At approximately 0445hrs on 7 July 2009, a tank began releasing ethyl acrylate vapors at the Dow Chemical Plant located in Hahnville, St. Charles Parish, Louisiana. The odors spread for at least 15 miles to the east into metropolitan New Orleans.
The tank had been taken out of service for maintenance and contained residual liquid ethyl acrylate and polymerized solid poly ethyl acrylate. The leak was detected when plant workers detected the odors. Further investigation revealed the the tank was heating up, and water was added to cool the tank and contents. At approximately 0530 hours the roof of the tank began to fail, releasing more vapors. Dow notified the St. Charles Parish Emergency Operations Center (EOC) at 0700 hours, and approximately 30 residents were evacuated. River Road (La Hwy 18) was closed near the plant. Twelve individuals were reported to have gone to area hospitals for treatment. All of them have been released.
Dow sprayed foam onto the contents of the tank to suppress vapors. Louisiana Department of Environmental Quality (LDEQ) and Louisiana State Police (LSP) responded to the site. Dow and LDEQ conducted air monitoring with flame ionization detectors (FIDs).
Although the PEL is 25ppm, the odor threshold is 0.001 ppm with an acrid, irritating odor.
EPA mobilized to the site at 1630 hours. EPA met with state and local officials, as well as representatives of Dow. EPA provided air monitoring support in the neighborhoods downwind of the plant. All EPA readings were less than 2ppm above background.
Dow's Incident Action Plan (IAP) involved maintaining a foam blanket to suppress vapors, conduct area and community air monitoring, and neutralize and empty the contents of the tank. Dow added a sodium hydroxide solution to the tank to neutralize the contents. The sodium hydroxide reacts with the ethyl acrylate to form sodium acrylate and ethanol. These products are less volatile and have higher odor thresholds. When the contents are neutralized and the odors have been contained, Dow will remove the contents from the tank for disposal. The tank contains an estimated 100,000 gallons of material including ethyl acrylate, polymer, caustic, water, and firefighting foam.
Dow will continue to maintain a foam blanket, conduct air monitoring, and neutralize the tank contents. EPA and LDEQ will continue to conduct air monitoring until the situation is stabilized.
Approximately 30 residents remain evacuated. River Road (La Hwy 18) remains closed near the plant.
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