Wellington Scoop

Toxic pollution from landfill continues in Owhiro Stream; urgent mitigation needed

News from Greater Wellington Regional Council
Since 6th April there has been discolouration, high flows and foam in the Owhiro Stream as a result of the ongoing discharge from T&T Landfill.

GWRC took water quality samples on the 10th April and have received the sample results. As with previous incidents, the sample results indicate that the concentrations of contaminants in the landfill tributary increased as a result of the passage of water through the landfill. This is likely to have resulted in chronic and acute toxicity effects on aquatic life during this period.

These results, while disappointing, were expected as the stormwater diversion channels are still under construction. This is why GWRC compliance focus is working with the landfill to get the diversion works done as quickly as possible. More on this below.

Ecological report

The ecological report commissioned by GWRC on the November 2016 incident has been finalised and will be released shortly. The assessment provided in this report was used to inform the enforcement decision which was made in relation to the incident late last year. The report will be available in the ‘relevant documents’ list on this page.

Key findings from the report are:

Long term monitoring data indicates that the discharges from T and T Landfill cause a number of significant adverse changes in water quality and ecology
“Spikes” in contaminant concentrations in the discharge have been measured, leading to effects greater than the ongoing discharge
The mitigation measures, diversion of stormwater and implementation of a treatment wetland are needed urgently to mitigate the effects of the discharge

Onsite construction works on mitigation measures

The work to install the stormwater diversion channels is underway and we have been onsite.

The landfill operator has also installed a pump to pump clean water from the Mitchell Street gully into the diversion channels. Pumping has occurred over the last few days and the gully is now empty of water – this was critical work as it reduced the amount of water that could have filtered through the fill material and would have drawn out more leachate if it was left to drain through the landfill. The pumping out caused some discolouration of the stream, but this was seen as a necessary step to reduce the overall impact on the stream.

We have received a more detailed works programme from the landfills engineer and this being reviewed by GWRC independent engineering consultant to ensure that it demonstrates the urgency which mitigation measures need to be put in place as expressed by the landfill and GWRC ecologists. Once finalised, the works programme will be made available. The construction of the stormwater diversion channels remains a priority as this will see the contamination levels in the stream reduces significantly.


T and T Landfills Limited operate a construction and demolition landfill in the Owhiro Stream catchment. The site holds a suite of resource consents to operate from Wellington Regional Council and Wellington City Council. The site is located at 289 Happy Valley Road.

In addition to T and T, two other landfills operate in the catchment, the Wellington City Council Municipal ‘Southern Landfill’ and another construction and demolition landfill known as C and D Landfill.

April 10: Five reports of pollution in stream

Official report on pollution


  1. Lindsay, 28. April 2017, 10:37

    Toxic pollution continuing, six months after the need for urgent mitigation was identified?

  2. Barbara, 28. April 2017, 15:01

    Not to mention the continual outflow of dirty stormwater into Island Bay.

  3. Marion Leader, 28. April 2017, 16:28

    The Regional Council is failing one of its most important jobs. And why is it letting streams and rivers in the Wairarapa get ruined?