HTI - Eau Claire - Executive Summary
EXECUTIVE SUMMARY |
HUTCHINSON TECHNOLOGY INCORPORATED
EAU CLAIRE, WISCONSIN FACILITY
a. Hutchinson Technology Incorporated's (HTI) accidental release prevention program involves policies and procedures that integrate technology, engineering, written procedures, and management practices to allow safe operation of the chlorine system. HTI follows all applicable requirements of the U.S. Environmental Protection Agency (USEPA) Prevention Program. These are summarized in Part (d) below. HTI's emergency response program includes response plans that are coordinated with emergency response activities available in the community. The emergency response program, summarized in Part (f) below, is in compliance with the USEPA's Emergency Response Program requirements.
b. HTI uses a chemical process for etching stainless steel sheets. These sheets are eventually processed into computer suspension assemblies used in the hard disk industry. HTI's Eau Claire facility uses only two chemicals inc
luded in the regulations: chlorine and propane. They are used in the following processes: (1) etchers use chlorine for oxidation purposes, (2) heating of process materials, process metal sludge, and working space use propane as an alternate fuel source, and (3) a thermal oxidizer uses propane as an alternate fuel source to burn organic air pollutants.
Chlorine is supplied to the etching process to maintain the etchant solution (iron chloride) in optimal etching condition. The chlorine is received as a liquid in DOT specified metal tanks which are stored in two specially engineered holding pits. These pits can hold a total of eight 1-ton chlorine tanks but only one tank feeds the system at a time. The liquid chlorine flows from the pits to a system that converts the liquid to a gas (vaporizer). The chlorine gas then flows to the mixing/holding tanks (called sumps) where it goes into solution to chemically maintain the etchant (iron chloride). Chlorine is fed into the etchant su
mps in a controlled manner by sensors that signal the feed rate. The storage pits, vaporizer, and delivery system contain multiple controls for redundancy, a chlorine monitoring system, and a scrubbing system that neutralizes chlorine if a leak should occur. An emergency response team is on call 24 hours a day to respond to all leaks that may occur.
Propane is used only as an alternative fuel source if the natural gas supply is interrupted. Propane is burned to heat office space, heat process materials, dry process iron-based metal sludge, and burn organic air pollutants. Liquid propane is stored in two 30,000 gallon tanks outside the main facility. These tanks are only filled to 80% capacity (24,000 gallons each) to allow for potential gas expansion. Outside the facility is a propane vaporizer and a propane air mixer. After the mixer, propane enters the same distribution system as natural gas.
c. The off-site consequences analysis includes consideration of two chemical releas
e scenarios called "worst case release" and "alternative release". The worst case scenario is defined by the USEPA as a scenario where "the owner or operator shall assume that the ... maximum quantity in the largest vessel ... is released as a gas over 10 minutes" due to an unspecified accident or failure. This scenario does not depend on how or why it occurred and does not depend on whether it has ever been observed to have happened anywhere. The requirements do not allow for any control of chlorine or propane to be assumed except for a control that is "passive" (not human, electrical, or otherwise actively activated). The alternative scenario is defined as "more likely to occur than the worst-case scenario," but there are no other requirements as to defining the quantity released, except that active controls can be included thereby reducing the likelihood of a release occurring or reducing the quantity that could potentially be released. Consequently, HTI determined the alterna
tive release scenario for chlorine would be one that could reasonably occur (even if it had not been observed) and would be one where a chlorine release could be controlled. The alternative release for propane did not take into account control except that the release is assumed to stop after 10 minutes due to active shutoff actions.
HTI's worst case scenario for chlorine is the release of one chlorine tank containing 2000 pounds. HTI's alternative release scenario is a valve failure in the storage pit releasing one pound of chlorine of which 0.75 pound is captured and controlled by the scrubber and 0.25 pound is released to the environment.
HTI's worst case scenario for propane is the release of one propane tank containing 24,000 gallons (101,800 pounds). The alternative release scenario involved a potential accident occurring during tank filling where 6600 gallons (28,000 pounds) are released to the environment.
USEPA requires that the release scenario quantities be used in a
tmospheric dispersion models to determine the distance traveled by the released chemical before its concentration decreases to a defined level. For chlorine, the defined level is the "toxic endpoint" selected by the USEPA as 0.0087 mg/L or 3 parts per million (ppm). The 3 ppm concentration for chlorine is defined by the American Industrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action." For propane, the defined level is the "vapor cloud explosion" endpoint, and this is the farthest point where either an explosion with an overpressure of 1 psi could occur or a radiant heat of 5 kilowatts per square meter for 40 seconds could develop.
The atmospheric dispersion models have to include meteorological conditions that ar
e "worse case." These worst case weather conditions include a low speed but steady wind and conditions that do not promote vertical atmospheric mixing (no turbulence) but keep the chemical low to the ground and minimally dispersed and diluted. The distances are used to determine a circle with a radius corresponding to the extent of the toxic or vapor cloud explosion endpoint within the worst case weather conditions. This radius is used to determine the residential population, schools, national/state parks and monuments, officially designated wildlife sanctuaries and refuges, and other sensitive receptors potentially affected.
Chlorine is held in two storage pits that have containment walls and numerous engineered safety features. The pits are covered with movable sealing lids to aid in keeping chlorine vapors contained. The storage pits and the building that houses the vaporizers (vaporizers change chlorine liquid into gas) are vented to a chlorine scrubber if a leak is detected
or a pull station alarm is activated. Air in the storage pits is automatically evacuated and scrubbed if a person enters it. The scrubber will contain the chlorine and neutralize it. Other control measures include safety valves, enclosures, special venting equipment for areas where the etcher tanks are located, and monitoring systems tied into alarms and chlorine shutoff valves. HTI uses computer controls to close safety valves and activate the scrubber system if chlorine levels exceed alarm levels. At 0.5 ppm chlorine in air, specially trained personnel are immediately alerted and alarms are activated. At 1.0 ppm chlorine concentration in air, the following are automatically triggered: chlorine emergency response personnel are notified, visual/audible alarms are activated, chlorine gas outlet isolation valves are closed, pressure regulating valves are closed, liquid supply isolation valves are closed, vaporizers are shut down, pressure reducing valves are closed, and ball shut
off valves are closed.
Propane is held in two aboveground tanks outside the facility and the system has numerous engineered safety features. The tanks are surrounded by a chain-link fenced with locked access. The tanks have pressure relief valves and the distribution system has automatic flow shutoff valves if the flow is too rapid. The propane filling port is over 70 feet from the tanks and the vaporizer and mixer are separated by over 50 feet from both the tank storage and the filling location.
d. The HTI accidental release prevention program is part of a long-established operating management system. Even though the facility itself has only been operating since 1995, the prevention program has been in use in HTI's Hutchinson, Minnesota facility for numerous years prior to opening the Eau Claire facility. The prevention program contains the following key components:
-- High level training for personnel involved in the chlorine system and operators of the iron chloride etcha
-- Predictive preventive maintenance programs for all components of the chlorine and propane system
-- Use of state of the art safety equipment, including chlorine monitors and control systems
-- Use of chlorine monitoring equipment and alarms
-- Use of accurate and effective operating procedures, written with the participation of employees
-- Regular process hazard analysis of equipment and procedures
-- Use of an auditing and inspection program
The prevention program also includes chlorine-specific exposure prevention steps including: (1) awareness training of the hazards and toxic properties of chlorine, (2) presence of chlorine detectors, and (3) special ventilation systems that can be manually activated when chlorine is detected. This special ventilation enhances employee safety by reducing chlorine exposure.
e. No accidental release of chlorine or propane has occurred at this facility in the past five years. The facility itself has only been in operation since 1995.
The HTI emergency response program is part of a long-established Emergency Management System. This program includes an emergency response team, decision process, response procedures, and notification plan. The emergency response program has been coordinated with the Eau Claire Fire Department, which is the key component of the Local Emergency Response Planning Committee (LEPC). The program also includes emergency response training and procedures for use, inspection, testing, and maintenance of emergency response equipment. Emergency operation and response procedure are reviewed on a periodic basis. Chlorine-specific exposure response steps are part of the program and these include: (1) awareness training of the hazards and toxic properties of chlorine, and (2) chlorine specific emergency repair training.
g. The process hazard analysis for the chlorine system was last reviewed and updated December 1998. In addition to the analysis, the following changes have been planned to im
prove the safety of the process and chlorine system:
-- implemented formal management of change system that includes a verification review of all proposed changes to enhance continued safety of the process
-- implemented documentation system for chlorine alarms
-- initiated nondestructive testing of piping on an annual basis to verify piping condition (integrity)
-- installed a vacuum break system on the chlorine distribution system as an additional measure of process control