Waimea Community Dam

Taylors Contracting Waimea Community Dam Earthworks Manager Alex Smith discusses key project challenges and achievements during the past year.

Key achievements (June 2022 – June 2023)

One of the big challenges for everyone working on the project was that the last big dam in the country was the Clyde Dam in the 1980s and 1990s. Most of the contractor staff working on the Waimea Community Dam have had to innovate and problem-solve without having worked on a dam project like this before.

The project has encountered a number of unexpected factors, such as the rock geology conditions on the site (i.e. the hardness and softness of the rock) and the relative slope stability. This resulted in an embankment design with different types of fill materials and fill zones that the earthworks team had to deal with.

“We thought it was going to be a lot harder to excavate, but the soft rock created its own challenges with slope stability and worker safety. A lot more temporary works were needed for worker protection because of the geology we found.

“We have very strict specifications to build the dam to. Managing fill placement and bulk cut operations has been much more tricky than usual. You only have one chance to do it right. You’ve got lots of things you’ve got to keep juggling. We‘re focused on doing things safely and efficiently, making sure we’re getting all our documentation and communications in writing and trying to look forward for construction planning and problem solving. It makes the work days go quickly!”

At the peak of the project, Taylors had a team of approximately 25 working onsite and was running an impressive array of equipment, some of which was purchased specifically for the project.

“At peak time we were running up to seven dump trucks. We bought a 90-tonne excavator to work here, we had a 50-tonne excavator, and five or six other-sized 30-tonne to 20-tonne diggers. We bought a new drill rig for this project and had three bulldozers working onsite at one point.”

After nearly 20 years in the construction industry, it has been a real thrill for Alex to be involved in this project and he’s keen to work on large infrastructure projects in the future.

By the end of May 2024 the permanent works for the discharge pipework to discharge water from the dam down the Lee River will be completed. Once Taylors finishes dam construction, Alex anticipates Taylors will continue to work with adjacent landowners, building and maintaining private forestry roads in the valley. How will the dam work once the project is completed?

“When the reservoir fills up and is full for most of the year it will flow over the spillway,” says Alex. “Water will come over the spillway/flip bucket and run off down the river. During the winter period the reservoir will hold water, so it fills up for later use. In the summer when people start irrigating down on the plains or if there’s a drought the intakes will become active and they’ll start drawing the reservoir down maintaining the river flows.

“The water will go through the intakes into a pipe which runs through the concrete conduit under the dam embankment. The pipe will discharge into the river so the community can use the volume of water in the summer period and avoid restrictions on irrigation during drought conditions and continue irrigating on the plains.

“People using the river for swimming and other recreational activities won’t notice any difference, in fact there will be more flow in the river which will make the swimming spots better.”

Waimea Community Dam Joint Venture Key Personnel

John Roche

Current Project Director

Fulton Hogan Taylors Joint Venture

Matt Taylor

Construction Manager

Fulton Hogan Taylors Joint Venture

Alex Smith

Earthworks Manager

Fulton Hogan Taylors Joint Venture

Project Highlights

Bulk Cut operations

During the embankment cut-to-fill operation.

Parapet wall installations across the crest of the dam

76 units, each unit weighing 21 tonne, had to be placed with a 120-tonne crawler crane to an accuracy of +/- 12mm. Units had to be placed and keyed together. Taylors controlled the works and did the base prep work, which had to be accurate within a millimetre so that the 4.4m high units sat correctly.

Crest backfill

The way in which filter zones come together at the crest of the dam and interlocked together required a precise building sequence and placing fill within a confined working space at the top of the dam.