Update July 13: Critical water main break affecting city-wide water usage

Water use

Yesterday, our water demand was 554 million litres, down from 565 million litres on Thursday. The use has dropped as the weather cools, which was expected. With Stage 3 Outdoor Water Restrictions in place, we are able to meet the current demand.

We remain in Stage 3 Outdoor Water Restrictions, which allows for some outdoor water use.

Status of the water feeder main

As of this afternoon, our monitors have not detected any further wire snaps along the water feeder main. Our total remains at three new snaps since last Sunday. We are constantly monitoring this.

As a reminder, the feeder main is made up of 16-foot segments of pipe, each one with a steel wire that coils around it approximately 350 times. A single snap is not a sign that a new break in the pipe is imminent but provides clues about how the pipe is responding to pressure.

The flow through the feeder main remains at 55 per cent of its capacity. What this means is that although the pipe is full of water, that water is moving at a little more than half of its normal speed. This is to keep pressure in the pipe low and reduce stress on the pipe.

Next steps and timing

To lower our Outdoor Water Restrictions and allow more outdoor water use, we need to increase the flow of water through the feeder main by turning on additional pumps at the Bearspaw Water Treatment Plant.

Increasing the flow in the pipe will increase pressure and stress on the pipe walls. Moving cautiously before increasing the flow helps safeguard against another major break.

This weekend we are working to analyze our information to decide whether increasing the flow is possible right now, or if we need to stay in Stage 3 Water Restrictions for a longer period of time. We need to approach this decision cautiously to minimize the risk of another break, so we don’t set back our progress.

We expect to have a decision and share more details on Monday.

More information, including details on what water use is allowed under Stage 3, can be found on calgary.ca/restrictions.