Riley Pass Pond Cleanout and Dam Reclamation

As part of its contract with Region One of the USFS, AESI provided geotechnical engineering, civil engineering, and construction management services for the Riley Pass Reservoir and Sediment Pond Cleanout and Dam Reclamation project. The Riley Pass Uranium Mine site is located in the Custer Gallatin National Forest in Harding County, South Dakota. Uranium mining activities during the 1950s and 1960s led to an accumulation of overburden material. Due to the highly erosive nature of the unconsolidated spoils, sediment loading to nearby watersheds and existing reservoirs became problematic. The USFS constructed sediment ponds in several of the drainages which required sediment removal and dam safety upgrades. This project’s scope of work included the following items:

• Design of the repair and reconstruction of the road leading to the sediment disposal area.
• Characterization of the pond sediments and determination if they are suitable for use in reclamation.
• Identification of alternatives for sediment hauling and removal to a disposal area.
• Design of the reclamation or decommissioning of five sediment pond dams and three larger downstream reservoirs that had also been impacted by sediment.
• Construction support engineering services.