Barge Nash Salvage Response - Case Study
The 260’ long barge NASH, loaded with magnesium chloride in an aqueous solution, essentially a by-product of solar desalinization, was part of a tandem tow between Mexico and Canada. The barge sank in the vicinity of Point Conception, just off the rugged California coastline near Santa Barbara.
With a specific gravity of 1.3, magnesium chloride is much heavier than water. This prevented the barge’s tanks from being completely filled, so as not to exceed the ABS load-line certificate for the barge. As the barge began to sink, the air contained within the aft cargo holds reached a depth at which the pressure differential between the seawater on the outside of the barge and the air on the inside caused the tanks to implode leading to catastrophic failure of the hull.
The barge’s stern came to a rest on the seafloor in 235’ of water. The undamaged forward cargo and bow rake tanks retained enough buoyancy to prevent the barge from “falling over”, which left the barge “aground” in a completely vertical orientation.
Global was contracted to render assistance in salvaging the barge. The barge was located just 600 yards south of an active high-capacity oil pipeline and just 600 yards north of a Marine Protected Area. The proximity to these critical resources added an element of urgency and need for a well executed plan. Global’s Casualty Response Group began developing a removal plan while dive and salvage equipment was mobilized out of Port Hueneme, CA.
The 6000 HP tractor tug DELTA LINDSEY was contracted from American Navigation (AmNav) to standby in the immediate vicinity of the NASH to ensure that she did not move closer to the pipeline or MPA.
An ROV inspection was promptly completed which revealed that the bow rake was leaking air through a weld in the main deck and that the hull was badly damaged in water depths greater than 100’. It became evident that refloating the barge to her traditional horizontal position was going to be difficult, and that an alternate removal strategy would be necessary.
Global, acting as Incident Commander in the Unified Command, worked with the US Coast Guard, the Bureau of Safety and Environmental Enforcement and State agencies to secure an emergency scuttle permit from the US Environmental Protection Agency. Global crews immediately began executing the salvage plan which consisted of offloading some of the cargo, adding enough air to the bow rakes and forward cargo holds to get the barge to float free of the seafloor and towing her 14 miles offshore to the EPA approved scuttling location. Divers gained access into the tanks and created openings to discharge the cargo. Divers then installed air lines to delicately introduce air into the tanks while an ROV positioned at the seafloor provided live video of the progress. The “DELTA LINDSEY” was brought alongside the NASH and deployed a tow wire to the barge’s bridal. When a suitable amount of air had been introduced into the forward compartments the tug began taking an easy strain. Just before high tide, the barge came free from her strand and the 14 hour, very challenging, tow to the EPA dump site begun.
Meanwhile, Global and the USCG developed a plan to scuttle the barge upon arrival at the dump site. The difficulty in scuttling the NASH lay in the fact that crew had worked feverishly to introduce air INTO the barge to keep it from sinking, but now that same air needed to come OUT of the barge very quickly. Sea conditions had grown worse during the tow offshore and it was not safe for anyone to board the vessel to manually cut holes in the barge.
The USCG came through with a method for rapidly sinking the NASH – The USCGC BLACK FIN, an 87’ cutter with a .50 caliber machine gun. The BLACK FIN was mobilized to the scuttling location and shot 500 armor piercing rounds at the exposed bow of the NASH. The bullet holes allowed air to escape and water to enter the barge. The NASH was last seen approximately 1 hour after the live fire when she left the surface and began her decent to her 2600’ deep watery resting place.