Top image: The Shire of Boddington, Western Australia.
As one of the world’s largest producers of major commodities, BHP Billiton integrates social and environmental considerations into all its business operations and stakeholder interactions. At the BHP Billiton Worsley Alumina Pty Ltd bauxite mine in Western Australia, community engagement has been an essential part of fully understanding and effectively addressing concerns about noise.
Spread over approximately 10,000 ha, the bauxite mine is located near the town of Boddington, about 130 km from the capital city of Perth. A 51 km overland bauxite conveyor system links the mine to an alumina refinery near the town of Collie. Mining has been part of the Boddington landscape for three decades. However, the expansion of mining operations in 2012 led to a rise in complaints from residents about noise, especially about mining activities at night.
This increase in complaints also resulted in an increase in operational downtime for Worsley – partly because hand-held noise monitoring was required to determine whether mining operations were in compliance with the prescribed limits, leading to extensive operational delays during complaint investigations.
Boddington Bauxite Mine digger and truck.
Monitoring in real time
Worsley decided to collaborate with Brüel & Kjær to customize a Noise Sentinel system to monitor noise generated by mining and ensure that the impact on neighbours was minimized by incorporating alert systems to allow for proactive management.
The monitoring network consists of 12 fixed, real-time noise monitors and 5 mobile, directional noise monitors, collecting real-time noise and weather data and transmitting the information to a live Internet-based system, which is monitored on a 24-hour basis by Worsley personnel. In addition, a community website was developed to display noise data, overlaid on an aerial map of the mine.
The noise monitors are programmed to generate alerts based on set thresholds for defined periods of time. Each alert has an associated 30-second sound recording to help determine the source of the noise and the cause of the alert. Worsley staff review each alert and its associated sound recordings and close alerts with relevant comments for later analysis. Where mining is the cause of the alert, actions are taken to ensure that operations are modified to be below prescribed limits.
51 km bauxite conveyor between mine and refinery.
Silver Kenny, Environmental Analysis and Improvement Specialist at Worsley, explains about one of the challenges, “Given the relatively low noise limits applied in Western Australia, it was important to differentiate noise from sources other than mining such as traffic and bird song”. The alert rules in the Noise Sentinel system were refined so that, for example, where passing road traffic was a significant noise source, threshold levels for alerts were increased to 60 dB(A) during the day to cover the peak traffic hours. Given that this time period had the lowest risk (highest prescribed limits), this approach was considered acceptable.
In addition, frequencies greater than 2 kHz were filtered to remove the majority of bird song and an additional filter was applied to prevent alerts when wind levels were greater than 5 m/s and when rain levels were greater than 0.25 mm/15 min. Together, this minimizes the impact of weather related noise and reduces the number of alerts not related to mining activities.
Community concern about Worsley’s mining noise was a major factor that drove the implementation of the Noise Sentinel system, and engaging local people was a key part of the successful solution. Community Liaison Committee meetings and forums helped to explain the purpose and value of the monitoring network and a stakeholder webpage provided residents with a traffic light system for all noise monitors, reflecting the alert status shown on Worsley’s monitoring screens. This transparency of the mine operations allowed the community to see when noise levels were below (green), close to (yellow), or over (red) prescribed limits.
Worsley mining operations showing locations of noise monitors and near neighbours. Yellow dots: Near Neighbours Red dots: Noise Monitoring Terminals Blue dots: BarnOwls Grey outline: Timber Reserve Boundaries.
Drop in complaints
Worsley’s Mine Community Liaison Committee, which includes representatives from across the community, has received positive feedback about Worsley’s improved management of the impact of mining noise. Worsley continues to meet regularly with its near neighbours to update them on mining activities and to get their feedback. From this engagement, it is clear that the local community trusts that noise is being managed proactively.
“The total number of complaints about noise from the mine dropped significantly from 77 in FY2013 to 20 in FY2014*,” explains Silver Kenny. In particular, since the installation of the Noise Sentinel system, the number of Level 2 com-plaints (where noise levels are above the prescribed statutory limit) has dropped from 18 in FY2013 to 6 in FY2014.
Based on the positive outcomes of implementing the Noise Sentinel system, Worsley received a Highly Commended award at the 2013 BHP Billiton HSEC Awards under the Environment category. This was welcome recognition of the work done to enhance environmental noise management and an acknowledgment of the improvements in community interaction. More recently, a mini perception survey was undertaken at an open day at the bauxite mine and this recorded a marked improvement in community perceptions since FY2013 for all metrics related to environmental and social performance.
Bauxite is refined to recover the alumina present. Once the alumina – aluminum oxide trihydrate – is recovered, it can be electrolytically reduced into metallic aluminium. Australia is the world’s biggest producer of bauxite with almost one-third of the world’s production.
*FY = financial year which runs from 1st July – 30th June
Compliance in Western Australia
The Environmental Protection (Noise) Regulations specify legal noise limits (LA10 dB(A))* for mining activities in Western Australia:
- 07:00 to 19:00 hrs Mon. to Sat. – 45 LA10 dB(A)
- 09:00 to 19:00 hrs Sun. and Public Holidays – 40 LA10 dB(A)
- 19:00 to 22:00 hrs All days – 40 LA10 dB(A)
- 22:00 hrs any day to 07:00 hrs Mon. to Sat. & 09:00 Sun. & Public Holidays – 35 LA10 dB(A)
*LA10 assigned level means an assigned level which, measured as an LA Slow value, is not to be exceeded for more than 10% of the representative assessment
period (3 or 4 hours).
This case was first presented at inter.noise 2014 as a conference paper written by Silver Kenny, BHP Billiton Worsley Alumina Pty Ltd, Australia and Douglas Manvell, Brüel & Kjær.