South County 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. The Department complies with all applicable procedures of the United States Environmental Protection Agency, the Florida Department of Environmental Protection and the Florida Department of Community Affairs. South County Advanced Wastewater Treatment Plant The South County Advanced Wastewater Treatment Plant is located at 520 Teco Road, Ruskin, Fl 33570. The site is at the north end of Teco Road and adjacent ot Interstate 75 at the northwest corner of the interchange with S.R. 674. In addition to the treatment facility, the complex includes wastewater transmission facilities, a reclaimed water system and pumping facility. The surface water disch arge facility is located off site. Offsite Consequence Analysis The offsite 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 assume that the ... maximum quanitity 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 utilized the EPA lookup tables for Risk Management Compliance. The worst case scenario at South County Advanced Wastewater Treatment Plant involves an unspecified failure of a single one-ton container of chlorine. The EPA -specified conditions assume the release of the entire amount as a gas in a 10 minute period, use of the one hour ERPG-2 guidelines 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 HCWD 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 (6) six percent of the area of the full circle Mitigation systems to be considered include chlorine leak detection system and vacuum piping. The South County Advanced Wastewater Treatment Plant chlorine system is a vacuum system. This type of system can be expected to significantly reduce the amount of chlorine released in case of a pigtail or piping failure. 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 inspection program Chemical specific prevention steps include the availability of self-contained breathing apparatus (SCBA) worn by the operators during connection / disconnection of chlorine containers, awareness of the hazardous and toxic properties of chlorine and the presence of chlorine leak detection systems. The facility also maintains a chlorine repair kit. Accidental Releases There have been no accidental releases of chlorine at this facility since it was placed into service in 1979. |