Study on Rehabilitation in Opencut Coal Mine and Utilization of Flyash

Acid mine drainage is a profound environmental problem in many mining environments that compromises the quality of surrounding surface and ground water resources. The process initiates when pyrite and other metal sulfides are exposed to near-surface atmospheric conditions and in presence of oxygen and water, oxidize to produce various hydrated metal sulfate salts. When reaching streams, lakes and rivers, the acid mine drainage can compromise natural equilibria and incorporate toxic metals into the aquatic food chain.A large amount of flyash from the coal combustion is produced. About 80% of flyash in Japan is now utilized and the remains are dumped at disposal sites; however, the life of these sites is limited. Therefore, in this study, an effort was made to analyze the filling materials by applying flyash as a part of its recycle and utilization. This paper describes some factors to generate acid mine drainage and discusses measures to control acid mine drainage in order to avoid environmental impacts from coal mines in Indonesia. Also, rehabilitation method using flyash is discussed and the fundamental study using the leaching test is carried out.