Flooding in the community of Lakeview has been a frequent and recurring problem. Like many older neighbourhoods in Calgary, Lakeview’s drainage system did not meet current service level expectations for stormwater drainage. An analysis of the storm drainage system in Lakeview revealed that the existing storm sewers provided inadequate conveyance resulting in less than a 1-in-2 year service level (50% chance of occurring) and that the overland drainage system was not designed to manage extreme events. As a result, recurring road flooding, sewer surcharge/backup and property flooding occurred during major storms.
The City of Calgary retained Dillon to investigate and determine the causes of the flooding problem and recommend solutions to reduce future flooding in the study area. This multi-phase project included community engagement, preliminary and detailed design and construction services. We developed a fully functional hydrologic and hydrodynamic model of the existing system and determined that many parts of the system had only a 1-in-2 year level of service or less. The recommended solutions improved the system to an overall 1-in-50 year service level (2% chance of occurring).
Phase 1 of this project consisted of upgrades and twinning of 3.2 km of storm sewer trunks to alleviate hydraulic bottlenecks in the community, as well as construction of a 3.2 ha retrofit storm relief wetpond in North Glenmore Park. The wetpond acts primarily as flood surge relief storage but also provides water quality enhancement prior to release into the Glenmore Reservoir. The wetpond also eliminated the need to construct storm sewer upgrades through the existing Earl Grey Golf Course, down the steep escarpment into the Glenmore Reservoir and further eliminated the need to construct a new outfall requiring additional regulatory approvals.
This phase of the project improved the quality of stormwater draining into the Glenmore Reservoir (the City’s main drinking water reservoir); allowed for an emergency spill isolation function in the event of a hazardous spill on Glenmore Trail SW (a hazardous goods route); provided a community amenity as an urban oasis; and increased biodiversity and habitat for flora and fauna.
Phase 2 consisted of an additional 4.2 km of upgrades to existing storm sewer trunks and replacement of local sewers within the area.
During the design process in this phase, the City added the replacement of a cast-iron watermain constructed in the early 1960s. The watermain location was constrained within a utility right-of-way with existing structures in close proximity. Dillon investigated alternative options for the replacement of the watermain and recommended pipe bursting. Pipe bursting allowed for minimal surface disturbance and a much shorter construction time.
The design solutions recommended for this project balanced economic costs, social, and environmental considerations with the objective of reducing flood risk in the study area.
This project was recognized with the 2015 Alberta Public Works Association Project of the Year Award in the Disaster & Environment Category.