Best Management Practices for Highway Construction Site Sedimentation Basins

The objective of this PhD research is to develop a set of stormwater Best Management Practices (BMPs) with respect to design, operation and maintenance of sedimentation basins (SBs). Stormwater BMPs may be defined as any program, technology, process, citing criteria, operating method, or device, which controls, prevents, or reduces pollution from stormwater runoff. Sedimentation Basins at construction sites are currently designed for runoff capture rather than for particle removal. Well designed SBs that capture particles effectively are essential for capturing sediments and particulate contaminants (iron, aluminum, manganese and phosphate). An integrated methodology for designing basins incorporating runoff capture, required level of particle removal and effective sediment containment is not available. Through this research an integrated method for designing SBs by applying, rainfall probability plots to determine basin settling volume, Revised Universal Soil Loss Equation (RUSLE) to identify sediment zone volume and overflow rate to identify particle removal in the basin was developed. Further a set of design curves were generated to understand the change in basin performance and cost with change in basin design parameters. In addition the capacity of sedimentation basins to neutralize naturally occurring mildly acidic seeps (pH 5-6) was identified. Best management practices of frequent sediment dredging and maintaining drainage time within five days were suggested for the control of algae growth and mosquito breeding in the basin respectively. The feasibility of adding polymer to enhance sedimentation in the basin during high flow conditions was demonstrated. The suggested integrated design method and the best management practices address runoff capture, particle removal, pollutant peak attenuation, acidic seep drainage, algae growth and mosquito breeding in the basins. The outcome of this research will yield a methodology for designing SBs that can protect water quality and control particulate contaminants (iron, manganese, phosphate and aluminum) released from construction activities. The new design methodology offers more input choices leading to a number of basin performance and installation cost outputs