Easterly Wastewater Treatment Plant - Executive Summary

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The City of Vacaville is required to develop and implement a Risk Management Program (RMP) for the Easterly Wastewater Treatment Plant under U.S. EPA RMP regulations and California Accidental Release Prevention (CalARP) Program regulations due to the facility's use and storage of up to 44,000 pounds of chlorine.  The RMP is subject to Program 3 guidelines because the worst-case release scenario endpoint distance for chlorine exceeds the distance to the nearest public receptor and the quantity of chlorine utilized is sufficient to make the facility subject to the Process Safety Management (PSM) regulations administered by U.S. OSHA.  The facility's RMP consists of an offsite consequence analysis based on computational modeling, procedures for accidental release reporting, a prevention program, and an emergency response program. 
 
The facility employs the standard-rate activated sludge process to treat raw influent wastewater to secondary treatment standards, and standard rate two-stage a 
naerobic digestion for raw and waste activated sludge.  The facility primarily uses and stores chlorine to disinfect secondary effluent prior to discharge to Alamo Creek.  Chlorine is also used for influent raw sewage odor control, partial disinfection of primary effluent bypassed directly to the Chlorine Contact Basin when influent flow exceeds 17 MGD, chlorination of Return Activated Sludge (RAS) for control of bulking, and chlorination of in-plant return flows for odor control.  At most four online and four standby one-ton chlorine cylinders can be connected to the chlorination system at a time.  Up to fourteen additional one-ton cylinders may be stored in the chlorine storage room at a time as well, bringing the maximum total chlorine inventory to 44,000 pounds.  This storage capacity minimizes the number of deliveries that are necessary to the plant, and therefore the risk associated with transporting and delivering chlorine to the facility. 
 
The current facility and chlorination  
system and equipment was designed between 1986 and 1988 by Kennedy/Jenks/ Chilton in accordance with recognized and generally accepted good engineering practices, federal, state, and local design regulations and codes, and industry-specific design codes and standards.  The chlorination system has three basic functional sections:  storage and gas pressure reduction, gas dispensing, and solution distribution and diffusion at the various points of application.  Liquid chlorine under pressure is piped from four on-line one-ton cylinders to an evaporator.  Water flow through ejectors and water champs induces a vacuum that draws the vaporized chlorine.  The chlorinators then control and meter the chlorine vapor, and it is introduced into #3 Plant Water by ejectors and water champs at various points of application.  The conveyance of vapor chorine under vacuum greatly increases the safety of the overall process in that if the vacuum is lost, as would be the case under most possible failure sc 
enarios, regulator valves in the affected chlorinators will shut and the flow of chlorine will cease. 
 
A Process Hazard Analysis (PHA) was conducted for the Easterly Wastewater Treatment Plant as part of developing the facility's PSM.  The PHA is an organized and systematic effort to identify and analyze the significance of potential hazards associated with the processing or handling of highly hazardous chemicals.  The PHA focuses on equipment, instrumentation, utilities, human actions (routine and non-routine), and external factors that might impact the process.  These considerations assist in determining the hazards and potential failure points or failure modes of a process.  When hazard scenarios are identified, existing or proposed designs and operations are assessed to determine if appropriate engineering and administrative controls are in place.  If the current level of protection is determined insufficient, recommendations are made to eliminate and mitigate the scenarios. 
 
In or 
der to provide a thorough analysis as specific as possible to the Easterly Wastewater Treatment Plant, the Hazards and Operability Analysis (HazOp) method, incorporating the guide-word approach, was selected for the PHA.  The HazOp Study was conducted on February 23, 1999 by a HazOp Team consisting of two employees of Block Environmental Services, with expertise in the HazOp process, and five members of the City's Staff, with collective expertise in the management and operations of both the City's water and wastewater treatment facilities.   
 
The PHA also included a seismic review to determine whether the facility and equipment are designed and installed sufficiently to withstand impacts from expected seismic events.  In addition, risks posed by the date change to the year 2000 (Y2K) and possible computer system complications were also assessed as part of the PHA.  Several other external events that might impact the chlorination system were also examined, including fire, power failure, 
sabotage, flooding, and tornado. 
 
In general, the HazOp Team concluded that existing engineering controls, safety systems, and procedures in place at the facility ensure that the lowest risk practicable is achieved for all deviations identified.  The chlorination equipment used incorporates many design standards for chlorine equipment that have been developed to utilize chlorine for disinfection as safely as is practical.  The procedures and practices in place at the facility are sufficient to ensure that the equipment will function as designed and that operators will respond quickly and properly to any deviations from design intent.  No improvements in procedures or equipment are recommended as a result of the HazOp study.  The team concluded that the type of release determined to pose the greatest risk is a breakage of the cylinder valve during cylinder changeover. 
 
The Assistant Director of Public Works is assigned overall responsibility for the development, implementation, and int 
egration of the RMP elements.  In addition, a management system is in place for implementing specific elements of the RMP.  The Utilities Operations Superintendent will implement most of these elements through supervisors, although certain tasks may be delegated to facility operators and maintenance personnel. 
 
The offsite consequence analysis portion of the RMP involves developing and modeling a worst-case and an alternative theoretical release scenario to estimate the impact an accidental release may have on the public and environment in the surrounding area.  The worst-case release assumes that the maximum amount of chlorine ever held in a single vessel at the facility is released into the atmosphere during meteorological conditions least conducive to expedient dilution of the released gas.  It is intended as a basis of comparison with other facilities, but it is not realistic to expect such a scenario to actually occur.  The alternative scenario was selected based on the PHA conduc 
ted for the facility.  It is both a more likely potential release scenario and of sufficient magnitude to reach receptors offsite.   For the alternative release scenario, more representative average daily atmospheric conditions are assumed.  OCA data reported for the RMP is based on data provided in the Risk Management Program Guidance for Wastewater Treatment Plants, published by U.S. EPA in October of 1998.  The toxic endpoint to be used for chlorine is 3 ppm, which is the maximum airborne concentration that most individuals could be exposed to for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms.  
 
The worst-case release is predicted to reach the toxic endpoint at a distance of 3.0 miles from the facility.  Although the width of the area affected by chlorine concentrations of this magnitude, or footprint, is limited and will only extend downwind from the source, a circle with a 3.0 mile radius is drawn to identify potential o 
ffsite impacts.  Using interpolation of 1990 census block group data, it is estimated that 4,100 people live within this radius.  There are eleven school and daycare facilities, one hospital, ten parks, and two golf courses located within this radius.  There are no environmental receptors within this distance. 
 
The alternative release scenario chosen was identified in the PHA as posing the greatest risk (i.e. highest likelihood of occurrence and severest consequences) out of several release scenarios considered.  It consists of a breakage of the cylinder valve during cylinder changeover due to an operator applying excessive force to the valve in attempting to open it.  Taking into account passive mitigation provided by the enclosure of the chlorine room, it is conservatively estimated that 35.9 pounds-per-minute of chlorine is released to the atmosphere over two minutes under such a scenario.  The endpoint for this release extends 0.3 miles from the facility.  Using interpolation of 19 
90 census block group data, it is estimated that 130 people live within this radius.  Of the nearby sensitive receptors, only one school is located within the alternative scenario endpoint distance.  There are no environmental receptors within this distance. 
 
Identifying these potential receptors is only an indication that they could be adversely affected by such a release.  The likelihood, type, or severity of potential impacts on either public or environmental receptors is not assessed in this document.  Furthermore, it is not possible for the entire area within the endpoint circle to experience concentrations of chlorine above the endpoint value, as concentrations of chlorine will only exceed the endpoint within a relatively narrow, oval-shaped footprint. 
 
The accidental release reporting section of the RMP gives the details and definitions for what must be reported in the event of a significant release of chlorine.  The facility has not had an accidental release of chlorine that re 
sulted in on-site deaths, injuries, or significant property damage;  or known offsite deaths, injuries, property damage, environmental damage, evacuations, or sheltering in place in the past five years. 
 
The prevention program requirements for Program 3 RMPs are taken verbatim from applicable sections of the PSM regulations.  This is a result of U.S. EPA's recognition that measures taken to reduce and mitigate hazards to facility workers will also serve the same purpose for the surrounding community and environment.  Thus, in order to eliminate redundancy, the PSM is  referenced in the RMP.  The PSM consists of several elements that contain or describe procedures that must be implemented on an ongoing basis, including chlorine and process safety information,  the process hazard analysis, operating procedures, employee training, contractor qualification, pre-startup safety reviews, mechanical integrity of equipment, management of change, incident investigation, and injury and illness p 
revention.  
 
The intent of the Process Safety Information (PSI) section is to compile system information for use in conducting the Process Hazard Analysis and to help facility operators to identify and understand the hazards posed by those processes involving highly hazardous chemicals.   PSI must include information on the hazards of the highly hazardous chemicals used in the process, information on the technology of the process, and information on the equipment in the process.  This information must be kept up-to-date as process changes or upgrades are made.  It should also be made available to all employees and be included, as necessary, in employee training programs. 
 
The PSI for the facility includes a list of hazardous chemicals stored at the facility, and information on the hazards of chlorine and the chemistry of the chlorination process.  This is followed by information specific to the facility's chlorination system, including design codes and standards utilized, handling one- 
ton chlorine cylinders, chlorination system equipment and operation, detectors and alarms, safety systems, the computer control and monitoring system, fire protection, signage, and security. 
 
The purpose of the operating procedures portion of the PSM program is to develop, implement, and maintain clearly written, detailed procedures, guidelines, rules and practices for the safe operation of the chlorination process during all operating phases.  A copy of the operating procedures must be readily accessible to all employees who work on or near the chlorination system.  All employees involved in the daily operation and maintenance of the chlorination process should have a full understanding of every operating phase.  This is to include an overview of the process, principles of using chlorine for disinfection, operating characteristics of the components and the associated safety hazards, and the proper steps to be taken to execute all system-related tasks in a safe manner.   
 
Standard Oper 
ating Procedures (SOPs) have been developed that include procedures for handling chlorine, system startup, normal operations, addressing deviations from normal operating conditions, normal shutdown, maintenance of specific equipment, and emergencies.  The SOPs must be reviewed as often as necessary to assure that they reflect safe operating practices, including updates that result from changes in the facility, technology, and/or equipment.  They must also be reviewed and certified annually by a team lead by the Chief Plant Operator.  A certification form is provided in the PSM for the annual review. 
 
All employees involved with the disinfection process must understand the safety and health hazards of the use of chlorine in the process.  Therefore, the City has developed a written training program for all employees involved in the operation, maintenance, and supervision of the chlorination system.  Each employee involved with disinfection system operation will, at a minimum, receive tra 
ining in understanding MSDS's, routine chlorination system operation, emergency chlorination system operation, normal and emergency chlorine safety and handling procedures, and the individual's role in emergency response.  This program includes the identity of employees to be trained, the training program technical content, competency requirements, documentation requirements for demonstration of competence, schedule for initial training and refresher training, and training for change.  In addition, contract and maintenance personnel also receive training as provided for in the Contractor Qualification Program.  The PSM includes a form for documenting all training provided to employees.   
 
The purpose of the Contractor Qualification Program is to help ensure that contractors and their employees are fully aware of the potential dangers involved in the use of chlorine and the disinfection system.  This awareness should lead to reduced risk of accidents, and thus improved safety for both c 
ontractor employees and the company's employees.  It applies to all contractors performing any type of work (e.g. maintenance, renovation) on or in the vicinity of the chlorination system.  The Contractor Qualification Program consists of a five part procedure to be used during the procurement of a contractor in order to verify that their employees are adequately informed and trained, and includes several forms to facilitate and document the process.   
 
The purpose for the pre-startup safety review is to help ensure that certain important considerations have been addressed prior to startup of a new or modified process involving chlorine.  Pre-startup safety reviews are required for all new facilities and for all modifications that result in a change to the process safety information.  The PSM includes a procedure and documentation form for conducting the pre-startup safety review.  The review consists of verifying that all written process safety information is updated, that the require 
ments for Management of Change have been completed, that all safety, operating, maintenance and emergency procedures are updated, implemented, and adequate, that construction and new equipment is in accordance with the design specifications, and that training for each employee involved in operating or maintaining the new equipment in the process has been completed. 
 
It is essential to maintain the mechanical integrity of critical process equipment to ensure it is designed and installed correctly, and operates properly.  The mechanical integrity program helps ensure that proper procedures are adequate and are being followed, such that all equipment used to process, store and handle chlorine is maintained properly.  The mechanical integrity program includes an inventory of all chlorination system equipment, including the date on which it was installed and its life expectancy, a list of scheduled maintenance tasks and inspections and a description of the City's maintenance program.  
 
Main 
tenance of the chlorination system is conducted on a daily, weekly, monthly, semi-annual, annual, and as-needed basis.  Maintenance task and schedules predominantly consist of preventative measures.  Administration of the maintenance program is computer-based, with the Data Stream MP2 software providing preventative maintenance, spare parts inventory, and work order tracking, as well as records, reports, and cost accounting for the City's water and wastewater utility facilities. 
 
A PSM compliance audit must be completed at least every three years.  The principal objective of the audit is determine whether the procedures and practices that have been developed to comply with the PSM regulation are adequate and are being followed.  The audit is to include an evaluation of the design and effectiveness of the PSM program and a field inspection of the safety and health conditions and practices to verify that the PSM elements are effectively implemented.  
The Assistant Director of Public Work 
s will select a trained individual or assemble a trained team of people to audit the PSM program.  The audit should include a review of the relevant documentation and process safety information, an inspection of the facility, and interviews with all levels of facility personnel.  The PSM includes forms to facilitate and document the compliance audit. 
 
Any facility or process is continually undergoing change in order to improve the efficiency, operability, or safety of the operation, or to replace mechanical equipment.  In order to facilitate necessary changes, while ensuring that unrecognized and/or unacceptable hazards are not introduced, the management of change (MOC) procedure has been developed.  The objective of the MOC procedure is to help ensure that all changes are properly reviewed, and that any hazards introduced by the implementation of the change are identified and controlled, prior to placing the change in operation.  The MOC procedure is intended to apply to all equipment 
and procedures involving the chlorination system, and to any change in procedures regardless of whether the change is considered major or minor, or is of a temporary or permanent nature.  As part of the PSM, definitions, procedures, and documentation forms were developed to accomplish the MOC. 
 
A procedure has been developed to investigate serious incidents or near-misses in order to understand what happened (or could have happened) and to prevent any recurrence of similar incidents, thereby improving the safety of the process.  Formal incident investigations will be performed any time there is an incident which resulted in, or which could reasonably have resulted in (near-miss), a catastrophic release of chlorine.  The procedure includes initial incident response, establishing an investigation team, determining the facts and cause of the incident, recommending corrective and preventive actions, communicating the results, and follow-up. 
 
California mandates that the facility develop a 
n Injury and Illness Prevention Program (IIPP), which is designed to identify hazardous workplace conditions, and to develop controls, procedures, and work practices to insure these hazards have been identified and corrected.  The program consists of several general areas supported by an overall philosophy of management commitment to zero injuries and illnesses, continuous improvement, and total quality management principles.  Portions of IIPP that cover the use of hazardous materials (i.e. Personal Protective Equipment, Hazardous Materials Operations and Emergency Response, etc.) have been integrated into the PSM in order to ensure consistency and eliminate redundancy and overlap between the documents. 
 
The City has developed two plans/procedures that comprise the Emergency Response Program (ERP) for the facility.  The Emergency Action Plan procedure identifies the safe actions that City employees, contractors, and site visitors must take in the case of an emergency condition or event 
at the facility.  Included are emergency evacuation procedures, employee rescue and medical duties, preferred reporting means (notifications), job titles of responsible persons, alarms (warning system) with a distinctive signal for each general type of emergency, and employee/contractor training including visitor orientation.   
 
Procedures for dealing with hazardous materials releases, including releases of chlorine, are covered more fully in the Hazardous Materials Operations and Emergency Response Procedures.  The procedure covers situations involving an unplanned, on-site hazardous materials release from the facility.  Also included is a hazardous material emergency notification list including City employees and City, County, State, and Federal agencies, as well as a list of all hazardous substances used at the facility with their locations.   
 
The ERP also includes maintenance and inspection procedures for emergency response equipment and emergency response training for employees, 
which are found in the mechanical integrity and training program sections of the PSM.   
 
The ERP will be reviewed and updated as necessary to reflect changes at the facility, with all employees informed and trained regarding revisions.
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