th-Woolwich Bridge_ ME Bath-Woolwich Bridge th-Woolwich Bridge_ ME

					                                   Bath-Woolwich Bridge, ME
                                                                                                                                         deep footing block with the top of the
                                                                                                                                         footing about three ft below low tide.
                                                                                                                                         This design is very efficient because it
                                                                                                                                         significantly reduces the depth at
                                                                                                                                         which the footing is constructed. How-
                                                                                                                                         ever, it does create the problem of how
                                                                                                                                         to construct an underwater footing
                                                                                                                                         suspended 28 ft off the river bottom.

                                                                                                                                         In order to address this problem and
                                                                                                                                         reduce the amount of work in the river,
                                                                                                                                         Ben C. Gerwick, Inc. proposed the fol-
                                                                                                                                         lowing construction sequence:

                                                                                                                                         • Pre-install the drilled shafts using a
                                   Mating of follower cofferdam to floating precast footing shell.                                         two stage template.
                                                                                                                                         • Construct a precast footing shell on
                                   Constructing bridge foundations under                                                                   shore and attach a temporary steel
                                                                                               Services Performed:
                                   water is an expensive operation and                                                                     follower cofferdam.
                                                                                               • Detailed Design
                                   usually represents 40-50% of the total                                                                • Launch the cofferdam and tow it to
                                   bridge cost. One way of reducing this                       • Constructability Studies                  the bridge site.
                                   cost is to perform as much of the                           • Precast Shells (Hulls)                  • Position the cofferdam over the
                                   foundation work as possible on shore                        • Tremie Concrete                           drilled shafts and fix it in position with
                                   by prefabrication and then floating (or                     • Casting Yards/Launch System               four spud piles.
                                   lifting) completed elements into posi-                      • Cofferdams and Caissons
                                                                                                                                         • Lower the cofferdam down over the
                                   tion. With this objective in mind, Ben                                                                  pre-installed drilled shafts with jacks
                                                                                               • Installation of Large-Diameter
                                   C. Gerwick, Inc. teamed with Flatiron                                                                   located on top of the spud piles.
                                   Structures Company of Longmont,                                                                       • Lock the footing to the drilled shafts
                                                                                               • Offsite Prefabrication
                                   Colorado to design a floating coffer-                                                                   by placing a four ft deep tremie seal.
                                                                                               • Positioning Control Systems
                                   dam system for the Bath-Woolwich                                                                      • Dewater the cofferdam and construct
                                   Bridge across the Kennebec River at                         • Construction Engineering                  the footing and pier shaft in the dry.
                                   Bath, Maine.                                                                                          • Flood and remove the follower
                                                                                                                                           cofferdam for reuse on the next pier.
                                                                                           The Maine DOT awarded the design-
                                                                                           construct contract for the 3,000 ft long      This construction sequence minimized
                                                                                           four-lane bridge to Flatiron and Figg         work in the river and allowed the drilled
                                                                                           Engineers in August of 1997, and              shaft installation to proceed concur-
                                                                                           shortly there after Ben C. Gerwick, Inc.      rently with the onshore fabrication and
                                                                                           was contacted by Flatiron to design a         launch of the cofferdams.
Ben C. Gerwick, Inc. 01-027e-02a

                                                                                           safe and economical cofferdam system
                                                                                           for the six main river piers. Figg’s de-
                                                                                                                                           Year of Completion: 2000
                                                                                           sign for the piers was based on using
                                                                                           eight ft diameter drilled shafts. A typical     Construction Cost: $35M
                                                                                           pier foundation is located in 45 ft of          Client: MAINE DOT,
                                                                                           water and contains four drilled shafts          Flatiron Structures Company LLC
                                                                                           supporting a 33 ft by 36 ft by 12 ft
                                   Float-in cofferdam.

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