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At least 325 records · Page 18Linked to original sources

USGS1976

Effects of drain wells on the ground-water quality of the western Snake Plain Aquifer, Idaho

Approximately 3,100 drain wells injects irrigation waste water, urban runoff, septic-tank effluent, and industrial waste water into the Snake Plain aquifer in Minidoka, Gooding, Jerome, and Lincoln Counties, Idaho. About 29,000 acre-feet of irrigation waste water, 100 acre-feet of urban runoff, 400 acre-feet of septic-tank effluent, and 1,000 acre-feet of industrial waste water are injected annually. The quality of irrigation waste water is highly variable, depending upon its source, method and rate of application, amount of fertilizer added, and other factors. The quality of urban runoff water is generally much better than irrigation waste water. Septic-tank effluent is relatively high in nutrient concentrations. Chloride concentrations also are high, and bacterial concentrations are exceedingly high. The only industrial waste water sampled during this study had been used for cooling. No chemical changes were noted, but temperature was significantly increased. The data indicate that drain-well inflow does move appreciable distances through the aquifer and can be detected in downgradient wells. (Woodard-USGS)

Open-File Report↗

USGS1978

Geology of the Arco-Big Southern Butte area, eastern Snake River Plain, and potential volcanic hazards to the radioactive waste management complex, and other waste storage and reactor facilities at the Idaho National Engineering Laboratory, Idaho

The Arco-Big Southern Butte area of the eastern Snake River Plain, Idaho, includes a volcanic rift zone and more than 70 Holocene and late Quaternary basalt volcanoes. The Arco volcanic rift zone extends southeast for 50 km from Arco to about 10 km southeast of Big Southern Butte. The rift zone is the locus of extensional faults, graben, fissure basaltic volcanic vents, several rhyolite domes at Big Southern Butte, and a ferrolatite volcano at Cedar Butte. Limited radiometric age data and geological field criteria suggest that all volcanism in the area is younger than 700,000 years; at least 67 separate basaltic eruptions are estimated to have occurred within the last 200,000 years. The average volcanic recurrence interval for the Arco-Big Southern Butte area is approximately one eruption per 3,000 years. Radioactive waste storage and reactor facilities at the Idaho National Engineering Laboratory may be subject to potential volcanic hazards. The geologic history and inferred past volcanic events in the Arco-Big Southern Butte area provide a basis for assessing the volcanic hazard. It is recommended that a radiometric age-dating study be performed on rocks in cored drill holes to provide a more precise estimate of the eruption recurrence interval for the region surrounding and including the Radioactive Waste Management Complex. It is also recommended that several geophysical monitoring systems (dry tilt and seismic) be installed to provide adequate warning of future volcanic eruptions.

Idaho↗

USGS1980

Sediment transport in the Snake and Clearwater rivers in the vicinity of Lewiston, Idaho

During the period 1972-79, the bedload in the Clearwater River ranged from about 50,000 tons (45,000 metric tons) per year in 1972 and 1974 to about 1,000 tons (910 metric tons) per year in the drought years of 1973 and 1977. Suspended-sediment load at the same location ranged from about 1,000,000 tons (910,000 metric tons) per year to about 50,000 tons (45,000 metric tons) per year for the same respective years. In the Snake River, bedload ranged from about 200,000 tons (180,000 metric tons) per year for 1972 and 1974 to about 10,000 tons (9,100 metric tons) per year in 1973; bedload was too low for determination in 1977. Suspended-sediment load ranged from about 5,000,000 tons (4,500,000 metric tons) per year in 1974 to about 50,000 tons (45,000 metric tons) per year in 1977. Bedload thus ranged from about 2 to 10 percent of suspended load and average about 5 percent. For either river, bedload particle size was bimodal. Modes were in the medium- to coarse-sand range and in the very coarse-gravel range. Suspended-sediment particle size was generally finer than sand.

Idaho↗

USGS1980

Chemical analyses of coal and coal-associated shale samples from the lower part of the Fort Union Formation, Little Snake River coal field, Sweetwater and Carbon counties, Wyoming

As part of a continuing program by the U.S. Geological Survey to collect and analyze representative samples of U.S. coals, 26 coal and 5 coal-associated shale samples were collected from 13 core and rotary-drill holes in the lower part of the Paleocene Fort Union Formation in the Little Snake River coal field, Sweetwater and Carbon Counties, Wyoming (fig. 1). The samples are briefly described in table 1. Twenty-six of the samples were collected from eight core holes that were drilled in connection with the Red Rim EMRIA (Energy Mineral Rehabilitation Inventory and Analyses) study (U.S. Department of the Interior, 1976). The locations of these eight holes and five other drill holes are shown in figure 2. Detailed geologic mapping of part of the sample collection area was done by Sanders (1974) in his work on the Riner quadrangle. Seven of the core holes (index map locations 1-7) are located in this quadrangle. In his discussion, Sanders (1974) describes the coal beds in the lower part of the Fort Union Formation as being thin, discontinuous, and generally lenticular. Few beds attain a thickness of more than five feet. In the Riner quadrangle coal beds in the lower part of the Fort Union Formation dip 12° to 24° northwestward.

Wyoming↗

USGS1984

Application of a parameter-estimation technique to modeling the regional aquifer underlying the eastern Snake River Plain, Idaho

A nonlinear, least-squares regression technique for the estimation of ground-water flow model parameters was applied to the regional aquifer underlying the eastern Snake River Plain, Idaho. The computer program simulates two-dimensional, steady-state ground-water flow. Hydrologic data for the 1980 water year were used to calculate recharge rates, boundary fluxes, and spring discharges. Groundwater use was estimated from irrigated land maps and crop consumptive-use figures. These estimates of ground-water withdrawal, recharge rates, and boundary flux, along with leakance, were used as known values in the model calibration of transmissivity. Leakance values were adjusted between regression solutions by comparing model-calculated to measured spring discharges. In other simulations, recharge and leakance also were calibrated as prior information regression parameters, which limits the variation of these parameters using a normalized standard error of estimate. Results from a best-fit model indicate a wide areal range in transmissivity from about 0.05 to 44 feet squared per second and in leakance from about 2.2 x 10 -9 to 6.0 x 10 -8 feet per second per foot. Along with parameter values, model statistics also were calculated, including the coefficient of correlation between computed and observed head (0.996), standard error of the estimates of head (40 feet), and parameter coefficients of variation (about 10-40 per-cent). Additional boundary flux was added in some areas during calibration to achieve proper fit to ground-water flow directions. Model fit improved significantly when areas that violated model assumptions were removed. Model fit also improved when y-direction (northwest-southeast) transmissivity values were larger than x-direction (northeast-southwest) transmissivity values. The model was most sensitive to changes in recharge, and in some areas, to changes in transmissivity, particularly near the spring discharge area from Milner to King Hill.

Idaho↗

USGS1925

Discovery of a Balkan fresh-water fauna in the Idaho formation of Snake River Valley, Idaho

In 1866 Gabb described Melania taylori and Lithasia antiqua "from a fresh-water deposit on Snake River, Idaho Territory, on the road from Fort Boise to the Owyhee mining country. Collected by A. Taylor." He states that a small bivalve, perhaps a Sphaerium, was associated with them.

Idaho↗

USGS2019

Coal geology and assessment of resources and reserves in the Little Snake River Coal Field and Red Desert Assessment Area, Greater Green River Basin, Wyoming

The U.S. Geological Survey is studying regional-scale assessments of resources and reserves of primary coal beds in the major coal bed basins in the United States to help formulate policy for Federal, State, and local energy and land use. This report summarizes the geology and coal resources and reserves in the Little Snake River coal field and Red Desert assessment area in the Greater Green River Basin, southwestern Wyoming. These areas are contiguous and referred to as the “assessment area” in this report. The assessment area covers about 2,300 square miles of the eastern section of the 15,400-square-mile Greater Green River Basin. This area was prioritized for assessment because no comprehensive resource assessment had previously been completed in the area; abundant, previously unavailable drill hole data from cooperators and stakeholders became available; and there are active coal mines in the Greater Green River Basin area producing from some of the same formations as those found in the assessment area. Coal-bearing Eocene, Paleocene, and Upper Cretaceous formations have a composite thickness of more than 11,000 feet in the assessment area. Stratigraphic sequences that contain multiple coal beds within a formation or member are referred to as coal zones in this report. Paleogene coal beds are found within coal zones in the Eocene Wasatch Formation and the Paleocene Fort Union Formation. Cretaceous coal beds are within coal zones in the Lance, Almond, and Allen Ridge Formations. A total of 4,214 drill holes and measured sections were used to construct a geologic database for this assessment. From these data, 7 coal zones containing 55 individual coal beds were identified. Not all 55 coal beds were assessed; only those beds that were at least 3 feet thick and had at least a 2-square-mile areal extent were considered. Using a geology-based assessment methodology, the U.S. Geological Survey estimated original, available, and recoverable coal resources for 33 coal beds that met those criteria. An original resource of 73.2 billion short tons of coal was calculated for the 33 coal beds that met the criteria in the assessment area. To be considered extractable by surface mining methods, coal beds had to be equal to or greater than 3 feet thick and less than 300 feet deep. Of the 73.2 billion short tons (BST), 19.3 BST were determined to be recoverable resources, of which approximately 2.1 BST were considered as recoverable resources by surface mining methods at a stripping ratio of 10:1 or less. (defined as recoverable resources for this assessment, based on economic modeling and regional mining analogs). Recoverable resources for underground mining methods (coal 8 to 15 feet thick and between 300 and 3,000 feet deep) totaled 17.2 BST. Out of the 19.3 BST assessed as recoverable coal resources, approximately 167 million short tons (MST) were considered to be reserves. Within the 7 coal zones, the Wasatch coal zone contains an original resource of about 6.8 BST billion short tons of coal, of which 2.6 BST are considered a recoverable resource and approximately 26.7 MST are considered reserves. The Overland coal zone, in the Fort Union Formation, contains an original resource of approximately 23 BST of coal, of which 8.4 BST are considered a recoverable resource and approximately 74 MST are considered reserves. The China Butte coal zone, in the Fort Union Formation, contains an original resource of 36.2 BST of coal, of which 6.3 BST are considered a recoverable resource and approximately 5.5 MST are considered reserves. The Almond coal zone, in the Almond Formation, contains an original resource of 7.0 BST, of which approximately 2.0 BST are considered a recoverable resource and 61 MST are considered reserves. Resources were not calculated for the coal zones within the Niland Tongue of the Wasatch Formation or the Cretaceous Lance and Allen Ridge Formations because the coal beds in those zones are relatively thin, discontinuous, and have a limited areal extent.

Wyoming↗

USGS2018

Geochemistry of groundwater in the eastern Snake River Plain aquifer, Idaho National Laboratory and vicinity, eastern Idaho

Nuclear research activities at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) in eastern Idaho produced radiochemical and chemical wastes that were discharged to the subsurface, resulting in detectable concentrations of some waste constituents in the eastern Snake River Plain (ESRP) aquifer. These waste constituents may pose risks to the water quality of the aquifer. In order to understand these risks to water quality the U.S. Geological Survey, in cooperation with the DOE, conducted a study of groundwater geochemistry to improve the understanding of hydrologic and chemical processes in the ESRP aquifer at and near the INL and to understand how these processes affect waste constituents in the aquifer. Geochemistry data were used to identify sources of recharge, mixing of water, and directions of groundwater flow in the ESRP aquifer at the INL. The geochemistry data were analyzed from 167 sample sites at and near the INL. The sites included 150 groundwater, 13 surface-water, and 4 geothermal-water sites. The data were collected between 1952 and 2012, although most data collected at the INL were collected from 1989 to 1996. Water samples were analyzed for all or most of the following: field parameters, dissolved gases, major ions, dissolved metals, isotope ratios, and environmental tracers. Sources of recharge identified at the INL were regional groundwater, groundwater from the Little Lost River (LLR) and Birch Creek (BC) valleys, groundwater from the Lost River Range, geothermal water, and surface water from the Big Lost River (BLR), LLR, and BC. Recharge from the BLR that may have occurred during the last glacial epoch, or paleorecharge, may be present at several wells in the southwestern part of the INL. Mixing of water at the INL primarily included mixing of surface water with groundwater from the tributary valleys and mixing of geothermal water with regional groundwater. Additionally, a zone of mixing between tributary valley water and regional groundwater, trending southwesterly, extended from near the northeastern boundary of the INL to the southern boundary of the INL. Groundwater flow directions for regional groundwater were southwesterly, and flow directions for tributary groundwater were southeasterly upon entering the ESRP, but eventually began to flow southwesterly in a direction parallel with regional groundwater. Several discrepancies were identified from comparison of sources of recharge determined from geochemistry data and backward particle tracking with a groundwater-flow model. Some discrepancies observed in the particle tracking results included representation of recharge from BC near the north INL boundary, groundwater from the BC valley not extending far enough south, regional groundwater that extends too far west in the southern part of the INL, and no representation of recharge from geothermal water in model layer 1 or recharge from the BLR in the southwestern part of the INL.

Idaho↗

USGS2019

Evaluation of chemical and hydrologic processes in the eastern Snake River Plain Aquifer based on results from geochemical modeling, Idaho National Laboratory, eastern Idaho

Nuclear research activities at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) produced liquid and solid chemical and radiochemical wastes that were disposed to the subsurface resulting in detectable concentrations of some waste constituents in the eastern Snake River Plain (ESRP) aquifer. These waste constituents may affect the water quality of the aquifer and may pose risks to the eventual users of the aquifer water. To understand these risks to water quality the U.S. Geological Survey, in cooperation with the DOE, conducted geochemical mass-balance modeling of the ESRP aquifer to improve the understanding of chemical reactions, sources of recharge, mixing of water, and groundwater flow directions in the shallow (upper 250 feet) aquifer at the INL. Modeling was conducted using the water chemistry of 127 water samples collected from sites at and near the INL. Water samples were collected between 1952 and 2017 with most of the samples collected during the mid-1990s. Geochemistry and isotopic data used in geochemical modeling consisted of dissolved oxygen, carbon dioxide, major ions, silica, aluminum, iron, and the stable isotope ratios of hydrogen, oxygen, and carbon. Geochemical modeling results indicated that the primary chemical reactions in the aquifer were precipitation of calcite and dissolution of plagioclase (An 60 ) and basalt volcanic glass. Secondary minerals other than calcite included calcium montmorillonite and goethite. Reverse cation exchange, consisting of sodium exchanging for calcium on clay minerals, occurred near site facilities where large amounts of sodium were released to the ESRP aquifer in wastewater discharge. Reverse cation exchange acted to retard the movement of wastewater-derived sodium in the aquifer. Regional groundwater inflow was the primary source of recharge to the aquifer underlying the Northeast and Southeast INL Areas. Birch Creek (BC), the Big Lost River (BLR), and groundwater from BC valley provided recharge to the North INL Area, and the BLR and groundwater from BC and Little Lost River (LLR) valleys provided recharge to the Central INL Area. The BLR, groundwater from the BLR and LLR valleys and the Lost River Range, and precipitation provided recharge to the Northwest and Southwest INL Areas. The primary source of recharge west and southwest of the INL was groundwater inflow from BLR valley. Upwelling geothermal water was a small source of recharge at two wells. Aquifer recharge from surface water in the northern, central, and western parts of the INL indicated that the aquifer in these areas was a dynamic, open system, whereas the aquifer in the eastern part of the INL, which receives little recharge from surface water, was a relatively static and closed system. Sources of recharge identified from isotope ratios and geochemical modeling (major ion concentrations) were nearly identical for the North, Northeast, Southeast, and Central INL Areas, which indicated that both methods probably accurately identified the sources of recharge in these areas. Conversely, isotope ratios indicated that the BLR and groundwater from the LLR valley provided most recharge to the western parts of the Northwest and Southwest INL Areas, whereas geochemical modeling results indicated a smaller area of recharge from the BLR and groundwater from the LLR valley, a larger area of recharge from the Lost River Range, and recharge of groundwater from the BLR valley that extended to the west INL boundary. The results from geochemical modeling probably were more accurate because major ion concentrations, but not isotope ratios, were available to characterize groundwater from the BLR valley and the Lost River Range. Sources of recharge identified with a groundwater flow model (using particle tracking) and geochemical modeling were similar for the Northeast and Southeast INL Areas. However, differences between the models were that the geochemical model represented (1) recharge of groundwater from the Lost River Range in the western part of the INL, whereas the flow model did not, (2) recharge of groundwater from the BC and BLR valleys extending farther south and east, respectively, than the flow model, and (3) more recharge from the BLR in the Southwest INL Area than the flow model. Mixing of aquifer water beneath the INL included (1) mixing of regional groundwater and water from the BC valley in the Northeast and Southeast INL Areas and (2) mixing of surface water (primarily from the BLR) and groundwater across much of the North, Central, Northwest, and Southwest INL Areas. Localized recharge from precipitation mixed with groundwater in the Northwest and Southwest INL Areas, and localized upwelling geothermal water mixed with groundwater in the Central and Northeast INL Areas. Flow directions of regional groundwater were south in the eastern part of the INL and south-southwest at downgradient locations. Groundwater from the BC and LLR valleys initially flowed southeast before changing to south-southwest flow directions that paralleled regional groundwater, and groundwater from the BLR valley initially flowed south before changing to a southsouthwest direction. Wastewater-contaminated groundwater flowed south from the Idaho Nuclear Technology and Engineering Center (INTEC) infiltration ponds in a narrow plume, with the percentage of wastewater in groundwater decreasing due to dilution, dispersion, and (or) degradation from about 60‒80 percent wastewater 0.7‒0.8 mile (mi) south of the INTEC infiltration ponds to about 1.4 percent wastewater about 15.5 mi south of the INTEC infiltration ponds. Wastewater contaminated groundwater flowed southeast and then southwest from the Naval Reactors Facility industrial waste ditch, with the percentage of wastewater in groundwater decreasing from about 100 percent wastewater adjacent to the waste ditch to about 2 percent wastewater about 0.6 mi south of the waste ditch.

Idaho↗

USGS2023

Determining three-dimensional hydrologic processes in the eastern Snake River Plain aquifer using geochemical mass-balance modeling, Idaho National Laboratory, eastern Idaho, with contributions by Treinen, K.C.

Idaho↗

USGS2023

Evaluation of hydrologic processes in the eastern Snake River Plain aquifer using uranium and strontium isotopes, Idaho National Laboratory, eastern Idaho

Waste constituents discharged to the eastern Snake River Plain aquifer at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) pose risks to the water quality of the aquifer. To understand these risks, the U.S. Geological Survey, in cooperation with the DOE, is conducting geochemical studies to better understand the hydrologic processes at the INL that affect the movement of groundwater and waste constituents. In this study, we used natural uranium ( 234 U/ 238 U) and strontium ( 87 Sr/ 86 Sr) isotope ratios of surface water and groundwater to identify the sources of water, the mixing of different source waters, and the flow directions in the shallow part (upper 250 feet) of the aquifer at the INL. Samples were collected from 17 sites at and near the INL that represent the source-water contributions to the aquifer. These source-water sites included surface water, regional groundwater, and springs. Groundwater samples from 63 sites were collected at and near the INL. For all sites, sample collection dates ranged from 1979 to 2019, but groundwater samples collected at the INL are representative of wet climate cycles when the Big Lost River (BLR) was flowing onto the INL. The 234 U/ 238 U activity ratios and 87 Sr/ 86 Sr from groundwater at the INL were plotted on graphs within ternary mixing webs in which the three end members of the mixing web represented specific sources of recharge. The large number of sources of recharge required numerous mixing webs, representing various geographic locations at the INL, so that each mixing web represented an area with just three sources of recharge. Considerations for determining the sources of recharge to groundwater sites included chemical signatures in addition to 234 U/ 238 U and 87 Sr/ 86 Sr, hydrologic context, and geographic location. The mixing webs were used to estimate the percentage of recharge from specific sources to groundwater at wells. The results of this study identified groundwater from the Lemhi Range as a source of recharge to the INL, which was a previously unsuspected source of recharge. The estimated spatial distribution of recharge from the BLR and groundwater from the Lost River Range also decreased and increased, respectively, relative to the spatial distribution estimated from an earlier study. Upwelling geothermal water was identified at only one well, which indicates that the upward movement of deep groundwater to the shallow part of the aquifer is largely nonexistent. Mixing between surface water and groundwater, different groundwater recharge sources, or both is ubiquitous at the INL. Mixing of water fully explains the distribution of 234 U/ 238 U and 87 Sr/ 86 Sr in groundwater at the INL and thus renders unnecessary the hypothesis that fast and slow flow zones at the INL are required to explain the distribution of 234 U/ 238 U and 87 Sr/ 86 Sr.

Idaho↗

USGS2008

Geologic map of upper cretaceous and tertiary strata and coal stratigraphy of the Paleocene Fort Union Formation, Rawlins-Little Snake River area, south-central Wyoming

This report provides a map and detailed descriptions of geologic formations for a 1,250 square mile region in the Rawlins-Little Snake River coal field in the eastern part of the Washakie and Great Divide Basins of south-central Wyoming. Mapping of geologic formations and coal beds was conducted at a scale of 1:24,000 and compiled at a scale of 1:100,000. Emphasis was placed on coal-bearing strata of the China Butte and Overland Members of the Paleocene Fort Union Formation. Surface stratigraphic sections were measured and described and well logs were examined to determine the lateral continuity of individual coal beds; the coal-bed stratigraphy is shown on correlation diagrams. A structure contour and overburden map constructed on the uppermost coal bed in the China Butte Member is also provided.

Scientific Investigations Map↗

USGS2011

Regional potentiometric-surface map of the Great Basin carbonate and alluvial aquifer system in Snake Valley and surrounding areas, Juab, Millard, and Beaver Counties, Utah, and White Pine and Lincoln Counties, Nevada

Water-level measurements from 190 wells were used to develop a potentiometric-surface map of the east-central portion of the regional Great Basin carbonate and alluvial aquifer system in and around Snake Valley, eastern Nevada and western Utah. The map area covers approximately 9,000 square miles in Juab, Millard, and Beaver Counties, Utah, and White Pine and Lincoln Counties, Nevada. Recent (2007-2010) drilling by the Utah Geological Survey and U.S. Geological Survey has provided new data for areas where water-level measurements were previously unavailable. New water-level data were used to refine mapping of the pathways of intrabasin and interbasin groundwater flow. At 20 of these locations, nested observation wells provide vertical hydraulic gradient data and information related to the degree of connection between basin-fill aquifers and consolidated-rock aquifers. Multiple-year water-level hydrographs are also presented for 32 wells to illustrate the aquifer system's response to interannual climate variations and well withdrawals.

Utah, Nevada↗

USGS2004

Use of short-term (5-Minute) and long-term (18-Hour) leaching tests to characterize, fingerprint, and rank mine-waste material from historical mines in the Deer Creek, Snake River, and Clear Creek Watersheds in and around the Montezuma Mining District, Colorado

Precipitation-induced runoff from historical mine-waste located adjacent to the headwaters of the Snake River, Deer Creek, Saints John Creek, Grizzly Gulch, Stevens Gulch, and Leavenworth Creek contributes to the degradation of water quality in these streams. Because historical mine-waste piles have had long-term exposure to the atmosphere, it is surmised that runoff from these piles, induced by meteorological events such as cloudbursts and snowmelt, may cause mobility of acid and metals into a watershed due to dissolution of soluble minerals. For this study, 13 mine-waste composite samples from various mine-wastes in these drainage basins were leached using both a short-term and a long-term leach test. Analytical results from this combination of leach tests are tools that allow the investigator to quantify (fingerprint) which geochemical components could be expected in runoff from these piles if they were leached by a cloudburst (5-minute leach test), as well as what the ?worst-case? geochemical profile would look like if the material were subject to extended leaching and breakdown of the mine-waste material (18-hour leach test). Also, this combination of leach tests allows the geoscientist the ability to see geochemical changes in the mine-waste leachate over time. That is, does the leachate become more or less acidic over time; does the specific conductance increase or decrease; and are there changes in the concentrations of major or trace elements? Further, use of a ranking scheme described herein will aid in prediction of which historical mine-waste piles have the greatest potential for impact on a watershed should runoff occur. Because of long-term weathering of these historical mine-waste piles, geochemical profiles, leachate time-trends, and relative ranking of the mine-wastes produced from analysis of the leachates are Hageman_SIR_2508.doc 1 7/21/2004 2:50 PM indicative of how the mine-waste piles can be expected to act in the environment and may help to identify the ?bad actors??this may aid in understanding the reasons for water-quality differences between the drainages.

Scientific Investigations Report↗

USGS2006

A conceptual model of ground-water flow in the eastern Snake River Plain aquifer at the Idaho National Laboratory and vicinity with implications for contaminant transport

Ground-water flow in the west-central part of the eastern Snake River Plain aquifer is described in a conceptual model that will be used in numerical simulations to evaluate contaminant transport at the Idaho National Laboratory (INL) and vicinity. The model encompasses an area of 1,940 square miles (mi2) and includes most of the 890 mi2 of the INL. A 50-year history of waste disposal associated with research activities at the INL has resulted in measurable concentrations of waste contaminants in the aquifer. A thorough understanding of the fate and movement of these contaminants in the subsurface is needed by the U.S. Department of Energy to minimize the effect that contaminated ground water may have on the region and to plan effectively for remediation. Three hydrogeologic units were used to represent the complex stratigraphy of the aquifer in the model area. Collectively, these hydrogeologic units include at least 65 basalt-flow groups, 5 andesite-flow groups, and 61 sedimentary interbeds. Three rhyolite domes in the model area extend deep enough to penetrate the aquifer. The rhyolite domes are represented in the conceptual model as low permeability, vertical pluglike masses, and are not included as part of the three primary hydrogeologic units. Broad differences in lithology and large variations in hydraulic properties allowed the heterogeneous, anisotropic basalt-flow groups, andesite-flow groups, and sedimentary interbeds to be grouped into three hydrogeologic units that are conceptually homogeneous and anisotropic. Younger rocks, primarily thin, densely fractured basalt, compose hydrogeologic unit 1; younger rocks, primarily of massive, less densely fractured basalt, compose hydrogeologic unit 2; and intermediate-age rocks, primarily of slightly-to-moderately altered, fractured basalt, compose hydrogeologic unit 3. Differences in hydraulic properties among adjacent hydrogeologic units result in much of the large-scale heterogeneity and anisotropy of the aquifer in the model area, and differences in horizontal and vertical hydraulic conductivity in individual hydrogeologic units result in much of the small-scale heterogeneity and anisotropy of the aquifer in the model area. The inferred three-dimensional geometry of the aquifer in the model area is very irregular. Its thickness generally increases from north to south and from west to east and is greatest south of the INL. The interpreted distribution of older rocks that underlie the aquifer indicates large changes in saturated thickness across the model area. The boundaries of the model include physical and artificial boundaries, and ground-water flows across the boundaries may be temporally constant or variable and spatially uniform or nonuniform. Physical boundaries include the water-table boundary, base of the aquifer, and northwest mountain-front boundary. Artificial boundaries include the northeast boundary, southeast-flowline boundary, and southwest boundary. Water flows into the model area as (1) underflow (1,225 cubic feet per second (ft3/s)) from the regional aquifer (northeast boundary-constant and nonuniform), (2) underflow (695 ft3/s) from the tributary valleys and mountain fronts (northwest boundary-constant and nonuniform), (3) precipitation recharge (70 ft3/s) (constant and uniform), streamflow-infiltration recharge (95 ft3/s) (variable and nonuniform), wastewater return flows (6 ft3/s) (variable and nonuniform), and irrigation-infiltration recharge (24 ft3/s) (variable and nonuniform) across the water table (water-table boundary-variable and nonuniform), and (4) upward flow across the base of the aquifer (44 ft3/s) (uniform and constant). The southeast-flowline boundary is represented as a no-flow boundary. Water flows out of the model area as underflow (2,037 ft3/s) to the regional aquifer (southwest boundary-variable and nonuniform) and as ground-water withdrawals (45 ft3/s) (water table boundary-variable and nonuniform). Ground-water flow i

Scientific Investigations Report↗

USGS2008

Statistical Stationarity of Sediment Interbed Thicknesses in a Basalt Aquifer, Idaho National Laboratory, Eastern Snake River Plain, Idaho

The statistical stationarity of distributions of sedimentary interbed thicknesses within the southwestern part of the Idaho National Laboratory (INL) was evaluated within the stratigraphic framework of Quaternary sediments and basalts at the INL site, eastern Snake River Plain, Idaho. The thicknesses of 122 sedimentary interbeds observed in 11 coreholes were documented from lithologic logs and independently inferred from natural-gamma logs. Lithologic information was grouped into composite time-stratigraphic units based on correlations with existing composite-unit stratigraphy near these holes. The assignment of lithologic units to an existing chronostratigraphy on the basis of nearby composite stratigraphic units may introduce error where correlations with nearby holes are ambiguous or the distance between holes is great, but we consider this the best technique for grouping stratigraphic information in this geologic environment at this time. Nonparametric tests of similarity were used to evaluate temporal and spatial stationarity in the distributions of sediment thickness. The following statistical tests were applied to the data: (1) the Kolmogorov-Smirnov (K-S) two-sample test to compare distribution shape, (2) the Mann-Whitney (M-W) test for similarity of two medians, (3) the Kruskal-Wallis (K-W) test for similarity of multiple medians, and (4) Levene's (L) test for the similarity of two variances. Results of these analyses corroborate previous work that concluded the thickness distributions of Quaternary sedimentary interbeds are locally stationary in space and time. The data set used in this study was relatively small, so the results presented should be considered preliminary, pending incorporation of data from more coreholes. Statistical tests also demonstrated that natural-gamma logs consistently fail to detect interbeds less than about 2-3 ft thick, although these interbeds are observable in lithologic logs. This should be taken into consideration when modeling aquifer lithology or hydraulic properties based on lithology.

Scientific Investigations Report↗

USGS2012

Multilevel groundwater monitoring of hydraulic head and temperature in the eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, 2009–10

During 2009 and 2010, the U.S. Geological Survey’s Idaho National Laboratory Project Office, in cooperation with the U.S. Department of Energy, collected quarterly, depth-discrete measurements of fluid pressure and temperature in nine boreholes located in the eastern Snake River Plain aquifer. Each borehole was instrumented with a multilevel monitoring system consisting of a series of valved measurement ports, packer bladders, casing segments, and couplers. Multilevel monitoring at the Idaho National Laboratory has been ongoing since 2006. This report summarizes data collected from three multilevel monitoring wells installed during 2009 and 2010 and presents updates to six multilevel monitoring wells. Hydraulic heads (heads) and groundwater temperatures were monitored from 9 multilevel monitoring wells, including 120 hydraulically isolated depth intervals from 448.0 to 1,377.6 feet below land surface. Quarterly head and temperature profiles reveal unique patterns for vertical examination of the aquifer’s complex basalt and sediment stratigraphy, proximity to aquifer recharge and discharge, and groundwater flow. These features contribute to some of the localized variability even though the general profile shape remained consistent over the period of record. Major inflections in the head profiles almost always coincided with low-permeability sediment layers and occasionally thick sequences of dense basalt. However, the presence of a sediment layer or dense basalt layer was insufficient for identifying the location of a major head change within a borehole without knowing the true areal extent and relative transmissivity of the lithologic unit. Temperature profiles for boreholes completed within the Big Lost Trough indicate linear conductive trends; whereas, temperature profiles for boreholes completed within the axial volcanic high indicate mostly convective heat transfer resulting from the vertical movement of groundwater. Additionally, temperature profiles provide evidence for stratification and mixing of water types along the southern boundary of the Idaho National Laboratory. Vertical head and temperature change were quantified for each of the nine multilevel monitoring systems. The vertical head gradients were defined for the major inflections in the head profiles and were as high as 2.1 feet per foot. Low vertical head gradients indicated potential vertical connectivity and flow, and large gradient inflections indicated zones of relatively low vertical connectivity. Generally, zones that primarily are composed of fractured basalt displayed relatively small vertical head differences. Large head differences were attributed to poor vertical connectivity between fracture units because of sediment layering and/or dense basalt. Groundwater temperatures in all boreholes ranged from 10.2 to 16.3˚C. Normalized mean hydraulic head values were analyzed for all nine multilevel monitoring wells for the period of record (2007-10). The mean head values suggest a moderately positive correlation among all boreholes, which reflects regional fluctuations in water levels in response to seasonality. However, the temporal trend is slightly different when the location is considered; wells located along the southern boundary, within the axial volcanic high, show a strongly positive correlation.

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USGS2013

Optimization of water-level monitoring networks in the eastern Snake River Plain aquifer using a kriging-based genetic algorithm method

Long-term groundwater monitoring networks can provide essential information for the planning and management of water resources. Budget constraints in water resource management agencies often mean a reduction in the number of observation wells included in a monitoring network. A network design tool, distributed as an R package, was developed to determine which wells to exclude from a monitoring network because they add little or no beneficial information. A kriging-based genetic algorithm method was used to optimize the monitoring network. The algorithm was used to find the set of wells whose removal leads to the smallest increase in the weighted sum of the (1) mean standard error at all nodes in the kriging grid where the water table is estimated, (2) root-mean-squared-error between the measured and estimated water-level elevation at the removed sites, (3) mean standard deviation of measurements across time at the removed sites, and (4) mean measurement error of wells in the reduced network. The solution to the optimization problem (the best wells to retain in the monitoring network) depends on the total number of wells removed; this number is a management decision. The network design tool was applied to optimize two observation well networks monitoring the water table of the eastern Snake River Plain aquifer, Idaho; these networks include the 2008 Federal-State Cooperative water-level monitoring network (Co-op network) with 166 observation wells, and the 2008 U.S. Geological Survey-Idaho National Laboratory water-level monitoring network (USGS-INL network) with 171 wells. Each water-level monitoring network was optimized five times: by removing (1) 10, (2) 20, (3) 40, (4) 60, and (5) 80 observation wells from the original network. An examination of the trade-offs associated with changes in the number of wells to remove indicates that 20 wells can be removed from the Co-op network with a relatively small degradation of the estimated water table map, and 40 wells can be removed from the USGS-INL network before the water table map degradation accelerates. The optimal network designs indicate the robustness of the network design tool. Observation wells were removed from high well-density areas of the network while retaining the spatial pattern of the existing water-table map.

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