Characterizing Urban Runoff Quantity and Quality

A method using simulated flows and measured pollutant concentrations was successfully applied to estimate pollutant loadings resulting from runoff during storm events from an urban area. The method was applied to a storm sewer outfall draining an area with a predominantly commercial land use into a natural water course. The method involves collection of runoff samples during the event, observation of rainfall amount and the use of a rainfall-runoff computer model. Runoff samples were analyzed for conventional as well as priority toxic pollutants. Delivered load and mean concentrations of pollutants were estimated for several rain events. The study indicated that the mean concentrations for oxygen-consuming and nutrient type of pollutants were higher than that of comparable sites studied in the National Urban Runoff Program (NURP). The quality of the runoff from the selected basin routinely exceeded point source discharge and surface water quality standards. Also discussed are some issues pertaining to comprehensive assessment of the pollution potential of storm water discharging from several outfalls into receiving waters.