On Friday June 25th 2004, the Ontario Government announced the approval for Ontario Power Generation to proceed with the creation of a 3rd tunnel under the City of Niagara Falls. This project, starting in 2005, is expected to be completed in 2012 or 2013 as opposed to its original completion date of 2009.
On Thursday August 18th 2005, Ontario Power Generation (OPG) announced that the Austrian, Strabag AG Company was contracted to build the $600 million dollar hydro tunnel. Upon completion, this third tunnel project is expected to be one of the largest tunnels built in North America.
The new tunnel will run parallel to the existing water tunnels but, at a lower depth of 140 metres, as opposed to the current tunnels that reach a maximum depth of 100 metres.
Strabag AG will also undertake some corrective work on the former Ontario Power Station, the Ontario Power Station Water Intake Gate House, and the former Toronto Power Station increasing the contract cost to $985 million dollars.
The path and depth of the new Niagara Tunnel had been predetermined many years ago. This can be attributed to the location of the original hydro canal (1921), the subsequent twin water tunnels (1955), the ancient buried St. David’s Gorge, and urban development over the years.
Initially, the hydro canal was designed to consist of two canals leading from the Welland River to the Chippawa-Queenston Power Station (also known as Sir Adam Beck #1). The route of the canal divided the city in an area that was, at that time, predominately rural. After the first canal was built successfully, the second canal plan was abandoned and the excess land was returned to the city for urban development.
In the early 1950’s, twin water tunnels, with a diameter of 14 metres (45 feet), were built under the city with a maximum depth of 100 metres. The starting location was near Chippawa and, as the tunnel progressed, slowly rose before surfacing and concluding near Whirlpool Road into a canal. Engineers have determined that the existing tunnels and canal would be too hazardous and too expensive to continue as they passed underground through the glacial silt of the buried St. David’s Gorge.
The strip of land utilized for the location of the twin tunnels was previously owned by either the hydro company, upon city land that was undeveloped, or a combination of the two.
History, geology, and urban development have influenced the current location and path of the new Niagara Tunnel with minimal room for flexibility. The new tunnel began in an area of land near the fore bays’ of the Sir Adam Beck Power Generating Stations.
The Niagara Tunnel had no alternative than to bore steeply underground in order to tunnel underneath the ancient buried St. David’s Gorge. Another safety precaution for the tunnel being underground is for separation from the existing tunnels. The current path of the Niagara Tunnel is to relatively follow the path of the existing twin tunnels.
The project involves boring a tunnel 14.4 metres (47.24 feet) at a maximum depth of 140 metres (459.3 feet) below the City of Niagara Falls. The tunnel will enhance the original engineering accomplishment of the Sir Adam Beck Hydro-Electric Generating Stations – Niagara Group in transporting water from a location up river from the Niagara Falls to the power stations at Queenston to increase its power output.
The new tunnel will complement the upgrading of the 16 generators at the Sir Adam Beck Power Station #2. This 9 year upgrading project cost $220 million dollars increased the potential peak output by 194 megawatts.
When the new Niagara Tunnel project is completed, it will enable the Beck Power Group to produce an additional 1.6 terawatt-hours of electricity for at least the next 90 years. It is expected to allow enough energy production to serve an additional 160,000 homes and increase power output at Sir Adam Beck by 14%. This is enough to meet the annual needs of a city of 700,000 persons.
Currently 1,800 cubic metres of water per second (63,566 cubic feet of water per second) are available to be diverted to the Sir Adam Beck Generating Stations for power production. Upon its completion, the new Niagara Tunnel will allow an additional 500 cubic metres of water per second (17,657.2 cubic feet of water per second) to be diverted for power generation.
On average, the Niagara Tunnel project expects to employ approximately 230 workers however this number can possibly peak to about 350 employees.
The Tunnel Boring Machine (TBM) to be used on the Niagara Tunnel project will be 14.4 metres (47.2 feet) in diameter, which is one of the largest to be used in the world. In comparison the Robbins TBM will be 2.5 times the size of the Toronto Subway tunnel and 1.5 times the size of the English Channel tunnels.
The Robbins Company designed and manufactured the largest hard rock TBM in the world solely for the Niagara Tunnel project. It is an open, hard rock, main beam TBM that utilizes the Robbins floating gripper design. The TBM has also been equipped with a state of the art ground support system. The cutter-head is powered with a 4,725 kW variable frequency drive system, which can be increased to 5,040 kW, if needed. For optimum performance Strabag chose to use Robbins 20-inch cutters mounted in a back-loading cutter-head. The cutting head typically revolves at 4 to 10 revolutions per minute (rpm).
The geology is varied on the path of the Tunnel consisting of limestone, dolostone, sandstone, shale, and mudstone. The rock strength ranges from 15 to 180 megapascals, with the majority of the rock in the 100 to 180 megapascal range. With the exception of sandstone, the geology is basically non-abrasive. Most of the rock debris removed from the tunnel consisted of Queenston Shale.
The Niagara Tunnel was expected to advance at a daily rate of 10-15 metres. Approximately 1.6 million cubic metres of material excavated from the tunnel will be left on Ontario Power Generation property between the two existing canals.
The new Niagara Tunnel will have a similar route as the existing two tunnels, which run parallel to Stanley Avenue. The new tunnel starts on Ontario Power Generation property at Queenston with a 7.82% decrease over the length of 1,500 metres and reaching a depth of up to 140 metres below the City of Niagara Falls. From the maximum depth, the tunnel proceeds with a relatively horizontal plane over a distance of approximately 7,400 metres. The tunnel ends on the Niagara River at the International Water Control Dam located one mile upriver from the Horseshoe Falls with an ascent gradient of 7.28% increase over the final 1,500 metres.
The inside diameter of the finished tunnel is expected to be 12.5 metres (41.1 feet) and will be lined with 50 centimetres (23.62 inches) of un-reinforced concrete with a double layer seal.
The TBM will operate 24 hours a day – 365 days a year on a 3 shift rotation (8 hours a shift) until completed. The Tunnel Boring Machine will be operated by two Chief Operators per shift with a crew of approximately 10 workers onboard. Additional men, around 20-30, will be employed on each shift for the required surface support.
On March 1st, 2008, the tunnel was 1800 metres long, which is approximately 5,905 feet
The Total Tunnel Length is expected to be 10,400 metres long (34,120 feet)
The Tunnel Boring Machine (TBM) is currently progressing at a rate of approximately 8 metres per day with a continuous 1.5 – 2.5 metre (over-break) rock fall from the roof of the tunnel. The rock stratum of the Queenston Shale remains very unstable and unpredictable. Numerous daily rock falls continued to cause many lengthy delays to the progress of the project. In order to resolve this ongoing problem, and to speed progress, Strabag and OPG agreed to alter the route of the tunnel to the east of the originally planned route. The tunnel is expected to follow a north-south route, which falls basically under Stanley Avenue. In addition the TBM will ascend to more stable rock strata of Whirlpool Sandstone.