Lake Murray Water Treatment Plant - Executive Summary
Lake Murray Water Treatment Plant |
1. Accidental release prevention and emergency response policies:
The Lake Murray Water Treatment Plant accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. Accidental release prevention is a function of the safety devices (technology) inherent in the facility design, safe material handling practices used (procedures), and commitment to training of plant employees (management practices). All applicable requirements of the U.S. Environmental Protection Agency (EPA) Risk Management Prevention Program (40 CFR 68.65-87) are adhered to. It is the goal of the Columbia Canal Water Treatment Plant to ensure plant and community safety through an aggressive program of preventive maintenance, equipment testing, standard operating procedures, and employee training.
The Lake Murray Water Treatment Plant emergency response policy involves the preparation of a emergency preparednes
s plan which is tailored to the facility and to the emergency response services available in the community. The emergency preparedness program includes procedures for notification of the City of Columbia Fire Department HAZMAT Team (off-site mutual aid response), LEPC (community response plan), and SCDHEC (state response plan). The Lake Murray Water Treatment Plant emergency preparedness program is based upon recommendation of the American Water Works Association (AWWA) and the Chlorine Institute and is in compliance with the EPA Risk Management Emergency Response Program (40 CFR 68.90) requirements.
2. Stationary source and regulated substances handled:
The regulated substance handled and used at the Lake Murray Water Treatment Plant is chlorine. The maximum intended inventory of chlorine at the facility at anytime is 40,000 pounds (20 ton containers).
The Lake Murray Water Treatment Plant provides potable water for residential, retail, and industrial use through out the Great
er Columbia area. Chlorine is used in the water treatment process to destroy nuisance and pathogenic microorganisms in the raw water supply (i.e., chlorine use as a water supply disinfectant is an industry standard). The chlorination process includes chlorine container handling and storage facilities, chlorine feed system (vacuum chlorinators, piping, and injectors), and related safety equipment and instrumentation. The Lake Murray Water Treatment Plant is manned 24-hours a day and access to the plant site is restricted to authorized personnel.
3. Worst-case release scenario and the alternative release scenario:
The worst-case release scenario is defined by EPA as the release of the maximum quantity of a regulated substance from a process vessel or pipe line failure that will result in the greatest distance to the designated endpoint. The probability of the release occurring is not considered, it is just assumed to happen. The worst-case chlorine release scenario at the Columb
ia Canal Water Treatment Plant involves a failure of a one ton chlorine container and the predicted release of 2,000 pounds of chlorine to the atmosphere. The offsite consequence analysis for this scenario was performed following conditions pre-defined by EPA, namely release of the entire amount of chlorine as gas in 10 minutes, chlorine toxic endpoint of 0.0087 mg/l (i.e., the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individuals ability to take protective action), and worst-case weather conditions (i.e., stable atmospheric conditions and a wind speed of 1.5 m/s). Also, no administrative or passive mitigation systems were considered in this scenario. The DEGADIS+ computer model was used to perform this consequence analysis. The results of the consequence analysis performed for the hypotheti
cal worst-case chlorine release scenario did predict an offsite impact.
EPA describes the alternative release scenario as simply a more realistic release than the worst-case release or a release that is more likely to occur than the worst-case release. The alternative release scenario chosen for the Lake Murray Water Treatment Plant involves a break in a 1/4-inch flexible pigtail connection on the chlorine manifold resulting in the predicted release of 1,990 pounds of chlorine to the atmosphere over a two hour period. The alternative chlorine release scenario chosen for the Lake Murray Water Treatment Plant was selected based on the results of a qualitative risk analysis of possible release alternatives. The offsite consequence analysis for this scenario incorporated less stable weather conditions (i.e., Stability D and wind speed of 3.0 m/s) and active mitigation (i.e., actuation of chlorine leak detector and emergency response by offsite mutual aid responders to control the leak)
. The DEGADIS+ computer model was used to perform this consequence analysis. The results of the consequence analysis performed for the hypothetical alternative chlorine release scenario did predict an offsite impact.
While EPA requires analysis of the consequence of a worst-case release scenario, worst-case sceanrios as defined by the EPA have an extremely low probability of occurance. The worst-case release could only happen if the majority of the safety and technology features in use failed at the same time. Additionally, it would have to occur at exactly the time the worst-case weather conditions also existed, a most improbable event. Further, certain consequence conditions such as the entire amount of chlorine will be released as a gas in ten minutes and comparison of a ten minute release to a toxic endpoint based on a one-hour value are unrealistic. However, there is no allowance in the Risk Management Program (RMP) rule for making an adjustment to the worst-case release sc
eanrio conditions. For this reason, the alternative release sceanrio should be the focus of prevention and preparedness efforts.
4. General accidental release program and the chemical-specific prevention steps:
The Lake Murray Water Treatment Plant complies with EPA's RMP Rule, OSHA's Process Safety Management standard (29 CFR 1910.119), and with all applicable state and local codes and regulations. The chlorination process was constructed, and is operated, in accordance with recommendations of the AWWA and Chlorine Institute. The Lake Murray Water Treatment Plant accidental release prevention program is based on the following key elements:
High level of training for operators and maintenance personnel
Equipment inspection, testing, and preventive maintenance
Use of "industry standard" process and safety equipment
Use of accurate and effective operating procedures
Performance of hazard review of equipment and procedures
Implementation of an internal and external au
Segregation of chemical processes for compatibility and fire prevention/control
Chlorine leak detectors and alarm system
Availability of SCBAs and chlorine container leak repair kit
Maintenance of approved parts inventory
5. Five-year accident history:
The Lake Murray Water Treatment Plant has had an excellent record of preventing accidental releases over the past five years. Due to the effectiveness of the release prevention program, there have been no accidental releases of chlorine during the past five years.
6. Emergency Response Program:
The Lake Murray Water Treatment Plant has an emergency preparedness plan that is integrated with the LEPC plan. The Lake Murray Water Treatment Plant maintains a mutual aid agreement with the City of Columbia Fire Department HAZMAT Team to provide emergency response services in the event of a chlorine release. Emergency response drills and drill evaluations are conducted with the City of Columbia Fire Department HA
ZMAT Team on a routine basis. The plant emergency preparedness plan includes procedures for the notification of offsite mutual aid responders, LEPC, SCDHEC, and the public along with a discussion of actions to be taken in the event of a chlorine release. The plan also addresses first aid and medical treatment.
7. Planned changes to improve safety:
The last Process Hazard Analysis (PHA) was performed in June 1995 and it resulted in no recommended changes. A PSM compliance audit was conducted in April 1999 and it resulted in a recommendation for minor changes (clarification) to the written SOPs and emergency prepardness plan. No other changes have been recommended.