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NRG Energy Inc. fired up its new state-of-the-art natural gas power plant this week after years of construction in Antioch, Calif., on Thursday, May 2, 2013. The Marsh Landing Generating Station, located off Wilbur Avenue just northeast of Antioch, will provide up to 720 megawatts of electricity , enough for up to 650,000 homes. (Dan Rosenstrauch/Bay Area News Group)

ANTIOCH -- It's out with the old and in with the new for one East Contra Costa power provider.

NRG Energy Inc. fired up its new state-of-the-art natural-gas power plant this week after years of construction, retiring its two 1960s-era units at the adjacent Contra Costa County Power Plant at the same time.

The Marsh Landing Generating Station, off Wilbur Avenue just northeast of Antioch, will provide up to 720 megawatts of electricity, enough for up to 650,000 homes.

"Our goal was to bring this facility online before the California summer peak arrived, and we were able to make it happen," John Chillemi, an NRG senior vice president, said in a news release.

County Supervisor Federal Glover, of Pittsburg, said, "It was a nice seamless transfer. Most people had no idea it had happened."

The plant that closed Wednesday used a method now deemed environmentally unfriendly called once-through cooling, drawing water from the San Joaquin River for cooling and spitting it back in at higher temperatures.

The new plant uses water and wastewater hookups provided by Antioch and Delta Diablo Sanitation District.

Marsh Landing's planned maximum use of 50 acre-feet of water per year is a 99.99 percent decrease from the old station's use, company officials said.

"It's just a major plus. It's more efficient, it's cleaner, uses modern-day technology and is better for the environment; that's why I've supported it," said Glover, whose district includes several power plants on the East Contra Costa waterfront.

Marsh Landing also utilizes fast-start technology that brings its production to full capacity in minutes, while it would take the old plant hours, NRG spokesman Jeff Holland said.

The project, built on a brownfield with five old oil tanks once sat, created nearly 600 local jobs during construction. Because of its efficiency, Marsh Landing requires fewer employees than the Contra Costa station. NRG will drop staffing from 38 employees to 11 at the new plant.

Of the new positions, five were filled with current employees with the "right skill set," Holland said.

Some represented employees were able to transfer to NRG's Pittsburg facility, while the company is working on the possibility of moving other Contra Costa County Power Plant employees to positions at other sites, Holland said.

Antioch and Contra Costa officials are in the process of working out a complex annexation deal that would include bringing the 27-acre power plant property within city limits.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.