Sunnyvale Water Pollution Control Plant - Executive Summary
Chemicals are widely used in industry, in the home, and in the environment. They are transported on roads, water, and railways. The City of Sunnyvale Water Pollution Control Plant (SWPCP) uses chemicals too, such as chlorine and sulfur dioxide to disinfect treated wastewater to provide safe water for discharge to the environment and for reclaimed water uses such as landscaping and irrigation. Storing large qualities of these chemicals can be a hazard. We take our safety obligations in storing and using hazardous chemicals as seriously as we take providing reliable wastewater treatment. This document describes what could happen if there were to be an accidental chemical release, the steps we take every day to ensure a safely operated plant, and how we respond to an emergency. To date, we have had an excellent record in preventing accidental releases. Please feel free to contact Lorrie Gervin, Environmental Division Manager, at (408) 736-7260 if you have any questions.
idental Release Prevention and Response Policies
The SWPCP has already implemented programs to comply with several other accidental release prevention regulations including California's OSHA Process Safety Management (PSM) program and California's Risk Management and Prevention Program (RMPP) because of use and storage of chlorine and sulfur dioxide. The California RMPP law was repealed in January 1997 and replaced by the CalARP regulation.
It is the policy of the SWPCP to develop, maintain, and implement this RMP/PSM Plan. This RMP/PSM plan complies with the U.S. Environmental Protection Agency's (EPA's) Risk Management Program (RMP), under Section 112 (r) of the Clean Air Act (CAA) Amendments of 1990, 40 Code of Federal Regulations (CFR) Part 68, the California Accidental Release Prevention (CalARP) Program under California Code of Regulations (CCR) Title 19, Division 2, Chapter 4.5, and the Process Safety Management Program under CCR Title 8, Division 1, Chapter 4, Section 5189 and
29 CFR 1910.119.
General Facility and Regulated Substances Information
The SWPCP is located at 1444 Borregas Avenue in Sunnyvale, near the southern tip of the San Francisco Bay. SWPCP treats wastewater from the City of Sunnyvale, a small section of San Jose, and a portion of Moffett Field Naval Air Station, located in Sunnyvale. The plant has a capacity of 29.5 million gallons per day; average flow is 18 million gallons per day. Plant processes include pretreatment to remove large solids and grit, primary treatment to remove settleable solids, oxidation ponds as secondary treatment, biological treatment to convert ammonia to nitrates, coagulation for algae removal, filtration to remove suspended solids, disinfection to inactivate disease-causing organisms and dechlorination.
The facility currently stores chlorine, sulfur dioxide, and digester gas; all regulated toxic substances under RMP and CalARP. Chlorine and sulfur dioxide are stored in 1-ton containers and exceed the RMP and Ca
lARP threshold quantities. Digester gas is stored in four digester domes, a gas holding tank, and associated process piping. Calculations maintained at the SWPCP demonstrate that the amount of gas stored does not exceed the RMP and CalARP rule threshold.
Chlorine is added to the wastewater to kill disease-causing organisms and is also used to control odors. Sulfur dioxide is used to remove any remaining chlorine after disinfection is completed to protect flora and fauna in the receiving water. Chlorine and sulfur dioxide are both used in the disinfection process and are stored, transported, and applied in physically separate, but similar systems. Chlorine and sulfur dioxide containers are delivered to the site on flat-bed trucks. Receipt of container deliveries is performed by SWPCP personnel. All chlorine and sulfur dioxide containers are immediately moved inside the storage buildings and are never left outside or unattended.
The chlorine and sulfur dioxide systems include several
safety features and are in full compliance with County of Santa Clara's (County) stringent Toxic Gas Ordinance (TGO). Safety provisions include:
7 Secondary containment-containers and all process equipment are located within the building and the building is under negative pressure under normal and emergency ventilation conditions.
7 3,000 cubic feet per minute (cfm) packed-bed scrubber to treat exhausted air if a release of chlorine or sulfur dioxide occurs.
7 Louvers automatically close upon detection of a leak and the room space is exhausted to the packed-bed scrubber.
7 Sulfur dioxide and chlorine storage and use rooms are equipped with smoke detectors, gas leak detectors, and seismic detectors and manually activated panic buttons at the chlorine and sulfur dioxide facility exits.
- Smoke detectors are provided with annunciators in the control room and can be used by plant operators to initiate automatic shutdown.
- Gas leak detectors in each chlorine and sulfur dioxide storage an
d use room are interconnected to the PLC system with a tiered action system that includes automatic shutdown of the building ventilation systems and door closers, activation of the scrubber system, activation of chlorine and sulfur dioxide shutoff valves, and activation of the the audible and visual alarm system (plant siren) if triggered. Automated dampers are used to direct air flow to the scrubber from the appropriate containment area. A sensor at the scrubber stack exit will provide automatic shutdown of the scrubber in the event of a detected release above the trigger level.
- Seismic detectors will cause liquid chlorine and sulfur dioxide supply valves to close and annunciate alarms to indicate the shutoff valves have closed in the event of significant seismic activity.
- Manually-activated panic buttons will cause the chlorine and sulfur dioxide supply valves to close and annunciate alarms to indicate the shutoff valves have closed.
7 Ancillary chlorine and sulfur dioxide proc
ess equipment used for handling chlorine and sulfur dioxide containers includes the following safety features:
- Containers are equipped with fusible plugs for pressure relief and steel protective housings for the valve area.
- All valves and fittings used on the chlorine system are certified for chlorine use.
- The header system is equipped with a frangible disk, shutoff valves, and a high pressure switch.
- The chlorine and sulfur dioxide evaporators are thermostatically controlled.
- The chlorine system pressure relief valve is vented through the scrubber.
7 The facility maintains a Chlorine Institute Emergency Kit B for use in responding to a leak from the ton containers and self-contained breathing apparatus (SCBAs) for use during equipment change out and emergency response situations.
7 The SWPCP is enclosed by a fence with controlled access.
System alarms are monitored at the computer control center staffed with operators 24 hours per day.
Offsite Consequence Analysis Results
The SWPCP has had an excellent safety record. However, we have evaluated scenarios that would result in offsite consequences as a way to communicate process risks to the public, to communicate response issues to the County emergency response organization, and as a tool in evaluating plant safety systems. The offsite consequence analysis for chlorine and sulfur dioxide included a worst case release scenario as defined by the RMP and CalARP regulations, and an alternative release scenario that, although unlikely to occur, is less unrealistic than the worst-case scenario.
The worst case scenario for chlorine and sulfur dioxide releases as defined by the RMP and CalARP regulations, consists of releasing the entire contents of one chlorine or sulfur dioxide and complete release of the container contents in 10 minutes. This scenario is extremely unlikely, and could result only from a catastrophic event such as an airplane crash. This scenario assumes that the incident occurs after the con
tainers have been delivered and are in the chlorine storage building because containers at this facility are not stored outside.
An EPA-developed air dispersion model called RMP*Comp was used to estimate the distance to a point where the concentration would become diluted to a level no longer considered hazardous to the public. The calculated distance for this worst-case scenario was 0.9 miles, which takes into account that the chlorine or sulfur dioxide use and storage is within a building in the event of a release. This distance, as calculated by RMP*Comp, may be exaggerated because of conservatisms in the model itself and the weather conditions used by the model. In addition, this scenario is extremely unrealistic and does not take into account SWPCP's existing safety and prevention programs or the scrubber and detection and alarm systems.
Using census data from LandView. III, the estimated population within the SWPCP vulnerability zone of 0.9 miles is 25 persons. It should be r
ecognized that this result is based on a highly unrealistic scenario, using a conservative model and weather conditions.
A second, alternative release, scenario was identified based on the process hazard analysis (PHA) as the occurrence of 0.1-inch diameter leak in a valve packing on either a chlorine or sulfur dioxide storage container. The SWPCP estimates that this type of leak could be secured within approximately 20 minutes. This scenario is less improbable than the worst-case release scenario. It takes into account that SWPCP's extensive safety and release prevention systems will help to mitigate the impacts of such a release. The relatively small quantity of chlorine or sulfur dioxide gas that is estimated would be released through this hole would be contained by the scrubber system. Thus, it was determined that there is no offsite impact associated with this alternative release scenario for either chlorine or sulfur dioxide. SWPCP has developed and implemented the systems in i
ts RMP/PSM program to prevent or mitigate such releases.
Five-Year Accident History
There have been no releases of chlorine or sulfur dioxide in the last five years that have resulted in deaths, injuries, or significant property damage onsite or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage. In the 25 years that these chemicals have been used onsite, the SWPCP has not had an accidental release that has required offsite response.
Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps
The SWPCP chlorine and sulfur dioxide systems are required to be managed under stringent release prevention and emergency response programs by both the OSHA Process Safety Management (PSM) Program regulations and the RMP/CalARP regulations because of the quantities stored and potential for offsite impacts. The SWPCP RMP/PSM Plan summarized herein addresses the chlorine and sulfur dioxide processes.
MP/PSM Plan is based on the following key elements:
7 Management system and levels of responsibilities and team member roles;
7 Comprehensive process safety information that is readily available to staff, emergency responders, and contractors;
7 A computerized preventive maintenance and work order tracking program;
7 A completed 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 accurate and effective operating procedures with participation of operations and maintenance staff for review and revision as required;
7 High level of training of operators and maintenance staff and on-going refresher training; and
7 Incident investigation, inspection, and auditing programs using qualified staff.
Process and Chemical Safety Information
Comprehensive chemical data have been assembled to include regulatory reporting and action thresholds, health hazards, and chemi
cal exposure limitations, as well as detailed physical properties of each regulated substance. This information was compiled from numerous sources prior to conducting the process hazard analysis and includes chlorine and sulfur dioxide background information, MSDS sheets, and chlorine and sulfur dioxide reaction chemistry.
Equipment safety information has been compiled on the chlorine and sulfur dioxide processes, including 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.
SWPCP also has procedures in place to update safety information if there is a major change that makes existing information inaccurate.
Process Hazard Analysis
A detailed initial PHA was conducted with plant staff, engineering, and administrative staff of the chlorine and sulfur dioxide processes in December 1993. The PHA team consisted of process operating and maintenance and inspection staff. The
PHA technique used was the "Hazard and Operability" (HAZOP) method, per acceptable approach guidance from EPA. The PHA was led by a person who was knowledgeable about the type of process being reviewed. The PHA is due for update or revalidation.
A list of actions to resolve hazard review findings from the initial PHA was prepared and all actions have been completed. A seismic evaluation of the chlorine and sulfur dioxide storage facilities and processes was conducted at the same time as the initial PHA (December 1993), prior to construction of building upgrades to comply with the 1994 County Toxic Gas Ordinance. The building upgrades included modifications to address issues identified during the initial seismic evaluation. The building modifications were constructed in accordance with 1994 Uniform Building Code requirements. A walkthrough to review and evaluate these modifications for compliance to current RMP/CalARP seismic requirements is scheduled.
maintains up-to-date, accurate, written operating procedures that include clear instructions for operation of the chlorine and sulfur dioxide processes. Operating procedures are incorporated into operation and maintenance training programs. Step-by-step written operating instructions have been developed for the chlorine and sulfur dioxide systems that include procedures for process startup, shutdown, and normal, alternate, and emergency operation. The SWPCP SOP Committee annually updates procedures and whenever a change occurs that alters the steps needed to operate safely. Operating procedures are developed and put in place prior to any new process equipment coming on line or a changed process starting back up.
Operations and Maintenance Training Program
Each SWPCP employee presently involved in operating or maintaining the chlorine and sulfur dioxide processes is trained in an overview of the process and detailed, applicable operating and maintenance procedures. The SWPCP training p
rogram provides information to help employees understand the nature and cause of problems arising from operations involving chlorine and sulfur dioxide onsite, and increases awareness of employees with respect to process hazards. The SWPCP training program includes both initial and refresher training that covers (1) a general overview of the processes, (2) the properties and hazards of chlorine and sulfur dioxide, and (3) a detailed review of process operating procedures and
safe work practices.
Training documentation maintained by SWPCP includes: the date of most recent review or revision to the training program; type of training provided; and the type of competency testing used to ensure that staff understand the training.
The SWPCP has developed and implemented procedures and policies to ensure that only contractors with good safety programs are selected to perform work on and around the chlorine and sulfur dioxide processes. Contractors are informed of process hazar
ds, process area access limitations, and emergency response procedures so that they may safely complete their work. SWPCP sets minimum contractor safety performance requirements to perform work on or around the chlorine and sulfur dioxide process areas and equipment, holds contractor safety briefings before allowing contractors near or in the process areas, controls access to process areas, and evaluates contractor performance.
Mechanical Integrity Program
The SWPCP maintains the mechanical integrity of all facility equipment, including covered process equipment, to help prevent equipment failures that could potentially endanger workers, the public, or the environment. We believe that this program is the primary line of defense against a release and addresses equipment testing and inspection, preventive maintenance schedules, and personnel training. The SWPCP mechanical integrity program includes the following:
7 Procedures for maintaining mechanical integrity through inspection and t
esting of process equipment based on instructions of manufacturers, equipment vendors, industry codes, and prior operating experience;
7 Implementation of the written procedures in performing inspections and tests on process equipment at specified intervals;
7 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; and
7 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
SWPCP requires employees and contractors to employ safe work practices when performing "hot work" in, on, or around the chlorine or sulfur dioxide processes, as well as other areas of the facility where flammable materials may be used or stored.
Management of Change and Pre-startup Safety Reviews
The SWPCP provides a system and approach to maintain and impl
ement changes or modifications to equipment, procedures, chemicals, and processing conditions. This system allows employees to identify and review safety hazards, provide additional safety, process, or chemical information to existing data, evaluate the proposed change to confirm that it would not compromise system safety, and establish training requirements before implementation.
The SWPCP 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.
Internal Compliance Audits
Safety audits are conducted at least annually. Internal compliance audits to verify compliance with RMP/PSM program data, systems, and procedures will be scheduled at least every three years.
The SWPCP assembles an audit team that includes personnel knowledgeable about the RMP/PSM Plan and about the process. This team evaluates whether the RMP
/PSM Plan and its implementation satisfies the requirements of the RMP/CalARP and PSM requirements and whether the RMP/PSM Plan is sufficient to help ensure safe operation of the chlorine and sulfur dioxide processes. The results of the audit are documented, recommendations are resolved, and appropriate enhancements to the RMP/PSM Plan are implemented.
In addition to its routine industrial accident investigation program, the SWPCP investigates all incidents involving chlorine or sulfur dioxide that caused or could reasonably have resulted in a serious injury to personnel, the public, or the environment so that similar accidents can be prevented. The SWPCP trains employees to identify and report any incident that requires investigation.
An investigation team is assembled to investigate covered process incidents. Results of the investigation are documented, recommendations are resolved, and appropriate process enhancements are implemented. Incident investigation
report findings are reviewed by affected staff, added or used to revise operating and maintenance procedures, and passed on to the Maintenance Manager and Supervisors for inclusion in existing training programs, if warranted, to prevent a future event.
Emergency Response Program Summary
The SWPCP has established a written emergency response program for employees to help safely respond to accidental releases of hazardous substances. This program has been coordinated with the City of Sunnyvale and the County emergency response agencies. The program includes emergency response procedures and an evacuation plan specific to the chlorine and sulfur dioxide processes. Chlorine area operators are trained as first responders. Emergency response drills and drill evaluations are conducted every 6 months. Emergency operation and response procedures are also reviewed at that time.
Planned Changes to Improve Safety
Several recommendations to improve safety (recommended actions) were previously id
entified for the chlorine and sulfur dioxide processes in the 1993 PHA performed pursuant to the California RMPP regulation. The principal change was upgrading the facility to comply with the County TGO requirements, which involved enclosure of the chlorine and sulfur dioxide storage and process areas, and addition of leak detection equipment and building safety features, including automatic shutdown systems and seismic upgrades. These modifications were implemented in 1994.
All recommended action items from the initial PHA have been resolved. Documentation of the closeout of corrective actions is maintained by the Operations Manager.