Edwardsville Wastewater Treatment Plant - Executive Summary
The City of Edwardsville (CE) has developed a Risk Management Plan (RMP) for management and prevention of risks associated with the storage and use of chlorine, a regulated toxic substance, at the Edwardsville Wastewater Treatment Plant. The RMP was prepared in compliance with 40 CFR Part 68 and Clean Air Act (CAA) Section 112(r)(1). The Prevention Program elements build upon the facility's Process Safety Management (PSM) system prepared in compliance with 29 CFR Part 1910.119. The PSM program is based upon the plant's contract operator's, PSG Services, existing program. |
Accidental Release Prevention and Emergency Response Policies
It is CE's policy to comply with applicable Federal and State requirements. The chlorination process at the Edwardsville Wastewater Treatment Plant uses chlorine, a hazardous toxic substance regulated by USEPA and OSHA. Due to the hazardous characteristics of chlorine, the Edwardsville Wastewater Treatment Plant observes various safety precautions in
the storage, conveyance and use of chlorine. The safety precautions are necessary to protect employees, contractors, and visitors at the Edwardsville Wastewater Treatment Plant and the immediately surrounding areas. Safety precautions include procedures and equipment to minimize the potential for accidental release, as well as a written emergency response program for response to any chlorine release that may occur.
The Stationary Source and Regulated Substances Handled
The Edwardsville Wastewater Treatment Plant provides treatment for up to 3.5 million gallons per day of wastewater. The regulated substance handled at the Edwardsville Wastewater Treatment Plant is chlorine.
Chlorine is delivered to the facility via truck in ton containers. The storage building has space for up to two full containers, a total of 4,000 pounds of chlorine. Chlorine containers are connected to vacuum chlorinators. The chlorinators regulate chlorine use. From the chlorinators, chlorine gas is distr
ibuted under vacuum to injectors. The injectors combine the gaseous chlorine with water. The chlorinated water is mixed with the wastewater plant flow for disinfection and odor control.
Worst-case and Alternative Release Scenarios
The worst-case release scenario was determined following USEPA's Risk Management Program Offsite Consequence Analysis Guidance. The worst-case release scenario is a vapor release of the entire contents of a ton container over a ten minute period (200 pounds of chlorine per minute). Other worst-case assumptions required by EPA include a low wind speed (1.5 meters per second), stable atmosphere (Class F), rural topography, and no active mitigation of the release.
USEPA requires the determination of the area (zone of vulnerability) which may be exposed to a chlorine concentration of 3 ppm or greater. According to the American Industrial Hygiene Association, 3 ppm is the maximum concentration of chlorine in air below which nearly all people could be expos
ed for one hour without serious health effects. Based on the worst-case assumptions, the zone of vulnerability was determined to extend 3.0 miles from the chlorine storage area. No active or passive mitigation was considered.
The following are known to be within the zone of vulnerability for the worst-case release scenario: residences, health center, schools, commericial, and a day care center.
Approximately 6,000 residents are located within a 3.0 mile radius of the chlorine storage area. Many of these residents would not actually be impacted in even a worst-case release, as the chlorine would travel in the direction of wind. No known environmental receptors (such as state parks or officially designated wildlife preserves) are located within the zone of vulnerability.
The conditions and parameters for the worst-case scenario are specified by USEPA. A more realistic alternative release scenario was examined, also following USEPA's Risk Management Program Offsite Consequence
Analysis Guidance. The alternative release scenario is a vapor release of the entire contents of a ton container through a broken 3/8 inch valve connection. The contents would be released at a rate of 20 pounds of chlorine per minute over a 90 minute period. The worst case/most pessimistic weather conditions are also used (wind speed of 1.5 meters per second, atmospheric stability Class F). Other conditions remain the same as in the worst-case scenario (rural topography and no mitigation of the release). Under more common weather conditions (D stability, 3 meters/sec wind speed) , the area of vulnerability is to likely be approximately 0.2 miles
The zone of vulnerability for the alternative release scenario is determined to extend 1miles from the chlorine storage area. Approximately 750 residents and a commercial nursery are located within a 1 mile radius of the chlorine storage area. These residents and recreation area could be impacted, depending on the direction of wind.
No known environmental receptors are located within the zone of vulnerability.
General Accidental Release Prevention Program and Chemical-specific Prevention Steps
PSG complies with USEPA and OSHA requirements for Prevention Programs and for PSM. Operators, maintenance staff and contractors are informed of chlorine hazards, and hazard signs are posted in the chlorine storage area. Standard operating and maintenance procedures have been developed, and employees who work with chlorine are provided training.
Emergency Response Program
PSG has an emergency response program in conjunction with the CE's Fire Department. Chlorine gas detectors are located within the storage area for early detection and warning of any leak. Leak repair kits are maintained on site, and the CE's Fire Department are trained in how to quickly stop any leak that may occur. The emergency response program is coordinated with the CE's Fire and Police Deparment's for notification of the public.
There have been no accidents on site in the last five years.
Planned Changes to Improve Safety
PSG uses Process Hazard Analyses (PHA) to identify and recommend changes to ensure a high level of safety. Issues identified from a PHA are then addressed in CE's Prevention Program. Recommendations from the most recent PHA include more frequent training in operating and maintenance procedures, and an improved preventative maintenance program. An audit of the RMP and PSM programs will be conducted within three years to verify the effectiveness of the program.