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Belle Mer: How an Oversized Drag Circle Missed a Dragging Anchor

🕑 5 min read words Safety • Incident • Navigation

Vessel: Belle Mer (Bulk Carrier)
Date: 15 November 2024
Location: Tongass Narrows, near Ketchikan, Alaska
Outcome: No injuries, no pollution, no vessel damage — $240,000 damage to a subsea fibre-optic cable
Human Factors: Anchoring Planning · Monitoring Under Normal Conditions
Source: NTSB Marine Investigation Report MIR-26-26 (Investigation DCA25FM005)

2 decision points · 4 min read

What Happened

On 15 November 2024, the bulk carrier Belle Mer was anchored in the Tongass Narrows near Ketchikan, Alaska. At about 1211 local time, the ship dragged anchor and its anchor fouled and damaged the Alaska United Southeast Cable Segment 2 — a subsea fibre-optic cable. There were no injuries and no pollution, and the ship itself was undamaged. The cable operator's repair bill came to an estimated $240,000.

Why It Dragged

The NTSB's investigation found the probable cause was the pilot and master's choice to anchor near a known restricted anchoring area, with an anchor chain scope that was inadequate for the water depth and the weather forecast at the time. Restricted anchoring areas around subsea cables exist precisely because a dragging anchor there causes exactly this kind of damage — the location itself was already a known constraint the anchoring plan needed to account for.

A second factor compounded the first: the crew's drag circle — the plotted boundary used to monitor whether the ship is holding position — was too large, and improperly plotted relative to the vessel's actual anchor-drop position and chain measurements. That meant the drag circle couldn't do its job. By the time the ship's actual movement would have shown up as a clear breach of a correctly-sized circle, it had already dragged far enough to reach the cable.

Recommended Actions

When choosing an anchoring position, treat proximity to charted hazards — including restricted anchoring areas around subsea cables — as a hard constraint on the plan, not a factor to weigh against convenience.
Size anchor chain scope to the actual water depth and forecast weather, not a standard default — holding power depends on both.
Plot drag and swing circles from the vessel's actual anchor-drop location and real chain measurements, not estimates or rules of thumb.
Once anchored, continually monitor position with regular fixes compared against the plotted drag circle, swing circle, and visual references — especially as wind or current increases.
Before anchoring near any charted subsea cable or pipeline, confirm the restricted area boundaries on the current chart edition, not an assumed safe margin.

Human Element Analysis

Anchoring Planning

The decision to anchor near a known restricted area, with a chain scope that didn't match the depth and forecast conditions, was made before the ship ever started dragging. Everything that followed was downstream of that planning choice.

Monitoring Under Normal Conditions

A drag circle that's the wrong size doesn't fail loudly — it just quietly stops doing its job. The crew had no reason to believe their monitoring wasn't working, right up until the anchor had already travelled into the cable.

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