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Walters, Dick, Kelly AFB, Texas ECOTONE, Vol 3 No 4, 1999/2000

A handful of horizontal wells at Kelly Air Force Base, Texas, will substitute for hundreds of yards of trenching alongside a neighborhood that has expressed concern at the possibility of remedial operations that might produce noise, dust, and industrial activity very nearly on their doorsteps. Originally, a Proposed Plan for an Interim Remedial Action to contain contaminated shallow ground water from a source at the northwest corner of East Kelly offered a series of collection trenches along the southern and eastern borders of the base. Wells were recommended as an alternative in areas where underground utilities made trenches impractical. The goal was to remove enough water from a capture zone near the base boundary to prevent further movement of contamination beyond the fence. The proposed trenches would have been 40 feet deep and 60 feet wide at the surface and would have involved digging out and replacing hundreds of tons of soil. A series of vertical wells was found to be costly and possibly insufficient to stop the contamination at the boundary because of the limited capture area surrounding each well. The environmental cleanup contractor and the Air Force decided to evaluate horizontal wells as a technology that could offer an effective and economical solution. Preliminary ground-water modeling studies indicated that horizontal wells would contain the shallow underground water as efficiently as the proposed trenches. A constructability study involving the installation of a horizontal well began March 9, 1999, on East Kelly. A horizontal well was installed that was able to affect a 600-foot area from the point where the drill rig was set up. The test was successful. The noise, dust, and inconvenience of excavating a trench or installing many wells will be avoided because each horizontal well affects a large area from a single location. The ground water is piped to an ultraviolet oxidation treatment system that breaks down the contamination molecules. Recent advances from the oil industry make it possible to precisely place a horizontal well in a thin layer of underground water like the ground-water configuration that exists at East Kelly. The well drilling equipment enters the ground at a single point, just as a vertical well would do. Then the drill bit makes an underground turn, so that the well casing and screened portion where water enters will be sideways, parallel to the surface. The drilling goes beneath underground utilities rather than around or through them as a series of wells or a collection trench would do. Air Force officials say that horizontal wells will result in a system as efficient as that originally proposed, but less costly and installed with less disturbance to the neighbors.

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