City of Petaluma Wastewater Treatment Plant - Executive Summary
Executive Summary |
Chemicals are widely used in industry, in the home, and in the environment. They are transported on roads, water, and railways. We at the City of Petaluma Wastewater Treatment Plant - Oxidation Ponds (Petaluma WWTP) use chemicals, too. For example, we use chlorine to disinfect our water to provide safe water discharges to the environment or for irrigation uses. Storing large quantities of chlorine can be a hazard. We take our safety obligations in storing and using chlorine as seriously as we do take providing the environment safe disinfected water.
To increase our workers' safety as well as that of the general public, in November 1999, we will be bringing on line a new disinfection system that uses a solution of sodium hypochlorite instead of gaseous chlorine. This will eliminate the potential hazards associated with chlorine.
The following document describes what could happen if there were to be an accident between now and November 1999, or prior t
o the discontinued use of chlorine gas for disinfection, and includes the steps we take everyday to ensure a safely operating plant, and what to do in the event of an emergency.
Accidental Release Prevention and Emergency Response Policies
The City of Petaluma accidental release prevention policy involves proven technology and staff that has been well trained on operation and maintenance practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures.
This document complies with the U.S. Environmental Protection Agency's (EPA's) Risk Management Program, under Section 112 (r) of the Clean Air Act (CAA) Amendments of 1990, 40 Code of Federal Regulations (CFR) Part 68 and the California Accidental Release Prevention (CalARP) Program under California Code of Regulations (CCF) Title 19, Division 2, Chapter 4.5. The Petaluma WWTP has a c
hlorination system that uses chlorine gas fed from liquid chlorine containers. This document summarizes our existing health and safety programs, our internal management response team, policies, procedures, and on-going actions that are designed to prevent or minimize impacts of accidental releases of chlorine to the environment. The Petaluma WWTP has prepared a detailed and comprehensive emergency response plan to handle any potential accidental releases that is designed to safeguard both on- and off-site people. To date, we have had an excellent record in preventing accidents from occurring. We have had no chlorine releases that caused safety or health problems (no deaths, injuries, property or environmental damage, evacuations, or sheltering in-place) at the Petaluma WWTP in the past 5 years.
General Facility and Regulated Substances Information
The Petaluma WWTP, operating since 1973, is located at 4400 Lakeville Highway in the City of Petaluma in Sonoma County. The plant, located
on a 162-acre property, is about 2 miles south of downtown Petaluma and 3/4 mile east of the Petaluma River. Wastewater is initially treated at the treatment plant at 950 Hopper Street. From there it is pumped to oxidation ponds at 4400 Lakeville Highway for additional treatment. Final clean and disinfected water is either discharged into the Petaluma River or pumped to customers as reclaimed water for golf course and agricultural irrigation. Wastewater treatment at the WWTP includes screening, grit removal, sedimentation, biological oxidation and chlorination before final discharge or reclamation use. The Petaluma WWTP handles wastewater flows up to 22 million gallons per day (MGD), with an average flow of between 4.0 to 5.2 MGD.
Chlorine is stored in up to 9 one-ton cylinders. Gas phase chlorine under pressure is withdrawn from one of two sets of on-line chlorine containers. Each set contains three 1-ton chlorine cylinders. As many as 3 back-up cylinders are stored in the same room
as the cylinders that are on-line. This results in a maximum inventory of 9 cylinders containing a maximum chlorine content of 18,000 pounds. This chlorine storage exceeds the listed threshold quantities in the RMP rule.
The pressurized chlorine gas from the 1-ton containers is reduced to vacuum, passed through a chlorinator and injected into the final effluent. The resulting chlorine solution is metered into the effluent wastewater for final disinfection. Chlorine leak detectors continuously monitor for leaks in the bulk storage area and in the chlorination room. Other alarms include chlorine feed and residual malfunction. These alarms are annunciated at the chlorine control panel, as well as, in the case of a leak an audible alarm and red flashing warning light on top of the building. The alarm is also sent to an autodialer and an alarm company for response.
The bulk storage tanks and the chlorinators are enclosed in separate rooms. The chlorinator room is equipped with a ventila
tion system. Emergency showers and eye wash stations are provided outside the storage room. Self-contained breathing apparatus (SCBA) equipment is worn whenever connections or maintenance activities are being made to the chlorine system. SCBA equipment is also available at the response team locker location at the Booster Pump Station No. 1, just off the site.
Access to the Petaluma WWTP is controlled at the Lakeville entrance by a gate. Visitors and contractors must be approved by Petaluma WWTP staff prior to entry into the facility. Operating staff are onsite during the day, during the water reclamation season, and alarms notify on-call staff during off-hours of any problems or situations that require follow-up investigations.
The chlorination facilities are also provided with an emergency generator. The generator will start within 3 seconds of a loss of electrical power and will supply power to the leak detectors, lighting, and ventilation systems.
Offsite Consequence Analysis Re
The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case" and "alternative" release scenarios. The worst-case scenario requires that that single largest vessel or pipe be evaluated for off-site impacts. An alternative release scenario for chlorine was a break in a pigtail connection to a chlorine tank.
The worst-case scenario assumes that the entire contents of the largest single container are released, regardless of how improbable that may be. In addition, only "passive" mitigation methods such as buildings or dikes (for liquids) can be considered. Passive mitigation, as defined, requires no mechanical, electrical, or human input. The regulations require that the worst-case scenario assume atmospheric conditions that are conservative and result in large impact areas. According to EPA's rule, the toxic gas worst-case scenario must assume the release of the single largest vessel or container over a period of 10 minutes. This di
ctates a release rate of 2000 pounds in 10 minutes or 200 lbs/min. For worst-case scenarios, releases are assumed to take place without consideration for physical cause or likelihood of occurrence.
The bulk tank rupture resulting in a chlorine release could be caused by catastrophic events, such as an earthquake. The released liquid is assumed to quickly volatilize and to disperse as a vapor cloud. The distance to the toxic endpoint was estimated using the EPA model RMP*Comp version 1.06. The EPA toxic endpoint is conservatively set by EPA to ensure public notification and that local emergency respond planning takes into account the greatest possible impacted area surrounding the release point. In practice this type of total release of a bulk tank would be unlikely and never occur during the lifetime of the plant. The EPA toxic endpoint is 3 ppm. In addition all required EPA-model input parameters where included in completing this activity, including conservative meteorological condit
ions - Stability F class, wind speed of 1.5 meters per second, temperature (77 degree F), and average humidity (50 percent).
The results of the dispersion modeling analysis for this worst case release scenario indicate that this scenario has an offsite impact. The distance to the chlorine toxic endpoint (3 ppm) was determined to be 3.0 miles.
The alternative release scenario is more of a possible release scenario that could occur compared to the worst-case release scenario. Unlike the worst case release scenario, active controls can be applied to minimize the leak or impacts. Active controls consist of mechanical, electrical, or human input. The scenario used was a rupture of a pipe leading from the bulk tank to the chlorinator. The tanks and associated piping are all in a building; and the building mitigation was considered. Under this scenario, the amount of chlorine released was calculated to be 14.6 lbs/min. This scenario assumes the release occurs for 60 minutes, an estimated t
ime for plant operators to respond to the event.
The same modeling approach was used as for the worst-case release scenario, except meteorological conditions were adjusted to the more likely conditions of Stability D Class, wind speed of 3.0 meters per second, average air temperature of 77 degrees F, and average humidity of 50 percent. The distance to the chlorine toxic endpoint (3 ppm) was determined to be 0.2 miles. The area within the distance to the toxic endpoint is 0.13 square miles. Using EPA's Landview III block group uniform density method, the estimated population within the chlorine endpoint circle 10 people. However, Landview III's block group uniform density method doesn't apply to this small area. Inspection of the site shows that here are no public or environmental receptors within the distance to the toxic endpoint.
Finally, no chlorine releases that could have caused a safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or she
ltering in place) occurred at Petaluma WWTP during the last five years. Some minor, incidental releases may have occurred over this period, but they were quickly handled by staff, were neutralized, or posed no safety or health hazards.
Summary of the Accidental Release Prevention Program and Chemical-specific Prevention Steps
Petaluma WWTP is in compliance with Federal and State Process Safety Management (PSM) requirements. Chemical-specific prevention steps include availability of self-contained escape breathing apparatus, worn by the operators during connection and disconnection of the chlorine tanks, and when conducting maintenance on the system, awareness of the hazardous and toxic properties of chlorine, and the presence of chlorine detectors and alarms.
Petaluma WWTP accidental release prevention program is based on the following key elements:
* Comprehensive safety process information that is readily available to staff, emergency responders, and contractors
* Detailed manage
ment system and clear levels of responsibilities and team member roles
* Comprehensive preventive maintenance program
* Use of inherently safe vacuum supply system in which pipe component leaks tend to bring air into the system rather than discharging chlorine to atmosphere
* Completed a 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 operations and maintenance staff participation
* High level of training of operators and maintenance staff
* Implementation of an incident investigation, inspection, and auditing program using qualified staff.
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 each regulated substance.
This information was compiled from numerous sources and is intended to be a one-stop source for the reader seeking data about these substances. This information includes chlorine background information, Material Safety Data Sheets (MSDS), and chlorine reaction chemistry.
Equipment safety information was meticulously compiled on the chlorine process. Specifications for each process are collected 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.
We also have procedures in place that are triggered to update 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 with plant staff, engineering, and administrative staff for the regulated process. The team consisted of process
operating and maintenance experts and process design engineers. The PHA technique used was the What-If study, per acceptable approach guidance from EPA. The PHA was lead by a knowledgeable person on the type of process being reviewed. This review will be updated again within a five-year period or whenever there is major change in the process. A list of actions to resolve any found significant hazard review findings was prepared and staff is currently working to resolve this action item list. Staff will document completion of any action item.
Petaluma WWTP maintains up-to-date, accurate, written operating procedures that give clear instructions for the chlorine process. Petaluma WWTP ensures effective operating practices by combining them with operating and maintenance training programs. Procedures include startup, shutdown, and normal, alternate, and emergency operation. Also included are maintenance and troubleshooting procedures, including consequences of devi
ation and the steps to avoid which may cause deviations. Petaluma WWTP will update procedures whenever a change occurs that alters the steps needed to operate safely. Operating procedures will be developed and in place prior to any new process equipment coming on line or a changed process starting back up.
Operations and Maintenance Training Program
Each Petaluma WWTP employee presently involved in operating or maintaining the chlorine process is trained in an overview of the process and detailed, applicable operating and maintenance procedures. Petaluma WWTP helps their employees understand, through training, the nature and cause of problems arising from operations involving chlorine on site, and to increase their awareness with respect to these hazards. Petaluma WWTP's training program includes both initial and refresher training that covers 1) a general overview of the processes, 2) the properties and hazards of the substances in the process, and 3) a detailed review of the proces
s operating procedures and safe work practices. Oral reviews and written self-evaluations are used to verify that an employee understands the training material and emergency use and practice with the "Chlorine Repair Kit B" before the process work can be resumed.
Training documentation includes: date of most recent review or revision to the training program, type of training required and the type of competency testing used to ensure staff understands the training.
Petaluma 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 process and that the contractors are properly informed of the hazards of chlorine, our access limitations to the chlorination process areas, our emergency response procedures. We oversee contractors' performance to assure that they are prepared to safely complete the work. Petaluma WWTP sets minimum contractor safety performance requirements to
do work at the Petaluma WWTP, holds contractor safety briefings before allowing them near or in the process area; controls access to the process areas, and evaluates the contractor's performance.
Pre-Startup Safety Review and Mechanical Integrity Program
Petaluma WWTP ensures that a pre-startup safety review is completed for any new covered-by-the-rules process at the plant, or for significant modifications to an existing covered process that requires a change in the process safety information. Petaluma WWTP maintains the mechanical integrity of process equipment to help prevent equipment failures that could endanger workers, the public, or the environment. Petaluma WWTP believes that this program is the primary line of defense against a release and addresses equipment testing and inspection, preventative maintenance schedules, and personnel training. Petaluma WWTP's 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 prior operating experience
* Implementation of the written procedures by performing inspections and tests on process equipment at specified intervals
* Training of maintenance personnel in procedures for safe work practices such as lockout/tagout, line or equipment opening, and avoidance and correction of unsafe conditions
* Procedures specifying training requirements for contract maintenance employees, as well as requiring contractors to use plant developed maintenance procedures for process areas.
Hot Work Permits and Management of Change
Petaluma WWTP requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the chlorination system. Petaluma WWTP uses a comprehensive permitting and training program to ensure hot work is conducted safely.
Petaluma WWTP provides a system and approach to maintain and implement any managem
ent of changes or modifications to equipment, procedures, chemicals, and processing conditions. This system allows Petaluma WWTP employees 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 are conducted every 3 years to verify compliance with the programs and procedures contained in the RMP. Petaluma WWTP assembles an audit team that includes personnel knowledgeable in the Risk Management Program rule and in the process, and this team evaluates 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 are documented, recommendations are resolved, and appropriate enhancements to the prevention program are implement
Petaluma WWTP investigates all incidents including any near misses that could reasonably have resulted in a serious injury to personnel, the public, or the environment so that similar accidents can be prevented. Petaluma WWTP trains employees to identify and report any incident that requires investigation. 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, added or used to revise operating and maintenance procedures, and passed onto the training unit for their inclusion in existing training programs, if warranted to prevent a future event.
Five-year Accident History Summary
No chlorine releases that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacu
ations, or sheltering in place) occurred at Petaluma WWTP during the last five years.
Emergency Response Program Summary
Petaluma WWTP has established a written emergency response program that is followed by the employees to help safely respond to accidental releases of hazardous substances. This program has been coordinated (reviewed) by the City of Petaluma Fire Department. This program includes an emergency response notification plan. Emergency response drills and drill evaluations are conducted at least every 12 months; emergency operation and response procedures are also reviewed at that time.
Planned Changes to Improve Safety
Several changes to improve safety (recommended actions) were identified for the chlorination process during the 1999 Process Hazard Analysis under the federal EPA RMP program. It is expected that the recommended actions will be evaluated and implemented by November 1999. The implementation of these recommendations will further improve the safety of the