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General Information

Why did OPG build a third tunnel?

The Niagara Tunnel will annually produce more power, on average, than cities the size of Niagara Falls or Kingston use every year.

Originally, the Canadian share of the water available for power generation was used at Toronto Power GS, Ontario Power GS, Rankine GS, as well as the Sir Adam Beck stations. All but the Sir Adam Beck stations have been retired.

Before the new tunnel was in service, Niagara River water available to Canada for power generation exceeded the capability of the existing Sir Adam Beck power canal and diversion tunnels (about 1,800 cubic metres per second) approximately 65 per cent of the time. With the tunnel, this is reduced to about 15 per cent of the time.

Why now?

​As the older, less efficient plants near the crest of the Falls (Toronto Power, Ontario Power and Rankine) have been retired, Ontario’s ability to fully utilize the Canadian share of the Niagara River water available for power generation has been reduced.

In 2004, the Ontario government endorsed OPG’s Board decision to proceed with the project.

Where is the Tunnel Boring Machine (TBM), Big Becky, right now?

​Big Becky was disassembled and removed from the tunnel following the 2011 breakthrough. Parts of it will be reused on other TBMs and most of the steel was recycled. A section of the cutterhead has been saved and discussions with the Niagara Parks Commission and the City of Niagara Falls are ongoing regarding how best to display it.

What method was used to build the tunnel?

The world’s largest hard-rock boring machine, named Big Becky, bored a tunnel 14.4 m in diameter under the City of Niagara Falls. The tunnel is about 1.5 times larger in diameter than the Euro Tunnel railway tunnels under the English Channel.
As it was being bored, the tunnel was reinforced with a combination of steel ribs, wire mesh, rock bolts and shotcrete that varied with the actual rock conditions encountered along the tunnel route.
As construction progressed, a waterproof membrane was applied and the final concrete liner was constructed.​

Where did the project begin, and when was it completed?

​In 2004 the Ontario government endorsed OPG’s Board decision to proceed with the project. Prior to that a lot of planning had been done.
Construction at the outlet began in September 2005. Construction at the intake, near the existing International Niagara Control Works, started in January 2006. The actual boring of the tunnel began on September 1, 2006. Boring was completed in May 2011, and the tunnel was placed in service in March 2013.​

Who built the tunnel?

​In 2005, through a competitive international proposal process Strabag AG, an Austrian company, was selected to design and construct the tunnel.
Strabag hired its construction workers through the local trades union halls. Strabag engaged several Ontario subcontractors for specific construction work on the tunnel intake and tunnel outlet.
OPG has also engaged Hatch Mott MacDonald, with Hatch Energy, as Owner’s Representative, to review and monitor the contractor’s design and construction activities.

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Water flow

Where is the water for the third tunnel coming from?

​The use of water flowing out of Lake Erie is governed by the 1950 Niagara Treaty (and subsequent notes) between the Governments of Canada and the United States. The Treaty requires the following flows to go over the Falls:
Tourist Flow = 2,832 cubic metres per second each April 1 - September 15 (8:00 a.m. to 10:00 p.m.) and September 15 - October 31 (8:00 a.m. to 8:00 p.m.)
Non-tourist Flow = 1,416 cubic metres per second during all other hours.
The International Niagara Committee was established under the Treaty to verify that the minimum flow over the Falls is met and to report on the withdrawal and use of water for hydroelectric generation.
The goal of the Treaty was to apportion water flowing from Lake Erie to Lake Ontario in a manner that balanced tourist requirements for scenic water with the water needed to operate the Canadian and US power plants.
The long-term average Niagara River flow is about 6,000 cubic metres per second. Over the course of a year, on average about one-third flows over the Falls for scenic purposes and about two-thirds is available for power generation, split equally between Canada (OPG) and the United States (New York Power Authority).
The Niagara River flow available to Canada for power generation is currently often greater than OPG’s existing diversion capability of 1,800 cubic metres per second, resulting in the use of some of the excess water in the New York Power Authority (NYPA) units through a unit rental agreement, or extra flow over the Falls.
The water in the new tunnel will be some of this excess Falls flow or rental flow.​

What is the effect on water flowing over the falls?

​The new tunnel enables OPG to better utilize Niagara River water to generate clean, renewable electricity. Excess water above and beyond what is required for tourism was “spilling” over the Falls some of the time. The new tunnel diverts that water for electricity production.
The amount of water going over the Falls now, and in future will be in compliance with the Treaty requirements.

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Why was the tunnel alignment changed?

​Initial progress of the tunnel boring machine was much slower than expected due to difficulties safely excavating and installing initial rock support in the Queenston shale formation.

This resulted in significant overbreak (excess rock removal) in the tunnel crown. In December 2008, the contractor initiated a realignment of the tunnel to minimize remaining excavation in the Queenston shale formation. This realignment reduces the tunnel length by about 200 metres, to 10.2 kilometres.

Where will the tunnel run?

​The route of the new tunnel follows the two existing OPG diversion tunnels which have been there since the 1950s. For much of its route the new tunnel is about 90 to 140 metres below the ground surface.
The tunnel runs from an intake located near the International Niagara Control Works, upriver of the Falls, to the outlet, located near the Sir Adam Beck generating stations. For the most part, the tunnels follow a route that runs below and to the west of Stanley Avenue under the City of Niagara Falls, Ontario. See the route the tunnel will take.

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How was the project funded?

​The province of Ontario committed to provide OPG with the required financing for the project and the costs will be recovered through the regulated price for future electricity generation from OPG’s Sir Adam Beck generating stations. The Ontario Energy Board will determine the amount added to the regulated electricity price in an open and transparent process.

What is the cost?

The value of the design/build contract for the Niagara Tunnel Project is about $1 billion. The total project is expected to cost about $1.6 billion. 

In addition to the design/build contract, this estimate includes:

•  Cost of remedial work at the retired Ontario Power and Toronto Power generating stations at Niagara Falls as part of their reversion to the Niagara Parks Commission and agreement on the long term disposition of water rights for use in the new tunnel;

•  Cost of satisfying the conditions of the project's Environmental Assessment approval;

•  Cost of retaining an external consultant with international tunnelling experience as Owner's Representative to review and monitor the design and construction activities on OPG's behalf;

•  Cost of a comprehensive insurance program;

•  Interest cost during construction, and;

•  Contingency to cover unforeseen circumstances. ​


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