In early October 2021, the Waimea Dam team completed 100 hours of multiple back-to-back concrete pours on the dam’s spillway. This nine-shift, 24-hours-a-day marathon was followed shortly after by a 600 cubic metre pour on the spillway’s ‘flip bucket’. The flip bucket, shown here, is designed to reduce the velocity (hence friction) of water on the spillway, by sending it upwards and ‘entraining’ air’ in it.

The spillway and dam face’s concrete is being laid by a process known as ‘slip forming’. Large hydraulic jacks, moving at less than 300mm per hour up the spillway, allow the team to apply concrete through formwork and shutters. It leads to a highly specified finish which, on the spillway, avoids cavitation (water undermining the integrity of the concrete).

“The forces of the water here require higher specifications for the concrete’s placement, finish and curing than for almost any other structure,” says Construction Manager Matt Loach.

In late 2022 the first of the 13 billion litres of water will enter the reservoir. Around 30 km south west of Nelson, the Waimea Dam is the largest dam to be built in New Zealand in 40 years. Fulton Hogan and Taylors Contracting are building it for Tasman District Council and Waimea Irrigators Ltd to irrigate the fruit, vegetables, hops and grapes of the Waimea Plains, alleviating the effect of crippling droughts in recent years.

The dam will be 180m wide at the base, six metres wide at the crest, 55 metres high, 220 metres long at the top and 80 metres at the base.