The first (out of 5) part of the project includes the construction of the Coxwell Bypass Tunnel where overflow water in periods of high precipitation will be stored. The tunnel will stretch for 10,5 kilometers and will be 6,3 meters wide. It will be realized at a cost of $400 million.
The main issue that Toronto faces is that 23% of the sewer systems in the city hosts both sewage and rainwaters. As a result, when heavy rainfalls struck the area, the system becomes temporarily inadequate and significant amounts of sewage is delivered into Lake Ontario.
According to John Tory, the Major of Toronto, until today, there was no other choice as the excess of wastewater would either be stored in the lake or return to people's residences. "Both of those alternatives are obviously unacceptable, but the choice was made to have the tainted water go into the lake," Major Tory, stated.
After the first phase of the project is completed, overflow water will be stored in the new tunnel and will be delivered to Ashbridges Bay Treatment Plant before it is transferred into the lake. “Through this tunnel we can capture and store rain and wastewater and transport it for treatment and disinfection so clean water is released into the lake,” Major Tory added.
About 30% of the endeavor's first phase is completed as two shafts have already been constructed. The tunnel will be excavated with the usage of a Tunnel Boring Machine (TBM). According to experts, the TBM will advance at a rate of at least 20 meters per day beginning from the start of 2020. The plan for the project is to be completed by 2024.
The whole project consists of a 22-kilometer tunnel network, 12 shafts along the tunnels, 7 storage tanks, 12 key points where rainwater and sewer flows will enter the tunnels and the technological equipment needed to regulate the flow into the complex system. "Once this work is complete, it will capture and store combined water-sewer outflows during significant rainfall," Major Tory, concluded.