Corona Del Mar Water Treatment Plant - Executive Summary |
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SECTION 112(r) RISK MANAGEMENT PLAN FACILITY: GOLETA WATER DISTRICTS CORONA DEL MAR WATER TREATMENT PLANT EXECUTIVE SUMMARY FACILITY DESCRIPTION The Goleta Water Districts (Goleta WD) Corona Del Mar Water Treatment Plant (CDMWTP) began operating in 1974. The plant treats raw water received from the Cachuma Reservoir for municipal water use. The treatment processes are designed to oxidize, disinfect, and remove suspended matter, such as clay particles and algae in the raw water, in order to meet California State Drinking Water Standards. The design capacity of the plant is 24 million gallons per day (mgd) with a peak capacity of approximately 36 mgd. A gaseous chlorine system is used for oxidation and disinfection of the raw water. A gaseous sulfur dioxide system is used periodically for dechlorination purposes. The plant is equipped with chlorine and sulfur dioxide gas detectors. FACILITY WILL DISCONTINUE USAGE OF ARPP-REGULATED CHEMICALS BY JANUARY 2000 The fa cility will discontinue the use of gaseous chlorine and sulfur dioxide before January 2000. The existing gaseous chlorine system will be replaced by an aqueous sodium hypochlorite system, which will not be subject to either the PSM or ARPP rules. Sulfur dioxide will not be used for dechlorination after January 2000, so the existing sulfur dioxide system will be removed. CHEMICALS CURRENTLY SUBJECT TO ARPP RULE AS OF JUNE 1999 As of June 1999 CDMWTP uses the following chemicals that are stored in quantities large enough to trigger the Environmental Protection Agencys Accidental Release Prevention Program (EPAs ARPP) and Californias Accidental Release Prevention Program (Cal ARPP): Chlorine One-ton cylinders of liquid chlorine are delivered to the plant by truck. A maximum of 8 one-ton chlorine cylinders are stored onsite. Goleta WD also periodically stores several 150 pound chlorine cylinders for other remote facilities. Sulfur Dioxide One-ton cylinders of liquid sulfur dioxide are delivered to the plant by truck. A maximum of 2 one-ton sulfur dioxide cylinders can be stored onsite. At the present time sulfur dioxide is stored but not used at the CDMWTP. The chemical storage room also has enough trunions to store an additional 6 one-ton cylinders of either chlorine or sulfur dioxide. ACCIDENTAL RELEASES DURING PAST 5 YEARS The CDMWTP 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 CDMWTP is subject to OSHAs Process Safety Management (OSHA PSM) regulations for all equipment and operations associated with its chlorine and sulfur dioxide systems. Goleta WD developed a formal safety program as part of Californias Risk Management and Accident Prevention Program in 1994. The safety program includes the following: Review of the design of all equipment and controls for the chlorine and sulfur dioxide sy stems to ensure they are properly designed and installed. A Process Hazard Analysis to evaluate safety issues. Training for all operators and maintenance staff. 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 inspections. Development of an emergency action plan. EMERGENCY RESPONSE PROCEDURES The Goleta WD uses its Emergency Action Plan for the CDMWTP to provide step-by-step procedures for emergency response in the unlikely event of an accidental release. The key elements of the response plan are as follows: All plant staff are trained in the specific elements of the program. The plant uses a combination of chlorine and sulfur dioxide detectors, audible alarms and visual alarm lights to alert the staff of a potential accident. In the event of a large release, the plant would immediately contact the Santa Barbara County Fire Department, who would conduct HazMat emergency response. 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. The Toxic Endpoint Concentrations for various compounds were specified by EPA, and are generally concentrations that would cause no physical harm but could interfere with peoples ability to leave the area. The Toxic Endpoint Concentrations for the RMP chemicals at the CDMWTP 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 temperat ure) is imported to the site by truck and stored in a one-ton containers for use in the oxidation/disinfection process. The Administrative Worst- Case Release Scenario assumes that the entire contents of one of the chlorine cyliners (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) that would result in minimal dispersion of the 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 onto 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 mile downwind distance. The worst-case dispersing gas cloud would not impact any densely 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 ground outside the chemical 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. To be conservative it was 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 onto the ground. Th e thermodynamic properties of chlorine dictate that 12% of the spilled chlorine 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 chlorines boiling point temperature (-29 degrees F), forming a puddle of chlorine ice. To be conservative it was assumed that 60% of the spilled chlorine ice would evaporate in the first 30 minutes. The rate of evaporation would decrease as the chlorine ice puddle shrank. Of the 1,000 pounds of liquid spilled from the dropped cylinder, 649 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 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 scarcely reach the facility boundary. Alternate Release Scenario for Sulfur Dioxide The Alternate Scenario for sulfur dioxide is identical to the one for chlorine: a 1-ton cylinder is dropped onto the ground, spilling 1,000 pounds of liquid sulfur dioxide that forms an ice puddle that slowly evaporates. The thermodynamic properties of sulfur dioxide dictate that 10% of the spilled liquid would immediately flash to a vapor, after which the spilled liquid would chill to its boiling point temperature of 14 degrees F. It was assumed that 60% of the remaining spill would evaporate in the first 30 minutes. 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 clou d 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 scarcely reach the facility boundary. Filename: execgole.txt |