I've seen work on Front in a number of locations. Never realized they were digging under there. Connecting the grid May 20, 2006. 02:40 AM JOHN SPEARS CITY HALL BUREAU Standing up to his ankles in muck at the bottom of a shaft 30 metres below ground near Sherbourne St. and the Esplanade, Larry Fawcett somehow keeps a straight face as he describes his day job for Hydro One. "I look after overhead lines," Fawcett explains, peering into the maw of a tunnel that burrows out from the bottom of the shaft and disappears into the murk. The shaft is the start of a 2.1-kilometre tunnel that will carry an array of electricity transmission lines to tie the east and west halves of the city together. The two halves are linked, but growing demand for power means the existing ties aren't adequate. That becomes an issue when a failure occurs â€” a transformer blows, perhaps, or a transmission line is knocked down by wind or ice. As things stand now, the east and west halves of the city's electricity system can't back each other up when part of the system is knocked out. Power feeds into Toronto from transmission lines at opposite ends of the city, but can't easily flow across an electric dividing line that cuts the city in half roughly at Yonge St. Expanding the links between east and west by running new transmission lines through the $44 million tunnel will let power flow more freely across the city, giving hydro officials more options to reroute power and keep the lights on when circuits get knocked out or are taken out of service for maintenance. But circuits and power lines seem a trifle remote in the gloom of the tunnel, driving through the thick layer of shale that underlies Toronto. They're just as remote way up above, where a diner ordering a pastrami and rye in Shopsy's at Yonge and Front Sts. has no idea of the drama going on below. Shale is a soft, dark rock that needn't be dynamited. Instead, work crews carve their way forward using a giant tunnel boring machine, or TBM. The snout of the machine is a rotating hemisphere, three metres in diameter, studded with almost diamond-hard steel nubs. Powerful electric motors spin the hemisphere, chewing through the shale in 107-centimetre bites. An overhead conveyor belt carries the rock back to a train of three cars that carry six tonnes of shale apiece. The carts shuttle back and forth on railway tracks, making the tunnel Toronto's newest subway, though not many commuters would relish the trip from surface to tunnel and back up. Equipment and shale are hauled up and down by crane; workers and visitors clamber up and down the 30-metre shaft the hard way, on a series of wooden ladders. "We're about half way there," Fawcett says of the tunnel's advance. Progress was halted for more than a week by a seam of clay in the bed of shale, just as the tunnel approached Yonge St. Clay is soft and easy to cut through, but unlike shale it needs to be shored up to keep it from collapsing. Normal tunnelling had to stop while crews lined the tunnel with hardwood boards, or lagging, supported at one-metre intervals by curved steel beams. Luckily, the clay seam was relatively narrow â€” just over 13 metres â€” according to construction technician Jim Goodfellow. "We were back into rock on Wednesday," he said. It has now crossed Yonge St. heading west. The man directly in charge of getting the tunnel there is engineer Gary Lukez, who works for Dibco Underground Ltd., the main tunnel contractor. Tunnelling is what Lukez does; he recently finished a job in Hamilton, boring a water intake tunnel under the Queen Elizabeth Way. The Hydro One job presents a few extra challenges. Because the tunnel drives through the heart of downtown Toronto, it crosses too many property lines to make negotiating easements a realistic proposition. Instead, the line stays on public property, following the city's roads. That means heading north on Frederick St. and then making a 90-degree turn onto Front. Sharp turns aren't normal in the tunnelling business. Subways, water intakes, traffic tunnels, mine drifts usually run as straight as possible. The tunnel boring machine and its conveyor system are 70 metres long: To negotiate the right-angle curves, the conveyor had to be split into five hinged sections. Tunnelling through the depths of the city means encountering surprises. Some are man-made. Water mains, sewers, gas lines and telecommunications conduits are carefully plotted in advance. But occasionally an underground installation goes missing. "We found one live gas line that wasn't supposed to be there," Lukez says. It had been installed to service gas streetlights dating back to the 1920s and though abandoned, still contained trapped gas. Other surprises are more natural. One morning crews arrived for work to discover a raccoon inspecting the farthest reaches of the tunnel. They shooed it more than a kilometre back to the entrance shaft and watched it clamber back up the ladders to the surface seeking daylight, garbage cans and a warm attic.