In modern logging operations, felled trees are often suspended from a cable and carried out of the woods, preventing the environmental damage that would be caused if the trees were removed by tractors. "Cable logging is much like an old-fashioned clothesline on a pulley," explains Bruce Hartsough, an associate professor of agricultural engineering at UC Davis. The cable is elevated by a mast atop the winch that reels in the cable. In rocky soils, typical of many mountainous logging areas, loggers must find suitable methods for anchoring the guy lines that hold the mast in place. In most cases, tree stumps serve as anchors, but as the average size of forest trees has decreased, manufactured anchors are needed. During a study of anchoring processes in the Sierra Nevada mountains east of Sacramento, Calif., Hartsough determined that the manufactured anchors, similar in concept to a ship's anchor, could best be driven into the rocky soil using an air track drill. Powered by an air compressor, the air track drill weighs as much as an automobile and is capable of drilling and driving the anchors to a depth of 10 to 20 feet. At that depth, the anchors have a holding capacity of 25 tons or more. The air track drill proved to be more successful than a hand-held jackhammer. Hartsough will report on his study at 3:20 p.m. on Thursday, Dec. 19, during a talk titled "Cable Logging Anchors for Rocky Soils."