The GTA Construction Report Special Feature
Work is expected to be completed during the spring of 2017 on Niagara Region’s Burgoyne Bridge project. The bridge, the largest the region owns and maintains, is one of only three crossing 12 Mile Creek and connecting the west and east sides of St. Catharines. It also connects the Western Hill community to the downtown core and is a vital link to downtown, drawing traffic from Highway 406.
St. Catharines Mayor Walter Sendzik says the bridge has been an iconic landmark since its construction in 1915. “Even in name the ‘Burgoyne’ Bridge is tied to our city’s heritage and development, as it was named after prominent businessman and former mayor, William Burgoyne. At that time the first Burgoyne Bridge was constructed, spanning the riverbank, it was a feat of engineering and the new bridge will be just the same.”
Niagara Region project lead Jason Marr says an inspection of the bridge in 2009 and 2010 by Hatch Mott MacDonald revealed the structure had five to seven years of useful life remaining before major rehabilitation or replacement word would be required.
Following a thorough Municipal Class Environmental Assessment (EA) study process that looked into numerous designs, alignments and styles, a decision was made to replace the bridge.
Marr says several challenges were identified during early design stages including geotechnical issues related to the stability of the slopes at the bridge’s approaches, which carried an overall safety factor of less than 1.3. “The soil conditions in the valley were also poor and varied in consistency resulting in a requirement for very robust deep foundations.”
These reinforced concrete foundations, supported by 1.2 m diameter reinforced concrete caissons, vary in length from 30 m (at the valley floor) to 55 m (at the abutment approaches).
The concrete caissons are socketed into the solid bedrock approximately six to eight metres. As well, Marr says, artesian groundwater conditions posed a constructability issue requiring all of the deep foundation work to be completed in hydrostatic conditions (in the wet).
Caissons were advanced with vibratory methods while excavation, rock socket drilling, and concreting were carried out in wet conditions. Concrete was completed using tremie methods. (The tremie concrete placement method uses a pipe, through which concrete is placed below water level. The lower end of the pipe is kept immersed in fresh concrete so that the rising concrete from the bottom displaces the water without washing out the cement content.)
“One of the major issues during the installation of the deep foundations (and construction of Phase 1 – East Bridge) was to perform the work while maintaining vehicular and pedestrian traffic on the existing bridge,” he said. “Because of the age and condition of the existing structure and the requirement to maintain traffic during construction a phased approach was required along with a very precise structural monitoring system.”
Marr says because the bridge provides such a critical link for the city, it remained open during construction. A staged construction approach was used to ensure that both vehicular and pedestrian traffic experienced minimal disruptions.
He says consultation and collaboration have been key throughout the project, beginning from the early environmental assessment stages through the completed construction.
Partners have included Transport Canada, Ontario’s Ministry of Transportation, the City of St. Catharines, emergency services, environmental agencies (such as the Ministry of the Environment and Environment Canada), the contractor, engineering consultants, Niagara Region and local businesses and residents.
Sendzik says with the commencement of daily GO train service, the connection from downtown to the train station by way of the bridge will “once again become a prominent transit point for residents and visitors” to the city.
“ With enhanced lighting, landscaping and the opening up of public spaces, the reopening of the bridge will create new gathering spaces in a busy and growing downtown,” he said.
Marr says: “The new bridge will not only provide a critical link to the down town area for the next 100 plus year but it will also provide a landmark structure to the region and a gateway to the City of St. Catharines.” Sendzik says: “The opening of the bridge will also signify the completion of several major infrastructure projects which have changed the face and experience of downtown St. Catharines. From the FirstOntario Performing Arts Centre, the Meridian Centre, Brock University’s Marilyn I. Walker School of Fine and Performing Arts, and now the new Burgoyne Bridge, these infrastructure projects complete the reconstruction of downtown St. Catharines into a modern, attractive, and accessible place for live, work, and do business. The opening of the bridge will fully open the city for new businesses, new traffic and new investment.”