clean sources". Construction The Niagara Tunnel was constructed using a Tunnel Boring Machine (TBM), affectionately named "Big Becky" in honour of Sir Adam Beck. The TBM machine bored a tunnel about long and about 14.4 metres (47 ft) in diameter under the City of Niagara Falls, Ontario, from the Niagara River to the SAB complex. The bored tunnel was subsequently lined with an impervious membrane and a concrete lining, pre-stressed by high pressure grouting. The massive undertaking created about 1.6 million cubic metres of rock and debris, and was designed for a minimum 90-year life span. The HP 471-316 TBM was driven by 15 electric motors totaling about 4.7 megawatts of power (6,375 horsepower), built by the Robbins Company of Solon, Ohio, and was the world's largest hard-rock tunnel boring machine as of 2006. The TBM operated as deep as below ground level to avoid the machine's vibrations being felt at surface level. The design-build contractor for the project was the Austrian construction company Strabag AG, a large construction group with extensive experience in large tunnel construction. Boring by the Hatch Mott MacDonald Engineering Company started on 15 September 2006 at the north end, located at and ended on 31 March 2011 at the south end, located at . Due to slower than projected boring progress caused by constant tunnel roof over-breaks, the project completion date was extended to at least December 2013, with a revised total projected cost of $1.6B. Completion and commissioning On 21 March 2013 the Ontario Power Generation Corporation (OPG) and the Ontario Government officially placed the new Niagara tunnel into service with a formal opening ceremony and tour. The OPG reported that the project will be financially rewarding despite being completed four years later than planned and about $500M over its originally estimated cost. OPG's president and CEO Tom Mitchell stated: "This was a large, complex project that will serve Ontario for more than 100 years". The tunnel project was completed at a total cost $100 million lower than its revised $1.6 billion budget, and with an in-service date of 9 March 2013. The operational start-of-service date was nine months sooner than the project's revised schedule that was drawn up in 2009 due to unexpected and difficult geological conditions encountered in the soft Queenston Shale Formation during the tunnel boring process. The new tunnel will provide enough additional water to the Sir Adam Beck generating