On June 16, 2004, about 1000 Alaska daylight time, a tundra tire-equipped Piper PA-18 airplane, N18ZF, sustained substantial damage when it encountered soft terrain and nosed over during the landing roll in a remote area, about 24 miles north-northwest of McGrath, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by the pilot. The commercial certificated pilot and the sole passenger were not injured. Visual meteorological conditions prevailed. The flight originated at the McGrath Airport about 0930. No flight plan was filed, nor was one required. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on June 16, the pilot reported that he was landing in an open area of tundra next to a creek. As the airplane touched down, the pilot said he realized that the tundra surface was soft and wet. During the landing roll, the main landing gear tires dug into the soft terrain, and the airplane nosed over. The pilot, who is a certificated aviation mechanic, reported that the airplane received damage to the left wing lift strut, the rudder, and the vertical stabilizer.