The National Transportation Safety Board (NTSB) has released an investigation report on the flooding and partial sinking of towing vessel Joanne Marie that took place in late June 2023 in New Orleans, Louisiana.
The incident
On June 25, 2023, about 0600 local time, the inspected towing vessel Joanne Marie was found partially submerged while moored at a shipyard on the Harvey Canal near New Orleans, Louisiana. There were no crewmembers or shipyard workers on board the vessel. An estimated 10 gallons of diesel fuel were released into the water. Damage to the vessel was $176,751.
Analysis
About a day and a half after being moored and deactivated at a shipyard on the Harvey Canal, the unattended Joanne Marie was found listing and partially submerged with its port quarter resting on the bottom of the canal. After the vessel was refloated, no water ingress into any vessel spaces was found, indicating the hull condition did not contribute to the flooding. Postcasualty testing found that, when water was pumped into the through-hull pipe for the propulsion shaft seals’ cofferdam overboard discharge, it entered the cofferdam (open to the engine room).
The vessel’s typical operating draft was estimated to be about 9 feet 2 inches. The port captain did not note the Joanne Marie’s draft during his rounds of the vessel on June 23 or June 24, and there were no records of the vessel’s draft at the time it was deactivated on June 23. Therefore, investigators were unable to definitively determine the vessel’s draft and, subsequently, the exact height of the through-hull pipe for the cofferdam overboard discharge above the waterline when the vessel was deactivated.
A company representative stated that the draft of the Joanne Marie was 8 feet when the fuel tanks were 62% full. However, on the day the vessel was deactivated, the daily boat log showed that the fuel tanks were 75% full—which equated to over 18,000 additional pounds of fuel. Given the weight from the additional fuel, the vessel’s draft on the day it was deactivated was likely greater than 8 feet and closer to the estimated normal operating draft of 9 feet 2 inches. This draft placed the through-hull pipe—which was located about 9 feet above the keel—near or potentially below the waterline. Therefore, because the opening of the through-hull pipe was so close to the waterline, water would have been able to enter the discharge line from a variety of sources, including the wake from passing vessels or a small list.
The shaft seal cofferdam discharge system had two bilge pumps whose discharges combined into a single overboard line. The discharge lines had valves installed to prevent water ingress. First, there was an overboard shutoff valve installed just before the through-hull pipe (combined overboard discharge) to prevent the accidental admission of water from moving through the discharge system into the engine room. However, company personnel stated that the overboard shutoff valve was left open when the Joanne Marie was secured on June 23 and this was typical for deactivated vessels.
Each pump also had a check valve on its individual discharge line before the lines combined. After the casualty, investigators found that a wire nut had lodged in a spring-loaded check valve on the starboard-side bilge pump discharge line, obstructing the valve and forcing it to remain partially open (the swing-type check valve on the portside bilge pump worked properly). Investigators could not determine how the wire nut had entered the cofferdam. The wire nut may have been inadvertently dropped or fallen into the cofferdam when the deck plate covering the cofferdam was removed for regular maintenance. The Coast Guard and company representatives found that the wire nut was small enough to pass through the cofferdam bilge pump inlet strainer, so when the cofferdam bilge pump activated, the wire nut was pulled through the strainer and subsequently the pump impeller and discharge line before reaching the spring-loaded check valve. The spring-loaded design of the check valve held the wire nut in place, leaving the valve in a partially open position and susceptible to backflow.
The overboard shutoff valve and spring-loaded check valve in the discharge line from the starboard cofferdam bilge pump both served to prevent accidental admission of water from water movement against the hull, water present in the lines with the pumps turned off, and water ingress if the through-hull pipe was submerged. However, with the overboard shutoff valve left open and the spring-loaded check valve stuck partially open, water entered through the through-hull pipe, causing the cofferdam—which was not watertight—to overflow and water to flood the engine room.
The port captain completed the deactivation tasks with the crew in accordance with the TSMS. However, the tasks were limited to housekeeping items and did not address the configuration of onboard systems to prevent a casualty (the port captain did tighten the shaft seals; however, this task was not captured in the company’s TSMS for vessel deactivation). The deactivation procedures in the operating company’s TSMS did not direct the crew to close the overboard shutoff valve. Had the TSMS deactivation procedures accounted for the configuration of vessel systems, such as closing the overboard shutoff valve, the procedures would have accounted for the possibility of the spring-loaded check valve becoming stuck and resulting in flooding. Following the casualty, the operating company replaced the spring-loaded check valve with a swing check valve (like the check valve on the other cofferdam bilge pump); the company also modified their checklist for vessels entering deactivation to include closing the overboard shutoff valve for vessels without shore power.
As water continued to ingress through the overboard discharge, the added weight from the water in the engine room would have increased the vessel’s draft near the stern, further submerging the through-hull pipe for the cofferdam overboard discharge. Based on the specifications of the 1.5-inch Schedule 40 pipe used for the cofferdam discharge system as well as the postcasualty examination of the springloaded check valve, which showed the wire nut blocked about 50% of the pipe/flow of water into the cofferdam, investigators calculated a rough initial rate of flooding of 1,508 gallons per hour once the center of the overboard discharge was submerged at a depth of 1 foot.
As the vessel’s stern sank lower and the overboard discharge moved further underwater, the rate of flooding would have increased until the port quarter rested on the bottom of the canal.
The flooding went undetected until about 0530 on June 25, about 17 hours after a port captain had completed a daily round of the Joanne Marie’s exterior on June 24. Per company policy, monitoring of deactivated vessels did not include checks of vessel interior spaces, such as the engine room. As such, the port captain’s June 24 round was not sufficient to detect water ingress. The vessel was equipped with bilge alarms as well as bilge pumps. However, the vessel was not connected to shore power at the time of the casualty (nor was it required to be), and therefore the alarms were not active. Without functioning bilge alarms or crewmembers conducting more thorough and frequent rounds, company personnel remained unaware of the flooding until the vessel had already partially sunk.
Probable cause
The National Transportation Safety Board determines that the probable cause of the flooding and partial sinking of the Joanne Marie was the ingress of water into the engine room through a through-hull pipe located near the waterline due to an obstructed spring-loaded check valve on a cofferdam bilge pump discharge. Contributing to the sinking were inadequate procedures for securing unattended vessels.
Lessons Learned
Ensuring Oversight of Inactive Vessels
It is good marine practice for owners and operators of towing vessels to assess risks and develop tasks in their towing safety management system (TSMS) for vessels that are unattended or in layup status. TSMS task lists for such vessels should address factors in the configuration of the vessel that could lead to a casualty. To reduce the potential for flooding, operators should consider closing through-hull fitting valves (such as skin valves or seacocks) and tightening packing glands for propulsion shaft seals, or other machinery, as needed. Additionally, conducting periodic rounds of vessel spaces and 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.
