City of Superior Wastewater Treatment Plant - Executive Summary |
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FACILITY DESCRIPTION: The Wastewater Treatment Plant is located at 51 East 1st street in Superior. It is located on the waterfront of the Superior Bay. The elevation of the plant is lower than that of the surrounding homes and highways. The plant usually has four chlorine containers, one-ton each, on site at all times. Two chlorine containers are in use and are located in a room constructed with concrete floor, concrete block and brick walls, and an aluminum ceiling. Two containers are in storage and are located in an unheated, garage area with a concrete floor and aluminum walls and ceiling. There are two entrances to each area. A chlorine leak detector is located in each area with alarms wired into the plant operator's control room. The plant is manned with one operator 24 hours a day. Between the hours of 7 a.m. and 3 p.m. Monday through Friday there is a potential of 24 employees on site. The plant area is fenced with an entry gate. The on duty operational personnel have direct radio communications with the Douglas County Emergency Communications Center. Phone lines are also available. WORST CASE SCENARIO: The worst case scenario was calculated using a model scenario in the EPA Guidance document Risk Management Program Guidance for Wastewater Treatment Plants. It assumes a total loss of two full interconnected chlorine one-ton cylinders. This would occur on a day with an atmospheric stability of F and a wind speed of 1.5 meters per second. The calculated distance to the endpoint is a circle with a radius of 1.9 miles. This scenario does not take into account the mitigating factors at the City of Superior WWTP. The chlorine cylinders are housed inside a concrete block room when interconnected. The wall structure would restrict the dispersion of the gas. The cylinders in the storage building are not connected together. For both tanks to rupture at the same time, a fire or explosion would need to occur. The storage building is constructed of non -flammable materials, and no flammables are allowed in the building. There are chlorine alarms in both the chlorinator room and the storage building. The likelihood of this scenario actually happening is quite remote. ALTERNATIVE SCENARIO The alternative scenario was calculated using a model scenario in the American Water Works Association's book Compliance Guidance and Model Risk Management Program for Water Treatment Plants. This scenario assumes a release occurs from a one-ton cylinder due to a bad connection or valve failure. The release is restricted to the 5/16-inch diameter valve body opening. Assuming a 60-minute duration, the total escaped gas would be 317 lbs. This corresponds to a circle with a 0.48-mile radius. The likelihood of this scenario happening is more realistic than the worst case scenario. There is the possibility of the valve being damaged during change-out of the cylinders or off loading the cylinders from the supplier. However, even this occurrence woul d be quite rare. CHLORINATION SYSTEM The chlorine is dispensed via a vacuum system, which will shut off the flow of chlorine in the event of a loss of vacuum. Staff is trained regularly to fully understand the safety and health hazards of chlorine and the chlorine processes they work with. The City of Superior WWTP attends annual training in chlorine tank safety and repair procedures put on by Superior Water Light and Power Company. The City of Superior WWTP has instituted a preventative maintenance program with checklists outlining things to observe, record and adjust. Every two years, a licensed technician services the chlorination system and equipment maintenance training is provided to all operational staff. ACCIDENTAL RELEASE PREVENTION PROGRAM The City of Superior WWTP complies with the OSHA Process Safety Management rule. This comprehensive plan covers all aspects of dealing with a hazardous chemical such as chlorine. The major objective of our process safety managemen t of chlorine is to prevent unwanted releases, which could expose employees and others to serious hazards. Our process safety management program applies a systematic approach to evaluating the whole process. Using this approach the process design, process technology, operational and maintenance activities and procedures, nonroutine activities and procedures, emergency preparedness plans and procedures, training programs, and other elements which impact the process are all considered in the evaluation. Our process safety management is a proactive identification, evaluation and mitigation or prevention of chemical releases that could occur as a result of failures in process, procedures or equipment. Our process safety plan incorporates employee participation, process safety information, process technology information, a Process Hazard Analysis, Operating Procedures and Practices, Employee Training, Contractor Safety Requirements, Pre-Startup Safety Procedures, Maintenance Requirements to Maintain Mechanical Integrity, A Management of Change Policy, An Pre-Startup Review, Compliance Audits, and Accident Investigation Procedures. 5 YEAR ACCIDENT HISTORY We have had no accidental releases of chlorine in the last 5 years. PLANNED CHANGES TO IMPROVE SAFETY The annual training in chlorine safety occurs every summer. The every two year maintenance and operational training will also be occurring this summer. The City of Superior has a comprehensive safety program that addresses PPE, lockout/tagout, confined space entry, hazard communications, fire prevention, first aid, etc. The human resources department is continually updating and improving on these policies. A mechanical hoist and trolley will be installed this summer, replacing a manual hoist and trolley. This system will give the operator greater control over the transfer of the cylinders from the storage facility to the chlorination room. EMERGENCY RESPONSE PROGRAM The City of Superior WWTP has adopted a set of eme rgency response procedures to address a full array of events. Responses are defined for fires, explosions, extended power failure, medical emergencies, flooding, loss of water, natural gas leak, methane leak, chlorine gas leak, sulfur dioxide gas leak, bomb threats, etc. These procedures include floor plans for all of the buildings at the plant and evacuation routes from every room are defined. Each scenario lists the names and phone numbers of the supervisory personnel or outside responders to be notified. The tasks required are identified as are the responsible employees. The City of Superior WWTP has worked with the Douglas County Emergency Response Coordinator to develop an emergency response plan to be used in the case of an emergency requiring evacuation of Superior residents. This plan was also sent to the City of Duluth. The Superior Fire Department will be the responder in the case of a chlorine leak acting in the role of the Regional Hazmat Response Team. They have been supplied with a map of the plant, locations of all chemicals of concern, and a copy of the Douglas County Emergency Response Plan for the City of Superior Wastewater Treatment Plant. They have toured the facility to become familiar with the locations of the chemicals on site. |