Environmental impact assessment is usually conducted in three stages which optimize the resources and increases the effectively of the assessment. The process of environmental impact assessment has to be integrated with the development.

The effects of a development activity should be examined at an early stage in the planning of the project and not after the decisions regarding its design and location have been decided by other factors. Three stages of environmental impact assessment precede every decision making step of the project – extending and intensifying itself as the project planning is elaborated. These steps are:

1. Initial scrutiny.

2. Rapid Environmental Impact Assessment.


3. Comprehensive Environmental Impact Assessment.

(1) Initial Screening:

The first step in the process of Environmental Impact Assessment is to decide whether the impact assessment is actually needed for the development project being undertaken or it is simply unnecessary. Screening helps to clear the type of project which is not likely to cause serious environmental problems quickly.

(2) Rapid Environmental Impact Assessment:


If it is felt that the project is likely to cause some detrimental effects on the environment, it is subjected to Rapid Environmental Assessment which involves:

1. Identification of the important impacts of the project on the environment.

2. Evaluation of the impact of the project on the locality or entire region.

3. Conducting cursory cast benefit analyses.


4. Listing of the issues which are unresolved and which need examination in detail.

Rapid Environmental Impact Assessment, thus, attempts to identify the key issues in a particular case so that attention or resources could be directed to relevant aspects. Issues which are not important enough to deserve further studies are omitted. This helps in optimizing our resources. Rapid Environmental Assessment usually involves interactions and discussion between public, various private organizations and experts as well as the scientific examination of impact caused by critical elements of project on the environment.

(3) Comprehensive Environmental Assessment:

Comprehensive Environmental Assessment is usually undertaken after the initial screening and Rapid Impact Assessment has been performed. The earlier work has already generated some information about the project and its likely impact on the environment and it is now a comprehensive study of the critical aspects of project which is taken-up in the Comprehensive Environmental Impact Assessment. It usually involves collection and evaluation of the following set of information.


1. Base-line data about the project, its description in detail along with the description of the existing environment.

2. Impact Identification.

3. Impact Prediction.

4. Evaluation of the impacts.


5. Mitigative measures and monitoring plans.

6. Informing the society and the decision makers.

1. Collection of Baseline Data:

The nature and the description of the project to be undertaken along with the details about the magnitude of activity which shall occur in the locality are the basic information’s required for Comprehensive Impact Assessment. The condition of the locality and the description of existing environment in which the project has to come up are also necessary requisites for the impact assessment.


The description of the environment should include all its components such as atmosphere, hydrosphere, lithosphere and the biosphere. Comprehensive Impact Assessment has to conduct socio-economic surveys also among the human settlements located nearby.

Data on population densities, age and sex distribution, ethnic groups, education level, morbidity and mortality rates etc. are very valuable for the assessment of the impact of development activities on human society. So also are the descriptions of the community, life styles, the needs and problems of the people, likely productivity levels, unemployment figures, and means of livelihood etc. which are necessary to assess the socio-economic aspects of the project.

2. Impact Identification:

Impact identification attempts to answer the question, “What will happen when the project enters its operational stage?” A list of important impacts such as changes in ambient air quality, changes in water and soil qualities, noise levels, wild life habitats, species diversity, social and cultural systems, employment levels etc. may be prepared. The important sources of impact like smoke emission, consumption of water, discharge of effluents etc. are identified.

3. Impact Prediction:

Impact prediction examines the extent of changes which occur in the system due to the project activity. As far as possible, impact prediction scientifically quantities the effect and examines its secondary and synergistic consequences for the environment and local community. The impact is closely studied and evaluated for its subsequent effects on the components of the environment.

For example, the discharge of effluents in the local waters causes deterioration in the quality of water, its secondary effect is degeneration of fishereis which is followed by detrimental economic effect on the fishermen of the locality. With means of livelihood gone the fishermen may have to migrate to other localities or seek some other alternative for livelihood. This could cause a rise in the crime graph of the locality.

4. Impact Evaluation:

Impact evaluation attempts to answer the question, “Do the changes really matter?” This step evaluates the predicted adverse impacts to determine whether they are significant enough to warrant mitigation. If the project has to come up on inhospitable land with very little biological significant localities around and no human settlements or very sparsely populated areas a little deterioration of the environment may be permitted.

However, if the development activity is undertaken in biologically significant locality even minor detrimental impacts should be avoided. Either adequate mitigative efforts should be taken up or the project could be shifted to some other locality. The judgement of significance is usually based on

1. Comparison of predicted information with accepted standards.

2. Reference to pre-set criteria such as protected places, features or species.

3. Consultation with relevant decision makers.

5. Mitigative Measures and Monitoring Plans:

If the changes caused by the developmental activities are significant, the process of environmental impact assessment proceeds to examine ways and means to mitigate the adverse effects. A wide range of measures may be proposed to prevent, reduce, remedy or compensate each of the adverse impact evaluated as significant. The measures are critically examined for their effectiveness. The possible mitigative measures may include:

1. Introduction of pollution control measures, waste treatment, strict monitoring etc. to mitigate the adverse effects caused by the developmental activity.

2. Changing project sites, routes, processes, raw materials, operating methods, disposal routes or location or wastes and engineering design.

3. Offering restoration of damaged resources, money to affected people, concessions on other issues, improvement in the quality of life for the community etc.

All mitigation measures cost something. This cost should be estimated and added to the value of the product. If a number of mitigative measures are proposed the cost of each of these measures should be estimated and compared. Environmental Impact Assessment should explicitly analyse implications of adopting different alternatives so as to make policy decisions easier. A thorough cost benefit analyses should be made to simplify the decision making process.

6. Informing the Society and Decision Makers:

Documentation and communication of the findings of the Environmental Impact Assessment to the relevant people also constitutes an important step of the impact assessment. Many technically sound Impact Assessment studies fail to exert their importance and impress the decision makers simply because of poor documentation.

The assessment can achieve its true purpose only if its findings are well documented and communicated to the policy-makers. For the effective communication one has to identify the target audience and then shape the report accordingly so that it becomes a meaningful document. For the purpose, Impact Assessment report may have to be written as a non-technical document as well, so that its contents are intelligible to non-technical administrators and general public while the technical document is studied by review committee and experts.