Doublestar Drilling was awarded the temporary shoring contract for the construction for the construction and excavation for Calgary’s largest upscale condo project
When completed in 2018, Calgary’s newest upscale condominium project – the Concord – will be one of the city’s most luxurious living quarters.
Situated downtown in the Eau Claire neighbourhood, construction on this 14-storey project, which began in April, will include two towers of condos and townhouses overlooking the south shore of the Bow River.
With the first of the two towers expected to be completed in 30 to 36 months (and the second tower approximately six months later) Vancouver-based builder Concord Pacific has already sold 50 per cent of the first tower’s units. This includes five penthouses ranging in price from $2.5 million to $7 million.
With the most expensive penthouse priced at $13 million, it’s no surprise that residents will enjoy swanky amenities such as private garages, carwashing facilities, an outdoor water garden that can become a winter skating rink, private elevators in approximately three-quarters of the units, fitness room, swimming pool, golf simulator and 24-hour concierge and security.
“Building more downtown communities fits in with the city’s view around increasing density in our city,” said Calgary Economic Development business development manager, Tom Dixon.
In all, there will be 218 units spanning 1,060 square feet to 6,200 square feet.
Doublestar Drilling of Calgary was awarded the temporary shoring contract for the construction and excavation of the Concord. The ground engineering firm (which also has offices in Edmonton and Regina) provides services that include project consultation and engineering, small- and large-diameter piling, shoring, anchor work, load tests, micropiles, CFA piles, shotcrete and soil nails, vibratory hammer work, post-tensioning, grouting, caissons and specialty drilling solutions.
The Doublestar team started on the Concord project on August 15, 2015. Piling was completed three months later in mid November, with anchors completed on March 21, 2016.
“The 15-metre deep excavation was designed with 19-metre secant piles, which was uniquely incorporated into the structure’s permanent engineered flood mitigation system,” said Nick Baldwin, director of projects for Doublestar Drilling.
“The parkade structure is located only metres away from the banks of the Bow River, and is four levels below the river elevation. The secant piles are 1 metre in diameter and interlocked 20 cm to provide decreased permeability of ground water. Full-length segmental casing was used for the entire depth due to the groundwater and heaving soil conditions due to the saturated silts. The 323 infill piles and 129 soldier piles were installed by Doublestar’s Liebherr LB36 and Liebherr LB28 drill rigs.”
Additionally, 422 temporary tieback anchors, located along four rows, were required to support the secant piles. Anchors were designed for working loads of 570kN and proof loaded to 133 per cent of the design loads. Test anchors tested to 200 per cent of the working loads were required at each level of the wall due to the varying soil conditions, water table and pressures.
“The average drilled depth for the anchors was 14 metres, and all anchors were required to be post grouted multiple times,” said Baldwin. “Two of Doublestar’s Davey Kent 725 drill rigs were used to drill the anchors. Air rotary drilling with a downhole hammer was required for the majority of the anchors.”
While Doublestar’s role in this mega project is certainly impressive, it was definitely not without its challenges.
“The drilling specifications required zero soil loss to prevent settlement of adjacent structures,” said Baldwin. “Typical challenges with access and logistics of working in the inner city were managed and planned for.”
The project was also located in a known problematic geological area called “the channel.”
“This area of the city has highly saturated silts due to the flow of subsurface water that travels from the Elbow River to the Bow River, known as ‘the channel,’” said Baldwin. “The channel has caused major issues with excavation projects in the past due to loss of soil, resulting in settlement issues. Doublestar worked closely with the design team to ensure that we maintained drilling techniques to mitigate soil loss due to heaving soils and ensure alignment and overlap of the secant piles to withstand the hydrostatic pressures produced by the high ground water levels.”
Due to the varied layers of geology below and above the silt, specifically designed drilling tools and techniques were developed and utilized specifically for this project.
“As a result of the project success, Doublestar Drilling became a highly preferred contractor of GeoPacific Consultants, the geotechnical engineering rm representing the owner,” said Baldwin. “We are very pleased with how the project is progressing.”
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