To Sink a Barge

As the conversation around sand sourcing continues, another idea occasionally surfaces alongside it. Instead of importing sand or dredging it from offshore, could a structure placed offshore reduce wave energy before it reaches the bluff?

 

The version most often mentioned is simple: sink a barge. In practice, the concept sits within a broader category of coastal engineering — artificial reefs and submerged breakwaters — which have been used in different parts of the world for erosion control, fisheries enhancement, and recreation.

 

The question is not whether the concept exists. It does. The question is how it performs, and whether conditions at 'Sconset align with where it has worked elsewhere.

 

Sinking a vessel offshore, when done intentionally, is a form of artificial reef creation. In coastal engineering terms, when used for shoreline protection, it functions as a submerged breakwater—a structure designed to reduce wave energy before it reaches shore.

 

As waves encounter the structure, part of their energy is dissipated offshore. In some cases, this can reduce wave height and change how energy reaches the beach. Depending on placement and configuration, these structures can also influence how sand settles or moves in the nearshore zone.

 

The Logistics: How Do You Find a Barge?

The casual suggestion to sink a barge implies a surplus of readily available vessels, but the logistics are more complex than a simple donation. Municipalities generally follow three paths to acquire reef material:

 

• Federal Programs: The U.S. Maritime Administration (MARAD) and the Navy have historically transferred obsolete ships to states for reefing. However, this is a state-level application process. A town like Nantucket would likely need to work through the Massachusetts Division of Marine Resources to petition for a vessel from the National Defense Reserve Fleet.
   

• Private Acquisitions: Municipalities can purchase retired "non-retention" commercial barges or tugs. While the purchase price may be low (often scrap value), the buyer assumes all liability for the vessel from the moment of transfer.
   

• The "Clean-to-Sink" Process: This is the most significant hurdle. Federal EPA and Coast Guard standards require vessels to be stripped of all hydrocarbons, PCBs, wiring, and loose debris. This remediation can cost hundreds of thousands of dollars, sometimes exceeding the cost of the structure itself.
   

Once a vessel is cleaned and permitted, it must be towed to the site, moored precisely, and flooded (often using small, controlled charges or by opening sea valves) to ensure it settles upright on the seabed.

 

The Physics of Depth and Scale

Offshore structures work best when they sit high enough in the water column to actually interact with incoming waves. To an engineer, height off the seabed refers to the vertical thickness of the structure — the deck-to-hull measurement. For a breakwater to be effective, its top (the crest) generally needs to reach a height equal to 60% to 80% of the local water depth.

 

If a structure is too "short," waves simply pass over it with limited energy loss. A typical deck barge is only about 10 to 12 feet thick from deck to hull. This creates a significant arithmetic problem off ’Sconset:

 

• In 20 feet of water: An effective structure needs to be 12–16 feet off the seabed (tall).

• In 30 feet of water: The requirement jumps to 18–24 feet.

• In 40 feet of water: It reaches 24–32 feet tall.
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These requirements lead to a difficult choice in placement:
 

• The Nearshore Zone (300 to 1,000 feet out): In shallow water (10–20 feet), a single barge is thick enough to meet the 60–80% ratio. However, because the barge's deck would sit just a few feet below the surface, it becomes a major collision hazard for boaters and swimmers. Additionally, this is the most "dynamic" zone, where shifting sand could bury the structure within a few seasons.
   

• The Offshore Zone (0.5 to 1.5 miles out): To avoid navigation hazards and target massive Atlantic swells, structures would need to be further out. But at these distances, water depth often exceeds 40 feet. A 12-foot barge sitting in 40 feet of water would be ineffective; waves would pass nearly 30 feet above it undisturbed.
   

To be effective at these greater depths, an installation would require stacking multiple vessels or building a massive rock mound — a project that looks less like a sunken barge and more like an underwater mountain range.
 

The Lessons from the Scuttled

Not all attempts to armor the seafloor succeed. The ocean is littered with the rusted remains of good intentions, perhaps none more infamous than the Osborne Reef off Fort Lauderdale. In the 1970s, millions of discarded tires were lashed together to create a massive artificial reef; instead, the straps perished, and the tires became a destructive underwater "carpet," scouring the seabed and smothering natural coral for miles.

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In the high-energy environment of ’Sconset, the primary enemy isn't just decay — it’s stability. Research warns that the sheer force of Atlantic swells can create scouring currents that dig out the sand beneath a solid structure. As Blair Perkins, a Nantucket fisherman and longtime observer, notes, the strong tides and swells east of Nantucket can gradually bury offshore objects. As this "self-burial" occurs, the crest elevation drops, and the structure’s ability to interact with waves vanishes.

 

The Concrete Precedent

Success stories, however, do exist where the material matches the environment. One of the best examples is the "Ghost Fleet" of Kiptopeke, Virginia. In 1948, nine concrete World War II cargo ships were intentionally scuttled to protect a ferry terminal. Because they were made of heavy concrete rather than thin-walled steel, they have resisted the corrosive power of the Chesapeake Bay for over 75 years, creating a massive "wave shadow" that permanently calmed the shoreline.

 

But, engineering success at one beach can mean disaster for the next. Data from submerged breakwaters in South Korea and Italy shows a recurring "Lee Effect" — if a structure isn't perfectly positioned, it can redirect currents in a way that actually accelerates erosion on the down-drift side of the coast.

 

This risk is precisely why Nantucket’s 2021 Coastal Resilience Plan refuses to move a single stone until the Islandwide Sediment Budget is complete. Without a full sand accounting, a sunken barge at the Bluff might save a few feet of Baxter Road today, only to starve the beaches of Tom Nevers tomorrow. 

 

For the engineers at Arcadis, the goal isn't just to sink a vessel — it’s to ensure that the cure doesn't simply move the problem down the shore.

 

Has This Been Considered for ‘Sconset?

There is no evidence in the formal project record that a submerged breakwater system has been advanced as a defined alternative for the ‘Sconset Bluff. To date, approaches have focused on sand-based solutions and shoreline stabilization.

 

The concept, however, is not entirely off the radar. Nantucket’s Coastal Resilience Plan formally categorizes the Sconset Bluff Nearshore Breakwaters Feasibility Study (ID 5-4) as a 'Second' priority project with an estimated study cost of $600,000 to $800,000. Far from a casual suggestion, the plan defines a clear 'Resilience Objective' for the structure: to reduce wave energy impacting the shoreline and encourage sediment deposition to mitigate erosion.

 

While the study was targeted for a 2025 start, it sits within a complex web of 40 island-wide projects. Its progress is currently tethered to a broader Island-Wide Sediment Budget, a foundational mapping of Nantucket's sand economy that must be completed to ensure that protecting ‘Sconset with offshore structures doesn't inadvertently starve the beaches of the South Shore. 

 

For now, the 'Underwater Mountain' remains a line item on a $900 million roadmap, waiting for the data, and the funding, to catch up to the vision.

 

Where This Leaves It

The feasibility of protecting 'Sconset from offshore is not simply a question of whether a structure can be placed there — it can. The real question is whether the water depth and exposure allow for a structure large enough and stable enough to be meaningful without becoming prohibitively expensive.

 

Effective systems are engineered installations, not individual objects. They require detailed modeling to ensure they don't accidentally redirect erosion. In the high-energy Atlantic waters off 'Sconset, the engineering lift is significantly heavier than the casual 'sink a barge' version suggests. 

 

For now, the concept remains an established theory that has yet to be translated into a viable, site-specific proposal.
 

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FROM STEEL TO SANCTUARY
 

While Nantucket’s Coastal Resilience Plan evaluates barges as potential wave-breakers, other coastal communities are already sinking them for a different reason: life.

This POV footage from Florida shows the intentional sinking of a 200-foot barge designed to create a thriving artificial reef. Unlike the "Underwater Mountain" required to break Atlantic swells off ’Sconset, these habitat-focused reefs are often placed in deeper, calmer water where they don't need to reach the surface to be successful.
 

Within months of hitting the seafloor, the steel hull seen in this video will be colonized by corals, sponges, and schools of fish — transforming a retired vessel into a permanent underwater city.

Watch it