This document may not be reproduced in full or in part without the written consent of Marshall Day Acoustics Limited Rp 001 R0 20210601 SJP (Waihi North Noise Assessment) ISSUE 37 of 79 9.0 WUG NOISE CALCULATIONS The WUG aspect of the project involves a new underground mine and associated mine infrastructure to the north of Waihi Township. It involves the following main activities with the potential to create noise effects: • Construction and operation of the Willows Portal, particularly from the portal to the first vent raise – where underground plant is nearer the portal; • Underground blasting and the transport of rock to stockpile (the Willows Rock Stack); • Construction of the Surface Facilities Area (SFA) site and associated trenching, roadworks and earthworks; • Construction and operation of a vent raise within the Rural Zoned landholding (the ‘farm raise’); • Construction of four vent raises in the Coromandel Forest Park, including helicopter movements and surface works; and • Ongoing operation of underground ventilation fans. Activities like construction, roadworks and stockpiling will only occur during the day. This is both to control noise and for operational reasons. Underground operations will progress on a 24/7 basis. While activity will mainly be confined to within the tunnel at night, there will be some need for service vehicles to enter and exit the portal. Drilling and raise boring/surface connection activities at the vent raise sites are also anticipated to be on a 24/7 basis, albeit for only a few weeks at any location. 9.1 Calculation Details Noise-generating aspects of each of the key phases are given in Table 14 below. The discrete scenarios below are referenced later in this report with respect to our noise modelling. Table 14: Modelled scenarios for WUG Project Phase Scenario Description Site Establishment 1a Services trenching; site earthworks and foundations 1b Surface infrastructure installation; internal roadworks; portal formation Tunnelling 2a Initial tunnel drive and initial vent raise 2b Later stages (after farm vent) 2c Night works Vent Raises 3a Orebody vent raises 3b Helicopter activity to support 3a above 3c Vent shaft operational fan noise Activities 1a, 1b, 3a and 3b are considered construction activities. Work to develop the tunnels and supporting facilities is expected to take around four years. This is broadly one year of site establishment and construction and three years of tunnel driving. We note that a plant access tunnel of approximately 5 km will also be constructed to connect the Dual Tunnels with the Processing Plant at Waihi. While this is a major engineering operation, it will have limited surface noise effects. Our calculations therefore do not consider this as a standalone element, as the main short-term effects from establishment of the tunnel portal is captured in activities shown in Table 13. The Willow Access Tunnel will initially be ventilated through use of an external, sound attenuated, containerised fan outside the portal entrance until the first raise is established on the farm site, which will permit conventional ventilation via fans located in the tunnel itself. These are discussed further in the next section. None of the operational scenarios allow for noise from any tonal reversing alarms; these have been excluded from our assessment. 9.1.1 Receivers The nearest dwellings to the main worksite are shown overleaf in Figure 23. This excludes the dwelling at 132 Willows Road, which will be owned by OGNZL during the project. Bunds have been proposed that help reduce the level of noise to the closest receivers as shown in Figure 22. We assume that these will be established relatively early on and therefore will be effective for all tunnelling phases (2a to 2c) as described in Table 14. All bunds in the Willows site area are modelled to be 3 metres high. This may have limited use in screening most of the main SFA works, but will provide screening of more localised noise sources. Examples would be mechanical plant, car door slams, vehicle and HGV movements, servicing, trailer coupling or washdowns. Whilst these are relatively small-scale sources, they would benefit from the bund, especially if this area is used at night. Figure 22: Example of bund layout around site access 9.1.2 WUG Noise Source Assumptions The following plant in Table 15 has been included in the model. Table 15: Noise source data used in WUG calculations Item Noise Level, dB LwA Source Height*, m Operating Time† 50t Excavator 109 2.5 75% 20t Excavator 103 2.0 50% Concrete Truck & Pump 103 2.0 50% Mobile Crane 102 2.5 75% Vibratory Poker 104 1.0 50% Telehandler/Forklift 104 1.5 75% General Light Tools 98 1.0 90% Grader 110 2.0 50% Vibratory Roller 109 2.0 50% Dump Trucks 110 3.0 90% 3t Mini Excavator 99 1.5 80% 12t Trenching Excavator 101 2.0 50% Trench Compactor/Roller 106 2.0 20% Large Truck Movement 108 1.5 100% Medium Truck 104 1.5 100% Small Truck 100 1.5 100% Light Vehicle/Ute 95 1.0 100% Underground Truck 114 2.0 100% Dozer 106 2.0 75% Water Cart 119 3.0 75% Temporary Ventilation Fan 114 3.0 100% Transformer 66 2.0 100% Compressor 103 1.0 100% Shaft Collar Installation 115 2.5 75% Large Generator 92 1.5 100% Water Pump 94 1.5 100% Exploration Drill Rig 106 2.0 20% Small Generator 84 1.0 100% *Modelled source emission height relative to the source’s local terrain elevation. † As percentage of shift duration for daytime activities. Used to calculate daytime noise averaging.
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