NIAGARA FALLS, Ont. - A six-mile feat of engineering called the Niagara Tunnel, four stories tall and 460 feet below the City of Niagara Falls, was put into service Thursday during ceremonies at the Ontario Power Generation Visitors’ Centre.

“The completion of this project will provide Ontario with a source of clean energy for the next 100 years,” said Bob Chiarelli, Ontario Minister of Energy. “Since 2003, more than 360 megawatts of new, upgraded and refurbished waterpower projects have come online in Ontario.”

The additional water flowing through the monster tunnel is enough to power 150,000 homes for 100 years and to fill an Olympic-sized swimming pool in a matter of a few seconds, according to Tom Mitchell, president and CEO of Ontario Power Generation.

It will generate 1.5 terawatt hours of energy at the Sir Adam Beck Hydro-Electric Power Generation Stations Group, reported OPG officials. One terawatt is the equivalent of one trillion watts.

Motivating the effort was Canada’s gradual transition from coal-burning fuel plants to solar, wind, hydroelectric and natural gas projects.

“Congratulations to our contractor and to the hundreds of men and women who worked with extremely difficult rock conditions to safely complete this engineering marvel,” said Mitchell, who was joined Thursday by Ontario Minister of Environment Jim Bradley, Kim Craitor, member of Provincial Parliament for Niagara Falls, and various OPG officials.

Also present were second-and third-graders from Port Weller Public School in St. Catharines, Ont., who sang the “Niagara Tunnel Song.”

The construction of the Niagara Tunnel, which is more than 1.5 times wider than the English Channel Tunnel, was spearheaded by an Austrian-based construction contracting firm called Strabag. Excavating the sedimentry rock was a challenge, according to the project director.

“There were challenges along the way, and there was relief when we were finally able to open the gate and have the water come through,” said Rick Everdell, OPG project director. “There’s not too many tunnels like this around.”

The rock in the Niagara region is sedimentry, and the layers are thin,” Everdell explained. “Forces in the rock caused it to fracture when the tunnel was being bored. It ended up adding 1.5 to two years to the excavation.”

The $1.5 billion project was launched in September 2005, and it received widespread media coverage.

It was on the April 2012 cover of Canadian Geographic magazine. In September 2008, Discovery Channel program host Matt Rogers featured the Niagara Tunnel on the TV series “Really Big Things.” The tunnel also was featured on CBC’s Rick Mercer Report, and written about in trade publications in Toronto and Ottawa.

Turning even more heads was the machine used to bore the tunnel, nicknamed “Big Becky” in a contest among schoolchildren. Manufactured by the Robbins Co. of Cleveland, Big Becky’s cutter head consisted of six major sections, each weighing about 60 tons.

“The machine worked for 4.5 years excavating rock,” said Everdell. Throughout the project, workers followed behind Big Becky laying concrete on the bottom third of the tunnel to help form a water-resistant membrane. There was enough concrete in the lining to build a sidewalk from Windsor to Quebec City – about 650 miles, reported OPG officials.

The massive effort resulted in the excavation of 1.6 million cubic meters, or enough rock to fill the domed Rogers Centre in Toronto. Part of the rock is Queenston Shale, destined for a brick manufacturer in Hamilton, said Everdell. The rest of the rock spoil will stay on site.

As for Big Becky, Everdell said its massive cutter head could be made into a monument commemorating an international construction crew of 580 workers who teamed up to create the tunnel.

“A lot of good friendships developed over the years,” said Everdell.