* New units to replace old units over next several years
* Plant could enter service in 2018 and 2020
* Old Huntington units run this summer due San Onofre shut
Aug 10 (Reuters) - California energy regulators started reviewing U.S. power company AES Corp's proposed 939-megawatt (MW) addition to the Huntington Beach power plant in Orange County.
AES wants to build two natural gas-fired, combined-cycle plants on a 28.6-acre site located within the existing footprint of the existing Huntington Beach facility about 30 miles (48 km) south of Los Angeles.
The California Energy Commission said in a release late Thursday the estimated capital cost of the project would be from $500 to $550 million. Power traders noted that cost was low and may only pay for one of the two combined cycle facilities AES is looking to build.
Each combined-cycle power block would consist of three-gas-fired combustion turbines and one steam turbine. The units would use dry cooling, eliminating the use of ocean water for cooling.
California will need new power plants like the proposed Huntington Beach plant to replace about 17,000 MW of existing generation expected to shut over the next several years because the old plants use so-called once through ocean water cooling systems that harm fish and other aquatic life.
If the commission approves of the new Huntington Beach plant by the first quarter of 2014, AES told the regulator the company could start construction during the first quarter of 2015.
Construction of Block 1 would last from the first quarter of 2015 through the second quarter of 2018. Work on Block 2 would run from the first quarter of 2018 through the second quarter of 2020, AES told the energy commission.
AES said the existing 226-MW Units 1 and 2 and another unit would be demolished for the new project. The other unit would be removed between the fourth quarter of 2014 and the end of 2015 to provide the space for the construction of Block 1. Units 1 and 2 would be demolished from the fourth quarter of 2020 through the third quarter of 2022.
The project would average 192 workers during the construction and demolition period, with a peak of about 230 workers for Block 1 and 240 workers for Block 2. There would be 33 employees when the project is operational, AES told the commission.
SAN ONOFRE SHUTDOWN
After both reactors at the 2,150-MW San Onofre nuclear power plant in Southern California shut in January due to problems with its steam generators, the California ISO, which operates the power grid for much of the state, called on AES to take Huntington Beach Units 3 and 4 out of retirement for at least for the peak summer demand months.
AES sold the 225-MW Unit 3 and 227-MW Unit 4 to Edison Mission Energy, a unit of California power company Edison International, so Edison Mission could shut the units to avoid producing more emissions in the area when its new 500-MW Walnut Creek power plant in the City of Industry enters service expected in 2013.
AES, which continues to operate Units 3 and 4 for Edison Mission, retired the units in January 2012 but brought them out of retirement by May for at least the summer.
With a heat wave blanketing the state this week, California needed the additional generation from Huntington Beach to avoid possible outages in the southern part of the state as customers crank up their air conditioners to escape the heat, stressing the grid.
San Onofre is owned by units of Edison International and Sempra Energy.