PITTSBURG — The Delta Energy Center power plant was shut down on Sunday after an explosion and fire destroyed the steam turbine generator.

At 3:43 p.m., calls came in to the Contra Costa Fire District line of a fire involving the hydrogen cooling system of the steam turbine at the Delta Energy Center power plant at 1200 Arcy Lane in Pittsburg.

Firefighters arrived on scene to find a lubrication oil fire that was slowly starting to dwindle after power plant staff purged the hydrogen and carbon dioxide from the system, which starved the fire of flammable gas. The fire took approximately two hours to fight and no injuries were reported.

“One end of the generator was destroyed in the fire, mostly because of the initial explosion of the hydrogen gas,” fire marshal Robert Marshall said. “There was concern about the gear lubrication oil going into a storm drain near there, but we were able to boom that and no oil made it down to the river.”

The Delta Energy Center is an 880-megawatt, natural gas-fired, “combined-cycle” plant, which uses both gas and steam to generate electricity. The plant uses three gas turbines to generate electricity and each are equipped with a heat recovery system that delivers steam to an additional steam turbine, which generates 70 percent more electricity, on average.

Calpine has said that the damage was isolated to the steam turbine’s generator and that the rest of the plant, as well as the neighboring communities, was not directly impacted.

Calpine is still assessing the accident and was not able to comment on the cause of the explosion nor the extent of the damage

“The fire was on the generator section, not on the steam turbine itself,” said Brett Kerr, director of external affairs for Calpine, which owns the plant. “In the steam turbine, hydrogen is used as a cooling unit in the generator. Friction at that speed produces a lot of heat.”

Kerr said that safety systems are in place and that the hydrogen, which is highly flammable, is not stored next to the generator.

The Delta Energy Center is second only to the 1.3 gigawatt Pittsburg Generation Station in terms of electricity generation capacity in the Bay Area. Calpine is also the owner and operator of the Los Medanos Energy Center, a 555-megawatt combined cycle plant in Pittsburg.

The Delta Energy Center is the 19th largest, in terms of generating capacity, in the state.

When running 24 hours a day, seven days a week, the Delta Energy Center can meet the electricity demands of more than 800,000 households. It is unknown when it will be back online.

“The entire facility is offline until we can make sure it’s safe to restart it,” Kerr said.

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According to the California Independent System Operator (CAISO), which oversees regional electrical grids and ensures competitive markets, the Delta and Los Medanos Energy centers have both been online since Dec. 14 to provide backup energy due to planned and forced transmission outages. Read the notice online at bit.ly/CPMnotice.

According to CAISO, the fire did not impact grid reliability.

“As far as where the energy comes from, we have outages often on the grid and our operators re-optimize the grid for the area and find generation that is the most feasible to deliver to the area at the lowest cost feasible,” said Steven Greenlee, spokesman for CAISO. “The market sets the price, so it’s equally plausible that the price could be lower.”