Waihi North Project Preliminary Site Investigation (Ground Contamination) Williamson Water & Land Advisory Limited 51 6. Conclusions This report has been prepared to support OGNZL’s proposed expansion of their Waihi mining operations, referred to as the Waihi North Project or WNP. This report has also been prepared commensurate with regulatory requirements for a PSI. This PSI has assessed the potential for contamination to be encountered within the existing operational facilities (where there are likely to be some minor upgrades/ soil disturbance) and in areas which are currently not utilised for mining operations but will have a significant role in the expansion. A number of potential sources of contamination associated with mining operations were identified within the operational parts of the site. These include the ore processing facilities (which include, for example, bulk storage and use of cyanide, acids, solvents), the WTP (which receives and treats all process and surface water in operational areas) and ancillary activities such as mechanical workshops, fuel storage, transformers, explosives storage and accidental contamination from spills or fires. Within currently undeveloped project areas, potential contamination sources are primarily related to farming activities (use of drenches, market garden chemicals and minor fuel storage) and asbestos use within dwellings and some sheds. With the exception of the existing TSFs (which will largely remain undisturbed through this project) contamination sources are predominantly ‘point sources’ and if contamination is present, it is likely to be confined to surface soils in the immediate vicinity of the activity. This means that the scale of the earthworks proposed will dwarf the volumes of contaminated soil that may be present. Soil sampling is proposed to occur in targeted areas as informed by the HAIL assessment prior to the commencement of earthworks associated with the WNP. This may be done in a staged manner to support works as required. Following soil sampling, remediation of isolated areas can be completed if necessary then contamination management methods removed (no longer apply) so that bulk earthworks can proceed under standard earthworks controls. While asbestos contaminated soils will likely require removal from site and disposal to a licensed landfill, other contamination will likely be mixed and diluted with parent rock and retained onsite (unless significant contamination is encountered, but this is considered highly unlikely). Resource consent is required for soil disturbance as a discretionary activity under the NESCS and the WRP (assuming isolated remediation is necessary). A SMP has been prepared by WWLA under separate cover to support consent applications.
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