Water Reclamation Facility - Executive Summary |
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A. Accidental Release Prevention and Emergency Response Policies The Padre Dam Municipal Water District, Water Recycling Facility (WRF) , has an effective and well implemented emergency response plan. This Plan has been developed and designed with the following in considerations: 1. To protect the lives of the WRF staff, support activities related to release prevention and mitigation, and to protect ANY public receptors within the toxic endpoints of an accidental release. 2. For the purpose of mitigating all potential releases from the WRF and to prevent injuries. 3. To minimize damage to property and to the surrounding environment. Padre Dam MWD has taken on an aggressive hazardous materials emergency response training program to prevent any potential releases from the Water Reclamation Facility. This activity has included the purchase of a 16' Hazmat Emergency Response Trailer which contains all the tools and communication equipment necessary for an effective response to a chemical release, a training program on emergency responses to hazardous material releases, and an annual hazardous materials emergency response drill coordinated with the Santee Fire Department, the City of San Diego Hazmat Unit and the County of San Diego Hazmat Unit. All personnel actively participate with the safety training and planning for the facility. The WRF's Hazardous Materials Business Plan as well as the safety plan provides the personnel organization and notification needed to effectively attend to chlorine and sulfur dioxide chemical release issues. The Emergency Response Plan identifies health hazards and mitigation procedures which will be implemented to respond effectively should an emergency situation arise. The plan is an active part of the operation of the WRF and as such is it updated on a regular basis and not less than once per year. All effort are made to ensure that the Plan meets compliance with the PSM, RMP, and CalARP regulations. Padre Dam Muni cipal Water District also maintains a safety committee that performs safety and hazardous materials audits its facilities on a regular basis including the WRF. The safety committee reviews documents related to the operation of the WRF facility including the Hazardous Materials Business Plan. B. Stationary Source and Regulated Substance Location of Padre Dam Municipal Water District WRF is 12001 North Fanita Parkway, in Santee, California 92071. Padre Dam Municipal Water District's WRF began operations in 1967. The WRF used chlorine injection until 1975, when it was discontinued due to a change in operations. Chlorine and sulfur dioxide were re-introduced to the facility in 1996/97 as a result of an upgrade and expansion of the WRF to a 2 million gallons per day (MGD) Water Reclamation Facility. The WRF treats wastewater as per the requirements of Title 22 reclaimed water standards for distribution into a reclaimed water system within the Santee region. * Chlorine The chlor ine feed system consists of one ton containers which are the storage vessels for chlorine. Chlorine gas is drawn from a single one-ton container at a time through a vacuum regulator to the chlorine feeder units. (A second container is connected in stand-by mode.) Still under vacuum from the chlorine feeder units, the gas is drawn to injectors and mixed with water for distribution through-out the wastewater treatment plant. The maximum intended inventory of chlorine is 5 tons ( 10,000 pounds). * Sulfur Dioxide The sulfur dioxide feed system consists of one ton containers which are the storage vessels for sulfur dioxide. Sulfur dioxide gas is drawn from a single one-ton container at a time through a vacuum regulator to the sulfur dioxide feeder units. (A second container is connected in stand-by mode.) Still under vacuum from the sulfur dioxide feeder units, the gas is drawn to injectors and mixed with water for distribution through-out the wastewater treatment plant. The maximum intended inventory of sulfur dioxide is 4 tons ( 8,000 pounds). C. Hazard Assessment Summary * Worst Case Release Result Summary The scenario with the greatest impact on the surrounding community was used as the "worst case" scenario. The chlorine and sulfur dioxide release scenarios reach have the same downwind distance to the same endpoint of 3 ppm; however, the sulfur dioxide building is situated approximately 100 meters south of the chlorine building, closer to the gate and residential population. Therefore, the sulfur dioxide release scenario will represent the "worst case" scenario for this facility. (Note that due to the limitations of the software, the population data is the same for both scenarios.) Scenario Description: Release of the maximum quantity of sulfur dioxide that can be stored in a single vessel (2,000 pounds) in 10 minutes. Even though the one ton containers are stored inside the building while in storage and operation, they are received while the door to t he building is open. There is a chance that a release could occur during the delivery or unloading process; therefore the requirements for passive mitigation of the enclosure are not satisfied and can not be taken into account. The total release rate is 200 pounds per minute. This release rate was used to determine the endpoint distance to 3 ppm. The most pessimistic meteorological conditions were used: 1.5 meters/second wind speed, and F stability for an urban topography. The distance to the toxic endpoint was determined using EPA's RMP Guidance for Wastewater Treatment Plants, Exhibit 4-6 for a release rate of 200 lbs./min. This release reaches off-site and may affect population receptors. Alternative Release Result Summary - Chlorine Scenario Description: A release of chlorine gas from a 0.25 inch diameter leak until the entire contents is released (210 minutes). This could result from a valve stem leak, a flange seal leak, or a line break. The release rate of chlorine due to the pressure of the tank is 9.5 pounds per minute. Passive mitigation measures were incorporated since all equipment is located inside a building. The release rate to the atmosphere was calculated as 5.2 pounds per minute and it was assumed that the chlorine scrubber failed. The meteorological conditions used were 3 meters per second wind speed, and D stability for an urban topography. The distance to the toxic endpoint of 3 ppm was determined using EPA's RMP Guidance for Wastewater Treatment Plants, Exhibit 4-12. This release scenario reaches off site but does not affect population or environmental receptors. Alternative Release Result Summary - Sulfur Dioxide Scenario Description: A release of sulfur dioxide liquid/gas from a 0.25 inch diameter leak at the valve stem, until the entire contents is released (20 minutes). The release rate of sulfur dioxide due to the pressure of the tank is 99.3 pounds per minute. Passive mitigation measures were incorporated since all equip ment is located inside a building. The release rate to the atmosphere was calculated as 54.6 pounds per minute and it was assumed that the sulfur dioxide water sprinkler knock-down system failed. The meteorological conditions used were 3 meters per second wind speed, and D stability for an urban topography. The distance to the toxic endpoint of 3 ppm was determined using EPA's RMP Guidance for Wastewater Treatment Plants, Exhibit 4-17. This release scenario reaches off site but does not affect population or environmental receptors. D. Accidental Release Prevention Program and Chemical-Specific Prevention Steps The Padre Dam Municipal Water District has an aggressive and active safety program in place to manage the handling of chlorine and sulfur dioxide gas. Practices and procedures proper chlorine handling were obtained from the Chlorine Institute Manual for the Safe Handling of Chlorine. Because sulfur dioxide gas is nearly identical in physical properties to chlorine and is s tored and feed in identical cylinders as Chlorine, same safety practices are used for sulfur dioxide. In addition to plant safety program for the handling of chlorine and sulfur dioxide, there is a gas detector in the chlorine storage room and the feed room. At a chlorine concentration of 1 ppm, the detection system will activate a visual/audible alarm and the scrubber system. In each of the sulfur dioxide rooms (2), there is a gas gas detector that will activate a visual/audible alarm and water mist sprinkler knockdown system at 1 ppm sulfur dioxide concentration. The entire chemical feed system at the facility is tied into a Factory Link - NT computer system(s) that monitors and operates the facility. In the event of an accidental release, detected by either activation of a scrubber or a sensor within the storage buildings, WRF personnel are notified by auto-dial pager systems. The system operates 24 hours per day and is tested on a daily basis. The auto-dialer system als o notifies other District personnel in addition to respond as backups or first entry individuals to mitigate the leak. E. Five Year Accident History Both the chlorine and sulfur dioxide systems were installed as part of a 1996/1997 plant upgrade and expansion project. The WRF has had no reportable release of chlorine or sulfur dioxide since that time. F. Emergency Response Program Padre Dam MWD has taken on an aggressive hazardous materials emergency response training program to prevent any potential releases from the WRF. WRF personnel are First Responders - Technician Level and trained to respond to a chemical release. The WRF is equipped with a 16' Hazmat Emergency Response Trailer which contains the tools and communication equipment necessary for an effective response to a chemical release, including, but not limited to Self Contained Breathing Apparatus, Level A suits, rubber boots, radios, etc. First Responder training includes drills of postulated hazardous material r eleases coordinated with the Santee Fire Department, the City of San Diego Hazmat Unit and the County of San Diego Hazmat Unit. All personnel actively participate with the safety training and planning for the facility. The WRF's Hazardous Materials Business Plan as well as the safety plan provides the personnel organization and notification needed to effectively attend to chlorine and sulfur dioxide chemical release issues. The Emergency Response Plan identifies health hazards and mitigation procedures which will be implemented to respond effectively should an emergency situation arise. The plan is an active part of the operation of the WRF and as such is it updated on a regular basis and not less than once per year. All effort are made to ensure that the Plan meets compliance with the PSM, RMP, and CalARP regulations. G. Planned Changes to Improve Safety The Padre Dam MWD has taken a pro-active approach to emergency response and safety at the WRF. The quarterly emergency re sponse drills are documented and mitigation measures to improve the Team's response are continuously being reviewed. Some planned changes to improve safety include the following items (note that some of these items have been completed since the initial submittal of June 1999): R01 - Place two additional windsocks at each end of the facility to augment the current five for visibility when coming on site. Complete - there are five windsocks throughout the facility. R02 - Purchase and install communication devices within the level A suits used for responses to chemical releases. Complete - these are maintained in the emergency response trailer. R03 - Expand future chemical response drills to include adjoining city fire departments. Complete - Lakeside, Riverview, and San Diego City Fire Departments have been in attendance at a WRF emergency response drill. R04 - Staff to have extended training on Incident Command System. Complete - Two additional staff personnel have been designate d as Incident Commanders. One has completed a drill with the County Hazmat team and the second will act as the incident commander during the next quarterly drill which is expected to occur before December 2000. R05 - Purchase 1 ton scrubber for SO2 storage room. Not Applicable - The room is already equipped with a sprinkler knockdown system. R06 - Change the design of the hoist crane in the Chlorine room for better handling of one ton cylinders. Complete - The access road was enlarged to better accommodate the large delivery vehicles which satisfies the intent of this recommendation. Re-designing the hoist crane is not feasible because it would require modifying the load-handling capacity of the building structure. R07 - Add additional reclaimed fire hydrant at N/E corner of facility. Complete R08 - Train staff on newly acquired 800hz radios for communication with emergency response personnel with County of San Diego. |