The pilot was attempting a landing on the unimproved runway, and porpoised, with the airplane bouncing and veering to the right. The pilot reduced power to idle, and manipulated the controls to hold the nosewheel out of the runway ruts. The airplane then encountered a three-foot-deep ditch, which angled it towards a power pole. The pilot applied left rudder and brake, diverting the airplane slightly to the left and into the rear quarter of a metal building at the end of the runway. The pilot reported that the airplane and engine had no mechanical failures or malfunctions during the flight.
