| | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 4 Executive Summary Oceana Gold (New Zealand) Limited (OGNZL) operates an open cut and underground gold mining operation at Waihi in the Waikato Region. Ongoing exploration and mine optimisation have identified further mineral resources that can be economically recovered. These new activities are referred to as the Waihi North Project (WNP). This report assesses the potential air quality effects of the following inter-related elements of the WNP collectively known as the Waihi Surface Facilities: ● A new open pit near the existing Processing Plant and centred over Gladstone Hill, to be called the Gladstone Open Pit (GOP); ● A new tailings storage facility to the east of existing TSF1A, called TSF3; ● A new rock stack (called the Northern Rock Stack (NRS)) at the current Northern Stockpile area; ● An upgrade of the existing Water Treatment Plant to double its current treatment capacity; and ● Upgrading the existing Processing Plant to enable ore processing up to 2.25 million tonnes per annum (MTPA) capacity, up from the current 1.25 MTPA. The results of ambient air quality monitoring and the complaints history for the site demonstrate that any increases above background concentrations of deposited dust, total suspended particulate (TSP), fine particles less than 10 microns in diameter (PM10) and silica, measured at sites in the vicinity of the previous and current mining operations, are small and well below the relevant standards and guidelines recommended by the Ministry for the Environment (MfE) and within the current resource consent limits. The concentrations of PM10 measured in Waihi are comparable to concentrations in other small towns in the Waikato Region. Emissions from the proposed WNP mining activities will be similar to those from the existing mining operations and will be similarly controlled in accordance with the Air Quality Management Plan. The assessment of potential effects described in this report has identified that there is a risk of sensitive receptors located within 100m of the proposed activities being exposed to infrequent, short duration discharges of deposited dust and TSP during dry, windy conditions. In order to mitigate this risk, it is recommended that some additional mitigation measures are implemented on site when weather conditions are conducive to the generation of dust. The concentrations of PM10, respirable crystalline silica (RCS), nitrogen oxides (NO2 and NO) and carbon monoxide (CO) will remain within the National Environmental Standards for Air Quality (NESAQ), guideline values and current consent limits beyond the boundary of the mine. Emissions from the Processing Plant will increase in response to the projected increase in the ore processing rate. Mercury emissions will also increase in response to the higher mercury content of the GOP and Wharekirauponga Underground Mine (WUG) ore. However, dispersion modelling indicates that the emission of mercury and other metals from the Processing Plant would not exceed relevant air quality criteria. OGNZL is proposing to install a retort oven before the processing of the GOP and WUG ore commences. The retort oven would substantially reduce mercury emissions from the plant. The assessment of effects described in this report concludes that, providing OGNZL continues to use the methods currently used to minimise discharges to air and adopts the additional mitigation measures recommended in this report, the adverse effects of discharges to air from the WNP will be adequately avoided and mitigated and consequently, the likelihood that these discharges will result in noxious, dangerous, offensive or objectionable effects is considered to be low.
RkJQdWJsaXNoZXIy MjE2NDg3