Henry N. Wochholz Wastewater Treatment Facility - Executive Summary |
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Chlorine and sulfur dioxide are the two most commonly used substances for treating wastewater. The Yucaipa Valley Water District Henry N. Wochholz Wastewater Treatment Plant (Yucaipa WWTP) also 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. Yucaipa WWTP takes safety obligations in storing and using chlorine and sulfur dioxide as seriously as it takes in providing the environment safe disinfected water. Yucaipa WWTP'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 d escription 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 responsepolicies. 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 Yucaipa WWTP Chlorination and dechlorination Systems are provided below. Accidental Release Prevention and Emergency Response Policies The Yucaipa WWTP 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 a pplicable procedures 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 Yucaipa WWTP emergency response policy involves the preparation of Emergency Response Plan which is tailored to the 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. Yucaipa WWTP has prepared an Emergency Response Plan for chlorine and sulfur dioxide to facilitate coordination and emergency planning with offsite response officials and facilities in the event of an emergency. The Emergency Response Plan has been coordinated with local response agencies, such as the San Bernardino County Fire Department. Yucaipa WWTP has an excellent record in preventing accidents from occurring. General Facility and Regulated Substance Information The Yucaipa WWTP is located on 880 W. Cou nty Line Road, in Yucaipa, California. The Wastewater Treatment Plant has operated since 1986. The design treatment capacity of the plant has increased in stages from the original 3.0 million gallons of wastewater per day (mgd) to current capacity of 4.5 mgd. The wastewater treated at the Plant originates mainly from approximately 27,000 domestic and industrial users in the communities of Yucaipa, Calimesa, San Bernardino and Riverside Counties. Wastewater treatment utilizes the 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 is delivered to the facility in one-ton containers and stored inside the chlorine storage room. Anhydrous sulfur dioxide used for dechlorination is also delivered to the facility in one-ton sulfur dioxide containers and stored inside the sulfur dioxide storage room. The 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. The chlorination system consists of eight one-ton chlorine containers, three chlorine detectors, three chlorinators and injectors, residual analyzers, mixers, chlorine contact tanks, piping and other equipment. The maximum quantity of chlorine present in the chlorine storage room can be as much as eight tons. Four one ton containers in two separate "banks" are connected for gas draw-off to a chlorine supply header. One "bank" may be put on-line while the other "bank" is on standby status. The system is provided with an automatic switch over. In the case of a major leak, the chlorine gas analyzers are used to sense chlorine leaks in the chlorine storage and chlorinator rooms. Upon detection of approximately 2 ppmv chlorine, the analyzers will send a signal which will shut down the normal ventilation system to contain the chlorine gas within the chlorine storage room. The ca ustic scrubber system is activated in the event of a chlorine leak. The purpose of the dechlorination system is to inject sulfur dioxide solution into the plant effluent to dechlorinate the effluent. This is done to meet the waste discharge requirements of the California Regional Water Quality Control Board. The sulfur dioxide system consists of eight one-ton sulfur dioxide containers, three sulfur dioxide detectors, two sulfonators and injectors, mixers, other piping and equipment, most of which is located in the chlorination/dechlorination building. Sulfur dioxide is diffused into the effluent channel at the discharge of the chlorine contact tanks. The maximum quantity of sulfur dioxide present in the sulfur dioxide storage room can be as much as 8 tons. Four one ton containers in two separate "banks" are connected for gas draw-off to a sulfur dioxide supply header. One "bank" may be put on-line while the other "bank" is on standby status. The system will automatically switch over to the standby unit at a preset container pressure. In the case of a major leak, sulfur dioxide gas analyzers are used to sense a sulfur dioxide leak in the sulfonator and storage rooms. Upon detection of approximately 2 ppmv sulfur dioxide, the analyzers 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 control room at the plant is manned 24 hours a day, year round. Access to the Yucaipa WWTP is through gates, which are closed after regular hours. Yucaipa WWTP is also provided with an emergency generator. 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, two scenarios were considered: (1) complete de-inventory of a 1-ton chlorine container and (2) complete de-inventory of a 1-ton sulfur dioxide container. A screening analysis performed using the EPA RMP*Comp software indicated that the toxic endpoint distance for the sulfur dioxide release would be larger in comparison to a chlorine release scenario. Thus, refined dispersion modeling was performed for only sulfur dioxide release for the worst-case release scenario. The 1-ton (2,000 pound) of sulfur dioxide represents the worst-case release quantity over a 10-minute duration for the covered processes at the Yucaipa WWTP facility. No passive mitigation measures were considered for estimating the release quantity of chlorine/sulfur dioxide to the atmosphere. The release rate will, accordingly, be 200 lb./minute. The released liquid chlorine/sulfur dioxide is assumed to form a denser-than-air cloud consisting of chlorine/sulfur dioxide 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 ensure public notification and that local emergency response planning takes into ac count 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 (115 deg F), and average relative humidity (59%) were used for the worst-case release scenario analysis. The results of the air dispersion analysis indicate that the worst-case release scenario 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 and sulfur dioxide are the only two r egulated toxic substance used at the facility, two alternative scenarios were selected for the offsite consequence analysis. 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 Yucaipa WWTP boundary) toxic endpoint distances. Similarly, no credible accident scenario was identified from the process hazard analysis, which would reach offsite. The scenarios selected for the Yucaipa WWTP chlorination and dechlorination systems involve the release of chlorine/sulfur dioxide from the pigtails connecting the ton containers to chlorination and dechlorination processes. These scenarios can occur if the operator uses a pigtail, which is worn or has a defe ct, which results in a crack in the pigtail during the withdrawal of chlorine/sulfur dioxide from the ton containers. It is assumed that the crack developed in the flex hose (diameter 0.25-inch) corresponds to a hole of 0.0625-inch (1/16 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 approximately thirty minutes would be required for operators or an emergency response team to respond and close the ton container valve. The chlorine release rate inside the storage room was estimated at 0.6 lb./min. However, the chlorine release rate to the atmosphere from the scrubber would be only 0.011 lb/min. The sulfur dioxide release rate inside the storage room was estimated at 0.3 lb/min. However, the sulfur dioxide release rate to the atmosphere from the scrubber would be only 0.034 lb/min. Since the chlorine and sulfur dioxide relea se 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 63 deg F, and average humidity of 59%. 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 0.5 ppm (0.03 ppm for chlorine and 0.10 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 are highly unlikely because the pig-tails are inspected during each connection/disconnection operation, and during operator rounds. Finally, no chlorine or sulfur dioxide releases that could have caused safety or h ealth hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the Yucaipa WWTP during the last five years. Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps Yucaipa WWTP is in compliance with Federal and State Process Safety Management requirements. Yucaipa WWTPP 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), worn by the operators during connection/disconnection of chlorine/sulfur dioxide supply, awareness of the hazardous and toxic properties of chlorine/sulfur dioxide, presence of chlorine/sulfur dioxide detectors and alarms, and chlorine/sulfur dioxide scrubber. 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. These information include chlorine and sulfur dioxide background information and MSDS sheets. Equipment safety information was meticulously compiled on the chlorine and sulfur dioxide processes. Specificati ons for chlorine and sulfur dioxide processes 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. Yucaipa WWTP 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/dechlorination 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 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 recommendations were provided to Yucaip a WWTP staff for their evaluation and implementation. Operating Procedures Yucaipa WWTP maintains written operating procedures that provide clear instructions for chlorine and sulfur dioxide processes. The Yucaipa WWTP ensures effective operating practices 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, and shutdown procedures. Yucaipa WWTP 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 equipment, and reconfiguration of the facilities. Training Yucaipa WWTP 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. Yucaipa WWTP 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. Yucaipa WWTP training program includes as a minimum the following elements: six elements: (1) process safety information (2) process technology and process equipment, including safety system, (3) maintenance procedures, (4) operating procedures for the chlorine and sulfur dioxide system, (5)RMP/PSM Program contents; and (6) emergency response program. 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 operating procedures. Refreshe r 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 Yucaipa WWTP 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. Yucaipa WWTP prepares and retains records of initial and refresher training. Contractors Yucaipa WWTP 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 and sulfur dioxide processes and that the contractors are properly informed of the hazards, access limitations to these process areas, and emergency response procedures, and prepared to safely complete the work. The contractors are informed, prior to the initiation of the work at the site, of the applicable provisions of the emergency response plan. Yucaipa WW TP 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 Yucaipa WWTP 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 and dechlorination systems that require a MOC procedure implementation. The required conditions prior to startup include: 7 Construction and/or equipment are in accordance with design specifications; 7 Safety, operating, maintenance, and emergency procedures are in place and are adequate; 7 A PHA has been performed for any new facilities and recommendations have been resolved or implemented prior to startup; 7 At modified facilities, MOC requirements have been met; and 7 Training of each operating and maintenance employee involved in the process is complete. 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. This constitutes a final check that the process and equipment are ready to go and that the recommendations of the PHA have been implemented or adequately addressed. This will ensure that the design and construction of a new or modified process is safely executed and that the facility is prepared to operate it. Henry N. Wochholz Wastewater Treatment Plant uses a manual system that assures inspection, testing, and maintenance of chlorination and dechlorination equipment are performed in accordance with the manufacturer and industry groups (i.e., Chlorine Institute) recommendations. Hot Work Permits and Management of Change Yucaipa WWTP requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process. Yucaipa WWTP uses a permitting and training pr ogram to ensure hot work is conducted safely on or near a process involving chlorine and sulfur dioxide. Yucaipa WWTP 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 Yucaipa WWTP 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 Yucaipa WWTP 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 Yucaipa WWTP 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 or sulfur dioxide releases that could have caused safety or health hazard (deaths, injuries, property or environmental damage, eva cuations, or sheltering in place) occurred at the Yucaipa WWTP during the last five years. Emergency Response Program Summary Yucaipa WWTP is a first responder, plant employees respond to chlorine and sulfur dioxide accidental releases. Depending on the severity of the accidental release, external resources such as the San Bernardino County Fire Department may be solicited to aid in handling a chlorine or sulfur dioxide release. As part of the emergency response program, the Yucaipa WWTP has developed en Emergency Response Plan for the purpose of protecting public health and the environment. 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, and (3) procedures for external notifications, including coordination with local agencies. Planned Changes to Improve Safety Based on the PHA, 41 changes to improve chlorine and sulfur dioxi de 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 and dechlorination systems. |