Work con­tin­ues along Sher­man Ac­cess

City re­plac­ing sta­bi­liza­tion walls

The Hamilton Spectator - - LOCAL - GORD BOWES Hamil­ton Com­mu­nity News

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.

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