how 316(b) could impact your power plant

Daniel Marmer & Kenneth Snell, Sargent & Lundy LLC

The U.S. Environmental Protection Agency (EPA) released final regulations implementing section 316(b) of the Clean Water Act earlier this year. These Phase II regulations apply to existing power plants that use cooling water intake structures (CWIS) designed to withdraw 50 million gallons (or more) per day from rivers, streams, lakes or other “waters of the United States.” This includes most open cycle, or once through, cooling systems. EPA estimates that 543 individual facilities will be subject to the Phase II regulations. (The Phase I regulations, which were published in 2001, apply to new power plant intake structures.)

The 316(b) regulations seek to minimize mortality to fish, eggs, larvae and other aquatic organisms that come in contact with the CWIS. The two main causes of this mortality are from impingement (where the species are trapped against the CWIS screen by force of the intake water) and entrainment (where the species are drawn into the cooling system itself and passed through the heat exchangers).

The final rule defines an “existing facility” as one that commenced construction prior to January 17, 2002. The definition would include a new unit at an existing site that utilizes the existing CWIS.

Under the final rule, the EPA has established national performance standards that require the use of the best technology available (BTA) to reduce aquatic mortality. The simplest way to comply with BTA is to reduce the intake velocity to that of a closed-cycle recirculating system (0.5 feet per second or less). This could be accomplished through the installation of cooling towers, dry cooling technology or additional intake cells to lower the velocity. These options have the least amount of requirements for monitoring source water flow and aquatic species data. No impingement mortality study would be required.

A facility can also comply with the 316(b) performance standards by implementing technologies and measures that reduce impingement mortality by 80 percent to 95 percent. If a CWIS withdraws more than 5 percent of the mean annual flow of a freshwater river or stream, the facility will also have to reduce entrainment mortality by 60 percent to 90 percent. These reductions are based on a theoretical baseline CWIS that is located on the shore, parallel with the shoreline, with a standard 3/8-inch debris screen, and no impingement or entrainment control systems. Many facilities will already have some level of reduction based on the design and location of their existing CWIS that would count towards compliance with the rule.

There are a number of technological, operational and restoration measures that can bring the mortality reductions up to the performance standards. Examples of technological modifications include the installation of aquatic filter barrier systems, fine-mesh traveling intake screens with fish return buckets and sprays, flow-altering louvers and fish behavioral deterrents. Operational measures may include seasonal shutdowns or reductions in cooling water flow during periods of high aquatic activity. Restoration measures may include fish restocking or wetland creation programs. A recent court case removed the restoration option from the Phase I 316(b) rule, and it is likely that the restoration option will similarly be challenged for Phase II.

If a facility chooses to pursue technological or operational measures to comply with the rule, then it must submit a comprehensive demonstration study to the state or local permitting authority. When the Phase II 316(b) regulations were proposed, many stakeholders commented that the vast amount of data collection required for a comprehensive demonstration study were too onerous. For the final rule, the EPA has approved a single rule-specific design and construction technology that would meet BTA without collecting flow and impingement data. A facility located on a freshwater river or stream can meet BTA by installing a submerged cylindrical wedgewire screen.

A facility also has the option of demonstrating that its cost of compliance with the BTA performance standards would be significantly greater than the EPA’s estimated costs for a similar facility. In order to pursue this option, a facility must submit a comprehensive demonstration study, which also includes additional components on cost evaluation. If accepted, the state or local permitting authority would issue a site-specific BTA determination for minimizing adverse environmental impact. This site-specific BTA must achieve level of protection that comes as close as practicable to the performance standards within reasonable costs.

Compliance with the 316(b) requirements will be concurrent with the renewal of each facility’s National Pollutant Discharge Elimination System (NPDES) permit. NPDES permits generally expire every 5 years, and an application for renewal must be submitted at least 180 days before expiration. All facilities will need to submit source water physical data, cooling water intake structure data and a narrative description of the entire cooling water system.

Facilities whose NPDES permits will expire within four years after the effective date of the final rule can request a deadline extension for submitting the above data and the comprehensive demonstration study (if required).

Marmer and Snell are environmental engineers who currently work as associates with Sargent & Lundy’s environmental services division. They can be reached at and respectively.


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