An investigation into the cause of a tank leak that led to the earlier-than-anticipated closure of Canada Games Pool has determined that “settlement of the sediments” under the pool caused the tank leak, according to a report to council.
At a workshop on Oct. 30, city council will receive a presentation about the findings of an investigation into the tank leak of Canada Games Pool – two years after the facility unexpectedly closed for good.
“The outcome of the investigation into the tank leak causation, as provided by the retained experts who oversaw the investigation, was that the CGP tank failure was caused by stress differential resulting from settlement of sediments under the pool,” said a report to council. “Multiple factors may have contributed to his results, including exacerbation of pre-existing soil conditions.”
According to the report, fulsome analysis concluded it’s not possible to accurately identify a single cause or a specific set of causes.
“As such, it has not been possible to attribute responsibility for the cause of the tank failure,” said the report.
Canada Games Pool had been scheduled to close and be decommissioned in August 2023, as part of the təməsew̓txʷ Aquatic and Community Centre project, which is being built next to the old Canada Games Pool facility. The facility, however, closed in November 2021
Here’s a timeline, as per the staff report to city council:
- April 2021: Construction begins on the təməsew̓txʷ Aquatic and Community Centre (TACC) project.
- September 2021: Canada Games Pool is closed for its annual scheduled maintenance shutdown
- Sept. 19, 2021: Following three days of heavy rains, pool staff observed a high water level in the mechanical put of the pool pump room, submerging the main pool circulation pump.
“A temporary sump and pump installed as part of the construction of TACC was noted to have stopped functioning or did not automatically engage as it was designed to do,” said the report. “When the sump pump was manually turned on, the pool pump room pit drained within a matter of minutes.”
- Sept. 27, 2021: The pool’s pump room flooded again when the temporary sump pump stopped working.
- Oct. 7, 2021: Pool staff noticed a drop in the water level in the pool tank – even though the pool was still closed to the public.
- Oct. 9, 2021: A sump alarm activated, indicating a high water level had been reached within that sump, trigger the pump
“Chemical testing of the water indicated that the sump was full of pool water. This coincided with another heavy rain event, and the site became saturated,” said the report.
According to the report, some temporary mitigation actions were taken, which reduced leakage from the pool tank to “minimal” levels, but it was suspected that some of the piping below the pool tank was damaged.
“Comprehensive analysis determined that repairing the pool was uneconomical, given the high cost of repair work, the length of time it would take to complete the repairs, and the remaining time available before CGP was scheduled to be decommissioned,” said the report. “Council made the difficult decision to permanent decommission CGP in November 2021.”
The city hired Stantec Consulting Engineers, a geotechnical engineering firm, to review the data to provide a professional opinion on probable cause of the tank failure. Its assessment included reviewing previously commissioned geotechnical reports and assessments of the development of the site, materials related to the existing Canada Games Pool building and the new TACC construction project, as well as weather and activity logs before and after the tank failure.
“Combining information from past analysis with new additional 3D modelling, Stantec concluded that the variability in depths of fill and silt layers throughout the site was considerable,” stated the report.
Stantec also considered whether construction activities at the təməsew̓txʷ Aquatic and Community Centre site, located right next to Canada Games Pool, had contributed to settlement of the soil under CGP.
“The geotechnical engineer noted that while these activities could have caused sufficient disturbance to exacerbate pre-existing conditions, the MV (Metro Vancouver) sewer line experienced vibrations within acceptable levels, and as the MV sewer line was closer to the construction that the CGP building, they expected that the same levels of vibration, if not less, was experienced at the CGP building,” said the report.
The staff report states that Stantec’s conclusion was that the tank failure at Canada Games Pool was caused by settlement of the foundational soils under the pool.
“Due to a complex site history and the potential for multiple causes, expert analysis was unable to identify a clear cause or causes of the soil settlement and subsequent tank failure,” said the report. “Possible causes and contributing factors include the age of the facility and its foundation, construction vibrations from the adjacent TACC building, the earlier standard to which CGP was built, prior damage caused to the pool tank, and the weakening and consolidation of the foundational soils from seasonal changes in the groundwater. These seasonal changes include the extreme wet and dry weather encountered immediately priority to the failure.”
