City of Defiance Water Treatment Plant - Executive Summary

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Executive Summary 
 
Facility Information and Regulated Substances 
 
The City of Defiance Water Treatment Facility (EPA ID # 2000111) supplies potable water to the City's residences, businesses and industries.  According to the 1990 census, the population of the City of Defiance was reported as 15,000 persons.  The primary activity of the plant is treatment of surface water from the Maumee River for drinking water purposes.  The use of chlorine gas, CAS # 7782-50-5, is a major component of this treatment process.  The chlorine used in the treatment process is containerized in steel cylinders in 2,000 pound quantities.  Up to ten of these containers can be housed at the facility at one time, however, no more than four vessels can be on-line at any one time during the treatment process. 
 
Accident Release Prevention and Emergency Response Policies 
 
This facility has made a commitment to safety and implementation of safe procedures by stressing on-the-job training and encouraging continued aw 
areness of employee safety procedures.  The facility has not had any reportable safety incidents in the last five years and a review of their safety policies and procedures was conducted in May of 1997.  The facility has not made any revisions to these procedures since the last review.   
 
Worst Case Release Scenario 
 
A worst case scenario was conducted for a release of chlorine gas from the aforementioned facility using RMP*Comp software obtained from the U.S. EPA.  The scenario assumed a release of all 8,000 pounds of chlorine gas from the on-line vessels used in the water treatment process.  Enclosure of the tanks in the treatment building was considered as active mitigation for the modeled, worst case scenario.   
 
Assuming a release duration of ten minutes, a wind speed of 1.5 meters per second and an atmospheric stability class F in an urban setting, the distance to toxic endpoint was calculated to be 1.9 miles.  A release of this magnitude would have a significant off-site impact, 
encompassing a large portion of the City (approximately 12,000 residents) (assuming a wind direction in an east/northeast direction).  Schools, hospitals, major commercial/ industrial areas and recreational areas would be affected by such a release.  Written operating procedures describing proper handling, storage and on-line placement of the vessels and the in-place leak detection systems would reduce the likelyhood of a release of this magnitude. 
 
Alternative Release Scenario 
 
An alternative release scenario was conducted for a release of chlorine gas from the aforementioned facility using RMP*Comp software obtained from the U.S. EPA.  This scenario assumed a release of all 8,000 pounds of chlorine at a release rate of 133 pounds per minute for duration 60 minutes in an urban setting.  The wind speed of 3.0 meters per second, and an atmospheric stability class of D were automatically selected by the model.  Enclosure of the tanks inside the treatment building was considered as activ 
e mitigation for the alternative release scenario.  
 
The model calculated a distance to toxic endpoint of 0.20 miles.  The off-site impact of a such a release would not be of major significance with only a few residences and businesses/industries being affected.  The population impacted by a release of this magnitude would be less than 1,000 people.  Written operating procedures and the in-place leak detection systems would reduce the likelyhood of a release of this duration. 
 
 
Five Year Accident History 
 
The City of Defiance Water Treatment Facility has not had any accidental releases of chlorine gas in the past five years. 
 
Emergency Response Program 
 
The City of Defiance has implemented an Emergency Response Program (ERP) which integrates both local and county wide police, fire, hazardous material and emergency response services.  This plan includes specific actions to be taken in response to an accidental release of chlorine gas from the water treatment facility.  This plan also sp 
ells out actions to be taken to inform the public and emergency health care services. 
 
Plannned Changes to Improve Safety 
 
The City of Defiance Water Treatment Plant is currently undergoing a safety review in conjunction with the filing of this Risk Management Pan.  The City has retained URS Greiner Woodward Clyde to provide training for accident prevention, hazard communication and emergency response.  The training will be complete and any new procedures in place by August of 1999.
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