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NTSB Releases Findings From DUKW Boat Investigation

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Salvage team raises Stretch Duck 7 (image courtesy USCG)

Published Apr 28, 2020 8:37 PM by The Maritime Executive

The National Transportation Safety Board has released an advance summary of its final report on the sinking of the DUKW amphibious passenger boat Stretch Duck 7. During a (remote) board meeting to discuss the report on Tuesday, NTSB officials said that the operator's decision to run tours during severe weather led to the fatal 2018 sinking on Table Rock Lake, Missouri.

The 33-foot-long, World War II-era DUKW amphibious passenger vessel, operated by Ride The Ducks of Branson, sank during a derecho - a high wind event accompanying a thunderstorm - on Table Rock Lake near Branson, Missouri. The vessel had 29 passengers and two crewmembers aboard for a tour. One crewmember and 16 passengers died in the accident.

According to NTSB, Ride the Ducks of Branson continued to operate waterborne tours after a severe thunderstorm warning had been issued. This exposed the vessel to a derecho, which resulted in waves flooding through a non-weathertight air intake hatch on the bow, causing the vessel to sink. The hatch was equipped with a springloaded damper that could not be secured against opening: it was held closed in the upward position only by spring force. As the bow dipped beneath waves, a substantial amount of water likely entered the vessel through the three-square-foot opening, NTSB found. 

As in the past, NTSB identified a contributing factor: the U.S. Coast Guard’s decision not to require more reserve buoyancy in amphibious passenger vessels. NTSB investigators found that the vessel was constructed with a low freeboard, an open hull, and no subdivision or flotation, resulting in a design without adequate reserve buoyancy for safe passenger operations. An improved Ride the Ducks boat, Stretch Duck 54, was on the same lake during the same weather event; with more freeboard, more reserve buoyancy and a securable bow hatch, Stretch Duck 54 made it to shore unharmed. 

Additionally, the NTSB noted the Coast Guard's previous inaction regarding regulation of emergency egress on amphibious passenger vessels with fixed canopies, which have been implicated in at least two DUKW boat casualties. In the case of the Stretch Duck 7, the closed starboard-side curtain aboard the vessel impeded the passengers’ escape and likely resulted in additional fatalities, the NTSB concluded. (Last week, the Coast Guard asked DUKW operators to voluntarily remove canopies.)    

The main factor in the sinking, NTSB asserted, was the operator's decision to sail. During the investigation, NTSB officials documented that the National Weather Service had issued a severe thunderstorm watch for the area several hours before the sinking. That watch was followed by a severe thunderstorm warning one minute before Stretch Duck 7 departed the shoreside boarding facility, which was about six miles from the lake where the tours began and ended. Investigators noted three other company vessels also entered the lake after the severe thunderstorm warning was issued.

“Had Ride The Ducks employees taken more appropriate actions and made better decisions, it is likely the duck boat would not have sunk, because they would not have continued operations based on the weather forecast and prevailing conditions,” said NTSB Chairman Robert Sumwalt.

The NTSB issued six safety recommendations, with three issued to Ripley Entertainment Inc. (dba Ride The Ducks) and three to the U.S. Coast Guard.  These recommendations address safety issues including company oversight, engine compartment ventilation closures, reserve buoyancy, survivability, weather training for mariners and Coast Guard guidance.

The NTSB issued two high-priority safety recommendations last November, calling for sufficient reserve buoyancy and improved emergency escape provisions on DUKW amphibious passenger vessels.

The NTSB's final investigation report is expected to be published in the next few weeks. In the interim, the abstract is available here