Committee divided over Colliery dam options
City staff members are recommending an $8.1-million fix for the Colliery dams, despite concerns the measure is too intrusive.
Last week, the City of Nanaimo released options and cost estimates for the Colliery dams, as well as information on the decision-making process and next steps.
The information comes after an eight-month and estimated $1.35-million process by the city’s technical committee to find solutions for the century-old dams and days after the Colliery Dam Park Preservation Society announced its withdrawal from the group over disagreements on mitigation options.
According to the report, two measures are recommended by an engineer to address flood risk at the lower dam: ‘overtopping’ for $7.2 million or increasing the size of the spillway for $8.1 million.
Engineers advise that doing nothing to the structures isn’t an option and a third solution – an alternative overtopping proposed by the preservation society’s own engineer – has not been considered because it lacks designs and costs, according to Toby Seward, the city’s director of social and protective services.
While the preservation society isn’t keen on the cost of the city’s overtopping solution, it also says it’s the most suitable for the park. It would involve cutting out several meters of soil on the embankment of the lower dam and mixing it with concrete to create a surface that would prevent erosion should water flow over the top.
Deepening and widening the spillway is a “monstrous intrusion” and destructive, says society spokesman Jeff Solomon, who explains it would reduce water levels to “two small little puddles,” hurt living organisms and see the temporary closure of the park.
However, the city’s recent report shows an executive committee of Snuneymuxw and senior city staff – a step above the technical committee in the decision-making chain – plans to recommend Nanaimo move ahead with spillway work.
Seward said the option is straight-forward and provides a long-term, relatively maintenance-free solution whereas overtopping involves uncertainties around soil conditions and process.
“Yes, there will be disruption and the lower lake will be drawn down by approximately three meters, but it will in no means be a puddle,” he said, adding both options would be intrusive and involve temporary park closures. “In both cases the hope is, or the plan is, to keep the middle dam and the reservoir there in use during this period.”
Work and research to address the Colliery dams has been ongoing since 2012 and has cost taxpayers an estimated $2.35 million.
Last year Nanaimo city council struck a technical committee as part of a two-year mitigation process to look at remediation of the middle and lower Colliery dams and re-examine the structures’ hazard rating. The committee has commissioned work that’s led the B.C. Dam Safety Branch to scale back its hazard ratings for the dams and has reduced remediation estimates from original costs of $17 million and $30.7 million.
However, the committee has acknowledged it has not been able to reach consensus on what options to pursue on the dams and parties don’t agree on how soon they need to fix the dams. While Seward believes there is a need to take action as soon as possible over heavy rainfall concerns, Solomon says there’s no urgency at all. The preservation society spokesman also believes the option to expand the spillway is extremely excessive and inappropriate.
“It’s incredible that they would even consider doing this at this stage,” Solomon said. “Literally for most of the year we have a couple of inches of water in the spillway. That’s it. They want to make it 10 or 11 feet deeper than it is now and much, much wider.”
Solomon wants to see accurate information given to the public and politicians and see the public given time to weigh options.
“There is no urgency, nothing should happen right now,” he said.
Nanaimo city council received a report recommending they ask staff to release minutes from the technical committee, schedule a public information session and report on next steps and options for funding at a future meeting. A decision was made after press time Monday.