Waimea Water – Waimea Dam Development: Gamechanger for area

“Water is New Zealand’s competitive advantage and our region will now be able to use it to support and grow our local economy and environment.”

Mike Scott, CEO of Waimea Water Ltd

Due to be commissioned in September this year, the Waimea Community Dam is a courageous game-changer that will secure water supply in the Nelson Tasman region for the next one hundred-plus years.

Located on the Lee River in the Lee Valley, just southeast of Brightwater, the dam is one of the region’s most important infrastructure projects ever, and the first large dam to be built in New Zealand in 25 years.

When completed, the reservoir created by the dam will contain approximately 13 million cubic metres/13 billion litres of water, and will be the first publicly funded large dam built in New Zealand since the Clyde Dam was completed in 1992.

A public/private partnership between the Tasman District Council (TDC) and Waimea Irrigators Ltd (WIL), the project will deliver a diverse range of benefits including water security for the region and better river health and water quality for people, plants, fish and animals.

The dam is also expected to strengthen the local economy, delivering an estimated $600-$900 million to the Nelson Tasman region in the first 25 years, through the success of primary industries and the subsequent growth of associated secondary and tertiary industries.

In 2018, Waimea Water Ltd (WWL) was established as a Council-Controlled Organisation (CCO) to manage the construction, operation and maintenance of the dam.

The project began in March 2019, with site works commencing August 2019.

Wellington consultancy Damwatch Engineering Ltd provide engineering for the dam and ensure it is constructed in accordance with the design. Their work is peer-reviewed by GHD Engineering.

Construction is being carried out as a joint venture by Fulton Hogan and Taylors Contracting Ltd.

At 53 metres high, 220 metres long and six metres wide at the crest, the dam is a concrete-faced rock-filled embankment and has been designed to the latest and highest international design standards under New Zealand and International Dam Safety Guidelines.

“This project is a significant scale for our region, and even our country,” says WWL CEO Mike Scott.

“The embankment is constructed of nearly 500,000 cubic metres of rock, and, when finished, it will have close to 30,000 cubic metres of concrete and more than 2,000 tonnes of reinforcing steel.”

The reservoir sits behind the dam and goes up the Lee Valley, holding enough water to cover a one in fifty-year drought.

During dry periods, the dam’s stored water is released to maintain even flows in the Lee and lower Waimea rivers.

The flowing rivers top up the Waimea aquifers to maintain water levels for extraction by horticultural and domestic water wells, reduce the risk of saltwater intrusion from the coast and maintain a healthy river habitat for plants and animals.

The first structure to be built was the 160-metre-long diversion culvert, which diverted the river to create a dry building site for construction.

Once the dam was completed, above the diversion culvert, in October 2022, the culvert was partially closed to install the temporary diversion pipework.

When this temporary pipework is commissioned in February 2023, the culvert will be closed and the reservoir will commence filling.

The dam and spillway are now sufficiently complete to function and accommodate floods.

As the reservoir fills, mechanical and commissioning works are then expected to be completed in September 2023, one year and eight months later than the original plan.

Mike says these delays have resulted from the dam structures taking longer than planned to complete; the impacts from COVID-19; weather events and the period of time to complete the river diversion and mechanical works expected to take over twice the time originally planned.

Despite significant cost overruns from the original $104 million budget resulting from unexpected geological issues impacting the dam’s construction; higher than expected mechanical and electrical costs during a period of high inflation; and COVID-19, Scott says the dam remains the most cost-effective solution for the region, recognising the aggregation of needs.

“There are a number of things that make this project remarkable. Firstly, a small team came together to build New Zealand’s first large dam in more than a generation.

Secondly, it’s TDC and WIL getting together and coming up with a joint solution to their respective water needs, for the greater good of the economy and environment.

Thirdly, while many regions in New Zealand are facing a lack of water storage and security, particularly in the face of climate change, TDC had the courage to execute its strategy and build the dam, which is a massive project for a small region, providing water security for generations to come.

New Zealand is two islands with lots of mountains and weather, but over 97% of our water just goes out to sea.

Water is New Zealand’s competitive advantage and our region will now be able to use it to support and grow our local economy and environment.”

© Waterford Press Ltd 2023 – Independent Print Media New Zealand

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