Sterling County Gas Plant - Executive Summary |
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(a) ACCIDENTAL RELEASE PREVENTION AND RESPONSE POLICIES Range Pipeline Systems, LP (Range), operator of the Sterling County Gas Plant, has a long-standing committment to the safety of our employees and the public. This commitment is demonstrated by the resources invested in accident prevention, such as training our plant personnel and considering safety in the design, installation, operation, and maintenance of our gas processing facilities. Our policy is to implement reasonable controls to prevent foreseeable releases of regulated substances. In the event a release does occur, our plant personnel are trained to control and contain the release. (b) DESCRIPTION OF STATIONARY SOURCE AND REGULATED SUBSTANCES The Sterling County Gas Plant, located approximately 12 miles north of Sterling City, Texas, operates a cryogenic process for extraction and recovery of natural gas liquids (NGLs) from natural gas delivered to the plant by pipeline. The products of this process are stripped na tural gas, which is redelivered to the gas pipeline for transportation to markets, and NGL raw mix, which is delivered to a liquids pipeline for transportation to market. The natural gas, both entering and leaving the process, consists predominantly of methane, a regulated flammable substance. The NGL mix consists of several regulated flammables, including ethane, propane, isobutane, butane, isopentane, and pentane. (c) HAZARD ASSESSMENT The worst-case release scenario (WCS) associated with a release of flammable substances in the Program 1 process at the Sterling County Gas Plant is a vapor cloud explosion involving the full inventory of the Inlet Slug Catcher, the largest process vessel containing regulated flammable components. Although this vessel normally operates with a very low liquid level, for the WCS, the vessel is assumed to be completely full of liquid containing methane and NGL components. The full vessel inventory of 26,000 lbs is assumed to instantaneously relea se, completely vaporize, and ignite, resulting in a vapor cloud explosion. The maximum distance to the 1 psi endpoint for this WCS is 0.26 mile (slightly over one-quarter mile). Although this vessel is equipped with level indicators, controls, and high level alarms to alert the plant operators of an abnormal situation, no credit for their mitigating effect was taken into account in evaluating this WCS. (d) GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM As a Program 1 process under the EPA RMP regulation, the Sterling County Gas Plant is not required to implement an accidental release prevention program. However, the Plant is also subject to the OSHA Process Safety Management (PSM) standard, which does require a prevention program. Therefore, the Plant has implemented a management system for compliance with the PSM standard. This system includes all the pertinent elements of the PSM standard; i.e., employee participation, process safety information, process hazard analysis, writt en operating procedures, employee training, contractor safety, pre-startup safety reviews, mechanical integrity, safe work practices, management of change, incident investigations, and compliance audits. In addition to the accident prevention program activities, the Sterling County Gas Plant has safety features throughout the process to help (1) quickly detect, (2) contain and control, and (3) reduce the consequences of a release of a controlled flammable substance. Such safety features include: hydrocarbon detectors with alarms and shutdowns, process relief valves that discharge to a vent system located a safe distance from the central process area, valves to permit isolation of the process, automatic shutdown systems for specific process parameters (e.g., high level, high temperature), automatic shutdown and isolation system for the entire Plant, redundant equipment, uninterruptible power supply for the process control system, atmospheric relief valves, and fire extinguishing syste ms. (e) FIVE-YEAR ACCIDENT HISTORY The Sterling County Gas Plant was commissioned in December 1994 and therefore has not yet accumulated a full five years of operating history. However, during the four and a half years of operation to date, there have been no accidental releases that resulted in deaths, injuries, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, or environmental damage. (f) EMERGENCY RESPONSE PROGRAM As a Program 1 facility, the Sterling County Gas Plant is not required under the EPA RMP regulation to maintain a written emergency response program. Pursuant to the OSHA PSM standard, the Plant does maintain an emergency response procedure for employees to respond to releases of flammable substances from the process. The primary response to other than a minor release is to execute an emergency shutdown and isolation of the Plant, evacuate all personnel, and contact the Sterling County Sheriff and Sterling City Volunteer Fire Department. Emergency procedures are reviewed with the Sheriff and the Volunteer Fire Department annually. (g) PLANNED CHANGES TO IMPROVE SAFETY Under the OSHA PSM standard, the Plant is required to conduct an initial process hazard analysis (PHA) and conduct updates and revalidations every five years. The initial PHA has been completed and the resulting action items reported to management. Responsibilities for resolving the action items have been assigned and resolutions are under way. In addition to resolving PHA action items, the Plant conducts on-going training of its operating staff in safe operating procedures and work practices. |