Very partially covered by signinum on its eastern side, at the bottom, which forms a basin-like structure (associated with walls 8396, 8397, and 8398) to be excavated in 2019. On its western side it is partially finished with opus signinum 8394, for the creation of a basin in Room I-22. The wall is closely associated with basins in Rooms I-22 and I-20 as indicated by the void through wall 8340 at the base of the basin in Room I-22.

SU 8340 served as the wall dividing apsidal room I-20 from I-22 to the west. Its construction appears to date to the original phase of construction of the building; however, it was modified in a later phase, with the construction of abutting basins on both sides. The hole connecting these basins was undoubtedly made at the same time; its irregular nature may be due to the robbing out of a pipe that once crossed through the wall. The precise function (and phasing) of the recesses set into both sides toward the south remains uncertain; they may have been used for revetment, some kind of shelving, or for supports of perishable material for a floor or surface.