Open-File Report 2011–1254
Prepared in cooperation with the U.S. Army Corps of Engineers, Mobile District Office
Borehole geophysical logs and flowmeter data were collected in April 2011 from eight boreholes to identify the depth and orientation of cavernous zones within the Miocene Tampa Limestone in the vicinity of Jim Woodruff Lock and Dam in Jackson County, Florida. These data are used to assess leakage near the dam. Each of the eight boreholes was terminated in limestone at depths ranging from 84 to 104 feet. Large cavernous zones were encountered in most of the borings, with several exceeding 20-inches in diameter. The cavernous zones generally were between 1 and 5 feet in height, but a cavern in one of the borings reached a height of about 6 feet. The resistivity of limestone layers penetrated by the boreholes generally was less than 1,000 ohm-meters. Formation resistivity near the cavernous zones did not show an appreciable contrast from surrounding bedrock, probably because the bedrock is saturated, owing to its primary permeability. Measured flow rates in the eight boreholes determined using an electromagnetic flowmeter were all less than ±0.1 liter per second. These low flow rates suggest that vertical hydraulic gradients in the boreholes are negligible and that hydraulic head in the various cavernous zones shows only minor, if any, variation.
First posted October 3, 2011
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Clarke, J.S., Hamrick, M.D., and Holloway, O.G., 2011, Borehole geophysical and flowmeter data for eight boreholes in the vicinity of Jim Woodruff Lock and Dam, Lake Seminole, Jackson County, Florida: U.S. Geological Survey Open-File Report 2011–1254, 25 p.
Purpose and Scope
Description of the Study Area
Borehole Geophysical and Flowmeter Data
Natural Gamma Log
Formation Resistivity and Spontaneous Potential Logs
Optical Televiewer Log
Fluid Temperature and Resistivity Logs
Appendix. Borehole Geophysical Logs and Flowmeter Data for Boreholes Near Jim Woodruff Lock and Dam, Lake Seminole, Jackson County, Florida