Hutchinson Technology Incorporated - Executive Summary |
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EXECUTIVE SUMMARY HUTCHINSON TECHNOLOGY INCORPORATED HUTCHINSON, MINNESOTA 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. Chlorine is supplied to the etching process to mainta in 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 sumps 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. c. The off-site consequences analysis includes consider ation of two chlorine release 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 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 deter mined that the alternative release scenario 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. HTI's worst case scenario 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. USEPA requires that the release scenario quantities be used in atmospheric dispersion models to determine the distance traveled by the released chlorine before its concentration decreases to a defined level. This 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 indivi duals 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." The atmospheric dispersion models have to include meteorological conditions that are "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 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. The chlorine is held in two storage pits that have containment walls and numerous engineered safet y 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 shutoff valves are closed. d. The HTI accidental release prevention program is part of a long-established operating management system. The prevention program contains the following key components: -- High level training for personnel involved in the chlorine system and operators of the iron chloride etchant. -- Predictive preventive maintenance programs for all components of the chlorine 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 has occurred at this facility in the past five years. f. 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 Hutchinson Fire Department, which is the key component of the Local Emergency Response Planning Committee (LEPC), known in Minnesota as the Community Awareness and Emergency Response (CAER) Committee. 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. Since December 1998, HTI has updated the process hazard analysis for the chlorine system. These are planned changes to improve safety of the process and chlorine system. The update has occurred in the following ways: -- prepared updated piping and instrument diagrams for a more accurate picture of the 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 -- conducted 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 |