Rules adopted by the California Water Resources Control Board on Tuesday will force 19 coastal power plants—including two nuclear plants—in that state to phase out “once-through cooling” practices to reduce their impact on marine life. The new rules—the first in the U.S. to restrict ocean water use for existing power plants—could have widespread implications, including massive costs and forced shutdowns.

The Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling, which now heads to the state Office of Administrative Law, establishes best technology–based standards to implement the federal Clean Water Act section 316(b). It will allow aging plants to develop replacement infrastructure—such as implementing a closed-cycle cooling system—before shutting down cooling systems.

The rules were developed to protect marine organisms “without disrupting critical needs of the state’s electrical generation and transmission system,” the regulatory body said on its website. The agency has estimated that upgrades will cost on average about 1 cent a kilowatt-hour, on average. 

California power plants currently have the ability to withdraw more than 15 billion gallons per day from state coastal and estuarine waters using a single-pass system. A majority will have until at least 2015 to comply with the regulations, though plants in the Los Angeles area will have until 2020 because of its complex power needs.

Among the plants affected are Dynegy’s South Bay plant near San Diego and its Morro Bay plant—both which may be shut down by 2015, the company told the board on Tuesday. The state’s two nuclear power plants, Diablo Canyon and San Onofre, will have until 2024 and 2022, respectively, to reconfigure their cooling systems. The operators of both plants have protested for the last three years that moving to cooling towers would be both massively expensive and likely impossible.

The state said that cooling water withdrawals cause adverse impacts when larger aquatic organisms, such as fish and mammals, are trapped against a facility’s intake screens (impingement) and when smaller organisms, such as larvae and eggs, are drawn through the cooling system (entrainment) and killed.

The five-member Water Resources Control Board voted unanimously to pass the regulations nearly five years after it was first proposed. The rules come one month after regulators in New York State denied a water-quality permit for Energy Corp.’s 2,000-MW Indian Point nuclear power plant.

California water board staff said that in developing the policy, it had consulted with representatives from the California Energy Commission, the California Public Utilities Commission, the California Coastal Commission, the California State Lands Commission, the California Air Resources Board, and the California Independent System Operator to “develop realistic implementation plans and schedules that will ensure electric grid reliability.”

Sources: California Water Resources Control Board, POWERnews