Silver King Mine Clean-up and Stream Restoration

By Alden Shallcross, State Lead - Montana/Dakotas Aquatic Habitat Management Program

The Missoula Field Office improved riverscape health, water quality, and associated fish/aquatic resource values in Sluice and Rock creeks by removing mine tailings contaminated with heavy metals, infilling a ditched stream segment, and restoring flow to the historic channel.

Sluice Gulch supports westslope cutthroat trout (a BLM Sensitive Status Species) and is a tributary to Rock Creek, which is a Blue Ribbon fishery that also supports threatened bull trout Designated Critical Habitat.

Despite the high resource values, a recent CERCLA evaluation noted moderate risk of heavy metal contamination associated with terrestrial, riparian, and aquatic habitat sediments within the historic mine area and adjacent Sluice Gulch Creek. Staff also noted that the miners had re-routed Sluice Gulch Creek into a ditch to drain the valley bottom and associated riparian-wetland soils, thereby facilitating access and related mining operations.

To mitigate water quality and habitat degradation from these historic practices, the BLM planned and contracted for removal and reposit of contaminated sediments, then partnered with Montana Trout Unlimited (TU) to realign Sluice Gulch Creek with the historic channel (Photo 5).

BLM’s scattered ownership in the project area required close coordination with several private landowners, contractors and TU. Access to the site was especially challenging, ultimately requiring heavy equipment to ford Rock Creek. To minimize or avoid adverse impacts, the BLM implemented timing restrictions to protect cutthroat and bull trout and required the use of large rubber mats to protect the streambanks from tracked and wheeled equipment (Photos 6a-c).

The stream realignment and restoration converted approximately 1,000 feet of straightened, homogenous riffle habitat to 1,200 feet of meandering riffles, runs and pools, bolstered with logs, rocks and a plethora of live sod and willow cuttings. Lastly, the BLM installed a short segment of fence to exclude livestock from the restoration area until the vegetation recovers.

The BLM, TU, and Montana Fish, Wildlife, and Parks will continue to monitor project effectiveness, including the spawning and recruitment of trout, as well as the extent to which restoration has reactivated the processes that historically sustained riverscape attributes and resource values at the site.