Braid: Your backyard garden soil can kill a giant water pipeline; more revelations from former officials

‘We’ve been frantically inspecting practically everywhere else in Calgary, and then Mother Nature comes up behind us and kicks us in the butt with this surprise — a bunch of corrosion and corrosive soil in a place that we really didn’t expect it’

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Toxic soil, talcum-powder pipes, polar bear bites — retired city experts reveal still more that you aren’t hearing from city hall.

First, they were dumbfounded by the riverside location of the Bearspaw South feeder failure.

“It’s just flabbergasting — typically, near river beds there isn’t any corrosion at all,” says Roy Brander, who was the city’s senior pipeline engineer until he retired in 2016.

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The sand and gravel of river soils don’t corrode pipeline concrete. Those areas are considered safe from “catastrophic” collapse (the city’s word).

Brander stretches to explain his surprise when he heard the location of the break.

“Imagine that I’m a crime investigator who’s just found a dead body with polar bear wounds — on the floor of the Grand Canyon.

“It’s that surprising. This is the last place in the entire city where I would expect to find corrosion.

“I thought somebody must have dumped a huge load of road salt right on that spot. What else could explain corrosion right beside the river?

“And then they found five more hotspots. Again, I’m flabbergasted. There must be something that dammed up bad soil against our pipe.”

The city will do a full third-party inquiry into the water pipeline failure, which may mean we’ll hear something in this decade.

If you want an instant preview, just listen to these experts who worked in city water system for years. They divulge details you’ll never hear from tame daily briefings.

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Former water transmission and distribution chief James Buker was the first to talk about how precast concrete pipe is porous and vulnerable to certain soils. He said that as long ago as 2004, a burst pipe on McKnight had deteriorated into “talcum powder.”

The earth itself corrodes the buried concrete. This in turn exposes reinforcing wires, which snap. Result: a giant water bomb.

Very dark soil — the kind you want in your unwatered garden — is the main culprit. “Farmers call it wonderful topsoil — we call it toxic waste,” says Brander.

“Most of the periodic table is bad for a concrete water main, if it’s chloride — like salt or potash. Certain petrochemicals can promote corrosion.

“We don’t want anything but clean sand and gravel around our mains. If you laid the same 1970s pipe in sand, it will probably last 200 years.”

Unless somebody dumps the wrong load on top of it, or even near it.

Brander adds: “We’ve been frantically inspecting practically everywhere else in Calgary, and then Mother Nature comes up behind us and kicks us in the butt with this surprise — a bunch of corrosion and corrosive soil in a place that we really didn’t expect it.”

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He says about 175 kilometres of feeder pipe is the type susceptible to corrosion.

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The Bearspaw South feeder was shut down for inspection in 2007, but there was little public concern because the Glenmore feeder could temporarily supply a much smaller population.

Today, a new north feeder is needed, either under Nose Hill (an option already discarded) or around it.

Any such project would be massively expensive. So are these repairs, although the city is mum about details.

What seems obvious is that pre-cast concrete water pipe, even properly installed, can later be ruined by overlays of soil and chemicals.

It’s not clear how much attention was paid to proper soil when the Bearspaw line was built in 1975, long before the corrosion problem was understood.

Water main repairs
Excavators operate over multiple pits on 16 Avenue N.W. east of 43 Street in Calgary on Tuesday, June 18, 2024 to repair a segment of a damaged water feeder main. Brent Calver/Postmedia

Both retired officials say the city has a more aggressive testing program than many other cities. In fact, pipeline testing of all kinds was virtually invented in Alberta.

“If you want a pipe inspected in Singapore or Libya, you call a company on 10th Avenue in Calgary,” Brander says.

“We’ve probably inspected more than half our pipe by now, maybe more than any town on earth.”

And yet, today’s officials failed to spot six problems on the Bearspaw South feeder. They have some explaining to do.

Don Braid’s column appears regularly in the Herald.

X: @DonBraid

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