Baxter Compressor Station - Executive Summary
This executive summary is a brief overview of the Risk Management Program and the associated policies at the Public Service Company of Colorado (PSC) Baxter Compressor Station. |
Prevention and Response Policies
The accidental release prevention and emergency response policies are represented in the Emergency Planning and Response Sections of the Baxter Compressor Station RMP manual for the natural gas condensate system. PSC takes an active role in preventing accidental releases at all of its facilities by ensuring that its employees are properly trained in the safe operation of covered processes and the safe handling of regulated chemicals. As for emergency response, PSC has established and maintained procedures for emergency notification and response. These are reviewed with employees on a periodic basis and revised to accommodate changes in staffing when they occur.
PSC management understands its duty to provide a safe working environment and to take measures to prevent accidents
that may have an effect on the surrounding community. This understanding is reflected in procedures described and referenced in the RMP manual. Additionally, PSC has determined that, despite qualification for Program 2 compliance, it is prudent to establish and maintain Program 3 compliance as a conservative safety and business approach.
Stationary Source and Regulated Substances
The Baxter Compressor Station processes 5-10 mmscf/day of natural gas produced from the Dakota formation in western Colorado. The station provides compression, dehydration, and recovery of liquid hydrocarbon compounds (natural gas condensate). Most of the gas processed at the station is distributed for local residential use.
The triethylene glycol (TEG) dehydrator removes water from the compressed natural gas by contacting "lean" glycol with the wet gas in a contactor tower. Generally, wet gas enters the bottom of the tower and lean glycol enters the top. Water and some higher molecular weight hydrocar
bons are absorbed by the glycol stream in the contactor. The "rich" glycol exits the bottom of the tower and is fed to the regenerator, where it is heated to drive off water vapor. In the regenerator process, some hydrocarbons absorbed from the gas stream are driven off with the water vapor. The regenerated (lean) glycol returns to the contactor tower, and the dry gas exits the tower at the top.
Baxter Compressor Station employs a technology recently developed by the Gas Research Institute (GRI) to reduce emissions of benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX) from the offgas of the glycol dehydration units. The R-BTEX process uses evaporative cooling to achieve emission control rather than conventional air-cooled or glycol-cooled condensation technologies. The condenser outlet temperature average 11o F below the ambient temperature, which allows for better emission control performance without the use of auxiliary refrigeration systems.
The offgas e
nters an air-cooled condenser, which condenses a significant fraction of the gas. This vapor/liquid stream then enters the water-cooled condenser, where all components but the light gases are condensed. The three phases are then separated: the water recycled for evaporative cooling, the hydrocarbons/condensate decanted and stored for subsequent sale or use in the two condensate storage tanks, and the noncondensable gas released to the atmosphere. An auxiliary gas-fired heater prevents the condensed water from freezing in severe weather.
One of the two condensate tanks has a maximum intended inventory of 10,822 gallons (54,759 pounds), while the second condensate tank has a maximum intended inventory of 4530 gallons (22,922 pounds). Filling of the tanks is administratively limited to 80% of the tank capacity by NFPA 58 requirements, as corrected for facility elevation.
The RMP-regulated portion of the facility starts at the bypass between the dehydrator and the J-T skid. The RMP
-regulated process includes the J-T skid, the condenser, and the condensate storage. Since the BTEX (from the emission control process) and the condensate are co-mingled, the RMP process includes the piping from the condensate storage tanks back toward the BTEX emission control process. The inclusion of the BTEX emission control process stops at the check valve after the pump at the BTEX condenser. The balance of the facility is regulated under the DOT Pipeline Safety regulations Parts 190-199.
This is a remote and unmanned facility exempt from OSHA PSM requirements. However, PSC operators perform periodic system checks and maintenance at the plant.
Worst-case and alternative release scenarios have been determined after careful review of the regulation and consideration of the storage vessel configuration at the facility. For worst-case release scenario, the regulation is clear. The assumption is that the single largest container of a regulated substance (the
10,822 gallon condensate tank or 54,759 pounds of natural gas condensate) is released over a ten-minute period. No active mitigation may be considered. Worst-case meteorological conditions are also assumed to be present. Reference Table 9 of the RMP Offsite Consequence Analysis (OCA) Guidance (dated May 24, 1996) was used to determine the distance to overpressure of 1.0 psi for a vapor cloud explosion of condensate. A distance of 0.31 miles to the flammable endpoint was determined for a release of 54,759 pounds in ten minutes.
The alternative release scenario for condensate consists of a release of 6709 pounds of natural gas condensate over a one-hour period due to continued release (and potential failure open) from a 5/16 inch relief valve on the tank. No active mitigation devices were considered to influence the release scenario. The ALOHA air dispersion model was used to determine the volume of condensate that would be released in sixty minutes, and Reference Table 9 of the R
MP OCA Guidance used to calculate the distance to overpressure of 1.0 psi. A distance of 0.114 miles to the flammable endpoint was determined.
Prevention Steps for Natural Gas Condensate
The prevention program and chemical-specific prevention steps are described in detail in the Baxter Compressor Station RMP manual. The prevention program includes the Program 3 elements:
7 Employee participation, which includes provisions for active participation by station employees in the development and implementation of the facility RMP program, as well as ready access to program information
7 Process safety information, which has been collated into the RMP manual located in the Baxter Compressor Station control room
7 Process hazard analysis (PHA) - The initial PHA for the liquids extraction process was conducted in July 1998. All recommendations from the PHA have been addressed.
7 Operating procedures for the facility operations, which are available at the plant
7 Training for all facility p
ersonnel involved in the operation and maintenance of the plant operations
7 Contractor management program, which includes provisions for the evaluation and selection of contractors to work on the regulated process, exchange of hazard information, system access control, and oversight during work activities on site
7 Pre-startup safety review procedure for implementation for significant system changes to ensure that the construction and equipment installation is according to design specifications, appropriate procedures are in place and accurate, a PHA has been done and the recommendations resolved, and employees are trained prior to startup of the modified system
7 Mechanical integrity program using the "Baxter Hydrocarbon Recovery Plant" Maintenance Form to ensure that the system equipment is maintained in good and safe working condition
7 Hot work procedures to require controls as specified in the Gas Standards Manual before hot work is performed on the condensate system
of change program to ensure that proposed system changes are comprehensively evaluated before implementing the change
7 Incident investigation procedures for the investigation of any catastrophic (or potentially catastrophic) incident associated with the condensate system, using the PSCo Root Cause Investigation Report form
7 Compliance audits to be conducted at least once every three years to ensure the continued compliance of the Baxter Compressor Station condensate RMP program
Within the five-year period prior to the submittal of this RMP, there were no accidental releases of regulated flammable materials meeting the requirements of 40 CFR 68.42.
Emergency Response Program
This facility has established and maintains an emergency response program that is coordinated with local response agencies. The program is described in detail in the Emergency Planning and Response section of the RMP compliance manual and meets the requirement of 40 CFR 68.95. The goals of th
e program are to protect onsite employees from the hazardous effects of chemical releases and to minimize the effects of releases on the general public. The program is routinely reviewed and updated to reflect personnel and regulatory changes.
Planned Changes for Improved Safety
Ideas for changes to improve safety are actively sought from employees. Employee safety meetings that focus on chemical safety issues are held regularly at this facility. Employees are encouraged and trained to recognize hazards and present ideas to eliminate them or to minimize the potential consequences of those hazards.
During the development of the Baxter Compressor Station RMP program, a process hazard analysis was conducted with key employees to meet the prevention program requirements. During the session, recommendations were made for the purpose of improving safety and preventing accidental chemical releases. Each recommendation has been or will be considered for implementation. Though not all r
ecommendations may be implemented, all will be considered. The exercise has provided all affected employees with a heightened awareness of safety issues related to the covered processes.