Town Creek Wastewater Treatment Plant - Executive Summary

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Chlorine is used by the City of Salisbury Town Creek Wastewater Treatment Plant for disinfection of wastewater prior to stream discharge.  Ton cylinders are stored in a covered facility with scales and a chlorine sensor alarm.  The sensor is checked monthly and replaced annually.  Operators wear SCBA gear when changing cylinders to provide them protection and time to repair any connections that may be leaking during a change out.  If the alarm sounds detecting a chlorine release at anytime other than cylinder change outs, then 911 is called to dispatch the HazMat Team and all plant site personnel are evacuated. Operators carry radios with them when on duty that have direct communications with 911 operators and fire personnel when needed to communicate the response conditions.  The HazMat Team is equipped with gas detectors for determining the vapor cloud concentrations. They are also equipped to repair the chlorine ton cylinder or place the endcap enclosure should a valve stem break. 
In our LEPC meeting on May 26, 1999, the Rowan County Sheriff's Department and City Police were explained the consequences of a chlorine release and communications required to dispatch HazMat Response to an outside city limits location. This meeting was the first of several to follow in planning how to handle this incident.  
In reviewing the 5-year accident history, no such evacuations or injuries had been documented. 
The worst case release scenario is 2,000 lbs released in 10 minutes. The maximum threat zone for level of concern is 4,677 feet or .89 miles.  Outdoor concentration is 61.6 ppm, while indoor concentration is only 3.54 ppm. The alternative release scenario was chosen for 500 lbs released in 30 minutes, as the estimated time to repair a significant leak.  The maximum threat zone for level of concern is .24 miles.  These release scenarios were calculated by using the ALOHA 5.2.1S air dispersion model.  Since the City of Salisbury Town Creek Wastewater Treatment Plant is lo 
cated near Interstate 85, this will involve detouring I-85 traffic in both worst case and alternative release scenarios. 
In 2000, the wastewater from this facility will be disinfected by ultra-violet light; therefore eliminating chlorine as part of the process.
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