It’s been more than half a century since the Sir Ambrose Shea Lift Bridge officially opened, connecting the Newfoundland and Labrador communities of Placentia and Jerseyside. The bridge was designed to span the “Placentia Gut”, a channel of water with tides that change direction every eight and a half hours. The tides themselves can attain speeds of up to nine knots.
Using an unusual design for its time, the Sir Ambrose Shea Lift Bridge consists of two approach spans and one centre vertical lift span. Each measures 30 metres in length. The centre vertical span – which can be raised from a clearance of three metres to a height of 21 metres in one and a half minutes – weighs 100 tons.
The centre span of the Sir Ambrose Shea Lift Bridge is raised, on average, 2,500 times each year. It comes as no surprise then that the provincial government’s Department of Transportation and Works was forced in 2011 to tender the construction of a new lift bridge that would replace the aging structure. A $40.6 million contract was eventually awarded in March 2013 to HJ O’Connell Construction Limited, a joint venture between a division of Bird Construction Inc. and Vancouver Pile Driving Ltd.
The government contract consists of replacing the aging Sir Ambrose Shea Lift Bridge with a new lift bridge in Placentia directly adjacent to the existing one, as well as realigning the adjacent roadway Route 100 and removing the old bridge once the new one is operational. Also included is the building and equipping of a control house for the bridge’s significant mechanical and electrical components.
The project is expected to take three years to finish, with an anticipated January 2016 completion date.
The new bridge was designed by Parsons (formerly Delcan), an engineering, construction, technical, and management-services firm.
“The bridge is located in a very harsh environment, so the reliability of its operations is a high priority,” states Joanne McCall, Division Manager, Parsons. “Recognizing that simple and conventional operating systems bring the highest degree of reliability and minimize maintenance, we determined that these conventional systems, both mechanical and electrical, should form the basis of the bridge design as much as practical. Special care was taken to select members, details and systems that are long lasting and enhance the durability of the structure. Details include closed structural sections, enclosure of mechanical machinery and components, and minimizing exposure to the elements.”
The new lift bridge requires the building of two 58-metre long temporary trestles, with 600 millimeter pipe piles and a deck, to enable the placement of a 150-ton crawler crane. The crane is used to construct the two new central piers deep in Placentia Bay.
“Each pier required that we build an L-shaped work trestle and a cofferdam out to each of the two piers,” states Clancy Lannon, Project Manager, Vancouver Pile Driving. According to Lannon, each of the two piers required 136 pipe piles of 325-millimetre diameter. Thirty additional pipe piles of the same size were required for each of the two abutments.
“The soil on the site was pretty complex. The Newfoundland and Labrador Department of Transportation and Works had boreholes drilled to 70 meters depth and found that the soil got looser with depth. Therefore, we had to do extensive PDA testing of the piles,” says Lannon, who adds that the testing was done by Ottawa-based Urkkada Technology Ltd. “We initially went in expecting to have end-bearing piles but we ended up with most of the load being borne by the friction between the shafts of the piles and the surrounding soil.”
In total, the new bridge will use: 9,920 metres of pipe piling; 2,200 metres of sheet pile (for the cofferdams); 4,100 cubic metres of concrete; and 1,000 tons of structural steel.
“Putting in the tremie concrete proved to be a bit of a challenge because of all the piles needed for the piers,” says Lannon. Another challenge was the strong current. “We had limited times to do certain work. For example, the sheet piles could be cut off primarily during the low tide. We built a small platform and shield that would deflect the tide a bit to get us more time. We ended up with having three hours during low tide and only an hour during high tide.”
The company used Gander-based Central Diving Ltd. for the underwater work.
“It took 11 days for the divers to cut off the steel piles on the south pier and it will probably take another 10 days to do the ones on the north pier,” states Lannon, who adds that the company is just finishing the concrete on the north pier. After that, the structural steel can be erected and then the mechanical components installed. “The next tricky bit will probably be the installation of the left span, which will take place this summer. Sectional barges will be needed to float in place so that the span can be lifted by cranes. Securing the barges is going to be tricky with that current.”
According to Lannon, the new bridge is located approximately 22 meters from the existing one.
“It more or less uses the same construction concept as the old one, just different materials,” he explains, noting that there were no piles used on Sir Ambrose Shea Lift Bridge. “The new superstructure will also be tubular instead of angular like the old one, which is primarily for aesthetics and maintenance.”
Vancouver Pile Driving was onsite for 18 months to complete the waterworks portion of this project.
In with the new
Sir Ambrose Shea Lift Bridge has remained and will continue to remain operational during the construction of its successor, aside from brief lane closures. Its 50-year life span, however, has come and gone. Although the bridge has recently been repaired to enable its use until 2016, the community has already shifted its focus to the new lift bridge nearing completion.
“The new Placentia lift bridge is a lasting and very necessary infrastructure investment which will benefit the people of Placentia and surrounding communities for many years to come,” stated the Honourable Paul Davis, Minister of Transportation and Works when announcing the awarding of the contract to HJ O’Connell Construction.
The Honourable Felix Collins, Minister of Intergovernmental and Aboriginal Affairs, and MHA for Placentia, echoed his sentiments. “This is a major development and will ensure the long-term social and economic viability of the Placentia region,” he stated.
The federal government has contributed $8 million toward the $40.6 million project.
“It’s been a really interesting project,” concludes Lannon. “It’s a complex one in that it has some unusual challenges, such as the tides, strong currents and high winds, not to mention the soil itself. But the end result will be a new bridge for the community – one that will have a lifespan of another 50 years or so.”