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Applications of Dual-Wall Reverse-Circulation Drilling in Ground Water Exploration and Monitoring |
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| Authors: | M Fred Strauss Steve L Story Norman E Mehlhorn |
| Institution: | M. Fred Strauss is a hydrogeologist and project manager with Hart Environmental Management Corp. (2041 Business Center Dr., Suite 110, Irvine, CA 92715). He earned a B.S. in geology from the University of Kansas and an M.S. in geology from Fort Hays State University. He has administered water supply and hazardous waste site drilling investigations throughout the western United States using the dual-wall techniques.;Steve L. Story is California area manager of Layne Environmental Services (16018 Valley Blvd., Fontana, CA 92335). He earned a B.S. in earth sciences from California State College in Bakersfield. He is responsible for overseeing all Layne-Western Co. Inc. geoenvironmental drilling programs in California where the dual-wall techniques are used.;Norman E. Mehlhorn is vice president of Layne-Western Co. Inc. responsible for all western region operations (12030 East Riggs Rd., Chandler, AZ 85249). He was instrumental in the design and engineering of the dual-wall systems in Calgary, Alberta, Canada, in 1959. His experience spans several continents and includes off-shore projects in the Far East. |
| Abstract: | Dual-wall reverse-circulation drilling uses flush-threaded double-wall drill pipe and high-pressure air to provide continuous return of formation and water samples. Cuttings and formation waters are not contaminated with drilling additives or mixed with other borehole material. Up-hole velocity of about 70 ft/sec provides reliable logging of water, mineral or contaminant-bearing strata. Water samples representative of specific strata may be airlifted or bailed to the surface. In the percussion hammer system, dual-wall drill pipe is advanced through chiefly unconsolidated material by the percussion action of an above-ground pile hammer. The borehole is drilled and temporarily cased in one pass. Wells or monitoring devices are installed as the drill pipe is hydraulically retracted during construction. A rotary head may be adapted as an option to allow dual-wall rotary drilling into consolidated or crystalline formations through a percussion hammer drill string temporarily left in place as a conductor. The complex geology and variety of geoenvironmental problems in southern California has provided a testing ground for dual-wall drilling on hazardous material site investigations. Several case histories have demonstrated the capabilities and versatility of this method, including: (1) the installation of 4-inch and 6-inch diameter gasoline monitoring and recovery wells through gravels and cobbles at a filling station where hollow-stem auger drilling failed; (2) the confirmation of a dry borehole initially drilled by direct rotary at a landfill; and (3) multiple installations of monitoring devices through municipal refuse at a city of Los Angeles landfill. |
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