Tāhunanui contaminated sawdust update: Plans for removal progress; remediation options under development

Plans for the removal of the contaminated sawdust pile at Tāhunanui are on track, with works expected to take place in the first half of next year.

The exposed face of the sawdust pile is covered by a geotechnical cloth, reinforced with a sand bund, after testing in May this year confirmed the presence of concentrations of arsenic, chromium, copper and boron as well as dioxins. The findings are consistent with at least part of the buried sawdust and wood pieces being treated. 

Nelson City Council is seeking to remove the contaminated sawdust and has now confirmed that York Valley Landfill is able to accept the material once it is extracted.  

Group Manager Community Services Andrew White says Council officers are looking at how to do this in the most environmentally conscious and efficient way.  

“There is quite a lot of material, with at least 6500m³ of contaminated sawdust to be removed and more contaminated sand underneath. Once it’s gone it will leave quite a large hole in the landscape. We’re very conscious that we don’t want to speed up the erosion of the back beach and that we are in keeping with the Tāhunanui Reserve Management Plan. 

“Removal of the sawdust will take some time. In part this will be due to the effect that the tides will have on the work, but it will also require specialised equipment to reduce further contamination of the wider area as the sawdust is removed and quite a large cordon. This could potentially take two to three months, but the exact timing has not been confirmed.” 

Council is now looking at the options available for restoring the site once the sawdust is removed, but costs and the impact of the options on the surrounding environment have not yet been completed.  

Potential options include grading and planting the site to establish an estuary or filling the area and planting the site to establish dune grasses. An option to create dunes on the northern face of the site and establish a parking area to the south of the site is also being considered. More details on these options will be made available as they are developed further.  

A final decision on a preferred remediation option is expected to be considered by elected members in February next year. Once a decision is made, another application to the Ministry for the Environment (MfE) will be made to cover the cost of the works. Council’s current application to MfE for funding to cover the site investigation and remediation options assessment is currently being assessed, but it is not yet known when a final decision will be made. 

In the meantime, the temporary sand bund covering the exposed face of the sawdust pile was topped up earlier this month, and the area will continue to be monitored over the Christmas/New Year period. 

Following further tests, an updated risk assessment of the back beach site has reconfirmed the risk of the contaminated sawdust to human health is low. The exposed face of the sawdust pile is contained, and the assessment found there was low risk of health effects for older children, adults or pets from the mixed sand/sawdust outside of this area.  

In addition to the back beach site, testing of other sawdust dumping sites has been carried out at three other locations: the Trafalgar Park Embankment, Corder Park and in front of Wakapuaka Cemetery. We are awaiting test results. As the embankment and Corder Park are existing HAIL sites, the results are expected to pick up contaminants from other historic sources.