||The potential effect of underground coal gasification on groundwater has been examined in a laboratory study. The study was directed at Fruitland Formation subbituminous coal of the San Juan Basin and at the groundwater found in this coal seam. Two wells were drilled into the coal seam at a potential UCG test site. Groundwater samples and core samples of overburden, underburden and coal were analyzed to establish baseline characteristics. A number of static leaching and sorption studies were performed on the overburden, underburden, and coal. Ash was prepared at several different temperatures and leaching characteristics were examined. Cations of the trace elements Be, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg and Pb and the anions F(-1), AsO4(-3), SeO3(-2), and MoO4(-2) were selected for coal sorption studies. Distribution coefficients for sorption on coal were determined for the cations and anions under conditions reasonably similar to those in the groundwater of the San Juan Basin. The effect of humic acid on the sorptive characteristics of coal was studied.