Niagara Falls is an awe-inspiring display of natural beauty, but it is also an important source of clean hydroelectric power. Beginning in 1922, the Sir Adam Beck generating station, on the Canadian side of the falls, has been taking advantage of that power. In 1954 a second station was built, drawing its water supply from two 5.6-mile (9km) diversion tunnels.
Responding to increased demand for electricity, Ontario Power Generation upgraded the new plant between 1996 and 2005. Coupled with that upgrade was an ambitious project to build a new tunnel that would direct more water to the generators.
The Niagara Tunnel is 6.3 miles (10km) long and 42 feet (12.8m) in diameter, more than one and a half times wider than the English Channel Tunnel. It allows an additional 500 cubic meters per second to be delivered to the generating station, enough to fill an Olympic-sized swimming pool in seconds.
As owner’s representative, we provided technical and management oversight for the project. Responsibilities included:
- Concept design of the tunnel
- Management of international expression of interest
- Design-build proposal evaluation and award process
- Project and construction management
- Contract administration
The joint venture also managed the preparation and negotiation of a three-part Geotechnical Baseline Report regarding life-critical lockout safety for part of the project in the river upstream from Niagara Falls.
The tunnel was constructed with the world’s largest hard-rock tunnel boring machine, named Big Becky in honor of Sir Adam Beck. The cutterhead consisted of six major sections, each weighing about 60 tons. Working as deep as 460 feet (140m) below ground level, the machine was driven by 15 electric motors drawing about 4.7 megawatts of power. About 56.5 million cubic feet (1.6 million cubic meters) of rock and debris were displaced.
Challenging ground conditions included rock with high in-situ stresses and prone to water-induced swelling. A two-pass lining system was used, consisting of initial rock support and a final lining including a double-layer waterproofing membrane, cast-in-place concrete, and contact and prestress grouting. Steep grades were used at either end of the tunnel in order to pass under an ancient buried gorge.
The tunnel project was completed in March 2013, earlier than scheduled and at a total cost C$100 million less than its revised budget of C$1.6 billion. Construction employed almost 600 people and the project brought a reported $1 billion in economic benefits to the region.
When the tunnel was formally opened, Ontario’s Minister of Energy said, “This project is a source of pride as an engineering feat and as a practical solution for meeting Ontario’s energy needs through clean sources.”
Tom Mitchell, president of OPG, described the project as a “world-class technological achievement.” He said, “It was completed safely, with a safety record twice as good as the industry average. It will not operate for the next 10 years, or 25 years, or even 50 years, but for the next 100 years and more.”
The tunnel, capable of producing enough additional power to supply 160,000 homes, is integral to Ontario’s green-energy plans, which aims to close all the province’s coal-fired generating plants. During construction it was the largest renewable-energy project of its type in the world.
On November 15, 2013, the Niagara Tunnel Project was named Canadian Tunnelling Project of the Year at the Awards Gala of the Tunnelling Association of Canada. The joint venture Hatch Mott MacDonald received the award as the Owner’s Representative. The award was engraved to show the cutterhead of “Big Becky,” the TBM used to create the tunnel.