Landsburg Water Treatment Plant - Executive Summary

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 Seattle Public Utilities (SPU) provides retail municipal and industrial water supply to its direct service area within the coroporate boundaries of the City of Seattle, and on a wholesale basis to wholesale water purveyors throughout King County.  SPU operates three primary water treatment plants which are subject to the Risk Management Program Rule under Section 112(r) of the Clean Air Act.  These are the Lake Youngs, Landsburg, and Tolt Water Treatment Plants.  All three plants use chlorine gas for water disinfection in excess of the RMP threshold quantity of 2500 lbs. 
    The Landsburg  Water Treatment Plant is located on the Cedar River south of Issaquah, WA.  It is located within the Cedar River Watershed, which is closed and inaccessible to the public.  There is a county day-use park and recreational trail approximately 1/2 mile downriver of the plant.  The Landsburg Water Treatment Plant stores up to 20 tons of chlorine gas in one-ton cylinders.  Cylinders not connected to th 
e process line are stored in an outdoor storage bay.  The treatment process area is in an enclosed building, but there is no scrubber system present nor was the building designed for gas containment.  The treatment building is equipped with gas detetctors.  The plant is staffed 24 hours a day by one Water Treatment Operator.  During normal business hours there may be other SPU employees, contractors, and/or consultants engaged in work in the watershed or on the nearby diversion dam facilities.  They do not enter the plant or the chlorine process area without direct supervision.   
    SPU management is committed to protecting employees, the public, and the environment and to preventing injury or death that could result from chlorine gas releases.  To do this, SPU has a variety of safety and emergency response policies in place that guide employees in general workplace safety, storage and handling of chlorine gas, fire prevention and suppression, and emergency response actions.   
he worst-case release scenario, as specified by EPA, would involve the release of the entire contents of a one-ton cylinder in a 10 minute period.  Based on modeling with EPA's RMP*COMP model, this could impact an area within a radius of 1.3 miles of the plant.  The worst-case scenario is highly unlikely because of the fact that, in order for the entire contents of a ton cylinder to be released within 10 minutes the cylinder would have to be split open.  Given the extreme strength of the cylinder design and the extremely safe industry-wide record of this technology, only the most direct and severe trauma to the cylinder would be capable of creating such conditions.  The LANDVIEW software package estimated a population of approximately 3,900 within the area of concern for the worst-case release scenario.  SPU believes this figure to be a substantial overestimate.  However, for the purposes of complying with the regulation SPU is including this figure in the RMP for this site. 
    The a 
lternative-case release scenario involves the potential rupture of a 5/16" valve or transfer line during a cylinder maintenance or replacement operation.  This scenario estimates the impacts of the release of approximately 320 pounds of chlorine over a 60 minute period.  When modeled with RMP*COMP, this could impact an area within a 0.1 mile radius of the plant.  This area of concern would be entirely within SPU's watershed property.  However, given the proximity of the county park, a scenario such as this would still require close attention to the possibility of recreationists being nearby. 
   There have been no reportable releases within the last five years from this plant.  SPU has an excellent safety record in its handling of chlorine gas.  SPU has had a corporate chlorine safety program in place for many years.  In addition to its corporate chemical safety program, SPU maintains open relations and communications with local fire departments responsible for serving its water treatm 
ent plants, including meetings and site visits.  SPU complies with OSHA's Process Safety Management standard and, as a result of increased awareness brought about through compliance with the RMP rule, SPU is increasing the level of effort and resources dedicated to its PSM compliance program including the assignement of additional staff and provision of additional funding.  SPU conducts ongoing training of its Water Treatment Operators in all aspects of safe plant operation, including emergency response measures, and Operators perform daily safety inspections of chlorine equipment at every shift change.
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