ALASD Wastewater Treatment Facility - Executive Summary |
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The City of Alexandria, Minnesota has prepared a Risk Management Plan (RMP) for the Wastewater Treatment Facility located at 2200 Nevada Street; Alexandria, MN 56308. The purpose of this plan is to help prevent or minimize risk of exposure to chlorine gas for both employees of the facility and also the surrounding community. I. FACILITY DESCRIPTION The ALASD Wastewater Treatment Plant treats an average of 2.2 million gallons of wastewater per day. The facility uses approximately 40 pounds per day of chlorine for disinfection. During normal operations, the facility may have up to 4,000 pounds of chlorine stored at the site. The chlorine is stored in 2,000 pound containers. The facility is required to create a Risk Management Plan (RMP) in compliance with Environmental Protection Agency Regulation 40 CFR 68. The reason for this is the facility maintains more than 2,500 pounds of chlorine on site at any given time. Creation of the RMP also provides compliance with the Process Saf ety Management (PSM) requirement in OSHA Regulation 29 CFR 1910.119. II. SAFETY CONSIDERATIONS The ALASD Wastewater Treatment Plant has been operating for 20 years with an excellent record for safely handling and feeding chlorine. The feed system operates on a vacuum principle with automatic shut-off if the vacuum is interrupted. This minimizes the risk of a major release as a result of damage to the chlorine piping system. The facility is also equipped with an emergency back-up generator capable of running the entire plant during a power outage. III. WORST CASE RELEASE SCENARIO The Risk Management Plan regulations require modeling the potential affects caused by the anticipated worst case chlorine release scenario. The worst case release scenario for the ALASD Wastewater Treatment Plant is defined as: * Catastrophic failure of a 2,000 pound chlorine container due to corrosion, impact, etc. * 2,000 pound total chlorine release * 200 pounds/minute release * 10 minute duration * Atmospheric Stability Class F * Wind Speed = 1.5 meters per second * Temperature of between 88 and 107 degrees Fahrenheit The influence radius of the worst case release is 2.63 miles according to EPA's Off-Site Consequence Analysis Guidance Reference Tables. The estimated population within the circle of influence is 9,200 based on Census numbers. There are several critical receptors within the influence circle including schools, residences, recreation areas, and major commercial/office areas. The Alexandria Municipal Airport is also located within the influence circle. IV. ALTERNATIVE RELEASE SCENARIO Alternative release scenarios more accurately reflect potential releases than the worst case scenario. Since alternative releases are more likely to occur, these scenarios are generally considered more useful to emergency planning. One possible scenario was considered for this facility. A. Alternative Release Scenario The alternative release scenario assumed the following co nditions: * Tubing failure, bad connection or valve failure resulting in release of chlorine gas through a 5/16" diameter opening * 317 pound total chlorine release * 10.5 pounds/minute release * 60 minute duration * Atmospheric Stability Class D * Wind Speed = 3.0 meters per second * Temperature of 77 degrees Fahrenheit The influence radius of this release scenario is 0.48 miles according to EPA's Off-Site Consequence Analysis Guidance Reference Tables. The estimated population within the circle of influence is 20 based on Census numbers. There are residences and the Alexandria Municipal Airport within the influence circle. V. EMERGENCY RESPONSE PROGRAM Emergency response would be required in the extremely rare occurrence of a major chlorine release. The ALASD Wastewater Treatment Facility is included in the community emergency response plan. In the event of an emergency chlorine release, an employee of the facility would be responsible for calling the Alexandria Fire Depar tment and the Morris HAZMAT team. These people are trained in handling emergency situations dealing with hazardous materials. The fire department and/or the HAZMAT team would be responsible for mitigating the effects of a release and coordinating evacuation procedures if necessary. A training program has been established to insure all employees of the wastewater treatment plant can identify an emergency situation and understand the procedure for notifying the proper authorities. As a part of this program, facility employees will annually meet with representatives of the fire department to discuss potential hazards. This will also allow the fire department to gain familiarity with the layout of the treatment plant and grounds. VI. IMPLEMENTATION OF THE RMP/PSM PROGRAM The facility has implemented written procedures in compliance with the RMP/PSM regulations to help minimize the risk of a chlorine release. The newly created RMP/PSM manual outlines training requirements, operating procedures, maintenance procedures, and defines responsible persons for implementing the different aspects of the plan. The RMP/PSM plan is a tool that will provide guidance for the facility in day to day operations thereby creating a safer and more effective work environment. |