As the depth is at what likely appears to be ground level, SU 8186 was possibly used as step in using the basin 8184. This feature was built later than 8156 and lined up against it, and likely built around the time 8184 was built. It is additionally possible that this corresponds to 8185 as the two are similar in alignment. Both are clearly associated with the mixing of mortar in basin 8184.
Mortar features and fill of basin
Mortar feature north of 8152; Wall east of SU 8156 Ashlar block east of wall su 8038; Mortar and rubble feature north of 8157; Mortar and rubble feature north of 8156