24401-16
          BACKGROUND  DOCUMENT
                     i
 RESOURCE CONSERVATION  AND RECOVERY ACT

SUBTITLE C - HAZARDOUS  WASTE MANAGEMENT
              SECTION 3001 - IDENTIFICATION  AND  LISTING
                          OF HAZARDOUS WASTE?
             SECTION 261.24 - EP TOXICITY CHARACTERISTIC
                  ENVIRONMENTAL PROTECTION AGENCY
                        OFFICE OF SOLID WASTE

                             May 2,  1980

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     Index to Extraction Procedure Toxicity  Characteristic
     Background Document
                                                                    Page

 I.   Proposed Regulation                                              1

II.   Development and Rationale for the  Characteristic                 7

     A.  Need for Toxicity Characteristic                             7

     B.  Nature of Toxicity Regulated Under  the  Subtitle  C            8
         Regulat ions

     C.  Scope of the Toxicity Characteristic                         12

         1.  Aspects of Toxicity Outside the Scope  of  the             13
             Toxicity Characteristic

             a.  Chronic Toxicity of Wastes  Containing                13
                 Contaminants Other than those Included  in
                 the National Interim Primary Drinking Water
                 Standards

             b.  Careinogenicity                                      14

             c.  Mutagenicity                                         15

             d.  Teratogenicity                                       16

             e.  Chronic Toxicity to Fish                             17

             f.  Phytotoxicity                                        18

     D.  Major Postulates Contained in  the Characteristic             18

         1.  Choice of Groundwater Exposure  Pathway                  18

         2.  Choice of Particular Disposal Environment Model          20

             a.  Choice of Landfill Disposal                          20

             b.  Choice of Degree of Simulated Leaching  Activity     22

                 1)  The Leaching Simulation Test                     22

                 2)  Arguments That the Leaching Test  is  Overly      24
                     Aggres s ive

                 3)  Arguments That the Leaching Test  is              29
                     Insufficiently Agressive

             c.  Remaining Features of  the Waste Disposal Model      31

         3.  Thresholds to Determine Unacceptable  Levels  of          33
             Cont aminat ion

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                                                                Page

III.  Rationale for the Extraction Procedure                      37

     A.  Genesis of the Extraction Procedure                     37

     B.  Choice of a Batch Test                                  40

     C.  Maximum Concentration Versus  Cumulative  Release         41

     D.  Explanation of How the EP Models  Physical  Factors       43
         Which Influence Leachate Formation  in  the  Assumed
         Disposal Environment

         1.  Sample Preparation                                  44

             a.  Liquid - Solid Separation                       44

                 1)  Sample Filtration                           45

             b.,  Sample Homogeniz at ion/Part ic le Size  Reduction   47
                 (including Structural  Integrity  Procedure)

         2.  Leaching Media Composition                          52

         3.  Sample to Extractant Ratio                          56

         4.  Agitation Methods, Number  of  Elutions  and           58
             Extraction Contact Time

             a.  Agitation Methods                               58

             b.  Extraction Contact Time                         60

             c.  Number of Elutions                              63

         5.  Post - Extraction Sample Handling                   64

 IV.   Basis for Attenuation Factor Used in Relating National     66
      Interim Primary Drinking Water Standards  to EP  Extract
      Values

     A.  Attenuation of Constituent Concentrations  in Leachate   67

     B.  EPA's Choice of An Attenuation Factor                   75

  V.   Response to Comments Received on  the Proposal and on       81
      the Noticed Reports

     A.  Adopt Existing Regulations                              81

     B.  Suitability of EP As A Regulatory Tool                  84
                                  • •
                                  11

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                                                                   Page

          1.  Appropriateness as a General  Tool  for  Determining     85
              Whether a Waste is a Hazardous Waste

          2.  Acceptance by Scientific Community                    86

          3.  Reproducibility of Test Procedure                     89

          4.  Accuracy of Test Procedure                           103

          5.  Propriety of Requiring Excercise of Scientific       105
              Judgment

      C.  Failure to Distinguish Between Chromium III  &            109
          Chromium VI

      D.  Operational Problems                                     113

          1.  Liquid-Solid Separation Procedure                    114

          2.  Structural Integrity Procedure/Grinding              119

          3.  Agitation                                            123

          4.  Adjustment of Extract pH                             126

          5.  Sample to Extractant Ratio                           127

          6.  Final Volume Adjustment                              129

          7.  Analysis of Multiphasic Extracts                     130

          8.  Extract Toxicity                                     131

      E.  Economics of Testing                                     132

      F.  Specific Comments on the Noticed  Reports                 133

 VI.  Promulgated Regulation                                       148

VII.  Bibliography                                                 158
                              in

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I.  Proposed Regulation

    (1)  Definition

         A solid waste is a hazardous  waste  if,  according to

    the methods specified in  paragraph (2),  the  extract  obtained

    from applying the Extraction Procedure  (EP)  cited  below

    to a representative sample of  the  waste  has  concentrations

    of a contaminant that exceeds  any  of  the following values:

                                          Extract  level
    Contaminant:                        milligrams  per liter

      Arsenic   	     0.50
      Barium    	    10.0
      Cadmium	     0.10
      Chromium  	     0.50
      Lead	     0.50
      Mercury   	     0.02
      Selenium  	     0.10
      Silver    	     0.50
      Endrin (l,2,3,4,10,10-hexacloro-6,7-
        epoxy-l,4,4a,5,6,7,8,8a-octahydro-l,
        4-endo, endo-5,8-dimethanonaph-
        thalene)  	   0.002
      Lindane  (1,2,3,4,5,6 hexachlorocyclo hexane
        gamma  isomer)	   0.040
      Methoxychlor  (1,1,1-Trichloroethane)
       2,2-bis  ( p-methoxypheny )	    1.0
      Toxaphene (C  H  CL   - technical chlorinated
        camphene, 67-69 percent cholrine)	   0.050
      2,4-D,   (2,4-Dichlorophenoxyacetic  acid  	   1.0
      2,4,5-TP      (Silvex)          (2,4,5-
        Trich lorophenoxypropionic  acid	   0.10

      NOTE: - Extract  levels  specified for the above  substances
      equal ten times  the EPA National Interim Primary Drinking
      Water Standards  for these substances.   These  standards
      are being revised.  Extract  levels  specified  above  will
      be changed to reflect revisions  to  these standards.   Also,
      EPA is considering use  of the  Water Quality  Criteria  under
      the Clean Water Act as  a basis .for  setting  extract  levels,
      in addition to the  EPA National Interim Primary Drinking
      Water Standards.

      (2) Identification Method

      (i) Extraction procedure.  (2) Identification  method.
      (A) Take  a representative sample (minimum  size  100  gms)
      of the waste  to  be tested and  separate it  into  its
      component phases using  either  the filtration  method or
      the centrifugation method described in this  section.

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Reserve the liquid fraction under  refrigeration  at  1-5°C
(34-4l°F) for use as described  in  paragraph  (F)  of  this
section.

(1)  Filtration Method.

Equipment:  Millipore YY22 142  30  filter holder  (Millipore
Corp., Beford, MA, 01730) equipped with an XX42  142  08 necessary
1.5 liter reservoir, or Nuclepore  Corp., Pleasanton,  CA 94566)
equipped with a 1.5 liter reservoir,  or equivalent  filter holder.

     Procedure: 1. Using the filter holder place  a  0.45 micron
filter membrane (Millipore type HAWP142, Nuclepore  type 112007,
or equivalent) on the support screen.  On top  of  the  membrane
(upstream) place a prefilter (Millipore AP25124,  Nuclepore
P040, or equivalent).  Secure filter  holder  as directed in
manufacturer's instructions.

2.  Fill the reservoir with the sample to be separated,
pressurize to no more than 75 psi  (7  kg/cm^),  and filter
until no significant amount of  fluid  (o.5 ml)  is  released
during a 30 minute period.

3.  After liquid flow stops, depressurize and  open  the top
of the reservoir, invert the filter unit, replace filter pads
as in step 1. above, and resume filtering.   Save  pads for
later use.  Repeat this step until no more fluid  can  be removed
from the waste at a pressure of 75 psi (7kg/cm2).

4.  Take the solid material, and any  pads used in filtration,
and extract as described in paragraph (B).   Subtract  tare
weights of filter pads in calculating the amount  of  solid
material.

(2)  Centrifugation Method

Equipment:  Centrifuge (e.g. Damon-IEC catalog no.  7165,
Damon-IEC Corp., Needham Heights, MA, or equivalent)  equipped
with a rotor for 600 ml to 1 liter containers  (Damon-IEC
catalog no. 976, or equivalent).  For flammable material
containing wastes, explosion proof equipment is recommended.

Procedure 1.  Centrifuge sample for 30 minutes at 2300 rpm.
Hold temperature at 20-40°C (68-104°F).

2.  Using a ruler, measure the  size of the liquid and solid
layers, to the nearest mm (0.40 inch).  Calcuate  the  liquid
to solid rat io.

3.  Repeat 1 and 2 above until  the liquid: solid  ratio calculated
after two consecutive 30 minute centrifugations  is  within 3%.

4.  Decant or siphon off the layers and extract  the  solid as
described in paragraph B.

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(B)  Take the solid portion  obtained  in  paragraph  (i),  and
prepare it for extraction by  either grinding  it  to  pass
through 9.5 mm (3/8) standard  sieve or by  subjecting  it
to the following structural  integrity procedure.

STRUCTURAL INTEGRITY PROCEDURE

Equipment:  Compaction  tester  having  a 1.25  inch  diameter
hammer weighing 0.73 Ibs. and  having  a free  fall  of 6  inches
(Figure 1) (one suitable device  is the Associated Design  and
Manufacturing Company,  Alexdria, Va.  22314,  catalog  no.  125).

Procedure: 1.  Fill the sample holder with the material to be
tested.   If the waste sample  is  a monolithic  block, then  cut
out a representive sample from the block having  the dimensions
of a 1.3" dia. x 2.8" cylinder.

2.  Place the sample holder  into the  Compaction  Tester and
apply 15  hammer blows to the  sample.

3.  Remove the now compacted  sample holder and transfer it
do the extraction apparatus  for  extraction.

(C)  Take the solid material  from paragraph  (B), weight it
and place it in an extractor.  A suitable  extractor will  not
only prevent stratification  of sample and  extraction  fluid
but also  insure that all sample  surfaces are  continuously
brought into contact with well mixed  extraction  fluid.  When
oprated at greater than or equal to 40 rpm,  one  suitable  device
is shown  in figure 2 and available as Part No. 3736 produced by
Associated Design and Mfg. Co., Alexandria, Va.  22314)

(D)  Add  to the extractor a  weight of deionized  water  equal to
16 times  the weight of  solid material added  to the  extractor.
This includes any water used  in  transferring  the solid material
to the extractor..

(E)  Begin agitation and adiust  the pH of  the solution to 5.0+ 0
using 0.5N acetic acid.  Hold  the pH  at  5.0+0.2  and continue
agitation for 24+0.5 hours.   If more  than  4 ml of acid for each
gm of solid is required to hold  the pH at  5,  then once 4  ml of
acid per  gm has been added,  complete  the 24 hour extraction
without adding any additional  acid.  Maintain the extractant
at 20-40°C (68-104°F) during extraction.   It  is  recommended that
a device  such as the type 45-A pH Controller  manufactured by
Chemtrix, Inc. Hillsboro, OR 97123, or equivalent,  be  used for
controlling pH.  If such a device is not available  then the
following manual procedure can be employed.

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                      MANUAL  pH ADJUSTMENT

1.  Calibrate  pH meter  in  accordance with manufacturer's
specificat ions.

2.  Add 0.5N acetic  acid  and adiust pH of solution to 5.0 + 0.2.
If more than 4 ml  of  solution to 5.0 + 0.2.   If more than 4 ml
of acid for each gm  of  solid is required to  hold the pH at 5,
then once  4 ml of  acid  per gm has been added complete the 24
hour extraction without adding any additional acid.  Maintain
the extractant at  20-40°c  (68-104° F) during extraction. -

3.  Manually adjust  pH  of  solution at 15,-30, and 60 minute
intervals  moving to  the next longer interval if the pH did
not have to be adjusted more than 0.5 pH units since the
previous adjustment.

4.  Continue adjustment procedure for a period of not less than
6 hours.

5.  Final  pH after a  24 hour period must be  within the range
4.9-5.2; unless 4  ml  of acid per gram of solid has already
been added.

6.  If  the conditions of  5 are not met, continue pH adjustment
at approximately one  hour  intervals for a period of not less
than 4  hours.

(F)  At the end of the  24  hour extraction priod, separate the
material in the extractor  into solid and liquid phases as in
paragraph  (A).  Adjust  the volume of the resulting liquid phase
with deionized water  so that its volume is 20 times that occupied
by a quantity  of water  at  4° C equal in weight to the initial
quantity of solid  material charged to the extractor (e.g., for
an initial weight  of  1  gm, dilute to 20 ml).  Combine this
solution with  the  original liquid phase from paragraph (A).
This combined  liquid, and  any precipitate which may later
form, is the Extraction Procedure Extract.

(ii) Analysis  - Analyses  conducted to determine conformance with
Section 250.13(b)(l)  shall be made in accordance with the
following  or equivalent methods:

  (A)   Arsenic - Atomic Absorption Method, "Methods for Chemical
Analysis of Water  and Wastes," pp. 95-96, Environmental Protection
Agency, Office of  Technology Transfer, Washington, D. C.  20460,
1974.

  (B)   Barium  - Atomic  Absorption Method, "Standard Methods for
the Examination of Water  and Wastewater" latest edition, or
Methods for Chemical  Analysis of Water and Wastes, "pp. 97-98,
Environmental  Protection Agency, Office of Technology Transfer,
Washington, D. C.  20460,  1974.

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  (C)  Cadmium - Atomic Absorption  Method,  "Standard Methods
for the Examination of Water  and Wastewater",  latest edition,
or "Methods for Chemical Analysis of  Water  and Wastes".
pp. 101-103, Environmental Protection  Agency,  Office of
Technology Transfer, Washington, D.  C.   20460, 1974.

  (D)  Chromium - Atomic Absorption Method,  "Standard Methods
for the Examination of Water  and Wastewater",  latest edition,  or
"Methods for Chemical Analysis  of Water  and  Wastes",  pp.  112-112,
Environmental Protection Agency, Office  of  Technology Transter,
Washington, D. C.  20460,  1974.

  (E)  Lead - Atomic Absorption Method,  "Standard  Methods  for
the Examinations of Water  and Wastewater",  latest  edition,  or
"Methods for Chemical Analysis  of Water  and  Wastes", pp.  112-
113, Environmental Protection Agency,  Office  of Technology
Transfer, Washington, D. C.   20460,  1974.

  (F)  Mercury - Flameless Atomic Absorption  Method, "Methods
for Chemical Analysis of Water  and  Wastes,"  pp. 118-126,,
Environmental Protection Agency, Office  of  Technology Transfer,
Washington, D. C.  20460.

  (G)  Selenium - Atomic Absorption Method,  "Methods for
Chemical analysis of Water and  Wastes,"  p.  145, Environmental
Protection Agency, Office  of  Technology  Transfer,  Washington,
D. C.  20460, 1974.

  (H)  Silver - Atomic Absorption Method, "Standard  Method  for
the Examination of Water and  Wastewater," latest edition, or
Methods for Chemical Analysis of Water and  Wastes",  p. 146,
Environmental Protection Agency, Office  of  Technology Transfer,
Washington, D. C.  20460,  1974.

  (I)  Endrin, Lindane, Methoxychlor,  or Toxaphene - as
desribed in "Method for Organochlorine Pesticides  in Industrial
Effluents", MDOARI, Environmental Protection  Agency, Cincinnati,
Ohio, November 28, 1973.

  (J)  2,4-D and 2,4,5-TP  Silver-as  described  in "Methods
for Chlorinated Phenoxy Acid  Herbicides  in  Industrial Effluents,"
MDQARI, Environmental Protection Agency,  Cincinnati, Ohio,
November 28, 1973.

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               Figure 1
                            COMBINED
                            WEIGHT
                              .73 Lb:
                        •U5D
 /-SAMPLE
/  /-POLYURETHANE
L—^SAMPLE HOLDER
                  1.3D
                             28
                           1
   COMPACTION TESTER
ft  , '  •    -'
 Polyurethane foam shall conform to requirements
 for Grade 21, performance Grade AD or BD,
 established In ASTM Standard D3453.
                                                Figure 2
                                          NON CLOGGING SUPPORT BUSHING

                                      1 inch BLADE AT 30° TO HORIZONTAL
                                                                                                      vo
                                             EXTRACTOR

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II.  DEVELOPMENT AND  RATIONALE  FOR THE  CHARACTERISTIC

  A.  NEED FOR A TOXICITY  CHARACTERISTIC

           Subtitle C  of  the  Solid Waste  Disposal Act,  as

      amended by the  Resource Conservation and Recovery Act

      (RCRA) creates  a regulatory  framework for controlling

      the management  of hazardous  waste.   Section 3001  of RCRA

      requires the U.S. Environmental  Protection Agency (referred

      to herein as the Agency)  to  identify the characteristics

      of and to list  hazardous  wastes.   Those  wastes  so

      identified are  then  included in  the waste management

      control system  set  forth  in  Sections 3002 to 3006 and

      3010 of RCRA.

           This Background Document describes  the process by

      which  the Agency identified  and  defined  one such  charac-
                                            «

      teristic, the "Extraction Procedure Toxicity Characteristic",

      and presents the rationale,  assumptions, models,  and

      scientific studies  employed  in defining  the characteristic.

      This document also  discusses the  comments received on

      the proposed characteristic  and  the changes made

      in response  to  those comments.*   For clarity the  name

      for this characteristic has  been  changed from the

      proposed "Toxicity  Characteristic to the Extraction

      Procedure Toxicity  Characteristic in the final  regulations.
*The distinction  between  a  waste  which  is  hazardous because
 it possesses  the  characteris tic  of  toxicity,  and a waste which
 is listed  as  hazardous because  it meets  the criteria of toxicity,
 is explained  in  detail in  the background  document on Identifica-
 tion and Listing  of  Hazardous Waste.

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  B.   NATURE OF TOXICITY REGULATED  UNDER  THE  SUBTITLE  C REGULATIONS

           Section 1004(5)  of  RCRA  defines  a  hazardous waste as

      one that may:

           (A)  cause or significantly  contribute  to  an increase

                in mortality or  an  increase in  serious irreversi-

                ble, or incapacitating  reversible,  illness;  or

           (B)  pose a substantial  present  or potential hazard

                to human health  or  the  environment  when improperly

                treated, stored,  transported, or disposed  of,  or

                otherwise managed.

     The usual conception of "toxicity" certainly  meets this

standard.*  Furthermore, section  3001(a)  requires  that

toxicity be taken  into aeccount in determining which wastes

are hazardous.

     As used in these regulations,  "toxicity" includes a wide

range of hazardous effects.  Acute  toxicity upon exposure

is one such effect.  Toxicity  is  also used  to encompass the

specific properties of aquatic and  mammalian  chronic  toxicity,

carcinogenicity, mutagenicity, teratogenicity,  and  phytotoxicity.

Another property of toxicity deemed  of  regulatory  significance

is the potential to bioaccumulate in animal tissue  (see

section 300l(a)).  The following  properties of  toxicity are

of particular regulatory concern:
*Websterfs New Collegiate Dictionary,  for  example,  indicates
 that toxic is synonomous with  poisonous.
                               8

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      ~  serious harm  to humans  resulting  from long  term

subacute exposure to chemicals released  from  the  waste  (i.e.,

death, incapacitat ion,  cancer, birth  defects,  damage to  future

generations through changes  in the  gene  pool);

     -  serious diminution of  fishing resources resulting  from

contamination of surface water bodies; and

     -  serious harm to  agricultural  resources  resulting from

use of water contaminated by waste  management  practices  for

irrigat ion.

     These choices are  easily  justifiable.  In  addition  to

the obvious need to regulate wastes which may  result in  death

or incapacitat ion, wastes posing a  threat  of  carcinogenicity

are of special concern.  Chemicals  present  in  the  environment,
     *
combined with dietary  and societal  influences,  have  been

implicated in the high  incidence of cancer  in  humans.  In
order to lessen human  exposures  to  carcinogens, it is necessary

to handle  and dispose  of wastes  containing  significant quantities

of carcinogens in a manner appropriate for  hazardous materials.

     An additional danger from which  society  requires stringent

protection is exposure  to chemicals capable of  damaging

genetic material (i.e., mutagens).  As a recent review in  the

American Chemical Society's  Chemical  and Engineering News  stated:

     The relationship  between mutagenicity  and  carcinogenicity
     debated by many,  up to  90%  of  the chemicals  so  far  tested
     and identified as mutagens  in  one or more  short term
     tests are carcinogens as well.

     Cancer is only one consequence of genetic  mutation,
     but the tragedy of  its  human dimension attracts public
     attention.  Another potential  serious  threat  from
     mutagens may lie  in store for  future  generations:

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     the insidious accumulation of subtle,  irreversible
     mutations in the gene pool conceivably could have
     horrific consequences for the human race.   By  the
     time the effects of such mutations become  apparant
     it'll be too late. (1)

     Protection of the unborn fetus is another  important

goal of the hazardous waste program under RCRA.  In  order  to

lessen the likelihood of birth defects occurring as  a

consequence of improper management of waste materials,  it

is important to identify and regulate management of  wastes

containing teratogenic substances.

     Protection of fishing resources is also  an  important

goal of the hazardous waste program.  Fishing is both a

major source of income and food to many people  and  serves  an

important recreational purpose as well.

     Congress cited several instances of fish kills

in describing the types of substantial harm caused  by

hazardous waste mismanagement (2), indicating an intent  to

protect this resource from improper hazardous waste  management

Furthermore, the Act requires the Agency to consider and

protect not only "human health" but "the environment" in

determining which wastes are hazardous (section  1004(5)).

     Serious harm to fishing resources due  to mismanagement

of wastes can occur in two important ways.  Discharge of

toxic chemicals to waterways can result in  the  immediate

death of large numbers of fish.  This has occured many  times

during the past decade as a consequence, most notably,  of

transportation accidents.  A second, more insidious  threat,


                              10

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is posed by long term, low level discharge of chemicals to




surface waters via groundwater transport.  These chronic




exposures can interfere with growth and reproduction,




as well as cause death, and can lead to long term dis-




appearence of aquatic resources of a water body.  The




Agency believes it is important to regulate wastes posing




such a risk in order  to safeguard this important national




resource.
                               11

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     Protection of  agricultural  resources  is  an additional

goal of the hazardous waste  program,  inasmuch as  large amounts

of ground and  surface water  are  used  in the United States

for crop irrigation.  According  to  the  U.S. Geologic Survey,

          "The quantity  of water withdrawn for irrigation
          in the United  States,  Puerto  Rico,  and  the Virgin
          Islands  in  1975 was  estimated at 160 million acre-
          feet. ..   This  was  an average  rate of 140 billion
          gallons  per day, and the  water was  used on approxi-
          mately 54 million  acres of  farmland.   This represents
          an increase in water use  of about 10.9  percent
          over the  1970  estimate and  an increase  in acreage
          of about  9.4 percent."(3)

Plants often absorb harmful  materials from their  environment.

It is therefore extremely important,  given the critical

importance of  agriculture, that  the  sources of water available

for irrigation be  kept safe  for  this  use.   Furthermore,

human exposure to  waste  contaminants  may result from ingestion

of food-chain  crops exposed  to contaminated water.   Again,

the threat to  human health and the  environment is plain,  and

warrants regulatory protection.

  C.  SCOPE OF THE  TOXICITY  CHARACTERISTIC

      After identifying  the  various  aspects of toxicity  that  are

of concern, the Agency attempted to  develop a definition

for the "Extraction Procedure  Toxicity  Characteristic" which

would encompass all of these aspects.   Detailed discussions

of the approach employed in  attempting  to  develop such a

broad characteristic have been detailed previously in materials

made available to  the public.  (4,5,6,7)
                               12

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           However,  the  Agency  was  unsuccessful in developing

such a definition.   The  EP  Toxicity Characteristic promulgated

today is limited  to  wastes  which  present a hazard to human

health due to  propensity to leach significant concentrations

of those toxicants  for which drinking water thresholds have

been established.   It  should be noted,  however, that although

the EP Toxicity  Characteristic  regulates only those wastes

containing toxic  constituents for which National Interim

Primary Drinking  Water Standards  (8)  have been established,

other wastes may  still be regulated as  toxic via the listing

mechanisms under  §§261.31 through 261.33 of the regulations.

(1)  Aspects of  Toxicity Outside  the  Scope of EP Toxicity
     Characteristic

     (a^  Chronic Toxicity  of Wastes  Containing Contaminants
          Other  Than Those  Included in  the National Interim
          Primary Drinking  Water  Standards

           In  addition to the 14  substances for which National

Interim Primary  Drinking Water  Standards have been established,

there exist  thousands  of other  chemicals which possess a signi-

ficant toxicity.   The  Agency has  wrestled unsuccessfully with

the problem  of setting definitional thresholds for these diverse

potential toxicants.  While one possible approach was outlined

in the proposed  Part 250.15 delisting requirements, adoption

of this approach  was found  to suffer  from a number of problems,

principally  the  lack of  a recognized  means of setting a
                               13

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threshold to measure  these  compounds1  chronic  toxicity.




In addition, there  is  believed  to  be  insufficient  laboratory




capacity to analyze generators'  wastes  or  waste extracts for




the thousands of  toxic species  involved.   At  the present




time, therefore,  only  wastes  containing the  drinking water




contaminants are  within the scope  of  the  characteristic.




      (b)  Carcinogenicity




          A number  of  groups  are active in identifying chemicals




which are carcinogenic to humans.   EPA's  Cancer Assessment




Group has taken  the lead for  the Agency in evaluating




available information  in order  to  determine  which  chemicals




show  substantial  evidence of  carcinogenicity.




      The Cancer  Assessment  Group has  evaluated the available




information on a  large number of such  chemicals.  They have




concluded (10) that for approximately  150  compounds  the




information was  sufficient  for  the compounds  to be considered




suspect human carcinogens.




      This list was  not made part of the se1f-regulating  EP




Toxicity Characteristic because  of:




        a.  the  lack  of laboratory capacity  to analyze




             all  wastes for the  presence  and  concentration




             of  these  compounds, and




        b.   the  absence of the  necessary  dose-response




             and  mobility relationships with  which to derive




             general  waste  threshold  levels  which  would




             withstand scientific  challenge.
                               14

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     In addition to  doing  reasearch  on  methodology for specific




compound identification  and  quantification,  the  Agency is




conducting research  to develop  rapid,  inexpensive  biological




screening methods  to  identify wastes  containing  carcinogenic




materials.  However,  until  such  time  as  these  methods  are




available, the Agency will  identify  specific  carcinogen




containing wastes  through  the listing mechanism.






     c.  Mutagenicity




         There are a  variety of  mechanisms  by  which  chemicals




can act to cause damage  to  DNA.   A program  of  waste  control




aimed  at identifying  and eliminating  human  exposure  to such




materials requires rapid,  inexpensive  procedures  to  pinpoint




dangerous materials.   In response to  this problem,  a number




of rapid and  potentially inexpensive  bacterial and in  vitro




cellular tests have  been developed.   These  tests  are designed




to identify mutagenic substances  by  detecting  genetic  damage




in the test species.   Because of  the  variety  of  types  of




DNA damage that  are  possible, no  one  test is  sufficient to




identify all  mutagenic substances.




     Although test procedures of  this  type  are in  general




use for identifying  potentially  hazardous chemicals, the




Agency has decided not to  require their  general  use  by the




regulated community  for  two  reasons:




         (1)  Research to  date  has not  been  sufficient to




              develop and  validate experimental  methodologies
                               15

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              for using  these  tests  to  evaluate the potential




              hazard posed  by  wastes;




         (2)  There  is  significant  scientific uncertainty as




              to the degree to which such  screening test




              results  correlate with human toxicity.




     There are currently a  number  of large scale programs being




conducted to determine  the  applicability  and  validity of




short term mutagenicity  test  systems.   Foremost among these




are the International  Program  for  the Evaluation of Short-Term




Tests for Carcinogenicity,  the Genetox  Program and  the National




Toxicology Program.  The "International Program" is approximately




three years old, while  the  other two programs have  been underway




for about two years  and  one year respectively.   Detailed con-




clusions relative to the utility of  short-term tests  for




mutagenicity are not yet available.-




     The Agency therefore has  decided to  postpone use of such




tests pending the results of  further studies.  Wastes found  to




contain compounds posing a  mutagenic threat  to humans or the




environment will be  regulated  through the  listing mechanism.




     d.  Teratogenicity




     There are at present no  suitable testing methods capable of




identifying teratogenic  wastes.   Consequently,  in order to lessen




the likelihood of birth  defects occurring  as  a consequence of




improper management  of waste materials, the  Agency  will rely




in the listing mechanism to reach  such  wastes.
                               16

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     e'  Chronic Toxicity  to  Fish




     The Agency encountered  two  problems  in developing a




toxicity test  protocol  for protection of  fisheries resources.




The first of  these  problems  was  the selection and development




of a scenario  to relate waste management  to contamination of




surface waters  in which fish  live.   The second problem was




in then establishing  thresholds  to  determine what an unaccep-




table  level of  surface  water  contamination would be.




     While  a  possible solution to  the first of these problems




(i.e., relating disposal to  exposoure) was presented in the




December 15,  1978 Draft Toxicity Background Document (6), the




contamination  model did not  account for exposure occurring




through either  direct discharge  or  surface runoff.  In addition




to its incompleteness,  the model suffered from the fact that




the mixing  zone dilution was  not based on actual environmental




data.




     The second major problem relates to  the unavailability of




thresholds  analogous  to the  drinking water standards.   The




Agency currently has  a  program underway to develop water




quality guidelines.  These guidelines will reflect the Agency's




best scientific judgment as  to maximum levels of toxic species




in waters consistent  with  protection of the aquatic resources.




However, until  such time as  these  guidelines are available,




the Agency  does not believe  it is  in a position to complete




development or  propose  a toxicity  characteristic for protection
                               17

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of fishery  resources.   Thus,  identification of wastes posing




a significant hazard  to fish  will  be  made using the listing



mechanism.







      f.   Phytotoxicity




          Besides  not  having  threshold  values  to measure




chronic exposure  levels for  fish,  the Agency lacks  threshold




toxic  exposure  levels  for  plants  as well.  Thus, in order to




protect against harm  to agriculture resources, the  listing




mechanism will  be  used to  bring phytotoxic wastes into the




hazardous waste control system.




   D.  MAJOR  POSTULATES CONTAINED  IN  THE  CHARACTERISTIC




       As noted above, the Extraction Procedure Toxicity




Characteristic  is  limited  to  evaluation of the substantiality




of hazard to  human health  posed by leachable waste  constituents




for which National Interim Primary Drinking Standards exist.




The major postulates  underlying the characteristic, and the




reasons therefor  are  set out  below.




       1.   Choice  of  Groundwater Exposure Pathway




            For  wastes  defined as  toxic  by Section 1004(5),




the hazard  posed  by a  waste  is  dependent  primarily  on two




factors:



            a.   the intrinsic  toxic properties  of the constituents




                in  the  waste  (e.g., acute  toxicity,  chronic




                toxicity,  genetic  activity, bioaccumulation); and
                               18

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           b.  the propensity  of  the  constituents in the waste




               to migrate  from the  waste  during management and




               result  in environmental  exposure.




     The first factor,  the  intrinsic  hazard,  defines the actual




health effect posed by  the  waste  when exposure  to the public




or environment occurs.  For the compounds  identified in the




characteristic promulgated  today,  sufficient  toxicological




information  (i.e., National Interim Primary Drinking Water




Standards) was available for EPA  to determine not only intrinsic




toxicity but safe exposure  levels  as  well.




     The second  factor  was  not as  well  defined.   That is,  no




test procedures  were available to  relate  concentrations of




toxic species in a waste to migration into  the  environment




during waste management.   Therefore,  in order to  develop the




Extraction Procedure Toxicity  Characteristic, the Agency




found it necessary to  develop  a procedure  to  evaluate the




propensity of a  toxic  material present  in  a waste to enter




the environment  and result  in  human exposure.




     In considering the various exposure  pathways of concern,




the Agency concluded (not  surprisingly) that  the  most probable




ones were groundwater,  surface water,  and  air.   The  ground-




water pathway is believed  to be the most  serious  for a number




of reasons:




     (1)  Protection of groundwater from  leachate contamination




          was one of Congress1  principal  objectives  in enacting




          RCRA.  (2)






                               19

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     (2)  Grbundwater serves as a  source  of  drinking water for

          at least half of the propulation of  the  United States,

          and almost one-fifth obtains  drinking  water directly

          from groundwater wells.  (11)

     (3)  Once contaminated, groundwater  aquifers  tend to  remain

          contaminated for extended periods  of time  since  their

          renewal times are very long.

     (4)  Groundwater aquifer contamination  is difficult  to

          detect, particularly in  its early  stages.   Significant

          human exposure may thus  occur before remedial  action

          can be taken.

     (5)  Numerous incidents of groundwater  contamination

          resulting from improper  waste management have  actually

          occurred.*

2.   Choice of Particular Disposal  Environment Model

    a.  Choice of Landfill Disposal

     In considering the various forms of  industrial  waste

management likely to occur which would  lead  to exposure  via  a
*The prevalence of the problem of groundwater  contamination
 is illustrated by a 1977 study  (12) of 50  land  disposal  sites
 that had received industrial wastes.  At 13 sites,  the study
 was able to obtain evidence that organic chemicals  had migrated
 from the disposal site to groundwater, and that  organic
 contamination of groundwater had occurred.  Similarily,  at  30
 of the sites, inorganic contaminants were  found  to  have
 migrated to groundwater.  At 26 of these sites,  hazardous
 inorganic constituents in the water at one or more  monitoring
 wells was found to exceed the EPA drinking water  limits.
 This study is but one indication of the potential  for  groundwater
 contamination posed by existing waste management.   Other
 damage incidents are collected  in open files  of  the EPA  Office
 of Solid Waste, Hazardous and Industrial Waste  Division,  and  are
 in the Subtitle C rulemaking record.

                              20

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groundwater pathway (e.g., 1andfilling,  land  treatment,  surface



impounding, biological treatment),  landfill disposal  was



believed to offer the greatest potential  for  mismanagement.



The Agency reached this latter conclusion  after  considering



the following factors:



     (1)  Land disposal of wastes  results  in  the  concentration



          of toxic species into a  relatively  small  area,



     (2)  Concentrating waste into  a small area  results



          in the population exposed to toxicants  emitted  from



          the waste receiving a higher dose;



     (3)  Since the degree of harm  posed by exposure  to toxic



          chemicals is a  function  of the  level of exposure,
                                                         •


          concentrating wastes into a  small area  is potentially



          more dangerous  to human  health  and  the  environment;



     (4)  Leaching or leakage of toxic chemicals  present  in a



          waste disposed  of in a landfill  can result  in



          contamination of potable  groundwater supplies;



     (5)  Landfilling is  believed  to be  the most  prevalent



          waste disposal  method and therefore the method most



          appropriate for modelling;



     (6)  The Agency believes that  due to  the lower cost  of



          disposal, industrial waste not brought  under Subtitle



          C control will  likely be  disposed of along  with



          municipal trash and refuse in  landfills.
                              21

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      The Agency thus  concluded  that  since landfill disposal




appeared to be the most  common method  of  disposal and appeared




to present a great potential  for  groundwater degradation,




it would be the management  scenario  to model in these initial




regulat ions.




     • b.  Choice of Degree  of Simulated Leaching Activity




          1) The Leaching Simulation  Test




      After determining  that  the  toxicity  characteristic




should evaluate the potential hazards  posed  by improper waste




landfilling and subsequent  environmental  release via a




groundwater exposure  pathway, the Agency  next had to decide




how  to measure wastes' potential  to  release  hazardous constituents




to groundwater under  these  circumstances,  i.e.,  wastes' capacity




to leach hazardous constituents  if improperly landfilled.




The  key question thus  became  what degree  of  leaching activity




the  test should induce.




      In devising this test,  the  Agency was  guided by the




statutory definition  of  hazardous waste,  which commands




implicitly that any test to determine  hazardousness be aggressive,




since all wastes potent ially  capable  of causing substantial




hazard if improperly  managed  are  to  be regulated as hazardous.




At the same time, there  must  be  some  upward  limit on the




aggressiveness of a test, since  virtually  any substance can be




hazardous if sufficiently mismanaged  (for  instance, dumped




directly into a drinking water supply), yet  the statute doe




not  contemplate Subtitle C  regulation  of  all wastes.  The




Agency thus determined that a test which  simulates a degree






                              22
s

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of leaching activity  very  unlikely to occur in most waste

management practice  is  overly  aggressive.

      The leaching test, contained in the  characteristic,

known as the Extraction Procedure  (EP),  is designed to satisfy

these competing  considerations.   As  will be explained in

greater detail below,  the  test  assumes wastes will be exposed

to an acidic leachate medium with  pH of 5.  This leachate

medium tends to  leach waste  constituents (particularly

metals) relatively aggressively,  yet, as discussed below, is

not so aggressive  as  to simulate  a level of leaching activity

beyond that which  could realistically occur.

      The choice of  the leachate  medium selected was premised

on a specific  physical  model,  which  is described below.

Importantly, however,  the  Agency  believes  that the predicted

degree of contaminant concentrations in leachate could reasonably

occur in the course  of  most  waste  management, whether or not

the specific waste management  conforms to  this physical

model.

      The specific environment  contemplated by the Agency in

developing a leachate test is  an  improperly designed and

managed municipal  landfill.  This  type of  landfill generally

becomes acidic during its  lifetime at which time the degree

of leaching induced  is  relatively  high.*  The Agency's
*Specific  features  of  this  model  are,
      the  landfill  receives predominantly domestic refuse
or, if not domestic  refuse, material  with similar chemical,
biological, and  toxicological  properties  (i.e.,  only 5% of
the fill is industrial  in nature).
  —  the  character  of  the  leaching  fluid that the waste
will be exposed  to  is  predominantly  a function of the
nonindustrial material  in the  landfill.
                               23

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concern is that potentially  hazardous  wastes,  if not brought

within the Subtitle C  system,  may  be  sent  to  municipal land-

fills, with a resulting high level of  leaching activity and

environmental insult  if the  landfill  was  not  designed specifi-

cally to prevent migration of  leachate into  the environment.

This concern was shared by the Congress  in promulgating

Subtitle C:

             Even more  threatening are the present
             disposal  practices  for hazardous  waste  ...
             In many  instances these  hazardous wastes
             are disposed  of in  the same  manner and
             location  as municipal refuse  —  in the
             local  landfill. H.  Rep.  No.  94-1491,  supra,
             at 12.

These wastes' potential to cause harm  in  this  environment

therefore  should be evaluated.*

        2)  Arguments  That The Lea'ching  Test  is Overly Agressive

      A great many  comments  were received  attacking  this

portion of the  characteristic  as being overly  aggressive

because the commenters1 wastes are not placed  in municipal

landfills.  To  the  extent  that these  comments  stated only

that individual generators chose not  to  send  their wastes  to

municipal  landfills the comments are  misplaced since the

wastes may still potentially be  managed  in municipal landfills

(absent Subtitle C  regulation).
*A specific  discussion  of  how the  leaching test simulates
 municipal landfill  waste  management  conditions appears  later
 in this document.
                               24

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      Certain generators,* however,  stressed  that  their wastes

are not managed in municipal  landfills,  and  are  highly unlikely

ever to be so managed whether  or  not  the wastes  are  regulated

under subtitle C.  The Agency  remains  convinced ^that  the

degree of contamination indicated  by  the EP  is nevertheless

sufficiently predictive of what may  occur even in  purely

industrial waste management practice  to  be a  regulatorily

valid means of evaluating hazardousness  of these wastes.

First, even wastes such as these  may  reasonably  come  in

contact with mildly acidic leaching media (i.e., pH  of approxi-

mately 5) during their management  histories.  For  example,

waste acid streams are often  disposed  along with large volume

waste streams. (13)  Acid rainfall and water  passing  through

acidic soils may be other sources  of  acidic  leaching  solution.

Other wastes, although normally considered to be neutral or

basic, may contain acidic constituents which  can be  released

on contact with water or air  to create acidic leaching condi-

tions.  Many mining wastes, for example,  contain pyritic

sulfur, which upon exposure to air and rain  forms  sulfuric

acid, resulting in acidic leachate.   Other types of  improper
*Among these generators are a number of  large volume waste
 generators, such as electric utilities  and mining wastes.
                              25

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waste management may  also  result  in exposure of waste to

acidic leaching conditions.*

     Furthermore,  large  volume  wastes  may cause an equivalent

degree of contamination  even  if not subiect to acidic leaching

conditions.   The large volume of  waste present in the site

tends to lead  to increased toxicant concentrations.   This
                         \

effect comes  about  because the  water (e.g., rain) acting

on the waste  travels  through  a  larger  amount of waste before

entering the  environment.   The  leachate thus tends to become

saturated with  the  contaminants.   By contrast, in municipal

landfills,  the  small  volume of  industrial waste present

limits the  contact  time  in which  toxicants can act to

saturate the  leachate.

      The Agency therefore believes there is at least the

potential for  most  wastes  to  come in contact with an acidic
*A number  of  commenters  agreed  that  their wastes  could come
 in contact with  acidic  leachate  media  even though not managed
 in municipal  landfills,  but  argued  that  the acidic leachate
 would be  buffered  (i.e.,  neutralized)  to a greater degree
 than would acidic  leachate  in  a  municipal landfill,  which
 would in  turn  result  in  a lesser degree  of waste constituent
 solubilization.  The  degree  of buffering in particular waste
 management settings  is,  however, very  difficult  to quantify,
 and the Agency believes  its  leachate  test strikes a  reasonable
 balance.  The  test  in the first  instance uses  a  relatively
 mild acid and  further takes  buffering  capacity into  account
 by limiting  the  amount  of acid used in performing the extrac-
 tion.  In the  case  of wastes with high buffering capacities,
 therefore, the waste  itself  largely determines the leaching
 media composition.   The  degree of buffering predicted, while
 obviously not  precisely  accurate for  every waste management
 situation, is  believed  to be sufficiently representative for
 use in the protocol.


                              26

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leachate medium, or to  cause  equivalent  degrees  of contami-

nation, so that the wastes' potential  to cause harm if

improperly managed can  reasonably  be measured by assuming
         ©
the presence of acidic  conditions.   It  should be noted further,

that the Agency is not  legally  obliged  to model  precisely

the circumstances of  individual  waste  management sites,  or

classes of waste management sites,  in  making determinations

of hazardousness.  Not  only does  the statutory definition of

hazardous waste itself  afford the  Administrator  great  leeway,

but courts in other contexts  have  upheld national environmental

standards based upon  physical models which did not conform

precisely to physical circumstances  of  affected  facilities.

See, e.g., Sierra Club  v.  EPA,  540 F.2d  1114, 1136 (D.C.
                                                             
-------
established on the basis  of  a  "simplistic"  physical model is

upheld; use of the model  is  not  an  arbitrary or capricious

exercise of authority);   Hercules,  Inc.  v.  EPA, 598 F.2d 91,

104-106 (D.C. Cir. 1978)  (toxic  effluent standard for

toxaphene established  on  the basis  of  toxaphene's effect on
         /
an aquatic species not  found in  the receiving waters of the

sole discharger).*

     It should also  be  mentioned that  the phenomenon of

leaching over the life  of a  waste management facility is

incompletely understood,  and can be characterized legitimately

as "on the frontiers of scientific  knowledge .  .  ."

Industrial Union Department, AFL-CIO v.  Hodgson,  499 F.2d

467, 474 (D.C. Cir.  1974).   There is also no consensus  within
                                            »

the scientific community  as  to an appropriate short-term

extraction test to measure this  phenomenon.   Health-based

regulations addressing  such  areas of uncertainty  have tradi-

tionally been accorded  considerable judicial deference.

Hodgson, supra, 499  F.2d  at  474-76;  Ethyl Corp. v.  EPA,  541

F.2d 1, 24-29 and cases  there  cited (D.C. Cir.  1976, en bane).

Again, under these circumstances, some imprecision  in the

leaching test is not only acceptable,  but eminently justifiable

As the court stated  in  Ethyl Corp.,  supra;
*It should be noted  further  that  in  each  of  these  cases,
 the physical model  was  used  to  establish  a  quantitative
 discharge standard,  as  compared  to  the  present  situation
 where a model is used only  to make  a  screening  determinati
 of wastes which must be  regulated  to  ensure proper  management,
 a less precise undertaking.  This  situation is  consequently
 a fortiori from the  cited cases.
.on

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             Questions involving Che environment
      are particularly prone to uncertainty.   Tech-
      nological man has altered his world  in ways
      never before experienced or anticipated.  The
      health effects of such alterations are often
      unknown, sometimes unknowable.  While a  con-
      cerned Congress has passed legislation provid-
      ing for protection of the public health  against
      gross environmental modifications, the regulators
      entrusted with the enforcement of such laws
      have not thereby been endowed with a pre-
      science that removes all doubt from  their
      decision making.  Rather, speculation, con-
      flicts in evidence, and theoretical  extra-
      polation typify their every action.  How
      else can they act, given a mandate to protect
      the public health but only a  slight  or non-
      existent data base upon which to draw?
      Sometimes, of course, relatively certain proof
      of danger or harm from such modifications can
      be readily found.  But, more  commonly, rea-
      sonable medical concerns and  theory  long pre-
      cede certainty.  Yet the statutes—and common
      sense—demand regulatory action to prevent
      harm, even if the regulator is less  than
      certain that harm is otherwise inevitable.
      Ethyl Corp. , supra, 541 F.2d  at 24-25.
                        9
             3)  Arguments That the Leaching Test
                 is Insufficiently  Aggressive

      The Agency's proposed leaching test  (and the EP  Toxicity

Characteristic as a whole) was also criticized as being

insufficiently aggressive because the test was not "designed

on the assumption that the waste will be disposed of  in  the

worst possible environment."* As noted above,  however, the

Agency does not believe it is iustified, nor is it advisable

to base a determination of hazardousness upon  waste mismanage-
*Report on Hazardous Waste Disposal,  Subcommittee  on  Oversight
 and Investigations of the House Committee  on  Interstate  and
 Foreign Commerce, 96th Cong.  1st  Sess.  53;  see  also  Comments
 of Environmental Defense Fund, March  16,  1979,  pp. 9-10.
                               29

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ment assumptions  —  including  assumptions as to leachate

medium composition --  which  are very unlikely to occur in

practice.

     Moreover,  it  should  be  remembered that the Extraction

Procedure Toxicity Characteristic (of which the leaching

test is  a part)  is not the sole means of bringing solid

wastes within  the  subtitle C regulatory framework.   The

other mechanism,  listing  of  hazardous wastes, allows the

Agency to interpret  leachate data in a more individualized

way, and to  take  into  consideration additional factors, such

as  indications  of  actual  waste mismanagement or unusual

waste management  practices,  which are not measured  by the

characteristic.*   Thus,  the  Agency has not ignored  all

waste mismanagement  situations beyond the situation modeled
     »
in  the toxicity characteristic; it has chosen to take them

into account  in a  more individualized manner.

      The Agency  believes this "Course preferable to basing a

test upon an  assumption  of absolute worst-case mismanagement.

If  a generator's  waste fails the test, the waste is irrevocably

within the  subtitle  C  system.   In the Agency's view, this

requires some  safeguard  in the test against indiscriminate

overinclusion,  which overinclusion might result from a leaching
*See, for  example,  Listing  Background Documents for Chromium
 Pigments,  Secondary  Smelting and Refining of Lead, and Primary
 Smelting  and  Refining  of  Lead,  all of which list wastes which
 conceivably might  not  fail the  toxicity characteristic
 but still  pose  a  substantial potential hazard because of the
 presence  of additional factors  not evaluated by the extraction
 procedure.
                               30

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test based upon assumptions  of  unusually deficient waste

management.*  The Agency  therefore  chose what it regards as

a plausibly-occurring  type  of mismanagement  model on which to

base its leaching test  and  toxicity characteristic.

      c.  Remaining  Features  of the Waste Disposal Model

      Once a constituent  is  leached from the waste matrix,

there remains the question  of  its  environmental  fate:   does

the constituent have sufficient mobility to  pass through

soils and reach groundwater,  and if it  reaches  groundwater,

is It persistent enough to  reach environmental  receptors in

concentrations  sufficient to  create a potential  substantial

hazard.  In evaluating  these  considerations, it  is assumed

that disposal will  occur  in an  environmentally  sensitive

area, and that  waste constituents  will  undergo  some

attenuation in  both  soil  and  groundwater before  reaching

environmental receptors.   The  postulated features of the

hypothetical model  which  reflect these  assumptions are:

             — The  waste landfill  is situated  over  an
             aquifer that serves as the sole source  of
             drinking  water for a  significant number of
             people;

             — The  soil  below  the  site is composed  of
             material  with  limited  attenuative  capacity;

             -- Persons using  the  aquifer as a  source  of
             drinking  water are being supplied  from  wells
             which  are  situated 150 meters (500  feet)
             downplume  of the  disposal  site  and  draw
             water  from the plume  of contaminated water.
*By contrast,  a  listing  determination is  not  irrevocable
 since individual  generators  may  petition the Administrator
 to have their waste  delisted.  See  §261.39.
                               31

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As is discussed later  in  this  background  document,  a rate of




leachate constituent attenuation  is  then  projected  based




upon this model.




      As with the  leachate  simulation test,  a plausibly




occurring type of  worst-case mismanagement  is assumed.




With respect to the assumption that  disposal occurs in  an




environmentally sensitive area, no  other  assumption would be




warranted in light of  the statutory  mandate  to protect  against




groundwater degradation  (as well  as  to protect human health




and  the environment).  Obviously,  any characteristic must be




designed not only  to protect against mismanagement  occurring




in areas of relatively low  mismanagement  potential  but  also




in areas of high potential.  Indeed, the  assumption of  mis-




management in environmentally  sensitive areas was not seriously




challenged by any  commenter.




      The decision to  take  attenuation into  account also appears




to be both straightforward  and desirable.   There  is clearly




sufficient physical evidence of environmental attenuation for




the  Agency to assume that waste constituents will undergo




some degree of attenuation  before  reaching  environmental




receptors.  This type  of  approach  has in  fact been  adopted




by EPA in other environmental  programs, with judicial acceptance




See, e.g., Hercules, Inc. v. EPA,  supra,  598 F.  2d  at 115-17




(mixing zone factor used  in establishing  toxic effluent




discharge standard).
                               32

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      3.   Thresholds to Determine  Unacceptable Levels of
          Contamination

          The final major  assumption  contained in the toxicity

characteristic is the choice  of  thresholds  to  determine

unacceptable levels of contamination.   Obviously, if a test is

used to measure toxicity,  contamin'ant  concentrations in the

test extract need to be related  to a  numerical standard,  viz.,

what concentrations of what  contaminants  give  rise to a sub-

stantial potential hazard.   For  these  values  to be defensible,

they should be based on recognized human  exposure health

effect thresholds.

      When the Agency evaluated  the available  toxicological

information it was found  that  the  only available established

benchmarks for toxic contamination of  drinking water which

were both scientifically  recognized and which  address

chronic exposure were the  National Interim  Primary Drinking

Water Standards (NIPDWS).*  These  standards were developed

pursuant to §1412 of the  Public  Health Service Act as amended

by the Safe Drinking Water Act  to  protect  the  nation's supply

of potable water.  They reflect  the best  available scientific

information relative to safe  levels for 14  potentially toxic

species in drinking water.
*The current approach used  in  the  California  hazardous  waste
 program, which ha's been recommended  as  a  model  for  the Federal
 regulations (see, e.g. , Report  on Hazardous  Waste Disposal,
 supra  at 40), is not  based upon  contaminant thresholds,  and
 thus provided no guidance  in  developing such thresholds.
                               33

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      The comment was made  that  the  Agency should broaden the

coverage of the Toxicity Characteristic  by incorporating the

"Water Quality Criteria" in addition to  the Interim Primary

Drinking Water Standards.   As  was  described in the Proposed

Regulation, this approach was  initially  considered but

rejected.  The principal reasons  for not using the

criteria are:

      (1)  The unavailability  of  the needed guidelines,  and

      (2)  the lack  of  available  resources in the regulated

           community  to  implement  such  an approach if adopted.

      During the time regulations  under  section 3001  were being

developed, Water Quality Criteria  for the 65 pollutants  listed

as toxic under the Clean Water Act were  first being formulated.

The preliminary drafts  then available received substantial

negative comment from the scientific community, both  from

within and from outside  the Agency.   The Agency thus  believed

that it would be a long  time before  the  final Water Quality

Criteria were available, and further felt that it was inadvis-

able to delay proposal  of RCRA regulations until the  criteria

were available.*

      The second reason why use  of the Water Quality  Criteria
*As it turned out, the  first  group  of  criteria  were  eventually
 proposed on March 15,  1979,  a  full  three  months  after  the
 RCRA section 3001 regulations  were  proposed.   The  last of
 the 65 were proposed on October  1,  1979.   Final  promulgation
 of the first group is  presently  scheduled for  this  summer.
                               34

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was not believed  to  be  viable  relates to the insufficient




scientific resources  to implement  such a regulatory approach.




In order to implement  a self-determinative regulatory program




which requires  generators  to  test  all wastes for a list of




toxic species,  reliable,  standardized testing protocols are




required.  Secondly,  the  regulated community has to have




available to  it  sufficient testing capability (i.e. ,  in-house




or through contractors) to conduct the required tests.   At




the time the  section 3001  regulations were proposed,  and to




a great extent  still today,  such  reliable standardized  methodology




was not available.   Furthermore,  the personnel and laboratory




facilities to perform the  analyses that  would be required under




such a regulatory approach are not available.




      In summary,  the  Agency  believed the suggested approach




(i.e., expand the characteristic  by including threshholds




for the 65 toxics for  which  Water  Quality Criteria are  being




developed) was  impossible  to  carry out and thus the present




listing approach  was  adopted.   It  should also be emphasized




that the Agency  may  still  bring into the hazardous waste




control system  any wastes  that contain toxicologica1ly  signi-




ficant quantities  of any  of  the 65 toxicants for which  Water




Quality Criteria  are being developed by  listing specific




waste streams.   Many of the  waste  streams listed in today's




Federal Register  in  fact  are  based upon  the presence  of many
                               35

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of these 65 toxicants, as well as upon the presence of other




toxicants not included within either the list of Water Quality




Criteria pollutants or the pollutants measured by the Extraction




Procedure Toxicity Characteristic.
                               36

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III.   RATIONALE FOR THE  EXTRACTION PROCEDURE



      For purposes of  easier  comprehensibility of the following


discussion, a description  of  the proposed Extraction Procedure


(EP)  is given at  this  point.   The background document then goes


on to decribe the genesis  of  the EP,  the decision to use batch


tests in the protocol,  the issue of whether the test should


be designed to measure  maximum concentration or cumulative
           B
release of waste  contaminants, and the physical justification


for the various steps  of the  EP.


      The proposed EP  consisted of a series of steps.  First


a representative  sample  of the waste was obtained.   The solid


portion of the waste was then separated from the liquid por-


tion by means of  filtration and centrifugation.   Next,  the


solid portion was ground,  or  subjected to a compaction  force


test for structural stability, and placed in an extractor


where it was extracted  with water acidified with acetic acid.


This  mixture was  agitated  and extracted for a period of 24


hours.  At the end of  the  24  hours the mixture was  again


filtered and the  resulting liquid extract was combined  with


the liquid portion which was  originally separated out.   The


combined extract  was then  analyzed for its  constituent  contami-


nants.  If analysis revealed  that the extract contained NIPDWS


contaminants in concentrations greater than 10 times those


specified in the  National  Interim Primary Drinking  Water


Standards, the waste was considered hazardous.


      A.  GENESIS OF THE EXTRATION PROCEDURE


     When the Agency embarked on the  devlopment  of  a testing



                                  37

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procedure to  detect  wastes capable of leaching toxic consti-


tuents into groundwater,  there were no standard methods for


measuring the  leaching  potential of a waste.  For that matter,


the processes  governing the formation of leachate in landfills


were only partially  understood.  Accordingly, EPA initiated


two parallel  research  efforts  to develop a standardized testing


procedure to  measure leaching  potential.  The first was a grant


awarded to researchers  at the  University of Wisconsin in July 1976.


This study, referred to hereafter as the Ham study, was commissioned


to study the  process of leachate generation from landfilled wastes,


to evaluate the  factors which  influence leachate generation and to


develop a leaching  test suitable for .assessing the leaching chara-


acteristics of  such  wastes.  This study was completed in July 1978

                                                           «
and the results  published in a May 1979 report entitled Background


Study on the  Development  of a  Standard Leaching Test (14).


     The second  research  effort was a grant awarded to  the  Mitre


Corporation to  compile  information on existing leaching tests and


to evaluate the  usefulness of  these tests  in assessing  the  leach-


ing potential  of  a waste.   Work on this grant was  completed  in


February 1978,  and  the  results published in a report entitled


the Compilat ion   and Evaluation of Leaching Test  Methods  (15).


This report discussed the  environmental factors which influence


leachate generation  and evaluated 26  different leaching tests


for their utility in assessing the leaching characteristics


of a waste.    The Mitre  report  recommended  that EPA single


out for further evaluation the leaching test  developed  by  IU


Conversion Systems,  the leaching test  developed by the  State
                                  38

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of Minnesota, and  the  leaching  test  being developed by Ham, et.  al

at the University  of Wisconsin.   A study of these three tests was

conducted by Ham as an  adjunct  to his  other study and the

results published  in a  July  1979  report entitled Comparison

of Three Waste Leaching Tests  (16).

     While these studies  were  going  on, EPA — as a consequence

of the time constraints mandated  by  Congress for promulgating

the regulations — entered  into  an agreement with the Department

of Energy's Oak Ridge  National  Laboratory (ORNL) to conduct

research into the  toxicity  of  the extracts  or leachates

generated by the test  procedure  then under  development by

Ham.  It soon became apparent  that the extraction fluid

developed by Ham was too toxic  to permit its use in bioassay

tests to determine whether  toxic  materials  were leaching  from

the wastes.  EPA was concerned  because it wanted to be able

to assess the toxicity  of the  waste  leachate through bioassay

procedures as well as  through  analytical detection of the

leachate constituents.* [See the  Draft Toxicity Background

Document prepared  in support of  the  proposed regulations.(6)]

An additional concern  with  the  Ham test was that it might be

too site-specific.

     Consequently, in  the fall  of 1977, EPA modified the

agreement with ORNL to  allow work to be performed in developing

a leaching procedure suitable  for use  with  bioassays (although

still relatively agressive).   Relying  heavily on the work

already done by Ham and Mitre  and on the work done by other


*Although the finally  promulgated test does not provide for
 bioassay tests on the  waste extract,  EPA envisions possibl
 incorporation of  such  tests into the  EP in the fut —


                               39
        e
ure .

-------
groups, such as the American  Society for Testing and




Materials (ASTM), ORNL  assisted  the Agency in developing the




Extraction Procedure  set  forth  in the proposed regulations.






      B.  CHOICE OF A BATCH  TEST




          While a number  of  aspects of aspects about the EP,




as finally proposed,  were not settled until relatively late




in the development process,  some were settled early.  As




noted in the Ham study  there  are two general approaches  to




evaluating the  leaching potential of a waste:  (1)   a very




intensive study of the  leaching  characteristic of both the




waste and its desposal  or (2)  a quick test using standardized




procedures (14).  Clearly,  the  intensive study — which  is




very expensive  and takes  a great deal of time -- is  unsuitable




for use in the  laboratory regime contemplated by the Act.




Consequently, EPA decided early  on to utilize a short-term




standardized test as  the  device  for assessing the leaching




potential of a  waste.




     There are  two tvpes  of  short-term tests commonly used




to assess the leaching  potential of a waste:  (1) batch  or




shake tests and (2) column tests.  Batch tests are  performed




by placing a representative  sample of the waste to  be tested




in a container  along  with the leaching solution.  The mixture




is then generally agitated for  a specific period of  time and




the resulting elutriate or leachate separated from  the re-




maining solid and analyzed for  its constituents.  Such tests




are cheaper, faster and more  reproducible than column tests,
                               40

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but the test procedures must  be  carefully modeled upon actual

landfill conditions  if  the  information obtained is to be at

all meaningful.   Column tests are  performed by placing the

waste in a column  and passing the  leaching solution through.

Such tests can give  a better  simulation of landfill conditions

than batch tests.  However,  these  tests suffer from a number

of disadvantages,  including:

     --channeling  and nonuniform packing

     --unnatural  clogging

     --unnatural  biological  effects

     —edge effects

     --lengthy time  requirements for  running the
       test (months  to  years)

    .--lack of reproducibility  (17).

     In light of  the above  difficulties,  particularly the

lengthy time requirements  for running column tests,  EPA  chose to

employ a standardized batch  test as the means  for  assessing waste

leaching potential.

C.  MAXIMUM CONCENTRATION VERSUS CUMULATIVE RELEASE

    Ham considered it important  for a leaching test  to provide

an indication of  both the maximum  concentration of toxic con-

stituents likely  to  be  attained  in the  leachate and  the

cumulative release of toxic  constituents  from  the  waste  over

time (14).  EPA on the  other  hand, considers  the maximum

concentration of  toxic  constituents in  the  leachate  to be  the

factor  which primarily  identifies  the  environmental  hazard

presented by the waste.  This is because  the  concentration  of
                              41

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toxic constituents in the  groundwater  rather than the aggregate




quantities released thereto  determines  the  health hazard




posed by groundwater contamination,  although of course the




two are related.




     EPA also considers maximum  concentration to be more import-




ant than cumulative release  because  of  the  lengthy residence  time




of contaminants  in the  groundwater.   Unlike surface waters,  ground-




water is not continually  flushing  itself out; consequently,  the




aggregate contribution  of  pollutants is not as important as  in




surface water pollution.   Accordingly,  EPA  has structured the EP




so as to concentrate on the  maximum  concentration of contaminants




in the  leachate.
                                  42

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D.  EXPLANATION OF HOW  THE  EP  MODELS PHYSICAL FACTORS WHICH
    INFLUENCE LEACHATE  FORMATION IN THE ASSUMED DISPOSAL
    ENVIRONMENT

    The Extraction Procedure  is 4esisned to evaluate a waste's

capacity to release  hazardous  constituents to the environment

if the wastes are  improperly  landfilled in a plausibly

occurring manner,  and  to gauge the resulting risk of substantial

potential hazard.   It  thus  becomes important to identify and re-

plicate  reasonably the  principal physical processes and environ-

mental  factors  influencing  leachate formation and subsequent en-

vironmental  contamination.   These processes and factors include:

      (1)   Leaching medium composition;

      (2)   The amount of leachate medium to which the waste is
           exposed;

      (3)   Surface area, particle size, and composition of the
           material being leached;

      (4)   Contact time between  the  leachate medium and Che
           waste and;

      (5)   Attenuative capacity  of  the  soil and of the underlying
           aquifer.

 The operative aspects of the  extraction procedure (both the

 proposed and the final EP) —  i.e. , the aspects of the

 procedure which model these factors — are:

      (1)  Solid material particle  size reduction;

      (2)  Phase separation;

      (3)  Leaching medium  composition;

      (4)  Ratio of waste to extractant  (solid-
           liquid ratio);

      (5)  Aggressiveness of agitation;

      (6)  Waste-extractant contact  time;

      (7)  Assumed level  of environmental  attenuation.
                                   43

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     A full discussion  of  the  EP's  component parts and how

these parts relate to the  physical  processes which the EP attempts

to model is set forth in  the  following pages.
              ^
1.   Sample Preparation
                                                                 •

     a.  Liquid-Solid Separation

     Ham surmises that  after  a waste is deposited in a landfill the

solid and liquid components of the  waste will separate independent

of any leaching action.  (14)  The  liquid component of the waste  might

flow downward due to gravity,  be  absorbed by surrounding materials,

or flow away  from the waste by capillary action.   After separation,

only the solid material  left  behind will be subjected to leaching

action by available  leaching  media.

     EPA therefore believes that  it is most appropriate to  subiect

only the solid component  of the waste to simulated leaching.

Consequently, EPA has provided that the initial  step in the EP  is

to separate the solid and  liquid  components of the waste.   After

extraction, the extract  of  the solid is combined  with the  original

liquid phase  of the  waste  to  gauge  the full extent of potential

contamination posed  by  the waste.*   This step models  the situation
*EPA recognizes that  the  separation  of  liquid  and  solid  compo-
 nents in the waste will  depend  on site-specific conditions,
 and so might not occur invariably.   Nevertheless,  it  believes
 that utilization of  the  solid-liquid separation technique
 recommended by Ham is justified.  The  Agency,  as  stated,  is
 attempting to model  worst  case  conditions,  and separating
 the phases prior to  extraction  of the  solid phase  is  the
 more aggressive test.  Secondly, under this approach  liquid
 wastes would tend to be  rated as more  hazardous than  solid
 wastes containing the same concentration  of a  given  toxicant.
 This result is believed  reasonable  since  liquids  are  more
 mobile than solids and would tend to migrate  more  rapidly,
 and in a more concentrated manner than solids.
                              44

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                                  a
where the liquid portion  of  the waste separates from the solid
                                e
portion, flows downward  and  becomes absorbed onto other material in

the fill.  Later,  leachate  generated from the remaining solid

migrates downward,  displacing and mixing with the absorbed liquid

phase and carrying  it  into  the aquifer.

     1)  Sample Filtration

     The Agency considered  several techniques in performing the

solid-liquid  separation  step, including filtration, sedimentation,

centrifugation and  screening.  EPA considered filtration and centri-

fugation to be the  most  appropriate techniques and elected to make

filtration the final  step in the separation process, with centrifug

tion as  a supplemental aid  in separating wastes which cannot easily

be separated  by filtration  alone.

     The choice of  a  filter  pore size has an important bearing on

the ultimate  concentration  of toxic contaminants subjected to

analysis, because  the  filter operationally defines both the liquid

which is presumed  to  separate out from the waste and the leachate

which is produced  by  the  leaching process.  In conformity with

Ham's suggestion,  EPA  has selected a filter pore size of 0.45

microns  because particles larger than 0.45 urn are usually removed

by passage through  the soils, as indicated by the low suspended

solids content of  most groundwaters (14).  It is therefore not

unreasonable  to assume that  particles larger than .45 urn will be

filtered out  by the soil  and will not reach groundwater.
45

-------
     The separation  procedure can be described as follows.

If the sample is not  obviously a solid, an attempt should be

made to filter it  through  a 0.45 urn filter under a pressure

differential of <_  75  psi.   If clogging occurs, centrifugation

is employed as an  aid  to  the separation.  Pressure filtration

acts to accelerate  the filtration process without changing

the nature of the  separation.  Centrifugation is particularly

useful where the nature of the mixture is such that even

pressure filtration  would  require a large expenditure of

time.  Although at  the time of the proposal the Agency believed

that centrifugation  could  be used as a direct replacement for

filtration, later  information indicates that using centrifugation

alone results in a  carryover of particles greater than 0.45 urn.

Consequently, the  final regulation provides that centrifugation

is only to be used  as  an  aid to the filtration process.  After

centrifugation a final filtration must be performed to remove

particles greater  than 0.45 um from the liquid phase and remove

residual liquid from the  solid phase.   Anything that cannot be

readily separated  by filtration and centrifugation is considered

a solid and is subjected  to the leaching aspect of the test.*

     A number of commenters said they  encountered severe

operational problems  running the extract procedure on
*Such wastes might  include the thixotropic materials such as
 drilling muds  and  paints  which were found to cause difficulty
 during evaluation  of  the  separation procedure.   (17,18).  Since^it
 is reasonable  to assume  that  such wastes will not separate out in
 actual landfill conditions,  such wastes should  be treated as solids
 and extracted  without  separation.
                               46

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liquid wastes which contain  a  very low percentage of solids
                                             v*
(e.g., <1% solids).  To  accomodate this problem, EPA has

elected to amend the proposed  regulation to provide that a

sample which contains  less than  0.5% solids need not undergo

the leaching procedure.   Rather,  such a sample,  after filtra-

tion,  should be considered the extract and should be analyzed

directly fqr its toxic constituents.  (Filtration is necessary

because of the assumption that only particles  less than  0.45

urn in size will appear in the  leachate.)  This  change will

make the EP considerably  easier  to perform for  liquid wastes

with very low solids content,  while not appreciably altering

total concentrations of  toxic  constituents in  the extract,

since extractions performed  on the small amounts of solid

present in such solutions  are  not  likely to generate much  in

the way of toxic contaminants.*

           b.   Sample Homogenization/Particle  Size Reduction
                (Including the Structural Integrity Procedure)

     To insure reproducibi1ity of  the leaching  test performed

on the solid portion of  the  waste,  a homogenous  portion  is  required
*During evaluation of the separation  procedure  by  Ham, ORNL,
 and EMSL-LV, very few operational  problems  were encountered,
 although one potentially serious problem  has been noted by
 ORNL (6).   Preliminary work  indicates  that  the  filtering  of
 aqueous solutions containing polyaromatic hydrocarbons  (PAH),
 using either Millipore, type HAWP, or  Nuclepore,  polycarbonate
 membrane filters, results  in the solutions  losing a  substantial
 amount of  their PAH content.  If this  effect is found to  be  the^
 case generally for organics , it suggests  that  the non-polar  toxi-
 cants may  not show up in the extract in as  large  a concentration
 as  they might in the real  world.   Unfortunately,  the magnitude
 of  the problem is not yet  known and  further work  must be  done
 before attempting to remedy  the problem.  If a  solution turns
 out to be  needed it will be  incorporated  into  these  regulations
 in  the future.
                         47

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0
This can best be accomplished by reducing the particle size




 f the waste through  subdivision (e.g., grinding, cutting) —




a process which tends  to  equalize the surface area, geometry,




and other such properties  of the waste making up the sample.




As a general matter,  the  more finely ground the waste, the




more reproducible  the  test results are likely to be.  At the




same time, because  grinding increases the surface are which




comes into contact  with  the leaching medium, the finer the




waste is ground, the  higher the concentrations of contaminants




in  the extract.




     It  is difficult  to  gauge the extent to which reduction




of  waste particle  size duplicates actual landfill conditions.




The arguments  that  can be made on behalf of very fine grinding




include  the  fact that  wastes will eventually degrade in a




landfill, and  that  fine  grinding probably comes closest to




representing the saturated conditions which occur when the




leaching medium percolates slowly through a column of waste.




However, very  fine  grinding tends to yield results which are




probably not representative of wastes which have been treated




for the  purpose of  reducing the mobility of the toxic species.




A variety of these  treatment processes have been developed




—  including the incorporation of the waste into a solid




matrix,  the  encapsulation of the waste in an impervious




coating, and the addition of binders.  These management tech-




niques are designed expressly to prevent breakdown during




disposal and need  special consideration with regard to sample





preparat ion.






                                  48

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     To accomodate wastes  which  have been treated in an attempt to

reduce 'the mobility  of  the toxic species or naturally are in a

bound form, EPA has  promulgated  alternative sets of requirements.

Wastes which have not been subjected to cementing processes or are

otherwise not found  in  a monolithic or block form are required to

be ground or otherwise  subdivided such that they pass through a 9.5

mm (3/8 in) standard sieve.   This requirement represents a compromise

between the very  fine grinding specified by the tests being developed

by the states of  Illinois  (20) and California (21)  and the use of

a monolithic mass specified  by ASTM (22) and IUCS (15).*  Wastes

which have been subjected  to special encapsulation  or fixing processes

— and are thus monolithic in form — may instead be demonstrated

to be structually stable  and exempt from testing in a subdivided

form  through use  of  a special procedure called the  Structural

Integrity Procedure  (SIP).  The  SIP is designed to  be a moderately

severe approximation of the  disintegration that might be expected

if heavy equipment passes  over the waste.

      Mahlock et al (23) have determined that a compaction test

identical to the  procedure of ASTM D-698-70, but using only 15

hammer blows, simulates the  corapactive effort that  might be expected

from  passing earthmoving  equipment over a placed landfill.  Their
*A few commenters  complained  that  the requirement of passage
 through a 9.5 mm  sieve  is  insufficiently flexible because it  fails
 to accomodate certain waste  particles which fail to pass through
 the sieve yet exhibit a surface area equivalent to waste particles
 which do pass through the  sieve.   EPA has taken care of this  pro-
 blem by specifying  that the  waste either be passed through a  9.5
 mm (3/8") sieve or  have a  surface area equal to or greater than
 3.1
                                  49

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15-blow test uses a (5.5-lb) hammer  impacting on a (.0333  ft3)

cylinder of sample after  dropping  (12  in).   This apparatus  would

exert an impact of (165  ft-lb/ft3)  on  the  sample:


     v2 » 2 (acceleration of gravity)  (distance)

        = 2 (32.2 ft/sec2)   (1  ft)

        = 64.4 ft2/sec2
        Kinetic energy
        volume of sample
        1/2
m v
         (1/30)
        = (.5)   (5.5/32)   (64.4)
            .0333

        « 165  ft-lb/ft3


     EPA has decided  to  employ a  modification of this  procedure.

The procedure  selected  is  one  based on a scaled  down verion  of

Mahlock's 15-blow  compaction  procedure.   The scaled  down  procedure

uses a .32  Kg  (0.73  Ib)  hammer acting on a (0.0022  ft3) sample

with a (6-in)  free  fall.   This device (Figure 1) has approximately

the same compaction  action as  the larger unit,  as demonstrated  by

the equation below.
Kinetic energy
volume of sample
2 a x

(2) (32.2) (0.5)

32.2

1/2 m v2
(.0022)

(0.5)  (0.73/32)  (32.2)
       ( .0022)

165 ft lb/ft3
                                  50

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The sample size designated  by  this  procedure will be approximately

100 gms,  which corresponds  nicely with the minimum sample size

required  for extraction.  To  account for the cushioning or energy

dissipation resulting  from  the compressibility of surrounding

wastes, a resilient sample  holder has  been incorporated in the design

     Weeter and Phillips  (24)  evaluated this procedure  using a flue

gas dusulfurization sludge  fixated  by  the addition of varying

amounts of water.  Three  samples  were  used in an attempt  to repre-

sent a full range of unconfined compressive strengths.


                               Table 1

     Sludge                  Density              21 day UCSa
   Sample No.                (lb/ft3)               (lb/in2)
      A                         50                     81

      B                        120                    586

      C                        101                   1450a
a Unconfined Compressive  Strength


     When subjected  to  a  series  of blows  by the .32  Kg  (0.73  Ib)

hammer, sample A  cracked  throughout the upper half  of  the  cylinder,

and the bottom half  remained  intact.   The pulverized particles

formed in the upper  half  of  the  cylinder  seemed to  dissipate  much

of the energy exerted by  the  hammer after the third  or  fourth blow.

As a result, the  succeeding  blows had little effect  on  the remaining

structure of the  cylinder.   No  visible change in structure was

noted in specimens B and  C  after the  SIP  procedure.
                                  51

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0
     One shortcoming  of  the  SIP as  currently formulated is the lack




 f any measure of weatherabi1ity.   Wastes deposited in or on the




land will be subjected  to  the  effects of water,  freeze-thaw cycles,




and seasonal and daily  temperature  changes.   EPA intends  to explore




these factors to determine  if  a testing procedure can be  devised




which incorporates  these additional factors.






2.   Leaching Media Composition




     It has been demonstrated  empirically that  the leaching media




to which a waste is exposed, whether it be water, an acidic solution




or whatever, has an important  influence on the  ultimate concentrations




of toxic contaminants  in the leachate.   Consequently, the choice




of a leaching medium  (extractant)  has an important bearing on  the




aggressiveness and  ultimate  shape  of any leaching test.




     As was explained previously in this document, EPA chose to




model the leaching  medium employed  in the EP upon the leaching




medium  likely to be found  in an actively decomposing municipal




landfill.  This was based  on several considerations.  First,  given




the considerable uncertainty and lack of information concerning




the phenomenon of  long  term  leaching, as well as its statutory




mandate, the Agency believed it should  be reasonably conservative




in its  choice of a  leaching  environment to model.  Second, the




Agency  was convinced  that  most  categories of waste have the potent-




ial of  being disposed in municipal  landfills.  Third, the Agency




believed that even  wastes  which are unlikely to  be disposed of in




municipal landfills are  reasonably  likely to come into contact
                                  52

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with a mildly acidic  leaching  medium at some point in their

management histories.   Finally,  the level of leaching activity

predicted could also  occur  even  if acidic leachate was not

present.

     The following  discussion  explains how the composition of

the extraction medium simulates  leaching media which could be

present in municipal  landfill.

     There is ample evidence that pH of the extracting solution

is  the most  important factor in  modeling an expected level of

leaching activity relative  to  metal migration (14).*  Further,

the pH of the leaching media of  a decomposing municipal land-

fill  leachate will  generally be  acidic sometime during its

lifetime, due to  the  presence  of biodegrading refuse (14).

The Agency therefore  chose  an  acidic leachate composition,

consisting of an  acetic acid solution with a pH of 5.

     Acetic  acid  was  chosen because it is the most prevalent

acid  found in municipal landfill leachate (14).  The pH

value  selected  is well within  the reported ranges of pH levels

for municipal landfills,  as shown in the following table:
*0ther important  factors  include solution buffering capacity,
 complexing  capacity,  redox potential,  organic solvency and
 ionic strength  (14).
                                  53

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Table 2.  pH RANGES  REPORTED BY VARIOUS AUTHORS FROM

             LANDFILL  OR LITERATURE SURVEYS (14)
                                            pH
	Source	  Range	


Chianetal.                           3.7     -8.5


Steiner et al.                         4.0     -  8.5

                                           £/
Clark et al.                           1.5     -  9.5


Encom Associates                       3.0     -  8.5


Pohland                                4.9     -  8.4
ji/  Site  received  acidic industrial wastes.




     Furthermore,  the pH value selected promotes relatively


aggressive  leaching of elemental waste constituents, and so


furthers  the  Agency's statutory mandate of protection of human


health and  the  environment.


     Another  important physical feature influencing toxicant


concentrations  in  leachate is buffering capacity.  The ultimate


buffering capacity of real world leachates is a consideration


which has received little attention from the research community.


Data gathered at EPA's Boone County Field Site (25) over a


period of 7 years  indicates that the leachate generated by


decomposing municipal waste contains approximately 0.14


equivalents of  acidity per kilogram of dry refuse.  Applying this
                                  54

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data Co the hypothetical  disposal  environment  (containing 5%




industrial waste and 95%  organic  refuse),  EPA  concluded  that




1 gram of industrial waste  could  potentially be  acted  upon




by approximatley 2 milliequivalents  of acid.  Translating




this into the terms of  the  test,  EPA determined  that  it




should set a limit on total  acid  added to  the  extraction




solution of 2.0 mi 1liequivalents  of  acid  per gram of  solid




material or 4 ml of 0.5 N acetic  acid per  gram of waste




being extracted.




     Certain other chemical  parameters,  notably  extractant




convplexing capacity and redox  potential,  are not  incorporated




in the EP leaching medium (or  are  incorporated only  to a




limited degree).  However,  the Agency's  -.failure  to exactly




replicate municipal landfill  leachate is  not necessarily a




shortcoming.  The ultimate  regulatory objective  is not to




precisely model leachate  from  a municipal  landfill,  but  to




devise a protocol which is  reasonably predictive  of  ultimate




levels of leaching activity  of a  great variety of wastes.




EPA believes that the present  protocol largely achieves




this objective  relative to  mobilization  of metals and, to a




limited extent, organics, and  is  thus promulgating the EP in




the present form.  EPA  is studying this  issue  further, however




and if it appears that  the  protocol  requires modifications




in order to remain reasonably  representative,  appropriate




revisions will  be made.
                               55

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     The Agency is aware  of  one  potentially serious regulatory

deficiency in its choice  of  leachate medium composition.

Studies performed by ORNL demonstrate that EPA's leaching

solution (and Ham's synthetic  solution)  are deficient in

their ability to adequately  model  the organic solubilizing

ability of real world  leaching media (7).*  Since the charac-

teristic is at present  designed  principally to evaluate

leaching propensity of  elemental,rather  than organic

contaminants, this deficiency  is  not deemed severe enough to

warrant additional delay  inplementing the  characteristic.

EPA is, however, working  to  develop a leaching media which

reflects more accurately  wastes'  capacity  to leach organic

toxicants .

3.   Sample to Extractant Ratio

     The solid-liquid  ratio,  that  is, the  ratio of the quantity  of

solid waste to the quantity  of leaching  solution used, can be  an

important factor in assessing  the  leachability of a waste,  since

the greater the amount  of waste  present  in the liquid, the more

toxic species there are to be  dissolved  and the higher their

concentration.**


*This is probably attributable to  the failure of EPA's
 leaching solution and  possibly  Ham's as well to include
 species such as fatty  acids,  alcohols and humic acids which
 have a great deal of  organic  character  (7).

**This dependency of concentration on solid-liquid ratio  is
  particularly characteristic  of  species whose concentration
  is not controlled by  a  solubility equilibrium.   On the  other
  hand, where the concentration  of the toxic  species is control-
  led exclusively by solubility  equilibrium,  the concentration
  of the species will not  vary with the  solid-liquid ratio,
  although Ham's experience  suggests that  there are very  few
  such species (14).

                               56

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      A high solid-liquid  ratio  is  probably better representative
              «

of actual landfill conditions,  inasmuch as the solid-liquid


ratio encountered by  a  drop  of  leachate percolating through a


landfill is likely to be very high.   In addition,  a high


solid-liquid ratio is more likely to reflect the maximum


attainable concentrations  which  are  the principal  focus  of


EPA's concern.  At the  same  time, a.  high solid-liquid  ratio


can cause difficulties  with  stirring or separation and can


cause the system  to  become saturated with readily  soluble


salts -- with the result  that  the less  soluble but more  toxic


species are left  behind in the  waste.   A low solid-liquid


ratio will promote greater ease  of  operation but will  tend to


magnify sampling  and  analytical  errors.


      After considering the  above factors,- EPA has elected to


use a 1:20 solid-liquid ratio.   EPA  believes this  ratio  will


attain reasonably high  concentrations  while preserving


operational precision.   Furthermore  the ratio selected is


well within the bounds  of  the  ratios used in other comparable


leaching tests, as shown  in  the  following table, and is


therefore believed to be  an  acceptable  value.
                               57

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   Table 3.   SOLID -  LIQUID  RATIO LEVELS UTILIZED IN OTHER
                       LEACHATE  TESTS (15)
   Test

   IUCS

   University of Wisconsin
   Standard Leaching  Test

   State of Delaware

   State of Minnesota
Solid - Liquid Ratio

        1:4

        1: 10


        1: 25

        1:40
     4.    Agitation  Methods,  Number of Elutions,  and Extraction
          Contact  Time

     Apart from  the  solid-liquid ratio,  already discussed,  the

remaining parts  of the  EP  which have the greatest bearing on the

concentration of toxic  constituents in the leachate are the agita-

tion method, the number of elutions performed,  and the contact

time between leaching  solution and the waste.   These are discussed

below.

     a.    Agitation  Method

     To ensure that  the surface area of  the waste is sufficiently

exposed to the synthetic leaching solution to  replicate the effects

of a leaching medium percolating slowly  through a landfill, and to

ensure reproducibile results,  it is important  to  employ a uniform,

non-destructive, efficient agitation.   Ham evaluated the following

five agitation methods:
                                  58

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          1.  Continuous  shaking  (Gyrotory/Shaker,  New
              Brunswick Scientific  Co.)


          2.  Continuous  mechanical paddle stirrring
              (Phipps  and Bird,  Inc.  Richmond va.)


          3.  Intermittent  shaking  by hand


          4.  Swing-type  shaking


          5\  Rotating at two  different  angles


     Ham concluded  that none  of  these methods resulted in ap-


preciably greater release of  toxic  constituents,  although the


rotating method gave  the  highest  release.   On the basis  of


the higher release  figures  for the  rotating method  and visual


observtions which suggested that  rotating  at two  different


angles gave the best  solid-liquid contact, Ham recommended


use of the rotating method  (14).


     The Agency has,  on its own,  developed a stirring  method
                                                       e
which is useable with  a wide  variety  of  wastes and  will  permit


the pH of the solution to be  continuously  monitored and


adjusted using automated  equipment.   This  device  is illustrated

in Figure 1 (see p.6).  ORNL  found  that  this device gave adequate


agitation when rotational speeds  greater than 40  rpm were


employed. (7,19)

     Rather than require  use  of  this  or  any other particular


equipment, EPA has  decided,  to simply specify that  a suitable


agitator or extractor  is  one  which  "will not only prevent

stratification of sample  and  extraction  fluid but also insure


that all sample surfaces  are  continuously  brought into contact
                                  59

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with well mixed extraction  fluid."  This is being done with




the intention of providing  the  regulated community with the




greatest flexibility  in  obtaining a suitable extractor.  A




number of commenters  interpreted the proposed regulations to




require that agitation be  performed with a particular piece




of equipment manufactured  by  the Associated Design and




Manufacturing Co.  (i.e.,  the  equipment EPA employed in many




of its own laboratory  studies).   This is not the case.  The




proposed regulation and  the final regulation allow the use




of any piece of equipment  that  meets the general objective




of insuring sufficient agitation so that stratification of




the sample and extractant  fluid  does not limit  the extraction




of potential contaminants.   This will give the  regulated




community the greatest flexibility in the choice of extraction




equipment .




     Extractors other  than  the  one developed by EPA have been




developed for use  in  evaluating  wastes.   One additional device




that deserves mention  (26)  (Figure 3) uses a simple jig to




hold and rotate a  number  of jars containing samples of waste




and extractant fluid.  Other  extractors  or agitation devices




are under study.   The  results of these evaluations will be




made public as they become  available.




b.   Extraction Contact  Time




     Ideally waste should  be  kept in contact with the leaching




solution long enough  to  insure  that maximum concentrations




of the toxic contaminants  are obtained.   Unfortunately,




however, this is not  always possible because small amounts






                              60

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                                                 2-liter plastic or  glass bottles
1/15 horsepower electric  motor
                                     .screws for holding bottles
                                                                                                £LvA
                                                                                                (XrStJ
                        Rotary Extractor

-------
of material may  continue to leach from the waste for years.




     Ham conducted  research into the effects of elution time




on cumulative  contaminant release.  He ran four elutions of




varying duration on the waste—i.e., durations of 2 hours, 24




hours, 48 hours  and 72 hours.  After each elution, the liquid




was  filtered  and analyzed for its constituents and the waste




was  contacted  with  an elution of fresh leaching solution.




The  results  showed  that cumulative release after three elutions




is  lower with  a  two hour contact time.  For contact times




over  24 hours  the results were variable and in no instance




were  equilibrium conditions apparently reached.  Ham suggested




that  a leaching  contact time of between 24-72 hours be chosen,




largely for  practical considerations (14).




      The Mitre survey indicates that there is no consensus




.among the  available leaching tests as to the appropriate




contact time  required to simulate landfill conditions (15).




This  survey  indicates that the contact times used in the




various tests  can be broken down as follows:




           Less than 24 hours    - 39 percent




           24  hours               - 39 percent




           Longer than 24 hours  - 21 percent




      In view  of  the above, EPA has chosen to employ a leaching




contact time  of  24  hours for the EP, based largely on practical




considerations.   The Ham research--although it dealt with  the




influence  of  contact time on cumulative release rather than




maximum concent rat ion—would appear to be applicable to maximum
                                  62

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concentration-oriented  procedures  in its conclusion that the




effect of employing an  elution  time longer than 24 hours is




inconsistent.  Consequently,  the  Agency has chosen a 24 hour




contact time to for the  convenience of the laboratory personnel.




     A number of comments  were  received in relation to the EP




contact time.  Some thought  the time to be too long and others




thought it to be too  short.   The  Agency acknowledges that, in




some instances, at extraction time of longer than 24 hours




might yield more information.  It  also recognizes that in




some instances a longer  extraction contact time might result




in a somewhat more conservative test.  It believes, however,




that concentrations obtained  during the 24 hour contact time




for one elution sufficiently  approximates the maximum obtainable




concentrations to justify  selection of this figure.




     c.  Number of Elutions




         Ham's procedure for  measuring maximum concentrations




of toxic contaminants  in the  leachate consists of running




successive extractions  or  contacts of the same leaching




solution on fresh waste.   His study of this procedure showed




that in some cases, steady state  maximum concentrations were




obtained after a very  few  extractions while in other cases




steady state concentrations were  not obtained even after 28




extractions performed  over the  course of eleven weeks.   The




most rapid increase in  concentration occurred in the first




extraction.  Ham concluded that there is no ideal number
                               63

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of extractions capable  of  generating maximum concentrations




of all toxic species  in the  waste.   Consequently, he recommended




three contacts—primarily  on the basis of practical




considerations. (14)




     EPA has determined that only one extraction need be




performed for the EP.   It  recognizes that a greater number




of contacts might result  in  higher  concentrations.   In the




absence of any demonstration that one number is clearly




better than another,  however,  and in view of the fact that




the first contact gives the  highest concentrations  for any




one elution, the Agency has  elected to go the less  conservative




route and require only  one extraction.




5.   Post-Extraction  Sample  Handling




     As noted above,  EPA has made the assumption that the




toxic species present in the liquid phase of the waste will




migrate from the solid  and eventually reach the underlying




aquifer independent of  any leaching action which takes place




on the solid.  In order to model this situation, the extract




obtained from the solid phase  of the waste is combined with




the waste's original  liquid  phase prior to testing.   While it




usually is more convenient to  analyze the combined  liquids as




one solution, in certain cases where a multiphasic  mixture is




obtained analysis may be  more  conveniently performed on the




separate phases.  In  such  situations the analytical results




are mathematically  combined, relative to the ratio  of the




phases, to determine  the  integrated Extraction Procedure
                               64

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extract concentrations.




     Once wastes are  extracted,  the extract should be preserved




in order to prevent changes  in the extract which might result




in spurious analytical  or  bioassay results.  When extracts




are to be subjected to  conventional chemical analysis only,




the applicable preservation  methods described in the EPA




publication "Test Methods  for Evaluating Solid Wastes" (27)




are employed.  In the event  bioassay test are performed on




the extracts, they  should  only be  preserved by refrigeration




at 4°C.  This will  prevent the introduction of potentially




toxic preservatives.   Irrespective of what sample preservation




technique is  employed,  extracts  should be analyzed as soon  as




possible after generation  to prevent possible problems.   One




such problem  relates  to the  formation of precipitates.  In




some cases  the Agency has  found  that precipitates form when




the extract sits  for  a  period of time.  While problems relating




to precipitate formation are readily overcome when the extract




is to be analyzed  (i.e., through employment of the digestion




procedures  described  in the  test methods specified for use




in evaluating solid wastes)  (27),  precipitate formation can




present a problem when  bioassay  procedures are used.   The




Agency will be conducting  further  studies to determine the




magnitude of  these  potential problems.
                               65

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IV.   BASIS FOR ATTENUATION  FACTOR USED IN RELATING NATIONAL
     INTERIM PRIMARY DRINKING WATER STANDARD TO EP EXTRACT
     VALUES


     The Extraction Procedure is designed to predict* the

potential concentrations  of toxic constituents which will

leach from the waste matrix itself.  There remains the question

of what will happen to  the  leachate after it leaves the waste

matrix and before  it reaches the point of environmental

exposure.  To accomodate  the attenuation in concentration

that can be expected to occur as the waste passes through the

soil barrier beneath the  landfill into the groundwater aquifer

and ultimately to  a drinking source, the Agency formulated a

dilution factor  designed  to acccount for expected attenuation

in groundwater.   This  attenuation or dilution factor was

calculated against  the  backdrop of the following fairly

conservative assumptions:

     (1)  The waste  landfill is situated over an aquifer

     that is a source  of  drinking water;

     (2)  The soil  below  the site is composed of material

     with limited  attenuative capacity; and

     (3)  Persons  using the aquifer as a source of drinking

     water are supplied from wells situated 150 meters

     (500 feet)  downgradient from the landfill.

     The choice  of  an  attenuation factor reflecting real-

world conditions  has proven to be one of the most difficult

tasks faced by the  Agency in formulating the EP Toxicity
                               66

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Characteristic.  Although  the various attenuation mechanisms




themselves are understood  reasonably well, the actual rate of




attenuation is highly  s i t e-specifHc .   Moreover,  there is very




little empirical data  on  attenuation occurring during actual




waste management,  compounding the difficulty of  generalization.




Under these circumstances,  it is  the Agency's view that the




choice of an attenuation  factor is at the present time as




much a question of  regulatory policy — i.e. what should the




scope of coverage  of  the  toxicity characteristic be — as of




regulatory judgment  relative to the expected degree of




attenuation that might occur during any specific type of




waste management.   The Agency believes   its  initial choice of




a dilution factor  of  10,  and its  final  choice of an attenuation




factor of 100  are  both justifiable by reference  to physical




processes—that is,  available data supports  either choice.   The




discussion below sets  forth  the physical  data bearing on




attenuative mechanisms affecting  constituent concentrations




in leachate.   The  policy  considerations which determined the




Agency's decision  to  increase the proposed dilution factor




are then described.



A.   ATTENUATION OF  CONSTITUENT CONCENTRATIONS IN LEACHATE




     Changes in the  composition of leachate  from a landfill




are usually achieved  through a series of  reactions.   As  the




leachate migrates,  constituent concentration may be affected




by passage through  various media.   During percolation through
                               67

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Che  landfill interior,  some  components  will be removed by




adsorptive and complexing  reactions,  and others wij.1 be added




by waste solubllization.   At  the  interface between the landfill




and the underlying strata,  some  further components may be




removed by precipitation,  filtration  of particles, and




absorption on gel precipitates.   The  existence below the




landfill of an unsaturated  zone with  a  liquid and a gas phase




increases the possibility  of  attenuation or delay of




contaminants.  In this  zone,  permeability is lower than that




of an all-liquid environment,  and flow  rates will probably




not be uniform, thereby allowing  some solute dispersion.  Some




insignificant attenuation  by  chemical or biochemical processes




may also occur depending on  the  thickness of the unsaturated




zone.  (28)




     At the boundary  between  the  unsaturated and saturated




zones, leachate movement changes  from vertical to predominantly




horizontal  flow.  This  is  in  keeping  with the fact that water




entering the ground first  moves  vertically through the




unsaturated zone then enters  the  saturated zone and travels




in a hydraulic gradient.  (28)  Groundwater flow is normally




laminar (i.e., characterized  by  parallel adjacent flow paths),




although mixing can occur  during  movement through large




fissures or in the immediate  vicinity of a pumping well which




alters the  flow pattern of  the groundwater. (29)
                               68

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     Leachate does not mix  readily with groundwater but tends




to move as a slug, a  plume,  or a mass of degraded water in a




manner governed by the groundwater flow pattern,  although




differences in density and  miscibility can cause  variation in




behavior between  the  plume  of contaminated water  and native




water.  The velocity  of  this  slug or plume of contaminated




water may be less  than,  equal to, or greater than that of




groundwater. (30)




     Pollutants entrained  in  groundwater flow tend to




become attenuated  with time and distance.   The attenuation




mechanisms involved  include dilution, adsorption, dispersion,




diffusion, precipitation,  and degradation.  The most significant




of these mechanisms  in the  saturated zone  may be  dilution of




the leachate as it follows  flow paths through the aquifer.




The rate of attenuation  will  be dependent  on the  local




hydrogeologic framework.   Leachate will tend to be contained




at sites underlaid by fine  grained,  compact materials with




low hydraulic conductivities  (slate, shale, soft  clays).




Migration with attenuation  is favored in formations exhibiting




intergranular flow (sands,  sandstones, sandy clays, gravels)




and formations displaying  marked fissure flow with an element




of intergranular  storage  (chalk) if  the intergranular conductivity




is greater than the maximum recharge rate.  Rapid leachate
                               69

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migration through coarse,  unconsolidated gravel formations

and fissured jocks  such  as  limestone and granite allows little

attenuation of pollutants.  (30)

     Where groundwater  flow is  rapid,  leachate from a point

source will form a  long  thin plume.   Where groundwater flow

is low, leachate may  tend  to disperse laterally.  Distortion

of the shape of the plume  can also be caused by variations in

permeability, the operation of  a pumping well, and changes

in the groundwater  flow,  recharge, and waste disposal rates,

(which can cause the  plume  to expand or contract.)  The plume

of a  leachate containing constituents having a greater

susceptibility to attenuation will be smaller than that of

one containing persistent  contaminants.  Additionally, a

plume  supported by  constant input of leachate will ordinarily

stabilize.

      As can be seen from the above,  the degree of pollutant

attenuation within  an aquifer basically depends on site-

specific  conditions;  therefore  it is impossible to choose

a dilution factor that  will be  appropriate in all cases.

While  some sites may  exhibit attenuations of 1,000-fold,

others may show no  attenuation  at all.   In some cases, with

time,  a site that originally exhibited a 1,000-fold attenuation

may become saturated  and begin  to flush at the identical

rate  at which it is being  charged.*


*A recent EPA - sponsored  synposium  on assessing attenuation
 likewise reached the conclusion that  leachate attenuation is
 difficult to quantify  outside  of site-specific conditions.
 See  "Pollution Prediction  Techniques  for Waste Disposal
 "sTFing,  a State-of-the-Art Assessment" (31)

                               70

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     The Agency has utilized  mathematical models in formulating
                                             i

an attenuation factor  for  regulatory use (32).   A mathematical


model is a simplified  representation of a real  system,  and


while difficulties  are often  encountered in quantifying


parameters and testing and verifying results under specific


field conditions,  the  model can supply information on potential


groundwater effects,   A model to estimate leachate dilution


in groundwater and  downgradient well discharge  has been


devised at the Water  Research Center of Medmenham Laboratory


in England (33).   This model  also suggests that there may be


a wide  range  of  dilution factors even if only a relatively


few variables  are  considered.  The model is based on the


following  assumptions:


        1.  Leachate of consistent composition is discharged


from  the entire  landfill at a constant rate.  (Lehr, Jay;


Combined Media Report  (34).


        2.  There is no chemical change in the leachate as it


migrates through the  aquifer.


        3.  The unsaturated zone is considered a delay mechanism



only.


        4.  In the  saturated zone, the aquifer is uniform and


the natural  groundwater gradient is constant.


        5.  Steady-state conditions exist.
                               71

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This model calculates  dilution  factors using the following

equation:


     C (ground water)  =  IC(leachate)

                           I  +  (UB/L)

wh e r e :


         C = pollutant concentration

         I = leachate  infiltration  rate

         U = groundwater  flow rate

         B = depth of mixing

         L « length of landfill  in  the direction of  groundwater
             flow (35)



     With  the use of this  equation, assuming  average  aquifer

characteristics and a  constant  leachate  production rate of

0.3 m/annum, dilution  factors were  calculated  for three

types of aquifers (Table  4).  Results  are  given  below:


	Table 4 Dilution Factors For Three  Types  of Aquifers	


                    Distance from landfill
 Aquifer	50meters  (164 ft)	300  meters (984 ft)

 Chalk            15 -  50                  100 - 250

 Sandstone         3-10                   15-50

 Gravel           100 - 200                  200 - 500
                              72

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     The lowest dilution  factor  obtained by these calculations

(3x)  was for a contaminant migrating through a sandstone aquifer

beneath a landfill 50 m  long.  A well directly downgradient

from the landfill would  thus  be  expected to contain water

(landfill leachate) exhibiting this  degree of attenuation

Any additional dilution  that  may occur would depend on how

fast water was withdrawn  from the well.   If high pumping

rates were employed water from outside the plume might be

drawn into the well thus  diluting the contaminated water (33).

     Existing empirical  data  (and there is not a great deal)

likewise indicates considerable  variability in pollutant

dilution factors  in groundwater.   The behavior of chloride
                                                  \
graphically illustrates  this.  The chloride ion is a highly

mobile and persistent contaminant.  It is readily leached

from waste and is resistant  to ion exchange, chemical re-

actions and adsorption.   Attenuation of chloride during

migration is due  to dispersion and dilution.  Some observed

dilution factors  for  chloride at various distances from

waste disposal sites  are  listed  in Table 5.
                               73

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             TABLE 5.  Chloride Dilution Factors  (14)

Site
Illinoi
Llangol
Connect
Fly ash
DuPage
Winnetk
Tythegs
s landf il 1
len, Delaware landfill
icut. landfill
settling pond
County, Illinois landfill
a, Illinois landfill
ton landfill, England
Distance D
650
650
200
500
32
800
330
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ilution Factors
4-5
27
2
8-9
2
13
2-3
Attenuation factors for hazardous  constituents  of  leachate




also vary widely.  Table 6  illustrates  data  from field




analyses of several waste disposal  sites.
                               74

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TABLE 6 - Pollutant Attenuati
            on
                                                    (14)
     Site
Iowa  landfill

Fly ash  settling  pond

Kings Kettle  landfill,
  England

Coatham  Stob  landfill
Pollutant
B**HM>IB^^BIMB^I^^MMMMI^m

Arsenic

Arsenic



Cyanide
                                    From Disposal
                                 Site Distance
At tenuat ion
   Factor
                                    400 ft.

                                    500 ft.


                                    430 ft.
12 - 13

 4


50
England
Mitco
Mitco
Mitco
Mitco
Chromium
Phenol
Nickel
Phenol
Zinc
500 ft.
ad j acent
ad i acent
ad j acent
ad i acent
100
>23
>170
>1000
>14

   The  results  illustrate the current rudimentary understanding

   of  leachate  attenuation and the difficulty  in arriving at a

   dilution  factor which reasonably reflects the dilution in

   concentration  from the point at which the contaminated leach-

   ate  leaves  the  disposal site to the point of human or environ'

   mental exposure.   In sum, there exist no widely accepted

   criteria  for gauging this diminution in concentration.

   B.   EPA'S CHOICE  OF AN ATTENUATION FACTOR

       In the  proposed regulation, EPA chose  a dilution factor

   of 10 as  a conservative,  but reasonable figure.  EPA based
                                 75

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this dilution factor  on  (1)  the figures computed from "the




mathematical model—figures  which incorporated EPA's original




assumptions of no attenuation between waste matrix and




groundwater aquifer,  and,  (2) the empirical analyses of




attenuation experienced  at  actual landfill sites.  EPA does




not believe that  this factor of 10 represented the minimal




level of dilution that  could be expected.   For instance,




leachate migrating  from  a  disposal site in Islip, New York




was not attenuated  by that  amount until it had migrated 805




meters (0.5 mile)(28).   It  did, however, believe that a




dilution factor of  10 provided a reasonable degree of protection




to  the public health  and the environment while at the same




time acknowledging  the  broad range of hydrogeologica1 conditions




at  waste disposal sites  across the country and the variety




of  contaminants likely  to  be released.




     A large number of  comments were received concerning  the




proposed dilution factor.   Most argued that the factor of 10




was arbitrary and far too  conservative.  Others argued that




the factor of 10  was  not conservative enough and that only a




factor of zero would  ensure  adequate protection to public




health and the environment.



     EPA has carefully  reevaluated its original choice of a




10-fold dilution  factor  and  has decided that a 100-fold




dilution factor would be more appropriate.  A number of




considerations have motivated EPA to make  this alteration.
                               76

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Probably the most  important  consideration is the relative




absence of empirical  data upon which to base an attenuation




factor, and strong  suggestions that choice of any of a wide




range of attenuation  levels  could be supported by what data




is available.  This absence  of empirical data is particularly




troubling because  the  dilution factor plays an exceptionally




important role in  defining the breadth of the EP's coverage.




     A second consideration  involves a shift in current




regulatory strategy.   The EP was initially viewed as the




principal mechanism for  bringing hazardous wastes into the




Subtitle C regulatory  system.   However, when it proved




impossible to develop  suitable characteristics for carcino-




genicity and other  aspects of  toxicity, (see pp. 12-18 above),




the Agency decided, at  least -for the present, to use the




listing mechanism  as  the chief means of coverage.  The overall




scope of coverage  of  the EP  thus became somewhat less  critical,




and a less conservative  attenuation factor more appropriate




(particularly since the  listing mechanism encompasses  wastes




containing EP contaminants).



     -Another consideration is  the absence of a variance




procedure for wastes  which exhibit  the property of EP  Toxicity




(i.e., wastes which fail the EP are conclusively deemed to




be hazardous).  The effects  of a waste being anomalously




brought into the system  by the EP are greatly aggravated by
                               77

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this  lack of a variance  procedure,  thus  dictating the need
                      «

for some caution.


     A further consideration  is  that  the EP is  a necessarily


less  precise instrument  than  Che  flexible listing procedure


for determining whether  a waste  which  straddles  the  line  is


in fact hazardous.  For  instance,  the  EP fails  to take  into


account the quantity of  a waste  generated—a factor  which


could make a difference  in  determining whether  a marginally


hazardous waste belongs  in  the  system  or out.   Similarly,


the EP fails to take into account  mismanagement  scenarios


specific to the waste which might  argue  for including the


waste in the system even though  it  passed the EP. Conse-


quently, EPA believed that  marginal determinations of hazard


might better be entrusted to  the  listing mechanism.


     EPA is also  concerned  that  its assumption  of zero  soil


attenuation may have been unduly  conservative,  since soil


attenuation may play a role in  many waste management situations.


A decision to take soil  attenuation into account also suggests


some  need to increase the attenuation  factor.


     EPA has therefore decided  to  adopt  a 100-fold factor.


It is convinced that waste  which  fails the EP at the 100-fold


factor has the potential  to present a  substantial hazard,


regardless of the waste's management circumstance, so that


coverage will certainly  not be  over-inclusive.   In order  to  bring


into  the system wastes which  present a potential substantial
                               78

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hazard but do not  fail  the  EP at the 100-fold dilution factor,




EPA. has listed and will  continue to list wastes which do not




fail the EP at this  100-fold factor.  Its adoption of the




100-fold factor will  thus  shift to the listing mechanism




some of the burden for  capturing wastes containing EP




contaminants.




     EPA emphasizes  that the change to the 100-fold dilution




factor is provisional.   If  forthcoming studies demonstrate




that another attenuation factor is more appropriate,  EPA




will switch to that  factor.   In taking the cautionary step




of moving to the  100-fold  factor, EPA recognizes it is empowered




to forge ahead in  the face  of scientific uncertainty.  By the




same token, however,  it  is  empowered to act cautiously—




especially when there is another means (here the listing




mechanism) of accomplishing its goal.




     The Agency is cognizant of the fact that for four of the




organochlorine compounds for which thresholds have been




established, the  threshold  exceeds the published water




solubility for the compounds.  However, the Agency does not .




believe this presents a  problem.




     The primary  purpose of the EP Toxicity Characteristic is




to iden-tify manufacturing  or process wastes containing




leachable contaminants  in  toxicologically significant levels.




When present in process  wastes or as formulated products, the




compounds are normally  present in admixture with other organic
                               79

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compounds which tend to  act  as  cosolvents  to increase the




apparant water solubility.   Thus  the  Agency believes  that the




water solubility is not  a  true  measure of  potential solubility




in the EP extract.




     A second factor leading the  Agency to conclude that  this




potential problem may  not  be a  serious one relates  to the




specific pesticides involved.   Several of  them enjoy  only




limited use and thus are unlikely to  actually be present  in




any significant number of  wastes.




     However, the Agency is  studying  this  apparant  problem




and if it is  determined  that corrective action is needed,




such changes  will be incorporated into future revisions  of




the regulations.
                               80

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V.   RESPONSE TO  COMMENTS RECEIVED ON THE PROPOSAL AND ON THE
     NOTICED REPORTS

A.   Adopt Existing  Regulations

          The Agency received several comments questioning

EPA's need to develop a new method of identifying toxic wastes

since there  are already a number of states with regulations

which address  this problem.  These states include Washington

(39), California (40), and Minnesota" (41).  Some commenters

specifically suggested that EPA model the Federal regulations

on  the  California and Washington regulations.

      The Agency believes that the hazard posed by a waste is

primarily dependent both on the intrinsic toxic properties of

 the waste constituents and the propensity of  constituents in

 the waste to migrate  from  the waste to  the "point of environmental

 exposure.  Except in  the case of direct  discharge to  sewers or

 surface water bodies,  contamination of  ground and surface

 water appears  to  be  a function of not just what is  in the

 waste,  but also  the  likelihood of the toxic constituents

 migrating from  the  paint of  disposal.   Therefore, in  formulating

 its leaching test,  the Agency has attempted to comprehensively

 incorporate into  the  test  consideration of  the waste's

 migration (i.e.,  leaching) potential.   Inasmuch as  many  of

 the outstganding  state regulations  fail to  give consideration

 to migration potential,  EPA  has  not  adopted  their approaches

 in constructing  the  EP.

      EPA has,  however, to  some  extent based  its  Hstin*  approach
                                81

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states whose regulatory  approaches  most resemble EPA's in this

regard are Minnesota  and  California.   In both the Minnesota and

California approaches, wastes  are  considered to be hazardous

based on the presence  in  the waste  of a designated toxic

specie (40,41).  In the Minnesota  regulations,  the waste  must

contain a given concentration  of the  toxic species.   In the

California regulations,  the mere presence of any one  of a long

list of chemical species  is presumed  to make the waste hazardous,

unless the generator  proves otherwise.   EPA's newly  formulated

criteria for listing  come  very close  to incorporating this

California approach.   Under these  criteria,  the presence  of a

hazardous constituent  is  deemed to  make the  waste hazardous
                                                            •
unless the Administrator,  after considering  any of a  number of

factors concludes  that the waste is not hazardous.  Most  of

these factors have a  direct bearing on  migration potential.

     EPA has elected  to  adopt  this  approach  in  the Extraction

Procedure Toxicity Characteristic  in  recognition of the

differences between the  two mechanisms.   The EP Toxicity  Charac-

teristic is a one-shot mechanism for  bringing wastes  into

the system; there  is  no  opportunity for generators  to present

mitigating data nor is there any variance procedure.   Conse-

quently, it is incumbent  on the Agency  to fully incorporate

consideration of migration potential  into the test protocol

accompanying the characteristic.  The  listing mechanism,  on

the other hand allows  for  some  generator  input  into the
                               82

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Agency's determination  and  is  accompanied  by a  variance




procedure.  Consequently  it  is permissible to create  what  is




in effect a presumption for  listing based  on the  mere presence




of the toxic  constituent  in  the waste (as  California  does  (4-°)




in view of the  opportunities provided for  subsequent  consider-




ation of migration  potential and the opportunities  for more




individualized  consideration of hazard.
                               83

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B.   Suitability  of  EP  As  a Regulatory Tool



          A number  of  comments were received concerning the


suitability of using  the  Extraction Procedure as a regulatory


test.  These  comments,  many of them similar, addressed the


reproducibility,  validity, accuracy, and scientific defensi-


bility of the procedure.   The comments came from all factions


of the affected  community including industry, government,
                                  X

environmentalists,  academia and citizens in general.


     The comments addressed one or more of the following


 five areas:


     1. Appropriateness of using a single test procedure,


 based  on a  single model of assumed management, to determine


 the hazardous potential of wastes which are disposed of in a


 wide variety  of  disposal  environments.


     2. Acceptability of  using for regulatory purposes a test


 procedure  that has not been fully accepted by the scientific



 community.


     3. Whether  the EP is reproducible enough for it to be


 acceptable  for  regulatory use.


     4. Accuracy of the Extraction Procedure.


     5. Propriety of having a hazardous waste definition employ



 a  test procei


 judgement.
idure which  requires  the  exercise  of  scientific
                               84

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1.    Appropriateness of Using a Single Test,  Based  on  a
     Single Model of Assumed Mismanagement,  to  Determine
     whether a Waste is Hazardous

          The vast majority of comments revolved  around the

Agency's use of a single test procedure, based  on a single

model of assumed mismanagement, to determine  whether a waste

is hazardous.  Many of these comments specifically  questioned

the appropriateness of the Agency's utilization of  a co-

disposal scenario.  Others expressed the view that  because

they handle  their waste in a manner very different  from that

described  in  the  scenario on which the Extraction Procedure

is modeled,  the  EP  should not  apply to them and a means should

be given to  permit  them to disprove the results of the EP.

Some commenters  were  especially  critical of the Agency's  use

of one  test  to  measure  environmental mobility in light of

 the  comments expressed  by Ham  et.  al.  (14,16).  Some specific

 statements of Ham that  were  pointed to  are:

       "A  standard leaching  test  provides a reproducible  set  of
 numbers that are a  function  of the interaction of waste  with  a
 specific  leaching solution  under a specific set of conditions.
 It  is  up  to the decision  maker to  evaluate those numbers  and
 make a prediction regarding  the  behavior of the waste in  a
 landfill.   Unfortunately,  the  multiplicity of factors affecting
 the  leaching characteristics of  a  waste, both in the test and
 in  the landfill? and  the  variability  of  landfill conditions
 dictate that interpretation  be done with «re "%-^^-JJ^"-
 tion of the waste and landfill characteristics.  Test results
 should not be interpreted rigidly, -g.,Developing or,  e.ia
 statins that a certain concentration  of a given  parameter
 in  the test leachate  automatically and without further
 in  tne cesc ie           h  t the waste is hazardous in the
 consideration indicates tnatcne                      h factors
 landfill.   Rather,  ""^"'^ '*™ ]* £ *nnual  net infiltration
 as  the amount of waste to be ^sposed             affecting the
 of  water  in the area  of th e  land fill,  t         d  from  the
 leaching  of the *"te (« f ^e,^ e interactions,  and the

 mi iri^l^i^^i ^  ;t i.sr  -  waste
 passes through wastes or soil. (16,  p. -3, &,
                               85

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     "Because of the major  differences  in a waste's leaching
characteristics as a result  of  the  leaching media composition
no one media can give  results  adequate  to describe properly the
leaching characteristics  of  a  waste." (14,p.2)

     "The importance of using  different leaching media was
indicated by the results."  .  .  .  "Without the use of several
leachates, test results could  be  very misleading and have  no
relation to the actual  landfill for a particular waste."  (16,  p.2)

      Proper interpretation  of  the  results  from the recommended
procedure is critical  to  its  usefulness.   The test was designed
to be aggressive;  the  numbers  obtained  are  expected to be  maximum
values which will  not  be  attained normally  in an actual land-
fill." (14, p.3)

     "Whatever standard test  is used, interpretation of test
results is the crucial  factor  in  determining the test's ultimate
value in predicting whether  a  waste is  hazardous when placed
in landfill.  Virtually any  leaching test which is properly
interpreted would  be more useful  in making  such a prediction
than would be a well designed  leaching  test which is poorly
interpreted." (16, p.7)

     "Unfortunately, the  multiplicity of  factors effecting  the
leaching characteristics  of  a  waste,  both in the test and  in
the landfill, and  the  variability of landfill conditions dictate
that interpretation be  done  with  care and with  consideration of
the waste and landfill  characteristics.  Test results should
not be interpreted rigidly,  e.g., developing criteria stating
that a certain concentration  of a given parameter in the test
leachate automatically  and without  further  consideration indicates
that the waste is  hazardous  in  the  landfill."  (16,  p.6)

     "One obvious  way  to  interpret  the  leachate composition
results is to compare  the concentrations  of the various  chemical
species to some standard, for  example,  drinking water standards.
This is dangerous, however,  and is  difficult to defend for  the
leaching test developed in  this study." .  .  .  "It was not designed
to provide realistic concentrations of  the  various species  for
a specific situation."  (14,  127)

     "Thus, once a standard  leaching  test has  been designed,
interpration of the test  results  becomes  a  crucial factor
in determining the applicability  of the test."  .  .  .   "It  is up
to the decision maker  to  evaluate ... and make a prediction
regarding the behavior  of the waste." (16,  p.  3)
                              85-A

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     "It may be possible  to  correlate test conditions  with
landfill concentrations by running  extensive verification
tests,  correlating a waste's  behavior in the test  with the
behavior of the same waste in a  carefully monitored  landfill.
Correlation coefficients  could then be developed for parameters
and conditions similar  to those  in  the verification  study and
the test result used to estimate landfill concentration."
(Background)(14, p. 124)

     "There is a lack of  data regarding leachate generation
at fullscale industrial waste landfills with which results
from the laboratory leaching  procedure can be compared.
Field verification studies are needed in which unattenuated  and
indiluted leachate from specific industrial wastes in  mono-  as
well as co-landfill situations can  be compared with  appropriate
leaching test results,  preferably on a long term basis."
(Background)(14 , p. 4)

     As was discussed earlier in this document,  EPA  believes

it has the authority to base  the EP Toxicity Characteristic

on a single plausibly-occurring  scenario of mismanagement

even if this mismanagement scenario does not precisely

correspond to the  circumstances  of  a particular  generator's

management practices.   Those  who quoted Ham on this  point

failed to appreciate that Ham's  goals differed somewhat from

the Agency's goals.  Ham  was  interested in designing a test which,

insofar as possible, evaluated the  leachability  of particular wastes

as they are actually managed  in  particular landfill  environments.

Recognizing that the leachability of a waste,  and  thus its ability  to

cause a hazard, is a situation-specific phenomenon,  Ham counseled

caution in applying the results  of  the test to specific landfill

situations.  EPA,  on the  other hand, is not as interested in the

leachability of a  waste as it is actually managed  as it is in the

leachability of the waste under  some plausibly-occurring  mismanagement

situation.  Thus,  while EPA  recognizes that its  test will not predict

the leachability of particular wastes as they are  actually managed,


                              85-B

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it believes that its  test  is  reasonably predicitve of the hazard




which a waste could present  if mismanaged.   EPA has intention-




ally refrained from making its definition of hazard dependent




on the actual management  to  which a waste is subjected,  because




it believes that the  Act  contemplates defining hazard in terms of




some assumed level of improper management.   Making the definition




of hazard completely  dependent on situation-specific management




practices would have  the  effect of excluding from the hazardous




waste management system those wastes which  are properly  managed,




with a consequent  sacrifice  of the continuing oversight  and




assurance of proper management provided by  the system.




     The above does not,  however, fully respond to those who




argued that, in constructing  its scenario of assumed mismanage-




ment, EPA should to the extent possible take into account  the




actual mismanagement  practices to which particular wastes




are likely to be subjected.   One of the principal comments




along this line was that  EPA  should use a variety of leaching




media in the EP to take into  account the fact that many  wastes




are not likely to  be  disposed of in municipal landfills, even




if improperly managed.



     The Agency recognizes this concern but  believes,  as arti-




culated in greater detail  above, that the single  leaching  medium




it has elected to  employ,  when considered in light of the  other




aspects of the test,  is reasonably predictive of  the the leach-




ability of mismanaged wastes,  even if those  wastes are not  disposed




of in municipal landfills.   The Agency also  believes that  its  de-




cision to employ a single  model of improper  management is






                              85-C

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justified by concerns about  the  administrative  feasibility




of employing more sophisticated  multiple models.   In  any




event,  to the extent the  commenters  are concerned  that, by




failing to tailor the model  of  improper management  to  specific




management conditions, EPA  is making its test  too  aggressive,




these concerns are  put to rest  by  EPA's switch  to  the  100-fold




dilution factor.  EPA  is  fully  convinced that  anything which




fails the EP at  the  100-fold factor  has the  potential  to




cause a hazard,  no  matter what  leaching medium,  etc.,  it  is




actually exposed to.
                              85-D

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2.   Acceptance by  Scientific  Community




         A number  of  comments questioned the acceptability of




using a test procedure  which  has  not  fully been accepted by




the scientific community.   Before addressing the acceptability




of using a test  procedure  for regulatory purposes that  has




not been fully accepted by the "scientific community,"  one




must first define  what  is  meant by the "scientific community".




         There are two  groups making  up membership in  this




community; those scientists working for industry, government,




and other entities who  will be directly affected by the




regulations and  scientists whose  only interest  is academic.




The first group  has  a direct  financial or institutional




interest in seeking  to  exempt from the system waste(s)  their




organization or  constituency  generates.  Obviously, these




members of the regulated community are concerned with  the




economic implications of any  test methodology employed  in




defining a hazardous  waste.   The  second group of scientists




are basically motivated by a  desire to assist the Agency in




developing regulations  utilizing  the  "best"  information




that the scientific  community possesses.




     In the main,  it  was the  regulated community that  commented




that methodology should receive scrutiny and acceptance  by




the "scientific  community" prior  to regulatory  use. The




Agency agrees with this comment.   Toward this end,  EPA




developed the proposed  test procedures in open  view of




all interested parties  in  hope that scientists  would then
                               86

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apply the procedures  being  developed to wastes of concern




and, with the data  so obtained,  assist the Agency in correcting




any problems with the proposed procedures.  With few notable




exceptions (35,  37,  42,  43)  this  did not happen.  Scientists




from the regulated  community have,  in the main,  concerned




themselves with  trying to  convince  the Agency to modify the




test procedures.  Their  go.al was  to make the test procedures




less aggressive  and,  thus,  less  likely to identify their




particular waste as  a hazardous  waste, rather than to determine




if the procedures were scientifically valid (i.e.,  accurately




identify wastes  needing  controlled  management).   Even though




the Agency extended  the  comment  period on March  12,  1979,




for an additional sixty  days (44  F_R 13548)^4)^  industry  did not




submit significant  amounts  of data.




     While many  comments were received commenting on the  invalid-




ity of the test  procedures,  few  commenters supplied  the necessary




scientific data  to  justify  their  concern.   The chemical industry




was especially unresponsive.  Studies sponsored  and  conducted




by the Agency(18 , 19 ),  the Electric  Power Research Institute(37),




and others (35,36)  have  indicated that the Extraction Procedure




is of acceptable reproducibility ' for regulatory  use.   Given




the lack of convincing data  to the  contrary from the affected




groups, the Agency  has  decided to employ the Extraction




Procedure in the regulations being  promulgated  today.  If




future research  uncovers better  test procedures  for  use in




§3001 regulations,  the  regulations  will  be amended.
                               87

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probably more  germane to the issue of the adequacy of the EP




and the analytical  techniques.  Third, the studies were not



designed for  comparison with other studies.  Thus, even when




results are presented on similar phenomena, e.g., the intra-




laboratory reproducibility of analyses results for barium and



chromium, the  statistics reported are not always sufficient to



make good comparisons.   For example, some of the studies (19,18)



use coefficients  of variations (the same as the relative standard



deviations, RSD)  to indicate the degree of variability in the



measures, while  others  (36) use a relative standard error (RSE).



Thus, when the specific means and standard deviations are not



reported, it  is  not possible to calculate uniform measures  of



reproducibility  that can be used across studies.



       Fourth,  none of  the studies were designed  to focus
                                           e


specifically  on  the questions of reproducibility.   The exception



might be the  complex design in the study conducted by the Electric



Power Research Institute (37), but the use of  geometric  analyses



makes the study  incompatible with research results in the other



studies.  Also,  no  interpretation of the results  from this



study (37) are offered  in the report which was  available.



Along this line  also,  none of the studies presented data on



analytical technique reproducibility for all  of the toxic metals



included in these regulations.  This leaves  open  the  question of



whether different levels of reproducibility  are characteristic



of different  toxic  metals.   This  limitation  is  important because



it cannot be  assumed that the analytical  precision of measures on



one element could be equally precise for  another  element.



                                91

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Apparent Reproducibility of the EP


       With the  above  in mind,  we turn to a review of these


studies insofar  as  they bear on the reproducibility of the EP.


The study by the American Electroplating Society (35) examined


twelve wastes  (sludges) generally representative from wastewater


treatment systems  in  the electroplating industry.   The study as


a whole consists of thirteen experiments, some of  which are


still in progress.   Two major deviations from the  EP  were


incorporated in  the study.   First, lumps of solids  in the  waste


samples were broken up  by stirring prior to the initial


centrifugation or  filtering of  the sample.   As stated in the


report, this stirring  could possibly cause  a higher level  of


toxic metals in  the final EP extract (35, p.2-2).   The second


deviation from the  EP  was involved when, after agitation,  the

                        o
beakers with the solid  waste material were  removed,  covered


with a parafin cover,  and allowed to stand  and settle overnight


(35, p. 2-4).  Both of  these deviations from the EP standard


invalidate any good estimate of the general reproducibility of


the EP.  It was  noted  in the report that filtering  vs.


centrifugation in  the EP can make the difference between passing


or failing the threshold values for toxic metals established by


the EPA (35, p.2-5).  However,  the experiment  involved  only two


metals, lead and chromium,  and  two levels of pH, pH 5 and  pH 7.


At the specified pH 5  level in  the EP,  the  threshold  value  for


lead was surpassed  when centrifugation  was  used to  separate the


solid material from the sample.   The threshold value  was not


reached when filtration was used.


                                92

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    The NUS Corporation  (36)  subjected samples of four waste

materials to the EP  and  analysis using the AA techniques.   Few

comments in the report  related specifically to the reproducibility

of the EP, except  that  the specified EP was used.  The NUS

study also compared  Toxic Extraction Procedures (TEP)  with the

EP.  The TEP is the  precursor to EPA's current EP.  One statement

from the NUS report  (36), however,  deserves special comment.

The report states  that  sampling error is a factor in the (inter-

laboratory) reproducibility test.   Even though the report  makes

the distinction between  "repeatability" (intra-laboratory

consistency) and "reproducibility"  (inter-laboratory concurrence),

the statement  is not appropriate if aliquots  of the same EP

extract are used.   Specifically, sampling  error relates to the

overall representativeness of the  waste material  to be charac-
     o
terized, not to the  precision of the EP or of the analytical

techniques.

       The Oak Ridge National Laboratory (19) employed the EP

and analyzed eighteen different wastes, including arsenic-

contaminated ground  water.  The standard EP was followed,  except

that extractors made of  different  materials or combination of

materials were used.  The report states that  "no  significant

problems were  encountered in  extracting or analyzing wastes  for

inorganic species"(19,  p.2),  but several suggestions were

offered with regard  to various aspects of  the EP.   For example,

stirring problems,  e.g.,  binding and sampling grinding, were

encountered with some of  the  wate material during extraction.
                                93

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Also,  the report recommended that a nonmetallic extractor should




be used to lessen  the  possibility of contamination occurring




during waste extraction.   In general,  however,  this report (19)




suggests that the  EP  is  relatively reproducible.   One statement




(19, p.15) suggests  that  reported values of chromium, nickel




and calcium indicate  an  EP variability trend that exceeds that




expected for analytical  determinations.   This statement  applies




only to the situation  when extractors  made of different  materials




are used.  Out  of  context, the statement would  suggest that  the




EP is unreproducible  in  either intra-  or inter-laboratory stiuations




       A total  of  twenty-five wastes from eleven  different




sites were examined  in the study by Environmental Monitoring




Systems Laboratory in  Las Vegas (18).   One specific deviation




from the EP was  employed  in the study.   All waste materials




were screened by inductively coupled plasma emission spectroscopy




(ICM) to select  those  wastes for EP and  analyses  by AA methods




(18,p.22).  Also,  different kinds of agitation, the wrist-arm




shaker and the  extractor  device, were  used in the study.   The




report states that preliminary results  suggest  good agreement




(from the analyses)  between the two types of agitation.   Like




the Oak Ridge National Laboratory Study  (19), this study  (18)




also suggests that steel  containers not  be used in the EP




because of its  possible  contamination  in tests  for chromium.




Also, the report states  that the variation in the tests  for




barium are due  to  the  analytical method  (not the  EP). Other




studies are planned which will address  the issue  of the




reproducibility  of the EP more directly, but there is little in




                                94

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the interim report  to  suesest t-hai- »•>,« v-a •             - ,
              r      w  ouggest cnat the EP is not generally
reproducible.
       Finally,  the  study  by the Electric Power Research
Institute (37) is  the  only investigation which clearly separates
out the question of  reproducibility of the EP and the analytical
techniques.  Further,  the  complex design partitions  (through
analysis of variance (ANOVA) techniques) variation of the  EP
and analysis techniques  which can be attributed to inter-  and
intra-laboratory results.   Four types of utility wastes were
subject to the EP  and  analyzed in the study.   The design  included
all the toxic metals except silver.  Also, the basic  design of
the study was intended to  compare flame and  furnace AA methods
of analysis.  Unfortunately, because of incomplete data and
values for toxic matal content which were sometimes below
detection limits,  a  variety of adjustments were incorporated
into the overall statistical analyses.   For  example,  simulation
methods were used  to produce enough observations to complete
the ANOVA design.   Geometric techniques were  employed because of
the highly skewed  observations,  i.e., results from the test of
toxic metals in  the  waste  materials.   In all, the results  of
the study should be  given  a very conservative interpretation.
As noted previously,  no  interpretation  of the results is offered
in the study report.   However, examination of the data presented
and communication  with those persons  who conducted the analyses
suggest two major  findings:
       First, as might be  expected, intra-laboratory  reproducibility
/     .  „    ^ f^  u^fh the EP and the analytical techniques tended
(consistency) for  ootn cne ^r
                                95

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to be better than  inter-laboratory reproducibility (concurrence).




Secondly, the reproducibi1ity of the EP overall (both intra-




laboratory and  inter-laboratory) appears to be better than the




overall reproducibility  of  the analytical techniques.  This  latter




finding suggests  that  the  overall reproducibility of the analytical




techniques may  be  more  of  a  problem than the EP itself.   This




is contrary to  assumptions  which have been made in some  studies




(36) and further  questions  the use of the analytical results of




EP extracts as  an  uncontrolled criterion to assess the




reproducibi1ity of the  EP.




Apparent Reproducibility of  the Analytical Technique




       Most of  the five  studies reviewed addressed,  to  some




extent, the general  reproducibi1ity of the analytical techniques.




The  data reported, however,  is sometimes too incomplete  to make




any  comparisons among  the  different studies.  Consequently,




caution has to  be  exercised  in generalizing about the




reproducibility of the  analytical techniques.  Some  discussion




about  the statistical  measures used to indicate reproducibility




is in  order before proceeding to the separate research  studies.




The  measures mentioned  or  employed across the studies have




included the following:




       0  standard deviations



       0  relative standard  deviation, i.e., the standard




          deviation  expressed as a percentage of the mean




       0  the coefficient  of variability, i.e., the  same as  the




          relative standard  deviation




       0  the range  of  values, i.e., the difference  between  the




                                96

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          highest  and  lowest value




          standard  error (unspecified), and




          relative  standard error, i.e., the standard error of




          the mean  expressed as a percentage of the mean.




       Each of  these measures can be used to assess relative




reproducibility  under  certain circumstances.  In some cases,




however, the measures  can be misapplied.  For example,  the best




indicator of reproducibility when replications are made of the




same test and the  values are averaged is the standard error of




the mean or the  relative standard error, not the coefficient of




variability, i.e.,  the relative standard deviation.  The




advantage of the standard error of the mean is that probability




statements can  be  made about hypothetical true values,  e.g.,




the threshold values,  or different mean values obtained from




other tests of  the  same waste material.  The only study to employ




the standard error  of  the mean (specifically the relative  standard




error) was the  NUS  Corporation study (36).   The relative standard




error (RSE) indicates  that one can be 95% confident that the




true value, e.g.,  level of toxic metal, is  within +_!  RSE of the




mean value obtained.   There is no direct way of comparing  the




coefficient of  variability and the RSE.  The advantage  of  the




relative standard  deviation or the relative standard  error is




that variation  is  expressed as a percentage of the mean, thereby




facilitating relative  comparisons of the variation around  the




mean,  i.e., reproducibility.



       The study by the American Electroplating Society (35)




presents data on the intra-laboratory reproducibility (consistency)




                                97

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of duplicate analyses  for three wastes on toxic levels of




cadmium, lead  and  chromium (35, p.  2-20).  The results for lead




are probably not  representative since the values for lead con-




tent were near  or  below the detection limits of the analytical




technique.  The other  results  of the analyses of the extracts




at pH 5 are presented  below in mg/1:




    Waste  '            Cadmium                 Chromium

2
7
9
Mean
120
1.7
— _
SD
6
.45
— —
RSE
+ 7%
+ 38%
_ —
Mean
3.3
.33
.40
SD
1.4
.09
.08
RSE
+ 60%
+ 39%
+ 28%
       The RSE  employed  above as  the indicator of reproducibi1itv




indicates the  95%  confidence interval as  a percentage  of  the mean.




For example,  there would be the probability of only  5  times out




of 100 that  the true  mean for cadmium in  waste 2  would be  out-




side of the  range  of  111.6 to 128.4.  The RSE  also permits




comparisons  by  the calculation of the 95% confidence  intervals




for each measure.   For  example, the  95% confidence intervals on




chromium levels in wastes 2, 7, and  9 would be 1.32  to 5.28,




0.20 to 0.46,  and  0.28  to 0.512,  respectively.  Thus,  one  could




say that the  chromium level in waste 2 is significantly (p <.05)




different from  the chromium levels  in either waste 7  or waste 9.




On the other hand,  because the confidence intervals  overlap,  it




cannot be said  that the  chromium  levels between wastes 7  and 9




are significantly  (p  <.05) different.  Further, it cannot  be




stated that  the chromium level in waste 9 is significantly




(p <.05) below  the threshold value  of .50 mg/1 proposed in 43




FR 58956(9).  However,  one can state, with confidence  that it






                                98

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less, but range  from  1.01  to 1.41.   These ranges  exclude analyses


where "the number  of  values  reported as  'below the detection limit'


was not so large as  to preclude statistical analyses,  but large


enough to make  the results less reliable" (3,  p.  3 of  Phase  I Report)


The effect of  the  simulated  values  on the CMs  is  not known


exactly.  Consequently,  only tentative conclusions,  or hypotheses,


about reproducibility seem justified from the  report.(37)


       In conclusion, the  above reports,  while not complete  enough


to permit any  firm conclusions, do  contain data which  is


suggestive on  the issue of reproducibility.  Of particular


interest  is  the suggestion in the EPRI data that  the EP is at


least as  reproducible, if  not more  reproducible,  than  the


analytical techniques.  In as much  as these analytical techniques
            •

have  generally been accepted by industry  and others  as being


sufficiently precise for regulatory use,  the EP should also


prove acceptable.
                               102

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4.     Accuracy  of  Test  Procedure





            A  number  of  commenters questioned whether the EP




was sufficiently accurate for use in a regulatory regime.  By




this they apparently  meant one of two things:  either that




the EP inadequately predicts the -leaching which might occur




under the disposal  conditions postulated in the EP's definitional




model or that  the EP  is  not sufficiently precise to enable




one to be confident in the results obtained from a given




testing.




            In response  to the first criticism, the Agency




believes, based  on  its hypotheses noted above,  that the  EP




(not including the  attenuation factor) is an accurate prediction




of the levels  of leaching which could occur in  a relatively




aggresive leaching  environment.  The Agency concedes however,




that it may have fallen  somewhat short of fully modeling the




leaching which could  occur in a actively decomposing municipal




landfill — in  part,  bacause its leaching medium  fails to  take




into account  the various chemical, biological and physical




factors whicli  bear  on the aggres s ivines s of municipal landfill




leaching media.   The  Agency further concedes that it had little




empirical data upon which to base its assumptions about  the




accuracy of leachability on site specific considerations.




Obtaining such empirical data may be an ephemeral goal.




Nevertheless,  the Agency hopes to assemble data on leachate




concentrations observed  at actual landfill sites in an attempt




to gauge the  representativeness of the EP.
                              103

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     In response to the  second  criticism,  the  Agency  believes




that the EP is sufficiently  precise  to  enable  one  to  obtain




reasonable confidence  in the results of the  test—especially




given the fact that one  can  always  obtain  greater  confidence




in the results by  running further replicates of the  test.




The width of  the confidence  interval has an  inverse  relationship




to the number  of tests run on a given sample.   Consequently,




if there  is a  question whether  a given  test  is reflective  of




the "true" result, it  becomes a simple  matter to  run  additional




samples  until  the  desired confidence is obtained.
                               104

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5'   Propriety of Requiring  Exercise of Scientific Judgement




       A number of  comments argued that the Extraction Procedure,




as  published in 43  JFR  58956<9>,  was not well enough defined to




permit the unambiguous  interpretation of how the procedure




should be followed.  Furthermore,  problems arose in conducting




the liquid-solid separation and  in agitating the sample during




the extraction phase of the procedure.




       The Agency  agrees with these comments and has taken  steps




to eliminate the difficulties.   Some of the specific changes  that




have been made relate  to:




       1. specification of  filtration as the final stage in




sample preparation  prior to measurement,




       2. specification that the purpose of centrifugation  is




to aid in liquid-solid  separation, not as the final means of




separat ion,




       3. use of a  generic  specification of the agitation equipment




       4. codification  of under  what conditions the sample  contains




so little solid  that  it can be  considered to be a liquid for  testing




purposes .



       In addition  to  changes that have been made in the pro-




cedure description* the Agency  is  making available to the public




a methodology manual  (27)  to present additional descriptive




information  on the  sampling and  testing methodologies used




in the evaluation  of wastes.  The  purpose of this manual is




to give  more specific  operational  information than would be




practical to put in the regulation itself.




* Appendix II of the  §3001  regulations.



                              105

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     This manual will  contain information about testing




specific wastes, including  clarification of any procedural




steps needed to correct  interpret ational difficulties.




The Agency intends  to  keep  the manual current by updating it




on a regular basis.




     However,  the Agency believes  that no laboratory procedure




for waste testing can  ever  by written that  unambiguously  addresses




all potential  interferences.   The  testing methods  have  been written




for use by experienced scientific  personnel.   It is  felt  that




such persons will be able to  overcome potential problems  and




obtain acceptable data,  given an adequate understanding of the




intent of each phase of  the testing  procedures.




     Specific  examples of how this  philosophy would  work  can




be gleaned from an  examination of  some of the comments.   One




organization subjected oak  and maple leaves to the Extraction




Procedure and  experienced significant difficulty in  attempting




to separate  the extractant  liquid  from the  leaves.   The intent




of the liquid-solid  separation step  is to remove all particles




of the extracted sample  having a particle size greater  than




0.45 micrometer from the extract.   Thus,  an experienced scientist




would know to  allow  the  leaf  particles to settle,  under the in-




fluence of either gravity or  centrifugal  force, decant  off




and filter the bulk  of the  liquid,  then transfer the remaining




mass of leaves to the  pressure or  vacuum  filter for  removal




of the small amount  of free liquid  that remains.   This
                              106

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change, though not  significant  from the standpoint of the final


results, would have  eliminated  the long filtration time experi-


enced by the commenter.



     A second example  which  serves to illustrate this point  re-


lates to the large  number  of comments the Agency received on the


agitation apparatus  described at  43 £R 58961 .   These comments


concerned problems  with  the  specific extractor  described  in
          a

the proposed regulations.   These  problems consisted  primarily


of jamming when  an  attempt was  made to extract  hard,  granular


wastes, and potential  extract contamination caused by using


a metallic extractor.



     As described  in the proposed regulation:



          "A suitable  extractor will not  only prevent strati-


          fication  of  sample and  extraction fluid  but also


          insure  that  all  sample  surfaces are continuously


          brought  into contact  with well  mixed  extraction


          fluid."(9)


     The Agency  believes that with this description  a competent



scientist can eliminate  any  problems,  of  the above types, en-


countered with specific  wastes  or agitators.  If the  sample  is


of such a size and  consistency  that jamming occurs due  to the



spacing between  the  extractor blade and the container,  then


either an agitator  with  a  different spacing should be used or,


if this does not  eliminate the  difficulty,  a different  type  of



agitator should  be  employed.  This latter approach was  used


by several commenters  in determining the  leachability of
                              107

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materials such  as  coal  combustion ash.   Though the studies

conducted at Oak  Ridge  National Laboratory (7,19) and Las Vegas

(18) indicated  that  contamination of the extract by an extractor

fabricated  of Type 316  Stainless Steel  was not a significant

problem,  the Agency  feels that if this  problem actually mani-

fests  itself, scientist conducting the  tests will know to

employ  an extractor  fabricated of either plastic or glass,

since  neither material  would hinder attainment of the agitation

conditions  specified in the regulation.

     The  most  significant problem encountered by commenters in

applying  the Extraction Procedure to a  specific waste, occurred

when filtering  samples  of drilling mud.  Due to the thixotropic

and pore  clogging properties of such materials, neither filtra-

tion nor  centrifugation was able to effect separation of the

liquid and  solid phases.  It is the Agency's position that, in

such cases, the whole waste should be treated as a solid and run
                                       cx>
through the extraction procedure.  If,  after performing the ex-

traction  procedure,  no extract is obtainable, the waste should

not be considered hazardous.
                              108

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C*   Failure to Distinguish Between Chromium III and Chromium VI

     A number  of  comments  argued that, basing an Extraction

Procedure Toxicity  threshold on total chromium in the extract
            ^k
was improper .  These  commenters argued that the two oxidation

states of chromium  present very different toxicity and environ-

mental problems and therefore the threshold should be based

only on the concentration  of chromium in the +6 oxidation

state.

   In support  of  this  position the following was cited.

          Cr(VI)  is significantly more toxic than Cr(IIl).

          Oxides  and salts of Cr(VI) are very soluble in water

          while  those  of Cr(IIl) are relatively insoluble.

          Cr(VI)  has been  shown to be a potent carcinogen in

          humans  while Cr(lll) on the o'ther hand has not been

          shown  to  be  carcinogenic in either humans or animals.

        0  Monitoring of groundwater below a landfill receiving

          tannery waste containing chromium in the reduced  +3

          state has shown  only limited migration after a period

          of  10  years. (45)

        0  There  is  no  data to indicate that under conditions  of

          land burial  Cr(IIl) can be converted to Cr(Vl).


*  The maior group affected by the application of thresholds,
appears to be  the leather  tanning industry.  According to a
study conducted  for the E.P.A.U6) and comments received in
response  to the  proposed regulations(47), the tanning industry
generates and  disposes of  approximately 200x10* Kg of waste^
per year  containing approximately 1000 metric tons of chromium.
                              109

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     In formulating  both  the National Interim Primary Drinking

Water Standards  and  these regulations, the Agency has chosen

not to adopt  separate  thresholds for the various oxidation

states of chromium.  The  reason for this is the Agency's

concern about  the  possibility of the conversion of chromium

from the relatively  nontoxic +3 form to the toxic +6 oxidation

state after disposal occurs.  This concern is based on studies

and observations  reported by researchers of the California

Department of  Health (48) and conditions known to occur in

municipal waste  disposal  environments.

     A great  deal  of controversy exists about the environmental

and health effects  of  chromium.  The two most important oxidation

states of chromium  for environmental purposes, are chromium III
                     •
and chromium  VI.   There is general agreement, as to the hazards

posed by the  chromium  VI  state since it exhibits toxic effects

to humans and  animals  by  every route of exposure and is reported
 OB
to be relatively  mobile in the environment(48).  On the other

hand, available  evidence  indicates a generally low oral toxicity

for chromium(III)  compounds.  The reason for the controversy

over the hazard  posed  by  wastes containing Cr(III) revolves

around its possible  conversion into the more toxic Cr(Vl)  form

under conditions  that  might  reasonably be expected to occur in


the environment.

     The California  researchers(48) found that upon exposure to

artificial ultra  violet light or sunlight, significant oxidation

of Cr(lll) to  Cr(Vl) takes place in water within a pH range
                              110

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V
of 7 to 10.  Exposing  an aqueous suspension containing both

soluble Cr(lll)  and  precipitated Cr(OH)3, to ultraviolet

light and air  for  5  days resulted in oxidation of approxiraatel

20% of the  total  chromium to the Cr(vi) state.  After 7 days

the percentage  of  chromium in the Cr(Vl) state approached

50% and after  41  days  the percentage approached 90%.  Definitive

evidence of  the  photo-oxidation of Cr(lll) in actual chromium

bearing tannery  wastes has not been obtained.  According to

the California  researchers:

         "Analysis of  these  wastes for Cr(Vl) has proven unreliable
      using  any  of the published methods.  These analytical
      methods  all  involve acidification of the Cr(Vl) solution
      prior  to  final analysis because the tannery wastes all
      contain  relatively high concentrations of dissolved organics,
      and because  Cr(Vl) is  quickly lost by reduction by the
      organics.   We  have found that this redox reaction takes  place
      very  rapidly and results in irreproducible results for Cr(Vl)
      concentrations.   It is commonly held that chromium tannery
      wastes do  not  contain  hexavalent chromium and  the basis  for
      this  belief  is negative analytical results based on the  EPA  or
      Standard  Methods procedures(49).  Close examination indicates
      that  these  negative chromium(VI) data may well be an artifact
      of the method  and do not reflect the true hexavalent chromium
      content  of  the tannery wastes."(48)

     Given  the  fact  that the oxidation of Cr(lll) to Cr(Vl)

has been demonstrated  to occur under relatively mild conditions,

and that this  demonstration  is consistent with the observation

that the predominant form of chromium in the surface layers

of the sea  is  the  hexavalent form (48),  the possibility that

Cr(lll) in  wastes  may  undergo oxidation after disposal cannot

be ruled out.

     In summary,  the Agency  believes that pending further studies

to determine the  extent to which this conversion does or does

not occur under  environmentally significant conditions,  the

only prudent course  of action is to consider all forms of

                              111

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chromium potentially  toxic.   The Tanners'  Council  of America

in their comments  on  the  proposed regulations  echoed this

conclusion. To quote:

          "A  study conducted in California found that ultra-
      violet  light and  sunlight promoted the oxidation of
      chromium.   It is  appropriate,  therefore, that the
      disposal of  waste's  containing  trivalent  chromium be
      regulated  so that these wastes are quickly and adequately
      covered  at  the  disposal site to minimize their exposure
      to sunlight ."(5)

      If  future research indicates that such a  course of action

 is not warranted,  then  the Agency will revise  the  definition

 of a  hazardous waste accordingly.
                               112

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D.     Operational  Problems

      Introduct ion

      The comments previously discussed,  dealt with what

could be termed  philosophical disagreements with the

proposed toxicity  characteristic.   In addition to these philoso-

phical questions,  a number  of comments were received concerning

the actual  operation of the Extraction Procedure.  These

comments can  be  grouped into the following areas:

      1. Liquid  - solid separation  procedures

      2. Structural integrity procedure/ Grinding of sample before
        extract ion

      3. Problems with the extraction equipment/agitat ion

      4. Adjustment of extract pH

      5. Sample:  extractant  ratio

      6. Final volume adjustment

      7. Analysis of multiphasic extracts

      8. Extractant toxicity as it  affects testing of the extract.

      This  section will address those changes made in the proposed

 procedure  as  a consequence  of these comments, and explain other

 suggested  changes that were not made.
                              113

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1.   Liquid-solid Separation  Procedure




     As was briefly  discussed  earlier,  significant  problems




were en countered by a  number  of commenters  in separating




the liquid phase of  the sample from the solid phase using




either the filtration or the centrifugation  procedure.   In




the case of thixotropic materials such  as  drilling  fluid and




paint these difficulties were  severe.




     As discussed above, the Agency believes that  if no  liquid




phase can be  generated  using the separation  procedure,  the




whole waste should be treated  as a solid and subjected  to




the extraction.  If, after the extraction  procedure




is performed,  no liquid is produced, the waste should be




considered nonhazardous.




     The separation  problems encountered with the wastes other




than paint and drilling fluid  appeared  to  be readily overcome




using standard laboratory techniques although, possibly  because




of the manner in which  the test procedures were written, the




availability  of these solutions may not have been  readily ap-




parent to  the laboratory personnel.  In the  main,  these  problems




consisted of  either  clogging of the filter membrane pores or




lack of a centrifuge which met the specifications  described




in the proposed regulation.
                              114

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     In order to  overcome  these problems,  the following




changes have been made.




     a. The centrifugation procedure is now defined in terms




of goals and no specific  equipment  is specified.  This change




clarifies the concept  that centrifugation  is actually more




a tool for prefiltration  sample preparation than  a final




separation technique  itself.




     b. The filtration step is  no longer defined  in terms  of




specific equipment.   The  procedures  manual(27)  will contain  all




references to specific equipment  to  make it clear that specific




pieces of equipment  are not being mandated.  The  procedures




manual(27) will also  clarify  for  the operator what procedural




changes one may make  without  invalidating  the test.




     These changes  in  the  description of the filtration step




should clear up any  uncertainty about the  use of  vacuum fil-




tration.  It is the  intent of the Agency that if  the  solid




phase does not require high (75 psi) pressure to  affect




separation, then  use  of the more  readily available vacuum  filter




is allowable.  The  use of  the pressure filter offers  a means of




operationally defining, at what point a wet solid can be




considered a solid  for purposes of extraction.   (For  example,




when to treat a sludge, though  it might actually  still contain




85% water, as a solid  for  extraction purposes.)




     The following  discussion will address  specific criticisms  and




operational problems  brought  out  in  the comments.   The first of  these




relates to the potential  clogging of the filter pad by wastes having
                              115

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low liquid to solid  ratios.   This situation may result in a
reduced degree of  separation and long filtration times.   The Agency
believes this potential  problem is easily overcome.   In  such
cases, if the solid  tends  to clog the filter pores,  an initial
centrifugation to  compact  the solid is recommended.   The liquid
thus obtained is  then  filtered to remove carryover particles,  and
the solid remaining  is  filtered under gradually increasing pre-
ssure.  Specific,  directions  will be given in the methodology
guidance manual(27)  for  those investigators unfamiliar with such
techniques.
     Section  250.13(d)(2)(1)(A)<1) of the proposal(9)  called for
filtration to continue  until no significant amount of  fluid
«0.5 ml) is  released  during a 30 minute period.  Commenters
felt that for many wastes  this is unnecessary.   In addition,
one commenter, suggested that filtration should be stopped
when gas issues  from the filter since allowing  gas to
bubble out of the  filter for up to 30 minutes  can cause  the
volatilization of  materials  from the filtrate.
     The Agency  agrees  with  these recommendations and  has
made the necessary changes  in the regulation.   In order  to
eliminate confusion  on  the  part of the testing  community
without resorting  to overspecification,  the regulation has been
changed to describe  what is  intended and to delete speci-
fication of the  filtration  time.  Laboratory personnel can
use whatever  filtration  time is required for the specific  waste.
In addition,  the  final  regulation specifies that filtration
should stop when  gas issues  from the filter.  This should
eliminate any potential  problems with gas discharge.
                              116

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     Section  250.13(d)(2)(i)(A)(l)  of the proposal(9) called




for inverting  the  filter  unit  when  changing the filter pads.




The Agency has been  told  that  filter holders supplied by one




manufacturer  cannot  be  inverted without leaking.   Thus,  the




regulations have been  changed  to eliminate this specification.




If membrane changes  are necessary to complete the required




separation, instructions  from  the manufacturer of the specific




filter holder  being  employed  should be followed.




     Some of  the commenters  reported that when the pressure




filtration technique was  applied to different wastes, filter




cakes with significantly  different  amounts of moisture were




obtained.  They  felt this indicated a problem with the tech-




nique.  The Agency disagrees with this interpretation.  The




filtration procedure is intended to simulate the  separation




that may occur in  a  landfill.   If the liquid refuses  to




separate out  during  pressure  filtration,  it will  also tend




not to drain  away  from  the waste when the waste is placed  in




a landfi11.




     Comments  were received which said that requiring two  con-




secutive 30 minute centrifugations  without an apparent change




in degree of  separation was excessive.   The Agency disagrees




with this comment  but notes that this concern has  been accomodated




by adoption of the more flexible centrifugation procedure.   Because




studies indicated  that  centrifugation alone resulted  in  carryover




of particles  > 0.45  urn, centrifugation is now simply  used  as




a means of achieving a  preliminary  separation in  order to
                              117

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speed up filtration.  All  centrates  are  to  be  filtered  to  remove




fine particles prior to  analysis.  This  change  in  the




centrifugation procedure  addresses the  concerns  of  other




comments relating  to addressed:




     a. Problems with centrifugation of  wastes  containing  solids




        having lower densities  than  the  liquid  phase, and




     b. The need to  define centrifugation  conditions  in terms of




        separation force (g forces)  instead of  rotor  speed




        and diameter.
                              113

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2.   Structural Integrity  Procedure/Grinding




     In order to accomodate  generators  whose wastes  are not




expected to undergo  significant  structural degradation after




disposal because of  their monolithic  structure or subjection




to special "fixing"  processes,  the  Agency developed  and




incorporated the Structural  Intgrity  Procedure into  the




proposed regulations(9).   This  procedure  received criticism




from several persons and  groups.  The specific criticisms




were :




     a. any alteration  of the  test  specimen is not representa-




tive of actual field conditions,




     b. the specific field conditions used as a model  for  the




Structural Integrity Procedure  are  completely contrary to




conditions that actually  exist  in the field,




     c. the equipment  specified  in  the  proposed regulations(9)




is unavailable and,  thus, industry  has  not been able to




adequately evaluate  the procedure,




     d. it is  impossible  to  obtain  an undisturbed field speci-




men of  the size and  shape required,




     e. the foam block  employed  as  a  sample holder is  subiect




to contamination,  and



     f. the Structural  Integrity  Procedure lacks sufficient




scientific validation,



     Though some of  these comments  are  valid, the Agency does




not believe that the information  presented in the comments is
                              119

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sufficient to warrant  either  dropping  or substantially modify-




ing the test procedure.




     The following states  the Agency's reasons  for retaining




the proposed Structural  Integrity  Procedure and the reasons  why




changes have not been  made.




     None of the comments  presented  any evidence to support




the claim that stabilized,  or other  monolithic  wastes,  fail




to undergo degenerative  structural changes  after disposal.




In fact, studies (51 and  52)  indicate  that  significant




deterioration actually occurs in  some  cases.   One such  situation




was found to occur with  fly  ash stabilized  with a popular




commercial fixation  process  (52).   Thus,  the  Agency believes




that in order to carry out  its mandate under  RCRA to consider




potential for harm under  improper  management  conditions,  it  is




reasonable to extract  wastes  in their  degraded  form if  degrada-




tion is actually going to  occur in the field.




     A second point  raised  by commenters  concerns the field  condi




tions modeled by the Structural Integrity Procedure.  While




subjecting stabilized  waste  to compaction stresses is not




routine practice, it is  by  no means  unknown.   Advertisements




have appeared in a number  of  publications,  including the




Washington Post, stressing  the beneficial uses  to which




stabilized waste can be  put.   Among  the uses  suggested  was




as a replacement for gravel  in construction applications  (e.g.,




forming bicycle paths).   Since such  uses  are  possible,  and,  in
                              120

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the case of some wastes probable,  it  appears  reasonable to


assume the waste may be subjected  to  the  compaction forces
                                           Sp
imparted by earthmoving equipment  such  as tractors.  Given

such an assumption, the Structural Integrity  Procedure,


which is a modification of  an  established procedure for

simulating the effects compaction  machinery has  on soils,

appears to be based on reasonable  assumptions.


     The comments made with  respect  to  the unavailability  of

the equipment were due to  a  misunderstanding  on  the part  of

the commenters.  The equipment  design belongs  to EPA,  not  to

any one company.  The design and  specifications  were published

at 43 FR 58691(9) and anyone desiring to  obtain  the equipment

could either fabricate it  in their own  facilities  or obtain

it from a competent machine  shop.   EPA  published the name  of

the particular supplier from which EPA  purchased its units

solely for the convenience  of  the  public.

     The Agency  agrees with  the concern that  obtaining an

undisturbed specimen of an  already disposed of monolithic

waste presents a problem.   However,  the agency envisions

preparing samples of the correct  size and geometry by  casting

the fresh waste  in a suitable  mold,  allowing  it  to cure for

the specified time, and then subjecting it to  the  procedure.

This is analogous to the methodology  commonly  employed in

the construction industry  for  testing the strength of  concrete
                              121

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For those situations  where  a  specimen is required of an already

inplace waste, geological  coring equipment (which is
                        *.
inconvenient and potentially  expensive)  can be employed.

     The Agency recognizes  the  concern with particles becoming

trapped in the cellular  polyurethane sample holder causing

contamination of subsequent samples.  To eliminate this potential

problem, the equipment  specifications have been broadened to

permit the use of  non-cellular  sample holders which are

easily cleaned between  tests.

     EPA believes  that  even though the reproducibi1ity of the

Structural Integrity  Procedure  has not been determined, the

advantages of including  the test in the  regulations outweigh

the potential disadvantages.  Elimination of the test would

require everyone testing waste  to grind  it to pass a 3/8"

sieve.  Retention  of  the Sturctural Integrity Procedure

imposes no additional burden  on the regulated community

and, at the same time,  allows generators who stabilize their

wastes against leaching  a  means of demonstrating this property.



Grinding

     A comment was received concerning the fact that some wastes

were difficult to  grind.   The commenter  reported that attempting

to grind a waste in a blender resulted in the blender breaking.

The Agency realizes that some wastes may be very hard.   A blender

is not designed to be a  grinder.  If a hard material is to

be ground, then equipment  designed for such use should be

employed.  Such equipment  is  readily available from companies


                              122

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servicing metallurgical  and  plastics  testing laboratories.




     In addition, if the material  to  be  tested  is  so strong




that ^grinding actually presents  a  problem,  then it is likely




that such a material would not  tend  to be  ground in the  environ-




ment and should  therefore be evaluated using the Structural




Integrity Procedure.




3 .   Agitat ion




     A number of comments were  received  concerning problems




people encountered, or envisioned, while employing the extractor




pictured in Figure  1 of  the  proposed  regulation (43 FR. 58961)(9),




These comments fall into the following groups:




     a. The extraction conditions  (40rpm)  do not prevent




strat ification.




     b. In certain  cases the extractor blade will  iam, with




the result that  the motor can burn out.




     c. When using  very  small samples  the  top blades  do not




contact the solution.




     d. When solids having a very  low  density are  tested,




there is insufficient room in the  extractor  to  accommodate




all the solution and still agitate the system vigorously.




     e. Use of stainless steel  as  the material  of  construct-




ion may result in contamination  of the extract  with various




metals.



     f. The extractor is not large enough  to permit the pre-




paration of sufficient amounts  of  extract  to allow one to




conduct the test procedures  described  in the Advance  Notice




of  Proposed Rulemaking (43 FR 59022)<9>.



                              123

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     The Agency recognizes  the  validity of these comments but




believes they are not  significant  enough to have required a




change in the proposed  regulation.   This conclusion was




reached because the  regulation,  as  proposed,  incorporated




sufficient flexibility  to  eliminate all these problem areas.




     Elimination of  these  potential problems  requires the exer-




cise of scientific  judgement  on the part of the investigator




conducting the tests.   The  proposed regulation did not specify




that any one specific  extractor is  required.   The Agency




found that this point  was  misunderstood by many people.   To




eliminate confusion  a  notice  was  placed in the Federal Register




on March 12, 1979 at 44 FR  13548(44).   This notice sought to




clarify that the Agency's  intent  in describing the particular




extractor was to illustrate one acceptable type of agitator.




The Agency did not  intend  the unit  so  described to be considered




the only one acceptab-le.




     The Agency believes  that the  specific extractor used in  any




particular investigation  should be  determined after considering:




     a. the physical characteristics  of the waste,




     b. the quantity of sample  to  be  extracted,




     c. the method  of  pH  adjustment to be employed,




     d. the analyses to be  performed  on the resulting extract,  and




     e. the number  of  waste evaluations to be performed concurrently.




     Under these conditions,  if the analyst is faced with any of  the




problems previously  mentioned,  it  becomes a simple matter to  select  an




extractor suitable  for  the  waste  in question.  For example,
                              124

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if a waste is being examined for  leachable metals, it would

    o
seem prudent to use an extractor  fabricated of a nonmetallic


material if aggressive conditions  are  to be employed during


extraction.  Similarly,  if  jamming  is  found to occur, an


extractor with either a  different  blade clearance or one


which does not require stirring  of  the particles should be


selected.
                               125

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4.   Adjustment  of  Extract  pH




     Two commenters  mentioned problems with the pH adiustment




during the course  of the  extraction.   The first commenter




concerned the potential  danger of adding acid to a waste




containing cyanide,  sulfide, or other constituent capable




of forming toxic  gas.   The second comment complained about




the cost of  the equipment  needed to automate the procedure.




     With respect  to the  danger of toxic gas formation,  the




Agency believes it is  only common sense to evaluate the




waste for the presence of  gas generation contaminants prior




to conducting the  Extraction Procedure.  This is especially




important since the  presence of such  constituents can make




the waste hazardous  under  the Reactivity Characteristic  even




if the waste does  not  contain other extractable toxicants.




     With respect  to the  cost of automating the pH adjustment




step, two points  need  to  be made.  The first is that automation




of the adjustment  step is  not required by the regulations.




Secondly, if a  laboratory  elects to employ automatic titration




equipment, for  purposes  of saving labor cos'ts,  the cost  of




such equipment  is  much less than the  commenter  quoted.   Spe-




cifically, the  equipment  described in the proposal, and  employed




during much  of  the developmental research conducted at  the




Oak Ridge National Laboratory, retails for $325 (Cole Farmer




Co.  Catalog #5997-20) while a  similar  competing unit




retails  for  $495  (Fisher  Scientific Co., Catalog #13-637-650).
                              126

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5.    Sample to Extractant  Ratio




     One commenter commented  as  follows:




     "The solid/liquid ratio  used  in the  EP test is  based on "as re-




ceived" (wet) weight.  This  severely complicates intersample and in-




ter labor at ory testing.  Also,  diluting from a ratio  of 1:16  to 1:20




requires careful quantitative  transfer procedures.   Why not  just use




1:20 or 1:10, since  solid  to  liquid ratios  tend to  be  arbitrary as




shown in the Wisconsin study."




     This comment addresses  two  concerns-problems  related




to working with materials  whose  composition may change if




care in their handling is  not  taken (e.g.,  the wet  samples




may dry out with a resulting  change in percent solid),  and




the fact that careful  laboratory techniques are required




throughout testing.  With  regard to the first point, the




Agency has chosen to use wet  weight for purposes of  computing




the solid/liquid ratio because use  of  dry weight might  not




prove representative of the  leachability  of the waste.   For




instance, if the solid residue obtained after the  initial




separation procedure still contained a fairly high  percentage




of liquid, drying the  solid  residue would dramatically increase




the concentration of toxic contaminants in  the solid sample




with a possible attendant  increase  in  the quantity  of




contaminants leached from  the waste.   At  the same  time drying




the solid residue could severely understate the leachability




of the waste, as in  the case  of  electroplating wastes.   Data
                              127

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in the  Agency's possession indicates  that,  for  some  unknown




reason  drying electroplating wastes results  in  lower contaminant




concentrations in the leachate  (35).




     With regard to  the  second  point,  the  Agency  believes




that the need for care  in  performing  the  analytical  transfers




does not justify changing  the  regulations  inasmuch  as  it  is




in the very nature  of analytical  chemistry to  require  such




care.
                              128

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6.   Final Volume Adjustment


     One commenter suggested  that  for  operational  convenience
                                                 «*>

it  may be desirable to  perform  the  extract  dilution  prior  to


the liquid solid separation  step.   The following  formula  for


determining the amount  of  water to  add was  suggested:


     V = (20)(w) - (16)(w) -  (a)(HOAc)


wh e r e :


     V = ml of water  to add


     w = weight in gms  of  solid charged to  extractor


     a - ml of acetic acid solution added  during  extraction.


     Since this procedural change  neither  changes  the  intent


 nor results of the dilution  step,  and  does  save the  laboratory


 investigator  time, the  Agency has  adopted  the suggestion


 and changed the regulations  accordingly.
                              129

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7.   Analysis of Multiphasic  Extracts


     A number of comments  were  received concerning the analysis

                              i*
of  multiphasic liquid  extracts.   These comments and questions


indicated to the Agency  that more guidance is needed in this


area.


     There are basically two methods  for handling multiphasic


liquid extracts.    The phases can be  separated, their volumes


measured, separately  analyzed and then mathematically combined


to determine the original  concentration for each species in


question.  Alternatively,  the operator can mix the multiphasic


mixture, using a high  shear  mixer (e.g., homogenizer), withdraw


 an aliquot,  then subject the aliquot  to a total extraction


 or digestion depending on  the species of interest.


     In  order  to eliminate confusion  on the part of the regu-


 lated community  the Agency has  added  clarifying wording to


 the regulation and  will give further  guidance in the methodology


manual(27).
                              130

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8.   Extract Toxicity




     A large number of  comments  expressed concern that the




presence of^acetic  acid,  or  acetate ion,  would interfere




with bioassay  testing  of  the extract.   This concern is parti-




ally valid inasmuch as  acetate is known to interfere,  in




some cases, with  the  phytotoxicity bioassay procedures currently




under development  by  the  Agency  (19).  However, since the




final regulations  do  not  call for any  bioassay testing to be




performed  on the  extract, this potential  for interference




is a moot  point.   Research at ORNL (7,19) indicates that EP




extracts can be  evaluated for both mutagenicity and aquatic




toxicity without  serious  interference  from the leaching




medium.  As noted,  above, the Agency is continuing work on a




 leaching medium  which  will not interfere  with bioassay testing.




     Some  commenters  expressed the concern that the acetate




would interfere  with  chemical analysis of the extracts.  The




Agency knows of  no  data to indicate that  this concern  is




anything but theoretical  and so  is not convinced that  a




change in  the  methodology is required.  If, in the future,




there is a demonstration  of  such interference appropriate




changes will be  made.
                              131

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E.   Economics of Testing
     A number of comments  were received on the cost of the
test procedures required  to  be performed by the regulated
community.  There  are  two  aspects to this concern.  The
first is the actual  cost  for performing the specific tests.
The second relates  to  the  question of what tests the regulated
community will be  required to perform on their wastes.
     In responding  to  this comment,  it should be noted at the
outset that RCRA does  not  require EPA to take costs into account
in formulating its  regulations.   The Agency believes,  however,
that the cost of running  the EP  on one's waste is, by  any standard
of judgement, reasonable.
     The cost of determining whether a waste meets the Extraction
Procedure Toxicity  Characteristic can be divided into  the cost for
obtaining the sample and  the cost of testing the sample.
     Sampling costs  are  largely  dependent on the waste, the gen-
erator, and even the plant involved.  The Agency believes that it
is only right to require  one who is  disposing of a waste to know
what the properties  of the waste are.  In order to accomplish
this one must have  a sample  of the waste.  Thus, collecting
a sample of one's  waste  is not felt  to be an unjust burden.
     The Agency has  found  that independent laboratories are
quoting prices for  testing a specific sample, using the
Extraction Procedure and  associated  analytical procedures,
to be in the range  of  $200-600 for the required tests.
These are single sample  prices and,  for most companies who
have several wastes  to test, would actually be at the  low
end of this range  (approximately $200).
                              132

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F.   Specific Comments  on  the  Noticed Reports





          Q



     Since publication of  the proposed regulations, the Agency




received and made  available  to the public a number of reports




dealing with the development  of the Extraction Procedure




Toxicity Characteristic.   These reports are:




          Compilation  and  Evaluation of Leaching Test




          Methods  (EPA-600/2-78-095)(l5>




          Comparison of Three Waste Leaching Tests (Final




          and Executive Summary)  (EPA-600/2-79-071)(16)




          Toxicity of  Leachate, Interim & Final Reports,




          Oak Ridge National  Labor at ory (? > 19 )




     0    Assessment of RCRA/EP Test Results on FBC Residues:




          Part  II(53^




     0    Electroplating  Wastewater Sludge Characterization,




          EPA-AES  Cooperative Agreement, September 12, 1979^35




     0    Evaluation of Solid Waste Extraction Procedures  and




          Various  Hazard  Identification Tests, NUS Project




          Number 6745(36)




     0    Proposed RCRA Extraction Procedure:  Reproducibility




          and Sensitivity,  EPRI,  November 1, 1979.<37)




     0    Evaluation of Procedures for Identification of




          Hazardous Waste,  Interim Report, EMSL-LV (18)




     0    Background Study on Development of Standard Leaching




          Test  (EPA-600/2-79->107)<14)
                              133

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     Approximately  30  comments  were  received in response to




the Agency's notice  of  these  reports.   In the main the comments




did not address themselves  to the  specific scientific results




reported in these studies.  Rather they addressed their




interpretation of the  meaning of  the work in relation to the




proposed toxicity definition  as  enunciated in the EP  Toxicity




characteristic and  the  criteria  for  delis ting.(9)




     While the comments  dealt with a number  of  issues,  most




of these have been  discussed  previously in this  background




document.  This section  will  address the  remaining issues  as




well as clarify several  points made  by  commenters who had




apparently not availed  themselves  of the  explanatory  material




made available in the  draft Toxicity Background  Document'"'




and thus were not aware  of  the  intent  and rationale behind




the work done during these  studies.
Comment:  No  factual  basis  for  defining  hazard  has  been




          developed in  these  studies  and no  recognized




standard of judgment  has  been applied  to this work.






Response: The basis for  the Extraction Procedure  developed  as




          a result of these studies has  been described previously




in this document.  The  basis  for  the  bioassay tests  has  been




discussed in  the aforementioned draft  Background  Document.'6^




The reason different  dilutions  of  the  EP extract  were  examined




for toxic effects  in  the  various  bioassays  relates  to  the




fact that the model of  environmental  exposure used  in  developing






                              134

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                        B
the EP Toxicity characteristic  postulates different degrees

of dilution for different  targets  of exposure (e.g., fish,

plants).  Chronicly  toxic  effects  toward the aquatic and

terrestrial plant  environments  were thus studied at the

expected levels of exposure.   The  organisms employed in these

studies were believed  to  be  sensitive enough for such an

approach to be used.



Comment:   "CMA recognizes that an uncomplicated short-term

           test is necessary  for initial screening of the large

body of wastes to  define  potential hazard.   The  single elution,

solid/liquid ratio,  and  the  time per elution of  the proposed

EPA are a practical  compromise  to  more complex procedures

such as the SLT reviewed  in  the subject  document.   The setting

of a threshold concentration  as the basis for defining hazard

makes proper use of  the  most  important data such tests develop".


Response:  The Agency  appreciates  the fact  that  these commenters

           took the  time  to  let EPA know they concur with our

conelus ion.


Comment:   Work done by  ASTM  under Phase II of a study supported

           by the  U.S. Department  of Energy indicated that

the EP  is not reproducible.


Response:  The Agency  is  aware  of  this study but has been unable

           to obtain a copy  of  the results  from  the sponsoring

ASTM subcommittee.   Thus,  the results of this work have not


                              135

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been "included  in  the  data base used to develop the EP charac-




teristic.







Comment:   The  quality  of the work performed at ORNL is




           suspect  since  less than adequate quality assurance




procedures were employed.







Response:  The  Agency believes the work performed at ORNI/7>9)




           to  be  scientifically valid pending any specific




evidence  to  the contrary.






Comment:   The  EP is  not  reproducible.






Response:  While  this point was raised in a number of comments,




           the  comments by two groups, the American Petroleum




Institute  (API) and the Utility Solid Waste Activities  Group




(USWAG) were the  most specific and detailed and thus have been




specifically addressed.






     In general,  the  Agency agrees with many of the criticisms




noted in  the API  and  USWAG comments relative to the incompleteness




of the data  base,  and its ability to precisely define the




reproducibility of  the  EP and analytical procedures.   However,




as with the  studies themselves, the commenters often do not




clearly distinguish in  their comments between reproducibility




as it relates  to  the  EP or as it  relates to the analytic tech-




niques.  Also,  there  appears to be some expectation that the




EP and analytic techniques should have similar reproducibility
                              136

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indicators for  each  of  the eight elements and for each of




many different  waste types.   This may represent a fundamental




misconception about  the reproducibility of both the EP and




the analytic techniques.   This expectation is somewhat similar




to expecting that  a  test  battery that measures vastly different




types of abilities  should have an overall reliability estimate




that applies equally to all  age groups.  Further,  as in the




studies themselves,  the comments do not indicate what would




be an acceptable  level  of reproducibi1ity.   Failure to provide




some guidelines  of  what general levels of reproducibi1ity




would be acceptable  for the  EP and the analysis techniques




tends to compromise  the criticisms offered.   The critical




issue is whether  the proposed EPA guidelines  and regulations




regarding  the EP  and analysis techniques have adequate repro-




ducibility to serve  as  a  screening mechanism  for identifying




potentially hazardous wastes.  It should be borne  in mind




that since the  Agency has raised the definitional  threshold t




100 times  the applicable  NIPDWS threshold,  many of the




criticisms made by  the  commenters do not apply.   This is  due




to the fact that  at  higher thresholds the toxicants  are




analytically easier  to  measure and the percent error would be




expected to decrease significantly.




API Comments



     The API comments concern a review and  discussion of  the




results of the  four  studies  (18,35,36,37) conducted  on the




reproducibility of  the  EP and AA analysis techniques.  The






                              137
:o

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four separate studies  were  conducted by Electric Power Research


Institute (EPRI),<37)  NUS  Corporation (36)f the American


Electroplater's Society  (AES)<35) and the EPA Environmen-


tal Monitoring Systems Laboratory,^1-8) respectively.


     Comments on  the NUS  study (36) tend to misinterpret the


relative standard  error  (RSE)  used by the NUS investigators


as an index of reproducibility.   For example the comments


include the statement  that  the standard error which defines


the distribution  of  the  means  is  related to the standard


deviation (36, p.4).   This  is  true, but the standard error


(of the mean) is  also  a  function  of the number of analytic


replications, an  important  component in determining the size
                                •

of the standard error  (of  the  mean).  In this regard,  the


comments state that  "API  would hesitate to accept any  procedure


with such a high  analytical error" (+_ 30% RSE) (36, p.4).


With a + 1 RSE representing the  95% confidence interval about


the mean value of  lead in  BOF  slag, one wonders what RSE


would be acceptable  to API.


     The Agency generally  agrees  that the NUS report is not a


thorough study and is  incomprehensible (36, p.5) but cannot


agree that levels  of toxic  metals below detection limits


should be reported as  0.000 ppra  and included in the analysis


(36, p. 5).   EPA  believes  that values at or near the limit


of detection  and  which are  orders of magnitude below the


threshold levels  should  not be included in reproducibility


estimates, only those  levels near the threshold values  or




                              138

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above should be  included.




     Comments regarding  the EP and Toxic Extraction Procedure




(TEP) comparisons  in  the API Comments are irrelevent since




the EPA regulations  specify only the use of the EP.




     API comments  on  the EPRI report^37) seem valid generally,




except that  the  comments regarding the Confidence Multipliers




(CMs) in the EPRI  report tend to ignore the study limitations




noted by the authors  of  the EPRI report.  Many of the extreme




confidence  intervals  include analyses which the authors of




the EPRI study note  should be interpreted with caution (because




of variability due to unallocated error or because the number




of values below  detection units are large enough to make the




results less • reliable)  (p. 3 of Phase I report).(37)   Also,




reporting extreme  90% confidence limits as percentage of the




mean is a somewhat misleading way to present reproducibility




data.  The  percentages  reflect both measurement error and 90%




of the area  included  under a normal distribution.




     API comments  on  the study by the EPA Environmental




Monitoring  Systems Laboratory (EMSL)^18^ in Las Vegas tend to




be confusing.  For example, ICP was used as a screening device




by EMSL to  determine  what wastes would be subjected to the




EP and the  AA analyses.   The API comments, however, discuss




the ICP results  as though they were indicators of the EP and




analytical  reproducibilities.  Specifically, the API comments




state that  the ICP analysis results indicate there is something




amiss with  the EP  or  analytical procedure.  The ICP has






                              139

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nothing to  do  with  EP reproducibility.   Also, the EMSL is

criticized  by  API  for being incomplete  even though the report^18)

is clearly  indicated  as  an interim report and includes statements
                                                             O
about further  analyses that are planned.

     API  comments  on  the AES study^35)  intersperse comments

on the design  of  AES  experiments with issues relating to the

reproducibility  of  the EP and analytic  techniques.  For example,

in the AES  experiment with different levels of pH used for

the EPA,  the  unreproducibi1ity of the EP  at the standard pH 5

levels is not  established simply because  different analytical

results were  obtained at other pH levels.  Even so,  the

analytic  results  at pH 5 seemed somewhat  more uniform than the

analytic  results  at the  other pH levels.   As indicated earlier,

the API comment  regarding the overall reliability of the EP

may reflect a  misconception that the EP should be equally

reproducible  for  all  types of solid wastes.

USWAG Comments

     The  comments  submitted by the Utility Solid Waste

Activities  Group  (USWAG) tend to be more  focussed through the

API comments  upon  the specific research results of three

studies regarding  the reproducibility of  the EP and  AA analytic

methods.  In  general, the review by USWAG consultants,

Envirosphere,  submitted  along with the  comments is a fairly

thorough  evaluation of the methodological and scientific

merits of each of  three  studies, the EPRI study,<3?) the EPA

EMSL study,CIS)  and the  NUS Corporation study.<36>   The USWAG


                              140

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comments regarding  the  variability of analytic results according




to the types of wastes  and  toxic  metals  examined tends to be




supported across  the  different  studies.   However,  as indicated




earlier, reproducibi1ity  estimates need  to be established




for each type  of  waste  and  for  each elemental analysis.




     The USWAG comment  regarding  the appropriateness of  the




use of any standardized leaching  test to "perform  more than




an initial screening  function"  is somewhat confusing.   The EP




and analytic techniques coupled with the threshold levels




serve as a screening  mechanism  for determining wastes  requiring




controlled management.   The accuracy of  the EP and analytic




techniques to  model actual  leaching at  specific disposal




sites will not be established until studies comparing  the




model results  with  actual disposal site  leaching are conducted.




As was discussed  previously,  the  EP is  not meant to model any




specific disposal site  but  is instead a  generalized model.




     As with the  API  comments,  the measures of the relative




standard error used in  the  NUS  report^36)  tends to be




interpreted as a  relative standard deviation (RSD) or




coefficients of variability in  the USWAG comments.  Also, the




USWAG comments on the EPRI  report^37) include most of  the




Confidence Multiplier  (CMs) for each element included  in  the




EPRI report.   If,  for example,  one only  includes those data




which are largely complete  for  the ANOVA design, a somewhat




different picture emerges of  the  reproducibi1ity of intra-
                              141

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laboratory analyses  (consistency)  and  inter-laboratory


analyses (concurrence).  The  following  distributions  of


CMs are found with  a more  conservative  extraction  of  the  EPRI
                       e

data (37, p. 14)  (indicators  of  inter-  and  intra-laboratory


reproducibility on  the combined  AA analysis  results).
                      Inter-Laboratory        Intra-Laboratory
                      Analysis   CMs           Analysis  -CMs
Intervals
1.01-1.25

1.26-1.50

1.51-1.75

1.76-2.00

2.01-2.25

2.26-2.50

2.51 +

Totals
N
13
0
1
2
1
0
8
' 25
1
52
0
4
8
4
0
32
100%
N_
20
4
1
0
0
0
0
25
_%
80
16
4
0
0
0
0
100%
     These  results  suggest  that  the reproducibi1ities  of

intra-laboratory  analysis  techniques (consistency)  are

appreciably better  than inter-laboratory analysis  reproduci-

bilities  (concurrence).  A  different (and less  positive)

picture emerges when all the data results are considered  as

in the API  comments  and the USWAG comments.   Also,  averaging

all the CMs  presented in the EPRI studyO7)  tends  to present

an inflated  picture  of the  CMs,  since the mean  is  affected
                              142

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by extreme values and  the  extreme  values  are very large CMs.


The USWAG comments regarding  the NUS  report,(36)  however,


seem justified, except  that RSEs are  reported as  relative

    £>
standard deviations  (same  as  coefficients  of variation).


     The report attached  to the USWAG comments,  completed  by


the Environsphere Company,  is  a thorough  and insightful review


of the three reproducibi1ity  studies.  However,  the  Agency


questions the  inclusion of  sampling  techniques as part  of


determining reproducibi1 ities  in the  "Toxic  Waste Test."   It

is generally understood that  the EPA  guidelines  regarding


sampling techniques  for solid  waste  need  further  refinement.


At the present  time,  the  precision and reproducibi1ity  of  the


EP and AA techniques  is the central  issue.   Also, presentation


of the "corrected mean  concentrations" of  elements from "the


EPRI report (37, pp.  17-19) does not  adequately  reflect

reproducibi1 ities of  the  analyt ic  procedures,  since  these


values incorporate variances  attributable  to both the EP and


to the analytic technique.

     The consultant's  report  addresses the  issues of the


incorrect statistical  summaries presented  in Table 8 of the


EMS!/18) report, yet  fails  to  point  out that their corrected

values indicate an increased  reproducibi1ity estimate  for  the


pH levels and  percent  solid determinations.   Also, the  Agency


cannot understand why,  in  both the EMSL^8)  study and  the

consultants review,  ANOVA  techniques  were  used without  multiple


comparisons tests.   A  simple  t-test  between  the  highest and



                              143

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lowest mean values  for  chromium in Pond P,  2A,  and lead in Pond

0, 2B, did not  indicate significant differences within three

replicate analyses  of  the  same  samples.  The consultants are

not particularly  clear  about  how they conducted their own ANOVAs

analyses .



Comment:  Specification of construction materials  for extractor
                 a
          must  be  flexible in order to accomodate  different

waste materials.



Response: Neither  the  proposed  nor final regulations  specify

          materials  of  construction for the  extraction

equipment.  The Agency  agrees that those evaluating waste

materials should  use materials  of construction  appropriate to

the properties  of  the waste and to the analyses to be conducted.



Comment:  None  of  the  reports evaluated analytical procedures

          for the  pesticides.



Response: Due to  the unavailability to the Agency  of  wastes

          containing significant  concentrations of pesticides,

these were not  included in the  test program.  However,  no

comments were received  indicating problems in analyzing EP


extracts for pesticides.


Comment:  Neither  vacuum  filtration nor mechanical agitation

          are appropriate  for determining if wastes contain


volatile materials.
                              144

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Response: The  Agency agrees and is not using the EP to




          determine  if a waste poses a potential hazard



due to its  content  of volatile compounds.






Comment:  Concentrating extracts prior to  analysis is in-



          appropriate since it does not simulate what happens



in the real  world.






Response: The  commenter appears to misunderstand the intent



          of the  concentration step.  The  purpose of



concentrating  the extract prior to analysis is  to improve the



accuracy  of  the  analytical determination.   Thresholds for



toxicity  are expressed on the basis of concentration in the



original  extract.   Concentrating the extract prior to analysis
                                                                c


does not  change  the  measure of toxicity.






Comment:  The  fact  that a sample of sewage sludge failed the



          proposed  criteria for cadmium and mercury indicates



the excessive  severity of the EP.






Response: The  Agency disagrees with this  comment.  Many municipal



          sewage  sludges contain concentrations of cadmium and



other metals sufficient to pose a  health  hazard if improperly



used for  soil  amendment or fertilization  use.   Thus these



sludges would  be  hazardous wastes  under RCRA.   However, using



the thresholds promulgated today (i.e., 100X NIPDWS), none of



the municipal  wastes tested would  have met the  definition of




hazardous waste.





                              145

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Comment:  Use  of  the  resin technique for concentrating organic




          materials  present in the extract as part of the




analytical  procedures  is  not suitable for all types of organic




compounds.







Response: The  Agency  agrees with this comment.  However, this




          technique  is currently under evaluation and has not




been included  in  the  regulations promulgated today.






Comment:  The  meaning  of  the results using the arsenic




          contaminated groundwater is in question given the




unknown handling  and  storage of the sample.






Response: The  groundwater sample was not -employed to determine




          if  any  specific waste was a hazardous  waste, but




rather served  as  an  investigatory tool.   Thus, irrespective




of its history,  since  its composition prior  to biological use




was determined,  the  results obtained are valid.






     A number  of  comments were received  relative to biological




test procedures  which  had been proposed  as part  of the de-




listing procedures under  Part  250.15.  Since these test pro-




cedures have  not  been  included in the regulation promulgated




today, a  detailed discussion of these comments will not be




included  in this  discussion.  In general,  the Agency agrees




with the  commenters who indicated that  the EP extractant




liquid seriously  interfered with the phytotoxicity test




procedure.  However,  the  Agency believes that this problem






                              146

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with the EP extractant fluid does not  apply  to  either  the




mutagenicity or Daphnia magna chronic  toxicity  assays.  As




has been discussed previously in this  Background Document,




the Agency does not believe, however,  that these assays are




ready for general use by the regulated  community.
                              147

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  VI.    PROMULGATED REGULATION


§261.24  Characteristic of EP Toxicity


         (a)  A solid waste  exhibits  the  characteristic  of  EP


  toxicity if, using the  test methods described  in Appendix II  or


  equivalent methods approved by  the  Administrator under the pro-


  cedures set forth in  §§260.20 and 260.21,  the  extract  from a


  representative sample of the waste  contains  any of  the


  contaminants listed in  Table I  at a concentration equal  to or


  greater than the respective value given in that Table.   Where


  the waste contains less  than 0.5  percent  filterable  solids,

  the waste itself, after  filtering,  is  considered to  be the


  extract for the purposes of this  section.

    •
         (b)  A solid waste  that  exhibits the  characteristic of


  EP toxicity, but is not  listed  as a hazardous  waste  in Subpart


  D, has the EPA Hazardous Waste  Number  specified in  Table  I


  which corresponds to  the toxic  contaminant causing  it  to  be


  hazardous.
                                148

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                          Table I
           Maximum  Concentration of Contaminants
           for  Characteristic of EP Toxicity
     EPA
Hazardous  Waste
   Number	_

   D004

   D005

   D006

   D007

   D008

   D009.

   D010

   D011


   D012
D013
DO 14
DO 15
D016
DO 17
                Contaminant
                                       Maximum
                                    Concentration
                                (milligrams per lite)
Arsenic  »»...„	„._...	    5.0
                                   Q

Barium	  100.0

Cadmium	    i.o

Chromium	.. .	............    5.0

Lead - » *	,	„....    5.0

Mercury	»	    0.2

Selenium .	. . ^ . . . .    1.0

Silver	    5.0


Endrin (1,2,3,4,10,10-hexachloro-l
  7-epoxy-l,4,4as 5,6,7,8,8a-octahydro-l
  4—endo, endo-5,8-dimethano  naph-
  thalene	-•	    0 .02

Lindane  (1,2,3,4,5,6-
  hexachlorocyclohexane, gamma
  isomer	^	    0.4

Methoxychlor  (1,1,1-Trichloro-2,2-bis
              [p-methoxyphenyl]ethane) .  10.0

Toxaphene (C10Hi0Cl8>  Technical
  chlorinated camphene,  67-69
  percent chlorine)	-	   0.5

2,4-D, (2,4-Dichlorophenoxyacetic
  acid)	10.0

2,4,5-TP      Silvex     (2,4,5-
  Trichlorophenoxypropionic acid)	   1.0
                                 149

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                      APPENDIX II

               EP  Toxicity Test Procedure


 A.  Extraction Procedure (EP)

       1.  A representative  sample of the waste to be tested

 (minimum size 100  grams) should be obtained using the methods

 specified in Appendix  I  or  any  other method capable  of yielding

 a representative sample  within  the meaning  of  Part  260.   [For

 detailed guidance  on conducting the various  aspects  of the  EP"

 see "Test Methods  for  the Evaluation of  Solid  Waste,  Physical/

 Chemical Methods," SW-846,  U.S.  Environmental  Protection Agency

 Office of Solid Waste, Washington,  D.C.  20460.*]

       2.  The sample should be   separated into its component

 liquid and  solid phases  using the  method described in

 "Separation Procedure" below.   If  the solid residue** obtained

 using  this  method totals less than  0.5% of the original weight

 of  the waste,  the residue can be discarded and the operator

 should treat  the  -liquid phase as the extract and proceed

 immediately  to Step 8.

       3.  The  solid material obtained from the Separation

 Procedure should  be evaluated for its particle size.   If

 the solid material  has  a surface area per gram of material


* Copies may be obtained  from Solid Waste Information, U.S.
  Environmental Protection Agency,  26 W.  St.  Clair Street,
  Cincinnati,  Ohio  45268

**The  percent  solids  is  determined  by drying the  filter pad  at
  80°C until it reaches  constant weight  and  then  calculating
  the  percent  solids  using the following  equation:

  (weight of pad  +  solid) -  (tare weight  of  pad)  X 100 =  %  solids
           initial  weight of sample

                         150

-------
equal to, or  greater  than,  3.1 cm2 or passes through a


9.5 mm (0.375  inch)  standard sieve,  the operator should


proceed to Step  4.   If  the  surface area is smaller or the


particle size  larger  than  specified  above, the solid material
            0

should be prepared  for  extraction by crushing,  cutting or


grinding the  material  so  that  it  passes through a 9.5 mm


(0.375 inch)  sieve  or,  if  the  material  is  in a single piece,


by subjecting  the material  to  the "Structural Integrity


Procedure" described  below.


      4.  The  solid  material obtained in Step 3 should be


weighed and placed  in  an  extractor with 16 times  its  weight


of deionized  water.   Do not  allow the material  to dry prior


to weighing.   For purposes  of  this test,  an acceptable


extractor is  one which  will  impart sufficient agitation


to the mixture to not  only  prevent stratification of  the


sample and extraction  fluid  but also insure that  all  sample


surfaces are  continuously brought into  contact  with  well


mixed extraction fluid.


      5.  After  the  solid material and  deionized  water are


placed in the  extractor,  the operator should begin  agitation


and measure the  pH  of  the solution in the  extractor.   If  the


pH is greater  than  5.0, the  pH of the solution  should be


decreased to  5.0 +_  0.2  by adding  0.5 N  acetic acid.   If the


pH is equal to or less  than  5.0,  no  acetic acid should be


added.  The pH of the  solution should be monitored,  as


described below, during the  course of the  extraction  and  if
                              151

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 the pH rises above 5.2, 0. 5N  acetic  acid  should be added to

 bring the pH down to 5.0  -f 0.2.   However,  in  no event  shall

 the aggregate amount of acid  added to  the  solution exceed

 4 ml of acid per gram of  solid.   The mixture  should be

 agitated for 24 hours and maintained at 20° - 40°C (68°-104°F)

 during this  time.  It is  recommended that  the operator

 monitor and  adjust the pH during  the course of  the extraction

 with a device such as the Type 45-A pH Controller  manufactured

 by Ghemtrix, Inc., Hillsboro, Oregon 97123 or its  equivalent,

 in conjunction with a metering pump and reservoir  of 0.5N

 acetic acid.  If such a system is not available, the follow-

 ing manual  procedure shall be employed:

           (a)  A pH meter should be calibrated  in  accordance
                with the manufacturer's specifications.

           (b)  The pH of  the  solution should  be,checked and,
                if necessary,  0.5N acetic acid should be
                manually added to the extractor  until the
                pH reaches 5.0 + 0.2.   The pH  of the solution
                should be  adjusted at 15, 30 and 60 minute
                intervals, moving to the next  longer interval
                if the pH does not have to be  adjusted more
                than 0.5N  pH units.

           (c)  The adiustment procedure should  be  continued
                for at least 6 hours.

           (d)  If at the end of the 24-hour extraction period,
                the pH of the solution is not below 5.2 and
                the maximum amount of  acid  (4 ml per gram of
                solids)  has not been added,  the  pH  should be
                adjusted to 5.0 +_ 0.2  and the extraction
                continued for an additional  four hours, during
                which the pH should be adjusted  at  one hour
                intervals.

       6.  At  the end of the  24 hour extraction  period, deionized

water  should  be added to the extractor  in  an amount determined
                              152

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by the following  equation:




          V=  (20)(W)  - 16(W)  - A




          V=  ml deionized water to be added




          W«  weight  in grams  of solid charged to extractor




          A-  ml of  0.5N acetic acid added during extraction




      7.  The material in the extractor should be separated




into it component liquid and  solid phases as described under




"Separation Procedure."




      8.  The liquids resulting from Steps 2 and 7 should be




combined.  This combined liquid (or the waste itself if it




has less  than 1/2 percent solids,  as noted in step 2) is the




extract and should  be analyzed for the presence of any of




the contaminants  specified in Table I of §261.24 using the




Analytical Procedures designated below.




                      Separation Procedure




Equipment:  A filter  holder,  designed for filtration media




having a  nominal  pore size of 0.45 micrometers and capable of




applying  a 5.3  kg/cm2 (75 psi) hydrostatic pressure to the




solution  being  filtered shall be used.  "For mixtures




containing nonabsorptive solids, where separation can be




affected  without  imposing a 5.3 kg/cm2 pressure differential,




vacuum filters  employing a 0.45 micrometrers filter media




can be used.   (For  further guidance on filtration equipment




or procedures see "Test Methods for Evaluating Solid Waste,




Physical/Chemical Methods.")
                              153

-------
Procedure:*

    (i)  Following manufacturer's directions, the filter

         unit  should  be  assembled with a filter bed consisting

         of a  0.45 micrometer filter membrane.   For difficult

         or slow  to  filter  mixtures  a prefilter bed consisting

         of the following  prefilters in increasing pore size

          (0.65 micrometer  membrane,  fine glass  fiber prefilter,

         and coarse  glass  fiber prefilter)  can  be used.

   (ii)  The waste should  be  poured  into the filtration unit.

  (iii)  The reservoir  should be slowly pressurized until liquid

         begins to flow  from  the filtrate outlet at which point

         the pressure in the  filter  should  be immediately lowered

          to 10-15  psig.   Filtration  should  be continued
                                                        a
          9
         until  liquid flow ceases.

   (iv)  The pressure should  be increased stepwise in 10 psi

         increments  to  75  psig and  filtration continued until
                                    tti

         flow  ceases  or  the pressurizing gas begins to exit

         from  the  filtrate  outlet.
*This procedure  is  intended  to  result  in separation of the "free"
 liquid portion  of  the  waste  from any  solid  matter having a
 particle size >0.45um.   If  the sample will  not  filter,  various
 other separation techniques  can be  used to  aid  in the filtration.
 As described above,  pressure filtration is  employed to  speed up
 the filtration  process.   This  does  not alter the nature of the
 separation.  If  liquid  does  not separate during filtration,  the
 waste can be centrifuged.   If  separation occurs during  centrifuga
 tion, the liquid portion (centrifugate) is  filtered through  the
 0.45um filter prior  to  becoming mixed with  the  liquid portion of
 the waste obtained  from the  initial filtration.  Any material
 that will not pass  through  the filter after centrifugation is
 considered a solid  and  is extracted.
                              154

-------
    (v) The  filter  unit  should be depressurized,  the solid




        material  removed and weighed and then transferred to




        the  extraction apparatus, or, in the case of final




        filtration  prior to analysis, discarded.   Do not




        allow  the material  retained on the filter pad to dry




        prior  to  weighing.




   (vi) The  liquid  phase should be stored at 4°C  for




        subsequent  use in Step 8.




B.  Structural  Intergrity Procedure




Equipment:   A  Structural Integrity Tester having  a  3.18  cm




(1.25 in.) diameter hammer  weighing 0.33 kg (0.73 Ibs.)  and




having a  free  fall  of  15.24 cm (6 in.) shall be  Used.   This




device is  available from Associated Design and  Manufacturing




Company,  Alexandria, VA., 22314,  as Part No. 125, or it  may




be fabricated  to  meet  the specifications shown  in Figure 1.




Procedure:




     1.   The sample holder  should be filled with  the material




to be tested.   If the  sample of waste is a large  monolithic




block, a  portion  should  be  cut from the  block having the




dimensions of  a 3.3 cm (1.3 in.)  diameter x 7.1  cm  (2.8  in.)




cylinder.  For  a  fixated waste,  samples  may be  cast  in  the




form of a  3.3  cm  (1.3  in.)  diameter x 7.1 cm (2.8 in.)  cylinder




for purposes of conducting  this  test.  In such  cases,  the




waste may  be allowed to  cure for  30 days prior  to further




testing.



     2.   The sample holder  should be placed into  the Structural




Integrity  Tester, then the  hammer should be raised




                              155

-------
to its maximum height  and  dropped.   This  should be  repeated




fifteen times.




     3.  The material  should  be removed from the sample




holder, weighed,  and  transferred to  the extraction  apparatus




for extraction.




Analytical Procedures  for  Analyzing  Extract  Contaminants  '




     The test methods  for  analyzing  the extract are as




fo1lows:




     (1)  For arsenic,  barium,  cadmium, chromium,  lead, mercury,




selenium or  silver:   "Methods for Analysis  of Water and Wastes,"




Environmental Monitoring  and  Support Laboratory, Office of




Research and Development,  U.S.  Environmental Protection Agency,




Cincinnati,  Ohio  45268  (EPA-600/4-79-020,  March 1979).




     (2)  For Endrin;  Lindane;  Methoxychlor; Toxaphene; 2,4-D;




2,4,5-TP Silver:  in  "Methods  for Benzidine,  Chlorinated Organic




Compounds, Pentachlorophenol  and Pesticides  in Water and




Wastewater," September  1978,  U.S. Environmental Protection




Agency, Environmental  Monitoring and Support Laboratory,




Cincinnati,  Ohio  42568.




as standardized  in  "Test  Methods for the  Evaluation of




Solid Waste, Physical/Chemical  Methods."




     For all analyses,  the method of standard addition  shall




be used for  the  quantification  of species concentration.




This method  is  described  in "Test Methods for the Evaluation




of Solid Waste."  (It  is  also  described in "Methods  for  Analysis




of Water and Wastes.")
                              156

-------
                             15.25cm
                               IS")
                             ze'^'Z:
                                    I
                                 ,.
                                 •'*>;.-
                             •&^'0
                             • ' ^ J » > •
                             »*•• . '-v • •Jr"
                             ',*•'•< !:'• A •
                             ^;V ^
                             •?C^^
                             ^V.r--.?s
                              3.3cm
                              Cl.a")
                              9.4cm
                              (3.7")
                                           COMBINED
                                         r WEIGHT
                                           (.731b)
                                       (3.15cm)
                                       (1.25")
                                        SAMPLE
                                         /- ELASTOMERIC*
                                           SAMPLE HOLDER
 /
                                         K
J.
     7.1cm
     (2.8")
*ELASTOMER!C SAMPLE HOLDER FABRICATED OF
 MATERIAL FIRM ENOUGH TO SUPPORT THE SAMPLE
               Figure  1
                    TION TESTER
                         157

-------
                           Bibliography
 1.   Dagani, Ron,  "Mutagencity  testing  labs  a  growing
       business,   Chemical  and Engineering  News,  58  (9):
       10-12, Mar.  3,  1980.

 2.   House Report  No.  94-1491, 94th  Congress, 2nd  Session.

 3.   Murray, C. Richard  and E.B.  Reeves, Estimated Use  of
       Water in the United  States  in 1975.  U.S.  Geological
       Survey Circular 765.

 4.   Preliminary Draft Background  Document, Hazardous Waste
       Identification  and Listing, Toxicity Section,  250.12(F),
       November, 1977.

 5.   Preliminary Draft Background  Document, Hazardous Waste
       Guidelines  and  Regulations, Subpart  A.   Criteria,
       Identification, and  Listing of Hazardous Waste,  Toxicity
       Section 250.12(F), March  1978.

 6.   Draft Background  Document,  Section  3001  Identification
       and Listing  of  Hazardous  Waste, Section  250.13.  Hazardous
       Waste Characteristics, Toxicity,  December  15,  1978.
                •
 7.   Epler, J.L. et. al., Toxicity of Leachate: Interim Progress
       Report, April 1,  1978  to  January  1,  1979.   Oak Ridge National
       Laboratory.  IAG No.  DOE-IAG-40 646-77, EPA-IAG-78-D-X0372 .
       January 1979.

 8.   Federal Register  Vol.  44, No. 9 1-Wednesday , December 24,  1975;
       National Interim  Primary  Drinking Water  Regulations, Rules
       and Regulat ions .

 9.   Federal Register  Vol.  43, No. 243-Monday,  December 18, 1978;
       Hazardous Waste Proposed  Guidelines  and  Regulations and
       Proposal on  Identification  and Listing.

10.   Office of Research  and Development, Carcinogen Assessment
       Group's List of Carcinogens,  April 22, 1980.

11.   EPA Report to  Congress on Waste Disposal Practices and their
       Effects on  Groundwater, January 1977,  at p. 16

12.   Geraghty and Miller, Inc.,  The  Prevalence  of  Subsurface
       Migration of Hazardous Chemical Substances  at  Selected
       Industrial Waste  Land  Disposal Sites,  U.S.  Environmental
       Protection  Agency, July 1977.
                              158

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13.  Comment No. 209,  Utility  Solid  Waste Activities  Group,
       March 16, 1979.   Vol.  I,  pp.  164-167.

14.  Ham, R., M.A. Anderson,  R.  Stegmann and  R.  Stanforth,
       "Background Study on  the  Development  of  a Standard
        Leaching Test,"  August  1978,  U.S. Environmental
        Protection Agency, Cincinnati,  OH 45268.   EPA
        600/2-79-107.

15.  Lowenback, W.,  "Compilation and  Evaluation  of Leaching
       Test Methods,"  May 1978,  Municipal Environmental
       Research Laboratory,  U.S.  Environmental  Protection
       Agency, Cincinnati, OH  45268.  EPA-600/2-78-095.

16.  Ham, R.K., M.A. Anderson,  R.  Stegmann and  R.  Stanforth,
       "Comparison of  Three  Waste  Leaching Tests," (Report
       and Executive Summary),  May 1979,  Municipal Environmental
       Research Laboratory,  U.S.  Environmental  Protection
       Agency, Cincinnati, OH  45268.  EPA-600/2-79-001.

17.  Unpublished Comments and  Personal  Communication  of American
       Society for Testing and  Materials' Subcommittee D-19.12
       to D. Friedman, Office  of Solid  Waste.

18.  Meier, Eugene P., Interim  Progress  Report,  "Evaluation  of
       the Procedures  for Identification  of Hazardous Waste,"
       December 5, 1979.   U.S.  Environmental  Protection Agency,
       Environmental Monitoring  Systems  Laboratory, Las Vegas,
       Nevada 89114, August  1979.

19.  Epler, J.L. et. al., "Toxicity  of  Leachates," April  1,
       1978 to May 18, 1979.   Oak  Ridge  National  Laboratory,
       Oak Ridge, Tennesee 37830.  IAG No. DOE-IAG-40-646-77,
       EPA-IAG-78-DX-0372.

20.  State of Illinois Pollution Control  Board,  Rules and
       Regulation's.  Standard  Leachate  Test,  Developed in
       1971.

21.  State of California, Department  of  Health  Services.
       Title 22 of the California  Administrative  Code.  Division
       4, Environmental  Health,  Chapter  30:   Minimum  Standards
       for Management  of Hazardous and  Extremely  Hazardous
       Waste.  Article 11:   Criteria  for  Identification of
       Hazardous and Extremely  Hazardous  Waste.   December  5,  1979

22.  American Society  for Testing  and Materials'  Proposed
       Methods for Leaching  of  Waste  Materials.   Committee
       D-19.12 on Water.   Philadelphia,  PA  19103, May 1979.
                              159

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23.  Mahlock, J.L.  et.  al.,  Pollution Potential of Raw and
       Chemically Fixed  Hazardous  Industrial Wastes and Flue
       Gas Desulfurization  Sludge,  Interim Report, July 1976.
       U.S. Environmental Protection Agency, Cincinnati,  OH
       45268.  EPA  600/2-76-182.

24.  Weeter, D.W. and H.L.  Phillips, Structural and Leaching
       Aspects of Testing Fixated  Solid  Wastes  via the
       Toxicant Extraction  Procedure, 1979.   Oak Ridge National
       Laboratory,  Oak  Ridge,  TN   37830.

25.  Letter from Dirk Brunner,  U.S.  EPA,  MERL,  Cincinnati,  OH 45268
       to D. Friedman,  U.S.  EPA, OSW, Washington,  D.C.,  20460
       regarding Acidity Data,  August 25,  1978.

26.  Unpublished Work from  Environmental  Protection Agency's
       Environmental Monitorng  and  Support Laboratory,
       Las Vegas, NV  89114.

27.  Test Methods for Evaluating Solid Wastes,  Vol.  I,  Physical/
       Chemical Methods.  May  1980.   U.S.  Environmental
       Protection Agency, SW-846.

28.  Oakes, D.B., "Use  of Idealized  Models in Predicting  the
       Pollution of Water Supplies  Due to  Leachate from
       Landfill Sites."  In  Proceedings;  Groundwater Quality,
       Measurement, Prediction  and  Protection,  A Water  Research
       Centre Conference, Reading,  1976.

29.  Smith, D.B., P.L.  Wearn, H.J.  Richards  and  P.C. Rowe,  "Water
       Movement in  the  Unsaturated  Zone  of High  and  Low
       Permeability Strata,  by  Measuring  Tritium," International
       Symposium on Is otope  Hydro logy, IAEA, Vienna, Austria,
       1970.

30.  Bouwer, Herman, Groundwater Hydrology.  New York,  NY
       McGraw Hill  Book  Company Inc.,  1978.

31.  Pollution Prediction Techniques for  Waste  Disposal Siting,
       Roy F. Weston, Inc.,  Final Report,  U.S.  Environmental
       Protection Agency, SW-162-C.

32.  Bachmat, Yehuda, Barbara Andrews, David Holtz,  and Scott
       Sebastian, "Utilization  of Numerical  Groundwater Models
       for Water Resource Management." Robert  S.  Kerr
       Environmental Research Laboratory,  U.S.  Environmental
       Protection Agency, Ada,  OK 74820.   EPA-600/8-78-012.
       June 1978.
                              160

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33.  Cooperative Programme  of  Research on the Behaviour of
       Hazardous Waste  in Landfill  Sites.  Final Report of
       the Policy  Review Committee,  J. Sumner, Chairman,
       London, Her Majesty's  Stationery Office,  1978.

34.  Lehr, J.H., Ground Water  Movement in Living Color: A Slide
       Show  (a collection of  articles  from 1963-1964).   Available
       from  the National Water Well  Association, 500 West Wilson
       Bridge Rd., Worthington,  Ohio 43085.

35.  American Electroplating  Society.   Interim Phase I  Report:
       Electroplating Wastewater Sludge Characterization.
       August 24,  1979. Revised September 12, 1979.

36.  Burd, R.M.  and  J.M. Riddle.  Final Report:   Evaluation of
       Solid Waste Extraction  Procedures and Various Hazard
       Identification Tests.  NUS Corporation, Cyrus Wm. Rice
       Division,  Pittsburg,  PA 15520 September 1979.

37.  Electric Power  Research  Institute, Proposed RCRA Extraction
       Procedure:  Reproducibility  and Sensitivity.  Palo Alto,
       California:   Environmental Assessment Department, November
       1,  1979.

38.  ''Methods for  Chemical  Analysis  of Water and Wastes," U.S.
       Environmental Protection Agency, Office of Technology
       Transfer,  Washington,  D.C.  20460, 1974.

39.  State of Washington, Washington Department  of Ecology,
       Olympia,  WA 98501, Hazardous  Waste Regulation, Chapter
       173-302 WAG.

40.  State of California, Department of Public Health,  Title
       22, Environmental Health, Sections 60001-60281.
       Sacremento, CA 95814.

41.  State of Minnesota, Minnesota  Code of Agency Rules,
       Pollution  Control Agency, Hazardous Waste,  6 MCAR
       §4.9001-4.9002,  June 1979.  St. Paul, MN   55155.

42.  Comment No.  683, Ferroalloys Association, Section  3001
       Dockett,  March  15,  1979.

43.  Response of  Selected Paper Industry Residuals to Evolving
       Toxicant  Extraction  Procedure,  Special Report, January
       1978, National Council  of the Paper Industry for Air
       and Stream  Improvement, Inc., New York, NY 10016.
                              161

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44.  Federal Register,  Vol.  44,  No.  49,  Monday,  March 12, 1979.
       Hazardous Waste  Guidelines  and Regulations, Extension of
       Comment  Period on  Extraction  Procedure.

45.  Comment No. 147, Wolverine  World Wide Inc., Section 3001
       Dockett, February  27, 1979.

46.  SCS Engineers,  Inc., "Final Report:   Assessment of
       Industrial  Hazardous  Waste  Practices - Leather Tanning
       and Finishing Industry,"  Reston,  VA  November, 1976.

47.  Comment No.  152, Thorstenson  Laboratory, Inc.,  Section
       3001 Dockett, February 27,  1979.

48.  Stephens,  R.D., D.L. Storm  and  K.C.  Ting,  "Environmental
       Oxidation of  Chromium," California Department of Health,
       Hazardous Materials Section,  Berkeley, CA 94704,  1977.

49.  "Standard  Methods  for the Examination of Water  and
       Wastewater,"  Method Number  3073.  14th Edition, American
       Public Health Association,  New York, NY  10019, 1975.

50.  Comment No.  388,  Tanners' Council of America, Section
       3001 Dockett, March 16, 1979.

51.  Monitoring the  Fixed FGD Sludge  Landfill,  Conesville, Ohio-
       Phase I, Electric  Power Research  Institute, EPRI FP-1172,
       Palo Alto,  CA  94304.  September,  1979.

52.  FGD  Sludge Disposal  Manual, Electric Power  Research
       Institute,  EPRI-FP-977, Palo  Alto, CA 94304.
       January, 1979.

53.  Sun,  C.C.  and J.T. McAdams, Assessment of  RCRA/TEP Test
       Rules on FBC  Residue, Part  I  - EPA Draft  Procedure of
       March  1978.  Westinghouse Research and Development
       Center,  Pittsburg, PA  15235.   December  4,  1978.
                              162

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