A final rule released by the Environmental Protection Agency (EPA) today will affect cooling water intake structures at 544 U.S. power plants and provide those plants with lower-cost compliance options than previously proposed to reduce fish impingement and entrainment.

The final rule issued under Section 316(b) of the Clean Water Act applies to facilities that each withdraw at least two million gallons per day of cooling water from waters of the U.S. The national requirements, which will be implemented through National Pollutant Discharge Elimination System (NPDES) permits, “puts implementation analysis in the hands of the permit writers so requirements can be tailored to the particular facility,” the EPA said today.

It requires that existing facilities that withdraw at least 25% of their water from an adjacent waterbody exclusively for cooling purposes reduce fish impingement. To “ensure flexibility,” the EPA gives generators seven options for meeting “best technology available (BTA)” requirements for reducing impingement.

The options identify four technologies (closed-cycle recirculating systems, reduced design intake velocity, reduced actual intake velocity, and existing offshore velocity caps) that will generally comply with the BTA impingement mortality standard. But it also provides that, if the NPDES permit director determines that modified traveling screens are insufficient to protect shellfish, the director may establish additional measures under § 125.94(c)(8) such as seasonal deployment of barrier nets, or if modified traveling screens are insufficient to protect other species, the director may establish additional protective measures under § 125.94(c)(9).

The final rule also requires that existing facilities that withdraw more than 125 million gallons per day of water conduct studies to help their permitting authority determine whether and what site-specific controls, if any, would be required to reduce the number of aquatic organisms entrained by cooling water systems. This decision process would include public input.

New units that add generation capacity at an existing facility have two options for compliance

The first alternative would require generators  to reduce actual intake flow at a new unit—at a minimum—to a level commensurate with that attained by a closed-cycle recirculating system, and that could include installing closed-cycle cooling. The second alternative would require generators to demonstrate that they have installed, and will operate and maintain, technological or other control measures for each intake at the new unit that achieves a prescribed reduction in entrainment mortality of all stages of fish and shellfish that pass through a sieve with a maximum opening dimension of 0.56 inches.

“EPA is making it clear that if you have cooling water intakes you have to look at the impact on aquatic life in local waterways and take steps to minimize that impact,” said Nancy Stoner, EPA’s acting assistant administrator for water said in a statement today.

Power sector groups lauded the EPA’s final rule’s overall compliance costs, which they said will be lower compared to the proposed rule. “Based upon our initial review of the rule, we are pleased that EPA has avoided imposing a categorical one-size-fits-all approach to compliance; has embraced significant elements of flexibility; and has acknowledged the importance of weighing costs with environmental protection,” said Edison Electric Institute (EEI) President Tom Kuhn in a statement today.

“However, the final rule will present significant operational and compliance challenges. We remain concerned that the rule will not provide states with sufficient flexibility to regulate cooling water impacts cost-effectively on a case-by-case basis.”

The agency issued the final rule three days after a court-set May 16 deadline. Issuance of the final rule under Section 316(b) following  a settlement agreement with a coalition of  environmental groups—including Riverkeeper Inc., Waterkeeper Alliance, Natural Resources Defense Council, Sierra Club, and Environment America—had previously been delayed five times.

Riverkeeper, on behalf of the coalition of environmental groups, today lambasted the EPA for wasting the opportunity to set “reasonable rules.” The EPA “has instead abdicated the responsibility to state agencies that are simply not equipped to make these decisions alone,” said Reed Super, an attorney representing Waterkeeper Alliance and others. “Unfortunately, EPA’s rule will perpetuate the unacceptable status quo that has allowed antiquated plants to withdraw nearly 100 trillion gallons of fresh and sea water each year, and indiscriminately kill fish and wildlife instead of recycling their cooling water or use dry cooling technology, as modern plants have done for the past three decades. We are beyond disappointed with this new rule.”

While Congress mandated that the EPA establish cooling water standards in 1972, Riverkeeper and other groups sued the EPA in 1993 and obtained a consent decree in 1995, requiring the EPA to issue a 316(b) rule in 1999. The consent decree was later amended to allow the EPA to issue the rule in three phases: Phase I (new plants) was finalized in 2001 and a portion of Phase III (new offshore and coastal oil rigs) was finalized in 2006; Phase II (large existing power plants) and the remainder of Phase III (small power plants and manufacturing facilities) were issued in 2004 and 2006, respectively, but were remanded by courts in 2009 and 2010.

For an in-depth analysis of how to evaluate site-specific factors essential for compliance with the 316(b) rule, see POWER’s upcoming June 2014 cover story.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)