Northeast Water Pollution Control Plant - Executive Summary
Executive Summary |
Chemicals are widely used in industry and in the home, as well as present in the environment. They are transported on roads, waterways, and railways. We at the Northeast Water Pollution Control Plant (Northeast WPCP) use chemicals too. For example, we use chlorine to disinfect our treated wastewater to provide safe discharge to the Delaware River. We also produce methane as a part of our wastewater treatment process. Storing large quantities of chlorine and methane can be a hazard. We take our safety obligations in storing and using chlorine and methane as seriously as we do providing the effective, safe treatment of wastewater. The following document describes what could happen if there were to be an accident, the steps we take everyday to ensure a safely operating plant, and what to do in event of an emergency.
Accidental Release Prevention and Emergency Response Policies
The Philadelphia Water Department (PWD) and Northeast WPCP accidental rel
ease prevention policy involves a unified approach that integrates proven technology, trains staff on operation and maintenance practices, and uses tested management system 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. The Northeast WPCP has a chlorination system that uses chlorine gas fed from rail cars. The plant sludge digestion system produces methane as a by-product of the process. 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 relea
ses of chlorine and digester gas to the environment. The Northeast WPCP 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.
General Facility and Regulated Substances Information
The Northeast WPCP, operating since 1929, is located at 3899 Richmond Street in the City of Philadelphia. The plant is located on property between Interstate 95 and the Betsy Ross Bridge in the Bridesburg section of Philadelphia. Wastewater treated at the Northeast WPCP is disinfected with chlorine and discharged to the Delaware River. The treated wastewater meets all EPA standards. This wastewater treatment includes preliminary screening, primary settlement and treatment, secondary sedimentation and treatment, and chlorination before final discharge. The Northeast WPCP discharges up to 315 million gallons per da
y (MGD) of treated wastewater, with an average flow of 200 MGD.
The facility currently stores chlorine, which is a regulated toxic substance under 40 CFR Part 68 - RMP. The Plant's chlorine storage exceeds the listed threshold quantity of 2,500 pounds in the RMP Regulations.Liquid chlorine is brought to the plant via rail lines that enter the plant property. Chlorine leak detector monitors continuously check for leaks in the bulk storage areas and in the chlorination rooms. Other indicators include chlorine feed and evaporator alarms. These alarms are annunciated at the central and local control panels at the plant in the main control room. In the case of a leak, the storage area has an audible alarm and red flashing warning light on top of the building. In addition, an evaporator shut-off and pressure reducing valve is designed to close if low evaporator gas temperature is detected; thus preventing liquid chlorine from reaching the gas piping system. These valves also reduce pressu
re and allow for quicker liquefaction to occur. All process related, factory-set pressure relief valves are set to protect the integrity of the equipment.
The rail car storage area is covered for sun protection and the chlorination room is enclosed in the effluent pumping station building. The chlorination room is equipped with an automatic ventilation system that activates when the chlorine leak detector detects 2 ppm of chlorine in the room. Emergency showers and eye wash stations are provided at each building. The rail car storage area and the effluent pumping station both have Self-Contained Breathing Apparatus (SCBAs) available.
The facility also currently produces methane as a by-product of its wastewater treatment process. Methane is a regulated flammable substance under 40 CFR Part 68 - RMP. The Plant's methane storage exceeds the listed threshold quantity in the RMP Regulations.
Methane is produced at the plant as a result of the digestion of sludge from the wastewater
treatment process. This is a naturally occurring process that happens in swamps and other locations. Methane leak detector monitors continuously check for leaks in the digester tank areas and in the process rooms. These alarms are annunciated at the central and local control panels at the plant in the main control room. In the case of a leak, each area has an audible alarm and red flashing warning light to indicate the presence of methane above safety threshold limits. The leak detectors are set to alarm at 20% of the lower explosive limit (LEL) for methane that is well below potential explosive levels.
The sludge digesters and storage tanks are equipped with pressure relief valves that enhance the safety of the system. The process rooms are equipped with a ventilation system that operates continuously to ensure no build-up of digester gas that could pose an explosive concern.
The Northeast WPCP is controlled at one main entrance on Richmond Street. Visitors and contractors must
check-in at the administration building and be approved by Northeast WPCP staff prior to entry into the facility. The plant is manned 24-hours a day, year round, and alarms notify staff of any problems or situations that require follow-up investigations at all times.
Offsite Consequence Analysis Results
The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case" and "alternative" release scenarios. The worst case scenario assumes that the entire content of the largest single container of chlorine is 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.
An alternative release scenario is also required.
he worst case release scenario for chlorine is focused on the 90-ton rail cars that store chlorine liquid. The scenario used for Northeast WPCP is the rupture of one chlorine rail car with a maximum capacity of 90 tons, resulting in a release of 180,000 pounds of chlorine over a 10-minute duration. The chlorine rail cars are stored in an area that is not totally enclosed, so no building mitigation factor can be applied at Northeast WPCP. The release rate for this scenario is 18,000 pounds per minute (lbs/min).
The rail car rupture resulting in a chlorine release could be caused by catastrophic events, such as an earthquake. In practice this type of total release of a rail car would be unlikely and never occur during the lifetime of the plant. The results of the dispersion modeling analysis for this worst case release scenario indicate that this scenario has an offsite impact.
The alternative release reflects a type of release that is more likely to occur, as compared to the worst c
ase scenario. Unlike the worst case scenario, the alternative release scenario may consider "active" mitigation, such as automatic shutoff valves and scrubbers. Active mitigation is defined as requiring mechanical, electrical, or human input. Lastly, the alternative release scenario assumes more realistic regional and seasonal meteorology.
Based on the process hazard analysis performed for the chlorine system, several alternative release scenarios were selected. 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 for chlorine was a failure of the excess flow valve on the chlorine rail car with no mitigation. Under this scenario, the amount of chlorine released was calculated to be 126.0 lbs/min. The results of the dispersion modeling analysis for the worst alternative release scenario indicate that this scenario has a slight offsite impact.
worst-case release scenario for methane is focused on the 110-foot diameter sludge digesters that produces the gas. The scenario used for Northeast WPCP is a release of 2887 pounds of methane and an instantaneous explosion hazard.
The explosion could be caused by catastrophic events, such as an airplane crashing into the digester. In practice this type of an explosion would be unlikely and never occur during the lifetime of the plant. The results of the worst-case release analysis indicate that this scenario has a slight offsite impact. Thus, alternative release scenario is required for this process.
The alternative release scenario for methane is focused on the waste gas flares that burn excess methane from the sludge digestion process. The scenario is the failure of the pilot light on a single flare, causing a release of methane to the surrounding environment. This release scenario shows no explosion hazard due to the release of methane from an unlit flare.
No chlorine releases that could have caused safety or health hazards to any individuals at off-site locations (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at Northeast WPCP during the last five years. Some minor, incidental releases may have occurred over this period, but they were quickly handled by staff or posed no safety or health hazards.
There was a single release on-site during the past 5-years that affected a single employee working on a chlorine solution drain line at the plant. The employee affected received minor medical treatment and returned to work the next day. There was no other damage resulting from this small incidental release.
No explosions/fires from methane that could have caused safety or health hazards to any individuals at on-site or off-site locations (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at Northeast WPCP during the last
Summary of the Accidental Release Prevention Program and Chemical-specific Prevention Steps
Northeast WPCP is in compliance with Federal Risk Management Planning (RMP) requirements. Chemical-specific prevention steps include availability of self-contained escape breathing apparatus, worn by the operators during connection and disconnection of the chlorine supply, awareness of the hazardous and toxic properties of chlorine and methane, and the presence of chlorine and methane detectors and alarms.
Northeast WPCP's accidental release prevention program is based on the following key elements:
* Detailed management system and clear levels of responsibilities and team member roles
* Comprehensive safety process information that is readily available to staff, emergency responders, and contractors
* Comprehensive preventive maintenance program
* Completion of a hazard review of equipment and procedures with operation and maintenance staff participation and review.
* Use of s
tate-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.
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 and methane background information, material safety data sheets (MSDS), and chlorine and methane reaction chemistry.
Equipment safety information was meticulously compiled on the chlorine and methane processes. Specifications for the process are collecte
d 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 is triggered to update safety information if there is a major change that makes existing information inaccurate.
In 1998, a detailed hazard analysis (HA) was conducted with plant staff, engineering, and administrative staff for the regulated processes. The team consisted of process operating and maintenance experts and process design engineers. The HA technique used was the "What-If" scenario and process checklist procedure, per acceptable approach guidance from EPA. The HA was lead by knowledgeable persons 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.
Northeast WPCP maintains up-to-date, accurate, written operating procedures that give clear instructions for the chlorine and digester gas process. Northeast WPCP ensures effective operating practices by combining them with operating and maintenance training programs. Standard operating procedures (SOPs) provide system descriptions, specifications, equipment inspection requirements, and operating procedures for the chlorine and digester gas system. Procedures include startup, shutdown, and normal, alternate, and emergency operation. Also included are maintenance and troubleshooting procedures, including consequences of deviation and the steps to avoid and correct deviations. Northeast WPCP will update procedures whenever a change occurs that alters the steps needed to operate safely. Ope
rating 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 Northeast WPCP employee presently involved in operating or maintaining the chlorine and digester gas processes is trained in an overview of the process and detailed, applicable operating and maintenance procedures. In fact, Northeast WPCP helps their employees understand, through training, the nature and cause of problems arising from operations involving chlorine on site, and to increase their employees awareness with respect to their hazards. Northeast WPCP'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 process operating procedures and safe work practices. Oral reviews and written self-evaluations are used to verify that an employee und
erstands the training material 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.
Northeast WPCP maintains the mechanical integrity of process equipment to help prevent equipment failures that could endanger workers, the public, or the environment. Northeast WPCP 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. Northeast WPCP's maintenance 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
Internal Compliance Audits
Internal compliance audits are conducted every three years to verify compliance with the programs and procedures contained in the RMP. Northeast WPCP and PWD 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 implemented.
Northeast WPCP investigates all incidents that could reasonably have resulted in a ser
ious injury to personnel, the public, or the environment so that similar accidents can be prevented. Northeast WPCP 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 on to the training unit for their inclusion in existing training programs, if warranted, to prevent a future event.
Emergency Response Program Summary
Northeast WPCP 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 with the City of Philadelphia Fire Department HAZMAT Uni
t, which is a member of the Local Emergency Response Planning Committee (LEPC). This program includes an emergency response notification plan. Emergency response drills and drill evaluations are conducted at a minimum frequency of every 12 months; emergency operation and response procedures are also reviewed at that time.
Planned Changes to Improve Safety
A few minor changes to improve safety (recommended actions) were identified for the chlorine and digester gas processes in 1998 during the hazard review process. These recommended actions have been evaluated and will be implemented as required. It is expected that the recommended actions will be evaluated and implemented by December 1999. The implementation of these recommendations will further improve the safety of the covered processes.
EXECUTIVE SUMMARY RISK MANAGEMENT PROGRAM