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August 15, 2014
Cooling water rule tilts toward industry

Both industry and environmental groups are pointing – with opposite sentiments – at the entrainment provision in the EPA’s new rule for cooling water intake structures at existing power plants and industrial facilities. 

Under the rule, requirements for entrainment – when aquatic organisms are drawn into cooling water intake structures – are placed in the hands of writers of the national pollutant discharge elimination system (NPDES) permits the CWA requires for cooling water intake.  NPDES permits are commonly provided by state agencies, and the rule provides the states and its permit writers with considerable flexibility to make site-specific decisions regarding how facilities must comply with the national requirement to protect organisms from entrainment.  While the EPA’s rule provides examples of the types of equipment that could meet the best technology available (BTA) requirement to control entrainment, the Agency also allows permit writers to require no additional controls.

This was a welcomed development for industry since it ensures that state permit writers, who are usually well acquainted with the circumstances of resident industries, will not be compelled to meet an inflexible federal standard.

“States retain authority to impose effective entrainment measures appropriate for the site-specific features of each facility,” commented Dominion Resources, one of the nation’s largest energy companies, in response to the rule. 

State capacity doubted

But for environmental groups, the provision amounts to avoiding any action that would in fact correct the existing problems with entrainment. 

“EPA has essentially abdicated its responsibilities under the Clean Water Act and passed the buck to the states, most of which have shown they don’t have the capacity or the will to safeguard our waterways from these sources,” said the Natural Resources Defense Council in response to the rule.

2nd try at Phase II

The rule establishes requirements under CWA section 316(a) for existing power generating facilities and existing manufacturing and industrial facilities that withdraw more than 2 million gallons per day (mgd) of water from waters of the United States and use at least 25 percent of the water they withdraw exclusively for cooling purposes.  The BTA requirements will apply to both entrainment and impingement, which occurs when aquatic organisms are pinned against cooling water intake structures.  According to the EPA, each year hundreds of billions of mostly juvenile fish, crabs, and shrimp fall victim to impingement and entrainment, and 2.1 billion are killed. 

The EPA has implemented the cooling water intake program in three phases with the Phase I rule covering all new facilities except offshore oil and gas facilities, which were addressed in the Phase III rule.  The Phase II rule, which covers existing facilities and was initially issued by the EPA in 2004, included a restoration provision that was invalidated by the court, which remanded the rule to the Agency for revision.

According to the EPA, the current rule will apply to about 1,065 facilities – 544 power plants and 521 manufacturing plants.


Under the new Phase II rule, the owner or operator (O/O) of an affected facility can come into compliance with the BTA requirement to control impingement by implementing one of seven options:

  • Operate a closed-cycle recirculating system.
  • Operate a cooling water intake structure that has a maximum through-screen design intake velocity of 0.5 feet per second (fps).
  • Operate a cooling water intake structure that has a maximum through-screen intake velocity of 0.5 fps.
  • Operate an offshore velocity cap.
  • Operate a modified traveling screen.
  • Operate any other combination of technologies, management practices, and operational measures that the permitting authority determines is BTA for impingement reduction.
  • Achieve the specified impingement mortality performance standard.


The site-specific entrainment provision reflects the EPA’s assessment that there is no single technology basis that is BTA for entrainment at existing facilities.  According to the Agency, site specific decision-making may lead to a determination by the NPDES permitting authority that entrainment requirements should be based on 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.  However, site-specific decision-making may also lead to no additional technologies being required.

Also under the rule, facilities that withdraw very large amounts of water – at least 125 million gallons per day – are required to conduct studies to assist their permitting authorities in determining whether and which site-specific controls, if any, would be required to reduce the number of aquatic organisms entrained.  This decision process would include public input.

New units

The rule specifies that new units at existing power plants will be required to implement one of two technologies.  First, the owner/operator must reduce actual intake flow at the new unit, at a minimum, to a level commensurate with what can be achieved by use of a closed-cycle recirculating system.  Alternatively, the O/O must demonstrate to the permitting authority that the facility has 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.

Phase II cooling water intake rule

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