Wright Smith, Jr. Wastewater Treatment Facility - Executive Summary |
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The Mobile Area Water and Sewer System (MAWSS) operates the Wright Smith, Jr. Wastewater Treatment Facility located at 1879 Conception Street Road in Mobile, Alabama. At the treatment plant, the facility stores approximately six (6) one-ton cylinders of chlorine. The one-ton cylinders of chlorine are used on-site as a disinfectant in the treatment of wastewater. In addition, there are four (4) one-ton cyinders of sulfur dioxide stored on-site. The one-ton cylinders of sulfur dioxide are used on-site for dechlorination of the wastewater effluent before discharge. The Wright Smith, Jr. facility has a minimum of 3 and a maximum of 13 employees on duty at any given time. Daily inspections of the areas storing and/or using chlorine and sulfur dioxide are conducted by the facility employees. The area that stores the one-ton cylinders of chlorine and sulfur dioxide is fully enclosed and is equipped with a caustic scrubber for control of a chlorine release. The caustic scrubber system is equ ipped with chlorine and sulfur dioxide that will automatically activate the scrubber system if a chlorine or sulfur dioxide concentration of 3 ppm or greater is detected. In addition, MAWSS has installed emergency valve actuators on the chlorine and sulfur dioxide cylinders which will shut off flow from the cylinders within 1.5 seconds after detecting a leak. In preparation of the Risk Management Plan (RMP), both worst-case and alternative scenarios were considered. Under worst-case scenario conditions, a catostrophic event would occur releasing a full one-ton cylinder. The radius of the potentially impacted surrounding area would be 1.3 miles. This scenario is highly improbable and did not consider the mitigation of a release by the enclosure, the emergency valve actuators, or the scrubber system. A more probable release event would occur if a transfer hose connecting the chlorine or sulfur dioxide cylinders to the chlorinator/dechlorinator was to fail. This scenario was the alterna tive scenario considered in the development of the RMP. This release event for both chlorine or sulfur dioxide would have a potential impact radius of less than 0.06 miles from the site. This scenario accounted for the mitigation factors inherent by the enclosed building, an operable caustic scrubber system, and the functioning emergency valve actuators. The Wright Smith, Jr. facility had one accidental release in the last five (5) years. There were no off-site impacts or people evacuated as a result of this release. In the event a significant releases occurs, the Mobile County Emergency Management Agency (MCEMA) would be notified immediately to respond. The MCEMA would dispatch experienced HAZMAT personnel trained to handle such situations. |