Asarco's current litigation with Union Pacific focuses on the cleanups in Omaha, Idaho's Silver Valley near the Washington border and the Big River mine area in southeast Missouri. All those lawsuits are pending in federal court, although the Missouri case is further along after a judge rejected the railroad's attempt to have the lawsuit thrown out earlier this month."Union Pacific has yet to pay its fair share for the important cleanup work," Evans said. Environmental Protection Agency spokesman David Bryan said the agency is planning to eventually look at whether rail lines in southeast Missouri are contributing to contamination, but generally regulators have not focused on railroad lines. The EPA focuses its resources on contamination that presents the greatest threat to human health, so Bryan said railroad lines that mostly cross remote areas haven't been the priority. EPA officials overseeing the cleanup in Idaho's Coeur d'Alene River Basin said after getting a letter from Evans last fall they're confident that Union Pacific's railroad lines are not polluting the valley. The Coeur d'Alene River Basin is one of the nation's largest Superfund sites, with heavy metals poisoning land, streams, wildlife and humans. The wastes washed into waterways and moved downstream, some extending into the state of Washington. Asarco paid $482 million as part of a settlement with the EPA for that cleanup. In the Omaha case, Asarco agreed to pay more than $200 million to help clean up lead contamination found on nearly 6,000 Omaha properties. Asarco ran a lead smelter on the banks of the Missouri River for more than a century before it closed in 1997. EPA officials have said they believe Asarco was the main source of lead contamination. Union Pacific agreed last year to pay $25 million in a settlement with the EPA to help deal with risks associated with lead paint in Omaha.