Chadbourne Diversion Concrete Repairs – Shields River FWP-DN-Fisheries-R3-25-007

Apr 8, 2025 9:52 AM

The purpose of this project is to eliminate hydraulics on the Chadbourne diversion that allow rainbow trout to breach the barrier, which threatens a basin-level stronghold of Yellowstone cutthroat trout. Blocking rainbow trout at the Chadbourne diversion will slow hybridization of Yellowstone cutthroat trout within the Shields River watershed upstream of the diversion. This project is consistent with the conservation strategy for Yellowstone cutthroat trout in Montana and FWP’s fish management strategy. A secondary component of the project is to repair concrete and displaced angle iron on the top of the structure. Conducting such repairs will reduce maintenance costs over the long term.

The diversion structure is in need of repair. It provides a route for rainbow trout to gain access over the diversion. The solution is to build a wingwall and raise the elevation of the front of the diversion by 3 feet. This retrofit would eliminate the hydraulics at the face of the dam and increase the leap height required to breach the dam to an elevation beyond the leaping ability of rainbow trout. Repairs due to cottonwoods encountering the diversion is also incorporated in the design.