Description: The system passively treats acid mine drainage (AMD) from a surface coal mine using limestone aggregate and a settling pond. The system consists of an AMD collection system, one limestone bed (LSB) and a settling pond. A general flow schematic follows. The LSB is manually drained empty on an as-needed basis to flush out accumulated metals solids. The draining water also flows to the settling pond. Both the LSB and settling pond have PVC liners covered with 6-12” of clay soil.