NZ Transport Agency Waka Kotahi logo

Te Onewa Pā | Stokes Point

Section menu

Background

Why did Waka Kotahi NZ Transport Agency look into the issue of soil contamination in the Te Onewa Pā | Stokes Point area?

Waka Kotahi became aware of residents’ concerns relating to the potential contribution of historic bridge maintenance activities to soil contamination around Stokes Point Reserve.

In order to provide assurance to the community, Waka Kotahi commissioned an external review to ensure that potential soil contamination from bridge maintenance activities was appropriately assessed from a public health perspective in the Stokes Point area.

Soil contamination report [PDF, 1.1 MB]

Stokes Point soil contamination terms of reference [PDF, 91 KB]

View all technical documents

What did the external review cover?

The review was limited to examining the potential for soil contamination from bridge maintenance activities in the Stokes Point area, such as abrasive blasting (eg, sand blasting) and re-painting. 

The review did not consider potential soil contamination from other sources, such as historic imported fill, or the historic use of leaded petrol by vehicles using the bridge.

What are the findings of the external review?

The external review panel concluded that there was no evidence that bridge maintenance has currently or historically resulted in soil contamination that poses an unacceptable risk to the health of residents on nearby properties.

In addition, it did not recommend that Waka Kotahi undertake a new health risk assessment or investigation of individual properties.

Was there any sampling or testing as part of the review?

The review focused on existing documentation and information. Soil sampling and testing was not  included as part of the review as it was not considered necessary by the expert review panel.

What can I do if I am still concerned about this issue?

Whilst the report does not recommend that Waka Kotahi undertake investigation of individual properties, this does not constitute advice to individual property owners whether or not to investigate or assess their own properties.

Generally speaking, some degree of contamination can be encountered on any older urban property and those that have been close to major traffic routes.

If you are still concerned about potential soil contamination on your property and would like this further investigated, please talk to a suitably qualified professional.

General enquiries related to soil contamination issues that are outside the scope of the external review can be directed to Auckland Council as the regulatory authority. More information about land contamination is available on the Auckland Council website.

Contaminated land information on Auckland Council website(external link)

How is Waka Kotahi working collaboratively with Auckland Council as regulator?

Waka Kotahi continues to work closely with Auckland Council. Once the external review was complete, it was shared with Auckland Council to consider in its role as a regulatory authority. We consulted with Auckland Council on the findings of the review and there were no further proposed recommendations or actions.

Technical information

What paint/ coatings have been used on the Auckland Harbour Bridge since it was built?

A number of paint/coating systems have been used on the Auckland Harbour Bridge since it was built mostly chromium, aluminium and zinc systems, and in isolated areas a lead-based primer. The primary purpose of the bridge paint and primer systems is to reduce corrosion of the bridge structure. When the bridge was built, a thermal zinc-aluminium coating with an enamel overcoat was used on the vast majority of the exterior of the bridge. A lead-based paint (primer) was used on the bridge exterior on one span (Span 7) at the southern end of the harbour and also on the inside (contained) of some bridge structural members, such as the box girders (which extend to the south from the southern end of Stokes Point) and chords. The lead-based primer, sometimes called “red lead” is visually identifiable during paint stripping/maintenance activities.

As technology has changed, new paints and primers have been trialled and used on the bridge. Over the years, paint and primer systems have improved, resulting in better corrosion protection and longevity, and fewer harmful substances in paints. For example the use of paints with chromium has been phased out, and from the outset of bridge maintenance activities paints with high levels of lead (‘lead-based paints’) were not allowed. This means that less bridge maintenance is required and also less potential harm to the environment.   

Was lead-based paint used on the bridge?

Our records show that lead-based paint was not used on the exterior of the Auckland Harbour Bridge near Stokes Point.  Lead-based paint was used on the bridge exterior on one span at the southern end of the harbour and also on the inside (contained) of some bridge structural members, such as the box girders (which extend to the south from the southern end of Stokes Point).

While lead-based paint was only used on limited parts of the bridge, relatively small amounts of lead may be present in bridge paint/coatings as an additive or as a pigment.  In comparison to lead-based paints the lead levels in these paints are approximately 10 to 100 times less.

It is unlikely that bridge maintenance activities are a significant source of lead in soil at the Stokes Point Reserve.

What are general sources of metals contamination?

Zinc and lead are very common contaminants associated with residential land use.  Sources include historic use of lead-based paint on houses, zinc from rooves and galvanised metal.  Other common sources of metals include imported fill, exhaust emissions from the historic use of leaded petrol in vehicles, and metal particulates from vehicle brake and tyre wear.  

What are you doing to prevent more contamination?

Since 2011, Waka Kotahi has progressively improved its maintenance methodology to significantly reduce the amount of abrasive and paint particulates discharged into the harbour and land during bridge maintenance activities. 

Improvements include reducing our re-painting activities through a more focused risk-based approach, and containment of particulates/abrasives over land.

As part of the conditions of the consents, all Auckland Harbour Bridge maintenance works need to comply with the Environmental Management Plan (EMP) that is approved by Auckland Council.  An Annual Report must be provided, summarising monitoring data, and showing compliance and mitigation. Specific reporting is required if an event occurs which results or has the potential to result in a breach of the conditions of consent or adverse effects on the environment, like a significant discharge into the air or water.

The most recent annual report covering 2019 and received in February 2020, indicated that maintenance works were completed in accordance with the EMP and consent conditions, and that all environmental monitoring results were again compliant with contaminant thresholds.

Resource consents for discharge of abrasive blast products annual reports

History of the issue

Why didn’t Waka Kotahi previously advise nearby residents of contamination found in soil at Stokes Point Reserve?

In late 2010 Waka Kotahi advised Auckland Council that contamination was found in soil at the Stokes Point Reserve. In early 2011 Auckland Council commissioned a soil assessment and had a comprehensive independent Human Health Risk Assessment carried out at Stokes Point Reserve, which was peer reviewed by Auckland Regional Public Health (ARPH). These found that levels of contaminants in the soil were acceptable from a public health perspective.

In discussions in 2012 Auckland Council and ARPH recommended that Waka Kotahi complete an additional Health Risk Assessment to confirm if contaminant levels in soil were sufficient to raise a public health concern at nearby residential properties.  Council and ARPH recommended that this be undertaken prior to notifying the community or seeking permission to test soil at residential properties. 

The Council’s and ARPH advice reflected the need for Waka Kotahi to be thorough in its assessments and planning to avoid unduly raising public health concerns. A Waka Kotahi health risk assessment was conducted in 2013. 

Waka Kotahi concluded based on the evidence available that residential properties adjacent to the Auckland Harbour Bridge would have acceptable contaminant concentrations, and no testing of residential properties was required.

What is Waka Kotahi doing to make sure the soil at my house is safe?

We commissioned an external review to ensure that potential soil contamination from bridge maintenance activities was appropriately assessed from a public health perspective in the Stokes Point area.

Whilst the report does not recommend that Waka Kotahi undertake investigation of individual properties, this does not constitute advice to individual property owners whether or not to investigate or assess their own properties.

If you are still concerned about potential soil contamination on your property and would like this further investigated, please talk to a suitably qualified professional.

Is the Stokes Point Reserve safe?

Auckland Council commissioned a soil assessment and had a comprehensive independent health-risk assessment carried out at Stokes Point Reserve, which found soil contaminant levels at the reserve were acceptable from a public health perspective.

What contaminants have been found in soil?

Soil investigations have been conducted at the Stokes Point Reserve and nearby public land and road reserve. These investigations found metals at concentrations above natural background levels, including lead, zinc and chromium.  Organic substances such as polycyclic aromatic hydrocarbons or PAHs and other hydrocarbons have also been detected.

However, investigations have also found that there is no unacceptable public health risk from any contaminants in the soil.

How often do you test soil? 

Soil testing is not a regular activity and is not required as part of the Auckland Harbour Bridge Maintenance consents.

In the recent past, soil testing at the Stokes Point Reserve and adjacent land was undertaken in 2010 in support of the bridge maintenance consent renewals, and also in 2015 in support of the Te Onewa Pa walkway project consenting.

Auckland Council undertook a separate investigation of soil contamination at Stokes Point Reserve in 2011.

Auckland Council compliance audits and inspections reports

Is soil contamination increasing?

Soil testing is not a regular activity and historic soil testing has not been conducted in a manner that would allow assessment of the change in contaminant levels with time.

However, it is unlikely that soil contamination would be increasing significantly as a result of bridge maintenance activities over the past ten years.  This is because we have reduced our bridge re-painting activities through a more focused risk-based approach and provided containment where these activities occur over land, including over Stokes Point.

Is Waka Kotahi complying with its consents?

Waka Kotahi most recently renewed its consents for bridge maintenance activities in 2011 and again in 2015. An assessment of the impact of the discharge of contaminants to land and the harbour was included in the 2011 resource consent application, and another assessment undertaken in 2014 as part of the 2015 consent application.  On the basis of these assessments, discharge thresholds were established for Auckland Harbour Bridge maintenance activities and approved by Auckland Council in granting these resource consents.  

The consent conditions require that maintenance works undertaken on the bridge to comply with an EMP approved by Auckland Council. Annual Reports are provided to Council, summarising monitoring data, and showing compliance with the discharge thresholds in the consent and mitigation.

The annual reports for each year (2015 to 2019) show that all bridge maintenance works have been undertaken in compliance with the consent conditions and the requirements of the approved EMP. The measured discharges of garnet particulates (used in sandblasting) and discharges of paint and zinc from paint removal and application have been consistently well below the thresholds permitted. 

  • Actual discharge of garnet has ranged from 34% to 59% of the permitted thresholds for each year. 
  • Actual discharge of paint has ranged from 5% to 23% of the permitted thresholds for each year. 
  • Actual discharge of zinc has ranged from 3% to 14% of the permitted thresholds for each year. 

These relatively low volumes of discharge demonstrate the effectiveness of the progressive improvements adopted by Waka Kotahi since 2011 to reduce the amount of abrasive and paint particulates discharged to the harbour and to land during bridge maintenance activities. Improvements have included reducing our re-painting activities through a more focused risk-based approach and containment where these activities occur over land, including over Stokes Point.

Maintenance discharge consent annual reports

Is the bridge impacting the marine environment?

Waka Kotahi most recently renewed its consents for bridge maintenance activities in 2011 and again in 2015. An assessment of the impact of the discharge of contaminants to land and the harbour was included in the 2011 resource consent application, and another assessment undertaken in 2014 as part of the 2015 consent application.  

These assessments found that discharges related to bridge maintenance had negligible impact on the harbour marine ecology, and the overall effect was low to very low. On the basis of these assessments, discharge thresholds were established for Auckland Harbour Bridge maintenance activities, and approved by Auckland Council in granting these resource consents. 

The actual discharges to the harbour from maintenance activities have been significantly less than these thresholds, demonstrating the effectiveness of the progressive improvements adopted by Waka Kotahi since 2011 to reduce the amount of abrasive and paint particulates discharged to the harbour during bridge maintenance activities. 

Contact us

If you have further queries, you can contact us at stokespoint@nzta.govt.nz

If you want to receive information about this matter by email, please also contact us at this email address and we can email further updates to you.

For more information about soil contamination at Stokes Point, please contact: stokespoint@nzta.govt.nz

Technical documents

Terms of reference

Compliance audits and inspections

Consent applications, assessment of environmental effects and decisions

Costing system reports and testing

Environmental and compliance reporting

Resource consents for discharge of abrasive blast products annual reports

Maintenance discharge consent annual reports

General

Official Information Act response to soil contamination

Responded: 11 December 2020

Traffic and travel information
Driver licences
Vehicles
Roads and rail
Commercial driving
Safety
Walking, cycling and public transport
Planning and investment