Layer of opus signinum constructed as a lining of cut 5833 for the construction of a sewer channel running north. This opus signinum is contemporary with opus signinum walls 5828, 5829, 5830, all of which line the cut 5833. Along with the tiles in the bottom of the cut (SU 5832) these features form a sealed channel running northward along the western side of room 21 before turning eastward along the northern wall.