National Park Service proposes 10.5-foot seawall raise at Castillo de San Marcos; P&Z recommends approval

The Planning and Zoning Board on Aug. 5 recommended approval of a National Park Service (NPS) request to repair and raise portions of the Castillo de San Marcos seawall to 10.5 feet to address structural deterioration and provide flood protection for the fort and nearby downtown.

The project team said the wall is actually five distinct historic segments built at different times and in different materials and that targeted repairs, a steel-sheet-pile support system and a granite/coquina facing would be used to preserve historic fabric while improving resiliency. Jackie Brower, coastal engineer supporting the project, said, “The wall was built in different sections over several hundred years ago and it is failing in some areas, particularly where the coquina has been eroded.”

Board members and members of the public focused questions on drainage and the potential for the raised wall to shift stormwater onto adjacent neighborhoods. The project team and NPS representatives said the seawall work is coordinated with an NPS drainage project completed earlier this year that increased on-site drainage capacity; the team said modeling shows the modest grading associated with the wall raise (shown as a narrow band in project plans) is contained within that drainage project and would not increase flooding off-site. NPS civil staff and a consultant confirmed that the drainage work was designed to allow for future pump installation if future conditions required additional capacity.

The presenters described construction staging concentrated on park property (the north lawn) and said most construction would be land‑based with temporary cofferdams at the waterline for limited marine-side access. Engineers said sheet piles would be vibrated into place (not impact-driven) and that vibration monitoring points would be used near the fort to document effects. Board member questions also covered expected construction duration (team estimated 8–18 months depending on contractor sequencing) and permit status; the presenters said the project is pending the State Historic Preservation Office memorandum and that federal permits from the U.S. Army Corps and FDEP were expected once that document is finalized.

After discussion the board voted to recommend approval of the conservation-overlay development application and related easements and permits. The board made clear its approval was tied to the current project design, the coordination with the NPS drainage work, and the mitigation measures discussed for vibration monitoring and staging.

The NPS team said construction bidding is expected later this year, with construction likely starting in early next year depending on permitting and contractor selection.