Significant results in the Park City and Salt Lake area mountains from ski area avalanche reduction work with artillery, explosives and ski cuts. Most slides breaking into old snow, some with October dirt layer on bed surface. Upper elevation N, E and NW facing, up to 3 feet deep, 700' wide. One slide 4-5 feet deep. Some sympathetic activity. Numerous Class 1's and 2's from explosives and ski cuts. Some slides with initial failures in storm, then stepping into facets.