The Environmental Impact Assessment (EIA) is an assessment tool applicable to some of the public utility infrastructure projects promoted by REN. The EIA comprises various stages:
Given the specific nature of the sector, in 2008 REN produced a methodology manual for the EIA of the National Electricity Transmission Grid - Overhead Lines. This manual was produced in partnership with the Agência Portuguesa do Ambiente and the Associação Portuguesa de Avaliação de Impactes and constitutes a key document for preparing environmental impact studies of this type of infrastructure and respective EIA processes. Diffetrent entities involved in the EIA process participated in this working group, in particular the Instituto Português de Arqueologia, the Instituto de Conservação da Natureza e de Biodiversidade and the Coordination and Regional Development Commissions.
In addition, in order to harmonise the procedures and methodologies associated with EIA processes, in 2011 REN published another methodology manual to assess the environmental impact of substations.