Not excavated in 2017. May be a (natural?) layer that pre-dates the construction of the ashlar phase (walls, drain, & slab floor). Certainly cut by the construction cut for the drain 7174, seemingly runs under slab floor 7067. In section - visible in cut 7190 - it appears that this layer is no more than 6-8 inches thick, and sits - at least in the east - directly on the bedrock.
Layer of compact dark brown silt with tufo inclusions at S of Room 1
Cut in northwest corner of Room H1; Circular fill in northwest corner of room H1; Fill of negative feature running west to east towards SE corner of Room 1; Silty layer between 7173 and 7174 on the eastern side; Cut into the center of SU 7076 towards the southern side of room 1; Ashy deposit adjacent to 7175 to the northwest in Room H1; Tufo drain structure in room H1; Layer of compact dark brown silt with tufo inclusions at S of Room 1
View from east
View from north