The Helium Sniffer (Friedman and Denton, 1976; Roberts and others, 1975) was used to measure the flux of helium permeating the soil at a site in southwest Utah where a new irrigation well had unexpectedly encountered hot water (110° C). About 200 soil-gas samples, taken 2 ft (0.61 m) below the surface,-were collected in the vicinity of the well, covering an area of some 2 mi2 (~5 km2), as shown in figures 1-3. Since only about half these data were taken over a uniform grid, the resulting pattern of helium concentrations is somewhat incomplete. Nevertheless, the more densely spaced data appear to delineate a dome beneath which hot water has accumulated, and into the side of which the well was drilled.
Throughout the survey, the weather remained dry and cool, averaging 55° F (13° C), with the wind from the southwest at zero to 13 mph (0-5.8 m/s), and the barometric pressure ranging from 24.91 to 25.25 inches of mercury (43.55-55.06 millibars). The soil in the region was fairly dry. It varied in texture from sandy to clayey near the well, to pea-size gravel in the foothills (southeast). The abundance of helium in the ambient atmosphere was found to be within 1 percent of 5,240 ppb. The sensitivity of the spectrometer itself remained within 10 percent of 18 parts per billion (helium in air) per leak detector unit.
