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C011,37A, L' ZTNE M A I N" FWON CENTER H DR. GY, GEOLOGY, AND MINERAL RESOURCES ZONE OF GB 459.4 S86 1975 TEC L REPORT NUMBER 31 SEPTEMBER 1976 DELAWARE COASTAL ZONE MANAGEMENT PROGRAM Y OLO OF THE C ksi @L DELAWARE TECHNICAL REPORT NUMBER 3 DELAWARE COASTAL ZONE MANAGEMENT PROGRAM September 1976 COASTAL ZONE INFOWVIATION CENTER Prepared From Unpublished Manuscript Hydrology, Geology and Mineral Resources of the Coastal Zone of Delaware by R. W. Sundstrom, T. E. Pickett, and R. D. Varrin Water Resources Center University of Delaware Newark, Delaware 19971 October 1975 Under Contract to Delaware State Planning Office, Executive Department Thomas Collins Building Dover, Delaware 19901 The preparation of this report was financed in part through a Coastal Zone Management Program Development Grant from the Office of Coastal Zone Management, National Oceanic and Atmospheric Administration, under provisions of Section 305 of the Coastal Zone Management Act of 1972 (Public Law 92-583). UNIVERSITY OF DELAWARE WATER RESOURCES CENTER ADMINISTRATION President of the University Edward A. Trabant Vice President, University Relations & Business Management Donald F. Crossan Director, Water Resources Center Robert D. Varrin WATER RESOURCES COUNCIL STATE ADVISORY BOARD William J. Benton, Assistant Dean Walter Fritz, Jr. College of Agriculture County Engineer, Kent County 0. P. Bergelin, Associate Dean William Henry College of Graduate Studies County Engineer, Sussex County Merna Hurd, New Castle County Robert B. Biggs, Assistant Dean Water and Sewer Management Office College of Marine Studies Robert Jordan, State Geologist Thomas W. Brockenbrough, Professor Delaware Geological Survey Department.of Civil Engineering David Keifer, Director Donald F. Crossan, Chairperson, V. Pres. State Planning Office Univ. Relations and Business Management Warren O'Sullivan, New Castle Co. Kermit G. Cudd, Assistant Dean Department of Public Works College of Business and Economics James Stingel Soil Conservation Service Robert D. Varrin, Secretary, Assoc. Prof. N. C. Vasuki, Director Department of Civil Engineering Division of Environmental Control Ronald H. Wenger, Associate Dean Norman Wilder, Executive Director College of Arts and Sciences Delawa re Nature Education Center DELAWARE STATE AGENCIES CONTRIBUTING University of Delaware, Water Resources Center Robert D. Varrin, Director Delaware Geological Survey Robert R. Jordan, State Geologist Delaware Department of Natural Resources.and Environmental Control John C. Bryson, Secretary Division of Environmental Control N. C. Vasuki, Director Delaware State Planning Office David Keifer, Director ve CONTENTS Page Introduction 1 Purpose and Scope of the Report 1 Personnel and Acknowledgments 1 Well-Numbering System 2 Definitions of Terms 2 Geology 9 Geology for Planning Purposes 9 Geology as a Constraint 9 Geology as a Predictor 9 General Geologic History of Delaware 10 The Piedmont .10 The Coastal Plain 10 Descriptions of Aquifers 14 The Potomac Formation 14 The Magothy Formation .15, The Monmouth Formation 15 The Rancocas Group 19 The Piney Point Formation 19 The Chesapeake.Group 19 The Pleistocene Aquifer 24 Mineral Resources of Delaware 24 Sand and Gravel 24 Clay 29 Potential Mineral Resources 32 Geologic Problems 32 Geologic Hazards 32 Flood Prone Areas 34 Faulting 34 Slumping 35 Resource Use Conflict 35 Lack of Geologic Knowledge, 36 Recommendations 36 Hydrology 39 Background 39 Hydrology for Planning Purposes. 39 The Use of Water 42 The Use of Water in New Castle County 42 The Use of Water in Kent County 42 The Use of Water in Sussex County 42 The Availability of Surface Water 42 General Ground-Water Hydrology 50 Hydrologic Cycle 50 Source and,Occurrence 51 Recharge, Movement and Discharge 53 vi i.. Chemical Quality of Ground Water as Related to Use 54 General Chemical Quality of Ground Water 54 Water Quality Considerations for Public Supply, 54 Domestic and Livestock'Use Water Quality Considerations for Irrigation Use 59 Water Quality Considerations for Industrial Use 69 The Availability of Ground Water 62 The Potomac Aquifers 62 Location of the Potomac Formation 63 Development of the Potomac Aquifers 63 Undeveloped Areas and Potential Use of the Potomac 63 Aquifers Hydrologic Potential of the Potomac Aquifers 63 Available Water from the Potomac Aquifers 65 Limits in Development of the Potomac Aquifers 65 Quality of Water in the Potomac Aquifers 65 Salt-Water Problems in the Potomac Aquifers 68 Unknown Hydrology of the Potomac Aquifers 68 The Magothy Aquifer 68 Location of the Magothy Aquifer 69 Development of the Magothy Aquifer 69 Undeveloped Areas and Potential Use of th e Magothy 69 Aquifer Hydrologic Potential and Available Water from the 69 Magothy Aquifer Quality of Water in the Magothy Aquifer 71 The Englishtown and Mount Laurel Aquifers 71 Location of the Englishtown and Mount Laurel 71 Aquifers Hydrology of the Englishtown and Mount Laurel 71 Aquifers Availability of Water fromthe Englishtown and 74 Mount Laurel Aquifers The Rancocas Aquifer 74 Location of the Rancocas Aquifer 74 Developed and Undeveloped Areas of the Rancocas 76 Aquifer 76 Hydrology of the Rancocas Aquifer Availability of Water from the Rancocas Aquifer 77 Quality of Water in the Rancocas Aquifer 78 Salt-Water Problems in the Rancocas Aquifer .78 The Piney Point Aquifer 81 Location of the Piney Point.Aquifer 81 'Areas of Development and PotentialDevelopment of 82 the Piney Point Aquifer Hydrology of the Piney Point Aquifer 82 Available Water from the Piney Poi.nt Aquifer 84 Quality of Water in the Piney Point Aquifer 85 Salt-Water Problems in the Piney Point Aquifer 85 viii. The Cheswold Aquifer, Location of the Cheswold Aquifer 85@ Development of the Cheswold Aquifer 89 Undeveloped Areas of the Cheswold Aquifer 89 Hydrology of the Cheswold Aquifer 89 Available Water from the Aquifer and Limits of 91 Development Quality of Water in the Cheswold Aquifer 91 Salt-Water Problems in the Cheswold Aquifer 91 The Federalsburg Aquifer 94 Location of the Federalsburg Aquifer 94 Development of the Federalsburg Aquifer 94 Undeveloped Areas of the Federalsburg@Aquifer' 94 Hydrology of the Federalsburg Aquifer 94 Pumping Tests to Determine Trantmissivity 97 and Coefficients of Storage Available Water from the Federalsburg Aquifer 98 Quality of Water in the Federalsburg Aquifer 98 Salt-Water Problems in the Federalsburg Aquifer 98 The Frederica Aquifer, 101 Location of the Frederica Aquifer 101 Development of the Frederica Aquifer 101 Undeveloped Areas of the Frederica Aquifer 101 Hydrology of the Frederica Aquifer 103 Quantity of Water Available'from the Frederica 104 Aquifer and Limits of Development Quality of Water in the Frederica Aquifer 105 Salt-Water Problems in the Frederica Aquifer 105 The Manokin Aquifer 105 Location of the Manokin Aquifer 105 Development of the Manokin Aquifer 105 Undeveloped Areas of the Manokin Aquifer 105 Hydrology of the Manokin Aquifer 109 Quantity of Water Available from the Manokin 110 Aquifer Quality of Water in the Manokin Aquifer 110 Salt-Water Problems in the Manokin Aquifer 110 The Pocomoke Aquifer 113 Location of the Pocomoke Aquifer 113 Development of the Pocomoke Aquifer 113 Undeveloped Areas of the Pocomoke Aquifer 113 Hydrology of the Pocomoke Aquifer 113 Quality of Water in the Pocomoke Aquifer 113 Salt-Water Problems in the Pocomoke Aquifer 113 The Quaternary Water-Table Aquifer 117 Availability of Water from the Water-Table Aquifer in 117 the Coastal Plain in New-Castle County Availabili ty of Water from the Quaternary and Miocene 117 Outcrop Water-Table Aquifers in Kent County Hydrology of the Pleistocene and Subcropping Miocene 118 Water-Table Aquifer in Sussex County ix. Estimated Thickness of Saturation in the. 118 Water-Table Aquifer Estimated Volume of Saturation in the@ 120 Water-Table Aquifer Effective Yield of the Water-Table Aquifer 121 The Water-Table Aquifer and Its Relation to 122. Streamflow Specific Capacities of Wells in the Water- 123 Table Aquifer Transmissivity of the Water-Table Aquifer 123 Coefficients of Storage in the Water-Table 124 Aquifer Recharge to the Water-Table Aquifer 124 Discharge of the Water-Table Aquifer 125 Availability of Water from the Water-Table Aquifer in 129 Eastern Sussex County Availability o.fWater from the Water-Table Aquifer in 129 Western Sussex County Quality of Water from the Quaternary Aquifer 131 Water Resources Problems 135 The Salt-Water Problem 135 The Piney Point Aquifer Crossed by Delaware Bay 135 The Interface Between Fresh and.Salt Water in the 136 Piney Point Aquifer The Cheswold AquiferCrossed by the Delaware Bay 136 The Interface Between Fresh and Salt Water in the 137 Cheswold Aquifer The Frederica Aquifer Crossed by the Delaware Bay 137 The Interface Between Fresh and Salt Nater in the 138 Frederica Aquifer Minor Artesian Aquifers in the Miocene Above the 138 Frederica Crossed by the Delaware Bay The Subcrop of the Manokin Aquifer and the Relation to. 139 Salt Water of the Atlantic Ocean and to the Salt-Water of the Inland Bays and@ Estuaries The Interface Between Fresh and Salt Water in the 139 Manokin Aquifer The Subcrop of the Pocomoke Aquifer and Its Relation 139 to Salt Water of the Atlantic Ocean and, Salt Water of the Bays The Quaternary and Subcropping Miocene Water-Table Aquifer' 140 Adjacent to Delaware Bay, the Atlantic Ocean, the Inland Bays and Stream Estuaries. Ground-Water Contamination 141 Potential Problem Areas. 142 Areas of Needed Research and Study Concerning the Prospects of 142 Using Artificial Recharge or Other New Sources of Water X, Summary and Conclusions 145 New Castle County 145 Kent County 147 Eastern Sussex County 149 Western Sussex County 153 Bibliography 15 7 List of Unpublished Reports and Data 169 Appendices 170: Appendix A: Supplemental Illustrations 170 Appendix B: Supplemental Tables 190 -Appendix C: Ghyben-Herzberg Pri nciple 238 xi. ILLUSTRATIONS a I "4jy- quo") r@@l e, I VJP uo 5^1@@-t@'PiRge Eal Figure I Map Showing the Coordinates for the 3 Well-Numbering System Figurje 2 A Geologic Map of Delaware 6J.50 bn5 aP"i0q0. bedatilJduqnLj 10112ti Figge 3 Geologic Cross-Section Showing Ground- N1 2 q cA o, A Water Aquifers of Delawame@k 071 1"13'.1 iskNqu*@;'@ OQ@' FgidrT ir&@n,g.--,,,@,m-,Tqqu2 : ax. t;h'A Figuri 4 Structural Map of the Potdrqdt@,,@,Fo, 3 x'b@'isq%46 Figure 5 Structural Map of the Magothy Formation 17 Figure 6 Structural Map of the Monmouth Group 18 Figure 7 Structural Map of the Rancocas Group 20 Figure 8 Structural Map of the Piney Point 21 Formation. Figure 9 Structural Map of the Cheswold and 22 Frederica Aquifers Figure 10 Structural Map of the Manokin and 23 Pocomoke Aquifers Figure 11 Thickness of the Pleistocene Aquifer 25 Figure 12 Mineral Resources of the Delaware Coastal 28 Plain Figure 13 Sample Locations 30 Figure 14 Geologic Hazards Map 33 Figure 15 Water Problem Map of Delaware 41 Figure 16 Hydrologic-Data Station Activities and 47 Investigations in Progress in Delaware as of February, 1974 Figure 17 The Hydrologic Cycle 52 Figure 18 Configuration of the Top and Areas of Use 64 and of Potential Use of the Nonmarine Cretaceous Aquifer Figure 19 Areas of Similar Chemical Quality of Ground Water and Areas of Potential,Saline-Water Intrusion in the Potomac Aquifer Figure 20 Configuration of the Top and Areas of Use 70 and of Potential Use of the Magothy Aquifer Figure 21 Areas of Similar Chemical Quality of Grou Ind 72 Water and Areas of Potential Saline-Water Intrusion in the Magothy Aquifer Figure 22 Configuration of the Top and Areas of Use 75 and of Potential Use of the Rancocas Aquifer Figure 23 Areas of Similar Chemical Quality of Ground 79 Water and Area of Potential Saline-Water Intrusion in the Rancocas Aquifer Figure 24 Configuration of the Top and Areas of Use 83 and of Potential Use of the Piney Point Aquifer Figure 25 Areas of Similar Chemical Quality of Ground 86 Water in the Piney Point Aquifer. Figure 26 Configuration of the Top and Areas of Use 88 and of Potential Use of the Cheswold Aquifer Figure 27 Areas of Similar Chemical Quality of Ground 92 Water and Area of Potential Saline-Water Intrusion in the Cheswold Aquifer Figure 28 Configuration of the Top and Areas of Use and 95 of Potential Use of the Federalsburg Aquifer Figure 29 Areas of Similar Chemical Quality of Ground 99 Water and Area of Potential Saline-Water Intrusion in the Federalsburg Aquifer Figure 30 Configuration of the Top and Areas of Use and 102 of Potential Use of the Frederica Aquifer Figure 31 Areas of Similar Chemical Quality of Ground 106 Water and Area of Potential Saline-Water Intrusion in the Frederica Aquifer Figure 32 Configuration of the Top and Areas of Use 108 and of Potential Use of the Manokin Aquifer Figure 33 Areas of Similar Chemical Quality of Ground Water and Areas of Potential Saline-Water Intrusion in the Manokin Aquifer xiii. Figure 34 Configurat ion ofthe Top and Areas of Use 114 and of Potential Use of the Pocomoke Aquifer Figure 35 Areas of Similar Chemical Quality of Ground 115 Water and Area of Potential Saline-Water Intrusion in the Pocomoke Aquifer Figure 36 Map Showing the Saturated Thickness of the 119 Water-Table Aquifer in the Pleistocene Deposits in Sussex County Figure 37 Map Showing Depth to Water in Feet Below 126 Land Surface in the Water-Table Aquifer in Sussex County Figure 38 Map of Eastern Sussex County Showing the 127 Altitude of the Water Table in the Water- Table Aquifer of the Pleistocene and Subcropping Miocene Sands Figure 39 Map Showing Contours on the Altitude of the 128 Water Table in Western Sussex County Figure 40 Areas of Similar Chemical Quality of Ground 134 Water and Areas of Potential Saline-Water Intrusion in the Quaternary Aquifer Figure 41 Water Resources Evaluation Map of,Delaware 144 xiv. TABLES* Page Table 1 Correlation Chart of the Coastal Plain Units 13 in New Jersey, Delaware and Maryland Table 2 Summary of Clay Data: Table 3 Average Daily Use of Water in Delaware for 43 Municipal, Industrial, Irrigation and Rural Purposes in 1953-57, 1966 and 1974 Table 4 Average Daily Use of Ground Water and Surface 44 Water in New Castle County for Municipal, Industrial, Irrigation and Rural Purposes in 1954, 1966 and 1974 Table 5 Average Daily Use of Water.in Kent County for 45 Municipal, Industrial, Irrigation and Rural Purposes in 1953, 1966-and'1974 Table 6 Average Daily Use of Water in Sussex County 46 for Municipal, Industrial, Irr 'igation and Rural Purposes in 1957, 1966 and 1974 Table 7 Summary of U. S. Geological Survey Streamflow 48 Data for Streams in Delaware Table 8 Source and Significance of Dissolved-Mineral 55-56 Constituents and Properties of Water Table 9 Water-Quality Tolerances for Industrial Appli- 60 cations Table 10 Quality of Ground Water and Area of Potential 67 Saline-Water Intrusion in the Nonmarine Cretaceous Aquifer, as Shown in Figure 19 Table 11 Quality of Ground Water and Areas of Potential 73 Saline-Water Intrusion in the Magothy Aquifer, as Shown in Figure 21 Table 12 Quality of Ground Water and Area of Potential 80 Saline-Water Intrusion in the Rancocas Aquifer, as Shown in Figure 23 Table 13 Quality of Ground Water in the Piney Point 87 Aquifer, as Shown in Figure 25 xv Table 14 Quality of Ground Water and Area of Potential 93 Saline-Water Intrusion in the Cheswold Aquifer, as Shown in Figure 27 Table 15 Quality of Ground Water and Area of Potential 100 Saline-Water Intrusion in the Federalsburg Aquifer, as Shown in Figure 29 Table 16 Quality of Ground Water and Area of Potenti al 107 Saline-Water Intrusion in the Frederica Aquifer, as Shown in Figure 31 Table 17 Quality of Ground Water and Areas of Potential 112 Saline-Water Intrusion in the Manokin Aquifer, as Shown in Figure .33 Table 18 Quality of Ground Water and Area of Potential 116 Saline-Water Intrusion in the Pocomoke Aquifer, as Shown in.Figure 35 Table 1-9 Quality of Ground Water and Potential Saline- 132 Water Intrusion in the'Quaternary Aquifer, as Shown in Figure 40 Table 20 Chemical Constituents in Water from 19 Wells, 133 Tapping the Columbia Deposits xvi. INTRODUCTION PURPOSE AND SCOPE OF THE REPORT The'Delaware State Planning Office is charged with the responsibi,lity to develop a coastal zone management program for the State's coastal regions. The geological and hydrological framework of the coastal regions is an essen- tial component for the accomplishment of this important goal. To this end, the State Planning Office contracted with the University of Delaware for a "state of the art" report on Delaware's geology, hydrology and mineral resources. This assignment was a logical extension of previous work by the University of Delaware Water Resources Center and the Delaware Geologi- cal Survey. Over the past decade, the team of Sundstrom and Pickett has pro- duced a series of publications on the hydrology and geology of Delaware that, when combined with the work of the U. S. Geological Survey, the Delaware Geo- logical Survey and the Delaware Department of Natural Resources and Environ- mental Control, constitute the definitive works on the'@ubject of this report. All this information is either summarized or referenced in this present study and, therefore, this report truly represents the state of'the art on.the geol- ogy, hydrology and mineral resources of Delaware as of 1975. Our hope is that this study will prove to be the valuable tool for.the effective management of Delaware's coastallands and waters. PERSONNEL AND ACKNOWLEDGMENTS This report describing the hydrology, geology, and mineral resources in the Coastal region of Delaware for planning purposes has been formulated and prepared principally by R. W. Sundstrom, Senior Hydrologist and consultant to the Water Resources Center; Dr. Thomas E. Pickett, Senior Geologist, Delaware Geological Survey; and Dr. Robert D. Varrin, Director, Water Resources Center, University of Delaware. The authors have had very able assistance in their study and preparation of this report by many people. Dr. Pickett has been ably assisted in preparing the geology section of this report by Mr. James Demarest. Mr. Demarest also helped Mr. Sundstrom in preparing water-altitude maps and saturated thickness maps of the water table in Kent County. -Dr. Pickett and Mr. Sundstrom both had the able assistance of Ms. Michelle Mayrath and Ms. Katherine Roxlo in drafting several of the illustrations presented in this report. A rather detailed inventory of the water used in Delaware in 1974 was done by Mr. Frederick Robertson with assistance by Ms. Roxlo. The results of Mr. Robertson's inventory are recorded in tables in the hydrology section of this report. The final drafting on many of the figures was done by the State Planning Office staff and,their efforts are appreciated. All three authors have had the excellent assistance of Mrs. Terri Reutter, clerk typist, and Mrs. Beverly Grunkemeyer, staff assistant, of the Water Resources Center in composing, compiling and getting the report ready for publication. The authors have had excellent cooperation with the Delaware State Plan- Natural Resources and Environmental Control, the University of Delaware's ning Office, the Delaware Geological Survey, and the Delaware Department of Cooperative Extension Service and the Agricultural Agents in Delaware's three counties,, city and industrial officials and many others who assisted by fur- nishing data and other material. WELL-NUMBERING SYSTEM For the purpose of numbering wells in Delaware, the State is di.vided in- to 5-minute quadrangles of latitude and longitude. The quadrangles are let- tered north to south with capital letters, and west to east with lower case letters. Each 5-minute quadrangle is further subdivided into 25,1-minute. blocks which are numbered from north to south in series of 10 from 10 to 50 and'are numbered from west to east i.n units from 1 to 5 (see Figure 1). Wells within these 1-minute blocks are assigned serial numbers as they are scheduled. Thus,.the identity of a well is established by prefixing the serial number with an upper and lower case letter followed by two numbers to.designate the 5-minute and 1-minute blocks, respectively, in which the well is'located. For example, well number Gd34-2 is the second well to be scheduled in the 1-minute block which has the coordinates Gd-34. The wells listed in many of the tables of this report can be approximately located on the-map in Figure 1 by applying .the well number coordinates of the well listed in the tables to the coordinates of the map. Exact locations of the well can be found on maps in the files of the Delaware Geological Survey. DEFINI.TIONS,OF TERMS Acre-foot - The volume of water required to cover 1 acre to a depth of 1 foot 73,560 cubic feet) or 325,851 gallons. Aquifer - A body of either consolidated or unconsolidated rock material that contains sufficient saturated permeable material to conduct ground water and to yield economically significant quantities of ground water to wells and springs. Artesian Aquifer - Artesian (confined) water occurs where an aquifer is over- lain by earth material of lower permeability (such as clay) that con- fines the water under pressure greater than *atmospheric. The water level in an artesian well will rise above the top of the aquifer even without pumping. 2 a b c d a A 7504e 30, SUBDIVISION OF BLOCK Gd 39045' 3904e WILtAING 11 121 13 1 14 15 rlw 21 22 23 24 25 D, 4: 31 32 33 34 35 w 41. 42 43 E CANAV, 30 z 30 F WELL GcI34-2 r G al COUNTY T, Y H SMYRNA 5 0 5 MILES 15' 15 KENT DOVER N COUNTY 3900d 3900d L 'I Y INARRING-ON ILFOi4D m L N USSEX 45'- N 45' 0 p RD COUNTY ')LAUREL 3803d @38030' R SELBYVI MARYLAN 75045' 3d 15' loo, a b c d s f g h i j - FROM RIMA,ETAL.,1964 T i.so 9@rw s6 FIGURE 1. MAP SHOWING THE COORDINATES FOR THE WELL-NUMBERING SYSTEM. 3 Available Drawdown - The lowering of the water table or piezometric surface caused by pumping (or artesian flow). In most instances, it is the dif- ference, in feet, between the static level and the pumping level. Barrier Boundary Effect - The result of a hydrologic boundary of restricted permeability Wh-Tch affects the radi,al growth of the cone of depression of a pumping well. This occurs after an elapsed pumping time. Because of this, the drawdown data of pumping tests are abnormal and the trans- missivity value obtained is.less than the true transmissivity. Clay - A rock or mineral fragment or a detrital particle of any composition (often a crystalline fragment of a clay mineral, having a diameter less than 1/256 mm., 4 microns, 0.00016 inches, or 8 phi units). Coastal Plain - A low, generally broad but sometimes narrow plain that has its margin on the shore of a large body of water and its strata either horizontal or very gently sloping toward the water. Coefficient of Storage, or Storativity - The volume of water an aquifer releases. from or takes into storage per unit of surface area of the aquifer per unit change in the component of head normal to that surface. Concretion - A hard, compact, rounded and normally subspherical mass of mineral material of a composition different from that of the earth material in which it is found and from which it is sharply separated.. Cone of Depression - Depression of the water table or piezometric surface sur- rounding a discharging well, more or less the shape of an inverted cone. Confining Bed - One which, because of its position and its impermeability or low permeability relative to that of the aquifer, keeps the water in the aquifer under artesian pressure. Contamination - An impairment of the quality of the water by sewage (high nitrate content), industrial waste (such as oil-field brines from improperly cased or plugged wells), or intraformational leakage from overlying or underlying strata that contain.undesirable water (Glen Rose Formation), to a degree which creates an actual hazard to public health. Continental Shelf - A part of the continental margin that is between the shore- line and the continental slope (usually about 200 m. maximum depth). Discharge - Rate.of flow at a given instant in terms of volume per unit of time. Earthquake - A sudden motion or trembling in the earth caused by the abrupt release of slowly accumulated strain (associated with faulting and/or volcanic activity). 4 Electric _'o A geophysical record of the uncased part of a well or borehole, obtailned by lowering and raising an electrode on a wire line and making in-situ measurements (continuously recorded at the surface) of the ' electrical properties of the geologic formations encountered at various depths. Evapotranspiration - Water withdrawn by evaporation from a land area, a water surface, moist soil, or the water table, and the water consumed by transpiration of plants. Fall Zone - An imaginary narrow zone connecting the waterfalls on several suc- cessive and nearly parallel rivers, marking the points where these rivers make a sudden descentfrom the upland to the lowland, as at the boundary between the Piedmont Province and the Coastal Plain. Fault - A surface or zone of rock fracture along which there has been displace- ment, from a few centimeters to a few kilometers in scale. Formation - The basic or fundamental rock-stratigraphic unit in the local cTassification of rocks, consisting of a body of rock characterized by some degree of internal lithologic homogeneity or distinctive,litholog- ic feature, and by mappability at the Earth's surface,- or traceability in the subsurface. Fossil - Any remains, traces, or imprints of a plant or animal that has been' preserved by natural processes in the Earth's crust since some past geologic time; any evidence of past life. Geology - The study of the planet Earth. Group - A major rock-stratigraphic unit next higher in rank than the formation, consisting wholly of two or more (commonly two to five),continuous'or associated formations having significant lithologic features in common. Head, or Hydrostatic'Pressure - The pressure exerted by the water at any given point in a body of water at rest reported in pounds per square inch or in feet of water. That of ground water is generally due to the weight of water at higher levels in the same zone of saturation. Hydraulic Conductivity - The rate of flow of water in gallons per day through a cross-sectional area of I square foot under a hydraulic gradient of 1 foot per foot. Hydraulic Gradient - The slope of the water table or piezometric surface, usually given in feet per mile. Hydrology - The science that deals with continental water, its properties, circulation, and distribution on and under the Earth's surface and in ,the atmosphere from the moment of its precipitation until it is re- turned to the atmosphere through evapotranspiration or is discharged into the ocean. 5 Intrusion - The process of emplacement of molten rocks into existing rocks@ Isopach - A line drawn on a map through points of equal thickness of a desig- nated stratigraphic unit or group of stratigraphic units. Lignite - A brownish-black coal that is intermediate in coalification between peat and subbituminous coal. Lithology - The description of rocks, especially sedimentary clastics,. and especially in hand specimen and in outcrop on the basis of color,' structure, mineralogy, and grain type. Marine Sediments Sediments which were deposited in a marine environmen t by mari-ne processes. Marsh - kwater-saturated, poorly-drained area, intermittently or permanently water-covered, having aquatic and grasslike vegetation, and essentially without peat accumulation. Milligrams Per Liter (mg/1) One milligram per liter represents 1 milligram of solute in 1 liter of solution. As commonlymeasured and used, one milligram per liter is numerically equivalent to one part per million (1 milligram of solute in 1 kilogram of solution). Mineral - A naturally-formed chemical element or compound having a definite chemical composition and usually a characteristic crystal form. Non-Marine Sediment - Sediment which was deposited in an environment not asso- ciated with marine waters, i.e. fluvial, brackish, lacustrine, eolian, etc. Outcrop - That'part of a geologic formation or structure that appears at the surface of the Earth. Permeability - The property or capacity of a porous rock, sediment,.or soil for transmitting a fluid without impairment of the structure of the medium; a measurement of the relative ease of fluid flow under unequal pressure. .Piedmont - Lying or formed at the base of a mountain range; in the U.S., the Piedmont is a plateau extending from New Jersey to Alabama and lying east of the Appalachian Mountains.' .Piezometric Surface - An imaginary surface that everywhere coincides with the static level of the water in the aquifer., The surface to which the water from a given aquifer will rise under.its full head. Pyrite A common,,pale-bronze or brass-yellow mineral; FeS2- 6 Recharge - The process by which water is absorbed and is added to the zone of saturation. Also used to designate the quantity of water that is added to the zone of saturation, usually given in acre-feet per year or in million gallons per day. Rejected Recharge - The natural discharge of ground water in the recharge area of an aquifer by springs, seeps, and evapotranspiration, which occurs when the rate of recharge exceeds@the rate of,transmission in the aquifer. Runoff - The water which flows on the surface is called the runoff though this term is used to include also the water which returns to the surface after a greater or less underground passage. Safe YieWr The rate at which water can be withdrawn from an aquifer for hu- man use without depleting the quantity or quality of the supply to such an extent that withdrawal at this rate will become no longer economi- cally feasible. The practical rate of withdrawing water from an under- ground,reservoir perennially for human use. Salt-Water Intrusion - The phenomenon occurring when a body of salt water, because of its greater density, invades a body of fresh water.' It can occ'ur,,e'ither i.n,surface or ground-water bodies. The balance'between the two, in static situations, is ex'ressed'by the Ghyben-Herzb6rg' p formula. Sand A rock fragment or detrital particle smaller than a granule and larger thana,coarse silt grain, having a diameter in the range of,1/1.6 to2, mm.. (62-200 microns, or 0.0025 - 0.08 inches, or 4 to I phi units, or the lower limits of visibility for a single grain to the size 6fthe head of a small wooden match). Silt - A rock:fragment or detrital particle smaller than sand and larger than_ clayj having a diameter in -the range of 1/256 to 1/16 mm. (4-62 microns, or 0.00016 - 0.0025 inches, or 8 to 4 phi units). Specific Capacity - The rate of yield of a well per unit of drawdown, usually' expressedas gallons. per minute per foot of drawdown. If the yield is 250.gallons per minute and,the drawdown is 10 feet, the specific capa- city is 25 g4ll'ons 'per minute per 'foot. Specific Yield - The quantity of water that an aquifer will yield by gravity if it is first saturated and then allowed to drain; the-ratio expressed in percentage of the,volume of water drained to volume of the aquifer that-.is drained., Static Water Level The water.level in an unpumped or n6nfl6wing wel'l measured in feet above or below the land surface or sea-level-datum. Stratigraphic Correlation The process by which stratigraphic - units in two or' more separate areas are demonstrated or determined to be latera'lly 7 similar in character or mutually correspondent in stratigraphic posi- tion, as based on geologic age, lithologic characteristics, fossil content, or any other property of the strata. Strike - The direction or trend that a structural su rface takes as it inter- sects.the horizontal. ,Structure - Said of or pertaining to features that are the result of crustal folding or faulting. ,Subcrop'- An occurrence of strata in contact with the undersurface of an over- lying stratigraphic unit. Subsurface @- The zone below the surface whose geologic features, principally stratigraphic and structural, are interpreted On the basis of drill records,and various kinds of geophysical evidence. Surface Water The water which rests or flows on the surface of the earth liFh-osphere. Transmissivit The number of gallons of water that will move in one day throuU a vertical strip of the aquifer one foot wide extending the vertical thickness of the aquifer when the-hydraulic gradient is one foot per foot. It is the product of the hydraulic conductivity and the saturated thickness of the aquifer. .Unconformity - A substantial break or gap in the geologic record where a rock unit is overlain by another that is not next in,stratigraphic succes- .sion, such as an interruption in the continuity of a depositional se- quence of sedimentary rocks. 'Variegated - Said of a,sediment or sedimentary rock showing variations of colors or tints in irregular spots, streaks, blotches, stripes., or reticulated patterns. Water Level - Depth to water, in feet below the land surface, where the water occurs under water-table conditions (or depth to the top of the zone of saturation). Vnder artesian conditions the water level is a'measure of the pressure on the aquifer, and the water level may be at, below, or above the land surface. Water-Table Aquifer - An aquifer in which the water,is unconfined; th e upper surface of the zone of saturation is under atmospheric pressure only .and the water is free to rise or fall in response to the changes in the-volume of water in storage. A well penetrating an aquifer under water table conditions becomes,filled with water to-the level of the water table. Yield of a Well - The rate of di scharge, commonly expressed as,gallons,per mli@iute, gallons per day,.or gallons per hour. 8 GEOLOGY GEOLOGY FOR PLANNING PURPOSES Geology as a Constraint The geologic framework is th e means by which current earth processes are controlled by past geologic processes. Man's input into this system adds another determinative factor to the present and future dynamics of the system. To better understand and manage our environment we must first understand the constraints'within which we must work as determined by the geologic conditions. The geologic framework of an area is the most important factor in deter- mining: drainage patterns; location, quality and quantity of water in the sub- surface; stability of the ground for construction uses; location, quality and quantity of mineral resources. There are no earth processes or conditions which are not controlled or greatly affected by geologic constraints. It is also important to understand the basic differences between the geo- logic constraints and man's input into the system.. Man's'policies, and there- fore his input into the system, can be changed and therefore man's effect on the system can be controlled and predicted. In contrast, geologic conditions are not changeable or manageable except on a very small scale with large inputs of energy. Geology as a Predictor By studying the geologic processes that formed our present environment, we not only can predict future environments, but we can also understand the processes involved in producing them. Therefore, changes man makes in these processes can also be taken into,account when predicting future environmental conditions. For example, understanding the geologic framework of aquifers enables us to identify recharge areas and areas of vulnerability of the aquifer. We will then be able to predict quantitatively what changes, if any, man's ac- tivities will have on water quality and quantity. Similarly, study of the geol- ogy of an area allows us to determine, in general, soil quality, stability of the ground, erosional hazards, etc., in areas without actually doing costly tests and studies on location in the area of interest. We can also predict the lateral extent of conditions by projection of the geologic situation under which these conditions exist, i.e., topography, surface lithology, subsurface lithology-and structure, geologic history, and present earth processes as de- termined by geologic history. 9 GENERAL GEOLOGIC HISTORY OF DELAWARE The Piedmont Delaware lies within two regional geologic provinces: the Appalachian Piedmont and the Atlantic Coastal Plain (Figure 2). The northernmost part of the State lies in the Piedmont. This area is characterized by very old crys- talline rocks which slope generally southeasterly under all-of Delaware. 'The minerology of:these rocks is very complex because they consist of sedimentary and igneous rocks which have been intensely metamorphosed throughout the area during the bu-ilding of an ancient mountain range which has now been-eroded. The Coastal Plain South of,the Fall Zone, the Piedmont-type'rocks are covered by a thick wedge of unconsolidated and semiconsolidated sedimentary rocks. This region is the Coastal Plain-Province (Figure 3). In the southeastern part of Delaware, these'sediments reach a thickness of about 8,000 feet, and although they are covered by water farther east, they continue out to the edge of the continental shelf with a-maximum thickness of about 8 to 10 miles. All these sediments are much younger than any of those found in the Piedmont by over 300 million years except for those found in the Bryn Mawr Formation north of Wilmington, which are much younger than the Piedmont rocks but have an-unknown age. The Coastal Plain sediments have been divided into units, each of which is called a forma- tion (at times formations are put together and called groups) whose lithology is distinctly different from the-sediments above and below it (Table 1). The oldest sediments in the Coastal Plain, which were deposited by streams on the subsurface extension of the Piedmont, are at the base of the Potomac Formation and,are,about 120 million years old. This unit is the most exten- sive sedimentary formation in Delaware. It consists of color-banded.clays with interbedded sands which eroded off the ancestral Appalachian Mountains to the northwest. During the deposition of the Potomac Formation a gradual tilt- ing down to the east allowed about 4,000 feet of sediment to accumulate. Above this the Magothy Formation was deposited after a period of erosion or nondeposition (an unconformity) which represents the encroachment of the sea over most of Delaware. The Magothy Formation is very distinct with'its white. sands and black lignite. The presence of lignite suggests that this unit, represents a transitional environment-from stream deposits to marine, much like that found in a delta or marsh. Above the Magothy are marine formations of Cretaceous through Eocene age. The units deposited during this time, from oldest to youngest, arejas follows:. Merchantville Formation, Englishtown Formation, Marshalltown Formation, Mt. Laurel Formation, Rancocas Group, Nanjemoy Formation, Pamunkey Formation (unit A), Piney Point Formation. 10, FIGURE 2 A GEOLOGiC MAP OF DELAWARE, PIEDMONT Wilmington New Castle Kpt; Potomac Formation; Varigarted red, gray, purple, yellow and white, frequently ligniti silts and clays containing interbedded white, gray, and rust-brown quartz 4 sandscand some gravel. Individual beds usually laterally restricted. 5 Km; Magothy Formation; White and buff, frequently sugary, clean quartz sand with beds of gray and black clayey silt containing much lignite, pyrite-filled limay clay concretions and sulfate blooms. Formation discontinuous along strike in subcrop. K v' Merchantville Formation; Dark gray to dark blue, micaceous, glauconitic, wmnd@ silt and silty fine sand; very sticky when wet. Placenticaras placenta, small iderite nodules, burrows by benthic organisms. Middl own Ket; Englishtown Formation; Light gray and rust brown, well sorted, micaceous, spa' ingly glauconitic, often "fluffy", fine sand with thin interbodded layers of dark gray silty send. Abundant nodulose burrows of Callianassa, particularlyin upper sands, Kmt; Marshalltown Formation; Dark greenish-gray, massive, highly glauconitic, very silty fine send. Abundant Exogyra ponderosa Kml; Mount Laurel Formation; Gray, green and red-brown, glauconitic, fine to medium, quartz sand with some silt. -,.w-gsmyr Tht: Hornerstown Formation; Green, gray and reddish-brown, fine to medium V silt , highly glauconitic send and sandy silt. Red sands are found locally in @__vltvl y CHESVVO.LD AQUIFER Odom area. Tvt; Vincentown Formation; Green, gray and reddish-brown, fine to coarse, highly quartzose glaucontitic, send with some silt. Tc; Chesapeake Group; Gray and bluish-gray silt, with some fine sand and Tover silt beds. FRE. E AQU IFER =MAJOR MIOENE AQUIFER Milford Rehoboth Beach let n Seaford M NOKIN'AQUI _ER ,ell, All POCOMOKE AQUIFER ...... . . . . . ATLANTIC CONTINENTAL SHELF WILMINGTON 400d NEWARK,DELAWARE NEW JERSEY COASTAL PLAIN CANYON 8%, N9 s I - c CRETACEOUS PALEOCENE-EOCENE ok co X&O" @v sood x Go' SUB SEA VO .-- ss" I@ jr A ... DOVER DELAWARE SAY SO - %@@ O\v V IN S COVER BRIDGEVILLE 5 @,.JSE' 12000, it ED Y A - v 0", @r Jr RAL E 0@, PLEI CENE,olvAlim, L, UNCONSOLI'ATED EOC,Eov@ Aflo COAS& SEDIME -Ir 'r 114AR Afi)COCE)k CEAFE AIARI IF) I MARYLAND ESSO NOA 1600d 4 1, P', CRE SEW AND rACe.- ONSOLIDATED SEDIMENTS CR'E r4 C rACeOUS (M4R, * 'r COUS (/VON- o\Or _,OcvkE 2000d + 74 t I've Cll!c\ 2400d lop. 0. r 005 2800d 32000 TRIASSIC x x , x x x x x 10000, CRYSTALLINE BASEMENT 1 000, 14000" FIGURE 3. GEOLOGIC CROSS-SECTION SHOWING GROUND-WATER AQUIFERS OF DELAWARE. 00 M 'M MAW M'M M, M'M, am M New J ersey Delaware Maryland Cape May Fm. Omar Walston Fm. Fm. (0 ca _P Quaternary Pleistocene Pehsauken Fm. Columbia Fm. - J:' Beaver- Ea E CL 3: 0 Bridgeton Fm. dam Fm. - Salisbury Fm. -0i WcL 0 0 Bryn Mawr Fm. Pliocene Beacon Hill Gravel Upland Gravels Cohansey Fm.. Yorktown Fm. Miocene Chesapeake Group St. Marys Fm. Kirkwood Fm. W CL,@-L Choptank Fm. Calvert Fm. 6 h Oligocene C+ Tertiary M Piney Point Fm. Piney Point Fm. Piney Point C") 0 fu Eocene Shark River Fm. a 0 U) C+ Manasquan Fm,. Nanjemoy Fm. Nanjemoy Fm. E- S_ Vincentown Fm. Vincentown Fm. LL_ CL Marlboro Clay 0 CL 0 CL C 0 C Paleocene U S_ U S_ = -0 C (M E E a CM to ro Hornerstown Fm. Hornerstown Fm. Brightseat Fm. Tinton Fm. OL 4-) Redbank Fm. = 0 CL 0 E C E S.- Navesink Fm. I=- U_ 3: M = CM r_ 0 0 Mt. Laurel Fm. Mt. Laurel Fm. Monmouth Fm. Upper Wenonah Fm. Cretaceous Marshalltown Fm. Marshalltown Fm. a Englishtown Fm. 3:,LEnglishtown rm. 4-) 4-3 :3: Woodbury Clay s-Merchantville Fm. (d dr- Matawan Fm. Cretaceous to (D r1l U_0 Merchantville Fm. 7: X: -0 Magothy Fm. @Magothy Fm. Magothy Fm. Raritan Fm. Patapsco Fm. Lower E Potomac Fm. 0 O-Arundel Fm. 4-3 $_ Cretaceous Potomac Fm. ? 01-" Patuxent Fm. Above this is an unconformity which represents a gap in the sedimentary record during which no sediments have been preserved (Oligocene age). Later, the sea again covered most of Delaware and deposited the Chesapeake Group (Miocene age). This group consists of interbedded silts and sands and reaches a maximum thickness of over 1,000 feet in southern Delaware. Many of the sandy layers contain important supplies of water for municipal and industrial use. 'From oldest to youngest, these units are as follows: the Cheswold, Frederica, Manokin, and Pocomoke aquifers. The repeated advance and retreat of continental glaciers during the past one to two million years (Pleistocene age) caused drastic changes in relative sea level and the configuration of streams draining from the glaciers. The Columbia Group and Formation, which covers most of the surface of Delaware up to the Fall--Zone, generally consists of channel deposits from meltwater runoff and marine deposits. The Columbia supplies most of the water used i.n the state as well as most of the sands and gravel for construction. Many of the stream and channel gravels have been reworked in southern Delaware by the sea during a higher-than-present sea level stand. This is, briefly, the history of the geologic framework which provides the constraints within which man must plan his activities. It is also important to realize that the processes of erosion, deposition, and sea level change are operating at present, slowly transforming the surface expression of this geo- logic framework. DESCRIPTIONS OF AQUIFERS The maps of the stratigraphic formations of Delaware's Coastal Plain are based on the most recent data available to the Delaware Geological Survey. These mapsare continually changed as more data are accumulated and must, therefore, be considered incomplete. Although their reliability exceeds pre- vious maps, which were based on less data, they still must be used with cau- tion. The maps are indicators. of the general structure of the formations-and therefore should only be used in a general way. If@a contour or isopach is more than a few miles from a data point, its exact positioning becomes more artistic than geologic. The maps indicate the*scarcity of data in some areas. The Potomac Formation The Potomac Formation, which overlies the crystalline rocks of the base- ment, consists of variegated silts and clays. These are red, gray, purple, yellow and white and contain some lignite. There are many beds of sand which are white, gray, or rust-brown, predominantly quartz, with some gravel, and which are usually laterally restrictive (Pickett, 1970a). 14 Between the Fall Zone and just north of the Chesapeake and Delaware Canal, the Potomac Formation (Figure 4) subcrops immediately below the sur- ficial Columbia Formation, and reaches a maximum thickness of about 600 feet. South of this area the Potomac is overlain by other sedimentary formations and dips toward the south., In southern New Castle County-the top of the Poto- mac reaches a depth of 650 feet below sea level and the formation is 1,700 feet thick. Because of extreme depth and because of salt-water contamination, it is not presently useful as an aquifer in Kent and Sussex Counties. The Magothy Formatton' The Magothy Formation (Figure 5) represents a transition from,the non- marine fluvial depositional environment of,the.underlying Potomac Formation to the marine depositional environment of the.cverlying formations.. It is a white and buff, often sugary, clean quartz sand with occasional-beds of gray and black clayey silt which contains much,lignite, pyrite-filled concretions and sulfate blooms (Pickett, 1970a). Because of its-clean sandy nature and consistent thickness of a few tens of feet, the Magothy Formation produces a distinctive@-"kick" on electric logs of wells;,therefo're, it is one of the most easily recognizable units in the Coastal Plain. There is a trough-ridg.esystem running nearly perpendicular to strike near the subdrop area, which accounts for its apparent discontinuity along strike. 'The cause of these structures is as yet unknown, although they may be associated with differential erosion of the Potom.acbef6re deposition of the Magothy. The Magothy Formation, like the Potomac FormattonS is too deep and salty to be useful as an aquifer in Kent and Sussex,Counties. The Monmouth Formation The Monmouth Formation (synonymous with,Mount Laurel Formation at the Chesapeake and Delaware Canal) consists of gray.to greenish red-brown glau- conitic, fine to medium sand with some sil-t (Pickett, 1970a). It was depos- ited under shallow marine conditions. The non-salty portion of the Monmouth-@ is found from the Chesapeake and Delawdre Canal to approximately Dover where it is located about 700 feet below sea level (Figure 6). 15 tlp foo, ............... ........ ...... ........ ........ 7@4 too DEPTil TO THE TOP OF T@4E .......... FORMATION (msi, datun) DATA POINT (feet, MSI dotuml O,w lso ,60 ...... ....... AREA OF SUBrRop BELOW T Vie 71, QUATERNOY SEDIMENTS *4.114 0 40 SALT WATER LINE (APPRO)OMATE) -200 .10 AQ -132 -6 ** j73 1 '1310 .350 400 FIGURE 4 "cl STRUCTURAL MAP OF THE POTOMAC FORMATION 00 ABS ABS -5 ABS -50 6 ABS 0 0 .100, -40 -50 4j281-60 '-52 ABS -5. -'o' .400 -49 0 145 -150 1 -15 ABS !5 -102 JABS -'50 DEPTH TO THE TOP OF THE '122 '1020 -135 .30 -90 0 @70 0 FORMATION (msI datum) -50 .127 0 105, -200 -100 A94 DATA POINTIleel,msl datum) .1 .250- AREA OF SUBCROP BELOW 150 -150 TA COLUMBIA FORMATION -300 o o o o o SALT WATER CONTAIVITNATION .200 LINE -256 % 0 -400 .237 .308 -250 -260 .500 'ZI 0. 0 .300 0 .600 0 -589 .400 0 0 0 0 0 0 .500) 0 FIGURE 5 00-0600 STRUCTURAL MAP OF 0 0 THE MAGOTHY FORMATION 17 . .......... 0 DEPTH TO THE TOP OF*THE FORMATION(msl datum) DATA POINT feet m8l datum) AREA OF SUBCROP BELOW THE QUATERNARY SEDIMENTS 50 ...... -54 -49 SALT WATER LINE (APPROXIMATE) -53 ...... -41 -100 -66 -41 0-80 0-55 9-65 -150 0-78 -54 GL86 -200 -102 250 -300 300 -350 -400 -450' -500 -550 -365 -600 -650 -700 0-1 -650 00 .0 OF #0 FIGURE 6, STRUCTURAL MAP OF THE MONMOUTH GROUP 18 The Rancocas Group The Rancocas Group consists of two formations, the Hornerstown and the Vincentown. These are differentiated by the relatively coarser component found in the younger Vincentown. The Rancocas Group is green, gray and reddish-brown, highly glauconitic sand with some silt (Pickett and Spoljaric, 1971). The subcrop area begins about three to four miles south of the Chesa- peake and Delaware Canal and underlies the entire Middletown-Odessa area (Fig- ure 7). The group pinches out inthe subsurface in the Cheswold area. Its maximum thickness is about 300 feet. The Piney Point Formation The Piney Point Formation in Kent County is a green, medium to fine grained, glauconitic sand of the Eocene Epoch (Jordan, 1962a). In Sussex County (Greenwood test well) it is a greenish-gray to bluish-gray, silty, sparingly to moderately glauconitic, very fine to coarse sand (Talley, 1975). The Piney Point is found in the area between Kent County and the rest of southern Delaware (Figure 8). It nowhere comes near the surface It is thickest and sandiest in Dover and adjacent area south. In most of Sussex County it is too salty to be useful as an aquifer (Cushing, et al, 1973). The Chesapeake Group The Miocene Chesapeake Group consists of gray and bluish-gray silts, with some sands (Pickett and Spoljaric, 1971). It contains four major aquifers (sands) and some minor aquifers, and thus has been only partially differen- tiated in Delaware. The major aquifers are the Cheswold (oldest), Frederica, Manokin, and Pocomoke (youngest) aquifers (Figures 9 and 10). These sands may have been deposited along ancient shorelines. The Cheswold is located from the Smyrna area,into northern Sussex County.. The Frederica extends from Dover to northern Sussex County. The discrepancy of overlapping Cheswold and Fred- erica aquifers shown in Figure 9 may be explained by the presence of the "Federalsburg aquifer." Cushing, et al (1973) mapped this sand between the Cheswold and Frederica; whereas in Figure 9 it is included within the Cheswold. The Manokin is confined to Sussex County, and the Pocomoke to southern Sussex County. Cushing, et al (1973) extend the Manokin into Kent County. Miller (1971) mapped the Manokin and Pocomoke, with the best available information, in greater detail than is present in Figure 10. 19 -150 DEPTH TO THE TOP Or THE .... . ... FORMATION msl datum) t14 DEPTH POINT (feet, msl datum) AREA OF SUBCROP BELOW THE OUATERNARY SEDIMENTS ............... PINCH OUT LINE 0 50 SOURCE! DELAWARE GEOLOGICAL SURVEY 100 . . . . ...... ... t3s -150 Ot25 ... C6 -J5 -185 -200 0-5 -250 -141 -170 -220 /A b. -300,-400/ -220 0-220 Abs FIGURE 7 STRUCTURAL MAP OF THE RANCOCAS GROUP 20 75 75 '40' 75 !35' 75.3d 75j25' 75-2d 75. IW 75.,Iv 75 05' 39*20' SASTLE CO. o F1 GURE 8 Co. SMYRNA STRUCTURAL MAP OF THE PINEY POINT FORMATION -300 7 -200 -100 DEPTH BELOW SURFACE (msi datum) DOVER 39* 10 FROM: SUMIATRON & PIC.ZTT, 190bil".11010 39-05, - -NO MARRVWGTON MILFORD .700 -400 .400 N .000 SCALE IKZMILES 39'50'- 1 0 1 3 4 SUSSEX Go. MILTON -low LEWES SO'4V - -500 REHODOTM SEACH 'GEORGETOWN 38-40' - // I IIIF f 0 38-33' - 600 v Mfi.LSBORO 0 ,If If SELOVVILLE f FENWiCK A ISLAND -700 -600 -900 -7.6. AGO -itob -1400 21 75-45' 75-40' 75-av 75-30' 75-2 5' 75-201 75-15, 75' 10' 75' 05' 39-20' 0 0 SASTL@ CO. 1@1 SMYRNA & XENTCO. X. FIGURE 9 39-M' .1 -100 STRUCTURAL MAP OF THE T CHESWOLD a FREDERICA -am AQUIFERS DOVER 0 CHESWOLD AQUIFER @o - - FREDERICA AQUIFER -350 DEPTH TO TOP OF AQUIFER( msl daium) 39'00'- I FROM: SUNDSTRUM B PICKETT, 1968119691 1970 .'Oo _'c_o'- o" a ess, - -250 HARRINS@PN *MILFORD -460 am -350 0-* "a ,P -300 SCALE IN MILES lel* 1 0 1 2 3 4 38-50, - @KENT CO-__ _ _E_.O. Ui. ol -a5o -am .11 * MILTON -.00 olo-* -.06 IDLEWES /* .1 oll eo* R HOSOTH BE EACH -100 *GEOR15JO N o" -4W / . . I /* 58-40' -0- 400 0' MILLSBORO -500 BETHANY BEACH SELBYVILLE FENWICK iSLAND 22 1.11w 75 RV 751.30, 75 25' 751.15, 75 ld 75. 05, 7 FIGURE 10 STRU.CTURAL MAP OF THE MANOKIN AND POCOMOKE AQUIFERS MANOKIN AQUIFER o-o-o POCOMOKE AQUIFER MMILFORD DEPTH TO TOP OF AQUIFER (mel datum) Irl @NT C SUSSEX CO. GREENWOOD -50 0 % %-150 0 MILT '1205 1 1. LEWE 0, -30 0 BRIDGEVILLE \0 0-0-0-0-0-0 EHOBOTH "50 EACH 5 /0 EGEORGETOWN 0 SEAFORD "o -]to In or7s -100 0-75 -100 100 0 0 0 175 0 0,0 i75 MILLSBOR( / o" 0 -@<12'5 LAUREL - / -176 s '41, 0 0-0-0-0-0 -0 0 T I ` 0 BETHANY ?e-i 0 ;J25 -0 'e., o/ BEACH .r5 0 40.10 8@ a.- FRANWFORd?k T 04glo 00" 0 0 0 -2- 0 01-0 -o" 0-0-010 'lp il / 0/ 0 ,o-o-el25 k /0 0'0'(@ -0,0 -0-0-0-0- 0,0,0@O 0 / 0 0- - 0-0 0 - . - a ol 0 0 --o 0 0-0-0- 0.11 -0_0100 0 kelo@- 0 .,G.:@O-o 'o @0,0@ 0 /0 /0 110 1@0@-0-0-00--@* 0-0-,57 0 a * I I \ PDIL 0-0-0 00, FENWICK . LMAR-JLO.16-0.0--k-o- -o-o-o-owso-0-0-0- 50 -i-5-55-lnig-75 ELBYVILLE ISLAND -150 :75---=r5 -1 5 ON 23 The Pleistocene Aqui@fer The topmost sediments.in much of'the Delawarb@Coastal,.Pla%n@are presumed to be Pleistocene in age and consist mostly of medJurvto..v 'ery coarse sand and gravel, generally of a yellow-orange to tdn-brown.c6lor. These are termed the. Columbia Formation. They were deposited in channel-fill and associated river environments, and, in the southern part of Kent County and in Sussex County, they are marine in origin. There is also some reworking of the older sediments by Pleistocene marine processes (Jordan, 1964). Figure .11 indicates the approximate thicknesses of these surficial de- posits.. It Js the thickness of the saturated sands and therefore includes some .areas of pre-Pleistocene sand subcrop. Because"the'largely sandy Columbia Formafion (lPleistocene?) is in some places underlain by older sediments which are also very sandy and often unfossiliferous, it is very difficult to differ- entiate Columbia from Miocene or possibly Pliocene age sediments. It is there- fore difficult to map the Columbia Formation. Figure 11, a sand thickness map, is presumed to be mostly of Pleistocene Columbia sediments. MINERAL RESOURCES OF DELAWARE Sand and Gravel Sand. and gravel are the most important mineral resources in Delaware. The State Division of Highways, the largest consumer of sand and gravel, has adopted strict regulations controlling.the quality required for concrete, road beds, and fill (Standard Specification's, 1974., Delaware Division of High- ways). The location of coarse pockets in the Columbia Formation appears to be -random and therefore difficult to predict. In general the pockets are1ocated by accident,, then tested and evaluated by the Highway people. Figure 11-1s a rough guide to the thickness of sand or gravel (undifferentiated) Which could be utilized. However, specific on-site investigations are needed before evaluating a given location. Figure 12, the mineral resources map, is an, attempt to summarize the available data on sand, gravel and other..resourcds... There are several variables whic,h'must be assessed before the value of a: gravel pocket can be calculated. The important ones are as follows:' 1. Variability in grain size (sorting); 2. The,average grain size; 3.- The amount of coarse material 'in the pocket; 4. Cost per ton. paid to the owner. Each of these criteria must,be evaluated before deciding which gravel pock -et should be used. For example, Tf the sand in a borrow pit-is not very well'' sorted, but is very close to the,construction sitej i,t may b&mor&-econom'1cal! 24 FIGURE IIA THICKNESS OF THE PLEISTOCENE AQUIFER (NEW CASTLE COUNTY) 0 0 ?o 00 2 0 134 50 2 0 10 10 0 1. 30 Ic 20 3( 00 30 20 20 30 40 so 30 20 30 20 20 to 10 50 20 30 10 10 20 20 30 20 3D 20 40 r,o 60 30 to 20 10 20 .0 ao 25 FIGURE 1.113 THICKNESS, OF THE PLEISTOCE.NE AQUIFER (KENT COUNTY) 50 60 0 20 20 30 5 40 20 -88 'o so 90,00 110 120. 20. 30 140 130 120 110 loo: 20 50 90 60 so 40 90 50 70 so 50 60 70 0 90 40 .so go 40 ao so -70 IGO 40 lw 50 170 160 50, 15 1 150 120 -----@llo '00 90 so 90 50 so 70 100 w 50 so 70 so 26. FIGURE 11C THICKNESS OF THE PLEISTOCENE AQUIFER (SUSSEX COUNTY) VV@ too too 40 50 50 90 100 so 50140 J20 110 60 oil 120 130 70 90 go Ito 100 100 too 130 w 1 01- 100 140 Ito ISO 1 120 110 100 00 P,10 - 120 too 27 25! 2o' ov 75, 5e 2W Cohonsey SEDIMENT DISTRIBUTION MAP pAr 2Cf MOWTRS 10 Sam 181 Egg Island Pt. NEW JE11SEY Maurice River part Mahan ............... ...... 0. DELAWARE St. Jones ........... River Muiderkill River 39 wspilliom" -L-- Rivet GRAVEL COPS May A, MG MVG LESENO - aftew folk, t945 QM -ro -Yel 11, (g1sm '(qims- W (9) slightly gravelly Trace IM sm S send MUD ):9 )i) 91 SAND s sandy SW #Clay M mud > 0625 mrn) SAND@MUD RAT)a (.0625- Zmm) pe Henloper m muddy 7-5j- 30' 0 751 FIGURE 12 . . . . . . . . . . MINERAL RESOURCES OF THE DELAWARE COASTAL PLAIN BEST POTENTIAL AREA FOR SAND@ AND GRAVEL EXTRACTION (OVER 30' THICK, EXCLUDING BEACH AREAS). -THINNER, BUT ACCEPTABLE DEPOSITS MAY 13E FOUND ELSEWHERE. GENERALLY MORE GRAVELLY N IN NEW CASTLE COUNTY. BEST POTENTIAL AREA FOR BRICK CLAY. OTHER, LESS DESIRABLE DEPOSITS MAY BE FOUND ELSEWHERE. BEST POTENTIAL AREA FOR GREENSAND. OTHER I Ll AREAS NEAR MIDDLETOWN ODESSA MAY BE ACCEPTABLE. A MAJOR, ACTIVE SAND AND GRAVEL PIT > 0 ACTIVE BRICK CLAY PIT. HARD ROCK (PIEDMONT) A, A A 1 28 to wash the gravel to remove the fine material, rather than transport higher quality gravel from farther away. In 1973 Delaware produced 3,408,000 tons of sand and gravel, valued at $3,678,000 (U. S. Bureau of Mines Yearbook, 1973). Figures for 1974 are expected to be roughly the same. Much sand and gravel is imported from adjacent'states. Stone is no longer quarried in Delaware. Clay There is at present only one commercial producer of clay in Delaware. The clay is used for the manufacture of bricks. In the past there were more brick plants; however, it now seems to be more economical to import bricks from Maryland. Clay production in Delaware in 1973 was about 15,000 tons, with a value of about $9,000 (U. S. Bureau of Mines Yearbook, 1973). The Delaware Geological Survey has cooperated with the U. S. Bureau of Mines for several years to test clays. Figure 13 shows the location of 48 clay samples analyzed under this program (Pickett,,1970). Table 2 summari,zes the results of the analyses, showing which samples are promising for various clay products and which have only marginal potential use.. The data show that clays for brickmaking are' common .(the Potomac Forma- tion is best). Marsh sediments are somewhat promising for lightweight aggre- gate (used for pre-cast concrete products). Preliminary research also indi- cates that spoils obtained by maintenance dredging of harbors in the Delaware River may be promising for lightweight aggregates. If power for roasting the material is available, a severe ecologic problem of how and where to,dispose of dredge spoils may be solved. Glauconite, a clay mineral, has potential use in wastewater treatment. Preliminary tests show that glauconite ("green'sand'.') has the ability to re- move heavy metals from industrial wastewater (Spoliaric and Crawford, 1975). In the past, greensand has been used as a w ater softener and as a fertil- izer. It still has limited use as a water softener, but, because of the long time necessary for it to release nutrients (potash), glauconite is not used as a fertilizer at the present time. The Rancocas Group, which subcrops in the Middletown-Odessa area, contains from 95 percent (along Drawyers Creek near Odessa) to 50 percent glauconite by weight. The greensands are also most accessible in these areas, outcropping along many of the streams.(Spoljaric, personal communication) [see Figure 121. Other formations have concentrations of 5 to 90 percent glauconite by weight. The Delaware Geological Survey is presently researching the potential of green- sands as a wastewater filtering agent. If these results are positive, indus- trial wastes, landfill effluents and many other wastes may be filtered of heavy metal contaminants. 29 017 N /048 WILMIN GTON 2.1 .13 1 310 0 9 EW CASTLE NEWARK 0 10 MILES 20 3 7 DELAWARE 1 22 23 CITY 4 185 109 FIGURE 13 2 12 11* SAMPLE LOCATIONS LIDet.E?TOWN 19 34 SMYRNA *33 046 &36 032 028 DOVER 5 0 37 13 *38 .929 113 HARRINGTON r,39 0 MILFORD 240 1 949 045 040 BRIDGEVILLE LEWES REHOBOTH GEORGETOWN BEACH 444 27 13 16 014 043 e15 LAUREL 25 26 -2-0 30 Table 2. Summary of Clay Data (Sample Numbers) Lightweight Glazed Sewer Brick Aggregate Tile Pipe Stoneware Prom'ising Marginal :Promising Marginal Promising Promising- Promising 6' @3 11 9 21 41 8 @4 10 30 41 42 19 16 46 43 21, 7 23 47, 46 30 17 24 47 31 18 38 33 39 34 37 43 44 47 From: Pic kett, 1970. 31 Potential Mineral Resources Potential mineral resources, not currently utilized, include: garnets for abrasives, kaolin for fine china, serpentinite and gabbro for building stone, feldspar for ceramics (all'in the Piedmont). In the Coastal Plain, potential mineral resources are: iron ore (at Iron Hill and bog iron ore in Sussex County); heavy minerals, such as those containing titanium (mostly in Sussex County); glass sands (mostly in Sussex County); and the possibility of phos- phate deposits. There are no known economic deposits of these commodities, but industrial interest has been displayed at.various times 'and the geologic conditions do not preclude their occurrence in Delaware in economically feasible amounts. The mineral resources of Delaware have been discussed.with an historic, perspective by Pickett (1973). Very little is known about the occurrence of mineral resources offshore Delaware. We know that sand for possible use as aggregate exists in state waters just east of Cape Henlopen (Hen and Chickens Shoal). Elongate bars of sand occur in Delaware Bay (see Figure 12). Phosphate and manganese nodules have been found in the Atlantic Continental Shelf, but next to nothing is known of their distribution off Delaware. The Delaware Geological Survey is devoting much time attempting to evaluate the hydrocarbon potential. Clearly, we need to assess the possibilities of all offshore mineral resources using new data. GEOLOGIC PROBLEMS Geologic Hazards Delaware has relatively few geologic hazards as compared to many other, states. However, the hazards which do exist can be severe. There are three major geolo 1 h ds prevalent in Delaware: floods, faulting (and associated earthquakes , and slumping caused by structural instability. The map of geologic hazards (Figure 1.4) provided with this section is ,only meant to identify in a general way the areas which are threatened by cer- tain geologic conditions. This map cannot be used for site specific problems, but should be useful for identifying general areas of possible geologic prob- lems. 32 .. ..... .. . . ... 1@ INGTON 1871 Pn 1973 FIGURE 14 GEOLOGIC HAZARDS MAP FLOOD. PRONE AREAS POTENTIAL FAULT ZONE SLUMPING HAZARD EARTHQUAKE EPICENTERS DOVER M FORDil,," GEORGETOWN SEAFORD 33 Flood Prone Areas Because of the low relief of the Coastal Plain of Delaware, most of the rivers in this area are prone to flooding. There are many factors, such as stream gradient, depth to water table, upstream drainage area, amount and dura- tion of rainfall, base level of streams, topography of the stream valley, and the ability of the ground to absorb water, which affect the flooding of an area. The designated "flood prone areas" were determined by the U. S. Geologi- cal Survey (1974) using tidal data,,high water marks from previous floods, and topography. As a result, their maps only indicate the potential for flooding. In detail, their lines may be considerably in error, depending on the extent to which the previously-mentioned factors pertain to the local area. These areas may be changed significantly as a result of man's activities as well. For example, changes in elevation of a site by filling could affect the potential for flooding of both that site and adjacent areas. Highways, housing, denudation, storm sewers, parking lots and increased surface slope all contribute to increased runoff, and therefore increase the hazard of flood- ing, especially in urban areas. Areas with extremely high water tables also are relatively more prone to flooding, since very little water can be absorbed into the ground. Also, as the water table fluctuates with total rainfall, @ I weather conditions over a several-month period prior to a heavy rain affect the likelihood of flooding. All of these factors must be evaluated for proposed land use areas in order to protect both the potential owner and the taxpayers, who often end up paying the bill for damages. Faulting The hazards map (Figure 14) has several zones designated as potential faulting areas. They have been tentatively identified using lineations on photos, evidence from seismic surveys, and analysis of subsurface geologic data (Spoliaric, 1975). The areas delineated are very generalized and tenta- tive. There is enough evidence to warrant further research into the possi- bility of faulting. Active faults have not been identified in these areas; in fact, no active faults have as yet been located anywhere in Delaware, although Th-ere are earthquakes on record originating in the state (Jordan, et al, 1972). The importance of potential earthquakes and faulting increases with the size of the project being considered. Nuclear power plants, dams, pipelines and other major projects can be endangered by this particular type of hazard. 34 Slumping Slumping represents a real and identifiable geological hazard in most of the Piedmont Province of northern Delaware. The surface slopes much more steeply In this area than in the rest of the state. As' a result, unconsoli- dated alluvium or soil on steep gradients, mainly along rivers or streams, can move downslope, or slump. This can be triggered by excavation, rainfall, earthquake (including even minor tremors), stream erosion, or surface loading by buildings. It is extremely important to evaluate this hazard before any' projects, even those on a small scale, are begun. In some cases this will require extensive geologic study of the area in order to understand the struc- tural stability at present, and also to evaluate how geologic an *d human pro- cesses will change the structural stability of the overburden. There is a similar hazard in the Coastal Plain, althoug h the process is not technically considered slumping. This is the settling and compaction of sediments. Again., it is not only 'very important to examine'the structural stability and engineering characteristics of the sediments, it is also impor- tant to understand how, for exampl&, a lowering water table or stream erosion will affect this stability. Resource Use Conflict Several potential conflicts between users of resources, developers, zoning officials, ecologists, and others is foreseen. The previously mentioned potential use of wetlands sediment to produce lightweight aggregate may precipitate a confrontation between industry and those who wish to preserve the wetlands. Because of land values, zoning regulations, and possible other economic factors, much aggregate and bricks are now imported into,Delaware. The spe- cific reasons for this are not known to geologists, because the resources, exist. Further problems for those desiring to produce aggregate in Delaware may be forthcoming if new construction and road building come associated with coastal zone development. If large support facilities for offshore drilling are built in Delaware, the necessary aggregate may be unavailable or scarce. If heavy minerals, glass sand, or other potential mineral resources dis- cussed previously are developed in Sussex County, the potential for conflict with those wishing to do otherwise'with the land is probable. This should be- recognized in planning for the long term in the Coastal Zone. There may be a demand for greensand extraction in the Middletown-Odessa area, with associated land use conflicts, if current research indicates the economic feasibility of its use in wastewater treatment. 35 Lack of Geologic Knowledge In the preparation of maps for this report, the lack of deep subsurface data was quite evident. No drill holes through the Coastal Plain sediments to basement crystalline rocks have ever beendrilled in Kent or Sussex County. Consequently, structural contour lines for most geologic units below the Miocene sediments have to be interpolated at a distance from Salisbury or other areas in Maryland. This makes the maps less accurate; and therefore, evaluations of water resources, possible hydrocarbonsi other mineral resources, and possible deep-seated faults are l.ess defin,ite. A lesser problem is a lack of information from shallow,drill holes, mostly in Kent and Sussex Counties. More data is needed for accurate delinea- tion of shallow geologic formations. .Our knowledge of the specific geology of earthquakes, flooding and earth slumps and other geologic hazards is increasing all the time, but is still in- sufficient. Research should detail more of the'specific role Delaware's geology plays in these processes. These processes should also be monitored. A seismic station is in operation at the University of.Delaware, and plans are made for a seismic net throughout the state to help pinpoint earthquake epi- centers. The Delaware Geological Survey cooperates with the National Weather Service and others to monitor flooding in the state's streams and is interested in the specific geologic parameters and,conditions which could lead to accurate flooding forecasts. RECOMMENDATIONS It is recommended that deg drilling to the basement rocks for geologic information be funded. This will provide information for resource evaluation, basic geology, and possible fault delineation. More shallow holes should be drilled, particularly in Kent and Sussex Counties. DriTTing -M-57d be accom- panied by seismic investigations ofthe subsurface. Also, deep geologic struc- tures for gas storage may be.found. Geologic hazards should be thoroughly investigated in Delaware, and our knowledge of them should be an important factor in planning for the use ofthe Coastal Zone. Environmental geologic quadrangle maps of selected impact areas should be made. s requires new data (drill hoTesT and might start with'the Lewes and. Big Stone Beach areas. In conjunction with the detailed geologic maps, the proposed cooperative topographic mapping program with.the U. S. Geological Survey should be funded so that accurate base maps are available to all those involved in land use and geology. Possible resource use conflicts should be recognized in planning for the Coastal Zone. It is further recommended that a geologic economic study be made 36 of the sand and gravel industry in Delaware to determine the specific reasons why aggregate has to be imported in large quantities from Maryland and is not produced here. The'railroad lines in Delaware should be repaired so that, among other commodities, sand and gravel and possible other mineral resources can be effi- ciently moved to where they are ne eded. Potential sand, gravel, and other mineral deposits should be investigated in Delaware Bay and offshore. This requires new data because practically nothing is known about subaqueous mineral resources in this area. It is suggested for coastal policy that the geologic limitations of the Coastal Zone be fully recognized in the planning process, -and as little as possible be done by man to interfere with geologic processes. It is recommended that the State.of Delaware review all legislation it has concerning the regulation of mineral extraction in the Coastal Zone. There are existing regulations for oil and gas, but apparently none for sand, gravel, clay, greensand, or other mineral resources. An exception to this may be some regulations dealing with worker safety and others on pollution of the air or water. As the demand for minerals increases with possible oil-related activities, there may be a need for mineral legislation. Although coastal erosion has been discussed well in the Coastal Zone management report of Kraft, et al, 1975, it should be re-emphasized that it should be the policy of the State of Delaware to recognize and plan around the fact that sea level is now rising. Thus, ultimately coastal erosion is inevitable within the foreseeable geologic future. Efforts at controlling coastal erosion must be ongoing and stopgap measures at best. 37 HYDROLOGY BACKGROUND Hydrology of the waters of D elaware received state-wide attention in 1967 when the University of Delaware, in cooperation and sponsorship with other - State agencies, began a.series of studies to appraise, define and evaluate the water resources of Delaware (Sundstrom, Pickett and others, 1967, 1968, 1969, 1970, and 1971). In 1972 the College of Marine Studies, University of Delaware, published a very comprehensive report on the coastal zone of Delaware giving the findings of the Governor's Task Force on Marine and Coastal Affairs. In 1973 the United States Geological Survey issued Professional Paper 882 entitled "Water Resources of the Delmarva Peninsula" (Cushing, Kantrowitz and Taylor, 1973). These reports and those listed in the bibliography of this paper con- stitute the basis of the maps and discussions pertaining to the hydrology of the waters of Delaware. The maps and discussion herein are made primarily for regional or state-wide water planning purposes in the coastal area. The hydrology of the surface and ground waters of.the Piedmont Plateau are dis- cussed in detail in a report on the availability of water in New Castle County (Sundstrom and Pickett, 1971). The Piedmont Plateau area,is not a part of this report. This report concerns primarily the mapping and discussion of hydrology of the surface water,of the Coastal Plain and the 12 ground-water aquifers of the Coastal Plain of Delaware. HYDROLOGY FOR PLANNING PURPOSES A properly planned and developed aquifer or ground-water reservoir is one that will supply the need for acceptable.quality water within the safe limits of development of theaquifer without seriously affecting the other useful and. sometimes necessary functions of the aquifer. Independent and co-dependent factors such as the geology, hydrology, water quality (chemical and bacterial), engineering, economics, well construction and development, and ecology are in-, volved in the planning, development and management of ground-water reservoirs. In the Coastal Zone of'Delaware, the geology and hydrology of 12 aquifers (ground-water reservoirs) are discussed at length in this report. Eleven of the 12 aquifers are artesian in character except in the outcrop or@subcrop areas. In the outcrop or subcrop area, the aquifers receive most of their re- charge from precipitation penetrating to the aquifer from the water falling only on the outcrops or subcrops. The aquifer that is not artesian in charac- ter is the Pleistocene or Quaternary aquifer in which.the precipitation perco- lates directly downward to the water table. The subcrops of the artesian aquifers underlying the Quaternary are also a part of the water-table aquifer. The water-table aquifer receives recharge by downward percolation of precipi- tation over the entire area of the aquifer, whereas the artesian aquifers 39 receive most of their recharge supply only from the outcrop or subcrop area. In a broad perspective, the water-table aquifer can be considered a storage reservoir receiving direct downward percolation of precipitation to be re- leased later as evapotranspiration, fairweather flow to streams, recharge to the artesian ground-water aquifers and water supply to wells and springs. In the same perspective the artesian aquifer can be considered primarily as a conduit, conveying water from the outcrop or subcrop area to discharge points (wells and springs) under pressure. The hydrologic characteristics of the aquifers determine the extent to which an aquifer can be developed and the best methods for withdrawing water from it. Land development involving impervious cover of the surface will have a direct effect at the place of development on the downward percolation of pre- cipitation for recharge to the water-table aquifer. In areas supplied by artesian aquifers this situation would not prevail except in the close prox- imity of the recharge area of the aquifer. For example, in Dover where the water is obtained primarily from wells drawing from the Cheswold and Piney Point artesian aquifers, impervious cover from land development in Dover would be several miles away from the major-recharge area of the artesian aquifers supplying the water to Dover. Dover lies in an area where the withdrawals from the Cheswold and Piney Point artesian aquifers are approaching or exceed- ing recharge. The problem, however, lies in the transmissive properties of the aquifers in moving water from the recharge area to the wells in Dover. These problems are discussed in considerable detail in.Sundstrom and Pickett, 1968, and the current report. New Castle County "corridor" is a part of the water-short area of metro- politan northern Delaware north of the Chesapeake and Delaware Canal and is in part of a subdivision of the water-short area of northern Delaware as a whole. In recent years, the U.S. Amy Corps of Engineers; the Delaware River Basin Commission; Whitman, Requardt and Associates for New Castle County; and others have brought into focus the need for developing the Brandywine, White Clay Creek or bringing water into the area from the Susquehanna River or other sources. In any event, the northern Delaware area north of the Chesapeake and Delaware Canal needs more water than appears to be available from the ground- water aquifers under it. The eastern half of the New Castle County "corridor" is shown in the area where present withdrawals are approaching or exceeding recharge or in the area of possible salt-water encroachment as mapped by the U.S. Geological Survey, 1974, and shown in Figure 15. The hydrology of the surface and ground-water resources for planning pur- poses is given in mapped areas and tables of the applied hydrology as it per- tains to the availability and use or potential use of water. In using the maps, tables and discussions, it is important to remember that both surface and ground water have the same source or origin; namely, the precipitation that falls on the respective drainage areas which, in most cases, are common to both ground-water recharge and surface water runoff. -Much of the fairweather flow of the streams is ground-water discharge to them. The hydrology of each of the ground-water aquifers is discussed or mapped to give graphically the location and depth of the aquifer; the developedand undeveloped parts of the aquifer; the hydrologic potential of the aquifer; the available water from the aquifer; the limits of development; and the salt-water problems. 40 . ol MEAGER GROUND WATER K IN CRYSTALLINE ROCK AREAS WHERE PRESENT WITHDRAWS ARE APPROACHING OR EXCEEDING RECHARGE AREAS OF POSSIBLE SALT WATER ENCROACHMENT HIGH WATER TABLE, SWAMP AND E DRAINAGE PROBLEMS c S T Z K E GEORGETOWN *SEAFORD SUSSEX MILES 4 0 1 2 ! 1 5 6 7 8 9 DELMAR 760 FROM USL GEOLOGICAL SUR EY, 1974 75* FIGURE 15: WATER PROBLEM MAP OF DELAWARE 41 THE USE OF WATER The average daily use of water in Delaware from 1953-5'6 through 1974 is given in Table 3. Table 3 gives the municipal use including institutional and military uses, industrial, irrigation, rural and other uses for the periods 1953-56, 1966 and 1974. Noteworthy statistics from Table 3 show that (1) the use of ground water for municipal, military and institutional purposes has almost tripled in the two decades, 1953-1974; (2) the use of surface water for the same purposes has almost doubled in the two-decade period; and (3) the overall use of water in the State has increased about 1.6 times in the period. The Use of Water in New Castle County The average daily use of water in New Castle County for municipal, indus- trial, irrigation and rural purposes from 1954 through 1974 is given in Table 4. The Use of Water in Kent County The average daily use of water in Kent County for municipal, industrial, military, institutional, irrigation, rural and other purposes from 1953 through 1974 is given in Table 5. The Use of Water in Sussex County The average daily use of water in Sussex County for municipal, industrial, irrigation, and rural purposes from 1957 through 1974 is given in Table 6. THE AVAILABILITY OF SURFACE WATER The quantities of water available within the drainage basins of the Delaware River system in Delaware and within the Coastal Basins of Delaware are fairly well known. For many years the United States Geological Survey has measured the daily flow of the Delaware River and many of its tributaries. Likewise, the U. S. Geological Survey has also measured the flow of streams of Delaware draining to Chesapeake Bay and the Atlantic Ocean. Figure 16 shows the streams and'stream measu,ring stations, in Delaware. Table 7 gives a sum- mary of the U. S. Geological Survey streamflow data for the Delaware River Estuary, the Piedmont Plateau and Atlantic Coastal Plain streams draining to 42 Table 3 Average Daily Use of Water in Delaware for Municipal, Industrial, Irrigation and Rural Purposes in 1953-57, 1966,,and 1974 Type of Use Ground Water Surface Water Total Remarks MGD MGD MGD 1953-57 Municipal, Institutional and 11.0 24.0 35.0 l/ 2/ Military Industrial 16.7 30.0 46.7 1/ Irrigation 1.7 .6 2.3 T/ Rural 5.4 -- 5.4 Other -- TOTAL 34.8 (38.9%) 54.6 (61.1%) 89.4 1966 Municipal, Institutional and 24.5 40.3 64.8 2/ 3/ Military Industrial 20.7 40.0 60.7 2/ 4/ 5/ Irrigation 9.2 1.2 10.4 Rural 111.4 -- 11.4 Other .3 --- 3 TOTAL 66.1 (44.8%) 81.5 (55.2%) 147.6 1974 Municipal, Institutional and 29.4 45.0 74.4 6/ Military Industrial 23.6 10.3 33.0@1@ 6/ Irrigation 12.1 1.8 13.9 C/ Rural 13.1 -- 13.1 6/ Other 2.5 -- 2.5 TOTAL 80.7 (58.6%) 57.1 (41.4%) 137.8 Source of data: l/ Marine and Rasmussen, 1955 T/ Parker and others, 1964 Whitman, Requardt and Associates, 1967 Stuart W. McKenzie, 1967 Sundstrom et al, 1967 Frederick N. Robertson, 1975 7/ Estimated -ffGD Million Gallons a Day 43 Table 4 Average Daily Use of Gro'und.Water and.Surface Water In New Castle County for Municipal., Industrial, Irrigation and Rural Purposes in 1954, 1966 and 1974- Type of Use Ground Water Surface Water Total Remarks MGD MGD MGD 1954 Municipal 4.5 24.0 28.5 l/ 21 Industrial 2.8 30.0 32.8 6/7 Irrigation 0.6 0.6 1.2 Rural 1.1 - 1.1 TOTAL 9.0 (14.2%) 54.6 (85.8%) 63.6 1966 Municipal 10.2 40.3 50.5 3/ Industrial 4.6 40.0 44.6 2/T/5/ 7/ Irrigation 1.0 1.2 2.2 Rural 2.0 2.0 TOTAL 17.8'(17.9%) 81.5 (82.1%) 99.3 1974 Municipal 15.2, @45.0 60.2 9/ Industrial 7.7 10.3 18.0 Irrigation 0.3 .1.3 1.6 Rural 2.2 -- 2.2 Other 2.5 -- 2.5 TOTAL 27.9 (33.0%) 56.6 (67.0%) 84.5 Source of data: l/ Marine and Rasmussen, 1955 21 Parker and others, 1964 Whitman, Requardt and Associates, 1967 Stuart W. McKenzie, 1967 Sundstrom et al, 1967 Does not include more than 200 MGD of surface waterused for cooling and mostly returned to stream, 7/ Does not include more than 600 MGD of surface water used for cooling and mostly returned to stream 8/ Estimated T/ Frederick N. Robertson, 1975 KGD Million Gallons a Day 44 Table 5 Averag e Daily Use of Water in Kent County for Municipal, Industrial, Irrigation and Rural Purposes in 1953, 1966, and 1974 Type of Use Ground Water Surface Water Total 'Remarks MGD MGD MGD 1953 Municipal, Institutional and 2.8 2.8 1/ Military Industrial 2.5 2.5 1/ Irrigation .7 7 Rural 1.1 1:1 1/ Other --- TOTAL 7.1 (100% 7.1 1966 Municipal, Institutional and 7.6 7.6 2/ Military Industrial 4.5 4.5 2/ Irrigation 2.2 2.2 T1 Rural 3.4 3.4 T/ Other 0.3 0.3 Y/ TOTAL 18.0 (100%) 18.0 1974 Municipal, Institutional and 7.7 7.7 3/ Military Industrial 4.0 4.0 3/ Irrigation 6.6 6.6 Rural 4.0 4.0 Other --- TOTAL 22.3 (100%) 22.3 Source of data: 1/ 1953 data - Bulletin 49 Delaware Geological Survey 2/ 1966 data - Delaware Water and Air Resources Commission and this study. Consumption,for rural,'domestic and livestock use estimated. on bases of census of rural population, livestock and poultry on the average water requirement for each in each category. 3/ 1975 data - Delaware Water Use Inventory for 1974, Frederick N. Robertson, 'Water Resources Center, University of Delaware. 45 Table 6 Average Daily Use of'Water.in Sussex County for Municipal, Industrial, Irrigation and Rural Purposes in 19 57,'1566, and 1974 Type of Use Ground Water Surface Water Total Remarks MGD MGD MGD 1957'@ Municipal, Institutional and 3.7 l/ Military Industrial 11.4 11.4 l/ Irrigation 0.4 0.4 T/ Rural 3.2 3.2 T/ TOTAL 18.7 (100%) 18.7 1966 Municipal, Military Institutional and 6.7 6.7 21 Industrial 11.6 .11.6 2/ Irrigation 6.0 6.0 T/ Rural 6.0 6.0 TOTAL 30.3 (100%) 30.3 1974 Municipal, Institutional and 6.5 6.5 3/ Military Industrial 11.9 11.9 3/ 'S/ Rural 6.9 -- 6.9 Irrigation 5.2 .5 5.7 TOTAL 30.5 (98%) .5- (2%) 31.0 Source of data: I/ Delaware Geological Survey., Bulletin 8 Inventory of the Use of Water in Delaware, Stuart W. McKenzie, Hydrologist, Water Resources Center, University of Delaware Delaware Water Use Inventory for .1974,.Frederick.N.. Robertson, Water Resources Center, University of Delaware JI FIGURE 16 HYDROLOGIC DATA STATION ACTIVI[TIES AND INVESTIGATIONS IN PROGRESS IN DELAWARE AS OF FEBRUARY 1974 A SURFACEWATER STATION 0 OBSERVATION WELL(FIGURE INDICATES NUM13ER OF WELLS IN SMALL AREA) 0 WATERGUALITY STATION NOTE Combined sybols indicate water quality data also collected at surface and (or) ground water station. 47 Table 7. Summary of U. S. Geological Survey Streamflow Data for Streams in Delaware Drainage Yrs. of Average Maximum Minimum Average Stream Location Area (sq Record Discharge Discharge Dischargel Discharge Remarks miles) l/ (CFS) 21 (CFS) (CFS) P@r Square Mile (CFS) Delaware River tstuary Delaware River Trenton, N., 0 56 11,930 329,000 1,220 1.76 Piedmont Plateau Streams Shellpot Creek Wilmington 7.46 26 9.34 6,850 0.10. 1.25 Records good White Clay Creek Nr. Newark 87.8 32 110 9,080 4.7 1.25 Same White Clay Creek Abv. Newark 66.7 17 76.7 10,200 4.6 1.15 Same Red Clay Creek Nr. Wooddale 47.0 29 61.7 4,780 4.5 1.31 Same Little Mill Creek Elsmere 6.7 9 9.59 3,960 0.10 1.43. -Same Brandywine Creek Chadds Ford, PA 287 52 381 23,800 42 1.33 Same Brandywine Creek Wilmington 314 26 451 29,000 56 1.44 Same Coastal Plains Streams Christina River Cooches Bridge 20.5 29 25.8 3,320 0.20 1.26 Records good Blackbird Creek Blackbird 3.85 16 4.47 712 0 1.16 Records fair St. Jones River Dover 31.9 14 33.3 11900 0 Records good Murderkill River Nr. Felton 13.6 14 18.3 21090 0.80 Same Beaver Dam Houston 2.83 14 3.57 176 0.20 Same Sowbridge Branch Nr. Milton 7.08. 16 9.93 134 0.47 Same Stockley Branch Stockley 5.24 29 6.98 132 0.13 Same Nanticoke River Nr. Bridgeville 75.4 29 91.6 2,360 6.3 Records fair Marshyhope Creek Nr. Adamsville 7.10 22 8.66 792 0 Records good I/ As of 1972. 2/ (CFS) Cubic feet per second. One US equals 646,323 gallons a day. so go, the Delaware Estuary and Bay and Delaware C oas tal Plain.streams draining to the Atlantic Ocean and Chesapeake Bay. The Delaware River Estuary receives from the river proper at Trenton, New Jersey, on the average nearly 12,000 cubic feet of water per second or 7.7 bil- lion gallons a day (Table 7). As the estuary progresses downstream to the Delaware state line, Keighton (1966) states that the flow at Marcus Hook is 1.43 times as great as it is at Trenton. This indicates that the Delaware Estuary receives on the average about 17,000 cubic feet per second or about 11 billion gallons a day of inflow before it reaches Delaware. Below the Pennsylvania-Delaware state line, the estuary and-bay of the Delaware receive from their tributaries on the average an additional inflow of about 1,700 cubic feet per second or 1.1 billion gallons a day before the Delaware River system @ischarges to the ocean. The average daily discharge of the estuary and bay increases about 6,700 cubic feet per second from the beginning of the estuary at Trenton to the Atlantic Ocean. Streams heading in the Piedmont Plateau in Pennsylvania and draining Piedmont Plateau areas-in Pennsylvania and northern Delaware furnish the bulk, of the water used for municipal and self-served industrial purposes, exclusive of cooling water. The streams providing most of the water are the Brandywine, Red Clay and White Clay Creeks. See Figure 3 for location of streams in the report area that are quantitatively'measured. The Brandywine Creek at Wilmington drains 314 square mil es in Pennsyl- vania and Delaware; and at Chadds Ford ' Pennsylvania, 287 square miles in Pennsylvania. At Wilmington the Brandywine has an average flow of 436 cubic feet per second or 282 mill-ion gallons a day@ The low flow of 56 cubic feet per second is about 36 million gallons a day. Wilmington, which uses the Brandywine for public supply,has protected its supply during the periods of low flow and attendant poor water quality in the Brandywine by,developing the 2.3 billion gallon Edgar M., Hoopes Reservoir in the Red Clay Creek watershed. The Hoopes Reservoir is filled by pumping water from the Brandywine to the reservoir-when the supply of water is ample. The reservoir is seldom used be- cause of lack of water in the Brandywine. It is more often used because of' poor quality Brandywine water during low flow. Red Clay Creek drains an area of about 53 square miles at the point where it joins White Clay Creek. Streamflow records of,47 square miles of the drain- age basin are summarized in Table 7. For the 47 square miles, the average dis- charge is 60.3 cubic feet per second or about 39 million gallons a day. The low flow of the stream is only 4.5 cubic feet per second or 2.9 million gallons a day. Without storage, the available water during dry periods is small. Water was taken at the confluence of Red Clay and White Clay Creeks for an average public and industrial supply of about 13,million gallons a day in -1966. White Clay Creek drains an area of about 104 square miles at its conflu- ence with Red Clay Creek. Streamflow data for 88 square miles of the drainage are summarized in Table 7. For the 88 square miles the average discharge is 104 cubic feet per second or about 67 million gallons a day. The minimum dis- charge is 4.7 cubic feet per second or only 3 million gallons a day. Studies 49 have been made by the U. S. Army Corps of Engineers (1960) and the Delaware River Basin Commission to increase the available supply from White Clay Creek by storage to augment the present available supplies in Red Clay Creek and the Christina River during low flow periods and to increase the@flow of White Clay Creek. The available supply of the three streams, thus, would be increased to a combined minimum total of 80 million gallons a day. Part of the Christina River heads in and drains part of the Piedmont Pla- teau, but the major part of its drainage is in the Coastal Plain. The river above its estuary at Smalleys Pond drains 46 square miles of which 20.5 square miles of the drainage above Cooches Bridge has been measured and is summarized in Table 7. The discharge at Smalleys Pond is about 2.24 times that at Cooches Bridge. Thus, for the 46 square miles of drainage the average discharge is about 57 cubic feet per second or about 36.8 million gallons a day. The mini- mum flow is 0.45 cubic feet per second or only 290,000 gallons a day. Engineer- ing studies have shown that the available supply can be assured to 9 million gallons a day with increased storage above Smalleys Pond. South of the Christina River many small rivers and creeks drain to the Delaware River system and to the Atlantic Ocean and Chesapeake Bay. The streams supply water for a large number of small ponds and shallow lakes which are, in many instances, used for fishing, swimming, rural water supply, and irrigation. The topography is flat, the slope of the stream beds is also flat, and the drainage areas of the streams are small. No sites are available to develop deep or large storage lakes. The streams south of the Christina River are, therefore, unimportant as sources of large supplies of water from storage reservoirs. Without adequate storage, the streams are unimportant because of the low flow during dry weather. Table 7 shows the low flow of seven Coastal Plain streams to range from 0.0 to 1.3 cubic feet per second. The average dis- charge of the seven streams is 1.22 cubic feet per second per square mile. Studies of the relation of surface water to ground water in Sussex County reveal that the discharge of the streams is about 80 percent ground-water drainage and only 20 percent overland runoff (Sundstrom, 1970). A detailed analysis of the surface-water yield and low flow-frequencies is given in the report by Cushing, Kantrowitz and Taylor, 1973, pages 11 through 37. GENERAL GROUND-WATER HYDROLOGY l/ Hydrologic Cycle The hydrologic cycle is the sum total of processes and movements of the earth's moisture from the sea, through the atmosphere, to the land, and even- tually, with numerable delays en route, back to the sea. Many courses that l/ Taken from Texas Water Development Board Report 195 (November 1975) with some modification. 50 the water may take to complete the hydrologic cycle are illustrated on Figure 17. Water occurring in the study region is derived, for the most part, from water vapor carried inland from the Gulf of Mexico. Source and Occurrence The primary source of ground water in the study region is the infiltra- tion of precipitation, either directly as recharge or indirectly as seepage from streamflow. A large percentage of precipitation is evaporated back to the atmosphere directly or is consumed by plants and returned to the atmosphere by transpiration. A large portion also becomes surface runoff because it moves rapidly over land surfaces which are steep or impermeable. If the rain is in- tense, surface runoff increases because the time available for absorption is inadequate even in sandy areas. A portion of the rainfall will percolate down- ward under the force of gravity to the zone of saturation where all the rock voids contain water. The upper surface of the zone of saturation is the water table. Water percolatingdown may be intercepted by a local impermeable layer of rock above the zone of saturation, thus forming a saturation zone above the main water table known as a perched water table. Two characteristics of funda- mental importance in the zone of saturation are porosity, or the amount of the interstices, voids, or open space contained in the rock; and permeability, Which i's the ability of the porous material to transmit water. Fine-grained sediments, such as clay and silt, generally have high porosity; however, because of their small voids they have little or no permeability and consequently do not readily transmit water. Sand and,gravel are usually porous and permeable, the degree depending upon the size, shape, sorting, and amount of cementation of the grains. In limestone or igneous rocks, or in tightly cemented or com- pacted rocks, porosity and permeability are controlled to some degree by the occurrence and extent of joints,,crevices, and solution cavities. For a forma- tion to be an aquifer, it must be porous,:pe.rmeable, water-bearing, and yield water in usable quantities. Water in an aquifer is either under water-table or artesian conditions. In the outcrop area, ground water generally occurs under water-table, or un- confined conditions; it is under atmospheric pressure and will rise or fall in response to changes in the volume of water stored. In a well penetrating an unconfined aquifer, water wil'l rise to the level of the water table. The hydraulic gradient in an unconfined aquifer coincides with the slope of-the water table which corresponds to the general slope of the land surface. Downdip from the outcrop or recharge area, ground water within an aquifer occurs under artesian or confined conditions as a result of being overlain by relatively impermeable beds which confine the water under a pressure greater than atmospheric. In a well penetrating an artesian aquifer, water will rise above the confining bed and, if the pressure head is large enough to cause the water in the well to rise above the land surface, the well will flow. The level or surface to which watervill rise in an artesian well is called the piezometric surface. The hydraulic gradient of an artesian aquifer is the slope of the piezometric surface. 51 EVAPORATION PRECIPITATION AND TRANSPIRATION EVAPORATION WATER TABLE Op IZARSH OCEAN LKE 0 ZONE OF SATURATION FRESH'. -WATER*-"- SA T WA FR.- r q SAND SHALE SPRING DIRECTION OF WATER MOVEMENT FIGURE 17 THE HYDROLOGIC CYCLE 100,6W"'Mmmew moo m wo ma'am W@mm M Recharge, Movement, and Discharge Recharge is the process by which water is added to an aquifer and may result from either natural or artificial processes. Precipitation on the out- crop of an aquifer is generally the most significant natural source of recharge; however, water may enter from surface streams and lakes on the outcrop and pos- sibly through intraformational leakage. Artificial recharge is the process of replenishing ground water in an aquifer and maybe accomplished by (1) injection wells, and (2) infiltration of storm-water runoff, irrigation water or properly treated industrial waste water and sewage. The amount of recharge must be con- sidered in determining the amount of water which can be safely developed from an aquifer, because it must balance the discharge over a long period of time or the water in storage in the aquifer will eventually be depleted. Factors which influence the amount of recharge received by an aquifer in its outcrop area are the amount and frequency of precipitation, rate of evaporation, types and condition of soil cover, topography, type and amount of vegetation, and the extent of the outcrop area. In addition, the ability of the aquifer to accept recharge and transmit it to areas of discharge influences the amount of re- charge it will eventually receive. Recharge is generally greater during winter months when plant growth and well use are at a minimum and evaporation rates are low. Ground water moves in response to the hydraulic gradient from areas of rea- charge to areas of discharge, or from points of higher hydraulic head to points of lower hydraulic head. Ground water under.artesian conditions generally moves in the direction of the aquifer's regional dip, while movement of ground water under water-table conditions is closely related to the slope of the land sur- face. However, in areas of large and extensive withdrawals, ground water moves from all directions toward the areas of pumpage or lowered pressure. The rate of movement of ground water is directly related to the porosity and permeabil- ity of the aquifer. In most sands and gravels, the rate of movement ranges from tenths of a foot to several feet per day, while in cavernous limestone, water flows in subterranean channels and may have velocities comparable to sur- face streams. Discharge is a process by which water is removed from an aquifer and may be either natural or artificial. Natural discharge includes springs, seepage to streams, lakes, and marshes which intersect the water-table, transpiration by vegetation, evaporation through the soil where the water table is close to the land surface, and intraformational leakage as a result of differences in head., Since ground water moves in response to gravity, its natural discharge from an aquifer is always at a lower elevation than that of the recharge area. Ground water is artificially discharged from flowing and pumped water wells, and by drainage ditches, gravel pits, and'other forms of excavation that inter- sect the water table. 53 CHEMICAL QUALITY OF GROUND WATER AS RELATED TO USE l/ General Chemical Quality of Ground Water All ground water contains minerals carried in solution, the type and con- centration of which depend upon the environment, movement, and source of the ground water. Precipitation is relatively free of minerals until it comes in contact with the various constituents which make up the soils and component rocks of the aquifer; then, as a result of,the solvent power of water, minerals are dissolved and carried into solution as the water passes through the aqui- fer. The concentration depends upon the solubility of the minerals present, the length of time the water is in contact with the rocks, and the amount of dissolved carbon dioxide in the water. In addition, concentrations of dis- solved minerals in ground water generally increase with depth and especially increase where circulation has been restricted due to faulting or zones of lower permeability. Restricted circulation retards the flushing action of fresh water moving through the aquifers, causing the water-to become highly mineralized. In addition to natural mineralization, man can adversely alter the chemical quality of ground water by permitting highly mineralized water to enter fresh water strata through inadequately constructed wells, by seepage from brine disposal pits used in disposing of highly mineralized water pro- duced with oil, and by disposal of animal wastes, sewage I or various industrial, waste into fresh water strata or into aquifer recharge areas., The principal chemical constituents found in ground water are calcium, magnesium, sodium, potassium, iron, silica, bicarbonate, carbonate, sulfate, chloride, and minor amounts of manganese, nitrate, fluoride, and boron. Con- centrations of these ions or chemical constituents are commonly reported in milligrams per liter (mg/1). Milligrams per liter are the preferred metric system units and may be considered equal to parts per million at concentra- tions less than about 7,000 mg1l. At higher concentrations the units are not directly interchangeable, as conversion must take into account the greater dif- ferences in density.of saline waters. The source, significance, the range of mineral constituents and properties of natural waters for the various aquifers in the study region are given in Table 8. Chemical analyses of water from selected wells in the study region are given for the various aquifers dis- cussed in this report. 'Water Quality Considerations for Public Supply, Domestic and Livestock Use The Delaware State Department of Health (1971) has established standards of drinking water to apply to all public water suppliers in the state. The I/ Taken from Texas Water Development Board Report 195 (November 1975) with some modification. 54 Table 8. Source and Significance 'of Dissolved-Mineral Constituents and Properties of Water CONSTITUENT OR PROPERTY SOURCE OR CAUSE SIGNIFICANCE Silica (S'02) Dissolved from practically 'elf Forms hard scale in pipes and boilers. Carried over rocks and soils, commonly loss in steam Of high pressure boilers to form deposits then 30 mg/l. High on blades of turbines. Inhibits deterioration of concentrations, as much as 100 zeollte-typs water softeners. mg/l, generally occur In highly alkaline water. iron (Fe) Dissolved from practically all On exposure to air, Iran in ground water oxidizes rocks and soils. May also be to reddish-brown precipitate. More than about 0.3 derived from iron pipes, pumps, mg/I stain laundry and utensils reddish-brown. and other equipment. Objectionable for food processing, textile processing, beverages, ice manufacture, brewing, and other processes. U.S. Public Health Service (1962) drinking water standards state that iron should not exceed 0.3 mg/l. Larger quantities cause unpleasant taste and favor growth of iron bacteria. I Dissolved from practically all soils Cause most of the hardness and scale-forming and and rocks, but especially from properties of water; soap consuming (see hardness). Magnesium (Mg) limestone, dolomite, and gypsum. Waters low in calcium and magnesium desired in Ca C'um Ice) Calcium and magnesium are electroplating, tanning, dyeing, and in textile found in large quanitites in some manufacturing. brines. Magnesium Is present In large quantities In sea water. Sodium (Na) Dissolved from practically all Large amounts, in combination with chloride, give : nd rocks and soils. Found al$OL.In a salty taste. Moderate quantities he" little affect otessium W oil-field brines, sea water, on the usefulness of water for most purposes. industrial brines, and sewage. Sodium salts may cause foaming in steam boilers and a. high sodium content may limit the use of water for irrigation. Bicarbonate'111,1663) Action of carbon dioxide in water Bicarbonate and carbonate produce alkalinity. and on carbonate rocks such as Bicarbonates of calcium and magnesium Carbonate (C03) limestone and dolomite. decompose in steam boilers and hot water facilities to form scale and release corrosive carbon-dioxide gasz In combination with calcium,and magnesium, cause carbonate hardness. Sulfate (S04) Dissolved from rocks and soils Sulfate in water containing calcium forms hard containing gypsum, iron sulfides, scale in steam boilers. In large amounts, sulfate in and other sulfur compounds. combination with other ions gives bitter taste to Commonly present in some water. U.S. Public Health Service (1962) drinkling industrial wastes. water standards recommend that the sulfate content should not exceed 250 mg/l. Chloride (CI) Dissolved from rocks and soils. In large amounts in combination with sodium, Present in sewage and found in gives salty taste to drinking water. In large large amounts in oil-field brines, quantities, increases the corrosiveness of water. we water, and industrial brines. U.S. Public Health Service (1962) drinking water standards recommend that the chloride content should not exc eed 250 mg/l. Fluoride (F) Dissolved in small to minute Fluoride in drinking water reduces the incidence of quantities from most rocks and tooth decay when the water is consumed during soils. Added to many waters by the period of enamel calcification. However, it may fluoridation of municipal sup- cause mottling of the teeth, depending on the plies. concentration of fluoride, the age of the child, amount of drinking water consumed, and susceptibility of the individual (Maier, 1950, p. 1120-1132.) Nitrate (N03) Decaying organic matter, sewage, Concentration much greater then the local average fertilizers, and nitrates in soil. may suggest pollution. U.S. Public Health Service (11962@ drinking water standards suggest a limit of 45 mg/l. Waters of high nitrate content have been reported to be the cause of methemoglobinernia (an often fetal disease in infants) and therefore should not be used in infant feeding (Maxcy, 1950, P. 271). Nitrate shown to be helpful in reducing inter-crystalline cracking of boiler steel. It. encourages growth of algae and other organisms which produce undesirable tastes and odors. 55 Table 8 cont. CONSTITUENT OR SOURCE OR CAUSE PROPERTY SIGNIFICANCE Boron (B) A minor constituent of rocks and An excessive boron content will make water of natural waters. Unsuitable for irrigation. Wilcox (1955, p. 11) indicated that a boron concentration of as much as 1.0 mo/I is permissible for irrigating sensitive crops; as much as 2.0 moll for sernitolerant crops; and as much as 3.0 mgVI for tolerant crops. Crops sensitive to boron include most deciduous fruit and nut tress and navy beans; sernitolerant crops include most small grains, potatoes and some other vegetables, and cotton; and tolerant crops include alfalfa, most root vegetables, and the date palm. Dissolved solids Chiefly mineral constituents U.S. Public Health Service (1962) drinking water dissolved from rocks and soils. standards recommend that waters containing more than 500 mg/I dissolved solids not be used if other lea mineralized supplies are available. For many purposes the dissolved-solids content is a major limitation on the use of water. A general classification of water based on dissolved-solids content, in mg/l, is as follows (Winslow and Kister, 1956, p. 5): Waters containing less than 1,000 mg/I of dissolved solids are considered fresh; 1,000 to 3,000 mg/l, slightly saline; 3,000 to 10,000 mg/l, moderately saline; 10,000 to 35,000 mg/l, very saline; and more then 35,000 mg/l, brine. Hardness at COC03 In most waters nearly all the Consumes soap before a lather will form. Deposits hardness Is due to calcium and soap curd an bathtubs. Hard water forms scale in magnesium. All of the metallic boilers, water heaters, and pipes. Hardness cations other than the alkali equivalent to the bicarbonate and carbonate Is metels also cause hardness. called carbonate hardness. Any hardness in excess of this Is called non-carbonate hardness. Waters of hardness up to 60 mil/l are considered soft; 61 to 120 mg/l, moderately hard; 121 to 180 mg/l, hard; more then 180 m9VI, very hard. Percent Sodium Sodium In water. A ratio (using milliquivalents per liter) of the M Na) sodium ions to the total sodium, calcium, and magnesium ions. A sodium percents" exceeding 50 percent is a warning of a sodium hazard. Continued Irrigation with this type of water will Impair the tilth and permeability of the soil. Specif Ic Mineral content of the water. Indicates degree of mineralization. Specific conductance conductance is a measure of the capacity of the (micromhos at 25'C) water to conduct an electric current. Varies with concentration and degree of Ionization of the constituents. Hydrogen Ion Acids, acid-generating salts, and A PH of 7.0 Indicates neutrality of a solution. concentration (pH) free carbon dioxide lower the pH. Values higher than 7.0 denote Increasing alkalinity; Carbonatec bicarbonate*, values lower than 7.0 indicate increasing acidity. hydroxides, phosphates, silicates, pH Is a measure of the activity of the hydrogen mW borat" raise the pH. Ions. Corrosiveness of water generally Increases with decreasing pH. However, excessively alkaline waters may also attack metals. Sodium-adsorption Sodium In water. A ratio for soil extracts and Irrigation waters used ratio (SAR) to express the relative activity of sodium Ions in exchange reactions with soil (U.S. Salinity Laboratory Staff, 1954, p. 72, 156). Defined by the following equation: Na+ SAR = - I C,++ + Mg++ +4 + M;;+ _2 Where Na+, Ca++, and Mg++ represent the concentrations In millisquivalents par liter (me/1) of the respective ions. 56 standards are designed to protect the public and may be Used to evaluate pub- lic and domestic water supplies. Some of these standards, in milligrams per liter,.are as follows: Maximum Concentration Recommended Substance (m 11) Chloride (Cl) 200.0 iron (Fe) 0.3 Manganese (Mn) 0.05 Nitrogen (N) (Nitrate plus Nitrite) 10.0 Sulfate (SOO 100.0 Total dissolved solids 500.0 In areas where the nitrate concent of water is excessive, a potential danger exists. Concentrations of nitrate in excess of 45 mg/l in water used for infant feeding have been related to the incidence of infant cyanosis @methemoglobinemia or ','blue baby" disease), a reduction of the oxygen content in the blood constituting a form of asphyxia (Makcy, 1956, p. 271). Since nitrates are considered to.be the final oxidation product of nitrogenous material, their presence in concentrations of more than a few milligrams per liter may indicate present or past contamination by sewage or other organic matter (Lohr and Love, 1954, p. 10). Excessive concentrations of iron and manganese in w 'ater cause reddish-brown or dark gray precipitates that stain clothes and plumbing fixtures. Water having a chloride content exceeding 250 mg/l may have a salty taste, and sulfate in excess of 250 mg/l may.produce a laxative effect. The hardness in water is caused principally by.the concentration of cal- cium and magnesium. Excessive hardness of water causes an increase in soap consumption and encrustation and formation of scale in hot water heaters, water pipes, and cooking utensils. The hardness of water becomes objection- able when it exceeds 100 mg/l (Hem, 1959, p. 147). A commonly accepted classi- fication of water.hardness is shown in the following table: Hardness Range (mg/1) Classification UsabiliSl 60 or less Soft Suitable for many uses without further softening 61 to 120 Moderately Usable except in some, hard industrial applications 57 Hardness Range (mg/1) Classification Usability 121 to 180 Hard Softening required by some More than 180 industries Very hard Softening desirable for most purposes The total dissolved solids content is a major limiting factor in the use of water. The following general classification of water is based on dissolved solids (Winslow and Kister, 1956, p. 5). Description Dissolved Solids Content (mg/1) Fresh Less than 1,000 Slightly saline 1,000 to 3,000 Moderately saline 3,000 to 10,000 Very saline 10,000 to 35,000 Brine More than 35,000 Quality limits for livestock are variable. The limits of tolerance de- pend principally on the kind of animal and, according to Heller (1933, p622), the total amount of soluble salts in the drinking water, more so than the kind. of salt, is the important factor. According to Hem (1959, p. 241), a high proportion of sodium or magnesium and sulfate in hi'ghly mineralized waters would make them very undesirable for livestock use. Heller also suggests that as a safety rule 15,000 mg/l dissolved solids content should be considered.the upper limit for most of the more common livestock animals. According to Hem (1959, p. 241), the California State Water Pollution Control Board (1952) quotes other investigators who have found concentrations as high as 15,000 mg/l to be safe for limited periods but not for continuous use. In a publi- cation (1950) relating to practices in Western Australia, the officers of the Department of Agriculture of that state quote the following upper limits.for dissolved solids concentration in livestock water (Hem, 1959, P. 241). Animal Dissolved Solids (mg1l) Poultry 2,860 Pigs 4,290 Horses 6,435 Cattle (Dairy) 7,150 Cattle (Beef) 10,000 Adult Sheep 12,900 58 Water Quality Considerations for Irrigation Use The chemical composition of ground water is important in determining its usefulness for irrigation in that it should not adversely affect the produc- tivity of the land. The extent to which chemical quality limits the suita- bility of ground water for irrigation depends on the nature, composition, and drainage of the soil and subsoil; the amounts of water used and methods of application; the kinds of crops grown; and the climate of the region, including the amounts and distribution of rainfall. The most important characteristics in determining the quality of ground water for irrigation, according to the U.S. Salinity Laboratory Staff (1954, P. 69) are (1) total concentration of soluble salts; (2) relative proportion of,sodium to other cations; and (3) concentration of boron or other elements that may be toxic. High concentrations of dissolved salts in irrigation water may cause a buildup of salts in the soil solution and may make the soil saline. Increased salinity of the soil may drastically reduce crop yields by decreasing the ability of the plants to take up water and essential plant nutrients from the soil solution. The tendency of irrigation water to cause a high buildup of salts in.the soil is called the salinity hazard of the water. The specific condu ctance of the water is used as an index of the salinity hazard. High concentrations of sodium relative to the concentrations of calcium and magnesium in irrigation water may adversely affect soil structure. Cations in the soil solution become fixed on the surface of the soil particles; cal- cium and magnesium tend to flocculate the particles, whereas sodium tends to deflocculate the colloidal soil particles. Consequently, soils may become plastic, movement of water through the soil can be restricted, drainage prob- lems can develop, and cultivation can be rendered difficult. This adverse effect on soil structure caused by high sodium concentrations in an irrigation water is called the sodium hazard. An index used for predicting the sodium hazard is the sodium-adsorption ratio (SAR), which is defined by the equation given in Table 8. Water Quality Considerations for Industrial Use The chemical quality of water suitable for industry is not necessarily referenced to potability and may or may not be acceptable for human consump- tion. The tolerance in chemical quality of water for industrial use differs widely for different industries and different processes. Suggested water- quality tolerances for a number of industries are presented in Table 9 (Amer- ican Water Works Association, 1950, p. 66-67). Water used by industry may be classified into three principal categories: cooling water, boiler water and process water. 59 TABLE 9. WATER QUALITY TOLERANCES FOR INDUSTRIAL APPLICATIONS J. [Allowable Limits in Milligrams Per Liter Except as Indicated] COLOR DIS- ALKA- N82SO4 +02 SOLVED LINITY TO TUR- CON- OXYGEN HARD- (AS TOTAL Fe+ Na2SO3 GEN- INDUSTRY BIDITY COLOR SUMED Iml/0 ODOR NESS CaC03) p,,H SOLIDS Cal Fe Mn Mn A1203 Si02 Cu F C03 HC03 OH CaS04 RATIO ERAL2 Air Conditioning3 - - - - - - - - 0.5 0.5 0.5 - A,B Baking 10 10 - (4) - - - - .2 .2 .2 - C Boller feed: 0-150 psi 20 so 100 2 - '75 - 8.0-1, 3,000- - 5 40 - - 200 50 50 - I to I - 1,000 1513-250 psi 10 40 50 .2 - 40 - 8.5+ 2,500- .5 20 - - loo 30 40 - 2 to I - Boo 250 Psi and up 5 5 10 0 a 9.0+ 1,500- .05 5 - - 40 5 30 3 to 1 - 100 Brevving:5 Light 10 Low - 75 6.5-7.0 500 100-200 .1 .1 .1 - - - 1 100-200 - C'O Dark 10 Low - 150 7.0- 1,000 200-500 .1 .1 .1 - - - 200-500 - C,D Conning: Legumes 10 Low 25-75 .2 .2 .2 - - - C General 10 Low - .2 .2 .2 - - - C Carbonated bev- arages6 2 10 10 - 0 260 so .850 - .2 .2 .3 - - - .2 C Confectionary - - - Low - - (7) loo - .2 .2 .2 - - - - Cooling8 50 - so - - - - .5 .5 .5 - - - - A,B Food, general 10 - Low - - - - .2 .2 .2 - - - - C ice (raw water)9 1-5 5 - - 30-60 - 300 - .2 .2 .2 - 10 - - C Laundering - - 50 - - - - .2 .2 .2 - - - - Plastics, clear, undercolored 2 2 - - 200 .02 .02 .02 - - - - Paper and pulpillo Groundwood 50 20 180 - 1.0 .5 1.0 - - - - A Kraft pulp 25 15 100 300 .2 .1 .2 - - - - Soda and sulfite 15 10 - 100 200 .1 .05 .1 - - - - Light paper, HL-Grade 5 5 - so 200 .1 .05 .1 - B Rayon (viscose) pulp: Production 5 5 8 so - 100 .05 .03 .05 <8.0 <25 <5 Manufacture .3 - 55 - 7.8-8.3 - .0 .0 .0 - - - Tanningli 20 10-100 50-135 135 8.0 - .2 .2 .2 - - - Textiles: General 5 20 20 - - - .25 .25 - - Dyeing12 5 5-20 20 - - - .25 :25 .25 - Wcmi scou'ing`13 - 70 20 - - - - 1.0 1.0 1.0 - Cotton bandaga13 5 5 Low 20 - - - - .2 .2 .2 - I American Water Works Association, 1950. 2 A-No corrosiveness; B-No slime formation; C-Conformance to Federal drinking -8 ter standards necessary; D@NaCl, 275 mg1l. 3 Waters with algae and hydrogen sulfide odors are most unsuitable for air conditioning. 4 Some hardness desirable. 5 Water for distilling must meet the same general requirements as for brewing (gin and spirits mashing water of light-beer quality; whiskey mashing water of dark-beer quality). 6 Clear, odorless, sterile water for syrup and carbonization. Water consistent in character. Most high quality filtered municipal water not satisfactory for beverages. 7 Hard candy requires PH of 7.0 or greater, as low value favors inversion of sucrose, causing sticky product. 8 Control of corrosiveness is necessary as is also control of organisms, such as sulfur and iron bacteria, which tend to form slimes. 9 Ca (HC03@2 Particularly troublesome. Mg (HC0312 tends to greenish color. C02 assists to prevent cracking. Sulfates and chlorides of Ca, Mg, Na should each be less than 300 mg1I 1white butts). 10 Uniformity of composition and temperature desirable. Iron objectionable as cellulose adsorbs iron from dilute solutions. Manganese very objectionable, clogs pipelines and is oxidized to permanganates by chlorine, causing reddish color. 11 Excessive iron, manganese, or turbidity creates spots and discoloration in tanning of hides and leather goods. 12 Constant composition; residual alumina 0.5 mg/l. 13 Calcium, magnesium, iron, manganese, suspended matter, and soluable organic matter may be objectionable. Cooling waterusually is selected on the basis of temperature and chemi- cal quality since any characteristic which may adversely affect the heat exchange surface is undesirable. Chemical substances such as calcium, mag- nesium, aluminum, iron, and silica may cause the formation of scale. Exces- sive hardness is objectionable because it contributes to the formation of scale in steam boilers, pipes, water heaters, radiators, and various other equipment where water is heated, evaporated, or treated with alkaline materials. The accumulation of scale increases costs for fuel, labor, repairs and replace- ment, and lowers the quality of many products. Some calcium hardness may be desirable because calcium carbonate sometimes forms protective coatings on pipes and other equipment and reduces corrosion. A high concentration of dissolved solids in a water may be closely associated with its corrosive properties, especially if chloride, calcium, magnesium chloride, sodium chloride in the presence of magnesium, acids, and oxygen and carbon dioxide are among the sub- stances. Water that contains a high concentration of magnesium chloride may be highly corrosive because the hydrolysis of this salt yields hydrochloric acid. Water used for boilers generally must meet rigid chemical-quality stan- dards, especially in high-pressure boilers where the problems of encrustation and corrosion are greatly intensified. Iron oxides in boiler water may cause priming and foaming and magnesium chloride to break down and form hydrochloric acid. In addition, magnesium, calcium, and silica in most waters cause scale, and in the case of silica, the tendency for forming scale intensifies with in- creased boiler pressure. Suggested water-quality tolerances for boiler water (Moore, 1940, p. 263), in milligrams per liter for various pressures in pounds per square inch (psi), are as follows: Over Constituent or Property 0-150 psi 150-250 psi 250-400 psi 400 psi Turbidity 20 .5 1 Color 80 40 5 2 Oxygen consumed 15 10 4 3 Dissolved oxygen* 1.4 .14 .0 .0 Hydrogen sulfide (H2S) 5** 3** 0 0 Total hardness as CaC03 80 40 10 2 Sulfate-carbonate ratio (Na2SO4-Na CO ) 1:1 2:1 3:1 3:1 Aluminum @xide ?A1203) 5 .5 .05 .01 Silica (Si02) 40 20 5 1 Bicarbonate (HC03)* 50 30 5 0 Carbonate (COI) 200 100. 40 20 Hydroxide (OH 50 40 30 15, Total dissolved solids*** 3,000-500 2,500-500 1,500-100 50 pH value (minimum) - 8.0 8.4 9.0 9.6 Limits applicable only to water entering'boiler, not to original water supply. Except when odor in live steam would be objectionable. Depends on design of boiler. 61 Some treatment of boiler water may be needed, and it may be better to appraise the water source from the viewpoint of suitability for treatment rather than for direct use of raw water. Process water is that water which is-incorporated into or comes in con- tact with final, manufactured products and is subject to a wide range of quality standards, usually rigidly controlled since they involve physical, chemical, and biological factors. In textile manufacturing, water used must generally be low in dissolved-solids content and free.of iron and manganese which cause staining. The paper industry, especially where high-grade paper is made, requires water in which all heavy metals are either absent or in small concentrations, and water approaching the quality of distilled water is re- quired for the manufacture of pharmaceuticals. Water free of iron, manganese$ and organic substances is generally required by many beverage industries. Un- like cooling and boiler water, much of the process water is consumed or under- goes a change,in quality in the manufacturing process and generally is not available for reuse. THE AVAILABILITY OF GROUND WATER Ground water is available in the Coastal Plain of Delaware from 12 aqui- fers of which 11 (except for their su'bcrop area beneath the Quaternary deposits) are artesian in character and one, the Quaternary and subcrop deposits of the artesian aquifers, is a water-table reservoir. The 12 ground-water aquifers are: (1) the upper sand zone of the Potomac Formation; (2) the lower sand zone of the Potomac Formation; (3) the Magothy aquifer; (4) thesand of the Englishtown-Mount Laurel Formations; (5) the Rancocas aquifer; (6) the Piney Point aquifer; (7) the Cheswold aquifer; (8) the Federalsburg aquifer; (9) the Frederica aquifer; (10) the Manokin aquifer; (11) the Pocomoke aquifer; and (12) the Quaternary aquifer, also called the Pleistocene and Columbia aquifer. The Potomac Aquifers The nonmarine Potomac Formation in Delaware contains upper and 1 ower sandy zones which vary considerably in thickness and water-transmitting pro- perties. About 170 square miles of the artesian part of the Potomac Formation in Delaware were studied by Sundstrom and others, 1967. Their report de- scribes the complexity of the geology and hydrology. The report should be studied in detail to understand the complexities of both the geology and hy- drology of the two Potomac Formation aquifers. 62 Lo6ation of the Potomac Formation The outcrop or subcrop of the Potomac Formation is shown in Figure 2. The structural map of the basement of the crystalline rocks on which the Potomac Formation lies is shown in Figure 4. The position of the Potomac Formation in a generalized cross-section of Delaware is shown in Figure 3. A map of the thickness of the Potomac Formation is shown in Figure 5. A structural map of the top of the Potomac Formation is shown in Figure 6. Development of the Potomac Aquifers The Potomac aquifers are completely developed so far as large wells are concerned in the area where development equals or exceeds the available re- charge as shown on the water problem map in Figure 15. The area of the Potomac aquifers developed to date is shown in Figure 18. Undeveloped Areas and Potential Use of the Potomac Aquifers The area of potential use of the Potomac aquifers is shown in Figure 18. Downdip from the area of potential use, the aquifers are believed to contain saline water. Hydrologic Potential of the Potomac Aquifers The hydrologic potential of the Potomac aquifers is small in terms of supplying large quantities of water to.wells. In the upper Potomac aquifer in the artesian part of the aquifer the transmissivity, storage and available drawdown were so low that only one well yielding 750,000 gallons a day was developed in the 5,000 acre tract of the Tidewater (now Getty) Oil Company; whereas, the company was able to develop more than four million gallons a day in the same tract from the lower artesian aquifer of the Potomac. The reason for the greater production lie's primarily in the larger available drawdown in the wells of the lower artesian aquifer. Based on the 12-year pumpage record ?f the tidewater well field and the observed decline in water levels elsewhere in the two Potomac aquifers, two rating curves (Figure Al.) were developed to give the effect of pumping on the upper and lower aquifers away from the Tidewater (Getty) well.field. By applying these curves to five selected cen- ters of pumping, Sundstrom and others, 1967, demonstrate the effects of 15 selected patterns of development along the Chesapeake and Delaware Canal. These are given in Table Bl. Table 81 indicates that five million gallons a day might be developed from a well, field similar to the Getty well field 63 WILMINGTON N AREA OF USE AREA OF POTENTIAL USE SMYR -800 Z -900 -1000 OVE -1100 -1200 a: N SA-y -Iwo -14M MILFORD 1500 LE S -1600 GEORGETOWN SEAFORD MILLSBORO. SUSSEX, MILE5 0 1 23 45 6 7 8 9 4=6-MI6 MIL - DELMAR- FROM CUS ING, KANTROWITZ, AND TAYLOR, 1973. FIGURE IS CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE NONMARINE CRETACEOUS AQUIFER. 64 located in the extreme western part of the canal area in Delaware. This amount of development would be predicated on the assumption that no new sub- stantial amounts of pumping would take place in the canal area in Delaware ?r adjoining Maryland from the Potomac aquifer. The centers of pumping tested in the 1967 study by,Sundstrom and others are shown in Figure A2. The loca- tion of wells in the.Potomac aquifer used for well data is given in Figure A3. Data on water levels, well data, and screen settings are given in Table B2. Specific capacities of wells and test wells in the Potomac aquifers are given in Table B3. Coefficients of transmissivity and storage determined from pump- ing tests of Potomac aquifer wells are given in Table B4. Available Water from the Potomac Aquifers Figure 17 shows that the present development of the.outcrop-subcrop area has reached or exceeded the available recharge in the eastern half of the area. The amount of development permissible in the western half of the subcrop area is not known, but is probably small in terms of supplies to wells of medium to large capacities. In the western part of the canal area studied by Sundstrom and others, 1967, there still remai,ns a capacity of about five million gallons a day provi'ded the well field is properly planned and developed and provided no other development takes place adjacent 'to the well field either in Delaware or Maryland. South of the Chesapeake and Delaware Canal, between the canal and the position of the fresh-salt water interface in the Potomac Formation, some additional water, perhaps three or four million gallons a day, may,be developed from the Potomac aquifers. Limits in Development of the Potomac Aquifers The known development and hydrology of the Potomac aquifers indicate that the limits of additional development of the aquifers is about eight or nine million gallons a day with proper use of the aquifers. Quality of Water in the Potomac Aquifers The quality of ground water and areas of potential saline water intrusion in the Potomac aquifers are shown in Figure 19. The chemical constituents in ground water in the Potomac aquifers (concentration of constituents in milli- grams per liter) are given in Table 10. 65 WILMINGTON TNJWAR AREAS OF POTENTIAL SALINE- WATER INTRUSION AREA I AREA. SEE TABLE 10 FOR RANGE IN CHEMICAL N CONSTITUENTS. S T AREA loe SMYRNA AREA 4 'y Z AREA 5 _j DOVER >_ Z) C4 Iq WIQ Me cr_ KE NT R-Y MILFORD T CK LE S GEORGETOWN SEAFORD MILLSBORO SUSSEX MILES 0123456769 DELMAR_ Too FROM C HING, KANTROWITZ,AND 1973. GE ORGET M 0 1 W L S EX R wl TZD 0@AN TAYLL FIGURE 19 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER AND AREAS OF POTENTIAL SALI;NE-WATER INTRUSION IN THE POTOMAC AQUIFER. 66 Table 10. Quality of Ground Water and Area of Potential Saline-Water Intrusion .in the Nohmarine Cretaceous Aquiferj as Shown in Figure 19. Chemical constituents in ground water in the nonmarine Cretaceous aquifer (concentration of constituents in milligrams per liter) Area 1 2 3 4 5 Dissolved <100 100-250 250 -500 500-1000 >1000 solids* Hardness 5-60 2-50 <10 <15 15-60 Sodium 2-14 14-70 70-200 200-340 >300 Bicarbonate 6-80 80-180 180 -450 450-750 --- Sulfate <1-25 3-25 20-40 20-60 --- Chloride 2-15 2-20 2-10 5-200 >200 Fluoride 0.0-0.3 0.1-0.6 0.6-3.01 1.0-4.0 --- Nitrate <1 -24 <1.6 <1.5 <1.3 Silica 3-10 10-1-5 10-15 10-15 --- Iron and 0-10 0.1-0.6 0.01-0.35 0.04-0.'4 manganese pH 5.6-7.0 7.0-8 .0 8.0-8. 6 8.2-8.9 *Dissolved solidsx 1.60 specific conductance (Micromhos at 250C) From Cushing, Kantrowitz and Taylor, 1973. 67 Salt-Water Problems in the Potomac Aquifers Although salt-water problems have not occurred in the part of.the Potomac aquifers yielding fresh water, salt-water problems could occur as shown on the map in Figure 19. This area is in the subcrop area where the water levels in. wells adjacent to the wetlands of the Delaware Estuary have been drawn down below sea level. To date no problem has developed from this situation, but a problem may occur later if the water levels in wells continue to be pumped down below sea level. There is also a danger of salt-water problems along the western part of the Chesapeake and Delaware Canal where the sands of the Magothy.aquifer are in direct contact with the upper Potomac aquifer and the Magothy sands outcrop in the Canal,which contains-salt water. Unknown Hydrology of the Potomac Aquifers Much of the hydrology of the very complex aquifers of the Potomac Forma- tion has been studied. The irregular occurrence of the sands-still leave some doubt about the total available water, especially in the western part of the canal area where development has been limited. In the fresh-salt-water inter- face area in the Potomac aquifers, data are still too meager for exact delinea- tion of the interface., The Magothy Aquifer The hydrology of the Magothy aquifer in and near its subcrop in Delaware is closely associated with the upper aqu-ifer zone of the Potomac Formation. The marine sediments that compose the Magothy aquifer rest directly on the non- marine sediments of the upper Potomac Formation. Where the sands of the Magothy aquifer lie on sand-of the Potomac., hydraulic continuity exists be- tween the two aquifers. As the aquifers become deeper downdip, marine clay sediments thicken and probably separate the two aquifers to some bxtent.., The Magothy aquifer and the upper sands of the Potomac probably should be con- sidered a single aquifer in hydrologic treatment. The ori ginal water levels in the Magothy were influenced by the hydraulic association with the'water levels in the upper Potomac. In the subcrop area the altitude of the water levels in the overlying Pleistocene sediments con- trolled the altitude of the water leVels.in the nonartesian part of the Magothy aquifer. They also controlled the artesian press,ure on both the Potomac and Magothy aquifers where they are confined. Measured artesian pressures in the Potomac aquifer zones suggest that by similarity the original artesian pressure in the Magothy aquifer, where it is confined, ranged from about 15 to 20 feet above sea level. 68 Location of the Magothy Aquifer The subcrop of the Magothy aquifer occupies two small areas as shown in Figure 2. The configuration of the top of the aquifer to a depth 1,400 feet below sea level is shown in Figure 20. A structural map of the Magothy Forma- tion above the fresh-salt water interface is shown in Figure 5. Development of the Magothy Aquifer The Magothy aquifer is developed in two areas shown in Figure 20. Pump- ing from the Magothy-Potomac upper zone south of the Chesapeake and Delaware Canal has been on a small scale. In 1959, the total pumpage mostly from the upper Potomac was reported (Rima and others, 1964) to be only 80,000 gallons. a day for all purposes. Undeveloped Areas and Potential Use of the Magothy Aquifer The potential undeveloped area of the Magothy aquifer is shown in Fig- ure 20. Hydrologic-Pot6ntial and Available Water from the Magothy Aquifer The hydraulic coefficients that control the water-yielding properties of the Magothy aquifer are not sufficiently known for a good appraisal of the aquifer. Geologic evidence indicates the aquifer is of a leaky nature in the updip part and becomes more confined downdip. The more leaky part of the aquifer lies on and is.hydrologically connected in places to the upper zone of the Potomac. Based on one pumping test at Middletown, the transmissivity of the Magothy is 4,000 gallons per day per foot as compared to an average transmissivity in 11 wells in the upper Potomac of 5,900 gallons per day per foot in the Chesapeake and Delaware Canal area (Sundstrom and others, 1967). The canal area comprises an area of about 170 square mil'es. The area of the Magothy from the beginning of the subcrop to the fresh-salt water interface is also about the same size. The available drawdowns in the upper Potomac aquifer and in the Magothy are similar in range of depths. Assuming that the trans- missivity of 4,000 gallons for the Magothy is representative of all the aqui- fer, then a comparison with the average transmissivity of the upper Potomac zone indicates that the Potomac upper aquifer will yield about one and one- half times as much water as the Magothy. Sundstrom and others (1967) tested 15 patterns of development at five hypothetical centers of pumping stretched across the canal area and assumed that the upper Potomac aquifer would be 69 WILMINGTON @NJWARK AREA OF USE AREA OF POTENTIAL USE A z .4 -900 -j VE >- -000 V C4 #q W#q Re cr -1106 -1300 _1200 MILFORD LE S GEORGETOWN EAFORD MILLSBORO -1300 SUSSEX MILES 0123456?69 DEL AR vile FROM CUSHING, KANTROWITZ, AND TAYLW% 197&& 400 FIGURE 20 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE MAGOTHY AQUIFER. 70 pumped at the five centers from one or more wells at rates ranging in total from 0.0 to 1.75 million gallons a day. Of the 15 patterns tested that were feasible, the maximum rate of pumpage from the upper Potomac aquifer in the canal area was 4.7 million gallons a day from the five centers. The 4.7 million gallons a day in the canal.-area would indicate 3.1 million gallons a day from Magothy from a similar hypothetical analysis of the Magothy laid out in the same direction across the county and centering in the vicinity of Middletown. The production well yields would probably range from 250 to 300 gallons a minute. The area as a whole is not favorable for centers of large development of water. For smaller supplies (wells yielding 10 to 50 gallons a minute), the Magothy north of the fresh-salt water interface is a good source of water. Quality of Water in the Magothy Aquifer Areas of similar chemical quality of ground water and areas of potential salt-wa 'ter intrusion into the Magothy aquifer are shown in Figure 21. For detailed discussions of the danger of salt-water intrusion into the Magothy and upper Potomac aquifers, see Sundstrom and others , 1967; SUndstrom and Pickett, 1971; and Cushing, Kantrowitz and Taylor, 1973. The chemical con- @tituents of the ground water from the Magothy for areas shown on Figure 21 is given in Table 11. The Englishtown and Mount Laurel Aqu ifers Location of the Englishtown and Mount Laurel Aquifers The subcrops of the Englishtown-Mount Laurel aquifers also sandwich in the Marshalltown Formation, which interconnects the two aquifers, but is of little value as an aquifer itself. The subcrops of the three formations are shown in Figure 2. Hydrology of the Englishtown-and Mount Laurel Aquifers The Englishtown aquifer and the Mount Laurel aquifer are minor aquifers of fair to poor water-yieldi,ng properties which are unimportant in terms of large individual supplies of water, but are-of considerable importance from the Chesapeake and Delaware Canal southward past Middletown for rural inhabi- tants. The two aquifers are separated by the Marshalltown Formation which, according to Pickett (1970a), consists of dark greenish gray, massive, glau- conitic, very silty.fine sand. The entire'unit, including the Englishtown 71 WILMINGTON @NJWARK AREA. OF POTENTIAL SALINE- WATER INTRUSION AREA I REA SEE TABLE 11 FOR RANGE IN CHEMICAL CONSTITUENTS. NEW CA L E AREA SMYRNA Z AREA 4/ DOVER 6*4 Iq w,9)7lc KE NT AREA 5 'lill-FORD LE S GEORGETOWN EAFORD MILLSBORO SUSSEX MILES 0112 3 456789 t__ DELMAR FROM USHING, KANTROWITZ, AND TAYLOR, 197& FIGURE 21 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER AND AREAS OF POTENTIAL SALINE-WATER INTRUSION IN THE MAGOTHY AQUIFER. 72 Table 11. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Magothy Aquifer, as shown in Figure 21 Chemical constituents in ground water in the Magothy aquifer (concentration of constituents in milligrams per liter) Area 1 2 3 4 5 Dissolved solids* <100 100-2 50 250-500 .500-1000 >1000 Hardness 4-70 4-70 <20 --- <20 Sodium 3-12 12-915 >95 --- >400 Bicarbonate 5-100 100-250 >250 >900 Sulfate 1-12 9-15 >10 --- >60 Chloride 1-3 2-5 <10 >50 Fluoride 0.1-0.3 0.2-1.1 >1.0 --- >5.0 Nitrate@ 0-1 0-2 < 2 --- <2 Silica 3-16 6-15 >10 --- >10 Iron and 2.0-24 0.03-4.4 <1 <1 manganese pH 6.1-7.5 6.8-8.2 >7.0 >8.0 *Dissolved solids x 1.60 = specific conductance (Micromhos at 250C) From Cushing, Kantrowitz and Taylor, 1973. 73 and Mount Laurel aquifers, may,be considered as one hydrologic unit, although the Marshalltown probably contributes little to the available water from the entire section. The pumpage in 1959 was reported by Rima and others (1964), to be on the average of 460,000 qallons a day from the Englishtown-Mount Laurel aquifers. Of this amount, rural water suppies used 290,OO0 gallons a day; the town of Middletown used 120,000 gallons a day; and vegetable processing industries used 50,000 gallons a day. Some increase in pumpage probably has taken place since 1959,but it is believed that the increase is not large because of the minor increase in rural development since 1959. The specific capacities of 25 wells in the Englishtown-Mount Laurel aqui- fers are reported by Rima. Of the 25 wells, only two have specfic capacities above two gallons a minute per foot of drawdown. The specifi capacities of 16 wells range between one and two gallons a minute per foot of drawdown and the remaining seven wells have specific capacities of 1ess than one gallon a minute per foot of drawdown. The yield of the 25 wells ranged from 10 to 123 gallons a minute. Only five wells yielded 60 or moregallons a minute. The most reliable value of transmissivity of the aquifers was determined from a pumping test at Middletown in 1961. Rima reports the transmissivity to be 1,800 gallons per day per foot and the coefficient of storage to be 0.00025. The transmissivity of the aquifers is generally very low. Availability of Water from the Englishtown and Mount Laurel Aquifers The availabiliy of water in large quantities for individual supplies from the Englishtown-Mount Laurel aquffers is impracticable because the water- yielding properties of the aquifers are only fair to poor. To develop a sup- ply of a million gallons a day would require, under favorable conditions, 10 to 15 costly and dispersed wells. On the other hand, the aquifers are impor- tant for rural supplies and small users of water in the area south of the Chesapeake and Delaware Cana1 southward past Middletown. Small users of water could probably withdraw a combined total of two to five million gallons throughout the area. The Rancoas Aquifer Location of the Rancocas Aquifer The, subcrop of the Rancocas aquifer is shown in Figure 2. The subcrop and structure of the top of the formation is shown in Figire 7. The configura- tion of the top and areas of use and of potential use of the Rancocas aquifer are given in Figure 22 and Table 85. 74 MINGTON N WARK AREA OF USE AREA OF POTENTIAL USE z DOVER D ed. #q W#9 re K E NIT MI LFORD LE S GEORGETOWN EAFORD MILLSBORO SUSSEX MIL S 0 1 23 4SE67 6 9 &-- DELMAR 7is FROM CUSHING, KANTROWITZ.AMO TAYLOR, 1973. GEORGETOWN MILLS X S @E 750 FIGURE 22 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE RANCOCAS AQUIFER, 75 Developed and Undeve loped Areas of the Ranc ocas Aquifer I The areas of use and potential use of the Rancocas aquifer are shown in Figure 22. Hydrology of the Rancocas Aquifer The Rancocas aquifer supplies more than 25 percent of the ground water used in New Castle County south of the Chesapeake and Delaware Canal (Rima and others, 1964). The aquifer is used for public supply at Middletown and Townsend, for supply at the Delaware State Correctional Institution near Smyrna, for industrial and commercial establishments and for much of the rural area. The Rancocas aquifer is available in the southern third of New Castle County and subcrops in the Middletown-Odessa area (see Figure 2). Water in the aquifer occurs under both water-table and artesian conditions. The water levels in the subcrop of the Rancocas aquifer are close to those in the overlying Pleistocene water-table aquifer, discussed later. The artesian pressure is also influenced by the altitude of the water table in the subcrop* Early water-level measurements of artesian pressure in the Rancocas at Clayton, about a half-mile south of the New Castle-Kent County line, indi- cate that the original artesian pressure was about 25 feet above sea level. The specific capacities of 25 wells in the Rancocas aquifer are reported by Rima and others (1964). The specific capacities ranged from 0.7 to 6.5 and averaged 2'3 gallons a minute per foot of drawdown. Sundstrom and Pickett (1968) reported specific capacities in five wells in the Rancocas aquifer in New Castle and Kent Counties as shown in Table B7. The transmissivity of the Rancocas aquifer has been computed from pumping tests made by A. C. Schultes and Sons Well Drilling Company in three wells at the Delaware Correctional Institution about two miles north of Smyrna. The transmissivity ranges from 14,000 to 19,200 gallons per day per foot. The four determinations of transmissivity are given in Table B8. The graphic plot of pumping-test data and computation of the coefficients of transmissivity and storage in Delaware State Correctional Institutional well (Gc54-2) are given in Figure A4. The time-distance-drawdown graphs, based on the coefficients of transmissivity and storage obtained from the pumping test in well Gc54-2, are given in Figure A5. Coefficients of storage in the Rancocas aquifer vary widely. In the sub- crop area the coefficient of storage approaches the specific yield of the aquifer which may be 5 to 15 percent. In the southern part of the county, the aquifer is tightly confined and the coefficients of storage.shown in Table B7 range from 0.00019 to 0.00028. 76 The subcrop area of the Rancocas, shown in Figure 2, is a recharge area and can be treated analytically as a recharge boundary or line source of water for the artesian part of the aquifer. Some recharge to the artesian aquifer also occurs from vertical leakage through the overlying confining beds in the extreme southern part of the county. Downdip from extreme southern New Castle @ounty, hydraulic boundary conditions are unknown. The Rancocas loses its identity as a formation in Kent County. The relation of pumpage in the Wheatley well to water level changes in the town of Clayton well indicates there is little, if any, barrier boundary effect discernable (Sundstrom and Pickett, 1968). The available drawdown in the subcrop area of the Rancocas is equal to the thickness of the aquifer plus the overlying saturated portion of the water- table aquifer of the Pleistocene. In the water-table part of the aquifer, it would be impracticable to use all of the available drawdown because of the diminishing yield of the well as the aquifer becomes unwatered. In the arte- sian part of the aquifer, the available drawdown is the distance to the top of the aquifer as shown in Figure 13 plus the altitude of the artesian pressure above sea level. The range in available drawdown in the artesian part of the aquifer is from about 50 to 250 feet, with the greatest available drawdown in the extreme southern part of the county. In the subcrop area of the Rancocas the water-table aquifer is discussed in conjunction with the overlying water- table aquifer of the Pleistocene. Availability of Water from the Rancocas Aquifer The Rancocas aquifer is an important source of small supplies of water throughout the area in which the aquifer exists in southern New Castle County. It is important as a source of water to wells yiel,ding 300 or more gallons a minute in the 'artesian part of the.aquifer only in the area east and northeast of Smyrna. The limited capacity of wells is attributed largely to the low specific capacity of wells and to the limited avail-able drawdown. Some evi- dence is available at Clayton (Wheatley well). and at the Delaware Correctional Institution well, Gc54-2, that specific capacities in the Rancodas wells might be improved considerably by using more screen, large well-type construction and better development of wells. If specific capacities of wells could be im- proved, much more water could be obtained with the limited available drawdown that exists. In appraising the availability of water from the Rancocas in Kent County, Sundstrom (1968) points out that the ultimate amount of water available from the aquifer depends upon the plan for total development. He demonstrated the feasibility of a line of seven wells, 5,000 feet apart, pumping 300 to 350 gal- lons a minute and yielding a total of 3A million gallons a day (Table B9). If the more favorable specific capacities of the Wheatley well (4.6 gallons a minute per foot of drawdown) and of the Delaware Correctional Institution well @3.4 gallons a minute per foot of drawdown) could be developed at all hypothet- ical wells, then it would be possible to readjust the pumpage slightly 77 and develop about six million gallons a day from a string of wells pumping from the@deeper part of the Rancocas aquifer across part of Kent and New Castle Counties. The ultimate yield of the Rancocas aquifer in the two counties is predicated on proper spacing and rate of pumping. If wells yielding 300 or more gallons a minute are used, the six million gallons a day indicated is probably the maxi*mum rate for the aquifer in the two counties. If smaller wells are used, more water can be obtained. Quality of Water in the Rancocas Aquifer The areas of similar chemical quality of ground water and area of poten- tial salt-water intrusion in the Rancocas aquifer are shown in Figure 23. The chemical constituents in ground water in the Rancocas aquifer in milligrams per liter are given in Table 12. .Salt-Water Problems in the Rancocas Aquifer The Delaware Bay extends 48 miles from the Atlantic Ocean to Liston Point, Delaware. The estuary of the river then continues upstream 86 more miles to Trenton, New Jersey. Above Trenton, the river ceases to be tidal. At the be-, ginning of the estuary at Trenton, the stream contains fresh water and the river's estuary remains relatively uncontaminated by salt water for many miles downstream from Trenton. At Memorial Bridge near Wilmington during periods of low river flow and high tide from the bay, chlorides are often above 1,000 parts per million and on occasions reach 1,700 or more parts per million. Downstream from Memorial Bridge about twelve and one-half miles at Reedy Island Jetty, Delaware, and about nine and one-half miles above the beginning of Kent County, the chlorides during similar periods will reach more than 6,000 parts per million. During these periods of high chloride, the low for the day may be no more than 2,000 parts per million below the daily high. All of Kent County is bounded on the east by the middle and lower part of the Delaware Bay, where- in the lower part of the chloride concentration approaches that of the ocean. The Rancocas aquifer outcrops in New Castle County adjacent to the Delaware River Estuary from a point opposite Reedy Island southward to the mouth of Blackbird Creek, an airline distance of about seven miles (see Rima, et al, 1964). These outcrop extremities lie 5 to 10 miles north of Kent County. In discussing the possibility of brackish water encroachment from the estuary to the fresh-water aquifers in southern New Castle County, Rima,et al, 1964, have this to say: "At the time of this investigation in 1962, no evidence was found of the encroachment of brackish water into fresh-water aqui- fers in southern New Castle County from either the Delaware estuary or the Chesapeake and Del aware Canal. Nonetheless, the 78 MINGTON WARK AREA OF POTENTIAL SALINE- WATER INTRUSION. SEE TABLE 12 FOR RANGE IN CHEMICAL CONSTITUENTS. A ARE RE E S AREA 2 v SMYRN AREA DOVER DC4AW#9ffC REA 4 KE NT MILFORD LE S GEORGETOWN SEAFORD MILLSBORO SUSSEX' MILES 0123456709 L DELMAR 4- FROM SHING, KANTROWITZ, AND TAYL R, 1973. Toe FIGURE 23 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND GE0R E T MI W L N LS S E X Owrrz. T LO R@ANGD AOY R. WATER AND AREA OF POTENTIAL SALINE-WATER INTRUSION IN THE RANCOCAS AQUIFER. 79 Table 12. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Rancocas Aquifer, as Shown in Figure 23 Chemical constituents in ground water in the Rancocas aquifer (concentration of'constituents in milligrams per liter) @Area 1 2 3 4 Dissolved <100 100-250 .250-500 >500 solids* Hardness <50 50-155 30-170 <30 Sodium <10 2-70 40-150 >200 Bicarbona te <50 50-200 2M-5 bo >500 Sulfate 0-20 0-15 0-12 10-15 Chloride <10 <10 4-55 <15 Fluoride <0.3. 0.1-0.9 0.2-2.0 3.5-4.2 Nitrate 0.1-12 0.1-30 <2 <1 Silica 10-25 10-40 10-20 10-20 Iron and -0.1-3.0 0.1-6.0 <0.5 <0.5 manganese pH 5.6-6.8 7.2-7.9 7.8-8.5 8.1-8.4 *.Dissolved solids x 1.55 specific conductance (Micromhos at 25-C) From Cushing, Kantrowitz and Taylor, 1973. 80 presence of bodies of brackish water along the northern and eastern borders of the area should be considered as potential 'threats to@the future development of aquifers in southern New Castle County. "The most likely places for encroachment to occur are near the suboutcrops of the principal aquifers beneath the Delaware estuary and the Chesapeake and Delaware Canal. The suboutcrops beneath the canal are covered by not more than a few feet of silt of low permeability. The suboutcrops beneath the estuary, however, are somewhat better insulated from the brackish water by the presence of thick alluvial muds, which line the channel of the estuary. As these muds are considerably less permeable than the aquifers, some protection.from encroachment is afforded the adjacent aquifers. Nevertheless, movement of water from the estuary into the fresh-water aquifers will occur if the natural hydraulic gradient is reversed by pumping from the aquifer.. Con- sequently, much care should be exercised in developing large ground-water supplies close to the estuary." A well to the Rancocas aquifer about two miles north of Smyrna yields water of only one part per million of chloride. The well is owned by,the Delaware Correctional Institution and was drilled in 1967. However, three wells east (Woodland Beach) and southeast of Smyrna yield and are reported to yield brackish water. These wells are@reported to be dri1led to a depth of about 270 feet and only cased to a depth of 170 feet. The wells have been reported to draw water from the Rancocas. Considering the depth of the casing and the position of the Rancocas, it appears doubtful that the wells obtain water from the Rancocas. Most of the Rancocas aquifer available for development in Kent County lies west and southwest of.Smyrna and is 10 to 22 miles remote from the near- est point the Rancocas outcrops or passes under the valley fill of the Delaware Estuary. The remote position of the estuary from the most usable part of the aquifer in Kent County precludes any problem of salt-water contamination in the Rancocas aquifer in the county. The Piney Point Aquifer Location of the Piney Point Aquifer A structural map of the Piney Point Formation is.shown in Figure 8. The Piney Point aquifer in Delaware is a segment of an extensive hydrologic unit. that has continuity from the Atlantic Coast between the Atl,antic City area and Cape May and extends southwesterly', veering more to the south as progression goes southwestward and southward to the other known extremity of the aquifer in Virginia. Thus, the aquifer'is known to extend from the Atlantic Coast in 81 New Jersey, through parts of Kent and Sussex Counties, Delaware, across the eastern shore of parts of Maryland to the Potomac River in the vicinity of Piney Point, where the aquifer gets its name, and beyond into Northcumberland and Westmoreland Counties, Virginia (Otton and Heidel, 1966). The aquifer is unusual in that it has no outcrop. E. 6. Otton (1955) in discussing the Piney Point, reveals that the Piney Point has not been recognized in surface exposure and has not been known to lie above an altitude of 75 to 80 feet below sea level. In Kent County the top of the Piney Point ceases about 200 feet below sea level. Areas of Development and Potential Development of the Piney Point Aquifer Configuration of the top and areas of use and of potential use of the Piney Point aquifer are shown in Figure 24. Hydrology of the Piney Point Aquifer The ground-water hydrology of the Piney Point aquifer has been reported and analyzed in considerable detail, especially as the hydrology applies to the Dover area, by Sundstrom and Pickett, 1968 '. The original artesian pressure in the Piney Point aquifer is not precisely known. The annual report of the New Jersey State Geologist for 1899 reports a well to the Piney Point aquifer in Kent County, Delaware, at the mouth of the Mahon River. The well was drilled in 1897 and the water rose 16 feet above tide or about 20 feet above sea level. A test well drilled to the Piney Point at Milford in 1938 is re- ported by Marine and Rasmussen, 1955, to have had artesian pressure 17 feet above mean sea level. The specific capacities of 12 wells drawing water from the Piney Point are given in Table B10. The specific capacities range from 0.3 to 14.6 gal- lons a minute per foot of drawdown. Two of the specific capacities listed are less than unity and represent one well that is near the downdip extremity of the aquifer at Milford. Eliminating these two observations of specific capacity, the remaining 10 wells have specific capacities ranging from 2.7 to 14.6 and averaging 6.6 gallons a minute per foot of drawdown. Specific capa- cities averaging as low as 6.6 indicate only moderate water-yielding proper- ties of the aquifer. The relatively low specific capacities also make necessary high pumping lifts to pump substantial quantities of water. Low specific capacities also affect the allowable rate of pumping. Assuming that a well has been properly designed, properly constructed and properly devel 'oped, the specific capacities give clues not only to the amount of water that can be developed from the well, but also to the hydrology of the ground-water reser- voir from which the well obtains water. If a well meets all of the criteria of good design, construction and development and is highly efficient when pumped, then there is a definite relation of well diameter, specific capacity 82 MINGTON YNIWARK AREA OF USE AREA OF POTENTIAL USE NEW CAS TLE z X 300 ILFORD -600 LE S, -700 GEORGETOWN AFOR Boo MILLS130RO S '�SEX MILES 012345t.789 LMA Too FROM USHING, KANTROWITZ, AND 1973. 750 FIGURE 24 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE PINEY POINT AQUIFER. 83 of the well and the coefficients of transmissivity and storagein the aquifer. This relationship has been illustrated graphically by Meyer (1963) and is shown in Figure A6. The transmissive properties of the Piney Point aquifer have been computed from pumping tests in wells in Kent County made by the Layne-New York Company, Shannahan Artesian Well Company, A. C. Schultes and Sons Drilling Company and R. D. Varrin, Director of the Water Resources Center of the University of Dela- ware. One pumping test made in a well to the Piney Point in Cambridge, Mary- land, by R. H. Brown and T. H. Slaughter is included in this report. The co- efficients of transmissivity determined by 13 computations from pumping test data from eight wells ranged from 6,000 to 41,000 gallons a day per foot in Kent County and from 42,500 to 47,500 gallons a day per foot in the well at Cambridge, Maryland. Non-leaky drawdown curves for six Piney Point wells are given in Sundstrom and Pickett, 1968. In the thicker part of the Piney Point aquifer (see thickness map, Figure 6 in the 1968 report), extending from Port Mahon almost true southwest to the state line, five wells, zero to three and one-half miles off this line, and extending a distance 10 miles southwestward from the Dover Air Force Base, have coefficients of transmissivity ranging from 21,000 to 39,000 gallons a day per foot. The average of the five coefficients of transmissivity is 31,800 gallons a day per foot. The low coefficients of transmissivity were found in two wells about five miles updip and the third about three miles updip from the thick axis of the aquifer. Coefficients of transmissivity determined from pumping tests are given in Tables Bll and B12. Two coefficients of storage for the Piney Point aquifer are available. One at the Dover Air Force Base was computed from a pumping test in which the water levels in well Je32-4 were observed while well Je32-5 was pumping. The other coefficient of storage was determined at Cambridge, Maryland, in well DorCe4 while well DorCe2 was pumping. The two locations are about 50 miles apart, but the two determinations are almost identical. At the Dover Air Force Base, R. D. Varrin determined the coefficient of storage to be 0.0003. R. H. Brown and T. H. Slaughter of the U. S. Geological Survey determined the coef- ficient of storage at Cambridge to be 0.00036. The coefficient of storage for the Piney Point used in this report is 0.0003. The low coefficient indicates a relatively non-leaky type artesian reservoir. Sundstrom and Pickett, 1968, devote much discussion to the determination of the aquifer coefficients and the relation of the computed coefficients to the actual drawdowns that have been observed. The entire hydrology section of the 1968 report should be studied as a supplement to this report. Available Water from the Piney Point Aquifer The quantity of water availab le from the Piney Point aquifer in Kent County is controlled by the geologic and hydraulic characteristics o 'f the aquifer and also by the location of the downdip extremity by the fresh-salt water interface in the aquifer. The data available from the wells drilled into the Piney Point show the aquifer has fairly good water-yielding 84 properties near and in the thicIkest part of the aquifer and poor water-yielding properties toward each flank of the aquifer. The axis of the best part of the aquifer would extend in an almost true north-east-southwest line across Kent County passing through the Dover Air Force Base'well Je32-5. The distance across Kent County on this line is about 21 miles. Several patterns of hypo- thetical wells in lines varying from one to three were laid out and tested for feasibility and to ascertain the probable yield of the Piney Point aquifer. Two feasible patterns of hypothetical wells, the allowable rate of pumping from each well, and the computed 'drawdown in each well are given in Tables 18 and 19 in the report by Sundstrom and Pickett (1968). In the hypothetical plan given in Table 18, the pumpage would be limited to 500 and 600 gallons a minute from the 22 wells, and the combined yield would be 17 million gallons a day. The aquifer is approaching full develop- ment in parts of the Dover and Dover Air Force Base area. Quality of Water in the Piney Point Aquifer Areas of similar chemical quality of ground water in the,Piney Point aqui- fer are given in Figure 25. The chemical constituents in ground water in the Piney Point aquifer in milligrams per liter are given in Table 13. Salt-Water Problems in the Piney Point Aquifer There are no known or anticipated salt-water problems in the Piney Point aquifer in Delaware. The aquifer lies about 200 feet beneath Delaware Bay. The aquifer becomes less transmissive downdip before the fresh-salt water interface is encountered. The Cheswold Aquifer Location of the Cheswold Aquifer The subcrop area of the Cheswold in Delaware is shown in Figure 2. The configuration on the top of the Cheswold is shown in Figure 26. 85 WILMINGTON @NFWARK SEE. TABLE 13 FOR RANGE IN CHEMICAL CONSTITUENTS. NEW CAS TLE `I@N ip MYRNA %@@ 10L- z AREA I D*R /I D d"409 w'q Me KE NT B A-y AREA 2 ARE 3 MILFORD AREA 4 LE -S GEORGETOWN SEAFORD MILLSBORO SUSSEX MILES 0123456769 DELMAR FROM CUSHING, KANTROWITZ, AND TAYLOR. 1973 rEORGETOWN MILLS X S @E FIGURE 25 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER IN THE PINEY POINT AQUIFER. 86 Table 13. Quality of Ground Water in the Piney Point Aquifer, as Shown in Figure 25 Chemical constituents* in ground water in the Piney Point aquifer (concentration of constituents in milligrams per liter) I Area 1 2 3 4 Dissolved solids* 200-250 250-500 500-1000 >1000 0 Hardness 90-20 20-90 15-45 >30 Sodium 4-30 30-190 190;-.500 >500 Bicarbonate 170-250 200-500 400-800 >600 Sulfate 3-15 3-20 7-100 >100 Chloride 1-7 1-25 3-200 >200 Fluoride <0.4 0.4-1.6 1.4-2.3 0.7-2 .0 Nitrate <2 <2 <2 <3 Silica 45-60 10-45 15-30 10-45 Iron and 0.1-1.5 0.0-0.4 0.0-0.5 >1.0 manganese pH 7.7-7.9 7.9-8.6 7.8-8.5 7.8-8.9 *In area 1, dissolved solids x 1.40 specific conductance (Micromhos at 25'C) In areas 2, 3, and 4, dissolved solids x 1.55 specific con- ductance From Cushing, Kantrowitz and Taylor, 1973. 37 WILMINGTON @NEWAIRK AREA OF USE AREA OF POTENTIAL USE NEW CAS TLE z AID C-6,09 wn)?c cr SEA I LLSIso -800 s S E X700 MILES -900 0 1 23 45 6 7 8 9 1 DE AIR 100 FROM C SHING, KANTROW/ITZ, AND TAYLOR, 1973. 750 1 FIGURE 26 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE CHESWOLD AQUIFER. 88 Development of the Cheswold Aquifer The area in which the Cheswold aquifer has been developed is shown in Figure 26. Sundstrom (1968) reports that the Cheswold aquifer was producing 30 percent of all of the ground water used in Kent County and most of the water was used in the Dover-Dover Air Force Base area. The Cheswold is a good aquifer in the Dover area and is developed to its capacity. Elsewhere northwest, west and south of the area, the Cheswold aquifer.is only fair to poor in water-yielding properties. Undeveloped Areas of the Cheswold Aquifer The undeveloped areas of the Cheswold aquifer are shown in Figure 26. As noted above, much of these areas are underlain by a Cheswold aquifer of poor water-yielding potential, but useful for local rural and domestic supply. Hydrology of the Cheswold Aquifer According to a report by Woolman, State Geologist of New Jersey, 1899, the original artesian pressure in the first well drilled to'the Cheswold aqui- fer in Dover was 12 feet above sea level in'1893. Prior to 1893, Woolman reports that Dover obtained its water supply from a four-inch well that ter- minated in a sand a few feet above the sands to which the new well was drilled. The static water level reported is eight feet less than the original static water level reported for the Piney Point. Pumpage from the Cheswold aquifer has been continuous for 75 years or more at a rate that has grown from a flowing well of 36 gallons a minute in 1893 to a complex of pumped wells that now produce an average of more than five million gallons a day in the county. The one hundredfold increase in the rate of pumping has caused the artesian pressure to decline sharply. The arte- sian pressure has been observed daily in all of the wells at the Dover Air Force Base, weekly in the City of Dover wells, and in an unused well about midway between Dover and the Air Force Base. The record shows that the aver- age high water level for July, 1965, was 97 feet below land surface or 67 feet below mean sea level at unused well Jd52-1 and is the recorded monthly low for the period of record. The average pumpage of the City of Dover and the Air Force Base totaled 4,600,000 gallons daily for the month of June of the same year. The specific capacities of 14 wells drawing water from the Cheswold aqui- fer are given in Table B10. The specific capacities range from 0.9 to 25.4 gallons a minute per foot of drawdown. The average specific capacity of the 14 wells is 11.2 gallons a minute per foot of drawdown. Only four of the 14 wells for which specific capacities have been determined are located outside 89 the Dover-Dover Air Force Base area. The specific capacities of the four wells range from 0.9 to 7.6 and average 4.7 gallons a minute per foot of drawdown. Most of the wells to the Cheswold aquifer to the northwest, west and south of the Dover-Dover Air Force Base area are believed to have low specific capaci- ties, evidenced by their moderate to low yield. The transmissive properties of the Cheswold aquifer have been computed from pumping tests made by Jack R. Woods, Superintendent of Public Works, City of.Dover; Shannahan Artesian Well Company; and R. W. Sundstrom of the Water Resources Center, University of Delaware. The coefficients of transmissivity determined by seven computations from pumping test data from six wells ranged from 11,200 to 32,800 gallons a day per foot. The average coefficient of trans- missivity is 18,300 gallons a day per foot. Two coefficients of storage for the Cheswold aquifer have been computed from pumping tests conducted by the Shannahan Artesian Well Company and by R. W. Sundstrom in two wells. Both wells are owned by the City of Dover, one at the East Dover Elementary School and one at the Danner Farm well site. The coefficients of storage in both wells indicate artesian conditions. The coef- ficient of storage at the East Dover Elementary School is 20 times higher than that at the Danner Farm well, although both are low. The coefficient of stor- age at the East Dover Elementary School is 0.0062 and at the Danner Farm test well 0.00031. The outcrop of the Cheswold aquifer in the northern part of Kent County is sufficiently close to the pumping in the Dover-Dover Air Force Base area so that its favorable recharge image effect o*h the pumping levels in the wells is substantial and must be taken into account in computing the mutual inter- ference between wells. Likewise, in any other part of the northern half of the county the recharge boundary effect will be favorable to the computed draw- downs. The transmissive properties of the Cheswold vary greatly from place to place. Northwest, west and south of the Dover-Dover Air Force Base area, the water-yielding properties of the Cheswold 'are not conducive to large yielding wells. No wells in this area are known to yield more than 300 gallons a min- ute, some are in the 100 to 200 gallons a minute range, many are in the 100 gallons a minute or less range, and in some localities, the Cheswold does not yield a satisfactory supply. Although the Cheswold has poor water-yielding properties in such places, it is believed that the continuity of the,aquifer is such that no barrier boundaries of substantial magnitude exist. The available drawdown at the time pumping began in the Cheswold aquifer ranged from no drawdown at 12 feet above sea level in the northwestern part of the county in the outcrop area to about 360 feet below sea level downdip at Milford. At Dover and at Milford the development of the Cheswold has been so intensive that the pumpage during peak demands in 1965, 1966 and 1967 has caused the drawdown to reach the top of the aquifer in four of the seven wells of the City of Dover and in one well in Milford. Table B13 lists the lowest pumping levels and the dates they occurred in the City of Dover wells along with the remaining available drawdown. The low drawdowns occurred 90 during periods when the pumpage in the Dover area from the Cheswold aquifer averaged about 6,500,000 gallons daily. Additional draft on.the Cheswold will necessitate adjustment in the rate of pumping of some of the Dover City wells. Available Water from the Aquifer and Limits of Development Sundstrom'and Pickett (1968) wrote about the City of Dover wells to the Cheswold aquifer as follows:' "The available drawdown in the Cheswold aquifer has been exceeded in four of the seven City of Dover wells during periods of heavy draft of about 6,500,000 gallons a day'in 1965, 1966 and 1967. Without readjustment of the rate'of pumping.in the over- pumped wells, it appears that additional draft cannot be made on the Cheswold and still supply the peak demand at Dover. On the other hand, with readjustment of the pumpage from some of the city wells, it might be possible to maintain pumping operations at the present average daily pumpage of about 5,500,000 gallons daily and allow a planned distribution of pumpage in other parts of the county to about eight million gallons daily from the Ches- wold aquifer. The present maximum rate of pumping in the Dover area of 6,500,000 gallons daily and the excessive drawdown in four of the city wells does-not allow additional draft from the Cheswold without altering the rate of pumping from at least four of the city wells." Michael Apgar of the Delaware Department of Natural Resources and Environ- mental Control reports that this has already been done (personal communication). Quality of Water in the Cheswold Aquifer. -Areas of similar chemical'quality of ground water and the area of poten- tial salt-water intrusion into the Cheswold,aquifer are shown in Figure 27: The chemical constituents in the ground water in the Cheswold aquifer in milli- grams per liter are given in Table 14. Salt-Water Problems in the Cheswold Aquifer Salt-water problems may arise in the subcrop area of the Cheswol*d aquifer where the subcrop and overlying Quaternary deposits are in contact with the 91 WILMINGTON @NEWARK AREA OF POTENTIAL SALINE- WATER INTRUSION SEE TABLE 14 FOR RANGEIN CHEMICAL NE W CONSTITUENTS. 'CAS TLE A@ Z %DOVER 'I I AR A 2 I AREA K EINT MILFORD -AREA 3 w :LE GEO OWN SEA D AREA MILLSBORO S U" S S EX MILES AREL -5 o125456789 I DELMAR- FROM CUSHING,, KANTROWITZ, AND TAYLOR, 1973 T50 FIGURE 27 AREAS OF S]MILAR CHEMICAL QUAL'ITY OF GROUND WATEtR AND AREA OF -POTENTIAL SALINE-WATER INTRUSION @I.N THE CHESWOLD AQUIFER. 92 Table 14. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Cheswold Aquifer, as Shown in Figure 27 Chemical constituents in ground water in the Cheswold aquifer (concen- tration of constituents in milligrams per liter) Area 1 2 3 4 5 Dissolved <100 100-250 250-500 500-1000 >1000 solids* Hardness <75 75-100, 20-100 <40 Sodium <5 5-30 30-150 150-200 >200 Bicarbonate <50 50-200 200-400 .>400 >450 Sulfate 5-20 2-10 >10 --- Chloride 1-5 2-10 10-100 >100 Fluoride --- 0-0.5 0.2-0.5 >0.3 --- Nitrate 0-8 <1 <1 <1 silica --- 30-60 50-60 50-60 Iron and --- 0.02-0.6 0.15-0.75 --- manganese pH 7.0-8.3 7.0-8.5 >8 1- 5 *In areas 1, 2, and 3, dissolved solids x 1.36 = specific conductance (Micromhos at 2500 In areas 4 and 5, di ssolved solids x1.59 specific conductance From Cushing, Kantrowitz and Taylor, 1973. 93 marshland containing tidal salty water. The area needs considerably more observation and study to define positively the conditions of and prospects of salt-water encroachment in and from the subcrop area. The Federalsburg Aquifer In 1969, Sundstrom wrote on the hydrology of the Miocene aquifer above the Cheswold, which was recognized in electric logs of wells at Dover and Milford, Delaware. Cushing, et al, (1973) observed the hydrology of the aquifer in nearby Federalsburg, Maryland, and named the aquifer the Federalsburg in U. S. Geological Survey Professional Paper 822. Location of the Federalsburg Aquifer The configuration of the top of the Federalsburg aquifer is shown in Fig- ure 28, as defined by Cushing, et al,(1973). Develop ment of the Federalsburg Aquifer The Federalsburg aquifer has been developed in the Dover and Milford areas in Delaware. The areas of development are shown in Figure 28. Undeveloped Areas of the Federalsburg Aquifer The undeveloped area of the Federalsburg aquifer in Delaware is shown in Figure 28. ilydrology of the Federalsburg Aquifer A Miocene aquifer above the Cheswold is shown on the electric log of N105-29. The electric log shows the aquifer from a depth of 276 feet to 358 feet with intervening clayey sections. The sands total about 62 feet in thickness with the best half of the sand sections at the top between depths of 276 and 314 feet. The aquifer appears to be separated from the Cheswold in test well Mel5-29 by a dense clay 20 feet thick lying 420 to 440 feet below the surface and by a clay of lesser density (more sandy) 10 feet thick lying 94 WILMINGTON @NJWARK AREA OF USE AREA OF POTENTIAL USE NEW CAS TLE 461, lp SMYR Z D jrj,,#q Wg ff C X B 19Y 30s LSBORO -70 -600 MILES 0123456799 m &- DELMA FROM CU INS, KANTROWITZ, AND TAYLOR, 1973. 740 -r 5- FIGURE 28 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE FEDERALSBURG AQUIFER. 95 between 466 to 476 feet below the surface. The aquifer is separated from the overlying Frederica aquifer by 46 feet of clay 228 to 274 feet below the sur- face. The ele6tric log of test well Og3l-l at Gravel Hill about 15 miles south-southeast of Mel5-29 suggests the continuity of the aquifer from Milford and places it 518 to 586 feet below the land surface. The original artesian pressure in the Miocene aquifer between the Cheswold and Frederica aquifers is unknown. It probably was about the same as that in the Cheswold aquifer, which has been estimated to have been between 16 and 20 feet above mean sea level. In August 1952, the Layne-New York Company recorded the static water level in city well Le55-5 as 17 feet below land surface or about three feet above sea level. This measurement was made before an eight- hour acceptance test and is believed to be low because of pumpage for well development before the acceptance test took place. Darton (1896) reports the artesian pressure in a Frederica aquifer well at Milford 14 feet above sea level. It is possible that the measurement was taken after the well had flowed for a short period of time. Meager data on the fresh-salt water interface in the Miocene aquifers below and including the Frederica aquifer suggest the original artesian pressure was equal to or slightly greater than 18 feet above mean sea level, but less than 20 feet above mean sea level. The first pumpage of any magnitude began in 1952 when the City of Milford began using well Le55-5 in Kent County north of the Kent-Sussex County line. The well was initially tested at 500 gallons a minute. During the year of 1955, the average daily pumpage amounted to 248,000 gallons. In 1956 the average increased to 312,000 gallons a day. For the four-year period, 1958 through 1961, the pumpage averaged 260,000 gallons a day. The present rate of pumping is estimated at about 300 gallons a minute or about 400,000 gallons a day. Water-level measurements have not been made to determine the decline in artesian pressure in the aquifer. The theoretical decline that should take place at any time after pumping began at any place on the piezometric surface can be computed by using the time-distance-drawdown graphs referred to later in this section. The specific capacity of well Le55-5 at Milford was computed from an eight-hour test on August 26, 1953. The specific capacity of the well was four gallons a minute per foot of drawdown at the end of the test. Both ma- jor sand sections were'screened in the well and the well was gravel packed throughout the aquifer. It is believed that the specific capacity probably represents a maximum for-the aquifer. The well is about nine times more pro- ductive than a test well at the Torsch Canning Company, where only the upper section of the aquifer is believed to have been tested. The Torsch test well yielded only 55 gallons a minute. Another test in the Milford area reports 100 gallons a minute with a drawdown of 77 feet indicating a specific capacity of 1.3 gallons a minute per foot of drawdown. No tests of the specific capa- city of the aquifer are known outside of the Milford area. Specific- capacities of wells in Sussex County and the surrounding area are given in Tables B14 and B15. The tables show that wells,drawing water from the water-table aquifer of the Pleistocene or the Pleistocene and 96 subcropping Miocene sands have,the-higher specific capacities. Of the 42 wells listed, three wells had specific capacities of 40 or more gallons a minute per foot of drawdown, one well had a specific capacity of 34.5 gallons a minute per foot of drawdown, six wells ranged between 30 and 20 gallons per minute per foot of drawdown. All wells except one (10.6 gpm/ft) that had specific capa- cities of more@than 10 gallons a minute per foot of drawdown obtained water from the water-table aquifer., The 20 wells listed in Table B14 of low specific capacity, with three exceptions, draw water from the artesian aquifers of Miocene and Eocene age. The three exceptions are believed to be poorly con- structed wells in the Pleistocene. The 17 wells, except two, drawing water from the artesian aquifers, had specific capacities of less than five gallons a,minute per foot of drawdown. The specific capacity of a well not only controls the amount of water that can be developed from a well, but also affects the amount of power required to pump a given quantity of water. Wells with very low specific capacities are therefore costly to pump. The overall evaluation of the aquifers based on specific capacities clearly demonstrates that the water-bearing properties of the Pleistocene and subcropping Miocene are good to excellent, whereas, the specific capacities of the wells in the artesian aquifers show the water-bearing properties to range from very poor to only fair, except in the Manokin aquifer when the water-bearing properties are usually good. Pumping Tests to Determine Transmissivity and Coefficients of Storage Pumping tests made in areas surrounding western Sussex County have been used to determine the coefficients of transmissivity and storage in the arte- sian and water-table aquifers of western Sussex County. The coefficients of transmissivity and storage coupled with other hydraulic characteristics of the aquifers have been used to appraise the available water from the artesian aqui- fers. The water-table aquifer of the Pleistocene and the Pleistocene and sub- cropping Miocene sands have been appraised by other methods of applied hydrol- ogy, and are partially supported by the results of pumping tests. The coef- ficients of transmissivity and storage determined from pumping tests in Sussex County and surrounding area are given in Table B16. Some of the computations of transmissivity and storage were computed from pumping tests made for pur- poses of acceptance of the well, and in some instances, lack the refinement desired. On.the whole, it is believed that the data given for transmissivity and coefficients of storage in Table B16 are i'n the right order of magnitude and serve reasonably well for quantitative computations that follow in later sections of this report. The transmissivity of the aquifer has been computed from the pumping test made in well Le55-5 by the Layne-New York Company on March 30, 1962. The graphic plot of the pumping test data and the computation of the coefficient of transmissivity are given in Figure A7. The results of the computation give a low transmissivity of 9,400 gallons per day per foot. The low transmissivity indicated an aquifer of only fair to low water-yielding properties. Based on 97 examination of the electric logs and on inspection.of the drill cuttings,.the transmissivity and. permeability are also low at wells Mel5-29 and Og3l-l. The coefficient of storage of the aquifer has not been determined from a pumping test. The electric log of test well Mel5-29 shows that the aquiferAs tightly confined by dense clay above the aquifer and possibly less tightly con- fined by clays below the aquifer. For the purpose of computing time-distance- drawdown relation, a coefficient of storage of 0.0003 has been assumed (Figure A8). The avai .lable drawdown' in the aquifer ranges from 270 feet in well Mel5- 29 in the northwestern part of the area to the depth of the aquifer before the fresh-salt water interface is reached. The available drawdown probably ranges from 270 to 600 or more feet below sea level. More than half of the aquifer in Sussex County probably contains fresh water. This part of the aquifer under- lies the northern, northwestern and western parts of the county. Available Water from the Federalsburg Aquifer On a basis of long-term pumping, the yield of wells will be less than 300 gallons a minute, and many may be as low as 100 gallons a minute or less. In downdip areas, where the pumping lift can be much greater, yields may increase. The time-distance-drawdown relation of the effect of pumping is given in Fig- ure A8. The graph shows large drawdown in the area of the pumped well, but only 18 feet at a distance less than two miles from the pumped well, after a long period of pumping. The aquifer may support a large number of small, costly wells. The ultimate yield of the aquifer is estimated to be less than five million gallons.a day. Quality of Water in the Federalsburg Aquifer Areas of similar chemical quality of ground water in the Federalsburg aquifer are shown in Figure 29. Chemical constituents in the ground water in the Federalsburg aquifer in milligram equivalents per liter are given in Table 15. Salt-Water Problems in the Feder alsburg Aquifer The area of potential salt-water intrusion in the subcrop area beneath the wetlands adjacent to Delaware Bay is shown in Figure 29. 98 MINGTON YNJWARK MI AREA OF POTENTIAL SALINE- WATER INTRUSION SEE TABLE 15 FOR RANGE IN CHEMICAL NEW CONSTITUENTS. CAS TLE ,fr@- SMYRN z DOVER Z) 6'4 loq WR Re cr KE N AREA I AREA 2 - MILFORD LE S AREA 3 GEOR TOWN CAFO AREA 4 M LSBORO SUSSE AR EA 5 MILES 0 1 2 3 4 5 6 7 0 9 DELMAR FROM CUS NG, KANTRO WITZ, AND TA YLOR, 1973. 75* FIGURE 29 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER AND AREA OF POTENTIAL SALINE-WATER INTRUSION IN THE FEDERALSBURG AQUIFER. 99 Table 15. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Federalsburg Aquifer, as Shown in Figure 29 Chemi'cal constituents in groundwater in the Federalsburg aquifer (concen- tration of constituents in milligrams per liter) Area 1 2 3 4 5 Dissolved <100 250-500 500-1000 >1000 solids* Hardness <5 5-170 100-150 50-100 <50->200 Sodium <7 6-25 25-200 300-350 >350 Bicarbonate <55 55-225 225-450 450-750 >750 Suffate 10-20 2-10 4-25 25-150 >150 Chloride <5 .<5 2-50 50-150 >150 Fluoride <0.3 0.2-0.5 0.2-0.7 0.7-1.0 >1.0 Nitrate 0.5-51 <1.0 <1.0 <1.0 <1.0 Silica <15 15-60 50-60 50-60 50-60 Iron and manganese 0.05-0.8 0.05-2.4 0.02-0.4 0.04-3.0 >3.0 pH 4.6-7.0 L 7.0-8.5 7.5-8.0 8.0-8.5 >8.5 *In areas 1, 2, and 3, dissolved solids x 1.35 = specific conductance (Micromhos at'.25'C) In areas 4 and 5, dissolved solids x 1.55 specific conductance From Cus hing, Kantrowitz and Taylor, 1973. 100 The Frederica Aquifer Location of the Frederica_Aquifer The configuration of the top of the Frederica aquifer is shown in Figure 30. The aquifer is available for development in the southern two-thirds of Kent County and all of Sussex County,except the southeast corner. Development of the Frederica Aquifer The areas of use of the Frederica aquifer are shown by Cushing and others (1973) in Figure 30. Sundstrom and Pickett, 1968 and 1969, wrote: "The Frederica aquifer is of importance in Kent County and in the northern part of Sussex County. Sundstrom (1968) grouped the Frederica and overlying Miocene sands together and reported that in Kent County the amount of pumpage from the aquifers was about 2,600,000 gallons daily. He also reported that peak demands reached 1,500,000 gallons daily from the two aquifers in the City of Milford. The report stated that these rates of pumping in Milford probably can go no higher without rearranging rates and locations of pumping. In the northern part of eastern Sussex County, other industrial wells add to the draft on the Frederica aquifer.and draw from it to the limit during the heavy summer can- ning, vegetable and poultry processing season. The Frederica aquifer has been used in the Milford area for a long period of time. Darton (1905) of the U. S. Geological Survey reports that in 1898 he received a letter from a City official of Milford who said: 'The depth of our well is 228 feet, ten-inch diameter. We can pump from the well 250 gallons a minute. Temperature 58'F. Water rises 4 feet above the surface.' This well may be the first well to the Frederica aquifer in Milford and is at the same loca- tion at which the City of Milford is pumping water from the Frederica today." Undeveloped Areas of the Frederica Aquifer The Frederica aquifer has not been developed in about three-fifths of the area it occupies in Delaware. The potential area of use is shown by Cushing, et al,(1973) in Figure 30. 101 WILMINGTON @NJWARK AREA, OF USE AREA OF POTENTIAL USE NEW CASTLE SMYRNA _j x BRY "o .. ...... . .. MILEi -600 0123456789 am-AML-mm"An-in - - / 760 FROM CUSHING, KANTROWITZ, AND TAYLOR, 1973 FIGURE 30 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE- FREDERICA AQUIFER. 102 Hydrology of the Frederica Aquifer The average daily consumption from the Frederica and younger aquifers of the Miocene is about 2,600,000 gallons. The Frederica and younger Miocene aquifers supply about 14.5 percent of the ground water produced in Kent County in 1966. The Frederica aquifer is developed from the central part of the county southward to the county line. The Frederica and overlying Miocene sands supply the towns of Felton, Frederica, Harrington and Milford. These aquifers also supply several food processing and poultry industries. The City of Mil- ford is the largest user where peak demands have reached 1,500,000 gallons daily and probably can go no higher without rearranging rates and loci of pumping. Pumpage from the Frederica aquifer in the Milford area is estimated to be over a million gallons a day. The City of Milford pumps an average of about 50,000 gallons daily from wells I and 2 at the downtown water plant. Indus- tries processing vegetables, poultry and canning food products use water from the Frederica on a variable seasonal basis. The pumpage is about five percent of the ground water used in eastern Sussex County. The decline in water levels in the Frederica has been great because of the low coefficient of storage, the low transmissivity of the aquifer, the rela- tively low specific capacity of wells and the concentration of pumping in one locality. Decline in static level of over 100 feet has been noted in a Milford well. This large decline, however, is believed to be due, in part, to the, drawdown caused by the pumping of other wells. Records of water-level fluc- tuations are inadequate to relate correctly with withdrawal to the decline in artesian pressure on an observed basis. Two determinations of specific capacity of wells in the Frederica aquifer range from 4.3 to 5.6 gallons a minute per foot of drawdown. No determinations of specific capacity in the Frederica downdip from Milford are available. The examination of the electric log of the test well at Gravel Hill (Og3l-l) sug- gests that the water-yielding properties of the Frederica are considerably less than at-Milford. At Milford the specifi'c capacities are moderately low. Ap- proximately 25 feet of drawdown is required to produce 100 gallons a minute. At Harrington in Kent County, about eight miles west of Milford, Sundstrom (1968) computed the transmissivity of the Frederica to be 12,300 gallons per day per foot (Figure A9). The transmissivity of the Frederica aquifer has not been determined in the report area. It is believed that the transmissivity at Milford is in the same range as the transmissivity at Harrington. Downdip from Milford the transmissivity is believed to decrease. Coefficients of storage have not been determined in the Frederica aquifer. The aquifer appears to be tightly confined by dense clays and probably has co- efficients of storage similar to the Cheswold aquifer. The coefficient of storage of the Cheswold is about 0.0003 and this figure has been used for the Frederica aquifer. 103 No significant hydraulic:bound-aries in the aquifer have been ident-ified. The aquifersubcrop i.n northern Kent County is about 23 miles north of the report area and is too remote to act effectively as a recharge:boundary for pumpage at Milford. Tne transmissive properties diminish in thedowndip direction from the northwestern bounda*ry, a1tho.ugh this decline is so gradual that i.t probably should not be simulated as a'barrier boundary. The available drawdown in the Frederica aquffer,below the origi,nal arte- sian pressure is about 190 feet at Milford and proba6ly reaches about 600 feet in the southern extremity ofthe area. The time-distance-drawdown rela- tion based on an assumed storage coefficient and a coefficient of transmissivity determined at Harrington are given i.n Figure AlO. Declines in the artesian pres- sure caused by heavy pumping in Milford limit further development locally. Out- side of Milford very littl-e.pumping has taken place from the Frederica. Quantity of Water Available from the Frederica Aquiferand Limits of Development The quantity of water available from the Frederica aquifer is-not large. This is demonstrated by placing a hypothetical 'line of 11 wells across the aquifer south of Milford and computing the.drawdowns caused by pumping each well. The computations were made by applying the Theis non-leaky nonequilibrium equation to determine the time-distance-drawdown relation caused by pumping each well. The computations show that in less than 30 years (10,000 days) the allowable drawdown will be reached or nearly reached with pumping rates of only 200 to 250 gallons a minute. The combined yield of all 11 wells is only 3,600,000 gallons a day. It may be assumed that the yield of the wells would be more several miles downdip where the allowable drawdown is greater. This assumption, however, is probably not true, for there is evidence from test we'lls at Lewes and Gravel Hill that this advantage may.be 'cancelled@bytbe poorer water-yielding proper- ties of the Frederica downdip. A well to the Frederica at Gravel Hill dril'led in 1962 is reported by Paul White, the driller,to have yielded on test 30 gallons a minute. The Frederica will supply water to wells of small yield over the northern part,of the area, and wil'l.probably yield 10 or more mill-ion gallons a day to small wells properly spaced. The cost of drilling the wells and producing water from them willbe high.. The development of the aqu,ifer with wells yielding 100 gallons a minute or:more wil'l probably not produce much more than three and a half million gallons a day. 104 guality of Water in the Frederica Aquifer Areas of similar,chemical quality of ground water from the Frederica aqui- fer are shown in Figure 31. The chemical constituents in the ground water in the Frederica aquifer are given in milligrams per liter in Table 16. Salt-Water Problems in the Frederica Aquifer The area of potential salt-water intrusion in the subcrop area is shown in Figure 31. The position of the fresh-salt water interface is unknown. By applying the Ghyben-Herzberg principle (1889,1901) to the original artesian pressure of the Frederica, the fresh-salt water contact should be 600 or more feet below sea level. On this basis, the Frederica should contain fresh water throughout most of the report area. Slaughter (1962) reports a well at Bishop- ville, Maryland, less than a mile south of the area, contained salt water at 640 feet. The Manokin-Aquifer Location of the Manokin Aquifer The subcrop of the Manokin aquifer and the configur 'ation on the top of the aquifer are given in Figures 2 and 32. In the subcrop area, the Manokin is overlain by the Quaternary deposits and in much of the area is a part of the water-table aquifer of the Quaternary. Development of the Manokin Aquifer The areas of use ofthe Manokin are shown in Figure 32. In the subcrop area some wells that are considered to have the Quaternary deposits as their source of water may also draw water from the Manokin. Undeveloped Areas of the Manokin Aquifer The areas of potential use of the Manokin aquifer are shown in Figure 32 from Cushing, et al , 1973. 105 WILMINGTON @NJWARK AREA OF POTENTIAL SALINE-WATER INTRUSION SEE TABLE 16 FOR RANGE IN CHEMICAL NEW CONSTITUENTS CAS TLE C/ SMYRNA D R I cr_ K@ NIT 4 ME AREA I AREA.2 MILFO D cr fi S AREA 3 GEORGETO N SEA ORD AREA 4 JA @RE' @M.1 L L.S@B 00 5 suss@ . AREA 5 M I L,ES 0 12 -3.4 5 6 7;8 .9 DE_ I 760 FROM :CUSHING, KANTROWITZ., AND TAY R, 1973. 5. .FIGURE 3.1 ARE.AS OF SIMILAR CHEMICAL QUALITY OF GROUND ,WATER AND AREA OF POTENTIAL SALINE-WATER INTRUSION IN THE FREDERICA AQUIFER. 106 Table 16. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Frederica Aquifer, as Shown in Figure 31 Chemical constituents in ground water in the Frederica Aquifer (concen- tration of constituents in milligrams per liter) Area 1 2 3 4 5 Dissolved < solids* 100 100-250 250-500 500-1000 >1000 Hardness <5 5-200 50-70 20-50 <20->500 Sodium <10 4-50 50-150 150-300 >.300 Bicarbonate <50 50-250 250-350 350-500 >500 Sulfate --- 2-10 5-15 15-100 >100 Chloride 2-10 2-50 50-150 >150 Fluoride --- 0.1-0.3 --- 0.8-1.0 Nitrate --- <1 <1 1.0-1.2 1.0-3.0 Silica --- 30-60 50-60 50-60 50-60 Iron and manganese --- 0.01-0.4 <0.3 <0.3 0.2-2.0 pH --- 7.5-8.0 >8.01 >8.0 >8.0 *Dissolved solids x 1.55 specific conductance (Micromhos at 250C) From Cushing, Kantrowitz and Taylor, 1973. 107 WILMINGTON @Nj WAR K AREA OF USE AREA OF POTENTIAL USE NEW CAS TLE SMYRNA Z DOVER 6'4 A wlq 1?c KE N "o M I L E S 4 Oii2315(L789 N 1'6 0 FROM C SHING, KANTROWITZ, AND TAYLOR, 1973. 750 FIGURE 32 CONFIGURATION OF THE TOP AND AREAS OF USE AND OF POTENTIAL USE OF THE MANOKIN AQUIFER. 108 Hydrology of the Manokin Aquifer The hydrology of the Manokin aquifer has been studied in two parts' by Sundstrom and Pickett, 1969 and 1970. In the eastern part of Sussex County, the subcrop of the Manokin occupies an area of about 75 square miles and in the western part about 125 square miles. Thus, the Manokin becomes an inte- gral part of the overlying Quaternary aquifer over an area of about 200 square miles in Delaware. Downdip from the subcrop, the Manokin begins to become confined by overlying silts and clays and becomes artesian in water-yielding properties. The water levels in the Manokin in the subcrop area are the same as those in the overlying Quaternary deposits and range from sea levelto about 48 feet above sea level. In the artesian part, the artesian pressure at Selbyville was reported 23.3 feet above sea level in 1957. The specific capacities of 10 wells pumping water from the Manokin, or Manokin and Pleistocene, range from 10 to 49 and average 23.4 gallons a minute per foot of drawdown. Eight of the 10 wells yield 500 or more gallons a min- ute and two wells yield more than 1,000 gallons a minute.- The maximum yield is 1,200 gallons a minute. The high specific capacities, coupled with the high yield of wells, indicate that the Manokin aquifer has good to excellent water-bearing properties. The transmissivity of the Manokin artesian aquifer has been computed from pumping tests at Bethany Beach in Sussex County, near Salisbury, Maryland and at Snow Hill, Maryland. The coefficient of transmissivity at Bethany Beach is 60,000 gallons a day per foot, computed from a pumping test conducted by the Middletown Drilling Company. Near Salisbury and at Snow Hill, pumping tests by the U. S. Geological Survey gave transmissivities of 40,000 gallons a day per" foot at both places. The graphic plot of the pumping-test data and computa- tion of the coefficient of transmissivity at the Bethany Beach well Qj32-12 are shown in Figure All. The time-distance-drawdown graphs, based on the transmissivity at well Qj32-12 and an assumed coefficient of storage and rate of pumping, are given in Figure A12. The electric log of well Pf23-2 (Fig- ure A13) south of Georgetown indicates that the water-bearing properties of the Manokin are probably better at well Pf23-2 than they are at Bethany Beach; therefore, the higher transmissivity at Bethany Beach appears to be more ap- plicable than the lower transmissivities determined in Maryland. The coefficient of storage has not been determined in the report area. In the subcrop area of the aquifer the effective specific yield is probably about 0.15 and in the same order of magnitude as the overlying Pleistocene sediments. In the artesian part of the Manokin the coefficient of storage is low, probably in the order of 0.0005 or less. Gill (1962) reports the determination of 26 coefficients of storage from aquifer tests in the Cohansey sand (Manokin?) in Cape May County, New Jersey, ranging from 0.0027 to 0.0012. The New Jersey coefficients may suggest some vertical leakage to the aquifer. In computing the time-distance-drawdown graphs in Figure A12 a coefficient of storage of 0.0005 was used. The Manokin aquifer does not reach sufficient depth in the report area to encounter the interface between fresh and salt water. The interface occurs 109 several miles downdip from the southern boundary of the report area and in the coastal outcrop area several miles east and southeast. The hydraulic boundary that is important to the artesian part of the Manokin aquifer is the favorable recharge boundary of the subcrop. The sub- crop is so close to the artesian part that the favorable effect of recharge from the subcrop will be substantial throughout the artesian portion. In using the time-distance-drawdown curves in Figure A12 to estimate the effect of pumping in the artesian area, favorable corrections of drawdown will have to be computed, based on the position of pumping and the recharge effect for that position. The recharge corrections can be computed by applying the image well theory described by Ferris, et al, (1962). In the downdip direction, or else- where in the Manokin, no barrier boundaries are believed to exist close to the report area. The available drawdown in the Manokin in the subcrop area includes the thickness of the Manokin aquifer plus thesaturated thickness of the overlying Pleistocene. The saturated thickness of both aquifers ranges from about 90 to about 200 feet. In the artesian part of the Manokin, the available drawdown ranges from about 100 to 225 feet. Quantity of Water.Available from the Manokin Aquifer The quantity of water available from the Manokin is considered in two parts. The first part is the amount available in the 200 square miles of sub- crop shown in Figure 2. The second part is the amount from that area of the Manokin which is confined and under artesian pressure. The amount of water available from the 200 square mile subcrop area is included in the available water from the Quaternary water-table aquifer discussed later. The available water from the artesian part of the aquifer is estimated to be 40 to 50 million gallons a day. Quality of Water in the Manokin Aquifer Areas of similar chemical quality of ground water in the Manokin aquifer are shown in Figure 33. Chemical constituents in ground water in the Manokin. aquifer in milligram equivalents per liter are given in Table 17. Salt-Water Problems in the Manokin Aquifer Potential saline intrusions into the subcrop area of the Manokin are shown in Figure 33. The interface of fresh-salt water in the artesian part of the aquifer is probably too far downdip in the aquifer to be a problem in Delaware. 110 WILMINGTON @Nj'#ARK AREAS OF POTENTIAL SALINE-WATER INTRUSION SEE TABLE 17 FOR RANGE IN CHEMICAL CONSTITUENTS. NEW 4, CAS TLE SMYRNA Z DOVER K E N B191y MILFORD. AREA I LE S GEORGETOWN SEAFORD MILLSBORO AREA SUSSEX M' LES 0 2 3 4 5 6 7 a 9 DELMAR AREA 2 FROM CUSHING, KANTROWITZ, AND TAYLOR, 1973 750 G GEORGETOWN EORGETOWN MILLS MILLS X X S @E FIGURE 33 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER AND AREAS OF POTENTIAL SALINE-WATER INTRUSION IN THE MANOKIN AQUIFER. Table 17. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Manokin Aquifer, as Shown in Figure 33 Chemical'constituents in ground water in the Manokin aquifer (concentrati.on of con- stituents in milligrams per liter) Area 1 2 Dissolved solids* <150 150-250 Hardness 5-60 60-150 Sodi.um 5-20 20-55 3icarbonate 3-125 100-225 Sulfate 0-23 0-7 Chloride <10 10-60 Fluoride 0.0-0.2 0.0-0.3 1 Nitrate 0.0-6.0 0.1-3.5 Silica 20-40 15-45 Iron and 0.3-5.0 0.06-12.0 manganese pH 6.0-6.8 6.4-8.0 (Micromhos at 250C) *Dissol.ved solids x 1.68 = specific conductance ,From Cu shing, Kantrowitz and Taylor, 1973. 112 The Pocomoke Aquifer. Location of the Pocomoke Aquifer The configuration of the top of the Pocomoke aquifer'is shown in Figures 2 and 34. The aquifer lies directly beneath the Quaternary water-table aqui- fer. Throughout the area occupied by the Pocomoke aquifer in Delaware, the water-table aquifer of the Quaternary (Pleistocene) and the Pocomoke are com- mon to each other. Development of the Pocomoke Aquifer The areas of use of the Pocomoke are shown in Figure 34. In some places the deeper water table of the Pocomoke is preferred because of the better quality of water contained in it. Undeveloped Areas of the Pocomoke Aquifer The undeveloped area of the Pocomoke in Delaware is shown in Figure 34. Hydrology of the Pocomoke Aquifer The hydrology of the aquifer is discussed later in this report as a part ,of the water-table aquifer of the Quaternary (Pleistocene). Quality of Water in the Pocomoke Aquifer Areas of similar qu6l,ity of ground water in the Pocomoke aquifer are shown in Figure 35. Chemical constituents.in the ground water in the Pocomoke in milligram equivalents per liter ,are given in Table 18, Salt-Water Problems in,the Pocomoke Aquifer The area of potentialsalt-water intrusion into the Pocomoke aquifer in Delaware is shown in Figure 35. 113 YN WILMINGTON ,fWARK AREA OF USE AREA OF POTENTIAL USE NEW CAS TLE c/ SMYRNA DOVER KE NT BRY 390 MILFORD SEAFORD s u MILES. 0123456769 DELMA FROM C SHING, KANTROWITZ, AND TAYLOR,1973 FIGURE 34 CONFIGURATION OF THE TOP AND AREAS OF USE 75- AND OF POTENTIAL USE OF THE POCOMOKE AQUIFER. 114 MINGTON TNJWARK 'AREA OF POTENTIAL SALINE-WATER INTRUSION SEE TABLE 18 FOR RANGE IN CHEMICAL CONSTITUENTS. NEW CAS TLE SMYRNA Z DOVER X KE NT B R-Y MILFORD AREA 2 GEORGETOWN SEAFORD AREA I MILLSBOR SU SEX AR' A 3 M' LES 0 1 2 3 4 5 6 7 9 9 L DELMA - REJ 4 Tie FROM CU HING, KANTROWITZ, AND 11973. TAY OR FIGURE 35 AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND 750 WATER AND AREA OF POTENTIAL SALINE-WATER INTRUSION IN THE POCOMOKE AQUIFER. 115 Table 18. Quality of Ground Water and Area of Potential Saline-Water Intrusion in the Pocomoke Aquifer, as Shown in Figure 35 Chemical constituents in ground water in the Pocomoke aquifer (concentration of constituents in milligrams per liter) Area 1 2 3 4 Dissolved <100 100-150 250-500 500-11000 solids* Hardness <25 25-50 50-200 50-200 Sodium <10 10-25 35-175 175-350 Bicarbonate <25 25-125 180-430 190-440 Sulfate 1-17 --- <1-6 <1-30 Chloride 3-15 5-15 20-100 100-450 Fluoride 0.0-0.3 0.2-0.5 Nitrate 0.0-29 0.2-4.1 --- Silica .20-40 --- 15-30 <15 Iron and 0.0-20 --- 0.3-3.0 0.0-2.0 Manganese pH 5.6-7.1 -7 7.3-8.4 *Dissolved solids x 1.53 specific conductance (Micromhos at 250C) From Cushing, Kantrowitz and Taylor, 1973. 116 The@Quaternary Water-Table Aquifer AvailabiliU of Water from the Water-Table Aquifer in the Coastal Plain in New Castle County The available water from the water-table aquifer i n the Coastal Plainof. New Castle County is small in terms of an adequate supply to large-capacity wells of 500 or more gallons a minute each. This is especially true north of the Chesapeake and Delaware Canal. Although the water-table aquifer where the Pleistocene sediments contain 10 or more feet of saturated material covers 182 square miles, the thickness of saturation of 40 feet or more needed to assure large-capacity wells occupies only 11 square miles, of which eight are south of the Chesapeake and Delaware Canal. The Pleistocene water-table aquifer prob- ably will supply large-capacity wells in these isolated areas in amounts equal to the available recharge which would amount to about three mil,lion gallons a day north of the canal and about eight million gallons a day on the south side of the canal in the Middletown-Odessa and Smyrna areas. The total available supply to'large-capacity wells in the county:is about 11 million gallons a day. The Pleis tocene aquifer is an important source of water to small wells over the entire area of 182 square miles where it has 10 or more feet of saturated thickness. Although the Pleistocene aquifer is a poor source of large supplies of water in the county, it has importance in maintaining the base flow of streams, in furnishing plant life moisture, in maintaining a reservoir of recharge water for the artesian aquifers, and in maintaining the hydraulic gradient that halts the ingress of salt water along the Delaware Estuary and Bay. The prospe cts of supplementing the water supply of.New Castle County by the use of artificial recharge to the ground-water reservoir of the Pleisto- cene aquifer is brought into focus in the report by Sundstrom (1971). Whether or not such recharge is practicable and feasible can be told only after re- quired research and study are made. Availability of Water from the Quaternary and Miocene Outcrop Water-Table Aquifers in Kent County The Pleistocene deposits cover about 88 percent of the land area in Kent County and almost everywhere small to moderate supplies for rural and-domestic purposes can be obtained, although the aquifer may be only a few feet thick. In other parts of the county, where the Pleistocene aquifer is thickenand in many instances underlain by Miocene outcrop or near outcrop sands, the total aquifer.thickness has been observed to reach a thickness of 178 feet and yields of 1,000 gallons a minute are reported.' 117 In appraising the availability of water from the,Pleistocene and Miocene outcrop aquifers, it must be kept in mind,that any development of the water- table aquifers is rel:ated and wil'l have an effect on the fai'rweather discharge to the streams. If the low flow stream discharge can be neglected, then the Pleistocene and@underlying Miocene outcrop aquifers probably could be pumped at a rate of 100 million gall'ons daily or more without seriously depleting the reservoir. If suc4a high rate of withdrawal is undertaken, there might be an associated problem of salt-water encroachment close to sources of salt water unless proper planning and pumping,rates are maintained. The problem is dis- cussed in the report by Sundstrom and Pickett, 1968. Udrolog of the Pleistocene and Subcropping Miocene Water-Table Aquifer in Sussex County The Pleistocene and, in some localities, subcropping Miocene sands form a water-table aquifer that supplies water to wells in all of Sussex County. The aquifer provides approximately 90 percent of the ground water pumped in the area. The water-table aquifer not only supplies water to municipalities, industries, irrigators, and the rural area; but also provides (1) a reservoir of water available to the artesian aquifers as a continual source of recharge; (2) a supply of water furnishing the fairweather flow of the streams; and (3) a supply of water that maintain@s the hydraulic gradient that prevents ingress of the salt water into the ground-water reservoirs from Del-aware Bay, the Atlantic Ocean, the tidal estuaries and the tidal marshlands in part of the coastal area. In some of the coastal area, the altitude of the water-table is not adequate to protect the deeper sections of the water-table aquifer. The many functions of the water-table aquifer make it necessary to give considera- tion to each of the functions the aquifer is now providing and integrate into these functions the effect of new and further development of the aquifer. If new development is done wisely, the aquifer can supply large quantities of ad- ditional water without seriously harming its contribution to the fairweather flow of the streams or its role in protecting against salt-water encroachment. In fact, there are many thousands of acres where the water table is too high, and withdrawal of ground water would help alleviate swampy conditions and excess evaporation and would induce more recharge to replace water pumped. Estimated Thickness of Saturation in the Water-Table Aquifer The thickness of saturation in the water-table aquifer in the Pleistocene in Sussex County has been,computed and is illustrated in Figure 36. The thick- ness of the saturated portion of the Pleistocene has been determined from the altitude of the water-table aquifer in 467 wells and the base 'of the Pleisto- cene, as shown in Figure 36. Records of wells giving the land surface, the altitude of the water-table, the depth of penetration in the water-table aqui- fer below sea level, the depth of the base of the Pleistocene and in some wells and the known thickness of the water-table aquifer is given in Table B18. The thickness of saturation in the Manokin has been estimated from its thickness 118 754 6 -@e le ldl@d 75-115' 1Id .1-11 1. NIU& MILFORD -' IIIIII - - - BOUNDARY BETWEEN EASTERN AND WESTERN 70 SUSSEX COUNTY REPORTS. 1/0 KENT CO 90 !!7x0co- 100 @tb GREENWOOD* 11 ml a -116 a o go *LEWES %10 1140, 80 140 150 /D BRIDGEVILLE S /Do /to 90 80 REHOBOTH BEACH 90 C) GEORGETOWN 100 0 ( _3846 \00 BAr C) SEAF 90 so fIXIIAN RIVER BAY 01) @o C) 80 90 oo o o_ LALIR too o BETHANY r. @b 10. BEACH o 110 120 110 0 ,ba 110 C) mo 13o- 14 1 AO 14 14> 9o 130 %3. Izo I'D FENWICK ISLAND 0 DELMAR SELBYVILLE FIGURE 36. MAP SHOWING THE SATURATED. THICKNESS. OF THE WATER-TABLE AQUIFER IN THE- PLEISTOCENE DEPOSITS IN SUSSEX OOUNTY. 119 in the eight wells that penetrate the aquifer. The average thickness of the Manokin in the eight wells is 45 feet, and this thickness is previously used in the computations of water in the Manokin subcrop. Three wells that penetrate the Pocomoke subcrop have thicknesses of water-bearing sand that average 30 feet. This average is used in the later computations of available water from the Pocomoke subcrop. No estimate of the thickness of ot her subcropping Miocene sands was pos- sible because of lack of data. The other subcrops, while adding to the total supply of the water-table ground-water reservoir, are unknown, but are believed to be minor when considering,the aquifer as a whole. The altitude of the water table in the Pleistocene is known With much more accuracy than is the position of the base of the Pleistocene. For this reason, the thickness ofthe water- table aquifer, including the Manokin subcrop, ranges from 41 to 194 feet. Estimated Volume of Saturation in the Water-Table Aquifer The volume of saturated material in the water-table aquifers of the Pleisto- cene, the Manokin subcrop and the Pocomoke subcrop has been computed. In com- puting the volume of saturated material, the volume of saturated material above and below sea level was first computed. The report area was subdivided into 5-minute grids of latitude and longitude, as shown in Figure 1. The area within each grid in acres was determined. The average.thickness of saturation above sea level was determined from the altitudes of the water levels of wells within the grid. The volume of saturation in each grid in acre-feet is the product of the area.of the grid in acres multiplied by the average thickness of satura- tion*in feet. The results of these computations for the,volume of saturation in the Pleistocene above and below sea,level are given in Table B19'. In deter- mining the thickness of saturation.below.sea level, the base of the Columbia Group (Pleistocene) is shown in Figure 11. The sum of the altitude above sea level, taken from the average altitude of the water level and the depth to the base of the Columbia Group, equals the total th.ickness of the saturated portion of the Pleistocene at concurrent points of measurement. The thickness of- saturation in the Pleistocene is shown-in Figure 36. The saturated subcrops of the Manokin and Pocomoke both are-below sea level. -The volumes of saturated material in'both aquifers have been computed by the product of the area in acres of the aquifers multiplied by their thickness in feet.. The Pleistocene aquifer contains about 22 million acre-feet of saturated material above sea level, and about 40 million acre-feet of saturated material below sea level, totaling 62 million acre feet. The volume of saturated mater- ial in the subcrop of the Manokin is estimated to be 4,500,000 acre-feet. The volume of saturated material in the subcrop of the Pocomoke is only 1,900,000 acre feet. The total volume of saturated material in the water-table aquifer of the Pleistocene and subcropping Manokin and Pocomoke aquifers is about 68 million acre-feet, or more than 20 cubic miles. 120, Effective Yield of the Water-Table Aquifer The sands and gravels that form the water-table aquifer will yield only a part. of the water contained in storage when the aquifer is pumped or drained by natural ground-water flow to a stream, spring or lake. Many water-table aquifers, similar to that of Sussex County, have effective specific yields to wells or natural drainage of,11 to 19 percent of the volume of the aquifer unwatered. In Sussex and Kent Counties, two wells tapping the water-table aquifer were observed and the declines during the extreme drought period from June to October, 1968, were analyzed for effective yield. Likewise, the rises @uring the extreme wet period from July 21 to August 20, 1969, when,13.27 inches of rain fell at.Georgetown, were analyzed for effectiverecharge to the aquifer. Figure A14 shows graphically the fluctuation in the two wells from March 1967 to December 1969. The effect of drought that extends over a long period of time, generally, is subject to analysis with better results because during the prolonged drought little or no recharge is taking place over the area under study. In making recharge analyses during periods of heavy preci- pitation the amount of rainfall often varies widely from place to place, and the water levels observed at one place may not be precisely correctin magni- tude to correlate with precipitation that was measured elsewhere. The period of drainage analyzed extends from water-level measu rements made in wells Md22-1 and Qe44-1 on June 6,,1968, to the measurements made in the wells on October 4, 1968. During this period the precipitation at,George,town was deficient by 9.76 'inches and at no time, except July 4, 1968, did more than an inch of precipitation fall...The rainfall on July 4 was 1.35.inches. No rainfall during the'period is believed to be adequate to af 'fect the decline of the water table. The water table declined 5.8 feet in well Md22-l and 5iO feet in well Qe44-1 between June 6, 1968, and October 4, 1968. The gravity drainage or specific yield 'in terms of deficiency in precipitation to.total decline in well Md22-1 is equal to 9.76/5.8 x 12 = 14.0 percent and in well Qe44-1 is equal to 9.76/5.0 x 12 = 16.2 percent. The figures of 14.0-and 16.2 percent represent a ratio of the deficiency in rainfall.to the decline in water level and approaches the true drainage or specific yield value. The average of these two values is 15.1 percent.: Sundstrom (Sundstrom and Pickett, 1968) in discussing the effective specific yield of the water-table aquifer,in Kent County, used 15 percent for his quantitative computation of the aquifer. The same figure is used for Sussex County. The period of recharge Ito,the aquifer analyzed extends from water-level measurements made in wells Md22-1 and Qe44-1 on July 23, 1969, to a measurement made in well. Md22-1 on September 11, 1969, and by an estimated water level in well Qe44-1 on September 11, 1969, by extending the rate or rise observed from. July 23 to August 28 onward to September 11, 1969. The rise in water level for the above period, July 23 to September 11, 1969, was 5.7 feetin well Md22-1 and 5.1 feet in well Qe44-1. During the period July 19 to August 21, 1969, a period of 34 days, 13.27 inches of rain fellat Georgetown. Based on an aver- age annual rainfall of 46.75 inches of rain at G6orgetown, the 13.27 inches of rain in a 34-day period represents an excess over average precipitation of 8.91 inches. The excess precipitation, when related to the rise in water levels in in wells Md22-1 and Qe44-1, shows that excess precipitation in depth is equal, 121 to 14.6 percent of the rise in water level in well Qe44-1 and 13 percent of the rise in water level in well Md22-1. Meyer and Bennett (1955) show graphically the water-level fluctuations in a well at the nearby Salisbury, Maryland, airport in response to precipitation that occurred from May 13 to 18, 1948. The graph is of value in quantitative analysis of the Pleistocene water-table aquifer in reflecting the relationship of water added to the aquifer to the volume of material saturated. During the five-day period 5.80 inches of rain caused the water level to rise to 48.12 inches. The volume of water precipitated on the surface above the aquifer amounted to a little more than 12 percent of the volume of the aquifer saturated. In the early part of the five-day period 2.31 inches of precipitation fell, causing a rise in the water table of 16.2 inches. During.this period, the vol- ume of water from rainfall is more than 14 percent of the volume 'of material saturated. The figure of 14 percent is nearly representative of the effective specific yield and approaches closely the figure of 15 percent used by Sundstrom and Pickett in the Kent County, Delaware, study (1968) and in the Sussex County studies (1,969 and 1970). The Water-Table Aquifer and Its Relation to Streamflow The water-table aquifer of the Pleistocene supplies nearly all of the fairweather flow of the streams. When the stage,of the aquifer is high, the discharge from it is high. When the water level in the aquifer diminishes, its discharge also declines. Precipitation or lack of precipitation causes the aquifer to fluctuate considerably, often in short periods of time. Figure A15 shows the composite fluctuation in 13 water-table wells in Delaware over a period of more than 11 years. Examples of the relation of the-stage of the ground-water reservoir to the flow of streams can be demonstrated by the fluc- tuations in wells Md22-1 and Qe44-1, shown in Figure A14 and the relation of'. the fluctuation of stage of the water table to the discharge of the Nanticoke River near Bridgeville, Delaware, and to the discharge of the Pocomoke River across the state line near Willards, Maryland. In June, 1968, the water level, in well Md22-1 measured 6.6 feet below,land surface. As the drought continued, the water level in well Md22-1 was measured 9.9 feet below land surface and in well Qe44-1 was measured 11.6 feet below land surface. The.average daily di.s- charge of the Pocomoke River for the same period was 49.2 cubic feet per second. In September 1968, the drought had decreased the average monthly flow of the Nanticoke to 34.2 cubic feet per second. The relation of ground-water stage to the average monthly discharge of the two rivers is summarized in Table.B20 (Sundstrom and Pickett, 1970). Table B20 shows that the average,daily dis- charge for the Nanticoke dropped from 46.9 million gallons,a day to 22.1 mil- lion gallons a day- representing'a decrease in discharge of 24.8 million gal- lons a day in the iour-month period. The average daily discharge of the Poco- moke dropped from 31.8 million gallons a day to three mil.lion gallons 'a day in the four-month period. During the drought period, the flow reams was mostly water-fed by the water-table aquifer. of boIth s t In a three-year study of the Pleistocene wAter-table aquifer in the Salis- bury area of Maryland, a few miles south of western Sussex County, Rasmussen 122 and Andreasen (1959) found very close relation between the stage of the water table and the base flow of Beaverdam Creek. The relation is shown in Figure A16. Similar studies now in progress by the U. S. Geological Survey and the Delaware Geological Survey will soon define the relation of the stage of.the water level in Pleistocene wells with the,stage of the Nanticoke and other Delaware streams in more detail. The studies are important in defining the ground-water contribution and the overland runoff to the streams. Specific Capacities of Wells in'the Water-Table Aquifer Specific capacities have been determined in 72 wells in the water-table aquifer. In 28 of these wells the specific capacity ranges-from 2.2 to 10.0 gallons a minute per foot,of drawdown. All of the wells-having a specific capacity below 10 are smaller-diameter wells, generally used for rural water supply. The low specific capacities@ of these wells are not representative of the specific capacities that would be obtained from larger-diameter and better-constructed wells at the same location. The 44 wells that have higher specific capacities, ranging from 10.0 to 49.0 gallons a minute per foot of drawdown, are more representative of the better-developed wells in the area. The specific capacities of the better wells-are better indicators of the.true water-yielding properties of the aquifer. Of the 44 wells that have s.pecific capacities over 10 gallons a minute per foot of drawdown, 29 wells range from 10 to 20 gallons a minute per foot of drawdown, nine wells range from 20 to 30 gallons a minute per foot of drawdown, two wells range from 30 to 40 gallons a minute per foot of drawdown', and four wells have specific capacities above 40 gallons aminute per foot of drawdown. The average specific capacity of the 44 wells Is 27.3 gallons a minute per foot of drawdown. The specific capacity, of individual wells is given in the report by Sundstrom and Pickett (1969) and.in the Table B16. Transmissivity of the Water-Table Aquifer The transmissiivity of the water-table aquifer has been determined from pumping tests conducted at Lewes and Rehoboth Beach by the V. S.. Geolog.ical Survey during the course of ground-water studies at the two cities. Seven pump'ing tests, five at Lewes and two at Rehoboth Beach, give coefficients of transmissivity ranging from 45,000 to 135,000 gallons a day per foot. The average of the seven determinations is 88,000 gallons a day per foot. One coefficient of transmissivity was determined at Laurel by.permeability deter-, minations made from samples collected in a place while diggi'ng a well by hand. The transmissivity was later determined by multiplying the average permeabil- ity by the thickness of the aquifer. The computed transmissivity at Laurel is 114,000 gallons a day per.foot. For purposes of quantitative study and analyses inthis report, a transmissivity of 100,000 gallons a day per foot has been used. Transmissivities determinedfrom individual tests have been reported by Sundstrom and Pickett (1969). 123 The time-distance-drawdown graph in Figure A17 demonstrates the effect of pumping a well at a rate of 1,000 gallons a minute on'the water' levels in the water-table aquifer after pumping continually for 100 and 1,000 days at dis- tances ranging from 10 to 25,000 feet. Figure A17 is based on the assumption that no recharge takes place during the period.of pumping and that the aquifer is not affected by gravity drainage. For the 100-day pumping period, no re- charge from rainfall would be unusual and for the 1,000-day period would be impossible, according to rainfall records. Figure A15 shows the effect of recharge from rainfall and drought on the water level in the water-table aqui- fer. Figure A15 clearly demonstrates by fluctuations in the water level in 1951-52 and in 1957-58 that the effect of rainfall and drought on the water level in a few months is greater than the effect of pumping a well continuously for 100 days on the water level in the Water-table aquifer 1,000 feet from the pumped well. Figure A17 also demonstrates that during the 100 days of continu- ous pumpingi the effect of pumping on the water'table would only reach less than a mile, and that beyond 1,000 feet from the pumped well the effect would be less than four feet. The graphs in Figure A17 have been computed using a coefficient of transmissivity of 100,000 gallons a*day per foot and a specific yield,'or coefficient of storage, of 0.15. Table B17 gives the yield and specific capacity of large-diameter wells tapping the Quaternary de osits and estimated transmissivity of the aquifer, from Richard H. Johnston M74). Coefficients of Storage in the Water-Table Aquifer Coefficients of storage have bee n determined from observations in three wells during pumping tests to determine aquifer coefficients. All of the determined values are too low. The true coefficient of storage probably ap- proaches the effective specific yield of the aquifer. Earlier discussion in this report indicates that the effective specific yield is in the order of 0.15. In nearby Salisbury, Maryland, Rasmussen and Sla.ughter (1957) report a coefficient of storage for the aquifer of 0.15. The figure is in harmony with the effective specific yield determined in this study from the fluctuation of water levels in wells Md122-1 and Qe44-1. The figure [email protected] was used for the effective specific yield in appraising the water-table aquifer in Kent and Sussex Counties (Sundstrom and Pickett, 1968 and 1969),and is the figure used. herein. Recharge,to the Water-Table Aquifer Recharge to the water-table aquifer is a substant ial part of the precipi- tation that falls on the surface of Sussex County. The average amount'of@pre-. cipitation is 46.55 inches annually. On an average daily basis, the precipita- tion is equal to slightly more than two billion gallons a day for the report area or about 2,200,000 gallons a day per square mile. Barksdale and others (1958) estimated.20 to 21 inches of the annual rainfall was available to recharge the outcrop and subcrop of the Raritan aquifer.in Delaware. The same 124 amount or slightly more should be available to recharge the water-table aquifer in Sussex County. In the Salisbury area of Maryland, Rasmussen and Andreasen (1959) report recharge to the water-table aquifer of 42.63 inches over a two- year period. In Sussex County, an average annual recharge of 21 inches seems reasonable. If this estimate is reasonable, then the average annual recharge to the area as a whole is about 950 million gallons daily, or one million gallons per day per square mile. The recharge is adequate to keep much of the aquifer brimful as shown in Figure 37, and in 'several areas swamps are general. Pumpage in parts of the aquifer might lower the water table and induce con- siderably more recharge. The stage of the aquifer-is illustrated in Figures 38 and 39. Discharge of the Water-Table Aquifer Discharge from the water-table aquifer is a continuous process. It pro- vides the fairweather flow of the streams, the ground water that is used in Sussex County, the recharge to the underlying artesian aquifer's and.a part of the evaporation directly to the atmosphere, and a part of the transpiration of, trees and plants growing in the area. The discharge of the water-table aquifer to the fairweather flow of the streams is quantitatively the mPstimportant. Many hydrologists have studied the relation of ground-water discharge to the total discharge of streams. Two important studies of this relation have been made in the nearby Beaverdam Creek watershed just south of the report area in Maryland. Rasmussen and Andreasen (1959) made a two-year study and found that nearly 26 percent of the rainfall that fell on the watershed reached Beaverdam Creek as ground-water discharge. Meyer and Bennett;(1955) analyzed. 14 years of streamflow records and-reported the average daily discharge of ' the stream as '764,000 gallons a day per square mile, of which 602,000 gallons a day per square mile was ground-water discharge. For the purpose of this study, Meyer's and Bennett's figure for ground-waterdischarge has been used because the precipitation during the two-year study of-Rasmussen and Andreasen was 5.64 inches annually le.ss.than normal.. The discharge of the Nanticoke River over a period of 24 years has aver- aged 776,000 gallons a day per square mile. The Nanticoke average discharge per square mile is almost identical with that reported by Meyer and Bennett. Using the same proportion for ground-water discharge as Meyer and Bennett used, the ground-water discharge of the Nanticoke River near Bridgeville was 611,000 gallons a day per square mile. Based on this analysis and applying it to Sussex County as a whole, the gravity drainage of ground water received by streams amounts to about 580 million gallons a day, or about 61 percent of the recharge to the aquifer. The overland or flood runoff to streams that does not enter the ground-water reservoir averages only 157 million gallons a day. 125 75-146 75135' @5.[3o' 7,,.1z5,1.2o, 75-115' 75-116 [email protected] ozISOURCE OF DATA! zo "2 U.S. GEOLOGICAL SURVEY (1964); WATER TABLE. *14So NURFACE -DRAINAGE AND ENGINEERING SOILS MAPS. *5 HYDROL GIC INVESTIGATIONS ATLASES r99,101.103 ml@FORD 107, too. 109,119,121 AND 122. - -@@..Iq to '*5 . . . BOUNDARY BETWEEN EASTERN AND WESTERN r.1 *11 SUSSEX COUNTY REPORTS. '17 to % #7 .12 *12 *13 013 04 *it *9" -is 's *is *14 -.95-6 *9 _S *7 .9 ra 87a 06 -5 *45 4 7@T :3.-6 4139to6 IENT Co 'S .'T _- USS '@ '2 i. '4 *4 *4 Co 16 98 *5*3 3*3 is if *6 615 .5 0.6GRAINWOOD @*3 \1 -_7*15 '*6 '09, *3 *4 *7 08-%*4 %.7 .3.,N.6 -4 '4 6 *4\MILTON.14 ""'A `4 *5 It .35*if is- * *25 4-3 '59to2.4 0-235 80Be to IS .16 012 *3 *LEWES *4 -4 .54.4 *2 -3 .3,% . 05 *6 _4 19- @3 -5 '2 15 '68 :3 e, *4 4 5\\3 pit '16 12 _.3q,,5,j *2-4 ?BR!DIE `6 040*12 is '4 *3 OGEV -12 05 -6 '7 18 o-3 ..3 is ite5*6 "7 3. "5 *4 09 *17 114-Q 08 11 015 *6 'o'7 635-e5 *5 *7704 *5 '6 !7 I%to *4 .63.5(6400to 'is0'14 .10 REHOBOTH *5916 BEACH 64 '02 *4 *a0 .1 '9 14 10 *9 _3 '-3 -4 OEORGETOWN *9 to 70 to *,a 1*9 *3 .3 @'5 .7 5-03.. 30.32'*14 19 @.:4 3.4 4-'.-5 to 4. to5li" mr@ao -3r4d *6 13 '19 *4 "6.7*77.7 gAr 'N *4 !4 5. 'TI'It Ir.?*13 is .5 SEAFORD '%6 oil ? *,,77' 4@;5..9 *a .8 3106 7e 14 '07 *7 .4 15 '*7 0 *4j5. *5 / *1 04 "7 e, *163 2.6 *13 0" 0" 604* *7 ,o,!9 .7 '1 40,% *6 7* 150 *13 .02 '100`7 *7 09 066301* .7 INDIA .0 *4 .6 Is 14o is. S. -6aNRIVER -5@@ *3 .6 06 es .6 A:54is -15 is AY F1271la is -38-35* 3. -4 .-it,56@' *5 `7 MILLSBORO 906 66 .5 -47T -4 125.617. -7 to. 15 '135%to. *6 UUJREL6'7-'157 *79:'5 to:, 121*.55605 09 0 @*015 '0553 5*'4 *3 to 15 -'*14 '*to 19 97 *5 *9 0,2 *9 69 68 to 76., .6 4112 -*3 *4 *7 .9 *5 *3 BETHANY 'T *[o *770-5 11Z1 *14 @2 .*2 *6 BEACH *64B09 Be 414 *4, *3 '12 07 .9 \ %*43*4 *3 05-40 @6 '[email protected]. @@S *7 *4 08 *7 ?3. 06 -6 '06 to *6 05 e4 *4 -3. 05 *4 07 .76*4 04 .6 *4 *6-2 *14 *7 -n' t3 to #46-70 !6,Ior ,*64.07 -7* '&0 tes '4 *4 4' .5 .0 .4*62*5 02 .6 ge 132'e2 *4 5 04 `6 *%6 qr 7 -9 -11 '7S.3 .5 06 074 . @F_27 to -4 .44 &6 #3 sgo -s B.6 .1 is 4- '2 to -3 SELBYVILLE4 15 ISLAND FIGURE 37.'MAP SHOWING DEPTH TO WATER IN:FtET-BELOW LAND SURFACE IN-THE WATER-TABLE AQUIFER IN SUSSEX COUNTY 126 751-40' 75. 12e TIP& Te-, 75-05' N IS I 641 MILFORD ';IP112--@4"All oil *13 eB zo *3 44 33J36 '3539 24 29 26 1? [1 Io s 6 52 1, 049 40 220239.151I'DA054 4: 41 *21*-.-'593 45 016 KENT CO. 9 gU-SSEX 384 5 0.352 47 45o 2346 31 76*94o43 0 48 2 015 14a Is 39 * MILTON0 3@z o014 02 3, 19 7 60 so,7*LEWES 29 *115.4 31 Is416 45' 400*24 23 21321 3Is 9135 40 Is 113 *14013 ID3 46o..32 *22 22 13 *14 .14 16 REHOBOTH 48 .37 35 31 115olo BEACH *44 41, 14T6. 'a 32'6 IS 4 GEORGETOWN 141 39 37 '344$1507 45 43 26o5 -38-40! ...TOuII TE.VA1.: 5FEET FROM ... LEVEL 111 63502REHO807H To lo FEE ABOVE SEA LEVEL AND 10 FEET FROM 441 320'8A Y 10 FE 46 240 LE V ET ABOVE SEA LEVEL TO 50 FEET ABOVE SEA 6. EL, .4000*31 C' C..TOURS, C NTROL POINTS. AND WATER LEVEL 45329 2130024 015 ALT ITUDES FoRaM U.S. GEOLOGICAL SURVEY HYDROLOGIC o43 22 280 1400oT*42 ATLASES OF T E HARRINGTON, MILFORD, MISPILLtON a426e$210, 0 RIVER, GREEN WH D, ELLENDALE. MILTON. LEWES 43 35 *16 014 DO 60 GEORGETOWN, HARBESON,REHQBOTH BEACH, TR@p 15 *33 SO 27 0150Is 12 POND, MILLSBOR N6 IRANKFORD AND BETHANY BEACH 4*2 10 013 1311 QUADRANGLES A AREA. 44 21 15 11 INDIAN 47 31. *2.T25*IS667 MIL SB RO6 43 38 27* Is 0 aSo2*3 46 445 e25 17 '12 '164 :4004 *47 31 29 51 19 11 *351364 *3 654 1 e 46833 27 6@ 60 **23 BETHANY y BEACH 42 @4' 91@50B -B 5 To el@ liee e35 3 043 21 Is- 8 3 37 37'327 34..*20 23 1 34 2 83o 23 18, 044 -3e.3d -22 is- 16 32e 32 ze 3o 31* 029 10 39 380 37 ,. 3506 32,0339 22 le sELBYVILLE illis 6%. FENWICK a_tI5 o- ISLAND 3s 36 3433 FIGURE 38. MAP OF EASTERN SUSSEX COUNTY SHOWING THE ALTITUDE OF THE WATER TABLE IN THE WATER-TABLE AQUIFIER OF THE PLEISTOCENE AND SUBCROPPING MIOCENE SANDS. 127 75-14d 75)3d =171 75J2O' 75-115' 7w 1to' 75-105 -1E 10 ILE$ CONTOURS, CONTROL POINTS AND WATER LEVEL ALTITUDES FROM U.S GEOLOGICAL SURVEY N HYDR LOGIC ATLASES OF THE MILLSBORO, ELLENoDALE, GEORGETOWN,TRAP PONDGREEN- WOOD, SEAFORD EAST, LAUREL, HICKMAN, SEAFORD WEST AND SHARPTOWN QUADRANGLES AND AREA& MILFORD CONTOUR INTERVALS: 10 FEET FROM 10 FEET ABOVE SEA LEVEL TO 50 FEET ABOVE SEA LEVEL. KENT CO 52 51 45 '54 0' 47 -4 5011.9 _i@ 5_4.- R&NW)OOD t4. 4 9420 -.7 15 51 503%5 51 4. :43 .47 *49 vol 317 06 '42 *4 MILTON 00" 41 5o@34@ 44 *41 -45444, *430*44 41 .35 39."a Is. 0 *45 35 *39 38044: 44 LEWES 3, 370 38 4 4. *38 %5 -58@5' ' 11 38 39, 2e AD *34 4BI EV 30 s.4 31 04 14112914 .2. '13 4.1.- .1 466 REHOBOTH '45 3EI a, %e *45 BEACH -4. -@l 4. On03 .7N*25 33 31. sAm 148 .7 *5 * @3- *241...424*43 GEORGETOWN r37 - .5 4.41 W. 16 4@ 4.' 32z 17 21 20 *41 -m4d 31 'bo Re, -,.,o- ,o*03 o37. 29 *44 035 %3*4 Is.a42 3`3- '42 4*3 aFORD 22*1 is*024 22 33 '22 *13 15 ao 40 ,,,40 is "t za zGe sos636 364 3* 3" 23 *2 4o 3*35 40 4le 3.*47 eAr 2*34 350 4 0s- X. *Is 0 26 39.634 35 -wn, 211 26 34 *36 31. *41 *45 MILLSBORO Iako 10 @o %2043 4" 1. 30735 3B 242 44 e@0 33- 37 %1 5U002.Is 14 LAUREL.1 19.30 *2311 2e3 zo *5022 33 1.., BETHANY 26 . .20 .2e 1,. 31 4*4 *4 *42 5. BEACH 31 as Z36 so so *41 3" .3. 37 34_ III..s*37 4@* *43 *43 55 32 39 *"5lb 9* @4. 41.go 36m35 -3, 32 .43 4o *39 -w5d .4@ e44 Q.41*IOse 4639 3*41 *43 42 .0 3e 37 *411 44 40 :49 40*`6 41 39 35 41(-? @l s7 .15 --466%5 '44 4s 45 *46 649 4-'4 -38 *34 41 : 7 4.%46 SELBYVILLE FENWICK 30 '34 41", 499 *4 '41 41" 43* 10 38 DELMAR 42 44 47 48 -wz- 41 - A@@n- Is, ISLAND Q 41 34 FIGURE 39. MAP SHOWING CONTOURS ON THE ALTITUDE OF THE WATER TABLE IN WESTERN SUSSEX COUNTY 128 Availability of Water from the Water-Table Aquifer in Eastern Sussex County Pleistocene deposits cover or underlie the entire area of eastern Sussex County. The water-table aquifer formed by the Pleistocene and subcropping Manokin and Pocomoke sands ranges from 70 to 150 feet in thickness and pro- vides moderate to large supplies of water to wells. In appraising the avail- ability of water from the aquifer, it must be kept in mind that the aquifer is not only a source of water to wells, but it also provides the fairweather flow of the streams in the area,.provides the hydraulic gradient that protects the aquifer from the ingress of salt water, provides recharge to the artesian aquifers, and provides more than 90 percent of all of the ground water used. The nearly 18 million gallons a day that are now used show little or no effect on the aquifer. The effect of departures from normal precipitation is estima- ted 10 to: 20 times greater than the effect of pumping. All of the water-table aquifer coefficients are favorablefor large de- velopment of ground water throughout most of the area. Development of large ,.supplies are feasible, except where limited by the salt-water problems or by the need for 'maintaining fairweather flow of streams. It is evident that by proper and planned development more than 100 million gallons a day can be ,developed from the water-table aquifer without seriously.haming the other useful functions of the aquifer. Availability of Water from the Water-Table'Aguifer in Western Sussex County The amount of ground water available from the water-table aquifer of the Pleistocene and subcropping Miocene sands is large and exceeds 100 million gallons daily. To assess the yield of the aquifer more closely, many hydrolog- ic facts concerning the aqu,ifer must be kept in mind, and in developing plans to use the aquifer these hydrologic facts must be weighed and applied in de- ciding the best and proper use of the aquifer. For example, if the ground- water contribution to streamflow were disregarded, Sundstrom and Pickett (1970) show that the gravity drainage amounting to 280 million gallons@a day, plus salvaged evaporation, could be used to boost the yield of the aquifer to wells past 300 milli-on gallons daily. Such development might be very beneficial to agricultural pursuits and at the same time would be detrimental to the water supply, recreational facilities and sanitary aspects of the streams. Some of the hydrologic factors that affect the water-table aquifer dis- n this report are: (1) on the average, slightly more'than one billion cussed 1 gallons of water fall in the report area daily; (2) of the water that precipi- tates on the area, about 460 million gallons a da 'lable for .y are avai recharge; (3) about 280 million gallons a day reach the streams as gravity drainage or ground-water discharge; (4) about 12 million gallons daily are pumped from wells; (5) an unknown small amount moves downdip in subcropping artesian ground-water 12.9 reservoirs; and (6) the remainder of the recharge is dissipated by evapotrans- piration or change in the volume of storage within the aquifer. In considering the precipitation that falls on the area, these observa- tions are apparent: (1) wet periods and droughts can make the water table fluctuate five to seven feet in a period of a few months (Figures A14 and A15); (2) drought periods have reduced the ground-water discharge to many small streams to zero, and in the Nanticoke at Bridgeville, the ground-water dis- charge to the river has been observed as low as 6.3 cubic feet per second, representing a ground-water flow to the river of only about 37 gallons a minute for each square mile of drainage area; (3) precipitation that falls on the area exceeds the recharge to the ground-water reservoir by an average of more than 640 million gallons a day with much of the water falli-ng in areas where the water-table aquifer is brimful and in areas of swamps where the Sur- face is covered with water at the time precipitation falls; (4y precipitation that falls on the area exceeds the overland surface runoff to streams by about 924 million gallons a day. In considering recharge to the water-table aquifer, these observations are apparent: (1) of the estimated average 460 million gallons daily available to recharge the aquifer, about 12 million gallons a day are removed from the aquifer by pumps, and about 280 million gallons a day are fed to the streams by gravity drainage; (2) the remaining 168 million gallons are largely paid out from the ground-water reservoir by evapotranspiration. Presently, the recharge to the aquifer is taking place under natural conditions. The aquifer could probably be developed to take more induced recharge by lowering the water table in some areas where it is close to the surface. This is possible in both intake and discharge areas. The streamflow would be affected in dis-' charge areas; swamps would be affected in the intake areas. A study of 24 years of streamflow data on the Nanticoke River near Bridge- ville indicates that, on the average, the discharge of the river is 776,000 gal lons a day per square mile of drainage area of which 79 percent of the dis- charge is computed to be from ground-water gravity drainage. The Nanticoke re- cords further show that during three months of drought in July, August and Sep- tember 1957, the flow of the river only amounted to 207,000 gallons a day per square mile of drainage area, or about 143 gallons a minute per square mile. On September 29, 1943, the discharge of the river declined to 54,000 gallons a day per square mile, or less than 40 gallons a minute per'square mile. The records show that storage is needed to supplement the ground-water discharge in order to maintain the flow during prolonged drought. Under prudent planning, development and management, the combined supply of ground and surface water supplying the streamflow in the area can be reasonably stabilized so that the ground-water supply can be increased ten- fold over the present usage or to about 120 million gallons a day. In, ' ac- complishing the increased ground-water withdrawal, water lost to evapot@ans- piration in the high water table and swampy areas should be salvaged as much as possible to minimize the effect on the fairweather flow of the streams. Base flow of the streams can be supplemented by pumped ground water during extreme drought periods if necessary. 130 Quality of Water from the Quaternary Aquifer Tables 19 and 20 show that the water from the Quaternary aquifer is generally of good quality except for the high iron and manganese content of samples of waterfrom some ofthe wells. The low hydrogen ion concentration in the water from many of the wells indicates that the water is acid in character. Consideration must be given to treatment of the water in several areas to make it suitable for some uses. Areas of similar chemical quality of ground water and areas of potential salt-water intrusion into. the Quater- nary aquifer are shown in Figure 40. 131 Table 19. otential Saline-Water Intrusion Quality'of Ground Water and P in the Quaternary Aquifer,,as Shown in Figure 40 Chemical constituents in ground water in the Quaternary aquifer (concentration of 'con- stituents in milligrams per liter) Area 1 2 Dissolved solids* <100 100-250 Hardness <35 35-150 Sodium 2-20 12-70 Bicarbonate 5-40 10-140 Chloride 5-20 .10-70 Fluoride <0.2 <0.2 Silica 10-30 1.5-40 Iron and 0.02-21 0.02-17 manganese pH 5.4-7.10 5.8-7.5 *In area 1, dissolved solids x 1.20 specific conductance (Micromhos at 250C) In area 2 dissolved solids x 1.45 specific conductance From Cushing, Kantrowitz and Taylor, 1973. 132 Table 20. Chemical Constituents in Water from 19 Wells Tapping the Columbia Deposits (Chemical Constituents in Milligrams Per Liter) Constituent of Minimum Maximum Average Chemical Property Silica (Si02) 9.8 25 16 Iron (Fe) .00 2.1 .33 C alcium (Ca) 1.6 17 7.6 Magnesium (Mg) 0.4 13 5.2 Sodium and Potassium (Na + K) 3.7 40 15 Bicarbonate (HC03) 4 38 17 Sulfate (S04) 0.4 40 13 Chloride (Cl) 4 86 21 Nitrate (N03) 0 36 13 Dissolved Solids 50 235 113. Hardness (as CaC03): Calcium, Magnesium 5 93 39 Noncarbonate 0 64 18, pH 5.4 7.5 6.1 From R. H. Johnston, 1974. 133 uj Lu z AREAS OF POTENTIAL SALINE-WATER INTRUSION SEE TABLE 19 FOR RANGE IN CHEMICAL CONSTITUENTS >1 FROM! CUSHING, KANTROWITZ, AND TAYLOR,1973 0 ui 0 Lu FIGURE 40-AREAS OF SIMILAR CHEMICAL QUALITY OF GROUND WATER a AREAS OF POTENTIAL SALINE- WATER INTRUSION IN THE QUATERNARY AQUIFER. 134 WATER RESOURCES PROBLEMS THE SALT-WATER PROBLEM This section of the report discusses the probability of salt-water prob- lems in the aquifers of eastern Sussex County. The Atlantic Ocean, the Delaware Bay, the four inl-and bays (Rehoboth, Indian River., Little Assawoman, and Assawoman) and the tidal estuaries draining t .o these bays all conta,in highly mineralized water. The Atlantic Ocean is indirect 'contact-with the water-table aquifer from Cape Henlopen to the southern end of the area near Fenwick Island. The inland bays, whose outlets are 'to the ocean and the,tidal estuaries discharging into the bays, all overlie the Pleistocene water-table' aquifer. In most places the aquifer is Idischarging fresh water into..the in- land bays and tidal estuaries. The subcrops of some of the artesian aquifers extend as far as northern Kent County so that they are crossed by Delaware.Bay as much'as 40 miles upstream from the,mouth of the bay. The Delaware Bay, with its mouth in direct contact with the Atlan tic Ocean, extends 48 miles upstream to the beginning of the Delaware River Es- tuary at Liston Point, Delaware. The estuary of the river then continues up- stream 86 more miles to Trenton, New Jersey. Above.Trenton, the river ceases to be tidal and the river proper begins. At the beginning of the estuary at Trenton, the stream contains fresh water and the river's estuary remains rela- tively uncontaminated,by salt water for,many miles downstream from Trentop. At Memorial Bridge near Wilmington during periodt,of low river'flow and high-, tide from the Bay, chlorides are often above 1, 1000 parts per million and on occasions reach 1,700 or more parts per million. Downstream from Memorial Bridge about 12.5 miles at Reedy Island Jetty, Delaware,'and about 9.5 mile.s above the New Castle-Kent County boundary line, the chlorides durfng similar periods wiWreach more than-6,000 parts per million. During,these periods of high chloride, the low for the day may not decline more than 2,000 parts per million from the high for the day. About two-fifths of eastern Sussex County is bounded on the northeast by the lower part of Delaware*Bay, where the.c.hlo- ride concentrati,on of the Bay approaches that of the Atlantic Ocean. The sub- crops of the lower Miocene artesian aquifers are of, sufficient distance.up-, stream to be crossed by the middle section of the'ba' Y. The Piney'Point Aquifer-Crossed by De'laware Bay The Piney Point aquifer lies at depths of 200 feet or more below sea level where it is crossed by Delaware Bay. The Cheswold, Frederica.and minor Miocene @quifers@ containing fresh water'lie above the Piney Point and are also cro 'ssed in subcrop'by the Delaware Bay in northern Kent County. .'No evidence of contam- ination from the Bay has been found in the overlying Cheswold.or Frederica., 135 aquifers in the s,u,bcrop area,.i,n Kent County. The confining clays and. over- lying sands of the Cheswdld and Frederica containing fresh water preclude salt-water contamination in the Riney Point. The Interface Between Fresh and Salt Water in the Piney Point Tquifer The interface between fresh and salt water is believed to be close to the. Kent-Sussex County boundary line. A test well] drilled tothe Piney Point at Milford in 1968 obtained, water that contained 540 parts per million of.chlo- ride.- 'This'amount of c Ihloride in relation to the depth of the aquifer and the originaI artesian pressure lends evidence that the,fresh-salt waterAnterface is nearby. The chloridecontent, although not sufficiently high to make the, water unusable*for some purposes, is more.than twice.as highzas recommended for public consumption on public carriers by the U. S. Public,Health Service. If the chlorides fbund in the water in the test,well are an indicator of the proximity of the interface, then the water shoOd increase considerably in salinity a few miles downdip., The Cheswold Aquifer Crossed by the Delaware Bay_ In considering the salt-water problem in kent County in 1968, Sundstrom wrote the,following about the outcrop of the Che�wold: ."The ou'tcrop of tht Cheswold aquifer extends across the north- ern part of Kent County. In the extreme northeastern' partof the County, the Cheswold.outcrop is.about two miles wide where it is crossed byithe.Delaware Bay. The problem of the possibility.of salt-wate'r leakage from the estuary of-the Delaware to the outcrops of the ground water aquifers cro 'ssed by the estuary was given con-!. si-derable study during an earlier investigation in 1967 of the availability of ground water from the Potomac Formation to the north in-New Castle County. No evidence of contamination.o.f. the. Potomac Formation by the estuary was found, and Dr. R. R. Jordan of the Delaware Geological Survey reports a Delaware Research Foundation study in progress in which he was of the belief that the nature of the sediments in the bed of1the estuary,that pro- tected the Potomac were such that they formed a-protective seal of the bottom of the estuary downstream past the southern New Castle County line. "Dr. Jordan has'continued his study of the Delaware E stuary and Bay sediments and presented his findings in a paper presented at toe, Northeastern Section Meeting of the Geological Society 'of,Ame'rica in Washington, D.C., February 17, 1968. The paper is entitled: 'Suspended and Bottom Sediments in the Delaware Estuary.' Jordan's 136 study reveals that in the Bay 10 to 11 miles southeast of Woodland Beach, Delaware,'a transition from fine to coarser sediments begins and that the sediments get progressively coarser to the mouth of the Bay where sand predominates. The Bay crosses the outcrop of the Cheswold aquifer about 9 to 12 miles above the transition zone of. the fine to coarser sediments in the Bay as described by Jordan. The outcrop of the Cheswold is overlain by fine Bay bottom sediments, and the distance to the coarser sediments affords protective cover to the outcrop of the aquifer. Protection from salt-water intrusion is further provided by the high water table in the Cheswold outcrop and overlying Pleistocene. (See the Smyrna Hydrologic Atlas of the U. S. Geological Survey.) Pumping has been in progress from the Cheswold for more than 75 years with no reports of intrusion into the aquifer anywhere in the County." The Interface Between Fresh and Salt Water-in the Cheswold Aquifer The position of the interface in the Cheswold is unknown. The aquifer yields fresh water at Milford and at Gravel Hill near Georgetown. In 1968, A.C. Schultet and Sons drilled test well Mel5-29 at Milford and sampled the water from sands in the Cheswold from 370 to 430 feet below land surface. The analysis of this sample showed nine parts per mill'ion of chloride. In 1969, Paul White Drilling Company drilled test well Og3l-l and obtained a sample of water from the Cheswold. The United States Geological Survey ana- lyzed the water and found 10 parts per million of chloride. This suggests that the Cheswold aquifer probably contains fresh water to.a depth consider.- ably below'600 feet below sea level. The test of the Cheswold near Georg6town@ and an early test near'Lewes indicated that the Cheswold was not a promising aquifer in terms of yield to wells. Dr. Pickett in Figure 9 of this report indicates that the Cheswold probably pinches out at a depth of about 700 'feet below sea level. On this basis a fresh-salt water interface in,the Cheswold does not exist in the report area. The Frederica Aquifer Crossed by the Delaware Bay The Frederica aquifer subcrops beneath the Pleistocene sediments in north- ern Kent County. In 1968, Sundstrom in studying the salt-water pro6lem in Kent County wrote about the Frederica aquifer crossed by the Delaware Bay as follows: "The outcrop of the Frederica aquifer is crossed by,the Dela-, ware Bay five to seven miles upstream from the, 'transition zone' from fine to coarser sediments and is about four miles closer to the zone than the outcrop of the Cheswold aquifer. The Frederica 137 outcrop is not,only protected by the.fine sediments in the bottom of the Bay,, but.it is a1so protected by the high water tabIe in the., outcrop and overlying-Pleistocene and by the clay cover downdip that forms the.confintng beds of the:Frederica artesian aquifer. No evidence of salt-water contamination of the Frederica was found and it is believed that the aquifer is safe from salt-water encroachment." The Interface Between Fresh and Salt Water in the Frederica Aquifer The Frederica contains fresh water at Milford, Lewes, Cape Henlopen and Gravel Hill near Georgetown. At Cape Henlopen and Gravel Hill the Frederica is reported to yield only 15 to 30 gallons a minute. The drill cuttings at Gravel Hill were inspected and indicated a poor-yielding aquifer. Dr. Pickett indicates in Figure 9 that the Frederica aquifer probably pinches out at a depth of about 400 feet below sea level. A fresh-salt water interface in the Frederica aquifer probably does not exist in the report area. Minor Artesian Aquifers in the Miocene Above the Frederica Crossed by the Delaware Bay Shallow artesian aquifers above the Frederica are found in the souithe rn part of Kent County. -These aquifers and perhaps others exist in the northern part of eastern Sussex County. Concerning the salt-water problem where these aquifers are crossed by the Delaware Bay, Sundstrom (1968) wrote: "Shallow artesian aquifers above the Frederica aquifer are found in the southern part of the county. Two of these aquifers are used in the vicinity of Milford and perhaps elsewhere inthe southern part of the county. Little is known about the areal extent of the reservoirs away from Milford. The outcrops of the aquifers, if they exist, probably lie south of the transition zone between the fine and coarser sediments and would probably be more susceptible to salt-water intrusion if the protective hydraulic gradient of the Pleistocene over their subcrop were lowered below sea level. There is no evidence of salt-water contamination of.the shal.low Miocene artesian aquifers." The Delaware Geological Survey reports the log of a well, Mh4l-l@ at Shorts Beach on Delaware Bay. The log records brackish water in Pleistocene sediments 36 to 50 feet below the surface,-and in Miocene sands 138 to 150 feet below the surface. the surface altitude at the well is five feet. The drillers log of the well shows only sand s 'ections between Pleistocene and Miocene sediments; thus the Miocene sands appear to be in direct contact with 138 Pleistocene sands. Contamination might be accounted for by either low water- table altitude or by hurricane flooding or by both. The Subcrop of the Manokin Aquifer and the Relation to Salt Water of the Atlantic Ocean and to the Salt Water of the Inland Bays and Estuaries The subcrop of the Manokin aquifer with the overlying Pleistocene removed is shown in Figure 2. In this illustration, Dr. Pickett shows the Manokin sub- crop removed by erosion along the Delaware Bay during Pleistocene time except for a narrow tongue of the subcrop reaching the Bay near the outlet-of the Broadkill River. The Broadkill River, containing saline water, crosses Pleisto- cene sediments over much of the eastern central part of the subcrop. In both the area of the tongue and in the area crossed by the Broadkill, the altitude of the water table is not adequate to protect some parts of the aquifer from salt water. The low altitudes below the five foot contour line are shown in Figure 38 and demonstrate some of the danger points. The depth to fresh or salt water in most of the water-table aquifer is established by the altitude of the water table and by the ratio of the densities of the fresh water in the aquifer to the salt water in contact with the fresh water. The Interface Between Fresh and Salt Water in the Tanokin Aquifer In the subcrop where the fresh water head has been more than four feet above sea level and the surface has not been periodically flooded with salt water from hurricane storms, there seems to be little danger of the presence of salt water in the aquifer. The base of the subcrop Manokin reaches a maxi- mum depth of about 150 feet below sea level. Where the fresh water head is less than four feet above sea level or where salt water floods from storms have occurred, there is a good possibility of salt water in the subcrop. Based on the altitude of water levels in the aquifer, it is believed that the closest source of salt water is at the subcrop near Delaware Bay or the estuary of the Broadkill River. The Delaware Bay area is the most likely source of contamina- tion. In the artesian part of the Manokin aquifer, the arte sian head is ade- quate to protect the aquifer. The Subcrop of the Pocomoke Aquifer and Its Relation to Salt Water of the Atlantic Ocean and Salt Water of the Bays The Pocomoke subcrop lies beneath the Pleistocene water-table aquifer. Dr. Pickett shows the position of the subcrop in Figure 2. The eastern boun- dary of the subcropis shown four to eight miles inland from the Atlantic 139 Ocean and i's overlain by salt water only in the northern part.by Ind@ian River Bay and by a small branch of Li'tt-le-Assawoman Bay in the eastern part. The contac.t, of course, is separated by the Pleistocene aquifer which overlies the Pocomoke@.. The.Pleistocene sediments are.in direct contact to the east with the ocean and@ the inland bays.. I,nd:ian River-Bay contains highly mineral'ized- water. Dr.- John- C. Kraft, Chairman of the Geology Department, University of Delaware, determined.the saltnity content of the bay i,n two sections through the tide-cycle.. The lower section, which, represents the midsection of the bay proper, shows. water contai:ning 28,000 to 30,000 parts per mill'ion of salinity. The upper section shows water conta.in.ing 6,000 to 11,000 parts per million of salinity through the tide cycle in the upper part of the bay. Dr. Kraft's observations were made July 17 and 20, 1967, and are given in Figure A18. Most of the Pocomoke subcrop and overlying Pleistocene aquifer are protec- ted from sal*t-water intrusion by adequate.head of fresh water in the water- table aquifer.. However, some of the area-lies beneath a water table less than four feet above sea leve.l. In the areas of low water table the same discussion given to the Manokin applies to the Pocomoke except that the Pocomoke, as shown fn Figure 2, is more remote from the ocean than the Manokin is from the Delaware Bay. The areas of low head inthe water-table aquifers of the Manokin, Poco- moke and-Pleistocene are shown in Figure 38.@ The illu,stration also shows the thickness of the Pleistocene aquifer above the Manokin and Pocomoke. The total thickness of Manokin and Pocomoke.subcrops combined with that of'the,Pleisto- cene aquifer i.s generally less than 160 feet in thickness. The Quaternary and SubcroRpjng Miocene.Water-Table Aquifer Adjacent to Delaware Bay, the.Atlanti'c.Ocean, the Inland Bays and Stream Estuaries Most,@ if not all, of the@sal't-water problems i n the water-table aquifer of the Ple,istocene and subcropping Mi,ocene.sands will occur in the area shown fn Ngure.38 where the altitudelof the water tableAs five feet above sea 1'evel or less. More than 20 percent of the report area is bounded by the five foot contour. In this area there are a few localities in which fresh water cannot be obtained. from the water-tab-le aq:uifer. This is true at some localities on the barrfer beach in the southern part of-the area. Some of the salt water in the aquiferprobably has never been replaced by fresh water because of the lack of fresh-water head to displace the salt water. Figure 38'shows several loca- tions where the fresh-water head is only one, two, or three feet above sea level. Sundstrom and Pickett's report of 1969 lists 69 wells in the water- table.aqui'fer in which the water level has been measured three feet or less above sea level. In these areas of very low water-table altitude and close proximity to salt water, the possibi1ity of contamination must be considered, although it is..believed that mos@t of the weIls- of small yield that are now producing fresh water wil'I continue to produce.fresh, water. In areas of low water-table'altitude where. pumpi,ng has been heavy, trouble can be expected and has been encountered, especially;at Lewes and Rehoboth Beach. Problems at both places have:been alleviated by moving away from the area of contamination and to an area of higher fresh-waterhead, in the aquifer. 140 The water-table aquifer, where the water table is five feet or less, is estimated to contain more than 300 billion cubic feet of material saturated with fresh water. Only about three percent of it lies above sea level. Salt- water problems can occur at many places in the area. In some places where the aquifer contains only salt water there is no remedy, except to go elsewhere for water. In most of the area, pumping of small quantities of water probably will not present a problem., Where heavy continuous pumping is contemplated, the wells should be developed in areas where the water-table head is 10 feet or more above sea level. GROUND-WATER CONTAMINATION Man-made ground-water contamina tion problems are many. Examples of such contamination can be cited; but it is believed that no overall study of the damages has ever been made. New Castle County has done a very large amount of work to determine the cause and cure of the Llangollen landfill leachate prob- lem. The results of these studies have been documented for the Department of Public Works, New Castle County, by Roy F. Weston and Associates, 1972 and 1974; by R. W. Sundstrom, 1974; and by the Delaware Department ofNatural Resources and Environmental Co ntrol. Delaware has many more landfill proj- ects; but the effect of contamination from leachate, if any, is unknown for most of them. Dredging along the Chesapeake and Delaware Canal is thought to be respon- sible for high chlorides in shallow wells in the vicinity of the dredging spill. This contamination may be of short duration over a' term of a few years because of the natural hydraulic gradient back toward the canal. Fertilizers (chemical and animal, especially chicken) pose problems of added nitrates to the water-table ground-water reservoir. However, an allow- able concentration of 45 parts per million in the ground water is seldom exceeded. Salt-water intrusion has taken place in the,water-table aquifer along the coast in eastern Sussex County. Bethany Beach, Rehoboth Beach and Lewes all have had their problems. Large-capacity wells were developed in areas where the fresh-water head was less than 10 feet above sea level and when heavy pumping started, the pumping levels were lowered many feet below sea level. Encroachment took place in accordance to the relation of fresh water to salt water as described in Appendix C of this re@port. Lewes and Rehoboth Beach took. care of their problem by moving their production wells to an area where the altitude of the water table was higher. The magnitude of the effect of contamination of ground-water reservoirs from cesspools and septic tanks is unknown. 141 POTENTIAL PROBLEM AREAS The New Castle County "corridor", when considered in terms of the "cor- ridor" itself and in terms of the requirements of New Castle County, lies in a water-short area where there is not enough available ground water within the corridor to supply the area. It has been pointed out that under present con- ditions of development about five million gallons a day might be produced in a 5,000 acre area at the western end of the Chesapeake and Delaware Canal in Delaware. If pumpage.should be developed in an adjoining area of Maryland, the overall pumpage would be reduced in Delaware by the pumpage in adjoining development in Maryland. .In the Lewes area development should be upgradient from the 10-foot con- tour shown on the water table. In upgradient areas adjacent to the 10-foot water-table contour, pumpage probably should be limited to 500,000 gallons a day per square mile and farther upgradient beyond the first mile to 750,000 gal.lons a day per square mile. In the Dover area, Dover and the Air Force Base can still develop the Piney Point in its deepest and best section in a southwesterly direction to the Maryland state line, see Sundstrom and Pickett, 1968. Dover could also find favorable supplies in the Quaternary deposits in parts of southern and western Kent County. AREAS OF NEEDED RESEARCH AND STUDY CONCERNING THE PROSPECTS OF USING ARTIFICIAL RECHARGE OR OTHER NEW SOURCES OF WATER Comprehensive research and -study of the prospects of using artificial re- charge as a supplement to the water supply of New Castle County is needed. Such research and study must establish, without a doubt, whether or not the development of supplemental water supply from artificial recharge is a feasible and practicable development from the economic, environmental, engineering, hydrologic, geologic, sanitary and public welfare consideration. Among many problems that must be resolved are: 1. Is there available water, over and above present and future require- ments, from the Brandywine, Red Clay and White Clay Creeks and the'Christina River for supplying artificial recharge? If there is a substantial amount of water from these sources, can these sources fulfill the feasibility and practi- cability requirements for development? Are there better methods of using the water? 2. Can flood waters be stored from the Brandywine, Red Clay and White Clay Creeks for artificial recharge? Aria detention reservoir sites available and feasible for storing the needed water? Are there better methods of holding and using the flood waters? 142 3. Can urban storm runoff through storm sewers be effectively captured and used for artificial recharge?. Would the amount of water captured be sig- nificant in the total water requirement needs? Would such development meet feasibility and practicality requirements? 4. Can the proper treatment of 70 or more million gallons a d ay of ef- fluent from municipalities and industries provide a supply of water that meets all requirements for water supply be used for artificial recharge? If this is possible, is this the best way to Use the,water? 5. Are ground-water reservoirs of adequate capacity and hydraulic proper- ties available for receiving and paying out to pumps the artificial recharge water? 6. Are artificial recharge waters compatible with the native ground water? 7. What method of inducing the recharge water to the aquifer should be employed? What part of the induced recharge can be recovered? 8. Can the proper treatment of the large supply of effluent water allow the direct recycling of the water without going through the artificial recharge process? If not, can a part of it be used for industrial or agricultural purposes? Problems such as the above must have adequate research, study and inte- gration into the overall water supply problems of New Castle County.before the prospects of artificial recharge can become a significant part of the county water supply. In the overall evaluation of water supply and problems ?f water supply, New Castle County north of the Chesapeake and Delaware Canal is in direct need of a new source or,sources of water (see Figures 17 and 41). 143 FIGURE 41 WATER RESOURCES EVALUATION MAP OF DELAWARE AREAS OF IMPENDING PROBLEMS QUANTITY QUALITY WATER SUPPLY SYSTEM CAUTION AREAS QUANTITY Fq QUALITY WATER SUPPLY SYSTEM AREAS WITHOUT KNOWN PROBLEMS S M60 SQ. MILE AVAILABLE MUNICIPAL OR WATER COMPANY SYSTEMS BOUNDARY OF DELAWARE RIVER DRAINAGE BASIN *% ........... ... ............ 144 SUMMARY AND CONCLUSIONS NEW CASTLE COUNTY New Castle County encompasses portions of two geological provinces whose ground-water reservoirs vary widely in water-yielding,properties. In northern New Castle County, the Appalachian Piedmont Province .occupies about 113 square miles. The remainder of the county lies in the Atlantic Coastal Plain Province. The ground-water reservoirs in the Piedmont are contained in very old rocks of igneous or metamorphic origin. Theaquifers of the Coastal Plain are in sedi- mentary material. The ground-water reservoirs of the Piedmont provide about 67 percent of the flow of the Brandywine, Red Clay and White Clay Creeks and more than'30 percent of the flow of the Christina River. The amount of water contributed to the streams from the ground-water reservoirs of the Piedmont amounts to an average of 500,000 gallons a day per square mile of drainage. The ground-water reservoirs of the Piedmont on the whole are very poor providers of water to wells except in the Cockeysville Marble. Water occurs in fractures in the rock and wells must be located such that they intercept fracture concentrations or the yields will be very low. The yields of 103 randomly located wells (Sundstrom and Pickett, 1971) average 15.6 gallons a minute. Of the 103 wells, 83 had yields less than average. Only six wells yield more than 50 gallons a minute. A number of wells are known that yield considerably more water than those list- ed by Sundstrom and Pickett (1971). The Artesian Water Company has six wells in the Cockeysville Marble which have a maximum capacity of greater than 3.5 million gallons a day and are supplying the Artesian Water Company an average of 1.6 million gallons a day. Artesian presently has an allocation from the Department of Natural Resources and Environmental'Control to pump up to 3.'0 million gallons a day and withdraw an annual average of 1.9 million gallons a day. Extensive monitoring of precipitation, streamflow, well withdrawals and water levels are required to assess whether this allocation represents a sus-w tainable yield for the aquifer and to determine the impact on existing Well owners and streamflow. The City of Newark has completed several wells in the Wissahickon schist whose initial capacities range from 100 to 200 gallons a minute. Weighing all data presented in the New Castle County report, it appears probable that the development of ground water from wells yielding 75 or more gallons a minute from the granodiorite, gabbro and schists which comprise 98 percent of the Piedmont area, will not produce more than an average of five million gallons a day. The Cockeysville Marble probably will yield an average of two million gallons a day to large wells if solution channels can be found. The Piedmont aquifers, although poor in water-yielding properties to large wells, are very important to the large rural area of the Piedmont where individual supplies of a few gallons a minute will suffice. The Piedmont aquifers are of great importance to the base flow of the Brandywine, Red Clay and White Clay Creeks and the Christina River which contribute substantially to the water supply of northern New Castle County. 145 The. ground-water reservotrs of the Potomac Formation consist of sands in two hydrologic zones in the Potomac Formation. The Potomac is a formation in which clays are more dominant than sands. In the outcrop and subcrops of the two aquifer zones, the sands of the Potomac are mantled in places by sands of the Pleistocene age so that, in places, sands of the Potomac and Pleistocene form a single water-table aquifer. The Potomac sands in outcrop or subcrop are estimated to cover about 60 square miles. Although the available recharge to the area amounts to about a million gallons a day per square mile, and under most favorable conditions could be pumped by wells, it is believed that the saturated thickness and low water-yielding properties of the aquifer in many places will cut the large-scale development of the outcrop or subcrop of the aquifer to about a third of its total areal extent, or to an available supply of about 20 to 25 million gallons a day. Of the available supply, 11 million gallons a day are now developed leaving 9 to 14 million gallons a day for future use. In the Chesapeake and Delaware Canal area, study has indicated the maximum amount of water from the artesian part of the Potomac aquifers to be about 11 million gallons a day, of which 4 million gallons per day have been developed. The canal study covers about 170 square miles extending six miles on each side of the canal in Delaware. There may be two to four million gallons a day available south of the area studied and north of the interface between the fresh and salt water in the aquifers. In all, about 18 to 25 million.gallons a day are believed to be available from the Potomac outcrop- subcrop area and the artesian aquifers of the Potomac. The available water from the Magothy aquifer is difficult to determine because of lack of the hydraulic coefficients required to determine the water- yielding properties of the aquifer. At Middletown the transmissivity of the aquifer is 4,000 gallons a day per foot of drawdown. If the Middletown test is representative of the aquifer as a whole, the water-yielding properties are about two-thirds that of the upper Potomac aquifer in the canal area. Using the hydraulic data of the upper Potomac aquifer in the Chesapeake and Delaware Canal area and applying it to the Magothy with proper adjustments, it appears that about three million. gallons a day are available from the .Magothy from properly spaced wells ranging.in yield from 250 to 300 gallons a minute. For smaller supplies (wells yielding 10 to 50 gallons a minute), the, Magothy, over an area of about 170 square miles north of the fresh.7--salt water- interface in the aquifer, is a good to fair source of supply for rural water. The availability,of water in large quantities for large supplies is im- practicable from the Englishtown-Mount Laurel aquifers because of the low water-yielding properties of the aquifers. At Middletown the transmissivity of the aquifers is only 1,800 gallons a day per foot, or less than.half of the transmissivity of the Magothy aquifer. The aquifer is of value only to those who need small supplies for individual use. The Rancocas is an important source of water in small quantities through- out the area in which the aquifer exists in southern'New Castle County. The Rancocas aquifer is important as a source of water to wells yielding 300 or more gallons a minute in the area east and northeast of Smyrna in.New Castle County. This is also true in a southwesterly direction from Smyrna in Kent County. The ultimate yield of the Rancocas aquifer in the deeper part in the 146 two counties probably will not exceed six or seven million gallons a day to wells properly spaced yielding 300 or more gallons a minute. A larger total supply can be developed from wells yielding smaller amounts of water. The available water from the water-table aquifer in the Coastal Plain of New Castle County is small in terms of an adequate supply to large-capacity wells of 500 or more gallons a minute each. This is especially true north of the Chesapeake and Delaware Canal. Although the water-table aquifer, where Pleistocene deposits contain 10 or more feet of saturated material, covers 182 square miles, the thickness of saturation of 40 feet or more needed to assure large-capacity wells occupies only 11 square miles, of which 8 are south of the Chesapeake and Delaware Canal. The Pleistocene water-table aquifer prob- ably will supply large-capacity wells in these isolated areas in amounts equal to the available recharge, which would amount to about three million gallons a day north of the canal and about eight million gallons a day on the south side of the canal in the Middletown-Odessa and Smyrna areas. The total avail- able supply to large-capacity wells in New Castle County is about 11 million gallons a day. The Pleistocene is an important source of water to small wells over the entire area of 182 square miles where the Pleistocene has 10 or more feet of saturated thickness. Although the Pleistocene is a poor source of large sup- plies of water in the county, it has importance in maintaining the base flow of streams, in furnishing plant life.moisture, in maintaining a reservoir of recharge water for the artesian aquifers, and in maintaining the hydraulic gradient that halts the ingress of salt water along the Delaware Estuary and Bay. The prospects of supplementing the water supply of New Castle County by the use of artificial recharge to the ground-water reservoir of the Pleisto- cene is brought into focus in the New Castle County report (Sundstrom and Pickett, 1971). Whether or not such recharge is practicable and feasible can be to.ld only after required research and study are made. KENT COUNTY The four major artesian aquifers of Kent County are the Rancocas, Piney Point, Cheswold and Frederica. The major water-table aquifer is found in the Pleistocene deposits that cover most of the surface of Kent County and in the underlying outcrop and near outcrop sands of the Miocene. Minor artesian aquifers are found in the Miocene deposits in the southern part of the county above and below the Frederica aquifer. In Kent County the Rancocas aquifer is available for development in the extreme northern and northwestern parts. The aquifer will supply water to wells generally in amounts ranging from 50 gallons a minute in the extreme northwestern part of the county to as much as 600 gallons a minute near the 147 downdip extremity of the aquifer at Clayton. The hydraulic properties.of the aquifer have been determined and applied to assess the quantity of water avail- able from the aquifer. Sundstrom and Pickett (1968) demonstrate that the ulti- mate yield under planned development does not exceed four million gallons a day in Kent County. The aquifer, because of its low specific capacity, coef- ficient of transmissivity, coefficient of storage and limited available draw- down is classified as fair to poor as a source of moderate quantities ranging from 200 to 600 gallons a minute. The Piney Point aquifer i&available for its maximum development along the axis of its thickest section which lies in a northeast-southwest direction from Port Mahon through the Dover Air Force Base well Je32-5 and beyond across Kent County, a distance of 21 miles. Two hypothetical plans for developing the aquifer have been presented in the Kent County report (Sundstrom and Pickett, 1968). The first plan shows that if 22 wells were used producing 500 to 600 gallons a minute, the aquifer would produce about 17 million gallons a day. The second plan demonstrates the use of 11 wells pumping 800 to 1,000 gallons a minute, which would produce about 14 million gallons a day. Both plans appear to be feasible and represent about the maximum amount of water that can be obtained with the given rates of pumping in the two hypothetical plans. Both plans take advantage of the thickest section of the aquifer. There is good evidence presented in the report,'however not conclusive, that the water-yielding properties of the Piney Point deteriorate rapidly both up- dip and downdip from the thick section of the aquifer and in Kent County at a distance of about 12 miles in each direction the Piney Point ceases to be an aquiferlof importance. Except in the northern part, the Cheswold aquifer is available in much of Kent County. It is a highly-developed aquifer in the Dover-Dover Air Force Base area where peak pumpage from it reaches an average of about 6,500,000 gallons a day. Evidence is presented that this rate of pumping is about the maximum from the aquifer without readjustment of pumping rates in some of the wells in Dover. With adjustments, the total withdrawal from the Cheswold can be increased to eight million gallons daily. The Cheswold aquifer is rated good in the Dover-Dover Air Force Base area, but elsewhere ranges from fair to poor. The Frederica aquifer is available in the southern part of the county. The hydraulic properties, as defined by the specific capacity, coefficient of transmissivity, coefficient of storage and available drawdown, are rela- tively low and for these reasons the aquifer is classified as only a fair water producer, Few wells produce over 300 gallons a minute from the artesian part of the aquifer and most of the wells produce much less. The maximum production of the Frederica, under planned control of spacing and yield, is about five million gallons a day., Minor artesian aquifers above and below the Frederica exist in the south- ern part of Kent County and@ are developed in the Milford area., The trans- missive properties of the aquifers have been tested and found to be low. The areal extent of the aquifers is not known and the available drawdown in them is small. It is estimated that the aquifers will not produce more than one million gallons a day. 148 Pleistocene age sediments cover about 88 percent of Kent County. In many places subcropping sands of Miocene age underlie the Pleistocene sediments to form a combined water-table aquifer. The aquifer furnishes meager to copious supplies of water to several hundred wells in the rural area of Kent County. Based on the saturated thickness of the water-bearing material in 161 wells, the water-table aquifer contains about 280 million cubic feet of water. The water in this reservoir is the recharge to the underlying artesian aquifers in their outcrop section; with the discharge from the aquifer that provides the. fairweather flow of the streams; with the discharge from the aquifer that is yielded to evapotranspiration; with the hydraulic gradient that prevents the ingress of salt water in the Delaware Bay area; and with the supply to many hundred rural and city wells in Kent County. All of these functions of the aquifer pose related problems that require consideration in the ultimate and wise use of the aquifer. Under proper development, it is evident that a mini- mum of 100 million gallons daily can be developed without destroying the other useful functions of the aquifer. Salt-water contamination from the Delaware Bay,and associated tidal estuaries and marshland adjoining the bay appears to be a problem only to the development of ground water in the Pleistocene and underlying Miocene water- table aquifer adjacent to the salt water. The water-table aquifer is now dis- charging water to the bay and is protected by the high hydraulic gradient in the aquifer. The gradient could be reversed by pumping too close and too heavily near the source of salt water. If this should happen, salt water would start to move into the fresh water aquifer. The Kent County report (Sundstrom and Pickett, 1968) concludes that there are about 34 million gallons daily available in the county from the artesian reservoirs and more than 100 million gallons daily available in the county from the water-table aquifer of the Pleistocene and subcropping Miocene sands. These available quantities are predicated on the proper development of the entire aquifers in the county. EASTERN SUSSEX COUNTY Sundstrom and Pickett (1969) summarize and give the following conclusions about their study of eastern Sussex County: The availability of ground water from the aquifers yielding potable water in eastern Sussex County has been determined or estimated by methods of applied ground-water hydrology. The report discusses and appraises the availability of ground water from seven artesian aquifers and one water-table aquifer. The artesian aquifers are the Piney Point, the minor Miocene aquifer below the Cheswold, the Cheswold, the Federalsburg, the Frederica and the minor Miocene aquifers above the Frederica and the Manokin. The water-table aquifer is com- posed of sediments of Pleistocene age and subcropping Manokin and Pocomoke aquifers of Miocene age. 149 The Piney Point aquifer is available in the extreme northern part of the area in a,strip less than four miles wide, bordering the northern boundary. Based on analysis of water from the aquifer, Milford is close to the fresh- salt water interface. The transmissive properties of the aquifer are extremely low. The extremely low transmissivity and the extremely low specific capacity of the Milford well indicate yields less than 30 gallons a minute. Wells will be costly to drill and pump. Total development of ground water in eastern Sussex County by many small wells will produce not more than one-half million gallons a day. For these reasons, the aquifer is not recommended for develop- ment. A minor Miocene aquifer below the Cheswold is available in the extreme north and northwestern parts of eastern Sussex County in a strip 6 to 12 miles wide. Downdip from this strip the aquifer is believed to contain salt water. Low specific capacity of wells coupled with low transmissivity of the aquifer preclude the development of wells with yields over 200 gallons a minute. The low aquifer coefficients and low specific capacities of wells indicate the costs of produci.ng water from the aquifer will be high. The aquifer may sup- port a large number of small wells, but the total production from them is not likely to exceed three million gallons a day. The Cheswold aquifer is available in the northern half of eastern Sussex County. It is encountered at a depth of 365 feet below sea level at Milford and about 600 feet below sea level at Lewes and Georgetown. It is believed that the aquifer disappears at a depth of about 700 feet below sea level in the vicinity of Rehoboth Beach and north of Millsboro. The aquifer is estimated to have a low transmissivity of about 6,000 gallons a day per foot,at Milford. The transmissivity is believed to diminish in a downdip direction to an ex- tremely low figure. Wells at Milford and near Georgetown have extremely low specific capacities. The unfavorable water-yielding properties of the aquifer indicate costly development. Generally, the quantity of water available from each well will not exceed 100 gallons a minute in the northern part or 30 gal- lons a minute in the southern part of the aquifer. The aquifer as a whole is unlikely to be developed. If developed, the production of 50 or more small wells is estimated at about 3,500,000 gallons a day. The Federalsburg aquifer is available in the northern part of eastern Sussex County. At Milford the aquifer is reached at 270 feet below sea level. At Gravel Hill, about four miles northeast of Georgetown, the top of the aqui- fer is 520 feet below sea level. Elsewhere little is known about the depth or areal extent of the aquifer. The aquifer may be available in the northern and northwestern parts of the area. The yield of wells in the northern part of the area is generally expected to be less than 300 gallons a minute. Most of the wells may yield as little or less than 100 gallons a minute. If the aquifer is extensive, the estimated production will be less than five million gallons daily. The Frederica aquifer is available over the northern part of eastern Sussex County. The aquifer is developed to capacity in Milford. Away from Milford, in the northern part of the area, wells yielding up to 250 gallons a minute may be developed. The meager data available in the central part of the 150 report area indicate wells of only low capacity (50 gallons a minute or less) are obtainable. In the northern half of the report area,- the aquifer may sup- ply 3,500,000 gallons a day to many small wells. The minor Miocene aquifer above the Frederica is used in the Milford area and is believed to supply water at Slaughter Beach. The aquifer may extend over more than the northern half of eastern Sussex County. In Milford the transmissive properties of the aquifer are slightly less than the underlying Frederica. Two city wells at Milford yield about 250 gallons a minute each. Downdip the water-yielding properties of the aquifer are believed to diminish progressively. If the aquifer is extensive in eastern Sussex County, it may yield a total of four to six million gallons a day to many small wells. The Manokin aquifer subcrops beneath Pleistocene sediments in an area of about 75 square miles in the southern part of eastern Sussex County. The southern and thickest part of the subcrop extends from the mouth of the Broad- kill River on Delaware Bay to the vicinity of Georgetown on the western bound- ary of the area. The thickness of the subcrop ranges from 0 to 40 feet. It is estimated that the subcrop contains about 144,000 acre-feet (47 billion gallons) of water available to wells. The water in the subcrop is not under artesian pressure. The subcrop, therefore, is part of the water-table aquifer of the overlying Pleistocene aquifer discussed later in this summary. The artesian part of the aquifer extends downdip from the southern extremity of the subcrop and is available for development to the southern boundary of the area. 'The artesian part of the aquifer has good to very good water-yielding properties. At Bethany Beach the transmissivity is 60,000 gallons a day per foot. It is estimated 20 to 30 million gallons a day can be developed from the artesian part of the aquifer. The Pocomoke aquifer occupies an area of about 90 square miles in the southern part of eastern Sussex County. The Pocomoke aquifer subcrops beneath the Pleistocene in its entirety. The water in the aquifer is not under arte- sian pressure. The aquifer is therefore hydraulically a part of the overlying Pleistocene aquifer. The Pocomoke part of the water-table aquifer contains about 200,000 acre-feet (65 billion gallons) of water available to wells. The water-table aquifer of Pleistocene age is available throughout east- ern Sussex County. In about 75 square miles the subcrop of the Manokin of the Miocene is part of and contributes to the overlying water-table aquifer. In about 90 square miles the subcrop of the Pocomoke of the Miocene is a part of and contributes to the water-table aquifer. The saturated material of the water-table aquifer in volume is equal to 10 cubic miles and holds about three cubic miles of fresh water. The water contained in the aquifer is adequate to cover the surface of the report area to a depth of 30 feet. The aquifer receives on the average about 490,000,000 gallons a day of recharge from pre- cipitation, most of which is rejected. The rejected recharge is about equally distributed between fairweather flow of streams and evapotranspiration. In about 20 percent of the area the water table in the aquifer is five feet or less above sea level. Salt-wate'r contamination is a problem in parts of this area and other parts of the area may be vulnerable to salt-water problems in the future. The water-table aquifer not only supplies more than 90 percent of the ground water used in eastern Sussex County, but also supplies the water 151 for fairweather flow of the streams, water that evaporates from the land and stream surfaces, water that transpires,from the,trees and plants, and water that recharges the artesian aquifers in:their-subcrops. Predicated on proper planning, development and use, the aquifer can supply more than 100 mil-lion gallons a day without seriously harming the other useful functions of the aquifer. The salt-water problems of the subcrops of the artesian aquifers, of the fresh-salt water interface in the artesian aquifers and of the water-table aquifer have been given consideration in the eastern Sussex County report. The Atlantic Ocean, the Delaware Bay, the four inland bays (Rehoboth, Indian River, Assawoman and Little Assawoman) and the tidal estuaries draining to these bays all contain highly mineralized water. Some of these bodies of water cross the subcrops of the artesian aquifer. In some places the major salt-water problems of the area occur in the water-table. aquifer where the water table is five feet or less above sea level. Major problems have occurred in the past at Lewes and Rehoboth Beach. Both cities solved their problem by moving their well fields. In a few localities the hydrology ap- plied in relating the low altitude of the water table to the thickness of the aquifer indicates that the aquifer has always contained salt water and the only solution is to seek water elsewhere. Where such areas exist there is evidence that fresh-water supplies can be found within a distance of a few miles or less. The conclusions concerning,the eight aquifers studied in eastern Sussex County are: (1) the extremely poor water-yielding properties of the Piney Point coupled with the apparent close proximity of the fresh-salt water interface preclude the development of the aquifer; (2) the poor water-yielding properties of the minor Miocene aquifer below the Cheswold preclude development of wells of more than 200 to 300 gallons a minute, and the total available water from the aquifer from many small wells is not likely to exceed three million gallons a day; (3) the unfavorable water-yielding properties of the Cheswold indicate that it will be costly to develop. Most of the wel.ls are estimated.to pro- duce at a rate less than 100 gallons a minute and the total available water does not exceed 3,500,000 gallons a day; (4) The fair water-yielding properti es'o'f the Federalsburg aquifer above the Cheswold in the northern part of the area indicates wells of 100 to 300 gallons a minute. The southern part of the aquifer will probably yield less than 100 gallons a minute to wells. The aquifer is estimated to have an avail- able supply of not more than five million-gallons a day to many small wells; (5) the fair to poor water-yielding properties of the Frederica indicate wells of 50 to 250 gallons a minute. The aquifer is totally developed at Milford. It is estimated the available water from the aquifer in the northern part of the area may be 3,500,000 gallons a day; 152 (6) the fair water-yielding properties of the minor Miocene aquifer above the Frederica produces 250 gallons a minute from each of two wells at Milford. Downdip the yields probably would diminish to less than 100 gallons a minute. If the aquifer is extensive, many small wells might produce as.much as six million gallons a day from the aquifer; (7) the good water-yielding properties of the artesian part of the Manokin aquifer indicate that it will yield water to wells up to 500 gallons a minute in some places, and the available water from the aquifer is estimated to be 20 million to 30 million gallons a day; (8) the water-table aquifer consisting of@the Pleistocene deposits and subcrops of the Manokin and Pocomoke are available for development throughout the eastern Sussex County area, except in a small part of the area where the salt-water problem precludes development. The very favorable water-yielding properties and available recharge of the water-table aquifer make the aquifer available for large supplies of water in most of the area. Available recharge to the aquifer averages about 490 million gallons daily. The aquifer not only supplies more than 90 percent of the ground water used, but it also furnishes the hydraulic head that protects most of the aquifer from the intrusion of salt water; the'fairweather flow of the streams; the recharge to the artesian aqui- fers; and the water that is discharged by evapotranspiration. It is evident that the aquifer can supply more than 100 million gallons daily to wells with- out seriously hindering the other useful functions of the aquifer, provided the development is properly planned and the pumping properly distributed. WESTERN SUSSEX COUNTY In summarizing and giving conclusions of'their study of the availabil ity of water in western Sussex County, Sundstrom and Pickett (1970) wrotei The geology and hydrology of seven artesian ground-water reservoirs''and one water-table aquifer in western Sussex County have been,careful ly stud.ied. From these studies, methods of ground-water hydrology have been appl,ied to compute or estimate the amount of ground Water available from each of the , aquifers. The study reveals that the water-table aquifer of the Pleistocene, Manokin and Pocomoke is by far the most prolific source of ground water,in the area and can be developed throughout the' area. Under prudent planning, development and management, the aquifer is capable of producing,more than 120 million gallons a day. By lowering the water table by pumpage in the swampy areas, more-recharge might be effected and the amount of water avail- able in western.Sussex County might'reach 140 millio n gallons.daily.or more. Pumpage at this rate will probably affect,to-some extent the faimeather . , flow of ground water to streams; but, if properly p'lanned, the effect will not be serious because much of the water will be derived-from the surface swamps and shallow ground water that is normally lost to.evapotranspirdtion.' The water-yielding properties of the water-table aquifer are good to excellent over the entire area. The aquifer should supply wells of proper construction and pumping facilities with supplies of water ranging from about 400 to 1,200 gallons a minute. 153 Of the seven artesian aquifers studied, only the Manokin artesian aquifer of the Miocene has good to excellent water-yielding properties. The Manokin occurs under both water-table and artesian conditions. In its water-table area, it is a subcrop of the Pleistocene water-table aquifer. The artesian part of the Manokin begins at the southeastern edge of the subcrop and extends under about 77 square miles of overlying Miocene clay. The artesian Manokin aquifer has a probable transmissivity of about 60,000 gallons per day per foot and probably can be developed to yield about 20 million gallons a day. The minor Miocene aquifers above the Frederica, the Frederica aquifer, the Federalsburg aquifer, the Cheswold aquifer, and the minor Miocene aquifer below the Cheswold are all of Miocene age and have not been developed in western Sussex County. Tests indicate that the aquifers are of very low transmissivity, and wells will have a very low specific capacity. Because of the very low water-yielding properties of the aquifers, it is very doubtful that the aqui- fers will be developed to any extent. If they are developed, it is doubtful that the five Miocene aquifers could produce more than 25 to 30 million gal- lons a day and the yield of the wells would probably range from less than 50 gallons a minute to about 200 gallons a minute. The Piney Point aquifer is believed to contain fresh water only in the extreme northwestern part of western Sussex County. No well produced water from the Piney Point. Based on surrounding data, the transmissivity of the Piney Point is probably less than 10,000 gallons a day per foot and the small area in the northwestern part of western Sussex County where the water may be fresh will probably produce only three to four million gallons a day if de- veloped. The only salt-water problems in the report area are in the interface area between fresh and salt water in the Piney Point and the minor Miocene aquifer below the Cheswold. The Cheswold, the Federalsburg and the Frederica lose their identity as aquifers before they reach the fresh-salt water interface. The Nanticoke River is tidal at Seaford and contains fresh water under present hydrologic conditions. If the fresh ground-water discharge were elim- inated all of the way to the Chesapeake Bay, a salt-water problem of a local nature might occur in the shallow water-table aquifer near the tidal part of the river. Finally, in western Sussex County it is concluded: (1) the use of ground water from the water-table aquifer can be expanded tenfold over the present use of the aquifer or to 120 million gallons a day; (2) the undeveloped artesian part of the Manokin aquifer is a potential source of about 20 million gallons a day; (3) the development of the deeper artesian aquifers below the Manokin.is not likely, because of the poor water-yielding properties of the aquifers; (4) no potential salt-water problems are anticipated; 154 (5) research may lead to additional water supply in the swampy areas by lowering the water table by pumpage to recover recharge water lost by evapora- tion; and (6) the maximum use of ground water is predicated on proper planning, development and management of the aquifers. Much of the discussion in this report leads to management recommendations, policies and controls to assure adequate water supply of good quality. This has been the concern of the Department of Natural Resources and Environmental Control and the Board of Health for many years. Many of these conclusions have been discussed with the above departments and the recommendations included in the report of the Governor's Task Force on Marine and Coastal Affairs entitled "The Coastal Zone of Delaware, 1972." Legislation may be needed in several areas of water resources development and management. 155 BIBLIOGRAPHY Al-Saad, Adnan Ahmad, 1971, Electric Analog Model Study of Piney Point Aquifer, Kent County, Delaware: Master's thesis, University of Delaware. American Water Works Association, 1950 'Water Quality and Treatment: Am. Water Works Assoc. Manual, 2d. ed., tables 374, p. 66-67. Anderson, J. L. and others, 1948, Cretaceous and Tertiary Subsurface'Geology: Maryland Dept. Geol. Mines and Water Resources Bull. 2. Back, William, 1966, Hydrochemical Facies and Ground-Water Flow Patterns in the Northern Part of Atlantic Coastal Plain: U. S. 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Schultes and Son, 1966b, Report of Ground-Water Investigation, Avisun Plant, New Castle, Delaware. Tidewater Oil Company, 1966, Available Basic Data on Tidewater W611 Field, Delaware City, Delaware. 169 APPENDICES APPENDIX A: SUPPLEMENTAL ILLUSTRATIONS. Page Figure Al Draw.down Curves,for Upper and Lower.potomac Aquifers 168 Figure A2 Location of Hy pothetical Centers of Pumping for Test- 169 ing Drawdow ns in the Canal Area Figure A3 Map Showing Location of Selected Wells in the Potomac 170 Formation Figure A4 Graphic Plot of Pumping Test Data and Computation of 171 the Coefficients of Transmissivity and Storage in Delaware State Correctio'nal Institution Well (Gc54-2) in the Rancocas Aquifer Correctional Institution Well Gc54-2 ware State 172 Figure A5 Nonleaky Artesian Drawdown Curves for*Dela Figure A6 Relation of Well Diameter, Specific Capacity, Trans 173 missivity and Coefficient of Storage Figure A7 Graphic Plot of Pumping Test Data and Computation of 174 Coefficient of Transmissivity in City of Milford Well 5 (Le55-5) in the Federalsburg Aquifer Figure A8 Nonleaky Drawdown Graphs for the City of Milford 175 Well 5 (Le55-5) Based on Theis Equation Figure A9 Graphic Plot of Pumping Test Data and Computation of 176 the Coefficient of Transmissivity in the City of Harrington Well (Ld5l-8) in the Frederica Aquifer Figure AID Nonloaky Drawdown Graphs for the City of Harrington 177 Well (Ld5l-8) in the Frederica Aquifer Based on Theis Equation Figure All Graphic Plot of Pumping Test Data and Computation of 178 Coefficient of Transmissivity in Town of Bethany Beach Well (Qj32-12) in the Manokin Aquifer Figure A12 Nonleaky Drawdown Graphs for the Town of Bethany 179 Beach Well (Oj32-12) in the Manokin Aquifer Based on Theis Equation Figure A13 Electrical Resistivity Log of Well (Pf23-2), Owned 180 by H. Kruger, Inc. 170 Figure A14 Graph Showing Depth to Water in Wells (Md22-1 and 181 Qe44-1) in the Water-Table Aquifer in Kent and Sussex Counties from March 1967 to December 1969 Figure A15 Composite Fluctuation of Water Levels in 13 Wells 182 in the Water-Table Aquifer of the Pleistocene in Delaware Figure A16, Relation of the Altitude of the Water Table in a 183 Well in the Water-Table Aquifer to the Baseflow of Beaverdam Creek Figure A17 Nonleaky Drawdown Graph for a Well After Pumping 184 100 Days and 1,000 Days at a Rate of 1,000 Gallons a Minute from an Aquifer Having a Transmissivity of 100,000 Gallons Per Day Per Foot and a Coef- ficient of Storage of 0.15, Based on the Theis Equation Figure A18 Salinity Cross-Sections of Indian River 185 171 DISTANCE, IN 1000 FEET FROM EFFECTIVE CENTER OF PUMPING FROM A WELL FIELD 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 0 20- UPPER ZONE 0 520 G.RM. 40- 60- LOWER ZONE Q 1220 G.P M. 80- 100 120- 14-0- 160- 180- 200 220 FIGURE Al DRAWDOWN CURVES FOR UPPER AND LOWER POTOMAC AQUIFERS. 75-150' 75.4e ?IP40 75-35, 75-30' 75-te A N .4 -39-50, 39-5d- N SCALE IN MILES 1 0 2 3 4 39-45' WILMINGTON 39-4e- WHjrE aA,, NEWARK -39 40' NEW sg-od- CASTLE 5 Ct,,,,SVNA N E W ELKTON J E S E Y 08-2 40 -"035' 11 39-35- A (GETTY) E C, do. CANAL CHESAPEAKE D CITY -39-34Y Is ORA yZ-R ODESSA tjK r I MIDDLETOWN 00-1 < -3 .9-25' IN 39-25- -39-2e 3- Sol SMY .RNA r 705d 175-4e 75-W 75p3d 75-je FIGURE A2. LOCATION OF HYPOTHETICAL CENTERS OF PUMPING FOR TESTING DRAWDOWNS IN. THE CANAL AREA. 173 f 75'40* 75'35@ 75-30' T5.25, L A 39'50'- N S E LES 2 CAL IN MI 0 1 4 39-45' WILMINGTON 39.45!- Cc24-7 aCc24-8 4-4 CcZ4-5 Cc34-15 cc 0.12 Cc34-19 see -5 U43.1 d4l-? Cd -11 K U41-18 c 5 d52154:0 C Ca55-3 c::- WHIrr a-Ay CRF NEWAR Ca55-.ft Cd52-"5.: -39040, Obil-30 * NEW D024-4 0 1@ DC12-4 CASTLE 39-4d- 22-11 DbI5-I0 DbI5-4 Dc 12-5 44...2 10 5 DC22-80 C24-1 5-9,7 0OG34-5 Db35-3 Dc23- 2 N E W Db35-4 DC32-2 ELKTON DC32-3 J E R S E Y 40 Dc42-1 DC51 4% a Db4l-: ft!@I-!? 9D.52-23 Dc5I-6 OC53-23t -39-31V DC53-31 39-se- Ec 12-1 E414-1 EbI5-4 1 EC15- 1 15015-1 Ec22-3 Eb2l2**Eb24-1 -3 EaU-a@4 I C. &D. CANAL Ec32-7 Eb34-3 CHESAPEAKE Ec44-1 CITY E451-1* Iillil-Ild WYER ODESSA R/ r1 0 I'll'? >I MIDDLETOWN z -39-25' 39-25,- 0,00 /X 39fte- %% RIVER .,SMYRNA 75-4d T5'3V 75 5d FISURE A3. MAP SHOWING- LOCATION OF SELECTED. WELLS IN' THE- POTOMAC FORMATION. 0 0.6 WELL 1-10413 PUMPI@G MODIFIED THEIS NONEQUILIB UM --ORIAUI@A 0 Pumpage (gpm) For Theis Formula So* Figure 8 r D Ito Purnpec Well T 2 T= Tronsmi ivity gpj/ft) 2.25 Tt it of Storage S= ra 0'3 Tto in English Unit! S= Coeff(ci: rl s = Drowdow 1 ( f t) t = Time in inutes lo= T oys Fro 0 D4wdovtn In 4rcipt 4 T 264gx 19,100-gpd,Ift 0 3 x 19 00 x .05( S 0 0002; (1 70)9 6 7.5 8 10 SOURCE OF BASIC DATA 12 Hour Purrping Test, March 28,196-1 By A.C.Schiltes Sons Drilling 0. 12 10 100 1,000 10,000 t FIGURE A4. GRAPHIC PLOT OF PUMPING TEST' DATA AND COMPUTATION OF THE COEFFICIENTS OF TRANSMISSIVITY AND STORAGE IN DELAWARE STATE CORRECTIONAL INSTITUTION WELL (Gc54-2) IN THE RANCOCAS AQUIFER. DISTANCE IN THOUSAND FEET, FROM PUMPED WELL 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 0 10 20 30 w 40 w ILL Z 50 0 < 60 70 After Pumping 100 Days 80 After Pumping 10,00b Days TRANSMISSIVITY = 19,100 gpd/ft COEFFICIENT OF STORAGE = 0.00028 90 WELL. DISCHARGE 0) 500 gpm 100 FIGURE A5. NONLEAKY ARTESIAN DRAWDOWN- CURVES FOR DELAWARE STATE CORRECTIONAL INSTITUTION WELL Gc 54-2 Based on Theis Nonequillbrium Equation RAAICOCAS AOUIFER iIm go, 60,601=1 Mae,," M.Ml wM.IMI M M LL L SPECIFIC CAPACITY AT END OF I DAY, IN GALLONS PER G) MINUTE PER FOOT OF DRAWDOWN rrl 0 0 . 0 p 0 0 0- 0 a) 0 r. w 05 L:p (0) m m -60 17- T, j I Ali h, m 00 z 0 -no z m 00 m 0 x m Z 444- m 0 X* r- rnm I I 11L 0 m r- 0 @u rn n > (An 1, m Fn -4 z 0 0 > ch rn zz 0 z 00 M in m m- 2 t U) > z cn 0 12 Fn- 01 0 'o 0 0 o om -0 o 0-0- 0 'o p 0 'o - -'o -"o --0- 0 0 0 0 0 00 o CF n 0 0 0 0 0 0 0 oo -FTo 0 Fiji 0 @o 0 W00001 900 0 X > 7-. COEFFICIENT 0 F TRA NSMISSIVI TY, IN GALLONS PER DAY PER FOOT 75 so 85 MODIFIED THEIS I UATION T z 2640- = @64X 500 = 9,400 GP)/FT As 14.0 T = TRANSMISSIBILITY IN GALLONS PER DAY ER FOOT S = DRAWDOWN, IN FEET t = TIME, IN MINUTES 90 As= DRAWDOWN IN ONE LOG CYCLE OF TIME co WELL SCREENED 293 TO 328 FEET 95 100 AS =1 05.25 - 91.2 514. 00 SOURCE OF DATA: LAYNE -NEW YORK CO., INC. PUMPING TEST 4-5-62 105 L 1 10 100 1,000 t CITY OF MILFORD WELL 5 (Le 55-5) THE FEDERALSBURG A00FER FIGURE AT GRAPHIC PLOT OF PUMPING TEST DATA AND COMPUTATION OF COEFFICIENT OF TRANSMISSIVITY IN CITY OF MILFORD WELL 5 (Le 55-5) IN THE FEDERALSBURG AOUIFER. IN FEET (A . -0 0 m 0 PD -.1 02 0 (A 0 40 z -n m 0 00 z 100 0 m -n > 0 rn rn V a z Ln rvi x > Ln (n CO) -n 0 10 -j lp it 0 r7l 0 !7 rvl fvl L71 CE) (n m 081 s IN FEE -0 0 0 0 m > 010 rn 0 0 aj 0 9 1 -1 a @, r -n 0 G) lz - -.' 0 -n m m m 3> z (n -0 c 0 m Ir n M c 0 m 0 cyl z z rn G) Go F r4 m Cl) Cl) 0 "Vi 74 X > a? z z 0 G) 4 0 0 0 z rn i6l M 0 m n -n 3 m z DO -A ra0 QD 0) N- w 0 4 N c -0 o 0 0 0 0 0 0 rnz 0 z rn m 8 -10 0 -.00 2 (,1 z z IE040 -4 CL x rn Cilz r-0 rn 0 am, -n0 rn ;o0 0 - n M 0z m 0 > M z >En z C) 0 c-n0 M z mm 7@4 m rn to r, m CD r, 74- m tp. m 0 P 0 OD 8 z 0 -n m M G-) > z m N@Socl I I I I I 1 1 2 THEIS RECOVERY EOUATION T 264 0 as T z COEFFICIENT OF TRANSMISSIBILITY IN GALLONS PER DAY PER FOOT Q a RATE OF PUMPING IN GALLONS A MINUTE AS'= RECOVERY OF WATER LEVEL DURING ONE LOG CYCLE OF TIME Q z 320GPM AS'= 1.4 FEET T 264'j'-O 60,000 GPD/FT. 1.4 00 w 7 10 100 11000 t (MINUTES) BETHANY BEACH WELL Qj 32 -12 MANOKIN AOUIFER FIGURE All. GRAPHIC PLOT OF PUMPING TEST DATA AND COMPUTATION OF COEFFICIENT OF TRANSMISSINITY IN TOWN OF BETHANY BEACH WELL (QJ32-12) IN THE MANOKIN AQUIFIER. m'm'm'm 0 NONLEAKY DRAWDOWN GRAPHS, BASED ON THEIS EQUATION 2 Tz 60,000 GPD/FT Sz .0005 (ASSUMED) 0=6006PM .010 0.00 000 0.01 Z z 0 0 10 3w __000 \0 12 000' 00 w 14 16 Is- 22 24 loo 1,000 10,000 100,000 DISTANCE FROM PUMPED WELL, IN FEET FIGURE A12. NONLEAKY DRAWDOWN GRAPHS FOR -THE TOWN OF BETHAN@ BEACH' WELL (Qj 32-12) IN THE MANOKIN AQUIFIER, BASED ON THEIS EQUATION. 10 20 30 w RESISTIV)TY 40 OHM -M/100 so 60 70 w w LL so z go LL -Z 100 z 110 0 J120 130 Lu w Z 140 0 ISO 160 170 ISO 190 200 L06 By,: K.D. WOODRUFF DELAWARE (3EOLOGICAL SURVEy FIGURE A13. ELECTRICAL RESI.STIVITY LOG OF WELL (PF23 KRUGER, INC, -2) -OWMED By 784 2 3- EST! M AT ED WELL Md22-1 5 All WEILL 0044- -000 co ks" 2 I J-1 i F M A M J J A S 0 N D J_ F M A M I J I-J A I S I N D 4 F M A M J JJ @A I S 0 N 196? 1968 1 1969 FIGURE A14. GRAPH SHOWING DEPTH TO WATER IN WELLS (MD 22-1 AND QE 44-1) IN THE WATER TABLE AQUIFER IN KENT AND SUSSEX COUNTIES FROM MARCH 1967 TO DECEMBER 1969. 98T AVERAGE DEPTH TO WATER, IN FEET BELOW LAND SURFACE m 0 o c rq C 0 0 0 Z M o z mile r 40 ro m Vf Jo" 49 030 48 _j 0 x w W_ > 06 0 w47- _j 6 x 4 46 w z 4 X11 < 6 w 7X 7 Z' 45 w Z> 8 EXPLANATION :3 0 8 0CD X18 01950 W <44- x 01951 ZW 10 X 1952 W Number Indicates Calendar Month LL 43-1 January-1 wz 0 oil 42- From Rasmus$*nand Andreassn', 1959 0 10 20 30 40 50 60 BASE FLOW, IN CUBIC FEET PER SECOND FIGURE A16. RELATION OF THE ALTITUDE OF THE WATER TABLE IN A WELL IN THE WATER TABLE AQUIFIER TO THE BASEFLOW OF BEAVERDAM CREEK. @4& X,.@2 3 _I 17 x 9 7,' 0011C 187 0 4- w w IWL NCR PC 00 00o cr !2 20 10 100 1,000 10@,000 100,000 DISTANCE FROM PUMPED WELL IN FEET FIGURE AIZ NONLEAKY, DRAWDOWN GRAPH FOR. A WELL AFTER PUMPING 100 DAYS AND 1000 DAYS AT A RATE OF 1000 GALLONS 'A MINUTE FROM AN AQUIFER HAVING A TRANSMISSIVITY OF IOOPOO GALLONS PER DAY PER FOOT AND A COEFFICIENT OF STORAGE OF 0,15, BASED ON THE THEIS EQUATION. SECTION A- MID-EAST INDIAN RIVER BAY SALINITY VARIATION (PARTS PER THOUSAND) 0 TIME OF SALINITY MEASUREMENT 10- VISABILITY LIMIT 8- TIDAL CYCLE w 6- w U. - 28 28 29 '30 CL 4- 29 w 2- 0- 4 6 s 10 12 14 16 Is 20 22 TIME (HOURS), JULY.20, 1967 SECTION B - NEAR WESTERN TIDAL LIMIT -INDIAN RIVER SALINITY (PARTS PER THOUSAND) VISABILITY LIMIT 4- w w U- 2- 6 8 9 7 .10 9 11 w Ole- or I - 5 7 9 11. 1.3 15 17 19 21 2:5 TIMEJHOURS) JULY 17,1967 JOMN C AFTER KRAFT, Iffs I@11 01 1 8@11 I I I FIGURE AIS. SALINITY CROSS SECTIONS OF INDIAN RIVER. .189 APPENDIX B: SUPPLEMENTAL TABLES Page Table Bl Selected Patterns of Development Along the Canal 188 and Their Effects Table B2 Records of Wells Drawing Water from the Potomac 189-190 Formation in New Castle County, Delaware Table B3 Specific Capacities of Wells and Test Wells in the 191 Chesapeake and Delaware Canal Area Table B4 Coefficients of Transmissivity and Storage Deter- 192-194 mined from Pumping Tests of Wells in the Potomac Formation in the Chesapeake and Delaware Canal Area Table B5 Static Water Levels and Pumpage Data in the Town 195 of Clayton Well Drawing from the Rancocas Aquifer Table B6 Early Artesian Pressure Data in Wells to the 196 Rancocas Aquifer in the Clayton Area Table B7 Specific Capacities of Wells and Test Wells in.the 196 Rancocas Aquifer in New Castle and Kent Counties, Delaware Table B8 Coefficients of Transmissivity and Storage Deter- 197 mined from Pumping Tests of Wells in the Rancocas Aquifer in New Castle County Table B9 Example of Computed Drawdowns Caused by Pumping 198 Seven Hypothetical Wells in the Rancocas Aquifer, 5,000 Feet Apart, from Clayton Southwestward toward the State Line in Kent County Table BIO Specific Capacities of Wells and Test Wells in Kent 199-202 County, Delaware, and Surrounding Area Table Bll Coefficients of Transmissivity and Storage Deter- 203-206 mined from Pumping Tests of Wells in Kent County, Delaware, and Surrounding Area Table B12 Coefficients of Transmissivity and Storage Deter- 207-208 mined from Pumping Tests of Wells in Eastern Sussex County, Delaware, and Surrounding Area Table B13 Lowest Pumping Levels and Available Draw down in 209 the City of Dover Wells to the Cheswold Aquifer Table B14 Specific Capacities of Wells in Eastern Sussex County, 210-214 Delaware, and Surrounding Area 190 Table B15 Specific Capacities of Wells in Western Sussex 215-218 County, Delaware, and Surrounding Area Table B16 Coefficients of Transmissivity and Storage Deter- 219-221 mined from Pumping'Tests of Wells in Sussex County, Delaware, and Surrounding Area Table B17 Yield and Specific Capacity of Large-Diameter 222-226 Wells Tapping the Columbia (Pleistocene) Deposits and Estimated Transmissivity of the Aquifer Table B18 Records of Wells in Western Sussex County Giving 227-229 the Altitude of the Land Surface, the Altitude of the Water Table, the Depth of Penetration in the Water-Table Aquifer Below Sea Level, the Depth to the Base of the Pleistocene Below Sea Level in Some Wells and the Known Thickness of the Water- Table Aquifer at Each Well Table B19 Estimated Area and Volume of Saturated Material Above 230-232 and Below Sea Level in the Water-Table Aquifer in the Pleistocene in Each 5-Minute Grid of Latitude and Longitude of Western Sussex County Table B20 The Relation of Ground Water Stage to the Average 233 Monthly Discharge of the Nanticoke and Pocomoke Rivers During Drought Recession June to October, 1968 191 Table Bl. Selected Patterns of Development along the Canal and their Effects Total Pumping Rate at Selected Drawdown-at Observation Point Well Field Site (mgd) Total in Selected Wel.1- Field Site (feet) Pattern Well Field Site Development A B C D E Number A C D E (mgd) L U L U L U L U L U 1 2. 5 1.7 1.8 2.5 2. 5 11.0 189 100 197 104 208 113 213 114 183 95 2 2. 5 1.8 2.2 3. 5 0 10.0 191 101 2,04 l'O 7 219 118 197 103 - - 3 2. 5 2.0 3. 5 0 0 8.0 186 98 207 108' 197 102 - 4. 2. 5 4.0 0 0 0 6.5 185 94 197 98 5 2. 5 0 5.0 0 0 7.5 157 84 203 102 - 6 2. 5 0 0 5.0 0 7.5 125 66* - - 187 93 - - 7 2. 5 0 0 0 5.2 7.7 112 57 - - 186 91 8 4. 1 0.9 0.9 1.25 1.25 8.4 190 197 . 171 91 147 82 131 72 110 57 9 4. 1 0.9 1.1 1.8 0 7.9 j 9 11 97 174 92 152 85 123 67 - - 10 4'. 1 1.0 1.75 0 0 6.85 188 96 176 92 140 7@ - 11 4. 2.0 0 0 0 6.1 187 93 '71 87. - - 1@ 4.i 0 4.0 Q 0 8.1 95 101 - - 4 10Q 191 13 4. 1 0 0 4.7 0 8.8 175 90 - - 190 96 - - 14 4.i 0 0 0 5.0 9.1 1,64 82 -- - - 189 93 15 0 0 0 0 3.0 3.6 @1 10 17 10 30 70 38 L Lower Zone of the Potomac Formation, U Upper Zone of the Potomac Formation Table B2. Records of Wells Drawing Water from the Potomac Formation-in New Castle County,-Delaware Delaware Water Altitude Geological Depth Level Date of of Ground Survey Local in Ft t Mean Measure- Surface Well Number Well Number. Feet 'Screened @Sea Level, ment in Feet Ca55-3 64.5 80 2-29-52 1019 Ca55-8 42 81 7-12-53 105 Cc24-5 Artesian Water 160 -12, 3-22-50 Company #17 Cs24-7 Artesian Water 163 0 3-24-50 76 Cc24-8 Company #20 lAO_ -22- 3-24-50 70 Cc34-15 112' 8 12-7-53 23.3 Cc45-5 302 278-288 -14 7-51 65 Cd4l-7 200 189+ 0 7-55 65 U41-18 80 43 3-18-61 69 U42-13 73 19 111-53 .40 U43-11 88 -21 4-16-52 13.2 U52-13 1 3@2 116-134, 5 8-20-52 12 U52-15 73 19 11-53 40 Dbll-38 192 52 3-12-64 75� Db15-1 136 27 1951 30 Dc5l-9 Getty #R4 340 252-270S 21 11-30-55 40.3 286-312 Dc53-7 Getty #12 657 534-539 16 9-20-54 54.9 Dc53-23 Getty #5C 710 538-543 8 9-16-54 32.2 Dc53-31 Getty #5A 613 400-406, 12 7-19-54 32.0 Eal5-1 55 201-207 62 11-27-53 65 Ea33-1 Goodrich TW #2 427 390-410 2 11-18-66 60 Ea33-2 Goodrich Obs #1 431 408-418 0 11-18-66 60 Ea33-3 Goodrich Obs #2 431 398-408 2 11-18-66 60 Ea33-4 Goodrich TW #1 695 580-585s 2 9-30-66 60 598-608 193 Tabl eB2 Continued Delaware Water Al ti tude Geological Depth Level Date of of Ground Survey Local in Ft � Mean Measure- Surface Well Number Well Number Feet Screened Sea Level ment in Feet EbI5-2 Getty #8 .636 240-245 26 10-13-54 65.5 Ebl5-4 Getty #03'., 556 510-541 14 10-25-55 69..5 Eb24-1 208 9+ 10-19-43 60+ Eb24-2 177 21 8-52 45 Eb34-3 845 442-462 -2 4-20-67 58.2 Ecll-2 Getty #7 565+ 560-565, +19 1.64 1955 41.5 E62-15 Getty #3B 734 340-345 10 9-19-54 57.5 Ecl2-20 Getty 09 558 525-558 -14 @4-56 13� Ecl3-6 Getty #16 705 523-563, 4 1-5-55 35.5 581-592 E04-1 Getty #13 757 678-685 6 9-20-54 4.4 Ecl5-26 701 631-6362 -44� 4-12-61 1,0� 675-695 Ec22-3 261- 235-260 13 2-16-53 10 Ec32-3 'Union Carbide TW 420 318-32 8, 1966 #2 (Site 1) 338-348 Ec32-7 Union Carbide TW 752 586-596, -33 1966-67 11.15 #1 (Site 1) 350 6 3-50 25 Ec44-1 Ed5l-l 473 447-473 6 1-20-56 11 194, MEN Mm"W"M W Table B3. Specific Capacities of Wells and Test Wells in the Chesapeake an'd Delaware Canal Area Specific Bottom -Owners Capacity Time of Screen Hydrologic Well Number Owner gpm/ft. Pumped feet Z o n-e Reported by Eb15-4 P-3 Getty Oil Company 1.7 24 Hrs. 541 Lower Potomac Delaware Geological Survey Dc5l -7 P-4 do 1.7 24 Hrs. 544 do do Dc4l-4 P-5A do 2.3 24 Hrs. 539 do do Dc42-6 P-6A do 1.5 24 Hrs. 698 do do Ec12-20 P-9 do 5.4 24 Hrs. 588 do do E c 14 - 7 P-10 do 4.4 24 Hrs . 702 do do Dc52-24 P-15 do 3.5 60 days 333 Upper Potomac do E c 13 - 6 P-16 do 2.1 24 Hrs . Lower Potomac do Ec32-3 TW-2 Union Carbide 6.0 24 Hr.s. 348 Upper Potomac Geraghty and Miller Corporation E02-7 TW-1 do- 0.9 8 Hrs. 595 Lower Potomac do Eb34-3 TW- I Cana,l Realty Co. 1.0 24 Hrs. 462 Upper? Potomac. do Ea33-1 TW-1 B.F.Goodrich. 1.5 Several 608 Lower Potomac do Hours Ea33-2 TW-2 do 7.0 24 Hrs. 427 do do Remarks: Production wells are indicated in owner's number column by the prefix "P". Test wells are indicated i-n the owner's number column by the prefix "TW". The sand screened in Canal Realty Co. well TW-1 is in the clayey zone just below the upper hydrologic zone (Sundstrom et al., 1967). Table B4. Coefficients of Transmissivity' and Storage Determined from Pumping Tests of Wells in the Potomac Formation in the Chesapeake and Delaware Canal Area Effective Coefficient Hydro- of Trans- logic Pumping Test Data Coefficient missivity Date Well zone Owner Conducted by Analyzed by of Storage gpd/ft. Remarks 1-24 to 16 Lower Tidewa- Leggette and Leggette 5,500 Source of data: 2-10-55 (Ecl3-6) Potomac ter Oil Brashears and Report by Zone Company Brashears Leggette and (Now Brashears to Getty Ti'dewater Oil Oil Co.) Co. on "Poten- tial Ground- Water Supply at Delaware City, Delaware" p. 45 do 5C do do do do 0.00019 4,700 do (Dc53-23) do 1C do do do do 0.00017 5,400 do (Dc52-31) do 6 do do do do 0.00011 9,600 do (Ecl2-3) do 3 do do do do 0.0003 6,400 do (Ecl2-2) 13 do do do do 0.00028 11,500 do rd o (E04-1) Table B4 Continued Effective Coefficient 'Hydro- of Trans- logic Pumping Test Data Coefficient missivity Date Wel I Zone Owner Conducted by Analyzed by of Storage g p d / f t Remarks do 5 C , I C do do do do 0.00021 7,500 Average of 6,3,13 above 5 wells 10-12, 5A do do Tidewater Oil Tidewater 5 900 13,1955 (Dc53_31) Company Oil Co. :11-8 to 6 do do do do 8,500 12-28-55 (Ec]2-3) to 6,000 do 13 do do do do 9,300 Ecl 4-1 Dec. 15 Upper do Leggette and Leggette 4,500 Pumped wel I 1954 D c 5 2 - 2 4Potomac Brashears and Source of data Zone Brashears same as for Well #16 above do 1-D do do do do 0.00017 4,100 Dc52-32) do 14-A do do do do 0.0005 7,100 D c 5 3 - 6 do 3-B do do do do .0.00006 4,700 (Ecl2-15) do 5-B do do do do @O 00025 7,200 (Dc53-32) Table B4 Continued Effective Coefficient Hydro@ of Trans- 10 g i c Pumping Test Coefficient missivity Da te Wel 1 Zone Owner Conducted by Analyzed by of Storage g p d / f t Remarks 9-29-55 I-H do do Tidewater Oil Tidewater 6,100 (Dc52-6) Company Oil Co. do 3-B do do do do 7,500 E c 12 - 15 do 9 do do do do 4,800 (Ec5l-3) Oct. TW@2 do U n i o n Geraghty and R. W. 6,100 Basic data 1966 E c 3 2 - 3 Carbide Mi 11 er Sundsirom furnished by Company Geraghty and M i 11 e r do OB-1 do do do do 6,500 do E c 3 2 - 4 do OB-2 do do do, do 6,500 do (E02@5) Nov. BFG Lower B. F. do do 12,300 do 1966 OB-1 Potomac Goodrich (Maryland) Zone Company do BFG do do do do 12,300 do OB-2 Ma ryl and) Remarks: Numbers in parenthesis are assigned by Delaware Geological Survey. Table B5. Static Water Levels and Pumpage Data in-the Town of Clayton Well Drawing from the Rancocas Aquifer Static Water Altitude of Level Below Static Water Discharge Pump Base Level Above Yield Pressure Date in Feet MSL GPM LBS Remarks 1954 31 14 350 410 ft. Total dynamic head Apr. 1964 98 -53 July 1965 123 -78 255 63 Pumping level 200 ft. do 318 0 Pumping level bel.ow 205 ft. June 196'7 103 -58 335 10 Pumping level 205 ft. Source of d'ata: Shannahan Artesian Well Company 199 Table B6. Early Artesian Pressure Data in Wells to the Rancocas Aquifer in the Clayton Area Altitude Altitude of Depth to of Artesian Water in Measuring Pressure Well Date Owner Feet Point in Feet Hc32-1 6 April 1943 W. L. 14 40 26 Wheatley Ib32-1 Oct. 21, 1949 Marvel 40 65 25 Everett Hc32-2 Mar.- 27, 1950 Townof 22 45 123 Clayton Table E17. Specific Capacities of Wells and Test Wells in the Rancocas Aquifer in New Castle and.Kent Counties, Delaware Specific Depth Owners Capacity Time of Well Well Number Owner, Aquifer GPM/Ft. Pumped in.Feet Hcl4-3 2 State of Delaware Rancocas 3.4 12 hrs. 271 Gc54-3 1 do do 1.1 12 hrs. 250 Hc32-2 Town of Clayton do 1.8 272 Hc32-16 4 W. L. Wheatley do 4.6 260 Ib32-1 Marvel Everett do 1.4 296 200 I* WK. AM no so t" WK 00 Table B8. Coefficients of Transmissivity and Storage Determined from Pumping Tests of Wells in the Rancocas aquife.r in New Castle County Coefficient Data of Trans- Date Well Aquifer Owner Pumping Test Analyzed Coefficient missivity Conducted by by Of Storage GPD/FT. Remarks 3-28-67 Gc54-2 Ran cocas State of A.C. Schultes R.W. 0.00028 19,100 Well He14 -3 Delaware and Sons Sundstrom Pumping CD 3-28-67 Gc54-3 do do do do 0.00027 19,200 do 4-10-67 Gc54-2 do do do do 0.00022 14,000 Well Gc54-3 Pumping 4-10-67 H c 14 - 3 do do do do 0.00019 16,800 Well Gc54-3 Pumping Table B9. Example of Cdmputed Drawdowns Caused by Pumping-Seven Hypothetical Wells in the Rancocas Aquifer, 5,000 Feet apart, from Clayton Southwestward toward the State Line in Kent County Well 1 2 3 1 4 5 1 6 7 Rate of Pumpage GPM 350 350 3001300 300 350 350 Drawdown effect, in feet, Well 1 140 17 15 13 12 11 10 Drawdown effect, in feet, Well 2 17 140 17 15 13 12 11 \ . - Drawdown effect, in feet, Well 3 13 15 120 15 13 12 10 Drawdown effect, in feet, Well 4 12 13 15 120 15 13 12 Drawdown effect, in feet, Well 5 10 12 131 15 120 15 13 Drawdown effect, in feet, Well 6 11 12 13 15 17 140 17 Drawdown effect, in feet, Well 7 10 11 12 13 15 17 140 Pumping Level, in feet, (10,000 days) 213 220 205 206 205 2 Allowable drawdown 220 feet Distance between wells 5,000 feet Time 10,000 days Transmissivity 16,800 gpd/ft. Coefficient of storage 0.00019 Specific Capacity 2.5 gpm/ft. Table B10. Specific Capacities of Wells and Test Wells in Kent County, Delaware, and Surrounding Area Specific Depth Owners Capacity Time of Well Wel I Number Owner _ Aquifer GPM/Ft. IPumped in Feet Source of Data Hcl4-3 2 State of Delaware Rancocas 3-4 12 271 Pumping test by A. C. Schultes & Sons 3-28-67 Gc54-3 1 do do 1.1 12 hrs. 250 do - 4-10-67 Hc32-2 Town of Clayton do 1 .8 272 Pumping test by Shannahan Artesian Well Co. 6,.-21-67 and using original static of 1950 Hc32-16 4 W. L. Wheatley do 4.6 260 Plant Engineer, W. L. Wheatley, C> 1955 Ib32-1 Marvel Everett do 1.4 296 Ennis Bros. Drillers Completion Report 10-21-49 i'He52-2 1 National Wildlife Piney 0.9 4 hrs. 262 De.lawarE Geological,Survey Refuge P o i n t Ifil-1 5 do do 3.6 Flowed 312 do Id53-3 FcKee Run City of Dover do 2.7 14 days 372 Layne-New York Co. Test 5-8-63 6 Id53-2 do do do 3.6 10 hrs. 379 do - 4-4-62 7 Jdl4-1 2 Division do do 6.1 5 hrs . 423 Shannahan Artesian Well Co. Street 10-19-61 Test Well Table B10 Continued S p e c i f i c Depth Owners Capacity Time of Well Well Number Owner Aquifer GPM/Ft. Pumped in Feet Source of DaLa Jd25-3 Danner City of Dover Pi,ney Point 14.6 484 Shannahan Artesian Well Farm #10 Co. Jd23-1 Crossgates do do 4.7 24 h rs. 435 Shannahan Artesian Well Co. Je32-5 D U. S. Air Force do 9.6 to 4 years 575 Daily observations by Dover Air Force 5.6 personnel of Air Force Base Base Kd 1,3- 1 Kent County do 5.9 Shannahan Artesian Well Vocational and Co. Pumping Test 6-15-65 Technical School Kd5l-5 3 Swift & Co. do 4.9 7-1/2 583 Layne-New York Co. hrs. 7-6-60 Kdll-8 2 Green Giant Co. do 10.8 12 hrs. 490 A. C. Schultes & Sons 3-11-59 Mel 5-29 Piney City of Milford do 0.3 3 hrs 788 A. C. Schultes & Sons Point 2-20-68 Test Well Id3l -18 7 International Cheswold 0.9 Several 163 Delmarva Drilling Co. Latex Co. hrs. Test 7-3-57 Id3l-2 8 do Cheswold, Upper 3.4 do 160 do Miocene and Pleistocene low so wip@ M @,abl e BI 0 Conti nued Specific Depth Owners Capacity Time of Well Well Number Owner Aquifer GPM/Ft.. Pumped in Feet Source of Data Jdl4-2 Power City of Dover Cheswold 7.9 Several 228 Shannahan Artesian Well Co. Plant #1 hrs. Pumping test 12-2-66 Jdl4-1 Division do do 5.5 38 hrs. 210 do - 2-17-64 Street #2 id24-1 Dover do do 12.0 24 hrs. 222 City of Dover Street #3 jdl4-6 Water do do 16.7, 1-1/2 221 Shannahan Artesian Well Co. Street #4 hrs. 1-4-61 Jdl5-2' Bayard do do 25.4 224 do Ave. #5 Pump'ing test 11-23-67 Jdl5-4 East Dover do do 16.6 06 hrs. 229 City of Dover - 1966 Pumpage and #8 Water Level, Records Jd25-2 Danner do do 6.2 641 hrs. 222 do Farm #9 1 Je32-3 Well A Dover Air do 11.2 to 5 years 268 Dover Air Force Base - 1966 Force Base 5.9 (inter- Pumpage and Water Level Records mittently) Joseph W. White, Chief Engineer Je3l-l Well B do do 27.6 @o -do 232 do 17.2 Je3l-2 Well C do do 15.7 to 7 days 233 do 13.6 Jd35-2 C. Zimmerman do 6.9 24 hrs. 213 Delaware Geological Survey- Bulletin 4 903 r- C- 0 CD M (D o. CL CL X: rn Ln Ul -;h Ul Ul 4t* m Cn 4t:- Ln w cn - N) CD .a CO -4 00 L" N) C) 0' (D C-*) rD -S 0 S C-) --I Ln w 0 C+ ::E l< l< sw w = z-:- sw -S -1 ul 0 0 C+ Ol :E "E: 0. --h 0 0 = l<o CD m 0 = 1 0 --h :E M M 0 too :3 a C+ -h n CD I< to 0 sw -S -h --h 0 0 CL I CD r+ M (D 0 -n -n fD -1 (D aw C+ M- fD M CL CL 0- 0 0 0 CL 0 0 rD CA 0 rD w ::c -h rD -1 a- 0 rD -a. 0 CD 0 < m W rD m C-) L/) Ul -V sw 10 = -0 CD 0) 4L- CD M M 1.0 -n 0 @J. C+ NJ -0 Ul M rlj a -S -S -1 -1 CD (D V) (A Ln V) (A 06 0 --h C:; N) N) PQ PQ (D 0) rl.) N) w w w -M Z:-0 co w -0. -P. @4 (D (D c+ (D (4 a) CA M (D (D (D r- (D -i tA -S < 0), @ C+ < 0) (D :E fDZ CD (D *: ,< l< 0) C-) M;a l< 0) V) -1 C+ 0 LA.) rD -S 0 (D I (D N -0 1 rD c 0 -1 -1 0 C (D C CD CD C+ C CD CD 0 N) C+ -0 @ I @. 0- 0 fD 0 (D 0 000 C< rD 0 -h C+ to C+ to C+ La LT, 0 0 (DO 0 pi 0) 0) CD C+ 0 CD -1 C+ C+ N -- Table Bl I Coefficients of Transmissivity and Storage Determined from Pumping Tests of Wells in Kent County, Delaware, and Surrounding Area Coefficient Data of Trans- Pumping Test Analyzed Coefficient missivity D a te Well by by of Storage GPD/Ft. Remarks uifer Owner Conducted 3-28-67 Gc54-2 RancocasState [email protected] & Sons R. W. 0.00028 19,100 Well Hel4-3 Delaware Sundstrom Pumping Data from Del . Geo- logical Survey well in New Castle County near county line 3-28-67 Gc54-3 do do do do 0.00027 19,200 do NO 4-110-671 Gc54-2 d o do do do o.b0022 14@000 Well-Gc54-3 C) Pumping 4-10-6 HC14-3 do do do do 0.00019 16,800 Well GC54-3 Pumping 4-4-62 McKee Run 6Piney City of Layne-New York Co. d o 6,000 Data from City (Id53-2) Point Dover of Dover 4-4-62 McKee Run 7 do do do do 8,500 do (Id53-3) 10- 19-61 Di vi si on St do do Shannahan Artesian do 28,000 do Test Well Well Co. (Jdl4-12) 8-2-65 Crossgates do do do do 21,000 do 11 First 2-1/2 hrs. (Jd23-1) of test Table Bll Continued Coefficient of Trans- Pumping Test Analyzed Coefficient missivity Date Well Aquife Owner Conducted by by of Storage GPD/Ft. Remarks 8-2-65 Crossgates Piney City of Shannahan Artesiar R. W. 9,900 Data from City 11 Point Dover Well Co. Sundstrom of Dover - (Jd23-1) Last 2-112 hrs. of test do do do do do do 9,000 Reco'very test 7-24-63 Je32-4 do U.S. Air R. D. Varrin R. D. 0.0003 32,000 Well Je32-5 Force Varrin Pumping do do do do do do 41,000 Recove@y do do do do do R. W. 0.00027 39,000 Using first 36 CD CO Sundstrom minutes and last 15. hrs. of drawdown curve 3-11-59 Kdll-8 do Green A. C. Schultes do 33,200 Data from A. C. IGiant Co. & Sons Schultes & Sons 7-6-60 Kd5l-5 do Swift Layne-New York Co. do 38,000 Data from Swift & Co. J* & Co. 7-23-51 DorCe4 do City of R. H. Brown and Brown and 0.00036 47,500 Drawdown test- Cambridge Cambridge T. H.,Slaughte r Slaughter Data from Bed 18 Md. Md. Maryland Dept of Geology Mines & Water Resource@_j tow 'aw" fti, Iw NO 00 sit, 41@ 0-4 1"* 4* 00, 0110 Table Bll Continued Coefficient Data of Trans- Pumping Test Analyzed Coefficient.missivity -Date Well Aquifer Owner Conducted by by of Storage GPD/Ft. Remarks 7-23-51 DorCe4 Piney City of R.H. Brown and Brown and 0.00038 42,500 Recovery test (Cambridge, Point Cambridg T.H. Slaughter Slaughter Md.) Md. i 2-19-6E(Mel5-29) Piney Ci*ty of A. C. Schultes R. W. 200 Point Milford and Sons Sundstro 3-1-68 Milford Miocene City of A. C. 8chultes A. C. 3,180 Drawdown in Test Well below Milford and Sons Schultes Miocene sands (Mel5-29B) Ches- and Sons from 480 to wold' 540 feet below' land s-urface 1-2-64 D i v i s i o nChes- City of J. R. Woods R. W. 32,800 Data from City r-j Street 2 wold Dover Sundstrom of Dover- CD (Jdl4-1) 2-17-64 Bayard do do Shannahan do 23,500 do Ave. 5 Artesian r (Jdl5-2) W01 Co. 12-30-63 E. Dover do do do do 19,000 do: El . School (Jdl5-4) 12-3(f-63 E. Dover do do do do 0.0062 16,300 Jdl5-4 Pumped El . School Test Well -(Jdl5-6) 3-25-68DannerFarm do do R-Sundstrom, E. do 0. 00031 11,200 Jd25-4 Pumped Test Well M.Cushing, and (Jd25-5) S.W.McKenzie Table Bll Continued Coefficient Data of Trans- Pumping Test Analyzed Coefficient missivitY Date -We 11 Aquifer Owner Conducted by by of Storage GPD/Ft. Remarks 3-26-68)annerFarm Ches-- City of R.Sundstrom, E. R. W. 13,600 Recovery Test Well wold Dover M.Cushing, and Sundstrom (Jd25-5) S.W.McKenzie 3-26-68)annerFarm do do do do 11,800 do Well 9 (Jd25-4) 10-19-65Harrington Fred- City of Alexander do 12,300 First 3 hrs. (Ld5l-8) erica Harring- Pump Co. of drawdown ton test 7-25-67 City Miocene City of Shannahan do 10,900 Drawdown test Well 8 sands' Milford Artesian Data from-City (Le54-3) above the Well Co. of Milford Frederica 3-30-62 City do do Layne- do 11,000 do Well 5 New York Co. (Le55-5) -0 so "at"t MR Table B12 Coefficients of Transmissivity and Storage,Determined from Pumping Tests of Wells in Eastern Sussex County, Delaware, and Surrounding Area Coefficient Data Coeffi- of Trans- Pumping Test Analyzed cient of mis.sivity' Date Well Aquifer Owner Conducted by b Istorage GPD/Ft. Remarks 3-1-68 Mel5-29B Miocene Milford A.C. Schultes R. W. 3,500 Screened 480 to below and Sons Sundstrom 540 feet. Cheswold 3-30-62 Le55-5 Miocene do Layne-New do 9,400 Screen@d 293 to above York Co. 328 feet. Cheswold 10-19-65 Ld5l-8 .,Frederica Harring- Alexander do 12,300 ton Pump Co. .7-25-67 Le54-3 Miocene Milford A.C Schultes do 10,900 above and Sons, Inc Frederica 6-9-67 Le54-1 do do do do .0066 10,,700 6-67 Qj32-1 2 Manokin 13ethany Midd letown do 60,000 Beach Drilling Co. 12-51 WorBh-l do Ocean G. E. G. E. .00001 26,500 De,pt. of Geol. City, Andreasen Andreasen Mines and Water Maryland Res. Bul. 16 10-3-47 WorDd 8 do Snow Rex R. Meyer Rex Meyer 40,000 do Hill, Maryland Table B12 Continued Coefficient Data Coeffi- of Trans- Pumping Test Analyzed cient of missivity Date We'l I Aquifer Owner Conducted by _by Storaqe GPD/Ft. Remarks 12-51 WorBh Pocomoke Ocean G. E. G. E. .00012 10,000 Dept.. -of Geol 6,7,8 City, An,dreasen Andreasen Mines and Water Maryland Res. Bul. 16 1-52 WorCg 5 do do do do .00014 14,000 do 12-23-54 Ni3 Pleisto, L.ew-es US Geological W. C. .0147 849000 Leaky non-artesian Obs 3 cene Survey Rasmussen aquifer. 12-23-54 Ni47 do do do do 106,000 do Obs 7 do Ni48 do do do do 87,000 do Obs 8 do Ni36 do do do do 135,000 do TW 1 do Ni37 do do do do 102,000 do TW 2 5-11-44 @OiN-I do Rehoboth do P, 1* *006 58,100 do Beach Smoor Wel,l 2.pumping. 1-21-52 Oi34-1 do do Shannahan do 45,000 do Artesian Recovery pumped Well Co. well. 1925 -1 ,Qd2l-2 do Laurel Permeability US Geol. 114,000 Average permeabil- Determin- Survey ity between depths ations of 21 and 80 feet times thickness. M No, M, 00, V*- 001 O-W 00 00, d* go, low, owl Table B13 Lowest Pumping Levels and Available Drawdown in the City of Dover Wells to the Cheswold Aquifer Lowest Depth to Depth to Available Drawdown Pumping Top of Top of To Top of To Top of Level Aquifer Screen Aquifer Screen Well in Feet Date in Feet in Feet -in Feet in Feet Remarks Power Plant 1 154 6-21-67 141 181 Below 27 Source of data: (Jdl4-2) Weekly measurements D i v i s i o nSt. 2181 7-28-65 175 195 Below 14 (Jdl4-1) and' made by the City of PQ 11-17-65 Dover. Pumping Dover St. 3 172 9-14-66 175 197 3 25 (Jd24-1) levels are below Water St. 4 172 6-23-65 169 189 Below 17 land surface datum (Jdl4-6) -and 9-14-66 at the well. Bayard St. 5 157 10-6-65 193 193 36 36 (Jdl5-2) E.Dover El S.8 174 8-30-67 188 188 14 14 (Jdl5-4) Danner Farm 9 183 7-7-65 175 175 Below Below J d 2 5 - 2 and 8-30-67 Table B14 Specific Capacities of Wells in Eastern Sussex County, Delaware, and Surrounding Area Specific Period of Depth of Capacity Pumping Well in Well Owner Aquifer GPM/Ft. Hours Feet Source of Data Mel5-29 City of Milford Piney Point 0.24 3 795 A. C. Schultes & Sons, Inc. Pumping Test 2-20-68 Mel5-298 do Miocene below 0.90 4 540 do--3-1-68 Cheswold Le55-5 do Federalsburg 4.0 8 328 Layne-New York Co. 8-26-53 Mel5-3 do Frederica 5.6 12 242 Delaware Geological Survey Mel5-5 Schine-Milf.ord do 4.3 225 do Theater Le54-2 City of Milford Miocene above 5.4 2.5 165 A. C. Schultes & Sons, Inc. Frederica Pumping Test 6-9-67 L.e54-3 do do 3.4 6 165 do---7-25-67 Qj22-3 Sussex Shore'st Manokin 9.5 8 1860 Delaware Water and Air Water.^_o. Resources Com@ission Qj22-4 do do 3.0 8 186 do Qj32-12 Bethany Beach do 17.3 2 230 Delaware Geological Survey Qj32-12 do do 18.7 2 230 Delaware Water and Air Resources Commission owl '00" -00, OMP, NO Ao Tabl e Bl 4 Conti nued Specific Period of Depth of Capacity Pumping Well in Well Owner Aquifer GPM/Ft. Hours Feet Source of Data Rh32-6 Town of Manokin 10.0 185 Delaware Geological Survey- Selbyville Bulletin 8 Qh5l-12 Hipro Pleistocene- 14.5 121 do Associates Pocomoke Me2l-l Diamond State 'Pleistocene 15.0 63 Delaware Geological Survey Nurseries Mfll-6 City of Milford do 24.6 48 68 Shannahan Artesian Well Co. Mf23-3 Roland Sharp do 2.2 84 Delaware Geological Survey Mg43-1 Carlton Clifton do 3.2 119 do Mg5l-l Carlton Clifton do 1.6.7 62 Delaware Geological Survey- B u 11 e t i n4 Nf34-2 Clyde Betts & do 4 91 Delaware Water and Air Sons Resources Commission Nh42-1 B. White do 5.7 68 Delaware Geological Survey- B u 11 e t i n4 Ni42-8 City of Lewes do 16.0 64 do Ni5l-6 do do 11.4 162 do Ni52-1 Diamond State do 20.0 94 do Poultry Co. Ni5l-13 F. Thorpe do .3.5 87 do 91Z CD C) CD C) C) C) C) C) C) C) _-Z =r (a LO I-b --h -+j C@. w N) N) Nj W 4:::. 4@- 4@r- Ln :E: a, w N) w N) r%3 (D I I I I I I I (D N) w 00 w CY) 4@:* C-) rD n 0 ;a M -0 Ln 0) Ln X:, C- C- 5W m :E --i C: 0) 0 C+ m 0 -1 0 _0 C-+ -S -1. 0 0 sw a iw -0 rD C+ Z: C) sw C+ - a a) C+ @ "s :E C: 0 -5 -a = C+ 0 Is CO rD @< M, rD M.. CD 0) -1 c: 0 ll,@@ = 0) m o- z:. W m C@ V) a l< = < -nm n= CD w m 0 m -1 un C+ CD n 0 00. m cr Cl+ 0- M :9 rD M In. Cl. 0 0 0 0. 0 0 0 C+ 0 0 0 C-t 0 C+ 0 X- 0 0 0 0 0 M CD m rD rD rD m CA 4::- v 0) _0 @n c) r,.) w r,..) co -i r,.) 4@:. c:>+ N) :K -0 rD @o C) @D C*0 Ln co Co co L" C+ l< -0 rD a 'a 0 00 co -. C:@- to 0 -"hl :E: m -n --a C) C:) ch co --i CD co co (D rt. 41- m rla -P. t.0 co CD CD 01) Ln -4 m ::r C+ 0 ou 1=7 co C@ CD C CD (D a (D pi aj pi oj ::E: (D :E (D ::E sw C+ 0) 01 C+ 0) -S @. -1 -S -. -5 Uo (D (D (D (D 0 a M -Pb a) 4b C) -1 rD m rD (D C') 0 0 0 (D 0_ CL Q. CL CL CL cx 0 0 0 0 0 0. 0 0 U"l -h Oj Cl+ V) (A V) (D (D CD (D L13 -0 -V C:@ Co C) C) C) C) C) CD to (M C-A. C". C.J. C-J. C-j. C-A. C-J. C-J. ow 01 t" 4z@- 4:h- 4:W 4:@- 4t,, 4.'::- 4:b 4z@- X: cr m PQ ko ca C) Co 00 m w C) CY) -n (A C- m -0 -5 C@ 0 w w ---j 0 0. CL IV C@ lw w a .J. m rn C-f- -S 0 0 iw C-t 0 A. tA C) I -S V) C> 0) 7Z (A X r_ I (n (D t< t7 m -S to 0 ;o I a; to 1= CD CL 0 0) n -1 0 (A (D to 0 (D (D -1 C+ 0 00 to C+ V) 0 CD -S (D -A. :E (D 0 a - (A a 0 (A (D -S pr rD m m m m cm 0) (D Q. CL 0- 06 CL m CL m m M, CL m (A c 0' 0 0 0 0 0 0 0 0 0 0 0 C+ 0 -h I 0 CD m -1 CD m C-) V) r%) 4@- C) rlo -ph Ul Ul -r-lb 0) Lo rlo Ln Cn M"D (D '-@ 0) 0 ;31 *Cn @n ;o @m '(.n 61 no C+ -J. C+ l< _0 CD 0 -a 0 m CD too :rL. rD M "D Ch *@4 14 C> 00 rlj C) C> CD f.0 -n @ c+ C) 0 (.n C) 0 C@ (A @4 C) C) 00 m - (D 0 -+) (D m C (D m m C CD fD tA 0) 0 0) 0) 0) x m :E r X (D X sw Cl+ tw -5 C+ 0) -S -4. -S 0 @. -S -1 0 m m m CD M (D CD a (A tA -1 v_;- 4z:b M X: 4b M m 0 C-) 0) m C-) 0) m CD m 0 C+ 0 0 C+ 0 0 C@L m CL CL (D 0- 0. 0. m CL 0 -1 0 0 0 -S 0 0 0 0 0 0 0 to to cA w V) 0i W = 0 A) iw -a. 0. 0) C+ m (D m .40 jo .40 @O C) dc) r-J. CA) CA) 4@b Cn cyl Lr F@ @4 00 C-) m V) CA a .-a -0 su :3 (D lw 0 X: tA 0 0 C7 ;0 V+ C-tb @o :3 (A iw 14 a m C M CD -1. J. 01:E M . 0) Cl+ CD @ jw, (00 C) 0 , , 1--, (A (D X a- C+ cm C+ a ". = :E a 0 < V) M 0 -S --A "S 0) (A 0) (D C+ 0 on l< m k< -% C+ (D C+ :3 C-) =r n < CD 0; -S 00 C-) C-) Qj -S n M C7 0 -J@ 0 0 pi CD 0 m 0 "a tn CD -It* CL CL M Ia. CL 0 0 0 0 ol ol 0 0 m m a) C-) (n jw "a !4 :M'O ID cm 0 C) CD M C) C:) 0 -0 (D 4r 0 C-0 0 00 -Pb -P-b -Pb -1 CL too CY m (D "0 0*1 Ch -4 r%) to (.n, 00 C) C) CD m (D (D CD (D (D CD' M (D 0 iw 0) 0 0) 0) a X X r- X :E c X -S at a# -5 0) of (n 0 -1 -5 0 -1 -1 0 M (D (D CD M (D 'M M r_ n jw M tw M, n Oj CD 0 C+ 0 0 C+ 0 '0 V+ (D " Ia (D, CL __j, -3 CD 0 0 0 0 0 0, 0, "S -tj (M . I to tA Do LA Q) tn = (n = 0) C+ 0 m (D l< no, Olt 'em, Novo 'low, up" 00: No 'go 00 1 owl sit TABLE B15 Specific Capacities of Wells in Western Sussex County Delaware, and Surrounding Area Specific Period of Yield of Depth of Capacity umping well well Well Owner Aquifer (gpm/ft) (hours) (gpm) (feet) Source of Data Mel5-29 City of Milford Piney Point 0.24 3 46 795 A. C. Schultes & Sons, Inc., Pumpi.ng,Test 2-20-68 Care Dd-TW2 Town of Denton, do 4.9 3 250 440 Delmarva Drilling Co. Md. Pumping Test 5-20-69 Care Dc-67 Caroline Poul- do 1.8 72 160 470 Rasmussen.and Slaughter try Farms 1957 Care Dc-122 do do 0.2 25 490 do Mel5-29 B City of Milford Miocene be- 0.9 4 46 540 A. C. Schultes & Sons, low Ches- Inc., Pumping Test wold 3-1-68 Le55-5 City of . Milford Federalsburg 4.0 8 480 328 Delaware Geological Sur- vey Me15-13 do Frederica 5.6 12 373 242 do Me 15-5 Schine-Mil- d o 4.3 400 225 do ford Theater Ld5l-l Town of Har- do 9.6 200 234 M. Pentz. Pumping Test rington 3-14-63 TABLE B15. Continued Specific Period of Yield of Depth of Capacity Pumping well well Well Owner Aquifer (gpm/ft)_ h o u r s (gpm) (feet) Source of Data Ld5l-2 do do 10.6 200 234 M. Pentz. Pumping Test 12-8-58 Care Ee-l L. B. Case Miocene 5.6 10 50 170 Rasmussen and Slaughter, above Fre- 1957 derica Le54-2 City of Milford do 5.4 6 210 165 A. C. Schultes &.Sons, Inc. Pumping Test 7-25-67 Le54-3 do do 3.4 6 280 165 A. C. Schultes & Sonso C) Inc. Pumping Test 6-9-67 Pbl3-l Phillips Can- do 1.6 303 Delaware Geological Sur- ning Co. vey Care Fd-6 Caroline Poul- do 4.0 8 200 Rasmussen and Slaughter, try Farms 1955 Care Fd-7 do do 4.o 8 200 306 do Rh32-6 Town of Sel- Manokin 10 100 185 Delaware Geological Sur- byville vey Rh32-2 do Manokin- 500 110 do Pocomoke Of42-23 Townsend Can- Manokin- 34.5 1,005 110 do ning Company Pleistocene --j M" '60 aw M MW a", IN 10 10 .0 @o jo 10 '40 .0 .0 M -0 0 U3 =r = =r =r CL 0. M 0. C-) -h m -h w Ul VI Lrl FV r13 4@- Ul - - - - - - - - - I I I I I I m rn Ln 4- W M Ul N) CD Yl C-) 0 (A m C+ m MC C-1) LI) C) . -S m 0 0 (D :3 C+ @n m -S VJ (D ;"z 0) < (A0 0) C+ a -1 :E CD Cl+ C> a 0. 0 -5 0. m 0. 0 - Oj a Ap -5 m :m 3cm 0 0 a < 0 0 0 -h rD to 11 (A 20 m 0 44 a lw l< m (D - m Cl) (A 0) r- -S C+ C-) -S m -5 0 -0 CD 0 .0 m cx CL a- 4A s CL M m m in. m rL m c 0 a 0 4r+ 0 0 0 0 0 0 0 0 7:1 --h I 0 M CD m z (D C-) (A Lo 0) "a 4bb 4@- 4b- 4:b CYI N) m m to OD N) 4@- a al 0 @4 @D %0 ko Q CTI 41@ N) -h - -h C+ C+ @-v m 03 - C-0 0 -fl. 0 r%) N) rla 4b- 14 -4 Ln Lri 00 rl) 'n (v r-j 4b- -Ph rl,) CD 0 w 4N C) w CD OD -4 '0 M - C) (D CD C) 0 0 0 CD 0 C:> C@ rL 0 ID M (D C+ Po a t.0 - 0 9D %0 to to M M =r 00 cn 00 - W 4:h ch CD p. C@l C+ 7h m m M (D (D -S 0 (D a m a) m -5 m m 0 - 0 m CL CL Q. a- m m m 0- - m - 0 0 0 0 0 0 0 0' 0 0 0 0 0 Im C7 tu C+ C-) 0 Ln Ln C 0. CD (D o- 0 0 n 0 r-j- 4:% W M r.7 r") r%.' 4@b w L" :c I (D M Ul -4:-- 0 ;a C) m -.h -4 r) m -h --A 3E --I 0 (D -S 0) 0. 00 0. 00 00 C+ :E -1 X a -5 x 0 X CL =3 @a CL M rL = X CD C@ JW of C> 0 o- su -I CL = 0 :3 0 0 X CD -h oo -5 0 a) 0 l< CD -h C; -h -h = m CD ;@ !- - , C C (D Cl < U) -0 U) m c< (D 0 (D 0 M co 0) = 0) (D a 0 - 0 Cl+ 1 0 Cl+ I m CD 20 20 0 (D -1 cr = (D 3:. 0 0 CD -0 D M CL M a- m CL CL m M IM. m -S - 0 0 0 0 0 0 0 0 0 = 0 0) (D c-+ CD '0 Z3 --0 C+ m -S 0 = to I (D Ln 4-- N) m 10 @a (D 0) 4 @4 w Sol o -0-. Cp (D C) C) 14 OLM -h -- -43 Cf C+ -A< --v M =r a 0 a ]S. C-0 0 5 @- 06 V) U) 4m 0) 4:b CK) CY) Lo :e (D ko (D 00 (n C) C) 4:b (n Co ko 'a (D C> CD CD 0 CD CD CD CD C) C@ C) a CL -h M (D m C+ 00 %0 C:) 14 OD ch, C) to ON (D Ol m 4b 4D 00 (A.) 00 C> L" 0 -h 0 CD M CL m m 06 Q. CL CL CL in. Ca. 0 0 0 0 0 0 0 0 0 0 0 -h su ct '00, go. .60,, 'DO, 90 '00 410 00 NO dW 90, VA' OW 00 00 d* Table B16. Coefficients of Transmissivity and Storage Determined from Pumping Tests of Wells in Sussex County, Delaware and Surrounding Area Coefficient Data Coeffi- of Trans- Pumping Test Analyzed cient of missivity Date Well Aquifer Owner Conducted by by Storage GPD/Ft- Remarks 2-19-68 Mel5-29 Piney Milford A. C. Schultes R. W. 200 Test well. 65 Point Sundstrom feet of screen 7-6-60 Kd5l-5 do Swift Layne-New York do 38,000 Data from and Company Swift and Co. Company 5-20-69 Care do Denton, Delmarva do 0.00042 11,900 Data from Del- DdTWl Md. Drilling marva Drilling Company Company 3-1-68 Mel5-29 Miocene Milford A. C. Schultes do 3,500 A. C. Schultes B below and Sons, Inc. and Sons, Inc. Cheswold Pumping Test 3-1-68 3-9-56 Tal- do Esskay Rasmussen and Rasmussen 0.0001 1,300 Data from Ras- Bf-73 Packing Slaughter and mussen and Company Slaughter Slaughter,1957 Cordova, Md. 1-16-56 Tal-Ce Cheswold Easton do do 0.0001 3,500 Data from Ras- 2,6,7 U t i 1 i t i e s mussen and and 8 Comm. Slaughter,1957 Wells in Eas- ton, Maryland Table B16 Continued Coefficient Data Coeffi- of Trans- Pumping Test Analyzed cient of missivitY Date Wel I Aquifer Owner Conducted by by Stora-qe GPD Ft. Remarks 3-30-62 Le55-5 Miocene Milford Layne-New York R. W. 9,400 Screened 293 to above Company Sundstrom 328 feet. Cheswold 10-19-65 Ld5l-8 Fred- Har- Alexander Pump do 12,300 erica rington Company 1 7-18-52 Cas-De do D .H. B 0 e s s D. H. 0.003 6,000 Data irom Ras- 0 ZI 9 -57 Boggess mussen and Slaughter,1957 7-25-67 Le54-3 Miocene Milford A. C. Schultes R. W. 10,900 above and Sons, Inc. Sundstrom Frederica 6-9-67 Le54-1 do do do do 0.006 10,700 6-7-67 Qj32-12 Manokin Bethany Middletown do 60,000 Beach Drilling Company - do Mardel U. S. Geol. 0.0003 40,000 Data from Otton Bypro- Survey and Heidel,1966 ducts Wells a few miles west of L Salisbury, Md. Table B16, Continued ,Coefficient Data Coeffi- of Tran s Pumping Test Analyzed cient of missivity Date Well Aquifer Owner Conducted by by Storage GPD/Ft Remarks 1073-47 Wor Dd do Snow Rex R. Meyer R. R. 40,000 Data from Ras- -8 Hi I I Meyer mussen and Md. Slaughter, 1955 12- -51 Wor Bh Pocomoke Ocean G. E. G. E. 0.0001 10,000 do 6,7,8 Citys Andreasen Andreasen Md. 1- -52 Wor Cg do do 14 do do 0.001 14,000 do -5 PQ 19 25 Od2l-2 Pleisto- Laurel Permeabi 1 i ty U.S. Geol. 114,000 Average permea- M) UI cene Determina- Survey bility between tions depths of 21 and 80 feet multi- plied by thick- ness in feet 4-6-50 Care do Federals- Brown and Brown and 170,000 Data from Ras- .Fd-2 burg, Md. Brookhart Brookhart mussen and Slaughter, 1957 3-6-56 Dor do U.S.G.S. U.S.G.S. U.S.G.S. 150,000 do Bg-33 State of Maryland Wi Ce do Salis- do do 0.15 100,000 do I to 13 bury, Md. Table B17 Yield and Specific Capacity of Large-Diameter Wells Tapping the Columbia (Pleistocene) Deposits and Estimated Transmissivity of the Aquifer Well Owner Depth Diameter Screened Yield Specific Estimated Transmissivity Number (feet) (inches) Interval (gpm) Capacity (feet) (gpm/ft) gal/day/ft ftz/day--.-- Cd 42-13 Artesian Water Co. 73 17 49 - 73 570 38 60,000 8,000 Cd 43-6 Atlas Chemical Industries, Inc. 71 26 52 - 67 600 27 40,000 5,300 Cd 51-1 Artesian Water Co. 47 17 24 - 47 350 10 18,000 2,400 .Db 31-19 E.I. duPont Co. 65 10 53 - 65 100 8 14,000 1,900 Db 31-35 E.I. Mont Co. 80 8 70 - 80 500 11 91000 1,200 Dc 53-5 Getty Oil Co. 90 8 70 - 90 525 48 72,000 9,600 Eb 55-4 Baker Brothers 40 17 16 - 40 600 19 30,000 4,000 Eb 55-5 Warren Baker 45 17 17 - 45 450 24 369000 4,800 Fb 23-6 Fred Wicks 71 8 30 - 70 100 8.3 12,000 1,600 Fb 34-16 University of Delaware 74 8 54 - 74 110 3.5 33,000 49500 Fb 51-4 George & Sam Brooks 44 17 24 - 44 520 19 29,000 49000 Fb 51-5 George & Sam Brooks 44 17 16 - 44 620 20 30,000 49000 Fb 51-6 Norman & Sam Brooks 54 17 300 12 19,000 2,500 Fb 53-7 Chris Wicks 80 17 21 - 80 580 9 14,000 19900 Ga 15-4 Gerald Zeh 63 17 30 - 60 1,120 61 769000 10,000 Hc 32-5 City Products Corp. 86 10 43 - 56 325 20 369000 4,800 Hc 32-12 W.L. Wheatley, Inc. 77 12 --- 780 14 25,000 39300 Hc 34-3 City of Smyrna 100 10 70 - 100 550 30 54,000 7,200 Hc 34-22 City of Smyrna 96 12 55 - 85 1,100 54 120,000 169000 Hc 43-3 George Wicks 115 10 --- 1,020 82 1509000 20,000 Hc 44-3 George Wicks 133 12 75 - 1@2 1,050 88 160,000 21,000 Hc 55-1 Walter Gibe 120 10 90 - 120 1,000 52 93,000 12,000 (See Figure I for approximate location of wells) M, 00, am, M) go, M 00 'M' 00 00 as No, 40 so go. so so '00, so Is" so so Table B17 Continued Wel 1 Depth Diameter Screened Yield Specific Estimated Transmissivity .Number Owner (feet) (inches) Interval (gpm) Capacity (feet) (gpm/ft) Ta-1/day/ft ftz/day Ic 32-4 Frank Johnson 48 12 --- 350? 5 91000 1,200 Id 24-4 Philip@Cartanza 157 17 25 - 157 1,050 20 30,000 4,000 Ie 31-1 Joseph Zimmerman 94 17 16 - 94 9.40 19 28,000 3,700 Ie 43-2 Philip Cartanza 106 17 16 - 103 1,400 50 75,000 10,000 le 53-2 Alfred Bilbrough 114 17 21 - 113 700 54 82,000 11,000 .Ie 53-3 Alfred Bilbrough 72 17 36 - 72 750 17 25,000 3,300 Ie 53-4 Alfred Bilbrough 70 17 13 - 69 720 21 32,000 4,200 Jc 34-1 Joseph Wild 97 17 20 - 96 900 17 25,000 3,300 Jd 12-2 Eugene Gagan 104 17 40 - 96 1,300 22 33,000 4,400 Jd 21-2 Papen Farms 96 17 40 - 96 760 17 23,000 3,100 Jd 41-1 Libby, McNeil & Libby, Inc. 125 10 87 - 109 400 9 15,000 2,000 Jd 54-1 Joseph Jackweiez 118 17 26 - 118 1 260 21 38,0.00 5,100 Je 12-2 Jacob Zimmerman 72 10 7-- 600 16 24,000 3,200 Je 13-1 Alfred Bilbrough 70 17 18 - 66 780 21 31,00 0 4,200 Kd 24-2 Joseph Kowalski 134 13 38 - 134 1,050 21 31,000 4,200 Ke 12-2 Kenneth Bergold 146 17 30 - 74; 1,600 44 67,000 9,000 122- 146 Ld 33-1 Walter Winkler 64 17 20 - 56; 1,400 39 60,000 8,000 60 - 64 Le 22-2 Charles West 73 8 13 - 73 400 11 17,000 2,300 Le 23-3 Charles West 74 13 22 - 74 380 9 14',000 11900 Le 51-2 Floyd Blessing 105 17 .1 200 64 96,000 13,000 Md 15-8 Libby, McNeil & Libby, Inc,. 67 10 41 - 67 280+ 22 40,000 5,300 Md 24-3 U.S. Geological Survey DE,Geological Survey 80 8 70 - 80 300+ 10 165,000 22,000 Table B17 Continued Well Owner Depth Diameter Screened Yield Specific Estimated Transmissivity Number (feet) (inches) Interval (gpm) Capacity (feet) (gpm/ft) gal/day/ft W/day Md 54-2 John Annet 82 17 30 - 82 1,180 53 80-'000 11,000 Me 24-5 City of Milford 80 8' --- 400 18 26,000 3,500 Me 24-6 City of Milford 69 12 39 - 59 520 29 42,000 5,600 Me 33-3 Donald Calhoun 74 17 38 - 70 700 30 45,000 6,000 Me 54-5 Delmarva Nursery 90 8 58 - 90 500 20 30,000+ 4,000+ Mf 11-6 City of Milford 67 -- 220 25 44,000 5,900 Mf 21-1 Diamond State Nurseries 63 8 --- 180 15 27,000 3,600 Mf 22-4 Brown Thawley 131 17 44 - 106 1,400 80 120,000 16,000 Mg 42-13 Draper Foods, Inc. 89 8 69 - 89 150+ 35 50,000 6,700 Nc 25-19 Bramble Canning Co. 84 -- --- 1,300 24 36,000 4,800 Nc 53-3 O.A. Newton & Sons 100 12 --- 1,080 22 33,000 4,400 ro Nd 33-1 J. Howard Lyons 92 17 1,200 30 45,000 6,000 00 Ng 12-1 Carlton Clifton 61 6 --- 300 17 31,000 4,100 Ng 31-1 Willard Workman 122 17 --- 900 74 110,000 15,000 Ng 41-2- Willard Workman 112 17 --- 1,080 32 48,000 6,400 Ng 42-1 Town of Milton 68 6 --- 200 31 56,000+ 7,500+ Ng 42-15 Draper Canning Co. 13 --- 1,300 65 100,000 13,000 Ng 42-16 Draper Canning Co. 84. 13. --- 1,020 49 73,000 10,000 Ng 55-4 U.S. Geollgical Survey- DE Geol-ogical Survey 70 8 60 - 70 200+ 7 104,000 14,000 Ni 31-3 Lewes Dairy 60 8 --- 100+ 14 25,000 3,300 Ni 51-16 Town of Lewes 97 10 --7 480 16 Ni 51-17 Town of Lewes 157 10 --- 500 11 Ni 51-18 Town of Lewes 89 10 --- 400 11 110,000 15,000 Ni 51-19 Town of Lewes 151 10 --- 975 Ni 51-20 Town of Lewes 146 10 --- 900 26 gal 6ZZ ,c) @C) -0 -0 -0 -b -0 -b -0 -0 -0, -0 -a -0 -0 C:) CD C) C) CD CD C) C) C) C) a- (a to ka 0. 0 0 n 0 0 0 0@ to to --h 0 0 0 C-) 4:j- Ln Ln Ln M L" Ln 4@r- W W W W M W W M M N) 4@- 4::b N) M a m 4t:- W W W 4:b -Ph W W W W W Ln 42- 4t:- W W W r-a 4@- 4:- 4::- 4@n- rl.) o- I I . I I I - L I f . I I I I I I I I I I I I I I M %0 C6 M@ 4@1- 40 Cn w Fla W N) rQ C) CO rTi m m m n -0 -0 Ln --A 1-4 0 0 0. 0 q a) " . -4. W o. 0 w w :E o . . . . n :E :E :E 0 m - 4-@ C+ --j :9 :E -1 -1 - :E -0 -0 -0 -V 0 w --j m -0 . . . . 4< -0 =$ w --h . . . . E3 -5 (A I = , a C+ 0 C+ 0. ol 0 0 a CD cl. 0. CL a 0 0 0 0 0 m n n n n = 0 -h --h un U) m c c r_ c -.% C) --h 20 = sw sw 0) 0) a- m 10 ". -0 10 "a "o - . CL = = = = c :E: o M M Is < o o C5 tn cl ;a ;v C+ C+ C-) C) =3 m su fD M 0 0 0 0 0 C+ m it C+ C+ ct w 4< =- = -0 -0 - 1--q = = = = 0) SW --h 0 0 0 0 C+ m r+. n 0 or D- a c Ro QQ S'zo m 0 0 0 0 -1 0 0 m C+ 0 0 C+ C+ L/) V) LIO -0 (< -S -5 =" -1 0 0 0 0 0 0 0 C-) C-) C+ 0 0 C, (D ,@D CD w w m 0) C> CD C) I-j co ko to w w C> -4 m C) CD ko C) to (D -0 w Ln -ob w 0 0 ko ---j w w w Cil km ra M -P:- C) M M M ko -P. (D C+ C+ --4 -4 CO Cb CO --4 -4 -4 -J CD C) CD C) --J N M M M C) M -4 M C) M M (D (D c+ (D -P@ 4@b - 14 0) C-n w m w 0 (-D"' (CD+ f-DI I 1 60 --j I (D -5 fD C+ < = a% CD C) w Di CD C> CD. to --j M CL %0 ko Ch a% Ln co to w w C-n ko -4 Ln CO 0) -0 (D On C) m CD 4@b C) M N) M 4::- Ln -4 M C) CD C) CD CD a @ 1, CD (D C) S 0 a 0 C) 0 CD 0 CD C) C) CD Co Cn CD CD C) (D CD C) -a- La 0) -0 10 -0 M -;::b -ob N W M -0- M M fkO 4t:- rQ -01. r1l) m - r*l) N) N) 0) 0 ka co m -4 tD to w cn C) w 4@i. 4h. fN3 oo ra w M 00 .0- -9- --4 Ln Ln CD r) C+ (+ La m 0) (n m Un L" CD 0) M 4N 4t% N) Ln M ul 0) 4@:-- CO N) W W W C+ 4::,- CD kO 4@- -4 (M CO W W W C) W ul w -i Ch W -4 Co CO M 4 w w . . w . . 4 b . w I . w . w . . w . CL a C) @:) C) C@ a 8, 0 a C) 0 0 0 C) CD CD CD CD CD CD CD C) C) CD C) w 0) CD CD C) C) 0 CI C) C) C> C) (D 0 C) (= C) C) C) CD C) C> C) C) L< & C) CD 0 0 a 0 C) 0 C) C) C) Cl C) C) CD CD C) I= CD C) C) CD CD (D + + C+ C+ V) C) co ra 01 '-4 w t)6 w 6" f-6 (n w -@4 @.o Ln W Ln Ui -Ph N (n '0" 4-40 w C) CD %4 -4 CO @,J -P- w (D C) ul (.n Zo co --4 C) CD M @D M C) CD C) CD CD C> a C) CD CD C) CD C) CD C) C3 w S C@ C) a CD 0 CD C) C) C) C) C) a) (D C) C@ C) C) co 0 a) CD CD CD CD CD CD CD CD C+ + + l< -n 0 CZ. ;a= X=) (= C) C) ICD A= =r 0- =r =7 =r C') r)@ 0 0 c X: a Low ol Ln Ln W r.,) a (D ;a N) -Ph 4@h 4t,- IV" I I I I M f'o -4 =r Pb C) su s CL -V m n 0 0 0. M 0 0) a 0 :E: :E :E 0 0 0 0 s 0 V) (A 0) CD -a C+ u -n - '-n pi -- E:: C) 0 (D,4 (D -5 -0 -1 -1 r)-., =- X 1w,0 W@l M- CD C+ C+ -+, LO 0 Q 0 -S -1 1:4 (D n 0 (D N) w CD CD C), co N) to m a Ln ko Ln. CD m CD M C+ 00 CO 00 00 00 14 -4 -4 m C+ (A CD" CD 00 00 -4 Ul C) C) m M (D M. M -S M, co C+ < =- N) C) C) cm Oj (D. Cn CD W,I W N) W -Ph Cn -0 ff, -P CD CD C> CD CD C) CD CD C), CD a- un 0) -a" "0 -0 M rj' r\) cD. w LO col C:)@ -;h N) c+'c+ LO m 0) (A C* -a) W co m -0. Cl co (D CD. C) cm C) 0) op C). C) Cno, CD C) CD'',CD C+ CD lc)@ C> C). (=)-..,C:) 25. CD im. --4 R- Ln. C+ rIO 4h -14 M -@-Ph 4, r). C) (DI C) -C) C) - C) C) C) 0) C) (o CD a c) CD c@ CD L< Table B18 Records of Wells in Western Sussex County piving the Altitude of the Land Surface, the Altitude of the Water Table, the Depth of Penetration in the Water-Table Aquifer below Sea Level, the Depth to the Base of the Pleistocene below Sea Level in Some Wells and the Known Thickness of the Water-Table Aquifer at Each We'll Depth of Base Known Thickness Altitude of Altitude of Depth of Penetration of Pleistocene of Water-Table Surface Water Table Below Sea Level below sea lev- Aquifer in Well in feet in feet in feet el in feet feet Nc25-1 50 45 21 21 66 Nd4l-l 45 31 46 77 Ne14-1 50 47 86 Pj Ne34-2 49 41 44 85 Ne54-1 45 35 49 84 Ob33-1 48 43 32 75 Ocl4-8 45 29 74 103 Oc35-2 45 31 39 70 Od23-1 43 30 133 84 163 Od24-1 36 33 127 160 Od32-1 25 11 89, 100 Od42-2 30 15 69 84 Oel5-1 47 40 47 87 Table B18Continued Depth of Base Known Thickness Altitude of Altitude of Depth of Penetration of Pleistocene of Water-Table Surface Water Table Below Sea Level below sea lev- Aquifer in Well in feet in feet in feet el in feet feet Of3l-l 47 43 47 90 Of42-16 55 .47 65 1112 Pbl3-l 46 39 44- 44 83 Pcl3-5. 33 28 69 97 Pc23-10 29 19 87 87 106 Pc25-9 16 9 90 .99 Pc32-6 17 10 78 78 88 Pc 3 3- 17 7 3 88 91 Pc45-1 43 35 56 91 Pc55-1 39 29 69 69 98 Pd2l-4 20 79 79 99 Pel5-1 50 47 45 �2 Pe23-5 50 40 62 62 102 Pe32-1 40 26 54 80 Pe33-1 42 36 52 88 P f 2 3 - 2 45 39 145 31 184 I" so" '40 Me, 'MI, .80, M) 'am, Am M, 4m M an an so as IMM Table B18 Continued Depth of Base Known Thickness Altitude of Altitude of Depth of Penetration of Pleistocene of Water-Table Surface Water Table Below Sea Level below sea.lev- Aquifer in Well in feet in feet in feet el in feet feet Qcl3-3 4 3 116 103 119 Qc24-6 24 12 97 109 Qd2l-5 25 5 77 77 82 Qd3l-l 32 20 62 82 Qd5l-l 41 33 42 75 qe42-2 40 36 104 75 140 Rb25-2 44 39 41 80 Rc22-2 50 41 60 101 Rd2l-l 50 45 54 99 Rd3l-8 40 37 126 157 Rf2l-3 52 37 94 94 131 Rf24-5 46 33 67 100 Rf32-4 50 40, 73 49 113 Rg22-1 40 37 120 157 TABLE B19 Estimated Area and Volume of Saturated Material above and below Sea Level in the Water-Table Aquifer in the Pleistocene in each 5 Minute Gri'd of Latitude and Longitude of Western Sussex County Thickness Volume Thickness Volume of TotaT Of of of Saturated Volume of Grid Area Saturation Saturation Saturation Material' Saturated (see Fig- in Above Sea Level Above Sea Level Below Sea Level Below Sea Level Material in u re 1 Acres in feet in Acre-feet in feet in Acre-feet Acre-feet Md 1 809 52 94,068 50 90,450 184,5)8 Me 580 55 31,900 50 Z9,000 60,900 Nb 10,381 39 404,859 50 519,050 923,909 Nc 16,682 50 834,100 50 834,100 1 668,200 Nd 16,682 46 767,372 50 834,100 1,601,472 Ne 13,708 43 589,444 50 685,400 1,274,844 Nf 4,042 46 185,932 50 202,100 388,032 Ob 9,268 43 398,524 52 481,936 880,460 Oc 16,682 46 767,372 52 867,464 1,634,836 Od 16,682 27 450,414 100 1 668,200 2,118,614 Oe 16,682 38 633,916 86 1 434,652 2,068,568 Of 6,117 45 275,265 73 446,541 721 806 TABLE B19- Continued Thickness Volume Thickness Vol.ume of Total of of of Saturated Volume of Grid Area Saturation Saturation Saturation Ma ter i a I Saturated (see Fig- in Above Sea Level Above Sea Level Below Sea Level Below Sea Level Material in ure 1) Acres in feet in Acre-feet in feet in Acre-feet Acre-feet Pb 7 970 30 239,100 44 350,680 589,780 PC 16,682 25 417 050 75 1 251 150 1 668,200 Pd 16,682 27 450,414 62 1 034,284 1,484,698 Pe 16,682 42 700,644 62 1 034,284 1 734,928 Pf 1 293 43 55,599 70 90,510 1 46's 109 Qb 6,673 20 133,460 45 300,285 433,745 QC 16,682 27 450,414 75 1 251 150 1 701 564 Qd 16,682 30 500,460 66 1,101 012 1 601 472 Qe 16,682 40 667,280 60 1 000,920 1 668,200 Qf 6,117 42 256,914 40 244,680 501 594 Qg 287 38 10,906 50 14,350 5 , 25 6 Rb 2j 844 39 110,916 60 170,640 281,,556 Rc 8,414 40 336,560 60 504,840 841,400 Rd 8,994 39 350,766 70 629,580- 980,346 Re 9,574 40 382,960 80 765,920 1,148,880 9cz 0, 1 W C+ -1 CD M r- MrD 'I rm, 0 M) ko, =31@ C+ w co -I M ol m rD 0) 4@- tA CD 0 < Ln m 0) C+ C@@ C> m -5 --h X- rD 0) SU z (D C+ (D C+ r-- Ln m 0 Ln < ci < w CD ko, :> (D c+ --- tD co -9@. a 0 V)--s 0 w Un, CD (D ap -h C rl.) Ch m Ioj C+ a C) Co --h - M CD r- 0 (DM C+,< 0 (4 --1 r+ r1l) kn@ V) c 0 0 CD. C@ --h (D -1 Pa C+ m 0 V) rD C), w co 0 :9 tn --- co cn CO :1> ::Ew lw 0 C) cn, 14@ 0 C+ C+ - I-J fD (D -5 -S CO M 10) - 0) (D co C) CD (D r- M 0 (DM CL --h C+ < (D M C) Ln 0 C+ tu 0 CD P. rl.). -5 M C-+ --i oD -J@ co CD S C: 0 C+ --h P. Qj (DI Aj -P. w CD - r+ 4b@ " CD m a -4 CD C@, C+ - Q. --+j Table B20. The Relation of Ground-Water Stage to the Ave-rage Monthly Discharge of the Nanticoke and Pocomoke Rivers During Drought Recession June to October 1968 Water Level Average Monthly Discharge Month (feet below land surface) (cubic feet per second)_ Well Md22-1 Well Qe44-1 Nanticoke R. Pocomoke R. -June, 1968 4.1 6.6 72.5 49.2 September, 1968 34.2 4.6 October, 1968 9.9 11.6 Decline 5.8 5.0 38.3 44.6 Drainage area of Nanticoke River 75.4 square miles Drainage area of Pocomoke River 60.5 square miles One cubic foot per second equals 646,323 gallons a day C: GHYBEN-HERZBERG PRINCIPLE During the course of an exfensive field and office study of the salt- water problem in the Atlantic City region by Barksdale and Sundstrom (1936), their report states in part: "The problem of obtaining fresh water from sands that are exposed for a part of their extent to the waters of the ocean has been studied in many parts of the world. The earliest scientific work on this problem was done in Europe, where the basic prin- ciples were first pointed out in 1887 by.Badon Ghyben, a Dutch captain of engineers, and in 1900 by Herzberg, who appears to have had no knowledge of the earlier work. The basic principles ' that govern the relation of salt water to fresh water in a water- bearing sand have now been fairly well established. "At the contact between the fresh and salt waters the zone of diffusion is surprisingly narrow. In Holland, Pennink found a range of salinity from 100 to 15,000 parts per million of chloride in distances varying' from 60 to 100 feet. In-the pre- sent investigation ranges from 800 to 8,000 parts per million and from 1,900 to 7,300 parts per million were observed.-in..,four feet of depth. "Salt water is heavier than fresh water and tends,to fill the lower parts of a formation. The fresh water in the..sand floats on the salt water much as ice floats on water, with most of its volume submerged. The position of the contact 'is deter- mined by the head of the fresh water above mean sea level, and by the relative specific gravities of the two waters. This is the principle developed by Badon Ghyben and Herzberg.! "This theory.is illustrated in Figure 33, A and B (Figure Cl in this report). Figure 33A shows a simple,U-type with both ends open to the air. The two legs of the tube are filled with two liquids of different specific gravities. The.liquids in the tube will come to rest in such a way that the pressure at the bottom of one leg is exactly equal to and balanced by that at the bottom of the other leg. The surface of the lighter liquid will, therefore, necessarily stand higher than that of the heavier liquid. Furthermore, as the heavier liquid fills the lower part of the tube in both legs up to the level of the contact between the liquids, the pressure at this level is equal in both legs, and the heights of the two columns of liquid above the level of the contact are inversely proportional to the specific gravities of the liquid. "In a small island or narrow peninsula composed entirely of pressure occurs between sea water and the lighter fresh water. permeable sand and surrounded by sea water, this same balance of 238, WE L WATER TABLE t MEAN SEA LEVEL t h H FRESH WATER h H 00 A: -.:SALT WATER R TABLE MEAN SEA LEVEL \.t FRESH WATER SALT WATER: WATER TABLE KE IN7'4 AR 4 IN W@TER TAB@E KE _j4 C4@ PIEZOMETRIC SURFA@E- MEAN SEA LEVEL 'Ye. ZONE 0 k .9 -NFTACT--. SALT WATER, IFRESH WATER JISPRING SALT WATER FROM BARKSDALE, SUNDSTROM AND BRUNSTEIN, 1936 Figure Cl. Relation between fresh and salt water in water-bearing sands when not disturbed by pumping. 239 Figure 33B represents a cross-section of such an island and shows that the salt water not only fills the sand around the island, but also extends entirely under it below the lens-shaped body of fresh water. In such an island the resistance of the sand to the flow of water causes th. e f@esh water from rainfall to build up a head above sea level sufficient to cause it to flow out into the ocean at the shores of the island. It also prevents the mixing of the salt and fresh waters in the sand below sea level by wave action. As the sand is permeable in all directions, the fresh- water head will cause a downward flow of fresh water until it fills the sand to a depth at which its head is balanced by the head of the salt water. When equilibrium has thus been reached, the depth of the fresh water below sea level at any point on the island will be proportional to the fresh-water head above sea level at that point, and the ratio between the depth and head of the fresh water will depend Upon the relation between the specific gravities of the fresh and salt waters. "The following explanation of the rel ation between salt water and fresh water under a small sand island is applicable both to Figure 33A and Figure 33B: Let H = total thickness of fresh water; h = depth of fresh water below sea level; t = height of fresh water above mean sea level; Then H = h + t. "But the column of fresh water 1-1 must be balanced by a column of salt water h in order to maintain equilibrium. Therefore, if g is the specific gravity of sea water and the specific gravity of fresh ground water is assumed to be 1, H = h + t = hg whence h = t in any case g-l will be the difference in specific gravity between fresh water and the salt water. "If it is assumed th at the specific gravity of sea water is 1.025, which is about an average figure, then h = 40t. In other words, for every foot that the fres.h water stands above sea level, it extends 40 feet below sea level. This ratio is so extreme that it is not practicable to show it in the various parts of Figure 33. For convenience, therefore, the first three parts of this figure have been drawn with a ratio of 1 to 10 between the head and depth of the fresh water. This would be the true condition if the specific gravity of the sea water were 1.100 instead of about 240 1.025. The fourth part of this figure is drawn with a ratio of 1 to 5 between the head and depth of the fresh water and represents an imaginary specific gravity of sea water of 1.200. The general relation between fresh and salt water shown by these diagrams is not affected in the least b@ this assumption of a specific gravity of sea water greater than the range that occurs in nature. The specific gravity of sea water varies from place to place, so that the figure of 1.025 used in the example above is only an approxi- mate average. "In nature a body of land composed entirely of permeable material to any great depth is rare. The occurrence of beds or layers of impermeable material does not change the basic princi- ples just discussed, but it does modify their application. If the island shown in Figure 33B were underlain by clay or bedrock that reached a level above the bottom of the fresh-water body, condi- tions such as those shown in Figure 33C would occur. Along the coast the position of the contact would be determined by the head of the fresh water, just as in an island composed entirely of sand, but under the center of the island fresh water would extend all the way down to the impermeable layer and would not be in direct contact with salt water. "The modification of conditions by impermeable formations is even more marked on the coasts of larger bodies of land, where water-bearing sands may lie under and between as well as above layers of impermeable material and may slope upward to remote in- take areas well above sea level. Along such a coast the condi- tions in a permeable sand underlain by impermeable material would be similar to those in the sand island underlain by impermeable material, except that the fresh water would be in contact with salt water only on the side exposed to the ocean. "Figure 33D shows two conditions which occur in water-bearing sands confined between layers of impermeable material. This dia- gram differs essentially from the others in that it shows the con- ditions that occur when the fresh water in the sand is under artesian head rather than under water-table conditions. In the upper sand in this diagram the salt water and fresh water are in balance,'just as in the preceding examples. Salt water fills the lower part of this sand, and fresh water fills the upper part of it. The position of the Contact is determined by the head of the fresh water, which in turn is determined by the elevation of the intake area. The similarity between the conditions in this sand and those in the U-tube in Figure 33 is easily apparent. "In an artesian sand the water is prevented from rising to the surface by the overlying impermeable bed. It is under a head that would cause it to rise in a well to a level above the bottom of the confining bed. The imaginary surface that would pass through the surface of the water in a well drilled to the sand at any poi nt 241 throughout its extent is called the "piezometric surface." The piezometric surface is therefore a pressure-indicating surface, and its elevation at.any point indicates the head on the water in the sand at that point. At the intake area of the sand it merges into the water table which, though hot imaginary, might be con- sidered a part of the piezometric surface. In a section such as Figure 33D the line representing the piezometric surface is the hydraulic gradient of the water in the sand along the section. As there is'no flow in the upper sand in this figure, the line repre- senting the piezometric surface is level and extends from the in- take area toward the ocean as far as the fresh water extends in the sand. "In the lower sand in Figure 33D the head of the fresh water is sufficient to cause aflow of fresh water into the ocean below sea level, forming a suboceanic fresh-water spring.. The fresh water fills the water-bearing formation down to the bottom edge of the overlying impermeable layer and far enough below this level to permit the water to flow - out into the ocean. Here again, the salt water fills the lowest part of the formation, but as the pressure in the main body of fresh water is greater than that in the salt water at the outlet, the salt water has been reduced below the pres- sure of the salt water by the resistance of the sand of its move- ment. The line representing the piezometric surface for this sand slopes gently downward from the intake area to the point where the thickness of the sand carrying fresh water is reduced by the intru- sion of salt water. From that point to the point of discharge the slope increases'. "If the basic-pr'i'nciples that govern the relation between fresh and salt waters in water-bearing sands are kept in mind, it is usually possible to develop a continuous supply of fresh water from sands that are exposed for a part of their extent to salt water. The amount of water that can be taken from such a supply without drawing in salt water will, however, depend on the methods used to develop the supply, on local conditions, and especially on'the amount of fresh water available for recharging the sand. "Any general lowering of the head of the fresh water in a sand exposed for a part of its extent to the waters of the ocean will permit the salt water to advance farther inland and occupy more of the sand. The lowering may be caused by natural condi- tions, such as a-dry year or a series of dry years, but lowering due to such causes is not likely to have any serious consequences, unless it occurs in conjunction with artificial withdrawal of water from the sand. This is usually accomplished through wells, either by pumping or by the natural flow from artesian sands. Pumping water from a water-bearing sand lowers the head of the water in it.materially in the immediate vicinity of the point of pumping and, to a decreasing extent, for a considerable distance 242 away. If this lowering of head or "cone of depression" occurs above or extends beyond the zone of contact, it will disturb the balance between fresh and salt water and permit the salt water to move up through the formation toward the well. The radius and depth of the cone of influence increase as the rate of pumping from the well is increased. It might, therefore, be possible to take a small amount of fresh water from a well in a water-bearing sand exposed to salt-water contamination without drawing in salt water, whereas if the same well were pumped at a higher rate the salt water would enter it. "The specific gravity ofsea water varies slightly from place to place and sometimes at different depths at the same place, but it is never much greater than that of fresh water. For the purpose of this report the specific gravity of fresh water may be considered to be 1.000. In the summer of 1913, Begelow (1915) found that the specific gravity of the water off the Atlantic coast of the northern United States at different places and at different depths ranged from 1.019 to 1.028. "Owing to the very small difference between the specific gravity of fresh water and that of salt water, a slight change in the head of the fresh water produces a very considerable change in the position of the zone of contact. If a water-bearing sand is exposed to sea water having a specific gravity of 1.025, the level of the fresh water in it must be maintained at 2.5 feet above mean sea level if the zone of contact is to be held at a depth of 100 feet below sea level. A fresh-water head of five fee t above mean sea level would be sufficient to hold back the sea water to a depth of 200 feet below sea level. Similarly, if.the fresh-water head in@such a sand were lowered only 2.5 feet, it would permit the salt water to rise 100 feet. If the fresh-water head in the sand were lowered to sea level, the salt water would rise to sea level. In a gently sloping confined sand, such as the upper sand in Figure 34B (Figure C2 in this report), a vertical rise of 100 feet might represent a movement of the salt water several miles inland. "The mere fact that a well or well field in a sand containing both salt water and fresh water yields fresh water when it is first pumped is no 6ssurance.that it will not eventually yield salt water. The adjustment of the position of the zone of contact to the lowering of the fresh-water head caused by pumpi,ng would not be instantaneous, but the upward movement of the salt water would begin as soon as the fresh-water head above the zone of contact was lowered. The salt water would continue to move upward until equi- librium was again established or until it entered the well. The rate of movement of the salt water would be goverened by the rate of pumpage from the well, because it would be necessary to remove, by pumping, the fresh water between the original position of the zone of contact and the position that it would occupy when equili- brium had again been established. If the well were situated in a 243 A. UNCONFINED AQUIFER WELL WATER TABLE MEAN SEA LEVEL xo;z FRESH WATER C, 0 F'\ ------ 7-7 WATER TABLE INTA! AR WATER TABLE /A( \/AREA PI-ZOMETRIC SURFACE -------- I MEAN SEA LEVEL .r.n: 4j@ OF SALT ONTACT'- WATERI 4. B. CONFINED AQUIFER FRESH WATER SPRING SALT WATER FROM BARKSDALE, SUNDSTROM AND BRUNSTEIN, 1956 Figure C2. Effect of pumping water from wells in sands exposed to salt-water con- tamination. _@w L @L _@@WAT E 244 uniform sand and if the lowering of head were enough to draw salt water into it eventually, a considerable part of the fresh water between the well and the zone of contact would have to be pumped out before-salt water could enter the well. Usually this would require a considerable period of time." More recently, the effect of the dynamics of flow, as controlled by the vertical and horizontal permeabilities, on the position of the interface of the fresh-salt water in coastal areas has been presented by Hubbert (1940); Henry (1964); DeWiest (1965); Rumer and Shiau (1968); and others. Their treatment of the interface tends to move it to allow for discharge of the aquifer which is not considered in the earlier application of the Ghyben- Herzberg principle. In the fresh-salt water interface relations of the Pleistocene water-table aquifer most of the recharge water is being dis- charged in the upper reaches of the aquifer as fairweather flow of the streams and by evapotranspiration. In many instances where evidence of the fresh-salt water contact is available from electric logs or from water samples the orig- inal Ghyben-Herzberg principle is sufficiently reliable for practical use a short distance inland. 245 E 3 6668 14109 941F