Tosches Creek Wastewater Treatment Plant - Executive Summary |
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The City of Union's Tosches Creek Wastewater Treatment Plant personnel continually strive to prevent unwanted or accidental releases of hazardous materials from their facility. Policies in effect relate to operations and maintenance of equipment, ongoing employee training, emergency response planning and coordination with appropriate local response agencies. These policies are embodied in the Risk Management Plan and OSHA Process Safety Manual, which together provide the means to comply with the City of Union's Policy on Safety and Environmental Affairs", which follows. The City of Union is committed to conducting its operations so as to minimize risk to the safety and health of employees, the public and the natural environment. It is the policy of the City that: * Employees shall consider safety and protection of the environment when performing all assignments, and will continually strive to eliminate unnecessary operating hazards, reduce risks and conduct work activities in c ompliance with all requirements. * Work places will be monitored to ensure that safe operating conditions are maintained. Personal protective equipment will be available and must be used. Procedures used by our employees and, where applicable, our agents, vendors and/or contractors, will be evaluated with the goal of ensuring safe handling. * Accidents and incidents will be investigated immediately, with action taken promptly to prevent recurrence. * Facilities will be designed, equipped and staffed with safety and environmental controls a primary concern. * Engineering controls, careful operating practices and continual training and education of employees will be employed to minimize generation of hazardous wastes. Wastes generated will be managed in an environmentally sound and legally acceptable manner. * Outside contractors will provide evidence of appropriate levels of insurance or other financial assurance for comprehensive general liability, professional liability a nd environmental impairment. Contractors entering our property will follow applicable requirements of the City's hazard communication program. Your personal commitment to this policy will provide a double check on its success. In case of any conflict in interpretation of the policy, contact your supervisor. The Tosches Creek WWTP is located off S.C. Hwy. 49 just to the west of the City of Union. This facility treats domestic and industrial wastewaters for subsequent discharge into Fairforest Creek under NPDES Permit No. SC0047244. Treatment processes include solids screening, extended aeration with return activated sludge, clarification and disinfection. Disinfection is accomplished by chlorination of the plant effluent just prior to discharge. Facilities in place to accomplish this task include pumping and chlorinator equipment to provide a chlorine solution at rates proportional to discharge flow rates. Chlorine for this process is stored and handled on-site in ton cylin ders. Normal operations include two cylinders on-line, with one spare in reserve. The on-line cylinders have individual vacuum regulators, and are manifolded on the vacuum side with automatic switchover to the chlorination equipment. Chlorine is the only regulated substance maintained on-site in quantities above the regulated threshold limit. The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative scenario". The first scenario is defined by 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 unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario". The worst-case release scenario involves a failure of two ton-cylinders which are manifolded together, resulting in a release of 4000 lb of chlorine in a 10-minute period. The ana lysis is followed by conditions pre-defined by EPA, including use of the one-hour average ERPG-2 as the toxic endpoint, wind speed of 1.5 meters per second, atmospheric stability Class F, appropriate temperature/humidity values, ground-level release, urban topography and related variables. Based on the above conditions, utilizing EPA's RMP Guidance for Wastewater Treatment Plants, the worst-case toxic endpoint occurs at a maximum distance of 1.9 miles from the release point, potentially affecting 1800 people. The alternative release scenario involves the rupture of the flexible connector (pigtail) to one of the cylinders. Assuming a hole with a diameter of one inch (conservative), the chlorine release rate is approximately 150 pounds per minute. Utilizing EPA's pre-defined conditions (wind speed 3 m/s, atmospheric stability Class D), the maximum toxic endpoint occurs at 0.2 miles from the release point, potentially affecting 10 people. The facility is equipped with chlorine de tection equipment, which is an active mitigation measure. Both scenarios are based on prescribed assumptions. In an actual release event, the plume of gas would be more elliptical than circular and extend downwind and/or downgradient, likely affecting a smaller area and population than the models predict. The general accidental release prevention program is a multi-faceted effort configured to comply with both EPA's RMP and OSHA's PSM rules. Key elements include a high level of employee training, an aggressive equipment maintenance routine, detailed operation procedures, hazard reviews and management controls. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), awareness of the hazardous and toxic properties of chlorine, and the presence of chlorine detection equipment. No accidental releases of chlorine have occurred at this facility in the past five years. The facility has an emergency response program, which has been coor dinated with the City of Union Fire Department, which is a member of the Local Emergency Response Planning Committee (LEPC). The program includes itemized response steps including notification instructions. Emergency action drills are conducted annually. Continual evaluation of technology and operations are performed to identify improvements that may help prevent or mitigate accidental releases. |