At approximately 0445 hrs 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.
Although the PEL is 25ppm, the odor threshold is 0.001 ppm with an acrid, irritating odor.
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).
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 maintained a foam blanket to suppress vapors. Dow added a sodium hydroxide solution to the tank to neutralize the contents. The sodium hydroxide reacted with the ethyl acrylate to form sodium acrylate and ethanol. These products are less volatile and have higher odor thresholds.
The evacuation order and the road closure of River Road (La Hwy 18) were lifted at 1530 hrs on 8 July.
Dow began transferring material from the tank into rail cars at approximately 2000 hours on 8 July. By 0600 hours on 9 July, three rail cars had been filled. At approximately 0900 hours on 9 July, St Charles Parish EOC received numerous reports of odors in surrounding neighborhoods. EPA and LDEQ air monitoring detected no readings greater than the 5ppm TLV. Dow added more water and sodium hydroxide to neutralize any remaining ethyl acrylate. DOW continued to maintain a foam blanket to suppress vapors.
EPA participated in a press conference held at the St Charles Parish courthouse on 9 July to update the public on the situation.
EPA and LDEQ discontinued air monitoring as of 2000 hours on 9 July. Dow took over all air monitoring at that time.
EPA demobilized from the site at 2000 hours on 9 July. LDEQ continued monitor activities at the site.
EPA tabulated all FID air monitoring data collected by EPA, LDEQ, and Dow through the morning of 13 July.
Dow continues to remove the material in the tank. LDEQ continues to monitor Dow activities.
EPA has demobilized from the site. Dow has taken over air monitoring from LDEQ and EPA. The St. Charles Parish EOC remains on alert status.
|
