On Friday July 29, 2011, at approximately 8:00 am, the chlorine gas monitors at the Weyerhaeuser plant in Longview, Washington detected chlorine gas near the two 130,000 gallon 1% Chlorine Dioxide tanks. At the same time, workers noticed that one of the tanks was leaking chlorine dioxide solution through a flange. The liquid was being captured by secondary containment, however some of the solution was converting to a green cloud of chlorine gas. Workers were moved out of the area which was then cordoned off with red "Danger" banner tape.
Around 9:30 am, the incident was reported to the NRC and on-site workers started applying a mist of water to the area to prevent the formation of chlorine gas. At the same time, ten responders from the Cowlitz 2 Fire and Rescue Department arrived on-site. From 12:30 pm to 3:00 pm, the Fire Dept. applied water to the area to prevent the formation of chlorine gas. Chlorine dioxide liquid leaking from the tank and fire fighting run-off water were captured in secondary containment and directed to the on-site water treatment facility.
The plant modified their paper-making process to pull a larger volume from the leaking tank in order to draw down the liquid level as fast as possible. At 2:33 pm, the liquid level in the tank dropped below the leaking flange and the leak slowed to almost a stop. The company plans to do a failure analysis once the pressure has been bled from the tank.
WDOE Spill Responder Curt Piesch arrived on-site at 1:20 pm and EPA OSC Kathy Parker arrived at 1:50 pm. START arrived on site at 3 pm. EPA conducted air monitoring for chlorine at the property perimeter and at the day care center across Industrial Way from the plant. All perimeter monitoring results were non-detect. EPA detected a concentration of 0.35 ppm chlorine gas in the air near the leaking valve at around 4 pm.
The company issued a news release that was picked up by "The Daily News Online - Serving the Lower Columbia" and posted at their website at 6:30 pm that night.
