Ventura Water Reclamation Facility - Executive Summary |
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SECTION 112(r) RISK MANAGEMENT PLAN FACILITY: CITY OF SAN BUENAVENTURAS WATER RECLAMATION FACILITY EXECUTIVE SUMMARY FACILITY DESCRIPTION The Ventura Water Reclamation Facility (VWRF) was originally constructed in 1958 to treat predominantly domestic wastewater generated within the City of San Buenaventuras (City) service area. Since 1958 the plant has been expanded several times to its current design capacity of 14.0 million gallons per day. The VWRF provides secondary treatment followed by effluent filtration, chlorination/dechlorination and discharge to the Santa Clara River Estuary. Effluent wildlife ponds are used for storage of chlorinated effluent prior to discharge. A portion of the effluent is reused for irrigation. VWRF employs a chlorination system for final effluent disinfection using chlorine gas and a dechlorination facility utilizing sulfur dioxide. The facility is equipped with chlorine and sulfur dioxide detectors and chlorine and sulfur dioxide s crubber systems. CHEMICALS SUBJECT TO EPAS ACCIDENTAL RELEASE PREVENTION PROGRAM The VWRF uses the following chemicals that are stored in quantities large enough to trigger the Accidental Release Prevention Program: Chlorine One-ton cylinders of liquid chlorine are imported to the facility by truck from a local supplier. A maximum of 30 one-ton chlorine cylinders are stored onsite in a building equipped with an emergency scrubber. Sulfur Dioxide One-ton cylinders of liquid sulfur dioxide are imported to the facility by truck from a local supplier. A maximum of 4 one-ton cylinders are stored onsite in a building equipped with an emergency scrubber. ACCIDENTAL RELEASES DURING PAST 5 YEARS The VWRF facility has not had any releases during the past 5 years that resulted in any injuries, off-site evacuations, or property damage. PROCESS SAFETY MANAGEMENT ACCIDENT PREVENTION PROGRAM The VWRF facility is subject to OSHAs Process Safety Management (PSM) regulations for a ll equipment and operations associated with its chlorine and sulfur dioxide systems. The City has developed a PSM safety program to minimize the potential for an accidental release. The PSM safety program includes the following elements: ? Review of the design of all equipment and controls for the chlorine and sulfur dioxide systems to ensure they are properly designed and installed. ? Updating of standard operating procedures to include specific information on safety procedures. All procedures must be reviewed and certified annually. ? Initial safety training and 3-year refresher training for all operators and maintenance staff. ? Procedures to ensure that all contractors receive the same level of safety training that the City provides for its own employees. ? Regular inspection of all equipment, monitoring systems and controls, with stringent documentation of all inspections. ? Prompt corrective action for any non-conforming items identified by the regular inspec tions. ? Rigorous safety reviews conducted prior to system startup, if any equipment or operations are modified. ? Stringent investigation of any incidents that have the potential to have caused chlorine or sulfur dioxide releases. ? Development of a plant-specific emergency action plan. ? Implementation of an employee participation program to ensure that all plant-wide staff are aware of the PSM program, and are actively consulted regarding safety issues. ? Independent audits of the entire PSM program and RMP program every three years. EMERGENCY RESPONSE PROCEDURES City staff utilizes its Emergency Action Plan to provide step-by-step procedures for emergency response in the unlikely event of an accidental release. The key elements of the Emergency Action Plan are as follows: ? All plant staff (including administrative and clerical staff) are trained in the specific elements of the program. ? The chlorine building and the sulfur dioxide building are equipped w ith electronic gas detectors and automatic emergency scrubber systems large enough to handle the entire contents of a 1-ton cylinder. The gas detectors have an audible alarm, automatically activate the emergency scrubber, and alert the Citys central operations control room. ? A team of engineers, supervisors and operators are trained, certified and equipped for hazardous materials (Hazmat) emergency operations to repair accidental releases. ? In the event of a large release, the facility would immediately contact the City of San Buenaventura Fire Department. The fire Department and the plants HazMat team would jointly conduct emergency response and repair the leak. CITYS RECENT STEPS TO IMPROVE SAFETY Based on recent safety reviews that were conducted as part of the evaluations for EPAs Accidental Release Prevention Program, the City has implemented the following actions to either reduce the likelihood or severity of potential chemical releases: ? Re-plumb the vent from the pressure safety relief valve on the sulfur dioxide system so it vents directly into the emergency scrubber. ? Update written operating procedures for the chlorine and sulfur dioxide systems to include PSM-required information. ? Upgrade signage and labeling on components within the chlorine and sulfur dioxide systems. ? Provide remote indication of chlorine and sulfur dioxide levels (i.e., SCADA) for monitoring purposes. ? Formalize employee training for loading/unloading cylinders, preventive maintenance program for scrubbers, city-wide tsunami policy, and emergency response plans. HYPOTHETICAL ACCIDENTAL RELEASE SCENARIOS The Risk Management Plan must assess the downwind impacts of hypothetical accidental releases. EPA requires facilities to model the distance that a plume of released gas would travel before it dispersed to an ambient concentration equal to the Toxic Endpoint Concentration. Toxic Endpoint Concentrations for various compounds w ere specified by EPA, and are generally concentrations that would cause no physical harm but could interfere with peoples ability to leave the area. Toxic Endpoint Concentrations for the RMP chemicals at the facility are 3 parts per million (ppm) of chlorine and 3 ppm of sulfur dioxide. In accordance with EPAs rule, the following hypothetical accidental release scenarios were developed: Worst-Case Release Scenario for Chlorine Liquid chlorine (chlorine gas that is stored as a liquid under pressure at ambient temperature) is imported to the site by truck and stored in one-ton containers for use in the disinfection process. The Administrative Worst-Case Release Scenario assumes that the entire contents of one of the chlorine cylinders (2000 pounds of chlorine) is emitted as a gas cloud in 10 minutes, during a period of exceptionally calm winds and stagnant atmospheric conditions (1.5 meter/second wind speed and F stability) which would result in minimal dispersion of t he gas cloud as it blew downwind. The thermodynamic properties of anhydrous chlorine indicate that such a large instantaneous gas release is probably impossible. If the entire 2000 lbs of liquid chlorine were somehow discharged from the container, it would spill on to the ground and immediately cool itself until it formed a puddle of chlorine ice, which would take much longer than 10 minutes to evaporate into a gas cloud. Nevertheless, the RMP rule dictates that the Worst-Case Scenario assumes the release of 2000 lbs of gaseous chlorine. Graphs from EPAs RMP Guidance for Wastewater Treatment Plants were used to calculate the downwind impacts. EPAs graphs indicate that the chlorine gas cloud would travel 1.3 miles before it dispersed to the 3 ppm Toxic Endpoint Concentration. Figure 1 shows a circle defined by the worst-case 1.3 miles downwind distance. Alternate Release Scenario for Sulfur Dioxide The Alternate Release Scenario for sulfur dioxide assumes that o ne of the 1-ton cylinders is dropped from the delivery truck onto the ground outside the dechlorination building. To be conservative it was assumed that the dropped cylinder lands on its weakest point, splitting a seam to cause an 8 x < crack. It was also assumed that the dropped cylinder comes to rest with the crack below the liquid level in the cylinder, allowing half of the liquid contents to immediately drain on to the ground. The thermodynamic properties of sulfur dioxide dictate that 10% of the spilled sulfur dioxide would immediately flash to a vapor that would form a dense cloud that could blow downwind. The thermodynamic properties also dictate that the spilled liquid would immediately chill to sulfur dioxides boiling point (14 degrees F), forming a puddle of sulfur dioxide ice. To be conservative it was assumed that 60% of the spilled sulfur dioxide ice would evaporate in the first 30 minutes. The rate of evaporation would decrease as the ice puddle shrank in size. Of the 1,000 pounds of liquid sulfur dioxide spilled from the dropped cylinder, 642 pounds would be emitted as a gas during the first 30 minutes. Graphs from EPAs RMP Guidance for Wastewater Treatment Plants were used to calculate the downwind impacts. EPAs graphs indicate that the sulfur dioxide gas cloud would travel only 0.1 mile before it dispersed to the 3 ppm Toxic Endpoint Concentration. Figure 1 shows a circle defined by the worst-case 0.1 mile downwind distance. The dispersing sulfur dioxide gas cloud would not reach any populated areas. Alternate Release Scenario for Chlorine The Alternate Release Scenario for chlorine assumes that one of the 1-ton cylinders is dropped from the delivery truck onto the floor inside the chemical building (the chlorine building is designed so the delivery truck is completely inside the building during unloading). To be conservative it was assumed that the dropped cylinder lands on its weakest point, splitti ng a seam to cause an 8 x < crack. It was also assumed that the dropped cylinder comes to rest with the crack below the liquid level in the cylinder, allowing 1,000 pounds of liquid chlorine to immediately drain on to the ground. The thermodynamic properties of chlorine dictate that 12% of the spilled chlorine (i.e., 120 pounds) would immediately flash to a vapor that would form a gas cloud. To be conservative it was assumed that the 120 pounds of initially-flashed gas escapes through the open bay doors. The gas detectors inside the chlorine building would detect the chlorine release, activate the emergency ventilation system and chlorine scrubber, and automatically close the bay doors. The thermodynamic properties of chlorine dictate that the remaining spilled liquid that did not immediately flash to vapor would immediately chill to chlorines boiling point (-29 degrees F), forming a puddle of chlorine ice. The ice puddle would slowly evaporate and the emergency scrubber would prevent any of this chlorine gas from escaping the building. Of the 1,000 pounds of liquid chlorine that leaked from the broken cylinder, only 120 pounds would be emitted to the outside air. Graphs from EPAs RMP Guidance for Wastewater Treatment Plants were used to calculate the downwind impacts. EPAs graphs indicate that the chlorine gas cloud would travel only 0.1 mile before it dispersed to the 3 ppm Toxic Endpoint Concentration. Figure 1 shows a circle defined by the worst-case 0.1 mile downwind distance. The dispersing chlorine gas cloud would barely reach the facility boundary. File execwwtp.doc |