Springbrook Water Reclamation Center - Executive Summary

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The City of Naperville's Springbrook Water Reclamation Center (SWRC) is an advanced wastewater treatment facility which has a mechanically aerated activated sludge process incorporating single-stage nitrification, tertiary filtration, chlorination/dechlorination, and biosolids processing.  Originally constructed in 1975 as a 10.0 million gallons per day (MGD) contact stabilization facility, SWRC underwent expansions in 1985, 1990, and 1995 bringing the plant to  the current design average flow of 22.5 MGD.  SWRC presently uses gaseous chlorine for process chlorination (disinfection) of treated wastewater effluent and sulfur dioxide for effluent dechlorination prior to discharge into the DuPage River. These chemicals are widely used for industrial applications, as well as pollution control purposes, and they are an integral part of everyone's daily lives. They are transported on roads, waterways, and railways. As part of our wastewater treatment process, chlorine disinfects our treated  
wastewater effluent prior to discharge into the DuPage River to protect individuals who use the river for recreational purposes. Chlorine also purifies our drinking water, disinfects our swimming pools, and can be truly life saving. In fact, the World Health Organization estimates that 25,000 children worldwide die every day from waterborne diseases resulting from the lack of a water disinfection agent such as chlorine. Although chlorine is very beneficial and fundamentally necessary in protecting public health, it must be removed from our effluent after a 30-minute disinfecting period. This is required by the Environmental Protection Agency (EPA) to prevent possible adverse effects of chlorine on  waterways and their ecosystems. All traces of chlorine in SWRCs effluent are removed by using sulfur dioxide gas in solution, injected prior to effluent discharge.  
 
Storing and using gaseous chlorine and sulfur dioxide does involve the potential hazard of accidental release into the surrou 
nding area.  We take our safety obligations in storing and using chemicals as seriously as we dedicate our goals towards the best possible wastewater treatment for environmental and public health protection. The storage quantities of these chemicals are above the regulatory threshold limits of 1500 lbs and 2500 lbs respectively as listed in Section 112 (r) of the Clean Air Act of 1990.  As a result, SWRC must comply with the 40 CFR Part 68 Risk Management Plan (RMP) requirements and submit an RMP to the Illinois Environmental Protection Agency by the June 21, 1999 deadline.  It should be noted that SWRC will need to comply with RMP requirements for only the current May 1, 1999 - October 31, 1999 chlorination/dechlorination period.  Construction will begin soon for the new liquid chlorination/dechlorination process to replace our existing gaseous systems during the current two-phase treatment plant expansion to 30 MGD. This new chlorination/dechlorination process will use liquid sodium  
hypochlorite and sodium bisulfite and is expected to be fully operational by May 1, 2000.  Once this system is fully operational, gaseous chlorine and sulfur dioxide will no longer be used and SWRC will not be required to maintain an RMP.  Following the startup of this new system, SWRC will submit a notification of de-registration to the IEPA. 
 
Modeled after OSHA PSM requirements for industries, the RMP regulations require that a hazard assessment be performed to determine the impacts of accidental release of  a facilitys hazardous compounds to the public.  Although these are extremely unlikely events, the RMP further ensures the prevention of accidental release due to additional requirements  such as hazard identification and assessment,  computer modeling of different accidental release scenarios, a five-year history of accidental release, a comprehensive management program for prevention of accidental release, and an emergency operations program in the event of an accidental releas 
e. 
 
SWRCs RMP identifies the two hazardous chemicals, chlorine and sulfur dioxide, as being above the Section 112 (r)  threshold quantities.  Currently, SWRC stores and utilizes a maximum of nine one-ton cylinders of gaseous chlorine (18,000 lbs) and six one-ton cylinders of gaseous sulfur dioxide (12,000 lbs).  These chemicals are stored in a non-venting building which provides passive mitigation (physical and structural chemical containment) in the event of an accidental release.  In addition, SWRC uses several process safety controls which are electronically and mechanically designed to prevent accidental release of these gases.  These include manually-controlled vents, relief valves, check valves, manual/automatic shutoff systems, interlocks, gas detectors and alarms.  
 
RMP requirements include worst case and alternative release scenarios to be determined using EPA-approved computer models.  The definition of a  worst case scenario is the accidental release of the entire c 
ontents of one cylinder  over a period of 10 minutes during calm weather conditions.  An alternative release scenario includes passive and active mitigation systems for chemical containment.  The computer model DEGADIS Breeze Version 3.1 determined a worst case scenario of the accidental release of the entire contents of one cylinder of sulfur dioxide.  The modeling indicated an impact of 1.91 mile radius and exposure for 4830 people.  It should be noted that a worst case scenario is an extremely unlikely event and does not take into account SWRCs  process safety features and equipment which are designed to prevent the accidental releases of  these chemicals outside the storage building and off-site to surrounding residential areas.  More realistic alternative release scenarios of both chemicals by DEGADIS computer modeling indicated  their toxic endpoints (0.22 mile radius for chlorine and 0.20 mile radius for sulfur dioxide) fall just a few feet outside SWRCs property line  
and would have no impact on public receptors. 
 
The RMP also requires a five-year history of the accidental release of these chemicals for all reporting facilities.  SWRC staff have always practiced a comprehensive program regarding chlorine and sulfur dioxide management, safety and training.  As a result, SWRC never had an accidental release of either one of these chemicals causing an impact on human health or the surrounding environment during the 24-year history of this wastewater treatment plant. 
 
Each of the facilities required to follow the RMP rule will fall under one of three RMP Programs.  Program One facilities have hazardous chemicals on-site but have no off-site public receptors and have the least amount of RMP requirements.  Program Three requirements are the most comprehensive and apply to those facilities which tend to be large industries, may have a five-year history of accidental release of hazardous chemicals, or are required to follow OSHA PSM requirements.  SWRC is a 
Program Two facility in which it must demonstrate compliance with seven elements that are the foundation of the accidental release prevention program.  These seven elements include safety information, hazard review, operating procedures, training, maintenance, compliance audits, and accident investigation.  As mentioned previously, SWRC complies with Program Two requirements. 
 
SWRC also has an Emergency Operations Program in the remote event of an  accidental release of chlorine  or sulfur dioxide gas.  This program includes the emergency procedure to notify the Naperville Fire Department Hazmat Team to respond to the emergency and  contain the gaseous leak and initiate repairs to the leakage area.  The Hazmat team is HAZWOPER trained and certified.  In addition, our Emergency Operations Program includes designation of key personnel and departments needed to coordinate, direct, and manage an accidental release emergency, an evacuation plan, a step-by-step emergency operations procedur 
e, a list of vendors and equipment available in the event of an emergency, layouts of the chemical storage building and plant site, and a follow-up post-emergency action program.  A chlorine leak drill at SWRC was conducted by SWRC personnel, the Naperville Police and Fire Departments, the Naperville Emergency Management Agency, and the Will County Office of Emergency Management during the fall of 1995.  The results of this drill indicated that the Emergency Operations Program was effective in allowing responders to quickly assess the extent of the emergency, evacuate the immediate area, stop leakage and make necessary repairs. 
 
SWRC staff recognizes the importance of public awareness and education regarding the on-site storage and use of hazardous gases and the possible risk to the surrounding community and will address these issues as needed. In addition, the local emergency planning committee and local emergency responders will continue to be routinely updated on chemical inventor 
ies, safety management and training, and emergency response procedures. It is our goal that the community understands the purpose of the RMP, the hazard assessment of SWRCs chlorine and sulfur dioxide and possible risk to the surrounding areas.  It must be emphasized to the public that the odds of an alternative release scenario occurring at SWRC is extremely unlikely;  a worst case  release scenario is even more remote.  In the unlikely event of an accidental release, SWRCs passive mitigation system, safety equipment and gas monitors in the chlorine/sulfur dioxide building would prevent a gas release outside the storage building itself and over SWRCs property line. SWRC staff would quickly respond to a gas leak by notification to emergency responders and activating the Emergency Operations Program. Finally, as part of the City of Napervilles goal in providing exemplary public safety and protection of our natural environment, construction of a new liquid chlorination/dechlorina 
tion system will begin this year during SWRCs current treatment plant expansion.  By May 1, 2000, this liquid chlorination/dechlorination system will be operational, and this will completely eliminate the risk of an accidental release of hazardous chemicals to the surrounding residential area and environment, and an RMP will no longer be required.
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