City of Bethlehem Wastewater Treatment Plant - Executive Summary |
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EXECUTIVE SUMMARY City of Bethlehem Wastewater Treatment Plant Accidental Release Prevention and Emergency Response Policies The facility has written Standard Operating Procedures (SOPs) in place for the operation and maintenance of the chemical feed system, employee training and emergency response. As a municipal agency, plant personnel work closely with appropriate agencies in the City of Bethlehem to assure safe operation of the plant, and expedient response in case of an emergency. Description of the Facility and the Regulated Substances Handled The City of Bethlehem operates a wastewater treatment plant located in Bethlehem, Pennsylvania. The toxic substance maintained as a part of the City of Bethlehem's Wastewater Treatment Plant operations is chlorine. The facility includes a Chlorine Storage Room, and a Chlorine Feed Room. The Chlorine Storage Room provides an area to store up to eight (8) one-ton containers. Additional storage for up to 14 one ton containers is p rovided outside on the dock for a maximum of 22 one-ton containers on site. The chlorine supply system consists of eight (8) one ton containers (four in use and four standby). The chlorine containers are stored on four container scales (each shared by a pair of containers) to keep track of inventory by weight loss. The containers are connected to a manifold header by means of a yoke and adapter connection, a container isolation valve, and a flexible connection leading to a manifold valve. Gaseous chlorine flows under pressure from ton containers to a vacuum regulator. From the vacuum regulator, chlorine gas flows under vacuum conditions by means of a remote eductor that uses a flow of supply utility water to produce a vacuum. The vacuum regulator between the pressurized and vacuum piping systems contains a gas inlet valve, a pressure relief valve and an automatic switchover device. The throttling action of the gas inlet valve reduces the varying gas supply pressure to a const antly regulated vacuum. A loss of vacuum for any reason will cause the gas inlet valve to close automatically. The pressure relief valve will automatically vent gas to the atmosphere if pressure develops. The automatic switchover device provides a continuous gas feed by automatically switching to the alternative gas supply when the supply in service is exhausted. A gas pressure gauge is located on each manifold above the vacuum regulator to provide a visual indication of the gas supply pressure. Two rack-mounted 1,000 pound chlorinators meter the chlorine flow rate. The chlorinator module contains a flow meter, a metering orifice, an automatic-manual feed rate control valve and an ejector vacuum gauge. The vacuum created as water flows through the ejector causing the gas inlet valve in the vacuum regulator to open and, with the supply valves open, allows chlorine gas to flow through to the ejector. The ejector that develops the vacuum causes the flow of chlorine gas through the system. At the ejector, the chlorine dissolves in water to form hypochlorous acid. This solution flows through the distribution lines to the chlorine contact tank. Worst-Case and Alternate Release Scenarios The Risk Management Program Guidance (40 CFR part 68) for Wastewater Treatment Plants was used to assess both of these scenarios. Worst-Case Scenario A ten-minute release under worst case meteorological conditions (F stability, 3.4 mi/hr wind speed and 77 degrees F ambient air temperature) was assumed for the worst-case scenario. A rural topography was used. A release of 2,000 lbs of chlorine (the entire contents of one container) was assumed, at a rate of 200 lbs/ min for 10 minutes. The distance to the toxic endpoint was estimated to be three (3) miles. It was estimated that a release under the worst-case scenario would affect 50,600 people. Alternative Scenario A flashing liquid release due to the shearing of a 1/4" pipe was assumed under stability class D and a windspeed of 6.7 mi/hr. The meteorological conditions used were an overcast day with a moderate wind. A release rate of 90 lb./min was used, along with a distance to toxic endpoint of 0.4 miles. It was estimated that a release under the alternative scenario would affect 190 people. Accidental Release Prevention Program and Chemical-Specific Prevention Steps The facility approaches release prevention by assuring that its containers, feed lines, valves and other mechanical apparatus in the chlorine supply system adhere to applicable ASTM and ANSI standards, as well as by providing training to its employees which allows them to safely and efficiently carry out their duties. Five-Year Accident History There have been no releases during the five year period from June, 1994 through June, 1999. Emergency Response Program There are two chlorine gas detectors, one located in the Chlorine Storage Room and one in the Chlorine Feed Room. These detectors continuously monitor the activit y in these locations. A chlorine alarm will sound if the chlorine concentration exceeds 1ppm chlorine by volume of air. The alarm will be activated in the Control Building to notify personnel. If there is a leak of liquid chlorine from a container, the liquid spill on the floor will quickly flash off into the air as a vapor, and the detectors will activate the alarm in the control building. Because the facility is included in the community emergency response plan developed under 42 USC 1103, it is exempted from compliance with the emergency response program requirements at 40 CFR 68.95. Instead, in the event of a release, one of the facility's Emergency Coordinators will be notified. The Emergency Coordinator on duty will immediately notify the Northampton County Emergency Management Agency, the local Fire Department and other appropriate agencies. Facility personnel will not respond to accidental releases of regulated substances. Once the Fire Department has arrived, they will evaluate the situation and determine whether it is a site or general emergency. They will evaluate and deny entry into the Chlorine Building and only allow emergency response personnel who are properly equipped and trained to enter the immediate area of the spill. The Fire Department will establish an on-scene command post and communications network. The potentially affected public can be alerted by radio, television, newspaper, or by the Police Department, which can individually contact affected people by having its cruiser cars use their loudspeakers or by sending police officers to perform door-to-door notification. A discharge of liquid chlorine will result in formation of chlorine gas. While the discharge will likely originate in the chlorine room, there is no method of containing the gas within that room, or of collecting and/or mitigating any released gas. Planned Changes to Improve Safety The facility is in the process of complying with the deficiencies outlined in the hazard review portion of the RMP. |