The Senate approved House Bill 3141 40-6 Wednesday evening, and after minor differences are worked out with the House, the measure will be sent to Gov. Gary Locke to be signed into law.

"It's great the state is finally acknowledging global warming," said Bill LaBorde, climate campaign director for the Northwest Energy Coalition.

The bill guarantees certain environmental considerations will be included with the approval of new power plants while providing builders with certainty over what those considerations will cost.

"This is a vote for the devil that's known versus the devil that's unknown," said Sen. Pat Hale, R-Kennewick.

Though plans for new generators have all but ground to a halt, the issue could be of long-term interest in the Mid-Columbia -- a potential hotbed for power plant development because of conveniently located natural gas and electric transmission lines.

Under current law, builders of large-scale fossil fuel power plants negotiate environmental conditions on a case-by-case basis with the state's Energy Facility Site Evaluation Council, which is responsible for granting operating licenses.

The bill and a separate siting council effort to write a new agency rule would produce one set of conditions for all new power plants and for existing plants that significantly expand their capacity. Oregon is the only state to have such standards.

Under the bill, which would trump any rule the site council adopts, power plant operators would be required to offset 20 percent of the carbon dioxide their plants would emit over 30 years at a rate of $1.60 cents per metric ton. That assumes plants would run 60 percent of the time.

That would cost the operator of a new 650-megawatt plant about $11.7 million, which would be used to support an array of environmental purposes including energy efficiency programs and efforts to build environmentally friendly power plants such as solar generators.

That's about 6 percent more than under the original draft rule the council issued last year, which many believed was inadequate. It's likely the council would be even more aggressive in refining its plan if it continued its rule-making process.

"We have sent a signal, not really too thinly veiled, that if we implemented a rule we will take a hard look at a higher number," said council Chairman Jim Luce.

The bill has no organized opposition though some stakeholders remain concerned the price is too high, especially considering the council would be allowed to increase it by as much 50 percent every two years. Others are skittish about new plants having to compete against old plants that wouldn't have to meet the same environmental conditions.

"We just see that as a disincentive to build new generation," said Dave Arbaugh, a lobbyist for Calpine Corp., an independent power producer.

The main opposition in the Legislature has been from lawmakers who believe global warming has not been adequately linked to human activity or that the plan opens the door for requiring mitigation for carbon dioxide emitted by vehicles or other sources.

"The science is unclear," said Rep. Jerome Delvin, R-Richland. "Why should we as a state go down this lone road that puts the burden on our businesses that no one else is?"

In a floor speech Rep. Lois McMahan, R-Gig Harbor, suggested carbon dioxide is good for the environment.