The North American Electric Reliability Corp.’s 2011 review of EPA’s cooling water regulations had assumed that the rule would affect 1,200 generators with once-through cooling systems. EPA’s announcement of the final rule yesterday said it would affect less than half as many plants, however.

Covered are:

• Existing facilities that withdraw more than 2 million gallons per day (MGD) of water from waters of the U.S. and use at least 25% of their withdrawals exclusively for cooling. They are required to reduce fish impingement using one of seven options.
• Facilities that withdraw at least 125 MGD, which must conduct studies to determine whether controls will be required to reduce entrainment.
• New units at an existing facility that are built to increase its generating capacity of the facility. They will be required to reduce the intake flow to a level similar to that of a closed-cycle system.