Clary Waste Treatment Plant - Executive Summary

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RISK MANAGEMENT PROGRAM 
 
EXECUTIVE SUMMARY 
Clary Waste Treatment Plant 
 
The Board of Public Works of Gaffney, South Carolina ( BPW ) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices.  This policy complies with all the applicable requirements of section 112(r) of the Clean Air Act (CAA) and all applicable procedures of the Environmental Protection Agency's Risk Management Program(RMP).  The BPW Risk Management Program involves the preparation of response plans that are tailored to each facility. 
 
The Broad River Waste Treatment Plant, the Clary Waste Treatment Plant, the Cherokee Water Treatment Plant, and the Victor Gaffney Water Treatment Plant are facilities owned by the BPW that exceed the OSHA Process Safety Management Program ( PSM ) ( 29 CFR 1910.119 ) threshold limit of 1500 pounds for Chlorine ( CAS: 007782-50-5 ).  These facilities are manned and are required by 1910.119 to establish a PSM progr 
am.  The BPW has implemented a PSM program that is unique to each facility.  Presently, all the facilities exceed the threshold limit of 2500 pounds of chlorine established by CAA 112r,therefore, each facility has implemented a Risk Management Program based on CAA 112r Program 3 requirements. 
 
Each facility has special characteristics such as number of employees, hours the facility is manned, density of the surrounding population, and public receptors that required the BPW to develop RMP for each of the facilities.  The facilities use many technological and managerial practices that are not unique, in fact are common in the water-waste water treatment industry. Liquid chlorine is delivered to each of the facilities in ton cylinders and placed in a tank storage area.  Gaseous Chlorine, collecting in the top of the tank as a function of temperature, is piped off by a vacuum chlorinating system and injected into potable water to form a solution of hypochlorite.  The solution is piped to c 
ontact chambers for the purpose of disinfecting water and wastewater.  The equipment at each facility includes a tank storage area, chlorinator room that contains the chlorinators, flow recorders, various safety equipment, and electrical panels.  A compete listing of equipment, along with block flow diagrams, and pipe and instrumentation diagrams are included in the BPW PSM for each facility. 
 
The offsite consequence analysis, required by CCA, includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative scenario".  The first scenario is defined by EPA, which states that "the owner or operator shall assume that the  maximum quantity in the largest vessel  is released as a gas over 10 minutes," due to an unspecified failure.  The alternative scenario is defined as "more likely to occur than the worst-case release scenario". 
 
Atmospheric dispersion model was performed for each facility based on the RMP COMP VER. 1.06. The RMP COMP PROGRAM 
was used to determine the distance traveled by the chlorine released before its concentration decreases to the " toxic endpoint" selected by EPA of 3 ppm or 0.0087 mg/L, which is the Emergency Response Planning Guideline Level 2 (ERPG-2).  This is defined by the American Industrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action."  The residential population within a circle with a radius corresponding to the toxic endpoint distance is defined, " to estimate the population potentially affected".  
 
 
 
WORST CASE RELESE SCENARIO 
 
The worst case release scenario for Clary Wastewater Treatment Plant involves a failure of a one ton cylinder (a total of 2000 lb. of chlorine).  The conditions for the worst case scenario are pre- 
defined by EPA (release of the entire amount of gas in 10 minutes).  The rate of release is equal to the amount in the cylinder divided by the time of the release or 2000 lb. / 10 minutes = 200 lbs. per minute.  The facility has containment walls, but not to the degree that the walls should be considered passive mitigation.  This includes the following conditions: rate of release 200 lb. per minute, urban conditions, f stability, 1.5 meters per second wind speed, 0.0087 toxic endpoint.  When using the RMP COMP analysis the distance to a toxic endpoint is 1.3 miles. 
 
When the RMP COMP analysis for worst case scenario is used to obtain the distance endpoint of 1.3 miles, an area of concern can be determined in order to obtain an estimate of the population affected.  In addition, other public receptors can be identified including schools, businesses, industries, and recreational facilities.  The receptors identified for the worst case scenario for the Clary Waste Treatment Plant are as fo 
llows: 
Clary Plant: population affected  615; schools 0; business and industry 04; parks and recreation 01; environmental 0. 
 
 
ATERNATIVE RELEASE SCENARIO 
 
The alternative release scenario for the Clary River Waste Treatment Plant involves the misalignment of the vacuum regulator valve that is connected to a ton cylinder.  This connection requires the use of a lead or composite washer.  Misalignment of the washer or improper torsion of the valve fitting could would cause a leak.  The leak would occur on the tank side of the vacuum regulator causing a pressure leak approximately equal to the tank pressure.  This scenario would allow chlorine gas to escape through a 3/8 inch (or smaller) opening resulting in the release of 960 lbs. of chlorine over a 60 minute release period   (16 lb/min).  The calculation for the release rate is taken from the EPA reference guide, section 8.1 and is as follows: QR (release rate) = HA (hole area in square inches) x Pt (tank pressure in pounds per square  
inch absolute (psia) x 1/square root of  Tt (tank temperture-kelvin) x GS (gas factor).  
 
Based on RMP COMP VER. 106 dispersion modeling (Dense Gas Distances to Toxic Endpoint) which assumes a 60 minute release, urban conditions, D stability, wind speed of 3.0 meters per second, toxic endpoint for chlorine of 0.0087 and a release rate of 16 lb/min. the toxic endpoint would be reached in the alternative scenario at 0.1 miles or 528 feet. 
 
The receptors identified for the worst case scenario for the Clary Wastewater Treatment Plant are as follows: population affected 00; schools 0; business and industry 00; parks and recreation 00; environmental 0.   
 
MITIGATION 
 
Even if the personnel responsible for the misalignment had left the tank storage area, actuation of the chlorine detector would cause the on duty operator to respond to the alarm. The response of the operator would take 60 minutes or less and is an active mitigation measure.  An additional active mitigation system is the remote  
vacuum type chlorinators.  This system will reduce significantly the amount of chlorine released in the case of a piping rupture.  
 
 
 
ACCIDENTAL RELEASE PREVENTION PROGRAM 
 
The Accidental Release Prevention Program at the Clary Waste Water Treatment Plant is based on the elements of the OSHA PSM Program.  The PSM Program is a comprehensive and detailed toxic chemical management program that is available for inspection at the plant.  The program includes the following accidental release prevention elements:   
 
7 High level and continuous training of the operators 
7 Preventive maintenance program 
7 The use of accurate and effective operating procedures, written with the participation of the operators 
7 The use of state of the art process and safety equipment 
7 Performance of a hazard assessment of equipment and procedures 
7 Implementation of an auditing and inspection program 
7 Continuous review of process information including study of  Material Safety Data Sheet which includes informat 
ion on the hazardous and toxic properties of chlorine 
7 Chemical-specific steps include the availability of full face respirators and self-contained breathing apparatus (SCBA), worn by the operators worn by operators during tank change outs and alarm response 
7 Chlorine detectors at all storage areas 
 
 
ACCIDENTAL RELEASES 
 
No accidental releases of chlorine occurred at this facility in the past five years. 
 
 
EMERGENCY RESPONSE PROGRAM 
 
This facility has an emergency response program, which is a requirement of the PSM program, which is a complete and comprehensive program.  The program includes clearly defined prioritized emergency actions and notifications.  Emergency drills are conducted on an annual basis and are coordinated with the local Emergency Preparedness Division.  The complete detailed plan is located in the plant office. 
 
 
HAZARD ANALYSIS 
 
Recent improvements to this facility include installation of windsocks, vacuum system, pipe and instrumentation diagrams and yard alarms 
, all of which were identified in the hazard analysis as needed improvements.
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