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Customer:Queenstown Lakes District Council Contract: Construct only Location:Queenstown, South Island, New Zealand   |
Fast Facts
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Protecting the environment and minimising disruption to existing operations were key to securing the second stage of the Shotover Wastewater Treatment Plant Upgrade in picturesque Queenstown.
Our project was the third (and final stage) of Queenstown Lakes District Council’s 20-year-long programme to transition the plant from the traditional Biological and Aerated Pond Treatment processes to the more effective and efficient ‘Activated Sludge Treatment’ method.
The new clarifier, reactor tank and the other improvements that we delivered doubled the plant’s capacity and helped future proof it to enable growth.
Efficient Programming
We streamlined our programme by working across multiple areas simultaneously, all while managing operational interfaces. For example, the staging of the earthworks meant we could decommission pond one and excavate for the ground improvements at the same time.
Our planning enabled the work to be programmed with only a single full plant shutdown. Close coordination with the plant team on timing, scope, and process also ensured the work was completed with minimal disruption.
Sustainable Construction
The method developed was designed so spoil and vegetation could be reduced and reused, and the team could use local suppliers, materials and recruit from the nearby commnuity.
The team reused 10,000 m3 of spoil generated during the site clearance. About 3500 m3 was shaped into a protection bund so the team could safely drain and clean out the old oxidation ponds. The balance of spoil was used to build the new stormwater attenuation area and the overflow pond.
The sludge from the old ponds was treated using geobags so it could be reused. The bags allowed the water to evaporate, killing bacteria, and managing the odour while this was taking place. The dried sludge was blended with material from the site and topsoil to form the new barriers of the calamity pond.
Ground stabilisation was a more sustainable and cost-effective option than engineering and building big concrete foundations. We reused existing material wherever possible and used aggregate and cement to achieve the required compaction rates and to form a mixed-mass raft foundation.
A significant sustainability win on the project was deciding to use e-crete, a low-carbon concrete, produced by Allied. The team reused all the concrete they ordered by casting any leftover concrete into blocks for use around the site. Find out more about e-crete here.
Another of the first sustainability initiatives the team took part in was building a woodshed and donating firewood from vegetation clearance on site to the local charity Happiness House.
The team supported Happiness House throughout the project, running the Queenstown Marathon to raise money and helping plant native trees with the Whakatipu Reforestation Trust.
Watch a project update from 2025 or visit our YouTube channel to see other videos about the project.
