Wellington Harbour (file image). Photo: RNZ / Rebekah Parsons-King
There is a high likelihood raw sewage has leaked into Wellington Harbour due to a broken pipe, Wellington Water believes.
The water provider first responded to the break after reports of the slip near the BP station on State Highway Two between Wellington City and Lower Hutt.
The 150mm wastewater main lies in a steep gully above the petrol station.
A geotechnical assessment on Wednesday identified that a joint had become disconnected on the pipe, with crews hoping to complete the repairs on Thursday.
Sucker trucks have been in place on the site since midday Wednesday.
Wellington Water told RNZ it was still waiting on water sampling results, but said it was likely any sewage leaked into the harbour would be untreated.
Greater Wellington Regional Council, the local regulator of water, has been notified.
The water provider said it was working as quickly and safely as possible, while minimising the impact on communities and the environment.
It could not yet say how much raw sewage could have leaked into the harbour or what broke the pipe.