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Objective To better identify and assess priority problem areas to reduce the risks of environmental contamination arising from acid mine drainage. Recommendation The RPDC acknowledges the Tasmanian Acid Drainage Reconnaissance Report and adopts the recommendations proposed in the Report (Gurung 2001). It is recommended that the Tasmanian Acid Drainage Reconnaissance Report is followed up with systematic environmental assessments of all the potential and actual acid-producing sites to enable the selection of priority sites for detailed characterisation and remediation options, as required under Section 37.5 of the Tasmanian State Policy on Water Quality Management (1997). The assessment process and identification of priority sites could be improved with: - routine sulphur analysis in all samples from geological and geochemical investigations to allow quick assessment of the potential acid-forming nature of host rocks in an area;
- the consideration of water quality monitoring requirements for acid mine drainage as part of the implementation of the Tasmanian Surface Water Quality Monitoring Strategy (see Improving Water Quality Recommendation);
- monitoring and assessment of surface waters and groundwaters for accurate delineation of catchment areas impacted by acid drainage from abandoned mines; and
- site-specific hydrogeochemical characterisation of potential acid-producing abandoned mines through a quantitative assessment of point and diffuse sources of acid drainage and downstream impacts from metal contaminant mass loading. Such a characterisation is important in effective implementation of remediation methods.
It is also recommended that broad scale water treatment programs are assessed, prioritised and implemented to counter acid mine drainage and achieve sustainable improvements in water quality. Key issues Acid mine drainage occurs as a result of the oxidation of sulphide-bearing rocks, and is recognised as one of the major sources of heavy metal pollution in many waterways near to metal-mining sites in Tasmania. The percolation of oxygenated water through mine workings and waste rock dumps generates an acidic fluid, rich in metals leached from the minerals in the rocks. Both the low pH and metals in this liquid can cause severe ecological damage when it enters streams and groundwater. Under Section 37.5 of the Tasmanian State Policy on Water Quality Management (1997) it was stated that 'an inventory of sources of acid drainage from historic mine workings should be carried out'. The 'Tasmanian Acid Drainage Reconnaissance' investigation (Gurung 2001), funded by the Natural Heritage Trust (NHT), provides a basis for this inventory. The development of remedial programs to address priority problem areas is also required under this policy. Further information is available within the Acid Mine Drainage Issue Report, and the NHT report is available in detail from Mineral Resources Tasmania. Some of the key points from the Issue Report include the following. - About 215 of the 681 metal-related abandoned mines across the State have a history of base-metal mining and contain sulphidic rock materials that are either currently producing acid drainage or have the potential to do so if exposed to oxidising conditions. Consequently, several are indicating pollution problems from the acid drainage and heavy metal contamination.
- Surface waters impacted by acid producing abandoned mines generally contain metal pollutants about 10 times higher than the ANZECC (1992) values for aquatic environments.
- Geochemical results indicate that occurrences of high sulphate and high metal waters are closely associated with abandoned mine sites containing sulphidic rock materials with high net acid producing potential.
- The extent of the impact of acid drainage and heavy metal contamination on the environment is difficult to assess from the currently available information. There is lack of detailed hydrogeochemical characterisation, as well as baseline data on mass loadings and environmental parameters. A hydrochemical assessment of acid drainage requires analysis of specific parameters not always measured in routine water quality analyses carried out for environmental monitoring of aquatic ecosystems.
- The inventory established by the reconnaissance investigation (Gurung 2001) is not complete and its reliability is largely dependent on the accuracy of the historical data used for geochemical classifications of rock types at, or close to, abandoned mine sites. The lack of sulphur analyses limits the geochemical characterization of acid-forming rocks from abandoned mine sites.
What has been achieved 1998-2003 There has been some progress in addressing the issue of acid mine drainage since the previous SoE Report in 1997. A number of the key areas of advancement include the following. - The State Policy on Water Quality Management (1997) highlighted the need to: adequately identify and assess the risks associated with acid mine drainage and mining operations; conduct an inventory of sources of acid drainage from historic abandoned mine workings; and develop remedial programs for problem areas. The Tasmanian Acid Drainage Reconnaissance investigation (Gurung 2001) provides a basis for the inventory.
- The Rehabilitation of Mining Lands Trust Fund was established in 1997 following the proclamation of the Mineral Resources Development Act 1995. The target of this trust fund is the rehabilitation of abandoned mining lands for which no person or organisation can now be held responsible. A portion of mining royalties raised by the Act is allocated for this purpose. Through the trust fund, various projects aimed at remedial works to address acid drainage problems at several abandoned mine sites around the State have been supported.
- Major mining operations in Tasmania that are handling waste in line with best practice in treating potential acid drainage include ABM Savage River Mines, Renison, Pasminco Rosebery, and Mt Lyell.
- A report on the 'Feasibility of Remediating Mt Lyell Acid Mine Drainage' was produced in 2001 detailing three main options and the costings, including full neutralisation, partial neutralisation, and copper recovery through solvent extraction. Public consultation was invited between December 2001 and February 2002, and the most supported option was for full neutralisation.
- The Clean up the King River Project was established, which was funded by the Natural Heritage Trust. One of its key aims is to improve the ecological health of the lower King River and Macquarie Harbour through treatment of the acid drainage associated with the Mount Lyell mine site (Environment Australia 2003).
- The Mt Lyell Acid Drainage Reduction Act 2003 has been passed to facilitate a reduction of acid drainage pollution at Mt Lyell.
- The Mt Bischoff Rehabilitation Program is being developed by Mineral Resources Tasmania and funded by RiverWorks (a Natural Heritage Trust program) to conduct site improvement and ameliorate the effects of acid mine drainage on the Arthur and Waratah Rivers, which has emanated from the former Mt Bischoff tin mining operations at Waratah.
- The Savage River Rehabilitation Project has been established, including a Strategic Plan (2001), for long term remediation of environmental harm resulting from pre-1997 operations at the Savage River and Port Latta sites in the north-east of the State. The principal cause of the degradation is thought to be acid drainage emanating from approximately 200 million tonnes of waste rock deposited in dumps around the site.
Tasmania Together Relevant Tasmania Together goals and standards for 'Land' are listed in the linked file. The Tasmania Together Progress Board reported on progress toward targets for benchmarks set (Tasmania Together Progress Board 2003). Indicators, targets and baseline data are available in the latest Progress Report June 2003. Further information, including progress report updates, is available from Tasmania Together. Related Issue Reports
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