Parsons Corp. utilizing ‘accelerated bridge construction’ on Gardiner

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Michael Lewis

Special to Ontario Construction News

The technical advisor on the second phase of Toronto’s Gardiner Expressway rehabilitation says the project will rely on “accelerated bridge construction” to reduce the time and impact of the critical work that threatens to cause major headaches for commuters.

Parsons Corp. said the accelerated technique using prefabricated concrete panels allowed replacement of an 800-metre section of the west deck of the elevated expressway to be wrapped up 27 per cent ahead of schedule in the first phase of the project.

“Rehabilitation of Section 2 will use a similar accelerated construction approach to the rehabilitation work completed for Section 1,” said the Virginia-based infrastructure technology provider, which is also acting as the City of Toronto owner’s engineer on the second segment.

The firm’s $10 million contract includes conceptual and preliminary design, procurement services, contract administration and inspection for the upgrading of Section 2 of the expressway that connects western Toronto to downtown.

Work on Section 2 is to begin as early as late March weather permitting. Barring delays due to supply chain disruptions and labour shortages, work is expected to be completed by mid-2027. Upgrades on the underside of the Gardiner began last November.

Toronto says $2.3 billion has been approved to fund most of the rehabilitation of the Gardiner, which extends 18 kilometres from Hwy 427 in the west to the Don Valley Parkway in the east. The Gardiner East section of the expressway that spans 6.8 kilometres and is elevated directly overhead of Lake Shore Boulevard opened in July 1966.

Rehabilitation of the elevated expressway, technically Ontario’s longest bridge, comes as the highway nears the end of its original design life and after extensive repairs became necessary in the early 1990s when chloride-induced corrosion caused spiralling concrete to fall off.

The city has considered proposals to demolish or move Gardiner East underground as part of downtown waterfront revitalization efforts, opting for rehabilitation given costs and commuter and commercial reliance on the high-speed artery.

Between 2014 and 2016 Toronto city council approved a six-part Strategic Rehabilitation Plan that employs accelerated bridge construction to replace concrete slabs and steel girders while protecting substructures that will service the new bridge deck.

Toronto has set 2030 as a tentative deadline for completion of the entire project, which is already years behind schedule in part due to pandemic related shutdowns. Work on the first section was finished in 2021.

Section 2 involves replacing 700 metres of concrete deck and girders, rehabilitating the structures underneath, as well as installing a new traffic management system and new street lighting.

Complex infrastructure specialist Grascan Construction Ltd. of Toronto, the design-build contractor for Section 2 in a more than $300 million contract with the city, said it will provide additional details in a construction notice. The city has scheduled a public consultation for early March as part of what it calls a public awareness campaign.

Given the complexities around the Gardiner Section 2 phase that requires rehabilitation of an elevated and narrow section of the busy expressway, much of the work must be done from underneath the roadway, severely limiting the construction staging and work zone areas. Drivers may not see workers along the Gardiner because of the work underneath, a city spokesperson said.

Section 1 of the Gardiner Project, which rehabilitated the westbound off-ramp leading to Yonge, Bay and York Streets, saw the concrete deck and steel girders of the expressway between Jarvis Street and Cherry Street replaced along with the westbound off-ramp at Sherbourne Street and the eastbound on-ramp at Jarvis.

The project used steel girder sections and prefabricated concrete deck panels to replace a 1.1 km elevated stretch of the expressway. Substructures were repaired using a galvanic encasement that the manufacturer says will provide corrosion protection for up to 40 years.

The accelerated construction method involved prefabricating new precast concrete deck panels using four hydraulic formwork lines at a rate of ten panels per week, Monday to Saturday, operating 24 hours a day on three shifts, said Section 1 contractor Construction Demathieu & Bard, the Canadian arm of the French-owned conglomerate.

During the first phase of the project, the largest by scale in North America, sections of the expressway were saw cut, hoisted out of place and transported to a fabrication yard to separate and recycle the concrete deck and steel girders.

In contrast to conventional cast-in-place method, the approach resulted in less dust and noise and reduced overall construction time and traffic impacts by up to 40 per cent, the city says.

In total, 409 unique panels were produced in the fabrication yard on Lake Shore Boulevard East just east of Cherry and then transported, hoisted with hydraulic lifts, and fitted onto the deck.

To allow for Section 2 work to proceed the Gardiner will be reduced to two lanes in each direction from Dufferin Street to Strachan Avenue for the duration of the project, with intermittent, additional lane closures to be required. The eastbound on-ramp from Lakeshore Blvd. east of Jameson Ave will also be closed during the construction.

Overnight activities including the shifting of traffic barriers and delivery of materials may take place and overnight construction work will be allowed when structural work is required over the Exhibition Go Station. Construction will primarily occur between 7 a.m. and 11 p.m.

Construction will pause and lane restrictions will be removed during the FIFA World Cup from May 2026 to the end of July.

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