EDMONTON -- EPCOR is currently working on a plan to fix a large sinkhole in the area of 61 Avenue and 109 Street.

According to an EPCOR spokesperson, workers were inspecting the sewer trunk line on Oct. 8 when they discovered an underground void. The ground opened up on Oct. 12.

It measures three metres long and one metre wide. It’s 23 metres deep, about the height of a six storey building.

“The apartment building I live in is not six storeys high, so it’s kind of scary to think about for sure,” said Edmonton resident Grant Longaphie. “It’s hard to even fathom, it’s hard to comprehend how deep it actually is.”

EPCOR says there is no risk to homes or businesses in the area. The void is entirely under the roadway.

CTV News Edmonton spoke with a geotechnical engineer who said he was surprised a sinkhole of any type within the city would be this deep.

“The hole formed as a result of a failure in a sewer trunk line that runs under and along 61 Avenue,” said Keltie Denton, with EPCOR. “The sinkhole is not as a result of any ground conditions in the area such as a coal mine.”

Denton went on to say that the exact cause of the failure is unknown, but it is speculated that “that H2S gas present in the sanitary system caused corrosion of the sewer line.”

“Wastewater was then allowed to enter the ground around the pipe and allowing materials to fall into the pipe creating the void,” Denton added.

In 2019 EPCOR began working on a project to address corrosion of drainage infrastructure. Denton said this project will allow the company to identify issues like this before they become emergencies.

Crews are working to install a bypass system to take the flow from the sewer line away from the work area.

There is no timeline or cost estimate currently for a permanent solution, and officials say it will take several months to complete the repairs.

EPCOR was unable to say how long the void had been in place or how long it might have been growing to its current size.

With files from CTV News Edmonton’s David Ewasuk