City of Mansfield Water Treatment Plant - Executive Summary

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The following is an Executive Summary of the City of Mansfield, Texas Water Treatment Plant's (MWTP) 40 CFR 68 Risk Management Program. 
7 Accidental Release Prevention and Emergency Response Policies 
The MWTP Accidental Release Prevention Policy requires training on chlorine safety, implementation of improvements identified in periodic process hazard analyses, operator training as required for treatment plant operators by the Texas Natural Resource Conservation Commission (TNRCC), specific training on written operating procedures developed for the plant chlorination system, training in written maintenance procedures, investigation of chlorine leaks or situations that could cause the release of chlorine, and periodic audits of the WTP's Risk Management Program (RMP). 
The MWTP's Emergency Response Policy considers the fact that ton chlorine containers are contained in a chlorine storage building equipped with a chlorine scrubber.  The MWTP has established four levels of events involvi 
ng the potential for a chlorine leak or an actual chlorine  leak.   
Level I.    Chlorine containers are being delivered by the vendor or are being installed by plant personnel.  Response to small leaks occurring upon connection of container or at other times involves shutting valves and isolating sections of lines and equipment for needed repair.  Notification of the Fire Department's Emergency Response Commander is voluntary. 
Level II.    Maintenance or replacement is being performed for a faulty online device such as a tank valve.  Chlorine is not being released.  However, the device cannot be easily isolated or the chlorine evacuated.  Though this operation is routine, the procedure by Plant Personnel will not begin until Fire Department personnel are adjacent to the Plant site in a standby role. 
Level III.    Chlorine gas is being released but the situation is under control.  Liquid chlorine is not being released.  The chlorine scrubber is operating properly, the release is currently conta 
ined in the chlorine building, and the release rate is not excessive.  Level III represents an emergency that requires a "911" call to the Fire Department.  Under no circumstances will entry be made into the chlorine storage area or repairs begun therein before Fire Department personnel arrive on the scene.  Stopping a leak using a chlorine container repair kit will not be attempted for a Level III situation. 
Level IV.    Chlorine gas is being released and the situation may be out of control.  The release rate is large or could likely become so.  The release may include liquid chlorine.  The chlorine scrubber may not be operating.  The release has or likely will escape the storage building and threaten the surrounding area.  Human life and health at and near the plant site could be endangered. Under no circumstances will entry be made into the chlorine storage area or repairs begun therein before Fire Department personnel arrive on the scene.  If it becomes necessary to use a chlorine co 
ntainer "B" repair kit, repairs will be made by a trained HazMat team from either the City of Arlington or the City of Fort Worth.  The City of Mansfield Fire Department has mutual aid agreements with both the Arlington and Forth Fire Departments and the Arlington Fire Department has HazMat teams in close proximity to the City of Mansfield. 
As indicated above, MWTP personnel will not attempt to stop a major chlorine leak.  However, procedures have been established for notifying the Fire Department and for protecting, rescuing, and accounting for plant personnel.   Procedures have also been established for notifying nearby schools and other public places and residences potentially affected by a chlorine leak.  Depending on the severity of the leak and prevailing wind conditions, people will be advised to either move immediately upwind of the leak or to remain indoors with windows closed and air conditioners and ventilation systems turned off. 
Facility Description/Regulated Substances  
The MWTP is a 9.5 MGD water treatment facility. Both chlorine and aqueous ammonia are handled at the WTP.  However, only chlorine is stored in quantitites subject to the requirements of 40 CFR 68. 
7 Worst-case and Alternative Release Scenarios 
The worst-case release scenario assumes a 1,100 pound release over ten minutes with a wind speed of 1.5 meters/second, an "F" stability class, and urban topography.  A passive mitigation factor of 0.55 has been assumed as the chlorine containers are stored in a building.  Using the Breeze Haz model and the above assumptions results in a worst-case distance to toxic endpoint of 1.54 miles.  The chlorine scrubber was assumed to not operate during the worst-case release. 
The alternative release scenario assumed a valve or pipe failure resulting in a one inch diameter opening.   Using the above-mentioned model, a wind speed of 3.0 meters/second, a "D" stability class, urban topography, and a 0.55 mitigation factor resulted in a 0.72 mile  
distance to the toxic endpoint for chlorine.  Credit was not taken for the chlorine scrubber in the alternative release scenario because the scrubber, if operating as designed, would prevent any measurable offsite impact. 
7 General Accidental Release Prevention Program 
This was summarized above under Accidental Release Prevention and Emergency Response Policies. 
7 Five-year Accident History 
There have been no accidents subject to reporting under 40 CFR 68.42. 
7 Emergency Response Program 
This was summarized above under Accidental Release Prevention and Emergency Response Policies. 
7 Planned Changes to Improve Safety 
As a result of the initial process hazard review conducted as part of this RMP, a number of steps have already been taken such as the installation of a wind sock, periodic testing of leak detectors, and the wearing of breathing protection during container connection or disconnection. Additional changes which are planned or underway to improve safety include: 
1. Im 
prove formalized training and documentation of such training; 
2. Increase frequency of  joint emergency response training with Fire Department; 
3. Audit and improve procedures for notifying emergency responders;  
4. Inventory and inspect all personal protective equipment and emergency repair kits; 
5. Train all operators on the correct response to alarms and conditions that exceed the operating limits of the system; 
6. Train all operators on the medical aspects and first aid associated with exposure to chlorine; 
7. Require operators to read and follow written operating procedures for chlorination system; 
8.  Require operators to wear approved escape-type respirators or SCBA gear when connecting or disconnecting chlorine containers; 
9.  Improve documentation for preventive maintenance, inspections, and testing; 
10. Post danger signs in chlorine storage and feed areas; and 
11. Periodically check to insure that all components of the chlorine delivery system are adequately labeled.
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