If you’ve ever dug a fence post in rocky ground, you know the drill. The shovel hits something hard, you work the blade under it, lever the rock out, toss it on a pile and keep going. The machine that just finished a tunnel under Winnipeg never had that option. It’s sealed inside its own bore, nobody rides in it, and it can’t back up. When a boulder showed up in front of the cutting head, the only way past it was through it.<\/p>\n
According to the contractor, that happened more than 2,000 times.<\/p>\n
Erritt Construction, a Canadian microtunneling specialist, announced on August 31<\/a> that its German-built Herrenknecht AVN2500D had completed a 5,600-foot (1,707-meter) drive beneath the city’s St. James district, on the Ferry Road storm sewer job. Somewhere along that route sat a stretch of roughly 2,000 feet (600 meters) packed with large boulders, and Erritt says the crew was staring at 10 to 15 of them crowding the excavation face at once in the worst spots. The machine ground through all of it, took two curves on the way, and still holed through with a bore that runs more than a mile end to end.<\/p>\n A microtunneling machine is basically a steel cutting head with no room for people. The crew stays at the surface, and an operator steers the whole thing from a control container next to the launch shaft, watching sensors instead of the ground. Down in the hole, hydraulic jacks shove a string of concrete pipe forward, and the machine rides at the tip of that string. The pipe’s the tunnel, and it’s also the drivetrain.<\/p>\n We watched the same trick play out under Ballard earlier this year, where a 7-foot machine passed beneath a Seattle main street<\/a> pushed by jacks parked in a shaft weeks behind it. The Winnipeg version is the same idea with a bigger appetite. The finished pipe here measures 2,400 millimeters across on the inside, about 7.9 feet, and that’s enough room to stand up in wearing a hard hat.<\/p>\n A surface excavator that hits a boulder picks it up and moves it. A tunnel machine that hits one it can’t handle usually forces a rescue shaft: crews dig down from the street to free the head, and the budget takes the hit. That’s the outcome every contractor plans around, and it’s why this drive didn’t end with a crane and an apology.<\/p>\n Herrenknecht<\/a> builds its AVN family for exactly this fight. A cone-shaped crusher sits in the chamber right behind the cutting wheel, and the wheel’s own rotation grinds whatever rock comes through against it until the pieces are small enough to pass a set of screened openings. From there the fragments get sucked into a slurry line, a loop of pressurized drilling fluid that carries the spoil back to a separation plant at the shaft, and that same fluid pushes against the ground up front so the face can’t collapse onto the machine. Every boulder on this drive left the site as gravel in a pipe.<\/p>\n Erritt’s numbers work out to roughly one boulder for every foot of advance through that 2,000-foot stretch, if the estimate holds up. I can’t independently check the count, and I’ll be straight with you about the sourcing: nobody was down there with a clicker, the tally comes from the contractor, and the primary source here is a LinkedIn post. LinkedIn posts aren’t peer review. It’s also the only count anyone has, so treat the 2,000 as an estimate from the people who ran the slurry plant, and that’s still a better vantage point than yours or mine.<\/p>\n The alignment included two horizontal curves, each on a 1,640-foot (500-meter) radius. That sounds gentle, and by road standards it pretty much is. Now steer it blind. The machine bends at an articulation joint in its middle, and hydraulic steering cylinders nudge the front half against the back half a fraction of a degree at a time, per Herrenknecht’s own description of the system. The operator steers off a guidance readout and a laser reference. There aren’t any windows on this thing.<\/p>\n Erritt says the drive took 16 weeks running 24 hours a day. That’s about 350 feet a week of progress, boulders and curves included, for roughly four months without a pause. Global Trenchless, the trade outlet that picked the story up on September 1<\/a>, ran it as a record drive, and Erritt frames it the same way. As far as I can tell, no independent body has certified a record here, so I’ll leave that word alone. A mile-plus bore in a single drive, through ground like this, is plenty impressive on its own.<\/p>\n What Erritt hasn’t published is the exact breakthrough date, or whether any single boulder actually stopped the head for a while. Sixteen weeks of continuous running suggests nothing stopped it for long.<\/p>\n None of this happened for the highlight reel. The new tube’s a land drainage sewer, a storm pipe, part of the Ferry Road and Riverbend sewer separation program<\/a> the City of Winnipeg has been building out across St. James in more than 20 separate contracts. The district still runs on combined sewers, the old setup where rain and sewage share one pipe, and a hard storm can push the mix straight into the river. Separating the two means laying big new pipes for the rainwater, and that’s what it looks like in practice: a 7.9-foot bore under a built-up neighborhood.<\/p>\n Which is arguably the least glamorous kind of infrastructure a city can buy, and also the kind you notice most when it’s missing. Your basement stays dry or it doesn’t.<\/p>\n Winnipeg, it turns out, sits on ground that punishes this sort of work. Canada’s become a genuinely busy market for these machines, enough that Toronto now imports its big borers from Germany<\/a> after its hometown builder shut down. The glacial soils across much of the country hide cobbles and boulders that stopped older machines cold and forced those rescue pits. Crushing 2,000 of them in one pass, if Erritt’s estimate is anywhere close, is a decent measure of how far the hardware’s come.<\/p>\n Erritt posted the completion announcement on August 31, 2026, and Global Trenchless carried it the following day. The AVN2500D is done. The 2,400-millimeter pipe it left behind stays under St. James for good.<\/p>\n","protected":false},"excerpt":{"rendered":" If you’ve ever dug a fence post in rocky ground, you know the drill. The shovel hits something hard, you … <\/p>\nSo what exactly was doing the digging?<\/h2>\n
So how does a sealed machine eat a boulder?<\/h2>\n
The route bent twice and the machine never stopped<\/h2>\n
The pipe is for rain, and this part of Winnipeg needs it<\/h2>\n