Source: Radio New Zealand
Sewage can be seen on Wellington’s South Coast after a leak from the Moa Point wastewater plant. Kate Taptiklis
Wellington Mayor Andrew Little says he will raise what he has called a “catastrophic” failure of the city’s sewage plant with the prime minister.
Wellington Water has released its first batch of samples, since wastewater from its Moa Point treatment plant started spilling into the ocean close to the shoreline.
Screened wastewater is now being discharged straight into the Cook Strait again after days of being discharged near the shoreline on the South Coast.
On Wednesday the Moa Point wastewater plant’s lower floors completely flooded when sewage backed up in the 1.8km outfall pipe, which normally sends treated wastewater into the Cook Strait.
Since then raw sewage has been spewing from a five-metre pipe directly into the southern coastline.
Little said he wad already scheduled to meet with Prime Minister Christopher Luxon on Monday before the failure of the sewage plant and would now discuss the issue with the plant during that meeting.
Little said one of the questions in the days ahead would be about setting up an appropriate investigation or inquiry into what happened.
“We can’t let this happen again,” he said. “We can’t let such a critical plant for a modern city fail in the way that this has and cause the environmental degradation that it has.
“It’s important we get the facts and it’s important we understand what we need to do to prevent it from happening again.”
Little said he had also enquired into how to ensure sample results published were more current.
“We’ve got to get that sorted out. People are expecting daily updates on the quality of the water, so we’ve got to get that right.”
Only three of the samples from Wednesday – the day the plant equipment failed – are above the threshold for safe swimming, but Wellington Water cautions that the samples do not reflect the current conditions and people still needs to follow public health advice and stay out of the water.
“Moa Point is continuing to discharge untreated wastewater,” it said. “Untreated wastewater poses a high risk to public health.”
The samples cover 18 sampling sites, from Ōwhiro Bay to Mahanga Bay. They were collected by Eurofins, an independent accredited laboratory, between 4-7pm on Wednesday, 4 February.
Wellington Water said the results from Hue Te Taka Peninsula, which was very close to the outfall, were many times over the safe limit.
“We are not able to draw any conclusions about the level of contamination or environmental impacts of the discharge from one set of samples. We will be conducting daily sampling and reviewing the results over several days to inform our response.”
Wellington Water said it would continue to sample around the eastern bays – Scorching Bay and Mahanga Bay – to confirm there was no indication of the discharge impacting the inner harbour.
“For clarity, while there were elevated levels detected in Wednesday 4th samples from Mahanga Bay and Ōwhiro Bay, these are considered to be caused by the rainfall earlier in the week, not the discharge from Moa Point,” it said. “These results may change.”
Wellington Water said discolouration in the inner harbour – Kilbirnie to Wellington CBD, around to Petone and Eastbourne – this week was very typical of rain and stormwater runoff being discharged by the Hutt River.
Wellington Water said reporting the results of water samples was delayed, because the bacteria needed 24 hours to grow in laboratory conditions.
“The results then need to be finalised to provide the most accurate data.”
It said sampling results could also be influenced by factors including wind, tide and rainfall.
Screened wastewater
In an discharge notice on Friday morning, Wellington Water said screened wastewater was now discharging to the long outfall pipe again.
Late on Thursday evening staff were able to get the long outfall pipe partially operating and the screens at the treatment plant working, Wellington Water said.
The screens remove items like sanitary pads and wet wipes from the wastewater, before it is discharged.
Wellington Water board chair Nick Leggett said currently they were only able to pump 900 litres per second of wastewater through the long outfall pipe.
“Which is most of the wastewater during an average day, but during peak flows throughout the day we will need to use the short outfall pipe,” he said.
Wellington Water said discharging screened wastewater out to sea via the 1.8km long outfall pipe allowed for greater dilution of the wastewater in the Cook Strait, reducing the amount of untreated wastewater flowing around the coastline, but the risk to public health still remained.
“For this reason, our advice to the public remains the same: we strongly advise that people avoid the coastal area along the south of Wellington until further notice. Do not enter the water or collect kaimoana from this area. Do not walk your dog along the beach,” said Leggett.
Leggett said while the situation remained serious, it was good to see progress.
“The team are working carefully throughout the weekend to increase the volume of flow through the long outfall pipe as much as possible, to reduce the use of the short outfall pipe,” said Leggett.
“However, the situation remains complex and at this stage we are unable to provide a timeframe of when this may be.”
Material being drained from longfall pipe, diver inspections taking place
Wellington Water said on Friday work was also being done to drain the clarifier tanks.
“There is some biological material that settles in the clarifier tanks that cannot be trucked, and the plan is to drain this via the long outfall pipe, where it is diluted.”
It said it was important to remove this material as soon as possible before it has a chance to become anaerobic and septic.
“This would cause an odour problem and pose a significant health and safety risk to workers onsite.”
However it cautioned that while the material was being drained people could see an increase of murky water in the area 1.8km out to sea.
Wellington Water said divers were also inspecting diffusers at the end of the outfall pipe on Friday.
“Shoreline inspections and clean-up of debris on the coastline around the short outfall continue three times daily, with a focus on completing these at low tide.”
A rāhui remains in place and covers anything the water touches/can touch with the high or low tides. While it is in effect, no public activities should be undertaken on or around the beaches on the southern coastline.
Mayor Andrew Little previously described the event a “catastrophic failure”, and said there must be an independent inquiry into what happened.
There were also concerns the leak could contaminate a nearby marine reserve and put several species at risk.
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
