Sep. 5--Portland General Electric announced plans late today to build two new natural gas power plants by 2015 and spend more than $500 million to keep its controversial Boardman coal-fired power plant burning for three more decades.

Oregon's largest electric utility also unveiled plans to ramp up conservation and wind power to help meet growing demand.

PGE's latest two-decade energy strategy would fall well short of Oregon's 2020 goals for cutting carbon emissions to combat global warming.

Environmental groups and other critics quickly denounced the plan, calling it risky for ratepayers and the environment, while business groups said it makes sense for PGE to bank on reliable power.

PGE officials said the 314-page draft plan, now out for public comment through Oct. 5, provides the best combination of cost and reliability of the 15 power supply scenarios it considered for its 817,000 business and residential ratepayers.

Boardman is PGE's cheapest source of day-to-day power after hydroelectric power and wind, PGE spokesman Steve Corson said.

The plan "meets our customers' priorities for energy efficiency and renewables, and at the same time makes good use of our existing resources," Corson said.

But critics said investing up to $560 million in pollution control upgrades at the Boardman coal plant would put ratepayers at risk if federal curbs on carbon emissions force the plant to close anyway.

They also questioned the plan's assumption that meeting Oregon's carbon reduction goals would require adding nuclear power instead of further increasing conservation and renewable power.

"That on its face is a ridiculous scenario," said Bob Jenks, executive director of the Citizens' Utility Board of Oregon, a ratepayer advocacy group.

PGE's projection of conservation savings remained roughly the same across all the many scenarios it considered, Jenks and other critics noted.

The utility said its conservation goals -- targeted to meet half of the growth in demand through 2020 -- are the most it can reliably achieve given current technologies.

Oregon utilities issue their energy strategies, known as "integrated resource plans," every two years. PGE's new plan will undergo particularly heavy scrutiny this time because of recent state requirements for more pollution controls at Boardman and the debate over global warming.

PGE serves more than 40 percent of Oregon's population. It projects growth in demand of 2.3 percent a year through 2020.

The utility also faces a drop in electricity supply from some Columbia River hydroelectric dams.