Garden Creek Restoration-City Diversion Removal

FISH PASSAGE
Approximately 1.1 miles of stream were made accessible through the removal of two fish passage barriers. The two barriers, 1) a sandbag diversion (partial barrier) and 2) a concrete/steel dam diversion (complete barrier) were removed. The sandbag diversion was approximately 200 feet upstream from the concrete/steel diversion; there was no excavation of the creek bed at this site and the creek was allowed to regrade the section naturally.

The concrete/steel diversion was removed. A rock ramp was designed and constructed to address the stream grade and the four foot drop that had been created by the previous diversion dam. The new ramp was constructed to a 3% grade over 0.024 miles of stream extending below and above former diversion. This ramp reduces stream velocity and provide holding and rearing areas for fish.

The instream rock ramp was a variation from the original project proposal, which had proposed installing step pools; the final engineering design was for the rock ramp.

FISH SCREENING
A component of the non-federal cash match for this project was the installation of a fish screen designed to NMFS specifications at the rock structure diversion by Idaho Department of Fish and Game using Bonneville Power Administration funds. Approximately 7 cfs of water will be screened and 3927 acres feet per year will be protected.

INSTREAM FLOW
To replace water withdrawal from Garden Creek by the City of Challis (from both diversions), this project proposed construction of a new municipal groundwater well. The new well was constructed, but production was not adequate to replace the city water needs. An existing well was tested and reconstructed to augment production from the new well. A new pump house, pump, and electrical components for the new well was constructed/installed.

The original proposal intended for city municipal needs and the city owned golf course irrigation needs to be serviced from the new groundwater well. New well production was not adequate for both; however, flow used from the old city municipal diversion that was removed (concrete and steel diversion) of 1.58 cfs will remain in Garden Creek and flow protected for 2.9 miles.

Two stream gages were installed by this project to measure and regulate water use; one was located in Garden Creek and the other at the groundwater well site.

INSTREAM HABITAT
The original project proposal indicated that instream reconfiguration/connectivity work and bank stabilization work would be done however these were not part of the final project design. The rock ramp that was constructed to facilitate fish passage align more closely with the fish passage metric than with the instream habitat metric. Streambank stabilization practices were not part of the final (actual) project design.

PROJECT MONITORING
Implementation monitoring was done during construction; compliance monitoring was completed to confirm that the final project design was implemented and this achieved the desired outcomes and further confirmed with post-project monitoring. The actual monitoring occurred onsite.

Through the removal of the Garden Greek fish barrier and the city diversion an additional 1.1 miles of stream passage will be accessible to ESA listed species.