"The reactor zone from the first test in the Rawlins UCG-SDB program has been characterized utilizing core holes, TV and sonar logs, and detailed examination of recovered cores. The results of the study are: the firepit mechanism was operative during apart of, if not all the test; an open water filled cavity has formed in the overburden with a volume approximately 26% that of the coal gasified; the reactor has stabilized by bulking; the thermally altered zone in the remaining coal is quite narrow; ash temperatures reach 1500C sometime during the test. The objectives were met with five drilled wells and cores from four of these wells. Sonar logging has been shown to be extremely effective in locating and characterizing the water filled cavity."