Upon their arrival at the bridge site, open wells lined with corrugated galvanized iron ran vertically through the compartmented walls of the boxes. After the caissons were sunk, steel pipe piles up to 270 feet long were driven to bed rock through these wells in the larger boxes. After being driven, the pipe piles were cleaned out, filled with concrete and then encased by concrete within the walls to pin the boxes permanently in place. As construction of the superstructure added dead weight, water was pumped from the boxes to effect the desired buoyancy. The hollow interiors are divided into reinforced compartments, with an intermediate slab running the length of each box.
Weep holes connect the compartments.
The two largest boxes are divided into 24 compartments, the two medium-sized boxes into 12 compartments, and the four smallest ones into eight. Any water present in the caissons from condensation, possible water entering through entrances to the interior of the caissons, or from any other source, are controlled by two pumps in each caisson. These pumps are installed in a sump at the low point in the caisson, into which the entire box drains. A control system on these pumps notifies administrative personnel that the pump is working, and in which caisson. Trap doors and fixed ladders permit access to all parts of the caisson level.