Leedey Refrigeration Plant - Executive Summary


The Leedey Refrigeration Plant (Leedey) has a long-standing commitment to worker and public safety.  This commitment is demonstrated by the resources invested in accident prevention, such as training personnel and considering safety in the design, installation, operation, and maintenance of the facility's processes.  The Reliant Energy Gas Transmission (REGT) policy is to implement reasonable controls to prevent foreseeable releases of substances. 
REGT operates Leedey located in Custer County, Oklahoma. Leedey is a cryogenic natural gas processing plant designed for the extraction of Liquid Petroleum Gas (LPG) from a gas stream.  The cryogenic extraction plant recovers LPG, which is comprised of ethane, propanes, butanes, and heavier hydrocarbons, from the inlet gas.  LPG from the liquid extraction plant 
is delivered via a pipeline.  As evidenced in the ensuing text and based on criteria outlined in the Accidental Release Prevention (ARP) Program, Leedey is a Program 1 process. 
Leedey was evaluated to determine if any regulated flammable or toxic substances were present in the process and if they exceeded the threshold quantity.  All equipment and vessels are considered to be connected and/or co-located; consequently, for the purposes of the ARP Program, all equipment and vessels are part of a single process.  The identification of even a single vessel exceeding threshold quantities of a regulated flammable or toxic substance would subject a process to threshold determination for offsite consequence analysis. 
REGT identified one regulated flammable substance (LPG, a.k.a. flammable liquid mixture) and zero regulated toxic substances along with the largest vessel quantity stored.  It was determined that a single vessel of the flammable liquid mixture exceeded threshold quantity.  The 
identification of this exceedance indicates that Leedey is a covered process with a regulated substance subject to offsite consequence analysis.   
Worst-Case Scenarios (WCS) 
The Environmental Protection Agency (EPA) has defined a worst-case release as "the release of the largest quantity of a regulated substance from a vessel or process line failure that results in the greatest distance to a specified endpoint."  A WCS analysis is required for each toxic substance in a covered process while only one WCS analysis is required for regulated flammable substances as a class.  WCSs are assumed to occur at ground level with meteorological conditions defined as atmospheric stability class F (stable atmosphere), wind speed of 1.0 meters per second (2.2 miles per hour), and an ambient air temperature of 25?C (77?F).  Topography for WCSs are distinguished between rural and urban. 
Flammable Substances 
Regulated flammable substances or mixtures containi 
ng flammable substances include both gases and volatile liquids.  The WCS assumes that the total quantity of a vapor cloud is released and detonates.  The endpoint for a WCS involving a regulated flammable substance or mixture is an overpressure of 1 pound per square inch (psi).  For a regulated flammable substance, consequence distance determination is based on its heat of combustion.  For regulated flammable mixtures, the component with the highest heat of combustion can be used for consequence distance determination or, if preferred, directly calculated using equation C-1 of the Offsite Consequence Analysis Guidance Document (OCAGD).  The quantity of a regulated substance/mixture used to determine distance to endpoint is the largest quantity of a regulated substance/mixture in a single vessel. 
The flammable liquid mixture evaluated at Leedey is a mixture of ethane, propanes, butanes, and heavier hydrocarbons contained in a pressurized storage vessel in liquid form.  The largest ve 
ssel quantity of the flammable liquid mixture at the site was contained in the Bullet Storage Tank having the capacity of approximately 23,793  gallons (97,480 lbs.). Using the criteria outlined in the ARP rule, this mixture represents the facility's WCS for flammables. 
Both propane and ethane comprise appoximately 35% of the LPG. However, ethane was identified as having the highest heat of combustion (45,509 kjoule/kg).  It was determined that its use would provide a more conservative consequence distance.  The distance to the endpoint of 1 psi overpressure for the worst-case release of the flammable liquid mixture was calculated and determined to be 0.37 miles.  The distance to endpoint is less than the distance to any public receptors- - a mandatory criterion for all Program 1 processes. 
Toxic Liquids and Gases 
Toxic gases include all regulated toxic substances that are gases at ambient temperature (temperature 25? C, 77?F), even if they are stored as liquids under pressure or r 
Leedey does not have any toxic substances held above the threshold quantity.  Analysis of one worst-case release scenario for all regulated toxic substances is, therefore, not required. 
Alternative Release Scenarios (ARS) 
An ARS describes an incident that is more likely to occur than those cited for a WCS.  One ARS analysis is required for each listed toxic substance in a Program 2 or 3  process that exceeds threshold quantity while only one ARS analysis is required for all flammable substances as a class in a Program 2 or 3 process.  For ARSs, both active and passive mitigation systems can be considered. 
Alternative release scenarios for flammable substances should have the potential to cause substantial damage, including on-site damage.  Alternative release scenarios for toxic substances should be those that lead to concentrations above the toxic endpoint beyond the process fenceline.  Those releases that have the potential to reach the public are of the greatest c 
Leedey Alternative Release Scenario for Regulated Flammables 
Leedey is a Program 1 process and is, therefore, not required to complete an ARS for regulated flammables. 
Leedey Alternative Release Scenario for Regulated Toxics 
Leedey does not have any toxic substances held above the threshold quantity and, in addition, is a Program 1 process.  Analysis of each regulated toxic substance is, therefore, not required. 
Leedey has not had any accidental releases during the past five years which meet the criteria for an accidental release as discussed in 40 CFR 68.42. 
Leedey has coordinated its emergency response activities with the local emergency planning and response agencies as required in 40 CFR 68.12(b)(3).  Although Leedey is not required by 40CFR68 to have its own emergency response plan, operators are equipped with an Emergency Plan Book that gives the procedures to follow in case of an emergency.
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