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At least 1,441 records · Page 80Linked to original sources
USGS1999

Effects of unsaturated zone on ground-water mounding

The design of infiltration basins used to dispose of treated wastewater or for aquifer recharge often requires estimation of ground-water mounding beneath the basin. However, the effect that the unsaturated zone has on water-table response to basin infiltration often has been overlooked in this estimation. A comparison was made between two methods used to estimate ground-water mounding-an analytical approach that is limited to the saturated zone and a numerical approach that incorporates both the saturated and the unsaturated zones. Results indicate that the error that is introduced by a method that ignores the effects of the unsaturated zone on ground-water mounding increases as the basin-loading period is shortened; as the depth to the water table increases, with increasing subsurface anisotropy; and with the inclusion of fine-textured strata. Additionally, such a method cannot accommodate the dynamic nature of basin infiltration, the finite transmission time of the infiltration front to the water table, or the interception of the basin floor by the capillary fringe.The design of infiltration basins used to dispose of treated wastewater or for aquifer recharge often requires estimation of ground-water mounding beneath the basin. However, the effect that the unsaturated zone has on water-table response to basin infiltration often has been overlooked in this estimation. A comparison was made between two methods used to estimate ground-water mounding - an analytical approach that is limited to the saturated zone and a numerical approach that incorporates both the saturated and the unsaturated zones. Results indicate that the error that is introduced by a method that ignores the effects of the unsaturated zone on ground-water mounding increases as the basin-loading period is shortened; as the depth to the water table increases, with increasing subsurface anisotropy; and with the inclusion of fine-textured strata. Additionally, such a method cannot accommodate the dynamic nature of basin infiltration, the finite transmission time of the infiltration front to the water, or the interception of the basin floor by the capillary fringe.

Journal of Hydrologic Engineering↗
USGS1975

The availability of ground water for irrigation in the Rice Lake-Eau Claire Area, Wisconsin

An abundance of ground water of excellent chemical quality for irrigating crops is available from glacial outwash sand and gravel and from the underlying sandstones in the Rice Lake-Eau Claire area. Thick deposits of glacial outwash sand and gravel in the valleys of the Red Cedar and lower Chippewa Rivers yield more than 1,000 gallons per minute (63 lit res per second) to many wells. Large tracts of irrigable soils, delineated in two subareas (Rice Lake and Cameron) in Barron County and one subarea (Menomonie) in Dunn County, lie within the outwash plains where ground water is available in large quantities. Yields are especially large in the Rice Lake and Cameron subareas where the sand and gravel is highly permeable and the thickness of saturated aquifer exceeds 250 feet (75 metres). Yields generally are less than 1,000 gallons per minute (63 litres per second) in the Menomonie subarea where large amounts of clay locally reduce the permeability of the aquifer and the thickness of saturated aquifer is less than 200 feet (60 metres). Adequate water for irrigation is available also from sandstone underlying the glacial outwash plains. Because the two aquifers generally are connected hydraulically, wells penetrating the sandstone also withdraw water indirectly from the glacial drift. Most irrigation wells in Barron County withdraw water from glacial outwash; more than half the irrigation wells in Dunn County withdraw water from sandstone. In most years, recharge to the ground-water reservoir is 6 to 8 inches (150 to 200 millimetres), which is more than ample to sustain pumping for irrigation without lowering the water table significantly. Ground water in the area is a calcium bicarbonate water that ranges in dissolved-solids concentration from 35 to 330 milligrams per litre. Concentrations of sodium and' boron are very low.

Wisconsin↗
USGS1996

Geochemical and isotopic composition of ground water with emphasis on sources of sulfate in the upper Floridan Aquifer in parts of Marion, Sumter, and Citrus counties, Florida

In inland areas of northwest central Florida, sulfate concentrations in the Upper Floridan aquifer are extremely variable and sometimes exceed drinking water standards (250 milligrams per liter). This is unusual because the aquifer is unconfined and near the surface, allowing for active recharge. The sources of sulfate and geochemical processes controlling ground-water composition were evaluated in this area. Water was sampled from thirty-three wells in parts of Marion, Sumter, and Citrus Counties, within the Southwest Florida Water Management District; these included at least a shallow and a deep well at fifteen separate locations. Ground water was analyzed for major ions, selected trace constituents, dissolved organic carbon, and stable isotopes (sulfur-34 of sulfate and sulfide, carbon-13 of inorganic carbon, deuterium, and oxygen-18). Sulfate concentrations ranged from less than 0.2 to 1,400 milligrams per liter, with higher sulfate concentrations usually in water from deeper wells. The samples can be categorized into a low sulfate group (less than 30 milligrams per liter) and a high sulfate group (greater than 30 milligrams per liter). For the high sulfate water, concentrations of calcium and magnesium increased concurrently with sulfate. Chemical and isotopic data and mass-balance modeling indicate that the composition of high sulfate waters is controlled by dedolomitization reactions (dolomite dissolution and calcite precipitation, driven by dissolution of gypsum). Gypsum occurs deeper in the aquifer than open intervals of sampled wells. Upward flow has been documented in deeper parts of the aquifer in the study area, which may be driven by localized discharge areas or rapid flow in shallow parts of the aquifer. Mixing between shallow ground water and sulfate-rich water that dissolved gypsum at the base of the aquifer is probably responsible for the range of concentrations observed in the study area. Other solutes that increased with sulfate apparently originate from the gypsum itself, from other mineral assemblages found deeper in the aquifer in association with gypsum, and from residual seawater from less- flushed, deeper parts of the aquifer. These ions are subsequently transported with sulfate to shallower parts of the aquifer where gypsum is not present. The composition of low sulfate ground water is controlled by differences in the extent of microbially mediated reactions, which produce carbon dioxide. This, in turn, influences the extent of calcite dissolution. Ground waters which underwent limited microbial reactions contained dissolved oxygen and were usually in ridge areas where recharge typically is rapid. Anaerobic waters were in lower lying areas of Sumter County, where soils are poorly drained and aquifer recharge is slow. Anaerobic waters had higher concentrations of calcium, bicarbonate, sulfide, dissolved organic carbon, iron, manganese, and silica, and had lower concentrations of nitrate than aerobic ground waters. For low sulfate waters, sulfate generally originates from meteoric sources (atmospheric precipitation), with variable amounts of oxidation of reduced sulfur and sulfate reduction. Sulfide is sometimes removed from solution, probably by precipitation of a sulfide minerals such as pyrite. In areas where deep ground water has low sulfate concentrations, the shallow flow system is apparently deeper than where high sulfate concentrations occur, and upwelling sulfate-rich water is negligible. The range of sulfate concentrations observed in the study areas and differences in sulfate concentrations with depth indicate a complex interaction between shallow and deep ground-water flow systems.

Water-Resources Investigations Report↗
USGS1990

Ground-water levels, flow, and specific conductance in unconsolidated aquifers near Lake Erie, Cleveland to Conneaut, Ohio, September 1984

This report described ground-water levels, flow, and specific conductance in aquifer along the southern shore of Lake Erie from Cleveland to Conneaut, Ohio. The data were collected in September 1984 as part of the U.S Geological Survey's Northeast Glacial Buried Valley Regional Aquifer-System Analysis. The study area is about 60 miles long, extends inland from the lake about 10 miles, and encompasses parts of Cuyahoga, Lake, and Ashtabula Counties. Water levels were measured in 202 existing wells, all of which were completed in the glacial deposits or at the contact with the underlying shale. Specific conductance was measured in 59 of the wells. Results of the survey are presented in table and map form. Unconsolidated material throughout the area consists primarily of till, whereas the bedrock consists of Devonian shale. The till is composed chiefly o silt and clay with some sand and gravel, and is less than 50 feet thick in most areas. Some valleys are filled with as much as 200 feet of glacial till and outwash deposits that are mainly sand and gravel. Ground-water levels in much of the area within 20 feet of the land surface. Contours of ground-water levels resemble a subdued version of those of the land surface, which indicates that ground water generally flows from high areas to low areas following the land-surface gradient. Locally, ground water discharges into streams. Regionally, flow is towards the north-northeast, to Lake Erie. Specific conductance ranged from 160 to 2,900 μ S/cm (microsiemens per centimeter at 25 degrees Celsius) with a median of 540 μ S/cm. Ground water with a specific conductance greater than 650 μ S/cm is localized, with no specific spatial pattern; possible sources of elevated specific conductance are road-deicing salt, leachate from landfills, natural brings associated with oil and gas drilling, and the leakage of saline water from bedrock.

Ohio↗
USGS1981

Ground-water quality along the Mojave River near Barstow, California, 1974-79

The quality of ground water in the alluvium along the usually dry Mojave River near Barstow, Calif., has been monitored since 1974. Degradation has occurred as a result of wastewater discharge and irrigation return. Characteristics of the degraded ground water include concentrations of dissolved solids exceeding 1,000 milligrams per liter, odor threshold numbers exceeding 5, dissolved organic carbon exceeding 2.0 milligrams per liter, chloride exceeding 250 milligrams per liter, phenols exceeding 1 microgram per liter, and methylene blue active substances exceeding 0.20 milligram per liter. Large flows in the river during the winters of 1977-78 and 1978-79 recharged the aquifer with water from storm runoff. The ground-water-quality monitoring data showed that few changes in the concentration and distribution of chemical constituents occurred between 1974 and 1977, but between 1977 and 1979 there were overall decreases in most constituents and in odor. The monitoring data also showed that between 1977 and 1979 the degraded ground water spread and moved downgradient, whereas prior to 1977 it had been generally confined to an area between Barstow and the U.S. Marine Corps Supply Center. (USGS)

Water-Resources Investigations Report↗
USGS1993

Ground-water conditions in Utah, spring of 1993

This is the thirtieth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, related changes in precipitation and streamflow, and chemical quality of water. Supplementary data, such as maps showing water-level contours, are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1992. Water-level fluctuations and selected related data, however, are described from the spring of 1988 to the spring of 1993. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Divisions of Water Rights and Water Resources, Utah Department of Natural Resources.

Utah↗
USGS2009

Occurrence of Pesticides in Ground Water of Wyoming, 1995-2006

Little existing information was available describing pesticide occurrence in ground water of Wyoming, so the U.S. Geological Survey, in cooperation with the Wyoming Department of Agriculture and the Wyoming Department of Environmental Quality on behalf of the Wyoming Ground-water and Pesticides Strategy Committee, collected ground-water samples twice (during late summer/early fall and spring) from 296 wells during 1995-2006 to characterize pesticide occurrence. Sampling focused on the State's ground water that was mapped as the most vulnerable to pesticide contamination because of either inherent hydrogeologic sensitivity (for example, shallow water table or highly permeable aquifer materials) or a combination of sensitivity and associated land use. Because of variations in reporting limits among different compounds and for the same compound during this study, pesticide detections were recensored to two different assessment levels to facilitate qualitative and quantitative examination of pesticide detection frequencies - a common assessment level (CAL) of 0.07 microgram per liter and an assessment level that differed by compound, referred to herein as a compound-specific assessment level (CSAL). Because of severe data censoring (fewer than 50 percent of the data are greater than laboratory reporting limits), categorical statistical methods were used exclusively for quantitative comparisons of pesticide detection frequencies between seasons and among various natural and anthropogenic (human-related) characteristics. One or more pesticides were detected at concentrations greater than the CAL in water from about 23 percent of wells sampled in the fall and from about 22 percent of wells sampled in the spring. Mixtures of two or more pesticides occurred at concentrations greater than the CAL in about 9 percent of wells sampled in the fall and in about 10 percent of wells sampled in the spring. At least 74 percent of pesticides detected were classified as herbicides. Considering only detections using the CAL, triazine pesticides were detected much more frequently than all other pesticide classes, and the number of different pesticides classified as triazines was the largest of all classes. More pesticides were detected at concentrations greater than the CSALs in water from wells sampled in the fall (28 different pesticides) than in the spring (21 different pesticides). Many pesticides were detected infrequently as nearly one-half of pesticides detected in the fall and spring at concentrations greater than the CSALs were detected only in one well. Using the CSALs for pesticides analyzed for in 11 or more wells, only five pesticides (atrazine, prometon, tebuthiuron, picloram, and 3,4-dichloroaniline, listed in order of decreasing detection frequency) were each detected in water from more than 5 percent of sampled wells. Atrazine was the pesticide detected most frequently at concentrations greater than the CSAL. Concentrations of detected pesticides generally were small (less than 1 microgram per liter), although many infrequent detections at larger concentrations were noted. All detected pesticide concentrations were smaller than U.S. Environmental Protection Agency (USEPA) drinking-water standards or applicable health advisories. Most concentrations were at least an order of magnitude smaller; however, many pesticides did not have standards or advisories. The largest percentage of pesticide detections and the largest number of different pesticides detected were in samples from wells located in the Bighorn Basin and High Plains/ Casper Arch geographic areas of north-central and southeastern Wyoming. Prometon was the only pesticide detected in all eight geographic areas of the State. Pesticides were detected much more frequently in samples from wells located in predominantly urban areas than in samples from wells located in predominantly agricultural or mixed areas. Pesticides were detected distinctly less often in sa

Scientific Investigations Report↗
USGS1955

Memorandum describing the geology and ground-water conditions in the vicinity of Simpsonville, Maryland

This memorandum summarizes briefly the result of a study of the ground-water conditions of a small area near Simpsonville, Maryland, underlain chiefly by the Guilford granite (granite-pegmatite) of early Paleozoic or late Precambrian age. The records. of 15 wells and 5 sprints are given, as are t he sample-study legs of 3 test wells drilled at the site of a planned industrial labratory. A geologic map revised some-what from a published map by Cloos and Broedel is included (fig. 1). The study of the hydrology in the vicinity of Simpsonville was undertaken as a part of the ground-water investigations in cooperation with the Maryland Department of Geology, Mines and Water Resources. It provides ground-water data in addition to those already available, as a basis for a decision by the Maryland Water Resources Commission in regard to the application of an industrial laboratory to appropriate 200,000 gallons of ground water a day at a site about half a mile northwest of Simpsonville (approximately 12 miles southwest of Baltimore). Also, it supplements existing information on the occurrence of ground water in crystalline rocks of the type underlying the site, which are widespread in the Piedmont of Maryland and other States.

South Carolina↗
USGS2014

A state‐wide program of periodic measurements of ground‐water level In Nebraska

The precipitation in Nebraska has been considerably less than normal in the last four years, and in consequence the ground ‐ water level in many parts of the State has declined to a marked extent. Moreover, in some parts of Nebraska the ground ‐ water level has declined as the result of land‐drainage, and in other parts it has risen as the result of irrigation with water diverted from streams. These changes in ground ‐ water level produced by drainage, irrigation, and decreased precipitation have caused wells to fail, streams to cease flowing, lakes to become dry, and land to become water ‐logged. Consequently, interest in fluctuations of ground ‐ water level has greatly increased, and the need of a systematic collection of base‐data for the future study of ground ‐ water problems has been recognized.

Nebraska↗
USGS1985

Ground-water and surface-water interactions in Minnesota and Wisconsin wetlands

The interaction between ground water and surface water in wetlands is complex and depends on the hydrologic setting of the particular wetland. Hydrologic characteristics have been used in Wisconsin to classify wetlands into four categories; surface-waterdepression wetlands, surface-water-slope wetlands, ground-waterdepression wetlands, and ground-water-slope wetlands, as described by Novitzki (1978). The degree of ground- and surface-water interactions differs between the four categories.

Minnesota, Wisconsin↗
USGS2007

Investigation of Ground-Water Contamination at Solid Waste Management Unit 12, Naval Weapons Station Charleston, North Charleston, South Carolina

The U.S. Geological Survey and the Naval Facilities Engineering Command Southeast investigated natural and engineered remediation of chlorinated volatile organic compound ground-water contamination at Solid Waste Management Unit 12 at the Naval Weapons Station Charleston, North Charleston, South Carolina. The primary contaminants of interest are tetrachloroethene, 1,1,1-trichloroethane, trichloroethene, cis-1,2-dichloroethene, vinyl chloride, 1,1-dichloroethane, and 1,1-dichloroethene. In general, the hydrogeology of Solid Waste Management Unit 12 consists of a surficial aquifer, composed of sand to clayey sand, overlain by dense clay that extends from about land surface to a depth of about 8 to 10 feet and substantially limits local recharge. During some months in the summer, evapotranspiration and limited local recharge result in ground-water level depressions in the forested area near wells 12MW-12S and 12MW-17S, seasonally reflecting the effects of evapotranspiration. Changes in surface-water levels following Hurricane Gaston in 2004 resulted in a substantial change in the ground-water levels at the site that, in turn, may have caused lateral shifting of the contaminant plume. Hydraulic conductivity, determined by slug tests, is higher along the axis of the plume in the downgradient part of the forests than adjacent to the plume, implying that there is some degree of lithologic control on the plume location. Hydraulic conductivity, hydraulic gradient, sulfur-hexafluoride measurements, and historical data indicate that ground-water flow rates are substantially slower in the forested area relative to upgradient areas. The ground-water contamination, consisting of chlorinated volatile organic compounds, extends eastward in the surficial aquifer from the probable source area near a former underground storage tank. Engineered remediation approaches include a permeable reactive barrier and phytoremediation. The central part of the permeable reactive barrier along the main axis of the contaminant plume appears to be actively removing contamination; however, ground-water contamination is moving around the southern end of the permeable reactive barrier. Changes in the contaminant concentrations along the path of ground-water transport reflect a complex variety of influences. Potential influences include dechlorination, sorption and desorption, transpirative removal by trees, lateral shifting of the plume, and the presence of zones of differing concentrations possibly reflecting one or more pulse releases of contamination from the source area. Near the source area at well 12MW-10S, volatile organic compound concentrations of cis-1,2-dichlorothene, vinyl chloride, 1,1-dichloroethane, and 1,1,1-trichloroethane continued an irregular decline, while tetrachloroethene and 1,1-dichloroethene showed marked fluctuations in concentration during 2005 and 2006. Volatile organic compound concentrations at well 12MW-03S continued to show decreasing concentrations with the June 2006 concentrations being the lowest yet recorded at that well for several volatile organic compounds. Concentration and delta carbon 13 data indicate that in the upgradient part of the plume, tetrachloroethene is being degraded to trichloroethene, which is being degraded to cis-1,2-dichloroethene, and cis-1,2-dichloroethene is accumulating faster than it is being depleted. Ground-water volatile organic compound concentrations also changed in some wells in the forested area in the midpart of the plume. Increasing tetrachloroethene and decreasing trichloroethene and 1,1-dichloroethene concentrations were observed at wells 12MW-05S and 12MW-29S, possibly reflecting a lateral shift in the axis of the contamination plume or an advancing contamination pulse. Substantial decreases in contamination occur in the forested area downgradient from well 12MW-05S. Probable major loss mechanisms in this area include evapotranspiration and sorption.

North Carolina, South Carolina↗
USGS1996

Ground-water conditions and quality in the western part of Kenai Peninsula, southcentral Alaska

The western part of Kenai Peninsula in southcentral Alaska is bounded by Cook Inlet and the Kenai Mountains. Ground water is the predominant source of water for commercial, industrial, and domestic uses on the peninsula. Mean daily water use in an oil, gas, and chemical processing area north of Kenai is more than 3.5 million gallons. Unconsolidated sediments of glacial and fluvial origin are the most productive aquifers. In the upper (northwestern) peninsula, almost all water used is withdrawn from unconsolidated sediments, which may be as thick as 750 feet. In the lower peninsula, unconsolidated sediments are thinner and are absent on many hills. Water supplies in the lower peninsula are obtained from unconsolidated sediments and bedrock, and a public-water supply in parts of Homer is obtained from Bridge Creek. Throughout the peninsula, ground-water flow occurs primarily as localized flow controlled by permeability of aquifer materials and surface topography. The concentration of constituents analyzed in water from 312 wells indicated that the chemical quality of ground water for human consumption varies from marginal to excellent. Even though the median concentration of dissolved solids is low (152 milligrams per liter), much of the ground water on the peninsula does not meet water-quality regulations for public drinking water established by the U.S. Environmental Protection Agency (USEPA). About 8 percent of wells sampled yielded water having concentrations of dissolved arsenic that exceeded the USEPA primary maximum contaminant level of 50 micrograms per liter. Concentrations of dissolved arsenic were as great as 94 micrograms per liter. Forty-six percent of wells sampled yielded water having concentrations of dissolved iron greater than the USEPA secondary maximum contaminant level of 300 micrograms per liter. Unconsolidated sediments generally yield water having calcium, magnesium, and bicarbonate as its predominant ions. In some areas, ground water at depths greater than a few hundred feet may be naturally too salty for human consumption. The leaking and spilling of fuel and chemical products and the disposal of industrial wastes has degraded the quality of ground water at numerous sites.

Open-File Report↗
USGS1991

Geochemical evolution of acidic ground water at a reclaimed surface coal mine in western Pennsylvania

Concentrations of dissolved sulfate and acidity in ground water increase downflow in mine spoil and underlying bedrock at a reclaimed surface coal mine in the bituminous field of western Pennsylvania. Elevated dissolved sulfate and negligible oxygen in ground water from bedrock about 100 feet below the water table suggest that pyritic sulfur is oxidized below the water table, in a system closed to oxygen. Geochemical models for the oxidation of pyrite (FeS 2 ) and production of sulfate (SO 4 2- ) and acid (H + ) are presented to explain the potential role of oxygen (O 2 ) and ferric iron (Fe 3+ ) as oxidants. Oxidation of pyrite by O 2 and Fe 3+ can occur under oxic conditions above the water table, whereas oxidation by Fe 3+ also can occur under anoxic conditions below the water table. The hydrated ferric-sulfate minerals roemerite [Fe 2+ Fe 4 3+ (SO 4 ) 4 ·14H 2 O], copiapite [Fe 2+ Fe 4 3+ (SO 4 ) 6 (OH) 2 ·20H 2 0], and coquimbite [Fe 2 (SO 4 ) 3 · 9H 2 O] were identified with FeS 2 in coal samples, and form on the oxidizing surface of pyrite in an oxic system above the water table. These soluble ferric-sulfate 11 salts11 can dissolve with recharge waters or a rising water table releasing Fe 3+ , SO 4 2- . and H + , which can be transported along closed-system ground-water flow paths to pyrite reaction sites where O 2 may be absent. The Fe 3+ transported to these sites can oxidize pyritic sulfur. The computer programs WATEQ4F and NEWBAL were used to compute chemical speciation and mass transfer, respectively, considering mineral dissolution and precipitation reactions plus mixing of waters from different upflow zones. Alternative mass-balance models indicate that (a) extremely large quantities of O 2 , over 100 times its aqueous solubility, can generate the observed concentrations of dissolved SO 4 2- from FeS 2 , or (b) under anoxic conditions, Fe 3+ from dissolved ferric-sulfate minerals can oxidize FeS 2 along closed-system ground-water flow paths. In a system open to O 2 , such as in the unsaturated zone, the aqueous solubility of O 2 is not limiting, and oxidation of pyrite by O 2 and Fe 3+ accounts for most SO 4 2- and Fe 2+ observed in acidic ground water. However, in a system closed to O 2 , such as in the saturated zone, O 2 solubility is limiting; hence, ferric oxidation of pyrite is a reasonable explanation for the observed elevated SO 4 2- with increasing depth below the water table.

Pennsylvania↗
USGS1992

Ground-water-quality assessment of the central Oklahoma aquifer, Oklahoma: Hydrologic, water-quality, and quality-assurance data 1987-90

This report presents data collected from 202 wells between June 1987 and September 1990 as part of the Central Oklahoma aquifer pilot study of the National Water-Quality Assessment Program. The report describes the sampling networks, the sampling procedures, and the results of the ground-water quality and quality-assurance sample analyses. The data tables consist of information about the wells sampled and the results of the chemical analyses of ground water and quality-assurance sampling. Chemical analyses of ground-water samples in four sampling networks are presented: A geochemical network, a low-density survey bedrock network, a low-density survey alluvium and terrace deposits network, and a targeted urban network. The analyses generally included physical properties, major ions, nutrients, trace substances, radionuclides, and organic constituents. The chemical analyses of the ground-water samples are presented in five tables: (1) Physical properties and concentrations of major ions, nutrients, and trace substances; (2) concentrations of radionuclides and radioactivities; (3) carbon isotope ratios and delta values (d-values) of selected isotopes; (4) concentrations of organic constituents; and (5) organic constituents not reported in ground-water samples. The quality of the ground water sampled varied substantially. The sum of constituents (dissolved solids) concentrations ranged from 71 to 5,610 milligrams per liter, with 38 percent of the wells sampled exceeding the Secondary Maximum Contaminant Level of 500 milligrams per liter established under the Safe Drinking Water Act. Values of pH ranged from 5.7 to 9.2 units with 20 percent of the wells outside the Secondary Maximum Contaminant Level of 6.5 to 8.5 units. Nitrite plus nitrate concentrations ranged from less than 0.1 to 85 milligrams per liter with 8 percent of the wells exceeding the proposed Maximum Contaminant Level of 10 milligrams per liter. Concentrations of trace substances were highly variable, ranging from below the reporting level to concentrations over the Maximum Contaminant Levels for several constituents (arsenic, barium, cadmium, chromium, lead, and selenium). Radionuclide activities also were highly variable. Gross alpha radioactivity ranged from 0.1 to 210 picocuries per liter as 230thorium. Of the wells sampled, 20 percent exceeded the proposed Maximum Contaminant Level of 15 picocuries per liter for gross alpha radioactivity. Organic constituents were detected in 39 percent of the 170 wells sampled for organic constituents; in most cases concentrations were at or near the laboratory minimum reporting levels. Ten of the wells sampled for organic constituents had one or more constituents (chlordane, dieldrin, heptachlor epoxide, trichloroethylene, 1,1-dichloroethylene, 1,1,1-trichloroethane) at concentrations equal to or greater than the Maximum Contaminant Level or acceptable concentrations as suggested in the Environmental Protection Agency's Health Advisory Summaries. Quality-assurance sampling included duplicate samples, repeated samples, blanks, spikes, and blind samples. These samples proved to be essential in evaluating the accuracy of the data, particularly in the case of volatile organic constituents.

Oklahoma↗
USGS2007

Robowell: An automated process for monitoring ground water quality using established sampling protocols

Robowell is an automated process for monitoring selected ground water quality properties and constituents by pumping a well or multilevel sampler. Robowell was developed and tested to provide a cost-effective monitoring system that meets protocols expected for manual sampling. The process uses commercially available electronics, instrumentation, and hardware, so it can be configured to monitor ground water quality using the equipment, purge protocol, and monitoring well design most appropriate for the monitoring site and the contaminants of interest. A Robowell prototype was installed on a sewage treatment plant infiltration bed that overlies a well-studied unconfined sand and gravel aquifer at the Massachusetts Military Reservation, Cape Cod, Massachusetts, during a time when two distinct plumes of constituents were released. The prototype was operated from May 10 to November 13, 1996, and quality-assurance/quality-control measurements demonstrated that the data obtained by the automated method was equivalent to data obtained by manual sampling methods using the same sampling protocols. Water level, specific conductance, pH, water temperature, dissolved oxygen, and dissolved ammonium were monitored by the prototype as the wells were purged according to U.S Geological Survey (USGS) ground water sampling protocols. Remote access to the data record, via phone modem communications, indicated the arrival of each plume over a few days and the subsequent geochemical reactions over the following weeks. Real-time availability of the monitoring record provided the information needed to initiate manual sampling efforts in response to changes in measured ground water quality, which proved the method and characterized the screened portion of the plume in detail through time. The methods and the case study described are presented to document the process for future use.

Ground Water Monitoring and Remediation↗
USGS1996

Susceptibility of ground water to surface and shallow sources of contamination in Mississippi

Ground water, because of its extensive use in agriculture, industry, and public-water supply, is one of Mississippi's most important natural resources. Ground water is the source for about 80 percent of the total freshwater used by the State's population (Solley and others, 1993). About 2,600 Mgal/d of freshwater is withdrawn from aquifers in Mississippi (D.E. Burt, Jr., U.S. Geological Survey, oral commun., 1995). Wells capable of yielding 200 gal/min of water with quality suitable for most uses can be developed nearly anywhere in the State (Bednar, 1988). The U.S. Geological Survey (USGS), in cooperation with the Mississippi Department of Environmental Quality, Office of Pollution Control, and the Mississippi Department of Agriculture and Commerce, Bureau of Plant Industry, conducted an investigation to evaluate the susceptibility of ground water to contamination from surgace and shallow sources in Mississippi. A geographic information system (GIS) was used to develop and analyze statewide spatial data layers that contain geologic, hydrologic, physiographic, and cultural information.

Mississippi↗
USGS1995

Streamflow, ground-water recharge and discharge, and characteristics of surficial deposits in Buzzards Bay Basin, southeastern Massachusetts

Streamflow measurements at 14 low-flow partial-record stations and two discontinued streamflow-gaging stations were related to concurrent streamflows at six long-term streamflow-gaging stations to estimate streamflows at selected flow durations from 50 to 99 percent for water years 1967-91. At low flows, stream discharge per square mile generally increased with increasing percentage of subbasin underlain by stratified-drift deposits. At the 70-, 90-, and 99-percent flow durations, subbasins underlain primarily by stratified-drift deposits had stream discharges per square mile at least 2, 4, and 8 times greater, respectively, than subbasins underlain primarily by till and bedrock deposits. Streamflow measured three times at the Paskamanset River showed that streamflows downstream of municipal pumped wells increased at a lower rate per unit drainage area than streamflows upstream of the pumped wells. When pumpage from wells near the river was added to measured streamflow at the most downstream station, the sum was similar to the potential streamflow at the station if its streamflow per unit area was the same as that upstream from the pumped wells. Mean ground-water recharge and discharge rates were computed from continuous records of daily mean discharge during water years 1967-91 for six streamflow-gaging stations in southeastern Massachusetts and Rhode Island. Estimates of mean ground-water recharge were 19.7 to 22.6 inches per year for stations with drainage areas primarily underlain by till and bedrock deposits, and 23.8 to 25.2 inches per year for stations with drainage areas primarily underlain by stratified-drift deposits. During drought years, annual ground-water recharge can be less than 50 percent of the mean ground-water recharge rate for water years 1967-91. Estimates of ground-water discharge rates generally were 1 to 4 inches per year less than estimates of ground-water recharge rates. Ground-water discharge-duration curves were calculated from hydrograph separation of streamflow records at the six continuous streamflow-gaging stations for water years 1967-91. When streamflows were less than the median streamflow (50-percent duration), ground-water discharges averaged 85.7 percent of the total streamflow at the six streamflow-gaging stations. Ground-water discharges were estimated at the 14 low-flow partial-record stations and two discontinued streamflow-gaging stations by multiplying streamflows at the selected flow durations from 50 to 99 percent for water years 1967-91 by 85.7 percent. Data on surficial deposits in the basin were obtained by drilling 10 wells, by conducting 12 seismic-refraction surveys, and by collecting well log data for 313 wells from consulting firms and the Massachusetts Department of Environmental Management. These data indicated that a few minor corrections could be made to existing saturated thickness maps for stratified-drift deposits in Buzzards Bay Basin. Few well logs were detailed enough to estimate transmissivities; thus existing transmissivity maps were not updated for stratified-drift deposits in the basin.

Massachusetts↗
USGS1996

Effectiveness of highway-drainage systems in preventing contamination of ground water by road salt, Route 25, southeastern Massachusetts; description of study area, data collection programs, and methodology

Four test sites along a 7-mile section of Route 25 in southeastern Massachusetts, each representing a specific highway-drainage system, were instrumented to determine the effectiveness of the drainage systems in preventing contamination of ground water by road salt. One of the systems discharges highway runoff onsite through local drainpipes. The other systems use trunkline drainpipes through which runoff from highway surfaces, shoulders, and median strips is diverted and discharged into either a local stream or a coastal waterway. Route 25 was completed and opened to traffic in the summer of 1987. Road salt was first applied to the highway in the winter of 1987-88. The study area is on a thick outwash plain composed primarily of sand and gravel. Water-table depths range from 15 to 60 feet below land surface at the four test sites. Ground-water flow is in a general southerly direction, approximately perpendicular to the highway. Streamflow in the study area is controlled primarily by ground-water discharge. Background concentrations of dissolved chloride, sodium, and calcium-the primary constituents of road salt-are similar in ground water and surface water and range from 5 to 20, 5 to 10, and 1 to 5 milligrams per liter, respectively. Data-collection programs were developed for monitoring the application of road salt to the highway, the quantity of road-salt water entering the ground water, diverted through the highway-drainage systems, and entering a local stream. The Massachusetts Highway Department monitored road salt applied to the highway and reported these data to the U.S. Geological Survey. The U.S. Geological Survey designed and operated the ground-water, highway- drainage, and surface-water data-collection programs. A road-salt budget will be calculated for each test site so that the effectiveness of the different highway-drainage systems in preventing contamination of ground water by road salt can be determined.

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