Lati coal mine is one of four mine sites owned and operated by PT. Berau Coal located in East Kalimantan. The mine is suffering from acid mine drainage (AMD) problem since most of the overburden as well as inter-burden materials are classified as potentially acid forming. Ukud River is located in the southern part of Lati mine site. The catchment area covers a total area of 1738.67 Ha consisting of 48.6% min e disturbed area and 51.4% of natural area. The river has been indicated to be impacted by AMD with pH value of 3-4 since in the past operation there was no segregation between potentially acid forming material and non-acid forming material when dumping the overburden. in this catchment. The hydrological responses in the river are strongly influenced by the dynamics of catchment area.
Ukud’s catchment area is divided into 11 sub-catchments. Monitoring has been conducted to evaluate the behavior of water quality flowing from each sub-catchment. Low pH has been measured in almost all monitoring points except one point representing the undisturbed natural condition with pH of 7.01. In 2009, the water quality simulation was conducted to identify the critical sub-catchment with highest contributors for AMD, i.e. sub-catchments A1, A8 and A10. Continuous monitoring campaign has shown that in 2013 the main contributors are sub-catchment A1 (active mine pit) and A7 (temporarily abandoned mine pit). The dynamic change of Ukud’s catchment area due to mine pit opening, waste dump enlargement as well as mine dewatering system are the challenges in AMD management. AMD treatment effort and reclamation of disturbed area should be integrated with the mine planning.