The Concourse storage tank provides 13,000m3 of wastewater storage which reduces overflows from Watercare’s Western Pump Station to the level permitted under the Auckland Air, Land and Water Plan.
Procurement of the tank was via a FIDIC design-build contract awarded to Brian Perry Ltd, with Beca as their designer. The design-build approach allowed the contractor to optimise the tank shape, aspect ratio and construction techniques to best suit their resources and capabilities and hence provide the best value for the project. The design-build approach reduced the overall completion time by streamlining the transfer from design to implementation as parts of the work could be approved and implemented earlier in the programme and other elements such as electrical and control system design could be completed during the construction phase.
This paper outlines the technical challenges, the design solutions developed and innovative construction techniques used to construct the tank. The main tank was constructed using ‘double-tee’ precast concrete sections, whilst the inlet pumping station was constructed as a caisson and sunk into the ground. The tank has an automatic cleaning system that uses a series of Steinhardt flushing gates that are released in sequence to scour the tank floor.