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Draft Environmental Assessment Skelly Gulch Culvert Fish Barrier

Development, Improvements, and Enhancements

Thu Jan 27 13:20:00 MST 2011

A genetically pure westslope cutthroat (WCT) inhabits Skelly Gulch on Helena National Forest Lands and on private lands below the Forest. Approximately six miles of the upper reaches of the stream contain exclusively WCT, while the lower reaches are inhabited primarily by Eastern brook trout. The two species are segregated by a culvert road crossing that acts as a partial fish barrier, preventing large-scale upstream movements by spawning or migratory brook trout. This project proposes to remove the existing road crossing, which acts as a partial barrier, and replace it with a culvert with appropriate size, slope, and drop to make the crossing a complete fish barrier. The current culvert is inappropriately sized for the stream, resulting in aggradation of sediments on the upstream end of the culvert, making it a partial fish barrier during base flows. The proposed project would replace the current pipe with an 80 linear foot 48 inch diameter corrugated metal pipe placed at least a 3% slope to act as a velocity barrier, with a 2 foot drop on the downstream end, and an 8 foot wide by 12 foot long splash pad to diminish fish jumping capabilities. The new pipe will pass 25 year flows without overtopping the road and will efficiently pass sediments during base and flushing stream flows.

Contact Information

George Liknes Region 4 Fisheries Bureau Montana Fish Wildlife & Parks 4600 Giant Springs Road Great Falls MT 59405 Phone: (406)454-5855