Road crews may need six weeks of round the clock work to fill a sinkhole that opened up two weeks ago under Highway 16 close to Topley.
On Thursday, a traffic control person was busy waving dump trucks filled with packing soil to the sinkhole site, while keeping her eye on the growing line of delayed cars and trucks headed towards Burns Lake.
“It’s been crazy the last two days,” she said, pointing to a bend in the road 100 metres away.
“I’ve got line-ups that go right around the corner.”
Drivers currently face up to a half-hour delay as they wait to cross over single lane that crosses over the sinkhole area, about two kilometres east of Topley.
Cam Schley, operations manager with the Ministry of Transportation, says sinkholes of this size are rare, and it will take a lot more digging to find out exactly how it formed.
“What we do know is that it doesn’t extend into the westbound lane,” he said.
Traffic had been avoiding the sinkhole area entirely via a long detour until engineers drilled under the highway to make sure the westbound lane could safely support cars and trucks.
No geotechnical work has been done in that area before, Schley said, although long-time residents say they remember workers laying extra rock to shore up the steep embankment in that area.
“We didn’t know what to expect. When we pulled the road base back and exposed the initial sinkhole, we couldn’t see the bottom of it,” he said, noting that the cavern was at least 11 feet across.
So far, engineers say the sinkhole likely formed around an old culvert that either split at the joints or rusted out.
That let water escape, eroding the silt that makes up the embankment on either side of the highway.
“Once they excavate all the way down to the culvert, they’ll be able to tell how deep that sinkhole actually is,” Schley said.
Until then, Schley said it’s impossible to know exactly how long the highway will be single-lane only, or how much the operation will cost. Once the main excavation work is done, workers will install a temporary, single-lane bridge over the site to make traffic management easier.
For updates on expected delays, check www.drivebc.ca.