OSWER DIRECTIVE 9481.QO-6C
                             EPA/530-SW-87-Q17
ALTERNATE CONCENTRATION LIMIT
              GUIDANCE
                PART I

    ACL POLICY AND INFORMATION
            REQUIREMENTS
               INTERIM FINAL
OFFICE OF SOLID WASTE
WASTE MANAGEMENT DIVISION
U.S. ENVIRONMENTAL PROTECTION AGENCY
401 M STREET, S.W.
WASHINGTON, D.C 20460
                                JULY 1987

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                                                    OSWER Directive 9481.00-6C
                               DISCLAIMER
     This document is intended to assist Regional and State personnel in exercising
the discretion conferred by regulation in evaluating applications for ACLs submitted
pursuant to 40 CFR 264,94. Conformance with this guidance is expected to result in
ACL applications that meet the regulatory standard of protecting human health and
the environment.   However,  EPA  will  not in all cases limit its review  to
demonstrations that comport with the guidance set forth herein. This document is
not a regulation (i.e., it does not establish a standard of conduct which has the force
of law) and should not be used as such. Regional and State personnel must exercise
their discretion in  using  this guidance  document as well as other relevant
information in  determining whether  an ACL demonstration meets the regulatory
standard.

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                                                  OSWER Directive 9481,QO-6C
                          ACKNOWLEDGEMENTS
    This document was developed by the EPA's Office of Solid Waste under the
direction of Dr. Vernon Myers, Chief of the Ground-Water Section of the Waste
Management Division.  The document was prepared by the joint efforts of
Dr. Myers, Mr. Mark Salee of the Permits and State Programs Division, and Mr. Jerry
Garman of the Waste Management Division.  Special thanks are expressed to the
numerous secretaries  who  survived the multitude of revisions during the
development of this document
                                   IV

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                                              OSWER Directive 9481.00-6C
                           CONTENTS

                                                            Page


     EXECUTIVE SUMMARY                                       ES-1


I.    INTRODUCTION                                             1-1


II.    PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE WASTE           2-1
     CONSTITUENTS


III,   HYDROGEOLOGICAL CHARACTERISTICS                          3-1


IV.   GROUND-WATER FLOW DIRECTION AND QUANTITY                 4-1


V.    PATTERNS OF RAINFALL                                       5-1


VI.   PROXIMITY OF SURFACE WATER AND GROUND-WATER USERS         6-1


VII.   CURRENT AND FUTURE USES OF GROUND WATER AND SURFACE        7-1
     WATER IN THE AREA


VIII.  EXISTING QUALITY OF GROUND WATER AND SURFACE WATER AND     8-1
     OTHER SOURCES OF CONTAMINATION


IX,   POTENTIAL HEALTH RISKS                                     9-1


X.    POTENTIAL DAMAGE TO WILDLIFE, VEGETATION, AGRICULTURE,      10-1
     AND PHYSICAL STRUCTURES


XI.   PERSISTENCE AND PERMANENCE OF POTENTIAL ADVERSE EFFECTS     11-1


XII.   SUMMARY AND CONCLUSIONS                                12-1


XIII.  REFERENCES                                              13-1

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                                                    OSWER Directive 9481.00-6C
                                CONTENTS
                                                           Page
APPENDICES
A.   Outline of Information that may be Cross Referenced        A-1
         from the Permit Application
B.   Summary of Tables, Figures, and Information Required       B-1
         to Support an ACL Demonstration
C.   Summary Sheet of Hazardous Constituent Properties         C-1
D.   Summary Sheet on Health Effects Factors                   D-1
E.   Standard Factors used in Exposure Assessments              E-1
                                    VI

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                                                     OSWER Directive 9481.00-6C
                           EXECUTIVE SUMMARY
     The hazardous waste regulations under the Resource Conservation and
Recovery Act (RCRA) require owners and operators of hazardous waste facilities to
utilize design features and control measures that prevent the leaking of hazardous
waste  into ground water.  Further, all  regulated units (i.e., all  surface
impoundments, waste  piles, land treatment  units, and  landfills that received
hazardous waste after July 26, I982)  are  also subject to the ground-water
monitoring and corrective  action standards  of 40 CFR  Part 264, Subpart F.  To
establish the facility's ground- water protection standard (GWPS) under Subpart F
(40 CFR 264,92), the Regional Administrator is  required  to establish  in the facility
permit, for each hazardous constituent entering the ground water from a regulated
unit, a concentration limit that cannot be exceeded. The concentration limits are
the "triggers" that determine when corrective action is required.

     There are three possible concentration limits that can be used to establish the
GWPS:

     I.    Background levels of the hazardous constituents,
     2.   Maximum concentrations listed  in Table I of Section  264.94{a) of the
         regulations, or
     3.   Alternate concentration limits(ACLs).

     The first two levels are established in the  facility permit as the  GWPS, unless
the facility owner or operator applies for an ACL  However, some States have non-
degradation policies (which are either regulatory or statutory requirements) that
prohibit the release of any pollutants into the  ground water.  These policies may
prevent the use of an ACL altogether if the State has an authorized program for 40
CFR Part 264, Subpart F.

     This document provides guidance to RCRA facility  permit applicants and
writers concerning the establishment of ACLs. To obtain an ACL, a permit applicant
must demonstrate that the hazardous constituents detected in the ground water
will not pose a substantial present  or potential  hazard to human health or the
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                                                     OSWER Directive 9481.00-6C


environment at the ACL levels, ACLs are granted through the permit process under
Parts 264 and 270, and are established in the context of the facility GWPS.  The 19
factors, or criteria,  that are used to evaluate ACL requests are  listed in Section
264.94(b) of the regulation.  Detailed information on each of these criteria is not
required in  every  ACL demonstration  because each demonstration  requires
different types and amounts of information, depending on  the  site-specific
characteristics, A separate chapter of this document is devoted  to each of these
criteria. The criteria are briefly discussed, along with the type, quantity, and quality
of information that  should be  provided, depending on the site-specific
characteristics.

     Chapter I is an introduction to the ACL guidance; it describes the purpose,
intent, and organization  of the document. The chapter also  defines an ACL,
describes Agency policy, and describes how ACLs fit  into the RCRA permitting
process. A procedure is presented that allows a permit applicant  to employ either
Agency- established maximum contaminant levels (MCLs) set under the authority of
the Safe Drinking Water Act, or Agency-reviewed reference doses or risk-specific
levels directly, or after a simple manipulation, as ACLs. For use as ACLs, these levels
would have to be approved by EPA for the specific site.  This chapter also points out
that data from the  RCRA Part B permit application may be cross- referenced in the
ACL demonstration.

     Experience gained over the last several years  has allowed the Agency to
develop a better understanding of ground-water contamination problems. This has
led EPA to develop general policy guidelines for the use of ACLs at RCRA hazardous
waste disposal facilities. These guidelines are designed to ensure  that ACLs will be
protective of human health and the environment.

     Three basic policy guidelines have been identified to assist the permit writer
and applicant in implementing the ACL process for useable ground water:

     1.   Ground-water contaminant plumes should not  increase in size or con-
         centration above allowable health or environmental exposure levels,

     2.   Increased facility property holdings should not be used to allow a greater
         ACL, and
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                                                     OSWER Directive 9481.QO-6C
     3.   ACLs should not be established so as to contaminate off-site ground
         water above allowable health or environmental exposure levels.

     These guidelines are further described in the first chapter. Also described are
the ways in which ACLs should be determined for five types of situations.

     Chapter I also discusses how the ACL process fits into the rest of the RCRA
ground-water protection program.  The applicant is cautioned that an ACL based on
attenuation mechanisms may not be acceptable to the permitting authority at the
end of the post-closure care period. At the conclusion of post-closure care, a more
stringent ground-water standard, based only on an allowable exposure level, may
be needed because the facility owner has no further RCRA obligations for managing
or monitoring the facility.

     EPA is also in the process of developing a ground-water protection program
for all solid waste management units at RCRA permitted facilities. This program  is
mandated by Section 3004{u) of the Hazardous and Solid Waste Amendments of
1984 (HSWA). The ACL process, as described in this document, may be useful when
assessing corrective action  measures at these solid waste management units.  In
developing this corrective action program, EPA will assess the  need to promulgate
some additional Subpart F regulations.

     Chapter II discusses the data  that the  permit applicant  must submit on the
physical and chemical characteristics of the waste constituents.  If the permit
application sufficiently defines the extent of contamination, additional  ground-
water sample collection  is probably not necessary for ACL purposes. The permit
applicant should submit ground-water contamination information in terms of
three-dimensional representations of constituent concentrations.  The permit
applicant needs to submit data on any factors relating to the stability and mobility
of the waste constituents in the ground water if the point of exposure is different
from the point of compliance.  These factors may include density, solubility, vapor
pressure, viscosity, and octanol-water partitioning coefficient of each constituent
for which an ACL is requested.
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                                                    OSWER Directive 9481.00-6C
     Chapter III discusses the data needed to describe the hydrogeologic properties
of the site.  General descriptions of the geologic and hydrologic conditions at the
facility should be part of alt ACL demonstrations.  The geologic and hydrologic
properties of each of the individual strata beneath  a site that are likely to affect
ground-water  contaminant migration  should  be submitted  in the ACL
demonstration.  Much of the data should already be available to the permit
applicant if other  RCRA  permitting  requirements have  been fulfilled.  The
important geologic attributes of a site include:

     I.   Soil and rock characteristics,
     2.   Geologic structure, and
     3.   Geomorphology and topography.

     In ACL demonstrations where soil and other matrix attenuation mechanisms
are used to  justify that exposure to ground-water contaminants will be minimal or
prevented,  data on attenuative properties must be discussed.  The near-surface
stratigraphic units located in the zone  of saturation  must be characterized for the
hydrologic  parameters of hydraulic conductivity (vertical and  horizontal), specific
yield (unconfined aquifer) or specific  storage (confined aquifer),  and effective
porosity.

     Chapter IV discusses  the ground-water quantity  and flow direction
information that is used to assess contaminant transport. The general RCRA permit
requirements specify the submittal of ground-water flow data.  This data should be
adequate for on-site determinations of ground-water quantity and flow direction;
however, additional data may be required if off-site determinations of quantity and
flow are  needed for the  ACL demonstration.  Ground-water quantity can  be
estimated from hydrologic parameters such as specific yield for unconfined aquifers
and specific storage for confined aquifers. The use of Darcy's law for determining
ground-water flow quantity is acceptable for homogeneous and isotropic aquifers.

     The hydrogeologic portion of all ACL demonstrations should include a general
description  of both horizontal and vertical ground-water flow components. ACL
demonstrations based on attenuation arguments need a more in-depth discussion
of ground-water flow.  In these  situations, the horizontal ground-water flow
description  should include a flow  net based on ground-water elevation measure-
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                                                     OSWER Directive 9481.00-6C


ments taken from monitoring wells or piezometers screened at similar elevations in
the same saturated zone.  Facilities should have several clusters of piezometers for
vertical gradient determinations.  Facilities that are located  in environmental
settings that exhibit temporal variation in  ground-water flow direction  should
describe the extent to which the flow change occurs.

     Chapter V discusses the types of precipitation data that should be submitted in
an ACL demonstration, ACL demonstrations based on contaminant attenuation
need to include a discussion of precipitation, which should be focused on the site's
hydrologic regime.  If the applicant's ACL demonstration clearly shows that ground-
water discharge to surface waters is unlikely, then the discussion of precipitation
effects can  be limited to  infiltration and ground-water recharge.  However, if
ground-water discharge to surface water is  an  important element of the ACL
demonstration, then precipitation events should be related to ground-water
recharge, discharge, and surface water hydrology.

     Chapter VI discusses  the proximity of surface water and ground-water users
and the  information that should be submitted on these users.  The level of
information necessary to satisfy the proximity of users requirement depends on the
basis of the ACL.  Only a general discussion of surface water and ground-water users
is necessary if ACLs are based on exposure to the contaminants at the point of
compliance, immediately at the edge of the waste management area.  However,
specific data on the physical characteristics of a surface water body are necessary if
the applicant is attempting to show that the contaminants will safely and  quickly
attenuate into a surface water body. In order to assess the likelihood of exposure of
ground-water users, ACL demonstrations  should discuss the proximity of ground-
water users to the facility.

     Chapter VII discusses the factors needed to determine current and future uses
of ground  water and  surface water in the vicinity of the facility. The  permit
applicant needs to examine only the pertinent aspects of ground-water and  surface
water uses.  Permit applicants must submit information on  the types of ground-
water uses  in the vicinity of  the facility,  unless they base  the ACL on  allowable
exposure levels at the point of compliance. Surface water uses should be discussed
by the ACL applicant if contaminated ground water can migrate to surface waters.
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                                                     OSWER Directive9481.00-6C


     Chapter VIII is concerned with the existing quality of ground water and surface
water and other sources of contamination.  In order for "benchmark" levels of
contamination to be set, the background levels of hazardous constituents in the
ground water and  surface water should be  established.  For ACL purposes,
background water quality is the quality that would be expected to be found if the
facility's regulated unit(s) was not leaking contaminants.  Background monitoring
wells must yield ground-water samples from the uppermost aquifer representative
of the  quality of ground water that has not been  affected by leakage from the
facility's regulated unit.  Background surface water quality needs to  be assessed
only in cases where surface  waters are receiving contaminated ground-water
discharges.  The permit applicant should also examine  the possibility of other
sources of contamination if the upgradient waters in the vicinity of the facility are
contaminated and ACLs are requested above allowable exposure levels.  This will
give the permit applicant information for assessing cumulative impacts associated
with any contamination emanating from the facility.

     ChapterIX discusses the health risk assessment. The purpose of the health risk
assessment is to determine allowable concentrations at the  point of exposure for
the constituents for  which ACLs are requested,  A detailed health  risk assessment
should be submitted in all ACL demonstrations, unless the point of  exposure  is
established at the point of compliance and either Agency-established  MCLs or
Agency-reviewed  allowable dose levels are used at this point.  If human exposure
could occur, the permit applicant is responsible for providing information on the
health effects of the hazardous constituents present in the ground water for which
ACLs are requested.  The health risk assessment should be based on conservative
health assumptions.  The applicant should distinguish between ground-water con-
taminants having threshold (toxic) and non-threshold (carcinogenic) effects.  The
Agency is currently  compiling toxicity information on many of the  hazardous
constituents which should be useful in preparing ACL demonstrations.

     Chapter X discusses data that should be submitted on the potential impacts to
the environment. The initial step in assessing possible environmental impacts is to
determine the probable exposure pathways for hazardous  constituents to reach
environmental receptors.  For ACL purposes,  the receptors of concern include
wildlife and vegetation in aquatic and terrestrial environments; agricultural crops,
products, and lands; and physical structures. The permit applicant should examine
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                                                    OSWER Directive 9481.00-6C


the potential impacts to the receptors discussed above if the ACLs are based on
attenuation and exposure to hazardous constituents is likely to occur. Otherwise,
the permit applicant should discuss specific data that support no probable exposure
and explain why the potential environmental impact assessment is not needed.  If
there is a likely  pathway for wildlife and vegetation to become exposed  to
contaminants, then environmental toxicity factors should be examined.

     The permit applicant should  discuss the  presence  of  any endangered  or
threatened species in terrestrial or surface water environments near the facility.  If
any endangered or threatened species are in the area, then the permit applicant
should discuss the potential impacts of the contaminated ground water, including
critical habitat impacts, on the species.

     Physical structures can also be adversely affected by hazardous constituents in
the ground water. The determination of potential impacts to and contamination of
physical structures in  the area around the facility requires  the examination  of
exposure  pathways, waste characteristics, and  construction materials and
techniques.  Physical structures of  concern include buildings, buried cables and
pipes, railroad beds, roads, parking areas, and machinery.

     Chapter XI discusses data  needed to determine the persistence  of the
contaminants in the environment and the  permanence of the adverse effects.   If
ACLs are based on attenuation arguments, the applicant should discuss the  process
by which  each ACL  constituent  will degrade, either from a  ground-water
perspective, surface water perspective, or a combination of both, depending on the
site-specific situation.  Data on the permanence of the adverse effects resulting
from  exposure to the ACL  constituents will be required  only if the ACL
demonstration is based on attenuation arguments. Data on permanence is needed
to determine the long-term effects  associated with  exposure  to  the ACL
constituents.

     Chapter XII  presents the summary and conclusions of the ACL guidance
document. This  chapter emphasizes the independent nature of each ACL
demonstration and presents the  time frame of the ACL process.  Information on
each of the criteria discussed in this guidance document is not required in every ACL
demonstration. Each ACL demonstration will reflect site-specific environmental
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                                                    OSWER Directive 9481.00-6C


properties and waste characteristics.  As part  of the ground-water protection
standard, an ACL is in effect during the compliance period. If, at the end of the
compliance period, the  owner or operator is engaged in a corrective action
program, the compliance period is extended until the owner or operator  can
demonstrate that the GWPS, which may contain ACLs, has not been exceeded for a
period of three consecutive years.

     Chapter XIII is a list of references cited throughout the guidance. The permit
applicant is advised to use these documents since approval  of an ACL is highly
dependent upon the technical strength of the demonstration.
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                                                     OSWER Directive 9481.00-6C
                                CHAPTER i

                              INTRODUCTION
     Hazardous waste facilities permitted under the Resource Conservation and
Recovery Act (RCRA) regulations (40 CFR Parts 264 and 270)  are required to  be
designed and operated in a manner that will prevent ground-water contamination.
If leakage of hazardous constituents into the ground water is detected at a RCRA
facility, the regulations require the establishment  of a ground-water  protection
standard at that facility. This standard establishes a limit on the amount of ground-
water contamination that can be allowed. The ground-water protection standard is
an essential element in the Agency's strategy to ensure that public health and the
environment are not endangered by any contamination of ground water resulting
from the treatment, storage, or disposal of hazardous wastes. As such, the standard
will indicate when ground-water clean-up  is necessary to  control contamination
that has emerged from a hazardous waste facility.

     The principal elements of the ground-water protection standard are discussed
in Section 264.92 of  the regulations. For each hazardous constituent entering the
ground water from a regulated unit, a concentration limit must be established that
will serve as a limit beyond which degradation of ground-water quality will not be
allowed. There are three possible concentration limits that can be used to establish
the ground-water protection standard:

     1.    Background levels of the constituents,
     2.    Maximum concentration levels listed  in Table 1 of Section 264.94(a) of
          the regulations, or
     3.    Alternate  concentration limits {see Figure  1).
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                                          05WER Directive 9481.00-6C
                         FIGURE 1

          RCRA GROUND-WATER PROTECTION PROCESS
                       GROUND-WATER
                        MONITORING
                                LEAK
                                DETECTED
                            SET
                         PROTECTION
                         STANDARD
 DEFAULT VALUE
MCL FOR 14 CHEMICALS
BACKGROUND
SITE-SPECIFIC
  - ACL
                           FURTHER
                          MONITORING
                                 STANDARD
                                 EXCEEDED
                       CORRECTIVE ACTION
                        AND ASSOCIATED
                         MONITORING
                           1-2

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                                                     OSWER Directive 9481.00-6C


     Section 264,94 contains the regulatory framework for these concentration
limits. The approach used by  the regulations is to adopt widely accepted
environmental performance standards (i.e., MCLs in Table 1), when available, as
concentration limits. However, because of the lack of currently available standards,
specific concentration limits for only a few specific constituents have been included
in the regulations.

     Maximum contaminant limits are established for 14 hazardous constituents
under the National Interim Primary Drinking Water Standards and  are listed in
Table I of Section 264,94(a) of the regulations. If a constituent is not listed in Table
1, the standard becomes no degradation beyond background water quality. In such
cases, the concentration limit is set at  background level.  However, variances from
these standards are available where the permit applicant can demonstrate that the
constituents will not pose a substantial present or potential hazard to human health
or the environment.  In such  cases, the applicant may ask for an "alternate
concentration limit" (ACL) under Section 264.94(b) of the regulations. This section
of the regulations lists nineteen criteria to be applied in ACL demonstrations. The
applicant should, however, be aware of any State or local laws regulating ground
water. Many States prohibit the release of any pollutants into the ground water.  If
the State has an authorized program for 40 CFR Part  264, Subpart F and does
prohibit such releases, ACLs may not be allowed.

     This document serves to provide  guidance to permit applicants seeking ACLs
and permit writers evaluating ACL demonstrations. The document describes EPA's
implementation guidelines and  elaborates on  the application  of the 19 criteria.
Nine of the criteria are for ground-water contamination pathways, and ten are for
surface water pathways.  The document is divided into 13 chapters that include an
introduction, an explanation of each of the criteria in the regulation, a conclusion,
and references.

     This guidance may also be useful for Record of Decision preparations pursuant
to the EPA CERCLA program (Superfund), for State permit writers, for performing
remedial facility  investigations, or for evaluating corrective action  programs for
other types of waste management facilities. In applying this guidance to Superfund
sites or for State  permits, the users must be cognizant of any differences between
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                                                    OSWER Directive 9481.00-6C


the requirements of their programs and the RCRA regulations and permitting
programs.

     Alternate concentration limits are discussed in the RCRA Standards for Owners
and Operators of  Hazardous Waste Treatment,  Storage, and Disposal Facilities
under SubpartF: Ground-water Protection (U.S. EPA I982a), The permit applicant
and the  reviewer should become familiar with the ground-water protection
regulations. Ads are granted through the permit process under Parts 264 and 270,
Through  this  process, the public  is afforded opportunity to participate in the
establishment of ACLs.

     The Agency is developing a strategy  for implementing corrective action  at
solid waste management units.  The overall goal  of this strategy is consistent with
that of the Agency's SubpartF ground-water protection program:  the protection of
human health and the environment.  The ACL process described in this document
may be useful when evaluating the corrective action programs at these solid waste
management units.

ACL Definitions

     To establish ACLs, two points must be defined on a RCRA facility's property
(see Figure 2); the Point of Compliance (POC) and the Point of Exposure (POE). The
POC is defined in the Subpart F Regulations (40 CFR  264.95) as a "vertical surface"
located at the hydraulically downgradient limit of the waste management area that
extends down into the uppermost aquifer underlying the regulated unit The POC is
the place in the uppermost aquifer where ground-water monitoring takes place and
the ground-water protection standard is set. The  ACL, if it is established in the
permit, would be set at this point.

     The point of exposure (POE) is the point at which it is assumed a potential
receptor can come in contact, either now or in the future, with the  contaminated
ground water. Therefore, the ground-water quality at the POE must be protective
of that receptor.  For example, a facility may have a ground-water contaminant
plume restricted to a small  portion of its property.  In this case, it may be
appropriate to assume that people will be exposed through a drinking water well to
the ground water immediately at the edge of the plume. The ground water at that
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                                                                 OSWER Directive 9481.00-6C
r
                Regulated  |
             :     Unit

             i	.	I
                            Point of
                           Compliance
I	
          Facility Boundary
 Point of
Exposure
lp*li|**ii**WI H     I
                          PLAN VIEW
                Regulated
                  Unit
  Facility
 Boundary~\
                     Point of
                    Compliance
         Point of
         Exposure
                     CROSS-SECTION VIEW

   POINT OF EXPOSURE (FOE) - Point at which potential
   exposure to contaminants is assumed. Location is site
   specific. Allowable exposure is met here,

   POINT OF COMPLIANCE (POC) - The point on the downgradient
   side of the unit where the ground-water protection
   standard is met. The ACL is set here,

   CONTAMINANT PLUME - The volume of ground water that
   contains the leaking  pollutants.

   FACILITY BOUNDARY - Tha property boundary of the
   facility,
   REGULATED UNIT - The area where tha hazardous
   wastes are kept {landfill, surface  impoundment),

                     Figure 2.  Definitions
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                                                    OSWER Directive 9481,00-SC


point, the POE, must then be safe for human consumption. Likewise, if the ground-
water contamination is discharging to on-site surface water, the potential receptor
may, in some cases, be an aquatic organism. In this example, the aquatic organisms
must be protected from adverse effects of the discharging contaminants.

     Understanding and identifying the spatial relationship between the POC and
the POE is critical in the establishment of an ACL  Mechanisms  that attenuate
contaminants may be considered only over the area between the POC and the
downgradient POE.  If the. POE is established  at  the  POC, then no form of
attenuation will be  considered in setting the ACL.  In such a case (POC = POE), the
ACL would be equal to the allowable health or environmental exposure level, with
the assumption that exposure would occur  at  the  waste management  unit
boundary. However, if the POE is removed a specified distance from the POC, then
appropriate and conservative estimates of contaminant attenuation may be used in
calculating the ACL. These mechanisms of attenuation would only be considered
over that distance between the POC and the POE. For example,  if the POE is 50
meters downgradient of the POC, then attenuation could be  conservatively
estimated from the volumetric transport of ground water in  relation to the mass
loading of the leaking constituents over that 50 meters.  The attenuation factor
could then be applied to the allowable health or environmental exposure level at
the POE to derive the ACL.

     The following  section discusses EPA's ACL policy.  After  presenting the basic
philosophy and guidelines of the policy, five case examples are described.  These
examples tell the reader where the POE should be  established in similar real-world
situations. Following these examples is a guide for employing this document to
prepare an acceptable ACL demonstration.

ACL Policy

     Experience gained  over the last several years has  allowed  the Agency to
develop a better understanding of ground-water contamination problems. This has
led EPA to develop general policy guidelines for the use of ACLs at RCRA hazardous
waste disposal facilities.  These guidelines are  designed to establish an  ACL
procedure that will be protective of human health and the  environment.
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                                                    OSWER Directive 9481.00-6C


     Three basic policy guidelines have been identified to assist the permit writer
and applicant in implementing the ACL process for useable ground water;

     1.    Ground-water contaminant plumes should not increase  in size or
          concentration above allowable health or environmental exposure levels;

     2.    Increased facility property holdings should not be used to allow a greater
          ACL; and

     3.    ACLs  should not be established so as to contaminate off-site ground
          water above allowable health or environmental exposure levels.

     Useable ground water is either a current or potential drinking water resource
or ground water that has some other beneficial use (see Chapter VII for more
discussion). ACLs in unuseable ground water will be assessed on a case-by-case
basis.

     Regardless of where the POE is established, there is one overriding policy.
That is,  contaminant  plumes in  useable  ground water will not  be  allowed to
increase in size above acceptable levels. This "no growth"  policy applies both to
the mass of contaminants releasing to ground water and to the volumetric extent of
the plume itself. The implementation of source control measures may be necessary
to prevent the release of contaminants above their permissible level, the ACL. This
may  require that a regulated unit  meet the appropriate Part  264 minimum
technology requirements if the unit has significant leakage. All facilities with RCRA
units that have plumes in useable ground water must prevent these plumes from
expanding out and contaminating more ground water.  This will require that the
leading edge of the plume not move. The leading edge of the plume is identified by
ground water that does not exceed an allowable health or environmental exposure
level.

     The policy of  not allowing plumes to increase in size or concentration  is
protective of human health and the  environment by eliminating  continued,
uncontrolled releases of hazardous constituents. By limiting the growth of ground-
water contamination, the degradation of the ground-water resource  is restricted
and the uncertainty of eventually cleaning up the contamination is reduced. This
                                   1-7

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                                                     OSWER Directive 9481.00-6C


effect applies to both the areal, extent of the contamination and the contaminant
concentrations within the plume. If the  extent of the contamination increases in
size, the  probability of ever capturing  and withdrawing the contamination is
significantly reduced. Likewise, if the contaminant concentrations within the plume
increase,  then the aquifer matrix may leach contaminants into the ground water
over a long  period  of time.  If  this is the case, then eventual cleanup of the
contamination may be impossible.

     In determining the extent of an on-site plume, the permitting authority should
consider  on!y  property that the facility owned at the  time of  initial permit
application.  A facility may  not use recently purchased property to encompass a
plume in order to  allow the use  of larger attenuation factors in their  ACL
calculations.  The permit writer should  consider only the original property, as
defined in the initial  Part B application, in determining an allowable ACL.

Corrective Action

     The Agency is in the process of developing a corrective action program for all
solid waste management units (SWMUs) at RCRA permitted facilities, This program
is mandated  by Section 3004(u) of the Hazardous and Solid Waste Amendments of
1984 (HSWA).  The ACL process, as  described in this document, may  be useful  in
determining  the appropriate corrective measures for ground-water contamination
at these other solid waste management units.

     In developing this SWMU corrective action program, EPA will also assess the
need to promulgate some additional regulations for ground-water corrective action
at regulated  units.

Closure

     If a  RCRA facility owner or operator is considering applying for an ACL, he or
she should be aware of EPA's closure and  post-closure regulations and policy as they
apply to ground-water monitoring. It is likely that if a contaminant is left in useable
ground water above a health or environmental exposure level, as might be the case
with an ACL  based on attenuation arguments, the post-closure care period for the
facility may  be extended beyond 30 years (40 CFR  264,117(a)(2)(ii)).  In this
                                    1-8

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                                                    OSWER Directive 9481.00-6C


situation, an owner or operator may discontinue post-closure care and  ground-
water monitoring only after successfully demonstrating that all the ground water at
a site  is safe for all potential receptors.  A more stringent ground-water standard,
based only on allowable exposure levels for units above useable ground water, may
be needed because the facility owner has no further RCRA obligations for managing
and monitoring the facility at the end of post-closure care.  If, at any time during
the post-closure care or the compliance period under 264.96, a substantial threat
to human health  or the environment is identified, the permit can be modified to
include a lower ground-water protection standard and an extended post-closure
care prog ram.

Examples

    To provide national  consistency in calculations used to estimate the potential
impacts of releases of hazardous constituents to ground water from regulated
units,  Agency policy is that the points of exposure be assumed as discussed below.
These POEs were chosen  because the Agency believes that they are realistic and
conservative estimates of where environmental or human receptors would likely be
exposed to the contaminants.

    The Agency  believes that this method is conservative enough to be protective
of human  health and the environment in situations that would be encountered
during the setting of ACLs. These POEs were also deemed necessary because of both
the persistent nature of many toxic chemicals in the environment and the need to
prevent the further migration of these compounds.

    Case 1: For regulated units located above useable ground water that have not
detected ground-water contamination at the time of permit issuance, the potential
POE will be assumed to be directly at the POC (Figure 3), That is, for units at which
no ground-water contaminant plume exists, the potential  point of exposure  is
assumed to be at the waste management unit boundary. Therefore, no attenuation
can be presumed for contaminants that leach from a unit in the future.  Fate and
transport arguments cannot be used to support ACL demonstrations if no ground-
                                   1-9

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                                          OSWER Directive 948LQQ-6C
                 |   Regulated  j
                 j     U*    !
                 i	i
               Facility Boundary
 Point of
Compliance
   and
 Point of
 Exposure
                           PLAN VIEW
                    Regulated
                 j"UnitM
     Watar Table
             Facility
            Boundary
                                    Point of
                                   Compliance
                                      and
                                    Point of
                                    Exposure
                     CROSS-SECTION VIEW
Figure 3, Case 1". No Contamination at Original Permit Issuance
                              1-10

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                                                    OSWER Directive 9481.QO-6C


water contamination plume exists at the time of permit issuance.  This policy will
help to prevent contaminants from entering the ground water above allowable
health and environmental levels. All new units seeking permits for operation and
old units that have not detected contamination will be held to this policy.

     Case 2:  For units located above useable  ground water that already  have
existing contamination that is confined to the  facility property, the POE  will be
assumed to be no farther from the POC than the outer edge of the existing plume
(Figure 4), If the permitting authority concludes it is protective of human health
and the environment, then the point of exposure may be set at the leading edge of
the plume.   In this situation,  mechanisms of contaminant attenuation (fate and
transport) may be considered  in establishing the ACL at the point of compliance.
Monitoring for the ACL constituents at the POE should be performed to verify the
attenuation mechanisms that were accounted for.

     Case 3:  For units  located over useable ground water, if the leading edge of
the plume extends off the facility property, the point of exposure will be assumed to
be no farther from the POC than the facility property boundary (Figure 5). Fate and
transport arguments may then  be applied to the ground-water contamination
between the POC and the POE at the facility  boundary, assuming there  is no
possible route of exposure on the facility property. At no time may the designated
POE be beyond the original facility boundary.

     Case 4:  ACLs may be based  on contaminant discharge into a surface water
body if a facility owns the property up to the surface water body (Figure 6),  The
permitting authority should allow this only if: (1)  the  contaminant plume has
already reached the surface water body, (2) the contaminants do  not cause a
statistically  significant increase over background  in  the surface  water
concentrations of those contaminants, and (3) the contaminants will not reach a
receptor at an unsafe ievel before they reach the surface water body,  Though it
may be acceptable to allow some contaminants in the ground water to discharge
into a nearby surface water body, in no case may the ACL be derived so as to allow
releases into  that surface water body that result in a statistically significant increase
in the concentration of the contaminants in the surface water body.
                                   1-11

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                                           OSWER Directive 9481.0Q-6C
r
        /- rcim
i	t	
Facility Boundary
                                     Point of
                                   Compliance
                                                 1
                                                      Point of
                                                   !  Exposure

                            PLAN VIEW
             ,   Rsgulated
             [* Unit -H
                  Point of
                 Compliance
                                                  Facility
                                                 Boundary"
                                                Point of
                                               Expouire
                        CROSS-SECTION VIEW
    Figure 4.  Case 2: Contamination Confined to Facility Property
                               1-12

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                                           OSWER Directive 948LOO-6C
             I   Regulated
             j     Unit
>         r raciiiiy t
Facility Boundary
                                                                 Point of
                                                                Exposure
                            PLAN VIEW
                Regulated
                Unit
                Point of
               Compliance
                                                 Facility
                                                Boundary
                                            Point of
                                           Exposure
                       CROSS-SECTION VIEW
       Figure 5. Case 3:  Contamination that Extends Off-Site

                               1-13

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                                             OSWER Directive 9481.00-6C
L:
             j   Regulated   I
                  Unit
           Facility Boundary
No Statistical
 Significance
                             PLAN VIEW
    Facility
   Boundary     Regulated
                  Unit 
  Water Table
                   Point of
                  Compliance
                No Statistical
                Significance
                        CROSS-SECTION VIEW
Figure 6. Case 4: Contamination Discharging into a Surface Water Body
                                 1-14

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                                                     OSWER Directive 9481.00-6C


     Case 5: For those units over a nonpotable aquifer, the location of the POE will
be established on a case-by-case basis (Figure 7).  Such  non-potable aquifers will
usually be highly saline, containing more than 10,000 pprn total dissolved solids.  In
such situations, protection of environmental receptors may be the overriding factor.
In any case, the ACL must be established so as to pose no unacceptable risk to public
health and the environment.  To  apply this option, the  permit applicant must
thoroughly demonstrate that the nonpotable aquifer is  isolated from any potable
aquifer.

ACL Information Requirements

     The type and amount of information needed for an ACL demonstration
depends on the placement of the point of exposure (POE) and  the site-specific
characteristics. An ACL demonstration may cross reference many sections of the Part
B Permit Application,  Appendix A contains a listing of the types of information that
may be cross referenced from the permit application.  For new units, units with no
ground- water contamination  (Case 1), or units  for which the owner or operator
desires an ACL to be set at the allowable health or environmental exposure level,
relatively little additional information beyond that already supplied in the permit
application will normally be required.  If the unit already has caused ground-water
contamination and the owner or operator wishes to take into account mechanisms
of attenuation in deriving the ACL (Cases 2-5), more information will be required.

     The simplest and quickest method for deriving the ACL in all situations will be
to establish the POE  at the POC.   Even for those sites with  gross contamination,
setting the POE at the POC may be the least expensive option because high levels of
contamination will usually require major source control and corrective action
measures, regardless  of the ACL.   By setting the  POE at the POC, the owner  or
operator may save significant amounts of time and money by not having to gather
and organize the additional information required for deriving an ACL that accounts
for attenuation mechanisms.
                                   1-15

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                                            OSWER Directive 9481.00-6C
             I
             j   Regulated    
             j     Unit    '   \
             i
             i	I
                                    Point of
                                   Compliance
i         r- Facility Boundary
I	_y	
                Point of
             t   Exposure
                            PLAN V11W
                Regulated
            UUnitM
                Point of
               Compliance
 Facility
Boundary

              Point of
             Expoiura
                        CROSS-SECTION Vlf W
      Figure 7, Cast 5: Contamination in a Non-Potable Aquifer
                               1-16

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                                                     OSWER Directive 9481.00-6C


     No matter where the POE is established, an allowable health or environmental
exposure level must be determined for each constituent for which  an  ACL is
requested.  The following  discussion  outlines the method used to choose the
appropriate health or environmental exposure level, and the types of information
necessary to derive the attenuation factor(s).  This section is meant to be used as a
guide to the rest of this document;  detailed technical discussions are reserved for
the following chapters. Five ACL Case Studies will be available in the Summer of
1987 to help the owner or operator prepare an acceptable ACL demonstration.

     The appropriate allowable health or environmental exposure level will be
dependent on the most vulnerable receptor near the facility. The most vulnerable
receptor is that receptor, human or environmental, that has the lowest tolerance to
the hazardous constituent(s) for which the ACL is being  requested. In most cases,
the receptors will be humans exposed to the contaminated ground  water via
ingestion (i.e., drinking). However, at times the most vulnerable receptor will be an
environmental receptor.

     Agency-reviewed dose levels for  humans are available to quickly  determine
allowable concentration levels for many hazardous constituents. Chapter IX of this
document discusses the method for determining an allowable exposure level for
humans. Essentially, the applicant can use Maximum Contaminant Limits (MCLs), or
if MCLs  are not available, obtain the appropriate allowable dose level (Reference
Dose (RfD) for systemic toxicant, Risk Specific Dose (RSD)  for carcinogens) from EPA
and use the appropriate formula on  page 9-7 of this  document to derive the
allowable concentration level for humans.

     If environmental receptors exist in the vicinity of the facility, the vulnerability
of these receptors must be  investigated. Chapter X provides a discussion of these
environmental receptors. In many cases, the critical environmental  receptor will be
aquatic  life in the nearest downgradient surface water  body  (including bogs and
wetlands); however, threatened and endangered species, terrestrial organisms,
agricultural products, and  physical  structures should not be overlooked.  The
applicant should compare the allowable exposure  levels for the various receptors
near the facility. The lowest level should be chosen as the concentration level at the
POE,  This method is necessary because the concentration of the contaminants at
                                   1-17

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                                                     OSWER Direct!we 9481.00-6C


the point of exposure must be protective of the  potential  receptor that is  most
vulnerable to that contaminant

     Once the allowable exposure concentrations for the point of exposure are
chosen, the applicant needs to collect and organize any other necessary additional
information. The following paragraphs guide the applicant to the relevant chapters
of this document that describe the types of information that should be submitted.
This discussion is organized around the five case examples described previously in
this chapter. Since some sites will not fit neatly into this scheme, some interpolation
may be necessary.  Appendix B contains a chapter-by-chapter summary of this
information.

Case 1

     The information requirements for this case are applicable in all situations in
which the permit applicant desires a direct health or environmental exposure level
without accounting for mechanisms of attenuation. This method of setting the ACL
is the standard for new units or for old units with no contamination at the time of
permit issuance. If the applicant is dealing with a site  that has ground-water
contamination, the application must include a description of all plumes, including
isopleth maps of all hazardous constituents  in the ground water.  All ACL
demonstrations using allowable  exposure levels  must include  the information
necessary to select the appropriate POE level [Chapters IX and X] and information
on the general ground-water use [Chapter VI].  If  the constituents for which ACLs
are requested do not have Agency-reviewed allowable dose or exposure levels, then
additional information on human and/or environmental  effects will be necessary.
The type of information will be dependent on the  potential receptors [Chapters IX
and X]. A general description of the site and the types and characteristics of the
wastes handled is also required [Chapter II].  General ground-water information is
also necessary and includes: a description of the horizontal and vertical extent of
the uppermost aquifer [Chapter III]; a description of the ground-water flow in the
aquifer [Chapter IV]; and a  listing of the background concentrations of  all
hazardous  constituents in the aquifer.  Most or all of  this information should
already be available in the permit application.
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                                                     OSWER Directive 9481.00-6C
Case 2

     If the facility has on-site ground-water contamination  and the  permit
applicant desires to account for attenuation mechanisms then  the ACL
demonstration should include all of the information required in Case 1, in addition
to the following: a description of the chemical and physical characteristics of the
contaminants for which an ACL is requested [Chapter II]; data on the  chemical-
specific degradation or attenuation rates and/or processes [Chapter II]; a description
of each soil type beneath the facility [Chapter III]; any other attenuation-related
information, including soil properties [Chapter III]; description of the extent and
hydrological properties of each local stratigraphic unit [Chapter III]; aquitard-
related data [Chapter III];  if applicable, information on the temporal  variations in
ground-water flow and  any  withdrawal drawdown effects [Chapter IV]; if  a
mathematical simulation model is used, verification that it meets the criteria listed
in Chapter IV; monthly precipitation data and effects on seasonal recharge [Chapter
V]; any local ground-water discharge pathways [Chapter V]; location of each nearby
(5 km) surface water body and an estimate of travel time for ground water from the
facility to the water bodies [Chapter VI]; additional information on the current and
projected demography and ground-water use when applicable [Chapter VI]; state
certification of the ground- water's  beneficial use [Chapter  VII]; if  background
ground-water is contaminated, information  on the sources and associated ground-
water quality data [Chapter VIII]; and an assessment of the degradation of the ACL
constituents, including degradation products and rates, when possible [Chapter XI].
It is very important that this information be synthesized to present a  conservative
attenuation argument.

Case 3

     The required information for this case, where the contamination extends off-
site and the ACL is based on attenuation mechanisms, is similar to that required for
Case 2.  However,  because the contamination extends  off-site,  a more in-depth
study of the human health and environmental effects will probably be  necessary
[Chapters IX and X].
                                   1-19

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                                                     OSWER Directive 9481.00-6C
Case 4

     For this case,  information will be necessary to demonstrate  both that the
proposed ACL is acceptable and that the contaminants allowed to  attenuate into
the surface water  body will  not cause any statistically significant  increase in
concentration in  the surface water body.   To do this,  the demonstration must
include the information required in the earlier cases (1, 2, and 3) in addition to the
data necessary to show no statistical significance [Chapter X].  If a model is used, it
should meet the  requirements discussed at the end of Chapter IV,  More specific
data on the effects of storm events and flooding will also be necessary [Chapter V].
Additional information  on the physical characteristics and discharge zone of each
water body [Chapter VI] may also  be necessary. The uses of these surface waters is
also important information that should be  documented  [Chapter VI!] along with a
discussion of  and  data on  other sources of surface water contamination
[Chapter VII].

CaseS

     The required information for this case includes the information specified for
Cases 1,  2, and 3  as well as information demonstrating that any off-site
contamination will not pose a threat to any potential receptor or degrade  any
beneficial use.  Additional information pertaining to the hydraulic isolation of the
uppermost aquifer [Chapter 111], the possibility of exposure due  to off-site
contamination {Chapters VI and VII], the ultimate  fate of the  contaminants
[Chapters II and XI], and the uses of local ground waters [Chapter VII] is also very
important.  Of course, background ground-water quality data demonstrating that
the aquifer is nonpotable, and an assurance from the State that the ground water
will not be used, is required.
                                   1-20

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                                                    OSWER Directive 9481.00-6C
                                CHAPTER II

    PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE WASTE CONSTITUENTS
                       (40 CFR 264.94(b)(1)(i) and (2)(i))
     The first step in any ACL demonstration is to identify the chemicals of concern.
These "hazardous constituents" are chemicals listed in Appendix VIII of Part 261 of
the regulations that have been detected in the ground water and may reasonably
be expected to be related to the hazardous waste facility. The applicant must also
account for the degradation products of all ACL constituents, especially if those
products have significant toxicological properties.  Once the hazardous constituents
are identified, an ACL demonstration  based  on attenuation arguments must
determine the physical and chemical characteristics of the constituents in order to
effectively determine their transport through the environment and their ultimate
fate. This chapter discusses the data that is needed to adequately characterize the
physical and chemical properties of the hazardous constituents.

     The permit applicant should  already know which hazardous constituents are
present in the ground water at the facility by the time an ACL demonstration is
being considered. The 270,14(c)  permitting requirements specify that the  permit
applicant must determine the extent of ground-water contamination when a
significant increase in a ground-water contaminant occurs at the compliance point.
Additional ground-water sample collection and analysis is usually not necessary for
ACL purposes.

     The hazardous constituents of concern during the permitting process can be
any of the 375 contaminants listed in 40 CFR Part 261, Appendix VIII.  The Agency
does not require sampling for Appendix VIII substances that are unstable in ground
water or for which no EPA-approved analytical method exists (U.S. EPA, I984b). The
permit applicant should  be aware that the Agency has proposed changing
Appendix VHI monitoring  requirements for ground water (July 24, 1986;  51 FR
26632).  When this proposal is finalized (expected in June 1987), the Agency will use
this list  along with any site-specific additions to the list made by the Regional
Administrator as the basis for detection and compliance  monitoring programs.
                                   2-1

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                                                     OSWER Directive 9481.00-6C


Currently, an Appendix VIII analysis is required whenever any leakage from  a
facility's unit is detected by 264.98 and 270.14(c)(4) monitoring.  Assuring the
absence of particular hazardous constituents emanating from a regulated unit  is
difficult to do simply by record-keeping. Wastes other than those that are currently
received  might have been placed in  the  unit in pre-record-keeping  times.  In
addition, the potential exists for unpredicted reactions between the constituents
and the formation of degradation products.

     The fulfillment of the 270,l4(c) permitting requirements should result in the
spatial characterization of each hazardous constituent found at the site. The permit
applicant should  submit, as part of the ACL demonstration, the data gathered to
satisfy these requirements and present the information in terms  of three-
dimensional representations of constituent concentrations. The three- dimensional
representation of ground-water contamination may not necessitate three-
dimensional modeling of the contaminant plume. A two-dimensional model in the
vertical and longitudinal  planes  may be sufficient in  many  cases, if the  site
hydrogeology is  fairly homogeneous, and if sufficient monitoring data exists to
describe the plume. See Chapter IV for further discussion of appropriate models.

     The permit  applicant  should also submit, as part of the ACL demonstration,
information on the chemical and physical characteristics of the wastes in the
regulated unit that was gathered pursuant to 264.13. This data will give the ACL
reviewer a better understanding of what may be expected to show up in the ground
water. Additional waste constituent analyses may  not  be needed  for the  ACL
demonstration if the applicant has fulfilled  the requirements of 264.13.

     Several physical and chemical characteristics of hazardous constituents are
critical to the modeling of contaminant transport in  ground water.   Permit
applicants should submit data on the  following characteristics of the constituents
for which ACLs based on fate and transport are requested; density, solubility, vapor
pressure, viscosity, valence state, and  octanol-water partitioning coefficient.  For
example, consider a facility  that is leaking  a hazardous  constituent at  a
concentration level  near or above the constituent's solubility level.  In this case,
there is a good possibility that a  two-phase  plume could result. One phase would be
the dissolved constituent plume in the ground water, and the other would consist of
relatively pure hazardous constituent.  This latter phase could either be floating on
                                    2-2

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                                                     OSWER Directive 9481.00-6C
the water table or sinking to an aquitard, depending on its density. The two phases
would probably move at different rates due to viscosity and density differences.

     Even when only one phase is  present, the transport model results are
dependent on  the  physical and chemical characteristics of the  constituents;
attenuation parameters for transport  models depend on specific characteristics of
the hazardous constituents. The permit applicant should submit in tabular form the
density, solubility, vapor  pressure, viscosity, and  octanol-water  partitioning
coefficient values of the hazardous constituents. The ability for one constituent to
mobilize other constituents should also be investigated. Appendix C contains an
example of a summary sheet that can be used to list the important properties of the
ACL constituents.

     An ACL demonstration that is based on attenuation should be supported by
data on fate-related characteristics of the  ACL constituents.   If a permit applicant
argues that the presence of an ACL constituent at the point of compliance is not
likely to cause exposure because it is not persistent in the ground water, then
special fate  and stability  related characteristics of the constituent should  be
discussed in the ACL demonstration.

     The stability of waste constituents in the subsurface  environment can  be
affected  by chemical, biological, and physical processes.  Important chemically
mediated subsurface processes may involve oxidation,  reduction, and  hydrolysis.
Important biologically mediated  processes  include biodegradation and
biotransformation reactions.  The subsurface physically mediated  processes can
involve  ion exchange,  precipitation, and complexation reactions.  If the ACL
demonstration is based  on any of these processes, then the results of site-specific
tests should  be submitted. Most of the degradation processes depend on the
properties of contaminants as well as environmental  factors such as  microbial
populations, solid surfaces, and dissolved constituents present in the ground water.
Because the  relevant environmental factors are  unevenly distributed  in nature,
degradation and reaction rates are not constant in ground-water environments and
must be assessed on a site-specific basis. Therefore, the use of general information
gathered from the literature will be of limited value when assessing the stability of
waste constituents.
                                    2-3

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                                                     OSWER Directive 9481,QQ-6C


     Degradation properties of the ACL  constituents are also important  in
determining the effects of the constituents. Since degradation products can be
more hazardous than the parent compound, all known and likely degradation
products should be discussed when describing  the characteristics of the waste
constituents.

     Grouping ground-water contaminants according to  stability characteristics
may be possible. If site-specific tests support the grouping of constituents, then the
fate and mobility of each constituent within a group can be based on the stability
characteristics of the most mobile and most persistent compounds in the group. This
would result in the fate and mobility coefficients for each constituent being set at
the coefficient values for the most mobile and most stable compounds in the group.
Before grouping the constituents, the applicant should investigate possible
degradation products associated with the constituents of concern. The ability  of
one contaminant to facilitate or hinder the movement of another contaminant (co-
solvent effects) should also be accounted for when possible. Although it is difficult
to decide which groupings of constituents are appropriate, grouping can reduce the
amount  of predictive modeling necessary for  quantifying environmental
concentrations and exposure pathways (see U.S. EPA  1986c).
                                   2-4

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                                                    OSWER Directive 9481.00-6C
                               CHAPTER III

                    HYDROGEOLOGIC CHARACTERISTICS
                      (40 CFR 264.94(b)(1)(ii) and (2)(ii))
     A general description of the hydrogeological characteristics of the facility is
needed in all ACL demonstrations. A more detailed assessment of ground-water
movement near a facility is essential to a demonstration based on attenuation. The
main  route  of exposure  to  ground-water contaminants usually  involves the
movement of the hazardous constituents through the soil to the ground water and
on to an existing or potential point of use. This chapter describes the information
needed to adequately determine the hydrogeologic properties required for
characterizing ground-water movement at a site.

     During the general RCRA permitting  process, the permit applicant is required
under 270,l4(c) to identify the uppermost aquifer.  The uppermost aquifer is
defined under 260.10 as the geologic formation nearest the natural ground
surface that is an aquifer as well  as lower aquifers  that are hydraulically
interconnected with this aquifer within the facility's property boundary. Saturated
zones above the uppermost aquifer are also of interest as contaminant migration
pathways. Therefore, for an ACL demonstration based on attenuation, information
on the geologic and hydrologic properties of each of the individual strata beneath a
facility, that are likely to influence ground-water contaminant migration, should be
submitted. This data is needed to adequately characterize ground-water transport
mechanisms. Much of the data should already be available to the permit applicant
if the Section 270J4(c) requirements have been fulfilled.

     The important geologic attributes of a facility include;

     1.  Soil and rock characteristics,
     2.   Geologic structure, and
     3.   Geomorphology and topography.
                                   3-1

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                                                     OSWER Directive 9481,00-6C


     When describing the soil characteristics of a facility,  the permit applicant
should use the Unified Soil  Classification  System or the U.S. Department  of
Agriculture's soil classification system.  Each  soil type beneath the site and within
the areal extent of the ground-water contaminant plume should be investigated.
The permit applicant should submit data describing the thickness, areal extent, and
hydraulic properties of each soil type. The soil information should be submitted in
both tabular and graphic form. The areal extent of soil types should be presented
on a map with a scale  no greater than one inch:200 feet.  The applicant should
submit copies of drilling and boring logs from monitoring and water wells that have
been installed.

     If the applicant uses soil or other matrix attenuation mechanisms to justify the
ACL, the additional data and calculations used to define the  attenuative properties
should be submitted.  The following attenuation mechanisms may be relevant to  an
ACL demonstration;

     1.    Dispersion, including hydrodynamic dispersion;
     2.    Retardation, including all sorptive  properties; and
     3.    Degradation, including mechanisms of biodegradation, oxidation,
          reduction, and hydrolysis.

     The permit applicant should submit data describing the organic and mineral
content, the cation and anion exchange capacity, and the grain size of each soil type
in the area of contamination.  Aquifer matrix characteristics that affect the stability
of the ACL constituents (see Chapter II) should also be described if they are used to
support attenuation claims.  The results of  tests to substantiate any attenuation
claims should be submitted by the applicant.  Likewise, sampling  and  laboratory
procedures used to determine the attenuation properties should be presented and
results tabulated.  Brady (1974) and  Freeze and Cherry (1979) provide in-depth
discussions of these specific soil characteristics, and the  permit applicant and
reviewer should consult these references for assistance.

     The permitting authority and the applicant should keep in mind the outcome
of the different types  of attenuation.  Although matrix  effects (binding) and
dispersion act to lower the concentration of the  contaminants at the point  of
exposure, they do not directly reduce their total mass. Constituents that attach to
                                    3-2

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                                                     OSWER Directive 9481.QO-6C


the matrix may become mobilized  at a  later time.  However, degradation
mechanisms  act to  eliminate  the contaminants themselves.  This form of
attenuation is permanent and, assuming the products are harmless, can be a final
solution to eliminating the contamination.

     If the ACL demonstration is attenuation-based, the permit applicant should
submit a set of maps that adequately depict the subsurface stratigraphy. The near-
surface stratigraphic units in the zone of saturation that affect or a re likely to affect
ground-water contaminant migration should be described. The areal and vertical
extent of the hydrogeologic units can be presented in several ways.   For complex
settings, the most desirable presentation is a series of structural contour maps for
the top or bottom of each unit. Vertical sections and isopach maps can also  be used
since  they are  generally more graphic and  are useful as  supplements to the
structural contour maps. Because the construction of any of these diagrams  involves
interpolation and extrapolation of data, the diagrams should show the location of
control points and the corresponding value at each control point. The site maps
should include the depth, thickness, and areal extent of each stratigraphic unit. The
maps  should  also adequately depict all  stratigraphic zones and lenses within the
near-surface zone of saturation. The site-specific stratigraphic maps should be
detailed and have a scale no greater than one inch:200 feet The applicant should
also submit  regional stratigraphy maps in order to show unique regional
characteristics and their relationships to the site and to justify claims concerning the
ultimate fate of a contaminant plume.  A  table that summarizes the subsurface
geologic data should be submitted.

     Each of  the stratigraphic units located in the  zone of saturation should be
characterized for the hydrologic parameters of hydraulic conductivity (vertical and
horizontal), specific  yield (unconfined aquifer) or specific storage {confined
aquifer), and effective porosity.  Hydraulic conductivity and porosity of  aquifer
material can be determined by  using  laboratory or field methods.  It is
recommended that all tests that are conducted to define the hydraulic properties of
each stratigraphic unit be performed in the field.  Laboratory tests may be  used to
substantiate field test results but should not  be the sole  basis for  determining
aquifer characteristics. Only in special cases will the submittal of laboratory analyses
be considered adequate for describing  aquifer characteristics.  Literature value
estimates for these parameters will rarely be acceptable.
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                                                     OSWER Directive 9481.00-6C
     Each of the hydrologic parameters can vary from point to point, even within
the same aquifer.  Therefore, the areal variations of the parameters within the
stratigraphic units should be characterized.  The amount of data  necessary to
characterize a stratigraphic unit will increase with the increasing heterogeneity of
the unit As an example, an aquifer of extensive homogeneous beach sand will
require  less investigation than  a glacial unit consisting  of lenticular deposits of
outwash sand and gravel interbedded with clayey till. However,  in order to save
time and effort, the applicant may  choose to make  simplified  "worst case"
assumptions of hydraulic conductivity and porosity.

     There  are many field  methods for measuring hydraulic conductivity and
porosity. Hydraulic conductivity is most effectively determined from the analysis of
pump test data. For units having low hydrologic conductivity, single-well tests are
generally used (i.e., a slug test).  For units having high hydraulic conductivity, multi-
well pumping tests are necessary.  The pump test methods are  normally designed to
evaluate the transmissivity and  storativity (storage coefficient) of the aquifer.
Hydraulic conductivity is determined  by dividing transmissivity by  the  aquifer
thickness. More information on determining aquifer characteristics can be found in
Freeze and  Cherry (1979), Kruseman and De Bidder (1979), U.S. EPA  (I983a), and
Walton (1970).

     Different laboratory methods can be used to substantiate field data. Hydraulic
conductivity may be determined on a core sample of the aquifer by using either a
constant-head or a falling-head permeameter. A description of the method can be
found in Todd (1980) and Bouwer (1978).  In the laboratory, effective porosity can
be determined as the ratio of the volume  of water yielded by gravity flow to the
volume of soil or rock material.

     If an aquitard separates two distinct ground-water zones, then  the physical
and hydraulic characteristics of that aquitard must be provided in sufficient detail to
illustrate the degree  of interconnection between the two  aquifers.  This
requirement can be fulfilled by  providing the results of an aquifer pump test
designed to show the effect of the pumping of the deeper aquifer on the shallow
aquifer. The shallow aquifer will exhibit significant drawdown during the pump
test if the two aquifers are interconnected.
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                                                       OSWER Directive 9481,QQ-6C
     A summary of the hydraulic properties of each stratigraphic zone within the
zone of saturation should be submitted by the permit applicant. This data should
be provided in a table that includes the aquifer name, stratigraphic zone, vertical
conductivity, horizontal conductivity, specific yield, transmissivity,  and storage
coefficient.
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                                                    OSWER Directive 9481.00-6C
                               CHAPTER IV

              GROUND-WATER FLOW DIRECTION AND QUANTITY
                     (40CFR264,94(b)(1)(iii)and(2)(iii))
     The amount or quantity of ground water at a site and the direction in which it
flows are two essential components of an analysis of the fate and transport of
hazardous constituents in the ground water. The ultimate fate of contaminated
ground water is a principal topic of every attenuation-based ACL demonstration
since a contaminant plume may discharge into  and mix with other ground or
surface waters.  This chapter describes methods that can be used to determine
ground-water flow direction and quantity at a site. The EPA publication Ground-
Water Monitoring Technical Enforcement Guidance Document (U.S. EPA 1986a)
may also be useful in making these determinations.  However, if a facility is located
over a relatively complex hydrogeologic system (e.g., fractured rock or karst
aquifers), setting the POE at the POC may  be the only acceptable method for
establishing the ACL.

     The primary processes that  control  the  migration of contaminants in
subsurface environments include:

     I.   Advection (movement of the ground water),
     2.   Hydrodynamic dispersion (mixing of  ground water having different
         levels of contamination), and
     3,   Chemical reactions.

     For ACL purposes, advection is defined as the migration of hazardous
constituents by actual motion or flow and is generally assumed to  be caused by
natural ground- water flow.  Consideration of advection alone presents the worst-
case calculations in terms  of peak arrival  times and concentration strengths.
Furthermore, qualitative and quantitative evaluation of advection in  terms of flow
pathways is possible.
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                                                     OSWER Directive 9481.00-6C


     The Section 270.l4(c)  permit requirements specify the submittal of ground-
water flow information. This data should be adequate for on-site determinations
of flow; however, additional data may be required if off-site determinations of
ground- water flow are needed for the ACL demonstration. The permit applicant
should evaluate ground-water flow  in terms of the flow  regime present at the
facility.  Flow from the facility to the water table will generally occur in the
unsaturated zone, although  it may go via  surface water.  Where subsurface
heterogeneities are not significant, it is reasonable to assume that flow through the
unsaturated zone will be predominantly downward.   This assumption is justified
because gravity is the primary force acting on a fluid in the unsaturated zone.

     Once in the saturated zone, dissolved constituents will move with the ground
water.  Evaluation of advective transport in the saturated zone  for  miscible
constituents can generally be based on the  observed ground-water flow field and
hydraulic properties (hydraulic conductivity gradient and effective porosity). The
observed flow field can be determined by a combination of areal water level maps
and vertical sections showing water levels.

     Calculations of ground-water quantity will require the use of the subsurface
hydrogeologic parameters described in Chapter III. Ground-water quantity can be
estimated by calculating the porosity of the aquifer.  The use of Darcy's law for
determining ground-water flow quantity is acceptable and can be found in any
standard ground-water textbook (e.g., Freeze and Cherry (1979)). Darcy's law can be
used to calculate specific discharge or volume rate of flow through a cross-sectional
area perpendicular to the flow direction in relatively homogenous systems.

     The determination of ground-water flow rates and directions is simple in
concept, If the distribution of hydraulic head and the hydrologic properties at the
site are known, then a flow net or water level contour map in conjunction with the
use of Darcy's law can be used to determine flow rates and directions.

     The permit applicant should be aware of a number of factors that can make
accurate determination of ground-water flow difficult. These include:

     I.    Low horizontal or relatively flat gradients,
     2.    High vertical or relatively steep gradients,
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                                                     OSWER Directive 9481.00-6C


     3,   Temporal variations in water levels,
     4.   Heterogeneous properties, and
     5.   Anisotropic properties.

     In areas of low horizontal gradients, small errors in water level measurements
or small transient changes in water levels can  make determination of flow direction
and rates difficult  High vertical gradients often exist in surficial units.  In recharge
areas, head decreases with  depth; whereas in  discharge areas, it increases with
depth. Often, a shallow water table aquifer may overlie an aquifer of higher
permeability, resulting in vertical head gradients. A very common mistake is made
when water level contour maps are constructed  using wells or piezometers at
different depths.  In  such a case, calculated horizontal flow directions may be
inaccurate.

     Water levels can vary temporally because of short-term stresses, tidal  effects,
atmospheric pressure variations, seasonal  effects, and long-term  trends.  In
determining flow direction, the annually  averaged water levels are of primary
interest.  Consideration of short-term effects is more important at sites with low
hydraulic gradients. In evaluating any water  level data, the uncertainty introduced
by neglecting short-term effects must be estimated. Seasonal variations in recharge
can result in significant water level  variations in  unconfined aquifers. Artificial
recharge  and certain types of ground-water pumpage often lead to seasonal
changes in  water levels.  These  changes  may occur  under both confined  and
unconfined conditions.

     The degree of heterogeneity in aquifers may range from fairly moderate to
extreme.  The potentiometric surfaces or water levels in  heterogeneous aquifers are
not smooth regular surfaces. At the contact between two geologic materials, the
hydraulic gradient will be discontinuous. For some aquifers, such as fractured rock
and karst aquifers, the heterogeneity is much  more  complex.

     Another property of an aquifer is its  anisotropy.   Hydraulic conductivity is a
property that  is dependent  on direction  and therefore has three principal
components. If the principal components are equal, then the aquifer is isotropic. If
not, the  aquifer is anisotropic.  For anisotropic aquifers,  flow lines are  not
perpendicular to equipotential lines or water levels.  Many aquifers display a
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                                                     OSWER Directive 9481,00-6C
horizontal-vertical anisotropy.  However, if the two horizontal components  of
hydraulic conductivity are equal, then, from an areal perspective, flow lines will  be
perpendicular to lines of equal potential,  Aquifers that may demonstrate
horizontal anisotropy include aquifers in fluvial sandstone, fractured rocks,  or
steeply inclined strata. Ground-water flow direction is difficult to determine from
water level data in these types of anisotrophic aquifers.

     The factors that make the determination  of  flow rates and directions
unreliable can often be overcome by an expanded effort in water level monitoring.
For seasonal variations in water levels, a higher frequency monitoring schedule is
necessary. For low horizontal gradients, the effects of short-term changes in water
levels can be analyzed by installation of continuous recorders in selected wells.  In
aquifers having significant vertical gradients, piezometers completed at various
depths may be required in order to provide a three-dimensional description of the
flow field.   For  heterogeneous and anisotropic aquifers, more water level
monitoring wells and more field tests for hydraulic properties are required.

     The hydrogeologic portion of the ACL demonstration must include  an
adequate description  of both horizontal and vertical ground-water flow
components.  This is required because it will help determine where the hazardous
constituents may migrate.  The horizontal ground-water flow description should
include a flow net based on ground-water elevation measurements taken from
monitoring wells or piezometers screened at the same  elevation in the same
saturated zone. The monitoring system must be designed to provide reliable results
of the ground-water flow direction  in the zone of saturation.  There may be sites
that will require the applicant to monitor for hazardous constituents at more than
one ground-water elevation. When this situation occurs, the permit applicant must
be especially careful to ensure that the monitoring plan is designed correctly.

     Information obtained from analyses of the hydrogeological properties and
flow direction will allow the calculation of ground-water flow velocity.  Well
identifier codes,  well depths, screened intervals, ground-water elevations, and
sampling data should be presented  in tabular form.  The flow net data should  be
graphically portrayed on  a  site map that includes ground-water elevations,
isopleths, and flow vectors. As discussed before, the ground-water flow velocity can
be  determined by  a simple modification of Darcy's equation if  the  aquifer is
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                                                    OSWER Directive 9481.00-6C


relatively isotropic.  All calculations and assumptions should  be included in the
discussion of flow rates.

     Vertical ground-water gradients and flow should also be described.  Facilities
should have several nested piezometers for vertical gradient determinations.
Vertical flow gradient will aid in determining discharge and recharge zones,
aquitard characteristics, and whether the monitoring  wells  are located and
screened at the appropriate depths. The data that should be submitted in tabular
form for each well nest includes  well identification code, well depth, screened
interval, ground-water elevation, and sampling  date.  All  calculations and
assumptions should be described in detail.

     Facilities that are located in environmental settings that  exhibit temporal
variation in ground-water flow direction should define the extent to which the flow
change occurs. The main causes of ground-water flow variation are:

     1.   Seasonality of recharge or discharge,
     2.   Ground-water withdrawals,
     3,   Underground injection,
     4,   Surface water elevation changes, and
     5.   Artificially induced recharge by basin flooding.

     In cases of seasonal ground-water flow variation, the permit applicant should
provide information describing those temporal changes in ground-water flow
direction using records com pi led over a period of no less than one year.

     The rate of withdrawal of ground water is an important factor that influences
ground-water and contaminant movement and exposure to contaminated water.
In attenuation-based demonstrations, the rate of ground-water withdrawal in the
vicinity (5 km radius) of the facility should be summarized in tabular form and
should include well location, depth, type of use, and withdrawal rates. The zone of
impact created by any major well or well field withdrawal should  be identified on a
site map.  The map should include drawdown isolines out to the 30 centimeter
drawdown  level.   Modeling of  drawdown  curves should use low recharge
assumptions such as drought conditions.
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                                                    OSWER Directive 9481.QQ-6C
Models

     Although not required for an ACL demonstration, mathematical simulation
models of ground-water flow and contaminant transport can be extremely useful
tools for the applicant. Models are more appropriate for relatively simple geologic
environments where conditions do not vary widely; in complex geologic areas,
modeling may be less useful.

     The permit applicant is responsible for ensuring that the models used simulate
as precisely as possible the characteristics of the site and the  contaminants and
minimize the estimates and assumptions required.  All models  used  in the
demonstration should;

     1.   Be compatible with the quality and type of input data available,
     2,   Have been demonstrated  to be applicable to the environmental
         conditions at the site,
     3.   Have been subjected to an independent quality assurance audit or to a
         level of professional peer review equivalent to that for publication in a
         scientific or technical journal,
     4.   Be internally  consistent in the use of boundary and initial  conditions,
         time steps, assumptions, and code modifications,
     5.   Have fully documented support available to the Agency, and
     6.   Be calibrated and verified for the site before being applied in a predictive
         mode.

     As discussed in Chapter II, a two-dimensional model of a ground-water system
may be used; however, all simplifying assumptions must be justified.  Whenever
possible, input parameters and assumptions should be  conservative  in nature;
worst-case scenarios may save  much effort.  If models are  used, the ACL
demonstration should include tables of the assumptions, the input parameters, and
any calibration data.
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                                                     OSWER Directive 9481.00-6C
                                CHAPTER V

                           PATTERNS OF RAINFALL
                           (40CFR264.94(b)(2)(iv))
     Precipitation is a driving factor for ground-water recharge and discharge.
These two processes are basic components of the hydrogeology at a facility.  To
verify a claim of attenuation due to dispersion, precipitation data in support of
ground- water flow and contaminant transport information must be submitted.
This chapter describes the type of precipitation information that  should  be
submitted in support of an attenuation-based demonstration.

     The permit applicant should focus the discussion of precipitation around the
site's hydrologic regime. If the applicant's ACL demonstration clearly  shows that
ground-water discharge to surface waters is  unlikely, then  the discussion of
precipitation events can be limited to effects on infiltration, evapotranspiration,
and ground-water recharge. However, if ground-water discharge to surface water
is an important element of the ACL demonstration, then precipitation events should
be related to recharge and discharge of ground water.

     Precipitation events are variable and occur with different intensities, amounts,
and durations. The geographical distribution of rainfall also varies from one area to
another within a region.   However, over a  long  period of time  (years), the
precipitation data for an area can be represented by events with definite amounts
that occur at various frequencies.  These frequencies are classified  in terms of
duration and yearly return  periods. For  example, a one-day/IO-year storm event is
defined as the amount of rainfall that is expected to occur during a 24-hour period
once every  10 years.  The amount of precipitation for a storm of specific return
period and duration is used  to produce an estimate of the amount of precipitation
for a given geographical area.

     Attenuation-based demonstrations should contain general information on the
precipitation characteristics  of a  site. This includes data  on rainfall and snowfall,
expressed as its equivalent  in rainfall.   The National Oceanic and Atmospheric
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                                                     OSWER Directive 9481.00-6C


Administration, the National Weather Service, or climate data in Ruffner (1980 and
1981) may be sources of this information if on-site data is unavailable. Regional
precipitation data may be used if it was generated within 15 km of the facility.
Regional data  from  greater than 15 km of the facility should be correlated with
available on-site data.  The monthly mean and range of this data, the specific time
period from which the data  was collected, and the location of the precipitation
gauge(s) in relation to the facility should be provided. The permit applicant should
discuss this information  in terms of temporal effect on infiltration  and seasonal
ground-water  recharge.  These processes  should be related to  any effects on
contaminant transport.

     If the ACL demonstration does not involve surface water exposures, then the
permit applicant can proceed to the next chapter.  However, if the facility is located
near surface water bodies (see Chapter VI),  or if surface water discharge is used as
an argument  in an ACL demonstration, then more  detailed information on
precipitation events should be submitted. The permit applicant should submit data
on specific storm frequency patterns and discuss how these storms relate to flood
and infiltration/discharge characteristics of the facility.

     The predicted amount of precipitation  produced over  a 24-hour period  by
storms of return frequencies of 1, 10, 25, and 100-years should be submitted. The I-
year and 10-year  storm  frequency  information gives  insight into ground-water
infiltration and discharge patterns.  The 25-year and 100-year storm frequency data
are useful in assessing discharge during flood conditions.

     The 100-year floodplain should be described on a USGS topographic map. The
floodplain information should be readily available to the applicant, since it is
required by Section 270.14{b) permitting  requirements.   Federal  Insurance
Administration flood maps can be a useful source for this information. If the facility
has any special flood prevention measures, they should also be shown on the map.
These measures could include any dikes, berms, dams, and special flood retention
walls. The effect of these devices on ground-water infiltration and discharge should
be discussed.  Furthermore, any special site conditions that affect infiltration and
discharge should be discussed.  These include site  topography, solar orientation of
the regulated unit, and wind patterns.
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                                                     OSWER Directive 9481,00-6C


     The ground-water discharge patterns at the facility should also be delineated
on a topographic map. All streams, ditches, culverts, and sewers that receive
ground water should  be  clearly  identified.  Normal ground-water discharge
patterns (1-year storm) and discharge during  flood conditions (25 and  100-year
storms) should be clearly marked. Snow melt pathways should be identified, if
appropriate.  Any discharge abatement or collection  devices,  such as detention
basins, swales, and canals, should also be described.

     Evapotranspiration should also be considered in both recharge and discharge
evaluations. Vegetation can use a large amount of water and reduce significantly
the amount of infiltration reaching the water table, especially during the growing
season.
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                                                     OSWER Directive 9481.00-6C
                               CHAPTER VI

          PROXIMITY OF SURFACE WATER AND GROUND-WATER USERS
                      (40 CFR 264.94(b)(1)(iv) and (2)(v))
     This chapter and the next chapter discuss important factors necessary  for
assessing probable exposure pathways for the ACL constituents through surface and
ground water. This chapter discusses the location of surface water and ground-
water users in the vicinity of the facility.  All ACL demonstrations should contain a
discussion of the proximity and  types of water  uses near the facility.  If the
demonstration is attenuation-based, then more detailed information will  be
necessary. The uses of surface and ground water in the vicinity of the facility are
discussed in Chapter VII,

     A key factor involved in assessing exposure is the proximity of surface water
and ground-water users to the facility.  For ACL demonstrations, "proximity" is
liberally defined to include both spatial and temporal concepts. Linear distance may
be more appropriate for judging potential surface water exposures, while time of
travel is important for ground-water exposures. Proximity  should be expressed in
terms of both linear distance and time required for  ground-water  flow and
contaminant transport.

     The level  of information necessary to satisfy the  proximity of  users
requirement depends on the basis of the ACL.  If the applicant is attempting to show
that contaminants will safely attenuate into a surface water body, then data on the
specific physical attributes of the surface water body will be  necessary. This includes
information necessary to estimate the mixing potential and mechanisms of the
water body. Likewise, if the aquifer is nonpotable, then data showing that it is not
fit for consumption must be supplied.
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                                                     OSWER Directive 9481 .GQ-6C
Surface Water

     ACL demonstrations  relying on transport mechanisms should  include a
discussion  of the potential effects of the facility on surface waters.  The  initial
evaluation includes assessing the facility's proximity to surface waters and involves:

     1,    Identifying each surface water body in the vicinity of the facility,
     2.    Determining the distance from the waste management area boundary to
          each surface water body, and
     3,    Identifying ground-water discharge pathways to surface waters.

     Each water body within five kilometers downgradient (or downstream) of the
facility boundary should be identified. The owner or operator of the facility should
supply an appropriately scaled map identifying each water body. All streams, rivers,
ponds, lakes, estuaries, and marine waters should be clearly marked.  All ditches,
streams, sewers, and runoff pathways that serve as ground-water discharge or
infiltration areas should be delineated on the map. A table specifying the name of
each water body and the distance from the waste management area to the closest
part of each water body should be provided by the owner or operator of the facility.

     The travel time of the ACL constituents from the facility to the discharge areas
should be discussed by the permit applicant.  Ground water and hazardous
constituents  may move at  various rates due to different physical and chemical
properties.  Therefore, discharge calculations should  include estimates of both
hydraulic transport and waste transport. The ground-water transport models and
methods discussed previously in Chapter IV should be used to estimate the hydraulic
and hazardous constituent loading rates.  Actual seepage measurements may be
necessary to  verify model estimates if ground-water discharges are estimated to be
a significant  portion of the annual hydraulic load to a water body.

     A greater level of detail on characteristics of surface water bodies is needed if
the applicant is attempting to show that the contaminants will attenuate safely into
surface water {i.e., not cause a statistically significant increase in concentration). In
these cases, the physical characteristics of each identified  downgradient (or
downstream) water body should be included in a table. Important lake and pond
characteristics are;
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                                                     OSWER Directive 9481.00-6C
     1.   Surface area,
     2.   Mean depth,
     3.   Volume,
     4.   Temperatu re stratification, and
     5.   Hydraulic residence time.

Information on estuarine and marine areas should include:

     1.   Surface area,
     2.   Mean depth, and
     3.   Tidal periodicity and amplitude.

Pertinent stream and river characteristics are:

     1.   Mean width,
     2.   Mean depth,
     3.   Flow  rate, including average flow and lowest flow that would be
         expected to occur during a continuous 7-day period, once every 10 years
         (Q7-IO), and
     4.   Lowest recorded flow rate.

     This information is necessary in order to estimate the discharge zones of each
type of surface  water in the vicinity  of  the facility.  The temporal  and spatial
variability of flow rates, tidal factors, and hydraulic residence times  are also
essential factors for establishing discharge zones.

     The permit applicant should synthesize this information to support arguments
of no statistically significant increase in surface water concentrations. The expected
amount of attenuation  and  the zones of probable discharge areas should be
discussed. The permit applicant should be aware that certain States have approved
surface water models that are used in the NPDES permitting program.  If approved
models are available, they should be used by the applicant to determine discharge
zones in surface waters. The EPA d ocument Tech meal Support Document for Water
Quality-Based Toxics Control (U.S. EPA 1985a) is a good source of this information.
In general, one quarter of the cross-sectional  area of a stream may be used in
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                                                     OSWER Directive 9481.00-6C


estimating the discharge zone.  This area could then be applied over the width of
the ground-water contaminant plume as it enters the river to derive the discharge
zone.

Ground Water

     In order to assess the likelihood of exposure of current ground-water users,
every ACL demonstration relying on attenuation  mechanisms must  discuss the
proximity of ground-water users to the facility. This requires determining:

     I.   The distance of the ground-water users' withdrawal point (i.e., well or
         spring) from the facility, and
     2.   The hydrologic transport time for the contaminants to reach the closest
         wells or springs.

     The users of ground water within a five kilometer radius of  the facility
boundary should be identified.  Both upgradient and downgradient wells should be
included because of their potential to change the direction or quantity of ground-
water flow. The  applicant should delineate each ground-water withdrawal or
injection well on  a scaled site map.  The distance of each  well  from the waste
management area should be given in  a table.  The  following uses of each well
should be clearly marked;

     1.   Potable (municipal and residential),
     2.   Domestic nonpotable,
     3.   Industrial,
     4.   Agricultural, and
     5.   Recharge.
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                                                    OSWER Directive 9481.00-6C
                               CHAPTER VII

             CURRENT AND FUTURE USESOF GROUND WATER AND
                       SURFACE WATER IN THE AREA
                      (40 CFR 264.94(b)(1)(v) and (2)(vi))
     Once the location of the surface water and ground-water users has been
determined, the nature of the use should be considered. A major objective of an
ACL demonstration relying on transport arguments is to show that ground-water
contamination at a facility will not adversely affect any water use. The supporting
arguments for the ACL can center around  the  fact  that the ground-water
contamination at the facility is not degrading the designated beneficial uses of the
water resources.  This requires the permit applicant to review federal, state, and
local standards or guidelines that govern the uses of both ground and surface water
to ensure that the presence of a  contaminant plume is not inconsistent with any
published regulations, ordinances, or guidelines. This chapter points out the types
of water uses that should be investigated, and the information that should be
submitted on those  water uses  to   support an attenuation-based  ACL
demonstration.

     All ACL demonstrations should generally discuss current and likely future uses
of water resources near their facility.  However, ACL demonstrations based on
attenuation arguments need to provide detailed  information on these uses.
Information gathered to satisfy  data requirements on the  proximity of water
resource users (see Chapter VI) will be adequate to identify major water resources
near the facility.   In order to aid the permit  reviewer, the  water resource  use
information should be structured around the following general categories;

     1.   Agricultural - irrigation and animal watering;
     2.   Industrial - process, cooling, and boiler water;
     3.   Domestic and municipal -  potable, bathing, washing, and lawn/garden
         watering;
     4.   Environmental - ground-water recharge or discharge, fish and wildlife
         propagation, unique areas; and
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                                                      OSWER Directive 9481.00-6C


     5,    Recreational - fishing, swimming, boating, and other contact uses.

     The permit applicant should examine pertinent aspects of both ground water
and surface water uses. Both the current uses and the possible future uses of the
water resources should be  discussed.   The specific type of ground-water use
information is described in the following section,

Ground-Water Usej

     It should  be obvious that ground-water use can be critical in the setting of
ACLs at a facility. Facilities that are contaminating or have contaminated ground
waters should examine local ground-water  uses  if their demonstration  is
attenuation-based.

     The U.S. EPA has developed a Ground-Water Protection Strategy (U.S. EPA,
1984a) that states that ground  water should be protected to its highest beneficial
use. Three general classes of ground water a re recognized;

     Class!:    Special ground waters  are those that are highly vulnerable to
              contamination  because  of the hydrological characteristics of the
              area under which they  occur and that are also characterized by
              either of the following two factors;

              a)   Irreplaceable-no reasonable alternative source of drinking
                   water is available to substantial populations, or
              b)   Ecologically vital-the aquifer provides the base flow for a
                   particularly sensitive ecological system that, if polluted, would
                   destroy a unique habitat.

     Class II:   Current and  potential sources of drinking water and waters with
              other  beneficial uses including all other ground  waters that are
              currently used or potentially available for drinking water or other
              beneficial uses.

     Class III:  Ground waters not considered potential sources of drinking water
              and of limited beneficial use are those that are heavily saline, with
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                                                     OSWER Directive 9481.00-6C


              total dissolved solids (JDS) levels over 10,000 mg/1, or are otherwise
              contaminated beyond levels that allow cleanup using methods that
              are reasonably employed in public water system treatment. These
              ground waters also must not migrate to Class I or II ground waters
              or discharge to surface water that could cause degradation.

     Facilities that are contaminating or have the  potential to contaminate Class I
or Class II ground waters should incorporate human health factors (see Chapter IX)
into their ACL demonstration because these resources are either potential or
current sources of drinking water. If the ground water is Class III, then health- based
concerns may be secondary to environmental concerns in the setting of ACLs. ACLs
in Class III ground water will be assessed on a case-by-case basis.

     The permit applicant should discuss the ground-water use in the vicinity of the
facility in terms of these  three classes or other appropriate State-approved
classification schemes.  The Agency's Office  of Ground-Water Protection is
developing guidance containing  specific criteria for designation of ground water as
Class l II, or III. These draft Guidelines for classifying ground water were available in
December 1986.  Until this guidance is finalized, we recommend only conservative
use of the "unuseable" criterion as a basis for an ACL

     Information from the State and/or local government as to the beneficial use of
the ground water should be included if the ground water has been  classified.
Otherwise, the permit applicant should have its ground-water classification data
reviewed by the State. When ground water has been classified on a State, regional,
or local level, this classification  should be re-evaluated and verified  using site
specific data. The State's review should be included in the ACL demonstration,

Surface Water Uses

     Surface water uses  should  be discussed  by the  permit applicant if
contaminated ground water  can migrate to surface waters.  The previous chapter
on proximity of surface waters should  aid in  deciding which water bodies are of
interest.  If no surface water impacts are likely, then the data discussed in this
section do not have to be submitted.
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                                                     OSWER Directive 9481,QO-6C


     The established guidelines, criteria, and/or standards for each water body
identified in Chapter V! should be examined.  The permit applicant should list in a
table the designated use of each  water body, a citation of the  local, State, or
Federal regulations  governing  the  use,  and the  agency responsible for
implementing the regulation.  The following general use categories should be used
by the permit applicant in preparing the table:

     1.   Drinking water source (including other domestic uses),
     2,   Fish and wildlife propagation area,
     3.   Industrial or agricultural water source,
     4.   Area of special ecological concern, and
     5.   Recreational area.

     The surface water use information will aid in determining appropriate ACLs by
identifying surface water exposures that can occur. The data gathered to fulfill the
requirements of this section  will be used to prioritize the likely exposure pathways
and  to determine whether  human health and  environment  factors should be
assessed in further detail (see Chapters IX and X),
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                                                    OSWER Directive 9481 .QQ-6C
                              CHAPTER VIII

         EXISTING QUALITY OF GROUND WATER AND SURFACE WATER,
                 AND OTHER SOURCES OF CONTAMINATION
                     (40 CFR 264.94(b)(1 }(vi) and (2)(vii))
     In order for "benchmark" levels of contamination to be set, the background
levels of hazardous constituents in the ground water should be determined in every
ACL demonstration. If surface water exposure to the ground-water contaminants is
part  of  the  ACL demonstration, the  background levels of the ground-water
contaminants in the surface water must also be determined. If the ground water
and surface water sampled for background levels appear to be contaminated, the
facility owner or operator  should  examine the possibility of  other  sources of
contamination  in the vicinity of the facility.  This chapter discusses the type of
background water quality data that should be submitted in an ACL demonstration
in  order to  adequately assess the cumulative impacts associated with  any
contamination emanating from the facility.

Background Water Quality

     For ACL purposes, background water quality is the quality that would be
expected to be found if the facility was not leaking contaminants.  Careful planning
must be used in deciding where representative background water samples should
be taken. Under Section 264.97, the regulations specify a procedure for establishing
background levels for hazardous constituents for purposes of setting ground-water
standards.  Essentially, background monitoring  wells must yield ground-water
samples  from the uppermost aquifer that represent the quality of ground water
that  has not been affected  by leakage from a facility's regulated unit. For most
sites, this is an upgradient area that can  be determined readily from the water level
data. The permit applicant is directed to the Draft RCRA Permit Writers' Manual for
Ground-Water Protection (U.S. EPA, I983a) and the RCRA Ground-Water Monitoring
Technical Enforcement: Guidance Document (U.S. EPA, 1986a) for further guidance
on ground-water monitoring and station locations.  Background surface water
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                                                    05WER Directive 9481.00-6C
quality must be assessed only in cases where surface waters receive contaminated
ground-water discharges (see Chapters VII and X).

     The permit applicant should submit a site map that identifies the location of
background  sampling stations and monitoring wells,  and the direction  of  both
stream flow  and  ground-water movement  Any flood discharge pathways and
directions should also be shown on the site map.

     The permit applicant may find historical ground-water monitoring studies and
ambient surface water  monitoring  programs  to be useful when assessing
background  water quality.  The U.S. Geological Survey, U.S. EPA, State, and  local
environmental program  offices can be good sources of  historical  data.  The
background concentrations in both ground water and surface water of constituents
for which ACLs are  being proposed should be included in a summary table.  The
uppermost aquifer and any surface water bodies that receive contaminants should
be listed separately.  If additional monitoring studies are necessary for determining
background  water quality, the  EPA Regional Office may assist by reviewing the
monitoring work plans. Regardless of the source of the background water quality
data, the permit applicant should submit quality assurance and quality control
information on  sample collection, sample  analysis, well  construction,  and
environmental conditions. Documents from which any data were taken should be
available for review if they are requested by the permit writer.

Ground-Water Contamination Sources

     The permit applicant  should investigate other sources of ground-water
contamination if background monitoring wells exhibit contamination and the ACL
demonstration is based on attenuation arguments. If no contamination is found, or
the POE is set at the POC, the permit applicant can omit the following discussion
and  proceed to the  surface  water discussion.  The types of upgradient pollution
sources and the impacts of the contamination on ground-water use are important
and should  be considered.  Identifying potential pollution sources is necessary in
order to assess the cumulative impact of pollution sources on human health and the
environment The following  potential pollution sources should  be identified within
a five kilometer radius of the site;
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                                                    OSWER Directive 9481.00-6C


     1.   Other RCRA facilities and Superfund sites,
     2.   Solid waste management units,
     3.   Industrial areas,
     4.   Deep well injection sites, and
     5.   Agricultural areas.

     Likely  sources of contamination should be  delineated on  a  map with an
appropriate scale. The distance of each source from both the  facility and  the
upgradient  monitoring wells should be discussed.  Available ground-water data on
any of the identified sources should be submitted and discussed.  Some areas may
have hazardous constituents present  in the ground water because of natural
processes occurring in the ground water. For example, some metals  may be found
at fairly high levels in certain ground waters. However, natural sources of synthetic
organic compounds  (e.g., chlorinated solvents) are not expected. If  synthetic
organic compounds are found in background samples, then the permit  applicant
should attempt to identify the source of contamination.

     The  water-use impacts from the contamination should be discussed by the
permit applicant if  upgradient ground  water  is  impaired by any source of
contamination. In Chapter VII  of this guidance, the current and future uses of
ground water are discussed in more detail.

Surface Water Contamination Sources

     The permit  applicant should examine other sources of surface water
contamination if the applicant's facility discharges to a surface water resource and
detectable quantities of  contaminants are found  in  the  surface  water,
Consideration  should be given to  both point  and nonpoint sources  of
contamination. Any point sources of pollutant loading to surface waters should be
identified on an appropriately scaled map. The point sources should include:

     1.   Discharges from industrial facilities,
     2.   Discharges from Publicly Owned Treatment Works (POTW), and
     3.   Past waste discharges,
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                                                     OSWER Directive 9481.00-6C


     The permit applicant should submit a table that includes the name of each
point source and the water body into which the point source discharges. The NPDES
permit number of each point source should also be included in this table.  If they are
available, the discharge rate, load allocations, permit discharge conditions, and
mixing zones should be provided and discussed. The applicant should focus these
discussions around the impact of the facility's discharge on these factors.

     Any nonpoint sources of pollution to surface waters that may affect the ACL
decision should  also be discussed. The permit applicant should submit information
on;

     I.   Urban storm run-off,
     2.   Agricultural run-off,
     3.   Ground-water infiltration, and
     4.   Other RCRA facilities and Superfund sites.

     Actual monitoring  data may  be submitted  along with loading  model
calculations, if they are applicable.
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                                                    OSWER Directive 9481.00-6C
                               CHAPTER IX

                         POTENTIAL HEALTH RISKS
                     (40 CFR 264.94(b)(1)(vii) and (2)(viii))
     A health risk assessment should be included in an ACL demonstration if human
exposure to the ground-water contaminants is likely. The applicant need not assess
possible health risks in detail if the probability of exposure can be shown to be quite
low; such a case may arise if the point of exposure is set at the point of compliance.

     The purpose of the health risk assessment is to determine allowable human
exposure concentrations at a point of exposure for the constituents for which ACLs
are requested. These allowable exposure concentrations can be proposed as ACLs
or they can be used as a basis to calculate the ACLs at the point of compliance. When
determining potential health risks, certain assumptions are usually made when
complete data on  specific human effects are  lacking.  Both the information
necessary to sufficiently support proposed allowable exposure concentrations and
the areas where assumptions may be necessary are discussed in this chapter.  The
applicant may find the EPA document Superfund Public Health  Evaluation Manual
(U.S. EPA, I986b) useful in making these determinations.

     There  are four components to an evaluation  of health risks.  An exposure
assessment is the first component of a health risk assessment. The exposure analysis
must identify and describe the current and potential human exposure pathways.
The second component, usually  referred to as hazard identification,  involves a
qualitative assessment of whether or not a chemical poses a hazard to humans.  The
third component, the dose-response assessment, attempts  to  quantitatively
describe the expected human response to a given dose of a hazardous constituent,
typically relying  heavily on data  from long-term animal studies.  The final
component is the risk characterization step. For purposes of developing ACLs, this
step involves the integration of the three  previous  steps to determine allowable
human exposure levels for the ACL constituents.  Depending on the results of the
environmental risk analysis described in Chapter X, the allowable human exposure
levels can be used as the ACLs or as the basis to calculate the ACLs.
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                                                     OSWER Directive 9481.00-6C
Exposure Assessment

     The exposure assessment should follow the Agency's final guidelines (U.S.EPA,
I986c).  The types of likely human exposure pathways that should be investigated
include;

     1,   Drinking water exposure from either a ground-water or a surface water
         source,
     2.   Ingestion of contaminated food (e.g., aquatic organisms, agricultural
         products), and
     3.   Inhalation of volatile compounds.

     The type of information needed to satisfy the health risk requirement depends
on the exposure pathway.  As an example,  if the facility  property boundary is
located adjacent to a surface water body that is a source of drinking water and a
sustained fishery, and the  contaminated ground water is discharging into this
surface water body, then the health risk information must  be based on exposure
from the consumption of contaminated ground water and  aquatic organisms. In
this case, the Ambient Water Quality Criteria for the protection of human health
from the consumption of contaminated water and aquatic organisms could be
proposed directly as the  ACLs (i.e., POE = POC). If an exposure pathway is from a
ground- water source of potential  drinking  water, the health assessment  must
address the consumption of contaminated drinking water.  In this case, the health-
based drinking water levels could be proposed as the ACLs.

     The inhalation exposure pathway should be considered in cases where volatile
compounds are either likely to volatilize from the contaminated ground water
during  use  (e.g., during  showering) or can be expected to penetrate subsurface
structures  such as  basements.   The permit applicant  should comment on the
probability  of the occurrence of these two types of exposures. The applicant will
have to address inhalation  in the health assessment in those situations where the
use of ground water or the presence of subsurface structures allows for probable
exposures.  It should be noted that the Agency is currently  examining air releases
from hazardous waste facilities. If standard inhalation assumptions are developed,
they may be appropriate for ACL decisions concerned with the inhalation pathway.
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                                                    OSWER Directive 9481.0Q-6C


     The location of the potential points of exposure is discussed in Chapter I. The
potential point of exposure to the ground-water contaminants is assumed to be at
the facility's waste management boundary, the plume boundary, or the property
boundary for most cases in which an ACL application is being prepared,

     If the applicant is proposing that the POE be at the facility property boundary
and  there are drinking water wells nearby, or some contaminants will be
discharging into a surface water body, then the possibility of multiple exposures
should be considered. For instance, if some members of the local population work-
in a factory where they are exposed to substance X, and the applicant is proposing
an ACL for this substance with the POE at the facility boundary, the applicant should
account for that workplace exposure in determining an allowable dose for the
population.   Similarly, if the  potentially  exposed population uses water that
contains some  naturally occurring compounds, the  interaction of ambient
constituents and the  constituents for which the ACLs are proposed should be
accounted for in the ACL demonstration.

     If any population or subgroup is or will be exposed to the ACL constituents,
the cumulative effect of multiple exposures should be accounted for whenever
possible. The likelihood of such  exposure occurring under the Agency's ACL policy is
small, but in some situations this may be a factor of concern.  The National Center
for Health Statistics, U.S. Department of Health and Human Services, may be a good
source of information on sensitive populations or individuals.

Hazard Identification

     The two principal sources of  data for determining hazard  potential are
epidemio- logical studies and experimental animal studies. The permit applicant is
responsible for providing  information  on health effects of  the hazardous
constituents present in the ground water for which ACLs are requested. This can be
as simple as providing the Agency maximum contaminant levels (MCLs), reference
doses (RfDs), or risk specific doses (RSDs) for the ACL constituents. Appendix D of
this document contains a survey sheet on health effect factors that can be used to
summarize the toxics information.
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                                                     OSWER Directive 9481.00-6C


     If an ACL constituent has no MCL, RfD or RSD, then the applicant should
perform  a comprehensive literature search for health effects data on that
contaminant. The applicant should distinguish between  ground-water
contaminants having threshold (toxic) and nonthreshold (carcinogenic) effects. The
permit applicant should discuss any other effects associated with the contaminants,
including odor and taste, mutagenic, teratogenic, reproductive, fetotoxic, and
synergistic or antagonistic effects.  A reference citation and a summary should be
submitted for each study that was used to determine the type of effect for each
contaminant.

     In the development of ACLs, the permit applicant may find that the grouping
of hazardous constituents is a useful simplification. The applicant  may investigate
health effects data developed for entire classes of compounds, such as polynuclear
aromatic hydrocarbons (PAHs), halomethanes, or polychlorinated biphenyls (PCBs),
as well as compound-specific data.  Grouping of constituents should follow a two-
step process.  First, the applicant should perform a qualitative assessment of the
constituents' physical, chemical, and toxkological  properties.   Second,  a
quantitative analysis should be performed to determine  the most hazardous
compound within each group identified in the first step. This step will be examined
in more detail in the dose-response section of this chapter.

     The qualitative assessment should include an initial screen  of the structure
activity relationships (SAR) of the constituents. Constituents with similar physical
and chemical structures may be initially grouped together. These groupings should
then be further evaluated on their toxicological effects.  The predominant adverse
biological effect for each constituent in each SAR group should be identified. The
final grouping(s) should contain constituents with similar physical and chemical
structures, and should result in the same toxic endpoints. This subgroup could form
the  basis for the exposure assumptions used in deriving  the  allowable
concentrations for the ground-water contaminants. All of this information should
be presented in tabular form to facilitate easy reference.

Dose-Response Assessment

     This assessment  attempts to  quantitatively describe the expected human
response to a given dose  of a hazardous constituent, typically relying heavily on
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                                                    OSWER Directive 9481.00-6C


data, from long-term animal studies. These animal studies are usually  based on
exposures at high dose levels, often orders of magnitude  higher than  doses
encountered by humans.  Therefore, mathematical models are used to estimate
allowable dose levels from low-dose extrapolations. The mathematical models yield
reference doses (RfDs) for toxic compounds and  potency factors  (PFs)  for
carcinogenic compounds.  The RfD refers to the amount of the chemical to which
humans can be exposed on a daily basis over long periods of time without suffering
an adverse effect. A PF represents, in most cases, the largest possible linear slope at
the 95%  upper confidence limit of low extrapolated doses that is consistent with
the dose- response data.

     If Agency-compiled data on threshold (toxic) contaminants are not available,
then the applicant can submit dose-response information  reflecting the acute,
subchronic, chronic, and "no-effect" levels for the threshold contaminants.  Body
surface area and weight, and absorption and excretion rates may  be assumed to
estimate equivalent oral doses based on data from inhalation or dermal exposure
studies,

     A conservative approach to risk assessment that includes groupings  of
compounds could reduce the amount of data needed to quantify potential human
health effects. The quantitative step for grouping compounds consists  of
identifying  the most potent compound in each group identified  in the hazard
identification step.  For toxic compounds, the  most potent compound would have
the lowest RfD. For carcinogens, the compound with the lowest RSD, or highest PF,
would be considered the  most potent.  This conservative number can then be
applied to each compound within the group.  It must be emphasized  that this
quantitative determination should only be performed after a qualitative assessment
of the chemical, physical, and toxicological properties of each compound has been
performed.

     As a simplified example of the grouping process, assume that an applicant's
contaminant plume contains PAHs. After analysis, the  PAHs are found to be
dibenzo(a,h)anthracene, benzo(|)fluoranthene,  benzo(a)anthracene,  benzo(b)-
flouranthene, and benzo(a)pyrene. Since all of these are suspected carcinogens and
their chemical structures are similar, these five could be qualitatively grouped.  A
literature search would reveal that benzo(a)pyrene is the most potent carcinogen,
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                                                    OSWER Directive 9481 .OQ-6C


and a RSD could then be obtained from EPA for this compound. The RSD could then
be applied to the other four PAHs to calculate allowable exposure levels.  To be
acceptable to the Agency, this example would require much  more supportive
information and a number of references.

Risk Characterization

     Allowable exposure concentrations can be derived by using MCLs or applying
appropriate exposure assumptions to established RfDs or PFs, or alternate dose
levels derived from the literature if established dose levels are not available.

     When deriving an ACL for those ground waters that are current or potential
sources of drinking water, MCLs set under the Safe Drinking Water Act  should be
examined for use in setting the allowable concentration level at the point of
exposure (POE),  In those  cases where a MCL does  exist for the  particular
contaminant, and the potential exposure route is human drinking water, the MCL
should normally be used as the allowable POE concentration.  If a MCL does not
exist for a hazardous constituent, then either RfDs or RSDs should be used to set the
allowable exposure levels.

     There are other circumstances where it may be necessary to apply an allowable
exposure level  other than the MCL at the POE. The circumstances depend on the
site-specific factors involved and include the following scenarios:

        Where there are multiple contaminants in the ground water at a site,
         individual contaminant levels may have to be set below the MCL in order
         to achieve an overall carcinogenic risk level in the range of 1CH and 10-7.

        Where drinking water is but one of the possible exposure routes.

In the first case, the permit applicant should examine the RSD  or RfD  value and
consider using some form of additivity to derive the appropriate POE concentration.
In the latter case, the MCL should be compared to the  allowable exposure levels for
the other potential receptors. The level at the POE should  be  set at the lowest
allowable exposure level in order to protect all potential receptors.
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                                                     OSWER Directive 9481.00-6C


     The permit applicant should use generally accepted standard factors in the
exposure assessment, some of which  are  listed in Appendix E.   The allowable
exposure level can be calculated for toxic compounds using the RfD and the
exposure assumptions of a 70 kg adult consuming two liters of water per day.  The
following  formula should be used to calculate  the allowable exposure
concentration;

              RfD Exposure level (mg/l)   =    RfD x 70
     A potency factor (PF) is used to estimate a risk specific dose for a hazardous
constituent concentration that corresponds to a particular statistical lifetime cancer
risk value. For example, a contaminant concentration corresponding to a lifetime
cancer risk of 10-6, assuming that a 70 kg adult consumes two liters of water per day,
is estimated by the following formula;

              RSD Exposure level (mg/l)      70 x 10-6
                                            2xPF

     In general, the Agency  has made decisions to allow concentrations of
carcinogens where the individual risk values have been within the range of IQ-4 to
IQ-7. In setting ACLs, the following factors should be considered in choosing a risk
level within the IQ-^to IQ-? range;

     I,    Other environmental health factors  borne by the affected  population,
          and
     2.    Level of uncertainty in the data base and models used in the risk analysis.

     As a general matter, a level of IO-6, the middle of the range, should be used as
the point of departure when proposing a risk level within the IQ-4 to IQ-? range for a
particular facility. Justification should then be provided for using  a different level
of risk.

     In order to account for cumulative impacts of the hazardous constituents for
which ACLs are requested, an assessment of the existing concentrations of the ACL
constituents in the  potentially affected ground water or surface water should be
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                                                     OSWER Directive 9481.00-6C


performed. This data is necessary to determine the total concentration of the ACL
constituents in the affected water resource, the health effects associated with the
concentrations, and the relative  exposure contribution of the ACL constituents
emanating from the site to the total exposure concentration. At a minimum, an
additive approach based on contaminants that produce the same adverse effects by
similar mechanisms should be used to estimate health effects from exposure to
mixtures of contaminants.

     The applicant should submit an  allowable health effects exposure level for
each ACL constituent. The health-risk  assessment should be based on conservative
health based numbers.  Table I lists the compounds for which RfDs and RSDs have
been derived by the U.S. iPA at the time of publication of this document (their
derivation is an ongoing process). The RfD summary sheets and the RSDs can be
obtained by contacting the Health Assessment Section, in the Office of Solid Waste
at the U.S. EPA in Washington D.C. (Phone number; 202-382-5219). If the applicant
uses less conservative  numbers  as a  basis  for the health risk assessment, the
applicant must submit information to justify the use of these numbers. As discussed
previously, the allowable exposure levels for a group of constituents can be based
on the toxicity of the most potent constituent within that group if such a grouping
is sufficiently justified. If sufficient toxicity information on any compound has not
been submitted, and the compound cannot be grouped, the concentration limit
will be set at the background level or at the maximum concentration listed in Table
1 of Section 264.94(a)of the regulations.
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                                                      OSWER Directive 9481.00-6C
                                  TABLE 1
                   A. CHEMICALS WITH POTENCY FACTORS
Acrylonitrile
Aldrin
Aniline
Arsenic
Benzene
Benzidene
Benz(a]anthracene
Benzo[a]pyrene
Bis(2-chloroethyl)ether
Cadmium
Carbon tetrachioride
Chlordane
Chlorinated ethanes
1,2-Dichloroethane
1,1,2,2-Tetrachloroethane
Chloroform
Chromium VI
DDT
Dibenzo(a,h)anthracene
3t3'-Dichlorobenzidine
1,1-Dichloroethylene
 (Vinylidene chloride)
Dichloromethane
 (Methylene chloride)
Dieldrin
2,4-Dinitrotoluene
1,4-Dioxane
Ethylene oxide
Hexachlorobenzene
Hexachlorobutadiene
3-Methylcholanthrene
4,4-Methyiene-bis-2-chIoroaniline
N-nitrosopyrolidine
Pentachloronitrobenzene
Pronamide
2,4,6-Trichlorophenol
Tetrachloroethylene
Trichloroethylene
Vinyl chloride
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                                                     GSWER Directive 9481.00-6C
                                TABLE 1 (continued)
                   B. CHEMICALS WITH VERIFIED REFERENCE DOSES
Acetone
Aldrin
Ally! alcohol
Antimony
Barium
Beryllium
Bis(2-ethy!hexy1)phthalate
Bromodichloromethane
Bromomethane
n-Butane
Carbon Disulftde
Carbon Tetrachloride
Chlordane
Chlorobenzene
Chlorodibromomethane
Chloroform
Crotonaldehyde
Cyanide (free)
2,4-D
DDT
D-n-butyiphthalate
1,2-Dichlorobenzene
Dichlorodifluoromethane
1,1-Dichloroethylene
2,4-Dichlorophenol
Diethylphthalate
2,4-Dinitrophenol
Disulfoton
Diphenylamine
Ethylacetate
Ethylbenzene
Ethyl Ether
Famphur
Fluoride
Heptachlorepoxide
Hexachlorobutadiene
Hexachlorocyclopentadiene
Isobutyl alcohol
Isophorone
Mercury (inorganic)
Methylene Chloride
Methanol
Methyl ethyl ketone
Methyl isobutyl ketone
Nitrobenzene
Pentachlorobenzene
Pentachloronitrobenzene
   (PCIMB)
Pentachlorophenol
Phenol
Pyridine
Silver
Styrene
1,2,4,5-Tetrachlorobenzene
Tetrachloroethylene
2,3,4,6-Tetrachlorophenol
2,4,5-Trichlorophenol
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                                                     OSWER Directive 9481.00-6C
                                CHAPTER X

               POTENTIAL DAMAGE TO WILDLIFE, VEGETATION,
                  AGRICULTURE, AND PHYSICAL STRUCTURES
                     (40 CFR 264.94(b)(1) (viii) and (2) (ix))

     In addition to risks to human health, environmental risks must be addressed in
an ACL demonstration.  Unless an ACL demonstration  is based on the  point  of
exposure at the point of compliance, and the nearest likely receptor is human, risks
to animals, plants, and structures resulting  from exposure to the  hazardous
constituents must be  considered.  This  environmental risk assessment involves an
exposure assessment and  an effects assessment.  This chapter  delineates the
information needed to perform the assessments of risks other than those to human
health.

     The initial step in assessing possible environmental impacts is to determine the
probable exposure pathways for hazardous constituents to reach environmental
receptors.  For ACL  purposes, the receptors of concern  include  wildlife and
vegetation in aquatic  and terrestial environments; agricultural crops, products, and
lands; and physical structures. The exposure assessment involves examining the
extent of the hazardous contaminant plume, and the location of receptors and
environments of concern.  The exposure assessment will result in delineation  of
likely exposure pathways. Information  submitted to fulfill requirements discussed
in previous chapters should be adequate to determine probable surface water and
terrestrial exposure pathways.  The permit applicant should examine the data
requirements of Chapters VI and VII before proceeding with  this chapter. The data
for assessing the effects of exposure of physical structures and agricultural crops,
lands, and products to the hazardous  constituents are  discussed in subsequent
sections of this chapter.

     The permit applicant must examine the potential impacts to all the receptors
discussed above if exposure to hazardous constituents is likely to occur.  Otherwise,
the permit applicant should discuss specific data that supports no probable
exposure as well as justify why the potential impacts assessment is unnecessary.
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                                                     OSWER Directive 9481.00-6C


     Generally, data on chronic toxicity levels of the hazardous constituents are
sufficient to characterize potential  environmental impacts.  However, chronic
environmental toxicity data may not be available for many waste constituents Sikely
to be the subject of ACL requests. In the absence of environmental toxicity data,
ACL  applicants may be able to argue  that a contaminant wilt have no adverse
environmental effects.  This argument could be based upon considerations of
exposure levels and the toxicities of similar chemical compounds. If environmental
receptors are actually being exposed to ACL constituents above chronic toxicity
levels, or above background levels if no chronic toxicity levels  are established, then
field assessments of the impacts can  be performed to support the proposed ACLs,
The types of field studies that should be carried out are discussed in  more detail in
the following sections.

Terrestrial Impact Assessment

     The quantification of  adverse terrestrial environmental effects is difficult.
However, examination of several environmental factors will provide  an estimate of
potential impacts to the environment  due to exposure to contaminated ground
water.

     Potential impacts to terrestrial  wildlife and vegetation can be assessed by
examining exposure and environmental toxicity factors.  The exposure assessment
involves determining whether the contaminated ground water at a facility has the
potential to impact any terrestrial environment.  The specific data necessary to
assess the exposure are discussed in Chapters II,  III,  and IV.  If there  is a likely
pathway for wildlife and vegetation to become  exposed to  contaminants, then
environmental toxicity factors should be examined. ACL applicants probably will
not need to address terrestrial environmental impacts in detail when there  are no
direct exposure routes between  terrestrial systems and ground water.  In these
cases, or when the POE is set at the  POC, the applicant can omit this section and
move on to the endangered species section of this chapter.

     The toxicity and bioaccumulation of hazardous constituents by terrestrial flora
and  fauna  should be examined  if exposure is likely. Terrestrial species  can be
exposed to toxicants either directly through assimilation  of or  contact with
contaminated ground water, or indirectly through food web interactions. Toxicants
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                                                      OSWER Directive 9481.00-6C


can  accumulate in exposed biota and  increase to levels that are lethal  or have
chronic effects. The permit applicant should perform a comprehensive literature
search  for toxicity and bioaccumulation values for the ACL constituents and their
degradation products.  The information should be summarized  in a table that
includes information on the toxicants, the test species, the specific effects, the effect
levels, the bioaccumulation potential, and the reference. The permit applicant can
base the potential terrestrial toxicity assessment on the most toxic constituent
within  a group of constituents if appropriate groupings of constituents exist for a
facility. If literature information is sparse or non-existent, then a  more thorough
analysis of potential environmental impacts may be necessary.  This analysis could
be based on consideration of exposure levels and the toxicities of  similar chemical
compounds. Bioassays could also be used to support the proposed ACLs; however,
techniques for performing bioassays on terrestrial ecosystems are not an exact
science, and they involve considerable time and expense to carry out. If the permit
applicant plans to perform bioassays, he/she should consult U.S. EPA  (1984d)  for
more discussions on the use of bioassays to characterize chemical waste sites.

     If terrestrial environments are presently being exposed to contaminants above
chronic toxicity  levels, or  above  background levels for constituents without
established chronic toxicity levels, then field studies can be used to support the
proposed ACLs.  The permit applicant should examine the dominant terrestrial
habitats in the vicinity of the facility. Evidence of any stressed vegetation should be
documented and can be supported with aerial infrared photography or ground
photography and vegetation surveys. Both a topographic map and low level aerial
photographs delineating any stressed terrestrial environments should be submitted.
Vegetation survey data on species and abundance of macrofloral plants, usually
trees and shrubs, should be collected. However, if the dominant habitat is an alpine
or prairie environment, grasses and other plants should  be examined. The
community floral diversity can be  calculated  from the species  information.
Discussions of  diversity  should include species richness and community structure.
This diversity information should be summarized in tabular form.  Any differences
between the background and affected habitats should be explained. The selection
of the  background habitat should be carefully planned so as to ensure that it  is
outside the influence  of the facility.   Sampling  protocols for diversity and
productivity studies along with  the data collected and a  complete discussion of
results should be submitted by the applicant.
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                                                     OSWER Directive 9481.00-6C
Endangered Species Impact Assessment

     Endangered and threatened species near the facility should be identified. The
facility owner or operator should contact the U.S. Department of the Interior, Fish
and Wildlife Service, for a current list of endangered or threatened species in the
vicinity of the facility. If any endangered or threatened species are in the area, then
the potential impacts of the contaminated ground water on the species, including
critical habitat impacts, should be discussed.  A table should be submitted that lists
the endangered and threatened species.

Aquatic Impact Assessment

     The permit applicant should assess potential aquatic environmental effects by
examining exposure  factors.  The exposure assessment for surface  waters was
discussed in Chapters VI and  VII.  Ground-water contaminants, flow direction,
discharge areas, and proximity of surface waters are important considerations. The
permit applicant should examine potential pathways of contaminant migration to
surface waters. If exposure to contaminants is likely, then aquatic toxicity factors
should be examined.  The Office of Water, U.S. EPA, has published a document that
the applicant and reviewer should find useful in evaluating aquatic impacts {U.S.
EPA, 1985a). If no hazardous constituents can reach surface waters, then the permit
applicant should provide supporting evidence of this fact.  The aquatic impact
assessment can be omitted if sufficient evidence is available to support a claim of no
surface water exposure.

     ACLs may be established based on contaminant discharge into a surface water
body. This is allowable only where the contaminant plume has already  reached the
surface water  body and the  constituents  do not cause a  statistically significant
increase in contaminant levels over background in the surface water concentrations.
That is, after accounting for the inherent variation  in the sampling and  analysis
data, the release of a constituent into a surface water body should not cause an
increase in the  background surface water concentration of that constituent.

     In order to make this determination of statistical significance, samples of
surface water should be taken during a period in which the flow (for rivers and
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                                                     OSWER Directive 9481 .QO-6C


streams) or standing volume (for ponds and lakes) of the water body is near average
conditions for the specific season.  It may also be necessary to collect sediment
samples to make this determination. The  permit applicant should determine the
flow of the surface  water at or  near the time of sampling and  supply this
determination, the actual monitoring data, and historical  information that
demonstrates that the flow at the time of sampling was near the seasonal average.

     Surface water samples should be collected within the discharge zone of the
ground- water contaminant plume. The discharge zone will have to be determined
on a site-specific basis, and is dependent on the local hydrogeology. Since ground-
water movement near surface water bodies can  be quite complex, some of the
initial samples may have to be collected adjacent to the  facility as well as some
distance downstream in order to identify the discharge zone. If, upon sampling in
the discharge zone, the levels of the constituent of concern are not detectable, a
statistical comparison of sampling data does not need to be  performed. However, if
the discharge levels are detectable, an appropriate statistical procedure should be
used to compare the constituent concentration in the  discharge  zone to the
constituent concentration  upstream in the surface water body. The Agency expects
to develop further guidance on appropriate statistical techniques for making these
comparisons.  The background concentration should be determined  by sampling the
surface water body in an area that is not expected to be affected by the RCRA
facility, and is also not near other sources of contamination.

     If a RCRA facility receives an ACL based upon the release of a contaminant into
a surface water body, the facility's permit should contain a requirement for periodic
surface water sampling. The sampling frequency  should be determined on a site-
specific basis  to assure that the constituent  concentration does not surpass a
statistically significant level over background in that surface  water body.

     If it is found that the ground-water contamination discharge  is not causing a
statistically significant increase over background in the surface water body, then an
ACL for an operating unit may be set at the contaminant levels currently at the
point of compliance.  However, if the ground-water contaminant  plume contains
much higher levels of contamination (i.e., hot spots) than have already reached the
surface water, these hot spots may have to undergo some form of corrective action,
so as to not violate the standard of statistical significance.  To meet this standard,
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                                                     OSWER Directive 9481.00-6C
appropriate ground-water contaminant plume management techniques will have
to be selected on a site-specific basis.

Agricultural Impact Assessment

    The potential impacts of ground-water contamination on agriculture should
be examined when the POE is not set at the POC, Exposure pathways, crop impacts,
and livestock impacts should be  included in the  assessment.  The exposure
assessment is used to determine if there are  likely  pathways for ground-water
contaminants to reach any agricultural lands or products. As part of the exposure
assessment, data on the agricultural land uses near the facility should be submitted
by the permit applicant  Specific uses such as  row crops, rangeland, grazing, tree
farming, and timber should be depicted  on an appropriately scaled map.  A table
that lists acreages of the specific uses should also be submitted.

    The potential exposure  pathways that the permit applicant should examine
include shallow ground  water, ground-water irrigation, and surface water
irrigation.  The shallow  ground-water flow direction, aquifer attentuation
mechanisms, and ground- water elevation  are important characteristics that are
used to determine exposure  due to direct crop uptake of ground water. These
topics were discussed in Chapters III and IV and must be evaluated by the permit
applicant during this exposure assessment. The irrigation wells near the facility
should be identified and  delineated  on a map employing the appropriate scale.
Chapter Vll lists specific use information that is necessary for this assessment of the
irrigation wells. Surface waters that are used for irrigation and have the potential
to be impacted by ground-water contamination must be evaluated (see Chapter VI).
The current and projected irrigation withdrawal rates should be determined from
each irrigation source.

    Agricultural  crop impacts should  be assessed by  the permit applicant if
exposure to ACL constituents is likely to occur.  The following potential agricultural
impacts should be assessed:

     1.    Direct crop impacts and reduced productivity, and
    2.    Bioaccumulation of contaminants.
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                                                     OSWER Directive 9481.QO-6C


     The permit applicant may be able to  estimate the expected  crop and
productivity impacts resulting from exposure  to hazardous contaminants in the
ground water by examining the literature.  Literature values that exist on crop
impacts from exposure to the contaminants should be summarized in a  table that
includes the contaminant, the crop tested, the effect  level, the bioaccumulation
potential, and the specific reference. The U.S. Department of Agriculture (USDA)
can be a source of crop effects information and testing  methods.   If  literature
information does not exist and crops are likely to be exposed  to ACL constituents,
the ACL demonstration may be denied and the ground-water standards may be set
at background levels. However, the permit applicant has the opportunity to carry
out experiments to estimate potential crop impacts. The applicant should be aware
that standard experimental protocols do not exist and that all data to support the
ACL demonstration must be submitted in a timely fashion. If tests are performed by
the permit applicant, all protocols and data should be submitted.

     The permit applicant  should describe potential  livestock impacts that may
occur from direct and indirect exposure to contaminants found in the ground water.
Direct exposure would include livestock contact  through watering.  Indirect
exposure could include contact during animal grazing and foraging. The applicant
should submit any available information on potential livestock impacts of the ACL
contaminants. If literature  values exist, the information should be summarized in
tabular form and include the factors discussed above  in the crop impacts section.
The USDA may have information on this topic. Permit applicants are not normally
expected to carry out experiments on exposed livestock because of the  high costs
and long-term nature of such experiments.  If exposure  modeling shows that
livestock  exposure occurs and sufficient literature  information does  not exist to
support an ACL, then the concentration limit may be set at background levels.

Physical Structure Impact Assessment

     Physical strucures can be adversely affected by hazardous constituents in the
ground water. The situation at Love Canal, NY, where toxicants entered basements
of homes, is just one example. The determination of potential damage to physical
structures in the area around the facility requires the examination of exposure
pathways, waste characteristics, environmental factors, and construction materials
and techniques.
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                                                     OSWER Directive 9481.00-6C
     Determining the potential exposure of the physical structures to waste con-
taminants requires identification of physical structures in the area and exposure
pathways.  All manmade structures including buildings,  buried cables and  pipes,
railroad beds,  roads, parking areas, and machinery near the facility should be
identified and delineated on a vicinity  map if they are  likely to be reached by
contaminants.  The possible exposure pathways of the ground-water contaminants
to the physical structures should be identified. The permit applicant should refer to
Chapter  IV to determine what information should be submitted  in  order to
determine contaminant migration  pathways.  If the exposure  assessment
determines that physical structures  are  likely to  come  in  contact  with ACL
contaminants,  then the potential  effects of the contaminants on the physical
structures should be examined.  Otherwise, the permit  applicant needs only to
explain why the assessment is not needed.

     The hazardous constituent characteristics of primary concern for the physical
structure impact  assessment are reactivity, ignitability, and migration  potential.
Two important categories of reactive  chemicals are  corrosives and solvents. The
ground-water contaminants that fall into either of these two categories should be
listed in a table by the permit applicant.  The potential effects of these compounds
on building materials such  as concrete, iron, steel, plastic, wood, asphalt, and
limerock  should  be identified and summarized in  a table.  The ability of the
contaminants to  permeate these materials should also be discussed.  The permit
applicant should submit data on the flammability  and ignitability of the ACL
constituents that have the potential to  permeate subsurface structures.  Volatile
organic compounds should be given special attention since they have been
implicated in sewer-line explosions.
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                                                     OSWER Directive 9481.00-6C
                                CHAPTER XI

        PERSISTENCE AND PERMANENCE OF POTENTIAL ADVERSE EFFECTS
                      (40 CFR 264.94(b)(1)(ix) and (2)(x))
     Many of the chapters in this guidance document discuss informational needs
for ACL demonstrations that are related to the persistence and permanence of the
ACL constituents. The general ACL policy will be to assume a worst case approach of
no degradation of the ACL constituents, unless information  on the persistence  of
the ACL constituents in the environment is submitted. Similarly, if a potential exists
for exposure to the ACL constituents to result in adverse effects, the adverse effects
will be considered  permanent  unless they are generally  accepted to be not
permanent or information is submitted by the permit applicant to justify that they
are not permanent.  This chapter describes the information that is needed  to
characterize  the persistence of the ACL constituents in the environment and the
permanence of their adverse effects if exposure occurs.

Persistence

     Information on the persistence of the contaminants in the environment should
be discussed in varying detail, depending on the basis of the ACL demonstration.
The applicant should discuss the process by which each ACL constituent will degrade
if the demonstration is attenuation-based. The processes should  be discussed from
a ground-water perspective, a surface water perspective, or any other environments
or combination of environments depending on the site-specific situation.
Contaminant  degradation in ground water  occurs predominantly through
chemically mediated processes. If the applicant is claiming attenuation as a means
of reducing the contaminant concentrations, the applicant must discuss the types  of
processes that may occur.  These  processes can include biodegradation, hydrolysis,
photolysis, oxidation, reduction, adsorption, dispersion, or precipitation, all  of
which were discussed in Chapter II.  The various degradation products, if known,
should also be discussed.
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                                                    OSWER Directive 9481.00-6C
     If surface water exposure is involved, bioeoncentration and biotransformation
processes are important.  Bioeoncentration  factors are important for evaluating
human intake levels of contaminants from consumption of aquatic organisms and
for assessing the permanence of ecological effects. Bioeoncentration factors can be
derived by experimentation or calculation or are provided in the literature. The
applicant should provide Justification for the use of any bioeoncentration factors,
Biotransformation is primarily carried out by microorganisms in the surrounding
media, A lag time or acclimation period usually occurs before the biodegradation
process begins.  If biotransformation  is used in  the ACL demonstration, the
applicant should determine  whether the microbes are acclimated to the
contaminant. A discussion of biotransformation and  the use of bioeoncentration
factors can be found in U.S. EPA (1980) and U.S. EPA (1979).

     If degradation processes are used in the ACL demonstration, the process rates
should be calculated.  Whether the mechanism of degradation is biological  or
chemical, all rates describing the  processes should be included in the ACL
demonstration.  The parameters, coefficients, and assumptions used by the permit
applicant to calculate  the degradation rates for  each contaminant should  be
submitted in tabular form.

Permanence

     Information on the permanence of the adverse effects resulting from exposure
to the ACL constituents will be  required only if the ACL demonstration is based  on
attenuation mechanisms.   This information should  be  included in the
demonstration's health  risk assessment (Chapter IX)  and  the environmental risk
assessment (Chapter X), Permanence information is necessary in order to give the
permit reviewer some idea of the long-term effects  associated with exposure to
each ACL constituent as well as a better understanding of which ground-water
contaminants are of most concern.

     Many  environmental systems exhibit  a high degree of  resiliency.   If the
damage is limited to individual organisms within the population and the gene pool
is  not irreparably  depleted, the environmental damage may  be reversible.
However, if irretrievable habitat change has occurred,  then environmental damage
may be permanent. The permit applicant should  examine the literature on the
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                                                     OSWER Directive 9481.00-6C


contaminant's environmental effects to determine the permanence of likely
ecological impacts. Many biological evaluations can be performed to examine the
resiliency and stability of an environmental system.  Some examples include tissue
analyses to determine bioaccumulation, diversity and recovery studies to estimate
elasticity, and intolerant species analyses to determine the degree of degradation.
A detailed explanation of these  studies is presented  in the Technical Support
Manual:   Waterbody^Surveys and Assessments for Conducting  Use Attainability
Analyses (U.S. EPA, 1983d). The permanence of the adverse effects is related to the
contaminant's concentration level at the point of exposure. The  acute and chronic
effects levels for each contaminant should be determined if the ACL demonstration
is based on attenuation considerations. The  effects should  be classified as either
reversible or irreversible.
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                                                    OSWER Directive 9481.00-6C
                               CHAPTER XII

                       SUMMARY AND CONCLUSIONS
     The factors involved in preparing and supporting an ACL demonstration were
discussed in the previous chapters. Chapter I outlined the Agency's policy quidelines
for implementation of the ACL process.  Information on each  of the  criteria
discussed in this guidance document is not required in every ACL demonstration
because every RCRA facility is unique with different environmental properties and
waste characteristics.  Therefore, each ACL demonstration based on attenuation
mechanisms must reflect site-specific conditions. Much of the information required
for an ACL demonstration may be taken from the facility's Part B permit application.
This guidance document points out when additional information that satisfies the
criteria should be submitted and  also when it may not be necessary. However, the
burden  is always on the permit  applicant to justify all arguments used  for not
submitting information on specific criteria. Appendix B contains a list of tables and
figures that can be submitted as  part of an ACL demonstration. The use of these
tables and figures will greatly facilitate the review of the ACL demonstration by the
permit writers,  Appendix B also contains a summary outline of the information that
can be used to support an ACL demonstration. The permit applicant should be sure
to submit all data necessary to fulfill the information requirements outlined in this
Appendix.

     Once the data have been submitted by the permit applicant, the permit writer
must assess the quality of the submitted information and determine the allowable
concentrations of contaminants at the point of exposure, and the ACLs at the point
of compliance.  In  many cases, the permit writer  will  have to use professional
judgement in determining the adequacy of the submitted information.

     The Agency will indicate its  decision on  the merits of the ACL demonstration
when it issues the  permit. The  permit  will  contain a  ground-water protection
standard (GWPS) for each ground-water contaminant The GWPS will contain either
background values or the National Interim Primary  Drinking Water Regulation
limits listed in Table I of Section 264.94{a) (if EPA rejects the ACL demonstration), or
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                                                    OSWER Directive 9481.00-6C
it will contain ACLs.  If any constituent exceeds its ACL, corrective action will be
necessary. The ACL then becomes the benchmark for the intensity and duration of
the corrective action.

     As part of the ground-water protection standard, an ACL is in effect during the
compliance period.  The compliance period is the number of years equal to the
active life of the waste management area, including the closure period. If, at the
end of the compliance  period, the owner or operator is engaged  in a  corrective
action program, the compliance period is extended until the owner or operator can
demonstrate that the GWPS, which may contain ACLs, has not been exceeded for a
period of three consecutive years.

     Once the ground-water protection standard has been set in the permit, the
permittee can only seek ACLs through permit modifications under the procedures
outlined in 40 CFR Part 124. Such modifications are always major and the  burden of
proof to  justify  the variance is on the applicant.  If a facility owner or operator
violates the ground-water protection standards,  he or  she cannot  postpone
corrective action in order to argue for ACL changes.
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                                                     OSWER Directive 9481.00-6C
                               CHAPTER XIII

                               REFERENCES
Bouwer, H., 1978. Ground-water Hydrology. McGraw Hill, New York, NY.

Brady, N.C., 1974. The Nature and Property of Soils. The MacMillan Company, New
York, NY.

Freeze, A.R. and J.A. Cherry, 1979. Groundwater. Prentice-Hall Inc.,
Englewood Cliffs, NJ.

Kruseman, G.P. and N.A. De Ridder, 1979. Analysis and Evaluation of Pumping Test
Data. International Institute for Land  Reclamation and  Improvement Bulletin  11,
Wageningen, The Netherlands.

Ruffner, J.A., 1980. Climates of the States. Gale Research Company, Detroit, Ml.

Ruffner, J.A. and F.E. Blair, 1981. The Weather Almanac. Gale Research Company,
Detriot, Ml.

Todd, O.K., 1980. Ground-water Hydrology. 2nd Ed., John Wiley and Sons, Inc., New
York, NY.

U.S. Environmental Protection Agency, 1979. Water-Related Environmental Fate of
129 Priority Pollutants Volumes I and II.  EPA-440/4-79-Q29a and b, Washington, D.C.

U.S. Environmental Protection Agency,  1980. Water Quality Criteria
Documents; Availability. Federal Register 45:79318-79357, November 28,1980.

U.S. Environmental Protection Agency, 1982a. Subpart F-Ground-water Protection.
Federal Register 47:32350-32356. July 26,1982.
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                                                    OSWER Directive 9481.QQ-6C
U.S. Environmental Protection Agency, 1983a. Draft RCRA Permit
Writers' Manual for Ground-water Protection. Contract No. 68-01-6464, October 4,
1983.

U.S.  Environmental Protection Agency,  1983d. Technical Support Manual:
Waterbody Surveys and Assessments for Conducting Use Attainability Analyses.
Office of Water Regulations and Standards, Washington, D.C, November, 1983,

U.S. Environmental  Protection Agency, 1984a. Ground-Water Protection Strategy.
Office of Ground-Water Protection, Washington, D.C. August, 1984.

U.S.  Environmental Protection Agency, I984b,  Hazardous  Waste Management
System; Ground Water Testing and Monitoring Activities; Proposed Rule. Federal
Register 49: 38786-38809, October I, I984.
U.S. Environmental Protection Agency, 1984d. Characterization of Chemical Waste
Site Contamination and Its Extent Using Bioassays (Draft Report). Contract No. DE-
AC06-76RLO 1830, December, 1984.

U.S. Environmental Protection Agency, 1985a. Technical Support
Document for Water Quality-based Toxics Control.  Office of Water, Washington,
D.C.

U.S. Environmental Protection Agency, 1986a. RCRA Ground-Water
Monitoring Technical Enforcement Guidance  Document, Washington, D.C.,
September, 1986.

U.S. Environmental Protection Agency, 1986b. Superfund Public Health Evaluation
Manual. Washington. D.C., October, 1986.

U.S. Environmental Protection Agency, 1986c. Final Guidelines for
Estimating Exposures.  Federal Register 51: 34042-34054, September 24,1986.

Walton, W.C,  1970.  Ground-water Resource Evaluation. McGraw-Hill Publishing
Company, New York, NY.
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                                                     OSWER Directive 9481.00-6C
Other resource documents

Black, C.A., 1965. Methods of Soil Analysis. American Society of Agronomy,
     Madison, Wl.

U.S. Environmental Protection Agency, 1978. Investigation of Landfill Leachate
     Pollutant Attenuation by Soils. EPA 600/2-78-158.

U.S. Environmental Protection Agency, 1980. Adsorption, Movement, and
     Biological Degradation of Large Concentrations of Selected Pesticides in Soils.
     EPA 600/2-80-124.

U.S. Environmental Protection Agency, 1982. Hand book for Remedial Action at
     Waste Disposal Sites. EPA-625/6-82-006, Washington, D.C.June, I982.

U.S. Environmental Protection Agency, 1982. Preamble-Section D; Ground-water
     Protection (Part 264 SubpartF). Federal Register 47:32291-32312. July 26.1982.

U.S. Environmental Protection Agency, 1982. Handbook for Performing Exposure
     Assessments (Draft). Washington, D.C., November, I982.

U.S. Environmental Protection Agency, 1983. Draft Guidelines for Deriving
     Numerical National Water Quality Criteria for the Protection of Aquatic Life
     and its Uses. Washington, D.C, July 5,1983.

U.S. Environmental Protection Agency, 1983. Protocol for Bioassessment of
     Hazardous Waste Sites. EPA-600/2-83-054, July, 1983.

U.S. Environmental Protection Agency, 1983. Water Quajitv Standards Handbook,
     Office of Water Regulations and Standards. Washington, D.C., December,
     1983.

U.S. Environmental Protection Agency, 1984. Soil Properties Classification and
     Hydraulic Conductivity Testing (Draft Report).  SW-925.
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                                   OSWER Directive 9481.00-6C
ACL POLICY AND INFORMATION REQUIREMENTS
               APPENDICES

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                                                     OSWER Directive 9481.00-6C
APPENDICES

A.   Outline of Information That May Be Cross Referenced
         From the Permit Application

B,   Summary of Tables, Figures, and Information Required
         to Support an ACL Demonstration

C.   Summary Sheet of Hazardous Constituent Properties

D.   Summary Sheet on Health Effects Factors

E.   Standard Factors Used in Exposure Assessments

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                                    OSWER Directive 9481.00-6C
               APPENDIX A
    Outline of Information That May Be
Cross Referenced from the Permit Application
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                                                      05WER Directi ve 9481.00-6C
The following information, required in the Part B permit, may be cross-referenced
in the ACL application:.

     270.14(b) General information requirements for all hazardous waste
              management facilities.

          (I)   General description of the facility.

          (2)  Chemical and physical  analyses of the hazardous  waste, in
              accordance with Part 264.

          (8)  Description of the procedures, structures, or equipment used at the
              facility to prevent contamination of water supplies.

          (II)  Facility location information;

              (i)   identification of the political  jurisdiction (e.g.,  county or
                   township) in which the facility is located,
              (ii)  If the facility is located in an area listed in Appendix VI of Part
                   264,  information  must  be submitted to demonstrate
                   compliance with the seismic standard under 264.l8(a),
              (iii)  Identification of whether a facility is located within a 100-year
                   floodptain,
              (iv)  Information required if a  facility is located in a 100- year
                   floodplain.

          (19) A topographic map clearly showing:

              (i)   Map scale (at least one inch; 200 feet) and date,
              (ii)  100-year floodplain area,
              (iii)  Surface waters including intermittent streams,
              (iv)  Surrounding land uses,
              (vi)  Orientation of the map,
              (vii) Legal boundaries of the facility,
              (ix)  Injection and withdrawal wells, both on-site and off- site,
                                    A-2

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                                                OSWER Directive 9481.00-6C


         (x)   Buildings, treatment, storage, or disposal operations, or other
              structures,
         (xi)  Barriers for drainage or flood controls, and
         (xii)  Location  of operational  units within the facility site, where
              hazardous waste is or will be.

270.14(c) Additional information required for the protection of ground
         water  for hazardous waste surface impoundments, piles,  land
         treatment units, and landfills.

     (1)  A summary of the interim status ground-water monitoring data.

     (2)  Identification of the uppermost aquifer and  aquifers hydraulically
         interconnected beneath the facility property,  including  ground-
         water flow direction and rate, and the basis for such identification.

     (3)  Additional information to be included on the topographic map:

         (a)   Delineation of the waste management area, the property
              boundary, and the proposed "point of compliance;"
         (b)   The location of ground-water monitoring wells; and
         (c)   The hydrogeologic information required under 270.14(c)(2).

     (4)  A description of any plume of contamination that has entered the
         ground water that:

         (i)   Delineates the extent of the plume on the topographic map,
              and
         (ii)   Identifies the concentration of each Part  261  Appendix VIII
              constituent throughout the plume, or identifies the maximum
              concentrations of each Appendix VIII constituent in the plume.

     (7)  Information  needed to establish a compliance monitoring program
         under 264.99:

         (i)   A description of the wastes previously handled at the facility;
                              A-3

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                                                     OSWER Directive 9481.00-6C


              (ii)   A characterization  of the contaminated ground water,
                   including concentrations of hazardous constituents;
              (iii)  A list of hazardous constituents for which compliance
                   monitoring will be undertaken  in accordance with 264.97
                   and 264,99;
              (iv)  Proposed concentration limits for each hazardous constituent,
                   based on the criteria set forth in 264.94(a),  including a
                   justification for establishing any ACLs;
              (v)   Detailed plans and  an engineering report describing the
                   proposed ground-water monitoring  program to  be
                   implemented to meet the requirements of 264.97; and
              (vi)  A description of the proposed sampling, analysis, and
                   statistical comparison procedures to be utilized in evaluating
                   ground-water monitoring data.

The following additional sections of the Part B permit application may also be used
in an ACL demonstration if they apply to the site-specific characteristics:

     27Q.I4(b)(5)   General inspection requirements under 264,l5(b),  if
                   applicable to the ACL demonstration.

         (13)  A copy of the closure plan and the post-closure plan, if applicable to
              the ACL demonstration.

         (20) Additional information necessary to satisfy other Federal law
              requirements under 270.3. These laws may include:

              (a)   The Wild and Scenic Rivers Act (16 USCI273),
              (b)   The National Historic Preservation Act of I966 (16 USC 470),
              (c)   The Endangered Species Act (16 USC I53I),
              (d)   The Coastal Zone Management Act (16 USC I45I), or
              (e)   The Fish and Wildlife Coordination Act (16 USC 66I).
                                   A-4

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                                               OSWER Directive 9481.00-6C


270.i4(c}(8)    Information needed to establish  either a corrective action
              program  that meets the  requirements of 264.100,  if
              applicable to the ACL demonstration, or a compliance
              monitoring program that meets the requirements of 264,99
              and270.!4(c)(6).
                              A-5

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                                    OSWER Directive 9481.00-6C
               APPENDIX B
      Summary of Figures, Tables, and
Information Required in ACL Demonstrations

                1. Figures
                2. Tables
                3, Information
                   B-1

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                                                    OSWER Directive 9481.00-6C
     This appendix can be used as a quick reference to determine what types of
information are needed for various types of ACL demonstrations. As was discussed
in earlier chapters, not all the information discussed in this document is necessary in
all applications.  The applicant is responsible for deciding what information  is
necessary for the site, though  the  appropriate permitting authority may provide
some help in  making this determination.  Most notably, a simplified ACL
demonstration may  be based  strictly on an EPA reviewed dose  level (with no
mechanisms of attenuation considered).  In some cases, as was discussed in the first
chapter, this may be the only type of ACL demonstration acceptable to EPA.

     However, all ACL applications are required to provide certain  information.  If
this information is not provided or is supplied in an unacceptable form, then the
ground-water protection standard  will be set at background or one of the MCLs
listed in the regulations (40 CFR 264.94(a)).  This appendix points out what
information is usually required in all  demonstrations,  and what additional
information may be required in some cases.

     This appendix is only a summary; it is not comprehensive. The applicant or
reviewer should refer to the  main body of the guidance for a more thorough
discussion of the types of information needed in an ACL application.
                                   B-2

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                                                     OSWER Directive 9481.00-6C
                                 FIGURES
A.   Figures That Should Be included in All ACL Demonstrations

     1.   Plume map(s) of each hazardous constituent
     2.   A site map showing:
            all structures
         *   ail waste management areas
         *   all monitoring wells and surface water sampling  locations (if
              applicable)
            all ground-water withdrawal and injection wells
            all surface water bodies
     3.   Horizontal and vertical ground-water flow map(s)

B.   Figures That Should Be Included in All Detailed Demonstrations

     1.   Area! soil map
     2.   Vertical soil map
     3.   Facility subsurface stratigraphy map(s)
     4.   Regional subsurface stratigraphy map(s)
     5.   100 year floodplain map
     6.   Ground-water recharge and discharge map
     7.   Agricultural land uses map

C.   Additional Figures That May Be Necessary in a Demonstration

     1.   Withdrawal well cones of depression
     2.   Map showing locations of other potential sources of pollution
     3,   Map showing locations of stressed terrestrial environments
     4.   Map showing locations of stressed aquatic environments
                                   B-3

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                                                     OSWER Directive 9481.00-6C
                                  TABLES
A.   Tables That Should Be Included in All ACL Demonstrations

     1.    Background concentration of each hazardous constituent in both ground
          water and each surface water body (if applicable)
     2,    Uppermost aquifer characteristics
     3.    Ground-water well location and use information
     4.    Health effects information of each constituent (including EPA-reviewed
          allowable dose levels if available)

B.   Tables That Should Be included in All Detailed Demonstrations

     1.    Location information of surface water bodies
     2.    Soil characteristics
     3.    Subsurface geology characteristics
     4.    Horizontal flow net data
     5.    Vertical flow net data
     6.    Ground-water withdrawal data (if applicable)
     7.    Annual and monthly precipitation data
     8.    Endangered and threatened species information (if applicable)
     9.    Degradation and attenuation properties of hazardous constituents
     10.   Soil attenuation properties
     11.   Mathematical models) assumptions (if applicable)
     12.   Ground-water use

C   Additional Tables That May Be Necessary in a Demonstration

     1.    Physical characteristics data of each water body
     2.    Designated uses of each surface water body
     3.    Point source information
     4,    Population characteristics
     5.    Toxicity information on terrestrial impacts
     6.    Terrestrial environment diversity information
                                    B-4

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                                                 OSWER Directive9481.00-6C
                         TABLES (CONTD)
7,    Aquatic toxicity information
8,    Aquatic diversity
9.    Agricultural crop impacts data
10.  Animal husbandry impacts data
11,  Agricultural land use information
12.  Physical structural impacts data
                                B-5

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                                                      OSWER Directive 9481-00-6C


                               INFORMATION

               Hazardous Constituent Characteristics (Chapter II)

1.    Extent of Ground-Water Contamination (270.14(c))

     A.    Information Required for All Demonstrations
              i.    Appendix VIII (under revision  to Appendix IX of Part 264}
                   ana lysis results
              ii,   plume definition of each hazardous constituent

2.    Waste Characteristics (264.13)

     A,    Information Required in All Demonstrations
              i.    quantity of waste in regulated unit
              iii,   characteristics of waste in regulated unit

3.    Characteristics of ACL Constituents

     A.    Information Required for a Detailed Demonstration
              i.    density
              ii,   solubility
              iii.   vapor pressure
              iv,   viscosity
              v.   octanol-water partitioning coefficient (if applicable)

     8.    Additional Information That May Be Required  Depending on Fate-
          Related Arguments
              i.    chemical degradation data
                   a.   oxidation
                   b,   reduction
                   c.    hydrolysis
              ii.   biological degradation data
                   a.   biodegradation
                   b.   biotransformation
                                    B-6

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                                    OSWER Directive 9481.00-6C
physical attenuation data
a.    ion exchange
b.    precipitation
c.    complexation
                 B-7

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                                                      OSWER Directive 9481.00-6C
                  Hydrogeological Characteristics (Chapter III)

1,    Identification of Uppermost Aquifer (270.14{c))

     A.    Information Required in all Demonstrations
          i.    horizontal extent
          it.   vertical extent

2,    Characteristics of Each Soil Type

     A.    Information Required for a Detailed Demonstration
          i.    thickness
          ii.   areal extent
          iii.  hydraulic  properties

     B.    Additional Information  That  May be  Required  Depending  on
          Attenuation Arguments
          i.    dispersion properties
          ii,   retardation and sorptive properties
              a,   organic and mineral content
              b.   cation and ion exchange
              c.   grain size

3.    Characteristics of Each Subsurface Stratigraphic Unit

     A.    Information Required in a Detailed Demonstration
          i.    horizontal and vertical extent
          ii.   hydrologic properties
              a.   hydraulic conductivity
              b.   specific yield or storage
              c.   effective porosity

     B,    Additional Information Required if Aquitard is Present
          i.    hydraulic  conductivity
          ii.   pump test results
                                    B-8

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                                                     OSWER Directive 9481.QO-6C
            Ground-Water Flow Direction and Quantity (Chapter IV)

1.    Ground-Water Flow Characteristics (270.14(c))

     A.   Information Required in All Demonstrations
         i.    horizontal flow in saturated zone
              a.    ground-water elevation data
              b.    storage or specific yield data
         ii.   vertical flow in saturated zone
              a,    nested piezometer data
              b.    storage data

     B.   Additional Information That May Be  Required Depending  on Site
         Conditions
         i,    temporal variability in ground-water flow
              a.    seasonal recharge patterns
              b.    surface water elevation changes
                   1.   tidal effects
                   2.   riverine or lake
         ii.   ground-water withdrawal effects on ground-water flow
              a.    drawdown effects
                                   B-9

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                                                       OSWER Directive 9481.00-6C


                             Rainfall {Chapter V)

1.    Precipitation Characteristics

     A.   Information Required in a Detailed Demonstration
          i.    monthly rainfall and/or snowfall
          ii.    effects of rainfall on seasonal recharge

     B,   Additional Information Required if  Surface Waters  are  Nearby  (see
          Chapter VII)
          i.    storm frequency patterns (1,10, 25,100 years)
          ii,    effects of storms on infiltration
          iii.   effects of storms or flood ing
               a.    100-year floodplain (270.14(b))
          iv.   site-specific characteristics affecting flooding and infiltration
          v,    ground-water discharge pathways
                                     B-10

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                                                      OSWER Directive 9481.00-6C


         Proximity of Surface Water and Ground-Water Users (Chapter VI)

1.    Surface Water Information

     A.   Information Required in a Detailed Demonstration
          i.    location of each water body within 5 km downgradient of facility
              a.   distance from facility
              b.   travel time of ACL constituents from facility to the water body

     B.   Additional Information is Required if Ground-Water Discharge of ACL
          Constituents is Likely to Reach Surface Waters
          i.    physical characteristics of each water body
              a.   dimensions
              b.   hydraulic residence time, flow rate, or tidal periodicity
          ii.   discharge zone size


2.    Ground-Water User Information

     A.   Information Required in All Demonstrations
          i.    location and distance from facility of ground water users
          ii.   types of users
              a.   potable
              b.   domestic
              c.   industrial
              d.   agricultural
              e.   recharge

     B.   Additional Information That May Be Required
          i.    demography of surrounding area
          ii.   zoning patterns
          iii.   projected population growth
          iv.   projected ground-water use
                                   B-11

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                                                      OSWER Directive 9481.00-6C


             Uses of Ground Water and Surface Water (Chapter VH)

1.    Ground-Water Uses

     A.    Information Required in a Detailed Demonstration
          i.    use or potential use of local ground water
          ii.   State certification of groundwater's beneficial use

2.    Surface Water Uses

     A,    Additional Information is Required if Surface Waters are Nearby  and
          Contaminated Ground Water Discharge is Likely
          i.    designated use of each water body
              a,   drinking water source
              b.   fish and wildlife propagation
              c.   industrial or agricultural use
              d,   area of ecological concern
              e.   recreational area
                                    B-12

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                                                     OSWER Directive 9481.00-6C
              Existing Quality of Ground Water and Surface Water
               and Other Sources of Contamination (Chapter VIII)

1,    Ground-Water Background Quality (264.99)

     A,   Information Required in All Demonstrations
         i.    ground-water assessment for Appendix VIII constituents
              a.    hydrologic units in uppermost aquifer
              b.    upgradient of facility

     B.   Additional Useful Information
         i.    historical regional ground-water quality information

2.    Surface Water Quality

     A.   Additional  Information is Required if Ground-Water Discharge of ACL
         Constituents to Surface Waters is Likely
         i.    surface water assessment for ACL constituents
              a.    each surface water  body that receives the contaminated
                   ground water or that is downstream from a water body that
                   does
         ii,   historical regional ground-water quality information

3.    Ground-Water Contamination Sources

     A.   Information Required in AH Detailed Demonstrations
         i.    statement as to the  presence or absence of  other contamination
              sources

     B.   Additional  Information is Required if Background  Ground Water is
         Contaminated
         i.    location of other potential sources of contamination, including
              other RCRA facilities, Superfund sites, landfills, industrial areas,
              surface impoundments, etc.
         ii.   available ground-water data from these sources
                                   B-13

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                                                     OSWER Directive 9481.00-6C
4.    Surface Water Contamination Sources

     A.   Additional Information is Required if Ground-Water Discharge of ACL
         Constituents to Surface Water is Likely
         i.    statement as to the presence or absence of other surface water
              contamination sources
         ii.   point source loading information including industrial facilities and
              publicly owned treatment works (POTWs)
              a.   NPDES permit information
              b.   waste load allocations
              c.   mixing zone information
              d.   monitoring data
         iii.  Non-point  source loading  information including run-off and
              infiltration sources
                                   B-14

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                                                     OSWER Directive 9481.00-6C
                      Potential Health Risks (Chapter IX)

1.    Exposure Assessment

     A.    Information Required in All Demonstrations
          t.    location of potential point of exposure (POE)
          ii,   information or type of assumptions used for exposure

     8.    Additional Information is Required Depending on Likelihood of Exposure
          (e.g., off-site plume, on-site ground-water use)
          i.    description of likely exposure pathways
              a.   drinking water (ground or surface water)
              b.   ingestion  of contaminated food (aquatic or agricultural
                   products)
              c,   dermal contact (bathing or recreation)
              d.   inhalation of volatile organics
          ii.   population information
              a.   sensitive subgroups

2,    Health Assessment

     A.    Information Required in All Demonstrations
          i.    allowable exposure levels for each ACL contaminant
              a.   Reference Dose level (RfD)
              b.   Potency Factor (PF)
          ii.   basic toxicological data if EPA approved allowable exposure levels
              are not available
          iii,   cumulative impacts if background is contaminated
          iv,   if applicable and available, data on additive impacts for mixtures of
              contaminants
                                   B-15

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                                                     QSWER Directive 9481.00-6C
                 Potential Environmental Impacts (Chapter X)

1.    Terrestrial Impacts

     A.   Information Required in All Demonstrations
         i.    statement as to the likelihood of any terrestrial environmental
exposure

     8.   Additional Information is Required if Terrestrial Environmental Exposure
         Can Occur
         i.    toxicity and bioaccumulation values for ACL constituents
         ii,   environmental effects for ACL constituents
              a.   literature description
              b.   stressed vegetation analysis and diversity studies if exposure
                   has occurred

2.    Endangered Species Impacts

     A,   Information Required in All Demonstrations
         i.    statement describing the  presence  of  any  endangered  or
              threatened species near the facility

     B,   Additional Information is Required if Endangered or Threatened Species
         are Found Near the Facility
         i.    assessment of habitat impacts due to ACL constituents
         ii.   assessment of species impacts

3.    Aquatic Impact Assessment

     A.   Information Required in All Demonstrations
         i.    statement as to the likelihood of aquatic environmental exposures
                                   B-16

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                                                      OSWER Directive 9481.00-6C


     B.    Additional Information is Required if Aquatic Environmental Exposure
          Can Occur
          i,    sampling protocol to show no statistical significance
              a.   QA/QC
              b.   sampling points and justification
          ii.   data requirements
              a.   water
              b.   sediment

4.   Agricultural Impacts

     A.    Information Required in All Demonstrations
          i.    statement as to the likelihood of agricultural operations exposures

     B.    Additional Information ts Required if Exposure is Likely
          i.    data on agricultural land use near the facility
          ii.   information on exposure pathways including shallow ground water
              and irrigation
          iii.   assessment of crop impacts
          iv.   assessment of livestock impacts

5.   Physical Structure Impacts

     A.    Information Required in AH Demonstrations
          i.    statement as to the likelihood of physical structure exposure

     B.    Additional Information is Required if Exposure is Likely
          i.    data on physical structures in area
          ii.   information on exposure pathways
          iii.   assessment of reactivity,  ignitability, and migration  potential of
              ACL constituents and their impact or physical structure
                                   B-17

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                                                     OSWER Directive 9481.00-6C
                Persistence of Contamination and Permanence
                           of Effects (Chapter XI)
1.    Persistence
     A,   Information Required in All Demonstrations
         i.    statement on whether degradation of ACL constituent is used as a
              fate-related argument

     B.   Additional Information is Required if Fate Arguments are Used
         i.    assessment of degradation of ACL constituents
              (Chapter II information)
              a.   biodegradation, bioconcentration, biotransformation
              b.   oxidation/reduction
              c.   hydrolysis
              d.   precipitation, ion exchange, complexation
         ii.   assessment of rates of degradation
              a,   parameters
              b.   coefficients
              c.   assumptions

2.    Permanence

     A.   Information Required in All Demonstrations
         i.    statement on whether acceptable risk arguments are used

     B.   Additional Information is Required if Exposures Do Occur
         i.    long-term effects associated with exposure to ACL contaminants
              a.   chronic effect levels
              b.   reversibility of effect
                                   B-18

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                                       05WER Directive 9841.00-6C
                  APPENDIX C





Summary Sheet of Hazardous Constituent Properties
                      C-1

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                                                     OSWER Directive 9841.00-6C

   PHYSICAL AND CHEMICAL PROPERTIES OF EACH HAZARDOUS CONSTITUENT
1.    Name of Constituent:     	
2.    CAS#:    	
3.    Molecular Weight;  	
4,    Physical state of product/chemical and quantity during storage or disposal.

Solid
Gas
Liquid
Storage



DisposaF



5.
6.
7.
Melting Point:
Boiling Point:
Solubilities in:
a.  "  Water:   _______
b,    Nonaqueous Solvent (specify):
8.    Dissociation Constant (specify):
9.    Partition Coefficient (Kow):
10.  Density:
11.   Reactivity (specify)
     a.    Photochemical Degradation:
     b,    Hydrolysis:     	
     c.    Chemical Oxidation: 	
     d.    Chemical Reduction:	
12,   Vapor Pressure:	
13.  Henry's Law Constant:
14.  Viscosity of Liquids:
15,  Biodegradation Characteristics:	
16.  Adsorption/Desorption Characteristics:
17.  Chemical Incompatibility: __^	
18.  pH: 	
19.  Decomposition Temperature:
20.  Decomposition Products:
                                    C-2

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                                   OSWER Directive 9841.00-6C
             APPENDIX D
Summary Sheet on Health Effects Factors
                 D-1

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                                                   OSWER Directive 9841.00-6C
SUMMARY SHEET ON HEALTH EFFECTS
Name of Constituent:
 CAS#
AGENCY-REVIEWED ALLOWABLE HEALTH LEVELS
MCL








Reference
Dose
Dose


Assumptions


Concentration

Risk Specific Dose
Potency Factor


Assumptions


Concentration at 10-6
risk

Other
(water quality criteria,
etc.)








HEALTH EFFECTS TESTING, IF AGENCY-REVIEWED LEVELS ARE UNAVAILABLE
1.    a.   Hasthe chemical been evaluated forthefollowing:
Effects
Qncogenicity
Carcinogenicity
Mutagenicity/Genotoxidty
Teratogenicity/Eetotoxidty
Chronic Toxicity
Subacute Toxicity
Other
Test
Performed
Yes







No







Effects Observed
Yes







No







     b.   What organization performed the toxicology testing?
     c.   Is a protocol for the testing available?
Yes
     d.   Are copies of the testing reports available?
     If yes, attach copies and check here;
    Yes
No
 No
                                  D-2

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                                                         OSWER Directive 984LOO-6C
2.  If a positive response was given in any part of Question 1.a then summarize test(s) below.  Make
   copies of the table and complete one table for each test performed on the subject chemical.
a. Test Subjects

b. Dose and Duration



c. Route of Exposure
d Effects Observed 1/

e. Protocol Followed


f. Comments*!/
g. Reference or Source
Sex; Species:

Dose:
frequency or administration :
Duration ot exposure:

P Oral p Dermal p Eyes P Inhalation
P Subcutaneous p Intramuscular
P Interperitonealp Intravenous P Other


0 Yes p No If yes, cite protocol:




    I/ Include non-tumorigenic and all other effects observed, dose levels at
      which the effects were observed, statistical evaluations of data, and
      latency periods observed.
    2/ Report any variables which may have affected the results obtained.
                                       D-3

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                                      OSWER Directive 9481.00-6C
                APPENDIX E
Standard Factors Used in Exposure Assessments
                    E-1

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                                               OSWER Directive 9481.00-6C
           Standard Factors Used in Exposure Assessments
A.   BIOLOGICAL PARAMETERS
Mass of Standard Humans1

     male adult; 70 kg
     female adult: 60 kg

Skin Surface Area?

     1.8m2    -    totally exposed (man 180cm high)
     0.3 m2    .    assuming short-sleeved, open-necked  shirts, pants,
                  shoes, with no gloves or hats
     0.09m2   -    assuming long sleeved shirts, gloves, pants, shoes,

Effective Pore Size of Skin and Other External Membranes^

     4 Angstroms (0.4 nm)

Amount of Food Consumption^

     1500 gm/day (excluding beverages)

Drinking Water Consumptions

     1.9 liters per day average with a range of 1 to 2.4 liters per day (2 liters
     per day is frequently used).
                               E-2

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                                                      OSWER Directive 9481.00-6C


Respiratory Rate5
                                  Adult man   Adult woman      Child (10 vr)
     minute volume (liters/min)
     resting                            7.5        6.0              4.8
     light activity                       20.0       19.0              13.0

     Liters of air breathed

     8 hr working "Lightactivity"         9,600      9,100             6,240
     8 hrnonoccupational activity        9,600      9,100            6,240
     8 hr resting                        3,600      2,900            2,300
Size of Respjrable Participates (aerodynamic diameter)3

     <1 pm ;  100% reach the alveoli; 0% retention in nasal passage
      2 urn :  80% reach the alveoli; 20% retention in nasal passage
      5 pm :  50% reach the alveoli; 50% retention in nasal passage
     >10 wm : almost complete retention in nasal passage
     - mouth breathers can inhale particles up to 15 um aerodynamic diameter
                                    E-3

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                                              OSWER Directive 948t.OQ-6C
     1980 U.S. Population by Age and Sex (in thousands)6

Total, all years
under 5 years
5-9 years
10-14years
15-1 9 years
20-24 years
25-29 years
30-34 years
35-39 years
40-44 years
45-49 years
50-54 years
55-59 years
60-64 years
65 ytars and older
median age (yrs.)
Time Spent in Various Activities?
activity budget for 8 hr workday
activity budget for 24 hr day :
Birth Rates
1980: 16,2 per 1,000 population
Death Rates
1980: 8.9 per 1,000 population
Average Life Expectancy^ (1980)
Male
110,032
8,360
8,538
9,315
10,752
10,660
9,703
8,676
6,860
5,708
5,388
5,620
5,481
4,669
10,303
28.8





Female
116,473
7,984
8,159
8,926
10,410
10,652
9,814
8,882
7,103
5,961
5,701
6,089
6,133
5,419
15,242
31.3
6 hr light work
2 hr heavy work
12 hrrest
10 hr light work
2 hr heavy work



Total
226,505
16,344
16,697
18,241
21,162
21,313
19,518
17,558
13,963
11,668
11,088
11,709
11,614
10,086
25,544
30.0





Male - 69.9 years
Female - 77.8 years
                           E-4

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                                                       OSWER Directive 9481.00-6C
Employment by Industry (1980)6
                                                       Total     Percent
                                                       (x 103)    Female

      Agriculture, forestry, fisheries                        3,470       19.5

      Mining                                              940       13.5

      Construction                                        6,065        8,0

      Manufacturing                  .                   21,593       31.4

      Transportation, communications, and other public     6,393       25,2
      utilities

      Wholesale and retail trade                          19,727       46.4
         Wholesale trade                                 3,827       25.8
         Retail trade                                     15,900       51.4

      Finance, insurance, and real estate                    5,860       58.2
         Banking and other finances                       2,504       65.7
         Insurance and real estate                         3,355       52.6

      Servicesa                                          27,983       61.3
         Business Services                                 2,308       45.1
         Automobile services                               924       12,6
         Persona I services*                                3,738       73.2
            Private households                            1,229       88.3
            Hotels and lodging places                      1,106       65.2
         Entertainment and recreation                     1,017       39.1
         Professional and related services                  19,472       65.7
            Hospitals                                     3,947       77.2
            Health services except hospitals                 3,281       74.3
            Elementary, secondary schools                  5,467       71.0
            Colleges and Universities                       2,066       48.8
            Welfare and religious agencies                 1,560       58.6

      Public administrationb                               5,240       35.8

     3  includes industries not shown separately
     b  Includes workers involved in uniquely governmental activities, e.g.,
        judicial and legislative
                                     E-5

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                                                     OSWER Directive 9481.00-6C
FarmsS(1980)
     number of farms in the U.S. - 2.4x106
     total farm acreage in the U.S. - 1 x 109 acres
     average farm size in the U.S. - 430 acres
Total Land in U.S.6
     2.3x 109 acres
Home GardensB
     average size- 750 ft2
     annual value of home grown produce - $14 billion
     percentage of U.S. household with gardens - 44%
     total amount of land used as gardens - 6 million acres
House Size9
     142-425 m3
Building Size for Typical Endosed Production  Facility *0
     7,000 - 26,000 m3 (250,000 - 925,000 ft3)

C.   CHEMICAL PARAMETERS

pH Ranges for Various Water Quality Cateqoriesi 1
     Category                                       Range
     Recreation and Aesthetics                        5.0 - 9.0
     Public Water Supplies                            6,0-8.5
     Fish, Aquatic, and Wildlife                        6.0 - 9.0
         Marine and estaurine organisms             6.7 - 8,5
         Wildlife                                   7.0-9.2
         Fresh water organisms                      6.0-9.0
     Agricultural Use                                5.5-9.0
     Irrigation Water Supplies                         4.5-9.0
                                    E-6

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                                                    OSWER Directive 9481.00-6C
D.   PHYSICAL PARAMETERS
Air Change Rate (Home Dwelling)?
     0,25-5 per hour
Characterization of Production Emissionsio
     Emission Route
     Process Vents
     Fugitive Emissions
     Storage and Transportation
     Solid and Liquid Waste
         Stream Emissions
Average Wind Speed 12
     5,5 m/sec
% of Total Emissions of Air
         66-70%
         15-20%
         8-10%
         2 - 5%
                                   E-7

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                                                     OSWER Directive 9481.00-6C
                               REFERENCES

1.    Abraham. S.. 1979. Weight and Height of Adults 18--74 Years of Age, United
     States, 1971-1974.  DHEW Publication No. (PHS) 79-1659, U.S. Department of
     Health, Education, and Welfare, Hyattsville, MD, 48 pp.

2.    SendroyJ., Jr., and L P. Cecchini, 1954. Determination of Human Body Surface
     Area From Height and Weight. Journal of Applied Physiology, 7(1): 1-12!

3.    Goldstein, A., et aj, 1969. Principles of Drug Action.  Harper and Row, N.Y., pp.
     108-160.

4.    Lehman, A.J., 1975. Appraisal of the Safety of Chemicals in  Foods, Drugs, and
     Cosmetics. The Association of Food and Drug Officials of the United States, p.
     1.

5.    Snyder,  W.S.,  1975.  Report of  the Task  Group on  Reference Man.
     International CommissionTori Radiological Protection No. 23. Pergamon Press,
     480 pp.

6.    Chapman, B., 1981. Statistical Abstract of the United States. U.S. Department
     of Commerce, Bureau of the Census, 1031 pp.

7.    Roddin,  M.F., H.T. Ellis, and M.W.  Siddiqee.,  1979,   Background Data for
     Human Activity Patterns. Draft Final report, prepared by SRI International for
     the U.STEnvironmental Protection Agency (Contract No. 68-02-2835), Research
     Triangle Park, NC.

8.    Yost, K.J., and LJ, Miles,, 1980.  Dietary Consumption Distributions of  Selected
     Food Groups for the U.S. Population   Prepared for the U.S. Environmental
     Protection Agency (Contract No. 68-01-4709), Office of Testing and Evaluation,
     Wash.,D.C,i3pp.

9.    Johnson, R.H,,  Jr., D.E. Bernhardt,  N.S. Nelson, and  H.W. Calley, Jr., 1973.
     Assessment  of  Potential Radiological Health Effects  from  Radon  in  Natural
     Gas. EPA-520/1 -73-004, U.S. Environmental Protection Agency. Wash..  D.C.

10.  Becker, D.,  E. Fochtman, A. Gray, and T. Jacobius., 1979.  Methodology for
     Estimating Direct Exposure to New  Chemical Substances. EPA-560/13-79-008,
     U.S. Environmental Protection Agency, Research Triangle Park, North Carolina,
     132pp.

11.  Liptak, B.C., 1974. Environmental  Engineers'  Handbook, Volume 1: Water
     Pollution. Chilton Book Co"., Radnor, Pennsylvania, p. 1321.

12.  Turner,  D.B.,  1971.  Workbook  of Atmospheric Dispersion  Estimates
     Publication No. AP-26, U.S. Environmental Protection Agency, Research
     Triangle Park, North Carolina.
                                    E-8

-------
                                                     OSWER Directive 9481.00-6C
                               REFERENCES

1.    Abraham. S.. 1979. Weight and Height of Adults 18--74 Years of Age, United
     States, 1971-1974.  DHEW Publication No. (PHS) 79-1659, U.S. Department of
     Health, Education, and Welfare, Hyattsville, MD, 48 pp.

2.    SendroyJ., Jr., and L P. Cecchini, 1954. Determination of Human Body Surface
     Area From Height and Weight. Journal of Applied Physiology, 7(1): 1-12!

3.    Goldstein, A., et aj, 1969. Principles of Drug Action.  Harper and Row, N.Y., pp.
     108-160.

4.    Lehman, A.J., 1975. Appraisal of the Safety of Chemicals in  Foods, Drugs, and
     Cosmetics. The Association of Food and Drug Officials of the United States, p.
     1.

5.    Snyder,  W.S.,  1975.  Report of  the Task  Group on  Reference Man.
     International CommissionTori Radiological Protection No. 23. Pergamon Press,
     480 pp.

6.    Chapman, B., 1981. Statistical Abstract of the United States. U.S. Department
     of Commerce, Bureau of the Census, 1031 pp.

7.    Roddin,  M.F., H.T. Ellis, and M.W.  Siddiqee.,  1979,   Background Data for
     Human Activity Patterns. Draft Final report, prepared by SRI International for
     the U.STEnvironmental Protection Agency (Contract No. 68-02-2835), Research
     Triangle Park, NC.

8.    Yost, K.J., and LJ, Miles,, 1980.  Dietary Consumption Distributions of  Selected
     Food Groups for the U.S. Population   Prepared for the U.S. Environmental
     Protection Agency (Contract No. 68-01-4709), Office of Testing and Evaluation,
     Wash.,D.C,i3pp.

9.    Johnson, R.H,,  Jr., D.E. Bernhardt,  N.S. Nelson, and  H.W. Calley, Jr., 1973.
     Assessment  of  Potential Radiological Health Effects  from  Radon  in  Natural
     Gas. EPA-520/1 -73-004, U.S. Environmental Protection Agency. Wash..  D.C.

10.  Becker, D.,  E. Fochtman, A. Gray, and T. Jacobius., 1979.  Methodology for
     Estimating Direct Exposure to New  Chemical Substances. EPA-560/13-79-008,
     U.S. Environmental Protection Agency, Research Triangle Park, North Carolina,
     132pp.

11.  Liptak, B.C., 1974. Environmental  Engineers'  Handbook, Volume 1: Water
     Pollution. Chilton Book Co"., Radnor, Pennsylvania, p. 1321.

12.  Turner,  D.B.,  1971.  Workbook  of Atmospheric Dispersion  Estimates
     Publication No. AP-26, U.S. Environmental Protection Agency, Research
     Triangle Park, North Carolina.
                                    E-8

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