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Aquifers and Groundwater Withdrawals, Kent and Sussex Counties, Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 2023-08) McLaughlin, P.M.; Tomlinson, J.L.; Lawson, A.K.
Groundwater is the sole source of drinking water and the main source of water for agriculture and industry in central and southern Delaware. This study mapped the depth and thickness of thirteen aquifers in Kent and Sussex Counties, used these maps to assign groundwater withdrawals for 2004 to 2008 to the appropriate aquifer, and analyzed withdrawals for each type of water use by geographic area. The geology of the Delaware Coastal Plain is characterized by a broad complex of surficial Quaternary deposits unconformably underlain by Cretaceous to Cenozoic sediments that dip gently to the southeast. Permeable sands within this succession are used as groundwater sources. The hydrogeologic framework of the study area was characterized by maps of the elevation and thickness of thirteen aquifers. The maps were created in a geographical information system by interpolating aquifer depth data extracted from a database encompassing approximately 6,600 boreholes. The unconfined aquifer occurs in surficial Quaternary and Neogene sands. It is generally less than 100 feet thick in Kent County but varies from a few feet to more than 200 feet thick in Sussex County. The confined aquifers mapped include one Cretaceous (Mount Laurel), two Paleogene (Rancocas and Piney Point), and nine Neogene sand units (lower Calvert, Cheswold, Federalsburg, Frederica, Milford, Middle Choptank, Upper Choptank, Manokin, and Pocomoke). These aquifers are typically tens of feet thick and occur at progressively greater depths southeastward from their recharge areas. The study found that annual groundwater withdrawals for all uses in the study area ranged from approximately 89 to 144 million gallons per day annually for 2004 to 2008. Withdrawals were assigned to aquifers using the aquifer maps and well-screen elevation data. For water-use categories where withdrawals could be attributed to specific wells – public, industrial, and golf courses – aquifers were determined by analyzing well-screen elevations relative to aquifer raster surfaces. For categories in which withdrawals could not be assigned to individual wells – irrigation, domestic self-supplied, and livestock – available well depth data in each category were analyzed by census block and compared to the aquifer raster surfaces; for each block, the proportion of wells in each aquifer was used as the basis for apportioning withdrawals to aquifers. The results indicate that the unconfined aquifer accounted for more than half of groundwater withdrawals. Three shallow, confined aquifers primarily used in Sussex County (confined Columbia, Pocomoke, and Manokin) each provided approximately between 8 and 11 percent of total withdrawals. Withdrawals for the three most important confined aquifers in Kent County (Cheswold, Frederica, and Piney Point) each represented 3 to 5 percent of total withdrawals. Estimated withdrawals were also computed by aquifer for each water-use category and each census block.
Clay And Clay-Size Mineral Composition Of The Cretaceous-Tertiary Section, Test Well Je32-04, Central Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1988-09) Spoljaric, N.
This study complements Delaware Geological Survey Bulletin No. 17 and deals exclusively with clays and clay-size minerals. The cored section at the location of Je32-04 has been subdivided into 25 clay zones on the basis of major changes in trends and degree of crystallinity of clay minerals. The composition of clay minerals varies from zone to zone. These clay minerals have been identified: kaolinite, berthierine, chlorite, illite, smectite, chlorite/smectite, illite/smectite, glauconite/smectite, and glauconite pellets. Other minerals present in the section include: zeolites (clinoptilolite-heulandite), gypsum, and elemental sulfur.
Columbia (Pleistocene) Sediments Of Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1964-09) Jordan, R.R.
The Columbia deposits of Delaware form a sheet of sand with a maximum thickness of approximately 150 feet which covers most of the Coastal Plain portion of the State. The dispersal pattern, deduced from foreset dip directions of cross-bedding, indicates that the sediment entered the study area from the northeast, i.e., from the direction of the valley of the Delaware River between Wilmington and Trenton, and spread south and southeast over Delaware.
Digital Model Of The Unconfined Aquifer In Central And Southeastern Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1977-05) Johnston, R.H.
The unconfined aquifer in central and southeastern Delaware occurs as a southward-thickening blanket of fine to coarse sand, and is recharged almost totally by precipitation and discharge is principally by seepage to streams, bays, and the ocean.
Engineering Materials Of Northern New Castle County
(Newark, DE: Delaware Geological Survey, University of Delaware, 1957-11) Ward, R.F.; Groot, J.J.
This investigation was undertaken to locate deposits of rock, sand, gravel, fill and borrow in northern New Castle County which may be potential sources of material for highway construction, and to prepare maps and descriptions of the surficial earth materials relative to their geologic and engineering properties.
Evaluation of Wastewater Treatment Options Used in Rapid Infiltration Basin Systems (RIBS)
(Newark, DE: Delaware Geological Survey, University of Delaware, 2015-12) Türkmen, M.; Walther, E.F.; Andres, A.S.; Chirnside, A.E.M.; Ritter, W.F.
This technical report evaluates several aspects of potential environmental risks, use, and regulation of rapid infiltration basin systems (RIBS) in Delaware. The report reviews and compares regulations regarding RIBS from Delaware, Florida,North Carolina, New Jersey, Maryland, and Massachusetts. Influent and effluent samples from ten advanced wastewater treatment systems that operate in conjunction with RIBS were collected and analyzed. Effluent data obtained from the Non-Hazardous Waste Sites database provided by the Delaware Department of Natural Resources and Environmental Control and other states were assessed. Performance evaluations of the treatment processes that discharge to RIBS were ascertained from the exceedance of concentrations of regulated pollutants in effluent samples. Although RIBS technology has the potential to be a beneficial alternative to surface discharge and a means for groundwater recharge, this technology is appropriate only if the adverse environmental impacts are minimized. Overall operation and maintenance practices play important roles in the performance of treatment plants. The most common and serious problems associated with treatment plants located in Delaware and neighboring states are high nutrient and pathogen concentrations in the effluent. In Delaware, the discharge of poorly treated effluent to RIBS creates a risk of nutrient and pathogen contamination in the receiving water body, the shallow Columbia aquifer. Years of application of treated effluent with high nutrient, pathogen, and organic content to RIBS will result in significant risks for the environment and public health.
Geological Studies Of Cretaceous And Tertiary Section, Test Well Je32-04, Central Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1985-06) Benson, R.N.; Jordan, R.R.; Spoljaric, N
A cored well 1,422 feet (433 meters) deep drilled two miles southeast of Dover is the basis for this integrated study of the lithology and paleontology of the Cretaceous-Tertiary section in central Delaware. The section is subdivided into lithostratigraphic, biostratigraphic, chronostratigraphic, and heavy mineral units. Data and results are presented on a common base in three plates.
Geology and Ground-Water Resources of the Newark Area, Delaware with a section on the Surface Water Resources
(Newark, DE: Delaware Geological Survey, University of Delaware, 1954-04) Groot, J.J.; Rasmussen, W.C.; Hulme, A.E.
This report describes the geological and lithological conditions in the Newark area, and the occurrence, quantity, and quality of the available ground-water supply. Newark is located on the Fall Line, the boundary between the rolling hills of the Piedmont on the north and the gentle slopes of the Coastal Plain on the south. Because the Piedmont is underlain by dense crystalline rocks and their weathered clayey soils, which are of low water-bearing capacity in contrast to the more permeable silts and sands of the Coastal Plain, the exploration for ground water was confined to the Coastal Plain south and southeast of Newark.
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.
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.
Ground-Water Problems In Highway Construction And Maintenance
(Newark, DE: Delaware Geological Survey, University of Delaware, 1953) Rasmussen, W.C.; Haigler, E.B.
This report discusses the occurrence of ground water in relation to certain problems in highway construction and maintenance. These problems are: the subdrainage of roads; quicksand; the arrest of soil creep in road cuts; the construction of lower and larger culverts necessitated by the farm-drainage program; the prevention of failure of bridge abutments and retaining walls; and the watercement ratio of sub-water-table concrete. Although the highway problems and suggested solutions are of general interest, they are considered with special reference to the State of Delaware, in relation to the geology of that State. The new technique of soil stabilization by electroosmosis is reviewed in the hope that it might find application here in road work and pile setting. Field application by the Germans and Russians is reviewed.
Ground-Water Resources Of Southern New Castle County Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1964-03) Rima, D.R.; Coskery, O.J.; Anderson, P.W.
Southern New Castle County has a land area of 190 square miles in north-central Delaware. It is predominantly a rural area with a population of about 9,000 people who are engaged chiefly in agriculture. By and large, the residents are dependent upon ground water as a source of potable water. This investigation was made to provide knowledge of the availability and quality of the ground-water supply to aid future development. The climate, surface features, and geology of the area are favorable for the occurrence of ground water. Temperatures are generally mild and precipitation is normally abundant and fairly evenly distributed throughout the year. The topography of the area is relatively flat and, hence, the streams have low gradients. The surface is underlain to a considerable depth by highly permeable unconsolidated sediments that range in age from Early Cretaceous to Recent.
Ground-Water Resources Of The Piney Point And Cheswold Aquifers In Central Delaware As Determined By A Flow Model
(Newark, DE: Delaware Geological Survey, University of Delaware, 1982-07) Leahy, P.P.
A quasi three-dimensional model was constructed to simulate the response of the Piney Point and Cheswold aquifers underlying Kent County, Delaware to ground-water withdrawals. The model included the Magothy, Piney Point, Cheswold, and unconfined aquifers, and was calibrated using historical pumpage and water-level data. Model calibration was accomplished through the use of both steady-state and transient-state simulations.
GROUNDWATER QUALITY AND MONITORING OF RAPID INFILTRATION BASIN SYSTEMS (RIBS), THEORY AND FIELD EXPERIMENTS AT CAPE HENLOPEN STATE PARK, DELAWARE
(Newark, DE: Delaware Geological Survey, University of Delaware, 2015-12) Andres, A.S.; Walther, E.F.; Türkmen, M.; Chirnside, A.E.M.; Ritter, W.
A rapid infiltration basin system (RIBS) consists of several simple and relatively standard technologies; collection and conveyance of wastewater, treatment, and discharge to an unlined excavated or constructed basin. By design, the effluent quickly infiltrates through the unsaturated or vadose zone to the water table. During infiltration, some contaminants may be treated by biological and/or geochemical processes and diluted by dispersion and diffusion. The combination of contaminant attenuation and dilution processes that may occur during infiltration and flow through the aquifer are termed soil-aquifer-treatment, or SAT. In the past decade, RIBS have been proposed more frequently for use in Delaware because they stop the direct discharge of treated effluent to surface water, can accommodate significant flow volumes typical of residential subdivisions, yet require much less land than options such as spray irrigation or sub-surface disposal systems. Decades of research on the shallow Columbia aquifer of the Delmarva Peninsula have clearly identified the high susceptibility of the aquifer from land- and water-use practices, and the processes that control the fate and transport of contaminants from their origin at or near land surface to points of discharge in creeks, estuaries, and wells. The risk of aquifer contamination is great because it is highly permeable, has little organic matter in the aquifer matrix, and the depth to groundwater is very commonly less than 10 ft below land surface. USEPA guidance documents and several engineering texts that cover RIBS design clearly identify these same factors as increasing risk for groundwater contamination but do not provide much information on means to monitor and mitigate those risks. Further, design criteria are based on a small group of experiments conducted in the 1970s prior to development of current understanding of the processes that control groundwater contaminant transport. Field and laboratory experiments to characterize the physical, chemical, and biological controls and processes associated with the rapid infiltration of treated sewage effluent through infiltration beds and the vadose zone were undertaken at a RIBS located at Cape Henlopen State Park (CHSP), Delaware. Field experiments to understand the geochemical effects of the long-term operation of a RIBS on ground and surface waters, and to evaluate monitoring systems were also conducted at the site. The CHSP RIBS has been in operation since the early 1980s. Significant concentrations of nitrogen and phosphorus occur in groundwater from the point of effluent entry at the water table to distances greater than 150 ft from the infiltration beds. The high hydraulic, nitrogen (N), phosporus (P), and organic loading rates associated with the operation of RIBS overwhelm natural attenuation (e.g., sorption and precipitation) processes. Data are not sufficient to indicate whether denitrification is occurring. If there is denitrification, the rate is insufficient to remediate RIBS effluent at the site — despite a 25-ft thick vadose zone, an effluent with enough organic carbon to facilitate anaerobic conditions that permit abiotic denitrification and feed microorganism-driven denitrification processes, and hypoxic to anoxic groundwater. Significant horizontal and vertical variability of contaminant concentrations were observed within the portion of the aquifer most impacted by effluent disposal. Despite the relatively small spatial extent of the disposal area in our study area, identification of the preferential flow zone and characterization of the vertical and temporal variability in the concentrations of contaminants required a multi-phase subsurface investigation program that included an analysis of data from samples collected at bi-monthly intervals from dozens of monitoring points and high frequency temperature monitoring in several wells. A well-designed monitoring system should be based on experimentally determined site specific evidence collected under conditions that duplicate the flow rates that are expected during full-scale operation of the RIBS. Conservative tracers should be used to determine if the monitoring wells are in locations that intercept flow from the infiltration beds.
Hydrogeology of a Rapid Infiltration Basin System (RIBS) at Cape Henlopen State Park, Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 2015-12) Andres, A.S.; Walther, E.F.; Türkmen, M.; He, C.
The hydrogeologic framework of Cape Henlopen State Park (CHSP), Delaware was characterized to document the hydrologic effects of treated wastewater disposal on a rapid infiltration basin system (RIBS). Characterization efforts included installation of test borings and monitoring wells; collection of core samples, geophysical logs, hydraulic test data, groundwater levels and temperatures; testing of grain size distribution; and interpretation of stratigraphic lithofacies, hydraulic test data, groundwater levels, and temperature data. This work was part of a larger effort to assess the potential benefits and risks of using RIBS in Delaware. The infiltration basins at CHSP are constructed on the Great Dune, an aeolian dune feature composed of relatively uniform, medium-grained quartz sand. The age of the dune, determined by carbon-14 dating of woody material in swamp deposits under the dune, is less than 800 years. Underlying the dune deposits are relatively heterogeneous, areally continuous, coarse-grained spit deposits of the proto-Cape Henlopen spit with interbedded and relatively fine-grained, discontinuous swamp and marsh deposits, and beneath, relatively fine-grained, continuous, near-shore marine deposits. The dune deposits can be 45 ft thick under the crest of the dune and nonexistent at the surface. Spit deposits range from 5 to 15 ft thick. Test drilling determined that the near-shore marine deposits are at least 10 ft thick in the vicinity of the infiltration basins. The complete thickness of these deposits was not determined in this study. Hydraulic testing and grain-size data indicate that the dune and spit deposits are relatively permeable, with average hydraulic conductivities of 140 ft/day and that the swamp and marsh deposits are more than one order of magnitude less permeable, with average hydraulic conductivity of 25 to 10 ft/day. The water-table aquifer is present in the sandier dune and spit deposits. The swamp, marsh, and near-shore marine deposits form a leaky confining unit. The water-table aquifer is 15 to 20 ft thick under the thickest section of the Great Dune and nonexistent where the dune deposits are absent. The vadose zone is greater than 25 ft thick under the infiltration basins. High-frequency groundwater level and temperature monitoring during periods of maximum wastewater disposal rates indicates that wastewater disposal causes increases in water-table elevations on the order of 1 ft. Groundwater elevations indicate that the water-table elevation is greatest under the infiltration basins and that most flow is directed southward toward a swampy discharge area. Maximum disposal rates typically occur in summer months when the numbers of park users and water use are greatest. Coincident with greater disposal rates are higher wastewater temperatures. These higher wastewater temperatures are observed in groundwater and provide a means to track the flow of water from beneath the infiltration beds towards a nearby discharge area. Tracking of the warmer groundwater and modeling two-dimensional particle tracking both indicate that wastewater discharged to the infiltration basins reaches the nearby discharge area within 180 days.
Hydrology Of The Columbia (Pleistocene) Deposits Of Delaware: An Appraisal Of A Regional Water-Table Aquifer
(Newark, DE: Delaware Geological Survey, University of Delaware, 1973-06) Johnston, R.H.
The Columbia (Pleistocene) deposits of Delaware form a regional water-table aquifer, which supplies about half the ground water pumped in the State. The aquifer is composed principally of sands which occur as channel fillings in northern Delaware and as a broad sheet across central and southern Delaware. The saturated thickness of the aquifer ranges from a few feet in many parts of northern Delaware to more than 180 feet in southern Delaware. Throughout 1,500 square miles of central and southern Delaware (75 percent of the State's area), the saturated thickness ranges from 25 to 180 feet and the Columbia deposits compose all or nearly all of the water-table aquifer.
Marine upper cretaceous formations of the Chesapeake and Delaware Canal
(Newark, DE: Delaware Geological Survey, University of Delaware, 1954-11) Organist, D.M.; Richards, H.G.; Groot, J.J.
In the Coastal Plain of Delaware, the non-marine Cretaceous sands and clays are separated from the Tertiary formations by a series of marine formations of Upper Cretaceous age. The sedimentary and hydrologic characteristics of these formations deserve detailed study because some of them are water-bearing beds. whereas others act as confining beds. A clear understanding of their relative age. and the presence or absence of unconformities is needed for proper correlation with formations found in wells throughout the State. as well as in Maryland and New Jersey.
Preliminary Report On The Geology And Ground-Water Resources Of Delaware
(Newark, DE: Delaware Geological Survey, University of Delaware, 1955-05) Marine, I.W.; Rasmussen, W.C.
Delaware has an abundant supply of ground water of a quality suitable for most purposes. About 30 million gallons of water a day was pumped from the ground in 1954. It is estimated that this is roughly 1/16 of the optimum yield. This water is derived from nine groups or series of water-bearing units and is obtained from wells which yield as much as 1,100 gallons per minute. Thousands of wells serve agriculture, industry, municipalities, and domestic users. Geographically, Delaware is situated along the Atlantic coast of the United States in two physiographic provinces: the Piedmont and the Coastal Plain. The Piedmont is a belt of rolling foothills of the Appalachian Mountains. It is separated from the Coastal Plain by the Fall Line, a narrow zone of rapids or falls along which rivers and creek descend rapidly from the mature valleys of the Piedmont to the sluggish tidal estuaries of the coastal area. The Coastal Plain is a flat or gently undulating plain of relatively low altitude, which borders the Atlantic Ocean and its estuarine embayments.
Salinity Of The Delaware Estuary
(Newark, DE: Delaware Geological Survey, University of Delaware, 1963-02) Cohen, B.; McCarthy, L.T. Jr.
The purpose of this investigation was to obtain data on and study the factors affecting the salinity of the Delaware River from Philadelphia, Pa., to the Appoquinimink River, Del. The general chemical quality of water in the estuary is described, including changes in salinity in the river cross section and profile, diurnal and seasonal changes, and the effects of rainfall, sea level, and winds on salinity. Relationships are established of the concentrations of chloride and dissolved solids to specific conductance. In addition to chloride profiles and isochlor plots, time series are plotted for salinity or some quantity representing salinity, fresh-water discharge, mean river level, and mean sea level. The two major variables which appear to have the greatest effect on the salinity of the estuary are the fresh-water flow of the river and sea level. The most favorable combination of these variables for salt-water encroachment occurs from August to early October and the least favorable combination occurs between December and May.
Sedimentary Petrology Of The Cretaceous Sediments Of Northern Delaware In Relation To Paleogeographic Problems
(Newark, DE: Delaware Geological Survey, University of Delaware, 1955-07) Groot, J.J.
The non-marine Cretaceous sediments of northern Delaware older than the Magothy formation cannot be divided accurately into formations or mappable geologic units because their lithologic characteristics are very similar. However, two heavy mineral zones can be distinguished in these deposits: a lower staurolite-kyanite-tourmaline-zircon zone, and an upper tourmaline-zircon-rutile zone with abundant alterites. They have been named the Patuxent zone and the Patapsco-Raritan zone respectively. The Magothy formation is characterized by abundant staurolite and also contains significant amounts of tourmaline. The marine Upper Cretaceous deposits have a greater variety of heavy minerals than the underlying non-marine sediments. They contain abundant epidote; chloritoid, first appearing at the base of the Merchantville formation, is persistently present. Garnet is found in the Merchantville and the Mount Laurel-Navesink formations. The heavy mineral composition of the Cretaceous sediments is shown in table IV.

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