WRP #4 - Executive Summary

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POLICY STATEMENT 
It is the policy of Coachella Valley Water District to conduct all district activities safely to prevent job related accidents, illnesses and injuries to employees and others and damage to district and others' property.  A well organized safety program provides a safe working environment and promotes increased efficiency at all levels.  (IIPP) 
 
ACCIDENT HISTORY 
None to report 
 
WORST-CASE LEAK SCENARIO 
This facility used EPA's "Risk Management Program Guidance For Wastewater Treatment Plants (40 CFR Part 68)" for performing offsite consequence analysis (OCA) for the worst-case leak scenario. 
 
The worst-case leak scenario is described in the compliance guide as the largest container losing all of it's contents in 10 minutes, this equates to a 200 lb/min leak of sulfur dioxide.  This facility is in a rural area and using the tables given in the complinace guide, a leak of this magnitude would effect a radius from the plant to 3.1 miles. 
 
It is unlikely that a leak of this 
magnitude would occur because the process system is inspected daily and the chlorine and sulfur dioxide containers are located in brick buildings that are monitored 24 hours a day for process leaks and all buildings have intruder alarms to guard against vandalism.  All plant operators and the Chlorine Response Team are trained to respond to and stop process leaks. 
 
ALTERNATIVE LEAK SCENARIO 
This facility uses the same compliance guide as mentioned above for performing the OCA for the alternative leak scenario.  A process hazard analysis PHA was performed on the chlorine and the sulfur dioxide systems at WRP #4 and it was determined that a more likely (yet not likely) leak scenario than the worst-case scenario, would be from the rupture or separation of the flexible connections from the 1-ton containers to the manifold system.  This could occur through an earthquake, vandalism or material defects, but the mitigating factors that make these situations unlikely will be explained in anoth 
er paragraph. 
 
Using the EPAs guide a leak as described above would come from a 5/16 inch opening (size of opening in valve body) producing a release rate of 15 lbs/min effecting a radius of 0.2 miles from the plant for each the chlorine and sulfur dioxide systems. 
 
It is unlikely that a leak described above would occur because of the following:  the process system is inspected daily; the chlorine and sulfur dioxide containers are monitored 24 hours a day for process leaks, and the alarms are well maintained and tested twice a month; all buildings have intruder alarms to guard against vandalism;  the flexible connections are replaced annually as per manufacturers recommendations; all 1-ton containers are bound with two chain binders each to prevent movement in case of an earthquake and finally all plant operators and a Chlorine Response Team are trained to respond to and stop process leaks. 
 
RESPONSE TEAMS 
Chlorine response and any work with chlorine and sulfur dioxide connections requ 
ire three employees.  All plant operators are trained in emergency response.  The crew of employees trained jin response to chlorien leaks at domestic will sites have been trained to respond to chllorine/sulfur dioxide gas leaks at the WRPs as well.  This two person crew will respond jto plants after hours with the standby olperator to unmanned plants or to plants that need assistance.  There will always be three employees on call with pagers ready to respond to chlorine leaks.  The employees on call for chlorine response are rotated weekly. 
 
TRAINING 
Chlorine response personnel are scheduled quarterly to be trained in use of emergency repair kits, personal protective equipment and emergency response procedures; scheduled annually to be trained in the hazards and handling of chlorine & CPR/First Aid.  The district has purchased a 1-ton container and a 150 lb cylinder to practice emergency repairs. 
 
ALARMS 
WRP #4 is equipped with leak detectors that will detect chlorine/sulfur dioxide g 
as in concentrations at or above 1 ppm.  When one of these detectors senses a gas leak of 1.0 ppm or above a visual and audible alarm on the annunciator panel will activate and a alarm will be transmitted to Control at district headquarters. 
 
At 3.0 ppm the beacon lights on top of the effected building will come on and the ventilation fan in the room will start up to evacuate the room of excess gas.  These alarms can only be reset and cleared after the leak detectors sense less than 1 ppm of gas.  These alarms are tested by the operators twice a month.  In addition the communications shop inspects, tests and calibrates the chlorine alarm system on a monthly schedule.  
 
CALL OUTS 
When a gas leak alarm occurs during the hours the plant is staffed, the plant operators will respond to the leak with three operators.  The Chlorine Response Team can be dispatched to the plant during the staffed hours if the plant staff is unable to respond to the leak with a three person team. 
 
When Control r 
eceives a gas leak alarm after hours the control operator will call out the Chlorine Response Team and the sanitation standby operator.  Upon arrival both will wait at the entrance gate for the other to arrive and will enter the plant together. 
 
RESPONSE TO MINOR LEAKS 
Two employees will respond with SCBA's, chlorine repair kit "B", gloves and a bottle of 26 degree baume ammonia.  The Third Person will also respond with a SCBA and stay near the truck radio. 
 
The First Person and Second Person will don their SCBAs, keeping each other in sight at all times.  Using the ammonia they will locate the leak.  Once the leak is located and is confirmed to be a system leak and not a vessel leak, the gas supply valve on the container can be shut off by turning the valve clockwise one full turn.  When this has been done the Third Person will let control know whether repairs have been made or if further assistance is needed. 
 
RESPONSE TO MAJOR LEAKS 
Same as above except the response team will wear f 
ully encapsulated suits if a severe gas leak has occurred or if the response team finds a vessel leak.  The Third Person will notify control to send police and fire department personnel to the scene to secure and evacuate the surrounding area if necessary.  The district's standby staff person and Training/Safety Specialist will be called as well. 
 
PLANNED CHANGES TO FACILITY 
The chlorine and sulfur dioxide systems at this facility are under pressure, a system leak has the potential to allow several lbs of chemical to be released before emergency response personnel are able to take the appropriate steps necessary to bring the leak to a stop.  Plans are underway to change the pressure system to a vacuum system which would automatically stop drawing chemicals from the containers if the process system is adversely effected.
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