Palo Alto Regional Water Quality Control Plant - Executive Summary
Accidental Release Prevention and Emergency Response Policies |
The management and staff of the Palo Alto Regional Water Quality Control Plant (PARWQCP) are committed to operating the Plant with the highest regard for the safety of the public, Plant personnel, and the environment. To ensure the safety of the public, Plant personnel, and the environment, PARWQCP has designed and implemented a management system that integrates the elements of Cal/OSHA's Process Safety Management (PSM) standard, T8 CCR '5189, EPA's Risk Management Program (RMP) rule, 40 CFR part 68, and the California Accidental Release Prevention (CalARP) program, T19 CCR Div. 2, Ch. 4.5. The policies and procedures integrated under PARWQCP's management system specifically address prevention of the release of chlorine or sulfur dioxide, and emergency response to an accidental release of chlorine or sulfur dioxide.
Description of Processes, and Regulated Substances Handled at PARWQCP
The Palo Alto Regional Water Qualit
y Control Plant, located on San Francisco Bay in northeastern Palo Alto, receives and treats wastewater from Palo Alto, Mountain View, Los Altos, Los Altos Hills, East Palo Alto, and Stanford University. The Plant processes 25-30 million gallons of domestic and industrial wastewater per day. The Plant provides primary and secondary treatment, final filtration, and disinfection.
Primary treatment removes scum and sludge from the wastewater influent. The primary settling tanks allow particulate matter to settle out or float to the surface and be removed from the flow.
Secondary treatment begins with BOD removal in aerobic, fixed-film reactors. Aerobic aeration basins, with a retention time of 5 hours, are used to convert ammonia to nitrogen and nitrates. From the aeration basins, the water moves into the secondary clarifiers, where settled activated sludge is removed.
Final filtration removes most of the oil, grease, and suspended solids from the secondary effluent. The filtered
water then flows through several chlorine disinfection steps and final dechlorination before being discharged into San Francisco Bay or diverted to the Reclamation Facility.
The water discharged into the San Francisco Bay is frequently tested to confirm that the water is not harmful to wildlife. In order to protect San Francisco Bay from the harmful effect of toxic substances such as heavy metals, PARWQCP requires residents, businesses, and institutions to reduce the amounts of these substances they release into the sewer. The first metal targeted for reduction was silver, which is toxic to wildlife and has accumulated in clams in San Francisco Bay. The Plant's discharge of metals into the Bay was reduced by 60 percent during the 1980's, as a result of the Industrial Waste Control Program and enhanced treatment at the PARWQCP.
There are two processes at PARWQCP which are subject to the RMP rule (as well as the CalARP program and the PSM standard): the Chlorination process, and t
he Dechlorination process.
Chlorine is the only regulated substance handled in the Chlorination process. Chlorine is used in the Chlorination process as a disinfectant. Disinfection entails the destruction of pathogens such as bacteria, protozoa, and viruses. Chlorine acts as an oxidizer on pathogens, organic compounds, and reduced nitrogen compounds. Typically, wastewater disinfection requires 40 to 60 grams of chlorine per cubic meter (about 264 gallons) of wastewater.
Chlorine is delivered to the Plant by tank truck. The tank truck capacity is 18 tons. The chlorine truck is connected to the chlorine unloading manifold with braided-steel, flexible hoses.
The Plant's chlorine bulk tank has a capacity of 25 tons. The tank is constructed of steel. The valves are identical to the valves on a chlorine railcar. The liquid and gas lines are equipped with excess flow valves that limit the flow rate out of the chlorine bulk tank to a maximum of 7000 pounds per hour. If chlorine i
s released within the chlorine storage room, an automatic eductor is activated. Chlorine vapor is removed from the chlorine storage room and routed to the chlorine contact tank, where it is consumed in the chlorination reactions. Two additional eductors within the chlorine building can be activated manually. The eductors are capable of removing 21,000 pounds of chlorine per day.
Ton containers of chlorine are kept on standby, for use in the event of bulk chlorine unavailability. The maximum amount of chlorine handled on-site (in bulk storage and ton containers) at any time is 74,000 pounds.
Chlorine vapor is metered through chlorinators on vacuum demand. Each chlorinator consists of a vacuum regulator, a flow meter, a control valve, and a differential pressure regulator. Downstream of the vacuum regulator, chlorine gas is handled at a pressure that is less than atmospheric. A leak downstream of the vacuum regulator would result in air intrusion, rather than a chlorine release.
On loss of vacuum, or on loss of chlorine supply pressure, the vacuum regulator closes.
Vacuum is generated by eductors (also referred to as "ejectors"). In the eductors, chlorine is mixed with water. The resulting solution is mixed with process water for treatment. The vapor pressure of the chlorine solution is low enough that the solution does not pose a significant risk upon release.
Chlorine is a greenish-yellow gas at ambient temperature. It has an intensely irritating odor, and is moderately toxic by inhalation. Chlorine vapor is denser than air. Chlorine is not flammable, although it will support combustion as an oxidizer. Chlorine is only slightly soluble in water. When chlorine reacts with water, a weak solution of hydrochloric and hypochlorous acids is formed. These acids are corrosive to most common metals. Chlorine reacts with many organic compounds to form chlorinated derivatives. Hydrogen chloride is often formed as a by-product of these reactions.
dioxide is the only regulated substance handled in the Dechlorination process. Sulfur dioxide is used in the Dechlorination process to consume residual free chlorine. This is necessary to prevent harmful effects on aquatic organisms near the PARWQCP outfall in the San Francisco Bay.
Sulfur dioxide is delivered to the Plant by tank truck. The maximum tank truck capacity is 20 tons. The sulfur dioxide truck is connected to the sulfur dioxide unloading manifold with braided-steel, flexible hoses.
The Plant's sulfur dioxide bulk tank has a capacity of 25 tons. The tank is constructed of steel. The liquid and gas lines are equipped with excess flow valves that limit the flow rate out of the sulfur dioxide bulk tank to a maximum of 8000 pounds per hour. If sulfur dioxide is released within the sulfur dioxide storage room, an automatic eductor is activated. Sulfur dioxide vapor is removed from the sulfur dioxide storage room and routed to the chlorine contact tank. Two additional e
ductors within the sulfur dioxide storage room can be activated manually. The eductors are capable of removing 21,000 pounds of sulfur dioxide per day.
Ton containers of sulfur dioxide are kept on standby, for use in the event of bulk sulfur dioxide unavailability. The maximum amount of sulfur dioxide handled on-site (in bulk storage and ton containers) at any time is 74,000 pounds.
Sulfur dioxide vapor is metered through sulfonators on vacuum demand. Each sulfonator consists of a vacuum regulator, a flow meter, a control valve, and a differential pressure regulator. Downstream of the vacuum regulator, sulfur dioxide gas is handled at a pressure that is less than atmospheric. A leak downstream of the vacuum regulator would result in air intrusion, rather than a sulfur dioxide release. On loss of vacuum, or on loss of sulfur dioxide supply pressure, the vacuum regulator closes.
Vacuum is generated by eductors (also referred to as "ejectors"). In the eductors, sulfur dioxide is
mixed with water. The resulting solution is mixed with process water for dechlorination. The vapor pressure of the sulfur dioxide solution is low enough that the solution does not pose a significant risk upon release.
Sulfur dioxide is a clear, colorless gas at ambient temperature. It has a pungent, choking odor. Sulfur dioxide is toxic by inhalation. Sulfur dioxide is not flammable. Sulfur dioxide is sparingly soluble in water, and will react with water to form a corrosive acid solution. Sulfur dioxide vapor is denser than air.
Worst-case Release Scenario, and Alternative Release Scenarios
The Plant's worst-case release scenario consists of a total release of the maximum inventory of the sulfur dioxide bulk tank. The maximum inventory is 50,000 pounds. While the maximum quantity of chlorine is also 50,000 pounds, the maximum distance to the endpoint for chlorine is shorter than the maximum distance to the endpoint for sulfur dioxide.
The sulfur dioxide bulk tank is locate
d within a building. In accordance with "Risk Management Program Guidance for Wastewater Treatment Plants," the release rate to the surroundings was calculated as 1700 lbs/min, with a duration of 10 minutes. Note that this conservatively ignores the effectiveness of the emergency eductors in the storage room.
The toxic endpoint for sulfur dioxide is 0.0078 mg/L, which corresponds to 3 ppmv. The worst-case release scenario was modeled with DEGADIS version 2.1. The following inputs were applied: wind speed, 1.5 m/s; stability class, F; surface roughness, 3 cm (appropriate for "rural"); release duration, 10 minutes; release rate, 12.88kg/s (corresponding to 1700 lbs/min). The maximum distance to the toxic endpoint was calculated as 4.8 miles.
Using Landview III, the population within 4.8 miles of the release point was estimated as 140,000. The following types of public receptors lie within 4.8 miles of the release point: schools, residences, hospitals, recreation areas, and majo
r commercial/office/industrial areas. There is also a civil aviation airport close to the Plant. There is an officially designated wildlife preserve within 4.8 miles of the release point.
The Plant's alternative release scenarios consist of a chlorine release and a sulfur dioxide release. In both cases, the release scenario entails a leak in the vapor unloading piping outside of the Chlorine/Sulfur Dioxide Building, which is conservatively assumed to persist for 10 minutes prior to isolation (which can safely and rapidly be accomplished remotely). The alternative releases scenarios are assumed to occur during chlorine and sulfur dioxide truck unloading, through a hole with an effective diameter of 1/16 inch (as in "Risk Management Program Guidance for Wastewater Treatment Plants"). The chlorine gas pressure during unloading is typically 70 psig, and the sulfur dioxide gas pressure during unloading is typically 25 psig. Under these conditions, 18 pounds of chlorine would be relea
sed (1.8 lbs/min), and 7.7 pounds of sulfur dioxide would be released (0.77 lbs/min).
The alternative release scenarios were both modeled with DEGADIS version 2.1. The endpoints for both substances correspond to 3 ppmv. Local meteorological data indicate that, coincidentally, 1.5 m/s, stability F is the most common wind speed/stability class combination (as was used for the worst-case release scenario). Using these inputs, the distance to 3 ppmv chlorine was calculated to be 2400 feet, and the distance to 3 ppmv sulfur dioxide was calculated to be 1700 feet.
The population within the distances to the endpoints described above is known to be 2. The following types of public receptors lie within the distances to the endpoints described above: residences, recreation areas, and major commercial/office/industrial areas. There is also a civil aviation airport across the street from the Plant. There is an officially designated wildlife preserve within the distances to the endpoints des
Accidental Release Prevention Program
The Plant's accidental release prevention program consists of the following elements: Process Safety Information; Process Hazard Analysis; Operating Procedures; Training; Contractors; Pre-Startup Safety Review; Mechanical Integrity; Hot Work Permit; Management of Change; Incident Investigation; Compliance Audits; and Employee Participation. The purpose and scope of each element is briefly described below.
Process Safety Information - The purpose of compiling the required Process Safety Information is to enable Plant personnel who work with the chlorine and sulfur dioxide processes to identify and understand the hazards posed by these processes. The Plant's Process Safety Information procedure addresses: Information requirements pertaining to the hazards of chlorine and sulfur dioxide; Information requirements pertaining to the technology of the processes; Information requirements pertaining to the equipment in the processes; an
d Process Safety Information accessibility requirements.
Process Hazard Analysis - The purpose of the Plant's PHA procedure is to describe the method for conducting process hazard analyses of the Plant's chlorine and sulfur dioxide processes. The Plant's PHA procedure addresses: PHA methodology; PHA scope; PHA team requirements; Employee participation requirements; System established to promptly address the PHA team's recommendations; PHA update and revalidation requirements; PHA report retention requirements; and PHA report distribution requirements.
Operating Procedures - The purpose of the Plant's Operating Procedure policy is to provide a method for developing and implementing written operating procedures to give clear instructions for safely conducting activities associated with the chlorine and sulfur dioxide processes. The Plant's Operating Procedure policy addresses: Development and implementation of written procedures to provide clear instructions for safely conducting a
ctivities involved in each covered process; Development and documentation of process operating limits; Development and documentation of process safety and health considerations; Operating procedure accessibility requirements; Operating procedure review requirements; and Safe work practice requirements for employees and contractors to provide for control of hazards during operations.
Training - The purpose of the Plant's Training procedure is to ensure that personnel involved in operating the Plant's chlorine and sulfur dioxide processes have received and understood training in: an overview of the chlorine and sulfur dioxide processes; the operating procedures required in the Operating Procedures element of the Plant's PSM program; safety and health hazards associated with chlorination and dechlorination; and applicable safe work practices. The Plant's Training procedure addresses: Initial training requirements; Refresher training requirements; Documentation of employee training; an
d Testing to ensure that required training has been understood.
Contractors - The purpose of the Plant's Contractors procedure is to establish a method for ensuring that all contractors are adequately trained to perform work on or near the Plant's chlorine and sulfur dioxide systems. The Plant's Contractors procedure addresses the responsibilities of the Plant and the contract employer with respect to ensuring the safety of contractors working on or near the Plant's chlorine or sulfur dioxide processes.
Pre-Startup Safety Review - The purpose of the Plant's Pre-Startup Safety Review procedure is to ensure that new or modified facilities that handle regulated substances are safely started up. The Plant's Pre-Startup Safety Review procedure (PSSR) addresses: PSSR Checklist completion prior to startup of new or modified facilities; The method for determining when a PSSR shall be performed, and PSSR Team selection; The system to ensure that new Process Safety Information has been comp
iled; The system to ensure that all materials and construction are in accordance with design specifications; The system to ensure that all safety, operating, maintenance, and emergency procedures are in place and adequate; The system to ensure that a Process Hazard Analysis has been performed for new facilities, and that recommendations have been addressed prior to startup; The system to ensure that Management of Change requirements are met prior to start-up of modified facilities; The system to ensure that operations and maintenance employees are trained prior to start-up; and Documentation of the Pre-Start Safety Review.
Mechanical Integrity - The purpose of the Plant's Mechanical Integrity policy is to establish the requirements of the Mechanical Integrity program at the Palo Alto Regional Water Quality Control Plant. The purpose of the Mechanical Integrity program is to ensure that process equipment used to handle chlorine and sulfur dioxide is designed, constructed, and maintain
ed to minimize the risk of accidental release. The Plant's Mechanical Integrity program addresses the following activities as they relate to the chlorine and sulfur dioxide processes: Training in the chlorine and sulfur dioxide processes and their hazards, and in the safe conduct of maintenance activities; Inspection and testing; Correcting deficiencies in equipment; and Quality assurance in fabrication, installation, and maintenance.
Hot Work Permits - The purpose of the Plant's Hot Work Permit procedure is to define how Hot Work Permits are issued and to ensure compliance with permit requirements before and during hot work. The Plant's Hot Work Permit procedure addresses: General requirements; The Hot Work Permit; Authorization of hot work; Fire prevention precautions; and Fire watchers.
Management of Change - The purpose of the Plant's Management of Change procedure is to establish the Plant's requirements for managing changes to processes that handle chlorine or sulfur dioxid
e. This procedure provides direction in identifying, reviewing, and authorizing process changes prior to their implementation in order to minimize their potential impact on safety and health. The Plant's Management of Change Procedure addresses the following: Identifying process changes; Reviewing process changes; Training necessitated by process changes; Updating Process Safety Information; Updating operating procedures; and Authorizing process changes. Specific actions included within reviewing process changes are: documenting the technical basis for the proposed change; assessing the impact of the proposed change on safety and health; modifying operating procedures, as necessary; and documenting and tracking the intended duration of the change (temporary vs. permanent).
Incident Investigation - The purpose of the Plant's Incident Investigation procedure is to provide a method for reporting, investigating, and preventing reoccurrence of incidents that result in or could reason
ably have resulted in a catastrophic release of chlorine or sulfur dioxide. The Plant's Incident Investigation procedure addresses: Reporting incidents; The procedure for initiating an incident investigation; The establishment of an Incident Investigation Team, and requirements for the selection of Team members; Investigating the incident; Preparation of the Incident Investigation Report and the minimum requirements of the Report; The system established to promptly address and resolve the report findings and recommendations; and The method for reviewing the findings of the Incident Investigation with all operating, maintenance, and other affected personnel (including contract employees) whose work assignments are relevant to the findings.
Compliance Audits - The purpose of the Plant's Compliance Audits procedure is to establish the requirements for an audit that verifies that the Plant is meeting the requirements of OSHA's Process Safety Management (PSM) standard, the CalARP program
, and EPA's Risk Management Program rule. The Plant's Compliance Audits procedure requires triennial review of the Plant's PSM program/RMP Prevention Program procedure documents, and evaluation of the implementation of these procedures by conducting records reviews, employee interviews, and field inspections. The Plant's Compliance Audit procedure also requires that recommendations be formulated to resolve any identified deficiencies. The Plant's Compliance Audits procedure addresses: Pre-audit activities; Conduct of the PSM program/RMP Prevention Program compliance audit; and Post-audit activities, including taking action to resolve any identified deficiencies.
Employee Participation - The purpose of the Plant's Employee Participation procedure is to document the method of actively involving PARWQCP employees in the development and conduct of the Plant's Process Safety Management elements. The purpose of involving employees in the development and conduct of the Plant's PSM eleme
nts is to foster commitment to the enhancement of process safety. The Plant's Employee Participation procedure addresses: The method of consulting employees (and their representatives) on the conduct and development of each element in the Plant's process safety management program; and The method for providing employees (and their representatives) access to all process safety management documents and records.
Five-year Accident History
Over the past five years, the Palo Alto Regional Water Quality Control Plant has not had any chlorine or sulfur dioxide releases that resulted in deaths, injuries, property damage, evacuations, sheltering in place, or environmental damage, either onsite or offsite.
Emergency Response Program
PARWQCP has an emergency response program that addresses the following: Evacuation; Emergency release notification; Emergency response procedures; Leak containment procedures; Spill control; and First aid/medical management. The Plant's leak response team is t
rained, evaluated, and equipped in accordance with 29 CFR 1910.120. The Plant's emergency response program is coordinated with the local Fire and Police Departments.
All operations, maintenance, and instrumentation personnel are trained quarterly in the use of personal protective equipment, and in the use of Chlorine Institute "B" and "C" leak kits. In June, all operations, maintenance, and instrumentation personnel are fit tested for respirator use.
Drills, involving all Plant personnel, are also conducted quarterly. The drills simulate evacuation, leak repair, chlorine/sulfur dioxide detection, and automatic isolation in response to detection. The drills are critiqued by Plant management and supervision.
Planned Changes to Improve Safety
As a result of the Plant's most recent internal compliance audit, the Palo Alto Regional Water Quality Control Plant has completely restructured its PSM program/prevention program. The new program elements have been integrated into a managem
ent system framework, in accordance with internationally recognized principles of total quality management. The management system is designed to ensure implementation of each program element, in compliance with the Cal/OSHA PSM standard, the CalARP program, and the EPA RMP rule. Authority, responsibility, and accountability are clearly and specifically assigned to Plant management, supervision, and staff. The means of documenting compliance have been improved for each prevention program element.