Published online 16 August 2005
Published in Vadose Zone J 4:614-619 (2005)
DOI: 10.2136/vzj2005.0072
© 2005 Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
SPECIAL SECTION: LOS ALAMOS NATIONAL LABORATORY
The Hydrogeology of Los Alamos National Laboratory
Site History and Overview of Vadose Zone and Groundwater Issues
Brent D. Newman* and
Bruce A. Robinson
Earth and Environmental Sciences Division, Los Alamos National Laboratory, P.O. Box 1663, MS J495, Los Alamos, NM 87545
* Corresponding author (bnewman{at}lanl.gov)
Received 6 June 2005.
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ABSTRACT
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This summary paper describes the hydrogeologic setting and site history for the Los Alamos National Laboratory (LANL), and as such, serves as an introduction to this special section in Vadose Zone Journal on the LANL site. Since 1943, LANL has operated on the Pajarito Plateau of north-central New Mexico, performing national security research and development, particularly involving nuclear weapons design and engineering. There is an ongoing environmental characterization and remediation program as a result of the legacy of these operations. The flow and transport processes in the thick vadose zone in this semiarid region have been examined extensively at this site, and significant scientific findings have advanced our understanding and predictive abilities. This special section highlights the noteworthy field and modeling investigations conducted at LANL. The authors believe that these articles will be of benefit to the community of hydrologists working on vadose zone flow and transport by providing complex observational data sets and accompanying modeling studies to interpret the field data.
Abbreviations: AEC, Atomic Energy Commission • ET, evapotranspiration • LANL, Los Alamos National Laboratory
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INTRODUCTION
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LOS ALAMOS NATIONAL LABORATORY and the town of Los Alamos, NM are considered the birthplace of the atomic age. The laboratory and town were built in 1943 in north-central New Mexico (Fig. 1) as part of the Manhattan Project to develop the world's first nuclear weapons. The 1945 testing at the Trinity site in New Mexico, and bombing of Hiroshima three weeks later and Nagasaki three days after that, are considered (at least symbolically) to mark the beginning of the nuclear era. Subsequently, Los Alamos was at the forefront of Cold War weapons development, and continues to this day as one of the U.S. Department of Energy, National Nuclear Safety Administration's largest weapons laboratories. Two legacies of the more than 50 yr of weapons and other research at the laboratory are a multitude of environmental contamination problems across the Pajarito Plateau and surrounding areas and concerns about the long-term performance and safety of active and 1940s through 1970s era waste disposal areas, which contain a wide range of inventories and a large variety of waste types, including radionuclides, organics, and metals. This special section of Vadose Zone Journal focuses on some of the key issues related to contaminants and waste disposal at Los Alamos. However, our goal for the special section is not just to highlight specific environmental examples at Los Alamos, but to also discuss broader scientific issues and findings relevant to current research in vadose zone hydrology, hydrogeology, and contaminant hydrology.
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BRIEF HISTORY AND MISSION OF LOS ALAMOS NATIONAL LABORATORY
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In 1942, the U.S. Army Manhattan Engineering District was established to develop the atomic bomb. As part of this effort, a remote site was needed for experimental work, and Dr. J. Robert Oppenheimer and General Leslie Groves of the U.S. Army selected the Los Alamos Ranch School for Boys in northern New Mexico as an appropriate location. The Undersecretary of War directed acquisition of the 390-ha school site, northwest of Santa Fe. The project ultimately acquired an additional 3111 ha of combined private and U.S. Forest Service land. In 1943, this land became known as Site Y, or the Los Alamos Site, and later as the Los Alamos Scientific Laboratory. It is now known as Los Alamos National Laboratory (Fig. 1). Because of the affiliation between Robert Oppenheimer and the University of California-Berkeley, the Laboratory has been operated by the University of California for the federal government since its inception. With the end of World War II and the development of the Cold War, a national policy of maintaining superiority in the field of atomic energy was established. Congress chose to continue work at Los Alamos, and the Atomic Energy Commission (AEC) received control of the Laboratory from the U.S. Army. Thereafter, the Laboratory continued to expand, first under the AEC and later under the Energy Research and Development Administration. In 1978, the Laboratory control was transferred to the U.S. Department of Energy (Hunner, 2004; Los Alamos National Laboratory, 2000; Rhodes, 1986).
Los Alamos National Laboratory and the neighboring communities of Los Alamos and White Rock are located in Los Alamos County, north-central New Mexico (Fig. 1). Los Alamos National Laboratory now occupies 11137 ha on the Pajarito Plateau (Fig. 2)
. Since its inception in 1943, the major focus of the Laboratory has been nuclear weapons research and development. The current mission involves development and application of science and technology related to national security. Specifically, the Laboratory mission is to (i) ensure the safety and reliability of U.S. nuclear deterrent; (ii) reduce the threat of weapons of mass destruction, proliferation, and terrorism; and (iii) solve national problems in defense, energy, environment, and infrastructure.
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Fig. 2. Aerial photograph of Los Alamos and the Pajarito Plateau looking east to west. The Rio Grande is in the foreground (off the photo) and the Jemez Mountains and Valles Caldera are in the background. The highly dissected mesa–canyon system of the plateau is clearly shown.
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Los Alamos Environmental Characterization and Restoration
As part of its research and development history, hazardous and radioactive materials were used extensively at Los Alamos. Some of these materials were disposed on the Laboratory site or were otherwise released into the environment. Beginning in the 1960s, Congress enacted basic legislation to protect the environment. As a result, the U.S. Department of Energy began to clean up areas of the Laboratory where releases, spills, and disposal had occurred. Hydrologic monitoring for contaminants began at Los Alamos in the early 1960s. Currently, the Laboratory regularly samples 74 surface monitoring stations and 137 groundwater-monitoring locations. This network evolves as cleanups proceed and new characterization data become available, and is currently being expanded based on agreements with the New Mexico Environmental Department and the U.S. Environmental Protection Agency.
There are a number of statutory and regulatory requirements that drive the environmental monitoring, characterization, and remediation at Los Alamos. Nearly all of the research presented in this special section was motivated by regulations affecting operations at the Laboratory. The U.S. Environmental Protection Agency has ranked facilities throughout the nation according to the potential hazard to human health and safety. Los Alamos was not ranked as a high-priority facility, and, therefore, does not fall under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), otherwise known as Superfund. Instead, Los Alamos falls under the U.S. Federal Resource Conservation and Recovery Act (RCRA), which is a major driver for environmental investigations and remediation at the laboratory.
Other significant regulatory drivers include the Los Alamos Hazardous Waste Facility Permit, issued by the New Mexico Environmental Department; the National Environmental Policy Act; U.S. Dep. of Energy Order 5820.2A (Radioactive Waste Management); and the Los Alamos Hydrogeologic Workplan. The latter is an 8-yr site characterization effort involving the drilling of numerous boreholes to the regional aquifer beneath the site. These boreholes and the accompanying modeling and interpretation were critical to our understanding of the vadose zone as conveyed in the articles in this special section. Additional applicable regulations and requirements are discussed in Los Alamos National Laboratory (2000). Currently environmental characterization is conducted primarily through the Los Alamos Environmental Restoration Project (http://erproject.lanl.gov/), and the Los Alamos Environmental Protection Program (http://em.lanl.gov/GPInfo.htm and http://em.lanl.gov/EPInfo.htm). Remediation activities are conducted through the Los Alamos Environmental Restoration Project. To illustrate the magnitude of environmental issues relative to the RCRA process at Los Alamos, more than 2000 Potential Release Sites (a "PRS" is a location where there was a known or potential contaminant release) were originally identified on the Pajarito Plateau. Since that time, several hundred of these sites have been removed from the active PRS list either through site investigations showing no further action is needed, cleanups, or consolidation with nearby sites. There are still several hundred sites that are currently undergoing site characterization or remediation by the Los Alamos Environmental Restoration Project.
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LOS ALAMOS AREA PHYSIOGRAPHY AND ECOLOGY
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The Laboratory site and the communities adjacent to it are situated on the Pajarito Plateau (Fig. 2). The plateau occupies the western part of the Española basin (Fig. 3)
, which is part of the Rio Grande Rift system. The plateau consists of a series of east-sloping finger-like mesas separated by deep canyons containing ephemeral and intermittent streams that run from west to east (Fig. 2). The plateau is bounded on the west by the eastern Jemez Mountains (Sierra de los Valles) and on the east by White Rock Canyon of the Rio Grande. Mesa tops range in elevation from approximately 2377 m on the flank of the Jemez Mountains to about 1890 m at their eastern termination above the Rio Grande valley. The eastern margin of the plateau stands 91 to 274 m above the Rio Grande. The Rio Grande is the primary river in north-central New Mexico. All surface water drainage and groundwater discharge from the plateau ultimately arrives at the Rio Grande (USDOE, 1979).
Because of the dramatic 1524-m elevation gradient, from the Rio Grande on the east to the Jemez Mountains 19 km to the west, there are significant precipitation and vegetation gradients on the plateau. Los Alamos has a semiarid, temperate climate. The area receives 33 to 50 cm of precipitation annually depending on elevation, with higher precipitation rates on the western side of the plateau. Approximately 35 to 40% of the annual precipitation normally occurs from thundershowers during July and August. Winter precipitation falls primarily as snow, with accumulations of 130 cm annually. Summers are generally sunny, with moderate, warm days and cool nights. Maximum daily temperatures in summer are usually below 32°C. Brief "monsoonal" afternoon and evening thundershowers are common, especially in July and August (Bowen, 1990).
The elevation and precipitation gradients coupled with the mesa canyon topography make the Pajarito Plateau a biologically diverse area. There are five major vegetation zones on the plateau (Los Alamos National Laboratory, 2000). From east to west (lowest to highest elevation/precipitation), these include juniper [Juniperus monosperma (Englem.) Sarg.]–savannah, piñon (Pinus edulis Englem.)–juniper, ponderosa pine (Pinus ponderosa C. Lawson), mixed conifer, and spruce (Picea pungens Engelm)–fir. The juniper–savannah community is found along the Rio Grande on the eastern border of the plateau and extends upward on the south-facing sides of canyons, at elevations between 1706 and 1890 m. The piñon–juniper community, generally in the 1890- to 2103-m elevation range, covers large portions of the mesa tops and north-facing slopes at the lower elevations. Ponderosa pines are found in the western portion of the plateau in the 2103- to 2286-m elevation range. The piñon–juniper and ponderosa pine cover types are present over most of the Laboratory. The mixed conifer cover type, at an elevation of 2286 to 2896 m, overlaps the ponderosa pine community in the deeper canyons and on north slopes and extends from the higher mesas onto the slopes of the Jemez Mountains. Based on ongoing surveys, at least four federally protected animal species, the American peregrine falcon (endangered), the bald eagle (endangered), the Mexican spotted owl (threatened), and the southwestern willow flycatcher (endangered) have been recorded on Laboratory and Los Alamos County lands (Los Alamos National Laboratory, 2000).
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OVERVIEW OF THE LOS ALAMOS SPECIAL SECTION
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This special section includes a variety of scientific studies performed at Los Alamos National Laboratory and covers various aspects of vadose zone and groundwater flow and transport at the site. We believe that the breadth of observations and scientific studies conducted at the site will make the articles of broad interest to the hydrologic community. The following is a brief synopsis of some of the important vadose zone and hydrogeologic issues that are addressed in this series of articles.
For sites such as Los Alamos, which cover large areas and have multiple contaminant sources, it is critical to have a good conceptual understanding of vadose zone processes to efficiently characterize and remediate sites, and to design adequate monitoring strategies. Birdsell et al. (2005) review the vadose zone conceptual models for Los Alamos and highlight the importance of semiarid, mesa–canyon topographic controls on hydrologic processes. They discuss the field observations, data, and numerical models that were used to develop and test these conceptual models. Many of the concepts are integral to the various vadose zone studies presented in the other articles of this special section. An important aspect of vadose zone and groundwater conceptual models (and numerical models of flow and transport) is a sound geologic framework. Broxton and Vaniman (2005) present a comprehensive discussion of the hydrogeology of the Pajarito Plateau and how it fits within the larger geologic structures of the Española Basin and the Rio Grande Rift. Besides providing a great deal of information on the geology of the Los Alamos area, the authors provide a good example of the complex geologic controls of vadose and groundwater systems along the margins of rift basins. Vaniman et al. (2005) explore the role of clay in water content beneath wet and dry canyons of the Pajarito Plateau.
Deep perched groundwater aquifers are relatively common within the thick vadose zones of semiarid landscapes, yet relatively little is known about the causes and characteristics of perched water. Deep perched zones occur in various locations beneath the Pajarito Plateau at depths below alluvium, often >100 m below ground surface. Robinson et al. (2005a) summarize an extensive observational data set of deep perched water on from the plateau, and discuss controls on the distribution of deep perched water and how perched zones may develop. The wide variety of hydrologic settings in which perched water was observed underscores the complexity of this important characteristic of vadose zone systems. They also present a new numerical formulation that allows perched water to be simulated efficiently in vadose zone numerical models.
Protection of drinking water supplies is one of the main motivations for vadose zone research, especially at Los Alamos. Therefore, we have included an article by Keating et al. (2005) that describes the regional aquifer beneath the Pajarito Plateau, which is currently the sole drinking water supply for Los Alamos County and the Laboratory. The authors present a numerical modeling approach that is useful for understanding hydrologic mechanisms, assessing the magnitudes of different terms in the overall water budget, and for interpreting contaminant migration velocities in the overlying vadose zone.
Addressing natural variability and heterogeneity in the vadose zone is often recognized as a major challenge in applied and basic hydrological research. For example, in areas with complex terrain and geology, such as at Los Alamos, how net infiltration varies spatially across the landscape, and how hydraulic properties vary within and between geologic units are difficult, but important problems to address. Kwicklis et al. (2005) discuss how a large-scale, conceptual and numerical model of net infiltration can be developed based on estimates of point infiltration and streamflow measurements. The approach uses maps of relevant environmental variables (e.g., soil and rock type, vegetation) and spatial algorithms implemented with GIS software to estimate net infiltration and how it varies across the large topographic gradients on the plateau. Focusing on the hydrogeological unit scale, Springer (2005) presents a comprehensive statistical analysis of the hydrologic properties of the Bandelier Tuff (which makes up much of the Los Alamos vadose zone). The study concludes that significant variability in the properties exists within units and across the site, and that site specific variability in hydraulic properties is an important consideration for vadose zone flow modeling.
Another open issue in vadose zone hydrology is the relative importance of fracture versus matrix flow, which can be a major contributor to conceptual and numerical modeling uncertainty. The velocities of contaminant transport to the regional aquifer and subsequent risk of contamination of municipal water supply wells depend critically on this issue. Three articles discuss field experiments and modeling results that examine the roles of matrix and fracture flow within the Los Alamos tuffs (Robinson et al., 2005b) and basalts (Levitt et al., 2005a; Stauffer and Stone, 2005). In the eastern part of the plateau, matrix flow appears to be dominant within the Bandelier Tuff, even in fractured tuff units. However, fracture flow is clearly significant within the Cerros del Rio Basalt. In their article, Robinson et al. (2005b) suggest that the hydrologic properties of the fractures and matrix control the extent of fracture flow and show how this knowledge can be translated into appropriate numerical formulations for flow in unsaturated, fractured media. In another article that used the numerical formulations confirmed in this first study, Robinson et al. (2005c) examine flow and transport beneath an important canyon on the LANL site using a three-dimensional numerical modeling approach. They demonstrate that a comprehensive understanding of vadose zone hydrologic and tritium transport processes can be obtained by integrating data from multiple characterization sources.
A common characteristic of semiarid landscapes is the presence of perennial or ephemeral streamflow that recharges alluvial aquifer systems in canyons and arroyos. In these systems there is a dynamic set of interactions that occur between the stream, alluvial aquifer, and the rest of the vadose zone. These interactions not only control fluxes and flow directions, but also have a major impact on contaminant transport. Reid et al. (2005) discuss these interactions in the context of high explosives and barium contamination; they utilize a combined hydrogeochemical and geomorphic characterization approach. The article highlights the complex interactions between surface water, alluvial groundwater, and the unsaturated zone, and how contrasting geochemical characteristics and transport mechanisms drive markedly different behaviors between the high explosives and barium.
In contrast to flow and transport in and beneath canyons, the mesas of the plateau are examples of a different set of hydrologic conditions and contaminant transport behaviors, including both liquid-phase and vapor-phase transport. Vapor phase transport in the mesa environment is especially important for volatile contaminants. Stauffer et al. (2005) examine the transport of trichloroethane in a mesa system using monitoring data and numerical modeling. The results show that vapor-phase diffusion can largely account for the observed contaminant distributions despite the likely presence of barometric and other advective driving forces for gas movement. McLin et al. (2005) discuss hydrologic and contaminant characterization associated with radioactive waste disposal pits in a mesa setting, including the importance of vapor phase transport of tritium. They also examine the utility of horizontal boreholes for environmental characterization and monitoring. They suggest that horizontal boreholes are underutilized as characterization tools, and that they can also be used as part of an effective vadose zone monitoring strategy.
Another area that has received attention by the vadose zone research community is the performance of landfill covers for buried waste. Evapotranspiration (ET) and capillary barrier type covers in particular are of current interest in dry regions. Field-based research at the LANL site has resulted in important long-term data and observations relevant to cover design. Nyhan (2005) discusses results from a 7-yr monitoring study of ET cover performance at four different slopes. These results can be used to help assess the appropriateness of ET covers for other sites and for optimizing cover design. Levitt et al. (2005b) compare water content monitoring results from a simple asphalt surface cover and an ET cover at the same site. Their results show that simply paving over a site with asphalt can create an adverse condition in terms of maintaining low water contents below the cover. Because covers are supposed to remain effective for multiple decades or longer, it is important to understand uncertainties related to the evolution of covers in the long term. However, there has been relatively little research on actual cover systems to examine this problem. Breshears et al. (2005) examine the evolution of ET and capillary barrier cover designs 10 yr after installation, and discuss the implications of their results for long-term cover performance.
Whether a cover is present or not, surface pathways can often be the biggest risk drivers in terms of human and ecological health effects in semiarid environments. Runoff and erosion can potentially expose waste and contaminants and transport them, increasing risk. Martens and Breshears (2005) show how a distributed hydrologic model can be used to provide an initial assessment and ranking of multiple waste sites in terms of their vulnerabilities from runoff processes. Finally, Hastings et al. (2005) describe the importance of spatial variability in rainfall erosivity and how this can have important consequences for understanding sediment transport in semiarid landscapes.
In addition to the contributions that these studies make to the understanding of vadose zone and other hydrologic processes, we believe strongly that they also demonstrate the importance of scientific studies to assist in the environmental decision making process. The general and site-specific knowledge gained at the LANL site has been instrumental for achieving the overarching goal of research conducted at the site, which is to ensure that environmental decisions are informed by science. In a hydrogeologic system as complex as the LANL site, a program of scientific studies that reflects the diversity of the situations requiring understanding and data is the best way to achieve this goal.
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ACKNOWLEDGMENTS
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This paper was written under the auspices of the Los Alamos National Laboratory Groundwater Protection Program and the LANL Environmental Remediation Program. The authors thank Charlie Nylander of the Groundwater Protection Program for his support in developing this special section of Vadose Zone Journal, and all of the authors and reviewers whose hard work made this special section possible. Some of the studies presented here were funded fully or partially through the Material Disposal Area G, Low Level Waste Site Performance Assessment Project, and we would like to thank Diana Hollis and Dennis Newell for their support.
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REFERENCES
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- Birdsell, K.H., B.D. Newman, D.E. Broxton, and B.A. Robinson. 2005. Conceptual models of vadose zone flow and transport beneath the Pajarito Plateau, Los Alamos, New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:620–636 (this issue).[Abstract/Free Full Text]
- Bowen, B.M. 1990. Los Alamos climatology. Rep. LA-11735-MS. Los Alamos Natl. Lab., Los Alamos, NM.
- Breshears, D.D., J.W. Nyhan, and D.W. Davenport. 2005. Ecohydrology monitoring and excavation of semiarid landfill covers a decade after installation. Available at www.vadosezonejournal.org. Vadose Zone J. 4:798–810 (this issue).[Abstract/Free Full Text]
- Broxton, D.E., and D.T. Vaniman. 2005. Geologic framework of a groundwater system on the margin of a rift basin, Pajarito Plateau, North-Central New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:522–550 (this issue).[Abstract/Free Full Text]
- Hastings, B.K., D.D. Breshears, and F.M. Smith. 2005. Spatial variability in rainfall erosivity versus rainfall depth: Implications for sediment yield. Available at www.vadosezonejournal.org. Vadose Zone J. 4:500–504 (this issue).[Abstract/Free Full Text]
- Hunner, J. 2004. Inventing Los Alamos: The growth of an atomic community University of Oklahoma Press, Norman, OK.
- Keating, E., B.A. Robinson, and V. Vesselinov. 2005. Development and application of numerical models to estimate fluxes through the regional aquifer beneath the Pajarito Plateau. Available at www.vadosezonejournal.org. Vadose Zone J. 4:653–671 (this issue).[Abstract/Free Full Text]
- Kwicklis, E.M., M. Witkowski, K. Birdsell, B. Newman, and D. Walther. 2005. Development of an infiltration map for the Los Alamos area, New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:672–693 (this issue).[Abstract/Free Full Text]
- Levitt, D.G., D.L. Newell, W.J. Stone, and D.S. Wykoff. 2005a. Surface water–groundwater connection at the Los Alamos Canyon weir site: Part 1. Monitoring site installation and tracer tests. Available at www.vadosezonejournal.org. Vadose Zone J. 4:708–717 (this issue).[Abstract/Free Full Text]
- Levitt, D.G., M.J. Hartmann, K.C. Kisiel, C.W. Criswell, P.D. Farley, and C. Christensen. 2005b. Comparison of the water balance of an asphalt cover and an evapotranspiration cover at Technical Area 49 at the Los Alamos National Laboratory. Available at www.vadosezonejournal.org. Vadose Zone J. 4:789–797 (this issue).[Abstract/Free Full Text]
- Los Alamos National Laboratory. 2000. Installation Workplan for the Environmental Restoration Project. Revision 8. Draft LA-UR-00–1336. Los Alamos Natl. Lab., Los Alamos, NM.
- Martens, S.N., and D.D. Breshears. 2005. Assessing contaminant transport vulnerability in complex topography using a distributed hydrologic model. Available at www.vadosezonejournal.org. Vadose Zone J. 4:811–818 (this issue).[Abstract/Free Full Text]
- McLin, S.G., B.D. Newman, and D.E. Broxton. 2005. Vadose zone characterization and monitoring beneath waste disposal pits using horizontal boreholes. Available at www.vadosezonejournal.org. Vadose Zone J. 4:774–788 (this issue).[Abstract/Free Full Text]
- Nyhan, J.W. 2005. A seven-year water balance study of an evapotranspiration landfill cover varying in slope for semiarid regions. Available at www.vadosezonejournal.org. Vadose Zone J. 4:466–480 (this issue).[Abstract/Free Full Text]
- Reid, K.D., S.L. Reneau, B.D. Newman, and D.D. Hickmott. 2005. Barium and high explosives in a semiarid alluvial system, Cañon de Valle, New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:744–759 (this issue).[Abstract/Free Full Text]
- Rhodes, R. 1986. The making of the atomic bomb. Simon and Schuster, New York.
- Robinson, B.A., D.E. Broxton, and D.T. Vaniman. 2005a. Observations and modeling of deep perched water beneath the Pajarito Plateau. Available at www.vadosezonejournal.org. Vadose Zone J. 4:637–652 (this issue).[Abstract/Free Full Text]
- Robinson, B.A., S.G. McLin, and H.S. Viswanathan. 2005b. Hydrologic behavior of unsaturated, fractured tuff: Interpretation and modeling of a wellbore injection test. Available at www.vadosezonejournal.org. Vadose Zone J. 4:694–707 (this issue).[Abstract/Free Full Text]
- Robinson, B.A., G. Cole, J.W. Carey, M. Witkowski, C.W. Gable, Z. Lu, and R. Gray. 2005c. A vadose zone flow and transport model for Los Alamos Canyon, Los Alamos, New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:729–743 (this issue).[Abstract/Free Full Text]
- Springer, E.P. 2005. Statistical exploration of matrix hydrologic properties for the Bandelier Tuff, Los Alamos, New Mexico. Available at www.vadosezonejournal.org. Vadose Zone J. 4:505–521 (this issue).[Abstract/Free Full Text]
- Stauffer, P.H., K.H. Birdsell, M.S. Witkowski, and J.K. Hopkins. 2005. Vadose zone transport of 1,1,1-Trichloroethane: Conceptual model validation through numerical simulation. Available at www.vadosezonejournal.org. Vadose Zone J. 4:760–773 (this issue).[Abstract/Free Full Text]
- Stauffer, P.H., and W.J. Stone. 2005. Surface water–groundwater connection at the Los Alamos Canyon weir site: Part 2. Modeling tracer test results. Available at www.vadosezonejournal.org. Vadose Zone J. 4:718–728 (this issue).[Abstract/Free Full Text]
- USDOE. 1979. Final environmental impact statement: Los Alamos Scientific Laboratory Site, New Mexico. DOE/EIS-0018. USDOE, Washington, DC.
- Vaniman, D., D. Broxton, and S. Chipera. 2005. Vadose zone clays and water content beneath wet and dry canyons of the Pajarito Plateau. Available at www.vadosezonejournal.org. Vadose Zone J. 4:453–465 (this issue).[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
