When Hurricanes Hit, Storage Tanks Can Float-Archimedes' Principle at Work

Arbitration, North America

Hurricane shutdown plans with respect to storage tank inventories can prevent tanks from floating during a flood surge. Baker & O'Brien investigated events leading to an oil spill and the adequacy of procedures vis-à-vis the prevailing standard of care. After submitting our report, the matter was settled.

When a hurricane approaches, with the potential for a storm surge or severe flooding, refiners must ensure that there is an adequate inventory level in each storage tank. This is to prevent tanks from floating off their foundations due to something called "Archimedes' Principle." In simple terms, this principle states that there will be a net upward force on an object if the weight of the water it displaces exceeds its own weight (i.e., the object will rise until the forces equalize, after which it will float).

In a case in which Baker & O'Brien became involved, a refiner had a hurricane shutdown plan that addressed the need for minimum tank levels to avoid potential tank flotation. However, one large crude oil tank-with a diameter almost the length of a football field-was inadvertently left only about 10% full. When the storm surge came, this tank floated off its foundation and struck a concrete abutment, which tore a hole in the bottom of the tank. There was no oil spill initially because the storm water flowed into the tank through the hole. When the flood waters receded, however, and the tank eventually settled to the ground, crude oil was noticed spilling from the tank.

Baker & O'Brien was engaged to investigate the incident and the sequence of events leading up to the oil spill. We were also asked to review the refiner's emergency shutdown procedures and assess whether they were adequate relative to the prevailing standard of care in the industry. Finally, we were asked to provide an opinion as to what other preventive measures, if any, could have been taken to avoid the oil spill. Our forensic analysis of the data and sequence of activities identified some alternative actions that may have served to prevent or minimize the spill. For example, one option might have been to open a valve and allow the inventory level in several of the large crude oil tanks to equalize. Although an arbitration was filed against the refiner, the matter was settled prior to the panel convening.

Charles J. Hirst

Executive Vice President

Petroleum Refining / Transportation and Storage
Standard of Care / Insurance Claims / Litigation / Arbitration / Operations and Maintenance
North America