West Calgary Storm Sewer Relief
As part of the Canada Alberta Infrastructure Program, the City of Calgary prioritized several stormwater management projects in 2002. Among those was the West Calgary Storm Sewer Relief project, which was intended to relieve drainage problems in a residential neighbourhood southwest of downtown Calgary. Accomplishing this objective would require approximately 4 km of large diameter storm sewer and a new 20,000 m3 detention pond.
The preliminary design stage of the project was completed and included an extensive constructability review of potential pipe routes. Given that the neighbourhood was well-established, finding horizontal and vertical pipe alignments that did not conflict with existing underground and surface infrastructure was very challenging. Three major pipe routes were evaluated, and one was identified as having the least potential for conflicts with existing utilities during construction. A feasible location to cross Crowchild Trail, a six-lane urban arterial roadway, with a 1500 mm diameter pipe, was also found.
Several stormwater models were utilized during the preliminary design stage. DDSWMM was used to determine hydrologic flow rates for each catch basin. XPSWMM was used to analyze the hydraulic capacities of the proposed storm sewer system. QHM was used for continuous rainfall simulations for the proposed detention pond, to estimate how often, and to what degree, the pond would have detained water during historic rainfall events.
Retrofitting major infrastructure improvements in an existing urban community is not only technically challenging, but can have significant impacts on the lives of residents as well. Early in the detailed design stage, a public open house was held to show the proposed improvements to neighbourhood residents and obtain their comments. In addition, City staff and selected members of the project team met several times with community representatives to maintain ongoing dialogue. An example of incorporation of community input is in the design of the detention pond, which includes landscaping improvements to an existing park and a new baseball diamond. The result of the public consultation process is a project that has been well received by the public.
Construction of the drainage improvements began and the project team worked to complete their work while minimizing impacts to residents’ everyday lives, maintaining the safety of pedestrians and children, and keeping traffic flow as normal as possible. Work adjacent to two neighbourhood schools was completed during the summer months to avoid conflicts during the school year. The open-cut crossing of Crowchild Trail was planned well ahead of time with City of Calgary traffic planning staff and was completed in two stages in successive weekends.
There are many mature trees in the project neighbourhood and impacts had to be kept to a minimum. This was particularly evident in a park through which new storm sewer pipe had to be installed. The pipe route was selected to minimize impacts on existing trees and playground structures, and those trees that had to be removed were replaced two-for-one. In addition, several upgrades to existing infrastructure, such as sidewalks and irrigation systems, were implemented during construction.