South Tahoe Public Utility District - Executive Summary |
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EXECUTIVE SUMMARY The South Tahoe Public Utility District mission statement reads in part "carry out District responsibilities with the safety and health of customers and employees as our primary concern". The South Tahoe Public Utility District uses Chlorine at the wastewater treatment plant for disinfection of treated wastewater. Up to nine one-ton containers can be in storage with another four on-line, connected to a manifold. The system is a vacuum feed type installed in 1998. The wastewater facility also has a 12,067 gallon propane tank, which is connected to a vaporizer and mixer units. Propane can be fed into a line which alternatively supplies natural gas. Both fuels are used for sludge incineration and general heating. The chlorine storage and feed equipment are in the same room. This room is hooked up to a scrubber which can neutralize the contents of a single overfilled ton container, thus the potential for an unmitigated release is minimal. However, the worst case scenar io considered here is if a ton container were to leak its entire contents just as it is being unloaded from the delivery truck into the storage room. Papros Inc. used their RMPRO model and determined the distance to endpoint at 7.2 miles. Both the worst case and alternative release scenarios have off site impact. No administrative controls were considered in the modeling effort. The alterative scenario selected involves a pipeline leak and a simultaneous failure of the scrubber system. This was postulated to be the failure most likely to involve some offsite impact. For Propane the worst case scenario assumed a vapor cloud explosion using the RMPRO model. The endpoint used was 1.0 psi and the distance to endpoint was 0.3 miles. Earthquake strapping was added to the propane storage tank. Employee vigilance is the hallmark of the District's excellent safety record handling hazardous substances. Written procedures, training, and employee input and involvement are essential to maintai ning a safe workplace. The District has not had a chlorine or propane accident in the last five years. The District maintains a dedicated chlorine alarm system. The initial response to a chlorine release is shelter-in-place. The surrounding community (within 0.25 miles) is instructed and participates in annual drills. The local police and fire departments have toured the facility and are aware of the onsite hazards. A full scale chlorine drill was completed in February of 1999. Installation of a fire suppression system in the chlorine storage room is anticipated during the summer or 1999. No modifications to the propane system are planned. |