ISO: Potrero Power Plant can be shut down after 2010

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By Rebecca Bowe

The California Independent System Operator (ISO), the body that for years has required the Mirant Potrero Power Plant to stay in operation despite grave health concerns raised by the surrounding community, put it in writing today that it will allow the entire plant to be shut down by the end of 2010. Following years of pressure from community activists and elected officials, the commitment signifies a hard-fought victory that will eventually mean better air quality in San Francisco's southeast sector.

In recent months, the ISO agreed to lift the operating requirement from Unit 3, the largest electricity generating unit at the plant, which produces smokestack emissions nearly 24 hours a day. Because the Trans Bay Cable, a transmission line that will run under the bay, is expected to go live as early as next month, the ISO agreed that Unit 3 would no longer be needed to ensure electricity reliability. But until today, the ISO would not budge on lifting the requirement for three smaller units -- known as Units 4, 5, and 6 -- which are diesel-fired and more polluting.

But during a telephone discussion with Mayor Gavin Newsom this morning, CEO Yakout Mansour of the ISO finally changed his tune, and then submitted in writing that the ISO would allow all units to be released from must-run status by the end of 2010. The reason is that Pacific Gas & Electric Co. has a re-cabling project underway that will fill in a power gap in the city, making it unnecessary to keep the three diesel units going. Mansour’s decision followed a technical study based on PG&E data.

“PG&E provided new data regarding the load carrying capability of two replacement underground transmission cables they are installing between Martin, Bayshore, and Potrero substations,” Mansour explained in a letter sent to Newsom this morning.