Lake of the Ozarks Wastewater Treatment Plant - Executive Summary |
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Facility and Process Description The Lake of the Ozarks Wastewater Treatment Plant serves the Cities of Osage Beach and Lake Ozark, Missouri and is operated under contract by Alliance Water Resources. Chlorine is stored at the Plant in ton containers that are co-located in a chlorine room. Chlorine is used at the Treatment Plant to disinfect treated effluent before being discharged to Bowlin Hollow Creek, a tributary to the Osage River. The facility is regulated under Missouri NPDES permit number MO-0103241, which requires effluent disinfection during the months of April through October of each year. The average treatment plant flow rate is 1.2 million gallons per day. Approximately 40 lbs of chlorine is fed per day. The primary process component is the Fischer and Porter Series 4400 chlorination system, which meters and controls chlorine gas from ton-containers stored in the chlorine room. The chlorination system consists of two frame-mounted vacuum regulators located in a con tainer room, and two gas dispenser cabinets located in an adjacent chlorinator room. Two water injectors located in the gas dispensing cabinets diffuse chlorine gas into non-potable water and the chlorine solution is piped into a chlorine contact chamber. Only one chlorinator is in service at any time. Worst-case Release Scenario The Worst-case Release Scenario was assumed to be the release of an entire ton-container stored in the chlorine container room. In the scenario, the cause of the leak would be a container valve that would be inadvertently open when the outlet cap is removed. The assumed released quantity was 2,000 lbs. of chlorine, released in a period of ten minutes. RMPComp, 1.06 was the model used to calculate the affected area of the release. Data inputs used in the model were a relative humidity of 50%, ambient temperature of 77 degrees Fahrenheit, chlorine temperature of 77 degrees before release, wind speed of 1.5 meters per second and an atmospheric stability of Class F. The facility is surrounded by a steep rock face, ridges and ravines, which create an urban surface roughness coefficient. The release would occur at ground level inside the chlorine building and all receptors are considered to be at ground level. The toxic endpoint for chlorine gas as given in 40 CFR, Part 68.22 is 0.0087 mg/L. The distance from the scenario point of release to the toxic endpoint was calculated at 0.9 miles. Receptors within this radius include approximately sixteen residences and 1.2 miles of the Osage River. To avoid the worst-case scenario, operators follow procedures to assure that container valves are closed before removing the outlet caps. As a backup safety measure, outlet caps are removed slowly to assure that the closed container valve is not leaking. If there is evidence of a leak, the cap can be tightened to stop the leak. Alternative Release Scenario The alternative scenario selected was a release of chlorine gas from a 1/16th inc h-diameter hole in the pressurized gas tubing from the container to the vacuum regulator. In the scenario, chlorine would be released for 120 minutes until the emergency response team would enter the room and close the container valve. The gas RMPComp, 1.06 was the model used to calculate the affected area of the release. Data inputs used in the model were a relative humidity of 50%, ambient temperature of 77 degrees Fahrenheit, chlorine temperature of 77 degrees before release, urban surface roughness coefficient, wind speed of 1.5 meters per second and an atmospheric stability of Class F. The release would occur at ground level inside the chlorine building and all receptors are considered to be at ground level. According to the gas model, the release of chlorine would impact a radius of 0.1 miles. The estimated affected area includes one residence. To prevent the alternative release scenario from occurring, gas tubing is inspected and replaced regularly. Accidental Release P revention Plan In accordance with OSHA regulations, a Process Safety Management program has been established for the chlorine process. The program includes preventive measures to prevent releases. These measures include process safety information, procedures, process hazard analysis, training, mechanical integrity, management of change, employee participation, pre-startup reviews, hot work permits, contractor safety, incident investigation and compliance audits. Five-year Accident History There have been no significant chlorine releases at the facility. Emergency Response Program The facility is considered a "non-responding facility" and is included with the Emergency Response Plan established by the City of Lake Ozark Fire Protection District and the Camden and Miller Counties Emergency Planning Committees. |