Part of a cliff-top Kakanui road has collapsed, taking with it sewer and water pipes.
Sewage is now seeping into the sea.
Kakanui's Beach Rd has been closed between Fortification Rd and Gees Rd, with diversions in place, as the cliff continues to crumble.
The first chunk of Beach Rd gave way at about midday, 300m north of Kakanui's Coast Cafe.
No-one was on the section of road at the time of the collapse and there have been no injuries.
Waitaki District mayor Gary Kircher, at the scene, said the cause of the slip was yet to be determined.
"It's a significant amount and now it's starting to come into the seal part of the roadway,'' Mr Kircher said.
"Contractors will be working on solutions as quickly as possible.''
The water pipe which had broken, supplying one farmer at the end of the line, would be temporarily fixed on Monday.
"The sewer pipe is more of a concern in that it carries all of the sewage from Kakanui to the treatment pond,'' he said.
"The short-term solution will be to keep sewage in the holding pond on the Kakanui side of the pipeline and that will need to be pumped out regularly and trucked away for treatment.''
Closure of the road would be a "major inconvenience" for people travelling between Oamaru and Kakanui.
The slip is in a popular paua spot.
"Because some raw sewage has gone into the sea there, I would highly recommend that a temporary moratorium be put in the taking of all shellfish in the immediate area until further notice,'' he said.
With good rock shelving, the area had not been identified as a problem.
''It's not an area where we expected we were going to have problems,'' Mr Kircher said.
- Rebecca Ryan
