ANALYSIS OF BACTERIAL WATER QUALITY IMPACTS DUE TO WET WEATHER DISCHARGES IN THE CITY OF EDMONTON

The City of Edmonton (Alberta, Canada) is one of several Cities in Western Canada served partly by combined sewer systems. The City has recently completed a Combined Sewer Overflow (CSO) control strategy and has begun implementing selected control measures. In Edmonton, CSOs typically occur between May and October, which is also the season in which the river is used for both contact and non-contact recreation. Therefore, it is critical to understand the combined sewer system's response to rainfall as well as the resulting impacts on the river water quality. This paper presents methodologies developed for identifying quantifiable graphical and statistical relationships between rainfall, volume of sewer overflow, areal extent and modelled peak fecal coliform concentrations in the river. These relationships can be used as guidelines by the City to design programs such as public warning notification and compliance monitoring.