This project replaced an undersized culvert near the mouth of the Little Tucannon River with a free span bridge. The Little Tucannon, a steelhead and bull trout rearing stream, is a tributary of the Tucannon River, a steelhead, bull trout, and spring chinook bearing stream in eastern Columbia County. The undersized culvert created a partial barrier due to slope and velocity. The culvert also created a constriction in the stream, causing deposition of streambed material and interfering with natural stream forming processes. Scour has started to undermine the culvert inlet, leading to concerns of scour failure causing a road washout.
Replacing the culvert with a free span bridge eliminates velocity barriers to juvenile salmonids and provides for a natural streambed under the crossing. The bridge eliminates a stream constriction and accommodates greater discharge, bedload, and woody debris.
The U.S. Forest Service, Washington Dept. of Fish & Wildlife, Snake River Salmon Recovery Board, and the Tri-State Steelheaders worked as partners to provide salmonids and other aquatic species with unrestricted passage to four miles of high quality habitat in the Tucannon River drainage.
