Precast concrete drainage products
used for high profile mixed-use development

Today's concrete pipe is designed to last more than 100 years.

Round and elliptical concrete pipe now service Bradley Gardens, a highly visible mixed-use development in the Georgetown area of the Town of Halton Hills, Ontario. Precast concrete products were used for the stormwater quality and quantity management system that channels the flow of stormwater from the site to a cold water fishery. Concrete products supplied to the site meet stringent provincial and national standards, as well as certification through the Plant Prequalification Program of the Ontario concrete pipe industry. The contractor, Drexler Construction Limited, prefers the use of concrete in sizes 450 mm diameter and larger because of efficiencies related to installation.

Bradley Gardens is a 22 ha. mixed-use site of houses, located on lands that were once the home of the Dominion Seed operation. The site was the last major agricultural enterprise near the centre of Georgetown, and is remembered for the fields of flowers harvested for bulbs and seeds. The planning process concluded with the approval of a mixed-use development by Parallax Development Corporation that included medium- and high-density residential, major retail, commercial, a school, and parkland areas.

Servicing of the site presented interesting challenges for the consulting engineer, KMK Consultants of Brampton, Ontario. The topography of the site slopes gently to the southwest with an average grade of 1.5% to 2%. Underlying soils were not well drained in many locations, making it difficult to meet a requirement of development set by Credit Valley Conservation for stormwater infiltration. The water supply of the Georgetown area is generated by deep wells, and it is important to include soil recharge techniques in any new development.

Existing storm sewers and sanitary sewers adjacent to the site were at elevations that determined the grade of the buried pipe needed to drain the site. In some locations, the installations were restricted to shallow bury. Circular concrete pipe was used to withstand loads from collector roads, and elliptical pipe at the outlet to the pond. Elliptical pipe carries the flow that discharges into an on-site stormwater management pond located adjacent to a major highway intersection.

The stormwater management plan for the site had to address quality and quantity issues for post-development flows for one in five and 100-year storms via overland flow routes. The pond includes 3,063 m³ of permanent pool storage below the elevation of 251.52 m and 985 m³ of storage capacity above the 251.52 metre elevation. Discharges from the pond are controlled by a single control structure with two orifice plates outletting to the receiving sewer. An emergency 15.2 metre wide overflow weir is also in place, in case of blockage of either of the outlets.

Centennial Concrete Pipe & Products supplied all of the precast concrete products. It offers a 100 year warranty on all its concrete pipe and associated products.

Round concrete pipe used for the stormwater management system ranged from 450 mm to 1200 mm in diameter. The 20.9 metres of elliptical pipe was 1090 mm x 1725 mm in rise and span. The elliptical pipe used for the storm outfall to the stormwater management pond was connected to the round concrete pipe with a 2400 mm x 1800 mm box manhole. The consulting engineer had originally considered a long run of elliptical pipe over a distance of approximately 468 metres, but decided to use a heavier class of round concrete pipe with additional cover to accommodate an access road into the site.

A sewage pump station was built on-site in case the downstream sanitary sewers being constructed by the Region of Halton were not commissioned by the time the new construction on the site was occupied and generating wastewater flows. The pump station was constructed using precast concrete manhole components. It may never be commissioned if the downstream sewers are constructed on schedule.

The need for soil recharge resulted in specially designed catchbasins used to collect stormwater at the rear of the residential units. Stormwater is channeled into a swale and then into catchbasins where it enters the infiltration galleries consisting of 250 mm diameter perforated pipe, geotextile socks, and clear stone. These galleries are located at the base of the catchbasins and installed parallel to the base. A second outlet pipe is located above the infiltration galleries on the proper slope to connect with the stormwater collection system. These pipes collect stormwater flow in heavy rainfall events. Stormwater generated by light rainfall is held in the catchbasins and directed into the infiltration galleries where the water is returned to the soil. The stormwater management pond has also been designed to retain rainfall so that it can infiltrate into soil.

By servicing the development with precast concrete products, there were immediate savings to the developer in the cost of materials and time, and construction was able to continue beyond December into January 2000, despite winter weather conditions. The site was ready for the 2000 construction season.

See our home page on how to order your subscription. We regret we can only accept orders from Canada and the United States.