Waste Burial in Arid Environments 

Application of Information From a Field 

Laboratory in the Mojave Desert, Southern Nevada

u

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U.S. Department of the Interior U.S. Geological Survey

Accumulation and management of waste is a pressing 

problem facing the United States today. Improper disposal of 

hazardous wastes poses a threat to public health and environmental quality. As arid sites increasingly are being sought for 

disposal of the Nation's radioactive and other hazardous wastes, 

concern about the potential effect of contaminants on water resources in the arid western United States is being raised. In 

addition, volumes of locally generated municipal and industrial 

wastes are increasing because of rapid population growth and 

industrialization of the region.

The suitability of a waste-burial site or landfill is a function 

of the hydrologic processes that control the near-surface water 

balance. Precipitation that infiltrates into the surface of a burial 

trench and does not return to the atmosphere by evapotranspiration from the soil and plants can percolate downward and 

come in contact with buried waste. Water that contacts the 

waste can enhance the release of contaminants for subsequent 

transport by liquid water, water vapor, or other gases.

A prevalent assumption is that little or no precipitation will 

percolate to buried wastes at an arid site. Thick unsaturated 

zones, which are common to arid regions, also are thought to 

slow water movement and minimize the risk of waste migration 

to the underlying water table. On the basis of these assumptions, reliance is commonly placed on the natural system to 

isolate contaminants at waste-burial sites in the arid West.

Few data have been available to test the validity of assumptions about the natural soil-water flow systems at arid sites, and 

even less is known about how the construction of a waste-burial 

facility alters the natural environment of the site. The lack of 

data is the result of (1) technical complexity of hydraulic characterization of the dry, stony soils and (2) insufficient field

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MOJAVE 

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Figure 1. Location of waste-burial site, Death 

Valley, and Mojave Desert of southwestern United 

States.

Figure 2. Undisturbed, vegetated area near waste-burial site, 

October 1991 (A); low-level radioactive waste burial trench (6); and 

nonvegetated surface of backfilled waste-burial trench with identifying 

monument, June 1988 (C).

studies that account for the extreme temporal and spatial 

variations in precipitation, vegetation, and soils in arid regions. 

In 1976, the U.S. Geological Survey (USGS) began a longterm study at a waste-burial site in the Mojave Desert near 

Beatty, Nev., to collect the necessary data and evaluate untested assumptions. This fact sheet summarizes the findings of 

investigations at the site and discusses how this information is 

important to issues of waste burial in an arid environment.
Mojave Desert Waste-Burial Site

The waste-burial site, 30 miles east of Death Valley National 

Park, is in one of the most arid parts of the United States 

(fig. 1). Precipitation in the area averages about 4 inches per 

year. The water table is about 360 feet below land surface. 

Vegetation in the area is sparse (fig. 2A). Burial trenches at the 

site have been used for disposal of low-level radioactive waste 

(1962-92) and hazardous-chemical waste (1970-present). 

Burial-trench construction includes excavation of native soil, 

emplacement of waste, and backfilling with previously stockpiled soil (fig. 2B). The surfaces of completed burial trenches 

and perimeter areas are kept free of vegetation (fig. 2C). 

Regulations governing burial of low-level radioactive waste do 

not require that trenches be lined with impervious materials. 

Prior to 1988, linings were not required for chemical-waste 

trenches. As a result, only the most recent chemical-waste 

trench at the site is lined.

Field Laboratory Established

Recognizing the need for long-term data collection, the 

USGS established a study area adjacent to the waste-burial site 

through agreements with the Bureau of Land Management and 

the State of Nevada. This 40-acre area serves as a field laboratory for long-term data collection and the study of hydrologic 

processes under natural-site and waste-burial conditions.

Lessons Learned to Date

Early (1962) evaluation of the general hydrologic conditions 

at and near the waste-burial site suggested that low average 

annual precipitation and high average annual evapotranspiration would prevent water from percolating downward more 

than 1 or 2 feet below land surface. This assumption, however, 

did not consider the extreme annual and seasonal variations in 

a desert climate. During 1985-92, annual precipitation measured at the USGS study site ranged from 0.55 to 6.51 inches 

and monthly precipitation ranged from 0 to 2.34 inches. 

Monthly average temperature ranged from 38 to 92 degrees 

Fahrenheit. Most of the precipitation falls during the cool

2.5

2.0

1.5

1.0

0.5

1.38

TOTAL ANNUAL PRECIPITATION, IN INCHES 

2.97 5.37 4.11 0.55 1.28 4.08

100

90

< O

1985 1986 1987 1988 1989 

YEAR

1990 1991 1992

Figure 3. Annual and monthly total precipitation and monthly average 

temperature measured at U.S. Geological Survey field laboratory 

during 1985-92.

winter months when evaporative demands are low (fig. 3). 

Initial water-balance modeling by the USGS demonstrated 

that, under particular climate and soil-moisture conditions, the 

potential for deep percolation does exist, in spite of high 

annual evaporative demands (Nichols, 1987).

Field investigations to define the rates and directions of 

water movement through the deep unsaturated zone beneath an 

undisturbed, vegetated area began in the early 1980's and continue today. A study of chloride concentrations in the unsaturated zone indicates that deep percolation of water was limited 

to the upper 30 feet during the past 16,000 to 33,000 years 

(Prudic, 1994a). To monitor present-day flow processes, an 

instrument shaft was installed that allows access for operation 

of electronic devices to a depth of 45 feet (fig. 4; Fischer, 

1992). Additional instrumentation has been installed to study 

flow processes throughout the unsaturated zone (Prudic, in 

press). Meteorological data are collected by an automated 

weather station (Wood and Andraski, 1995).

Water movement in the unsaturated zone is complex. 

Several variables water content, water potential, humidity, 

and temperature must be monitored to define rates and

Figure 4. Installation of vertical shaft used for soil-moisture 

monitoring in upper 45 feet of unsaturated zone beneath 

undisturbed, vegetated area. Photograph by David S. 

Morgan, U.S. Geological Survey, August 1983.
directions of water movement. Water content indicates how 

much water is held in the soil. Water potential indicates how 

tightly the water is held by the soil matrix. Water moves 

through soil in liquid and vapor form, and the two forms can 

move simultaneously as a consequence of water-potential, 

humidity, and temperature gradients in the soil.

Ongoing investigations at the undisturbed, vegetated site 

indicate that the natural soil-plant-water system effectively 

limits the potential for deep percolation. During more than 

5 years of monitoring, downward percolation was limited 

to the upper 3 feet of soil (Fischer, 1992; Andraski, 1994). 

Between the depths of 40 and 160 feet, water movement, as 

liquid and as vapor, is consistently upward. Preliminary evidence indicates that upward flow of water vapor through the 

thick unsaturated zone may potentially serve as a contaminantrelease pathway (Prudic, 1994b; Prudic and Striegl, 1994).

Little is known about how, or to what degree, features of 

the natural system may be altered by installation of a disposal 

facility. Investigations to determine the effects of disturbance 

on soil properties and the long-term soil-water balance began 

in 1987. Two nonvegetated test trenches and an area of bare 

soil are monitored (fig. 5; Andraski, 1990). The effects of 

disturbance are evaluated in terms of observed differences 

between data collected at the undisturbed, vegetated site and 

data collected at the disturbed sites.

show that this lower limit is not adequate for nonirrigated, 

desert soils and plants, nor is it appropriate for the extremely 

dry backfill material produced by trench construction. Thus, 

characterization of hydraulic properties at the site has been 

extended to include data measured over a soil-moisture range 

that is representative of seldom-studied arid conditions 

(Andraski, in press).

Backfilling with very dry material will, at least initially, 

increase the importance of vapor flow as a potential transport 

mechanism in the trench fill (Andraski, in press). These initial 

dry conditions can change substantially, however, in response 

to subsequent precipitation and a lack of vegetation. On an 

annual basis, no water accumulates in the vegetated soil 

because water is removed by the plants (fig. 6). In contrast, 

even under conditions of extreme aridity, water accumulates in 

the nonvegetated soil and test trenches. Water that has accumulated at the three disturbed sites is continuing to percolate 

downward (Andraski, 1994). Thus, the construction of wasteburial trenches and removal of native vegetation markedly alters 

the natural site environment and may increase the potential for 

release of contaminants (Gee and others, 1994). Surprisingly, 

such changes typically are not considered in the evaluation of a 

proposed waste site and may not be considered in management 

of existing sites.

Well-informed Decisions Needed

Accurate characterization of hydraulic properties is critical 

to calculations of water movement through soil. Characterization data normally are measured to a minimum water-potential 

value referred to as the permanent wilting point for crops. 

Below this value, water is held so tightly by the soil matrix that 

a crop plant cannot extract the water and will wilt and die. Data 

collected by the USGS at the Mojave Desert site, however,

Regulations governing the licensing of solid-waste landfills 

and hazardous-waste sites require an assessment of the potential 

for deep percolation of water through buried waste before 

disposal operations can begin. Numerical models commonly 

are relied on for this assessment. For a proposed low-level 

radioactive waste site, 1 year of preoperational monitoring of 

site conditions also is required. Thus, data used in numerical

UNDISTURBED SOIL; 

VEGETATION REMOVED

NONVEGETATED

TEST TRENCH 2

(drums randomly placed)

15 FEET

EXPLANATION

1

Drum filled with soil 

(simulated waste)

Subsidence plate and rod

Surface subsidence/ 

erosion pin

Neutron access tube for 

monitoring soil-water 

content

Thermocouple psychrometer 

for monitoring soil-water 

potential and temperature

Figure 5. Schematic diagram of instrumentation used to determine 

effects of vegetation removal and trench construction on water 

movement through unsaturated zone. Subsidence and erosion are 

monitored to determine changes in structural integrity of test trenches. 

In second test trench (not shown), soil-filled drums are stacked in 

orderly fashion.

60

50

- 40

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2

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tr

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< 20

O 10

-20

Undisturbed, vegetated soil 

Undisturbed soil, vegetation removed 

Nonvegetated test trench 1 

Nonvegetated test trench 2

Nov. 21, 1988 Sept. 21, 1989 Sept. 18,1990 Dec. 18,1991 Sept. 24, 1992

Figure 6. Cumulative changes in quantity of water being held in 

uppermost 4 feet at four monitoring sites: undisturbed vegetated soil; 

undisturbed soil where native vegetation was removed; and two 

nonvegetated test trenches. Values are based on measurements 

during first 5 years following vegetation removal and trench 

construction at disturbed study site in October 1987.
analysis of a proposed waste-burial site may be based solely on 

hydraulic information available in the literature, or the data may 

include some site-specific information, which typically is limited to natural conditions and a short period of time. This approach is of particular concern for waste sites in arid regions 

because, compared with the amount of information available 

for more humid sites, the amount of hydraulic-property data 

and long-term field data for arid sites is negligible. In addition, 

although significant advances have been made in the development of soil-water flow models, the lack of long-term field data 

has resulted in these models remaining largely untested as to 

how well they represent flow systems at arid sites.

Long-Term Benchmark Information

Ongoing work by the USGS at the Mojave Desert field 

laboratory continues to provide long-term, quantitative "benchmark" information about the hydraulic characteristics, water 

movement, and the potential for release of contaminants 

through the unsaturated zone in an arid environment. Monitoring methods developed and tested at the Mojave Desert site 

have helped others in their study and evaluation of wasteisolation processes at the Nevada Test Site, and at proposed 

waste sites in Texas and California. The U.S. Nuclear Regulatory Commission and Pacific Northwest Laboratory have chosen the Mojave Desert waste site for use in numerical modeling 

of infiltration because it is representative of burial operations in 

an arid environment. Data collected at the USGS field laboratory are being provided for this effort. The National Academy of 

Sciences also has used information from the site in the evaluation of issues related to waste disposal in an arid environment.

Because of the potentially harmful effect of improper waste 

disposal on water resources in the arid West, comprehensive 

laboratory and field studies are critical to identifying likely 

contaminant-release pathways and the potential for waste 

migration at arid sites. However, the quandary for those charged 

with assessment of the suitability of potential disposal sites is 

that site characterization and evaluation must be accomplished 

in a relatively short period of time only 1 to 2 years.

Data collection at the Mojave Desert field laboratory 

provides the needed long-term benchmark against which shortterm data from proposed arid sites can be compared. The data 

base and monitoring facilities developed at the field laboratory 

also provide an excellent foundation upon which to build collaborative efforts with universities and local, State, and other 

Federal agencies to further the study and understanding of 

hydrologic processes in an arid environment.

B.J. Andraski, David E. Prudic, and William D. Nichols

References Cited

Andraski, B.J., 1990, Water movement and trench stability at a 

simulated arid burial site for low-level radioactive waste near 

Beatty, Nevada: LaGrange Park, 111., American Nuclear 

Society, Nuclear Waste Isolation in the Unsaturated Zone, 

Las Vegas, Nev., September 1989, Proceedings, p. 166-173.

 1994, Disturbance effects on soil properties and water 

balance at a low-level radioactive waste site, Amargosa 

Desert, Nevada [abs.]: American Society of Agronomy, 

Agronomy Abstracts, v. 86, p. 227.

 in press, Properties and variability of soil and trench fill at 

an arid waste-burial site: Soil Science Society of America 

Journal.

Fischer, J.M., 1992, Sediment properties and water movement 

through shallow unsaturated alluvium at an arid site for 

disposal of low-level radioactive waste near Beatty, Nye 

County, Nevada: U.S. Geological Survey Water-Resources 

Investigations Report 92-4032, 48 p.

Gee, G.W., Wierenga, P.J., Andraski., B.J., Young, M.H., Payer, 

M.J., and Rockhold, M.L., 1994, Variations in water balance 

and recharge potential at three western desert sites: Soil 

Science Society of America Journal, v. 58, no. 1, p. 63-72.

Nichols. W.D., 1987. Geohydrology of the unsaturated zone at 

the burial site for low-level radioactive waste near Beatty, 

Nye County, Nevada: U.S. Geological Survey Water-Supply 

Paper 2312, 57 p.

Prudic, D.E., 1994a, Estimates of percolation rates and ages of 

water in unsaturated sediments at two Mojave Desert sites, 

California-Nevada: U.S. Geological Survey Water-Resources 

Investigations Report 94-4160. 19 p.

 1994b, Effects of temperature on water movement at the 

arid disposal site for low-level radioactive wastes near Beatty, 

Nevada [abs.]: Geological Society of America, Abstracts with 

Programs, v. 26, no. 7, p. 391.

 in press, Water-vapor movement through unsaturated 

alluvium in Amargosa Desert near Beatty, Nevada Current 

understanding and continuing studies, in Stevens, P.R., and 

Nicholson, T., eds., Conference on Disposal of Low-Level 

Radioactive Waste, Reston, Va., May 1993: U.S. Geological 

Survey Water-Resources Investigations Report 95-4015.

Prudic, D.E., and Striegl, R.G., 1994, Water and carbon dioxide 

movement through unsaturated alluvium near an arid disposal 

site for low-level radioactive waste, Beatty, Nevada [abs.]: 

Eos, American Geophysical Union Transactions, v. 75, 

no. 16, p. 161.

Wood, J.L., and Andraski, B.J., 1995, Selected meteorological 

data for an arid site near Beatty, Nye County, Nevada, 

calendar years 1990 and 1991: U.S. Geological Survey OpenFile Report 94-489, 49 p.

For more information about the Mojave Desert 

studies, contact:

Brian J. Andraski 

U.S. Geological Survey 

333 W. Nye Lane 

Carson City, NV 89706 

(702) 887-7600, ext. 7636 

andraski@usgs.gov

August 1995 Fact Sheet FS-179-95