Hialeah Water Treatment Plant - Executive Summary |
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EXECUTIVE SUMMARY Chlorine is the most commonly used substance for disinfecting drinking water. The addition of chlorine or chlorine compounds to water is called chlorination. Chlorination is considered to be the most important process for preventing the spread of water borne disease in drinking water. There are two methods of chlorination, breakpoint chlorination and chloramination. The breakpoint chlorination process consists of adding enough chlorine to the water to satisfy the chlorine demand so that free available chlorine residual can be measured. Chloramination is the process of adding chlorine and ammonia to water, which produces a mono-chloramine residual. The chloramination process lowers the trihalomethane levels in the finished water. The Miami-Dade Water & Sewer Department (MDWASD) Hialeah Water Treatment Plant (WTP) uses chlorine and ammonia for disinfecting and lowering the trihalomethane levels in the finished drinking water to protect public health per state and federal water quality standards. Storing and handling large quantities of chlorine and ammonia can create hazardous situations. The Hialeah WTP does not store chlorine on site, it imports chlorine via underground pipeline from the MDWASD's John E. Preston Water Treatment Plant. The quantity of chlorine present in the pipeline is less than the RMP threshold and therefore this process is not subject to the Risk Management Program/Plan (RMP) requirements. The Hialeah WTP takes safety obligations in storing and using all chemicals, including ammonia as seriously as it takes care in providing safe drinking water. The Hialeah WTP ammonia handling process is subject to the U.S. Environmental Protection Agency (EPA) Risk Management Program Rule. This rule requires submission of a Risk Management Plan (RMP). An integral part of the RMP is a summary of policies and procedures followed to safely operate the facility, including a description of the possible consequences in case of an accid ent and the actions, which will be taken, by the facility in an event of an emergency. The following information is specifically required in the RMP Executive Summary: * Accidental release prevention and emergency response policies. * General facility and regulated substances information. * Offsite consequence analysis results. * Summary of the accidental release prevention program and chemical-specific prevention steps. * Five-year accident history summary. * Emergency response program summary. * Planned changes to improve safety. The above information for the Hialeah WTP ammonia system is provided below. Accidental Release Prevention and Emergency Response Policies The MDWASD accidental release prevention policy involves a unified approach that integrates proven technology, trains staff in operation and maintenance practices, and uses tested and proven management system practices. All applicable procedures of the EPA's Prevention Program are adhered to, including key ele ments such as training, systems management, and emergency response procedures. The MDWASD emergency response policy involves the preparation of emergency response plans for hazardous materials which are tailored to each facility and to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program Requirements. Hialeah WTP has prepared an Emergency Response Plan for the treatment plant to facilitate coordination and emergency planning with offsite response officials and facilities in the event of an emergency. Hialeah WTP has an excellent record in preventing accidents from occurring. General Facility and Regulated Substance Information The MDWASD Hialeah WTP is located at 700 West 2nd Avenue, in Hialeah, Florida. Hialeah WTP is bounded to the North by West 9th Street (and John E. Preston WTP), to the West by West 3rd Avenue, and to the South by Okeechobee Road, which follows the Miami Canal. The facility stores ammonia, which is a regulated toxic substance under RMP rule. Ammonia is stored in two storage tanks of capacity 15,000 gallons (primary tank) and 2,000 gallons (auxiliary tank). The quantity of ammonia in the tank is determined by means of a float gauge which is calibrated to report the percent of the total capacity based on depth of ammonia in the tank. These tanks are filled up to 80 percent of their capacities. Thus, the maximum quantity of ammonia in a single vessel present at the Hialeah WTP will be 12,000 gallons. The maximum quantity of ammonia present at the Hialeah WPT at any given time exceeds the listed threshold quantity in the EPA rule. It also exceeds the listed threshold quantity in the federal Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) Standard. Ammonia is brought to the treatment plant in ammonia trucks and transferred to the bulk storage tanks. Gaseous ammonia is supplied to the ammoniators under pressure from the top of the storage tank. The ammonia gas flows through piping to a pressure-reducing valve, which reduces the pressure to a range of 30 to 40, psig. From the pressure reducing valve (pressure regulator), the ammonia gas then flows through piping to ammoniators located in the ammoniator room. The ammoniator room houses three ammoniators, each ammoniator is equipped with a rotameter and an orifice for controlling the feed rate manually. Downstream of the ammoniators, the ammonia gas from each ammoniator flows into a common manifold. The ammonia flows through this single pipe to the feed points in the treatment process. Hialeah WTP ammonia system is equipped with a number of safety features to protect the employees and the surrounding community from exposure resulting from accidental release or minimize the consequences of an ammonia leak. The four important safety features are (1) shut-off valves, (2) pressure relief valves, (3) check valves, and (4) ammonia leak detectors. The shut-off va lves are located immediately downstream of both the primary and auxiliary supply tanks. The shut-off valves can also be activated by pressing one of the emergency shut-off buttons. The emergency shut-off buttons are located on the exterior wall of the ammonia control on the interior wall of the chlorine room, and on the wall of the flocculators near the chlorine system expansion chambers. When the button is pressed and the valves close, both ammonia supply sources are isolated from the system. The pressure relief valves mounted on the storage tanks are equipped with three-way isolating (flapper) valves, which can be utilized to isolate one of the two relief valves. The three-way valve allows either of the two safety relief valves to be isolated while the second relief valve maintains protection for the storage tank. A spring loaded check valve is located on the liquid fill line, inside each storage tank. The check valve prevents liquid ammonia from backflowing out of the storage tank while the tank is being filled or in the event the isolation valve was to fail or leak. Ammonia leak detectors provided near the ammonia storage tanks and inside the ammoniator room monitors continuously for ammonia leaks. If ammonia gas is detected at 10 ppm, the alarm sounds. The Hialeah WTP is surrounded by a perimeter fence and locked security gates. The plant operates three shifts with employees onsite 24 hours per day, 365 days per year. The Hialeah and Preston (adjacent to Hialeah) WTPs are provided with a backup emergency power generator that supplies power to the entire facility. Offsite Consequence Analysis Results The offsite consequence analysis includes consideration of two ammonia release scenarios, identified as "worst-case release scenario" and "alternative release scenario". The first scenario is defined by EPA, which states that "the owner or operator shall assume that the maximum quantity in the largest vessel is released over 10-minutes," due to an unsp ecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario". Ammonia is the only regulated toxic substance stored and handled at the Hialeah WTP, which is subject to the RMP rule. Thus, ammonia was selected for the worst-case release scenario. Only passive or administrative controls are allowed under this scenario to reduce off-site impacts. The scenario used for the Hialeah WTP is the rupture of one ammonia tank of maximum capacity of 12,000 gallons resulting in the release of 67,200 pounds of ammonia over a 10-minute duration. Administrative controls are used to limit the filling of the bulk tank to only 12,000 gallons. There are no passive mitigation at the Hialeah WTP for the ammonia storage tanks; thus, the ammonia release rate will be 6,720 lbs./min. The released anhydrous ammonia is assumed to form a denser-than-air cloud consisting of ammonia vapor and liquid droplets (aerosols) and then disperse in the atmosphere. The distance to the toxic endpoint was estimated using the EPA's RMP*Comp software (version 1.06). The toxic endpoint selected by EPA rules for ammonia is 200 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). The toxic endpoint was conservatively set by EPA to ensure public notification and that local emergency response planning takes into account the greatest possible impacted area surrounding the release point. EPA-mandated meteorological conditions, namely atmospheric Stability Class F, wind speed of 1.5 meter per second, highest daily maximum temperature (77 deg F), and average relative humidity (50%) were used for the worst-case release scenario analysis. The results of the dispersion analysis indicated that the worst-case release scenario has offsite impacts. RMP rules require that a scenario which results in offsite toxic endpoint distance and is more likely to occur than the worst-case scenario should be selected as the alternative release scenario, unless no such scenario exists. Unlike the worst-case scenario, the alternative release scenario may consider "active" mitigation such as automatic shutoff valves, excess flow valves, and containment with scrubbers. Active mitigation is defined as requiring mechanical, electrical, or human input. The alternative release scenarios must consider the facility accident history and/or failure scenarios identified in the process hazard analysis. A review of the past five-year accident history data for the ammoniation facility pursuant to these rules indicated that there were no ammonia releases, which could have resulted in offsite (outside the Hialeah WTP boundary) toxic endpoint distances. Similarly, no credible accident scenario was identified from the process hazard analysis, which would reach offsite. Thus, an acceptable/credible alternative release scenario had to be selected based on expert judgement. The alternative release scenario selected involves the release of ammonia f rom a crack or hole in the piping connecting the storage tanks in the ammoniation processes. It is assumed that the crack or hole, which develops in the piping (diameter 1-inch), corresponds to a hole of 0.3125-inch (5/16-inch) diameter. The control room would have been warned of the ammonia leak by the ammonia monitors installed at the facility. It is assumed that approximately ten minutes would be required for operators or an emergency response team to respond and activate the remote controlled shutoff valves. The ammonia release rate for this alternative release scenario was estimated at 180 lbs./min. No passive mitigation was considered for the estimation of ammonia release rate. However, human input in closing the shut-off valve was taken into account as an active mitigation, which will reduce the quantity of ammonia released to the atmosphere. The alternative release scenario toxic endpoint distance was estimated using lookup table from EPA's Wastewater Treatment Plant RMP Guidance document. Toxic endpoint for ammonia is 200 ppm. EPA suggested typical meteorological conditions used were Stability D, wind speed of 3.0 meter per second, average air temperature of 77 deg F, and average relative humidity of 50 percent. The results of the toxic endpoint distance analysis indicated that the alternative release scenario has offsite impacts. Finally, no ammonia releases that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the Hialeah WTP during the last five years. Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps Hialeah WTP is in compliance with Federal and State Process Safety Management requirements. Hialeah WTP accidental release prevention program is based on the following key elements: * Detailed management system * Comprehensive process safety information that is readily available to staff, emergency re sponders, and contractors. * Comprehensive preventive maintenance program. * Performance of process hazard analysis of equipment and procedures with operation and maintenance staff participation and review. * Use of state-of-the-art process and safety equipment. * Use of accurate and effective operating procedures, written with the participation of the operators. * Training of the operators and maintenance staff. * Implementation of an incident investigation program. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), awareness of the hazardous and toxic properties of ammonia, presence of ammonia detectors and alarms, and remotely controlled shutoff device on the ammonia storage. Process and Chemical Safety Information Comprehensive chemical data have been assembled to include regulatory reporting and action thresholds, health hazard, and chemical exposure limitations, as well as detailed physical properties of ammonia. This i nformation includes ammonia background information and MSDS sheets. Equipment safety information was meticulously compiled on the ammonia process. Specifications for ammonia process are collected and provided in one place for easy reference. Details such as maximum intended inventory; safe upper and lower temperatures; safe upper and lower pressures; and codes and standards used to design, build, and operate the processes are on file at the facility. Process Hazard Analysis In 1997, detailed Process Hazard Analysis (PHA) was conducted for the ammonia system equipment and procedures. To further assess the integrity of the ammonia system for the preparation of this RMP, an ammonia system checklist was used to assess the overall general condition of the ammonia system operation and maintenance, including human factors that affect personnel performance and system integrity. The PHA will be updated again within a five-year period or whenever there is major change in the process. A list of recommended actions were developed to further improve the ammonia safety and staff is currently evaluating these recommendations. Staff will document the completion of recommended actions. Operating Procedures MDWASD Hialeah WTP has prepared written operating procedures that provide clear instructions or steps for safely conducting activities relating to the ammoniation process. They are consistent with the ammonia Process Safety Information. Written operating procedures include: initial startup, normal operations, emergency shutdown, normal shutdown, and start up after emergency shutdown. In addition, Hialeah WTP developed Standard Operating Procedures (SOPs) for the following steps in the ammoniation process: receipt of ammonia delivery and ammonia release/spill response. Operating procedures will be developed and put in place prior to any new process equipment coming on line or changes made in the handling of ammonia equipment, and reconfiguration of the facilities. Training Hialeah WTP employees presently involved in operating or maintaining the ammonia process are trained in an overview of the process and the applicable operating and maintenance procedures. Hialeah WTP ensures that each employee newly assigned to the process, is trained and tested to be competent in the operating procedures listed pertaining to their duties. Each employee (presently involved in operating the ammonia process) has been trained to receive the required knowledge, skills, and abilities to safely carry out the duties and responsibilities, including ammonia emergency response, as provided in the operating procedures. Refresher training is provided every three years or less to each employee operating the covered process to ensure that the employee understands and adheres to the current operating procedures. In addition, the Hialeah WTP ensures that operators are trained in any updated or new procedures prior to startup of a process after a major change as indic ated in their Management of Change procedures. The Hialeah WTP prepares and retains records of initial and refresher training, provides certification of the records, which includes the identity of the employee, the date of training, and the signature of the person (s) administering the training. Contractors MDWASD Hialeah WTP has procedures and policies in place that specify the information required to be provided to the contractors performing work on the ammoniation process, the training requirements for contractor employees, and mechanism to obtain assurance from contractors that they have informed their employees of the appropriate safety rules. MDWASD Hialeah WTP is required to provide information and explanations concerning the hazards and processes and obtain and evaluate information regarding the contractor's safety program. Pre-Startup Safety Review and Mechanical Integrity Program MDWASD Hialeah WTP has procedures in place to ensure that a pre-startup safety review is co nducted prior to starting up a new covered process or after shutdown event, or prior to starting up modifications to the ammoniation process that requires a MOC procedure implementation. Hot Work Permits and Management of Change The Hialeah WTP requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process. The Hialeah WTP uses a permitting program to ensure that hot work is conducted safely on or near a process involving ammonia. Internal Compliance Audits Internal compliance audits will be conducted every 3 years to verify compliance with the programs and procedures contained in the RMP. The Hialeah WTP will assemble an audit team that will include personnel knowledgeable in the Risk Management Program rule and in the process. This team will evaluate whether the prevention program satisfies the requirements of the Risk Management Program rule and whether the prevention program is sufficient to help ensure saf e operation of the process. The results of the audit will be documented, recommendations resolved, and appropriate enhancements to the prevention program will be implemented. Incident Investigation The Hialeah WTP investigates all incidents that could reasonably have resulted in a catastrophic release (serious injury to personnel, the public, or the environment) so that similar accidents can be prevented. An investigation team is assembled and the investigation is initiated within 48 hours of the incident. The results of the investigation are documented, recommendations are resolved, and appropriate process enhancements are implemented. Information found during the investigation is reviewed by affected staff and added or used to revise operating and maintenance procedures. Five-year Accident History Summary No ammonia releases that could have caused safety or health hazard (deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the Hialeah WTP during the last five years. Emergency Response Program Summary The Hialeah WTP is a first responder, plant employees respond to ammonia accidental releases. Depending on the severity of the accidental release, external resources such as the Hialeah Fire Department may be solicited to aid in handling an ammonia release. As part of the emergency response program, the Hialeah WTP has developed and implemented an emergency action plan for the purpose of protecting public health and the environment. The emergency response plan has been coordinated with local response agencies (Hialeah Fire Department). The main elements of the emergency response plan are: (1) ammonia response flow chart, responsibilities of various personnel at the facility, duties of on-scene incident commander, site response team, and site safety representative, (2) details of emergency recognition and prevention at the facility, (3) procedures for planning and coordination with off-site emergency respon se organizations, and (4) details of the training program for all employees involved with the ammoniation process. Planned Changes to Improve Safety Numerous changes to improve safety (recommended actions) were previously identified for the ammonia process in 1997 for ammoniation system equipment and procedures, when a Process Safety Management (PSM) Plan was prepared. All of these recommended actions have been evaluated for implementation as required. |