Lawton Valley Water Treatment Plant - Executive Summary

| Accident History | Chemicals | Emergency Response | Registration | Source | 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 Lawton Valley Water Treatment Plant, installed in 1945, serves the Portsmouth, Rhode Island community by disinfecting drinking water.  The water treatment plant is located at the corner of West Main Road and route 114.  The water treatment plant contains a storage barn, which contains liquid chlorine ton cylinders; a chlorinator, which mixes the chlorine with water and regulates the flow of chlorine to various stages  
of the treatment process; an instrument room, which contains flow recorders and other electronic panels, and various safety equipment.  Within the storage barn, one one-ton cylinder is on-line, one one-ton cylinder is in reserve and five 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. 
 
The 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 residential 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 Lawton Valley 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 resi 
dential population potentially affected of 5480  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 plant 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 25 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 (devel 
oped 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 Lawton Valley Water Treatment Plant in the past five years. 
 
The water treatment plant has coordinated its emergency response procedures with City of Portsmouth 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 Lawton Valley Water Treatment Plant.  The water treatment plant will evaluate the recommendations and implement all feasible  recommendations in a timely manner.
Click to return to beginning