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U.S. GEOLOGICAL SURVEY
Data Series 284

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Site Description

The ADRS is near a waste-burial facility about 17 km south of Beatty, Nev., and 20 km east of Death Valley, Calif. (fig. 1A). The ADRS is in the Mojave Desert ecosystem, one of the most arid regions in the United States. Vegetation in the area is sparse, covering about 6 to 8 percent of the land surface at the ADRS (Andraski and others, 2005) based on 2001 and 2003 data collected using the line-transect method (Smith, 1974). Creosote bush (Larrea tridentata), an evergreen shrub, is the dominant species. At the site, creosote bush averages about 0.7 m in height, with a major and minor axial diameter of 1 m and 0.7 m, respectively. The Amargosa Desert is in the Basin and Range physiographic province. Sediments beneath the study area and the waste-burial facility primarily are basin fill consisting of unconsolidated alluvial fan, fluvial, and marsh deposits (Clebsch, 1968). The basin fill is estimated to be more than 170-m thick (Nichols, 1987, p. 8). Depth to the water table ranges from 85 to 115 m below land surface (Fischer, 1992, p. 12).

Other studies at the ADRS facility have been established to support research of flow and transport processes within the thick unsaturated zone above the water table. The research site has two fenced areas; one encloses a vertical, 13.7-m instrument shaft (figs. 1B and 2; Fischer, 1992), and the other encloses simulated waste trenches (figs. 1B and 3; Andraski, 1990). A weather station, two precipitation gages, and three neutron-probe access tubes are within the instrument-shaft area (fig. 2). The instrument-shaft area is used for monitoring soil-water content in a vegetated, native-soil profile. Six neutron-probe access tubes and a single precipitation gage are within the simulated waste-trench area (fig. 3). The tubes are used to measure soil-water content under nonvegetated, simulated waste-trench conditions and under devegetated, but undisturbed native-soil condi­tions. Ground-water levels have been measured period­ically since 1987 at well MR-3 (fig. 1B).

Throughout the thick unsaturated zone, deep test holes (UZB‑1, 2, and 3; fig. 1B) have been used for obtaining mea­surements of soil temperature, water potential, air pres­sure, and for collecting soil-gas samples (Prudic and Striegl, 1995; Andraski and Prudic, 1997; Prudic and others, 1999; Mayers and others, 2005). An ET station (fig. 1B) is located approximately 200 m south of the fenced area enclosing the instrument shaft area. Not shown in the figures is an array of soil-gas sam­pling tubes that are used for periodic collection and analysis of the chemical composition of unsaturated-zone air to a depth of about 1.5 m (Striegl and others, 1998; Healy and others, 1999). Similarly, numerous plant-sampling sites have been established to evaluate soil-plant-atmosphere interactions and ultimately to determine how those interactions affect the potential release of contaminants (Andraski and others, 2005).

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