Wet Weather Flow Treatment Facility - Executive Summary

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Accidental Release Prevention and Emergency Response Policies 
The Wet Weather Flow Treatment Facility (WWFTF) has a very good history with maintenance and chemical safety.  The facility is included in the DuPage County Office of Emergency Management Emergency Response Plan.  Safety items are checked on a monthly basis.  Inspections are documented to record problems or maintenance items that may need repair.  Alarms for chemical leaks are monitored in the facility, currently at the police station and within the next few months through the supervisory control and data acquisition (SCADA) system.  These alarms are monitored 24 hours a day 7 days a week.  The Village of Villa Park also has a Risk Manager that oversees all safety issues and concerns for the Facility.  Loss prevention evaluations are performed by outside agencies on a regular basis.  Records of all inspections are available for review and good housekeeping practices are in use.  The following safety rules are kept at the fac 
ility chlorine, compressed gas/cylinder use and compresses gas - regulators.  All employees have been given these safety rules and in the event of an emergency are required to contact DuPage County Public Safety Communications, DuCOMM.  The safety rules are detailed on how to handle the equipment, safety inspection checks to follow and labels to look for when receiving any delivery of these items. 
 
Facility and Regulated Substances 
The WWFTF is a secondary wastewater treatment plant.  Its primary purpose is to treat the sanitary and storm water overflow during periods of heavy rainfall.  The Village of Villa Park essentially operates three sewer systems: sanitary, storm and a combined system.  The WWFTF operates as a stand-by wastewater treatment plant.  During periods of wet weather, combined and stormwater enter the WWFTF through separate sewers and pass through mechanical bar screens held in wet wells until the water level reaches a preset elevation.  Pumps will then discharge the r 
aw water in the wet wells into a first flush tank to remove large particles from the water.  The water then enters settling tanks to remove settleable organic solids.  The solids settle to the bottom and any floating materials such as oil or grease is skimmed from the surface.  The effluent is then discharged over weirs into a collection system.  The effluent is then treated with a liquid chlorine solution.  The most chlorine stored on-site at any one given time is two 1-ton cylinders.  The chlorine is injected using a chlorine evaporator.  The 1-ton cylinders are connected directly to the evaporator and chlorine gas is withdrawn from a single container.  After the chlorine gas is mixed with water to form a chlorine solution, the effluent is discharged to the chlorine contact chamber before being discharged into the storm sewer system.  In the contact chamber the effluent is held for a preset time in order for the chlorine solution to reduce the number of organisms to acceptable levels 
.  There is an air ventilation system, pressure relief system and alarms to detect leaks or any problems that may arise. 
 
Worst-Case Release Scenario 
The worst-case release scenario was conducted using the OCA Guidance and RMP*Comp V1.06.  The analysis considered one 1-ton cylinder rupturing during delivery.  The vessel would release 200 lbs per minute of chlorine gas outside for 10 minutes.  There were no mitigation measures considered.  The release scenario takes place in urban surroundings with a wind speed of 3.4 miles/hour (1.5 meters/second), a stability class of F and the air temperature at 770 F (25 C).  The likelihood of this scenario occurring is very small.  The cylinders are equipped with check valves to minimize the probability of the vessels failing. 
 
Alternative Release Scenario 
The alternative release scenario also used OCA Guidance and RMP*Comp V1.06 to model the situation.  The release scenario considered a ruptured vessel releasing 200 lbs/minute for a 10 minute dura 
tion.  The mitigation measure considered was the release of the toxic gas occurring in an enclosed space, i.e., a building.  A wind speed of 6.7 miles/hour (3 meters/second), stability class of D and an air temperature of 770 F (25 C) were used to model this scenario.  This scenario was used because a vessel rupturing inside the chlorine room due to a faulty valve or tank is a probable situation.  Although safety precautions are followed during the connection of the cylinder to the chlorination system, a malfunction of the vessel is possible. 
 
General Accidental Release Prevention Program and Chemical-Specific Prevention 
The WWFTF is subject to OSHA Regulation at 29 CFR 1910.38.  The facility has a written procedure to follow in case of an emergency.  The WWFTF also follows the National Pollution Discharge Elimination System (NPDES).  The facility operates under permit number IL0033618.  The effluent discharged by the Wet Weather Flow plant is monitored by the Illinois EPA and must adh 
ere to the guidelines as stated in the NPDES permit.  Any violations of the permit must be reported to IEPA. 
 
A monthly inspection on all safety equipment is performed and records of the inspection are filed.  Regular scheduled loss prevention evaluations are performed.  Any items recommended for maintenance or improvement are usually corrected within a month.  The Village of Villa Park has a Risk Manager who also performs routine inspections for potential safety and risk perils.  The WWFTF has a backup power supply, leak detectors, alarms and an air ventilation system to help reduce the severity if an accidental release occurred.  The following safety rules are kept at the facility chlorine, compressed gas/cylinder use and compresses gas - regulators.  All employees have been given and trained to adhere to these safety rules and guidelines. 
 
Five-Year Accident History 
There have been no accidents at this facility. 
 
Emergency Response Program 
If an alarm sounds while at the facility, e 
mployees must exit the building immediately.  They are to contact DuPage Public Safety Communications (DuCOMM) at once to send the fire department.  After DuCOMM is contacted then they are to contact their supervisor.  Employees are never to enter an area without the appropriate safety equipment where another person has been injured or collapsed.  Back-up personnel must always know their location. 
 
All employees receive training in how to respond to accidental releases.  Employees are trained in how to use and inspect all safety equipment.  The immediate supervisor must investigate any accident or near miss, which occurs, and the Department Head within 48 working hours of the incident.  It is then the responsibility of the immediate supervisor to generate and distribute the report.  The report is given to the Fire Department, DuPage County Office of Emergency Management and Risk Manager.  The public is notified after an incident through the local newspaper and press releases. 
 
Planned  
Changes to Improve Safety 
Currently the Village of Villa Park is updating their current SCADA system.  This will include the Wet Weather Flow Treatment Facility.  Chlorine leak detection alarms will be programmed into the system.  In the event of an alarm, the SCADA system automatically pages the WWFTF operator.  The operator can then see which alarm has been detected to correct the situation quickly and efficiently.  The operator can also quickly notify the responsible party to rectify and control the problem.
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