EPA 600/5 74-002
APRIL 1974
Socioeconomic Environmental Studies Series
of Environmental
Impact Assessment Methodologies
I
55
\
Ul
o
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
U. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the SOCIOECONOMIC
ENVIRONMENTAL STUDIES series. This series
describes research on the socioeconomic impact of
environmental problems. This covers recycling and
other recovery operations with emphasis on
monetary incentives. The non-scientific realms of
legal systems, cultural values, and business
systems are also involved. Because of their
interdisciplinary scope, system evaluations and
environmental management reports are included in
this series.
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EPA-600/5-74-002
April 1974
A REVIEW OF ENVIRONMENTAL IMPACT
ASSESSMENT METHODOLOGIES
by
Maurice L. Warner
Edward H. Preston
Contract No. 68-01-1871
Project Officer
Harold V. Kibby
Implementation Research Division
Washington Environmental Research Center
Washington, D.C. 20460
Prepared For
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 70 cents
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EPA REVIEW NOTICE
This report has been reviewed by the Environmental Protection
Agency and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation of use.
ii
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FOREWORD
The wide spread use of environmental impact analysis as a means
of making Federal agency decisions responsive to environmental concerns
was initiated by the passage of the National Environmental Policy Act of
1969 (NEPA). The Act required that Federal Agencies prepare statements
assessing the environmental impact of their major actions which significantly
affect the quality of the human environment. In subsequent years Federal
agencies developed procedures for the preparation of environmental impact
statements, often requiring similar analysis and statements from local
governments and the private sector as a requirement for the award of a
Federal permit or grant. The Council on Environmental Quality recently
developed guidelines to define uniform procedures and approaches in the
preparation of impact statements. While these guidelines specify what is
desired in Federal impact statements, technical approaches to meeting these
objectives are not always available and universally acceptable.
Among the several obstacles to the meaningful review of environ-
mental impacts of proposed major Federal actions has been the general lack
of adequate methodological tools. Under the pressures of an immediate backlog
of projects already "in the pipeline" and a gradually unfolding judicial
interpretation of the law, it is not surprising that agencies have, to date,
paid far greater attention to procedural rather than content aspects of
environmental impact statements. Recently, attention has begun to shift to
the quality of impact statements as decision input and public information
documents. Similarly, the proliferation of impact analysis methodological
tools has been a recent phenomenon.
As part of a series of socioeconomic environmental studies, the
Environmental Protection Agency, Office of Research and Development, is
conducting research designed to
Improve the technical quality of environmental impact
analyses in areas of agency responsibility
Improve the ability of the agency to provide substantive
technical review of environmental impact statements
prepared by other agencies, and
iii
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Improve the effectiveness of the use of environmental
impact analyses in influencing decision-making at all
government levels.
This report reviews 17 currently available methodological
approaches to impact analysis to highlight their strengths, weaknesses,
and range of applicability. In assembling this review, only content-
oriented methodological tools, as distinct from procedure-oriented
guidelines for impact statement preparation produced by individual
Federal agencies and the Council on Environmental Quality, have been
included.
P. CrJL.
Alan P- Carlin, Director, Implementation Research Division
Edwin B. Royce, Chief, Eco^ergical Studies and Technology
Assessment Branch
iv
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ABSTRACT
Seventeen tools or methodologies designed for or applicable to the
preparation of environmental impact statements are reviewed to identify their
strengths, weaknesses, and potential range of use. Specific criteria are
suggested for evaluating the adequacy of an impact assessment methodology
in terms of:
Impact Identification
Impact Measurement
Impact Interpretation
Impact Communication
Resource Requirements
Replicability
Flexibility.
The reviews presented serve as an introduction to the range of tools
available and demonstrate that no single approach to impact assessment is
superior in all circumstances.
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TABLE OF CONTENTS
Page
A REVIEW OF ENVIRONMENTAL IMPACT ASSESSMENT METHODOLOGIES 1
Choosing a Methodology < 1
Categorizing Methodologies 3
Review Criteria 4
Methodology Descriptions 9
LITERATURE CITED 25
vi
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A REVIEW OF ENVIRONMENTAL IMPACT
ASSESSMENT METHODOLOGIES
Environmental impact analysis, as required by the National Environ-
mental Policy Act of 1969 (NEPA) , is more art than science. There are no uni-
versally applicable procedures for conducting an adequate analysis. There are,
however, a wide variety of assessment tools and even comprehensive methodologies
that may make preparation of an environmental statement a less formidable and
more meaningful task. This report describes and critically analyzes 17 of
these tools and offers suggestions on choosing those tools or methodologies
which may apply to the specifics of a particular environmental assessment
situation.
In only a few cases are the tools discussed full-blown methodologies
developed specifically for impact statement preparation. More commonly, they
are more limited ideas borrowed from other fields with potential application
to NEPA environmental assessments. None of these tools has been widely applied
as yet in actual impact statements; indeed, many have never been so used.
This discussion is not intended as a step-by-step "cookbook" to
the use of these tools; very rarely would any of them be directly applicable
to any specific situation without modification. Instead, key ideas that one
may find useful are discussed and the tools are described in sufficient detail
to help the reader identify those which he or she might wish to examine
more fully.
Choosing a Methodology
There is no single "best" methodology for environmental impact
assessment. Characteristics of a methodology such as types of impacts or
projects covered and resources required may be virtues in one instance,
vices in another. Only the user can determine which tools may best fit a
specific task. In selecting the most appropriate tools the following key
considerations may be useful:
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1. Use. Is the analysis primarily a decision or an information
document? (A decison document is vital to determining the best course
of action, an information document functions primarily to reveal the
implications of a single, clearly best choice.) A decision document
analysis will generally require greater emphasis on the identification of
key issues, on quantification, and on direct comparison of alternatives.
An information document requires a more comprehensive analysis concentrating
on interpreting the significance of a broader spectrum of possible impacts.
2. Alternatives. Are alternatives fundamentally or incrementally
different? If differences are fundamental, such as preventing flood
damage by levee construction as opposed to flood plain zoning, for example,
then impact significance can better be measured against some absolute
standard than by direct comparison of alternatives since impacts will differ
in kind as well as size. Fundamentally and incrementally different alter-
native sets require different levels of analysis to discriminate between
alternatives, in that incrementally different alternatives require a greater
degree of quantification.
3. Public Involvement. Does the anticipated role of the public
in the analysis involve substantive preparation, token review, or vital
review? The first two roles allow use of more complex techniques such as
computer or statistical analysis that might be difficult to explain to a
previously uninvolved but highly concerned public. A substantive prepara-
tion role will also allow a greater degree of quantification or weighting
of impact significance through the direct incorporation of public values.
4. Resources. How much time, skill, money, data, and computer
facilities are available? Generally, more quantitative analyses require
more of everything.
5. Familiarity. How familiar is the analyst with both the type
of action contemplated and the physical site? Greater familiarity will im-
prove the validity of a more subjective analysis of impact significance.
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6. Issue Significance. How big is the issue in terms of contro-
versy and scope? All other things being equal, the bigger the issue the
greater the need for explicitness, quantification, and identification of
key issues and the less appropriate become arbitrary significance weights or
specific formulas for trading off one type of impact (e.g., environmental)
against another type (e.g., economic).
7. Administrative Constraints. Are choices limited by agency
procedural or format requirements? Specific agency policy or guidelines
may rule out some tools by specifying the range of impacts to be addressed,
the need for analysing trade-offs, or the time frame of analysis.
Categorizing Methodologies
The various methodologies examined can be divided into five types,
based on the way impacts are identified:
(1) Ad hoc: These methodologies provide minimal
guidance to impact assessment beyond suggesting
broad areas of possible impacts (e.g., impacts
on flora and fauna, impacts on lakes, forests,
etc), rather than defining specific parameters
to be investigated.
(2) Overlays: These methodologies rely on a set
of maps of environmental characteristics
(physical, social, ecological, aesthetic)
for a project area. These maps are overlaid to
produce a composite characterization of the
regional environment. Impacts are identified
by noting the impacted environmental charac-
teristics lying within the project boundaries.
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(3) Checklists: These methodologies present a specific
list of environmental parameters to be investigated
for possible impacts but do not require the estab-
lishment of direct cause-effect links to project
activities. They may or may not include guidelines
on how parameter data are to be measured and interpreted
(4) Matrices; These methodologies incorporate a list of
project activities in addition to a checklist of po-
tentially impacted environmental characteristics.
These two lists are related in a matrix which identifies
cause-effect relationships between specific activities
and impacts. Matrix methodologies may specify which
actions impact which environmental characteristics or
may simply list the range of possible actions and
characteristics in an open matrix to be completed by
the analyst.
(5) Networks: These methodologies work from a list of
project activities to establish cause-condition-effect
networks. They are an attempt to recognize that a
series of impacts may be triggered by a project action.
These approaches generally define a set of possible
networks and allow the user to identify impacts by
selecting and tracing out the appropriate project
actions.
Review Criteria
To serve the purposes of the National Environmental Policy Act of
1969 (NEPA), an environmental Impact asaessment must effectively deal with
four key problems:
Impact identification
Impact measurement
Impact interpretation
Impact communication to information users.
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Based upon experience with impact assessments to date, a set
of 20 criteria for methodology evaluation can be defined covering these
four key problems. These are:
Impact Identification
1. Comprehensiveness. An impact methodology should
address a full range of impacts including:
ecological, physical-chemical pollution, social-
cultural, aesthetic, resource supplies, induced
growth, induced population or wealth redistri-
butions, and induced energy or land use patterns.
2. Specificity. A methodology should identify
specific parameters (subcategories of impact
types) to be examined.
3. Isolate Project Impacts. A methodology should
require and suggest methods for identifying project
impacts as distinct from future environmental
changes produced by other causes.
4. Timing and Duration. A methodology should require
and suggest methods for identifying the timing
(construction phase vs. short-term operation
vs. long-term operation phase) and the duration
of impacts.
5. Data Sources. A methodology should require iden-
tification of the sources of data used to identify
impacts.(Data sources should also be listed for
impact measurement and interpretation.)
Impact Measurement
6. Explicit Indicators. A methodology should suggest
specific measurable indicators to be used to
quantify impacts on parameters.
7. Magnitude. A methodology should require and pro-
vide for the measurement of impact magnitude as
distinct from impact significance.
8. Objectivity. A methodology should emphasize objec-
tive rather than subjective impact measurements.
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Impact Interpretation
9. Significance. A methodology should require explicit
assessment of the significance of measured impacts
on a local, regional, and national scale.
10. Explicit Criteria. A methodology should require
that the criteria and assumptions employed to
determine impact significance be stated.
11. Uncertainty. A methodology should require an
assessment of the uncertainty or degree of confi-
dence in impact projections made.
12. Risk. A methodology should require identification
of any impacts of low probability but high potential
damage or loss.
13. Alternatives Comparison. A methodology should
provide a specific method for the comparison of
alternatives, including the no-project alternative.
14. Aggregation. A methodology may provide a mechanism
for aggregating impacts into a net total or composite
estimate. If aggregation is provided for, specific
weighting criteria or processes to be used should be
identified. The appropriate degree of aggregation
is a hotly debated issue on which no judgment has
been made in this review.
15. Public Involvement. A methodology should require
and suggest a mechanism for public involvement in
the interpretation of impact significance.
Impact Communication
16. Affected Parties. A methodology should require
and suggest a mechanism for linking impacts to
the specific affected geographical or social groups.
17. Setting Description. A methodology should require
a description of the project setting to aid state-
ment users in developing an adequate overall
perspective.
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18. Summary Format. A methodology should provide a
format for presenting in summary form, the results
of the analysis.
19. Key Issues. A methodology should provide a format
for highlighting key issues and impacts identified
in the analysis.
20. NEPA Compliance. A methodology should provide
guidelines for summarizing results in terms of the
specific points required by NEPA and subsequent CEQ
guidelines.
In addition to the above "content" criteria, methodological tools
should be evaluated in terms of their resource requirements, replicability,
and flexibility. The following considerations, used in arriving at the
generalized ratings for these characteristics (shown in Table 1), may be
useful in considering the appropriateness of tools. Important specific
requirements and limitations are discussed for each tool reviewed in the
methodology descriptions below.
Resource Requirements
1. Data Requirements. Does the methodology require
data that is presently available at low retrieval
costs?
2. Manpower Requirements. What special skills are
required ?
3. Time. How much time is required to learn to use
and/or actually apply the methodology?
4. Costs. How do costs of using a methodology compare
to costs using other tools?
5. Technologies. Are any specific technologies (e.g.,
computerization) required to use a methodology?
Replicability
1. Ambiguity. What is the relative degree of ambiguity
in the methodology?
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TABLE 1. SUMMARY OF METHODOLOGY EVALUATIONS
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10.
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17.
Adkins
Dee (1972)
Dee (1973)
Georgia
Krauskopf
Leopold
Little
McHarg
Moore
New York
Smith
Sorensen
Stover
Task Force
Tulsa
Walton
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9
0
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9
9
9
9
9
9
9
9
9
9
9
9
9
Specificity
0
0
0
0
0
0
0
0
0
0
0
9
0
9
0
0
0
u
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Isolate Pro.
Lnpacts
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Timing and
Duration
0
0
0
0
0
0
0
9
0
0
0
0
0
0
0
m
Data Source
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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a
Explicit In
0
0
0
0
0
0
0
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0
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Magnitude
0
0
0
0
0
0
0
0
0
0
Objectivity
0
0
0
9
0
0
9
0
0
9
0
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Significanc
0
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0
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Explicit Cr
0
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9
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9
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Uncertainty
0
0
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0
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Risk
Alternative
Comparison
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
Aggregation
0
9
-
0
0
-
-
9
-
9
-
9
9
-
Public
Involvement
0
0
9
0
0
0
9
0
0
0
0
0
0
9
0
0
9
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0
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9
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Key to types: A ad hoc
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C - checklist
M - matrix
N network
Key to evaluation symbols:
0 substantial compliance, low resource needs,
or few replicability-flexibility limitations
9 " partial compliance, moderate resource needs, or
moderate limitations
0 no or minimal compliance, high resource needs,
or major limitations
- aggregation not attempted.
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2. Analyst Bias. To what degree will different impact
analysts using the methodology tend to produce
widely different results?
Flexibility
1. Scale Flexibility. How applicable is the methodology
to projects of widely different scale?
2. Range. For how broad a range of project or impact
types is the methodology useful in its present form?
3. Adaptability. How readily can the methodology be
modified to fit project situations other than those
for which it was designed?
Methodologies were rated for their degree of compliance with
the 20 content criteria, their level of resource requirements, and their
replicability-flexibility limitations as follows:
= Substantial compliance, low resource needs, or few
replicability-flexibility limitations
« = Partial compliance, moderate resource needs, or
moderate limitations
o = No or minimal compliance, high resource needs, or
major limitations.
The resulting ratings, shown in Table 1, should be regarded as
subjective judgments only, but do provide a shorthand characterization
of the important features of the methodological tools examined.
Methodology Descriptions
The 17 methodologies or tools discussed were examined via the above
set of review criteria with results summarized in Table 1 on page 8. A brief
description of each methodology follows, discussing the following points.
The methodology type
The general approach used
The range of actions or project types for
which the methodology may be applicable
The comprehensiveness of the methodology
in terms of the range of impacts addressed
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10
The resources required (data, manpower, time, etc).
The limitations of the methodology (replicability,
ambiguity, flexibility)
Key ideas or particularly useful concepts offered
Other major strengths and weaknesses as identified
by the review criteria.
Because of the brevity and subjectivity of these characterizations,
they should not be considered as adequate critiques of the tools examined.
They may instead serve as a useful introduction to the range of techniques
now evolving.
1. Adkins, William G. and Dock Burke Jr., Interim Report:
Social, Economic, and Environmental Factors in Highway
Decision Making, research conducted for the Texas
Highway Department in cooperation with the U.S.
Department of Transportation, Federal Highway Admin-
istration: College Station, Texas; Texas Transportation
Institute, Texas ASM University (October 1971).
The Adkins methodology is a checklist using a +5 to -5 rating system
for evaluating impacts but providing no guidelines for measuring impacts.
The approach was developed to deal specifically with the evaluation of
highway route alternatives. Because the bulk of parameters used relate
directly to highway transportation, the approach is not readily adaptable
to other types of projects.
The parameters used are broken down into categories of transportation,
environmental, sociological, and economic impact. Environmental parameters
are generally deficient in ecological considerations. Social parameters
emphasize community facilities and services.
Route alternatives are scored +5 to -5 in comparison to the present
state of the project area, not the expected future state without the project.
Since the approach uses only subjective relative estimations of impacts, the
data, manpower, and cost requirements are very flexible. Reliance on sub-
jective ratings without guidelines for such ratings greatly reduces the
replicability of analysis and generally limits the valid use of the approach
to a case-by-case comparison of alternatives only.
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11
The detailed listing of social and, to a lesser extent, economic
parameters may be helpful for identifying and cataloging impacts in other
types of projects. An interesting feature of possible value to other
analyses using relative rating systems is the practice of summarizing the
number as well as the magnitude of plus and minus ratings for each impact
category. The number of pluses and minuses may be a more reliable indicator
for alternative comparison since it is less subject to the arbitrariness
of subjective weighting. These summarizations are additive and thus
implicitly weigh all impacts equally.
2. Dee, Norbert, et al, Environmental Evaluation System
For Water Resources Planning, report to the U.S.
Bureau of Reclamation, Columbus, Ohio: Battelle
Memorial Institute (January 1972).
This methodology is a checklist procedure emphasizing quantita-
tive impact assessment. It was designed for major water resource projects
but most parameters used are also appropriate for other types of projects.
Seventy-eight specific environmental parameters are defined within the four
categories of ecology, environmental pollution, aesthetics, and human
interest. The approach does not deal with economic or secondary impacts
and social impacts are only partially covered within the human interest
category.
Impacts are measured via specific indicators and formulas defined
for each parameter. Parameter measurements are converted to a common base
of "environmental quality units" through specified graphs or value functions.
Impacts can be aggregated using a set of preassigned weights.
The resource requirements are rather high, particularly data
requirements. These requirements probably restrict the use of the approach
to major project assessments.
The approach emphasizes explicit procedures for impact measurement
and evaluation and should therefore produce highly replicable results. Both
spatial and temporal aspects of impacts are noted and explicitly weighted
in the assessment. Public participation, uncertainty, and risk concepts
are not dealt with. An important idea of the approach is the highlighting
of key impacts via a "red flag" system.
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12
3. Dee, Norbert, et al., Planning Methodology for Water
Quality Management; Environmental Evaluation System,
Columbus, Ohio: Battelle Memorial Institute (July 1973).
This unique methodology of impact assessment defies ready classi-
fication since it contains elements of checklist, matrix, and network
approaches. Areas of possible impacts are defined by a hierarchical system
of four categories (ecology, physical/chemical, aesthetic, social), 19
components and 64 parameters. An interaction matrix is presented to indicate
which activities associated with water quality treatment projects generally
impact which parameters. The range of parameters used is comprehensive,
excluding only economic variables.
Impact measurement incorporates two important elements. A set
of "ranges" is specified for each parameter to express impact magnitude on
a scale from zero to one. The ranges assigned to each parameter within a
component are then combined by means of an "environmental assessment tree"
into a summary environmental impact score for that component. The signi-
ficance of impacts on each component is quantified by a set of assigned
weights. A net impact can be obtained for any alternative by multiplying
each component score by its weight factor and summing across components.
The key features of the methodology are its comprehensiveness,
its explicitness in defining procedures for impact identification and
scoring, and its flexibility in allowing use of best available data.
Sections of the report explain the several uses of the methodology
in an overall planning effort and discuss means of public participation.
The data, time, and cost requirements of the methodology when used for impact
assessment are moderate, though a small amount of training would be required
to familiarize users with the techniques used.
Because of its explicitness, the methodology possesses only minor
ambiguities and should be highly replicable. Because the environmental
assessment trees are developed specifically for water treatment facilities,
the methodology cannot be adapted to other types of projects without re-
constructing the trees though the parameters could be useful as a simple
checklist.
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13
One potentially significant obstacle to use of the approach is
the difficulty of explaining the procedures to the public. Regardless
of the validity of the "trees", they are unfamiliar devices developed by
highly specialized multivariant analysis techniques and public acceptance
of conclusions reached by their use may be low.
4. Institute of Ecology, University of Georgia, "Optimum
Pathway Matrix Analysis Approach to the Environmental
Decision Making Process: Test case: Relative Impact
of Proposed Highway Alternatives", Athens, Georgia:
University of Georgia, Institute of Ecology (1971)
(mimeographed).
The "Georgia"methodology incorporates a checklist of 56
environmental components. Measurable indicators are specified for each
component. The actual values of alternative plan impacts on a component
are normalized and expressed as a decimal of the largest impact (on that
one component). These normalized values are multiplied by a subjectively
determined weighting factor. This factor is the sum of one times a weight
for "initial" effects plus ten times a weight for "long-term" effects.
The methodology is used to evaluate highway project alternatives
and the components listed are not suitable for other types of projects.
A wide range of impact types are analyzed including land use, social, aes-
thetics, and economic>impacts.
The lower replicability of the analysis produced by using sub-
jectively determined weighting factors is compensated for by conducting
several passes at the analysis, and incorporating randomly generated error
variation in both actual measurements and weights. This procedure provides
a basis for testing the significance of differences in total impact scores
between alternatives.
The procedures for normalizing or scaling measured impacts to
obtain commensurability, and testing of significant differences between
alternatives are notable features of potential value to other impact
analyses and methodologies. These ideas may be useful whenever several
project alternatives can be identified and compared.
The Georgia methodology places rather high resource demands on
the user since computerization is necessary to generate random errors and
make the large number of repetitive calculations.
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14
5. Krauskopf, Thomas M., and Dennis C. Bunde, "Evalua-
tion of Environmental Impact Through a Computer
Modelling Process", Environmental Impact Analysis;
Philosophy and Methods, (eds.) Robert Ditton and
Thomas Goodale, Madison, Wisconsin: University of
Wisconsin Sea Grant Program (1972), pp. 107-125.
This methodology employs an overlay technique via computer
mapping. Data on a large number of environmental characteristics are
collected and stored in the computer on a grid system of 1 km square cells.
Highway rqute alternatives can either be evaluated by the computer (by
noting the impacts on intersected cells) or new alternatives may be
generated via a program identifying the route of least impact.
The environmental characteristics used are rather comprehensive,
particularly as regards land use and physiographic characteristics. Though
the methodology was developed and applied to a highway setting, it is
adaptable, with relatively small changes in characteristics examined, to
other project types with geographically well defined and concentrated im-
pacts. Because the approach requires considerable amounts of data on the
project region, it is not practical for the analysis of programs of broad
geographical scope. The high manpower-skill, money, and computer technology
requirements of the approach may also make it impractical at the present
time for any but major projects, or in situations where a statewide, computerized
data base exists (New York, Minnesota, Iowa, etc).
The estimation of impact importance is done through the specification
of subjective weights. Because the approach is computerized, the effects
of several alternative weighting schemes can be readily analyzed.
The methodology is attractive on several viewpoints. It allows
a demonstration of which weighted characteristics are central to a particular
alternative route; it presents a readily understandable graphic representation
of impacts and alternatives; it easily handles several subjective weighting
systems; the incremental costs of considering or generating additional
alternatives is low; and it fits well with developing regional and statewide
data bank systems.
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15
The mechanics of the approachhow impacts are measured and
combinedare not readily apparent from the reference cited. Considerable
training beyond the information available in this reference would be
required to use the approach.
6. Leopold, Luna B., et al., A Procedure for Evaluating
Environmental Impact, Geological Survey Circular 645,
Washington: Government Printing Office (1971).
This is an open-cell matrix approach identifying 100 project
activities and 88 environmental characteristics or conditions. For each
action involved in a project, the analyst evaluates the impact on every
impacted environmental characteristic in terms of impact magnitude and
significance. These evaluations are subjectively determined by the analyst.
Ecological and physical-chemical impacts are treated comprehensively,
social and indirect impacts are less well handled, and economic and
secondary impacts are not addressed.
Because the assessments made are subjective, resource requirements
of the approach are very flexible. The approach was not developed in re-
ference to any specific type of project and may be broadly applied with
some alterations.
Guidelines for use of the approach are minimal and several
important ambiguities are likely in the definition and separation of impacts.
The reliance on subjective judgment, again without guidelines, reduces the
replicability of the approach.
The approach is chiefly valuable as a means of identifying project
impacts and as a display format for communicating results of an analysis.
7. Arthur D. Little, Inc., Transportation and Environment;
Synthesis for Action; Impact of National Environmental
Policy Act of 1969 on the Department of Transportation,
Vol. 3, Options for Environmental Management, prepared
for Office of the Secretary, Department of Transportation
(July 1971).
This is less a complete methodology than an overview discussion
of the kinds of impacts that may be expected to occur from highway projects
and the measurement techniques that may be available to handle some of
them. A quite comprehensive list of impact types and the stages of project
development at which each may occur are presented. As broad categories,
the impact types identified are useful for other projects as well as for
highways.
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The approach suggests the separate consideration of an impact's
amount, effect (public response), and value. Some suggestions are offered
for measuring the amount of impact within each of seven general categories:
noise, air quality, water quality, soil erosion, ecologic, economic, and
sociopolitical impacts.
Five possible approaches to the handling of impact significance
are presented. Three of these are "passive" (requiring no agency action)
such as "reliance on the emergence of controversy". The other two involve
the use of crude subjective weighting scales. No specific suggestions are
made for the aggregation of impacts either within or between categories.
In general, the reference cited is a useful discussion of some
of the important issues of impact analysis, particularly as they apply
to transportation projects, but does not present a complete analytical
technique.
8. McHarg, Ian., "A Comprehensive Highway Route-
Selection Method", Highway Research Record,
Number 246, 1968, pp. 1-15, or McHarg, Design
With Nature, Garden City, New York: Natural
History Press, 1969, pp. 31-41.
The McHarg approach is a system employing transparencies of
environmental characteristics overlaid on a regional base map. Eleven
to sixteen environmental and land use characteristics are mapped. The
maps represent three levels of the characteristics, based upon "compatibility
with the highway". These references do not indicate how this compatibility
is to be determined but available documentation is cited.
This approach is basically an earlier, noncomputerized version
of the ideas presented in the Krauskopf reference. Its basic value is as
a method for screening alternative project sites or routes. Within this
limited use, it is applicable to a variety of project types.
Limitations of the approach include its inability to quantify
as well as identify possible impacts and its implicit weighting of all
characteristics mapped.
Resource requirements of the McHarg approach are somewhat less
demanding, in terms of data, than those of the Krauskopf approach because
information is not directly quantified, only categorized into three levels.
High degrees of skill and training are required, however, to prepare the
map overlays.
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The approach seems most useful as a "first cut method" of
identifying and sifting out alternative project sites, preliminary to
detailed impact analysis.
9. Moore, John L., et al., A Methodology for Evaluating
Manufacturing Environmental Impact Statements for
Delaware's Coastal Zone, Report to the State of
Delaware, Columbus, Ohio: Battelle Memorial Institute
(June 1973).
This approach was not designed as a method for impact analysis
hut its principles could be adapted for such use. It employs a network
approach, linking a list of manufacturing-related activities-to potential
environmental alterations-to major environmental effects, and finally-to
human uses affected. The primary strength of the set of linked matrices
is their utility in displaying cause-condition-effect networks and tracing
out secondary impact chains.
Such networks are useful primarily for identifying impacts and
the issues of impact magnitude and significance are addressed only in
terms of high, moderate, low, or negligible damage. As a result of these
subjective evaluations the approach would have low replicability as an
assessment technique. For such a use, guidelines would likely need to be
proposed to define the evaluation categories.
The approach incorporates indicators especially tailored to
manufacturing facilities in a coastal zone though most indicators would
also be pertinent to other types of projects.
The approach would perhaps be valuable as a visual summary of
an impact analysis for communication to the public and decision makers.
10. Central New York Regional Planning and Development
Board, Environmental Resources Management, prepared
for Department of HUD (October 1972) (available
through the National Technical Information Service
PB 217-517).
This methodology employs a matrix approach to assess in simple
terms the major and minor, direct and indirect impacts of certain water
related construction activities. It is designed primarily to measure only
the physical impacts of water resource projects in a watershed, and is
based on an identification of the specific, small-scale component activities
that are included in any project. Restricted to physical impacts on nine
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different types of watershed areas (e.g., wetlands) and fourteen types
of activities (e.g., tree removal), the procedure indicates four possible
levels of impact-receptor interactions (major direct through minor indirect).
Low to moderate resources in terms of time, money, or personnel are required
for the methodology, due principally to its simple way of quantification
(major versus minor impact). However, the procedure is severely limited in
its ability to compare different projects or the magnitude of different
impacts. There is no spatial or temporal differentiation, hence the full
range of impacts cannot be assessed. Impact uncertainty and high damage-
low probability impacts are also not considered. Only two levels of the
magnitude of an impact are identified while the importance of the impacts
are not assessed, resulting in moderate replicability. The lack of objec-
tive evaluation criteria may produce ambiguous results. NEPA requirements
for impact assessments are not directly met by this procedure.
The value of this methodology is less in the actual assessment
of the quantitative impacts of a potential project than in a "capability
rating system" which determines recommended development policies based on
existing land characteristics. Thus, guidelines on desirable and undesirable
activities with respect to the nine types of watershed areas are used to
map a region in terms of the optimum land use plan. The actual mapping
procedure is not described, however, and hence that aspect of the impact
assessment methodology cannot be evaluated here.
11. Smith, William L., "Quantifying the Environmental
Impact of Transportation Systems", Van Doren-
Hazard-Stallings-Schnacke, Topeka, Kansas (undated)
(mimeographed).
The Smith approach, as developed for highway route selection,
is a checklist system based on the concepts of probability and supply-
demand. The approach attempts to identify the alternative with least
social cost to environmental resources and maximum social benefit to
system resources. Environmental resources elements are listed as:
agriculture, wildlife conservation, interference, noise, physical features,
and replacement. System resources elements are listed as: aesthetics,
cost, mode interface, and travel desires. For each element, categories
are defined and used to classify zones of the project area. Numerical
probabilities of supply and of demand are then assigned to each zone for
each element. These are multiplied to produce a "probability of least
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social cost" (or maximum social benefit). These least social cost
probabilities are then multiplied across the elements to produce a
total for the route alternative under examination.
The approach is tailored and perhaps limited to project
situations requiring comparison of siting alternatives. The range
of environmental factors examined is very limited, but presumably
could be expanded to cover more adequately ecological, pollution, and
social considerations.
Since procedures for determining supply and demand probabilities
are not described, it is difficult to anticipate the amounts of data, man-
power and money required to use the approach. The primary limitations of
this methodology are difficulties inherent in assigning probabilities,
particularly demand probabilities, and the implicitly equal weightings
assigned to each element analyzed when multiplying to yield an aggregate
score for an alternative.
12. Sorensen, Jens, A Framework for Identification and
Control of Resource Degradation and Conflict in
the Multiple Use of the Coastal Zone, Berkeley:
University of California, Department of Landscape
Agriculture (1971), and Sorensen and James E. Pepper,
Procedures for Regional Clearinghouse Review of
Environmental Impact Statements Phase Two, report
to the Association of Bay Area Governments (April
1973). .
These two publications present a network approach usable for
environmental impact analysis. The approach is not a full methodology but
rather a guide to the identification of impacts. Several potential uses
of the California coastal zone are examined through networks relating
uses-to causal factors (project activities)-to first order condition
changes-to second and third order condition changes, and finally-to
effects. The major strength of the approach is its ability to identify
the pathways by which both primary and secondary environmental impacts
are produced.
The second reference also indicates types of data relevant to
each effect identified, though no specific measurable indicators are
suggested. In this reference some general criteria for identifying projects
of regional significance are suggested, based on project size and types of
impacts generated, particularly land use impacts.
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Because the preparation of the required detailed networks is
a major undertaking, the approach is presently limited to some commercial,
residential, and transportation uses of the California coastal zone for
which networks have been prepared. An agency wishing to use the approach
in other circumstances might develop the appropriate networks for reference
in subsequent environmental impact assessments.
13. Stover, Lloyd V., Environmental Impact Assessment;
A Procedure. Miami, Florida: Sanders and Thomas,
Inc. (1972).
This methodology is a checklist procedure for a general
quantitative evaluation of environmental impacts from development activities.
The type and range of these activities is not specified, but is believed
to be comprehensive. Fifty different impact parameters are sufficient to
include most possible effects, and thereby allow much flexibility. Sub-
parameters indicate specific impacts, but there is no indication of how
the individual measures are aggregated into a single parameter value. While
spatial differences in impacts are not indicated, both initial and future
impacts are included and explicitly compared. Resource requirements are
moderate to heavy, especially in terms of an interdisciplinary personnel
team which grows as more subparameters are included, requiring additional
expertise in specific areas. However, the actual measurements are not
based on specific criteria and are only partially quantitative, with seven
possible values ranging from an extremely beneficial impact to an extremely
detrimental one. Therefore, there is potential for ambiguous and subjective
results, with only moderate replicability. Impact areas are implicitly
assumed to be of equal importance. A specific methodology is mentioned
for choosing the optimum alternative in terms of benefits and adverse
effects. The procedure for alternatives comparison may be the most
interesting aspect of the procedure, with results given in terms of the
proportional significance of an impact vis-a-vis other potential alterna-
tives. There is no explicit mention of either public involvement in the
process, or environmental risks.
The impact assessment procedure is presented as only one step
in a total evaluation scheme which includes concepts of dynamic ecological
stability and other ideas. An actual description of the entire process
is not included, however.
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21
14. Multiagency Task Force, "Guidelines for Implementing
Principles and Standards for Multiobjective Planning
of Water Resources", Review Draft, Washington: U.S.
Bureau of Reclamation (1972).
The Task Force approach is an attempt to coordinate features
of the Water Resources Council's Proposed Principles and Standards for
Planning Water and Related Land Resources with requirements of NEPA. It
develops a checklist of environmental components and categories organized
in the same manner as the WEC Guidelines. The categories of potential
impacts examined deal comprehensively with biological, physical, cultural,
and historical resources, and pollution factors but do not treat social or
economic impacts. Impacts are measured in quantitative terms where possible
and also rated subjectively on "quality" and "human influence". In
addition, uniqueness and irreversibility considerations are included where
appropriate. Several suggestions for summary tables and bar graphs are
offered as communications aids.
The approach is general enough to have wide applicability to
various types of projects, though its impact categories are perhaps
better tailored to rural than urban environments. No specific data or
other resources are required to conduct an analysis, though an interdisci-
plinary project team is specified to assign the subjective weightings.
Since quality, human influence, uniqueness, and irreversibilities are all
subjectively rated using general considerations only, results produced
by the approach may be highly variable. Significant ambiguities include
a generally inadequate explanation of how human influence impacts are to
be rated and interpreted.
Key ideas incorporated in the approach include explicit identifi-
cation of the without-project environment as distinct from present conditions,
and use of uniqueness rating system for evaluating quality and human
influence (worst known, average, best known, etc). The methodology is
unique among those examined in not labeling impacts as environmental
benefits or costs but only as impacts to be valued by others. The approach
also argues against the aggregation of impacts.
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22
15. Tulsa District, U.S. Army Corps of Engineers,
Matrix Analysis of Alternatives for Water Resource
Development, draft technical paper (July 31, 1972).
Despite the title, this methodology can be considered a checklist
under the definitions used here since, though a display matrix is used to
summarize and compare the impacts of project alternatives, impacts are
not linked to specific project actions. The approach was developed to
deal specifically with reservoir construction projects but could be readily
adapted to other project types.
Potential impacts are identified within three broad objectives:
environmental quality, human life quality, and economics. For each impact
type identified, a series of factors are described, indicating possible
measurable indicators. Impact magnitude is not measured in physical units
but by a relative impact system. This system assigns the future state of
an environmental characteristic without the project a score of zero; then
assigns the project alternative possessing the greatest impact on that
characteristic a score of +5 (for positive impact), or -5 (for negative
impact). All other alternatives are assigned scores between 0 and 5 by
comparison. The raw scores thus obtained are multiplied by weights
determined subjectively by the impact analysis team.
Like the Georgia approach, the Tulsa methodology tests for the
significance of differences between alternatives by introducing error
factors and conducting repeated runs. The statistical manipulations
are different from those used in the Georgia approach, however, and con-
sidered by the Corps' writers to be more valid.
Resource requirements of the Tulsa methodology are variable.
Since specific types or levels of data are not required, data needs are
quite flexible. The consideration of error, however, requires specific
skills and computer facilities.
The major limitations of the approach, aside from the required
computerization, are the lack of clear guidelines on exactly how to
measure impacts and the lack of guidance on how the future no-project
state is to be defined and described in the analysis. Without careful
description of the assumptions made, replicability of analyses made using
the approach may be low since only relative measures are used. Since all
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23
measurements are relative, it may also be difficult in some cases to deal
with impacts that are not clearly definable as gains or losses.
The key ideas of wider interest incorporated in the Tulsa
approach include reliance on relative rather than absolute impact
measurement, statistical tests of significance with error introduction,
and specific use of the no-project condition, as a base line for impact
evaluation.
16. Walton, L. Ellis, Jr., and James E. Lewis, A Manual
for Conducting Environmental Impact Studies, Virginia
Highway Research Council (January 1971) (available
through the National Technical Information Service
PB-210 222).
The Walton methodology is a checklist, unique in its almost
total reliance on social impact categories and strong public participation.
The approach was developed for the evaluation of highway alternatives and
identifies different impact analysis procedures for the conceptual,
corridor, and design states of highway planning. All impacts are measured
by either their dollar value or a weighted function of the number of persons
affected. (The weights used are to be determined subjectively by the study
team.) The basis for most measurements is a personal interview with a
representative of each facility or service impacted.
Resource requirements for such a technique are highly sensitive
to project scale. The extensive interviewing required may make the approach
impractical for many medium-size or large projects because agencies pre-
paring impact statements seldom have the necessary manpower or the money
to contract for such extensive interviewing.
Analyses produced by the approach may have very poor replicability
due to the lack of specific data used and the criticality of the decision
regarding boundaries of the analysis since many impacts are measured in
numbers of people affected. There is also no means of systematically
taking into account the extent to which these people are affected.
The key ideas of broader interest put forth by the approach
are the use of only social impacts without direct consideration of other
impacts (pollution, ecology, etc), the heavy dependence on public in-
volvement and specific suggestions on how the public may be involved,
and the recognition of the need for different analyses of different stages
of project development.
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17. Western Systems Coordinating Council, Environmental
Committee, Environmental Guidelines (1971). (Mr.
Robert Coe, Southern California Electric Company,
Environmental Committee Chairman.)
The Environmental Guidelines are intended primarily as a planning
tool for siting power generation and transmission facilities. However,
they address many of the concerns of environmental impact analysis and
have been used in the preparation of impact statements. Viewed as an
impact assessment methodology, the approach is an ad hoc procedure,
suggesting general areas and types of impacts but not listing specific
parameters to examine.
The approach considers a range of pollution, ecological,
economic (business economics), and social impacts but does not address
secondary impacts such as induced growth, or energy use patterns. The
format of the approach is an outline of considerations important to the
selection of sites for each of several types of facilities e.g.,
thermal generating plants, transmission lines, hydroelectric and pumped
storage, and substations. An additional section offers suggestions for
a public information program.
Since the approach does not suggest specific means of measuring
or evaluating impacts no particular types of data or resources are required.
The application of this approach is limited to the siting of electric
power facilities with little carry over to other types of projects.
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LITERATURE CITED
1. Adkins, William G. and Dock Burke Jr., Interim Report; Social,
Economic, and Environmental Factors in Highway Decision Making,
research conducted for the Texas Highway Department in coopera-
tion with the U.S. Department of Transportation, Federal Highway
Administration: College Station, Texas; Texas Transportation
Institute, Texas A&M University (October, 1971).
2. Dee, Norbert, et al, Environmental Evaluation System For Water
Resources Planning, report to the U.S. Bureau of Reclamation,
Columbus, Ohio: Battelle Memorial Institute (January, 1972).
3. Dee, Norbert, et al., Planning Methodology for Water Quality
Management; Environmental Evaluation System, Columbus, Ohio:
(July, 1973).
4. Institute of Ecology, University of Georgia, "Optimum Pathway
Matrix Analysis Approach to the Environmental Decision Making
Process: Test case: Relative Impact of Proposed Highway
Alternatives", Athens, Georgia: University of Georgia, Institute
of Ecology (1971). (mimeographed).
5. Krauskopf, Thomas M., and Dennis C. Bunde, "Evaluation of Envir-
onmental Impact Through a Computer Modelling Process", Environmental
Impact Analysis; Philosophy and Methods, (eds.) Robert Ditton and
Thomas Goodale, Madison, Wisconsin: University of Wisconsin Sea
Grant Program (1972), pp. 107-125.
6. Leopold, Luna B., et al., A Procedure for Evaluating Environmental
Impact, Geological Survey Circular 645, Washington: Government
Printing Office (1971).
7. Arthur D. Little, Inc., Transportation and Environment; Synthesis
for Action; Impact of National Environmental Policy Act of 1969
on the Department of Transportation, Vol. 3, Options for Environ-
mental Management, prepared for Office of the Secretary, Depart-
ment of Transportation (July, 1971).
8. McHarg, Ian., "A Comprehensive Highway Route-Selection Method",
Highway Research Record, Number 246, 1968, pp. 1-15, or McHarg,
Design With Nature, Garden City, New York: Natural History Press,
1969, pp. 31-41.
9. Moore, John L., et al., A Methodology for Evaluating Manufacturing
Environmental Impact Statements for Delaware's Coastal Zone, Report
to the State of Delaware, Columbus, Ohio: Battelle Memorial Institute
(June, 1973).
10. Central New York Regional Planning and Development Board, Environmental
Resources Management, prepared for Department of HUD (October, 1972)
(available through the National Technical Information Service PB 217-
517).
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26
11. Smith, William L., "Quantifying the Environmental Impact of
Transportation Systems", Van Doren-Hazard-Stallings-Schnacke,
Topeka, Kansas (undated). (mimeographed)
12. Sorensen, Jens, A Framework for Identification and Control of
Resource Degradation and Conflict in the Multiple Use of the
Coastal Zone, Berkeley: University of California, Department of
Landscape Agriculture (1970), and Sorensen and James E. Pepper,
Procedures for Regional Clearinghouse Review of Environmental
Impact Statements Phase Two, report to the Association of
Bay Area Governments (April, 1973).
13. Stover, Lloyd V., Environmental Impact Assessment; A Procedure,
Miami, Florida: Sanders and Thomas, Inc. (1972).
14. Multiagency Task Force, "Guidelines for Implementing Principles
and Standards for Multiobjective Planning of Water Resources",
Review Draft, Washington: U.S. Bureau of Reclamation (December,
1972).
15. Tulsa District, U.S. Army Corps of Engineers, Matrix Analysis of
Alternatives for Water Resource Development, draft technical paper
(July 31, 1972).
16. Walton, L. Ellis, Jr., and James E. Lewis, A Manual For Conducting
Environmental Impact Studies, Virginia Highway Research Council
(January, 1971) (available through the National Technical Informa-
tion Service PB-210 222).
17. Western Systems Coordinating Council, Environmental Committee,
Environmental Guidelines (1971). (Mr. Robert Coe, Southern
California Electric Company, Environmental Committee Chairman.)
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27
ACKNOWLEDGMENTS
This research was partially funded under contracts to the
Environmental and Land Use Planning Section of Battelle Memorial
Institute's Columbus Ohio Laboratories from the Ecological Studies
and Technology Assessment Branch, Implementation Research Division
of the Environmental Protection Agency and the U.S. Army Corps of
Engineers' Construction Engineering Research Laboratory, Champaign,
Illinois. Judgments contained in this report are solely the author's
and do not necessarily reflect the opinions of any of these organizations.
October 15, 1973 Maurice L. Warner
Edward H. Preston
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
w
4. Title
A Review Of Environmental Impact Assessment
Methodologies
Author(s) Warner, M.L.
Preston, E.H.
Battelle-Columbus
505 King Street
Columbus, Ohio 43201
5. Report Date
6.
8. i -form, g Orga. .zation
Rcpo't No.
10. Project No.
12. S; oson'r Organ -tion
IS ''.; iplememaiy Nntes
t}. c oiiract' Grant No.
68-01-1871
13 Type f Kept, t and
Period Covered
Environmental Protection Agency, report number,
EPA-600/5 - 74-002, April 1974.
16. Abstract
Seventeen tools or methodologies designed for or applicable to the preparation
of environmental impact statements are reviewed to identify their strengths,
weaknesses, and potential range of use. Specific criteria are suggested for
evaluating the adequacy of an impact assessment methodology in terms of:
Impact Identification
Impact Measurement
Impact Interpretation
Impact Communication
. Resource Requirements
. Replicability
. Flexibility
The reviews presented serve as an introduction to the range of tools available
and demonstrate that no single approach to impact assessment is superior in all
circumstances.
17a. Descriptors
17b. Identifiers
Assessments, Evaluation
Environmental Impact Statements
CO WRR Field
Q7C
/>' Availability
19. Security Class.
(Repor'j .
Abstractor
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 2O24O
V.RSIC 1C2 H
I87H
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