Case study 5: Unplanned closure
The Bottle Creek Gold Project is 95 km northwest of Menzies in the Northern Goldfields of Western Australia. The mine commenced operation in June 1988 but, due to a limited gold resource, ceased operation in November 1989. Three open pits and waste landforms, a plant site, a run-of-mine pad and two tailings storage facilities were established during the operational stage of the project.
In May 1990, Norgold Limited submitted a proposal to rehabilitate the site to the then WA Department of Minerals and Energy (DME). In 1992, the Minister for Mines approved a refined plan and required unconditional performance bonds to be lodged.
The mine was largely rehabilitated by 1994 but, soon afterwards, 300 mm of cyclonic rainfall resulted in significant erosion and gullying on the landforms. The DME asked Norgold to undertake appropriate rehabilitation works to repair the damage caused by the cyclone.
In September 1996, Norgold requested that DME release the bonds. The environmental inspector raised a number of tasks that needed to be done before the bonds could be retired, including remediating erosion gullies, reseeding poorly vegetated areas, battering down-slope angles (on some of the remaining structures), applying topsoil to several areas, and backfilling drillholes. Two subsequent joint site inspections were made, in October 1996 and in June 1997. Norgold was asked to submit a new rehabilitation plan to detail how, when and to what standard it would do the remediation works required by the DME. In November 1997, Norgold submitted a new rehabilitation plan. The work was completed by May 1998. DME made another site inspection in May 1998 and identified further small works.
In November 1998, Norgold submitted a compliance review as well as a monitoring report that included a validation of the rehabilitation undertaken and of the developing ecosystem using ecosystem function analysis. This monitoring system, developed by Tongway and Hindley of CSIRO (http://csiropedia.csiro.au/systems-developed), reports on the condition of the ecosystem by comparing the level of functionality displayed by the rehabilitation with that at control or analogue sites in the surrounding region.
A closure inspection in December 2000 identified two issues that had not been resolved to the satisfaction of the DME: the potential for acid rock drainage and the presence of feral goats within the fenced area.
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Rio Tinto (which acquired Norgold) investigated and subsequently addressed these issues to the satisfaction of the DME, which recommended that the bonds be returned and that all tenement conditions relating to the project be deleted from the schedule of conditions attached to each tenement. In November 2001, the Minister for Mines deleted all the conditions and returned the bonds, confirming that Norgold had rehabilitated the site to the satisfaction of the state mining engineer.
Persistence in closure works, consultation and meeting final requirements eventually worked for Norgold and Rio Tinto. The use of a robust monitoring technique over time was able to adequately demonstrate completion criteria in the rehabilitation. This evidence was accepted by the regulator, leading to relinquishment.
The regulator continues to monitor Bottle Creek Mine by conducting occasional monitoring programs with departmental officers and a Perth-based consultancy, which retrieves and analyses ecosystem function analysis data from the fixed monitoring transects at the site.
This case study of unplanned closure demonstrates three important points:
•It can take considerable persistence by a company to achieve relinquishment, particularly if early rehabilitation is inadequate for the task.
•The selection of a robust and verifiable process to monitor and demonstrate completion criteria is crucial for closure.
•Early establishment of verifiable completion criteria is critical to receiving acceptance and approval for relinquishment from the regulator.
Bottle