HSL-1 is a monitoring site on Mammoth Mountain and in an area of anomalously high CO2 concentrations that has resulted in a massive tree-kill. HSL-1 was drilled to learn more about variations in concentrations of CO2 in the unsaturated zone and the chemistry and isotopic composition of ground water. Four 0.1-in. polythylene tubes were installed over a range of depths from 15 ft to near the water table (generally less than 150 ft) for collecting soil-gas samples.The well also has a 2-in diameter polyvinyl chloride pipe extending to the full depth of the well, with perforations in the bottom 10 ft, for collecting water samples and measuring water levels. Water level is monitored using a pressure transducer and recorded on a datalogger every 30 minutes.Click here for schematics of a permanent soil-gas sampler installation and the monitoring-well site.

For more information on carbon dioxide emissions at Mammoth, see our webpage, or read Magmatic carbon dioxide emissions at Mammoth Mountain, California (USGS WRIR 98-4217).