Waikato Regional Council’s acid sulfate soils technical guidance

Following completion of an assessment of the probability of acid sulfate soil (ASS) occurrence in the Waikato region (GHD, 2024), Waikato Regional Council commissioned GHD Limited to prepare this guidance document.

The intent of this guidance is to provide technical advice to help improve the assessment of ASS and guide the regulatory response.

In particular, the aim is to standardize ASS assessment and management to reduce the risks presented by ASS to the environment and infrastructure.

This document will support the reader in the following ways:

• Introduce and define ASS
• Identify the circumstances whereby ASS may present a risk
• Identify how to conduct an investigation and test soil
• Present methods that can be adopted to manage or reduce risks arising from the disturbance of ASS.

This document has been deliberately compiled as a concise summary. As such it does not go into detail on some matters, such as where ASS are to be found in New Zealand or the complex considerations for site specific ASS risk assessment. If further supporting information is required, the reader is directed to the Australian guidance references listed in the document. 

Report: TR 2025/25

Authors: Sarah Gilmour and Jade McConchie (GHD Limited)