By: TrueNorth Steel
The Idaho Soil and Water Conservation District sponsors various projects with grants and engineering for land owners with fish bearing streams to access their land and provide easy fish passage for the local spawning trout and steel head.
The engineer worked with TrueNorth Steel to develop a proper geometry for the site, cost estimates for project feasibility and selected an 11.5’x20’x10ga 3×1 ALT2 steel plate arch. The steel plate arch is a bottomless structure to provide a natural pathway for fish to spawn annually. Using this structural steel plate arch allows for either footing pads or spread footings and either option requiring embedment below scour depth. In order to maintain the vertical rise of the structure, spread footings were chosen over the corrugated footing pads. The added benefit with the spread footings, it allowed the installing contractor to simulate the stream bed after the footings were installed and before the structural steel plate arch was installed. The contractor now the ability to place the river rock with an excavator, opposed to hand placement.
With limited easement access, corrugated metal headwalls and wingwalls were used to maintain a maximum allowable travel way width for the gravel wearing surface. Dead man anchors and wale beams provided the fortitude for the headwalls and wingwalls.
Special thanks to the following for making this project come alive:
Major Sponsor: Idaho Soil and Water Conservation DISTRICT
Landowner Contact: Nathaniel Davis
Technical Contact: Eileen Rowan and Bill Lillibridge, Idaho Soil and Water Conservation Commission
Contractor: Gordon Eckel, Flash Excavation Inc.