Client: Department of Conservation 

The Little Tahiti landfill is located on the north side of the Cleddau River within Fiordland National Park approximately 3 km upstream of Milford Sound, Piopiotahi.  

Due to the proximity of the river, the landfill is vulnerable to flooding and river scour, which are expected to be exacerbated by the effects of climate change. Cross section surveys completed between 2009 and 2019 observed more than 8 metres of erosion beside the landfill. Because of its location in an extremely sensitive receiving environment, a breach of the landfill, despite its small size, could have significant consequences for public health, ecosystems, and the local economy. 

e3Scientific was engaged by the Department of Conservation, with support from the Ministry for the Environment’s Contaminated Sites Remediation Fund (CSRF), to complete a combined Preliminary and Detailed Site Investigation at the site. Field work included test pitting, installation of monitoring wells, and collection of soil, surface water and groundwater samples in a remote and sensitive environment. Test pit observations were used to develop a 3D model to better quantify the volume of waste within the landfill. Soil and water analytical results helped understand risks human health and ecological risks associated with the landfill.  

The findings of the investigation were used to identify and evaluate indicative methodologies that are capable of isolating, managing or removing risks associated with the Little Tahiti Landfill. Preliminary work identified two plausible options for reducing risks associated with the landfill to an acceptable level: excavation and off-site disposal or protecting the landfill in place with flood mitigation. A clear, high-level qualitative assessment of the environmental, social, and economic impacts, adapted from the Sustainable Remediation Forum UK (SuRF) Framework, was completed and documented in a Remedial Options Report (ROR) to help with stakeholder consultation and decision-making.  

Remedial planning is currently underway.