MODULE III

CET415: ENVIRONMENTAL IMPACT

ASSESSMENT
EIA methodologies: Ad hoc, checklist, matrix, network and overlay- Impact

Prediction, Evaluation and Mitigation-Prediction and assessment of the

impact on water (surface water and groundwater), air, and noise

environment- assessment of ecological impacts and Socio economic Impacts.

 EIA methodologies
• There are about five methodologies followed in literature for determining
the impacts and to adhere to the stipulations of regulating agencies, which
in our case is Ministry of Environment and Forest.
• Choice of methodology will depend on the specific user and project being
undertaken. The key considerations are:
i) Use: Whether the document is for information or a decision document. The
decision document requires more details and greater emphasis is on key
issues, quantification and comparison of alternatives.
ii) Alternatives: Much would depend on what alternatives to the project are
available since these would require a more thorough quantification and
comparison.
iii) Public involvement: The role of stake holders and their participation may
also require issues which are relevant and need discussion and thus details.
iv) Resources: What resources are available for the document preparation
in terms of experts available, data, time and money.
v) Familiarity: Familiarity with ground conditions will also be a keen
element. Greater familiarity will improve the validity of subjective
significance.
vi) Issue significance: If the issues involved are larger than more details
are needed, quantification is important and hence the choice
vii) Administrative: Are the documents being prepared are dictated by
procedure of implementing agency
 EIA Methodologies

• Ad-HOC method
• Check list method
• Over lays method
• Matrix method
• Network method
 Ad-HOC method
• Ad hoc methods indicate broad areas of possible impacts by listing
composite environmental parameters (Ex: flora and fauna) likely to be
affected by the proposed activity.
• These methods involve assembling a team of specialists who identify
impacts in their area of expertise.
• Here, each parameter is considered separately and the natures of impacts
(long term or short term, reversible or irreversible) are considered.
• These methods give a rough assessment of total impact while giving the
broad areas and the general nature of possible impacts.
• In this method, the assessor relies on an intuitive approach and makes a
broad-based qualitative assessment
• Ad hoc method is useful when time constraints and lack of information
require that the EIA must rely exclusively on expert opinion.
• When more scientific methods are available, it is not recommended.
This method serves as a preliminary assessment and helps in
identification of important areas like:

 Wildlife  Groundwater
 Endangered species  Noise
 Natural vegetation  Air quality
 Exotic vegetation  Visual description and services
 Grazing  Open space
 Social characteristics  Recreation
 Natural drainage  Health and safety
• Types of Ad hoc method
 Opinion polls.
 Experts opinion.
Delphi methods
The Delphi method is a forecasting process framework based on the
results of several rounds of questionnaires sent to a panel of experts.
Several rounds of questionnaires are sent out, and the anonymous
responses are aggregated and shared with the group after each round.
The experts are allowed to adjust their answers in subsequent rounds.
Since multiple rounds of questions are asked and the panel is told what
the group thinks as a whole, the Delphi method seeks to reach the
correct response through consensus
Advantages
• Specialists on a particular area will provide guidance.
Disadvantage
• It require expert.
• Short/long term impact are merely examined on guess basis.
• Identification, prediction and interpretation of impacts are quite poor
• It gives no assurance that a comprehensive set of all relevant impacts
have been studied.
Example: EIA Study for High way Construction Project
 OVERLAY METHOD
• Depends on a set of maps of a project area's environmental characteristics covering
physical, social, ecological and aesthetic aspects
• It enables separate mapping of critical environmental features at the same scale as
project's site plan (Ex: wetlands, steep slopes, soils, floodplains, bedrock outcrops,
wildlife habitats, vegetative communities, cultural resources, etc.)
• In the old technique, environmental features were mappped on transparent plastic
in different colors
• Modern technique of the same activity is done using computer software, hardware,
data and skilled people. It is called GIS (Geographic Information Systems)
• The advantages of this method are:
✔ It is easy to understand and use
✔ It has a good display and
✔ It is good for setting site selection
• The disadvantages of this method are:
✔ It does not address impact duration or probability
✔ It addresses only direct impacts
 CHECK LIST METHOD

Environmental factors are listed in a structured format by giving importance, weightings for factors
and application of scaling techniques for impacts of each alternative. Checklists are strong indicators
of impact identification.
Checklists may be:
● Simple
● Descriptive
● Scaling or
● Weighting
A typical checklist might contain entries such as:
1.Earth: mineral resources; construction material; soils; land form; force fields and background
radiation; unique physical features;
2. Water: surface (rivers, lakes and reservoirs, estuaries); coastal seas and ocean, underground; quality;
temperature; recharge; snow, ice, and permafrost;
3. Atmosphere: quality (gases, particles); climate (micro, macro); temperature;
4. Flora: trees; shrubs; grass; crops; microflora; aquatic plants; endangered species; barriers; corridors;
5. Fauna: birds; land animals including reptiles; fish and shellfish; benthic organisms; insects;
microfauna; endangered species; barriers; corridors;
6. Land use: wilderness and open space; wetlands; forestry; grazing; agriculture;
residential; commercial; industrial; mining and quarrying;
7. Recreation: hunting; fishing; boating; swimming; camping and hiking;
picnicking; resorts.
• Simple checklists are a list of parameters without guidelines regarding either
interpretation or measurement of environmental parameters or specific data
needs or impact prediction and assessment.
• Descriptive checklists include list of environmental factors along with
information on measurement, impact prediction and assessment.
• Scaling and weighting checklists facilitate decision making. Such checklists are
strong in impact identification. While including the function of impact
identification, they include a certain degree of interpretation and evaluation.
The aforementined factors make these methods attractive to decision-making
analysis
The advantages of this method are:
• It is simple to understand and use
• It is good for site selection and priority setting

Disadvantages of this method are:

• It does not distinguish between direct and indirect impacts
• It does not link action and impact
• It is cumbersome at times
 MATRIX METHOD
• This methodology provides a framework of interaction of different activities
of a project with potential environmental impacts caused by them.
• A simple interaction matrix is formed when project actions are listed on one
axis (usually vertical) and environmental impacts are listed along the other
axis.
Comparison with checklist method:
• Checklists tend to be long. It also requires a lot of work in describing an
impact or writing it out in words. In matrices, this ambiguity and extra work is
removed by introducing a quantitative aspect in the assessment of an impact.
• Checklist tends to get confusing when you assess multiple levels of impacts
descriptively. This is resolved in matrices, to an extent, with the help of
customized matrices. Matrices are also versatile, as they can be used for small
and large-scale projects alike.
Simple matrix: This is simply a list of environmental aspects listed along
the vertical axis, against which we determine whether an activity would
have an adverse effect, no effect or beneficial effect. A simple “x” or “tick”
is given under the appropriate column.
Sometimes, the activities are listed along the horizontal axis with the environmental aspects in the
vertical axis, and the same “x” is given to those pairs that have an interaction between themselves.
LEOPOLD MATRIX:
• This was designed by Leopold in 1971. Leopold matrix is among the two
major forms of matrices used in EIAs.
• The cells of the matrix are divided by a diagonal line.
• The top division is used to describe the magnitude of the impact that
activity will have on the environmental aspect, and the bottom division
is used to describe the significance of that impact.
• It does not explicitly describe spatial and temporal effects of the
environmental activity.
• It tends to be too simplified when you require a comprehensive analysis
of the impacts on the project area.
• They cannot explain linkages between two environmental aspects. In
other words, it does not describe secondary and tertiary impacts.
The advantage of the matrix method is :
• It links action to impact
• This is a very good method for displaying EIA results

The disadvantages of this method are listed below:

• It is difficult to distinguish between direct and indirect impacts using this method
• There is potential for double-counting of impacts
• It is qualitative in nature and does not refer to quantity of impact

Application of matrices:
• Matrices can be applied in medium to large scale projects where the number of
developmental activities are many (up to 100).
• This will obviously result in effects on many environmental aspects. All of these
cannot be covered easily in checklists.
• It is perfectly acceptable to customize the matrix according to the project at hand.
• Matrices are flexible, which is why they have been accepted and used the world
over.
 NETWORK METHOD

● This method uses the matrix approach and extends it to include both the
primary as well as the secondary impacts.

● It is shown in the form of a tree called impact tree. This diagram is also called as
reference or sequence diagram.

● Identification of direct, indirect along with short, long-term impact is a crucial

and basic step of making an impact tree.

● The impact tree is used to identify cause-effect linkages.

● The impact tree is a visual description of linkages

ENVIRONMENTAL IMPACT
• As per ISO 14001:2004 – Definition of impact is:
“Any change to the environment, whether adverse or beneficial, wholly or
partially resulting from an organization’s environmental aspects”
• Environmental aspect: Element of an organization's activities or products or
services that can interact with the environment”.
• An impact is defined where an interaction occurs between a project activity and
an environmental receptor.
IMPACT INDICATOR
• An element or a parameter that provides a measure of the significance of the
effect
• The magnitude of an environmental impact.
• The selection of a set of indicators is often a crucial step in the impact assessment
process
• The most widely used impact indicators are those within statutory laws, acts.
• Indicators such as air and water quality standards that have statutory authority.
IMPACT SIGNIFICANCE ASSESSMENT
• Environmental and Social Impact Assessment (ESIA) - GUIDELINES
• “Significance” determined by considering “project activity”, “event magnitude” and
“receptor sensitivity”
• Determining event magnitude requires the identification and quantification (as far as
practical) of the sources of potential environmental and socio-economic effects from routine
and nonroutine project activities.
• Determining receptor environmental sensitivity requires an understanding of the
biophysical environment

IMPACT IDENTIFICATION
• A wide range of methods has been developed for the purpose.
• Many of the methods were developed in response to the NEPA (National Environmental
Policy Act) and have since been expanded and refined.
• The simplest involves the use of lists of impacts to ensure that none has been left out.
• The most complex include the use of interactive computer programme, networks showing
energy flows and schemes to allocate significance weightings to various impacts.
In choosing a method, however, the analyst needs to:
· ensure compliance with regulations;
· provide a comprehensive coverage of a full range of impacts including
social, economic and physical;
· distinguish between positive and negative, large and small, long-term
and short-term, reversible and irreversible impacts;
· identify secondary, indirect and cumulative impacts as well as direct
impacts; distinguish between significant and insignificant impacts;
· Consider impacts within the constraints of an areas carrying capacity;
incorporate qualitative as well as quantitative information;
· be easy and economical to use; be unbiased and to give consistent
results;
· be of use in summarizing and presenting impacts in the EIS.
SOCIO-ECONOMIC IMPACTS
The socio-economic impact assessment (SEIA) will use a semi-qualitative assessment approach to
describe and evaluate impacts. Factors taken into account to establish impact significance will
include probability, spatial extent, duration and magnitude of the impacts in addition to the
sensitivity of receptors. Indirect socio-economic impacts (i.e. induced effects) will also be assessed
using the same approach.
Social impacts
• Social impacts can be defined as the consequences to people of any proposed action that changes
the way they live, work, relate to one another, organize themselves and function as individuals and
members of society.
• This definition includes social - psychological changes, for example to people’s values, attitudes and
perceptions of themselves and their community and environment.
• Indeed, some SIA practitioners consider social impacts to be only ‘as experienced’ (e.g. stress,
disruption, hunger) and differentiate these from the causal processes (e.g. over-crowding,
infrastructure pressure, poverty).

Socio-economic analysis (SEA) is a tool to assess impacts:

• What are the benefits of a regulatory action?
• What are the corresponding costs?
• How do benefits and costs compare?
Questions to be asked in SEIA:
Points to be analysed in SEIA:
IMPACT PREDICTION
• The accumulated knowledge of the findings of the environmental
investigations form the basis for the prediction of impacts.
• Once a potential impact has been determined during scoping process,it is
necessary to identify which project activity will cause impact,and its
magnitude and extent.

METHODS OF IMPACT PREDICTION

• Best estimate professional judgement.

• Quantitative mathematical models.
• Experiments and physical models.
• Case studies as analogues or references.
POINTS TO CONSIDER FOR IMPACT PREDICTION

• Baseline condition
• Un certainty
• Spatial limits
• Temporary boundaries
• Incremental condition
• Quantitative and Qualitative methods
IMPACT EVALUATION
• Its purpose is to assign relative significance to predicted impacts
associated with the projects and to determine the order in which
impacts are to be avoided ,mitigated or compensated
Criteria for Evaluating Potential Effects:
• Importance of affected resource
• Magnitude and extent of disturbance
• Duration and frequency
• Risk/likelihood of occurrence
• Reversibility
• Contribution to cumulative impacts
 PREDICTION AND ASSESSMENT OF IMPACTS
ON THE NOISE ENVIRONMENT
• Noise is unwanted sound which may be hazardous to health, interfere
with speech and verbal communications or is otherwise disturbing,
irritating or annoying.
• Sound is defined as any pressure variation in air, water or other fluid
medium which may be detected by the human ear.
• Characteristics of sound wave:
◦ Amplitude
◦ Frequency (Hz)
Sound Pressure Level
• The human response is essentially logarithmic, therefore noise
measurements are expressed by the term “sound pressure level” (SPL)
which is logarithmic ratio of sound pressure to a reference pressure and
is expressed as a dimensionless unit of power, the decibel (dB)
• The equation for sound pressure level is as follows:
SPL = 20 log (P/P0)
• Where SPL = sound pressure level
• P = sound pressure, microbar
•P0 = reference pressure, 0.0002 microbar
Noise Impacts
• Noise impacts can be concern during the construction and the operational
phases of projects.
• Factors which are important in determining noise levels that will potentially
impact as populations include:
• ◦ distance from the noise sources
• ◦ natural or man-made barriers between the source and the impacted
population
• ◦ weather conditions which could potentially absorb, reflect, or focus sound
(such as wind speed and direction and temperature inversions)
• ◦ the scale and intensity of the particular construction phase.
• Two types of noise emissions are of concern: –
• ◦ Impulse noise : that is noise of short duration and high density such as
explosions, sonic booms, and artillery fire
• ◦ Continuous noise : that is longer duration and lower intensity noise such as
that from construction or traffic
Conceptual approach
The six generic steps associated with noise environment impacts are:
1. Identification of level of noise emissions and impact concerns related to construction
and operation of the developed projects
2. Description of the environmental setting in terms of existing noise levels and noise
sources, along with land use information and unique receptors in the project area
3. Procurement of relevant laws, regulations, or criteria related to noise levels, land use
compatibility and noise emission standard
4.Conduction of impact prediction activities, including the use of simple noise source
specific models, comprehensive mathematical models, and/or qualitative prediction
techniques based on examination of case studies and the exercise of professional judgment
5. Use of pertinent information from step-3, along with professional judgment and public
input, to assess the significance of anticipated beneficial and detrimental impacts
6. Identification, development and incorporation of appropriate mitigation measures for
the adverse impacts