Waihi North Project Preliminary Site Investigation (Ground Contamination) Williamson Water & Land Advisory Limited 31 3.2 Processing Plant and Water Treatment Plant site Site description summary The main ore processing and ancillary facilities (workshops, process chemicals and hazardous materials storage, miners base etc) are located in the southeast of the Processing Plant and WTP site. The conveyor from the Martha Pit traverses the Processing Plant and WTP site area from west to east. The WTP is in the centre of the site, north of the conveyor, with the Polishing Pond Stockpile (rock from the underground mines) stockpiled north of the conveyor, within the southern half of the proposed facilities expansion area. Farmland is further to the north/ northwest. Proposed developments Expansion activities are proposed to occur to the north of the Processing Plant/WTP site where the aforementioned Polishing Pond Stockpile is located and on land that is currently pastoral. A portion of the western side of the property (<20% of the total) will be used for the WUG portal and associated platform with the remainder being relatively unchanged. Earthworks will be significant within the portal/ platform area. Minimal work is expected within the existing processing facilities as all existing infrastructure will be maintained. Where soil disturbance is required, it will largely be isolated to shallow soils to prepare foundations. Site history summary The proposed expansion area to the north of the existing facilities was predominantly farmland before being developed for mine processing in the early 1990s. Any dwellings that may have contained asbestos or lead paint have been removed and the ground since modified. A historic pond in the west of the site is no longer present but has also not been filled (only drained). HAIL activities identified at the Processing Plant and WTP site are summarised in Table 4 and shown on Figure 12. Table 4. Potential for contamination: Processing Plant and WTP upgrades Land use Potential contaminants Possible extent of contamination HAIL Assessment Areas potentially impacted Storage of chemicals and fuel HAIL Activity A17: Storage tanks or drums for fuel, chemicals or liquid waste Wide ranging including cyanide, solvents, acids, bases, cement, oils, hydrocarbons, etc There are multiple chemical and fuel storage areas around the Processing Plant. The most significant of these is the cyanide storage and mixing areas, as well as the chemicals stored in the water treatment plant (wide range). While most are bunded and well maintained, there is high potential for low to moderate levels of contamination to exist immediately surrounding most dangerous goods stores, most likely only extending to shallow soils. (Note: this also includes storage of domestic volumes of pesticides for on-site pest control (e.g. rat bait), fuel storage, chemical storage in mechanical workshops, the WTP, etc). HAIL Activity A17 applies to site. The entire Processing Plant and WTP site. Transformers HAIL Activity B2: Electrical transformers Metals, hydrocarbons, PCBs (unlikely given age) Potential for contamination from transformers is limited given their modern nature (post-dating PCBs) and high level of maintenance. However, isolated contamination in their immediate footprint cannot be ruled out, but if present would be localised and shallow. HAIL Activity B2 applies to site. Two transformer locations near offices in the south and WTP in the north. Explosives storage HAIL Activity C1: Explosives storage Ammonium nitrate, metals, sodium hydroxide Explosives storage areas are very tightly controlled. While there is some potential for contamination due to the large volumes of some materials stored, the careful nature of handling, and the fact that no explosives are produced at the site, means overall potential for contamination is low. HAIL Activity C1 applies to site. Magazine areas in the west of the Processing Plant and ammonium nitrate storage northwest of the WTP.
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