Three Rivers Filtration Plant - Executive Summary |
|
The City of Fort Wayne Three Rivers Filtration Plant (TRFP) staff is committed to safety and is continually evaluating ways to improve safety programs. Facility staff works closely with other city and county agencies to coordinate safety and emergency response training activities. The TRFP uses chlorine, a regulated substance, in 1-ton cylinders to purify drinking water for the City of Fort Wayne, Indiana. In 1998 the facility installed a new, state-of-the-art, chlorine containment system and has subsequently won a national award from the City-County Communications & Marketing Association for its computerized operating procedures. Chlorine cylinders are used and stored inside the Chlorine Storage Building where chlorine sensors continously monitor air in the building. If sensors detect chlorine above 1ppm, a blower is automatically turned on which exhausts building air through the emergency chlorine scrubber and an alarm is activated alerting plant personnel to a possible chlorine leak. The emergency chlorine scrubber system contians 22 tons of CHLOROSORB, an activated alumina material which absorbs and neutralizes chlorine. The scrubber system is capable of effectively removing over 1 ton of chlorine (the contents of one overfilled cylinder). The scrubber system is also capable of handling air containing up to 100% chlorine gas and discharges on a continuous basis at less than 0.005 ppm chlorine concentration. The TRFP regularly submits samples of scrubber media to the supplier to monitor its depletion rate and replaces the media as recommended. In the Chlorine Storage Building liquid chlorine is converted to chlorine gas. Before leaving the Chlorine Storage Building chlorine gas is piped through two vacuum controlled valves in series which control the flow of chlorine gas throughout the rest of the chlorination process. A loss of vacuum in the process lines due to a leak or other equipment malfunction automatically closes both vacuum controlled valves; thereby, preventing an off-site release of chlorine gas outside the Chlorine Storage Building. Only one vacuum controlled valve has to close to stop the flow of chlorine. The two valves in series provide safety backup, if one should fail to close. The worst-case release scenario was modeled according to EPA guidelines and involved the catastrophic failure of one, full 1-ton cylinder. EPA guidelines do not allow active mitigation systems such as scrubbers to be considered in the worst-case release scenario. Therefore, no mitigaton measures were considered for this scenario. It is not likely that such an event would occur. EPA also requires that five alternative release scenarios be considered and that one more likely to occur than the worst-case scenario be used in an off-site consequence analysis. The facility has no history of chlorine releases under EPA's alternative release scenarios. EPA allows active mitigation measures to be considered for this scenario. Allowing for t he active mitigation systems, it is not possible for an off-site release to occur. Any potential scenario of a leak in the Chlorine Storage Building, including the catastrophic failure of a full, 1-ton chlorine cylinder would be neutralized to less than 0.005 ppm before exhausting to the outdoors which is well below the 3 ppm toxic endpoint for chlorine. Any potential leak of chlorine gas from the rest of the chlorination system outside the Chlorine Storage Building would automatically cause the vacuum controlled valves in the Chlorine Storage Building to close and stop the flow of chlorine preventing an off-site release. The TRFP has safely chlorinated the City of Fort Wayne water for decades. The facility continues evaluating ways to improve the safety of this chlorine system. The facility is covered by the Allen County Local Emergency Planning Committee (LEPC) community emergency response plan and has procedures for notifying local emergency responders in the event of an accide ntal release of chlorine. |