Rapid response and coordinated emergency assistance helped to repair and restore service on Calgary’s crucial Bearspaw South Feedermain

On June 5, 2024, the City of Calgary experienced a catastrophic break in the Bearspaw South Feedermain, the largest pipe in Calgary’s drinking water conveyance system with the capacity to convey over 450 million litres per day. The loss of the feedermain led The City to declare a State of Local Emergency and retain Associated Engineering for emergency response services to repair and reinstate service.

The 1,950 millimetre diameter prestressed concrete cylinder-type pipe conveys water from The City's Bearspaw Water Treatment Plant to the largest of Calgary’s 35 pressure zones. The Bearspaw South Feedermain also supplies the 33 Avenue NW, Shaganappi, Memorial Drive, Hillhurst, and Nose Creek Pump Stations.

As an immediate response, The City of Calgary initiated their emergency management system to coordinate a response to the Bearspaw South Feedermain break, with the single purpose of maintaining critical water service. Two key requirements to maintain water services were modifications made to pump station operations and restoring critical water services back to normal as quickly as possible by expediting the design and construction of the feedermain repairs. With the Bearspaw South Feedermain out of commission, pump station modifications were needed to move water from the south to the north to service the city; this required analysis of system risks and quick decision-making.

Within hours of the feedermain break, Associated Engineering began providing operational and infrastructure analysis, and corresponding solutions to maintain critical water service. Project Manager and Vice President, Urban Infrastructure, Duane Strayer, explains, "We completed an operational review and provided recommendations, undertook hydraulic transient analyses and site reviews, and produced recommended repair designs, surveys, in-situ forensics investigations (including stray current and soil testing), and construction inspection."

Parallel to redirecting water, Associated's team reviewed operational data from the Bearspaw Water Treatment Plant and Shaganappi Pump Station SCADA systems. Within one day, we received and analyzed thousands of information points from The City, and presented initial findings that indicated pump operations were not a contributing factor to the feedermain break.

Associated applied first-hand knowledge of the pump station’s operating pressures and design setpoints for the pressure-reducing valves to bypass flow. The project team developed a plan to reverse flow from the Glendale zone through the Shaganappi Pump Station (designed by Associated), allowing for the return of water to be pumped into the North Hill zone.

Following the resolution of the immediate emergency, The City needed to understand the condition of the rest of the feedermain, to confirm if there were any other vulnerabilities that required immediate attention and provide assurance that the feedermain would continue to provide essential service.

Duane says, "As the ruptured pipe was being repaired, electromagnetic inspections were performed upstream and downstream of the rupture. These inspections detected additional distressed pipe sections downstream of the rupture." Based on the data collected and subsequent inspections, The City decided to complete additional repairs in three phases.

Associated was also responsible for identifying field coordinates for each repair location in all three repair phases. This was a vital first step as accuracy was paramount, because the contractors were already mobilized on-site and ready to excavate.

Associated's team provided continuous surveillance of the pipe exposure process. This included verifying the distress noted by the electromagnetic inspection. Data collection followed and included observations and measurements of the in-situ pipe and soil conditions.

Strong collaboration between Associated, City of Calgary, subconsultants, and contractors were key to success

Duane explains, "This information guided the forensic analyses The City tasked Associated Engineering to carry out and was also used to validate the corresponding results from the electromagnetic inspections." As a result of our on-site attention, coordination, and responsiveness, the contractors sustained their productivity, while valuable forensic data was collected.

In addition to the original rupture, the electromagnetic inspection identified five distressed pipe segments that needed immediate attention. To expedite the repairs, The City retained three contractors to undertake the work on a 24 hours per day, 7 days a week basis. Associated provided construction engineering support for all five segments. In addition, urgent repairs by concrete encasement were needed in 21 locations along the 1,950 millimetre pipe, and planning and design work was expedited in the summer.

Associated was supported by subconsultants, Tronnes Geomatics, Thurber Engineering, and Corrpro Canada, and supported the work of Whissell Contracting, Volker Stevin, LBCO Contracting, and Graham Construction & Engineering, and Xylem (Pure Technologies).

Associated's key personnel included Duane Strayer, Craig Pass, Jacqueline Le, Lee Hang-Liu, Joe Lisella, Joe White, Timothy Nesher, Nony Cuppen, Chris Hiscott, Eliman Camara, and Jiayu Li.