Tāhunanui Back Beach remediation options to be considered

Removal of the contaminated material from Tāhunanui’s back beach, reinstatement of low-level dunes and a small car park at a cost of $5.8 million is recommended by Nelson City Council staff following a comprehensive site assessment.   

The recommended option aims to prevent further erosion, protect people and animals from contaminated material, and avoid any adverse ecological effects to the area. It, along with a series of other options, will be considered by Council’s elected members at the upcoming March 7 Council meeting. 

Nelson Mayor Nick Smith says the contamination problem on Tāhunanui Beach cannot be ignored and Council staff have done a good job of developing a workable solution.  

“The $5.8m cost of the remediation is a large, unbudgeted expenditure and I will be doing all I can to secure Government support from the Contaminated Sites Remediation Fund to offset the cost to ratepayers.” 

The recommended remediation options for the site - removal of the contaminated sawdust and underlying sand to landfill, followed by refilling, and planting of the area to create low dunes, also includes the addition of a new, smaller car parking area near the entrance to the current car park.  The estimated $5.8m cost of the work includes disposal costs of up to $3.4m and a project contingency of $1.06m. Council is working closely with the Ministry for the Environment to seek central government funding towards this cost.

The graphic above shows the 11,500m3 of sawdust and sand proposed for removal from the back beach. 

Group Manager Community Services Andrew White says the recommended option is considered the best way to protect this highly sensitive and important part of our shoreline. 

“In assessing the options for the area, Council commissioned a comprehensive coastal assessment. This has shown that removing the contaminated material and reinstating the area is unlikely to have a material impact on erosion of the shoreline and the material being removed makes up only a small percentage of the overall sand spit volume.” 

The options assessed for remediation of the contaminated sawdust and underlying sand were to leave it; treat it on site; remove and use as aggregate and remove it and take to landfill. 

The options assessed for reinstatement of the site were; do nothing; establish a coastal wetland; establish low-level dunes; establish high-level dunes; build a small car park and low-level dunes and; rebuild the car park. 

“Having considered the options, we are recommending removing the sawdust and contaminated underlying sand to York Valley Landfill as a timely and effective way to deal with the material that ensures it does not pose any further risk to the environment or beach users.  

“Filling and re-planting the site to create low dunes will have minimal impact on the beach, while providing additional habitat for coastal species. The smaller parking area south of the site, while only about a third of the size of the existing car park, will provide continued easy access for those that regularly visit the area. Replacing the car park in full is inconsistent with the Tāhunanui Reserve Management Plan and would cost considerably more to install and maintain in an area that will continue to erode. 

Council staff are recommending removing the contaminated material and refilling and replanting the site to create low dunes. 

“However, ultimately the decision on how the area is remediated will be a decision for elected members, and we are still gathering feedback from Tāhunanui Business and Citizens Association on the options.” 

All remediation options for the site, including the preferred options, will be presented at the March 7 Council meeting for consideration. The cost of the remediation options ranges from $5.3m - $6.2m. Once a decision has been made, any agreed work is expected to begin mid-year, with funding support from central government anticipated to significantly reduce the cost to ratepayers. 

To read more about the options please see https://shape.nelson.govt.nz/tahunanui-back-beach-sawdust-remediation.