Inver Grove Heights Water Treatment Plant - Executive Summary |
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The City of Inver Grove Heights, Minnesota has prepared a Risk Management Plan (RMP) for the Water Treatment Facility located at 7400 Babcock Trail; Inver Grove Heights, MN 55077. 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 Inver Grove Heights Water Treatment Plant treats an average of 2.2 million gallons of water per day. The facility uses approximately 30 pounds per day of chlorine to disinfect the water system. 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 c ompliance with the Process Safety Management (PSM) requirement in OSHA Regulation 29 CFR 1910.119. II. SAFETY CONSIDERATIONS The Inver Grove Heights Water Treatment Plant has a state of the art facility for safely handling and feeding chlorine into the city's water system. The system was put on line in July of 1998 and incorporates the most modern technology. The feed system operates on a vacuum principle with automatic shut-off valves if the vacuum is interrupted. This minimizes the risk of a major release due to damage of the chlorine piping system. The facility is also equipped with a chlorine scrubber. In the case of a major leak (example of a major release would be the rupture of a 2,000 pound chlorine container), the scrubber is capable of removing 2,000 pounds of chlorine gas from the air prior to being vented to the atmosphere. This is the primary line of defense in protecting the surrounding community from the hazards associated with a major chlorine release. All rel ease scenarios used in this plan assume the scrubber is not operating during the release. In reality, a major chlorine release would not have any noticeable affect on the community because the scrubber would remove the chlorine from the air prior to release. The assumption of an inactive scrubber during a major release is considered a worst case scenario. 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 Inver Grove Heights 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 * Chlorine scrubber is not operating 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 17,000 based on Census numbers. There are several critical receptors within the influence circle including schools, residences, recreation areas, and major commercial/office areas. City Hall and the South St. Paul Municipal Airport are also located within the influence circle. 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 to emergency planning. All alternative release scenarios assume the scrubber is not operating during the release. As with the worst case scenario, if the scrubber is operating effectively (as would normally be the case), it would be capable of removing chlorine from the air prior to release to the atmosphere. Two possible scenarios were considered for this facility. A. Alternative Release Scenario #1 The first alternative release scenario assumed the following conditions: * Complete failure of a 1" diameter pipe 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 * Chlorine scrubber is not operating 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 1,300 based on Census numbers. There are residences and recreation areas within the influence circle. B. Alternative Release Scenario #2 The second alternati ve 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 * Chlorine scrubber is not operating 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 570 based on Census numbers. There are residences and recreation areas within the influence circle. V. EMERGENCY RESPONSE PROGRAM Emergency response would be required in the extremely rare occurrence of a major chlorine release when the scrubber is inactive. The Inver Grove Heights 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 Inver Grove Heights Fire Department and the St. Paul 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 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 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 minim ize 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. |