Century-old silver mines are long gone. But tainted tailings are still polluting Park City. Now the feds are suing to clean up the Superfund site.

What are now world-class ski runs used to be profitable mountainsides where 19th-century miners dug silver out of the dirt and mud.

The materials left over from that mining and processing are called tailings, and a lot of them were dumped into Silver Creek — the stream that runs from the south side of Park City northeast to Wanship. The federal government has had plans to clean up the tailings and the poisonous chemicals that come with them.

The plan has stalled, partly because the United Park City Mines Co. hasn’t followed through on a 2014 agreement to scrub the biggest tailings site and owes the federal government for work that has been done, according to a lawsuit filed Monday in federal court.