Description:

The Hunua Views vacuum pump station is located on the eastern side of State Highway 1 between Drury and Ramarama to the south of Auckland. Much of the surrounding land was formerly agricultural and is increasingly being used for residential development. The area is relatively flat with clusters of mature trees. To the east is a quarry and the Hingaia stream which leads from Ararimu to the Pahurehure inlet of the Manukau harbour.

The site is located in the Auckland council with a ‘Mixed Housing Urban’ Planning zone. As the subsequent owner and operator, the pump station also had to comply with Watercare’s engineering standards. Due to the specialist nature of the pump equipment, and to expedite construction, one Building consent was obtained for the building shell while the engineering fixtures were covered by a separate consent.

The Pump station provides wastewater reticulation for up to 1000 dwellings in the adjacent Hunua Views Development which consists primarily of standalone housing with a local centre. The brief required that it relate well to this development, acting as a marker building. In response it was expressed in a functional way with patterned concrete and a utilitarian front yard, while the pitched metal roof and apertures were forms more residential in nature with dynamic roof geometry creating a point of interest. Also key was ensuring that houses to the south were not subjected to excessive noise, so all vents were acoustic rated with none to the south and the Control room was positioned on the south side providing an acoustic buffer to the residential boundary.

Precast concrete panels were chosen as the primary structure due to their structural properties, ability to double as a cladding, durability, acoustic and fire performance and options for aesthetic treatment. Precast construction is also quick to install and quiet, with a significant portion of the work carried out off site. To achieve the irregular roof geometry, each of the 17 prefabricated timber trusses was different. This was simple to achieve with the automated process of fabrication. Dark coloured lightweight metal roofing continued down the walls balancing the weight of the concrete while reducing the scale of the building and accentuating its unique geometry. Removeable steel grate flooring is utilised in the pump chamber for visibility and ease of maintenance.

The pump station had to accommodate very specific engineering functions and required careful coordination between the architect, civil, structural, services & acoustic engineers, precast fabricator and vacuum pump specialist. In order to reduce the size of the steel members, a structural ceiling diaphragm was utilised which also incorporated stringent fire and acoustic requirements. In another instance, to meet both ventilation and acoustic requirements, a 1.2m thick internal louvre (acoustic rating of 12-56 SRI) was installed in the wall between the Pump chamber and Control room. Penetrations in the precast concrete for pump pipework had to be precisely dimensioned prior to fabrication, while a waterproofing specialist coordinated the below ground membranes, joint waterstopping and concrete admixtures.