Bay Metro Water Treatment Plant - Executive Summary |
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Certification Letter for Bay Metro Water Treatment Plant, 2691 N. Euclid Rd., Bay City, MI 48706 Certification Statement for Program Level 2 & 3 Processes: To the best of the undersigned's knowledge, information, and belief formed after reasonable inquiry, the information submitted is true, accurate, and complete. John A. DeKam _____________________________ ________________________ Superintendent June 19, 1999 ____________________________ _________________________ Executive Summary for Bay Metro Water Treatment Plant Bay City, Michigan This modern municipal water treatment plant purifies and pumps potable drinking water for approximately 90,000 people in the City of Bay City and throughout Bay County. The plant was built in 1979 at a cost of $22 million and is own ed and operated by the City of Bay City, Michigan. It is well maintained by a motivated, highly trained staff of 23 employees. The purification process includes disinfection to destroy harmful bacteria, viruses and protozoa. Chlorine is the primary disinfection agent used, and it is the storage and use of chlorine that drives the need for the development and submission of this Risk Management Plan. Safety is of the utmost concern to the staff. Safety concerns are centered on three broad areas: 1. SAFETY OF THE WATER. The essential purpose of this facility is to provide safe drinking water. A very high quality safe drinking water is produced, meeting all requirements of the Safe Drinking Water Act. The plant superintendent and assistant superintendent each have nearly 29 years of experience in municipal water treatment facilities. The management and operators of the facility are trained and licensed by the Michigan Department of Environmental Quality (MDEQ). The water qual ity and operation of the plant is closely monitored and regulated by the MDEQ. 2. SAFETY OF THE EMPLOYEES. While equipment and chemicals are used to purify and pump the water, it is the employees who actually operate and maintain the processes. The employees must have a safe environment to work in or they will not be available to operate and maintain the equipment and processes. The staff has developed written safety plans and safe working procedures. Regular safety training meetings are held with the staff. 3. SAFETY OF THE SURROUNDING POPULATION. It would be ludicrous for the staff to put effort into providing safe water for the general population while ignoring potential risks to the population of citizens surrounding the water treatment plant. The staff has taken many steps to design and install storage and handling equipment that will prevent and/or contain chemical spills and leaks to protect the public and the environment. Chlorine has been widely used in water treatmen t since the early 1900's. Prior to the widespread use of chlorine, there were numerous instances of large outbreaks of typhoid, cholera, and other diseases killing thousands of people. These diseases are practically unheard of in developed countries today, primarily since the advent of chlorination of public water supplies. This use of chlorine was, and still is, the single most important step in assuring the safety of the water for human consumption. While it is well known that there are certain hazards associated with the storage and application of chlorine, the safety record in municipal water and wastewater treatment plants is very good. Through proper design, modern equipment, mechanical and administrative controls, and thorough training, the Bay Metro Water Treatment Plant has never experienced an off-site release of chlorine gas, nor any on-site injuries resulting from chlorine gas exposure. The process of chlorine delivery, storage, handling and application is as follows: 1. One-ton cylinders of liquid chlorine are stored on-site, in a tight concrete block room. The cylinders are delivered approximately every two months by Department of Transportation approved trucks and delivery methods. 2. The cylinders are off-loaded from the trucks with an approved and frequently inspected overhead crane system. The cylinders are placed on special racks to prevent movement and bumping damage. 3. The storage and chlorine feed rooms each have an automated chlorine gas detector and alarm. Any gas leakage, above 1 part per million (ppm) by volume, in the room atmosphere, will sound an alarm siren throughout the facility. Response to an alarm is further described later in this summary. 4. The storage and feed rooms also have a ventilation system which can be activated externally to ventilate the room of any small discharges, however this ventilation system is never activated if there are sufficient quantities of chlorine present to cause an off-site release. Th is passive mitigation resulting from the concrete block enclosure will retain considerable quantities of chlorine gas within the confines of the storage and/or feed rooms. 5. When readied for use, the cylinders are placed on a secure rack mounted on a built in scale. The scale is used as a cross-check to monitor the weight of chlorine that is applied to the water. 6. While up to five cylinders may be connected to the process piping at a time, only one cylinder is turned on (valve opened) at a time, until the volume of the opened cylinder reaches approximately 400 pounds. At that time, a second cylinder valve is opened. However, the regulator on the full cylinder is still held closed by the tank mounted vacuum regulator. The full cylinder does not come on-stream until the first cylinder is completely empty. 7. A new state-of-the-art vacuum chlorination system was recently installed, replacing the original pressure chlorination equipment. With this system a vacuum regulator is a ttached directly to the gas discharge valve of each cylinder. A high flow of water, downstream in the process application piping, flows through an "eductor" that creates a vacuum to draw chlorine gas out of the cylinder. The vacuum line is connected to the chlorine regulator mounted on the cylinder. With this "fail-safe" system, if there is any loss of vacuum or leak in the line, the regulator valve will automatically close, thus stopping all flow and/or leakage of chlorine gas. This is a mechanical control that will prevent virtually any off-site escape of chlorine gas. In fact, this system even prevents minor on-site releases. 8. Once the chlorine gas, under vacuum, reaches the "eductor", it is mixed with water to form a chlorine solution. This chlorine solution is carried, through rust proof PVC pipes, to the application points in the primary flow of water. 9. If there is a break in any chlorine solution line, the chlorine gas will continue to be mixed with the water and wil l result in a maximum loss of twenty (20) pounds per hour. However, this chlorine solution will be contained within our facility and cannot result in an off-site release of chlorine gas. 10. In the highly unlikely event of any accidental release of chlorine gas, two (2) automatic chlorine gas leak detectors will sound an alarm throughout the facility. Staff has been instructed and trained to immediately go to an area outside of the chlorine storage room, and to then close the valve of the chlorine cylinder that is in use. Special valve wrenches have been installed, with long extensions, connected to the shutoff valve of each cylinder, and extending through the wall through a sealed fitting, so that the cylinder valves can be closed without entering a hazardous atmosphere. 11. An aqueous phase chlorine residual analyzer is installed to continuously monitor the chlorine residual downstream of the application point. A slight drop in the chlorine residual in the water will sound an alarm, requiring operator investigation. The drop in chlorine residual could result from other causes, such as an increase in chlorine demand, but any chlorinator malfunction or leak of chlorine gas or leak of chlorine solution will also cause this decrease in chlorine residual. Thus, we have a third, completely independent and different type of alarming system. WORST CASE SCENARIO One ton chlorine cylinders are very, very rugged. They are built to even withstand falling off a truck on the highway. The valves are attached to a recessed end to prevent damage from accidental bumping. Also built into the recessed ends are several "fusible plugs" that are designed to melt at 162 degrees F to slowly reduce pressure buildup, rather than explosion, in event of a fire. The Worst Case Scenario described in the RMP would be the release of 2,000 pounds of chlorine in a 10-minute duration. While this fast of a release would be nearly impossible, we are planning for the impossible so tha t we will also be prepared for something less catastrophic. EPA's RMP*Comp(tm) software was used to calculate that a resulting plume would extend 0.90 miles from the facility. Using LandView III software with the Census Bureau population database for Bay County, the population within this radius was estimated to be 1,686 people. Much of the area surrounding the facility is wooded private property. Depending on wind direction, an off-site release could move on very sparsely populated land. Some areas, especially to the South, and West are more populated to moderate density along rural roads. The prevailing winds in this area are from the Southwest. The area to the Northeast of the plant is primarily wooded, with a State Park campground and the Saginaw Bay approximately 3/4 miles away. Approximately 1/4 mile to the South of the plant is an elementary school. ALTERNATIVE RELEASE SCENARIO The Alternative Release Scenario described in the RMP would be a release of 50 pounds of a 10-minute duration. This release would be contained almost entirely on our own grounds. There are no residences or schools within the predicted 0.10 mile radius of the chlorine room. |