City of Dover Water Treatment Plant - Executive Summary |
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DOVER WTP RISK MANAGEMENT PLAN EXECUTIVE SUMMARY The City of Dover Water Treatment Plant (Dover WTP) is a 6 million gallons per day (MGD) facility located east of I-77 and north of U.S. 211 in Dover, Ohio. The plant was constructed in 1998 and is in operation 16 hours per day. The Dover WTP uses a groundwater supply as its source water. Treatment processes include oxidation, manganese green sand filtration, corrosion control, and disinfection. Chlorine gas is used for oxidation and disinfection at the Dover WTP. Chlorine gas is the only regulated substance addressed by the Risk Management Plan (RMP) that is used and/or stored at the plant. Chlorine is purchased in one-ton cylinders and stored in the chlorine room located at the northwest corner of the filter building. During normal operating procedures, the maximum number of full cylinders at this location is three. Only one cylinder is in service at any given time. Chlorine gas is fed from the cylinder through a 3/8-inch reg ulator to a 3/4-inch plastic line where it flows to gas chlorinators and is converted to solution. The chlorine solution is then sent to rotometers where it is diluted and sent to feed points within the plant. Chlorine feed system equipment is inspected on a daily basis. Dover WTP personnel will shortly enhance their current program for preventing the accidental release of chlorine. A 16-step written procedure for changing chlorine cylinders will be completed and maintained on file for use by employees when changing cylinders. Employees will be required to review the procedure on an annual basis. A list of chlorine maintenance procedures will also be maintained on file and used by employees for the periodic checking, cleaning, and maintaining of all chlorine feed system components. Safety information and Material Safety Data Sheets (MSDS's) for chlorine already exist and are maintained on file in the plant's Right-to-Know area where they are easily accessible by plant personne l. An Emergency Procedures Plan for the City of Dover Water Department exists which provides detailed instructions of procedures in response to the accidental release of chlorine. Instructions are provided for detection, notification, and evacuation procedures. The Dover WTP is covered under the Emergency Response Program of the Local Emergency Planning Committee of Tuscarawas County. Plant employees are not to respond directly to the release of regulated substances but are to call 911 to notify the Dover Fire Department. As a requirement of the Risk Management Plan, different scenarios for the release of chlorine gas from the Dover WTP to the environment were performed. The release scenarios were modeled using EPA's RMP*Comp model, and included both worst-case and alternative release scenarios. The worst-case scenario assumes that the largest single container will release its entire contents to the environment over a ten-minute period. For the Dover WTP, the largest containe r is a one-ton cylinder that is located in the plant's chlorine room. Criteria used within the RMP*Comp model included a release rate of 110.0 pounds per minute (lbs/min), wind speed of 1.5 meters per second (m/sec), an atmospheric stability class of F, and urban topography. The enclosed storage of the chlorine in the chlorine room is considered a passive mitigation measure that reduces the potential exposure to the environment by approximately 33 percent. The projected area impacted by the worst-case release scenario, based on the EPA model, is presented on Figure 1. The affected area is a circle of 0.9-mile radius that includes educational, residential, commercial and industrial areas within the City. The affected area's population, based on 1990 Census population density information, is approximately 2,600. Although the worst-case release scenario is a requirement of the Risk Management Plan, there is an extremely low probability that such an event would occur. A more reali stic scenario that would be encountered at the Dover WTP is a leak from the chlorine feed line, which is addressed by an alternative release scenario. The alternative release scenario assumed that a leak or break would occur at the 3/8-inch regulator connection between the chlorine tank and chlorine feed line. The alternative release scenario assumed that the leak would be released to the environment over a ten-minute period (the release duration did not affect the size of the affected area). Criteria used within the RMP*Comp model included a release rate of 20.9 lbs/min, wind speed of 3.0 m/sec, an atmospheric stability class of D, and urban topography. As with the worst-case release scenario, the location of the chlorine feed equipment in the chlorine room is considered a passive mitigation measure that reduces the potential exposure to the environment by about 33 percent. The projected area impacted by the alternative release scenario, based on the EPA model, is presented on Figure 2. The affected area is a circle of 0.1-mile radius that only affects a limited residential off-site population, approximately 10 people, southeast of the Dover WTP. The Dover WTP has had no accidents since it came on line last year. Although the plant has only been operating for less than a year, it meets the Risk Management Plan's requirement of having no accidents during the last 5 years. The Risk Management Plan specifies that WTPs must have a prevention program in place for each process. For the Dover WTP, chlorine gas is the only regulated substance and the chlorine feed system is the only regulated process. Since the worst-case release scenario modeling results indicated that the public is within the potential effected area of a chemical release, the possible prevention programs available to the Dover WTP included Program 2 (default program) and Program 3 (consistent with Occupational Safety and Health Association [OSHA] program). Although the Dover WTP could hav e sought coverage under the less stringent Program 2, plant personnel have chosen to meet Program 3 to be consistent with OSHA's Process Safety Management (PSM) standards. Program 3/OSHA PSM standards require implementation of a prevention program with several tasks. The Dover WTP has existing programs for several of these tasks including review of safety information, training programs, and equipment inspections. As part of the Risk Management Plan requirements for Program 3, the plant has developed written procedures for process hazard analysis, operations, maintenance, management of change, employee participation plans, and hot work permits. It is anticipated that these additional management and safety procedures will help ensure that the Dover WTP will maintain a perfect record of no chemical release accidents in the future. |