On September 16, 2009 the State of Maine Department of Transportation awarded Reed & Reed a $9.6 million contract to rehabilitate the underwater portions of the two main towers on the Deer Isle – Sedgwick Bridge. The 2048 foot suspension bridge between Deer Isle and Sedgwick was constructed in 1939 and is a sister bridge to the Tacoma Narrows Bridge in the State of Washington. The work consists of constructing two 40 ft. x 72 ft. cofferdams around the existing piers, placing a tremie concrete seal, removing half inch steel jackets that were used to form two 14 foot diameter concrete shafts at each pier, removing deteriorated concrete, installing new steel jackets and placing new concrete. There are several challenging aspects to the project. We have already witnessed 4 to 5 foot high waves on several occasions at Eggemoggin Reach. We can not use the existing bridge for access, therefore, all the materials have to be loaded onto a barge and shuttled 500 to 1500 feet to the piers. The cofferdams require 85 foot long sheets and we only have 70 of clearance under the existing superstructure, which requires an innovative plan to install the cofferdam. Because of the extreme water depth, multiple external and internal frames are required to resist the concrete pressure during seal placement and then to resist the water pressure when the cofferdam is dewatered. The frames have been prefabricated in the Woolwich Fabrication Shop for assembly on the job. Access from a 200-ft long work trestle allows us to deal with the 10-ft tides at the site. We will build one cofferdam and complete the concrete repair work before moving to the second pier where we will reuse the cofferdam materials. Work will be complete by the end of 2010.
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