In 2013, historic flooding of the Bow River devastated the City of Calgary. St. George’s Island, home of the world-renowned Calgary Zoo since the 1920s and situated within the river, was engulfed by floodwater due to mountain runoff and significant rainfall in southwestern Alberta. As a result, the Calgary Zoo was severely impacted, facing approximately $80 million in damages to buildings and critical infrastructure, for the cost of protecting animals, and for a loss of revenue due to closure. Recent flood maps show the zoo is at risk of near complete inundation during a 1:20 year event.
To protect the zoo from future events, the City of Calgary invested in the Zoo Flood Mitigation Project to preserve one of Calgary’s greatest assets and most important landmarks, allowing the zoo to continue teaching and delighting Calgarians and visitors from around the world for generations to come.
The project included flood protection measures to protect against ground water flooding/saturation via a cut off wall and an above ground wall to prevent against overland flooding. The wall was designed to 1m above the 2013 flood levels, which is half a metre above the 1:100-year flood levels. Internal pumps were also part of the design to dispel water that might enter the zoo.
The scope of the project was expanded to include a full reconstruction of Zoo Road to help all users feel safer and more comfortable for daily use, and to ensure a safe emergency route out of the Inglewood and Ramsay neighbourhoods existed. Improvements include wider vehicle lanes, a new four-metre pathway for pedestrians and cyclists, and improved lighting. The Calgary Zoo will also benefit from the floodwall, because a new enclosure on the east portion of the island will house the new lemurs exhibit scheduled to open later this summer.
During the construction of the wall, the Calgary Zoo remained open and fully operational. Construction commenced in April 2016 and was completed in December 2016.
Once project details were released, Keller Canada and PCL Construction Management began pursuing the project as partners. The tender process involved pre-qualification followed by a request for proposal (RFP). Due to early involvement as a team, Keller Canada and PCL found execution efficiencies and created a detailed execution plan with the submission.
Keller also implemented a test program at a nearby site that had similar soil conditions to St. George’s Island. The advantage of doing testing during the tender stage helped to ensure the design was constructible and assisted in allowing the project team to optimize installation techniques. Ultimately, it played a key role in understanding the safety, quality, schedule and cost issues prior to project award and startup.
The pursuit process went extremely well and allowed the team to disclose ideas, brainstorm and solve issues freely, openly and collaboratively. Ultimately, PCL Construction Management was awarded the project and, soon after, Keller Canada was issued a subcontract from PCL to supply and install the sheet pile portion of work.
The project consisted of 1,578 paired sheet piles that ranged in length from 30 ft. to 72 ft. Sheet lengths were dependent on bedrock elevation in relation to working grade around the 2.1-kilometre perimeter of the island. The design required sheet piles to be advanced one metre into bedrock to act as a cutoff wall and, in specified areas, sheets were to remain three plus metres above grade to prevent overland flooding.
As a result of the pre-bid test program, Keller chose to install the sheet piles using the vibratory method.
NZ 26 sheet piles were manufactured by Skyline Steel, one of Keller’s preferred steel suppliers, to allow for shorter lead times, due to the quick start-up upon award.
For initial installation, Keller deployed two of their Leibherr LRB 255 units fixed with 40VML hammers and a LRB 155 fixed with a VML23 hammer. These units were key to setting and installing the sheets in tight areas. A secondary drive was performed with an 110T crane fixed with a hanging APE 200-6 vibratory hammer. This was done to ensure the sheets were advanced into the underlying rock.
On the southern portion of the island a “cap” sandstone rock was encountered. The vibratory hammers struggled to break through the extremely hard rock and it was decided to replace one of the LRB 255 VML 40 hammers with a V-9 impact hammer to ensure penetration through the cap rock. To the delight of the project team and the consultants, this approach worked extremely well. Using these installation techniques, all 1,578 paired sheets were installed into the rock as per the design requirements and were ultimately accepted by the design engineers.
One of the many successes of the project was the advancement to the initial installation schedule, while keeping the zoo fully operational during construction. The original milestone schedule as part of the tender package indicated piling to be completed May 2017. Keller and PCL revised the schedule and proposed that pilling be completed on Dec. 23, 2016. As such, Keller installed the final sheet pile on Dec. 21, 2016.
The daily crew consisted of approximately 20 workers and totaled over 25,225 man-hours with all 1,578 paired sheets installed reaching their required acceptance criteria.
One of the critical success factors of the project was the collaborative team approach. From the initial stages, the group openly discussed the project together, including a detailed partnering session post-award. This partnering session included the consultants for the project, key stakeholders, PCL and Keller Canada. It provided an opportunity for all parties to voice their concerns and discuss what each member would be relying on from one another within the group. Opening the lines of communication early made problem solving throughout the project much easier, following the vision of the late Calvin McClary from ISL Engineering, who was the engineer of record for the project. Cal was a great leader for the group and he was dearly missed when he passed away a few weeks prior to the final sheet being installed. Cal’s approach to the project was so ingrained that the team continued to maintain his initial vision for the project after his passing. The project continued with a heavy heart, but we all know that he would have been extremely proud of the team’s achievement.
The Calgary Zoo is well established with mature vegetation and several existing structures. It is currently occupied by a wide variety of animals and sees over 1.2 million visitors a year. These factors needed to be carefully considered while planning the project to ensure the design was met while not impacting the environment or day-to-day operations of the Calgary Zoo. Access to sheet locations for installation and the logistics of sheet delivery was also extensively planned to eliminate disruption. All in all, the project was an overwhelming success thanks to the close working relationship of all partners and stakeholders involved.
Submitted by Keller Canada