City of Poughkeepsie Water Pollution Control Plant - Executive Summary

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Chlorine is used as a disinfectant in the City of Poughkeepsie Water Pollution Control Plant. The finished water is disinfected by chlorine before discharge into the Hudson River. On average, the plant treats approximately 7 million gallons per day of raw water. Water inputs to the plant are from two mains that join inside the facility. One main is the combined City of Poughkeepsie sewage line and the other main is from nearby Marist College. In addition to these two sources of wastewater, the plant receives an average of 30,000 GPD of septic tank waste by truck. 
Chlorine is delivered by truck to the plant in one-ton containers. A maximum of 15 one-ton containers of liquid chlorine is stored on site. The chlorination is performed in a concrete block building that has two separate rooms, one for storage containers and one for the chlorination equipment. Both rooms are equipped with chlorine detectors and evacuation fans. Security is maintained by only iss 
uing keys to the locked doors only to trained employees of the staff. 
The City of Poughkeepsie Water Pollution Control Plant receives chlorine at the facility in one-ton containers. A maximum of 15 containers of liquid chlorine can be stored on site in the chlorine storage room. 
The City of Poughkeepsie Risk Management Program (RMP) includes the following key elements to mitigate the effects of potential chlorine release hazards: 
7 Operator training 
7 Preventive maintenance program 
7 Process-specific safety equipment (e.g., "B" kits and a SCBA) 
7 Safe and effective standard operating procedures, written and with operator participation 
7 Hazard review of equipment and procedures 
7 Auditing and inspection programs 
7 Comprehensive management program 
Further, the plant has an active environmental, health and safety program with the following elements specifically supporting the safe handling of c 
hlorine and the chlorination process: 
7 Respiratory protection (SCBA) program 
7 Chlorine detectors 
7 Chemical right to know program 
7 Personal protective equipment program 
The raw water can be pretreated with a number of chemicals including but not limited to chlorine. After removal of grit and settling in the primary clarifiers, the water is aerated before being settled in the secondary clarifiers. The treated water is then disinfected with chlorine prior to discharge. Chlorine is the only substance handled at the facility that is regulated by 40 CFR Part 68 Accidental Release Prevention Requirements: Risk Management Program under Clean Air Act Section 112(r)(7). 
The worst-case release scenario as postulated in the regulation (40 CFR 68.25) is the release of the greatest quantity of chlorine in a single vessel. The contents of the vessel are assumed to have been released as a gas ove 
r a 10-minute period.  The largest single vessel at the treatment plant is a one-ton container. Therefore, 2,000 pounds of liquid chlorine will be released as a gas over a 10-minute period in the worst-case scenario.  A release of this magnitude would only be possible if the shell of the container failed and the liquid chlorine formed a pool and vaporized over a 10-minute period. The likelihood of this type of catastrophic release is very minimal. According to EPA's model RMP*Comp, using the urban site option, the distance to the endpoint is 1.3 miles. According to 1990 census data, there is an estimated population of 9,400 within a 1.3-mile radius of the facility, including the estimated full seating capacity of 3,500 in the main gymnasium at the Marist College. There are seven schools and one hospital within 1.3 miles of the facility. 
The meteorological conditions associated with the worst-case release scenario, as prescribed in the regulation, is a wind speed of 1.5 meters per seco 
nd (3.4 miles per hour) and very stable (Class F) atmospheric conditions. These stable atmospheric conditions limit the mixing of the chlorine gas with the ambient air as the gas travels downwind from the point of release.  The cloud formed by the chlorine release would grow in size and decrease in concentration as it travels downwind. 
The alternate release scenario is one that is more likely to occur than the worst case release scenario.  For this scenario, it was assumed that a 3/8-inch OD, type K copper tubing pigtail is sheared off and mitigation occurs for one hour. The pigtail connects the 1-ton container to the manifold.  This assumption is based on the alternate release scenarios listed in Edition 3 of The Chlorine Institute Pamphlet No. 74 - Estimating the Area Affected by a Chlorine Release, Section 4.5.6, April 1998. The calculated chlorine release rate is 21.0 pounds/minute over a one-hour period. For this scenario, the meteorological  
conditions prescribed in the regulation are neutral atmospheric stability conditions (Class D) and wind speeds of 3 meters per second (6.7 miles per hour). According to EPA's dispersion model, RMP*Comp, using the urban site option, the distance to the endpoint is 0.1 miles. The population within this endpoint distance is 3,600, including the estimated maximum seating capacity of 3,500 in  the main gymnasium of Marist College. There are no hospitals or schools within the 0.1 mile endpoint distance computed for the alternate case.   
The City of Poughkeepsie Water Pollution Control Plant complies with EPA's accident prevention rule and all applicable state and local codes and regulations. The chlorine system is designed, installed, and maintained in accordance with applicable codes and state law. 
The treatment plant maintains one set of Self-Contained Breathing Apparatus (SCBA) and one Chlorine Inst 
itute Emergency Kit "B" for one-ton containers.  The plant personnel are in the process of updating the SCBA equipment and fit testing to meet the latest OSHA standards. The "B" kit equipment is stored in a room that is adjacent to the chlorine storage room. Plant personnel receive training on the use of the breathing apparatus and the emergency kit.  The kit contains the necessary tools and other equipment to contain valve leaks and repair small holes in a ton container. It also contains capping devices for the fusible plugs in the ton containers.  Ton containers of chlorine are equipped with six fusible metal pressure relief devices, three in each end.  The fusible metal is designed to melt between 158 degrees F and 165 degrees F to relieve pressure and prevent rupture of the container in case of fire or other exposure to high temperature.   
Chlorine gas is heavier than air and will settle to the lowest elevation when released.  The chlorine storage room and the chlorination room ar 
e each equipped with two roof-mounted exhaust fans that draw air from near the floor on an outside wall. The fans can be activated by a switch located outside the building and also by the light switch inside the building. The fans also operate whenever the door of either of the rooms is open or when the chlorine detector alarm is activated. 
Over the past five years, the City of Poughkeepsie Water Pollution Control Plant has not had an accident involving chlorine that required hospitalization or care by a physician, or that caused deaths, injuries, property or environmental damage, evacuations, or sheltering-in-place. 
The City of Poughkeepsie Water Pollution Control Plant has a site-specific Emergency Response Plan (ERP) that outlines employee procedures in the event of an emergency.  Since the facility does not attempt to perform disaster response actions on its own, the primary response organizations are the Town of Pough 
keepsie Water Treatment Plant and the Fairview Fire Department. The fire department makes an annual visit to the facility to evaluate any changes and to familiarize new fire department personnel with the facility. The fire department has full access to the locked chlorination facility by using a passkey that is kept in a locked box near the main gate of the facility. The fire department has access to the locked box. A plant layout has also been given to the fire department. 
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