United States       Office of Solid Waste and  Publication 9355.4-23
Environmental Protection   Emergency Response    July 1996
Agency          Washington, DC 20460

Superfund


Soil Screening Guidance


User's Guide
                           Second Edition

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                                  EPA/540/R-96/018
                                      July 1996
Soil Screening  Guidance:
        User's  Guide
           Second Edition
 Office of Emergency and Remedial Response
    U.S. Environmental Protection Agency
         Washington, DC 20460

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                                       ACKNOWLEDGMENTS
The development of this guidance was a team effort led by the staff of the Office of Emergency and Remedial Response.
David Cooper served as Team Leader for the overall effort.  Marlene Berg coordinated the series of Outreach meetings with
interested parties outside the Agency.  Sherri Clark, Janine Dinan and Loren Henning were the principal authors.  Paul White
of EPA's Office of Research and Development provided tremendous support in the development of statistical approaches to
site sampling.

Exceptional technical assistance was provided by several contractors. Robert Truesdale of Research Triangle Institute (RTI)
led their team effort in the development of the Technical Background Document under EPA Contract 68-W1-0021. Craig
Mann of Environmental Quality Management, Inc. (EQ) provided expert support in modeling inhalation exposures under
EPA Contract 68-D3-0035. Dr. Smita Siddhanti of Booz-Allen & Hamilton, Inc. provided technical support for the final
production of the User's Guide and Technical Background Document under EPA Contract 68-W1-0005.

In addition, the authors would like to thank all EPA, State, public and peer reviewers whose careful review and thoughtful
comments contributed to the quality of this document.

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                                               DISCLAIMER
Notice: The Soil Screening Guidance is based on policies set out in the Preamble to the Final Rule of the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), which was published on March 8,  1990 (55 Federal Register
8666).

This guidance document sets forth recommended approaches based on EPA's best thinking to date with respect to soil
screening.  This document does not establish binding rules. Alternative approaches for screening may be found to be more
appropriate at specific sites (e.g., where site circumstances do not match the underlying assumptions, conditions and models
of the guidance). The decision whether to use an alternative approach and a description of any such approach should be
placed in the Administrative Record for the site. Accordingly, if comments are received at individual sites questioning the
use of the approaches recommended in this guidance, the comments should be considered and an explanation provided for the
selected approach. The Soil Screening Guidance: Technical Background Document (TBD) may be helpful in responding to
such comments.

The policies set out in both the Soil Screening Guidance: User's Guide and the supporting TBD are intended solely as
guidance to the U.S. Environmental Protection Agency (EPA) personnel; they are not final EPA actions and do not
constitute rulemaking. These policies are not intended, nor can they be relied upon, to create any rights enforceable by any
party in litigation with the United States government. EPA officials may decide to follow the guidance provided in this
document, or to act at variance with the guidance, based on an analysis of specific site circumstances. EPA also reserves the
right to change the guidance  at any time without public  notice.

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                                      TABLE  OF  CONTENTS
1.0 INTRODUCTION  	   1
    1.1     Purpose	  1
    1.2     Role of Soil Screening Levels	  2
    1.3     Scope of Soil Screening Guidance	  3
2.0 SOIL SCREENING PROCESS   	   5
    2.1     Step 1:  Developing a Conceptual Site Model  	   5
           2.1.1    Collect Existing Site Data  	   5
           2.1.2    Organize and Analyze Existing Site Data	   5
           2.1.3    Construct a Preliminary Diagram of the CSM 	   5
           2.1.4    Perform Site Reconnaissance  	   7
    2.2     Step 2:  Comparing CSM to SSL Scenario  	   7
           2.2.1    Identify Pathways Present at the Site Addressed by Guidance   	   7
           2.2.2    Identify Additional Pathways Present at the Site Not Addressed by Guidance 	   8
           2.2.3    Compare Available Data to Background  	   8
    2.3     Step 3:  Defining Data Collection Needs for Soils  	   9
           2.3.1    Stratify the Site Based on Existing Data  	   9
           2.3.2    Develop Sampling and Analysis Plan for Surface Soil	   12
           2.3.3    Develop Sampling and Analysis Plan for Subsurface Soils  	   14
           2.3.4    Develop Sampling and Analysis Plan to Determine Soil Characteristics   	   17
           2.3.5    Determine Analytical Methods and Establish QA/QC Protocols	   18
    2.4     Step 4:  Sampling and Analyzing Site Soils  & DQA 	   18
           2.4.1    Delineate Area and Depth of Source  	   20
           2.4.2    Perform DQA Using Sample Results   	   20
           2.4.3    Revise the CSM  	   20
    2.5     Step 5:  Calculating Sitespecific  SSLs  	   20
           2.5.1    SSL Equations—Surface Soils  	   21
           2.5.2    SSL Equations-Subsurface Soils  	   23
           2.5.3    Address Exposure to Multiple Chemicals  	   32
    2.6     Step 6:  Comparing Site Soil Contaminant Concentrations to Calculated SSLs 	   33
    2.7     Step 7:  Addressing Areas Identified for Further Study  	   36
REFERENCES  	   37

ATTACHMENTS
    A.     Conceptual Site Model Summary	A-l
    B.     Soil Screening DQOs for Surface Soils and Subsurface Soils  	B-l
    C.     Chemical Properties for SSL Development 	C-l
    D.     Regulatory and Human Health Benchmarks Used  for SSL Development	D-l
                                                    111

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                                          LIST  OF  EXHIBITS
Exhibit 1        Conceptual Risk Management Spectrum for Contaminated Soil 	  2
Exhibit 2        Exposure Pathways Addressed by SSLs	  4
Exhibit 3        Key Attributes of the User's Guide  	  4
Exhibit 4        Soil Screening Process  	  6
Exhibit 5        Data Quality Objectives Process	   10
Exhibit 6        Defining Study Boundaries  	   11
Exhibit 7        Designing Sampling and Analysis Plan for Surface Soils	   13
Exhibit 8        Designing Sampling and Analysis Plan for Subsurface Soils  	   15
Exhibit 9        U.S. Department of Agriculture Soil Texture Classification	19
Exhibit 10       Site-Specific Parameters for Calculating Subsurface SSLs	   25
Exhibit 11       Q/C Values by Source Area, City, and Climatic Zone	   27
Exhibit 12       Simplifying Assumptions for SSL Migration to Ground Water Pathway  	   29
Exhibit 13       SSL Chemical with Non-carcinogen Toxic Effects on Specific Target Organ/Systems	   34
                                                     IV

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                                        LIST  OF ACRONYMS
ARAR
ASTM
CERCLA
CLP
CSM
CV
DAF
DNAPL
DQA
DQO
EA
EPA
HBL
HEAST
HELP
HHEM
HQ
IRIS
ISC2
MCL
MCLG
NAPL
NOAEL
NPL
NTIS
OERR
PA/SI
PCB
PEF
PRO
Q/C
QA/QC
QL
RAGS
RCRA
RfC
RfD
RI
RI/FS
RME
ROD
SAB
SAP
SPLP
SSL
TBD
TCLP
USDA
VF
VOC
Applicable or Relevant and Appropriate Requirement
American Society for Testing and Materials
Comprehensive Environmental Response, Compensation and Liability Act
Contract Laboratory Program
Conceptual Site Model
Coefficient of Variation
Dilution Attenuation Factor
Dense Nonaqueous Phase Liquid
Data Quality Assessment
Data Quality Objective
Exposure Area
Environmental Protection Agency
Health Based Limit
Health Effects Assessment Summary Table
Hydrological Evaluation of Landfill Performance
Human Health Evaluation Manual
Hazard Quotient
Integrated Risk Information System
Industrial Source Complex Model
Maximum Contaminant Level
Maximum Contaminant Level Goal
Nonaqueous Phase Liquid
No-Observed-Adverse-Effect Level
National Priorities List
National Technical Information Service
Office of Emergency and Remedial Response
Preliminary Assessment/Site Inspection
Polychlorinated Biphenyl
Particulate Emission Factor
Preliminary Remediation Goal
Site-Specific Dispersion Model
Quality Assurance/Quality Control
Quantitation Limit
Risk Assessment Guidance for Superfund
Resource Conservation and Recovery Act
Reference Concentration
Reference Dose
Remedial Investigation
Remedial Investigation/Feasibility Study
Reasonable Maximum Exposure
Record of Decision
Science Advisory Board
Sampling and Analysis Plan
Synthetic Precipitation Leaching Procedure
Soil Screening Level
Technical Background Document
Toxicity Characteristic Leaching Procedure
U.S.  Department of Agriculture
Volatilization Factor
Volatile Organic Compound

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            1.0  INTRODUCTION
1.1   Purpose

The Soil Screening Guidance is a tool that the U.S.
Environmental Protection Agency (EPA) developed
to help standardize and accelerate the evaluation and
cleanup  of contaminated  soils at  sites  on the
National Priorities List (NPL) with future residential
land use.1 This guidance provides a methodology for
environmental science/engineering professionals  to
calculate risk-based, site-specific,  soil screening
levels (SSLs) for contaminants in soil that may be
used to identify areas needing  further investigation
at NPL sites.

SSLs are not national  cleanup standards.  SSLs
alone do not trigger the need for response actions  or
define "unacceptable" levels of contaminants in soil.
In this guidance, "screening" refers to the process  of
identifying  and  defining  areas, contaminants, and
conditions,  at a particular site that  do not require
further Federal attention.  Generally, at sites where
contaminant concentrations fall below SSLs, no
further  action  or  study  is warranted  under the
Comprehensive   Environmental   Response,
Compensation and Liability  Act (CERCLA). (Some
States have developed screening numbers that are
more stringent than the generic  SSLs presented here;
therefore, further study may be warranted under
State  programs.) Generally,  where  contaminant
concentrations equal or exceed SSLs,  further study
or  investigation, but  not necessarily cleanup,  is
warranted.

SSLs are risk-based concentrations  derived  from
equations  combining   exposure   information
assumptions with EPA toxicity data. This User's
Guide  focuses on the application of a simple  site-
specific  approach by providing  a  step-by-step
methodology to  calculate site-specific SSLs and is
part of a larger framework that includes both generic
and more  detailed  approaches  to calculating
screening   levels.  The  Technical  Background
Document  (TBD)  (EPA,  1996),  provides more
information about these  other  approaches. Generic
SSLs  for the most common contaminants  found  at
NPL sites are included in the TBD.  Generic  SSLs are
calculated from the same equations presented in this
guidance, but are  based on a number  of default
assumptions chosen to be  protective  of human
health for most site conditions. Generic SSLs can be
used  in  place of site-specific  screening levels;
however,  in general, they are expected to be  more
conservative than  site-specific levels.   The site
manager should weigh the cost of collecting the data
necessary to develop  site-specific SSLs  with  the
potential  for deriving a higher SSL that provides an
appropriate  level  of protection.

The framework presented in the TBD also includes
more  detailed modeling  approaches for developing
screening  levels  that  take  into account  more
complex site conditions than the simple site-specific
methodology emphasized in this guidance.  More
detailed approaches may be  appropriate when site
conditions (e.g., a thick vadose zone)  are  different
from  those assumed  in the simple  site-specific
methodology presented here. The technical details
supporting the  methodology  used in  this  guidance
are provided in the TBD.

SSLs developed in accordance with this guidance are
based on future residential land use assumptions  and
related exposure scenarios. Using this guidance for
sites where  residential  land use assumptions do  not
apply could result in overly conservative screening
levels; however, EPA recognizes that  some parties
responsible  for sites with non-residential  land  use
might still find benefit in using the SSLs as a tool to
conduct a conservative  initial screening.

SSLs  developed in accordance  with  this  guidance
could also be used for  Resource Conservation and
Recovery Act  (RCRA)  corrective action sites as
"action levels," since the RCRA  corrective action
program currently  views the role of action levels as
generally  fulfilling  the same  purpose as  soil
screening  levels.2  In addition, States may use this
guidance  in  their voluntary cleanup programs, to the
extent they  deem appropriate. When applying  SSLs
to RCRA corrective action sites or for sites  under
State  voluntary cleanup programs, users of this
guidance should recognize, as stated above, that  SSLs
are based on residential land use assumptions. Where
these assumptions  do not apply,  other approaches

1  Note that the  Superfund program defines "soil" as having a  particle
  size under 2mm, while the RCRA program allows for particles under
  9mm in size.

2 Further information on the role of action levels in the RCRA corrective
  action program is available in an Advance Notice of Proposed
  Rulemaking (signed April 1996).

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for determining the need for further study might be
more appropriate.

1.2   Role  of  Soil  Screening  Levels

In identifying and managing risks  at  sites,  EPA
considers   a   spectrum    of   contaminant
concentrations.  The level of concern associated
with those concentrations depends on the likelihood
of  exposure to  soil contamination  at levels  of
potential concern to human health or to ecological
receptors.

Exhibit  1  illustrates  the  spectrum  of  soil
contamination encountered at Superfund  sites and
the conceptual range of risk management responses.
At one end  are levels of contamination  that clearly
warrant a response action; at the other end are
levels that are below regulatory concern. Screening
levels  identify   the   lower   bound  of   the
spectrum—levels below which EPA believes there is
no  concern  under  CERCLA,  provided conditions
associated  with the SSLs are  met. Appropriate
cleanup goals for a particular site may fall anywhere
within  this range depending  on  site-specific
conditions.
       No further study
       warranted under
         CERCLA
Site-specific
 cleanup
 goal/level
 Response
action clearly
 warranted
     "Zero"      Screening
  concentration     level
       Response
        level
        Very high
       concentration
     Exhibit 1. Conceptual  Risk Management
         Spectrum  for Contaminated Soil
EPA  anticipates the use  of SSLs as  a tool to
facilitate prompt identification of contaminants  and
exposure  areas  of  concern during both  remedial
actions and some removal actions under  CERCLA.
However, the  application of this or any screening
methodology  is not  mandatory at  sites being
addressed under CERCLA or RCRA.  The framework
leaves discretion to the site manager and technical
experts  (e.g.,  risk  assessors, hydrogeologists) to
determine whether  a  screening  approach  is
appropriate for the  site and, if  screening is to be
used, the proper  method  of implementation. If
comments are received at individual sites questioning
the use of  the  approaches recommended in this
guidance, the comments should be considered and an
explanation provided as part of the site's Record of
Decision (ROD). The  decision to use a screening
approach should be made  early  in the process of
investigation at the  site.

EPA developed  the Soil  Screening Guidance to be
consistent   with and  to   enhance  the  current
Superfund investigation process and anticipates  its
primary use  during the early  stages of a remedial
investigation (RI) at NPL sites.  It does not replace
the Remedial Investigation/Feasibility Study (RI/FS)
or risk assessment,  but use of screening levels can
focus the RI and risk assessment on aspects of the
site that are more  likely to  be a  concern under
CERCLA.  By screening  out areas of sites, potential
chemicals of concern,  or exposure  pathways  from
further investigation, site managers and technical
experts can limit  the  scope  of  the remedial
investigation or risk assessment.  SSLs can  save
resources by helping to  determine which areas  do
not require additional Federal  attention early in the
process.  Furthermore,  data gathered during the soil
screening process can be used in later Superfund
phases, such as  the  baseline  risk  assessment,
feasibility study, treatability  study, and remedial
design. This  guidance  may also be  appropriate for
use by the  removal program when  demarcation of
soils above residential risk-based numbers coincides
with the purpose and scope of the removal action.

The process  presented in this  guidance to  develop
and apply simple, site-specific soil screening levels is
likely to be most  useful where it is difficult to
determine whether areas of soil are contaminated to
an  extent that  warrants further investigation  or
response (e.g., whether areas of soil at an NPL site
require further investigation under CERCLA through
an RI/FS).    As  noted above,  the screening levels
have been developed assuming residential land use.
Although  some of  the  models  and  methods
presented  in this guidance  could be modified to
address exposures under  other  land uses, EPA has
not yet standardized assumptions for those other
uses.

Applying  site-specific screening levels involves
developing   a   conceptual site model (CSM),
collecting a  few easily  obtained site-specific soil
parameters (such as  the dry bulk density and percent

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moisture), and sampling to measure contaminant
levels in surface and subsurface soils. Often, much of
the information needed to develop the CSM can be
derived from previous  site investigations  [e.g., the
Preliminary  Assessment/Site Inspection  (PA/SI)]
and, if properly  planned,  SSL  sampling can  be
accomplished in one mobilization.

An  important  part  of  this  guidance  is  a
recommended sampling approach that balances the
need for  more data to  reduce uncertainty with the
need to limit data collection costs. Where data are
limited such that use of the  "maximum test" (Max
test) presented here is not appropriate, the guidance
provides  direction on the use of other conservative
estimates of  contaminant  concentrations  for
comparison with the SSLs.

This guidance provides the information needed to
calculate  SSLs  for 110  chemicals.   Sufficient
information  may not be available to develop  soil
screening levels  for additional  chemicals. These
chemicals should not be screened  out, but should be
addressed in  the baseline risk assessment for the site.
The  Risk Assessment Guidance for  Superfund
(RAGS),  Volume 1:  Human  Health Evaluation
Manual (HHEM), Part A, Interim Final. (U.S. EPA,
1989a) provides guidance on conducting baseline
risk assessments for NPL sites.   In  addition, the
baseline   risk  assessment  should  address  the
chemicals, exposure pathways, and areas at the site
that are not screened out.

Although SSLs  are  "risk-based,"  they do  not
eliminate the need to  conduct a site-specific risk
assessment.  SSLs   are  concentrations   of
contaminants  in soil  that  are  designed  to  be
protective of exposures in a residential setting. A
site-specific  risk assessment is an evaluation of the
risk posed by exposure to site contaminants  in
various media. To  calculate SSLs, the  exposure
equations and pathway models are run in reverse to
backcalculate   an   "acceptable  level"  of a
contaminant  in soil. For the  ingestion, dermal,  and
inhalation pathways, toxicity criteria are used to
define an acceptable  level of contamination in soil,
based on a one-in-a-million (1O6) individual excess
cancer risk for carcinogens and  a hazard quotient
(HQ)  of  1  for  non-carcinogens.   SSLs   are
backcalculated for  migration  to  ground water
pathways using ground water concentration limits
[nonzero  maximum  contaminant  level  goals
(MCLGs), maximum contaminant levels (MCLs), or
health-based limits (HBLs) (1O6 cancer risk or a HQ
of 1) where MCLs are not available].

SSLs can be used as Preliminary Remediation Goals
(PRGs) provided appropriate conditions are met
(i.e., conditions found at a specific site are similar to
conditions assumed in  developing the SSLs). The
concept of calculating risk-based contaminant levels
in soils for use as PRGs (or "draft" cleanup levels)
was introduced in  the  RAGS  HHEM,  Part B,
Development   of  Risk-Based   Preliminary
Remediation   Goals.  (U.S. EPA,  1991c).  The
models,  equations,  and assumptions  presented
in  the Soil Screening Guidance to address
inhalation    exposures   supersede   those
described   in   RAGS  HHEM,  Part  B,  for
residential  soils. In  addition, this  guidance
presents  methodologies  to  address  the
leaching of contaminants  through soil to an
underlying  potable  aquifer.  This  pathway
should be  addressed in  the  development of
PRGs.

PRGs may then be used as the basis for developing
final  cleanup  levels  based on  the  nine-criteria
analysis described in the National Contingency Plan
[Section 300.430  (3)(2)(I)(A)].  The  directive
entitled Role of the  Baseline Risk Assessment in
Superfund Remedy Selection Decisions (U.S. EPA,
199Id) discusses  the  modification  of PRGs  to
generate cleanup levels. The SSLs should  only be
used as cleanup levels when a site-specific nine-
criteria evaluation  of the SSLs  as PRGs for soils
indicates that a selected remedy achieving the SSLs
is protective, complies  with Applicable or Relevant
and Appropriate  Requirements (ARARs), and
appropriately balances  the other  criteria, including
cost.

1.3 Scope  of  Soil  Screening
     Guidance

In  a  residential setting, potential  pathways  of
exposure to contaminants  in soil are as follows (see
Exhibit 2):

• Direct ingestion
• Inhalation of volatiles and fugitive dusts

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•  Ingestion of contaminated ground water caused by
   migration  of  chemicals through  soil  to an
   underlying potable aquifer

•  Dermal absorption

•  Ingestion of homegrown produce that has been
   contaminated via plant uptake

•  Migration of volatiles into basements.
                 Direct Ingestion
                    of Ground
                  Water and Soil
                                    Blowing _^
                                    Dust and
                                    ^Volatization
                             Also Addressed:
                             • Plant Uptake
                             • Dermal Absorption
     Exhibit 2. Exposure  Pathways Addressed
                    by  SSLs.

The Soil Screening Guidance addresses each of these
pathways to the greatest extent practical. The first
three  pathways -- direct  ingestion, inhalation of
volatiles and fugitive dusts, and ingestion of potable
ground water  — are  the  most  common routes of
human exposure to contaminants in the  residential
setting.  These pathways  have  generally accepted
methods,  models,  and  assumptions   that lend
themselves  to a standardized  approach.  The
additional  pathways   of  exposure   to  soil
contaminants, dermal absorption, plant uptake,  and
migration of volatiles  into  basements,  may also
contribute  to  the risk  to  human health from
exposure to specific  contaminants  in a  residential
setting. This guidance addresses these pathways to a
limited extent based on available empirical data. (See
Step 5 and the TBD for further discussion).

The  Soil  Screening  Guidance  addresses  the
human exposure pathways  listed  previously
and will  be appropriate for most  residential
settings. The  presence  of  additional  pathways
or  unusual site  conditions does not preclude
the use of  SSLs in  areas  of the site that are
currently   residential   or  likely   to  be
residential  in  the  future.  However,  the risks
associated   with   additional   pathways  or
conditions  (e.g., fish consumption,  raising of
livestock, a heavy truck  traffic  on unpaved
roads) should be  considered in the  RI/FS to
determine   whether  SSLs  are   adequately
protective.

An  ecological  assessment  should  also  be
performed  as  part  of  the RI/FS  to evaluate
potential  risks to ecological  receptors.

The Soil Screening Guidance  should  not be
used for areas with  radioactive contaminants.

Exhibit 3  provides key attributes   of the Soil
Screening Guidance: User's Guide.
   Exhibit 3:  Key  Attributes of the User's
                    Guide

  •  Standardized equations are presented to
     address human  exposure pathways in a
     residential setting consistent with
     Superfund's concept of "Reasonable
     Maximum Exposure" (RME).

  •  Source size (area and depth) can be
     considered on a site-specific basis using
     mass-limit models.

  •  Parameters are  identified for which site-
     specific information is needed to develop
     SSLs.

  •  Default values are provided to calculate
     generic SSLs when site-specific information
     is not available.

  •  SSLs are based on a 10-6 risk for
     carcinogens or a hazard quotient of 1 for
     noncarcinogens. SSLs for migration to
     ground water are based on (in order of
     preference): nonzero maximum contaminant
     level goals (MCLGs), maximum contaminant
     levels (MCLs), or the aforementioned risk-
     based targets.

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   2.0  SOIL  SCREENING  PROCESS
The soil screening process (Exhibit 4) is a step-by-
step approach that involves:

•  Developing a conceptual site model (CSM)
•  Comparing the  CSM to the SSL scenario
•  Defining data collection needs
•  Sampling and analyzing soils at site
•  Calculating site-specific SSLs
•  Comparing site soil contaminant concentrations
   to calculated SSLs
•  Determining which areas of the  site require
   further study.

It  is  important to follow this  process to implement
the Soil Screening Guidance properly. The remainder
of this guidance discusses each activity in detail.

2.1   Step 1: Developing  a
                 Conceptual  Site
                 Model

The CSM is a three-dimensional "picture" of site
conditions that illustrates  contaminant distributions,
release mechanisms, exposure  pathways  and
migration routes,  and potential receptors. The CSM
documents  current site conditions and is supported
by maps,  cross  sections, and  site  diagrams  that
illustrate  human and  environmental  exposure
through contaminant release  and migration to
potential receptors. Developing an accurate CSM is
critical to proper  implementation of the  Soil
Screening Guidance.

As a key component of the RI/FS and EPA's Data
Quality Objectives (DQO) process, the CSM should
be updated and revised as investigations produce  new
information about a site. Data  Quality Objectives for
Superfund: Interim  Final  Guidance (U.S.  EPA,
1993a) and Guidance for  Conducting Remedial
Investigations  and  Feasibility Studies  under
CERCLA  (U.S.  EPA, 1989c)  provide a general
discussion  about  the  development  and use of the
CSM during RIs.  Developing the CSM involves
several steps, discussed in the following subsections.

2.1.1     Collect Existing Site Data. The initial
design of the CSM is  based  on existing site data
compiled during previous  studies. These data may
include site  sampling data, historical records, aerial
photographs, maps, and State soil surveys, as well as
information  on local and  regional  conditions
relevant  to  contaminant  migration and  potential
receptors. Data sources   include  Superfund  site
assessment  documents  (i.e.,   the   PA/SI),
documentation of removal actions, and records of
other site characterizations or  actions.  Published
information  on local  and regional  climate, soils,
hydrogeology,  and ecology  may be  useful.  In
addition,  information on the population and land use
at and surrounding the site will be important to
identify potential exposure pathways and receptors.
The  RI/FS guidance (U.S.  EPA, 1989c)  discusses
collection of existing data  during RI  scoping,
including an extensive list of potential data sources.

2.1.2    Organize and  Analyze Existing Site
Data. One  of the most  important  aspects of the
CSM development process  is  to  identify  and
characterize all potential  exposure pathways  and
receptors at  the site by considering site conditions,
relevant exposure  scenarios, and the properties of
contaminants present in site soils.

Attachment  A,   the  Conceptual  Site  Model
Summary, provides four forms for organizing  site
data  for soil  screening purposes. The CSM summary
organizes site  data  according to  general  site
information,   soil    contaminant    source
characteristics, exposure pathways and receptors.

Note: If a CSM has already been developed for the
site  in  question,   use the  summary  forms  in
Attachment A to ensure that it is adequate.

2.1.3  Construct a Preliminary Diagram of the
CSM.  Once the   existing  site data  have been
organized and a basic  understanding of the site has
been attained, draw a preliminary "sketch" of the
site conditions,  highlighting source areas, potential
exposure  pathways, and receptors.

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                                                      Exhibit  4

                                            Soil  Screening  Process

Step  One:      Develop  Conceptual  Site  Model
                 •    Collect existing site data (historical records, aerial photographs, maps, PA/SI data, available background
                      information, State soil surveys, etc.)
                      Organize and analyze existing site data
                         Identify known sources of contamination
                         Identify affected media
                         Identify potential migration routes, exposure pathways, and receptors
                      Construct a preliminary diagram of the CSM
                      Perform site reconnaissance
                         Confirm and/or modify CSM
                         Identify remaining data gaps
Step  Two:      Compare  Soil  Component  of  CSM  to  Soil Screening  Scenario
                      Confirm that future residential land use is a reasonable assumption for the site
                 •    Identify pathways present at the site that are addressed by the guidance
                 •    Identify additional pathways present at the site not addressed by the guidance
                 •    Compare pathway-specific generic SSLs with available concentration data
                 •    Estimate whether background levels exceed generic SSLs
Step  Three:     Define  Data  Collection  Needs  for Soils  to  Determine  Which  Site  Areas  Exceed  SSLs
                 •    Develop hypothesis about distribution of soil contamination (i.e., which areas of the site have soil
                      contamination that exceed appropriate SSLs?)
                 •    Develop sampling and analysis plan for determining soil contaminant concentrations
                         Sampling strategy for surface soils (includes defining study boundaries,  developing a decision rule,
                         specifying limits on decision errors, and optimizing the design)
                         Sampling strategy for subsurface soils (includes defining study boundaries, developing a decision rule,
                         specifying limits on decision errors, and optimizing the design)
                         Sampling to measure soil characteristics (bulk density, moisture content,  organic carbon content,
                         porosity, pH)
                      Determine  appropriate field methods and establish QA/QC protocols
Step  Four:      Sample  and  Analyze Soils  at  Site
                      Identify contaminants
                      Delineate area and depth of sources
                      Determine  soil characteristics
                      Revise CSM, as appropriate
Step  Five:      Derive  Site-specific  SSLs,  if  needed
                      Identify SSL equations for relevant pathways
                      Identify chemical of concern for dermal exposure and plant uptake
                      Obtain site-specific input parameters from CSM summary
                      Replace variables in SSL equations with site-specific data gathered in Step 4
                      Calculate SSLs
                         Account for exposure to multiple contaminants
Step  Six:       Compare  Site  Soil   Contaminant  Concentrations  to  Calculated  SSLs
                      For surface soils, screen out exposure areas where all composite samples do not exceed SSLs by a factor of 2
                 •    For subsurface soils, screen out  source areas where the highest average soil  core concentration does not
                      exceed the  SSLs
                 •    Evaluate whether background  levels exceed SSLs
Step  Seven:    Decide How to Address  Areas  Identified for Further  Study
                      Consider likelihood that additional areas can be screened out with more data
                 •    Integrate soil data  with other  media in the baseline risk assessment to estimate cumulative risk at the site
                 •    Determine  the need for action
                      Use SSLs as PRGs

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Ultimately, when site investigations are complete,
this sketch will be refined into a three-dimensional
diagram  that summarizes the data. Also,  a  brief
summary of the contamination  problem  should
accompany the CSM.  Attachment A provides an
example of a complete CSM summary.

2.1.4     Perform Site Reconnaissance. At this
point, a site visit would be useful because conditions
at the site may have changed since the PA/SI was
performed  (e.g., removal actions may have  been
taken).  During  site reconnaissance,  update site
sketches/topographic maps with  the  locations of
buildings,  source  areas,  wells, and  sensitive
environments.  Anecdotal information  from nearby
residents or site workers may reveal undocumented
disposal practices and thus previously unknown areas
of contamination that may affect the current  CSM
interpretation.

Based  on the new information gained from site
reconnaissance,  update the  CSM as  appropriate.
Identify any remaining data gaps in the CSM so that
these  data needs  can  be  incorporated into the
Sampling and Analysis Plan (SAP).

2.2   Step 2:  Comparing CSM  to
                  SSL Scenario

The  Soil  Screening Guidance  is likely to  be
appropriate for sites where residential land use is
reasonably anticipated. However, the CSM may
include  other sources and exposure pathways that
are not covered by this guidance. Compare the  CSM
with the assumptions and limitations inherent in the
SSLs  to determine  whether additional  or  more
detailed assessments are needed for any exposure
pathways or chemicals. Early identification of areas
or conditions  where  SSLs are not applicable is
important  so  that  other characterization   and
response efforts  can be considered when planning
the sampling strategy.

2.2.1     Identify  Pathways  Present  at  the
Site Addressed by Guidance. The  following are
potential pathways of exposure to soil  contaminants
in a residential setting  and are addressed  by this
guidance document:
•  Direct ingestion

•  Inhalation of volatiles and fugitive dusts

•  Ingestion of contaminated ground water caused by
   migration of chemicals through soil to an under-
   lying potable aquifer

•  Dermal absorption

•  Ingestion of homegrown produce that has  been
   contaminated via plant uptake

•  Migration of volatiles into basements.


This guidance quantitatively addresses the ingestion,
inhalation, and migration to ground water pathways
and also addresses, more qualitatively, the potential
for dermal absorption and plant  uptake based on
limited  empirical  data. Whether some  or all of the
pathways are relevant at the site depends upon the
contaminants and  conditions at the site.

For surface  soils under  the  residential land use
assumption, routinely consider the direct ingestion
route in the soil  screening decision. Inhalation of
fugitive dusts and dermal absorption  can be of
concern for certain chemicals and site conditions.

For  subsurface  soils, risks from  inhalation of
volatile  contaminants and  migration  of  soil
contaminants to an underlying aquifer are potential
concerns for this  scenario. The inhalation pathway
may be  eliminated  from further analysis if the
presence of volatile contaminants  are not suspected
in the subsurface  soils.  Likewise, consideration of
the ground water pathway may  be  eliminated  if
ground water beneath or adjacent to the site is not a
potential source of drinking water. Coordinate this
decision on a site-specific  basis with State or local
authorities  responsible  for ground water use and
classification.  The rationale  for excluding  this
exposure pathway should  be  consistent  with  EPA
ground  water policy (U.S. EPA, 1988a,  1990a,
1992a, 1992c, and 1993b).

The  potential for plant uptake  of  contaminants
should be addressed for both surface and  subsurface
soils.

In addition to the  more  common  pathways of
exposure in a residential setting, concerns have been
raised  regarding  the potential  for  migration of

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volatile organic compounds (VOCs) from subsurface
soils  into basements.  The Johnson and  Ettinger
model (1991) was developed to  address  this
pathway, and an analysis of the potential use of this
model for soil screening is provided in the TBD
(U.S.  EPA, 1996). The analysis suggests that the use
of the model is limited due to its sensitivity to a
number  of parameters such as distance  from the
source to the building, building ventilation rate and
the number and size of cracks in the basement wall.
Such  data are difficult to  obtain for a current use
scenario, and extremely uncertain for any future use
scenario. Thus, instead of relying exclusively on the
model, data from a comprehensive  soil-gas survey
are recommended  to  address the  potential for
migration of VOCs  in the  subsurface.  Soil-gas data
and site-specific information on soil permeability
can be used to replace default parameters  in the
Johnson  and  Ettinger model  to  obtain  a  more
reliable  estimate for the impact of this pathway on
site risk.

2.2.2     Identify    Additional   Pathways
Present at  the  Site  Not  Addressed by
Guidance. The presence of additional pathways
does not preclude the use of SSLs in site areas that
are currently residential or likely to be residential in
the future. However, the risks associated with these
additional pathways  should also be considered in the
RI/FS to determine whether SSLs are  adequately pro-
tective.  Where the  following conditions  exist,  a
more  detailed site-specific  study  should be
performed:

•  The site is adjacent to bodies of surface  water
   where the potential for contamination of surface
   water  by   overland  flow  or  release  of
   contaminated ground water  into  surface water
   through seeps should be considered.

•  There  are  potential  terrestrial  or  aquatic
   ecological  concerns.

•  There are  other  likely   human  exposure
   pathways  that  were  not  considered in
   development of the  SSLs  (e.g.,  local  fish
   consumption, raising  of beef, dairy, or other
   livestock).

•  There are unusual site  conditions such as the
   presence  of nonaqueous phase liquids (NAPLs),
   large  areas  of contamination,  unusually high
   fugitive  dust levels  due to  soil being tilled  for
   agricultural use, or heavy  traffic on unpaved
   roads.

•  There are certain subsurface  site conditions
   such  as  karst,  fractured  rock  aquifers,  or
   contamination extending below  the water table,
   that result in the screening models  not being
   sufficiently conservative.

2.2.3    Compare   Available   Data   to
Background.  EPA may be  concerned with two
types of background at sites: naturally occurring and
anthropogenic.   Natural background  is  usually
limited to  metals;  whereas, anthropogenic  (i.e.,
man-made)  background can include both organic and
inorganic contaminants.  A comparison of available
data (e.g., State  soil surveys) on local background
concentrations  with generic  SSLs  may indicate
whether background concentrations at the  site  are
elevated.   Although background  concentrations
exceeding generic SSLs do not necessarily indicate
that a health threat exists, further investigation may
be necessary.

Generally,  EPA does  not cleanup below  natural
background levels;  however, where  anthropogenic
background levels exceed SSLs  and   EPA has
determined  that a response action is  necessary and
feasible,  EPA's goal   will  be  to develop  a
comprehensive response to address  area soils.  This
will often  require  coordination  with  different
authorities that have jurisdiction over other  sources
of contamination in the area (such as a regional  air
board  or RCRA program).  This  will help avoid
response actions that create "clean  islands"  amid
widespread  contamination.

To determine the need  for a response action,  the
site  investigation  should include gathering site-
specific background data for any potential chemicals
of  concern   and   their speciation,  because
contaminant solubility in water and bioavailability
(absorption into  an  organism)  are  important
considerations  for the risk assessment.  Speciation
of compounds such  as metals and congener-specific
analysis of similar  organic chemicals [e.g., dioxins,
polychlorinated biphenyls (PCBs)] can  sometimes
provide  improved  estimates  of  exposure and
subsequent  toxicity   of  chemically   related
compounds. While water solubility  is not  often a

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good predictor  of uptake of a toxicant into the
blood  of an exposed receptor for physiological
reasons,  relative bioavailability and toxicity  can
sometimes   be  estimated  through  analytical
speciation  of related compounds.  For example,
various forms of metals are more or less toxic  and
can behave as quite disparate compounds in terms of
exposure and risk.  Inorganic forms of metals are
not likely to cross biological membranes as easily or
may   not   bioaccumulate   as   readily   as
organometallics.  Different valences of metals  can
produce  dramatically  different  toxicities  (e.g.,
chromium).   Different matrices can render metals
more  or  less  bioaccessible  (e.g., lead in  auto
emissions from leaded gas vs. lead in mine wastes).
Similarly, the position and number of halogens on
complex  organic molecules can affect uptake  and
toxicity  (e.g.,  dioxins).   When   applying  these
concepts  to  a screening analysis, the risk assessor
should establish  a credible  rationale  based  on
relevant literature and site data that supports actual
differences  in  uptake and/or toxicity, since  one
cannot predict bioavailability from  simple solubility
studies. More likely,  such an in-depth evaluation of
chemical speciation and bioavailability would be
conducted as part of a more detailed  site-specific
risk assessment.

2.3   Step  3: Defining  Data
                  Collection  Needs for
                  Soils

Once the CSM has been  developed and  the  site
manager  has determined  that  the  Soil  Screening
Guidance is  appropriate to use at  a site, an  SAP
should be developed. Attachment A, the Conceptual
Site Model Summary, lists the data needed to apply
the Soil Screening Guidance. The summary will help
identify data gaps in the CSM that require collection
of site-specific data.  The soil SAP  is likely to
contain different sampling strategies that address:

•  Surface soil
•  Subsurface soil
•  Soil characteristics

To develop  sampling strategies that will properly
assess  site contamination, EPA recommends that
site managers consult with the  technical experts in
their Region, including risk assessors, toxicologists,
chemists and hydrogeologists.   These experts can
assist the site manager to use the DQO process to
satisfy Superfund program  objectives. The DQO
process is a systematic planning process  developed
by EPA  to ensure that sufficient data are collected
to support EPA decision making. A full discussion of
the  DQO  process is  provided  in  Data Quality
Objectives for Superfund: Interim Final Guidance
(U.S.  EPA,  1993a) and the  Guidance for the Data
Quality Objectives Process (U.S.  EPA, 1994a).

Most  key elements  of the  DQO  process  have
already  been incorporated as  part  of this Soil
Screening Guidance (see Exhibits 5 through 8 and
Attachment B). The  remaining  elements  involve
identifying the site-specific  information needed to
calculate SSLs. For example,  the  dry bulk density
and the fraction of organic carbon content will need
to be collected for the subsurface soil investigation.

The following sections present an overview of the
sampling strategies needed to use the Soil Screening
Guidance. For a  more detailed discussion, see the
supporting TBD.

2.3.1     Stratify the Site Based on  Existing
Data. At this  point in the  soil screening process,
existing  data can  be used to  stratify the site into
three  types  of areas requiring  different  levels of
investigation:

• Areas  unlikely to be contaminated

• Areas  known to be highly contaminated

• Areas that may be contaminated and  cannot be
  ruled out.

Areas that are unlikely to be contaminated generally
will not require further investigation if historical site
use information  or other  site  data,  which are
reasonably  complete  and  accurate,  confirm  this
assumption. These may  be areas of the site  that
were  completely undisturbed  by hazardous-waste-
generating activities.

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        Exhibit 5:  Data Quality Objectives Process
                  1.  State the Problem

Summarize the contamination problem that will require new environmental
    data, and identify the resources available to resolve the problem.
                2.  Identify the Decision

         Identify the decision that requires new environmental
             data to address the contamination problem.
          3.  Identify Inputs to the Decision

      Identify the information needed to support the decision, and
     specify which inputs require new environmental measurements.
           4.  Define the Study Boundaries
     Specify the spatial and temporal aspects of the environmental
      media that the data must represent to support the decision.
    7.  Optimize the Design for Obtaining Data

   Identify the most resource-effective sampling and analysis design
      for generating data that are expected to satisfy the DQOs.
Expanded in
  Exhibit 6
              5.  Develop a Decision Rule

 Develop a logical "if... then ..." statement that defines the conditions that
  would cause the decision maker to choose among alternative actions.
        6.  Specify Limits on Decision Errors

Specify the decision maker's acceptable limits on decision errors, which are
  used to establish performance goals for limiting uncertainty in the data.
   Surface Soils
Expanded in Exhibit 7
                                                                       Subsurface Soils
                                                                    I Expanded in Exhibit 8j

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                   Exhibit 6: Defining the Study Boundaries
1.  Define Geographic Area
    of the Investigation
             Study Boundaries
2.  Define Population
    of Interest
Surface Soil (usually top 2 centimeters)
                                       Subsurface
                                          Soil
                      Water Table
                     (Saturated Zone)
3. Stratify the Site
                             Area Unlikely to be
                               Contaminated
        Area of Suspected
          Contamination
 Area of Known
 Contamination
(possible source)
4. Define Scale of Decision Making
   for Surface or Subsurface Soils
                 0.5-acre exposure
                    areas (EAs)
             Subsurface Soils
                                                                     Contaminant
                                                                       Source
                    Back to Exhibit 5, Step 5, "Develop a Decision Rule"
                                      11

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A crude estimate of the degree of soil contamination
can be made for other areas of the site by comparing
site concentrations to the generic SSLs in Appendix
A of the TBD. Generic SSLs have been calculated
for  110  chemicals using default values in the  SSL
equations, resulting in conservative values that will
be protective for the majority of site conditions.

The pathway-specific generic SSLs can be compared
with available concentration data from previous site
investigations or removal actions to help divide the
site  into  areas  with  similar  levels   of  soil
contamination and develop  appropriate  sampling
strategies.

The  surface soil  sampling  strategy discussed in this
document is most appropriate for those areas  that
may be  contaminated and  can not be designated  as
uncontaminated.   Areas  which are  known to be
contaminated (based  on   existing  data)  will be
investigated and characterized in the RI/FS.

2.3.2    Develop Sampling and Analysis Plan
for  Surface  Soil. The surface  soil  sampling
strategy is designed  to collect  the data needed  to
evaluate exposures  via  direct ingestion, dermal
absorption, and inhalation of fugitive dusts.

As  explained in  the Supplemental  Guidance  to
RAGS:  Calculating the Concentration Term (U.S.
EPA, 1992d), an  individual is assumed  to move
randomly across an exposure area (EA) over time,
spending  equivalent amounts of  time  in  each
location.  Thus, the concentration contacted  over
time is  best represented by the spatially averaged
concentration over the EA.  Ideally, the surface soil
sampling  strategy  would  determine  the  true
population mean  of contaminant concentrations  in
an EA.  Because determination of the "true" mean
would require extensive sampling at high costs, the
maximum  contaminant   concentration  from
composite samples is  used as a conservative estimate
of the mean.

This Max test strategy  compares  the  results  of
composite  samples with the  SSLs. Another, more
complex strategy called the Chen test is presented  in
Part 4 of the TBD.

The  User's Guide uses  the  Max test rather than the
Chen test  because the Max test is based on  a
statistical null hypothesis that is  more appropriate
for NPL  sites  (i.e., the  EA  requires  further
investigation). Although  the Chen test is not well
suited for screening decisions at NPL sites, it may be
useful in a non-NPL, voluntary cleanup context.

The  depth over which surface soils  are  sampled
should reflect the type of exposures expected at the
site.   The   Urban  Soil  Lead   Abatement
Demonstration  Project (U.S. EPA 1993d)  defined
the top 2 centimeters as the depth of soil where
direct contact predominantly occurs.   The decision
to sample soils below 2 centimeters depends on the
likelihood of deeper soils being disturbed and brought
to the surface (e.g.,  from gardening, landscaping or
construction activities).

Note  that the  size,  shape,  and  orientation of
sampling volume (i.e., "support") for  heterogenous
media have a  significant  effect  on  reported
measurement values.  For instance, particle size has
a  varying affect  on  the  transport  and  fate of
contaminants  in the environment  and  on   the
potential  receptors.   Comparison of data  from
methods  that are based on different supports can be
difficult.   Defining the  sampling  support  is
important  in   the   early   stages  of   site
characterization.   This  may be accomplished
through the DQO process with existing knowledge
of the site, contamination, and identification of the
exposure pathways  that  need to  be characterized.
Refer to  Preparation of Soil Sampling Protocols:
Sampling Techniques and Strategies (U.S. EPA,
1992e) for more information about soil sampling
support.

The SAP developed for surface  soils should specify
sampling and analytical  procedures as well as the
development of QA/QC procedures.  To identify the
appropriate analytical procedures, the  screening
levels must be known. If data are not available to
calculate  site-specific  SSLs (Section 2.5.1), then the
generic SSLs in Appendix A of the TBD  should be
used.

The  following  strategy can be used  for surface
soils  to  estimate  the  mean  concentration of
semivolatiles, inorganics, and pesticides  in an
exposure  area.  Volatiles  are not included  in  the
estimations because  they are not expected  to remain
at the surface for an extended period of time.
                                                12

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         Exhibit 7: Designing a Sampling and Analysis Plan for Surface Soils
  1.   Subdivide Site
     Into EAs
  2.  Divide EA
     Into a Grid

  3.  Organize
     Surface
     Sampling
     Program for
     EA
01
Q4 °2
OS
OS


04
OB
Q3

Q2
3
Q3
03 °4 02
°6 Q1
O5
0 O"
Q3
Q2 OB
For surface soils, the individual
unit for decision making is an
"EA," or exposure area.  It
measures 0.5 acre in area or
less.
This step defines the number of
specimens (N) that will make up
one composite sample.
Placement of sample locations
on the grid was developed
using a default sample size of
6 (which is based on
acceptable error rates for a CV
of 2.5) and a stratified random
sampling pattern.
                      If the EA CV is suspected to be greater than 2.5, use the table
                      below to select an adequate sample size or refer to the TBD for
                      other sample design options.
                 Probability of Decision Error at 0.5 SSL and 2 SSL Using Max Test

Sample Size b
6
7
8
9
CV=2.5a
E0.5C
E2.0d
CV=3.0
EO.S
E2.0
CV=3.5
EO.S
E2.0
CV=4.0
EO.S
E2.0
C = 4 specimens per composite8
0.21
0.25
0.25
0.28
0.08
0.05
0.04
0.03
0.28
0.31
0.36
0.36
0.11
0.08
0.05
0.04
0.31
0.36
0.42
0.44
0.11
0.09
0.07
0.07
0.35
0.41
0.41
0.48
0.16
0.15
0.09
0.08
 The CV is the coefficient of variation for individual, uncomposited measurements across the entire EA,
 including measurement error.
 Sample size (N) = number of composite samples
 Eg 5 = Probability of requiring further investigation when the EA mean is 0.5 SSL
 £20 = Probability of not requiring further investigation when the EA mean is 2.0 SSL
eC = number of specimens per composite sample, when each composite consists of points from a stratified
 random or systemic grid sample from across the entire EA.

NOTE: All decision error rates are based on 1,000 simulations that assume that each composite is
representative of the entire EA, half the EA has concentrations below the limit of detection, and half the EA
has concentrations that follow a gamma distribution (a conservative distributional assumption).
                                             13

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•   Divide areas  to  be sampled in the screening
    process into 0.5-acre exposure areas, the size of
    a suburban residential lot. If the site is currently
    residential,  the exposure  area should be  the
    actual residential  lot size. The exposure  areas
    should not be laid out in such a way that they
    unnecessarily combine areas of high and low
    levels of contamination.   The  orientation and
    exact location of the  EA,  relative to  the
    distribution of the contaminant in the soil, can
    lead  to instances  where  sampling the EA may
    have contaminant concentration results above
    the mean, and in  other instances, results below
    the mean.  Try to avoid  straddling  contaminant
    "distribution units" within the 0.5-acre EA.

•   Composite surface soil  samples. Because  the
    objective of surface soil screening is to estimate
    the   mean  contaminant  concentration,  the
    physical  "averaging"  that  occurs  during
    compositing is consistent with  the intended use
    of the data. Compositing allows sampling of a
    larger number of locations while  controlling
    analytical costs, since several individual samples
    are physically mixed (homogenized) and one or
    more  subsamples  are  drawn from  the mixture
    and submitted for analysis.

•   Strive to achieve a false negative error rate of 5
    percent (i.e., in only 5 percent of the cases, soil
    contamination is  assumed  to be  below  the
    screening level when it  is really above  the
    screening level). EPA also strives to achieve a
    20 percent false positive error rate (i.e., in only
    20 percent of the  cases,  soil contamination is
    assumed to be above the  screening level when it
    is really below the screening level).  These error
    rate  goals influence the number of samples to be
    collected in  each exposure  area.  For this
    guidance, EPA has defined the  "gray region" as
    one-half to 2  times the SSL.   Refer to Section
    2.6 for further discussion.

•   The  default sample size chosen  for this guidance
    (see Exhibit 7) provides adequate coverage for a
    coefficient of variation  (CV)  based upon 250
    percent  variability  in  contaminant values
    (CV=2.5). (If a CV larger  than 2.5 is expected,
    use an appropriate sample size from the table in
    Exhibit 7 of the User's Guide, or tables in  the
    TBD.)
•   Take six composite  samples, for each exposure
    area, with each composite sample made  up of
    four individual samples. Exhibit 7 shows other
    sample sizes needed  to achieve the decision error
    rates for  other  CVs.   Collect  the composites
    randomly across  the EA and through the top 2
    centimeters  of  soil,  which are  of greatest
    concern for incidental ingestion of soil, dermal
    contact, and inhalation of fugitive dust.

•   Analyze the six  samples per exposure area to
    determine  the contaminants present and their
    concentrations.

For further information on compositing across or
within EA sectors,  developing a random  sampling
strategy, and  determining  sample sizes that control
decision error rates, refer to the TBD.

Note  that  the  Max  test  requires  a Data Quality
Assessment (DQA)  test  following  sampling  and
analysis  (Section 2.4.2) to  ensure  that the  DQOs
(i.e., decision error rate goals) are achieved. If DQOs
are not met, additional sampling may be required.

2.3.3    Develop Sampling  and Analysis Plan
for Subsurface  Soils. The subsurface and surface
soil sampling strategies  differ because the exposure
mechanisms   differ.   Exposure   to  surface
contaminants  occurs  randomly as individuals move
around a residential  lot. The surface soil  sampling
strategy reflects this type of random exposure.

In general, exposure to subsurface  contamination
occurs when chemicals migrate up to the surface or
down to an underlying aquifer. Thus, subsurface
sampling focuses  on  collecting the data required for
modeling the  volatilization and migration to ground
water   pathways.   Measurements   of   soil
characteristics and estimates of the  area and  depth
of  contamination and  the average contaminant
concentration  in  each  source area are needed to
supply the  data necessary  to calculate the inhalation
and migration to ground water SSLs.
                                                 14

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        Exhibit 8: Designing a Sampling and Analysis Plan for Subsurface Soils

 1.   Delineate Source Area
                                   Contaminant
                                     Source

2.  Choose
    Subsurface
    Soil Sampling
    Locations
3.   Design Subsurface
    Sampling and Analysis
    Plan

        Lab/Field
     Analysis for soil
       parameters'3
                               For screening purposes, EPA
                               recommends drilling 2 to 3
                               borings per source area in
                               areas of highest suspected
                               concentrations. Soil sampling
                               should not extend past water
                               table or saturated zone.
       Soil Boring       a
(depth below ground surface in feet)
 Lab Analysis for
soil contaminants
 Picture depicts a continuous boring with 2 foot segments. For information on other methods such as interval sampling and
 depth weighted analysis, please refer to 2.3.3 of the User's Guide or 4.2 of the TBD.
b
 Soil Texture, Dry Bulk Density, Soil Organic Carbon, pH. Retain samples for possible discrete contaminant sampling.
                                             15

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Source areas are the decision units for  subsurface
soils.   A source area is defined by the horizontal
extent,  and   vertical   extent  or  depth   of
contamination.  For this purpose, "contamination"
is  defined  by  either  the Superfund's  Contract
Laboratory  Program (CLP) practical quantitation
limits  (QLs) for each contaminant,  or  the SSL.
Sites  with multiple  sources  should develop
separate SSLs  for each  source.

The  SAP developed  for  subsurface  soils  should
specify sampling and analytical procedures as well as
the development of QA/QC procedures.  To identify
the appropriate procedures,  the  SSLs  must  be
known.  If data are not available to calculate site-
specific SSLs (Section 2.5.2),  then the generic SSLs
in  Appendix A of the TBD  should be used.

The  primary  goal of the  subsurface  sampling
strategy  is to  estimate  the mean  contaminant
concentration and average soil characteristics within
the source  area. As with  the  surface soil sampling
strategy, the subsurface  soil  sampling strategy
follows the DQO process (see Exhibits 5, 6, and  8).
The decision rule is based on comparing the mean
contaminant   concentration   within   each
contaminant source with source-specific SSLs.

Current  investigative  techniques and  statistical
methods cannot accurately  determine  the  mean
concentration  of subsurface   soils  within  a
contaminated source without a costly and intensive
sampling program  that is well beyond the level of
effort generally appropriate  for  screening.  Thus,
conservative assumptions should be used to develop
hypotheses  on likely contaminant distributions.

This guidance bases the  decision to investigate a
source area  further on the  highest mean soil boring
contaminant concentration  within  the source,
reflecting  the  conservative  assumption that  the
highest mean subsurface  soil boring concentration
among a set of borings taken from the source area
represents  the  mean of  the  entire source area.
Similarly, estimates of contaminant depths should be
conservative. The  investigation should include the
maximum  depth  of  contamination  encountered
within the  source  without going below the water
table.
For each source, the guidance recommends taking 2
or 3 soil borings located in the areas suspected of
having  the highest  contaminant concentrations
within the  source. These subsurface  soil sampling
locations are based primarily on knowledge of likely
surface  soil contamination patterns (see Exhibit 6)
and subsurface conditions. However, buried sources
may not be discernible at the  surface.  Information
on past practices at the site included in the CSM can
help identify subsurface source areas.

For sites contaminated with VOCs, the subsurface
sampling strategy should include soil gas surveys as
well as  soil matrix sampling. VOCs are commonly
found in vapor phase in  the unsaturated zone, and
soil  matrix samples  may yield  results  that are
deceptively low.  Soil gas data are needed to help
locate  sources,  define source size,  to place  soil
boring locations within a source, and can also be used
in conjunction  with  modeling  to  address  VOC
transport  in  the  vadose  zone for both  the
volatilization  and migration to ground  water
pathways.

Take  soil cores  from the soil boring using  either
split spoon sampling or other appropriate sampling
methods.   Description   and   Sampling   of
Contaminated Soils: A  Field  Pocket Guide (U.S.
EPA,  199If), and Subsurface Characterization and
Monitoring Techniques: A  Desk Reference Guide,
Vol. I & II (U.S. EPA, 1993e),  can be consulted for
information on  appropriate subsurface  sampling
methods.

Sampling should begin at the ground  surface and
continue  until  either  no  contamination  is
encountered  or the  water  table   is  reached.
Subsurface sampling intervals  can be  adjusted
at a  site  to  accommodate  site-specific  infor-
mation   on   subsurface    contaminant
distributions  and  geological  conditions (e.g.,
thick  vadose zones in the  West). The concept of
"sampling support" introduced  in Section 2.3.2 also
applies to subsurface sampling.  For example, sample
splits  and  subsampling  should be  performed
according  to  Preparation   of  Soil  Sampling
Protocols: Sampling Techniques and Strategies
(U.S.  EPA, 1992e).
                                                16

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If each subsurface soil core  segment represents the
same subsurface soil interval (e.g., 2 feet), then the
average concentration from the surface to the depth
of contamination is  the simple arithmetic average
of contaminant  concentrations measured for  core
samples  representative  of each  of the  2-foot
segments  from  the  surface  to  the   depth  of
contamination.   However, if the sample intervals
are not all of the same length (e.g.,  some are 2 feet
while others are  1  foot  or 6  inches), then  the
calculation of the average concentration in the total
core  must account for the different lengths of the
segments.

If c;  is the concentration measure in a core sample,
representative of a  core  interval  or segment  of
length 1;, and the n-th segment is considered to  be
the last segment sampled in the core (i.e., the n-th
segment is at the depth of contamination), then the
average concentration in the core from the surface
to the depth of contamination  should be  calculated
as the following depth-weighted average (c).
Alternatively, the average boring concentration can
be  determined by  adding  the total contaminant
masses  together (from the sample  results)  for all
sample  segments to get the total contaminant mass
for the  boring.  The total contaminant mass is then
divided by  the  total dry weight of the  core  (as
determined by the dry bulk  density measurements)
to estimate average soil boring concentration.

For the leach test option, collect discrete samples
along  a soil boring  from  within the  zone of
contamination and  composite them to produce  a
sample  representative  of the average soil  boring
concentration.  Take  care to split  each discrete
sample  before analysis  so  that information  on
contaminant  distributions with depth  will not be
lost. A  leach test may be conducted on each soil
core.

Finally, the soil investigation for the migration to
ground  water pathway should not  be conducted
independently  of  ground  water  investigations.
Contaminated  ground  water  may indicate  the
presence of a nearby source area that would leach
contaminants from soil into aquifer systems.

2.3.4    Develop Sampling  and Analysis Plan
to  Determine Soil Characteristics. The soil
parameters necessary for SSL  calculations are soil
texture, dry bulk density, soil organic  carbon, and
pH. Some can be measured in the field,  while others
require   laboratory  measurement.   Although
laboratory  measurements  of these  parameters
cannot  be  obtained  under  Superfund's  CLP,
independent  soil  testing laboratories across  the
country can perform these tests at a relatively low
cost.

To  appropriately  apply the  volatilization  and
migration-to-ground water models,  average  or
typical soil properties should be used for a source in
the  SSL equations (see  Step 5). Take  samples for
measuring  soil  parameters  with samples  for
measuring contaminant concentrations. If possible,
consider splitting  single samples for contaminant
and soil parameter measurements.  Many soil testing
laboratories  can  handle and  test  contaminated
samples. However, if testing contaminated samples
for  soil parameters is a  problem, samples may  be
obtained from clean areas of the site as long as they
represent the same  soil texture and are taken from
approximately the same  depth as the contaminant
concentration samples.

Soil Texture.  Soil  texture  class  (e.g., loam, sand,
silt loam)  is necessary  to  estimate average soil
moisture conditions and  to apply the Hydrological
Evaluation of Landfill Performance (HELP) model
to estimate  infiltration rates (see Attachment A).
The appropriate texture classification is determined
by a particle size analysis and  the U.S. Department
of Agriculture (USDA) soil textural triangle shown
in Exhibit 9. This  classification system is  based  on
the USDA soil particle size classification.

The particle size analysis  method in Gee and Bauder
(1986) can provide  this  particle  size  distribution.
Other  methods  are  appropriate  as  long as they
provide  the  same  particle size breakpoints  for
sand/silt (0.05 mm) and silt/clay (0.002 mm). Field
methods are an alternative for  determining soil
                                                17

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textural class;  Exhibit 9 presents an example  from
Brady (1990).

Dry Bulk  Density. Dry soil bulk density (pb) is
used to calculate  total soil  porosity and  can be
determined for any soil horizon by weighing a thin-
walled tube soil sample (e.g., Shelby tube) of known
volume and subtracting the tube  weight [American
Society for Testing and Materials (ASTM) D 2937].
Determine  moisture content (ASTM 2216)  on a
subsample  of the tube sample to adjust field bulk
density to dry bulk density. The other methods  (e.g.,
ASTM  D   1556, D 2167, D 2922)  are  generally
applicable only to surface soil horizons and are not
appropriate for subsurface characterization. ASTM
soil  testing methods  are readily available in the
Annual Book of ASTM Standards, Volume 4.08, Soil
and Rock;  Building Stones, available from ASTM,
100  Barr Harbor Drive,  West Conshohocken, PA,
19428.

Organic Carbon  and pH.  Soil organic carbon is
measured by burning off soil carbon in a controlled-
temperature oven  (Nelson and  Sommers,  1982).
This parameter is  used to  determine  soil-water
partition coefficients from the organic carbon soil-
water partition coefficient,  Koc.  Soil pH is used to
select site-specific  partition coefficients for metals
(Table C-4, Attachment  C)  and  ionizing organics
(Table  C-2,   Attachment   C).   This  simple
measurement is made with a pH meter in a soil/water
slurry (McLean, 1982) and may be  measured in the
field using a portable pH meter.

2.3.5    Determine  Analytical  Methods  and
Establish  QA/QC Protocols.  Assemble a list of
feasible sampling and analytical methods during this
step. Verify that a  CLP method and a field method
for analyzing  the samples exist and that the
analytical  method  QL  or  field  method  QL is
appropriate for (i.e., is below) the site-specific or
generic SSL.  Sampler's Guide to  the  Contract
Laboratory Program (U.S. EPA,  1990b) and User's
Guide  to the Contract Laboratory Program (U.S.
EPA, 1991e) contain  further information on  CLP
methods.

Field  methods,  such  as  soil   gas  surveys,
immunoassay, or X-ray fluorescence, can be used if
the field method quantitation limit is below the SSL.
EPA recommends the use of field methods where
applicable  and appropriate.  However,  at  least 10
percent  of both  the  discrete  samples  and the
composites should be  split and  sent  to a CLP
laboratory for  confirmatory  analysis.  (Quality
Assurance for  Superfund  Environmental  Data
Collection Activities, U.S. EPA, 1993c).

Because  a  great amount of variability and bias can
exist in the collection, subsampling, and analysis of
soil samples,  some  effort should  be  made to
characterize this variability and bias.  A Rationale
for the Assessment of Errors in the Sampling of Soils
(U.S.  EPA,  1990c)  outlines  an approach  that
advocates the use  of a suite of QA/QC  samples to
assess variability and bias. Field duplicates and splits
are some of the best indicators of overall variability
in the sampling and analytical processes.

Field methods will be useful in defining the  study
boundaries (i.e., area  and depth of contamination)
during both site reconnaissance and sampling. The
design  and   capabilities   of   field   portable
instrumentation are rapidly evolving.  Documents
describing the standard operating procedures for field
instruments are available  though  the  National
Technical Information Service (NTIS).

Regardless of whether surface or subsurface soils are
sampled, the Superfund quality assurance program
guidance (U.S. EPA,  1993c) should  be consulted.
Standard limits on the precision and bias of sampling
and analytical operations conducted during  sampling
do  apply and should be  followed to give consistent
and defensible results.

2.4   Step  4: Sampling  and
                  Analyzing  Site Soils
                  &  DQA

Once the sampling strategies have been developed
and implemented,  the samples  should be  analyzed
according  to  the  analytical laboratory and field
methods  specified in the SAP. Results  of  the anal-
yses should identify the concentrations  of potential
contaminants  of concern for which site-specific
SSLs will be calculated.
                                                18

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     Exhibit  9:  U.S. Department of  Agriculture  soil  texture classification.
                                       100
                               Vx  , • » Clay Loam
                               V \ v     y
                                    X&
                                      Percent Sand
Criteria Used with the Field Method for Determining Soil Texture Classes  (Source: Brady, 1990)
Criterion
1.

2.

3.

4.




Individual grains
visible to eye
Stability of dry
clods
Stability of wet
clods
Stability of
"ribbon" when
wet soil rubbed
between thumb
and fingers
Sand Sandy loam
Yes Yes

Do not form Do not form

Unstable Slightly stable

Does not Does not form
form



Loam
Some

Easily
broken
Moderately
stable
Does not form




Silt loam
Few

Moderately
easily broken
Stable

Broken appearance




Clay loam
No

Hard and
stable
Very stable

Thin, will break




Clay
No

Very hard
and stable
Very stable

Very long,
flexible



                  0.002
Particle  Size, mm

        0.05       0.10 0.25 0.5
1.0
2.0
      U.S.

   Department
  of Agriculture
Clay
Silt
Very Fine
Fine
Med.
Coarse
Very Coarse
Sand
Gravel
                                      Source: USDA.
                                             19

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2.4.1 Delineate Area and  Depth of Source.
Both spatial area and depth  data,  as well as soil
characteristic data,  are  needed to  calculate site-
specific SSLs  for the inhalation of volatiles and
migration  to  ground  water  pathways  in the
subsurface. Site information from the CSM or soil
gas surveys can be used to estimate the areal extent
of the sources.

2.4.2     Perform DQA Using Sample Results.
After sampling has been completed,  a DQA should
be conducted if all composite samples are less than 2
times the SSL. This  is necessary to determine if the
original CV estimate (2.5), and hence the number of
samples collected (6), was adequate for screening
surface soils.

To conduct the DQA for a composite sample whose
mean is below 2  SSL, first calculate  the sample CV
for the EA in question from the sample mean (x),
the number of specimens per composite sample (C),
and sample standard deviation (s) as follows:
                 cv =
Use the sample size table in Exhibit 7 to check, for
this CV, whether the sample size is adequate to meet
the DQOs  for the  sampling  effort.   If sampling
DQOs are not  met, supplementary sampling may be
needed to achieve DQOs.

However, for EAs with small sample means (e.g., all
composites  are less than  the SSL), the  sample  CV
calculated using the equation above may not be  a
reliable estimate of the population CV  (i.e., as x
approaches  zero,  the  sample CV will  approach
infinity). To protect against unnecessary additional
sampling in such  cases, compare all  composites
against  the  formula SSL ///C . If the  maximum
composite sample concentration is below the value
given by the equation, then the sample size may be
assumed to  be adequate and  no  further DQA is
necessary. In  other words, EPA believes that  the
default sample size will  adequately support walk-
away decisions when all composites are well below
the SSL. The TBD  describes the development of this
formula  and provides  additional information on
implementing the DQA  process.
2.4.3    Revise the CSM. Because these analyses
reveal new information about the site, update the
CSM accordingly.  This revision could  include
identification of site areas that exceed the generic
SSLs.

2.5   Step 5: Calculating  Site-
                 specific SSLs

With the soil properties data collected in Step 4 of
the screening process,  site-specific  soil screening
levels can now be  calculated using the equations
presented in this section. For a description of how
these equations  were  developed,   as  well  as
background  on  their assumptions and limitations,
consult the TBD.

All SSL equations were developed to be consistent
with RME in the residential setting. The Superfund
program  estimates the  RME  for chronic exposures
on a site-specific basis by combining an average
exposure-point concentration  with reasonably con-
servative values for  intake and duration (U.S. EPA,
1989a;  RAGS  HHEM, Supplemental Guidance:
Standard Default Exposure  Factors,  U.S.  EPA,
1991a).  Thus,  all  site-specific  parameters  (soil,
aquifer,  and meteorologic  parameters) used  to
calculate SSLs should reflect average or typical site
conditions in order to  calculate average exposure
concentrations at the site.

Equations for calculating SSLs  are presented for
surface and subsurface soils in the following sections.
For   each  equation,   site-specific   input
parameters  are  highlighted  in   bold  and
default  values  are provided for use when site-
specific data are not  available.  Although these
defaults  are  not worst  case, they are conservative.
At most  sites, higher, but still protective SSLs can be
calculated  using  site-specific  data.  The  TBD
describes development  of these default values and
presents generic SSLs  calculated using the  default
values.

Attachment  D provides  toxicity  criteria for 110
chemicals commonly  found  at NPL  sites.  These
criteria   were  obtained  from  Integrated Risk
Information  System (IRIS)  (U.S.  EPA,  1995b)  or
Health  Effects  Assessment  Summary  Tables
(HEAST) (U.S. EPA,  1995a), which are regularly
                                               20

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updated. Prior  to  calculating SSLs  at a  site,
check all  relevant chemical-specific values  in
Attachment D against  values  from IRIS  or
HEAST. Only  the  most  current values should
be used to calculate SSLs.

Where  toxicity values  have  been  updated,  the
generic SSLs should also be recalculated with current
toxicity information.

2.5.1     SSL   Equations-Surface   Soils.
Exposure  pathways  addressed in the process for
screening surface soils  include direct ingestion,
dermal contact,  and inhalation of fugitive dusts.

Direct  Ingestion.  The  Soil Screening Guidance
addresses  chronic exposure to noncarcinogens  and
carcinogens   through    direct   ingestion   of
contaminated  soil  in a  residential  setting.  The
approach  for  calculating noncarcinogenic  SSLs
presented in this guidance leads  to screening levels
that are approximately 3  times  more conservative
than  PRGs calculated  based  on  the approach
presented in RAGS HHEM, Part B (i.e.,  using a 30-
year,  time-weighted  average soil ingestion rate for
comparison to  chronic toxicity criteria).  Because a
number of  studies  have shown  that  inadvertent
ingestion of soil is  common among children age 6
and younger (Calabrese et al., 1989; Davis et al.,
1990: Van Wijnen et al.,  1990), several commenters
suggested that screening values should be based on
this increased exposure during childhood. However,
other  commenters believe that  comparing a six-year
exposure  to  a  chronic  reference  dose (RfD) is
unnecessarily conservative. In their analysis of this
issue, the Science Advisory Board (SAB) stated that,
for most chemicals, the approach of combining the
higher six-year exposure for children with chronic
toxicity criteria is  overly protective (U.S.  EPA,
1993f).  However, they  noted  that the approach
may be  appropriate for chemicals with chronic RfDs
based on  toxic  endpoints that  are  specific  to
children (e.g., fluoride and nitrates)  or where the
dose-response  curve  is steep  [i.e., the difference
between  the   no-observed-adverse-effect  level
(NOAEL) and  the  adverse effect level is small].
Thus  for the purposes  of screening, Office  of
Emergency  Remedial Response (OERR)  opted to
base  the  generic   SSLs  for  noncarcinogenic
contaminants on the more  conservative "childhood
only" exposure  (Equation  1).   The issue of whether
to  maintain  this  more  conservative  approach
throughout  the Baseline  Risk  Assessment  and
establishing remediation goals will  depend on how
the specific chemical's toxicology relates to the
issues raised by the SAB.
 Equation  1: Screening Level Equation  for
             Ingestion  of Noncarcinogenic
             Contaminants  in Residential
             Soil
  Screening
    Level
   (mg/kg)
   THQxBWxATx365d/yr
1/RfD0 x 10-6 kg/mg x EF x ED x IR
 Parameter/Definition  (units)
 THQ/target hazard quotient
 (unitless)
 BW/body weight (kg)
 AT/averaging time (yr)
 RfD0/oral reference dose (mg/kg-d)

 EF/exposure frequency (d/yr)
 ED/exposure duration (yr)
 IR/soil ingestion rate (mg/d)
              Default
              1


              15
              6a
              chemical-specific
              (Attachment D)
              350
              6
              200
 aFor noncarcinogens, averaging time equals to
  exposure duration.

For carcinogens, both the magnitude and duration of
exposure are important.  Duration is critical because
the toxicity criteria are  based on "lifetime average
daily dose." Therefore, the total dose received,
whether it be over 5 years or 50 years, is averaged
over a lifetime of 70 years.  To  be  protective of
exposures to carcinogens in the residential setting,
Superfund focuses on exposures to individuals who
may live in the  same residence for a high-end period
of time (e.g., 30 years)  because exposure to soil is
higher during  childhood and decreases with age.
Equation 2  uses  a  time-weighted  average  soil
ingestion rate for children and adults. The derivation
of this time-weighted average is presented in U.S.
EPA, 1991c.

Default values  are used for  all input  parameters in
the direct ingestion equations. The amount of data
required to derive site-specific  values for  these
parameters  (e.g.,  soil ingestion  rates,  chemical-
specific bioavailability)  makes  their collection  and
use  impracticable for screening.  Therefore,  site-
specific  data are not generally available  for  this
                                                 21

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exposure route.  The  generic  ingestion  SSLs
presented  in  Appendix  A  of the  TBD  are
recommended for all NPL sites.
Equation 2: Screening Level Equation for
Ingestion of Carcinogenic
Contaminants in Residential Soil
Screening Level = TR x AT x 365 d/yr
(mg/kg) SF0 x 10-6 kg/mg x EF x IF soi|/adj
Parameter/Definition (units)
TR/target cancer risk (unitless)
AT/averaging time (yr)
SF0/oral slope factor (mg/kg-d)-1
EF/exposure frequency (d/yr)
IFsoil/adj/age-adJusted soil
ingestion factor (mg-yr/kg-d)
Default
10-6
70
chemical-specific
(Attachment D)
350
114
Dermal  Contact. Contaminant absorption through
dermal contact may contribute risk to human health
in a residential setting. However,  incorporation of
dermal exposures into the soil screening process is
limited by the amount  of data available to quantify
dermal absorption from soil for specific chemicals.
Previous  EPA studies suggest that absorption via the
dermal route must  be greater than  10 percent to
equal or exceed the ingestion  exposure (assuming
100 percent absorption of a chemical via ingestion;
Dermal  Exposure  Assessment:   Principles  and
Applications, U.S. EPA, 1992b).

Of the  110 compounds  evaluated, available  data
show greater than 10 percent dermal  absorption for
pentachlorophenol  (Wester et  al.,  1993).
Therefore, pentachlorophenol is the only chemical
for which  the  Soil  Screening Guidance directly
considers dermal exposure. The ingestion SSL for
pentachlorophenol should  be  divided in  half to
account  for the  assumption that  exposure via the
dermal route is  equivalent to the ingestion route.
Preliminary studies show that  certain  semivolatile
compounds  (e.g., benzo(a)pyrene) may also be of
concern for this exposure route. As adequate dermal
absorption  data are developed  for such chemicals,
the ingestion SSLs  may need to  be adjusted. The
Agency  will provide updates on  this  issue  as
appropriate.
Inhalation  of Fugitive  Dusts.  Inhalation  of
fugitive dusts is a consideration  for semivolatile
organics and metals in surface  soils.  However,
generic  fugitive dust SSLs for semivolatile organics
are several orders  of magnitude  higher than the
corresponding generic ingestion SSLs. EPA believes
that  since  the  ingestion route  should  always  be
considered  in screening decisions for surface soils,
and  ingestion  SSLs  appear  to  be  adequately
protective for inhalation exposures  to fugitive dusts
for organic compounds, the fugitive  dust exposure
route need  not  be  routinely considered for organic
chemicals in surface soils.

Likewise, the ingestion SSLs are significantly more
conservative than most of the generic fugitive dust
SSLs. As a result, fugitive dust  SSLs need  not  be
calculated  for most metals.  However, chromium is
an exception. For chromium, the  generic fugitive
dust  SSL is below  the ingestion SSL. This is due to
the carcinogenicity of hexavalent chromium, Cr+6,
through the  inhalation  exposure route.  For most
sites, fugitive  dust  SSLs  calculated  using the
conservative  defaults will be adequately protective.
However, if site conditions that will result in higher
fugitive dust  emissions than the  defaults  (e.g., dry,
dusty  soils;  high average annual  windspeeds;
vegetative  cover less than 50 percent)  are  likely,
consider calculating a site-specific fugitive dust SSL.

Equations 3 and 4 are used to calculate fugitive dust
SSLs for carcinogens and noncarcinogens. These
equations  require calculation  of  a  particulate
emission factor (PEF, Equation  5) that relates the
concentration  of  contaminant  in soil  to the
concentration of dust particles  in air.  This PEF
represents an annual average emission rate based  on
wind erosion that should be compared with chronic
health criteria. It is not appropriate for evaluating
the potential for more acute  exposures.

Both the   emissions  portion and the  dispersion
portion  of the PEF equation have been updated
since the first publication of RAGS HHEM, Part  B,
in 1991. As in Part B, the emissions part of the PEF
equation is  based on the "unlimited  reservoir" model
developed  to estimate particulate emissions  due  to
wind erosion (Cowherd et  al.,  1985). Additional
information on the update  of the  PEF equation is
provided in the TBD.  Cowherd et al. (1985) present
methods for site-specific  measurement  of the
                                                22

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parameters necessary to calculate a PEF. A site-
specific dispersion model (Q/C)  is then selected as
described in the section on  calculating SSLs for the
volatile inhalation pathway  later in this document.
                                   assume an infinite  source, they can violate mass-
                                   balance considerations, especially for small sources.
 Equation  3: Screening Level Equation  for
             Inhalation of  Carcinogenic
             Fugitive  Dusts from  Residential
             Soil
   Screening
    Level
   (mg/kg)
      TRxATx365d/yr
URF x 1,000 |ig/mg x EF x ED x  1
                        PEF
 Parameter/Definition  (units)  Default
 TR/target cancer risk (unitless)
 AT/averaging time (yr)
 URF/inhalation unit risk factor
 EF/exposure frequency (d/yr)
 ED/exposure duration (yr)
 PEF/particulate  emission
        factor  (m3/kg)
              10-6
              70
              chemical-specific
              (Attachment D)
              350
              30
              1.32  x  109
              (Equation  5)
Equation 4: Screening Level Equation for
Inhalation of Noncarcinogenic
Fugitive Dusts from Residential
Soil
Screening Level = THQ x AT x 365 d/yr
(mg/kg) EFxEDx [1x1]
RfC PEF
Parameter/Definition (units)
THQ/target hazard quotient
(unitless)
AT/averaging time (yr)
EF/exposure frequency (d/yr)
ED/exposure duration (yr)
RfC/inhalation reference
concentration (mg/m3)
PEF/particulate emission
factor (m3/kg)
Default
1
30
350
30
chemical-specific
(Attachment D)
1.32 x 109
(Equation 5)
2.5.2    SSL  Equations-Subsurface Soils.
The Soil Screening Guidance addresses two exposure
pathways for subsurface soils: inhalation of volatiles
and ingestion of ground water contaminated by the
migration of contaminants through soil to an under-
lying  potable  aquifer.  Because  the  equations
developed  to calculate SSLs for these pathways
Equation 5: Derivation of the Particulate
Emission Factor
PEF (m%g) = Q/C x 3,600 s/h
0.036 xCI-VJxflVUtpxFfx)
Parameter/Definition (units)
PEF/particulate emission factor (m3/kg)
Q/C/inverse of mean cone, at
center of a 0.5-acre-square
source (g/m2-s per kg/m3)
V/fraction of vegetative cover
(unitless)
Um/mean annual windspeed
(mis)
U, /equivalent threshold value of
windspeed at 7 m (mis)
F(x)/function dependent on
Um/Ut derived using Cowherd
et al. (1985) (unitless)
Default
1.32x 109
90.80

0.5 (50%)
4.69

11.32

0.194

                                   To address this concern, the guidance also includes
                                   equations for calculating mass-limit SSLs for each of
                                   these pathways  when  the size  (i.e., area and
                                   depth) of the  contaminated  soil  source  is
                                   known or  can be estimated  with confidence.

                                   Attachment D provides the toxicity  criteria and
                                   regulatory  benchmarks   for   110   chemicals
                                   commonly  found at NPL sites. These criteria were
                                   obtained from IRIS (U.S. EPA,  1995b), HEAST
                                   (U.S. EPA, 1995a), and Drinking Water Regulations
                                   and Health Advisories (U.S. EPA, 1995c), which are
                                   regularly updated. Prior to calculating SSLs at a
                                   site,  all  relevant chemical-specific  values  in
                                   Attachment D  should  be checked against  the
                                   most recent version of their sources to ensure
                                   that they are up to date.

                                   Toxicity data are not available for all chemicals for
                                   the inhalation exposure route.  At the request  of
                                   commenters,  EPA  has looked into methods  for
                                   extrapolating  inhalation  toxicity values  from oral
                                   toxicity data.  The TBD presents the results  of this
                                   analysis along with information  on current EPA
                                                23

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practices  for  conducting  such  route-to-route
extrapolations.

Chemical properties necessary to calculate SSLs for
the inhalation and migration to ground water path-
ways  include solubility, air and water diffusivities,
Henry's law constant, and soil/water partition coeffi-
cients.  Attachment  C provides  values  for 110
chemicals commonly found at NPL sites.

Site-specific parameters necessary to calculate SSLs
for subsurface soils are listed on Exhibit 10, along
with  recommended  sources  and  measurement
methods. In addition to the soil parameters described
in  Step  3, other  site-specific input  parameters
include  soil  moisture,  infiltration  rate,  aquifer
parameters, and  meteorologic  data.  Guidance for
collecting or estimating these other parameters at a
site is provided on Exhibit 10 and in Attachment A.

Inhalation of Volatiles. Equations 6 and 7 are used
to calculate SSLs for the inhalation of carcinogenic
and noncarcinogenic volatile contaminants.To use
these  equations  to  calculate inhalation SSLs, a
volatilization factor (VF) must be calculated.

The VF  equation can be  broken into two separate
models:  a  model to  estimate the  emissions and a
dispersion   model (reduced to the term Q/C) that
simulates the dispersion of contaminants in ambient
air. In addition, a soil saturation limit (C sat) must be
calculated to  ensure that the VF model is applicable
to soil contaminant conditions at a site.

Volatilization  Factor (VF). The  soil-to-air VF
(Equation  8)  is  used to  define  the relationship
between the concentration of the contaminant  in
soil and the  flux of the volatilized contaminant to
air. The Soil Screening Guidance  replaces the
Hwang  and  Falco  (1986) model  used  as the
basis  for  the  RAGS  HHEM,  Part  B, VF
equation   with   the   simplified   equation
developed by Jury et al. (1984).

The Jury model calculates the  maximum flux of a
contaminant from contaminated soil  and considers
soil moisture  conditions in calculating  a VF. The
models are similar in their assumptions of an infinite
contaminant source  and vapor phase diffusion as the
only transport mechanism (i.e., no transport takes
place  via nonvapor-phase diffusion and there is no
mass flow due to  capillary  action).  In  some
situations, information about the  size of the source
is  available and SSLs can be calculated using the
mass-limit  approach.
 Equation  6: Screening  Level  Equation for
             Inhalation  of  Carcinogenic Volatile
             Contaminants  in  Residential  Soil
  Screening
    Level
   (mg/kg)
      TRxATx365d/yr
URF x 1,000 |ig/mg x EF x ED x  1
                         VF
 Parameter/Definition  (units) Default
 TR/target cancer risk (unitless)
 AT/averaging time (yr)
 URF/inhalation unit risk factor
 EF/exposure frequency (d/yr)
 ED/exposure duration (yr)
 VF/soil-to-air  volatilization
    factor (m3/kg)
               10-6
               70
               chemical-specific
               (Attachment D)
               350
               30
               chemical-specific
               (Equation  8)
Equation 7: Screening Level Equation for
Inhalation of Noncarcinogenic
Volatile Contaminants in
Residential Soil
Screening Level = THQ x AT x 365 d/yr
(mg/kg) EF x ED
Parameter/Definition (units)
THQ/target hazard quotient
(unitless)
AT/averaging time (yr)
EF/exposure frequency (d/yr)
ED/exposure duration (yr)
RfC/in halation reference
concentration (mg/m3)
VF/soil-to-air volatilization
factor (m3/kg)
X [ 1 X 1 ]
RfC VF
Default
1
30
350
30
chemical-specific
(Attachment D)
chemical-specific
(Equation 8)
Other than initial  soil concentration, air-filled soil
porosity is the most  significant soil parameter
affecting  the  final  steady-state  flux  of volatile
contaminants from soil (U.S. EPA, 1980). In other
words,  the higher the  air-filled  soil porosity, the
greater the emission flux of volatile constituents.
                                                 24

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               Exhibit 10.   Site-specific Parameters for  Calculating Subsurface SSLs
                                        SSL Pathway
Parameter
              Migration to
Inhalation    ground water   Data source
                                                                                 Method
Source Characteristics
   Source area (A)
   Source length (L)

   Source depth
                             Sampling data       Measure total area of contaminated soil
                             Sampling data       Measure length of source parallel to ground water
                                                flow
                             Sampling data       Measure depth of contamination or use
                                                conservative assumption
Soil Characteristics
   Soil texture                         O


   Dry soil bulk density (pb)             •

   Soil moisture content (w)             O

   Soil organic carbon (foc)              •
   Soil pH                            O

   Moisture retention exponent (b)        O
   Saturated hydraulic conductivity       O
   (Ks)
   Avg. soil moisture content (6W)        •
                   O         Lab measurement


                   •         Field measurement

                   O         Lab measurement

                   •         Lab measurement
                   O         Field measurement

                   O         Look-up
                   O         Look-up

                   •         Calculated
Particle size analysis (Gee & Bauder, 1986) and
USDA classification; used to estimate 6W& I
All soils: ASTM D 2937; shallow soils: ASTM D
1556, ASTM D 2167, ASTM D 2922
ASTM D 2216; used to estimate dry soil bulk
density
Nelson and Sommers (1982)
McLean (1982); used to select pH-specific Kx
(ionizable organics) and Kj  (metals)
Attachment A; used to calculate 6W
Attachment A; used to calculate 6W


Attachment A
Meteorological Data

   Air dispersion factor (Q/C)
                             Q/C table (Table 5)   Select value corresponding to source area,
                                                climatic zone, and city with conditions similar to
                                                site
Hydrogeologic Characteristics (DAF)
   Hydrogeologic setting


   Infiltration/recharge (I)
   Hydraulic conductivity (K)
   Hydraulic gradient (i)
   Aquifer thickness (d)
                   O         Conceptual site
                             model

                   •         HELP model;
                             Regional estimates
                             Field measurement;
                             Regional estimates
                             Field measurement;
                             Regional estimates
                             Field measurement;
                             Regional estimates
Place site in hydrogeologic setting from Aller et
al. (1987) for estimation of parameters below
(see Attachment A)
HELP (Schroeder et al., 1984) may be used for
site-specific infiltration estimates; recharge
estimates also may be taken from Aller et al.
(1987) or may be estimated from knowledge of
local meteorologic and hydrogeologic conditions
Aquifer tests (i.e., pump tests, slug tests)
preferred; estimates also may be taken from
Aller et al. (1987) or Newell et al. (1990) or may
be estimated from knowledge of local
hydrogeologic conditions
Measured on map of site's water table
(preferred); estimates also may be taken from
Newell et al.  (1990) or may be estimated from
knowledge of local hydrogeologic conditions
Site-specific  measurement (i.e., from soil boring
logs) preferred; estimates also may be taken
from Newell et al. (1990) or may be estimated
from knowledge of local hydrogeologic conditions
• Indicates parameters used in the SSL equations.
O Indicates parameters/assumptions needed to estimate SSL equation parameters.
                                                             25

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 Equation  8:   Derivation  of  the Volatilization
               Factor
 VF (m3/kg) = QIC x  (3.14 x DA x T) 1/2 x irj-4 (m2/cm2)
                        (2xpbxDA)
 where
           DA=
Parameter/Definition  (units)

VF/volatilization factor (m3/kg)
DA /apparent diffusivity (cm2/s)
Q/C/inverse of the  mean
   cone,  at the center of a
   0.5-acre-square  source
   (g/m2-s per kg/m3)
T/exposure interval (s)
Pb/dry soil bulk density
(g/cm3)
6a /air-filled soil porosity (Lair/LsoN)
n/total soil porosity (Lpore/Lsoi|)

6w/water-filled soil  porosity
   (Lwater/Lsoil)
ps /soil particle density (g/cm3)
Dj/diffusivity in air (cm2/s)
H'/dimensionless Henry's law
   constant
Dw /diffusivity in water (cm2/s)
KCJ /soil-water partition coefficient
(cm3/g) = Koc foc (organics)
Koc /soil organic carbon partition
coefficient (cm3/g)
foc/fraction organic  carbon  in
   soil (gig)
                                 Default
                                 68.81
                                 9.5 x 108
                                 1.5
                                 1-(Pb'Ps)
                                 0.15


                                 2.65

                                 chemical-specific3
                                 chemical-specific3

                                 chemical-specific3
                                 chemical-specific3


                                 chemical-specific3

                                 0.006  (0.6%)
3See Attachment C.

Among the  soil parameters used  in  Equation  8,
annual average water-filled soil porosity (6W) has the
most significant effect on air-filled soil  porosity (0a)
and   hence   volatile  contaminant   emissions.
Sensitivity  analyses  have  shown  that soil bulk
density (pt,) has too limited a range  for surface soils
(generally between 1.3 and  1.7  g/cm3)  to  affect
results with nearly the  significance of soil moisture
content (U.S.  EPA,  1996).

Dispersion Model (Q/C). The box model in RAGS
HHEM, Part B has  been replaced with a Q/C term
derived from the modeling exercise using the AREA-
ST model incorporated  into EPA's Industrial Source
Complex  Model (ISC2)  platform. The AREA-ST
model was  run  with a full year  of meteorological
data  for  29 U.S.  locations  selected  to  be
representative  of a range of meteorologic conditions
across the Nation (EQ, 1993). The results of these
modeling  runs are presented in Exhibit 11 for  square
area  sources  of  0.5 to  30  acres  in  size.  When
developing  a  site-specific VF for the  inhalation
pathway,  place  the site into a climatic zone  (see
Attachment B).  Then select a  Q/C  value  from
Exhibit 11  that best represents  a  site's size and
meteorological conditions.

So/7 Saturation Limit (Csat). The soil saturation limit
(Equation 9)  is the contaminant concentration  at
which soil pore air and pore water are saturated with
the chemical  and the adsorptive  limits of the soil
particles   have  been  reached.  Above   this
concentration, the contaminant may be  present  in
free  phase.  Csat concentrations  represent  an  upper
limit to the  applicability  of the SSL VF  model
because a basic principle of the model (Henry's  law)
does  not  apply  when contaminants are  present  in
free  phase.  VF-based inhalation  SSLs are reliable
only if they  are at  or below Csat.

Equation  9  is used to  calculate the soil saturation
limit for each organic chemical in site soils.  As an
update to  RAGS HHEM, Part B, this equation takes
into  account the amount of contaminant that is  in
the vapor phase in the pore  spaces of the soil  in
addition to  the amount dissolved in the  soil's pore
water and sorbed to  soil particles.  Csat values  should
be  calculated using the  same  site-specific  soil
characteristics used to calculate  SSLs (e.g., bulk
density, average water  content,  and organic carbon
content).  Because VF-based SSLs are  not accurate
for soil concentrations above Csat, these SSLs  should
be compared to  Csat concentrations before they are
used for soil screening.
                                                  26

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Exhibit 11.  QIC Values  by Source Area, City, and Climatic Zone
QIC (g/m2-s

Zone I
Seattle
Salem
Zone II
Fresno
Los Angeles
San Francisco
Zone III
Las Vegas
Phoenix
Albuquerque
Zone IV
Boise
Winnemucca
Salt Lake City
Casper
Denver
Zone V
Bismark
Minneapolis
Lincoln
Zone VI
Little Rock
Houston
Atlanta
Charleston
Raleigh-Durham
Zone VII
Chicago
Cleveland
Huntington
Harrisburg
Zone VIM
Portland
Hartford
Philadelphia
Zone IX
Miami
0.5 Acre

82.72
73.44

62.00
68.81
89.51

95.55
64.04
84.18

69.41
69.23
78.09
100.13
75.59

83.39
90.80
81.64

73.63
79.25
77.08
74.89
77.26

97.78
83.22
53.89
81.90

74.23
71.35
90.24

85.61
1 Acre

72.62
64.42

54.37
60.24
78.51

83.87
56.07
73.82

60.88
60.67
68.47
87.87
66.27

73.07
79.68
71.47

64.51
69.47
67.56
65.65
67.75

85.81
73.06
47.24
71.87

65.01
62.55
79.14

74.97
2 Acre

64.38
57.09

48.16
53.30
69.55

74.38
49.59
65.40

53.94
53.72
60.66
77.91
58.68

64.71
70.64
63.22

57.10
61.53
59.83
58.13
60.01

76.08
64.78
41.83
63.72

57.52
55.40
70.14

66.33
per kg/m3)
5 Acre

55.66
49.33

41.57
45.93
60.03

64.32
42.72
56.47

46.57
46.35
52.37
67.34
50.64

55.82
61.03
54.47

49.23
53.11
51.62
50.17
51.78

65.75
55.99
36.10
55.07

49.57
47.83
60.59

57.17

10 Acre

50.09
44.37

37.36
41.24
53.95

57.90
38.35
50.77

41.87
41.65
47.08
60.59
45.52

50.16
54.90
48.89

44.19
47.74
46.37
45.08
46.51

59.16
50.38
32.43
49.56

44.49
43.00
54.50

51.33

30 Acre

42.86
37.94

31.90
35.15
46.03

49.56
32.68
43.37

35.75
35.55
40.20
51.80
38.87

42.79
46.92
41.65

37.64
40.76
39.54
38.48
39.64

50.60
43.08
27.67
42.40

37.88
36.73
46.59

43.74
                              27

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 Equation  9:  Derivation of the Soil Saturation
              Limit
            Csat =
H'9,
                  Pb
 Parameter/Definition  (units)
 Csat/soil saturation concentration
    (mg/kg)
 S/solubility in water (mg/L-water)

 pb/dry soil  bulk density  (kg/L)

 Kd/soil-water partition coefficient
    (L/kg)
 Koc/soil organic carbon/water
    partition coefficient (L/kg)
 foc/fraction  organic  carbon  in
    soil (gig)

 0w/water-filled  soil  porosity
    (LWater/LSoil)
 H'/dimensionless Henry's law
    constant

 6a/air-filled soil porosity (Lair/Lsoi|)

 n/total soil porosity (Lpore/Lsoi|)

 ps/soil particle density (kg/L)
 Default



 chemical-specific3
 1.5

 Koc x foc (chemical-
 specific3)
 chemical-specific3


 0.006   (0.6%)


 0.15


 chemical-specific3
 1-(Pb'Ps)
 2.65
 3See Attachment C.

Csat values represent chemical-physical limits in soil
and  are not  risk  based.   However, since  they
represent the concentration at which soil pore air is
saturated  with a contaminant, volatile emissions
reach their maximum at Csat. In other words, at Csat
the emission flux from soil to air for a chemical
reaches a plateau. Volatile  emissions  will  not
increase above this  level no matter how much more
chemical is added to the  soil.  Chemicals with VF-
based SSLs above Csat are not likely to  present  a
significant  volatile  inhalation  risk  at  any  soil
concentration.  To  illustrate this point,  the TDB
presents an analysis of the inhalation risk levels at
Csat  for a number of chemicals commonly found at
Superfund sites whose generic SSLs (calculated using
the default parameters shown in Equation  9) are
above Csat.
The analysis indicates that these Csat values are all
well below the screening risk targets of a 10-6 cancer
risk or an HQ of 1.

Although  the  inhalation  risks  appear  to  be
negligible, Csat  does  indicate  a  potential  for
nonaqueous phase liquid  (NAPL) to be present in
soil and a possible risk to ground water. Thus, EPA
believes  that further investigation  is  warranted.
Table  C-3 (Attachment C)  provides the physical
state,  liquid or  solid, of  various  compounds at
ambient soil temperature. When an inhalation SSL
exceeds  Csat for compounds  that  are liquid at
ambient  soil temperature, the SSL is set  at  Csat.
Where soil concentrations exceed a Csat-based SSL,
site managers  should  refer to EPA's  guidance,
Estimating the Potential for  Occurrence of DNAPL
at Superfund Sites  (U.S.  EPA, 1992c)  for  further
information on determining the likelihood of dense
nonaqueous phase liquid (DNAPL) in the subsurface.
Note that free-phase  contaminants may be present
at concentrations below  Csat if  multiple  organic
contaminants are present.  The DNAPL guidance
(U.S. EPA, 1992c) also  provides tools  for evaluating
the potential for such multiple component mixtures
in soil.

For organic compounds  that are solid at ambient soil
temperature,  concentrations  above Csat do not pose
a significant  inhalation risk or a potential for NAPL
occurrence. Thus, soil screening decisions should be
based  on the  appropriate  SSL for  other  site
pathways (e.g.,  migration to ground water,  direct
ingestion).

Migration  to  Ground  Water  SSLs. The Soil
Screening Guidance uses a simple linear equilibrium
soil/water partition  equation or a  leach  test to
estimate contaminant  release  in soil leachate. It also
uses a  simple water-balance  equation to calculate a
dilution  factor  to  account  for reduction  of  soil
leachate concentration from mixing in an aquifer.

The methodology for developing SSLs for the migra-
tion to ground water  pathway was designed for use
during the early stages of a site evaluation when
information  about  subsurface conditions may  be
limited. Hence, the methodology is based on rather
conservative, simplified  assumptions  about  the
release and transport  of  contaminants  in  the
                                                  28

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subsurface  (Exhibit 12). These assumptions are
inherent in the SSL equations and should be reviewed
for consistency with the conceptual site model (see
Step 2) to determine the applicability of SSLs to the
migration to ground water pathway.
   Exhibit  12:  Simplifying  Assumptions  for
   the  SSL Migration to  Ground  Water
   Pathway

   •  Infinite source (i.e., steady-state
      concentrations are maintained over the
      exposure period)

   •  Uniformly distributed contamination from the
      surface to the top of the aquifer

   •  No contaminant attenuation (i.e., adsorption,
      biodegradation, chemical degradation) in soil

   •  Instantaneous and linear equilibrium soil/water
      partitioning

   •  Unconfined, unconsolidated aquifer with
      homogeneous and isotropic hydrologic
      properties

   •  Receptor well at the downgradient edge of the
      source and screened within the plume

   •  No contaminant attenuation in the aquifer

   •  No NAPLs present (if NAPLs are present,  the
      SSLs do not apply).
To calculate SSLs for the migration to ground water
pathway, multiply  the acceptable ground water
concentration by the  dilution factor to obtain  a
target  soil leachate  concentration. For example, if
the dilution factor is 10 and  the acceptable ground
water  concentration  is  0.05 mg/L,  the  target
soil/water leachate concentration would be 0.5 mg/L.
Next, the partition equation is used to calculate the
total soil concentration (i.e., SSL)  corresponding to
this  soil leachate concentration. Alternatively, if a
leach test is used, compare the target soil leachate
concentration to extract  concentrations  from  the
leach tests.
 Equation  10:  Soil  Screening  Level
                Partitioning Equation  for
                Migration  to Ground Water
Screening Level
  in Soil (mg/kg)   =
                              (9w+9aH')]

                                   Pb
 Parameter/Definition  (units)
 Cw/target soil leachate concentration
    (mg/L)

 Kd/soil-water partition coefficient
    (L/kg)
 Koc/soil organic carbon/water
    partition coefficient (L/kg)
 foc /fraction organic carbon in
    soil  (gig)

 6w/water-filled  soil porosity
    C-water"-soil)

 9a/air-filled soil porosity (Lair/Lsoil)

 pb/dry  soil  bulk density (kg/L)

 n/soil porosity (Lpore/Lsoil)

 ps/soil particle density (kg/L)

 H'/dimensionless Henry's law
 constant
                             Default
                             nonzero MCLG,
                             MCL, or HBLa x
                             dilution factor
                             chernical-specificb
                             KOC x foe (organics)
                             chemical-specific13
                             0.002  (0.2%)


                             0.3
                             1.5
                             2.65

                             chemical-specific13
                             (assume to be zero
                             for inorganic con-
                             taminants except
                             mercury)
 aChemical-specific (see Attachment D).
 bSee Attachment C.

Soil/Water Partition Equation.  The  soil/water
partition   equation   (Equation   10)   relates
concentrations of  contaminants  adsorbed  to  soil
organic carbon to soil leachate concentrations in the
zone  of  contamination.  It  calculates  SSLs
corresponding to target soil leachate contaminant
concentrations (Cw). An adjustment has been added
to the equation  to relate sorbed concentration in
soil  to the measured total soil concentration. This
adjustment assumes that soil-water, solids, and gas
are conserved during sampling. If soil gas is lost
during sampling, 0a should be assumed to be zero.
Likewise,  for   inorganic  contaminants  except
                                                  29

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mercury, there is no significant vapor pressure and
H' may be assumed to be zero.

The  use of the soil/water  partition equation  to
calculate  SSLs  assumes  an  infinite source  of
contaminants extending to the top of the aquifer.
More detailed  models  may  be used to  calculate
higher  SSLs  that are still  protective  in some
situations.  For example, contaminants at sites with
shallow sources, thick unsaturated zones, degradable
contaminants, or unsaturated  zone characteristics
(e.g., clay layers) may attenuate before they reach
ground water.  The  TBD provides information on
the  use  of unsaturated zone models  for soil
screening. The decision to use such models should be
based on balancing the additional  investigative and
modeling costs  required to apply the more complex
models against the cost savings that will result from
higher SSLs.

Leach Test. A leach test may be used instead of the
soil/water partition equation. In some instances, a
leach test may be more useful  than the partitioning
method, depending on the constituents of concern
and the possible  presence of RCRA wastes. If this
option is chosen, soil parameters are not needed for
this pathway.  However, a dilution factor must still
be calculated. This guidance suggests using the EPA
Synthetic Precipitation Leaching Procedure (SPLP,
EPA SW-846 Method 1312, U.S. EPA, 1994d). The
SPLP was developed to model an acid rain leaching
environment and is  generally appropriate for a
contaminated soil scenario.  Like  most leach tests,
the SPLP may not be appropriate  for  all  situations
(e.g., soils contaminated with oily  constituents may
not yield suitable results).  Therefore,  apply the
SPLP with discretion.

EPA is aware that many leach tests are available for
application at hazardous waste  sites, some of which
may be appropriate in specific situations  (e.g., the
Toxicity Characteristic Leaching Procedure (TCLP)
models  leaching   in   a   municipal   landfill
environment).  It is  beyond  the scope  of this
document to discuss in detail leaching procedures and
the appropriateness of their use.

Stabilization/Solidification of CERCLA and RCRA
Wastes (U.S. EPA,  1989b)  and  the  EPA SAB's
review of leaching tests (U.S. EPA,  1991b) discuss
the application  of various leach  tests to various
waste disposal scenarios.  Consult these  documents
for further information.

See Step 3 for guidance on collecting subsurface soil
samples that can be used  for leach tests. To  ensure
adequate precision of leach test results,  leach tests
should be conducted in triplicate.

Dilution Factor Model.   As  soil  leachate  moves
through  soil   and  ground water,  contaminant
concentrations  are  attenuated by  adsorption  and
degradation. In the aquifer, dilution by clean ground
water   further  reduces  concentrations  before
contaminants reach receptor points (i.e.,  drinking
water wells). This reduction in concentration  can be
expressed by a  dilution attenuation factor (DAF),
defined as the  ratio of soil leachate concentration to
receptor point concentration.   The lowest possible
DAF is 1, corresponding to the  situation where there
is  no  dilution  or attenuation of a contaminant (i.e.,
when the  concentration in the receptor well is equal
to  the soil leachate  concentration).  On the other
hand,  high DAF  values  correspond to  a large
reduction in contaminant concentration from the
contaminated soil to the receptor well.

The Soil Screening Guidance addresses only  one of
these dilution-attenuation processes:  contaminant
dilution  in  ground water. A  simple mixing zone
equation derived from a water-balance relationship
(Equation  11) is used  to calculate a site-specific
dilution factor. Mixing-zone depth is estimated from
Equation  12, which  relates  it  to aquifer thickness
along with the  other parameters from  Equation  11.
Mixing  zone  depth  should  not  exceed aquifer
thickness  (i.e., use aquifer  thickness as the upper
limit for mixing zone  depth).

Because of the uncertainty resulting from the wide
variability  in  subsurface conditions that  affect
contaminant migration in ground water, defaults are
not provided  for the  dilution  model  equations.
Instead, a default DAF of 20  has been selected as
protective for  contaminated soil  sources up  to 0.5
acre in size. Analyses using the mass-limit models
described below suggest that a DAF of 20 may be
protective of larger sources as well; however,  this
hypothesis should be  evaluated  on a site-specific
basis. A discussion of the basis for  the default DAF
and a description of the mass-limit analysis is found
in  the TBD. However, since  migration  to ground
                                                 30

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water SSLs are most  sensitive to  the  DAF, site-
specific dilution factors  should be calculated.
Equation 11: Derivation of Dilution Factor
dilution factor = 1 + Kid
IT
Parameter/Definition (units)
dilution factor (unitless)
K/aquifer hydraulic
conductivity (m/yr)
i/hydraulic gradient (m/m)
I/infiltration rate (m/yr)
d/mixing zone depth (m)
L/source length parallel to
ground water flow (m)
Default
20 (0.5-acre
source)
 Equation  12:  Estimation  of  Mixing  Zone Depth
        d = (0.0112 L2)0-5 + da {1 - exp[(-LI)/(Kida)]}
 Parameter/Definition  (units)

 d/mixing zone depth  (m)
 L/source length  parallel to  ground water
    flow  (m)
 I/infiltration rate  (m/yr)
 K/aquifer  hydraulic  conductivity  (m/yr)
 i/hydraulic gradient  (m/m)
 da/aquifer  thickness  (m)
Mass-Limit  SSLs. Use of infinite source models to
estimate volatilization and  migration to ground
water  can violate mass  balance  considerations,
especially for small sources. To address this concern,
the Soil Screening Guidance includes models for
calculating  mass-limit SSLs  for  each  of  these
pathways (Equations  13  and  14)  that provide  a
lower limit to SSLs when  the area and depth
(i.e., volume) of  the  source are  known or  can
be  estimated reliably.

A  mass-limit  SSL  represents  the  level  of
contaminant in the subsurface that is still protective
when the entire  volume  of contamination either
volatilizes or leaches  over  the 30-year  exposure
duration  and the  level  of contaminant at  the
receptor does not exceed the health-based limit.

To  use mass-limit SSLs, determine  the  area  and
depth of  the source, calculate both  standard  and
mass-limit SSLs, compare them for each chemical of
concern and select the higher of the two values.
Analyze  the inhalation and migration to ground
water pathways separately.
                                                     Equation 13: Mass-Limit Volatilization  Factor
                                                                VF = QIC x [Tx(3.15x1Q7s/yr) ]
                                                                            (Pbxdsx106g/Mg)
                                                     Parameter/Definition  (units)
                                                     ds/average source  depth  (m)

                                                     T/exposure interval(yr)
                                                     Q/C/inverse of mean  cone,  at
                                                       center of a square source
                                                       (g/m2-s per kg/m3)

                                                     pb/dry  soil bulk density  (kg/L
                                                     or  Mg/m3)
                                Default
                                site-specific

                                30
                                68.81


                                1.5
Equation 14: Mass-Limit Soil Screening Level
for Migration to Ground Water
Screening Level
in Soil = (C^xIxED)
(mg/kg) pb x ds
Parameter/Definition (units)
Cw/target soil leachate concentration
(mg/L)
ds/depth of source (m)
I/infiltration rate (m/yr)
ED/exposure duration (yr)
pb/dry soil bulk density (kg/L)
Default
(nonzero MCLG,
MCL, orHBL)ax
dilution factor
site-specific
0.18
70
1.5
aChemical-specific, see Attachment D.

Note that Equations 13 and 14 require a site-specific
determination   of   the   average  depth   of
contamination  in  the source.  Step  3  provides
guidance  for conducting subsurface sampling to
determine source depth.  Where  the  actual average
depth of contamination is uncertain,  a conservative
estimate should be used (e.g., the maximum possible
depth in the unsaturated zone).  At many sites, the
average water table depth may be used unless there is
reason to believe that contamination  extends below
the water table. In this case SSLs do not apply and
                                                 31

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further investigation  of the  source  in  question is
needed.

Plant Uptake. Consumption of garden fruits and
vegetables  grown in contaminated residential soils
can result in a risk to human health. This exposure
pathway applies to both surface and subsurface soils.

The  TBD includes  an evaluation of the soil-plant-
human pathway along with a discussion of the site-
specific  factors that influence plant uptake  and
plant  contamination   concentration.   Generic
screening levels are calculated for arsenic, cadmium,
mercury,  nickel,  selenium, and zinc based  on
empirical data on the uptake  (i.e., bioconcentration)
of these inorganics into plants. In addition,  levels of
inorganics  that  have   been  reported to  cause
phytotoxicity (Will and  Suter, 1994) are presented.
Organic compounds are not addressed due to lack of
empirical data.

The  empirical data indicate that site-specific factors
such as soil type, pH, plant type, and chemical form
strongly influence  the uptake of metals into plants.
Where site  conditions allow for the mobility and
bioavailability of metals, the results  of our generic
analysis suggest that the soil-plant-human  pathway
may be  of  particular concern  for sites with soils
contaminated with cadmium  and arsenic. However,
the phytotoxicity of certain  metals  may limit the
amount that can be bioconcentrated in plant tissues.
The  data on phytotoxicity suggest  that, with the
exception of arsenic, metal  concentrations in soil
that are considered toxic to plants are well below the
levels that may impact  human health through the
soil-plant-human   pathway. This   implies   that
phytotoxic effects  may  prevent completion of this
pathway for these  metals.  However,  like  plant
uptake, phytotoxicity is  also  greatly influenced by
the site-specific factors mentioned above. Thus, it is
necessary to evaluate on a site-specific basis, the
potential bioavailability  of certain inorganics for the
soil-plant-human pathway  and the  potential for
phytotoxic effects in order to assess possible human
health and ecological impacts through plant uptake.

2.5.3    Address  Exposure  to   Multiple
Chemicals. The SSLs generally correspond to  a
1O6  risk level for carcinogens and a hazard quotient
of 1  for noncarcinogens.   This  "target" hazard
quotient  is  used to  calculate a soil  concentration
below which it is unlikely that sensitive populations
will experience adverse health effects. The potential
for additive effects has not been  "built in"  to the
SSLs  through apportionment. For carcinogens, EPA
believes that setting a  1O6 risk level for individual
chemicals  and pathways  generally will  lead to
cumulative  site risks  within  the  1O4 to 1O6 risk
range for the  combinations of chemicals typically
found at NPL sites.

For noncarcinogens, there is no widely accepted risk
range, and  EPA  recognizes that  cumulative risks
from noncarcinogenic  contaminants  at a site could
exceed the  target hazard  quotient. However, EPA
also recognizes that noncancer  risks  should be
added only for  those chemicals with the same
toxic  endpoint or mechanism  of action.

Ideally, chemicals would  be grouped according to
their exact mechanism  of action, and effect-specific
toxicity criteria would be available for chemicals
exhibiting multiple  effects. Instead,  data are often
limited to  gross  toxicological effects in an organ
(e.g.,  increased liver  weight) or an entire  organ
system  (e.g.,  neurotoxicity), and RfDs/reference
concentrations (RfCs)  are available for just one of
the several possible  endpoints of  toxicity for a
chemical.

Given   the   currently  available   criteria,
noncarcinogenic  contaminants should be  grouped
according to the critical effect listed  as the basis for
the RfD/RfC.  If more than one chemical  detected at
a site  affects the same target organ/system, SSLs for
those  chemicals should be divided  by the number of
chemicals present in the  group.  Exhibit 13  lists
several chemicals with noncarcinogenic affects in
the same target organ/system. However, the list is
limited, and a toxicologist should be  consulted prior
to using SSLs on a site-specific basis.

If additive risks are being considered in developing
site-specific SSLs for subsurface soils, recognize that,
for certain  chemicals, SSLs  may be based on a
"ceiling  limit"  concentration  (Csat)  instead of
toxicity. Because  they are  not  risk-based, Csat-based
SSLs  should  not  be modified  to account for
additivity.
                                                 32

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2.6   Step 6: Comparing Site  Soil
                 Contaminant
                 Concentrations to
                 Calculated  SSLs

Now that the site-specific SSLs have been calculated
for the potential contaminants of concern, compare
them with the site contaminant concentrations. At
this point, it is reasonable  to review the CSM with
the actual site data to confirm its  accuracy and the
overall applicability of the Soil Screening Guidance.

In theory, an exposure area would be screened from
further investigation  when the true  mean of the
population of  contaminant  concentrations  falls
below  the established screening level.  However,
EPA recognizes  that data  obtained from sampling
and analysis are never perfectly representative and
accurate, and that the cost of trying to  achieve
perfect results would be  quite high.  Consequently,
EPA acknowledges  that some uncertainty in data
must be  tolerated, and focuses  on controlling the
uncertainty which affects decisions based on those
data. Thus, in the Soil Screening Guidance, EPA has
developed an  approach for  surface  soils to minimize
the chance of incorrectly deciding to:

•    Screen  out areas when the  correct decision
     would be to investigate further (Type  I error);
     or

•    Decide to investigate further when the correct
     decision would be to  screen out the area (Type
     II error).

The approach sets  limits  on the probabilities  of
making such decision  errors, and acknowledges that
there is a range (i.e., gray region) of contaminant
levels  around  the  screening  level where  the
variability  in  the  data  will  make  it difficult  to
determine  whether  the   exposure  area  average
concentration is actually above or  below  the
screening level.   The Type I and Type II  decision
error  rates have been  set at  5  percent  and 20
percent, respectively, and the  gray region has been
set between one-half and two times the  SSL.  By
specifying the upper edge of the gray region  as twice
the SSL,  it is possible that exposure areas with mean
contaminant concentration values slightly above the
SSL  may be  screened  from  further  study.
Commenters have expressed concern that this is not
adequately   protective   for   SSLs   based  on
noncarcinogenic effects.   However, EPA believes
that the approaches taken in this  guidance to address
chronic   exposure  to   noncarcinogens   are
conservative enough  for the  majority  of site
contaminants  (i.e.,  comparison  of  the  6  year
"childhood only"  exposure to  the  chronic RfD);
and, use of  maximum  composite  concentrations
provide high  coverage of the true  population mean
(i.e., there is  high  probability that the  value equals
or exceeds the true population mean).

Thus,  for   surface  soils,   the  contaminant
concentrations in each composite sample from  an
exposure  area are compared to two times the  SSL.
Under the Soil Screening Guidance DQOs, areas are
screened  out  from further study when contaminant
concentrations in all of the composite samples are
less than  two times the SSLs. Use of  this decision
rule (comparing  contaminant  concentrations  to
twice the  SSL) is appropriate only when the quantity
and  quality  of data  are comparable to  the levels
discussed in this guidance, and  the  toxicity of the
chemical has been evaluated against the criteria
presented in  Section 2.5.1.

For existing data sets that may be more limited than
those discussed in this guidance, the 95 percent
upper-confidence limit on  the arithmetic mean of
contaminant concentrations in surface soils (i.e., the
Land method as  described in  the Supplemental
Guidance to  RAGS: Calculating the Concentration
Term  (U.S. EPA,  1992d) should be used for
comparison to the SSLs.  The  TBD discusses the
strengths  and weaknesses  of using  the Land method
for making screening decisions.
                                                33

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     Exhibit  13: SSL  Chemicals  with  Noncarcinogenic Toxic  Effects  on  Specific  Target
                                            Organ/System
  Target  Organ/System
Effect
Kidney
  Acetone
  1,1-Dichloroethane
  Cadmium
  Chlorobenzene
  Di-n-octyl phthalate
  Endosulfan
  Ethylbenzene
  Fluoranthene
  Nitrobenzene
  Pyrene
  Toluene
  2,4,5-Trichlorophenol
  Vinyl acetate
Liver
  Acenaphthene
  Acetone
  Butyl benzyl phthalate
  Chlorobenzene
  Di-n-octyl phthalate
  Endrin
  Ethylbenzene
  Flouranthene
  Nitrobenzene
  Styrene
  Toluene
  2,4,5-Trichlorophenol
Central  Nervous  System
  Butanol
  Cyanide (amenable)
  2,4 Dimethylphenol
  Endrin
  2-Methylphenol
  Mercury
  Styrene
  Xylenes
Adrenal Gland
  Nitrobenzene
  1,2,4-Trichlorobenzene
Increased weight; nephrotoxicity
Kidney damage
Significant proteinuria
Kidney effects
Kidney effects
Glomerulonephrosis
Kidney toxicity
Nephropathy
Renal and adrenal lesions
Kidney effects
Changes in kidney weights
Pathology
Altered kidney weight

Hepatotoxicity
Increased weight
Increased liver-to-body weight and liver-to-brain weight ratios
Histopathology
Increased weight; increased SCOT and SGPT activity
Mild histological lesions in liver
Liver toxicity
Increased liver weight
Lesions
Liver effects
Changes in liver weights
Pathology

Hypoactivity and ataxia
Weight loss, myelin degeneration
Prostatration and ataxia
Occasional convulsions
Neurotoxicity
Hand tremor, memory disturbances
Neurotoxicity
Hyperactivity

Adrenal lesions
Increased adrenal weights; vacuolization in cortex
                                                  34

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                                      Exhibit  13:  (continued)
  Target  Organ/System
Effect
Circulatory  System
  Antimony
  Barium
  frans-1,2-Dichloroethene
  c/s-1,2-Dichloroethylene
  2,4-Dimethylphenol
  Fluoranthene
  Fluorene
  Nitrobenzene
  Styrene
  Zinc
Reproductive  System
  Barium
  Carbon disulfide
  2-Chlorophenol
  Methoxychlor
  Phenol
Respiratory  System
  1,2-Dichloropropane
  Hexachlorocyclopentadiene
  Methyl bromide
  Vinyl acetate
Gastrointestinal  System
  Hexachlorocyclopentadiene
  Methyl bromide
Immune  System
  2,4-Dichlorophenol
  p-Chloroaniline
Altered blood chemistry and myocardial effects
Increased blood pressure
Increased alkaline phosphatase level
Decreased hematocrit and hemoglobin
Altered blood chemistry
Hematologic changes
Decreased RBC and hemoglobin
Hematologic changes
Red blood cell effects
Decrease in erythrocyte superoxide dismutase (ESOD)

Fetotoxicity
Fetal toxicity and malformations
Reproductive effects
Excessive loss of litters
Reduced fetal body weight in rats

Hyperplasia of the nasal mucosa
Squamous metaplasia
Lesions on the  olfactory epithelium of the nasal cavity
Nasal epithelial lesions

Stomach lesions
Epithelial hyperplasia of the forestomach

Altered immune function
Nonneoplastic lesions of splenic capsule
Source: U.S. EPA, 1995b, U.S. EPA, 1995a
                                                  35

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In this guidance, fewer samples are collected for
subsurface  soils than for  surface soils;  therefore,
different decision rules apply.

Since subsurface soils are not characterized as well,
there is  less confidence  that the  concentrations
measured are representative of the entire source.
Thus, a more conservative approach to screening is
warranted. Because it may not be protective to allow
for comparison  to  values  above the SSL,  mean
contaminant concentrations from each soil boring
taken in a  source area are  compared  with  the
calculated SSLs. Source areas with any  mean soil
boring contaminant concentration greater than  the
SSLs generally warrant further consideration. On the
other hand, where the mean soil boring contaminant
concentrations within a source are all less than the
SSLs, that source area is generally screened out.

2.7   Step 7: Addressing Areas
                 Identified  for Further
                 Study

The  chemicals,  exposure pathways, and  areas that
have been  identified for further study  become a
subject of the RI/FS. The results of the baseline risk
assessment conducted  as  part of  the RI/FS will
establish  the basis for taking remedial action. The
threshold for taking action differs from the criteria
used for screening.  As  outlined in Role of the
Baseline  Risk Assessment in  Superfund Remedy
Selection Decisions (U.S. EPA,  1991d), remedial
action  at NPL  sites  is generally warranted where
cumulative risks for current or future land use exceed
IxlO-4  for carcinogens or  a  HQ  of 1  for
noncarcinogens.  The   data  collected   for  soil
screening  are useful in the RI  and baseline risk
assessment. However, additional data will probably
need to be collected during future site investigations.

Once the  decision has been made to  initiate remedial
action, the  SSLs can  then serve  as preliminary
remediation goals.  This process is referenced in
Section 1.2 of this document.
     FOR  FURTHER  INFORMATION

More  detailed  discussions  of  the  technical
background  and  assumptions  supporting  the
development of  the  Soil Screening Guidance are
presented in the Soil Screening Guidance: Technical
Background  Document (U.S.  EPA,  1996).  For
additional copies of this guidance  document, the
Technical Background Document,  or  other  EPA
documents, call the National Technical Information
Service (NTIS) at (703)  487-4650  or  1-800-553-
NTIS (6847).
                                               36

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U.S. EPA. 1990b. Sampler's Guide to the Contact
  Laboratory Program. Office of Emergency and
  Remedial  Response, Washington, DC.  NTIS
  PB91-92133OCDH.

U.S. EPA 1990c.  A Rationale for the Assessment
  of  Errors  in  the  Sampling  of Soils.
  Environmental   Monitoring   Systems
  Laboratory,   Office   of   Research   and
  Development,  Las Vegas, NV. EPA/600/4-
  90/013.  NTIS PB90-242306.

U.S. EPA. 1991a. Human  Health Evaluation
  Manual (HHEM), Supplemental Guidance:
  Standard Default Exposure Factors.  Office of
  Emergency   and  Remedial   Response,
  Washington, DC. Publication 9285.6-03. NTIS
  PB91-921314.

U.S. EPA.  1991b.  Leachability  Phenomena.
  Recommendations and Rationale for Analysis
  of Contaminant Release by the Environmental
  Engineering  Committee.  Science Advisory
  Board, Washington, DC.  EPA-SAB-EEC-92-
  003.

U.S. EPA. 1991c. Risk Assessment Guidance for
  Superfund (RAGS), Volume 1: Human Health
  Evaluation   Manual   (HHEM),  Part  B,
  Development  of  Risk-Based  Preliminary
  Remediation Goals. Office of Emergency and
  Remedial  Response,  Washington,  DC.
  Publication 9285.7-01B. NTIS PB92-963333.

U.S. EPA. 1991d. Role of the Baseline Risk
  Assessment in  Superfund  Remedy  Selection
  Decisions. Office of Emergency and Remedial
  Response,  Washington,   DC.  Publication
  9355.0-30.  NTIS PB91-921359/CCE.

U.S. EPA. 1991e.  User's Guide to  the Contract
  Laboratory Program. Office of Emergency and
  Remedial  Response, Washington, DC. NTIS
  PB91-921278CDH.

U.S. EPA, 199If.  Description  and Sampling of
  Contaminated  Soils: A Field Pocket  Guide.
  Office    of    Environmental  Research
  Information,  Cincinnati,  OH.  EPA/625/12-
  91/002.

U.S. EPA.  1992a. Considerations  in  Ground-
  Water Remediation at Superfund Sites  and
  RCRA Facilities—Update. Office of Emergency
  and  Remedial  Response,  Washington, DC.
  Directive    9283.1-06.   NTIS    PB91-
  238584/CCE.

U.S. EPA. 1992b. Dermal Exposure Assessment:
  Principles and Applications. Interim  Report.
  Office  of  Research and  Development,
  Cincinnati, OH. EPA/600/8-91/01 IB.
                                             38

-------
U.S.  EPA.  1992c.  Estimating  Potential for
   Occurrence  of DNAPL at Superfund Sites.
   Office of Emergency and Remedial Response,
   Washington,  DC.  Publication 9355.4-07FS.
   NTIS PB92-963338.

U.S. EPA.  1992d.  Supplemental Guidance  to
   RAGS; Calculating the Concentration Term.
   Volume 1, Number 1, Office of Emergency and
   Remedial  Response,  Washington,  DC. NTIS
   PE92-963373

U.S. EPA. 1992e. Preparation of Soil Sampling
    rntnrnlv   Sampling   Techniques  and
                 Office  of  Research  and
.S. EPA.  1992e. Preparation of Soil Sampling
 Protocols:  Sampling   Techniques   and
 Strategies.   Office   of   Research  and
 Development, Washington, DC.  EPA/600/R-
 92/128.
U.S. EPA.  1993a. Data  Quality Objectives for
  Superfund:   Interim  Final   Guidance.
  Publication 9255.9-01. Office of Emergency
  and Remedial Response, Washington, DC. EPA
  540-R-93-071. NTIS PB94-963203.

U.S. EPA.  1993b. Guidance for  Evaluating
  Technical Impracticability  of Ground-Water
  Restoration.   EPA/540-R-93-080.  Office of
  Emergency   and   Remedial   Response,
  Washington, DC. Directive 9234.2-25.

U.S. EPA.  1993c.  Quality  Assurance  for
  Superfund  Environmental  Data  Collection
  Activities. Quick Reference Fact  Sheet. Office
  of  Emergency  and  Remedial  Response,
  Washington, DC. NTIS PB93-963273.

U.S. EPA  1993d.   The  Urban Soil Lead
  Abatement  Demonstration Project.  Vol I:
  Integrated  Report Review Draft.  National
  Center for Environmental  Publications  and
  Information.   EPA 600/AP93001/A.  NTIS
  PB93-222-651.

U.S. EPA,  1993e. Subsurface Characterization
  and Monitoring Techniques: A Desk Reference
  Guide. Vol.  I & II . Environmental Monitoring
  Systems  Laboratory,  Office of Research and
  Development,  Las  Vegas,  NV.  EPA/625/R-
  93/003a.

U.S. EPA,  1993f. Risk Assessment  Guidance for
  Superfund (RAGS), Human Health  Evaluation
  Manual  (HHEM).  Science Advisory Board
  Review  of the  Office of  Solid Waste  and
  Emergency Response draft. Washington, DC.
  EPA-SAB-EHC-93-007.

U.S. EPA. 1994a. Guidance for the Data Quality
  Objectives  Process.   Quality  Assurance
  Management Staff, Office of Research and
  Development, Washington, DC. EPA QA/G-4.

U.S. EPA.  1994c. Methods for  Evaluating the
  Attainment of Cleanup Standards—Volume 3:
  Reference-Based Standards for Soils and Solid
  Media.   Environmental   Statistics   and
  Information  Division,  Office  of  Policy,
  Planning, and Evaluation,  Washington, DC.
  EPA 230-R-94-004.

U.S. EPA.  1994d. Test Methods for Evaluating
  Solid Waste, Physical/Chemical Methods (SW-
  846), Third Edition, Revision 2. Washington,
  DC.

U.S. EPA. 1995a. Health Effects  Assessment
  Summary Tables  (HEAST): Annual  Update,
  FY1993.  Environmental  Criteria   and
  Assessment  Office,  Office of  Health and
  Environmental Assessment, Office of Research
  and Development,  Cincinnati, OH.

U.S. EPA.  1995b. Integrated Risk Information
  System (IRIS). Cincinnati, OH.

U.S. EPA. 1995c. Drinking Water Regulations and
  Health   Advisories.  Office  of  Water,
  Washington, DC.

U.S. EPA. 1996. Soil  Screening  Guidance:
  Technical  Background  Document. Office of
  Emergency   and  Remedial  Response,
  Washington, DC. EPA/540/R95/128.

Van Wijnen, J.H., P. Clausing, and B. Brunekreef.
  1990.  Estimated  soil  ingestion by  children.
  Environ Research  51:147-162.

Wester et al. 1993.  Percutaneous absorption of
  pentachlorophenol from soil. Fundamentals of
  Applied Toxicology, 20.

Will, M.E. and G.W.  Suter II. 1994. Toxicological
  Benchmarks  for  Screening  Potential
  Contaminants  of Concern for Effects  on
  Terrestrial Plants,  1994 Revision. ES/ER/TM-
  8/R1.  Prepared for the  U.S. Department of
  Energy  by  the   Environmental  Sciences
  Division of Oak Ridge National Laboratory.
                                              39

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-------

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                            Attachment A



                   Conceptual Site Model Summary
Form 1. General Site Information
Form 2. Site Characteristics
Ground Water Flow Direction

-------
Aquifer Parameters.
Infiltration Rate.

-------
Meteorologic  Parameters.
Form 3. Exposure Pathways and Receptors
   Table A-1. Example Identification of Exposure Pathways Not Addressed by SSLs
 Receptors/
 Exposure Pathways
Contaminant
Characteristics
Site Conditions
 Human /Direct Pathways
  ingestion
  (acute exposure)
  inhalation - fugitive dusts (acute
  exposure)
acute health effects
(e.g., cyanide, phenol)
acute health effects
residential setting

high fugitive dusts (e.g., from soil
tillage, heavy traffic on dirt roads;
construction)
Human / Indirect Pathways
consumption of meat or dairy
products
fish consumption
bioaccumulation,
biomagnification
biomagnification
nearby meat or dairy production
nearby surface waters with
recreational or subsistence fishing
Ecological Pathways
aquatic
terrestrial
aquatic toxicity
toxicity to terrestrial
organisms (e.g., DDT, Hg)
nearby surface waters or wetlands
sensitive species on or near site

-------
Figure A-1. U.S. climatic zones
            A-4

-------
Form 4. Soil Contaminant Source Characteristics
Average soil moisture content (6W)
                                             Pb) as follows:






                                n = 1 - (pb/p

-------
            Table A-2. Parameter Estimates for Calculating Average Soil
                             Moisture Content (6W)
Soil texture
Sand
Loamy sand
Sandy loam
Silt loam
Loam
Sandy clay loam
Silt clay loam
Clay loam
Sandy clay
Silt clay
Clay
Ks(m/yr)
1,830
540
230
120
60
40
13
20
10
8
5
1/(2b+3)
0.090
0.085
0.080
0.074
0.073
0.058
0.054
0.050
0.042
0.042
0.039
          Source: U.S. EPA, 1988.


Worksheets
CSM Diagram

-------
References

-------
                                   Soil Screening Guidance
                           Conceptual Site Model Summary  Forms
Form 1: General Site Information
EPA Region	
                      Site Name
Contractor Name and Address:
State Contact:
                                     Date
1.   CERCLISIDNo.
    Address  	
    C o u nty	
State
                                            _City
Zip Code
Congressional District_
2.   Owner Name
    Owner Address
    City	
           State
          _Operator Name	
          _Operator Address_
          _City  	
                   State
3.   Type of ownership (check all that apply):
    D Private   D Federal Agency	
    Other
                              D State
                              D County
                              Ref.
                      D Municipal
4.   Approximate size of property
                      acres
                                             Ref.
5.   Latitude
     . 	"   Longitude  	 o	|	
                            "  Ref.
6.   Site status  D Active    D Inactive    D Unknown
                                             Ref.
7.   Years of operation   From_
               To
                 D Unknown    Ref.
    Previous investigations
       Type               Agency/State/Contractor
                                   Date
                                                                   Ref.
                                                                   Ref.
                                                                   Ref.
                                                                   Ref.
                                                                   Ref.
                                                                   Ref.
Ref. = reference(s) on information source

-------
                                   Soil Screening Guidance
                           Conceptual Site Model Summary Forms
Figure A-1.  U.S. climatic zones
           Site Name
Hydroqeoloqic Characteristics (migration to ground water pathway)
Is ground water of concern at the site?   Dyes  D no (if no, move to Infiltration Rate below).
Heath region 	Hydrogeologic setting	
(attach setting diagram)
Check setting characteristics that apply:   D  karst  D fractured rock    D solution limestone
Describe the stratigraphy and hydrogeologic characteristics of the site. (Attach available maps and cross-sections.
Ref.
Identify and describe nearby sites in similar settings that have already been characterized.
Ref.
  Aquifer Parameters     Unit   Typical    Min.
      Max.
         Reference or Source
hydraulic conductivity (K)
hydraulic gradient (i)
thickness (dg)
m/y
m/m
m












General direction of ground water flow across the site (e.g., NNE, SW):
(attach map.) Ref.  	
Infiltration rate (I)
m/yr
Method
Meteorological Characteristics (inhalation pathway)
climatological zone:  	
fract. vegetative cover (V)	
mean annual windspeed (U  )	
(zone#, city)  Q/C	
(unitless)     Reference
m/s          Reference
                       _(g/m2-s per kg/m3)
equivalent threshold value of windspeed at 7 m (Ut)
fraction dependent on Um/Ut 	
Comments:
                      _m/s
                      Junitless)

-------
                                   Soil Screening Guidance
                           Conceptual Site Model Summary Forms

Form 3: Exposure Pathways and Receptors        Site Name 	
Land Use Conditions
Current site use:                        Surrounding land use:                   Future land use:
	residential                           	residential                          	residential
	industrial                            	industrial                           	industrial
	commercial                          	commercial                         	commercial
	agricultural                          	agricultural                          	agricultural
	recreational                          	recreational                         	recreational
	other                               	other                              	other

Size of exposure areas (in acres) 	
Contaminant Release Mechanisms (check all that apply):
Source*	D  leaching   D volatilization  D fugitive dusts  D  erosion/runoff D uptake by plants
Source*	D  leaching   D volatilization  D fugitive dusts  D  erosion/runoff D uptake by plants
Source*	D  leaching   D volatilization  D fugitive dusts  D  erosion/runoff D uptake by plants
(describe rationale for not including any of the above release mechanisms)
Media affected (or potentially affected) by soil contamination.
Source*	  D air D ground water  D surface water D sediments  D wetlands
Source*	  D air D ground water  D surface water D sediments  D wetlands
Source*	  D air D ground water  D surface water D sediments  D wetlands

Check if present on-site or on surrounding land (attach map showing locations)
D wetlands D surface water D subsistence fishing D recreational fishing D dairy/beef production

Check  SSL  exposure  pathways  applicable  at   site;   describe   basis  for   not  including   any
pathway
D ingestion D inhalation D migration to ground water D dermal D soil-plant-human

Check Potential for:
D Acute Effects (describe)

D Other Human  Exposure Pathways (describe)

D Ecological concerns (describe)

-------
                                   Soil Screening Guidance
                           Conceptual Site Model Summary Forms

Form 4: Soil  Contaminant Source Characteristics          Site Name	
Source No.:  	
Name:	 (e.g., drum storage area)
Type: 	 (e.g., spill, dump, wood treater)
Location:	 (site map)
Waste type:  	 (e.g., solvents, waste oil)
Description (describe history of contamination, other information)
Describe past/current remedial or removal actions
Source depth:	  m (D  measures D estimated)    Ref. 	
Source area: 	acres  	  m2 (D  measures D estimated)   Ref. 	
Source length parallel to ground water flow:  	m (if uncertain, use longest source dimension)
Contaminant types (check all that apply):   D volatile organics  D other organics  D metals D other inorganics
Soil Contaminants Present (list):	
(attach Worksheet #1)
Describe previous soil analyses, (attach available results and map showing sample locations)
(attach Worksheet #2)
Are NAPLs suspected?       D Yes  D No   Reason_
Average Soil Characteristics
average water content (0W)	(L wate/L soi|)   Ref.
fraction organic carbon (foc) 	g/g           Ref.
dry bulk density (pb)  	(kg/L)        Ref.
pH  	                                                  Ref.

-------
Worksheet 1. Contaminant-specific properties
Regulatory and  Human Health  Benchmarks1
Site Name
Contaminant









CAS#









MCLG,
MCL, or
HBL (mg/L)









Sources
(no.)









RfD
(mg/kg/-d)









SF0
(mg/kg/-d)-1









URF
(ng/m3)-1









RfC
(mg/m3)









Chemical Properties2
Contaminant









CAS#









Sources
(no.)









K0c3
(L/kg)









Kd4
(L/kg)









H5









D. 5
ia
(cm2/s)









D. 5
IW
(cm2/s)









S5
(mg/L)









        1. Attachment D
        2. Attachment C
        3. For organic compounds
        4. For metals and inorganic compounds
        5. Not applicable to metals except mercury

-------
Worksheet 2. Contaminant concentrations by source       Site Name




Source #:

Contaminant









CAS#









average









standard
deviation









number of
samples









minimum









maximum









variance









Source #:

Contaminant









CAS#









average









standard
deviation









number of
samples









minimum









maximum









variance










-------
Worksheet 3. Surface SSLs by Exposure Area (EA)
                               Site Name
EA #:
SSL type:   D site-specific D generic (default)

Contaminant









CAS#









Soil Screening Level
ingestion









other (plant uptake; fugitive dust)









EA #:
SSL type:   D site-specific D generic (default)

Contaminant








CAS#








Soil Screening Level
ingestion








other (plant uptake; fugitive dust)









-------
Worksheet 4. Subsurface SSLs by source        Site Name 	




Source #:	  SSL type:   D site-specific   D generic (default)
Contaminant









CAS#









Soil Screening Level
inhalation of volatiles









migration to ground water









Source #:
SSL type:   D site-specific   D generic (default)
Contaminant








CAS#








Soil Screening Level
inhalation of volatiles








migration to ground water









-------
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Figure A-2.  Example conceptual site  model diagram for  contaminated soil
                     (adapted  from  U.S.  EPA,  1989).
                                  A-16

-------
                     WOODED AREA
LAKE
                                 SHALE BEDROCK
                                                     REGIONAL
                                              GEOLOGIC CROSS SECTION
                                                         WOODED AREA
                                     FILL MATERIAL
                    DEPRESSION
     (DIRECT CONTACT)
                  \
                         LACUSTRINE DEPOSITS
                    'GLACIAL TILL
               "SHALE BEDROCK
POTENTIAL
CONTAMINANT
MIGRATION
PATHWAY
                                               SITE CROSS SECTION
              Figure A-3. Example Site Sketch (adapted from U.S. EPA, 1987)

-------
                     Attachment B




Soil Screening DQOs for Surface Soils and Subsurface Soils

-------

-------
                   Soil  Screening  DQOs for  Surface Soils Using the  Max  Test
         DQO  Process  Steps
                   Soil  Screening  Inputs/Outputs
State  the Problem
Identify scoping team

Develop conceptual site model (CSM)
Define exposure scenarios

Specify available resources
Write brief summary of contamination
  problem
Site manager and technical experts (e.g., toxicologists, risk assessors,
  statisticians)
CSM development (described in Step 1)
Direct ingestion and inhalation of fugitive particulates in a residential setting;
  dermal contact and plant uptake for certain contaminants
Sampling and analysis budget, scheduling constraints, and available personnel
Summary of the surface soil contamination problem to be investigated at the site
Identify  the  Decision
Identify decision

Identify alternative actions
Do mean soil concentrations for particular contaminants (e.g., contaminants of
  potential concern) exceed appropriate screening levels?
Eliminate area from further study under CERCLA
or
Plan and conduct further investigation
Identify Inputs to  the Decision
Identify inputs

Define basis for screening
Identify analytical methods
Ingestion and particulate inhalation SSLs for specified contaminants
Measurements of surface soil contaminant concentration
Soil Screening Guidance
Feasible analytical methods (both field and laboratory) consistent with program-
  level requirements
Define the  Study Boundaries
Define geographic areas of field
  investigation
Define population of interest

Divide site into strata
Define scale of decision making

Define temporal boundaries of study
Identify practical constraints
The entire NPL site, (which may include areas beyond facility boundaries),
  except for any areas with clear evidence that no contamination has occurred
Surface soils (usually the top 2 centimeters, but may be deeper where activities
  could redistribute subsurface soils to the surface)
Strata may be  defined so that contaminant concentrations are likely to be
  relatively homogeneous within each stratum based on the CSM and field
  measurements
Exposure areas (EAs) no larger than 0.5 acre each (based on residential land
  use)
Temporal constraints on scheduling field visits
Potential impediments to sample collection, such as access, health, and  safety
  issues
Develop  a Decision Rule
Specify parameter of interest
Specify screening level

Specify "if..., then..." decision rule
"True mean" (|i) individual contaminant concentration in each EA. However,
  since the determination of the "true mean" would require the collection and
  analysis of many samples, another sample statistic, the maximum composite
  concentration, or "Max Test" is used.
Screening levels calculated using available parameters and site data (or generic
  SSLs if site data are unavailable)
Ideally, if the "true mean" EA concentration exceeds the screening level, then
  investigate the EA further.  If the "true mean" is less than the screening level,
  then no further investigation of the EA is required under CERCLA.
                                                    B-l

-------
            Soil Screening  DQOs for  Surface  Soils Using  the  Max Test (continued)
       DQO  Process  Steps
                 Soil  Screening  Inputs/Outputs
Specify  Limits on Decision Errors*
 Define baseline condition (null
  hypothesis)
 Define the gray region**
 Define Type I and Type II decision errors
 Identify consequences

 Assign acceptable probabilities of Type I
  and Type II decision errors
 Define QA/QC goals
The EA needs further investigation


From 0.5 SSL to 2 SSL
Type I error: Do not investigate further ("walk away from") an EA whose "true
  mean" exceeds the screening level of 2 SSL
  Type  II error: Investigate further when an EA's "true mean" falls below the
  screening level of 0.5 SSL
Type I error: potential public health consequences
Type II error: unnecessary expenditure of resources to investigate further
Goals:
  Type  I: 0.05 (5%) probability of not investigating further when "true mean" of
    the EA is 2 SSL
  Type  II: 0.20 (20%) probability of investigating further when "true mean" of
    the EA is 0.5 SSL
CLP precision and bias requirements
10% CLP analyses for field methods
Optimize the  Design
Determine how to best estimate "true
mean"
 Determine expected variability of EA
 surface soil contaminant concentrations
 Design sampling strategy by evaluating
 costs and performance  of alternatives
Samples composited across the EA as physical estimates of EA mean (x).
Use maximum composite concentration as a conservative estimate of the true
EA mean.
A conservatively large expected coefficient of variation (CV) from prior data
 for the site, field measurements, or data from other comparable sites and
 expert judgment.  A minimum default CV of 2.5 should be used when
 information is insufficient to estimate the CV.
Lowest cost sampling design option (i.e., compositing scheme and number of
 composites) that will achieve acceptable decision error rates
 Develop planning documents for the field
 investigation	
Sampling and Analysis Plan (SAP)
Quality Assurance Project Plan (QAPJP)
    Since the DQO process controls the degree to which uncertainty in data affects the outcome of decisions that are
    based on that data, specifying limits on decision errors will allow the decision maker to control the probability of making
    an incorrect decision when using the DQOs.

    The gray region represents the area where the consequences of decision errors are minor, (and uncertainty in
    sampling data  makes decisions too close to call).
                                                    B-2

-------
                             Soil Screening  DQOs  for Subsurface  Soils
 DQO  Process Steps
                   Soil  Screening  Inputs/Outputs
State  the Problem
Identify scoping team

Develop conceptual site model (CSM)
Define exposure scenarios

Specify available resources

Write brief summary of contamination
  problem
Site manager and technical experts (e.g., toxicologists, risk assessors,
  hydrogeologists,  statisticians).
CSM development (described in Step 1).
Inhalation of volatiles and migration of contaminants from soil to potable
  ground water (and plant uptake for certain contaminants).
Sampling and analysis budget, scheduling constraints, and available
  personnel.
Summary of the subsurface soil contamination problem to be investigated at
  the site.
Identify the  Decision
Identify  decision

Identify  alternative actions
Do mean soil concentrations for particular contaminants (e.g., contaminants
  of potential concern) exceed appropriate SSLs?
Eliminate area from further action or study under CERCLA
or
Plan and conduct further investigation.
Identify Inputs  to the  Decision
Identify decision


Define basis for screening
Identify analytical  methods
Volatile inhalation and migration to ground water SSLs for specified
  contaminants
Measurements of subsurface soil contaminant concentration
Soil Screening Guidance
Feasible analytical methods (both field and laboratory) consistent with
  program-level requirements.
Specify the  Study Boundaries
Define geographic areas of field
  investigation

Define population of interest
Define scale of decision making

Subdivide site into decision units
Define temporal boundaries of study
Identify (list) practical constraints
The entire NPL site (which may include areas beyond facility boundaries),
  except for any areas with clear evidence that no contamination has
  occurred.
Subsurface soils
Sources (areas of contiguous soil contamination, defined by the area and
  depth of contamination or to the water table, whichever is more shallow).
Individual sources delineated (area and depth) using existing information or
  field measurements (several nearby sources may be combined into a single
  source).
Temporal constraints on scheduling field visits.
Potential impediments to sample collection, such as access, health, and
  safety issues.

-------
 Soil  Screening  DQOs for Subsurface  Soils  (continued)
Develop a  Decision  Rule
Specify parameter of interest

Specify screening level

Specify "if..., then..." decision rule
Mean soil contaminant concentration in a source (i.e., discrete contaminant
  concentrations averaged within each boring).
SSLs calculated using available parameters and site data (or generic SSLs if
  site data are unavailable).
If the mean soil concentration exceeds the SSL, then investigate the source
  further. If mean soil concentration in a source is less than the SSL, then no
  further investigation is required under CERCLA.
Specify  Limits on  Decision  Errors
Define QA/QC goals
CLP precision and bias requirements
10% CLP analyses for field methods
Optimize the  Design
Determine how to estimate mean
  concentration in a source
Define subsurface sampling strategy by
  evaluating costs and site-specific
  conditions
Develop planning documents for the field
  investigation
For each source, the highest mean soil boring concentration (i.e., depth-
  weighted average of discrete contaminant concentrations within a boring).
Number of soil borings per source area; number of sampling intervals with
  depth.

Sampling and Analysis Plan (SAP)
Quality Assurance Project Plan (QAPJP)
                                                    B-4

-------
            Attachment C




Chemical Properties for SSL Development

-------

-------
   Attachment C



Chemical Properties

-------
Table C-1. Chemical-Specific Properties used in SSL Calculations
CAS No.
83-32-9
67-64-1
309-00-2
120-12-7
56-55-3
71-43-2
205-99-2
207-08-9
65-85-0
50-32-8
111-44-4
117-81-7
75-27-4
75-25-2
71-36-3
85-68-7
86-74-8
75-15-0
56-23-5
57-74-9
106-47-8
108-90-7
124-48-1
67-66-3
95-57-8
218-01-9
72-54-8
72-55-9
50-29-3
53-70-3
84-74-2
95-50-1
106-46-7
91-94-1
75-34-3
107-06-2
75-35-4
156-59-2
156-60-5
120-83-2
78-87-5
542-75-6
60-57-1
84-66-2
105-67-9
Compound
Acenaphthene
Acetone
Aldrin
Anthracene
Benz(a)anthracene
Benzene
Benzo(£>)fluoranthene
Benzo(/()fluoranthene
Benzole acid
Benzo(a)pyrene
Bis(2-chloroethyl)ether
Bis(2-ethylhexyl)phthalate
Bromodichloromethane
Bromoform
Butanol
Butyl benzyl phthalate
Carbazole
Carbon disulfide
Carbon tetrachloride
Chlordane
p-Chloroaniline
Chlorobenzene
Chlorodibromomethane
Chloroform
2-Chlorophenol
Chrysene
ODD
DDE
DDT
Dibenz(a,/?)anthracene
Di-n-butyl phthalate
1,2-Dichlorobenzene
1,4-Dichlorobenzene
3,3-Dichlorobenzidine
1,1-Dichloroethane
1,2-Dichloroethane
1 ,1-Dichloroethylene
c/s-1 ,2-Dichloroethylene
frans-1 ,2-Dichloroethylene
2,4-Dichlorophenol
1 ,2-Dichloropropane
1 ,3-Dichloropropene
Dieldrin
Diethylphthalate
2,4-Dimethylphenol
KOC
(L/kg)
7.08E+03
5.75E-01
2.45E+06
2.95E+04
3.98E+05
5.89E+01
1.23E+06
1.23E+06
6.00E-01
1.02E+06
1.55E+01
1.51E+07
5.50E+01
8.71E+01
6.92E+00
5.75E+04
3.39E+03
4.57E+01
1.74E+02
1.20E+05
6.61E+01
2.19E+02
6.31E+01
3.98E+01
3.88E+02
3.98E+05
1.00E+06
4.47E+06
2.63E+06
3.80E+06
3.39E+04
6.17E+02
6.17E+02
7.24E+02
3.16E+01
1.74E+01
5.89E+01
3.55E+01
5.25E+01
1.47E+02
4.37E+01
4.57E+01
2.14E+04
2.88E+02
2.09E+02
°i,a
(cm2/s)
4.21 E-02
1.24E-01
1.32E-02
3.24E-02
5.10E-02
8.80E-02
2.26E-02
2.26E-02
5.36E-02
4.30E-02
6.92E-02
3.51 E-02
2.98E-02
1.49E-02
8.00E-02
1.74E-02
3.90E-02
1.04E-01
7.80E-02
1.18E-02
4.83E-02
7.30E-02
1.96E-02
1.04E-01
5.01 E-02
2.48E-02
1.69E-02
1.44E-02
1.37E-02
2.02E-02
4.38E-02
6.90E-02
6.90E-02
1.94E-02
7.42E-02
1.04E-01
9.00E-02
7.36E-02
7.07E-02
3.46E-02
7.82E-02
6.26E-02
1.25E-02
2.56E-02
5.84E-02
D|,w
(cm2/s)
7.69E-06
1.14E-05
4.86E-06
7.74E-06
9.00E-06
9.80E-06
5.56E-06
5.56E-06
7.97E-06
9.00E-06
7.53E-06
3.66E-06
1.06E-05
1.03E-05
9.30E-06
4.83E-06
7.03E-06
1.00E-05
8.80E-06
4.37E-06
1.01E-05
8.70E-06
1.05E-05
1.00E-05
9.46E-06
6.21 E-06
4.76E-06
5.87E-06
4.95E-06
5.18E-06
7.86E-06
7.90E-06
7.90E-06
6.74E-06
1.05E-05
9.90E-06
1.04E-05
1.13E-05
1.19E-05
8.77E-06
8.73E-06
1.00E-05
4.74E-06
6.35E-06
8.69E-06
S H1
(mg/L) (dimensionless)
4.24E+00
1.00E+06
1.80E-01
4.34E-02
9.40E-03
1.75E+03
1.50E-03
8.00E-04
3.50E+03
1.62E-03
1.72E+04
3.40E-01
6.74E+03
3.10E+03
7.40E+04
2.69E+00
7.48E+00
1.19E+03
7.93E+02
5.60E-02
5.30E+03
4.72E+02
2.60E+03
7.92E+03
2.20E+04
1.60E-03
9.00E-02
1.20E-01
2.50E-02
2.49E-03
1.12E+01
1.56E+02
7.38E+01
3.11E+00
5.06E+03
8.52E+03
2.25E+03
3.50E+03
6.30E+03
4.50E+03
2.80E+03
2.80E+03
1.95E-01
1.08E+03
7.87E+03
6.36E-03
1.59E-03
6.97E-03
2.67E-03
1.37E-04
2.28E-01
4.55E-03
3.40E-05
6.31 E-05
4.63E-05
7.38E-04
4.18E-06
6.56E-02
2.19E-02
3.61 E-04
5.17E-05
6.26E-07
1.24E+00
1.25E+00
1.99E-03
1.36E-05
1.52E-01
3.21 E-02
1.50E-01
1.60E-02
3.88E-03
1.64E-04
8.61 E-04
3.32E-04
6.03E-07
3.85E-08
7.79E-02
9.96E-02
1.64E-07
2.30E-01
4.01 E-02
1.07E+00
1.67E-01
3.85E-01
1.30E-04
1.15E-01
7.26E-01
6.19E-04
1.85E-05
8.20E-05

-------
Table C-1 (continued)
CAS No.
51-28-5
121-14-2
606-20-2
117-84-0
115-29-7
72-20-8
100-41-4
206-44-0
86-73-7
76-44-8
1024-57-3
118-74-1
87-68-3
319-84-6
319-85-7
58-89-9
77-47-4
67-72-1
193-39-5
78-59-1
7439-97-6
72-43-5
74-83-9
75-09-2
95-48-7
91-20-3
98-95-3
86-30-6
621-64-7
1336-36-3
87-86-5
108-95-2
129-00-0
100-42-5
79-34-5
127-18-4
108-88-3
8001-35-2
120-82-1
71-55-6
79-00-5
79-01-6
95-95-4
88-06-2
Compound
2,4-Dinitrophenol
2,4-Dinitrotoluene
2,6-Dinitrotoluene
Di-n-octyl phthalate
Endosulfan
Endrin
Ethylbenzene
Fluoranthene
Fluorene
Heptachlor
Heptachlor epoxide
Hexachlorobenzene
Hexachloro-1 ,3-butadiene
a-HCH (a-BHC)
I3-HCH (I3-BHC)
y-HCH (Lindane)
Hexachlorocyclopentadiene
Hexachloroethane
lndeno(1 ,2,3-cd)pyrene
Isophorone
Mercury
Methoxychlor
Methyl bromide
Methylene chloride
2-Methylphenol
Naphthalene
Nitrobenzene
A/-Nitrosodiphenylamine
A/-Nitrosodi-n-propylamine
PCBs
Pentachlorophenol
Phenol
Pyrene
Styrene
1 , 1 ,2,2-Tetrachloroethane
Tetrachloroethylene
Toluene
Toxaphene
1 ,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethylene
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
KOC
(L/kg)
1.00E-02
9.55E+01
6.92E+01
8.32E+07
2.14E+03
1.23E+04
3.63E+02
1.07E+05
1.38E+04
1.41E+06
8.32E+04
5.50E+04
5.37E+04
1.23E+03
1.26E+03
1.07E+03
2.00E+05
1.78E+03
3.47E+06
4.68E+01
—
9.77E+04
1.05E+01
1.17E+01
9.12E+01
2.00E+03
6.46E+01
1.29E+03
2.40E+01
3.09E+05
5.92E+02
2.88E+01
1.05E+05
7.76E+02
9.33E+01
1.55E+02
1.82E+02
2.57E+05
1.78E+03
1.10E+02
5.01E+01
1.66E+02
1.60E+03
3.81E+02
(cm2/s)
2.73E-02
2.03E-01
3.27E-02
1.51 E-02
1.15E-02
1.25E-02
7.50E-02
3.02E-02
3.63E-02
1.12E-02
1.32E-02
5.42E-02
5.61 E-02
1.42E-02
1.42E-02
1.42E-02
1.61 E-02
2.50E-03
1.90E-02
6.23E-02
3.07E-02
1.56E-02
7.28E-02
1.01E-01
7.40E-02
5.90E-02
7.60E-02
3.12E-02
5.45E-02
—
5.60E-02
8.20E-02
2.72E-02
7.10E-02
7.10E-02
7.20E-02
8.70E-02
1.16E-02
3.00E-02
7.80E-02
7.80E-02
7.90E-02
2.91 E-02
3.18E-02
(cm2/s)
9.06E-06
7.06E-06
7.26E-06
3.58E-06
4.55E-06
4.74E-06
7.80E-06
6.35E-06
7.88E-06
5.69E-06
4.23E-06
5.91 E-06
6.16E-06
7.34E-06
7.34E-06
7.34E-06
7.21 E-06
6.80E-06
5.66E-06
6.76E-06
6.30E-06
4.46E-06
1.21E-05
1.17E-05
8.30E-06
7.50E-06
8.60E-06
6.35E-06
8.17E-06
—
6.10E-06
9.10E-06
7.24E-06
8.00E-06
7.90E-06
8.20E-06
8.60E-06
4.34E-06
8.23E-06
8.80E-06
8.80E-06
9.10E-06
7.03E-06
6.25E-06
S H1
(mg/L) (dimensionless)
2.79E+03
2.70E+02
1.82E+02
2.00E-02
5.10E-01
2.50E-01
1.69E+02
2.06E-01
1.98E+00
1.80E-01
2.00E-01
6.20E+00
3.23E+00
2.00E+00
2.40E-01
6.80E+00
1.80E+00
5.00E+01
2.20E-05
1.20E+04
—
4.50E-02
1.52E+04
1.30E+04
2.60E+04
3.10E+01
2.09E+03
3.51E+01
9.89E+03
7.00E-01
1.95E+03
8.28E+04
1.35E-01
3.10E+02
2.97E+03
2.00E+02
5.26E+02
7.40E-01
3.00E+02
1.33E+03
4.42E+03
1.10E+03
1.20E+03
8.00E+02
1.82E-05
3.80E-06
3.06E-05
2.74E-03
4.59E-04
3.08E-04
3.23E-01
6.60E-04
2.61 E-03
4.47E-02
3.90E-04
5.41 E-02
3.34E-01
4.35E-04
3.05E-05
5.74E-04
1.11E+00
1.59E-01
6.56E-05
2.72E-04
4.67E-01
6.48E-04
2.56E-01
8.98E-02
4.92E-05
1.98E-02
9.84E-04
2.05E-04
9.23E-05
—
1.00E-06
1.63E-05
4.51 E-04
1.13E-01
1.41 E-02
7.54E-01
2.72E-01
2.46E-04
5.82E-02
7.05E-01
3.74E-02
4.22E-01
1.78E-04
3.19E-04

-------
                                   Table C-1 (continued)
CAS No. Compound
108-05-4 Vinyl acetate
75-01-4 Vinyl chloride
108-38-3 m-Xylene
95-47-6 o-Xylene
106-42-3 p-Xylene
Koc = Soil organic carbon/water partition coefficient.
DJ a = Diffusivity in air (25 -C).
DI w = Diffusivity in water (25 -C).
S ' = Solubility in water (20-25 -C).
H' = Dimensionless Henry's law constant (HLC [at
KOC
(L/kg)
5.25E+00
1.86E+01
4.07E+02
3.63E+02
3.89E+02
°i,a
(cm2/s)
8.50E-02
1.06E-01
7.00E-02
8.70E-02
7.69E-02
D|,w
(cm2/s)
9.20E-06
1.23E-06
7.80E-06
1.00E-05
8.44E-06
S H1
(mg/L) (dimensionless)
2.00E+04
2.76E+03
1.61E+02
1.78E+02
1.85E+02
2.10E-02
1.11E+00
3.01 E-01
2.13E-01
3.14E-01
m-m3/mol]*41)(25-C).
= Soil-water partition coefficient.

-------
Table C-2. Koc Values for Ionizing Organics as a Function of pH
PH
4.9
5.0
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
6.0
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
7.0
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8.0
Benzole
Acid
5.54E+00
4.64E+00
3.88E+00
3.25E+00
2.72E+00
2.29E+00
1.94E+00
1.65E+00
1.42E+00
1.24E+00
1.09E+00
9.69E-01
8.75E-01
7.99E-01
7.36E-01
6.89E-01
6.51 E-01
6.20E-01
5.95E-01
5.76E-01
5.60E-01
5.47E-01
5.38E-01
5.32E-01
5.25E-01
5.19E-01
5.16E-01
5.13E-01
5.09E-01
5.06E-01
5.06E-01
5.06E-01
2-
Chloro-
phenol
3.98E+02
3.98E+02
3.98E+02
3.98E+02
3.98E+02
3.98E+02
3.97E+02
3.97E+02
3.97E+02
3.97E+02
3.97E+02
3.96E+02
3.96E+02
3.96E+02
3.95E+02
3.94E+02
3.93E+02
3.92E+02
3.90E+02
3.88E+02
3.86E+02
3.83E+02
3.79E+02
3.75E+02
3.69E+02
3.62E+02
3.54E+02
3.44E+02
3.33E+02
3.19E+02
3.04E+02
2.86E+02
2,4-
2,4-Dichloro-Dinitro- Pentachloro-
phenol phenol phenol
1.59E+02
1.59E+02
1.59E+02
1.59E+02
1.59E+02
1.58E+02
1.58E+02
1.58E+02
1.58E+02
1.58E+02
1.57E+02
1.57E+02
1.57E+02
1.56E+02
1.55E+02
1.54E+02
1.53E+02
1.52E+02
1.50E+02
1.47E+02
1.45E+02
1.41E+02
1.38E+02
1.33E+02
1.28E+02
1.21E+02
1.14E+02
1.07E+02
9.84E+01
8.97E+01
8.07E+01
7.17E+01
2.94E-02
2.55E-02
2.23E-02
1.98E-02
1.78E-02
1.62E-02
1.50E-02
1.40E-02
1.32E-02
1.25E-02
1.20E-02
1.16E-02
1.13E-02
1.10E-02
1.08E-02
1.06E-02
1.05E-02
1.04E-02
1.03E-02
1.02E-02
1.02E-02
1.02E-02
1.02E-02
1.01E-02
1.01E-02
1.01E-02
1.01E-02
1.01E-02
1.00E-02
1.00E-02
1.00E-02
1.00E-02
9.05E+03
7.96E+03
6.93E+03
5.97E+03
5.10E+03
4.32E+03
3.65E+03
3.07E+03
2.58E+03
2.18E+03
1.84E+03
1.56E+03
1.33E+03
1.15E+03
9.98E+02
8.77E+02
7.81 E+02
7.03E+02
6.40E+02
5.92E+02
5.52E+02
5.21 E+02
4.96E+02
4.76E+02
4.61 E+02
4.47E+02
4.37E+02
4.29E+02
4.23E+02
4.18E+02
4.14E+02
4.10E+02
2,3,4,5-
Tetrachloro-
phenol
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
9.
8.
7.
6.
5.
4.
3.
3.
2.
2.
1.
1.
1.
1.
8.
6.
5.
4.
73E+04
72E+04
70E+04
.67E+04
65E+04
.61E+04
.57E+04
52E+04
.47E+04
40E+04
32E+04
24E+04
.15E+04
05E+04
.51E+03
48E+03
.47E+03
49E+03
58E+03
74E+03
99E+03
33E+03
76E+03
28E+03
87E+03
53E+03
25E+03
02E+03
31 E+02
79E+02
56E+02
58E+02
2,3,4,6-
Tetrachloro-
phenol
4.45E+03
4.15E+03
3.83E+03
3.49E+03
3.14E+03
279E+03
2.45E+03
2.13E+03
1.83E+03
1.56E+03
1.32E+03
1.11E+03
9.27E+02
775E+02
6.47E+02
5.42E+02
4.55E+02
3.84E+02
3.27E+02
2.80E+02
2.42E+02
2.13E+02
1.88E+02
1.69E+02
1.53E+02
1.41 E+02
1.31 E+02
1.23E+02
1.17E+02
1.13E+02
1.08E+02
1.05E+02
2,4,6-
2,4,5-Trichloro- Trichloro-
phenol phenol
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
1.
1.
1.
1.
1.
1.
1.
1.
1.
9.
8.
7.
5.
5.
4.
3.
2.
.37E+03
36E+03
36E+03
35E+03
34E+03
33E+03
32E+03
.31E+03
29E+03
.27E+03
24E+03
21E+03
.17E+03
12E+03
06E+03
99E+03
.91E+03
82E+03
71E+03
60E+03
.47E+03
34E+03
21E+03
.07E+03
43E+02
.19E+02
03E+02
99E+02
.07E+02
26E+02
.57E+02
98E+02
1.04E+03
1.03E+03
1.02E+03
1.01E+03
9.99E+02
9.82E+02
9.62E+02
9.38E+02
9.10E+02
877E+02
8.39E+02
7.96E+02
7.48E+02
6.97E+02
6.44E+02
5.89E+02
5.33E+02
4.80E+02
4.29E+02
3.81 E+02
3.38E+02
3.00E+02
2.67E+02
2.39E+02
2.15E+02
1.95E+02
178E+02
1.64E+02
1.53E+02
1.44E+02
1.37E+02
1.31E+02

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                 Table C-3. Physical State of Organic SSL Chemicals
Compounds liquid at soil temperatures
CAS No. Chemical
67-64-1 Acetone
71-43-2 Benzene
117-81-7 Bis(2-ethylhexyl)phthalate
111-44-4 Bis(2-chloroethyl)ether
75-27-4 Bromodichloromethane
75-25-2 Bromoform
71-36-3 Butanol
85-68-7 Butyl benzyl phthalate
75-15-0 Carbon disulfide
56-23-5 Carbon tetrachloride
108-90-7 Chlorobenzene
124-48-1 Chlorodibromomethane
67-66-3 Chloroform
95-57-8 2-Chlorophenol
84-74-2 Di-n-butyl phthalate
95-50-1 1,2-Dichlorobenzene
75-34-3 1,1-Dichloroethane
107-06-2 1,2-Dichloroethane
75-35-4 1,1-Dichloroethylene
1 56-59-2 c/s-1 ,2-Dichloroethylene
1 56-60-5 frans-1 ,2-Dichloroethylene
78-87-5 1,2-Dichloropropane
542-75-6 1,3-Dichloropropene
84-66-2 Diethylphthalate
117-84-0 Di-n-octyl phthalate
100-41-4 Ethylbenzene
87-68-3 Hexachloro-1,3-butadiene
77-47-4 Hexachlorocyclopentadiene
78-59-1 Isophorone
74-83-9 Methyl bromide
75-09-2 Methylene chloride
98-95-3 Nitrobenzene
100-42-5 Styrene
79-34-5 1 ,1 ,2,2-Tetrachloroethane
127-18-4 Tetrachloroethylene
108-88-3 Toluene
120-82-1 1,2,4-Trichlorobenzene
71-55-6 1,1,1-Trichloroethane
79-00-5 1,1,2-Trichloroethane
79-01-6 Trichloroethylene
108-05-4 Vinyl acetate
75-01-4 Vinyl chloride
108-38-3 m-Xylene
95-47-6 o-Xylene
106-42-3 p-Xylene


Melting
Point (°C)
-94.8
5.5
-55
-51.9
-57
8
-89.8
-35
-115
-23
-45.2
-20
-63.6
9.8
-35
-16.7
-96.9
-35.5
-122.5
-80
-49.8
-70
NA
-40.5
-30
-94.9
-21
-9
-8.1
-93.7
-95.1
5.7
-31
-43.8
-22.3
-94.9
17
-30.4
-36.6
-84.7
-93.2
-153.7
-47.8
-25.2
13.2


Compounds solid at soil temperatures
CAS No. Chemical
83-32-9 Acenaphthene
309-00-2 Aldrin
120-12-7 Anthracene
56-55-3 Benz(a)anthracene
50-32-8 Benzo(a)pyrene
205-99-2 Benzo(6)fluoranthene
207-08-9 Benzo(/()fluoranthene
65-85-0 Benzole acid
86-74-8 Carbazole
57-74-9 Chlordane
106-47-8 p-Chloroaniline
218-01-9 Chrysene
72-54-8 ODD
72-55-9 DDE
50-29-3 DDT
53-70-3 Dibenzo(a,/?)anthracene
106-46-7 1,4-Dichlorobenzene
91-94-1 3,3-Dichlorobenzidine
120-83-2 2,4-Dichlorophenol
60-57-1 Dieldrin
105-67-9 2,4-Dimethylphenol
51-28-5 2,4-Dinitrophenol
121-14-2 2,4-Dinitrotoluene
606-20-2 2,6-Dinitrotoluene
72-20-8 Endrin
206-44-0 Fluoranthene
86-73-7 Fluorene
75-44-8 Heptachlor
1024-57-3 Heptachlor epoxide
118-74-1 Hexachlorobenzene
319-84-6 a-HCH(a-BHC)
319-85-7 I3-HCH (I3-BHC)
58-89-9 y-HCH (Lindane)
67-72-1 Hexachloroethane
193-39-5 lndeno(1,2,3-cd)pyrene
72-43-5 Methoxychlor
95-48-7 2-Methylphenol
621-64-7 A/-Nitrosodi-n-propylamine
86-30-6 A/-Nitrosodiphenylamine
91-20-3 Naphthalene
87-86-5 Pentachlorophenol
108-95-2 Phenol
129-00-0 Pyrene
8001-35-2 Toxaphene
95-95-4 2,4,5-Trichlorophenol
88-06-2 2,4,6-Trichlorophenol
115-29-7 Endosullfan
Melting
Point (°C)
93.4
104
215
84
176.5
168
217
122.4
246.2
106
72.5
258.2
109.5
89
108.5
269.5
52.7
132.5
45
175.5
24.5
115-116
71
66
200
107.8
114.8
95.5
160
231.8
160
315
112.5
187
161.5
87
29.8
NA
66.5
80.2
174
40.9
151.2
65-90
69
69
106
NA = Not available.

-------
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-------

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                      Attachment D.  Regulatory and Human Health Benchmarks Used for SSL Development
Number Chemical Name
83-32-9 Acenaphthene
67-64-1 Acetone (2-Propanone)
309-00-2 Aldrin
120-12-7 Anthracene
7440-36-0 Antimony
7440-38-2 Arsenic
7440-39-3 Barium
56-55-3 Benz(a Janthracene
71-43-2 Benzene
205-99-2 Benzo(fa Jfluoranthene
207-08-9 Benzo(fc Jfluoranthene
65-85-0 Benzole acid
50-32-8 Benzo(a Jpyrene
7440-41-7 Beryllium
1 1 1 -44-4 Bis(2-chloroethyl)ether
1 1 7-81 -7 Bis(2-ethylhexyl)phthalate
75-27-4 Bromodichloromethane
75-25-2 Bromoform (tribromomethane)
71-36-3 Butanol
85-68-7 Butyl benzyl phthalate
7440-43-9 Cadmium
86-74-8 Carbazole
75-15-0 Carbon disulfide
56-23-5 Carbon tetrachloride
57-74-9 Chlordane
106-47-8 p -Chloroaniline
108-90-7 Chlorobenzene
124-48-1 Chlorodibromomethane
67-66-3 Chloroform
95-57-8 2-Chlorophenol
Maximum
Contaminant Level
Goal
(mg/L)
MCLG Drf a
(PMCLG) Ker


6.0E-03 3

2.0E+00 3






4.0E-03 3






5.0E-03 3





1.0E-01 3
6.0E-02 3


Maximum
Contaminant Level
(mg/L)
MCL (PMCL) Ref. "


6.0E-03 3
5.0E-02 3
2.0E+00 3

5.0E-03 3



2.0E-04 3
4.0E-03 3

6.0E-03 3
1.0E-01* 3
1.0E-01 * 3


5.0E-03 3


5.0E-03 3
2.0E-03 3

1.0E-01 3
1.0E-01 * 3
1.0E-01* 3

Water Health Based
Limits
(mg/L)
HBL" Basis
2E+00 RfD
4E+00 RfD
5E-06 SF0
1 E+01 RfD



1 E-04 SF0

1 E-04 SF0
1 E-03 SF0
1 E+02 RfD


8E-05 SF0



4E+00 RfD
7E+00 RfD

4E-03 SF0
4E+00 RfD


1 E-01 RfD



2E-01 RfD
Cancer Slope Factor
(mg/kg-d)'1
Class'0 SF° Ref' "
D
B2 1.7E+01 1
D

A 1.5E+00 1

B2 7.3E-01 4
A 2.9E-02 1
B2 7.3E-01 4
B2 7.3E-02 4

B2 7.3E+00 1
B2 4.3E+00 1
B2 1.1E+00 1
B2 1.4E-02 1
B2 6.2E-02 1
B2 7.9E-03 1
D
C

B2 2.0E-02 2

B2 1.3E-01 1
B2 1.3E+00 1

D
C 8.4E-02 1
B2 6.1 E-03 1

Unit Risk Factor
(ug/m3)-1
Class0 URF Ref' "
D
B2 4.9E-03 1
D

A 4.3E-03 1

B2
A 8.3E-06 1
B2
B2

B2
B2 2.4E-03 1
B2 3.3E-04 1
B2
B2
B2 1.1E-06 1
D
C
B1 1.8E-03 1


B2 1.5E-05 1
B2 3.7E-04 1

D
C
B2 2.3E-05 1

Reference Dose
(mg/kg-d)
RfD Ref. "
6.0E-02 1
1.0E-01 1
3.0E-05 1
3.0E-01 1
4.0E-04 1
3.0E-04 1
7.0E-02 1




4.0E+00 1

5.0E-03 1

2.0E-02 1
2.0E-02 1
2.0E-02 1
1.0E-01 1
2.0E-01 1
1.0E-03** 1

1.0E-01 1
7.0E-04 1
6.0E-05 1
4.0E-03 1
2.0E-02 1
2.0E-02 1
1.0E-02 1
5.0E-03 1
Reference
Concentration
(mg/m3)
RfC Ref. a




5.0E-04 2















7.0E-01 1



2.0E-02 2



* Proposed MCL = 0.08 mg/L, Drinking Water Regulations and Health Advisories , U.S. EPA (1995).
** Cadmium RfD is based on dietary exposure.

-------
                                                                  Attachment D (continued)
Number Chemical Name
7440-47-3 Chromium
16065-83-1 Chromium (III)
18540-29-9 Chromium (VI)
218-01-9 Chrysene
57-12-5 Cyanide (amenable)
72-54-8 ODD
72-55-9 DDE
50-29-3 DDT
53-70-3 Dibenz(a,n Janthracene
84-74-2 Di-n -butyl phthalate
95-50-1 1,2-Dichlorobenzene
106-46-7 1,4-Dichlorobenzene
91-94-1 3,3-Dichlorobenzidine
75-34-3 1,1-Dichloroethane
107-06-2 1,2-Dichloroethane
75-35-4 1,1-Dichloroethylene
156-59-2 cis -1,2-Dichloroethylene
156-60-5 trans -1,2-Dichloroethylene
120-83-2 2,4-Dichlorophenol
78-87-5 1,2-Dichloropropane
542-75-6 1,3-Dichloropropene
60-57-1 Dieldrin
84-66-2 Diethylphthalate
105-67-9 2,4-Dimethylphenol
51-28-5 2,4-Dinitrophenol
121-14-2 2,4-Dinitrotoluene**
606-20-2 2,6-Dinitrotoluene**
1 1 7-84-0 Di-n -octyl phthalate
115-29-7 Endosulfan
72-20-8 Endrin
Maximum
Contaminant Level
Goal
(mg/L)
MCLG „ f a
(PMCLG) KeT'
1.0E-01 3



(2.0E-01) 3





6.0E-01 3
7.5E-02 3



7.0E-03 3
7.0E-02 3
1.0E-01 3










2.0E-03 3
Maximum
Contaminant Level
(mg/L)
MCL (PMCL) Ref. a
1.0E-01 3

1.0E-01 3*

(2.0E-01) 3





6.0E-01 3
7.5E-02 3


5.0E-03 3
7.0E-03 3
7.0E-02 3
1.0E-01 3
5.0E-03 3









2.0E-03 3
Water Health Based
Limits
(mg/L)
HBL" Basis

4E+01 RfD

1 E-02 SF0

4E-04 SF0
3E-04 SF0
3E-04 SF0
1 E-05 SF0
4E+00 RfD


2E-04 SF0
4E+00 RfD


1 E-01 RfD

5E-04 SF0
5E-06 SF0
3E+01 RfD
7E-01 RfD
4E-02 RfD
1 E-04 SF0
1 E-04 SF0
7E-01 RfD
2E-01 RfD

Cancer Slope Factor
(mg/kg-d)'1
aass'* SF° Ref'a
A

A
B2 7.3E-03 4
D
B2 2.4E-01 1
B2 3.4E-01 1
B2 3.4E-01 1
B2 7.3E+00 4
D
D
B2 2.4E-02 2
B2 4.5E-01 1
C
B2 9.1 E-02 1
C 6.0E-01 1
D
B2 6.8E-02 2
B2 1.8E-01 2
B2 1.6E+01 1
D


B2 6.8E-01 1
B2 6.8E-01 1


D
Unit Risk Factor
(ug/m3)-1
Class0 URF Ref' '
A 1.2E-02 1

A 1.2E-02 1

D
B2
B2
B2 9.7E-05 1
B2
D
D
B2
B2
C
B2 2.6E-05 1
C 5.0E-05 1
D
B2
B2 3.7E-05 2
B2 4.6E-03 1
D






D
Reference Dose
(mg/kg-d)
RfD Ref. a
5.0E-03 1
1.0E+00 1
5.0E-03 1

2.0E-02 1


5.0E-04 1

1.0E-01 1
9.0E-02 1


1.0E-01 7

9.0E-03 1
1.0E-02 2
2.0E-02 1
3.0E-03 1

3.0E-04 1
5.0E-05 1
8.0E-01 1
2.0E-02 1
2.0E-03 1
2.0E-03 1
1.0E-03 2
2.0E-02 2
6.0E-03 2
3.0E-04 1
Reference
Concentration
(mg/m3)
RfC Ref. a










2.0E-01 2
8.0E-01 1

5.0E-01 2



4.0E-03 1
2.0E-02 1









* MCL for total chromium is based on Cr (VI) toxicity.
** Cancer Slope Factor is for 2,4-, 2,6-Dinitrotoluene mixture.

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                                                                Attachment D (continued)

Number Chemical Name
100-41-4 Ethylbenzene
206-44-0 Fluoranthene
86-73-7 Fluorene
76-44-8 Heptachlor
1024-57-3 Heptachlor epoxide
118-74-1 Hexachlorobenzene
87-68-3 Hexachloro-1,3-butadiene
319-84-6 a-HCH (a-BHC)
319-85-7 p-HCH (p-BHC)
58-89-9 y-HCH (Lindane)
77-47-4 Hexachlorocyclopentadiene
67-72-1 Hexachloroethane
193-39-5 lndeno(1,2,3-cc/)pyrene
78-59-1 Isophorone
7439-97-6 Mercury
72-43-5 Methoxychlor
74-83-9 Methyl bromide
75-09-2 Methylene chloride
95-48-7 2-Methylphenol (o -cresol)
91-20-3 Naphthalene
7440-02-0 Nickel
98-95-3 Nitrobenzene
86-30-6 A/ -Nitrosodiphenylamine
621-64-7 A/ -Nitrosodi-n -propylamine
87-86-5 Pentachlorophenol
108-95-2 Phenol
129-00-0 Pyrene
7782-49-2 Selenium
7440-22-4 Silver
100-42-5 Styrene
79-34-5 1,1,2,2-Tetrachloroethane
Maximum
Contaminant Level
Goal
(mg/L)
MCLG R f ,
(PMCLG) Ker
7.0E-01 3





1.0E-03 3


2.0E-04 3
5.0E-02 3



2.0E-03 3
4.0E-02 3











5.0E-02 3

1.0E-01 3

Maximum
Contaminant Level
(mg/L)
MCL (PMCL) Ref. a
7.0E-01 3


4.0E-04 3
2.0E-04 3
1.0E-03 3



2.0E-04 3
5.0E-02 3



2.0E-03 3
4.0E-02 3

5.0E-03 3






1.0E-03 3


5.0E-02 3

1.0E-01 3

Water Health Based
Limits
(mg/L)
HBL" Basis

1 E+00 RfD
1 E+00 RfD



1 E-03 SF0
1 E-05 SF0
5E-05 SF0


6E-03 SF0
1 E-04 SF0
9E-02 SF0


5E-02 RfD

2E+00 RfD
1 E+00 RfD
1E-01 HA*
2E-02 RfD
2E-02 SF0
1 E-05 SF0

2E+01 RfD
1 E+00 RfD

2E-01 RfD

4E-04 SF0
Cancer Slope Factor
(mg/kg-d)'1
££ SF° Ref-a
D
D
D
B2 4.5E+00 1
B2 9.1 E+00 1
B2 1.6E+00 1
C 7.8E-02 1
B2 6.3E+00 1
C 1.8E+00 1
B2 1.3E+00 2
D
C 1.4E-02 1
B2 7.3E-01 4
C 9.5E-04 1
D
D
D
B2 7.5E-03 1
C
D
A
D
B2 4.9E-03 1
B2 7.0E+00 1
B2 1.2E-01 1
D
D
D
D

C 2.0E-01 1
Unit Risk Factor
(ug/m3)-1
aa^s* URF Ref-a
D
D

B2 1.3E-03 1
B2 2.6E-03 1
B2 4.6E-04 1
C 2.2E-05 1
B2 1.8E-03 1
C 5.3E-04 1
C
D
C 4.0E-06 1
B2
C
D
D
D
B2 4.7E-07 1
C
D
A 2.4E-04 1
D
B2
B2
B2
D
D
D
D

C 5.8E-05 1
Reference Dose
(mg/kg-d)
RfD Ref. a
1.0E-01 1
4.0E-02 1
4.0E-02 1
5.0E-04 1
1.3E-05 1
8.0E-04 1
2.0E-04 2


3.0E-04 1
7.0E-03 1
1.0E-03 1

2.0E-01 1
3.0E-04 2
5.0E-03 1
1.4E-03 1
6.0E-02 1
5.0E-02 1
4.0E-02 6
2.0E-02 1
5.0E-04 1


3.0E-02 1
6.0E-01 1
3.0E-02 1
5.0E-03 1
5.0E-03 1
2.0E-01 1

Reference
Concentration
(mg/m3)
RfC Ref. a
1.0E+00 1









7.0E-05 2



3.0E-04 2

5.0E-03 1
3.0E+00 2



2.0E-03 2







1.0E+00 1

* Health advisory for nickel (MCL is currently remanded); EPA Office of Science and Technology, 7/10/95.

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                                                                                Attachment D (continued)
Number Chemical Name
127-18-4 Tetrachloroethylene
7440-28-0 Thallium
108-88-3 Toluene
8001-35-2 Toxaphene
120-82-1 1,2,4-Trichlorobenzene
71-55-6 1,1,1-Trichloroethane
79-00-5 1,1,2-Trichloroethane
79-01-6 Trichloroethylene
95-95-4 2,4,5-Trichlorophenol
88-06-2 2,4,6-Trichlorophenol
7440-62-2 Vanadium
108-05-4 Vinyl acetate
75-01-4 Vinyl chloride (chloroethene)
108-38-3 m -Xylene
95-47-6 o -Xylene
106-42-3 p -Xylene
7440-66-6 Zinc
Maximum
Contaminant Level
Goal
(mg/L)
MCLG R f ,
(PMCLG) Ker
5.0E-04 3
1.0E+00 3

7.0E-02 3
2.0E-01 3
3.0E-03 3
zero 3





1.0E+01 3*
1.0E+01 3*
1.0E+01 3*

Maximum
Contaminant Level
(mg/L)
MCL (PMCL) Ref. a
5.0E-03 3
2.0E-03 3
1.0E+00 3
3.0E-03 3
7.0E-02 3
2.0E-01 3
5.0E-03 3
5.0E-03 3




2.0E-03 3
1.0E+01 3*
1.0E+01 3*
1.0E+01 3*

Water Health Based
Limits
(mg/L)
HBL" Basis







4E+00 RfD
8E-03 SF0
3E-01 RfD
4E+01 RfD




1 E+01 RfD
Cancer Slope Factor
(mg/kg-d)'1
££ SF° Ref-a
5.2E-02 5
D
B2 1.1E+00 1
D
D
C 5.7E-02 1
1.1E-02 5

B2 1.1E-02 1


A 1.9E+00 2
D
D
D
D
Unit Risk Factor
(ug/m3)-1
aa^s* URF Ref-a
5.8E-07 5
D
B2 3.2E-04 1
D
D
C 1.6E-05 1
1.7E-06 5

B2 3.1E-06 1


A 8.4E-05 2
D
D
D
D
Reference Dose
(mg/kg-d)
RfD Ref. a
1.0E-02 1
2.0E-01 1

1.0E-02 1

4.0E-03 1

1.0E-01 1

7.0E-03 2
1.0E+00 1

2.0E+00 2
2.0E+00 2
2.0E+00 1 **
3.0E-01 1
Reference
Concentration
(mg/m3)
RfC Ref. a

4.0E-01 1

2.0E-01 2
1.0E+00 5





2.0E-01 1





* MCL for total xylenes [1330-20-7] is 10 mg/L.
** RfD for total xylenes is 2 mg/kg-day.

' References:     1  = IRIS, U.S. EPA (1995)
                2 = HEAST, U.S. EPA (1995)
                3 = U.S. EPA (1995)
                4 = OHEA, U.S. EPA (1993)
                5 = Interim toxicity criteria provided by Superfund
                   Health Risk Techincal Support Center,
                   Environmental Criteria Assessment Office
                   (ECAO), Cincinnati, OH (1994)
                6 = ECAO, U.S. EPA (19941)
                7 = ECAO, U.S. EPA(1994h)
1 Health Based Limits calculated for 30-year exposure duration, 10B risk or hazard quotient = 1.
c Categorization of overall weight of evidence for human carcinogenicity:
          Group A:  human carcinogen
          Group B:  probable human carcinogen
               B1:  limited evidence from epidemiologic studies
               B2:  "sufficient" evidence from animal studies and "inadequate" evidence or
                    "no data" from epidemiologic studies
          Group C:  possible human carcinogen
          Group D:  not classifiable as to health carcinogenicity
          Group E:  evidence of noncarcinogenicity for humans

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