What happened?
At 1312 local time on May 27, 2016, the lake freighter (laker) Roger Blough ran aground near the Gros Cap Reefs Light off Sault Sainte Marie, Ontario, Canada. The grounding occurred as the vessel entered the Birch Point Course section of the St. Marys River federal navigation channel from Whitefish Bay in eastern Lake Superior. No one was injured and no pollution was reported. The vessel sustained $4.5 million in damage to its hull and cargo system.
The Roger Blough was downbound in Lake Superior with a cargo of taconite iron ore pellets. By late morning, the vessel was approaching the St. Marys River at the eastern end of the lake. Near the entrance to the river, the Gros Cap Reefs Light marked shoal water to the north of the navigation channel.
Confirmed Overtaking Arrangements
At 1138, the second mate on watch aboard the Roger Blough radioed VTS St. Marys River to make a mandatory position report. VTS advised him that downbound tugboat Anglian Lady was towing a stricken laker about 10 miles ahead of the Roger Blough and about 4.9 miles from Gros Cap Reefs Light. Because the Roger Blough was making full “sea speed” of about 14.5 mph and the Anglian Lady tow was making only about 5 mph, the Roger Blough second mate hailed the Anglian Lady master and proposed to overtake the tow. The two vessels confirmed overtaking arrangements at 1232.
The Roger Blough master had told the mate to reduce speed to about 13.5 mph when the vessel was 2 miles north of Gros Cap Reefs Light and down to about 11.5 mph when abreast of the light. The second mate later acknowledged that despite these instructions, he did not slow the ship.
The accident and playback
At 1310, the Roger Blough’s centerline was on the outer edge of the left side of the channel, with its port side outside the channel and its speed began to slow. About 1312, the vessel passed over a charted 30-foot depth curve near the Gros Cap Reefs and hit bottom. The Roger Blough’s heading shifted about 8 degrees to port as the vessel continued to move forward for another 2 minutes, dragging the hull an additional ship length over the reef’s bedrock until the vessel came to rest.
A postaccident playback of the Roger Blough’s charting system showed that the vessel was straddling the edge of the channel as it approached Gros Cap Reefs, but the second mate told investigators that he was looking out the bridge windows and was not monitoring the track on the electronic chart.
Effect of Squat
The vessel’s departure drafts were 27 feet 10 inches forward and 28 feet aft. Given that the Roger Blough was transiting at full speed in shallow water, it is likely that the effect of squat―an increase in the overall draft of a vessel when transiting at high speed through shallow water―exacerbated the existing dangerous situation presented by the vessel’s straddling the channel boundary near the charted 30-foot depth curve near Gros Cap Reefs.
Two watchstanders were on duty at VTS St. Marys River on the day of the accident, and they told investigators that they were not aware that the Roger Blough was in danger until the crew reported that it had run aground. Had the watchstanders effectively monitored the vessel’s track, they likely would have noticed that the Roger Blough was operating at the edge of the channel and approaching the shallow water near Gros Cap Reefs.
Probable Cause
The NTSB determined that the probable cause of the grounding of the lake freighter Roger Blough was the second mate’s failure to use all navigational resources to determine the ship’s position as it approached shallow water near Gros Cap Reefs. Contributing to the accident was inadequate monitoring of the vessel by VTS St. Marys River.
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Source: NTSB
