Arapahoe Station - Executive Summary

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This executive summary is a brief overview of the Risk Management Program and the associated policies at the Public Service Company of Colorado (PSC) Arapahoe Station. 
Prevention and Response Policies 
The accidental release prevention and emergency response policies are represented in the Emergency Planning and Response Sections of the Arapahoe Station PSM/RMP manuals for the chlorine and sulfur dioxide/sulfur trioxide systems. 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 treatment 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 a 
ccidents that may have an effect on the surrounding community.  This understanding is reflected in procedures described and referenced in the RMP manuals. 
Stationary Source and Regulated Substances 
Arapahoe Station is a coal-burning electric generating station.  The regulated substances handled at this facility are chlorine and sulfur dioxide/sulfur trioxide.  The chlorine is used for cooling and process water biocidal control and is stored in one-ton containers with a maximum intended inventory of 4 containers on site.  The maximum sulfur dioxide inventory at the Arapahoe Station is 6500 gallons (73,600 pounds) in the main tank, as maintained using administrative inventory controls.  The maximum amount of SO2 in the day tank is 450 pounds.  (Sulfur trioxide is the result of the chemical reaction between the sulfur dioxide and vanadium pentoxide catalyst.  Sulfur trioxide is consumed for emission control by further chemical reactions as it is generated.) 
Release Scenarios 
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 (one-ton container of chlorine and/or 6500 gallons of sulfur dioxide) is released over a ten-minute period.  No active mitigation may be considered.  Worst-case meteorological conditions are also assumed to be present.  The RMP*Comp air dispersion model was used to determine distances to toxic endpoints.  For sulfur dioxide/sulfur trioxide, a distance of 9.1 miles to the toxic endpoint was calculated for a release of 73,600 pounds in ten minutes.  For chlorine, a distance of 1.3 miles to the toxic endpoint was determined for a release of 2000 pounds in ten minutes.  Since the sulfur dioxide release produces the largest radius of influence, the results of the worst-case release scenario for 
sulfur dioxide are included in the RMP registration. 
The alternative release scenario for chlorine consists of a release of 965 pounds of chlorine over a one-hour period due to a severed 5/16 inch pigtail on the one-ton container.  No active mitigation devices were considered to influence the release scenario.  A distance of 0.1 miles to the toxic endpoint was determined. 
The alternative release scenario for sulfur dioxide consists of a release of 55,960 pounds of sulfur dioxide over a one-hour period due to overpressurization and subsequent failure of the 2 inch safety relief valve on the sulfur dioxide storage tank.  A distance of 1.3 miles to the toxic endpoint was calculated. 
Prevention Steps for Sulfur Dioxide and Chlorine Systems 
The prevention program and chemical-specific prevention steps are described in detail in the Arapahoe Station Sulfur Dioxide/Sulfur Trioxide System and Chlorine System PSM/RMP manuals.  The prevention programs include the following elements: 
7 Employe 
e participation, which includes provisions for active participation by plant employees in the development and implementation of the plant PSM/RMP programs, as well as ready access to program information 
7 Process safety information, which has been collated into the PSM/RMP manuals located in the Arapahoe Station Controlled File Document Room 
7 Process hazard analyses (PHAs) - The initial PHA for the chlorine system was conducted in July 1994, while the initial PHA for the sulfur dioxide/sulfur trioxide system was conducted in June 1995.  The PHAs were revalidated in March 1999.  All recommendations from the PHAs have been addressed, or will be addressed by June 30, 1999. 
7 Operating procedures for both processes, which are included in the system PSM/RMP manuals 
7 Training for all personnel involved in the operation and maintenance of the chlorine and sulfur dioxide/sulfur trioxide systems 
7 Contractor management policy, which is not to allow contractors to operate or maintain the chlor 
ine or sulfur dioxide systems 
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 through the facility SSR system to ensure that the chlorine and sulfur dioxide/sulfur trioxide systems equipment is maintained in good and safe working condition.  Facility personnel conduct daily visual inspections of the chlorine and sulfur dioxide systems.  The date and equipment included in 7.7b and c address the most recent major PM activity. 
7 Hot work procedures to require the evacuation of the regulated chemicals from the system equipment (using the Arapahoe Station Clearance Procedures) before hot work is performed on the chlorine and/or sulfur dioxide/sulfur trioxide 
7 Management 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 chlorine and/or sulfur dioxide/sulfur trioxide systems, 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 Arapahoe Station chlorine and sulfur dioxide/sulfur trioxide PSM/RMP programs.  A PSM audit was conducted on these processes in 1996; a PSM/RMP audit was conducted on the systems in 1999.  Issues identified in the audit were, or are being, addressed. 
7 Trade secrets provisions allowing contractors and employees or their representatives access to system information 
Accident History 
Within the five-year period prior to the submittal of this RMP, there were no accidental releases of either sulfur dioxi 
de/sulfur trioxide or chlorine 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 PSM/RMP compliance manuals and meets the requirement of 40 CFR 68.95.  The goals of the 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 
During the development of the Arapahoe Station PSM/RMP program, process hazard analyses were conducted with key employees to meet the prevention program requirements.  During these sessions, 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 recommendations 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.
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