Reclamation Plan for the Redex Mine Reach of Whitewood Creek, South Dakota

Mussetter Engineering, Inc. (MEI) developed a channel and valley floor reclamation and restoration plan for 2 miles of a severely tailings-impacted and placer-mineded reach of Whitewood Creek in the Black Hills of South Dakota. The project objectives were to provide a geomorphically stable system that would require minimum maintenance and improve and maintain water quality in the creek. The design criteria included the development of an integrated landscape in which both the valley floor and the channel functioned to pass a range of flows and their sediment loads in a manner that would not cause excessive lateral migration of the channel, significant deposition of the bed material load in the channel or excessive erosion of the regraded and revegetated valley floor.

To develop a basis for design, MEI conducted topographic surveys of the project reach, mapped the surface and subsurface geology, sampled the bed material in the channel, and conducted a detailed geomorphic characterization of the project reach, as well as up- and downstream reaches that had been unaffected by placer mining. Hydrologic analyses included developing a peak flow frequency curve and a flow-duration curve from an upstream gaging station using WRC Bulletin 17B procedures. HEC-2-based hydraulic analysis was used to determine existing water-surface elevations, incipient motion discharges (critical discharges) and sediment continuity. Based on the results of the existing conditions analyses, a two-stage compound channel was designed with the lower stage designed to convey the mean annual flood (500 cfs) and the upper stage designed to convey the 5-year flood (2,000 cfs). Overbank regrading was designed to withstand flows in excess of 2,000 cfs, and two tributaries were integrated into the design. Boulder-step structures were designed to provide grade control within the reach and to ensure that there would be no upstream stability problems associated with the project reach stabilization. Fish habitat enhancement was integrated into both the bed stabilization elements and the bank protection measures, where possible throughout the project reach.

Major Project Features

• Geologic and Groundwater Analysis
• Hydrologic Analysis
• Sediment Transport Analysis
• Fluvial Geomorphic Analysis
• HEC-2 Hydraulic Analysis
• Channel and Floodplain Design