Detroit Wastewater Treatment Plant - Executive Summary |
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Executive Summary The owner or operator of a stationary source subject to the risk management program rule under the Clean Air Act, section 112 (r) (7) of 40 CFR Part 68 is required to submit a single Risk Management Plan that includes the information required in '' 68.155 through 68.185 for all covered processes. As specified in ' 68.155, the owner or operator must provide an executive summary that includes a brief description of the Risk Management Plan. At Detroit Wastewater Treatment Plant (DWWTP), chlorine is the only regulated substance that is being handled above the EPA threshold of 2,500 lbs. The following elements describe the Risk Management Plan as per ' 68.155, for the Chlorination Process at the Detroit Wastewater treatment Plant. 1. The accidental release prevention and emergency response policies at the stationary source. Detroit Water and Sewerage Department, under which DWWTP is being operated, is strongly committed to employee, public and environmental safety. T he chlorination process in Detroit Wastewater Treatment Plant has been designed and constructed per the applicable codes and engineering standards. Currently, the process is working and meets the good engineering practices. Also, a preventive maintenance program consisting of equipment calibration and replacement of components to maintain process performance has been implemented. Chlorine tank car inspection, cleaning, repair, interior system tests and relief valve tests are made by the supplier. At DWWTP, a set of nine (9) detectors are placed throughout the roof of the administration building and at the junction chamber. Their function is to warn of chlorine gas in the air and to activate the automatic shut off mechanism of the air intake to the various parts of the building affected. These detectors are set to detect one part per million (1 ppm) chlorine gas by volume in air; activate an alarm and shut off heating, ventilating and air conditioning systems at 5 ppm of con centration. The signals from these detectors are transmitted to the Computer Control Room and the Special Laboratory. The chlorine detection system has three (3) sensors inside the chlorination building to monitor the ambient air chlorine concentration. Two of these sensors have an activation level of 1 ppm and the third one has the activation level of 3 ppm of chlorine gas. When the chlorine gas content exceeds the activation level, visual and audible alarms are triggered. The caustic soda air wash system chemically neutralizes chlorine from a leak inside the chlorination building before the gas escapes to the outside atmosphere. Flashing red lights are provided at all the entrances to the chlorination building. This is to alert the area personnel that there is or was a leak inside the building. Flashing red light at the Junction Chamber is a signal that indicates that there is or was chlorine in the vicinity of Chlorine Chamber. Detroit Wastewater Treatment Plant has a n emergency response plan. We are in the process of training personnel to form an emergency response team. The fire department will be notified for assistance. The plant supervisor will also notify the police to be prepared for an evacuation of the neighboring residents if the need occurs. Other agencies to be notified in the event of an accidental release of chlorine are City of Detroit Local Emergency Planning Committee ( LEPC ), Michigan Department of Environmental Quality (MDEQ) Pollution Emergency Alert System, The Environmental Protection Agency (EPA), The National Response Center (NRC) which will notify the appropriate federal agencies, Ontario Ministry of Environment, Canada Consulate General Office, and Detroit Water and Sewerage Department's Systems Control Division. 2. Stationary source and regulated substances handled. Detroit Wastewater Treatment Plant provides secondary treatment for flows up to 930 MGD. During wet weather periods, incremental flows above 930 MGD rec eive primary treatment and disinfection prior to discharge to the Detroit River. At the pump stations, raw wastewater from the Jefferson Interceptor, Oakwood Interceptor and North Interceptor-East Arm receive coarse screening and grit removal and is then pumped to the primary tanks. Ferrous chloride is added to the raw wastewater for phosphorous removal. The wastewater is pumped from the Intermediate Lift Station to the secondary treatment facilities where treatment is provided by the activated sludge method. Following final clarification, the wastewater is disinfected by the addition of chlorine and discharged to the Detroit River. Treated wastewater can be discharged to the Rouge River if hydraulically or structurally necessary. The primary solids and secondary activated solids are gravity thickened and dewatered by either centrifuge or belt filter presses. The main sludge disposal method is by incineration and landfill of the ash. Excess sludge is lime stabilized and landfill ed. The primary components of the chlorination process are four (4) 90 ton rail cars, two (2) steam vaporizers, nine (9) hot water evaporators, one (1) auxiliary steam boiler, two (2) hot water circulation pumps, one (1) gas fired hot water heater, eleven (11) chlorinators, one (1) chlorine contact chamber, and the caustic soda air wash system. The Plant keeps one spare chlorine tank car as a back up unit. 3. The Worst Case Release Scenario and The Alternative Release Scenario. The gas dispersion model ALOHA ( Areal Locations of Hazardous Atmospheres ) which is recommended by the EPA has been employed by our facility to conduct the worst case and alternative case scenarios. The following paragraphs provide details of the chosen scenarios. The Worst Case Release Scenario involves the release of 90 tons of chlorine in a gaseous form over 10 minutes. Under worst case weather conditions, namely Class F atmospheric stability and 1.5 meters/second (m/s) wind speed, the distance o f more than 6 miles is obtained corresponding to a toxic endpoint of 0.0087 mg/L. The Alternative Release Scenario involves the breakage of one of the header pipes. In this event, chlorine is released at its maximum limit of 15,000 lb./hr over a duration of 30 minutes which is the maximum allowed duration for correcting any release problem. Under class D atmospheric stability and 3 m/s wind speed, the maximum distance of 2.1 miles is obtained corresponding to a toxic endpoint of 0.0087 mg/L. 4. The general accidental release prevention program and chemical-specific prevention steps. Periodic training is provided for the operations laboratory and maintenance staff personnel assigned to the chlorination process. The training consists of reviewing the chlorination manual and actual hands-on field operation of the equipment. Leak detection and equipment isolation procedures are also included in this training. The preventive maintenance program consists of equipment calibratio n and replacement of components to maintain process performance. The chlorine monitoring devices are calibrated monthly and after each alarm event. Rupture disc replacement is performed annually to prevent premature chlorine releases caused by eroded or fatigued disks. A total inspection and/or replacement of the process piping are performed at 5 year intervals. 5. The five -year accident history. We have had 13 accidental releases of chlorine in the past five years (from June 1994 to June 1999) and they were all small and contained within the chlorination building. No one was seriously injured. In one case two persons were sent to the hospital/clinic for check up. There was no permanent injury. These releases did not have any offsite consequences. 6. The Emergency Response Program. The Detroit Wastewater Treatment Plant has a written Emergency Response Plan to deal with accidental releases of chlorine. The plan includes all aspects of emergency response including adequa te first aid and medical treatment, evacuations, notification of local emergency response agencies and the public, as well as post-incident decontamination of affected areas. The Wastewater Treatment Plant personnel that have the potential for responding to accidental releases of chlorine have received formal emergency response training (i.e., 40-Hour Hazardous Waste Operations and Emergency Response (HAZWOPER) training). We are in the process of forming an emergency response team. Until the team is established, the DWSD WWTP will utilize an outside contractor to provide emergency response services. In the event of fire and other emergencies at the DWWTP, employees are alerted by an alarm system to evacuate the affected area to the safe zone. The person who activates the alarm would communicate by telephone to the outside contractor for emergency response. The public will also be notified. Flashing red lights are provided at all the entrances to the chlorine building and at the junction chamber to indicate the presence of chlorine. 7. Planned changes to improve safety. DWWTP has planned several modifications to the chlorine facility such as relocation of the current facility and installation of new equipment to improve the overall safety of the chlorination process. HAZMAT training will be provided to more plant personnel to be the part of the emergency response program. Maintenance section has planned to intensify their training of new employees on the new equipment. |