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 14 of 79 3.0 EXISTING NOISE ENVIRONMENT 3.1 Existing Township Noise Measurement Data (OGNZL) We have been provided with noise measurement data that have occurred at Waihi from the OGNZL archives from 2010 to 2020. These measurements have been undertaken for: • Complaint response monitoring; and • Compliance monitoring. The results of the compliance monitoring are compiled and issued in a quarterly compliance report to the HDC. The compliance obligations within the District Plan are also summarised in OGNZL’s Noise Management Plan. Recent compliance monitoring nowmainly occurs at two positions, ‘Scout Hall’ and ‘Purcells’, as shown on Figure 4 below. Figure 5 shows the average noise level as well as an indication of the range of all measured noise levels at those positions. Whilst compliance monitoring in the past focused on the Martha Pit, because no works have occurred there since 2015, compliance monitoring has been focussed on the other operations. Measurements have been undertaken both day and night at these locations for compliance purposes. Figure 4: Regular noise monitoring positions used by OGNZL Data for the last 10 years at the two main positions are collated in Figure 5 opposite. Also shown in Figure 4 is the position ‘C’ on Clarke Street. Monitoring is conducted here only infrequently, and detailed data has only been gathered since 2019. This position is therefore not included in Figure 5. Figure 5: Chart showing mean noise levels over last 10 years The average noise level at the Clarke Street position is 43 dB LAeq with a measured range from 38 to 50 dB LAeq. It effectively sits between the two ranges of values shown above in terms of noise levels. Generally, our analysis indicates that for receivers potentially adversely affected by WNP, the noise levels are only slightly influenced by whether the Martha mine is operating or not, and whilst mining operations would be audible, other anthropogenic noise sources are also clearly audible and contributing to the overall noise environment. Noise levels are generally between 35 and 50 dB LAeq, which is typical of a small regional town environment during the daytime. Noise levels at Purcells (Position B) have mainly been obtained during the night and are generally below 40 dB LAeq. It is unclear what caused the maximum measured noise level at Scout in 2017, it is possible it could be localised operations occurring very close, or measurements conducted for a particular purpose, or indeed an unrelated noise event not associated with mining. As can be seen for both locations the noise levels are similar with and without pit operations. Overall, in terms of resultant noise effects from current operations, this means that there is an appreciable contribution from other noise sources to the noise environment, so the impact of mining noise is somewhat reduced. In our opinion, this also means it is problematic to always determine whether the mining operations are compliant with the controls or not. We understand that there is some concern that there are times when complaints have been received and there has been a conclusion drawn that noise levels are non-compliant, despite mining noise being below the compliance limit, simply because the measured noise levels (of all sources) are above the compliance limit. The noise measurement results reported by OGNZL in the annual noise monitoring report do attempt to apply corrections to account for this, however it is not clear whether this adequately addresses the issue. It can be seen that for much of the time combined noise levels from mining operations and extraneous noise sources (that have not been removed from the measurement data set) are lower than the District Plan noise limits. This means mining activity noise must be at or below the prescribed limits. The activities and associated
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