Coneross Creek Treatment Facility - Executive Summary |
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RISK MANAGEMENT PROGRAM RISK MANAGEMENT PROGRAM EXECUTIVE SUMMARY Oconee County Sewer Commission The Oconee County Sewer Commission of Seneca, South Carolina (OCSC) accident release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. This complies with all the applicable requirements of section 112(r) of the Clean Air Act (CAA) and all applicable procedures of the Environmental Protection Agency's Risk Management Program (RMP). The OCSC Rick Management Program involves the preparation of response plans that are tailored to each facility. The Coneross Waste Treatment Plant is a facility owned by the OCSC that exceeds the OSHA Process Safety Management Program (PSM) (29 CFR 1910.119) threshold limit of 1500 pounds of Chlorine (CAS:007782-50-5). These facilities are manned and are required by 1910.119 to establish a PSM program. The OCSC has implemented a PSM program that is unique to this facility. Presently, the facility exceeds the threshold limit of 2500 pounds of chlorine established by CAA 112r, therefore, the facility has implemented a Risk Management Program based on CAA 112r Program 3 requirements. The facility uses many technological and managerial practices that are not unique, in fact are common in the water-wastewater treatment industry. Liquid chlorine is delivered to the facility in ton cylinders and placed in a tank storage area. Gaseous Chlorine, collecting in the top of the tank as a function of temperature, is piped off by a vacuum chlorinating system and injected into plant utility water to form a solution of hypochlorite. The solution is piped to contact chambers for the purpose of disinfecting wastewater. The equipment at this facility includes a tank storage area, chlorinator room that contains the chlorinators, feed indicators, various safety equipment, and electrical panels. A complete listing of equipment, along with block flow diagrams, and pipe and instrumentation diagrams are included in the OCSC PSM for the facility. The offsite consequence analysis, required by CAA, 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 based on EPA RMP*COMP V1.06 was performed for the facility. This program was used 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 Industrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is belie ved 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 is defined, "to estimate the population potentially affected". WORST CASE RELESE SCENARIO The worst release scenario for the facility involves a failure of a one ton cylinder (a total of 2000 lb. of chlorine). The conditions for the worst case scenario are pre-defined by EPA (release of the entire amount of gas in 10 minutes). The rate of release is equal to the amount in the cylinder divided by the time of the release or 2000 lb. / 10 minutes = 200 lbs. per minute. Since the facilities have containment walls, the release rate can be diminished by using the EPA passive mitigation factor of 0.55 or .55 x 200 = 110 lbs. per minute. EPA RMP*COMP V1.06 was use d to find the toxic endpoint based on a release of chlorine of 110 lbs. per minute. This includes the following conditions: rate of release rounded to 110 lb. per minute, urban conditions, F stability, 1.5 meters per second wind speed, 0.0087 toxic endpoint. . When using these EPA assumptions, the distance to a toxic endpoint is 0.9 miles. When the EPA RMP*COMP V1.06 for worst case scenario is used to obtain the distance endpoint of 0.9 miles, an area of concern can be determined in order to obtain an estimate of the population affected. In addition, other public receptors can be identified including schools, businesses, industries, and recreational facilities. The receptors identified for the worst case scenario at the Coneross Creek Treatment Facility are as follows: population affected 88; schools 0; business and industry 0; parks and recreation 0; environmental 0. ATERNATIVE RELEASE SCENARIO The alternative release scenario for the Coneross Waste Treatment Plant involves the mi salignment of the vacuum regulator valve that is connected to a ton cylinder. This connection requires the use of a lead or composite washer. Misalignment of the washer or improper torsion of the valve fitting could/would cause a leak. The leak would occur on the tank side of the vacuum regulator causing a pressure leak approximately equal to the tank pressure. This scenario would allow chlorine gas to escape through a 3/8 inch (or smaller) opening resulting in the release of 87 lbs. of chlorine over a 10-minute release period (8.70 lb/min). The calculation for the release rate is taken from the EPA reference guide, section 8.1 and is as follows: QR (release rate) = HA (hole area in square inches) x PT (tank pressure in pounds per square inch absolute (psia) x 1/square root of Tt (tank temperture-kelvin) x GS (gas factor). Based on EPA RMP*COMP V1.06, which assumes a 10 minute release, urban conditions, D stability, wind speed of 3.0 meters per second, toxic endpoint for chlorine of 0 .0087 and a release rate of 8.70 lb/min. The toxic endpoint would be reached in the alternative scenario at 0.1 miles or 528 feet. The receptors identified for the alternative release scenario for Coneross Waste Treatment Plant are as follows: population affected 0; schools 0; business and industry 0; parks and recreation 0; environmental 0. MITIGATION Even if the personnel responsible for the misalignment had left the tank storage area, actuation of the chlorine detector would cause the on duty operator to respond to the alarm. The response of the operator would take 10 minutes or less and is an active mitigation measure. An additional active mitigation system is the remote vacuum type chlorinators. This system will reduce significantly the amount of chlorine released in the case of piping rupture. ACCIDENTAL RELEASE PREVENTION PROGRAM The Accidental Release Prevention Program at the Coneross Plant is based on the elements of OSHA PSM Program. The PSM Program is a comprehens ive and detailed toxic chemical management program that is available for inspection at the Coneross Plant. The program includes the following accidental release prevention elements: / High level and continuous training of the operators / Preventive maintenance program / The use of accurate and effective operating procedures, written with the participation of the operators / The use of state of the art process and safety equipment. / Performance of a hazard assessment of equipment and procedures / Implementation of an auditing and inspection program / Continuous review of process information including study of Material Safety Data Sheets which includes information on the hazardous and toxic properties of chlorine / Chemical-specific steps include the availability of full-face respirators worn by the operators during tank change outs and self-contained breathing apparatus (SCBA) for alarm response. / Chlorine detectors at the storage area. ACCIDENTAL RELEASES No acci dental releases of chlorine occurred at this facility in the past five years. EMERGENCY RESPONSE PROGRAM This facility has an emergency response program, which is a requirement of the PSM program, this is a complete and comprehensive program. The program includes clearly defined prioritized emergency actions and notifications. Emergency drills are conducted on an annual basis and are coordinated with the local Emergency Preparedness Division. The complete detail plan is located in the plant office. HAZARD ANALYSIS Recent improvements to this facility include installation of windsocks, vacuum system, pipe and instrumentation diagrams and yard alarms, all of which were identified in the hazard analysis as needed improvements. |