City of Newport Station #1 - Executive Summary
The City of Newport Utilities Department accidental release prevention policy involves a unified approach that combines technologies, procedures and management practices. All applicable prevention procedures of the U.S. Environmental Protection Agency's (EPA) Risk Management Program will be adhered to. The City of Newport Utilities Department's emergency response policy involves the preparation of evacuation and notification procedures and coordination of emergency response procedures with the Local Emergency Response Committee (LEPC) and the local fire department. |
The Station #1 Water Treatment Plant, installed in 1992, serves the Newport, Rhode Island community by disinfecting drinking water. The water treatment plant is located at 100 Bliss Mine Road. The water treatment plant contains a chlorine storage room; which contains liquid chlorine ton cylinders, a chlorinator room; which mixes the chlorine with water and regulates the flow of chlorine to various stages of the treatmen
t process, an instrument room; which contains flow recorders and other electronic panels, and various safety equipment. Within the storage room, one one-ton cylinder is on-line, one one-ton cylinder is in reserve and three one-ton cylinders are in storage. The facility operates on three shifts with a minimum of two operators per shift. The chlorine storage area and the chlorinator room are monitored with chlorine detectors.
At the Station #1 Water Treatment Plant, gaseous chlorine is taken from the one-ton cylinders under pressure to vacuum regulators. The gaseous chlorine is under pressure for a short distance within the chlorine storage room. From the vacuum regulators, located within the chlorine storage room, the gaseous chlorine travels under vacuum to the chlorinators and then onto the treatment of the water. As the chlorine is under vacuum, any failure or leak of the piping system within the chlorinator room will break the vacuum and will stop flow of chlorine gas.
water treatment plant's offsite consequence analysis includes consideration of two release scenarios involving chlorine. These scenarios are identified as "worst-case" and "alternative". EPA states that for the worst-case scenario "the owner or operator shall assume that the maximum quantity in the largest vessel is released as a gas over 10 minutes". The worst-case scenario is to result from an unspecified failure. EPA defines the alternative scenario as one that is "more likely to occur that the worst-case scenario".
The purpose of the release scenarios is to determine the distance to "toxic endpoint", which is defined by the American Industrial Hygiene Association as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action". Additionally, the resi
dential population within a circle, which is made using the distance to toxic endpoint as its radius, has to be defined as an estimate of the population potentially affected. For the purpose of determining worst-case and alternative release scenarios distance to toxic endpoint, the water treatment plant utilized EPA's RMP*Comp software.
The worst-case release scenario at the Station #1 Water Treatment Plant involves a failure of a one-ton cylinder. The distance to toxic endpoint was determined to be 1.3 miles and an estimate of the residential population potentially affected of 14,460 was obtained.
The water treatment plant used, as an alternative release scenario, a leak during hook up of a ton cylinder. The leak came from the 3/8" whip which carries the gaseous chlorine from the ton cylinder to a one inch gas rated steel pipe. As described in EPA's CEPPO's Risk Management Program Guidance for Wastewater Treatment Plants, a choked gas release was assumed as the treatment p
lant pulls gaseous chlorine from the cylinder. The distance to toxic endpoint for the alternative scenario was determined to be 0.1 miles and an estimate of the residential population potentially affected of 180 was obtained.
The general City of Newport Utilities Department's accidental release prevention program is based on training of the operators, implementation of preventive maintenance, auditing and inspection programs; continual review and upgrade of process and safety equipment; use of accurate and effective operating procedures (developed with the participation of the operators); and execution of periodic hazard reviews of equipment and procedures.
No accidental releases of chlorine have occurred at the Station #1 Water Treatment Plant in the past five years.
The water treatment plant has coordinated its emergency response procedures with City of Newport Fire Department and the District 7 Local Emergency Response Committee (LEPC). Procedures have been developed for the
effective and timely notification of response personnel and the community and for the safe evacuation of employees.
A hazard review conducted on June 3, 1999 identified a number of recommended actions which when implemented will improve the safe handling and storage of chlorine at the Station #1 Water Treatment Plant. The water treatment plant will evaluate the recommendation and implement all feasible recommendations in a timely manner.