Aberdeen East Lagoon Facility - Executive Summary
The Aberdeen East Lagoon Facility has been successfully treating sanitary sewage in Aberdeen, Mississippi for over two years. Located in the southeast corner of Aberdeen on MS Highway 25 at US Highway 45, the facility lies in an undeveloped area of the City. The facility has not had an accident to report since it began operation in 1996. 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 facility, a Risk Management Plan has been developed for chlorine, a hazardous chemical used in the 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 Lagoon Facility has accomplished this through constant employee safety training, the use of proper methods and equipment for handling the chemicals, and the preparation of emergency response procedures.
ine is an essential chemical in the treatment of municipal sanitary sewage. It is a strong disinfectant and is used in the treatment process to eliminate pathogenic organisms in the final effluent. The chemical is stored on-site in ton cylinders on a concrete pad adjacent to the chlorination building in the center of the facility. A maximum inventory of 6,000 pounds of chlorine can be found at the facility at one time. The chlorination/dechlorination building serves to supply and meter the chlorine from the ton cylinders to a gas induction unit that applies it to the final effluent in the chlorine contact tank.
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 o
f this chemical, the hazards can be controlled.
As part of the Risk Management Plan, both a worst case and an alternative case release scenarios 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 1,200 people), a hospital, recreational areas, and various industrial and commercial areas. This scenario, although possible, is very unlikely to occur at Aberdeen's East Lagoon Facility.
The alternative release scenario chosen is a much more probable assumption in the unlikely event of a sp
ill. This scenario assumes a ton cylinder is dropped during unloading at the facility, creating a 0.25 inch hole in the bottom of the cylinder 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 minimal off-site impact. No facilities of any type or recreational areas lie within 0.20 miles of the East Lagoon Facility, therefore, no population would be put in danger. Also, the Lagoon Facility is not constantly manned; the plant operator makes daily rounds to inspect the equipment but is not stationed there. Therefore, it is possible that a release such as this vessel leak would not cause harm to any individuals. A self contained breathing apparatus (SCBA) is located at the facility in the event a leak occurred while the operator was at the facility.
Another part of the Risk Management Plan is the prevention program. This progr
am 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 East Lagoon Facility keeps current material safety data sheets on chlorine available to the staff at all times. There are also equipment specifications and the appropriate codes and standards used to operate the process available at the facility and at the public utilities office building.
A hazard review of the chlorination process was conducted on May 11, 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, overpressu
rization of a cylinder, and equipment failure. Safeguards in place to protect against these hazards include check valves, vent lines, manual shutoff valves, and fire resistant walls on the chlorination building. Emergency air supply is also available for employees in the case of a release. Leak detectors are mounted outside next to the ton cylinders and inside the chlorination building and will trigger audible and visible alarms outside the chlorination building. A schedule has been established to have a remote alarm installed by August 31, 1999. This alarm will sound at the public utilities office building.
Operating procedures are available to all employees in the manufacturers' manuals, which are located at the Lagoon Facility and at the public utilities office building. An equipment manual was also put together by Engineered Environmental Equipment, Inc. and is likewise available to the employees. These procedures cover normal operations of each piece of equipment in the
chlorination process, including the applicable operating limits. All operators working in the plant have been properly trained on the plant operations and emergency procedures. In the case of a release, they have been trained to stop at the front gate and immediately call the posted emergency number. Monthly safety meetings are conducted by an outside contractor to refresh employees on safety issues in the work place. There is also a plant operator certified in the use of the self-contained breathing apparatus (SCBA.) Routine maintenance of the equipment is conducted by trained operators during the daily facility inspections. An outside contractor will be brought in when necessary to service the chlorination equipment.
Due to the safety procedures discussed above and the adherence to these procedures by the plant operators, the East Lagoon Facility has never had an accidental release. Although it is unlikely that the plant will have an accidental release in the future, emergenc
y response plans are in place in the event one does occur. The Lagoon Facility has coordinated with the Monroe County Local Emergency Planning Committee (LEPC) to be included in the community emergency response plan. By being included in this plan, the LEPC will respond to a potential release at the facility. This emergency response plan will help the Aberdeen East Lagoon Facility carry on its tradition of maintaining a flawless safety record.