A storm that triggered “significant soil erosion” leading to a semi-blocked culvert is being blamed for disrupting the Alaska Highway near Muncho Lake, British Columbia, according to the federal government.
Most highways are provincial or territorial jurisdiction, with the exception of highways running through national parks and a portion of the Alaska Highway. The federal department of Public Services and Procurement Canada is responsible for this affected portion of the Alaska Highway, which serves as a key artery to the Yukon.
In a June 27 email, the department said it learned that heavy rainfall had occurred June 21 in the Muncho Lake area.
The storm resulted in a “large and rapid runoff event” that caused the soil to break down in the area upstream of the section of the highway between kilometres 710 and 711. The resulting run-off carried small stones and wood which led to partial plugging of a culvert under the highway, according to the department.
“With restricted culvert flow, the storm runoff then backed up, eventually to the point where it overflowed across the road surface,” the email said.
The runoff debris built up on a 35-metre stretch of the highway. The road shoulder of the northbound lane was “severely eroded” as a result of the overflow, which made passage “unsafe” for travellers on a 365-metre section of the highway.
Meanwhile, on June 21, Environment Canada had issued a weather statement in a tweet that was followed by a rainfall warning the next day.
In the public services department’s email, the highway maintenance contractor was notified and arrived on-site on June 22 to conduct traffic control, flagging and mobilizing equipment.
Once the culvert was unplugged and the highway surface was cleared, single-lane traffic assisted by a pilot vehicle was allowed through this section of the highway.
Engineered repairs to the eroded shoulder areas and surface inspections had been done by June 25.
The highway has been reopened to two-lane traffic.
As part of repairs, the paved road with bituminous surface treatment (BST) had to be removed from the 365-metre section. It is expected to be replaced within a month.
A temporary gravel surface will remain in place until the new BST can be installed. The speed limit in the area will go unchanged.
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As previously reported by the News, a video taken by David Dominic on June 11 and posted to Facebook the following day which shows the turquoise waters of Muncho Lake creeping up towards the height of the highway and the Northern Rockies Lodge.
In a June 20 email, Dominic said the road infrastructure had not been impacted by the high waters and the highway along the perimeter of the lake had not been closed or affected by washouts due to water levels at the time.
In Whitehorse, a section of Robert Service Way along the clay cliffs reopened June 16 after being shut down for almost seven weeks due to a large landslide on April 30. During that road closure, two more landslides on May 27 and 28 had prompted evacuation orders for three at-risk homes along the base of the escarpment in the city’s downtown.
Mayor Laura Cabott told reporters May 30 the slides in Whitehorse are being set off by the significant high level of water, previously in the form of snow, that has saturated the ground. A sheet piling wall and berm have been put in place to prevent further slides from reaching the road.
Dealing with the escarpment landslides that have hit the city since April has cost a total of $1.2 million so far.
READ MORE: Landslide closes Robert Service Highway, Millenium and Airport trails
READ MORE: Two more large slides prompt property evacuation orders in downtown Whitehorse
— With files from Stephanie Waddell
Contact Dana Hatherly at dana.hatherly@yukon-news.com