By MATTHEW BROWN
BILLINGS, Mont. (AP) — A subsidiary of London-based oil giant BP agreed to finish its cleanup of a 300-square mile site in Montana that’s contaminated with arsenic and other pollutants from decades of copper smelting. Under a legal decree filed Friday in U.S. District Court, the Atlantic Richfield Company committed to finishing cleanup work in residential yards in the towns of Anaconda and Opportunity. It also will clean up soils in the surrounding hills, address remaining piles of contaminated waste at the site and repay the U.S. government $48 million in response costs.. Arsenic and toxic metals spewed from a 585-foot-tall smokestack in Anaconda for nearly a century. The pollution settled into the ground for miles around.