City of St. Helena Waste Water & Reclamation Plant - Executive Summary |
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FEDERALLY MANDATED RMP SUBMISSION EXECUTIVE SUMMARY 1. Accidental Release Prevention and Emergency Response Policies The City of St. Helena uses chlorine and sulfur dioxide at the Wastewater Treatment Facility (CSH-WWTP). The chlorine and sulfur dioxide stored in the Chemical Storage Building are liquefied gases under pressure and are considered hazardous materials; Chlorine gas and sulfur dioxide gas are also Regulated Substances under the California Accidental Release Program (CalARP). The Napa County Environmental Health Division recognized the CSH-WWTP as a Stationary Source under the CalARP regulations and requested this Risk Management Plan (RMP). The County of Napas policy is to adhere to all applicable Federal and State of California rules and regulations. Safety depends upon proper construction design and safety features of the facility, accurate operating and emergency procedures, and effective training of personnel. 2. Stationary Source and Regulated Substances Th e Chemical Storage Building at CSH-WWTP is a masonry-wall / wood-roof structure located at #1 Chaix Lane in St. Helena, California. As a Stationary Source, there are two Federally Regulated Processes. The chlorine process includes chlorine gas unloading and storage, a chlorinator, and the chlorine injector. The sulfur dioxide process includes sulfur dioxide unloading and storage, a metering/mixing device, and the sulfur dioxide injector. When either the chlorine gas or the sulfur dioxide gas is dissolved in water, it is no longer a Regulated Substance in the CalARP. The chlorine gas and the sulfur dioxide gas is trucked to the facility in one-ton containers. Four one-ton containers of chlorine and one one-ton container of sulfur dioxide are stored in the Chemical Storage Building; Two of these one-ton containers of chlorine are connected to the chlorinator and one one-ton container of sulfur dioxide is connected to the metering/mixing device. The two remaining containers of chlo rine are kept in reserve. After the chlorine gas is dissolved in water in the chlorinator and the sulfur dioxide gas is dissolved in the meting/mixing device, the chlorine in solution and the sulfur dioxide in solution are conveyed in separate underground conduits to the chemical injection point (contact chamber). 3a. Worst Case Release Scenario The Worst Case release scenario for interconnected equipment must consider the largest quantity of a regulated substance handled on site in a single vessel at any time, taking into account administrative controls on the vessels contents and usage as per the CCR Title 19 Division 2 Chapter 4.5 Article 2 Section 2750.3(b). Preliminary modeling results indicated that a release of chlorine gas would result in a longer distance to the endpoint than would the sulfur dioxide gas. One of the four 2,000-lb chlorine containers is considered the largest vessel in the chlorine feed system. The one-ton container is, at most, filled with 2,000 lb o f liquid chlorine. The Worst Case release scenario for the one-ton container is the release of the entire capacity at a rate of 200 lbs per minute for a ten-minute duration. The distance to the 3 ppm end point (0.0087 mg/L) would extend beyond the boundaries of the stationary source. 3b. Alternative Release Scenario The Alternative Release scenario for the one-ton container is complete failure and separation of a quarter-inch fuse plug in the end of the container. All 2,000 lbs of chlorine is assumed to flash to vapor. The distance to the chlorine end point of 3 ppm (0.0087 mg/L) would extend beyond the boundaries of the stationary source. The distance to the sulfur dioxide end point of 3 ppm (0.0078 mg/L) would extend beyond the boundaries of the stationary source. 3c. Administrative Controls Administrative controls to limit the distances for each reported scenario exist to restrict, to a minimum, the amount of chlorine lost from a one-ton container if an accidental release were to occur; and preferably to not have a release occur. These administrative controls are inherent in the operational procedures for the chlorine unloading process system and the training provided to the operators. Administrative controls are also in place for the regulated processes. 3d. Mitigation Measures Mitigation measures to limit the distances for each reported scenario exist to restrict the amount of chlorine released to a minimum, if a release were to occur; and preferably to not have a release occur. The mitigation measures are based on the design, inspection, testing, and maintenance of the regulated processes and their related equipment and components. 4. General Accidental Release Prevention Program and Chemical Specific Prevention Steps The facility complies with all applicable Federal and State codes and regulations. There are safety meetings and safety training. The Process Safety Management (PSM) program implemented at the facility for the regulated process es and their related activities and equipment represents the facilitys main active commitments to an accidental release prevention program. 5. Five Year Accident History There have been no accidental releases of regulated substances within the last five years. 6. Emergency Response Program The Emergency Response Program is based upon the alerting of personnel at the facility to evacuate or shelter-in-place and await the arrival of responders from the local area responder at the assembly location if a release occurs that causes the evacuation or the shelter-in-place to be initiated. 7. Planned Changes To Improve Safety Current applicable codes and regulations are reviewed as part of the Process Hazard Analysis element of the Process Safety Management (PSM) program to determine if commitments need to be made to achieve increased operational safety for the regulated processes. These commitments address prevention and mitigation measures for accidental releases of the regulated sub stances. The completion schedules for these commitments are included in the PSM. |