Big pipe hides in bowels of river


Relocating fish and working around endangered birds have been unique challenges for workers constructing a crucial new wastewater pipeline under the Ashburton River.

The $7.7 million pipeline project was officially opened on Monday and contractors Seipp will be staying on to lay another sewer pipe that will take wastewater from Ashburton east to the new river crossing.

The projects have a combined pricetag of nearly $16m and are designed to cope with the growth of Ashburton town for at least another 50 years.

Flush a toilet in Ashburton and the wastewater goes through pipes to the side of the river near Milton Road. Seipp has constructed a new pipeline deep under the riverbed to near
the Ashburton District Council’s treatment plant at Wilkins Road.

It replaces an old siphon that ran under the river, parts of which were in poor condition.
The river pipe runs at a slight gradient and on the Tinwald side a new pumping station was
built to pump it to the treatment ponds at the plant.

From there it is piped 11km to Ocean Farm, where it is filtered by wetlands and irrigated onto farm land.

An electronic smart brain in the pumping station keeps an eye on wastewater levels in two
wet wells and triggers four pumps on rotation to pump it on. The station is powered by
electricity, with generator back-up, so even if the power is out, the wastewater can keep

The river pipe and pump station has been a major project for council projects and operations manager Shyamal Ram. He has been giving regular updates to councillors
during the life of the project.

He moved from Auckland nearly two years ago and has been supervising the work. He
has ushered the project in on time and on budget. He has helped relocate fish when the
bulldozers needed to change the flow of the river and laid eyes on thousands of pages of
engineering and contracting documents.

Don’t forget all this happened during uncertain times around Covid-19.

Mitch Arnold has been in charge of Seipp crews from Christchurch travelling to work on the project. He has learned a lot about the complicated nature of braided rivers and
endangered birds, such as the black-billed gull and black-fronted terns.

His crew installed sheet piles to temporarily divert water under the ground so the 1m diameter pipe could be laid.

The new pumping station is now fenced for security and fruit trees have been planted around the perimeter.

While Ashburton mayor Neil Brown officially turned a knob to start one of the pumps, the station has actually been operating for about a month during the rigorous testing

Mr Brown said it had been a great project for council and one that would future-proof the
town and its growing population for decades to come.

Work on the new Netherby sewer will begin in the new year and should be complete by
March 2022.

About 40 invited guests, including councillors, council staff, engineers and contractors, attended the official opening on Monday.

The Lake Hood river trail that runs alongside the new pumping station will be open on
Christmas Eve to bikers and walkers; that section has been shut while contractors worked.


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