Designers of buried infrastructure have ready access to products, materials and standards to make economical use of land planned for urban development. Canadian engineers, architects and planners have advanced the science of stormwater management with software, environmental legislation, and a wide variety of containment schemes. Now, in rapidly growing cities like North York, Ontario, new technology is being applied to solve an old problem inherent to land development.

Land for stormwater management facilities is scarce in North York. Because developable land is also expensive, land owners and city officials must work together to provide the best development opportunities for the market. Unlike some urban areas in the Greater Toronto Area (GTA), the City of North York does not have provisions for maintaining stormwater management ponds. The designer, Condeland Engineering, of the Bowan Court residential development project was faced with the problem of providing a 1,600 m3 storage facility without the benefit of a pond.

The solution was determined to be two large precast concrete storage cells buried at varying depths beneath Bowan Court that has a finished road grade between 3.5% and 5%. The size and length of the precast concrete box culverts were a function of volume, production, delivery and installation time to complete the project. The precast concrete units of the cells were designed in accordance with the materials specification for nine standard sizes of units under OPSS 1821. With design approval in place under OPSS 1821, the design and manufacturing stage was expedited, thereby gaining efficiencies for the engineer, contractor and precaster. The units were produced in a controlled environment at Con Cast Pipe in 17 production days (6 per day).

The two cells are each 125.71 m long. Both have a single 375 mm drop pipe entering the up stream end, and a 300 mm pipe located at the outlet. They also have a 200 mm orifice pipe at the invert of the downstream cap. The project called for 102 (3000 mm x 2100 mm) gasketed box units with 2.4 m lay lengths and 254 mm thick slabs and walls. The units weighed 18,300 kg apiece. The gaskets used were the self-lubricated "SuperSeal" gasket, produced by Hamilton Kent in Etobicoke. The units were delivered to the site with the gasket glued to the spigot end of each unit.

Murray Winter, project manager with Con Drain, said, "Con Cast helped us meet our deadline by supplying us with precast gasketed box units. They were easily installed in bad weather without the need for any additional work to achieve a watertight system."

Other special products precast for the project included two (3000 mm x 2100 mm) concrete plugs with hole for the inlet pipe, and two (3000 x 2100 mm) concrete caps with two outlet holes each. Con Cast Pipe also supplied 30 catchbasins, valve chambers, 300 mm to 675 mm concrete pipe and 30 maintenance holes. Eight of the precast units were utilized to create four maintenance hole tees.

This article has been abridged.