By Rebecca Bowe
On Dec. 31, 2008, Mirant’s wastewater-discharge permit expired — but the gas and diesel-fired power plant still runs an average of nearly 20 hours a day, according to figures released by the California Independent System Operator (Cal-ISO).
One unit at the facility uses a system called once-through cooling, which means it takes in huge quantities of water from the bay to cool the machinery, then dumps it all back at temperatures high enough to impact surrounding ecosystems. This process is regulated by a permit issued by the San Francisco Bay Regional Water Quality Control Board. A spreadsheet on the agency’s Web site shows that more than five months into 2009, a hearing to outline the terms of a new wastewater-discharge permit still hasn’t been scheduled. The water board is waiting on a state policy decision regarding once-through cooling before it acts, a note explains.