Circumstances and results of tests of a three-chambered REDSOD built for attachment to a Caterpillar D9 tractor are discussed. The Caterpillar D9 tractor was chosen for its drawbar capability of 4000 lb/ft of width, bare weight of approximately 70,000 lb, and 10 ft width. Tests in straight trenching operations were performed at two sites: one in an area with a clay overburden, the other in sand.From the data presented, it is concluded that a REDSOD machine, with a 1200 ft3 min air compressor, handled by a skilled operator, can produce a 2 ft deep trench at approximately 2000 yd3/h. The noise level is not damaging to operator or adjacent structures or personnel. The use of higher air pressures increases production rates. The recoil produced by REDSOD has no appreciable effect on production rate or tractor reliability.