The new Liz van Welie Aquatics Centre features a swimming facility and adjoining carpark. The unique swimming pools are the first of their kind to be used in commercial operation in New Zealand. It utilises the MagnaPool system, using Magnesium and Potassium, for water treatment. The building ground floor of 1000m2 accommodates two pools [12mx6m and 25mx15m], reception, offices, changing rooms and operational facilities. The mezzanine of 200 m2 provides additional office space and an elevated public viewing area. We were engaged to provide structural, geotechnical, fire and civil services.
Not only was there a tight construction programme to be met, the Natare stainless steel pool manufacturer had strict specification limitations on the backfill material surrounding the pools – no compaction of fill or heavy machinery was allowed adjacent the pools.
“Glue laminated portal frames with hidden epoxy grouted connections are a standout feature of the built space”
The site testing revealed that the ground conditions were variable. This meant we designed foundations that were acceptable for lower bearing capacity. In addition as aforementioned, no compaction of fill or heavy machinery was allowed adjacent the pools. This limitation meant the main supporting foundations for the superstructure needed to be deepened to be founded on material with a suitable bearing capacity.
The set-out of civil works levels to where the proposed finished floor level and adjoining paving areas surrounding the building was challenging. The space available meant that there were minimal in-ground pipes and a reinforced concrete protection slab was introduced. The design of the filter flushing attenuation tank required some special attention. Due to the shallow depths required for the backflow attenuation tank it was decided to adopt a 600dia Solo Plastics pipe placed in the narrow lane to the east of the building. This allowed for a shallow tank with a gravity feed to the existing sanitary sewer connection and avoided the need for deep excavations which would undermine the already constructed buildings foundations. A great result that satisfied the construction team and clients.
There were many fire issues encountered in this project in relation to material selection and perimeter wall fire rating requirements and proximity to boundaries. The most significant issue being the creation of light, air and fire easements to allow the fire spread requirements of the swim school to be taken to the far side of the easements as they will be no-build zones. The west wall design was also considered in relation to fire engineering requirements and the outcome is a design that in its post-fire condition will cantilever. In order to achieve this, deep piles were required due the proximity to the pool and the aforementioned restrictions by the pool manufacturer.
Construction sequencing to meet the tight construction programme meant the building shell was constructed prior to the pool construction. Conventionally, most projects are built from the ground up with deep work done first. In this case, we had to create the concrete floors to receive the pools, and then put the building structure over the top.
Careful planning and close collaboration with the contractor were the key to the successful outcome of this project. The building opened on time and has over 3500 visitors a week, all benefitting from the time and energy that we, the clients, contractor and architect put into the facility.