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Research about Nevada

Source-linked reports with geographic coverage including Nevada.

At least 631 records · Page 35Linked to original sources
USGS1997

Tritium, deuterium, and oxygen-18 in water collected from unsaturated sediments near a low-level radioactive-waste burial site south of Beatty, Nevada

Pore water was extracted in March 1996 from cores collected from test holes UZB-1 and UZB-2 drilled November 1992 and September 1993, respectively, in the Amargosa Desert south of Beatty, Nevada. The test holes are part of a study to determine factors affecting water and gas movement through unsaturated sediments. The holes are about 100 meters south of the southwest corner of the fence enclosing a commercial burial area for low-level radioactive waste. Water vapor collected from test hole UZB-2 in April 1994 and July 1995 had tritium concentrations greater than would be expected from atmospheric deposition. An apparatus was built in which pore water was extracted by cryodistillation from the previously obtained core samples. The extracted core water was analyzed for the radioactive isotope tritium and for the stable isotopes deuterium (D) and oxygen-18 ( 18 O). The isotopic composition of core water was compared with that of water vapor previously collected from air ports in test hole UZB-2 and to additional samples collected during May 1996. Core water becomes increasingly depleted in D and 18 O from the land surface to a depth of 30 meters, indicating that net evaporation of water is occurring near the land surface. Below a depth of 30 meters the stable-isotopic composition of core water becomes nearly constant and roughly equal to that of ground water. The stable isotopes plot on an evaporation trend. The source of the partly evaporated water could be either ground water or past precipitation having the same average isotopic composition as ground water but not modern precipitation, based on 18 months of record. Profiles of D and 18 O in water vapor roughly parallel those in core water. The stable isotopes of core water appear to be in isotopic equilibrium with water vapor from UZB-2 when temperature-dependent fractionation is considered. The data are consistent with the hypothesis of evaporative discharge of ground water at the land surface. The concentration of tritium in core water from depths less than 50 meters was higher than that of present-day atmospheric air, indicating that elevated tritium concentrations preceded the drilling. The concentrations of tritium in core water from the deepest sample (85 meters) and in UZB-2 groundwater (110 meters) were below detection. Thus, tritium in the unsaturated zone is not being introduced through ground water. The shape of the tritium profile for core water was similar to the shape of the tritium profile for water vapor collected April 1994, except that concentrations were consistently lower in core water than in water vapor. Tritium concentrations in water vapor increased from April 1994 to May 1996. Similar to the stable isotopes, the highest tritium concentrations were measured at shallow depths. Concentrations of tritium in water vapor during core collection were estimated assuming isotopic equilibrium with core water. The computed concentrations for November 1992 and September 1993 form consistent temporal trends with subsequent tritium concentrations in water vapor collected April 1994, July 1995, and May 1996. Observations of a bimodal distribution of tritium, in which the highest concentrations are in a gravel layer at a depth of 1-2 meters, indicate lateral migration of tritium through the vicinity of UZB-2.

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USGS1997

Test-trench studies in the Amargosa Desert, southern Nevada: Results and application of information to landfill covers in arid environments

As arid sites in the western United States are increasingly sought for disposal of the Nation's hazardous wastes and as volumes of locally generated wastes increase, concern about the potential effect of contaminants on environmental quality is being raised. Studies at the U.S. Geological Survey's Amargosa Desert research site near Beatty, Nevada are being done to evaluate mechanisms that can affect waste isolation in an arid environment. Precipitation at the site averages about 108 mm yr -1 . Results have shown that, under undisturbed conditions, the naturally stratified soils in combination with native plants are effective in limiting the potential for percolation of precipitation. Under nonvegetated waste-site conditions, data indicated the accumulation and shallow, but continued, penetration of infiltrated water, However, water potentials below the test trenches and below the 2-m depth for nonvegetated soil indicated the persistence of an upward driving force for water flow during the 5-yr test period. General trends in trench-cover subsidence suggested a positive relation with cumulative precipitation, but subsidence did not appear to have a measurable effect on the water balance. Erosion rates were inversely related to near-surface rock-fragment content. Results suggest that the ultimate fate of contaminants buried at properly managed solid-waste sites may be determined largely by the interactions among climate and the surface-cover features of the disposal facility, and how these factors change with time.

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USGS1997

Hydrologic inferences from strontium isotopes in pore water from the unsaturated zone at Yucca Mountain, Nevada

Calcite is ubiquitous at Yucca Mountain, occurring in the soils and as fracture and cavity coatings within the volcanic tuff section. Strontium is a trace element in calcite, generally at the tens to hundreds of ppm level. Because calcite contains very little rubidium and the half-life of the 87 Rb parent is billions of years, the 87 Sr/ 86 Sr ratios of the calcite record the ratio in the water from which the calcite precipitated. Dissolution and reprecipitation does not alter these compositions so that, in the absence of other sources of strontium, one would expect the strontium ratios along a flow path to preserve variations inherited from strontium in the soil zone. Strontium isotope compositions of calcites from various settings in the Yucca Mountain region have contributed to the understanding of the unsaturated zone (UZ), especially in distinguishing unsaturated zone calcite from saturated zone calcite. Different populations of calcite have been compared, either to group them together or distinguish them from each other in terms of their strontium isotope compositions. Ground water and perched water have also been analyzed; this paper presents strontium isotope data obtained on pore water.

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USGS1996

Carbonate deposition, Pyramid Lake subbasin, Nevada: 3. The use of 87Sr values in carbonate deposits (tufas) to determine the hydrologic state of paleolake systems

Sierran rivers that discharge to the Lahontan basin have much lower (∼4.5‰) δ 87 Sr values than the Humboldt River which drains northeastern Nevada. The δ 87 Sr values of tufas deposited during the last lake cycle were used to determine when Humboldt derived Sr entered the Pyramid Lake subbasin. Prior to ∼15,000 yr B.P., the Humboldt River flowed to the Smoke Creek-Black Rock Desert subbasin. During the recession of Lake Lahontan, the Humboldt River diverted to the Carson Desert subbasin. This study has demonstrated that 87 Sr can be used to determine drainage histories of multi-basin lake systems if the δ 87 Sr values of rivers that discharge to the basins are sufficiently different.

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USGS1996

Middle Devonian-Mississippian stratigraphy on and near the Nevada Test Site: Implications for hydrocarbon potential

Paleozoic strata on the Nevada Test Site and surrounding area are affected by the intersection of several important geologic trends, including the early Paleozoic rift margin and the Late Devonian-Early Mississippian Antler orogenic foredeep. Upper Paleozoic strata are lithologically diverse and include siliciclastic sediments (carbonaceous shale, clean quartzose sands, bedded chert, and chert-lithic conglomerate and sand) and various carbonates. These are interpreted to have been deposited in a range of environments and water depths. The resulting complex stratigraphy with its dramatic vertical and lateral changes is difficult to correlate, even between nearby surface and subsurface sections. Our detailed stratigraphic studies on and near the Nevada Test Site show that at least three distinct, and largely coeval, Mississippian facies assemblages can be recognized. When dated, correlated, and restored to their original relative geographic positions, these sections allow a new reconstruction of the Devonian and Mississippian geologic history that includes (1) delineation of the Antler foredeep basin and its clastic fill, (2) description of the muddy marginal shelf that lay inboard of the foredeep, and (3) correlation from that shelf to the outer fringes of the carbonate platform that characterizes the edge of the Mississippian epicontinental sea. The position and delineation of the mud-dominated marginal shelf environment is particularly important because shales deposited under such conditions elsewhere in the Great Basin are the hydrocarbon source rocks for the Pine Valley and Railroad Valley oil fields. On the Nevada Test Site, Mississippian shale probably generated hydrocarbons in the past, and still has an organic content and a thermal history appropriate for generating hydrocarbons.

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USGS1996

Factors affecting tritium and 14carbon distributions in the unsaturated zone near the low-level radioactive-waste burial site south of Beatty, Nevada

Interpretations of the distributions of tritiated water vapor (HTO V ) and 14 carbon dioxide gas ( 14 CO 2 ) concentrations in the unsaturated zone adjacent to the low-level radioactive-waste burial site south of Beatty, Nevada, suggest that observed concentrations of 14 CO 2 could be explained by either diffusive or advective transport of the radioactive gas from the site. The distribution of HTO V cannot be explained by vapor transport, either by diffusive or advective mechanisms. Thus, liquid transport appears to have played a role in moving HTO V to well UZB-2. Although the process by which this occurred cannot be determined from available data (and indeed may never be known), it is likely that liquid wastes disposed directly into the trenches during the period from 1962 to 1975 contributed to the offsite contamination. Liquid transport may have been enhanced by precipitation and runoff into open trenches that resulted in the occasional accumulation of ponded water in the trenches and flow along preferential pathways in the underlying unsaturated zone

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USGS1996

Faults, lineaments, and earthquake epicenters digital map of the Pahute Mesa 30' x 60' quadrangle, Nevada

This map database, identified as Faults, lineaments, and earthquake epicenters digital map of the Pahute Mesa 30' X 60' quadrangle, Nevada, has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. This digital map compilation incorporates fault, air photo lineament, and earthquake epicenter data from within the Pahute Mesa 30' by 60' quadrangle, southern Nye County, Nevada (fig. 1). The compilation contributes to the U.S. Department of Energy's Yucca Mountain Project, established to determine whether or not the Yucca Mountain site is suitable for the disposal of high-level nuclear waste. Studies of local and regional faulting and earthquake activity, including the features depicted in this compilation, are carried out to help characterize seismic hazards and tectonic processes that may be relevant to the future stability of Yucca Mountain. The Yucca Mountain site is located in the central part of the Beatty 30' by 60' quadrangle approximately 15 km south of the south edge of the Pahute Mesa quadrangle (fig. 1). The U.S. Geological Survey participates in studies of the Yucca Mountain site under Interagency Agreement DE-AI08-78ET44802. The map compilation is only available on line as a digital database in ARC/INFO ASCII (Generate) and export formats. The database can be downloaded via 'anonymous ftp' from a USGS system named greenwood.cr.usgs.gov (136.177.48.5). The files are located in a directory named /pub/open-file-reports/ofr-96-0262. This directory contains a text document named 'README.1 ST' that contains database technical and explanatory documentation, including instructions for uncompressing the bundled (tar) file. In displaying the compilation it is important to note that the map data set is considered accurate when depicted at a scale of about 1:100,000; displaying the compilation at scales significantly larger than this may result in distortions and (or) mislocations of the data.

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USGS1996

Selected meteorological and micrometeorological data for an arid site near Beatty, Nye County, Nevada, calendar year 1992

il-heat-flux data were collected at a study site adjacent to a low-level radioactive-waste burial facility near Beatty, Nevada, for calendar year 1992. Data were collected in support of ongoing studies to estimate the potential for downward movement of radionuclides into the unsaturated sediments beneath waste-burial trenches at the arid facility. Data collected for the whole year include air temperature, relative humidity, vapor pressure, incident solar radiation, windspeed, wind direction, barometric pressure, and precipitation. Net radiation, soil temperature, and soil-heat flux data also were collected for part of the year. The data are summarized in tables and graphs. Instrumentation used at the site is discussed. The discussion includes the type, reported accuracy, and the mounting height of each sensor. During 1992, the hourly and 20-minute mean air temperatures ranged from -8.6 degrees Celsius, in January, to 42.3 degrees Celsius, in July. Hourly and 20-minute mean relative humidity ranged from 2 percent to 100 percent. Hourly and 20-minute mean vapor pressures ranged from 0.07 to 2.47 kilopascals. Daily maximum incident solar radiation values ranged from 115 to 1,021 watts per square meter. Daily maximum net radiation values ranged from 195 to 632 watts per square meter. Daily mean windspeed ranged from 0.6 to 8.1 meters per second. Wind direction was primarily from the northwest in fall, winter, and spring and was from the southeast, southwest, or northwest during the summer. Barometric pressures ranged from 100.16 kilopascals to 103.38 kilopascals. Total precipitation for 1992 was 165.3 millimeters, with more than 50 percent in February and March. Daily mean soil temperatures at a depth from 2 to 6 centimeters ranged from 10.7 to 39.1 degrees Celsius between June and October. Daily mean soil-heat flux at a dep*h of 8 centimeters ranged from -13.4 to 12.2 watts per square meter during the same period.

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USGS1996

Water Resources Data, Nevada, Water Year 1995

Water resources data published herein for the 1995 water year comprise the following records: Water discharge for 178 gaging stations on streams, canals and drains. Discharge for 113 peak-flow stations and miscellaneous sites, and 46 springs. Stage and contents for 22 lakes and reservoirs. Water-quality data for 171 stream, lake, canal, spring, precipitation, and drain sites, and 111 wells. Precipitation totals for 58 stations. Water levels for 17 continuous record wells, and 1022 observation wells. Additional water-data, collected at various sites that are not part of the systematic data-collection program, are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Nevada.

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USGS1996

Trends in chloride, dissolved-solids, and nitrate concentrations in ground water, Carson Valley and Topaz Lake Areas, Douglas County, Nevada, 1959-88

Rapid population growth in Douglas County, an area of approximately 750 square miles in west-central Nevada, has led to concern about the present and future effects of development on ground water. This report describes the results of two nonparametric statistical procedures applied to detect trends in concentrations of chloride, dissolved solids, and nitrate in ground water. The water-quality data consist of analytical results from ground-water samples collected and analyzed by the U. S. Geological Survey and ground-water-quality data provided by the Nevada Bureau of Health Protection Services for the Carson Valley and Topaz Lake areas of Douglas County, Nevada. For purposes of this study, statistical significance, expressed as the p-value, was set at 0.1. The Mann-Whitney-Wilcoxan rank-sum test detected increasing step-trends for nitrate in one of seven residential areas and for dissolved-solids concentrations throughout the study area. Decreasing step-trends for chloride and dissolved-solids concentrations were detected in the west Carson Valley area. Kendall's Tau detected monotonic trends for increasing nitrate concentrations at four domestic wells and for increasing dissolved-solids concentrations at two domestic wells. No other statistically significant trends were indicated by either test. Land-use relations to areas where increasing trends were detected suggest that the density of individual wastewater-treatment systems may exceed the capacity of soils to treat wastewater leachate.

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USGS1996

Geohydrologic reconnaissance of Lake Mead National Recreation Area: Las Vegas Wash to Virgin River, Nevada

This study is the last of a series of eight geohydrologic reconnaissance studies that were done in the Lake Mead National Recreation Area. The studies were done to evaluate the water resources in the recreation area and to identify areas having potential for the development of water supplies that would be adequate for marinas and campgrounds. The study area includes about 250 square miles north of Lake Mead from Las Vegas Wash to the Virgin River (Overton Arm), Nevada. Volcanic rocks, consolidated sedimentary rocks, and unconsolidated to semiconsolidated sedimentary rocks underlie the area. Surface-water sources include the Colorado River, Virgin River, Muddy River, and Las Vegas Wash. Elsewhere in the area, streamflow is meager and extremely variable. Ground water originates from four sources: (1) subsurface flow in local basins, (2) infiltration of water from Lake Mead into permeable rocks near the lake, (3) subsurface flow in valleys of perennial streams, and (4) subsurface flow in consolidated rocks of the Muddy Mountains. The quantity of water from Lake Mead that has saturated rocks adjacent to the lake probably is greater than the quantity of ground water from all the other sources. Rocks saturated by water from the lake probably extend less than 0.5 mile inland from the lake shore. The quality of virtually all the ground water in the area is not acceptable for drinking purposes. The most favorable areas for obtaining ground water are those underlain by the coarse-grained deposits of the older alluvium and the younger alluvium adjacent to Lake Mead. The least favorable areas are those underlain by the mudstone facies of the Muddy Creek Formation and fine-grained rocks of the Horse Spring Formation. Four areas identified as having potential for ground-water development are (1) near Overton Beach, (2) west of Callville Bay, (3) near Middle Point, and (4) in the lower Moapa Valley. Usable quantities of water probably can be obtained at these sites, but the quality of the water may not be acceptable for drinking purposes. Test drilling for potable water supplies should be considered only as exploration.

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USGS1996

Summary of hydrogeologic controls on ground-water flow at the Nevada Test Site, Nye County, Nevada

The underground testing of nuclear devices has generated substantial volumes of radioactive and other chemical contaminants below ground at the Nevada Test Site (NTS). Many of the more radioactive contaminants are highly toxic and are known to persist in the environment for thousands of years. In response to concerns about potential health hazards, the U.S. Department of Energy, under its Environmental Restoration Program, has made NTS the subject of a long-term investigation. Efforts supported through the U.S. Department of Energy program will assess whether byproducts of underground testing pose a potential hazard to the health and safety of the public and, if necessary, will evaluate and implement steps to remediate any of the identified dangers. Test-generated contaminants have been introduced over large areas and at variable depths above and below the water table throughout NTS. Evaluating the risks associated with these byproducts of underground testing presupposes a knowledge of the source, transport, and potential receptors of these contaminants. Ground-water flow is the primary mechanism by which contaminants can be transported significant distances away from the initial point of injection. Flow paths between contaminant sources and potential receptors are separated by remote areas that span tens of miles. The diversity and structural complexity of the rocks along these flow paths complicates the hydrology of the region. Although the hydrology has been studied in some detail, much still remains uncertain about flow rates and directions through the fractured-rock aquifers that transmit water great distances across this arid region. Unique to the hydrology of NTS are the effects of underground testing, which severely alter local rock characteristics and affect hydrologic conditions throughout the region. Any assessment of the risk must rely in part on the current understanding of ground-water flow, and the assessment will be only as good as the understanding itself. This report summarizes what is known and inferred about ground-water flow throughout the NTS region. The report identifies and updates what is known about some of the major controls on ground-water flow, highlights some of the uncertainties in the current understanding, and prioritizes some of the technical needs as related to the Environmental Restoration Program. An apparent deficiency in the current understanding is a lack of knowledge about flow directions and rates away from major areas of testing. Efforts are necessary to delineate areas of downgradient flow and to identify factors that constrain and control flow within these areas. These efforts also should identify the areas most critical to gaining detailed understanding and to establishing long-term monitoring sites necessary for effective remediation.

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USGS1996

Nitrate and ammonia in shallow ground water, Carson City urban area, Nevada, 1989

As part of the National Water-Quality Assessment program (NAWQA) of the U.S. Geological Survey, a network of 26 wells at 20 sites was established in 1989 to investigate the quality of shallow ground water beneath the oldest and most developed part of the Carson City urban area. Nitrate was detected in water samples from 16 of the sites. The nitrate, as nitrogen, concentration was between 0.1 and 3.0 mg/L (milligrams per liter) at four sites, greater than 3.0 mg/L but less than 10 mg/L at six sites, and 10 mg/L, the Nevada drinking-water standard, or greater, at six sites; the highest concentration measured during the study was 38 mg/L. Ammonia, as nitrogen, concentrations exceeded 0.15 mg/L at 2 of the 20 sites; the highest concentration detected during the study was 0.26 mg/L. Nitrate concentrations were positively correlated with dissolved-oxygen concentrations, and negatively correlated with ammonia, dissolved-iron, and dissolved-manganese concentrations. Ammonia concentrations were positively correlated with calcium, magnesium, potassium, bicarbonate, iron, manganese, strontium, and dissolved organic carbon concentrations, and were negatively correlated with nitrate and dissolved-oxygen concentrations. Principal components analysis identified five groups of water quality constituents that suggest that the ammonia or nitrate source might be nitrogen-based fertilizers, septic systems, or leaking municipal sewer lines, and that nitrification and denitrification, or nitrate reduction, control nitrate and ammonia concentrations as well as dissolved-oxygen, iron, and manganese concentrations in the shallow ground water beneath the Carson City urban area.

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