Past Project: Neihart Superfund Site Waste Rock Removal

The 9,000-acre Carpenter Snow Creek Mining District is a Superfund site in the Little Belt Mountains of southern Cascade County, Montana. Mining began in the area in the 1880s when silver deposits were discovered near what is now the town of Neihart. Mines in the district primarily yielded silver, lead, and zinc ores. Lead and zinc were produced in large quantities during the 1920s. The mining district has been largely inactive since the 1940s, but historic mining operations at the site contaminated the soil, groundwater, surface water, and sediment with metals and other hazardous chemicals.

In 2018, Olympus Technical Services was contracted to close a mine shaft and remove waste rock from the site of an abandoned mine in a steep, wooded area near several homes along O’Brien Creek Road in Neihart. The work included the installation of a silt fence to protect Belt Creek, removal of trees and wood debris from the former mine entrance, filling the mine shaft with waste rock, widening a temporary access road, excavation of waste rock and contaminated soil, and revegetation of the disturbed areas. The waste rock was hauled to a temporary repository where the stockpile was stabilized using Soil-Sement polymer emulsion. The waste rock will be moved to a permanent repository in a future phase of work.

Completion of this project was complicated by the steep terrain of the waste rock pile, poor site access roads, the presence of nearby residences, steep and narrow access roads to the temporary repository, and a bridge on the haul route with a low weight limit. To accommodate the conditions imposed by the site constraints, work was completed with small equipment that was able to perform on the steep, narrow roads and meet the bridge load limits.

Mine shaft entrance

Mine entrance (before)

Large pile of waste rock

View of waste rock pile from below (before)

View from above of waste rock pile

View of waste rock pile from above (before)

Silt fence on steep slope

Installation of silt fence

Mini excavator atop a pile of soil

Removal of waste rock with a mini excavator

Worker hydroseeding soil surrounded by trees

Subcontractor hydroseeding site after removal of waste rock