Institute: South Dakota
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-02-28
Total Federal Funds: $14,913 Total Non-Federal Funds: $29,826
Principal Investigators: Jennifer Benning, Arden Davis, Scott Kenner
Abstract: This research will focus on characterizing channel bed sediments as a source of coliform bacteria (fecal and E. Coli) contamination in stormwater runoff. Surface water bodies in South Dakota with a designated beneficial use of immersion recreation require E. Coli bacteria concentrations to be a maximum of 235 coliform forming units (CFU)/100mL. Several watershed studies conducted by the principle investigators, the SD Department of Environment and Natural Resources (SDDENR) and others have shown that concentrations of bacteria in runoff exceed water quality criterion, often by orders of magnitude. This occurs in urban, rural and agricultural watersheds. The proposed study will seek to identify the contribution of bacterial contamination from sediments in stormwater runoff and will apply that information to the development of recommendations for best management practices (BMPs) to reduce the bacteria load during runoff. Although watershed assessment studies identify the potential sources of bacterial contamination, the specific sources and percent contributions are not clearly understood. Additionally, watershed studies and modeling for these studies do not account for bacterial loading from sediments. Recent sampling and analysis by the principle investigators show that coliform bacteria exist, persist and potentially grow in the bed sediments in drainage channels. During runoff, sediments are scoured and thus serve as a potential source of bacterial contamination in runoff. There is ample evidence in literature to suggest that coliforms, particularly those that are associated with sediments, may persist in the environment and be resuspended during events; however, these phenomena are very site specific, as they potentially depend on temperature, moisture, soil type, organic carbon content, pH, and even source type. As a result, the processes are not well-understood and there is no information specifically on the relative contribution from the sediment to the total bacteria load. Furthermore, because the coliforms may act as a secondary source and are potentially non-point source in origin, further studies as to their possible contribution to surface water quality issues versus other possible sources are needed in the South Dakota watersheds in order to efficiently guide management strategies. The objectives of this research are to: 1) Collect surface runoff samples during events and bed sediment samples, routinely, capturing both before and after storm runoff events throughout a year and analyze both for E.coli, fecal coliform, and fecal streptococcus. 2) Use samples collected for this research and previous work to evaluate decay/growth models for the representation of coliform bacteria in sediments. 3) Characterize the sediments in the bed and the sediments in the runoff to determine if the sediments in the runoff are characteristic of the sediments in the bed. 4) Use the mass bacterial load in the bed sediment, sediment concentrations in the runoff and coliform bacterial concentrations in the runoff to determine the percent contribution of bacterial loading in the runoff emanating from the sediment. 5) Apply the results of the study towards the development of recommendations for cost-effective BMPs that will promote the beneficial uses of the surface waters and enhance the economic opportunities associated with those uses for South Dakota.