Work continues along Sherman Access
City replacing stabilization walls
With no cars and the sounds of the city muffled by forests of trees in full foliage, one might start to think time is nearly standing still.
But one look at the edge of the pavement along the Sherman Access and it’s easy to see how time marches on — and nothing stands in the way of the changes it brings.
Steel retaining walls installed more than four decades ago have rusted through, allowing the earth and rock it was holding back to wash away.
“Those bin walls have been eroded completely,” says Dave Mullen, the city’s project manager in charge of the reconstruction of the west leg of the Mountain access.
In some spots, the ground around the guardrails at the edge of the road has disappeared. Some of it has slipped away during excavation in preparation for new retaining walls. But some of it was gone prior to the downbound lane being closed in March.
“That’s the power of water,” says Mullen.
While the walls were built with drainage to keep the water from affecting the steel, over time things change. Water follows the path of least resistance, so once a small hole forms in the steel it only gets worse.
The Mountain News last week was given a walking tour of the west leg of the access, which has been closed completely since July 4. Prior to that, it was down to one lane for about three months because of failing retaining walls.
Those walls, installed in the 1970s, are smaller versions of the ones installed to keep rock from falling onto the Claremont Access.
These ones, however, are never seen by drivers. They are at road level where the shoulder ends, supporting the road bed.
The Sherman Access opened in 1927. The last long-term closure was in 2006, when several retaining walls were replaced. Mullen was also project manager for that work.
Six sections of retaining walls are being replaced, or installed where there were none, during this summer’s $3-million project.
Steel I-beams will be driven into bedrock about three metres apart to hold the precast concrete panels that will form the new wall. A similar design was used in some sections during the 2006 reconstruction. It’s the current state-of-the-art — but so were the steel retaining walls in the 1970s.
“Time tells us how to rebuild,” says Jeff Collett of Bronte Construction, the contractor for this year’s work.
Knowledge is gained every time something is constructed, he says, and improvements are made accordingly. Since the steel walls were installed 40 years ago, “we’ve learned a lot.”
How long will the new walls last? Neither Mullen nor Collett want to speculate.
They’ll be inspected regularly and sections will be replaced as needed, but they won’t give an estimate on longevity.