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braid: the bearspaw water line came with a big shiny promise that turned out to be false
when calgary’s giant super-soaker water pipe was instal...
aug 8 2024
3 minute read
city of calgary workers inspect the damaged water main pipe after it was removed at the repair site in montgomery on monday june 10, 2024.
gavin young/postmedia
when calgary’s giant super-soaker water pipe was installed in 1975, nobody dreamed that the concrete would someday decay, wires would snap, and water would burst out.
“i recall having discussions as late as 2000 saying that the concrete is so passive that soil just can’t corrode it,” says roy brander, who retired from the city in 2016 after many years as the senior pipeline engineer.
the belief that concrete pipe was completely impervious “was like some kind of magic spell . . . it just would not corrode, period.”
the city learned this was false in 2004, when a major line burst on mcknight boulevard. the pipe was so decayed that it “looked like talcum powder,” former official james buker told me in june.
buker had worked on the 1975 project as a young engineer. the faith in concrete pipe was universal.
“we thought we were bulletproof until mcknight happened, and all of a sudden we realized concrete can get eaten away by aggressive soils,” he said to me thursday.
the city immediately ramped up inspection. calgary became a national leader in the field. but the escalating damage to the huge bearspaw feeder was somehow missed — until it exploded on june 5 .
the line never had full testing with “ pipe diver ” technology that was becoming available. buker, who retired in 2016 as the city’s head of water transmission and distribution, says “they just never got around to that one because it was so big and so critical.
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“they probably would have done it eventually, but now it’s just a bit too late, isn’t it?”
brander doesn’t fault today’s technical response to the latest crisis, but he’s contemptuous of the city’s communications. “they’re the worst. the new ethic is, the more information you give people, the more adversarial questions you’ll get. so never give out information.
“i’m just so glad to actually have some information to give you and let people know what’s going on.”
he has plenty of answers but also sees an evolving mystery.
“it would just be absolutely shocking to me if the concrete itself were badly made. it’s enormously more probable that something got dumped on that pipe, that we were absolutely caught by surprise by a pocket of bad soil that really shouldn’t have been there.
“but that’s what’s getting more and more mysterious about this. you can’t talk about a surprise pocket of bad soil when it’s already happened in more than a dozen different locations. i really am quite baffled by how the soil got that bad.”
the city certainly has no answers on that one. just as it never bothered to inspect the most crucial water line.
the bearspaw feeder is a very specific type of pipe — known at c301e.
brander says it comes with “with thinner wire and higher tension. that’s the one that failed.”
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buker confirms that the bearspaw line is the only one of that type. that should have made inspection more likely, not less, because there was no identical pipe for comparison.
the bearspaw dam in calgary on thursday, august 8, 2024.
darren makowichuk/postmedia
but there’s no disagreement with the city’s method of fixing the 16 new hotspots — pouring new concrete around the wiring.
“that’s actually a perfectly legitimate thing to do,” brander says.
“if the problem with these pipes is that they’ve lost the structural strength on the outside so that they tend to explode, then simply supplying that structural strength by pouring concrete around it is a perfectly good solution.”
he notes that sections with problems are probably less than one per cent of the 11-km bearspaw feeder. most of the line could remain sound for years to come.
replacing the whole line would be massively expensive — about $150 million, says buker. one alternative would be to run plastic pipe through the existing line. that would mean smaller diameter and thus less flow, but it would be relatively cheap.
there’s one clear message for city hall in all this — don’t fall for new technologies that come with big, unproven promises. they might not bite for half a century, but when they do it really hurts.
don braid’s column appears regularly in the herald
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x: @donbraid
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