Alliance  Technologies Corporation
Bedford,  MA
Aug  85
                 U.S. DEPARTMENT OF COMMERCE
              National Technical Information Service

                Prepared for
Land Disposal Branch, Office  of Solid Waste
           Washington,  DC   20460

          Contract No.  68-01-6871
           Work Assignment No.  51
        EPA Work Assignment  Manager
                George Dixon

             Draft Final Report
                August  1985
                 Prepared by

             Steven  C.  Konieczny
                Lisa Farrell
             Michelle  M. Gosae
                Barbara Myatt
                 Brenda  Kay
                 Ronald Bell
               Theresa Murphy
             Neil M. Ram, Ph.D.
              GCA  CORPORATION
       Bedford,   Massachusetts  01730
             REPRODUCED BY
                  NATIONAL TECHNICAL
                  INFORMATION SERVICE
                  SPRINGFIELD, VA 22161

                                                                           3. Recipient'! Accession No.
 4. Title end Subtitle
    Corrective measures for releases to  soil from solid  waste
    management units
                                                  5, Report Date
                                                  Aug.  85
 7. Aothor(s)
    S.C. Konieczny
                                                  8. Performing Organization Rept. No.
 9. Performing Organization Name ana Address
    GCA Corp.
    CCA/Technology  Division
    Bedford,  MA  01730
                                                  10. Project/Task/Work Unit No.
                                                   WA 51	
                                                  11. Contract(C) or Grant(G) No.


 12. Sponsoring Organization Name and Address
    U.S. Environmental Protection  Agency
    Office of Solid  Waste
    401 M Street,  SW
                 Ti.C..	7.0460	
                                                  13. Type of Report & Period Covered

                                                   Draft Final Report
 15. Supplementary Notes
 16. Abstract (Limit: 200 words)
    Upon discovery  of a release from a solid waste management  unit at  a RCRA facility,
    a complete site investigation  should  be performed  to determine nature and extent
    of the  release.   Once  the release and its extent has been  characterized, and
    determined to be a threat to human health or  the environment, corrective measures
   'must be implemented.   The draft final report      discusses the various  types  of
    removal/containment (includes  disposal) and  treatment technologies which are
    applicable to remediation of releases to soils.
 17. Document Analysis •. Descriptors
    b. Identifiers/Open-Ended Terms
   c. COSATI Field/Group
 18. Availability Statement
                                                           19. Security Class (This Report)
                                                           20. Security Class (This Page!
                                                             21. No. of Pages
                                                             22. Price
                                          See Instructions on Reverse
                                                                                      OPTIONAL FORM 272 (4-77)
                                                                                      (Formerly NTIS-35)
                                                                                      Department of Commerce

     This Draft Final Report was furnished to the Environmental Protection
Agency by the GCA Corporation, GCA/Technology Division, Bedford, Massachusetts
01730, in fulfillment of Contract No. 68-01-6871, Work Assignment No. 51.  The
opinions, findings, and conclusions expressed are those of the authors and noc
necessarily those of the Environmental Protection Agency or the cooperating
agencies.  Mention of company or product names is not to be considered as an
endorsement by the Environmental Protection Agency.

Figures	«	      iv
Tables 	       v

     1.   Introduction	    1-1
               Background	    1-1
               Definition/Identification of Solid Waste Management
                 Units		    1-2
               Identifying Releases to Soils	    1-5
     2.   Assessing the Need for Corrective Measures	    2-1
               Introduction	    2-1
               General Approach to Risk Characterization ........    2-2
               Summary	    2-7
     3.   Overview of Corrective Measures	    3-1
               General	    3-1
               Proven Technologies 	    3-5
               Imminent Technologies 	    3-42
     4.   Case Studies	    4-1
               Introduction	    4-1
               Fairchild Republic Company - Hagerstown, Maryland ....    4-4
               Whitmoyer Laboratories - Myerstown, Pennsylvania	    4-9
               Enterprise Avenue - Philadelphia, Pennsylvania	    4-12
               Frontenac Site - Frontenac, Missouri	    4-15
               Crystal Chemical - Houston, Texas 	    4-19
               Silresira - Lowell, Massachusetts	    4-22
     5.   Recommendations on How to Select and Implement Corrective
            Measures	    5-1
               Introduction	    5-1
               Important Considerations in Selecting Corrective Measures
                 for Releases to Soils	    5-5
               Summary	    5-18
               Case Study Example	    5-22
References	    R-l

     A.   Fate and Transport	    A-l
     B.   Exposure Assessment	    B-l


Number                                                                     Page

 4-1    Worksheet for screening case studies	  .     4-2

 4-2    Outline for case studies write-up	     4-6


Number                                                                     Page

 3-1    Removal (Containment)/Treatment Technologies	     3-2

 3-2    Summary of Proven Removal/Treatment Technologies	     3-3

 3-3    Unit Costs - Excavation of Uncontaminated Soil	     3-7

 3-4    Capping/Surface Sealing Materials  	     3-10

 3-5    Capping/Surface Sealing Unit Costs	.	     3-13

 3-6    Modification of Soil Parameters	     3-20

 3-7    Compounds or Classes of Compounds  that Have Been  (or could be)
          Degraded by Commercially Available Microbial  Augmentation
          Productions	     3-24

 3-8    Micro-organisms Known to Metabolize Organochlorine Pesticides  .     3-25

 3-9    Atmospheric Reaction Rates and Residence Times  of Selected
          Organic Chemicals .......... 	     3-29

 3-10   Liming Materials.	     3-33

 3-11   Advantages and Disadvantages Rotary Kiln Incinerator	     3-40

 3-12   Advantages and Disadvantages of Fluidized-Bed Incineration. .  .     3-45

 3-13   Relative Oxidation Power of Oxidizing Species 	     3-49

 3-14   Oxidation Reactivity for Organic Chemical Classes 	     3-51

 3-15   Some Chemicals That Do Not Oxidize at Soil and  Clay Surfaces.  .     3-52

 3-16   Chemical Groups that React with Peroxides to  Form More Mobile
          Products	     3-52

 3-17   Chemical Reductive Treatment for Degradation  of Paraquat in
          Soil	     3-54

                               TABLES (continued)
Number                                                                     Page

 4-1    Types of Release(s) and Remedial Response(s) Implemented at
          Selected Sites	     £-5

 5-1    Pertinent Issues for Selection and Implementation of Corrective
          Measures	     5-2

 5-2    Permit Writers' Checklist 	     5-19

 5-3    Summary of Soil Removal/Treatment/Containment (Disposal)
          Technologies	     5-21

                                   SECTION  1


     The 1984 amendments to the Hazardous and Solid Waste Act (HSWA) provide
the Agency with additional authorities for corrective action at facilities
seeking permits, and for facilities with interim status under Section
3005(e).  The amendments for corrective action address:

     •    continuing releases at permitted facilities (Section 206);
     •    corrective action beyond facility boundaries (Section 207);
     •    financial responsibility for corrective action (Section 208); and
     •    interim status corrective action orders (Section 233).

The new authorization allows EPA to require corrective action in response to a
release of hazardous waste or hazardous constituents from any solid waste
management unit (SWMU) to the environment, regardless of when the waste was
placed in such unit.  This authority addresses releases to all media,
including soil.
     Based on the 1984 amendments, the U.S. EPA, Office of Solid Waste (OSW),
Land Disposal Branch, must develop technical guidance for permit writers to
implement the "continuing releases" provision.  Implementation of these new
requirements will typically take place in three stages:  (1) determining
whether there is a release at a facility that warrants further investigation,
(2) collecting additional information to define the nature and extent of the
release, and (3) selecting and performing the corrective measures.  This
report is intended to provide guidance on selecting corrective measures in

response Co a hazardous constituent release to soil.  Guidance is provided on
parameters and criteria which should be considered in selecting a particular
remedial response for specific site conditions and identified compounds.
     The remainder of this section identifies and defines the various types of
solid waste management units (SWMUs).  It also identifies releases to soil.
Section 2 discusses the need for corrective measures through review of the
potential for hazardous constituents released to soil to be transported to
other environmental matrices (air, surface water, ground water) and the
potential risk associated with such transport to human health and the
environment.  Section 3 provides an overview of corrective measures including
surface soil treatment technologies.  Section 4 discusses case studies where
releases to soil from SWMUs have occurred and identifies the corrective
measures undertaken at the site to clean up the contaminated soil.  The
concluding section, Section 5, provides recommendations for the application of
corrective measures to soil releases.  Finally, Appendices A and B provide
detailed information on fate and transport mechanisms, and exposure and risk
assessments, as briefly described in Section 2.


     Congress defined the term solid waste management unit (SWMU) to include
any unit at a facility "from which hazardous constituents might migrate,
irrespective of whether the units were intended for the management of solid
and/or hazardous wastes."  SWMUs represent a broad category of waste
management units of which hazardous waste management units are a subset.
Under the new requirements, Subtitle D landfills and other units (at
facilities seeking a RCKA permit) which primarily handle nonhazardous solid
waste could be required to take corrective action if there is evidence of a
release of hazardous constituents from these units.  The definition of SWMU
includes both active, or operating units, and inactive, or nonoperating
units.  This definition also includes certain units that have previously been
exempted from 40 CFR Part 264 requirements, such as wastewater treatment tanks.
     The new requirements also extend to spills and other releases from SWMUs
that may occur during the normal operation of these units.  However, spills
that cannot be linked to SWMUs, such as those originating from production
areas or product storage tanks, are not covered under the continuing release

provision.  These spills are illegal,  however,  under other RCRA provisions
(Sobotka, 1985).  The types of units included in the SWMU definition are (in

alphabetical order):

     •    container storage areas;

     •    incinerators;

     •    landfills;

     •    land treatment units;

     •    surface impoundments;

     •    tanks (including 90-day accumulation tanks);

     •    transfer stations;

     •    (underground) injection wells;*

     •    waste handling areas;

     •    waste piles;

     •    waste recycling operations;  and                                    »

     •    wastewater treatment tanks.

     A container, as defined in 40 CFR Part 260.10, is any portable device in

which a material is stored, transported, treated, disposed of, or otherwise
handled.  A container storage area is the location where the container

resides.  Container storage areas typically consist of 55-gallon drums, but
may vary  in size.  These areas usually include a spill containment system,

typically a diked area above a low permeable barrier that underlies the

storage area, and sometimes include a cover to shed precipitation.
*Underground injection wells are not discussed in the body of this report.
 By virtue of their operation, they are not as susceptible to release to soil
 as other SWMUs since potential releases occur only during equipment failure
 or waste spilling prior to injection into the subsurface.  A detailed
 discussion of the regulatory status and the potential and cause of release
 from underground injection wells is provided in the Appendix of the draft
 report entitled "Corrective Measures for Releases to Ground Water from Solid
 Waste Management Units", prepared by GCA/Technology Division, August 1985.

     An incinerator, as defined in 40 CFR Part 260.10,  is an enclosed device
using controlled flame combustion, the primary purpose  of which  is to
thermally break down hazardous waste.  Examples of incinerators  are  rotary
kiln, fluidized bed, and liquid injection incinerators.
     A landfill, as defined in 40 CFR Part 260.10, is a disposal tacility or
part of a facility where hazardous waste is placed in or on land and which  is
not a land treatment facility, a surface impoundment, or an injection well.
This facility typically consists of wastes placed on a  liner system  to
collected liquids draining from waste and includes a similar liner system
(cover) on top of the waste to prevent incident precipitation from entering
the waste.
     A land  treatment facility, as defined in 40 CFR Part 260.10, is a
facility or  part of a facility at which hazardous waste is applied onto or
incorporated into the soil surface; such facilities are disposal facilities if
the waste will remain after closure.  Land treatment involves degradation of
organic compounds through physiochemical biologic degradation.  Nutrient and
biological seeding  frequently occurs with aeration of the soil/waste mixture
by rototilling, plowing or harrowing.
     A surface impoundment or impoundment, as defined in 40 CFR Part 260.10,
means a facility or part of a facility which is a natural topographic
depression,  manmade excavation, or diked area formed primarily of earthen
materials (although it may be lined with manmade materials), which is designed
to hold an accumulation of liquid wastes or wastes containing free liquids,
and which is not an injection well.  Examples of surface impoundments are
holding, storage, settling, and aeration pits, ponds, and lagoons.
     A tank, as defined in 40 CFR Part 260.10, is a stationary device,
designed to  contain an accumulation of hazardous waste  which is  constructed
primarily of nonearthen materials (e.g., wood, concrete, steel,  plastic) which
provide structural  support.
     A transfer facility, as defined in 40 CFR Part 260.10, is any
transportation related facility including loading docks, parking areas,
storage areas, and  other similar areas where shipments  of hazardous waste are
held during  the normal course of transportation.

     Waste handling areas include container filling and emptying areas, and
transfer locations (e.g. from trucks to tanks) associated with all waste
management facilities.  Waste handling areas are usually associated with waste
transfer, such as solvent reclamation staging, incineration charging, or
transfer from tank truck to tank, or drum storage area to trucks.
     A (waste) pile, as defined in 40 CFR Part 260.10, is any noncontainerized
accumulation of solid, nonflowing hazardous waste that is used for treatment
or storage.  This facility typically consists of wastes placed on a liner
system to collect liquids draining from the waste.
     Waste recycling operations are areas where operations involving the
processing of waste materials for recovery are undertaken.
     A wastewater treatment unit, as defined in 40 CFR Part 260.10, is a
device which:  (1) is part of a wastewater treatment facility which is subject
to regulation under either Section 402 or Section 307(b)  of the Clean Water
Act; (2) receives and treats or stores an influent wastewater which is a
hazardous waste as defined in 40 CFR Part 261.3,  or generates and accumulates
a wastewater treatment sludge which is a hazardous waste as defined in 40 CFR
Part 261.3, or treats or stores a wastewater treatment sludge which is a
hazardous waste as defined in 40 CFR Part 261.3,  and (3)  meets the definition
of tank in 40 CFR Part 260.10 (as previously discussed).


     Prior to implementation of a corrective measure at a SWMU, a release to
soil must be identified and its extent characterized.  "Contaminated soils"
can be defined as affected soils found between the ground surface and the mean
high ground-water table.  These soils are affected by a "release" which is
defined to include any spilling, leaking, pumping, pouring, emitting,
emptying, discharging, injecting, escaping, leaching, dumping, or disposing
into the environment, but excludes permitted discharges or releases.
     Contamination in soils can be discovered in a variety of ways.  If
contamination is uncovered through ground water sampling and analysis at a
RCRA facility, there is a possibility that a release from a solid waste
management unit (SWMU) has migrated through the soils and into the ground


water, thus impacting soils.  Surface water  sampling and  analysis could  also
reveal a release from a SWMU that has contaminated  soils  and made its way via
surface runoff into various surface water bodies.    .      .
     Visual observations during  normal  inspections, or  if ordered by the EPA,
may reveal evidence of a release in the area of  a SWMU.   Dead  or dying trees,
general vegetative stress  and obvious signs, such as substrates found in
surface soils or highly discolored soils should  be  investigated as  a sign of
release.  Once suspected,  soil sampling can  be performed  at various depths  to
determine the extent of the contamination.   For  example,  the hazardous
constituent  type, migration rate, lateral and vertical  extent, and  impact on
ground water should be determined.  Also, during inspections the lack of
physical  integrity of a SWMU may indicate the need  for  sampling to  determine
if a  release has occurred.  Examples of this may be the poor quality of  a tank
or deterioration in a container  storage area which may make these SWMUs  more
susceptible  to such release as leakage.  Additionally, design  characteristics
of various disposal units  may make them more susceptible  to a  release.   For
example,  single-lined or unlined landfills may be more  likely  to have a
release  than some other units.
      Electromagnetic methods, ground penetrating radar, shallow geothermic  and
remote  sensing are other techniques often used to define  a hazardous
constituent  ground-water plume.  These methods may  also aid in the  selection
of appropriate areas for soil sampling.
      Once a  release  is discovered and its type and  extent determined, some
type  of  corrective action  may be necessary.  There  is no  definition as to the
quantity  of  a  release that represents a safe level  in soils.   However, if
there is  a potential adverse  impact to human health, welfare,  or the
environment, then some corrective measure must be undertaken to ensure that
the  impact is minimized or eliminated.  The  following section  assesses the
need  for  and the extent of corrective measures necessary  for releases to soil.

                                    SECTION  2


     Prior to selecting and implementing corrective measures for releases to
soils, a needs assessment should be conducted.   The assessment of the need for
corrective measures under RCRA is based on protection of human health and the
environment.  In the case of releases to soil,  a standard for the protection
of human health and the environment is not currently available.  In the
interim, the relevant and applicable standards  for corrective action provided
in the CERCLA feasibility guidance should be met.
     The assessment of the need for corrective  measures should define facility
conditions and the extent of hazardous constituent release,  identify the goal
of corrective measures, assist in the selection of corrective measures and
establish a time frame for implementation of corrective measures.  The
assessment follows a stepwise process including the following six components:
source characterization; extent of contamination;  fate and transport; exposure
assessment; hazard (toxicity) assessment and characterization.  Each of the
components is discussed briefly below with emphasis on the assessment of
releases of hazardous constituents to soil from a SWMU.  Information essential
to each component is presented in outline form for easy reference and is
comparable to a checklist.
     Detailed procedures for the assessment of transport and fate are
presented in Appendix A of this report.  Procedures for performing exposure
assessment are detailed in Appendix B.  Appendix B also contains additional
information on hazard assessment and risk characterization;  however, it should
be recognized that the subjective aspects of hazard and risk assessment should
only be performed by a trained toxicologist.


Description of Facility Area

     The  first step in the needs  assessment  is  to  delineate  the  study  area and
characterize  the geophysical  conditions  that  define  the  facility.   Combined
with nearby land use  patterns,  this  information provides a general  description
of  the area and population activity  at or near  the facility.   Such  information
can be helpful in  identifying localized  areas of potential concern,  both  as
sources of hazardous  constituent  release and  hazardous constituent  exposure.
The information required to adequately describe the  facility  or  study  area
should include:

     1.   The geographic setting:
          a.   local  topography;
          b.   hydrological and geological setting;
          c.   ground and surface  water  flow; and
          d.   soil  types.
     2.   The meteorological  conditions  with  particular  emphasis on:
          a.   seasonal variation;
          b.   episodic events; and
          c.   climatic factors that may affect the  transport and fate of
These  parameters  give an indication  of the potential importance  of  air, water
and land  (.both sediment and soils) in both the  transport and  fate of chemical
     13.   The land use patterns including:
          a.   industrial - heavy/light;
          b.   residential;
          c.   agricultural;
          d.   recreational;  and
          e.   wetlands and/or other protected  ecosytems.

Extent of Contamination

     The next step in the needs assessment process identifies and determines,
to the extent possible, the hazardous constituents present and the
concentrations of hazardous constituents in the soil medium.  To determine the
extent of contamination the following information should be obtained:

     1.   The identification of the hazardous constituents released at the
          facility by:
          a.   source of contamination; and
          b.   location of release.
     2.   The concentrations of the constituents observed within the soil
     3.   The location (receptor sites) and chemical form of the constituents
          to which exposure occurs.
     4.   References to the analytical methodology/models used and QA/QC
          documentaion (particularly significant for enforcement activities).

Transport and Fate

     The purpose of this part of the needs assessment is to describe and
quantify, when possible, the potential for migration of hazardous
constituents.  This includes determining the potential for intermedia and
intramedia transport and transformation and predicting or estimating the
direction and magnitude of constituent migration.   This can be accomplished by

     1.   The chemical and physical properties of the released hazardous
          constituents including:
          a.   solubility;
          b.   Henry's Law Constant;
          c.   octanol/water partition coefficient;
          d.   vapor pressure; and
          e.   soil/sediment adsorption coefficients.

    2.   The completed  transport  and  fate  section should  characterize, the
         hazardous constituents  released at  a  facility by:

         a.    the chemical  form  of  each constituent  to which exposure occurs;

         b.    the potential chemical,  physical and biological partitioning of
               the constituents in various  media;  and

         c.    the reactive  pathways that affect migration of the hazardous
               constituents  in the facility area including:

               1)   adsorption and desorption processes,
               2)   volatilization,
               3)   degradation/decomposition rates,
               4)   photolysis,
               5)   oxidation,
               6)   precipitation,
               7)   hydrolysis,
               8)   complexation,
               9)   half-lives.

     3.   The intermedia and intraraedia transport  and transformation of
         constituents including:

          a.    the  potential for  volatilization from  soil  to air;

          b.    the  potential for  leaching from  soil to ground water/surface
               water; and

          c.    the  potential for  adsorption to  soil and subsequent movement in
               air  as fugitive dusts or via overland  flow  with surface run-off.
Exposure Evaluation

     The purpose of this step of the needs assessment is to identify actual or

potential pathways and routes of exposure, characterize the populations

exposed and determine the extent of the exposure.   Depending on the needs  of

the facility assessment and the data available,  this exposure evaluation may

be performed either as a qualitative or quantitative assessment.   To

accomplish this:

     1.   The location and magnitude of hazardous  constituent release to soil
          should be identified and quantified.

     2.    The  constituent  releases to soil  at  the facility should be
          characterized to the  extent possible by:

          a.    identifying all  hazardous constituents;

          b.    quantifying the  chemical loading into the receiving medium
               (soil);  and

          c.    identifying and  predicting the  chemical  fate of hazardous
               constituent releases - focusing on intermedia and intramedia

     3.    The  exposed populations must be characterized:

          a.    by age and  by demographics (e.g.  size and distribution);

          b.    by subpopulations at special health  risk; and

          c.    by location and  distance from the facility.

     4.    The  potential exposure points must be identified for both human and
          non-human populations by identifying:

          a.    the likely  pathways of hazardous constituent release and

          b.    population  activity and land use patterns at and near exposure
               points;  and

          c.    magnitude,  source and probability of exposure to specified
               hazardous constituents.

     5.    Identification of the contribution to the overall risk (exposure)
          for each exposure route posed by releases to  soil should be
          determined including:

          a.    dermal contact with soils;

          b.    ingestion of soils (particularly important for ages under 6);

          c.    inhalation of airborne particulates  (with subsequent
               reingestion); and

          d.    ingestion of contaminated biota.
Hazard Assessment

     The purpose of hazard assessment is to determine the nature and extent of

health and environmental effects associated with exposure to the hazardous

constituents identified in the assessment of the extent of contamination.


This section can be divided into two subsections consisting of a toxicplogical
review and a dose-response assessment.  Toxicological and dose-response
assessment information for hazardous constituents of concern can be found in
the Health Effects Assessment (HEA; documents available through EPAs Office of
Emergency and Remedial Respones (OERR) or in the Toxicological profiles
available through EPAs Office of Waste Programs Enforcement.

Risk Characterization

     The purpose of risk characterization is to integrate the findings of all
the previously described sections in order to estimate facility specific risk
to human health and the environment.  Individual lifetime risks and total
population risks can generally be calcuated for average and maximum levels of
hazardous constituents in soil and other affected media (e.g., air, biota).

     1.   The risk characterization should address all types of potential or
          actual risks posed by the constituent release including:
          a.   carcinogenic risks;
          b.   non-carcinogenic risks; and
          c.   environmental risks.
     2.   The weight of evidence associated with each step in the risk
          characterization process must be considered and include:
          a.   estimated uncertainties;
          b.   assumptions; and
          c.   data gaps.
     3.   Risk estimations can be determined for
          a.   carcinogens - by multiplying carcinogenic potency value by the
               current and projected chronic exposure levels;
          b.   non-carcinogens - by comparing the projected exposure levels to
               acceptable levels; and

          c.    environmental risk
               1)    by identifying the toxic effects of exposures to the
                    chemicals of concern to wildlife, and
               2)    by discussing the effects of exposure on indigenous
                    species, on the food chain and on the habitat.
     4.   The overall risks from exposure to hazardous constituents may be
          determined by:
          a.    estimating the exposures from individual hazardous constituents
          b.    estimating the exposure from specific exposure routes;
          c.    determining the additive/synergistic/antagonistic effects that
               may result from exposure to multiple constituents by various
               exposure routes; and
          d.    reviewing the metabolic/reactive/adsorptive pathways of
               hazardous constituents.

     The above generic approach can be used to develop a comprehensive
understanding of the risk posed by release of a hazardous constituent from a
SWMU at a RCRA facility.  The underlying components of the SWMU
assessment/exposure assessment process are closely integrated and build upon
each other.  An organized, logical evaluation process ensures that all issues
have been examined either qualitatively or quantitatively, and that risk
characterization efforts are developed on a sound, documented data base.  This
generic approach can be used as a framework to identify the particular release
(e.g. soil) and routes of exposure at any given RCRA facility, that presents
adverse threats to public health and the environment.

                                   SECTION 3
                         OVERVIEW OF  CORRECTIVE MEASURES


     Upon discovery of a release from a solid waste management unit at a RCRA
facility, a complete site investigation should be performed to determine the
nature and extent of the release.  Once the release and its extent has been
characterized, and determined to be  a threat to human health or the
environment,  corrective  measures must be implemented.  This section discusses
the  various  types of removal/containment (includes disposal) and  treatment
technologies  which are applicable  to remediation  of releases to soils.
      Table  3-1  lists the proven and  imminent removal/treatment technologies
discussed in this  section,  and also  lists emerging technologies.   Proven
 technologies  are those technologies  that have been used successfully  at
 various  sites to clean up  hazardous  wastes  from  soils.  Imminent  technologies
 are  those that  have  been proven  in the  laboratory and  successfully used  in  the
 field on pilot-scale studies.  Emerging technologies  are  those  technologies
 that, at the present time,  are  in  the laboratory  testing  stage  or possibly
 have been used  in the  field with either unknown  or variable results.
      Much of the information in  subsequent  discussions on the  following  proven
 and  imminent technologies  were  excerpted from a  report by JRB  Associates
 entitled "Review of  In-Place Treatment  Techniques for Contaminated Surface
 Soils,"  September 1984;  these technologies  include chemical oxidation,
 chemical reduction,  photolysis,  biodegradation,  sorption, attenuation,
 neutralization,  and  extraction (soil flushing).
      Table 3-2  provides  an overview of  the  hazardous  constituents which are
 amenable to each proven removal/treatment technology,  presented in this
 report,  along with some  general  comments about the  technology.   Following this
 table are more  detailed  discussions of  each proven and imminent removal/
 treatment technology.   In addition to these technologies, natural treatment

           Proven Technologies
                                          Imminent Technologies
                                         Emerging Technologies
Offsite Disposal
Onsite Capping
Onsite Landfill ing
Soil Solidification
In situ Biodegradation
Above-Grade Biodegradation
Rotary Kiln Incineration
Mobile Rotary Kiln Incineration
Mobile Hazardous Waste Extraction
Fluidized-Bed Incineration
Mobile Advanced Electric Reactor
Chemical Oxidation
Chemical Reduction
Extraction (Soil Flushing)3
Multiple-Hearth Incineration
In Situ Vitrification
Chemical Degradation
Ion Exchange
Reduction of Volatilization
     alncludes mobile EPA unit.

     Removal/Treatment Technology

Removal (ContmioMnt)       Treatment
Hazardoua Conatituenta
Cap InatallaCion
and Surface Sealing
                                              All conacituent Cypea
Moat conacituent Cypea*
Offaite Oiapoaal
Oaaite Landfill
                                              All conacicuent Cypea
                                              All Cypea of soil
                                               Inorganics are more
                                               amenable Chan organic!
                        (In iicu/Above-Grade)
Sooe organica**
Factora affecting Che  feaaibilicy of  thia
technology include*:    depth  of
contamination,  and ground-water  table, duat
problem, acabilicy of aoila,  acceaaibility,
and volume of contaminated  aoil.

Capping prevenCa direcC contacC  with  hazardoua
conatituenca and may minimize  offaite
migration via ground-water  contamination.
May not be effective in areaa  with a  high
ground water cable. Capping  doea not comply
with RCRA regulationa  for  land diapoaal of
hazardoua conaciCuenCa. Regular maintenance
of Che cap ia required Co maintain the
integricy of Che unic.

Factora affecting the  feaaibilicy of  thia
alternative include;   availability of offaice
diapoaal capacicy, hatardoua  conacicuenc
toxicity, diatance to  diapoaal facility,
transportation  hazarda, and coata.

Faccora affeccing Che  feaaibilicy of  thia
technology include: depth  of  ground  wacer
table, volume of haxardoua  conacituenta to be
diapoaed, aeiamic condition!,  conatituent
Coxicity, peraiacance  of hazardous
conatituenta, and auitabilicy  of geology for
landfill conatruction.   Regular maintenance
ia required to maintain the integrity of the
unic.  Can be deaigned to comply with RCRA
land diapoaal regulaciona.

Solidification altera  Che phyaical and/or
chemical acate  of the  hazardoua  conatiCuenca
within the aoil which  rendera  them leaa
leachable, leaa toxic, and  more  eaaily
handled, tranaported and diapoaed.  The
primary aolidification proceaaea are
cement-baaed and pozzolanic proceaaea.
Solidified materiala generally have low
durability and rout,  therefore,  be protecced
from freeze/thaw and wet-dry  cyclea.
Solidification greacly increaaea the  volume
of hazardoua material.

Biodegradacion ia a highly  effective  and
generally coac-effective biological treatment
technology for hazardoua conatiCuenca which
are readily biodegradable.  Shallow aoila may
be treated in aitu whereat  deep  concamination
may need to be excavated and  treated  above
grade.  The rate of decompoaicion of  an
organic conatituenc dependa on ita chemical
composition and choae  factora which affect
the aoil environment auch  aa  pH, temperature,
moisture content, aeration  and oxygen supply,
nutrienta, and carbon/nitrogen ratio.

                                           TABLE  3-2  (continued)
     Removal/Treatment Technology

Removal (Containment)       Treatment
Hazardous Constituent!
Organic compounds with
moderate to strong
adaorption in Che
>290 nai wavelength
                                               Acidic or baaic
Heavy aetals and
                         Rotary Kiln
Organic constituents
Fhotodegradation results when ultraviolet
energys break the carbon-halogen bond,  thus
dehalogenating the molecule.   Photolysis  is  a
•ajor fate of many organic compounds.   The
photochemical characteristics of the
hazardous constituents and climatic
conditions affect the suitability of this

Neutralization can reault in  metal
immobilization, decreased corrosivity,
enhanced microbial activity,  etc.  Factors
influencing the effectiveneas of
neutralization include:   hazardoua
conatituent characterization, soil
conditions, depth of contamination, and
geological/hydrologies!  conditions.

Agricultural products, sewage sludge, and
activated carbon, among  other organic
materials, have been utilized to immobilize
hazardous constituents in soils.  The
technology is more reliable over the short
term.  In the case of organics,  sorption may
immobilize constituents  until they can  be

Stationary rotary kilna  have  proven to  be
effective for incineration of -  wide variety
of solid hazardous waatea. Long residence
times in the rotary kiln and  high
temperatures result in complete  incineration
of organic materials.  High costs are
associated with thia technology.  Three
commercial units available are:   Rollins
Environmental Services,  Deer  Park, Texas;
ENSCO, El Dorado, Arkanaaa; and  SCA Services,
Chicago, Illinois.  Mobile rotary kilns have
also been proven to be effective for
incineration of solid wastes.
 'Capping of highly soluble hazardoua  constituents is not recommended.

 **Only those constituents amenable  to biological attack.

mechanisms such as volatilization, photolysis and biodegradation may
effectively remove hazardous constituents from soil.  Variables affecting
these mechanisms include soil and climate conditions, hazardous constituent

characteristics, toxicity, teachability and depth.
     Each of the proven technologies will be discussed under the following

     •    General Description - discusses the technology and the various
          procedures and parameters that are involved.

     •    Hazardous Constituents Amenable to the Technology - describes the
          types of hazardous constituents that, when contained in the soil
          horizon, can or cannot be adequately treated with the technology.

     •    Performance - presents the effectiveness of a corrective measure in
          mitigating a human health or environmental risk in terms of its
          overall performance.

     •    Reliability - discusses the demonstrated performance and operation
          and maintenance requirements of corrective measures; including
          various parameters that may optimize or adversely affect the
          reliability of a measure.

     •    Implamentability - presents the various parameters that affect the
          relative ease of initiating a corrective measure such as onsite and
          offsite conditions along with time to characterize the
          constructability of  the corrective measure.

     •    Cost  -  reports  the general costs  for the proven technologies.
          However,  it must be  stressed that  in most  cases costs are highly
          variable due  to various site-specific and  constituent-specific
          characteristics.  Therefore, reported costs  should only be used for
           technology  comparisons.

 General Description—

      Excavation is an important technology for the treatment and disposal of
 contaminated soils.  Excavation can normally be performed in a relatively
 quick,  efficient,  and cost-effective manner.   However,  if the contaminated

 soils are very deep or below the water table,  excavation can become expensive,
 technically difficult and,  therefore, may not be a viable corrective measure.


     Excavation is also performed in conjunction with other technologies.
Many corrective measures such as capping, onsite landfilling, offsite
disposal, or many treatment technologies  rely on the ability  to  excavate  the
contamination in order to be able to implement  the  corrective measure.
However, if hazardous constituents cannot be excavated  due  to economic  or
technical issues, an in situ treatment method should be considered.
     Excavation is widely used  for removing surface and subsurface
contaminated soils.  This activity is normally  conducted with the  following
types of equipment:

     •    backhoe,
     •    front-end  loader,
     •    bulldozer,
     •    clamshell, and
     •    dragline.

 Hazardous Constituents Amenable to  the  Technology—
     Essentially all types  of  contaminated  soils can be excavated  with  any
 readily available machinery (indicated  above).  However, an important
 consideration during excavation is  the  health and  safety of workers.  Fugitive
 dust emissions which are easily generated must  be  minimized throughout
 excavation processes by various methods of  dust suppression.

      Excavation of contaminated soils is a very effective method of dealing
 with a soil release from a SWMU.  Once  the soils  are  excavated  there are many
 options for cleanup that may be implemented.   Therefore, the ability to
 excavate the soils is a benefit when attempting to develop and  implement a
 corrective measure.

      Excavating contaminated soils is a very reliable  removal method as long
 as sampling is performed to ensure that all of  the contaminated soils  are
 removed.  Removal of all contaminated soil eliminates the hazardous constituent
 source and its potential impact on human health and the environment.

     Site conditions are the principal factors effecting the ability to
excavate contaminated soil.  For example a leak or spill that has only
contaminated shallow soils may easily be removed.  However, soils that are
deep (i.e., under a landfill) or below the water table may require quite
extensive excavation methods which greatly increase the time needed to
implement a corrective measure.  However, once soils are removed, beneficial
results  should be realized immediately and the threat to human health and the
environment should be mitigated.

     Costs for excavation must also be considered in the final overall
decision.  Excavation costs can, however, vary greatly depending on the depth
of  contamination and proximity to the ground-water table.  Table 3-3 indicates
1985 unit costs for various types of excavation equipment.  Actual costs for
excavation can be increased by 50 percent or more for health and safety
reasons  (SCS Engineers,  1981).

Front-end Loader
Power Shovel
1985 Unit Cost
2.44 -
1.66 -
3.23 -
.31 -
.84 -
3.11 -
2.11 -
1.25 -

            Source:   R.S Means,  1985.

      Technical difficulties can also  greatly increase the cost of excavation.
 If the contaminated soils are deep, below the water table or if
 sheeting/shoring is needed to support the excavation, costs can greatly be
 increased due to a loss of efficiency.

Qffaite Disposal

General Description—
     Offsite  disposal  is  a  removal/containment corrective measure,  and can be
implemented once  the extent of soil contamination is determined.   It requires
additional remedial measures involving the excavation,  loading and hauling of
contaminated  soils to  an  approved facility for final disposal.

Hazardous Constituents Amenable to This Technology—
      Essentially  all contaminated soils can be disposed of at a properly
permitted facility.  Most hazardous constituents, as a result of the 1984 HSWA
 amendments,  require disposal at a double-lined facility.  Some contamination
 such as foundry wastes, however, may be disposed of in a single-lined landfill.

      Offsite disposal is a very effective long-term disposal action for
 contaminated soil.  If the extent of contamination is well-defined and
 sampling  is performed during soil excavation then essentially all of the
 contamination (i.e.,  soil) should be effectively removed.  This measure has a
 long useful  life  since, once removed, the contaminated soil will not cause any
 additional problems at the SWMU.

      Offsite disposal is a very reliable corrective measure since the
 contaminated soils are removed  from the facility and therefore, continued
 operation and maintenance  activities are not required.  However, based on the
 1984 HSWA amendments, landftiling of untreated hazardous wastes are soon to be
 banned thereby,  requiring  that  contaminated soils be treated prior to disposal.

      The  implementability  of offsite disposal is subject to the limitations of
 excavation which  have previously been discussed.  Additionally, issues such as
 hauling  distances, availabiity  of  landfill space, and quantities of soil must
 also be  considered since they greatly influence  the implementability and costs
 associated with  the corrective  measure.  A considerable amount of time will be

needed to complete the remedial action if the soils are difficult to excavate,
are large in quantity, or if the permitted landfill is a long distance away.
However, once the contaminated soils are removed, beneficial results should be
realized immediately.
     Accidental spillage during transportation must be considered as a safety
issue.  All soils must be shipped in accordance with various EPA and DOT
regulations to minimize the possibility of problems during transportation.

     Factors which effect excavation costs also influence offsite disposal
costs.  Additionally, hauling distance and availability of landfill space
effect overall disposal costs.  Costs have recently (March 1985) been reported
to GCA Corporation for disposal (i.e., tipping fee) by GSX Corporation of
Pinewood, North Carolina as being approximately $100/yd .  Transportation
costs are generally  high, very site-specific, and influenced by hauling
distances and equipment availability.

Cap  Installation  and Surface Sealing

General Description—
      Cap  installation and  surface sealing are corrective measures which can be
performed to excavated contaminated  soils or over existing in-place
contamination.  Capping consists of  either  impermeable capping which acts  to
prevent  surface water infiltration and eliminates direct hazardous constituent
contact,  or permeable capping  which  differs  from impermeable  in  that it allows
surface water  infiltration.
      Impermeable  capping  can  consist of  a  single synthetic or natural  cover
system  which includes:  a  topsoil layer, atop a  buffer/drainage  layer, atop an
impermeable layer,  atop a  bedding  layer; or, a multimembrane  system which
includes  a  topsoil  layer,  atop a synthetic  membrane,  atop a bedding  layer,
atop a  natural  impermeable layer (i.e. clay).
      Table  3-4  lists the  types of materials  used to  cap  contaminated soils.

                 Synthetic Materials                    Natural Materials


Bitumen cements or concretes                            Bentonite

Bituminous fabrics                                      Clay

Butyl rubber                                            Soil

Elasticized Polyolefin

EPDM  (ethylene-propylene-unsaturated dienoterpolymer)


Liquid emulsified  asphalts or  tars

Neoprene  rubber

Polyolefin (Polyethylene  and chlorinated polyethylene)

Portland  cements or  concretes

PVC (Polyvinyl chloride)

Sulfur (thermoplastic  coating)

Teflon -  coated fiberglass  (TFE)

Source:   EPA,  1983b.

Hazardous Constituents Amenable to the Technology—
     Most types of contaminated soil can be disposed in an impermeable'capped
structure.  The use of bottom liners, however, is required to comply with
various RCRA regulations.
     Hazardous constituent/membrane compatability is an issue of concern when
considering impermeable capping.  Hazardous constituents contacting an
impermeable membrane can lead to premature membrane degradation and failure.
Problems  can arise when an impermeable cap is placed above soils contaminated
with highly soluble constituents without the added protection of a bottom
liner  and leachate collection/detection system.  If the cap is breeched,
constituents with high aqueous solubilities and low octanol-to-water partition
coefficients will tend to mobilize from the soils and migrate into the ground
water.  Therefore, the impermeable capping of soils with soluble hazardous
constituents is not advisable unless there is a bottom liner or unless site
conditions dictate that migration is unlikely.  This restriction is also
applicable to  permeable capping of contaminated soil whereby permeable capping
may be acceptable if  the hazardous constituents are not mobilized by surface
water  infiltration.

      Impermeable capping is,  in general, relatively effective as a removal/
containment measure,  in  that  it can  prevent surface water  infiltration and can
preclude  human contact with contaminated soil.  This corrective measure is
best  suited  in areas  where  there  is  a  safe distance between the bottom of the
contaminated  soils and  the mean high ground water  table.   This environmental
feature will  act to protect ground water in the event of a breech in the cap
with subsequent hazardous constituent  generation.  Impermeable capping is
enhanced  when  site soils are  of the  type which minimize hazardous constituent
migration.  This  situation  is particularly advantageous if a bottom  liner  is
not present.   Capping suffers the disadvantage  that cap failure may  result  in
surface water infiltration  and  subsequent constituent migration.
      A permeable cap  like  the impermeable cap  is a relatively effective means
of isolating  contaminated  soil  as  long as  its  limitations  are recognized.   A
permeable cap  is expected  to  have a  long useful  life as  long as  the  cover

material is properly maintained and erosion is eliminated.  However,  if
erosion occurs then direct contact with  the contaminated  soils would  be

     Impermeable  or permeable  caps must  be maintained  to  function properly.
Operation  and maintenance activities  such as  inspections  to ensure continued
cap  integrity, mowing  and revegetation and erosion  control measures are
crucial  to obtaining the maximum  useful  life  for  this  type of structure.
Ground water monitoring  is also required to detect  leachate generation or
hazardous  constituent  migration.  This corrective measure is often used  in
conjunction with  other remedial measures for  site clean up.  For  example,
pumping  or frenoh drains are used to  aid in ground  water  cleanup.   The use of
 impermeable and  permeable caps to isolate  soils must be carefully investigated
 prior  to their installation  at a  SWMU.  It must be  determined that the cap
 will be  able  to  perform as  intended  and  that  the  soil  contamination will not
 migrate  or impact human health and  the environment.

      The principal consideration  in regards  to implementing  and  installating a
 cap are site  conditions,  and time.   While  permeable and impermeable caps can
 usually be installed in a relatively short (i.e.,  several months) time period,
 equipment and material constraints  can increase  the period  of  time required  to
 implement these measures.

      Some general costs for permeable and impermeable  materials are presented
 in Table  3-5.  These costs do not include any costs for excavation or any
 other site activities.

 Onsite Landfill

      An onsite landfill may be used  to dispose of contaminated soil from a
 release at a SWMU.  However,  if  the  SWMU is a landfill and  the leak/release
 can be repaired,  then the newly  contaminated soil can be returned to the

Unit Cost (June 1985)*
Topsoil (sandy loam), hauling, spreading, and grading
(within 20 miles)

Clay-rich soil, hauling, spreading, and compaction

Sand, hauling, spreading, and compaction

Portland cement concrete (4 to 6 in. layer), mixed,
spread, compacted onsite

Bituminous concrete  (asphalt pavement) (4 to 6 in.
layer), including base  layer

Lime or Portland cement, mixed into 5 in. of cover soil

Bentonitic clay  (2 in.  layer) spread and compacted

Sprayed asphalt  (1/4 in. layer), with cover soil,

PVC membrane  (20 mil),  installed

Chlorinated PE membrane (20 to 30  mil),  installed

Elasticized polyolefin  membrane, installed

Hypalon membrane  (30 mil),  installed

Neoprene membrane,  installed

Ethylene propylene  rubber  (EPDM) membrane,  installed

Butyl  rubber  membrane,  installed

Teflon-coated fiberglass (TFE) membrane  (10 mil),



$10.17 - $16.95/yd2

$5.08 - $8.19/yd2

$2.43 - $3.39/yd2


$2.26 - $3.84/yd2

$1.97 - $3.05/yd2

$3.67 - $4.86/yd2

$3.50 - $4.69/yd2



$4.07 - $5.3l/yd2

$4.07 - $5.76/yd2

 Fly ash and/or sludge spreading,  grading,  and  rolling     $1.69  -  $2.82/yd2

 Source:  Radian Corporation,  1983.

 *Costs updated to June 1985 dollars by GCA Corporation/Technology Division.

repaired landfill.  If the landfill has installation defects or quality
control was poor during installation,  then conceivably a completely  new
landfill may need to be constructed to adequately  protect  human health and  the

General Description—
     Landfilling  of contaminated  soils has been used  for many  years  as a  means
of  storage  and  permanent  disposal of  all  types of  contaminated soils.
Landfilling generally  consists  of placing soils into  either a  lined  or unlined
excavated area  and  then placing a cap over these soils.  If the ground water
table  is very  shallow, landfills  can  also be  constructed above grade in
mounds.  The general  types  of  landfills  include:

     •   "state-of-the-art" RCRA-designed landfills,
     •    single-lined landfills, and
     •    unlined landfills.

     A "state-of-the-art" RCRA-designed  landfill  generally consists  of
 impermeable liners,  and  leachate  collection  and  leak-detection systems for
 both its cap and bottom liner  systems.  Of the  three  types of  landfills
 identified above, a RCRA landfill offers the greatest amount of  protection  to
 the environment since it essentially eliminates  surface  water infiltration  and
 hazardous constituent migration into the ground  water.   A  30-year post closure
 ground water monitoring period is, however,  required.
      A single-lined landfill consists of one liner,  a leachate collection
 system comprised of a drainage layer and perforated pipes, and an impermeable
 cap.  Such landfills also require post-closure  ground water monitoring  for  a
 30-year period.
      An unlined landfill consists of an unlined  trench with an impermeable  cap
 and no leachate collection system.  While this  type of landfill  can be
 effective under certain conditions,  there is always the possibility of
 leachate being generated and subsequently migrating to the ground water.
      Factors that must be considered when assessing the suitability of
 landfill ing include:

     •     The physical  state  and solubility of wastes within the contaminated
          soils to be landfilled.   The materials must be amenable to being
          compacted and securely placed to eliminate differential settling and
          avoid landfill failure.
     •     Present land  use and the depth to ground water.
     •     Geologic conditions such as soil permeability, location of bedrock,
          impermeable strata, and seismic zones.
     •     Location within a 100-year floodplain.

Hazardous Constituents  Amenable to the Technology—
     Generally most types of  contaminated soil can be landfilled.  However,
the compatibility of any generated hazardous constituent and the liner must  be
determined prior to installation to ensure that hazardous constituents
generated will not adversely affect the integrity of the liner.   Adverse
effects on the liner can lead to premature breeching and decrease in useful

     RCRA landfills are expected to be very effective in containing
contaminated soils since they have many safeguards against hazardous
constituent  discharge.  This type of double-lined landfill encapsulates the
soils thereby minimizing hazardous constituent generation and preventing
constituent  release  into the environment  (assuming QA/QC procedures during
construction and operation are  strictly adhered to).
     A  single-lined  landfill will be somewhat less effective in containing
contaminated soils since it only has one  liner.  This type of landfill is also
not  expected to  have as  long a  useful  life as a double-lined RCRA landfill.
     An unlined  landfill is even less  effective at providing protection to
human health and the environment since cap failure can  occur thus allowing
hazardous constituent migration into ground water.  Unlined landfills must be
carefully sited.

     Properly  designed  and installed  landfills  are generally quite  reliable.
There are, however, many operational and  maintenance  activities  that  are
necessary to ensure  proper functioning of the  landfill.  For example,


maintenance and repair to the cap during establishment of  the vegetative cover
is a critical and extensive  activity.  Landfills  having  leachate  collection
and leak detection  systems also  require continuous monitoring.  Other
activities  such as  cleaning  collection system drain  pipes  may occasionally be
necessary.  All of  these  activities  greatly  effect the  reliability of
landfilling contaminated  soils.

      Some  of  the  site conditions that may  affect  the implementability  of  an
onsite landfill are:

      •    bedrock outcropping;
      •    shallow ground  water  table; and
      •    physical space  for the landfill.

      If the bedrock is shallow or if outcroppings are erratic  then siting  a
 landfill may be impossible due to the lack of depth.  Very shallow ground
 water makes installation difficult since  dewatering  may be required to
 excavate and place the landfill layers.   In these cases an above-grade or
 mounded landfill may be applicable.
      Landfills can generally be constructed within a few months;  however  this
 is greatly dependent on the amount of soil to be landfilled and the overall
 site conditions.   Once the soils are placed in the landfill, immediate
 beneficial results should be realized, since the soils will no longer
 contribute to continued contamination.

      A double-lined  landfill can be  constructed  for approximately $60 to
 $80/yd3 (GCA, 1985b)-  A single-lined landfill can be constructed for
 approximately 15 percent less than  a double-lined facility and therefore,
 ranges from $50  to $70/yd .  An unlined landfill consisting of an
 impermeable cap  can  be expected to  cost approximately $30/yd .


General Description—
     Soil solidification or stabilization is a process that alters the
physical and/or chemical state of the hazardous constituents within the soil
rendering them less leachable, less toxic, and more easily handled,
transported, and disposed.  With current solidification technologies,
inorganic constituents are essentially the only types of constituents that are
amenable to solidification.  Generally contaminated soils containing greater
than 10 to 20 percent organics cannot be solidifed (U.S. EPA, 1980).  The main
types of solidification for soils consist of:

     •    cement-based processes; and
     •    pozzolanic processes.

     Cement-based  processes generally consist of a soil/slurry mixed with a
Portland cement.   This mixture then hardens  in a matter of hours or days
forming  a  rock-like mass  incorporating the hazardous constituents  into the
crystalline  structure.
     Most  types  of hazardous  constituents contained in  soils and slurried in
water  can  be  solidified  since suspended  solids are readily incorporated into
 the structure.   There  are also chemical  reactions  that  occur when  the
hazardous  constituents and cement are combined that can alter  the  state of the
hazardous  constituents.   The  final  product  from  the process  is generally
stable and inert,  however,  leaching can  still occur.  To prevent this, surface
coating  for  the  solidified mixtures consisting of  asphalt, asphalt emulsion
and vinyl  have been  investigated  quite extensively.  However,  surface coatings
are currently not  used with great  success due  to poor adhesion.
      Pozzolanic  solidification processes involve the reaction  of lime with
 fine-grained siliceous (pozzolanic) materials  plus water  to  produce a
 concrete-like mass.   Pozzolanic materials generally consist  of fly ash, ground
 blast-furnace slag and cement-kiln  dust. These  products  are byproducts of
 commercial products  with very little  economic  value.  This  activity can be
 advantageous since two constituent  products are  combined  to  form a solid  mass
 that can be  easier to  dispose.

     As with the cement-based process, the pozzolanic process does not
completely eliminate leaching in all cases.  Therefore, disposal" of the'se
solidified hazardous constituents necessitates the use of a specially designed
landfill that will contain and remove leachate if produced.

Hazardous Constituents Amenable to the Technology—
     Inorganics are the principal types of hazardous constituents that are
amenable to solidification.  During  the solidification process chemical
conversions can occur as  the contaminated soil and binding agent are mixed.
For  example, toxic metals can be easily precipitated as insoluable hydroxides
or carbonates by  the high pH of the  cement.  Other materials such as soluble
salts  of zinc, copper,  lead, manganese, and  tin  tend to cause variations  in
setting times which greatly reduces  the physical strength of the mixture.
Also,  the presence of  fine organic particles such as those passing through a
No.  200 mesh sieve are  undesirable and tend  to weaken the bond between cement
particles  (EPA,  1980).  Also,  soils  that  contain high levels of  sulfates
greatly  increases the  swelling  of concrete which can cause spalling.

      Solidification  is normally used on  sludges  and aqueous wastes.  The
process  of  solidification is  generally quite effective, however, since
 leaching is not completely eliminated, disposal  in  a secure  landfill is
necessary  (EPA,  1980).  Over  the  short term  this corrective measure may
perform quite  adequately, however, various  processes (i.e«,  freeze-thaw,
 contact  with water)  can reduce  the  long-term effectiveness.

      This  process is reported to  be  quite reliable  as  long  as  the hazardous
 constituent/solidifying agent compatibility  are  taken  into  account;  types of
 hazardous  constituents that  can be  solidified  have  been discussed previously.
 After solidification,  if  the  material is  to  be landfilled,  testing should be
 conducted to ensure  that  no harmful  reactions  will  occur  if  leachate is

Imp lenient ability—
     The solidification process is, in general, easily implemented.  In both
the cement-based and pozzolanic processes, materials are readily available and
extensive hazardous constituent/soil dewatering is not necessary.  Special
equipment is generally unnecessary since lime is a common additive and
cement-mixing is a common technology.

     The costs  for solidification with Portland cement is dependent on the
physical state  of the hazardous constituents and amount of soil to be
solidified.  Portland cement is estimated to cost from $65 to $90/ton (Radian
Corporation, 1983).
     The costs  for solidification using pozzolanic processes are estimated to
be from $0.04 to $0.15/gallon  for industrial sludges (EPA, 1982b).

In Situ Biodegradation

General Description—
     Biodegradation  is a biological  treatment process which constitutes the
molecular  breakdown  of organic substances by living organisms.  It is a
significant  mechanism for degrading  organic compounds in soil environments
which  typically contain diverse raicrobial populations including bacteria,
actinomycetes,  and  fungi.   Important  parameters in the soil environment which
affect biodegradation include  pH,  soil moisture content, soil oxygen content,
nutrient  concentrations, and  temperature.   In  situ biodegradation  of
contaminated soils  can be enhanced by modifying soil parameters or by
supplementing  existing microbial  populations with other natural microbes,
adapted  microbial  cultures, or bioengineered microbial strains.  Soil
parameters,  as  summarized  in  Table 3-6 and  subsequently discussed, are
modified  to  enhance  raicrobial  growth and  substrate utilization.  This
 includes:   (1)  increasing  soil temperatures to  between 50° and  60°C;
 (2)  increasing  soil  water potential  to greater  than -15 bars;  (3)  adjusting
 soil pH  to between 5 and 9;  (4)  adjusting the  oxidation-reduction  (redox)
potential  of the  soil; and  (5) addition of  nutrients.  While  the  status  of the
 in situ biodegradation technology is at various stages of  development,

 Soil Parameter
Control Method
           Comment s
  Humic substance
Vegetation and mulching regulate
incoming and outgoing radiation,
other methods alter the thermal
conductivity of soils themselves
Moisture content
• Irrigation
                        •  Drainage
                        • Additives
Most suitable irrigation
treatment for contaminated
soils appears to be sprinkler
(overhead) irrigation due to
adjustable application rates,
uniform water distribution, and
control over erosion

Includes surface drains, i.e.,
open ditches and lateral
drains, and subsurface drains,
i.e., open ditches, buried tube
drains, and well points

Includes commercially available
water storing agents, water
repelling agents, surface
active agents and evaporation
 • Liming
                        • Sulfur or acid-
 Calcium or  calcium  and
 magnesium-containing compounds
 used  to raise  the pH

 Substances  used  to  lower  the  pH,
 little  experience in field

                              TABLE  3-6  (continued)
 Soil Parameter
      Control Method
Oxygen content    • Aerobic conditions

                    - Tillage
                    - Well-point injection
                    - Drainage
                             Surface soils (<2 ft deep)
                             Soils >2 ft deep (saturated)
• Commercial fertilizers
Usually nitrogen or phosphorus

depending upon the technique used and the hazardous constituents being
treated, the control methods corresponding to each soil parameter presented  in
Table 3-6 have been field tested.
     Soil temperature is one of  the more  important factors  in  controlling
microbiological activity, the rate of organic matter decomposition, and  the
rate of volatilization of compounds from  soil.   It can be modified by
regulating  incoming and outgoing radiation through vegetation  and mulching,  or
by changing the thermal properties of the soil with irrigation/drainage,
compaction/tillage and the  addition of humic substances (JRB Associates, 1982).
     The degradation of hazardous organic compounds can be  accelerated by
optimizing  soil moisture.   Limited experimentation indicates that degradation
rates are highest  at a soil water potential between 0 and -.9869 atm.  Typical
methods of  moisture enhancement  include irrigation and synthetic soil
additives.   If  the soil  is  too wet, surface erosion due to  runoff will
mobilize contaminated soils and  render  them unavailable to  biodegradation.
Therefore,  soil drainage  is also an important method of moisture control.
Care must be taken however  not to promote hazardous constituent migration  in
the  process (JRB  Associates,  1982).
     Depending  upon the  nature of the hazardous  constituents contaminating the
soil,  it may be advantageous  to  optimize  the soil  pH for a  particular segment
of the  microbial  population.   Some  fungi  have a  competitive advantage at
slightly  acidic pH, while  actinomycetes  flourish at slightly alkaline pH.
Near neutral pH values  are  probably most  conductive to microbial functioning
 in general.  Contaminated  soil can be treated with crushed  limestone or  lime
products  to raise the  pH to the  desired  range, or  with acid-producing
materials  or sulfur to  lower  the pH  (JRB  Associates,  1982).
      The  oxygen content  of  the soil  can also determine the  mechanism of
biodegradation through  anaerobic and  aerobic processes; only aerobic processes
will be discussed in  the document.  Aerobic  processes are more
 energy-efficient  and microbial decomposition processes are  more  rapid under
 these  conditions.   The  majority  of  organisms  in  soils decompose  under aerobic
 conditions.  Common methods of aeration are  tilling or draining  the soil.   If
 deep soils  require aeration,  a backhoe  (or  other form of  construction
 equipment)  or a well  point  system for diffusers  can be used.

     Microbial degradation may also be limited by nutrient availability,
particularly if available carbon (C) is in large excess relative to the
nitrogen (N) and/or phosphorus (P) required by the microorganisms that degrade
it.  If the ratio of organic C:N:P is greater than about 300:15:1 and
available (extractable) inorganic forms of N and P do not narrow the ratio to
within these limits, supplemental nitrogen and/or phosphorus should be added
(Alexander, 1977; Kowalenko, 1978).
     Adding fertilizer to hasten the decomposition of crop residues is used in
agriculture (Alexander, 1977), and has been used in the treatment of hazardous
waste (oil spill) contaminated soils (Thibault and Elliott, 1980).  For
detailed discussions on the soil parameters previously presented that can be
modified to promote biodegradation refer to JRB Associates (1982).
     Table 3-7 lists some of the organic compounds amenable to microbial
degradation.  Table 3-8 lists microbial strains which have been effective at
degrading pesticides.

     Enhanced biodegradation by soil modification has been widely and
successfully performed in the agricultural industry.  The use of specially
adapted microorganisms has been demonstrated in the laboratory and has been
used successfully in several full-scale soil decontamination operations
(i.e., chemical  spills).
     The  level of treatment for in  situ biodegradation can be variable and
depends on  the soil conditions and  the type of contamination.  High percent
removals  of  soil contaminants has been demonstrated after adequate pH
adjustment,  nutrient addition and application of adapted microorganisms.
     The  optimization  of  soil conditions  for enhanced biodegradation, however,
may  result  in  the release and subsequent  transport of hazardous constituents
via  the following mechanisms:  leaching,  erosion, dissolution, or

     The  reliability of  in  situ biodegradation enhancement  technologies  for
modifying soil parameters is moderate because they require  considerable
maintenance  or reapplication.  The  use of adapted microbial  populations  is


  n-Butyl alcohol

Alkyl Halides

  Ethylene dichloride (1,2-Dichloroethane)
  Methylene chloride (Dichloromethane)
  Propylene dichloride (1,2-Dichloropropane)



Aromatic Hydrocarbons

  Divinyl  Benzene
  Polynuclear  Aromatic Hydrocarbons  (PNAs)
  Styrene  (Vinyl Benzene)

Chlorinated Aromatic3

  Polychlorinated  biphenyls  (PCBs)







  Resorcinol (1,3-Benzenediol)

Crude  and refined oils


 Source:   EPA,  1984b.

       Pseudomonas spp.
       Pseudomonas spp.


  Endrin, DDT
  Endrin, DDT
  Endrin, Aldrin, DDT
  Endrin, Aldrin, DDT
  Dieldrin, Aldrin, Endrin, DDT
  Lindane, Aldrin




       Chlorella and  Dunaliella
      Source:   DeRenzo,  1980.

also moderately reliable due to their dependence on soil parameters.
Biodegradation generally results in less complex, though not necessarily  less
toxic, compounds.  For example, the degradation products of some halogenated
organica such as DOT, DDE, and ODD have been  found to be more  toxic  and
persistant than their parent compounds.

     The implementability of this treatment technology  is variable because  it
depends rather heavily on soil properties and site conditions  including
moisture content, trafficability, and depth of contamination.  Usually
standard agricultural equipment and techniques, and commercially available
materials  are  required.

      Costs for in situ biological treatment are highly  variable and  site
specific,  and  therefore  are not readily approximated (Ronyak,  1985).

Above-Grade Biodegradation

General  Description—
      The previous  discussion on biological  treatment focused on ^n situ
methods  for enhancing  biodegradation.  Above-grade biodegradation, a
 biological treatment technology,  differs  from in  situ biodegradation in  that
 it can be implemented  in instances  where  in situ  treatment  is  not possible;
 for example, when the  contaminated  soil  is  at considerable  depth.  Other
 conditions such as  a high water  table, potential  for migration of hazardous
 constituents,  the need to recirculate bacterial  and nutrient  solutions,  and
 numerous other factors may  require  that  the contaminated  soils be excavated
 and located above grade for subsequent biodegradation.
      In above-grade biodegradation  treatment, the preliminary  activity  is the
 excavation of contaminated soils.   The excavated  soils  are  then  placed  in a
 lined impoundment to facilitate  the recycling of  nutrient  and  bacterial
 solutions, and to collect the  generated  leachate. Alternatively,  the
 excavated soil can be  placed  directly on natural  soils  for  subsequent
 landfarming activities.

     The reliability of above-grade biodegradation treatment varies widely
depending upon the nature of the contaminated soils to be treated.  For
example, soils contaminated with petroleum waste products may be readily
biodegradable whereas soils contaminated with PCBs may not be suitable for
treatment.  The ability to effectively treat a contaminated soil can be
ascertained by laboratory and pilot field tests.

     Provided that biodegradation of a specific hazardous constituent has been
proven  to be effective, the process can be highly reliable.  After treatment,
sampling can be conducted to determine the effectiveness of the process.
Higher  levels of biodegradation are generally obtained when longer periods of
biotreatment are used.

     Above-grade biodegradation is generally readily implementable.
Sufficient  land must be available to spread out the contaminated soils for
treatment.  Construction of aeration tanks, impoundments, and irrigation
systems are the major construction-related activities.

     As previously  stated  for  in  situ biodegradation, costs can be highly
variable and are  site  specific  (Ronyak,  1985).

Photolysis  (Photooxidation)

General Description—
      Photolysis  or  photooxidation is  the process  by which  ultraviolet  photons
break the carbon-halogen bond  (usually C-CL),  resulting  in a  dehalogenated
molecule.   Such  loss of halogens  is  considered favorable because  lower-order
halogenated organics usually have less toxic  properties  and are more
biodegradable.   Photodegradation  is  enhanced  by the presence  of  a hydrogen
donor which replaces the chlorine on the molecule.  Hydrogen  donors  are
 applied and depending on the depth of contamination,  the soil is  tilled to
expose  hazardous  constituents  to  the  light.

     Activated carbon adsorption of organics followed by chemical addition and
photolysis has been reported by React Environmental Crisis Engineers, St.
Louis, Missouri (1983).  The method involves the addition of activated carbon
to the soils, removal of the most highly contaminated materials, and mixing
the remaining soil with sodium bicarbonate  to  increase  soil pH.  The soil  is
then allowed to react photochemically resulting in the  photolysis of the
parent material.  The level of treatment is expected to be fairly high.  An
increase  in soil pH is the major secondary  impact of the treatment method.

Hazardous Constituents Amenable to Treatment—
     Photodegradable organic constituents are amenable  to this form of
treatment.  Generally, this includes compounds with moderate to  strong
absorption in the 290 run wavelength range.  Table 3-9 lists the  of compounds
which  are amenable  to photodegradation.

      The level  of  treatment achievable  is potentially quite high, based on
 limited  experimental data.  Effectiveness also depends  on the amount of
 tillage  possible  at the  site  and  the depth  of  contamination.  However, the
 potential for the  production  of hazardous compounds  from photodegradation
 needs to be  further researched.   Production of hazardous compounds from the
 photodegradation  of pesticides has been documented,  e.g., dieldrin formation
 from aldrin,  paraoxon  formation  from parathion, phosgene formation from
 chloropicrin (Crosby,  1971),  and  the formation of PCBs  from the  photoreaction
 of DDT (Woodrow et al.,  1983).  The potential  for such  occurrences is expected
 to be high and  further research  is needed  to  identify potential  toxic product
 formation to ensure the  safe  application of this  treatment methodology.
 Another  concern is the  potential  induction  of  volatilization of  organic
 constituents from the  soil without  subsequent  photodegradation.

      Unless  the hazardous constituents  in the  contaminated  soil  and  their
 photodegradation products are known,  this  is  not  a  reliable method,  since
 toxic by-products may  be formed.

Allyl chloride

Benzyl chloride

Bio(Chloromethyl) Ether

N> Carbon Tetrachloride

Chloromethyl methyl ether



Dich lorobenzene6

Dimethyl Nitrosamine

kOH x 1012 Direct
(cm-* molecule'^ Photolysis
sec~l) Probability
16 Probable
44a Probable
28a Possible

3a Possible

4s Possible


0.4a Possible

3a Possible

46a Probable


0.3,» Possible

39a Probable

Remova 1















0. 004-3. 9d





Anticipated Photoproducts
H2CO, C02
chlorinated hydroxy carbonyls,
OCHO, Cl; ring cleavage
products chloromethyl-phenols
Chloromethyl formate

C12CO, CL°

Chlorophenols, ring cleavage
C12CO, Cl~
Chloromethyl and methyl
formate, CIHCO
chlorohydroxy acids, aldehydes
hydroxynitrotoluenes, ring
cleavage products
Chlorinated phenols, ring
cleavage products
aldehydes, NO
oxygenated formates

                                                     TABLE 3-9  (continued)
Ethylene Dibromide
Ethylene Dichloride
Ethylene Oxide
Uexach lorocyc lo- pentad iene
Maleic Anhydride
Methyl Chloroform
Hethylene Chloride
Methyl Iodide
kOH x 10 12
(cn>3 molecule"1
Reroova 1
. 0.1
Anticipated Photoproducts
CO, C02
n 1
2CO, diacyclchlorides,
ketones, Cl
C02, CO; acids, aldehydes,
and esters which should
H2CO, C12CO, Cl-
H2CO, 1°, ICHO, CO
Nitrophenols, ring cleavage
Aldehydes, nitroamines
Aldehydes, Nitroamines
Aldehydes, nitroamines
Aldehydes, ether.s

                                            TABLE 3-9  (continued)
Perch loroe thy lene
kOH x 1012
(cm^ molecule"1
Remova 1
Anticipated Photoproducts
C12CO, C12C(OH)COC1, Cl°
Diphydroxybenzenes ,
 Phosgene'                       ~0

 Polychlorinated  Biphenyls       < la

 POM (Benro(a)-pyrene)

 Propylene  Oxide                  1.3

 Toluene                          6

 Trichloroethylene                2.2

 Vinylidene Chloride              4a

 o-,m-,p-xylene                  16

Possible     Unlikely         >11

Possible     Probable           8

             Unlikely           8.9

             Unlikely           1.9

Possible     Unlikely           5.2

Possible     Unlikely           2.9

             Unlikely          ~0.7
                                                                                     nitrophenols, ring  cleavage
        , HC1
Hydroxy PCBs, ring cleavage



Benzaldehyde, cresols, ring
cleavage products, nitro

C12CO, C1HCO. CO, Cl-


Substituted benzaldehydes,
hydroxy xylenes, ring clevage
products, nitro compounds
"Hate constant by method of Hendry and Kenley (1979).
''Material is not expected to exist in vapor phase at normal temperatures.   Residence  time calculation  assumes the
 chemical is substantially absorbed by aerosal particles and that the  aerosol  particles have a  residence  time ot
 approximately 7 days.
cThe shorter residence time includes a photolysis rate as given in Graedel  (1978).
^Decomposition in moist air is expected.  The shorter residence time includes  the cited decomposition  rate.
eValues given are averages for the various isomers.
^Reaction with 0('D) is possible; k»3.6xlO~10 cur* molecule"! sec"*-, and  [0('D)]-0.2 molecules cm~3
 implies a tropospheric lifetime of 440 years.  In addition, slow hydrolysis is expected.
Source:  EPA, 1984b.

     Soil tilling may be easy or difficult depending on  the  trafficability  of
the site and the depth of contamination.  Runon and runoff controls may  be
necessary to manage the drainage and erosion.

     Costs  for  this technology can  be  quite  variable and are highly site
dependent.  If  contamination is at  the surface, then only tilling may  be
needed.  If soils are somewhat deeper,  then  excavation followed  by spreading
at the  surface  will be necessay, thereby  increasing costs.


General Description—
     Neutralization is the  addition of chemicals  to contaminated soil  to
increase pH values to pH  7  or above.   Control  of  soil pH can result in metal
immobilization, decreased corrosivity, and enhanced microbial activity.   The
most common method of soil  neutralization is liming, which involves the
addition of any calcium  or  calcium  and magnesium-containing  compound to  soil.
The  use of  acidic chemicals to  lower  soil pH is not commonly employed  at this
 time.   Lime correctly  refers  to  only  calcium oxide, but  is commonly used to
 refer  to calcium hydroxide, calcium carbonate, calcium-magnesium carbonate,
 and  calcium silicate  slags.  A  summary of commonly used  liming materials is
 presented  in Table 3-10.
      The choice of a liming material  depends upon several factors.  Calcitic
 and  do1oraltic  limestones are the most commonly used materials.  To be  rapidly
 effective,  these materials  must be  ground because the  velocity of  reaction  is
 dependent  on the surface in contact with the soil. The  finer the materials
 are  ground, the more rapidly they react with the  soil.   However, a more  finely
 ground limestone product usually contains a  mixture of fine  and  coarse
 particles  in order to effect a pH change rapidly  and  still  be relatively
 long-lasting as well as  reasonably  priced.   Many  states  require  that  75  to
 100 percent of the limestone pass an 8- fo  10-mesh sieve and that  20  to
 80 percent  pass anywhere from an 8- to 100-mesh  sieve.   Calcium oxide  and
 calcium hydroxide are manufactured as powders and react  quickly.

                                                   TABLE  3-10.   LIMING MATERIALS
                Liming Material
           Limestone,  calcitic
           Limestone,  dolomitic
     , 100 percent purity
65 percent CaC03 + 20 percent
MgC03, 87 percent purityb
           Limestone,  unslaked lime,   CaO, 85 percent purity
           burned lime,  quick  lime
           Hydrated  lime,  slaked
           lime,  builder's lime
          Blast  furnace  slag
          Waste  lime products
Ca(OH)2, 85 percent purity
     , 50 percent purity
    100       Neutralization value usually
              between 90-98 percent because of
              impurities;  pulverized to desired

     89       Pure  dolomite (50 percent MgC03
              and 50  percent CaCC^) has
              neutralizing value of 109 percent;
              pulverized  to desired fineness

    151       Manufactured by roasting calcitic
              limestone;  purity depends on purity
              of raw  materials;  white powder,
              difficult to handle—caustic; quick
              acting;  must be mixed with soil  or
              will  harden  and cake

     85       Prepared by  hydrating CaO; white
              powder,  caustic,  difficult to
              handle;  quick acting

     50       Soft, unconsolidated deposits of
              CaCOj,  mixed with earth,  and
              usually quite moist

   75-90      Byproduct in manufacture of pig
              iron; usually contains magnesium
Extremely variable in composition
          aCalcium carbonate equivalent (CCE):  neutralizing value compared to pure calcium carbonate,  which  has  a
           neutralizing value defined as 100.
           State laws specify a calcium carbonate equivalent averaging 85 percent.
          Source:  EPA, 19845.

     The amount of lime required for soil pH adjustment is dependent on
several soil factors, including soil texture, type of clay, organic matter
content, exchangeable aluminum and buffering capacity (Follett et al. , 1981).
Differences among soils in their buffering capacity reflect differences in  the
soil cation exchange capacities and will directly affect the amount of lime
required to adjust soil pH.  The amount of lime required is also a function of
the depth of incorporation at the site, i.e., volume of soil to be treated.
The amount of  lime required  to effect a pH change in a particular
site/soil/waste system is determined in laboratory short-term treatability
studies or soil-buffer tests (McLean, 1982).  Lime requirements may also be
affected by acid  precipitation and acid-forming fertilizers.

Hazardous Constituents Amenable to Treatment—
     Soil contaminated with  acidic or basic constituents.

     Liming  is a  common  agricultural technique where the achievable level of
treatment  is high,  though care must be  taken  to ensure that hazardous
constituents are  not mobilized  from the change in soil pH.

     Reliming  will  probably  be  necessary  to maintain an adequate level of

     The implementability  is quite  variable,  depending on  the  trafficability
 of the site  and the depth  of soil contamination.  Because  the  soil
 necessitates tilling, runoff controls  are necessary  to control  drainage and
 erosion.   Lime is usually  applied  from a  V-shaped truck bed with a
 spinner-type propeller in  the  back  (Follett  et al.,  1981).  Uniform  spreading
 is difficult with this equipment,  and  wind losses can be  significant.  A more
 accurate but slower and more costly method is a  lime  spreader  (a covered
 hopper or conveyor)  pulled  by  a tractor.   Limestone  does  not migrate easily in
 the soil since it is only  slightly  soluble,  and  must  be  placed where needed.
 Plowing and/or discing surface-applied lime  into the  soil  may  therefore be


     The application of fluid lime is becoming more popular, especially when
mixed with fluid nitrogen fertilizer.  The combination results in less trips
across the soil, and the lime is available to counteract acidity produced by
the nitrogen.  Injection of a lime slurry may also be feasible to reach
contamination at relatively deep depths.

     Costs for neutralization are highly dependent on the quantities of
materials used to neutralize the waste and the type of materials used for


General  Description—
     Adsorption  refers  to the process which results in a higher concentration
of  a chemical  (sorbate) at a solid surface (sorbent) or within the pore
structure of the sorbent than is present in bulk  solution.  Actual sorption
mechanisms are often not known.  Sorption is the  major general retention
mechanism  for many organic compounds and metals onto soils.  Adsorbed
compounds  are in equilibrium with  the soil solution and are capable of
desorption (Bonazountas and Wagner,  1981)-
      Several processes  are  involved  in  adsorption including:

      •    ion exchange;
      •    physical  adsorption  through weak atomic and molecular  interaction
           forces (van der Waal  forces);
      •    specific  adsorption  exhibited by anions involving the  exchange  of
           the ion with surface  ligands  to  form partly covalent bonds;  and
      •    chemisorption involving  a  chemical  reaction between the  compound  and
           the surface of the  sorbent.

      The effectiveness of  utilizing  sorption  to immobilize a hazardous
material can generally be  predicted  by  the compounds adsorption  isotherm,
 which expresses the  relationship between the  amount of  constituent adsorbed
onto a solid and the concentration of  solute  in solution at equilibrium.   One
 frequently used relationship is the  Freundlich isotherm,  which is:

                                    X = kCN                                 (3-1)
where:  X = amount of constituent adsorbed per unit dry weight of  soil,
        k and N are constants, and
        C = solution phase equilibrium concentration.

     The percentage adsorbed under  natural moisture conditions can be
estimated by:

                        Percent  sorbed =	—r-r-—-                  (3-2)
                                           1     A  l/N  £
                                                k       X
where:   9 =  fraction  soil moisture content  (weight basis).
     When adsorption  is  linear, N=l,  and  the percent  sorbed  is not a  function
of  the  amount  sorbed  per unit weight  of soil (X).  However,  when adsorption  is
not linear,  the  percent  adsorbed  becomes  a  function of X.  Equation 3-2  shows
the percent  of chemical  adsorbed  as a function  of k and  X.
     Materials used for  adsorption  include  various agricultural products and
by-products, sewage sludges,  activated carbon,  and other organics.  The
organic material can be  applied to  the soil by  harrowing or  disking.  The
amount  of  organic material  which  is required to immobilize the hazardous
constituent  is primarily dependent  on the adsorbability  of the constituent and
 the organic  content of the  soil matrix.
     Desorption is also  important with respect  to  treatment  effectiveness
because of chemical release from soil into  percolating water.  Generally the
extent  of  desorption also follows the Freundlich isotherm, but with different
K and N values.   Factors directly associated with  desorption include  the
 amount  of  leachate (soil/water ratio) and the  amount  of  hazardous  constituent
 contaminating the soil (soil/constituent  ratio).  The extent of desorption
 will decrease with an increase of these  ratios.

 Hazardous  Constituents Amenable to  Treatment—
      Heavy metals and organic constituents are  amenable  to adsorption.

     Adsorption is a treatment technology which has proven to be effective for
the removal of metals or organics.  It is, however, only considered as a means
of short-term soil remediation since hazardous constituents may slowly desorb
with time and, potentially, the sorbent may degrade and result in the release
of the hazardous constituents.  Conversely, in the case of organic
constituents, a sorbent may immobilize the hazardous constituents until they
are naturally biodegraded.  Repeated application of an adsorbent may be
required to provide a high level of performance.

     The reliability of adsorbtion to immobilize hazardous constituents in
soils  is highly dependent on  the nature of the constituents and site
conditions.  Degradation or mineralization of the adsorbent could result in a
release of hazardous constituents to the environment.  In general, adsorbtion
is expected  to be moderately  reliable over the short term, and somewhat less
reliable over the long term.

     The implementability  of  adsorption varies widely depending on site
conditions.  Sites most suitable  for treatment are those which are accessible
 to heavy equipment  and for which  the depth of soil contamination  is shallow.
The  organic  sorbents can  then be  easily applied to the surface and tilled into
 the  soil.

     Costs for  adsorption are highly variable due  to hazardous constituent
 type,  quantity  and  sorbent necessary  for  immobilization.

 Stationary/Mobile Rotary  Kiln Incineration

General  Description—
     Rotary kiln incineration has been in use  for  many years  and  can  be  used
 to destroy contaminated  soils from a  release at a  SWMU.   A rotary kiln
 generally  consists  of  a  cylindrical refractory-lined  shell mounted at a  slight
 incline  (i.e.,  less  than  5 degrees).   The shell rotates  (5 to 25  times per


hour) during the incineration process to control residence times and mixing
with combustion air to ensure that maximum destruction is achieved.  In most
cases, a secondary chamber is used to further the destruction process.
However, the secondary unit can be used alone to burn flammable liquids.
     There are two basic designs of rotary kilns, the cocurrent and
countercurrent designs.  The cocurrent design is a unit that has an auxiliary
fuel burner at the front end of the incinerator where contaminated soils are
fed  in.  The countercurrent design has the fuel feed at the lower end of the
unit,  therefore the combustion gases flow countercurrent to the flow of
contaminated soils.  Each design adequately  incinerates hazardous
constituents, however  the countercurrent design is better suited for
constituents with a low heating value (such  as saturated material) due to the
fact that  temperature  is controlled at both  ends of the unit.  This feature
tends  to minimize overheating of the refractory liner (Bonner, 1981).
      Residence  times vary  from a few seconds for highly combustible gas to a
few hours  for  low combustible solid wastes (i.e. contaminated soils).  In
dealing with  the  incineration of various  types of hazardous constituents and
mediums to which  they  are  attached, the following variables must be adressed
 (GCA,  1983c):

      •    size  and  physical  state  of  the  hazardous constituents within the
      •    chemical  characteristics of  the hazardous constituents within the
      •    rate  of volatilization,
      •    rate  of  ignition,
      •    feed rate and  volumetric heat release,
      •    kiln dimensions,  slope,  and  rotational speed,
      •    thermal  decomposition  and oxidation rate,
      •    presence  of  heat  sinks such  as  water or excessive ash,
      •    slag  formation and  composition,
      •    heat  losses, and
      •    secondary chamber  configuration and size.

Incineration temperatures can be varied from 800° to 1400°C depending on the
heat requirements necessary to incinerate various hazardous constituents in
contaminated soils.  For example, soils contaminated with dioxins require a
temperature of at least 1200°C to ensure adequate destruction (destruction and
removal efficiency - ORE = 99.9999%).
     The rotary kiln incineration method is used at three of the largest
commercial incineration facilities (Rollins Environmental Systems in Deer
Park, Texas; Environmental Systems Company (ENSCO), El Dorado, Arkansas; and
SCA Chemical Services in Chicago, Illinois).  Table 3-11 shows some of the
major advantages and disadvantages pertaining to the use of a rotary kiln.
     Mobile rotary kiln incinerators are also used for the destruction of
contaminated soils.  These systems consist of flat-bed mounted units that can
be trucked to a site for onsite  incineration.  The EPA-ORD mobile incinerator
has recently undergone a test burn for the destruction of contaminated soils,
while the ENSCO mobile rotary kiln is currently undergoing active testing.

Hazardous Constituents Amenable  to the Technology—
     Essentially all organic types of constituents in soils including PCBs and
dioxins  can be  incinerated by using  a rotary kiln (Bonner, 1981).  There are,
however, hazardous constituents  such as heavy metals, high moisture content
wastes,  inert materials, inorganic salts, and the general group of wastes that
have high  inorganic content that are unlikely candidates for incineration
(Bonner,  1981).

     The previously  listed commercial land-based  incinerators are a very
effective means  of destroying contaminated  soils.  Each  incinerator can handle
various  RCRA wastes, however, only the Rollins  incinerator is permitted  to
burn PCB-contaminated  soils.
     The mobile EPA-ORD  unit has been  tested on dioxin  soil  in Missouri  and
has  the  capability of  burning soils  at a  rate of  2,000  Ib/hr  (Hasel,  1985).
EPA  has  reported a successful test burn of  dioxin soils  to a  destruction  level
of 99.9999%  (Hasel,  1985).  ENSCO has reported  that  they have two units  capable
of  incinerating  soils  and are constructing  a third.  These units are  expected


 1.  Can incinerate a wide variety of  liquid and  solid hazardous  wastes.
 2.  Can incinerate materials which are passing through  a melt  phase.
 3.  Capable of receiving liquids and  solids independently or in  combination.
 4.  Capable of receiving drums and bulk containers.
 5.  Adaptable to wide variety of feed mechanism  designs.
 6.  Characterized by high turbulence  and air exposure of solid wastes.
 7.  Continuous ash removal which does not  interfere with the waste  oxidation.
 8.  No moving parts inside the kiln  (except when waste  transport chains  are
 9.  Adaptable for use with a wet gas  scrubbing system.
10.  Retention or residence time of the nonvolatile component can be
     controlled by adjusting the rotational speed.
11.  Waste  can be fed directly into the kiln without any preparation (such  as
     preheating, mixing, etc.).
12.  Can be operated at  temperatures  in excess of 1400°C (2500°F), making them
     well suited for the destruction  of toxic compounds  that are  difficult  to
     thermally degrade.
13.  Rotational speed control of the  kiln also allows a  turndown  ratio
     (maximum to minimum operating range) of about 50 percent.


 1.  High capital cost for installation.
 2.  Operating care necessary to prevent refractory damage; thermal  shock is a
     particularly damaging event.
 3.  Airborne particles may be carried out  of kiln before complete combustion.
 4.  Spherical or cylindrical items may roll through kiln before  combustion is
     completed (insufficient residence time).
 5.  Frequently requires additional makeup  air due to air leakage via the kiln
     end seals.
 6.  Drying or ignition  grates, if used prior to  the rotary kiln,  can cause
     problems with melt  plugging of grates  and grate mechanisms.
 7.  High particulate loadings to air pollution control  equipment.
 8.  Relatively low thermal efficiency.
 9.  Maintenance of seals at either end of  the kiln; a significant operating
10.  Formation of clinker or ring residue on refractory  walls,  due to drying
     of aqueous sludge wastes or melting of some  solid wastes.

Source:  Bonner, 1981.

to have RCRA permits by the end of the year for soil incineration.  One unit
is in Florida burning liquids and sludge while the other is being readied for
a test burn on dioxins in Arkansas.

     Rotary kiln units both mobile and stationary have been used successfully
to incinerate and thus, destroy various types of contaminated soils.

     Stationary incinerators are  readily implementable for the destruction of
contaminated soils  since incineration facilities are available.  However,
concerns such as the ability to excavate the contaminated soils and haul
distances must be considered.  Long haul distances and difficult excavation
will greatly increase  the  costs and time needed to destroy the soils.
     Implementability  is of greater concern when using a mobile incinerator in
that,  in addition to excavation concerns,  issues pertaining to the incinerator
location and space  (land)  requirements at  specific sites must also be
considered.  If incineration is to occur in a residential-type area, issues
concerning  public health and safety must be considered.

     Stationary incinerator costs were reported by Rollins at $.65 to $.75/lb
(Murphy, 1985).  SCA,  Inc., which requires soils to be placed in  150 to 200 Ib
fiber  or plastic bags,  reported costs of £.35 to $.40/lb (Mullen, 1985).
These  costs include post-incineration handling of the various residues.
However, these costs do not  include excavation or hauling thereby greatly
increasing  the cost of incineration.
     Costs  for  incineration with  a mobile  unit were reported  from ENSCO  as
being  $400  to $500/yd   (Lanier,  1985).  A  consideration with  onsite
 incineration is that residues  must be disposed of properly after
 incineration.  The  various options depend  on  how the  residue  is classified,
 i.e. hazardous vs.  nonhazardous  (delisted).   The options consist  of  using  the
 residue as  an onsite construction waste, disposal in  a  sanitary landfill or in
an approved RCRA  landfill.  There is  a wide variation between these  options,
 thereby resulting  in  a wide  variation in disposal costs.


Storage Vaults

General Description—
     This type of corrective action strategy is a fairly new technology and  to
date has not acquired the appropriatre RCRA permits.  It may, however, prove
to be an acceptable method for long-term storage of contaminated soils.
Rollins Environmental Services has developed a vault to contain hazardous
wastes or soils with an expected useful life of approximately 50 years.  The
vaults are very much like an above-grade landfill except it uses lined
concrete retaining walls to contain the soils.  The basic components of the
vault consist of:

     •    an umbrella cap,
     •    storm water collection system,
     •    cap monitoring system,
     •    secondary  cap,
     •    lined  concrete containment  walls,
     •    drain  protective  layers,
     •     leachate  collection  system,
     •    primary liner,
     •     leachate  monitoring  system,
     •     secondary liner,  and
     •     a clay or concrete tertiary liner.

 Like a double-lined landfill the  vault appears  to have  sufficient  layering to
 adequately  contain the  soils in conjunction with  the  leachate
 collection/detection systems.

     These vaults may be quite effective in containing contaminated  soils  but
at this time have limited demonstrated performance and are only recognized  by
the EPA as a temporary  storage unit.  Rollins  reports that the vaults  can  be
installed essentially anywhere, as  long as soils are stable enough to  support
the structure.   Sizes can range from  10 to 30  ft high walls and cover  one  half
to 25  acres or more.  Rollins also  reports that organic  sludges,  soils, and
contaminated equipment  can  be safely  disposed  of in these vaults.

Mobile Hazardous Waste  Extraction from Excavated Soils

General Description—
     This  is a new  and  emerging technology that is being sponsored by  the
EPA.   There  is a unit available at  this time that is capable of
decontaminating  soil at a rate of 3 to 5 yd  /hr.  The goal of  this project
 is  to  be  able  to "scrub" soils clean  enough  so they can  be redeposited in  the
place  from which they were  excavated.
     The  system  generally consists  of a hydraulically  lifted bucket,  feed
 hopper,  and soil metering paddle  that places the soil  into the unit.   The
 soils  are then washed  or "scrubbed" with water and/or  additives  for  hazardous
 constituent removal.  The unit  contains various screens  and water knives for
 scrubbing purposes, along  with  rinsing areas and hydrocyclones for
 dewatering.  Once  soils are completely rinsed, dewatered,  and  dried  they may
 be  returned to  the excavation area.  Water and additives are  collected and
 reused to keep operating costs  down.

      It is reported that fine clays cannot be  effectively  "scrubbed",  however,
 small  particles  greater than 2  mm can be  cleaned  in  this process. Also, most
 inorganic compounds, most  water soluble  or readily  oxidized  organic  chemicals
 and some  partially miscible-in-water organics  can be  treated  with water or
 water plus an additive (Milanowski and Scholz, 1983).
      EPA reported  that  the  unit has successfully  removed lead from soils,
 however the unit did have a number of operation problems in the field and  is
 presently being  retrofitted (Traver,  1985).   Prior  to this,  laboratory

experiments on phenols, arsenic trioxide, and PCBs in  two  soil matrices of
sand/gravel/silt/clay and organic loam were completed  and  found  to be quite
successful.  If further testing is performed on  the applicability of  this
unit, it may prove to be a very effective method of treating  releases to soils
from all types of SWMUs.

Fluidized-Bed Incineration

General Description—
     A fluidized-bed incinerator  consists of a vertical  refractory-lined
cylinder that contains a bed of inert, granular material which usually
consists of  sand.  The diameter of the units normally  ranges  from a few meters
to  15 meters  (GCA, 1983c).  Temperatures for incineration  are normally 450°  to
980°C  (Bonner,  1981) and  are  limited  by  the softening  point of sand which  is
1100°C.  The  sand  bed  particles are fluidized by blowing low  velocity air
upward  through  the medium.  This  rate of air movement  is a direct relation to
particle  size and  acts to  suspend the bed  in a fluid-like  manner.
     Hazardous  waste materials including liquids,  slurries, gases, sludges,
and contaminated  soils can be  incinerated  with the  fluidized  bed.  However,
hazardous  constituents such as sludges  or  contaminated soils  must be
 pretreated involving  sorting,  drying, shredding, and  special  feed
 considerations  (Bonner,  1981).  Generally,  as with the rotary kiln, the
 fluidized bed can incinerate  most hazardous constituents.  However, the
 fluidized bed does necessitate the use  of  an  after-burner  since  hazardous
 constituents are  volatilized from the soil in  the  main unit and  then  destroyed
 in the vapor phase by the after-burner.  This  occurs  due to  the  low operating
 temperatures of this  type of incineration.  Table  3-12 lists  advantages  and
 disadvantages of the  fluidized-bed incinerator.
      A recently developed circulating fluidized-bed incinerator  by G.A.
 Technologies of San Diego, California involves  the use of  the contaminated
 soil as the bed material and uses an air flow of 3 to 5 times as great  as  that
 in conventional systems.   The increased air flow also increases  the  turbulence
 which makes for a more turbulent combustion environment.   This allows the  use
 of lower temperatures and precludes the use of  an after-burner.


 1.  General applicability for the disposal of combustible hazardous  solids,
     liquids, and gaseous wastes.
 2.  Simple design concept, requiring no moving parts  in  the combustion zone.
 3.  Compact design results from high heating rate per unit volume  (100,000  to
     200,000 Btu/hr-ft3  (900,000 to 1,800,000 kg/cal/hr-m3)) which  results
     in relatively low capital costs.
 4.  Relatively low gas  temperatures and excess air requirements which tend  to
     minimize nitrogen oxide formation and contribute  to  smaller, lower-cost
     emission control systems.
 5.  Long incinerator life and low maintenance costs.
 6.  Large active surface area resulting from fluidizing  action enhances  the
     combustion efficiency.
 7.  Fluctuation in the  feed rate and composition are  easily tolerated due to
     the large quantities of heat stored in the bed.
 8.  Provides for rapid  drying of high-moisture-content material, and
     combustion can take place in the bed.
 9.  Proper bed material selection supresses acid gas  formation; hence,
     reduced emission control requirements.


 1.  Difficult to remove residual materials from the bed.
 2.  Requires fluid bed  preparation and maintenance.
 3.  Periodic feed must  be selected to avoid bed degradation caused by
     corrosion or reactions.
 4.  Hay require special operating procedures to avoid bed damage.
 5.  Operating costs are relatively high, particularly electric power costs.
 6.  Possible operating  difficulties with materials high  in moisture  content.
 7-  Formation of eutectics (compounds with low melting or fusion
     temperatures) is a  serious problem.
 8.  Hazardous waste incineration practices have not been fully developed.
 9.  Not well suited for irregular, bulky wastes, tarry solids, or  wastes with
     a  fusible ash content.
 Source:   Bonner,  1981.

     The circulating fluidized-bed  incinerator  is  reported  to  be  a
transportable unit however,  it was  stated  that  large  amounts of soil would
have to be  incinerated  in order  for a move to be made.   It  was also  reported
that a test burn on PCB  soils has been  completed and  preliminary  results  show
a very high level of destruction (G.A.  Technologies,  1985).  The  unit  that  was
used in the test burn is a  16-in. inside diameter  unit  with the capability  of
destroying  500  to 1,000 Ib/hr.   G.A. Technologies  also  stated  that  if  the burn
proves to be  successful  a commercial unit  with  five times  the  capacity could
be  constructed  very  shortly.

Mobile Advanced Electric Reactor

General Description—
     The  advanced  electric  reactor, often  referred to as a high-temperature
 fluid  wall  reactor,  uses radiant energy to destroy organic constituents by
 pyrolysis (chemical  decomposition)  at  high temperature.  The radiant energy
 which  is  produced  by six electrically  heated carbon electrodes is focused on
 the waste through a  porous  ceramic  core.   The electrodes are heated  to
 approximately 400°F.
      Soils  that are  fed into the unit  must be nonflowing,  nonagglomerating  and
 smaller than 100 mesh (Thagard Research Corporation,  1984).  However,  it  is
 expected that 10 mesh soils will be acceptable.  Soils  are fed through the  top
 of the reactor and fall through the core.   Residence  times for 100 mesh solids
 are reported to be one-tenth of a  second for a 30-ft  high reactor.
      Thagard Research has built a  12-in.  diameter mobile unit for Vulcan
 Associates.  The system is truck-mounted and can incinerate 40 tons of soil
 per day.   However,  test results are not available for this unit.
      J.M. Huber has a 12-in. immobile unit and a 3 in.  mobile pilot-scale
 unit.   The 12-in.  reactor has successfully incinerated  PCB-contaminated soils
 and the 3-in. reactor has also destroyed dioxin-contaminated soils at Times
 Beach, Missouri.

     This type of reactor can destroy essentially all types of hazardous
constituents including soils contaminated with PCBs and dioxins.  However,
Huber may sell the license or shelf the technology until it is more applicable
(Huber, 1985).


General Description—
     This technology generally consists of mixing contaminated soils with
clean soils  to reduce concentrations of the hazardous components to acceptable
levels.   It  can be done only in  the upper soil levels and can consist of
mixing  subsoil, uncontaminated soil from another area of the site or purchased
soil with the  contaminated  soils.

     Attenuation  is  reported to  be viable only in the upper 2 ft of soil
 (i.e.,  that  within  the  plow layer).  It is useful in the attenuation of metals
 and organics although  this  technology has only been reported to work well with
metals  (EPA, 1984b).   This  technology's implementation  is dependent upon
 site/soil trafficability  considerations and  depth of contamination.  Other
 issues  that  must  be considered are  increased erosion of tilled area, therefore
 requiring runon/runoff controls  and  possible alteration of  soil horizon
 characteristics which  may allow  increased mobility of  the hazardous
 constituents.   This technology  is reported  to have had  some field  applications
 (EPA,  1984b).

 Chemical Oxidation

 General Description—
      Chemicals naturally undergo reactions  in soil  that may transform  them
 into more or less toxic products, or which  may increase or  decrease  their
 mobility within the soil system.  Chemical  treatment  of contaminated soils
 entails the reaction of hazardous constituents with  reagents,  resulting  in
 products which are less toxic,  or which become immobilized  in the soil
 column.  These reactions may be  classified  as oxidation reactions, reduction

reactions, and polymerization reactions.  Oxidation reactions are discussed at
this point, reduction reactions will be discussed subsequently and
polymerization will not be presented because it has not yet been field  tested.
     Chemical oxidation is a process in which the oxidation state of an atom
is increased.  This is accomplished by the  transfer of electrons from the  atom
to an election acceptor such as oxygen.   Chemical oxidation represents  a
significant treatment process in  soil systems.  As a  result of oxidation,  a
substance may be  transformed, degraded, and/or immobilized in soil.  Oxidation
of hazardous organic constituents in soil can be an effective method of
environmental degradation.  Oxidation of  heavy metals, with the exception  of
arsenic  however,  is not usually desirable because heavy metals become more
mobile at  higher  oxidation states.  Oxidation reactions within the soil matrix
may  occur through management of the natural processes in  a soil, or through
addition of an oxidizing  agent.
      In  the  natural  soil  environment, it  is the role  of the soil to provide
electron acceptors for  the oxidation of organics and  other compounds.   Oxygen
 is  usually the  electron acceptor. However, when oxygen is not available,
other reducible  compounds such  as nitrate,  Mn(IV), M(III), Fe(III), and S(VI)
can function as  electron acceptors.  Typically, oxidation will occur in soil
 systems  where the redox potential (ability  to accept  electrons) of the  soil is
 greater than that of the hazardous constituent  (i.e., 0.8V).  It is important
 to  note  that  hazardous  chemical constituents are more extensively oxidized in
 less-saturated  soils.   Therefore, soil  moisture control is desirable in
 promoting natural oxidation  processes.
      Oxidizing  agents may be utilized  to  degrade organic  constituents in  soil
 systems.  Oxidation reactions  are usually limited  in  application due to their
 substrate specificity and pH dependence.   Common oxidizing agents considered
 for in-place treatment include ozone,  hydrogen  peroxide,  and  chlorinate
 (hypochloriate).  The latter,  however,  is not desirable for  in  situ oxidation
 of contaminated soil because it can lead  to undesirable chlorinated
 by-products.   The relative oxidizing ability  of these chemicals compared  with
 other well-known oxidants is indicated  in Table  3-13. A  serious potential
 limitation to the use of oxidizing agents for  soil treatment  is  the additional
 consumption of  the oxidizing agent(s)  by  nontarget constituents  in  the  soil.
      In some instances hydrogen peroxide  and  ozone have been  used
 simultaneously  to degrade compounds which are  refractory  to  either material
 individually.  When ozone is the oxidant  used,  the pH of  the  soil must  be

                               Oxidation                     Relative
   Species                  potential volts               oxidation power
Fluorine                         3.06                          2.25

Hydroxyl radical                 2.80                          2.05

Atomic oxygen                    2.42                          1.78

Ozone                            2.07                          1.52

Hydrogen peroxide                1.77                          1.30

Perhydroxyl radicals             1.70                          1.25

Hypochlorous acid                1.49                          1.10

Chlorine                         1.36                          1.00

Source:  EPA,  1984b.

carefully controlled since the rate of decomposition of ozone is strongly
influenced by pH.  At high pH direct reactions between ozone and the hazardous
constituents in the soil are reduced.  When hydrogen peroxide is used,  the
metal content of the soil must be considered because metals act as catalysts
causing autodecomposition of peroxide.  The result will be an increase  in the
soil dissolved oxygen but no direct oxidation of hazardous constituents by the
     One problem common to strong oxidants in general is their ability  to
oxidize the natural organic matter in the soil which often acts as sorption
sites for organic constituents, resulting in decreased sorption capacity in
soils for some organics.  Therefore, some hazardous constituents' mobility may
be increased.  Nevertheless, successful field application of strong oxidants
has been completed.  Examples of rn situ oxidation of contaminated soils using
ozone are provided  in Nagel et al., 1982.

     General characteristics of organic chemicals likely to undergo oxidation
include:  (1) aromaticity, (2) fused ring structures, (3) extensive
conjugation, and (4) ring substituent fragments.  Certain compounds are more
oxidizable  in soils  that others.  The reactivity of organic chemical classes
with respect to  chemical oxidation is summarized in Table 3-14.
     For natural oxidation of hazardous constituents at soil surfaces, water
soluble organic  substances with half-cell potential below the redox potential
of a well-oxidized  soil are needed.  Chemical constituents which do not
oxidize at  soil  surfaces are given in Table 3-15.
     For in situ oxidation by addition of ozone as an oxidizing agent,  the
following reactivity trends apply:  (1) phenol, xylene, toluene, benzene, and
(2) dichtoro-, trichloro-tetrachlorophenol, pentachlorophenol.  Constituents
not readily oxidized by ozone include:

     •    inorganic  compounds in which cations and anions are in their highest
          oxidation state;
     •    organics  which are highly halogenated; and
     •    saturated  aliphatic compounds which do not contain easily oxidized
          functional groups, i.e., aliphatic hydrocarbons, aldehydes, and


                   High                         Moderate                          Low

     Phenols                           Alcohols                      Halogenated hydrocarbons
     Aldehydes                         Alkyl-substituted aromatics   Saturated aliphatic compounds
     Aromatic amines                   Nitro-substituted aromatics   Benzene
     Certain organic sulfur compounds  Unsaturated alkyl groups      Chlorinated insecticides
                                       Aliphatic ketones
                                       Aliphatic acids
                                       Aliphatic esters
                                       Aliphatic amines
     JRB Associates, 1982.

     Source:  Compiled by EPA, 1984b.

                                 Chemical Name
               Acetamide                       Q-Carotene
               Acetone, anisilidene-           Cyclohexylamine
                -,dianisilidene-               Monoethanolamine
                -,dicinnaraylidene-             Triethylamine
                -,d ibenzyIidene-

               Dragun and Helling, 1982.
               Source:  Compiled by EPA,  1984b.

Pesticides such as aldrin,  heptachlor, DDT, parathion, and malathion are
oxidized to other hazardous compounds and are, therefore, not suited to such
     Oxidation with hydrogen peroxide has been demonstrated for cyanide,
aldehydes, dialkyl sulfides, dithionate, nitrogen compounds, phenols, and
sulfur compounds.  Chemical groups incompatible with peroxide oxidation due to
their resultant increased mobility are given in Table 3-16.

                      MORE MOBILE PRODUCTS

         Acid chlorides and anhydrides     Cyanides
         Acids, mineral, nonoxidizing      Dithio carbamates
         Acids, mineral oxidizing          Aldehydes
         Acids, organics                   Metals and metal compounds
         Alcohols and glycols              Phenols and cresols
         Alkyl halides                     Sulfides,  inorganic
         Azo, diazo  compounds, hydrazine   Chlorinated aromatics/alicycles

         Source:  EPA,  1984b.

     Soil-catalyzed oxidation reactions have been tested in the field for
several  chemical classes.  However, factors such as aeration of the soil and
soil moisture effect the level of treatment attainable.

     The use of oxidizing agents is not that well tested in soil systems but
have been used in wastewater treatment.  Care must also be taken since-
oxidizing agents can cause violent reactions when used in conjunction with
metals and also, soil hydraulic properties may be greatly affected,
particularly in a structured soil.

Chemical Reduction

General Description—
     Chemical reduction is a process in which the oxidation state of an atom
is decreased.  Reducing agents are electron donors, with reduction
accomplished by the addition of electrons to the atom.  Reduction of chemicals
may occur naturally within the soil system.  Certain compounds are more
susceptible to reduction  than others because they will accept electrons.
Addition of reducing agents to soil to degrade reducible compounds can be used
as  an  in-place  treatment  technology for organics, chromium, selenium, and
     Chemical  reduction using catalyzed metal powders and sodium borohydride
has  been  shown  to degrade toxic organic constituents.  Reduction with
catalyzed  iron,  zinc,  or  aluminum affect  treatment  through mechanisms
including  hydrogenolysis, hydroxylation,  saturation of aromatic structures,
condensation,  ring  opening, and rearrangements  to  transform toxic  organics  to
innocuous  forms.
     The  use  of catalyzed metal powders,  though used  successfully  for aqueous
solutions  passed through  beds of  reactant diluted  with an inert solid (Sweeney,
1981), has not been demonstrated  in  the  soil environment.  However,  small-scale
field  experiments  of chemical reduction  of organic  constituents in soils with
 sodium borohydride and zinc have  been successful.   Results of reductive treat-
ment for  degradation of  paraquat  in  soil  are summarized  in Table  3-17.   Results
 indicate  that sodium borohydride  and  powdered  Zn/acetic  acid  combinations
achieved  very effective  degradation  of paraquat in soil  and  sand  media.

                      PARAQUAT  IN SOIL
Paraquat in soil (ppra)
Powdered Zn acetic acid
Initial (1 day)
None detected
None detected
4 Months
None detected
None detected
Violent foaming
No foaming
Some bubbling
   Staiff et al., 1981.
   Source:  Compiled by EPA, 1984b.
     Hexavalent chromium Cr(VI) is highly toxic and mobile in soils and must
be reduced to trivalent chromium Cr(III) which is far less mobile and toxic.
The reduction can be accomplished by adding acidification agents such as
sulfur and reducing agents such as leaf litter, acid compost, or ferrous
iron.  These additives are not always necessary if sufficiently acidic soil
conditions are present whereby the reaction will occur naturally.  After
reduction, Cr(III) is precipitated via lime addition; Cr(III) precipitates
over a pH of 4.5 to 5.5.  Caution is required, however, since trivalent
chromium can be oxidized to Cr(VI) under conditions prevalent in many soils,
i.e., under alkaline and aerobic conditions in the presence of manganese.
With the exception of lime addition, the above also holds true for hexavalent
selenium reduction to either selenite (Se(IV)) or elemental selenium Se
which are far  less mobile.  It is important to note, however, that selenite
(Se(lV)) is an anion which leaches at high pH and thus, selenium could not be
treated if increased pH were required as part of the treatment for other

     Soils contaminated with chlorinated organics, unsaturated aromatics and
aliphatics, miscellaneous other reducible organics, hexavalent chromium, and
hexavalent selenium (when significant amounts of other metallic constituents
are  not present) are treatable by chemical reduction.

     The achievable level of treatment is potentially high for hazardous
constituents susceptible to reduction, and for limited areas of
contamination.  The soil must be without large quantities of competing
constituents susceptible to reduction, or the level of treatment may be
greatly decreased.
     The use of reducing agents for organic constituents may also degrade soil
organic matter.  The extent of impact on soils is not known at the present
time.  The products of reduction may present problems with respect to
toxicity, mobility, and degradation however, this information is not presently
available.  Iron reductants appear to be the least damaging to soil systems,
though iron has a secondary drinking water standard and is of concern with
respect to aesthetics.  Addition of metals with acetic acid may possibly
increase metal mobility by decreasing soil pH.  Addition of sodium borohydride
may adversely  impact soil permeability, depending on the type and content of
clay and ionic constituents in the soil solution.
     It is reported that this technology may not be able to treat soils to
acceptable levels during initial treatment, therefore necessitating a second
round  of treatment.

Extraction (Soil Flushing)

General Description—
     This  technology  involves the  removal of hazardous constituents from the
soil horizon  by  flooding the site  with  a  flushing solution and collecting the
elutriate  in  shallow  wells  to prevent migration  and  further contamination to
soils  and ground water.  Flushing  solutions can  include water, acidic aqueous
solutions  (sulfuric,  hydrochloric, nitric,  phosphoric, and carbonic acid),
basic  solutions  (e.g.,  sodium hydroxide), and surfacants  (e.g., aIky1benzene
sulforate).   Once  the  soils have been properly flushed and the elutriate
collected  it  can  then be put through  a  treatment system and disposed.
Sampling and  analysis  would  then be necessary to ensure that  the contamination
has  been removed  and  also  to ensure that  the  flushing solution has been
adequately  removed.

     Another development in this technology by the EPA is a mobile _in situ
containment/treatment system.  It generally consists of grout injection to
isolate the contaminated area; grout must be effective in the soil of concern
and be compatible with the hazardous constituents in the soil.  The area is
then flushed with either water or appropriate additives to remove
contamination.  This unit is reported to have the capability of treating an
area of approximately 80,000 ft .  At the present time the unit is being
prepared for a field test (Fall 1985) at Air Force property in Wisconsin on a
solvent spill; this will be its first field test (Traver, 1985).

     This  technology is in initial stages of development.  However, the mobile
unit or a  stationary setup at a site may in the near future prove to be a
viable technology  for remediation of releases to soils.  Much of research at
this time  is going  towards the development of solvents or flushing agents that
can adequately and  safely remove hazardous constituents from soils.
     In general, water  can be used to extract water-soluble or water-mobile
constituents;  acidic  solutions can be used to recover metals and basic organic
constituents;  and  basic solutions can be used for removal of metals and some
phenols.   At  present,  this  technology is not  imp lenient able at a site.
However,  after the slated field test of EPA1s mobile unit it may be a viable
corrective measure.

Multiple-Hearth  Incineration

General  Description—
     A multiple-hearth incinerator  generally  consists of  a refractory-lined
 circular steel shell,  a control  shaft that rotates,  a series of solid flat
 hearths,  a series  of rabble  arms with teeth  in  each  hearth, an air blower,
 wall-mounted  fuel  burners,  an ash  removal  system, and a waste feeding system
 (Bonner,  1981).  There  are  also  side  ports for  fuel  injection, liquid waste
 burners,  and  an  after-burner is generally  necessary  for soil incineration.

     The multiple-hearth incinerator while designed to incinerate sewage and
hazardous type sludges may also be used to treat contaminated soils, given
sufficient pretreatraent to attain a constant size and moisture content.
     Due to the low temperatures used during incineration, contaminated soils
usually require the use of an after-burner to achieve complete destruction.
Devolatilization  is realized in the main chamber with the gaseous phase being
destroyed in  the  after—burner.
     Generally  the  same types of hazardous constituents  that can be
incinerated with  a  rotary kiln can also be destroyed with a multiple-hearth
incinerator.  Some  unlikely candidates for multiple-hearth incineration
consist of uncombustible hazardous constituents such as  heavy metals, inert
material, inorganic salts, and generally substances with high organic
content.  In  general,  the multiple-hearth incinerator is not expected to be as
effective as  the  rotary kiln-type  incinerator.

                                    SECTION  4
                                  CASE STUDIES


    GCA conducted a search for case studies which would demonstrate how to
select and implement corrective measures for releases to soils from SWMUs.
Approximately 100 sites were reviewed to develop a list of sites for potential
case study analysis.  Information was obtained from several data sources
including EPA Headquarters, EPA Regional offices, and literature searches.
    The site review focused on finding examples of sites where remedial
responses were either ongoing or completed.   Site Selection Worksheets were
completed for sites which met this initial criteria.   The worksheet (.shown in
Figure 4-1) contained information which was used to screen the sites for
potential case study evaluations.
    The criteria used for final selection of case studies included:

    •    availability and completeness of site information and monitoring data;
    •    type of remedial measures implemented;
    •    types of wastes and hazardous constituents present at the facility;
    •    site characteristics;
    •    geographic locations; and
    •    waste management practices.

In reviewing potential case studies, those case studies that were designated
as being most representative ot a variety ot the above criteria and
constituents of each criterion were selected.




YEARS OF OPERATION/DISCOVERY OF RELEASE  (How & when release discovered)
                Figure  4-1.   Worksheet  for  screening  case  studies.


HYDROLOGY (Ground Water & Surface Water)
RESPONSE ACTIONS (Including Designed and Implemented)
 SUCCESS/FAILURE OF  REMEDIATION  (Removal Efficiency, Containment Effectiveness)
                             Figure 4-1  (continued)


    A list of the selected sites and a summary of the remedial responses at
these sites is presented in Table 4-1.  Case studies were prepared using the
outline shown in Figure 4-2.  These case studies are presented below.


Facility Description

    The Fairchild Republic Company used chemical solutions to clean sheet
aluminum that is used in the manufacture of airplanes.  Between 1950 and 1967,
waste sludges and liquids from the cleaning processes were disposed in an open
landfill.  The landfill had an irregular shape with a maximum length of about
160 ft and a refuse depth of about 5 ft.
    During the mid-1960s, an improved waste treatment plant was constructed
which enhanced the removal of heavy metals through chemical addition.  The
concentrated sludge was dewatered through filter presses and placed in several
permitted, clay-lined sludge lagoons.  The sludge was subsequently hauled to a
licensed disposal facility.  After trivalent chromium was declassified as a
hazardous  substance, the trivalent chromium sludge was disposed in a local
sanitary landfill.
    As a result of these disposal practices, the surrounding soil and the
underlying ground water became contaminated with chromium and organic

Site Characteristics

    Climate in the area of  the site is continental.  Average temperatures
range from 21"F I late January to early February; to 88UF (.late July).  Annual
precipitation averages 37.08 in. (1953 to 1983), and is generally evenly
distributed throughout the year.

    The soils at the site consist of silty clay loam in the Hagerstown-
Diffield-Frankstown Association.  These soils are generally classified as
reddish, well-drained, deep and medium textured.

         Site Nine/Location
                                     Type of Facility
                                                               Hazardous Constituents Preaent
                                                                 Typed) of Releaaea
                                                                                                                                    Remedial Response
         1.   Fairchild

         2.   Uhitmoyer
            Frontenac Site/
Open landfill
(3SO ft x 160  ft  x SIS ft)
used for disposal of waate
•ludge from plant operations.
Uastewater generated by the
manufacturing plant treated
with lime; alurry disposed
in to unlined lagoon.
City of Philadelphia  landfill
used for the  disposal of
industrial wastes.
Storage tank  area uaed for
waste oils and  chemical
Landfill,  5~acres used for
wastes from herbicide
manufacturing process.
Chemical reclamation facility
                               Heavy Metals, miscellaneous
                               organic  solvents (Cr, Cu, Zn,
                               Al, TCE,  Xylenea, Toluene,
                               methyl chloride, ethyl benzene,

                               Arsenic  (inorganic and organic).
                               Volatile  organics, metals,
                               organic halides.
                               2,3,7,8-TCDD  (dioxin), PCBs,
                                                              Arsenic, phenols.
                               Volatile  organica, PCBs,
                               pesticides, some metals.
                                                                                                Ground water,  aoila
Ground water,
aurface water,
                                                                                                Ground waterD  soils
                                                                                                Soils, sediments
                                                                 Soils (89,000
                                                                 ground water,
                                                                 surface water
                                                                 (from runoff)
Ground water,  soils,
surface runoff
•  Removal of contaminated materials
•  Backfilling
•  Capping
•  Grading, topsoil,  and seeding

•  Excavation of contaminated  sludge's
   and soils
•  Concrete storage bins
•  GW treatment and recovery
   (counter pumping)

•  Excavation of contaminated  soils
•  Offaite disposal/treatment
•  Backfilling
•  Capping
•  Grading, topsoil,  seeding

•  Asphaltic concrete cap over
   gravel subgrade
•  Toe-trench filled  with rip-rap  rock
•  Wire cable/steel stakes lence
   around site

•  Contaminated water (trom Hooding)
   was removed
•  Equipment and buildings removed
•  Waste pits filled  in
•  1-2 in. temporary  clay cap  and
   plastic cover installed
•  Proposed:  permanent capping, in situ
   treatment, and slurry wall

•  Construction of berms and placement
   ot absorbent till  material  in trenches
•  Removal of drums and chemicals  in
   bulk storage
•  Removal of buildings and containers
•  Installation of 2  ft compacted  clay
   cap with gas venting system


      A.   TYPE OF SWMU/SYSTEM DESIGN (Including any  leak detection and/or
           monitoring system)


      A.   CLIMATE
      C.   SOILS
      D.   GEOLOGY
      E.   HYDROLOGY  (Ground Water & Surface Water)


      B.   MECHANISMS FOR DETECTION  (Include how & when  release was detected)
           media contaminated, and area or volume of  contamination)


      A.   RESPONSE
           1.    IMPLEMENTED
           2.    UNDER CONSTRUCTION
           4.    MONITORED/TESTED
      B.   SUCCESS/FAILURE  OF REMEDIATION (Include summary of results  from
           available  monitoring data)
                 Figure 4-2.  Outline for case studies write-up.


    The bedrock underlying the site is composed of limestone with numerous
fractures and cavities.  The stratigraphy of the bedrock is a series of
parallel folds with the axial traces trending N 15" E, and the joint
measurements trending in two directions:  strike N 80" E, dip 85" NW, and
strike W 5" E, dip 60" SE.

    A carbonate aquifer lies beneath the site, with the water table ranging
from 34.1 ft below the surface (during dry fall months; to 11.4 ft below the
surface (during wet winter months)-


Types/Causes of Releases—
    As a result of rainfall and surface water percolating through the sludge,
the surrounding soil and ground water became contaminated with chromium and
organic chemicals.  Additionally, hazardous constituents released to ground
water migrated to nearby domestic water wells.

Mechanisms  for Detection—
    Fairchild Republic Company had a State permit to operate two onsite sludge
lagoons, which expired in 1978.  Prior to reissuing a permit for the lagoons,
the Maryland Department of Natural Resources, Water Resources Administration
(WRA) conducted ground water monitoring activities (in August 1978).  WRA's
monitoring  results revealed high levels of chromium contamination
approximately 40U ft away from the sludge lagoons.  The source was determined
to be the nearby open landfill containing chromium sludge.

Extent of Contamination—
    The major hazardous constituents found at the site included heavy metals
(such as chromium, copper, zinc, and aluminum), and organic compounds (such as
1,1,1-trichloroethane, 1,1-dichloroethylene, ethylbenzene, methylchloride,
toluene, trichloroethylene, and xylenes).  Chromium was found to be the

dominant hazardous constituent present at the site with total chromium
concentrations ranging from 20 mg/kg to 280,000 mg/kg with the natural
background level of total chromium in the range of 50 to 100 mg/kg.
    The estimated volume of material in the waste disposal area is
5,400 yd .  Approximately 50 percent of this material was determined to be
contaminated soils, with the remainder being only partially contaminated.
Contaminated materials were found to be near or directly on the bedrock in
some areas.

Remedial Actions

    Contaminated soils were excavated down to the bedrock (determined by State
inspectors to be the practical limit for excavation).  Composite soil samples
were then collected from the excavated area.  Subsequent analyses indicated
that the total and hexavalent chromium levels were within EPA standards.
    Remedial measures were continued by placing a layer of compacted clay
approximately 2 ft thick directly over the exposed bedrock to inhibit the
infiltration of precipitation.  The pit was then backfilled with clean soil
and crushed rock and then compacted.
    A  clay cap was installed over the site area.  The cap was graded to allow
runoff  and to minimize surface ponding (thereby decreasing the amount of
vertical  infiltration of precipitation and contaminants).  A perimeter drain
was installed around the facility to further minimize the movement of runoff
water  onto the site.  A topsoil cap of approximately 6 to 8 in. was placed
over the clay layer and seeded with a grass-legume mixture to mitigate erosion
of the  clay layer and to further inhibit water infiltration (by
    Continued monitoring of the site is being performed, using wells
previously installed, to determine the long-term effects of the response

Success/Failure of Remediation—
    The remedial actions taken appear to have been effective in reducing the
chromium constituents.  Ground water monitoring wells have shown a continual
decrease in chromium levels.  Limited monitoring data is available for organic

contamination and therefore, the effectiveness of the organics removal cannot
be adequately evaluated at this time.  The volatile organics found on the site
are generally highly soluble and very mobile in water.  However, most ot these
should volatilize, degrade chemically or biologically, or be diluted in the
ground water over time.
    While the percolation of precipitation has been virtually eliminated, the
variation of ground water elevation has not been controlled.  Fractured
bedrock zones remain contaminated with precipitated heavy metals.  The
precipitation of heavy metals is enhanced by limestone and dolomite bedrock
because of the high pH associated with these formations.  However, rising
ground water levels will lower the pH conditions, causing the metal
precipitates to become dissolved in the ground water and potentially
transporting them through the ground water regime.

Reference:  U.S. EPA,  1984a.


Facility Description

    Beginning in 1934, and continuing to the present, Whitmoyer Laboratories
has operated a pharmaceutical manufacturing facility at the site.  Until 1964,
wastewater generated by the manufacturing processes was treated with lime and
handled as a slurry.  The wastewater slurry was then disposed in an unlined

Site Description

    The average annual precipitation in the site area is 44 in.  Average
annual snowfall is 35 in.  Average temperatures range from 30"F (January) to
76UF (July) with an annual average of 53"F.  The average windspeed is 7.7 mph.

    Soils overlying the site consist of a 5 to 7 ft thick layer of alluvial
sand, silt, and gravel.  These soils are fairly permeable, and allow for rapid
recharge to the bedrock aquifers.                     . ,.,  ..

    Bedrock underlying the plant site consists of limestones and dolomites
which strike east-northeast and exhibit a dip of 30"  to the southeast
(Ontelaunee Formation (Dolomite) = 900 ft thick; underlying Annville Formation
(.high calcium limestone) = 1,500 ft thick north of the plant).

    The  site lies adjacent to Tulpehocken Creek (37 miles upstream from its
confluence with the Schuylkill River, which in turn flows to Delaware Bay).
The drainage basin of Tulpehocken Creek covers 211 mi* and is 33.5 miles
long.  The average and minimum flows at the confluence of Schuylkill River are
58 cfs and 56 cfs, respectively.  The average annual  flow for the creek is
approximately 200 cfs and the maximum flood flow was  9,890 cfs (on December 7,
1953).   The creek flows east-northeast (following the strike of the carbonate
    Ground water beneath the site is potable and is used by local residents
and  farmers.  There are some artesian wells near the  site, but the static
water  level in most wells lies near the ground water  table.  The site lies
close  to a ground water divide in a system of limestone aquifers underlying
the  Lebanon Valley.


Types/Causes of Releases—
     Improper waste disposal in an unlined surface impoundment (lagoon) caused
releases to ground water underlying the site, soils onsite, and a nearby
stream (Tulpehocken Creek).

Mechanisms for Detection—
    In July 1964, Whitmoyer Laboratories, Inc. became a subsidiary of
Rohm & Haas Company.  Extensive arsenic contamination of the soils, ground
water, and a nearby stream became apparent to Rohm & Haas Company officials
during an inspection of the facility.

Extent of Contamination—
    Extensive ground water, soils, and surface water contamination exists in
the site area.  Hazardous constituents primarily include organically-bound
arsenic compounds, calcium arsenate, and calcium arsenite.

Remedial Actions

Response Actions—
    Onsite treatment and disposal practices were discontinued in December
1964.  Sludge was removed from the lagoon.  Contaminated soils underlying the
lagoon were also removed.  The contaminated soil and sludge materials were
deposited in an  impervious concrete  storage bin, which was filled to capacity
and then covered.
    Four recovery wells were used to purge ground water containing arsenic
compounds.  The contaminated ground  water was treated by adding two-parts
^62(80^)3 to one-part arsenic and adjusting the pH to neutral conditions
(by adding lime).  Recovered water was handled in alternating batch mixing
tanks on a continuous feed treatment schedule and sent to the lagoons to
dissipate via slow percolation to the subsoil.
    The plant reopened in the Spring of  1965 on a no-discharge basis.  Treated
wastes were trucked to a New Jersey  holding area awaiting ocean dumping.  In
1966, additional wells were installed.  Production wells formed cones of
depression east of the plant to stop migration of ground water.  Production
rate  is partially dependent on the purging rate.  From 1968 to early 1971, the
purged water was discharged directly to Tulpehocken Creek.
    It was decided that it would be  too expensive to dredge Tulpehocken Creek,
and the constituent levels are declining through dilution.  Whitmoyer
Laboratories currently supplies bottled water to area residents whose wells
remain affected.


Success/Failure of Remediation—
    The first phase of remedial action cleanup and recovery involved the
removal of sludge and contaminated soils.  The manufacturing processes were
halted until a process could be developed to remove arsenic- from the
wastewater, thereby eliminating the possibility of new arsenic compounds being
added to the soils, and subsequently to the ground and surface water.
    The next phase, which involved removal of the arsenic constituents from
the ground water, was also successful.  The recycling and treatment of the
purged water did reduce the level of arsenic in the ground water, and
succeeded in controlling its movement.
    Little has been done to remove the hazardous constituents from the
sediments and surface water of Tulpehocken Creek, because of the costs
involved in dredging miles of creek bottoms and banks.  Through dilution, the
arsenic levels in  the creek water have been brought within the limits set by
the U.S. Department of Health, and monitoring has shown that the levels
continue to decline.
    Finally, routine monitoring of the site is being performed to ensure that
the arsenic levels do not increase, either through the release of arsenic from
bottom muds, or  via spills from the plant.

Reference:  EPA,  1981.


Facility Description

    The Enterprise Avenue landfill site occupies approximately 57 acres,
40  acres of which  have been filled.  The  site is located in an industrial
area.  The closest residential population is located approximately 2 miles
northwest  of the site.
    The Enterprise Avenue site was used by the city of Philadelphia for the
disposal of incineration residues, fly ash, and debris.  Drums containing
various industrial and chemical wastes were illegally buried at the site by
several waste handling firms.

Site Characteristics

    The site is relatively flat.  Vegetation is- present over most of the site

    Soils overlying the site consist of a low permeability, silty clay layer
ranging in thickness from i> ft on the western boundary to 2i ft along the
eastern perimeter.  Underlying the silty-clay horizon is a gravelly sand.

    Two ground water aquifers underly the site.  The uppermost water—bearing
zone is a perched water table and is encountered above the silty clay layer.
Portions of the shallow aquifer zone are mounded into the bottom of the fill
material.  The deeper, confined aquifer is found in the sands and gravels that
lie beneath the silty clay.  The ground water present in these water-bearing
zones is not used in the general area of the site.   However, the deeper
aquifer may recharge sources of ground water for portions of southern New
Jersey.  The observed flow in the deep aquifer is east towards the Delaware


Types/Causes of Releases—
    Illegal burying of drums containing industrial and chemical wastes at the
site resulted in contamination of soils and ground water onsite.  Hazardous
constituents leaked from the drums to the surrounding soils and into the
underlying ground water.  Infiltration of precipitation caused leaching of
hazardous constituents and further transport of constituents to soils and
ground water.

Mechanisms for Detection—
    In response to reports of unauthorized dumping of  industrial wastes,  the
Philadelphia Water Department (PWD) conducted exploratory excavations during
January 1979 to investigate these reports.  Initially, approximately 1,700
55-gallon drums were uncovered.  Most of the drums were broken and
fragmented.  Subsequently, sampling and analysis activities were conducted to
determine the extent ot contamination.

Extent of Contamination—
    The drums which were illegally disposed onsite contained industrial wastes
and chemical wastes such as paint sludges, solvents, oils, resins, metal
finishing wastes, and  solid inorganic wastes.  The total number of drums
disposed of at the site was estimated to be between 5,000 and 15,000 drums.
Approximately 532,000  yd3 of material were landtilled.
    The site lies on the 100-year floodplain of the Delaware River.  The
analysis of surface water samples in the site area did not indicate any
quantifiable pattern of contamination contributed by the landfill.
    The shallow water-bearing zone within the site boundary was found to be
contaminated.  The contamination in the shallow aquifer was localized and
primarily organic in nature.  The underlying deep aquifer was essentially
unaffected by the wastes disposed at the site.  The presence of the silty clay
layer  under the site serves as  a barrier to vertical movement of water from
the shallow to the deep aquifer.

Remedial Actions

    The initial response (Phase I) at the site was funded by the Philadelphia
Water  Department.  Drums and drum fragments were removed and disposed
offsite.  Contaminated soils were excavated and stockpiled into two piles; one
pile for offsite disposal or treatment, and the other  pile for backfilling
onsite.  The soils were separated on the basis of analytical results.
Indicator limits were  set for TOX (25 ppra), volatile organics (.12 to 15 ppb) ,
and metals; those soils which measured above the indicator limits were placed
in the pile for offsite disposal or treatment, and those which were below the
limits were placed in  the pile  for backfilling onsite.

    After .12,000 yd* of soils had been excavated, the Philadelphia Water
Department ran out of funds.  At this time, 17,000 yd3 of the excavated
soils were disposed offsite and the other 15,000 yd3 remained onsite.
    Remedial actions continued at the site when Superfund money became
available.  Stockpiled soils were resampled and analyzed by the EPA.
Excavation of the contaminated soils was continued.  The contaminated soils
were disposed of offsite at an EPA-approved facility.  The remainder of the
soils were backfilled onsite.  The site was then graded with a layer of low
permeability clay overlain by sandy soil and topsoil.  Finally, the topsoil
was reseeded and revegetated.

Success/Failure of Remediation—
    Monitoring data collected has shown that the remedial action has been
effective in removing the contaminated soil material.  It is expected that the
infiltration of precipitation to the ground water aquifer will be minimal.
Although measures were not taken to clean up contaminated ground water and/or
control its migration, site investigations have shown that it will probably
not present a problem to public water supply.  Hazardous constituents in the
ground water are expected to volatilize, degrade chemically or biologically,
or be diluted over time.

References:  Hernandez, 1985; Roy F. Weston, Inc., 1985; Versar, Inc, 1985.


Facility Description

    During the 1970s, the Frontenac site was used as a storage area for waste
oils and chemical wastes hauled by a waste oil company.  The illegal storage
and transfer of 2,3,7,8-TCDD-contarainated wastes at the site resulted in
contamination of the soils onsite and an adjacent creek (Deer Creek).  Through
improper waste handling and disposal practices, oils containing chemical
contaminants were allowed to leak from storage vaults onto the surrounding
soils and drain into Deer Creek.

Site Characteristics

    The annual average precipitation (1944 to 1983) in the site area is
36.41 in.  Average daily mean temperatures (.1951 to I960; range from 32.3"F
(winter) to 76.9UF (summer) with an annual average daily mean  temperature of
55.4°F-  The annual average wind speed (1949 to 1983) is 4.3 m/sec.

    The Frontenac site lies at an elevation of approximately 525 ft above mean
sea level (MSL).  The site is relatively flat, but slopes slightly southeast
toward Deer Creek.  Onsite surface water drains toward the southeast corner of
the site into the adjacent Deer Creek by way of a drainage swale.

    The soils at the site are mostly floodplain sediments consisting of
stratified sands, silts, and clays.  Gravel, cinders, and concrete fragments
are present near the site surface.

    The Frontenac site lies within the southeastern corner of  the Dissected
Till Plains geologic subprovince of Missouri.  Bedrock formations that
underlie the  site are chiefly Mississippian-aged limestones that become shaley
toward  the basal part of the Mississippian system.

    The Frontenac site lies adjacent to and on the 100-year floodplain of Deer
Creek,  which  flows approximately 7.5 miles to the southeast where it empties
into the River des Peres, a tributary of the Mississippi River.
    Deer Creek is a major source of flooding within the city of Frontenac.
Flash  floods  which occur along this stream are generally caused by localized,
intense thunderstorm activity which is typical of the northwest.  The size of
the Deer Creek watershed in the area of the site is 5.7 square miles.  The
peak discharge at this location for the 10-, 50-, 100-, and 500-year floods
are 3,500, 5,700, 6,800, and 9,500 cfs (cubic feet per second), respectively.


    Ground water in the area ot the Frontenac site occurs within limestone
bedrock formations.  Water may be obtained in limited quantities from wells
penetrating the limestone at depths of 150 to 200 ft.  This water occurs in
fractures and dissolution channels, with highly variable yields.  Most of
these wells yield a maximum of 10 to 15 gpm (gallons per minute); below this
depth the water becomes very saline and is generally unfit for use.  Drinking
water in the site area is obtained from the metropolitan St.  Louis area public
water supply which obtains water from the Missouri and Mississippi Rivers.


Types/Causes of Releases—
    The owner/operator of the storage site illegally accepted chemical wastes
containing dioxin (2,3,7,8-TCDD) for storage at the Frontenac site and
subsequent disposal at other sites.  Improper handling of these chemical
wastes caused hazardous substances (.predominantly dioxin-contarainated wastes)
to be released (through spillage, leakage, and runoff) to onsite surface soils
and an adjacent creek (Deer Creek).

Mechanisms for Detection—
    A safety inspection was conducted at the site in 1976 by Industrial
Testing Laboratories and the Frontenac City Fire Chief.  The ground around  the
tanks was found to be so saturated with spilled material that a continuous
stream of seepage could be observed to be entering Deer Creek.
    An additional site inspection, which was conducted by the U.S. EPA
Region VII Emergency Response Section in April 1977, concluded that the
Frontenac site did not have the required Spill Prevention and Countermeasure
(SPCC) Plan and thus, was in violation of 40 CFR 112.3(a),(d).
    During an EPA investigation of dioxin contamination at several horse arena
sites in Missouri, it was learned that the waste oil company may have been a
responsible party.  Subsequent sampling and analysis performed at the site in
1983 revealed the presence of 2,3,7,8-TCDD (dioxin).

Extent of Contamination—
    Sampling and analysis efforts conducted at the Frontenac site have
demonstrated that 2,3,7,8-TCDD exists onsite, within at  least  the uppermost
foot of soil.  The soil contamination extends over most,  if not all, of the
area where the storage tanks were formerly located.  Additional 2,3,7,8-TCDD
contamination has been confirmed in sediment samples collected from a portion
of Deer Creek (200 ft of the 300 ft reach of Deer Creek  adjacent to the site)
at a depth interval of 0 to 2 in.  2,3,7,8-TCDD has not  been detected in
samples taken upstream and downstream of the Frontenac site.

Remedial Actions

    During the period from 1977 to 1979, the sludge and  waste materials were
removed from the storage tanks and the tanks were removed from the site.  The
dioxin-contarainated wastes were sent to an EPA-approved  incineration facility
in Louisiana.  The remaining wastes were transferred into 55-gallon drums and
buried in an approved hazardous waste landfill in Missouri.  Following the
removal of the storage tanks, the area where the tanks were formerly located
was covered by the owner with a layer of crushed gravel.
    In April 1984, the site was listed as a CERCLA Superfund site.  During
June  1984, interim remedial measures were undertaken at  the Frontenac site.
The site was paved with asphaltic concrete over a newly  placed gravel
subgrade.  A toe-trench was dug near the creek and filled with rip-rap to
prevent erosion of the stream bank.  In order to restrict access to the paved
area, a 1/2-in. wire cable was strung on 5 ft steel stakes spaced at 20 ft
intervals around the east, north, and west perimeters ot  the site.

Success/Failure of Remediation—
    The remedial actions taken at the Frontenac site are  considered interim
measures only.  Although sampling and analysis has not been performed since
the installation of the interim measures, periodic site  inspections have shown
that  these measures have been effective in preventing erosion and infiltration
of precipitation.  Final measures are being considered at this time.
Reference:  GCA, 1984c.


Facility Description

    The Crystal Chemical site is an abandoned herbicide manufacturing plant.
During 1956 through 1981, the plant produced arsenic; phenolic; and
amine-based herbicides.  Wastes from the manufacturing process were placed in
four onsite evaporation ponds.  Originally, there was no leak detection or
monitoring system present at the site.  The site is currently on the list of
Superfund sites and is in litigation (i.e., the EPA is currently negotiating
with the responsible parties for site cleanup;.

Site Characteristics

    Soils underlying the site consist of silty clays in the upper 10 to
18 feet.  Sandy silts and clays are found below this depth.  Permeability of
the silty fine sands has been estimated to range from 10~-* to 10"^ cm/sec.

    The site is situated on the outcrop of the Beaumont Formation of
Pleistocene Age.  The Beaumont Formation, which is found in the site area at
depths of 0 to 150 ft consists of backswamp, point bar, natural levee,  and
stream channel deposits containing clay, silt, and sand.  Underlying this
layer to a depth of 650 ft are the Montgomery, Bentley, and Wilis Formations
which consist of clays, silt, and sand with minor amounts ot siliceous  gravel.

    Surface runoff from the site flows to a flood control channel (western
boundary of the site) and drains to the Brays Bayou (approximately 1-mile from
the site).  Since elevated levels of arsenic were detected in the adjaent
flood control channel,  it is suspected that Brays Bayou may have become
contaminated following flooding.

    Two water-bearing zones underlie the site; both are contaminated.  The
depth to the first sand water-bearing zone is approximately 15 ft below the
surface.  The second sand water-bearing zone is located at a depth of 3i> ft
below the surface.  Although there are interconnections between the
water-bearing zones, hazardous constituents have not been detected in the
major water-bearing zone (i.e., used for Houston water supply) located
approximately 200 ft below the surface.


Types/Causes of Releases—
    Raw and finished containerized materials were stored on the ground in the
open.  Materials spilled occasionally and leached into the surface soils.
Additionally, arsenic trioxide was received in bulk by rail and poor
containment practices were used during unloading.
    Periodic flooding occurred at the site.  Dikes were used in an attempt to
convey  surface water runoff from the process operation area to an area in
close proximity to the manufacturing facilities.  In 1976, a significant flood
occurred which overflowed the dikes releasing hazardous constituents into an
adjacent flood control channel and possibly into Brays Bayou.
    In  addition to surface water and ground water relases, airborne arsenic
was released to offsite areas during mechanical aeration of the waste
evaporation ponds.

Mechanisms  for Detection—
    In  1971, the Texas Water Quality Board (now the Texas Department of Water
Resources)  noted during an inspection that there was a potential for both
onsite  and  offsite contamination.  During subsequent routine inspections (late
1970's), Crystal Chemical Company was cited for several license violations
including spills, poor housekeeping, worker safety violations, and discharge
of contaminated wastewater and storrawater runoff.  In 1977, the company was
cited and  fined by  the Texas Water Quality Board for unauthorized discharge of
arsenic contaminated wastewater.

    Complaints Erom residents of nearby apartment complexes and.businesses  of
discolored water resulted  in further investigations by the Texas Water Quality
Control Board.  Arsenic  contamination was discovered in air conditioning
filters in residences  immediately downwind of the waste evaporation ponds.   It
was determined  that  the  Crystal Chemical site was the source of contamination.

Extent  of  Contamination—
    Phenol-based and  arsenic-based herbicide manufacturing wastes were
disposed  at  the site,  resulting in arsenic and phenol contamination.  An
estimated 89,000 yd3  of  soils onsite are contaminated with  100 mg/kg of
arsenic.   Ground water under the entire site is contaminated to the 35 ft sand
layer.  The  contaminated ground water plume has migrated 150 ft offsite,
extending approximately  200 ft to the north in a somewhat oval-shaped
pattern.   Although sampling and analysis activities have not been conducted  in
Brays  Bayou,  it is likely  that surface water contamination from surface runoff
exists in Brays Bayou.

Remedial  Actions

     Contaminated  surface water (from the flooding incident) was removed.
Equipment and buildings were removed (i.e., site was leveled).  Former waste
nits (lagoons)  were backfilled and the entire site was capped with a 1 to
2 in.  clay layer overlain by a plastic top to serve as a temporary cap.
     Periodic  sampling  and analysis has been performed since 1983.  Currently,
there  are 13  monitoring wells in operation.

Success/Failure of Remediation—
     n  1  interim measures (emergency removal actions) have been taken to
        T*.  RT/FS has been completed (as ot June 1984) and reviewed at EPA
date.   lne R  '
        ..„,•<,   Appropriate remedial actions currently being considered by the
Headquarters.  «FK
          A •  capping, and the construction of a slurry wall.
EPA inclua6'  i- PK  o

        ^OG-  Gilrein,  1985; Versar, Inc., 1985; D'Appolonia Waste Management
             Services, et.  al.,  1984.



Facility Description

    During the period from 1971 to 1978, the site was used for the operation
of a chemical reclamation facility which was designed and licensed for the
ultimate disposal or recycling of chemical wastes.  Solvents were recovered
through a distillation process (evaporation/concentration system); and wastes
were stored and/or disposed onsite.  In 1978, the company's license was
revoked and the site was abandoned leaving approximately 1-million gallons of
hazardous wastes  stored in drums and bulk storage tanks.  The site is
currently under Superfund status.

Site Characteristics

    The vertical  relief in the site area is approximately 5 ft.

    Soils  in  the  site consist of  fine-  to medium-grained sands, and are
moderately well drained.  The sand-silt strata  is approximately 100 ft thick.

    The  site  is  located on a glacial outwash plain.  The depth to bedrock is
approximately 5  ft.   The  bedrock  material is permeable.

    The  ground water table  is parallel  to the  site's surface  topography.  The
distance  to  the  shallow aquifer  is  less  than  5  ft.  Maximum ground water
contamination occurs at depths  of 20  ft  or  less.  Ground water movement is to
 the north  at  a rate  of  approximately  16 ft/yr.
    River  Meadow Brook  is located approximately 300  ft  west of the site.  Low
 levels of  contamination were  found  in  the surface water.


Types/Causes of Releases—
    Surface runoff caused hazardous constituents to be -transported to soils on
the site and to River Meadow Brook (.approximately 300 ft west of the site).
Leachate from the contaminated soils permeated the bedrock and contaminated
the shallow ground water aquifer.

Mechanisms for Detection—
    In 1974, the company experienced financial problems and began to be
unselective about the types of wastes it would accept.  Permit violations were
discovered during a routine MWPC inspection conducted in 1975.  Additional
license violations were discovered in 1977.  The company's license was revoked
in 1978, after continued violations.  Operations ceased and the site was
abandoned.  Site investigations and monitoring activities have been ongoing
since the original discovery of contamination.

Extent of Contamination—
    Chemical reclamation wastes from over 35 different chemical processes were
disposed at the site, including acids, alkalis, solvents, pesticides, and
plating wastes.  Hazardous constituents found at the site include:  volatile
organic compounds, PCBs, pesticides, and some metals.
    Contamination has been found in air, surface water (River Meadow Brook),
surface runoff, soils, and ground water.  Maximum soil contamination occurs at
a depth of 10 ft or less below the surface.  High levels of hazardous
constituents have been found in the shallow aquifer.  The extent of the
hazardous constituent plume is approximately 50 ft deep, 1,000 ft north/south,
and 800 ft east/west.

Remedial Actions

    In March 1978, berms were constructed and absorbent fill material was
placed in the disposal trenches (.surface impoundments) to reduce the spread of
surface contamination.


    In 1981, drums and chemicals in bulk storage tanks were removed, with the
exception of approximately 78,000 gallons of PCB-contaminated solvent waste
(in bulk storage.).
    In 1982, the buildings and most of the containers were removed (with the
exception of a few underground tanks,).  Approximately 6,000 gallons of
volatile organic compounds are reportedly beneath the site.  It is estimated
that 8 percent by weight are in the ground water, and 92 percent by weight are
in the soil.
    During  1983 and 1984, the site was capped using a 14 in. layer of
compacted clay with gas-venting system to minimize surface water and rainwater
    Periodic sampling and analysis has been performed since 1976, using eight
monitoring  wells now present on the site.  A new evaluation is scheduled for
1985 because the removal of buildings, etc., is believed to have changed the
ground water table.

Success/Failure of Remediation—
    Remedial response actions taken to date are considered to be interim
measures.   The interim measures have slowed the migration of hazardous
constituents, but not significantly.  The RI/FS is currently being prepared
(Perkins-Jordan prepared a report similar to an RI/FS in 1979).  Wells
continue to be monitored to define the rate and nature of migration.

References:  Ciiello, 1985; Versar, Inc., 198b.

                                    SECTION  5
                               CORRECTIVE  MEASURES

    An overview of corrective measures for soil releases has been presented in
Section 3.  The proven, imminent and emerging technologies,  summarized in
Table 3-1, are used to treat, destroy or dispose of contaminated soil in order
to eliminate or mitigate a threat to human health and the environment.
    There are many technologies presently available that are capable of
treating or disposing of contamination within the soil horizon.   These range
from such methods as excavation followed by capping or landfilling to newer
technologies such as incineration, which can typically render the hazardous
constituents non-hazardous.  An important consideration in selecting
corrective measures is to examine available technologies with respect to types
of hazardous constituents prevalent at the site and site characteristics.  The
most appropriate corrective action can then be selected and recommended.  As
can be seen from summary Table 3-2, certain hazardous constituent types and
technologies are amenable to each other while others are not.  Therefore, the
appropriateness of certain corrective measures must first be determined for
specific constituent types.  Following initial screening of appropriate
technologies, the site characteristics must also be considered in selecting
the final corrective measure.  For example, contamination present at great
depths may not be amenable to in situ methods of treatment.  Capping and
landfilling may also be inappropriate in such circumstances if a high ground
water table is present or in conjunction with highly permeable soils.  These
measures would not likely provide adequate long term protection to human
health and the environment.  Table 5-1 is a summary of pertinent issues
discussed in this section.

                    CORRECTIVE MEASURES
Site Investigation

    Characterize extent and
    type of hazardous constituent
    Soil Conditions
    Site Location
 Screening  of Measures

   Technical Considerations

•  Waste types and amounts released
•  Extent of migration
•  Chemical and physical properties of
   the waste
•  Fate and transport of chemicals to
   Soil type
   Cation exchange capacity
   Redox potential
   Organic carbon content
   Engineering parameters such as
   plasticity, atterberg limits and
   moisture content

   Proximity of local population
   Proximity of municipal and private
   ground water sources
   Locations of drainage areas and
   surface water bodies
   Local climate including precipi-
   tation, temperature and wind data

   Overburden characteristics
   Bedrock characteristics including
   extent of weathering, fracturing,
   jointing and foliation
   Depth to ground water
   Location of uppermost and useable
   Hydraulic gradients
   Hydraulic conductivity
   Ground water velocity
   Effectiveness of measure to perform
   intended functions, including
   demonstrated performance
   Overall time period a measure will
   adequately perform (useful life)

                             TABLE 5-1 (continued)
  Public Health Considerations
  Environmental Considerations
  Institutional Considerations
  Cost Considerations
•  Ability to protect human health and
•  Operation and maintenance character-
   istics of the corrective measure

•  Ease of installation under given
   site conditions
•  Ease of installation under
   conditions external to the site
•  Time required to implement and
   attain desired results

•  Short term safety issues concerning
   workers and local populations
•  Long term safety issues concerning
   onsite employees and local

•  Site contaminant, extent and nature
•  Fate, transport and exposure of
•  Anticipated dose, and frequency of
   exposure by receptors
•  Toxicity of contaminant

•  Identify impacted environments
•  Ensure corrective measures address
   environmental threat posed
•  Assess possible future impacts from
   corrective measure

•  Compliance with Federal, State and
   local regulations
•  Identify possible non-compliance
   areas where variances may be needed

•  Detailed cost analysis including
   direct and indirect capital costs
•  Present worth analysis
•  Operation and maintenance costs
•  Determine most cost effective measure
                                       •  Ensure all aspects of site investi-
                                          gation and screening are adequate
                                       •  Select measure that focuses on and
                                          will effectively mitigate the posed

                              TABLE  5-1  (continued)
Conceptual Design
                                          Permit writer must ensure that the
                                          proposed corrective measure is
                                          adequate and may recommend more
                                          applicable measures if necessary
                                       •  Detailed corrective measure design
                                       •  Detailed drawings and specifications
                                       •  Work schedules
                                       •  Process descriptions
•  Unit or process installation
•  Field inspections
•  Quality control on construction

•  Monitor unsaturated zone and ground
   water to determine success or
   failure of corrective measure

Section Objectives

    This section of the report will develop for the permit writer an approach
for selecting and implementing a corrective measure.  It will provide a
logical sequence of decision making processes and activities to guide the
permit writer in reviewing proposed corrective measures for releases to soil.
    This progression involves the following important considerations:

    •    adequate site investigation,
    •    screening,
    •    selection,
    •    recommendations,
    •    conceptual design,
    •    implementation, and
    •    monitoring.

    Case studies presented in Section 4 and corrective measures described in
Section 3 will also be used to illustrate remedial actions taken at various
SWMUs and other facilities for release to soils.  These will be used to
demonstrate  the success or failure of the remedial measure taken, and to
analyze why  these successes and failures occurred.  The interaction between
technology,  hazardous constituent types, and site characteristics will be
discussed in terras of how  the particular remedial action was chosen and why
expected results were or were not realized.  Finally, this section will
provide the  permit writer  with a summary of the important issues and
considerations that are necessary in the selection process.


    Once a release has been documented, or suspected  to have occurred as
evidenced by a preliminary site assessment, it may be necessary  to  implement  a
corrective measure.  The correct selection of an appropriate corrective  action
requires that the applicant follow a logical progression of decision making
processes presented previously, to be able to select  the corrective measure

that is the most technically sound, that will provide the most protection to
human health, the environment, and that will comply with various environmental
laws, and that is cost effective.  This progression should also be performed
by the permit writer to be assured that the applicant has considered all
available corrective measures and has selected the most appropriate one.

Site Investigation

    Once a preliminary site assessment indicates that a release has occurred
and that the release is a potential hazard to public health and the
environment, a thorough site investigation is necessary to determine specific
site characteristics.  The permit writer must examine the available data
submitted by the applicant and decide upon the adequacy of the site
investigation with respect to selecting an appropriate corrective measure for
remediation.  The permit writer should identify any data gaps that may affect
the final selected action.  The following must be properly characterized:

    •    Hazardous constituent characteristics (migration potential),
    •    Extent of contamination (potential receptors),
    •    Soil Considerations,
    •    Site Location,
    •    Geology, and
    •    Hydrology.

These parameters will greatly influence the selection of an appropriate
corrective measure and its final engineering design.  Many of the
characteristics needed to be identified may already be available through
previous site investigations which should be used as a base-line for any
further investigation.

Characterization of Extent and Type of Hazardous Constituent Release—
    During the site investigation the extent and type of hazardous
constituents) that was released must be determined.  The type of hazardous
constituent that is released will influence the selection, design and

implementation of a corrective measure.   As shown in Section 3 of this report,
certain technologies may only pertain to certain types of soil contamination.
For example, biodegradation,  either in situ or above grade, is only applicable
to organic constituents.
    The chemical and physical properties of a chemical type must also be known
in order to determine appropriate remedial actions.   Parameters such as water
solubility, adsorbability onto soil particles, volatility and biodegradability
are important in the final selection of  a corrective measure.  If possible,
the amount of hazardous constituents released should be quantified to assess
the magnitude of the spill or release.  Knowledge about the toxicity of the
hazardous constituent and about the fate and transport of the chemicals to
potential environmental receptors is also critical in deciding if the release
poses a potential threat to human health and the environment and if immediate
corrective actions must be taken.  If highly toxic materials have been
released, and environmental receptors identified, then immediate responses may
be warranted to mitigate an impending risk to human health and the environment.
    The soils at the site must be adequately defined and the hazardous
constituent levels in the soil horizon must be properly characterized.  This
normally can be accomplished through the excavation of tests pits or from soil
borings if contamination is expected to  be at substantial depths.  Shallow
surface sampling can easily be performed to determine the extent of surficial
contamination.  The sampling approach should characterize both the lateral and
vertical extent of contamination.  This  is needed to determine if the
contamination exists below the mean seasonal high water table, and to estimate
the amount of soils that will require excavation and/or treatment.

Soil Conditions—
    The determination of soil characteristics, soil types, permeability and
porosity is needed to assess the potential of hazardous constituent migration
from the soil into ground water and resulting offsite migration to possible
    Several chemical parameters also affect hazardous constituent migration
Erom soil.  Soil pH greatly effects the  mobility of many metals, as well
cation exchange capacity.  High cation exchange capacities, for example, tend

to immobilize metals within the soil.  The redox potential  (Eh), of a s.oil also
effects the oxidation state and resulting stability of  both organics and
metals in the soil.
    Other parameters such as total organic carbon content,  plasticity  limits,
Atterberg limits, and moisture content also influence hazardous constituent
migration and should, therefore, also be examined.  Such parameters will
influence the appropriateness of the selected corrective measure as well as
the engineering design and methods of implementation.

Site Location—
    The site location is very important in the final selection of a corrective
measure.  Factors such as proximity to local populations can effect the
corrective action selected and its implementation.  For example, if there are
nearby populations and there is a release of organics to soils, biological
treatment may be considered as a viable treatment option.  However, these
populations may be impacted by persistent odors generated throughout the
treatment period therefore eliminating this measure from further consideration.
    The proximity of the contaminated soil to municipal or private ground
water  supplies is also a major concern.  Options for clean up must adequately
protect against the contamination reaching the ground water and migrating
offsite, thereby causing a possible human health concern.  The proximity of
surface water bodies, such as lakes, rivers and streams, must also be
assessed.  Surface water run-off from the contaminated  soil must not be
allowed to impact nearby water bodies.  Care must also be taken not to allow a
release, or effects from corrective action implementation,  to impact local
ecological systems.
    Additionally,  information on the local climate is an important part of the
selection process.  Temperature data including monthly, seasonal and yearly
means  along with depth of frost, if applicable, are crucial parameters.  Such
knowledge permits the proper scheduling and implementation of treatment
processes, which are influenced by ambient temperature.  Such processes as
biological treatment are impaired by cold temperatures and, therefore,  may
only be viable during warm seasons.  The depth of frost is very important in
designing an impermeable cap or landfill.  Adequate coverage over the
impermeable synthetic material or clay layer is necessary.  Freeze-thaw cycles


can cause cracking in clays and decrease the integrity of synthetic liners at
a rapid rate.  This in turn decreases the reliability, performance and useful
life of the unit.
    Monthly, seasonal, and annual precipitation values are important in
determining hazardous constituent migration rates through soils.  This must
also be known to determine the water balance of the site.  Corrective measure
implementation is also affected by seasonal precipitation values.  This is
especially true if the measure involves extensive excavation at great depths
or if contamination is close to water table elevations.  Determination of
these data are important in scheduling construction activities.
    Wind direction and speed also affect corrective measures that involve
large amounts of excavation.  Local populations may be subjected to fugutive
dust emissions, unless effective dust suppression methods are used.  Odors may
also be carried to nearby populations through prevailing winds, thereby
creating health hazard.

    The hydrogeology of a site is one of the most important factors concerning
the selection of a corrective measure.  The overburden and bedrock at the site
in the area of the release must be adequately characterized to assess the
pathways of migration.  Parameters such as sand and gravel overburden^ highly
weathered bedrock, fracturing, jointing and existence of foliation can greatly
increase the hazardous constituent migration rate.  All of these parameters
must be well defined through such methods as field mapping and subsurface
borings.  Sites with fractured or highly jointed bedrock may not be amenable
to on-site storage because hazardous constituent migration may be quite
rapid.  This type of site condition may require removal or ultimate treatment
in order to mitigate potential hazardous constituent migration.
    Such hydrologic parameters as depth to water table during wet and dry
seasons and definition of the uppermost and useable aquifers must be
considered when deciding on a corrective measure, its engineering design and
implementation. Depth to ground water is important in determining if soils can
be easily excavated or if capping or landfilling are viable corrective
measures for implementation at the site in question.

    Other parameters such as hydraulic gradient, hydraulic conductivity,
porosity and ground water velocity should be considered in assessing hazardous
constituent migration from soil into ground water.  Furthermore, both the
lateral and the vertical extent of contamination must be characterized -to
select an appropriate ground water interception and treatment method.


    Upon adequate completion of the site investigation, the next step in
selecting a corrective measure involves the development and screening of
possible corrective measures.  The initial step in the screening process is
the development of general response objectives to identify the goals and
extent of the corrective measure to be used.  The site investigation should
identify the possible receptors.  Corrective measures that will mitigate the
threat posed to these receptors can then be formulated.  For example, if
exposure to the hazardous constituent release is determined to be by direct
contact of onsite workers or trespassers, then capping and access restriction
may be adequate.  However, if the release is found to be highly toxic with the
possibility of migration into ground water, a measure that will treat the
hazardous constituents to acceptable levels, or excavation and removal may be
    All applicable  technologies should be gathered for consideration.  These
should then be screened to eliminate those that are clearly not as applicable
as others using the  following criteria:

    •    Technical,
    •    Public Health,
    •    Environmental,
    •    Institutional, and
    •    Cost.

Technical Considerations—
    A primary concern when screening proposed measures is to identify those
that are technically feasible under given site conditions.  Both proven and
imminent technologies should be investigated in some detail in terms of
engineering design and overall implementability.  Some of the technical issues
that are addressed in a CERCLA feasibility study can also be considered when
assessing corrective measures for a hazardous constituent release to soil at a
RCRA facility (i.e. SWMU).  The following discusses some of the technical
issues that a permit writer should consider when reviewing an application for
corrective measures implementation.  The following technical considerations
will be discussed:

    •    Performance,
    •    Reliability,
    •    Implementability, and
    •    Safety.

    Performance—It is important to be able to determine how well a corrective
measure will perform once implemented.  In order to do this the effectiveness
of  the measure or its ability to perform its intended functions must be
analyzed.  Therefore, it must be demonstrated that the remedial action
selected whether it be removal, containment, destruction or treatment, will
properly perform and be effective as a corrective measure in eliminating
present and  future human health and environmental impact.
    Another aspect of performance is the useful life of the proposed
measures.  Each measure should be examined to determine the length of time it
will be able to adequately perform.  The useful life of the remedial action
must, therefore be determined to assess the overall performance of the measure.

    Reliability—Each remedial measure must be assessed in terms of its
reliability  in protecting human health and the environment considering both
hazardous constituents present and site conditions.  Therefore, the
demonstrated performance of a corrective measure should be determined.  This
assessment can consist of evaluating the performance of the technology at
similar sites or by using pilot scale studies to evaluate actual performance.

    The amount of operation and maintenance that is required by a corrective
measure also effects its reliability.  A measure may be  less reliable if  it
involves many complicated operation and maintenance activities, whereas a
measure with simple and less frequent operating and maintenance activities can
be considered more reliable.  Treatment technologies,  for example, may render
contaminated soil non-hazardous, thereby enabling  it to  be disposed of; as per
applicable regulations.

    Implementability—Each proposed measure must be evaluated  in terras of its
ease of installation at the site in question.  In  order  for a measure to  be
selected for remediation it must be readily implemented  in a reasonable period
of time.  It must be ascertained that both site conditions and conditions
external to the  site will be amenable to the proposed  corrective measure.
    Time to implement and the amount of time to see desired results must  be
investigated.  It is important  that a corrective measure not take too long to
implement since  contamination may migrate from the soil  into the ground
water.  Also, measures  that quickly mitigate the threat  posed  by a release are
more desirable than those that  take a longer period of time.

    Safety—The  final technical evaluation of a corrective measure is safety.
The evaluation should include the safety provided  to onsite workers and
offsite  local and distant populations both during  and  after final
implementation.  Measures that  expose workers and  populations  to potentially
hazardous conditions should not be as highly regarded  as those that minimize
these  conditions.  Corrective measures should be designed such that they
minimize risk during the construction/implementation phase and should be
evaluated regarding the ability of the final design to provide continued

Public Health Considerations—
    For a corrective measure to be implemented at  a SWMU it must provide
protection to public health, including both onsite workers and offsite
residents.  The  key components  of such an evaluation include:

    •    extent  and nature  of  sLte contamination,
    •    fate and transport of hazardous constituents from the site,
    •    exposure of local  and distant populationstboth human and nonhuman) to
         the hazardous constituents,
    •    projected dose of  the contamination to environmental receptors,
    •    anticipated frequency of hazardous constituents exposure to
         environmental receptors,
    •    toxicity and health hazard of the hazardous constituents,  and
    •    risk assessment with  exposure to the hazardous constituents.

    The initial step in considering human health risks is to evaluate  all
pertinent data from the site investigation.  Factors such as constituent
types, quantities, spilled, and extent of contamination are critical issues to
be addressed.  The populations) at risks should also be determined.
    An important part of choosing a corrective measure is to ascertain the
potential for hazardous constituent migration and  the potential exposure
routes.  Mechanisms by which populations will be exposed to the contamination
greatly influences the final decision on corrective measures and their
design.  If a release to soil  has the potential to migrate into a useable
aquifer, then care must be  taken to ensure that the measure chosen will either
treat the contaminated soil to appropriate levels or remove it so the  public
will not be affected through contaminated drinking water.
    Air quality standards and  water quality standards must not be violated due
to the release.  If standards  have been exceeded due to a release,  then any
corrective measures implemented should ensure that required levels be  attained.

Environmental Considerations—
    The next step in the screening process is to make an environmental
assessment concerning impacts  to the environment.   Again, data from the site
investigation is a primary  source of information.   It must be ensured  that the
corrective measure achieve  adequate protection and/or improvement to the

    Each proposed measure must be analyzed to determine the extent of
environmental benefit that will be attained through its implementation.  It
must be determined what part of the environment is, or potentially will be,
impacted from the release.  The following consist of environments that may be

    •    Ground water,
    •    Surface water,
    •    Soils,
    •    Air,
    •    Sole source  aquifers,
    •    Wetlands,
    •    Flood plains,
    •    Coastal zone,
    •    Critical habitats,
    •    Prime agricultural lands,
    •    Federal parklands,
    •    National forest,
    •    Wildlife sanctuaries/refuges,  and
    •    Habitat productivity.

Another area of  environmental  concern  is  the affect on various human resources
such as:

    •    Commercial,
    •    Residential,
    •    Recreational,
    •    Aesthetic,  and
    •    Cultural.

Corrective measures must try to minimize the impact to these re-sources.  For
example, loss of water supplies and unpleasant odors can reduce local property
values in a residential community.1  Migration of contamination to a stream or
lake can impact the population of the surface water body and result in a loss
of recreational area.
    Another area that must be explored in the environmental assessment is the
environment which has been affected and whether or not it can be returned to
its previous condition.  Additionally, potential impacts on the environment as
a result of corrective measure implementation, must also be assessed.

Institutional Considerations—
    Each of the proposed corrective measures that is being screened should
consider various institutional concerns.  This involves assuring that the
corrective measure used for remediation is in compliance with existing federal
(EPA), state and local laws.  Some of the federal regulations that should be
considered consist of:

    •    Ground Water Protection Strategy.
    •    The Wild and Scenic Rivers Act,
    •    The National Historic Preservation Act,
    •    The Endangered Species Act,
    •    Archeological and historic preservation,
    •    The Coastal Zone Management Act,
    •    Fish and Wildlife Coordination Act,
    •    Flood Disaster Protection Act,
    •    Uniform Relocation Assistance and Real Property Acquisition Policies
         Act, and
    •    Executive Order 12372, 11988 and 11990.

    State  regulations concerning flood plains, wetlands, surface water and
development of new aquifers should also be considered when screening
corrective measures.

    Along with federal and state regulations, local laws pertaining to. erosion
control, zoning,  building permits, rights of way and sewer, water and
electrical permits should be addressed during the screening process.
    A corrective measure that institutionally complies with as many
regulations as possible may be a more desirable choice since fewer permits and
variances may be necessary upon installation.  This in turn may facilitate the
implementation process, which can aid in mitigating threats to human health
and the environment by expediting cleanup.

Cost Considerations—
    A detailed cost analysis should be performed for each proposed corrective
measure to evaluate its overall cost effectiveness.  This should include
analysis of all direct and indirect capital costs that would be incurred
during  the implementation of the corrective measure.  Also included should be
any operating and maintenance costs that may be necessary to ensure the
continued effectiveness of the measure.  A present worth analysis should also
be performed which allows the cost of a measure to be compared to a single
present worth value.  This value is equivalent to the amount of money that
must be invested in a base year and disbursed as needed to cover the cost of
the measure over its intended life.  Overall cost effectiveness can be
compared by examining the present worth value of each measure.


    From the site investigation and the screening process a final decision
concerning the most applicable corrective measure must be made.  The permit
writer  must look at all aspects of the applicant's report including the
completeness of the site investigation.  As previously stated, much of the
site investigation material may be readily available fom other investigations
conducted at the site; however, the permit writer must ensure that available
information properly characterizes all parameters that may affect the release
and corrective measure implemented.
    From the technology screening, the applicant should arrive at the most
appropriate measure for remediation.  The permit writer should be certain that
the measure is adequately focused on the risk posed by the hazardous


constituent release; i.e.,  that the endangerment or risk to human health and
the environment is mitigated by the remedial action.  The permit writer should
evaluate the corrective measure in terras of each endangerment issue and should
consider the effectiveness of the remedial action in mitigating migration from
the soil horizon to other mediums such as ground water, surface water or the

    If the permit writer is not completely satisfied that the applicant has
properly addressed the issues in the site investigation and screening process,
then the proposed corrective action plan should not be implemented.  At this
point the permit writer may convey to the applicant any deficiencies apparent
in the site investigation or thought process in obtaining the corrective
    The permit writer may also suggest to the applicant other measures that he
or she feels may be more applicable to the site in question.  Pilot studies to
evaluate the overall performance and effectiveness of a selected measure may
also be suggested.  Such studies can be very useful in recommending and
selecting the corrective measure to be used for remediation.

Conceptual Design/Implementation

    Once the corrective measure has been chosen, a detailed conceptual design
must be completed prior to implementation.
    Important activities which must be carried out during the implementation
of the measure include field inspections to ensure quality control during
construction, and to ensure that design specifications for construction and
materials are being adhered to.  Any alteration that occurs during
construction must be investigated by an engineer to determine if it will
affect the performance of the measure.  These inspections during
implementation must include monitoring to determine that contamination is
being properly treated (i.e. to appropriate levels) or if being removed, that
all contaminated soils are adequately excavated and disposed.  These
monitoring and inspection activities are important in ensuring that the
corrective measure will perform as designed.


    Upon completion of the corrective measure, a monitoring plan must be
initiated to ensure that the corrective measure has been properly  installed
and is performing as specified.  If  failure or only partial success occurs,
then monitoring data can be used to  determine what further type of remediation
may be necessary.
    Monitoring can be done in both the upgradient and downgradient ground
water through the use of monitoring  wells to reveal if contamination is
continuing to migrate into the ground water.  Lysimeters can also be used to
monitor the unsaturated zone for hazardous constituent concentration and
migration.  This type of monitoring  can be very applicable to  landfarm areas
or below landfills or capped structures.  Through the use of lysimeters,
contamination can be detected prior  to migration into the ground water.  It
may also be applicable to monitor the area through the use of  soil borings to
determine if contamination still remains in the soils and at what depths they
occur.  Air quality monitoring may also be applicable in many  cases.
    Table 5-2 presents a checklist of important considerations that should be
addressed during the selection and implementation of a corrective measure.
The final part of this section will  use a case study presented in Section 4 to
illustrate remedial actions taken for releases to soils.


    To assist the permit writer  in reviewing applications for  corrective
measures for releases to soils,  a summary table was generated.  Table 5-3
illustrates  the  type of removal, disposal, treatment and containment
corrective measures available for remediation of contaminated  soils.  The
applicability of measures  regarding  site characteristics and amenable
hazardous constituents are discussed in Section 3.  Table 5-3  was developed
from  detailed technology/corrective  measure discussions provided in Section 3
and case studies, presented in Section 4.  The usefulness of this table can be
illustrated  by evaluating  in detail, one of the case studies.

                     TABLE 5-2.  PERMIT WRITERS' CHECKLIST
    Has an adequate site investigation been conducted concerning:  (yes/no)

              Hazardous constituent characteristics                      	
              Extent of contamination                                    	
              Soil considerations                                        	
              Site locations                                             	
              Site geology                                               	
              Site hydrology                                             	

    Have all applicable corrective measures been adequately screened
    concerning technical issues?  (yes/no)

         •    Performance                                                	
         •    Reliability                                                	
         •    Implementability                                           	
         •    Safety                                                     	

    Have public health considerations been adequately identified and
    addressed?  (yes/no)

              Extent and nature of contamination                         	
              Fate and transport of hazardous constituent(s)             	
              Exposure potential                                         	
              Contamination dose to receptors                            	
              Frequency of exposure                                      	
              Toxicity of hazardous constituent(s)                       	
              Risk assessment                                            	
              Proximity of local populations                             	

    Have environmental considerations been addressed during corrective
    measure screening and selection?  (yes/no)

         •    Impact on surrounding environments
         •    Impact on human resources

    Have institutional considerations been adequately addressed?  (yes/no)

         •    Compliance or noncompliance with Federal regulations
         •    Compliance or noncompliance with State regulations
         •    Compliance or noncompliance with local regulations

    Have accurate cost analyses been completed during the screening
    process?  (yes/no)


                         TABLE  5-2  (continued)
Selection of a corrective measure.  (yes/no)

     •    Has an adequate site investigation been completed?
     •    Have screening parameters been properly addressed?         _
     •    Has the selection considered all available technologies?

Recommendation.  (yes/no)

     •    Does the permit reviewer have recommendations for other
          corrective measures that may be more appropriate?          	

Has a conceptual design been adequately prepared?  (yes/no)          	

Implementation:  Are the following adequately characterized?  (yes/no)

     •    Field inspections during construction                      	
     •    Quality control check during construction                  	
     •    Monitoring activities
Has an adequate monitoring plan been proposed in terms of:  (yes/no)

     •    Soils
     •    Ground water
     •    Surface water
     •    Air


Removal /Containment /Treatment
Removal /Containment

Removal /Disposal

Remova 1/Trea tment

In Situ Treatment





• H



• H




• H

• pi


• H





I— 4


c- (

• ft



• r4
O •





X '. X









£f fectiveness/Coaments
Ability to excavate the soils and hazardous
constituent types influence the applicability
of this technology. This technology does not
comply with RCRA land disposal regulations due
to the fact that there is no bottom
liner/ leachate collection system.
^ ^___ ^^^^^^^_
Implementation is dependent on the ability to
excavate the soils (refer to Section 3).
Generally quite effective technologies, however
replacement of containment unit is inevitable.
Most effective and reliable when used in
conjunction with treatment prior to disposal.
Implementation is dependent on the ability to
excavate the soils, and site specific, geologic
and hydrologic parameters. Hazardous
constituents dictate type of treatment that is
applicable. Refer to Section 3 and Table 3-2
for hazardous constituents amenable to
Effectiveness/implementation dependent upon
site characteristics, geology, hydrology and '
hazardous constituents. Refer to the
discussion in Section 3 and Table 3-2
concerning hazardous constituents amenable to


    The case study "Enterprise Avenue, Philadelphia, PA" will be considered in
detail.  By reviewing the technology discussions in Section 3, the
applicability of the corrective measures implemented at this site can be
assessed.  This facility was a landfill used for disposal of incineration
residues, flyash and debris by the city of Philadelphia.  However, at some
point drums of various industial and chemical wastes were illegally buried at
the site.  If applying for a RCRA permit, this type of situation would fit the
description of a SWMU requiring corrective measures, as stated in Section 1 of
this report.
    The site characteristics appear to be quite well described.  Site
conditions dictate that a deep aquifer below the site is protected from
contamination due to overlying silt and clay layers.  This deep aquifer may
recharge municipal ground water sources for New Jersey and, therefore, if
contaminated could impact human health.  A shallow and somewhat limited
aquifer was, however, impacted by the contamination.
    Remediation consisted of soil excavation including sampling and analysis
to determine that contamination was adequately removed.  Excavated soils that
were found to be contaminated were disposed of offsite in an approved EPA
facility.  The site was then graded and capped with a low permeability clay.
This remediation was reported to be successful.  No ground water recovery or
treatment was installed at this facility to clean up the contaminated shallow
ground because the source was removed and the impermeable cap minimized
further surface water infiltration through the site.
    It is evident from information in this case study that soil contamination
did not extend to great depths.  An excess of 32,000 ydj of soils was
removed which does not constitute an extremely large quantity of soil and
therefore allows excavation to be an applicable technology.  Removing the
source of contamination through excavation in this case was also desirable
because the deep confined aquifer may act as a recharge to a municipal water
supply.  Source removal would therefore minimize any future impacts and as
stated in the case study shallow ground water is expected to clean itself up
with time through volatilization, chemical or biological degradation and/or
dilution and therefore not impact the deeper aquifer.


    The corrective measures chosen for remediation at this facility appear to
have been appropriate to mitigate the threat posed to human health and the
environment.  Removal followed by offsite disposal in an EPA approved facility
is a common remedial measure although expensive and dependent upon offsite
landfill capacities.
    By referring to Table 5-2, it is evident that the removal/disposal
corrective measures implemented at the site for remediation of contaminated
soils are applicable.  Further review of Section 3S  which discusses corrective
measures and Table 3-2 which provides information concerning wastes amenable
to various treatment technologies verifies this fact.

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                                   Reference  6

                                   APPENDIX A
                               FATE AND TRANSPORT

    Hazardous constituents released to soil have the potential to migrate from
the original point of release.  This movement may be within or by means of the
soil medium, or the constituents may migrate from the soil into another
medium, such as air, ground water, or surface water.  In addition, the
hazardous constituents released to these media may also be subject to
degradation or removal mechanisms that decrease the amount of the contaminants
in the soil.  Alternatively, the hazardous constituents may be resistant to
such degradation and may persist in the environment.  An estimate of the
mobility and persistence of a contaminant within the particular soil
environment is key to evaluating the potential risk posed by the release.
Such information provides the basis for performing the exposure assessment
described in Appendix B.  In addition to determining exposure potentials and
characterizing risk, one must also be able to assess potential movement within
and between environmental media to determine appropriate corrective actions to
be applied to the release.
    The following sections provide a brief description of the factors
influencing contaminant transport and fate and the mechanisms by which
hazardous constituents may be transported or degraded.  Guidelines are
provided to assist the permit writer in evaluating chemical and physical
parameters of hazardous constituents with respect to their potential transport
and fate from soil releases.  Generalizations of environmental behavior  for
selected chemical classes are also provided.  Other site-specific,
environmental factors that would  influence hazardous constituent  transport and
fate are listed for consideration in assessing actual releases.


Mechanisms Affecting Transport

    A number of environmental transport and attenuation mechanisms that are
applicable to soil contaminant releases are influenced by physical and
chemical properties of the hazardous constituent.  Additionally, soil
conditions and other environmental factors will influence the action of these
mechanisms on a site-specific basis.  A general description of these transport
mechanisms follows:

    Adsorption to soil materials can immobilize contaminants or slow their
movement through soil (attenuation).  Factors influencing adsorption include
soil types, charged sites and ion exchange capacity of the soil materials,
structure and charge of the hazardous constituents released, and chemical
solubility and volatility.  Tendency for adsorption to soil organic matter can
be estimated for some organic chemicals by using the log of the octanol/water
partition coefficient (KQW).  In addition, high solubility or volatility
could be expected to decrease adsorption tendency; therefore, these parameters
should  be evaluated.

    Volatilization  from soil may occur at soil surfaces or through pore
spacings in unsaturated soils.  This mechanism may remove hazardous
constituents from the soil medium via transport into the air medium or may be
a means by which contaminants move through the unsaturated soil medium.
Factors influencing volatilization include soil pore space size, adsorption to
soil, aqueous solubility (in wet soils), and general volatility.  Physical and
chemical parameters that can be used to estimate potential to volatilize
from/in soils include vapor pressure, KQW, aqueous solubility, and Henry's
Law constant.  The Henry's Law constant expresses the equilibrium distribution
of a compound between air and water and indicates the relative ease with which
the compound may be removed from aqueous solution.  None of the individual

paramelers is adequate to predict volatilization from/in soil owing to the
complexity of the medium; rather, the factors considered together produce a
general overview of likely behavior.

    Dissolution or solubilization of organic and inorganic hazardous
constituents may occur in the presence of water from rainfall or other
contaminants present (solvents) that result from co-release of such
materials.  For inorganics, dissolution will depend primarily on the
solubility of the compound form released, and the pH and ionic strength of the
rainfall or solvent solution introduced.  Solubility data for inorganic
constituents can be found in standard reference works of Weast (1977-78)  and
Dean (1979).  For organic constituents, aqueous solubility values are also
often available from standard reference works.   In addition, the K   can be
used to assess a compound's relative preference for the neutral organic phase
(octanol) and the polar aqueous phase (water).   This can be used as an
indicator of potential migration induced by infiltrating rainwater/solvents
relative to a compound's tendency to remain adsorbed onto soil organic matter.

Mechanisms Affecting Fate

    Another group of mechanisms to which hazardous constituents may be
subjected are primarily involved in determining the environmental fate of
these compounds.  Rather than directing the migration of the compounds within
and between media, these fate mechanisms determine persistence or rates of
degradation.  In general, susceptibility of hazardous constituents to these
fate mechanisms is documented by empirical evidence (case studies and research
projects) rather than prediction based on physical/chemical parameters.  If
such empirical information is not available in chemical profiles or Callahan
et al.  (1979), some generalizations can be made based on compound class,
chemical structure, and using some physical and chemical properties for
support.  Because of the complexity in assessing the significance of
environmental fate mechanisms, each is discussed in some detail with general
guidelines provided, where possible.  In most cases, however, it is more

relevant to discuss the significance of the mechanisms in a given medium to
the individual compound class or type; as appropriate, this is the approach
followed here.

    Biodegradation can occur in the soil medium or in aqueous media to which
hazardous constituents may be transported.  The most important factor to
consider in evaluating the role of biodegradation is that it is dependent on
local environmental conditions and a native microbial population capable of
metabolizing the hazardous constituents of concern.  Therefore, it may not
occur at any given site, and its occurrence would be difficult to predict
without bench scale tests.
    Surface and shallow soils are generally expected to support aerobic
degradation due to their proximity to the atmosphere and high oxygen levels.
Deeper soils  (in the saturated zone) may support either aerobic or anaerobic
degradation depending on dissolved oxygen levels in the associated ground
    Factors which  influence the rate of biodegradation in soil include:
amount of water present; temperature; soil pH; aeration or oxygen supply;
nutrient availability (N,P,K,S); soil texture and structure; and the nature of
indigenous microflora (if any).  In addition, properties of the hazardous
constituents  (i.e., wastes) themselves as they interact with soil are
important and include:  chemical composition; physical state (liquid, slurry,
or sludge); carbon:nitrogen ratio; water content and solubility of waste;
chemical reactivity or dissolution effects of the waste on the organic matter
present in the soil; volatility; pH of the waste; biological oxygen demand
(BOD); and chemical oxygen demand (COD).  This information is more readily
available in  literature on land treatment, and is of greater utility for land
farming situations than for releases from other types of SWMUs.  For further
information on the relevance of these waste and soil characteristics to
biodegradability refer to Parr, et al. (1983); this document is, however,
primarily directed at land farming operations.
    A more general discussion and overview on biodegradation is provided in
DeRenzo (1980) as  the result of experimentation on chemical mixtures.
Generalities of biodegradability (DeRenzo, 1980) are as follows:

    •    Nonaromatic  or cyclic  compounds are preferred over aromatics.

    •    Materials  with unsaturated  bonds in their molecules (e.g.,  alkenes,
         alkynes,  tertiary amines,  etc.) are preferred over materials
         exhibiting saturated bonding.

    •    The comparative stereochemistry of certain compunds make them more or
         less susceptible to attack by microbial enzymes.   The n-isomers of
         the lighter weight molecules are preferred over branched isomers and
         complex polymeric substances.

    •    Soluble organic compounds  are usually more readily degraded than
         insoluble materials.  Biological waste treatment  is most efficient in
         removing dissolved or  colloidal materials which are more readily
         attacked by enzymes and transported through cell  membranes.  Readily
         dispersed compounds are usually degraded more rapidly because of the
         increased surface area that is presented to the individual
         mic roorganisms.

    •    The presence of key functional groups at certain  locations  in the
         molecules can make a compound more or less amenable to
         biodegradation.  Alcohols,  for example, are often more readily
         degraded than their alkane or alkene homologues.   On the other hand,
         halogenation of certain hydrocarbons may make them resistant to

    Similar generalities correlating substituent groups and biodegradability

(Howard, 1975) are as follows:

    •    Alcohols, aldehydes, acids, esters, amides, and amino acids appear to
         be more susceptible to microbial attack and breakdown than the
         corresponding alkanes, olefins, ketones, dicarboxylic acids,
         nitriles, amines, and  chloroalkane groups.

    •    Meta-substituted phenols were found to be usually more resistant to
         biodegradation than the ortho- or para-isomers.


    Photolysis is primarily a significant fate mechanism only for organic

compounds in the air medium.  However, photolysis may also occur on soil

surfaces or in shallow surface  waters to the depth of penetration of

sunlight.  Alteration or degradation of organic constituents may occur by

direct or indirect photolysis.   Direct photolysis is the reaction of the

compound as a result of its absorbing ultraviolet (UV) radiation.   Indirect,

or sensitized, photolysis occurs when the UV energy is transferred  via another
chemical species.

    Predicting a hazardous constituent's potential for photodegradatiqn
requires a knowledge of that constituent's tendency to absorb UV light.  Some
reference works on compound degradation (Callahan, et al, 1979) contain
information on priority pollutant compounds including UV absorption maxima for
many.  Having an absorption maximum in the UV range could indicate potential
for photodegradation.
    Empirical information on environmental photolysis is usually limited to
photo-oxidation in the ambient atmosphere.  These studies done in smog
chambers and in the presence of oxidants such as nitric oxide (NO) and ozone
are not relevant to photolysis of hazardous constituents in soil, primarily
because such oxidants would not be present at the soil surface.  Photolysis
would not be expected to be a significant fate mechanism for hazardous
constituents in soil; rather, it could be important for constituents that have
volatilized from soil.

    Chemical oxidation of organic compounds, for the most part, uses
mechanisms which involve free radicals or singlet oxygen compounds.
Generally, phenols,  aromatic amines, olefins and dienes, and alkyl sulfides
are  the most susceptible to oxidation in soil and water systems.  Oxidation of
saturated compounds  and their haloalkane, alcohol, ketone, and ester
derivatives occurs slowly in these media and is not significant as a fate
mechanism for  these  compound classes (Dilling et al, 1976).
    Oxidation of inorganics is dependent on the presence of compounds in the
soil capable of oxidizing the inorganic hazardous constituents released.  In
general, extremely strong oxidizers will not be present in soil because of
their rapid reaction with moisture or soil organic matter.  Of primary concern
would be oxidizers co-released with other hazardous constituents.  If proper
handling and disposal practices have been followed, this event would be
unlikely.  Refer to  40 CFR Part 264, Appendix V, for examples of potentially
incompatible wastes, including oxidizers.  It should be noted for inorganics,
particularly elemental metals, that oxidation would tend to dissolve the
hazardous constituent and permit mobilization into the aqueous phase rather
than resulting in its degradation.

    Precipitate formation is-the interaction of dissolved species that exceed
their solubility product constant (K  ) and form a solid that settles out of
solution.  Precipitates of metal ions that are most likely to occur in the
environment are sulfides, carbonates, and hydroxides that will form when these
anions are present at elevated concentrations.  Precipitate formation is also
dependent on temperature and pH.
    The tendency for metal precipitates to form in a given environment can be
used as an indicator of potential attenuation of metal-containing releases.
Metals that are compound forms of sulfides, carbonates and hydroxides are
likely to transport more slowly than more soluble metal salts.  These latter
compound types could be leached more readily by rainwater infiltration through
soils and could thereby be transported to the ground water medium.

    Hydrolysis of organic compounds can result from a neutral reaction with
water, or it can be catalyzed in the presence of an acid or a base, with the
end result being the replacement of a functional group (-X) by a hydroxyl
group (-OH).  In soils, the structure-activity rates for hydrolysis are hard
to predict.  They depend on complex pH conditions at the soil surface, the
influence of metal-ion catalysis, and the presence of such functional groups
as phenols, amines, or sulfides in the soil which could lead to catalysis.


    A number of physical and chemical properties of a hazardous constituent
can be used as indicators of the compound's probable environmental behavior.
It should be recognized that these properties are most relevant to the
transport mechanisms such as adsorption, volatilization, and dissolution.
Most are only pertinent to organic compounds and classes; an exception is
aqueous solubility which is also important (and available) for inorganic
compounds.  The most useful properties and their application to assessing
potential envrionmental transport are described in some detail with examples
of their use given as appropriate.  To actually find the values of the
parameters for hazardous constituents that may be released from SWMUs, refer


to Che Health Effects Assessments (HEAs) prepared for the Offic.e of Emergency
and Remedial Response (OERR) or the Toxicity Profiles prepared for OWPE.
These profiles contain chemical/physical property data, information on
toxicity and other health hazards, and as available, information on
environmental transport and fate.  Additional sources of portions of this
information are Callahan, et al. (1979), Verscheuren (1983), Dean (1979), and
Weast (1977-78).  The last two references will be very important for obtaining
solubility data specific to inorganic compound forms.

Vapor Pressure

    Vapor pressure is the pressure exerted by a gas in equilibrium with its
solid or liquid state at a given temperature.  Generally, values are reported
for 20° to 25°C, typical ambient air temperatures, and consistent with
evaluating the transport of hazardous constituents released to soils.  Vapor
pressure values are for the pure compound and represent maximum values under
equilibrium conditions; the vapor pressure of a chemical is always lowered
when  it is dissolved in another substance.  However, vapor pressure can be
used  as an indication of the volatilities of hazardous constituents released.
High  vapor pressure (>10 torr) would suggest significant potential to volatize
while low vapor pressure (<0.01 torr) suggests low volatility.  By combining
vapor pressure data with aqueous solubility and adsorption tendency, one can
determine whether a constituent is more likely to be transported in the air,
water or soil medium, thereby providing focus in the evaluation of a
constituent's likely movement and environmental fate.

Vapor Density

    Vapor density describes the mass per unit volume of a gas at its
equilibrium vapor pressure as described above.  It is often given relative to
the density of air, defined as unity, so that one can determine the behavior
of the gas upon release from the solid or liquid phase.  If the density is
significantly greater than unity, the gas will remain at the surface of the
source and will be transported along the ground.  If toxic in nature, it may
thereby pose a potential health hazard.  If the vapors are released below soil

surface, they may remain there rather than rising through the pore spacings  to
volatilize away from the surface soils.  If the vapor density is less than or
equal to unity, the gas will rise and disperse easily.

Water Solubility

    Water solubility describes the mass of a compound that dissolves in or is
miscible in water at a given temperature and pressure, usually 20° to 25°C and
one atmosphere, and usually expressed in mg/L or ppm.  Water solubility is
important because it indicates a compound's affinity for the aqueous medium.
High water solubility permits greater amounts of the compound to enter the
aqueous phase and, therefore, be removed from the soil environment.  High
solubility is indicative of an increased tendency to leach from soil media
while low solubility would indicate a tendency to remain adsorbed onto the
solid phase (i.e., soil).  This property is particularly significant when
determining whether a release will remain relatively immobile on soil in the
unsaturated zone or whether it will migrate readily to the saturated zone via
rainwater infiltration.  Solubility can be used to establish the potential of
a hazardous constituent to enter and remain in the hydrological cycle.  One
might then focus on movement and reactions of the constituent in ground and
surface waters rather than pursuing volatilization and soil adsorption as
primary transport mechanisms and thus potential exposure routes.
    Aqueous solubility can also be related to fate mechanisms including
biodegradation.  Compounds having high aqueous solubility are generally more
biodegradable  than insoluble compounds, because the former are more readily
available to microorganisms in aqueous media.  Compounds with low aqueous
solubility are often less biodegradable and tend to bioaccuraulate and adsorb
to soil organic matter.

Log Octanol/Water Partition Coefficient

    The log of the octanol/water partition coefficient (K  ) is a measure of
the relative affinity of a compound for the neutral organic and inorganic
phases  represented by n-octanol and water, respectively.  It is calculated
from a ratio (P) of the equilibrium concentrations (C) of the compound in each

                       P = -7	, and K   = log P.
                            C.             ow

The K   has been directly correlated to a number of  factors for determining
environmental fate and transport.  These include adsorption on soil organic
matter, bioaccumulation, and biological uptake (Chiou,  1983,  1979 and  1977).
It also bears an inverse relationship to aqueous solubility.  The K    of a
hazardous constituent is very important for evaluation  of adsorption on
various soil types with its resulting effect on degradation.  The greater the
soil adsorption and immobilization, the slower the constituent will transport
to aquifers and surface waters.  Organic constituents with an aqueous
solubility of less than 5 ppm and KQW of greater than 5 tends to accumulate
in river sediments (Lopez-Avila, 1979), and some degree of adsorption  on soil
organic matter would be expected for constituents with moderate solubility
(approximately 1,000 ppm) and KQW = 2.  It is essential to note that KQW
indicates potential for adsorption only on the organic matter portion  of a
particular soil or sediment.  It does not correlate  to adsorbability by soils
that are primarily inorganic (i.e., clays and minerals).
    To use a constituent's KQW  to determine environmental transport and
fate, one should determine whether soils near the release are likely to have
low, medium, or high organic matter content.  This is discussed in more detail
later  in this section.  If sufficient organic matter is present at the release
location to  suggest possible adsorption, one should  then examine the K  of
the hazardous constituent released.  If the KQW is less than 2, adsorption
will not be  a significant attenuation mechanism for  the hazardous
constituent.  If KQW is between 2 and 4, some adsorption may occur; and if
K   is greater than 4, adsorption onto soil organic matter is expected to be
significant  in immobilizing the hazardous constituent.

Henry's Law Constant

    The Henry's Law constant of a compound is the relative equilibrium ratio
of a compound in air and water  at a constant temperature.  It is more
significant  to releases to water but may be considered  where water is  present
on the soils or accumulated nearby.  The Henry's Law constant can be estimated


using the vapor pressure, aqueous solubility, and molecular weight of the
compound (Thibodeaux, 1979).  It is often.reported in units of atra-ra /mole.
The Henry's Law constant expresses the equilibrium distribution of the
compound between air and water and indicates the relative ease with which the
compound may be removed from aqueous solution.  Increasing value of the
Henry's Law constant indicates increasing favorability of volatilization as a
transport mechanism.  In addition, the constant provides more information than
a comparison of vapor pressure and aqueous solubility.  It is emphasized,
however, that this constant is representative of equilibrium conditions for a
pure chemical compound and may not accurately predict behavior under actual
environmental conditions.

Other Physical Properties

    Several additional physical properties influence environmental behavior
and can be used to supplement evaluations based on the properties discussed
above.  Two of these properties, melting point and boiling point, are obvious
in their use.  These two properties indicate the physical state of the
hazardous constituent at standard conditions.  This will be the basis for
looking at how a hazardous constituent release may migrate.  Use of physical
state information is discussed later in this section.
    Molecular weight is another property that can be used to assess potential
transport  if more specific chemical and physical property  data (i.e., K
Henry's Law constant) are not available.  The use of molecular weight in
assessing hazardous constituent transport and fate is somewhat less obvious
than for some properties, and warrants a brief discussion.  Molecular weight
relates  to the size and density of the molecules of a compound.  All other
factors being equivalent (i.e., adsorptive surface, compound polarity, atomic
charge, etc.), a higher molecular weight, and thus larger compound, will
adsorb more strongly to another material than will a smaller compound.
Therefore, if one could generalize behavior by assigning a constituent to a
particular structural class, one could (based on size) extrapolate behavior of
the constituent in question relative to those members of the class for which
empirical data are available.  It should be noted that molecular weight  is
only a secondary factor  in assessing adsorption and that it should only  be
used in conjunction with other constituent properties.

    Viscosity is another physical property that will significantly influence
hazardous constituent migration in the soil medium.  Liquid compounds with
high viscosity would move more slowly through soil than would liquids with low
viscosity.  However, to obtain numerical values of this property," one would
have to access reference works that may not be readily available.  Therefore,
it is recommended that the reader consult the HEAs or toxicity profiles for
the hazardous constituent in question to determine whether the general
description provides an indication of viscosity.  It is probable that
constituents exhibiting high viscosity will be so noted.  Otherwise, a
conservative assumption is that the viscosity would be comparable to water and
that the  liquid hazardous constituent would potentially move through soil at a
rate comparable to water.


    Hazardous constituent transport and fate is a highly complex process and
cannot be accurately predicted with information that is readily available.
However,  by combining information on the chemical and physical characteristics
of  the hazardous constituents released with site-specific information, such as
soil types, climate, and release area activity patterns, it is possible to
generalize potential transport and fate.  This can then provide the basis for
estimating potential exposure and risk posed by the release; it can also
direct the efforts  of further data gathering to focus on locations and media
of  primary concern.  The following is a summary of items to be considered in
assessing potential  transport and fate of a hazardous constituent release.  It
attempts  to lay out  in step-wise fashion a logical approach to collecting and
evaluating relevant  information.  It is not intended to provide exact answers
for all constituent  releases.

Type of Hazardous Constituent Released

    •     Does this hazardous constituent belong to a class or type of compound
          for which previous environmental behavior has been documented or

              Very  often,  if  a  constituent  can  be  classified  or. grouped with
              similar  compounds,  for  which  empirical  data  are available,  the
              behavior of  an  unknown  constituent can  be  estimated based on
              these structural  or physiochemical similarities.   Table A-l
              lists organic compound  classes  and generalizes  what is  known or
              postulated about  their  environmental behavior following release
              to soils.  Inorganic hazardous  constituents  are primarily
              metals,  and  their environmental behavior cannot as easily be
              generalized.  Therefore,  they have not  been  addressed in this
              table, but guidance on  clay  sorption and huraic  complexes of
              metals are provided later in  this section.

         What are the  physical  and chemical properties of  the constituents)
         which may  influence  transport  and  fate?

              As previously discussed,  certain  physical  and chemical
              properties can  be used  to estimate transport of a constituent
              following release to soil.  Table A-2 lists  some  of these
              properties and  broadly  applies  ranges of values that may result
              in the specified  behavior.  Note  that other  factors such as the
              presence of  certain functional  groups and  site-specific
              environmental factors may alter actual  transport  from that
              expected when considering only  physical and  chemical
              properties.  Relevant properties  for individual chemicals can be
              found in HEAs available from  OERR, Callahen  et  al.  (1979),
              Verscheuren  (1983), Weast (1977-78),  and Dean (1979).

         What is the physical form of the hazardous constituents) released?

              Whether  the  release is  liquid,  solid or semisolid,  such as
              sludge,  the  physical form of  the  release can strongly influence
              transport.   If  the release is a solid and  remains solid under
              ambient  conditions, then it  could remain on  the soil surface
              unless mobilized  by dissolution in rainwater or other hazardous
              constituents (solvents) or by entrainment  in ambient air (as
              could be caused by wind or similar action).   If the release is a
              liquid,  it  is  likely to move  below the  soil  surface at  rates
              dependent on its  viscosity and  adsorptive  tendencies.   If the
              release  is  a seraisolid, it may  separate into two phases that
              will  tend to be mobilized at  different  rates and possibly by
              different mechanisms.
Location of Release
         Characterize the location of the release as fully as possible.   Use
         the categories below for guidance.

              chemical activity - What chemicals used in the area could act to
              mobilize the hazardous constituent released?  Have any such
              chemicals been released in the area where the hazardous
              constituent(s)  in question were released?  What are the chances
              of future releases of solvents in the same area?  Chemicals of
              concern would include:


Compound Claaa
Aliphatic hydrocarbona
Aromatic hydrocarbona
Halogenated aliphatic*
Halogenated aromatica
Nitro/nitroso compounds

Amines/ amides

Cyanidea/azo compounds

Bi-phenyl compounds
Polynuclear aromatics (PAHs)

Carbamate insecticides

Phenoxy acids, esters, salts
Organophoaphorus compounds
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Low to moderate

Low to moderate

Low to moderate

Moderate to high
Moderate to high

Data not available

Moderate to high
Moderate to high


Low except in pre-
sence of acid or
for cyanogen halide


Moderate to high
Moderate to high
Moderate to high
Moderate to high
Moderate to high

Moderate Co high




Moderate to high
Moderate to high
Bio trana format ion
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Varies with compound;
moat low; residues
2 to 10 months in soil
Varies with complexity
of compound; simpler
are more readily
Low to moderate

Low to moderate
Low; trana forma t ions
occur within the
cyclodiene class
Data not available

Low to moderate
Moderate to high
Chemical Reaction
Generally very slow in *oil
Generally very (low in soil
Generally very slow in soil
Generally very slow in soil
Low to moderate
Low to moderate

Possible; significance unknown

Possibly moderate

Low to moderate
within the cyclodiene class

Known to degrade in soil; rates
and significance unknown
Moderate to high (hydrolysis
Moderate to high


to soil
Leaching from/
through soil
from soil
Octanol/water Parti-
tioning (Kow)
Soil typeb
Aqueous solubility
Vapor pressure
Henry's Law constant
Range and Susceptibility
Low Moderate High
<2 2 to 4 >4
Mineral Clay Organic Matter0
<10 mg/1 1,000 mg/1 > 10, 000 mg/1
£0.1 torr 1 torr >10 torr
-4 atm-m3 -3 -2 atm-m3 -1 0 attn-m3
-U mole 1U C° IU mole 10 tO 10 mole
      aSummary table for general guidance only; does not consider functional groups or multiple chemical

      "While not actually a chemical property of a hazardous constituent, the soil type is incuded here
       because it is highly significant to transport of a substance released to the soil medium.

      cThe soil organic matter content (low, medium, or high) relates to likelihood of adsorption based
       on Kow predictions.

     chlorinated solvents;
     aliphatic and aromatic hydrocarbons;
     water;  and
     aqueous solutions of any of the above.

Climatic Conditions - What are the typical climatic conditions
for the region and how could they influence transport and fate?

—   Annual Rainfall - Rain could act as a dust supressant  for
     soil-adsorbed hazardous constituents; in arid climates,
     generation of contaminated dust would be more likely.  Rain
     could act as a solvent for soluble or slightly soluble
     compounds; infiltrating rain could leach hazardous
     constituents out of the soil and transport them to ground
     water.   Surface run off from rainfall could mobilize
     contaminated particles and move the contaminated soil via
     overland flow.

—   Temperature - Volatilization will increase with increasing
     temperature.  In hot weather, greater amounts of volatile
     and semivolatile hazardous constituents would migrate from
     soil into the vapor state.

—   Prevailing Wind Direction/Magnitude - Assessment of
     potential transport via fugitive dust requires knowledge of
     the magnitude and direction of prevailing winds.  A wind
     rose, as required in the Part B permit application,
     provides data by which to evaluate transport of dust and to
     indicate where contaminated dusts would be most likely to
     be carried.

Physical Characteristics of Release Location - Are there
conditions in the release area that will influence transport and
fate of the hazardous constituents?

—   Vegetative Cover - Plants growing in the area of the
     release can help reduce mobility of contaminated soils by
     affording protection from wind erosion or light traffic
     (foot) generation of dusts.  Plant roots can hold soil so
     that channeling is minimized and surface runoff does not
     carry large amounts of contaminated soil from the release

     Surface Drainage Patterns - Surface water (or runoff) flow
     patterns over the release area should be studied to
     determine whether runoff is moving into or out of the
     area.  If significant runoff flows through the contaminated
     area, there is a greater chance of movement of the
     contaminated soils and also a greater chance of leaching of

          soluble  or  partially  soluble  compounds.   Channeling or
          manmade  drainage  ditches  in the  area  of  the discharge are
          of  special  concern.

          Saturated or Unsaturated  Soils - The  amount of moisture in
          the soil will influence whether  constituents can volatilize
          through  pore spacings or  whether they will be hindered by
          an  inability to dissolve  in the  aqueous  phase.  For soluble
          constituents, saturation  can  be  a means  of transport by
          leaching the hazardous constituents  from soil.  In moist,
          unsaturated soil, the soluble constituents may dissolve but
          remain associated with soil particles through the
          adsorption  of water onto  the  particles.

     Human Activity - Do people utilize the area near the release in
     such a way as to enhance mobilization of  the  hazardous
     constituents? Are heavy equipment and other  vehicles operated
     in the area capable of generating  dust containing contaminated

Is the release to  surface soil  or the subsurface?

-    This question is important because releases to surface and
     subsurface soils present different risks  of exposure and are
     subject  to different transport mechanisms. A release to
     subsurface soils generally does not present a significant hazard
     from exposure to the soil  itself;  rather,  hazardous constituents
     may move through the soil  resulting in exposure via other media
     such as  air (vapor transport  through  pore  spacings) or ground
     water (dissolution in aqueous  medium). Exposure to surface soil
     releases can  be  by direct  contact, ingestion  or inhalation of
     airborne particulate.  This latter exposure could be caused by
     wind action on contaminated soil or by activity within the
     contaminated  area causing  dust to  be  generated.

What types of soil are present  in  the area of  the  release?

     The  type of soil to which  a hazardous constituent is released
     will strongly influence the transport of  that constituent.  For
     organic constituents, a parameter  used to assess soil adsorption
     is the Kow; this value has been correlated to adsorption on
     soil organic  matter (Chiou, et al, 1979 and 1983).  Therefore,
     the  organic carbon content of  the  soil is significant in
     assessing transport.  Because  actual  data are often not
     available, one can look at whether the release is to a subsoil
     (organic carbon content of 2  to 4  percent), topsoil (organic
     carbon content of 12 to 18 percent),  or to a  peat type soil
     (organic carbon content often  greater than 50 percent).
     Additional soil type information relevant to  assessing transport
     would be whether the soils were comprised of  clay or mineral
     materials.  Minerals would be  expected to have a rather
     insignificant ability to adsorb organic or inorganic hazardous


              constituents and attenuate their movements.  However, clay soils
              with their high surface area and frequently large number of ion
              exchange sites could be expected to adsorb both organic and
              inorganic constituents.  Figure A-l provides estimates (Forstner
              and Wittman, 1979) of bonding strength of several heavy metals
              (1) adsorbing onto and into clay lattice structures and (2)
              forming insoluble complexes with natural organic materials
              (humic substances).
Checklist for Assessment of Transport and Fate

    A listing of the information discussed above is provided in Figure A-2 as
a checklist for investigating releases to soil from SWMUs.  The two major
categories of information that are needed are physical and chemical
characterization of the hazardous constituent release and characterization of
the location of the release.  Primary sources of this information are the
facility's Part B permit application including the Exposure Information Report
(EIR) and the Health Effects Assessments (HEAs) available from OERR.  These
must be supplemented by site specific information obtainable from a facility
inspection and, as necessary, by chemical data from standard reference works.
    Information on chemical composition of wastes handled at the SWMU at which
the release occurred should be available in the Part B permit application.
This will indicate the chemical compounds that may be expected in the release
and may possibly indicate the physical form of the release (i.e., solid,
liquid, sludge).  Chemical  information on the specific compounds released must
be obtained from the HEAs supplemented as necessary by standard reference
    Information on the location of the release must be obtained in part from
the RCRA facility's (i.e. SWMUs) Part B permit application but with extensive
input obtained during an onsite inspection and/or from interviews with
facility personnel.  Human  activity patterns in the area of the release and
the handling of potentially reactive wastes should be elucidated from
information required in the Part B permit application and the EIR.  Other
relevant information that should be obtained from these same documents
includes rainfall data, prevailing wind direction (wind rose),  and surface
runoff and drainage patterns.  The EIR should also include information on site
conditions that could substantially affect transport and fate (e.g.  high water
table, porous soils, etc.).


     Empirical affinity series for ion exchange adsorption

          Pb > Ni > Cu > Zn

     Strength of incorporation into clay lattice structure

          Strong:  Cu, Fe, Ag

          Moderate:  Pb,  Mn, Zn, Co

          Weak:  Cd


     Bonding strength

          UO2,* > Hg2* > Cu2+ > Pb2+ > Zn2* > Ni2+ > Co2+

     Complex stability series for soils

          Pb > Cu > Ni >  Co > Zn > Cd > Fe > Mn

     Complex stability series for metal-humic substances

          Strong:  Cu, Sn, Pb

          Moderate:  Zn

          Weak:  Ca, Mg,  Mn, alkali metals
        Figure A-l.  Metals Adsorption  and  Complex Formation.


1.   Compound type or class

2.   Functional groups present

3.   Relevant chemical/physical properties

     a.   Aqueous solubility
     b.   Octanol/water partition coefficient
     c.   Henry's Law Constant
     d.   Vapor pressure
     e.   Vapor density
     f.   Other physical properties

4.   Physical form of release


1.   Characteristics of the area

     a.   Chemical activity (existing or potential release of other
          reactive chemicals)
     b.   Climatic conditions
          (1)  annual rainfall
          (2)  temperature
          (3)  wind rose
     c.   Physical characteristics
          (1)  vegetative cover
          (2)  surface drainage patterns
          (3)  saturated or unsaturated soils
     d.   Human activity (potential soil disturbances)

2.   Release to surface or subsurface soils

3.   Soil types at release location

     a.   Mineral
     b.   Clay
     c.   Organic matter content
          (1)  low (subsoil, sandy soil)
          (2)  medium (top soil, loamy soil)
          (3)  high (peat)
      Figure A-2.  Checklist/Summary for Assessment of Potential
                   Transport and Fate.



    Potential transport and fate of hazardous constituents released to the
soil can be estimated by following the procedure that has been outlined in
this appendix (Appendix A).  The need for such an assessment is twofold.
First, a determination of the transport pathways and migration potential of
the hazardous constituent is necessary for one to identify potential exposures
to nearby populations and environments.
    Second, migration, persistence, and potential exposure can be used to
assess the need for and effectiveness of proposed corrective actions.   For
soil releases and exposures to the soil medium, the transport pathways of
concern include soil transport via surface runoff,  fugitive dust, adsorption
with immobilization on surface soils, and uptake by biota.  If the hazardous
constituents are expected to migrate to other media (e.g. volatilization to
ambient air, dissolution in surface water or ground water), refer to the
individual guidance documents for those media (GCA, 1985a; GCA, 1985b;
E. C. Jordan, 1985).  However, if the hazardous constituents remain in the
soil medium and are expected to transport via the pathways listed above, one
should consult the remainder of this guidance document.  Appendix B provides
information on conducting an exposure assessment for a hazardous constituent
release to soil.  It explains what constitutes an exposure assessment and what
information is needed to conduct qualitative and quantitative exposure
assessments.  General procedures for hazard and risk assessment are also
discussed in Appendix B.

                                  APPENDIX  B
                              EXPOSURE ASSESSMENT


    This section has been prepared consistent with  the EPA  guidance  set  forth
in the following documents:

    •    Schultz, et al., Draft  Supertund  Exposure  Assessment  Manual,  prepared
         for the U.S. EPA, Office of  Toxic Substances, August  17,  1984.
    •    EPA, 1984c and EPA,  1985.
    •    ICF, Inc., Draft Superfund Health Assessment  Manual,  prepared for the
         U.S. EPA, Office of  Emergency and Remedial Response,  May  22,  1985.

    Other sources ot information used in preparation of  this section are
presented in the references section of this  report.
    Pending publication of guidance specific to RCRA enforcement,  two of these
documents (e.g. Schultz, et al., 1984; ICF,  Inc.,  1985)  developed  for use in
assessment under CERCLA represent the best available information for
assessment of public exposure (and risk) resulting  from  soil releases.
Although these documents primarily concern human population exposure (and
risk) assessment, they also provide  the basis  for evaluating exposure (and
risk) to non-human populations.
    The purpose of the exposure  assessment is  to determine all routes of
exposure to human (and non-human) populations  resulting  from hazardous
constituent releases to soil  and other environmental media contaminated as a
result of transport from the  soil medium.   Determination of whether or not
exposure to humans (or other  receptors) will occur at a  source at-present or
in the future typically involves determination of:

    •    the fate and transport of hazardous constituents to soil and" other
         related environmental media through identification of likely pathways
         of constituent release and transport from identified sources,  and,
    •    human (and non-human) populations at risk o-f exposure to hazardous
         constituents in soil and related environmental media through
         identification of activity patterns near the source or point of

    Appendix A provides guidelines for evaluating transport potential and fate
of releases of hazardous constituents to soil.   Appendix B will focus on
evaluating exposure to human (and non-human) receptors from identified
releases and will provide guidance on conducting exposure assessments.
    The following six subsections of Appendix B describe the components
necessary for exposure assessment, and provide  guidance for the selection and
performance of an appropriate exposure assessment methodology.  The first
subsection will concern exposure pathway analysis, and will provide guidance
for identifying exposure pathways and determining whether pathways are
complete.  Determination of complete exposure pathways will establish the
course of subsequent exposure analysis.
    Subsection 2 will discuss the types and levels of exposure analysis for
the permit writer to consider.  Exposure assessments can be either qualitative
or quantitative; however, regardless of the method or level of assessment
employed, the outcome ot the exposure analysis  terms as a basis for
characterizing risks to human health associated with exposure.  Exposure
assessments which are qualitative in nature are usetul because they target key
pathways and routes of human exposure, and therefore can be used to derive
qualitative estimates of human risk associated  with exposure.  Exposure
assessments which are quantitative in nature are useful because they also
identify significant pathways and routes of human (and non-human) exposure,
and quantify actual human intake, thus establishing baseline conditions for
quantitative risk assessment.
    Subsection 3 will discuss the rationale for selecting and performing
qualitative or quantitative exposure analysis.   Informational requirements for
each level ot analysis will be described in detail to assist the permit writer
in selecting the most appropriate method.

    Subsections 4 and 5  will describe in  detail  the necessary steps f-or
performing qualitative and quantitative exposure analysis,  respectively.  Uses
of exposure information  from these various levels of assessment (e.g.
qualitative or quantitative) will also be discussed in these sections.  In
particular, guidance will be provided to  assist  the permit  writer in utilizing
derived exposure information for two purposes:

    •    to determine the level and means of corrective actions necessary to
         adequately reduce human exposure (and risk) associated with
         identified release ot hazardous  constituents to soil,  and
    •    to provide an approach for evaluating public health impacts
         associated with such releases to soils.

    The sixth and final subsection will describe the risk characterization
process.  Guidance will be provided to assist the permit writer in
characterizing risks to human (and non-human) populations associated with
exposure to hazardous constituents.  Methodologies, informational
requirements, and limitations of risk characterization processes will also be


    Assessment of exposure to human (and  non-human) populations (e.g.
receptors) proceeds directly from identification of complete exposure
pathways.  A complete exposure pathway has the  following four necessary
components: (Da source of chemical release into the environment, (2) an
environmental transport medium (e.g. air, surface water) for the released
chemical, (3) a potential exposure point, and (4) a human (or non-human)
exposure route at the contact point.  Identification ot exposure pathways
establishes the course of subsequent exposure analysis.  Thus,  the permit
writer should focus on identifying exposure pathways and determine whether the
pathway is complete.  Pathways which are  complete (e.g. where a release,
movement of hazardous constituents through environmental media, and likelihood
of human or non-human exposure are all evidenced), will require exposure
characterization so as to qualify or quantify the magnitude, frequency, and


duration of human exposure to contaminated media.  Pathways which are'not
complete will, in most instances, be eliminated from further analysis, or may
identify existing data gaps which must be filled in order to assess more
conclusively the potential for and impact of human exposure via those
pathways.  Guidance for determining potential exposure pathways is provided in
Table B-l.  For further guidance in the determination and evaluation of
potential exposure pathways, the reader is referred to ICF, Inc., 1985.


    Depending on the available information and the permit writer's need,
varying levels of exposure assessment can be performed.  Basically, exposure
assessments can be either qualitative or quantitative.   Assessments which are
qualitative are referred to as level I analyses, while  those which are
quantitative are referred to as level II (or level III) analyses.  In general,
a level I analysis is a qualitative evaluation which provides a preliminary
screening of on-site hazardous constituent release sources, environmental
pathways through which constituents migrate off-site, and possible human (and
non-human) population exposure points and mechanisms.  A level I analysis
gives an indication of the nature and extent of public  health threats
resulting from exposure to a hazardous constutuent source.  Level II
(quantitative) analyses develop estimates of the quantities of the release
(e.g. mass loading) ot chemicals of concern from sources identified in level
I, and considering hazardous constituent transport and  environmental fate,
estimate the degree of potential population exposure (and risk) resulting from
exposure.  Level II exposure analyses also allow for estimation of intake (or
dose) incurred by human (and non-human) receptors.  A further refinement of a
level II analysis is also possible given the degree of  sophistication ot
existing data.  This very detailed analysis is referred to as a level III
assessment.  In level III assessments, those key hazardous constituent release
and exposure scenarios targeted in level II are quantitatively analysed in
detail.  It is basically an indepth level II analysis,  although the analytical
tools necessary for the analysis are more resource intensive than those
required for level II analysis, and the results are of  significantly greater

                                                   Name  of  Source:

      Release          Release             Exposure              Exposure
 Source/Mechanism	Medium	Point	Route	

1.  Contaminated      air media        nearby  playground     inhalation (pos-

    surface soil                       	     sible reingestion

1.  List release source.

2.  List release medium.

3.  Describe the nature of the exposure point.

4.  List exposure route:  e.g. ingestion,  inhalation,  dermal contact,
    including possible indirect routes, such as uptake by biota and subsequent
    ingestion by humans.


    List all major assumptions in developing the data for this worksheet:

Source:  ICF, Inc.,  1985.               B-5

accuracy (e.g. computer modeling or environmental monitoring).  The
characteristics of each level of analysis are briefly summarized in Table B-2
(Schultz, et al., 1984).


    The determination of which level of assessment is appropriate for
evaluation of a hazardous constituent release to soils (or other environmental
media) will ultimately be a judgement decision by the permit writer;  however,
the selection should be based on criteria associated with the baseline
conditions of the hazardous constituent source. These criteria concern:  (1)
conditions at and around the source, (2) the level of detail needed in the
analysis, and (3) the ultimate intended use of the exposure analysis  (e.g. to
establish permit conditions, determine corrective measures, etc.).   Table B-3
shows how these criteria can be used to determine the level of exposure  and
risk assessment appropriate for evaluation of a source of hazardous
constituent release to soils.  In order to define conditions at and around the
facility, the permit writer must have available the following information:

    •    source background data;
    •    disposal history (and records, if available);
    •    chemical analysis data for locations at and near the source;
    •    source characterization data (e.g. topography,  hydrogeology);
    •    information on local human population;
    •    any human body burden and health effects data (unlikely to be
         available  for most sources); and
    •    types of corrective measures considered.

    The  primary  sources for this information are RCRA Part b Applications,
site  inspections, and analytical data and reports available from past or
ongoing  facility characterization.  Depending on the  level of need of the
permit writer, data used  to evaluate baseline conditions at and around the
source can  be used  to determine what corrective measures, it any, should  be


Analytical                         Level of    Characteristic       Resource
  Level	Nature of Analysis     Detail	Analytical Tools    Intensiveness
Level I      Qualitative:  Broad
             Scale Screeing
Decision Networks
Level II     Quantitative:
             Minimal targeting
Moderate   Simple Estimation
Level III    Quantitative:
             Highly targeted
 High      Computer Modeling;     High
Source:  Schultz et. al., 1984.

                                      Level of Assessment Necessitated

    Conditions at the
(2)  Conditions around
    the facility
(3) Level of need
        Level I

-contamination is confined
 to and migrated little
 from the facility,  and
 direct contact by human
 populations is unlikely.
-topographical and  geolog-
 ical data indicate that
 releases would travel
 very slowly in environ-
 mental media, and  no
 large or sensitive popu-
 lations are located near
 the facility
-the exposure assessment
 need not be rigorous be-
 cause the qualitative
 evaluation will be used
 to determine what correc-
 tive actions, if any,
 will be taken at the
 source, or will be
 utilized to establish
 relative degrees of haz-
 ardous contaminant release
 to soils which are consi-
 dered acceptable.
 Reliable sources:  e.g.,
 analytical data, time,
 money, expertise, warrant
 a Level I analysis
  Level II (or Level III)

-the quantity, frequency,
 and potential toxicity
 of an observed release
 indicates migration from
 the facility into a trans-
 port medium (e.g. out,
 surface water).
-if exposures have already
 occurred or are  imminent

-topographical and geolog-
 ical data indicate that
 releases would travel at
 moderate or rapid rates in
 environmental media
-presence of a large popu-
 lation near facility
 (despite limited migration
 potential of hazardous
 constituents from the

-the exposure assessment
 will be used, or is likely
 to be used to determine
 what corrective  actions,
 if any, will be  taken at a
 source, or to establish
 acceptable levels of re-
 leases to soil in the
 absence of existing
 standards.  Available re-
 sources: e.g. analytical
 time, money, exper-
 tise warrant a Level II
 analysis necessary.
Source:  IGF, Inc., 1985.

taken at Che source,  or in the case of post-remediation,  to evaluate-the
efficacy of the chosen corrective measure at  reducing releases of hazardous
constituents to an acceptable (target) level.
    The initial decision as to which level of  assessment  is to be performed at
a source should be preliminarily determined (if possible) during initial
review of the baseline facility data.   At this time,  the  extent of chemical
contamination at the  source can be estimated,  and based on existing conditions
at the facility and affected (e.g. exposed) population profiles, a decision on
the appropriate level of exposure (and risk)  assessment can be made.  Initial
selection of level I  or level II, however,  is  not necessarily final.  As the
exposure assessment proceeds it may become clear that the initial level of
analysis chosen is not appropriate when considering all available data.  At
that point, the level of analysis may  change.   At the time of initial  decision
of the level of detail required existing gaps  in the  quality and quantity of
available data should also be identified.   If  necessary,  measures can  be taken
to obtain information necessary for adequate  exposure evaluation.  For
example, should the permit writer, after review of a  facility's Part B
Application, determine that a level II analysis is required but not possible
given available information  requests  for additional  information to perform
the more detailed analysis can be specified.


    The key element of the qualitative (level  I) exposure assessment is a
comprehensive exposure pathway analysis, in which potential pathways are
indentified and characterized.  The assessment involves preliminary
determination of complete exposure pathways by performing three analysis
steps.  These include:

    •    hazardous consittuent release characterization and analysis,
    •    environmental fate analysis (e.g., identification of environmental
         pathways through which hazardous constituents migrate from the
         source), and

    •    exposed population analysis (e.g., identification of possible human
         and non-human exposure points and mechanisms)-

The level I exposure evaluation can have a wide range of detail, although the
extent to which hazardous constituent releases can be quantified is dependent

on previously gathered analytical data.  No new analytical data, or

quantification, is generally required.  Therefore, calculation of human doses

(at identified receptor points) cannot be conducted.

    Once a hazardous constituent release to soils has been identified, the

permit writer can effectively perform a level I analysis by utilizing a series

of decision networks for each of the three exposure pathway analysis steps

cited above (i.e., hazardous constituent release, environmental transport and

fate, and exposure point and route analysis).  The decision networks provide a

framework for performing each exposure analysis step via a series of questions

relevant to the analysis process.  The answers to these questions provide

information which can serve in determination of the following:

    •    existing exposure pathways (e.g., release/transport/human exposure
         pathways) which are complete.  Those exposure pathways which are
         incomplete may be eliminated from further analysis, unless subsequent
         data are obtained which modifies conclusions drawn from existing
         analytical data.

    •    the relative magnitude (e.g. low, moderate, high significance) of
         exposure pathways associated with hazardous constituent release at
         the facility.  This can be used to target those pathways for which
         more in-depth  (level II) analysis is required versus those pathways
         which appear of more minor significance or which can be adequately
         characterized  by level I analysis.

    •    existing gaps  in the (quantity and quality of) available analytical
         data.  This can be used to develop strategies for acquiring
         additional data in order to conduct quantitative (level II or III)
         analyses if they are warranted.

    •    corrective measures which may be applicable for implementation at the

          The three basic steps in performing a level I (qualitative) exposure
         assessment include analysis of: (1) the source of hazardous
         constituent release; (2) environmental transport and fate; and (3)
         potentially exposed populations.  The following subsections describe
         these three steps of the qualitative analysis process, and provide as
         guidance the decision networks with which they can be effectively
         evaluated.  The qualitative exposure analysis is a stepwise process;
         e.g., the output of each step in the exposure analysis process serves
         as input to and provides direction for the following step.
         Therefore, the output of the hazardous constituent release analysis
         serves as the  input for the environmental fate analysis, which in
         turn, serves as input for the exposed population analysis.


Hazardous Constituent Release Analysis

    Based on available information trom site inspections, analytical data and
reports available from past or ongoing source investigations, and RCRA Part B
Applications, the nature and magnitude of releases to soils from hazardous
constituent sources can be determined.  Data obtainable from these sources
relevant to release characterization include:

    •    chemical/physical properties of the hazardous constituents;
    •    climatological regime of the area;  and
    •    the location and manner of placement at the facility (e.g. buried in
         landfill, present in surface lagoon).

    Depending on the location of hazardous  constituents and manner of waste
disposal, hazardous constituent release from a  source may occur via any or all
of the following mechanisms:

    •    Source leaching;
    •    Surface runoff;
    •    Episodic overland flows;
    •    Fugitive dust generation/deposition;  and
    •    Tracking.

The procedure for characterizing the nature  and probable significance of
release (e.g.,  environmental loading) can be faciliated by means of a decision
network,  as shown in Figure B-l.  The output of this analysis,  in turn, is
used as input to the second step in the evaluation process,  environmental fate

Environmental Fate Analysis

    Analysis of the environmental transport  and fate of hazardous constituents
released  to the soil medium involves determination of two inputs: (l) the


                                                                         ARE TOXICS PRESENT IN
                                                                                SOIL?  '
                                                                               ARE TOXICS  SPILLED, LEAKED,
                                                                                   OR SURFACE APPLIED?
                                                                                                  IS ONSITE TREATMENT
                                                                                                       AN OPTION?
            DOES SOIL COVER
    TO AIR
                                                                       GO ON TO
                                                             ENVIRONMENTAL FATE ANALYSIS
                              Figure B-l.    Release  decision  network:   Hazardous constituents.

extent (e.g. magnitude) of release to soil,  and (2)  the potential for
migration in environmental media.  Both intermedia transport mechanisms (e.g.
adsorbtion and/or eTitrainment in air, and bioaccumulation) and iritramedia
transformation processes (e.g. photolysis, oxidation,  hydrolysis, and
biodegradation) are qualitatively considered during this second step.  The
evaluation will be based on results of the hazardous constituent release
analysis.  Information required tor the environmental  fate analysis is
similiar to that of the previous section,  including:

    •    physical/chemical properties of the hazardous constituents;
    •    manner of placement or disposal;  and
    •    relevant climatological, hydrogeological source condition information.

The outcome of the qualitative environmental fate analysis is a determination
of the likely extent of release to the environment from the facility (e.g.,
environmental loading).  The nature of the hazardous constituents involved and
probable magnitude of their release are also considered.  When the outcome of
this analysis is integrated with information concerning populations affected
by the source, subsequent evaluation of potentially exposed human populations
can be performed.  Because the environmental fate analysis is such an integral
part of the exposed population analysis, decision networks used to evaluate
the former are more appropriately considered in the latter section, exposed
population analysis.

Exposed Population Analysis

    The third step in performing a qualitative exposure assessment is the
exposed population analysis.  Analysis of  potentially  exposed human (and
non-human) populations involves determination of the likely routes and extent
of population exposure to contaminants released to soils.   It also considers
the duration ot expected exposure (e.g., either short-term or long-term).   The
exposed population analysis is the final step in identification of those
exposure pathways which are complete, and  thereby completes the level I

qualitative assessment; it also serves as a basis for planning-and conducting
subsequent quantitative (e.g., level II and III) assessments.  By determining
the magnitude of probable exposure via pathways identified, those pathways
which are considered to be of major significance may require level II (and/or
level III) analysis, while those which are considered of minor significance or
can be easily characterized may be adequately evaluated by the level II
analysis.  The analysis is straightforward and involves identification of two

    (1)  the land use and activity patterns of human populations near the
         source; and
    (2)  the areas ot potential human exposure to hazardous constituents
         released to soils (as identified in Step 2, the environmental fate
The exposed population analysis can be performed via several decision
networks, one for each of the transport mediums identified in the previous
step, environmental fate analysis.  Decision networks for those transport
media  of concern (when considering release of hazardous constituents to soil)
are presented below.   In essence, the decision networks are frameworks for the
environmental-fate-and-exposed-population analysis because they combine the
information derived from the envionroental fate analysis with the projected
likelihood of population exposure to contaminated areas (as identified by
human  activity  and  land use patterns near the facility).  They provide a
qualitative  estimate  of  the relative magnitude of human exposure (and risk)
via  identified  exposure  pathways  and routes.  The duration of  expected
exposure  is  also determined at this step  in the exposure analysis.  Guidance
for determination  of  exposure duration is based on baseline conditions of
 contamination at the  facility, and can be summarized by the criteria shown in
 Table B-4.
     When considering releases of hazardous  consituents  to  soil,  several  routes
 of human (and non-human) exposure should  be evaluated,  including:

     •    direct contact  with  soils;
     •    inhalation of airborne  particulates  to  which  contamination  is
          adsorbed,  with  possible reingestion  of  particulates;




1.   Access to the facility or areas contaminated as a result of migration from
     the facility:  Is the facility:

     •   accessible to,

     •   restricted (e.g. by a fence or physical source conditions) from, or

     •   otherwise unaccessed (e.g. due to great distance) by human populations?

     a.  If restricted, to what extent?  (e.g. the presence of a fence is not
         sufficient indication that access is prevented).

2.   Are there natural manraade features of the source or surrounding area such

     •   abondoned buildings,

     •   standing water or streams

     which may attract people, in particular children?

3.   Are there human use areas, such as:

     •   playgrounds

     •   schools

     •   parks

     located near the facility which may be frequently utilized by people, in
     particular children, despite efforts to restrict access to the area?

    •    ingestion of soils (e.g., by a child exhibiting pica); and
    •    ingestion of food products into which hazardous constituents in soil
         have been uptaken.
Assessment of exposure to humans (and non-humans) via  ingestion of food
products and inhalation of airborne particulates (with possible reingestion)
involves consideration of intermedia transport (e.g.,  to air or into biota) of
hazardous constituents originally released to soils.  These routes of exposure
can be evaluated via the environmental-fate-and-exposed-population networks
shown in Figures B-2 and B-3.  Assessment of exposure via direct contact or
ingestion of soils (e.g., by a child exhibiting pica, an abnormal craving for
non-food items) can be performed at any hazardous constituent exposure point
because the release/transport/and human exposure media are the same (e.g.,
soil) because no intermedia transport is involved.
    Once the permit writer has performed the 3 steps of the qualtitative
exposure analysis  (e.g., release, transport, and exposed population analysis),
he has determined  which exposure pathways are complete, and has thus set the
conditions necessary for characterizing risk (associated with exposure).
Depending on the level of need, available resources (e.g., available source
monitoring data),  and projected significance of exposure (and risk), complete
exposure pathways  may be used as a basis for qualitatively evaluating risk
associated exposure via those pathways and routes, or may be further evaluated
by quantitative exposure analysis (e.g., level II or III), after which
quantitative risk  characterization will be performed.  For instance, if the
permit writer wishes to perform the exposure assessment to determine the
relative significance (e.g., low, moderate, high) of exposure via identified
routes and does not require in-depth (e.g., quantitative) assessment of
exposure, then level I exposure analysis will be sufficient.  If, on the other
hand, the permit writer does desire in-depth exposure analysis (e.g., because
the release is obviously significant or he wishes to plan corrective measures
to eliminate exposure to a defined level), then level II analysis will be
required.  He will not be able to perform the level II analysis, however,
unless sufficient  environmental monitoring data are available.

                                            HAZARDOUS CONSTITUENT
                                              RELEASE EVALUATION
              OF HAZARDOUS
                                   SIGNIFICANT RELEASE OF FUGITIVE
                                     DUST/HAZARDOUS  CONSTITUENT
                                      PARTICULATES FROM SITE?


                                CONSIDER DIRECTION AND DISTANCE OF
                              PARTICULATE MOVEMENT WITH WIND CURRENTS.

                            MAJOR MECHANISMS:   WIND SPEED, PARTICLE SIZE:
                              GRAVITATIONAL SETTLING, PRECIPITATION.

                               ESTIMATE AREAS RECEIVING SIGNIFICANT
                              SETTLEOUT/RAINOUT OF PARTICULATE MATTER.
                                    PERSONS RESIDING, WORKING, OR CARRYING
                                    OUT ACTIVITIES WITHIN REACH OF AIRBORNE
                                       HAZARDOUS CONSTITUENTS  CONSTITUTE
                                      POPULATIONS EXPOSED VIA  INHALATION.
                                                  GO ON TO
                                               RISK ASSESSMENT
         Figure  B-2.   Environmental  fate  and  human exposure  analysis  decision
                           network:   Hazardous  constituents  in  air.

                                  Source:    Schultz,  et  al.,  1984.


                                    AMBIENT CONCENTRATION DATA
                                  FROM AIR,  WATER,  GROUND WATER
                                          FATE ANALYSES
                                    SIGNIFICANT CONCENTRATIONS
                                     OF HAZARDOUS SUBSTANCES
                                     IN AMBIENT ENVIRONMENT?
                              CONSIDER BIOTIC SPECIES  WITHIN AREAS OF
                               ELEVATED  AMBIENT HAZARDOUS SUBSTANCE
                               CONCENTRATIONS AS  POTENTIAL VECTORS
                                     OF HAZARDOUS SUBSTANCES
                                      WITHIN BIOLOGIC  MEDIA

                                   MATERIAL THROUGH FOOD CHAIN
                                (BIOTIC UPTAKE;  BIOMAGNIFICATION)
                                PERSONS USING ORGANISMS  OR  ORGANISM
                                 CONSIDER POPULATIONS EXPOSED VIA
                                 DIGESTION OF FOOD PRODUCTS  FROM
                                      CONTAMINATED ORGANISMS
                                             GO ON TO
                                         RISK ASSESSMENT
            Figure B-3.   Environmental  fate and human  exposure  analysis
                            decision  network:   food chain.
                              Source:   Schultz,  et  al.,  1984.



    The initial step of a quantitative exposure analysis is an evaluation of
available source data to determine their completeness arid adequacy, and to
identify existing data gaps which must be filled prior to performance of the
analysis.  Once requisite data are acquired, quantitative evaluation of human
(and non-human) exposure (either as a level II or III analysis) can proceed
via the framework shown in Figures B-4.  The first three steps of the
quantitative exposure analysis process are similiar to those for the
qualitative (e.g., level I) analysis process, and include:

    •    hazardous constituent release analysis;
    •    environmental fate analysis; and
    •    analysis of population exposure points and routes.

Unlike  the qualitative exposure analysis process where each step in the
analysis is qualitatively evaluated, each step of the quantitative exposure
analysis process  is quantitatively evaluated.  Because level II (and III)
assessments are quantitative in nature, they allow for determination of
hazardous constituent intake or dose incurred by human receptors at identified
exposure points.  Determination of human intake or dose is performed
subsequent to  the three analyses cited above, and combines the output of each
of  the  analysis steps.  The goal of the level II (and level III) exposure
assessment is  the development of quantitative determinations of both
individual risk and risk to exposed populations, which are preferably
expressed as average versus maximum projected exposure (e.g., intake or
dose).  Because the quantitative exposure (and risk) assessment is performed
by  a series of analysis steps (e.g., release/transport/exposed population
analysis), all of these steps must be quantitatively defined; e.g., the output
of  the  release analysis must be expressed in terms of average and maximum
release values, the output of the environmental fate analysis must predict
average and maximum hazardous constituent concentrations in environmental
media,  and average and maximum population exposures must be determined by the
extent  to which the general population comes into contact with the average and


                                                       LOADING TO
                                      OF IMPORTANT
                                    FATE AND TRANSPORT
                          HAZARDOUS CONSTITUENT  RELEASE
                                                                              ENVIRONMENTAL FATE
                                                                         EXPOSURE AND DOSE
                                                                  DOSE ESTIMATES
                                                 RISK    I
                                              ASSESSMENT  |
                              Figure B-4.    Overview of integrated  exposure  assessment process,
  Source:   Schultz,  et.  al.,  1984.

maximum environmental concentrations.  The last step of the quantitative
exposure analysis, (e.g. quantification of human intake or dose) is then
considered in conjuction with toxicological data for hazardous constituents of
concern, and serves as the baseline risk assessment.  The use of exposure
information to characterize risk will be further discussed in this section.
    For those sources, pathways, and routes of exposure evaluated in the level
II analysis which are determined to be of minor significance and/or are
sufficiently characterized (e.g., as determined by need), the level II
analysis alone is sufficient.  However, for those sources, pathways, or
receptors which are of great magnitude or sensitivity (and available data and
level of need permit), additional level III analysis may be performed.  The
primary distinctions between level II and level III quantitative analyses are
shown in Table B-2.  In brief, they concern four characteristics, including:

    (1)  The nature of the analysis: e.g. both levels II and III are
         quantitative, although level II requires minimal determination of
         significance, and level III intense determination of significance of
         exposure pathways and routes,
    (2)  Level of detail: level II are moderately and level III are highly
         detailed analyses,
    (3)  Characteristic analytical tools required: level II involves simple
         estimation equations, while level III requires either computer
         modeling or environmental monitoring to quantify hazardous
         constituent releases, environmental transport, and exposure point
         concentrations, and
    (4)  Resource intensiveness: the level II is moderately and the level III
         is highly resource-intensive.
    The permit writer may perform either a level II or III analysis, depending
on the quality of available data and degree of detail needed.  A description
of the use and methodology for performing both level II and level III analyses
will therefore be discussed in the subsequent subsections.
    There are 3 basic steps in performing quantitative (level II or III)
exposure analysis.  They include:

    (1)  hazardous constituent release analysis,
    (2)  environmental fate analysis, and
    (3)  exposed population analysis.

Utilizing Che output from each of these three steps, the exposure analysis
enables the permit writer to quantify human exposure (e.g., as intake or
dose).  Informational requirements and guidelines for performing the three
basic steps of the quantitative exposure-analysis and for-quantifying human
exposure (as intake or dose) are presented below.  If additional information
is desired, the reader is referred to sources cited below.

Quantitative Hazardous Constituent Release Analysis

    The first step of the quantitative exposure analysis is the quantitative
hazardous constituent release analysis.  Quantitative analysis of releases of
hazardous constituents to soils utilizes the results of the qualitative
analysis performed at level I; e.g., the source of release identified in the
level I analysis I is re-analysed at the level II and the release rate (e.g.,
mass  release per unit time) is quantified.  The output of the analysis is a
measure of  the mass loading of the hazardous constituents to the soil medium
as well as  to other media contaminated as a result of intermedia transport.
The output  of the analysis, in turn, serves as input for the second step of
the exposure analysis, quantitative environmental fate analysis.  A flow chart
depicting  the nesessary decision criteria for quantitative hazardous
constituent release analysis (level II and III) is shown in Figure B-5.
    Both level II and III assessments yield quantitative estimates of releases
to soils based on hazardous constituent-and-site-specific factors.  These
estimates  represent levels of environmental hazardous constituents to which
human (and  non-human) populations could potentially be exposed, either
directly at the source or at points of hazardous constituent migration (e.g.,
as determined in subsequent analysis steps 2 and 3, environmental fate
analysis and exposed population analysis).  Quantification of hazardous
constituent levels at this initial step of the exposure/risk analysis process
is therefore fundamental to obtaining quantitative estimates of human exposure
(e.g., intake or dose) as the final output to the quantitative exposure
analysis process.

         SITE DATA

                                             DATA ACQUISITION
                                              MODELING, ETC.)
                 Figure B-5.   Quantitative hazardous  constituent  release  analysis (Levels  II and  III).

                                                Source:   Schultz,  et  al.,  1984.

    Quantitative release analyses (either at level II or level LID are
expressed as release rates (e.g. mass release per unit time).  Various methods
are available for estimating release rates of hazardous constituents to
environmental media from a variety of sources.  Each release medium (e.g.
soil, air) must be addressed separately; however, intermedia release of
hazardous constituents must also be considered.  In the case of releases of
hazardous constituents to soils, there is one primary and two secondary
release media of concern.  They include:

    •    soil (as a primary release medium),
    •    air (as a secondary release medium, via entrainment of airborne
         particulates to which hazardous constituents have adsorbed), and
    •    biota  (as a secondary and indirect release medium, via plant uptake
         of hazardous constituents adsorbed to or otherwise associated with

Methods  available for level II and III quantitative analysis of release to
soils are referenced in Table B-5.  Quantitative methods of release analysis
to  air  (e.g., as a  secondary environmental release medium) are also referenced
in  the  table.   Uptake by biota,  (e.g., as a secondary, indirect release
medium)  can be  evaluated by consideration of release to soils, since plant
uptake  occurs directly  from the  soil medium.  The limitations and assumptions
inherent in performing  quantitative  level II and level III contaminant release
analyses are presented  below.

Assumptions/Limitations  of Level  II Hazardous Constituent Release Analysis—
     Procedures  available for calculating environmental release estimates can
be  limited  in  that  they:  (1) often do  not take into account  the full range of
variables which affect  source release  (e.g., hazardous constituent-specific
and site-specific  factors), and  (2) often assume steady state conditions
(e.g.,  do not address reduction  in levels of hazardous constituents present
due to  release  losses,  and the  associated reduction in release loading over
time, corresponding  to  the decreased reservoir of hazardous constituents).
Given these constraints, the quantitative release analysis is not expected to

MEDIUM;  Soil (e.g. from a
   lagoon or pond, spill,
   intentional placement
   in ground)
MEDIUM:  Air (e.g. via
         entrainment of
       LEVEL II

Estimation equations using
analytical sampling data
(and/or monitoring data,
if available).

-surface soil:  use sampling
 • average contamination:
   average sample concen-
 • maximum contamination:
   highest sample concen-
-subsurface soi/1: use
 sampling data, if avail-
 able, or refer to:
 Schultz et. al., 1984
-refer to: IGF, Inc., 1985
 and EPA, 1984c, for
 hazardous constituent
 release quantification
 methodologies - refer to
 soil conservation service
 sources  for site-specific
 soil and climatic data for
 use in above, if necessary
       LEVEL III

Computer modeling;
facility monitoring data
-surface soil: use
 monitoring data
 • average contamination:
   take average sample
 • maximum contamination:
   take highest sample
-subsurface soils: use
 monitoring data,  if
 available, or use com-
 puter modeling* to
 derive average and maxi-
 mum concentration values
 of subsurface soils

-utilize air monitoring
 data (both upwind and
 downwind of the source)
 and/or use computer
 modeling to derive aver-
 age and maximum contam-
 ination concentrations
     Models applicable to quantitative analysis of hazardous constituent release
     to soil and air media are referenced in Table B-6.

be wholly representative of conditions at the facility, and application of the
analysis outcome should be limited to the following situations (EPA, 1984c):

    •    estimation of the level of release of specific hazardous constituents
         at a facility, and

    •    projection of approximate release reduction as a result of corrective
         measures taken at the facility.
In other words, the limited applicability of the level II release analysis to
these situations should govern the permit writer's use of level II analysis in
general.  If  the permit writer desires an estimate of environmental release
which is highly accurate or wishes to use the analysis outcome to estimate the
efficacy of corrective measures to a specified environmental release level,
then level II analysis will not be sufficient; level III analysis will be
required to obtain a more  sophisticated and accurate estimate of release.
However, if level III analyses are desired but are not able to be performed
(e.g.,  due to lack of resources, analytical data, etc.), then professional
judgement must be used in  the level II analysis, in order to account for the
inherent reductions in release rates over time and to specify more accurate
estimates of  environmental releases.

Assumptions/Limitations of Level III Hazardous Consitutent Release Analysis—
    Level III hazardous constituent release analysis generally involves the
use of  modelling  to specify exact estimates of environmental concentrations.
Several criteria must be  taken into consideration when selecting a level III
model to quantify releases of hazardous constituents to  soil.  They include:

    •    data requirements of the model versus availability and reliability of
         resources; e.g.,  source sampling data or monitoring data, time, and
    •    fit  of the model  to site-specific and hazardous constituent-specific
    •    form and content  of model output: does  it estimate mass loading to
         soils or air (i.e., environmental loading per unit time).

Models capable of quantifying release of hazardous constituents-to sur-face
soils (and the subsequent degree of contamination to subsurface soils) and air
are referenced in Table B-6.  Of note, is the necessity to match available
source sampling data to the results of the model in order to validate the
model's results.  The consistency of the two estimates will also provide a
measure of reliability for both sources of information.

Environmental Fate Analysis

    Environmental Fate Analysis is the second step in quantitative exposure
analysis.  The purpose of quantitative environmental fate analysis is to
generate estimates of the direction of migration and areal extent of
contamination as well as the ambient concentrations of hazardous constituents
within the soil media.  The average release rate estimates derived from the
release analysis (Step 1) serve as input to this analysis, and by application
of  environmental transport, transformation, and removal mechanisms,
environmental fate estimates are calculated.  Regardless of the level of
exposure performed (e.g., level II or III), estimates of environmental
concentrations which should be determined include: (1) maximum expected
ambient concentrations (e.g., representing short-terra worst-case conditions),
and (2) average ambient concentrations (e.g., representing most-probable
conditions over a long time period).
     The suggested approach for evaluation of the environmental fate of
hazardous constituents released to soils is to consider separately the major
transport and transformation processes of the constituent released to each
environmental medium of concern.  In the case of releases to soil, both soil
(as a direct release medium), and air (as an indirect medium, via entrainment
of  dusts) must be considered.  Methods available for use in quantitative
(level II and III) analyses of environmental fate of releases to soils (and
indirectly,  to air) are referenced in Table B-7.  Limitations and assumptions
inherent in  analyses of environmental fate at these levels (II and III) are
described briefly below.

                         IN SOIL AND AIR MEDIA*


     For available models applicable to release environmental fate analysis in
     soils, the reader is referred to the following sources:

     •   Schultz et. al., 1984

     •   McNeils et. al., 1984

     •   EPA, 1982a.


     For available models applicable to release and environmental fate
     analysis,  the reader is referred to the following sources:

     •   EPA, 1982a

     •   GCA, 1983a
         GCA, 1983b.

     •   Schultz  et. al., 1984

     •   McNeils  et. al. , 1984

     •   ICF, Inc.,  1985
'descriptions  and  uses  of  available models  are  presented  in  these  sources.

                        FATE IN SOIL AND AIR MEDIA
                                LEVEL  II

                         Estimation  equations  using
                         analytical  sampling data
                         (and/or monitoring data,
                         if available).
MEDIUM;  Soil (e.g. from a  -surface soil: use sampling
                             • average contamination:
                               take average sample
                             • maximum contamination:
                               take highest sample
                            -subsurface soil: use
                             sampling data, if avail-
                             able, or refer to:
                             Schultz et. al., 1984
lagoon or pond,  spill,
intentional placement
in ground)
MEDIUM:  Air (e.g. via
         entrainment of
                         •refer to:  Schultz et.  al.,
                          1984; ICF,  Inc,  1985 for
                          hazardous  constituent
                          environeratal fate
                          quantification method-
                          ologies -  refer to:   soil
                          conservation service
                          sources for site-specific
                          soil and climatic data for
                          use in above,  if necessary

Computer Modeling;
monitoring data
-surface soil: use
 monitoring data
 • average contamination:
   take average sample
 • maximum contamination:
   take highest sample
-subsurface soil: use
 monitoring data, if
 available, or use com-
 puter modeling* to
 derive average and maxi-
 mum concentration values
 of subsurface soils

-utilize air monitoring
 data (both upwind and
 downwind of facility,
 and/or use computer
 modeling* to derive
 average and maximum con-
 tamination concentra-
*Models applicable to quantitative analysis of environmental (migration and) fate
 in soil and air media are referenced in Table B-6.

Limitations/Assumptions of Level II Environmental Fate Analysis--
    Level II procedures for quantifying hazardous constituent fate in soil and
air media are based on the predominant mechanisms of transport within these
media and generally disregard transfer or transformation processes.  They
produce conservative estimates of final ambient concentrations and
environmental migration.  The purpose of conservatism at this step in the
exposure/risk estimation process is twofold: (1) to eliminate from additional
consideration those potential exposure points which are not expected to be
affected by hazardous constituents migrating from the source, and (2) to
provide conservative estimates of hazardous constituent concentrations as
input to subsequent exposure (e.g. intake or dose) and risk assessment.  By
disregarding the effects of transfer or transformation processes in the
environmental fate analysis step, environmental concentrations utilized as
input to exposure (and risk) analysis will tend to overstate actual ambient
concentrations.  At best, these concentrations will represent "worst-case"
environmental constituent levels.  The significance of each exposure pathway
evaluated  in the exposure analysis will therefore be conservatively
estimated.  This will aid in identification of those pathways which are of
minimal, moderate, and major significance under presumed "worst-case"

Limitations/Assumptions  of  Level  III Environmental Fate Analysis—
     Level  III environmental  fate  analyses generally involves use of computer
models  to  specify  exact  estimates of environmental concentrations.  When
selecting  a level  III model  to  estimate environmental concentrations of
released hazardous constituents  (e.g.,  to soil or air), the permit writer
should  consider the  following criteria  (Schultz, et al., 1984):

     •    data requirements  of  the model versus availability and reliability of
         available resources:  (e.g., source sampling or monitoring
         information,  time,  finances, and level of need),
     •    capability  of  the  model  to account for important  transport,
         transformation,  transfer processes.
     •    "fit"  of  the model  to  site-specific and hazardous
         constituent-specific  parameters, and
     •    form and  content of model output (e.g., does it address important
         questions regarding human exposure, environmental effects?).

    Again, it is important to note the necessity of comparing available source
sampling and/or monitoring data to model output in order to "check" the
reliability of both sources of information.  Table B-6 references the models
available for estimating environmental concentrations of hazardous
constituents which have been released to and are expected to remain in the
soil medium, and those which have been released to soils and entered the air
medium, respectively.

Exposed Population Analysis

    The final step of the quantitative exposure analysis process is the
exposed population analysis.  Input necessary for the exposed population
analysis  is derived from previous steps, hazardous constituent release
analysis  (Step 1) and environmental fate analysis (Step 2).  For example,
level  II  analysis of air contamination will yield isopleths (lines of equal
concentrations of) hazardous constituents.  Areas of soil contamination will
also be identified and the levels of contamination quantified.  These
quantitative environmental levels are then considered together with
information concerning potentially exposed populations (as described below) to
identify  and predict the likelihood of human (and non-human) contact with
hazardous constituents released to soil.  The analysis invovles determination
of  three  parameters, as shown in Figure B-6.  Briefly, they include:

    (1)   identification and enumeration of exposed populations; e.g., by
          considering the areal extent of contamination (as determined in step
          2, environmental  fate analysis), populations which potentially or
          actually come into contact with contaminated soil or air are
          identified.  Populations consuming contaminated food products (e.g.,
          vegetables grown  in contaminated soils) are similiarly identified.
    (2)   population characterization; e.g., determining those groups within
          the exposed populations which, are expected to experience the greater
          risk than the average population (e.g., a sensitive  sub-population)
          at a given exposure level, due to specific health effects of some
          hazardous constituents.  Examples of such sensitive  subpopulations
          include pregnant  women, children, the elderly, and the chronically

                                                                         FATE ANALYSIS
          OF EXPOSED

                                                                                                                             DERMAL ABSORPTION





, * *

                                   Figure  B-6.    Quantitative  exposed  population analysis,

Source:    Schultz,  et.  al.,  1984.

    (3)   activity analysis;  e.g.,  determining the mix of human activities
         conducted by the  population through which exposure occurs.   Key
         activity-related  exposure determinants to be quantified for each
         exposure route-relevant to hazardous constituent releases to soil
         (e.g.,  inhalation^  ingestion,  and dermal contact) are shown in
         Table B-8.  The procedure for  conducting the exposed population
         analysis is the  same for a level II assessment as for a level III
         assessment, except  for the fact that average or estimated levels of
         hazardous constituents are used in level II, and more accurate,
         source-specific data are used  in level III.   The three parameters
         necessary for exposed population analysis are discussed briefly
         below.   The reader  is referenced to other sources of information if
         such information  is not presented here.
Identification and Enumeration of Exposed Populations—
    Identification and enumeration of exposed populations is the first
parameter necessary to perform the exposed population  analysis step of the
quantitative exposure analysis.  The primary population database that can be
accessed to determine the size, distribution, and demographic characteristics
of a geographically-defined population is the Census of Population.  For
further information on the aquisition and use of census data, the reader is
referred to EPA, 1984c.  The manual also provides guidance for the
identification and evaluation of human populations exposed to hazardous
constituents in air (via inhalation), food (via ingestion),  and soil (via
inhalation/ingestion and direct contact).

Population Characterization—
    Population characterization is the second parameter necessary to perform
the quantitative exposed population analysis.  Again,  the reader is referred
to EPA, 1984c, for guidance in defining this parameter of the exposed
population analysis.

Activity Analysis—
    Activity analysis is the third and final parameter necessary to perform
quantitative exposed population analysis.  The activity analysis is fairly
straightforward; however, the permit writer is required to make some
generalizations.  In the analysis, the activities of the members of a given
population or subpopulation are determined in order to predict the level of

     •    Length of time (frequency and duration) spent in each related

     •    Nature of the activity in terms of light, medium, heavy, or maximum
          exertion (per unit time).

     •    Amount of contaminated food or water ingested (per unit time).


     •    Length of time (frequency and duration) spent in each related
          activity per unit time.

     •    Location of exposure (e.g. on human body) and areal extent of

aMany of these exposure criteria are considered as "standards" in the
     following sources:  Schultz et. al., 1984; ICF, Inc., 1985.  The reader
     is referred to these information sources in his analysis of human
     activity related to exposure to hazardous constituents.

Source:  Schultz et. al., 1984.

exposure which is actually experienced.  Generalization is involved in
predicting the human activity patterns which result in exposure to
environmental contamination.  For example, persons whose lifestyle or
employment involves frequent strenuous activity will ventilate larger volumes
of air per unit time than will those persons living a more leisurely
lifestyle, and will therefore experience a greater degree of exposure to
airborne constituents.  Activity patterns which affect other exposure routes
are similarly analyzed.  Because human behavior is difficult to predict,
hypothetical situations (i.e., scenarios) are developed to represent the
exposure associated with human activity patterns.   Human activity scenarios
typically involve determination of "average" and maximum (i.e., "worst-case")
population exposures, by determining the extent (i.e., duration,  frequency) to
which the population comes into contact with average and maximum environmental
concentrations.  The quantitative exposed population analysis is performed by
first defining the three parameters (cited above): (1) exposed population
identification and enumeration, (2) exposed population characterization, and
(3) exposed population activity analysis.  The results of the exposed
population analysis are then combined with those of the first and second steps
of the quantitative exposure analysis process (i.e., hazardous constituent
release and environmental fate analysis), and human exposure is quantified.
There are basically two measures of quantitative human exposure;  they are:

    (1)  intake estimates, and
    (2)  dose estimates.

    The use of a particular measure is dependent upon assumptions and
limitations inherent in the development of the measure.  Both of these
measures (estimates) of human exposure are discussed briefly below; use of
these estimates in the risk characterization process and their inherent
limitations and assumptions are discussed in more detail in Section 6  risk

Intake Estimates—
    One quantitative estimate of human exposure is intake (i.e., the amount of
substance taken into the body per unit body weight per unit time).  The intake
estimate does not take into account bodily absorbtion of the hazardous
constituent, and is therefore a more conservative estimate of human exposure
than is the dose estimate.  Given the limited amount of available human
absorbtion data, its use is more applicable to a variety of exposure
situations and hazardous constituents than is the dose estimate.  In other
words, the permit writer is not limited (in his quantitative exposure
analysis) to the amount of available data concerning absorbtion rates for
specific chemicals through specific biological barriers.  By using information
acquired from the quantitative environmental fate and exposed population
analyses (steps 2 and 3 in the overall quantitative exposure analysis)
together with standard "intake" values (e.g., average ventilation rates,
average body weights) he is able to estimate human intake resulting from
exposure.  An example of intake estimation for exposure to airborne
constituents is shown below.  The standard intake valves utilized in this
equation (e.g., the average ventilation rate and body weight) were derived
from  ICF, Inc., 1985).
 average  (or maximum)    average daily         average body
 environmental         * ventilation  rate  —  weight of
 concentration  (in
 airborne  dusts)
    of exposed
average (or
daily intake
     3 mg/m3
*  20m3/day    _^_
70 kg body    =   0.857 mg/kg/day
  weight (adult)     intake       j
 Intake values  are  calculated  separately  for exposures to hazardous
 constituents in each medium identified in a complete exposure pathway i.e.,
 each medium  identified  in  the release/transport/exposure pathway).  For
 releases  to  soil,  relevant exposure media are soil and air (and indirectly,
 biota).   Standard  assumptions of human intake (e.g., average ventilation rates
 and average  body weights)  are utilized to derive the actual intake estimates
 from exposure  to these  media.  For further information and guidance on the use
 of intake assumptions and  equations to estimate human intake values from

exposure to air contaminants, the reader is referred to Schultz, et al. ,
1984.  For guidance in the assessment of less common, but potentially
significant routes of exposure (e.g., direct contact with contaminated  soils,
ingestion of inhalated contaminated dusts or food products).  The EPA Office
of Emergency ^nd Remedial Response (OERR) Washington, D.C., is developing
further information in this area.

Dose Estimation—
    A second estimate of quantitative human exposure is the dose estimate;
i.e., the amount of substance which is actually absorbed by the body as a
result of exposure to contaminated media.  It is derived by considering
existing concentrations of hazardsou constituents in environmental media
together with the frequency of exposure, route of exposure, and amount of
contaminant contacted per exposure (i.e., the "exposure coefficient").  Like
the  intake estimate, the dose estimate also assumes standard population intake
rates for various routes of exposure (e.g., ventilation rates, consumption
rates).  In addition, it also assumes standard rates of absorption for
chemicals into the human body.  The dose estimate is, therefore, less
conservative than is the intake estimate; but, provided that the assumed
absorption rate used in the dose calculation is accurate for the hazardous
constituent and site of biological uptake of concern, it provides a more
specific and accurate measure of human exposure.  Alternatively, if the
assumed absorption rate used in the dose calculation is not accurate for the
hazardous constituent and site of biological uptake of concern, then the dose
estimate will not provide an accurate measure of human exposure, but will tend
to understate it.  Further information and guidance on estimating human dose
resulting from exposure to releases to soil via relevant exposure routes
(e.g., direct contact, inhalation, and ingestion), the reader is referred to
Schultz, et al., 1984.  An example of dose estimation via direct contact with
hazardous constituents in soils is shown in Figure B-7, (Schultz, et al.,
1984).  Assumptions inherent in the calculation of human dose estimates are
discussed under risk characterization.

   Ug absorbed
   ug exposed
                          INHALATION DOSE
               Figure B-7.   Inhalation dose calculation.

                    Source:   Schultz,  et al.,  1984.

    In summary, quantitative exposure analysis involves 3 steps, each of which
is quantitatively analyzed.  These steps include:

    (1)  hazardous constituent release analysis,
    (2)  environmental fate analysis, and
    (3)  exposed population analysis.

The output of each of these steps serves as input to the subsequent step; the
final outcome of the analysis process is a quantitative measure of human
exposure, expressed as either intake or dose.  The permit writer must decide
which estimate of human exposure will be calculated, however, consideration of
the following criteria can aide in the decision process:

     (1)  Toxicological Profiles:  What are the hazardous constituents of
          concern, and by what routes of exposure do they exert their primary
          toxicological effects?  Is adequate data available to define
          biological absorbtion rates for the target organs of concern?  For
          instance, if a hazardous constituent has been widely researched,
          accurate human absorbtion rates (for biological target organs of
          concern) may be available, and dose estimation will be possible.
     (2)  Level of Need:  Are estimates of human dose (resulting from
          exposure) desired, given the projected level of significance of
          human exposure (estimated in the level I analysis) and the intended
          use of the exposure estimate in establishing permit conditions or
          corrective measures?
     For instance, if exposure to a hazardous constituent has been determined
in level I analysis to be only minimally or moderately significant, efforts to
define exact human dose may not be necessary; intake estimates will not only
provide more conservative estimates of human exposure for the specified
exposure pathways, but are also easier to calculate and are generally based on
fewer assumptions than are dose estimates.  However, if an accurately defined
measure of human exposure  is required in order  to establish permit conditions
or evaluate the efficacy of corrective measures, (given the availability of
human absorbtion data), dose calculations preferred over intake estimates.

Both human intake and dose estimates are equally useful measures of human
intake; and both can be used to form the basis of quantitative risk
characterization.  Descriptions, uses, informational requirements, and
limitations of both qualitative and quantitative risk assessment strategies
will be discussed in the following section.


Components of the Risk Characterization Process

     The process of determining the risk to human (and non-human) populations
associated with exposure to contaminant releases to soils involves input from
two components:

    •    Exposure Assessment to determine  the magnitude, pathways, and routes
         of human (and non-human) exposure to hazardous constituents; and
    •    Hazard Assessment, to determine the chemical toxicity and related
         hazard of a contaminant to which  there is exposure.

    By combining the results of these  two  components (i.e., exposure and
hazard assessment), the actual and potential health risks resulting from
exposure  to hazardous constituent releases to soils can be characterized.
Like the exposure assessment process,  the  risk characterization process can be
either qualitative or quantitative.  Determination of the risks to human (and
non-human) populations (as a result of exposure to environmental constituents)
serves two purposes  for the permit writer:

    (1)  It provides a way to determine the level and means of correction
         measures necessary to eliminate the risks to populations associated
         with release to environmental media, and in the absense of existing
         standards and guidelines,
    (2)  It provides an approach for evaluating public health impacts
         associated with hazardous constituent exposures in order to establish
         permit conditions.

    The following two sections provide brief descriptions of these two
components of the risk characterization process, exposure assessment and
hazard assessment, and provide guidance for the use of these components to
qualitatively and quantitatively evaluate risk.

Hazard Assessment—
    Following exposure assessment, a hazard assessment is the next component
of the risk characterization process.  The hazard assessment is essentially a
two-step process involving both "hazard identification" and "dose-response"
assessment for the releases of concern.  The purpose of the hazard
identification is to determine the nature and extent of health and
environmental hazards associated with exposure to hazardous constituents at
the facility.
    The first step in the hazard assessment, the hazard identification, is a
qualitative evaluation of the scientific data to determine the nature and
severity of actual or potential health and environmental hazards associated
with exposure to a hazardous constituent.  The hazard identification involves
a critical evaluation and interpretation of toxicity data from
epidemiological, clinical, animal and in vitro studies and results in a
toxicity profile for each hazardous constituent of concern.  Toxicity profiles
present a review of the primary literature on the types of adverse effects
manifested (e.g., chronic, acute, carcinogenic, etc.), doses employed, routes
of administration (e.g., oral, dermal, inhalation, etc.), the quality and
extent of test data, the reliability of the test data and other factors.
Toxicity profiles provide the weight-of-evidence that the hazardous
constituents of concern pose potential hazards to human health or the
    Once the hazard identification determines that a hazardous constituent is
likely to cause a particular adverse effect, the next step is to determine the
potency of the chemical.  The second step in the hazard assessment, the
dose-response assessment, is a quantitative estimation of risk from exposure
to a  toxic chemical.  It defines the relationship between the dose of  a
chemical and the incidence of the adverse effect.  (Life Systems, Inc., 1985).
    The dose-response assessment involves presentation of all pertinent
criteria, guidelines, and standards for the protection of human health and the


environment.  The dose-response assessment is performed for chemicals which
are carcinogens as well as non-carcinogens.  A brief discussion of the
components of the dose-response assessment for both of these types of
chemicals is as follows.
    For dose-response assessment of toxic substances (non-carcinogens) EPA has
established no observed adverse effect levels (NOAELs); no observed effect
levels (NOELS) and lowest observed adverse effect levels (LOAELs) based on
relevant toxocologic data.   Using these values and incorporating a safety
factor (e.g., 10, 100,  1000, etc) the acceptable daily intake (ADI) can be
calculated.  The ADI is defined as the largest amount of toxicant (in mg/day)
to which a  70-kg person can be chronically exposed which is not anticipated to
result in any adverse effects.  Of importance to note is that ADIs are
calculated  for individual compounds and do not reflect the possible adverse
effects resulting from  exposure to other chemicals present or the synergistic
and/or antagonistic effects that a chemical mixture may produce.  Use of ADI
values to assess hazard associated with chemical mixtures will be discussed in
a  subsequent  section.
    For dose-response assessment of carcinogenic chemicals the EPA Carcinogen
Assessment  group  (GAG)  has developed "unit risk" levels, or chemical potency
indexes.  These  unit risk levels are expressed as the lifetime human cancer
risk  per mg/kg body weight/day.  They are based on the best available human
and animal  study data and are  derived using mathematical models of the
chemical's  dose-response relationship.  They are not, however, adjusted for
facility-specific conditions.
    EPA has developed toxicity hazard profiles on a number of hazardous
constituents.  These profiles  define the "acceptable levels" of exposure to
non-carcinogenic chemicals  and the estimates of unit cancer risk for
carcinogenic  chemicals. Toxicological hazard profiles of these substances can
be found  in a set of Health Effects Assessments (HEAS) for hazardous chemicals
typically  found  at uncontrolled waste sites or which may be disposed of at
RCRA  facilities.  Copies of the HEAS for specific chemicals are available from
EPA's Office  of  Emergency and  Remedial Responses (OERR) in Washington, D.C.
In addition to the HEAS, toxicological information for hazardous constituents
of concern  can be found in  the Toxicological Profiles available through EPA's
Office of Waste  Programs Enforcement in Washington, D.C.


    The end-product of a hazard assessment is a qualitative description of the
toxic properties of the hazardous -constituents of concern'at the site and a
quantitative index of the toxicity for each constituent at the site, if the
data are sufficient for such an assessment.  (Life Systems, Inc., 1985).  Use
of the hazard assessment information (for both carcinogens and
non-carcinogens) together with the exposure analysis information, as generated
in the previous step, to characterize risk to human (and non-human)
populations resulting from exposure to releases to soils will be discussed in
the following section levels of risk characterization (e.g., qualitative,
quantitative) and the criteria used to select the appropriate level of risk
characterization to perform will also be presented.


    The risk characterization process can be either qualitative or
quantitative in nature.  The decision as to which level of risk analysis is to
be performed is dependent primarily on two factors:  (1) the primary effect of
hazardous constituents involved (e.g., carcinogenesis or toxic effects), and
(2) the level of exposure analysis (e.g., qua-litative or quantitative)
performed prior to the risk characterization.
    For chemicals which are carcinogens or suspected carcinogens quantitative
risk characterization is usually performed.  For non-carcinogens, either
qualitative or quantitative risk characterizations can be performed; the
decision as to which type is to be performed is usually dependent on the level
of exposure analysis conducted prior to the risk characterization.  If the
exposure analysis performed prior to the risk characterization is qualitative
in nature, qualitative risk characterization must be performed; e.g., no human
exposure estimates (such as intake or dose levels) have been calculated,
therefore quantitative risk characterization is not possible.  If the previous
exposure analysis was quantitative in nature, the permit writer has a choice
as to whether to use those estimated human intake or dose levels to perform a
quantitative risk analysis or to 'simply perform a qualitative analysis.  To
make this decision,  the following additional criteria should be considered:
(1) the level of expertise should be needed (and available) to perform the

risk analysis; e.g., quantitative risk characterization generally requires  a
greater amount of expertise in the field of toxicology and public health  than
does qualitative risk analysis due primarily to the greater number of
assumptions and generalizations needed to be made (to be discussed below);  and
(2) the time available to perform the risk characterization; e.g.,
quantitative risk characterization is generally more complex and
time-consuming than is qualitative risk characterization.
    The following sections describe the two levels of risk characterization
(e.g., qualitative and quantitative); guidance in the performance of these
risk characterization processes is also included.  For additional information
regarding risk characterization processes, the reader is referred to sources
given below.

Qualitative Risk Characterization

    A qualitative risk characterization is usually performed subsequent to  a
qualitative exposure analysis and provides a relative index of human risk
associated with exposure  to hazardous constituent releases to soil, and
indirectly to other contaminated media, such as air (through inhalation) or
biota (through  ingestion).  Qualitative risk characterizations are usually
performed  for chemicals which are non-carcinogens, but can also be performed
for chemicals which are carcinogens and which have either:  (1) been
qualitatively evaluated in the (previous) exposure analysis or, (2) have been
quantitatively  evaluated  in the previous exposure analysis and are expected to
pose  little or  no risk to human (or non-human) health.
    The  qualitative risk  characterization process involves an assessment of
two components:  (1) the  toxicological and biomedical evidence available for
the hazardous constituents of concern (as discussed previously in the hazard
assessment),  and (2) the  exposure potential for constituents of concern ( as
determined previously  in  the exposure assessment).
    The  first step  in  the qualitative risk characterization involves an
evaluation of all pathways of human  (and non-human) exposure determined to  be
"complete" in the exposure analysis.  The relative magnitude (significance) of
exposure  (rated as  high,  moderate, or low) for each exposure pathway is also
considered, and provide a means of preliminarily determining which routes of
exposure  potentially pose the greatest risk to human  (and non-human) health.

    The next step in the qualitative risk characterization process involves an
evaluation of the toxicological and bioraedical evidence of hazardous
constituents of concern, (as determined in the previous hazard assessment
phase) to determine the nature and severity of actual or potential health (and
environmental) hazards associated with these hazardous constituents of concern.
    By combining the information on the relative likelihood and significance
of exposure to human (and non-human) population via the pathways and routes
(identified in the exposure analysis) with the probability and nature of
potential hazards of the chemicals involved (identified in the hazard
assessment), the relative probability, magnitude, and type of risks to human
(and non-human) populations can be determined.  Determination of risk to these
identified populations (receptors) is qualitative in nature.  However, for
many conditions involving actual or potential exposure to human ( and
non-human ) populations, a qualitative characterization is adequate for
describing the risk to these receptors.  Whether or not a qualitative risk
characterization is adequate is dependent primarily on:  (1) the level of need
of the permit writer (e.g., the permit writer does not need to use the risk
characterization to evaluate the efficacy of corrective actions or to
establish permit conditions to a defined level), and (2) the projected
significance of the risk to specific receptors, as determined in the exposure
analysis.  For instance, if the chemicals of concern are of limited toxicity,
are at low environmental levels or are not expected to be associated with
exposure to human (or non-human) receptors, a qualitative characterization may
be adequate to describe the risk to these receptors.


    A quantitative risk characterization is usually performed for chemicals
which are known or expected carcinogens, and is frequently performed  for
chemicals which are non-carcinogens.  Despite the type of hazardous
constituents involved, a quantitative risk characterization can only  be
performed subsequent to a quantitative exposure analysis.  In other words, if
the permit writer, upon initial consideration of a cause of action to take a
given hazardous constituent release to soils, feels that he is not in need of
an indepth evaluation of exposure (and risk) or that available analytical data

is not complete or accurate enough to be used to perform an indepth exposure
(or risk) analysis, then he does not need to perform a quantitative risk
characterization.  He should, instead, perform qualitative (risk and exposure)
    A quantitative risk characterization consists of comparing the projected
human exposure levels (e.g. the intake or dose levels, as determined in the
previous section, quantitative exposure analysis) of the hazardous
constituents present to the acceptable dose levels (e.g., standards, criteria
and guidelines) established by various goverment agencies for these
compounds.  Such comparisons give an indication of the magnitude of the
adverse health and environmental effects that may result from exposure to
these substances.  The type and extent of risk posed by any facility depends
upon  the nature, duration, and level of exposure, as well as the type of
populations exposed.  For most hazardous constituent sources, the human (and
non-human) populations and conditions of exposure potentially affected by the
facility are quite diverse and cannot be assimilated by a single condition of
exposure to give a single absolute risk for the source.  For this reason, most
sources  are evaluated in terms of the risk posed to populations via separate
pathways and routes  of exposure.  To predict the risk ot populations
associated with  exposure to environmental constituents, hypothetical exposure
scenarios are  developed.  Exposure scenarios describes distinct exposure
conditions (e.g. estimated frequency duration exposure) to average and maximum
ambient  environmental constituent levels.
    Methods of quantitatively characterizing the risks to human (and
non-human) populations associated with exposure to environmental media
contaminated as  a  result of  release to soils is presented below.  Quantitative
risk  characterization processes  for evaluating chemicals which are
non-carcinogens  as well as carcinogens is presented.  In classifying a
chemical as a  carcinogen  (versus a non-carcinogen) it is meant that the
primary  effect (endpoint) of the chemical is carcinogenesis, although the
chemical may have  other non-carcinogenic (e.g. toxic) endpoints.  Because it
is  common for  a  source of hazardous constituent release to involve more than
one type of chemical, characterization of risks associated to chemical
mixtures is also presented.

Quantitative Risk Characterization of Non-Carcinogens

    A quantitative risk characterization for non-carcinogens involves
consideration of:  (1) the existing standards, guidelines, and criteria
developed by various regulatory agencies which represent the best scientific
estimates of health risk at given environmental concentrations (as presented
in the hazard assessment phase) and, (2) the (human) intake estimates
calculated in the exposure analysis phase, for each exposure route of concern.
    The human health guidelines established for non-carcinogens are
represented by the NOAELs, NOELs, LOAELs, and incorporating a safety factor to
account for uncertainty in the data on which these indices are based, ADI
values.  The ADI is commonly defined as the largest amount of toxicant in
mg/day for a 70 kg person which is not anticipated to result in any adverse
effects after chronic exposure.  To perform the risk characterization, the
first step is to consider the exposure scenarios for each route and condition
of exposure at the facility (as developed in the quantitative exposure
    For each exposure scenario (e.g., representing average, most-realistic
conditions, or maximum, worst-case conditions of exposure) the level of risk
is characterized.  To characterize the risk associated with exposure
conditions represented in each scenario, the estimated (human) intake level
(for  the route of exposure being evaluated in the scenario) is compared with
the ADI value for the hazardous constituent of concern.  If the estimated
intake level is  in excess of the ADI value, then the exposure conditions
described by the scenario represent an "unacceptable" risk to human health.
If the opposite  is true, e.g.  the intake value for  that route of exposure and
chemical is less than the corresponding ADI value,  then the conditions
represent an "acceptable" risk to human health.  The intake values for each
route of exposure of concern are evaluated in a similar fashion.  For releases
to soils, this the relevant routes of exposure include:

    •    Direct contact (with soils)-
    •    Inhalation (of fugitive dusts), with possible reingestion".
    •    Ingestion of food products and soil).


There are limitations and assumptions inherent in any risk characterization
process especially when the characterization process involves routes of
exposure which are difficult to assess.  Some of the limitations and
assumptions inherent in characterizing risks via these routes of exposure are
present in the final section.

Quantitative Risk Characterization of Carcinogens

    Like the quantitative risk characterization process for non-carcinogens,
the process of characterizing risks associated with exposure to chemicals
whose primary effect is carcinogenesis involves consideration of the existing
standards, guidelines and criteria which represent the best scientific
estimates of health risk at given environmental concentrations as presented in
the hazard assessment phase.  Unlike non-carcinogens, however, the second
consideration in evaluating risks associated with exposure to chemicals which
are carcinogens is the estimated dose incurred by receptors, as calculated in
the previous quantitative exposure analysis phase, for each route of exposure
of concern.
    For  chemicals which are carcinogens, the guidelines used to perform
quantitative risk characterizations are called "risk levels", i.e., the
incremental risk of developing cancer from exposure to the hazardous
constituent of concern.  The EPA in its Ambient Water Quality Criteria
Documents  uses a  range of risk levels from 10   to 10   to describe the
increased  risk of cancer predicted for exposure to low dose levels of
chemicals  (e.g., which are  typical of environmental conditions).  A
one-in-one-million  increase  in risk (10  ) is  the mean value of this range
and  is often used as a baseline  level.  This base level does not necessarily
represent  a  level of "acceptable" risk, but is used as reference for which
assessments of risk  to populations can be made.
    The  calculated  environmental cancer risks  are derived using the projected
exposure  (e.g., dose)  levels calculated in the exposure analysis phase and the
measure  of chemical  hazard  or potency associated with that chemical (the unit
risk  level presented in  the hazard assessment  phase.  The calculated cancer
risk  level is compared to  the baseline value of 10   , in order to provide an

indication of the magnitude of the risk present.  These resulting risk
estimates are interpreted as probabilities of incremental cancer risks over
lifetime exposure.
    To perform the quantitive risk characterization for carcinogens the first
step is to consider the exposure scenarios developed in the previous exposure
analysis phase.  For each exposure scenario, (e.g., those representing
average, most-realistic conditions, as well as those representing maximum,
worst-case conditions of exposure), the risk is characterized.  To
characterize the risk associated with the hypothetical exposure conditions
represented in each scenario the estimated human dose value (calculated in the
quantitative exposure analysis phase) is multiplied by the unit risk level for
the chemical of concern.  The resulting estimate of risk is then compared with
the baseline risk value of 10~  to predict the incremental increase in risk
associated with the exposure route and scenario being evaluated.  The flow
diagram in Figure B-8 shows how the human dose value (calculated in the
quantitative exposure analysis phase) can be used to predict risk associated
with exposure  to a given medium, in this example, soils.  The process depicted
in the diagram can be used to estimate the risks associated with all routes of
exposure being evaluated, provided that estimates of dose for the exposure
routes are provided.
    An example of a typical risk calculation is presented below:
               Risk = daily dose *(carcinogenic) unit risk factor
                      over 70 years
                      of life
Of  importance to note is that this equation can only be used at low
environmental levels for hazardous constituents of concern.  For sources where
chemical intakes may be large (e.g., carcinogenic risk labove 0.10), an
alternate model should be considered.  In this situation, the permit writer
should consult EPA Headquarters for guidance in use of the appropriate model.
    It should be recognized that, like the calculated non-carcinogenic risk
estimate, the carcinogenic risk estimate is dependent on numerous assumptions,
and many uncertainties and limitations are inherent in the process.  The
following section briefly describes some of the uncertainties and assumptions

                          (e.g.  intake dose estimate)
                        A:  Yes
                                         Ql:  Is the primary effect of
                                              the hazardous constituent
                                             A:  No
What is the Unit
Cancer Risk (UCR)
                              What is the ADI?
                              (or other relevant
                              criteria, standards
                              of acceptable human
                                              RISK CHARACTERIZATION
What  is the average
expected incremental
risk  (over 70 years)?
What is the
maximum expected
incremental risk
RISK =  Carcinogenic Potency Factor
       *Average  (or Maximum)
        expected  lifetime dose

     •  present  assumptions and
        uncertainties of results
Q3:  Is the estimated
     exposure value
     (intake) for that
     route of exposure
     in excess of the
     ADI?  (or other
     relevant criteria,
     standard of
     acceptable human
                                                  present assumptions and
                                                  uncertainties of results
 aThis assumes  that  the primary effect of the hazardous constituent is carcin-
 ogenesis; other noncarcinogenic endpoints can be evaluated via the method of
 risk evaluation depicted here.
    Figure B-8.  Schematic  flow diagram of alternate methods of quantitative
                 human risk characterization (given a determined dose incurred
                 by  receptor populations).

common in characterizing risks associated with exposure to releases to'soils
for exposure routes of concern (e.g., direct contact, inhalation, and
ingestion).  For additional information on characterizing risks to human
populations via these routes, the reader is referred to ICF.Inc.. 1985.


    Some of the major sources of uncertainty in any risk characterization
process involve the hazard information for the chemicals of concern.  Some
common sources of uncertainty include:  (1) the toxicity information used to
estimate risks to human populations which is derived from animal studies, and
must be extrapolated to humans; and (2) many of the toxicity studies are
performed at high dose levels and must be applied to situations of low level
environmental contaminant levels, typical of chemical releases; extrapolation
from high to low doses increases the uncertainty in the results.  Uncertainty
can also be introduced at the exposure analysis phase, such as when exposure
modeling (e.g., level II or III analysis using equations or models,
respectively) is used in the calculation of intake or dose and which is based
on many simplifying assumptions.  Uncertainty is almost always introduced when
the possible routes of exposure are difficult to qualify and quantify,
although they may be extremely important to certain populations at risk.  The
following  subsections describe some of the assumptions and uncertainties
inherent in the characterization of risk associated with exposure via pathways
and routes relevant to hazardous constituent releases to soils; e.g., direct
contacts (with contaminated soils), inhalation of airborne particulates to
which hazardous constituents have adsorbed with possible reingestion, and
ingestion of food products (into which hazardous constituents  in soil have
been uptaken).

Dermal Contact with Contaminated Soils

    Dermal contact (with contaminated soils) is a route of exposure for which
there is limited information on which to base estimates of human risk.
Characterization of risk for this route of exposure  therefore  requires making
numerous assumptions, and a cetain degree of uncertainty is inherent  in  the


evaluation.  Many of these uncertainties are introduced at the exposure
analysis phase with the development human exposure scenarios and the
estimation of the frequency and duration of exposure.  Other uncertainties are
introduced at the hazard assessment phase with the estimation of human
absorbtion percentages for the hazardous constituents of concern.  Some of the
assumptions and uncertainties inherent in characterization of risk for this
route of exposure are as follows:

    •    determination of the amount of soil actually contacting the skin
         (during exposure), and the relative amount of pure hazardous
         constituent to which there is exposure,
    •    determination of the parameters associated with the part of the body
         contacted  (e.g., surface  area, actual part of body contacted, etc.),
    •    the  percent absorbtion of the hazardous constituent  contacting the
         body (e.g. based on the physical/chemical properties of constituents
         involved,  available human absorption data, etc.),
    •    age  of  individuals contacted,
    •    human activity pattern associated with exposure (e.g., frequency,
         duration exposure, etc.), and
    •    human activity pattern after exposure (e.g. washing, bathing, eating,
 Any assumptions and uncertainties  introduced  into  the  risk  characterization
 process  should be identified  and presented.   Consideration  of  these
 limitations will help to more accurately  interpret  the risk estimates  that are

 Ingestion of Contaminated Soils  (by a Child Exhibiting Pica)

     Ingestion of contaminated soils is not a  common route of human exposure,
 and primarily involves young  children who come  into contact with  contaminated
 soils (e.g. while playing)  and either accidentally  ingest the  soil or  exhibit
 pica, an abnormal craving for non-food objects.  Because exposure via  this
 route is expected to be infrequent, and generally  at low levels,  the human
 risks associated with the exposure are usually  not  considered  significant.  An
 exception would be under circumstances involving close proximity  to the

facility of an area heavily utilized by children (e.g. a playground) i-n which
exposure via this route would be more common.  The assumptions and limitations
inherent in risk characterization for this route of exposure are introduced
primarily at the exposure analysis phase (e.g. with the development of
exposure scenarios and the determination of frequency and duration of
exposure) and the hazard assessment phase (e.g. with the estimation of the
amount of absorbtion of the chemical into the body after ingestion).  They are
as follows:

    •    determination of human use areas near the facility and the associated
         human activity patterns,
    •    determination of the frequency, duration, and quantity of soil
    •    determination of age of exposed population, and
    •    determination of the percent absorption of hazardous constituents
         into the body upon ingestion.

Again,  the  assumptions and limitations introduced into the risk characteri-
zation process for this route of exposure should be presented with the
interpretation of the calculated risk estimates.

Inhalation  (if Airborne Particulates to Which Hazardous Constituents Have
Adsorbed) with Possible Reingestion

    The  estimation of human risk assessment associated with exposure via
inhalation  contaminated dusts (e.g. airborne particulates) has been widely
researched,  and  information relevant to the estimation and interpretation of
risk estimates calculated for this route of exposure are presented primarily
in two  sources:  (1) ICF, Inc.,  1985 (Draft EPA Superfund Health Assessment
Manual), and (2) Schultz, et al.,  1984 (Draft EPA Superfund Exposure
Assessment  Manual).
    Despite  the  availability of  information for use in characterizing risks
associated  with  exposure via inhalation of airborne particulates,  little
evidence is  available for use in characterizing risks to human populations
exposed  to  hazardous constituents  via reingestion of  inhaled particulates.
Exposure via this indirect route is generally considered of limited

significance due to Che speradic nature of the exposure and the generally  low
levels of hazardous constituents to which there is exposure.  In brief, some
of the assumptions and uncertainties inherent in the characterization of risk
associated with exposure via this route include:

    •    determination of duration, frequency, and quantity of air hazardous
         constituent exposure;
    •    determination of the age of exposed population (e.g. as it affects
         the average ventilation rate);
    •    determination of the percent absorbtion of the chemical of concern
         within the respiratory system;
    •    determination of the particulate size (and its affect on absorbtion
         in  the respiratory tract); and
    •    determination of the extent to which reingestion of respired
         particulates occurs, and the resulting absorbtion rate of the
         chemicals  in the digestive tract.

Again,  any  assumptions and limitations introduced into the risk characteri-
zation  process  should be presented.

Ingestion of Biota  (Into Which  Hazardous Constituents Have Been Uptaken)

     Ingestion of  biota  is a route of human exposure for which risk characteri-
zation  is generally very difficult  to  perform.  This  is due primarily to the
limited availability  of data  to define the potential  for uptake of hazardous
constituents by plant  species.  Because of this common limitation, many
assumptions must  be made during the risk characterization process in order  to
define  the  extent of contaminant  uptake by biota and  the subsequent risk to
human populations via  ingestion.
     Some of these assumptions  and  uncertainties include:

     •    determination  of levels  of hazardous constituents  in plants exposed
          to contaminated soils  and  subsequently ingested;
     •    determination  of the  frequency, duration, and quantity of hazardous
          constituent  exposure;
     •    absorbtion rate of  ingested hazardous constituents; and
     •    age of population exposed.

Because there is limited information with which to perform risk "characteriza-
tions for this route of exposure, quantitative risk characterizations are
generally not possible.  Quantitative risk characterization would involve
direct sampling and analysis of the food products, and oftentimes this
information is not available.  Characterization of risks associated with
exposure via this route is, therefore, generally quanlitative in nature.


    In summary, the risk characterization process involves assessment of two
components, the exposure assessment and the hazard assessment.  By combining
the information in each of these components, actual or potential risks to
human health and the environment can be characterized.  Risk characterizations
can be either qualitative or quantitative.  The decision as to which level is
performed is dependent primarily on the level of exposure analysis performed
prior to the risk characterization (e.g. qualitative, quantitative).
Regardless of the level of risk characterization performed, however, the
outcome of the analysis is a determination of the actual or potential risks to
human (and non-human) populations resulting from exposure to media
contaminated as a result of release to soils.  Because there is no one set
method for performing risk characterizations, the risk characterization
process used to evaluate each pathway and route of exposure for a given
environmental medium involves making numerous assumptions.  This is
particulary true for exposure pathways and routes which are difficult to
characterize.  The making of assumptions introduces a certain amount of
uncertainty into the risk characterization process.  Because of this, the
results of the risk characterization process must be cautiously interpreted.
Despite the inherent uncertainty in the results of the risk characterization
process, however, the  information so derived can be used, at a minimal, to
identify potential risks to human (and non-human) population associated with
exposure to environmental contaminants (i.e., hazardous constituents).