Feds issue final report on tank collapse
Volume 24, No. 4
Defective welds in a storage tank at a Chesapeake, VA, transfer facility resulted in the release of two million gallons of liquid fertilizer in November 2008 that flooded residential neighborhoods and reached the nearby Elizabeth River, a report issued by the U.S. Chemical Safety Board in May states.
The board recommended that the Commonwealth of Virginia regulate or authorize local jurisdictions to regulate the design, construction, maintenance and inspection of large fertilizer storage tanks located on the Elizabeth River.?
On Nov. 12, 2008, an aboveground storage tank catastrophically failed releasing two million gallons of liquid urea ammonium nitrate (UAN) fertilizer and seriously injuring two workers.?The release overtopped a containment dike and flooded sections of a nearby residential neighborhood, requiring remediation of the soil. At least 200,000 gallons of spilled fertilizer could not be accounted for, and some reached the nearby Elizabeth River, which flows into the Chesapeake Bay.
CSB investigators found that the tank involved in the accident - referred to as Tank 201 - had undergone welding work in 2006 as part of a project to strengthen four fertilizer tanks that were constructed in 1929 by replacing vertical riveted seams.
Contractors replaced the seams with welded plates with the intent of strengthening the joints.
"That in itself was not a mistake," investigations supervisor Robert Hall told IFW. "But we found that the welding was defective and that the company did not perform post-inspection radiography of the welds. Those defects went undetected."
?The CSB investigation found that the welding performed on the tanks did not conform with recommended industry practices, Hall said. Welds were found to have insufficient reinforcement, porosity and weld undercut.
Additionally when the tank was filled to its maximum capacity for the first time leaking joints revealed were not properly sealed.
"We are talking about a mixture that has a density of about 11 pounds per gallon compared to the typical five pounds per gallon for petroleum products," Hall told IFW. "It was a very heavy product that put a lot of stress on the tank."
The report noted that the U.S. Environmental Protection Agency regulates the safety of petroleum storage tanks, but liquid fertilizer and other non-petroleum tanks are regulated by individual states.?Virginia is one of 33 states that do not currently have regulations for liquid fertilizer tanks, the CSB said.
The transfer facility involved in the November incident has about 20 large storage tanks in the million to two million gallons range, Hall said. Fertilizer and petroleum products were transferred from barges to railcars and trucks.
Federal investigators found numerous welding defects in three other liquid fertilizer tanks included in the 2006 renovation. City officials ordered the company to drain one of those tanks.
Residential neighborhoods bordered the transfer terminal on two sides, Hall said. The concentrated fertilizer bleached and burned everything green.
"A number of residences had their yards flooded with liquid fertilizer," he said. "There is ongoing remediation to clean up their properties and restore them to pre-accident conditions." That remediation involves replacing the top layers of the soil.
Community leaders have requested $2.5 million in federal funds to help redevelop the affected area.
?In addition to calling for state action to regulate storage tanks, the Board urged the EPA to revise and reissue a safety bulletin on liquid fertilizer tank hazards and asked The Fertilizer Institute (TFI), a trade association, to urge member companies to require appropriate inspections of tanks used to store liquid fertilizer at terminal facilities.?
?In December 2008, the board issued an urgent recommendation calling on the same company to take immediate action to reduce the risk of a catastrophic failure of three tanks located at its facility -- one about 250 feet from the South Hill Neighborhood. The CSB also recommended that the company select an independent engineering firm to evaluate the specified tanks and within 30 days provide a report prepared by the independent tank engineering firm to the City of Chesapeake. ?The independent report resulted in the company significantly reducing the maximum liquid levels of the remaining tanks.
The CSB investigation identified sixteen other tank failures at nine facilities in other states between 1995 and 2008.?These sixteen failures resulted in one death, four hospitalizations, one community evacuation, and two releases into waterways.
CSB Board Member William Wark said, "By recommending regulation of similar storage tanks located on the Elizabeth River, we hope to protect not only communities and workers but also the vitality of the Chesapeake watershed."