An open overboard shutoff valve and a failed verify valve led to the sinking of a laid-up towboat at a yard in New Orleans final yr, the NTSB has concluded. 

At about 0600 within the morning on June 25, 2023, an worker discovered the towboat Joanne Marie itemizing closely and partially flooded on the Bollinger Quick Repair Shipyard exterior New Orleans. The ship was in layup on the time, with out energy or crew, and nobody was injured within the partial sinking.   

The Joanne Marie was an occasional-use vessel for the operator, performing fleeting operations as wanted and shutting down between jobs. On June 23, two days earlier than the incident, the crew introduced the towboat again to her customary layberth and tied up subsequent to a different towboat. The port captain got here on board and helped with shutting down and buttoning up the boat for an indefinite keep. The process included tightening the shaft packing glands to no-drip, however gas tank crossover valves and overboard shutoff valves have been left open. This was a matter of routine observe and didn’t violate firm process. 

Early within the morning of June 25, an organization worker seen that Joanne Marie was itemizing closely and known as the port captain. The vessel was partly submerged on the stern, itemizing to port, and touching the underside on the port quarter. (Luckily the canal was solely 15 toes deep.) 

Under the circumstances, the injury was comparatively restricted. Joanne Marie’s port aspect was submerged as much as the highest of the principle deck stage, however the vessel was steady and had launched only some gallons of gas into the atmosphere. The crew plugged the gas vents, and a heavy elevate crane was known as in to refloat the ship. By 1600 the identical day, Joanne Marie was efficiently refloated.

Both of Joanne Marie’s major engines and diesel turbines have been broken, together with a few of her electrical gear and her crew areas. The price of restore got here to about $175,000. 

Investigators got here aboard after the refloat to find out the reason for the sinking. The proprietor’s surveyor used a hose to pressurize every discharge pipe from the skin, and located water leaking from the inlet strainer on the bilge pump on the starboard aspect cofferdam. The piping had a verify valve between the pump and the overboard line, however when the corporate’s engineers opened up the verify valve to take a look, they discovered that an on a regular basis orange wire nut (twist connector for electrical wires) had in some way gotten sucked into the pump and jammed the valve open. Since the ball valve on the discharge line had additionally been left open, there was nothing to stop water from flowing backwards by the road, by the pump, and into the cofferdam.

The wrongdoer: a easy plastic wire nut jamming open the verify valve (USCG)

Ordinarily the discharge pipe was above water, however the vessel had extra gas in her tanks than regular, and was sitting a couple of foot decrease than her ordinary working draft – low sufficient that the discharge would have been at or close to the waterline. Water from a passing vessel’s wake or from a slight record possible flowed again by the road and flooded the engine room. 

Since the boat had no energy, her bilge pumps didn’t come on to counteract the flooding. Once the boat began to record, gas would have flowed “downhill” from the starboard aspect tanks into the port aspect tanks by the open crossover valves, including to the buildup of mass on the low aspect of the boat. 

Based on lessons-learned, the operator has modified their guidelines for vessel layup to incorporate closing the overboard discharge valve when the vessel has no energy. 

“To reduce the potential for flooding, operators should consider closing through-hull fitting valves,” concluded NTSB. “Installing high-water bilge alarms and fire detection systems that remotely alert responsible personnel facilitates the early detection and mitigation of potential safety risks, such as flooding or fire.”