Ocean City Wastewater Treatment Plant - Executive Summary |
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Risk Management Plan Executive Summary A. Accidental Release Prevention Policy The Town of Ocean City Division of Public Works accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. All applicable procedures of the US EPA Prevention Program are adhered to. The Division of Public Works continues to evaluate and improve its procedures and practices with regards to its accidental release prevention policy. The Division of Public Works response policy involves the preparation of response plans which are tailored to each facility and to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program requirements. B. System Description and Regulated Substance Handled The Town of Ocean City Waste Water Treatment Plant (WWTP) treats the wastewater from the Town of Ocean City and discharges the clean water. The WWTP is located at 6401 Seabay Drive in Oc ean City, Maryland. Disinfection of wastewater with chlorine is part of the treatment process and is required by both the EPA and Maryland Department of the Environment. After disinfection is completed the chlorine is removed with sulfur dioxide and then the clean wastewater is discharged. This process is known as dechlorination. Both chlorine and sulfur dioxide are regulated by 40 CFR Part 68. Chlorine and sulfur dioxide liquid is stored and handled at the WWTP for the disinfection (or chlorination) and dechlorination processes. The WWTP chlorination system has a chlorine storage room and a chlorination room. Equipment at the facility includes liquid chlorine containers, chlorine liquid manifolds, chlorine liquid evaporator, chlorine gas manifolds, a vacuum feed system, chlorinators, safety equipment, chlorine leak detectors and an emergency scrubber. The WWTP dechlorination system has a sulfur dioxide storage room and a sulfonation room. Equipment at the facility includes l iquid sulfur dioxide containers, sulfur dioxide gas manifolds, a vacuum feed system, sulfonators, safety equipment, sulfur dioxide leak detectors and an emergency scrubber. Typically, twelve (12) tons of chlorine are stored on site with two tons on-line. Also, eight (8) one-ton containers of sulfur dioxide are usually on site and two of the eight containers are on-line. The WWTP is manned 24 hours a day so operators are immediately available to respond to chlorine or sulfur dioxide leak indicator alarms that may occur. C. Offsite Consequence Analysis The Offsite Consequence Analysis includes the consideration of two chlorine release scenarios identified as "Worst-Case Release" and "Alternative Scenario". The first scenario is defined by EPA, stating that, "the owner or operator shall assume that the...maximum quantity in the largest vessel...is released as a gas over 10 minutes" due to an unspecified failure. The Alternative Scenario is defined as "more likely to occur than th e Worst-Case Release Scenario." The Offsite Consequence Analysis for the WWTP was conducted with the use of the EPA Risk Management Program Guidance for Wastewater Treatment Plants. 1. Based on the tables and information provided for a worst-case chlorine or sulfur dioxide release, the following was determined: a. The "Worst-Case Release Scenario," as defined by EPA, would be for a one-ton container of chlorine or sulfur dioxide to release, as a gas, in a ten minute period. b. The toxic endpoint for Cl2 gas and sulfur dioxide is 3 ppm. c. Passive mitigation can be expected from the building housing the chlorine and this will reduce the release rate by 45%. d. The distance from the release site to the toxic endpoint is 0.9 miles. It should be noted that the design of the chlorine feed and the sulfur dioxide feed system and the presence of an emergency scrubber system make the possibility of the EPA described "worst-case" scenario practically impossible. 2. The "Alternative (R elease ) Scenario" for chlorine was evaluated with the use of the EPA Risk Management Program Guidance for Wastewater Treatment Plants. For the WWTP a possible alternative release scenario would be a leak of chlorine gas from a flexible stainless steel tubing (pigtail) connection to the one-ton container. Such a leak would be very small and not have an impact outside the facility boundaries. The reason for this is because of the active and passive mitigation measures that are in place. These are: a. Chlorine gas leak detectors b. Emergency scrubber, that ventilates, captures and treats 99.9% of the chlorine gas c. Dike and Building Enclosure 3. The "Alternative (Release ) Scenario" for the sulfur dioxide system was evaluated with the use of the EPA Risk Management Program Guidance for Wastewater Treatment Plants. For the WWTP a possible alternative release scenario would be a PRV release of sulfur dioxide through a 1/8 inch i.d. sulfur dioxide gas pipe. Such a leak would not have an impact outside the facility boundaries. The reason for this is because of the active and passive mitigation measures that are in place. These are: a. Vacuum feed system and pressure relief vents b. sulfur dioxide gas leak detectors c. Emergency scrubber, that ventilates, captures and treats 99.9% of the sulfur dioxide gas. d. Dike and Building Enclosure D. The general WWTP accidental release prevention program and chemical-specific prevention steps are based on the Town of Ocean City's program and consists of the following key elements: 1. Highly skilled and trained operators (State licensed) 2. Preventive Maintenance Program 3. Use of state-of-the-art process and safety equipment. 4. Performance of a Process Hazard Analysis of equipment and procedures 5. Implementation of an auditing and inspection program 6. Availability of SCBA to the emergency responders 7. Awareness of the toxic properties and hazards of chlorine and sulfur dioxide 8. The presence of chlorine and sulfur dioxide leak detectors 9. The presence of an emergency scrubber E. Five-Year Accident History No accidental release of sulfur dioxide has occurred at this facility in the past five years. Two accidental release of chlorine have occurred in the last five years. One accident occurred when the facility was under construction. An incident investigation revealed that a chlorine release occurred when a contractor reconnected system lines with inappropriate materials. The resulting leak to the environment was about 45 lbs. At the time of the incident the emergency scrubber was newly installed and not yet connected to sensors and automatic controls. The emergency scrubber is now connected to leak detectors and will be activated automatically if a leak is detected. A second accident occurred when an operator was exposed to chlorine gas from a pressure regulator failure. The small volume of released gas was estimated at about 5 pound. The incident investigati on indicated that the leak detectors activated an alarm but the operator did not observe the alarmed condition and entered the room unawares to perform routine duties. As a result of the incident investigation strobe alarms and horns were placed at each door of the chlorine room. Also, preventative maintenance of the pressure regulator unit was increased. F. Emergency Response Program The WWTP has an emergency response program that is coordinated with Town of Ocean City Volunteer Fire Department and the Ocean City Special Hazardous Intervention Team (HAZMAT). The program includes an organizational structure of emergency responders and their responsibilities. Emergency response to a leak at the WWTP would include selected personnel of the Town of Ocean City Division of Public Works, who have specific knowledge and training for chlorine and sulfur dioxide gas leak response. Emergency-response drills and emergency-procedure evaluations are conducted regularly. G.. Planned Chang es to Improve Safety Planned changes to improve safety of chlorine and sulfur dioxide handling at the facility have occurred over the last five years and included: 1. Installation of an emergency scrubber system that is sized to handle the simultaneous release of all on-line chlorine gas and sulfur dioxide gas. 2. New visible and audible alarms at the doors to the chlorine room. 3. For the sulfur dioxide, a vacuum feed system beginning at the one-ton container has been installed 4. The WWTP operators and supervisors are evaluating the effectiveness of emergency shut-off valves for the chlorine and sulfur dioxide containers. |