"During the fall of 1980 the Laramie Energy Technology Center conducted a post-burn drilling study at the Hanna II, Phases 2 and 3 underground coal gasification (UCG) site. Twenty-two drill holes were drilled and logged. Core samples and geophysical logs were used to interpret the gasification zone. Caliper, gamma, gamma-gamma density, neutron, directional, and temperature logs were used. Char zones were delineated using petrographic studies and chemical analyses. Vertical cross sections were constructed to show the size and shape of the burn cavity and the location of rubble, paralava and char."