On September 26, 2000, at 1100 mountain daylight time, a Piper PA-28-235, N9281W, sustained substantial damage while taxiing from landing at Jefferson County Airport, Broomfield, Colorado, when it struck a tractor in a non-movement area. The certified flight instructor and sole occupant was not injured. Visual meteorological conditions prevailed for this personal flight operating under Title 14 CFR Part 91 and no flight plan was filed. The flight departed Boulder, Colorado, at 1030. According to the accident notification from Jefferson County Air Traffic Control Tower, the collision ruptured a wing tip fuel tank causing a fuel spill. According to the pilot, he was taxiing on the ramp and maneuvering between a Mooney and a tractor (which was parked on the grass beside the ramp). The pilot said his left wing struck the tractor rupturing the wing tip fuel tank. The pilot reported the collision to ground control and shut down the aircraft. Ground crew used an absorbent material to soak up the fuel and the aircraft was towed to parking. The tractor was not damaged, but did have fuel spilled on it. Documents supplied by The New Piper Aircraft Company provided information that on the PA-28-235, the fuel tanks consist of one aluminum tank located in the inboard leading edge section of each wing plus fiberglass tanks located in each wing tip. The main tanks have a capacity of 25 gallons each and the tip tanks each hold a maximum of 17 gallons. The attached diagrams, supplied by Piper Aircraft, provide information that the tip tanks are an integral part of the wing structure. According to Jefferson County Airport personnel, the non-movement construction area was advertised under a Notice to Airmen (NOTAM).