Update July 12: Critical water main break affecting city-wide water usage

Status of the feeder main

Our monitors detected one additional wire snap in the feeder main on Wednesday, bringing the total to three since Sunday. As of this afternoon, no further snaps have been detected, but we continue to monitor things closely.

Water use

On Thursday, our water demand was 565 million litres, down from the peak of 567 million litres on Wednesday. Having our water use increase during periods of extreme heat is a normal pattern and is expected.

With Stage 3 Outdoor Water Restrictions in place, we have been able to meet the current demand. Our Stage 3 restrictions remain very important right now, because with our current water flow, it would be harder to provide enough water for the increased demand of things like sprinklers.

To increase our water supply, we need to increase the flow of water through the feeder main, which also increases pressure and can cause stress on the pipe. Currently, our water flow through the pipe remains at approximately 55% capacity. This means that although the pipe is full, the water is moving through it more slowly.

We are being very careful about adding additional pressure and stress to the pipe walls given that there are some spots of structural weakness within the pipe. We need to make sure that when we turn on the additional pumps at Bearspaw Water Treatment Plant to add more flow through the pipe, we are doing it in a way that does not risk another break and set back our progress.

Next steps

Over the weekend, we will be working to assess whether to increase flow through the pipe or to stay in Stage 3 Water Restrictions for a longer period. By Monday we will be making a decision and will share more information about what that means for water restrictions.

Some of the things we will be looking at as we make this decision are:

• Continued monitoring and analysis on the condition of the pipe, taking into consideration the recent wire snaps that we have heard.
• Options for turning on more pumps at the Bearspaw Water Treatment Plant.
• The impact of the additional pressure in the pipe that would be caused by turning on more pumps.

We are currently designing the fibre optic system that will be added to the feeder main to improve our monitoring of the pipe. More information will be available on the status and design of the installation as this progresses.

We are also awaiting results from the pipe diver device that we deployed to collect additional information and will provide more information as it becomes available.

Concerns from the Irrigation Association

This week we have met with the Irrigation Association to hear concerns and to clarify what activities they can continue while current restrictions are in effect.

This information has been shared with the Association’s members and is now also available online as part of our FAQ page on calgary.ca/restrictions, so that businesses can access it directly.

We are committed to continuing to work together to address their concerns and provide what help we can.