oEPA
UnflM states
Enyironmsnui Protection
Office of Ground-Water
Protection (WH-S50G)
Washington, DC 20*60
June 1988
Offio of w«t«r
Guidelines for
Ground-Water
Classification Under
the EPA Ground-Water
Protection Strategy
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GUIDELINES FOR GROUND-WATER CLASSIFICATION
UNDER THE EPA GROUND-WATER PROTECTION STRATEGY
JUNE 1988
OFFICE OF GROUND-WATER PROTECTION
U.S. Environmental Protection Agency
401 M Street. S.W.
Washington, D.c. 20460
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ACKNOWLEDGEMENTS
These Guidelines were prepared by the Office of Ground-
Water Protection under the overall guidance of the Director,
Marian Mlay. The project aanger was Ron Hoffer, with
additional technical support provided by Joee Valdes and
Donna Fletcher. Assistance in developing the socioeconomic
and ecological aspect of the system was provided by Brendan
Doyle and Arthur Koines of the Office of Policy Planning and
Evaluation. Joyce Edwards of OGWP helped in the secretarial
and logistical aspects of this document from the inception of
the project. The efforts of the Classification Guidelines
Work Group in the development of the Final Draft
Classification Guidelines (December, 1986) are especially
appreciated.
Technical consultants played a significant role in the
preparation of these guidelines. The primary technical
consultant was Geraghty & Miller, Inc. (G&M), Dr. William
Doucette, project manger. Other members of the G&M support
team included Don Lundy, Michele Ruth and Laurie Haines.
Shirley Reeder and Xaren Kotschenreuther at G&M performed the
majority of word processing. Subcontract assistance was
provided by ICF, Inc., Peter Linguiti and Paul Bailey,
project managers. Other ZCF support team members were
Richard Norton and Joseph Karam.
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DISCLAIMER
These Ground-water Classification Guidelines are meant
to assist the U.S. Environmental Protection Agency as the
Agency moves forward in ground-water protection. The
Guidelines do not create any rights or obligations,
substantive or procedural, enforceable by any party in an
administrative, civil, or criminal proceeding.
6-27
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TABLE OF CONTENTS
PAGE
ACKNOWLEDGEMENTS
TABLE OF CONTENTS i
LIST OF FIGURES v
LIST OF TABLES... vii
EXECUTIVE SUMMARY E-l
CHAPTER ONE: INTRODUCTION 1-1
1.1 EPA's Ground-Water Protection Strategy. l-l
1.2 Purpose of the Classification Guidelines 1-2
1.3 Guideline Development 1-2
1.4 Organization of Guidelines Document... 1-3
CHAPTER TWO: OVERVIEW OF THE GROUND-WATER
CLASSIFICATION SYSTEM AND PROCESS 2-1
2.1 Ground-Water Classes 2-2
2.1.1 Class I - Special Ground Waters 2-2
2.1.2 Class II - Current and Potential Sources
of Drinking Water and Water Having other
Beneficial Uses. 2-2
2.1.3 Class III - Ground Water Not a Potential
Source of Drinking Water and of Limited
Beneficial Use 2-4
2.2 General Classification Procedures 2-5
2.3 Collection of Basic Information 2-8
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TABLE OF CONTENTS (CONT.)
CHAPTER THREE: THE CLASSIFICATION REVIEW AREA 3-1
3.1 Purpose of the Classification Review Area 3-1
3.2 Determining the Classification Review Area........ 3-2
3.2.1 Introduction 3-2
3.3 Expansion of the Classification Review Area 3-4
3.3.1 Introduction 3-4
3.3.2 Determining Whether Expansion is Warrant ad... 3-5
3.4 Subdivision of the Classification Review Ar«a 3-10
3.4.1 Introduction . .*. 3-10
3.4.2 Concepts of Ground-Water Units and
Interconnection 3-12
3.5 Characterizing the Classification Review Area 3-14
3.6 Location of the Classification Review Area
Boundary Relative to the Facility/Activity
Boundary 3-19
CHAPTER FOUR: CLASSIFICATION CRITERIA FOR CLASS I
GROUND WATER 4-1
4.1 Overview of the Decision Process 4-1
4.1.1 Definitions • 4-1
4.1.2 General Procedures 4-2
4.2 Procedures for Determining "Irreplaceable
Source for • Substantial Population" • • • • 4-8
4.2.L Step 1: Determination of Substantial
Population 4-10
4.2.2 step 2: Screening Tests to Make Preliminary
Determinations 4-11
4.2.3 step 3: Use of Qualitative criteria for
Final Irreplaceability Decisions 4-28
4.3 Procedures for Determining Ecologically Vital
Areas 4-30
ii
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TABLE OF CONTENTS (CONT.)
4.4 Procedures for Determining Highly Vulnerable
Areas ., „ 4-32
4.4.1 Factors Related to Vulnerability 4-33
4.4.2 Evaluation Aids for Assessing Vulnerability. 4-40
CHAPTER FIVE: CLASSIFICATION CRITERIA FOR CLASS II
GROUND WATER , 5-1
5.1 Overview, of the Decision Process 5-1
5.1.1 Subclass IIA: Current Source of Drinking
Water 5-1
5.1.2 Subclass IIB: Potential Source of Drinking
Water 5-4
5.2 Classification Procedures 5-5
CHAPTER SIX: CLASSIFICATION CRITERIA FOR CLASS III
GROUND WATER 6-1
6.1 Overview of the Decision Process 6-1
6.1.1 Definition of Class III 6.1
6.1.2 Purpose of and Policies Related to
Class III 6-1
6.1.3 General Procedures 6-2
6.2 Class III Designation Based on Insufficient
Yield 6-4
6.3 Class III Designation Based on Ground water
Quality and Treatability 6-6
6*3.1 Areal Extent of contamination 6-6
6.3.2 Standards and Criteria for Treatment 6-10
6.3.3 Overview of Class III Treatability Test,.... 6-11
6.3.4- Reference Technology "Screening Test1*.. 6-11
6.3.5 Economic Untreatability Test 6-22
6.4 Subclasses of Class III 6-25
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TABLE OF CONTENTS (CONT.)
BIBLIOGRAPHY B-l
GLOSSARY G-l
APPENDIX A: Supplemental Information: Classification
Review Area A-l
APPENDIX B: Supplemental Information: Class I
Procedures B-l
APPENDIX C: Supplemental Information: Class III
Procedures _ c-i
APPENDIX D: Supplemental Information: Class I and
Class III Economic Tests : D-l
iv
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LIST OF FIGURES
2-1.
2-2.
3-1.
3-2.
3-3.
3-4.
3-5.
3-6.
4-1.
4-2.
4-3.
4-4.
4-5.
4-6
4-7.
5-1.
5-2.
6-1.
6-2.
6-3.
Summary of Ground-Water Classes
Schematic Chart of General Classification
Procedures
Hypothetical Classification Review Area
Shoving Potential Class Determining
Factors
Ground Water Regions of the U.S
Large Facility
Large, Multiple-Activity/Facility
Small, Multiple-Activity/Facility.
Long, Irregularly Shaped Facility
General Procedure for Class I
Suggested Method for Determining Irreplace-
ability to Substantial Populations
Potential Institutional Constraints
Outline of Procedure for Analyzing Potential
Institutional Constraints to the Use of an
Ninetieth Percentile Economic Thresholds by
System Size
Ninetieth Percentile Economic Thresholds by
Illustration of Drastic Mapping
. Example Class IZ - Current Source of
Drinking Water
Example of Contamination that Should Not
Example of Contamination that May Qualify
For Class III Designation
2-3
2-6
3-3
3-7
3-20
3-21
3-22
3-22
4-3
4-9
4-17
4-18
4-26
4-27
4-47
5-3
5-6
6-3
6-8
6-9
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LIST OF FIGURES (CONT.
6-4. Alluvial Aquifar Separated Into Two Ground-
Water Units with High Interconnection to
a River 6-27
6-5. Cloned Basin/Arid Cliaatie Setting Containing
a Classification Rtvisv Area with a Singl«
Ground-wat«r unit 6-28
6-6. Exaapla of Probabl* Class IZB Ground Water.. 6-30
vi
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LIST OF TABLES
4-1. Generally Applicable Uncommon Pipeline
Distances 4-15
4-2. Factors Relevant to Judging Vulnerability
to Contamination 4-34
4-3. Ranges and Ratings for Depth to Water as
Used in the Numerical Rating System
DRASTIC . 4-49
4-4. Generalized Site Grade Based on Critical
Hydrogeologic Parameters 4-52
6-1. Reported Typically Achievable Contaminant
Removal Efficiencies 6-13
6-2. Description of Treatment Process 6-14
6-3. Effluent Quality Working Table from Sample
Problem 6-21
vii
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EXECUTIVE SUMMARY
Introduction
In August 1984, the U.S. Environmental Protection Agency
(EPA) issued a Ground-Water Protection Strategy, setting out
the Agency's plans for enhancing ground-water protection
efforts by EPA and the states. A central feature of the
Strategy is a policy framework for EPA's programs which
accords differing levels of protection to ground water based
on the resource's use, value to society, and vulnerability to
contamination. A three-tiered ground-water classification
system was established in the Strategy as a key operational
tool to help implement this policy.
The classification system recognizes that special ground
water exists due to its high vulnerability to contamination
and high value for drinking-water purposes or its importance
to a unique ecological habitat (Class I). The vast majority
of the nation's ground water falls within Class II which
encompasses all non-Class I current or potential sources of
drinking water. Class III ground water is not a potential
source of drinking water primarily due to levels of
contamination either from naturally occurring conditions or
the effects of broad-scale human activity that cannot be
feasibly cleaned up.
These Final Guidelines for classifying ground water
augment the Ground-Water Protection Strategy by
e Further defining the key terms and concepts of the
classification system, and
e Describing procedures and data requirements to
assist in classifying ground water.
The procedures in the Final Guidelines are generally
intended for site-specific ground-water classification based
on a review of the segment of ground water in relatively
close proximity to a particular source. Although the
specific procedures are not designed specifically for broader
aquifer classification, many of the concepts and procedures
developed for site-by-site classification will also be useful
in such classification efforts.
The manner and extent to which the Guidelines will be
incorporated into EPA regulatory, permitting, and planning
decisions are addressed in a supplemental Implementation
Policy statement being issued concurrently with the
Guidelines.
The key criteria for each class and procedural
approaches for determining whether the criteria are met are
outlined as follows:
E-l
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Classification Review Area
The first step in making a classification decision is
defining the area around the source that should be evaluated.
Once this Classification Review Area has been determined,
information regarding public and private wells, demographics,
hydrogeology, and surface water and wetlands is collected and
a classification decision is made based on the criteria for
each class as described below.
The Guidelines specify an initial Classification Review
Area as the area within a 2-mile radius of the boundary of
the facility or activity under review. Under certain
hydrogeologic conditions an expanded or reduced
Classification Review Area is allowed.
It should be emphasized that the Classification Review
Area defines a study area as one necessary »-j evaluate the
appropriate ground-water class in connection with a specific
site analysis and does not imply that action needs to be
taken relative to other facilities within the area.
Class 1 - Special Ground Water
Class I ground waters are defined as resources of
particularly high value. They are hicthlv vulnerable and are
either an irreplaceable source of drinking water for a
substantial population or ecologically vital.
e Hiohlv vulnerable ground water is characterized by
a relatively high potential for contaminants to
enter and/or be transported within the ground-water
flow system. The Guidelines provide both
quantitative and qualitative decision aids for
determining vulnerability based on hydrogeologic
factors.
• An irreplaceable source of drinking water for a
•ubstantial population is ground water yhose
replacement by water of comparable quality and
quantity from alternative source* in the area would
be economically infe&sible or precluded by
institutional barriers. The determination of
irreplaceability is based on a three-step process
that includes identifying the presence of a
substantial population, applying screening tests
designed to produce a preliminary determination,
and reviewing relevant qualitative criteria in
order to produce a final determination.
e Ecologically vital ground water supplies a
sensitive ecological system located in a ground-
water discharge area that supports a unique
E-2
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habitat. Unique habitats include habitats for
endangered species listed or proposed for listing
under the Endangered Species Act as veil as certain
Federally managed and protected lands.
C?.ass II - Current and Potential Sources of Drinking
and Ground Water Having Other Beneficial Uses
Class II ground waters include all non-Class I ground
water that is currently being used or is potentially
available for drinking water or other beneficial use.
Subclass IIA is a current source of drinking water.
Ground water is classified as IIA if within the
Classification Review Area there is either (1) one or
more operating drinking-water wells or springs, or (2) a
water-supply reservoir watershed (or portion of it) that
is designated for water-quality protection by either a
State or a locality.
Subclass IIB is a potential source of drinking water.
This ground water (1) can be obtained in sufficient
quantity to meet the minimum needs of an average family;
(2) has total dissolved solids (TOS) of less than 10,000
milligrams per liter (mg/L) ; and (3) is of a quality
that can be used without treatment or that can be
treated using methods reasonably employed by public-
water systems.
Class III - Ground Water Not a Potential Source of Drinking
Water and/or Limited Beneficial Use
Class III drinking waters have either (1) a TDS
concentration equal to or greater than 10,000 mg/L; or (2)
contamination by naturally occurring conditions or by the
effects of broad-scale human activity that cannot be cleaned
up using treatment methods reasonably employed in public-
water systems. A two-step teat, based on technical and
economic feasibility, is presented in the Guidelines. Class
III also encompasses those rare conditions where (3) yields
are insufficient to meet the minimum needs of an average
household. Subdivisions within Class III include the
following:
Subclass IIIA around water has an intermediate decree of
interconnection with adjacent ground-water units and/or
are interconnected with surface waters.
•Subclass TUB ground water has a low degree of
interconnection with adjacent ground-water units.
E-3
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CHAPTER ONE
INTRODUCTION
1.1 EPA'8 Ground-Hater Protection Strategy
EPA currently administers more than eight statutes which
direct the Agency toward reducing.or eliminating threats to
ground water from a large number and variety of sources..
This is a far-from-simple task and one which commands a major
part of the Agency's budget and personnel resources. Changes
in statutes and resulting regulations have occurred in the
past, and will continue to occur in the future, to further
manage these pollution sources. Through EPA's long-range
planning efforts and, more recently, an Agency-wide direction
toward overall risk management, ground-water protection on a
cross-media basis is receiving increased attention.
An important tool in this cross-program phase was made
available in August 1984 when EPA released its Ground-Water
Protection Strategy. The Strategy consists of four major
elements:
• Strengthen State Institutions — through technical
assistance and State Grants.
• Cope with Contamination Sources of National Concern
— through source-specific protection programs.
• Zaprov« consistency in Ground-water protection
decision* — through the establishment and
implementation of protection policies.
•. Strengthen EPA Institutions — through the
establishment of coordinating functions within the
Offices of Ground-Water Protection at Headquarters
and in the Regions.
Pursuant to the third element, the Agency adopted a
differential protection policy which acknowledges that ground
waters vary in terms of their current use, relative value to
society, and vulnerability to contamination. Ground-water
classification was introduced in the Strategy as an approach
for setting priorities for regulatory action and resource
management within this framework.
1.1
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1.2 Purpose of the Classification Guidelines
This document provides technical guidelines for the
classification system established in the Ground-Water
Protection Strategy. When the procedures and methods
outlined in this document are followed, ground water that may
be affected by a facility or activity under EPA review will
be placed within a relevant class or classes which represent
an implied hierarchy of protection. This document should be
viewed essentially as a set of technical guidelines for
ground-water evaluation via classification. The issue of
implementation of the Classification Guidelines by EPA
programs is addressed in a separate Implementation Policy
Statement.
It is important to note that these Guidelines are not
designed specifically for classifying large segments of land,
aquifers, etc., in advance of any specific decision.
Instead, the system, focuses on the classification of the
ground water around specific sites or areas where a decision
related to a permit, degree of clean up or regulation, etc.,
is to be made. The methods and techniques in the Guidelines
will, however, provide useful information for State or local
governments that choose to review or implement broader
classification systems.
1.3 Guidelines Development
The?^development of these Guidelines began in August
1984, an*consisted of three phases: definition, testing, and
review. Throughput the process, the Office of Ground-Water
Protection (OGWP) worked closely with representatives from
several states, EPA regions, other EPA programs,'and the U.S.
Geological Survey.
In the definition phase, key terms and concepts related
to the classification scheme described in the strategy were
analyzed in detail. These key terms and concepts included
irreplaceable source of drinking water to a substantial
population, ecologically vital, highly vulnerable, and
current source of drinking water. Several alternative
options for defining each term were drawn up, along with data
requirements and methodologies for employing each. Many of
1-2 .
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the alternative options were derived from approaches used by
other EPA, State, and local programs to address similar or
related concepts. Each approach was examined with respect to
the following:
• Adaptability with statutes, other programs,
and with the overall intent of the Strategy;
• Flexibility for accommodating State- and
region-specific characteristics or concerns;
• Arbitrariness; and
• Potential difficulties or complexities in
implementation.
The next phase involved the preparation of detailed test
case studies. The information acquired from this phase led
to refinements of the classification procedures.
Finally, the project focused on review and revision of
several drafts. A Final Draft was released for public
comment in December 1986. The public comments received were
considered in developing these Final Guidelines.
1.4 Organization of Guidelines Document
Chapter One introduces EPA's Ground-Water Protection
Strategy and discusses the purpose and development of the
classification Guidelines. Chapter Two provides an overview
of the classification system and general classification
procedures. The remaining chapters focus on individual
aspects of the classification system. Chapter Three contains
information about the Classification Review Area, including
its purpose, the determination of the basic 2-mile radius
review area, and the factors pertaining to its expansion or
subdivision. Chapters Four, Five, and Six focus on Classes
I, II, and III respectively. Each chapter contains a basic
review-of the class definition, as well as a discussion of
key terms and concepts pertinent to the class. In each case
the classification decision process is presented and
discussed in detail. In addition, various techniques and
background information that nay be helpful in arriving at a
classification decision are also presented*
A glossary and a series of appendices follow Chapter
Six. Appendix A contains information supplemental to Chapter
Three, including the technical basis for the 2-mile radius
Classification Review Area as well as detailed procedures for
1-3
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determining expanded or subdivided review area dimensions.
Appendices B and C provide supplemental information for the
non-economic aspects of class I and Class II (Chapters Four
and Six). Appendix D provides guidance for applying the
common aspects of the Class I and Class II economic tests.
1-4
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CHAPTER TWO
OVERVIEW OF THE GROUND-WATER CLASSIFICATION SYSTEM AND PROCESS
The three basic ground-water classes established in the
1984 EPA Ground-Water Protection Strategy, which represent a
hierarchy of ground-water resource value to society, are as
follows:
• Class I - Special Ground Waters
• Class II - Current and Potential Sources of Drinkinqr
Water and Water Having Other Beneficial Uses
e Class III - Ground Water Not a Potential Source of
Drinking Water and of Limited Beneficial Use
The classification system is, in general, based on the
principle that drinking water is the highest beneficial use
of the resource. All drinking-water sources would fall
within Class I or Class II.
Ground water is used in other beneficial applications,
such as manufacturing, electric-power generation, livestock
production, irrigation, and ecosystem support. Class I or
Class II ground waters are compatible with such applications,
in that water of a quality suitable for drinking will also be
of suitable quality to serve as a raw-water source for most
other beneficial uses. Class I does include a special non-
drinking-water component for ecologically vital ground water.
Class III ground waters, although not potential sources of
drinking water, may be of limited beneficial use, such as for
industrial process cooling water.
Some) ground-water classification systems, generally
termed anticipatory classification systems, classify and map
aquifer* or aquifer portions in advance of management or
remediation decisions. Although the criteria and concepts in
EPA's system can be used for such anticipatory classifica-
tion, EPA's system is primarily designed for classifying the
ground water in the vicinity of a particular facility or
activity as appropriate within a given regulatory program.
In this site-by-site classification approach, the
classification criteria are applied on the basis of informa-
tion collected in a review area, referred to as -the Clas-
sification Review Area, around the site or activity.
This chapter provides an overview of the EPA ground-
water classification system, each component of which is
discussed in more detail in subsequent chapters.
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2 .1 Ground-Water Classes
As previously mentioned, the EPA Ground-Water
Classification System consists of three major classes. Two
of these classes are further differentiated into subclasses,
allowing for the refinement in the hierarchy of recognized
resource values (Figure 2-1). Key terms and concepts define
the classes and subclasses.
2.1.1 Class I - Special Ground Waters
Class I ground waters are defined as resources of
unusually high value. They are highly vulnerable to con-
tamination and are (1) irreplaceable sources of drinking
water to substantial populations and/or (2) ecologically
vital. Ground water that is highly vulnerable to
contamination is characterized by a relatively high potential
for contaminants to enter and/or to be transported within the
ground-water flow system. The number of Class I designations
is expected to be small.
Ground water may be considered irreplaceable to a
substantial population if alternative water-supply sources of
comparable quality and quantity are beyond a reasonable
transport distance, would be economically infeasible to
develop, or are precluded from delivery (or would be very
difficult to deliver) because of institutional constraints.
Ground water may be considered ecologically vital if it
supplies a sensitive ecological system located in a ground-
water discharge area that supports a unique habitat. A
unique habitat is defined to include habitats for endangered
or threatened species that are listed or formally proposed
for listing pursuant to the Endangered Species Act (as
amended in 1982), as well as certain types of Federally
managed and protected lands.
A more detailed explanation of Class I concepts and
procedures is provided in Chapter Four.
2.1.2Class II - Current and Potential sources of Drinking
Water and Water Having other Beneficial Uses
All non-Class I ground water currently used, or poten-
tially available, as a source of drinking water and for other
beneficial use is included in this category, whether or not
2-2
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FIGURE 2-1
SUMMARY OF GROUND-WATER CLASSES
CLASS
KEY TERMS
HIGHLY VULNERABLE
AND EITHER
IRREPLACEABLE TO
SUBSTANTIAL POPULATIONS
SB.
ECOLOGICALLY VITAL
IIA
CURRENT SOURCE Of
DRINKING WATER
I1B
POTENTIAL SOURCE OF
DRINKING WATER
IIIA
NOT A SOURCE OF DftlNKINO WATER
INT—MEDIATE TO HIGH INTERCONNECTION
A* OPOOMG/L TDS OR UNTREATA3LE
. SOURCE OF DRINKING WATER
E TO INSUFFICIENT YIELD
UIB
NOT A SOURCE OF DRINKING WATER
LOW INTERCONNECTION
MGA. TOS OR UNTREATABLE
-------
it is particularly vulnerable to contamination. This class
is divided into two subclasses: current sources of drinking
water (Subclass IIA), and potential sources of drinking water
(Subclass IIB).
The concept of a current source of drinking water is
rather broad by intent. Only a portion of the ground water
in the Classification Review Area must supply drinking water.
Ground water is considered a current source of drinking water
under two conditions: (1) one or more operating drinking-
water wells (or springs used as sources of drinking water);
or (2) a water-supply reservoir watershed (or portion of a
water-supply reservoir watershed), designated for water-
quality protection by either state or local government, oust
be present within the Classification Review Area. In some
circumstances, intakes on surface water (used for drinking
water supply) may also warrant a Class IIA determination.
A potential source of drinking water ie .one capable of
yielding a quantity of drinking water to a well or spring
sufficient for the minimum needs of an average-size family.
Drinking water is defined as water with a tptal-dissolved-
solids (TDS) concentration of less than 10,000 milligrams per
liter (mg/L) that can be used for drinking purposes without
first being treated, or that can be rendered drinkable after
being treated by methods reasonably employed in a public
water-supply system. All around waters are presumed to meet
both the yield and quality criteria for a current or
potential source of drinking water unless a successful Claas
III demonstration is performed.
Class II ground waters constitute the majority of the
nation's ground-water resources that may be affected by human
activity. Class II ground waters will generally receive the
very high level of protection that represents the baseline
degree of protection which is the standard for EPA programs.
The procedures for making a Class II determination are
discussed in greater detail in Chapter Five.
2.1.3 CXlM III - Ground Water Not a Potential Source of
Drinking Water and of Limited Beneficial Use
Ground waters that are saline, or otherwise contaminated
beyond levels that would permit their use for drinking or
other beneficial purposes, are in this class. These include
ground waters which (1) have & TDS concentration equal to or
greater than 10,000 mg/L, or (2) are so contaminated by
naturally occurring conditions, or by the effects of broad-
scale human activity (unrelated to a specific activity) that
they cannot be cleaned up using treatment methods reasonably
employed in public water-supply systems. In addition, Class
2-4
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Ill encompasses ground waters in those rare settings (3)
where yields are insufficient to meet the minimum needs of an
average household.
Two tests are provided to assist in determining Class
III treatability. The first test, referred to as the
reference technology test, is a screening tool which compares
the treatment scheme needed to treat contaminated ground
water in the area surrounding a facility, . to a list of
technologies which appear* relevant for public water-supply
treatment. If none is appropriate, then the ground water may
be technically untreatable, pending economic analysis. The
second treatability test, referred to as the economic
untreatability test, is applied to determine whether
treatment of the water for a hypothetical user population
would be economically feasible. Both of these tests are
described in more detail in Chapter Six.
Class III is subcategorized primarily on the basis of
the degree of interconnection with adjacent ground-water
units or surface waters. Subclass IIIA ground waters have an
intermediate degree of interconnection to adjacent ground-
water units and/or are interconnected with surface waters.
As a result, they may be contributing to the degradation of
the adjacent waters. Class IIIA ground waters may be managed
at a level similar to a level at which Class II ground waters
are managed, depending upon the potential for producing
adverse effects on the quality of adjacent waters. In ad-
dition, Subclass IIIA encompasses all ground waters from low-
yield settings unless Class I or Class II criteria have been
demonstrated.
Subclass IIIB ground waters are characterized by a low
degree of interconnection to adjacent ground-water units
within the Classification Review Area. These ground waters
are naturally isolated from sources of drinking water in such
a way that there is little potential for producing additional
adverse effects on human health and the environment. They
have low resource values outside of mining, oil and gas
recovery* or waste disposal.
Detailed information concerning Class III determinations
as well as hypothetical examples are provided in Chapter Six.
2.2 General Classification Procedures
'This section provides guidance for initiating the
classification process. An outline of general classification
procedures is given in Figure 2-2. A likely sequence of
classification steps, as well as alternative sequences are
2-5
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FIGURE 2-2
SCHEMATIC CHART OF GENERAL CLASSIFICATION PROCEDURES
DELINEATION OF
CLASSIFICATION REVIEW AREA
BASIC DATA COLLECTION
•
SOURCE OF OMINKINO WATCH OR ECOLOGICALLY VITAL AREAS
I
Ot
CLAS<
MIONLV
VULNERABLE
ECOLOGICALLY
VITAL AREAS
I 1 »
/--
^
t
1
•ROCE
-"N
^
s
OURC
HIONLY
VULNERABLE
IRREPLACEABLE
SOURCE OF
ORINNINO WATER
TO A SUBSTAN-
TIAL POPULATION
NO-*-
CLASS II
PROCEDURES
YES
o
NOT A S
>URCE OF
DRINKINO WATE'ft
1
CLASS 111
PROCEDURES
VI
-------
discussed in this section, cross references are made to
those chapters that contain more detail on a specific
classification procedure. Sources of infornation and data
needed for classification are discussed, generally, in
Section 2.3.
The first step in EPA's site-by-site classification
procedure is to draw a 2-mile radius around the sit* that is
to be classified — this is the standard Classification
Review Area. The second step is to collect basic information
about the classification Review Area concerning demography/
local use of ground water, general hydrogeologic conditions,
and the presence of ecologically vital areas and surface
waters. The information collected may indicate that expan-
sion or subdivision of the standard 2-mile radius
Classification Review Area would be appropriate. If the
Classification Review Area is expanded, additional data about
the expanded portion is normally gathered. If subdivision is
contemplated, the classifier will typically collect
additional hydrogeologic information to support a subdivision
demonstration. Detailed procedures for determining the size
and configuration of the Classification Review Area,
including expansion and subdivision, are discussed in Chapter
Three.
The third step in the classification procedure is to
assign the ground water to a particular class, based on the
data collected. A classifier beginning this step will
typically face two choices: (1) to assess the likelihood
that the ground water is a source of drinking water or
ecologically vital (Class I or II), or (2) to assess the
likelihood that the ground water is not a source of drinking
water (Class III). (This procedure is illustrated in Figure
2-3.) Preliminary information should indicate which of the
two choices is most likely. If the classifier chooses to
begin the analysis with an initial look at the likelihood of
a Class III determination, it is still necessary to
demonstrate that the ground water is not a current or
potential source of drinking water or ecologically vital.
For example, while the ground water may be initially
considered contaminated and untreatable, if a private
drinking water well is present in the review area, the ground
water should be assigned to Class II. Most classifiers will
find it aost efficient to begin with an analysis of the
likelihood of a Class I determination, and then review the
possibility of a Class III determination if there are no
wells, drinking-water reservoirs or springs, and no ecologi-
cally vital areas within the Classification Review Area.
The classification procedure is an iterative process,
with each iteration building upon the previous one. For
example, if the classifier has gone through the classifica-
tion process and determined that the ground water will most
likely be Class I, it may be necessary to go back to Step 2
2-7
-------
and collect additional information to ensure that the most
appropriate class decision is made. This process can be
repeated until an accurate and appropriate classification is
obtained.
2.3 Collection of Basic Information
Basic inforaational needs for classification are
outlined in this section. More detailed information is
provided in Chapter Three (The Classification Review Area),
as well as in subsequent chapters, which discuss each of the
classes in turn. The collection of basic information is
meant to reflect an approach to classification that begins
simply and directly. It will typically include a well and
reservoir survey, demographic information, basic water-
quality data, and identification of ecologically vital areas.
Regional and local hydrogeologic data will normally be
gathered if an interconnection analysis is undertaken.
Otherwise, a general description of the regional geology,
ge©morphology, and hydrogeology would normally suffice.
Again, the emphasis is on available information rather than
on detailed in-field analyses. A more rigorous analysis is,
in general, necessary to support a Class III determination.
Well information may be obtained from water authorities,
utilities, public-health agencies, regulatory agencies
permitting well drilling, well drillers, or other State or
local entities. Basic water-quality information is usually
available from local health agencies, other State and local
agencies, and national data bases such as STORET. In some
cases, university research departments may be able to supply
needed data. Assistance in identifying ecologically vital
areas may be obtained from the U.S. Fish and Wildlife
Service. Regional and/or local hydrogeologic and geologic
information may be available from county/regional reports of
the U.S. "iiB& State geologic surveys. Demographic information
can be obtained from the U.S. Census Bureau.
2-8
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CHAPTER THREE
THE CLASSIFICATION- REVIEW AREA
3.1 Purpose of the classification Review Area
Classifying ground water involves applying the clas-
sification system's criteria to a segment of ground water.
In some systems, generally termed anticipatory classification
systems, criteria are applied on a regional or aquifer basis,
and class determinations are mapped in advance of specific
management decisions. Although the criteria and concepts in
EPA's system can be used for such anticipatory classifica-
tion, EPA's system is primarily designed for classifying the
ground water in the vicinity of a particular facility or
activity as appropriate within a given regulatory program.
Thus, this first step in EFA's site-by-site classification
procedure is to determine the size and configuration of the
Classification Review Area around the site to which the
classification criteria will be applied.
EPA believes that it is appropriate to look at a broad
area for characterizing the ground water which may be
affected by the activity(ies) at a particular site. Within
the Classification Review Area, basic information is
collected concerning hydrogeologic conditions, public-supply
wells, populated areas not served by public supply, wetlands,
and surfaeet waters, as described in Section 3.5 of this
chapter. Through applying the use, value, and vulnerability
criteria, a ground-water class determination is aade which
may be used as a factor in determining what specific
regulatory action or decision is appropriate for the site.
However', it should be noted that a classification decision
will apply only to the specific facility or site in question
and for which the Classification Review Area was drawn.
-------
3.2 Determining the Classification Review Area
3.2.1 Introduction
As a first step, an 'initial Classification Review Area
will most often be determined by drawing a 2-mile radius from
the facility or activity for which the class determination is
being made. Some EPA programs utilize a somewhat larger
review area, the use of which is covered by the
Implementation Policy Statement.
A Classification Review Area with a 2-mile radius around
a proposed facility is shown on Figure 3-1. The site of the
facility is approximately 500 feet in dimeter. Water
supplies in the Classification Review Area i.-";lude a public
water-supply system well and a densely settled area of
private wells. A river with a wetland runs through the
review area. Each of these facts may bear on the decision of
the class of ground water.
EPA selected 2-miles as a typically appropriate radius
size for the Classification Review Area after analysis of
three sources of data that provided insight into the length
of the flow path over which high degrees of interconnection
occur and indicated distances contaminants could be expected
to move in problem concentrations should they be accidentally
introduced into the ground-water system. The sources of data
examined were as follows:
• A survey of contaminant plumes from investigations of
existing spills, leaXs, and discharges.
• A survey of the distances to downgradient surface
waters from hazardous-waste facilities.
e calculations of the distances from which pumping
walls draw ground water under different hydrogeologic
.conditions. .
Analyses of the data .indicate that in 95 percent of the
cases, the lengths and distances of contaminated ground-water
plumes from hazardous waste facilities to downgradient
surface waters likely to be discharge points for shallow
ground water are less than 2 miles. A detailed discussion of
these data and their interpretation is provided in Appendix
A.
3-2
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FIGURE 3-1
HYPOTHETICAL CLASSIFICATION REVIEW AREA
SHOWING POTENTIAL CLASS DETERMINING FACTORS
LJ
I
—vvirvvirirviri^Jiririrwiririririr
-------
Under certain hydrogeoiogic conditions, however, expan-
sion or subdivision of the 2-nile radius Classification
Review Area may be appropriate. Sections 3.3 and 3.4 provide
guidance on the types of situations where expansion or
subdivision of the Classification Review Area nay be
warranted, as well as procedures for making these
adjustments. Basic data needs for the characterization of
the Classification Review Area prior to application of the
classification criteria are discussed in Section 3.5.
Guidance for drawing the Classification Review Area
boundaries from various sized, regularly and irregularly
shaped facilities is given in Section 3.6.
3.3 Expansion of the Classification Review Area
3.3.1 Introduct ion
As mentioned previously, under some hydrogeoiogic
conditions, a 2-mile radius review area may be insufficient
for characterizing the ground water that may potentially be
affected by a facility. In areas of very high flow
velocities that occur over distances greater than 2 miles,
there is a potential for activity-related contaminants to
move beyond a 2-mile radius in a relatively short time frame,
especially under the influence of large-scale ground-water
withdrawals. -hough it is expected that the 2-mile review
area will be . :ficient in extent to accommodate the vast
majority of classification decisions, this section presents
guidance for identifying those unusual situations where an
expanded review area nay be appropriate. In addition,
general procedures are suggested to establish the dimensions
of the expanded Classification Review Area based on available
informatiflto concerning hydrogeoiogic characteristics. . (Note
that semi-SPA programs routinely use • somewhat larger review
area; this* section addresses situations where a still larger
area might be warranted due to hydrogeoiogic conditions.) A
detailed discussion of Classification Review Area expansion
is presented in Appendix A.2.
3-4
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3.3.2 Determining Whether Expansion Is Warranted J
Deciding whether to expand the Classification Review
Area is a judgment of the classifier, made on a case-by-case
basis. As a general'rule-of-thumb, expansion is intended for
those situations likely to result in the transport of
contaminants beyond 2 miles during a period of 10 years or
less. This translates to cases where ground-water velocities
exceeding 1,000 feet/year (ft/yr) over a substantial distance
are prob-able. Ten years is assumed to be a reasonably
conservative tine period for controlling contaminant.(s) after
the contaminants have been detected. Very few settings have
ground-water migration exceeding a distance of 2 miles within
a 10-year period; therefore, Classification Review Area
expansion is likely to be the exception rather than the rule.
It is not necessary to have precise ground-water
velocity data for the review area in order to decide if
expansion is appropriate; however where possible, such data
should be examined. It is anticipated that investigations
pertaining to RCRA land-disposal facilities or Superfund
ground-water contamination sites will, as a routine matter,
already incorporate the information necessary to determine
ground-water velocities.
Other situations will likely not be investigated in
sufficient detail to gauge ground-water velocity; a general
screening procedure can be employed in the absence of
velocity information. """ This procedure involves matching
hydrogeologic conditions 'in the 2-mile review area to generic
hydrogeologic settings, where high velocities are very
commonly found. The following sections provide a discussion
of high-velocity settings for the classifier's reference.
Note that there may be specific high-velocity settings known
to regional or State authorities that are not discussed here.
High-Velocity Hvdroaeoloav
Hydrogeologic settings can generally be classified into
two type* of ground-water flow regimes, Darcian and non-
Dare ian. The identification of the dominant flow regime at a
specific site can be useful in evaluating the need to expand
the Classification Review Area.
Darcian flow refers to the movement of water under
conditions where Darcy's law applies. Typically, these
conditions involve intergranular, laminar flow, without
turbulence. Darcy's law states that the velocity of flow, v,
is equal to the product of a factor called hydraulic conduc-
tivity, X, and the hydraulic gradient (e.g., slope of the
water table in an unconfined aquifer) divided by the aquifer
3-5
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porosity. (These terss are defined in the glossary.) When
turbulent flow occurs, as in water moving in a pipe, Darcy's
law does not apply for determining flow velocities. Gen-
erally, the non-Darcian flow settings have higher velocities,
due to the pipe-like flow, than Darcian flow settings and,
for this reason, are strong candidates for an expanded review
area.
Non-Darcian flow occurs in geologic settings where
secondary porosity dominates the ground-water flow regime.
Secondary porosity refers to relatively large continuous
openings, fractures, or tunnels (i.e., the pipe-like .fea-
tures) that transport water. Intergranular flow moving
according to Darcy's law contributes a proportionately
insignificant volume of flow in these settings. Examples of
non-Darcian flow settings include mature karst, fractured
rock, and extrusive igneous rocks (basaltic lava). For
hydrogeologic settings with predominantly non-Darcian flow,
it is likely that the flow velocity is so great that
Classification Review Area expansion is appropriate.
In Darcian settings, it will be unlikely that flow
velocities as high as 1 mile a year will occur except over
very short distances not representative of flow throughout a
ground-water unit. However, velocities in the range of 1,000
ft/yr, although rare, can be expected and would be supportive
of an expanded Classification Review Area. Settings where
Darcian flow predominates and high velocities frequently
occur include alluvial basins, other alluvial materials,
coastal plains, and glacial outwash settings, that is,
aquifers that are primarily composed of coarse sand and
gravel.
Descriptions of high-velocity hydrogeologic settings,
Darcian and non-Darcian, and where these settings are likely
to occur are provided in the following subsections. The
likelihood of encountering high-velocity flow regimes can.be
roughly associated with selected ground-water regions. Heath
(1984) developed a map of ground-water regions (Figure 3-2)
and summarized the hydrogeologic characteristics of each
region. .The) general hydrogeologic conditions characteristic
of each cj£ the regions can be used to preliminarily evaluate
the likelihood of encountering a high-velocity ground-water
regime at a- specific site. Information from the review area
should .be relied on for the final judgment concerning
expansion.
Non-Dareian Settings. Non-Darcian settings can be grouped
into three general categories: karst, fractured rock, and
extrusive igneous rocks (e.g., basalts). These settings are
very common in some regions and are expected to account for a
significant, but not dominant, portion of hydrogeologic
settings. For judging review area expansion, it is important
to determine if the subject ground-water unit is
3-6
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FIGURE 3-2
GROUND WATER REGIONS OF THE U.S. (Heath 1984)
-------
predominately non-Darcian flow. If non-Darcian flow
contributes to a minor part of the flow in the subject
ground-water unit, the setting should be treated as a Oarcian
flow setting with respect to review area expansion.
Karst settings that are most likely candidates for an
expanded Classification Review Area are those where the
subject ground water is relatively shallow (
-------
Jcr vn to be high yielding and are primarily used for non-
ce,--unity domestic supply.
Fractured-rock settings are most prevalent in the
following ground-water regions (Heath, 1984):
Northeast and Superior Uplands.
Piedmont and Blue Ridges.
Western Mountain Ranges.
Columbia Lava Plateau.
Colorado Plateau and Wyoming Basin.
Non-Glaciated Central Region.
Glaciated Central Region.
Extrusive igneous rocks (s.g., basalts) will usually
have zones of high transmissivities and velocities. They are
often found in association with sedimentary rocks in the
Columbia Lava Plateau Region. These aquifers are composed of
sequences of basaltic lava flows that have developed
extensive secondary porosity. A lava flow cools rapidly at
the surface. As a result, brittle crust forms and is broken
into angular fragments by the continued movement of
underlying lava. These lava flows may also have lava tubes
that act like large-diameter pipes. In addition, the lava
flows are subject to fracturing, as lava cools, and the
formation of bedding joints. The result is an earth material
with considerable secondary porosity that, when saturated,
may have a very high transmissivity. These settings are very
common in the following ground-water regions (Heath 1984):
e Columbia Lava Plateau.
e Hawaiian Islands.
Darcian Settings. Darcian-type flow settings where high
ground-water flow velocities can be expected are rare and are
restricted to aquifers with relatively high hydraulic
conductivities or transmissivities. Such settings are
predominated by coarse grain size, e.g., sand and gravel,
with very minor inclusions of silt and clay. Hydraulic
conductivities in coarse-grained materials can sometimes be
greater than 500 gallons per day per square feet
(gal/day/ft2) and have ground-water velocities greater than
1,000 ft/yr. Such Darcian settings aay be found in any
region of the country. Generally, they are found in alluvial
basins, other alluvial materials, coastal plains, and glacial
outwash settings.
3-9
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3.4 . Subdivision of the Classification Review Area
3.4.1 Introduction
For most classification determinations, the assumption
is that all the ground water within the Classification Review
Area is highly interconnected and, therefore, is classified
as one unit. Sometimes, however, the classifier may wish to
subdivide the Classification Review Area into separate
ground-water units, as there may be naturally occurring
ground-water bodies of significantly different use and value
within the Classification Review Area that need to be
considered as part of the decision-making process for the
activity or facility involved. These ground-water units may
be adjacent laterally and/or vertically to one another. The
principal technical issue is to what degree the adjacent
units are interconnected, that is, to what extent would an
adverse effect on water quality in one unit produce an
adverse change in water quality in the adjacent unit. A low
degree of interconnection suggests little 'potential for
ground-water migration; a high degree suggests the need to
consider the impact of potential migration between units.
The concepts of ground-water units and the interconnec-
tion between adjacent ground-water units are especially
important in Class III determinations, where degree of
interconnection distinguishes the subclasses IIIA and IIIB
(see Chapter Six). Subdivision of the review area may also
be appropriate in determining whether there is discharge to
ecologically vital areas for Class I determinations.
Finally, the classifier may wish to subdivide the
Classification Review Area to permit a more sophisticated
hydrogeologic analysis of the potential impacts of a facility
or activity as a step in determining the specific prevention
measures or remedial action to be employed at a site.
Subdivision of the Classification Review Area will
generally be necessary to demonstrate the existence of the
following types of conditions:
• Relative to a specific site, deep ground-water units
with Class IIIB water are overlain at a shallow depth
by ground-water units with Class r or II water.
e The ground-water unit associated with ah activity
does not discharge to an ecologically vital area
present in the Classification Review Area.
3-10
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• Relative to a specific site, a shallow, ground-water
unit with Class IIB ground water (i.e., a potential
source of drinking water) is underlain by a deeper
ground-water unit with Class IIA ground water (i.e. a
current source of drinking water).
Hydrogeologists routinely assess the interconnection
between bodies of ground water for such purposes as designing
water-supply systems, monitoring systems, and corrective
actions to address contaminated water. Where ground-water
bodies are shown to have low interconnection, it is possible
to consider them separately in assessing their use and value.
Waters within a ground-water unit are inferred to be highly
interconnected and, therefore, a common use and value can be
determined.
Prevention or cleanup decisions for a ground-water unit
with low interconnection to adjacent ground water or surface
water can be expected to have no, or very limited, impact on
the quality of the adjacent waters. Conversely, where there
is high interconnection to adjacent ground water or surface
water, the classifier's decision should take into account the
potential impact that contamination of one ground-water unit
(which may not itself be of great value) may have on higher-
quality ground-water units.
The identification of ground-water units and the evalu-
ation of interconnection between ground-water units may, in
critical cases, require a rigorous hydrogeologic analysis.
The analysis may be dependent upon data collected off-site
that is not part of the readily available information nor-
mally used in a classification decision. For these reasons,
subdivision is expected -to be on an exception basis rather
than a routine part of classification; EPA will, in most
cases, assume a high degree of interconnection within the
Classification Review Area.
Once ground-water units within the Classification Review
Area have been identified, each unit that say be affected by
an activity/facility under review is reviewed according to
the criteria or methods in these Guidelines. Note that in
the relationship between subdivision and classification:
• -All ground water within a ground-water unit has a
single class designation with respect to the facility
being considered.
e Boundaries separating waters of different classes
must coincide with boundaries of ground-water units.
3-11
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• Boundaries of the Classification Review Area do not
constitute ground-water unit boundaries unless they
meet the conditions for subdivision boundary (Type 1,
2, 3, or 4 boundaries).
•If a subdivision boundary cannot be acceptably
demonstrated, then the existence of a single ground-
water unit should be assumed.
3.4.2 Concepts of Ground-Water Units and Interconnection
Ground-water units are components of the ground-water
regime, which is defined as the sum total of all ground water
and surrounding geologic media (e.g., sediment and rocks).
The top of the ground-water regime would be the uppermost
surface of the zone of saturation while the bottom would be
the base of significant ground-water circulation. Tempor-
arily perched water tables within the vadose zone (see
Glossary) would generally not qualify as the upper boundary
of the regime. The Agency recognizes that upper and lower
boundaries are sometimes difficult to define and their
location must be established based on the best available
information and professional judgment.
The ground-water regime/ encompassed by the Classifica-
tion 'Review Area, can be subdivided into mappable, three-
dimensional, ground-water units. These are defined as bodies
of ground water that are determined on the basis of four
types of boundaries as described below,
Type l: Permanent ground-water flow divides. These
flow divides should be stable under all
reasonably foreseeable conditions, including
planned manipulation of the ground-water
regime.
Typex 2: Extensive, low-permeability (non-aquifer)
geologic units (e.g., thick, laterally exten-
sive confining beds), especially • where
characterized by favorable hydraulic head
relationships across them (i.e., the direc-
tion and magnitude of flow through the low-
permeability unit). The most favorable
hydraulic head relationship is where flow is
toward .the ground-water unit to be classified
and the magnitude of the head difference
(hydraulic gradient) is sufficient to
maintain this* direction of flow under all
foreseeable conditions. The integrity of the
low-permeability unit should not be inter-
rupted by improperly constructed or abandoned
3-12
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wells, extensive, interconnected fractures,
nine tunnels, or other apertures.
Type 3: Permanent fresh-water/saline-water contacts
(saline waters being defined as those waters
with greater than 10,000 mg/L of IDS). These
contacts should be stable under all
reasonably foreseeable conditions, including
planned manipulation of the ground-water
system.
Type 4: Hydraulic gradient-based boundaries separat-
ing permanent upgradient from permanent
downgradient parts of a shallow ground-water
unit, (uppermost aquifer). These boundaries
must be simulated assuming worst-case
withdrawal rates in the upgradient region.
The type of boundary separating ground-water units
reflects the degree of interconnection between those units.
Adjacent ground-water units demarcated on the basis of
boundary Type 2 are considered to have a low degree of
interconnection. A low degree of interconnection implies a
low potential for an adverse water-quality change in one
ground-water unit to cause a similar adverse change in an
adjacent ground-water unit due to the migration of
contaminants. A low degree of interconnection is expected to
be permanent, unless improper management (e.g., presence of
significant numbers of improperly installed or abandoned
wells) causes the low-permeability flow boundary to be
breached. The lowest degree of interconnection occurs where
a Type 2 boundary separates naturally saline waters in a
deeper ground-water unit from overlying fresh waters (less
than 10,000 mg/L TDS), and the hydraulic gradient (flow
direction) across the confining layer (Type 2 boundary) is
toward the saline waters.
Type 2 boundary conditions are particularly important
for distinguishing Subclass IIIB ground-water units. In this
regard, the Type 2 boundary criteria encompass, but are not
limited to, the vertical interconnection criteria for Class I
injection veils pursuant to the Underground Injection Control
program.
Adjacent, ground-water units demarcated on the basis of
boundary Type 1 (ground-water flow divide), Type 3 (fresh-
water/saline water contact), and Type 4 (gradient based) are
considered to have an intermediate degree of interconnection.
An intermediate degree of interconnection also implies a
relatively low potential for adverse water-quality changes in
one ground-water unit due to migration of contaminated waters.
from an adjacent ground-water unit.
3-13
-------
A high degree of interconnection is inferred when the
conditions for a lower degree of interconnection are not
demonstrated. High interconnection of ground waters is
assumed to occur within a ground-water unit and where ground
water discharges into adjacent surface waters. A high degree
of interconnection implies a significant potential for cross-
contamination of waters if a component part of these settings
becomes polluted.
The degree of interconnection across the boundary types
defined here depends on selected key physical and chemical
processes governing movement of water and dissolved solute in
the subsurface. Under steady-state ground-water flow
conditions, the principal mechanisms affecting potential
contaminant movement across Type 1, 3, or 4 boundaries would
be mechanical dispersion and chemical diffusion. These con-
ditions are considered by EPA to represent an intermediate
degree of interconnection. Under transient flow conditions
caused by pumpage or accelerated recharge of fluids within
the Classification Review Area, the potential exists to spat-
ially displace any of these three boundari-ts; For this
reason EPA believes that foreseeable changes in aquifer
stresses and increased ground-water use in the Classification
Review Area should be considered in determining the perma-
nence (i.e., location over time) of such boundaries.
The primary mechanism for contaminant transport across a
Type 2 boundary is the physical movement of ground water into
or from the low-permeability geologic unit. The Agency
recognizes that the physical and chemical processes that
control fluid and solute transport through low-permeability
non-aquifers is not as well understood as it is for aquifers.
However, for the purposes of assessing the degree of inter-
connection, it is assumed that the flow rate of water through
the non-aquifer is very small relative to the flow rates
through adjacent aquifers.
Appendix A.2 presents further guidance and examples on
how boundaries between ground-water units are identified.
3.5 Characterizing the classification Review Area
After the Classification Review Area dimensions have
been determined, the first step in making a classification
decision involves collecting basic information about the
Classification Review Area. This basic information on
demography, the presence of ecologically vital areas, the
local use of ground water for water supply, and the
hydrogeology will serve as the starting point for the
3-14
-------
classification process, pointing the way to where more
detailed data collection or analysis nay be needed to arrive
at a class determination. At this stage, the emphasis is on
collecting the most current, best data that is readily
available.
The basic data needs are keyed to the principal distinc-
tions between the ground-water classes. Use and value
distinctions are based on the extent to which the ground
water is now or could be used in the future as a source of
drinking-water supply, and if contamination of the ground
water could affect ecologically vital areas. Other distinc-
tions between classes are based on hydrogeologic considera-
tions, such as vulnerability and degree of interconnection
with adjacent ground water and surface water.
Collection of the btsic data needed to characterize the
Classification Review Area is discussed below, along with
suggestions for possible sources of data. For some deci-
sions, the level of detail at this stage will be sufficient
to make a class determination; for other decisions, or where
readily available information is inadequate for making a
class distinction, more detailed data collection and analysis
may be needed. Subsequent chapters discuss each of the
classes and provide further guidance on informational needs
related to each respective class.
It is recommended that the sources of all information
collected be recorded for future reference. When information
is not readily available, noting this fact in the file along
with what avenues were pursued, may avoid retracing steps at
a later time.
Well Survey
A well survey to identify the presence of drinking
water-supply wells, public and/or private, in the Classifica-
tion Review Area is needed to determine local use of the
ground water.
Public water-supply systems are defined under the Safe
Drinking Water. Act a* those serving more than 25 person* or
with more than 15 service connections. In the well survey,
the location of any existing public water-supply wells 'and
their puapage capacity should be identified. Information on
well depth and screened intervals may also prove useful,
particularly if more detailed hydrogeologic analysis of the
area is to be undertaken*
A detailed inventory of private residential wells is not
necessary. One method for estimating the number of private
wells is to obtain census data regarding the density of
settlement in the area. The area served by public-water
systems (surface or ground) is delineated and it is assumed
3-15
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that the remaining hones have private wells. General
characteristics of private veils, such as depth and screened
intervals, nay also be useful, if available.
Well information may be obtained from water authorities,
public-health agencies, regulatory agencies permitting well
drilling, well drillers, or other State or local entities.
Water-Supply Reservoirs and Surface Water Intakes
Water-supply reservoir watersheds designated for water-
quality protection are specifically recognized in the ground-
water classification system and should be identified and
described if any are located within the Classification Review
Area. The location of surface-water intakes for drinking
supply purposes will also be relevant under certain
conditions. Again, State and local agencies should be able
to provide the information. A more detailed discussion
concerning the identification of protected water-supply
reservoirs is presented in Chapter Five.
Demography
Information on populations served by public and private
wells will be needed if it is apparent that substantial
populations may be involved, a finding that could lead to a
Class I decision. A first-cut approximation for public-
supply veils in the area can be made by dividing the total
pumpage capacity by the typical per capita consumption rates
for the region. Estimates of the number of private wells in
densely settled areas within the Classification Review Area
will also be necessary. Densely settled areas can be located
on U.S. Census Bureau maps. Detailed procedures for deter-
mination of substantial population are provided in Chapter
Four.
Ecologically Vital Areas
Ecologically vital arsas are also recognized by EPA's
classification system and are defined as those ground-water
discharge^ areas that provide habitat for threatened or
endangers** species (pursuant to the Endangered Species Act)
or discBivge areas that are Federally managed for ecological
value. It any areas that provide habitat for threatened or
endangered species are located within the Classification
Review Area, candidate discharge areas such- as springs,
streams, caves, lakes, wetlands, estuaries, coastlines,
embayments, and piayas, should be identified. (Further
analysis of the hydrogeology may be needed to prove actual
ground-water discharge; see Chapter Four.) The Regional
Office of the U.S. Fish and wildlife. Service and the State
Endangered Species coordinator or Heritage Program adminis-
trator are two sources for information regarding unique
habitats and/or endangered or threatened species. A detailed
-------
discuss! on methods to identify ecologically vital areas is
presents in Section 4.3. Information about Federal lands
may alsc ce obtained from Federal land-management agencies,
such as che National Park Service, U.S. Forest Service, and
Bureau of Land Management. The presence of Federal lands is
indicated on most State and county road maps and U.S.
Geological Survey quadrangle sheets.
Hydrocreologic Data
Information on the hydrogeology in the ' Classification
Review Area is pertinent to class distinctions based on
vulnerability (Class I) and degree of interconnection to
adjacent ground water or surface water (Class III). In
characterizing the hydrogeology, for these purposes, general
data needs may include the following:
e Regional geology (e.g., surficial geologic maps).
e Depth to water/thickness of vadose zone.
e Regional ground-water recharge rates.
e Aquifer and ground-water flow system
characteristics.
e Soil and vadose zone characteristics.
e Topography (slope).
• Landscape position/land form.
• Location of surface-water features.
This information may likely be obtained from
county/regional reports and also State geologic surveys or
the U.S. Geological Survey. The best available sources of
published hydrologic/geologic information are the U.S.
Geological Survey publications, State geological surveys,
scientific books and journals, and U.S. Department of Agri-
culture county soil surveys. Data supporting facility permit
application*, (e.g., for RCRA-related activities), Clean
Water Act Section 208 studies, as well as Environmental
Impact Statements, nay also be useful. The U.S. Geological
Survey District offices are a primary source of area-specific
data and information.
The U.S. Geological Survey has two- subdivisions which
nay supply useful information. These are the Rydrelogie
Information Unit and the Geologic Inquiries Group. They are
described below.
3-17
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1. The Hvdroloeric Information Unit
The Hydrologic Information Unit answers general ques-
tions on hydrology, water as a resource, and hydrologic
mapping, as well as on the products, projects, and services
of the Water Resource Division. Inquiries should be directed
to the following:
The Hydrologic Inquiries Group
United States Geological Survey
419 National Center
Reston, VA 22092
(703) 648-6818
2, The Geologic Inquiries Group
The Geologic Inquiries Group is the primary information
group of the geologic division of the U.S. Geological Survey.
The geologic Inquiries Group provides information and answers
inquiries on the activities and products of the geologic
division. Questions concerning all aspects of geology, such
as geology of specific areas, geochemistry, geophysics, and
other geoscientific disciplines, as well as geologic map
coverage should be directed to the following:
Geologic Inquiries Group
United States Geological Survey
907 National Center
Reston, VA 22092
(703) 648-4383
The hydrogeologic information collected during this
characterization phase may suggest that there could be
potential impacts in an area larger than the usual 2-mile
radius (or other program-specific radius) of the Classifica-
tion Review Area. Section 3.3.2 of this chapter describes
those unique; hydrogeologic conditions of very high ground-
water flair-velocities where an expanded Classification Review
Area mayf.tfc warranted and provides guidance on determining
the size o* the expansion.
Similarly, this review may indicate a need to evaluate
the interconnection of ground water with adjacent ground-
water units and with surface water, such as when a Class III
determination is considered possible or when subdivision of
the Classification Review Area into ground-water units is
planned (e.g., to address multiple, layered aquifers).
Section 3.4.2 of this chapter describes the information needs
and considerations involved in assessing interconnection to
adjacent water and in subdividing the Classification Review
Area into ground-water units.
3-18
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3.6 Location of the Classification Review Area Boundary
Relative to the Facility/Activity Boundary
The facilities and activities subject to EPA actions
range in surface area from very small (under 1 acre) to very
large (over 40 acres). In some cases, there say be-multiple
activities located at the sane facility for which a single
class determination is desired. There may also be an
unusually shaped unit or condition, such as a pipeline or an
elongated plume. Drawing the limits of a Classification
Review Area a given distance away from a facility/activity
boundary obviously requires that the boundary be established
first.
Because the Classification Review Area is intended to be
a simple approximation of the zone where ground water may
most likely be affected by a facility/activity, precise
location of this boundary is not necessary* In general, the
facility/activity boundary should encompass all potentially
polluting activities related to the Federal action for which
the classification decision is needed.
In some cases, it may be appropriate to use the legal
boundaries of the facility/activity. Because classification
will be in response to a Federal (e.g., regulatory) action,
the definition of facility/activity boundary for the purpose
of drawing the Classification Review Area limits should be
consistent with regulatory definitions of the
facility/activity, where applicable.
Figures 3-3 through 3-6 are provided as generic aids to
assist in delineating the Classification Review Area for
large multiple-activities or unusually-shaped facilities for
which the classifier deems that a simple circle from the
center of the activity/facility is inappropriate.
3-19
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FIGURE 3-3. IARGE FACILITY
Approach 1:' Draw circle encoapassing entire facility. Draw
radius froa center of circle.
Approach 1: Draw radius froa facility boundary (solid line).
Approach 2: Draw circle encompassing entire facility. Draw
radius froa boundary of circle (dashed line).
I MILE
2 MILES
3-20
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FIGURE 3-4. tfABCE. MULTIPLE-ACTIVITY/FACILITY
(e.g., activities separated by more than 1/4 mile)
Approach 1: Draw radius from facility boundary.
Approach 2: Draw individual radii from each activity.
Approach 3: Draw circle encompassing all activities,
Orav radius from boundary of circle.
2 MILES
3-21
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FIGURE 3-5. SMALL. MOLTIPIJ>AeriVITY/FftfiTT|TTY
(e.g., under 40 acres)
Approach 1: Draw circle encompassing entire facility. Draw
radius froa center of circle.
FIGURE 3-6. LONG, IRREGULARLY SHAPED FACILITY
Approach 1: Draw radius froa facility boundary (solid line).
Approach 2: Draw circle encoapassing entire facility. Draw
radius froa boundary of circle (dashed line).
I MILE
2 MILES
3-22
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CHAPTER FOUR
CLASSIFICATION CRITERIA FOR CLASS I GROUND WATER
4.1 overview of the Decision Process
4.1.1 Definitions
In EPA's classification system, Class I ground water is
ground water of unusually high value. Class I ground waters
are defined as highly vulnerable to contamination and are (1)
irreplaceable sources of drinking water and/or (2) ecologi-
cally vital. The definitions and procedures for identifying
Class I ground water are designed to distinguish these
special ground waters from the vast majority of other ground
waters.
Ground water is considered irreplaceable to a
substantial population if it would be economically infeasible
to develop an alternative water-supply source of comparable
quality and quantity in the area, or if delivery from an
already existing alternate source is precluded by institu-
tional constraint* or transport distance. Ground water is
considered Class I - Ecologically Vital primarily if it
supplies a sensitive ecological system that supports a unique
habitat. Such ground waters will generally have an unusually
high value due to either the potential risk to the large
number of people dependent upon the ground water as a source
of drinking water or the risk of further endangerment to
endangered or threatened species that depend on the unique
habitat supported by that ground-water resource. Certain
Congressionally-designated Federal land management areas,
managed.for the purpose of ecological protection, may also be
considered unique habitats in some cases.
Chapter Four provides definitions and discussions of key
words and concepts important to a Class Z decision and
discusses in detail the procedures for making a Class I
determination. This chapter covers the possible sequence of
classification steps, corresponding data needs, and technical
methods for each step in the decision process. The clas-
sification procedure ultimately relies on the professional
judgment of the classifier. The procedures presented here
4-1
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may help to simplify and clarify the classification process
and to promote consistency between classification decisions.
Supplemental information about the Class I classification
process is provided in Appendices B and D.
4.1.2 General Procedures
The, Class Z decision process will generally begin with
either a determination of irreplaceability or the identifica-
tion of ecologically vital areas, followed by a determination
of ground-water vulnerability. Preliminary data may Indicate
that one of the Class I criteria can be more easily demon-
strated than another. If so, the classification process
should begin with the criterion that can be most easily
demonstrated. It is important to note that, the order in
which Class I steps are performed is not fixed. The sim-
plest, least expensive, and most appropriate method of
arriving at the classification decision should be applied in
any given situation. It will be up to the classifier to
determine the order in which a Class I procedure is
performed.
The general procedures that are followed in a Class I
decision are illustrated in Figure 4-1. The steps involved
in each general procedure, as well as basic data needs and
techniques that may be used to evaluate each step are
discussed below.
Determine Presence of Drinking-water Wells
The presence of drinking water wells within the Clas-
sification Review Area may indicate to the classifier the
possibility of a Class I - Irreplaceable Source of Drinking
Water decision.
Basic data collection within the review area will most
likely include a general survey of wells used for drinking
water. W*ll surveys commonly include location, use, and
pumpage capacity of existing public water-supply wells or
fields within the Classification Review Area. A detailed
inventory of private residential wells would be valuable, but
should not be considered necessary. As a preliminary step,
the delineation of areas not served by public-water supplies
and the approximate number of homes in the review area can be
evaluated. Census data can also ba used to estimate the
nuabar of privata veils vithin the Classification Ravisv
Area. The classifier may wish to summarize the well data to
estimate the number of public and private wells present.
Other general characteristics of aquifers used in the
Classification Review Area may also provide information
concerning vulnerability to contamination.
4-2
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FIGURE 4-1
GENERAL PROCEDURE FOR CLASS I DETERMINATION
CLASSIFICATION REVIEW AREA
DELINEATION
•ASIC DATA COLLECTION
IS GROUNDWATER
IRREPLACEABLE TO
A SUBSTANTIAL
POPULATION
-NO—
ARE ECOLOGICALLY
VITAL AREAS
PRESENT
1
f
YES
IS GROUNOWATER
IRREPLACEABLE TO
A SUBSTANTIAL
POPULATION
\
i
-NO-
ARC ECOLOGICALLY
VITAL AREAS
PRESENT
YES
IS GROUND WATER HIGHLY VULNERABLE TO CONTAMINATION
\ <
YES
GO TO
CLASS It
PROCEDURES
CLAM I
DECISION
SEQUENCE A
i >
YES
CLASS I
DECISION
00 TO
CLASS II
PROCEDURES
SEQUENCE B
4-3
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Wall information nay be obtained from water authorities,
public-health agencies, regulatory agencies that permit well
drilling, well drillers, or other state and local agencies.
If wells do not exist within the Classification Review Area,
the classifier will go to procedures for determining the
presence of ecological vital areas within the Classification
Review Area. A detailed discussion of information needs is
presented in Chapter Three.
Determine Irreolaceabilitv to a Substantial Population
A ground-water source may be classified as irreplaceable
if it serves a substantial population and if creation of an
alternate supply source would be economically infeasible or
if reliable delivery of water of comparable quality and
quantity from already existing alternative sources in the
region is precluded by transport distance or institutional
constraints. It is important to emphasize that the irre-
placeability criterion is a relative test in that its goal is
to identify those ground waters of relatively high value
(compared to others). As a result, these may deserve to be
treated as unique or special.
The first step in the evaluation of irreplaeeability to
a substantial population involves determining whether the
user population is substantial. In general, user populations
of 500 persons or more may be considered substantial for the
purpose of these classification Guidelines. Ground water
serving populations of less than 500 persons also may be
considered irreplaceable in some cases, based upon factors
discussed later in this section.
The Agency has adopted the 500-person value as a general
substantial population threshold. Population size
considerations are important given that, from a risk-related
perspective, it is intended that the identification of Class
I ground water be associated with the greater aggregate risk
•nd potential economic damage faced by larger populations.
The 500-person number also has the advantage of making
implementation reasonable as it is the level at which many
States apply well registration.
If the ground water under review does serve a
substantial population, then the second step of the
determination of irreplaeeability is to make a preliminary
determination by applying a number of screening tests. These
screening tests, designed to demonstrate irreplaeeability,
include the following:
4-4
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• Uncommon pipeline distance.
• Institutional constraints.
• Comparable quality.
e Comparable quantity.
• Economic irreplaceability.
Each test is discussed briefly here; a more detailed
discussion is presented in the next section; The order in
which the tests are presented is according to the relative
cost and effort involved in collecting and applying each
test, with the less costly tests discussed first* The tests
may be applied in a different order, however, depending on
site-specific situations.
Screening Test 1; Uncommon Pipeline Distance. The
concept of an uncommon pipeline distance provides a means for
estimating the limits of the area within which potential
alternative water sources may be located. without such a
boundary, any water source in the country might be considered
a replacement for any other water source, making the irre-
placeability concept unworkable. If there are no replacement
sources within a distance smaller than the uncommon pipeline
distance, then the preliminary determination would be that
the ground water under review is irreplaceable.
Screening Test 2; Institutional Constraints. For
purposes of the classification Guidelines, institutional con-
straints are defined as legal or administrative restrictions
that preclude, or make very difficult, replacement water
delivery and that may not be alleviated through administra-
tive procedures or market transactions. Such constraints
limit access to alternative water sources and may involve
legal, administrative, or other controls over water use. The
existence of institutional constraints can eliminate one or
more possible alternative sources from consideration (and,
likewise, indicate which alternate supplies are more viable
than others) and, therefore, can result in a preliminary
determination of irreplaceability.
Screening Test 3; Comparable Quality. Comparable
quality is defined in terms of the quality of raw sources of
drinking water used in the area, considering in a general
way, both the types of contaminants that are present and
their relative concentrations. The intent is to make rough
order-of-magnitude comparisons to determine whether the
potential alternative is of the same general quality as the
source and as other water used for drinking in the region,
without conducting a specific, parameter-by-pmraa«tsr
comparison. If none of the potential replacement sources is
comparable in quality to the current source or typical
sources within the region, then the preliminary determination
for the current source would be that it is irreplaceable.
This test is considered a true "screening approach" since the
4-5
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utility of an alternative water source based on quality
considerations is more completely assessed by the economic
irreplaceability test.
Screening Test 4; Comparable Quantity. Comparable
quantity means that the alternative source or sources,
whether surface or ground water, is/are capable of reliably
supplying vater in quantities sufficient to meet the year-
round needs of the population served by the ground water. If
none of the potential replacement sources can provide a
comparable quantity of ground water, then the preliminary
determination for the current source would be that it is
irreplaceable.
Screening Test 5; Economic Irreolaeeability. The
Agency has defined economic irreplaceability of an
alternative water source principally in terms of total water
supply costs per household. This does not in anv way imply
that the Agency expects that communities will be required to
replace water supplies or pay for such replacements. Again,
this is a relative measure to determine the extent to which
ground waters potentially affected by a facility/activity are
truly special. The economic infeasibility test is designed
to identify situations where the cost of replacing a water
supply would place an unusually high economic burden on the
population served if the ground water now being used became
unusable. If the cost of replacing the current source would
be economically unreasonable, then the. preliminary
determination for that source would be that it is
irreplaceable.
The third and final step for completing the determina-
tion of irreplaceability following the application of any of
the five screening tests, or if the user population is not
substantial, is to review site-specific, qualitative condi-
tions and make a final determination (i.e., either irreplace-
able or not irreplaceable). The following qualitative
factors have been compiled by EPA for consideration during
this steps the presence of transient populations; projected
trends ia population size, economic conditions, and water
development projects; and the use of unreliable transport
mechanism*. These factors are discussed in more detail in
Section 4.2.3.
Determine Presence of Ecologically Vital Areas
Ecologically vital areas are primarily defined as
ground-water discharge areas that serve as habitats for
species that are listed, or proposed for listing, as
endangered or threatened (pursuant to the Endangered Species
Act as amended in 1982). The location of proposed endangered
or threatened species habitats, or any Federal lands managed
for ecological values within the Classification Review Area
should be identified. The Regional Office of the U.S. Fish
4-6
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and Wildlife Service and the State Endangered Species
coordinator or Heritage Program administrator are two sources
of information regarding unique habitats and/or endangered or
threatened species. Information about Federal lands nay also
be obtained from Federal land-management agencies, such as
the National Park Service, U.S. Forest Service, and Bureau of
Land Management. The presence of Federal lands is indicated
on most State and county road maps and on U.S. Geological
Survey quadrangle sheets.
For the ground water to be considered ecologically
vital, the ground water must discharge to a unique habitat as
defined above. Another step in this determination, then, is
locating discharge areas that may affect the unique habitat.
Such areas may include springs, streams, caves, lakes,
wetlands, estuaries, coastlines, embayments, and playas.
Discharge areas can be located using topographic maps or
Federal and State Water Resource reports. Section 4.3
provides detailed information on identifying Ecologically
Vital Areas.
Determine Vulnerability
The determination that a setting is highly vulnerable to
contamination is based on a best professional judgment
approach. When attempting to evaluate vulnerability, a
classifier should select the most appropriate vulnerability
assessment tools for a given situation. The selection should
be based on factors such as regional hydrogeologic
conditions, availability of data, and professional experience
of the classifier or support staff. It is recommended that
the classifier examine multiple lines of evidence to support
a vulnerability determination. Such an approach might
include an evaluation of hydrogeologic factors relevant to
vulnerability, matching the subject hydrogeologic setting to
a highly vulnerable descriptive/qualitative setting as
provided in this guidance, and/or employing one or more
technical evaluation aids.
In Section 4.4.1, guidance is provided regarding the
hydrogeologic factors to consider for evaluating vulner-
ability. Selected vulnerability evaluation aids are also
presented. Where appropriate, benchmarks indicative of
highly vulnerable hydrogeology are provided.
4-7
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4.2 Procedures for Determining Irreplaceable scures for
a Substantial Population
The purpose of evaluating the irreplaceability of
ground-water supplies for substantial populations is to
identify those waters of relatively high value. For the
purposes of classification, this is not meant to require
extremely rigorous or costly analyses. On the other hand;
these Guidelines are designed to ensure that truly special
ground waters, due to their use and irreplaoeability, are
identified and addressed appropriately.
The determination of irreplaceability process outlined
here involves a three-step approach that is intended to be
straightforward and to rely on readily available data. The
purpose of this process is to determine whether the ground
water within the Classification Review Area is irreplaceable
to a substantial population. In the first two steps, a
preliminary determination of irreplaceability is made based
on the population size and a series of screening tests. The
third step, in turn, produces a iinal irreplaceability
determination that reflects consideration of several factors
that may warrant adjustment of the initial determination.
In brief, the first step involves estimating the size of
the ground-water user population and determining if the
population should be considered substantial for the purposes
of classification. It the population is not considered
substantial, then the site in question may be given a
preliminary not-irreplaceable determination and the
classifier may proceed to the third step of the process
(i.e., a qualitative review). if, on the other hand, the
population is deemed substantial, then the second step of the
determination of, irreplaceability may be applied. The second
step involves applying five screening tests related to
population size and irreplaceability that are designed to
yield a preliminary determination (i.e., either irreplaceable
or not-irreplaceable). These screening tests include an
uncommon pipeline distance test, an institutional constraints
test, a comparable quality test, a comparable quantity test,
and an economic irreplaceability test. Having made a
preliminary determination in Steps l or 2 (e.g., not
irreplaceable), based either on the population size or the
outcome of the screening tests, the classifier may then apply
a number of qualitative criteria designed to .recognize site-
specific factors that may warrant making a different final
determination (e.g., irreplaceable). The end result of this
third step, therefore, is the final determination of
irreplaceability. Figure 4-2 presents a flow-chart designed
to illustrate how a classifier might move through this three-
4-8
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FIGURE 4-2
SUGGESTED METHOD FOR DETERMINING
IRREPLACEA8ILITY TO SUBSTANTIAL POPULATIONS
START HERE
IS THERE A
SUBSTANTIAL
POPULATION
REPLACEMENT
SOURCES WITHIN
OF
PIPELINE 03STANC
AND OUTSI
CRA
STITUTI
CONSTRAINTS
PRECLUDE USE OF
REPLACEMENT
SOURCES
USE OF
REPLACEMENT
SOURCE IS
ECONOMICALLY
INFEAS1BLE
REPLACEMENT
SOURCES ARE
OF COMPARABLE
QUANTITY
REPLACEMENT
SOURCES ARE
OF COMPARABI i
QUANTITY
PRELIMINARY DETERMINATION
IRREPLACEABLE
PRELIMINARY DETERMINATION
NOT IRREPLACEABLE
QUALITATIVE
QUALITATIVE
FINAL DETERMINATION:
IRREPLACEABLE
FINAL DETERMINATION:
NOT IRREPLACEABLE
CONSIDER OTHER SCREENING TESTS
IF NECESSARY
•• A clMflMcr **) apply lht«» criteria in • different order, if warranted bf elle-epecillc condlllont
-------
step method in order to make a ground-water classification
decision.
Hot* that each of the five screening tests is designed
to demonstrate that a ground-water supply is irreplaceable.
Moreover, none of the tests can be used in and of itself to
demonstrate that a ground-water supply is not irreplaceable.
Therefore, if any single screening test demonstrates
irreplaceability and is - consistent with the appropriate
qualitative criteria, the ground water would then be
considered irreplaceable and the classifier would not need to
perform any further analysis. On the other hand, if a given
screening test cannot be used to demonstrate
irreplaceability, then the next test should be applied. Only
if none of the five screening tests, along with the
qualitative review, demonstrates irreplaceability should the
classifier conclude that the ground water is not
irreplaceable.
The three steps for determining irreplaceability to a
substantial population are described in detail below.
4.2.1 Step 1: Determination of Substantial Population
The first step of the determination of irreplaceability
involves assessing whether the user population should be
considered substantial. This step entails estimating the
actual size of the user population first and then making the
substantial size determination itself. Both .of these
decisions involve judgment by the classifier. A suggested
process for making this estimation and determination is
presented below.
For the purposes of estimating the size of the user
population, persons using the ground water in question
generally: include those individuals served by the following:
• Public water-supply well(s) within the Clas-
sification Review Area (or appropriate sub-
division) i or
• Private veils within the Classification Review Area
or appropriate subdivision for persons living in a
densely settled area (i.e., census definition based
on 1,000 persons per square mile, see Appendix
B.I); or
e A combination of the above.
4-10
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This definition of a user population is based largely on
concepts already used by the Census Bureau. The population
data necessary to make these determinations are widely
accessible and sufficiently up-to-date.
In most instances, making these population determina-
tions should be straightforward. If the well(s) in the
Classification Review Area or appropriate subdivision serve a
public-water system, then an estimate of the number of user
households multiplied by the average number of persons per
household (2.75 on a national basis, although each State or
locality may be somewhat different) should approximate the
total population served; if the population is served by other
water sources, these should be accounted for proportionately.
water supplied for industrial and agricultural purposes
should not be included. For private well users, it will be
necessary both to estimate the population in the Classifica-
tion Review Area not served by public-water systems and to
calculate the population density. The EPA maintains a data
system called GEMS (Graphical Exposure Modeling System) which
can be used to estimate both population and population
densities for a variety of areas around a point (see Appendix
B.2 for details). The degree of uncertainty associated with
making these estimates for a particular situation may
necessitate greater or lesser reliance on reasonable and
conservative assumptions.
Once the population size has been estimated, the
classifier should decide whether the population is
substantial. User populations of 500 persons or more may be
considered substantial for the purpose of this
classification. Likewise, populations less than 500 persons
may warrant a preliminary not-irreplaceable determination
immediately (i.e., skipping the second step of the determina-
tion of irreplacaability), with the possibility of shifting
to a final irreplaceable determination based on a review of
site-specific conditions (i.e., the third step). Population
estimate* close to 500 persons in size will require best
professional judgment.
4.2.2 Step 2: Screening Tests to Make Preliminary Deter-
minations
The second step of the determination of irreplaceability
involves applying five separate screening tests in order to
make a preliminary determination. Each of the five tests
reflects the size of the user population or some measure of
the ground water's irreplaceability or both. The tests are
designed to identify ground waters that are truly special.
4-11
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The test* are presented in a suggested order that attempts to
minimize the level of effort and cost associated vith the
determination. Specific situations, however, may indicate
applying the tests in a different order.
The five screening tests for making preliminary clas-
sification decisions are as follows:
1. Uncommon or unreasonable pipeline distance.
2. Institutional constraints.
3. comparable quality.
4. Comparable quantity.
5. Economic irreplaceability.
The following sections describe methods for applying these
screening tests. Each section also identifies and charac-
terizes data sources that are relevant to the tests. The
data sources are generally available from Federal and State
agencies or other easily accessible sources.
Screening Test 1; Uncommon or Unreasonable Pipeline Distance
If there is no indication that a different test should
be applied first (e.g., the classifier knows that all
potential replacement sources will be unavailable due to
institutional constraints), then the uncommon pipeline
distance test will probably be the most appropriate test to
apply first when making a preliminary determination. This
test sets a hypothetical outer radial boundary around the
site being classified which, in conjunction with the inner
boundary set by the Classification Review Area, or
subdivision thereof, establishes the zone within which
alternative water supplies can reasonably be considered
(i.e., tft« zone between the two boundaries). In other words,
the te«ftf restricts the number of alternative sources that
need be considered in the irreplaceability determination by
excluding those sources that are unreasonably far away.
In theory, an uncommon pipeline distance could be
defined as the typical maximum distance water is currently
piped from the raw-water source to the distribution system
for each population category within a given geographic
region.. Given this definition; currant pipeline distances
may vary, considerably within a .region due to a number of
factors. For example, regions with diverse topographic,
geologic, hydrologic, or seismic characteristics may have a
wide variation in pipeline distances and, therefore, may not
have a single typical pipeline distance. Moreover, pipeline
4-12
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distances nay vary greatly in length due to other factors,
such as the availability of developed water resources (e.g.,
lakes, reservoirs, etc.), institutional constraints on water
development, water demand, and economic resources, all of
which may vary within a region. This variability in
pipeline distance is especially apparent when considered
across regions. In the semi-arid regions of the West, for
example, water may be conveyed 50 miles or more from the
source to the distribution system. On the other hand, water
is typically piped 5 miles or less in the East due to other
factors such as greater annual rainfall, a different set of
property rights, and different levels of urbanization and
population density. Finally, piping distances can range
considerably even among neighboring states.
If sufficient data exist in a specific situation to
determine an uncommon pipeline distance for the population in
question, then the classifier may choose to use a value
derived from that data. In doing so, the classifier should
ascertain a consistent uncommon pipeline distance based on a
reasonably defined geographic region (e.g., statewide) and
populations similar in size to the population in question.
If, on the other hand, sufficient data are unavailable
or pipeline distances vary widely for populations that are in
the same region and are of similar size to the population in
question, then it may not be practical to define an uncommon
distance in this manner. Therefore, a second approach can be
used in applying this test. This second approach is based on
the observation that, due to economies of scale, water-supply
systems serving larger populations can afford to pipe
alternative sources of water from increasingly farther
distances. In other words, for a given level of economic
burden (i.e., the maximum affordable cost of piping a
replacement water supply as a percent of average annual
household income), larger populations will have larger areas
within which they can consider alternative sources (i.e.,
longer uncommon pipeline distances).
In the absence of an exhaustive survey of pipeline dis-
tances, the threshold distances presented in these Guidelines
are based on information provided by EPA's research labora-
tories and the Federal Reporting Data System (FRDS) managed
by EPA»s Office of Drinking Water. More specifically, data
from EPA's Cincinnati water-quality laboratories were used to
estimate the costs of transporting various quantities of
water over various distances. Using this information,
information concerning the water requirements of various
population sizes, and household income data, a relationship
between population size and uncommon distance was defined.
There are two benefits to using this approach for
defining uncommon pipeline distances. First, this approach
allows a reasonable and consistent method for delineating the
4-13
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area within which classifiers aight cr-*ider alternative
sources. Second, this approach allows . fairly definitive
measure of irr«.placeability t±~sd on the economic burden cf
transporting water as it relates to population size.
Table 4-1 can be used to assess whether a preliminary
irreplaceable determination is appropriate. The pipeline
distances can be used as lower limits of uncommon pipeline
distances. For example, if the user population is between
500 and 5,000 persons, then pipeline distances greater than
25 miles could be considered uncommon or unreasonable.
Therefore, if there are no alternative water supplies within
25 miles of the site under review and outside the
Classification Review Area, then the ground water in question
would be considered irreplaceable for the preliminary
determination.
After the appropriate pipeline distance has been
established, the final step of the preliminary determination
is to ascertain whether potential replacement water-supply
sources are in fact present within the uncommon pipeline
distance and beyond the Classification Review Area.
Potential sources may include both surface or ground water
outside of the ground-water unit under review. Common
examples of surface water that can be considered as a
replacement source are rivers, streams, natural lakes, and
impoundments. Alternative ground-water sources nay be
located in the same aquifer, or in another nearby aquifer,
horizontally or vertically separated from the source aquifer.
If a preliminary irreplaceable determination is made on
the basis of the uncommon pipeline test and if there are no
relevant qualitative criteria that would warrant a final not-
irreplaceable determination (as described in Step 3), then
the final determination would be irreplaceable. Note that if
an alternative source falls within close range of the
uncommon pipeline boundary, then a best professional judgment
should be made by the classifier as to whether the source
could b« considered. Note also that if the final
determination is based on this test (i.e., no alternative
sources^ exist within an uncommon pipeline distance bound*ry),
no further analysis need be done. It a final irreplaceable
determination is not warranted -Mt this point, however, the
classifier should continue to the next screening test.
Screening Test 2; Institutional Constraints
The second* screening test to be applied when determining
the irreplaceability of a ground-water supply is whether
institutional constraints exist which sight preclude, or make
very difficult, the delivery of an alternative supply. This
section defines institutional constraints, provides a process
4-14
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TABLE 4-1*
GENERALLY APPLICABLE UNCOMMON
PIPELINE DISTANCES
Uncommon
Population Size Pipeline Distance
500 - 5,000 25 miles
5,000 - 10,000 35 Biles
10,000 - 25,000 70 miles
25,000 - 100,000 100 miles
> 100,000 150 miles
*Note: In developing this uitminim pipeline distance function (i.e.,
population size versus unocnmon pipeline distance), a 1 percent economic
threshold was used consistently across all population size
order to make the distance calculations as described above. This single
ries in
threshold level differs from the economic infeasibility screening test,
•toffiTrlfr^ below, which uses an absolute dollar economic burden threshold
that varies based on population size. These two tests differ for thro
reasons. Firstf use of a single economic threshold simplifies the
calculation of mmauuui pipeline distances. Second, even in situations
where replacement water supplies are deemed to be within a cannon
pipeline distance using the 1 percent threshold, the economic
irreplacability test will still be used to assess irreplaceability based
on the size-dependent, absolute dollar threshold. There is no need,
therefore, to calculate ui minium pipeline distances using variable
economic burden thresholds.
4-15
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for categorizing institutional constraints, and provides
guidance for applying the screening test itself.
Institutional constraints involve legal, administrative,
and other similar forms of control over access to water. For
purposes of these Guidelines, the Agency has adopted the
following definition of institutional constraint:
An institutional constraint is a situation in which, as
a result of a legal or administrative restriction, delivery
of replacement water may not be assured through simple
administrative procedures or market transactions.
Note that this definition applies to situations where
replacement, even though not strictly precluded, is made very
difficult by institutional constraints.
While a detailed examination of legal and institutional
issues is rarely called for, a preliminary 'review should
indicate whether an institutional constraint is present. The
following discussion presents a breakdown of potential
institutional constraints and a general procedure for
determining whether a binding institutional constraint is
present in a particular situation. Appendix B.3 provides a
more detailed description of constraints, as well as sources
of information.
The Agency has identified various kinds of potential
constraints and determined which are probably binding,.which
may be binding in some cases or possibly binding, and which
are unlikely to be binding. For a straightforward
assessment, corcarison of the constraints affecting a
particular source of water, as presented in Figure 4-3,
should suffice. In those cases where a detailed assessment
is warranted, the procedure outlined in Figure 4-4 is
suggested. The case study presented in the next section,
illustrating a somewhat complicated institutional constraint
situation, may also prove useful when making less-
straightforward assessments.
Institutional Constraint Case Study. A potential source
of replacement water (e.g., the Rio Grande River) may- be
subject to an international treaty (e.g., the 1944 Treaty
between* the United States and Mexico on Utilization of the
Waters of the Colorado and Tijuana Rivers and of the Rio
Grande) limiting the amount of water that may be withdrawn by
users in the United States, and to an Interstate Compact
limiting the amount of water that may be used within a
particular state. In addition, that portion of the rivsr
flow assigned to a particular state may already be fully
taken up by other users. Finally, the use for which the
water is being considered as a potential alternative source
may be situated some distance from the river and require a
right-of-way in order to get access to the water.
4-16
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FIGURE 4-3
POTENTIAL INSTITUTIONAL CONSTRAINTS
Probably Binding Constraints
0 Water is subject to international treaty.
• Water is subject to interstate water apportionment
compact of litigation among states.
• Water is subject to Federal or Indian reserved
right.
Possibly Binding Constraints
• Water is allocated by litigation among persons.
• Water is allocated by permit.
• Water is allocated by local water district or
another local authority.
• Amount of water that may be used is limited:
By public trust doctrine.
By instream flow protection requirements.
By state law.
By permit.
By local management authority.
By prior appropriation(s) that are all for
highest beneficial use.
- By Federal navigational servitude.
• Place of use of water is limited:
- By state law.
By permit.
By local authority.
Constraints Unlikely to be Binding*
• Water is subject to prior appropriation (unless for
highest beneficial use).
• Water is subject to riparian right.
« Physical access to property is restricted:
-* By property rights of other persons limiting
rights-of-way for pipes, ditches, conduits, etc.
- By Federal or State statutes requiring environ-
mental impacts assessment or establishing other
procedural requirements.
* Upon application of simple administrative procedures or
market transactions.
4-17
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FIGURE 4-4
OUTLINE OF PROCEDURE FOR ANALYZING POTENTIAL INSTITUTIONAL
CONSTRAINTS TO THE USE OF AN ALTERNATIVE SOURCE OF WATER
INSTITUTIONAL COTUTIAIKTS
•CLATCO TO IOVHCC
OC1
or
CONSTRAINT*
itt
ACE or
U*C
•CITKICTIC
ACCIIS
•CtTHICTfO
H**«fT
Mwnet
AITCIUTIVC tt
•MJCCT TO *
1TMMT
AMIIHIVTMTIVC
4-18
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In this situation, the treaty, the interstate compact,
the water-allocation system, and the property rights of other
persons, are all potential institutional constraints. Each
should be considered separately. The treaty and the inter-
state compact may be impossible to avoid or change through
simple administrative procedures. A telephone call to the
State office in charge of water allocation would probably
indicate that the water allocation could potentially be
revised by a simple administrative procedure or that market
transactions can be used to change the current allocation of
water. Similarly, informal contact with a State Attorney
Generalfs office should indicate that the problem of access
could potentially be resolved through purchase of an easement
or right-of-way, or that the administrative process of
eminent domain could potentially be used to provide access to
the water. In such situations, a binding institutional
constraint probably would not be present, despite the
potential constraints that were identified.
Once the institutional constraints for a classification
decision have been categorized in terms of their potential
for being binding, the screening test itself should be
applied. That is, if the institutional constraints affecting
the delivery of alternative sources are considered to be
sufficiently binding, then the classifier may conclude that
the user population's current ground-water supply is irre-
placeable for the preliminary determination. Note that the
classifier should make a best professional judgment if
several alternative sources with varying levels of constraint
are available. If, upon review of the relevant qualitative
criteria (Step 3), the final determination is also irre-
placeable, then no further analysis need be performed. If
application of this screening test in conjunction with the
appropriate qualitative criteria does not result in an
irreplaceable determination, however, then the classifier
should apply the next screening test.
Screening Test 3; Comparable Quality Analysis
One* m potential alternative source(s) has been located
within the boundary of an uncommon pipeline distanca and
outside the Classification Review Area and the classifier has
determined that no institutional constraints exist that would
preclude, or make very difficult, delivery of water frca the
alternative source, the next step is to determine whether the
source offers water of quality and quantity comparable to the
user population's current ground-water supply. This section
describes the comparable quality screening test while the
next section describes the comparable quantity test. Note
that the comparable quality test need not be applied before
the comparable quantity test. If the situation and
availability of data suggest that the quantity test should be
4-19
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applied first (and followed by the quality test if need be) ,
then the tests may be applied in that order.
The term comparable quality is defined as the level of
water quality that is not substantially poorer than other raw
drinking-water resources in the region. To be considered of
comparable quality, the quality of the alternative water
resource should be (within an order-of-magnitude) as good as
or better than existing drinking-water resources, taking into
account the precision of the measurement of each parameter.
For example, an existing water source may have an average of
93 ag/L IDS, with a range of 75 mg/L to 100 mg/L. An
alternative water source may be considered not of comparable
quality if it has an average TDS of 930 mg/L with a range of
750 mg/L to 1,000 mg/L. For some parameters of concern
(e.g., taste, color, odor), the evaluation may be highly
subjective. Again, the test is meant to be a relative
evaluation which considers a few general categories of
parameters (e.g., TDS, organic compounds, heavy metals,
radionuclides, and other secondary physical/chemical
properties).
The rationale for incorporating this test is to allow
for quick and inexpensive appraisals of the utility of
alternative water sources. More comprehensive assessments of
irreplaceability can be obtained through the economic
irreplaceability analysis outlined in Screening Test 5. This
test does include a water treatment component.
Existing information on water quality should be used,
given the very high cost of new series of sampling and
analysis. The comparison is intended to be relative and
subject to professional judgment. At the Federal level,
three important sources for water-quality information may be
consulted: EPA, the Army Corps of Engineers, and the U.S.
Geological Survey. Each of these agencies has conducted, or
continues to conduct, comprehensive surveys that describe
water resources in the United States. Although not always
designed specifically to provide detailed water-quality data,
these studies provide information sufficient to facilitate
the comparable quality considerations of the ground-water
classification system.
EPA has funded comprehensive studies of Regional water
quality to determine the principal point and non-point
sources of pollution. These studies, conducted under Section
208 of the Clean Water Act, for example, give a broad
overview of water quality (USEPA, 1980b). They are generally
obtainable through the state and local agencies which
received the funding. The Army Corps of Engineers conducts
similar regional water-resource studies in order to examine
water supply and demand within specified river and lake
basins in the United States. The most useful data resource
from the U.S. Geologic Survey will often be the published
4-20
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basin-vide investigations of ground- and surface-water
resources. The U.S. Geological Survey also maintains the
National Water Data Exchange (NAWDEX), which is designed to
assist users in the identification, location, and acquisition
of information on water resources. The National Water Well
Association (NWWA), Dublin, Ohio, maintains a library of all
U.S. and state Geological Survey information on water supply
and quality. Using automated searching capabilities, the
NWWA can identify and list all publications concerning a
specific geographic area.
On a more local level, regional planning boards and
government councils also may have information on potential
drinking-water supplies and river, lake, and stream quality
in their regions. State agencies that administer environ-
mental protection, land-use planning, agricultural, geo-
logical survey, public health, and water programs, are
excellent sources of information. state universities (par-
ticularly land-grant universities) may sometimes serve as
repositories of information concerning ground- and surface
water supplies.
Screening Test 4; Comparable Quantity
The fourth screening test that may be applied to
determine the irreplaceability of a user population's ground
water supply is the comparable quantity test. As noted in
the comparable quality test discussion, the quality and
quantity tests can be applied in either order depending on
the situation or availability of data. Regardless of.which
test is applied first, however, the second test would be
applied if the first test does not demonstrate that the
ground-water source is irreplaceable. The remainder of this
section describes how the comparable quantity test should be
applied.
The term comparable quantity is defined as the level of
water quantity that is essentially equal to the quantity
supplied by the current ground-water source. Determining
whether the alternative source, or sources, can yield
adequate quantity requires three analytical steps:
,e Determine current supply needs of
water users.
e Characterize potential sustainable
water yield of the alternative water
supply. '
e compare alternative water supply and
existing water demand.
4-21
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Step 1; Determine Current Supply Neefls of Water
Users. If the ground water to be classified supplies a
public-water system, current supply needs will be known by
the water utility. If the ground water to be classified
serves a substantial population using private wells, current
water needs must be estimated using population figures and
assumptions concerning typical water use. For the purpose of
this exercise, the Agency recommends using the assumption
that the average household uses 100,000 gallons of water per
year and consists of 2.75 persons.
St»p 2: Characterize Potential Sustainable 'Water
Yield of Mhe Alternative Water Supply. The second step of
this screening test is to estimate the potential sustainable
yield of alternative water supplies. The information
necessary to make this estimate is best obtained from the
published studies discussed in Chapter 6 (Insufficient Yield
Test) of these Guidelines. When making the estimate, the
classifier should note that routine water- shortages in
communities currently served by an alternative source may
indicate that the alternative source would be theoretically
unable to provide water for an additional population
increment. Rapidly falling ground-water levels over time
also may indicate that an alternative source would not be
capable of consistently providing sufficient yield year-
round. Finally, even if levels are not falling, the
alternative source may be unavailable for additional usage if
proper resource management techniques are maximizing the
yield while holding the water level constant. In cases where
the ability of an alternative source to meet the needs of the
substantial population is unclear, a more quantitative
analysis may be necessary*
Step 3; Compare Alternative Water Supply and Existing
Water Demand. The final step of this screening tes'- is to
compare the potential yield of the alternative water supply
with current water needs. For this step, water needs may be
considered on an annual or monthly basis. In cases where the
alternative source is located in a water-rich area, the
comparison of user needs and source yield may be done on an
annual basis. The comparison should be conducted on a
monthly basis, however, if the. alternative source is ground
water under existing or potential stress or if the
alternative source is a surface water with considerable
month-to-month variability in flow. Important sources for
water-quantity information include local water utilities,
State water agencies, and the U.S. Geological Survey.
Once the user needs and replacement source yields have
been derived and compared, the comparable quantity test
itself should be applied. That is, the classifier should use
professional judgment to determine whether the replacement
source could adequately supply the user population with
sufficient quantities of water. If the replacement source
4-22
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cannot supply essentially all of the user population's water
requirements, then the current ground-water source should be
considered irreplaceable for the preliminary determination.
If this determination is made and review of the relevant
qualitative criteria does not warrant a different final
classification, then the final determination would be
irreplaceable and no further analysis need be done. If
application of the comparable quantity test does not
demonstrate that the current ground-water supply is
irreplaceable, on the other hand, then the final screening
test can be applied.
Screening Test 5; Economic Irreplaeeability
Having determined the location of acceptable
replacement water sources that are institutionally available
and of comparable quality and quantity, the final screening
test to be applied is the economic irreplaceability test.
The remainder of this section discusses the rationale behind
the economic irreplaceability test, methods of estimating the
cost of replacement water supplies, and the application of
the test itself.
The Agency has defined economic irreplaceability of an
alternative water source principally in terms of cost per
household of using the alternative water source. This does
not in anv way imply that the Agency expects that communities
will be required to replace water supplies or pay for such
replacements. Rather, this relative measure is designed to
determine the extent to which ground waters potentially
affected by a facility or activity are truly special. The
economic irreplaceability test itself is designed to balance
different levels of replacement water affordability against
various population sizes. Again, this approach is based on
the concept that larger populations potentially face greater
aggregate health risks and adverse economic impacts should
ground-water contamination occur. Further, the test
recognizes that smaller populations generally pay a higher
per unit price for water than do larger populations due to
economies of scale. Therefore, the test is designed to
identify ground waters that are truly special by comparing
economic burden of replacement to systems of similar size.
Based on this rationale, the economic test presented here
gives general guidance on when the costs of replacement for a
given population size should be sufficient to warrant a
preliminary irreplaceable determination.
In order to apply the economic irreplaceability test,
the classifier will have to estimate the total cost of the
user population's replacement water-supply system (i.e., once
the affected systsm components, or the entire system, h«v«
been replaced) in terms of cost per household. Having made
this estimate, the classifier can then compare the cost of
the replacement system against an economic irreplaceability
4-23
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threshold in order to determine whether or not the economic
burden of replacing the existing supply would be
unreasonable. The economic irreplaceability test, therefore,
consists of three steps, including the estimation of the
replacement supply costs, the determination of the
appropriate economic irreplaceability threshold, and the
application of the test itself. These three steps are
discussed in more detail below.
step 1. Estimate the Replacement Water-Supply Cost.
The cost estimate for the replacement of a user population's
water supply should reflect the annual costs of the total
system once the potentially affected components of the
existing system have been replaced. For example, the
existing system may consist of public water supply wells, a
treatment plant, and a distribution system. Further,
conversion to a replacement water supply, in this case, might
consist of sinking new wells in an aquifer outside of the
Classification Review Area. The total annualized cost for
the replacement water-supply system, therefore, would include
current annual costs for treatment and distribution plus the
annualized costs for the new wells and transmission of the
new water to the existing system. If the' current user
population consists entirely of private wells, on the other
hand, then the replacement system may consist of a new
source, a new treatment plant, a new distribution system, and
service costs associated with a water-supply utility. The
replacement costs in this situation, therefore, would consist
of the annualized total costs for creating an entirely new
public water-supply system.
Appendix D provides detailed guidance for estimating
the per household costs of replacement water-supply systems.
Once the classifier has determined which components of the
user population's existing water-supply system would require
replacement, the annualized cost per household for the new
system should be calculated using the methodology presented
in Appendix D.
Step 2. Calculate the Economic Irreplaceabilitv
Threshold. The second step of the economic irreplaceability
test is to calculate the irreplaceability threshold for a
replacement water-supply system comparable in size to the
system . under review. The approach used for establishing
economic irreplaceability thresholds for these Guideline* is
based on three primary observations. These primary
observations are as follows:
1. Due to a wide range of site-specific
factors, the cost of water to typical
household users varies significantly
throughout the country.
4-24
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2. Due to the economies of scale
associated with delivery of water
supplies, however, large user
populations tend to pay less, on a
per capita basis, for their water
than do individuals receiving water
from a small system. Nonetheless,
even for systems of the same size,
water costs may vary widely.
3. A threshold value that defines the
maximum feasible cost of a replace-
ment water source can be developed
for various water system sizes by
specifying the replacement water-
supply cost that exceeds a reasonable
economic burden (e.g, observable
extreme water system costs). This
threshold will vary as a function of
system size.
Given these observations, the Agency determined that,
for a given population size, the per household water-supply
cost (i.e., system costs such as operation and maintenance
costs, capital costs, and interest payments) below which 90
percent of the households in a user population typically
face, can reasonably be used as the economic irreplaceability
threshold. In other words, if a replacement water supply
would cost as much or more than the per household cost
observed by only 10 percent of households, then the current
ground-water source is irreplaceable. Therefore, the
economic irreplaceability threshold for a replacement water
supply can be calculated as the ninetieth percentile per
household water-supply cost for water-supply systems of a
given size (i.e., user population).
Using the best available data on community water
supply system costs, the Agency derived an equation
describing ninetieth percentile, per household water-supply
costs as a function of system size. Using this equation,
classifiers can calculate the appropriate economic
irreplaceability threshold. Appendix D presents the
derivation of this cost function and the methodology that
should -be used to calculate irreplaceability thresholds.
Figures 4-5 and 4-6 present two representations of the cost
function used to calculate threshold values; the first figure
covers system sizes between 500 and 1,000,000 persons, while
the second focuses on systems between 500 and 10,000 persons.
Classifiers should note that the full implementation
of the Amendments to the Safe Drinking Water Act passed in
1986 will undoubtedly lead to higher costs for water-supply.
In response to this statute, the Agency is conducting an
4-25
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I
M
O\
$1.200
$1.100 -
$1.000 -
$900 -
I « $800 -
M 11
* 1
H • $700 -\
• 3
5 °
£ v. $eoo -
• M
c
z
$500 -
$400 -
$300 -
$200 -
$10O -
$0
riCURE 4 - s
Ninetieth Percentile Economic Thresholds by System Size
T 1
200,000
1
400,000
1
600.000
1
aoo.ooo
1.000.000
System Size
(User Population Served)
Source:
Incorporated Analytic of Data Collected by Imertan <1987)
Date: 1968
-------
CURE 4-6
I
10
vj
$860
$aoo -
$750 -
« $700 -
• g
I s.
. «
C *
• 1
$600 -
$550 -
$500 -
$450
$400
Ninetieth Percentile Economic Thresholds by System Size
1
2,000
1
4.000
1
6.000
System Size
(User Population Served)
1 T
e.ooo
10.000
Source: ICf incorporated Analysts of D•ta CoItected by I«mer••n (1987)
0 n t e : 1 VB8
-------
extensive review of community water-supply system
affordability. once published and available, these
conclusions and criteria may lead to changes in the approach
for calculating economic irreplaceability presented here.
Step 3. Apply the Economic Jrreplaceabilitv Test.
Having estimated the total cost of the replacement water-
supply system for the user population under review and
calculated the appropriate ninetieth percentile threshold,
the classifier should determine whether the per household
cost of the replacement supply would be economically
unreasonable. If the replacement supply cost is
significantly higher than the threshold, then the economic
burden of the replacement supply would be unreasonable and
the existing water supply should be considered economically
irreplaceable for the preliminary determination. If the
replacement supply cost is relatively close to the threshold,
especially if it is less than the threshold, then the
classifier should consider the variability intrinsic in the
threshold cost function and use best professional judgment to
make a determination. Finally, if the replacement cost is
significantly less than the threshold, then the economic
burden of the replacement system would not be unreasonable,
and the existing source should not be considered economically
irreplaceable for the preliminary determination.
Following any of these preliminary determinations, the
classifier should consider the relevant qualitative criteria
and, if this test is the last of the five screening tests to
be applied or if the test demonstrates irreplaceability, make
a final determination of irreplaceability. Likewise, if the
economic test is not the last test and the test does not
demonstrate irreplaceability, then the remaining screening
tests should be applied.
4.2.3 Step 3: Use of Qualitative Criteria for Final
' Irreplaceability Decisions
The third and final step for completing the determina-
tion of.irreplaceability for any of the five screening tests,
or if the user population is not substantial, is to review
relevant qualitative criteria that either substantiate the
preliminary determination or warrant changing the determina-
tion. Therefore, as discussed throughout this section,
review of these criteria in conjunction with a given
screening test can result in (1) substantiation of a pre-
liminary irreplaceable determination based on that test; (2)
an indication that the next screening test should be applied;.
or (3) if all five screening tests have been applied or the
4-28
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population is not substantial, a final irreplaceable or not
irreplaceable determination.
A list of qualitative criteria compiled by EPA is
given below. Although the discussion for each criterion
indicates whether the criterion can suggest a determination
of irreplaceable or not-irreplaceable, the decision of
whether the criterion is applicable and how much importance
the criterion should be given is left to the judgment of the
classifier.
Presence of Transient Populations
This criterion could be applied to recognize the
presence of large transient populations or transient popula-
tions residing for relatively long periods of time for whom
replacement water might be required. one approach to such
situations would be to weight the transient population based
on the duration of their residence. For example, a resident
using ground water from within the Classification Review Area
for 3 months out of the year would be assigned one-quarter of
the weight given a permanent resident. If the preliminary
determination was not clear, this criteria could favor
changing a preliminary not-irreplaceable determination to a
final irreplaceable determination.
Projected Trends (Population. Economic, and Water Develop-
ment)
These criteria address situations of projected growth or
decline in user population size, economic conditions, or
water-development projects or use. If these projections are
based on demonstrably likely events (e.g., a subdivision is
under construction), reflect changes expected in the near
future (i.e., town has issued bids for construction of a new
water-supply well to be constructed within 2 to 3 years), and
are significantly different from current conditions (e.g.,
substantially larger or smaller population to be dependent on
the supply), then the classifier may be justified in Baking a
determination according to the projections. Therefore, this
criteria could favor shifting a preliminary determination in
either an upward or downward manner, depending on how the
relevant conditions were projected to change.
Unreliable Transport Mechanism
This criterion recognizes that although a pipeline or
some other mechanism to transport an alternative water supply
(e.g., use of a barge to bring water to an island) may be
economically feasible, the aechanism may also be subject
periodically to severely inclement weather or some other
risk. If this risk were unacceptably high, thus making the
ground water in question less replaceable, then a final
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irreplaceable determination could be favored over a not-
irreplaceable decision.
4.3 Procedures for Determining Ecologically Vital
Areas
Ground water may be considered ecologically vital if
it supplies a sensitive ecological system located in a
ground-water discharge area that supports a unique habitat.
A unique habitat is defined to include habitats for endan-
gered or threatened species that are listed or formally
proposed for listing pursuant to the Endangered Species Act
(as amended in 1982}, as well as certain types of Federally
managed and protected lands.
In the above definition are two terms which require
explanation. A sensitive ecological system is.interpreted in
these Guidelines as an aquatic or terrestrial ecosystem
located in a ground-water discharge area. A unique
terrestrial or aquatic habitat is primarily defined as a
habitat for a species that is listed or proposed for listing
as endangered or threatened, pursuant to the Endangered
Species Act (as amended in 1982). In some cases, certain
Federal land management areas, Congressionally designated and
managed for the purpose of ecological protection, may also be
considered unique habitats for ground-water protection,
regardless of the presence of endangered or threatened
species per se. Among those most likely to be included are
the following:
• Portions of National Parks.
• National wilderness Areas.
• National wildlife Refuges.
• National Research Natural Areas.
A discharge area is an area of land through which
there is a net annual transfer of water from the saturated
zone to a surface-water body, the land surface, or the root
zone. The net discharge is physically manifested by an
increase of hydraulic heads with depth (i.e., upward ground-
water flow). These zones may be associated with natural
areas of discharge, such as seeps, springs, caves, w*tlands,
streams, bays, or playas.
Ground-water discharge to surface-water bodies occurs
in many hydrogeologic settings and is the dominant condition
in high rainfall areas. Where poor-quality ground-water
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discharges to surface water, a potential to impact the
quality of those surface waters exists.
The procedures for locating the presence of a
Federally protected endangered or threatened species or the
habitat of an endangered or threatened species is as follows:
1. Locate the appropriate (by state) U.S. Fish and
wildlife Service, Office of Endangered Species,
Field Office.
2. Submit to the Field Office a letter describing
the area of interest, including a nap if
possible, and the nature of the present habitat
(e.g., cultivated field or mature woodland). The
letter should request information on endangered
or threatened species and their habitats located
in the area.
3. The office will usually respond within 30 days.
The U.S. Fish and wildlife Service is required under
the Endangered species Act to provide information about
endangered or threatened species. Section 7 of the
Endangered Species Act provides a consultative process for
considering any action authorized, funded, or carried out by
a Federal agency that is likely to jeopardize the continued
existence of any endangered or threatened species or result
in the destruction or adverse modification of the species
habitat. The U.S. Fish and Wildlife Service's, field offices
are responsible for providing this information upon request.
A list of regional and field offices is presented in Appendix
B.
In addition to the U.S. Fish and wildlife Service,
individual states also maintain agencies that keep track of
endangered or threatened species, particularly, those
candidate endangered species and rare species not Federally
listed. In most cases State-specific information can be
obtained through the Natural Heritage Program (a list of
program offices is presented in Appendix B) or through the
non-game program within the various State Departments of
Natural Resources. EPA offices such as the Marine,
Estuarine, and Wetlands Programs, may also have information
regarding important ecological habitats.
Information about Federal lands may also be obtained
from Federal land management agencies such as the National
Park Service, and Bureau of Land Management. The presence of
Federal lands is indicated on most State and county road maps
and U.S. Geological Survey quadrangle sheets.
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4.4 Procedures for Determining Highly Vulnerable Area*
In addition to being an irreplaceable eource of
drinking water to a substantial population and/or
ecologically vital, Class I ground water oust also be highly
vulnerable to contamination, i.e., the ground water must be
determined to be highly vulnerable in order for a Class I
designation to apply. Highly vulnerable ground water is
characterized by a relatively high potential for contaminants
to enter and be transported within the ground-water flow
system. Thus, vulnerability encompasses the leaching
potential of the soil and/or vadose zone and the ability of
the saturated flow system to move contaminants over a large
geographic area (not just beneath any given site).
Vulnerability to contamination occurs across a continuum from
very high to very low just as leaching potential and ground-
water velocities occur in a continuum from high to low. For
classification purposes, only situations at the higher end of
the continuum are of concern.
The concept of ground-water vulnerability focuses only
on the inherent hydroqeological characteristics of the
Classification Review Area. The determination that a setting
is highly vulnerable to contamination is based primarily on
the best professional judgment of the classifier or technical
support staff. This approach provides the flexibility needed
to address the wide variation in hydrogeologic conditions
that occur across the nation.
When attempting to evaluate vulnerability, a
classifier should select the most appropriate vulnerability
assessment tools based on consideration of factors such as
regional hydrogeologic conditions, availability of data, and
professional experience of the classifier or support staff.
Classifiers are encouraged to examine multiple lines of
evidence to support a vulnerability determination. Such an
approach might include an evaluation of hydrogeologic factors
relevant to vulnerability, matching the subject hydrogeologic
setting to a highly vulnerable descriptive/ qualitative
setting as provided in this guidance, and/or employing one or
more technical evaluation aids.
In the following subsections, guidance is provided
regarding the hydrogeologic factors to consider for evalu-
ating vulnerability. Selected vulnerability evaluation aids
are also presented. Where appropriate, benchmarks indicative
of highly vulnerable hydrogeology are provided.
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4.4.1 Factors Related to Vulnerability
A large number of factors may influence the
vulnerability of a specific setting to ground-water con-
tamination. Table 4-2 provides a comprehensive, though not
exhaustive, list of these factors. The relative influence of
any one factor on the degree of vulnerability to contamina-
tion varies from region to region and may vary from setting
to setting within a region. For example, recharge rate may
be more important in arid regions than in humid regions. The
factors are also highly interrelated. A change in the
magnitude of one factor may result in changes in the mag-
nitude of other factors. The factors presented are to assist
in the following discussion and not to be taken as a
checklist for each classification decision.
The classifier will need to select a set of the most
appropriate factors for evaluation based on a knowledge of
the regional hydrogeology and the interrelationships between
factors. No single factor will be likely to distinguish
highly vulnerable from less vulnerable hydrogeologic set-
tings. A combination of factors should be evaluated.
Several of the vulnerability evaluation aids described in a
subsequent section incorporate subsets of these hydrogeologic
factors. The following discussion is intended to provide an
overview of each factor and its importance to evaluating
vulnerability. The discussion and list are not meant to be
binding. In some settings, only a few factors will need to
be assessed. Rarely will all or nearly all need to be
reviewed in detail.
Regional Recharge
Recharge of precipitation is the principal means by
which a contaminant released at or near the surface is
leached and transported through the vadose zone to ground
water. Met recharge rate is considered by many hydrogeo-
logists to be one of the most important factors to consider
in a vulnerability assessment. Nst recharge can be thought
of as the quantity of precipitation that is available for
transport, dispersion, and dilution of a pollutant from a
specific point/area of introduction.
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Table 4*2
Factors Relevant to Judging
Vulnerability to Contamination
(Not. Listed in Specific Order)
• Regional Ground-Water Recharge Rate
Natural recharge
- Artificial recharge
e Topography
Slope
e Landscape Position/Land form
- Recharge/discharge area location
- Proximity to water bodies, discharge areas
Geomorphic position or land form (e.g., river
terraces, alluvial fans)
e Soil/Vadose-Zone Characteristics
- Depth to water/thickness of vadose zone
Depth to the seasonal-high water table
Depth to the zone of saturation
Thickness of the unsaturation zone
- Soil texture/clay content
- Clay mineralogy
Infiltration capacity
- Porosity (primary and macro/secondary)
- Hydraulic conductivity/permeability
- Attenuative capacity
filtration
biodegradation
•orption
fixation/precipitation
volatilization
- Vadose-zone media
silt/clay; shale; limestone; sandstone; bedded
limestone, sandstone, shales; sand and gravel
with silt and clay; metamorphic/igneous;
basalt; karst limestone
e Aquifer and Ground-Water Flow System Characteristics:
- Hydraulic conductivity
- Effective porosity (primary and secondary)
- Hydraulic gradient (horizontal and vertical)
- Ground-water flow velocity
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Attenuativc capacity
. path length/media contact time
. sorption properties
. ion-exchange capacity
. conditions conducive to chemical demobilization
Aquifer media
. rock type (shale, sandstone, limestone,
metamorphic and igneous rocks, karst
limestone)
. mineralogy
. grain-size distribution
. organic carbon content
Sequence of aquifers and non-aquifers
Degree of confinement
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In general, the higher the recharge rate, the greater
the potential for ground-water pollution where a source is
present. In areas where there is little precipitation/ there
is correspondingly little rech&rge. For this reason, areas
of low precipitation will tend to be considered as less
vulnerable to contaaination than areas of high precipitation.
The amount of precipitation that ultimately recharges
is dependent on a number of site-specific parameters,
including slope (topography) and soil/vadose conditions.
Slope of the land is an indicator of the proportion of
precipitation that runs off. Steeper slopes usually mean
more runoff and less recharge. Soils that develop on steep
slopes are generally thinner and less mature (i.e., lower
subsoil clay content) than those that develop on less steep
slopes. The attenuation capacity of the steep slope soils
is, as a result, lower. Areas with low-permeability soils
(e.g., clayey textured soils with low macro-porosity) also
tend to have lower recharge rates and higher runoff rates.
Recharge rates and, thus, the potential for pollution,
can be augmented by artificial recharge and irrigation.
Artificial recharge is defined as any process by which man
fosters the transfer of surface water into the ground-water
system (Freeze and Cherry, 1979). In some areas, artificial
recharge and irrigation are considerable and should, there-
fore, be factored into the vulnerability evaluation.
Topooraohv
Topography (or slope) influences the likelihood that a
pollutant will run off or recharge the ground water. In
general, the flatter the slope, the more likely recharge will
occur and contaminants will infiltrate to the ground water.
A steeper slope implies a greater proportion of runoff than
recharge and, therefore, less contaminant infiltration.
Slopes greater than 18 percent have the greatest runoff
capacity (Aller et al., 1985).
Soil/vadose zone conditions also influence the propor-
tion of runoff and recharge (see below). Sandy textured
soils generally allow for more recharge than clayey soils.
For this reason, both topography and soil/vadose zone
conditions must be considered together. Note that in the
alluvial basins in southwestern states, most recharge occurs
in the steep alluvial fans at the base of the mountains.
water-table gradients may be related to topography.
Areas with steep slopes are more likely to have high ground-
water flow velocities due to the generally steeper ground-
water gradients. The ground-water flow velocity influences
potential for attenuation in aquifer media. High ground-
water flow velocities usually result in lower attenuation due
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to the shorter contact time between the contaminant and the
soil and aquifer media.
The classifier should be aware that topography may not
be very relevant to a vulnerability evaluation if significant
artificial changes to control runoff (e.g., storm drains or
drainage ditching) have occurred.
Landscape Position/Land Form
The position of a potential contamination source
within the landscape or geomorphic landform can be used to
screen ground-water vulnerability because of certain associ-
ated hydrogeologic conditions. For example, recharge and
discharge areas are commonly inferred from landscape
positions. Because recharge is the primary mechanism by
which contaminants are leached and transported to ground
water, contamination is more likely to occur if a
facility/activity is located in a ground-water recharge area.
On the other hand, discharge areas are less vulnerable to
contamination because recharge is minimal. The net movement
of water is to the surface in these areas and recharge is
less likely to penetrate to an appreciable depth, except
under some unusual conditions of highly induced head or
geochemical density effects.
The position of a facility/activity within certain
geomorphic units or landforms can also be used to screen for
ground-water vulnerability. The topography and physical
characteristics of certain geomorphic units/ landforms are
sufficiently predictable in some regions to generally
determine their hydrologic behavior. For example, alluvial
fans and glacial outwash plains are commonly characterized by
coarse-grained material which generally implies high hydrau-
lic conductivities and ground-water flow velocities, both of
which tend to increase vulnerability. Glacial moraines, on
the other hand, may be composed of clayey till in some areas
and be judged to be less vulnerable due to generally lower
hydraulic conductivities.
Soil/Vadose-Zone Characteristics
Soil and vadose-zone characteristics influence ground-
water vulnerability with respect to the amount and rate of
recharge and attenuation of infiltering contaminants. The
pollution mitigating potential of the soil/vadose-zon« is
dependent on the grain size (texture) and physical and
chemical characteristics of the soil/vadose zone media.
Attenuation mechanisms include mechanical filtration,
volatilization, dispersion, chemical alternations (e.g.,
fixation and precipitation) , neutralization, oxidation-
reduction, ion-exchange, and biological (biodegradation)
processes.
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Soil/vadose-zone media characteristics, including
grain size/texture, shrink/swell potential of the clay,
porosity (primary and macro/secondary), and permeability,
control the amount and rate of recharge that occurs. Soil
texture includes considerations of the amount and size of
various particle sizes (i.e., sand, silt, and clay). A soil
with a high clay content or lov secondary/macro-porosity, in
general, allows less infiltration than a soil with high sand
content or high secondary/macro-porosity. ' In general, a
soil/vadose zone with a large grain size and/or large macro-
porosity has a high pollution potential.
A longer path length and contaminant travel time
through the soil/vadose zone allows for the maximization of
attenuative processes. The depth-to-water/thickness of the
vadose zone, in part, controls the path length and, thus, the
time it takes for a contaminant to reach the aquifer. As
path length and travel time increase, the time the
contaminant is in contact with oxygen or the surrounding
media increases. The attenuation processes of ion-exchange,
adsorption, oxidation/reduction, bio-degradation, filtration,
and Volatilization are more likely to occur if the depth to
water is great because contact time with surrounding media is
increased.
Chemical attenuation processes include adsorption
(e.g., ion-exchange and surface complexation) and
precipitation reactions. The degree of attenuation that
oc rs due to adsorption processes is primarily a function of
mi ralogy (i.e., iron and manganese oxides and organic
me ar content). A high clay content generally increases the
at -mation capacity of the soil/vadose zone because of the
ic exchange and complexation reactions that occur at highly
c!r ged surfaces on clay particles. The presence of iron and
m.-: ganese oxy-hydroxides enhances the adsorption of inorganic
contaminants, particularly cationic metals, due to surface
bonding and coprecipitation. The fraction of organic matter
within the soil strongly influences the attenuation of
organic contaminants because organic molecules preferentially
partition to organic substances rather than inorganic
mineral* or water. Precipitation reactions are a function of
redox conditions and pH. Oxidation and reduction processes
are controlled by the presence of oxygen in the soil media.
Redox -reactions may decrease the solubility of some
contaminants. For example, heavy-metal contaminants are
likely to precipitate in oxygen-rich environments because of
the formation of insoluble metal oxides and hydroxides. A
high carbonate content tends to raise the pH of soil water,
also causing heavy metals to precipitate. Contaminant
concentrations are thus reduced due to precipitation of the
contaminant from solution.
Mechanical attenuation processes include dispersion
and filtration. Dispersion of contaminants results from flow
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around particles and across pore spaces. This causes the
contaminant to spread or disperse so as to gradually occupy
an increasing volume. The greater the heterogenity, the more
dispersion of contamination. Mechanical filtration removes
contaminants which are larger than pore spaces of the host
medium (Aller et al., 1985). Thus, fine-grained materials
such as clay and silt, tend to remove contaminants with
greater efficiency than a more coarse-grained media.
Aquifer and Ground-Water Flow System Characteristics
Aquifer and ground-water flow system characteristics
govern the attenuation capacity of the ground-water environ-
ment and the ability of this environment to transport
contaminants. Ground-water velocity, which is a function of
hydraulic conductivity, hydraulic gradient, and porosity,
controls the time available for attenuation processes to
occur. Low permeability and small gradient will result in a
slow ground-water velocity. Compared to hugher velocity
settings, the contaminant remains in contact with the aquifer
medium for longer periods of time. This allows the attenu-
ation processes, such as adsorption and precipitation, to
occur to a much greater extent than if the ground water were
moving at a faster velocity.
Aquifer media characteristics, such as clay and iron
and manganese oxide content, mineralogy (e.g., carbonate con-
tent) , and organic carbon content, also affect the attenu-
ation capacity of an aquifer. The discussion on these
attenuation processes as presented in the previous section
concerning the soil/vadose zone also applies to the saturated
zone.
Aquifer porosity and hydraulic conductivity are con-
trolled, in part, by media type. In granular and clastic
rocks, water travels primarily through primary, intergranular
pore spaces (although these rock types can have fracture
permeability as well). In nonclastic and nongranular rocks,
water travels primarily through fractures and solution
openings. A larger grain size or an abundance of fractures
and solution openings within the aquifer usually indicate a
relatively high hydraulic conductivity or transmissivity and
a relatively low attenuation capacity and, consequently, a
greater pollution potential.
Mechanical attenuation processes include dispersion
and filtration. Dispersion of contaminants results from
ground-water flow velocity variations around particles and
across pore spaces. This causes the contaminant to spread or
disperse so as to gradually occupy an increasing volume of
the flow system (Aller et al., 1985). The greater the
heterogenity, the more ground-water flow variations possible,
thus, more dispersion of contamination. Mechanical filtra-
tion removes contaminants which are larger than the pore
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•paces of the host medium (Aller et al., 1985). Thus, fine-
grained materials, such as clay and silt, tend to remove
contaminants with greater efficiency than a more coarse-
grained media.
4.4.2 Evaluation Aids for Assessing vulnerability
In this section, selected evaluation aids are
presented as tools which may be used to assist in a
vulnerability assessment. After selecting the most
appropriate hydrogeologic factors, the classifier may choose
to employ one or more of these quantitative evaluation aids.
The aids provide a framework for examining the importance and
interrelationships between factors. Each type of aid is
described and general procedures for use in the vulnerability
evaluation are provided. Vulnerability evaluation aids
include the following:
e Descriptive/Qualitative Aids
- Historical Evidence
- Descriptions of General Hydrogeologic Scenarios
e Quantitative Evaluation Aids
- Multiple Factor Methods
- Numerical Ranking Systems
- Zntegrative Methods
The choice of which evaluation tool to use is dependent
on the quantity and quality of available data. If limited
data are available, then it is best to use the descriptive/-
qualitative tools. The quantitative approaches are generally
dependent on detailed information for the Classification
Review Area.
Descriptive/qualitative evaluation aids nay be used as
part of a screening process which would help determine if-the
ground waters are likely to be classified as highly
vulnerable. In some cases, the vulnerability of the ground
water to contamination may be readily apparent solely on the
basis of descriptive/qualitative aids. The quantitative
evaluation aids, along with available benchmarks indicating
relative ;lnerability, could be used when vulnerability is
less appaxant and more detailed sraa^spscific information 1*
available.
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Descriptive/Qualitative Aids
Two descriptive/qualitative aids nay be considered at a
screening level, historical evidence and vulnerability
scenarios. These aids generally require a minimum of
information about the hydrogeology of the review area. The
historical evidence approach is meant to be a "quick-and-
dirty" assessment where information on water quality is
available. It is not meant to be an analysis that can stand
alone. The vulnerability scenarios are intended to help
identify those areas where vulnerability is readily apparent.
Historical evidence of a number of serious ground-water
contamination incidents in the ground-water unit or
Classification Review Area is generally a good indication
that an area is highly vulnerable to contamination. The lack
of contamination does not necessarily mean that the area is
not highly vulnerable, especially if no source activities
have been present. On the other hand, a lack of significant
contamination in areas with significant source activities may
suggest a lower level of vulnerability or initiate a more
detailed review.
Information about existing water quality is usually
available through State and local health departments, the
U.S. Geological Survey Water Resources Division, State
geological surveys, and the EPA. Information about historic
land-use activities can be gained from tax assessment maps,
zoning maps, land deeds, air photos, facility permit applica-
tions, Environmental Impact Statements, and interviews with
people familiar with the area.
Historical evidence is best used as one line of evidence
indicative of vulnerability. The hydrogeologic factors as
well as other evaluation aids should be examined.
A second qualitative approach is to compare a setting to
vulnerability scenarios representing highly vulnerable and
not highly vulnerable conditions. The general procedure for
implementation is to match a real, candidate setting to a
conceptual vulnerability scenario.
The regional hydrogeologic data necessary . to implement
this procedure may be available from U.S. Geological Survey
reports, State geological surveys, U.S. Department of
Agriculture (USDA) Soil Conservation Service soil surveys,
scientific books and journals, county/ regional reports,
facility permit applications, Clean Water Act Section 208
studies, Environmental Impact statements, and Safe Drinking
Water Act Sole Source Aquifer (SSA) studies.
Scenarios that are more likely to be judged highly
vulnerable include the following hydrogeologic settings:
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• Shallow unconfined sand and gravel aquifers with
•andy soils/vadose zones.
• Karstic aquifer systems exhibiting conduit flow where
this aquifer is exposed at the land surface or is
covered by highly permeable surficial deposits vith
shallow depth to water.
• Shallow, basaltic, volcanic rock aquifers with
extensive fractures, lava tubes, weathered zones, and
large secondary porosity where such aquifers are
overlain by highly permeable soils or soils developed
in volcanic materials.
• Islands comprised of porous, sandy soils with an
unconfined, fresh-water aquifer.
• Shallow coastal plain aquifers composed primarily of
coarse sand and gravel, over semiconsolidated
carbonate rocks or fine-grained aquitards.
• Other areas with thin, highly permeable unsaturated
zones and/or saturated zones with rapid ground-water
velocities (e.g., fractured bedrock areas).
Scenarios that are less likely to be judged highly
vulnerable include the following hydrogeologic settings:
• Confined aquifers overlain by a very thick confining
unit of low permeability.
• A buried valley aquifer overlain by thick, clayey
deposits.
• Vary low permeability stratigraphic units in close
proximity to ground surface (s*g., clay, shales,
unfractured crystalline or metamorphic rocks).
• Oischarg* areas or other areas with extremely low
• recharge.
Quantitative Evaluation Systems
Three general types of technical evaluations are
available: multiple-factor criteria listing,- msmnrical rating
systems, and integrative analyses. Multiple factor criteria
listing evaluations tend to require lower levels of sophis-
tication and data, numerical rating systems require greater
levels, and integrative analyses require the highest levels.
Benchmarks indicative of highly vulnerable are provided only
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for selected numerical rating systems and integrative
analyses.
Multiple-factor Criteria Listing
A common method for evaluating vulnerability is the
Multiple-Factor Criteria Listing Approach. This type of
measure requires the selection of specific, measurable
hydrogeologic factors (e.g., depth to water) and a criterion
for each factor against which a real, highly vulnerable type
of setting will be compared (e.g., less than 10 feet depth to
water). The criterion for each hydrogeologic factor will
commonly be selected based on a knowledge of the natural
range of that factor in the region. Criteria selection must
consider the interrelationships between factors, such that
mutually exclusive criteria are not selected. For example, a
low-hydraulic conductivity soil, a thick vadose zone, and a
high recharge rate, are usually mutually exclusive.
Assessing compliance to the criteria, however, typically
assumes that the factors are independent.
It is essential to establish decision rules for judging
if a setting is highly vulnerable. For example, the decision
rules could require that a setting be considered highly
vulnerable if any single factor meets the highly vulnerable
criterion. Alternatively, it may be decided that it is
necessary for all, or perhaps a subset, of the factors to
meet the highly vulnerable criteria in order to establish a
setting as highly vulnerable.
The principal problem with the Multiple Factor Criteria
Listing Approach is that interrelationships between factors
are typically ignored when establishing the decision rules.
Ignoring the interrelationships between factors can lead to
erroneous vulnerability decisions, as well as inflexibility
in considering unusual circumstances or compensating factor
values. For instance, for a given hydrogeologic setting, the
trade-off between a slightly below criterion, depth to water
table measure and an above criterion, aquifer transmissivity
measure Might not be considered in a multiple-factor
criteria-listing approach. A more sophisticated aid for
evaluation may be needed to fully represent such
relationships. As a result, the multiple-factor, criteria-
listing measure can be somewhat inflexible when considering
compensating hydrogeologic characteristics if the decision
rules are inflexible.
One criteria-listing approach that will allow more
flexibility is to use a classification system composed of
three or more classes for each factor. One class is reserved
for the true highly vulnerable conditions that are judged to
be beyond compensation. Another class is established for the
ideal true, not highly vulnerable conditions. The
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intermediate class is designed for consideration of
compensating factors.
The most troublesome aspect of multiple-factor criteria
listing concerns the selection of a highly vulnerable
criterion for each factor. Typically, the criterion value
indicating a highly vulnerable setting may simply be chosen
from the infrequently occurring values within the natural
range of factor values. Alternatively, the selected
criterion may be a surrogate for a more sophisticated
analysis, such as time of travel or risk. Zn general,
assigning a highly vulnerable cutoff value to a particular
factor is a matter of best professional judgment. For
example, it is difficult to find a cut-off value for depth to
water such that a setting with a depth to water slightly less
than the cutoff will always be considered highly vulnerable
and a setting with a depth to water slightly greater than the
cut-off value will always be considered not highly
vulnerable. The selection of a highly vulnerable criterion
for depth to water has no one correct value.
The multiple-factor, criteria-listing approach is
exceptionally easy to implement where the factors selected
are easy to measure or estimate. Any number of factors can
be considered. Few single factors or criteria, though, will
be appropriate at a regional or national scale; and a set of
factors and criteria developed for one region may not be
identical to a set of factors developed for another region.
It is recommanded that at least three hydrogeologic
factors listed in the numerical rating system referred to as
DRASTIC (see the next section) be considered. At the State
level, it may be possible to compare highly vulnerable
criteria to the criteria for siting hazardous-waste disposal
facilities. An acceptable site under such criteria would
likely be considered not highly vulnerable. According to
Monnig (1984), a majority of states have established such
criteria.
Ranking Svstemfs^
The) numerical rating type of assessment tool, in
addition to establishing factors, assigns hierarchial ranges
to each 'factor. The range for each factor is subdivided and
assigned a relative numerical rating indicating the relative
importance of that range interval to vulnerability. For
example, the factor depth to water could be subdivided into
seven categories, as shown in Table 4-3 (see page 4-49).
Each category would be given a rating from 1 to 10, with 1C
being the most vulnerable. In this way, a vulnerability
continuum is established. The numerical factor ratings can
also be multiplied by a weight in order to reflect the
relative importance of the factors. For example, depth to
water may be a factor considered twice as important as the
4-44
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slope of land. Therefore, the depth-to-water factor rating
would ba multiplied by .a weighting factor of 2. Finally, the
factor ratings, or weighted factor ratings, are added to give
a total vulnerability score.
A number of numerical rating systems have been developed
for various purposes. Those most appropriate for assisting
in a vulnerability assessment generally meet the following
criteria:
• Should not be activity specific (i.e., only relevant
for one very specific contamination source).
• Should consider only hydrogeologic factors or the
hydrogeologic section should be separable from the
rest of the calculations.
• Should consider only a ground-water, contamination
pathway.
• Should be suitable for the setting in which it is
being applied.
Two numerical ranking systems are presented as generally
consistent with this vulnerability concept:
• DRASTIC (Aller et al., 1984)
• LeGrand System for Evaluating Water-Disposal Sites
(LeGrand, 1980)
This list is not intended to be exhaustive. Other systems
may meet the criteria listed above and may be deemed
appropriate.
In preparing this list, a number of numerical rating
systemmsjiwre examined, other systems were not listed because
they eaioBpass other contamination pathways (direct contact,
surface^water, or air) and/or source and contaminant charac-
teristic* which were found to ba inconsistent with the
concept of vulnerability. For come rating systems, the
hydrogeologic portions could not be isolated and used
separately as indicators of vulnerability. In some cases,
the rating systems are too data intensive, too activity
specific, or employ one of the systems listed above.
For each numerical ranking system listed, a bench mark
score has been suggested that signals if an area may be
classified as vulnerable. For example, in the DRASTIC
system, a score of around 15C or greater generally indicates
4-45
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that a review area is highly vulnerable for high rainfall
areas.
The degree of confidence in a numerical rating syste*
•core is, in part, a function of the reliability of the
hydrogeologic information uaed to rate each factor and the
experience of the rater. In settings where the hydrogeologic
information is veil established, due to localised ground
water and geologic studies, for example, the score will have
a narrow confidence band. As in any procedure involving
professional judgment, a more experienced or better trained
evaluator will provide a more accurate portrayal of ground-
water vulnerability to contamination.
A numerical rating system can be applied to the Classi-
fication Review Area using one of two approaches. In the
most general approach, the actual range of each hydrogeologic
factor can be estimated from available information and a
single score generated for the entire Classification Review
Area. The average rating for each factor would be chosen
where the range in the values of factor parameters spans two
or more ratings. For example, if the depth to water across
the Classification Review Area ranged from 5 to 30 feet, and
this range covered two range categories (e.g., the 5 to 10
foot category and the 10 to 30 foot category), an average
rating would be chosen. This approach does not allow for the
differentiation between contrasting hydrogeologic settings
within the Classification Review Area where the vulnerability
•core is distinctly different.
The second approach is to map out the major hydro-
geologic settings that have significantly different vul-
nerabilities within the Classification Review Area. Dif-
ferences in numerical rating scores of 10 to 20 percent are
generally considered significant, where vulnerability units
are mapped out, an area -weighted, average score can be
computed. However, if the activity occupies any portion of a
highly vulnerable map unit, a judgment that the ground water
is highly vulnerable; is appropriate.
As An illustration of the mapping approach, consider the
proposed activity shown in Figure 4-7. Within the Classifi-
cation Review Area, three hydrogeologic settings have been
mapped and labeled using the DRASTIC numerical rating system.
The DRASTIC index for each hydrogeologic setting labeled A,
B, and C is 180, 140, and 100, respectively. The areal
proportion of the review area for each setting is 20 percent,
45 percent, and 35 percent, respectively. The weighted
average DRASTIC index is calculated as follows:
4-46
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FIGURE 4-7
ILLUSTRATION OF DRASTIC MAPPING
MAP UNIT B
DRASTIC *I4O
MAP UNIT A
DRASTIC'ISO
MAP UNIT B
DRASTIC «I4O
MAP UNIT C
DRASTIC* 100
EXPLANATION
. •
fCtASSIFICATION REVIEW AREA BOUNDARY
t MILCS
4-47
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Area*
Map DRASTIC Proportion Weighted
Unit • Index of Area Index
A 180 0.20 36
B 140 0.45 63
C 100 0.35 35
Weighted Index 134
* DRASTIC index multiplied by the proportion of area.
For this illustration, the nap-unit, area-weighted
DRASTIC index of 134 is less than the recommended benchmark
highly vulnerable criterion of 150. If the activity had
occurred in map unit A, the designation of highly vulnerable
would have been justified.
Each of the recommended numerical ranking systems is
reviewed in turn. A brief discussion comparing the various
system follows the review.
DRASTIC Methodology. DRASTIC is a numerical ranking
system developed by the National Water Well Association
(Aller et al., 1985) under contract to EPA. The DRASTIC
methodology can be performed using readily available informa-
tion. It yields a single numerical value referred to as the
DRASTIC index. DRASTIC was prepared using a Delphi approach
(a consensus building approach) on a panel of highly experi-
enced, practicing professional hydrogeologists familiar with
the potential for ground-water contamination across the
county. It builds on earlier systems such as those of the
LeGrand System (LeGrand, 1980) and the Surface Impoundment
Assessment system (Silka and Sweringer, 1978). It is
applicable: en a regional level (i.e., several square miles)
on par.with the size of the Classification Review Area. It
was designed to overcome problems of more simplistic methods
that may ignore relevant factors or the relative importance
of a factor compared to other factors.
DRASTIC is an acronym representing seven key hydrogeo-
iogic factors correlated to the potential for ground-water
contamination listed below:
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D - fiepth to the water table
R - Net Berharge to ground water
A - Aquifer media
S - £oil media
T - Topography (slope of the land)
I - Impact of the vadose zone
C - Hydraulic Conductivity of the subject
ground-water flow system
The DRASTIC methodology consists of several steps
leading toward a single DRASTIC index number. In the first
step, each factor is given a rating between 1 and 10 (except
for net recharge, which is rated between 1 and 9) depending
upon the range of parameter values within a hydrogeologic
setting. Consider the range of values for depth to water,
and corresponding ratings, shown in Table 4-3. A setting
with a depth to water of 28 feet would be rated as a 7.
TABLE 4.3
RANGES AND RATINGS FOR DEPTH TO WATER
AS USED IN THE NUMERICAL RATING SYSTEM DRASTIC
(ALLER ET AL. 1985)
Depth to Water
(feet)
Rang* Rating
0-5 10
5-15 9
15-30 7
30-50 5
50-75 3
75 - 100 2
100* 1
Weight: 5
4-49
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In the second step, each factor rating is multiplied by
a factor weight to give a factor index. For instance, the
weight for depth to water is 5 and, thus, if the rating is 7,
the factor index is 35 (7 times 5). For the final step, the
individual factor indices are added together to arrive at the
DRASTIC index.
DRASTIC has been designed to account for a number of
different conditions, among which are multiple aquifers and
confined aquifers. The DRASTIC methodology allows for the
depth-to-water rating to be adjusted for confined aquifers.
With this technique, different aquifers within the Clas-
sification Review Area could receive a different DRASTIC
index. If the aquifers are believed to be highly intercon-
nected as defined Chapter 3 then the most vulnerable aquifer
should be evaluated.
The focus of the DRASTIC system in assessing
vulnerability is the uppermost aquifer. Where the uppermost
aquifer is found to be vulnerable, all ground water with a
high degree of interconnection to the uppermost aquifer is to
be considered highly vulnerable. Confined aquifers with a
low-to-intermediate interconnection to the uppermost aquifer
are considered less vulnerable.
The DRASTIC method also establishes a separate and
different set of factor weights for agricultural activities.
Because the Agency has decided to consider vulnerability as
independent of activity, only the regular factor weights will
be applied.
A two-tier DRASTIC highly vulnerable benchmark is
suggested. The tiers are distinguished according to hydro-
logic regions. In regions where estimated annual potential
evapotranspiration exceeds mean annual precipitation, the
DRASTIC benchmark for highly vulnerable is suggested to be
120. In regions where estimated annual potential
evupotranspiration does not exceed mean annual precipitation,
the DRASTIC benchmark for highly vulnerable is suggested to
be 150.
LeGrand System. The LeGrand method (LeGrand, 1980) is a
numerical rating system designed to evaluate the potential of
ground-water contamination from waste-disposal sites. The
evaluation is divided into four stages which are subdivided
into ten steps. The first stage.- n hydrogeologic analysis.
is developed in the first seven steps, contaminant charac-
teristics are not considered in the first stage. Stages 2,
Note there are three versions of the LeGrand System.
Only the most recent version is referenced here.
4-50
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3, and 4 develop descriptions, ratings, and grades that
consider both site and contaminant characteristics.
Because EPA has decided that a classification decision
should be independent of activity and contaminant considera-
tions, only Stage 1 of the Le Grand system is directly
applicable to a vulnerability assessment.
The hydrogeologic evaluation is based on four key
parameters:
• The distance on the ground from a source of con-
tamination to the nearest well, surface stream, or
property boundary.
e The depth of water table below the waste or con-
tamination source.
e The approximate slope of the water table and direc-
tion of ground-water flow.
e The character of earth materials through which a
contaminant is likely to pass, expressed in terms of
permeability and sorption.
The first four steps in Stage l involve estimating
values for each of the four key hydrogeologic parameters.
Steps 5 and 6 provide for the addition of letters that
identify special features with respect to the site. In Step
7, the site numerical description is completed by adding the
four values obtained in Steps 1 through 4, to get a total
point value for the site.
The following is an example of a LeGrand site numerical
description.
18 - 1539AA WQ
Step Source
1 Distance to nearest water
supply
2 Depth to water table
3 Water-table gradient
4 Permeability sorption
5 Confidence in accuracy of
ratings
H,Q 6 Miscellaneous site identifiers
18 7 Total point value, sum of Steps
1 to 4
The lower the total point value the less vulnerable a
site; however, the total point value cannot be relied on
4-51
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•olely. A site nay have a favorable rating for three
parameters and be exceptionally unfavorable for the fourth.
For example, at site may be ideal in all respects except for *
high water table. The total point value is, therefore,
followed by the values of the individual parameters. This
allows both the weak and strong features of a site to be
graphically recorded (LeGrand, 1980}.
The total point value has been divided into five ranges
(see Table 4-4). These five ranges are assigned grades which
evaluate a site as to its ground-water pollution potential.
The total number of points possible is 32. The higher the
point value, the more vulnerable a site is to contamination.
A site with a total point value >20 is assigned a grade of E
or F which indicates it is a poor to very poor place to site
a waste-disposal unit. This implies that the ground water is
highly vulnerable to contamination. A total point value of
around 20 can, therefore, generally be considered indicative
of a highly vulnerable setting for the LeGrand rating system.
TABLE 4-4. (LeGrand, 1980)
GENERALIZED SITE GRADE BASED ON
CRITICAL HYDROGEOLOGIC PARAMETERS
Total
Grade Points
A. Excellent <10
B. Very Good 11-14
C. Good 15-17
D. Fair 18-20
E or F. Poor to Very Poor >20
A classifier attempting to stay within a narrow defini-
tion of vulnerability will most likely ignore Step 1 of the
analysis^ (i.e., Measuring the distance from the contamination
source to the nearest water supply or boundary) as
consideration of well distance blends a use measure into what
is intended to be essentially a hydrogeologically based
determination. If Step l is ignored, the total maximum point
value is 23 points. In this case, a benchmark of 15 may be
generally considered to be indicative of a highly vulnerable
setting.
For a more detailed discussion of the LeGrand methodol-
ogy, including parameter ranking values and examples, see "A
Standardized System for Evaluating Waste Disposal Sites"
(LeGrand, 1980).
4-52
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Intearative Methodology
Integrative methodologies are often considered the most
sophisticated evaluation aids because they can represent the
interaction and relative importance of the various hydrogeo-
logic factors. The most common type of integrative method is
a flow calculation based on the hydraulics of the ground-
water flow system. There are two calculations available-
velocity and time of travel. The tiae-of-travel measure is
used to establish an acceptable time of travel within the
ground-water flow system; the velocity must be known and a
specified point, or a specified distance, must be given.
Flow calculations can be made for aqueous transport
(i.e., movement of water molecules only) or for specific
constituents where a reliable retardation factor can be
determined. Because vulnerability is not constituent-
specific by definition, only the aqueous transport flow
calculations should be considered.
The principal advantage of a flow calculation measure is
that it provides a more direct measurement of hydrogeologic
system behavior. This type of measure uses factors directly
related to ground-water flow, according to their theoretical
relationship. For aqueous transport, travel velocity and
travel time are calculated as follows:
distance
time of travel -
velocity -
where:
K • hydraulic conductivity
Z - hydraulic gradient, and
• effective porosity.
The velocity measure can be reliably derived using analytical
data generated from hydrogeologic investigations and time of
travel.
The difficulties of this type of measure are in selec-
ting a defensible travel distance or exposure point and
selecting the time of travel criterion. Both these values
will be somewhat arbitrary and difficult to justify on
technical merit alone. Flow calculation measures, in order
4-53
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to be accurate, also raguire considerable data for th« entire
Clarification Ravi aw Araa and, therefore, can laad to rathar
high coats for a vulnerability assessment.
The Office of Solid Waste has instituted a time-of-
travel (TOT) criterion as part of RCRA vulnerability assess-
ments. Vulnerable settings in the area immediately
contiguous to the facility are defined to have a TOT of less
than 100 years to travel 100 feet. In addition/ the high-
level radioactive vast* (HLW) program within the Department
of Energy has also established a time-to-exposure criterion
as a site-evaluation criterion. Ten thousand years from
point of release to a potential exposure is the HLW travel
time criterion.
Due to the high cost and data needs for performing flow
calculations, it is not expected that such evaluation aids
will be used routinely. The two programs mentioned above use
such approaches a* well as stringent threshold values,
because of the high risk to human health from unexpected
contaminant releases from such facilities.
4-54
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CHAPTER FIVE
CLASSIFICATION CRITERIA FOR CLASS II GROUND WATER
5.1 Overview of the Decision Process
A Class II designation is provided for all ground water
that is currently or may be used as a source of drinking
water regardless of its degree of vulnerability. The
majority of ground water classification decisions are
expected to fall within Class II. Class II ground waters
generally receive the very high level of protection that
represents the "baseline" of EPA programs designed to ensure
ground-water quality for present and future generations.
All non-Class I ground water that is currently used or
is potentially available as a source of drinking water is
included in Class II, whether or not it is particularly
vulnerable to contamination. This class is divided into two
subclasses; current sources of drinking water (Subclass IIA),
and potential sources of drinking water (Subclass IIB). It
is assumed that any ground water which is currently used for
drinking water will fall in Subclass IIA, unless Class I
criteria apply. A detailed discussion of the decision
process for the identification of Class I ground water is
presented in Chapter Four. other ground waters are
considered potentially usable as a source of drinking water,
both from quality and yield standpoints (Subclass IIB),
unless a lower resource value is demonstrated.
The relatively shorter length of this section reflects
the complementary interrelationship between the
classification criteria for Class II and those for Class I
and III Aground water. The other relevant sections of the
document should be consulted as indicated.
5.1.1 subclass IIA; Current Source of Drinking Water.
Ground water is considered a current source of drinking
water under two conditions. The first and most common
condition is the presence of one or more operating drinking-
5-1
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water veils (or springs) within the Classification Review
Area. The second condition occurs in the absence of wells or
springs, and includes ground-water discharge to a water-
supply reservoir (see Figure 5-1).
The concept of a current source of drinking water is
rather broad by intent. only a portion of the ground water
in the Classification Review Area must supply drinking water
to wells or springs or to water-supply reservoirs. It should
also be noted that a current source of drinking water, which
meets the irreplaceable/highly vulnerable criteria, is Class
I.
Ground waters that discharge to a water-supply reservoir
or portion of the reservoir watershed within the
Classification Review Area are also classified as Class IIA,
a current source of drinking water, if the reservoir has been
designated by State or local government for water-quality
protection. Water-quality protection can be shown by the
following:
a. Specific measures providing more stringent protec-
tion within the watershed than in adjoining areas.
The protective measures may include the following:
e Sediment-control regulations that may consist of
limiting the impervious surface area and encour-
aging the use of infiltration and wet ponds.
e Lot-size restrictions.
e Regulations for best-management practices.
e Limiting waste disposal and working with waste-
treatment plants to try and upgrade discharge
standards.
• Restrictions on land-use activities within the
watershed (e.g., mining, logging, certain recrea-
tional practices).
b. Legislation or a memorandum of understanding with a
• general policy statement that indicates that
watershed lands are to be protected so that reser-
voir water quality will be maintained or protected.
A protected watershed could also include lands purchased by
the water-supply utility and managed to preserve water
quality and yield.
5-2
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FIGURE 5-1
EXAMPLE CLASS II - CURRENT SOURCE OF DRINKING WATER
*
/
I
i
*
\
DRINKING WATER
WELL
\
UNPROTECTED
WATERSHED
FACILITY
PROTECTED
WATERSHED
DRINKING WATER
SUPPLY RESERVOIR
5-3
-------
There also may be circumstances where a water-supply
intake on a stream or other surface-water body is located
within or adjoining the Classification Review Area. The
classifier may have evidence to indicate that such surface
waters receive significant discharge of ground water from the
Classification Review Area and these surface waters might be
reasonably expected to be contaminated if the ground water
were impacted. In such cases, best professional judgment
should be exercised to ascertain whether a Class IIA
designation is warranted.
5.1.2 Subclass IIB: Potential Source of drinking water
A potential source of drinXing water in the Classifica-
tion Review Area is one that is capable of yielding a
quantity of drinking water to a well or spring sufficient for
the minimum needs of an average family. It is assumed that
all ground-water units are capable of supplying a yield suf-
ficient to meet the minimum needs of an average family,
unless an insufficient yield can be demonstrated as part of a
Class III determination (see Chapter 6 for a discussion of
the insufficient yield concept). Water is considered to be
suitable for drinking if it has total-dissolved-solids (TDS)
concentration of less than 10,000 mg/L and either can be used
without first being treated or can be rendered drinkable
after being treated by methods reasonably employed in a
public water-supply system. All around water should be
presumed to meet this standard for drinking water, unless
demonstrated otherwise according to a Class III demonstration
described in Chapter Six.
An uppermost limit of 10,000 mg/L TDS was chosen for
several reasons. Many State and Federal programs currently
use 10,000 mg/L TDS to distinguish potable from nonpotable
water. Some States set lover limits because the TDS of
drinking water is usually wall below 10,000 mg/L. A survey
of rural water supplies (EPA, I984a), for which ground water
was the1 principal source, found a maximum TDS level of 5,949
mg/L. lighty-five percent of rural water-supply systems used
sources 'of water that contained less than 500 mg/L TDS.
Given th* rang* of TDS values, 10,000 mg/L provide the
flexibility needed in a nationwide program. This
concentration also ensures that other beneficial uses of
ground water will be encompassed in Class II determinations.
5-4
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5.2 Classification Procedures
Assigning a Class II designation is, perhaps, the
simplest of all the classification procedures. It is assumed
that all ground waters currently used for drinking water or
other beneficial uses will fall into Subclass IIA unless
Class I criteria apply. All other ground waters are con-
sidered potentially usable as a source of drinking water (or
water for other beneficial uses), both from a 'quality and
yield standpoint, and are thus Subclass IIB, unless Class ill
criteria are demonstrated.
The general Class II classification procedure is
outlined in Figure 5-2. If wells and/or springs used as a
source of drinking water are present, or ground-water
discharge to a water-supply reservoir occurs, then the ground
water is considered Subclass IIA. All other ground waters
would be considered Subclass IIB, unless a Class III
demonstration is made.
Specific classification procedures and data needs for
water-quality testing and water-yield testing were not
established as part of the Class II criteria. The general
rule is to presume, in the absence of data, that the quality
and yield of a ground-water resource is sufficient to meet
the criteria for a potential source of drinking water. Where
the ground water can be demonstrated to fail the quality or
yield criteria, the result could be a Class III designation.
The classifier is referred to Chapter 6 for a detailed
discussion of the decision processes for Class III ground-
water identification.
5-5
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FIGURE 5-2
FLOW CHART FOR CLASS II PROCEDURES
CLASS I
PROCEDURES
CHAPTER FOUR
—MO
IS A
PROTECTED
WATERSHED
PRESENT
YES*
CLASS III
PROCEDURES
CHAPTER SIX
ui
I
YES
YES
NO
CLASS II B
POTENTIAL SOURCE
OF DRINKING
WATER
* OR MATER-SUPPLY INTAKE UNDER CERTAIN CIRCUMSTANCES
** ASSUME CLASS III CRITERIA ARE
NOT MET UNLESS DEMONSTRATED OTHERWISE.
-------
CHAPTER SIX
CLASSIFICATION CRITERIA FOR CLASS III GROUND WATER
6.1 overview of the Decision Process
6.1.1 Definition of Class III
Class III ground waters are those that are not potential
sources of drinking water because of one or more of the
following reasons:
1. Salinity (i.e., greater than or equal to 10,000 mg/L
TDS.
2. Contamination, either by natural processes or by
broad-scale human activity (unrelated to a specific
pollution incident), that cannot be cleaned up using
treatment methods reasonably employed in public
water-supply systems.
3. Insufficient yield at any depth to provide for the
minimum needs of an average-size household.
Subclasses are differentiated primarily on the basis of
degree of interconnection to adjacent ground waters and
surface water*.
6.1.2 Background of Class III : .
In EPA's ground-water classification system, class III
is reserved for ground water that has virtually no potential
as a sourcs of drinking water. Because of the very low
likelihood that Class III ground water would be used as a
drinking-water source and thus pose a risk to humans, it may
be appropriate in some situations to manage existing
contamination differently or take different preventative
measures than would be taken for Class I and II ground waters
6-1
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where there is a greater possibility that contamination could
result in human exposure.
Several of the following key technical points relative
to the Classification procedures support this policy:
e All ground water is presumed to be a current or
potential source of drinking water (Class I or II),
unless a successful demonstration is made that the
ground water meets the criteria for Class III.
• A contamination plume is not, per se, evidence of
widespread contamination; the term untreatable is
intended to describe general ground-water quality in
the Classification Review Area.
• Ground water will not be considered Class III when
contamination is due to an action or in-action on
the part of the facility in question.
6.1.3 General Procedures
The first step in the Class IZI procedure is to decide
whether to pursue a Class III determination based on the
insufficient yield criteria or the water-quality criteria.
Preliminary data may indicate that evidence of one determin-
ing criteria will be less difficult to demonstrate than
another. It is important to note, however, that the order in
which Class III steps are performed is left to the
classifier.
Figure 6-1 illustrates the general steps that are
followed in the Class III procedure. In most cases, it is
probably easiest to address the yield criteria first, unless
data indicate otherwise. A demonstration of insufficient
yield automatically results in a Class IIIA designation.
The sufficient yield criterion is discussed in detail in
Section 0.2 of this chapter. In general, a ground-water unit
is considered capable of producing a sufficient yield if it
can protfttee> enough water to meet the minimum needs of an
averagej-ttise family. If the ground-water regime is not
capable of meeting the minimum needs of an average-size
family, it is automatically Class IZZA: Insufficient Yield
unless .Class I or Class II criteria have been demonstrated.
Ground-water quality and treatability in the Classifi-
cation Review Area or unit of interest can also be used as
criteria for a Class III designation. Ground water that has
a IDS concentration of greater than or equal to 10,000 parts
6-2
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FIGURE 6-t
STEPS IN THE CLASS 111 PROCEDURE
ESTABLISH CLASSIFICATION REVIEW AREA AND COLLECT BASIC INFORMATION
O»
I
DOES THE CLASSIFICATION
REVIEW AREA INTERCEPT
AN ECOLOM6ALiV VITAL ,
AREA OR CONTAIN WELL(S)
OR PROTECTCO WATERSHEDS 7
IS THERE AN AQUIFER
IN THE CLASSIFICATION
REVIEW AREA THAT HAS
SUFFICIENT YIELD f
IS THE WATE* QUALITY
EITHER GREATER THAN OR
EQUAL TO 10,000 MO/L
OR UNTREATA8l£
IS THE INTERCONNECTION
TO ADJACENT GROUND OR
SURFACE WATERS LOW ?
ECOLOGICALLY
VITAL. WELLS
OR PROTECTED
WATERSHEDS
SUFFICIENT
YIELD
210,000 MG/L TDS
UNTREATABLE
LOW
INTERCONNECTION
CLASS 11 IB
LOW INTERCONNECTION
YES
PROCEED TO CLASS I OR
CLASS n PROCEDURES
NO
CLASS IIIA
INSUFFICIENT YIELD
NO
CLASS II
POTENTIAL SOURCE
OF DRINKING WATER
NO
CLASS IIIA
HIGH INTERCONNECTION
-------
per million (ppm) is Class III unless criteria for Class x or
Class II are met. Ground water that has less than 10,000 ppm
TDS, but can be shown to be untreatable according to the
definition in these Guidelines, is also Class III. The
subclass designation A or B is assigned on the basis of
degree of interconnection to adjacent ground-water units and
surface-water.
Two treatability tests are presented in these
Guidelines. The . first is referred to as the reference
technology test and is used as a screening step to identify
various kinds of treatment methods needed to attain relevant
health standards. If none of the treatment technologies
currently employed to treat drinking water can adequately
treat the ground water under review, then that ground water
is initially considered technically untreatable, to be
confirmed or denied by further economic analysis. If one or
more currently available treatment technologies could be used
to treat the water to the relevant quality standard, however,
then the water is initially considered technically treatable
(i.e., Class II). In this situation, the second treatability
test, referred to as the economic untreatability test, could
be applied if further analysis is warranted. The economic
untreatability test is designed to determine whether the
costs of treating the ground water would be reasonably
expensive for a hypothetical user population. If the costs
are deemed unreasonable, then the ground water may be
considered Class III, untreatable. If the costs fall below
the threshold, on the other hand, then the ground water
should be considered a potential drinking-water supply (i.e.,
Class II) . Treatability and water quality are discussed in
greater detail in Section 6.3.
Subclassification of Class III is based on the degree of
interconnection of ground-water units. For a Class IIIB
determination, a low degree of interconnection must be
demonstrated; otherwise, the ground-water unit is designated
as Class IIIA. A detailed discussion of the interconnection
criteria has been provided in Chapter Three.
6.2 Class III Designation Based on Insufficient Yield
One of the three criteria that can be used to define a
ground-water unit as Class III is insufficient yield. Yield
is defined as the quantity of water that can be extracted or
produced from the ground-water regime. In order for yield to
be considered insufficient, it must be practically infeasible
to produce a sufficient supply of ground water to meet the
minimum needs of an average-size household. Agricultural,
6-4
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industrial, or municipal uses of these marginal, water-
bearing areas would require significantly higher yields than
a domestic well. The insufficient yield criterion is based,
therefore, on a conservatively low yield, below which it is
generally considered unlikely or impractical to support basic
household needs. The insufficient yield concept is that all
ground-water units within the Classification Review Area
(regardless of the potential for subdivision), must be
evaluated, if one such ground-water unit is found to provide
sufficient yield, then a Class III A-Insufficient Yield
designation should not apply.
A determination of insufficient yield will be made on a
case-by-case basis at the discretion of the classifier
considering the factors listed below:
• Water needs of an average family.
• Sustainability of yield.
e Number of wells per household.
e Minimum pumping rates.
e Use of storage.
The minimum water needs of an average person are
estimated to be approximately 50 to 70 gallons-per-day
(USEPA, 1975). However, most values reported in the litera-
ture are greater than 50 gallons-per-person-per-day, which
can likely be attributed to non-essential uses such as
irrigation of lawns and gardens. Hater needs also vary for
different regions of the country. Determination of this
value is, therefore, left to the judgment of the classifier
whose decision will be based on available data and considera-
tion of other factors.
One factor that must be considered is that water is not
used at a constant rate throughout the day; there are peak
periods when demand is high and low periods when demand is
not as great. A low-yielding well may be capable if it is
possible to create adequate storage during low-use periods
for use during high-use periods.
Barring more detailed information, a value of
approximately ISO gallons-per-day (gpd) per household is a
generally acceptable yield threshold. This value is based on
EPA's water-supply guidelines that indicate per capita
residential water minimum needs range from 50 to 75 gpd (EPA,
1975) for a single-family residence. Waste flows from
single-family dwellings using septic systems average 45 gpd
per capita (EPA, 1980, page 51). Based on an average family
size of 2.75 persona, therefore, and a per capita water need
of approximately 50 gpd, a value of about 150 gpd was
obtained.
6-5
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Classifiers should not* that a per capita water need
value of approximately 100 gpd (or 100,000 per household per
year) is used for the Class I economic irreplaceability test
and the Class III economic untreatability test (see Appendix
D) . The Agency believes that this higher 100 gpd value is
more appropriate for sizing hypothetical public-water supply
systems because such systems usually meet needs over and
above basic household consumption requirements.
A sufficient yield threshold should be sustainable over
time without temporary (e.g., seasonal) depletion of the
resource. The yield can be obtained from any number and type
of household wells, including drilled wells, dug wells, or
any other type of well available.
Readily available hydrogeologic information exists that
may assist a classifier in determining if a ground-water unit
(or units) has a lithology capable of meeting the minimum
yield requirements. This information can be obtained from
U.S. Geological and State Geological Survey water resource
publications. Logs and specific yield tests may be available
for wells drilled in the area. Additional information can be
obtained from university research publications and scientific
journals. However, in some cases, the classifier may need
more site-specific aquifer test data to determine the
hydraulic properties of a particular ground-water unit. It
is important to note that if an active water-supply well is
present and in use, the ground-water unit is considered to
have a sufficient yield and should be designated Class II.
6.3 Class III Designation Based on Ground Water Quality
and Treatability
6.3.1 Areal Extent of Contamination
A Class III designation can be assigned to those ground
waters that are naturally saline, or otherwise contaminated
beyond levels that would permit their use for drinking or
most other beneficial purposes. In order to be Class III,
the ground waters oust be so contaminated by naturally
occurring conditions, or by the effect of broad-scale human
activity (that is unrelated to a specific activity), that
they cannot be cleaned up using treatment methods reasonably
employed in public water-supply systems.
The determination that ground-water contamination is a
result of broad-scale human activity is left to best
professional judgment. The following lines of evidence are
6-6
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suggested for assessing if ground-water contamination from
broad-scale human activity is present:
e History of multiple contamination incidents.
e Nature and extent of contamination.
e Adequacy of water^quality data base.
An area that has been affected by a number of industrial
and other potentially polluting activities over a long period
of time in some cases may meet the concept of broad-scale
human activity. Candidate areas will likely be identified by
the presence of a large number and variety of potentially
polluting sources that have been in operation over a number
of years. In some cases, all or a portion of the sources may
no longer be in existence, however, residual contamination
remains. In any case, the contamination should not be
traceable to a single source.
It is critical to recognize the difference between an
untreeitable plume, a concept irrelevant to classification,
and untreatable ground water which receives the plume, a
relevant classification factor. An example of a
contamination plume that can be traced back to a specific
activity is shown in Figure 6-2. The ambient ground water
is, however, potable. Under these conditions a Class III
designation should not apply. Figure 6-3 shows another
contamination plume, however, in which extensive regional
contamination is found that is technically and economically
infeasible to treat with public-water-system technologies.
In the latter case, a Class III designation may be
appropriate.
In general, ground-water contamination due to broad-
scale human activity is characterized by multiple
constituents. Both constituent concentrations and the suite
of constituents will also vary from point to point. Water-
quality data would be expected to show the presence of
relatively high concentrations of a few ubiquitous compounds,
together with lover concentrations of a larger number of
other constituent*. The most commonly reported (i.e.,
ubiquitous) ground-water pollutants include chlorinated
solventsi pesticide*; miscellaneous hydrocarbons, such as
gasolin«* metal*; salinity; and radionuclides (USEPA, I985a).
The entire ground-water unit being classified does not
necessarily have to meet Class III untreatable criteria, but
a major volume portion would. The definition of such
significant portion is left to the best professional judgment
of the classifier.
The water-quality data base, collected in support of the
Class III determination, should reflect the full spatial
variability of the various constituents, both vertically and
6-7
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FIGURE 6-2
EXAMPLE OF CONTAMINATION THAT SHOULD NOT QUALIFY
FOR CLASS III DESIGNATION
CONTAMINATION
PLUME FROM
ACTIVITY
CLASSIFICATION REVIEW AREA
BOUNDARY
FACILITY / ACTIVITY
OftOUMO WATER UNTREATABLE USINO METHODS REASONABLY
EMPLOYED IN PUBLIC WATER SUPPLY SYSTEMS..CONTAMINATION
DIRECTLY RELATED TO ACTIVITY.
6-8
-------
FIGURE 6-3
EXAMPLE OF CONTAMINATION THAT MAV
FOR CLASS III DE8zS£Tx55
AREA
FACILfTV / ACTIVITY
6-9
-------
horizontally. The Boat useful monitoring network for
determining ambient conditions would employ a sampling
pattern that minimized interdependence between samples. A
monitoring network intended to determine a specific plume
geometry will rarely suffice to provide full spatial
representation across the ground-water unit.
The degree of uniformity of the sampling pattern can be
measured using the statistical methods of quadrant analysis
and nearest-neighbor analysis. Quadrant analysis is
performed by dividing the area under consideration into a
number of equal-sized subareas, such that each subarea
contains a number of sampling points. If the data points are
distributed uniformly, each subarea should contain the same
number of points. The alternative to quadrant analysis is
nearest-neighbor analysis which is performed on the distances
between sampling points. For a more detailed discussion of
statistics used to analyze uniformity, see "Statistics and
Data Analysis in Geology,1* (Davis, 1973).
6.3.2 Standards and Criteria for Treatment
Both tests for defining Class III based on treatability
imply that analyses of treatment methods should consider
relevant standard* and criteria for long-term drinking-water
use. No one set of numbers is available and thus some
professional judgment may be required.
EPA has issued National Interim Primary Drinking Water
Regulations (NIPDWR) under the Safe Drinking Water Act.
These regulations set maximum contaminant levels (MCLs) for a
number of inorganic, organic, and microbiological
contaminants in drinking water. These values are based on
both health factors and technical/economical feasibility.
In addition to MCLs, which are enforceable standards,
maximum contaminant levels goals (MCLGs) are set, reflecting
EPA's goal of no known or anticipated adverse health effects.
Both MCLG and MCL values are updated periodically. EPA also
provides drinking-water suppliers with additional guidance.
Under the authority of the Safe Drinking Water Act, EPA is
now in the process of developing MCLGs for additional
contaminants to serve as guidance for establishing new
drinking-water MCLs. The Agency is accelerating the pace of
both MCLG and MCL issuance. For current MCL and MCLG values
contact- the Agency at the following address:
The U.S. Environmental Protection Agency
Criteria and Standards Division
Office of Drinking Water (WH-550D)
401 M Street, S.W.
Washington, DC 20460
6-10
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Other constituents may be intermittently encountered in
a water system, and are believed to pose a risk, yet are not
currently the subject of any MCL or MCLG. some of these are
addressed in the form of Health Advisories. The Health
Advisories are not mandatory for public-water systems, but
provide information for emergency situations. They are
calculated at three exposure levels: 1 day, 7 or 10 days,
and longer term (1 to 2 years). A margin of safety is
factored in to protect the most sensitive members of the
general population (EPA, 1985b; Federal Register, 1985).
They are also available at the Office of Drinking Hater at
the address .above.
Finally, the RCRA program in developing its corrective-
action regulations and in responding to the land-disposal-
bans portion of the RCRA amendments of 1984, is examining the
applicability of other sets of criteria and standards for
both carcinogenic and noncarcinogenic contaminants. These
will likely be useful for addressing the large number of con-
taminants without current MCLs, MCLGs, or Health Advisories.
Moreover, to the extent that EPA develops other standards
related to ground-water or drinking-water quality, such
standards should be given appropriate consideration.
6.3.3 Overview of Class III Treatability Tests
The first of two tests presented in these Guidelines is
a reference technology test, which is a screening tool to
determine if techniques commonly employed to treat water
supplies are adequate to achieve Federal criteria or
Guidelines relevant to the contamination found in the ground
water. This test employs a relatively simple decision
framework that does not involve detailed engineering or cost
analyses.
The second test is an economic untreatability test. The
purpose of this test is to augment the screening tool by
assessing whether such technologies would be economically
feasible. This two-tiered technical and economic feasiblity
approach is discussed in the following sections.
6.3.4 Reference Technology Screening Test
Water-treatment technologies can be categorized at any
point in time to fall into one of three categories:
6-11
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• Methods then in common use in public water-treatment
systems.
e Methods than known to be in use in a limited number
of cases or under special circumstances in public
water-treatment systems.
• Methods not then in use in public water-treatment
systems.
At this time, methods in the first category (common use)
are as follows:
e Aeration e Chlorination
e Air Stripping e Flotation
e Carbon Adsorption e Fluoridation
e Chemical Precipitation e Granular Media Filtration
Methods in the second category, known to be used under
special circumstances at this time include:
e Desalination (e.g., reverse osmosis, ultrafiltration,
and electrodialysis).
e Ion exchange.
• Ozonation.
• Granular Media and other simple point-of-use and
point-of-entry technologies made available typically
by water utilities on a short-term basis to a limited
number of consumers.
When considering the application of these technologies, the
classifier should also consider the treatment efficiencies
given in Table 6-1 and the treatment descriptions given in
Table 6-2. Soae technologies, for example, may be
appropriate for minor concentrations of contaminants and
inappropriate for larger concentrations of the same
contaminants.
Treatment methods not now believed to be in use by
public water-treatment systems include distillation and wet-
air oxidation. These methods are considered new to water
treatment, although they have been applied for industrial
purposes in the past.
6-12
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IABIE 6-I
tCPGRKO TVPICAUV ACHIEVEA81E CONTAMINANT REMOVAL EFFICIENCIES •. b
i
i
Arsenic . :
Bariu* :
ieruene • :
Cadaiue :
Carbon Tatrachloride
Chlordarw
Chrosriiai Ml
1.1-Dichtorocthylene
1.2c Dlchloroethylene
1,2t Dichloroethylone
Dich lor one than*
2.40
p-Dioxane
Endrin
Ethyl en* plycol
flow-ids
Formaldehyde
n Hexane
lead
lindsne
Mercury
Methyl Ethyl Ketone
Nitrate
PCI
Selenius
Silver
TetrechlcToethylene
Toluene
loxaptiew
1 , 1 . 1 • Tnchloroetherae
f r i ch 1 or aethy 1 ene
2.4.5-TP
Trihaloettthanes
Xylenes •
Air Stripping
Ml Aeration
Oc
0 c
98
0 c
96
Good d
Oc
98
97
n
80
Poor •
0 c
0 c
Good d
Good d
99
0 c
Oc
0 c
99
0 c
0 c
0 c
98
9$
Good d
ao
90
Poor d
75
99
Carbon
Adtorpt ion
50
30
75
as
Moderate d
Good d
95
97
70
95
70
Good d
99
Good d
0
95
95
90
15
IS
10
25
99
75
99
99
Poor d
Good d
99
CheBJcal
Precipitation
65
M
70
90
95
'
98
98
30
60
Good d
75
65
Good d
80
96
70
70
95
75
50
60
95
90
Desalination
95
95
75
60
90
15
60
65
90
70
97
40
80
SO
98
Good d
AO
80
flotation
45
60
75
50
40
98
85
75
97
45
30
40
Good d
80
97
GranuUr Media
Filtration
60
70
40
70
90
40
50
55
90
40
30
SO
50
55
10
20
60
20
0
65
97
60
75
Ion
Exchange
99
95
99
9o
97
90
98
99
SO
Ottmetion
o
97
Moderate d
30
SO
99
40
a Data represent the percent of contaminant which can be expected to be removed tram solution using treatment sysicn tlailar to those currently inttalled in
full scale or pilot scale uater treatment operations. Percent reaoval is oeneraled from available literature e* listed at the end of this section, and are
rounded to the nearest 5 percent (below 95 percent). These maters are representative of achievable efficiencies, and are not absolute indicators of specif
system treatawnt efficiencies.
b Blanks indicate that no data were reported in the available literature.
c Although reported data were unavailable, the physical nature of those contaminants precludes effective removal via air stripping.
d Only qualitative data were available in the literature.
1C
-------
Tabl. 6.2
OEscximoH or TUATWTT raoczss
: ADVANTAGES
: Low Optra 1 and OUt
; High raeoval *fflclanclas tor tomm
: eencanlnanti
: Pracraacoant I* generally not
: required for (round water
: Cqulpcent purcha*ed off the (half
ADVANTAGES
Low eneriy requlreaMnti
High r«movtl *fflclencle* for *
vide rant* of contaalnant* ov«r
• broad concentration range
ADVANTAGES
Equipment t» readily available and
•a»y to operate
Low energy requlrieMnia
: Low capital and OUt eoiti
ADVAHTACtS
Ejce«H«ot tmmaml or nh«raa«l
anloa* and eattoo*
Goad r«*ovat. at high •nlarttaT
wal^ht orcanie*
Effactlv* trcauwnt far raawral
of dii»olw«d (Oiida
Air Strtpplac/Aaratlon
OISADVAVTACES
T««p«iratur« tan«lclv« (cold)
rnnraalniim
Ma7 raault la air pollur'an ar a na
na«d for billion Control
Carboa Adaorpcloo
DISADVAFTACB1
Mana««ta«nt of *p«nt carbon can ba
•xpanjLva and problaaatle
-Racanaratlon
-Dlspoaal
-Raplaca*ant
ai»h capital and ooaraetn« eo«t*
Chaaileal Praelplcatlon
OISADVAJITACIS
Q«n«var*« oaaoil*. ultraf llcraclon
DISADVARACXI
•l«b anaur roqulraaxnt*
l«qulc** aartaxuton pilot aa*lr»ai
for aa*h afttaa
Il«hl7 e«phl»tloatad Ina-truBanta-
tlon and control
C«o«racaia • eoneantratod brlna
which m*j r«qulro craataant
Pratraatawnt alaoat alway* raquir«d
Bltn capital and 04M ee«t»
LIMITATIONS
Riaav«f only volatile eontaalnanta
Su»p«idad aollda in Influant aaf
laad to raaoval ttfieitner It,**
dua to biological growth
(air atrtpplnc only).
LIMITATIOHS
For organic* ranoval whara eaneantra-
tlooi ara high, fraquant carbon
raganaration naeanary
Su*pandad tollt should not ajicaad
SO a«/U
Oil and graaaa ahould net axeaad 10 mg/L
Kaqulraa icaady hydraulic loading!
LIMITATIONS
Fraquant laboratory taatlng If raqulrad
to Balntaln high afflelanela*
pB dapandant
Ho eonoantratlon llalt
:
.
!
LIMITATIONS
:
: Suapamdatf aallda amiat ba low to pravant
foul la*
: OpacatiA* taagt«ratur«« mat ba batwaan
: 43 and «3 F
;
:
:
:
:
6-14
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Table 6.2 (Cone.)
DESCRIPTION or TREATMENT mociss
ADVANTAGES
Highly reliable
Relatively *Lta>lei easy to oparata
•ad control
Multiple oadla can be uaed to laprove
«£f lcl*nele»
ADVANTAGES
Synthetic realm can tolerate • vlda
range of temperature and pi
Can reaove a variety of cat tonic and
aalonlc Inorganic and organic
eontaaloanta
Low aaargy reo^ilreaMnti .
ADVANTAGES
Reduce* chaalcal raalduala |«earatad
(particularly trlttalrmarhanaa)
No dl»««lv»d «olld» •«o«ratl bchaaf*
DI5ADVAHTACIS
Hl|h !**•! of training nac««hould not
ascaad 200 o«/L
Pratraataant «ay IM raoulrad If
*oap«n4ad tellda axcaad 100 o«/L
LIMITATIONS
Influant concent ratlaoi «houid aot
•«c««tl 4,000 ag/L
OK ihould not aieaad 10 mg/L
Influant should not contain chamlcaL
ojildaata (a.g., osona)
filtration la required aa pretraataant
If auapandad aalldt encaad 20 ag/L
In tha Influant
LIMITATIONS
Traaea only eontaailnanti which can ba
i»ldl»ad
Ooaa not raanva Iron-eyanlda cooplaxea
LIMITATIONS
Harrow ranca af raaoval - e.g., not
affactlva for aontaalnants vlth
daaalty greater than that of watac
t
6-15
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The technologies currently used for treating surface and
ground water that serve as public drinJcing-water supplies can
be classed into five general categories:
• Volatile organic chemical removal.
• Non-volatile organic chemical removal.
• Metals removal.
• Non-metallic inorganic chemicals removal,
• Disinfection.
Some technologies are effective in reducing only a few types
of contaminants, while other* may efficiently treat several
contaminant classes simultaneously. Although most processes
are designed to treat a single class of contaminants, many
will remove other types of contaminants. Brief descriptions
of several generic treatment technologies and the applica-
tions are provided in Appendix C-l.
Although most of the reference technologies noted above
are currently in use at public water-supply systems
throughout the country, not all necessarily remove toxins
(e.g., carbon adsorption is sometimes used in taste and odor
applications and not for removal of volatile organics). The
exceptions are desalination, ion exchange, and ozonation;
these treatment technologies may be considered reasonably
employed in certain circumstances, as noted above. Air
stripping, which is most often used for removal of volatile
organic solvents from ground waters, should b« considered
available for Claas III analyses, despite its limited use in
public water-supply systems.
Distillation techniques have long been employed for
treating industrial process water, for example, but are
generally reserved for areas such as islands, where potable
water is scarce. Biological treatment techniques have been
used for in-situ cleanup of ground waters rather than to
treat supplies for general water distribution. Wet air
oxidation techniques are currently used primarily in industry
for removal of organic* from process wastewater.
A partial bibliography of resources and references to
assist in treatability analyses is given in Appendix C.2.
Treatment Efficiencies
Evaluation of treatment efficiencies for a single
contaminant or group of contaminants requires the evaluation
of interferences and interactions of contaminants. General
6-16
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background data on treatment performance indicate ranges of
values for efficiency. For example, EPA's Treatability
Manual for Priority Pollutants (EPA, 1980a), presents
examples of typically achievable, contaminant-removal ef-
ficiencies for a range of contaminants and technologies.
More precise determination requires pilot testing or
comparison by experts with '-'•her similar waste streams. The
general level of success the various treatment technologies
have with frequently encountered contaminants is indicated in
Table 6-1. Removal efficiencies are not reported in the
literature for all contaminants, as experience using certain
treatment technologies for removal of some contaminants is
limited.
Contaminant concentration, physical conditions (e.g.,
pH, temperature), solution chemistry, and the presence of
competing or interfering contaminants can all contribute to
the large variations in removal efficiencies that are
reflected in the literature. For situations in which a more
accurate assessment of treatment efficiencies is desired, the
user of these Guidelines may wish to consult the reference
sources listed in Appendix C.2.
Some of the major advantages, disadvantages, and
limitations associated with each treatment process are listed
in Table 6-2. It is important to know the composition of the
ground water to be treated in order to develop process
configurations. Evaluation of potential interference
problems and matrix effects is critical for some scenarios.
If a system uses both granular media filtration for solids
removal and ion exchange for softening, for example, the
filtration stage should precede the ion-exchange stage in
order to assure that potential resin-fouling solids are
eliminated from suspension. As another example, plants with
solvent contamination will commonly use air stripping or
carbon adsorption to remove the organics prior to chlorina-
tioh to prevent the formation of halogenated organics, which
are less efficiently removed. The examples discussed above
are only two of a very large number of potential chemical
interactions that may interfere with the removal of con-
taminants and affect the treatment process configuration for
a given condition. These factors must be considered and are
likely to require professional judgment to properly evaluate
the potential for treatment of contaminated ground water.
Example Procedures for Conducting Reference Screening
Technology Tests
One approach which can be used in this screening test
involves five steps:
6-17
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1. Describe the contamination problem.
2. Determine the desired effluent quality.
3. Define and assess process configurations.
4. Evaluate treated water quality.
5. Determine if desired water quality is met.
Each of these steps is described in detail below.
Step l; Describe the Contamination Problem
A description of the contamination probl »r might include
data on the natural or background water quality, the extent
of contamination, and the physical factors influencing both
ground water and treatment. The natural quality of a ground
water may be inferred from historical data or by comparison
to background ground waters in the site vicinity.
Contaminants in the ground water of concern will then
typically be specified and the range in concentrations noted.
In particular, if the type and concentration of contaminant
vary spatially, this may be indicated, as this variance has
design implications for treatment configurations.
Presentations of analyses used and the range of sampling and
measurement errors included would assist the reviewer in
understanding the degree of certainty of contamination. It
is important to address the areal extent of contamination to
be sure it meets the basic notion that contamination is not
related to an individual facility or activity.
The physical parameters of concern include flow pat-
terns, climatology, and other site-specific issues. Many of
the treatment processes are highly sensitive to temperature
fluctuations. Ambient temperature ranges, therefore, are
important in selecting appropriate technologies or housing
requirements. The climate in the area of concern, including
data on the freeze/thaw cycles, and any storm or wind events
that nay affect the treatment processes, must also be con-
sidered. Other site-specific considerations may become
important, on a case-by-case basis.
To determine the desired quality of the treated water
following completion of all .reatment processes, acceptable
target concentrations are established for each contaminant.
Relevant Federal criteria include the MCL, the MCLG, the
longest-term Health Advisory for each contaminant, and any
other appropriate standards or criteria developed by EPA
relating to ground-water or drinking-water quality.
6-18
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3? - Define and Assess Available Process Configura-
tions
The classifier then typically defines a set of treatment
process configurations that may be used to remove
contaminants from the ground water. These process
configurations would be developed considering efficient
contaminant removal to the minimum level required. The
technologies selected would then be assessed based on their
current and projected near-term future availability.
Step 4; Evaluate Treated Water Quality
To evaluate typically achieved water quality using any
given treatment process configuration, the concentration of
specific contaminants in the ground wacer/ influent, levels of
background water-quality parameters (pH, TDS, etc.)/ and the
removal efficiencies of each contaminant using each treatment
process should ideally be known.
Background data and/or manuals on treatability developed
by EPA can be consulted for initial guidance on treatment
(e.g., EPA 's Treatabilitv Manual for Priority Pollutants.
Contaminant removal efficiencies for common treatment
technologies are presented in Table 6-2. A qualified water
treatment engineer could also determine the relative
contaminant removal effectiveness due/ for example, to
interference effects.
step 5: Determine If Desired Water Quality Is Met
Once the approximate effluent concentration of each
contaminant has been evaluated for a given treatment process,
these can be compared to the appropriate water-quality
standard. If ail effluent concentrations are less than the
desired water quality, the ground water can be cleaned up
using treatment methods reasonably employed in public water-
supply systems. Thus, a Class II determination is warranted:
If some effluent contaminant concentrations exceed desired
water quality, the treatment process configuration does not
adequately clean the ground water, and an alternative
configuration should be evaluated for contaminant
treatability. Zf all available treatment process configura-
tions do not remove contaminants to the levels that meet
desired vater quality, the ground water cannot be cleaned up
using treatment methods reasonably employed in public water-
supply systems; these units will then be candidates for Class
III. •
Hypothetical Example
The following example is illustrative in nature and is
not meant to represent conditions at any specific facility.
6-19
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A permit, applicant has asked to site a facility and has
made the claim that the site location will only affect Class
III ground water. The chemical contaminants in the ground
water, listed in Table 6-3, are apparently from multiple
sources and occur throughout the Classification Review Area.
For trichloroethylene, carbon tetrachloride, cadmium,
and selenium, the applicant defines the desired maximum
effluent contaminant concentrations to be equal to the MCLs
for those constituents. For tetrachloroethylene, a long-term
Health Advisory was used.
The treatment processes that most readily remove
volatile organics, such as carbon tetrachloride and
tetrachloroethylene, include carbon adsorption and air
stripping. Metals, such as cadmium and selenium, can be
removed using chemical precipitation, desalination, and ion
exchange. Granular media filtration would probably be
considered for removal of residual particulate matter,
following a chemical precipitation step, particularly if
desalination, carbon adsorption, or ion exchange processes
followed. All of these processes are currently in use in
public water-supply systems.
Achievable effluent quality must be evaluated for each
treatment process configuration to determine if the ground
water can be treated to meet desirable levels. Process and
contaminant specific removal efficiencies are provided for
all five contaminants. (Please note: these values are to
illustrate the process and are not intended to be actual
efficiencies.) As indicated by calculated WQO values and
comparing them with WQ^ values (Table 6-3), treatment process
configuration A can result in removal of trichloroethylene,
tetrachloroethylene, and carbon tetrachloride, such that
acceptable levels are achieved. However, levels of cadmium
and selenium, following treatment using process configuration
A cannot meet the desired water quality. Therefore, the
applicant must consider an additional treatment process
configuration.
Removal efficiencies for the process configuration B
including air stripping, chemical precipitation, filtration,
and desalination can achieve acceptable water-quality levels
for all contaminants. Thus, according to this methodology,
this ground water is technically treatable using treatment
method* reasonably employed in public water-supply systems.
In this situation, therefore, the economic untreatability
test should be applied to determine whether treatment
configuration B would be economically feasible.
6-20
-------
TABLE 6-3
EFFLUENT QUALITY WORKING TABLE FROM SAMPLE PROBLEM
Conta»inant
Process Conf inure! ion A
Trlchloraethylcmi
Tetrachloroethylene
Carbon Tutrachlorlde
CadMiUH
Seleniuat
Process Configuration B
Tr ichlorcethy lene
Tetrachlcroethylene
Carbon Tetrachloride
Cadmus
Seleniuai
«%»
0.6
150.0
40.0
0.5
2.0
0.6
150.0
40.0
0.5
2.0
«tf
0.005*
1.9
0.005*
0.01
0.01
0.005«
1.9
0.005*
0.01
0.01
Treatment Process Reaoval Ef t ictenciesc
Process A Process B Process C Process 0 Process E Process f
Air Stripping Cheatcal Prectp. Filtration
98 60 7
98 95 0
98 95 90
0 90 70
t
0 70 60
Air Stripping Cheaical Precip. Filtration' Desalination
98 60 77
98 95 0 80
98 95 90 7
0 90 70 60
0 70 60 97
wQ0d
0.004
O.IS
0.004
0.015
0.24
0.004
0.01
0.004
0.006
0.007
Desired Water
Quality Achieved?
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
I
N>
" WQj - the Influent conta»inant concentration, in •*/!
b WQd « the desired iMiisjua effluent contaminant concentration, in
c BesM>wal efficiencies report in percent
d WQ0 * the calculated effluent contaminant concentration, in mg/1
e These MCLs are effective January 9. 1989
-------
6.3.5 Economic Untreatability Test
The economic test has been developed to identify ground-
water sources that have particularly low economic value under
present or foreseeable future conditions. Water sources of
low value are defined as those where future treatment and use
of such ground waters for drinking purposes would be very
costly and thus highly unlikely. This definition implies
that ground waters may be considered to be of low value even
though there may. be technical procedures available to render
these water sources drinkable (i.e., procedures identified in
the reference technology test) . Ground waters with
particularly low value nay warrant a lower level of
protection than other ground waters.
As with the econoaic irreplaceability test used for
class I determinations, the economic untreatability tes.t is
based on t -pical per household costs of drinking-water
supplies. Total water-supply system costs are again
estimated for a user population and then compared against
threshold values to gauge economic feasibility. The process
for applying the economic untreatability test, therefore, is
generally consistent with the economic irreplaceability
methodology.
The Class III economic untreatability test, however,
differs from the economic irreplaceability test in two
respects. First, the economic untreatability test is based
on a hypothetical drinking-water system because a Class III
candidate ground water by definition is not currently used.
Second, the Class III untreatability test is designed to
emphasize the ground-water treatment costs of the supply
system while the Class I test considers all types of costs
equally. The Class III test is constructed in this manner to
ensure that ground water that meets both the technically and
economically feasible treatment criteria will not be
classified as Class III.
Because of these dissimilarities with the class I
economic irreplaceability test, the economic untreatability
test* involves four steps rather than three, with the
addition*! step being the estimation of a hypothetical user
population size.
Thsv four steps for applying the economic untreatability
test arc as follows:
1. Estimate the hypothetical user population size.
2. Estimate the hypothetical system cost.
3. Calculate the economic untreatability thresholds.
4. Apply the economic untreadability test.
6-22
-------
Each of these step* la described in detail below.
step 1; Estimate t;ha Hypothetical User Population Size
The first step in the economic untreatability test is to
estimate the size of the hypothetical user population that
could potentially use the ground water as a source of
drinking water. The size of the hypothetical user population
should be determined as the population that could be served
by the maximum sustained yield of the aquifer in question.
A number of data sources are available . for estimating
the yield of an aquifer. The U.S. Geological Survey office
(e.g., District Office) in the State or the State geological
or water surveys will often have hydrogeological information
(e.g., maps, reports, and surveys) on most aquifers within a
state. Consultation with these sources and other individuals
with local expertise and experience can likely provide a
reasonable estimate of an aquifer's sustained yield. For
more detailed assessments, a review of boring logs,
geotechnical evaluations or other data sources will be
needed. Field assessments and ground-water monitoring also
may be needed to assess not only aquifer yield, but quality
parameters as well.
Once the sustained yield is estimated, a population
equivalent can be determined based on a per capita water use
of 100 gallons per day, which is roughly equivalent to a per
household water use of 100,000 gallons per year. For
example, geotechnical and hydrogeological data may indicate
that a ground-water source that is being classified has an
estimated sustainable yield of 50 gpm or 72,000 gpd, The
population equivalent that could be served by this yield is
720 (72,000 gpd divided by 100 gpd/person).
Step 2; Estimate the Hypothetical System Cost
The second step of the economic untreatability test is
to estimate) the cost of the ground-water supply system that
could serve) the hypothetical user population determined in
Step 1. This test is structured around the four major
component* of water-system costs: acquisition, treatment,
distribution, and service. As with the economic
irreplaceability test methodology, Appendix D presents the
cost-estimating methodology to assist in conducting such
analyses.
Note that because the primary focus of this test is the
treatability of the ground water under review, site-specific
treatment costs should be used in all cases when estimating
the total system cost. Moraovsr, the treatment costs used
6-23
-------
should be based on the least expensive of all technically
feasible treatment trains. With regard to appropriate costs
for the remaining components, the default (i.e., nationally
typical) values presented in Appendix 0 for acquisition,
delivery, and service are provided for assistance. Even if a
typical regional cost estimate is used in lieu of the typical
national costs given in Appendix D, extreme costs for
acquisition, delivery, and service generally should not be
used in ordar to ensure that tti« results of the treatability
test primarily reflect the costs of treatment rather than the
costs of other system components.
Step 3. Calculate the Economic ffntreatability Threshold
The third step of the economic untreatability test is to
calculate the threshold against which the annualized pejr
household water-supply system cost will be compared. As with
the Class I economic irreplaceability test, and for the
rationale noted in the economic irreplaceability discussion
in Chapter 4, the threshold that should be used for a given
classification is the ninetieth percentile of household
water-supply cost for water systems serving populations
similar in size to the hypothetical user population. The
methodology for calculating this threshold is presented in
Appendix D. For reference, Figures 4-5 and 4-6 (in Chapter
4) graphically illustrate this cost function for system sizes
ranging froa 500 to 1,000,000 persons and 500 to 10,000
persons, respectively.
As noted in Chapter 4, the Agency is currently reviewing
the question of community water-supply system affordability
which may lead to future changes in the way Class III
assessments are performed.
Step 4. Apply the Economic Untreatabilitv Test
Having estimated the size of the hypothetical user
population, the annualized total cost of providing water to
that population given site-specific treatment requirements,
and the appropriate ninetieth percentile threshold, the final
step of the economic untreatability test is to compare the
estimated cost of the water-supply system to the threshold
value to determine whether the ground water could be
economically treated and provided to a user population.
If~ the cost of the hypothetical water supply
significantly exceeds the ninetieth percentile threshold,
then th« classifier nay conclude that the costs of treating
the ground water would make the viable use of that water for
drinking purposes highly unlikely. The ground water,
therefore, is not a potential source of drinking water and
should be classified as Class III - Economically Untreatable.
Further, the classifier should proceed to the next section of
6-24
-------
this chapter in order to determine in which Class III
subclass the ground water belongs.
If the cost of the hypothetical water supply is
significantly less than the threshold, then the cost of
treating the ground water would not make the total costs of
using the water for drinking purposes economically
infeasible. Because the ground water is capable of providing
a sufficient yield and is both technically and economically
treatable, it, therefore, represents a potential source of
drinking water and should be classified as Class IIB.
Finally, if the cost of the water supply is relatively
close to the threshold, then the classifier should consider
the variability intrinsic in the function used to derive the
ninetieth percentile thresholds and make a final
determination based on best professional judgment.
6.4 Subclasses of Class III
The subclasses of Class III ground water are differen-
tiated in part by the relative degree of interconnection
between these waters and those in adjacent ground-water units
and/or surface waters. A discussion of ground-water units
and the concept of degrees of interconnection are provided in
Chapter Three. The subdivision of Class III into A and B
designations provides further definition of the relative
potential for contaainant release incidents to significantly
reduce the quality and value of a valuable water resource.
Subclass IZIA ground-water units are defined as having
an intermediate degree: of interconnection to adjacent ground-
water units and/or are interconnected to surface waters.
Subclass IIIA is also associated with shallow, naturally
saline ground water within a single ground-water unit that is
continuous throughout the Classification Review Area. Note
that all Class ZZZ designations based on insufficient yield
are considered Class ZZZA regardless of interconnection.
As mentioned in Chapter Three, a high degree of
interconnection is inferred when the conditions for a lower
degree of interconnection (low: Type 2 boundary or
intermediate: Types 1, 3, and 4) are not demonstrated. High
interconnection of waters is assumed to occur within a
ground-water unit and where ground water discharges into
adjacent surface-water bodies. The latter situation is
especially relevant in identifying Subclass IZZA ground
waters.
6-25
-------
Subclass IllB ground-water units are defined as having a
low degree of interconnection to ground-water units within
the Classification Review Area. Generally, Subclass IIIB
excludes (1) unconfined and eemiconfined ground-water units
as well ae (2) extensively confined ground-water units under
natural conditions where substantial numbers of improperly
cased and/or sealed wells significantly compromise such
confinement. Note that the low degree of interconnection
criteria includes, but is not limited to the interconnection
criteria for Class I injection wells as regulated under the
Safe Drinking Water Act.
Examples of Class IIIA Ground Water
Two examples of Class IIIA ground-water conditions are
provided. The first example concerns an area with ground-
water contaminated due to broad-scale human activity. The
second concerns shallow, naturally saline (TDS greater than
or equal to 10,000 mg/L) ground water. Note that these
examples are extrapolated from a knowledge of similar
settings, but do not represent any specific location or site.
The first example of Subclass IIIA is associated with
shallow, unconfined, aquifers that have been contaminated to
untreatable levels via broad-scale human activity. Figure 6-
4 shows a hydrogeologic setting with an urban/industrial area
located near a major surface water and overlying an alluvial
aquifer with a relatively shallow depth to water. The area
contains numerous diffuse sources of contamination that have
degraded ground-water quality. As shown, the degraded water
comprises the major volume of the ground-water unit that
discharges to the local surface-water body. A ground-water
unit boundary was identified coincident with the river,
thereby allowing subdivision.
A second example of Subclass IIIA is associated with
shallow naturally saline ground water within a single ground-
water unit that is continuous throughout the Classification
Review Area. In some hydrogeologic settings, such as the
closed basin/arid climatic setting illustrated in Figure 6-5,
it is possible that the extent of the saline ground waters
could be very large compared to the review area. The
Classification Review Area in Figure 6-5 represents only a
small portion of the total extent of the saline ground
waters. By definition, the saline ground-water unit within
the Classification Review Area would be highly interconnected
to other ground water both within and outside the review area
boundaries. Under the conditions described, the shallow,
saline, unconfined to samiconfined ground water would receive
a Subclass IIIA designation.
6-26
-------
FIGURE 6-4
ALLUVIAL AQUIFER SEPARATED INTO TWO GROUND-WATER UNITS
WITH HIGH INTERCONNECTION TO A RIVER
CLASSIFICATION REVIEW AREA
I
to
BEDROCK
EXPLANATION
71g| UNTREATABLE WATER
*. GROUND-WATER FLOW DIRECTION
2._ WATER TABLE
-------
FIGURE 6-5
CLOSED BASIN/ARID CLIMATIC SETTING CONTAINING A
CLASSIFICATION REVIEW AREA WITH A SINGLE GROUND-WATER UNIT
Ok
i
KJ
- GROUND-WATER FLOW DIRECTION
CRA CLASSIFICATION REVIEW AREA
-------
Example of Class IIIB Ground Water
An example of a Class IIIB ground-water unit within a
sedimentary basin is shown in Figure 6-6. Sedimentary basins
commonly contain multiple fresh-water aquifers, each
separated by a regionally extensive low-permeability
confining unit (Type 2 boundary) overlying deeper saline
water. Figure 6-6 is an example of such a basin where
ultimate discharge of the deep fresh water through overlying
low-permeability confining units (flow barriers) is to local
steams/ the atmosphere, and the ocean. Deeper ground waters
in these basins will be characterized by TDS concentrations
that may be much greater than the 10,000 mg/L limit for Class
III ground waters, and interconnection is considered to be
low, even though hydraulic gradients are in the direction of
less saline water.
The deep saline water unit can be considered to be
naturally isolated from overlying fresh ground-water units.
The reasons for the low degree of interconnection are as
follows:
• The flow of water through the confining units is
exceedingly small.
e Travel time through the confining unit is very great.
e There are no significant breaches of confinement due
to improperly cased or sealed wells.
Deep, confined, saline ground-water units with a low
degree of interconnection to overlying fresh ground-water
units are currently the primary hydrogeologic setting into
which wells can be permitted to inject hazardous wastes under
present EPA and State Underground Injection Control (UIC)
regulations. These waters are encompassed within Class III,
Subclass B ground water.
6-29
-------
FIGURE 6-6
EXAMPLE OF PROBABLE CLASS IIIB GROUND WATERS
I
ut
o
„ CfttlTALLMC
/ , •ASCMCNT
*<*" I
INJCCTION . ' - \ /
S *Ul \ / \
EXPLANATION
HIGHLY SALINE GROUND WATER
DIFFUSION ZONE
S WATER TABLE
—— GROUND-WATER FLOW DIRECTION
CRA CLASSIFICATION REVIEW AREA
GROUND-WATER UNIT A
GROUND-WATER UNIT 8
DIFFUSION ZONE
TYPE 3 BOUNDARY
GROUND-WATER UNIT C
-------
BIBLIOGRAPHY
Act, Systems, Inc., 1977. Volumes I and II, The Cost of
Water Supply & Water Utility Management,11 Prepared for
U.S. EPA Water Supply Research Division, MERL.
Act, Systems, Inc., 1979. Volumes I & II, Managing Small
Water Systems: A Cost Study Prepared for U.S. EPA, Water
Supply Research Division. Municipal Environmental
Research Labs, MERL.
Aller, Linda, Truman Bennett, Jay H. Lehr, and Rebecca J.
Petty, 1985. DRASTIC: A Standardized System for
Evaluating Ground Water Pollution Potential Using
Hydrogeologic Settings. R.S. Kerr, Envir. Res. Lab.,
EPA/600/2-85/018; Ada, Oklahoma.
American Water Works Association, 1981. 1981 Water Utility
Operating Data.
Gulp, R.L., G.M. Wesner, and G.L. Culp, 1978. Handbook of
Advanced Wastewater Treatment. 2nd Edition. Van Nostrand
Reinhold, New York, New York.
Davis, J.C., 1973, Statistics and Data Analysis in Geology,
Wiley & Sons, Inc., New York.
Flach, Y.W., 1973. Land Resources. In: Recycling Municipal
Sludges and Effluents on Land. University of Illinois;
Champaign, Illinois.
Freeze, R.A. and J.A. Cherry, 1979. Groundwater. Prentice-
Hall, Inc. Englewood Cliffs, N.J.
Freeze, R.A. and P. A. Witherspoon, 1967. Theoretical
Analysis of Regional Ground-Water Flow: 3. Quantitative
Interpretations. Water Resources Research 4.
Gummermsj*, R.C., R.L. Culp, and S.P. Hansen, August, 1972.
"Estimating Water Treatment Costs. Volume 1. Summary."
Prepared for U.S. Environmental Protection Agency,
Office of Research and Development. Cincinatti, OH. EOA
-600/2-79-162A.
Heath, R.C., 1984. Ground-Water Regions of the United
States. U.S. Geological Survey Water Supply Paper 2242,
U.S. Government Printing office, Washington, D.C.
B-l
-------
Hubbert, M.K., 1940. The Theory of Ground-Water Motion. J.
Geo. , 48.
launerman, Fredrick W. , 1987. Final Descriptive Summary:
1986 Survey of Community Water Systems. Prepared by the
Research Triangle Institute, Research Triangle Park,
North Carolina, for the Office of Drinking Water, U.S.
EPA.
LeGrand, Harry E., 1980. A Standardized System for Evalua-
ting Waste-Disposal Sites. National Water Well Associ-
ation, Worthington, Ohio.
Monnig, E.G., 1984. Review of State Siting Criteria for the
Location of Hazardous Waste Land Treatment, Storage and
Disposal Facilities. Prepared for the U.S. EPA, Office
of Solid Waste and Emergency Response, Washington, D.C.
National Water Well Association, 1979. Water Well Drilling
Cost Survey. NWWA, Worthington, Ohio.
Quilan, J.E. and R.O. Ewers, 1985. Ground-Water Flow in
Limestone Terranes: Strategy, Rationale and Procedure
for Reliable, Efficient Monitoring of Ground-Water
Quality in Karst Areas. From Proceedings, 5th National
symposium and Exposition on Aquifer Restoration and
Ground-Water Monitoring, National Water Well Associa-
tion, Worthington, Ohio.
Silka, Lyle R. and Ted L. Sweringer, 1978. A Manual for
Evaluating Contamination Potential of Surface Impound-
ments. U.S. Environmental Protection Agency, Office of
Drinking water, EPA 570/9-78-003; Washington, D.c.
Todd, David K. , 1959, Ground Water Hydrology, John Wiley &
Sons, Inc., New York.
U.S. Bureau of the Census, Statistical Abstract of the US:
1987 (107th edition) , Washington, DC, 1986.
U.S. Environmental Protection Agency, Office of Water
Programs, 1975. Manual of Individual Water Supply
U.S. SPA, Washington, D.C.
U.S. Environmental Protection Agency, 1980a. Water Quality
Management Directory, Agencies and Funding Under Section
20.8, 4th Edition. U.S. SPA, Washington, D.C.
U.S. Environmental Protection Agency, 1980b. Treatability
Manual for Priority Pollutants. U.S. EPA, EPA 600/8-80-
042, a-e; Washington, D.C.
B-2
-------
U.S. Environmental Protection Agency, I980c. Design Manual:
Onsite Wastevater Treatment and Disposal Systems.
Office of Research and Development Municipal Environ-
mental Research Laboratory. Cincinnati, Ohio.
U.S. Environmental Protection Agency, I984a. National
Statistical As«essme«+- of Rural Water Conditions.
Office of Drinking Water (WH-550) Publication EPA 570/9-
84-OC4, Washington, D.C.
U.S. Environmental Protection Agency, 1984b. Ground-Water
Protection Strategy. Office of Ground-Water Protection,
Washington, D.C.
U.S. Environmental Protection Agency, Office of Solid Waste,
1984c. Permit Writer'* Guidance Manual for the Location
of Hazardous Waste Land Storage and Disposal Facilities
- Phase 1; Criteria for Location Acceptability and
Existing Regulations for Evaluating Locations. U.S.
Environmental Protection Agency, Washington, D.C.
U.S. Environmental Protection Agency, Office of Water
Regulations and Standards, 1985a. National Water
Quality Inventory: 1984 Report to Congress. EPA 440/4-
85-029, U.S. Environmental Protection Agency,
Washington, D.C.
U.S. Environmental Protection Agency, 1985b. Guidance on
Feasibility Studies Under CERCLA, EPA/540/6-85/ 003.
U.S. Environmental Protection Agency, 1985c. Draft Report-
Liner Location Risk and Cost Analysis Model, Appendix C.
Office of Solid Waste, Economic Analysis Branch,
Washington, D.C.
U.S. Geological Survey, 1984. National Water Summary 1984.
Water Supply Paper 2275. United States Government
Printing Office, Washington, D.C.
B-3
-------
APPENDICES
Three groups of supplemental informational materials are
appended for the classifier's use. The technical basis for
the initial 2-mile radius of the Classification Review Area
is discussed in Appendix A. Derailed procedures for
expanding or subdividing the Classification Review Area are
also provided. Supplemental materials for the non-economic
aspects of Class I and Class III determinations are provided
in Appendix B and Appendix C, respectively. Supplemental
guidance for applying the common aspects of the Class I and
Class III economic tests is provided in Appendix 0.
-------
APPENDICES
APPENDIX A: SUPPLEMENTAL INFORMATION: CLASSIFICATION REVIEW
AREA
APPENDIX B: SUPPLEMENTAL INFORMATION FOR CLASS I PROCEDURES
APPENDIX C: SUPPLEMENTAL INFORMATION FOR CLASS III
PROCEDURES
APPENDIX D: SUPPLEMENTAL INFORMATION FOR CLASS I AND CLASS
III ECONOMIC TESTS
-------
GLOSSARY *
AQUIFER - A geologic formation, group of geologic formations,
or part of a geologic formation that yields significant
quantities of vater to veils and springs.
AQUIFER SYSTEM - A heterogeneous body of intercalated perme-
able and less permeable material that acts as a water-
yielding hydraulic unit of regional extent.
AQUITARO - A confining bed that retards, but does not prevent
the flow of water to or from an adjacent aquifer; it
does not readily yield water to wells or springs.
CONE OP DEPRESSION - A depression in the POTENTIOMETRIC
SURFACE of a body of ground water that has the shape of
an inverted cone and develops around a pumped well.
CONFINED CONDITIONS - Exists when an aquifer is confined
between two layers of much less pervious material. The
pressure condition of such a system is such that the
water level in a well penetrating the confined aquifer
usually rises above the top of the aquifer.
CONTAMINANT PLUME - Irregular volume occupied by a body of
dissolved or suspended pollutants in ground water.
CRA - Abbreviation of Classification Review Area.
DISCHARGE AREA - A discharge area is an area of land beneath
which there is a net annual transfer of water from the
saturated zone to a surface-water body, the land surface
or the root zone. The net discharge is physically
manifested by an increase of hydraulic heads with depth
(i.e., upward ground-water flow to the water table).
These* zones may be associated with natural areas of
discharge such as seeps, springs, caves, wetlands,
streams, bays, or playas.
ECOLOGICAL SYSTEM (ECOSYSTEM) - An ecological community
together with its physical environment.
* For general information only — not to be viewed as
suggested or mandatory language for regulatory purposes.
G-l
-------
ECOLOGY - The science of the relationships between organisms
and their environment.
ECOSYSTEM - See ECOLOGICAL SYSTEM.
FLOW NET - A graphical presentation of ground-water f ? ow
lines and lines of equal pressure head.
GEOLOGIC FORMATION - A body of rock that can be distinguished
on the basis of characteristic lithologic features such
as chemical composition, structures, textures, or fossil
content.
GROUND-WATER - Subsurface water within the zone of satura-
tion.
GROUND-WATER BASIN - (a) A subsurface structure having the
character of a basin with respect to the collection,
retention, and outflow of water, (b) An aquifer, or
system of aquifers, whether or not basin-shaped, that
has reasonably well-defined hydrologic boundaries and,
more or less, definite areas of recharge and discharge.
GROUND-WATER FLOW DIVIDE - An imaginary plane (or curved
surface) distinguished by the limiting flow lines of
adjacent flow systems. Conceptually there is no flow
across this plane between the flow systems.
GROUND-WATER FLOW REGIME - The sum total of all ground water
(water within the saturated zone) and surrounding
geologic media (e.g., sediment and rocks). The top of
the ground-water regime is the water table while the
bottom would be the base of. significant ground-water
circulation* Temporarily perched waters within the
vadose zone would generally not qualify as part of the
ground-water regime.
GROUND-WATER FLOW SYSTEM (GROUND-WATER SYSTEM) - A body of
circulating ground water having a water-table upper
boundary and ground-water flow divide boundaries along
all other sides. These boundaries encompass distinct
recharge and discharge areas unique to the flow system.
GROUND-WATER SYSTEM - See GROUND-WATER FLOW SYSTEM.
HYDRAULIC CONDUCTIVITY - The capacity of earth materials to
transmit water.
HYDRAULIC GRADIENT - The change in STATIC HEAD per-unit-of-
distance in a given direction.
HYDPAULIC HEAD GRADIENT - See HYDRAULIC GRADIENT.
PIEZOMETRIC SURFACE - See POTENTIOMETRIC SURFACE.
G-2
-------
POTABLE WATER - Water that is safe and palatable for hunan
use; concentrations of pathogenic organisms and dis-
solved toxic constituents have been reduced to safe
levels, and it has been treated so as to be tolerably
low in objectionable taste, odor, color, or turbidity,
POTENTIOMETRIC SURFACE (PIEZOMETRIC SURFACE) - An imaginary
surface representing the STATIC HEAD of ground water and
defined by the level to which water will rise in a well.
The WATER TABLE is a particular potentiometrie surface.
RECHARGE AREA - A recharge area is an area of land beneath
which there is a net annual transfer of water through
the vadose zor.a into the ground-water regime. The net
recharge is manifested by a decrease in hydraulic heads
with depth (i.e., downward ground-water flow from the
water table).
SATURATED ZONE - A subsurface zone in which all the voids are
filled with water under pressure greater than that of
the atmosphere. This zone is separated from the over-
lying zone of aeration (unsaturated zone) by the WATER
TABLE.
STATIC HEAD (HYDRAULIC HEAD) - The height above a datum plane
of the surface of a column of water (or liquid) that can
be supported by the static pressure at a given point.
STRESS (PUMPING STRESS) - Drawdown of water level and change
in HYDRAULIC GRADIENT induced by pumping ground water.
SURFACE-WATER DIVIDE - The line of separation, or ridge,
summit, or narrow tract of high ground, marking the
boundary between two adjacent drainage basins, or
dividing the surface waters that flow naturally in one
direction from those that flow in the opposite direc-
tion.
TOTAL DISSOLVED SOLIDS (TDS) - The quantity of dissolved
material in a sample of water determined either from the
residue on evaporation by drying at 180°C, or, for
waters containing more than 1,000 parts per million,
fresjr the sum of determined constituents.
UNCONFIMED CONDITIONS - Exists when the upper limit of the
aquifer is defined by the water table itself. At the
water table, water in the aquifer pores is at atomos-
pheric pressure.
UNSATURATED ZONE - See VADOSE ZONE.
G-3
-------
VADOSE ZONE (ZONE OF AERATION) - A subsurface zone containing
water under pressure less than that of the atmosphere,
including water held by capillarity, and containing air
or gases generally under atmospheric pressure.
WATER TABLE - The surface of a body of unconfirmed ground
water at which the pressure is equal to that of the
atmosphere.
WATER-TABLE GRADIENT - The change in elevation of the water
table per unit of horizontal distance.
G-4
-------
TABT.E QF CONTENTS
Page
APPENDIX A: SUPPLEMENTAL INFORMATION: CLASSIFICATION
REVIEW AREA A-l
A.I Technical Basis for Initial 2-Mile Radius
of the Classification Review Area A-l
A. 1.1 Plume Survey ; A-2
A.1.2 Distance to Dovngradient Surface Waters... A-4
A. 1.3 Pumping Well capture zones A-4
A.2 Determining Expanded Review Area Dimensions.... A-8
A.3 Subdividing the Classification Review Area A-16
A.3.1 Identifying Ground-Water Units and
Analyzing Interconnection A-16
A.3.2 Example of Subdividing a Classification
Review Area A-35
A. 4 Appendix A References A-40
APPENDIX B: SUPPLEMENTAL INFORMATION FOR CLASS I
PROCEDURES B-l
B. 1 Densely Settled Criterion B-l
B.2 Use of GEMS System for Estimating
well Density B-2
B.3 General Background Information on
Institutional Constraints B-3
B.4 List of Offices of Endangered Species,
U.S. Fish and wildlife Services B-8
B.5 List of State Natural Heritage
Program Offices (October 1985) B-14
B. 6 Appendix B References B-2o
APPENDIX C: SUPPLEMENTAL INFORMATION FOR
CLASS ZII PROCEDURES C-l
C. 1 Overview of Treatment Technologies C-l
C.2 Partial Bibliography of References
evaluating Water Treatment Technologies c-7
-------
TABLE OF CONTENTS (CONTINUED)
APPENDIX D: SUPPLEMENTAL INFORMATION FOR CLASS I
AND CLASS III ECONOMIC TESTS D-l
D. 1 Components and Types of Costs D-l
D.I.2 Cost Components D-3
D.I.2 Types of Cost D-4
D. 2 General cost Estimation Procedures D-5
D. 2 .1 overview of Cost Estimation D-6
D.2.2 Methods for Estimating Costs D-7
D.2.3 Final Cost Estimate D-12
D.3 Cost Estimation for the Class I - Economic
Irreplaceability Test D-l5
D.3.1 Class I Cost Estimating Procedure......... D-l5
D.3.2 Hypothetical Example of Class I Cost
Estimation. D-17
D.4 Cost Estimating for the Class III Economic
Untreatability Test D-18
D.4.1 Class III Cost Estimating
Procedure D-18
D.4.2 Hypothetical Example of Class III Cost
Estimation D-19
D.5 Derivation and Calculation of Economic
Thresholds D-21
D. 5.1 Derivation of Economic Thresholds D-21
D.5.2 Methodology for Calculating Econoaic
Thresholds D-2 2
D.5.3 Illustrative Applications of Econoaic
Thresholds D-2 4
D.6 Appendix D References. D-26
ii
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LIST OF FIGURES
APPENDIX A
A-l.
A-2.
A-3.
A-4.
A-5.
A-6
A-7.
A-8.
A-9.
A-10.
A-ll.
A-12.
A-13.
A-14.
A-15.
A-16.
A-17.
Plume Length Distribution
Dovngradient Distance to Surface Water
Well Capture Zone
Hypothetical Karat Terrain with 2 -Mile Review
Area
Generalized Grose Section of a Karat
Hydrogeologic Setting
Example of Overflow Across Ground-Water
Basins
Hypothetical Xarst Terrain with Expanded
Hypothetical Example of Review- Area Expansion
in a Fractured Rock Setting
Hydrogeologic Sections Showing Flow Systems of
Increasing complexity with Type 1 Boundaries..
Example of Type 1 Flow Divide Boundary...
Example of Type 2 Boundary
Example of Type 3 Boundary Through an
Unconf ined Aquifer in a Coastal Setting
Example of Type 3 Boundary in an Evaporite/
Saline Water Setting
Example of Type 3 Boundary Through Basin Fill
in a Closed Basin/Arid Climatic Setting
Sacample of a Type 4 Gradient-Based Boundary
Defined on the Basis of Simulated Ground-Water
Plow Patterns
• Hypothetical Setting for Demonstrating the
Subdivision of a Classification Review Area..
Hypothetical Classification Review Area
A-3
A-5
A-6
A-10
A-ll
A-12
A-14
A-15
A-18
A-20
A-2 4
A-2 8
A-29
A-31
A-34
A-3 6
A-37
iii
-------
LIST OF FIGURES ICOKT.)
A-18. Subdivision of a Hypothetical Classification
Review Area into the Ground-Water Units A-38
APPENDIX D
D-l. Ninetieth Percentile Economic Threshold by
System Size 0-23
LIST OF TABLE?
APPENDIX A
A-l. Lateral and Dovngradient Well Capture
Distance A-7
A-2. Range of Values of Hydraulic Conductivity
and Permeability A-26
APPENDIX D
0-1. Components and Types of Water Supply System
COBtS 0-2
0-2. Water Supply System Cost Worksheet 0-8
0-3. Typical Components of Selected Treatment
Technologies .. 0-10
0-4. Annualized Costs of Typical Treatment
Components for Four Plant Sizes D-li
O-5. Typical Water Supply system Costs 0-13
D-6. Component Costs as Percentage of Total
Water Supply System Costs D-14
iv
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APPENDIX A
SUPPLEMENTAL INFORMATION:
CLASSIFICATION REVIEW AREA
-------
APPENDIX A
SUPPLEMENTAL INFORMATION: CLASSIFICATION REVIEW AREA
A.I Technical Basis for Initial 2-Mil* Radius of the
Classification Review Area
The EPA classification system utilizes ths concept of a
Classification Review Area around a specific facility or
activity. EPA has deterained that in general a
Classification Review Area 2-miles in radius is a good
starting point for this analysis. A larger radius may be
appropriate in certain hydrogeologic conditions or in
accordance with specific program practice.
The EPA examined three sources of data as the basis for
identifying 2-miles as a generally appropriate Classification
Review Area radius. The data provided insight into the
length of the flow path over which high degrees of
interconnection occur. In addition, the data indicate
distances contaminants could be expected to move in problem
concentrations should they be accidentally introduced into
the ground-water system. The three sources of information
examined were as follows:
• A survey of existing contaminant plumes documented
through investigations of spills, leaks, and dis-
charges .
• A survey of the distances to downgradient surface
waters from hazardous-waste facilities.
• Calculations of the distances from which pumping
wells draw ground water under different hydro-
geologic settings.
These sources are described below.
A-l
-------
A. 1.1 Plume Survey
A survey of contaminant plume geometries (i.e., length,
width and depth) was prepared in connection with the develop-
ment of a stochastic model of corrective action costs at
hazardous-waste management facilities (Geraghty t Miller,
Inc., 1984). The plume survey was updated by Geraghty &
Miller, Inc., in 1987. The plume survey provides generalized
information on the distances contaminants have been known to
migrate regardless of time, source type, or hydrogeologic
setting. This information indicated the area that may be
affected if contaminants were accidentally released from the
site.
The data base for the survey included ground-water
quality investigations, consultant reports, and other
publicly available literature (e.g., scientific journals).
The availability of data was limited by the confidential
nature of many privately funded contamination investigations
and the relatively small number of off-site investigations
conducted by the government prior to the implementation of
the Superfund program.
The survey found 74 contaminant plumes containing
inorganic and organic contaminants. Hydrocarbon plumes
consisted of dissolved and liquid phase (undissolved)
materials. The sources of the plumes were spills/ leaks, and
discharges from diverse sources including municipal and
industrial sites, transportation accidents, and unknown
sources. Plume boundaries were generally defined as a
detectable increase above background quality.
The survey showed that the median plume length was 1700
feet. Ninety-five per cent of the plumes were less than
miles in length. A histogram of plume lengths is provided in
Figure A-l.
The data were too limited to determine whether the
plumes in this survey had reached their maximum lengths.
Theoretically, if a contamination source is continuous and
the contaminant is not degraded, transformed, or immobilized
in route, the plume length will eventually be equal to the
distance to • dovngradient discharge point. other factors
that could prevent plumes froa reaching their natural
discharge) points include insufficient time since the contam-
inant release, and the implementation of an effective
remedial program. In some cases a steady-state condition may
be reached between contaminant input by the source and
dilution due to recharge. Although it is not known whether
the plumes in this survey had reached equilibrium, it is not
likely that any one of the above factors had any
of influence on the results.
A-2
-------
figure A-l
I
Ul
00*0.9 IO-L9 2.0-£9 36-34 4.0-49 5.0-3.9 tO-03 TO-T9 AO-6.9 9.0-9.9 10.0-109 >ILO
PLUME LENGHMh Ihowor* «f fM,)
-------
A. 1.2 Distance to Downqradient Surface-Watera Survey
ICF, Incorporated, conducted a survey of 117 hazardous-
waste management facilities for development of the EPA Liner/
Location Model (USEPA, 1985). For each site, the down-
gradient distance to surface waters (e.g., lakes, streams,
ocean, bay, or marsh) was calculated providing insight into
the distance at which a flow boundary for the shallow ground-
water system is likely to be encountered, thus, limiting the
area potentially impacted by a facility.
Some of the facilities in the survey were included in
EPA's site visit facility survey. Other sites were selected
from among available Part B Permits. A site was included in
the survey only if it provided information sufficient to
operate the liner/location model (e.g., comprehensive
facility design parameters and hydrogeologic information).
Facility sites were located on U.S. Geological Survey
topographic maps using latitude and longitude data. Geraghty
& Millar assisted ZCF by identifying the general direction of
ground-water flow from the site on the topographic map. The
frequency distribution histogram for distance to downgradient
surface waters is shown on Figure A-2. Ninety-five percent
of these distances are less than 2 miles.
A. 1.3 Pumping Well Capture Zones Survey
One of the criteria for establishing the typical radius
of the Classification Review Area was to identify the zone of
influence supplying water to the pumping well. In examining
the relationship between a 2-mile radius and the
identification of water-supply wells capturing water from
under a site, a formula (Todd, 1976) was used to determine
the generalized dimensions of well-capture zones under
different hydrogeologic conditions. The formula, illustrated
in Figure A-3, provides a calculation of the maximum
downgradient extent of well capture (XL) and the lateral
distance) (YL) (perpendicular to nonpumping, ground-water flow
gradient*). Lateral and downgradient capture distances were
calculate* for a range of transmissivities and water-table
gradient* under pumping condition* of 0.5 to 3.0 millions of
gallons per day (mgd). Incompatible well yields and
transmissivities vere not used. The governing equations and
the results of the calculations are shown in Table A-l. The
well yields were selected to represent the common range of
pumping rates for water-supply wells. With the exceptions
noted below/ water-supply wells are generally smaller than 2
mgd. The largest»lateral capture distance for a 2 mgd supply
well for the transmissivities and gradients examined is
A-4
-------
FIGURE A-2
OOWNCRADIENT DISTANCI TO SURFACE WATER
(SOUHCEi EPA. 1985)
IN
IS
K>
II
TOTAL till SITCS
0.5 • 1700 It
0.93.10,00011.
mot • 20,000 ft.
1000 2000 3000 4000 9000 6000 7000 6000 9000
DISTANCE (Ft)
12000 14000 MOOO 1(000 20000
-------
FIGURE A-3
WELL CAPTURE ZONE (Todd, 1976)
REGIONAL FLOW LINE
WATER-TABLE CONTOURS
r
DOWNGRAOIENT
CAPTURE DISTANCE
LATERAL
CAPTURE DISTANCE
-------
TABLE A-l.
LATERAL AND DOWNGRADIENT WELL CAPTURE DISTANCE (infect)
(after Todd, 1976)
Transmissivity/Gradient (ft/mi)
10,000/30-50 50,000/10-30 100,000/5-10
0.5 MGD Lateral 4400-2640
Dovngradiant 1400-840
2640-880
840-280
2640-1320
840-420
1.0 MGD Lateral N.A.
Dovngradient N.A.
5280-1760
1680-560
528C-2640
1680-840
2.0 MGD Lateral N.A.
Dovngradient N.A.
10,560-3520
3360-1120
10,560-5280
3360-1680
3.0 MGD Lateral N.A.
Dovngradient N.A.
15,840-5280
5040-1680
15,840-7920
5040-2520
Governing Equations
Lateral Distance YL • Q/2T1
Dovngradient Distance XL - Q/2Tf Ti
YL - ft
XL - ft
Q • flov rate
T - transmissivity
i - Hydraulic Gradient
N.A. - Not applicable.
A-7
-------
miles. Thus, the 2-mil* radius would identify the majority
of individual water-supply wells that could be drawing water
from under a proposed facility or site in directions other
than the downgradient direction.
NOTE: Sxceptions include the basalt aquifers of the
Columbia Plateau and Hawaii, where common well sizes are
up to 4 mgd and SOB* may exceed IB cgd; the Florida
aquifer in Florida and Georgia where common yields are
up to 7 mgd and may exceed 8 mgd; and the Chicot aquifer
of the Lake Charles Formation in Louisiana where common
yields up to 3.5 agd are found. Other regionally
extensive high-yielding aquifers where wells may exceed
2 mgd include the Texas Edwards aquifer, thick members
of the Atlantic and Gulf Coastal Plains, alluvium and
older sedimentary basins in California and the 'Sparta
Sands in Arkansas.
In summary, the plume survey and survey of distances to
discharge boundaries support the 2-mile typical radius
concept. The plume data indicate the distance that
contaminants are known to migrate in problem concentrations,
and the distance to discharge points data indicate the
likelihood that a flow boundary will be intercepted. Pumping
well capture distances provide the basis for including
lateral and upgradient areas in the review area. Thus, 2-
miles is a reasonable distance to use for initially
identifying potentially highly interconnected ground waters
related to a site under classification.
A. 2 Determining Expanded Review Area Dimensions for Non-
Dare ian Settings
This appendix provides guidance for determining the
dimensions of the expanded review area. In general, the
dimensions of the) expanded review area are governed by
hydrogeologic conditions, particularly ground-water flow-
system boundaries, flow directions, and flow velocities. The
cases betlov illustrate various conditions and suggest methods
for arriving at appropriate expanded review area dimensions.
For non-Darcian flow settings, the dimensions of the
expanded review area can generally be based on the boundaries
of the ground-water basin. A basin includes all areas
extending from flow divides at the boundaries of recharge
areas to the major perennial stream where discharge occurs.
When the information base is too small to fully define these
boundaries, the classifier can use the distance to the
A-a
-------
LATERAL AND OOWNGRA
(af
Transm:
10,000,
0.5 MGD Lateral 4400-
Dovngradiant 1400-
1.0 MGD Lateral
Dovngradient
2.0 MGD Lateral
Dovngradient
3.0 MGD Lateral N.A
Dovngradient N.A
Governing Equations
Lateral Distance
Dovngradient Distance
YL - ft
XL - ft
Q - flov rate
T - transaissivity
i - Hydraulic Gradient
N.A. - Not applicable,
-------
nearest downgradient, perennial stream/ where ground water
from the activity area is likely to discharge, to establish
the expanded review-area dimension.
Karat Setting^
In karat hydrogeologic settings, the boundaries of a
ground-water basin may vary considerably depending on water-
level stage in the cave-stream complex. A hypothetical karst
terrain, characterized by sinkholes, sparsity of surface
streams and an integrated system of subsurface drainage
conduits within a carbonate bedrock complex is shown on
Figure A-4. Directly west of the activity, streams drain an
upland area, flowing eastward to the sinkhole plain, on the
plain, the streams intersect sinkholes, and surface water is
diverted to the underground network of solution conduits
within the karst bedrock. This zone where surface water is
rerouted to the subsurface represents the termination of the
eastwardly extent of the more resistant sandstone formation
overlying limestone and dolomites. Without the resistant
sandstone, surface water has reworked the carbonate bedrock
into a network of vertical and horizontal solution cavities
and conduits that drain the sinkhole plain eastward to the
Little Blue River. A cross-section of this hypothetical
terrain is shown on Figure A-5.
In a karst terrain, ground-water circulation occurs
through a system of conduits having a variety of shape* and
capacities. The ground-water flow system undergoes major
changes depending upon the magnitude of a precipitation
recharge event. For example, in the hypothetical example
during periods of lov flow (little or no precipitation),
surface, water recharges the carbonate aquifer at the sinkhole
plain and travels through a series of solution cavities to
the ground-water Basin B trunk conduit (Figure A-6 [A]).
Under these conditions, each ground-water basin hydraulically
operates as a separate entity. The general direction of flow
in Basin B (although tortuous) is toward the Little Blue
River.
As shown in Figure A-6 (B), recharge to the aquifer via
sinkholes and swallets during peak rainfall events, causes
ground-water levels within the Basin B trunk conduit to
increase, to the point where upper cavity transverse conduits
are Intersected and ground water migrates into the trunk
conduit* of Basins A and C. This process is termed ground-
water piracy. During high-intensity recharge events, ground
water from Basin B, which could potentially contain
contaminants from the activity, will travel to all three
ground-water basins.
Xarst basins can be mapped using dye-tracing studies
field mapping, spelunking, geochemical reconnaissance, and
water-level maps. However, due to the expense of such
A-9
-------
FIGURE A-4
HYPOTHETICAL KARST TERRAIN WITH 2-MILE REVIEW AREA
EXPLANATION
• PROPOSED
CLASSIFICATION REVIEW AREA BOUNDARY
o~ SPRING/SEEP
—v—- FLOW ROUTE
-* H^M-IXVEL OUTFLOW ROUTE
—— OHdOND-YttTCT BASIN SOONOARY
^^-• SWttUET OF SINKING STREAM
A-10
-------
FIGURE A-5
GENERALIZED CROSS SECTION OF A KARST HYDROGEOLOGIC SETTING
WEST
SANOSTO
FACIUTY
LITTLE BLUE
RIVER
GROUND-WATER
FLOW CONDUITS
•"n-"-i
EAST
-------
FIGURE A-6
EXAMPLE OF OVERFLOW ACROSS GROUND-WATER BASINS
80-
60-
40-
20-
0-
-2O-
-40-
ta
BASH C
BASH B
SAStN A
BASE FLOW CONOmONS
(A)
80
6O-
40-
2O-
SAStN C
BASIN B
FLOW ORECTONS
BASIN A
ECOLOGKALUr
VITAC AREA
HIGH INTEf^SJTY H-GW
(B)
A-12
-------
studies, few basins have been mapped. As a surrogate, it is
recommended that the distance to the nearest downgradient,
perennial streaa be eaployed to establish the expanded
review-area dimensions as illustrated in Figure A-7.
Generally, the appropriate perennial stream segment will be
spring fed (i.e., cave-stream discharge springs) and not
subject to disappearance into cave-stream flow (i.e., sinking
stream).
The classifier is cautioned that the nearest perennial
stream may not be downgradient and, therefore, not the
discharge point for the subject ground-water basin. Such an
error can be minimized by locating the topographic high (the
water-shed divide) between the nearest perennial streaa and
adjacent streams. The correct perennial streaa to employ in
this suggested methodology is generally on the saae side of
the topographic high as the activity. The ground-water basin
of interest will generally be discharging to the perennial
stream on the same side of the topographic high as the
activity/facility. In rare cases, the activity or facility
is located in the vicinity of the topographic high between
perennial streaas. In such a case, the expanded review area
should extend to the nearest perennial streaa on all sides of
the topographic high, unless site-specific data concerning
ground-water flow direction are available.
Other settings
The expansion of review area dimensions for fractured
rock and extrusive igneous (basaltic lava) settings can also
be based on ground-water basin boundaries. In these types of
settings, there is a strong potsntial for flow to be pref-
erentially channeled through fracture zones at high veloci-
ties. Bedrock fractures are often expressed in surface
features, such ass streaas and other surface depressions, and
can often be identified through aerial photography and other
forms of fracture trace analysis. The identification of
thess fracture zones can be very useful in predicting the
direction and extent of non-Darcian, high-velocity flow.
This information can then be employed to establish the
expanded review-area dimensions. A hypothetical example is
shown in Figure A-8. Similar to its use in the evaluation of
karst settings, topography can be utilized to help identify
the likaly discharge points for ground watsr originating at
the facility.
A-13
-------
FIGURE A-7
HYPOTHETICAL KARST TERRAIN WITH EXPANDED REVIEW AREA
EXPLANATION
• PROPOSED FACILITY
CLASSIFICATION REVIEW AREA BOUNDARY
•: *•;•: I EXPANDED CLASSIFICATION REVIEW AREA
• 3MMG HOUSE FOR DOMESTIC USE
»- 90UNO/SEEP
ROADWAY
A-14
-------
A-8
HYPOTHETICAL EXAMPLE OF REVIEW-AREA EXPANSION
IN A FRACTURED Rrvv ctWT»~ PANSION
FRACTURED ROCK SETTING
EXPLANATION
[||i| UMNOCO KVICW ANCA
Hj FACO.ITY ACTIVITY
V OSTAMCC TO NCAUCST B<«CHA«Oe POINT
A-15
-------
A.3 Subdividing the Classification Review Area
A.3.1 Identifying Ground-WaterUnits and Analyzing
I n t a rconnect ion
Subdivision of the ground-water regime .into ground-water
unite generally involves collacting and avaluating informa-
tion related to geology, hydrology, and management of ground-
water resources (controls on withdrawals/recharge, properly
abandoning deep wells, etc.). The description of the ground-
water regime and any potential subdivisions should be as
quantitative as possible. The Agency recognizes that the
degree of accuracy with which the Classification Review Area
can be subdivided is limited by the abundance and quality of
available data. Supplementing the existing data base with
field and laboratory investigations both on-site and off-site
nay be needed to accurately confirm the existence of subdivi-
sions. The following discussion will serve to guide the
types of data needed to justify the subdivision of the
Classification Review Area.
Background information on geologic formations and
occurrence/movement of ground water can be obtained at a
regional scale of accuracy from State and Federal agencies.
Topographic maps published by the U.S. Geological Survey are
now available at useful scales for most of the nation. These
can help identify ground-water flow directions and flow
divides for the uppermost aquifer. Data on the distribution
and characteristics of soils are available from the U.S.
Department of Agriculture Soil Conservation Service. General
information on precipitation, run-off, and recharge rates can
be obtained from the U.S. Geological Service and can be
supplemented by climatic data from weather stations around
the country. Ground-water pumpage and locations/depths of
wells can generally be obtained from State agencies that
issue well permits or from local public-health agencies and
water districts.
Thev first step is to identify all aquifers occurring
within the ground-water regime of the Classification Review
Area. In areas that have been well-studied, these will be
recognized and documented in government agency reports. In
poorly studied areas, proper recognition of aquifers can be
inferred from litholbgic descriptions of geologic formations,
structural features of the area (if flov is mainly through
fractured rock), and the depth and design of wells. The
areal and vertical extent of hydrogeologic units within the
ground-water regime can be shown in a series of cross-aec-
A-16
-------
tions and saps. For most hydrogeologic settings, it will be
moat useful to interpolate between location* where conditions
are known (i.e., walla, outcrops, excavations, etc.) and
present variationa in thicknaaa and elevations of important
unita with contour maps prepared at a common scale.
Aftar the. identification and graphical representation of
the geologic framework, it is possible to identify ground-
water units within the ground-water regime using the guidance
provided in subsequent sections.
Type 1 Boundaries? Ground-Water Flow Divides
The concepts of ground-water flow systems may not be
faailiar to some readers and, therefore, may need to b«
reviewed so that the reader can understand the concept of
flow-divide boundaries between ground-water units. Figure A-
9 shows in vertical cross section a series of adjacent,
shallow, ground-water flow systems for a single-layer, water-
table aquifer. The systems are bounded at the base by a
physical impermeable boundary. As is typical in humid
regions, the water-table profile conforms to the topographic
profile.
The flow net in Figure A-9 (a) shows that ground-water
flow occurs from the recharge area in the highlands to the
discharge areas in the lowlands (i.e., valleys). Vertical
line segments AB and CD beneath the valleys and ridges
constitute ground-water flow divides, i.e., imaginary im-
permeable boundaries across which there is no flow. In the
figure, these grou 1-water flow divides separate adjacent
flow systems ABCD and ABFE which, for purposes of subdivi-
sion, correspond to ground-water units separated by Type i
boundaries.
In simplified, symmetrical systems, such as those il-
lustrated in Figure A-9 (a), ground-water flow divides coin-
cide exactly with surface-water divides and extend vertically
to the base of the aquifer. In more complex topographic and
hydrogeologic settings, these properties may diverge substan-
tially from the situation illustrated.
A ecsjparison of Figures A-9 (a) and (b) reveals how flow
pattern* and divides are altered when the undulations in the
water table are superimposed on the regional hydraulic
gradient towards a more regional stream and discharge area.
Ground-water flow divides in Figure A»9 (b) extend through
the full thickness of the aquifer only at either end of the
entire flow regime. The full dimension of the flow regime
may or may not be encompassed by the. 2-mile radius. The
total length, S, in the figures, can range from hundreds to
thousands of feet.
-------
FIGURE A-9
HYDROGEOLOGIC SECTIONS SHOWING FLOW SYSTEMS OP
INCREASING COMPLEXITY WITH TYPE 1 BOUNDARIES
TYPE I BOUNDARIES
0.2 S
OUCHANM TO
MMIOMAI. STMCAM
AMO WITLANDS
—TYPE I
BOUNDARY
01S 0.2 S 03S 04 S 05S 0.65 07S 08S 0.9S
0.2 S
—TYPE I
BOUNDARY
OIS 025 03S 0.4S 05S 0.65 0.7S 0-8S 0.9S
A-18
-------
Figure A-9 (c) is an example of more complex conditions
in which the flow patterns and flow systeas are affected by
both topography and regional .variations in hydraulic conduc-
tivity of layered earth materials. Given adequate data, com-
puterized models of real sites can provide approximations of
ground-water flow patterns. In general, the level of sophis-
tication employed to demonstrate the presence of a Type 1
boundary should be commensurate with the complexity of the
hydrogeologic setting.
The spatial location of the water-table and ground-water
flow divides may be stable under natural flow conditions but
can be modified by man-made hydraulic stresses, such as
large-scale ground-water withdrawals or recharge. In some
case* it will be necessary to estimate the permanence (i.e.,
location with time) and position of ground-water flow divides
under stressed conditions from available hydrologic and
geologic data and foreseeable changes in water use.
A good example of ground-water units separated by a Type
1 flow divide boundary is shown in Figure A-10, The setting
illustrated consists of two alluvial valleys with high-yield
wells completed in sand and gravel deposits, separated by
sandstone bedrock that can only provide limited supplies to
domestic wells. Ground water in the alluvium is derived from
precipitation and from the bedrock and discharges to the
river under natural conditions. Under pumping conditions,
the water pumped by the high-yield wells is derived largely
from the river, from local precipitation, and from the
bedrock. Near the wells in the western valley, flow-system
boundaries are affected by ground-water withdrawals and are
stable as long as the well discharges are steady. The
ground-water flow divide separating the two valley aquifers
is not affected by pumpage, and provides the essential
characteristic that allows the delineation of ground-water
units A and B.
Flow Analysis. In order to provide a defensible ground-water
flow-divide delineation, a limited flow analysis is generally
necessary. An acceptable approach is to prepare a water
budget for the ground-water unit in order to show a
reasonable* order-of-aagnitude balance on flow into and out of
the system. This water budget could involve the preparation
of a ground-water flow net (see Glossary for definition) for
the uppermost aquifer with accompanying estimates of volume-
tric flow into and out of the unit. The flow net can be gen-
eralized and need not be rigorously correct in a quantitative
sense.' The analysis should be carried out even though part
of the ground-water system continues outside the Classi-
fication Review Area, that is, if part or all of the dis-
charge or recharge area of the unit extends beyond the
Classification Review Area.
A-19
-------
FIGURE A-10
EXAMPLE OF TYPE 1 FLOW DIVIDE BOUNDARY
^
GEOLOGIC MAP
2 MILES
HYDROGEOLOGIC CROSS SECTION
GftOtMHMTCR FLOW DIVIDE
A(WtSt)
40OFT
ZOO FT
ALLUVIAL AQUFER
SANDSTONE AQUIFER
GENERAL FLOW DRECTION
Acrnvc
MUNICIPAL
SUPPLY WELL
'/'/ ' BASE OF ORCULATION
! CLASSIFICATION REVIEW
AREA BOUNDARY
A-20
-------
The semiquantitative flow net of the,,uppermost aquifer
should be supplemented by a vertical hydrogeologic cross
section and supporting data shoving that the uppermost
aquifer is, in fact, underlain by an extensive aquitard or
crystalline rock non-aquifer within the Classification Review
Area. The flow net can be based on available water-table
elevation data, as interpreted from water levels in rela-
tively shallow wells, as well as on locations/elevations of
springs, wetlands, and perennial streams, and supplemented
with topographic elevations. The rates and directions of
flow can be estimated in plan view given a water-table
contour map and estimates of aquifer thickness and hydraulic
conductivity. The conductivity can be obtained from the
area-specific reports, field or laboratory tests, or by
estimating a range from the scientific literature based on
earth material type. Flow patterns inferred from these data
must also consider significant spatial and directional
variations in conductivity in areas having more complex
stratlgraphie and structural geologic conditions.
At the beginning of the flow analysis, it is important
to determine whether the ground-water flow system is in a
state of steady or transient flow. Areas that are charac-
terized by a lack of ground-water development and usage can
generally be assumed to be in steady state. This will
simplify the analysis because the estimate of system dis-
charge can be equated to recharge. If the natural recharge
rate compares favorably with a reasonable percentage of mean
annual precipitation, the ground-water flow divides can be
considered reliable. The applicant can go to the ground-
water literature to obtain reasonable estimates to recharge
in any geographic/ground-water region of the United States
(e.g., see USGS Water-Supply Paper 4 by R.C. Heath, 1984).
In areas characterized by large-scale withdrawals of
ground water from shallow or deep aquifers, the flow regime
is more prone to be in a transient state. Evidence of
transient conditions are as follows:
e Declining ground-water levels.
e Depletion of ground-water storage.
e Movement of flow divides.
When suafc evidence of transient conditions exists, it may be
necessary to estimate the ultimate steady-state position of
the flow divides assuming conservatively large withdrawal
rates and saall water-flow and storage properties.
Type 2 Boundaries; Low-Permeability Geologic Units
The Agency would generally assign a low degree of
interconnection across the low-permeability geologic unit
(Type boundary) if the following conditions can be shown:
A-21
-------
• The low-permeability geologic unit is laterally
continuous beneath the entire area "and/or limits the
lateral continuity of- the more permeable geologic
unit.
e There are no known wells, mine shaft*, etc. that are
improperly abandoned or unsealed through the geologic
unit.
• The geologic unit has a small permeability relative to
both adjacent geologic units and to geologic media in
general.
• The flow of water through the geologic unit per unit
area is insignificant relative to the flow of water
pc~ unit area through adjacent strata.
Low-permeability geologic units include fine-grained
sediments and sedimentary rocks, such as clays and shales, as
well as crystalline igneous and metamorphic rocks that have
few interconnecting fractures. Because these materials have
small permeabilities, small quantities of water will be
transmitted through them in response to hydraulic gradients.
Such favorable head relationships further ensure that the
direction of ground-water movement at the boundary serves to
inhibit the migration of contaminants into and across this
type of boundary into the adjacent ground-water unit.
In selected environments, such as deep geologic basins,
it may be possible to show that the flow of fluids is
negligibly small through the low-permeability unit. The
actual cut-off values of key variables such as permeability,
thickness, and hydraulic gradient are not specified in these
Guidelines and are left to professional judgments.
A setting where the presence of a thick, regionally
extensive aquitard establishes a low degree of
interconnection between a shallow ground-water unit and a
deeper underlying ground-water unit (aquifer) is shown in
Figure A-ll. This configuration is common in the Atlantic
and Gulf coastal plain settings where the lower aquifer is
the principal regional aquifer and is a source of water
supply. It is overlain by an extensive confining clay that
may be tan* of feet thick. The shallow ground-water aquifer
system supplies only limited amounts of water to wells. The
reasons for the low interconnection between aquifers in this
setting* are as follows:
• The flow of water through the aquitard is exceedingly
small.
• Water travel time through the aquitard is very great.
A-22
-------
FIGURE A-ll
EXAMPLE OF TYPE 2 BOUNDARY
CLASSIFICATION REVIEW AREA
2-MILES 2-MILES
MSL
10
ALLUVIAL AQUIFER
(UPPER GROUND-WATER
UNIT}
FACILITY
SO
AQUI7ARO
85
o
4O
6O
AOOFER
(LOWER GROUND-WATER UNIT)
TO *-
A-23
-------
In general, the demonstration of the existence of a Type
boundary requires that the laterally "continuous, low-
permeability non-aquifer that conotitutee the boundary be
identified and characterized. The following factors should
be considered in making this demonstration:
e stratigraphic setting a.iJ lithologic characteristics.
e Structural setting and joint/fracture/fault charac-
teristics.
• Hydrogeologic setting and hydraulic head/fluid flow
characteristics.
The first distinction should be between whether the non-
aquifer is of sedimentary or igneous/metamorphic origin. If
it is sedimentary in origin, an identification of the envir-
onment of deposition will permit inferences about the ex-
pected geometry, thickness, and continuity of individual
strata. These inferences should be defended with geologic
sections including data from well logs and/or measured
sections. The age of the unit, the degree of cementation,
and degree of compaction are all qualitatively related to
water-bearing characteristics (hydraulic conductivity and
porosity).
If the unit is an igneous or metamorphic rock, the
continuity and thickness can usually be inferred from geo-
logic maps and reports for the region in which the Classifi-
cation Review Area exists. Identification of igneous rocks
that have tabular geometries such as volcanic flows, ash-fall
deposits, or intrusive sills and dikes will allow inferences
about thickness and continuity. These may serve as aquifers
or aquitards within a sequence of sedimentary rocks.
Crystalline basement rocks of igneous and metamorphic origin
underlie the entire North American continent. In areas where
these rocks are fractured and exposed at or near the land
surface, they generally serve as poor-yielding aquifers.
However, significant circulation can be assumed to be
restricted to the upper few hundred feet because the
fracture* tend to close with depth. In other areas, where
these recks) are buried by younger rocks, they can generally
be assuaset to represent the base of active circulation unless
there i» evidence to the contrary. In these situations the
Type 2 boundary is equivalent to the bottom of the ground-
water regime (see Glossary).
A general knowledge of the tectonic setting and struc-
tural geologic history of the region will provide insight
into the types and frequency of geologic structures to be
found in the classification Review Area. Numerous field
studies have shown that significant ground-water flow in
A-24
-------
consolidated sedimentary and crystalline rocks is controlled
by geologic structures. These feature's include folds,
faults, and associated joints- and fractures in the rock.
Major structures such as fault zones that intersect
consolidated rock formations may hydraulically connect
multiple aquifers into a system of aquifers. Fault zones in
consolidated rocks are known to collect water from large
areas and control the locations of ground-water discharge at
major springs. in uneonsolidated n«dimento and in soae
structural settings, fault zones can have the opposite effect
by producing barriers to flow. Individual joints and small
fractures in consolidated rocks and sediment can be mapped
systematically with field studies; however, proof of their
absence is the more important element in demonstrating the
presence of a Type boundary.
The best evidence of low-permeability, non-aquifer
conditions constituting a Type boundary are those related to
the hydrogeologic setting and measured hydraulic parameters.
The hydraulic conductivity of both sedimentary deposits and
igneous/metamorphic rocks can be estimated within several
orders-of-magnitude on the basis of lithology alone as shown
in Table A-2. In parts of the United States associated with
large ground-water usage, there has been a need to understand
the ground-water regime, and these areas often will have been
studied by various government agencies. Consequently, the
hydraulic properties of aquifers and aquitards will be known
in quantitative terns. In these areas the thickness, lateral
extent, and hydraulic conductivity will be documented. A
favorable condition would then be associated with a recog-
nized aquitard or aquiclude that is known to be relatively
thick, homogeneous, widespread, and poorly permeable. The
optimum head condition would be such that vertical hydraulic
gradients are directed upward through the unit, i.e., across
the Type boundary.
Type ? Boundarj.es; Freshwater/Saline Water Contacts
Type 3 boundaries between bodies of ground water with
contrasting TDS concentrations most commonly occur within the
following types of hydrogeologic settings:
• ar»e-water intrusion into fresh-water aquifers in
coastal regions.
•Saline waters associated with ancient evaporite de-
posits in sedimentary basins.
• Saline waters associated with closed topographic
basins in arid regions.
A-2 5
-------
TABLE A-2
RANGE OF VALUES OF HYDRAULIC CONDUCTIVITY^AND PERMEABILITY
(AFTER FREEZE AND CHERRY, 1979)
Rocks ^nconsol'dof«d K K K K
^ deposits (f MJov) (cm/s) (m/s) (adi/Ae*
\ \
1 |
O "5 T
S £
I
-
1
"3
o
0
„
S 2 o
S « i *
-ST, g
Z o c ,/• .22
SS2ts **•
C5 =S §
Q. S .y- **
c |5 3^
"° ° ° j,*?
•2fJ'|c gl
o£S— — ~~-
^ J'l 1
J 0
CO _
J 1
j «52
i!s if
32 ° i
Ilfl 1
511*?
1*1
1
;
to6
•IO s
!%/
-IO4
-IO 3
-JO2
-10
• f
-10-'
-io-2
- to-3
LtO'4
f
•
•
• 1O"5
to2
-to
-1
• to"
-to-2
- tO"3
-to-4
-to-5
-to-6
-to-7
•to'8
•10'9
•10- l«r*
L1o-7 L,0-»
pi
HO6
-10"
-to-2
-to-3
-to-4
-to-5
-io-6
1C'7
tO'a
to-9
IO"0
to-11
to"2
IO"3
-to5
-to4
-to3
M
•to2
m, ^^^
1 \J
• 1
-1
'irr*
JO
J^^ *
J^J
to-3
to-4
_
to"3
io-7
A-26
-------
• Saline brines in deep geologic basins.
•*
• Geothermal fluids in tectonically active regions.
In the above settings, the IDS of naturally occurring
saline water nay be 3 to 10 times greater than the 10,000
mg/L criterion. Owing to natural concentration gradients, a
zone of diffusion is normally observable between the saline
and fresh ground waters. The 10,000 mg/L TDS isometric
surface will generally be situated within the diffusion zone
separating the waters of contrasting salinities.
Figure A-12 illustrates how a wedge of sea water that
has intruded into an unconfined aquifer is identified as a
separate ground-water unit of higher salinity and density
relative to an adjacent ground-water unit, in the same
aquifer, that contains fresh water. In this setting, there
exists a zone of diffusion between two flow systems that
contain fresh water and sea water. The type 3 salinity
boundary would occur along the 10,000 mg/L TDS isometric
surface.
A second hydrogeologic setting characterized by the
presence of near-surface evaporite deposits overlying deeper
bedrock units is shown in Figure A-13. Salts are dissolved
from the evaporite units by the circulating ground waters,
and a shallow zone of saline waters coexists with fresh
ground waters within the same flow system. However, based on
the delineation of a Type 3 boundary, two distinct ground-
water units can be identified.
Although the saline water is primarily confined to the
low-permeability evaporite formation, this water leaks into
the underlying aquifer creating a zone of diffusion within
the underlying aquifer. The boundary between the. two ad-
jacent ground-water units would be drawn along the 10,000
mg/L TDS isometric surface within the diffusion zone. The
diffusion zone would be a stable feature assuming the flow
system is in both hydraulic and geochemical steady state.
The degree of interconnection between these adjacent ground-
water units) is defined to be intermediate. The type of
setting illustrated in Figure A-13 is not as common i» the
coastal intrusion setting illustrated in Figure A-l, but it
is known to exist in selected parts of the United States.
In the above two settings, the intermediate degree of
interconnection between ground-water units is due to the
limited potential for the exchange of waters across a Type 3
boundary within a diffusion zone. In the first setting, the
salt water and fresh water are in separate, but adjacent flow
systems. In the second case, the diffusion zone is more
extensive and may or may not be within a single flow system.
A-27
-------
FIGURE A-12
EXAMPLE OF TYPE 3 BOUNDARY THROUGH AN
UNCONFINED AQUIFER-IN A COASTAL SETTING
(GROUND-WATER UNIT)
TYPE 3
BOUNDARY
m& SALINE WATER :8^$8W3
>:::*£•:: (GROUND-WATER UNITj SW&ra&W&S
BASE OF AQUIFER
EXPLANATION
- a. -
>30,000mg/l TOS WATER
DIFFUSION ZONE
GROUND-WATER FLOW DIRECTION
WATER TABLE
CLASSIFICATION REVIEW AREA
tO.OOOmf/l TOS ISOCONCENTRATION LINE
A-28
-------
FIGURE A-13
EXAMPLE OF TYPE 3 BOUNDARY IN AN EVAPORITE/SALINE WATER SETTING
UPPER
BEDROCK AQUIFER
(JJPPER GROUND-WATER UNIT
ALLUVIAL
AQUIFER
ZONE OF
DIFFUSION
TYPE 3
BOUNDARY
10,000 MG/L IDS
EXPLANATION
EJlJilllf HIGHLY SALINE WATER
I J DIFFUSION ZONE
_a_ WATER TABLE
^ GROUND-WATER FLOW DIRECTION
CRA CLASSIFICATION REVIEW AREA
-------
A third case involves a single regional flow system with the
diffusion zona in tha deapar and more downgradient and of the
system.
Tha third aatting include* naturally aaline ground vatar
contained within topographically-closed structural basins
within arid parts of the western United States (e.g., the
Great Salt Lake Desert). An example of such a setting wh«re
the water is recharged froa runoff froa mountain ranges
adjoining the basin, circulates to the center of the basin
and discharges to playa lakes and the atmosphere is shown in
Figure A-14. These settings are known to have brine waters
whose salinity greatly exceeds the 10,000 mg/L Class III
criteria within the discharge area to depths as great as 000
feet below land surface.
Distinct ground-water units can be delineated based on
the identification of Type 3 boundaries as shown in Figure A-
14. Under natural conditions, the diffusion zones encom-
passing these boundaries are stable, and ground-water units A
and B can be identified as shown. Large-scale withdrawals
from upgradient fresh ground water or injection into the
saline ground water can laterally displace the diffusion
zone. The pumped wells may eventually yield saline water and
will cease to be sources of drinking water. Thus, the
potential to cause adverse water-quality effects may result
from improper resource management.
Type 3 boundaries are equivalent to the 10,000 mg/L TDS
isometric surface through the ground-water regime. These
boundaries can then easily be recognized and mapped when TDS
data are available for ground waters froa various depths and
locations in the Classification Review Ares. The elevations
at which ground-water TDS is equal to or greater than 10,000
mg/L has been mapped and published for selected basins and
regions. The principal sources for such data are the U.S.
Geological Survey and State geological surveys, especially in
states having abundant oil and gas resources. In areas of
known sea-water intrusion, or upcoming of salt water due to
pumpage, published data are occasionally available that will
show in vertical section or plan view the extent of the salt-
water wedge. This may be conservatively taken as the 10,000
ag/L TO* boundary where more specific TDS data are not
available. In areas of known high-temperature geothermal
resource** published data are available to estimate the Type
3 boundary location. Because these areas are few in number
and are limited in areal extent, fev will be co-located with
potential Classification Review Areas. Equally limited are
data bases for saline-water settings associated with soluble
evaporite deposits. At specific sites in these areas, the
relationship between water quality, soluble strata, and
ground-water flow directions can be established and the Type
3 boundary mapped. This relationship can be assuimd in
adjacent areas, where the stratigraphy and flow patterns are
A-30
-------
FIGURE A-14
EXAMPLE OF TYPE 3 BOUNDARY THROUGH BASIN FILL
IN A CLOSED BASIN/ARID CLIMATIC SETTING
IMPERMEABLE
CRYSTAL tNE
BEDROCK
TYPE 3
BOUNDARY
EXPLANATION
lliljliiljjjl HIGHLY SALINE WATER
[ ___] DIFFUSION ZONE
__f __ WATER TABLE
— GROUND-WATER FLOW DIRECTION
CRA CLASSIHCATION REVIEW AREA
-------
known, in order to extrapolate the Type 3 boundary to other
parts of the Classification Review Area. ^
Tvoe 4 Boundaries? Gradient-Based Boundaries
A Classification Review Area can also be subdivided on
the basis of ground-water flow relationships under certain
specific conditions such as, if the region of the
Classification Review Area that will always remain upgradient
of the facility or activity can be identified as another
ground-water unit. The boundary separating the upgradient
and downgradient regions is termed a Type 4, gradient-based
boundary.
The demonstration of a gradient->ased boundary must show
that the section of the Classification Review Area upgradient
from the facility/activity in question will not be
significantly affected by any releases from such a
facility/activity, even under worst-case conditions. These
conditions would include the maximum sustainable level of
hydraulic stresses associated with waste releases and ground-
water withdrawals that cause the greatest change in ground-
water flow pattern. If it can be shown that a section of the
Classification Review Area would still remain far enough away
in an upgradient or cross-gradient position from the
facility/activity to preclude ground-water movement from the
facility/activity to that section, EPA may recognize a Type 4
boundary separating these two sections.
The gradient-based boundary would generally be associ-
ated with a shallow uppermost aquifer that has a relatively
small water-transmitting capacity (i.e., transmissivity) by
virtue of its low-to-noderate hydraulic conductivity and/or
small saturated thickness. When the transmissivity is small
relative to the ground-water withdrawal rate at a well field,
a steep and areally limited cone of depression develops
around the well field. Ground-water flow pattern alterations
would tend to be smaller and more restricted to the proximity
of the area in which water is being added or withdrawn.
Thet maximum sustainable stress scenario for a worst-case
analysis! would assume two conditions:
• Ground-water withdrawal rates in the non-affected
. upgradient areas would be at the maximum steady
sustainable yield of the aquifer.
• Leachate release rates at the facility/activity would
be at a maximum steady rate given any excess hydraulic
head at the facility/activity as well as the vertical
hydraulic conductivity of earth materials beneath the
facility/activity.
A-32
-------
These stresses and the resulting steady-state ground-water
flow regime within the ground-water unit can be simulated in
order to define the gradient-based boundary. Numerous
computerized flow models are now commercially available to
make this simulation. This type of hydrologic modeling will
involve special skills and professional judgment, but would
not necessarily consume more resources than simulation
modeling needed to support identification of Type 1 and 3
boundaries.
The modeling effort would generally proceed through the
following steps:
e Characterize the key hydraulic parameters governing
flow within the region to be simulated (hydraulic
conductivities, thicknesses, and flow or hydraulic
head conditions along boundaries of the region).
e Determine the areal distribution and magnitude of
pumpage that would permanently draw ground-water
levels down hear the base of the aquifer.
e Simulate the steady-state drawdown and ground-water
levels (heads) across the region and superimpose these
on the pre-existing potentiometric surface of the
aquifer in question.
e Infer the ground-water flow pattern from the simulated
worst-case potentiometric surface.
e Identify the gradient-based boundary on the basis of
flow patterns.
The Type 4 boundary can be recognized as the flowline
that delimits a set of flowline* terminating at the ground-
water withdrawal point* in the upgradient region. An example
of such a limiting flowline is illustrated in Figure A-15.
On the upgradient side of thin flowline, all ground water is
ultimately contained by maximum sustained withdrawals at
hypothetical valla. on the downgradient side, all ground
water continues) flowing around and away from the withdrawal
area. This ground water eventually flows beneath or near the
facility depending on the magnitude of volumetric releases at
the facility. Significant releases can cause mounding of the
water table and a local reversal of ground-water movement in
an upgradient direction. In the particular hypothetical
situation depicted in Figure A-15, this hydraulic stress is
seen to be snail relative to the withdrawal stresses in the
upgradient region.
A-23
-------
FIGURE A-15
* A TYPE 4 GRADIENT-BASED BOUNDARY DEFINED
ON THE BASIS OF SIMULATED- GROUND-WATER FLOW PATTERNS
NON-Aff«cttd
Upgrodient Region
Potentially Affected
Downgradient Region
C R A Boundary
Type 4
Gradient-Based
Boundary
EXPLANATION
Fociity / Activity
Hypothetical center of pumping
Generalized flow direction
Limiting f lowtine / Type 4 Boundary
•V- Stagnation Point
CRA Classification Review Area
A-34
-------
Under the worst-case flow pattern scenario, no ground
water from the facility/activity can cross the limiting
flowline and enter the upgradlent region. The only mechanism
for contaminants to enter the upgradient region would be by
chemical diffusion and mechanical dispersion across the
flowline. Because these mechanisms may be operable under a
worst-case scenario, the Agency considers Type 4 boundaries
to offer an intermediate rather than low degree of
interconnection.
A.3.2 Example of Subdividing a Classification Review Area
Figures A-16 through A-18 illustrate how a hypothetical
Classification Review Area is subdivided into ground-water
units. It should be emphasized that for purposes of an
actual classification decision not all the subdivisions
illustrated here would be necessary, as only the ground-
water relevant to the facility in question would be classi-
fied.
The geology of the Classification Review Area consists
of essentially flat-lying sedimentary formations overlying a
crystalline basement composed of undifferentiated granitic
and metamorphic rocks. Three local aquifers and two aqui-
tards are recognized in the area. The uppermost aquifer is a.
water-table aquifer defined as the saturated part of a sand
and gravel deposit overlying a low-permeability shale forma-
tion. This aquifer is recharged by the infiltration of
precipitation and discharges primarily to the stream and
wetland areas. It is locally used for water supply by
domestic wells in a nearby residential development.
Figure A-16 shows a deeper middle aquifer that is
interbedded between two regionally extensive shales that
serve as aquitard confining beds. Ground water is pumped
from the middle aquifer at a municipal well that supplies
water to a nearby city. The city also receives water pumped
from deeper well* in the lower aquifer; however, these wells
are located on the other side of the city off the left edge
of Figurer A-16. Pumpage from these wells has caused sea
water tot intrude into the lowest aquifer froa the ocean
(located off the right edge of Figure A-16). The lower
aquifer is underlain by crystalline rocks which have low
permeabilities and are not used as an aquifer in the area.
Figure A-17 illustrates the cylinder-shaped volume of
earth material that underlies the Classification Review Area.
The ground-water regime is defined to include all grcur.d
water and earth materials between the water tabla in the
uppermost aquifer and the contact between the lower aquifer
and the basement rocks. Figure A-18 shows how the regime can
A-35
-------
FIGURE A-16
HYPOTHETICAL SETTING FOR DEMONSTRATING THE SUBDIVISION OF A CLASSIFICATION REVIEW AREA
City
i
u>
(ft
iJvirirLTLTirirLriTrLriJiririJiririrvir
rt^tj^-T^-K-!^-T^*^7^^r^Tr^r^iir«L*^-^j^jtL^_*^L**-*^-^ ** ™*-"^TT "*_
^"iTiTirxiririrvirtriTirirvLrLriiJVirir'ir^
-------
FIGURE A-17
HYPOTHETICAL CLASSIFICATION REVIEW AREA
Mlddl*
Low«r
Aquifer
A-37
-------
FIGURE A-18
SUBDIVISION OF A HYPOTHETICAL CLASSIFICATION
AREA INTO THE GROUND-WATER UNITS
TYPE I
BOUNDARY
UNlT I
UNIT 2
TYPE 2
BOUNDARY
UNIT 3
TYPE 2
BOUNDARY
TYPE 3
BOUNDARY
UNJT
-------
be subdivided into five ground-water unit*. For purposes of
an actual classification decision, only the"ground-water unit
that could potentially be affected by the facility would be
pertinent.
Ground-water units 1 and 2 are subdivided along a Type l
ground-water flow divide bourclary beneath the sinuous peren-
nial river. This boundary is inferred from a napping of the
flow pattern within the uppermost aquifer. The aquitard
beneath the aquifer exhibits no evidence of discontinuities
within the Classification Review Area. It is present in all
deep wells in the area and consistently shows large vertical
gradients across it. Even so, the estiaate of the rate of
ground-water flow per unit area through the unit (based on
these gradients and hydraulic conductivities) is no greater
than 10'6 cm/sec, which is negligibly small relative to
ground-water flow rates in adjacent aquifers. Based on these
characteristics, the aquitard constitutes a Type 2 low
hydraulic conductivity, non-aquifer boundary. The vertical
extent of ground-water units 1 and 2 is thus delineated by
the existence of this physical boundary.
Ground water within the middle aquifer is identified as
a third ground-water unit with the overlying and underlying
aquitards constituting Type 2 boundaries. In addition to the
characteristics described above for the uppermost aquitard,
long-term aquifer tests have been performed on the municipal
wells completed in the middle and lower aquifer. These tests
indicate that less than 10 percent of water pumped from the
aquifers is derived from the leaking aquitards, thus their
designation as Type 2 boundaries is justified.
Ground water within the lower aquifer is generally
moving towards a major pumping center located outside of the
Classification Review Area. A significant part of the water
in this aquifer has been replaced by sea water having IDS
concentrations in excess of 30,000 mg/L. The problem has
been studied by the U.S. Geological Survey in cooperation
with the city. The movement of the interface between fresh
and saline water is being monitored with a few deep wells
(not shown in the illustrations). The approximate location
of the interface at the time of subdivision was approximately
known and, lacking specific TDS data, is taken as the 10,000
mg/L TO* Type) 3 boundary separating ground-water units 4 and
5 on Figur* A-18. Because the actual 10,000 mg/L TDS
boundary is probably several hundred feet further towards the
wej.1 field, use of the interface as this boundary makes
ground-water unit 4 larger and unit 5 smaller than they may
actually be. However, lacking specific data, such use of
reasonable and conservative assumptions is necessary and
appropriate.
A-39
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A. 4 Appendix A References
Freeze, R.A. and J.A. Cherry, 1979. Groundwater. Prentice-
Hall, Inc. Englewood Cliffs, NJ.
Geraghty fc Killer, Inc., 1984. Stochastic Model of Correc-
tive Action costs at Hazardous Waste Management Facili-
ties. Final Report prepared for USEPA, office of Solid
Waste; Annapolis, Maryland.
Heath, R.C., 1984. Ground-Water Regions of the United
States. U.S. Geological Survey Paper 4, U.S. Government
Printing Office, Washington, DC.
Todd, David X., 1976, Ground Water Hydrology, John Wiley 6
Sons, Inc., New YorJc.
U.S. Environmental Protection Agency, 1985. Draft Report-
Liner Location Risk and Cost Analysis Model. Appendix
c. Office of Solid Waste, Economic Analysis Branch;
Washington, DC
A-40
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APPENDIX B
SUPPLEMENTAL INFORMATION
FOR CLASS I PROCEDURES
-------
APPENDIX B
SUPPLEMENTAL INFORMATION FOR CLASS I PROCEDURES
B.I Densely Settled Criterion
The determination of a substantial population is related
to private wells in a densely settled area (i.e., a census-
designated densely settled area). Urbanized areas and Census
Designated Places (CDPs) also by definition are densely
settled. The latter are unincorporated places with a
population density of at least 1,000 persons per square mile
(e.g., 500 persons located within a 0.5 square mile area).
They are outlined on Census tract naps for metropolitan areas
and on block-numbering area maps in non-metropolitan areas of
less than 10,000 people.
Key terms used by the Census Bureau are as follows:
e Metropolitan statistical area (MSA): (a) a city of
at least 50,000 population, or (b) a Census Bureau-
defined urbanized area of at least 50,000 with a
total metropolitan population of at least 100,000
(75,000 in New England). There are 277 HSAs (as of
June 30, 1984). Every state has at least one MSA.
• Urbanized area (UA): a population concentration of
50,000 or more, generally consisting of a central
city together with its surrounding densely settled
contiguous territory or suburbs (the urban fringe).
There are about 420 UAs.
e Prban place; any population living within urbanized
areas; or places of 2,500 or more people outside
urbanized areas.
e Densely nettled area; not an official statistical
division, but used by the Census Bureau to indicate
an area with a population density of at least 1,000
persons per square mile within an urbanized area or
Census Designated Place (CDP).
B-l
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Urbanized Areas nay include areas which do not qualify
as densely settled (e.g., leas than 1,000 persons per square
mile) but are included within such geographic boundaries
because of one of the following reasons:
e Eliminate enclaves of less than 5 square miles
which are surrounded by built-up areas.
• Close indentations in the boundaries of densely
settled areas that are no more than 1 mile across
the open end and encompass no more than 5 square
miles.
• Link outlying areas of qualifying density, provided
that the outlying areas are as follows:
Connected by road to, and are not more than 1 1/2
miles from, the main body of the urbanized area.
Separated from the main body of the urbanized area
by water or other undevelopable area, are connected
by road to the main body of the urbanized area, and
are not more than 5 miles from the main body of the
urbanized area.
e Are nonresidential urban areas (e.g., industrial
parks, office areas, or major airports), which have
at least one-quarter of their boundaries contiguous
to an urbanized area.
MS As and their components are listed in the i960 census
of Population -Supplementary Report; Metropolitan Statis-
tical Areas and are mapped on State MSA outline maps.
Urbanized area (UA) outline maps are generally contained
within MSA publications.
B.2 Use of 6EXS System for Estimating Well Density
Onsj Beans of estimating private well usage in areas
where no local information on private wells is available is
to use* population data for the area of interest available
through the Graphical Exposure Modeling System (GEMS)
maintained by EPA's office of Toxic Substances (OTS), or a
private census data service.
Information on the GEMS system is available from EPA's
OTS modeling team. Using the GEMS Census Data (CO) pro-
B-2
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cedure, it is possible to retrieve population and housing
count data from the 1980 Census for circular areas around a
point, which can be designated using latitude and longitude
coordinates or the ZIP code of the location. The system
provides information within defined concentric rings ranging
from 0.1 to 10,000 km in radii. It is necessary to supply
the number of sectors into which the rings are divided; the
procedure allows from 1 to 16. Sectors are numbered clock-
vise with the first sector centered at zero degrees (the
north compass point direction). The program tabulates total
population and housing counts by ring distance and sector. A
simple mathematical conversion can be used to transform the
population counts into density.
The manner in which population data are recorded by the
Bureau of the Census and reported by GEMS can result in
reports of no population for some areas where people are
living. This information can be verified or corrected by
consulting local officials. It is unlikely that such areas
would satisfy the densely settled test, however.
B.3 General Background Information on Institutional Con-
straints
Institutional constraints on the availability of water
can arise from at least six general sources. Each of these
is discussed below.
State Law
State law creates basic rights to the withdrawal and use
of surface and ground water. For example, State law may
regulate the rights to or ownership of water; the withdrawal,
uses, and allocation of water; conjunctive use of surface and
ground water; protection of in-stream users; and measures
required to protect ground water. The law in most states,
however, does not create a right to unlimited amounts of
water, and may restrict where the water may be used (Council
of State Governments, 1983). The States have created
different methods for establishing rights to water and
resolving conflict* over rights to withdraw and use water.
There are three major systems of regulation of water with-
drawal and use:
• The Eastern (common law) doctrine, used in about 3?
states, provides that ownership of land carries with
it a right to water in adjacent lakes or watercourses
(a riparian right) and to water beneath the land.
B-3
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The use of the water, however, nay be restricted.
Under the absolute use doctrine, itT is possible for a
landowner to withdraw unlimited amounts of water,
without liability for damage to other landowners, and
to transport the water off the land. Under the
reasonable-use doctrine, it is possible to withdraw
an amount of water necessary for the use or enjoyment
of the overlying land, but the water may not be tran-
sported away from that land. Under the correlative-
rights doctrine, the right to withdraw ground water
is based on the relationship between the size of the
aquifer and the area of the overlying land.
e The Western (appropriation) doctrine, used in about
13 states, provides that water is a public resource,
and right* to water may be acquired by actual use.
Conflicts in priority of use are ordinarily settled
by the principle of "first in time, first in right."
Hierarchies of use, however, may also be established.
e Permit systems, used in about 31 states, may be used
in conjunction with the common law or appropriation
doctrines, and may be applied to surface and/or to
ground water. Rights to water under a permit system
are acquired by application to a regulatory author-
ity. If the authority determines that no superior
claim exists to the water, it records the claim,
issues a permit for use, and polices the actual use.
Permit systems may co-exist with other forms of water
regulation, such as designated ground-water protec-
tion zones or management areas. Many permit systems
specify priorities for different types of uses of
water (beneficial uses), generally making domestic
use, such as drinking water, the highest beneficial
use and Baking other uses, such as commercial or
industrial use and irrigation, lower beneficial uses.
Conflicts among users, or prospective users, of water
are resolved by most states in three ways: the conflict may
be decided by the administrative organization that ad-
ministers the water rights system in the State, particularly
if water use; permits are required; special organizations may
be crea&stf to resolve water disputes; and the State or local
courts Wj&- resolve; disputes. State lav in certain circum-
stances My allow the use of eminent domain powers to shift
water from one use to another, or to allow physical access to
water, ' and State law may grant the use of eminent domain to
the Federal government for certain purposes. Frequently,
when insufficient water exists for all claimed uses, lower
beneficial uses may give way to higher beneficial uses.
Some states have attempted by law ,to restrict or
preclude the export of water to users in other states, either
B-4
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by requiring legislative approval of water exports, by
requiring reciprocity agreement* with the' states receiving
the water, or by absolute prohibitions. All of these forms
of restriction have recently been subject to legal challenge.
A number of states, particularly in the West, designate
ground-water protection zone* or management areas, and seek
to coordinate surface- and ground-water use (conjunctive
management). Measures of conjunctive management may include
restrictions on punping ground water, requirements for
aquifer recharge, and well spacing requirements. Some states
(e.g., Texas, Nebraska) delegate aquifer protection authority
to local administrative bodies.
Federal Law
As a user of water, the Federal government generally
defers to state regulation of water. Federal laws often
pertain to Federal and Indian reserved rights to water and
Federal activities affecting water. In common law states,
Federal rights to water are linked to ownership or control of
land. In prior appropriation and permit states, Federal
agencies (e.g., the Bureau of Reclamation) register claims to
water. The Federal government may, however, have special
access to water in certain circumstances. Statutes (e.g.,
the Oil and Gas Well Conversion Act) or executive orders
(e.g., the Executive Order of April 17, 1926) may reserve
water rights on Federal public lands for particular purposes.
For certain categories of Federal lands withdrawn from
the public domain and reserved for such uses as national
forests, wildlife refuges, and parks, Federal reserved rights
doctrine can provide access to water irrespective of state
law. The courts have created this doctrine, which holds
generally that reservation of public domain lands for a
particular purpose carries with it an implied reservation of
sufficient water to satisfy the purposes for which the land
was reserved. The right is not created by use or lost
through non-use. Therefore, in certain circumstances, even
if the water is being used by another person, the Federal
government can obtain water for its own use. The purpose of
the watar i» determined as of the time the land reservation
was created, and the reserved right is limited to that
purpose. (For exaaple, if the reservation was created to
provida agricultural land, reserved rights to irrigation
water nay exist, but there are no reserved rights to water
for industrial purposes.)
An Indian-reserved right, similar to the Federal
reserved right, has also been created by the courts. This
doctrine is apparently based on the presumption that in
creating an Indian reservation ths resident and/or Congress
intended to reserve sufficient water for the use of the land.
Indians may hold superior rights to water connected with
B-5
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reservation lands. Apparently, such rights may be sold,
although it is unclear whether only the amount of water
actually being used or the. entire potential right may be
transferred. in addition to reserved rights, in a few
instances Indians also hold special water rights based on
treaties (e.g., Treaty of Guadalupe Hidalgo).
Federal water resource agencies, such as the Corps of
Engineers, the Bureau of Reclamation, and the Soil Conser-
vation Service, as well as such Federally chartered agencies
as the Tennessee Valley Authority and the Bonneville Power
Authority, can affect water availability, either through the
water rights that they hold or through their decisions
concerning water management (Congressional Budget Office,
1983). Numerous other Federal agencies and laws can affect
water-resource decisions indirectly. Examples of such
agencies or laws include the Forest Service and Bureau of
Land Management (right-of-way decisions), the Fish and
Wildlife Service (requirements under the Fish and wildlife
Coordination Act), the National Environmental Policy Act
(Environmental Impact Assessment requirements), Clean Water
Act (dredge and fill permit requirements), and the Wild and
Scenic Rivers Act and National Wilderness Preservation
requirements.
Interstate Compacts
Conflicts among two or more states or the Federal
government concerning rights to water in streams generally
are resolved either through interstate compacts or through
litigation (Clyde, 1982, 1984; Schwartz, 1985; Sporhase vs.
Nebraska, 1984). The result in either case is usually a
decision allocating the in-stream flow among the states
claiming the water. In a few cases, ground water has also
been allocated among states by interstate compact or court
decision.
Interstate compacts are agreements among states that
have been ratified by the legislatures of the participating
states and the U.S. Congress. The compact creates a binding
law within the participating states and a binding contract
among the states. In certain cases, the Federal government
also joins the compact, and the compact is then also binding
on they Federal government. The members and powers of the
compacts* currently in existence vary widely, from bilateral
agrecMifts) (e.g., Snake River Compact between Idaho and
Wyoming} to agreements affecting large numbers of states
(e.g., Colorado River Compact), and from compacts exclusively
devoted to. allocating river water (e.g., Arkansas River
Compact of 1949) to compacts establishing regional multi-
purpose water resources management (e.g., Delaware River
Basin Compact). Approximately 25 interstate compacts
currently are in operation.
B-6
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In the absence of a resolution of Conflicting claims
through an interstate compact, litigation among states before
the U.S. Supreme Court may be the only means to resolve the
conflict. in deciding such cases, the Court ordinarily
attempts to carry out "an equitable apportionment of the
interstate stream. Because the Court has been called upon
less frequently to resolve disputes among states over ground
water, the standard used in such cases is less clear.
Local Regulations
Local administrative bodies with jurisdiction over
sources of water in particular areas may exercise powers such
as well spacing and pumping rates that affect the avail-
ability of water. As previously nottd, State legislatures
may delegate power to local bodies to administer particular
aspects of the water allocation or water protection system in
the state. Examples of such local agencies include under-
ground water conservation districts (Texas), which are
empowered to provide for spacing of wells and to regulate
well pumping in order to minimize the drawdown of the water
table; ground-water management districts (California), which
are authorized to manage ground-water withdrawals; and water
conservation districts (Nebraska), which are authorized to
regulate ground-water use. Other special purpose districts
may also affect water availability. The Texas Harris-
Galveston coastal subsidence district, for example, is
authorized to regulate withdrawal of ground water in order to
limit land subsidence.
Treaties and International Laws
Treaties between the United States and its neighbors,
Mexico and Canada, allocate the waters of rivers flowing
between the countries. The 1944 Treaty of Utilization of the
Waters of the Colorado and Tijuana Rivers and the Rio
Grande, for example, apportions the waters of those rivers
between the two countries and creates an International
Boundary and Water Commission (IBWC) to apply the treaty and
settle disputes. Although ground water use is not fully
covered by the treaty, the IBWC has attempted to address the
management of International ground-water resources.
In addition to treaties signed by the United States,
certain international law proposals being developed by the
United Nation* and the International Law Association may
sometime in the future establish general principles for the
allocation of ground and surface waters between two coun-
tries.
Property Law
State lav governs the ownership and use of land. In
particular, property law affects physical access to water
3-7
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supplies through restrictions on rights of way and easements,
or defining powers of eminent domain. State and local lavs
generally regulate land use and access to land by persons who
are not. landowners. Access to water, including the location
of pipes, storage, pumping, treatment, and other facilities,
can be delayed or restricted by the property rights of
persons whose land must be crossed or used for such
facilities. Special procedures, such as easements, eminent
domain, and condemnation, may be required to obtain necessary
rights-of-way. Special procedures vary from state to state.
B.4 List of offices of Endangered Species, U.S. Fish and
Wildlife Services
The Fish and wildlife Service, a unit of the U.S.
Department of the Interior, has been delegated the main
responsibility for coordinating national and international
efforts on behalf of Endangered Species.
In the case of marine species, however, actions are taken in
cooperation with the Secretary of Commerce, through the
Director of the National Marine Fisheries Service. simi-
larly, in the area of import/export enforcement for Endan-
gered plants, the Department of Interior cooperates with and
is assisted by the Department of Agriculture through the
Animal and Plant Health Inspection Service.
PROGRAM MANAGER—ENDANGERED SPECIES
Associate Director-Federal Assistance
U.S. Fish and Wildlife Service
U.S. Department of the> Interior
Washington, D.C. 20240
Telephone: 202/343-4646
CATEGORY COORDINATOR—ENDANGERED SPECIES
Deputy Associate Director—Federal Assistance
U.S. Fish and Wildlife Service
w.s. Department of the Interior
Washington, D.C. 20240
Telephone: 202/343-4646
Office of Prograa Development and Administration
U.S. Fish and Wildlife Service
1000 North Glebe Road, Room 629
Arlington, Virginia
Telephone: 703/235-1726, 7, 8
B-8
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Mailing Address for Office of Program Development
and Administration
U.S. Fish and wildlife Service
Washington, D.C. 20240
Office of Endangered Species
U.S. Fish and Wildlife Species
1000 North Glebe Road, Suite 500
Arlington, Virginia
Telephones 703/235-2771, 2
Mailing Address for Office of Endangered Species
U.S. Fish and wildlife Service
Washington, O.C. 20240
Branch of Biological Support
Telephone: 703/235-1975, 6, 7
Branch of Management Operations
Telephone: 703/235-2760, 1, 2
Federal Wildlife Permit Office
U.S. Fish and Wildlife Service
1000 North Glebe Road, suite 600
Arlington, Virginia
Telephone: 703/235-1937, 8, 9
Mailing Address for Federal Wildlife Permit Office
U.S. Fish and Wildlife Service
Washington, O.C. 20240
Division of Lav Enforcement
U.S. Fish and Wildlife Service
1735 K Street, NW., Third Floor
Washington, D.C.
Telephone! 202/343-9242
P.O. Box 28006
Washington, O.C. 20005
Sp«cial~Ag«nt-in-Charge, Branch of Investigations
Telephone: 202/343-9242
B-9
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Office of the Scientific Authority
U.S. Fish and Wildlife Service
1717 H Street, NW. , Room 536
Washington, D.C.
Telephone: 202/653-594-8, 49, 50
Mailing Address for Office of the Scientific Authority
U.S. Fish and. Wildlife Service
Washington, O.C. 20240
Regional Endangered Species Coordinators
The U.S. Fish and wildlife Service is comprised of seven
Regional Offices. Each office has a senior official who has
been designated as a Regional Endangered Species Coordinator.
Additionally, each of the regions has several Field Offices.
Problems of a local nature should be referred to these
offices.
Region 1 Regional Director
U.S. Fish and Wildlife Service
Suite 1692, Lloyd 500 Building
500 NE. Multnomah Street
Portland, Oregon 97232
Telephone: 503/231-6131 (FTS: 8/429-6131)
Field Offices
California
1230 "N" Street, 14th Floor
Sacramento, California 95814
Telephone: 916/440-2791 (FTS: 8/448-2791)
Idaho
4696 Overland Road, Room 566
Boise, Idaho 83705
Telephone: 208/334-1806 (FTS: 8/554-1806)
Great Bavin Complex
4«*0 Kietzke Lane, Building C
Reno, Nevada 89502
Telephone: 702/784-5227 (FTS: 8/470-5227 or
• 5228)
Washington/Oregon
Building-3, 2625 ParJcmont Lane
Olympia, Washington 98502
Telephone: 206/733-9444 (FTS: 8/434-9444)
B-10
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Pacific Islands Administrator
300 Ala Moana Boulevard, Room 5302 "
P.O. BOX 50167
Honolulu, Hawaii 96850
Telephone: 808/546-5608 ' (FTS: 8/546-5608)
Region 2 Regional Director
Endangered Species Specialist
U.S. Fish and Wildlife Service
500 Gold Avenue, SW.
P.O. Box 1306 -
Albuquerque, New Mexico 87103
Telephone: 505/766-3972 (FTS: 8/474-3972)
Field Offices
Arizona
2934 West Fairmont Avenue
Phoenix, Arizona 85017
Telephone: 602/241-2493 (FTS: 8/261-2493)
New Mexico
P.O. BOX 4487
Albuquerque, New Mexico 87196
Telephone: 505/766-3966 (FTS: 8/474-3966)
Oklahoma/Texas
222 South Houston, Suite A
Tulsa, Oklahoma 74127
Telephone: 918/581-7458 (FTS: 8/736-7458)
Texas
C/o CCSU, Box 338
6300 Ocean Drive
Corpus Christ!, Texas 78411
Telephone: 512/888-3346 (FTS: 8/734-3346)
Fritz Lanham Building, Room 9A33
819 Taylor Street
Port Worth, Texas 76102
Telephone: 817/334-2961 (FTS: 8/334-2961)
Region j Regional Director
Endangered Species Specialist
• U.S. Fish and wildlife Service
Federal Building, Fort Snelling
Twin Cities, Minnesota 55111
Telephone: 612/725-3276 (FTS: 8/725-3276)
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Region 4 Regional Director „
Endangered Species Specialist
U.S. Fish and wildlife Service
The Richard B. Russell Federal Building
75 Spring Street SW.
Atlanta, Georgia 30303
Telephone: 404/221-3583 (FTS: 8/242-3583)
Field Offices
Alabaroa/Arkansaa/Louisiana/Misaissippi
Jackson Mall Office Center
300 Woodrow Wilson Avenue, Suite 3185
Jackson, Mississippi 39213
Telephone: 601/960-4900 (FTS: 8/490-4900)
Florida/Georgia
2747 Art Museum Drive
Jacksonville, Florida 32207
Telephone: 904/791-2580 (FTS: 8/946-2580)
Kentucky/North Carolina/South Carolina/Tennessee
Plateau Building, Room A-5
50 South French Broad Avenue
Asheville, North Carolina 28801
Telephone: 704/258-2850 ext. 382
(FTS: 8/672-0321)
Puerto RicoZVirqin Islands
P.O. Box 3005
Marina Station
Mayaguez, Puerto Rico 00709
Telephone: 809/833-5760 (FTS: 8/967-1221)
Region 5 Regional Director
U.S. Fish and wildlife Service
Suite 700, On* Gateway Center
Newton Corner, Massachusetts 02158
Telephone: 617/965-5100 ext. 316
(FTS: 8/829-9316, 7, 8)
Field Office*
Cfltuietcticut/Mainc/Varmont/Massachusetts/New
Hpup^htt^/Rhode Island
P.O. BOX 1518
•Concord, New Haapshire 03301
Telephone: 603/224-9558, 9 (FTS: 8/834-4726)
District of Colufflfrjaypelaware/Marvland
Virginia/West Virginia
1825 Virginia Street
Annapolis, Maryland 21401
Telephone: 301/269-6324 (FTS: 8/922-4197)
B-12
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New Jersey/Pennsylvania ^
112 West Foster Avenue -
State College, Pennsylvania 16801
Telephone: 814/234-4090 (FTS: 8/727-4621)
New York
100 Grange Place
Cortland, Naw York 13045
Telephone: 607/753-9334 (FTS: 8/882-4246)
Region 6 Regional Director
U.S. Fish and Wildlife Service
P.O. Box 25486, Denver Federal Center
Denver, Colorado 80225
Telephone: 303/234-2496 (FTS: 8/234-2496)
Field Offices
Colorado/Utah
Room 1406, Federal Building
125 S. State Street
Salt Lake City, Utah 84138
Telephone: 801/524-4430 (FTS: 8/588-4430)
Kansas/Nebraska/North Dakota/South Dakota
223 Federal Building
P.O. Box 250
Pierre, South Dakota 57501
Telephone: 605/224-8692 (FTS: 8/782-5226)
Montana/Wyoming
Federal Building, Rooa 3035
316 North 26th Street
Billings, Montana 59101
Telephone: 406/657-6059 or 6062
(FTS: 8/657-6059)
Region 7 Regional Director
1011 E. Tudor Road
Anchorage, Alaska 99503
Telephone: 907/786-3435
(FTS: 8/907/786-3435)
B-13
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B.5 List of State Natural Heritage Program Offices (October
1985)
Nongame Branch
ARIZONA HERITAGE PROGRAM
Arizona Game & Fish Department
2222 W. Greenway Road
Phoenix, Arizona 85023
Telephone: 602/942-3000 ext. 245
ARKANSAS NATURAL HERITAGE INVENTORY
225 E. Markham, Suite 200
Little Rock, Arkansas 72201
Telephone: 501/371-1706
CALIFORNIA NATURAL DIVERSITY DATABASE
c/o CA Department of Fish 6 Game
1416 9th Street
Sacramento, California 95814
Telephone: 916/322-2493
COLORADO NATURAL HERITAGE INVENTORY
Department of Natural Resources
1313 Sherman Street, Room 718
Denver, Colorado 80203
Telephone: 303/266-3311
CONNECTICUT NATURAL DIVERSITY DATABASE
Natural Resource center
Department of Environmental Protection
State Office Building, Room 553
165 Capitol Avenue
Hartford, Connecticut 06106
Telephone: 203/566-3540
FLORIDA NATURAL AREAS INVENTORY
254 E. 6th Avenue
Tallahassee, Florida 32302
Telephone: 904/224-8207
HAWAII HERITAGE
1116 Smitt* Street, #201
Honolulu, Hawaii 96817
Telephone: 808/537-4508
IDAHO NATURAL HERITAGE PROGRAM
4696 overland Road, Suite 518
Boise, Idaho 83705
Telephone: 208/334-3402 or 3649
B-14
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INDIANA HERITAGE PROGRAM
Division of Nature Preserves, IN DNR
612 State Office Building
Indianapolis, Indiana 46204
Telephone: 317/232-4078
IOWA NATURAL AREAS INVENTORY
State Conservation Commission
Wallace State Office Building
Des Moines, Iowa 50319
Telephone: 515/281-8524
KENTUCKY HERITAGE PROGRAM
Kentucky Nature Preserves commission
407 Broadway
Frankfort, Kentucky 40601
Telephone: 502/564-2866
LOUISIANA NATURAL HERITAGE PROGRAM
Department of Natural Resources
Coastal Management Division
P.O. BOX 44124
Baton Rouge, Louisiana 70804-4124
Telephone: 504/342-4602
MAINE NATURAL HERITAGE PROGRAM
Maine Chapter
122 Main Street
Topsham, Maine 04086
Telephone: 207/729-5161
MARYLAND NATURAL HERITAGE AND ENVIRONMENTAL REVIEW
Department of Natural Resources
C-3, Taves state Gfflce Building
Annapolis, Maryland 21401
Telephone: 261-1402, 3656 or 269-3656
MODEL NATURAL HERITAGE PROGRAM
The Nature Conservancy
1800 N. Kent Street, suite 800
Arlington, Virginia 22209
Telephone: 703/841-5307
MASSACHUSETTS HERITAGE PROGRAM
Division of Fisheries and Wildlife
100 Cambridge Street
Boston-, Massachusetts 02202
Telephone: 517/727-9194
MICHIGAN NATURAL FEATURES INVENTORY
Mason Building, 5th floor
Box 30028
Lansing, Michigan 48909
Telephone: 517/373-1552
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MINNESOTA NATURAL HERITAGE PROGRAM
Department of Natural Resources
Box 6
St. Paul, Minnesota 55155
Telephone: 612/296-4284
MISSISSIPPI NATURAL HERITAGE PROGRAM
111 N. Jefferson street
Jackson, Mississippi 39202
Telephone: 601/354-7226
MISSOURI NATURAL HERITAGE INVENTORY
Missouri Department of Conservation
P.O. Box 180
Jefferson City, Missouri 65102
Telephone: 314/751-4115
MONTANA NATURAL HERITAGE PROGRAM
State Library Building
1515 E. 6th Avenue
Helena, Montana 59620
Telephone: 406/444-3009
NAVAJO NATURAL HERITAGE PROGRAM
Box 2429
Window Rock, Arizona 86515-2429
Telephone: 602/871-6453 or 5449
NEVADA NATURAL HERITAGE PROGRAM
Department of Conservation and Natural Resources
c/o Division of State Parks
Capitol Complex, Nye Building
201 S. Fall Street
Carson City, Nevada 89710
Telephone: 702/885-4360
NEW HAMPSHIRE NATURAL HERITAGE PROGRAM
c/o Society for the Protection of N.H. Forests
54 Portsmouth Street
Concord, New Hampshire 03301
Telephone: 603/224-8945
NEW JERSW NATURAL HERITAGE PROGRAM
Office oft natural Land* Management
109 w. S«ate street
Trenton, Sttv Jersey 08625
Telephones 609/984-1339 or 1170
NEW MEXICO NATURAL RESOURCES SURVEY SECTION
Villagra Building
Santa Fe, New Mexico 87503
Telephone: 505/827-7862
B-16
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NEW YORK NATURAL HERITAGE PROGRAM
Wildlife Resources Center
Delmar, New YorJc 12054-9767 .
Telephone: 518/439-8014 ext. 203
NORTH CAROLINA NATURAL HE'RITAGE
Jepartment of Natural and Economic Restoration
Division of State Parks
Box 27687
Raleigh, North Carolina 27611
Telephone: 919/733-7795
NORTH DAKOTA NATURAL HERITAGE INVENTORY
North Dakota Game and Fish Department
100 N. Bismarck Expressway
Bismarck, North Dakota 58501
Telephone: 701/221-6310
OHIO NATURAL HERITAGE PROGRAM
Ohio DNR, Division of Natural Areas and Preservation
Fountain Square, Building F
Columbus, Ohio 43224
Telephone: 614/265-6453
OKLAHOMA NATURAL HERITAGE PROGRAM
Oklahoma Tourism and Recreation Department
500 will Rogers Building
Oklahoma City, Oklahoma 73105
Telephone: 405/521-2973
OREGON NATURAL HERITAGE PROGRAM
Oregon Field Office
1234 NW 25th Avenue
Portland, Oregon 97210
Telephone: 503/228-9550
PENNSYLVANIA NATURAL DIVERSITY INVENTORY
Bureau of Forestry
Department of Environmental Resources
34 Airport Road
Middletown, Pennsylvania 17057
Telephone: 717/783-1712
PROGRAMA PRO-PATRIMONIC NATURAL
Apartado 5887
Puerta de Tierra, Puerto Rico 00906
Telephone: 809/724-0960
RHODE ISLAND HERITAGE PROGRAM
Department of Environmental Management
Division of Planning and Development
22 Hayes Street
Providence, Rhode Island 02903
Telephone: 401/277-2776
B-17
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SOUTH CAROLINA HERITAGE TRUST
S.C. Wildlife and Marine Resources Department
P.O. BOX 167
Columbia, South Carolina 29202
Telephone: 803/756-0014
SOUTH DAKOTA NATURAL HERITAGE
South Dakota Department of Game, Fish & Parks
Division of Parks and Recreation
Sigurd Anderson Building, 3-114
Pierre, South Dakota 57501
Telephone: 605/773-4226
TENNESSEE HERITAGE PROGRAM
ECOLOGICAL SERVICES DIVISION
Tennessee Department of Conservation
701 Broadway
Nashville, Tennessee 37203
Telephone: 615/742-6545
TEXAS NATURAL HERITAGE PROGRAM
General Land Office
Stephen F. Austin Building
Austin, Texas 78701
Telephone: 512/475-0660, 0661, 0621, 0800
TVA REGIONAL HERITAGE
Office of Natural Resources
Morris, Tennessee 37828
Telephone: 615/494-5600
VERMONT NATURAL HERITAGE PROGRAM
Vermont Field Office
138 Main Street
Montpelier, Vermont 05602
Telephone: 802/229-4425
WASHINGTON NATURAL HERITAGE PROGRAM
Department of Natural Resources
Mail Stop EX-13
Olympia, Washington 98504
Telephone: 206/753-2448
WEST VUHZVZA WILDLIFE/HERITAGE DATABASE
wildlifar Resources Division
DNR Operations Center
P.O. BOX 07
Elkins, West Virginia 26241
Telephone: 304/636-1767
B-18
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WISCONSIN NATURAL HERITAGE PROGRAM
Endangered Resources/4
Department of Natural Resources
101 S. Webster Street, Box 7921
Madison, Wisconsin 53707
Telephone: 608/266-0924
WYOMING NATURAL HERITAGE PROGRAM
1603 Capitol Avenue, Rooa 323
Cheyenne, Wyoming 82001
Telephone: 303/860-9142
NATIONAL OFFICE HERITAGE TASK FORCE
Vice President, Science 841-^320
Director, Heritage 841-5325
Assistant Director 841-5367
Director, PS&D 841-5322
Budget Specialist 841-5368
National Ecologist 217/367-8770
Classification Ecologist 217/367-8770
Director, National Database 841-5361
National Databases Associate 841-5360
National Information Manager 841-5360
Microcomputer Analyst 841-5355
Microcomputer Specialist 841-5355
Senior Programmer/Analyst 841-5356
Administrative Assistant,HFA 841-5354
Part-time Secretary, HFA 841-5354
Executive Secretary, Science 841-5321
REGIONAL
EASTERN HERITAGE TASK FORCE
The Nature Conservancy
294 Washington Street
Boston, Massachusetts 02108
Telephone: 617/542-1908
r,
MIDWEST HERITAGE TASK FORCE
Midwest Regional Office
The Nature Conservancy
1313 Fifth Street, SE
Minneapolis, Minnesota 55414
Telephone: 612/379-2207
ROCKY MOUNTAIN HERITAGE TASK FORCE
The Nature Conservancy
1370 Pennsylvania Street, Suit* 190
Denver, Colorado 60203
Telephone: 303/860-9142
B-19
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B.6 Appendix B References
Council of State Governments, Interstate Compacts and
Agencies. 1933, provides annual listing of names and
phone numbers of commissioners of interstate compacts
and compact administrators and citations to state and
Federal legislature enactments of components.
U.S. Bureau of Census, statistical Abstract of the US: 1986
(107th edition), Washington, DC 1986.
B-20
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APPENDIX C
SUPPLEMENTAL INFORMATION
FOR CLASS III PROCEDURES
-------
APPENDIX C
SUPPLEMENTAL INFORMATION FOR CLASS III PROCEDURES
C.I Overview of Treatment Technologies
The following discussions of treataent technologies
indicate the typical area of application and limitations of
particular significance and the potential problems encoun-
tered when treating water that contains multiple contami-
nants. A series of references that can be used for general
background data is included. Many treatment processes,
particularly those used in water polishing, develop reduc-
tions in treataent efficiencies in the presence of inter-
fering contaminants, so that pretreatment is required. In
existing water-treatment facilities, pretreatment require-
ments are net by employing successive processes — in an
order that progressively removes various interferences. For
example, a facility that receives a water with high levels of
adsorbable organics and high suspended solids may use
granular media filtration prior to carbon adsorption in an
effort to minimize the levels of solids in the influent to
the carbon adsorption; the load of solids to the adsorption
column will disrupt this process.
If several processes in a treatment configuration have
disruptive interference problems, the particular combination
of processes cannot be reasonably employed to treat the
water. This situation might occur if an influent contained
high levels of dissolved organics and inorganic chemical
oxidants, and the treataent configuration under consideration
was a combination of desalination and ion exchange. The
dissolved organics, which would be removed by desalination,
could aavarely disrupt the ion exchange efficiencies, while
the chemical oxidants (removable by ion exchange) could
disrupt th« desalination process. This particular treatment
configuration would, in this instance, be eliminated from
further consideration because additional pretreatoent would
be required to manage the chemical interferences.
c-l
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Air Stripping/Aeration
Air stripping and aeration can be used for removal of
volatile contaminants from ground water, as well as for
introduction of oxygen to the water. Air is passed through
the water or the water is finely sprayed into the air,
enhancing transfer of dissolved gases from the water to the
air, which may be treated further or discharged. Cost-
effective and efficient treatment requires continuous or
semicontinuous flow. The process has been used for ammonia
removal, hydrogen sulfide removal, and volatile organic
carbon removal in both water and wastewater treatment
operations. The treatment efficiencies and design are a
function of the contaminant loading to the air, water ratio,
the length of contact time, contaminant volatility, and
temperature. Removal efficiencies of volatile organics
ranging from 10 percent to greater than 99.0 percent have
been reported in the literature.
Although air stripping is a relatively inexpensive
technology for removal of volatile contaminants, its use in
public water-supply systems to date has been somewhat
limited. Its limited use is due primarily to a lack of need
for the technology, which is in widespread use in Super fund
remedial action and wastewater treatment operations.
Traditional aeration, which is in common use among public-
water utilities, has typically been installed to provide
oxygenation of waters, and the removal of volatile con-
taminants is merely a beneficial side-effect.
Temperature limitations in regions experiencing severe
winters may be such that air stripping and aeration processes
must be housed indoors or in thermally protected facilities.
If the treated water contains high levels of suspended solids
(unlikely to occur with ground waters), some pretreatment,
such as filtration or pH adjustment, may be required prior to
air stripping.
Aeration and air stripping pose potential air pollution
problems if large amounts of volatile contaminants in the
treated waters are transferred to the air. If this is a
problem* emission control devices are required. Most ground
water*, However, are not likely to contain concentrations of
volatile contaminants sufficiantly large to warrant such con-
trols.
Carbon- Adsorption
Carbon adsorption treatment of ground waters entails
contacting the water with activated carbon, which adsorbs
contaminants and removes them from solution.• Granular
activated carbon, used in beds or columns, is the most
commonly used form, although powdered activated carbon has
been used in some wastewater treatment applications.
C-2
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Treatment processes can use both batch and continuous-feed
operations. Activated carbon- adsorption effectively removes
many organic and inorganic contaminants from solution.
Treatment efficiencies are a function of the type of carbon
used, the concentration and type of contaminants present, the
length of contact time for each unit of water, and t'*e
interval between carbon regeneration or replacement. Removal
efficiencies ranging from 0 to greater than 99.9 percent have
been reported in the literature.
Although activated carbon adsorption theoretically can
provide limitless removal of contaminants, in reality there
are economic limitations to the applicability of activated
carbon treatment. Removal of high concentrations of contam-
inants may require overly frequent carbon replacement, while
hard to remove contaminants may require enormous treatment
facilities with several carbon contact systems: both
situations may incur excessive expense, and though tech-
nically feasible would be effectively unavailable.
Influent to the carbon adsorption process must be
relatively free of suspended solids and oil/grease to prevent
clogging of the adsorption beds. Suspended solids of less
than 50 mg/L and oil/grease of less than 10 mg/L are recom-
mended concentrations to avoid interferences. Biological
activity in the carbon beds may become a problem in some
instances, causing clogging and taste or odor generation.
Removal efficiencies in carbon adsorption systems are
affected by changes in influent flow and influent chemical
composition. The presence of multiple contaminants in the
influent may reduce adsorption efficiency for some of the
constituents, although in some instances where multiple
contaminants are involved, increased removal efficiencies
have been noted. For any given water to be treated, the
selection of the appropriate carbon and system design
requires laboratory testing to determine the specific
adsorption efficiencies and interferences for that influent.
Chemical Precipitation
Cheaical precipitation, coagulation, flocculation. and
sedimentation are all interrelated processes that arc most
often us«d to remove metals and certain organics from
solution. For waters containing dissolved solids, a pre-
cipitant is added which reacts with th« contaminant to form a
solid, or to shift solution chemistry in such a way that the
contaminant solubility is reduced. The precipitated con-
taminant can then be removed by gravity sedimentation or
mechanical solids removal processes. ' commonly. used pre-
cipitanta include lia«, caustic, soda ash, iron salts, and
phosphate salts. Some waters contain colloidal suspended
solids which cannot be readily removed using conventional
sedimentation. Treatment of these contaminants, which are
C-3
-------
usually organic in nature, entails addition of a coagulant
(usually alum, cuprous sulfate, or ferrous sulfate) that
forces the suspended solids to agglomerate into larger
particles, which can then be removed using gravity sedi-
mentation. Some facilities add polymeric coagulant or
precipitation aids, which have been shown to enhance removal
efficiencies in some cases, chemical precipitation processes
can be run as batch or continuous-flow operations. Treatment
efficiencies depend upon the contaminant type and concen-
tration present, the solution pH and temperature, the
precipitants added, time and degree of mixing, and the time
allowed for sedimentation.
Precipitation of metals from solution can be inhibited
by the presence of chelating agents in the waters, such as
humic materials (naturally occurring organic acids) or other
organic compounds. This problem can be eliminated by using
precipitants with stronger affinities for the metal than the
complexion agent or by using pH adjustment to disrupt the
metal complex.
Use of chemical precipitation processes generates a
sludge that must be disposed of appropriately. Sludges
containing heavy metals or certain organics may be considered
to be hazardous wastes and as such should be disposed in
RCRA-regulated facilities.
Desalination ;
Desalination processes remove contaminants from the
influent using membranes to separate an enriched stream
(high-contaminant concentration) from a depleted stream.
Reverse osmosis and ultrafiltration use a pressure
differential to drive the separation, while electrodialysis
depends on an electric field. The concentrated or enriched
stream frequently requires further treatment, while the
depleted stream is usually potable. Desalination processes
have been used to purify waters to drinking-water quality in
certain regions of the country where fresh water is in short
supply. The processes are in more widespread use for
treatment of industrial process waters which must be of
extremely high quality. Treatment efficiencies are a
function of the molecular size and concentration of
contaminant*, strength of the separation driving force,
membraner type, and system configuration. Removal
efficiencies of greater than 90 percent have been reported in
the literature.
Desalination processes are highly sensitive to vari-
ability in the influent, and drastic changes in pK, tempera-
ture, or suspended solids. Any of these factors can effec-
tively reduce treatment efficiencies and the membrane life.
The suspended solids in a desalination influent should be
minimized to particle sizes 10 microns or less in order to
C-4
-------
prevent membrane fouling. Biological activity can severely
impair the process efficiency, and disinfection may be
required prior to desalination. The presence of chlorine may
also disrupt efficient desalination, dechlorination or. non-
chlorine disinfection processes may be desired.
Desalination processes are very expensive and energy-
intensive. Because of this, desalination is not frequently
used for removal of contaminants that are readily removed via
other treatment processes. However, for high IDS waters and
waters with large dissolved molecules, these processes may
provide cost-effective contaminant removal.
Flotation
Flotation is used to remove oil %nd grease or suspended
particles from the aqueous phase. The process involves
introduction of a gas (usually air) into the solution, and
subsequent attachment of the gas bubbles to particulate
matter, which then floats to the surface. The floating
particulates can be skimmed and removed for disposal or
further treatment. Surfactants and pH-modifications are
often used to improve process performance. Flotation is used
in many public-water utilities across the nation for removal
of organic matter from surface waters, but the most common
use of the process is removal of oils and grease from indus-
trial petroleum wastewaters. Removal efficiencies are a
function of concentration, size, mass of contaminant partic-
les, air-loading rate, types of chemical additives used,
hydraulic-loading rate, and skimmer design. Removal effici-
encies over 95 percent have been reported in the literature.
Flotation is effective for contaminants with densities
less than or near to that of water, but is relatively
ineffective for contaminants denser than water. It is not
particularly effective for removing dissolved contaminants,
although chemical additives can be used to decrease con-
taminant solubility. If volatile contaminants are present in
the influent, flotation may result in simultaneous stripping
of these contaminants from solution.
Granular Media Filtration
Granular media filtration is widely used to separate
solids from aqueous streams. Water is fed (via gravity or
applied pressure) through a bed of granular media, which may
consist of sand, gravel, coke, or combinations of the three.
Periodically the filter is backwashed, which removes the
filtered particles into a relatively ssall volume of vaste-
water which must be disposed of or treated further. Granular
media filtration is commonly used in water utilities follow-
ing chemical precipitation to ensure that turbidity standards
are met. Filtration performance depends upon the solubility
of the contaminant*, the strength and size of contaminant
C-5
-------
particles, the type of granular aadia used, the hydraulic
loading rate, and the interval between backwashings. Removal
to suspended solid levels less than to mg/L has been
reported.
ion Exchange
Ion exchange processes, like carbon adsorption, operate
by removing contaminants from solution onto a receptor. The
ion exchange process uses a chemically reactive resin that
exchanges innocuous ions for the contaminant ions in solu-
tion. The reaction is reversible, which allows a facility to
regenerate the ion exchange resin and reuse it. Ion exchange
processes are most commonly used to generate high-quality
industrial, processes waters, but recent applications have
also included wastewater treatment and ion exchange water
softening to remove hardness in drinking-water supplies. Ion
exchange can be used for removal of almost any ion from
solution, but is not very effective for removing uncharged
contaminant species. Removal efficiencies, which have been
reported in excess of 99.9 percent, are dependent upon the
ionic charge of the contaminants, contaminant concentration,
type of resin used, hydraulic loading, and interval between
resin regeneration.
Although almost any ionic contaminant can be removed
using ion exchange processes, the specific ion exchange
resins used are usually specific to certain types of contam-
inants. Resin selectivity is based on the type (positive, or
negative) and degree of charge on the contaminant ions. If
several types of contaminants with varying charge are
present, efficient ion exchange treatment may require a
series of different resins.
Changes in pH or the presence of organic and inorganic
complexing agents may cause certain ionic species to form
uncharged or differently charged chemical complexes, which in
turn can reduce: the efficiency of ion exchange treatment.
These problems are often overcome by adjusting pH so that the
desired ionic species are present, or by pretreating the
influent to remove complexing agents. Pratreatment may also
be required if the influent to the ion exchange process
contains excessive suspended solids which will clog the bed
or foul the resin.
Qzonatlon
Ogonation is a chemical oxidation process in which the
influent stream is contacted with ozone, which breaks refrac-
tory (nonbiodegradable) organic compounds into smaller,
treatable or nontoxic compounds. Used alone or in con-
junction with ultraviolet radiation, it is a highly effective
means of treating dilute concentrations of organics. The
process can achieve both effective disinfection and up to 99
C-6
-------
percent removal of certain organic compounds, including
pesticides, chlorinated hydrocarbons, alcohols, chlorinated
aromatics, and cyanides.
The efficiency of contaminant removal using ozonation is
dependent upon the retention time of the process reactor, the
ozone dose rate, the ultraviolet light dcse rate, and t^e
conLaminant type and loading. Treatability studies are
required prior to installation of ozonation processes to
treat specific influent streams.
ozonation is currently used by only a few public-water
supply systems, primarily as a disinfection process. It is
an expensive process which is readily replaceable with
chlorination for disinfection, but which has been gaining
acceptance for use in public water-supply systems because it
does not cause any byproduct trihalomethane formation. Lack
of use of ozonation in public water-supply treatment systems
may be due to economic constraints and limited need for the
technology.
Disinfection and Fluoridatipr^
Two water-treatment processes that are universally
available are chlorine disinfection and fluoridation.
Chlorine disinfection is the most commonly used means of
destroying bacteria in public-water supplies. Fluoridation
of water supplies is used to prevent dental health problems.
The processes do not remove chemical contamination from the
wastestream; they serve instead as preventive measures taken
to control disease and to maintain public health.
C.2 Partial Bibliography of References Evaluating Water
Treatment Technologies
American Water Works Association. Research Foundation and
Keuringsinstituut voor Waterleidingartikelen (Coopera-
tive Report). "Occurrence and Removal of Volatile
Organic Chemicals from Drinking Water.1* Denver, CO.
1983.
American Water Works Association. Water Quality Treatment.
Denver, CO. 1971.
Argo, D.6., "Control of Organic Chemical Contaminants in
Drinking Water.1* U.S. Environmental Protection Agency
Seminar, 1978.
c-7
-------
Argo, D.R., "Use of Lime clarification and -Reverse osmosis in
Water Reclamation." Journal Water Pollution Control
federation 56:1238-1246. December, 1984.
Gulp, R.L., C.M. Wesner, and G.L. Culp. Handbook of Advanced
Wastewater Treatment. 2nd Edition. Van Nostrand
Reinhold, New York, New York. 1978.
Environmental Science and Engineering, Inc., Malcolm Pirnie,
Inc. "Fort Lauderdale Water Quality and Treatment
Study.1* Prepared for the City of Fort Lauderdale,
Florida. 1981.
Ferguson, T.L. "Pollution Control Technology for Pesticide
Formula tore and Packagers.** Prepared for U.S. Environ-
mental Protection Agency, Office of Water and Hazardous
Material* Programs. January, 1975. EPA-660/2-74-094.
Glaze, W.H., et al. "Oxidation of Water Supply Refractory
species by Ozone With Ultraviolet Radiation." U.S.
Environmental Protection Agency. EPA-570/9-74-020.
1974.
Gummerman, R.C., R.L. Culp, and S.P. Hansen. "Estimating
Water Treatment Costs. Volume 1. Summary.11 Prepared
for U.S. Environmental Protection Agency Office of
Research and Development. Cincinnati, OH. August,
1972. EOA-600/2-79-162a.
Hoigne, J., and H. Bader. "Ozone Requirements and Oxidation
Competition Values of Various Types of Water for
oxidation of Trace Impurities.1* U.S. Environmental
Protection Agency. EPA-570/9-74-020. Washington, D.c.
1979.
Joyce, M. "Smyrna, Delaware Solves a Water Problem."
Jpurpa.1 of Environmental Healtft 42 (2): 72-74. September/
October 1979.
Kim, N.K., and D.W. Stone. "Organic Chemicals and Drinking
Water." NYS Department of Health, Albany, N.Y. 1981.
Larson, C.D. "Tetrachloroethylene Leached from Lined
AsJpgsjtQtt Cement Pipe into Drinking Water.*1 Journal of
April 1983.
Mackison, F.W., R.s. Stricoff, and L.J. Partridge, Jr., eds.
"Occupational Health Guidelines for Chemical Hazards."
U.S. Department of Health and Human Services and U.S.
Department of Labor. NIOSH/ OSHA. Washington, D.c.
January, 1981. DHHS (NIOSH) 81-123.
C-8
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Malarkey, A.T., W.P. Lambert, J.w. Hammond, and P.J. Marks.
"Installation Restoration General Environmental Tech-
nology Department. Final Report. Task 1. Solvent and
Heavy Metals Removal from Groundwater." Roy F. Weston,
Inc., West Chester, PA. Prepared for U.S. Army Toxic
and Hazardous Materials Agency. January, 1983.
McBride, K.K. "Decontamination of Ground Water for Volatile
Organic Chemicals: Select Studies in Nev Jersey" in
Aquifer Restoration and Ground Water Rehabilitation — A
Light at the End of the Tunnel. Proceedings of 2nd
National Symposium on Aquifer Restoration and Ground
water .Monitoring. David Nielsen, ed. Columbus, OH.
pp. 105-113. May 26-28, 1982.
Mccarty, "Volatile Organic Contaminants Removal by Air
Stripping.H Proceedings, AWWA Seminar, 99th Annual
National AWWA Conference, San Francisco, CA. June,
1979.
Metcalf and Eddy, Inc. "Volatile Organic Removal: Two
Ground Water Supply Case Histories." Presented at the
Nev York Section AWWA. 1980.
Nabolsine, Kohlman, Ruggiero Engineers, P.C. "Technical
Memorandum: Well Water Supply Testing for the Removal
of Organic Contaminants." Office of the Mayor, Glen
Cover, New York. 1978.
O'Brien, R.P., et al. "Trace Organics Removal from Contam-
inated Ground Waters with Granular Activated Carbon."
Presented at the National ACS meeting, Atlantic,
Georgia. 1981.
Plimmes, J.R., ed. Pesticide Chemistry in the 20th Century.
ACS Symposium, Division of Pesticide Chemistry. Nev
York, N.Y. April, 1976.
Schvinn, D.E., D.F. storrier, R.J. Moore and w.s. carter.
"PCB Removal by Carbon Adsorption.11 Pollution Engin-
eering- 16m!2Q-21. 1984.
Shukle, R.J. "Rocky Mountain Arsenal Ground-Water Reclama-
tion Program11 in Aquifer Restoration and Ground Water
p^ft^frf,! Itatiori—A Light at the End of the Tunnel.
Proceedings of 2nd National symposium on Aquifer
Restoration and Ground Water Monitoring. David Nielsen,
ed. Columbus, OH. May 26-28, 1982. pp. 367-374.
Singley, J.E., et al. "Use of Powered Activated Carbon for
Removal of Specific organic Compounds." Proceedings,
AWWA Seminar, 99th Annual AWWA Conference. San
Francisco, California. June 1979.
C-9
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APPENDIX D
SUPPLEMENTAL INFORMATION
FOR CLASS I AND CLASS III
ECONOMIC TESTS
-------
APPENDIX D
SUPPLEMENTAL INFORMATION FOR CLASS I AND
CLASS III ECONOMIC TESTS
This appendix provides background material on the
economic tests of irreplaceability (for Class I candidate
sites) and untreatability (for Class III candidate sites) and
is organized into five sections. Section D.I presents the
components and types of water-supply system costs. Section
D.2 describes general procedures for estimating the costs of
water-supply systems. Sections D.3 and D.4 emphasize cost-
estimation procedures for Class I and Class III candidate
sites, respectively, and present illustrative examples.
Section D.5 explains the derivation of the economic threshold
against which water-supply costs are compared and continues
the examples started in Sections D.3 and D.4. Section D.6
provides references used in developing Class I and Class III
economic tests.
D.I Components and Types of Costs
Water-supply system costs can be broken down into four
major components:
1. Acquisition.
2. Treatment.
3. Distribution and transmission.
4. Support services,
These 'cost components are describsd in more detail in Section
D.I.I. For each of the four components, costs are
distributed between two types of costs: (1) capital costs,
and (2) operation and maintenance (O&M) costs. Furthermore,
capital costs and O&M costs can be combined to derive total
annualized costs. Section D.I.2 describes the various types
of costs with an emphasis on how to derive total annualized
costs. The composition of water-supply-system costs by cost
component and type of cost is illustrated in Table D-l.
D-l
-------
TABLE D-l
COMPONENTS AND TYPES OF WATER SUPPLY SYSTEM COSTS A/
Type of Coat
Cost Component Capital Costs O&M Costs
Acquisition Land Labor
Right»-of-way Materials
Dams/reservoirs Utilities
Well field Recurring
payments for
water rights
Treatment Land Labor
Facilities Materials
Equipment Utilities
Parts and
inventory
Distribution and Rights-of-way Labor
Transmission Distribution network Materials
Pumping stations Utilities
Support Services Building Administration
a/ List of capital and O&M cost items is provided for illustrative
purposes and is not meant to be comprehensive.
D-2
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D.I.I Cost Coaponenta
Acquisition costs are the costs of producing or
acquiring vater and can be thought of as the costs of getting
the water from the source to the treatment point. These
costs include the capital and O&M costs of veils, reservoirs,
and aqueducts, and payments to suppliers for purchased water.
Treatment costs include the costs of treatment plants and
equipment, and the costs of chemicals that are added to the
water. Distribution and transmission costs are the costs of
pumping the water from the treatment points to the service
population and incorporate the capital and O&M costs of the
piping network. Support services are the costs of
administrative and customer services that are not directly
related to the physical process of delivering water.
Acquisition
Acquisition costs depend primarily on the
characteristics of the water sources for the system and the
distance from the water source to the treatment point. At
one extreme, these costs may be very low where reliable
natural sources are sufficient to meet the needs of the
system. For example, the Culpepper, Virginia, water utility
acquired all of its water in 1976 from a free-flowing stream
that fed directly into its treatment plant. The flow of the
stream was regulated by upstream reservoirs constructed to
control flooding using Federal funds. Therefore the utility
had .no acquisition costs. Other systems benefit from
proximity to natural surface-water bodies, or reliable stream
or river sources. In these cases, acquisition costs
typically are limited to pumping water from the natural
source to the treatment plant, although payments for rights
to use the water may be required. In general, acquisition
costs may be incurred in the construction and maintenance of
dams and reservoirs to collect and store surface water, in
the development and operation of well fields to utilize
ground-water sources, and in pumping water from the source to
treatment plants.
Treatment costs depend on the quality of the water
source: The physical, chemical, and bacteriological
characteristics of surface water can vary on a daily and
seasonal basis, depending on rainfall, temperature, flow
rate, and the character of materials deposited over the run-
off area or discharged upstream. Daily monitoring and
adjustment of the treatment process may therefore be
necessary. On the other hand, for some New England water
D-3
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controlled, and the water may undergo natural filtration
during run-off and consequently require no treatment, or
merely a small volume of chemicals added directly to the
reservoir. Similarly, ground water may require only limited
treatment. Treatment costs typically range from 0 to 300
dollars per million gallons, but in extreme cases nay be as
much as three times greater. Costs are likely to increase,
however, in the full implementation of the Safe Drinking
Water Act, as amended in 1986.
Distribution and Transmission
Distribution *nd transmission costs depend primarily on
the distance from creatment points to the service population,
the altitude of the population served relative to the
treatment points, and the density of the service population.
As the distance or height that water must be pumped to the
service population increases, the unit costs of distribution
and transmission increase. Similarly, increased dispersion
of the service population raises costs. This component of
cost is a substantial fraction of total costs for water-
supply utilities and typically ranges between $200 and $500
per million gallons supplied.
Support Service*
The unit costs of support services are essentially
independent of the physical characteristics of the system.
These costs are primarily admin.strative and customer service
costs . and therefore depend primarily on the characteristics
of the service population and the level of service chosen by
the utility; however they are typically about $200 per
million gallons.
D.I.2 Types of Cost
capital costs are expenditures for items such as land,
buildings, and equipment that have a long economic life. O&M
costs ars recurring expenses for items such as labor,
materials, and utilities. Capital costs and O&M costs can be
combine* to derive total annualized costs using the following
formula?
TAG - f CC + CMC (1)
where: TAG ars total annualized costs ($ per year);
f is the annualization factor;
CC are capital costs: and
CMC ars the operation and maintenance costs ($ per
ysar).
D-4
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Because capital expenditures generally are for investments in
capital goods that have a relatively long life expectancy,
capital costs are in units of dollars over many years.
The annual ization .factor is derived to obtain equal
annual payments of capital costs in constant dollars. It can
be derived using the following formula:
f - r / (1 - l/(l+r)n) (2)
where: r is the real discount rate; and
n is the life expectancy of the capital investment.
This formula is the same as the one used to obtain a total of
n equal annual payments for a fixed mortgage in real dollars,
where r is the real interest rate for the mortgage. As a
first approximation, an annualization factor equal to 0.1 may
be used.
The choice of real discount rate depends on the costs of
available financing for the water-supply system. The U.S.
Office of Management and Budget (OMB) recommends that a 10
percent rate (i.e., r - 0.1) be used to discount capital
costs in the analysis of regulatory options. Therefore, a
discount rate of 10 percent may be used to derive the
annualization factor. Alternatively, real interest rates on
tax-exempt bonds used to finance water projects can be used
in the analysis. For a real discount rate of 10 percent,
Equation (2) suggests annualization factor values of 0.131
and 0.106 for Jife expectancies n of 15 and 30 years,
respectively. For a real discount rate of 5 percent (i.e., r
• 0.05), the annualization factor is equal to 0.096 and 0.065
for life expectancies of 15 and 30 years, respectively.
D.2 General Cost Estimation Procedures
This section is organized in three subsections as
follows: Section 0.2.1 presents a general overview of the
cost-estimation techniques and assumptions for the economic
tests. Section O.2.2 discusses three general approaches to
cost estimation, and Section 0.2.3 shows how to derive the
final cost estimate for either of the two economic tests used
in these Guidelines.
0-5
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D.2.1 Overview of Cost Estimation
The economic tests of irreplaceability and
untreatability are intended to tost whether total water-
supply costs after replacement or treatment would exceed a
given economic threshold. For Class I candidate sites, if
total costs after replacement would exceed the economic
threshold, then the ground water underlying the site is class
I-irreplaceable. For Class III candidate sites, if total
costs after treatment would exceed the economic threshold,
then the ground water underlying the site is Class III-
untreatable. The economic tests therefore can be written as
follows:
TAG > TACtfc (3)
where TAG is the total annual ized costs for the system
(S/yr/hh) ; and
TACth is th* threshold cost for the economic tests
(§/yr/hh).
Cost estimates in Equation (3) are in units of dollars per
year per household. For unit conversions, the classifier may
assume 100,000 gallons per year per household.
Total annual ized costs for a water-supply system can be
calculated as the sun of total annualized costs over the four
cost components identified in Section D.I:
TAC - TACa + TACt + TAC
-------
where: TACa are the total annualized costs for the
acquisition component;
f is the annualization factor;
cca are capital costs of acquisition; and
OMCa are operation and maintenance costs of
acquisition.
D.2.2 Methods for Estimating Costs
There are several approaches to estimating the costs of
water-supply systems/ including the following:
1. Engineering cost estimates, i.e., estimates derived
assuming certain design, construction, and
operation specifications;
2. Existing system costs, i.e., costs currently
incurred by specific water-supply systems; and
3. Typical system costs, i.e., costs typically
incurred by water-supply systems in the nation.
Other approaches include combinations of the three methods
mentioned above. Regardless of the cost estimation approach
used, the matrix-form worksheet in Table D-2 can be used to
estimate the cost of a water-supply system. This worksheet
breaks down water-supply system costs by cost component
(e.g., acquisition) and type of cost (e.g., capital costs).
Engineering Cost Estimates
Engineering cost estimates begin with a thorough
inventory of items or activities resulting in costs. Table
D-l illustrates a sample of these cost items for each cost
component broken down between capital costs and OSM costs.
Except for a site-specific analysis of engineering
costs, cost estimates can be derived using engineering-based
cost equations for the various capital and 0&M cost items.
These cost equations are available in the published
literature for a number of possible water-supply system
designs. For example, EPAs Gulp et al. report (1978)
presents capital and O&M cost curves and cost tables for
construction. Another useful source of data for acquisition
costs is the NWWA Nationwide Water Well Drilling Cost Survey
(NWWA, 1979). The results of this survey are summarized in
the form of tables giving drilling and casing costs as a
function of the well diameter, hydrogeologic conditions, and
D-7
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TABLE D-2
WATER SUPPLY SYSTEM COST WORKSHEET
Total
Type of Cost Annualized
Cost Component Capital Costs O4M Costs Costs
Acquisition
Treatment
Distribution and
Transaission
Support Services
TOTAL
0-8
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other factors. Although this survey dates back to 1979, it
provides useful information on costs which must be escalated
to account for inflation.
Zn addition, several reports have been published by EPA
on the costs of water treatment, including the following:
e Estimating Water Treatment Costs. Gummerman, Gulp,
and Hansen, EPA 600/2-79-162a.
• Treatabilitv Manual. Technologies for the
Control Removal of Pollutants. EPA 600/2-82-
001C
e Estimation of Small System Water Treatment Costs.
EPA 600/2-84-184a.
When using published cost curves, it is important to identify
the system components included in the cost curve. Table 0-3
lists the system components typically required for each
treatment technology. Table D-4 indicates engineering-based
annual ized cost estimates for typical treatment components
for four typical plant sizes.
Cost data provided in the sources mentioned previously
must be updated to account for inflation and geographical
variations (e.g., in costs of labor and energy). The
Engineering News Record publishes cost indices for such items
as materials, energy, and labor. Also, updated cost
assessments will likely be available from EPA or the water
utility industry under the public water-supply provisions of
the Safe Drinking Water Act. •.-?. •• : ..- -;^
If engineering cost estimates are used for a given cost
component, then estimates of capital costs and O&M costs must
be entered into the worksheet for this component. Total
annual ized costs for this component then are calculated as
the sum of O&M costs and annualized capital costs as
indicated in Equation (5) .
Costs
As an alternative to engineering cost estimates, the
costs of an existing water-supply system can be estimated
rather accurately if detailed accounts («.g«, financial
statements) are available from the water utility that
owns/operates the system. Not all water-supply systems may
be willing to share detailed cost data with the classifier.
In the absence of such detailed accounts, it is possible to
use rates charged by the utility as an indicator of the
system costs. However, rates charged and true system costs
may differ for a number of reasons.
D-9
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TABLE D-3
TYPICAL COMPONENTS OP SELECTED TREATMENT TECHNOLOGIES
Aeration/Air stripping
Aeration tower
In-plant pumping
Filtration
Granular media filtration
beds
Granular media
Backwash pumping
Washwater sewage .basin
Activated Carbon
Carbon columns
Backwash pumping
Washwater surge basin
Ion Exchange
Pressure ion exchange
system
Chemical Precipitation
Line feed system
contact clarifier
Sludge pumping
Sludge drying beds
Sludge hauling
Flotation
Dissolved air flotation
Sludge pumping
Sludge drying beds
Sludge hauling
Desalination
Reverse osmosis
In-plant pumping
Ozonation
Ozonation system
Ancillary Operations
Administrative
RMMflster pumping
Polished water pumping
Clearwell storage
D-10
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TABLE D-4
ANNUALIZED COSTS OF TYPICAL
TREATMENT COMPONENTS FOR FOUR PLANT SIZES
Treatment
Component
Aeration/
User Peculation Size
500
$16,500
2,500
$20,700
5,000
$28,000
25, COO
$70,200
Air Stripping
Activated
Carbon
Chemical
$18,600
$35,200
$27,000
$51,500
$33,900
$62,700
$113,900
$127,700
Precipitation
Desalination
Flotation
Filtration
Ion Exchange
ozonation
Ancillary
$43,900
$30,100
$56,200
$10,100
$6,000
$25,900
$109,500
$37,300
$61,400
$26,400
$7,000
$24,000
$171,500
$48,900
$69,100
$38,900
$9,300
$46,200
$595,600
$109,800
$107,700
$74,800
$19,200
$110,900
All figures in 1982 dollars.
D-ll
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The utility may not set rate* on the basis of economic
coats of supply or the utility may not face the true economic
costs. The utility may charge different rates to different
types of users in such a way that one type of user (e.g.,
industrial users) implicitly subsidizes other types of users
(e.g., households). Also; some systems may receive subsidies
from the Federal government or other public agencies; in such
a sitution the rates charged by the system would be less than
true economic costs.
Typical System Costs
Finally, it may also be possible to determine typical
costs based on survey data drawn from water systems
throughout the country- Typical system costs ar« defined
here as the median (i.e., 50th percentile) cost of all water
supply systems of equivalent size in the nation. Estimates
of typical water-supply system costs are provided in Table D-
5 for each of seven user population size ranges.
If typical estimates are used for a given cost
component, then total annualized costs can be entered
directly for this cost component. Typically, total
annualized costs for a given component are equal to a certain
fraction of the total annualized costs of the whole system
(i.e., SUB over all components of total annualized costs for
each component). Table D-6 indicates this fraction of the
total system cost-by-cost component and system size range.
For example, the typical cost of acquisition for a water-
supply system serving a population of 5,000 persons is equal
to roughly $40 per household (i.e., the product of $180 per
household from Table 0-5 multiplied by the 22 percent value
from .Table D-6) .
D.2.3 Final Cost Estimate
The total annualized costs for a given water-supply
system are reported in the lower right cell of the cost
estimation worksheet in Table D-2. As indicated earlier, the
total annual ized costs for the system can be derived by
sunning op total annualized costs for each of the four cost
components (Equation 4). Section D.2.2 explained several
possible methods for estimating total annualized costs for
each component. As discussed in the following two sections,
the choice of cost estimation method depends on the economic
test considered.
D-12
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TABLE D-5
TYPICAL WATER SUPPLY SYSTEM COSTS
User Population Median Annual Cost
Size ($/household)
101-500 240
1,001-3,300 190
3,301-10,000 180
10,001-25,000 130
25,001-50,000 12u
50,001-500,000 100
500,001+ 70
Total annualized costs, i.e., annualized capital costs
(debt service of capital expenditures) plus O&M costs.
Depreciation costs are not included. Costs are rounded to
the nearest ten dollars.
Source: Data collected by the Research Triangle
Institute (Inmennan, 1987) and analyzed by Cadmus, Inc. and
ICF Incorporated.
D-13
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TABLE D-6
COMPONENT COSTS AS A PERCENTAGE OF
TOTAL WATER SUPPLY SYSTEM COSTS
User Population Size
Coat Component 300-75,000 75,001+
Acquisition 22% 19%
Treatment 18% 13%
Delivery 43% 38%
Service 17% 30%
Total annualized cost* of a component as a percentage of
total annualized costs for the system.
Source: ACT Systems, Inc., 1979.
D-14
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D.3 COST ESTIMATION FOR THE CLASS I - ECONOMIC
IRREPLACEABILITY TEST
Given the general procedures described above for
estimating the cost of a water-supply system, the procedures
used for a specific Class I or Class III classification
should reflect the intent and design of the economic
irreplaceability test or the economic untreatability test,
respectively. This section provides guidance for estimating
costs in keeping with specific Class I, economic
irreplaceability requirements while Section 0.4 explains the
cost estimation procedure for Class III.
D.3.1 Class I Cost Estimating Procedure
As noted in the discussion of the economic
irreplaceability test for Class I sites (Chapter 4) , the
purpose of this test is to determine whether the economic
burden of replacing an existing ground-water supply would be
unreasonable. If the burden of the replacement costs would
be unreasonable, then the ground water is Class I —
economically irreplaceable.
In order to apply this test, the annualized total system
cost after the affected component(s) of the existing system
has been replaced must be calculated. The replacement
process may range from simply sinking a new well (or tapping
a surface-water source) to creating an entirely new public-
supply system for households previously served by private
wells. Therefore, the classifier should first establish
which components will remain unaffected and which will need
replacement in the event that the ground water in the
Classification Review Area becomes unusable. Once this
division is established, the classifier can compile the
various cost estimates to yield a total system cost.
in general, the classifier should rely on readily
available; cost information and use best professional judgment
to determine which data sources are most appropriate when
making-a cost estimate. The classifier should note, however,
that the Agency believes that some data sources (e.g.,
existing system costs) are more accurate and therefore
preferable to other data sources.
D-15
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For system components that will not require replacement
(e.g., the distribution network for an existing system),
current annual costs for those components represent the most
accurate source of data and should be preferred. If the
water-supply system(s) in question will not make these costs
available, then engineering costs as described in section
O.2.2 are probably the next best source of accurate costs.
Costs for the relevant components of similarly sized existing
systems in the same geographic region as the ground water
under consideration Bay also provide reasonably accurate
information. If the total costs for the system(s) in
question are available but not broken down into component
costs, these aggregate cpsts could be disaggregated using the
component proportions provided in Table D-6.
As a final source of data, the typical cost estimates
for specific components can be developed by combining the
information in Tables 0-5 and D-6. In using these typical
costs, however, the classifier should verify that the cost of
the component at a particular site is unlikely to differ
significantly from the median cost across the country of the
system component. Classifiers should be aware that if the
typical cost values presented in Table 0-5, which represent
national median values, are used in all cases, then the total
system cost estimate will never exceed the ninetieth
percentile threshold values demonstrating irreplaceability.
For system components that will require replacement,
costs that are drawn directly or imputed from existing system
components very similar to the anticipated replacement
components should be preferred. If these costs are not
available or are not disaggregated among cost components,
then engineering costs are preferable. Likewise, costs drawn
or imputed from existing system components of comparable
systems in the same geographic region may be useful.
If only the total costs of the system (s) in question are
available, then the classifier may be able to disaggregate
total costs using the proportional values presented in Table
D-6. In doing so, the classifier should recognize that these
proportions represent entire components (e.g., the entire
acquisition system). If only a part of the component (e.g.,
a singles, vail) is being replaced, therefore, the classifier
should correct the calculations accordingly to avoid
overestisfefeion of costs.
Finally, if no other sources of data are available and
the classifier can verify that the replaced component (s) will
not differ significantly in cost from the typical
component (s) throughout the country, then the typical cost of
the replaced component(s) can be estimated by combining the
data provided in Tables 0-5 and D-6»
D-16
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One* the classifier has compiled the appropriate cost
estimate* for both unaffected and replacement components,
these costs should be converted into annual household costs
using the methodology presented in Section 0.2.1. The
following section presents a hypothetical example to
illustrate this process.
D.3.2 Hypothetical Example of Class I Cost Estimation
This section provides an Illustrative example of cost
estimation procedures for a Class I candidate site. Within
the Classification Review Area, there are 500 private wells,
each serving a single household and one public well field
serving a public-water system of 2,475 persons. Given an
average of 2.75 persons per household, there are estimated to
be 3,850 persons using water from within the Classification
Review Area (i.e., 1,375 private well users plus 2,475 public
system users). The classifier determines that, in the event
that the ground water becomes unusable, the public water
system will develop a new well field outside the
Classification Review Area and the private well users will
require connection to the public-water system.
The annualized per-household cost after replacement of
the ground water is estimated as the sum of the four cost
components. First, total annualized acquisition cost is
estimated at $142 baaed on the technical specifications of
the new well field and the distance from the new well field
to the existing treatment plant. Second, total annualized
treatment costs are assumed to remain constant at $118 on a
per-household basis because the water quality of the
replacement is comparable to ground-water quality within the
Classification Review Area and the addition of the private
well users does not increase the total system size
significantly. Third, total annualized costs for delivery
are increased to $248 to reflect extension of the existing
delivery system to the private well users. Finally, per-
household support service costs are assumed to remain the
same at $92. In this example, total costs are estimated at
$600 per household per year.
D-17
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D.4 COST ESTIMATING FOR THE CLASS III ECONOMIC
UNTREATABILITY TEST
As with the Class I economic irreplaceability test, the
general procedures for estimating water-system costs, as
presented above, should reflect the intent and design of the
economic untreatability test when performing a Class III
determination. This section provides guidance for estimating
costs in keeping with specific Class III economic
untreatability requirements.
D.4.1 Class III Cost Estimating Procedure
A« noted in the discussion of the Class III economic
untreatability in Chapter 6, the purpose of this test is to
determine whether the costs of treating a ground-water source
would sake the total system cost of a hypothetical water-
supply system unreasonably expensive. If the total system
cost would exceed the applicable economic threshold due to
excessive treatment costs, then the ground water would not be
considered a potential source of drinking water.
In order to apply this test, the annualized per
household cost of a hypothetical ground-water supply system
must be estimated. Because the cost estimate is based on a
hypothetical system, the total cost estimate should include
costs for each system component, including acquisition,
treatment, delivery, and services.
In order to ensure that the test focuses on treatment
costs rather than on costs for the remaining components,
typical cost values derived from the information presented in
Tables D-5 and D-6 are provided as a source of default values
for acquisition, delivery, and services. In some
circumstances, the classifier may chose to use cost estimates
for nontraatment components that are based on costs typical
of similsjrlysized systems in the same geographic region as
th« groundt water under review if these costs are clearly and
substantially different from the national median costs.
In all cases/ the cost estimate derived for the
treatment component of the hypothetical system should be
based strictly on site-specific treatment costs and njo£ on
default or typical national costs. Moreover, in applying
this test, the classifier should ensure that the treatment
csaponant cost used is based on the least expensive,
technically feasible treatment train. While the
D-18
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identification of the least expensive treatment train may not
be possible until all feasible train* are reviewed, some
trains may be disregarded immediately. For example, any
treatment train (e.g., aeration and flotation) that includes
other technically effective treatment trains (e.g., aeration)
clearly will be less cost effective and nay be disregarded.
In estimating the cost o£ a feasible treatment train, a
detailed site-specific engineering cost estimate should be
compiled if possible. If such detailed costs are
unavailable, then the classifier can compute costs using the
methods given in Section D.2.2, which presents a discussion
of engineering cost sources, typical components of potential
treatment trains, and annualized costs for those treatment
trains. Site-specific treatment costs may be calculated,
therefore, by applying the engineering cost-estimation
information presented in Section D.2.2 to the site-specific
treatment trains available for the site under review and
choosing the least expensive treatment train. This treatment
cost, prepared as an annualized per household cost, should
then be added to the cost estimates for acquisition,
delivery, and services in order to produce a total system
cost estimate.
The following section illustrates how a hypothetical
water-supply system cost may be estimated using typical cost
estimates for acquisition, delivery, and services and site-
specific engineering cost estimates for treatment.
D.4.2 Hypothetical Example of Class III Cost Estimation
This hypothetical example is based on a ground-water
source that is contaminated by trichloroethylene,
tetrachloroethylene, carbon tetrachlor ide, cadmium, and
selenium at levels that are above relevant water-quality
standards. The ground water, therefore, would require
treatment before it could be usable for drinking purposes.
Based on information provided by the U.S. Geological Survey,
it is estimated that the aquifer could sustain a daily yield
of 440,000 gallons. Assuming a daily per capita need of
roughly 100 gallons, the hypothetical user population that
could be supplied by this well would be 4,400 persons, or,
assuming 2.75 persons per household, 1,600 households.
Using this hypothetical population size, the annualized
household cost for a water system that would include
treatment technologies necessary to treat the water to
relevant standards could be calculated using the following
steps.
D-19
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First, the default values for acquisition, delivery, and
service can be calculated using the information presented in
Table* D-5 and D-6. According to Table D-5, the median
annual household cost for a total water-supply system serving
a population of 4,400 people would be $180. Likewise, Table
0-6 indicates that, for a system of 4,400 people, acquisition
is typically 22 percent of the total system cost; delivery is
typically 43 percent; and service is typically 17 percent.
Based on these values, therefore, the default values would
equal:
Acquisition - $39.60 (180 x .22),
Delivery • $77.40 (180 x .43),
Service - $30.60 (180 x .17).
Second, the reference technology test identified three
possible treatment trains that could adequately treat the
ground water to appropriate standards. These treatment
trains include the following:
1. Air stripping and chemical precipitation.
2. Chemical precipitation and filtration.
3. Chemical precipitation, filtration, and
desalination.
Because the third treatment train would add a treatment
component to the second treatment train that is not necessary
to meet relevant standards, the third treatment train may be
disregarded. The) costs of the remaining two treatment trains
may be estimated using the engineering cost information
provided in Table D-4. According to Table D-4, the cost of
air stripping for a system size of 4,400 (rounding off to
5,000) is $28,000. Likewise, the cost of chemical
precipitation is $62,700 while the cost of filtration is
$69,100* Inflating these figures from 1982 to 1986 dollars
(i.e., that year used to calculate the ninetieth percentile
threshold function) using the Construction Cost Producer
Price Index (i.e., an 8.1 percent increase) yields $30,300,
$67,800, and $74,700 respectively. The first treatment
train,• therefore, would cost $98,100 while the second
treatment train would cost $142,500. The first train is thus
the least expensive. Because these costs are for the entire
system, the cost of $98,100 should be divided by 1,600 in
order to yield the cost per household of about $61. Finally,
this treatment cost can be added to the default values
D-20
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calculated above to yield an annualized total system cost per
household of $209.
D.5 Derivation and Calculation of Economic Thresholds
Economic thresholds are used for both the Class I and
Class III economic tests. For the economic irreplaceability
test (Class I) , the threshold is used to determine whether
the cost of a replacement water-supply system would impose an
economically unreasonable burden on the user population,
hence making the existing source irreplaceable. For the
economic untreatability test (Class I±I), the threshold is
used to determine whether the cost of a water-supply system
to a hypothetical user population would be made unreasonably
burdensome by the need to treat the ground-water source in
question, hence making that ground-water source economically
untrcatable. In both cases, the Agency has determined that
if the annualized total costs of the replacement or
hypothetical water-supply systems would exceed the costs
faced by 90 percent of community water-supply system users,
then the replacement or hypothetical systems would be
economically unreasonable. The thresholds used for both
tests, therefore, are the ninetieth percentile per household
costs for community water-supply systems. This section
briefly describes the derivation of the cost function used to
calculate threshold values and then presents the actual
methodology for making calculations. Two examples of the
use of the thresholds are also presented.
D.5.1 Derivation of Economic Thresholds
As described in section D.2.2, water-supply rates
charged to residential users often do not reflect true
economic costs. The costs used to develop threshold values
for these Guidelines, therefore, are community water-supply
system costs and not water rates. Using data collected by
the Research Triangle Institute for the EPA Office of
Drinking Water report "Final Descriptive Summary: 1986
Survey of Community Water Systems" (Zmmerman, 1987),
ninetieth percentile water-system costs were calculated.
Becauser the thresholds are to be applied as a function of
system size (i.e., user population), for reasons noted in the
economic irreplaceability test discussion of Chapter 4, the
ninetieth percentile values were derived for each of the
twelve size categories employed in the 6DW report. Finally,
based on the assumption that the average household water
usage is 100,000 gallons per year, the data from the report,
D-21
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given as cants per 1,000 gallons, war* converted to dollars
per household per year.
In order to Bake the twelve observations (i.e., the
ninetieth pereentile cost for each of the twelve system
sizes) from the OOW survey usable for a continuous range of
system sizes, a linear regression was performed with system
size as the independent variable and cost per household as
the dependent variable. The purpose of a linear regression
analysis is to Mathematically define the function which best
describes the relationship between two variables. After
adjusting the scale of systea size with a logarithmic
transformation, the following equation was developed:
THRESHOLD- (-200.255 X LOG (SIZE)) -I- 1248.727
R2 - .712
Standard error of Y estimate » 179.44
N • 12 (i.e., the number of systsm sizs
categories)
where, THRESHOLD • threshold cost in dollars per household
per year, and
SIZE - user population (individuals).
Figure D-l presents this function graphically, along with the
twelve observations used to define the function.
As the analysis results indicate, the equation appears
to approximate the relationship between cost and system size
fairly well, explaining roughly 71 percent of the variation
in costs around different systea sizes. Note, however, that
the standard error of the estimate, which can be taken as the
range above or below the estimate within which the true value
will fall soae 67 percent of the time, is somewhat large.
The classifier should use best professional judgment,
therefor*, when making a determination of irreplaceability
based on these threshold values; especially if the cost of
the replacement water systea falls very close to the
threshold value.
D.5.2 Methodology for Calculating Econoaic Thresholds
In order to calculate the ninetieth pereentile
thresholds for either the economic irreplaceability or
untreatability tests, the classifier should take the
following three steps.
D-22
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Figure D-l
O
Ninetieth Percentile Economic Thresholds by System Size
200.000
400.000
600.000
aoc.ooo
1.000.000
System Size
(User Population Served)
SOURCE: ICF Incorporated Analysis of Data Collected by Immerman (1987)
DATE: 1988
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First, the classifier should determine the number of
individuals served by the water system. For Class I
candidate sites, this number should have been estimated
already for the substantial population analysis. For Class
III situations, this number should be based on the maximum
sustained yield of the aquifer in question as explained in
Chapter 6. If the available size data is for households
only, the classifier should convert households to individuals
by assuming an average of 2.75 persons per household.
Second, the classifier should take the logarithm (base
10) value of the user population size. This transformation
is necessary in order to manipulate the size variable in the
proper scale. Most hand calculators have function keys
allowing the easy log transformation of numbers.
Finally, the classifier should solve the equation given
above by multiplying the log value of size by -200.255 and
adding this value to 1248.272. The solution of this equation
is the ninetieth percentile economic threshold for a user
population the size of the system under review.
As an illustration of this methodology, consider a
replacement water-supply system which would serve a user
population of 4,500 persons and which is under review for a
Class I determination. The cost function for estimating the
ninetieth percentile economic infeasibility threshold should
be applied as follows:
THRESHOLD - (-200.255 X LOG(4,500)J + 1248.728
- (-200.255 X 3.653) + 1248.728
- -731.532 * 1248.728
- $ 517.20.
If the annualized total cost per household of the
replacement water-supply systea would be greater than roughly
$517, then the coat of that systea would be an unreasonable
economic: burden on the user population and the current
ground-water supply could be considered irreplaceable.
D.5.3 Illustrative Applications of Econoalc Thresholds
This section extends the examples related to Class I and
Class III procedures provided in Sections Do3.2 and D.4.2,
respectively, to demonstrate the use of economic thresholds.
D-24
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Claaa I Example
Section 0.3.2 presented an example of a Class I
candidate sits. In the example, a system with a user
population of 3,850 parsons was determined to face a par-
household cost of $600 in the event that the ground water in
the Classification Review Area became unusable. .By using the
equation described in Section D.5.2 above, - an economic
threshold of $530 . for a system of this size is calculated.
Because $600 exceeds $530, the ground water cannot be
replaced at reasonable cost. Accordingly, the site is
classified as Class I - irreplaceable.
Class III Example
Section D.4.2 illustrated the estimation of total system
costs that reflected treatment of contaminated ground water
at a Class III candidate site. Based on the maximum
sustainable yield of the aquifer in question, the
hypothetical water system was determined to have a size of
4,400 persons. Moreover, per household costs were estimated
at $209. For a system of this size, the economic threshold
is estimated at $519. The total costs of $209 fall below the
threshold of $519; the site is not Class III and is instead a
Class IIB - potential source of drinking water.
D-25
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D.6 APPENDIX 0 REFERENCES
ACT, Syataaa, Inc. 1979. Voluaaa I * II, Managing Small
Water Syataaa: A Coat Study Praparad for U.S. EPA, watar
Supply Raaaarch Diviaion. Hunicipal Environmental Raaaarch
Laba, XERL.
Gulp, R.L., 6.X. Weaner, and 6.L. Gulp, 197t. Handbook of
Advancad Haatavatar Treatment. 2nd Edition. Van Noatrand
Rainhold, Nav York, Nav York.
Immerman, Fradriek W., 1987. Final Daacriptiva Summary:
1986 Survay of Community Watar Systems). Praparad by tha
Raaaareh Triangla Inatituta, Raaaarch Triangla Park, North
Carolina, for tha Offica of Drinking Watar, USEPA.
National Watar Wall Association, 1979. Watar Wall Drilling
Coat Survay. NWWA, Worthington, Ohio.
Traatability Manual. Taehnolocriaa for tha Contra?. Ram oval of
Pollutants. EPA 600/2-82-001C.
Eatimatien of Small Syataa Watar Traataant Coal^a. EPA 600/2-
84-184a.
D-26
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o o
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