| Air Discharges and Associated Mitigation Methods | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 33 The amount of ventilation provided within the exploration drive will be sufficient to provide a safe working environment for underground workers. This means that the concentration of contaminants will be required to be below the Workplace Exposure Standards (2020) set by Worksafe New Zealand. This means that any effects from exposure after discharge from the ventilation raises will be negligible. OGNZL will carry out regular monitoring of the underground air quality to ensure that the Worksafe air quality standards are being met. Conditions within underground exploration drives are usually damp. However, if necessary, any dust generated from tunnelling activities will be controlled using water carts and sprayers and muck piles will be watered prior to placing material onto trucks for transport to the surface. 5.4.4 Emissions from blasting Blasting using ammonium nitrate/fuel oil explosives (ANFO) will be used to construct the tunnel (including the portal if required) and during mining. Blasting generates emissions of CO, NOx and small quantities of SO2, as well as dust particulates from the shattering of rock. Low sulphur diesel is used in the ANFO. During blasting operations, the area of the tunnel in proximity to the blast is evacuated and machinery emissions cease, therefore the emissions generated from diesel engines, vehicle movements and excavation will not occur at the same time as blasting emissions. Blasting exhaust and any emissions from vehicles during tunnelling will initially exit through the portal. However, once the tunnel has been advanced and the ventilation crosscut and raises have been developed, primary fans will be installed at a bulkhead at the base of the raises and exhaust air will exit through the ventilation raises. The fans previously located outside the portal will then be moved down the tunnel and hung in the decline backs approximately 50 m from the ventilation raises. This will provide the ventilation for the remainder of the tunnel. Following blasts, the air quality within the tunnel will be tested and cleared before personnel are allowed to enter. Contaminant emissions (particulates, CO, NOx) from the Favona ventilation shaft (which will be similar to the WUG mine ventilation shafts) were measured in August 2007 by Watercare Services Ltd during a series of 5 blasts. The results are summarised in Section 6.3. The concentrations of contaminants are expected to decrease rapidly with distance from the source (either the portal or raise) and to be well below NESAQ and AAQG guideline levels where members of the public may be exposed beyond the site boundary. 5.5 Air Discharges from Wastewater Treatment and Effluent Disposal Area An MBR (membrane bioreactor) wastewater treatment system will be installed to cater for toilets and staff washing and lunchroom facilities. An MBR plant produces a high-quality effluent with low organic load, suitable for discharge to land. The treated effluent will be discharged to a subsurface disposal field to the northwest of the Topsoil Stockpile Area. The discharge of treated effluent is not expected to cause any adverse odour nuisance issues due to the high-quality wastewater and subsurface-based discharge. The disposal field will be located at least 200m from the nearest privately owned dwelling which is an appropriate separation distance.
RkJQdWJsaXNoZXIy MjE2NDg3