South Afton Field - Executive Summary

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1.1 Accidental Release Prevention and Emergency Response Policies 
It is the policy of Venoco that its employees, environment, property, and the general public be protected from any harm that may occur as a result of its operations.  To achieve this end, Venoco strives to operate is facilities in compliance with applicable federal, state, and local safety, health, and environmental regulations. The Santa Clara Valley Gas Plant has a long-standing commitment to worker and public safety.  This commitment is demonstrated by the resources invested in accident prevention (e.g., training of personnel, considering safety in the design, installation, operation, and maintenance of the facility, etc.). Venoco's philosophy is to implement reasonable mitigation measures to eliminate preventable releases of regulated substances as well as other substances.  
Venoco's emergency response policies are implemented to comply with the overall Venoco policy of providing  
its workers with a safe workplace and minimizing risk to the public.  This is considered to be of prime importance; therefore, all procedures must be carried out in the appropriate manner.  The safety of emergency and non-affected personnel must have priority.  Only then can safely executed rescue and medical activities be considered.  Another priority is protection of the environment.  Only after life, safety, and environmental concerns are addressed will the focus shift to the secondary issues of property conservation and business recovery. The facility is exempt from PSM since it is a remote facility, and it is maintained and serviced by employees who visit the unmanned facility only periodically to check its operation (California Final Regulation, sec. 5189 (b)(3)). 
1.2  Facility Description 
The South Afton Field is located in Butte city, California.  It is approximately 100 miles inland from the Pacific Ocean.  The nearest major highways are Interstate 5 and Route 126.  Th 
e facility is 2.6 miles south of HWY 162, and 12.6 miles east of Interstate 5. The facility is relatively remote and bounded by undeveloped private properties.   The closest major waterway is the Sacramento River, which is approximately 1.8 miles west of the facility.    
The proposed addition of a 18000 gallon propane/butane mix storage vessel consists of one Program 1 process which stores butane/propane for injection into an existing pipeline. 
The produced gas from gas wells flows up naturally (no pumping) into a gathering line. The line enters a dehydration unit, and enter a separate gas scrubber and then flow through a compressor skids where the gas is compressed to Gas Company specifications and then gets transferred into the PG&E plant.  The propane/butane is injected into the stream to bring the quality of gas to the PG&E specification. 
1.3  Regulated Substances 
A regulated flammable mixtures containing propane and butane is present at the facility.  No regulated to 
xic substances are present at the facility in excess of the threshold quantities established by this regulation.    
1.4 Summary of Offsite Consequence Analysis Results 
1.4.1  Worse-Case Release Scenario 
The worse-case release, as defined in the regulation, is a release of flammable materials resulting in a vapor cloud explosion of the maximum inventory of the largest vessel.  Even though the normal operating inventory for this equipment is less than the maximum capacity and this equipment is protected by high level alarms/shutdowns, pressure relief valves, periodic inspections, and routine monitoring by operating personnel, this maximum inventory must be assumed to be released in 10 minutes and ignited at the point of release.   
The worse-case release scenario modeled for the South Afton Field Storage Vessel is a release of the  entire volume of the flammable material stored in the largest of four Butane/Propane storage vessels.  The worse-case release scenario identifi 
ed some off-site impacts, but the impact area includes minimal public receptors and no residential (publicly or privately owned buildings) receptors.   
1.4.2 Alternative Release Scenario 
The examination of alternative release scenario is not required for this faulty since it is eligible for Program 1. 
1.5 Five-Year Accident History 
The South Afton Field Storage Vessel is a new process. Therefore,  no incidents with off-site impacts involving a regulated substance as defined in the regulation in the past five years would have occurred for this facility.
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