Customer: Queenstown Lakes District Council
Contract: Construct only
Location: Queenstown, South Island, New Zealand
McConnell Dowell signed the official contract to complete Stage Three of the Shotover Wastewater Treatment Plant Upgrade in early July 2023.
The project is 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 ‘Activated Sludge Treatment’ method.
The new clarifier, reactor tank and other improvements will future-proof the plant and double its current capacity. The new process is more efficient than the traditional effluent treating effluent to a higher standard.
Our approach to planning the project has been focused on finding simple, sustainable ways to upgrade the plant while minimising disruption to the existing plant and impacts on the environment.
The programme has been streamlined by planning work so it can be delivered across multiple areas simultaneously while managing operational interfaces.
The staging of the earthworks means we can decommission pond 1 and excavate for the ground improvements with one activity.
MCD’s careful planning has enabled the work to be programmed with only a single full plant shutdown. Close coordination with the plant team on timing, scope, and process will ensure the work is completed with minimal disruption.
The method developed is designed so we can reuse and recycle spoil and vegetation and look to recruit, buy materials, and contract services locally.
The team will reuse 10,000 m3 of spoil generated during the site clearance. About 3500 m3 will be shaped into a protection bund so the team can safely drain and clean out the old oxidation ponds. The balance of spoil will be used to build the new stormwater attenuation area and the overflow pond.
The sludge from the old ponds will also be treated using geobags. The bags allow the water to evaporate, kill bacteria, and manages the odour while this occurs. The dried sludge will then be blended with material from the site and topsoil to form the new embankments of the calamity pond.
Stabilisation can be a more sustainable and cost-effective option than engineering and building big concrete foundations. We will reuse existing material wherever possible, and aggregate and cement will be mixed in to achieve the compaction rates required, forming a mixed mass raft foundation.
One of the first sustainability initiatives the team completed was building a wood shed and donating firewood from early vegetation clearance works, to local charity Happiness House. Watch a timelapse of the work below.
August 2023 - the temporary bund construction is 50 percent complete
Animation of the progrmanne and new plant process.