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T and T Landfill - information about the site and water quality issues

T and T Landfill - information about the site and water quality issues

Updated 5 February 2019 2:06pm

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.

Latest News - January 2019

Monitoring of the Owhiro Stream by T&T Landfill shows that the site still exceeds contamination limits – particularly after heavy rain. Investigations into the cause have identified that the two dams and swales installed in 2017 to divert clean water around the landfill, are not as water tight as they should be. This means that more water than intended is continuing to enter the landfill, which means too much water ends up in the wetland treatment pond. Because there is too much flow entering the wetland treatment pond, the water is not spending enough time in the pond for the contaminants to fall out of the water and be properly treated.

What are T&T Landfill doing to fix this?

T&T Landfill and their engineers have put together a schedule to address the known issues. Click here to see a construction plan showing areas of remedial work.

Items listed as ‘Priority 1’, ‘Priority 2’, ‘Priority 3’ and ‘Priority 5’ have been completed as at December 2018. Recent monitoring has shown that the Western Dam has started to lose water, and fixing it is now the new priority. T&T Landfills have had to wait for the wet weather in November to stop to undertake these repairs. However, they will not be able to wait any longer, as their resource consent requires that the dams and swales are to be working as intended by 31 January 2019.

Below is a series of photos of the site showing the upgrades to the dams and swales at T&T landfill

Treatment wetland

Western dam monitoring

Upgraded works to reline the base of the south western swale as identified as Priority 1

Water flowing as designed in the repaired area identified as Priority 2

Upgraded works to reline the base of the south western swale as identified as Priority 5


What else is going on?

In July 2018 various resource consents held by T&T Landfill were changed to include stricter monitoring requirements. As a part of this, the landfill has had to submit for approval, and act in accordance with; a Landfill Operational Management Plan, a Discharge Monitoring Plan, a Landscaping and Reclamation Mitigation Plan, and a Monitoring and Maintenance Plan for the dams and swales. The purpose of these different plans is to ensure T&T Landfill staff can operate the landfill in an agreed way that reduces environmental risk to the environment. Monitoring plans are to ensure that the right monitoring is being undertaken to know what effect the landfill is having on the environment, and if the infrastructure improvements undertaken throughout 2017-2018 will improve water quality in the Owhiro Stream.

Further information

The following pages aim to provide easily accessible information to the public and community affected by these water quality issues and to assist in understanding the process for reporting environmental incidents to GWRC.

Frequently asked questions

Logging an environmental incident to GWRC

Previous updates 

If you have a question or would like to find out more, please contact our Environmental Help Desk at 04 830 4255 or



    Update from GWRC Environmental Science – 8 Dec 2016 


    GWRC Environmental Scientists have completed an initial review of water quality data from sample taken on 22 and 28 November. This review has focussed on the potential ecological impact from the discharge (not any human health impacts). Their initial review has concluded that the discharge from the landfill would have caused some adverse effects to the in-stream environment, over and above those impacts allowed by the landfills resource consent. 


    What impacts did the discharge likely cause?


    GWRC Environmental Science advised that the discharge from the landfill may have had the following impacts on stream ecology - however, what is to early to say at this stage is the severity of these impacts (more on this below):


    Physical disturbance due to smothering from high suspended sediments and iron/manganese flocculant

    Toxicity associated with high metal loads both in dissolved and total phase

    ·         Reduced light penetration thus impacting on aquatic plant life

    ·         Potential reduction in oxygen availability in the stream

    ·         Clogging of gills of resident aquatic biota (invertebrates/crustaceans as well as fish),

    ·         Probable toxicity from ammoniacal-N and reduced dissolved oxygen availability

    ·         Ongoing aesthetic impacts of deposited orange precipitate


    We appreciated that these effects do raise concern, and that is why this initial 'screening' of the water quality samples have highlighted the need for a more intensive ecological assessment of the stream environment, to understand the degree of any impact from this discharge event in late November.

    Further stream/ ecological investigation


    The purpose of this will be to understand the effects of this event, and to enable any follow up assessment of the recovery of the stream ecology to be quantified. We are currently in the process of engaging an expert to undertake this work, and are preparing a scope for this.



    Source of the foam?


    Foam forms when the water contains higher concentrations of dissolved organic matter (DOM) – such as from decaying matter washing downstream as well as that potentially mixed from the landfill.  It can be naturally occurring.  In this case, it is probably a combination of both naturally occurring DOM washing rapidly downstream from the surrounding catchment, mixed in with an unknown concentration of organic based chemical leachate from the landfill that has been flushed out of this system.  It is unlikely that the foam is purely landfill based contaminant leachate, and will contain a high amount of DOM washed down from the catchment.


    Source of the red deposits on the stream bed?


    This is largely due to deposited iron/manganese flocculant, sourced from the landfill leachate. This type of orange coloured precipitate occurs when reduced groundwater (i.e. low oxygen, but containing elevated concentrations of dissolved iron & manganese) then enters surface water and comes into contact with oxygen.  The iron & manganese then become oxidised in the surface water which forms the orange/rust coloured precipitate/floc that is then deposited as a fine layer in the stream bed.