Who permits a seawall in the Middle Keys?
Start with your address, not your mile marker. Four governments issue seawall permits in the Middle Keys, and the city lines do not follow the islands neatly.
| Where your wall is | Who permits it | Call first | Local guide |
|---|---|---|---|
Marathon: Vaca Key, Boot Key, Knight Key, Stirrup Key | City of Marathon Building Department | (305) 289-5052 | |
East Marathon: Fat Deer, Crawl, Long Point and Grassy Keys | City of Marathon Building Department | (305) 289-5052 | |
Key Colony Beach | City of Key Colony Beach Building Department | (305) 289-1212 ext. 3 | |
Duck Key | Monroe County Building Department, Marathon office | (305) 289-2501 | |
Conch Key and Walker's Island | Monroe County Building Department, Marathon office | (305) 289-2501 | |
Layton, on Long Key | City of Layton, with contracted building code administration | City Hall, (305) 664-4667 | |
Long Key outside Layton | Monroe County Building Department, Marathon office | (305) 289-2501 |
Sources: Marathon Charter Sec. 10 City of Marathon Building Key Colony Beach Building Department Monroe County Marathon office City of Layton contact page City of Layton staff page
- Marathon's charter runs from the east end of the Seven Mile Bridge, about MM 47, to the west end of the Toms Harbor bridge, about MM 60. It excludes Key Colony Beach by name. Marathon Charter Sec. 10
- Monroe County's Marathon office at 2798 Overseas Highway serves unincorporated parcels. A City of Marathon address goes to City Hall at 9805 Overseas Highway instead. City of Marathon Building Monroe County Marathon office
- Duck Key, at about MM 61, sits just outside Marathon, so the county permits it. City of Marathon history page 2020 Census Gazetteer
Marathon limits new seawalls; Key Colony Beach requires them
The policy flips when you cross into Key Colony Beach. Marathon and Monroe County treat a vertical wall as a last resort, while Key Colony Beach treats it as the default.
| Question | City of Marathon | Key Colony Beach | Monroe County (Duck, Conch, Long Key) |
|---|---|---|---|
New vertical wall on open water? | Not permitted (Marathon code 106.36) | Seawalls are required wherever state or federal agencies allow them (Sec. 5-25) | Not permitted (county code 118-12(k)(3)) |
New wall on a canal? | Only where riprap or a sloping revetment will not suffice, as the City Biologist decides | Required, built along the full frontage at one time, never sloping (Secs. 5-53, 5-54) | Only on manmade canals, channels or basins to stop severe erosion, when vegetation or riprap will not work |
Replacing an existing wall? | Allowed; open-water repairs keep the existing footprint (Marathon code 108.20) | Allowed; walls nonconforming since 1971 face a 50% cost test (Sec. 5-65) | Allowed, keeping the existing footprint as far as practicable (county code 118-12(k)(4)) |
Cap and yard | Cap up to 2 ft wide; a swale, berm or curb of at least 6 inches behind the wall | Cap 5 to 10 ft wide, 5.5 ft above an old mean-sea-level datum or matching the higher neighbor (Secs. 5-51, 5-52) | Grade behind the wall at least 6 inches below its top |
Riprap | Landward of mangroves, no steeper than 2:1, no more than 8 ft out | Sloping seawalls are prohibited | Placed at the toe of solid seawalls where feasible, landward of mangroves |
Sources: Marathon code 106.36 Marathon code 106.36 Marathon code 106.36 Marathon code 106.36 Marathon code 108.20 KCB Code Sec. 5-25 KCB Code Secs. 5-52 to 5-55 KCB Code Sec. 5-51 KCB Code Sec. 5-65 county code 118-12(k)(3) county code 118-12(k)(4) county code 118-12(k)
Layton leans away from walls too. Its comprehensive plan tells the city's land rules to require riprap, vegetation or cantilevered platforms "instead of vertical bulkheads." Layton Comprehensive Plan Policy 5.d
Of the four cities this site covers, only Key Colony Beach writes a seawall height into its code. Its "mean sea level" is an old Coast and Geodetic datum, so have a surveyor convert it to NAVD88 before anyone quotes a cap elevation. KCB Code Sec. 5-51 See seawall height requirements.
Middle Keys storm surge record: Georges, Wilma and Irma
The Vaca Key tide gauge in Marathon holds the region's measured record. Hurricane Wilma pushed it to about 5.8 feet above mean higher high water (MHHW, the average daily high tide) on Oct. 24, 2005. NOAA Vaca Key datums
| Storm | What was recorded |
|---|---|
Georges, September 1998 | 4 to 5 ft of surge at Vaca Key and Grassy Key; a 96-knot gust at the county emergency center in Marathon; an 84-knot gust at Duck Key |
Wilma, October 2005 | Gauge record of about 5.8 ft above the average high tide at Vaca Key; storm tides of 5 to 8 ft above mean sea level in Marathon; a visual estimate near 9 ft in the Marathon area |
Irma, September 2017 | 4 to 6 ft of water above ground across the Middle Keys; a 3.7-ft high-water mark in Marathon; a Vaca Key gauge peak of 2.6 ft above the average high tide |
Helene and Milton, 2024 | Vaca Key gauge peaks of about 1.4 and 2.0 ft above the average high tide |
Sources: Hurricane Center Georges report Hurricane Center Georges report Hurricane Center Georges table NWS Key West Wilma summary Hurricane Center Wilma report Hurricane Center Irma report Hurricane Center Helene report Hurricane Center Milton report
Wind can matter as much as the tide. From 1996 to 2018 the largest positive surge at Vaca Key reached 75.2 inches, about double the 37.0-inch peak at Key West. Monroe County king tide and wind setup memo
Keep datums straight before you compare any of this with a cap elevation. At Vaca Key, MHHW sits about 4 inches below NAVD88, and the Hurricane Center's Irma ranges are measured above ground, not above a datum. NOAA Vaca Key datums
- Middle Keys re-entry after an evacuation uses Zone 2 aqua stickers, which cover the Long Key Bridge to the Seven Mile Bridge. Tax Collector offices issue them, and out-of-county owners qualify with a property tax bill. Monroe County re-entry stickers
- For what to do after the water drops, see the storm damage guide.
Bigger tides on the Atlantic side of the Middle Keys
The daily range at the Vaca Key gauge, on the Florida Bay side, is about 1 foot, roughly half of Key West's. NOAA Vaca Key datums Ocean-side canals see more.
The county puts the highest astronomical tide at 22.3 inches above mean sea level at the old Key Colony Beach gauge, against 13.8 inches at Vaca Key. Monroe County king tide memo
| Alert | Water level above the average high tide |
|---|---|
Coastal Flood Statement | 1.1 ft |
Coastal Flood Advisory | 1.6 ft |
Coastal Flood Warning | 2.1 ft |
Source: NWS Key West flood thresholds
- On Oct. 28, 2026, Key Colony Beach relayed Coastal Flood Warnings for the whole Keys, with docks expected to overtop as north-northeast winds met a full-moon perigee tide. City of Key Colony Beach notice
- Monroe County expects king tides from September through December and asks for flood photos at greenkeys@monroecounty-fl.gov. Monroe County king tides page
- Sea level at Vaca Key has risen about 1.7 inches per decade since 1971. NOAA sea level trend, station 8723970
Middle Keys seawall permit fees compared
Fees follow the permitting government, so the same wall costs a different amount to permit on each side of a city line.
| Permitting office | Seawall fee | Extras to expect |
|---|---|---|
City of Marathon | $17.50 per $1,000 of contract price; $93.50 minimum | $4 education fee and state surcharges; for 30 days after a hurricane only the minimum is due at issue |
City of Key Colony Beach | $100 up to $2,500, then $35 per $1,000 or part | 2.5% surcharge; triple fees plus $500 if work starts first; a $50,000 bond before barge equipment enters the city |
Monroe County (Duck Key, Conch Key, Long Key outside Layton) | Bands per $1,000 of value; $5,000 to $99,999 at up to $62.18 across building, planning and environmental | $976 Notice to Proceed fee when the permit waits on state or federal approval |
City of Layton | No fee schedule posted | Ask City Hall for the fee in writing |
Sources: Marathon Res. 2025-73 Marathon Res. 2025-73 KCB Res. 2026-01 KCB Res. 2026-01 KCB Code Sec. 5-61 Monroe County Res. 277-2025 Monroe County Res. 277-2025 Layton FY 2024/25 permit report
On an $80,000 contract, Marathon's base fee is $1,400. Key Colony Beach's comes to about $2,800 before its surcharge. Monroe County scales its building fee by the reviews a job needs, so ask the county for a figure. See the seawall cost guide for construction budgets.
Flood insurance discounts differ by town
Each government earns its own Community Rating System (CRS) class, which sets the flood insurance discount for policies there. FEMA CRS list, Oct. 2026
| Community | CRS class | Discount |
|---|---|---|
Unincorporated Monroe County | Class 3 | 35% |
City of Layton | Class 5 | 25% |
City of Key Colony Beach | Class 6 | 20% |
City of Marathon | Class 6 | 20% |
Marathon says the whole city is coastal floodplain, so its flood rules apply on every lot. City of Marathon floodplain page
None of these discounts pays for the wall. The standard NFIP policy lists seawalls, bulkheads and docks as property not insured. Federal flood policy (Dwelling Form) More in seawall insurance.
State and federal approvals come first
In Marathon, Key Colony Beach and unincorporated Monroe County, the state and the Army Corps go first. Key Colony Beach issues a seawall permit only after Corps and DEP approval. KCB Code Sec. 5-30
Marathon wants federal, state and water management district approvals in hand for shoreline work in its buffers. Monroe County issues its permit, then holds all work until a Notice to Proceed. Marathon code 106.38 county code 118-12(k)(9)
| Office | What it decides | Contact |
|---|---|---|
Florida DEP, Southeast District, Marathon branch | Exemptions, environmental resource permits, state submerged land and mangrove trimming | 2796 Overseas Hwy, Suite 221; (305) 289-7070 |
Army Corps, Keys Permits Section | Federal authorization for in-water work | (305) 526-7181; SEAppls@usace.army.mil |
Florida Keys National Marine Sanctuary | Review where work could affect corals; apply at least 90 days ahead | fknms.authorizations@noaa.gov |
Sources: DEP Marathon branch Corps Keys Permits Section NOAA sanctuary permits NOAA sanctuary submissions
- The Corps' Keys general permit, SAJ-82, expired on June 24, 2026, and no reissued version was found. Plan for longer federal review. Corps SAJ-82
- The full sequence is in the seawall permit guide.
Middle Keys seawall guides
- Marathon: Vaca Key and Boot Key Harbor: the city canal program, Marathon code 106.36 limits and the Wilma gauge record. FloridaCommerce Keys oversight report
- Grassy Key, Crawl Key and Fat Deer Key: a few canals beside Curry Hammock State Park. county canal street list
- Key Colony Beach: the 2026 seawall ordinance, the cap height rule and the barge bond. KCB Code Sec. 6-45
- Duck Key: canal 164, the arch bridge rebuilds and a breakwater turning into a living shoreline. Monroe County canal inventory
- Long Key, Layton and Conch Key: a small city, county land and Conch Key's road elevation project. Monroe County road projects
West of the Seven Mile Bridge, start with the Lower Keys overview.
Show sourcesHide sources
- City of Marathon Charter, Sec. 10 Land DescriptionSource reviewed 2026-10-28
- BuildingSource reviewed 2026-10-28
- Building Department and Code EnforcementSource reviewed 2026-10-28
- Building and PermittingSource reviewed 2026-10-28
- Contact UsSource reviewed 2026-10-28
- City StaffSource reviewed 2026-10-28
- About Marathon (History)Source reviewed 2026-10-28
- 2020 Census Gazetteer Files: Places, FloridaSource reviewed 2026-10-28
- LDR Sec. 106.36 Criteria For Approval (Hardened Shorelines)Source reviewed 2026-10-28
- LDR Sec. 108.20 Nonconforming Docks And Shoreline Stabilization StructuresSource reviewed 2026-10-28
- Code of Ordinances Ch. 5, Art. III Marine Construction and Improvements, Docking of BoatsSource reviewed 2026-10-28
- Monroe County Land Development Code, Chapter 118 - Environmental ProtectionSource reviewed 2026-10-28
- Comprehensive Plan Amendment Package (Ord. No. 2022-11-01), adopted June 1, 2023Source reviewed 2026-10-28
- CO-OPS Metadata API: Vaca Key, FL (8723970) datumsSource reviewed 2026-10-28
- Preliminary Report: Hurricane Georges (Table 2)Source reviewed 2026-10-28
- Hurricane Wilma (2005) event summarySource reviewed 2026-10-28
- Tropical Cyclone Report: Hurricane Wilma, 15-25 October 2005Source reviewed 2026-10-28
- Tropical Cyclone Report: Hurricane Irma (AL112017)Source reviewed 2026-10-28
- Tropical Cyclone Report: Hurricane Helene (AL092024), 24-27 September 2024Source reviewed 2026-10-28
- Tropical Cyclone Report: Hurricane Milton (AL142024), 5-10 October 2024Source reviewed 2026-10-28
- Appendix G: King Tide and Normal Wind Setup Analysis for Monroe County, FloridaSource reviewed 2026-10-28
- Resident Reentry Windshield StickersSource reviewed 2026-10-28
- Coastal Flooding & the Florida KeysSource reviewed 2026-10-28
- Weather Brief - Coastal Flooding - Florida Keys of Monroe CountySource reviewed 2026-10-28
- King Tides & High TidesSource reviewed 2026-10-28
- CO-OPS Derived Product API: relative sea level trends (sealvltrends.json)Source reviewed 2026-10-28
- Resolution 2025-73, Exhibit A Permit Fee ScheduleSource reviewed 2026-10-28
- Resolution No. 2026-01 (Fee Schedule for Building Department Permits and Services)Source reviewed 2026-10-28
- Resolution No. 277-2025 (Building Department permitting fee schedule)Source reviewed 2026-10-28
- Building Permit and Inspection Utilization Report, FY 2024/25Source reviewed 2026-10-28
- CRS Eligible Communities, October 1, 2026 Effective DateSource reviewed 2026-10-28
- FEMA Floodplain ManagementSource reviewed 2026-10-28
- 44 CFR Part 61, Appendix A(1): Standard Flood Insurance Policy, Dwelling FormSource reviewed 2026-10-28
- LDR Sec. 106.38 Allowable ActivitiesSource reviewed 2026-10-28
- SED Marathon OfficeSource reviewed 2026-10-28
- Jacksonville District Regulatory Office LocationsSource reviewed 2026-10-28
- PermitsSource reviewed 2026-10-28
- Nearshore Construction PermitsSource reviewed 2026-10-28
- Regional General Permit SAJ-82Source reviewed 2026-10-28
- Florida Keys Area of Critical State Concern Annual Report, FY23-24 (reporting period July 1, 2023 - June 30, 2024)Source reviewed 2026-10-28
- Canal, Roads Names and Areas (List of Keys Residential Canals by location)Source reviewed 2026-10-28
- Code of Ordinances Ch. 6 Buildings, Art. II, Sec. 6-45 Seawall conditions; compliance requirements; enforcementSource reviewed 2026-10-28
- Monroe County Residential Canals (Google Earth KMZ layer 'Residential_Canals_WGS', linked as 'Google Earth Document with Downloaded Canal Information')Source reviewed 2026-10-28
- County Road ProjectsSource reviewed 2026-10-28