City of Nacogdoches WWTP - Executive Summary

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EXECUTIVE SUMMARY 
 
 
1.0    REGULATED SUBSTANCES 
 
The City of Nacogdoches Wastewater Treatment Plant (WWTP) uses two regulated chemicals, chlorine and sulfur dioxide, in the treatment of municipal wastewater.  
 
Chlorine is used in the disinfection of municipal wastewater. Chlorine is stored prior to and during use in 1-ton containers on an unenclosed, covered, concrete pad. The chlorine is stored as a pressurized liquefied gas, and is released into wastewater using a vacuum-regulated system. The maximum intended chlorine inventory at the facility is 24,000 pounds which exceeds the RMP threshold quantity of 2,500 pounds. 
 
The facility uses sulfur dioxide in the removal of chlorine from treated wastewater. Sulfur dioxide is stored prior to and during use in 1-ton containers on an unenclosed, covered, concrete pad. The sulfur dioxide is stored as a liquefied gas and released into wastewater using a pressurized system. The maximum intended sulfur dioxide inventory at the facility is 24,000 pou 
nds which exceeds the RMP threshold quantity of 5,000 pounds. 
 
 
2.0    POLICIES 
 
Chlorine and sulfur dioxide are toxic chemicals and precautions must be taken in order to prevent unnecessary exposure to facility personnel and to reduce the threat of accidental release which might result in exposure to the surrounding community and to the environment. It is our policy to adhere to all applicable Federal, State, and industry rules, regulations, and guidelines. Chemical safety at the City of Nacogdoches WWTP is dependent upon strict operating procedures, safe handling methods, and thorough training of employees. Chlorine and sulfur dioxide safety devices are also inherent in the design of the facility and in the equipment used in the chlorine and sulfur dioxide chemical processes. 
 
 
3.0    WORST CASE/ALTERNATIVE CASE SCENARIO ANALYSES INCLUDING ADMINISTRATIVE CONTROLS AND MITIGATION MEASURES TO LIMIT THE DISTANCES FOR EACH REPORTED SCENARIO 
 
EPA defines the worst-case scenario as total failure  
of the largest vessel. The alternative-case scenario is defined as a release that is more likely to occur than the worst case scenario. The alternative-case scenario should also reach an offsite endpoint, unless no such scenario exists. 
 
At the City of Nacogdoches WWTP, the worst-case scenario for chlorine would result in a release of 2,000 pounds of chlorine gas. The impact radius would be 1.3 miles and affect 300 persons. Public receptors would include residences and major commercial or industrial areas. There were no environmental receptors within the impact radius. 
 
The alternative-case scenario for chlorine would result in a release of 2,000 pounds of chlorine gas. The impact radius would be 0.1 miles and affect 10 persons. There were no public or environmental receptors within the impact radius. 
 
The worst-case scenario for sulfur dioxide would result in a release of 2,000 pounds of sulfur dioxide. The impact radius would be 1.3 miles, affecting 300 persons. Public receptors woul 
d include residences and major commercial or industrial areas. There were no environmental receptors within the impact radius. 
 
The alternative-case scenario for sulfur dioxide would result in a release of 2,000 pounds of sulfur dioxide. The impact radius would be 0.1 miles and affect 10 persons. There were no public or environmental receptors within the impact radius. 
 
 
4.0    PREVENTION PROGRAM AND CHEMICAL SPECIFIC PREVENTION STEPS 
 
The City of Nacogdoches WWTP complies with the EPA's Accidental Release Prevention Rule and with all applicable State codes and regulations. Our facility has taken all the necessary steps to comply with the accidental release prevention requirements under 40 CFR Part 68. The following sections briefly describe the elements of the release prevention program that is in place at our facility. 
 
Safety Information 
 
The City of Nacogdoches WWTP maintains a detailed record of safety information that describes the chemical hazards, operating parameters, and equipme 
nt designs associated with the wastewater disinfection process. 
 
Hazard Review 
 
Our facility conducts detailed studies to ensure that the hazards associated with our chlorine and sulfur dioxide processes are identified and controlled efficiently. The studies are undertaken by a team of qualified personnel and are revalidated at least once every five years. Any findings related to the hazard review are addressed in a timely manner. 
 
   Operating Procedures 
 
For the purposes of safely conducting activities within our chlorine and sulfur dioxide processes, the City of Nacogdoches WWTP maintains written operation procedures. These procedures address various modes of operation such as initial startup, normal operations, temporary operations, emergency shutdown, emergency operations, normal shutdown, and startup after a turnaround. The information is regularly reviewed and is readily accessible to operators involved in the processes. 
 
   Training 
 
The City of Nacogdoches WWTP has a comprehensive 
training program to ensure employees who are operating the chlorine and sulfur dioxide processes are competent in the operations procedures associated with the processes.  
 
    Maintenance 
 
The City of Nacogdoches WWTP conducts regular maintenance checks on process equipment to ensure proper operations. Process equipment examined by these checks includes; pressure vessels, storage tanks, piping systems, relief and vent systems, emergency shutdown systems, controls, and pumps. Maintenance operations are carried out by qualified personnel with previous training in maintenance practices.  Any equipment deficiencies identified by the maintenance checks are corrected in a safe and timely manner. 
    
   Compliance Audit 
 
The City of Nacogdoches WWTP conducts audits on a regular basis to determine whether the provisions set out under the RMP rule are being implemented. These audits are carried out at least every three years and any corrective actions required as a result of the audits are undertak 
en in a safe and prompt manner. 
 
   Incident Investigation 
 
The City of Nacogdoches WWTP promptly investigates any incident that results in, or could reasonably result in a catastrophic release of chlorine or sulfur dioxide. These investigations are undertaken to identify the situation leading to the incident as well as any corrective actions to prevent the release from reoccurring. All investigation reports are retained for a minimum of five years. 
 
    
5.0    FIVE YEAR ACCIDENT HISTORY 
 
In the past five years, there have been no accidental releases of chlorine or sulfur dioxide that resulted in deaths, injuries, or significant property damage onsite, or known offsite deaths, injuries, property damage, environmental damage, evacuations, or sheltering in place. 
 
 
6.0    EMERGENCY RESPONSE PROGRAM  
 
The City of Nacogdoches WWTP employees will not respond to a chemical emergency at the plant. As required by 40 CFR Part 68.90, the City of Nacogdoches is included in the community emergency response  
plan and appropriate mechanisms are in place to notify emergency responders when there is a need for response. 
 
 
7.0    PLANNED CHANGES TO IMPROVE SAFETY 
 
The City of Nacogdoches WWTP has contracted with AVIA Environmental, LLC, to assist with developing chemical specific operating procedures, training procedures, and maintenance procedures. These procedures will then be implemented in order to attain compliance with RMP regulation requirements as well as to ensure the safe operation and mechanical integrity of the RMP regulated process.
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