CANMORE – A small area of ground collapsed on the disc golf course in the Three Sisters neighbourhood, but an investigation by the Town of Canmore reveals the sinkhole is unlikely due to undermining.
Municipal officials say a review of undermining reports for the area suggests this isn’t related to undermining from old coal mines, noting there is evidence a storm pipe is damaged and likely contributing to settlement of the surrounding soils near the ninth hole.
“In this case, it’s very unlikely it’s related to undermining … and there is no risk to the public,” said Andy Esarte, the Town of Canmore’s manager of engineering, adding that the area has been fenced off as a precaution so people don’t trip and fall.
“The disc golf course does have mine workings below it, but they’re quite deep, and so deep workings generally don’t cause subsidence at the surface.”
The ninth hole of the disc golf course is in an area with storm pipes coverage as part of the area’s stormwater management system.
“There’s evidence, with quite a lot of organic material in the pipe, that likely there’s been some damage to the pipe somewhere, and that’s allowing for water to get out of the pipe into the ground, carry some material away and cause subsidence,” said Esarte.
“That’s the more probable cause, something along those lines. The undermining that’s happened at the disc golf course poses no risk. There’s been a study, it’s been mitigated and there’s no expected significant subsidence and so no risk to the public whatsoever.”
The next step is for the Town of Canmore to dig up and repair the pipes.
“We’ll have a look to see exactly what’s going on and switch the pipes and remove the fencing,” said Esarte.
In 2010, an old mine shaft collapsed after a nearby water line ruptured, taking out a public trail on Dyrgas Gate at Three Sisters.
It was at the location of an airshaft known as B14 that was dug to access the No. 4 coal seam of the No. 4 mine in 1938. After several years, it was fixed in 2017.