On June 5, 2004, approximately 1150 mountain daylight time, a Cessna 310J, N415SW, piloted by an airline transport pilot, was substantially damaged when it departed the runway and collided with a hangar during landing roll at Morgan County Airport (42U), Morgan, Utah. Visual meteorological conditions prevailed at the time of the accident. The business flight was being conducted on a visual flight rules flight plan under the provisions of Title 14 CFR Part 91. The pilot and his two passengers were not injured. The flight originated in Mountain Home, Idaho, approximately 1010. The following is based on the accident report and a subsequent telephone interview with the pilot. He said he had made a "standard approach" to runway 21. The approach was flown at an approach speed between "105 to 110 knots." [According to the Cessna 310J Owner's Manual, landing approach speed should be 102 mph (88 knots).] The pilot used 35 degrees of flaps [the Cessna 310J Landing Performance Chart indicates that if flaps are extended 35 degrees, there is no wind, and maximum brakes are applied, between 766 and 1,114 feet of runway will be required for landing.) The airplane touched down 500 to 700 feet from the approach end of the runway and the pilot immediately applied brakes. He described the braking action as "ineffective." The airplane drifted off the right side of the runway and collided with a hangar. The left main fuel (tip) tank sheared off and the nose gear collapsed. The airplane spun around 120 degrees and struck a fuel truck. FAA postaccident inspection revealed no system anomalies in the airplane. Runway 21 is 3,800 feet in length and 50 feet wide. The pilot said the runway had a downhill slope. He also said that the braking action was poor due to "seal coating" of the runway. An FAA inspector described the runway surface as having the consistency of "putty." A "coal-tar sealer/rejuvinator" was applied to the runway by Brewercote in October of 2003. According to the specifications provided by the Utah Division of Aeronautics, the coal-tar sealant "is to seal the pavement from oxidation, and to rejuvenate the asphalt binder in place." It is composed of a minimum of 35 percent coal-tar pitch conforming to ASTM D-490, RT-12, Standard Specification for road Tar. On June 18, 2004, using highway vehicle test equipment, the Utah Division of Aeronautics conducted a "skid test" on runway 03/21. The test revealed skid values ranging from 2.4 to 10.9, with an average value of 6.3. These corresponded to MU-meter friction values which ranged from .035 to .160, with the average MU-meter friction value being .093. According to the Operations Friction Correlation Chart, this friction rating is "poor."