Waihi North Project Preliminary Site Investigation (Ground Contamination) Williamson Water & Land Advisory Limited 36 3.4 Existing Tailings Storage Facilities Site description summary The TSFs comprise two large tailings ponds and the Northern Stockpile. The TSFs collect tailings (surplus material from ore processing) as a slurry and allows the solids to settle out into a condensed mass at the base of each pond. TSF2 is no longer used and water quality has improved to a point where it is able to discharge to the Ohinemuri River. TSF1A is currently in use. A range of subsurface and perimeter drains capture leachate and runoff for treatment in the WTP. Proposed developments Minimal upgrade activities; eventually TSF1A will be retired and TSF3 commissioned (Section 3.3). Site history summary Prior to the TSFs being built, the area was farmland with isolated dwellings, farm sheds and a market garden. These have now all been removed and the site significantly reworked so that there is no evidence of their original existence. We have considered all potential contaminating (HAIL) activities for the existing TSFs in Table 6 below. Refer to Figure 14. Table 6. Potential for Contamination: Existing TSFs Land use Potential contaminants Possible extent of contamination HAIL Assessment Areas potentially impacted Transformer HAIL Activity B2: Electrical transformer Metals, hydrocarbons, PCBs (unlikely given age) Potential for contamination from the transformer is limited given its modern nature (post-dating PCBs) and high level of maintenance. However, isolated contamination in the immediate footprint cannot be ruled out. HAIL Activity B2 applies to site. Transformers Asbestos use in buildings (historic) HAIL Activity E1: Asbestos in a degraded condition Asbestos No asbestos was observed on current buildings. Historic buildings that may have contained asbestos were demolished approximately 40 years ago so potential for contamination to remain is negligible. HAIL Activity E1 does not apply to the site. - Mining HAIL Activity E7: Mining industries Wide ranging but including cyanide, acids, metals, hydrocarbons and a range of other contaminants used in processing Tailings comprise all of the wastes associated with the ore processing activities. These are confined to the existing TSF1A and TSF2 footprints. The TSFs are constructed according to a landfilling standard with clean water diversion, basal lining and underdrainage collection and treatment. While they are themselves contaminated the affected materials are contained and managed. These are not expected to be disturbed. HAIL Activity E7 applies to the site. All tailings storage areas.
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