EIA is an exercise to be carried out before any project or major activity is undertaken to ensure that it will not in any way harm the environment on a short term or long term basis. Any developmental endeavor requires not only the analysis of the need of such a project, the monetary costs and benefits involved but most important, it requires a consideration and  detailed assessment of the effect of a proposed development on the environment.

  The environment impact process was introduced with the purpose of identifying /evaluating the potential beneficial and adverse impacts of development  projects on the environment, taking in to account environmental, social, cultural and aesthetic considerations. All of these considerations are critical to determine the viability of a project and to decide if a project should be granted environmental clearance. 

 An EIA concentrate on problems, conflicts and natural resource constraints  which might affect the viability of a project. It also predicts how the project could harm to people, their homeland, their livelihoods, and the other nearby developmental activities. After predicting potential impacts, the EIA identifies measures to minimize the impacts and suggests ways to improve the project viability.  

The aim of an EIA is to ensure that potential impacts are identified and addressed at an early stage in the projects planning and design. To achieve this aim, the assessment  finding are communicated to all the relevant groups who will make decisions about the  proposed projects, the project developers and their investors as well as regulators , planners and the  politicians. Having read the conclusions of an environmental impact assessment, project planners and engineers can shape the project so that its benefits can be achieved and sustained with out causing adverse impacts. 

In recent years, major projects have encountered serious difficulties because insufficient account has been taken of their relationship with  the surrounding environment. Some  projects have been found to be unsustainable because of resource depletion. Others have been abandoned because of public opposition, financially encumbered by unforeseen costs, held liable for damages to natural resources and even been the cause of disastrous accidents. Given this experience, it is very   risky to undertake finance, or approve a major project without first taking in to account  its environmental consequences and then siting and designing the project so as to minimize adverse impacts. 

 Due to public pressure on the government to accept accountability for the activities of its agencies the National Environmental Policy Act (NEPA) was formed in USA during 1970. This was the basis for the development of a mechanism which came to be known as Environmental Impact Assessment (EIA).