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Previous updates - 2016

Previous updates - 2016

Updated 8 January 2018 9:43am
Latest news – 15 December 2016

Here is the latest news from GWRC, as our investigation into the discharges from T and T landfill, and our follow up on on-site compliance matters.

Soil testing results

We received the lab results from the soil testing at the community gardens on 14 December 2016. The soil was tested for the concentrations of metals including arsenic, chromium, copper, iron, manganese and zinc. GWRC undertook this soil testing to provide information to the community (and ultimately reassurance from RPH on any health effects). The presence of these metals in the soils does not indicate that the stream water was the ‘source’ of these – the historical land use of the area, and products brought onto site play a much larger role.

GWRC environmental scientist, Dr John Drewry completed an initial screening (noting that this is not a public health assessment) and has advised:

Arsenic: Marginally above or at similar level to some guidelines.

The measured concentration (22 mg/kg) is marginally above the National Environmental Standard (NES for Contaminated sites) soil contaminant standard for residential land use for 10% or 25% produce (20 and 17 mg/kg respectively). The environmental guideline value used for GWRC's State of the Environment (SOE) soil quality monitoring is 20 mg/kg. Typical values for our SOE monitoring for various land uses  range from <LOD (limit of detection) to 30 mg/kg.

Recent draft ecological soil guideline value developed by Landcare Research is 20 mg/kg for arsenic for agricultural land.

Chromium: Well below our guidelines

The measured concentration (20 mg/kg) is well below the NES value for residential for 10% or 25% produce (460 and 290 mg/kg respectively).

The measured concentration is well below the soil SOE guideline (600) and the draft ecological soil guideline value (300).

Copper: Well below our guidelines

The measured value was well below the NES value for residential for 10% or 25% produce (>10,000 mg/kg).

The measured concentration is well below the soil SOE guideline (100) and the draft ecological soil guideline value (eg 130-150 but varies for agricultural land).

Iron and manganese

The measured concentration of iron and manganese is within the range of recently measured soil SOE range of values.


The measured concentration (121 mg/kg) is below the NES value for residential for 10% or 25% produce (210 and 160 mg/kg respectively).

The measured concentration is well below the soil SOE guideline (300) and the draft ecological soil guideline value (530) for agricultural land.


There is no value in the NES.

The measured concentration (300 mg/kg) is marginally on the soil SOE guideline (300 mg/kg) and above the draft ecological soil guideline value (values vary depending on soil age, circumstances etc, (eg 130-190 for agricultural land).

Soil pH

Not of general concern. Value for garden vegetables should be slightly acidic, but varies with crop type. Some contaminant availability can vary with pH.

RPH have been provided with the results and also note that the arsenic level is elevated, but not to a level were additional measures to those already outlined in the FAQ’s are required.

Click here to see the test results.

Works on-site at T and T

The site was inspected on 14 December 2016 and officers observed that T and T had:

  • Completed the set out of the wetland areas and were excavating the area to enlarge the treatment volume
  • Cleared out 75% of the dead and decaying vegetation which may be causing deoxygenated water to flow though the landfill (which could result in higher contaminant concentrations in the leachate).

We have also received a set of plans for the initial works needed to begin parts of the clearwater diversion channel. We expect these works to begin early in the new year.

Water sampling

GWRC officers completed an extensive sampling round on 14 December 2016, taking some 60 samples from the site to the sea.  This is our fourth round of sampling, as we begin to get a fulsome picture of the water quality impacts.


GWRC officer taking a water sample on 14 December 2016

We will provide a summary table of our water sampling to date in our next update.

T and T ecological assessment – adaptive management triggered

T and T water sampling in the October quarter saw some contaminant levels exceeded. This ‘set off’ the adaptive management process in the consent conditions. This required a re-test within one month. These November 2016 results have also exceed the contaminant levels, showing that there is a potential long term effect that needs to be understood. The consent now requires T and T to undertake an ecological assessment. This is to be completed by T and T’s consultants, MWH. MWH expects to undertake this in the week beginning 19th December 2016.  T and T must then submit a report on the findings and this must include recommendations to ensure the water quality comes back into compliance with the specified limits.

GWRC ecological assessment

As part of our investigation into this event, we have been trying to engage an ecologist to complete an assessment of the effects of this incident, beyond the boundary of the site. Trying is the operative word as most of our preferred ecologists are fully booked up till the new year. We are now seeking advice from our environmental science team as to other ecologists who may be available in and outside the region.

Meeting with community members

Councillor Sue Kedgley chaired a meeting on 15 December 2016 at GWRC offices with 6 people from the Owhiro Bay community. Representatives from Wellington City Council and Regional Public Health also attended to provide information. The group discussed a range of matters – and a set of actions and agreements made at the meeting will be posted up soon. However, it was clear that there was considerable interest and goodwill from the community and all parties to have a regular forum in which to discuss issues that occur in the Owhiro Bay catchment.

Latest news – 8 December 2016

Here is the latest news from GWRC, as our investigation into the discharges from T and T landfill continues. This update includes advice from Regional Public Health (RPH).

It’s fair to say at this point that we don’t have all the answers yet – and appreciate that there are many questions. Please bear with us as we try to do our regulatory work in a co-ordinated systematic way.

Onsite inspection

On 7th December 2016 we met with the landfill operator, their planning consultant and engineer to discuss any immediate actions that can be taken onsite to avoid, remedy or mitigate the effects of this discharge. T and T advised they will:

  • Enlarge the wetland/ stilling basin onsite to increase its volume and therefore detention time. This wetland/ stilling basin receives all water that flows through the site and the engineer was confident that this would increase treatment.
  • Begin works to divert clean water in the gully systems upstream of the landfill around the active landfill area before it enters the stream. This will reduce the amount of water leaching through the landfill.
  • Remove dead vegetation from a gully which may be decaying and causing deoxygenation which could result in higher contaminant concentrations.

Water use

We have received many queries about whether it is safe to use the water from the stream to water plants and the like. At this point in time, we recommend that people take a precautionary approach and find another source of water. Although it is unlikely that the stream water will make the vegetables unsafe, GWRC and RPH consider this the best course of action at this point in time while the recent discharge is being investigated. While we have our first set of water sampling results back in, we need to take the time to accurately interpret these.

In general, stream water would not be recommended for watering vegetables during and for 48 hours following heavy rain, as urban streams can be contaminated by run-off from surrounding land.

Soil and plants

In addition to concerns about the water quality in Owhiro Stream, people have asked if it’s still safe to eat the plants that they have watered with the stream water and if the soil is contaminated.  . Regional Public Health advice is that vegetables can continue to be consumed but should be thoroughly washed to remove dirt from roots and deposits on leaves, and to peel root vegetables, before eating.  GWRC have sampled the soil at the community gardens to better understand the soil quality. We are awaiting the results of testing on the soil. These sampling results should also assist the community in understanding the current state of the soil quality and if there is any further advice for users of the community garden.

Human health impacts

While we do not envisage any human health impacts from this discharge, GWRC and RPH still feel that until we have all the information back from soil and water testing, that the community should follow best practice advice around staying healthy around recreational water and home gardening:

  • Avoid swimming in the stream and at the beach within 48 hours of rainfall
  • Thoroughly wash all vegetables and fruit before eating
  • Use gloves when gardening, and wash hands after removing gloves.
  • Remove any footwear used in the garden before entering the house.

Water sampling and results

We are now starting to receive lab reports back from the sampling we have undertaken. This data is ‘raw’ and we need to interpret this against relevant guidelines and standards. Correct interpretation of this data is critical so we make the right decisions going forward. GWRC environmental scientists are currently assessing the results and we will be able to provide more information next week. This information will also be shared with Regional Public Health.


At this point, GWRC and RPH feel that signage would not be useful. We do note that Wellington City Council already has a sign at the ‘beach bridge’ across the Owhiro Stream. This recommends that no one swims in the area 48 hours after rainfall.  We consider that this existing signage and its precautionary approach is appropriate in the circumstances.

Ecological impacts

It’s clear from our inspections of the stream that there is a visible ‘iron/manganese flocculant’ in the bed of the stream, and this is still clear on the Owhiro Bay beach. While this is ‘visually’ concerning, we have sought advice from our GWRC Science Team as to what ecological assessment of the stream life needs to be done.  We also sought their view on the causes of the ‘foam’ which was present in the stream during rain.

Update from GWRC Environmental Science – 8 Dec 2016

GWRC Environmental Scientists have completed an initial review of water quality data from samples 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.  

Update - 06 December 2016

  • GWRC has received the sample results today. Our Environmental Science team are interpreting these for us and we will place them on the website once they are in a readable form with any comments they can provide.
  • GWRC is also discussing the sample results and what we know about the discharge with Regional Public Health; any feedback or advice we receive will be published on this webpage. We will also explore the requirements for signage in the area and the appropriate message(s) to put on this.
  • GWRC has been in contact with T and T consultants to explore potential solutions to the discharge. No easy fixes have been identified to date and as a result we intend to meet them on site this week to find out what short term/emergency measures can be taken.
  • GWRC understand from the reports today that the discolouration has intensified and 2 dead eels have been seen. The duty officer is out there now investigating and taking further samples.

GWRC will continue to update this webpage with any new information we have. Please be assured we are also concerned about this discharge and will endeavour to work with T and T to find a solution as quickly as possible.

Latest news - November / December 2016

What is GWRC doing now

Our primary focus is to ensure that the T and T Landfill are taking all steps to mitigate the effects of the discharge. To this end we are in close contact with the site and their engineers to see what additional measures can be put in place. We will be getting onsite more regularly to check compliance with the site operational practices. This will be our key focus over the coming weeks. We will be reviewing quarterly water quality monitoring data (which is a requirement of T and T Landfill's resource consent) against the findings from the lab analysis.

Alongside this, we are investigating T and T Landfills non-compliance with resource consent conditions. If any site or operation is found to be in breach of their consent, a rule in a regional plan, or the RMA, we have a range of powers under the Resource Management Act 1991 to require sites to take action as well as punitive measures.

What are T and T Landfills doing now

We have instructed T and T Landfills to complete a full site investigation and undertake all necessary additional measures to avoid, remedy and mitigate the effects of the discharge. We are awaiting to hear from T and T regarding what additional measures they can put in place.