Dams in Nanaimo could kill hundreds if they fail says expert

The Middle Colliery Dam is identified as being vulnerable if an earthquake hit, which could result in the deaths up to 100 people and destroy residential buildings below it. A dam safety engineer told Nanaimo city council it is in need of repairs to fix cracked concrete and upgrade an under-sized spillway. Photo: Lauryn Mackenzie / CHLY 101.7FM

A dam safety engineer told Nanaimo city council that there would be serious consequences if dams the city owns and maintains were to fail.

Dave Bonin, a senior hydrotechnical engineer with Hatch Ltd. presented at Monday’s governance and priorities committee meeting that he is concerned that at least two of the city’s dams could fail if an earthquake hit.

“We are majorly concerned about Middle Colliery Dam, because it has been found to be susceptible to seismic and has been out of compliance with the regulation for a while.” he said. “South Fork is actually also one that we know is extremely vulnerable.”

There are 10 dams in Nanaimo. The level of consequence should one of them fail ranges from low to very high. The Old Reservoir Number One dam, which was emptied nine years ago, sits at low, but the Jump Creek, South Fork and Lower Colliery dams are categorized as having very high levels of consequences in the event of a failure.

That means if the dam fails, up to 100 people may die from flooding, damage to infrastructure and the city’s economy would be very high with severe damage to residential areas and significant loss of environmental or cultural values that would be impractical to restore.

As the owner of the dams, the city would be liable for any damage or loss caused by the failure of a dam, if one fails in a way that could have been detected and prevented.

The Middle Colliery Dam is the first dam that is up for its 10-year review and is categorized as a high-consequence dam, meaning that up to 10 people could die if it failed and it would cause high economic damage including destruction of residential buildings.

That dam has been under an order to bring it up to provincial standards. A full dam safety report for the Middle Colliery Dam is expected to be presented to council in the fall. Bonin says that a cost estimate for the work will also be available at that time.

“We need to perform some maintenance to preserve the dam,” he said. “The concrete is in really bad shape, being underneath that bridge there, I've done the inspection and there's concrete falling on you, exposed rebar, all those great things. We need to do some of this recent restoration/maintenance work while also respecting the public’s wants and needs. Because we do understand that this is an important space. And frankly, I do want to preserve it for future generations because it is a big part of your history.”

Bonin says that while the consequences of a dam failure would be very serious, the city also needs to ensure that people who use the dams as swimming and fishing spots are safe too. He says there have been over 300 documented deaths at dams in Canada compared to 11 deaths from dams failing in the past 100 years.

“We know that people use our dams, people recreate near them,” he said. “But they are also not really aware of a lot of the hazards that they may be facing and that's a big problem.”

Mike Squire, the city’s manager of water resources, says the city has taken steps to ensure the safety of people who use the lakes and reservoirs for recreation.

“We've had many deficiencies that we've been trying to address over the last several years that need to get done to satisfy not only dam safety requirements, but ensure that we're protecting the public,” he said. “A lot of fencing and signing has been put up over the last couple of years and then the spillway boom was extended on the Lower Colliery Dam.”

Bill Sims, the city’s general manager of engineering and public works, said Monday’s presentation was to remind council, and the public, of the ongoing risks with dams in the city.

“Part of the rationale today is to introduce the whole topic, not only to council but also the public,” he said. “This is a refresher, we're back again and certainly, previous efforts were concerning for the public and we acknowledge that.”

Funding Note: This story was produced with funding support from the Local Journalism Initiative, administered by the Community Radio Fund of Canada.