St. Marys Wastewater Treatment Plant - Executive Summary
City of St. Marys |
Wastewater Treatment Plant
Risk Management Program
A. The accidental release prevention policy at the City of St. Marys wastewater treatment facility involves a combined effort between management, operating, and local emergency personnel. The facility has an ongoing effort to identify hazards, review safety techniques, and implement employee training through operation, maintenance, and inspection procedures to manage the risk of a chlorine gas release.
B. The City of St. Marys treatment facility has been in operation since 1961. The facility currently has the capacity of treating an average flow of 2.87 million gallons per day. The treatment facility allows a wet weather flow of 7.87 million gallons per day. Gaseous chlorine, which is stored in a separate room, is utilized to disinfect the effluent prior to discharging to the receiving water. The amount of chlorine handled equals two 1-ton containers and five 150-pound cylinders for a total
of 4,750 pounds. The chlorine gas feeders are wall-mounted and are designed for conveying the gas under vacuum. The wastewater treatment plant operating personnel inspect the chlorine system two times a day during the week and once a day on the weekends.
C. The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case" and "alternate case". EPA's RMP Guidance for Wastewater Treatment Plants Reference Tables were utilized in the evaluation of both scenarios. For both the worst case and alternate case, urban topography was selected due to forested and mountainous regions in the immediate area of the wastewater treatment facility.
As defined by EPA, the worst case analysis is based upon a release of chemical in a quantity equal to the greatest amount held in a single vessel over a period of 10 minutes. In the case of the City of St. Marys WWTP, the release quantity would equal 2,000 pounds. Utilizing EPA's assumptions, a dista
nce to toxic endpoint of 1.3 miles and an estimate of population potentially affected of 770 resulted.
The alternate case scenario involves a faulty connection between the flexible hose and chlorine cylinder, causing a chlorine gas leak through an opening 3/8" diameter. For this scenario, it was assumed that the leak started at the same time the wastewater treatment facility became unmanned. Due to the St. Marys treatment facility having the auto-dialer system, the release of chlorine will not go unnoticed for a significant length of time. Within 5 minutes of the leak being detected, the local fire department will be on-site. Again utilizing EPA's assumptions relative to meteorological conditions and a chlorine release time of approximately 20 minutes, a distance to toxic endpoint of 0.1 mile and an estimate of population potentially affected of 5 people resulted. In the determination of an "alternate case" scenario, actuation of the chlorine detection/alarm and auto-dialer syste
ms were both considered. Another form of active mitigation present at the City of St. Marys wastewater treatment facility are the vacuum-type chlorinators with all chlorine gas piping under vacuum.
D. In general, the City of St. Marys Wastewater Treatment Facility's accidental release prevention program is based on the following:
* Compilation of safety information for chlorine storage
* Review of potential on-site hazards of the chlorine process
* Preparation of written operating procedures for safely conducting any activity involving the chlorination process
* Implementation of employee training program
* Preparation of written maintenance and inspection techniques and schedule for safe operation of the chlorine system
As an integral part of the prevention program, the City of St. Marys Wastewater Treatment Facility will perform a compliance audit at least once every 3 years. The compliance audit will include a review of all aspects of the risk management program in conjunction
with corrective actions if any deficiencies exist. Written documentation of the audit will be maintained on-site.
Any incident that results in, or could have resulted in, a catastrophic release of chlorine will be investigated immediately. A summary of the investigation and corrective actions will be documented and maintained at the treatment facility.
Chemical-specific prevention measures include the facility having appropriate safety equipment on-site including a chlorine detection/alarm device, an auto-dialer system, and self-contained breathing apparatuses. The facility promotes training and educating the employees relative to acceptable operating and handling techniques of chlorine gas.
E. No accidental releases of chlorine have occurred at this facility in the past five years.
F. The facility is included under the Local Emergency Planning Committee (LEPC) of Elk County's written Emergency Response Plan. Emergency notification procedures, release response procedures and re
sponsibilities by all involved parties, protective actions and training exercises are included within the plan. The City of St. Marys WWTP employees are notified of a release at which time they report to the site. However, the WWTP employees do not become actively involved in the response procedures for an accidental release of chlorine gas. Emergency responders will primarily include the local fire, police and ambulance departments and County HAZMAT team. The Local Emergency Planning Committee is responsible for updating the plan annually.
G. There are no actions planned to improve safety regarding the chlorine system at this time.