Yuba City Water Treatment Plant - Executive Summary |
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RMP Executive Summary 1. Accidental Release Prevention and Emergency Response Policy The Yuba City Water Treatment Plant (WTP) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhearde to. The WTP emergency response policy involves the preparation of response plans which are tailored to it's facility and to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program Requirements. 2. Stationary Source and Regulated Substances The WTP has been installed to disinfect treated water for potable purposes. The station includes treatment plant offices, a chlorination room, a chemical storage area, instrument rooms, and additional miscellaneous offices. The amount of chlorine connected to the manifold system is 1 one-ton cylinder. There are a maximum of 4 one-ton cylinders in the area with a maximum of one connected to the manifold. 3. Worst Case Release and the Alternative Release Scenario The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst cas release" and alternative scenario". The first scenario is defined by EPA, which states that "the owner or operator shall assume the the ... maximum quantity in the largest vessel ... is released as a gas over 10 munutes," 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 enpoint" 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 Asociation (AIHA) as the "maximum airborne concentrati on 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 helth effects or symptoms which could impair an individual's ability to take protective action." The residential population with a circle with a raduis corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected". The worst-case release scenario at the WTP involves a failure of the one- ton cylinder. The offsite consequence analysis for this scenario was performed for the following conditions. The conditions are pre-defined by EPA, namely release of the entire amount as a gas in 10 minutes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. EPA set these conditions to facilitate the performance of the offsite consequence analysis. EPA-mandated 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 for the worst case scenario was performed using the EPA assumptions, a distance to toxic endpoint of 1.3 miles and an estimate of residential population potentially affected of 7,000 was obtained. The alternative release scenario involves the rupture of the flexible connections (pigtails) connected to the one-ton cylinder. The amount of chlorine released is 900 lbs, at an average rate over one hour (the duration of the release) of 15.0 lb/min. The typical meteorological conditions used were Stability D, wind speed 3.0 m/s, average air temperature of 62 degrees F, and 63% average humidity. The estimated distances traveled to the toxic endpoint is .1 mile. Actuation of the chlorine leak detection system is an active mitigation measure used at this facility. As the facility is staffed 24 hours per day, this will alert on-site staff who can activate the emergency response plan. 4. General Accidental Release Prevention Program The WTP accidental release prevention program is in compliance with the OSHA PSM rule and this rule. It is based on the following key elements: * High level of training of the operators * 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 presence of chlorine detectors. 5. Five Year Accident History No accidental releases of chlorine have occurred at this facility in the past five years. 6. Emergency Response Program The facility has an e mergency response program, which has been coordinated with local emergency response agencies. Joint training drills are planned to be conducted with the local fire department on an annual basis. Emergency operation and response procedures are also reviewed at that time. 7. Planned Changes to Improve Safety A chemical scrubber system will be install at this facility, scheduled for completion December 1999. |