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At least 1,423 records · Page 79Linked to original sources
USGS2014

Introduction to selected references on fossil fuels of the central and southern Appalachian basin

The Appalachian basin contains abundant coal and petroleum resources that have been studied and extracted for at least 150 years. In this volume, U.S. Geological Survey (USGS) scientists describe the geologic framework and geochemical character of the fossil-fuel resources of the central and southern Appalachian basin. Separate subchapters (some previously published) contain geologic cross sections; seismic profiles; burial history models; assessments of Carboniferous coalbed methane and Devonian shale gas; distribution information for oil, gas, and coal fields; data on the geochemistry of natural gas and oil; and the fossil-fuel production history of the basin. Although each chapter and subchapter includes references cited, many historical or other important references on Appalachian basin and global fossil-fuel science were omitted because they were not directly applicable to the chapters.

Appalachian basin↗
USGS1980

Shallow, low-permeability reservoirs of northern Great Plains: Assessment of their natural gas resources.

Major resources of natural gas are entrapped in low-permeability, low-pressure reservoirs at depths less than 4,000 ft (1,200 m) in the northern Great Plains. This shallow gas is the product of the immature stage of hydrocarbon generation and is referred to as biogenic gas. Prospective low-permeability, gas-bearing reservoirs range in age from late Early to Late Cretaceous and include most of the section from the base of the Mowry Shale to the top of the Judith River Formation. For detailed examination, the potential reservoir section was divided into five intervals represented by one or more formations and their correlatives. The intervals selected correspond to (1) Mowry Shale, (2) Belle Fourche Shale and Greenhorn Formation, (3) Carlile Shale, (4) Niobrara and Telegrap Creek Formations and Eagle Sandstone, and (5) Claggett Shale and Judith River Formation and their equivalents. Within each interval, several different facies are developed. The following facies were identified and mapped for each interval: nonmarine rocks, coastal sandstones, shelf sandstones, siltstones, shales, and chalks. Two types of shelf sandstone were differentiated but generally not mapped separately because of lack of well log control. The "sand ridge" type has reservoir properties comparable to coastal sandstones and occurs as isolated tongues as much as 75 ft (23 m) thick. The second type of shelf sandstone is in beds commonly less than 1 in. (3 cm) thick which are interbedded with shale and contain a high content of allogenic silt- and clay-size material. It is impossible to differentiate these individual beds on conventional well logs. The siltstone and shale facies are grouped to ether because conventional logs cannot distinguish between these two rock types, particularly when they are interbedded. For future evaluation of natural gas resources from low-permeability reservoirs, it will be necessary to differentiate between the siltstone and shale facies and to identify individual beds, particularly very thin ones, within the shelf sandstone facies. Each facies contains distinct reservoir types, some of which are low in permeability. The most promising low-permeability reservoirs are developed in the shelf sandstone, siltstone, and chalk facies. Reservoirs within these facies are particularly attractive because they are enveloped by thick sequences of shale which serve as both a source and a seal for the gas. When naturally fractured, these shales also may be low-productivity gas reservoirs similar to the Devonian shales of the Appalachian basin. In addition, facies with low-permeability reservoirs are present over most of the study area when maps for all of the intervals are combined. Natural gas is produced from low-permeability reservoirs in the northern Great Plains in the southern part of western Canada. Established production covers an area of approximately 8,000 sq mi (20,700 sq km) where reported recoverable reserves average as much as 2 Bcf sq mi. Using these reserve data as an analog, the United States portion may contain resources of natural gas in excess of 100 Tcf. The volume of recoverable gas in the United States will depend on the development of improved recovery technology and higher gas prices relative to costs.

northern Great Plains↗
USGS1977

Selected water-level records for western Oklahoma, 1975-1976

A systematic program to collect water-level records in Oklahoma began in 1937. The objectives of this program are (1) to provide long-term records of water-level fluctuations in representative wells, (2) to facilitate the prediction of water-level trends and indicate future availability of ground-water supplies, and (3) to provide information for use in basic research. Water-level data in table 1 are from wells that are measured annually, prior to the irrigation season to achieve the most natural representation of the static water level. Water level measurements listed in the column under 1975 may have been made during December, 1974 or January or February, 1975. Measurements listed in the column 1976 may have been made during December 1975 or January or February 1976. Figure 1 shows the counties and number of wells therein, where data were obtained for this report. The stratigraphic nomenclature and age determinations used in this report are those accepted by the Oklahoma Geological Survey and do not necessarily agree with those at the U.S. Geological Survey. Records of water levels in Oklahoma are collected through a cooperative program by the U.S. Geological Survey and the Oklahoma Water Resources Board. The records are tabulated and published by the U.S. Geological Survey on an annual basis.

Oklahoma↗
USGS1977

Selected water-level records for western Oklahoma, 1950-1975

A systematic program to collect water-level records in Oklahoma began in 1937. The objectives of this program are (1) to provide long-term records of water-level fluctuations in representative wells, (2) to facilitate the prediction of water-level trends and indicate future availability of ground-water supplies, and (3) to provide information for use in basic research. Water-level data in table 1 are from wells that are measured annually, prior to the irrigation season to achieve the most natural representation of the static water level. Figure 1 shows the counties and number of wells therein, where data were obtained for this report. The stratigraphic nomenclature and age determinations used in this report are those accepted by the Oklahoma Geological Survey and do not necessarily agree with those at the U.S. Geological Survey. Records of water levels in Oklahoma are collected through a cooperative program by the U.S. Geological Survey and the Oklahoma Water Resources Board. The records are tabulated and published by the U.S. Geological Survey on an annual basis.

Open-File Report↗
USGS1988

Selected hydrologic data for Pahvant Valley and adjacent areas, Millard County, Utah, 1987

This report contains hydrologic data collected in Pahvant Valley and adjacent areas from 1909 to 1987. The report area is mainly comprised of Pahvant Valley on the east and the southern part of the Sevier Desert on the west (plate 1). The area is in west-central Utah, within the Basin and Range physiographic province, and includes about 1,600 square miles. Most of the data in this report were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights, from 1985 to 1987. Some of the earlier data were previously published by Enright and Holmes (1982), Meinzer (1911), Mower (1963 and 1967), and Mundorff (1970). The purpose of this report is to provide hydrologic data for use by the general public and by officials managing the area's water resources, and to supplement interpretive reports for the area. Tables 1 to 6 contain information about wells including well completions, drillers' logs, water levels, flowing-well discharges, and chemical quality. Spring and surfacewater site data are listed in tables 7 to 9. Hydrologic-data sites are shown on plate 1.

Utah↗
USGS2023

A global ecological signal of extinction risk in marine ray-finned fishes (class Actinopterygii)

Many marine fish species are experiencing population declines, but their extinction risk profiles are largely understudied in comparison to their terrestrial vertebrate counterparts. Selective extinction of marine fish species may result in rapid alteration of the structure and function of ocean ecosystems. In this study, we compiled an ecological trait dataset for 8,185 species of marine ray-finned fishes (class Actinopterygii) from FishBase and used phylogenetic generalized linear models to examine which ecological traits are associated with increased extinction risk, based on the International Union for the Conservation of Nature Red List. We also assessed which threat types may be driving these species toward greater extinction risk and whether threatened species face a greater average number of threat types than non-threatened species. We found that larger body size and/or fishes with life histories involving movement between marine, brackish, and freshwater environments are associated with elevated extinction risk. Commercial harvesting threatens the greatest number of species, followed by pollution, development, and then climate change. We also found that threatened species, on average, face a significantly greater number of threat types than non-threatened species. These results can be used by resource managers to help address the heightened extinction risk patterns we found.

Cambridge Prisms: Extinction↗
USGS2009

Ground-Water Quality Data in the Upper Santa Ana Watershed Study Unit, November 2006-March 2007: Results from the California GAMA Program

Ground-water quality in the approximately 1,000-square-mile Upper Santa Ana Watershed study unit (USAW) was investigated from November 2006 through March 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The Upper Santa Ana Watershed study was designed to provide a spatially unbiased assessment of raw ground-water quality within USAW, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 99 wells in Riverside and San Bernardino Counties. Ninety of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells). Nine wells were selected to provide additional understanding of specific water-quality issues identified within the basin (understanding wells). The ground-water samples were analyzed for a large number of organic constituents (volatile organic compounds [VOCs], pesticides and pesticide degradates, pharmaceutical compounds, and potential wastewater-indicator compounds), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], 1,4-dioxane, and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, carbon-14, and stable isotopes of hydrogen and oxygen in water) and dissolved noble gases also were measured to help identify sources and ages of the sampled ground water. Dissolved gases, and isotopes of nitrogen gas and of dissolved nitrate also were measured in order to investigate the sources and occurrence of nitrate in the study unit. In total, nearly 400 constituents and water-quality indicators were investigated for this study. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. Volatile organic compounds (VOCs) were detected in more than 80 percent of USAW grid wells. Most VOCs detected were at concentrations far less than thresholds established for drinking water to protect human health; however, six wells had VOC concentrations above health-based thresholds. Twenty-four of the 85 VOCs investigated were detected in the study unit;11 were detected in more than 10 percent of the wells. The VOCs detected above health-based thresholds in at least one well were dibromochloropropane (DBCP), tetrachloroethene (PCE), trichloroethene (TCE), carbon tetrachloride, and 1,1-dichoroethene. Pesticide compounds were detected in more than 75 percent of the grid wells. However, of the 134 different pesticide compounds investigated, 13 were detected at concentrations greater than their respective long-term method detection limits, and only 7 compounds (all herbicides or herbicide degradates) were detected in more than 10 percent of the wells. No pesticide compound was detected above its health-based threshold, although thresholds exist for fewer than half of the pesticide compounds investigat

Data Series↗
USGS2015

Detailed interpretation of aeromagnetic data from the Patagonia Mountains area, southeastern Arizona

The induced magnetic field and the remanent magnetic field of rock masses are important to geologic modeling based on Earth’s magnetic field data. The orientation of the induced magnetic field is approximately parallel to the orientation of Earth’s geomagnetic field and its intensity can be derived from measured magnetic susceptibilities of rocks in a study area. The orientation and intensity of the natural remanent magnetic field is much harder to determine; therefore, few investigators have included magnetic remanence as a contributing factor to studies of continental magnetic anomalies. All rocks have remanent magnetism and, in intrusive or volcanic rocks, this component of the total magnetic intensity of the Earth’s magnetic field can be as large as or larger than the induced component. The Patagonia Mountains in southeastern Arizona were selected to produce a subsurface geologic model from aeromagnetic data by incorporating physical properties of rock including measured magnetic susceptibilities, estimated remanent magnetic field orientations and intensities, a known association of intrusive events, and information from existing geologic mapping. The result is a model of geology at depth that may better represent reality than previous poorly substantiated cross sectional models. This new model includes concealed intrusive rocks and defines areas where concealed mineral deposits may be found. It also shows that volcanic rocks might occupy basins at relatively shallow depths in basins with low aeromagnetic anomalies. Euler deconvolution depth estimates derived from aeromagnetic data with a structural index of 0 show that mapped faults on the northern margin of the Patagonia Mountains generally agree with the depth estimates in the new geologic model. The deconvolution depth estimates also show that the concealed Patagonia Fault southwest of the Patagonia Mountains is more complex than recent geologic mapping represents. Additionally, Euler deconvolution depth estimates with a structural index of 2 locate many potential intrusive bodies that might be associated with known and unknown mineralization.

Arizona↗
USGS1992

Monitoring radionuclide and suspended-sediment transport in the Little Colorado River basin, Arizona and New Mexico, USA

From July 1988 through September 1991, radionuclide and suspended-sediment transport were monitored in ephemeral streams in the semiarid Little Colorado River basin of Arizona and New Mexico, USA, where in-stream gross-alpha plus gross-beta activities have exceeded Arizona's Maximum Allowable Limit through releases from natural weathering processes and from uranium-mining operations in the Church Rock Mining District, Grants Mineral Belt, New Mexico. Water samples were collected at a network of nine continuous-record streamgauges equipped with microprocessor-based satellite telemetry and automatic water-sampling systems, and six partial-record streamgauges equipped with passive water samplers. Analytical results from these samples were used to calculate transport of selected suspended and dissolved radionuclides in the uranium-238 and thorium-232 decay series.

Arizona;New Mexico↗
USGS1987

Changes in water quality of Michigan streams near urban areas, 1973-84

Monthly water-quality monitoring of streams was begun by Michigan Department of Natural Resources in 1973 to (1) determine temporal and spatial variability, (2) detect long-term trends, and (3) describe changes in water quality near urban areas. This report provides a statistical analysis and summary of data collected from 1973 through 1984. Concentrations and discharges of nine commonly measured water-quality constituents and specific conductance are examined. Twenty-three sites on inland streams (streams draining basins wholly within Michigan) and 20 sites on Detroit River are discussed. The changes in water quality in 9 rivers near 12 urban areas in Michigan's southern Lower Peninsula and the relation between streamflow and selected waterquality characteristics, including phosphorus, chloride, sulfate, nitrogen, specific conductance, and solid residues are described. Results show that the median dissolved-solids concentration in Clinton River downstream from Pontiac exceed Michigan's 1986 stream water-quality standard. Among inland streams, constituent concentrations and discharges generally were greatest in Saginaw River and least in Grand River upstream from Jackson. Upstream from Detroit, constituent concentrations in Detroit River did not differ appreciably across the Windmill Point Transect; downstream from Detroit, at the Fermi Transect across Detroit River, most constituent concentrations were higher near the American and Canadian shorelines. Among urban areas, greatest changes in constituent concentrations occurred in the Grand River near Jackson, in the Clinton River near Pontiac, and in the Tittabawassee River near Midland; the least changes in constituent concentrations occurred in the Saginaw River near Saginaw, in Detroit River near Detroit and the Kalamazoo River near Battle Creek. Greatest changes in constituent discharges occurred in the Detroit River near the Detroit area; the least occurred in the Chippewa River near Mount Pleasant. Of the 230 regressions between streamflow and constituent concentrations in inland streams, about 73 percent were significant at the 5-percent level. The degree of the correlation and nature of the relation varied among sites and constituents. Generally, higher streamflows were associated with lower concentrations. Changes in streamflow and changes in constituent concentrations near urban areas were correlated in 57 percent of the 120 analyses. Generally, higher changes in streamflow were associated with lower changes in concentrations.

Michigan↗
USGS2015

Natural soil reservoirs for human pathogenic and fecal indicator bacteria

Soils receive inputs of human pathogenic and indicator bacteria through land application of animal manures or sewage sludge, and inputs by wildlife. Soil is an extremely heterogeneous substrate and contains meso- and macrofauna that may be reservoirs for bacteria of human health concern. The ability to detect and quantify bacteria of human health concern is important in risk assessments and in evaluating the efficacy of agricultural soil management practices that are protective of crop quality and protective of adjacent water resources. The present chapter describes the distribution of selected Gram-positive and Gram-negative bacteria in soils. Methods for detecting and quantifying soilborne bacteria including extraction, enrichment using immunomagnetic capture, culturing, molecular detection and deep sequencing of metagenomic DNA to detect pathogens are overviewed. Methods for strain phenotypic and genotypic characterization are presented, as well as how comparison with clinical isolates can inform the potential for human health risk.

Book chapter↗
USGS2006

Monitored natural attenuation of chlorinated solvents: Moving beyond reductive dechlorination

Monitored natural attenuation (MNA), while a remedy of choice for many sites, can be challenging when the contaminants are chlorinated solvents. Even with many high-quality technical guidance references available, there continue to be challenges implementing MNA at some chlorinated solvent sites. The U.S. Department of Energy, as one organization facing such challenges, is leading a project that will incorporate developing concepts and tools into the existing toolbox for selecting and implementing MNA as a remediation option at sites with chlorinated solvent contamination. The structure and goals of this project were introduced in an article in the Winter 2004 issue of Remediation (Sink et al., 2004). This article is a summary of the three technical areas being developed through the project: mass balance, enhanced attenuation, and characterization and monitoring supporting the first two areas.

Remediation Journal↗
USGS1988

Using laser micro mass spectrometry with the LAMMA-1000 instrument for monitoring relative elemental concentrations in vitrinite

The variation in relative elemental concentrations among a series of coal macerals belonging to the vitrinite maceral group was determined using laser micro mass spectrometry (LAMMS). Variations in Ba, Cr, Ga, Sr, Ti, and V concentrations among the coals were determined using the LAMM A-1000 instrument. LAMMS analysis is not limited to these elements; their selection illustrates the application of the technique. Ba, Cr, Ga, Sr, Ti, and V have minimal site-to-site variance in the vitrinite macerals of the studied coals as measured by LAMMS. The LAMMS data were compared with bulk elemental data obtained by instrumental neutron activation analysis (INAA) and D. C. arc optical emission spectroscopy (DCAS) in order to determine the reliability of the LAMMS data. The complex nature of the ionization phenomena in LAMMS and the lack of standards characterized on a microscale makes obtaining quantitative elemental data within the ionization microvolume difficult; however, we demonstrate that the relative variation of an element among vitrinites from different coal beds in the eastern United States can be observed using LAMMS in a "bulk" mode by accumulating signal intensities over several microareas of each vitrinite. Our studies indicate gross changes (greater than a factor of 2 to 5 depending on the element) can be monitored when the elemental concentration is significantly above the detection limit. "Bulk" mode analysis was conducted to evaluate the accuracy of future elemental LAMMS microanalyses. The primary advantage of LAMMS is the inherent spatial resolution, ~ 20 ??m for coal. Two different vitrite bands in the Lower Bakerstown coal bed (CLB-1) were analyzed. The analysis did not establish any certain concentration differences in Ba, Cr, Ga, Sr, Ti, and V between the two bands. ?? 1988 Springer-Verlag.

Mikrochimica Acta↗
USGS2009

Conservation of northern bobwhite on private lands in Georgia, USA under uncertainty about landscape-level habitat effects

Large-scale habitat enhancement programs for birds are becoming more widespread, however, most lack monitoring to resolve uncertainties and enhance program impact over time. Georgia?s Bobwhite Quail Initiative (BQI) is a competitive, proposal-based system that provides incentives to landowners to establish habitat for northern bobwhites (Colinus virginianus). Using data from monitoring conducted in the program?s first years (1999?2001), we developed alternative hierarchical models to predict bobwhite abundance in response to program habitat modifications on local and regional scales. Effects of habitat and habitat management on bobwhite population response varied among geographical scales, but high measurement variability rendered the specific nature of these scaled effects equivocal. Under some models, BQI had positive impact at both local farm scales (1, 9 km2), particularly when practice acres were clustered, whereas other credible models indicated that bird response did not depend on spatial arrangement of practices. Thus, uncertainty about landscape-level effects of management presents a challenge to program managers who must decide which proposals to accept. We demonstrate that optimal selection decisions can be made despite this uncertainty and that uncertainty can be reduced over time, with consequent improvement in management efficacy. However, such an adaptive approach to BQI program implementation would require the reestablishment of monitoring of bobwhite abundance, an effort for which funding was discontinued in 2002. For landscape-level conservation programs generally, our approach demonstrates the value in assessing multiple scales of impact of habitat modification programs, and it reveals the utility of addressing management uncertainty through multiple decision models and system monitoring.

Landscape Ecology↗
USGS1979

Robust estimation of population size when capture probabilities vary among animals

A model is given for multiple recapture studies on closed populations which allows capture probabilities to vary among individuals. The capture probability of each individual is assumed to be constant over time. Based on this model we give a nonparametric estimation procedure for population size. The estimator involves selecting one of a sequence of estimator which are each linear combinations of the capture frequencies. The individual estimators are derived from the generalized jackknife method. We also give a goodness of fit test for the model's assumption that individual capture probabilities do not change during the study. The robustness of the estimation procedure is investigated with a simulation study. By virtue of this study, and the theoretical nature of the estimator, it is judged to be robust to moderate variations in individual capture probabilities which may occur in commonly used short-term livetrapping studies.

Ecology↗
USGS2009

Decision Support System for Evaluation of Gunnison River Flow Regimes With Respect To Resources of the Black Canyon of the Gunnison National Park

This report describes and documents a decision support system for the Gunnison River in Black Canyon of the Gunnison National Park. It is a macro-embedded EXCEL program that calculates and displays indicators representing valued characteristics or processes in the Black Canyon based on daily flows of the Gunnison River. The program is designed to easily accept input from downloaded stream gage records or output from the RIVERWARE reservoir operations model being used for the upstream Aspinall Unit. The decision support system is structured to compare as many as eight alternative flow regimes, where each alternative is represented by a daily sequence of at least 20 calendar years of streamflow. Indicators include selected flow statistics, riparian plant community distribution, clearing of box elder by inundation and scour, several measures of sediment mobilization, trout fry habitat, and federal reserved water rights. Calculation of variables representing National Park Service federal reserved water rights requires additional secondary input files pertaining to forecast and actual basin inflows and storage levels in Blue Mesa reservoir. Example input files representing a range of situations including historical, reconstructed natural, and simulated alternative reservoir operations are provided with the software.

Open-File Report↗
USGS2023

Distribution of chlorinated volatile organic compounds and per- and polyfluoroalkyl substances in groundwater and surface water at the former Naval Air Warfare Center, West Trenton, New Jersey, 2018

Groundwater wells and surface-water storm sewers contaminated with volatile organic compounds (VOCs) and per- and polyfluoroalkyl substances (PFASs) at the former Naval Air Warfare Center (NAWC) site in West Trenton, New Jersey were sampled in 2018 as part of the Navy’s long-term monitoring program. Trichloroethene (TCE), cis-1,2-dichloroethene (cisDCE), and vinyl chloride concentrations were plotted in map view and selected cross sections to elucidate the vertical and horizontal extent and distribution of contamination, along with a tabular comparison between 2018 and previous analytical results. The 2018 data showed that the areas of VOC contamination (>1 microgram per liter) decreased slightly on the north and east sides of the NAWC site from previous sampling dates; these decreases are attributed to the influence of the pump-and-treat system, natural attenuation processes, and various engineered bioaugmentation experiments that have occurred onsite. Off-site groundwater samples indicate the VOC contaminated groundwater is likely hydraulically constrained by the pump-and-treat system and appears to not be moving offsite to the south and west of NAWC. Only one offsite well, 50BR, located along the eastern margin of the site, was found to have detectable TCE and cisDCE concentrations, indicating that VOC contamination continues to migrate a short distance offsite to the east. Detectable VOC contamination was found in wells as deep as 200 and 221 feet on both the east and west sides of the NAWC site. Comparisons of present-day data to data from past sampling efforts indicate that TCE concentrations in most wells have decreased slowly over time. Results from surface-water samples indicate that VOCs enter surface water predominantly through the West Ditch drainage system. Concentrations and fluxes of VOCs are higher when groundwater levels are higher, indicating contaminated groundwater discharges into the surface water system. Higher VOC concentrations at the Interceptor site relative to other sites in the West Ditch indicate the contamination in the West Ditch system is likely caused by contaminated groundwater discharging to the West Ditch storm sewer near manhole MH-140 when water table levels are high. The pump-and-treat extraction wells at the former NAWC site were sampled for per- and polyfluoroalkyl substances (PFAS) in 2018. The suite of reported PFAS include perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid, and perfluorobutane sulfonate. Concentrations were plotted in map view to determine the areal extent of the PFAS contamination at the site. Extraction well 48BR sampled on the eastern half of the site was found to have PFOS and PFOA concentrations greater than the New Jersey Department of Environmental Protection Drinking Water maximum contaminant levels (MCLs), which is consistent with the distribution of highest PFAS concentrations in surface water in the OF-4 storm sewer system that drains that area, as well as previously collected PFAS concentrations in monitoring wells. On the western half of the site, the extraction well 08BR sample exceeded MCLs for PFOA and PFOS and the extraction well 22BR sample exceeded the MCL for PFOA, but samples from all other extraction wells were below the MCLs or other criteria for all PFAS analyzed. Concentrations of PFOA exceeded concentrations of PFOS on the west side of NAWC in both groundwater and surface water, which contrasts with the conditions on the east side of NAWC where PFOS concentrations exceeded PFOA concentrations. However, this observation was based on a limited number of samples on the west side of NAWC from 2018 and previous years, so more PFAS sampling is needed on the west side to assess this further.

New Jersey↗
USGS1996

Use of a ground-water flow model with particle tracking to evaluate ground-water vulnerability, Clark County, Washington

A ground-water flow model was used in conjunction with particle tracking to evaluate ground-water vulnerability in Clark County, Washington. Using the particle-tracking program, particles were placed in every cell of the flow model (about 60,000 particles) and tracked backwards in time and space upgradient along flow paths to their recharge points. A new computer program was developed that interfaces the results from a particle-tracking program with a geographic information system (GIS). The GIS was used to display and analyze the particle-tracking results. Ground-water vulnerability was evaluated by selecting parts of the ground-water flow system and combining the results with ancillary information stored in the GIS to determine recharge areas, characteristics of recharge areas, downgradient impact of land use at recharge areas, and age of ground water. Maps of the recharge areas for each hydrogeologic unit illustrate the presence of local, intermediate, or regional ground-water flow systems and emphasize the three-dimensional nature of the ground-water flow system in Clark County. Maps of the recharge points for each hydrogeologic unit were overlaid with maps depicting aquifer sensitivity as determined by DRASTIC (a measure of the pollution potential of ground water, based on the intrinsic characteristics of the near-surface unsaturated and saturated zones) and recharge from on-site waste-disposal systems. A large number of recharge areas were identified, particularly in southern Clark County, that have a high aquifer sensitivity, coincide with areas of recharge from on-site waste-disposal systems, or both. Using the GIS, the characteristics of the recharge areas were related to the downgradient parts of the ground-water system that will eventually receive flow that has recharged through these areas. The aquifer sensitivity, as indicated by DRASTIC, of the recharge areas for downgradient parts of the flow system was mapped for each hydrogeologic unit. A number of public-supply wells in Clark County may be receiving a component of water that recharged in areas that are more conducive to contaminant entry. The aquifer sensitivity maps illustrate a critical deficiency in the DRASTIC methodology: the failure to account for the dynamics of the ground-water flow system. DRASTIC indices calculated for a particular location thus do not necessarily reflect the conditions of the ground-water resources at the recharge areas to that particular location. Each hydrogeologic unit was also mapped to highlight those areas that will eventually receive flow from recharge areas with on-site waste-disposal systems. Most public-supply wells in southern Clark County may eventually receive a component of water that was recharged from on-site waste-disposal systems.Traveltimes from particle tracking were used to estimate the minimum and maximum age of ground water within each model-grid cell. Chlorofluorocarbon (CFC)-age dating of ground water from 51 wells was used to calibrate effective porosity values used for the particle- tracking program by comparison of ground-water ages determined through the use of the CFC-age dating with those calculated by the particle- tracking program. There was a 76 percent agreement in predicting the presence of modern water in the 51 wells as determined using CFCs and calculated by the particle-tracking program. Maps showing the age of ground water were prepared for all the hydrogeologic units. Areas with the youngest ground-water ages are expected to be at greatest risk for contamination from anthropogenic sources. Comparison of these maps with maps of public- supply wells in Clark County indicates that most of these wells may withdraw ground water that is, in part, less than 100 years old, and in many instances less than 10 years old. Results of the analysis showed that a single particle-tracking analysis simulating advective transport can be used to evaluate ground-water vulnerability for any part of a ground-wate

Open-File Report↗