by Connor J. Haugh
This report is available as a pdf below
Arnold Air Force Base (AAFB) occupies about 40,000 acres in Coffee and Franklin Counties, Tennessee (fig. 1). The primary mission of AAFB is to support the development of aerospace systems. This is accomplished through test facilities at Arnold Engineering Development Center (AEDC), which occupies about 4,000 acres in the center of AAFB.
The J4 test cell is one of the major test facilities located at AEDC. The J4 test cell was constructed in the early 1960's to support the testing of rocket motors. The cell is approximately 100 feet in diameter, extends approximately 250 feet below land surface, and penetrates several aquifers. Ground water is pumped continuously from around the test cell to keep it structurally intact. Because of its depth, dewatering has depressed the water levels in the aquifers around this site. Additionally, contaminants - predominately volatile organic compounds - are present in the ground-water discharge from the test cell and in ground water at several other sites within the AEDC facility. As part of the United States Air Force Installation Restoration Program (RP), the U.S. Geological Survey (USGS), in cooperation with the U.S. Air Force and Arnold Air Force Base (AAFB), is conducting an investigation of the effect of dewatering at the J4 test cell on the local hydrology.
Objectives of the investigation are to (1) define the subsurface lithology; (2) describe the aquifer characteristics; (3) determine the shape and extent of the cone of depression that has developed by dewatering at the J4 test cell; (4) determine the potential for introducing contaminants from aquifers overlying the Chattanooga Shale, a regional confining unit, to aquifers underlying that unit; and (5) document current water-quality characteristics.
Sites were identified near the J4 test cell where data were needed. Between December 1993 and March 1994, 27 wells were drilled at 12 sites to provide information on subsurface lithology, aquifer characteristics, water levels, and ground-water quality. Three of the wells were drilled through the Chattanooga Shale to provide information on the deep ground-water system.
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Last modified: Thursday, January 10 2013, 08:58:10 PM