Valley Sanitary District Water Reclamation Plant - Executive Summary |
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Chlorine is the most commonly used substance for treating wastewater. The Valley Sanitary Water District Water Reclamation Plant (VSDWRP) also uses chlorine for treating wastewater to provide safe water discharges to the environment. Storing and handling large quantities of chlorine can create hazardous situations. VSDWRP takes safety obligations in storing and using chlorine as seriously as it takes in providing the environment safe disinfected water. VSDWRP's chlorine handling process is subject to the U.S. Environmental Protection Agency (EPA) Risk Management Program and Plan and also to the California Accidental Release Prevention (CalARP) Program. These Programs require a summary in the Risk Management Plan (RMP) of policies and procedures followed to safely operate the facility, including a description of the possible consequences in case of an accident 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: 7 Accidental release prevention and emergency response policies. 7 General facility and regulated substances information. 7 Offsite consequence analysis results. 7 Summary of the accidental release prevention program and chemical-specific prevention steps. 7 Five-year accident history summary. 7 Emergency response program summary. 7 Planned changes to improve safety. The above information for the VSDWRP chlorination system is provided below. Accidental Release Prevention and Emergency Response Policies The VSDWRP 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 State of California and EPA's Prevention Program are adhered to, including key elements such as training, systems management, and emergency action procedures. VSDWRP is a non-responding faci lity, which means that the facility employees will not respond to chlorine accidental release. Instead, the facility has coordinated with local response agencies to respond to any chlorine release that may occur at the plant. General Facility and Regulated Substance Information The VSDWRP is located on 45-500 Van Buren Street, in Indio, California. The treatment facility is located on a land area of approximately 81 acres. The Valley Sanitary District facility has operated since 1925. The design treatment capacity of the plant has increased in stages from the original 1.5 million gallons of water per day (mgd) to current capacity of 7.5 mgd. The wastewater treated at Valley Sanitary district originates mainly from approximately 20,000 domestic and industrial users in the communities of Riverside county. Wastewater treatment utilizes the activated sludge process and oxidation ponds to yield secondary effluents for purposes of re-use, and with post Chlorination for discharge. Th e purpose of the chlorination system is to prevent the spread of water borne diseases by means of chemically treating the plant effluent to kill disease-causing organisms. Anhydrous chlorine used for chlorination is received in chlorine trailers and transferred to a 2700-gallon (16 ton) capacity storage tank located inside a chlorine shed. The maximum quantity of chlorine present in the bulk storage tank at any given time is 13.5 ton (27,000 pounds). In addition to the storage tank, the chlorination system consists of three chlorinators and injectors, piping and other equipment, and one chlorine detector with two sensors. Gaseous chlorine s withdrawn from the bulk storage tank under its own pressure and flows through a pressure reducing valve, then a vacuum regulating valve to the chlorinators. The chlorinators regulate the chlorine vapor flow to the injectors. Chlorine vapor is pulled by vacuum created by a Venturi effect of the service water flow at the injectors. The injecto rs mix chlorine vapor with plant service water to create a chlorine solution that flows to the point of injection in the treatment process at service water pressure. The chlorine gas sensors are used to sense chlorine leaks in the chlorine storage and use area. Upon detection of approximately 1 ppmv chlorine, the chlorine analyzer will activate a yellow warning light and an audible alarm at the chlorine shed. A signal is also transmitted to a central alarm system in the control building to activate the alarm on the auto dialer and show an alarm indicator on the auto dialer panel. The chlorine leak detection system is equipped with aback up battery supply. The plant is manned 10 hours a day, year round. Access to the plant is through gates, which are closed after regular hours. Offsite Consequence Analysis Results The offsite consequence analysis includes consideration of two release scenarios, identified as "worst-case release scenario" and "alternative release scenario". The f irst scenario is defined by EPA, which states that "the owner or 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 defined as "more likely to occur than the worst-case release scenario". RMP and CalARP regulations for Program 3 processes require the performance of a consequence analysis for one worst-case release scenario that is estimated to create the greatest distance in any direction to a toxic endpoint resulting from an accidental release of regulated toxic substances from covered processes. Only passive or administrative controls are allowed under this scenario to reduce offsite impacts. The 13.5 ton (27,000 pounds) of chlorine over 10-minutes represents the worst-case release quantity for the single covered process at the VSDWRP. Administrative controls are used to limit the filling of the bulk tank to only 27,000 pounds. The release rate will thus b e 2,700 lb./min. The released liquid chlorine is assumed to form a denser-than-air cloud consisting of chlorine 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 and CalARP rules for chlorine is 3 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. In practice, this type of a total failure of bulk storage tank would be unlikely. 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 scenario analysis. The results of the air dispers ion analysis indicated that the worst-case release has offsite impacts. RMP and CalARP 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. Since chlorine is the only regulated toxic substance used at the facility, one alternative scenario was selected for the offsite consequence analysis. The scenario selected for the VSDWRP chlorination system involves the release of chlorine from the flexible hose connecting the storage tank to chlorination process. This scenario can occur if the operator uses a flex hose which is worn or has a defect, which re sults in a crack in the flex hose during the withdrawal of chlorine from the storage tank. It is assumed that the crack developed in the flex hose (diameter 1 inch) corresponds to a hole of 0.25-inch (1/4 inch ) diameter. The control room would have been warned of the chlorine leak by the chlorine monitors installed at the chlorination facility. It is assumed that approximately sixty minutes would be required for an emergency response team to respond and close the angle valve on the bulk storage tank. The chlorine release rate was estimated at 9 lb./min. The alternative release scenario toxic endpoint distance was also estimated using the RMP*Comp (version 1.06) software. Toxic endpoint for chlorine is 3 ppm. EPA suggested meteorological conditions used were Stability D, wind speed of 3.0 meter per second, average air temperature 77 deg F, and average relative humidity of 50 percent. The results of the dispersion modeling analysis indicated that the alternative release scenario has no offsite impacts. Finally, no chlorine release that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the VSDWRP during the last five years. Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps VSDWRP is in compliance with Federal and State Process Safety Management requirements. VSDWRPP accidental release prevention program is based on the following key elements: 7 Detailed management system and clear levels of responsibilities and team member roles. 7 Comprehensive process safety information that is readily available to staff, emergency responders, and contractors. 7 Comprehensive preventive maintenance program. 7 Performance of process hazard analysis of equipment and procedures with operation and maintenance staff participation and review. 7 Use of state-of-the-art process and safety equipment. 7 Use of accurate and effective operating procedures, written with the participation of the operators. 7 High level of training of the operators and maintenance staff. 7 Implementation of an incident investigation, inspection, and auditing program using qualified staff. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), awareness of the hazardous and toxic properties of chlorine, and presence of chlorine detectors and alarms. 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 chlorine. This information include chlorine background information and MSDS sheets. Equipment safety information was meticulously compiled on the chlorine process. Specifications for the chlorine process are collected and provided in one place for easy reference. Details such as maximum intended inventory; safe upper and lower temperatures; and safe upper and lower pressures are on file at the facility. VSDWRP also has procedures in place that is triggered to update process safety information if there is a major change that makes existing information inaccurate. Process Hazard Analysis In 1999 a detailed process hazard analysis (PHA) was conducted for chlorination system equipment and procedures and 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 improve the chlorine safety and staff is currently evaluating these recommendations. Staff will document the completion of recommended actions. A seismic walkthrough was recently completed based on the 1997 UBC, and recommendations were provided to VSDWRP staff for their evaluation and implementation. Operating Procedures VSDWRP maintains written operating procedures that provide clear instructions for chlorine process. The operating procedures incl ude start-up, normal operation, and shutdown procedures. 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 chlorine equipment, and reconfiguration of the facilities. Training VSDWRP employees presently involved in operating or maintaining the chlorine process are trained in an overview of the process and detailed applicable operating and maintenance procedures. VSDWRP 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. VSDWRP training program includes as a minimum the following five elements: (1) process safety information (2) process technology and process equipment, including safety system, (3) maintenance procedures, (4) operating procedures for the chlorine system, and (5) RMP/PSM Program contents. Each employee (presently involved in operating the chlorination process) has been trained to receive the required knowledge, skills, and abilities to safely carry out the duties and responsibilities, including chlorine emergency action. Refresher training is provided annually to each employee operating the covered process to ensure that the employee understands and adheres to the current operating procedures. In addition, the VSDWRP ensures that operators are trained in any updated or new procedures prior to startup of a process after a major change as indicated in their Management of Change procedures. VSDWRP 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 VSDWRP has procedures and policies in place that ensure that only contractors with good safety programs are selected to perform work on and around the chlorine process and that the contractors are properly info rmed of the hazards, access limitations to these process areas, and emergency action procedures, and prepared to safely complete the work. VSDWRP holds contractor safety briefings before allowing them near or in the process areas; controls access to the process areas, and evaluates the contractor's performance. Pre-Startup Safety Review and Mechanical Integrity Program VSDWRP has procedures in place to ensure that a pre-startup safety review is conducted prior to starting a new covered process or prior to making modifications to the chlorination system that require a MOC procedure implementation. These procedures ensure that no new/significantly modified process will start-up and no regulated substances will be introduced into such a process prior to the pre-startup safety review. VSDWRP uses a manual system that assures inspection, testing, and maintenance of chlorination equipment in accordance with the manufacturer and industry groups (i.e. Chlorine Institute.) Hot Work Perm its and Management of Change VSDWRP requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process. VSDWRP uses a permitting program to ensure hot work is conducted safely on or near a process involving chlorine. VSDWRP provides a system and approach to maintain and implement any management of change or modifications to equipment, procedures, chemicals, and processing conditions. This system allows VSDWRP staff to identify and review safety hazards or provide additional safety, process, or chemical information to existing data before the proposed change would either compromise system safety or need training to be completed. 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 VSDWRP will assemble an audit team that will include personnel knowledgeable in the Risk Management Program rule and in the proc ess. 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 safe 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 VSDWRP 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 chlorine releases that could have caused safety or health hazard (deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the VSDWRP during the last five years. Emergency Response Program Summary VSDWRP is a non-responding facility which means that the facility employees will not respond to chlorine accidental release. Instead, the facility has coordinated with local response agencies to respond to any chlorine release that may occur at the plant. Planned Changes to Improve Safety Based on the PHA, 31 changes to improve chlorine safety were identified. It is expected that these recommended actions will be evaluated by December 1999. The implementation of these recommendations will further improve the safety of the chlorination system. |