Reclaimed Water Plant - Executive Summary |
|
South Island PSD Reclaimed Water Plant 1. Accidental release prevention and emergency response policies: The South Island Public Service District (PSD) Reclaimed Water 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 a goal of the South Island PSD Reclaimed Water Plant to ensure plant and community safety through an aggressive program of hazard analysis, preventive maintenance, equipment testing, standard operating procedures, and employee training. The South Island PSD Reclaimed Water Plant emergency response p olicy involves the preparation of a emergency preparedness 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 Beaufort County HAZMAT Team (off-site mutual aid response), Beaufort County LEPC (community response plan), and SCDHEC (state response plan). The South Island PSD Reclaimed Water Plant emergency preparedness program is based upon recommendations of the Water Environment Federation (WEF), Compressed Gas Association, 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 substances handled and used at the South Island PSD Reclaimed Water Plant are chlorine and sulfur dioxide. The Maximum intended inventory of chlorine at the facility at anytime is 28,000 pounds. The Maximum intended inventory of s ulfur dioxide at the facility at anytime is 24,000 pounds. The South Island PSD Reclaimed Water Plant provides biological treatment for sanitary wastewater collected from through out the South Island service area. Chlorine is used in the reclaimed water treatment process to destroy nuisance and pathogenic microorganisms present in the wastewater (i.e., chlorine use as a wastewater disinfectant is an industry standard). The chlorination process includes chlorine container handling and storage facilities, chlorine feed system (piping, vacuum chlorinators, and injectors), and related safety equipment and instrumentation. Sulfur dioxide is used in the reclaimed water treatment process to remove residual chlorine from the treated wastewater prior to discharge from the plant (i.e., sulfur dioxide use to dechlorinate treated wastewater is an industry standard). The dechlorination process includes sulfur dioxide container handling and storage facilities, sulfur dioxide feed system (piping , vacuum sulfonators, and injectors), and related safety equipment and instrumentation. The South Island PSD Reclaimed Water 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 scenarios: 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. A Program 3 regulated source must perform one worst-case release scenario analysis that is representative of all regulated toxic compounds that are present at the plant site above their designated threshold quantities. The worst-case release scenario at the South Island PSD Reclaimed Water Plant involves a catastrophic failure of a one ton sulfur dioxide container and the release of 2,000 pounds of sulfur dioxide 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 sulfur dioxide as gas in 10 minutes, sulfur dioxide toxic endpoint of 0.0078 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 hypothetical worst-case sulfur dioxide release scenario did predict an offsite impact. EPA describ es 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. A Program 3 regulated source must perform an alternative release scenario analysis for each toxic compound that is present at the plant site above its designated threshold quantity. The alternative chlorine release scenario chosen for the South Island PSD Reclaimed Water Plant involves the complete failure of the container mounted vacuum regulator resulting in the predicted release of 1,520 pounds of chlorine to the atmosphere over a two hour period. The alternative sulfur dioxide release scenario chosen for the South Island PSD Reclaimed Water Plant involves the a break of a ton container pigtail resulting in the predicted release of 1,850 pounds of sulfur dioxide to a building enclosure and then two the atmosphere over a two hour period. The alternative release scenarios chosen for the South Island PSD Reclaimed Water Plant were selected based on the results of a qualitative risk analysis of possible release alternatives. The offsite consequence analysis for these scenarios incorporated less stable weather conditions (i.e., Stability D and wind speed of 3.0 m/s), passive mitigation (building enclosure sulfur dioxide only), and active mitigation (i.e., actuation of leak detector and emergency response by offsite mutual aid responders to control the leak). The DEGADIS+ computer model was used to perform the consequence analysis. The results of the consequence analysis performed for the hypothetical alternative chlorine release scenario did predict an offsite impact. The results of the consequence analysis performed for the hypothetical alternative sulfur dioxide release scenario also predicted an offsite impact. While EPA requires analysis of the consequence of a worst-case release scenario, worst-case scenarios as defined by the EPA have an extremely low probability of occurrence. The w orst-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 mandated consequence conditions such as the entire amount of chlorine or sulfur dioxide 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 exposure value are unrealistic. However, there is no allowance in the EPA Risk Management Program (RMP) rule for making an adjustment to the worst-case release scenario conditions. For this reason, the alternative release scenarios should be the focus of prevention and preparedness efforts. 4. General accidental release program and the chemical-specific prevention steps: The South Island PSD Reclaimed Water Plant complies with EPA's RMP rule, OSHA's Process Safety Management standard (29 CFR 1910.119), and wit h all applicable state and local codes and regulations. The chlorination and dechlorination processes were constructed, and are operated, in accordance with recommendations of the WEF, Compressed Gas Association, and Chlorine Institute. The South Island PSD Reclaimed Water 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 auditing program Segregation of chemical processes for compatibility and fire prevention/control Chlorine and sulfur dioxide leak detectors and alarm systems Availability of chlorine and sulfur dioxide container leak repair kits Approved parts inventory 5. Five-year accident his tory: The South Island PSD Reclaimed Water 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 or sulfur dioxide during the past five years. 6. Emergency Response Program: The South Island PSD Reclaimed Water Plant has an emergency preparedness plan that is integrated with the LEPC plan. The South Island PSD Reclaimed Water Plant maintains a mutual aid agreement with the Beaufort County HAZMAT Team to provide emergency response services in the event of a chlorine or sulfur dioxide release. Emergency response exercises are conducted 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 or sulfur dioxide release. The plan also addresses first aid and medical treatment. 7. Planned changes to improve safety: The latest chlorination and dechlorination Process Hazard Analysis (PHA) updates were performed in May 1999 and they resulted in no recommended process or operational changes. A PSM compliance audit was conducted in May 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. |