Geology topics

Research about Roane County, Tennessee

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

3 recordsLinked to original sources

USGS1988

Preliminary evaluation of ground-water flow in Bear Creek Valley, the Oak Ridge Reservation, Tennessee

Bear Creek Valley, Tennessee contains hazardous waste disposal sites where contaminants leach into ground and surface water. Groundwater flow and the potential migration of contaminants is poorly understood. The Valley is underlain by calcareous shale that contains limestone units. Ridges to the north and south are underlain by interbedded sandstones, siltstone and shale, and by massive, siliceous dolomite, respectively. The bedrock, which dips about 45 degrees southeast, is overlain by regolith to a maximum thickness of 80 ft. Observed hydraulic conductivities for the regolith range from 0.01 to 13 ft/day, and for the bedrock, from 0.001 to 11 ft/day. Groundwater flow is probably toward streams and is preferential along strike because of an areal anisotropy in hydraulic conductivity. A cross sectional groundwater flow model was used to test the conceptualized flow system and to help identify areas where additional data are needed. The preliminary model shows a pattern of recharge at both ridges, flow toward the valley, and upward flow that discharges into Bear Creek. Final model values of hydraulic conductivity in the bedrock range from 0.01 to 0.1 ft/day and reflect an areal anisotropy ratio of 1:5. Simulated recharge was 10 inches/year. (USGS)

Tennessee↗

USGS1987

Surface-geophysical investigations in Melton Valley, Oak Ridge Reservation, Tennessee

Surface geophysical methods were found to be valuable for refining knowledge of the geohydrology of Melton Valley, an area used for burial of low-level radioactive waste at the Oak Ridge Reservation in Tennessee. The valley is characterized by locally complex geologic structures in lithologies of interbedded shale and limestone. Radionuclides have been transported away from the burial areas by groundwater along paths that are, in part, controlled by geologic structures and rock type. Direct current resistivity soundings were used to determine the depth to bedrock and to aid in the delineation of subsurface stratigraphy. Depth to bedrock, as indicated by an increase in resistivity in the interpreted geoelectric layering, was compared to auger-hole data at five sites, where bedrock depths ranged from 1 to 14 ft and were within 3 ft at four sites. The subsurface contact between shale and limestone was indicated by an increase in model calculated resistivity from < 100 to > 150 ohm-meters at four different sites. Terrain conductivity profiles were used to aid in mapping surficial geologic contacts between shale and limestone units. Terrain conductivity for shale at 33-ft coil separation was generally greater than 15 millimhos/m and ranged from about 10 to 40 millimhos/m. Conductivity for limestone was generally < 15 millimhos/m and ranged from 5 to 25 millimhos/m. Azimuthal conductivity surveys indicated that conductivity was generally greatest when the transmitter and receiver coils were oriented parallel to strike. This anisotropy in terrain conductivity shows the need to keep the coil orientation consistent throughout the length of a profile. (Author 's abstract)

Tennessee↗

USGS1986

Ground-water flow in Melton Valley, Oak Ridge reservation, Roane County, Tennessee; preliminary model analysis

Shallow land burial of low-level radioactive waste has been practiced since 1951 in Melton Valley. Groundwater flow modeling was used to better understand the geohydrology of the valley, and to provide a foundation for future contaminant transport modeling. The three-dimensional, finite difference model simulates the aquifer as a two layer system that represents the regolith and bedrock. Transmissivities, which were adjusted during model calibration, range from 8 to 16 sq ft/day for the regolith, and from 0.2 to 1.5 sq ft/day for bedrock. An anisotropy ratio of 1:3 for strike-normal to strike-parallel transmissivity values, in conjunction with recharge rate = 6% of precipitation that is uniformly distributed over the model area, produces the best match between simulated and observed water levels. Simulated water levels generally compare well to observed or estimated 1978 groundwater conditions. Simulated water levels for the regolith for 39 of 69 comparison points are within +/- 10 ft of average 1978 levels. Simulated vertical flow components are in the observed direction for 9 of 11 comparison points. Preliminary simulations indicate that nearly all groundwater flow is within the regolith and discharges to either the Clinch River or the White Oak Creek-Melton Branch drainage systems. Less than 3% of the flow is between the regolith and bedrock, and < 1% of total groundwater flow discharges to the Clinch River through bedrock. Additional data needed to refine and further calibrate the model, include: (1) quantity and areal distribution of recharge; (2) water levels in the regolith near the model boundaries and beyond the Clinch River; (3) water levels and aquifer characteristics for bedrock; and (4) additional surface water data. (Author 's abstract)

Tennessee↗