On July 24, 1996, about 0815 hours Pacific daylight time, a Piper PA-31-350, N48DH, operated by Union Flights as Flight 9906, was substantially damaged during landing at Kneeland, California. The flight was being operated under the provisions of 14 CFR Part 135 as a cargo flight. The pilot received minor injuries. Visual meteorological conditions prevailed and a company flight plan was filed. Witnesses stated that the pilot landed "hot" about midfield leaving skid marks on the runway over a distance of 280 feet. The airport superintendent stated that he measured 330 to 350 feet of skid marks. There are no services available at the airport; it is an alternate landing site used when the coastal airports are fogged in. The pilot reported that he flew a left downwind for runway 33 at a pattern altitude of 3,537 feet. He stated that he was about 500 feet low on base leg. He increased his base leg altitude to a point that he felt was appropriate and turned final. He stated that he was high over the threshold. He reduced the power, but the aircraft began to float in ground effect. The pilot reported that he touched down on the 2,200-foot-long runway, about halfway between the threshold and the midfield point. As the midpoint was passed, he lowered the nose and began braking, but not locking the wheels. About 2/3 down the runway heavy braking was initiated, but the aircraft was not going to stop in the remaining distance. The left rudder was pushed and the aircraft turned sideways and left the runway over the embankment. The pilot reported no mechanical malfunction with the aircraft prior to the accident.