Calgary considering micro-tunnelling option to make water feeder main more reliable

The city is exploring a preferred option to make repairs to the Bearspaw south feeder main that would involve micro-tunnelling to build a parallel pipe, after last summer's emergency water restrictions.

Councillors on the city's infrastructure and planning committee heard Tuesday about the plan as a way to make the Bearspaw south feeder main more reliable.

Administration expects the micro-tunnelling plan would minimize the disruption to Calgary's water use, and minimize service outages. The construction would be on a maximum length of five kilometres, for a section of the pipe built using prestressed concrete.

The plan would involve building a parallel pipe to create redundancy, allowing needed repairs to be done on the current feeder main. It would also ensure that if future service is needed on that section of pipe, the city's water service won't be as severely disrupted.

The plan fits the the city's criteria to minimize impact and service disruption on Calgarians, said Steve Wyton, the city's manager for asset management and planning. But he added the plan will still require some surface work, leading to disruption.

"Micro-tunnelling is an option that really does fit that bill. It will still require some sort of surface work where we will have to dig down to allow the micro-tunnelling work to occur, so there will be some service disruption to the travelling public that we would anticipate," Wyton said.

The exact cost and duration of the project is still being finalized, but city administration told councillors that construction could begin by the end of this year.

City administration's report adds that challenges like population growth that's increasing demand leads to a greater need for system redundancy to make it more reliable. Other infrastructure projects are underway, such as planning a new water treatment plant, expanding the Glenmore Water Treatment Plant, as well as three major feeder main projects.

Wyton added an alternative plan to install a liner inside the feeder main, rather than the micro-tunnelling option, was considered. But it would need larger holes to be dug, leading to more significant disruption and multiple service outages over a longer period of time.

The preferred plan follows a report in December that found several failure mechanisms, including microcracks along the pipe and surrounding soil conditions, that led to the Bearspaw south feeder main's deterioration and eventual rupture.

The 11-kilometre pipe, which was built in 1975, distributes the majority of Calgary's treated water. Its catastrophic break in June led to a local state of emergency and various levels of water restrictions for Calgary and surrounding communities throughout the summer.

Coun. Sonya Sharp said she's concerned that when council tells Calgarians there's going to be disruptions that affect water, it will create stress after last summer's emergency — especially in Bowness and Montgomery, areas she represents that were hit especially hard by water restrictions.

Sharp noted a more proactive communication strategy with the city's businesses and residents should help alleviate some of that stress.

The preferred micro-tunnelling option is the least disruptive option for the city that's on the table, the Ward 1 councillor noted. While it will be a pricey strategy, it would cost more the longer it's put off, and large expenses such as this project have been repeatedly deferred in the past, which can lead to emergencies like last year's water main failure.

"When I see the prices and when I look at everything that's happening, everything is catching up to us. For the last decade, it's been deferred, deferred, deferred, and not been probably a top priority," Sharp said.

Ward 7 Coun. Terry Wong noted the option administration presented is the least disruptive approach. But he added the presented timeline to begin work by the end of this year presents a significant test given the amount of work the city faces.

"Considering they want to have plans for design by summertime, and into the ground by the fourth quarter of 2025, there's going to be a lot of pressure in 2026 to get it all completed," Wong said.

"If they can get it done? Great. Does it push into 2027? Possible."

Wong and Wyton added it's unclear what effect a potential trade war between the U.S. and Canada would have on increasing the cost of construction materials.

Wong said the city would hope to source all the steel it needs from within Canada, but the potential need for steel from other countries, and the associated cost in an uncertain global market, is a concern.