5.5 gallons per bag of cement, maximum size of gravel was 1 1/2 inch, 
cement factor was 6 bags per cubic yard of concrete, and the 28-day 
compressive strength of the concrete was 3,500 psi. Each pontoon was 
fabricated in two pours; the first included all but the deck and the 
second the deck only. 
In 1963 the second floating bridge on Lake Washington was opened to 
automotive traffic. It is 3 nautical miles from the first floating 
bridge. The biggest of the 35 prestressed concrete pontoons in the 
second bridge is 360 feet long, 60 feet wide, and 15 feet high. The 
weights (in air) of the pontoons range from 4,700 to 6,700 tons. 
