication  through  the food-chain, and for future exposure to
humans  by  direct contact if  treatment  to levels below  toxic  levels  is  not
successful.


                                      26

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3.4.2  The Use of Capping as a Final  Cover

     Capping  is  the process  by which  an HWLT  unit  is  covered  to  prevent
surface  water  infiltration,  control  erosion,  and  isolate  and  contain  the
contaminated soil/waste mixtures at  the  unit.   A  variety of cover materials
and capping  techniques  are available for  use.   The  choice of an appropriate
capping material  and method  of application  is  dependent  on site-specific
factors,  including:

     (1)   local  availability and costs  of cover materials

     (2)    desired  function  of  cover  material  (e.g.,  control  of  water
infiltration, water  and wind  erosion  control,  crack  resistance, settlement
control and  waste  containment, side slope stability,  support of vegetation,
suitability for  future  site use)

     (3)   type and properties of waste/soil mixture being  covered

     (4)   local  climate and hydrogeology

     (5)   projected future  use of the site

     The  use of capping  at waste disposal sites is discussed in  the Handbook
for Remedial Action  at  Waste  Disposal Sites  (U.S. EPA 1982a),  in Design  and
Construction of  Covers  for  Solid  Waste  Landfills (Lutton et  al.  1979}.,  HI"
Evaluating Cover Systems for  Solid  and Hazardous Waste (Lutton 1982), and  in
the RCRA  Guidance  Document:  Landfill  Design, Liner  Systems  and  Final   Cover
(Draft) (U.S. EPA 1982b).	

3.4.2.1  Description of  Capping as  a  Closure Method--

       Soil  materials  used for  capping  an   HWLT  unit  must  be relatively
impermeable and  erosion-resistant.   Fine-grained  soils  such  as clays and  silty
clays  have  low  permeability  but  tend  to  be  easily eroded  by wind  if  left
exposed,  especially  in  arid climates.    Coarse,  heavy  grained soil  materials
provide more protection  from wind erosion,  but are  highly  permeable.

     Fine- and large-grained  soil materials may  be mixed  to enhance strength
of the soil cover,  minimize wind erosion, and  reduce infiltration.  Mixing may
be  accomplished  in  situ using a blade  or harrow to  turn and mix  the  soil
materials.

     Laboratory  and  field-testing  of  physical   and  chemical  properties of
potential  soil materials may be required  to choose  an appropriate material for
use as a  capping  material.   Technical guidance  concerning interpretation of
test results is  given in Lutton et  al.  (1979).

     Other techniques to  form  a  protective  cover  over an  HWLT  unit  include
adding amendments  to the native soil  or using  synthetic capping materials.   If
the unit  is  to  be closed  as  a hazardous waste  landfill,  the unit  should be
closed in  conformance  with guidance  provided in  the  RCRA guidance  document
(U.S.  EPA  1982b).

                                     27

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     Grading  techniques are  used  in  conjunction  with capping  to  modify
topography and runoff characteristics to control  infiltration and erosion.  A
discussion of grading and associated costs  are  presented  in  the Handbook for
Remedial Action  at Waste Disposal  Sites  (U.S. EPA 1982a).  The cap should  also
be vegetated to  stabilize the  surface of  the HWLT unit.

3.4.2.2  Advantages and  Disadvantages of  Capping--

     In general,  the-use of  capping  as  a  closure method for a HWLT unit is not
recommended.   HWLT  relies  on  aerobic soil  conditions  to  degrade  applied
hazardous waste constituents.   Conditions  under a  cap  are  likely  to  become
anaerobic, thus  inhibiting or  preventing  additional treatment that could occur
during  the  post-closure period.   Anaerobic  conditions    may also  favor  the
production of toxic compounds (e.g., methylation of mercury  and arsenic)  and
the mobilization of toxic metals.   The  use of capping,  however, may  be  more
appropriate if the unit  was  operated  as a landfill de facto.

     In  addition,  the cap  must  be  graded to  reshape  the surface  to  manage
surface water infiltration and runoff and re-vegetated to provide a stabilized
surface.  Caps also require  long-term maintenance and  care.  Unsaturated zone
monitoring must  also be  conducted  in such a manner  as  to ensure the integrity
of the cap.

3.5  CONTINUED GROUNDWATER MONITORING AS  A CLOSURE METHOD

     Groundwater  monitoring  provides a means for addressing  the objective of
control  of migration  (265.280  (a)) by  the owner/operator  of  a  HWLT  unit.
Monitoring data_can_be used  to make  changes in the closure and/or post-closure
plants).  BasecTon results of groundwater monitoring it  may also be necessary
to undertake corrective  action measurements at the HWLT site.   If constituents
are  present  in   groundwater monitoring  samples  at  trigger  levels  then
corrective action  measures  may be  necessary during  the  closure  or post-
closure period.   Therefore,  continued groundwater monitoring  provides  a means
for determining  appropriate  responses, if any are required, to ensure that the
objective of control  of  migration  is  achieved during closure and post-closure.

3.6  IN-PLACE TREATMENT  AS A CLOSURE  METHOD

     In-place  treatment technologies  may be  used  as  a  closure method  to
contain the source of contamination  (e.g.,  by immobilization)  or to remove it
through treatment  (e.g.,  by degradation).   Technical  guidance  concerning  the
selection  and  implementation  of  in-place  treatment  techniques  is  given  in
Review of  In-P1ace  Treatment  Techniques  for  Contaminated  Surface  Soils  (U.S.
EPA 1984).

3.6.1  Description of  In-Place Treatment

     In-place  treatment techniques may be  divided  into the  following
categories, defined in  terms  of  their  primary action on  the contaminants in
the soil:  immobilization, degradation,  and reduction of volatilization  (U.S.
EPA 1984).  These techniques include using  the  naturally occurring  capacities
of the soil to accomplish treatment, supplemented as required with  amendments

                                     28

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or management  and  operational  practices to  accomplish  the  desired  degree of
treatment.

     Immobilization  techniques  are  designed  to  retain  waste constituents
within  the  contaminated soil,  reducing  the  rate  of  migration  of  the
constituents to  groundwater,  surface  water,  or atmosphere exposure pathways.
Soil systems have  inherent capacities  for  immobilization  of both organic and
inorganic constituents,  but  if additional capacity  is required,  amendments may
be added to alter soil-properties  that  improve  the  immobilization capacity.

     Immobilization  includes  sorption,  ion  exchange,  and  precipitation.
Sorption  processes  are  important  in  the  immobilization of  both  organic and
inorganic constituents.   Organic matter, both naturally occurring in soils and
added in  the form of manures  and  other agricultural  by-products,  may  be used
for sorption of  waste  constituents.   Activated carbon may  also be  used as  a
sorbent, especially for  organics.

     Ion exchange is a process in  which minerals and resins  in  contact with a
solution release ions  in preference  for ions  of another type in the solution.
In  soils,  clays and  organic  matter participate  in ion  exchange  reactions.
Synthetic resins and zeolites  as well  as clay minerals and organic matter may
be added to enhance the  natural  capacity of the soil to remove constituents by
ion exchange.  Soil ptt  is also  important in  the  exchange  capacity  of  a soil.
Ion exchange is  important in  immobilizing  hazardous metals,  but  also may be
applicable to organic  constituents.

     Precipitation is  a process  in  which  inorganic  constituents that  are
initially soluble react  and  form  compounds  of  very low  solubility,  and are
thereby retained in the soil  instead  of being  removed  by percolating water.
Precipitating agents can be  added  directly t   the  soil  or generated  in-place
by a chemical or biochemical reaction.

     Degradation techniques  are used  to  convert waste  constituents into
innocuous or  less  toxic  compound or  compounds and  are  generally  applicable
primarily to organic constituents.

     Biological degradation utilizes the action of micro-organisms.  Naturally
occurring micro-organisms found in nearly  every soil system can often  degrade
organic constituents.  Promotion of biological degradation can be accomplished
by altering  selected soil properties,  such  as  moisture and  pH,  aerating the
soil,  or  adding  nutrients.    Addition  of  selectively adapted  or genetically
engineered organisms may enhance degradation  of some wastes.

     Chemical  degradation processes  include oxidation  reactions,  reduction
reactions, and  polymerization  reactions.  Naturally occurring reactions can be
enhanced  by  adding  additional  reagents  to  the  soil  system or  by  modifying
selected soil properties such  as soil moisture.

     Photodegradation  of organic constituents  can occur  by  the  action  of
incident  solar  radiation.   The organics must  be  present  or brought   to  the
surface of the  soil  (e.g., by  volatilization  or mechanical mixing of the soil)
for  this  process  to   be  effective.    Enhanced  photodegradation  may  be

                                     29

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accomplished through  the  addition of various proton donors to the contaminated
soils.

     Volatilization  of  constituents  from  the  HWLT  unit  may  require  control  to
reduce air emissions  or to retain constituents within the soil  system to allow
for other in-place treatment  processes  to occur.   Reduction  of volatilization
may  be   accomplished  by  reduction  of  soil  vapor  volume,  use   of
physical/chemical  barriers, and soil cooling.

     Design and  implementation  of   an  in-place  treatment  process  requires
information on characteristics of  the  soil/waste  system.   In  general,  these
types of processes are most applicable to soils contaminated to shallow  depths
and  are  only applicable to  waste constituents treatable  by the  specific
process.   Treatability  studies  of  a  specific process  using  the  waste
constituents of concern and the soils present at the  HWLT unit  are  recommended
to determine the  natural  capacity of the  soil system as well  as the capacity
of the  amended  or modified  soil system  to  achieve  a  satisfactory  level  of
treatment.

     After closure using  in-place treatment technology has been completed,  the
soil  surface  must  be stabilized  to prevent  water and  windborne erosion  and
runoff.

3.6.2  Advantages  and Disadvantages of In-Place Treatment Techniques

     In-place  treatment  techniques  allow for continued  treatment  of  waste
residues  in  the  soil system,  thus  reducing the  potential  for migration  of
these constituents to  the  environment.    Many  of the  techniques  are  easily
implemented and relatively inexpensive.

     However,  because the wastes are left in place, there does  exist potential
for  migration of,  as  well  as direct   contact with,  the waste  residues.
Long-term stability of many types if immobilized constituents has not yet been
well-defined,  especially  under changing  environmental conditions.  Degradation
processes may result in  intermediate products equally or more  hazardous  than
the parent compounds.
                                    30

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                                  Chapter  4

                          MANAGEMENT DURING  CLOSURE
4.1  INTRODUCTION

     In  addition to  the requirements  given  in  Subpart  G, Part  265,  which
includes the  continuation  of groundwater  monitoring  to ensure  that closure
performance standards  are met (Section  265.112  (b)  (5)), the owner or operator
of  an  HWLT~ unit must  continue  unsaturated zone  monitoring,  maintain run-on
control  and  runoff  management,  and  control  wind dispersal  of particulate
matter during the closure period (Section  265.280  (d)  (1),  (2), (3),  and (4)).

4.2  UNSATURATED ZONE  MONITORING

     The  owner  or  operator must  continue  unsaturated  zone  monitoring,
including soil pore liquid and  soil  core  sampling during  the closure period.
The purpose  of the monitoring  is  to  detect  vertical  migration  of  hazardous
waste and hazardous waste  constituents under  the  active portion  of the HWLT
unit  and  to  provide  information  on the  background concentration  of  the
hazardous waste  and hazardous  waste   constituents  in  similar but  untreated
soils.

    Results  of monitoring may  be  used to assess the effectiveness  of  the
selected method of  closure as  it is being  implemented. Monitoring  below the
treatment zone  will  indicate whether  constituents are migrating out  of  the
treatment zone.  Monitoring through  depth  within  the treatment zone  allows the
owner or operator to determine  the extent  of degradation and immobilization of
constituents.

     Soil-pore liquid  monitoring detects rapidly moving waste constituents, so
movement of these constituents  should occur soon  after  the  last application of
waste, depending on the  input of moisture  to the  site  (i.e., precipitation or
irrigation  at  the  site).   Therefore,   soil  pore  liquid  monitoring may  be
terminated 90  days  after the last  application  of waste to the treatment zone
(Section 265.280(d)(l)).   However,  it  is  recommended that soil  pore liquid
monitoring continue until three consecutive samples are free of statistically
significant  increases  of hazardous  constituents  over background   (U.S.  EPA
1983).

     The soil  pore and  soil  core  liquid  monitoring  system  used  during  the
active life of the facility should  be continued to be used during the closure
period.   Technical guidance concerning  unsaturated  zone  monitoring  may  be
found  in  the  Guidance  Manual  on Unsaturated  Zone Monitoring  for   Hazardous


                                     31

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Waste Land Treatment Units  (U.S.  EPA  19865),  and  in  The  Permit  Guidance Manual
on Hazardous Waste Land Treatment Demonstrations  (U.S. EPA  1986b).

4.3  RUN-ON AND RUN-OFF CONTROL

     Water control is required during the  closure  period of  an  HWLT unit  (Part
265.280(d)(2) and (3)), since water  may be  the  primary  means of transport of
hazardous  constituents  to  off-site  land  surfaces,  surface  waters,  or
groundwater.   Hazardous  constituents may either  be  transported as dissolved
substances or suspended  in  the water.   Water management is used to limit the
amount of water contacting  treated areas  and  to minimize precipitation run-off
from treated  areas.   Any precipitation run-off  is  collected for storage and
disposal.

     A  HWLT  unit undergoing  closure under  Part  265 should  already  have in
place an operating run-on control system  as  required  under Part  265.272(b) and
a precipitation  run-off  management system as required under Part 265.272(c).
Guidance  concerning  the design  and  operation of precipitation  run-on and
run-off  control  management  systems  may  be  found in Chapter  8 of Hazardous
Waste Land Treatment  (U.S.   EPA 1983),  and in J.  Skinner Memorandum, November
4, 1984, Management  of Precipitation  Runoff  from Land  Treatment  Units.

4.4  CONTROL OF DISPERSAL OF PARTICULATES

     Many hazardous  constituents  can  be tightly bound  to  soil materials.  .Soil
particles from  an HWLT  unit  can be  entrained  into  the air  and transported
off-site by wind,resulting   in human  exposure by  direct  inhalation.   Indirect
exposure  can  result  if  these particulates  are   deposited  in-agr-icul tural
fields,  pastures,  or waterways  and  thereby  enter  the   food-chain  (U.S. EPA
1985).

     Control of wind erosion may  be accomplished by reducing windspeed  on the
soil  surface  or  by  forming  a new,  less erodible  soil surface.   Technical
guidance design and  management of wind erosion control systems may be found in
Dust Control  at  Hazardous  Waste  Sites (Rosbury  1985)  and  in Hazardous  Waste
Land Treatment (U.S. EPA 1983).
                                     32

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                                  Chapter 5

                       MANAGEMENT DURING POST-CLOSURE
5.1  POST-CLOSURE REQUIREMENTS

     The owner or  operator  of the HWLT unit must develop a post-closure plan
that will identify activities that will be carried on after closure  to comply
with  the  requirements of  Section 265.117,  including  groundwater monitoring
requirements (Subpart F of Part 265) and specific requirements for HWLT units
in Subpart M, Section 265.280 (f).  During  the  post-closure care  period, which
may  extend  for  30  years after  the date  of completion of  closure  (unless
shortened according to Section 265.117 (a) (2)  (i)), the following activities
must be performed:

     (1)  ground water monitoring  must  be  continued  in accordance with Subpart
F of Part 265;

     (2)  soil  core monitoring must  be  continued;

     (2)   access  to  the-unit  must be restricted  as  appropriate  for  its
post-closure use  (Section 265.117 (c)).  Guidance concerning  site security  is
presented in Hazardous Waste Land  Treatment (U.S.EPA  1983);

     (3)  growth  of  food chain crops must comply with  the  guidance  given  in
Section 265.276;  and

     (4) wind dispersal  of  hazardous wastes must be controlled.

     Post-closure use of property  on or in  which hazardous wastes remain after
closure must never be  allowed to  disturb  the integrity of the final  cover  or
any  other  components of  the  containment  system  or   the  function of  the
monitoring systems (Section  265.117  (c)).

5.2  DURATION OF POST-CLOSURE CARE

     The  Regional  Administrator  may reduce  the post-closure care  period
specified in the post-closure plan if there is  evidence  that the  secure nature
of the  facility  indicates that post-closure  care requirements  may be reduced
or eliminated  (Section  265.117 (a)  (2)  (i)).   Such evidence  might include
leachate or  groundwater  monitoring  results.   The  Regional  Administrator may
also extend  the  post-closure  care period   if necessary  to  prevent threats  to
human health and the environment (Section  265.118  (a) (2) (i)).
                                      33

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     Additional  reasons  for  reducing  the post-closure  care  period might
include site conditions where threats to human health  and the  environment  from
the applied  waste  are  very low, i.e., there  is  low  potential  for migration
from the site.   Such  a site could include the following  characteristics:   deep
groundwater (e.g.,  greater  than  200  feet),   low  precipitation  and  high
evaporation  (e.g.,  desert  environment),  no  surface water  body  nearby,  soil
conditions  that are suitable for easy establishment of  volunteer vegetation,
little wind  action  to  prevent  dispersal  of airborne  contaminants,   and no
observation of  soil movement (e.g^,- soil  creep) during the closure period.
                                    34

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                                 REFERENCES


APHA.  1985.   Standard  methods  for  the examination of water  and  wastewater.
     Sixteenth edition.   American Public Health Association, Washington,  DC.

Barth, 0. S.,  and 8.  J.  Mason.   1984.   Soil sampling quality assurance  user's
     guide.    EPA-600/4-84-043,  Environmental  Monitoring Systems  Laboratory,
     U.S. Environmental  Protection Agency,  Las Vegas, NV.

Felmy, A.  R., D.  C.  Girvin, and  E.  A.  Jeanne.    1984.    MINTEQ-A  computer
     program for  calculating  geochemical equilibria.  EPA-600/3-84-032,  Athens
     Environmental  Research  Laboratory,  U.S.  Environmental  Protection Agency,
     Athens, GA.

Klute, A.  1986.   Methods of  soil analysis. Part 2: Physical and mineralogical
     properties.    Monograph  No. 9,  Soil  Science  Society  of America  and
     American  Society  of Agronomy, Madison, WI.

Lutton,  R.  1982. Evaluating cover  systems for  solid  and  hazardous waste.
     SW-867, Office of Solid Waste  and Emergency Response,  U.S. Environmental
     Protection Agency,  Washington, DC.

Lutton, R.,  G. Regan,  and L. Jones.   1979.  Design and construction  of  covers
     for  solid  waste  landfills.    EPA-600/2-79-165,  U.S.  Environmental
     Protection Agency,  Cincinnati, OH,

Mason, 8. J.  1983.   Preparation of soil  sampling  protocol:   Techniques  and
     strategies.    EPA-600/4-83-020,  Environmental  Monitoring  Systems
     Laboratory,  U.S.  Environmental Protection Agency, Las Vegas, NV.

Overcash, M. R.,  W.  L. Nutter, R. L. Kendall, and J. R. Wallace.  1985.   Field
     and  laboratory evaluation  of  petroleum  land  treatment  system  closure.
     EPA-600/2-85-134, Robert S. Kerr  Environmental  Research Laboratory,  U.S.
     Environmental  Protection Agency, Ada, OK.

Page, A.  L.  (Ed.).   *jQ2.   Methods of  soil  analysis. Part 2:  Chemical  and
     microbiological  properties. Monograph  No.  9,  Soil  Science  Society of
     America and  American Society of Agronomy, Madison, WI.

Plumb, R. H.,  Jr. 1984.   Characterization of hazardous waste sites  -  a methods
     manual:     Volume   III.   Available  laboratory  analytical  methods.
     EPA-600/4-84-038,  Environmental  Monitoring  Systems  Laboratory,  U.S.
     Environmental  Protection Agency, Las Vegas, NV.
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Rosbury,  K.  0.,  1985.   Handbook:  Dust  control  at  hazardous  waste sites.
     EPA-540/2-85-003,  Hazardous  Waste  Engineering  Research  Laboratory,  U.S.
     Environmental Protection Agency, Cincinnati, OH.

Sims,  R.  C.,   and  J.  E.  McLean.   1986.  Protection  of  Groundwater  by
     Immobilization of  Heavy Metals in Industrial Waste Impacted  Soil  Systems.
     Grant No.  14-08-0001-G-939-06, U.S. Geological  Survey, Washington, DC.

Sims, R.,  D.  Sorensen, J.  Sims,  J. McLean,  R.  Mahmood,  R.  Oupont,  and J.
     Jurinak.    1986.    Contaminated  Surface Soils  In-Place  Treatment
     Techniques.   Noyes Publications, Park Ridge, NJ.

Streebin,  L.  E,, J.  M.  Robertson,  A.  B.  Callender,  L.  Doty,  and  K.
     Bagawandoss.  '  1984.    Closure  evaluation  for  petroleum  residue  land
     treatment.    EPA-600/2-84-162,  Robert  S.  Kerr  Environmental Research
     Laboratory,  U.S. Environmental Protection  Agency,  Ada, OK.

U.S. EPA.   1979.   Methods  for  chemical  analysis  of water  and  wastes.
     EPA-600/4-79-020.   Environmental Monitoring and Support Laboratory,  U.S.
     Environmental Protection Agency, Cincinnati, OH.

U.S.  EPA.  1982a.   Handbook for remedial  action  at  waste  disposal sites.
     EPA-625/6-82-006,  Municipal  Environmental Research  Laboratory,  U.S.
     Environmental Protection Agency, Cincinnati, OH.

U.S. EPA.  1982c.  Test methods for evaluating  solid  waste:   Physical/chemical
     methods.   Second Edition.   SW-846,  Office of Solid Waste  and Emergency
     Response,  U.S. Environmental Protection Agency,  Washington,  DC.

U.S. EPA.   1983.  Hazardous  waste land treatment.   Revised Edition.  SW-874,
     Office of  Solid  Waste and Emergency Response, U.S.  Environmental
     Protection  Agency, Washington, DC.

U.S. EPA.  1984.  Review of  In-Place  Treatment Techniques  for  Contaminated
     Surface  Soils.  Volumes  1  and  2.    EPA-540/2-84-003a  and  b, Municipal
     Environmental Research-Laboratory, U.S. Environmental  Protection Agency,
     Cincinnati,  OH.

U.S. EPA.   1985a.  Guidance  for  the analysis  of refinery  wastes.   Office of
     Solid Waste and  Emergency Response, U.S. Environmental Protection Agency,
     Washington,  DC.

U.S. EPA.   1985b.   Petitions to delist hazardous  wastes:  A guidance manual.
     Office of  Solid  Waste and Emergency Response, U.S.  Environmental
     Protection  Agency, Washington, DC.

U.S. EPA.   1986a.  Permit guidance  manual  on  hazardous waste land treatment
     demonstrations.   EPA/530-SW-86-032,   Office of Solid Waste  and Emergency
     Response,  U.S. Environmental Protection Agency,  Washington,  DC.
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U.S. EPA.   1986b.   Permit  guidance manual  on unsaturated zone monitoring for
     hazardous waste land treatment units.   EPA-530/SW-86-040, Office of Solid
     Waste  and  Emergency  Response   U.S.  Environmental  Protection  Agency,
     Washington,  DC.

U.S. EPA. 1987.   RCRA  guidance  document:   Landfill design, liner systems and
     final  cover  (Draft).  Office of Solid Waste and Emergency Response, U.S.
     Environmental Protection  Agency, Washington, DC.
                                     37

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                                  APPENDIX A
            TABLE A.I.  CONSTITUENTS OF PETROLEUM REFINING WASTES
 1.  Metals

•  "  Antimony
    Arsenic
    Barium
    Beryllium
    Cadmium
    Chromium
    Cobalt
    Lead
    Mercury
 -   'Nickel
    Selen i urn
    Vanadium

 2.  Volatiles

    Benzene
    Carbon disulfide
    Chlorobenzene
    Chloroform
    1,2-Oichloroethane
    1,4-Dioxane--
    Ethyl benzene
    Ethylene dibromide
    Methyl ethyl ketone
    Styrene
    Toluene
    Xylene

 3.  Semi volatile Base/Neutral
    E'x tract able Compounds

    Anthracene
    Benzo(a)anthracene
    Benzo(b)fluoranthene
    Benzo(k)fluoranthene
    Benzo(a)pyrene
    Bis(2-ethylhexyl) phthalate
    Butyl  benzyl phthalate
    Chrysene
    Dibenz(a,h)acridine
    Dibenz(a,h)anthracene
    Dichlorobenzenes
    Diethyl phthalate
    7,12-Dimethylbenz(a)anthracene
    Dimethyl phthalate
    Di(n)butyl phthalate
    Di(n)octyl phthalate
    Fluoranthene
    Indene
    Methyl chrysene
    1-Methyl naphthalene
    Naphthalene
    Phenanthrene
    Pyrene
    Pyridine
    Quinoline

4.  Semivolatile Acid-Extractable
    Compound?

    Benzenethiol
    Cresols
    2,4-Dimethylphenol
    2,4-Dinitrophenol
    4-Nitrophenol
    Phenol
                                      38

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