On February 12, 2004, at approximately 1630 mountain standard time, a Cessna 152, N66952, operated by ALTA Aircraft Maintenance, Inc., was substantially damaged when it nosed over during a forced landing in a snow-covered field near West Jordan, Utah. The commercial certificated flight instructor and a student pilot, were not injured. Visual meteorological conditions prevailed. No flight plan had been filed for this local instructional flight being conducted under Title 14 CFR Part 91. The flight originated from Salt Lake City, at approximately 1600. According to the instructor, they were practicing ground reference maneuvers at approximately 6,000 feet msl when the engine began to "run rough." The instructor said they were unable to maintain altitude, and while returning to the airport the "engine quit." The instructor made a forced landing in a snow-covered field approximately 3 1/2 miles south of the Salt Lake City Municipal 2 Airport (U42). The airplane struck the ground and nosed over. The airplane's nose landing gear was displaced aft, buckling the firewall. The empennage was buckled just aft of the rear window, and the vertical stabilizer was crushed. The instructor said the field was covered with over a foot of snow. According to an FAA inspector, an examination of the airplane's engine revealed a hole in the number 1 piston, and a fractured exhaust valve for the number 1 cylinder. No other deficiencies were noted.