Tunnel Business Magazine

OCT 2018

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TUNNELINGONLINE.COM 1 9 TBM: TUNNEL BUSINESS MAGAZINE // OCTOBER 2018 working with the conventional Carne- gie joint that the joint tended to separate as a result of microtunnelling activities, allowing dirt to enter into the joint gap and potentially affecting performance of the pipeline during pressure testing. To combat this, Ward & Burke worked with Decast to develop a new hybrid joint de- sign that met the project requirements. Other than modifying the joint, the jack- ing pipe was built to specifications com- monly used on previous Ward & Burke microtunnelling projects. Corrosion resistance was achieved using a sulfate-resistant cement in the concrete pipe, although one section of the new sewer called for an HDPE liner cast into the pipe in an area where H2S gas concentrations were expected due to high sewer turbulence. In the coming months, crews will commission the new line in advance of handover to the client, months ahead of schedule. To complete the project ahead of schedule, the Ward & Burke team had up to three microtunnel boring ma- chines operating at one time. The team used a combination of two Herren- knecht A enknecht A enknecht A 1500. For long drives and curved drives, Ward & Burke use T guid- ance system. In the event that extra power was needed for the longer drives, Ward & Burke installed upward of 20 interjack stations (IJSs), but they were able to keep jacking forces low enough that the IJSs were not employed. Challenges Ground conditions for the Twinning of the East Brampton Trunk Sewer consist- ed primarily of glacial till, which is fairly typical for the Greater Toronto Area. The till consists of a mixture of clays, sands and silts with cobbles, boulders and occa- sional gravels. While the ground itself can be challenging, the GTA-based contactor has a great deal of experience in this type of soil. "We are very familiar with these types of conditions," said Grennan. "We were able to maintain low jacking forces over the entire job, so the job was very successful from a tunneling perspective." What did prove to be a challenge was dealing with parties along the project alignment. While verifying utility loca- tions at the north end of the project, the project team found that a 600-mm gas main that feeds a power plant was in di- rect conflict with the alignment of the new sewer. To remediate the conflict, a vertical curve was introduced to raise the tunnel path above the gas main, with the gas company requiring 0.6 m of separation between the main and the new sewer. As a result of the change, the revised alignment conflicted with a fiber-optic duct back farther upstream. Because the gravity-fed pipe could not be lower, the utility company had to expose and relo- cate their infrastructure to allow the tun- nel to pass unimpeded. "Dealing with third parties to keep the project moving forward was quite chal- lenging," Grennan said. "But we were able to get all the stakeholders together and redesign the alignment. The good news is that we were able to find the discrepancies as we were doing our due diligence rather than finding the c " Another first on the project was a crossing of Highway 407, a major thor- oughfare that is a leased toll road in the project area. Ward & Burke worked with the concessionaire, 407 ETR Con- cession Co. (Cintra/CPP Investment -Lavalin), to assure that tun- nelling activities did not interfere with roadway operations. Ward & Burke Passes Test for East Brampton Sewer Project F E AT U R E S T O R Y

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