Generation of hydrogen gas as a result of percussion drilling within an unconfined aquifer, south-central Washington

A 240-m deep borehole (Yakima Barricade borehole), located on the US Department of Energy`s (DOE) Hanford Site, was drilled as part of a DOE research program to investigate microbial processes in deep subsurface environments and to evaluate geochemical and geohydrological controls on subsurface microorganisms. A combustible gas was detected during drilling of the Yakima Barricade borehole (YBB). Once it was established that the major combustible gas was H{sub 2}, a series of tests were performed to evaluate the process by which H{sub 2} occurred within the borehole. This paper presents evidence for the generation of H{sub 2} in boreholes during percussion drilling below the water table and discusses mechanism of H{sub 2} generation and their implications for subsurface microbial processes.