Seawall caps in Key Largo

When a new cap is the right fix

A cap replacement suits a wall whose panels are sound but whose cap is cracked, spalled or too low.

• Cracked or spalled cap with rust staining
• Wall a little below the city's new height
• Panels separating at the top

Where a seawall is allowed at all

Monroe County allows vertical seawalls only to stabilise severely eroding shorelines on man-made canals, channels or basins, and never on open water. Lawfully existing walls may be repaired or replaced on the same footprint, the yard behind must sit at least 6 in below the top of the wall, and riprap goes at the toe wherever feasible.

A new cap is often the cheapest way to reach that height, if the old wall can carry the extra weight.[1]

Ocean side tide at Rock Harbor

NOAA's Rock Harbor station on the Atlantic side of Key Largo records a 2.09 ft mean range and a 2.37 ft great diurnal range, with mean higher high water about 0.25 ft above NAVD 88 (1983 to 2001 epoch). There is no NOAA datum station on the bay side near Key Largo, so for bay side lots we measure the water on site.

Caps are formed and poured above the water, but the tide decides how high the new cap must sit to give real freeboard.[2]

What makes Key Largo different

The special exception application asks owners to describe the submerged lands the dock crosses, such as sand, seagrass or coral, and the minimum extra length needed to reach adequate water depth. The site plan must be prepared by a Florida registered architect, engineer or landscape architect and show the mean high water line and shoreline setbacks.[3]

Sanctuary, seagrass and manatees

Projects inside the Florida Keys National Marine Sanctuary needed prior Sanctuary approval under SPGP VI. The same permit let boat lifts and minor structures in Monroe County go into existing boat slips without a seagrass survey. All in-water work follows the state manatee conditions.[4][5]

Permits in Key Largo

• Monroe County Planning and Environmental Resources Department: Dock length special exceptions under County Code section 118-12(m)(15).
• Florida Keys National Marine Sanctuary: The Sanctuary starts at mean high water, so Key Largo canal and bay work is inside it; SPGP VI required its prior approval.
• Florida DEP or South Florida Water Management District: State permit or exemption, which Monroe County needs to see before it issues a Notice to Proceed for docks, seawalls and ramps.
• US Army Corps of Engineers, Jacksonville District: Federal permit, also required before the County's Notice to Proceed.

Can the wall take a new cap?

Not always. Whether a cap can be added depends on whether the existing wall can bear the weight, which a marine or structural engineer must assess. A wall that cannot take it needs replacing instead.[7]

Permits for cap work

Miami-Dade DERM gives cap repair or replacement an expedited administrative authorisation when the building department has approved the structural plans. At the state level, seawall caps, batter piles and king piles used only to stabilise and repair seawalls fall under an exemption in rule 62-330.051(12)(d).[8][4]

Caps and city height rules

In Miami Beach a wall may be built to 4 ft NAVD if it is designed to support a future 5.7 ft NAVD, so the cap and footing need to be designed for that later raise. In Boca Raton the city must approve a location survey before the cap is poured, and a final engineer report confirms the cap elevation.[9][10]

Frequently asked questions