Geohydrology of test well USW H-1, Yucca Mountain, Nye County, Nevada

This report contains the results of hydraulic testing, hydrologic monitoring, and geophysical logging of test well USW H-l, one of several wells drilled in the southwestern part of the Nevada Test Site in cooperation with the U.S. Department of Energy for investigations related to the isolation of high-level radioactive wastes.All rocks penetrated by the well to a total depth of 1,829 meters were of volcanic origin and of Tertiary age.Hydraulic head in the zone 688 to 741 meters below land surface was 730 meters above sea level and at a depth of 572 meters below land surface.Deeper zones had hydraulic heads of 781 meters above sea level or higher, indicating an upward component of ground-water flow at the site.The most transmissive zone, with an apparent transmissivity of about 150 meters squared per day, is in the Prow Pass Member of the Crater Flat Tuff in the depth range from 572 to 688 meters below land surface.The remainder of the penetrated rocks in the saturated zone, 688 to 1,829 meters, has an apparent transmissivity of about 1 meter squared per day.The most transmissive part of the lower depth range is in the Bullfrog Member of the Crater Flat Tuff in the depth interval from 736 to 741 meters.The apparent hydraulic conductivity of the rocks in this lower depth interval from 688 to 1,829 meters commonly ranges between 10~4 and 10~7 meter per day.Water chemistry is typical of tuffaceous rocks of southern Nevada.The water is a sodium bicarbonate type and has an apparent age of 12,000 to 13,000 years before present, as determined by carbon-14 dating.