Browsing by Author "Woodruff, K.D."
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Item Application Of Geophysics To Highway Design In The Piedmont Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1971-06) Woodruff, K.D.The feasibility of using geophysical techniques in determining the amount of overburden and the nature of the subsurface along a proposed highway was tested in the Piedmont area of Delaware. The area is underlain by crystalline rocks capped by varying amounts of unconsolidated material or regolith. Seismic refraction and surface resistivity methods were used at selected stations and the interpretations were later compared to results from test holes and to the material exposed in road cuts. In general, interpretation of the seismic refraction results compared quite well with test borings and with field observations made after construction was started. Resistivity data were inconclusive in themselves but provided some additional control points when correlated with seismic refraction data. With proper control, it is concluded that such techniques could be useful in the Piedmont of Delaware for highway planning.Item Earthquakes In Delaware And Nearby Areas, June 1973 - June 1984(Newark, DE: Delaware Geological Survey, University of Delaware, 1984-07) Woodruff, K.D.Earthquakes in Delaware and surrounding areas have been well documented historically since about the early 1700’s and since 1972 by instrumental records. Most of the Delaware events have occurred in the Wilmington area immediately adjacent to or within rocks of the Wilmington Complex. Since the compilation of earthquakes by Jordan and others (1974) which lists events through May 1974, six felt earthquakes have occurred in northern Delaware and about 20 additional events in Delaware have been recorded on seismographs of the Delaware Geological Survey. Four of the felt events took place from November 1983 through February 1984 and ranged from a magnitude 1.5 to 2.9. The highest intensity for this series of earthquakes was a possible V (Modified Mercalli). Epicenters were generally in the north Wilmington area as determined both instrumentally and by felt reports.Item General Ground-Water Quality In Fresh-Water Aquifers Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1970-07) Woodruff, K.D.Information on ground-water quality in Delaware has become critical for three reasons: (1) increased water demand, (2) need for a better understanding of ground-water flow patterns, (3) need for a "base" against which future quality changes can be measured. Analyses of about 150 water quality samples from wells show that Delaware's fresh ground waters are suitable for most purposes. High iron content may occur, however, in wells tapping the Columbia and the Potomac formations. Overall, total dissolved solids in Delaware aquifers are relatively low except in the Cheswold and Frederica aquifers (Miocene), and possibly parts of the Piney Point Formation (Eocene).Item Geohydrology of the Chesapeake and Delaware Canal Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1986) Woodruff, K.D.Item Geohydrology of the Dover area, Delaware(Newark: Delaware Geological Survey, University of Delaware, 1972) Woodruff, K.D.Item Geohydrology of the Middletown-Odessa Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1990) Woodruff, K.D.Item Geohydrology of the Newark Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1977) Woodruff, K.D.Item Geohydrology of the Wilmington Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1981) Woodruff, K.D.Item Geologic Field Trips In Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1977-05) Benson, R.N.; Hahn, W.F.; Jordan, R.R.; Pickett, T.E.; Talley, J.H.; Thompson, A.M.; Woodruff, K.D.The information contained in this Guidebook was compiled on the occasion of the Annual Meeting of the Association of American State Geologists held in Delaware in June 1977. The Delaware Geological Survey is pleased to have been selected to host this national meeting. The field trip logs were designed to familiarize geologists from across the United States with basic features of Delaware's geology and resources. We have also sought to identify some points of historical and cultural interest that may help the visitor become familiar with our State. Experience has shown that field guides retain their usefulness beyond the event that they initially served. They may assist classes, other groups, and individuals seeking additional information about their physical environment. Therefore, this Guidebook has been published as an Open File Report for public distribution. All users of this information are urged to exercise caution, especially at rock faces and along waterways, and to obtain specific permission for visits from landowners where necessary.Item Geology And Ground Water, University Of Delaware, Newark, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1972-05) Woodruff, K.D.; Miller, J.C.; Jordan, R.R.; Spoljaric, N.; Pickett, T.E.The results of an intensive ground-water study on University of Delaware lands in the Newark area revealed additional sources of available ground water. Geophysical techniques, air-photo interpretation, studies of existing data, field mapping, test drilling, and pump tests were used as the bases for guiding additional well development. The study, conducted by the Delaware Geological Survey, was a cooperative effort between the University of Delaware and the City of Newark in response to mutual water supply problems. A potential ground-water yield of about 500 gpm was discovered on the University Laird Tract in the Piedmont Province. Ground water available from other locations in the Coastal Plain portion of the study area may total about 175 gpm. However, careful well development and proper well spacing will be necessary to obtain optimum yields.Item Geology And Hydrology Of The Cockeysville Formation Northern New Castle County, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1995) Woodruff, K.D.; Plank, M.O.; Werkheiser, W.H.The effect of rapid growth in the Hockessin and Pleasant Hill areas in northern Delaware has caused concern about possible declines in ground-water recharge to the underlying Cockeysville Formation. The Cockeysville is a major source of ground water (aquifer) in the Hockessin area from which about 1.5 million gallons of water per day is withdrawn for public water supply, even though it receives recharge over a relatively small area of 1.6 square miles. The Cockeysville in the Pleasant Hill area is currently used as a source at water supply for individual domestic users and one school. Results of ground-water exploration in the Pleasant Hill area suggest that the Cockeysville is capable of yielding several hundreds of gallons per minute to individual wells for water supply. A two-year investigation was undertaken to map the extent of the Cockeysville Formation and address questions of long-term ground-water yields. the sources of recharge, and the effects of additional development on ground-water supplies. Results of various field studies were integrated to determine the basic geologic framework and those elements that particularly affect ground-water supply.Item Geology of the Newark Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1972) Woodruff, K.D.; Thompson, A.M.Item Geology of the Wilmington Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1975) Woodruff, K.D.; Thompson, A.M.Item Geology, Hydrology, And Geophysics Of Columbia Sediments In The Middletown-Odessa Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1970-08) Spoljaric, N.; Woodruff, K.D.Columbia sediments in the Middletown-Odessa area are composed of boulders, gravels, sands, silts and clays. These sediments are exposed in four gravel pits where their structures and textures were studied. Subsurface geology was interpreted on the basis of the well-log data from 40 holes drilled in the area of study. Columbia sediments were laid upon a surface made up of the greensands of the Rancocas Formation (Paleocene – Eocene age). The contact between the Rancocas and Columbia Formations is an erosional unconformity.Item Ground Water in Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1998-02) Woodruff, K.D.Because of its "renewability" water is unique among earth resources that sustain and enhance life. No other mineral resource that we extract on a long-term and continuous basis can be counted on for at least some degree of replenishment within a human lifetime. This attribute allows a great deal of flexibility in management of the resource. In Delaware local rainfall, approximately 40" to 44" per year, renews part or all of our water supply on a regular basis. However, not all of the rain that falls is available for use. From this total rainfall must be subtracted the water that evaporates (about 20"/ year), the amount that is used by plants (about 3"/year), and the amount that runs overland to surface streams during storms (about 4"-5"/year). The remainder, approximately 13" to 15" is Delaware's bank of water for the year. This water is stored in a system of ground-water reservoirs, or aquifers, that underlie most of the State. Not only do these ground-water reservoirs provide water to wells but they also maintain the flow in surface streams during times of no rainfall. Streamflow between rainfall events is nothing more than the discharge of excess ground water.Item Ground-Water Levels In Delaware January, 1962 - June, 1966(Newark, DE: Delaware Geological Survey, University of Delaware, 1967-04) Woodruff, K.D.This report deals with fluctuations in nine observation wells during the period 1960 - 1966. These wells are part of a state-wide ground-water monitoring network and are located in areas of little or no pumping. Eight of the wells respond to water-table conditions; the ninth well appears to reflect artesian conditions. Although precipitation throughout Delaware was generally below average during the period covered by this report, annual average water levels declined very little in the wells reported on here. There is some evidence, however, for a lowering of water-table levels by three to four feet during the period 1960 - 1962.Item A Numerical Indicator Of Water Conditions For Northern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1982-05) Jordan, R.R.; Woodruff, K.D.Numerical indicators, or indices, are widely used to measure the status of complex relationships. As such, indices have become accepted by researchers and the public in such disparate fields as economics, air quality, and weather. In this paper we explore the formulation of an indicator of water conditions in northern Delaware, propose formulas that may be applicable, and test those proposals against long-term records of basic data. The need for a simple indicator of water supply conditions in Delaware, and especially in New Castle County, has become increasingly apparent. The Delaware River Basin Commission (DRBC) has applied an index to the Delaware River Basin, which includes a portion of Delaware. The Governor's Drought Advisory Committee has sought an objective means of determining when water supply conditions might warrant conservation measures. Discussions of the subject have also been held within the State Comprehensive Water Management Committee. We are pleased to acknowledge the constructive comments of these groups and of other colleagues with whom we have discussed this work. George R. Phillips of the Delaware Department of Natural Resources and Environmental Control (DNREC) was especially helpful in analyzing the practical implications of using the index presented in this paper. John R. Mather, Delaware State Climatologist, provided Palmer Drought Severity Index values with the cooperation of the National Weather Service. This report was reviewed by Richard N. Benson and John H. Talley of the Delaware Geological Survey (DGS).Item The Occurrence Of Saline Ground Water In Delaware Aquifers(Newark, DE: Delaware Geological Survey, University of Delaware, 1969-08) Woodruff, K.D.The location of the fresh-salt-water-boundary in the deeper aquifers of Delaware is related mainly to head values. Near coastal areas, dynamic conditions may prevail that affect the interface position within shallow aquifers open to the sea. Holocene and Columbia sands which form Delaware's shallow water-table aquifers contain brackish water in scattered coastal areas while brackish water in the artesian aquifers is found at various depths. Water from Chesapeake Group sediments (Miocene) is fresh in Kent County but is salty in poorly defined areas of Sussex County. The interface in the Piney Point Formation (Eocene) lies just north of Milford and extends in a northeast-southwesterly direction across the State. Brackish water exists in the Magothy and Potomac formations of Cretaceous age a few miles south of Middletown. Heavy pumping near sources of brackish water should be avoided for the present. Proper location of monitoring wells is necessary for detection of future chloride movement.Item Preliminary Report On Seismic Events In Northern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1972-04) Jordan, R.R.; Pickett, T.E.; Woodruff, K.D.Earthquakes are an unfamiliar phenomenon in Delaware. Because of the great public and scientific interest in the seismic events that have recently affected northern Delaware, this Open File Report has been prepared to present currently available information concerning the earthquakes and the investigation pursued by the Delaware Geological Survey. This is not a final scientific explanation of the events. To many persons it is shocking to realize that the earth that they regard as stable is, in fact, an active body. The present earth is a product of 4.5 billion years of history, during which time most geologic forces have acted so slowly as to be almost imperceptible. Therefore, sudden movements are disturbing. Earthquakes are the vibrations caused by relatively sudden slippage of deeply buried rocks. Earthquakes occur in a vast range of sizes; many are too small to be felt and others cause great damage. The events in Delaware that are described on these pages were relatively small and, although they warrant further study, which may lead to some precautionary measures, they do not represent cause for alarm.Item Preliminary Report On The Earthquake Of February 28, 1973(Newark, DE: Delaware Geological Survey, University of Delaware, 1973-04) Woodruff, K.D.; Jordan, R.R.; Pickett, T.E.This report has been prepared to fill an immediate need for information on the earthquake that affected northern Delaware on February 28, 1973. Public interest in seismic events has grown in the past two years because of a series of small, local events (Jordan et al., 1972) and has been heightened considerably by the event described in this report. Various stresses on and within the earth lead to periodic adjustments or changes by the rocks making up the earth's crust. Many changes are too slow or small to be measured within a human lifetime, but earthquakes can be a very perceptible phenomenon, expressing more rapid adjustment. Indeed, earthquakes in many areas of the world are a serious geologic hazard and a threat to life and property. Thus, it must be recognized that the earth is a dynamic body and its processes are not bound to the convenience of man.