Quality and Variation of Pollutant Loads in Urban Stormwater Runoff

Stormwater runoff from a homogeneous residential area in Windsor, Ontario, was studied over a 1 year period of time. Hourly grab samples were taken and analyzed for 21 constituents. Seasonal and annual concentration data are reported along with the most significant correlations among constituent concentrations. Other influences on runoff quality are discussed. Rainfall for all 25 storms was measured, and discharge was measured for 13 storms. The discharge data and rainfall data were used to generate runoff hydrographs for 9 storms without measured hydrographs. The hourly discharges and concentrations were used to calculate loadings on an annual and seasonal basis. The loadings' variation on an hourly basis is listed. The results of an empirical analysis of the average annual loadings contained in percentage amounts of annual runoff are reported. Significant correlation was found between the preceding two variables for all constituents whose loads were calculated. A comparison is made between annual loadings of stormwater runoff and raw sewage for biochemical oxygen demand and total suspended solids and orthophosphates.