Concrete Pipe Journal

No Hitches With CON/SPAN®

By Adam Polski, C.E.T., VP Engineering Services
Con Cast Pipe
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Constructing massive precast concrete structures with CON/SPAN® presents choices to design engineers and assembly options to contractors. Working with 30 tonne CON/SPAN units on the Denison Road Storm Water Retention Tank in Toronto required highly skilled installers and a Goldhofer self-propelled modular hydraulic transporter. In addition, a 160 tonne all terrain mobile crane was required for offloading and placing the units on the Goldhofer transporter used to assemble a portion of the 144.5m structure located one metre below the finished grade of Denison Road. Without modern technology and the precast concrete CON/SPAN system, the precast units for the tank could not have been assembled within the 10-day period in the summer of 2014.

The Denison Road retention tank (Georgetown South Project) by Metrolinx (GO Transit) is one of many applications of CON/SPAN. It is not a new application, but the size and installation method of the Georgetown South Project makes the application remarkable. Design and construction of the storm water retention tank was needed for the treatment and disposal of stormwater runoff from a total catchment area of 4.86 hectares. In addition, the structure was required to provide
enhanced water quality protection and discharge via an existing storm sewer network located along old Denison Road West to the Humber River for all storm events up to and including the 100-year return storm.

Design of the system resulted in a 4,000 [cubic meter] underground stormwater retention tank comprised of 62 precast concrete units, 9755mm wide by 2740mm high. Some pieces were specially designed with skewed end units for bends, while other pieces were narrower at the beginning and end of the structure. All were designed to S6.1S1-10 – Supplement #1 to S6.1-06, Commentary on CAN/CSA-S6-06, Canadian Highway Bridge Design Code and CSA A23.4-09 (R2014) – Precast concrete – Materials and construction. Pre-project planning started in 2011 with the concept for the CON/SPAN option, which would require a cast-in-place foundation and channel. The units were produced and shipped from the Guelph facility of Con Cast Pipe.

Upon completion of the installation, Dufferin Construction, a division of Holcim (Canada) Inc., constructed cast-in-place bulkheads at each end, connected catch basins into the CON/SPAN structure, and constructed a cast-in-place maintenance-hole base on top so that precast riser sections could be installed to the finished grade of Denison Road. The stormwater would be pumped from the tank to an oil/sediment control structure before treated storm water is discharged into the storm sewer system located on Weston Road.

Because of wide load restrictions in Toronto during morning and late evening commuter traffic, four loads were delivered the previous night to begin installation early in the morning, rather than trucks arriving after 10:00 a.m. Having the four units available to install in advance of 10:00 a.m. helped expedite the installation that was affected by the City of Toronto delivery time restriction for wide loads. Jim Malpass, P.Eng. Technical Service Engineer with Con Cast Pipe was involved in much
of the pre-installation planning, and Larry Wunder, Con Cast Pipe’s Technical Service Representative, was on site assisting Cambridge Rigging with the installation.

Included in the rationale for selecting a precast concrete retention system was the complexity of the location of the tank; directly underneath the Denison Road GO Transit grade separation and a metre below Denison Road that passes under the railway overpass. The structure had to be constructed in a short period within an established neighbourhood and roadway right-of-way where it was difficult to make use of heavy equipment outside of the old Denison Road right-of-way. Cambridge Rigging’s 300-tonne mobile all-terrain crane was used to install CON/SPAN units to the grade separation, but the Goldhofer transporter was needed to install units under the rail overpass. Using precast concrete units saved time, limited the impact of construction on the neighbourhood and commuters, and helped the contractor meet the construction schedule.

Construction of the tank began with excavation for a poured-in-place channel that would also serve as the base of the CON/SPAN structure. Footings for the CON/SPAN units were poured-in-place. The first unit was set on June 24, using the 300-tonne mobile crane.

As installation approached the grade separation, Cambridge Rigging switched the installation method from an all terrain crane to the Goldhofer transporter to install the precast units where the crane became ineffective. Cambridge Rigging and their engineering division, Engineering In Motion were responsible for planning and executing the installation of all of the
precast sections on behalf of Dufferin, including the sections installed with the 300-tonne crane.

A precast unit was carefully centred on the Goldhofer transporter with a 160-tonne mobile all terrain crane and tied securely. The CON/SPAN unit was rotated on the Goldhofer transporter 60 degrees so it fit between the footings. The wireless remote controlled, diesel powered hydraulic transporter then began its slow pace toward the overpass. A Kevlar strap joined the Goldhofer transporter to a prime mover that served as both an anchor and safety vehicle to slow the downhill movement of the transporter.

When the Goldhofer transporter arrived to deliver its payload, it was maneuvered into position to gently place the CON/SPAN unit into the footing to rest on a neoprene strip that aids in waterproofing while shimming the legs.

The Goldhofer transporter then began its slow trip back to its starting point to be loaded with another precast unit.

The final CON/SPAN unit was placed on July 3, completing the 10-day installation.

Construction of the retention tank was only one component of this complex project. Metrolinx retained R.V. Anderson Associates Limited to carry out detailed design and provide services during construction for a new railway grade separation for improved rail service, and for the Union Station–Pearson Airport Rail Link. The project included two reinforced concrete railway bridges, tieback retaining wall system, and the new precast storm retention tank.

Jewell Engineering Inc. was the structural designer of the CON/SPAN system and prepared the general arrangement drawing from the R.V. Anderson/Morrison Hershfield design. Con Cast Pipe sales representative, Mark Eaton, introduced Dufferin Construction to Mike Farrell of Cambridge Rigging who supplied the Goldhofer transporter and the all-terrain
cranes to complete the installation under the grade separation.

When completed, the public will see the Denison Road grade separation that accommodates a rail system for commuters and travellers to and from Lester B. Pearson International Airport, a pedestrian underpass, and improved road pavement. What won’t be visible is a modern underground precast concrete storm water retention and treatment system that is designed to last for generations.

Ministry of the Environment Ontario, Amended Certificate of Approval, Municipal and Private Sewage Works, Number 3745-8H7MD.

GO Transit, Georgetown South Project

R.V. Anderson Associates Limited