Subsidence Monitoring Program

Transcription

1 Subsidence Monitoring Program West Wallsend Colliery Page 1 of 27

2 Contents West Wallsend Colliery 1.Introduction Background Purpose and Scope Relationship with Other Documents Statutory Requirements Project Approval SMP Approval Vertical Subsidence and Ground Movement Built Feature Monitoring Visual Subsidence Inspections Evaluation of Monitoring Results Review and Improvement External Reporting Review Accountabilities References Legislation West Wallsend Colliery Appendix 1 Stage one subsidence Monitoring Program LW44 (Chainage 1175 to 300 m) Stage 1 LW Proposed Monitoring Built Features Monitoring Inspections and Monitoring Landscape Feature Monitoring Management Plan Monitoring and Inspections Recording, Reporting and Review of Monitoring Results Monitoring Method and Accuracies Appendix 2 - survey monitoring marks and procedures Appendix 3 landscape Features Inspection Form appendix 4 - Subsidence Cracking Report Form Plan KA Control and Revision History Document Information Revisions Page 2 of 27

3 1. INTRODUCTION 1.1 Background Oceanic Coal Australia Pty Limited (OCAL) manages and operates West Wallsend Colliery (WWC) on behalf of the Macquarie Coal Joint Venture (MCJV). OCAL is owned by Xstrata Coal. West Wallsend Colliery (WWC) is located approximately 25 kilometres southwest of Newcastle in the Lake Macquarie Government Area (refer to Figure 1). WWC has been granted Project Approval (PA 09_0203) for continued operations through the approval of the West Wallsend Colliery Continued Operations Project (WWCCOP) Environmental Assessment (EA), assessed under Part 3A of the Environmental Planning and Assessment Act 1979 (EP&A Act). Project Approval was granted on 25 January 2012 by the NSW Department of Planning and Infrastructure (DP&I) Director-General. The Project Approval allows for the continuation of mining operations at WWC and enables the consolidation of existing approvals for underground mining and infrastructure utilised for WWC. The WWCCOP assessed the coal reserves for WWC, the existing pit top and other related ancillary surface facilities, including the Mining Services Facility. WWC and associated mining infrastructure are shown in Figure 1. This has been prepared as a component of the WWC Longwall 44 & 45 Extraction Plan (WWC SD PLN 0061), in accordance with Condition 5(m), Schedule 3 of the Project Approval. The program also proposes monitoring to be undertaking in accordance with the DRE Subsidence Management Plan (SMP) approval condition. A staged monitoring approach has been developed in consultation with DRE to include, Stage 1 from the start position on LW44 to twice the angle of draw for zero subsidence on Wakefield Road (chainage 1175 m to 300 m). The remaining section of LW44 (300 m to 0 m) will be monitored by the stage two monitoring program and WWC will seek approval from DRE for the monitoring programme. 1.2 Purpose and Scope The purpose of this plan is to outline the subsidence monitoring programme for WWC for longwall 44. The stage one subsidence monitoring program incorporates LW44 s extraction area from chainage 1175 m to 300 m. This monitoring program includes the SMP/Extraction Plan Area for Longwall 44 at WWC as shown on Plan KA Relationship with Other Documents This has been developed as a component of the WWC Longwall 44 & 45 Extraction Plan (WWC SD PLN 0061), and should be read in conjunction with the Extraction Plan/SMP. The monitoring program outlined in this document is a summary of the extensive subsidence monitoring outlined in more detail in the following documents: WWC SD PLN 0050 Water Management Plan; WWC SD PLN 0052 Biodiversity Management Plan; WWC SD PLN 0057 Built Features Management Plan; Page 3 of 27

4 WWC SD PLN 0058 Land Management Plan; WWC SD PLN 0059 Public Safety Management Plan; WWC SD PLN 0060 Subsidence Contingency Plan; WWC Survey Monitoring Marks and Procedures; and WWC SD PLN 0062 Aboriginal Cultural Heritage Management Plan. Page 4 of 27

5 Page 5 of 27

6 2. STATUTORY REQUIREMENTS 2.1 Project Approval The Project Approval for WWC was assessed under the Environmental Planning and Assessment Act 1979 (EP&A Act). Approval for WWCCOP was granted by the DP&I Director- General on 25 January The requirement for this arises from Condition 5(m), Schedule 3 of the WWC Project Approval which is shown in Table 1 below. Table 1 Project Approval requirements Project Approval Condition Section of this Document Extraction Plan 5. The Proponent shall prepare and implement an Extraction Plan for second workings on site to the satisfaction of the Director-General. Each extraction plan must: (m) include a subsidence monitoring program, which has been prepared in consultation with DRE and OEH, to: Entire document provide data to assist with the management of the risks associated with subsidence; 3.0 validate the subsidence predictions; 4.0 analyse the relationship between the predicted and resulting subsidence effects and predicted and resulting impacts under the plan and any ensuing environmental consequences; and 4.0 inform the contingency plan and adaptive management process SMP Approval This has been developed in accordance with DRE s SMP approval condition 12. In the event that changes to this document are required by DRE, the amended program will also be re-submitted to OEH & DP&I. Page 6 of 27

7 3. SUBSIDENCE MONITORING PROGRAM The Stage One proposed subsidence monitoring for LW44 is shown on plan Proposed Subsidence Monitoring Stage 1 Start to 300 m KA A summary of the monitoring program is provided in the sections below. 3.1 Vertical Subsidence and Ground Movement LW44 subsidence induced ground movement will be measured by comparing Airborne Laser Scanning (ALS) survey results pre mining and post mining. A pre mining ALS survey was conducted in July The ALS monitoring will provide a full coverage of ground movement for the longwall panel as opposed to previous methods of centre and cross line surveys on a limited number of points. Surveys using ALS methodology will minimise the environmental impacts in the Sugarloaf State Conservation Area (SCA) associated. OEH granted WWC a licence by OEH for the installation of survey marks and monitoring activities in the SSCA. In addition to the ALS surveys cross lines above LW44 and Central Creek as shown on plan KA3-996 (at chainage 350m) will be installed to monitor subsidence movements in relation LW44. Surveys will be undertaken in accordance with the WWC Survey Monitoring Marks and Procedures (refer to appendix 2) and record subsidence movement, prior to subsidence effects and posting mining Built Feature Monitoring The built features in the stage one subsidence monitoring program area include dirt access tracks and trails located in the SSCA as show in Figure 2. The public safety risks on access tracks will be monitored by undertaking daily inspections of the access tracks and trails in the Subsidence Affected Surface Zones (SASZ), during subsidence affectation. The six Transgrid towers (90TL101 & 92/93TL33E, 90TL102 & 92/93TL34E, 90TL103, & 92/93TL35E) are (DGS 2012) located at angles of draw of between 62 to 76 from the proposed extraction limits of the longwalls and are outside the predicted 20 mm subsidence contour or 26.5 angle of draw. The four towers (90TL101 & 92/93TL33E & 90TL102 & 92/93TL34E) were mined beneath by the Newstan Colliery longwalls and have been fitted with reinforced concrete cruciform footings thereby reducing the impacts of strains on the towers from WWC s longwalls. Two of the towers (90TL103 & 92/93TL35E) are located outside the Newstan longwall area and consist of steel and concrete footings. The six towers are unlikely to be affected by measureable vertical subsidence due to their distance from the extraction area. It is possible however, that the towers are within the distance that could be affected by farfield horizontal displacements. The low level of predicted far-field horizontal displacements and strains are unlikely to impact on the towers or require mitigation works. WWC will monitor the survey marks on the tower footings and ground marks at each tower for X, Y & Z movements and implement the Trigger Action Response Plans (TARP) in the Transgrid Transmission Tower Management Plan to manage any subsidence movements of a greater magnitude then predicted. 3.2 Visual Subsidence Inspections In addition to the monitoring of subsidence and ground movements, WWC will undertake visual inspections to identify subsidence impacts on the environment and built features. These include but are not limited to the following: Daily inspection of access tracks and trails when affected by subsidence ; Page 7 of 27

8 Monthly inspection of the general SASZ and landscape features; Weekly inspection of the Transgrid transmission towers and surface; Post mining assessment of landscape features; and Post remediation inspections of subsidence cracks and impacts. These visual inspections are outlined in more detail Appendix 1 and in the relevant management plans included within the WWC Extraction Plan (refer to Section 1.3). 4. EVALUATION OF MONITORING RESULTS All subsidence monitoring results are to be reported in the WWC Annual Review and the WWC End of Panel Report which are both provided to relevant government agencies. The Annual Review and End of Panel Report will provide a summary of subsidence monitoring results and a comparison against subsidence predictions for the relevant extraction area. This comparison will be undertaken by a suitably qualified subsidence consultant and if relevant the WWC subsidence model will be updated to provide revised predictions for the following longwall. In the event that subsidence predictions are revised, the affected management plans (e.g. built features plans) will be updated accordingly and submitted to relevant government agencies and placed on the WWC website ( Additionally, subsidence monitoring results received from built feature monitoring (e.g. services easement and F3 Freeway) will be assessed immediately against trigger levels developed and reported accordingly. 5. REVIEW AND IMPROVEMENT 5.1 External Reporting An Annual Review will be prepared in accordance with the Project Approval and will document subsidence monitoring results as outlined in Section 4. Exceedance of any relevant subsidence predictions or performance criteria will be reported in accordance with the Project Approval to any relevant stakeholders. An End of Panel Report will also be prepared for each longwall and submitted to DRE. The End of Panel Report will also include a summary of the subsidence monitoring results as outlined in Section Review Ongoing monitoring and review on the performance and implementation of this document will be undertaken in accordance with WWC Environmental Management Strategy. In accordance with Condition 5 of Schedule 6, WWC shall review, and if necessary revise, the strategies, plans, and programs required under Project Approval to the satisfaction of the Director-General, within 3 months of the submission of: (a) (b) (c) (d) the submission of an annual review; the submission of an incident report; the submission of an audit report; and any modification to the conditions of this approval (unless the conditions require otherwise), Page 8 of 27

9 The will reflect changes in requirements, technology, operational procedures and subsidence predictions. Updated versions of the approved plan will be made publicly available on the WWC website ( 6. ACCOUNTABILITIES Role WWC Operations Manager WWC Subsidence Management Coordinator WWC Mine Surveyor All employees and contractors Accountabilities for this document Provide sufficient resources for the effective implementation of this plan. Coordinate the subsidence monitoring requirements of the WWC Extraction Plan; Report to relevant stakeholders the subsidence results of this plan and update of subsidence predictions as required by this plan; Coordinate the reporting required by this plan Undertake subsidence monitoring requirements of the WWC Extraction Plan; Coordinate the reporting of monitoring results under this plan. Comply with all requirements of this plan. Report all subsidence impacts to their supervisor immediately. 7. REFERENCES 7.1 Legislation Environmental Planning and Assessment Act 1979 Mining Act 1992 Mine Subsidence Compensation Act West Wallsend Colliery WWC SD PLN 0061 Longwall 44 & 45 Extraction Plan and Subsidence Management Plan WWC SD FWK 0013 WWC Environmental Management Strategy WWC SD PLN 0050 Water Management Plan WWC SD PLN 0052 Biodiversity Management Plan WWC SD PLN 0057 Built Features Management Plan WWC SD PLN 0058 Land Management Plan WWC SD PLN 0059 Public Safety Management Plan Page 9 of 27

10 WWC SD PLN 0060 Subsidence Contingency Plan WWC SD PLN 0062 Aboriginal Cultural Heritage Management Plan WWC SD PLN 0077 F3 Freeway Management Plan WWC & Telstra Corporation Ltd Management Plan Longwall Mining (LW44 & 45) Western Domain Adjacent to Telstra Network. WWC SD PLN Jemena, Caltex, Optus, Nextgen, Western Domain Subsidence Management Plan. Page 10 of 27

11 8. APPENDIX 1 STAGE ONE SUBSIDENCE MONITORING PROGRAM LW44 (CHAINAGE 1175 TO 300 M) 8.1 Stage 1 LW44 The purpose of this program is to outline the subsidence monitoring to be undertaken for LW44 chainage 1175 m to 300 m as shown on plans KA Proposed Monitoring The proposed subsidence monitoring for LW44 Stage 1 relates to the extraction between 1175 m to 300 m chainage as shown on plan KA3-996 (refer to Section 12). The surface of the Stage 1 subsidence monitoring program for LW44 includes bushland which forms part of the Sugarloaf State Conservation Area (SSCA) managed by the Office of Environment and Heritage (OEH). LW44 subsidence induced ground movement will be monitored by comparing Airborne Laser Scanning (ALS) survey results pre mining and post mining. A pre mining ALS survey was conducted in July The ALS monitoring will provide a full coverage of ground movement for the longwall panel as opposed to previous methods of centre and cross line surveys on a limited number of points. Surveys using ALS methodology will minimise the environmental impacts in the Sugarloaf State Conservation Area (SSCA). WWC has a licence from OEH allowing the installation of survey marks and monitoring activities in the SCA in accordance with established WWC environmental management procedures. In addition to ALS surveys a cross line above LW44 as shown on plan KA3-996 (at chainage 350m) will be installed and monitored as shown in Table 1. Surveys of the LW44 cross line will be undertaken in accordance with the WWC Survey Monitoring Marks and Procedures (refer to appendix 2) and record subsidence movement in 3D (X, Y & Z) prior to subsidence effects and posting mining. Following comments from DRE, WWC will install a survey monitoring line as shown on plan KA3-996 in Central Creek (a tributary of Palmers Creek) to monitor for subsidence movements at the archaeological site Axe Grinding Grove 3 (AGG3) and the valley either side of AGG3. The survey line (AGG3 Line) as shown on plan KA3-996 will be installed and monitored as per the Survey Monitoring Marks and Procedures (refer to appendix 2) and will record subsidence movements in 3D (X, Y, Z). 8.3 Built Features Monitoring The six Transgrid towers (90TL101 & 92/93TL33E, 90TL102 & 92/93TL34E, 90TL103, & 92/93TL35E) are to be located at angles of draw of between 62 to 76 from the proposed extraction limits of the longwalls and are outside the predicted 20 mm subsidence contour or 26.5 angle of draw. The towers are unlikely to be affected by measureable vertical subsidence due to their distance from the longwalls. However the towers are within the distance that could be affected by far-field horizontal displacements. The low level of predicted far-field horizontal displacements and strains are unlikely to impact on the towers or require mitigation works. WWC will install and monitor the survey marks shown on plan KA3-996 on the towers footings and ground marks at each tower to record subsidence related movements in X, Y & Z as shown in Table 1. Surveys will be conducted as per the Survey Monitoring Marks and Procedure (refer to appendix 2). Weekly inspections of the towers and surface for subsidence impacts (refer to Table 1) will be undertaken from the start of LW44 and will continue in consultation with DRE until approval to cease monitoring is granted. Page 11 of 27

12 8.4 Inspections and Monitoring This section outlines the inspection and monitoring regime to be implemented to ensure the public safety for the extraction of Longwall Panel Landscape Feature Monitoring WCC personnel will undertake pre mining and monthly inspections of landscape features as shown in Table 1 in the SASZ and record these on the landscape features form (refer to appendix 3). The pre and post mining landscape feature monitoring will be compared against the landscape features impact criteria in the PA to assess performance against the criteria as, described in the Land Management Plan. In addition, inspections of the general surface including creek lines within the SASZ will be undertaken on a monthly basis and recorded on the WWC Surface Cracking Inspection Report Form (refer to appendix 4). The sections of Riparian Paperbark Peppermint Forest GDE (refer to the Biodiversity Management Plan) and drainage lines of Central within the subsidence affectation zone will be inspected to identify any subsidence cracking and loss of surface water flows. The monthly surface inspections will continue in consultation with DRE until approval is granted to cease. These inspections will record the surface condition and status of the existing control measures including: - General surface subsidence cracking and drainage lines for loss of surface water flow; demarcation warning tape on landscape features; Transgrid transmission tower subsidence impacts; existing OEH gates (Quarry Trail) on entry points to SASZ, and warning signs. Page 12 of 27

13 Table 1: Public Safety & SMP Approval Conditions Description 12.a) Inspection Regime Features to be Monitored Surveying of monitoring marks on and Transgrid transmission towers legs and ground marks :- Pre mining survey After 200 m of extraction After the completion of LW44. Surveying of monitoring marks on LW44 cross line and AGG3 line prior to subsidence effects and post mining. Monthly surface and landscape feature visual inspection by WWC. Weekly visual inspection of Transgrid Transmission Towers from the start of LW b) Layout of Monitoring Points Layout of proposed survey marks shown on plans KA c) Parameters to be measured Parameters to be measured on survey monitoring marks including: - X,Y,Z on tower legs and ground marks Strains ground marks. Parameters to be monitored for general surface and landscape feature inspection form are provided in appendices 3 and 4. Inspections of the surface at the Transgrid Towers and drainage lines will be recorded in the Subsidence Cracking Report Form (refer to Appendix 4). 12.d) Monitoring methods and accuracy As per WWC Survey Monitoring Marks and Procedures (refer to appendix 2). Visual inspections recorded on subsidence cracking and landscape feature inspection forms, GPS camera, and handheld GPS accurate to +/- 2 to 5m. Tilt meter accurate to +/ mm. Page 13 of 27

14 SMP Approval Conditions Description 12. e) Timing & frequency of surveys & inspections Features to be Monitored Surveying of monitoring marks on and Transgrid transmission towers legs and ground marks :- Pre mining survey After 200 m of extraction After the completion of LW44. Weekly inspections from the start of LW44 of Transgrid Transmission Towers. These will continue in consultation with DRE until approval is granted to cease monitoring. Surveying of monitoring marks on LW44 cross line & AGG3 line prior to subsidence effects and post mining. Monthly inspections at surface and landscape feature within SASZ. These will continue in consultation with DRE until approval is granted to cease monitoring. 12. f) Recoding and reporting of monitoring results Survey monitoring results recorded on WWC survey spreadsheets. Recorded on subsidence cracking and landscape feature inspection forms and then recorded in the WWC ArcGIS mapping system. Reported fortnightly & quarterly to DRE in Subsidence Management Status Reports. Within an end of panel report for LW Management Plan Monitoring and Inspections All inspections and monitoring will be undertaken in accordance with: WWC SD PLN 0061 Longwall 44 &45 Extraction Plan and Subsidence Management Plan WWC SD FWK 0013 WWC Environmental Management Strategy WWC SD PLN 0050 Water Management Plan WWC SD PLN 0052 Biodiversity Management Plan WWC SD PLN 0057 Built Features Management Plan WWC SD PLN 0058 Land Management Plan WWC SD PLN 0059 Public Safety Management Plan WWC SD PLN 0060 Subsidence Contingency Plan WWC SD PLN 0062 Aboriginal Cultural Heritage Management Plan Page 14 of 27

15 WWC SD PLN 0077 F3 Freeway Management Plan WWC SD FRM 0158 Surface Cracking Inspection Form WWC & Telstra Corporation Ltd Management Plan Longwall Mining (LW41) Western Domain Adjacent to Telstra Network. WWC SD PLN Jemena, Caltex, Optus, Nextgen, Western Domain Subsidence Management Plan 8.5 Recording, Reporting and Review of Monitoring Results The results of inspections will be recorded in the field on the landscape features inspection form, GPS camera, and handheld GPS. The impacted areas will be recorded in the WWC ArcGIS mapping system to record photos and results within a central database. The results of inspection and monitoring will be reported to the PSE in the Subsidence Management Status Report in accordance with SMP condition 15.7 and will report against the conditions in 17 (a) to 17 (g). The status report will provide the PSE and other relevant stakeholders with information specifically addressing public safety by addressing the above conditions. WWC will review the monitoring results from the program to inform the extent of the SASZ s. 8.6 Monitoring Method and Accuracies The proposed survey monitoring will be conducted in accordance with the document WWC Survey Monitoring Marks and Procedures attached in Appendix 2. The results from inspections will be recorded in the field on the landscape features inspection form, GPS camera, and handheld GPS. GPS measurements are accurate to between +/- 2 to 5m. Page 15 of 27

16 9. APPENDIX 2 - SURVEY MONITORING MARKS AND PROCEDURES Page 16 of 27

17 Page 17 of 27

18 Page 18 of 27

19 10. APPENDIX 3 Landscape Features Inspection Form Longwall: Date: LW Face Position: Landscape Feature Morphology Landscape Feature Type Landscape Feature No. Description Height (m) Length (m) Face Slope ( ) Aspect ( ) Start (Coordinates) Finish (Coordinates) Landscape Feature Attributes Lithology Page 19 of 27

20 Bedding Spacing Bedding Dip/ Strike Bedding Planarity/infill Joint Spacing Joint Dip/ Strike Joint Planarity/infill Joint Spacing Joint Dip/ Strike Joint Planarity/infill Photos Cracking Locations Crack Width (mm) Crack Depth (m) Vegetation Grass/Shrubs Vegetation Trees Other/ comments Page 20 of 27

21 Hazard Identification Potential instability Potential rock falls Potential tree falls Location of hazards in relation to public access points Mitigation works required (signage, demarcation, physical removal Public Safety comments Identified Possible Instability Block/slip size Likelihood of Instability Activation trigger Risk Rating AGS Page 21 of 27

22 Sketch Page 22 of 27

23 11. APPENDIX 4 - SUBSIDENCE CRACKING REPORT FORM Instructions 1. This form is to be used for inspections of the surface for subsidence and public safety effects, above the panel, creek lines and Transgrid Transmission Towers. 2. A separate inspection form is to be used for inspections relating to cliff lines and steep slopes. Details Longwall Date Completed By Inspection Type (Circle one) Longwall Area - Monthly Access Tracks Daily Other Describe : Details of Cracking / Ponding Location & Length Width Depth Surface Strata Topography Feature Type (m) (mm) (m) Page 23 of 27

24 Have cracks been uploaded to GIS? Have photos been taken? Subsidence warning signs present Existing gate locked at Quarry Trail Barrier tape checked Warning signs checked Any evidence surface cracking or damage on Transgrid Transmission Tower Have relevant stakeholders been informed? General Comments: Page 24 of 27

25 12. PLAN KA3-996 Page 25 of 27

26 13. CONTROL AND REVISION HISTORY 13.1 Document Information Property Approved by Document Owner Value Environment and Community Manager Subsidence Management Coordinator Effective Date 20/03/2013 Keywords Subsidence, SMP, monitoring 13.2 Revisions Version Date reviewed Review team (consultation) Nature of the amendment 1 Jan 2013 E&C Dept Original document LW44 & 45 extraction plan. 2 May 2013 E&C Dept Update to included DRE comments in plan. Page 26 of 27

27 Page 27 of 27