Seawalls in Key Largo

State and federal limits

Replacement walls and riprap repairs may sit no more than 18 inches waterward of the old wet face, and new riprap no more than 10 ft waterward of mean high water, under SPGP VI. No seagrass survey was needed within the 18 inch line.[1][2]

Working in Keys water

All in-water work follows the state's manatee conditions: work stops if a manatee comes within 50 ft, vessels run at idle speed and no wake, and turbidity barriers must not trap or block manatees.[3]

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.

Height is the first question on any wall job here, because it decides whether a repair can stay at the current cap or turns into a raise.[4]

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.

The tide also sets how much of the wall can be worked on dry at low water, which changes crew time.[5]

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.[6]

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.[1][3]

Permits for seawalls 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.

Which permits does seawall work need?

In Miami-Dade, any work in, on, over or upon tidal waters needs a DERM Class I permit under Section 24-48 of the County Code, including inside cities. Minor repairs are exempt, cap and tieback work gets an expedited authorisation, and rebuilding a wall at the mean high water line or up to 18 inches waterward is a short-form permit approved by staff.

The city building department also issues a structural permit. A state exemption does not remove county and city permits: Florida Statute 403.813 says its exemptions do not relieve anyone from county and municipal requirements, so in Miami-Dade a DERM Class I permit still applies.[8][2]

How long does a seawall last?

Fort Lauderdale's seawall ordinance FAQ assumed a design life of about 50 years, and city engineers described a 30 to 50 year lifespan for a wall built today. Salt water, wave action from boat wakes and rising tides shorten that when cracks and failed joints are left open.[10]

Why heights matter now

Cities are raising the bar. Miami Beach requires new and substantially repaired seawalls to reach 5.7 ft NAVD, Coral Gables sets bulkheads at a minimum of 6 ft NGVD 1929, and Fort Lauderdale requires 5 ft NAVD. A repair that triggers these rules can turn into a raising job, so we check the local standard before we price.[9][12][13]

Frequently asked questions