South-side sinkhole repairs extended into late July

Work to fix a sinkhole discovered last October deep underneath 61st Avenue at 109th Street will continue into late July, Epcor says.

"Public safety is our No. 1 priority, and unfortunately that's why the extension of time to July," Richard Brown, Epcor's director of construction services, said Wednesday.

"We've done a geotechnical survey in that area to make sure that before we open the road the ground conditions are completely stable."

The sinkhole was discovered Oct. 8 during an inspection of a sewer trunk line 23 metres below 61st Avenue, part of a major crosstown traffic route on the city's south side.

The intersection was shut down. Detours were put in place, causing drivers ongoing headaches.

To permanently repair the deteriorating sewage trunk line responsible for the sinkhole, Epcor had to order a 50-metre stretch of fibreglass pipe from Dubai.

The new pipe, which arrived in Edmonton late this month, had to match the dimensions and shape of the sewage pipe, which is roughly 1.6 metres in diameter.

Brown said the original pipe is between 50 and 60 years old and had been eroded by sewer gases.

Epcor had expected to finish fixing the trunk line earlier this year, but cold February weather made filling below-ground air pockets unworkable, Brown said.

"Because of its age it's unique," Brown told CBC's Edmonton AM.

"It's oval in shape, but also we needed the pipe to be manufactured quickly and that company [in Dubai] was the one that was able to meet all the requirements."

Brown said he suspects the damage that resulted in the sinkhole was most likely caused by hydrogen sulfide, a corrosive and toxic byproduct of wastewater.

The new pipe is corrosion resistant.

"Once it's in place there shouldn't be an issue again," Brown said.

In 2018, a sinkhole appeared on Allendale Road, a few blocks east of the sinkhole on 61st Avenue and 109th Street.

Epcor also found hydrogen sulfide gas at the Allendale Road sinkhole, but the exact cause of that problem is still unknown.  

The discovery of hydrogen sulfide at the Allendale Road sinkhole was part of the reason that Epcor started its corrosion and odour reduction strategy.

The strategy aims to prevent the toxic gas from forming in Edmonton sewer systems.