New environmental figures could help settle a vexing debate, which has pitted environmentalists, Bayview activists and energy corporations against public power champions and real estate interests, over how best to burn fossil fuels.
A Mirant Corp. plan — which would add smokestacks and gas-powered turbines to three non-waterfront backup diesel generators at its Potrero Hill site — would spew more air pollution over San Francisco per operating hour than a proposed city-owned plant, according to a three-page San Francisco Public Utilities Commission analysis.
But the proposed city-owned plant, on the edge of the nearby Bayview neighborhood, would need to run more frequently than Mirant’s three backup generators are currently allowed to run in order to repay construction-related debts.
As a result, the proposed city-owned plant would churn out at least double the soot and airborne nitrogen and sulfur pollution as Mirant’s backup units, unless the company or a new owner changes or violates the permit. San Francisco previously sued Mirant for running its backup units more than it was allowed when power prices spiked.
The San Francisco Bay Regional Water Quality Control Board has indicated it is reluctant to renew Mirant’s water permit, which is needed to operate its main plant, once it expires at the end of the year because of damage caused to the Bay. The plant currently is propped up with ratepayer subsidies because it is considered critical to protecting San Francisco against blackouts.
Only one of the two proposed power plant projects would qualify for ratepayer subsidies once the main plant shuts, said Sidney Davies, the assistant general counsel for California Independent Systems Operator.
“We need one or the other — not both,” she said.
The Mirant retrofit is proposed on the company’s 27-acre swathe of contaminated land next to the up-and-coming Dogpatch neighborhood and a planned billion-dollar city redevelopment.
The retrofitted units might run for five years before the site is redeveloped, Mirant California President John Chillemi said.
The city-owned plants would need to run for 18 years if millions of dollars in construction-related costs are to be repaid through electricity sales and ratepayer subsidies, according to SFPUC figures.
Rewiring plan never reached intended desk
A plan to rewire The City to offset the need for new or retrofitted power plants appears to have stalled.
The Board of Supervisors in June voted to present a Pacific Gas & Electric Co. proposal to state regulators that would see hundreds of millions of dollars in ratepayer subsidies spent rewiring The City.
The proposed rewiring plan could power San Francisco using homegrown renewable electricity along with fossil-fuel-generated power imported through cables from facilities outside of The City.
The latest steps toward developing 103 megawatts of solar power and 140 megawatts of wind power, which would be directly piped to consumers in and around The City through PG&E’s transmission lines, were approved by city leaders in 2007.
But the California Independent System Operator, which assigns limited ratepayer subsidies, has not received the proposal from The City, agency spokeswoman Stephanie McCorkle said.
Instead, she said, the agency is negotiating with Mirant, which applied for subsidies to retrofit its backup power generators.
The San Francisco Public Utilities Commission is trying to woo potential customers for the program and then plans to search for power providers, spokeswoman Laura Spanjian said. — John Upton
By the numbers
Mirant backup generators
- 8 Most hours the Mirant backup units can currently run each week
- 1.3 Tons of soot produced annually if the Mirant units run 3.5 hours per week (for comparison)
- 3 Tons of soot produced annually if the Mirant units run 8 hours per week
- 1.7 Tons of airborne nitrogen pollution annually if the Mirant units run
- 3.5 hours per week (for comparison)
- 3.9 Tons of airborne nitrogen pollution produced annually if the Mirant units run 8 hours per week
- 37 Hours the city-owned plant is expected to run weekly to recover costs
- 77 Maximum hours the city-owned plant would be permitted to run each week
- 0.7 Tons of soot produced annually if the city-owned plant runs 3.5 hours per week (for comparison)
- 7.1 Tons of soot produced annually if the city-owned plant runs 37 hours per week
- 1.2 Tons of airborne nitrogen pollution produced annually if the city-owned plant runs 3.5 hours per week (for comparison)
- 12.5 Tons of airborne nitrogen pollution produced annually if the city-owned plant runs 37 hours per week
- 145 Megawatts that would be produced by retrofitted Mirant units or by new city-owned plant
- 970 Megawatts used by city at peak times
Sources: SFPUC; PG&E Co.