Inattentive Anchor Watch Led To $17m in Damage

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The National Transportation Safety Board says the bridge crew’s lack of attention to a ship’s position let it drag anchor and hit another anchored ship and a dock.

Incident

The anchored general cargo vessel collided with the anchored bulk carrier on the Lower Mississippi River near New Orleans, Louisiana, after the cargo vessel began to swing and drag its anchors in the current. 

After colliding with the bulk carrier, which had been anchored directly behind the cargo ship, the cargo ship then struck a nearby chemical dock and grounded on the bank. No injuries were reported. 

The cargo ship released an estimated 13 gallons of lube oil into the river. Damage to both vessels and the dock was estimated at $16.9 million.

Analysis 

The cargo ship positions and headings suggested that the cargo ship did not initially settle at its original anchor position. After the starboard anchor was let go, the ship moved about 730 feet away from the original starboard anchor drop position towards the right descending bank, a distance double the amount of chain that was set on the anchor, indicating that the starboard anchor likely dragged. 

The pilot departed the bridge while the vessel was still moving, although he said he had no concerns about the cargo ship holding anchor.

The second officer had set an ECDIS anchor watch alarm, which would have sounded had the vessel moved beyond the set radius.

Neither the second officer nor chief officer recalled hearing the anchor alarm activate, and, given that the initial estimated distance from the stern of the cargo vessel to the bow of the bulk carrier was 490 feet, the anchor watch alarm radius setting of 590 feet was too large to provide for a timely alarm of the ship dragging. 

Just before the change of the watch between the second officer and chief officer, the ship began to swing to starboard and dragged anchor, moving about 800 feet over about 6 minutes.

Even after the initial alert by the Atlantic Venus to monitor their holding position, the chief officer did not take any follow-up action to address the concern, only communicating that their engines were ready on short notice.

There was no evidence of either watch officer checking the ship’s position at frequent intervals or by means other than the ECDIS watch alarm to determine if the ship was secure at anchor or not.

By the time the cargo ship master was called to the bridge, he had lost about half the original distance between his vessel and the bulk carrier in which to react to and mitigate the situation. Knowing that a pilot was required to get underway in the Lower Mississippi River, he contacted New Orleans VTS and the ship’s agent to request a pilot but was informed he would have to wait hours. 

Seven minutes before the collision, the main engine was ready for use on the bridge—but VTS had told the cargo ship not to heave anchor and to maneuver only with their engine until a pilot arrived. The master followed the instructions from VTS, keeping the anchors out. 

However, this severely limited the bridge team’s ability to control the vessel in the strong current, even while using the main engine up to full ahead, the bow thruster, and rudder.

Investigation 

The National Transportation Safety Board determines that the probable cause of the collision between the cargo vessel and bulk carrier was the bridge team on the cargo ship not effectively monitoring the vessel’s position and therefore not detecting that the vessel was dragging anchor and had moved from its original position during high-water conditions in proximity to other vessels.

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Source: ntsb

 

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