Screening is the first key decision of the EIA process. Some type of screening procedure is necessary because of the large number of projects and activities that are potentially subject to EIA. The purpose of screening is to determine whether a proposal requires an EIA or not. It is intended to ensure that the form or level of any EIA review is commensurate with the importance of the issues raised by a proposal.
The conduct of screening thus involves making a preliminary determination of the expected impact of a proposal on the environment and of its relative significance. A certain level of basic information about the proposal and its location is required for this purpose. The time taken to complete the screening process will depend upon the type of proposal, the environmental setting and the degree of experience or understanding of its potential effects. Most proposals can be screened very quickly (in an hour or less) but some will take longer and a few will require an extended screening or initial assessment. Similarly, the majority of proposals may have few or no impacts and will be screened out of the EIA process. A smaller number of proposals will require further assessment. Only a limited number of proposals, usually major projects, will warrant a full EIA because they are known or considered to have potentially significant adverse impacts on the environment; for example, on human health and safety, rare or endangered species, protected areas, fragile or valued ecosystems, biological diversity, air and water quality, or the lifestyle and livelihood of local communities.
The screening process can have one of four outcomes:
- no further level of EIA is required;
- a full and comprehensive EIA is required;
- a more limited EIA is required (often called preliminary or initial assessment); or
- further study is necessary to determine the level of EIA required (often called an initial environmental evaluation or examination [IEE]).
Screening establishes the basis for scoping, which identifies the key impacts to be studied and establishes terms of reference for an EIA. Many EIA systems have formal screening and scoping procedures. In some cases, however, these terms may be used differently or applied at the discretion of the proponent. Also, on occasion, the screening and scoping stages may overlap, for example, when a further study (or IEE) is undertaken to determine whether or not the potential impacts are significant enough to warrant a full EIA.
The requirements for screening and the procedure to be followed are often defined in the applicable EIA law or regulations. In many cases, the proposals to which EIA applies are listed in an annex. Usually, the proponent is responsible for carrying out screening, although this is done by the competent authority in some EIA systems. Whatever the requirements, screenng should occur as early as possible in the development of the proposal so that the proponent and other participants are aware of the EIA obligations. It should be applied systematically and consistently (so that the same decisions would be reached if others conducted the screening process).
The screening procedures employed for this purpose can be classified into two broad, overlapping approaches:
- prescriptive or standardised approach â€“ proposals subject to or exempt from EIA are defined or listed in legislation and regulations; and
- discretionary or customised approach â€“ proposals are screened on an individual or case-by-case base, using indicative guidance.
Specific methods used in screening include:
- legal (or policy) definition of proposals to which EIA does or does not apply;
- inclusion list of projects (with or without thresholds) for which an EIA is automatically required; exclusion list of activities which do not require EIA because they are insignificant or are exempt by law (e.g. national security or emergency activities); and
- criteria for case-by-case screening of proposals to identify those requiring an EIA because of their potentially significant environmental effects.
Both prescriptive and discretionary approaches have a place and their specific procedures can be combined into a comprehensive procedure (as shown in the figure below). Where inclusive project lists are used, the disposition of most proposals will be immediately apparent. However, some proposals will be on the borderline in relation to a listed threshold and for others, the environmental impacts may be unclear or uncertain. In these situations, case-by-case screening should be undertaken, applying any indicative guidelines and criteria established for this purpose. This process gives the proponent or competent authority greater discretion than mandatory lists in determining the requirement for EIA.
In this context, screening is a flexible process and can be extended into preliminary forms of EIA study. These â€˜extended screeningâ€™ procedures include:
- initial environmental examination â€“ carried out in cases where the environmental impacts of a proposal are uncertain or unknown (e.g. new technologies or undeveloped areas);
- environmental overview â€“ carried out as a rapid assessment of the environmental issues and impacts of a proposal; and
- class screening â€“ carried out for a family of small projects or repetitive activities, where the environmental effects and means of mitigation are known but there is potential for cumulative impacts (e.g. dredging, road realignment, bank stabilisation).