Apple Valley Water Treatment Facility - Executive Summary |
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The City of Apple Valley has prepared a Risk Management Plan (RMP) for the Water Treatment Facility located at 6426 West 140th Street; Apple Valley, MN 55124. 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 Apple Valley Water Treatment Plant treats an average of 5.3 million gallons of drinking water per day. The facility uses approximately 110 pounds per day of chlorine to disinfect the water system. During peak summer operations, the facility may have up to 6,000 pounds of chlorine stored at the site. Under normal operating conditions, the facility would have 4,000 pounds of chlorine. The chlorine is stored in 2,000 pound containers. The facility is required to create a Risk Management Plan in compliance with Environmental Protection Agency Regulation 40 CFR 68. The reason for this is the facility maintains more than 2,500 pounds of chlor ine on site at any given time. Creation of the RMP also provides compliance with the Process Safety Management (PSM) requirement in OSHA Regulation 29 CFR 1910.119. II. SAFETY CONSIDERATIONS The Apple Valley Water Treatment Plant has been safely treating the community's drinking water for ten years. In that time, no significant chlorine releases have occurred. Prior to the water plant being constructed, chlorine was maintained at each well site which increased chances of a leak. 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 due to damage of the chlorine piping system. The worst case and alternative release scenarios used to prepare this report assume the vacuum shut-offs have failed. The facility is also equipped with an emergency back-up generator capable of running the entire plant and one well during a power outage. III. WORST CASE RELEASE SCENARIO The Risk Management P lan regulations require modeling the potential affects caused by the anticipated worst case chlorine release scenario. The worst case release scenario for the Apple Valley Water 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 44,000 based on Census numbers. There are several critical receptors within the influence circle including schools, residences, recreation areas, and major commercial/office areas. The Minnesota Zoo and City Hall are also located within the influence circle. This worst case release scena rio is based on conservative assumptions that are improbable. IV. ALTERNATIVE RELEASE SCENARIOS 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 for emergency planning. Two possible scenarios were considered for this facility. A. Alternative Release Scenario #1 The first alternative release scenario assumed the following conditions: * 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 1,500 based on Census numbers. Critical receptors within the influence circle include residences and a local park. B. Alternative Release Scenario #2 The second alternative release scenario assumed the following conditions: * Complete failure of the switchover valve causing a chlorine gas release from two 2,000 pound containers. * 634 pound total chlorine release * 23.4 pounds/minute release * 27.1 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 0.72 miles according to EPA's Off-Site Consequence Analysis Guidance Reference Tables. The estimated population within the circle of influence is 3,300 based on Census numbers. There are several critical receptors within the influence circle including schools, residences, and recreation areas. V. EMERGENCY RESPONSE PROGRAM Emergency response would be required in the rare occurrence of a major chlorine release. The Apple Valley Water 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 Apple Valley Fire Department. The fire department would assess the situation and contact the State Duty Officer if necessary. The State Duty Officer would determine if a HAZMAT team needs to be notified. 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 water 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 discu ss 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. |