Bigge Crane and Rigging Co.'s Seattle WA office loaded a 1,200-ton Caisson this month at the Swan Island Shipyard in Portland, Oregon. Caissons are large watertight retaining structures used in shipyards to keep water out of graving type dry docks.
The 1,200-ton Caisson standing 53-feet tall and 130-feet long was fabricated onsite by Oregon Iron Works. Bigge first moved the Caisson out of the building to an outfitting area and then transported it a quarter mile to the launch barge. To load the unit onto a heavy duty SPMT Scheuerle Transporter, Bigge engineers devised a support system that served as the Caisson's supporting structure and as its lift points holding the Caisson steady in an upright position. These lifting points allowed the 140-foot SMPT trailer to drive underneath and lift the Caisson for transport without side assistance.
To launch the Caisson into the water, Bigge placed it onto a barge that was lifted up to dock elevation by a floating dry dock. After Bigge removed its transporter, the barge and dry dock were submerged so the Caisson could float off. After further outfitting and commissioning, the Caisson was towed down the Columbia River, up the Washington coast and into Puget Sound.