Newport Utilities Board Wastewater Treatment Plant - Executive Summary |
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Executive Summary (40 CFR 68.155) a) The Newport Utilities Board (NUB) Wastewater Treatment Plant's accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to. The emergency response policy involves providing training to onsite operators to ensure their recognition of emergency situations. Preparation for response to an accidental release of chlorine involves coordination and communication with the local emergency response agencies who are familiar with the hazards associated with chlorine releases and who would respond in the event of a release. b) The Wastewater Treatment Plant is designed to provide disinfected water to the City of Newport. The facility has a chlorine storage and handling building where the one-ton cylinders of chlorine are stored and used. The building includes a chlorination room, which contains the one-ton chlorine cylinders, a chlorinator, and various pieces of safety equipment; and an instrument room, which contains a flow recorder, and various electrical panels. Water treatment operators are onsite around the clock and respond to any alarms, should they occur. c) The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as a "worst case release" and an "alternative scenario". The worst-case release scenario is defined by EPA in 40 CFR 68, which states 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 one that is more likely to occur than the worst-case release scenario. The specific worst-case scenario presented for NUB's Wastewater Treatment Plant is considered to be an unrealistic scenario; however, EPA has required presentation of a worst-case scenario to facilitate dialogue between the community and the regulated entities. The specific alternative release scenario for NUB is considered to be more likely than the worst-case scenario, but is still an unlikely occurrence. The most likely release scenarios at NUB involve gaseous releases from inadequately tightened connection valves. However, such releases would trigger the automatic chlorine detection alarms at low chlorine concentrations. Response to such situations would be immediate, and no offsite impact would be anticipated under this sort of release scenario. Hence a larger, less likely alternative release scenario with potential to have an impact offsite was chosen for presentation. The worst-case release scenario is represented by the release of the entire contents of one of the one-ton chlorine cylinders. For chlorine, which is a toxic substance that is normally a gas at ambient temperature, the RMP regulations require the analysis to assume that the chlorine is released as a gas over a 10-minute period. The release of the contents of a single cylinder (2000 pounds chlorine) over 10 minutes (i.e., 2000 lb/10 min) results in a release rate of 200 pounds per minute. Using a release rate of 200 pounds and the tables provided in the EPA guidance document RMP Offsite Consequence Analysis Guidance, the distance to the toxic endpoint was determined to be 3.0 miles. The circle of impact, defined by the distance to the toxic endpoint as the circle's radius, includes an estimated 9,595 people. However, it is likely that significantly fewer people would be affected by such a worst-case gas release, since only the areas directly downwind of the release would experience the effects of the gas. The alternative release scenario is represented by the shearing of one of the 3/8-inch flexible tubing pipes that connects the one-ton chlorine cylinder to the delivery pipes. The flexible tubing is suspended between the tank and the delivery pipes, which are mounted to the wall. The flexible tubing could potentially be sheared by dropping a heavy tool on it or by a person collapsing on the suspended piping. Since the tubing is directed away from and protected from traffic areas, this scenario is unlikely. Based on a release rate of 37 pounds per minute into the building, the release rate to the atmosphere, accounting for passive mitigation provided by the building, is calculated to be 15 pounds per minute. These results are based on based on tables provided in EPA's Risk Management Program Guidance for Wastewater Treatment Plants (40 CFR 68). The resulting distance to the toxic endpoint for the alternative release scenario is, thus, 0.2 miles. The affected population within the circle of impact is estimated to be 12 people. In actual fact, there appear to be no dwellings within the 0.2 mile radius circle, so 12 people is probably an overestimate for the number of people potentially affected by this scenario. d) The general NUB accidental rel ease prevention program is based on the following key elements: 7 High level of training of the operators 7 Preventive maintenance program 7 Use of safety equipment 7 Use of accurate and effective operating procedures, written with the participation of the operators 7 Performance of a hazard review of equipment and procedures 7 Implementation of an auditing and inspection program Chemical-specific prevention measures include availability of self-contained breathing apparatus (SCBA), operator training for the purpose of developing an awareness of the hazardous and toxic properties of chlorine, and presence of chlorine detectors to provide warning of very low-level releases. e) No accidental releases of chlorine have occurred at this facility in the past five years. f) EPA has adopted a policy for non-responding facilities (specifically regarding emergency response to release of toxic chemicals) similar to that adopted by OSHA in its Hazardous Waste Operations and Emergency Res ponse (HAZWOPER) Standard (29 CFR 1910.120), which allows certain facilities to develop an emergency action plan to ensure employee safety, rather than a full-fledged emergency response plan. The rationale behind this policy is that facilities without large numbers of employees are not equipped to respond effectively to an accidental release; thus, it is considered safer to rely on outside emergency responders who are trained to handle emergency situations and have the resources to respond effectively. Since NUB employees will not be responding to accidental releases of chlorine, if any releases should occur, the plant is not required to comply with the Risk Management Program's emergency response plan and program requirements. Instead, NUB has coordinated with local response agencies to ensure that they will be prepared to respond to an emergency posed by a release of chlorine from the NUB plant. This has been accomplished by the following: 7 NUB has set up a way to notify emerge ncy responders when there is a need for a response, 7 NUB has worked with the local emergency response planning committee to ensure that the NUB facility is included in the community emergency response plan prepared under the Emergency Planning and Community Right-to-Know Act (EPCRA) regarding a response to a potential release of chlorine, and 7 NUB has worked with the local fire department regarding a response to a potential release of chlorine. g) The primary risk of chlorine release is due to leakage around connections and fittings leading from the valve of the chlorine cylinder to the chlorine delivery system. NUB currently has a chlorine detection system that warns the operators if a leak is detected. The operators are trained to enter the chlorine building safely and turn off the valve to the chlorine cylinder, thereby stopping the gas leak. NUB has committed to installing an automatic valve shut-off system. The automatic shut-off mechanism will be activated by the chlorin e detection system, so that any gas leak will be halted immediately and safely, without requiring personnel to enter the chlorine containment building. This safety upgrade will provide state-of-the-art technology for ensuring the safety of not only the plant personnel, but the surrounding community. |