Historic coal mine under Nanaimo street causing headaches for city crews

Work to modernize part of Downtown Nanaimo has run into a snag more than a century in the making.

The city has suspended construction on new water main infrastructure along Commercial Street, after drilling confirmed loose rock and voids several metres below the surface.

The voids are part of Nanaimo’s legacy of coal mining. Nanaimo general manager of engineering and public works Bill Sims explained that miners were at work under Commercial Street between 1854 and 1938.

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“It has been laying quiet ever since,” he said.

The city was aware of the old mines in the area, and did some preliminary drilling at the site in 2023 to confirm their presence.

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When crews set up to begin the water main work this year, they did further exploratory drilling which confirmed a potential risk under Commercial Street.

“We made an allowance for when we were back here for construction to do some further drilling, and that further drilling actually revealed the presence of a larger void in the intersection of Bastion and Commercial,” he explained.

Sims said the void is about three metres below the surface, which would put it about a metre below the water main trench.

“We just had this potential risk for worker safety, if they are down in the trench, down close to that void, we wouldn’t want the trench bottom to go out. We put construction on pause,” he said.

“We will map out a series of drill holes, and then we will just simply pump grout, a loose, sloppy grout, into the void, and that will just seep into the air pockets underneath the ground and stabilize it.”

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While Sims said there is no risk to the general public, businesses in the area say they’re worried that the issue will prolong major construction work on Commercial Street.

“Obviously we are extremely concerned because this is going to affect our business, it’s going to affect our community, we’ve got staff to take care of, sales are dropping every second of the day. It’s tough,” said Connor Welsh, general manager of Modern Cafe.

“We are hopefully going to have this fixed by the summer, but if it’s not fixed by the summer it’s very likely you will start to see a lot of businesses around here decline, and potentially even close down.”

While contractors address the void problem, they’ve shifted infrastructure work to other locations.

The city said it’s not yet clear how the underground surprise will affect the project’s budget or timeline.