Van Dyke Wastewater Treatment Plant - Executive Summary

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The Hillsborough County Water Department (HCWD) has an accidental release prevention policy integrating  technology, established procedures and management practices into a unified approach to risk management.  The HCWD operates a number of water and wastewater teatment facilities in unincorporated Hillsborough County.   These plants adhere to all applicable procedures and policies of the United States Environmental Protection Agency and the Florida Department of Environmental Protection and the Florida Deaprtment of Community Affairs.  
Van DYke Wastewater Treatment Plant 
The Van Dykes Wastewater Treatment Plant is located at 191410 Ramblewood Road,  Tamap, FL.  This site is in Northwest Hillsborough County.  
Offisite Consequence Analysis 
The offsie consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and alternative scenario.  The first scenario is defined by the EPA, which states that "the owner or operator shall assu 
me that the ... maximum quantity in the largest vessel ... is released as a gas over ten minutes,"  due to an unspecified failure.  The alternative scenario is identified as "more likely to occur than the worst case scenario." 
The worst case scenario at Van Dyke WWTP involves an unspecified failure of a single one ton container of chlorine. The off-site consequence analysis was performed for two sets of conditions both utilizing EPA lookup charts.  
The first followed the EPA definition for worst case and assumed the release of the entire amount as a gas in 10 minutes,  use of the ERPG-2 as the toxic endpoint and consideration of the population within a full circle with radius corresponding to the toxic endpoint distance.  EPA set these conditions to facilitate the performance of the offsite consequence analysis. The Hillsborough County Water Department believes the EPA assumptions to be unrealistic because: 
    A.     Only a fraction of the compressed liquified chlorine released to 
the atmosphere flashes to a vapor.  The remaining liquid forms liquid droplet aerosols.  This results in the formation of a very dense chlorine cloud consisting of vapor and liquid droplets with dispersion characteristics significantly different than for a cloud of only chlorine gas. 
    B.     Only the population within an elliptical plume extending downwind of the release point is potentially affected.  The plume area, or footprint, is approximately six percent of the area of the full circle. 
Mitigation systems to be considered at the Van Dyke Wastewater Treatment Plant include a chlorine leak detection system and the vacuum piping.  The system is  expcted to significanlty reduce the amount of chlorine released in case of a pigtail or pipiping failure. 
Release Prevention Program 
The general Water Department release prevention program is based on several key elements: 
    A.     A high level of training for operations and maintenance staff 
    B.     A vigorous preventative m 
aintenance program 
    C.     State of the art process and safety equipment 
    D.     Accurate, effective operating procedures 
    E.     Hazard review of equipment and procedures 
    F.     An in-house inspection program 
Chemical specific prevention steps include the availability of self-contained breathing apparatus (SCBA) worn by operators during connection / disconnection of the chlorine containers, a high level of recognition of the hazardous and toxic properties of chlorine, and the presence of chlorine detection equipment.  The facility also maintains a chlorine repair kit.
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