City of Houston Southeast Water Purification Plant - Executive Summary

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Executive Summary 
United Water Services contract operates the Southeast Water Purification Plant for the City of Houston, Texas.  The facility is located at 3100 Genoa-Red Bluff Road in Houston Texas and borders the north side of Ellington Air Force Base.  The facility is designed to treat 80 million gallons of drinking water per day for the city and surrounding municipalities.  In order to disinfect the treated water, and thereby reduce the risk of waterborne disease, chlorine and ammonia are added during the treatment process to form chloramines.  While several alternative methods have been developed for the disinfection of drinking water, the combination of chlorine and ammonia is by far the most cost effective and widely utilized for this type facility.  Due to the quantity of chlorine and ammonia that must be stored at the facility, the Environmental Protection Agency's Risk Management Program regulations apply to these process chemicals.  This Document was reviewe 
d by the City of Houston with the assistance of their technical consultants, Camp, Dresser, and Mckee Engineering. 
Accidental Release Prevention 
United Water Services has committed itself to reducing the likelihood of an accidental chemical release from the Southeast Water Purification Plant.  The facility staff conducts an annual review of the all operating, safety, maintenance, and emergency response procedures.  Additionally annual refresher training for the facility staff, the fire department emergency response teams, and training for all new employees and all contractors is conducted.   
Operations personnel conduct regularly scheduled daily checks of the chlorine and ammonia storage and feed systems and any irregularity or possible hazard is rectified immediately.    
Chlorine leak detectors are installed in the storage, feed, and at all points of chemical application.  These leak detectors are tested to insure that they function as intended on a regular basis.  The leak detector 
s activate a visual and audible alarm that alerts the facility staff to any release. 
The Southeast Water Purification Plant complies with the OSHA Process Safety Management requirements,  and strives to maintain a safe working environment for its employees and the surrounding communities.   
Chemical Quantities and Storage 
The Southeast Water Purification Plant utilizes one ton chlorine containers for its facility operations.  The maximum inventory of chlorine is 60,000 pounds or 30 one ton containers.   Ammonia is delivered to the Southeast Water Purification Plant in an aqueous solution.  The maximum quantity of aqua ammonia solution on site is 66,900 pounds.  
Release Scenarios 
The EPA's risk Management Program requires that two accidental release scenarios be evaluated for each covered chemical, a worst case scenario and an alternate release scenario.  United Water Services evaluated these scenarios by using software developed by the EPA to study the possible offsite impact of a  
regulated chemical release.   
The worst case scenario for chlorine was conducted assuming a 2,000 pound leak over a ten minute period.  The toxic endpoint was 3.0 miles and could affect up to 61,000 persons.  The Aqua ammonia worst case scenario was conducted assuming a 33,400 pound spill over a ten minute duration.  The toxic endpoint was 1.10 miles and could affect up to 17,000 persons. 
The alternate case scenario for chlorine was conducted assuming a 2,000 pound release over a 31 minute period.  The toxic endpoint was 1.5 miles and could affect up to 21,000 persons.  The alternate case scenario for aqua ammonia assumed a 18,700 pound release over a 10 minute period.  The toxic endpoint was 0.4 miles and could affect up to 2,100 persons. 
Emergency Response 
The emergency response program in place at the Southeast Water Purification Plant includes training for the facility staff and the City of Houston Fire Department Emergency Response Team.  Standard operating procedures are in  
place to insure proper response in the event of any accidental release.  All members of the facility staff have been trained in the proper evacuation procedures, and are aware of their role in the event of an emergency.   The emergency response plan is reviewed on an annual basis and is revised if necessary. 
While the Southeast Water Purification Plant has utilized both chlorine and ammonia for over five years without a major release, the potential for an accidental release exists whenever these chemicals are utilized. 
The facility staff strives to remain well trained and equipped to deal with any possible emergency, and continues to look for ways to improve the safety of the facility.
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