The California Energy Commission (CEC) on Wednesday unanimously approved two natural gas-fired electric generation plants that would add more than 800 MW to the state’s generation fleet, which is under pressure along the coast where 20 plants need to meet new once-through-cooling (OTC) rules later in this decade or shut down.

In two separate actions, the five-member CEC gave the green light to the 200 MW Mariposa Energy Project, a gas-fired peaking plant seven miles east of Livermore, CA, in the far southeastern part of the East San Francisco Bay Area. It is being developed by a subsidiary of Mitsubishi Corp., Diamond Generating Corp.

The CEC also approved the 624 MW combined-cycle gas-fired Oakley Generating Station in eastern Contra Costa County in a more northerly part of the East Bay Area. A somewhat controversial project that has been around for a decade under several different developers, Oakley holds a long-term supply/ownership contract with Pacific Gas and Electric Co. (PG&E), but by limitations placed on it from the California Public Utilities Commission (CPUC), the contract cannot be activated before 2016, at least two years after the plant is supposed to start commercial operations.

“Approving these natural gas power plants will help meet California’s growing energy needs,” said CEC Chair Robert Weisenmiller. “When these facilities come online, they will provide reliable power for homes and businesses all around the East Bay.”

Weisenmiller stressed that additional gas-fired power plants help facilitate California’s expansion of renewable energy-based power generation, such as wind and solar, because of “their consistent and reliable power supplies.”

The Mariposa project is a simple-cycle peaking facility and will only operate during periods of high electricity demand. The peaker project will be constructed on a 10-acre portion of a 158-acre parcel south of PG&E’s natural gas Bethany Compressor Station and Kelso electric substation. Construction is to begin this year with commercial operations by the mid-part of next year.

For the Oakley project, now being developed by Contra Costa Generating Station LLC, a limited liability corporation owned by Radback Energy Inc., the timeline is much longer, taking 33 months. When construction starts it will be on a 21.95-acre site in the city of Oakley, CA.

Late last year the CPUC reversed an earlier denial and approved the PG&E contract with the Oakley developers. Earlier in 2010 the CPUC determined that the project was not needed to fulfill the utility’s short-term reliability needs. PG&E subsequently brought the project back to the regulators with a deferred date from 2014 to 2016 for its taking ownership. In the two ensuing years, Contra Costa Generating will operate the plant as a merchant facility.

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