T.L. Amiss Water Purification Plant - Executive Summary

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The T.L. Amiss Water Purification Plant is a surface water treatment facility that supplies drinking water to the City of Shreveport.  Following conventional treatment, the water is dosed with chlorine and ammonia to form chloramines, providing a long-lasting disinfectant residual in the distribution system.  Historically, chlorine and ammonia have been provided in the gaseous form due to low cost and ease of operation.  During the last five years, there have been no reportable accidents associated with the use of chlorine gas and ammonia gas.  The hazard assesment performed for the risk management program revealed several areas of concern, most of which have already been remedied by plant personnel.  However, the results of the initial evaluation performed for the risk management program indicate that disinfection process evaluations should be performed and carefully measured against the inherent risk of using gaseous chlorine and ammonia gas during the upcoming design effort for reha 
bilitation of the T.L. Amiss Water Purification Plant. 
The worst case release scenario for chlorine gas suggests that a radius of 3 miles around the facility could be affected should a one-ton chlorine cylinder rupture.  Persons within this zone could potentially be exposed to a 3 ppm concentration of chlorine gas, assuming wind speed was 1.5 meters per second and the stability of the atmosphere was classified as "F".  From U.S. census data, the population per square mile in Shreveport, Louisiana is approximately 194.3 persons per square mile, indicating that approximately 5,500 persons could potentially be affected during the worst case release scenario of chlorine gas.  Several schools and hospitals are located within this radius of concern.  It should be noted, however, that the actual population affected would most likely be much less than this since almost one-fourth of the area of concern is the unpopulated area of Cross Lake itself. 
The alternative release scenario for chlorin 
e gas that could be more likely to occur would involve a tubing failure, bad connection, or valve failure resulting in the release of chlorine gas through a 5/16-inch diameter valve body opening.  This scenario could potentially affect a radius of 0.56 miles or almost 50 persons.  The circle of concern does not include any schools or hospitals or other public recptors outside of residential dwellings. 
Similarly, the alternative release scenario for ammonia gas that could potentially occur could result from a liquid leak from a tank truck unloading hose.  Assuming a liquid pool forms and a vapor release occurs for ten minutes, the affected radius would be less than 300 feet and would not affect persons off-site. 
Current safety, training, operation, and maintenance practices at the T.L. Amiss Water Treatment Plant follow the guidelines set forth in the risk management program.  Deficiencies noted during the hazard review are presently being addressed.  Procedures documenting compliance 
with the legislation provided in 40 CFR 68.48 through 60 are provided in a three-ring binder located in the chemical safety coordinator's office at the plant.  It will be the chemical safety coordinator's task to perform the compliance audit every three years and update this document as required.
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