Southeast Regional Wastewater Treatment Facility - Executive Summary |
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a. THE ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES - The Manatee County Southeast Regional Wastewater Treatment Facility accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. Applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to. The Manatee County emergency response policy is coordinated with the Braden River Fire Department and the Emergency Management Department. b. REGULATED SUBSTANCE HANDLED AT THE FACILITY - The Manatee County Southeast Regional Wastewater Treatment Facility, located at 3331 Lena Road, in Bradenton, Florida, serves to disinfect wastewater by the addition of chlorine. A maximum of twenty tons of pressurized liquid chlorine is stored at the facility in one-ton containers and a maximum of two one-ton containers is connected to the chlorination system at any time. Gaseous chlorine is withdrawn from the containers. T he facility is manned by 10 full time employees and there is always at least one person on site to respond to any trouble alarms which may occur. c. THE WORST-CASE RELEASE SCENARIO AND THE ALTERNATIVE RELEASE SCENARIOS - 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 an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario". Atmospheric dispersion modeling has to be performed to determine the distance traveled by the chlorine released before its concentration decreases to the "toxic endpoint" selected by EPA of 3 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). This is defined by the American Ind ustrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action." The residential population within a circle with a radius corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected". The worst-case release scenario involves a failure of a one-ton container containing 2,000 pounds of chlorine. EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, RMP*Comp default temperature (770F), and default humidity (50%) were used for the consequence analysis. EPA's RMP*Comp software was used for estimating the toxic endpoint distance. The results of the dispersion modeling parameters indicated that the worst-case scenario has offsite impacts. The alte rnative release scenario involves a release from a hole or crack in the one-ton container pressurized pigtail due to a defect or excessive wear. It is assumed that the crack developed in the < inch diameter pigtail corresponds to a hole of 0.0625-inch (1/16-inch) diameter. The control room would have been warned of the chlorine leak by the chlorine detectors installed at the chlorination facility. It is assumed that approximately 10 minutes would be required for operators or an emergency response team to respond. The amount of chlorine released is 6 lbs at an average rate of 0.6 lb/min over 10 minutes (the duration of the release). Toxic endpoint distance to ERPG-2 level has been estimated using RMP*Comp software. The results of the dispersion modeling analysis indicated that the alternative release scenario has offsite impacts. The meteorological conditions used were Stability D, wind speed 3.0 m/s, RMP*Comp default temperature (770F), and default humidity (50%). d. THE GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL SPECIFIC PREVENTION STEPS - The general accidental release prevention program is based on the following key elements: 7 Training of the operators 7 Preventive maintenance program 7 Use of the industry recommended process and safety equipment 7 Use of effective operating procedures 7 Performance of a process hazard analysis of equipment and procedures Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), worn by the operators during connection/disconnection of chlorine supply, awareness of the hazardous and toxic properties of chlorine, and presence of chlorine leak detectors. e. THE FIVE YEAR ACCIDENT HISTORY - No accidental releases of chlorine have occurred at this facility in the past five years. f. THE EMERGENCY RESPONSE PROGRAM - The facility has an in-plant emergency response program in place, which has been coordinated (reviewed) by the Braden River Fire Department, which is a member of the Local Emergency Response Planning Committee (LEPC). The facility is prepared to deal with an accident in the remote case one should occur. The employees are trained in ways to minimize the results. The plan includes an emergency response decision tree and a notification plan. Emergency response drills and drill evaluations are conducted every six months; emergency operation and response procedures are also reviewed at that time. g. PLANNED CHANGES TO IMPROVE SAFETY - A number of changes to improve safety (recommended actions) were identified in June 1999, when a process hazard analysis was performed for the chlorination equipment and procedures. It is expected that these recommended actions will be evaluated by December, 1999. The implementation of these recommended actions will further improve the safety of the chlorination system. |