Piers 3 and 4 support the lifting span in addition to the approach spans. They are constructed of a pair of circular reinforced concrete caissons founded in the river bed. The caissons are linked by a concrete structure, positioned at approximately low tide level, which accommodates the machinery room and bearings for the lifting span. Two concrete towers extend above road level; both the towers and their piers are hollow as to allow them to support the lifting cables and counterweights. The towers are braced near the top by two concrete beams.