Thief River Falls Water Treatment Plant - Executive Summary

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   The Thief River Falls Water Treatment Plant Risk 
Management Plan was developed to protect both the  
residents of the community and Water Department personnel  
through policy and procedures governing the operation of  
the facility.  This plan is a cooperative effort of plant  
staff, administration, and City Government.  It is based  
on the requirements of OSHA Process Safety Management,  
USEPA Risk Management, and Minnesota's Workplace Accident  
and Incident Reduction (AWAIR) law requirement. 
   The commitment of the City of Thief River Falls City  
Council is demonstrated by the Thief River Falls Employee  
Safety Committee.  This is an independent committee  
reporting directly to the City Council.  It includes  
supervisory, department head, union personal and two City  
Council members who take an active role in addressing  
safety issues and concerns for all City employees. 
   The Thief River Falls Water Treat 
ment Plant uses  
gaseous chlorine and anhydrous ammonia for disinfection of  
the drinking water supplied to the community.  The  
anhydrous ammonia inventory is maintained below the  
minimum quantities as required by OSHA PSM and EPA RMP  
requirements.  Maximum quantity is 560 pounds. 
   The WTP Chlorine inventory control procedure calls for  
the chlorine inventory to be maintained between 500 and  
3000 pounds, using cylinders of one ton capacity.  When  
the on-line chlorine cylinder is reduced to approximately  
1000 pounds, another cylinder is ordered.  The replacement  
cylinder is delivered before the on-line cylinder reaches  
500 pounds.  This procedure limits the amount of chlorine  
on site to a maximum of one full cylinder and one partial  
cylinder.  The purpose of this policy is to maintain an  
adequate inventory of chlorine for disinfection while  
limiting WTP operator and public exposure to a accidental  
chlorine release. 
   Worst-case and alternative relea 
se scenarios have been  
determined after careful review of the regulation and  
consideration of the storage vessel configuration.  No  
active mitigation measures or devices, such as scrubbers,  
could be considered for analysis of worst-case releases. 
   For this worst-case scenario, the regulation specifies  
the release conditions and meteorological conditions at  
the time of the release.  When these conditions were  
modeled, using the USEPA Off Site Consequence Analysis,  
the results were as follows: 
   Worst-case release scenario: 
   *  Quantity released = 2000 pounds 
   *  Release duration = 10 minutes 
   *  Release rate = 200 pounds per minute 
   *  Distance to endpoint = 2.2 miles 
   For the alternative release scenario, the following 
   results were obtained: 
   *  Quantity release = 317 pounds 
   *  Release duration = 60 minutes 
   *  Release rate = 10.6 pounds per minute 
   *  Distance to end point = leaking gas contained in 
                              the sto 
rage room.  No off 
                              site consequence. 
   The Thief River Falls PSM/RMP and AWAIR prevention  
programs include the following sections: 
   *  Employee participation 
   *  Process safety information 
   *  Operating procedures 
   *  Personnel training 
   *  Contractor safety 
   *  Prestartup safety review 
   *  Preventative maintenance/mechanical integrity 
   *  Hot work permits 
   *  Management of change 
   *  Incident investigation 
   *  Compliance audits 
   The first line of defense against an accidental  
chlorine release is the WTP Preventative Maintenance  
Program.  This is a mechanical integrity program requiring  
annual inspection of all hazardous chemical equipment.   
Certain equipment components require monthly inspections.   
The schedule is based on and adjusted according to actual  
inspection and test results.  Components such as gas  
pressure regulators, feeder master control units 
, and auto  
switch-over valves are tested and calibrated on a test  
bench that simulates the actual operation of the systems.   
New replacement components are tested in this manner  
before installation or placement in inventory.  The spare  
parts inventory in maintained with all components  
necessary to repair any equipment failure.  In addition,  
the chemical feed process equipment has redundancy to  
provide back-up equipment operation while problem  
equipment is in repair or inspection. 
   There have been no reportable release incidents in the  
history of the Thief River Falls Water Treatment Plant. 
   Response to a leak is by plant personnel trained in  
mitigation of chlorine leaks, using self contained  
breathing apparatus, personal protection equipment, and a  
chlorine Emergency Kit "B" system. 
   Evacuation of surrounding population, and back up  
safety personnel for the plant operators, is provided by  
the Thief River Falls Fire Depa 
rtment and local Law  
Enforcement Center officers. 
   A leak in the chlorine system, as signaled by either  
of two chlorine detectors, triggers the start up of the  
chlorine scrubber system and triggers the WTP alarm  
system.  This provides notification to the plant operator  
to implement the Water Treatment Plant Emergency Response  
Plan . 
   The chlorine storage room is designed to contain a  
chlorine leak in the room while the scrubber neutralizes  
the gas or liquid release.  The scrubber is designed to  
neutralize 2000 pounds of chlorine as either a liquid,  
gas, or both. 
   Employee input on improved safety and operations is  
encouraged and requested as a matter of City Policy. 
   Training of WTP staff is conducted in-house, and at  
seminars and workshops sponsored by the Minnesota Section  
of the American Water Works Association, Minnesota Rural  
Water Association, and the Minnesota Department of Health. 
These seminars also provide a netwo 
rking vehicle for the  
sharing of information and innovations on the operations  
and safety procedures in the water works industry. 
Frequent training seminars are used as a tool to keep all  
safety issues on the minds of WTP staff. 
   The full plan is available for review at the office of  
the Thief River Falls Water Superintendent.
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