Wellington Water says substantial amounts of petrochemicals have been found at the Seaview Wastewater Treatment Plant. Photo: Supplied / Wellington Water
An investigation has been launched into large quantities of highly flammable chemicals found in petrol and paint being illegally dumped down sewerage pipes in the Hutt Valley.
Wellington Water told RNZ there had been four instances where substantial amounts of petrochemicals were found in Lower Hutt's Seaview Wastewater Treatment Plant.
The chemicals were first detected in March last year, with the latest finding having occurred in June this year.
The chemicals were a significant risk to the facility due to them being explosive, causing extra odour and the inability to remove them completely from the water - which meant they would get into the environment.
Hutt City Council head of environmental protection Justin Roberts told RNZ they had sent letters to businesses in the Lower Hutt suburb of Seaview to raise awareness of the illegal dumping.
Roberts said the council had been investigating some "promising leads", but nothing firm had been found yet.
"The hope is that someone knows something or sees something, and either reports this to council or dissuades the culprit against future dumping."
There was a minor fire at the Seaview plant on 2 September, which was still under investigation.
A Wellington Water spokesperson said it was highly unlikely the petrochemical contaminations were a contributing factor to that blaze.
Wellington Water network management general manager Jeremy McKibbin told RNZ there had been instances in the past where businesses had let oils go into the wastewater network.
Such problems could also be caused by households pouring paint down the drain, he said.
McKibbin urged people to follow product instructions for how to dispose of items like paint.
In the past year, the Seaview Wastewater Treatment Plant had been the subject of hundreds of complaints made about its odour.
Last month, in its role as a regulator, Greater Wellington Regional Council issued an abatement notice to Hutt City Council, Upper Hutt City Council and Wellington Water requiring upgrades to the plant's biofilter to be completed by 4 October.
If the work was not done on time, the councils could face fines or legal action under the Resource Management Act.