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Laurence J. McGreevy

Publications and source records attributed to Laurence J. McGreevy.

6 recordsLinked to original sources

Development of a digital model of ground-water flow in deeply weathered crystalline rock, Chester County, Pennsylvania

The model developed in this study simulates .recharge to, flow through, and discharge from the water-table aquifer in the upper Pickering Creek basin, a 5.98-square-mile basin representative of most of Chester County, Pennsylvania. The two-dimensional finite-difference model of Trescott, Pinder, and Larson was used with slight modification. The way ground-water evapotranspiration varies with depth was modified, and a minimum transmissivity was used to prevent the model from "going dry" during water-table simulations. Tests of the model showed good correlation with field data, but also showed that certain additional types of information would be useful to make the model more reliable. Particularly helpful would be more water-level and evapotranspiration data, synoptic base-flow measurements in the subbasins, and better information on the variation of permeability and specific yield with depth. Predictive simulations made by the model show the effects of imposing various changes on the hydrologic system. Residential development was simulated in 1 square mile of the basin by combinations of the following conditions: 1-acre, 1/2-acre, and 1/4-acre lot size; wastewater disposal by septic systems or by public sewers; domestic wells or public-supply wells for water supply; and 0, 1, and 5 percent reduction in recharge in the developed area. Where water is supplied locally by wells, decreased lot size and reduced recharge result in increased drawdowns and reduced base flow. When wastewater is exported by sewers, these effects are magnified. The simulations by the model show the relative severity of the effects of various development schemes.

Pennslyvania↗

Ground-water resources of Chester County, Pennsylvania

Fifty gallons per minute (3 liters per second) or more may be obtained from wells in almost all parts of the county, but not at all locations. Adequate exploration to find fracture or solution openings is required. Five hundred gallons per minute (30 liters per second) or more may be obtained from some of the carbonate rocks. Linear features are visible on 1:1,000,000-to 1:24,000-scale aerial imagery. Many linear features, but not all, have geologic or hydrologic significance, and some may indicate fractured rock that might be tapped by wells. Dissolved-solids concentration of most ground water is less than 500 milligrams per liter. Chemical-quality problems are predominantly caused by acidity, iron and manganese, or nitrate. Base (ground-water) runoff during a near-average year, 1968, was about 420 million gallons per day (18 cubic meters per second).

Pennsylvania↗

Selected hydrologic data, Chester County, Pennsylvania

This report presents selected hydrologic data collected during a study of the ground-water resources of Chester County, Pennsylvania. The study was made during 1973-76 by the U. S. Geological Survey in cooperation with the Chester County Water Resources Authority. This report is intended to make the data conveniently available and to supplement an interpretive report that will be published separately.

Pennsylvania↗

Ground-water resources of the Wind River Indian Reservation, Wyoming

The area of this investigation is in the western part of the Wind River Basin and includes parts of the Absaroka, Washakie, Wind River, and Owl Creek Mountains. The purposes of the study were to determine the general hydrologic properties of the rocks in the area and the occurrence and quality c f the water in them. Structurally, the area is a downfolded basin surrounded by upfolded mountain ranges. Igneous and metamorphic rocks of Precambrian age are exposed in the mountains: folded sedimentary rocks representing all geologic periods, except the Silurian, crop out along the margins of the basin; and relatively flat-lying Tertiary rocks are at the surface in the central part of the basin. Surficial sand and gravel deposits of Quaternary age occur along streams and underlie numerous terraces throughout the basin. The potential yield and quality of water from most rocks in the area are poorly known, but estimates are possible, based on local well data and on data concerning similar rocks in nearby areas. Yields of more than 1,000 gpm are possible from the rocks comprising the Bighorn Dolomite (Ordovician), Darby Formation (Devonian), Madison Limestone (Mississippian), and Tensleep Sandstone (Pennsylvanian). Total dissolved solids in the water range from about 300 to 3,000 ppm. Yields of as much as several hundred gallons per minute are possible from the Nugget Sandstone (Jurassic? and Triassic?). Yields of 20 gpm or more are possible from the Crow Mountain Sandstone (Triassic) and Sundance Formation (Jurassic). Dissolved solids are generally high but are less than 1,000 ppm near outcrops in some locations. The Cloverly and Morrison (Cretaceous and Jurassic), Mesaverde (Cretaceous) and Lance(?) (Cretaceous) Formations may yield as much as several hundred gallons per minute, but most wells in Cretaceous rocks yield less than 20 gpm. Dissolved solids generally range from 1,000 to 5,000 ppm but may be higher. In some areas, water with less than 1,000 ppm dissolved solids may be available from the Cloverly and Morrison Formations. Tertiary rocks yield a few to several hundred gallons per minute and dissolved solids generally range from 1,000 to 5,000 ppm. Wells in the Wind River Formation (Eocene) yield about 1.-500 gpm of water having dissolved solids of about 200-5,000 ppm. Yields of a few to several hundred gallons per minute are available from alluvium (Quaternary). Dissolved solids range from about 200 to 5,000 ppm. Many parts of the Wind River Irrigation Project have become waterlogged. The relation of drainage problems to geology and the character and thickness of rocks in the irrigated areas are partly defined by sections drawn on the basis of test drilling. The drainage-problem areas are classified according to geologic similarities into five general groups: flood plains, terraces, underfit-stream valleys, slopes, and transitional areas. Drainage can be improved by open drains, buried drains, relief wells, and pumped wells or by pumping from sumps or drains. The methods that will be most successful depend on the local geologic and hydrologic conditions. In several areas, the most effective means of relieving the drainage problem would be to reduce the amount of infiltration of water by lining canals and ditches and by reducing irrigation water applications to the optimum. Water from underground storage in alluvium could supplement water from surface storage in some areas. A few thousand acre-feet of water per square mile are in storage in some of the alluvium. The use of both surface and underground storage would reduce the need for additional surface-storage facilities and also would alleviate drainage problems in the irrigated areas.

Water Supply Paper↗

Ground water east of Jackson Lake, Grand Teton National Park, Wyoming

The project area, which lies east of and adjacent to Jackson Lake is on the downthrown eastern block of the Teton fault, a normal fault that trends northward along the west edge of Jackson Lake. Rocks of pre-Cretaceous age are deeply buried beneath this area. Sedimentary rocks of Cretaceous age and sedimentary and volcanic rocks of Tertiary age, which have an aggregate thickness of about 30,000 feet, are exposed in the northern and eastern parts of the area. Along most of the east side of Jackson Lake, unconsolidated glacial and interglacial deposits of Quaternary age overlie the rocks of Cretaceous and Tertiary age. The unconsolidated deposits were penetrated by test drilling to a depth of 206 feet, but the maximum thickness is probably much greater. Test wells were drilled in five localities to evaluate the deposits of Quaternary age as possible sources of ground water for National Park Service facilities. In the Pilgrim Creek valley, test wells were capable of yielding 200 gpm (gallons per minute); properly constructed production wells could obtain much greater yields. Test wells at Lizard Point and Jackson Lake Campgrounds yielded more than 100 gpm, and a test well near the confluence of the Buffalo Fork and Snake rivers yielded 30 gpm. A test hole drilled in the NW1/4 sec. 36, T. 46 N., R. 115 W., was dry at 200 feet. Unconsolidated deposits of Quaternary age are the most promising source of additional ground water. Because of the extreme range in grain size and sorting, these deposits vary greatly in permeability. Their saturated thickness ranges from 0 to more than 130 feet and changes seasonally; variations of as much as 36 feet were measured (1961-62) in the Pilgrim Creek valley. In most localities where deposits of Quaternary age are ,present, small to moderate ground-water supplies can be developed; larger ground-water supplies can be developed in parts of the Pilgrim Creek valley. One well taps the Bivouac Formation of Late Pliocene or Pleistocene age, but no other wells are known to tap rocks of possible pre-Quaternary age. The Harebell Formation and Bacon Ridge Sandstone of Late Cretaceous age and the Bivouac Formation offer the best possibilities for development of additional water supplies from the consolidated rocks. Chemical analyses of water samples from 11 wells in the deposits of Quaternary age and 1 well in the Bivouac Formation indicate that the water is of generally good quality for drinking and most other purposes. Water from one well tapping lacustrine(?) sand had a dissolved-solids content of 321 ppm (parts per million); all other samples had from 87 to 145 ppm.

Wyoming↗

Stratigraphy of the area between Hernando and Hardee counties, Florida

Eocene, Oligocene, Miocene, and Recent rocks are exposed between Hernando and Hardee Counties. Eocene and Oligocene formations are fossiliferous limestones but Miocene rocks are largely unconsolidated sands and clays in which fossils are scarce. Correlation of Miocene strata therefore is necessarily based mainly on lithology and stratigraphic position. Where rocks are altered by weathering, correlation is based on original rather than present gross Tithelogy. Quartz sand was found to be valuable in correlation because it is not affected by weathering. Rocks in the report area previously mapped as the upper Miocene or lower Pliocene Alachua and Bone Valley formations .were found to range from lower to middle Miocene and are assigned to the Tampa and Hawthorn formations. The Citronelle formation of Pliocene or later age apparently does not extend into peninsular Florida, Clayey sand that has been considered as Citromelle equivalent in the report area is late middle Miocene or early upper Miocene in age. Hardrock phosphate deposits in the area are in lower Miocene beds which are assigned to the Tampa Limestone. Hardrock phosphate particles appear to consist of two types: cementation concretions and limestone replacements. Land-pebble phosphate deposits range in age from middle Miocene to Pleistocene. In the area of this report they are mainly residual deposits of middle Miocene age. In the report area uranium is confined mainly to lower and middle Miocene rocks with the greatest concentrations in the Hawthorn formation.

Florida↗