City of Pocatello POTW - Executive Summary

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EXECUTIVE SUMMARY 
 
Pocatello's Wastewater Treatment Plant is located west of the city at 10733 Rio Vista Road.  The 
plant treats all wastewater generated by the City of Pocatello and the City of Chubbuck. Treatment  
consists of primary and secondary treatment with disinfection using a final 
chlorination/dechlorination process prior to being discharged to the Portneuf River.  Because the 
City of Pocatello exceeds the threshold quantity for the chemicals Chlorine and Sulfur Dioxide it 
must comply with the mandated EPA Risk Management Plan (RMP).  
 
The two major elements in the RMP for Pocatello are the Off Site Consequence Analysis' for 
chlorine and sulfur dioxide and a Prevention Program. The City of Pocatello's Waste Water 
Treatment Plant is also required to do Offsite Consequence Analysis for  a worst case release 
scenario and alternative release scenario. Pocatello's Prevention Plan includes information about 
safety, process hazards, operating procedures, training programs, maintenan 
ce programs, compliance 
audits, and accident investigation.  
 
The RMP offsite consequence analysis for both the worst case release scenario and alternative 
release scenario were performed for accidental release of the toxic gases chlorine and sulfur dioxide  
using the EPA software program, RMP*Comp. 
 
For Chlorine: 
The worst-case scenario analysis requires considering the release chlorine from the largest single 
vessel.  The largest single vessel of chlorine is a one ton cylinder. The analysis considers  a release 
rate of 200 pounds per minute, with a release time of 10 minutes. The topography is urban 
surroundings. However, the building is not used as a mitigation measure because the chlorine is 
delivered outside. The estimated distance to toxic endpoint is 1.3 miles. 
 
The alternative scenario analysis considers the release chlorine a 1/4 inch hole from a pigtail 
connection breaking.  This analysis uses a release rate of 9 pounds per minute, with a release time 
of 222 minutes (Risk Man 
agement Program Guidance for Wastewater Treatment Plants, Chapter 4, 
Exhibit 4-15). The topography is urban surroundings. The chlorine cylinders are stored inside a 
building.  However, the building is not used as a mitigation measure because the chlorine is 
delivered outside. The estimated distance to toxic endpoint is 0.1 miles. 
 
For Sulfur Dioxide: 
The worst-case scenario analysis requires considering the release of sulfur dioxide from the largest  
single vessel.  The largest single vessel of sulfur dioxide is a one ton cylinder. The analysis considers 
a release rate of 200 pounds per minute, with a release time of 10 minutes. The topography is urban 
surroundings.  The building is not used as a mitigation measure because sulfur dioxide is delivered 
outside of the building. The estimated distance to toxic endpoint is 1.3 miles. 
 
The alternative scenario analysis considers the release of sulfur dioxide from a 1/4 inch hole from 
a pigtail connection breaking.  The analysis considers a r 
elease rate of 4 pounds per minute, with a 
release time of 500 minutes (Risk Management Program Guidance for Wastewater Treatment Plants, 
Chapter 4, Exhibit 4-19). The topography is urban surroundings. The sulfur dioxide cylinders are 
stored inside a building. The building is not used as a mitigation measure because the chlorine is 
delivered outside.  The estimated distance to toxic endpoint is <0.1 miles. 
 
Estimating Offsite Receptors:  
 
FIVE YEAR ACCIDENT HISTORY 
 
There have been no accidental releases of chlorine or sulfur dioxide in the past five years.  The 
objective of this plan is to continue this history and prevent any accidental releases,  and to respond 
effectively and timely in the unlikely event there is a release.  Pocatello's RMP includes an incident 
report form will be used in the unlikely event there is an accidental release. 
 
MANAGEMENT SYSTEM 
 
The roles and responsibilities of the staff that oversees the risk management program elements will 
help to ensure effective  
communication about process changes between divisions; clarify the roles 
and responsibilities related to process safety issues; avoid problems and conflicts among various 
people responsible for implementing elements of the program; avoid confusion and allow team 
work; and ensure that the program elements are integrated into an ongoing approach to identifying 
hazards and managing risks. 
 
PREVENTION PROGRAM (PROGRAM 2) 
 
Pocatello's Prevention Plan has integrated the seven basic elements - safety information, process 
hazard analysis, operating procedures, training programs, maintenance programs, compliance audits, 
and accident investigations into a risk management system.  Safety information was used to perform 
a process hazard analysis and the results of the analysis were used to revise and update operating and 
maintenance procedures. Training programs to ensure employees to understand and manage risks 
have been revised and continued training is provided. 
 
PROCESS SAFETY INFORMATION 
 
Chl 
orine and sulfur dioxide have been used for many years in the chlorination and dechlorination 
process at Pocatello's Wastewater Treatment Plant.  As references for chlorine and sulfur dioxide 
handling Pocatello uses The Chlorine Manual (The Chlorine Institute, 1986, 5th edition), Chlorine 
And Its Properties, (Capital Controls Company, Inc., 1990, Pub. No. 381-5), Sulfur Dioxide And Its 
Properties (Capital Controls Company, Inc. 1989, Pub. No.482-2), Material Safety Data Sheets 
(MSDS) BOC GASES, 1996;. and The City of Pocatello Operating Procedures for Chlorine and 
Sulfur Dioxide Cylinder Handling and Storage, 1999.  
 
OPERATING PROCEDURES      
 
Operating procedures and instructions are important for training personnel and insuring safe 
operations of the chlorine and sulfur dioxide systems.  The standard operating procedures (SOPs) 
for operating the chlorine and sulfur dioxide systems and associate equipment are located in the 
operations office, maintenance office and  operators lab whic 
h are accessible to all plant personnel.  
The SOPs cover everything from receiving the ton cylinders through valving the chlorine and sulfur 
dioxide to the various discharge points.  They include the start-up and shut down of all the related 
chlorine and sulfur dioxide handling equipment.  These SOPs are updated when ever there are any 
changes made to any part of the chlorine system. 
 
New employees are give general training in the hazards of chlorine and sulfur dioxide as part of their 
plant employee orientation.  New operators are required to review and understand the chlorine and 
sulfur dioxide related standard operating procedures and given on the job training (OJT) on all 
chlorine and sulfur dioxide related tasks they are required to perform as part of their operational 
duties.  The maintenance employees also receive OJT on the chlorine and sulfur dioxide systems 
before they are allowed to independently work on the chlorine or sulfur dioxide systems. 
 
Yearly refresher training is g 
iven on the nature and hazards of chlorine and sulfur dioxide.  
Documentation of this training is kept in the plant safety training records. 
 
MAINTENANCE 
 
Written procedures for inspection and testing are incorporated into a preventive maintenance (PM) 
program and have been in effect since construction completion in 1992. The PM is conducted in 
accordance with the manufactures recommended procedures and sound engineering practices.  The 
PM program is operated by a computer system that generates the needed information when a piece 
of equipment is in need of inspection or service.   
 
Technical manuals for the chlorination/dechlorination processes consist of three volumes which are 
current and located in the maintenance library. 
 
Initial training on the chlorination/dechlorination systems were conducted by construction contractor 
and equipment manufactures at completion of construction.  Safety training requirements for 
maintenance personnel are the same as for operations personnel.  
 
 
INCIDENT INVESTIGATION 
 
The intent of the incident investigation is to learn from past experiences and avoid future similar 
incidents.  The incidents employees are expected to recognize and initiate the investigation process 
are the types of events that result or could have reasonably resulted in a major chlorine or sulfur 
dioxide release.  This is what we may refer to as a "near miss," meaning that serious consequences 
did not occur, but could have. 
 
COMPLIANCE AUDIT 
 
The wastewater treatment plant  is required under EPA regulations to conduct a self-audit and 
document compliance on a signed document every three years.  The certification will verify that the 
procedures and practices are adequate and are being followed.  A report of the findings of the audit 
will be developed. 
 
The Wastewater Superintendent or designee will determine and document a response to each 
deficiency identified in the compliance audit.  Any deficiency noted in the audit will be corrected 
and documented as su 
ch. 
 
The wastewater treatment plant will keep the two most recent compliance audit reports on file for 
internal purposes and EPA inspection. 
 
 
EMERGENCY RESPONSE PLAN 
 
Any time a chlorine or sulfur dioxide emergency is apparent or suspected, the operator in charge will 
initiate the procedure to assess the severity of the emergency. The procedure requires a minimum 
of two individuals to be present when an emergency is apparent or suspected.  A minimum of "Level 
B" respiratory protective equipment will be required.  The reason for a two party assessment is due 
to staffing levels.  
 
Once the level of emergency has been assessed, the operator in charge will then make a 
determination as to what Action Response Procedure will be followed based on the information 
provided by the assessment.  The operator in charge will immediately begin a record of the event.  
 
Small leaks that are contained within the chemical building area may be repaired or alleviated 
through immediate action of trained pl 
ant personnel.  Large releases that may effect public and/or 
private receptors or risk personal injury to plant personnel will be responded to by the Regional 
HAZMAT Team.
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