Munster Wastewater Treatment Plant - Executive Summary |
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LDEQ Facility ID Number: 27960 27960 LDEQ FACILITY ID NUMBER RISK MANAGEMENT PLAN FOR MUNSTER WASTEWATER TREATMENT PLANT ST. BERNARD PARISH EXECUTIVE SUMMARY INTRODUCTION In 1990, the United States Congress amended the Clean Air Act to address Chemical Accident Prevention by requiring the USEPA to develop chemical accident prevention/community right-to-know regulations referred to as the Risk Management Program Rule. The Rule requires covered facilities, whether they be Public, Commercial, or Industrial entities, to create and implement a risk management/accident prevention program and to submit a structured Risk Management Plan (RMP) to the USEPA by not later than June 21, 1999. A covered facility is one that stores any of a long list of dangerous chemicals (e.g., chemicals that are either toxic, flammable, or explosive), in quantities greater than the threshold leve ls listed in the Rule. Listed toxic chemicals and their respective threshold quantities can be found in the Federal Regulations at 40 CFR 68. The stationary (potential) source that is addressed herein is the Munster Wastewater Treatment Plant. The Plant's location is identified as follows: 1) Street Address: 3300 Munster Blvd. Meraux, LA 70075 2) Geographical Location: 29o56'47" North Latitude 89o55'39" West Longitude Chlorine gas, an air toxic chemical, is listed. Chlorine is used by most water treatment and wastewater treatment plants as a disinfectant. The threshold quantity listed for chlorine is 2,500 pounds. The Munster Wastewater Treatment Plant stores chlorine gas in quantities that exceed the threshold quantity and, as a result, is a covered facility. Accordingly, St. Bernard Parish has conducted a Program 2 Hazard Review, a Compliance Audit, and developed this RMP for the wastewater treatment plant. The Parish also is preparing written Safety, O&M, and Emergency Response Plans for the safe handling of the toxic gas, as required by the USEPA. It is pertinent to note, however, that the Munster Wastewater Treatment Plant has been in continuous operation for more than 31 years. During that long operational history, there has never been a release of chlorine gas of such a magnitude so as to cause injury to people, pets or property surrounding the wastewater treatment plant. Pure chlorine gas (an air toxic), used to disinfect the Parish's treated wastewater supply, is received and stored at the above location in the form of a gas that is liquified under pressure. The liquified chlorine gas is supplied in steel pressure cylinders that contain one ton (2000 lbs) of chlorine when received. Typical inventory of chlorine at the Munster Wastewater Treatment Plant is six ton cylinders. OFF-SITE CONSEQUENCE ANALYSIS "Worst-Case" Scenario The USEPA regulations require an assessment of risk and emergency response planning for accidental release of any of the listed air toxics under two (or more) different scenarios. That is, the regulations call for analysis/planning for a "worst-case" scenario based on rigid scenario conditions for any air toxic. These "worst-case" scenario - required conditions are identified as follows: Release Duration 10 minutes Quantity of Air Toxic Released 2000 lbs Release Rate 200 lbs/min Endpoint Toxic Concentration (safe level) 0.0087 mg/l Windspeed 1.5 M/sec (3.36 mph) Meteorological Stability Conditions "F" Ambient Relative Humidity 50 % (rare in New Orleans area) Ambient Air & Chemical's Temperature (before release) 77o (OK for air, not for chemical which drops temperature as released) Under the USEPA's regulations the above requirements must be plugged into any offsite consequence analysis (OCA) modeling, regardless if any of the factors are unrealistic or very unlikely to occur. The resulting risk area for this "worst-case" scenario was determined from the USEPA's Risk Management Program Guidance for Wastewater Treatment Plants for the Munster Wastewater Treatment Plant. For an urban setting, such as is the condition at the Munster Wastewater Treatment Plant, the distance to t he endpoint (or safe exposure distance) is listed in Exhibit 4-12 in the Guidance document as a 1.3 miles radius around the wastewater treatment plant. Additionally, the USEPA regulations provide for consideration of passive mitigation in "worst-case" assessments, i.e., enclosure of air toxic containers/feed systems within a building is considered a valid, passive mitigation condition. Passive mitigation presence provides for a toxic gas release area reduction of 45 percent (i.e., by multiplying the model "worst-case" radius by a factor of 0.55). However, the Munster Wastewater Treatment Plant has no passive mitigation present. Thus, the USEPA's model endpoint for chlorine remains 1.3 miles for the Munster Wastewater Treatment Plant in the "worst-case" scenario. Alternative Scenario The regulations also permit planners to provide one or more realistic, alternative scenarios involving accidental release of air toxics. The alternative scenario considered for the Munster Wa stewater Treatment Plant was based on a tubing failure, a bad connection or valve failure resulting in the release of chlorine gas through a 5/16 inch-diameter whole or opening in a ton cylinder. This scenario was modeled by the USEPA study, (see Exhibit 4-15 in the Guidance document) and produced the following information. The release described above would last for 60 minutes with an average maximum gas flow rate of 15 lbs/min. Again, for an urban setting, the release impact area, i.e., the distance from the source out to the endpoint concentration for chlorine (0.0087 mg/l or 3 ppm) was found to be 0.1 miles. Further, while only passive mitigation can be considered for the "worst-case" scenario, the regulations permit inclusion of active mitigation factor(s) for the alternative scenario modeling that can further reduce the estimated toxic gas spread area (i.e., distance to endpoint). A few examples of active mitigation are air scrubbers, emergency shut-down systems, and sprinkler systems. However, the Munster Wastewater Treatment Plant employs no form of active mitigation. Thus, the USEPA's model endpoint for chlorine remains 0.1 miles for the Munster Wastewater Treatment Plant in the "alternative" scenario. The Parish has developed a toxic gas release Emergency Response Plan (ERP) that is applicable to both the Parish's Water and Wastewater Treatment Plants. The plan has been coordinated with the Parish's Fire and Police Departments. During the operational history of the plant and certainly for the past 5 years, there have been no toxic gas releases from the plant. |