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G.B. Carleton

Publications and source records attributed to G.B. Carleton.

4 recordsLinked to original sources
USGS2005

Fractured-aquifer hydrogeology from geophysical logs; the passaic formation, New Jersey

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground‐water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid‐transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km 2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding‐plane partings and (2) high‐angle fractures. Bedding‐plane partings are the most numerous and have an average strike of N84°W and dip of 20° N. The high‐angle fractures are oriented subparallel to these features, with an average strike of N79° E and dip of 71° S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east‐west strike. Inspection of fluid temperature and conductance logs in conjunction with flow meter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding‐plane partings exhibit transmissivities that average roughly 5 m 2 /day and that generally diminish in magnitude and frequency with depth. The high‐angle fractures have average transmissivities that are about half those of the bedding‐plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding‐plane partings. As depth increases, the high‐angle fractures apparently become more dominant hydrologically.

Ground Water↗
USGS2005

Aquifer properties, stream base flow, water use, and water levels in the Pohatcong Valley, Warren County, New Jersey

A study was conducted to define the hydrogeology and describe the ground-water flow in the Pohatcong Valley in Warren County, N.J. near the Pohatcong Valley Ground Water Contamination Site. The area is underlain by glacial till and alluvial sediments and weathered and competent carbonate bedrock. The northwest and southeast valley boundaries are regional-scale thrust faults and ridges underlain by crystalline rocks. The unconsolidated sediments and weathered bedrock form a minor surficial aquifer. The carbonate rocks form a highly transmissive fractured-rock aquifer with well yields commonly as high as 500 gallons per minute. Ground-water recharge and flow in the crystalline-rock aquifer bordering the valley is minor compared to flow in the carbonate-rock aquifer, and little ground water flows into the carbonate-rock aquifer directly from the crystalline-rock aquifer. The thrust faults separating the carbonate and crystalline rocks may further impede flow between the two rock types. Interpretations of water-level and transmissivity data collected during 2000 to 2003 indicate that the carbonate formations generally can be considered to be one aquifer. The transmissivity of the carbonate-rock aquifer was estimated from the results of four aquifer tests conducted with two public supply wells. The transmissivity estimated from aquifer tests at a well located in Washington Borough is about 8,600 square feet per day. An aquifer test at a well located near the southwest border of Washington Borough was conducted to estimate transmissivity and the direction and magnitude of anisotropy. The estimated direction of maximum horizontal transmissivity near the second well is about 58? east of north and the magnitude is 7,600 square feet per day. The minimum horizontal transmissivity is 3,500 square feet per day and the ratio of anisotropy (maximum transmissivity to minimum transmissivity) is 2.2 to 1. Stream base-flow data indicate that Pohatcong Creek steadily gains flow, but most of the gain is from tributaries originating in the crystalline rock areas (valley walls). Therefore, it is concluded there are no major heterogeneities (such as karst springs) in ground-water discharge to surface water. During periods of low ground-water levels, it is likely that, within the study area, Pohatcong Creek gains no flow from the carbonate-rock aquifer and may even lose flow to the surficial aquifer (which then recharges the carbonate-rock aquifer). There are few sites in the Pohatcong Valley with large-scale (greater than 10 million gallons per year) ground- or surface-water withdrawals. The only substantial withdrawals in the valley are from two public supply wells and from two industrial facilities. Average annual withdrawals during 1997-2002 at these four locations totaled 298 million gallons per year. About 95 percent of the water withdrawn by the large industrial user (108 million gallons per year) is re-injected into the aquifer. In some locations throughout the valley, water levels in the shallow surficial deposits were substantially higher than those in underlying carbonate-rock aquifer. Water levels in the deep part of the surficial aquifer and underlying carbonate-rock aquifer were similar, although the gradients were often (but not always) downward. Furthermore, data collected during aquifer tests at a public supply well in Washington Borough and a public-supply well west of Washington Borough show that the deep part of the surficial aquifer is hydraulically well connected to the underlying carbonate-rock aquifer at these two locations. The shallow surficial deposits, however, are not well connected to the deep surficial deposits and carbonate rock at these two locations. The overall ground-water-flow pattern in the valley appears to be that precipitation recharges the surficial aquifer and is discharged from the surficial aquifer to the underlying bedrock aquifer and the Pohatcong Creek and its tri

Scientific Investigations Report↗
USGS1999

Hydrogeology of, water withdrawal from, and water levels and chloride concentrations in the major Coastal Plain aquifers of Gloucester and Salem Counties, New Jersey

Eight aquifers underlying Gloucester and Salem Counties in the southwestern Coastal Plain of New Jersey provide nearly all the drinking water for the 295,000 people who live in the area. Ground-water withdrawals in the two-county area and adjoining counties have affected water levels in several of these aquifers. Ground-water withdrawals in the two-county area also have affected the quality of water, increasing the chloride concentration in several of the aquifers as a result of saltwater intrusion. This report contains hydrologic data from the two-county area, including geometry and extent of hydrogeologic units, thickness and altitude of each aquifer, withdrawals from and water levels in major aquifers, and chloride concentrations in water from each aquifer. Reported ground-water withdrawals in Gloucester and Salem Counties during 1975-95 averaged 7,800 Mgal/yr (million gallons per year) for public supply, 4,900 Mgal/yr for industrial use, 700 Mgal/yr for irrigation, 500 Mgal/yr for power plants, 50 Mgal/yr for commercial use, and about 40 Mgal/yr for mining. Withdrawals for domestic self-supply in 1994 are estimated to be about 2,600 Mgal/yr, but only about 20 percent (520 Mgal/yr) is thought to be consumptive use; the remainder is returned to the aquifer through septic systems. The most heavily used aquifer in Salem and Gloucester Counties is the Upper Potomac-Raritan-Magothy aquifer, followed by, in decreasing order of use, the Middle Potomac-Raritan-Magothy aquifer, the Lower Potomac-Raritan-Magothy aquifer, the Kirkwood-Cohansey aquifer system, and the Wenonah-Mount Laurel aquifer. Reported withdrawals from these aquifers during 1975-95 averaged 5,000, 3,700, 3,200, and 330 Mgal/yr, respectively. Withdrawals from the Wenonah-Mount Laurel aquifer in Gloucester County increased during 1993-96 because of New Jersey Department of Environmental Protection restrictions on new withdrawals from the deeper Potomac-Raritan-Magothy aquifer system. Because of the increased rate of withdrawal, water-level altitudes in the Wenonah-Mount Laurel aquifer in some parts of the two counties in 1996 were from 5 to 40 ft lower than water levels measured in 1993 and previous years, reaching a low of almost 40 ft below sea level in Washington Township, Gloucester County. Ground water in the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers in the study area is withdrawn from the outcrop areas near the Delaware River downdip to the Glassboro vicinity. Water-level altitudes in 1993 in the three aquifers were near sea level in the outcrop areas near the Delaware River, but were as low as 80 ft below sea level in parts of Gloucester County that were affected by withdrawals in Camden County and were 20 to 60 ft below sea level near major withdrawal centers in the study area. Chloride concentrations in water samples from selected wells in seven aquifers throughout Gloucester and Salem Counties have been monitored since 1949. These aquifers include the Kirkwood-Cohansey aquifer system, the Vincentown and Wenonah-Mount Laurel aquifers, the Englishtown aquifer system, and the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers. The results of chloride analyses of 4,221 samples from 496 wells indicate the extent and magnitude of saltwater intrusion in these aquifers, six of which have been affected to varying degrees by saltwater intrusion. The confined Piney Point aquifer and the unconfined Kirkwood-Cohansey aquifer system show no measurable effects of saltwater intrusion in the study area. Chloride concentrations in water from selected public-supply wells screened in the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers have increased over time in communities along the Delaware River and further inland in both Gloucester and Salem Counties. Elevated chloride concentrations in the Potomac-Raritan-Magothy aquifer system are widespread in this area but rarely exceed the drinking-water standard of 250 milligrams per liter.

Water-Resources Investigations Report↗