NTSB: Probable Cause of UTV Grounding, Sinking

The uninspected towing vessel Stephen L. Colby struck hard bottom in the Upper Mississippi River (UMR) and partially sank off the right descending riverbank in LeClaire, Iowa, on November 25, 2013, at 1555 Central Standard Time.

Six of the nine crewmembers on board made it to the riverbank on their own. The nearby towing vessel Aaron F. Barrett recovered the remaining three crewmembers from the partially sunken vessel. No one was injured.

The area of the UMR where the Stephen L. Colby grounded is known to require particular caution during periods of low water because the bottom is hard rock with a stepped or shelf formation. On November 16, 2013, the port captain for Marquette Transportation sent an e-mail reminder to all company vessel operators to use caution while transiting two specific areas of the waterway: the area just below Lock & Dam 14 and the vicinity of UMR mile 497, just upstream of the accident site. The e-mail warned, in part, “There are rock shelves in those areas and there have been several incidents over the years of a boat . . . hitting those rocks and puncturing the hulls.” The mate stated that he was not aware of this e-mail, but he knew those areas of the UMR presented special risks.

The National Transportation Safety Board determines that the probable cause of the grounding and sinking of the Stephen L. Colby was the failure of the master and mate to ensure sufficient underkeel clearance for the intended transit through the accident area.

Read the full briefing here.