Assessment and Recommendations for the Operation of Standard Sumps as Best Management Practice for Stormwater Treatment (Volume 1)

Standard sumps are installed in many urban and suburban storm sewer systems. They may qualify as a best management practice (BMP) to pre-treat stormwater runoff by removing suspended sediment from the water. However, no data exist on the effectiveness of sediment removal by and maintenance requirements for sumps. Such data could justify giving pollution prevention credits to transportation departments, municipalities, counties and other local governments for the use of standard sumps.

To determine whether the standard sumps remove suspended sediments from stormwater runoff, two standard sumps with different sizes were tested in a laboratory setting to determine their removal efficiencies under lowflow conditions as well as the effluent concentrations under high-flow conditions. The removal efficiency tests included feeding a specific sediment size and concentration into the influent pipe and then collecting, drying and weighing the sediments removed by the sump at the test conclusion. The high-flow condition tests involved placing a commercial sediment mix inside the sump and assessing the amount of sediment remaining after the sump was subjected to high flows for a period of time.

At the conclusion of testing, removal efficiency functions as well as washout functions were developed for the sumps, which can be used to predict the performance of all standard sumps. In addition, an uncertainty analysis was conducted to aid with data interpretation.