Aucklanders are being told to avoid Waitematā Harbour after a sewer in central Auckland became completely blocked from a wastewater pipe collapse.
Watercare said a tomo - which is a hole - has formed above the Orakei Main Sewer, causing a blockage.
Watercare was alerted to a hole in the ground on Monday afternoon by a company undertaking work at a site on St Georges Bay Rd in Parnell, above the sewer.
Watercare said the 2.1m-diameter brick sewer is approximately 13 metres underground and serves large parts of central and west Auckland.
The top of the wastewater pipe has collapsed, according to Watercare.
Watercare chief operations officer Mark Bourne said people are advised to avoid Waitematā Harbour as Watercare hasn't been able to confirm overflow locations.
"As we haven't yet been able to confirm overflow locations, we have raised black water quality pins on Safeswim and are urging Aucklanders to avoid swimming, fishing and recreational activity in the Waitematā Harbour. Warning signs are currently being erected at all inner-city beaches," he said.
"Once the blockage has been cleared, wastewater will be able to flow through the pipe again and we'll progress with planning for its repair. Safeswim status will be regularly updated."
According to Safeswim's website, all beaches to the west of St Heliers are closed.
"A wastewater overflow has been detected in the area," a notice on Safeswim's website read.
Watercare said it took immediate steps on Tuesday to address this situation, including seeking advice from geotechnical engineers.
"Our crews worked until early this morning, removing material to strategically widen the tomo, stabilising the ground and preventing further material entering the pipe," Bourne said.
"Unfortunately, the situation has worsened with the sewer becoming completely blocked this morning, which may be causing overflows elsewhere in the network."
Bourne said Watercare crews are currently working with a large excavator to further widen the top of the hole to remove the debris causing the blockage.
"Safety is our number one priority. The ground near the tomo is unstable so we have established an exclusion zone around the site to ensure the safety of the public, staff and contractors," he said.
"We're working hard to confirm any overflow locations and to minimise any environmental impact as much as possible."
