Horowhenua leading the way with land-irrigated wastewater

The successfully-completed upgrade of the Shannon Wastewater Treatment Plant takes Horowhenua a significant step closer to seeing nearly all of the District’s wastewater irrigated to land.

District Mayor Brendan Duffy says that in moving towards land discharge for treated wastewater, the “Council is leading the way, both regionally and nationally”.

The treatment plant upgrade was celebrated this afternoon when it was officially opened by Minister for the Environment, the Hon. Dr Nick Smith.

The new 10,000 cubic-metre storage capacity and land irrigation system will result in 80 percent of the treated wastewater discharge not entering the nearby waterway. Previously, and ever since 1969 when the plant was built, all the treated wastewater had been discharged to water, via Stansells Drain that fed into the Mangaore Stream and into the Manawatu River.

Now, for approximately 355 days of the year all the treated wastewater will be irrigated over purpose-bought Council-owned farmland. For the remaining 10 days of the year, on average, when the Manawatu River is in high flow, the treated wastewater will be discharged through two 1 x 6 metre gabion baskets - wire mesh encasing small rocks - to an artificial wetland and gently-sloping channel planted with grass and flax, leading to an adjacent waterway. Council is undertaking a five-year trial to explore if more than the 80 percent can be irrigated to land and subsequently reduce the discharge to water even further.

Mayor Duffy says the project was completed well-within the allocated budget of $9.5 million and this enabled further optimisation of the whole system. The funding included a Ministry for the Environment contribution of $1.192 million.

“$9.5 million is a significant sum and shows how much Horowhenua District Council has committed to improving the Manawatu River and demonstrates its commitment to the Manawatu River Leaders Accord,” he said.

Horowhenua has six community wastewater discharges. With the completion of the Shannon treatment plant’s land discharge scheme and the planned upgrade for the Foxton Wastewater Treatment Plant, currently going through the resource consent process, Horowhenua will see 100 percent of the District’s wastewater discharged to land and not into waterways.

“For a relatively small district this is an astounding achievement. Only 22 percent of wastewater plants regionally, and 30 percent nationally, have a land-discharge component,” Mayor Duffy said.

“More importantly on a volume basis, about 95 percent of the District’s total wastewater volume will be irrigated to land in a way that not only avoids wastewater discharging to water, but also provides for treatment of nutrients and pathogens and in a way where the vegetation grown can use the applied water. This compares to only 4.5 percent of wastewater generated at a national level being beneficially used for irrigation.”

The Shannon Wastewater Treatment Plant upgrade project was approved by the Environment Court in May 2015, following over two years of consultation and mediation with local iwi and other interested parties. Council worked within strict Resource Consent criteria to complete the project.

“The Council has not completed this work alone. We have worked with the community and formed the Shannon Wastewater Treatment Plant Working Party which included Horizons Regional Council, Iwi, contractors and consultants. This group has been instrumental in delivering this project,” Mayor Duffy said.

“Council is currently going through a consenting process to also remove 100 percent of the treated wastewater discharge from the Foxton Loop and irrigate this to land. We are sincerely committed to cleaning our waterways in a responsible manner and take this chance to thank all stakeholders involved in this journey.”

ENDS

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