BLUE HILL (AP) – Three companies involved in the development and operation of the Kerramerican copper and zinc mine during the 1960s and 1970s have reached an out-of-court settlement on who will pay the $11 million cost of the ongoing cleanup at the site.

Details of the agreement among California-based Kerramerican Inc., and Black Hawk Mining Ltd. and Denison Energy Inc., both Canadian companies, were not released.

A 2004 lawsuit by the state of Maine and the Department of Environmental Protection asked the U.S. District Court to identify the three companies as “responsible parties,” for the cleanup at the mine site.

Kerramerican agreed last summer to pay the cleanup costs while retaining the right to seek reimbursement from the other two companies, an issue that was scheduled to go to trial this summer.

“Basically, Kerramerican came to the table and said we’re here and we’re willing to deal with you. So we dealt with Kerramerican,” Hank Aho, acting director of the DEP’s remediation division, said Tuesday. “They continued their action against the other two potentially responsible parties.”

The mining operation involved the extraction of copper and zinc from deposits at the site off Route 15. Black Hawk and Denison began to develop the mine site in the mid-1960s, which included driving a mine shaft and developing almost 10,000 feet of tunnels, according to the original suit. Those activities ended in 1967.

In 1970, Black Hawk and Keradamex Inc., a predecessor of Kerramerican, formed a joint venture to continue to develop the mine site, including extraction, crushing and processing of minerals. That operation ended in 1977. The DEP approved the closure of the mine in 1985.

As erosion exposed waste materials from the mining operations, initial studies in the 1990s indicated that metals including arsenic, cadmium, copper, lead, silver and zinc, had leached into groundwater and surface water around the site.

With the Environmental Protection Agency considering the site as a Superfund candidate, Kerramerican agreed to the DEP’s suggestion to work together on the cleanup. Since 1999, the company worked with the agency on a cleanup plan.

Work on the site began last summer.