The ceremonial groundbreaking for a major infrastructure tunnel project designed to reduce how often storms send sewage overflows into the Ottawa River happened on Tuesday, with the project itself expected to be fully operational by 2020.

Three levels of government were on hand on the Ottawa River Pathway behind the Supreme Court of Canada in Ottawa on Tuesday afternoon to mark the announcement of funding for the Combined Sewage Storage Tunnel.

The project comes with a hefty $232-million price tag and involved years of lobbying for federal and provincial government funding. The federal and provincial governments are each contributing about $62.09 million, while the city has committed $107 million.

Ottawa Centre MPP Yasir Naqvi, federal Minister of Environment Catherine McKenna and Ottawa Mayor Jim Watson look at a map of the combined sewage storage tunnel. (Stu Mills/CBC)

The CSST project will involve the building of two storage tunnels: an east-west tunnel through the downtown core and a north-south tunnel along Kent Street from Catherine Street to existing infrastructure behind the Supreme Court of Canada.

The tunnels will hold up to 43,000 cubic metres of sewer overflow during major rainfalls, or the equivalent capacity of approximately 18 Olympic-sized pools, according to the city.

Once rainfall has subsided, this water will be treated and returned safely to the Ottawa River, the city said in a news release.

In addition to "greatly" reducing the frequency of sewage overflows into the Ottawa River during storms, the city says the storage tunnel project will also reduce the risk of basement flooding for low-lying lands in the Glebe/O'Connor area.

"We had to make sure we had the funding available and we do now, we had to make sure we signed off with the new federal government and I think it's been worth the wait because it's going to be done properly," said Ottawa Mayor Jim Watson.

Watson, federal Environment Minister Catherine McKenna and Bob Chiarelli, Ontario's minister of infrastructure, took part in the announcement.