Before the newly constructed pontoons are assembled, crews are refurbishing three pontoons from the west-half replacement to be used in the new east-half. At Terminal 91, the old roadway and superstructure has been removed from the pontoons and new superstructure and roadway is being built to match the new east-half design. View pictures of refurbishing in the Photo Gallery.
At Todd Pacific Shipyards in Seattle, Kiewit-General (K-G) crews are connecting the individual pontoons into large sections, building the elevated roadway sections on top of the pontoons, installing all electrical and mechanical parts and testing the draw span retractable assembly units.
Pontoon assembly is started in fall 2007 after the first two cycles of pontoons werre constructed and floated to Seattle. Assembling every component correctly is essential to completing the project on time and to keeping the Hood Canal site work (and bridge closure) to a minimum.
In December 2007, pontoons PA, PB, Q, NA and NB were assembled together to form a “U” shape area around the location where the draw span retractable assembly units pull back. Pontoons YD, YE and YF were then lowered underwater, positioned underneath the other pontoons and connected.
When the third cycle of pontoon construction is completed, the two pontoons that make up the retracting section of the draw span will be connected together and assembled with the other eight draw span pontoons.
After the last pontoon construction cycle, the final roadway section made up of pontoons U, V, W and X will be connected together.
Once the three existing pontoons (R, S, and T) are moved to Seattle and all the 14 new pontoons are assembled, work can proceed on outfitting, or adding the electrical and mechanical components to the pontoons, such as wiring, hydraulic piping and junction boxes.
The elevated roadway sections on top of the pontoons are constructed from the ground up. First, two large round concrete columns are constructed. Second, a concrete crossbeam is placed on top of the two columns. Then, four concrete girders (large beams) are placed on top of two crossbeams, spanning the distance between them. These girders provide support for the roadway. With all four girders in place, the concrete deck (or roadway) is poured. When the deck has cured, concrete traffic barriers and steel railings are added to the edges of the deck.
This process is repeated over and over until the entire deck for all the pontoons is completed. When outfitting work comes to a close by December 2008, work will then turn toward installing all the electrical and mechanical systems and testing the draw spans retractable assembly units.
This animation demonstrates the outfitting process described above.
Outfitting (Windows Media / 0:42 sec)
Thousands of feet of electrical conduit, electrical wiring, and hydraulic piping run through the pontoons, into the draw span retractable assembly units and into the maintenance buildings.
Both the mechanical and electrical systems on the draw span will be tested extensively before it is floated to the bridge site for installation. K-G crews are focusing on doing as many tasks as possible before floating the pontoons to Hood Canal in order to keep the bridge closure in May-June 2009 as short as possible.