Los Coyotes Water Reclamation Plant - Executive Summary |
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Chlorine and sulfur dioxide are the two most commonly used substances for treating wastewater. The County Sanitation Districts of Los Angeles County (CSDLAC) Los Coyotes Water Reclamation Plant (LCWRP) uses chlorine (for chlorination) and sulfur dioxide (for dechlorination) for treating wastewater to provide safe water discharges to the environment. Storing and handling large quantities of chlorine and sulfur dioxide can create hazardous situations. For this reason, LCWRP follows all industry recommended practices for safely storing and handling these chemicals. LCWRP's chlorine and sulfur dioxide handling processes are 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: * 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 LCWRP chlorination and dechlorination systems is provided below. Accidental Release Prevention and Emergency Response Policies The County Sanitation Districts of Los Angeles County LCWRP 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 proc edures of the State of California and EPA's Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures. The CSDLAC emergency response policy involves the preparation of Hazardous Materials and Hazardous Waste Consolidated Contingency Plans (HMHWCCP) for handling hazardous materials which are specific for each facility and to the emergency response services available in the community, and is in compliance with the EPA and CalARP Program Emergency Response Program Requirements. The CSDLAC has prepared a HMHWCCP for the LCWRP for storing and handling hazardous materials, including chlorine and sulfur dioxide to facilitate coordination and emergency planning with offsite response officials and facilities in the event of an emergency. The HMHWCCP has been coordinated with the local response agency (County of Los Angeles Fire Department). The LCWRP has an excellent record in preventing accidents from occurring. Gen eral Facility and Regulated Substance Information The LCWRP is located at 16515 Piuma Avenue, in Cerritos, California. The treatment facilities are located on a land area of approximately 34 acres, bounded on the south side by the Artesia (91) Freeway, on the east side by the San Gabriel River Valley (605) Freeway, on the north side by Cerritos Iron Wood Nine golf course and on the west side by the San Gabriel River. The CSDLAC has operated LCWRP facility since 1970. The design treatment capacity of the plant is currently 37.5 million gal of wastewater per day (mgd). The wastewater treated at LCWRP originates mainly from approximately 350,000 domestic users in the San Gabriel Valley region; a small fraction is of industrial origin. Wastewater treatment utilizes the step feed/aeration activated sludge process with post-chlorination and dechlorination to yield a tertiary effluent for purposes of re-use and/or discharge. Anhydrous chlorine used for chlorination at LCWRP is received in chlorine trailers and transferred to storage tanks located inside the building. Anhydrous sulfur dioxide used for dechlorination is also received at LCWRP in sulfur dioxide trailers and transferred to storage tanks located inside the building. The chlorination system consists of two chlorine bulk storage tanks, evaporators, chlorinators, residual analyzers, ejectors, diffusers, chlorine contact tanks, piping and other equipment. The capacity of each chlorine bulk storage tank is 25 tons; however, the maximum quantity of chlorine present in a tank at any given time is only 18 tons. In case of a major chlorine leak, the bulk storage tanks and the chlorine tank trailer can be isolated by the emergency shutoff valves located on the piping downstream of the bulk storage tank manway and at the end of the flexible hoses that connect to the tank trailer. There are emergency shutdown switches located at each door into the chlorine building, and on the chlorine shutdown (emergency) valve control panel located on the mezzanine of the chlorine transfer area. On the chlorine shutdown (emergency) valve control panel, there are individual control switches for each valve. Chlorine gas detectors are used to sense chlorine leaks in the bulk storage and chlorination rooms. Upon detection of approximately 1 ppmv chlorine, the detectors will send a signal, which will shut down the normal ventilation system to contain the chlorine gas within the chlorination and storage rooms. The caustic scrubber system is activated in the event of a chlorine leak. The sulfur dioxide system consists of two sulfur dioxide bulk storage tanks, evaporators, sulfonators, residual analyzer, ejectors, diffusers, piping and other equipment. In addition to the main dechlorination system, there is a separate system with sulfonators for dechlorinating the waste filter backwash water. The capacity of each sulfur dioxide bulk storage tank is 20 tons; however, the maximum quantity of sulfur dioxide pres ent in a tank at any given time is only 17 tons. In case of a major sulfur dioxide leak, the bulk storage tanks and the sulfur dioxide tank trailer can be isolated by the emergency shutoff valves located on the piping downstream of the bulk storage tank manway and at the end of the flexible hoses that connect to the tank trailer. Similar to the chlorine system, there are emergency shutdown switches on the sulfur dioxide system. Sulfur dioxide gas detectors are used to sense a sulfur dioxide leak in the bulk storage room. Upon detection of approximately 5 ppmv sulfur dioxide, the detectors will send a signal which will shut down the normal ventilation system to contain the gas within the storage room. The caustic scrubber system is activated in the event of a sulfur dioxide leak. The chlorine/sulfur dioxide scrubber system is equipped with an emergency generator set. The emergency generator will automatically start one second after the loss of regular power and will continue to ru n for 5 minutes after regular power is restored. The emergency generator powers the entire scrubbing system including alarms, the scrubber fan, caustic recirculation pumps, electrically operated valves, and the sump pump. The generator also powers portions of the chlorine and sulfur systems including the automatic shutoff valve system (including the air compressors), lighting in both areas as well as lighting in the scrubber area, gas detectors, and the building ventilation fans. The plant is manned 24 hours per day but the control room is not. Access to LCWRP is through a main gate, which is closed after regular hours. In addition, a closed circuit TV is provided on the main gate. 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 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 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. For the worst-case release scenario analysis for the LCWRP, two scenarios were considered: (1) rupture of one chlorine tank with a maximum capacity of 18-tons, resulting in a release of 36,000 pounds of chlorine over a 10-minute duration, (2) rupture of one sulfur dioxide tank with a maximum capacity of 17-tons, resulting in a release of 34,000 pounds of sulfur dioxide chlorine over a 10-minute duration. Administrative controls are used to limit the filling of the chlorine bulk tank to only 18 tons and the sulfur dioxide tank to 17 tons. The release rate reduction from the enclosed building is estimated to be approximately 82% reduction of the release rate from the bulk tank, per guidance from EPA regarding control efficiencies levels for buildings storing chlorine and sulfur dioxide. The release rates for chlorine and sulfur dioxide were thus estimated to be 662 pounds per minute and 625 pounds per minute (lbs/min), respectively. The released liquid chlorine/sulfur dioxide 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 Dense Gas Air Dispersion (DEGADIS 2.1) Model. The toxic endpoint selected by EPA and CalARP rules for both chlorine and sulfur dioxide is 3 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). The toxic endpoint was conservatively set by EPA to ens ure 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 tanks would be unlikely. EPA-mandated meteorological conditions, namely atmospheric Stability Class F, wind speed of 1.5 meter per second, highest daily maximum temperature (108 deg F), and average relative humidity (74%) were used for the worst-case release scenario analysis. The results of the air dispersion analysis indicated that the toxic endpoint distance would be longer for the release of sulfur dioxide in comparison to chlorine release. However, worst-case release for both chemicals have 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 scen ario, 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 chlorination and dechlorination facilities pursuant to these rules indicated that there were no chlorine or sulfur dioxide releases, which could have resulted in offsite (outside the LCWRP 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. Since chlorine and sulfur dioxide are the only two regulated toxic substance used at the facility, t wo alternative scenarios were selected for the offsite consequence analysis. The scenarios selected for the LCWRP chlorination and dechlorination involve the release of chlorine/sulfur dioxide from the monel flexible hose connecting the storage tanks to chlorination and dechlorination processes. These scenarios can occur if the operator uses a flex hose, which is worn or has a defect, which results in a crack in the flex hose during the withdrawal of chlorine/sulfur dioxide from the storage tanks. It is assumed that the crack developed in the flex hose (diameter 1-inch) corresponds to a hole of 0.1875-inch (3/16 inch) diameter. The control room would have been warned of the chlorine/sulfur dioxide leak by the chlorine/sulfur dioxide monitors installed at the chlorination/dechlorination facility. It is assumed that a maximum of sixty minutes would be required for operators or an emergency response team to respond and activate the remote controlled shutoff valves installed on the flex hoses. The chlorine release rate inside the storage room was estimated at 87 lb./min. However, the chlorine release rate to the atmosphere from the scrubber would be only 0.003 lb/min. The sulfur dioxide release rate inside the storage room was estimated at 56 lb/min. However, the sulfur dioxide release rate to the atmosphere from the scrubber would be only 0.01 lb/min. Since the chlorine and sulfur dioxide release from the scrubber stacks would be neutrally buoyant, EPA's SCREEN3 model was used for the air dispersion analysis. The meteorological conditions used for the alternative release scenario analysis were Stability D, wind speed of 3.0 meters per second, average air temperature of 61 deg F, and average humidity of 74%. The results of the dispersion modeling analysis indicated that the maximum ground level one hour average concentration for both regulated substances (chlorine and sulfur dioxide) would be less than 0.1 ppm (0.01 ppm for chlorine and 0.03 ppm for sulfur dioxide). These concentrations are significantly lower than 3 ppm, the toxic endpoints for chlorine and sulfur dioxide, and will have no offsite impacts. It may be noted that the occurrence of these scenarios is highly unlikely because the flex hoses are inspected and pressure tested every two years. Finally, no chlorine or sulfur dioxide releases that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the LCWRP during the last five years. Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps LCWRP is in compliance with Federal and State Process Safety Management requirements. LCWRP accidental release prevention program is based on the following key elements: * Detailed management system and clear levels of responsibilities and team member roles. * Comprehensive process safety information that is readily available to staff, emergency responders, a nd 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. * High level of training of the operators and maintenance staff. * Implementation of an incident investigation, inspection, and auditing program using qualified staff. Chemical-specific prevention steps include the use of supplied air respirators (SAR) and self-contained breathing apparatus (SCBA), worn by the operators during connection/disconnection of chlorine/sulfur dioxide supply, the use of air purifying respirators (APR) worn by the drivers during connection/disconnection of chlorine/sulfur dioxide supply and availability of SCBA to the drivers, awareness of the hazardous and toxic properties of chlorine/sulfur dioxide, pre sence of chlorine/sulfur dioxide detectors and alarms, remotely controlled shutoff valves, and chlorine/sulfur dioxide scrubbers. 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 and sulfur dioxide. This information includes chlorine and sulfur dioxide background information and MSDS sheets. Equipment safety information was compiled on the chlorine and sulfur dioxide processes and is 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. CSDLAC also has procedures in place that are triggered to update process safety information for LCWRP if there is a change that makes existing information in accurate. Process Hazard Analysis In 1992, detailed process hazard analyses (PHAs) were conducted for the chlorination/ dechlorination system equipment and procedures, and were reviewed in 1977. The PHAs were further reviewed in January 1999 and will be updated again within a five-year period or whenever there is major change in the process. A list of recommended actions was developed in January 1999 to further improve the chlorine and sulfur dioxide 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 LEPC 1 guidance document. Recommendations were provided to LCWRP staff for their evaluation and implementation. Operating Procedures CSDLAC WRP section maintains up-to-date, accurate, written operating procedures for the LCWRP that provide clear instructions for chlorine and sulfur dioxide processes. CSDLAC ensures effective operating p ractices by combining them with operating and maintenance training programs. Standard operating procedures (SOPs) provide system descriptions, specifications, equipment inspection requirements, and operating procedures for the chlorine and sulfur dioxide systems. The operating procedures include start-up, normal operation, shutdown, and non-standard operating procedures. Also included are the maintenance and troubleshooting procedures. CSDLAC updates procedures whenever a change occurs that alters the steps needed to operate safely. 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 or sulfur dioxide equipment, and reconfiguration of the facilities. Training LCWRP employees presently involved in operating or maintaining the chlorine and sulfur dioxide processes are trained in an overview of the process and detailed applicable operating and maintenance procedures. CSDLAC ensures th at each LCWRP employee newly assigned to the process, is trained and tested to be competent in the operating procedures listed pertaining to their duties. LCWRP training program includes four elements: (1) initial training, (2) refresher training, (3) documentation, and (4) and testing. Each employee (presently involved in operating the chlorine and sulfur dioxide processes) has been trained to receive the required knowledge, skills, and abilities to safely carry out the duties and responsibilities, including chlorine and sulfur dioxide emergency response, as provided in the HMHWCC. 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. Operators at LCWRP are also provided quarterly refresher training on current safety procedures. In addition, the CSDLAC ensures that operators and maintenance personnel at LCWRP are trained in any updated or new procedures prior t o startup of a process after a major change as indicated in their Management of Change procedures. CSDLAC 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 Contractors are properly informed of the hazards, access limitations to these process areas, and emergency response procedures. The contractors are informed, prior to the initiation of the work at the site, of the applicable provisions of the emergency response plan. CSDLAC Field Engineering and Environmental Health & Safety Section holds contractor safety briefings before allowing them near or in the process areas; controls access to the process areas, and evaluate the contractor's performance. Pre-Startup Safety Review and Mechanical Integrity Program CSDLAC WRP Section ensures that a pre-startup safety review is completed for any new covered-by-the-rules process, or for significant modifications to an existing covered process at LCWRP that requires a change in the process safety information. CSDLAC maintains the mechanical integrity of process equipment at LCWRP to help prevent equipment failures that could endanger workers, the public, or the environment. CSDLAC mechanical integrity program for LCWRP includes the following: * Written procedures for maintaining mechanical integrity through inspection and testing of process equipment, based on instructions of equipment vendors, industry codes, and prior operating experience. * Implementation of the written procedures by performing inspections and tests on process equipment at specified intervals. * Training of maintenance personnel in preventive maintenance program procedures; safe work practices such as lockout/tagout, line or equipment opening, and avoidance and correction of unsafe conditions; and safe use and application of special equipment and/or uniq ue tools. Hot Work Permits and Management of Change CSDLAC requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process at LCWRP. LCWRP uses a permitting program to ensure hot work is conducted safely on or near a process involving chlorine and sulfur dioxide. CSDLAC provides a system and approach to maintain and implement any management of change or modifications to equipment, procedures, chemicals, and processing conditions at LCWRP. This system allows CSDLAC 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 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. CSDLAC 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 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 CSDLAC 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 mai ntenance procedures. Five-year Accident History Summary No chlorine or sulfur dioxide releases that could have caused safety or health hazard (deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the LCWRP during the last five years. Emergency Response Program Summary LCWRP trained operators are first responders to chlorine and sulfur dioxide leak alarms and accidental releases. Depending on the severity of the accidental release, external resources such as the Los Angeles County Fire Department will be called to aid in handling a chlorine or sulfur dioxide release. As part of the emergency response program, the CSDLAC has developed and implemented a Hazardous Materials and Hazardous Waste Consolidated Contingency Plan for the purpose of protecting public health and the environment. HMHWCC has been coordinated with the local response agency (Los Angeles County Fire Department). The main elements of the emergency response plan are: (1) initial discovery equipment and procedure, (2) response to an emergency, including procedures for immediate action and internal notifications, (3) procedures for external notifications, including coordination with Local Governments, Incident Commanders, (4) incident action plan, including mitigation actions, response resources, (5) implementation of tactical plan, and (6) termination and follow-up actions. Planned Changes to Improve Safety Numerous changes to improve safety (recommended actions) were previously identified for the two covered processes in 1992 as part of the PHAs conducted under the California Risk Management and Prevention Program (RMPP). The PHAs were reviewed in 1997 under the Process Safety Management (PSM) Program. These recommended actions have been evaluated and implemented as required. In addition, the process hazard analyses for the two covered processes were further reviewed in 1999 under the RMP and CalARP requirements. Based on this review, 24 add itional changes were identified to further improve the safety of chlorine and sulfur dioxide systems. 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 and dechlorination systems. |