Design of Street Sump Inlet

Abstract

Sump inlets are used to collect storm water on the streets or to release stored water in detention basins. The complication in sump inlet hydraulics arises in the transition from weir to orifice flow regimes. Conventionally, the capacity of a sump inlet has been assumed to be either weir or orifice flow, whichever is smaller for a given water depth. Although this practice might not result in a failure to the storm drain, it has led to randomly oversized or undersized inlets. This paper presents a laboratory investigation of the interception capacities of several different types of sump inlets, including bar and vane grates, and 3- and 5-ft curb opening inlets. The observed data revealed significant differences from the recommended HEC 22 design procedure. In this study, new formulas and procedures are developed with the coefficients calibrated by the laboratory data.