"Thermoelectric generating plants and manufacturing facilities withdraw large volumes of water for production and, especially, to absorb heat from their industrial processes. Water withdrawals by power producers and manufacturers represent more than one-half of water withdrawn daily for various uses in the United States. Although water withdrawal is a necessity for these facilities, it also presents special problems for aquatic resources. In particular, the process of drawing surface water into the plant through cooling water intake structures (CWIS) can simultaneously pull in fish, shellfish, and tiny organisms, injuring or killing them. Congress enacted Section 316(b) of the Clean Water Act (CWA) specifically to address CWIS. Regulatory efforts by the Environmental Protection Agency (EPA) to implement Section 316(b) have a long and complicated history over 35 years, including legal challenges at every step by industry groups and environmental advocates. Currently most new facilities are regulated under rules issued in 2001, while rules for existing facilities were challenged and remanded to EPA for revisions. In response to the remands, in March 2011 EPA proposed national requirements affecting approximately 1,150 existing electric powerplants and manufacturing facilities. Even before release, the proposed regulations were highly controversial among stakeholders and some Members of Congress. The issue for Congress has been whether a stringent and costly environmental mandate could jeopardize reliability of electricity supply in the United States. Many in industry feared, while environmental groups hoped, that EPA would require installation of technology called closed-cycle cooling that most effectively minimizes the adverse environmental impacts of CWIS, but also is the most costly technology option."
CRS Report for Congress, R41786