Assessment and Recommendations for Operation of Standard Sumps as Best Management Practices for Stormwater Treatment

Project summary:

Standard sumps are installed in many urban and suburban storm sewer systems. To improve the performance of standard sumps as a best management practice (BMP) in treating stormwater runoff, a porous baffle, called the "SAFL Baffle," was designed to be installed as a retrofit in standard sumps. The effect of the SAFL Baffle on the performance of standard sumps was assessed by conducting laboratory tests on small-scale and 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 was 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 show 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 is reduced to near zero.