Designed in 1998. The project comprised the design of a loop track off of the Union Pacific main line just west of Mountain Home, Idaho. The purpose of this loop is for the delivery of up to 100 unit trains (100 cars per train) per year of 100-ton grain cars. A loop track design was chosen to optimize the functionality of the track and add flexibility for future expansion while minimizing the length of track to be constructed which thereby reduced the cost of construction. In comparison to a straight siding track, a loop track does not require separate track for loaded and unloaded cars as the train continues around the loop as it unloads. This utilization of the same track for loads and unloads reduced the trackage required for a unit train by 5-6,000 ft. Therefore, this reduces the cost of construction significantly.
The Simplot loop track utilizes a short siding track offset from the UPRR main line to enter and exit the loop track. The siding track begins with two No. 14 turnouts from the UPRR main line then proceeds through two No. 10 turnouts to form a 7400' loop track. The track is designed for a maximum curvature of 7½ degrees and utilizes 133RE rail, CXT concrete ties and Pandrol FastClip fasteners. Provision was made for a future 2nd loop track on the inside of the existing loop and also for future spurs to the east and south. A gravel access road was placed around the loop to provide access to the track at all points.