City of Myrtle Beach SWTF and WRF - Executive Summary |
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EXECUTIVE SUMMARY FOR THE CITY OF MYRTLE BEACH'S SURFACE WATER TREATMENT FACILITY AND WATER RECLAMATION FACILITY ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The City of Myrtle Beach's accidental release prevention and emergency response policies show that they are 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 Myrtle Beach's policy to implement appropriate measures to prevent possible releases of regulated substances. STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED The City of Myrtle Beach's Surface Water Treatment Facility and Water Reclamation Facility are considered as one stationary source for the purposes of RMP. EPA defines a stationary source as any "buildings, structures, equipment, installations or substances emitting stationary activities which belong to the same industrial group, which are located on one or more contiguous properties, which are under the control of the same person (or persons under common control), and from which an accidental release may occur." The two facilities belong to the same industrial group, are located on contiguous properties and are under control of persons under common control; therefore, the City of Myrtle Beach's Surface Water Treatment Facility and Water Reclamation Facility meet the requirements to be classified as a single stationary source. The City of Myrtle Beach uses one (1) regulated substance at both facilities above the threshold quantity. The regulated substance is chlorine with a threshold quantity of 2,500 pounds. Chlorine is used in both the water and wastewater treatment processes. Chlorine is handled in one ton cylinders and the maximum amount of chlorine handled at each facility is 30,000 pounds. The City of Myrtle Beach is mandated to meet Program 3 requirements. HAZARD ASSESSMENT 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 Myrtle Beach 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 the City of Myrtle Beach involves a catastrophic release from a one ton cylinder (2,000 lb.) of chlorine in a gaseous form over 10 minutes. The chlorine at the Surface Water Treatment Facility is enclosed; therefore, a release from the plant would be mitigated passively (reduced by 45%). However, the chlorine storage area at the Water Reclamation Facility is not enclosed; therefore, a release from this plant would be considered worst case since there would not be any passive mitigation. The worst case release rate was calculated to be 200 lb/min. The worst case release was analyzed at Class F atmospheric stability, 1.5 m/s wind speed, 98 F, 73% 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 full valve failure in a one ton cylinder (2,000 lb.) of chlorine inside the chlorine feed area which is enclosed. The failure released the entire contents of chlorine in a gaseous form thro ugh the 1" diameter opening. The mitigated alternative release rate was calculated to be 62.15 lb/min. The alternative release scenario was analyzed at Class D atmospheric stability, 3.0 m/s wind speed, 63.5 F, 73% 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 ho ur 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 The City of Myrtle Beach 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 facilities 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 City of Myrtle Beach Surface Water Treatment Facility and Water Reclamation Facility have excellent records of preventing accidental releas es over the last five years. Due to the effective release prevention policies, there have been no accidental releases during the last five years at the Surface Water Treatment Facility and only one accidental release during the last five years at the Water Reclamation Facility. No one was seriously injured in the accidental release and the operating procedures have been modified to prevent the release from occurring in the future. EMERGENCY RESPONSE PLAN The City of Myrtle Beach facilities have 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 Hazard Analysis was performed in January 1995. The Process Hazard Analy sis resulted in no recommended changes at the Surface Water Treatment Facility and a few recommended changes at the Water Reclamation Facility at that time. The Water Reclamtion Facility has replaced the chlorine hoist, chlorinators and modified the chlorine header line due to the recommended changes. |