The groundwater problem at Mae Moh mine has drawn attention as the mining excavation goes
deeper, thus resulting in detailed investigation of hydrogeological condition. One of the problems
facing the mining is floor heave influenced by groundwater. The control of groundwater pressure in
deep-seated aquifers with high elevation becomes important in the mining. In addition, the
underground water at Mae Moh mine is naturally contaminated by arsenic. Therefore, the
developments of 3D groundwater model of deep pit mine using Modflow simulation and the
studies of underground water treatment are needed for the future planning. The predictive
simulations were carried out for eight years (2007 to 2015). Because stability of the Mae Moh mine
shows how can be closely linked to the water environment, this paper aims to report the field Visits
to the water related facilities of the mine, which were conducted during 2010-2013. The result
reveals that the potentiometric head level is strongly increased, which might be a potential risk for
the floor heave; thus, depressurization is required. Field measurements reveal pH level at 8 and a
range of total dissolved solid (TDS) at 870-2020 ppm. Treatment efficiency shows that more than
95% of the arsenic can be successfully removed using ferric chloride.
