Document 3NGvd5npqYb2wmjzyRVaJjRo0

ABDOO133324 4 CONDEA Vista Company Highway 25 Aberdeen, Mississippi 39730-0091 (601) 369-8111 July 7, 1999 CERTIFIED MAIL RETURN RECEIPT REQUESTED Z 559 721 840 Mr. Mohammad Yassin, PE Mississippi Department ofEnvironmental Quality Office of Pollution Control P. O. Box 10385 Jackson, MS 39289-0385 X Dear Mr. Yassin: As required by 40 CFR, Section 61.65 (a), this letter provides the details of a release of vinyl chloride monomer (VCM) from CONDEA Vista Company's Aberdeen, Mississippi PVC plant. At approximately 9:50 a.m. on July 6, 1999, a relief valve lifted on the vinyl chloride storage sphere resulting in a release of vinyl chloride to the atmosphere. The release was approximately 300 pounds. The storage sphere is used to store VCM unloaded from railcars. As the unloading operation was finishing the morning of July 6th, pressure increased in the sphere to just over 100 psig. The sphere is equipped with rupture disks under relief valves set to relieve at 100 psig. The release lasted approximately 10 minutes. During the release, the in-plant fixed point monitors detected little or no VCM, there was no visible vapor cloud, and no frost or ice was visible on the relief device. This indicates that the material relieved was mostly inerts (nitrogen). This also explains the excessive pressures that were experienced. The vapor pressure of VCM alone at the temperature during the release is <70psig. Although the investigation is still proceeding, preliminary indications are that one or more of the railcars offloaded that morning contained an excessive amount of inerts. To prevent future occurrences, we have added high-pressure shutdown interlocks that automatically stop the unloading operation in the event of high pressure. During the release and response activities, the area downwind of the release was monitored for vinyl chloride and no indications of significant quantities of vinyl chloride were detected beyond plant boundaries. The National Response Center was notified ofthe release. Although there were no off-site impacts due to the release, the Mississippi Emergency Management P.O. Box 91 Aberdeen, Mississippi 39730-0091 ABDOO133325 Agency was notified as a courtesy. Sincerely, Environmental Manager CC: Richard Ball, MDEQ