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 3 of 79 SUMMARY We have investigated and assessed proposed noise emissions from the Waihi North Project (WNP). WNP is broadly made up of Gladstone Open Pit (GOP) and other ancillary operations, the Northern Rock Stack (NRS), Tailings Storage Facility 3 (TSF3) and the Wharekirauponga Underground Mine (WUG). Our assessment is based on the activities proposed to be undertaken, the existing noise environment, the currently consented operations and the mitigation that can be implemented. Overall, our assessment indicates that generally noise levels would be compliant with the recommended criteria An important aspect in our considerations relates to what we consider is construction activity and what is operational. Following discussions with OGNZL, we defined the construction activities to which less stringent noise criteria would apply. Construction noise levels remain compliant in almost all circumstances. There may be some limited localised exceedances, but these would be managed through appropriate management plans. There are some receivers where the operational noise levels without mitigation are slightly above 50 dB LAeq. For these receivers, there would be a small adverse impact on the level of amenity for these people. Mitigation for these receivers is required. This is discussed in Section 11.0. We note that the proposed conditions OGNZL is committing to would not allow that to occur so remedial action prior to operations commencing is necessary. Our overarching conclusion is that if the noise limits enshrined in the proposed conditions are met, then noise effects as a result of the WNP project are acceptable. The assessment at each location is summarised below. Gladstone For identified construction activities, predicted noise levels will be around 45 dB LAeq at the closest dwellings. This is well below the normal construction noise limits. Unmitigated operational noise levels from the Gladstone Pit are calculated to be below 50 dB LAeq at all receivers except for 27 dwellings located on Moore Street, Barry Road and George Street. For these residents, model results show there would be a small exceedance of 50 dB LAeg in the first two years which would equate to a small adverse impact on the level of amenity these properties experience. However, the proposed conditions require that a noise management plan (NMP) be prepared to outline the methods to be used to ensure noise levels do not exceed 50 dB at any residence not owned by OGNZL or subject to or with an agreement with OGNZL. The NMP will prescribe a noise mitigation development process that will occur prior to operations commencing, that will set out the options considered, and provide certification that noise levels comply at those residences OGNZL does not have an agreement. These options would include (but not be limited to); • The use of quieter machinery (determined by a noise source characterisation procedure) • Restrictions on operating hours • Bespoke screening of individual sources • Screening of noise sensitive receivers • Noise monitoring programmes (including noise modelling and measurement regimes) On this basis and with the above measures in place, we consider the Gladstone noise emissions would be able to comply with the noise limits in the proposed conditions, and therefore would be reasonable from a noise effects perspective. Process Plant The Processing Plant will be upgraded to facilitate the additional throughput and extended lifespan resulting fromWNP. The calculations show that there is a general increase in noise levels from the processing plant only (3-5dB) as a result of the upgrades but also a small decrease to the south-west. This is a barely discernible to just noticeable increase. During the day, taking account of the fact that generally, other mining operations often contribute more noise to these receivers, increased processing plant noise levels are unlikely to be discernible for much of the time. Overall, noise emissions for the processing plant are also compliant during the day. However, it is possible that noise levels at night may just exceed the night-time noise limit of 40 dB by a small margin. As the processing plant design is not possible to accurately model at this stage because the equipment is relatively unique, being sourced from other OGNZL sites around the country, and is currently not operational so we cannot measure the noise emissions, we have necessarily included some conservatism in the calculations. This means it is possible that once established on site, there is likely to be lower noise levels in practice. In any event, and as for Gladstone, the proposed conditions require that a noise management plan (NMP) be prepared to outline the methods to be used to ensure noise levels do not exceed 40 dB at any residence not owned by OGNZL or subject to or with an agreement with OGNZL. The mitigation methods would include (but not be limited to); • Restrictions on operating hours • Bespoke screening of individual sources (primarily by the use of full enclosures) • Screening of noise sensitive receivers • Noise monitoring programmes (including detailed noise modelling of the new plant when installed and measurement regimes) On this basis and with the above measures in place, we consider the processing plant noise emissions would be able to comply with the noise limits in the proposed conditions, and therefore would be reasonable from a noise effects perspective. NRS For identified construction activities, calculated noise levels associated with the construction of the earth bunds will be compliant at the closest dwellings. Operational noise is also compliant with the recommended criteria and the noise effects, in our opinion, are considered reasonable. TSF3 The overall TSF3 construction activity is sufficiently long and similar in character to normal mining activities that we consider it as an ‘operational’ activity, rather than ‘construction’. However, topsoil stockpiles, the clean water diversion drains and haul road construction are treated and assessed as construction noise. Further, predicted operational noise levels are below 50 dB LAeq and are therefore below the proposed compliance limit assessment criteria and the noise effects in our opinion, are considered reasonable. WUG We assessed the potential noise effects from the construction and establishment phase of the project, including the WUG access tunnel. Our assessment included consideration of noise effects on rural receivers, and receivers in the DOC conservation area. For the Willows Road SFA site, with the recommended mitigation in place, construction and operational noise levels received at the nearest rural receivers would comply with the recommended noise limits and we therefore consider to be acceptable overall. For the ventilation raise sites, noise levels from the construction of the raises, both on ground and from helicopter operations would potentially have some small effect on recreational users of the DOC land, but would be of no appreciable significance due to the relatively short duration and the infrequent use by recreational users.
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