SU 5519 is the eastern wall of a channel intended for water drainage, a feature bounded on the western side by the parallel wall SU 5420. At its northern limit it turns east 90 degrees, creating a T-intersection with 5520 and 5518, apparently to drain water from areas east and west. The channel thus created cuts through the red tufo wall SU 5417 to the west, and is covered by the construction of concrete wall SU 5386 to the east. The feature therefore belongs to the later phase of concrete walls in this area.