Located on an island in the Bow River, the Calgary Zoo, a major tourist attraction, is susceptible to flooding during extreme weather and high water levels in the river. During the 2013 Calgary flood, Calgary Zoo was inundated, resulting in emergency evacuation of hundreds of animals and causing an estimated $50 million in damage to the zoo.
The City of Calgary Transportation Infrastructure department retained ISL Engineering, with Associated Engineering as its main subconsultant, to design a flood mitigation system for the zoo. The goal of the system is to prevent damage to the zoo for floods up to a 1:100 year event.
Reducing flood risks allows the zoo to exhibit pandas from China, which was conditional on the zoo being protected from flooding up to a 1:100-year event
Associated Engineering provided hydrogeological, stormwater, electrical, process mechanical (pump) design and inspection services, and led construction administration and coordination with the contractor and the zoo. Key personnel involved on this project were Robin Clee, Jacques Groenewald, Joe White, Scott Witzke, Corinne Arkell, Neal Barretto, and Emma Sauriol.
Project Manager, Robin Clee, tells us, “The design includes a two kilometre long berm around the island perimeter to protect the zoo from overland flooding and a continuous sheet pile wall down to bedrock also acts as a cofferdam to eliminate groundwater inundation of the zoo.” The sheet pile wall was constructed during the winter to minimize impact to visitors and zoo operations.
Our team also designed an underground, dewatering system to manage the groundwater level within the cofferdam. The automated pump system maintains groundwater within a prescribed range. Groundwater from within the island is pumped from ten dewatering wells and discharged to the Bow River via five new outfalls. Sensors in separate wells monitor groundwater levels, and transmit data to the Cloud so the information can be accessed remotely.
The dewatering system was design to be expandable, since its effectiveness could not be confirmed until the cofferdam was completed. This provision proved to be prudent as two additional wells and pumps were required to achieve the required discharge rates. Senior Hydrogeologist, Jacques Groenewald, says, “Drawdown testing of the groundwater after construction allowed us to calibrate and re-run the hydrogeological model to check the achieved dewatering capacity against that required, and confirm that the dewatering system could handle the 1:100 flood event.”
The Calgary Zoo Flood Mitigation project received an Award of Excellence in the Water Resources category at the 2019 Consulting Engineers of Alberta Showcase Awards Gala.