Wisconsin Public Service Corp, Pulliam Power Plant - Executive Summary
SULFUR DIOXIDE RISK MANAGEMENT PROGRAM (RMP) |
WISCONSIN PUBLIC SERVICE CORPORATION (WPS)
PULLIAM POWER PLANT
GREEN BAY, WI
June 14, 1999
The WPS Pulliam power plant is a public utility company located in Green Bay, WI. The plant uses sulfur dioxide to condition flue gas. The sulfur dioxide is converted to sulfur trioxide which is injected into the boiler flue gas stream lowering the flyash resistivity and thereby, improving the electrostatic precipitator particulate collection efficiency. Since the plant stores more than the threshold quantity of 5,000 lbs of sulfur dioxide onsite, the sulfur dioxide process is the only process which is subject to USEPA Risk Management Program (RMP) regulations which are codified in 40CFR Part 68. Sulfur dioxide is an easily liquefiable colorless gas with a characteristic irritating pungent odor that is listed by the USEPA as a regulated toxic substance for accidental release prevention. Sulfur dioxide can be safely ut
ilized under regular plant conditions if handled appropriately with care.
Sulfur Dioxide Process
Liquefied sulfur dioxide is brought into the plant by tanker trailers from an outside vendor. The plant stores the sulfur dioxide in a single pressure vessel which is heated to 40-50?F when the ambient temperature is lower and at a maximum operational pressure of approximately 26 psig. Gas-phase sulfur dioxide is passed through a converter to produce sulfur trioxide which is used to condition the boiler flue gas by lowering the flyash resistivity.
Accidental Release Prevention and Emergency Response Policy
The WPS Pulliam plant is committed to manage and operate the plant in accordance with relevant USEPA regulations and general good operating practices to ensure minimization of the risk of an accidental release of sulfur dioxide from the SO2 process. The state of Wisconsin has adopted the OSHA (Occupational Safety and Health Administration) Process Safety Management (PSM) program. In
response to this regulation, the plant has proactively implemented an OSHA PSM program for the sulfur dioxide process. In order to ensure periodic monitoring and continual evaluation of the RMP/PSM program elements being implemented at the plant, the WPS Pulliam plant has instituted a command-and-control emergency response (ER) organizational structure within the plant. In addition to their regular duties, members of this structure have additional RMP/PSM-related responsibilities to consolidate the long-term management of the RMP/PSM program.
Worst-case Release Scenario
The worst-case release scenario was assumed to be the complete loss of contents of the 60-ton sulfur dioxide storage tank which is located outdoors next to the main building in the vicinity of the ESP superstructure. In this analysis, no applicable passive mitigation measures were accounted for. Typically,
the USEPA guidance for defining a worst-case release scenario for unmitigated release of gas is to estimate the
release rate over a 10-minute period of the largest quantity resulting from a pipe or vessel failure. Thus, the sulfur dioxide emission rate from the worst-case release scenario was given as the
loss of 120,000 lbs of sulfur dioxide averaged over a 10-minute period, i.e., 12,000 lbs/min. The worst-case accidental release was modeled using USEPA's public-domain RMP*Comp model to determine the distance to the toxic endpoint of 0.0078 mg/lit (or 3 ppm). The toxic endpoint distance does go offsite. It should be noted that any potential offsite impact due to the accidental release is greatly minimized on account of the location of the plant which is buffered by Green Bay on the north and east.
Although the worst-case release scenario assumed the complete loss of contents for the 60-ton sulfur dioxide storage tank, for the last couple of years the tank has only been filled up to 40 tons. It should also be noted that WPS Pulliam plant employees regularly inspect the sulfur dioxide storag
e tank for potential leaks and overall structural integrity. This effort minimizes the chance that the sulfur dioxide storage tank would fully discharge its contents in an accidental release that would result in an offsite impact.
Alternative Release Scenario
Based on discussions with WPS personnel, the following alternative release scenario was modeled - a complete rupture of the 1.25-inch diameter line from the sulfur dioxide storage tank to the main building. The line rupture was assumed for a duration of 15 minutes till appropriate mitigation could be applied. This active mitigation would be manifest as an emergency shutoff valve which would be activated by trained plant personnel wearing PPE with the onset of a preset line pressure departure.
The above alternative release was modeled using USEPA's public-domain RMP*Comp model to determine the maximum distance to the toxic endpoint of 0.0078 mg/lit (or 3 ppm). No passive mitigation was specified. The toxic endpoint distance does
go offsite, but only nominally. As in the case of worst-case releases, it should be noted that any potential offsite impact due to the accidental release is greatly minimized on account of the location of the plant which is buffered by Green Bay on the north and east.
It should also be noted that WPS Pulliam plant employees regularly inspect piping around the sulfur dioxide storage tank for potential leaks and overall structural integrity. This effort minimizes the chance that a line from the sulfur dioxide storage tank would rupture and discharge significant quantities of sulfur dioxide in an accidental release that would result in an offsite impact.
Accidental Release Prevention Program
The WPS Pulliam plant has proactively implemented an OSHA Process Safety Management (PSM) program (codified in 29CFR Part 1910.119) for the sulfur dioxide process. The scope of the PSM program encompasses various facets of accident release prevention, e.g., it engenders employee participation, inc
reases employee awareness about the hazards of handling sulfur dioxide, establishes safe standard operating procedures and enhances access to process safety information. In February 1999, the plant performed a PSM audit and a HAZOP process hazards analysis (PHA) on the sulfur dioxide system with the help of an outside consultant in order to review existing operating procedures, equipment maintenance schedules, operational safeguards and identify some action items to render the process safer. The WPS Pulliam plant management has already initiated activities to implement some of the recommended action items. Following the PHA, the plant invested in developing a written PSM program with the help of an outside consultant. The written PSM program provides the procedural backbone for various safe operability functions (i.e., continual review of safe operating procedures, review of mechanical integrity of equipment, improved maintenance schedules, increased training, better access to proces
information and hazard awareness for both employees and onsite contractors, and effective emergency response planning) and thereby, allows the plant to maintain, review and evaluate the program on a periodic basis.
In addition, the plant will soon invest in completing an upgrade of the sulfur dioxide safety system. Additional check valves and emergency shutoffs will be installed to mitigate accidental releases of sulfur dioxide. These system upgrades should complement the organizational and procedural aspects of the prevention program which will hopefully minimize the risk of an accidental release of sulfur dioxide from the WPS Pulliam plant process.
Five-year Accident History
The WPS Pulliam plant has had no reportable sulfur dioxide releases over the past five years. The plant has been operational since the turn of the century. In the past five years there have been no serious onsite injuries, no offsite injuries and no offsite environmental damage due to accidental sulf
ur dioxide releases from the WPS Pulliam plant process.
Emergency Response Program
The WPS Pulliam plant has already instituted emergency procedures for responding to and handling accidental releases of hazardous chemicals stored and used onsite such as, sulfur dioxide. These emergency procedures are documented in the plant's Procedures Manual. As part of the written PSM
program, the WPS Pulliam plant has adopted the aforesaid emergency procedures as being adequate and compliant in satisfying the need for Emergency Planning and Response to conform to applicable PSM regulations. Since it would be counterproductive to develop a separate emergency response plan under RMP regulations, the plant has developed an Emergency Response Program (ERP) that has adopted the existing emergency procedures and added elements to ensure compliance with relevant RMP Part 68 requirements of the RMP rule.
The WPS Pulliam plant has developed a well delineated emergency response (ER) organization under t
he command of the Site Emergency Director (SED, typically the Plant Shift Supervisor on duty) or his designee with a set of clearly defined responsibilities and procedures for ER team members. ER team members are regularly appraised, receive updated training and conduct practice emergency response drills on a scheduled basis. Besides onsite training and practice, ER team members are responsible for coordinating emergency response activities (e.g., agency notification) with local emergency responders such as the Brown County LEPC and Green Bay Fire Department through established channels of communication. The ERP contains detailed notification procedures that are followed and practiced by ER team members.
The plant has also developed detailed evacuation procedures customized for the plant in the event of an accidental release of sulfur dioxide. Upon notification of evacuation orders from the SED, the evacuation team will initiate and supervise evacuation procedures for both onsite em
ployees and contractors. To ensure the efficacy of the ERP, the plant has designated a READYROOM which will be the operational nerve center and communications center during an accidental release emergency. The READYROOM is equipped with the appropriate emergency response equipment in readiness for immediate application.
Changes to Improve Safety
The WPS Pulliam plant is committed to supporting the emergency response (ER) organization and its prescribed functions in the event of an accidental release. ER team members are drawn from the existing employee pool and the organizational concept fosters pride and emphasizes concerns for safe operation of the plant. Ultimately, any safe operation is a grassroots movement that must be nurtured within the plant perimeter with the employees themselves. The addition of a well defined ER organization at the WPS Pulliam plant operating in conjunction with local emergency responders such as the Brown County LEPC and the Green Bay Fire Department sho
uld greatly alleviate any safety concerns about handling sulfur dioxide at the plant.
In addition, the WPS Pulliam plant will soon be completing an upgrade of the sulfur dioxide safety system. Additional check valves and emergency shutoffs will be installed to mitigate accidental releases of sulfur dioxide. Thus, in addition to new and improved training and organizational changes, this equipment and mitigation system upgrades to the sulfur dioxide system demonstrates the commitment to safety that WPS has made to both the Pulliam plant employees and the surrounding community.