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1,079 records · Page 60Linked to original sources
USGS2022

Evaluation of the Bushy Park Reservoir three-dimensional hydrodynamic and water-quality model, South Carolina, 2012–15

The Bushy Park Reservoir is a relatively shallow impoundment in southeastern South Carolina. The reservoir, located under a semi-tropical climate, is the principal water supply for the city of Charleston, South Carolina, and the surrounding areas including the Bushy Park Industrial Complex. Although there was an adequate supply of freshwater in the reservoir in 2022, water-quality concerns are present over taste-and-odor and saltwater-intrusion issues. From 2013 to 2015, the U.S. Geological Survey (USGS), in cooperation with the Charleston Water System, engaged in a multi-year study of the hydrology and hydrodynamics of Bushy Park Reservoir to better understand factors affecting water-quality conditions in the reservoir. As part of this study, Charleston Water System worked with Tetra Tech, Inc., a consulting and engineering firm, to develop a Bushy Park Reservoir hydrodynamic and water-quality modeling framework, built upon earlier efforts by both Tetra Tech and the U.S. Army Corps of Engineers. At the completion of the new modeling framework, the USGS was requested to evaluate the calibrated hydrodynamic and water-quality model. The Bushy Park Reservoir Environmental Fluid Dynamics Code (EFDC) model was calibrated for the time period from January 1, 2012, to December 31, 2015. The general modeling approach for the newly revised modeling framework, as briefly detailed in this report, was developed with EFDC. The EFDC is a grid-based modeling package that can simulate three-dimensional flow, transport, and water quality in surface-water systems. This report evaluated the capacity of Tetra Tech’s Bushy Park EFDC model to simulate water discharge, water circulation, surface elevations, temperature, salinity, and other water-quality parameters. The USGS model review focused specifically on the following criteria: (1) determine if the model, with additional effort, could be developed into an adequate planning tool for Bushy Park Reservoir; (2) assess the capacity of the model to specifically address water-quality issues in the reservoir related to taste-and-odor and saltwater intrusions; and, (3) evaluate three preliminary water-management scenarios related to reduced water withdrawals in the reservoir and the effect on saltwater intrusion. Overall, the model was able to simulate discharge, flow velocity, and water-surface elevations with generally good agreement between the simulated and measured values. Specifically, the model was able to demonstrate good agreement for discharge at two USGS continuous discharge locations (USGS station 02172002; USGS station 02172040), with Wilmott index of agreements of 0.86 and 0.75, respectively. A total of seven USGS streamgages, located on the West Branch of the Cooper River, Durham Canal, and the Cooper River, were available for water-surface elevations, with index of agreements ranging from 0.74 to 0.99. However, model-simulated water-surface elevation ranges were appreciably high (compared to measured ranges) for two locations near Pinopolis Dam, farthest upstream on the West Branch of the Cooper River. This result may indicate that too much simulated tidal energy propagated through the model domain. For water temperature, 16 calibration stations were available for at least part of the 4-year simulation. The index of agreement range for temperature comparisons was from 0.95 to 1.00, indicating excellent agreement between the measured and simulated results. One of the primary future applications for the Bushy Park Reservoir EFDC model is to determine the extent of saltwater intrusions. A wide range in the salinity prediction quality was simulated with the model. The prediction quality ranged from an index of agreement of 0.15 at Cooper River approximately 2.75 miles southeast of the Tee, South Carolina, to 0.92 at West Branch Cooper River near Moncks Corner, South Carolina. Although the model did not accurately simulate some of the larger salinity deviations resulting during individual hydrologic events, the seasonal salinity trends were adequately simulated with the model during the study period (2012–15). Therefore, it may be difficult to simulate extreme hydrologic events, such as during large storms, where high salinity water is exchanged with Bushy Park Reservoir. There was agreement in model simulation with the measured data either on the quantitative index of agreement values or qualitative agreement in the seasonal salinity data trends. For water quality, the index of agreement values were generally low for total nitrogen, ammonia, nitrate, total Kjeldahl nitrogen, total phosphorus, and orthophosphate. Although general trends were adequately simulated at specific stations, particularly for Bushy Park Reservoir, the model-simulated fit was low across all the constituents described above with index of agreements usually below 0.50. A limitation for simulating nutrient concentrations across the model domain was the lack of characterization for the constituents directly entering Bushy Park Reservoir, or the lack of data directly attributed to the boundary condition (for example, the Cooper River). The other two calibrated water-quality constituents (besides the nutrients mentioned above) were dissolved oxygen and chlorophyll a . Dissolved oxygen varied from index of agreement values from 0.58 to 0.94 for 11 stations, generally indicating agreement with the available measured data. Chlorophyll a , calibrated for seven stations, had a wider range from 0.11 to 0.74 for the index of agreement. With the current modeling framework, taste-and-odor events, related to cyanobacterial blooms, cannot be directly simulated. However, indirect estimates of cyanobacteria concentrations may be obtained by using the chlorophyll a model outputs, which represent total phytoplankton biomass, and the phytoplankton biovolume data by group (diatoms, green algae, cyanobacteria and others) collected from 2012 to 2015. For the Bushy Park Reservoir modeling framework to be used directly for taste-and-odor issues, cyanobacteria must be simulated and calibrated based on observations of cyanobacteria biomass concentrations. In addition to the cyanobacteria sampling conducted within the reservoir between 2012 and 2015, the new model calibration would also require new algae biomass data-collection efforts to characterize the external sources of cyanobacteria entering the Bushy Park Reservoir from tributaries, as well as the internal cycling, production, and decay of cyanobacteria in the hydrologic system. Further improvements to the EFDC model would include expanding the collection of boundary condition datasets, such as water-quality monitoring to determine improved nutrient loads into the model domain. Along with improved water-quality monitoring for the major boundary conditions, continuous discharge, for both Foster Creek and the Back River, would further constrain the flow balance and the loads into Bushy Park Reservoir. In addition to better boundary-condition characterization, it is important to better characterize possible shortcomings specifically to the model domain, such as the grid resolution, bathymetry, and numerical hydrodynamic errors. Further consideration of the model may involve a sensitivity analysis to determine if errors in the simulation outputs, such as discharge, water-surface elevations, and salinity, were more likely caused by poor boundary condition characterization or, specifically, the model setup. Three model scenarios were run with the revised Bushy Park Reservoir model: (1) reduced withdrawals from one of the large intake-discharge locations for Bushy Park Reservoir, the Williams Station; (2) elevated (above background levels) ocean water level causing saltwater intrusion from the ocean through Durham Canal into Bushy Park Reservoir; and (3) overtopping of the Back River Dam at the southernmost end of Bushy Park Reservoir. For the reduced withdrawals scenarios, the largest shift in flow resulted near the Williams Station intake, with the next largest flow change at the southern end of Bushy Park Reservoir, and a net increase in flow out of the Bushy Park Reservoir to the Cooper River by way of the Durham Canal. The effect resulting from scenario 3 on water quality and salinity was small, with larger increases for dissolved oxygen than other constituents at several monitoring stations. For the two scenarios related to saltwater intrusion (including dam overtopping), the changes in salinity generally were found to dissipate in the following 2 weeks and generally back to baseline salinity conditions within 3 months. This result did vary depending on the severity of the storm or length of the dam overtopping event.

South Carolina↗
USGS2024

Simulated mean monthly groundwater-transported nitrogen loads in watersheds on the north shore of Long Island Sound, 1993–2022

Elevated nitrogen loads are pervasive in the Long Island Sound, an estuary that receives freshwater and nutrients from both surface-water and groundwater discharge. Surface-water nitrogen loads to the Long Island Sound are relatively well characterized, but less is known about groundwater-transported nitrogen loads. Prior work on the northern shore of Long Island Sound (Connecticut and areas of New York and Rhode Island) suggested that groundwater travel times are relatively short (median less than 2 years) and that decade-long nutrient legacies are not widespread. Because the travel times are short, groundwater flow and nutrient loads likely vary substantially between months. In the current study, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency’s Long Island Sound Study and the Connecticut Department of Energy and Environmental Protection, developed a set of models to better characterize spatial and temporal patterns of groundwater-transported nitrogen loading from atmospheric deposition, septic systems, and fertilizers within the study area. The models provide an estimate, with uncertainty, of groundwater-transported nitrogen loads in the study area, filling a key gap in the nitrogen budget for Long Island Sound. The models also highlight the spatial and temporal variation in nitrogen loading throughout the study area. The modeling workflow involved four models. (1) A soil-water-balance model was developed by using the Soil-Water-Balance software to simulate groundwater recharge across the study area for water years 2005 through 2022. The simulated mean monthly recharge from the soil-water-balance model was used as input into a groundwater-flow model. (2) The groundwater-flow model was developed by using the MODFLOW 6 software and data for water years 1993 through 2022 and simulates average monthly hydrologic conditions. The groundwater-flow model was calibrated by using the Iterative Ensemble Smoother method within the PEST++ software. The Iterative Ensemble Smoother method generates an ensemble of sets of parameter values, with each set producing reasonable simulated hydrologic parameter values. (3) An ensemble of MODPATH particle-tracking simulations were run to generate particle flow paths and travel times, with each simulation using a different set of the flow model parameters. (4) A nitrogen load model uses the MODPATH simulation outputs to track nitrogen from the land surface through multiple attenuation zones until it discharges into fresh or saline surface water. As with the groundwater-flow model, the nitrogen model simulated average monthly groundwater-transported nitrogen loads for water years 1993 through 2022. One novel aspect of the nitrogen load model is that the nitrogen attenuation parameters were calibrated to observed nitrogen loads. Across the ensemble of simulated nitrogen loads, the median study-area-wide monthly simulated nitrogen loads from the aquifer to Long Island Sound throughout the year ranged from 900 to 18,600 kilograms of nitrogen per day, with a median load of 5,100 kilograms of nitrogen per day. The simulated loads were based on average monthly conditions for water years 1993 through 2022. Loads were highest during the winter and early spring and lowest during the late summer. However, simulated travel times for groundwater and nitrogen loads discharged to Long Island Sound during summer were longer than travel times for groundwater and loads discharged during the winter, indicating that, on average, groundwater discharged during summer traveled along different, and longer, flow paths, than groundwater discharged during winter. This indicates that summer loads would respond more slowly to changes in nitrogen inputs at the water table than winter loads. Over the entire study area, approximately 15 percent of the simulated load is from atmospheric deposition sources, 30 to 40 percent is from fertilizer, and 50 to 60 percent is from septic systems. The final analysis of the study involved simulating the change in groundwater-transported nitrogen load in response to upgrading septic systems or reducing fertilizing inputs to areas of turf grass. Both management interventions reduced the groundwater-transported nitrogen load, and reductions were greater in areas with greater loads from septic systems or turf-grass fertilizers. The delay between management actions and substantial reductions in groundwater-transported nitrogen loads varied seasonally; loads during the late summer months remained elevated longer than the winter loads.

Connecticut, Rhode Island↗
USGS2015

Field-based description of rhyolite lava flows of the Calico Hills Formation, Nevada National Security Site, Nevada

Contaminants introduced into the subsurface of Pahute Mesa, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas at Pahute Mesa and into the accessible environment is greatest by groundwater transport through fractured volcanic rocks. The 12.9 Ma (mega-annums, million years) Calico Hills Formation, which consists of a mixture of rhyolite lava flows and intercalated nonwelded and bedded tuff and pyroclastic flow deposits, occurs in two areas of the Nevada National Security Site. One area is north of the Rainier Mesa caldera, buried beneath Pahute Mesa, and serves as a heterogeneous volcanic-rock aquifer but is only available to study through drilling and is not described in this report. A second accumulation of the formation is south of the Rainier Mesa caldera and is exposed in outcrop along the western boundary of the Nevada National Security Site at the Calico Hills near Yucca Mountain. These outcrops expose in three dimensions an interlayered sequence of tuff and lava flows similar to those intercepted in the subsurface beneath Pahute Mesa. Field description and geologic mapping of these exposures described lithostratigraphic variations within lava flows and assisted in, or at least corroborated, conceptualization of the rhyolite lava-bearing parts of the formation. In the area south of the Rainier Mesa caldera, surface exposures and nearby subsurface equivalents were studied through compilation of geologic maps, new field mapping, subsurface information from boreholes, and data extracted from three-dimensional geologic framework models. Rhyolite lava flows within the Calico Hills Formation are described in terms of lithostratigraphic variations established for rhyolite lava flows in other volcanic fields. In general, the flows consist of a core of crystallized, flow-banded rhyolite lava, surrounded by a carapace of obsidian, commonly mantled by blocky, pumiceous rhyolite lava and flow breccia. Rhyolite lava flows were correlated and mapped on the basis of distinctive appearance in outcrop, stratigraphic sequence, and the presence of stratigraphic markers. Pyroclastic deposits that are spatially, temporally, and genetically related to the rhyolite lava flows consist of a series of intercalated pyroclastic flows, bedded ash-fall, and reworked tuff that have varying amounts of pumice and volcanic rock clasts. In the area south of the Rainier Mesa caldera, surface and subsurface geologic data are combined to interpret the overall thickness of the Calico Hills Formation and the proportion of lava flow lithology across the study area. The formation is at least 500 meters (m) thick and contains the greatest proportion of rhyolite lava flow to the northeast of Yucca Mountain in the lower part of Fortymile Canyon. The formation thins to the south and southwest where it is between 50 and 200 m thick beneath Yucca Mountain and contains no rhyolite lavas. Geologic mapping and field-based correlation of individual lava flows allow for the interpretation of the thickness and extent of specific flows and the location of their source areas. The most extensive flows have widths from 2 to 3 kilometers (km) and lengths of at least 5–6 km. Lava flow thickness varies from 150 to 250 m above interpreted source vents to between 30 and 80 m in more distal locations. Rhyolite lavas have length-to-height ratios of 10:1 or greater and, in one instance, a length-to-width ratio of 2:1 or greater, implying a tongue-shaped geometry instead of circular domes or tabular bodies. Although geologic mapping did not identify any physical feature that could be positively identified as a vent, lava flow thickness and the size of clasts in subjacent pyroclastic deposits suggest that primary vent areas for at least some of the flows in the study area are on the east side of Fortymile Canyon, to the northeast of Yucca Mountain.

Nevada↗
USGS2011

Monitoring a large volume CO2 injection: Year two results from SECARB project at Denbury’s Cranfield, Mississippi, USA

The Southeast Regional Carbon Sequestration Partnership (SECARB) early project in western Mississippi has been testing monitoring tools and approaches to document storage efficiency and storage permanence under conditions of CO 2 EOR as well as downdip injection into brine. Denbury Onshore LLC is host for the study and has brought a depleted oil and gas reservoir, Cranfield Field, under CO 2 flood. Injection was started in July 2008 and has now achieved injection rates greater than 1.2 million tons/year though 23 wells, with cumulative mass injected as of August, 2010 of 2.2 million metric tons. Injection is into coarse grained fluvial deposits of the Cretaceous lower Tuscaloosa Formation in a gentle anticline at depths of 3300 m. A team of researchers from 10 institutions has collected data from five study areas, each with a different goal and different spatial and temporal scale. The Phase 2 study began at the start of injection and has been using pressure and temperature as a tool for assessing permanence mostly in the oil productive interval. Real-time read-out shows high sensitivity to distant changes in injection rate and confirms the geologic model of reservoir compartmentalization. Above-zone pressure monitoring ∼120 m above the injection interval is used to test the sensitivity of this approach for documentation of integrity of the confining system in an area of numerous well completions as pressure increase is induced in the reservoir by more than 70 bar. Monitoring of the High Volume Injection Test (HiVIT) area includes repeat measurements of aqueous geochemistry in the injection zone. Rock-water- CO 2 interactions in the reservoir as CO 2 dissolves are minimized by mineral “armoring” by abundant chlorite cement in high permeability reservoir sandstone. Geochemical monitoring of confined freshwater aquifers at depths of 70–100 m is underway. Groundwater analysis focuses on assessment of the sensitivity of this method to detect leakage above background variability. A repeat seismic survey of the HiVIT is planned for late 2010 to assess saturation change especially in downdip brine-only areas. A study focused on feasibility of monitoring the shallow subsurface to separate leakage from normal complex surface fluxes is underway at an monitoring array installed in October 2009 to assess the interactions of recharge, soil gas, and shallow groundwater aquifers. Recent well re-entry and tracer injection will provide further information to interpret observed elevated deep-sourced methane. The Detailed Area Study (DAS) is collecting dense time-lapse data from closely-spaced three well array of an injector and two observation wells. The observation wells were completed with fiberglass casing to facilitate electrical resistance tomography (ERT) measurements, and a diverse array of instrumentation was both cemented behind casing and suspended on tubing. Injection started at the DAS December 1, 2009. We have measured pulsed neutron and resistivity via wireline, downhole and above-zone pressure, distributed temperature, and fluid chemistry including introduced pulses of perfluorocarbons, noble gases, and SF6 as tracers. Between wells, time-lapse crosswell seismic and electrical resistance tomography (ERT) are used to measure saturation change. The goals are to measure changes as fluids evolve from single phase (brine) to two phase (CO 2 –brine) in order to document linkages between pressure and sweep efficiency. A time-lapse VSP survey bridges the vertical resolution and areal coverage between cross-well and surface seismic. The repeat surveys for many tools are scheduled for September, 2010. Reservoir characterization based on cores, historic and new wireline log data, production history, hydrologic tests, fluid analysis, and a three-D seismic survey have been used in multiple numerical models to predict reservoir response in order to design effective monitoring strategies and optimize deployment. History matching of observed response to predicted response is used to interpret results and improve confidence in conceptual models and numerical approaches. Probabilistic methods have been used to assess the significant uncertainties resulting from reservoir heterogeneity.

Mississippi↗
USGS2014

Simulated effects of existing and proposed surface-water impoundments and gas-well pads on streamflow and suspended sediment in the Cypress Creek watershed, Arkansas

Cypress Creek is located in central Arkansas and is the main tributary to Brewer Lake, which serves as the primary water supply for Conway, Arkansas, and the surrounding areas. A model of the Cypress Creek watershed was developed and calibrated in cooperation with Southwestern Energy Company using detailed precipitation, streamflow, and discrete suspended-sediment data collected from 2009 through 2012. These data were used with a Hydrologic Simulation Program—FORTRAN model to address different potential gas-extraction activities within the watershed. The calibrated Hydrologic Simulation Program—FORTRAN model was used to simulate four land-use scenarios and examine the potential effects of these land-use changes on the streamflow and water quality within the Cypress Creek watershed. These simulated scenarios included (1) the conversion of all nonforested land to forest, representing a time period before extensive grazing activities and no gas-extraction activities; (2) a land-use change to that of 1949, representing a time period with some grazing activities and no gas-extraction activities; (3) a time period with current land-use conditions, but without any gas-extraction activities, that is, the exclusion of gas-well pads/pipelines, associated gravel roads, and surface-water impoundments; and (4) a time period with current land-use conditions, but with increased gas-extraction activities (for example, increased gas-well pad and surface-water impoundment activities) to represent a possible future natural gas full-development condition for the area. A current-conditions simulation also was built and calibrated and represents the current conditions (2013) within the watershed. This simulation was used as the comparison basis for the four land-use scenarios described above. The current-conditions simulation used the 2006 land-use conditions, which consisted primarily of forest and pasture, as well as the current (2013) 35 gas-well pads and pipelines and 6 surface-water impoundments, which account for approximately 1.6 percent of the land use. Simulating a time period before extensive-grazing activities and no gas-extraction activities for scenario 1 resulted in a decrease in suspended-sediment loads and volume of streamflow within the Cypress Creek watershed compared to the current-conditions simulation. Simulating a time period before any gas-extraction activities but with some grazing activities for scenario 2 also resulted in a decrease in suspended-sediment loads and volume of streamflow within the Cypress Creek watershed. Simulating current conditions, but without any natural gas-pad land use or related activities (including pipelines and associated gravel roads), for scenario 3 resulted in mostly unchanged suspended-sediment loads and volume of streamflow within the Cypress Creek watershed, as compared to the current-conditions simulation. Finally, simulating potential future conditions of increased gas-well pad and surface-water impoundment activities for scenario 4 resulted in a decrease (compared to the current-conditions simulation) in suspended-sediment loads and a slight increase of volume of streamflow within the Cypress Creek watershed. The Arkansas Natural Resources Commission and the Arkansas Department of Environmental Quality list suspended sediment from “poor pastures” as a primary source of nonpoint-source pollution in north-central Arkansas, but unpaved (gravel) roads are another important source of suspended sediment. Because of the high sediment-loading rates associated with gravel roads and the large amount of pasture within the watershed, the factors most responsible for suspended sediment within the Cypress Creek watershed are likely associated more with the pastureland and gravel roads, than factors associated with gas-well pads/pipelines.

Arkansas↗
USGS2014

Geographic information system (GIS)-based maps of Appalachian basin oil and gas fields

One of the more recent maps of Appalachian basin oil and gas fields (and the adjoining Black Warrior basin) is the U.S. Geological Survey (USGS) compilation by Mast and others (1998) (see Trippi and others, this volume, chap. I.1). This map is part of a larger oil and gas field map for the conterminous United States that was derived by Mast and others (1998) from the Well History Control System (WHCS) database of Petroleum Information, Inc. (now IHS Energy Group). Rather than constructing the map from the approximately 500,000 proprietary wells in the Appalachian and Black Warrior part of the WHCS database, Mast and others (1998) subdivided the region into a grid of 1-mi 2 (square mile) cells and allocated an appropriate type of hydrocarbon production (oil production, gas production, oil and gas production, or explored but no production) to each cell. Each 1-mi 2 cell contains from 0 to 5 or more exploratory and (or) development wells. For example, if the wells in the 1-mi 2 cell consisted of three oil wells, one gas well, and one dry well, then the cell would be characterized on the map as an area of oil and gas production. The map by Mast and others (1998) accurately shows the distribution and types of hydrocarbon accumulation in the Appalachian and Black Warrior basins, but it does not show the names of individual fields. To determine the locality and name of individual oil and gas fields, one must refer to State oil and gas maps (for example, Harper and others, 1982), which are generally published at scales of 1:250,000 or 1:500,000 (see References Cited), and (or) published journal articles. Other recent USGS Appalachian basin oil and gas field maps show the distribution of oil and gas production with a cell size as small as 0.25 mi 2 , such as the maps converted by Trippi and others (this volume, chap. I.1) from proprietary well-location maps used in the USGS 2002 assessment of oil and gas resources of the Appalachian basin (Milici and others, 2003). Another set of Appalachian basin oil and gas cell maps (based on a cell size of 0.25 mi 2 ) was created for the USGS 1995 National Assessment of United States Oil and Gas Resources (Gautier and others, 1995; Beeman and others, 1996). Between 1991 and 1994, R.T. Ryder (with R.E. Mattick, J.B. Roen, and J.R. San Filipo, USGS, Reston, Va.) compiled oil and gas fields on stable-base mylar greenline base maps (scale 1:500,000) for selected plays in the Appalachian basin. These map compilations included field names and field numbers where assigned by State agencies. The purpose of the maps was to provide supporting data for the USGS 1995 National Assessment of United States Oil and Gas Resources (Gautier and others, 1995). In particular, the greenline oil and gas field maps were linked, where possible, with production data from State records and (or) published literature in order to determine ultimate sizes for conventional fields and estimated ultimate recovery (EUR) values for wells in continuous accumulations (for definitions of the conventional and continuous terminology, see USGS National Oil and Gas Assessment Team, 1995; Schmoker, 1997; Schenk and Pollastro, 2002). This approach was used in the 1995 national oil and gas assessment because ultimate field size and EUR data were unavailable in the Appalachian region from Petroleum Information, Inc., and other commercial sources. In 2006 and 2007, the greenline Appalachian basin field maps were digitized under the supervision of Scott Kinney and converted to geographic information system (GIS) files for chapter I.1 (this volume). By converting these oil and gas field maps to a digital format and maintaining the field names where noted, they are now available for a variety of oil and gas and possibly carbon-dioxide sequestration projects. Having historical names assigned to known digitized conventional fields provides a convenient classification scheme into which cumulative production and ultimate field-size databases can be organized. Moreover, as exploratory and development drilling expands across the basin, many previously named fields that were originally treated as conventional fields have evolved into large, commonly unnamed continuous-type accumulations. These new digital maps will facilitate a comparison between EUR values from recently drilled, unnamed parts of continuous accumulations and EUR values from named fields discovered early during the exploration cycle of continuous accumulations.

Appalachian basin↗
USGS1976

Geology and hydrology of radioactive solid-waste burial grounds at the Hanford Reservation, Washington

The geology and hydrology of radioactive solid waste burial grounds at the Hanford Reservation were investigated, using existing data, by the U.S. Geological Survey as part of the waste management plan of the Richland Operations Office of the Energy Research and Development Administration. The purpose of the investigation was to assist the operations office in characterizing the burial sites as to present environmental safety and as to their suitability for long-term storage (several thousand to tens of thousands of years) of radioactive sol id wastes. The burial ground sites fall into two classifications: (1) those on the low stream terraces adjacent to the Columbia River, mainly in the 100 Areas and 300 Area, and (2) those lying on the high terraces south of Gable Mountain in the 200 Areas. Evaluation of the suitability of the burial grounds for long-term storage was made almost entirely on hydrologic, geologic, and topographic criteria. Of greatest concern was the possibility that radionuclides might be leached from the buried wastes by infiltrating water and carried downward to the water table. The climate is semi-arid and the average annual precipitation is 6.4 inches at the Hanford Meteorological Station. However, the precipitation is seasonally distributed with about 50 percent occurring during the months of November, December, January, and February when evapotranspiration is negligible and conditions for infiltration are most favorable. None of the burial grounds are instrumented with monitoring devices that could be used to determine if radionuclides derived from them are reaching the water table. Burial grounds on the low stream terraces are mainly underlain by permeable materials and the water table lies at relatively shallow depths. Radionuclides conceivably could be leached from these burial grounds by percolating soil water, and radionuclides might reach the Columbia River in a relatively short time. These sites could also be inundated by erosion during a catastrophic flood. For these reasons, they are judged to be unsuited for long-term storage. Local conditions at several of these burial grounds are particularly unfavorable from the standpoint of safety. Depressions and swales at some burial grounds, such as numbers 4 and 5 in the 300 Area in which runoff can collect, enhance the possibility of water infiltrating through the buried wastes and transporting radionuclides to the water table. Also, during a high stage of the Columbia River, the water table conceivably could rise into burial grounds l and 2 of the 100 F Area. Most of the burial grounds on the low terraces contain either (1) reactor components and related equipment bearing activation products, principally cobalt-60, or (2) less hazardous radioactive materials such as uranium. The inventory of activation products in these burial grounds will decay to a safe level in a relatively short period of time (about 100 years), according to estimates made by C. D. Corbit, Douglas United Nuclear, Inc., 1969. The inventory of radionuclides is not considered by the ERDA staff to be complete, however. At these burial grounds containing activation products or less hazardous materials, investigations should be made of the radioactivity in soil and ground water beneath selected representative sites to verify that radionuclides are not migrating from the burial grounds. If migration is detected, field investigations should be made to determine the source or sources of the radionuclides and the desirability of removing the source wastes. Other burial grounds on the low terraces contain plutonium and fission products, which require long-term storage. Both the 300 WYE and the 300 North burial grounds are reported to contain plutonium in large quantities. Burial ground no. l in the 300 Area reportedly also contains plutonium. The inventory records of any other burial grounds on the low terraces suspected of containing plutonium should be reviewed to determine if pl

Open-File Report↗
USGS2012

Evaluation of quality-control data collected by the U.S. Geological Survey for routine water-quality activities at the Idaho National Laboratory, Idaho, 1996–2001

The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collects surface water and groundwater samples at and near the Idaho National Laboratory as part of a routine, site-wide, water-quality monitoring program. Quality-control samples are collected as part of the program to ensure and document the quality of environmental data. From 1996 to 2001, quality-control samples consisting of 204 replicates and 27 blanks were collected at sampling sites. Paired measurements from replicates were used to calculate variability (as reproducibility and reliability) from sample collection and analysis of radiochemical, chemical, and organic constituents. Measurements from field and equipment blanks were used to estimate the potential contamination bias of constituents. The reproducibility of measurements of constituents was calculated from paired measurements as the normalized absolute difference (NAD) or the relative standard deviation (RSD). The NADs and RSDs, as well as paired measurements with censored or estimated concentrations for which NADs and RSDs were not calculated, were compared to specified criteria to determine if the paired measurements had acceptable reproducibility. If the percentage of paired measurements with acceptable reproducibility for a constituent was greater than or equal to 90 percent, then the reproducibility for that constituent was considered acceptable. The percentage of paired measurements with acceptable reproducibility was greater than or equal to 90 percent for all constituents except orthophosphate (89 percent), zinc (80 percent), hexavalent chromium (53 percent), and total organic carbon (TOC; 38 percent). The low reproducibility for orthophosphate and zinc was attributed to calculation of RSDs for replicates with low concentrations of these constituents. The low reproducibility for hexavalent chromium and TOC was attributed to the inability to preserve hexavalent chromium in water samples and high variability with the analytical method for TOC. The reliability of measurements of constituents was estimated from pooled RSDs that were calculated for discrete concentration ranges for each constituent. Pooled RSDs of 15 to 33 percent were calculated for low concentrations of gross-beta radioactivity, strontium-90, ammonia, nitrite, orthophosphate, nickel, selenium, zinc, tetrachloroethene, and toluene. Lower pooled RSDs of 0 to 12 percent were calculated for all other concentration ranges of these constituents, and for all other constituents, except for one concentration range for gross-beta radioactivity, chloride, and nitrate + nitrite; two concentration ranges for hexavalent chromium; and TOC. Pooled RSDs for the 50 to 60 picocuries per liter concentration range of gross-beta radioactivity (reported as cesium-137) and the 10 to 60 milligrams per liter (mg/L) concentration range of nitrate + nitrite (reported as nitrogen [N]) were 17 percent. Chloride had a pooled RSD of 14 percent for the 20 to less than 60 mg/L concentration range. High pooled RSDs of 40 and 51 percent were calculated for two concentration ranges for hexavalent chromium and of 60 percent for TOC. Measurements from (1) field blanks were used to estimate the potential bias associated with environmental samples from sample collection and analysis, (2) equipment blanks were used to estimate the potential bias from cross contamination of samples collected from wells where portable sampling equipment was used, and (3) a source-solution blank was used to verify that the deionized water source-solution was free of the constituents of interest. If more than one measurement was available, the bias was estimated using order statistics and the binomial probability distribution. The source-solution blank had a detectable concentration of hexavalent chromium of 2 micrograms per liter. If this bias was from a source other than the source solution, then about 84 percent of the 117 hexavalent chromium measurements from environmental samples could have a bias of 10 percent or more. Of the 14 field blanks that were collected, only chloride (0.2 milligrams per liter) and ammonia (0.03 milligrams per liter as nitrogen), in one blank each, had detectable concentrations. With an estimated confidencelevel of 95 percent, at least 80 percent of the 1,987 chloride concentrations measured from all environmental samples had a potential bias of less than 8 percent. The ammonia bias, which may have occurred at the analytical laboratory, could produce a potential bias of 5-100 percent in eight potentially affected ammonia measurements. Of the 11 equipment blanks that were collected, chloride was detected in 4 of these blanks, sodium in 3 blanks, and sulfate and hexavalent chromium were each detected in 1 blank. The concentration of hexavalent chromium in the equipment blank was the same concentration as in the source-solution blank collected on the same day, which indicates that the hexavalent chromium in the equipment blank is probably from a source other than the portable sampling equipment, such as the sample bottles or the source-solution water itself. The potential bias for chloride, sodium, and sulfate measurements was estimated for environmental samples that were collected using portable sampling equipment. For chloride, it was estimated with 93 percent confidence that at least 80 percent of the measurements had a bias of less than 18 percent. For sodium and sulfate, it was estimated with 91 percent confidence that at least 70 percent of the measurements had a bias of less than 12 and 5 percent, respectively.

Idaho↗
USGS1991

A method for the concentration of fine-grained rutile (TiO2) from sediment and sedimentary rocks by chemical leaching

Quaternary marine sediment in the Gulf of Maine basins contains 0.7 to 1.0 wt percent TiO 2 (determined by X-ray fluorescence spectrometry). Most of this TiO 2 exists in the form of silt-size rutile crystals that are visible by using the petrographic microscope with transmitted light (Valentine and Commeau, 1990). The identification of rutile was confirmed by using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) system. To quantify the amount of TiO 2 in the sediment contributed by rutile and its polymorphs, anatase and brookite, it was necessary to eliminate as many of the other minerals as possible, especially titanium-bearing minerals such as ilmenite, ilmenomagnetite, biotite, hornblende, oyroxene, and sphene. We accomplished this by developing a method of chemical dissolution that removed the bulk of the raw material and left the TiO 2 minerals intact. Many methods using acids and bases have been developed over the years to dissolve rocks, minerals, and sediments for chemical analysis or to concentrate specific minerals (Dolcater et al., 1970; Church, 1971; Campbell, 1973, and the references cited therein). The method developed by Raman and Jackson (1965) to concentrate rutile and anatase in soils and sediments requires digesting the sample in concentrated hydrofluoric acid (HF) for 24 hours. However, Campbell (1973) found that digestion in HF for more than 2 hours results in a loss of anatase. The method of Dolcater et al. (1970) for concentrating titanium as a free oxide requires the use of hydrofluotitanic acid (H 2 TiF 6 ), which is difficult to find on the commercial market. The acid can be prepared by the reaction of concentrated HF (48%) with an excess of TiO 2 , but the procedure requires 36 hours to complete and should be attempted with caution because it is highly exothermic. Jackson (1979) provides a detailed method for digesting soils, but many of the recommended pretreatment steps employ sodium compounds such as sodium bicarbonate (NaHCO 3 ), sodium citrate (Na 3 C 6 H 5 O 7 -2H 2 O), and sodium dithionate (Na 2 S 2 O 4 ), which are used for the removal of calcium carbonate, iron oxides, and phosphates. In combining the methods of Dolcater and Jackson, sodium compounds must be thoroughly washed from the sample because they form sodium fluotitanate (Na 2 TiF 6 ) in the presence of hydrofluotitanic acid (Fig. 1K). French and Adams (1973) described an inexpensive method for decomposing silicates by HF digestion in polypropylene containers. Their technique was effective for a wide variety of rock types. However, it did not address the problem caused by the precipitation of insoluble fluorides, nor did it outline a procedure to concentrate any residue that remained. As no one method gave the results we required, we modified procedures described in the literature and developed a process that removes 96 to 98 wt percent of the raw sample material. The residue is composed of rutile and minor amounts of micro- and cryptocrystalline TiO 2 (Fig. 1A-J), barite (Fig. 1L), elemental carbon (coal), and insoluble fluorides (Fig. 1J). The fluorides precipitate during the decomposition of siliceous material in hydrofluoric acid (e.g., MgF 2 and MgAlF 5 -2.7H 2 O; Lanmyhr and Kringstad, 1966). Most of the sample analyzed by the method described were marine muds collected from the Gulf of Maine (Valentine and Commeau, 1990). The silt and clay fraction (up to 99 wt% of the sediment) is composed of clay minerals (chiefly illite-mica and chlorite), silt-size quartz and feldspar, and small crystals (2-12 um) of rutile and hematite. The bulk sediment samples contained an average of 2 to 3 wt percent CaCO 3 . Tiher samples analyzed include red and gray Carboniferous and Triassic sandstones and siltstones exposed around the Bay of Fundy region and Paleozoic sandstones, siltstones, and shales from northern Maine and New Brunswick. These rocks are probable sources for the fine-grained rutile found in the Gulf of Maine.

Economic Geology↗
USGS2013

A USANS/SANS study of the accessibility of pores in the Barnett Shale to methane and water

Shale is an increasingly important source of natural gas in the United States. The gas is held in fine pores that need to be accessed by horizontal drilling and hydrofracturing techniques. Understanding the nature of the pores may provide clues to making gas extraction more efficient. We have investigated two Mississippian Barnett Shale samples, combining small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) to determine the pore size distribution of the shale over the size range 10 nm to 10 μm. By adding deuterated methane (CD 4 ) and, separately, deuterated water (D 2 O) to the shale, we have identified the fraction of pores that are accessible to these compounds over this size range. The total pore size distribution is essentially identical for the two samples. At pore sizes >250 nm, >85% of the pores in both samples are accessible to both CD 4 and D 2 O. However, differences in accessibility to CD 4 are observed in the smaller pore sizes (~25 nm). In one sample, CD 4 penetrated the smallest pores as effectively as it did the larger ones. In the other sample, less than 70% of the smallest pores (<25 nm) were accessible to CD 4 , but they were still largely penetrable by water, suggesting that small-scale heterogeneities in methane accessibility occur in the shale samples even though the total porosity does not differ. An additional study investigating the dependence of scattered intensity with pressure of CD 4 allows for an accurate estimation of the pressure at which the scattered intensity is at a minimum. This study provides information about the composition of the material immediately surrounding the pores. Most of the accessible (open) pores in the 25 nm size range can be associated with either mineral matter or high reflectance organic material. However, a complementary scanning electron microscopy investigation shows that most of the pores in these shale samples are contained in the organic components. The neutron scattering results indicate that the pores are not equally proportioned in the different constituents within the shale. There is some indication from the SANS results that the composition of the pore-containing material varies with pore size; the pore size distribution associated with mineral matter is different from that associated with organic phases.

Texas↗
USGS1956

Uranium-bearing coal in the central part of the Great Divide basin, Sweetwater County, Wyoming

Field work leading to this report was done by the U.S. Geological Survey for the Division of Raw Materials of the U.S. Atomic Energy Commission. Nearly 24 townships were mapped in the central part of the Great Divide Basin, Sweetwater County, Wyoming. Fourteen of these townships contain outcrops of uranium-bearing coal. Thirty coal beds were mapped, but only seven of them have uranium-bearing coal reserves as defined in this report. Coal beds 2.5 or more feet thick are considered in calculating coal reserves, and of these, only beds containing 0.003 or more percent uranium are considered in calculating reserves of uranium in coal. Reserves of uranium in coal ash include those beds 2.5 or more feet thick that contain 0.015 or more percent uranium in coal ash. Measured and indicated coal reserves total about 700,000,000 short tons which contain about 2,600 short tons of uranium in the coal, or about 2,400 short tons of uranium in the coal ash. Strippable reserves, defined as reserves in beds beneath 60 or less feet of overburden, are about 250,000,000 short tons of coal containing about 1,100 short tons of uranium in coal, or about 600 tons of uranium in coal ash. The thickest coal beds underlie a relatively narrow belt that trends northwest and coincides approximately with the axis of the Red Desert syncline. The coal beds contain the most uranium on the east flank of the syncline near the southwesternmost edge of the Battle Spring formation (new). This formation is of early and middle Eocene age and consists predominantly of very coarse-grained arkosic sandstone which is highly permeable. It intertongues southwestward with the Tess permeable Green River and Wasatch formations. The Green River formation consists from youngest to oldest of the Morrow Creek and Laney shale members and the Tipton and Luman (new) tongues. The Wasatch formation interfingers with the Green River formation and consists from youngest to oldest of the Cathedral Bluffs, Niland, and Red Desert tongues. The latter two are here recognized for the first time and contain all the coal beds in the Wasatch formation. The Morrow Creek member of the Green River formation is of middle Eocene age. The Laney member and Cathedral Bluffs tongue of the Green River and Wasatch formation, respectively intertongue and are in part equivalent, and are of early or middle Eocene age. The other units are of early Eocene age. A broad gentle arch which is either the eastern extension of the Wamsutter arch, or a separate arch en echelon to it, separates the Washakie Basin the southeastern part of the map area from the Red Desert syncline in the northeastern part. The Red Desert syncline plunges gently northwest into the nearly circular structural Niland basin. The south flank of the Wamsutter(?) arch dips southeastward at an average rate of about 230 feet per mile. The northern flank of the arch dips northeastward at an average rate of about 140 feet per mile. North of the Niland basin, the structure is more complex and is dominated by a northwestwardtrending graben which parallels and includes the Cyclone Rim in the northern part of die map area. Schroeckingerite deposits in the northeastern part of the map area lie within this graben in a sequence of arkosic sandstone and clay shale stratigraphically equivalent to the lower part of the Cathedral Bluffs tongue of the Wasatch formation and to the uppermost part of the Tipton tongue of the Green River formation. Weakly radioactive tuffaceous sandstone beds of the Browns Park formation that probably once blanketed the entire Great Divide Basin are preserved a short distance north and northwest of the schroeckingerite deposits. The geologic settings of the schroeckingerite and uranium-bearing coal are similar and their source of uranium is probably the same. The uranium probably was leached from tuffaceous beds in the Browns Park formation and carried to its present site of deposition by groundwater whose circulation was guided by structure and changes in facies.

Wyoming↗
USGS2021

Simulation of groundwater budgets and travel times for watersheds on the north shore of Long Island Sound, with implications for nitrogen-transport studies

Aquatic systems in and around the Long Island Sound (LIS) provide a variety of ecological and economic benefits, but in some areas of the LIS, aquatic ecosystems have become degraded by excess nitrogen. A substantial fraction of the nitrogen inputs to the LIS are transported through the groundwater-flow system. Because groundwater travel times in surficial aquifers can exceed 100 years, multiyear lags are introduced between inputs at the water table in recharge areas and discharge to inland or coastal receiving waters. The U.S. Geological Survey, in cooperation with the Connecticut Department of Energy and Environmental Protection and the U.S. Environmental Protection Agency’s Long Island Sound Study, developed a steady-state groundwater model of the watersheds draining from the northern shore of the LIS for the purpose of calculating groundwater budgets and travel times to coastal waters. The model was developed by using the MODFLOW–NWT software and existing spatial data on aquifers, river networks, land-surface altitudes, land cover, groundwater recharge, and water use. Coastal waters were delineated on the basis of the National Wetland Inventory; all non-coastal waters were collectively termed “inland waters.” A coarse-resolution model was calibrated by using the PEST++ software, long-term records of water levels in 65 wells, stream altitudes from 477 streams, base-flow records for 14 streamgages that are relatively unaffected by withdrawals, and error metrics based on incorrectly simulated flooding and incorrectly simulated dry streams. The calibrated values were used in a fine-resolution model in which the mean absolute residuals were 4.5 meters for groundwater levels, 1.3 meters for stream altitudes, and 7,200 cubic meters per day (2.9 cubic feet per second) for base flow. About 89 percent of the terrestrial cells were correctly simulated with the water table below land surface, and nearly 90 percent of the cells representing streams were correctly simulated as having the water table above the stream bottom. Together, these metrics suggest that this model is robust for simulating regional-scale groundwater patterns. Simulated groundwater budgets were compiled for the entire study area, for each HUC12 (Hydrologic Unit Code no. 12) watershed and its adjacent coastal waters, if applicable, within the study area, and for 14 coastal-embayment watersheds. Most groundwater (90.6 percent of inflows) discharged to inland waters, with smaller fractions to coastal waters (7.0 percent) and well withdrawals (2.4 percent). When computed for HUC12 watersheds with coastal discharge, the portions of groundwater discharging to coastal waters ranged from 0.02 to 66 percent of groundwater outflows, with a median of 13 percent. Within priority-embayment watersheds, the portions of groundwater discharging to coastal waters ranged from 2 to 56 percent, with a median of 15 percent. Groundwater travel times also were simulated for the entire study area, for each HUC12 watershed and its adjacent coastal waters, if applicable, within the study area and for 14 priority coastal embayments. Within the entire study area, the median groundwater travel time was 1.9 years, with an interquartile range of 0.1 to 5.9 years. Sensitivity analysis of groundwater travel times within a subbasin in the study area indicates that the travel times are a function of the grid resolution, with coarser grids resulting in shorter median travel times. Travel times for groundwater discharging to coastal waters were similar to travel times for groundwater discharging to inland waters, with a median of 1.9 years. Median travel times for the HUC12 watersheds ranged from 0.9 to 53.5 years, with a median of 1.8 years. Among HUC12 watersheds that include coastal areas, travel times for groundwater discharging to coastal waters ranged from less than 1 to 61.6 years, with a median of 2.8 years. The HUC12 watersheds with the longest simulated travel times were in the urban area near New York City where the model performance is less accurate. Median travel times for groundwater discharging to coastal waters within the priority-embayment watersheds ranged from less than 1 to 18.6 years, with a median of 2.3 years. A more focused analysis was conducted for the Niantic River watershed to demonstrate the applicability of the regional model to local-scale nitrogen-transport analyses by using nitrogen-input and -attenuation rates from literature sources. Nitrogen inputs were estimated by using land-cover-based loading factors, and attenuation was estimated by using attenuation factors based on geologic zones and soil properties. Based on this analysis, groundwater transports an estimated 22,000 kilograms of nitrogen per year (2.9 kilograms of nitrogen per hectare per year) to streams, rivers, and coastal waters within the Niantic River watershed. Approximately 36 percent of discharging nitrogen is from atmospheric-deposition sources, 38 percent is from fertilizers, and 26 percent is from septic systems. Most of the groundwater-transported nitrogen (88 percent) discharges first to streams and rivers, with only 12 percent discharging directly to coastal waters. Travel times for groundwater-transported nitrogen ranged from less than 1 day to more than 100 years, with a median of 1.6 years.

Connecticut, New York, Rhode Island↗
USGS2024

An update of hydrologic conditions and distribution of selected constituents in water, eastern Snake River aquifer and perched groundwater zones, Idaho National Laboratory, Idaho, emphasis 2019–21

Since 1952, wastewater discharged to infiltration ponds (also called “percolation ponds”) and disposal wells at the Idaho National Laboratory (INL) has affected water quality in the eastern Snake River Plain (ESRP) aquifer and perched groundwater zones underlying the INL. The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy (DOE), maintains groundwater-monitoring networks at the INL to determine hydrologic trends and to delineate the movement of radiochemical and chemical wastes in both the aquifer and perched groundwater zones. This report presents an analysis of water-level and water-quality data collected from the ESRP aquifer and perched groundwater wells from the USGS groundwater monitoring networks during 2019–21. From March–May 2018 to March–May 2021, water levels in wells completed in the ESRP aquifer increased in the northern part of the INL and decreased in the southwestern part. Water-level increases ranged from 0.02 to 1.04 feet in the northern part and decreases ranged from 0.03 to 2.94 feet in the southwestern part of the INL. Detectable concentrations of radiochemical constituents in water samples from wells in the ESRP aquifer at the INL generally decreased or remained constant during 2019–21. Decreases in concentrations were attributed to radioactive decay, changes in waste-disposal methods, and dilution from recharge and underflow. In 2021, tritium was detected above reporting levels in water samples collected from 46 of 105 aquifer wells and ranged from 150±50 to 4,280±150 picocuries per liter (pCi/L). Tritium concentrations from eight wells completed in deep perched groundwater near the Advanced Test Reactor Complex (ATRC) generally were greater than or equal to the reporting level during at least one sampling event during 2019–21, and concentrations ranged from 160±50 to 2,097±107 pCi/L. Concentrations of strontium-90 in water from 12 of 45 aquifer wells sampled in 2021 exceeded the reporting level, and concentrations ranged from 2.5±0.7 to 299±6 pCi/L. During 2021, concentrations of strontium-90 from five wells completed in deep perched groundwater at the ATRC equaled or exceeded the reporting levels, and concentrations ranged from 3±0.9 pCi/L to 27.8±1.3 pCi/L. Concentrations of cesium-137 were less than the reporting level in all but one aquifer well, and concentrations of plutonium-238, plutonium-239, -240 (undivided), and americium-241 were less than the reporting level in water samples from all aquifer wells sampled during this study period. Dissolved chromium concentrations in water samples from 64 ESRP aquifer wells ranged from less than (<) 0.5 to 76.4 micrograms per liter (μg/L). During 2019–21, dissolved chromium was detected in water from wells completed in deep perched groundwater above the ESRP aquifer at the ATRC, and concentrations ranged from <1 to 82.1 μg/L. In 2021, concentrations of dissolved sodium in water from most ESRP aquifer wells in the southern part of the INL were greater than the western tributary groundwater background concentration of 8.3 milligrams per liter (mg/L). During 2021, dissolved sodium concentrations in water from 15 wells completed in deep perched groundwater ranged from 11.7 to 122.5 mg/L. Variations in sodium concentrations in aquifer wells and perched groundwater zones are attributed to either migration of remnant water from the former chemical-waste ponds or disposal volume and composition variability in percolation ponds installed in 2008. In 2021, concentrations of chloride in most water samples from ESRP aquifer wells south of the Idaho Nuclear Technology and Engineering Center (INTEC) and at the Central Facilities Area (CFA) exceeded background concentrations. Chloride concentrations in water from wells south of the INTEC have generally decreased because of discontinued chloride disposal to the legacy percolation ponds since 2002 when the discharge of wastewater was discontinued. During 2019–21, dissolved chloride concentrations in deep perched groundwater above the ESRP aquifer from 18 wells at the ATRC ranged from 8.15 to 231 mg/L. In 2021, sulfate concentrations in water samples from ESRP aquifer wells in the south-central part of the INL that exceeded the background concentration of sulfate, ranged from 21 to 141 mg/L. The greater-than-background concentrations in water from these wells are attributed to sulfate disposal at the ATRC infiltration ponds or the legacy INTEC percolation ponds. In 2021, sulfate concentrations in water samples from aquifer wells near the Radioactive Waste Management Complex (RWMC) were mostly greater than background concentrations. The maximum dissolved sulfate concentration in shallow perched groundwater near the ATRC was 575 mg/L in 2021. During 2021, dissolved sulfate concentrations in water from wells completed in deep perched groundwater near the cold waste ponds at the ATRC ranged from 22.3 to 519 mg/L. In 2021, concentrations of nitrate in water from most ESRP aquifer wells at and near the INTEC exceeded the western tributary groundwater background concentration of 0.655 mg/L. Concentrations of nitrate in aquifer wells southwest of INTEC and farther away from the influence of disposal areas and the Big Lost River, in intermittent source of surface water recharge to the aquifer, show a general decrease in nitrate concentration over time. Two aquifer wells south of INTEC show increasing trends that could result from wastewater beneath the INTEC tank farm being mobilized to the aquifer. During 2019–21, water samples from several ESRP aquifer wells were collected and analyzed for volatile organic compounds (VOCs). Twelve VOCs were detected, and 1–4 VOCs were detected in water samples from 10 wells. The most frequently detected VOCs include carbon tetrachloride (tetrachloromethane), trichloromethane, tetrachloroethene, 1,1,1-trichloroethane, and trichloroethene. In 2019–21, concentrations for all VOCs were less than their respective maximum contaminant levels (MCLs) for drinking water, except carbon tetrachloride in one well, trichloroethene in two wells, and vinyl chloride in one well. During 2019–21, variability and bias were evaluated from 34 replicate and 14 blank quality-assurance samples. Results from replicate analyses were investigated to evaluate sample variability. Constituents with acceptable reproducibility were major ions, trace elements, nutrients, and VOCs. All radiochemical constituents including gross alpha- and beta- radioactivity, strontium-90, cesium-137, and tritium, had acceptable reproducibility. Bias from sample contamination was evaluated from equipment, field, and source-solution blanks. Chloride and sulfate were detected slightly above their respective method detection limits in equipment and field blanks, but at concentrations well below the co-collected sample for that well. These chloride and sulfate detections in the field and equipment blanks were inconsequential because they weren’t detected above the analysis-specific variability for those constituents as determined by replicate sample result evaluation. None of the detections of nutrients and trace inorganic constituents were high enough to indicate environmental sample or analytical procedure bias.

Idaho↗
USGS2013

Characterization and data-gap analysis of surface-water quality data in the Piceance study area, western Colorado, 1959–2009

The U.S. Geological Survey, in cooperation with Federal, State, county, and industry partners, developed a Web-accessible common data repository to provide access to historical and current (as of August 2009) water-quality information (available on the Internet at http://rmgsc.cr.usgs.gov/cwqdr/Piceance/index.shtml ). Surface-water-quality data from public and private sources were compiled for the period 1931 to 2009 and loaded into the common data repository for the Piceance Basin. A subset of surface-water-quality data for 1959 to 2009 from the repository were compiled, reviewed, and checked for quality assurance for this report. This report contains data summaries, comparisons to water-quality standards, trend analyses, a generalized spatial analysis, and a data-gap analysis for select water-quality properties and constituents. Summary statistics and a comparison to standards were provided for 347 sites for 33 constituents including field properties, nutrients, major ions, trace elements, suspended sediment, Escherichia coli, and BTEX (benzene, toluene, ethylbenzene, and xylene). When sufficient data were available, trends over time were analyzed and loads were calculated for those sites where there were also continuous streamflow data. The majority of sites had information on field properties. Water temperature data was available for 316 sites where data were collected between 1959 and 2009. The only trend that was detected in temperature was an upward trend at the Gunnison River near Grand Junction, Colorado. There were 326 values out of a total of 32,006 values in the study area that exceeded the aquatic-life standard for daily maximum water temperature. For the entire study area, 196 sites had dissolved-oxygen data collected between 1970 and 2009, and median dissolved-oxygen concentrations ranged from 6.8 to11.2 milligrams per liter (mg/L). There were 185 concentrations that exceeded the dissolved oxygen aquatic-life standard out of a total of 11,248 values. The pH data were available for 276 sites, and median pH values ranged from 7.5 to 9.0. There were 241 values that exceeded the high pH standard and 13 values that were less than the low pH standard of the 16,790 values in the study area. Nutrients within the study area were not well represented in each basin and were often not being sampled currently. For the entire study area, 62 sites had nitrate data collected between 1958 and 2009, and median nitrate concentrations ranged from less than detection to 3.72 mg/L as nitrogen. The maximum contaminant level for domestic water supply for nitrate is 10 mg/L and was exceeded once in 3,736 samples. Total phosphorus was collected at 113 sites between 1974 and 2009, and median total phosphorus concentrations ranged from less than detection to 5.04 mg/L. The U.S. Environmental Protection Agency recommendation for phosphorus is less than 0.1 mg/L, and 1,469 of 4,842 samples exceeded this recommended standard. An upward trend in both nitrate and total phosphorus was detected in the White River above Coal Creek near Meeker, Colo. Standards for major ions exist only for chloride and sulfate. For the entire study area, 118 sites had both chloride and sulfate concentration data collected between 1958 and 2009. Median chloride concentrations ranged from 0.085 mg/L to 280 mg/L. Median sulfate concentrations ranged from 4.57 mg/L to 15,000 mg/L. Both chloride and sulfate domestic water-supply standards are 250 mg/L. There were 120 chloride concentrations and 1,111 sulfate concentration samples that exceeded these standards. A downward trend in dissolved solids was detected at the Colorado River near the Colorado-Utah state border and could be a result of salinity control work near Grand Junction, Colo. Trace elements were relatively well represented both temporally and spatially in the study area though the number of trace element samples per site was not typically enough to compute trends or loads except for selenium. There were 127 sites that had dissolved iron concentration data collected between 1961 and 2009, and median iron concentrations ranged from less than detection to 1,100 micrograms per liter (µg/L). The 30-day drinking-water standard for iron is 300 µg/L, and 203 samples exceeded the standard. Selenium was the best represented trace element with selenium concentration data collected at 197 sites between 1973 and 2009, and median selenium concentrations range from less than detection to 181 µg/L. The chronic standard of 4.6 µg/L for selenium concentrations was exceeded in 899 samples, and the acute aquatic-life standard of 18.4 µg/ for selenium was exceeded in 629 samples. High concentrations of selenium are of concern in the Lower Gunnison River Basin because of the combination of geologic formations and land use. There were significant downward trends in selenium at both main-stem sites on the Gunnison River at Delta, Colo., and the Gunnison River near Grand Junction, Colo. High selenium concentrations correlate with high salinity concentrations; thus, when salinity control efforts are conducted in selenium-rich areas in the Lower Gunnison River Basin, both salinity and selenium have the potential to decrease. Spatial, temporal, and analytical data gaps were identified in the study area. The spatial coverage of sampling sites could be expanded in the White River Basin by adding more tributary sites. No water-quality data exist for tributary streams in the area north of Rangely, Colo., where extensive energy development has occurred in a complex geologic setting. Douglas Creek has a drainage area of 425 square miles and has limited historic water-quality and water-quantity data. Limited data were available for field properties, major ions, nutrients, and trace elements on the main stem of the Colorado River between Glenwood Springs and Cameo, Colo. Nutrient data were minimally collected upstream from Colorado River at the Colorado-Utah state border and on the Gunnison River (major tributary in the reach). Approximately 30 percent of the samples for total phosphorus in the Lower Gunnison River Basin exceeded the recommended standard, yet there were insufficient data to do trends analysis in the Lower Gunnison River Basin except at the Gunnison near Grand Junction site. There is limited trace element data except for selenium in the Lower Gunnison River Basin. Additional sampling is necessary to understand the occurrence, concentrations, and loads of these constituents.

Colorado↗
USGS2020

An update of hydrologic conditions and distribution of selected constituents in water, Eastern Snake River Plain aquifer and perched groundwater zones, Idaho National Laboratory, Idaho, emphasis 2016–18

Since 1952, wastewater discharged to infiltration ponds (also called percolation ponds) and disposal wells at the Idaho National Laboratory (INL) has affected water quality in the eastern Snake River Plain (ESRP) aquifer and perched groundwater zones underlying the INL. The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, maintains groundwater-monitoring networks at the INL to determine hydrologic trends and to delineate the movement of radiochemical and chemical wastes in the aquifer and in perched groundwater zones. This report presents an analysis of water-level and water-quality data collected from the ESRP aquifer and perched groundwater wells in the USGS groundwater monitoring networks during 2016–18. From March–May 2015 to March–May 2018, water levels in wells completed in the ESRP aquifer declined in the northern part of the INL and increased in the southwestern part. Water-level decreases ranged from 0.5 to 3.0 feet (ft) in the northern part of the INL and increases ranged from 0.5 to 3.0 ft in the southwestern part. Detectable concentrations of radiochemical constituents in water samples from wells in the ESRP aquifer at the INL generally decreased or remained constant during 2016–18. Decreases in concentrations were attributed to radioactive decay, changes in waste-disposal methods, and dilution from recharge and underflow. In 2018, concentrations of tritium in water samples collected from 46 of 111 aquifer wells were greater than the reporting level of three times the sample standard deviation and ranged from 260±50 to 5,100±190 picocuries per liter (pCi/L). Tritium concentrations in water from 10 wells completed in deep perched groundwater above the ESRP aquifer near the Advanced Test Reactor (ATR) Complex generally were greater than or equal to the reporting level during at least one sampling event during 2016–18, and concentrations ranged from 150 ±50 to 12,900 ±200 pCi/L. Concentrations of strontium-90 in water from 17 of 60 ESRP aquifer wells sampled during April or October 2018 exceeded the reporting level, ranging from 2.2±0.7 to 363±19 pCi/L. Strontium-90 was not detected in the ESRP aquifer beneath the ATR Complex. During at least one sampling event during 2016–18, concentrations of strontium-90 in water from eight wells completed in deep perched groundwater above the ESRP aquifer at the ATR Complex equaled or exceeded the reporting levels, and concentrations ranged from 0.57±0.17 to 34.3±1.2 pCi/L. During 2016–18, concentrations of cesium-137 were less than the reporting level in all but one ESRP aquifer well, and concentrations of plutonium-238, -239, and -240 (undivided), and americium-241 were less than the reporting level in water samples from all ESRP aquifer wells. In April 2009, the dissolved chromium concentration in water from one ESRP aquifer well, USGS 65, south of the ATR Complex equaled the maximum contaminant level (MCL) of 100 micrograms per liter (μg/L). In April 2018, the concentration of chromium in water from that well had decreased to 76.0 μg/L, less than the MCL. Concentrations in water samples from 62 other ESRP aquifer wells sampled ranged from less than 0.6 to 21.6 μg/L. During 2016–18, dissolved chromium was detected in water from all wells completed in deep perched groundwater above the ESRP aquifer at the ATR Complex, and concentrations ranged from 4.2 to 98.8 μg/L. In 2018, concentrations of sodium in water from most ESRP aquifer wells in the southern part of the INL were greater than the western tributary background concentration of 8.3 milligrams per liter (mg/L). After the new percolation ponds were put into service in 2002 southwest of the Idaho Nuclear Technology and Engineering Center (INTEC), concentrations of sodium in water samples from the Rifle Range well increased steadily until 2008, when concentrations generally began decreasing. The increases and decreases were attributed to disposal variability in the new percolation ponds. During 2016–18, dissolved sodium concentrations in water from 18 wells completed in deep perched groundwater above the ESRP aquifer at the ATR Complex ranged from 6.37 to 143 mg/L. In 2018, concentrations of chloride in most water samples from ESRP aquifer wells south of the INTEC and at the Central Facilities Area exceeded the background concentrations. Chloride concentrations in water from wells south of the INTEC generally have decreased since 2002 when chloride disposal to the old percolation ponds was discontinued. After the new percolation ponds southwest of the INTEC were put into service in 2002, concentrations of chloride in water samples from one well rose steadily until 2008 then began decreasing. During 2016–18, dissolved chloride concentrations in deep perched groundwater above the ESRP aquifer from 18 wells at the ATR Complex ranged from 3.89 to 176 mg/L. In 2018, sulfate concentrations in water samples from ESRP aquifer wells in the south-central part of the INL exceeded the background concentration of sulfate and ranged from 22 to 151 mg/L. The greater-than-background concentrations in water from these wells probably resulted from sulfate disposal at the ATR Complex infiltration ponds or the old INTEC percolation ponds. In 2018, sulfate concentrations in water samples from wells near the Radioactive Waste Management Complex (RWMC) mostly were greater than background concentrations and could have resulted from well construction techniques and (or) waste disposal at the RWMC or the ATR complex. The maximum dissolved sulfate concentration in shallow perched groundwater above the ESRP aquifer near the ATR Complex was 215 mg/L in well CWP 3 in April 2016. During 2018, dissolved sulfate concentrations in water from wells completed in deep perched groundwater above the ESRP aquifer near the cold-waste ponds at the ATR Complex ranged from 65.8 to 171 mg/L. In 2018, concentrations of nitrate in water from most ESRP aquifer wells at and near the INTEC exceeded the western tributary background concentration of 0.655 mg/L. Concentrations of nitrate in wells southwest of the INTEC and farther away from the influence of disposal areas and the Big Lost River show a general decrease in nitrate concentration through time. Two wells south of the INTEC show increasing trends that could be the result of wastewater beneath the INTEC tank farm being mobilized to the aquifer. During 2016–18, water samples from several ESRP aquifer wells were collected and analyzed for volatile organic compounds (VOCs). Sixteen VOCs were detected. At least 1 and as many as 7 VOCs were detected in water samples from 15 wells. The primary VOCs detected include carbon tetrachloride, trichloromethane, tetrachloroethene, 1,1,1-trichloroethane, and trichloroethene. In 2016–18, concentrations for all VOCs were less than their respective MCLs for drinking water, except carbon tetrachloride in water from two wells and trichloroethene in one well. During 2016–18, variability and bias were evaluated from 37 replicate and 15 blank quality-assurance samples. Results from replicate analyses were investigated to evaluate sample variability. Constituents with acceptable reproducibility were major ions, trace elements, nutrients, and VOCs. All radiochemical constituents had acceptable reproducibility except for gross alpha- and beta-particle radioactivity. The gross alpha- and beta-particle radioactivity samples that did not meet reproducibility criteria had low concentrations. Bias from sample contamination was evaluated from equipment, field, and source-solution blanks. Cadmium had a concentration slightly greater than its reporting level in a source-solution blank, and chloride and ammonia had concentrations that were slightly greater than their respective reporting levels in field and equipment blanks. Subtracting concentrations of chloride and ammonia in field blanks from the concurrently collected equipment blank indicates that adjusted concentrations for chloride and ammonia in the equipment blanks were less than their respective reporting levels. Therefore, no sample bias was observed for any of the sample periods.

Idaho↗
USGS2013

An update of hydrologic conditions and distribution of selected constituents in water, eastern Snake River Plain aquifer and perched groundwater zones, Idaho National Laboratory, Idaho, emphasis 2009–11

Since 1952, wastewater discharged to infiltration ponds (also called percolation ponds) and disposal wells at the Idaho National Laboratory (INL) has affected water quality in the eastern Snake River Plain (ESRP) aquifer and perched groundwater zones underlying the INL. The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, maintains groundwater monitoring networks at the INL to determine hydrologic trends, and to delineate the movement of radiochemical and chemical wastes in the aquifer and in perched groundwater zones. This report presents an analysis of water-level and water-quality data collected from aquifer, multilevel monitoring system (MLMS), and perched groundwater wells in the USGS groundwater monitoring networks during 2009–11. Water in the ESRP aquifer primarily moves through fractures and interflow zones in basalt, generally flows southwestward, and eventually discharges at springs along the Snake River. The aquifer primarily is recharged from infiltration of irrigation water, infiltration of streamflow, groundwater inflow from adjoining mountain drainage basins, and infiltration of precipitation. From March–May 2009 to March–May 2011, water levels in wells generally declined in the northern part of the INL. Water levels generally rose in the central and eastern parts of the INL. Detectable concentrations of radiochemical constituents in water samples from aquifer wells or MLMS equipped wells in the ESRP aquifer at the INL generally decreased or remained constant during 2009–11. Decreases in concentrations were attributed to radioactive decay, changes in waste-disposal methods, and dilution from recharge and underflow. In 2011, concentrations of tritium in groundwater from 50 of 127 aquifer wells were greater than or equal to the reporting level and ranged from 200±60 to 7,000±260 picocuries per liter. Tritium concentrations from one or more discrete zones from four wells equipped with MLMS were greater than or equal to reporting levels in water samples collected at various depths. Tritium concentrations in water from wells completed in shallow perched groundwater at the Advanced Test Reactor Complex (ATR Complex) were less than the reporting levels. Tritium concentrations in deep perched groundwater at the ATR Complex equaled or exceeded the reporting level in 12 wells during at least one sampling event during 2009–11 at the ATR Complex. Concentrations of strontium-90 in water from 20 of 76 aquifer wells sampled during April or October 2011 exceeded the reporting level. Strontium-90 was not detected within the ESRP aquifer beneath the ATR Complex. During at least one sampling event during 2009–11, concentrations of strontium-90 in water from 10 wells completed in deep perched groundwater at the ATR Complex equaled or exceeded the reporting levels. During 2009–11, concentrations of plutonium-238, and plutonium-239, -240 (undivided), and americium-241 were less than the reporting level in water samples from all aquifer wells and in all wells equipped with MLMS. Concentrations of cesium-137 were equal to or slightly above the reporting level in 8 aquifer wells and from 2 wells equipped with MLMS. The concentration of chromium in water from one well south of the ATR Complex was 97 micrograms per liter (μg/L) in April 2011, just less than the maximum contaminant level (MCL) of 100 μg/L. Concentrations of chromium in water samples from 69 other wells sampled ranged from 0.8 μg/L to 25 μg/L. During 2009–11, dissolved chromium was detected in water from 15 wells completed in perched groundwater at the ATR Complex. In 2011, concentrations of sodium in water from most wells in the southern part of the INL were greater than the background concentration of 10 milligrams per liter (mg/L); the highest concentrations were at or near the Idaho Nuclear Engineering and Technology Center (INTEC). After the newpercolation ponds were put into service in 2002 southwest of the INTEC, concentrations of sodium in water samples from the Rifle Range well rose steadily until 2008, when the concentrations generally began decreasing. The increases and decreases were attributed to disposal variability in the new percolation ponds. Concentrations of sodium in most wells equipped with MLMS generally were consistent with depth. During 2011, dissolved sodium concentrations in water from 17 wells completed in deep perched groundwater at the ATR Complex ranged from 6 to 146 mg/L. In 2011, concentrations of chloride in most water samples from aquifer wells south of the INTEC and at the Central Facilities Area exceeded the background concentrations of 15 mg/L, but were less than the secondary MCL of 250 mg/L. Chloride concentrations in water from wells south of the INTEC have generally increased because of increased chloride disposal to the old percolation ponds since 1984 when discharge of wastewater to the INTEC disposal well was discontinued. After the new percolation ponds were put into service in 2002 southwest of the INTEC, concentrations of chloride in water samples from one well rose steadily until 2008 then began decreasing. Chloride concentrations in water from all but one well completed in the ESRP aquifer at or near the ATR Complex were less than background and ranged between 10 and 14 mg/L during 2011, similar to concentrations detected during the 2006–08 reporting period. During 2011, chloride concentrations in water from two aquifer wells at the Radioactive Waste Management Complex (RWMC) were slightly greater than concentrations detected during the 2006–08 reporting period. The vertical distribution of chloride concentrations in wells equipped with MLMS were generally consistent within zones during 2009–11 and ranged from about 8 to 20 mg/L. During April 2011, dissolved chloride concentrations in shallow perched groundwater at the ATR Complex ranged from 7 to 13 mg/L in water from three wells. Dissolved chloride concentrations in deep perched groundwater at the ATR Complex during 2011 ranged from 4 to 54 mg/L. In 2011, sulfate concentrations in water samples from 11 aquifer wells in the south-central part of the INL equaled or exceeded the background concentration of sulfate and ranged from 40 to 167 mg/L. The greater-than-background concentrations in water from these wells probably resulted from sulfate disposal at the ATR Complex infiltration ponds or the old INTEC percolation ponds. In 2011, sulfate concentrations in water samples from two wells near the RWMC were greater than background levels and could have resulted from well construction techniques and (or) waste disposal at the RWMC. The vertical distribution of sulfate concentrations in three wells near the southern boundary of the INL was generally consistent with depth, and ranged between 19 and 25 mg/L. The maximum dissolved sulfate concentration in shallow perched groundwater near the ATR Complex was 400 mg/L in well CWP 1 in April 2011. During 2009–11, the maximum concentration of dissolved sulfate in deep perched groundwater at the ATR Complex was 1,550 mg/L in a well located west of the chemical-waste pond. In 2011, concentrations of nitrate in water from most wells at and near the INTEC exceeded the regional background concentrations of 1 mg/L and ranged from 1.6 to 5.95 mg/L. Concentrations of nitrate in wells south of INTEC and farther away from the influence of disposal areas and the Big Lost River show a general decrease in nitrate concentrations through time. During 2009–11, water samples from 30 wells were collected and analyzed for volatile organic compounds (VOCs). Six VOCs were detected. At least one and up to five VOCs were detected in water samples from 10 wells. The primary VOCs detected include carbon tetrachloride, chloroform, tetrachloroethylene, 1,1,1-trichloroethane, and trichloroethylene. In 2011, concentrations for all VOCs were less than their respective MCL for drinking water, except carbon tetrachloride in water from two wells. During 2009–11, variability and bias were evaluated from 56 replicate and 16 blank quality-assurance samples. Results from replicate analyses were investigated to evaluate sample variability. Constituents with acceptable reproducibility were stable isotope ratios, major ions, nutrients, and VOCs. All radiochemical constituents and trace metals had acceptable reproducibility except for gross beta-particle radioactivity, aluminum, antimony, and cobalt. Bias from sample contamination was evaluated from equipment, field, container, and source-solution blanks. No detectable constituent concentrations were reported for equipment blanks of the thief samplers and sampling pipes or for the source-solution and field blanks. Equipment blanks of bailers had detectable concentrations of strontium-90, sodium, chloride, and sulfate, and the container blank had a detectable concentration of dichloromethane.

Idaho↗
USGS2020

Sediment and chemical contaminant loads in tributaries to the Anacostia River, Washington, District of Columbia, 2016–17

A study was conducted by the U.S. Geological Survey (USGS) in cooperation with the Washington, D.C., Department of Energy & Environment to estimate the loads of suspended-sediment-bound chemical compounds in five gaged tributaries and four ungaged tributaries of the Anacostia River (known locally as “Lower Anacostia River”) in Washington, D.C. Tributaries whose discharge is measured by the USGS are the Northeast and Northwest Branches of the Anacostia River, referred to in this report as “Northeast Branch” (NEB) and “Northwest Branch” (NWB), respectively; Watts Branch (WB); and Hickey Run (HR). A USGS streamflow-gaging station was established in 2016 on Beaverdam Creek (known locally as “Lower Beaverdam Creek” [LBDC]) to support this study. The ungaged streams studied include Nash Run; Pope Branch; an unnamed stream at Fort DuPont, referred to in this report as “Fort DuPont Creek”; and an unnamed stream at Fort Stanton, referred to in this report as “Fort Stanton Creek.” The gaged streams were sampled during four to five storms and two low-flow events during January, March, May, and July 2017. The ungaged streams were sampled during one storm and one low-flow event during July 2017. Storm sampling involved collecting large-volume (60- to 70-liter) composite samples, then removing sediment by filtration in the laboratory. Low-flow samples were obtained by filtering streamwater directly in the field. Continuously recording data sondes were deployed throughout the study to measure turbidity and other water-quality characteristics. During sampling, multiple discrete samples of streamwater were collected to determine suspended-sediment concentration (SSC) and particulate organic carbon (POC) concentration. Shortly after each storm, bed sediment was collected for chemical analysis. Sediment samples were analyzed for 209 polychlorinated biphenyl (PCB) congeners; 35 polyaromatic hydrocarbon (PAH) compounds, including 20 nonalkylated and 15 alkylated species; and 20 organochlorine pesticide (OP) compounds. Sediment from one storm was analyzed for 23 metals. Relations were developed among turbidity, discharge, and measured SSC by using multiple linear regression of log-transformed data. These relations were used to estimate SSC from continuous records of discharge and turbidity and were subsequently used to estimate sediment loads for the 2017 calendar year. USGS continuous records of turbidity in NEB, NWB, Watts Branch, and Hickey Run were available for 2013–17, which allowed sediment loads to be calculated for these years. Sediment loads for the ungaged streams were estimated by using loads measured in Watts Branch adjusted on the basis of stream-basin areas. Sediment loads for 2017 total 3.10×10 7 kilograms (kg), with 1.02×107 kg (33 percent of total) from the NEB, 1.55×10 7 kg (50 percent) from the NWB, 4.45×10 6 kg (14 percent) from LBDC, 5.62×10 5 kg (2 percent) from Watts Branch, and 2.82×10 5 kg (1 percent) from Hickey Run. Sediment yields were highest from NWB and LBDC (3.13×10 5 kilograms per year per square mile [kg/yr/mi 2 ] and 3.01 kg/yr/mi 2 , respectively). As a result of gaps in turbidity and discharge data, the load for LBDC reported here was calculated from measurements representing only 88 percent of the year (2017), and thus underestimates the actual load. All other gaged tributaries had datasets covering 100 percent of the year and are considered to fully represent actual loads. Estimated sediment loads for the ungaged streams during 2017 total 3.5×10 5 kg, with 1.2×10 5 kg from Nash Run, 6.2×10 4 kg from Pope Branch, 1.1×10 5 kg from Fort DuPont Creek, and 5.6×10 4 kg from Fort Stanton Creek. Concentrations of PCBs, PAHs, and chlorinated pesticides in streamwater are presented for stormflow and low-flow conditions. Average concentrations (in stormflow and low-flow samples) of total PCBs (sum of all congeners, including coelutions) are 5.9 micrograms per kilogram (µg/kg) for NEB, 6.6 µg/kg for NWB, 130 µg/kg for LBDC, 34 µg/kg for Watts Branch, and 69 µg/kg for Hickey Run. Average concentrations of total PAHs (tPAH) (total of nonalkylated and alkylated species) are 2,000 µg/kg for NEB, 3,300 µg/kg for NWB, 2,200 µg/kg for LBDC, 2,400 µg/kg for Watts Branch, and 18,000 µg/kg for Hickey Run. tPAH concentrations among the ungaged streams were highest in Nash Run (5,500 µg/kg); concentrations in the other ungaged streams were less than (<) 700 µg/kg. The general magnitude of tPCB and tPAH concentrations in streamwater samples was low-flow samples greater than (>) stormflow samples greater than or equal to (≥) bed-sediment samples. PCB congener profiles in the three types of samples were nearly identical in each stream and were similar in all streams except for LBDC, where the dominant PCBs shifted to the lighter di- through tetra- homologs. LBDC showed higher tPCB concentrations and a distinct congener profile from the other streams. The similarity in congener makeup supported that averaging PCB concentrations in stormflow and low-flow samples was appropriate for calculating chemical loads. Loads of tPCB, tPAH (total of alkylated and nonalkylated forms), and pesticides were estimated for each stream by multiplying average contaminant concentrations by the respective sediment loads. Total PCB loads for 2017 were estimated to be 820 grams (g) with 8 percent (60 g) from NEB, 12 percent (95 g) from NWB, 75 percent (590 g) from LBDC, 3 percent (25 g) from Watts Branch, and 2.5 percent (19 g) from Hickey Run. PCB toxicity totaled 3.8×10 −3 µg/kg, with the largest contribution (47 percent) derived from LBDC. Total PAH loads (sum of alkylated and nonalkylated forms) for 2017 were estimated to be 89,000 g, with 23 percent (20,000 g) from NEB, 59 percent (52,000 g) from NWB, 11 percent (9,800 g) from LBDC, 2 percent (1,400 g) from Watts Branch, and 6 percent (5,200 g) from Hickey Run. These results indicate that the largest contributor (75 percent) of PCBs to the Anacostia River is LBDC, although it contributes only 15 percent of the sediment and its basin area represents only 10 percent of the area of the Anacostia River watershed. The majority of the PAH load originates from NWB (59 percent of total) and NEB (22 percent). The ungaged tributaries contribute extremely small loads of PCBs and PAHs, totaling 8.1 g and 765 kg, respectively. More than 94 percent of the total load from the ungaged tributaries is derived from the Nash Run Basin. Various organochlorine pesticides were present in suspended and bed sediment from all gaged and ungaged tributaries; however, elevated detection levels associated with the analytical methods resulted in numerous unquantifiable concentrations in the suspended-sediment samples. Only the pesticide chlordane was found in measurable concentrations in all gaged tributaries. As a result, in this report, a combination of analytical data from suspended-sediment and bed-sediment samples was used to estimate the maximum pesticide loading for each tributary. Chlordane was the principal compound present in the gaged tributaries; the highest average concentration (average of stormflow and low-flow samples from each stream) was 62 µg/kg in sediment from Watts Branch. Chlordane loads for 2017 totaled 1,100 g, of which 7 percent (430 g) was from NEB, 28 percent (320 g) was from NWB, 28 percent (310 g) was from LBDC, 5 percent (56 g) was from Watts Branch, and 1 percent (11 g) was from Hickey Run. Chlordane was not present in suspended or bed sediment from any of the ungaged tributaries. Loads of the other pesticides were estimated by using the highest concentration measured in the combined suspended-sediment and bed-sediment data for each stream. Notable loads include dieldrin (860 g from NWB), methoxychlor (205 g from LBDC), endrin aldehyde (150 g from NWB), and 4,4-DDT (79 g from Watts Branch). Compared with pesticide loads from the gaged streams, those from the ungaged streams were minimal, with only the Pope Branch contribution exceeding 1 gram per year for 4,4-DDE (1.05 g) and 4,4’-DDT (1.3 g). The results of this study show that the dominant source of PCBs and chlordane is LBDC, despite its relatively small basin area. PAHs are ubiquitous throughout the study area, with the largest sources being NEB and NWB; this finding is a result of the large sediment load originating from these basins. The small, ungaged streams supply only minimal PCB and PAH loads, with Nash Run being the largest contributor.

District of Columbia↗