The City of Toronto broke ground on the largest stormwater-management program in its history on December 14.

Mayor John Tory and Councillor Jennifer McKelvie were on hand to mark the beginning of tunnel boring for the Coxwell Bypass Tunnel. The project is the first stage of the Don River and Central Waterfront Wet Weather Flow System—five connected projects that aim to keep combined sewer overflows out of local waterways, and improve water quality in the Don River and along the central waterfront of Lake Ontario.

The total budget for all five phases is more than $3 billion.

The Coxwell Bypass Tunnel will span 10.5-kilometres and run at a depth of 50 metres parallel to the Don River. It aims to capture, store and transport combined sewer overflows for treatment at the Ashbridges Bay Treatment Plant. The tunnel is being dug by a machine named Donnie, which is 115 metres in length and weighs nearly 1,000 tonnes.

"I am pleased to mark the arrival of the tunnel boring machine as the City prepares to dig the Coxwell Bypass Tunnel,” said Tory. “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. This project is of great importance to our city and the future of our waterways.”

The machine was lowered into the 50-metre-deep and 20-metre-diameter shaft at the Ashbridges Bay Treatment Plant in sections and then assembled. Once testing is complete in the new year, the machine will work its way west along Lake Shore Boulevard East to Don Roadway, north up the Don River valley to the North Toronto Treatment Plant and then east to the Coxwell Ravine Park shaft site where the tunnel ends.

The machine can bore at least 20 metres of tunnel per day. The Coxwell Bypass Tunnel is expected to be completed in 2024.

Other phases of the tunnel system include the Taylor Massey-Creek Tunnel and Inner Harbour Tunnel, 12 wet weather flow storage shafts along the tunnels, 27 connection points to the tunnels for stormwater and combined sewer overflow, seven off-line storage tanks, and new real-time control systems that will allow staff to regulate flows.

The city says the project will help improve water quality, enhance recreational uses, improve aquatic habitat for fish and other wildlife, and support revitalization efforts along the Central Waterfront.

At the moment, funding for the project is being provided exclusively by the City of Toronto. Tory said that the city was faced with a difficult choice between ignoring the sewage overflow problem or funding the project without assistance from other levels of government.

"While we're continuing to urge the federal and provincial governments to partner with is in this crucial environmental initiative, we're not waiting to get going," he said. "It is a core responsibility that we have for our generation … but also for the next generation to stop dumping raw sewage into Lake Ontario and into the waterways that flow into it. We can't allow the status quo to prevail.”