Dreams of a clean-swimming Wellington summer down the drain
Monday, 29 December 2025
The problem of dealing with Wellington’s sewage has led to a wastewater warning on the capital’s south coast beaches – due to work which was intentionally timed for the summer months.
On a day forecast to hit between 20C and 22C across Wellington beaches – from the city to Lower Hutt and Kāpiti – Sunday looked like swimming weather, but Land Air Water Aotearoa and the Greater Wellington Regional Council had warnings in place.
Recent heavy rain had flushed contaminants into the water meaning the risk of illness from contact was elevated at a vast majority of beaches. Three Paraparaumu beaches, one Raumati beach and two Waikanae River swimming spots were deemed “unsuitable” for swimming.
By late morning, most of Wellington had been deemed suitable but parts of Hutt Valley still had caution advised while areas of Kāpiti were sill “unsuitable”.
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But Wellington’s south coast had an additional warning in effect: From October to May a new ultraviolet disinfection system was being installed at the Moa Point wastewater treatment plant so it was working at reduced capacity.
“When it's raining, wastewater volumes are higher than usual, and some wastewater may bypass the full treatment, resulting in a discharge of partially treated wastewater via the long outfall pipe, 1.8km offshore,” the warning says.
“Any discharges in this location, will be heavily diluted due to significant tidal flows.”
It was always best to avoid swimming for 48 hours after heavy rain but people should take “extra care” due to the potential discharge on south coast beaches.
MetService data shows about 21mm of rain fell at Wellington Airport on Boxing Day, which was just over a third of the historic average for all of December. Falls of 5mm or greater are classified as “very wet”.
The existing Moa Point wastewater treatment plant sits alongside the Wellington City Council’s under-construction sludge treatment plant – which recently had an $83 million cost blowout. Wellington City Council spokesperson Richard MacLean said the current issue was unrelated to the sludge plant.
Wellington Water is running the wastewater treatment plant work and, in a statement, said work was timed for the drier months to reduce the risk of discharges.
“Moa Point, like other treatment plants in the region, is ageing,” said Jeremy McKibbin from Wellington Water.
“These upgrades are essential to ensure safe, effective operation and to reduce environmental impacts. While operating at reduced capacity isn’t ideal, this work is critical to prevent future UV system outages.”
The upgrade work meant each of the two UV disinfection channels were closed one at a time. On rainy days, all wastewater went through “initial screening and grit removal” but some could miss the “full biological treatment and UV disinfection process”.