CASE STUDY: Post-closure remote monitoring to provide early warning of potential issues The Benambra mine is located in the remote upper catchment of the Tambo River in north-eastern Victoria. It was operated by Denehurst Ltd as an underground base metal mine from October 1992 to July 1996. During operations, 927,000 tonnes of ore was processed on site to produce copper and zinc concentrate, and nearly 700,000 tonnes of tailings from the process plant was delivered by pipeline to a nearby tailings dam. With the help of consultants, the Victorian Department of Primary Industries (DPI) developed a rehabilitation strategy to restore the site to as near to premining conditions as possible. An environmental management plan, including a detailed monitoring program, was established for the rehabilitation works and post-rehabilitation phase. DPI is responsible for implementing the plan. Review of the plan, including the monitoring program, by the DPI and the Environment Protection Authority Victoria (EPA) is scheduled to take place annually for the first four years postrehabilitation and thereafter at a frequency agreed by the DPI and EPA. The key environmental risk is the potential for water quality issues associated with acid and metalliferous drainage (AMD) from the tailings. The water monitoring program undertaken during rehabilitation involved the collection of water quality data and samples for laboratory analysis. At the completion of rehabilitation, a remote monitoring system was installed at the tailings dam to continuously monitor rainfall, water level and key water quality indicators—pH, temperature and electrical conductivity—in order to monitor the effectiveness of rehabilitation and provide early warning of potential water quality issues. Rainfall data are logged in 0.2 millimetre increments; the remaining parameters are logged on a daily basis. The data are downloaded by satellite phone weekly or as required.
Remote monitoring station at the Benambra tailings dam. Source: Victorian Department of Primary Industries. (continued) EVALUATING PERFORMANCE: MONITORING AND AUDITING
73