SU 8401 is a late phase concrete wall built in order to bisect Room I-22 for the creation of a signinum basin for industrial or productive purposes. This basin is clearly to be associated with that in Room I-20, to which it would have drained. The construction technique is rather different from the earlier petit appareil walls, and perhaps more similar to nearby wall plug SU 8346, which may have been built in the same phase of reorganization.

Serves as a partition in Room I-22 between the basin and an area of unknown usage (which was not excavated in 2018). Full depth and southern limit to be documented in future seasons. Appears to be a later construction in phase with the basin and the opus signinum lining of the basin.