Huge pond to enhances efficiency

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Barrhill Chertsey Irrigation’s (BCI) new multi-million dollar water storage facility was made on time and within budget. It will give BCI members access to water at peak times.┬áReporter Toni Williams found out about BCI and the Akarana Storage Pond construction.

 

 

Akarana Pond gets its name from the farm site where it sits, on Barkers Road near Methven.

The pond was designed by NZ company Damwatch Engineering, and built by Canterbury based contractors, Rooney Earthmoving Limited.

Carrfields Irrigation, Electraserve and Rubicon Water Management were also involved.

At a cost of $11million, and constructed over eight months, it came in on time and within budget.

It was fully funded by BCI and its bankers, with BCI shareholders to service the ongoing cost of infrastructure.

BCI board chairman Malcolm Cairns said the completion of the pond, which sits next to the Rangitata Diversion Race (RDR) northeast of Methven township, was a “significant step forward for BCI” who had a strong focus on investing in high quality intergenerational infrastructure.

The 1.5 million cubic meter storage pond was considered an enhancement to the scheme’s operational efficiency and reduced the reliance of on-demand pumping.

“It allows us to reduce our reliance on the pump station above us at Highbank…allows us to make more efficient use of this water.

“It dovetails neatly into our strategic initiative of owning key pieces of infrastructure where appropriate.”

The pond enables BCI to supply the peak seasonal demand for irrigation water without requiring additional pumping capacity at Trustpower’s Highbank Pumping Station.

While traditionally irrigation ponds were designed to improve reliability of supply, this dam was to store water for the periods of peak demand from BCI’s shareholders.

“Rather than install more pumps down in the Rakaia River and pay all the electricity connection charges and those things, it was more cost effective to build this, then hold the water and release it for a few weeks of the year when demand was high,” BCI general manager John Wright said.

It gave BCI better control around the long-term costs of delivering water, which was expected to provide economic benefits to the local community.

After two years of successful collaboration between BCI and local landowners, regulators, and contractors construction started February 2018.

The grass was peeled away, top soil and shingle was used to create the floor and banks.

The shell was built out of shingle.

Then gravel embankments were covered with geotextile cloth – an internal HDPE geomembrane liner was used on the sides and a loess/silt liner was used on the base of the pond.

It was filled using diesel generator-powered transfer pumps from the RDR and was connected to the existing BCI Methven pipeline to utilise the water by gravity.

Despite the pond being built ten metres high, the water in the site has a maximum water depth of five metres.

It is considered unsuitable for recreational use, due to the slippery state of the high sides.

When full it will give BCI 12 to 15 days of water during peak delivery times.

BCI’s consent to take water from the Rakaia River has restrictions, some months of the year, based on minimum environmental flows in the river.

The company use Lake Coleridge as their primary storage site and have a contractual arrangement with Trustpower Limited (who manage Lake Coleridge and hydro generation from the lake) that surplus water not used by irrigators when the river is flowing strongly, is stored in the lake and released to meet demand when the river flows were below minimum levels.

The water from the Akarana Storage Pond is filled from the RDR and used to satisfy peak demand.

WHO IS BCI

BCI started with two separate farmer groups seeking to source water for the Barrhill and Chertsey areas. With the obvious source of water being the strong Rakaia River, Barrhill Chertsey Irrigation Limited was formed as a farmer owned co-operative company in 1998 and in 2001 was granted a consent to abstract 17 cumecs of water from the river and irrigate 40,000 ha in Mid Canterbury.

Nearly a decade of developmental challenges ensued before BCI delivered its first irrigation water in 2010.

Its Development

The initial BCI development was a great example of collaboration within a community.

BCI formed a joint venture with local electricity lines co-operative Electricity Ashburton Limited in late 2009, and that joint venture developed the first BCI irrigation infrastructure in 2010.

It also licensed three cumecs of water to the Acton Scheme which was developed in the same year on the back of existing stock water infrastructure east of Rakaia.

And entered contractual arrangements with Trustpower Limited to install and operate river intake, fish screening, and pumping facilities to deliver the water from the Rakaia River to the RDR using some of the existing Highbank Power Station facilities.

Water swap arrangements were also agreed with RDR Management Limited to give water delivery to the BCI buffer ponds in the upper plains. BCI installed a piped distribution network from those buffer ponds delivering pressurised water to irrigator customers.

New projects

In 2015 BCI embarked on its next big development installing a Rakaia River intake and pipe network spanning from Barrhill to Chertsey. The infrastructure included a small hydro generation plant to utilise water for electricity generation. By 2016 BCI was delivering water to 20,000 ha in the district, having grown from 7,000 ha in 2010.

In 2017 Barrhill Chertsey Irrigation Limited (BCIL) got 100% ownership of the irrigation scheme infrastructure, buying out the share of Electricity Ashburton Limited, who had helped with the development of the scheme, providing technical support, governance support, and confidence to bank funders.

BCI Today

Mid Canterbury continues to be a powerhouse of food production in New Zealand, now comprising over 220,000 ha irrigated area, of which BCI makes up around 10%. It has nine main distribution networks across the district.

BCI is focused on being a positive influence in the local community, especially around environmental management.

The Akarana Storage Pond is their latest achievement, and having successfully been commissioned at the end of October 2018, was expected to benefit BCI shareholders for years to come.