Media Release
Horizons Regional Council

Friday 26 April, 2012

River Testing Nears Completion

Horizons staff have been working overtime to complete the required sampling for the joint work programme investigating the effects of the Palmerston North City Council’s wastewater discharge into the Manawatu River.

Thanks to the warm, dry weather we have been experiencing over the past few weeks Horizons staff have been sampling nearly every day, including weekends and public holidays in order to collect information. The information is needed in order to understand what’s causing algal growth downstream of the PNCC treatment plant.

If the weather holds, additional sampling may continue for a few weeks until the Manawatu River experiences a high flow event which will flush the river out.

“Our staff have been working really hard to ensure all of the sampling required has been completed, and we have been fortunate with the weather conditions over the past few weeks,” says Horizons head of science Dr Jon Roygard.

“The sampling over this summer will help us identify what the trigger points may be which are leading to reduced aquatic life in the water downstream of the treatment plant discharge compared with upstream.”

A Memorandum of Understanding between PNCC and HRC requires the monitoring programme to complete a range of tests. Two synoptic surveys have been carried out, plus weekly water quality monitoring and periphyton testing. The synoptic survey testing involves sampling at 15 sites in one day. This looks at other potential discharge sources along the river and can characterise how things change (or not) at different points in the river. The water quality monitoring and periphyton testing has been carried out at five sites – three sites up river of the PNCC sewerage treatment plant, and two sites downriver.

Due to the low flows Horizons staff have also been able to carry out invertebrate sampling over the past couple of weeks. This testing of the river’s insect life hadn’t been possible until now due to the lack of a long period (3 weeks) without a high flow event.

Samples are either analysed locally or sent to Auckland, Christchurch or Nelson for testing, with results usually taking about three weeks to come through. All the results will then be available to Horizons staff and PNCC contractors, Opus for analysis. The findings will then be sent to NIWA for independent review.

Results will be presented to councillors of both Horizons and PNCC in August with recommendations on what actions are needed to address the issues in this specific stretch of the river.

ENDS

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