Spatial Patterns And Floodplain Contributions Of Mining-Related Contaminants In Chat Creek Watershed, Southwest Missouri

Past mining activities have left a legacy of water quality problems in the Tri-State Mining District. Contemporary environmental risks stem from the release of lead and zinc from mine tailings previously dispersed far downstream in alluvial deposits as well as abandoned tailings piles. This study examines mining-related heavy metal contamination in the Chat Creek Watershed. Chat Creek drains the area near Aurora, Missouri on the eastern edge of the Tri-State District where mining occurred from 1886 to about 1930. This study identifies the spatial distribution of metal contamination in fluvial sediments and quantifies the role of bank erosion as a secondary source of contamination to the watershed. The three objectives of this study are to: (1) determine the spatial distribution of lead and zinc contamination in the watershed; (2) determine erosion rates due to lateral stream migration; and (3) develop a sediment-metal budget for floodplain erosion. Sediment samples were taken from active channel and floodplain deposits to determine the current distribution of metals. Historical aerial photographs are used to determine lateral migration rates. Sediment-metal concentration data were combined with migration rates to determine a short-term sediment-metal budget for the 5. 5 km study area. Lead concentrations in active channel sediment range from 60 ppm to 2,068 ppm. Zinc concentrations range from 286 ppm to 19,666 ppm. Average floodplain lead concentrations range from 59-643 ppm while zinc ranges from 191 ppm to 5,377 ppm. Bank erosion releases 929 Mg of sediment into Chat Creek each year. Floodplain erosion also releases 84 kg/yr of lead and 321 kg/yr of zinc into Chat Creek. This study provides resource managers, in charge of Total Maximum Daily Load determination, with data concerning metal contamination in Chat Creek and the amounts of metals being introduced into the system due to reworking of floodplain deposits