City of Greer Water Treatment Plant - Executive Summary |
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The Greer CPW's Water Treatment Plant personnel continually strive to prevent unwanted or accidental releases of hazards 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 prevent or mitigate accidental releases. The Greer CPW Water Plant is located off S.C. Highway 14 on River Road, north of the City of Greer. This facility treats raw water from the South Tyger River to supply potable water for the City of Greer and surrounding areas. The plant operates under SCDHEC System ID #23009. Treatment processes include physical/chemical steps for solids settling and filtration, and chlorination for disinfection. Facilities in place to accomplish chlorination include pumping and chlorinator equipment to introduce a chlorine solution into the water stream. Chlorine for this process is stored on-site in ton cylinders. Normal operations include two cylinders on-line, with up to four spares in reserve. The on-line cylinders are manifolded together to a single vacuum regulator. 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 the largest vessel on site containing chlorine, resulting in a release of 2000 lb of chlorine in a 10-minute period. The analysis 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 1.3 miles from the release point, potentially affecting 1,400 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 40 people . The facility is equipped with chlorine detection 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 em ergency response program, which has been coordinated with the City of Greer 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. |