With Environment Canterbury increasing pressure on dairy farms, Swannanoa farmer Brian Tinomana saw the need for more effluent storage on his 300ha farm.
His search for a contractor led eventually to a contract with Worthington Contracting, which managed the entire project from resource consent requirements and design to construction and reinstatement. “I looked around a few years ago, then [Worthington Contracting] came and saw me,” Tinomana says.
To comply with his current Environment Canterbury resource consent, he needed increased effluent storage and effective irrigation systems. Tinomana already had effluent distribution across his farm via a centre pivot irrigation system, helped by relatively free draining silt loam soil.
He had very little storage capacity however which meant risking saturation problems during periods of heavy rain. Any release of effluent waste could then have caused pooling in which the waste water sinks below the grass root level, contaminating the environment. In this event the stagnant water can prevent surrounding grass and plants from receiving nutrients and can directly affect milk yield, since cows will decline to eat grass covered in effluent.
Worthington completed the design and excavation while subcontracting the transfer systems, electrical work and pond lining to Plucks, Nairn Electrical and Viking Containment, respectively.
The completed pond measures 72m x 32.5m with a 6,454m3 volume. Anticipating the effects of flooding, the pond batters were built 500mm above ground level. To save time and costs, the soil cut from excavation was used to build the batters. Geotextile was installed to protect from rough ground conditions before a 1.5mm HDPE liner was installed to achieve the resource consent conditions of less than 1x 10-9 m/s permeability.
The pond was constructed precisely between the wheel tracks of Tinomana’s centre pivot irrigation using GPS, helping to maximise the pond size while minimising the area of favourable grazing paddock it occupied.
The completed pond now gives Tinomana the sufficient amount of storage he needs to satisfy Environment Canterbury. He can store at least 6.5million litres of effluent and stormwater run-off before having to disperse it across his paddocks.
Tinomana was satisfied with the overall project and his new pond. “I’m very happy. As far as a turn-key operation is concerned, from resource consent through to turning the key everything has run smoothly.”
Most recently the Effluent Pond won the 2014 New Zealand Contractors Federation (Canterbury/West Coast Region) award for contracts up to $250,000. It was also the key project in Worthington’s prize-winning entry in the Enterprise North Canterbury Business Awards, agribusiness category.
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