Most likely a layer of post-abandonment accumulation inside of a robbery/spoliation cut (7151).
Deposits and Fills in Room H-5
Concrete wall running E-W at S limit of Room 5; Concrete wall running N-S at W limit of Room 5; Concrete wall running E-W at SW corner of Room 4; Stone threshold between Rooms H4 and H5; Concrete wall running E-W at SE corner of Room 4; Stone threshold between Rooms H4 and H5; Long ashlar wall running N-S at eastern limit of rooms 4, 5, and 6; Four large square tufo blocks along E wall of Room 5; Line of small stones along W face of blocks 7198; Cut into SU 7150 E of wall 7117; Fill of cut 7155; Cut into SU 7150 in center of Room 5; Fill of cut 7151
View from north