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Watercare is looking at installing a new temporary wastewater pipe in part of Warkworth in an effort to reduce the number of overflows that regularly discharge thousands of litres of raw sewage into the Mahurangi River, forcing oyster farmers to shut up shop.
The old pipe currently runs from the north along Elizabeth Street to the pump station in Lucy Moore Memorial Park, but in recent years there have been regular sewage overflows into the street or, more frequently, into the river and harbour via the stream that runs behind shops.
The leaks have led to several cases of norovirus in the town basin and forced local oyster farmers to stop harvesting until water quality had returned to safe levels (MM, Aug 4).
However, Watercare’s chief strategy and planning officer Prihan Perera said on October 2 that a temporary solution, such as a bigger pipe, was being sought as decision-making on the new permanent sewage pipeline dragged on.
“Recognising the number of overflows we’re having, we are putting some effort into interim options to reduce the impact on the environment and businesses,” he told a Rodney Local Board workshop.
“There are a couple of aspects we’re looking at and one is an interim upsizing of the Elizabeth Street pipeline – the pipe that runs across that bridge is quite small.”
He said a team was looking at what could be done to upsize the pipe and implement controls at pump stations at either end, with designs currently being drawn up.
Perera, together with other Watercare executives, met with Mahurangi oyster farmers and local MPs Chris Penk and Jenny Marcroft after the workshop, but at least one grower who attended was unimpressed, not least since a storm that night had led to yet another discharge and harbour closure.
“That night, they poured 116 cubic metres, or 11,000 litres of sewage down that pipe,” he said.“This year, we’ve been closed up to 70 days and this one will tip it over 80. Last year it was 81 days.
That’s half our money flushed down the toilet.
“We take it seriously about norovirus, but they don’t. I’m really disappointed.
“We’ve been waiting four years for them to fix it and they basically told us the new pipeline was five years away and to talk to One Mahurangi about the delay.”
Perera had earlier expressed the project team’s own frustration at the time it was taking to decide on a route for the new pipeline.
“They get a little bit frustrated at times,” he told local board members. “We’re looking at 900 metres of pipe and it’s taken us three years to navigate this scenario.
“We’ve learned a lot, but at the same time we are going to have to make some pretty difficult decisions and sometimes those decisions will not be popular.
“We have to strike a balance between what’s right for the future and what needs to be done for now.”
He said the project was about delivering the best asset for the community for the next 100 years, not just for today.
“There’s no simple solution here. There’s pressure on other businesses, the oyster farmers and growers, and they have a different pressure – to stop the overflows.”
The workshop heard that three possible routes were currently being assessed: Watercare’s preferred open trench down Queen Street, plus alternatives put forward by One Mahurangi – a trenchless tunnel along Queen Street, or an above-ground pipe topped with a boardwalk around the riverbank, which Perera said could take two years longer.
He said the local board and community played a huge part in influencing any final decision, as did environmental impacts, geotechnical constraints, construction feasibility and cost, but in the end, “we look for the best technical solution”.
Watercare will share the results of its current route assessments with One Mahurangi by the end of the month, before going through its engineering optioneering process. A decision is expected by December.
Eight month road closure on cards, says Watercare
Meanwhile, digging the northern section of the new pipeline could lead to an eight-month road closure between Hill Street and the community transport hub just south of Warkworth Showgrounds.
Rodney Local Board members heard that laying that section of pipe would take 13 months if Great North Road was kept open for single lane traffic, but five months less if the road was completely closed.
Traffic would be diverted via Hill Street or Matakana Road, adding just two or three extra minutes of travel time, according to Watercare project manager Michael Zhou.
“If we could close off this section of road, the construction crew can go faster and we can probably save half the construction time and it will be 15 to 16 per cent cheaper,” he said.
“Full road closure is faster, cheaper and safer for both the construction crews on the site and also for the public, plus we can keep the footpaths open all the time.”
Zhou added that as a result of community feedback, construction materials and work crews would not use Shoesmith Domain or Kowhai Park as bases, as had previously been proposed.
He said sites just south of the community transport hub and at the showgrounds would suffice.
