DESIGNS FOR DEWATERING AND OPTIMIZATION OF PIT SLOPES IN SAPROLITE OVERBURDEN: A CASE STUDY OF THE PT. KAYAN PUTRA UTAMA COAL PROJECT by Antony Lesmana B.A.Sc., University of British Columbia, 2010 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in The Faculty of Graduate Studies (Mining Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) September 2012 © Antony Lesmana, 2012 ABSTRACT Effective dewatering and environmental program poised to have a significant impact on the feasibility of saprolite mining operations. It is therefore necessary to strike a balance between an effective dewatering program and sound environmental policy. Using assessments such as rainfall, climate studies, groundwater flow, and aquifer characterizations, the Separi coal dewatering program includes the construction of water channels, flood protection levees, water wells, and placing various environmental monitoring sites. The construction of water channels and flood protection levees has reduced the water runoff that entered the mining area by approximately 75%. For a six- month testing period, the average pumping rate of the dewatering well was 24.78 m3/day. These pumping rates were determined to result in groundwater level that would generally be 10 meters below the lowest mining benches at all times. Ten meters is the recommended single bench height based on the slope stability analysis. After six months of dewatering, the groundwater level was lowered 10.88 meters, permitting the mining project may begin its mining operation to commence. A re-design of maximum pit slope angle is indicated in this research. During the testing period, the environmental management plan did not show any negative impacts of dewatering programs on surface and groundwater resources. The monitoring sites all yield acceptable range of water quality parameters, such as Electrical Conductivity (EC), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), and pH value. The company continues to monitor the water resources to maintain acceptable water quality in the study areas. ii TABLE OF CONTENTS ABSTRACT ....................................................................................................................ii TABLE OF CONTENTS .............................................................................................. iii LIST OF TABLES .......................................................................................................... v LIST OF FIGURES ........................................................................................................ vi LIST OF ACRONYMS ................................................................................................viii ACKNOWLEDGEMENT .............................................................................................. ix 1. INTRODUCTION ....................................................................................................... 1 1.1 Research Overview .............................................................................................. 1 1.2 Separi Coal Deposit ............................................................................................. 4 1.3 Hypothesis and Proposed Solution ....................................................................... 6 2. METHODOLOGY .................................................................................................... 10 2.1 Instrumentation and Data Collection .................................................................. 10 2.2 Data Validity and Limitation .............................................................................. 13 2.3 Data Analysis .................................................................................................... 13 2.4 Case Study – Malinau Coal ................................................................................ 14 3. SAPROLITE & WATER MANAGEMENT: A LITERATURE REVIEW ................ 16 3.1 Saprolite Characteristics .................................................................................... 18 3.2 Shear Strength of Saprolite ................................................................................ 20 3.3 Hydrogeology and Aquifer................................................................................. 21 3.4 Indonesia Environmental Regulation.................................................................. 23 4. SEPARI DEWATERING PLAN ............................................................................... 28 4.1 Malinau Coal ..................................................................................................... 29 4.2 Regional Climate ............................................................................................... 32 4.2.1 Groundwater Recharge................................................................................... 32 4.2.2 Rainfall and Intensity Prediction .................................................................... 42 4.2.3 Surface Water Runoff .................................................................................... 44 4.3 Morphology of the Study Areas ......................................................................... 46 4.4 Hydrogeological and Aquifers Study ................................................................. 52 4.5 The Dewatering Plan ......................................................................................... 59 iii 4.5.1 Controlling Surface Water Runoff .................................................................. 59 4.5.2 Groundwater Control ..................................................................................... 65 4.6 Environment Water Management ....................................................................... 68 4.7 Slope Stability Analysis ..................................................................................... 69 5. DISCUSSION, ANALYSIS, AND RECOMMENDATION ...................................... 75 5.1 Water Channels and Flood Protection Levees .................................................... 75 5.2 Dewatering Wells .............................................................................................. 77 5.3 Environmental Impact ........................................................................................ 80 5.4 Effect of Dewatering on Mine Closure ............................................................... 84 5.5 Risk Assessment ................................................................................................ 85 6. CONCLUSION ......................................................................................................... 86 6.1 Research Significance and Contributions ........................................................... 86 6.2 Conclusion ......................................................................................................... 86 REFERENCES.............................................................................................................. 89 APPENDIX 1 ................................................................................................................ 94 APPENDIX 2 ................................................................................................................ 96 APPENDIX 3 .............................................................................................................. 100 APPENDIX 4 .............................................................................................................. 102 APPENDIX 5 .............................................................................................................. 107 APPENDIX 6 .............................................................................................................. 108 APPENDIX 7 .............................................................................................................. 111 iv LIST OF TABLES Table 3.1 Soil and rock parameters in Malinau Coal mine (Haryoko, 2009)..................................................................................................................................21 Table 4.1 Monthly average temperatures (Badan Metereologi dan Geofisika Bandara Temindung Samarinda, 2010)......................................................35 Table 4.2 Total monthly precipitate (Badan Metereologi dan Geofisika Bandara Temindung Samarinda, 2010).....................................................36 Table 4.3 Total number of rainy days from 2000 to 2009 (Badan Metereologi dan Geofisika Bandara Temindung Samarinda, 2010).....................38 Table 4.4 Type of climate based on Q value by Schmidt and Ferguson (as cited in Irfan, 2006)..............................................................................39 Table 4.5 Daily rainfall statistic precipitation at study areas............................................42 Table 4.6 Rainfall prediction for 24-hour periods............................................................43 Table 4.7 Rate of discharge for each watershed...............................................................45 Table 4.8 Characteristics of the aquifers...........................................................................56 Table 4.9 Groundwater discharge rate..............................................................................58 Table 4.10 Groundwater monitoring data trigger levels....................................................69 Table 4.11 Factor of safety for each rock material............................................................71