During the spring of 1980, a field program was begun to evaluate the hydrogeology of the LETC underground coal gasification site near Hanna, Wyoming. Four holes were cored and twenty two new hydrology wells were drilled in the Hanna No. 1 coal seam and in the overlying strata. A comprehensive set of geophysical logs were run. The Hanna no. 1 coal seam and two separate strata in the overburden were identified as water bearing. A series of slug tests and injection tests were run to determine hydrologic characteristics of the aquifers. Values of transmissivity for the Hanna no. 1 coal aquifer were found.