It’s not a sexy project but it is certainly a necessary one, said Dave Dyer, general manager of engineering and public works for the City of Prince George Friday morning.
The excavation of the sinkhole at the Winnipeg and Carney intersection will most likely end up going further into the road, and worst-case scenario will see the entire intersection closed in all directions in the coming weeks.
The delay in repair is because city staff have yet to determine the cause of the sinkhole.
The trouble seems to be the backwash working its way along the metal stormwater pipe that has no downward slope away from the intersection as it travels underground into Carrie Jane Gray Park’s water channel. From there the water continues to flow through to the Hudson’s Bay wetland, underneath Queensway and ultimately into the Fraser River.
Another variable is road debris, including gravel and salt used on the road to combat icy winter conditions. Debris has resulted in large amounts of sediment, which is sitting in the pipe. Dyer suspects there’s a hole in the pipe caused by corrosion from all the debris from the road.
Another best-guest is the pipe might have separated from where there’s a transition from concrete to metal.
To explore the entire pipe to see what’s causing the trouble crews will soon create a temporary dam in Carrie Jane Gray Park to stop the water from flowing back into the sinkhole.
That means the pathways through the park will be closed to pedestrians.
Crews will then pump the water out of the pipe, Dyer explained.
Once the water is out crews can then remove the sediment using a vactor truck so they can send a camera along the pipe to hopefully discover the issue, he added.
“Once the problem is determined, a repair plan will be confirmed and we will be able to determine how much more we need to excavate the area to fix the (problem),” Dyer said.
If the repair needs to be made at the sinkhole site, which is the most likely scenario, further excavation down two to three metres more will be necessary and that’s when the hole will most likely go further into the roadway spurring a detour.
Estimated time for exploration, excavation and repair is six to eight weeks.
The cost of the project is estimated into the hundreds of thousands of dollars.
