SHUBENACADIE EAST - An engine revs and small, dark clouds of diesel smoke puff out from the exhaust stack of a nearby crane.
© Harry Sullivan - Truro Daily News
Branko Knezevic, site foreman for Cherubini Metal Works of Dartmouth at the Shubenacadie River bridge project, oversees the movement of a large, steel bathtub crib structure that used to form part of the old bridge.
Steel cables lose their slack and become taut as the operator ever so slowly increases the tension. The engine revs some more and a low, deep rumbling begins, followed by the sharp screech of metal and bit by little bit the large steel “bathtub crib” inches forward.
Site foreman Branko Knezevic watches closely and then signals for the crane to stop.
“Yeah, ya gotta straighten out his track because you’re pointing this way now,” he shouts, over the sound of the crane’s engine to crewmembers standing by.
And so continues the inch-by-inch removal of the old bridge that spans the Shubenacadie River on the southbound lanes of Highway 102.
Mere metres away, up and over the other side of a steel retaining wall, a steady ribbon of vehicles zip by at dizzying highway speed – tractor trailers delivering goods to the city; business people and vacationing families heading for the nearby airport; shoppers heading to the big malls looking for Christmas bargains – on and on, a relentless stream of ever-pounding rubber on asphalt.
“It was due for replacement,” Knezevic says, of the old bridge, which was built about 35 years ago.
At an average of 10,000 vehicles per day, according to statistics provided by the Transportation and Infrastructure Renewal (TIR) Department, that amounts to a whopping 127.7 million cars and trucks that have passed across its surface since the structure was put in place three and a half decades ago.
“This bridge, when you drove over it, it was always full of potholes, it was always damaged, you couldn’t just patch it with asphalt so something was giving somewhere, right?” Knezevic says, of the reason for its replacement.
The new bridges (both north and southbound lanes are to be replaced) are designed to last twice as long as the old spans because of the “innovative construction techniques,” being used, says TIR spokeswoman Pam Menchenton.
The deck joints that allow the bridge to expand and contract with temperature will no longer be situated on the bridge decks, thereby preventing salt water from reaching vulnerable components below the deck surface and which lead to premature deterioration.
“This is an important bridge project, especially because it’s located on the busiest economic corridor in the province,” she says. “Highway 102 links Halifax to the other Atlantic Provinces and the rest of Canada.”
But, first, of course, the existing structures have to go.
After the asphalt and decking were removed (by Dexter Construction, the primary contractor), what is left are steel bathtub cribs (so named because of their shape) that span 180 metres (600 ft.) across the river from abutment to abutment in each lane.
There are two such cribs in each lane for both directions of travel and their removal is where Knezevic and his three-man crew from Cherubini Metal Works of Dartmouth come into play.
At this point in the project, after about 60 metres (200 ft.) has been removed from one end of the first crib in the southbound lane, the structure still weighs about 139,500 kilograms (310,000 lbs.), he says.
“We’re ironworkers (from Local 752),” Knezevic says. “And this is what we do. You have an old structure that needs to come out and you have a new structure that needs to go in. We will assemble it here on site and either push it or pull it in place.”
At the moment, however, the crew is concentrating on the removal of the first crib, which involves slowly pulling the structure ahead to a point where it is more easily accessible to a crewmember with an acetylene cutting torch.
“We’re taking them out in 30-metre (100 ft.-) sections,” he said. “We’re cutting them in sections that are easy to ship (about 22 ft. per length).
Those sections are then loaded onto a tractor-trailer for shipment to a scrap yard and eventual recycling.
In the meantime, thousands of motorists continue to pass by daily, for the most part completely oblivious to the small crew working to dissemble the old structure.
The uninterrupted passage of the travellers is made possible through the temporary construction of a Bailey Bridge, which will be removed once the work to these lanes has been completed and then re-assembled to begin construction in the north-bound lanes.
When the iron-workers have completed removing the old structures and have their replacements secured, Dexter’s Construction (the primary contractor for the job) will return to complete the decking and asphalt stages.
Construction on both bridges is expected to be complete during the summer of 2015 and, so far, all appears to be on schedule.
At that point, motorists will continue to pound the pavement, for the most part, perhaps, never giving thought to the complex process that has taken place to provide safe passageway across the muddy, meandering Shubenacadie River.
And undoubtedly, a greater number than 127-million vehicles will pass across the span before the structure is replaced again in about 70 years or so.
“It’s just going to be built stronger and better than this one was,” a confident and smiling Knezevic says.
Note: Corrected version.
- The bridges are around 35 years old and were nearing the end of their useful life. The new bridges are to designed to last twice as long as the old because of innovative construction techniques;
- Once installed, they should last for 75 years;
- This is a multi-year contract that will allow contractors to anticipate and budget their costs so they can provide longer, year-round employment to their workers;
- The existing foundations were inspected and determined to be in good condition, therefore, they will remain in place and will be used to support the new bridges, resulting in significant cost savings and a shorter construction schedule;
- The bridge replacement will cost $23 million in provincial funding;
- The temporary panel (Bailey) bridge is $1.5 million and is re-usable (cost is factored into the $23 million);
- Each bridge carries approximately 10,000 vehicles per day – with a peak of around 1,400 vehicles per hour;
- Bridges are replaced after consideration of its age, condition, use of the structure, volume of traffic and weights and class of roadway where the structure is located;
- Construction is expected to be complete in summer 2015.