The SU is the floor of Room I-13. As of the end of the 2017 season, it is unclear whether the SU is the original floor in Room I-13 or part of a later phase of floor construction. At some point after the floor was constructed, it was truncated by later activity associated changing uses of Room I-13. A series of six postholes were cut in a rough line, perhaps to create a platform, roof, or other wooden structure. The floor near the doorway of Room I-13 has been robbed out, apparently with picks, based on pick marks still visible on the surface of the SU nearby. It is not clear at present whether the circular cuts in the floor correspond with the original use of the room or a later use (probably the latter).