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Training bank construction under way in Shotover delta

Sunday 17 July 2011, 8:25PM

By Otago Regional Council

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OTAGO

Construction of training and revetment banks for the Shotover River delta has begun, extending from the existing oxidation ponds and out about 700m from the edge of the delta, where the Shotover meets the Kawarau River.

Otago Regional Council director of environmental engineering and natural hazards Gavin Palmer said around 15,000m3 of rock and gravel from Victoria Flats landfill would go into the banks.

This would assist the passage of floodwaters at the junction of the Shotover and Kawarau Rivers and provide protection to the Queenstown Lakes District Council’s proposed wastewater disposal field, Dr Palmer said. The training line will help direct the flow of the river and affect the deposition of gravel shifted by floodwater.

QLDC strategic project manager Martin O’Malley said the revetment line will reduce erosion and scouring on the river’s western flank. It is also a condition of the wastewater designation to prevent erosion of infrastructure put in place for treated wastewater disposal. It was most cost-effective for the revetment to be constructed at the same time as the ORC’s training line, Mr O’Malley said.

Studies show that the flood hazard for Lake Wakatipu is increased whenever the Shotover meets the Kawarau at the western side of the delta. Dr Palmer cautioned that while the training line at the western side of the delta will prevent that happening, it will not eliminate the flood risk for Wakatipu communities.

Members of the public should keep away from the area during construction for safety reasons. The construction, which is happening now, because the river flows are lowest in winter, is due to be completed by early September. It involves excavating and stockpiling of river rock.