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At least 919 records · Page 51Linked to original sources
USGS2001

Biodegradation potential of chlorinated solvents in ground water at the Naval Surface Warfare Center, Louisville, Kentucky, July 1999 to February 2000

The U.S. Geological Survey, in cooperation with the U.S. Department of the Navy, Southern Division Naval Facilities Engineering Command, investigated the potential for biodegradation of chlorinated solvents in ground water at the Naval Surface Warfare Center (also known as the Naval Ordnance Station, or the station), Louisville, Kentucky. The subsurface down to at least 100 feet at the station is characterized, from shallowest to deepest, by overburden deposits, a shale layer, and limestone. In general, all of the strata are poorly permeable. The permeable zones of the overburden and the limestone make up the overburden aquifer and the bedrock aquifer, respectively. Observed concentrations of redox-sensitive solutes suggest that the predominant anaerobic terminal electron accepting process in the overburden aquifer can shift between iron reduction and sulfate reduction, possibly as a result of rainfall-induced oxidation events. Daughter-product concentrations and laboratory experiments indicate that a variety of mechanisms, including reductive dechlorination and cometabolic oxidation, appear to be actively

Kentucky↗
USGS2002

Spatial patterns and temporal variability in water quality from City of Albuquerque drinking-water supply wells and piezometer nests, with implications for the ground-water flow system

Water-quality data for 93 City of Albuquerque drinking-water supply wells, 7 deep piezometer nests, and selected additional wells were examined to improve understanding of the regional ground-water system and its response to pumpage. Plots of median values of several major parameters showed discernible water-quality differences both areally and with depth in the aquifer. Areal differences were sufficiently large to enable delineation of five regions of generally distinct water quality, which are consistent with areas of separate recharge defined by previous investigators. Data for deep piezometer nests indicate that water quality generally degrades somewhat with depth, except in areas where local recharge influenced by evapotranspiration or contamination could be affecting shallow water. The orientations of the five water-quality regions indicate that the direction of ground-water flow has historically been primarily north to south. This is generally consistent with maps of predevelopment hydraulic heads, although some areas lack consistency, possibly because of differences in time scales or depths represented by water quality as opposed to hydraulic head. The primary sources of recharge to ground water in the study area appear to be mountain-front recharge along the Sandia Mountains to the east and the Jemez Mountains to the north, seepage from the Rio Grande, and infiltration through Tijeras Arroyo. Elevated concentrations of many chemical constituents in part of the study area appear to be associated with a source of water having large dissolved solids, possibly moving upward from depth. Hydraulic-head data for deep piezometer nests indicate that vertical head gradients differ in direction and magnitude across the study area. Hydraulic-head gradients are downward in the central and western parts of the study area and upward across much of the eastern part, except at the mountain front. Water-quality data for the piezometers indicate that the ground water is not well mixed, even in areas of large vertical gradients. Water levels in most piezometers respond to short-term variations in ground-water withdrawals and to the cumulative effect of long-term withdrawals throughout the area. In most piezometers screened below the water table, water levels respond clearly to seasonal variations in ground-water withdrawals. Water levels decline from about April through July and rise from about September through January. Water levels seem to be declining in most piezometers at a rate less than 1 foot per year. Water-quality data for unfiltered samples collected over a 10-year period from 93 City of Albuquerque drinking-water supply wells were examined for variability and temporal trends in 10 selected parameters. Variability generally was found to be greatest in the Western and Northeast water-quality regions of the study area. For the 10 parameters investigated, temporal trends were found in 5 to 57 wells. Dissolved-solids, sodium, sulfate, chloride, and silica concentrations showed more increasing than decreasing trends; calcium, bicarbonate, and arsenic concentrations, field pH, and water temperature showed more decreasing than increasing trends. The median magnitudes of most of these trends over a 1-year period were not particularly large (generally less than 1.0 milligram per liter), although the magnitudes for a few individual wells were significant. For the 10 parameters investigated, correlations with monthly pumpage volumes were found in 10 to 32 wells. Calcium and sulfate concentrations, field pH, and water temperature showed more positive than negative correlations with monthly pumpage; dissolved-solids, sodium, bicarbonate, chloride, silica, and arsenic concentrations showed more negative than positive correlations.

New Mexico↗
USGS2001

Evapotranspiration from a cypress and pine forest subjected to natural fires, Volusia County, Florida, 1998-99

Daily values of evapotranspiration from a watershed in Volusia County, Florida, were estimated for a 2-year period (January 1998 through December 1999) by using an energy-budget variant of the eddy correlation method and a Priestley-Taylor model. The watershed consisted primarily of pine flatwood uplands interspersed within cypress wetlands. A drought-induced fire in spring 1998 burned about 40 percent of the watershed, most of which was subsequently logged. The model reproduced the 449 measured values of evapotranspiration reasonably well (r 2 =0.90) over a wide range of seasonal and surface-cover conditions. Annual evapotranspiration from the watershed was estimated to be 916 millimeters (36 inches) for 1998 and 1,070 millimeters (42 inches) for 1999. Evapotranspiration declined from near potential rates in the wet conditions of January 1998 to less than 50 percent of potential evapotranspiration after the fire and at the peak of the drought in June 1998. After the drought ended in early July 1998 and water levels returned to near land-surface, evapotranspiration increased sharply; however, the evapotranspiration rate was only about 60 percent of the potential rate in the burned areas, compared to about 90 percent of the potential rate in the unburned areas. This discrepancy can be explained as a result of fire damage to vegetation. Beginning in spring 1999, evapotranspiration from burned areas increased sharply relative to unburned areas, sometimes exceeding unburned evapotranspiration by almost 100 percent. Possible explanations for the dramatic increase in evapotranspiration from burned areas could include phenological changes associated with maturation or seasonality of plants that emerged after the fire or successional changes in composition of plant community within burned areas. Variations in daily evapotranspiration are primarily the result of variations in surface cover, net radiation, photosynthetically active radiation, air temperature, and water-table depth. A water budget for the watershed supports the validity of the daily measurements and estimates of evapotranspiration. A water budget constructed using independent estimates of average rates of rainfall, runoff, and deep leakage, as well as evapotranspiration, was consistent within 3.8 percent. An alternative water budget constructed using evapotrans-piration estimated by the standard eddy correlation method was consistent only within 9.1 percent. This result indicates that the standard eddy correlation method is not as accurate as the energy-budget variant.

Florida↗
USGS2002

Hydrogeologic framework, availability of water supplies, and saltwater intrusion, Cape May County, New Jersey

During 1960-90, saltwater intrusion forced the abandonment of at least 10 public-supply wells, 3 industrial-supply wells, and more than 100 domestic-supply wells in Cape May County, N.J. Actual or imminent ground-water contamination caused by land-use practices and human activities has forced the closure of at least six shallow public-supply wells and many domestic-supply wells. Freshwater in Cape May County flows in many small streams and is held in wetlands and natural and artificial ponds. More importantly, freshwater from precipitation passes through and is stored in five aquifers-- Holly Beach water-bearing zone, estuarine sand aquifer, Cohansey aquifer, Rio Grande water-bearing zone, and Atlantic City 800-foot sand. Surface-water discharges were measured at 14 stream sites. The Tuckahoe River is the largest stream in Cape May County. The mean annual discharge for the Tuckahoe River at Head of River was 43.8 ft3/s (cubic feet per second) or 10,800 Mgal/yr (million gallons per year) during the period of record (1969-93). Mean daily discharge ranged from 25 ft3/s or 16 Mgal/d in September to 73 ft3/s or 47 Mgal/d in April. Mean daily discharge at the eight largest streams wholly within the county ranged from 15.9 to 3.05 ft3/s (3,750 to 720 Mgal/yr). Total water use in the county was about 8,600 Mgal/yr in 1990, including about 25 Mgal/yr of surface water, 3,000 Mgal/yr from the Holly Beach water-bearing zone, 1,000 Mgal/yr from the estuarine sand aquifer, 2,200 Mgal/yr from the Cohansey aquifer, 200 Mgal/yr from the Rio Grande water-bearing zone, and 2,200 Mgal/yr from the Atlantic City 800-foot sand. Water-level data collected during April 1991 for more than 200 wells show that in some locations ground-water flow directions and rates have changed when compared with those shown on historical potentiometric-surface maps. In 1991, water levels in the Holly Beach water-bearing zone were nearly identical to levels prior to development. A cone of depression has developed in the estuarine sand aquifer; the water-level altitude near the center of the cone was about -5 ft in 1991. An extensive cone of depression has developed in the Cohansey aquifer; the water-level altitude near the center of the cone was about -20 ft. A small cone of depression has developed in the Rio Grande water-bearing zone; the altitude near the center was -5 ft. An elongated cone of depression has developed in the Atlantic City 800-foot sand; the water-level altitude was about -70 ft in Ocean City and -20 ft in Stone Harbor. Waterlevel maps from predevelopment, 1958, 1978, 1983, and 1988 show that the cones of depression are getting deeper and are expanding in the Atlantic City 800-foot sand. The 250-mg/L (milligram per liter) line of equal chloride concentration and 50 mg/L line of equal sodium concentration have moved inland, possibly since the early 1900's. Chloride concentrations have increased in many wells in the confined aquifers along the coastline in the southern part of the county. Nitrate concentrations greater than 1 mg/L were present in water samples collected from 10 wells that tap the Holly Beach water-bearing zone. Concentrations of nitrate greater than 10 mg/L in samples collected in Lower, Middle, Upper, and Dennis Townships may result from effluent from septic systems or from agricultural activities. A water budget shows that the mean annual precipitation is about 42 in., and about 119,000 Mgal falls each year on uplands and freshwater wetlands in the county. About 63,600 Mgal/yr is evapotranspired, 8,200 Mgal/yr becomes overland flow, and 47,200 Mgal/yr recharges the Holly Beach water-bearing zone. In northern Cape MayCounty, most recharge ultimately is discharged to streams. In southern Cape May County, about 20 percent of recharge is diverted to withdrawal wells. Because saltwater intrusion has occurred in the confined aquifers along the Atlantic and Delaware Bay coastlines, new supply wells placed along th

Water-Resources Investigations Report↗
USGS2001

Characterization of surface-water quality based on real-time monitoring and regression analysis, Quivira National Wildlife Refuge, south-central Kansas, December 1998 through June 2001

Because of the considerable wildlife benefits offered by the Quivira National Wildlife Refuge in south-central Kansas, there is a desire to ensure suitable water quality. To assess the quality of water flowing from Rattlesnake Creek into the refuge, the U.S. Geological Survey collected periodic water samples from December 1998 through June 2001 and analyzed the samples for physical properties, dissolved solids, total suspended solids, suspended sediment, major ions, nutrients, metals, pesticides, and indicator bacteria. Concentrations of 10 of the 125 chemicals analyzed did not meet water-quality criteria to protect aquatic life and drinking water in a least one sample. These were pH, turbidity, dissolved oxygen, dissolved solids, sodium, chloride, phosphorus, total coliform bacteria, E. coli bacteria, and fecal coliform bacteria. No metal or pesticide concentrations exceeded water-quality criteria. Twenty-two of the 43 metals analyzed were not detected, and 36 of the 46 pesticides analyzed were not detected. Because dissolved solids, sodium, chloride, fecal coliform bacteria, and other chemicals that are a concern for the health and habitat of fish and wildlife at the refuge cannot be measured continuously, regression equations were developed from a comparison of the analytical results of periodic samples and in-stream monitor measurements of specific conductance, pH, water temperature, turbidity, and dissolved oxygen. A continuous record of estimated chemical concentrations was developed from continuously recorded in-stream measurements. Annual variation in water quality was evaluated by comparing 1999 and 2000 sample data- the 2 years for which complete data sets were available. Median concentrations of alkalinity, fluoride, nitrate, and fecal coliform bacteria were smaller or did not change from 1999 to 2000. Dissolved solids, total suspended solids, sodium, chloride, sulfate, total organic nitrogen, and total phosphorus had increases in median concentrations from 1999 to 2000. Increases in the median concentrations of the major ions were expected due to decreased rainfall in 2000 and very low streamflow late in the year. Increases for solids and nutrients may have been due to the unusually high streamflow in the early spring of 2000. This was the time of year when fields were tilled, exposing solids and nutrients that were transported with runoff to Rattlesnake Creek. Load estimates indicate the chemical mass transported into the refuge and can be used in the development of total maximum daily loads (as specified by the U.S. Environmental Protection Agency) for water-quality contaminants in Rattlesnake Creek. Load estimates also were used to evaluate seasonal variation in water quality. Seasonal variation was most pronounced in the estimates of nutrient loads, and most of the nutrient load transported to the refuge occurred during just a few periods of surface runoff in the spring and summer. This information may be used by resource managers to determine when water-diversion strategies would be most beneficial. Load estimates also were used to calculate yields, which are useful for site comparisons. The continuous and real-time nature of the record of estimated concentrations, loads, and yields may be important for resource managers, recreationalists, or others for evaluating water-diversion strategies, making water-use decisions, or assessing the environmental effects of chemicals in time to prevent adverse effects on fish or other aquatic life at the refuge.

Kansas↗
USGS2002

Comparisons of water quality during various streamflow conditions in five streams in northern New Jersey, 1982-97

Relations between water-quality and flow characteristics and the relative importance of constant (point sources and ground-water discharge) and intermittent (nonpoint storm runoff) sources were determined for eight water-quality stations located on the Flat Brook and the Delaware, Musconetcong, Whippany, and Saddle Rivers. Water-quality and streamflow data were categorized on the basis of streamflow at the time of sample collection. Differences in concentrations and yields of selected water-quality constituents, including nutrients and bacteria, (1) among the stations during eight streamflow conditions and (2) at each station (a) between base flow and stormflow; (b) among before, during, and after a storm; and (c) among low, medium, and high flows were determined and related to the predominant type(s) of land development in the areas contributing drainage. At the station on the Delaware River, yields of fecal-coliform bacteria were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharges; yields during a storm [7.0 x 108 (MPN/d)mi2 (most probable number per day per square mile)] were greater than yields during base flow (3.7 x 108 (MPN/d)mi2). Yields of nitrate plus nitrite, alkalinity, and chloride were affected more by contributions from point sources and ground-water discharges than by contributions from storm runoff; yields of these constituents were not significantly different during base flows and stormflows. At the Flat Brook and Whippany River stations, yields of most water-quality constituents were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge. For example, yields of nitrate plus nitrite were greater during stormflow (1.20 (lb/d)/mi2 (pounds per day per square mile) and 15.88 (lb/d)/mi2, respectively) than during base flow (0.26 (lb/d)/mi2 and 8.20 (lb/d)/mi2, respectively). At the Musconetcong River station, yields of total nitrogen, alkalinity, and chloride were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge. At three of the four water-quality stations on the Musconetcong River, yields of total phosphorus and bacteria were affected less by contributions from storm runoff than by contributions from point sources and ground-water discharge. At the Saddle River station, yields of alkalinity and chloride were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge; for example, yields of chloride during stormflows (707 (lb/d)/mi2) were greater than during base flows (401 (lb/d)/mi2). Yields of total phosphorus were affected less by contributions from storm runoff than by contributions from point sources and ground-water discharge; yields during base flows (4.00 (lb/d)/mi2) and stormflows (4.67 (lb/d)/mi2) were similar. Concentrations and yields of total phosphorus and nitrogen, and nitrate plus nitrite were strongly related to the amount of development in each drainage basin. At stations on the Saddle and Whippany Rivers, which drain areas with substantial development, concentrations and yields for all streamflow categories were higher than at stations on the Flat Brook and Delaware River, which drain areas with little development. Results of the Tukey test indicate that there are significant differences in total phosphorus concentrations at Saddle River and Flat Brook during base flows (0.77 mg/L (milligrams per liter) and 0.02 mg/L, respectively) and stormflows (0.42 mg/L and 0.02 mg/L, respectively).

New Jersey↗
USGS2001

Computed and estimated pollutant loads, West Fork Trinity River, Fort Worth, Texas, 1997

In 1998 the U.S. Geological Survey, in cooperation with the Trinity River Authority, did a study to estimate storm-runoff pollutant loads using two models—a deterministic model and a statistical model; the estimated loads were compared to loads computed from measured data for a large (118,000 acres) basin in the Dallas-Fort Worth, Texas, metropolitan area. Loads were computed and estimated for 12 properties and constituents in runoff from two 1997 storms at streamflow-gaging station 08048543 West Fork Trinity River at Beach Street in Fort Worth. Each model uses rainfall as a primary variable to estimate pollutant load. In addition to using point rainfall at the Beach Street station to estimate pollutant loads, areal-averaged rainfall for the basin was computed to obtain a more representative estimate of rainfall over the basin. Loads estimated by the models for the two storms, using both point and areal-averaged rainfall, generally did not compare closely to computed loads for the 12 water-quality properties and constituents. Both models overestimated loads more frequently than they underestimated loads. The models tended to yield similar estimates for the same property or constituent. In general, areal-averaged rainfall data yielded better estimates of loads than point rainfall data for both models. Neither the deterministic model nor the statistical model (both using areal-averaged rainfall) was consistently better at estimating loads. Several factors could account for the inability of the models to estimate loads closer to computed loads. Chief among them is the fact that neither model was designed for the specific application of this study.

Texas↗
USGS2002

Three-dimensional hydrogeologic framework model for use with a steady-state numerical ground-water flow model of the Death Valley regional flow system, Nevada and California

The U.S. Geological Survey, in cooperation with the Department of Energy and other Federal, State, and local agencies, is evaluating the hydrogeologic characteristics of the Death Valley regional ground-water flow system. The ground-water flow system covers an area of about 100,000 square kilometers from latitude 35? to 38?15' North to longitude 115? to 118? West, with the flow system proper comprising about 45,000 square kilometers. The Death Valley regional ground-water flow system is one of the larger flow systems within the Southwestern United States and includes in its boundaries the Nevada Test Site, Yucca Mountain, and much of Death Valley. Part of this study includes the construction of a three-dimensional hydrogeologic framework model to serve as the foundation for the development of a steady-state regional ground-water flow model. The digital framework model provides a computer-based description of the geometry and composition of the hydrogeologic units that control regional flow. The framework model of the region was constructed by merging two previous framework models constructed for the Yucca Mountain Project and the Environmental Restoration Program Underground Test Area studies at the Nevada Test Site. The hydrologic characteristics of the region result from a currently arid climate and complex geology. Interbasinal regional ground-water flow occurs through a thick carbonate-rock sequence of Paleozoic age, a locally thick volcanic-rock sequence of Tertiary age, and basin-fill alluvium of Tertiary and Quaternary age. Throughout the system, deep and shallow ground-water flow may be controlled by extensive and pervasive regional and local faults and fractures. The framework model was constructed using data from several sources to define the geometry of the regional hydrogeologic units. These data sources include (1) a 1:250,000-scale hydrogeologic-map compilation of the region; (2) regional-scale geologic cross sections; (3) borehole information, and (4) gridded surfaces from a previous three-dimensional geologic model. In addition, digital elevation model data were used in conjunction with these data to define ground-surface altitudes. These data, properly oriented in three dimensions by using geographic information systems, were combined and gridded to produce the upper surfaces of the hydrogeologic units used in the flow model. The final geometry of the framework model is constructed as a volumetric model by incorporating the intersections of these gridded surfaces and by applying fault truncation rules to structural features from the geologic map and cross sections. The cells defining the geometry of the hydrogeologic framework model can be assigned several attributes such as lithology, hydrogeologic unit, thickness, and top and bottom altitudes.

Water-Resources Investigations Report↗
USGS2001

Concentrations and annual fluxes for selected water-quality constituents from the USGS National Stream Quality Accounting Network (NASQAN) 1996-2000

This report contains concentrations and annual mass fluxes (loadings) for a broad range of water-quality constituents measured during 1996-2000 as part of the U.S. Geological Survey National Stream Quality Accounting Network (NASQAN). During this period, NASQAN operated a network of 40-42 stations in four of the largest river basins of the USA: the Colorado, the Columbia, the Mississippi (including the Missouri and Ohio), and the Rio Grande. The report contains surface-water quality data, streamflow data, field measurements (e.g. water temperature and pH), sediment-chemistry data, and quality-assurance data; interpretive products include annual and average loads, regression parameters for models used to estimate loads, sub-basin yield maps, maps depicting percent detections for censored constituents, and diagrams depicting flow-weighted average concentrations. Where possible, a regression model relating concentration to discharge and season was used for flux estimation. The interpretive context provided by annual loads includes identifying source and sink areas for constituents and estimating the loadings to receiving waters, such as reservoirs or the ocean.

Water-Resources Investigations Report↗
USGS2002

Characteristics of shallow deposits beneath Rillito Creek, Pima County, Arizona

Characteristics of the stream-channel and basin-fill deposits beneath a 12-mile reach of Rillito Creek, Pima County, Arizona, were obtained to describe the geohydrologic system. The findings presented here are part of a larger project to improve the understanding of recharge processes beneath ephemeral streams. The stream-channel deposits, which range in thickness from 15 to 40 feet, generally are sandy gravels or gravelly sands. On average, the stream-channel deposits are 44 percent gravel, 51 percent sand, 2 percent silt, and 3 percent clay. The underlying basin-fill deposits also are sandy gravels or gravelly sands but have, on average, a larger component of silt and clay than the stream-channel deposits?about 9 percent silt and 6 percent clay. Porosity values for the stream-channel and basin-fill deposits are similar: about 31 and 34 percent on average, respectively. Volumetric moisture content and percent saturation, however, generally were lower in the stream-channel deposits than in the basin-fill deposits. Moisture content in the stream-channel deposits ranged from 2 to 40 percent and averaged about 18 percent, whereas moisture content in the basin-fill deposits ranged from 7 to 47 percent and averaged about 24 percent. Saturation in the stream-channel deposits ranged from 9 to 100 percent and averaged about 58 percent; saturation in the basin-fill deposits ranged from 30 to 100 percent and averaged about 69 percent. Porosity and moisture content correlate with silt and clay content. Cumulative thickness of water in the 100- to 125-foot thick unsaturated zone obtained by integrating the moisture content over depth, ranged from 17.2 to 40.4 feet. Matric potential for saturation levels at the time of sample collection generally was less than -1 bar for deposits that were less than 35 percent saturated. Matric potential generally was greater than -0.1 bar for deposits that were more than 65 percent saturated. Moisture-retention curves are a function of the physical properties, such as porosity and grain size, of the sediments. The shapes and van Genuchten fitting parameters of moisture-retention curves for the stream-channel deposits are different from those of the basin-fill deposits. For instance, the fitting parameter, a, for stream-channel deposits ranged from 4.56 to 1,220 bar-1 and averaged 220 bar-1, whereas a for basin-fill deposits ranged from 4.22 to 67.9 bar-1 and averaged 22.8 bar-1. The residual water content for the basin-fill deposits is greater than that for the stream-channel deposits. Relative hydraulic conductivity of the stream-channel deposits is less than relative hydraulic conductivity of the basin-fill deposits at the same matric potential. Unsaturated hydraulic conductivity for moisture conditions that existed at the time of sample collection typically was more than two orders of magnitude less than saturated hydraulic conductivity. Saturated vertical hydraulic conductivity of the stream-channel deposits is about an order of magnitude greater than that of the basin-fill deposits. The equivalent hydraulic conductivity of stream-channel deposits ranges from 2 to 7.3 feet per day, and averages about 4 feet per day, whereas the equivalent hydraulic conductivity of the basin-fill deposits ranges from 0.06 to 1.5 feet per day and averages 0.61 foot per day. The equivalent vertical hydraulic conductivity of the entire unsaturated zone cored is 0.75 foot per day. Assuming no vertical to horizontal anisotropy, the equivalent horizontal hydraulic conductivity generally is about two to three times that of the equivalent vertical hydraulic conductivity. The difference between average equivalent vertical and horizontal hydraulic conductivity values results from the differences in methods used to calculate the respective values. Electrical methods were useful in discriminating between stream-channel deposits and basin-fill deposits. In general, electrical conductivity of the stream-channel deposits was less than 30 millimhos per meter and averaged 27 millimhos per meter. The conductivity of the basin-fill deposits was greater than that of the stream-channel deposits and averaged 44 millimhos per meter. The greater conductivity probably is related to factors such as greater moisture content and fraction of fine sediments in the basin-fill deposits. Apparent resistivity measured with two-dimensional resistivity soundings generally decreased with depth. The resistivity values from the near-surface measurements represent dry stream-channel deposits and averaged 303 ohm meters. The resistivity values for basin-fill deposits generally were less than 140 ohm meters and less than 100 ohm meters when saturated. Seismic-velocity values for the recent alluvium (stream-channel and terrace deposits) ranged from 1,150 to 2,200 feet per second, whereas values for basin-fill deposits ranged from 2,000 to 11,650 feet per second. The average seismic velocity for the stream-channel deposits (1,300 feet per second) was less than that for the terrace deposits (1,600 feet per second). Saturated basin-fill deposits had an average velocity of 7,800 feet per second, whereas unsaturated basin-fill deposits had an average velocity of 2,750 feet per second.

Arizona↗
USGS2002

Three-dimensional measurements of flow in uncased wells completed in basalt, Mountain Home Air Force Base, Idaho, March 2000

Several ground-water monitoring wells on the Mountain Home Air Force Base in southwestern Idaho were constructed in February 2000 to replace existing monitoring wells that became ineffective as a result of declining water levels. Upon completion of the replacement wells, borehole geophysical logs were collected, including natural gamma radiation, electromagnetic induction, caliper, fluid temperature, and resistivity. A prototype borehole acoustic doppler velocimeter (B-ADV) was used to make experimental three-dimensional measurements of lateral and vertical flow in two of the replacement wells, MW11–2 and MW3–2, each 450 feet deep, to better understand ground-water flow in the basalt underlying this area. Measurements indicated two independent flow zones in each well: unit B, from about 380 to about 415 feet below land surface, and unit C, from about 415 to about 430 feet below land surface. In each well, direction of flow in unit B was north-northwest toward Canyon Creek and, in unit C, south-southwest toward the Snake River. Measurements also indicated downward intraborehole flow in both wells. Unit B appeared to represent a local-scale flow regime; unit C appeared to represent a regional flow regime. This information suggests the existence of a complex three-dimensional hydrogeologic setting that cannot be discriminated easily on conventional waterlevel maps. Although data from only two wells are insufficient to construct a conceptual model of the ground-water flow regime, these experimental results demonstrate the capability of the B-ADV to obtain detailed flow measurements that, combined with data from other types of geophysical logs, discrete measurements of hydraulic head, and water chemistry, would aid in future studies and management of the ground-water resources, including contaminant transport and remediation.

Idaho↗
USGS2002

Effects of highway-deicer application on ground-water quality in a part of the Calumet Aquifer, northwestern Indiana

The effects of highway-deicer application on ground-water quality were studied at a site in northwestern Indiana using a variety of geochemical indicators. Site characteristics such as high snowfall rates; large quantities of applied deicers; presence of a high-traffic highway; a homogeneous, permeable, and unconfined aquifer; a shallow water table; a known ground-water-flow direction; and minimal potential for other sources of chloride and sodium to complicate source interpretation were used to select a study area where ground water was likely to be affected by deicer application. Forty-three monitoring wells were installed in an unconfined sand aquifer (the Calumet aquifer) near Beverly Shores in northwestern Indiana. Wells were installed along two transects that approximately paralleled groundwater flow in the Calumet aquifer and crossed US–12. US–12 is a highway that receives Indiana’s highest level of maintenance to maintain safe driving conditions. Ground-water quality and water-level data were collected from the monitoring wells, and precipitation and salt-application data were compiled from 1994 through 1997. The water-quality data indicated that chloride was the most easily traced indicator of highway deicers in ground water. Concentration ratios of chloride to iodide and chloride to bromide and Stiff diagrams of major element concentrations indicated that the principal source of chloride and sodium in ground water from the uppermost one-third to one-half of the Calumet aquifer and downgradient from US–12 was from a halite highway-deicer source. Borehole logs of relative electromagnetic conductivity defined a distinct plume of deicer-affected water in the uppermost 8 feet of aquifer at about 9 feet horizontally from the paved roadway edge and a zone of higher conductivity than background in the lower one-third of the aquifer. Chloride and sodium in the deep parts of the aquifer originated from natural sources. Chloride and sodium from highway deicers were present in the aquifer throughout the year. The highest concentrations of chloride and sodium in ground water were determined in samples collected during the spring and summer from wells open to the water table within about 9 feet of the highway. Chloride concentrations in ground water that were attributable to highway deicers also were found in tested wells about 400 feet downgradient from US–12 during the fall and winter and at greater depths than in wells closer to US–12. Chloride concentrations exceeded the U.S. Environmental Protection Agency’s (USEPA) secondary maximum contaminant level of 250 milligrams per liter for drinking water at seven wells downgradient from the highway during late winter, spring, and summer samplings. The chloride standard was exceeded only in water from wells with total depths that are less than about 10 feet below land surface. Sodium concentrations in water periodically exceeded the USEPA drinking-water equivalency level of 20 milligrams per liter in both the uppermost (deicer 2 Effects of Highway-Deicer Application on Ground-Water Quality in a Part of the Calumet Aquifer, Northwestern Indiana affected) and lower one-thirds of the aquifer. Sodium concentrations in ground water downgradient from US–12 and in the upper 5 feet of the aquifer also occasionally exceeded drinking-water standards for sodium (160 milligrams per liter) as set by the State of Florida and a standard for taste (200 milligrams per liter) as set by the World Health Organization. Dispersion was identified by analysis of aquifer-test data, isotopic dating of ground water, and water-quality data to be the process most responsible for reducing concentrations of highway deicers in the aquifer. Chemical analyses of the sand composing the aquifer indicated that cation exchange decreased the mass of deicerrelated sodium in ground water, although the sand has a limited capacity to sustain the process. Automated daily measurements of specific conductance, correlated to chloride concentrations, indicated that some deicer is retained in the aquifer near the highway throughout the entire year and acts as a continuous chloride source for ground water. Peak concentrations of deicerrelated constituents occasionally were detected by the daily, automated measurements of specific conductance that were made between the monthly samplings of ground water. Data analysis indicated that more frequent sampling than monthly intervals would be necessary if maximum chloride concentrations were to be measured. Some deicer may be retained in the aquifer and unsaturated zone between annual salt-application periods. Chloride concentrations at wells 1-DG-WT and 2-DG-WT remained greater than background through much or all of the year. The estimated masses of chloride transported in ground water past 2-DG in 1995 and 1996 were either slightly greater than (1995) or less than (1996) the masses of chloride applied to US–12 during the study.

Indiana↗
USGS2002

Evaluation of borehole geophysical logging, aquifer-isolation tests, distribution of contaminants, and water-level measurements at the North Penn Area 5 Superfund Site, Bucks and Montgomery Counties, Pennsylvania

Borehole geophysical logging and aquifer-isolation (packer) tests were conducted at the North Penn Area 5 Superfund site in Bucks and Montgomery Counties, Pa. Caliper, naturalgamma, single-point-resistance, fluid-temperature, fluid-resistivity, heatpulse-flowmeter, and digital acoustic-televiewer logs and borehole television surveys were collected in 32 new and previously drilled wells that ranged in depth from 68 to 302 feet. Vertical borehole-fluid movement direction and rate were measured with a high-resolution heatpulse flowmeter under nonpumping conditions. The suite of logs was used to locate water-bearing fractures, determine zones of vertical borehole-fluid movement, select depths to set packers, and locate appropriate screen intervals for reconstructing new wells as monitoring wells. Aquifer-isolation tests were conducted in four wells to sample discrete intervals and to determine specific capacities of discrete water-bearing zones. Specific capacities of isolated zones during packer testing ranged from 0.12 to 15.30 gallons per minute per foot. Most fractures identified by borehole geophysical methods as water-producing or water-receiving zones produced water when isolated and pumped. The acoustic-televiewer logs define two basic fracture sets, bedding-plane partings with a mean strike of N. 62° E. and a mean dip of 27° NW., and high-angle fractures with a mean strike of N. 58° E. and a mean dip of 72° SE. Correlation of heatpulse-flowmeter data and acoustic-televiewer logs showed 83 percent of identified water-bearing fractures were high-angle fractures.

Pennsylvania↗
USGS2002

Conceptual hydrogeologic framework of the shallow aquifer system at Virginia Beach, Virginia

The hydrogeologic framework of the shallow aquifer system at Virginia Beach was revised to provide a better understanding of the distribution of fresh ground water, its potential use, and its susceptibility to contamination. The revised conceptual framework is based primarily on analyses of continuous cores and downhole geophysical logs collected at 7 sites to depths of approximately 200 ft. The shallow aquifer system at Virginia Beach is composed of the Columbia aquifer, the Yorktown confining unit, and the Yorktown-East-over aquifer. The shallow aquifer system is separated from deeper units by the continuous St. Marys confining unit. The Columbia aquifer is defined as the predominantly sandy surficial deposits above the Yorktown confining unit. The Yorktown confining unit is composed of a series of very fine sandy to silty clay units of various colors at or near the top of the Yorktown Formation. The Yorktown confining unit varies in thickness and in composition, but on a regional scale is a leaky confining unit. The Yorktown-Eastover aquifer is defined as the predominantly sandy deposits of the Yorktown Formation and the upper part of the Eastover Formation above the confining clays of the St. Marys Formation. The limited areal extent of highly permeable deposits containing freshwater in the Yorktown-Eastover aquifer precludes the installation of highly productive freshwater wells over most of the city. Some deposits of biofragmental sand or shell hashes in the Yorktown-Eastover aquifer can support high-capacity wells. A water sample was collected from each of 10 wells installed at 5 of the 7 core sites to determine the basic chemistry of the aquifer system. One shallow well and one deep well was installed at each site. Concentrations of chloride were higher in the water from the deeper well at each site. Concentrations of dissolved iron in all of the water samples were higher than the U.S. Environmental Protection Agency Secondary Drinking Water Regulations. Concentrations of manganese and chloride were higher than the Secondary Drinking Water Regulations in samples from some wells. In the humid climate of Virginia Beach, the periodic recharge of freshwater through the sand units of the shallow aquifer system occurs often enough to create a dynamic equilibrium whereby freshwater flows continually down and away from the center of the ridges to mix with and sweep brackish water and saltwater back toward the tidal rivers, bays, salt marshes, and the Atlantic Ocean. The aquifers and confining units of the shallow aquifer system at Virginia Beach are heterogeneous, discontinuous, and without exact marker beds, which makes correlations in the study area difficult. Investigations using well cuttings, spot cores, or split-spoon samples with geophysical logs are not as definitive as continuous cores for determining or correlating hydrogeologic units. Future investigations of the shallow aquifer system would benefit by collecting continuous cores.

Water-Resources Investigations Report↗
USGS2002

Hydrogeological investigation at Site 5, Willow Grove Naval Air Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania

The U.S. Geological Survey conducted borehole geophysical logging, collected and analyzed water-level data, and sampled sections of a rock core to determine the concentration of volatile organic compounds in the aquifer matrix of the Stockton Formation. Borehole geophysical logs were run in three monitor wells. At well 05MW04I, the vertical gradient was upward at depths above 42 feet below land surface (ft bls), downward between 42 and 82 ft bls, and upward below 82 ft bls. At well 05MW05I, a downward vertical gradient was present. At well 05MW12I, the vertical gradient was downward above 112 ft bls and upward below 112 ft bls. Three water-bearing fractures in a 17-foot long rock core from 23.5 to 40.5 ft bls were identified and sampled. Three samples were analyzed from each water-bearing fracture—at the fracture face, 2 centimeters (cm) below the fracture, and 4 cm below the fracture. Fifteen compounds were detected; however, concentrations of seven compounds were less than 1 microgram per kilogram (mg/kg) when detected. Concentrations of benzene (from 0.39 to 3.3 mg/kg), 1,1-dichloroethene (1,1-DCE) (from 0.15 to 13 mg/kg), 1,1,1-trichloroethane (TCA) (from 0.17 to 22 mg/kg), and trichloroethylene (TCE) (from 0.092 to 9.6 mg/kg) were detected in all samples. The highest concentrations detected were for toluene, which was detected at a concentration of 32 and 86 mg/kg in the samples from unweathered sandstone at 2 and 4 cm below the fracture, respectively. Concentrations generally decreased with distance below the fracture in the mudstone samples. Concentrations of benzene and toluene increased with distance below the fractures in the unweathered sandstone samples. Concentrations of 1,1-DCE, TCA, and TCE were higher in the mudstone samples than in the samples from sandstone. Toluene concentrations were higher in unweathered sandstone than in weathered sandstone or mudstone. The effect of the pumping of Horsham Water and Sewer Authority public supply well 26 (HWSA-26), 0.2 mile southwest of the base boundary, on groundwater levels on the base was determined by shutting the well down for 6 days to allow water levels to recover. Water levels in 22 nearby wells were measured. The only well (02MW01I) that showed an unambiguous response to the shutdown of well HWSA-26 is 1,350 feet directly along strike from well HWSA-26. The recovery of well 05MW11I in response to the shutdown of well HWSA-26 is masked by recharge from snowmelt but probably does not exceed about 0.2 feet on the basis of the water level in well 05MW11I, which showed a response to the pumping of well HWSA-26 that ranged from 0.5 to 0.15 foot. Horizontal gradients differ with depth, and the rate and direction of ground-water flow and contaminant movement is depth dependent. The potentiometric-surface map for water levels measured in wells screened between 5 and 44 ft bls in the aquifer shows a ground-water mound that is the high point on a regional ground-water divide. From this divide, ground water flows both northwest toward Park Creek and southeast toward Pennypack Creek. The hydraulic gradient around this mound is relatively flat to the southeast and particularly flat to the northwest. The potentiometric-surface map for water levels measured in wells screened between 40 and 100 ft bls in the aquifer shows a very flat hydraulic gradient. Differences in the elevation of the potentiometric surface are less than 2 feet. The potentiometric-surface map for water levels measured in wells screened between 105 and 179 ft bls in the aquifer shows a steep hydraulic gradient between Sites 5 and 2 and a relatively flat hydraulic gradient between Sites 5 and 3. Water levels measured on October 7, 1999, showed downward vertical head gradients for all well clusters at Site 5. Vertical gradients ranged from 0.01 at well cluster 05MW10 to 0.2 at cluster 05MW11. Most gradients were between 0.01 and 0.026. Vertical head gradients vary with time. The variability is caused by a difference in the magnitude of water-level fluctuations between shallow and the deep fractures. The difference in the magnitude of water-level fluctuations is because of differences in lithology and aquifer storativity.

Pennsylvania↗
USGS2002

Interpretation of borehole geophysical logs, aquifer-isolation tests, and water quality, supply wells 1 and 2, Willow Grove Naval Air Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania

Ground water pumped from supply wells 1 and 2 on the Willow Grove Naval Air Station/Joint Reserve Base (NAS/JRB) provides water for use at the base, including potable water for drinking. The supply wells have been contaminated by volatile organic compounds (VOC's), particularly trichloroethylene (TCE) and tetrachloroethylene (PCE), and the water is treated to remove the VOC's. The Willow Grove NAS/JRB and surrounding area are underlain by sedimentary rocks of the Triassic-age Stockton Formation, which form a complex, heterogeneous aquifer. The ground-water-flow system for the supply wells was characterized by use of borehole geophysical logs and heatpulse-flowmeter measurements. The heatpulse-flowmeter measurements showed upward and downward borehole flow under nonpumping conditions in both wells. The hydraulic and chemical properties of discrete water-bearing fractures in the supply wells were characterized by isolating each water-bearing fracture with straddle packers. Eight fractures in supply well 1 and five fractures in supply well 2 were selected for testing on the basis of the borehole geophysical logs and borehole television surveys. Water samples were collected from each isolated fracture and analyzed for VOC?s and inorganic constituents. Fractures at 50–59, 79–80, 196, 124–152, 182, 241, 256, and 350–354 ft btoc (feet below top of casing) were isolated in supply well 1. Specific capacities ranged from 0.26 to 5.7 (gal/min)/ft (gallons per minute per foot) of drawdown. The highest specific capacity was for the fracture isolated at 179.8–188 ft btoc. Specific capacity and depth of fracture were not related in either supply well. The highest concentrations of PCE were in water samples collected from fractures isolated at 236.8–245 and 249.8–258 ft btoc, which are hydraulically connected. The concentration of PCE generally increased with depth to a maximum of 39 mg/L (micrograms per liter) at a depth of 249.8? 258 ft btoc and then decreased to 21 mg/L at a depth of 345.3–389 ft btoc. Fractures at 68–74, 115, 162, 182, 205, and 314 ft btoc were isolated in supply well 2. Specific capacities ranged from 0.08 to less than 2.9 (gal/ min)/ft. The highest specific capacity was for the fracture isolated at 157–165.2 ft btoc. Concentrations of detected VOC's in water samples were 3.6 mg/L or less. Lithologic units penetrated by both supply wells were determined by correlating naturalgamma and single-point-resistance borehole geophysical logs. All lithologic units are not continuous water-bearing units because water-bearing fractures are not necessarily present in the same lithologic units in each well. Although the wells penetrate the same lithologic units, the lithologic location of only three water-bearing fractures are common to both wells. The same lithologic unit may have different hydraulic properties in each well. A regional ground-water divide is southeast of the supply wells. From this divide, ground water flows northwest toward Park Creek, a tributary to Little Neshaminy Creek. Potentiometric-surface maps were prepared from water levels measured in shallow and deep wells. For both depth intervals, the direction of ground-water flow is toward the northwest. For most well clusters, the vertical head gradient is downward from the shallow to the deeper part of the aquifer. Pumping of the supply wells at times can cause the vertical flow direction to reverse.

Water-Resources Investigations Report↗