Hurricane Harvey caused a great deal of destruction due to flooding and shutting down power around the Gulf Coast. While cleanup efforts continue, details of chemicals released during and after the hurricane provide some lessons to be learned in securing an above ground storage tank.
The Associated Press has identified at least 34 above ground storage tank and tank battery failures during Harvey. Such spills resulted in the release of more than 600,000 gallons of combined crude oil, gasoline, and other chemicals. The largest spill reported was 461,000-gallons of gasoline from an above ground tank in Galena Park, a Houston suburb. While most of the spill was held by the containment berms of the Magellan Midstream Partners storage tank farm, some gasoline did escape. Nevertheless, less than 20% of the gasoline spilled was recovered. The rest either evaporated or soaked into the ground. The company has started the soil cleanup process.
The biggest offender to permit releases was floating roofs used on above ground storage tanks. Exxon Mobil, Shell, Valero, and Kinder Morgan all reported floating roof tank failures that resulted in the release of chemicals. The floating roofs are designed to minimize how much a fossil fuel is lost to evaporation by the roof rising and falling depending on the volume of the tank.
A study done after the 2005 hurricanes of Katrina and Rita concluded that these roof designs are susceptible to buckling and becoming dislodged during hurricanes. The above failures from hurricane Harvey further support this conclusion. With the East Coast being prone to hurricanes on an annual basis, these failures beg the question of the whether floating roofs can be designed to withstand hurricane forces.
Based on the failure reports, the issue with the floating roofs is their inability to withstand the weight of significant water sitting on the roof. So likely design fixes would either involve making the structural integrity of the roof stronger to withhold more weight or a method to dispose of water on the roof in a faster manner. Time will tell if such needed engineering will be done.
Keeping gases processed or used at natural gas and petrochemical facilities at a particular temperature in an above ground storage tank was also an issue reported during hurricane Harvey. Such gases pose risk of explosion when not refrigerated. This is what happened at the Arkema petrochemical plant in Crosby, Texas. The facility lost power and their backup generators failed due to flooding. Explosions resulted and 500,000 pounds of organic peroxides burned, releasing over 2,000 pounds of carbon monoxide and 3,000 pounds of volatile organic compounds.
Due to the volatility of such gases and the hazard of their release, better methods need to be in place to maintain power during hurricanes. While hurricane Harvey was a record setting storm, climate change will likely bring more same-sized or larger challenges to the hurricane prone East Coast.
