Jonesborough Water Treatment Plant - Executive Summary |
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1. The Town of Jonesborough Water Treatment Plant accidental release prevention policy involves an approach that integrates technologies, procedures, and management practices. This approach uses the Process Safety Plan, along with active and passive mitigation practices and procedures. 2. The Jonesborough Water Treatment Plant has storage capacity for four, one-ton cylinders of chlorine. This amount of chlorine is kept on-hand for use as a disinfectant in potable water treatment. The facility is normally manned 24 hours per day. 3. The off-site consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative scenario". The first scenario is defined by the Environmental Protection Agency, EPA, which states that "the owner or operator shall assume that the...maximum quantity in the largest vessel...is released as a gas over 10 minutes", due to an unspecified failure. The alternative scenario is define d as "more likely to occur than the worst-case release scenario". The worst-case release scenario at the Jonesborough Water Treatment involves a failure of one of the two sets of ton-containers, which are connected. The set of conditions pre-defined by the EPA for a total release of the two-cylinders over a 10-minute period resulted in a toxic end point of 2.3 miles. Within a radius of 2.3 miles is a total population of approximately 3,000 people who could potentially be affected. The alternative release scenario involves the total loss of the contents of a one-ton cylinder over a 60-minute period of time. Using the EPA pre-defined set of conditions resulted in a toxic endpoint of 1.7 miles. Within a radius of 1.7 miles resides an estimated population of 1,100 people who could potentially be affected. The area of chlorine storage and use is enclosed in a building and monitored constantly by chlorine detection equipment. The process equipment used in inherently safer by design than a gas under pressure system. There is a spring-loaded diaphragm at the cylinder valve, which is pulled open by an applied vacuum. Gas is then withdrawn from the cylinder for use as a disinfectant of potable water. The loss of the vacuum for any reason results in the diaphragm closing from energy contained in the compressed spring. This action effectively isolates the cylinder from all associated piping. 4. The general accidental release prevention program is based on the following key elements: - Training of the operators - Preventive maintenance program - Use of process monitoring and safety equipment - Constant assessment of equipment and procedures - Implementation of an inspection program Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), to be worn by certified emergency response personnel, 10-minute emergency escape self-contained breathing apparatus for operational personnel and visitors. Also , an awareness of the hazardous and toxic properties of chlorine, and the presence of a chlorine detector. 5. No accidental releases of chlorine have occurred at this facility in the past five years. 6. The facility has an emergency response plan, which has been reviewed by the Johnson City-Washington County Emergency Management Association. The facility is covered under a blanket aid agreement with the EMA, which covers all Washington County municipalities and utilities. 7. The Jonesborough Water Treatment Plant is planning the addition of automatic shut-off valves to be used in conjunction with the gas under vacuum type feed system. This should add an additional safety factor to our chlorine handling system. Additional training is planned for all operational personnel. This should keep at the forefront an awareness of chlorine safe handling and use. |