Silver Bow Creek/Butte Area is an 85-mile Superfund site in Montana shaped by more than 100 years of mining, milling, and smelting. Those operations left behind arsenic, heavy metals, and other contaminants in soil, sediment, groundwater, and surface water. The affected area includes 26 miles of Silver Bow Creek and its streamside habitat downstream from Butte. EPA and the Montana Department of Environmental Quality have led cleanup work here since 1983.
The site is divided into seven active operable units, each targeting a different area or contamination source. Work on the Streamside Tailings unit covered 26 miles of creek and ran from 1999 to 2019. The Butte Mine Flooding unit addresses the Berkeley Pit and flooded underground mine workings. A water treatment plant there processes up to seven million gallons per day, and waterfowl protection programs are in place. Three sediment settling ponds at Warm Springs hold roughly 19 million cubic yards of material. A 16-acre former timber treating plant contaminated with creosote and arsenic finished its main cleanup in 1997 and remains under groundwater monitoring.
Active work continues on several fronts. The Butte Priority Soils unit focuses on the historic mining district on Butte Hill and includes multiple sub-projects. One of those, Grove Gulch, started construction in August 2024. The West Side Soils unit began a comprehensive investigation in 2018, with a Remedial Investigation Report expected in late 2024 and a Feasibility Study also underway. Across the site, completed and ongoing actions include removing tailings and contaminated soils, planting vegetation in creek corridors, capping waste dumps, installing stormwater controls, and capturing and treating groundwater.
Residents can take part in a Residential Metals Abatement Program that assesses lead, arsenic, and mercury at homes in the area. Medical monitoring offers blood lead and urine arsenic testing. In October 2025, EPA updated its soil lead guidance, lowering the residential screening level from 400 parts per million to 200 ppm, or 100 ppm at properties with multiple lead exposure sources. A sixth five-year review of overall cleanup progress is currently underway, giving the public another avenue to track how the site is moving forward.
