Even hardened tunnelling veterans get excited when they're about to punch their way through to daylight.
In the mud and moisture about 30 metres below the island airport, a small crew gathered Friday for the breakthrough of the coming pedestrian tunnel. Behind them stretched the passage through which passengers eventually will walk. Just ahead was the shaft where escalators will rise to the surface.
All that stood between was the last metre and a half of shale.
"A big [tunnel] like this, under Lake Ontario, it's really exciting for all of us," said Joseph DiMillo, supervisor for Technicore Underground, which is doing the dig. A few minutes later, with everything ready, he called: "Time to make history."
One man fired up an excavator fitted with a hoe ram – essentially a leg-sized jackhammer – at the end of its extending arm while the rest of the crew waited expectantly. At least one had a smartphone ready to record the milestone.
A deafening metallic thudding filled the tunnel and dust began to swirl at the face. Even as visibility dimmed, the man kept pounding away, shifting his aim as he methodically weakened the remaining barrier. After what seemed like a long time, a small bit of light suddenly appeared low on one side. Whoops broke out among the crew and Mr. DiMillo raised his arms like a victorious prizefighter.
It was a key stage in the building of the tunnel, which is due to be finished late next year. The passageway will make it more convenient for passengers to access the island airport.
"This is a watershed moment," Toronto Port Authority board chairman Mark McQueen said in a statement. "The pedestrian tunnel is well on its way to being complete, now that the most technically difficult element of the project is behind us."
The tunnel crosses well below the western channel before sloping up slightly on the island side.
For now it is accessible to few other than construction workers. Visitors have to be trained on self-rescue equipment, and access from the base of the mainland-side shaft is about 35 metres down a series of ladders. Once there, the 186-metre tunnel stretches ahead, lit by a series of bare bulbs. It is currently about five by six metres but will be made bigger in the next stage of excavation.
During the breakthrough Friday, the tunnel's powerful ventilation system blew the dust out the first hole, which was quickly joined by a second. The two were soon connected and work sped up. At times it was reminiscent of a building collapse, as envisioned by Hollywood, with debris raining down and dust billowing.
In short order, the entire top half of the face had been punched out, leaving a heap of rock that the crew climbed over, proffering a company banner triumphantly as they emerged into the sunlight.
Company dignitaries were waiting for them there. After posing for photos, they climbed out of the shaft while the crew clambered back over the pile of broken rock to continue clearing the gap.
The next step is to use a road-header, a cutting tool mounted on an excavator, to widen the tunnel and shape its walls. The tunnel then must be lined and finished. By the time the first passengers walk through, the crews who dug it will have gone on to other jobs. And while they take pride in the work and relish the milestone of a breakthrough, there was little sentimentality.
"I've seen a lot of rock. I don't really take any souvenir," Mr. DiMillo said. "I take it home, I guess, in my laundry enough."