The U.S. Environmental Protection Agency recently published final regulations to establish requirements for cooling water intake structures at existing facilities. According to the EPA, “cooling water is withdrawn for the purpose of dissipating waste heat from industrial processes.  Over half of all water withdrawn in the United States each year is for cooling purposes. By far, the largest industrial use of cooling water is for thermoelectric generation, but cooling water is also used in the manufacture of aluminum, chemicals and allied products, food and kindred products, pulp and paper, refined petroleum products, and steel, as well as in other industries.”  EPA identified several potential problems with cooling water withdrawals, including impingment and entrainment:

“The withdrawal of cooling water by existing facilities removes and kills hundreds of billions of aquatic organisms from waters of the United States each year, including plankton (small aquatic animals, including fish eggs and larvae), fish, crustaceans, shellfish, sea turtles, marine mammals, and many other forms of aquatic life.  Most impacts are to early life stages of fish and shellfish.  Aquatic organisms drawn into cooling water intake structures are either impinged (I) on components of the intake structure or entrained (E) in the cooling water system itself. . . . In addition to direct losses of aquatic organisms from I&E, a number of indirect, ecosystem-level effects may also occur, including (1) disruption of aquatic food webs resulting from the loss of impinged and entrained organisms that provide food for other species, (2) disruption of nutrient cycling and other biochemical processes, (3) alteration of species composition and overall levels of biodiversity, and (4) degradation of the overall aquatic environment.”

This rule includes a national performance standard as the Best Technology Available (“BTA”) to address impingement mortality at existing cooling water intake structures.  The standard is based on modified traveling screens with fish returns.  With regard to entrainment, this rule contains a national BTA standard that is a process for a site-specific determination of entrainment mitigation requirements at existing cooling water intake structures.  The entrainment provision reflects EPA’s assessment that there is no single technology basis that is BTA for entrainment at existing facilities, but instead a number of factors that are best accounted for on a site-specific basis. Those site-specific factors are: variable speed pumps, water reuse, fine mesh screens, a closed-cycle recirculating system, or some combination of technologies that constitutes BTA for the individual site.