Waihi North Project Preliminary Site Investigation (Ground Contamination) Williamson Water & Land Advisory Limited ii Investigation Summary Williamson Water & Land Advisory (“WWLA”) has prepared this Preliminary Site Investigation (“PSI”) to inform the design and planning of the Waihi North Project (“WNP” or “project”) proposed by OceanaGold (New Zealand) Limited (“OGNZL”). The objective of this PSI is to identify potential ground contamination in the project footprint (which comprises multiple separate sites) and provide recommendations to support project planning, design and approval processes. As such, this PSI: • Describes the relevant site history and likelihood of encountering ground contamination in the WNP area; • Recommends methods to manage contamination that may be intersected by the project; and • Identifies approval requirements under the Resource Management (National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health) Regulations 2011 (“NESCS”). The key findings of this PSI are summarised below. Table 1. Summary of Preliminary Site Investigation Land use history and potential for ground contamination [Section 3] Various land uses listed on the Hazardous Activities and Industries List (“HAIL”) with potential to cause ground contamination are present within the WNP area. Existing HAIL activities within the project footprint are generally localised and limited in magnitude and pose low potential for significant effects on human health, the environment and the overall project. The presence of ‘mining industries’ in parts of the WNP area (such as the Processing Plant and Water Treatment Plant area) results in an overlay of HAIL Activity E.71 in those established areas. • Other HAIL activities present within the existing Processing Plant and Water Treatment Plant site, rock stockpiles and Tailings Storage Facilities (“TSFs”) include: - Dangerous goods, waste and hazardous materials storage. - Process chemical use. - Heavy machinery workshops. - Fuel storage and use. - Water treatment. - Tailings disposal. There is potential for dangerous goods/hazardous materials storage and use areas to contain contamination. However, the materials storage and handling practices implemented by OGNZL are modern, bunding and overflow management systems are in place, and the storage areas are well maintained. No visual or olfactory evidence of contaminant spills or poor handling practices was noted. • Within the Willows Road Property, proposed Tailings Storage Facility 3, proposed Gladstone Open Pit and proposed Northern Rock Stack areas, farming activities predominate. HAIL activities in these areas typically relate to Asbestos-Containing Material (“ACM”) present in buildings, fuel storage and localised agricultural activities such as the storage of chemicals for weed spraying and livestock drenching. Offal pits may also occur. No evidence of livestock dips was noted. Conceptual site model (CSM) [Section 6] A Conceptual Site Model (“CSM”) was developed to illustrate known and potential sources of contamination, routes of exposure (pathways), and the receptors (people or the environment) that are affected by contaminants moving along those pathways. The CSM directs the requirement for investigations to identify any remedial actions, relevant earthworks mitigation, and contamination-specific health and safety measures. The CSM prepared for this PSI shows: • The current operational areas of the site such as the Processing Plant and Water Treatment Plant use modern and well-maintained hazardous materials storage facilities and handling systems. As such, there is a ‘Low’ risk of significant adverse effects in a contaminant spill scenario. During upgrades in these operational areas, controls will need to be in place to ensure the integrity of the storage and containment systems for hazardous materials are maintained and any soils/water affected by hazardous materials are managed appropriately. • Outside of the current operational areas, the risk to people and the environment presented by soil disturbance and land use change associated with development of the proposed new facilities is ‘Low’. Potentially 1 “Mining industries (excluding gravel extraction) including exposure of faces or release of groundwater containing hazardous contaminants, or the storage of hazardous wastes including waste dumps or dam tailings”.
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