Severe floods during 2011 led to the Musselshell River cutting around the Egge Diversion. Surrounding landowners elected to work with Montana Fish, Wildlife & Parks to remove the non-functioning irrigation diversion dam and open up several miles of channel to fish migration. AESI provided design services for dam removal, scour hole fill, and bank restoration. AESI’s stream restoration design included two lifts of fabric encapsulated soil (FES) with willows planted in-between soil lifts to stabilize the bank. Conifer fascines were placed below the first lift of FES to add roughness to the face of the FES to facilitate sediment deposition along the restored bank line. The restored bank was also set lower than the adjacent bank to create a bench that better interacts with floods, thus creating more riparian habitat. Existing and proposed conditions were modeled in HEC-RAS to ensure functionality of the design. AESI also provided assistance with bidding, intermittent construction oversight, and project closeout assistance during the construction phase. Major project elements included:
- Removal of roughly 120-foot long concrete diversion dam
- Fill scour hole (over 3,000 CY) with locally sourced material
- Approximately 180 lineal feet of fabric encapsulated soil bank restoration (2–lifts)
- Construct approximately 10 woody trenches on the restored floodplain to increase roughness and promote willow growth
- Planting of over 6,000 locally sources willow poles