Iowa City Wastewater Treatment North Plant - Executive Summary

| Accident History | Chemicals | Emergency Response | Registration | Source | Executive Summary |

City of Iowa City Wastewater Division North Plant 
Accidental release prevention and emergency response policies of the City of Iowa City Wastewater  Division 
   This program was developed to prevent the occurrence of, or minimize the consequences of, catastrophic releases of toxic materials from the Iowa City wastewater treatment North Plant.  It is the policy of the Wastewater Division to provide its employees with a safe and healthful work environment and to conduct its operations in such a manner as to have minimal impact on the environment and the surrounding community. Every effort has been made to provide the greatest degree of safety possible for City employees and the citizens of Iowa City. This RMP addresses all required elements of the pertinent OSHA standard and EPA regulations. Wastewater Division employees,  representatives of  emergency response organizations, and the people of Iowa City will be provided full access to our Process Safety and Risk Manag 
ement program. 
Primary activities  
   The Wastewater Divisions mission is to provide primary and secondary treatment of Iowa City wastewater. This is partly accomplished through the use of  liquified chlorine gas as a sewage disinfectant, and  the use of sulfur dioxide as a de-chlorination agent to reduce the chlorine toxicity of the treated effluent. Ton containers of chlorine and sulfur dioxide gas are stored in inside the Chemical Building at the North  wastewater treatment facility, located at 1000 S. Clinton Street in Iowa City. Chlorine and sulfur dioxide are delivered to the wastewater stream through a system of chlorinators, sulfonators, and evaporators, and associated piping. The maximum amount of chlorine and sulfur dioxide in storage at both wastewater treatment plants is 8,000 pounds. Only a single container each of chlorine and sulfur dioxide is connected to the chlorination and de-chlorination systems at any one time. Sewage sludge undergoes further treatment during the s 
ludge digestion process. This process reduces the volume of sewage, and at the same time produces potentially flammable methane/sewage gas. The gas accumulates in the digester tanks and is used in heating the digester buildings, or is periodically vented to a waste gas burner. The amount of methane generated by this process is less than the 10,000 pound minimum amount specified by the EPA, and was therefore not included in the development of any worst-or alternate-case scenarios. 
General accidental release prevention program and chemical-specific prevention steps in place at the City of Iowa City Wastewater Division 
   The City of Iowa City Wastewater Division has in place a preventive maintenance program covering all components of the chlorination/dechloriation systems.  The preventive maintenance program is intended to ensure the continued integrity of process equipment and to minimize the risk of a catastrophic chlorine or sulfur dioxide release.  The preventive maintenance program  
requires regular inspection and testing of chlorination and de-chlorination equipment by operations and maintenance personnel. The Wastewater  Division also has in place an employee education and training program which encompasses all necessary training in safe operations and maintenance of the wastewater treatment process. All affected personnel receive training at the time of their initial assignment, and whenever there is a process modification, alteration of operating procedures, or change in job duties. It is the belief of the Wastewater Division that compliance audits are needed to evaluate the effectiveness of the process safety and risk management programs. These audits will be conducted at regular intervals by a multi-disciplinary employee-management team, and this team will review the Process Safety Management program in force at the time of the audit for its effectiveness and applicability,  and make recommendations for changes and revisions, as necessary. 
Five-year accid 
ent history 
   There have been no chlorine or sulfur dioxide releases at the Iowa City North Plant which resulted in death or injury to Wastewater  Division personnel or the general public, or significant property or environmental damage on- or off-site during the five year period immediately proceeding the date of this report. 
Worst-case and alternate-case release scenarios 
   In the worst-case scenario, a ton container of chlorine gas ruptures, and releases approximately 2000 pounds of Cl2 gas to the atmosphere.  The contents of the container are expected to be released within ten minutes over urban terrain. The distance to the toxic endpoint for the worst case scenario will cover an approximately 1.3 mile radius from the North Plant under conditions of category F (most stable) atmospheric stability and wind speed of  1.5 meters per second, as determined by the RMP COMP modeling program. In the alternate case for a chlorine or sulfur dioxide gas release, failure of a check value inside  
the Chemical Building results in approximately 0.30  pounds of chlorine or sulfur dioxide released in 10 minutes. The distance to the toxic endpoint for these scenarios, as determined by the RMP COMP program, is <0.1 miles, using category D (neutral) atmospheric conditions, wind speed of 3 meters per second, and urban terrain.  
Emergency response program  
   The Wastewater Division has adopted an emergency response and action plan to deal with both major and minor chlorine and sulfur dioxide releases. The scope of the Wastewater Divisions emergency response and action plan includes both minor chlorine and sulfur dioxide releases controllable by Wastewater Division staff and contained within the wastewater treatment plant, and uncontrolled, major releases requiring assistance from local emergency responders.  All Division personnel receive initial training in emergency response and evacuation procedures, and undergo refresher training at least once every three years thereafter. Emerge 
ncy response will be coordinated with the Iowa City Fire and Police Departments,  Johnson County Disaster Services,  Johnson County Hazardous Materials Response, and local area hospitals.  The Iowa City Fire Department has responsibility for emergency rescue and initial medical response during a chlorine or sulfur dioxide emergency; the 24-hour emergency response telephone number is 911.  Notification of residences and neighboring facilities will be the responsibility of Iowa City Police Department and Johnson County Disaster Services. Decontamination and clean up efforts will be coordinated with the Johnson County Hazardous Materials Response Team. Wastewater treatment personnel will also offer technical assistance to emergency responders. 
Planned changes to improve safety. 
   The Wastewater Division is committed to improving the quality of employee training and education programs.  These programs will be evaluated at regular intervals and updated and revised as necessary. Employee tra 
ining will be documented to the fullest extent possible.  Division personnel will continue to participate in drills and cooperative training with emergency responders in the local area. The chlorination and de-chlorination systems preventive maintenance programs will also be evaluated, and if unsatisfactory conditions are noted or recommendations for corrective action are made, these conditions or recommendations will be promptly addressed and any outstanding problems will be resolved in a timely manner.
Click to return to beginning