The story behind PG&E's decision to close 

A letter by Mark Henry mistakenly asserts that the reason PG&E decided to close the Diablo Canyon nuclear plant by the end of 2025 was because of the California requirement that PG&E cease to use once-through cooling in order to protect marine life. The alternative would have been for PG&E to build expensive cooling towers ("Re: Diablo is a marine life killer," Dec. 31).

The facts, as stated in documents from the California Water Resources Control Board and from PG&E, prove otherwise.

In 2010, California enacted the Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling. This mandate required that by 2015 all coastal power plants must have in place replacement cooling systems that conserve water and protect the marine environment. But Diablo Canyon was excused from compliance with this policy precisely because of the expenses of cooling towers.

Hence, the expenses of building cooling towers had nothing to do with PG&E's decision to close the Diablo Canyon reactors. Here is how PG&E explained its reasoning in a press release dated Sept. 20, 2018:

"California's energy landscape is changing dramatically. State policies that focus on renewables and energy efficiency, coupled with projected lower customer electricity demand in the future, will result in a significant reduction in the need for the electricity produced by DCPP [Diablo Canyon Power Plant] past 2025."

Jane Swanson

Mothers for Peace

San Luis Obispo