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At least 163 records · Page 9Linked to original sources
USGS2011

Enhancement of USGS scientific investigations in Texas by using geophysical techniques, 2005-10

Geophysical techniques are an increasingly important tool for scientific investigations, environmental planning, and resource management. During 2005-10 the U.S. Geological Survey Texas Water Science Center greatly expanded its capabilities of using surface and borehole geophysical techniques to gain insights into how groundwater systems work and the occurrence and distribution of certain contaminants. Geophysical techniques provide a relatively quick and inexpensive means to characterize the subsurface hydrology and lithology.

Fact Sheet↗
USGS2000

Ground geophysical study of the Buckeye mine tailings, Boulder watershed, Montana

The Buckeye mine site is located in the Boulder River watershed along Basin Creek, in northern Jefferson County, Montana. This project is part of the Boulder River watershed Abandoned Mine Lands Initiative, and is a collaborative effort between the U.S. Geological Survey and Bureau of Land Management in the U.S. Department of the Interior, and the U.S. Forest Service in the U.S. Department of Agriculture. The site includes a large flotation milltailing deposit, which extends to the stream and meadows below the mine. These tailings contain elevated levels of metals, such as silver, cadmium, copper, lead, and zinc. Metal-rich fluvial tailings containing these metals, are possible sources of ground and surface water contamination. Geophysical methods were used to characterize the sediments at the Buckeye mine site. Ground geophysical surveys, including electromagnetics, DC resistivity, and total field magnetic methods, were used to delineate anomalies that probably correlate with subsurface metal contamination. Subsurface conductivity was mapped using EM-31 and EM-34 terrain conductivity measuring systems. The conductivity maps represent variation of concentration of dissolved solids in the subsurface from a few meters, to an approximate depth of 30 meters. Conductive sulfides several centimeters thick were encountered in a shallow trench, dug in an area of very high conductivity, at a depth of approximately 1 to1.5 meters. Laboratory measurements of samples of the sulfide layers show the conductivity is on the order of 1000 millisiemens. DC resistivity soundings were used to quantify subsurface conductivity variations and to estimate the depth to bedrock. Total field magnetic measurements were used to identify magnetic metals in the subsurface. The EM surveys identified several areas of relatively high conductivity and detected a conductive plume extending to the southwest, toward the stream. This plume correlates well with the potentiometric surface and direction of ground water flow, and with water quality data from monitoring wells in and around the tailings. The electrical geophysical data suggests there has been vertical migration of high dissolved solids. A DC sounding made on a nearby granite outcrop to the north of the mine showed that the shallow conductivity is on the order of 5 millisiemens/m. Granite underlying the mine tailings, with similar electrical properties as the outcropping area, may be more than 30 meters deep.

Montana↗
USGS2003

Descriptions of mineral occurrences and interpretation of mineralized rock geochemical data in the Stikine geophysical survey area, Southeastern Alaska

Detailed descriptions of some of the more significant mineral occurrences in the Stikine Airborne Geophysical Survey Project Area are presented based upon site-specific examinations by the U.S. Geological Survey in May of 1998. Reconnaissance geochemical data on unmineralized igneous and sedimentary host rocks, and mineralized rocks are also presented and are accompanied by a brief analysis of geochemical signatures typical of each occurrence. Consistent with the stated goal of the geophysical survey; to stimulate exploration for polymetallic massive sulfides similar to the Greens Creek deposit, the majority of the described occurrences are possible members of a belt of Late Triassic mineral deposits that are distributed along the eastern edge of the Alexander terrane in southeastern Alaska. Many of the described occurrences in the Duncan Canal-Zarembo Island area share similarities to the Greens Creek deposit. When considered as a whole, the geology, mineralogy, and geochemistry of these occurrences help to define a transitional portion of the Late Triassic mineral belt where changes in shallow to deeper water stratigraphy and arc-like to rift-related igneous rocks are accompanied by concomitant changes in the size, morphology, and metal endowments of the mineral occurrences. As a result, Late Triassic mineral occurrences in the area appear as: 1) small, discontinuous, structurally controlled stockwork veins in mafic volcanic rocks, 2) small, irregular replacements and stratabound horizons of diagenetic semi-massive sulfides in dolostones and calcareous shales, and as 3) larger, recognizably stratiform accumulations of baritic, semi-massive to massive sulfides at and near the contact between mafic volcanic rocks and overlying sedimentary rocks. Empirical exploration guidelines for Greens Creek-like polymetallic massive sulfide deposits in southeastern Alaska include: 1) a Late Triassic volcano-sedimentary host sequence exhibiting evidence of succession from tectonic activity to quiescence (such as conglomeratic and/or mafic volcaniclastics or flows overlain by platform carbonate or shale sequences), 2) presence and proximity to Late Triassic mafic-ultramafic intrusions, 3) presence of quartz-carbonate-fuchsite altered ultramafic bodies, 4) pyritic, graphitic shales, 5) presence of barite and/or iron-manganese-rich carbonates, 6) low-iron sphalerite and antimony-rich sulfosalt minerals, 7) a geochemical signature including Fe-Zn-Pb-Cu-Ag-Au-Sb-Hg-As-Cd-Ba-Mn-Mo-Tl and the ultramafic-related suite of elements Ni-Cr-Co, and 8) a geophysical signature characterized by the coincidence of a sharp resistivity contrast with evidence for buried intrusive rocks. Critical factors for the development of larger, economic orebodies are significant thickness of pyritic, graphitic shale indicating that a locally reducing sedimentary setting was established and that accumulation of an insulating shale blank occurred, and proximity to Late Triassic aged hypabyssal mafic-ultramafic intrusive rocks.

Open-File Report↗
USGS2003

Description of borehole geophysical and geologist logs, Berks Sand Pit Superfund Site, Longswamp Township, Berks County, Pennsylvania

Between October 2002 and January 2003, geophysical logging was conducted in six boreholes at the Berks Sand Pit Superfund Site, Longswamp Township, Berks County, Pa., to determine (1) the waterproducing zones, water-receiving zones, zones of vertical borehole flow, orientation of fractures, and borehole and casing depth; and (2) the hydraulic interconnection between the six boreholes and the site extraction well. The boreholes range in depth from 61 to 270 feet. Geophysical logging included collection of caliper, natural-gamma, single-point-resistance, fluid-temperature, fluid-flow, and acoustic-televiewer logs. Caliper and acoustic-televiewer logs were used to locate fractures, joints, and weathered zones. Inflections on fluid-temperature and single-point-resistance logs indicated possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance, natural-gamma, and geologist logs provided information on stratigraphy. Flowmeter measurements were conducted while the site extraction well was pumping and when it was inactive to determine the hydraulic connections between the extraction well and the boreholes. Borehole geophysical logging and heatpulse flowmetering indicate active flow in the boreholes. Two of the boreholes are in ground-water discharge areas, two boreholes are in ground-water recharge areas, and one borehole is in an intermediate regime. Flow was not determined in one borehole. Heatpulse flowmetering, in conjunction with the geologist logs, indicates highly weathered zones in the granitic gneiss can be permeable and effective transmitters of water, confirming the presence of a two-tiered ground-water-flow system. The effort to determine a hydraulic connection between the site extraction well and six logged boreholes was not conclusive. Three boreholes showed decreases in depth to water after pumping of the site extraction well; in two boreholes, the depth to water increased. One borehole was cased its entire depth and was not revisited after it was logged by the caliper log. Substantial change in flow rates or direction of borehole flow was not observed in any of the three wells logged with the heatpulse flowmeter when the site extraction well was pumping and when it was inactive.

Open-File Report↗
USGS2001

Borehole geophysical data from Eastland Woolen Mill Superfund site, Corinna, Maine, March 1999

Borehole-geophysical data were collected in cooperation with the U.S. Environmental Protection Agency in seven bedrock wells at the Eastland Woolen Mill Superfund site, Penobscot County, Corinna, Maine, in March, 1999. The data were collected as part of a reconnaissance investigation to provide information needed to address concerns about the distribution and fate of contaminants in ground-water at the site. The borehole geophysical data were also needed to guide subsequent data collection associated with the development of a remediation workplan. The borehole geophysical logs collected included: natural gamma, caliper, fluid temperature, fluid conductivity, electromagnetic conductivity, electromagnetic resistivity, spontaneous potential, and single-point resistivity.

Maine↗
USGS2007

Geophysical Characterization of Pre-Cenozoic Basement for Hydrocarbon Assessment, Yukon Flats, Alaska

The Cenozoic basins of interior Alaska are poorly understood, but may host undiscovered hydrocarbon resources in sufficient quantities to serve remote villages and for possible export. Purported oil seeps and the regional occurrence of potential hydrocarbon source and reservoir rocks fuel an exploration interest in the 46,000 km2 Yukon Flats basin. Whether hydrocarbon source rocks are present in the pre-Cenozoic basement beneath Yukon Flats is difficult to determine because vegetation and surficial deposits obscure the bedrock geology, only limited seismic data are available, and no deep boreholes have been drilled. Analysis of regional potential field data (aeromagnetics and gravity) is valuable, therefore, for preliminary characterization of basement lithology and structure. We present our analysis as a red-green-blue composite spectral map consisting of: (1) reduced-to-the-pole magnetics (red), (2) magnetic potential (green), and (3) basement gravity (blue). The color and texture patterns on this composite map highlight domains with common geophysical characteristics and, by inference, lithology. The observed patterns yield the primary conclusion that much of the basin is underlain by Devonian to Jurassic oceanic rocks related to the Angayucham and Tozitna terranes (JDat). These rocks are part of a lithologically diverse assemblage of brittlely deformed, generally low-grade metamorphic rocks of oceanic affinity; such rocks probably have little or no potential for hydrocarbon generation. The JDat geophysical signature extends from the Tintina fault system northward to the Brooks Range. Along the eastern edge of the basin, JDat appears to overlie moderately dense and non-magnetic Proterozoic(?) and Paleozoic continental margin rocks. The western edge of the JDat in subsurface is difficult to distinguish due to the presence of magnetic granites similar to those exposed in the Ruby geanticline. In the southern portion of the basin, geophysical patterns indicate the possibility of overthrusting of Cenozoic sediments and underlying JDat by Paleozoic and Proterozoic rocks of the Schwatka sequence. These structural hypotheses provide the basis for an overthrust play within the Cenozoic section just south of the basin.

Open-File Report↗
USGS2010

Geophysical Data Collected off the South Shore of Martha's Vineyard, Massachusetts

The U.S. Geological Survey Woods Hole Science Center conducted a nearshore geophysical survey offshore of the southern coast of Martha's Vineyard, in the vicinity of the Martha's Vineyard Coastal Observatory in 2007. This mapping program was part of a larger research effort supporting the Office of Naval Research Ripples Directed-Research Initiative studies at Martha's Vineyard Coastal Observatory designed to improve our understanding of coastal sediment-transport processes. The survey was conducted aboard the Megan T. Miller August 9-13, 2007. The study area covers 35 square kilometers from about 0.2 kilometers to 5 kilometers offshore of the south shore of Martha's Vineyard, and ranges in depth from ~6 to 24 meters. The geophysical mapping utilized the following suite of high-resolution instrumentation to map the surficial sediment distribution, bathymetry, and sub-surface geology: a dual-frequency 100/500 kilohertz sidescan-sonar system, 234 kilohertz interferometric sonar, and 500 hertz -12 kilohertz chirp subbottom profiler. These geophysical data will be used to provide initial conditions for wave and circulation modeling within the study area.

Open-File Report↗
USGS2011

Geophysical data from offshore of the Gulf Islands National Seashore, Cat Island to Western Horn Island, Mississippi

This report contains the geophysical and geospatial data that were collected along the western offshore side of the Gulf Islands of Mississippi on the research vessel Tommy Munro during two cruises in 2010. Geophysical data were collected by the U.S. Geological Survey in Woods Hole, Massachusetts, and St. Petersburg, Forida, in cooperation with the U.S. Army Corps of Engineers Mobile District. Bathymetric-sonar, sidescan-sonar, and Chirp seismic-reflection data were acquired with the following equipment, respectively: Systems Engineering and Assessment, Ltd., SwathPlus interferometric sonars; Klein 3000 and 3900 dual-frequency sidescan sonars; and an EdgeTech 512i Chirp sub-bottom profiling system. The long-term goals of this mapping effort are to produce high-quality, high-resolution geologic maps and interpretations that can be utilized to identify sand resources within the region, to better understand the Holocene evolution, and to anticipate future changes in this coastal system. Processed geospatial data files and the geophysical data provided in this report help attain these goals.

Mississippi↗
USGS2014

Investigations into near-real-time surveying for geophysical data collection using an autonomous ground vehicle

The U.S. Geological Survey and the National Aeronautics and Space Administration are cooperatively investigating the utility of unmanned vehicles for near-real-time autonomous surveys of geophysical data collection. Initially focused on unmanned ground vehicle collection of magnetic data, this cooperative effort has brought unmanned surveying, precision guidance, near-real-time communication, on-the-fly data processing, and near-real-time data interpretation into the realm of ground geophysical surveying, all of which offer advantages over current methods of manned collection of ground magnetic data. An unmanned ground vehicle mission has demonstrated that these vehicles can successfully complete missions to collect geophysical data, and add advantages in data collection, processing, and interpretation. We view the current experiment as an initial phase in further unmanned vehicle data-collection missions, including aerial surveying.

California↗
USGS2021

Geophysical and video logs of selected wells at and near the former Naval Air Warfare Center Warminster, Bucks County, Pennsylvania, 2017-19

The U.S. Geological Survey (USGS) collected borehole geophysical and video logs in 17 open-hole wells in Northampton, Warminster, and Warwick Townships, Bucks County, Pennsylvania during 2017–19 to support detailed groundwater investigations at and near the former Naval Air Warfare Center (NAWC) Warminster, where groundwater contamination with per- and polyfluoroalkyl substances (PFAS) had become a concern since 2014. The area is underlain by the Triassic Stockton Formation, which forms a fractured-sedimentary-rock aquifer used for private, industrial, and public drinking-water supply. The geophysical and video logs were used to characterize the boreholes and identify potential water-bearing fractures for subsequent detailed investigations. Of the 17 wells that were logged, subsequent investigations were conducted by USGS in 15 wells and included hydraulic tests of discrete water-bearing zones using a straddle-packer system in 13 wells and depth-discrete point sampling in 2 wells. These 15 wells ranged in depth from about 210 to 604 feet (ft) below land surface (bls) and included six new 6-inch diameter wells drilled to initial depths of 600 ft bls on the former NAWC Warminster base property in 2018 and nine 8- to 12-inch diameter existing former production or unused test wells. Partial geophysical or video logs also were collected by USGS during 2018 in two other wells that were not included in subsequent detailed investigations. Most wells had numerous water-bearing fractures or openings throughout the depth of the open boreholes. Most of these water-bearing features appeared to be openings parallel to bedding or high-angle fractures approximately orthogonal to bedding. Casing lengths ranged from about 19 to 93 ft bls. Depth to the ambient water level at the time of logging ranged from about 1.8 ft above land surface in a flowing well to about 55 ft bls. Measured borehole flow was predominantly downward in most of the deepest wells (greater than 400 ft), which were commonly located at the highest land-surface elevations, and contained inflow from fractures at relatively shallow depths and outflow through fractures near or below depths of 500 ft bls. Borehole flow was predominantly upward in most wells less than 400 ft in depth.

Pennsylvania↗
USGS1975

Geophysical logs from a geologic test hole near Charleston, South Carolina

On March 2, 1975, the U.S. Geological Survey completed a series of geophysical well logs in the Charleston Project Deep Core Hole No. 1 located at Latitude 32° 53.2 'N and Longitude 80° 21 . 5'W in Dorchester County near Charleston, South Carolina. The land surface is at an elevation of 5.4 m (18 ft) above mean sea level. The total depth of the test hole is 793 m (2,600 ft) and the geophysical logs were recorded through fresh barite mud to the bottom. The deep geologic. test hole penetrated the entire section of Atlantic Coastal Plain sediments and extended about 40 m (130 ft) into basement rock composed of basalt flows. The purpose of the logging is to assist in the interpretation of the depositional environments, stratigraphy, structural, and geological history of the onshore and offshore areas surrounding Charleston, S.C. The purpose of this report is to make the uninterpretated geophysical recordings of the entire log suite publicly available . The logs available are shown in table 1, along with the operating depth intervals, total footage, scale, units of measure, combination log, and other pertinent data.

South Carolina↗
USGS1979

A slingram survey on the Nevada Test Site: part of an integrated geologic geophysical study of site evaluation for nuclear waste disposal

A slingram geophysical survey was made in early 1978 as part of the integrated geologlcal-geophysical study aimed at evaluating the Eleana Formation as a possible repository for nuclear waste. The slingram data were taken over an alluvial fan and pediments along the eastern flank of Syncline Ridge about 45 km north of Mercury, Nevada, on the Nevada Test Site. The data show that the more conductive argillaceous Eleana Formation varies in depth from 40 to 85 m from west to east along traverse lines. Northeast-trending linear anomalies suggest rather abrupt changes in subsurface geology that may be associated with faults and fractures. The results of the slingram survey will, when interpreted in the light of other geologic and geophysical evidence, assist in understanding the shallow parts of the geologic setting of the Eleana Formation.

Open-File Report↗
USGS1982

Geophysical studies of the Syncline Ridge area, Nevada Test Site, Nye County, Nevada

A wide variety of geophysical methods were employed to study a proposed nuclear waste site at Syncline Ridge on the Nevada Test Site, Nev. The proposed site was believed to be a relatively undisturbed synclinal structure containing a thick argillite unit of Misslsslppian age, the Eleana Formation unit J, which would be the emplacement medium. Data acquisition for the geophysical studies was constrained because of rugged topography in a block of Tipplpah Limestone overlying the central part of the proposed site. This study employed gravity, magnetic, seismic refraction and reflection, and four distinct electrical methods to try and define the structural integrity and shape of the proposed repository medium. Detailed and regional gravity work revealed complex structure at the site. Magnetics helped only in identifying small areas of Tertiary volcanic rocks because of low magnetization of the rocks. Seismic refraction assisted in identifying near surface faulting and bedrock structure. Difficulty was experienced in obtaining good quality reflection data. This implied significant structural complexity but also revealed the principal features that were supported by other data. Electrical methods were used for fault identification and for mapping of a thick argillaceous unit of the Eleana Formation in which nuclear waste was to be emplaced. The geophysical studies indicate that major faults along the axis of Syncline Ridge and on both margins have large vertical offsets displacing units so as not only to make mining difficult, but also providing potential paths for waste migration to underlying carbonate aquifers. The Eleana Formation appeared heterogeneous, which was inferred to be due to structural complexity. Only a small region in the northwest part of the study area was found to contain a thick and relatively undisturbed volume of host rock.

Open-File Report↗
USGS1982

Geophysical logs of four drill holes, Acord Lakes and Emery West quadrangles, Sevier County, Utah

This report presents the geophysical logs for four drill holes drilled during 1981 in the Skumpah Creek area (Acord Lakes quadrangle) and The Pines area (Emery West quadrangle), Sevier County, Utah. Figures 1 and 2 show drill-hole locations, and figures 3-7 are the geophysical logs. The drilling was done by a private drilling company under contract to the U.S. Geological Survey. The sites of all the drill holes are within the Wasatch Plateau Known Recoverable Coal Resource Area (KRCRA). Three of the sites are in the Richfield Ranger District of the Fishlake National Forest and one site is in the Ferron Ranger District of the Manti-LaSal National Forest. The purpose of the drilling was to identify and evaluate coal resources under public lands that may be included in a future coal leasing program. The area is underlain by Cretaceous and younger rocks (table 1). The coal seams of economic interest are in the lower 200 ft of the Upper Cretaceous Blackhawk Formation, a complex sequence of intertonguing sandstone, shale, and coal. Regional dip of the strata in the area is approximately 2° to the northwest. The geology and coal resources of the area were described by Spieker (1931), Doelling (1972), and Smith (1981). The drill holes were rotary drilled and the thicknesses and depths were determined from geophysical logs. In order to obtain data on the quality of the coal, the coal-bearing section in one hole was core drilled. Table 2 gives the drilling and logging information for the four completed holes. All drill holes were bottomed in the Upper Cretaceous Star Point Sandstone.

Utah↗
USGS1982

Phase 3 geophysical studies in the Wadi Bidah District, Kingdom of Saudi Arabia

Detailed geophysical measurements have been made in the Rabathan area, Wadi Bidah district, Kingdom of Saudi Arabia, at the site of diamond drill holes RAB-1, -2, and -3; these measurements suggest that the causative source for the anomalous EM (electromagnetic) and SP (self-potential) responses is probably highly conductive zones of Precambrian siliceous-carbonaceous rocks. Although many of the zones are no more than a few meters wide, they commonly contain 50 to 80 percent carbonaceous material and locally abundant pyrite. In places, several thin layers of highly concentrated carbonaceous material interlayered with chert form a multiple conductive zone that is seen in the geophysical data as complex anomaly patterns. In the geologic environment of Wadi Bidah, massive sulfide-bearing zones cannot be distinguished from siliceous-carbonaceous zones on the basis of the EM-SP responses. In North America in similar environments, complex resistivity methods used in experimental research have successfully discriminated between sulfide and carbonaceous conductors. Tests of such methods in the Wadi Bidah district are recommended. Geologic, geochemical, and geophysical data at the Jabal Mohr prospect suggest the possibility of mineralized rocks at depth over a possible strike length of 400 m.

Open-File Report↗
USGS1982

Geology of areas marked by geophysical anomalies (B-35 and B-34), Wadi Bidah District, Kingdom of Saudi Arabia

Geophysical surveys in the Wadi Bidah district, in the southwestern part of the Kingdom of Saudi Arabia, have revealed anomalies of the type that may be caused by deposits of massive sulfides. Accordingly, a study was undertaken to investigate the geologic environment associated with the geophysical anomalies and to determine whether mineral exploration of the anomalous areas might be warranted. An extensive geochemical sampling program did not disclose any evidence of ore mineral concentrations in the rocks. Detailed geologic mapping shows the anomalous areas to be underlain by Precambrian carbonaceous graywacke, the outcrop patterns of which closely fit the anomaly patterns. Field evidence and petrologic studies indicate that carbonaceous material in the rocks is the cause of the geophysical anomalies. Nothing was found in the anomalous areas that suggests the presence of mineral deposits of commercial grade, and further mineral investigations or exploration in the areas is not recommended.

Open-File Report↗
USGS1988

Borehole geophysics applied to ground-water investigations

The purpose of this manual is to provide hydrologists, geologists, and others who have the necessary training with the basic information needed to apply the most useful borehole-geophysical-logging techniques to the solution of problems in ground-water hydrology. Geophysical logs can provide information on the construction of wells and on the character of the rocks and fluids penetrated by those wells, in addition to changes in the character of these factors with time. The response of well logs is caused by: petrophysical factors; the quality; temperature, and pressure of interstitial fluids; and ground-water flow. Qualitative and quantitative analysis of the analog records and computer analysis of digitized logs are used to derive geohydrologic information. This information can then be extrapolated vertically within a well and laterally to other wells using logs. The physical principles by which the mechanical and electronic components of a logging system measure properties of rocks, fluids and wells, and the principles of measurement need to be understood to correctly interpret geophysical logs. Planning the logging operation involves selecting the equipment and the logs most likely to provide the needed information. Information on well construction and geohydrology are needed to guide this selection. Quality control of logs is an important responsibility of both the equipment operator and log analyst and requires both calibration and well-site standardization of equipment. Logging techniques that are widely used in ground-water hydrology or that have significant potential for application to this field include: spontaneous potential, resistance, resistivity, gamma, gamma spectrometry, gamma-gamma, neutron, acoustic velocity, acoustic televiewer, caliper, and fluid temperature, conductivity, and flow. The following topics are discussed for each of these techniques: principles and instrumentation, calibration and standardization, volume of investigation, extraneous effects, and interpretation and applications.

Open-File Report↗
USGS1997

Evaluation of geophysical logs, Phase I, at Willow Grove Naval Air Station, Montgomery County, Pennsylvania

Between April and June 1997, the U.S. Navy contracted Brown and Root Environmental, Inc., to drill 20 monitor wells at the Willow Grove Naval Air Station in Horsham Township, Montgomery County, Pa. The wells were installed to monitor water levels and allow collection of water samples from shallow, intermediate, and deep water-bearing zones. Analysis of the samples will determine the horizontal and vertical distribution of any contaminated ground water migrating from known contaminant sources. Eight wells were drilled near the Fire Training Area (Site 5), five wells near the 9th Street Landfill (Site 3), four wells at the Antenna Field Landfill (Site 2), and three wells near Privet Road Compound (Site 1). Depths range from 73 to 167 feet below land surface. The U.S. Geological Survey conducted borehole-geophysical and borehole-video logging to identify water-bearing zones so that appropriate intervals could be screened in each monitor well. Geophysical logs were run on the 20 monitor wells and 1 existing well. Video logs were run on 16 wells. Caliper and video logs were used to locate fractures, inflections on fluid-temperature and fluid-resistivity logs were used to locate possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, video logs, and driller's notes, all wells were screened such that water-level fluctuations could be monitored and discrete water samples collected from one or more shallow and intermediate water-bearing zones in each borehole.

Open-File Report↗