Geology topics

M. W. Bradley

Publications and source records attributed to M. W. Bradley.

15 recordsLinked to original sources

USGS1992

Hydrogeology, water quality, and potential for transport of organochlorine pesticides in ground water at the North Hollywood Dump, Memphis, Tennessee

Geologic, hydrologic, and water-quality data indicate that ground-water contamination is confined to shallow horizons within the unconfined aquifer underlying the North Hollywood Dump in Memphis, Tennessee. The dump is a closed municipal-industrial landfill that has been ranked as Tennessee's potentially most dangerous hazardous-waste site. Toxic constituents of concern at the dump include residues from the manufacture of organochlorine pesticides. The dump overlies an unconfined aquifer of unconsolidated sands, silts, and clays. During average hydrologic conditions, ground waterflows beneath the dump at a mean velocity of approximately 3 feet per day and discharges to the Wolf River. Leachate from the dump mixes with underlying ground water, resulting in increased concentrations of dissolved solids and organic carbon downgradient from the dump. The mobility of chlordane, a representative organochlorine pesticide, is limited by its low solubility and its strong affinity for sand, silt, and clays of the aquifer. Degradation of chlordane may occur slowly, if at all, in the aquifer. Based on estimates of mean ground-water velocity and retardation of the pesticide due to sorption, mean travel times for chlordane migrating from the dump to the ground-water discharge zone are of the order of 50 to 500 years. Simulations of chlordane concentration resulting from the discharge of contaminated ground water and complete mixing in the Wolf River are sensitive to assumptions about chlordane persistence in the unconfined aquifer. If the half life of chlordane in the aquifer is assumed to be 30 years or less, the simulated concentration of chlordane in the Wolf River under average flow conditions is less than the most stringent water-quality criterion.

Tennessee↗

USGS1991

Ground-water hydrology and the effects of vertical leakage and leachate migration on ground-water quality near the Shelby County landfill, Memphis, Tennessee

An investigation of potential leakage of leachate from the Shelby County landfill near Memphis, West Tennessee, was conducted during 1986-87. The migration of leachate from the landfill to the shallow alluvial aquifer system and the potential leakage to the deeper confined Memphis aquifer of Tertiary age were investigated. A network of observation wells was drilled to determine water levels and aquifer properties in the shallow and deep aquifers as well as in the confining layer. Water samples were collected to define potential leachate occurrence. A depression in the water table within the shallow alluvial aquifer was defined from the water-level data. Drawdowns within the cone of depression are as much as 14 feet lower than the adjoining Wolf River. Recharge from the river and leachate from the landfill moves toward the depression. The presence of leachate within the shallow aquifer was confirmed from determinations of dissolved solids and dissolved chloride concentrations and comparisons with areas away from the aflected zone. Leakage from the water-table aquifer to the Memphis aquifer was confirmed from chemical analyses and hydraulic-head data. Dissolved-solids concentrations in water samples from the upper Memphis aquifer near the landfill are higher than in samples from the Memphis aquifer in unaffected areas. Tritium activities in water samples from the upper Memphis aquifer were as high as 34 pico-Curies per liter indicating recent recharge to the Memphis aquifer. The presence of synthetic organic compounds and elevated concentrations of dissolved solids, chloride, and trace metals indicate the leachate has aflected water quality in the alluvial aquifer. Vertical migration of ground water could transmit leachate down to the Memphis aquifer. Although water-quality data indicate that water is leaking from the alluvial aquifer to the Memphis aquifer, most of the data do not indicate the occurrence of leachate in the Memphis aquifer. Chemical data from one well in the Memphis aquifer near the landfill indicates a slightly elevated dissolved-chloride concentration, but the data are limited.

Tennessee↗

USGS1987

Construction, geologic, and hydrologic data for observation wells in the Reelfoot Lake area, Tennessee and Kentucky

Twenty-three observation wells were installed at 12 sites in the Reelfoot Lake area of Kentucky and Tennessee during July 1986. The wells were installed to supplement an existing water level network and to provide additional data on the hydraulic characteristics and vertical hydraulic gradients in the alluvial aquifer near Reelfoot Lake. Well yields ranged from less than 20 gallons per minute to about 140 gallons per minute. The specific capacities of the wells ranged from less than 1 to 17.1 gallons per minute per foot of drawdown. Three stratigraphic sequences were encountered during drilling. Clay and silty clay was about 40 feet deep near the southwest corner of Reelfoot Lake. Predominantly medium- to coarse grained sand occurred below about 15 feet of silt and clay near the west and northwest sides of Reelfoot Lake. Along the western limit of the study area, near Lake No. 9 and the Mississippi River, about 20 to 30 feet of silt and silty sand occurred below land surface.

Kentucky, Tennessee↗

USGS1986

Delineation and description of the regional aquifers of Tennessee; basal sandstone aquifer west of the Valley and Ridge Province

The basal sandstone aquifer is believed to underlie most of Tennessee west of the Valley and Ridge Province. It is a Cambrian sandstone that overlies the granites of the Precambrian basement complex. The basal sandstone is a poorly known resource defined only by 14 data points (wells) for the entire state of Tennessee. Because the aquifer occurs at depths of more than 5 ,500 feet below land surface, and is overlain by about 1,000 feet of low permeability Paleozoic carbonates and shales. Consequently vertical recharge to the aquifer is probably very small per unit area. Data from two sampling sites indicate that the basal sandstone aquifer has low porosity and permeability. The concentrations of dissolved solids in water from the basal sandstone aquifer range from less than 10,000 mg/L to more than 200,000 mg/L. It is believed that some of the values above 50 ,000 mg/L are due to contaminants from nearby disposal wells. This aquifer is not being used as a source of drinking water because of its great depth, the presence of shallower sources, suspected low yields, and possible concentrations of more than 10,000 mg/L dissolved solids. (USGS)

Open-File Report↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee – The central basin aquifer system

The Central Basin aquifer system is composed of Devonian and Ordovician carbonate and shale rocks. This aquifer occurs west of the Valley and Ridge province and crops out in the Central Basin and the Sequatchie Valley of Tennessee. Ground water in the Central Basin aquifer occurs primarily in solution openings and fractures, and the flow system is generally limited to 300 feet or less below land surface. However, some fracture and minor faults may allow vertical recharge to the underlying Knox Group, which marks the lower boundary of the Central Basin aquifer system. Away from the Central Basin, the upper limit of the Central Basin aquifer system is the Chattanooga Shale, an effective confining unit. The Central Basin aquifer system, an important source of drinking water, supplies most of the rural domestic and many public supplies of drinking water in the Central Basin and the Sequatchie Valley. Dissolved-solids concentrations often are less than 500 milligrams per liter where the aquifer is part of a dynamic flow system. Dissolved-solids concentrations may reach thousands or tens of thousands of milligrams per liter below the zone of dynamic flow.

Tennessee↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee -- Highland Rim aquifer system

The Highland Rim aquifer system is primarily composed of Mississippian carbonates. This aquifer system occurs west of the Valley and Ridge province. It crops out in the Highland Rim and the Sequatchie Valley. It has been removed by erosion from the Central Basin. Ground water in the Highland Rim aquifer system occurs primarily in secondary openings. These openings include solution openings, joints, and faults. The Chattanooga Shale is the lower confining layer for the Highland Rim aquifer system. Under the Cumberland Plateau, this aquifer system is separated from the overlying Pennsylvanian formations by the Pennington Shale. The Highland Rim aquifer system is an important source of drinking water. It supplies most of the rural, domestic and many public supplies of drinking water in the Highland Rim. Where there is a dynamic flow system, dissolved-solids concentrations are less than 500 milligrams per liter. However, isolated cells may exist where the ground water has dissolved-solids concentrations of more than 1,000 milligrams per liter.

Tennessee↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee: The east Tennessee aquifer system

The east Tennessee aquifer system occurs in the Valley and Ridge and the Blue Ridge provinces of Tennessee. These areas are underlain by rocks of Precambrian to Pennsylvanian age which have been structurally deformed and faulted during the Appalachian orogeny. Groundwater in the Valley and Ridge occurs primarily in solution openings in carbonate rocks and in fractures in sandstone and shale. Fractures in the crystalline rocks store and transmit most of the groundwater in the Blue Ridge province. The east Tennessee aquifer system is important as a source of rural and municipal drinking water. Within 300 ft of land surface, groundwater generally contains less than 500 milligrams/L dissolved solids. At greater depths, fractures and solution openings are smaller and fewer in number. There are very little data to define groundwater occurrence at depths greater than about 300 ft. Groundwater flow may be restricted and the dissolved solids concentrations in the groundwater may reach thousands or even ten thousands of milligrams/L.

Tennessee↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee– Tertiary aquifer system

The Tertiary aquifer system in Tennessee is composed of sands and clays of Quaternary and Tertiary age. The aquifer system occurs in west Tennessee from the Mississippi River east to the outcrop of the Porters Creek Clay. Groundwater in the Tertiary aquifer system is recharged at outcrops and through overlying permeable deposits. The underlying Porters Creek Clay acts as the lower confining layer. The Tertiary aquifer system is the single most prolific source of groundwater in Tennessee. The water quality is excellent with generally less than 500 mg/L dissolved solids.

Tennessee↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee– The Cretaceous aquifer system of west-Tennessee

The Cretaceous aquifer system in western Tennessee is composed of sand, gravel, and clay. The aquifer system is under confined conditions except in the outcrop area. Ground water is recharged by precipitation on the outcrop area and through some overlying permeable deposits. The hydraulic gradient in the confined aquifers is about 1 foot per mile generally toward the west. The Cretaceous aquifer system unconformably overlies the consolidated Paleozoic formations and is overlain and confined by the Porters Creek Clay. The Cretaceous aquifer system is used as a source of water supply primarily in the outcrop area. West of the outcrop of this aquifer system, ground water can be obtained at shallower depths and with better water quality. The water of the Cretaceous aquifers generally have very good quality in the outcrop area. The dissolved solids increase down gradient to more than 1,000 milligrams per liter in parts of Shelby County. High iron concentrations are present in some areas.

Tennessee↗

USGS1986

Preliminary evaluation of the Highland Rim aquifer system in Tennessee for receiving injected wastes

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 carbonate rocks and occurs from the Valley and Ridge of East Tennessee to west of the Tennessee 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 Environmental Protection Agency’s Underground Injection Control criteria for exempting aquifers to receive injected waste.

Tennessee↗

USGS1986

Preliminary evaluation of the basal sandstone in Tennessee for receiving injected wastes

The U.S. Environmental Protection Agency is authorized, under the Safe Drinking Water Act, to administer the Underground Injection Control program. This program allows for the regulation of deep-well disposal of wastes and establishes criteria to protect underground sources of drinking water from contamination. The basal sandstone in Tennessee occurs west of the Valley and Ridge province at depths of 5,000 to 9,000 feet below land surface. The basal sandstone consists of about 30 to 750 feet of Cambrian sandstone overlying the crystalline basement complex. The basal sandstone is overlain and confined by shale and carbonate rocks of the Middle and Upper Cambrian Conasauga Group. Hydrologic data for the basal sandstone, available from only three sites (four wells) in Tennessee, indicate that the basal sandstone generally has low porosity and permeability with a few zones having enough permeability to accept injected fluids. Limited water-quality data indicate the basal sandstone contains water with dissolved-solids concentrations exceeding 10,000 milligrams per liter. Since the dissolved-solids conce ntrations exceed 10,000 milligrams per liter, the basal sandstone is not classified as an underground source of drinking water according to U.S. Environmental Protection Agency regulations.

Tennessee↗

USGS1986

Preliminary evaluation of the Knox Group in Tennessee for receiving injected wastes

The U.S. Environmental Protection Agency is authorized under the Safe Drinking Water Act to protect underground sources of drinking water from contamination. However, an aquifer may be exempted from protection and used for injected wastes where the aquifer meets criteria established in the U.S. Environmental Protection Agency's Underground Injection Control program. The Knox Group in Middle and West Tennessee occurs primarily in the subsurface, and the top of the Knox Group ranges from about 350 to 3,000 feet below land surface. The upper part of the Knox Group (upper Knox aquifer) is an important source of drinking water in parts of the Central Basin and the Highland Rim provinces. The lower part of the Knox Group is currently being used for injected wastes at New Johnsonville on the western Highland Rim and at Mount Pleasant in the Central Basin.

Tennessee↗

USGS1985

Delineation and description of the regional aquifers of Tennessee — The Knox Aquifer in central and west Tennessee

The Knox aquifer is composed of the Cambrian and Ordovician age carbonate rocks of the Knox Group. This aquifer occurs throughout Tennessee, west of the Valley and Ridge province. The Knox crops out in the Sequatchie Valley and in the Wells Creeks cryptoexplosive structure on the Northwestern Highland Rim. Groundwater in the upper Knox occurs primarily in solution openings. The aquifer may be recharged through fractures and faults in the overlying Ordovician limestones in Middle Tennessee. The underlying Conasauga Shale acts as the lower confining layer. Throughout parts of the Central Basin province, the Knox aquifer is an important source of water for rural domestic supplies. In these areas, groundwater from the Knox generally has less than 1,000 milligrams/L dissolved solids. Away from the Central Basin, the dissolved solids concentrations increases. It may approach brine concentrations under the Cumberland Plateau.

Tennessee↗

USGS1985

Preliminary evaluation of the Central Basin aquifer system in Tennessee for receiving injected wastes

The U.S. Environmental Protection Agency is authorized to protect underground sources of drinking water from contamination. However, an aquifer may be used for injected wastes where the aquifer meets criteria established in the Environmental Protection Agency’s Underground Injection Control program. The Central Basin aquifer system in Tennessee consists of Ordovician to Devonian carbonate rocks and it occurs from the Valley and Ridge province to west of the Tennessee River. This aquifer system is currently used for drinking water in the Central Basin and western Highland Rim, but is not used for drinking water in the northern Highland Rim nor the Cumberland Plateau provinces.

Tennessee↗

USGS1984

Ground water in the Dickson area of the western Highland Rim of Tennessee

A hydrologic study of the Dickson, Tenn., area provided additional information on the occurrence of ground water in the Mississippian carbonate rocks of the western Highland Rim. Twenty-six wells were drilled to determine the occurrence of ground water in relation to topographic position, regolith thickness, streamflow gains or losses, lithology of the underlying formations, and linear features. Yields of 26 test wells ranged from 0 to about 300 gallons per minute and averaged about 68 gallons per minute. Nine wells yielded 80 to about 300 gallons per minute; specific capacities ranged from about 0.71 to 12.7 gallons per minute per foot of drawdown. Seven of these nine wells yielded water from solution openings in the Warsaw Limestone. The other two wells yielded water from gravel and sand in the regolith. Aquifer tests were conducted on two wells. One well was pumped at an average rate of 350 gallons per minute for 72 hours with 39.77 feet of drawdown. The second well was pumped for 8 hours at 120 gallons per minute with 20.86 feet of drawdown. The water from both wells was of generally good quality. Water from one well had a dissolved solids concentration of 170 milligrams per liter. The dissolved solids in the water from a second well was estimated from specific conductance as about 160 milligrams per liter. Thick regolith and the presence of fine-grained limestone interbedded with coarse-grained limestone near the base of the regolith appear to be significant conditions for the development of solution openings that yield large amounts of water. Seventy percent of the test wells in which these conditions occurred yielded 80 gallons per minute or more.

Tennessee↗