On August 1, 2004, approximately 1430 Pacific daylight time, a Cessna 150C, N7815Z, lost altitude and struck trees during the initial takeoff climb from the Lost River Resort Airport, Mazama, Washington. The airplane sustained substantial damage, the private pilot received serious injuries, and the passenger received minor injuries. The airplane was being operated by the pilot under the provisions of Title 14, CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was originating at the time of the accident with an intended destination of Arlington Municipal Airport, Arlington, Washington. According to a report prepared by a deputy with the Okanogan County Sheriff's Office, who responded to the accident site, the pilot told the deputy that he was taking off in the airplane on runway 29 and "could not get lift and clear the trees at the end of the runway." The deputy reported that he did not see any indication the airplane hit the trees located at the end of the runway, but actually cleared those trees, then descended, contacted the ground and slid about 40 feet into another group of trees. The airplane came to rest about 150 yards from the departure end of the runway. The deputy reported that the temperature was 92 degrees Fahrenheit (F), the humidity was 23%, and the wind was from the north at about 6 mph. In a telephone interview conducted by the NTSB investigator-in-charge on August 3, 2004, the pilot stated that he noted no problems with the airplane during the preflight inspection and the engine runup. After liftoff, the airplane climbed to treetop level, at which point a gust of wind pushed the airplane left towards the trees bordering the runway. The pilot had to bank the airplane to avoid the trees, and the airplane stopped climbing. After "barely clearing" the trees at the end of the runway, the pilot elected to put the airplane back on the ground as he was concerned the airplane might not clear trees located further ahead. He selected a streambed as an emergency landing site. During the emergency landing, the airplane contacted trees along the edge of the streambed. The pilot reported that the temperature was 88 degrees F and the winds were from 300 degrees at 3 knots. The pilot did not recall the current altimeter setting. At 1453, the nearest weather reporting station, located at Omak, Washington approximately 41 nautical miles east of the accident site, reported an altimeter setting of 29.74 inches. Using the airport elevation of 2,415 feet, a temperature of 88 degrees F, and an altimeter setting of 29.74 inches, the density altitude was calculated as 5,048 feet.