With Ministry of the Environment approval, the City’s combined sewers are designed to overflow into the Ottawa River in heavy storms, when the amount of sewage reaches the capacity of the pipes. However, the regulator gates should close as soon as the volume of sewage subsides.
In August 1 to August 3, 2006, the City experienced extremely heavy rains, resulting in a number of designed overflows. Unfortunately, one of the regulator gates became jammed open, which the City did not discover until August 15, 2006. During this period, about 764 million litres of sewage was discharged into the Ottawa River. Upon learning of the jam, the City took immediate steps to return the gate to proper operating condition. However, it did not notify the MOE of the discharge until the following April. The ministry does not claim that the discharge resulted in a fish kill or other distinct environmental harm.
Climate change is expected to increase the frequency of such overflows, because it increases the frequency of unusually intense storms and their strain on municipal infrastructure. As climate change is also likely to increase water temperature and drop water levels, the impacts of such overflows on water quality will also increase. More information on the likely health impact of such spills is available in Health Canada’s Human Health in a Changing Climate: a Canadian Assessment of Vulnerabilities and Adaptive Capacity.