DECAST Provides Stormwater Storage Solution

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The Greater Toronto Area (GTA), which includes the City of Toronto, Regions of Peel, Halton, York, and Durham, continues to see significant year-over-year growth. From 2021 to 2022, the population grew to 6,313,000 at just under 1% (0.93%). Given this continued expansion of the GTA and its surrounding municipalities, developable land is becoming more costly, and solutions to maximize the use of every square meter are being implemented. One of these solutions was used on a project in the municipality of Vaughan, which lies in the Region of York just north of the City of Toronto. The City of Vaughan, approved a subdivision of townhouses (174 total units), but was challenged by the requirement of using a significant portion of land for a stormwater management pond.

DECAST worked with Schaeffer & Associates to propose an innovative solution that would provide the stormwater storage capacity without utilizing surface area aboveground, as would be the case for a typical stormwater management pond. The solution was the use of a precast concrete I-STORM underground stormwater management structure. The I-STORM is a modular system that allows for various configurations. This was required due to the shape and constraints surrounding the site. Picture 2 shows how the I-STORM structure was configured to fit in the irregular area allocated for the stormwater management facility. We met the municipality’s stormwater management requirements with the I-STORM tank, which has an efficient void ratio that maximizes the volume available.

The I-STORM system was originally designed over 25 years ago in Japan to withstand earthquake loads by mechanically connecting all the precast components to form a single unified structure. The current I-STORM system produced and supplied by DECAST is designed as per the Canadian Highway Bridge Design Code (CHBDC) and can support parks, football fields, soccer pitches, parking lots and roadways. DECAST has done extensive testing and modeling to ensure that the service life of the I-STORM system exceeds 100 years. The I-STORM is also designed with several access points, such as grates, maintenance holes and removable slabs that allow skid steers to be lowered into the structure to facilitate rapid inspection and maintenance.

DECAST provided Schaeffer & Associates with the required structural designs for the system. The design information included buoyancy calculations to ensure floatation would not be an issue. The benefit of this system is to provide the required stormwater capacity without utilizing precious land areas in the subdivision. In this example, the I-STORM storage structure was constructed underneath public parkland, complete with trails and benches for the local community use. Utilizing the same surface area for two functions is a major advantage of underground stormwater systems. By eliminating the stormwater management pond, community safety is improved by removing access to open pond water.

As the project was the first of its kind for the City of Vaughan, Schaeffer & Associates and DECAST worked diligently with our industry partners to ensure the stormwater management facility meets the city’s requirements regarding safety, ease of maintenance and accessibility. During the installation, DECAST supported the general contractor, including the installation requirements, logistical coordination, and discussions on the preferred equipment that should be utilized on-site (such as cranes, jigs and hand tools to make the crew’s work more efficient). I would like to thank the DECAST design, production, and logistical teams for their involvement in our project, as well as our partners at the City of Vaughan. Together, we implemented an innovative solution to address the infrastructure challenge.

Hagop Sarkissian, P.Eng.
Partner
Schaeffer & Associates Ltd.
Precast Producer: DECAST Ltd.