Salisbury Water Treatment Plant - Executive Summary |
|
Chlorine is used by the City of Salisbury Water Treatment Plant for disinfection of raw water and final disinfectant levels required for distribution of finished product. Ton cylinders are stored in one building which is separate from any other process building. A chlorine leak detector is located in this building with an audible alarm. This is checked monthly and replaced yearly. After a PHA was conducted, vacuum regulators were placed on each ton cylinder to eliminate all pressurized lines. 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. The City of Salisbury is fortunate to have a team trained to this response level and located within 6 blocks of the Water Treatment Plant. Operators carry radi os 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 since all city and county offices and downtown shopping area of Salisbury would have to evacuated. 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, although the HazMat Team had responded several times to minor releases. 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 Water Treatment Plant is located downtown, public receptors listed are many. In the 5-year capital plan an engineering review will be made to evaluate the alternatives to chlorine gas as a disinfectant for the drinking water system. |