Then all hell broke loose...

The tankerman refused to secure the loading arm to the apparently unstable barge, and everyone at the site feared the worst was to come. Sure enough, at nearly six o'clock that evening, the barge slowly rolled to port, coming to rest upside down next to Sterling Chemical's dock.

The tug backed off while it rolled, then gently pushed on the side of the barge to hold it next to the dock. The barge was in the same slip as the French ship Grandcamp had been when its cargo of ammonium nitrate fertilizer exploded back in 1947, killing hundreds and injuring thousands of Texas City residents.

Setting Up for Salvage
Federal, state, and local officials descended upon the scene. T&T Marine Salvage, based in nearby Galveston, Texas, was contracted to provide the salvage expertise necessary to safely roll the vessel upright and offload the cargo. T&T Marine owners Rudy and Kevin Teichman were at the site in a matter of minutes, bringing T&T's 53-foot mobile command center to house the many officials charged with establishing the Incident Command.

The steel tank barge contained 99 percent sulfuric acid, which is relatively stable and non-corrosive at concentrations above 97 percent. When diluted with water, however, it is extremely corrosive to steel. The violent reaction produces rapid metal loss, high temperatures, and explosive hydrogen gas.

With the barge inverted, and a sulfuric acid specific gravity of 1.8, the cargo was thought to be exiting the barge through the cargo vents and sinking to the bottom of the 30-foot deep slip. Air monitoring and water sampling was established in order to ensure the safety of the response personnel and to determine the extent of the spill.

The "intensity," or corrosivity, of an acidic solution is defined by its pH, which is measured on a scale from 1 to 14. For example, neutral water has a pH of seven; a very caustic solution (concentrated drain cleaner) has a pH of 14; and a very acidic solution has a pH of one. The pH was measured at five-foot increments in the water column throughout the harbor. The pH of the water immediately around the barge measured 1 to 2 in the bottom ten feet (3m) of the water column, confirming the cargo was leaking from the barge.

On the surface of the water, a neutral pH of seven to eight was measured, demonstrating the effect of the dense sulfuric acid and relatively low currents in the Texas City harbor.

Preparing to Roll the Barge
There are several ways to roll a barge upright. The most common method uses rolling wires run under the barge and secured to fittings such as padeyes or mooring bitts on the opposite side of the vessel. Derrick barges are used to pick up on the wires, which roll the barge upright.

Typically, divers are used to secure the rolling wires underwater. Padeyes can be welded above the waterline and a rigging crew utilized to secure the rolling wires topside.

However, increasing temperature measurements taken on the sides of the cargo and wing tanks showed a chemical reaction was taking place in the barge and welding was out of the question. Messenger wires were pulled under the barge while it was still afloat in order to facilitate the placement of the lift slings in case the barge sank.

Danger to the Divers
The diver's dress used on this project was the Gates Pro HD dry suit with attached boots. Cuff rings secured the gloves to the dress, and a Desco yoke was attached to mate the air hat directly to the suit. The standby diver dressed out exactly as the diver entering the water.

Sulfuric acid aggressively corrodes the stainless steel, brass, and copper parts of a dive helmet throughout most concentration ranges, but this attack is visible and occurs over a period of time. Metal loss in the range of 20 mils per year is common. Available literature on the diver's dress gave a breakthrough time of 480 minutes on the seams of the dry suits in a 10 percent solution of sulfuric acid.

However, acid and seawater do not mix uniformly due to the large density differences between each other. Sulfuric acid is completely soluble in water, but we did not know how much acid was being released, how fast it was being released, or how it was being mixed with the seawater in the harbor. These unknow factors did not allow us to anticipate the environment we were dealing with at any given time, making the dry suit the apparent weak link in the diver's dress.

Because of these unknowns, having divers enter the water was deemed an unnecessary risk. Rather, we continued to monitor the pH of the water column and establish a dilution rate. Monitoring after the initial release and computer modeling of the acid movement suggested that the impact might extend 100m to 300m from the release point and last only one to three days.

The Barge Rolls Again
The next morning, having discharged sufficient cargo to once again become unstable, the barge rolled slowly onto its port side. The tug backed off once again as the barge settled into its new position at the dock.

After the barge stabilized, it appeared to be still afloat. The mooring bitts on either end of the barge were above the waterline, which gave us the opportunity to quickly run the rolling wires under the barge and secure them to the bitts without having to use the divers.

Standard salvage practice dictates that the hatches of a casualty be secured to preserve any flotation that may be left. The salvage team quickly secured the visible hatches along the starboard side of the vessel in order to keep the vessel afloat as long as possible and hasten the placement of the slings. Without the use of divers, it was critical that the barge be slung as quickly as possible.

The rolling wire was swept under the stern and T&T Marine's 600-ton derrick Big T was secured to the stern of the barge.

Next, the bow rolling wire was run and the 350-ton derrick Josie T was secured to the bow. Catch wires were carefully measured and secured to keep the barge from rolling past the upright position.

More Hazards to Overcome
As the catch wires were being secured, the sideshell of the barge began to bulge noticeably. Temperature readings on the sides of the cargo tanks had climbed between 125 to 145 degrees fahrenheit and the constant release of bubbles from the cargo tank vents indicated that a dangerous reaction between the sulfuric acid, seawater, and steel was taking place.

Since the byproduct of the reaction is hydrogen gas, the only thing necessary for a catastrophic explosion was an ignition source. The bulging continued until the welds holding the sideshell to the frames began to break.

Salvage personnel were evacuated from the scene and an 800m safety zone was established while the barge was blanketed by a water fog. The Texas City Ship Channel was closed and Sterling Chemical evacuated all non-essential personnel. The Texas City Emergency Operations Center issued a Level 2 emergency and the T&T Marine command center was moved to a location on the opposite side of the hurricane protection levee, which made an ideal blast wall.

T&T Marine's wireless remote camera system was set up to allow the barge to be monitored from the command center as well as anywhere within a five-mile radius.

Several options to relieve the hydrogen pressure inside the barge were discussed. Drilling holes in the sideshell using a remotely-operated drill was considered the most viable option.

The hydraulic drill was set in place by the crane barge George T and a single one-inch hole was drilled in each of the five wing tanks. Over time, the pressure in the tanks was relieved and the sideshell of the barge was flat. The wing tanks were then inerted by the introduction of a nitrogen blanket, significantly decreasing the possibility of an explosion.

Enter the Divers
Once T&T Marine started to roll the barge upright, it was found that the bow rolling wire was out of position. At this point, the pH readings were near neutral throughout the water column and divers were permitted to enter the water and shift the wire.

During the dives, monitors with pH probes were stationed around the diver and the pH of the water column, particularly near the bottom, was continuously monitored. The diver also carried an independent pH probe. If any of the readings dropped below 5.0, the diver was immediately removed from the water.

The diver confirmed that the barge had settled onto the bottom and was sitting on timber piles. An airlift was utilized to dig a hole under the bow of the barge. High concentrations of hydrogen sulfide were detected when the airlift was started, but they gradually subsided.

The diver again entered the water using a jet to finish the hole and run the rolling wire into position. T&T etablished a decontamination station on the stern of the barge adjacent to the dive ladder. Upon exiting the water, the diver was flushed with a spray of water while on the dive ladder and then stepped into a decon pool where the pH of the diver's dress was tested. Pallets of soda ash were on hand in case it became necessary to neutralize any acid. Once the pH of the diver's dress was confirmed to be neutral, the diver was allowed to doff the hat and suit.

Time to Lift the Barge
Everyone involved with the project was concerned that the corrosion was so severe that the barge could structurally fail before or during the salvage operation. Picking a barge up by each end puts the highest stresses in the center of the vessel, but running the wires anywhere but the ends of the barge would cut the cargo tank top, release more acid, and further reduce the structural integrity of the barge.

To everyone's relief, the barge rolled upright without an incident. Pumping operations commenced as the cargo was pumped into the harbor in a metered release. The US Coast Guard, EPA, NOAA scientists, Fish and Wildlife, and the owners had decided that it was unacceptable to pump the diluted cargo into another barge and risk starting another reaction. Even a vessel, tank truck, or rail car with a stainless steel liner would not be sufficient protection, given the various concentrations of the sulfuric acid.

Finally, more than a week after the nightmare had begun, enough cargo had been offloaded to stabilize the barge. It was then towed to a Houston shipyard to dispose of the remaining 64,000 gallons of diluted cargo. Just another week in the life of a salvage contractor. UW

Tom Flesner is project manager and salvage master for T&T Marine Salvage in Galveston, Texas. He has over 30 years of experience in marine salvage, participating in over 250 recovery projects. Tom was a commercial diver for 26 years, and was salvage master for the salvage of Cal Dive's capsized Balmoral Sea and the oil recovery project on the SS Union Faith. He is the salvage and diving adviser for the Houston/Galveston Area Committee for the National Planning and Response System.