Two Crises, One Map

Calgary council is voting on whether to repeal blanket rezoning the same week the city lifted its third water restriction in 22 months. Both stories have been covered. They've been covered separately, like they have nothing to do with each other. They have everything to do with each other.

I pulled three of Calgary's open datasets from the data.calgary.ca portal: every public water main (60,740 segments, with install year and material), every documented water main break since 1956 (37,487 records), and every R-CG infill permit filed since blanket rezoning took effect in August 2024 (1,499 permits). I matched the breaks to the actual pipes they broke on using true point-to-line distance against the multilinestring geometry. The match rate was 100%.

Here's the part that genuinely surprised me.

Half of every Calgary water main break in the last four years happened on pipes installed between 1950 and 1969. That cohort is only 14 percent of the network.

The pipes that are failing in Calgary right now are not random. 95% of recent breaks are on pipes installed before 1990. Iron pipe is 56% of the breaks but only 15% of the network. Modern plastic is more than half the network and accounts for less than 6 percent of breaks. The median pipe that broke in the last four years is 62 years old. The average Calgary pipe is 34. Failure isn't spread out across the system. It's concentrated on a specific generation of pipe.

That's the first half. Here's the second.

The new R-CG permits aren't spread evenly across Calgary either. They cluster in ten neighborhoods. Seven of those ten neighborhoods are also on the top-25 list for recent water main breaks. Bowness alone has 120 new permits and more than 30 broken pipes since 2022. Top-25 break communities hold 39 percent of all R-CG permits, which is about 5 times what you'd expect if they were distributed randomly. Top-10 break communities hold 19 percent (6× chance rate). And the filings literally double every time council threatens to repeal the policy. Developers are racing the window before it closes.

The City's claim, tested

The City of Calgary's official position is that less than 1 percent of R-CG permits have required infrastructure upgrades. That figure comes from a December 2025 report by Maggie Choi, the city's manager of growth infrastructure planning, which examined roughly 1,949 homes approved since October 2024. Ward 10 Councillor Andre Chabot pushed back at the time, arguing that the concentration of new development "will trigger a need to improve or add capacity to some of that infrastructure at some point in the future." But neither the City's analysis nor Chabot's response actually tested the underlying main condition where the new permits are landing. So I did.

Two thirds of R-CG permits sit within 200m of at least one expected water main break in the next decade. Twenty-eight percent sit in zones with two or more expected breaks. The 50 most exposed permits cluster in Banff Trail, Bowness, Mount Pleasant, Highland Park, Elboya, and Montgomery — the same neighborhoods that already lead the recent break list.

This isn't a forecast

What I want to be clear about: I'm not predicting anything. The pipes I'm flagging are the pipes that are already failing. Half of every break in the last four years already happened on this cohort. The model is just describing what's currently happening and connecting it to where the new permits are landing.

And I'm not arguing against density. The Bearspaw South Feedermain Independent Review Panel, in its January 2026 final report, found that Calgary's low population density and rapid growth have left it with "more kilometres of pipe per resident than any other large Canadian peer city," and that those pressures "stretched capacity and added maintenance and asset integrity costs" for the water utility (Final Report, p. 19). Densifying already-built inner neighborhoods is structurally the right move. The problem isn't the density. It's where the density is being placed.

The question isn't whether Calgary can handle density. It's whether the new density is being placed on the right pipes.

Right now the answer is no. The new permits are landing on the most failure-prone cohort in the city, and there isn't a public plan to coordinate renewal of those pipes with the approval of the new units. Mayor Jeromy Farkas has called the Bearspaw South Feeder Main "terminally ill" and is rushing a $381 million emergency replacement, part of a $609 million water-system capital boost council approved in March 2026. The same diagnosis applies to most of the network the rezoning fight is about.

Methodology

All three datasets came from data.calgary.ca and are linked in the right rail of the map. The spatial join uses point-to-line distance against the multilinestring pipe geometry, matched within 30 meters (100% match rate). Cohort failure rates are computed over a 20-year window (2005–2024) where the dataset is most complete: rate = breaks ÷ km ÷ 20 years. The per-permit exposure metric is the sum of expected break events for every pipe segment whose midpoint is within 200m of the permit, computed as cohort_rate × pipe_length × 10 years. It's a pure expected-value calculation with no arbitrary weights, and the methodology block in the right rail of the map walks through every assumption explicitly. Anyone with the open data can reproduce it.

If you're a Calgary planner and you think I missed something, my email's in the Planada about page. I'd rather be corrected publicly than wrong publicly.