The valves are used to flood or empty the tanks built into the wing walls to lower or raise HMB-1. The system is designed more like a submarine than a normal floating drydock. For example, like a submarine it floods through open ports at the bottom of the tanks, and vents through the top. A modern floating drydock normally is closed on the bottom and uses pumps to remove ballast water.
HMB-1 was unmanned during Azorian with the air compressors and control equipment residing on a separate barge. Submarine water tight doors and a lockout chamber could be used to enter the wing walls in an emergency, but were not normally used. The system was significantly modified for the Sea Shadow project. Generators and compressors were added to the tops of the wing walls. The pressurized control rooms on each wing wall were manned. A lot of the tanks on HMB-1 were not needed or used during the Sea Shadow period. The system was run, "Kentucky Windage", looking at clinometers instead of any fancy system.
HMB-1 as configured during project Azorian
HMB-1 with the control barge Ore Quest visable on the left.
HMB-1 fully submerged with the stability pontoons vertical during project Azorian.