USING SURVEY DATA AND HEC-RAS MODELING TO ASSESS MINING-CONTAMINATED SEDIMENT DEPOSITION BEHIND A RIFFLE RAMP REMEDIATION STRUCTURE IN BIG RIVER, BONNE TERRE, MISSOURI

Sediment deposition in river channels can be intensified by flooding, channel structures, or dredging. On the Big River, the United States Army Corps of Engineers and the United States Environmental Protection Agency constructed a riffle structure to trap lead contaminated sediments for remediation purposes. Due to the unique hydraulic and sediment conditions at this site it is important to monitor and model the effectiveness of the structure. Timing and seasonal variation of events are variables that influence sedimentation. The understanding of where lead contaminated sediment is being stored, how it will be affected by flood events, and the timing of contaminated sediment removal are the overarching goals of the project. Findings discussed in this presentation include the level of contamination of trapped sediment, the area of trapped sediment, and analysis of the hydraulics of this reach of the Big River using HEC-RAS. The level of contamination was determined using X-ray fluorescence. The area of trapped sediment was completed by the analysis of cross-sectional data. Hydraulic modeling was completed by collecting channel survey data and determining Manning’s n values from published literature and calibrating n to match observed flow conditions. This model will allow for comparison of observed and predicted sedimentation of the reach.