On December 14, 2012, at 0918 central standard time, a Swearingen SA227-AC, N3108B, operated by Encore Air Cargo, was involved in a runway incursion with a snowplow at the Sloulin International Airport (ISN), Williston, North Dakota. The pilot was not injured and the airplane was not damaged. At the time of the incident, the airplane was being repositioned under 14 Code of Federal Regulations Part 91 on an instrument flight rules flight plan. Instrument meteorological conditions prevailed. The flight was originating at the time of the incident with an intended destination of the Joe Foss Airport (FSD), Sioux Falls, South Dakota. The pilot reported he made several radio calls announcing his intention to depart on runway 29. He did not hear any radio calls from other aircraft or vehicles. He initiated the takeoff and at the end of the takeoff roll he heard a "garbled" transmission stating something about runway 11/29. He stated that as he lifted off, he saw a snowplow on the runway heading in the opposite direction as him. He continued the takeoff and flew over the snowplow. The snowplow driver reported that he did not hear any radio transmissions from the airplane until after it was airborne when the pilot reported that he was airborne and leaving the area. The driver stated he had been plowing in the area for about 30 minutes and had made radio calls announcing his position every 2 -3 minutes. ISN is a non-towered airport which is fully certificated under CFR Part 139. Snow removal personnel are employees of the airport. According to the airport manager, airport vehicle drivers receive initial training upon being hired and annual training thereafter. This training addresses airport communications operations around aircraft. The airport manager also stated they were in the process of upgrading the radios in all of the airport vehicles. The snowplow involved in this incident was a new vehicle with an upgraded radio. The radio in the snowplow functioned normally when checked after this incident. Local visibility and cloud conditions recorded about 13 minutes prior to the incident was ¾ mile with mist and 100 foot overcast, respectively. Another pilot who landed about 30 minutes after the incident reported seeing a "semi truck size snow broom" sitting on taxiway A on the west side of runway 2/20. He cleared the runway and as he was taxiing to the ramp, the snowplow crossed runway 2/20 and was also on the ramp. He did not hear the snowplow driver make any radio calls. The Federal Aviation Administration FAA Guide to Ground Vehicle Operations, states: "Always yield the right-of-way to moving aircraft." The guide also states, "Before you cross a runway, ensure that no potentially conflicting aircraft are taxiing, landing or taking off."