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AUGUST 2017 | 91 Borden Park Natural Swim Experience RENDERINGS COURTESY CITY OF EDMONTON Borden Park Natural Swim Experience by PETER STENNING P ublic swimming pools have undergone extensive design evolution over the decades, to the point where you don't have to be very old to recall the bunker-style facilities of one's youth compared to the fun park-theme pools of today. But the Borden Park Natural Swim Experience in Edmonton, Alberta, is not so much an evolution as it is a fundamental rethinking of what recreational aquatic activity can be. The project, the first of its kind in Canada, provides a chemical- free swimming pool facility for up to 400 people (split between a 150-square-metre toddler's pool and a 42-metre long, 16.8-metre wide adult pool), augmented by change- room facilities, first aid room, staff areas and concession, along with outdoor showers and picnic areas. The City of Edmonton proposed that the historic Borden Park, which provided an uninterrupted history of swimming on site from 1924 to 2012, would be redeveloped to include a Natural Swim Experience (NSE) system consisting of a constructed body of water contained by isolating membranes, with the clarifying and cleaning of the water achieved by passing it through gravel filters and regeneration ponds. Popular throughout Europe, the NSE ponds consist of biological filters and plants rooted hydroponically into the system. Because there is no soil, plants and microbes must get all of their nutrients from the water, therefore consuming the nutrients that would otherwise feed algae growth. "This project wasn't entirely unprecedented," says Carol Belanger, Edmonton's city architect. "Borden used to have a natural swimming hole in the early 20th century." A feasibility study in the fall of 2010 confirmed the viability of the NSE as part of a master plan to upgrade key areas of the park. After the project was approved and funded via the 2012 Capital Budget Process, the city retained Toronto architects gh3, which had designed the striking Borden Park Pavilion several years' prior (a drum-like structure with mirrored surfaces that give it a jagged form of invisibility during daylight), and German consultant Polyplan was retained to ensure the NSE would be successfully implemented. "The latter proved to be invaluable in guiding us," says Aaron Schneider, project manager for EllisDon Construction Services Inc. Jesse Banford, director, facility infrastructure delivery for the City of Edmonton's integrated infrastructure services, says, "the design went through several iterations before being finalized in the spring of 2014, and we decided for budgetary reasons not to include winter skating and late night swimming as had originally been proposed." Robb Heit, the city's project manager, adds, "the design was very much influenced by public consultation, and locals loved the concept of having an NSE in the neighbourhood." With the positive experience of the Borden Park Pavilion still fresh in mind, the City provided gh3 with functional guidelines and left the design to its discretion. "With the right company, this approach simplifies the design process – and with our evaluated procurement process we are able to the secure the right architect to help design these legacy infrastructures," says Banford. Gh3 is known for its minimalist esthetic, and this is evident in the stark, rectangular surface of the main swimming pool and accompanying rectangular form of the change room facilities (originally, the swimming basins had a curved, organic shape). An early plan for poolside decking was replaced by sand (ultimately, 1,643 metric tonnes of sand quarried in Thorhild along with 11 species of native plants were required to create the impression of being at the beach). "To retain the original ambiance of this area of the park, we tied the new facility into the existing concession building," says Belanger. EllisDon broke ground on the site in March of 2016, and despite the unique nature of the project, Schneider says certain elements were easy to accomplish. "The two regeneration ponds were basically just holes in the ground lined with plastic and outfitted with piping inlet and outlets," he points out. However, to ensure that the construction process was precise, Schneider interacted often with Polyplan. "Plus, they flew in from Germany several times, which was enormously helpful," he says, adding that custom-made elements such as a phosphate absorber tank located in the mechanical room were one-of-a-kind items that had to function trouble-free. One of the biggest challenges for EllisDon was something seemingly innocuous. "Originally the aggregate filter material based on the German experience was to be limestone, but our regional limestone proved to be unusable because particles would accumulate at the bottom of the filters and cause organisms to attach to them," says Schneider. "So our next choice was granite – but it took considerable effort to find a supplier to grind a relatively small amount to the grade we required," says Schneider. Another major challenge was constructing the facing of the change room complex. "Instead of a building envelope there would be gabion walls; essentially, metal mesh baskets filled with slate limestone stacked on top of each other," says Schneider. "It proved to be extremely difficult to achieve precise height measurements with this system, and it was also difficult to interface with traditional materials. Also a challenge was getting clean cuts and finished edges using a tropical marine hardwood/plywood from the Philippines as an interior material." However, Schneider stresses that the extra effort expended on construction has been worth it. "For us it was a unique undertaking, and the final results are really beautiful." With a soft opening scheduled for later this summer, the City of Edmonton hopes that the Borden Park Natural Swim Experience will become a mainstay of recreational activity for locals and tourists. "This is a legacy project for us and we're proud of how it has turned out," says Banford. "The architects, EllisDon and the sub trades have outdone themselves, and we think end users will be delighted by the experience." A LOCATION 7615 Borden Park Road, Edmonton, Alberta OWNER/DEVELOPER City of Edmonton ARCHITECT/LANDSCAPE ARCHITECT gh3 HERITAGE ARCHITECT ERA Architects Inc. GENERAL CONTRACTOR EllisDon Construction Services Inc. STRUCTURAL/MECHANICAL/ ELECTRICAL CONSULTANT Morrison Hershfield POOL CONSULTANT Polyplan TOTAL SIZE 8,826 square feet (building site) TOTAL COST $14.5 million 3:47 PM 3:45 PM 3:43 PM

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