Several design considerations went into developing a stormwater management plan for this subdivision. There was a high groundwater table, a natural river subject to flooding, and the normal requirements for dealing with stormwater runoff from an urban subdivision. The final result was that the Stormwater Management Facility was designed so that the normal water level was set based on the elevation of the groundwater incorporating the flow from the groundwater into the design of the facility and outlet structures.
This design eliminated the requirement for a liner which saved several million dollars in construction costs. As noted, the excavation of this facility was completely below groundwater so special requirements (both design and contractual) were put in place to arrive at a successful project. In addition, the material that was excavated from the facility was gravel that was used as the base for all roads within the subdivision.
Alberta Environment was involved from the onset of design due to the above-noted challenges. Due to a moratorium on Sheep River, the Stormwater Management Facility had to be designed so there were no net losses to the acquifer.
Landscaping of the storm ponds included creation of planting benches and the incorporation of wetland plantings, including emergents, marginals and aquatics.
