A new development in Barrhaven, Ontario (just south of Ottawa) needed a bridge structure to allow for both vehicular and pedestrian traffic to access this new subdivision, as well as maintain the integrity of an outlet channel for the Clarke Stormwater Management (SWM) Pond to the Jock River. M CON Products Inc. played a key role in the project.
Mattamy Homes, the developer, selected DSEL (David Schaeffer Engineering Ltd.) as the prime consultant for this project.
This project contained several interesting challenges:
• The Clark SWM Pond services a drainage area of 123.41 ha. and treats flows for quality control prior to discharge to the Jock River.
• The outlet channel was sized to convey the maximum 100-year flow of approximately 22m3/s.
• The outlet channel was part of a Department of Fisheries and Oceans (DFO) Authorization for the Barrhaven South Community, where it represents a portion of the compensation for loss of fish habitat. As such, the channel was designed using principles of natural channel design.
• Natural channel design consists of a low flow meandering channel with riffles and pools, designed by a fluvial engineer.
• There is a trunk sanitary sewer that was planned along Perseus Avenue, across the channel, in the overall servicing plan for the Barrhaven South area (per the Barrhaven South Master Servicing Study (MSS). The downstream outlet was constructed/existing and there were no opportunities to lower the sanitary sewer.
• There was limited clearance between the bottom of the channel (low flow channel per fluvial design) and the fixed sanitary crossing, resulting in insufficient clearance to incorporate a four-sided box culvert.
• There were challenges in determining the final design of the three-sided culvert as the footing was deeper than the fixed sanitary trunk elevation.
To address the challenges with respect to the sanitary trunk crossing the footing of the three-sided culvert, the following design modifications were incorporated into the final design:
• A 1.0m gap in the footing was provided to allow for the installation of the sanitary sewer which is contained in a steel sleeve.
• The rise of the culvert (leg length) was increased to allow for a reduction in the elevation of the top of the footings.
• Due to the low bearing capacity of the in-situ soil, the culvert was designed to be supported by a cast-in-place concrete strip footing that was to be supported on a granular pad. This design was provided by the Paterson Group (geotechnical engineer).
M CON Products, located west of Ottawa in Carp, Ontario, was chosen as the precast concrete producer for this project. M CON was awarded the structural design, fabrication and delivery of the three-sided culvert.
While ensuring that the structure met the required 9.144m span, 3.048m rise and total run length of 33.54m, M CON optimized the number of pieces to be produced while maximizing their size. Respecting weight limits as well as ensuring safe and efficient delivery were key factors in determining the maximum size of each piece.
The final structure was designed to have 17 pieces. Each piece weighed in at approximately 38 metric tonnes. Another advantage of having M CON provide the structural design permitted them to optimize the production by ensuring the steel reinforcement detail would provide efficient fabrication of the structural elements. The structure’s 17 pieces were produced in 34 days.
In conjunction with Vanson Transportation, M CON was able to coordinate the logistical requirements to allow for the structure to be installed in two days.
Utilizing the advantages of precast concrete and working with the M CON team on the engineering, manufacturing and logistics provided this project with a high-quality structure that addressed some very challenging site conditions while keeping this project on schedule.
Jennifer Ailey, P.Eng.
DSEL (David Schaeffer Engineering Ltd.)
Precast Producer: M CON Products Inc
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