Environmental investigations of in situ coal gasification experiments. [Hoe Creek]

Although in situ coal gasification offers important environmental advantages when compared with more conventional methods of coal utilization, there are significant environmental concerns that need to be investigated. Groundwater sampling and subsidence measurements have been carried out at the sites of two in situ coal gasification experiments conducted in northeastern Wyoming by the Lawrence Livermore Laboratory (LLL). Changes in groundwater quality and the possible effects of subsidence and ground movement induced by the gasification cavity represent important environmental concerns associated with the in situ coal gasification process. Our groundwater quality measurements near the site of the first experiment (Hoe Creek I) show a continuing decrease, after more than a year, in the concentration of important contaminants such as phenolic materials. Laboratory measurements have provided detailed information concerning phenol adsorption by coal. Long-term effects due to groundwater flow, and the detailed behavior of other contaminants remain to be investigated. Data from subsurface geotechnical instruments installed at the second gasification experiment (Hoe Creek II), as well as measurements of groundwater levels indicate that roof collapse has connected the gasification cavity with overlying aquifers. The implications of this interconnection for the dispersal of underground contaminants are being investigated.