Careful planning and Auckland weather plays ball for second concrete pour

We're cementing our work to boost the resilience of Auckland’s water supply with the completion of our second of four concrete floor pours at the Redoubt Road Reservoir complex.

The reservoir complex can store up to 120 million litres and more than 80% of Auckland’s treated water passes through it each day. The addition of a third reservoir - which is currently on track to be finished mid-2024 – will increase resilience in the network, thereby future-proofing Auckland’s water supply and catering for growth.

Once completed, the $60 million reservoir will be 106 metres long, 77 metres wide, 8 metres in height and consist of 650 tonnes of steel reinforcing. It will hold the equivalent to 18 Olympic-sized swimming pools.

Because of the success of the first pour in November, the challenge going into the second pour was looking at how we could best fine-tune the approach, says project manager Buena Van Wyk. “After the first pour, it was important for our project team – consisting of specialists from Watercare and Fulton Hogan – to come together and review what did and didn't work.

“By taking learnings from the first pour, we were able to increase the number of concrete trucks as well as run two batching plants during peak traffic hours, which enabled us to maintain our supply and finish the pour ahead of schedule.

"So instead of concrete trucks coming in and out of the area throughout the night, we had them all stationed on site, helping us to get the work done faster.

Van Wyk says the weather during and immediately after the pour was very much on their side. "We had a perfect weather window – especially with the rain and cool weather in the afternoon only a few hours after the final surfacing of the concrete was complete and the covers were pulled over the slab.

Van Wyk says the pragmatic and forward planning and techniques going into the build result from the practical challenges the project team are facing on site.

"Because hills surround the site, landmarks, critical infrastructure, all create access issues and has meant that the reservoir has to be built from the inside out, technically making it a more complex build as materials and equipment are transported onto the site as needed. Our planning and staging really needs to be on point.”
Van Wyk says concrete structures like the Redoubt Road Reservoir are carbon intensive.

“The project team has offset its carbon emissions by adding Fly Ash to the cement mix and transporting clay fill from on-site to help construction works at Puketutu Island, where we are rehabilitating volcanic cones that were quarried in the 1950s, says Van Wyk.

“Besides reducing Co2 emissions, Fly Ash also has greater workability and robustness thereby reducing shrinkage cracks when compared to other water-based cement mixes.

“Overall, sharing fill between construction sites has helped us to offset approximately 559,000 kilos of carbon. Transporting fill from our construction sites like Redoubt Road to Puketutu Island not only reduces carbon emissions but respects Te Ao Māori value of what is given by the land should be returned to the land.”