Canadian Consulting Engineer

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Gatineau has 1,300 combined sewer-stormwater overflows in a year


The city of Gatineau, adjacent to the Canada’s capital, is tackling the problem of frequent sewage releases into the Ottawa River.

For the first time the city is installing technology to monitor the amount of combined sewage and stormwater it is releasing. According to its own staff estimates, the city had 1,300 overflows during 2015. By contrast, Ottawa only recorded 80 in the same period.  Ottawa has spent millions of dollars to attenuate its impacts on the river with a 17-project program called Ottawa River Action.

Gatineau has 92 sites with combined sewer-stormwater outflows, 10 of which are so problematic they overflow even when there is no big storm event.  The situation used to be worse. Before new provincial regulations came into force in 2014, the city was discharging through 120 combined outlets.

A CBC News report by Kate Porter of August 15 said the city has been monitoring the outlets by sending an employee to the sites “to see if a little piece of floating wood in the sewer had moved,” which would indicate an overflow.

Now the city is installing technology to monitor outlets in real time on 50 of the outlets.  Chantal Marcotte, head of the city’s environment department, told Porter that monitoring the outlets will help them to focus their efforts in order to meet the regulatory requirements by 2017. Porter writes: “It will be a balancing act between the ultimate solution of spending money to separate all sewage and storm water into separate pipes, which could cost $350 million, or dealing mainly with problem areas.”

The city’s wastewater treatment plant in the east end is also overloaded and currently in the process of a $150-million upgrade.

On the other side of the river, Ottawa is working to further reduce its combined storm and sewage effluent reaching the river by building two large interconnected storage tunnels, one north-south, and another east-west. The project is costing $195-million.

To read the CBC report, click here.