On August 28, 2006, at 1635 Pacific daylight time, a Glaser Dirks DG 300 glider, N302N, overshot the runway at Truckee-Tahoe Airport, Truckee, California. The pilot landed the glider in a nearby field and the empennage fractured from the structure. The private pilot (foreign-based) was operating the glider, which was registered to a private individual, under the provisions of 14 Code of Federal Regulations Part 91. The pilot was not injured; however, the glider sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot departed from Truckee-Tahoe Airport at 1300, and was landing when the accident occurred. According to the pilot, he was aloft in the glider for 4 hours at altitudes in excess of 10,000 feet mean sea level. During the flight he began to experience symptoms of hypoxia. He attempted to land at Truckee but overshot the runway and landed in a field beyond the runway. The pilot suspected that the cannula-type oxygen system in the glider may have not been supplying adequate oxygen because he was breathing through his mouth. The owner of the glider reported that following the accident, the oxygen and flow meter system functioned normally.