On July 31, 2005, about 1154 Alaska daylight time, a Piper PA-18-150 airplane, N120CS, sustained substantial damage when the taxiway edge collapsed during taxi for takeoff on a private gravel airstrip, about 3 miles east of Wasilla, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) personal local flight under Title 14, CFR Part 91, when the accident occurred. The solo private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on August 2, the pilot said he was taxiing for takeoff, and taxied too close to the edge of the taxi area, and the edge of the taxiway gave way. He said he originally thought the left main wheel was in a hole or rut, and when he applied power, the wheel encountered a ditch, and the left main landing gear collapsed. The airplane received substantial damage to the left wing. The pilot reported that there were no preaccident mechanical problems with the airplane.