Saluda Lake Water Treatment Plant - Executive Summary |
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RISK MANAGEMENT PROGRAM EXECUTIVE SUMMARY Easley Combined Utilities Saluda Lake Water Treatment Plant The Easley Combined Utilities, South Carolina (ECU) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. This policy complies with all the applicable requirements of section 112(r) of the Clean Air Act (CAA) and all applicable procedures of the Environmental Protection Agencys Risk Management Program (RMP). The ECU Risk Management Program involves the preparation of response plans that are tailored to each facility. The Saluda Lake Water Treatment Plant and Middle Branch Wastewater Treatment Plant are facilities owned by the ECU that exceed the OSHA Process Safety Management Program (PSM) (29 CFR 1910.119) threshold limit of 1500 pounds for Chlorine (CAS: 007782-50-5). These facilities are manned and are required by 1910.119 to establish a PSM program. The ECU has implemented a PSM program that is unique to each facility. Presently, all the facilities exceed the threshold limit of 1500 pounds of chlorine established by CAA 112r, therefore, each facility has implemented a Risk Management Program based on CAA 112r Program 3 requirements. Each facility has special characteristics such as number of employees, hours the facility is manned, density of the surrounding population, and public receptors that required the ECU to develop RMP for each of the facilities. The facilities use many technological and managerial practices that are not unique, in fact, are common in the water and wastewater treatment industry. Liquid chlorine is delivered to each of the facilities 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 potable water to form a solution of hypochlorite. The solution is piped to contact chambers for the purpose of disinf ecting water and wastewater. The equipment at each facility includes a tank storage area, chlorinator room that contains the chlorinators, flow recorders, various safety equipment, and electrical panels. A compete listing of equipment, along with block flow diagrams, and pipe and instrumentation diagrams are included in the ECU PSM for each 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 model was performed for each facility based on the RMP COMP VER. 1.06. The RMP COMP PROGRAM was used to determine the distance trave led by the chlorine released before its concentration decreases to the " toxic endpoint" selected by EPA of 3 ppm or 0.0087 mg/L, 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 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 individuals 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 RELEASE SCENARIO The worst case release scenario for Saluda Lake Water Treatment Plant 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. The facility has containment walls so that 0.55 mitigating factor was calculated for passive mitigation. The mitigating factor would reduce the rate of release to 110 lb/min. This includes the following conditions: rate of release 110 lb. per minute, urban conditions, f stability, 1.5 meters per second wind speed, 0.0087 toxic endpoint. When using the RMP COMP analysis the distance to a toxic endpoint is 0.9 miles. When the RMP COMP analysis 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 for each of the faci lities are as follows: Saluda Lake Water Treatment Plant: population affected 141; schools 0; business and industry 6; parks and recreation 2; environmental 0. ALTERNATIVE RELEASE SCENARIO The alternative release scenario for the Saluda Lake Water Treatment Plant involves the rupture of the flexible connections (pigtails) connected to a ton cylinder. The pigtail connection is moved during normal tank change over and could possible fatigue causing it to fail. In addition, the pigtail connection requires manual articulation resulting in the possibility of human error. The failure of a pigtail would allow chlorine gas to escape through a 3/8 inch opening resulting in the release of 960 lbs. of chlorine over a 60 minute release period (16 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 o f Tt (tank temperature-kelvin) x GS (gas factor). Based on results of the RMP COMP analysis which assumes a 60 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 16 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 case scenario for the Saluda Lake Plant are as follows: population affected 4; schools 00; business and industry 0; parks and recreation 0; environmental 0. MITIGATION Actuation of the chlorine detector would cause the on duty operator to respond to the alarm. The response of the operator would take 60 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 a piping rupture. ACCIDENTAL RELEASE PREVENTION PROGRAM The A ccidental Release Prevention Program at all the ECU facilities is based on the elements of the OSHA PSM Program. The PSM Program is a comprehensive and detailed toxic chemical management program that is available for inspection at each of the ECU facilities. 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 Sheet which includes information on the hazardous and toxic properties of chlorine Chemical-specific steps include the availability of full face respirators and self-contained breathing apparatus (SCBA), worn by the operators worn by operators during tank change outs and alarm response Chlorine detectors at all storage areas ACCIDENTAL RELEASES No accidental 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, which 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 detailed 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. The initial Process Hazard Analysis was conducted for this facility as required by the Process Safety Manage ment Program and can be found in the PHA section of that program. |