The pilot reported that on final approach to the runway, an airplane appeared to be taking the active runway, so he radioed the airplane and confirmed his position. The airplane advised that he was not going to takeoff. The pilot stated that he decided to land longer than planned; during the flare/touchdown the airplane ballooned. The pilot stated that he added some power and as he passed the buildings the airplane encountered a right crosswind, followed by the right wheel touching the ground. The airplane then veered off the right side and headed toward the excavation for the new runway. He stated that he attempted to bring the airplane back onto the runway, but the right wheel slipped off the edge and the airplane slid down the ravine. He reported that there was no mechanical malfunction, and the accident could have been prevented if there was adequate shoulder along this runway as the excavation comes within 8 feet of the runway.