Kaikōura earthquake leads to “Peketa Phenomenon”

The discovery of an oil-like slick in a Kaikōura drain appears to be the remnants of ancient wetlands.

Nicknamed the "Peketa Phenomenon", a smelly, oily substance was recently found on the surface of water in Peketa drains.

Complaint leads to unusual discovery

Kaikōura zone manager Kevin Heays said he received a complaint in May from Pekata residents that the drain was smelly, discoloured, and stagnant - potentially a health hazard.

Environment Canterbury and Kaikōura District Council staff checked the site.

"Together we visited and noted yes the residents were right, it stunk like [human effluent], it was black, had an oily sheen on top of it, was stagnant and very uncomfortable to live beside or around," Kevin said.

Environment Canterbury took water samples for testing and contacted the Canterbury District Health Board while Kaikōura District Council notified Health and Safety Standards.

"Initially we thought, all septic tanks in the village could be earthquake-wrecked, and so perhaps the septic tanks are going into the drain. It smelt like human effluent," Kevin said.

Staff followed the drain and located the source of the oil slick to a paddock.

"It's a phenomena the farmer has never seen before, after 40 years of farming there. He's never seen it so wet, and he's never seen oily, black, smelly stuff in the drains," Kevin said.

Considering Kaikōura's history as a wetland, and knowing the particular paddock was located on top of ancient wetlands, Kevin believes the substance is a natural occurrence caused by the earthquake.

"Like other historical swamps around here, rotting vegetation and swamp material goes down very, very deep and when it's wet it is smelly and horrible and oily looking.

"We believe now that the earthquake has squeezed it like a sponge and this stuff has come to the surface and now it's following that drainage system," he said.

Water samples support natural cause for "Peketa Phenomenon"

And the water sampling results appear to support that conclusion.

"The test results showed absolutely no human effluent at all and any animal effluent in the tests was so insignificant they had to search for it, so it's certainly not from humans or animals so it's definitely from vegetation or from the ground."

While this phenomenon has only been reported in Peketa so far, it may occur elsewhere, Kevin said.

"It's something to look out for in other places, especially here because the Kaikōura flats was just one big swamp for thousands of years."

Measurements taken to clear the drains

In the meantime, Environment Canterbury staff have tried to get a flow of water going through the drain and out to sea to try to get rid of it for residents.  Scientists are working to determine whether the water tables around Kaikōura will return to normal or stay high and what that means for landowners in the area.

"The actual effect of the earthquake on water quality is something we haven't seen much of before and didn’t know what it was.  It's a prime example of another effect an earthquake can have on our environment,” Kevin said.