On July 4, 1998, at 0910 mountain daylight time, a Cessna T-210K, N8132G, was substantially damaged during landing overrun at Del Norte Municipal Airport, Del Norte, Colorado. The commercial pilot and her passenger were not injured. The airplane was owned by Western Eagles and operated by the pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the personal cross-country flight which originated at Camp Verde, Arizona, approximately 2 hours 10 minutes before the accident. No flight plan had been filed. According to the pilot, she circled the field to "lose altitude and evaluate the weather at the field." She stated that "indicators on the field showed the wind to [be] calm," and she "flew a standard left traffic pattern for runway 8 (3,775 ft. X 49 ft., asphalt)." The pilot stated that she "flew the normal indicated airspeed, however, at the high altitude (approximately 8,000 feet), the ground speed was higher." She further stated that the "last 200 to 300 feet of runway 8 sloped markedly downhill." The airplane overran the runway, crossed a gravel road, and impacted a ditch. The airplane's engine mount keel beam and engine fire wall were subsequently bent. The Investigator-In-Charge (IIC) computed the density altitude to be 10,032 feet at the time of the accident. The IIC referred to the owner's manual for the airplane and determined that the airplane was capable of stopping in a distance of approximately 980 feet (provided that there were no obstacles at the end of the runway.) The owner's manual for the airplane does not provide any landing data or guidance for landing down slope. Witnesses reported to the IIC that there are no obstructions to the approach end of runway 08 and that the accident airplane was observed to touch down "half way down the runway" for its full stop landing.