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

http://www.gw.govt.nz/t-and-t-landfill

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

Updated 23 May 2017 2:11pm
Overview 

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 - 23 May 2017

The landfill operator and their consultant have prepared a construction programme for the completion of the already commenced stormwater solution over the next 7 months. The programme of works has been reviewed by GWRC to ensure that it reflects the urgency with which the works are required to be completed and that the works will not create downstream flooding effects. GWRC’s reviewer has confirmed that the construction programme is appropriate and reasonable. The construction programme timetable and a more detailed staging plan are available on this page. The construction of the stormwater diversions is a substantial undertaking and requires the construction of two dams in the headwater streams (to ensure that downstream flooding effects are not exacerbated). All works on the stormwater diversion system are scheduled to be completed by the end of December 2017. Completion of the different stages of work will be as follows:

  • Completion of bottom swale to outlet into the stream by mid-June 2017
  • Completion of eastern swale by end September 2017
  • Completion of eastern dam by mid October 2017
  • Completion of western swale by end October 2017
  • Completion of western dam by end December 2017

GWRC will be meeting with the landfill operator and their consultant on site at least once a month to check progress of the works against the programme of works. We will continue to keep you updated as the works progress.

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 notifications@gw.govt.nz

 

     

    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.