Geology topics

J.J. Starn

Publications and source records attributed to J.J. Starn.

6 recordsLinked to original sources

USGS1997

Simulation of ground-water flow and application to the design of a contaminant removal system, Loring Air Force Base, Maine

The fractured-bedrock aquifer underlying the former Fire Training Area at Loring Air Force Base, Maine, has been contaminated with petroleum products as a result of fire training activities. A numerical model of the ground-water-flow system near the Fire Training Area was developed to provide information for the design and operation of a contaminant removal system. The goals of the simulation modeling were to (1) determine the maximum pumping rate that could be sustained, giventhe constraint that water levels not rise above a specified altitude, and (2) determine the effect of seasonal variation in recharge on the ability of a transient pumping scenario to capture contaminants. A steady-state simulation model of ground-water flow was used to determine the optimal pumping rate at the site. The optimal pumping rate was 8,570 ft3/d (44 gal/min). Monthly recharge rates wereestimated for use in a transient simulation model. During a typical year, most recharge probably occurs during two periods-one during snowmelt in early spring and another, possibly less significant period, during the late fall. The transient response of the water table to 8.5 inches of recharge in April, 2 inches of recharge in October, and 0.25 inches of recharge per month for each remaining month wassimulated. Fluctuations in ground-water levels caused by simulated seasonal variation of recharge would have minimal effect on the operation of thecontaminant removal system because the system is not pumped when recharge is lowest, ground-water velocities are lowest, and ground-water flow past the trench is minimal.

Water-Resources Investigations Report↗

USGS1996

Geohydrology and conceptual model of a ground-water-flow system near a Superfund site in Cheshire, Connecticut

Degradation of ground-water quality has been identified in an area of the north-central part of the town of Cheshire, Connecticut. An investigation by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, was done during 1994-95 to characterize the unconsolidated glacial deposits and the sedimentary bedrock, integrate the local geohydrologic conditions with the regional geohydrologic system, and develop a conceptual understanding of ground-water flow in the study area. A regional ground-water-flow model developed for the region near the study area indicates that perennial streams, including Judd Brook and the Tenmile River, form hydrologic divides that separate the larger region into hydraulically independent flow systems. In the local study area, synoptic water-level measurements made in June 1995 indicate that ground water near the water table flows west and southwestward from the low hill on the eastern side of the area toward the pond and wetlands along Judd Brook. Water-level data indicate that there is good hydraulic connection between the unconsolidated materials and underlying fractured bedrock. Unconsolidated materials in the study area consist principally of glacial stratified deposits that are fine sand, silt, and clay of glaci- olacustrine origin; locally these overlie thin glacial till. The glacial sediments range in thickness from a few feet to about 25 ft in the eastern part of the study area and are as much as 100 ft thick in the western and southern part of the study area beneath the Judd Brook and Tenmile River valleys. Fluvial redbeds of the New Haven Arkose underlie the glacial deposits in the region; in the study area, the redbeds consist of (1) channel sandstone units, which are coarse sandstone to fine conglomerate, generally in 6- to 15-ft- thick sequences; and (2) overbank mudstone units, which are siltstone and silty sandstone with some fine sandstone, generally in 6- to 50-ft-thick sequences. Thin-bedded zones of siltstone that are particularly fissile are present locally within the mudstone units. Rock units strike northward and dip eastward at about 20. The eastward-dipping strata are cut by a consistent set of west to west-northwest dipping, high-angle fractures. These fractures are oriented perpendicular to bedding and are present mostly in the channel sandstone units, but locally extend into the mudstone units as well. Borehole-geophysical logging indicates that ground water flows along bedding planes in fissile zones and between fissile zones in high-angle fractures, which are perpendicular to bedding. The combined fracture types form an aquifer system in which ground water follows a stair-step flowpath, flowing horizontally through fissile zones and vertically through high-angle fractures. Heat-pulse flow meter measurements and borehole fluid-conductivity and temperature logs indicate that only a small subset of the fissile zones and some high-angle fractures are hydraulically significant. A generalized local-scale ground-water flow model based on a nonspecific, but realistic, rock and fracture geometry was developed for the study area. Simulations show that under nonpumping conditions at a hypothetical well located in the middle of the model, ground-water flow was separated into upper and lower zones in which flow paths differed but were generally from northeast to southwest. Several short-duration aquifer tests conducted in the study area indicate that there is good hydraulic connection in the fractures between the pumping well (CS-221) and two bedrock wells located approximately 100 ft to the north and south along bedding strike. During the short duration of the aquifer tests, there was no hydraulic connection in bedrock wells located to the east, perpendicular to the strike. A range of transmissivity of 27 to 46 ft2/d was calculated from the aquifer-test data for the fractured-bedrock aquifer at CS-221 and TH-2. Individual fracture zones identified by bo

Open-File Report↗

USGS1996

Hydrogeology and simulation of ground-water flow in the alluvial aquifer at Louisville, Kentucky

The alluvial aquifer at Louisville, Ky., lies in a valley eroded by glacial meltwater that was later partly filled with outwash sand and gravel deposits. The aquifer is primarily unconfined, and the direction of flow is from the adjacent limestone and shale valley wall toward the Ohio River and major pumping centers. Pumpage and water-level data indicate that the alluvial aquifer was in a steady-state condition in November 1962 and again in November 1983. Between these two dates, water-level data indicate a general rise in the water table. A two-dimensional finite-element ground-water-flow model of the alluvial aquifer was calibrated for both the steady-state and the transient-state period of 1962-83. The year 1962 represented a period in time when pumping was nearly three times that in 1983. The simulated steady-state water budget for 1962 indicated that of the total recharge to the aquifer of 5.19 million feet per day, 37.2 percent was flow from the river to pumped wells, 28.3 percent was recharge from rainfall, 19.7 percent was flow across the eastern valley wall, and 14.8 percent was upward flow from the bedrock. Discharge from the aquifer was to wells (68.9 percent) and to the Ohio River (31.1 percent). The simulated steady-state water budget for 1983 indicated that of the total recharge to the aquifer of 4.11 million feet per day, 42.6 percent was recharge from rainfall, 18.2 percent was flow across the eastern valley wall, 17.8 percent was flow from the river to pumped wells, 15.6 percent was upward flow from the bedrock, and 5.8 percent was flow from septic systems. The transient simulation resulted in an acceptable match between measured and simulated hydrographs. This gave additional confidence to the model calibration, choice of boundary conditions, and published values of specific yield. Both steady-state and transient-state models demonstrated that the main source of water needed to meet increased pumping requirements was induced flow from the Ohio River.

Water-Resources Investigations Report↗

USGS1995

Geohydrology and simulation of ground-water flow in the aquifer system near Calvert City, Kentucky

The U.S. Geological Survey, in cooperation with the Kentucky Natural Resources and Environmental Protection Cabinet, constructed a two-dimensional, steady-state ground-water-flow model to estimate hydraulic properties, contributing areas to discharge boundaries, and the average linear velocity at selected locations in an aquifer system near Calvert City, Ky. Nonlinear regression was used to estimate values of model parameters and the reliability of the parameter estimates. The regression minimizes the weighted difference between observed and calculated hydraulic heads and rates of flow. The calibrated model generally was better than alternative models considered, and although adding transmissive faults in the bedrock produced a slightly better model, fault transmissivity was not estimated reliably. The average transmissivity of the aquifer was 20,000 feet squared per day. Recharge to two outcrop areas, the McNairy Formation of Cretaceous age and the alluvium of Quaternary age, were 0.00269 feet per day (11.8 inches per year) and 0.000484 feet per day (2.1 inches per year), respectively. Contributing areas to wells at the Calvert City Water Company in 1992 did not include the Calvert City Industrial Complex. Since completing the fieldwork for this study in 1992, the Calvert City Water Company discontinued use of their wells and began withdrawing water from new wells that were located 4.5 miles east-southeast of the previous location; the contributing area moved farther from the industrial complex. The extent of the alluvium contributing water to wells was limited by the overlying lacustrine deposits. The average linear ground-water velocity at the industrial complex ranged from 0.90 feet per day to 4.47 feet per day with a mean of 1.98 feet per day.

Water-Resources Investigations Report↗

USGS1994

Annotated bibliography of selected references on ground-water resources and geohydrology of the Louisville area, Kentucky, 1944-93

Ground water resources in the Louisville area have long been the subject of intense research and investigation. Many investigations have resulted in reports that cover a variety of topics relative to the availability and use of ground water. This bibliography was prepared because of the continued interest in ground water in the Louisville area and the need for a single source of selected references published since 1944. The bibliography is intended to assist interested parties in finding needed information but is not intended to be a complete compilation of all references. The annotated bibliography provides a synopsis of 36 reports and 4 geologic maps.

Open-File Report↗

USGS1993

Geohydrology of parts of Muhlenberg, Ohio, Butler, McLean, Todd, and Logan counties, Kentucky

Water-level, water-use, water-quality, and aquifer-yield data were collected during a well inventory in 1991 in part of western Kentucky. The data were overlaid on digital maps, using a Geographic Information System, to interpret the geohydrologic conditions within the study area. The discontinuous lithology of rocks in the area results in aquifers of limited areal extent in which local ground-water flow systems are developed; however, the regional ground-water flow generally is toward the broad alluvial areas along the Green and Rough Rivers. Fewer wells were in use in 1991 than in the 1960's when a similar well inventory was conducted; this decrease is probably due to expansion of service areas of several public water-supply systems. The quality of ground water is generally suitable for domestic use, except for a few wells that produce water with low pH and high concentrations of metals. The specific capacity of wells was found to range from 0.08 to 0.3 gallons per minute, per foot of draw- down. This range is somewhat less than values previously reported.

Water-Resources Investigations Report↗