Geology topics

Research about Shelby County, Tennessee

Source-linked reports with geographic coverage including Shelby County, Tennessee.

12 recordsLinked to original sources

USGS2020

Microbiology and oxidation-reduction geochemistry of the water-table and Memphis aquifers in the Allen well field, Shelby County, Tennessee

The shallow and Memphis aquifers in Shelby County, Tennessee, are valuable natural resources that are used for domestic, public-supply, and agricultural water use. The Memphis aquifer is the primary source for public supply in West Tennessee and provides 170 to 175 million gallons of water per day for more than 900,000 people (Robinson, 2018). The shallow aquifer includes the unconfined water table, provides domestic water supplies in Shelby County, and is susceptible to contamination from urban and industrial activities, underground storage tanks, old dumps, and other sources. Both aquifers are likely to be stressed in the future by factors such as population increase, contaminant migration from historical contamination sites, industrial and agricultural activities, climate change, and other competing demands on the water resources.

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USGS2018

Preliminary evaluation of the hydrogeology and groundwater quality of the Mississippi River Valley alluvial aquifer and Memphis aquifer at the Tennessee Valley Authority Allen Power Plants, Memphis, Shelby County, Tennessee

The hydrogeology, groundwater quality, and potential for hydraulic connection between the Mississippi River Valley alluvial aquifer and the Memphis aquifer in the area of the Tennessee Valley Authority (TVA) Allen Combined Cycle and Allen Fossil Plants in southwestern Memphis, Tennessee, were evaluated from September through December 2017. The study was designed as a preliminary assessment of the potential for leakage of groundwater from the Mississippi River Valley alluvial aquifer through the underlying upper Claiborne confining unit into the underlying Memphis aquifer at the plants. A short-term aquifer test of four of the five Memphis aquifer production wells installed at the Allen Combined Cycle Plant induced drawdown in water levels in the Mississippi River Valley alluvial aquifer, locally. The largest drawdown occurred in the eastern and southeastern parts of the TVA plants area, and generally was coincident with locations where stratigraphic data show increased thickness of and depth to the base of the alluvium and decreased thickness and inferred offset in the base of the confining unit relative to nearby locations. In contrast, stratigraphic data for most other locations at the site indicate shallower depths to the base of the alluvium and more consistent thickness of and depth to the base of the confining unit, which corresponds with areas where less drawdown was observed during the test. Water-quality results for samples from the production wells and from monitoring wells screened in the Mississippi River Valley alluvial aquifer indicate that groundwater with higher dissolved-solids concentrations and tritium from this shallow aquifer has mixed with water in the upper part of the Memphis aquifer at one of the production wells. Results of the study collectively confirm that the Mississippi River Valley alluvial and Memphis aquifers are hydraulically connected near the TVA plants area.

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USGS1998

Rainfall and water-level data for a wetland area near Millington, Shelby County, Tennessee, October 1996 through September 1997

Rainfall amounts and water levels at a degraded wetland area near Millington, Shelby County, Tennessee, were collected to assist the Tennessee Department of Transportation with a program designed to restore the wetland to a more natural condition. The site is located along a channelized reach of Big Creek Drainage Canal, east of State Route 240, and near the southeastern boundary of the Naval Support Activity Memphis, Millington. Rainfall amounts were recorded at 5-minute intervals using a tipping-bucket rain gage from October 1, 1996 through September 30, 1997. Total rainfall for this period was 70.16 inches. In general, water levels at the wetland were above or near the ground surface during the 6-month period from the first of January through June 1997. For the remainder of the year, water levels generally subsided to several feet below land surface. However, some locations within the wetland were wet or highly saturated year round.

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USGS1997

Rainfall and water-level data for a wetland area near Millington, Shelby County, Tennessee, October 1995 through September 1996

Rainfall amounts and water levels were collected at a wetland area near Millington, Shelby County, Tennessee, to assist the Tennessee Department of Transportation with a program of wetland restoration. The site is located along a channelized reach of Big Creek Drainage Canal, east of State Route 240, and near the southern boundary of Naval Support Activity Memphis. Rainfall amounts and water levels for the site were recorded from October 1, 1995 to September 30, 1996. Total rainfall for this period was 47.58 inches. In general, water levels at the wetland were above or near the ground surface during the 6-month period from the first of January through the end of June 1996. For the remainder of the year, water levels generally subsided to several feet below land surface. However, some locations within the wetland were wet or highly saturated year round.

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USGS1996

Hydrologic data at a wetland site, Millington, Shelby County, Tennessee, June 1993 through June 1994

Hydrologic data at a wetland site near Millington, Shelby County, Tennessee, were collected from June 1993 through June 1994. The data were collected to support the efforts of the Tennessee Department of Transportation to better understand hydrologic properties at the site prior to wetland restoration. Water levels were monitored in thirteen 8-inch- diameter wells, approximately 2 feet deep. The casing in each well was slotted and screened from land surface to a depth of about 2 feet. Water-level recorders provided continuous records of stage during periods of wetland inundation, and depth to water table during periods of noninundation. A continuous-stage recorder was installed in a pond. Precipitation data were obtained from the Naval Air Station-Memphis, Millington, Tennessee. Land surface at the wells was inundated from 0 to 56 percent of the study period. Additionally, water levels in the wells were not more than 1.5 feet below land surface for 16 to 68 percent of the study period.

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USGS1995

Hydrogeology, ground-water quality, and source of ground water causing water-quality changes in the Davis well field at Memphis, Tennessee

An investigation was conducted by the U.S. Geological Survey from 1992 to 1994 to collect and interpret hydrogeologic and water-quality data to determine the source of ground water causing water-quality changes in water from wells screened in the Memphis aquifer in the Davis well field at Memphis, Tennessee. Water-quality changes in aquifers used for water supply are of concern because these changes can indicate a potential for contamination of the aquifers by downward leakage from near-surface sources. The water-quality changes at the Davis well field were detected by Memphis Light, Gas and Water Division, which has periodically sampled and analyzed water from many of the 14 production wells since the well field began operation in 1971. Memphis Light, Gas and Water Division analyzed the water samples primarily for hardness, alkalinity, chloride, ulfate, and iron. Results of the e analy es and results of more recent (1992) analyse of water samples by the U.S. Geological Survey indicate that the quality of water from eight of the production wells has changed since the well field began operation. For example, from 1972 to 1991, hardness of water from one well has increased from 90 to 292 milligrams per liter (224 percent). The confining unit, which separates the fluvial deposits aquifer from the Memphis aquifer in the area of the well field, is relatively thick and contains many clay layers. However, a test hole drilled for one of five shallow wells installed in the alluvial aquifer in the Mississippi Alluvial Plain just west of the well field indicated that the confining unit separating the alluvial aquifer from the Memphis aquifer locally is absent. Differences in hydrauLic head between the alluvial and fluvial deposits aquifers and the Memphis aquifer favor downward leakage of ground water. Thus, the absence of the confining unit beneath the Mississippi Alluvial Plain just west of the well field provides a direct pathway for water in the alluvial aquifer to enter the Memphis aquifer. Comparison of selected water-quality properties and major inorganic and trace element constituent concentrations in samples from the alluvial, fluvial deposits, and Memphis aquifers indicates that the source of ground water causing waterquality changes at the Davis well field is the alluvial aquifer west of the well field . The presence of tritium and chlorofluorocarbons in water from wells screened in the Memphis aquifer in the western part of the well field indicates that relatively young (post-1940) water from the alluvial aquifer has entered the Memphis aquifer. NETPATH geochemical model code was used to mix waters from the alluvial aquifer with water from the Memphis aquifer using chloride as a conservative tracer. The resulting models indicated that a mixture containing 3 percent alluvial aquifer water mixed with 97 percent unaffected Memphis aquifer water would produce the chloride concentration measured in water from the Memphis aquifer well most affected by water-quality changes. NETPATH also was used to calculate mixing percentages of alluvial and Memphis aquifer Abstract waters based on changes in the concentrations of selected dissolved major inorganic and trace element constituents that define the dominant reactions that occur during mixing. These models indicated that a mixture containing 18 percent alluvial aquifer water and 82 percent unaffected Memphis aquifer water would produce the major constituent and trace element concentrations measured in water from the Memphis aquifer well most affected by water-quality changes. However, these model simulations predicted higher dissolved methane concentrations than were measured in water samples from the Memphis aquifer wells.

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USGS1992

Hydrogeology, ground-water quality, and potential for water-supply contamination near the Shelby County landfill in Memphis, Tennessee

An investigation was conducted from 1989 to 1991 to collect and interpret hydrogeologic and ground-water-quality data specific to the Shelby County landfill in east Memphis, Tennessee. Eighteen wells were installed in the alluvial and Memphis aquifers at the landfill. Hydrogeologic data collected showed that the confining unit separating the alluvial aquifer from the Memphis aquifer was thin or absent just north of the landfill and elsewhere consists predominantly of fine sand and silt with lenses of clay. A water-table map of the landfill vicinity confirms the existence of a depression in the water table north and northeast of the landfill and indicates that ground water flows northeast from the Wolf River passing beneath the landfill toward the depression in the water table. A map of the potentiometric surface of the Memphis aquifer shows that water levels were anomalously high just north of the landfill, indicating downward leakage of water from the alluvial aquifer to the Memphis aquifer. An analysis of water-quality data for major and trace inorganic constituents and nutrients confirms that leachate from the landfill has migrated northeastward in the alluvial aquifer toward the depression in the water table and that contaminants in the alluvial aquifer have migrated downward into the Memphis aquifer. The leachate plume can be characterized by concentrations of certain major and trace inorganic constituents that are 2 to 20 times higher than samples from upgradient and background alluvial aquifer wells. The major and trace constituents that best characterize the leachate plume are total organic carbon, chloride, dissolved solids, iron, ammonia nitrogen, calcium, sodium, iodide, barium, strontium, boron, and cadmium. Several of these constituents (specifically dissolved solids, calcium, sodium, and possibly ammonia nitrogen, chloride, barium, and strontium) were detected in elevated concentrations in samples from certain Memphis aquifer wells. Elevated concentrations were detected in samples from the Memphis aquifer beneath the leachate plume where the confining unit is thin or absent. The distribution of halogenated alkanes (specifically dichlorodifluoromethane and trichlorofluoromethane) and halogenated alkenes (specifically 1,2-trans-dichloroethene and vinyl chloride) in samples from wells screened in both the alluvial and Memphis aquifers is similar to the distribution of major and trace inorganic constituents that characterize the leachate plume. The ground-water supply most susceptible to contamination from the Shelby County landfill is the Sheahan well field of the Memphis Light, Gas and Water Division. This well field is about 5 miles downgradient from the landfill in the direction of ground-water flow. Based on an estimated velocity of 0.5 to 1.5 feet per day, ground water would require about 50 to 150 years to travel from the Shelby County landfill to the Sheahan wellfield. Given the time and distance of transport, any contaminants in the ground water would not likely persistto reach this well field because of the effects of various physical, chemical, and biological processes, including dilution and adsorption.

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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.

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USGS1988

Construction, geologic, and ground-water data for observation wells near the Shelby County landfill, Memphis, Tennessee

Forty-one observation wells and two stratigraphic test holes were drilled near the Shelby County landfill in east Memphis. These wells were installed as part of an investigation on possible vertical leakage of groundwater from the alluvial aquifer into the Memphis Sand aquifer. The alluvial aquifer consists of about 45 to 55 ft of alluvial silt, sand, and gravel. This is separated from the underlying Memphis Sand aquifer by about 30 to 60 ft of silt, silty sand, and clay in the confining layer. Thirty wells completed in the alluvium were generally less than 50 ft deep. The depth to the water table ranged from about 15 to more than 45 ft below land surface. Four observation wells were completed in the upper part of the Memphis Sand aquifer. Water levels in the Memphis Sand aquifer were generally 35 to 40 ft below land surface.

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USGS1984

Flood frequency and storm runoff of urban areas of Memphis and Shelby County, Tennessee

Techniques are presented for estimating the magnitude and frequency of peak discharges and storm runoff on stream in urban areas of Memphis, Tennessee. Comprehensive analyses were made in which physical characteristics of streams are related to snythetic flood characteristics at gaging stations. Equations derived from analyses provide estimates of peak discharges with recurrence intervals of 2 to 100 years on streams that have drainage areas less than 20 square miles. The regression analyses indicated that size of drainage area and condition of channel (paved or unpaved) are the most significant basin characteristics affecting the magnitude and frequency of floods in urban streams. Data from 27 gaging stations with 8 years of record were used in the analyses. Flood frequency at each gaging station was computed from calibrated parameters in a rainfall-runoff model. Techniques are also presented for estimating discharge hydrographs for individual floods by using the unit hydrograph, lag time, and rainfall excess. (USGS)

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USGS1973

Wolf River at Memphis, Tennessee: floodflow characteristics along proposed Interstate Highway 240, Shelby County

This report has been prepared by the U.S. Geological Survey at the request of Mr. Henry Derthick, Engineer of Structures of the Tennessee Department of Transportation, under the authority of a cooperative agreement between the two agencies. It supplements information contained in a report with the same title dated September 1966. The Department of Transportation proposes to construct a segment of Interstate Highway 240 and several bridges across the Wolf River on the northern side off Memphis, Shelby Count. Mt. Derthick has requested an analysis of the 50-year flood or the maximum flood of record to determine the possible effect of the proposed construction on flood profiles along the Wolf River.

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USGS1948

Electrical resistivity investigations at Memphis, and Bolivar, Tennessee

This geophysical investigation was undertaken upon request of Elliott M. Cushing of the Ground Water Division Office at Memphis, Tennessee. The field work was performed during the period March 13 to 28, 1947; the apparent resistivity curves were interpreted during November and December; and the report was written subsequent to the interpretation of the curves. The writer is grateful to Elliott M. Cushing and his staff for the splendid cooperation and generous assistance extended to him in obtaining the measurements. It is also a pleasure to acknowledge the assistance of George J. Edwards in obtaining the field measurements.

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