Mirant's last gasp?

Green City: A multipronged effort -- and raised hopes -- to shut down the controversial fossil-fuel-fired facility


GREEN CITY A new multipronged effort to shut down San Francisco's Mirant Potrero Power Plant is raising hopes that the end could be in sight for the controversial fossil-fuel-fired facility.

An ordinance proposed by Sup. Sophie Maxwell suggests that the entire facility — including the primary unit 3 and the smaller, diesel-fired units 4, 5, and 6 — could be shut off without having to create any new fossil fuel generation within city limits. The legislation would direct the San Francisco Public Utilities Commission to figure out how to bridge the in-city electric generation gap using energy efficiency, renewable power, and other alternatives.

Meanwhile, a lawsuit filed against Mirant by City Attorney Dennis Herrera targets Mirant's failure to perform seismic upgrades. The effort wouldn't close the plant directly, but could make it more burdensome for Mirant to do business here. Mirant did not return calls for comment.

"Mirant has been given a free pass for a while, and the city doesn't want to give it to them any more," Deputy City Attorney Theresa Mueller told the Guardian. "Part of the reason they've gotten away with not doing it is because it was expected to close."

City efforts to replace the Mirant plant's power with combustion turbines that San Francisco already owns were derailed last year after Mayor Gavin Newsom withdrew his support for the plan, instead backing an alternative pushed by Pacific Gas & Electric Co. that would have retrofitted the Mirant plant, a proposal that consultants said didn't pencil out and that failed to win Board of Supervisors' approval (see "Power possibilities," 11/5/08).

Despite various city efforts to shutter the plant going back nearly a decade, Mirant Potrero still runs an average of 20 hours per day, according to figures released by the California Independent System Operator (Cal-ISO). In 2007, the plant released 235 tons of harmful pollutants into the air, and 336,300 tons of carbon dioxide.

For now, Cal-ISO requires Mirant to continue running to guarantee that the lights would stay on in the city even if major transmission lines fail. But with the installation of the Trans Bay Cable — a high-voltage power cord that will send 400 MW of electricity under the bay from Pittsburgh in 2010 — Mirant's largest unit will be unnecessary.

"We assume that the Trans Bay Cable will be in service sometime in mid 2010. We can then drop Potrero [unit 3]" from the reliability contract, says Cal-ISO spokesman Gregg Fishman. The dirtier, diesel-powered units 4, 5, and 6 would still be required, he says.

Not everyone accepts this as the final word on the matter. Maxwell's legislation calls for the SFPUC "to take all feasible steps to close the entire Potrero power plant as soon as possible." That ordinance, expected to go before the Land Use Committee on May 11, would direct the SFPUC to update a plan for the city's energy mix, called the Electricity Resource Plan, to reflect a goal of zero reliance on in-city fossil-fuel generation.

The original plan, issued in 2002, was also designed to eliminate the Potrero plant. This time around, key assumptions have changed. Last year, as Newsom and some members of the Board of Supervisors battled over the Mirant-related projects, PG&E sponsored a study indicating that the city might not need new local power generation.

Maxwell's new proposal, citing information from the PG&E assessment, now suggests that after the installation of the Trans Bay Cable and other transmission upgrades, the electricity gap for in-city generation will be much smaller than previously assumed. This gap, which Joshua Arce from the Brightline Defense Project likes to refer to as the "magic number," has apparently shrunk to 33 MW in 2012, as opposed to 150 MW.

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