Prefracture water quality and hydrology analyses have been completed for the TESI site near Rock Springs, Wyoming. Sampling were conducted primarily at six observations wells designed to monitor the characteristics of the two primary aquifer in the site area. The locations of these aquifers have been identified at depths of 249 to 273 feet and 414 to 442 feet respectively. Laboratory analyses of the core sample, confirmed by visual inspection, indicates that rock in the test zone is of low permeability and that water can be expected to flow mainly through fracture zones. There results were confirmed by the presence of fractures from which bubbling and flowing water emanated as observed through the down-hole camera. Pump tests performed on each observation well indicate that the specific capacity of the shallow aquifers varied from 0.005 to 0.21 GPM/FT, while for the deep aquifers the specific capacity ranged from 0.002 to 0.009 GPM/FT. It was noted that the specific yield of observation well 0-6 was relatively high, indicating a local occurrence of large fractures which contain and transmit significant amounts of water. Water quality analyses conducted for both the lower and upper aquifers indicated that the lower aquifer was significantly cleaner than the upper aquifer, reflecting better filtration of the water at the lower level. Species concentrations were generally 20 times higher in the upper aquifer. The water can be classified as very poor and not suitable for use even as irrigation water.