Calpine Corp. said today that its chairman and chief executive and its chief financial officer have left the company in moves that its board said will help the power provider address its financial challenges. Its shares sank 26 percent to below $1 in early trading.

The company is hoping to build a liquefied natural gas import terminal at the mouth of the Columbia River near Warrenton, one of four that has been proposed for the lower Columbia.

On Dec. 15, the Warrenton City Commission will vote on whether to grant the company a zone change for the East Skipanon Peninsula and surrounding waters, which would be required for the LNG facility.

Calpine said founder Peter Cartwright, who was chairman, president and CEO, and Robert D. Kelly, its executive vice president and CFO, have each left the company.

“The board believes that these management changes are essential to better address Calpine’s financial challenges and to provide a new direction for the company,” the company said in a statement.

The company appointed board member Kenneth T. Derr as chairman and acting chief executive and said it expects to announce a permanent replacement for Cartwright in the near future. Derr was the chief executive of Chevron Corp. from 1989 to 1999.

Eric N. Prior, executive vice president and deputy chief financial officer, was selected as interim CFO.

Calpine shares tumbled 33 cents to 92 cents in early trading on the New York Stock Exchange.

Calpine has been shedding assets in an attempt to improve its financial condition. The company lost about $242 million in 2004 and $684 million in the first nine months of 2005.

Cartwright founded Calpine in 1984 and had been chairman, president and CEO since 2001. Earlier this year, Cartwright pledged to shed $3 billion in debt this year and trim $200 million from Calpine’s annual expenses.