The east leg of the Sherman Access will remain not reopen today (Monday), the city says.
The road has been closed since Wednesday night after a rock slide from the Niagara Escarpment onto the eastbound lanes of the access, between the Sherman Cut and Kenilworth Access,. The city said Friday t will remain closed between between the Sherman Cut and the Kenilworth Access to allow for scaling operations.
Engineers are investigating the cause and will make recommendations. Smith said the engineers may determine it was a “localized failure and you don’t have to do anything” or “they may say there is some loose stone there that you have to take care of.”
Drainage problems were behind the 2011 slide and last winter’s warm and wet weather was cited as a cause for the March, 2012, collapse.
Four cars were in the vicinity when the latest slide hit during the 6 p.m. rush hour. One car was hit by the rocks, but no one was hurt.
Paramedics arrived at the scene shortly after and checked two people, but determined they did not require transport to a hospital.
Smith said the city paid a contractor $23,500 in March and April of this year to do “scaling” on the escarpment. The contractor checked for loose rock on the escarpment and removed it to prevent it from falling on the roadway at a future date.
“It is a natural shale geological feature,” he said. “That’s what happens with shale. The escarpment moves and it moves by shedding rock. We inspect it. We inspect it regularly, but this kind of failure can happen without any visual clues or any forewarning. It just happens.”
Smith added: “Drivers should always be careful.”
He said old shock crete — a concrete mixture applied to the shale rock to stop the pieces from falling — was part of the debris that came down in the slide.
“Shock crete is like netting,” Smith explained. “It’s put on to actually catch small pieces so they don’t fall.”
He said the city is trying to determine when the mixture was applied.
The debris was removed by city crews first thing Thursday morning and before Smith arrived on the scene. He could not say how much rock came tumbling down.
Wilf Ruland, a local geo-scientist who works with various provincial municipalities and environmental groups, believes the change of season spurs the most risk for rock slides.
“Every time the temperatures go up and below zero there’s an expansion and contraction of soil and rock and the water binding them,” he said. “If you’re going to have something like this happen, this time of year, or the spring, is when you can expect it.”
Ruland expressed concern that other cars stopped after one vehicle was hit by falling debris.
“The one place I wouldn’t want to be is parked at the base of a slope where a rock slide has just occurred,” he said. “I would suggest people move well clear of that area. Everything has been (loosened) by the slide that just happened and the chance of more debris coming down is great.”
This is the fifth rock slide in the Hamilton area in the last year. Apart from the three slides on the Sherman Access, there was a slide on Highway 403 and the Claremont Access. The latter had a retaining wall fail in February, spilling mud and rock across the busy roadway.