(2009) Big River - Mining Sediment Assessment
The Old Lead Belt is a historic lead and zinc mining district within the Southeast Missouri Lead Mining District, and was a leading producer of lead worldwide from 1869 to 1972. There are major concerns about the long-term stability and toxic risk of mill waste dumps and mining sediment in rivers draining the mining areas of the Old Lead Belt. (As used here, mill tailings-derived materials released to the river that are transported and deposited downstream are referred to as mining sediment.)
Six major chat piles and tailings impoundments in the Old Lead Belt have been identified as major original source points of contaminated mining sediments within the Big River watershed. These abandoned dump sites are located in the towns of Leadwood, Desloge, Elvins/Rivermines, Park Hills/Federal, Flat River/National, and Bonne Terre. Historically, mine/mill wastes have been discharged directly into streams, were gradually eroded into streams, or catastrophically released into streams en masse due to tailings dam failures.
Past and ongoing releases of tailings have contaminated channel sediments and floodplain deposits along 90 miles of the Big River and its tributaries (MDNR, 2007), with lead and zinc in excess of Probable Effects Concentrations (PEC) established by MacDonald et al. (2000). The Missouri 2004/2006 303(d) List identifies over 93 miles of the Big River as impaired due to tailings sediments and cadmium, lead, and zinc, and another 10 miles along its tributaries.
A TMDL has been approved for lead, zinc, and sediment for the Big River and Flat River Creek (MDNR, 2007). There are also documented ecological consequences of mining contamination in the Big River. Reduced mussel numbers and diversity have been documented in reaches below tailings input points (Buchanon et al., 1979; Schmitt et al., 1987; Roberts and Bruenderman, 2000). A 2007 screening level survey of mussel populations and sediment metal concentrations in the Big River demonstrated that mussels are less abundant and less diverse in sampling locations below mining impacts where sediment concentrations exceed the PEC for lead and/or zinc (Mosby et al, 2008). Moreover, elevated levels of metals have been found in aquatic plants and animals in contaminated segments of the Big River (Schmitt and Finger, 1982).
- Quantify the volume and downstream distribution of mining sediment storage in channel bed and bar deposits,
- Quantify the volume and downstream distribution of contaminated sediment in overbank floodplain areas, and
- Determine the rates of mining sediment transport and probable residence times in the Big River Watershed