^{June 1, 2020} Powerline Plus Finds ‘Best’ Solution for Highway Crossing Project

Team opts for trenchless Jack and Bore tunneling to install electrical infrastructure under Toronto highway

Needing to cross a major highway with power infrastructure can be a complicated endeavor. Sometimes going overhead simply isn’t an option, which is why Powerline Plus Ltd. (Powerline) selected the best underground solution to connect power between two locations for Toronto Hydro.

As a “one-stop shop,” Powerline provided the design and engineering, civil construction, and electrical construction for this important project, which began in October 2019 and was completed in April of the following year.

“We have all the needed expertise in-house. We can do design, we can procure materials, we own the equipment ourselves,” Powerline team members said. “We really are a one-stop shop.”

For this project, the city utility Toronto Hydro needed the underground electrical infrastructure (distribution feeder cables) moved from one side of the highway to the other. Shutting down all the lanes of traffic was not a viable solution, and performing the tunneling work one lane at a time would have taken too long.

Due to those factors and the length and size of the needed tunnel, Powerline selected the Jack and Bore trenchless method of tunneling which would be less disruptive, safer, and more efficient using a modified auger boring machine.

Jack and Bore tunneling is performed by placing an augur boring machine in a shaft. As the machine’s augur turns and bores the tunnel it also installs a steel casing which becomes like a solid shell around the proposed assets. The casing Powerline installed is strong enough to withstand the pressure of surrounding soil and moving traffic above.

“This was the best way to get the assets under the highway,” Powerline’s construction team said.

Challenges can still arise using the best method for the job. In this case, the soil under the highway varied from dirt to shale – natural rock that is as hard as concrete. Powerline purchased a special cutting head for the machine to break through shale wherever they could, but one section was so hard, they still had to access it from above to identify the problem and find a solution.

They obtained permission to close one lane of traffic, and rotated crews so that work could continue for 24 hours and disrupt the traffic for as short a time as possible. In one day, working around the clock, they were able to identify the obstruction, remove it, backfill, and allow traffic to resume in all lanes.

Once tunneling had been completed and cable chambers installed, the electrical construction team was able to install the new infrastructure connecting the relocated feeders. From start to finish, construction took seven months including all the electrical work.

Extra Measures to Keep Tunnel Crews Safe

Tunneling safely begins during the engineering and design to make sure to avoid any other underground utilities. Powerline’s designers talk at length with other asset owners and the construction team to review the plans thoroughly so that other underground utilities are not disrupted during construction.

Keeping construction crews safe on a tunneling project also requires different measures than above-ground work. Powerline implemented several specialized safety procedures, beginning with training.

Everyone involved with the project was required to go through tunnel training even if they had taken it previously. This is a policy Powerline enforces on all of its projects that requires tunneling.

The training went over all the procedures that must be followed working in the tunnel, rescue procedures in case of incidents or emergencies, and rescue procedures related to the access shaft.

Powerline also used a safer, method to build the access shaft to the tunnel. Despite the time and cost for construction, they’ve chosen to use it for all their tunneling projects to keep their people safe.

Anyone who would be entering the steel casing was also specially trained to work in the enclosed space, and provided with proper lighting, ventilation and radios for communication.

These thorough safety measures ensured the work was performed successfully and safely, with no recordable incidents taking place on the project.