Back to Index:
INEEL Annual Site Environmental Report -
Appendix C - U.S. Geological Survey 2002 INEEL Publication Abstracts
Estimated Age and Source of the Young Fraction of Ground Water at the Idaho National Engineering and Environmental Laboratory (Busenburg et al. 2001)
The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, used concentrations of chlorofluorocarbons (CFCs), sulfur hexafluoride, helium (He), and tritium (3H) to determine the estimated age of the young fraction of groundwater at and near the Idaho National Engineering and Environmental Laboratory (INEEL). These environmental tracers were introduced into the Snake River Plain Aquifer by natural recharge, return flow of irrigation water, and wastewater disposal at facilities at the INEEL. The source of the water and the fraction of young water in the samples also were used to date the groundwater. The data indicate that most groundwater samples are mixtures containing young fractions of water recharged after 1950 and older regional groundwater.
Data indicate that water in samples from wells in the southeastern part of the INEEL are a binary mixture of local recharge and very old regional ground water, and samples from most of the wells are about 20 to 50 percent young water that is about 14 to 21 years old. Two main mechanisms of recharge of the young fraction of groundwater were recognized in samples from the northern part of the INEEL: (1) water recharged by rapid focused recharge through the thick unsaturated zone and (2) water recharged by slow infiltration through the thick unsaturated zone. Some of the wells in the northern part of the INEEL contained all old regional water. Three wells in the northeastern part of the INEEL contained water that was strongly affected by agricultural practices and likely was recharged in the Terreton-Mud Lake area. This water was present in Wells 4, 27, and 29 and had estimated ages or 5, 10-13, and 24-28 years, respectively.
Water samples from wells that contained a young fraction of water that recharged in the central, western, and southwestern parts of the INEEL area complex contained mixtures of regional groundwater, agricultural return flow, natural recharge, and artificial recharge from infiltration ponds and injection wells at the various facilities at the INEEL. The chemistry and age or the young fraction of the samples varied greatly and could be correlated with distance from the source of recharge, depth of the open interval below the water table, length of the interval sampled, and location of the well with respect to the different sources of recharge. Age increasedwith distance from the source of recharge and increased with depth below the water table. The young recharge water comprises a very small fraction of the total volume of water in the Snake River Plain Aquifer, and this young water was sampled because most or the wells at and near the INEEL are completed in the upper 15 m of the aquifer.
Concentrations of fluoride (F), boron (B), lithium (Li), strontium (Sr), oxygen isotope ratios (δ18O ), dissolved atmospheric gases, helium (He), and tritium (3H), were used to determine the sources of water in the Snake River Plain Aquifer at and near the INEEL. Three natural groundwater types were identified from their He, Li, and F concentrations: (1) northeastern regional water with very high He, Li, and F concentrations, (2) recharge from the southeast with moderate He and high Li and F concentrations, and (3) recharge from mountain valleys in the western part of the INEEL with low concentrations of He and Li and high concentrations of Ca, Mg, and alkalinity. The water was modified locally by mixing with agricultural runoff and wastewater from INEEL facilities. The d18O ratios were used to calculate the fraction of young water in the samples from the western part of the INEEL. Terrigenic He and 3H concentrations were used to calculate the fraction of infiltration recharge at the INEEL.
A preferential ground water flowpath that extends from the Little Lost River and Big Lost River Sinks southward through central INEEL past Big Southern Butte was identified. Flow velocities were estimated from tritium/helium ages and were about 3 m per day through the preferential flowpath. Flow velocities decreased to 1 m or less per day outside this preferential flowpath.
In areas where fractured basalts are exposed at the surface, both tritium and CFCs were present in the groundwater. The presence of these constituents indicates that focused recharge of post-1950s infiltration water occurred along preferential flowpaths through the unsaturated zone. This type of recharge was recognized in many areas at and near the INEEL.
Recharge temperatures were calculated from nitrogen and argon concentrations for many of the ground water samples and are useful indicators of the source of water in the Snake River Plain Aquifer at the INEEL. Recharge temperatures of about 6oC characterize underflow from Birch and Camas Creeks and Little Lost and Big Lost Rivers. Recharge temperatures of 9 to 13oC were calculated for the regional ground water of the Snake River Plain Aquifer at the INEEL.
Groundwater near the Radioactive Waste Management Complex, the Test Reactor Area, and the Idaho Nuclear Technology and Engineering Center contains concentrations of chlorofluorocarbans (CFCs) that are indicative of contamination. A large CFC-12 waste plume originating near the INTEC extends beyond the southern boundary of the INEEL.
Water in wells that are cased a few tens of meters below the water table contained no halocarbons, except for water in wells downgradient from injection wells. Greater-than-atmospheric concentrations of CFCs and other halocarbons were found in soil gases obtained from a depth of 1 m as far as 20 km south of the southwest corner of the INEEL. High concentrations of halocarbons also were found in unsaturated zone air blowing from the annulus of some wells in the southwestern part of the INEEL. The advective transport of CFCs and other halocarbons throughout the unsaturated zone probably occurs preferentially both vertically and horizontally along fractures associated with volcanic vent corridors. Barometric pumping appears to be the primary mechanism controlling the distribution of gases in the unsaturated zone in the southwestern part of the INEEL. Diffusion is the primary mechanism of gas transport of the northern and northeastern part of the INEEL in the areas that are covered by thick lacustrine and sedimentary playa deposits.
Introduction to the Hydrogeology of the Eastern Snake River Plain (Bartholomay et al. 2002)
This chapter gives a general overview of the hydrogeology of the eastern Snake River Plain and the INEEL and a description of the INEEL Lithologic Core Storage Library, a source of data for many of the chapters in this volume. It also summarizes definitions and lithostratigraphic terminology for the volume. This volume summarizes geoscience research on the INEEL site in the 1990s. The chapters are written by scientists from many organizations, including INEEL contractors, universities, the U.S. Geological Survey, the state of Idaho, and the Idaho Water Resources Research Institute.
This chapter presents studies of cores from drill holes. It provides detailed petrographic descriptions, paleomagnetic characterization and correlation, and conventional K-Ar and40Ar/39Ar dating, which allow examination of the process of accumulation of basaltic lava flows in a part of the eastern Snake River Plain, Idaho. Core holes at various locations in the INEEL demonstrate variable accumulation rates that can be fitted by linear regression lines with high correlation coefficients. Hiatuses of several hundred thousand years are represented in many of the core holes, but accumulation of flows resumed in most of the areas sampled by these core holes at rates nearly identical to previous rates. The studies show that an area of the eastern Snake River Plain north of its topographic axis, including the area of the INEEL, has undergone a hiatus in eruptive activity for the past ~200 thousand years. The data also allow enhanced interpretations of the volcanic hazard to the INEEL with regard to lava flow inundation, prediction of lava flow thickness, and assessment of eruption recurrence-time intervals.
The search for extraterrestrial life may be facilitated if ecosystems can be found on Earth that exist under conditions analogous to those present on other planets or moons. It has been proposed, on the basis of geochemical and thermodynamic considerations, that geologically derived hydrogen might support subsurface microbial communities on Mars and Europa in which methanogens form the base of the ecosystem. This article describes a unique subsurface microbial community in which hydrogen-consuming, methane-producing archaea far out number the bacteria. More than 90 percent of the 165 ribosomal DNA sequences recovered from hydrothermal waters circulating through deeply buried igneous rocks in Idaho are related to hydrogen-using methanogenic microorganisms. Geochemical characterization indicates that geothermal hydrogen, not organic carbon, is the primary energy source for this methanogendominated microbial community. These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets.
Tension Cracks, Eruptive Fissures, Dikes, and Faults Related to Late Pleistocene-Holocene Basaltic Volcanism and Implications for the Distribution of Hydraulic Conductivity in the Eastern Snake River Plain, Idaho (Kuntz et al. 2002)
Tension crack-eruptive fissure systems are a key characteristic of most late Pleistocene-Holocene basaltic lava fields in the eastern Snake River Plain, Idaho. Models based on elastic displacements that accompany dike intrusion and the dimensions of tension cracks and eruptive fissures give new perspectives on the size and shapes of dike systems in the eastern Snake River Plain. Elastic-displacement models predict faults related to dike intrusion, but these are absent at the late Pleistocenecene-Holocene lava fields. Numerous faults in the Box Canyon area of the Arco-Big Southern Butte volcanic rift zone can be misinterpreted as being related to dike-emplacement processes. Our data strongly suggest that these faults are tectonic in origin and related to the Lost River range-front fault.
Data about size and shapes of dike systems, in conjunction with detailed mapping and regional paleomagnetic studies, are used to interpret the style of volcanism in a part of the Idaho National Engineering and Environmental Laboratory and for the entire eastern Snake River Plain. The mapping-paleomagnetic studies suggest that sections of dike systems as long as ~40 km can be active simultaneously or within periods of time as short as a few hundred years.
The characteristics and locations of dikes, eruptive fissure systems, and tension cracks have implications for the movement of groundwater and migration of radioactive and chemical wastes in the Snake River Plain Aquifer at the INEEL. Buried zones of northwest-trending dikes, eruptive fissures, and tension cracks, referred to as vent corridors, are perpendicular to the regional direction of groundwater flow and probably control some of the lowest and highest estimates of hydraulic conductivity in the aquifer.
Kilometer-Scale Rapid Transport of Naphthalene Sulfonate Tracer in the Unsaturated Zone at the Idaho National Engineering and Environmental Laboratory (Nimmo et al. 2002)
To investigate possible long-range flow paths through the interbedded basalts and sediments of a 200-m-thick unsaturated zone, we applied a chemica1 tracer to seasonally filled infiltration ponds on the Snake River Plain in Idaho. This site is near the Subsurface Disposal Area for radioactive and other hazardous waste at the INEEL. Within 4 months we detected tracer in 1 of 13 sampled aquifer wells, and in 8 of 11 sampled perched-water wells as far as 1.3 km away. These detections show that (1) low-permeability layers in the unsaturated zone divert some flow horizontally, but do not prevent rapid transport to the aquifer, (2) horizontal convective transport rates within the unsaturated zone may exceed l4 m/d, perhaps through essentially saturated basalt fractures, tension cracks, lava tubes, or rubble zones; and (3) some perched water beneath the Subsurface Disposal Area derives from episodic surface water more than 1 km away. Such rapid and far-reaching flow may be common throughout the Snake River Plain and possibly occurs in other locations that have a geologically complex unsaturated zone and comparable sources of infiltrating water.
Geochemistry of the Little Lost River Drainage Basin, Idaho (Swanson et al. 2002)
The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, are conducting studies to describe the chemical character or groundwater that moves as underflow from drainage basins into the Snake River Plain Aquifer (SRPA) system at and near the INEEL and the effects or these recharge waters on the geochemistry of the SRPA system. Each of these recharge waters has a hydrochemical character related to geochemical processes, especially water-rock interactions, that occur during migration to the SRPA. Results of these studies will benefit ongoing and planned geochemical modeling of the SRPA at the INEEL by providing model input on the hydrochemical character of water from each drainage basin.
For this study, water samples were collected from six wells and two surface-water sites from the Little Lost River drainage basin during 2000 and analyzed for selected inorganic constituents, dissolved organic carbon, stable isotopes, tritium, and selected gross measurements of radioactivity. Four duplicate samples were collected for quality assurance. Results showed that most water from the Little Lost River drainage basin has a calcium-magnesium bicarbonate character. Water in two wells contained elevated chloride concentrations relative to water from the other sites. The computer code NETPATH was used to evaluate geochemical mass-balance reactions in the Little Lost River basin. Attempts to model water from the Little Lost River valley sites to that in the most downgradient wells, Mays and Ruby Farms, were unsuccessful. On closer inspection of these two wells, it was determined that they are much deeper than the other sample locations and the water could reflect the chemistry of the SRPA. Apparently another of the sample locations was contaminated as a result of local agricultural practices. Water in one well contained concentrations that mirrored Little Lost River water. Of all the sites sampled, only two upgradient wells contained water representative of the system. Mass-balance modeling of the system indicated that dissolution of dolomite is the major reaction taking place in the system. Nitrification of ammonium ion to nitrate and dissolution of inorganic fertilizers are chemical processes that also occur in the system. To better understand the geochemistry or the Little Lost River drainage basin, more samples that better represent the natural geochemistry or the basin need to be collected and evaluated.
During 1994-1999, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collected samples for tritium analyses from 19 springs along the north side of the Snake River near Twin Falls and Hagerman, Idaho, to address public concern over migration of approximately 31,000 Ci of tritium discharged in wastewater at the INEEL. Evaluating tritium for the Twin Falls-Hagerman area is part of a long-term project to monitor water quality of springs discharging from the Snake River Plain Aquifer downgradient from the INEEL. Routine and two quality assurance replicate samples have been collected annually since 1990 as part of the U.S. Geological Survey's quality assurance program.
The springs were characterized on the basis of their locations and tritium concentrations: Category I, II, and III. The differences in tritium concentrations in Category I, II, and III springs are a function of the groundwater flow regimes, land uses, and irrigation practices in and hydraulically upgradient from each category of springs. Tritium concentrations during the 1994-1999 water years ranged from a low 6.5 ± 0.6 pCi/L to a high of 65.0 ± 4.5 pCi/L. During 1999, tritium concentrations in the 19 springs ranged from 6.5 ± 0.6 to 46.1 ± 3.2 pCi/L. Mean annual tritium concentrations measured from 1990 to 1999 in selected spring's from each category show decreasing trends in tritium values, likely the result of natural isotope decay.
Bartholomay, R.C., Davis, L.C., and Link, P.K., 2002, "Introduction to the Hydrogeology of the Eastern Snake River Plain," in Geology, Hydrogeology, and Environmental Remediation: Idaho National Engineering and Environmental Laboratory; Snake River Plain, Idaho, edited by P.K. Link and L.L. Mink, Geological Society of America Special Paper 353, Boulder, Colorado, p. 3-9.
Champion, D.E., Lanphere, M.A., Anderson, S.R., and Kuntz, M.A., 2002, "Accumulation and Subsidence of Late Pleistocene Basaltic Lava Flows of the Eastern Snake River Plain, Idaho," in Geology, Hydrogeology, and Environmental Remediation: Idaho National Engineering and Environmental Laboratory; Snake River Plain, Idaho, edited by P.K. Link and L.L. Mink, Geological Society of America Special Paper 353, Boulder, Colorado, p. l75-192.
Chapelle, F.C., O'Neill, K., Bradley, P.M., Methe', B.A., Clufo, S.A., Knobel, L.L., and Lovely, D.R., 2002, "A Hydrogen-based Subsurface Microbial Community Dominated by Methanogens," NATURE, 415:3l2-315.
Kuntz, M.A., Anderson, S.R., Champion, D.E., Lanphere, M.A., and Grunwald, D.J., 2002, "Tension Cracks, Eruptive Fissures, Dikes, and Faults Related to Late Pleistocene-Holocene Basaltic Volcanism and Implications for the Distribution of Hydraulic Conductivity in the Eastern Snake River Plain," in Geology, Hydrogeology, and Environmental Remediation: Idaho National Engineering and Environmental Laboratory; Snake River Plain, Idaho, edited by P.K. Link and L.L. Mink, Geological Society of America Special Paper 353, Boulder, Colorado, p, 111-133,
Nimmo, J.R., Perkins, K.S., Rose, P.E., Rousseau, J.P., Orr, B.R., Twining, B.V., and Anderson, S.R., 2002, "Kilometer-scale Rapid Transport of Naphthalene Sulfonate Tracer in the Unsaturated Zone at the Idaho National Engineering and Environmental Laboratory," Vadose Zone Journal, 1(1): 89-101.
Swanson, S.A., Rosentreter, J.J., Bartholomay, R.C., and Knobel, L.L., 2002, Geochemistry of the Little Lost River Drainage Basin, Idaho, U.S. Geological Survey Water-Resources Investigations Report 02-4120, DOE/ID-22l79.
Twining, B.V., 2002, Tritium in Flow from Selected Spring's That Discharge to the Snake River, Twin Falls-Hagerman Area, Idaho, 1994-99, U.S. Geological Survey Open-File Report 02l85, DOE/ID-22180.