by MW Bradley — Bon Aqua – Lyles Utility District. Hickman. Collinwood. Wayne. Cowan. Franklin. Cum berland City. Stewart. Cunningham. ‘tiontgomery. Dechard. Franklin.
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PRELIMINARY EVALUATION OF THE HIGHLAND RIM AQUIFER SYSTEM IN TENNESSEE FOR RECEIVING INJECTED WASTES By Michael W. Bradley U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 85-4252 Prepared in cooperation with the U. S. ENVIRONMENTAL PROTECTION AGENCY Nashville, Tennessee 1986
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UNITED STATES DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information Copies of this report can be write to: purchased from: District Chief U.S. Geological Survey A-41 3 Federal Building U.S. Courthouse Nashville, Tennessee 37203 Open-File Services Section Western Distribution Branch U.S. Geological Survey Box 25425, Federal Center Lakewood, Colorado 80225
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CONTENTS Abstract 1 Introduction 1 Purpose and scope 2 Geohydrology 2 Application of criteria to the Highland Rim aquifer system 3 Drinking-water use 3 Hydrocarbon resources 3 Water quality 3 Contamination 4 Aquifers potentially suitable for waste injection 4 Selected references 25 ILLUSTRATIONS Figure 1. Map showing the area1 extent of the Highland Rim aquifer system and physiographic provinces in Tennessee 2. Generalized geologic section of the Highland Rim aquifer system showing water quality and use 8 3-7. Maps showing: 6 3. Areas where the Highland Rim aquifer system is used as a source of drinking water 10 4. Hydrocarbon resources of the Highland Rim aquifer system 16 5. Dissolved-solids concentrations and water type in the Highland Rim aquifer system 18 6. Contamination sites and karst areas in the Highland Rim aquifer system 20 7. Areas in the Highland Rim aquifer system that meet EPA criteria for exemption and may be used for receiving injected wastes 22 TABLES Table 1. Geologic formations of the Highland Rim aquifer system, and confining units 5 2. Summary of public-water systems that use the Highland Rim aquifer system as a source of drinking water 7 3. Dissolved-solids concentrations of water from selected wells and springs in the Highland Kim aquifer system 12 4. Contamination sites in the Highland Rim aquifer system 24 . . . 111
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Factors for Converting Inch-Pound Units to International System of Units (SI) For the convenience of readers who may want to use International System of Units (SI), the data may be converted by using the following factors: Multiply !?Y To obtain inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (rn) foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) mile (mi) square mile (mi2) 0.609 kilometer (km) 2.590 square kilometer (km21 gallon per minute (gal/min) 0.00006309 cubic meter per second (m3/s) National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada,formerly called mean sea level. NGVD of 1929 is referred to as sea level in this report. iv
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PRELIMINARY EVALUATION OF THE HIGHLAND RIM AQUIFER SYSTEM IN TENNESSEE FOR RECEIVING INJECTED WASTES By Michael W. Bradley ABSTRACT The U.S. Environmental Protection Agency has authority under the Safe Drinking Water Act to protect underground sources of drinking water from contamination by deep well injection. An aquifer, however, may be exempted from protection and used for injected wastes where the aquifer meets criteria established in the Agency™s Underground Injection Control program. The Highland Rim aquifer system in Tennessee consists of Mississippian age carbon- ate rocks and occurs from the Valley and Ridge of East Tennessee to west of the Tennes- see River. This aquifer contains potable water and is an important source of drinking water for municipal and domestic supplies on the Highland Rim. The Highland Rim aquifer system under parts of the Cumberland Plateau is not currently used as a source of drinking water and is not expected to be used in the future. These areas meet parts of the Environ- mental Protection Agency™s Underground Injection Control criteria for exempting aquifers to receive injected waste. INTRODUCTION Part C of the Safe Drinking Water Act (Public Law 93-523) authorized the U.S. Envi- ronmental Protection Agency (EPA) to establish regulations to assure that the underground injection of waste will not endanger existing or potential sources of drinking water. In order to regulate underground injection, EPA needs to identify and protect aquifers that are existing or potential drinking-water sources and to identify the aquifers or parts of aquifers that are not and will not be used as drinking-water sources. Under part 146.04 of the Federal Underground Injection Control program (U.S. Envi- ronmental Protection Agency, 19811, an underground source of drinking water is protected from receiving injected wastes. However, EPA may exempt an aquifer or part of an aqui- f er and allow the injection of wastes into an aquifer if: (A) It does not currently serve as a source of drinking water; and (B) It cannot now and will not in the future serve as a source of drinking water because: (1) It is mineral, hydrocarbon, or geothermal energy producing; (2) It is situated at a depth or location which makes recovery of water for drinking-water purposes economically or technologically impractical; 1
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Below the Cumberland Plateau, the Highland Rim aquifer system is overlain by the Pennington Formation (fig. 2). This formation acts as an upper confining layer that sepa- rates the Highland Rim aquifer system from the overlying Cumberland Plateau aquifer system. The Highland Rim aquifer system is at or near land surface in the rest of the area of occurrence and does not have an upper confining layer. The Highland Rim aquifer sys- tem is confined from below by the Maury Shale and the Chattanooga Shale (table 1; fig. 2). Ground water in the Highland Rim aquifer system occurs in the regolith above bed- rock and in solution-enlarged bedding-plane openings and fractures in the rock (Burchett and Hollyday, 1974; Bradley, 1984). The rocks comprising the Highland Rim aquifer system generally have low primary porosity and permeability. Solution and fracture openings provide zones of secondary permeability for movement and storage of ground water. In parts of the southeastern Highland Rim, the Fort Payne Formation weathers to a regolith with permeable zones of gravel-sized chert fragments above the bedrock (Burchett and Hollyday, 1974). Most of the ground-water flow in the Highland Rim aquifer system is within 300 feet of land surface. The ground-water reservoir is recharged from precipitation occurring over the outcrop area. Ground water then moves through solution openings and regolith to local discharge points at springs and along streams. APPLICATION OF CRITERIA TO THE HIGHLAND RIM AQUIFER SYSTEM Drinking-Water Use The Highland Rim aquifer system is used as a source of drinking water for 35 munici- pal water systems in central Tennessee (table 2; fig. 3). This aquifer system also supplies drinking water for most of the rural domestic and non-community use in the Highland Rim. The aquifer system is not currently used as a source of drinking water in the Cumber- land Plateau. The Cumberland Plateau aquifer system overlies the Highland Rim aquifer system (fig. 2) and can supply adequate amounts of ground water for drinking-water use throughout the Plateau. Hydrocarbon Resources The formations of the Highland Rim aquifer system are producing hydrocarbon resources (oil and gas) in the northern Cumberland Plateau (fig. 4). Exploration is taking place in other areas in the Cumberland Plateau. There are no current mineral uses, other than construction material, and no geothermal resource uses of the formations of this aquifer system. Water Quality Most of the ground water in the outcrop area of the Highland Rim aquifer system is a calcium bicarbonate type. Dissolved-solids concentrations are generally less than 1,000 3
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mg/L (table 3; fig. 5). In the northwestern Highland Rim, the presence of evaporite miner- als in the Fort Payne Formation or Warsaw Limestone probably causes higher minerali- zation of the ground water, with dissolved-solids concentrations being more than 1,000 mg/L in some areas. In this part of the Highland Rim aquifer system, ground water is primarily a calcium sulfate type. Water type has been illustrated by Stiff diagrams (fig. 5) which show chemically equivalent concentrations (milliequivalents per liter) of calcium, magnesium, sodium, potassium, bicarbonate, carbonate, sulfate, and chloride. The diagrams form a distinct pattern for different water types (Hem, 1970). The degree of mineralization is indicated by the width of the pattern. For example, water in a well in Dickson County is a miner- alized calcium sulfate water type with about 3,200 mg/L dissolved solids. The correspond- ing Stiff diagram is wide with large peaks for calcium and sulfate (fig. 5). Water from another well in the same county is a calcium bicarbonate type with 195 mg/L dissolved solids. The Stiff diagram is narrower, has a different shape, and has small peaks for calcium and bicarbonate (fig. 5). In the Cumberland Plateau, very little quantitative water-quality information for the Highland Rim aquifer system is available. Driller™s reports generally describe the water qualitatively as fifresh, fl fisulfur water,fl or fisalty.fl Dissolved-solids concentrations in water from the Mississippian formations in the northern Cumberland Plateau probably are more than 1,000 mg/L. One oil well in Morgan County produced water having dissolved-solids concentrations greater than 100,000 mg/L (fig. 5). Water-quality data in the southern Cumberland ‚Plateau are limited to two points near the Sequatchie Valley. Ground water at both sites had less than 1,000 mg/L dissolved solids. Additional data are needed to define the quality of the water and the hydrology of the Highland Rim aquifer system in the Cumberland Plateau. Contamination Contamination of the Highland Rim aquifer system is documented in several local- ized areas (table 4; fig. 6). At two sites, landfill leachate has contaminated nearby wells and springs, and at three sites contamination involved dumping of wastes into sinkholes (table 4). The Highland Rim aquifer system is vulnerable to contamination through sinkholes in areas of karst terrain (fig. 6). In these areas, sinkholes channel surface runoff and any con- taminants that may be present directly into the subsurface (Miller and Sitterly, 1977). The relatively rapid movement of waste through sinkholes and solution openings can contam- inate surface water as well as ground water. AQUIFERS POTENTIALLY SUITABLE FOR WASTE INJECTION The Highland Rim aquifer system is not currently used as a source of drinking water in the Cumberland Plateau; and in the northern Plateau, the aquifer system is not expected to serve as a source of drinking water because of the presence of hydrocarbon resources (fig. 7). Alth ough this area meets some of the EPA criteria for exemption, the Tennessee Department of Public Health has proposed regulations that would prevent the subsurface injection of wastes into aquifers that contain extractable energy related resources. 4
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At some sites, dissolved-solids concentrations in water from the Highland Kim aqui- fer system exceeds 3,000 mg/L. There are also some sites of local contamination in the Highland Rim aquifer system. The pockets of mineralized ground water and the contam- ination sites, however, are small, isolated occurrences in the outcrop area, with the aquifer system being used as a source of drinking water in the area surrounding these sites. Con- sequently, injection of wastes at these shallow sites could cause contamination of nearby drinking-water supplies. Table I.–Geologic formations of the Highland Rim aquifer system, and confining units Mississippian System Pennington Formation (confining unit) Bangor Limestone Hartselle Formation Upper Monteagle and Ste. Genevieve Mississippian – Limestones St. Louis Limestone -Warsaw Limestone Lower Fort Payne Formation _ Mississippian Maury Shale (confining unit) Devonian System – Upper Devonian – Chattanooga Shale (confining unit) Modif ied from Miller, 19 74.
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