‘Underwhelming’ is how one Calgary city councillor describes an upcoming 596-page review into the Bearspaw water feeder main rupture.

The report is set to come to the Dec. 11 Infrastructure and Planning Committee meeting, just two weeks after a preliminary report received by city council.

City admin summarized the latest report, going over many of the same factors that likely contributed to the June 5 break, including microcracking of the mortar covering, wire snaps due to corrosion and hydrogen embrittlement. Hydrogen embrittlement is when hydrogen atoms are absorbed into the metal, making them prone to cracking.

The report does conclude that there’s a strong correlation between the distress and corrosion found in the wires and higher levels of chlorides in the soil. The report said this is likely due to the use of road de-icers. It also stated, however, that chlorides can be deposited on to the mortar of a pipe if the water table fluctuates.

Some pipes showed visible mortar cracking, and some of the distressed pipes did have chlorides penetrate the mortar, the report showed.

“Severe pitting and corrosion of prestress wires was present, as well as significant quantities of brittle wire failure,” the report read.

The result of a metallurgical analysis showed that the steel cylinder wires met the standards at the time, but the prestress wires had poor torsional ductility (the ability to deform under torsion or twisting), which wasn’t a requirement at the time.

The report also confirmed that the pipes met manufacturing standards at the time and were operated well within their parameters.

Much of the information is similar to the recent updates, according to Ward 1 Coun. Sonya Sharp, who represents the Bowness area.

“It’s underwhelming,” Sharp said.  

“That’s how I look at this, and it’s everything they’ve been saying since the investigation, or since the rupture happened in June. It just seems to me as a synopsis of everything we’ve heard and all those daily updates.”

Sharp said she still feels like there’s no hard evidence on what caused the pipe burst, including the city’s handling of the older pipe structure.

Ongoing monitoring is necessary: Mayor Gondek

Calgary Mayor Jyoti Gondek said that when the preliminary report was delivered three weeks ago, it raised soil conditions and corrosion as potential contributing factors.

“What we were told at that time is, there’s not necessarily a direct correlation, because there are some areas where the soil conditions were different, but there was still breakage and wire snap, so it’s hard to tell what the causality was,” she told LWC.

The report does state that there is no clear evidence as to how the chlorides or moisture could have reached the prestress wires.

Sharp said the report still leaves a lot of questions unanswered, particularly around why the City of Calgary hadn’t inspected the pipe since the 2013 flood.

“I would like to know how we mitigate this from this happening in the future, and you’re telling me, we’ve never gone in underground in the last 10 years, especially after the flood, to see if our like underground system is working,” Sharp said.

Mayor Gondek said it possible that monitoring technology available today wasn’t available a decade or more ago, so they could have kept tabs on the line.  Regular exterior inspection then would have required digging up sections of the pipe area to test it or shut the pipe down to have an interior inspection.

“I don’t know that we had the monitoring systems in place before anywhere, frankly, in North America, that would have allowed us to see the condition the pipe was in,” Mayor Gondek said.

Monitoring of the pipe in this area moving forward is a priority, the mayor said. Fibre optic monitoring, along with acoustic monitoring will be done along the stretch of the Bearspaw main.

The City admin presentation indicates they will also increase soil sampling along critical feeder mains, with a focus on chlorides. They’ll focus on ongoing feeder main risk and redundancy, continue to investigate how the chlorides got into the soil and review the design guidelines of future feeder mains.

“I think this was definitely a wake-up call for us,” Mayor Gondek said.