2024 June 6: Where the Giant Water Main Break Is

Below, the GIS map near where there is a small lake in Calgary this morning. The red arrow indicates where the water showed up, at the intersection of Home Road and the Trans-Canada Highway. The black lines are 1m contours, so you can look uphill from that spot for large watermains that might have leaked it.

The light-blue and green lines on the city blocks above it are "distribution mains", just 150mm and 200mm in diameter, and couldn't possibly cause this much water.

Oddly enough, directly uphill is our old house on Montalban Dr. But I'm pretty sure it didn't leak from our house. I'm prone to suspecting the GARGANTUAN water main right underneath the intersection. 1950mm = 78", the largest main in Calgary, carrying much of the Bearspaw Plant output. That's as bad a loss as the system can suffer.

Fortunately, a big break 20 years ago made us prepare for this, and repairs should be days, rather than weeks, as it was in 2004.

The second image shows all the "feedermains" (over 400mm) that push water across Calgary between pressure zones. At the upper left, three red arrows show the Bearspaw plant pushing water out in every direction. The red X shows the break, where the one largest main is blocked right at the river crossing. Arrows to the south show where water is also pushed north up from Glenmore, which will have to do a lot of extra duty for a few days.