Jump to main content or area navigation.

Contact Us

Water: Cooling Water Intakes (316b)

Cooling Water Intakes

Cooling towers

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Thousands of industrial facilities use large volumes of cooling water from lakes, rivers, estuaries or oceans to cool their plants. Cooling water intake structures cause adverse environmental impact by pulling large numbers of fish and shellfish or their eggs into a power plant's or factory's cooling system. There, the organisms may be killed or injured by heat, physical stress, or by chemicals used to clean the cooling system. Larger organisms may be killed or injured when they are trapped against screens at the front of an intake structure.

Section 316(b) of the Clean Water Act requires EPA to issue regulations on the design and operation of intake structures, in order to minimize adverse environmental impacts. EPA promulgated regulations in 2001, 2003, 2006 and 2014. The requirements are included in the NPDES permit regulations, 40 CFR Parts 122 and 125 (Subparts I, J, and N). 

Facilities Covered

The regulations apply to facilities that use cooling water intake structures to withdraw water from waters of the U.S. and have or require an NPDES permit. Applicability for a specific facility depends on the industrial sector and the facility size. Many industrial sectors are affected; the sectors with the largest number of regulated facilities are:

  • Electric generating plants
  • Pulp and paper mills
  • Chemical manufacturing plants
  • Iron and steel manufacturing
  • Petroleum refineries
  • Food processing
  • Aluminum manufacturing.

For precise definitions of coverage, see the regulations at 40 CFR 125.81, 125.91 and 125.131.

Final Rule for Existing Electric Generating Plants and Factories – 2014

This rule covers roughly 1,065 existing facilities that are designed to withdraw at least 2 million gallons per day of cooling water. EPA estimates that 521 of these facilities are factories, and the other 544 are power plants.

  • The facilities are required to choose one of seven options to reduce fish impingement.
  • Facilities that withdraw at least 125 million gallons per day must conduct studies to help their permitting authority determine whether and what site-specific controls, if any, would be required to reduce entrainment of aquatic organisms.
  • New units added to an existing facility are required to reduce both impingement and entrainment that achieves one of two alternatives under national entrainment standards.
  • EPA has concluded Endangered Species Act consultation with the Fish and Wildlife Service and the National Marine Fisheries Service.

new icon Implementation Support

  •       Additional resources for permit writers, affected facilities and other interested stakeholders.

Rulemaking History

  • Information on earlier rules (2001-2006) and support documents

Additional Information

After reviewing the materials above, if you still have questions, please contact Paul Shriner, shriner.paul@epa.gov, at 202-566-1076.


Jump to main content.