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Power-Plant Cooling: How Many Fish Per kWh?

EPA flounders on the Clean Water rule, while producers tackle the real enemy—shortage.

Fortnightly Magazine - July 2005
  • would cover only 5 percent of potential Phase-III facilities, but 45 percent of the total potential water intake.
  • Option 3 The rule would apply only to facilities that withdraw at least 100 MGD from an ocean, estuary, tidal river, or one of the Great Lakes. This option would cover only the most sensitive water bodies. It would cover only 4 percent of the facilities potentially covered under Phase III, and 18 percent of the total potentially covered water intake. (Note, for example, that this option would not apply to a small gen plant taking cooling water from the Colorado or Snake Rivers in the West, as these water bodies are not “tidal.”)

Cost-Benefit Analyses. EPA estimates that the proposed options would affect anywhere between 19 and 136 existing facilities, and would protect between 30 million and 50 million aquatic organisms annually from death or injury by cooling water intake structures. However, the associated “use benefits” (identifiable dollar benefits from commercial and recreational fishing) would range only from $1.3 million to $1.9 million per year, depending on the design intake flow threshold of the proposed options. That would fall way short of the estimated compliance cost, which EPA has estimated as between $17.4 million and $46.8 million per year, depending upon which of the 3 regulatory options is chosen:

  • Option 1  Estimated cost outweighs estimated benefit by about 26 to 1. (EPA estimates compliance cost at $47.3 million to $50.1million per year, or between $348,000 and $368,000 on average annually per covered facility. Total annual “use” benefits run from $1.5 million to $1.9 million.
  • Option 2  Cost outweighs benefits by about 19 to 1. (Cost runs $22.8 million to $24.1 million, or between $912,000 and $964,000 annually per covered facility. “Use-value” benefits run $0.98 million to $1.26 million per year.)
  • Option 3   Cost outweighs benefits by about 13 to 1. (Cost runs between $17.6 million to $18.2 million, or $926,000 to $958,000 per year per covered facility. Benefits range from $1.1 million to $1.4 million in annual use-value.)

The “No Rule” Option. If it so chooses, EPA may decide to refrain from issuing any sort of national standard for Phase III facilities, and instead would throw the matter back to the states for permitting on a case-by-case basis.

(See generally,, and public comments filed in EPA Docket OW-2004-0002. )—BWR


A Primer on Dry Cooling

In General. Dry-cooling systems transfer heat to the atmosphere without the evaporative loss of water. As a result, water consumption rates run very low for dry cooling as compared to wet cooling systems. However, since the dry-cooling unit does not rely on evaporative cooling as does a wet cooling tower, larger volumes of air must be passed through the system. As a result, dry-cooling towers need larger heat transfer surfaces and, therefore, tend to be larger in size than comparable wet cooling towers.

Technology Types. There are two types of dry-cooling systems for power-plant applications: direct and indirect.

  • Direct Dry Cooling . Uses air to condense steam directly. The most common version of