Project updates

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Update: Wednesday 20 September, 2023

The emergency remediation work carried out at the end of last month to cover and protect the exposed sawdust pile has so far withstood the weather and spring tides.

While there has been some erosion of the sand bund, no additional erosion of the face of the sawdust pile has taken place. We will continue to closely monitor and maintain the sand bund, which remains the most cost and time effective way of managing the exposed sawdust at this time.

A risk assessment using existing test results from the sawdust pile has been carried out, and both this assessment, and feedback from Te Whatu Ora, has concluded that the risk to human health from the sawdust is low. Further testing is expected to take place next month. The updated test results will allow us to determine if the sawdust, once removed, can be transported to local landfills for disposal.

A funding application for the testing and sawdust remediation action plan has been submitted to the Ministry for the Environment.

Update: Thursday August 24, 2023

Tāhunanui back beach will be closed on Friday, 25 August as Nelson City Council contractors work to cover and protect the exposed face of the contaminated sawdust pile.

Heavy rain on Saturday 19 August, and large waves resulted in some further erosion and undercutting of the exposed face of the sawdust pile. The fencing around the area has been adjusted, and during the Friday closure period, an asphalt bund will be installed to divert water runoff from the carpark away from the beachfront edge, and the exposed sawdust will be wrapped with a geotextile cloth and partially covered with sand to protect it from large spring tides expected next week.

Council has been able to undertake this work under the Resource Management Act's emergency provision.

The closure period will be between 5.30am-6pm, on Friday 25 August. Please see the map for details of the restricted area. The carpark and surrounding area will be open as usual after this time.

If you are visiting the beach, please be mindful of machinery working and feel free to speak to the staff helping keep the area safe.

In addition to this work, Council has appointed a specialist consultant to manage the sawdust remediation and removal. Their first task will be to produce a risk assessment report and identify any further investigation required.

An application to the Ministry for the Environment’s Contaminated Sites Remediation Fund is expected to be submitted by the end of the week. We will then work collaboratively with MFE staff to complete the application.

Tāhunanui back beach work 25 August 2023

Tāhunanui back beach work area

Map of closed area of Tāhunanui back beach


A request for $450,000 to carry out urgent short-term erosion mitigation work at the site to prevent further erosion of the sawdust into the environment and work to plan for the sawdust’s removal was unanimously approved by elected members in the 10 August Council meeting. Work on a short-term remediation plan to contain the exposed sawdust will begin immediately, with the appointment of a specialist consultant to advise us on the best plan of action.

The amount of money requested was a best-guess estimate, to allow Council to begin work quickly, and in expectation that any remediation for the site is likely to be complex.

Mayor Nick has written to the Government, seeking support from the Ministry for the Environment’s Contaminated Sites Remediation Fund to help with the costs of remediation for this site. A formal application for those funds is now underway.

We are engaging a consultant to advise us on the best course of action to remediate the situation. They will offer short-term, mid-term and long-term solutions. This could involve covering the sawdust material, or a barrier of some sort to mitigate wave action at the base of the material, but until we have the consultants advice, we do not yet know what the next steps will be.

The Envirolink report has recommended that the sawdust be removed, due to the constant erosion and discharge of the contaminated material. How and when this can be done, and where the contaminated material can be taken after its removal, will be determined in consultation with specialist consultants familiar with dealing with contamination in marine environments.

The testing report states that much of the material is capped (protected) by the sealed car park and surrounding topsoil and/or sand thus preventing direct human exposure. While the face of the sawdust pile along the foreshore is exposed to the public, it is not readily accessible, is now covered, and would not be a location where prolonged exposure occurs.

While we are awaiting further work to assess the level of risk to human health in this area we have installed more fencing and more warning signs as a precaution. We ask that you stay away from the area and do not let your pets in the area. However, one off exposure events are not considered a high risk at this stage.

National Public Health – Nelson Marlborough agrees that the risk is low. The risk of contaminants drifting from the erosion site on to recreational areas is low, and the risk from the particular contaminants and levels identified is generally through longer term exposures and repeated doses. However, while waiting for further expert advice, as a precautionary approach we would suggest avoiding eating food or young children playing in the area.

The car park is open, with safety fencing in place to stop people and vehicles getting too close to the erosion site, and it continues to be monitored.

Council has implemented a policy of ‘managed retreat’ since the adoption of the Tāhunanui Reserve Management Plan (RMP) in 2004 ( ), removing fallen large trees, scoured carparks and roadways.

The RMP is specific to the management of coastal erosion, “there are no hard protection works planned for the western end of the beach, north of the embayment, even though car parks at the west end of the reserve are threatened by the eastward migration of the Blind Channel’.Further, “Car parks at the west end that are threatened by erosion will be closed as necessary and structures removed, rather than constructing protection works.”

There may be other sites around the city where sawdust material was deposited. Council records show other sites were considered in addition to the Tāhunanui Beach site, and similar site tests on these areas will be carried out, but due to these being areas that are not actively eroding, we do not expect similar public and environmental exposure.

Yes, this site has been deemed a HAIL site and has been added to the online maps that show all HAIL sites.

The testing report recommends that the sawdust should be removed from its current location. It is one thing to allow what we thought was untreated sawdust to erode naturally, it is quite another to consider letting this continue now that we know the pile contains treated timber.

The investigation phase will consider the environmental, public health, consent and risk cost benefits.

Council initially did not believe the sawdust was a pollutant and believed it would break down over time. However, we were continuing to monitor the area and following concerns raised in 2022 about wood offcuts that had been uncovered, we committed to testing the sawdust. This initial testing showed that some of the sawdust originated from pieces of timber that had been chemically treated. This prompted further, more in-depth testing of 27 test pits to confirm the use of copper, chromium, arsenic, boron (CCAB) and and other treatment chemicals such as pentachlorophenol (PCP), as well as the exact dimensions of the sawdust stockpile.

While the results confirm that CCAB has been used at the facility where the wood waste was created, we believe there is also a large amount of sawdust/wood waste material that isn’t treated due to the variable concentrations that have been detected.

The August 2022 weather event naturally became a staff priority for many months following the event and our normal business as usual had to be put on hold as a result of this. It did take some months to appoint and then commission a consultant who was able to do this work. We met with a consultant in March 2023 and met onsite in April 2023 with the first report received in May 2023 and then follow up testing completed last month.