The Y arm cavity bottom was lightly vacuumed, using the same procedure that we typically use on BSC domes (HEPA vac with custom stainless steel brush attached). Mark L. was in the tube and Chris was on the outside. Vacuuming started at BSC8 and proceeded toward GV5. No significant issues were encountered and final inspection showed that the large debris (relative term) that had littered the bottom of the tube was gone. As anticipated, the very fine (mostly metal?) particulate "rain" from the top of the tube was not significantly improved by vacuuming.

Since the Apollo crew was in the neighborhood, we also installed the BSC flooring (without hardware at this point) and a 60" dust barrier to facilitate the upcoming Arm Cavity Baffle install.