Relinquishment criteria verification: Quality assurance/quality control using unmanned aerial vehicles

Abstract

Leigh Creek Coalfield is located approximately 550 km north of Adelaide, in an arid area of South Australia. It was formerly operated by the state-owned Electricity Trust and has over 70 years of open cut mining history. The coal was hauled 250 km south by rail to fuel the Port Augusta Power Stations, once producing up to 40% of South Australia's electricity demand. The mine, currently under Flinders Power control, was leased in 2000, and coal mining operations ceased in November 2015 due to the closure of the Port Augusta Power Stations. A swift decision to close the mine, with partially built landforms and legacy issues from early mining practices, created rehabilitation challenges. The mine closure plan identified the major risks as spontaneous combustion of the in-pit and surface waste dumps, public safety and surface water control. A comprehensive mine closure plan and set of relinquishment criteria were developed and agreed with the regulator. The challenge was to demonstrate to the regulator the successful completion and achievement of the relinquishment criteria. Procedural control, timely data capture, effective quality assurance/quality control (QA/QC) and independent verification, are critical components in demonstrating completion of mine closure relinquishment criteria. However, these components are not necessarily second nature to mining operators. The Leigh Creek closure team developed an innovative solution, the Inspection Test Plan (ITP), utilising state-of-the-art unmanned aerial vehicle (UAV) technology it captures all the critical components in one package. Presented in the paper is the Leigh Creek ITP, the operational implementation of the ITP, and how the ITP was successfully employed to achieve verification of the mine closure relinquishment criteria at Leigh Creek. Key components of the ITP include: Design approval and operational implementation procedural control, including hold points. Inert material rehabilitation cover thickness verification against design using UAV technology. Digital elevation model created using UAV survey data for watershed analysis of individual constructed evaporation ponds, with verification against design criteria. Real-time onsite material sampling program including laboratory confirmation. Thermal imaging data, photographic timeline and operational response to non-compliance. Structured design component sign-off and independent verification process. Some operational statistics from the successfully completed Leigh Creek mine rehabilitation project include: 14 million loose cubic metres of earthworks including 4 million loose cubic metres of cover placed. 65,000 machine hours and over 2,500 km flown with a UAV. 480 surface water sub-catchments created and assessed. 293 evaporation areas totalling 2,100 hectares created. 153 km of surface water bunds created.