Henry J. Mills Filtration Plant - Executive Summary

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The Metropolitan Water District of Southern California (MWDSC) distributes drinking water to member water agencies throughout Southern California.  MWDSC provides approximately 60 percent of the drinking water used by nearly 16 million people living on the southern California coastal plain between Ventura County and the Mexican border. 
Disinfection is a critical process used by MWDSC in the treatment of its drinking water.  Disinfection helps to protect public health by killing pathogens in the water and preventing the spread of waterborne diseases.  The use of chlorine as a disinfectant in the treatment of drinking water and wastewater has been the dominant disinfection method in the United States since it was introduced, around the beginning of this century.  MWDSC currently utilizes bulk chlorine for disinfection at all of its water treatment plants, including the Henry J. Mills Filtration Plant (Mills Plant). 
As one might expect from its superior disinfection p 
roperties, chlorine is a hazardous substance.  Thus, storing and handling chlorine can present a risk to employees and the public without proper precautions.  MWDSC regards safe practices in the storing and usage of chlorine to be of primary importance and has an excellent safety record with chlorine. 
Mills Plant's chlorine storage and usage process is subject to the U.S. Environmental Protection Agency (EPA) Risk Management Program Rule (RMPR) and also to the California Accidental Release Prevention (CalARP) Program regulation.  Both of these regulations require 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 accident and the actions, which will be taken, by the facility in 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 Mills Plant Chlorination System is provided below. 
Accidental Release Prevention and Emergency Response Policies 
The MWDSC accidental release prevention policy for chlorine 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 RMP Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures. 
In addition, all MWDSC chlorine systems have undergone a high priority evaluation for Y2K readine 
ss.  They will be Y2K compliant by July 31, 1999, although no Y2K problems are anticipated. 
The MWDSC emergency response policy for chlorine involves the preparation of integrated contingency plans, which address emergency response for hazardous materials and are tailored to each facility.  These plans integrate with the emergency response services available in the community and are in compliance with the RMPR and CalARP Program Emergency Response Program Requirements.  Mills Plant has prepared an Emergency Response Plan for Hazardous Materials to facilitate coordination and emergency planning with offsite response officials and facilities in the event of an emergency.  This emergency response plan is being  coordinated with local response agencies (City of Riverside Fire Department).  Mills Plant has an excellent safety record with chlorine use. 
General Facility and Regulated Substance Information 
The Henry J. Mills Filtration Plant is located at 550 E. Alessandro Boulevard in Rive 
rside, California.  The plant is situated west of Interstate Highway 215 and south of State Highway 60, covering approximately 256 acres.  The facility was constructed in 1978. The plant is designed to treat drinking water including disinfection with chlorine.  The facility currently stores and uses chlorine, a regulated toxic substance under the EPA and CalARP Program rules. Chlorine is received at the Mills Plant and stored by the unloading platform located immediately north of the Chlorine Building.  The chlorine evaporators are in the Evaporator Room and the chlorinators are in the Chorination Room; both rooms are in the Chlorine Building.  The chlorine storage and use at the Mills Plant is subject to EPA and CalARP rules, as well as the federal and California Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) Standards. 
The chlorine unloading area located immediately north of the Chlorine Building is continuously monitored in the control room by  
chlorine leak detectors.  Chlorine leak sensors are also provided in the Chlorine Building (evaporator and chlorinator rooms) and chlorine vent boxes, located outside the building.  The alarms are annunciated at the chlorine alarm panel as well as at the operator's console in the control room.  Once alerted, fully trained personnel will assess the chlorine leak.  In addition, each storage vessel valve connecting to the process, is provided with a remotely actuated (pneumatic) emergency shutoff system.  In case of a major chlorine leak, chlorine supply can be stopped almost instantaneously by closing the shutoff system from any of the two control panels: unloading platform and control room. Emergency showers and eye wash stations are also provided on the chlorine unloading platform and outside the Chlorine Building. 
The chlorine pressure reducing valves, leak detectors, and computer control system are connected to an uninterruptible power supply (UPS) system.  In the event power is los 
t at the chlorination facility, an alarm will alert the control room.  The filtration plant has an emergency generator system, which provides backup power to run the filtration plant in the event of a power failure.   
The control room at the plant is manned 24 hours a day, year round.  Access to the plant is through guarded security gates, which are closed after regular hours. 
Offsite Consequence Analysis Results 
The offsite consequence analysis includes consideration of two chlorine 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". 
For the worst-case as well as alternative release scenarios, the released liquid chlorine  
is assumed to form a denser-than-air cloud consisting of chlorine vapor and liquid droplets (aerosols) which disperse in the atmosphere.  The distances to the toxic endpoints were 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. 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.  No passive mitigation measures were considered for the worst-case release scenario.  However, administrative controls were considered, which limit the qu 
antity of chlorine in the storage vessel.  The results of the 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. 
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 facility pursuant to these rules indicated that there were no such chlorine releases, which could have resulted in offsit 
e (outside the Mills Plant boundary) toxic endpoint distances.  Similarly, no credible accident scenario was identified from the process hazard analysis, where a release 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 chlorine from the monel flexible hose connecting the chlorine storage vessel to the chlorination process.  This scenario can occur if the operator uses a flex hose that is worn or has a defect, resulting in a crack during withdrawal of chlorine from the chlorine storage vessel. 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.  If such a leak were to occur, the control room would be immediately warned by the chlorine monitors installed at the facility.  It is assumed that approximately fifteen minutes would be required for an emergency response te 
am to be notified, don personal protective equipment, and evaluate the situation.  Then the emergency response team or the operator would activate the remote controlled shutoff actuator and immediately close the valve at the chlorine storage vessel (chlorine flow from storage is stopped in approximately 3 seconds after the activation of remote controlled shutoff actuator).  The activation of the shutoff actuator is considered as an active mitigation.  This will reduce the total quantity of chlorine released to the atmosphere during an accident. 
It may be noted that the occurrence of this scenario is highly unlikely because the flex hose is carefully inspected during each connection/disconnection operation, and during operator rounds, once each shift.  In addition, under the Mills Plant preventive maintenance schedule, the flex hoses are replaced at least every two years (more frequently than recommended by the manufacturer).   
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 typical meteorological conditions used were Stability Class 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 dispersion analysis indicated that the alternative release scenario has offsite impacts. 
Finally, no chlorine releases that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the Mills Plant during the last five years.   
Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps 
Mills Plant complies with Federal and State Process Safety Management requirements.  Mills Plant accidental release prevention program is based on the following key elements: 
* Detailed management system and clear levels of responsibilities and team member roles. 
* Com 
prehensive process safety information that is readily available to staff, emergency responders, 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. 
* 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 availability of self-contained breathing apparatus (SCBA), worn by the operators during connection/disconnection of chlorine supply, awareness of the hazardous and toxic properties of chlorine, presence of chlorine detectors and alarms, and remotely controlled shutoff device on the chlorine storage vessel. 
Process and Chemical Safety 
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 includes chlorine background information and MSDS sheets. 
Equipment safety information was meticulously compiled on the chlorine process.  Specifications for chlorine 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.  Mills Plant also has procedures in place that are triggered to update process safety information if there is a major change that makes existing information inaccurate. 
Process Hazard Analysis  
In 1992, 1994, and 1995, detailed process hazard analyses (PHAs) were conducted for the chlorination system equipment 
and procedures.  The PHAs were further reviewed in November 1998 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 in November 1998 to further 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 Region 1 LEPC CalARP Guidance, and recommendations were provided to Mills Plant staff for their evaluation and implementation.  
In addition, all MWDSC chlorine systems have undergone a high priority evaluation for Y2K readiness.  They will be Y2K compliant by July 31, 1999, though no Y2K problems are anticipated. 
Operating Procedures 
Mills Plant maintains up-to-date, accurate, written operating procedures that provide clear instructions for the chlorine process.  The Mills Plant 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 system.  The operating procedures include connection/disconnection for chlorine storage vessel, start-up and shutdown for chlorine evaporators, after maintenance start-up for chlorine evaporators, maintenance shutdown for chlorine evaporators, start-up and shutdown for ejectors, start-up and shutdown for chlorinators, chlorine system emergency shutdown, start-up following an emergency shutdown, and temporary operations.  Also included are the maintenance and troubleshooting procedures, including consequences of deviation and the steps to correct or avoid deviations. Mills Plant 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 th 
e handling of chlorine equipment, and reconfiguration of the facilities. 
Mills Plant 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. Mills Plant 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.  Mills Plant training program includes four elements: (1) initial training and awareness training, (2) refresher training, (3) documentation, and (4) and testing.  Each employee presently involved in operating the chlorine process has been trained to receive the required knowledge, skills, and abilities to safely carry out the duties and responsibilities, including chlorine 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 en 
sure that the employee understands and adheres to the current operating procedures.  In addition, the Mills Plant 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 and/or Pre Startup Safety Review procedures. 
Mills Plant prepares and retains records of initial and refresher training, which includes the identity of the employee, the date of training, and the signature of the person (s) administering the training. 
Mills Plant has procedures and policies in place that ensure that the contractors are properly informed of the hazards, access limitations to these process areas, and emergency response procedures, and are 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.  Mills Plant holds contractor safety briefings before allowing them near 
or in the process area; controls access to the process areas, and evaluates the contractor's safety performance. 
Pre-Startup Safety Review and Mechanical Integrity Program 
Mills Plant ensures that a pre-startup safety review is completed for any new process covered by this regulation, or for significant modifications to an existing covered process that requires a change in the process safety information.  Mills Plant maintains the mechanical integrity of process equipment to help prevent equipment failures that could endanger workers, the public, or the environment.  Mills Plant mechanical integrity program 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 practice, and prior operating experience. 
* Implementation of the written procedures by performing inspections and tests on process equipment at specified intervals. 
* Training of mai 
ntenance 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 unique tools. 
Hot Work Permits and Management of Change  
Mills Plant requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process.  Mills Plant uses a permitting and training program to ensure hot work is monitored and conducted safely on or near a process involving chlorine. 
Mills Plant 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 Mills Plant 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 tra 
ining 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 Mills Plant 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 
Mills Plant 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 withi 
n 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.  There have been no such incidents involving the Mills Plant chlorine system. 
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 Mills Plant during the last five years. 
Emergency Response Program Summary 
Mills Plant is a first responder facility (i.e. specially trained plant employees respond to chlorine accidental releases). Depending on the severity of the accidental release, external resources such as the City of Riverside Fire Department will be called to aid in handling a chlorine release.  As part of the emergency response p 
rogram, the Mills Plant has developed and implemented a Hazardous Materials and Hazardous Waste Contingency Plan (HMHWCP) for the purpose of protecting public health and the environment.  The HMHWCP has a special focus on responding to chlorine emergencies. 
The HMHWCP plan is being coordinated with local response agencies (City of Riverside Fire Department).  The main elements of the emergency response plan are: (1) chlorine response flow chart, responsibilities of various personnel at the facility, duties of on-scene incident commander, HazMat responder team, (2) details of emergency recognition and prevention at the facility, (3) procedures for planning and coordination with off-site emergency response organizations, and (4) details of the training program for all HazMat responders.  
Planned Changes to Improve Safety 
Numerous changes to improve safety (recommended actions) were previously identified for the chlorine process in 1992, 1994, and 1995 for the chlorination system equip 
ment and procedures, when a Risk and Hazard Analysis (following California Risk Management and Prevention Program (RMPP) guidelines) and a Process Safety Management Program were prepared for the Mills Plant.  These recommended actions have been evaluated and are being implemented as required.  Additional changes to improve chlorine safety were identified in November 1998, when the process hazard analysis was reviewed.  It is expected that these recommended actions will be evaluated and implemented by December 1999. 
As part of this ongoing commitment to chlorine safety, MWDSC is also planning a future capital project to replace the bulk chlorine at the Mills Plant with sodium hypochlorite as an alternative disinfectant.
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