31. However, acid water continues to enter the river due to mine dewatering and run-off from the waste rock dumps. 32. A project to remove waste rock piles in the watershed of the creek was carried out in 2006 and 2007. 33. Often these voids ( stopes ) would be re-filled with waste rock from other diggings after ore removal was complete. 34. Coal strip mining methods and the surface disposal of waste rock results in the contamination of surface and ground waters. 35. The deposits must be machined to extract the metals in question from the waste rock and minerals from the reservoir. 36. Costs at BHP's coal mines in Queensland state rose due to increased waste rock removal charges and higher maintenance costs. 37. After production ceased, the area was recultivated, including flooding the mine, removing the mine buildings and covering the waste rock area. 38. The mine produces 9.3 million tons per year of ore and an additional 37 million tons per year of waste rock . 39. They have predicted pollution will occur at several locations as water drains through the waste rock that will be left behind. 40. The mine produces 3.6 million tons per year of ore and an additional 15 million tons per year of waste rock .
