DAYTON WATER TREATMENT PLANT - Executive Summary |
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EXECUTIVE SUMMARY CITY OF DAYTON WATER TREATMENT PLANT 1. The City of Dayton Water System has an on-going Emergency Response Plan that includes steps to be taken in the event of an accidental release or spill of a toxic and/or hazardous chemical. A chlorine leak presents the most severe situation because it can affect a large number of people in a short amount of time. This Risk Management Plan will use a "worst case" and an "alternative" scenario to help determine the effects of a chlorine leak. 2. The City of Dayton Water Treatment Plant is located at 1463 Armstrong Ferry Rd. approximately 2 miles east of Dayton's city limits and about = mile from the Tennessee River. Chlorine is used to disinfect the raw water that comes from the river. The City of Dayton Water System serves about 6,000 customers around the Dayton area including Rhea and Bledsoe counties. Chlorine is stored on-site at the water treat-ment plant with maximum storage of about 6,000 pounds. The chlor ination process includes a chlorination room, ton containers, 2 chlorinators, exhaust fans and fresh air vents, a chlorine leak detector which is con-nected to an outside warning light and an audible alarm inside the operations area. A self contained breath-ing apparatus is mounted nearby and an Emergency Kit B (for ton containers) is located inside the lab area. The operations area and the chlorination room are adjacent to one another. The facility is manned when the plant is operating and all chlorine container valves are closed when the plant is not operating as added precautions. 3. The offsite consequence analysis includes consideration of two accidental chlorine release scenarios - a "worst case" and an "alternative" release. The worst case scenario, as defined by the EPA, assumes that the maximum quantity of the largest on-site container is released as a gas during a 10-minute period. In our case, 2,000 pounds of chlorine is released at a rate of 200 lbs/min. Atmospher ic dispersion modeling has to be performed to determine the distance traveled by the chlorine release before its concentration decreases to the "toxic end-point" selected by the EPA as 0.0087 mg/l (ppm). The toxic end-point as defined by the American Industrial Hygiene Association is the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action." Also, the residential population within a circle with a radius corresponding to the toxic endpoint distance has to be determined. The worst case release scenario for the City of Dayton Water Treatment Plant involves the failure of a one-ton container of chlorine located on-site. The RMP*COMP model software available from the EPA was used to determine the radius to the toxic end-point. EPA mandated meteorological co nditions were used as data for the software. Conditions entered were Stability F and wind speed 1.5 m/sec. Also, a release rate of 200 lb/min for 10 minutes and a rural topography were used. The model estimated that the distance to the toxic end-point was 2.2 miles. We estimate that approximately 4,000 people could be affected within this area. The alternative release scenario involves the rupture of a flexible connection to the one-ton container pos-sibly due to material corrosion and/or breakdown or even operator error. The amount of chlorine released during a 30 minute period at 10 lb/min or a loss of 300 pounds was used as data for the RMP*COMP model. Note: Because we have personnel on-site at all times of operation and with the safety devices that are in place, we believe that such a high loss could not occur. After input of this rate of loss along with the EPA mandated meteorological conditions, the estimated distance to the alternative toxic end-point is 0.1 miles o r 528 feet. We estimate that approximately 30 people could be affected. The general accidental release prevention program includes the following: a) operator training of process controls, self-contained breathing apparatus, repair kit, first aid, etc., b) Preventive maintenance program, c) Use of process and safety equipment. 4. No accidental releases of chlorine have occurred at the Dayton Water Plant in the past 5 years. 5. The City of Dayton Water and Wastewater Plants have an emergency response program that is coordinat-ed with the City of Dayton Fire Department, City of Dayton Police Department, Rhea Co. Emergency Management Office and the Rhea Co. Sheriff's Department. This program includes an emergency response and notification plan. Emergency response drills and evaluations are conducted regularly. 6. The Dayton Water Plant has just upgraded the chlorination processes with installation of new chlorine feed equipment and safety detection equipment. |