Granite Creek Reclamation Project
In the late 19th century and early 20th century, Virginia City and Alder Gulch were the location of extensive floodplain dredging to mine placer gold deposits found along Alder Gulch Creek. Dredging activities left large piles of cobbles and boulders in Alder Gulch Creek’s floodplain. The extensive dredge piles left behind by the mining activities severely impacted the confluence of Granite Creek with Alder Gulch, prevent the ability of lower Granite Creek and Alder Gulch from development of new channels, inhibit channel movement, and in some cases, create impoundments that disallow the free movement of surface water altogether.
Many large dredge piles are located around the area where Granite Creek formerly entered Alder Gulch Creek downstream of the Highway 287 Bridge. Several dredge piles now block Granite Creek from joining Alder Gulch Creek and force Granite Creek into a series of dredged ponds and straightened channels. The obliteration of the former confluence of the two channel has resulted in the accumulation of large quantities of sediment around the Highway 287 Bridge, which has significantly reduced the capacity of the bridge to convey high flow events. Water passes over the bridge and roadway during high-flow events and during ice buildup, leading to dangerous road conditions, road closures, and an increased potential for the stream to undermine the road and bridge structure.
To repair these issues, a new bridge will be constructed by MDT in a location that is more appropriate to alleviate aggradation and flooding issues. A 1,660-foot segment of Granite Creek will be relocated to accommodate the new bridge alignment. The channel will be sized to better transport sediment, provide healthy aquatic habitat, and be revegetated with appropriate riparian and wetland species. The new channel alignment will re-establish a confluence of Granite Creek and Alder Gulch near where these two creeks historically merged. Soils contaminated with mercury from historic mining practices will be removed and replaced with clean material in order to shape the stream bed.
The Ruby Valley CD will work with Montana FWP and landowners to establish a fish barrier in the project area. This fish barrier will be installed to prevent upstream migration by non-native fish including brook, brown, and rainbow trout that currently reside in Alder Gulch. Montana FWP will remove non-native fish assemblages upstream of the barrier and manage Granite Creek for native fish including Westslope cutthroat trout and mountain whitefish.
Funding from this project comes from MT DNRC Reclamation and Development Grant, MT Department of Transportation, and MT Fish, Wildlife, and Parks Future Fisheries Initiative Grant.