Wellington stream flooded with purple paint

A Wellington stream, once considered the most polluted urban waterway in the country, was accidently flooded with bright purple paint waste.

The waste flowed into the Waiwhetu Stream in Naenae earlier this year from a cracked sewer pipe, despite a $6.5 million clean-up that started in 2009.

A Greater Wellington Regional Council investigation found a tree root blockage was the cause.

It caused the wastewater to back up and escape through a crack in the sewer pipe in the nearby Resene Paints Limited factory.

The purple waste seeped through the soil into the public stormwater system, which flowed into the stream.

However, the investigation also found that prompt responses from locals helped limit pollution.

"We are satisfied that a series of unforeseen events that caused this incident and that no fault was lies with Resene," council environmental regulation manager Alistair Cross said.

"In fact we commend them for their prompt and thorough actions to stop the discharge and find the cause and also for their help with our investigations afterwards."