Santee Cooper Regional Water System - Executive Summary |
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Executive Summary ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Santee Cooper Regional Water System's accidental release prevention and emergency response policies show that the SCRWS 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 emergency recognition, evacuation routes, emergency medical treatment and procedures for notifying local emergency response personnel (i.e., Fire Department, etc.). It is the RWS's policy to implement appropriate measures to prevent possible releases of regulated substances. STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED The SCRWS has only one (1) regulated substance at the facility above the thr eshold quantity. The regulated substance is chlorine with a threshold quantity of 2,500 pounds. Chlorine is utilized as a disinfectant in the water treatment process. The chlorine is received at the facility in one ton containers. The maximum inventory of chlorine containers stored on site at the SCRWS does not exceed sixteen (16). The SCRWS is mandated to meet Program 3 requirements of the RMP rule. HAZARD ASSESSMENT The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as the "Worst case" and "alternative case ". 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. Santee Cooper Regional Water System chose to use DEGADIS+ to perform the air dispersion consequence modeling due to the nature of the chemical and the relea se scenarios. The worst case release scenario submitted for SCRWS involves a catastrophic release from a one ton cylinder (2,000 lb.) of chlorine in a gaseous form over 10 minutes. The chlorine is stored in an enclosed building; therefor, passive mitigation was taken into account. The mitigated release rate was calculated to be 110 lb/min. The worst case release was analyzed at class F atmospheric stability, 1.5 m/s wind speed, 100.00F, 75.8% relative 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 slow leak at a partially open valve body of a one ton container (2,000 lb.) of chlorine. The partially open valve released the entire contents of the chlorine in a gaseous form. The chlorine is stored in an enclosed building; therefore, passive mitigation was taken into account. The mitigated release rate was calcul ated to be 4.4 lb/min. The alternative release was analyzed at Class D atmospheric stability, 3.0 m/s wind speed, 660F, 75.8% relative 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 when chlorine is released at such a high rate, the chlorine will most likely freeze over the opening in the container which would prohibit more gas from escaping the cylinder. Also, it is not appropriate to compare a 10 minute release to a one hour 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, since a person can withstand a certain concentration over a one hour period with no health effects, they could withstand a higher concentra tion 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 such allowance in the RMP rule by the EPA to make this adjustment. ACCIDENTAL RELEASE PREVENTION AND CHEMICAL SPECIFIC PREVENTION Santee Cooper Regional Water System has taken all the necessary steps to comply with the accidental release prevention requirements set out under 40 CFR part 68. 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 performed, date 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 SCRWS 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. FIVE-YEAR ACCIDENT HISTORY The SCRWS has had and 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. EMERGENCY RESPONSE PLAN The Santee Cooper Regional Water System has a written emergency response plan that deals with accidental releases of chlorine from the process. The plan establishes minimum requirements and procedures to follow during an after a chorine emergency. These procedures include adequate first aid and medical treatment, plant evacuation routes as well as proper notification of local emergency response official who will respond to an emergency (i.e., fire department, LEPC). PLANNED CHANGES TO IMPROVED SAFETY The last process safety hazard Analysis was performed in May 1999 and it resulted in several recommended changes at that time which have been noted and changed. |