Recovery of a Toxic Cargo from a Sunken Tank Barge: Lessons Learned and Policy Implications

Based on the National Oceanic and Atmospheric Administration (NOAA) Remediation of Underwater Legacy Environmental Threats (RULET) study, dated March 2013, the tank barge ARGO sank during a storm on October 20, 1937.¹ The ARGO, O.N. 164617, measures approximately 120-ft by 35-ft with a depth of 12-ft. While no vessel drawings or specifications were available at the time of the assessment, the tank barge was described as a single-skin, steel, riveted hull design with eight cargo tanks, constructed in 1911. The total oil cargo carried, as reported in a 1937 newspaper article, was approximately 4,762 barrels (over 200,000 gallons) of “one half benzol and one half crude oil” (NOAA, 2013). Note, a catastrophic discharge of the cargo would equate to a major oil spill in the Great Lakes region.

Following the discovery of the sunken barge by the Cleveland Underwater Explorers, T&T Marine Salvage was contracted by the U.S. Coast Guard to conduct an assessment of the wreck at 41–38.359 N / 082–29.599 W in Lake Erie at a depth of approximately 50-feet of water. Based on diving operations conducted in October 2015, the sunken barge matched the length and width of the ARGO; however, it was discovered buried in bottom sediment with approximately 5-ft of hull visible above the mudline. Note, the barge was not in Canadian waters as originally predicted. In addition to being partially buried below the mudline, the tank barge was covered in heavy marine growth and no name markings were observed. Underwater visibility was less than one-foot at depth at the time of the assessment. Due to the limited visibility, the diving survey was required to be conducted hand-over-hand. The multi-day diver assessment ultimately revealed eight closed hatch covers aft and four open hatches forward. Sediment samples were collected in the open tanks as well as of the bottom sediment adjacent to the barge in an effort to determine if contaminants had migrated from the cargo tanks.

During the initial diving operations, a leak was detected from a rivet hole that allowed a small volume of cargo to be released. This release created an “immediately dangerous to life and health (IDLH)” atmosphere on the surface due to the high percentage of benzene and other volatile organic compounds in the cargo. Additionally, following diving operations, it was discovered that the toxic cargo quickly deteriorated the rubber valves on the diver’s drysuit and also etched the faceplate on the diver’s helmet. While the leak was quickly patched by the salvage crew, this discovery of the nature of the cargo transitioned the project from an assessment to a response operation. A comprehensive multi-agency Safety Plan was developed to complement the operational work plan. The primary objective was to protect workers from exposure to the cargo that, upon analysis, was characterized as 70% benzene, 22% toluene, and xylenes. Benzene is regulated as a carcinogen with low-level exposure limits (ACGIH TWA 0.5 ppm, ACGIH STEL 2.5 ppm, OSHA TWA 1 ppm, OSHA ST 5 ppm and IDLH 500 ppm). The U.S. Coast Guard National Strike Force and T&T Marine Salvage conducted comprehensive air sampling throughout the operation with evacuation protocols in place. Continuous air monitoring action levels included 10% LEL, 19.5–22% O2, 5 ppm volatile organic compounds, 0.5 ppm benzene, and 5 ppm H₂S. Air monitoring equipment included MultiRAE and BW GasAlertMicro five gas monitors and the UltraRAE 3000 PGM-7360 benzene and volatile organic compound (VOC) detector. Based on a multi-agency risk assessment, it was determined that divers should be fully-encapsulated in a chemically resistant drysuit mated to a positive pressure helmet. It was further determined that surface workers on the support vessels would be adequately protected wearing Self-Contained Breathing Apparatus (SCBA) as required by continuous air monitoring with splash resistant Tyvek suits and chemically resistant gloves (Level-B) supplemented with a personal flotation devices.

Based on the discovery of the eight closed cargo tanks, the Unified Command requested T&T Marine Salvage hot-tap each intact tank in an effort to recover any remaining cargo.³ The overall cargo offload operation was proposed in three phases:

A prototype installation was first completed on Cargo Tank 3P, the cargo tank that had previously leaked during the assessment, as a proof-of-concept prior to moving forward with the remaining cargo tank off-load operations. All operations were conducted in accordance with the Area Contingency Plan and coordinated with the Unified Command and Natural Resource Trustees, including the U.S. Coast Guard, U.S. Environmental Protection Agency and Ohio Environmental Protection Agency. Barge hot-tapping operations were designed and executed to minimize the further release of product from the sunken vessel.

The first phase of the project involved preparing the hull for hot tapping and the installation of a ball valve for hydraulic submersible pump connection and a standpipe with internal tank pressure monitoring device on each cargo tank. As such, two penetrations were made on each of the eight tanks: one to remove cargo and the other, with a non-return valve, to equalize the pressure during pumping operations. Prior to installing the valves and standpipes, commercial divers conducted low pressure removal of marine growth and prepared the steel tank tops for baseplate connections. Additionally, prior to penetrating the hull, thickness readings of the tank tops were taken with a Cygnus Ultrasonic Thickness Gauge to ensure the hull was capable of withstanding the penetrations and anticipated pressure differentials during operations.

All diving operations were conducted in accordance with the U.S. Coast Guard, Occupational Health and Safety Administration, and Association of Diving Contractors International guidelines and regulations, as well as the T&T Subsea Diving Safe Practices and Operations Manual. Divers were protected with a hydrocarbon/chemical resistant drysuit, mating gloves and boots, and positive pressure helmet. T&T Marine Salvage provided commercial diving, hot tapping, submersible pumping, pollution prevention, safety equipment, and experienced personnel to manage and execute the hot tapping and accessible cargo offload operations. A summary of marine salvage and diving personnel and equipment is provided in Table 1.

Once it was determined that the steel thickness was sufficient for installing the ball valves and standpipes, T&T Marine Salvage successfully used a historically proven and effective hot tapping system to remove material from the cargo tanks. The diver directed hydraulic hot-tap system includes a magnetic drill to mount base flanges with self-tapping bolts, a hot tap system that cuts 3-1/2” hull penetrations, the diesel driven hydraulic power unit, and associated hydraulic pumps, hoses, valves and flanges.

The procedure to hot tap a tank includes (1) cleaning the hull surface; (2) connecting the base flange with Teflon gasket to the hull using the magnetic drill to drive self-tapping bolts with Teflon wrap; (3) applying epoxy to the internal base flange and hull interface to prevent leakage; (4) installing a 4” ball valve assembly; (5) inserting the hot tap through the valve assembly and cutting the hull penetration; (6), removing the hull coupon and hot tap; and (6) securing the ball valve. Once the hot tap is removed and valve secured, the hydraulic submersible pump is connected to the assembly.

The second phase of the operation involved pumping cargo from the submerged barge to portable receiving tanks onboard a deck barge. Two types of hydraulic pumps were assessed during the operation: The MSP-300 hydraulic submersible pump and the Börger AL75 Rotary Lobe Pump. The MSP-300 hydraulic submersible pump is capable of a 300m³/hour and 100m head. It is constructed of stainless steel and can pump a wide variety of liquids, including Bunker C oil. While the MSP-300 has been successfully used on historical oil hot tapping operations, given the project requirements that included a potentially flammable cargo sensitive to static charge and toxic in nature, the AL 75 rotary pump was ultimately selected as it could be placed topside on the support barge, minimizing vibration at the connection points and allowing divers to quickly move hose fittings between tanks as opposed to requiring the pump to be moved by the diver on the bottom. The lobes on the AL 75 were replaced with chemical resistant Viton.⁴ The oil and chemical resistant discharge hose was constructed specifically for oil and chemical transfer operations and all hoses were tested prior to operations to at least 1.5 times the maximum allowable working pressure.

Prior to the commencing pumping operations, the receiving tanks and associated equipment were grounded and bonded to prevent static charges that could have potentially ignited the flammable cargo. The salvage team used a Declaration of Inspection procedure during this process in accordance with 33 CFR 156.150 to ensure all safety standards were met. With the unique nature of the transferred product, the team constantly monitored for potential static discharges and leakage during pumping operations.

To ensure the cargo tanks equalized during the cargo offloading operation, a standpipe with a non-return valve and pressure-monitoring device was installed on each cargo tank to be offloaded. To accomplish this task, a commercial diver installed the hot tap assembly discussed above followed by installing a pre-fabricated 2½ ″ nominal diameter standpipe fitted with a swing type check valve (one-way valve) at the free end. The standpipe’s lowest point was located at approximately 1’6 ¾” above bottom plate to avoid interference with bottom structural members as the bottom scantling arrangement of the barge was unknown. The check valve (one-way valve) installed at the free end of the standpipe reduced the possibility of product escaping from the tank during the installment. Teflon gaskets were installed at the entry point to the ball valve after installation to act as a sleeve to prevent the discharge of cargo during entry. The pressure within the tank, both before and during the cargo offloading process, was continuously monitored by a pneumo system pre-fabricated inside the standpipe as a total assembly. The pneumo was connected to a pressure gauge on deck and continuously monitored during offload operations. With the standpipe installation, each tank proved capable of self-equalizing during cargo offload operations. With this particular arrangement, water from the lake filled into the tank boundary via the standpipe opening at above main deck level, providing a self-equalizing system as the cargo floated to the discharge pump during the cargo offloading process.

Once the pump was connected, the product was pumped to the surface where it flowed through a manifold that included a sampling portal prior to discharging into a series of six 21,000 gallon receiving closed-top portable tanks designed for purpose. The six receiving tanks were placed onboard a deck barge inside containment with sorbent lining with a deck load capacity of 2,200 tons. The estimated weight of the six fully loaded receiving tanks was approximately 608 tons, less than one-third of the deck barge’s carrying capacity. The U.S. Coast Guard’s Salvage Engineering Response Team reviewed all calculations and plans.

Prior to loading, the receiving tanks were purged with nitrogen to mitigate potential explosive conditions from occurring inside the tank. This process involved displacement purging, utilizing nitrogen to “displace” hazardous atmospheres inside the receiving tank. This process typically followed the procedure outlined in Table 2.

A 500 cfm vapor treatment system was also installed on the six receiving tanks with a manifold. The connections to the tanks were placed at the highest point at the 3” connection. A 500 cfm blower provided a vacuum to the header and all six tanks. The vapors were sent to a two stage activated vapor carbon system with the vessels operating in series. The carbon units were 10,000 lb vessels equipped with sample ports, gauges, and proper valves for operation. A 10-foot stack was placed on the treatment vessel to exhaust the treated vapors to atmosphere. Once secure connections were established with the port or starboard tank to be transferred, and pumping operations commenced, a stationary monitor was placed on the deck adjacent to hose connections and/or adjacent to the vapor recovery and treatment system. Continuous air monitoring action levels included 10% LEL, 19.5–22% O2, 5 ppm volatile organic compounds, 0.5 ppm benzene, and 5 ppm H2S. As a contingency, though never required during the operation, if elevated readings were detected using the MultiRAE and BW GasAlertMicro five gas monitors and the UltraRAE 3000 PGM-7360 benzene and VOC detector, engineering control changes to transfer operations and donning appropriate respiratory protection to check/inspect hose connections to treatment unit were outlined. Once a tank was filled, to limit head space, the pressure relief valve was discharged through the vapor recovery system, and then a technician wearing Level B personal protective equipment and personal floatation device with continuous air monitoring collected a representative sample of the receiving tanks contents. The spent carbon was disposed through the regeneration process and certificates of destruction were provided. Once the tanks were loaded, the barge was towed to a designated facility where the receiving tanks were offloaded and transported for proper disposition.

Throughout the operation, T&T Marine Salvage maintained oil spill response equipment onboard the support vessels on-site, including 1,000 feet of containment boom, Foilex weir skimmers, and sorbent booms and pads. Portable tanks were maintained on-site as a contingency for temporary storage of any recovered oil. Two oil spill response boats were also on ready standby with additional containment boom and oil spill response equipment onboard. At least one response boat remained on-site during underwater hot tap and transfer operations. An additional response trailer was also staged with 2,400-feet of additional containment boom; two double-drum skimmers with associated hoses, hydraulic power units, and air compressors; and multiple bales of sorbent pads and boom. Given the flammability of the cargo, a portable fire pump was placed onboard the barge and ready for operations.

The salvage team was successful in safely pumping the remaining and accessible cargo from the sunken tank barge ARGO. Based on the salvage team’s experience, the following lessons learned and recommendations were developed in an effort to improve future subsea response operations:

1. Operational Planning: Projects such as the ARGO and the other high priority sunken wrecks identified by NOAA that remain on the seabed require coordinated operational planning. On the ARGO project, the salvage company worked effectively within the Unified Command construct, coordinating operational planning with the U.S. and Canadian Coast Guards, U.S. Environmental Protection Agency, NOAA, and State of Ohio, among other governmental agencies. However, due to the prevalent winter weather and associated limited weather windows for operations, the Unified Command ultimately pushed to conduct around-the-clock diving and pumping operations to complete the project prior to the pending ice season. Based on this experience, future RULET projects should be planned in advance of leakage so that responders are not compelled to push operational limits in an effort to protect public health and the environment. For example, NOAA’s two top priority sunken wrecks, the GULFSTATE with an estimated worst case discharge of 86,000 barrels of crude oil (18 times the ARGO worst case discharge) thought to be located off the Florida Keys, and the ESSO GETTYSBURG with an estimated worst case discharge of 132,000 barrels of crude oil (27 times the ARGO worst case discharge) thought to be located offshore Savannah, Georgia, have yet to be located. Of note, the Argo was charted in Canadian waters, until it was discovered by chance and found to be leaking in U.S. waters. Given the potential magnitude of these worst-case discharges and the associated potential environmental impacts, it would be prudent to manage the crude oil offload operations in a planned, controlled manner as opposed to after the wrecks begin to leak or catastrophically discharge a large volume of oil.

2. Focus on Safety: The ARGO project involved multiple safety concerns including the toxic cargo (70% benzene, 22% toluene and xylenes) which created “immediate dangerous to life and health (IDLH)” atmospheres when released. Of note, based on a NOAA analysis, a catastrophic release of the barge’s contents, given an easterly wind, would have potentially affected a population center, adversely impacting public health and safety. Additional hazards included diving operations, cold and heavy weather, and heavy lift and boat operations. Operations required top-side personnel to conduct continuous air monitoring and often don self-contained breathing apparatus, and, as discussed previously, divers to wear fully-encapsulated, positive-pressure diving suits. Based on this project, it is imperative to select qualified and experienced contractors to perform high-risk subsea recovery projects. For example, in addition to divers experienced in contaminated water operations that are also certified Hazardous Waste Operations and Emergency Response (HAZWOPER) responders, personnel should also be certified in First Aid, CPR and AED standards, and also OSHA Qualified Riggers. Crane operators should, for example, be certified in accordance with the National Commission for the Certification of Crane Operators (NCCCO) standards. In addition to contracting highly qualified and experienced personnel, a comprehensive safety plan with on-site safety oversight should be developed and implemented. The National Strike Force (NSF), Coast Guard’s Salvage Engineering Response Team (SERT), NOAA Scientific Support Coordinator (SSC), and District Response Advisory Team (DRAT) were critical in ensuring the safety of the responders and public.

3. Marine Salvage Industry: Based on the ARGO project and historical case studies, traditional Oil Spill Removal Organizations (OSROs) often do not have the capabilities demanded to conduct subsea operations. Westerholm and Lloyd note “the technological complexities of attempting lengthy, industrial style work underwater will require a vastly different collection of experts, equipment, and operational plans than those commonly used for oil spill response” (Westerholm and Lloyd, 2008). Following the response to a non-floating oil release in the Mississippi River, Sawyer et al observed “…although OSROs are well versed and skilled in on-water oil spill containment and recovery, the designated salvor was better positioned with greater breadth of expertise for allocating resources and implementing/managing tactics for sunken oil recovery” (Sawyer et al, 2017). As such, experienced and qualified marine salvage and commercial diving contractors should be contracted to perform subsea oil and hazardous material recovery operations.

In 2016, three months after the completion of the ARGO project, the U.S. Coast Guard issued new requirements for contractors to develop a capacity to recover sunken and submerged oil at all ocean depths, now collectively referred to as “non-floating oil” (U.S. Coast Guard, 2016). The Coast Guard’s new OSRO requirements were based, in part, on the American Petroleum Institute’s 2016 ,Sunken Oil Detection and Recovery Technical Report and Operational Guide (API, 2016).

With this new classification of qualified contractors, the U.S. Coast Guard and potentially affected State, local and tribal governments should coordinate a national initiative to address the highest priority submerged wrecks identified in the NOAA RULET assessment. Considering the top ten RULET priority wrecks have nearly a million barrels or three times the oil discharged during the EXXON VALDEZ incident, as noted in the lessons learned, the time to address these potentially polluting wrecks is before a leak occurs. As the majority of these ship wrecks are a result of World War II era incidents, the potential for release increases with time. Many of the wrecks, such as the JOSEPH M. CUDAHY that was torpedoed and sank off the coast Florida in 1942 and the COIMBRA that was torpedoed and sank in Long Island Sound that same year, are already leaking. As noted in a 2014 analysis on advancements in underwater oil detection and recovery operations, such an initiative would further advance subsea oil detection and recovery techniques, and help in advancing national submerged oil detection and recovery capabilities (Elliott and DeVilbiss, 2014).