Bombay Quarry, just south of Auckland, is one of the Auckland region's most important sources of aggregate. The quarry was established in 1997 and currently produces over 700,000 tonnes of high-quality basalt quarry material annually. Throughout its life, Bombay Quarry has also been extensively involved with its local community through the operation of a community liaison group.
While the Bombay Quarry operates within strict noise limits stipulated in its resource consents, a low-frequency noise was identified by neighbours. The main source of the noise appeared to be emanating from the quarry's primary crusher. Holcim consulted a sound engineer who recommended installing panels of auto-claved aerated concrete and cement-wood fibre. These products were installed as noise barriers around the primary crusher and designed so that they could be easily removed for maintenance.
Quarry Manager James Boyce says "The results have been excellent, with the panels reducing noise transmission, so that peak noise measurements have dropped by 6 dB adjacent to crusher. The project has been an excellent example of community cooperation and technical innovation and the solution is now being considered for use in other Holcim New Zealand locations".
Following discussions with the community liaison group, Holcim also undertook several other improvements to minimise quarry noise including:
- Replacing reverse beepers with flashing lights
- Changing the screen into the vibrating feeder of the primary crusher
- Implementing oversize rock breaking technology, such as choke feeding the primary crusher
- Replacing some metal screens with plastic or rubber
- Replacing the scrubber gearbox
- Using a loader to tip into the bin instead of the dump truck
Feedback from the community and noise monitoring results confirm that collectively these initiatives have made a significant improvement to quarry noise.