On July 22, 1996, approximately 0130 Pacific daylight time, a Cessna T210N, N6439N, registered to and operated by Noland-Decoto Flying Service, Inc., and being flown by a commercial pilot, was substantially damaged during a forced landing following a total loss of power while descending for landing at the Sunnyside airport, Sunnyside, Washington. The pilot received minor injuries. Visual dark night meteorological conditions existed at the time, and a VFR flight plan had been filed. The flight, which was a return (positioning) flight following a 14CFR135 passenger drop-off at Portland, was to have been operated under 14CFR91, and departed the Portland International Airport at 0038. The pilot reported that while descending through 4,000 feet, and with the left fuel tank selected, the engine began to surge and lose power. The pilot turned on the electric fuel boost pump and reported regaining power for 1.5 to 2 minutes before power was lost for a second time. He then reported checking the mixture rich, magnetos on and selecting the right fuel tank. A total power loss followed and the pilot executed a gear up, flaps down, forced landing into a field, colliding with low, brushy trees during the ground slide. The fueler at the Yakima airport where the aircraft originally began its trip, was interviewed by an FAA inspector, and reported that on Saturday, July 20th, he refueled the aircraft by adding 15 gallons of fuel to the left tank. This brought the fuel level up to the "tab" (the bottom edge of the fuel filler neck). This would have amounted to a fuel load of 32 gallons in the left tank. The fueler reported that he did not add any fuel to the right tank and that the aircraft was not flown after it was fueled until it departed for Portland late on July 21st. The pilot was telephonically interviewed by the investigator in charge and reported that he departed Yakima, Washington, approximately 2310 en route to Portland with approximately 64 gallons of fuel (32 gallons per side) and arrived at Portland at midnight. The pilot reported that the aircraft was not fueled during its ground stay at Portland. The air traffic control tower reported that the aircraft departed Portland at 0038. The pilot reported that he took off from Portland on the right tank but switched to the left tank upon reaching his cruise altitude, remaining on that tank until the engine surge on descent. On-site examination by law enforcement and fire department personnel, as well as an FAA inspector, revealed no fuel in either fuel tank nor any odor of aviation fuel at the accident site. Additionally, the right tank fuel cap was observed to be missing and there was no connecting chain attached to the retaining tab within the fuel filler orifice. Also, there were no paint abrasions or scratch marks noted on top of the wing in the vicinity of the fuel filler cap nor was there any evidence of fuel staining on the upper surface of the wing. The fuel selector was observed in the left tank position at the accident site.