SPOKANE, Wash. — In a settlement with state regulators, Kaiser Aluminum & Chemical Co. has agreed to spend $20 million to clean contaminated property at its defunct Mead smelter near Spokane.

The proposed legal settlement, announced Wednesday, still must go through a formal public review and be approved by a U.S. bankruptcy court judge.

The settlement calls for transferring a 50-acre parcel of land at the smelter site into a trust that will oversee cleanup of a site where spent potliners were buried.

Cyanide and fluoride leaching from the 120,000-ton pile have contaminated groundwater for decades.

A thorough cleanup of the 1,200-acre smelter property northeast of Spokane would have cost $100 million, the Washington Department of Ecology said.

“Although this settlement does not allow for a complete cleanup, we feel it gives us the minimum resources to protect the public and prevent the contamination from spreading further,” said Carol Kraege, manager of Ecology’s industrial section in Olympia.

The settlement represents a “fair, responsible and appropriate” approach to cleaning Mead pollution, Kaiser spokesman Scott Lamb said in a prepared statement.

The settlement is an example of progress Kaiser is making to address its legal liabilities as the company continues its Chapter 11 bankruptcy reorganization, the company’s statement said.

Chemicals from the potliners – carbon liners that protect the steel shells of the pots where molten aluminum is made – were discovered in 1978 in neighbors’ wells along the Little Spokane River, about a half-mile to the northwest of the smelter.

Because of the groundwater pollution, Kaiser’s Mead property became one of eight Spokane Superfund sites in 1983.

Kaiser’s chemicals have contaminated portions of the Spokane aquifer and the Little Spokane River, according to a January 2000 Ecology cleanup order to Kaiser.

Kaiser will finance the cleanup trust with $2.25 million in cash and an $18 million insurance policy that will pay for remedial action.

The Little Spokane River will be tested for ongoing pollution and a large, capped toxic waste pile will be monitored for centuries.

Ecology had been working with Kaiser on a cleanup plan before the company declared Chapter 11 bankruptcy in February 2002, citing $3.1 billion in debts and liabilities.

Commercial Development Co. of St. Louis bid $7.4 million for the smelter this spring and plans to use a part of it to manufacture anodes used to make aluminum.

Kaiser also has been selling parcels of the Mead site to real estate developers.

From 1942 to 1978, the spent potliners were disposed of in the northwestern corner of the Mead site. In the 1970s, spent potliners from a Tacoma smelter also were disposed of at the site.

In 1990, the company began shipping the potliners to a hazardous waste landfill at Arlington, Ore.

Last September, Kaiser agreed on a separate $24.5 million settlement involving additional Superfund cleanup claims at 66 sites, including the Spokane Junkyard in Hillyard and Commencement Bay in Tacoma.