Risk keeps Sherman Access closed
Wet weather, failing infrastructure force the closure of three Mountain accesses so far this year
UNSTABLE ESCARPMENT slopes above and below the Sherman Access have now closed all but one lane of the three-kilometre road that climbs the Mountain.
The east leg of the access — used by about 9,000 vehicles a day — could stay closed to all traffic for a week or more after several large boulders and the remains of an old tree slid down the slope and onto the edge of the road on the weekend.
No one was injured and no vehicles were damaged in the rock slide, but several trees are “perched precariously” at the edge of the collapsing cliff and remain a danger to drivers, said city technical operations manager Brian Hughes.
“We can’t reopen the road with that big one looming over the edge,” said Hughes, who noted inspections Monday showed one mature tree in particular is at risk of tumbling down the slope. “With all the rain we’ve been having, it wouldn’t take much for it to come down.”
A mix of bad weather and failing infrastructure has forced closures of three major Mountain-climbing roads this year — so far.
The weekend rock fall came just weeks after record rains caused a mudslide that briefly closed the Kenil-
All downbound lanes of the Claremont Access were closed for nearly four months starting last November to allow for the $1.1-million emergency removal of failing metal bin walls along the road.
Shortly after those lanes reopened, however, the city closed the outside lane of the west leg of the Sherman Access, citing concerns about failing retaining walls and slope stability underneath the roadway. About 15,000 vehicles travel on that stretch each day.
Don’t look for a reopening any time soon: The city will close all lanes of the west leg in July or August to do major repairs to the suspect retaining walls.
“It’s been a tough year for escarpment roads all over,” said Hughes, pointing the finger in particular to a soggy spring that dumped close to 170 mm of rain on the city in April alone, with periodic deluges in May, too.
“All of that rain has just created more problems for us.”
Despite the bad weather, Hughes added the latest rock slide was “a bit of a surprise” given it happened along a stretch of the road not identified as in need of work.
It was also a bit of bad luck, with the rocks sliding down a section of slope without concrete barriers along the road. A block retaining wall is visible just a few metres down the slope, while concrete jersey barriers are installed about a dozen metres up the road.
The biggest boulder, a flat slab about a metre in width, slid down the slope with a tangle of tree roots just in front of a yellow and black sign warning motorists about the potential for falling rocks.
Hughes said it’s too early to determine what preventive work will happen in the area, but he thought more concrete barriers would be considered.
The Spec reported on a study of rock slide risk last year that recommended rock scaling, the addition of concrete barriers or protective steel mesh at locations along both legs of the Sherman Access.
The city has already done much of that work, said Hughes — but until now, the section that collapsed on the weekend “was not considered a particular risk.”
The city had planned to install more protective mesh along sheer sections of
cliff on the east leg of the access this year — but problems on the Claremont and Kenilworth have already burned through the $450,000 budgeted for escarpment work for all of 2017.
The weekend rock slide on the east leg of the access was “a bit of a surprise,” occurring along a stretch of the road not identified as in need of work.
The east leg of the Sherman Access could stay closed to all traffic for a week or more after several large boulders and the remains of an old tree slid down the slope and onto the edge of the road on the weekend.