City of Bishopville Wastewater Treatment Facility - Executive Summary

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Bishopville's accidental release prevention and emergency response policies show that the City of Bishopville is strongly committed to employee, public and environmental safety and adheres to all applicable regulations.  The comprehensive accidental release prevention program covers areas such as safety, hazard analysis, operating procedures, maintenance and employee training  associated with the processes at the facility.  The effective emergency response plan covers response procedures such as pre-emergency employee training, lines of authority, emergency recognition, evacuation routes and procedures and emergency medical treatment.  It is the City of Bishopville's policy to implement appropriate measures to prevent possible releases of regulated substances. 
The City of Bishopville Wastewater Treatment Faci 
lity has one (1) regulated substance at the facility above the threshold quantity.  The regulated substance is chlorine.  Chlorine is used in the wastewater treatment process.  Chlorine is handled in one ton cylinders and the maximum amount of chlorine handled is 4,000 pounds.  The City of Bishopville is mandated to meet Program 3 requirements. 
The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative scenario".  The worst case release scenario is defined by EPA as a release of the largest storage vessel over a ten (10) minute period due to an unspecified failure.  The alternative release is defined by EPA as a release that is more likely to occur than the worst case release.  The City of Bishopville chose DEGADIS+ to perform the air dispersion consequence modeling due to the nature of the chemical and the release scenarios. 
The worst case release scenario submitted for Bishopville 
involves a catastrophic release from a one ton cylinder (2,000 lb.) of chlorine in a gaseous form over 10 minutes.  The worst case release was analyzed at Class F atmospheric stability, 1.5 m/s wind speed, 103 F, 72% humidity and 0.1 m surface roughness for the maximum distance to the toxic endpoint of 0.0087 mg/L (3 ppm).  The worst case release did result in offsite impact. 
The alternative release scenario for Chlorine involves a fusible plug failure in a one ton cylinder (2,000 lb.) of chlorine.  The failure released the entire contents of chlorine in a gaseous form over 30 minutes. The alternative release scenario was analyzed at Class D atmospheric stability, 3.0 m/s wind speed, 61.4 F, 72% humidity and 0.1 m surface roughness for the maximum distance to the toxic endpoint of 0.0087 mg/L (3 ppm).  The alternative release did result in offsite impact. 
The alternative release is much more likely to occur at the facility than the worst case release scenario. The worst case release 
is unrealistic because at that high of a release rate, the chlorine will most likely freeze over the hole in the container which will prohibit more chlorine gas from escaping.  It is not appropriate to compare a 10 minute release to a one hour exposure time standard. The toxic endpoint concentration is based on a one hour exposure time, while the worst case release occurs over a ten minute period.  Therefore, the ten minute release period is used as the averaging time instead of one hour exposure time.  Realistically, if a person can withstand a certain concentration over a one hour period with no health effects, they could withstand a higher concentration over a ten minute period.  One solution would be to adjust the toxic endpoint value to correlate to the ten minute exposure during a worst case release instead of the one hour standard.  However, there is no allowance in the RMP rule by the EPA to make this adjustment. 
The City of Bishopville has taken all the necessary steps to comply with the accidental release prevention requirements set out under 40 CFR part 68 of the EPA.  The process is subject to the OSHA PSM standard under 29 CFR 1910.119 and is already in compliance.  The following steps are key to the prevention program: 
1. Detailed records of safety information describing the chemical hazards of chlorine, process technology, and process equipment. 
2. Comprehensive process hazard analysis are conducted to ensure that hazards are recognized and evaluated. 
3. Operating procedures have been developed and implemented which describe tasks to be preformed, dates to be recorded, operating conditions to be maintained, emergency operating procedures and safety and health precautions to be taken. 
4. Employee training program is in effect to ensure that the employees of the Bishopville Wastewater Treatment Facility are properly trained and aware of all safety practices, hazards, emergency procedures 
and maintenance procedures. 
5. An on-going mechanical integrity program is in place to ensure safe process operation. 
6. Incident investigation procedures are in place to ensure that all unplanned events affecting process safety are properly investigated in a timely manner to identify the causes of the incident and to implement corrective action. 
The City of Bishopville Wastewater Treatment Facility has had an excellent record of preventing accidental releases over the last five years.  Due to the effective release prevention policies, there have been no accidental release during the last five years. 
The City of Bishopville Wastewater Treatment Facility has a written emergency response plan to deal with accidental releases of chlorine and other hazardous materials, which has been coordinated with the local emergency response personnel.  The plan includes all aspects of emergency response including adequate first aid and medical tre 
atment, evacuations, and notification of local emergency response agencies and the public. 
The last Process Safety Hazard Analysis was performed in March 1999 and it resulted in no recommended changes at that time.
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