Duck Key seawall repair and replacement
Every canal lot on Duck Key shares one interconnected system, county canal 164. Duck Key is unincorporated, so Monroe County permits your seawall, not Marathon.
Describe your project on this page ↓
Duck Key at a glance
- Who permits it
- Monroe County Building Department
- Call first
- Monroe County, Marathon office, (305) 289-2501
- The water
- Canal 164: one system, 287 parcels, five mouths
- Storm record
- Georges, 1998: 84-knot gust measured on Duck Key
- Local rule to know
- No new vertical seawalls on open water (county code 118-12)
Get to know your waterfront
Duck Key sits at about mile marker 61, just past Marathon's limit at the Toms Harbor bridge. Four historic arch bridges tie its islands together, and the Toms Harbor Channel Bridge links it to U.S. 1. Its single canal system opens to the water through five mouths.
Monroe County Residential Canals (Google Earth KMZ layer 'Residential_Canals_WGS', linked as 'Google Earth Document with Downloaded Canal Information') · About Marathon (History) · State of the County 2023 · Duck Key Bridge Updates
Canal 164, the bridge jobs and Duck Key's shoreline
The county maps Duck Key's waterways as a single canal, number 164. It serves 287 parcels along about 9,800 feet, with five mouths, existing cuts and culverts, and a Good water-quality label. Monroe County canal inventory
The street list ties it to Seaview Drive, Bimini Drive, Indies Drive, Greenbriar Road, Duck Key Drive and Schooner Lane. Tree-named streets such as Banyan and Sabal are on it too. county canal street list
The Hawk's Cay, Duck Key and Conch Key wastewater service area has finished its sewer connections, a plus for canal water. FloridaCommerce Keys oversight report
What the bridge rebuilds found at the canal edge
The county's bridge jobs are the best public record of what lies under Duck Key's canal banks. Read them before you choose a method.
| Project | What the county reported | What to ask your contractor |
|---|---|---|
Harbour Drive Bridge | Sheet pile driven along the canal on both sides; holes pre-drilled for precast piles under vibration monitoring; a change order of about $33,000 for buried wood pilings, concrete and debris. Complete in early 2026. | Will you pre-drill, and will you monitor vibration at my house and my neighbors'? |
Seaview Drive Bridge | Sheet pile at both canal ends in fall 2025 and concrete walls beside the drainage outlets; reopened Feb. 19, 2026. | How will the new wall meet any outlet or culvert on my frontage? |
Toms Harbor Channel Bridge | A $1,196,041 repair of spalled concrete, corroded steel and pile jackets with cathodic protection; notice to proceed March 18, 2026, for 365 days. | Will bridge work affect barge or truck access to my lot this year? |
Sources: Monroe County Duck Key bridge updates Monroe County Duck Key bridge updates Monroe County Duck Key bridge updates
Treat these as site evidence, not prices: they are public bridge budgets. Ask for a buried-debris allowance in any bid, and see the seawall cost guide for home budgets.
The county calls the arch bridges historically significant, and the replacements keep the arch form while adding a sidewalk. State of the County 2023
A breakwater turning into a living shoreline
Monroe County plans to rebuild 10,650 linear feet of existing breakwater wall as a living shoreline. Mangrove and seagrass plantings are part of the design. The $3,327,266 DEP grant project was expected to start in March 2026. Monroe County resilience update, Feb. 2026
The county rates Duck Key highly exposed to surge and sea-level rise by 2070. It recommends reinforcing the bridge to the Overseas Highway and restoring mangroves. Monroe County vulnerability assessment See living shorelines.
Roads, tides and wind
- Sixteen Duck Key road segments, 9,449 feet in all, are on the county's most-critical 25% list. They include Indies Drive, Seaview Drive and Harbour Drive. county roadway prioritization
- Area 27-A, 1,650 feet, is in the road study's 2025 adaptation group. The much larger 27-B, about 5.7 miles, sits within half a foot of projected 2025-2035 king tides. county roadway study county roadway study
- The canal layer's tidal range field reads about 1.3 feet. Monroe County canal inventory
- Georges brought 70-knot sustained winds and an 84-knot gust to Duck Key in 1998. Hurricane Center Georges table
Ask the county about the road plan for your street before you settle on a cap height. How caps are set is covered in seawall height requirements.
What could the work cost?
Monroe County prices residential permits per $1,000 of job value in bands. It adds a $976 Notice to Proceed fee when the permit waits on state or federal approval. Ask bidders to list pre-drilling, vibration monitoring and a buried-debris allowance as separate lines, since the county's Harbour Drive bridge job needed all three.
Calculator ranges come from a 2026 national cost guide and one Key West public bid. None is a quote; your written, itemized scope sets your price.
Compare quotes and plan a budget →Find the relevant permits and records
| Starting point | What to resolve | Prepare and look up |
|---|---|---|
Monroe County Building Department, Marathon office | Building permit for seawall, riprap and dock work on Duck Key, filed online in OPAL. | A signed, notarized Work Over the Water Notice at issue. 2798 Overseas Hwy, Suite 300; (305) 289-2501. |
Monroe County Planning & Environmental Resources | county code 118-12 review: replacement in the existing footprint, and no new vertical walls on open water. | Existing and proposed wall line. Environmental Resources: (305) 289-2502. |
Florida DEP, Marathon branch | State exemption for seawall work in legally existing residential canals, or a permit when the exemption does not fit. | An exemption verification request. (305) 289-7070. |
Army Corps Keys Permits Section, then the county Notice to Proceed | Federal authorization; the county holds all work until it issues a Notice to Proceed. | The Corps approval filed with the county, plus the $976 NTP fee. Corps: (305) 526-7181. |
Your Duck Key seawall checklist
Four things to do this week if your Duck Key wall needs work.
Confirm your canal record
Find your lot on the county's canal map. Duck Key's canal is number 164, and the map shows its mouths and existing culverts.
Monroe County Residential Canals (Google Earth KMZ layer 'Residential_Canals_WGS', linked as 'Google Earth Document with Downloaded Canal Information') · Canal Restoration
Pull your permit history
Search the county's OPAL system for past permits. Anything processed before Oct. 1, 2022 sits in older paper files, so ask the county for those.
Ask how the wall goes in
Ask each bidder about pre-drilling, vibration monitoring and an allowance for buried debris, the three issues the Harbour Drive bridge job met.
Photograph king tides
King tides run September through December. Email photos with your address, date and time to greenkeys@monroecounty-fl.gov.
Plan your Duck Key seawall project
Tell us your street, what you see at the cap and toe, and how a barge or truck would reach your lot. We will help you work out what comes next.
Every answer here links to the public record behind it.
Duck Key project questions
Is Duck Key part of the City of Marathon?
No. Marathon ends at the west end of the Toms Harbor bridge, about mile marker 60, and Duck Key at MM 61 is unincorporated. Monroe County permits your seawall; its Marathon office is at (305) 289-2501.
About Marathon (History) · 2020 Census Gazetteer Files: Places, Florida · Building and Permitting
What did the bridge work show about Duck Key's canal banks?
On the Harbour Drive Bridge, the contractor pre-drilled pile holes under vibration monitoring. Crews also hit unforeseen wood pilings, reinforced concrete and concreted debris. Ask your bidders how they would handle the same.
Can I start work as soon as the county issues my permit?
Not if the permit is conditioned on Army Corps or DEP approval. No construction or inspection can begin until the Building Official issues a Notice to Proceed, which carries a $976 fee. The county’s 2022 handout says the permit expires within 180 days if those documents are not filed.
Notice To Proceed Instructional Handout (Internet Archive copy) · Resolution No. 277-2025 (Building Department permitting fee schedule)
What is happening to the Duck Key breakwater?
Monroe County plans to rebuild 10,650 linear feet of existing breakwater as a living shoreline with mangrove and seagrass plantings, under a DEP grant. Work was expected to start in March 2026.
February 2026 Updates Presentation (Monroe Resilience & Environmental Projects)
Keep planning
Nearby waterfront guides
Marathon: Vaca Key & Boot Key Harbor, Long Key, Layton & Conch Key, Grassy Key, Crawl Key & Coco Plum (east Marathon)
Show sourcesHide sources
- 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
- About Marathon (History)Source reviewed 2026-10-28
- State of the County 2023Source reviewed 2026-10-28
- Duck Key Bridge UpdatesSource reviewed 2026-10-28
- Canal, Roads Names and Areas (List of Keys Residential Canals by location)Source 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
- February 2026 Updates Presentation (Monroe Resilience & Environmental Projects)Source reviewed 2026-10-28
- Monroe County Vulnerability Assessment Update & Compliance, Final Project Report (DEP Agreement No. 22PLN66)Source reviewed 2026-10-28
- Appendix K: Prioritization of Roadway Segments (Technical Memorandum, Dec. 29, 2020; Initial 25% Critical Roadways list dated 6/10/2021)Source reviewed 2026-10-28
- Monroe County Roadway Vulnerability Study Final Report (Table 2: Adaptation Plan List)Source reviewed 2026-10-28
- Preliminary Report: Hurricane Georges (AL071998), 5 January 1999, updated 9 September 2014Source reviewed 2026-10-28
- Building and PermittingSource reviewed 2026-10-28
- Online Permitting ServicesSource reviewed 2026-10-28
- Work Over the Water NoticeSource reviewed 2026-10-28
- Environmental ResourcesSource reviewed 2026-10-28
- Monroe County Land Development Code, Chapter 118 - Environmental ProtectionSource reviewed 2026-10-28
- Rule 62-330.051, F.A.C. (Exempt Activities)Source reviewed 2026-10-28
- SED Marathon OfficeSource reviewed 2026-10-28
- Jacksonville District Regulatory Office LocationsSource reviewed 2026-10-28
- Notice To Proceed Instructional Handout (Internet Archive copy)Source reviewed 2026-11-05
- Resolution No. 277-2025 (Building Department permitting fee schedule)Source reviewed 2026-10-28
- Canal RestorationSource reviewed 2026-10-28
- King Tides & High TidesSource reviewed 2026-10-28
- 2020 Census Gazetteer Files: Places, FloridaSource reviewed 2026-10-28