Muncher Chlorides are highly soluble, Calgary has a river flowing through it so it’s possible the current levels are the result of natural process as well as run off from human activities. That is an interesting idea, but if the lot is paved the water is going to flow into some sort of a drain, they might just use dry wells which ends up sending the water directly into the grown in that local area. Edges near the end of the paving could also see higher amounts of the stuff if the water collects on the pavement but runs off to one side onto the land besides it. It also can be found naturally in groundwater so if that is used to water crops the levels build up over time, if the area is dry such as areas in the SW the water evaporates before it ever gets to a stream or creek leaving the material behind eventually making the soil useless to grow anything in. The map of the pipeline shows a couple of places with high amounts of chlorides, perhaps they fit with local land usage in the same way too.
Testing the soil around areas in which this infrastructure is or will be placed certainly provides insight as to how bad or good the site is, I am not into construction so I have no idea if that is one of the standard tests civil engineers do to assess an area for a project but it might be added on out there given the cost of the repairs and economic damage from the outage.