Municipal Plant #2 - Executive Summary |
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The Municipal Plant #2 has been successfully providing water to the community of Laurel, Mississippi for almost twenty years. Located at 1310 Hillcrest Drive, the plant lies in the southwest section of Laurel. On average the plant treats 2 to 3 million gallons of groundwater per day and uses approximately 75 pounds of chlorine per day. The Plant has never had a chlorine-related accident to report and has never had any incident that affected a public receptor. This flawless safety record can be attributed to the awareness and conscientiousness of the administration and staff. To further improve the overall safety of the plant, a Risk Management Plan has been developed for chlorine, a hazardous chemical used in the water treatment process. When dealing with hazardous chemicals, it is imperative to take all necessary precautions to protect the safety of the employees and the surrounding community. The Municipal Plant #2 has accomplished this through employee safety training, the us e of proper methods and equipment for handling chlorine, and the preparation of emergency response procedures. Chlorine is an essential chemical in the treatment of drinking water. It is a strong disinfectant and is used in the treatment process to eliminate any pathogenic organisms in the final supply. The chlorine at Plant #2 is stored on-site in one-ton cylinders in the chlorination room, which is a separate room of the main building. A maximum inventory of 4,000 pounds can be found at the plant at one time. The chlorination room serves to supply, meter, and apply the chlorine to the final water stream. Chlorine is listed by the EPA as an extremely hazardous substance (EHS.) It has a characteristic penetrating odor and is greenish yellow in the gas phase and clear amber under pressure in the liquid phase. Chlorine gas is primarily a respiratory irritant, while liquid chlorine will cause burning to the eyes and skin. Yet, with the proper equipment and proper handling of th is chemical, the hazards can be controlled. As part of the Risk Management Plan, both a worst case and an alternative case release scenario were examined and the off-site impacts were analyzed. Scenarios established and recommended in the EPA's Risk Management Program Guidance for Wastewater Treatment Plants-Off-Site Consequence Analysis were used for the analysis. The worst case release scenario assumes the release of 2,000 pounds of liquid chlorine over a 10 minute interval. The distance to the toxic endpoint, or the affected area, for this type of release is 1.3 miles from the spill. Facilities that would be impacted off-site within this radius include residences (approximately 5,500 people), schools, recreational areas, and various industrial and commercial areas. An airport, located directly west of the Plant, is also located within this radius of impact. This scenario, although possible, is very unlikely to occur at Laurel's Plant #2. This model assumes that the spill ta kes place outside. Yet, both cylinders at the facility are stored inside the chlorination room in the main building, which would serve as an enclosure for the gas. The only time the cylinders are outside is during unloading from the vehicles upon delivery to the plant. The EPA suggests using a factor of 0.55 to determine the actual release rate if the chemicals are inside a building, but the original release rate was chosen to cover the minor amount of time the cylinders are being unloaded outside. The alternative release scenario chosen for chlorine is a much more probable assumption in the unlikely event of a spill. This scenario assumes the failure of a fusible plug, a portion of the pressure relief device, resulting in a 0.25-inch hole through which liquid chlorine escapes. This release allows 2,000 pounds of chlorine to spill at a rate of 150 pounds/minute. The affected radius for this type of spill is 0.20 miles, which would cause some off-site impact. A population of 15 0 people could be affected within this radius of impact, along with a small number of commercial and industrial facilities. As with the worst case scenario, this type of release would also most likely occur indoors. Therefore, this spill would be enclosed and not spread to as great of an area as predicted before it could be controlled. Another part of the Risk Management Plan is the prevention program. This program covers safety information, a review of potential hazards, operating procedures, employee training, and maintenance of equipment. It is essential to have up-to-date and complete information available on these topics to protect the employees and the surrounding community by eliminating possible hazardous situations. The Municipal Plant #2 keeps current material safety data sheets on chlorine available to the staff at all times. There are also equipment specifications and safe upper and lower parameters for the process available in the main building. A hazard review of the chlorination process was conducted on September 24, 1999. The purpose of the hazard review is to identify all hazards associated with the chemical and the process, opportunities for equipment malfunction or human error, safeguards in place, and detection or monitoring equipment in place or needed. Possible hazards identified include toxic releases, overpressurization of a cylinder, and equipment failure. Safeguards in place to protect against these hazards include vent lines, relief and check valves, manual shutoffs, emergency power, fire resistant walls, and the fact that the cylinders are stored inside a building. Leak detectors are provided in the chlorine process room and will trigger audible and visible alarms in the chlorination room and in the operators' room. Operating procedures are available to all employees in the manufacturers' instruction manuals, which are located in the main office building. These procedures cover normal operations, including start-up and shutdown, of each piece of equipment in the chlorination process. Also, emergency procedures to be carried out in the case of a chlorine leak are posted in the chlorination room. All operators working in the plant have been properly trained on the plant operations and emergency procedures. On-the-job training is conducted continuously to keep employees current on safe handling procedures. Routine maintenance of the equipment is conducted each day by trained operators. An outside contractor is brought in if the chlorination equipment requires repair service. Due to the safety procedures discussed above and the adherence to these procedures by the plant operators, the Municipal Plant #2 has never had an accidental release. Although it is unlikely that the plant will have an accidental release in the future, emergency response plans are in place in the event one does occur. The Plant has coordinated with the Laurel Fire Department to respond to emergency situations. Therefore, t he fire department maintains emergency repair kits and self-contained breathing apparatuses (SCBA's) for the plant. In the event of a chlorine leak, the Laurel fire Department has an interlocal agreement with the Hattiesburg haz-mat team to respond. Emergency numbers for the fire department are posted in the chlorination room and in the operator's room. Also, the Plant has also been furnished with notices from the Chlorine Handling Institute, Inc. that outline first aid procedures to be carried out during an emergency release. These emergency procedures will help Laurel's Municipal Plant #2 carry on its tradition of maintaining a flawless safety record. |