Cypress Creek Pumping Station - Executive Summary |
|
EXECUTIVE SUMMARY a. The Cypress Creek Pumping Station was installed to chlorinate water obtained primarily from the Cypress Creek Wellfield, and also receives flow from the Crossbar, Cypress Bridge, and Morris Bridge Wellfields. Seventy-five percent of flow leaving Cypress Creek Pumping Station is destined for Pinellas County, with the remainder flowing to Pasco, Hillsborough, and Pinellas Counties and the City of St. Petersburg. The facility is located on Pumping Station Road off SR 583, adjacent to the Cypress Creek Wellfield. The station includes a chlorine building, which contains cylinders of compressed chlorine gas, two pre- and post-chlorinators, caustic soda, and various types of related safety equipment. A maximum of 36 one-ton cylinders of chlorine is found in the enclosed chlorine storage building. Up to twenty-four ton-cylinders are connected to the chlorination system at any given time. The facility is occupied by personnel at all times, and qualifies as a Program 3 facility under U.S. Environmental Protection Agency (EPA) guidelines. b. The Tampa Bay Water accidental release prevention program at Cypress Creek Pumping Station involves a unified approach that integrates technologies, procedures, and management practices, and adheres to all applicable procedures of EPA. The Tampa Bay Water emergency response program is in compliance with EPA Emergency Response Program ("ERP") requirements. c. The offsite consequence analysis includes consideration of two chlorine-related release scenarios, identified as "worst-case release" and "alternative release." The first scenario is defined by EPA, which states that, "the owner or operator shall assume that themaximum quantity in the largest vesselis released as a gas over 10 minutes," due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario." Atmospheric dispersion modeling must be performed to determine the distance traveled b y the chlorine released before its concentration decreases to the "toxic endpoint" selected by EPA of 3 parts per million ("ppm"), which is the Emergency Response Planning Guideline Level 2 ("ERPG-2"). This is defined by the American Industrial Hygiene Association ("AIHA") as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action." The residential population within a circle corresponding to the toxic endpoint distance must be defined, "to estimate the population potentially affected." i. The worst-case release scenario at the Cypress Creek Pumping Station involves a failure of a single one-ton cylinder (2,000 lb). The offsite consequence analysis for this scenario was performed using EPA-defined conditions: release of the entire amount as a gas in 10 mi nutes, use of the one-hour average ERPG-2 (3 ppm) as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. EPA-mandated meteorological conditions, namely atmospheric stability F, wind speed of 1.5 m/s, highest daily maximum temperature (96oF), and average relative humidity (74%) were inputs for analysis of the worst-case scenario. When atmospheric dispersion modeling for the worst case scenario was performed using the EPA assumptions, a distance to toxic endpoint of 3.6 miles and an estimated residential population affected of 4,386 was obtained. Enclosure of chlorine cylinders within a building was considered a form of passive mitigation. An EPA-recommended release rate-multiplicative factor of 55% was applied to the worst-case modeling input data. ii. The alternative release scenario involves detachment of a transfer line from a one-ton cylinder and partial release of the cylinder's contents . Using an EPA-recommended chlorine discharge equation, 540 lb of chlorine is released over 60 minutes. Typical meteorological conditions were used: atmospheric stability of D, wind speed of 3.7 m/s, average air temperature of 72.2oF, and 74% relative humidity. The estimated distance to a toxic endpoint of 3 ppm was 0.28 miles, and the estimated population affected was 120. EPA requires that the toxic endpoint of the alternative release scenario be beyond facility property lines, unless no such scenario conceivably exists. To meet this requirement, enclosure of chlorine within a building was not applied to the chlorine release rate when calculating the alternative release scenario toxic endpoint. d. The Tampa Bay Water accidental release prevention program is based on the following key elements: 7 High level training of the operators 7 Preventive maintenance program 7 Use of state-of-the-art process and safety equipment 7 Use of accurate and effective operating procedures, writ ten with the participation of the operators 7 Performance of a process hazard analysis of equipment and procedures Chlorine-specific prevention steps include: 7 Training in the practices of safe chlorine handling 7 The availability of self-contained breathing apparatus (SCBA), worn by operators during connection / disconnection of chlorine supply 7 Awareness of the hazardous and toxic properties of chlorine 7 Presence of chlorine detectors. e. No accidental releases of chlorine have occurred at this facility in the past five years. f. Cypress Creek has an emergency response program, which includes emergency response training of personnel, establishment of specific procedures to be followed in the event of an accidental release, and coordination with the Pasco County Fire Department. |