Howard, Adam K.

In order to improve the performance of standard sumps as a best management practice (BMP) in treating stormwater runoff, a baffle was designed to be installed as a retrofit in standard sumps. The retrofit is a porous baffle called "SAFL Baffle." The effect of the SAFL Baffle on the performance of standard sumps was assessed by conducting laboratory tests on small scale as well as full scale straight flow-through standard sumps equipped with the baffle. In addition, a number of tests were conducted to determine the performance of standard sumps with the SAFL Baffle when the baffle is clogged with debris like trash and vegetation. Furthermore, the performance of two other configurations of the baffle was studied: (1) the SAFL Baffle in a sump with an outlet pipe 90 degrees to the inlet pipe, and (2) the SAFL Baffle in a sump with some water entering the sump through an overhead inlet grate. Standard sumps equipped with the SAFL Baffle were evaluated using two metrics: (1) How well the system captures sediment during low flow conditions (Removal Efficiency Testing), and (2) how well the system retains the previously captured sediment during high flow conditions (Washout Testing). The results of the tests showed that the SAFL Baffle dissipates the energy of water entering the sump and as a result, at low flow rates, it captures sediment better than a standard sump with no baffle. More importantly, at high flow rates, the washout of the previously captured sediment reduces to near zero. Vol 1 is 2011-08.

Volume I: 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.