Deer Isle-Sedgwick Bridge, Spanning Eggemoggin Reach between Sedgwick & Deer Isle at Route 15, Sedgwick, Hancock County, ME

Significance: The Deer Isle-Sedgwick Bridge, named for the two townships it connects, was the first bridge built between Deer Isle and the mainland, replacing an inadequate ferry crossing system and effectively opening the island to tourism opportunities. It is notable for the innovation of its designers and contractors in creating a durable, long-span, high-level structure across a navigable arm of the Atlantic at minimal cost. Unprecedented use of prefabricated and previously-used materials simplified construction and minimized costs, and much of the outdoor work was completed under poor weather conditions. The challenges facing David B. Steinman, his firm, and their contractors were numerous. The popularity of Eggemoggin Reach as a yachting area called for a 200' wide channel at midspan with a minimum 85' underclearance, placing the roadway at 98.7' above mean water level. At the same time, the depth required for foundations at this location called for minimizing the length of the approach spans. This height problem was solved by employing steep 6-1/2 percent approach grades and a fairly short 400' vertical curve at the center of the main span. In this manner, the needed height was attained and the approach viaducts were kept to a minimum length. The project was also complicated by its required early-summer completion date, meaning that much of the work had to be done during the winter and early spring months when weather conditions posed a significant challenge. Robinson and Steinman and their contractors solved this difficulty by prefabricating many of the components offsite and completing the bulk of the assembly quickly, working between high tides. Site-specific innovations in prefabrication and construction methods minimized outdoor work at the site and departed from conventional bridge-building practice. This careful consideration and planning resulted in a project completed on schedule and at low cost, despite the extreme conditions. The substructure, in particular, employed prefabrication at an unprecedented level. Instead of assembling the steel sheet-pile cofferdams and the metal forms for the main tower pedestals on site, Merritt-Chapman & Scott had them prefabricated at their yard on Staten Island and brought to Maine by barge. Their use of secondhand steel materials for the dams, along with the prefabrication and careful timing of the construction schedule, saved a great deal of money. The prefabricated dams were assembled for use on barges near the work site. After mud was removed from the bottom and the rock foundation carefully sounded, the dam bases were torch-cut to fit the profile of the irregular bedrock on which they were to be set. Finally, the dams were filled with concrete.
Survey number: HAER ME-66
Building/structure dates: 1937-1939 Initial Construction