December 1, 2013
By James Whitaker
To be a competent builder, one must have the ability to adapt quickly to manage unusual known or unknown circumstances as they arise throughout the design-build process. This reality is particularly palpable in the business of aquatic construction. Pool and spa builders face many of the same challenges as those who construct homes and commercial buildings, in addition to the various challenges that are specific to the aquatics industry. To provide the owner with quality assurance, pool/spa builders have to make decisive and often radical changes to the equipment on site, labour allotment, labour skill-sets, design components, and special provisions to manage site conditions effectively.
This adaptability was necessary throughout the design and construction of the Wayne Gretzky Sports Centre (WGSC) expansion project in Brantford, Ont., which officially opened in September, where Acapulco Pools Ltd., of Kitchener, Ont., installed a new 25-m competition pool and lifestyle pool.
In order to accommodate one of the fastest growing regions in Canada, the city recognized the need to adapt by upgrading and expanding its existing sports centre. In fact, the WGSC has been the only indoor aquatic facility in Brantford since it was built in 1974. The facility needed an upgrade and its overflowing schedule demanded more space to accommodate the region’s growing needs. Numerous programs operate out of the facility, including swimming lessons, which drew more than 7,500 participants in 2012. The existing 65-m pool is an essential attraction to the facility drawing athletes from surrounding areas such as Hamilton, Simcoe, and Six Nations.
Brantford’s lack of aquatic space and growing demands made it necessary to conduct a study to review the facility’s degree of sustainability in the years to come. Host to community activities, swim team practices, synchronized swim training, diving competitions, Special Olympics team events, and more—the aquatic centre had reached its capacity.
Thanks to a Trillium Grant, proper studies were allowed to be conducted to assess the athletic facility and project the possible future for the WGSC and the region of Brantford. The grant outlined a broad vision of the facility’s future, bringing together the community’s needs in a new aquatic and multi-purpose athletic facility that would help promote an active and healthy lifestyle.
The aquatics addition to the facility was originally going to comprise a lifestyle pool and a leisure pool; however, the latter was replaced with an eight-lane, 25-m pool, which is a key component for athletes currently training at the natatorium as well as those looking for competitive aquatic space. This pool is an integral part of the aquatic program as it adds essential space for additional activities and special events at the facility. It will also host numerous competitions and swim practices, which will free up time in the 65-m pool and leisure pool for various community events. Adding to the natatorium’s multi-event capacity, sliding doors were added between both pools to allow for two separate events to take place at the same time. To merge the new pools with the facility, Ball Construction Ltd., removed a portion of an existing wall.
The competition pool comprises Omega starting blocks (similar to what was used in the 2012 Olympics), and spray features, while a timing system for competitive swimming was roughed-in. The lifestyle pool features a shallow bathing area, which is suitable for swimming lessons, as well as a massage bench, spray features, and ballet rails for water fitness.
As part of the project, a new gas chlorination system, capable of providing sanitation for both new and existing portions of the expanded facility, was also installed. The upgraded system, designed by Aqua Plans Design Group in Kitchener, Ont., also includes digital scales and a remote readout panel located in the lifeguard’s office. This panel displays individual tank weights, and will alert staff of high atmospheric chlorine levels in the event of a leak.
Despite the success of the grand opening, no project is without challenges, and this installation was no exception.
For instance, the main challenge was integrating the new expansion as architecturally seamless as possible without disrupting any of the ongoing activities or diminishing the community’s enjoyment of the facility. This meant the facility’s existing 65-m pool, complete with bulkheads, dive tower, and a water slide—which transitions from indoor to outdoor—needed to remain open during construction.
The existing sanitary sewer system was also a consideration in constructing the new pools as the backwash volume and flow rate would exceed the capacity of the system if sand filters were installed. Therefore, to reduce the amount of backwash water, the new pools were designed with regenerative diatomaceous earth (DE) filter systems, which provide superior filtration and water clarity while using a fraction of the backwash water required for sand filters. These filters, along with the implementation of a backwash water holding tank, allow the discharged water outflow to be regulated, minimizing the load on the existing sanitary sewer system, and negating the need to install a larger sanitary system.
Further, as soil conditions are always a major consideration for pool designers/builders, soil engineers were consulted by the project’s general contractor, Ball Construction (Kitchener, Ont.), at the onset of the project to perform bores for a snapshot of the site’s average conditions. The resulting reports indicated very fine saturated sand and a high water table, making it clear from the get-go this was not going to be a typical, straightforward build.
After obtaining a dewatering permit, site wells were installed below the excavation elevation at intervals of approximately 2 m (6.5 ft) around the perimeter of the excavation. Dewatering pumps operated 24-7 to evacuate the area to allow construction to progress. Upon excavation, the soils investigation proved accurate regarding the nature of the material as the sand substrate had no cohesion and flowed like sand in an hourglass. With any rainfall, it would flow like lava to the deepest parts of the pools.
Ball Construction performed the excavation, which required the footprint of the dig to be expanded to compensate for the low angle of repose established by the sand. In order to construct the pool floor, which had areas of slope up to 27.5 per cent, Acapulco Pools needed to install a mud bed of lean fill over the excavated slopes to allow workers to move around the excavation effectively. This also prevented the pool’s sloped areas from eroding when it rained. A footing also had to be poured to provide a suitable base to form the pool walls as the loose sand substrate would not support any formwork, making it impossible to retain a set elevation in such a ‘fluid’ material.
Finally, the lap pool’s design called for an accessible tunnel to be installed around the entire perimeter, which would allow all of the pool/drain piping and heating, ventilation and air conditioning (HVAC) ducts to be inspected. It would also eliminate the possibility of moving seals, which can damage buried pool piping.
Therefore, the design needed to account for the high water table around the pool deck. Both the pool and the accessible tunnel needed to be protected from leaking and hydraulic lift. To do this, hydrostatic pressure relief valves and collection tubes were installed in the main drains to allow excessive external water pressure to be relieved into the pool.
Hydrostats work great, but the truth is they are not an absolute assurance the pool will never float. This was a real concern for the new pools being installed given the known water table condition.
To combat this, Halcrow Yolles designed portions of the pool floor to be sufficiently massive (almost 1 m [3.3 ft] thick), making the pool shell heavier than the water it would displace. Further, with this ballast in place, it is impossible for the empty pool to become buoyant in the surrounding ground water even if the hydrostatic relief valves became plugged.
When there is so much water around a structure, corrosion of the reinforcing steel is also a concern; therefore, a C-1 concrete mix was provided to offer corrosion resistance. Sufficient and well-placed water stops and concrete coverage over the steel was also particularly important in this scenario. The specified C-1 concrete mix design for the pool tank included a liquid corrosion inhibitor admixture, which is added during the batching process. It chemically inhibits the corrosive action of chlorides on reinforcing steel in concrete. The corrosion inhibitor is also known to act as a concrete set accelerator, which aggravated the slump and made it more difficult to place the concrete. A transit time of 45 minutes to an hour from the batching plant to the site made the concrete difficult to pump, place, and finish, thus providing no forgiveness for mistakes or moving too slowly.
Further, as the concrete swimming pool vessels were constructed during the hot summer months, Acapulco Pools provided continuous water curing of the concrete to prevent it from cracking. To do this, the concrete was covered with burlap, which soaked up the water to keep the pool’s walls and floors constantly wet. In some cases, the concrete mix design needed to be changed and the concrete and substrate had to be protected via use of tarps and water to keep some moisture on the structural steel to prevent it from overheating. Finally, as the concrete’s set time was much shorter, more labour was required to pour a slab than originally anticipated.
Wind was another factor as it can dry out the concrete’s surface along with wreaking havoc on layout strings and tarps. Snow removal also presented a challenge as the concrete needed to be insulated to allow it to cure properly.
As is often the case with tunnel pools, a surface-applied crystalline waterproofing was specified for the project. The chemicals present in the penetrating cementitious material react with moisture and free lime in the concrete, creating insoluble crystalline complexes, which seal the capillaries and minor shrinkage cracks in the concrete. Once the crystalline is cured, it must be completely removed from the surface for thin set tile applications as it acts as a release agent causing tile delamination. Typically, the surface is blasted to a concrete surface profile (CSP) between three to five (i.e. a light to medium-heavy shotblast) for tile installation. This is a fairly aggressive texture where the aggregate is significantly exposed. The corrosion inhibitor added to the concrete is also known to promote strength development in the concrete. The specified C-1, 35 MPa mix design has 28-day cylinder test strength results of up to 68.9 MPa. This remarkable high strength made concrete blasting more difficult as well as more time consuming than it would normally take to achieve the proper CSP. To speed up this process, Acapulco Pools used a 40,000 PSI hydro blaster.
Both pools were finished with 3175 x 6350 mm (125 x 250 in.) ceramic tiles that have a 100-year warranty. The lap pool has oversized deck level gutters with PVC grating to manage surge conditions and keep the surface of the pool still during competitions.
The lap pool also has the usual requirements of a level-modulated surge tank and sufficient surge capacity based on bather load; however, the gutter around the perimeter is approximately 381 mm (15 in.) deep and has a tapering width of 305 mm (12 in.) to 203 mm (8 in.) from top to bottom.
To allow for the installation of the gutter, the reinforcing steel and bearing strength adequate to carry the suspended slab deck—approximately 75 per cent of the wall’s mass—is on the top of 50 per cent of the wall. As such, the wall is quite top heavy, unbalanced when initially formed, and vulnerable to fracture early in the cure process before the suspended slab is in place.
To create the haunch block-outs were stick-formed inside the forms to create the proper shape. The outside face of the formwork was left in place to hold the top heavy portion of the walls while the concrete cured.
|AQUATICS AT THE WAYNE GRETZKY SPORTS CENTRE|
|The Wayne Gretzky Sports Centre (WGSC) features a number of aquatic amenities, including:
• 65-m swimming pool
• 25-m competition pool
• Diving boards
• Warm-water pool
• Hydrotherapy pool
• 45-m (150-ft) waterslide
• Various pool toys and slidesAs part of the expansion, the WGSC also offers a number of aquatic programs and activities, including:
• Swimming lessons
• Water fitness classes
• Length & circle swimming
• Recreational swimming
• Aquatic day camps
• Registered aquatic programs
• Pool party packages
Adaptability is the name of the game when it comes to construction. Unlike other professions, construction is not only affected by circumstances such as human error, personality conflicts, or budget issues, it is mostly affected by nature, the one thing that is completely out of the builder’s control.
Whether it is instable ground or heavy snow, it is important to always adjust to the circumstances that are presented. It is possible to bend without breaking: adapt, find a sustainable resolution and succeed. There is no question the WGSC will thrive in the future.
James Whitaker is a project co-ordinator for Acapulco Pools Ltd., a commercial and institutional aquatic center builder and service provider based in Kitchener, Ont. After completing the architecture-construction engineering technology course at Conestoga College in 2009, Whitaker joined Acapulco Pools team. During this time he has completed approximately 60 projects throughout Canada and the United States. He can be reached via e-mail at firstname.lastname@example.org.
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