South Edmonton intersection could be closed for months after 23-metre-deep hole discovered

Epcor has shut down the intersection of 61stAvenue and 109th Street after a deep hole was discovered thatcould take months to repair.

On Oct. 8,Epcor crews discovered a void under the intersection while inspecting a sewer trunk line. A few days later on Oct. 12, a hole formed in the roadway of the intersection.

The hole is close to three metres long, one metre wide, and 23 metres deep.

The full extent of the underground void is unknown and being investigated, Epcor communications manager Keltie Denton saidon Monday.

There is no structural risk to homes and business in the area, Epcor's website states.

The sewer trunk line, which is 1,650 millimetres in diameter, carries storm and sanitary flows. To determine the extent of the damage of the hole,Epcor is installing a complexbypass system

The system takes flows from the below ground drainage system and carries it through an above ground pipe before discharging it into a manhole away from the site. Three shafts will be constructed on 61st Avenue to support installation of the bypass and allow safe access to the trunk line.

Traffic in the area will be affected as the intersection is expected to be shut down for several months.

Residents may experience sewer odours as a result of the bypass system, Epcor states on its website. Epcoralso mentions the bypass will generate "continual, low decibel noise." The work site will be lit at night for continual monitoring.

Information related to the hole and the ongoing repair was sent to residents on Thursday.

Irina Vassilieva lives across the street from the hole and the current construction site. She's not bothered by the inconvenience of the shutdown of the intersection, but is more so grateful that the underground void was discovered without any incident.

"It was a quick response, a lot of machinery was brought up here and I have to say I was really impressed," she said. "I really appreciate that somebody did detect this hole before a horrible accident could happen."

2018 hole on Allendale Road

In 2018, blocks away from the current hole, avoidwas discovered on Allendale Road near Calgary Trail. That void started 16 metres below the road, and reached all the way to the 23-metre mark.

• 'Completely closed off': Road detours hurting Allendale businesses

The exact cause of that void cannot be confirmed, Denton stated in an email to CBC News.

"Our best assessment is that H2S(hydrogen sulphide) gas present in the sanitary system caused corrosion of the sewer line," the email states. "Wastewater was then allowed to enter the ground around the pipe and erode the ground creating the void."

In 2019,Epcor received approval from city council to carry out a corrosion and odour reduction strategy to address issues around Edmonton related to corrosion of drainage infrastructure caused by gas and odours associated with H2S.

Epcor believes the situation at 61st Avenue and 109th Street is similar in nature, but the exact cause is still under investigation.