SU 5489 is a patch of tufo floor preparation abutting tufo pavers 5505 (=0321, 5485) and threshold 5368. SU 5318, East-West wall, was built on top of this floor prep and thus this SU is equal to SU 5357 (the continuation of this tufo floor prepe ti the North of 5318); the earlier concrete wall SU 5367 seems to have been built against this surface (contra term).