Orange County Water District - 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. The Orange County Water District (OCWD) uses chlorine for disinfecting the drinking water supply to protect public health per state and federal water quality standards. Storing and handling large quantities of chlorine can create hazardous situations. The OCWD takes safety obligations in storing and using chlorine as seriously as it takes its obligation to provide safe drinking water. The OCWD chlorine handling process is subject to the U.S. Environmental Protection Agency (EPA) Risk Management Program Rule and also to the California Accidental Release Prevention (CalARP) Program regulations. 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 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 OCWD chlorination system is provided below.
Accidental Release Prevention and Emergency Response Policies
The OCWD 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 response procedures.
The OCWD emergency response policy involves the preparation of an emergency response plan for hazardous materials which are tailored to each facility, integrates with the emergency response services available in the community, and is in compliance with the EPA and CalARP Program Emergency Response Program Requirements. OCWD 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. The emergency response plan is being coordinated with the local response agency (City of Fountain Valley Fire Department). OCWD has an excellent safety record with over 20 years of chlorine use.
General Facility and Regulated Substan
The Orange County Water District is located at 10500 Ellis Avenue in Fountain Valley, California. The plant is situated just south of the 405 freeway and west of the Santa Ana River. The chlorination system was installed in 1976 to disinfect water for public uses. Anhydrous chlorine used for disinfection is received at the OCWD in chlorine truck trailers to supply the 25-ton bulk storage tank stored inside the chlorine room. The existing chlorination system consists of four main subsystems: (1) storage, which includes a 25-ton bulk storage tank (containing a maximum of 25-tons of chlorine), five 1-ton backup containers, and feed piping; (2) feed, which includes two evaporators, five chlorinators, and their associated piping; (3) distribution, which includes chlorine vacuum piping, five ejectors, and solution lines; and (4) control, which includes flow and residual chlorine feedback control. The chlorine room can store a maximum inventory of 30 tons of chlorine, whic
h includes a 25-ton bulk storage tank and five 1-ton containers. The system draws chlorine from the bulk storage tank while the five 1-ton chlorine containers serve as backup supply. Of the five 1-ton containers, only two can be connected to a valved manifold ready to be switched over when supply from the bulk tank has been depleted. The remaining ton containers rest on trunnions inside the chlorine room. Chlorine is withdrawn from the bulk storage tank to the evaporators where chlorine is converted from liquid to gas. The chlorine vapor from the evaporator passes through a pressure reducing valve to a vacuum regulating valve and then to the chlorinators. The chlorinators regulate the chlorine vapor flow to the ejectors. Chlorine vapor is pulled by vacuum created by the venturi effect of the service water flow at the ejectors. The ejectors mix chlorine vapor with plant service water to create a chlorine solution that flows to the point of injection in the treatment process at s
ervice water pressure.
In case of a major leak, chlorine leak detectors are provided to monitor the presence of chlorine gas in the chlorine storage and chlorinator rooms. There are three leak detectors in the chlorine storage room and one in the chlorinator room. Upon detection of a chlorine leak at a minimum concentration of 1 ppm, an alarm is activated locally and remotely at the Main Control Room panel and the chlorine emergency scrubber is automatically initiated.
The chlorine storage at the OCWD 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 site is enclosed by a fence with locked gates. The chlorination facility is in a building with a locked door. The chlorine storage building is continuously monitored by a video camera after normal hours and the site is manned 24-hours per day.
Offsite Consequence Analysis Results
The offsite consequence anal
ysis 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 OCWD, one scenario was considered: rupture of the chlorine bulk storage tank with a maximum capacity of 25-tons, resulting in a release of 50,000 pounds of chlorine over a 10-min
ute duration. Only passive or administrative controls are allowed under this scenario to reduce offsite impacts. Administrative controls are used to limit the filling of the chlorine bulk tank to only 25-tons, which could be filled with 26 tons of chlorine. The chlorine bulk storage tank is located in an enclosed building, which results in a passive mitigation of any chlorine release. The release rate reduction from the building is approximately 45 percent per guidance from EPA. The release rate for chlorine was thus estimated to be 2,750 pounds per minute.
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 Dense Gas Air Dispersion (DEGADIS 2.1) Model. 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 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 (112 deg F), and average relative humidity (76%) were used for the worst-case release scenario analysis. The results of the air dispersion analysis indicate that this 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.
Based on the process hazard analysis performed for the chlorination facility, one alternative release scenario was selected. The scenario selected involves the release of chlorine gas from the one-inch flex hose connecting the bulk storage tank to the chlorination process. It is assumed that a crack develops in the one-inch diameter flex hose corresponding to a hole of 0.1875-inch (3/16-inch) diameter. The control room would have been warned of the chlorine leak by the chlorine monitors installed at the chlorination facility at a chlorine concentration of 1 ppm. At a concentration of 3 ppm, the scrubber is automatically activated at the facility. It is assumed that approximately 15 minutes would be required for operators or an emergency response team to respond. The chlorine release rate inside the chlorine storage room was estimated at 87
lb./min. However, the chlorine release rate to the atmosphere from the scrubber would be only 0.004 lb./min. Since the chlorine 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 63 deg F, and average humidity of 76%. The results of the dispersion modeling analysis indicate that the maximum ground level one hour average concentration for chlorine would be less than 0.01 ppm. This concentration is significantly lower than 3 ppm, the toxic endpoint for chlorine. Thus, this scenario has no offsite impacts.
It may be noted that the occurrence of this scenario is highly unlikely because the flex hoses are carefully inspected during each connection/disconnection operation, and during operator rounds.
Finally, 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 OCWD during the last five years.
Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps
OCWD is in compliance with Federal and State Process Safety Management requirements. OCWD 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 effective operating procedures, written with the participation of the operators.
7 Training of the operators and maintena
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 supply, awareness of the hazardous and toxic properties of chlorine, presence of chlorine detectors and alarms, and a 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. 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 upp
er and lower pressures; and codes and standards used to design, build, and operate the processes are on file at the facility. OCWD 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 1999 a detailed process hazard analysis (PHA) was conducted for chlorination system equipment and procedures. 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 was developed 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 OCWD staff for their evaluation and implementation.
OCWD maintains written operating procedures that provide instruct
ions for the chlorine process. The OCWD ensures effective operating practices by combining these with operating and maintenance training programs. Standard operating procedures (SOPs) provide system descriptions, specifications, equipment inspection requirements, and operating procedures for the chlorine system. Operating procedures have been developed for system start-up, normal (routine) operations, and shutdown of the chlorine process. OCWD 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.
OCWD employees presently involved in operating or maintaining the chlorine process are trained in an overview of the process and applicable operating and maintenance procedures. OCWD ensures that each employee newly assigned to the process, is
trained and tested to be competent in the operating procedures listed pertaining to his or her duties. 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.
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 OCWD 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.
OCWD prepares and retains records of initial and refresher training, which includes the name of the employee, the date of training, and the signature of the person (s) administering the training.
OCWD has procedures and po
licies in place that ensure that only contractors with good safety programs are selected to perform work on and around the chlorine process. 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. OCWD 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
OCWD 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 that requires a change in the process safety information. OCWD maintains the mechanical integrity of process equipment to help preven
t equipment failures that could endanger workers, the public, or the environment. OCWD's mechanical integrity program includes the following:
7 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.
7 Implementation of the written procedures by performing inspections and tests on process equipment at specified intervals.
7 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 unique tools.
Hot Work Permits and Management of Change
OCWD requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the covered process. OCWD uses a permitting program to ensure hot work is monitored and condu
cted safely on or near a process involving chlorine.
OCWD 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 OCWD 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 three years to verify compliance with the programs and procedures contained in the RMP. The OCWD 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 implemented.
OCWD 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. There have been no such incidents at OCWD involving the 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) o
ccurred at the OCWD during the last five years.
Emergency Response Program Summary
OCWD is a first responder, plant employees respond to chlorine accidental releases. Depending on the severity of the accidental release, external resources such as the City of Fountain Valley Fire Department will be called to aid in handling a chlorine release. As part of the emergency response program, the OCWD has developed and implemented a Hazardous Materials Contingency (HMC) Plan for the purpose of protecting public health and the environment.
The HMC plan is being coordinated with the local response agency (City of Fountain Valley Fire Department). The main elements of the emergency response plan are: (1) The Core Plan; including Emergency Coordinators, Off-site Emergency Services, Agencies Notifications, and Coordination with local emergency services agencies, (2) Emergency Response Procedures for Hazardous Materials, and (3) Chlorine Emergency Response Procedures.
Planned Changes to Impr
A number of changes to improve safety (recommended actions) were identified during the performance of the process hazard analysis in March 1999. It is expected that these recommendations will be evaluated by December 1999. The evaluation and implementation of these