May 11--The Salt River Project will go ahead with plans to build a new coal-fired power plant at Tucson Electric Power Co.'s Springerville Generating Station in Eastern Arizona.

The 400-megawatt plant, expected to cost between $600 and $650 million, will be owned by SRP and operated by TEP.

The unit is expected to begin commercial operation in late 2009.

SRP, the water and power authority that serves the Phoenix area, said Wednesday its governing board voted to approve the new power plant.

The SRP plant will be the fourth unit at TEP's Springer-ville complex, expanding the availability of coal-fired power in the region.

The new unit will stand alongside Springerville Unit 3, which is under construction and is expected to be placed on line during the third quarter of this year.

That 400-megawatt unit will be leased from a financial owner by Tri-State Generation and Transmission Association, a wholesale power cooperative that will control the unit's output. TEP will operate both new units along with the two existing 380-megawatt units at the site.

"This project gives us another opportunity to generate additional value from our existing investments and plant operating experience," James Pignatelli, chairman and CEO of TEP and its parent company, UniSource Energy Corp., said in a statement.

Environmental groups had sought to block the SRP plant, contending it was unnecessary and objecting to the additional air pollution it would cause. The state Court of Appeals threw out the lawsuit in February.

TEP said that, like Unit 3, Unit 4 will use "best available control technologies and equipment to limit emissions" to reduce sulfur dioxide, particulates and other emissions.