Dry Tortugas National Park, FL
2005 (Phase I); Ongoing (Additional Phases)
Phase I: Grieves Worrall Wright O’Hatrick; Additional Phases: Lord Aeck Sargent
National Park Service
Fort Jefferson, which is located at the western-most tip of the Florida Keys, is the largest masonry fort in the Americas. Silman’s work on the fort, built as part of the seacoast defensive system known as the Third System, included temporary stabilization and permanent repairs of thick, coral concrete and brick masonry walls to prevent further masonry deterioration. The challenge was to design creative repair solutions within a limited economic framework for a massive structure suffering from extremely serious structural deficiencies.
Silman developed a comprehensive model of the case-mates along Front 3 from archival documents and targeted field measurement. This model was used to define the loads imposed on the deteriorated scarp wall and was critical to guiding the analysis of the structure and communicating the scope of repairs to the client.
The biggest cause of degradation to the masonry was the iron Totten shutters -hinged swinging doors installed on cannon openings- which had rusted and expanded since originally being embedded in the scarp wall. Silman replaced these with non-ferrous material and advocated implementing repairs as opposed to utilizing temporary shoring. The firm will be performing another piece of the Historic Structures Report for the fort’s civil war-era parade ground structures.