THE BATTLE OVER the city's energy future – and the health and safety of people living in the southesast part of town – took a startling and ugly turn last week when the state agency that runs California's electric grid issued a written threat to local environmental activists: either back off your opposition to the upgrade of Mirant Corp.'s power plant at the foot of Potrero Hill, or the state will refuse to shut down the filthy and dangerous Hunters Point plant.

The Independent System Operator put the state firmly on the side of continuing pollution and unsustainable fossil-fuel energy generation and raised the possibility that one of the worst stationary sources of toxic emissions in the city will continue to operate for years to come. The letter was a challenge not only to environmentalists but also to the city of San Francisco – and Mayor Gavin Newsom needs to denounce the ISO and make it clear he will fight to shut down the Hunters Point plant.

As Matthew Hirsch reports on page 13, the ISO – which has too much power and too little accountability anyway – is unhappy because Communities for a Better Environment is demanding a full environmental review of Mirant's plans to retrofit its natural gas-fired Potrero plant. The agency insists San Francisco must have 400 megawatts of power generated within city limits; Mirant provides 207, and the Hunters Point plant provides 163. The ISO, along with Pacific Gas and Electric Co., is also pushing for a new high-voltage power line up the peninsula – a move that has angered peninsula residents and looks suspiciously orchestrated as a divide-and-conquer strategy to pit Hunters Point residents concerned about pollution against their neighbors to the south, who are worried about exposure to power-line radiation.

The Potrero Hill-or-Hunters Point threat carries the same stench – but fortunately, nobody in the community is buying it. As CBE points out, with good evidence, the 400 megawatt estimate is bogus, and the Potrero expansion (which will take the plant off-line for six months) is the real blackout threat. Besides, the city is and ought to be moving toward an energy policy based on the cheapest, safest, most reliable resources – conservation, solar, and, perhaps one day, tidal energy – and in the long term, the city doesn't need either the Hunters Point plant or the Potrero expansion. Besides, both are privately owned generators, and the city is moving toward creating a local public power system that will have no room for private energy companies.

On the larger issue, of course, CBE has every right (if not every obligation) to demand a full environmental review of the new turbine. For the ISO to threaten the health of the Hunters Point community in an effort to ram the Mirant project through is political extortion, pure and simple.

Newsom, who has been far too quiet on this entire issue, needs to denounce the ISO's position and make it plain that shutting down the Hunters Point plant isn't negotiable – and that the city will fight with its full political and legal resources to force the pollution-belching plant to close its doors.

Newsom and the supervisors need to show some good faith to the residents of the southeast neighborhoods, who have been lied to repeatedly and forced for generations to put up with just about every unpleasant, dirty, foul-smelling, toxic facility the city wants to dump out of sight. Taking on the ISO and pushing for the closure of the Hunters Point plant would be a good start – and after that the city needs to give the neighborhood a legally binding, written guarantee that the new "peaker" plants the San Francisco Public Utilities Commission wants to operate on the Mirant site won't ever be turned on until PG&E's plant is turned off, for good, and the Mirant expansion is halted in its tracks.