Placerville Waste Water Treatment Plant - Executive Summary |
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RMP Executive Summary 1. Accidental Release Prevention and Emergency Response Policy The City of Placerville Wastewater Treatment Plant (WWTP) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and nagement practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adheared to. The WWTP emergency response program involves the preparation of response plans which are tailored to it's facility and to the emergency response services available in the comunity, and is in compliance with the EPA Emergency Response Program requirements. 2. Stationary Source and Regulated Substances Handled The WWTP chlorination/dechlorination station has been installed to disinfect treated wastewater. The station includes treatment plant offices, laboratory, chemical building, instrument rooms and chemical scrubber. The amount of chlorine and sulfur dioxide connected feed manifold are 1 one-ton cylinder of each chemical. There are a maximum of 8 one-ton cylinders of chlorine/sulfur dioxide in the chemical building. 3. Worst Case Release Scenarios and the Alternate Release Scenarios The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case release" and alternative scenario". Scenarios were conducted for both chlorine and sulfur dioxide releases. The first scenario is defined by EPA, which states the "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 release 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 and sulfur dioxide released before its concentration decreases to the "toxic enpoint" selected by EPA. These levels are the Emergency Response Plannning Guide line 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 irriversible 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 defined to estimate the population potentially affected. The works-case release scenarios at the WWTP involves 1) failure of a one-ton cylinder of chlorine; and, 2) failure of a one-ton cylinder of sulfur dioxide. The offsite consequence analysis for these scenarios was performed for the following conditions. The conditions are pre-defined by EPA, namely release of the entire amount of gas in 10 minutes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the populati on residing within a full circle with radius corresponding to the toxic enpoint distance. EPA set these conditions to facilitate the performance of the offsite consequence analysis. For the worst-case scenario, EPA manadated meteorological conditions, namely stability F, wind speed of 1.5 m/sec, temperature (25 degrees C), and average humidity (65%) were used. When atmospheric dispersion modeling charts were used for the worst case scenarios were performed using the EPA assumptions, Chlorine had a distance to toxic endpoint of 1.3 miles and an estimate of residential population potentially affected of 1000 was obtained. For sulfur dioxide, a toxic endpoint of 1.3 miles and an estimate of residential population potentially affected was 1000. The alternative release scenario involves the rupture of the flexible connectors (pigtails) connected to the one-ton containers. The amount of chlorine (and sulfur dioxide) released is 540 lbs. at an average rate of one hour (the duration of t he release) of 9.0 lbs. per minute. The meteorological conditions used were stabilty D, wind speed 3.0 m/s, average air temperature of 62 degrees F, and 63% average humidity. For chlorine, the estimated distance traveled to the toxic endpoint is .1 mile. For sulfur dioxide, the estimated distance traveled to the toxic endpoint is .1mile. This facility is provided with a chemical scrubber system that activates upon gas leak detection system. This scrubber system will contain any uncontrolled releases of chlorine or sulfur dioxide during normal conditions. The emergency response system is activated at the same time via a telemetry system to operators during normal working hours and off hours. 4. General Accidental Release Prevention Program The WWTP chlorine/dechlorination station accidential release prevention program is in compliance the the OSHA Process Safety Management (PSM) rule and this rule. It is based on the follwing key elements: * High level of training of the oper ators, * Preventive maintenance program, * Use of state-of-the-art process and safety equipment * Use of accurate and effective operating procedures, written with the participation of the operators * Performance of a hazard review of equipment and procedures * Implementation of an auditing and inspection program. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), awareness of the hazardous and toxic properties of chlorine and sulfur dioxide, presence of chemical leak detectors, and the use of a chemical scrubber system. 5. Five Year Accident History No accidental releases of chlorine or sulfur dioxide have occurred at this facility in the past five years. 6. Emergency Response Program The WWTP facility has an emergency response program, which has been coordinated with local emergency response agencies. Joint training drills are planned to be conducted withthe local fire departmetn on an annual basis. Emergency operation a nd response procedures are also reviewed at that time. 7. Planned Changes to Improve Safety There are no plans to improve safety of the WWTP facility at this time. The most recent safety improvement was the installation of the chemical scrubber, completed January 1999. |