Horse Creek Pollution Control Facility - Executive Summary |
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EXECUTIVE SUMMARY FOR HORSE CREEK POLLUTION CONTROL FACILITY ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES Aiken County Public Service Authority's (PSA) accidental release prevention and emergency response policies show that the Horse Creek Pollution Control Facility 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 Aiken PSA's policy to implement appropriate measures to prevent possible releases of regulated substances. STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED The Horse Creek Pollution Control Facility has two (2) regulated substances at the facility above the substance's threshold quantity. One regulated substance is chlorine with a threshold quantity of 2,500 lb. Chlorine is used in the wastewater treatment process at the facility. Chlorine is handled in one ton cylinders and the maximum amount handled is 20,000 pounds. The other regulated substance is sulfur dioxide with a threshold quantity of 5,000 lb. Sulfur dioxide is used in the wastewater treatment process at the facility. Sulfur dioxide is also handled in one ton cylinders and the maximum amount handled is 8,000 pounds. Aiken PSA is mandated to meet Program 3 requirements. HAZARD ASSESSMENT The offsite consequence analysis includes consideration of two different types of 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 unsp ecified failure. One worst case release is required to be reported for all regulated toxic substances. Therefore, chlorine is reported as the worst case release scenario since it resulted in a greater offsite distance than the worst case release of sulfur dioxide. The alternative release is defined by EPA as a release that is more likely to occur than the worst case release. One alternative release scenario is required to be reported for each regulated toxic substance. Therefore, one alternative release is reported for chlorine and one alternative release is reported for sulfur dioxide. Aiken PSA 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 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 rate would be 200 lb/min. The worst case release was analyzed at Class F atmospheric stabi lity, 1.5 m/s wind speed, 103 F, 71% 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 resulted in offsite impact. The alternative release scenario for chlorine involves a lead washer failure on a one ton cylinder (2,000 lb.) resulting in the release of gas through the opening. The lead washer failure released the entire contents of chlorine in a gaseous form. The alternative release rate would be 16.2 lb/min. The alternative release scenario was analyzed at Class D atmospheric stability, 3.0 m/s wind speed, 62.9 F, 71% 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 for chlorine did go offsite, but did not result in any offsite impact. The alternative release scenario for sulfur dioxide involves a fusible plug failure on a one ton cylinder (2,000 lb.) resulting in the release of gas through the 3/4-inch opening. Th e fusible plug failure released the entire contents of sulfur dioxide in a gaseous form. The alternative release rate would be 30.4 lb/min. The alternative release scenario was analyzed at Class D atmospheric stability, 3.0 m/s wind speed, 62.9 F, 71% humidity and 0.1 m surface roughness for the maximum distance to the toxic endpoint of 0.0078 mg/L (3 ppm). The alternative release for sulfur dioxide resulted 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 releas e 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. ACCIDENTAL RELEASE PREVENTION AND CHEMICAL SPECIFIC PREVENTION Aiken PSA 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 Horse Creek Pollution Control 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. FIVE-YEAR ACCIDENT HISTORY The Horse Creek Pollution Control 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. EMERGENCY RESPONSE PLAN The Horse Creek Pollution Control 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 treatment, evacuations, and notification of local emergency response agencies and the public. PLANNED CHANGES TO IMPROVED SAFETY The last Process Safety Hazard Analysis was performed in May 1999 and it resulted in one recommended change at that time. Since the PHA, PSA has ordered and will install a warning/alarm system with remote alarms and sensors. |