Subsidence Management Plan - Quetools

Mt Owen Rail Spur Line and Associated InfrastructureThe Mt Owen Rail Spur and associated infrastructure has been identified asthe main surface improvement that is likely to be impacted by subsidencewithin the Application Area.It is considered likely that the Rail Spur would be able to remain serviceablethroughout the period of mining with frequent monitoring and restressing ofthe rails from time to time likely to be required. The monitoring andmanagement experience during the mining of Longwalls 7 to 9 will betterdefine the nature and frequency of remedial work that would be anticipated.Subsidence monitoring is also recommended, to confirm that actualsubsidence impacts are within the predictions. A similar monitoring regimeto that contained in the Rail Line Management Plan for longwalls 7 to 9 isconsidered appropriate, and will be specified in the Rail Line ManagementPlan for LW 10-17 which will be submitted separately. The monitoringrecommended for Longwalls 11 to 17 is likely to be much reduced from theinitial monitoring over Longwalls 7 to 10 (SCT, 2006). Monitoring ofsubsidence impacts on the Rail Line will be the responsibility of XMO.Bridges over Bettys CreekA better indication of the strains and tilts at the bridges over Bettys Creek willbe available from monitoring previously undermined sections of the Mt OwenRail Spur prior to mine subsidence impacting on the bridge structuresthemselves. The structure of the bridges, ie deck beams supported on pilecaps, is such that the peak horizontal and tilt movements are likely to be ableto be accommodated. The bridge structures would need to be inspected toconfirm how much relative movement can be accommodated.Prior to undermining the Mt Owen Rail Spur a specific management planincorporating the bridges over Bettys Creek will be developed based onprevious experience of monitoring over Longwalls 7 to 9. The development ofthe management plan at a later stage will allow more detailed and appropriatemonitoring strategies to be developed as a result of previous experience.Rail Maintenance RoadSubsidence is not expected to significantly affect the serviceability of theunsealed rail maintenance road and consequently no additional monitoringbeyond the current inspection regime employed by the Rail Maintainer hasbeen recommended.ENVIRONMENTAL RESOURCES MANAGEMENT AUSTRALIA 0038321/FINAL/3 JANUARY 200715