River Oaks Advanced 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 treatment facilities throughout unincorporated Hillsborough County, Florida. All applicable procedures of the United States Environmental Protection Agency, the Florida Department of Environmental Protection and Department of Community Affairs are stringently obeyed. The HCWD emergency response policy involves the preparation of response plans specific for each facility. Each facility is in compliance with the EPA emergency response program requirements. The River Oaks Advanced Wastewater Treatment Plant is located at 8425 North Sheldon Road, Tampa, Fl. The site is on the northeast corner of Waters Avenue and Sheldon Road. In addition to the treatment facility, the complex includes wastewater transmission facilities, a rec laim water system and surface water discharge facilities. The off-site 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 "the owner of operator shall assume that the ... maximum quantity in the largest vessel ... is released as a gas over 10 minutes," due to an unspecified failure. The alternative scenario is identified as "more likely to occur than the worst case scenario." The HCWD has utilized the EPA lookup tables for its release modeling. The worst case scenario at ROAWT involves an unspecified failure of a one-ton container of chlorine. The EPA-specified conditions assume the release of the entire amount as a gas in ten minutes, use of the one-hour ERPG-2 as the toxic endpoint, and consideration of the population residing 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 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 (6) percent of the area of the full circle. EPA mandated meterological conditions, Stability F, wind speed of 1.5 m/second, highest daily maximum temperature and average humidity were used for the modeling. Mitigation systems to be considered at ROAWT include chlorine leak detection system and vacuum piping. The ROAW T chlorine injection system is a vacuum system. This type of system can be expected to significanlty reduce the amount of chlorine released in case of a pigtail or piping failure. Release Prevention Program The general HCWD release prevention program is based on several key elements: High level of training of operations and maintenance staff Preventative maintenance program State of the art process and safety equipment Accurate, effective operating procedures Hazard review of equipment and procedures An in-house inspeciton program Chemical specific prevention steps include the availabiltiy of self-contained breathing apparatus (SCBA) worn by operators during connection / disconnection of the chlorine containers, awareness of hazardous and toxic properties of chlorine and the presence of chlorine detection systems. The facility also maintains a chlorine repair kit on site. |