MEMC - ST Peters - Executive Summary
This Risk Management Plan (RMP) fulfills the requirements of the Clean Air Act's Section 112(r) for the three regulated chemicals at MEMC Electronic Materials, Inc.'s (MEMC's) St. Peters Plant (MEMC - St. Peters): anhydrous hydrogen chloride, hydrogen, and trichlorosilane. MEMC is a leader in silicon technology, providing polished and epitaxial silicon wafers for the electronic integrated circuit (chip) manufacturers.
ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES
MEMC's overall approach to chemical safety can be summarized in its Corporate Environmental, Safety, and Health Policy: "We will strive to achieve an injury-free and healthful workplace for our employees, work towards zero-effect on the surrounding environment, and ensure the safety of our community neighbors." MEMC has emphasized accident prevention from the start. It believes in the old adage, "A ounce of prevention is worth a pound of cure." All the programs and procedures required by the
Risk Management Program had previously been implemented by MEMC. It is MEMC policy to proactively adhere to all applicable federal, state, and local laws. MEMC - St. Peters works closely with Central County Fire and Rescue. If an emergency with the potential to effect the community were to occur, it is MEMC - St. Peters' policy to call Central County Fire and Rescue.
MEMC has always put safety first, before quality, delivery, production, and cost. This is indoctrinated into all employees: safety, then quality, then delivery, then production, and then cost. They all must be done in that order of priority.
The effectiveness of these policies is shown in that MEMC - St. Peters has never had an accidental release with offsite consequences in the 40-year history of the facility. Awards showing MEMC - St. Peters' commitment to safety and the environment are: recipient of Liberty Mutual's Gold Award for Safety, recipient of the first Missouri Governor's Pollution Prevention Award, rec
ipient of Industry Weeks' Top 10 Plant Award, recipient of Missouri Quality Award, recipient of Missouri Energy Conservation Award, and recipient of MEMC President's Award.
PLANT DESCRIPTION AND REGULATED SUBSTANCES HANDLED
MEMC Electronic Materials, Inc.'s St. Peters plant (MEMC - St. Peters) in O'Fallon, Missouri produces silicon wafer for the electronic industry. It is one of the largest silicon wafer manufacturing plants in the world. Located on 200 acres in O'Fallon, Missouri, MEMC employs over 1,800 people with an annual payroll of $55 million.
The silicon wafer manufacturing begins with other locations converting sand into ultra-pure silicon. MEMC - St. Peters first converts the ultra-pure silicon into silicon crystal rods, then cuts the rods into wafers. The cutting results in surface damage that must be removed to provide a surface where the electronic device, chip, can be built by depositing layers on top of the wafer. After lapping, etching, and polishing remove the
surface damage, some of the wafers get an epitaxial layer in the EPI process. This process uses the regulated hazardous substances covered by this RPM. The regulated substances are anhydrous hydrogen chloride, hydrogen, and trichlorosilane.
Anhydrous hydrogen chloride is received in and used from 21,000-pound tube trailers and 600 pound cylinders. The tube trailers consist of 7 separate 3,000-pound hydrogen chloride cylinders and are kept in an enclosed room. There is usually one trailer onsite. The room has a location for a second trailer to be used when the first trailer is about out of hydrogen chloride. The room has several hydrogen chloride sensors and a water deluge system. If the hydrogen chloride sensors detect the presence of any hydrogen chloride in the room, the deluge system is activated to absorb and remove the hydrogen chloride from the air. The storage and usage locations of the 600-pound cylinders have the same sensors and deluge systems.
The hydrogen is store
d in a 20,000-gallon cryogenic, double wall tank that can hold a maximum of 11,820 pounds of hydrogen. Blast walls located on the east and south sides of the tank would reduce the effect of an explosion on anyone outside the plant. The low density of hydrogen causes it to rise quickly and disperse. This greatly reduces the likelihood of the hydrogen exploding.
THE WORST-CASE RELEASE SCENARIO
The worst-case scenario for a hazardous material release at MEMC - St. Peters was calculated at the complete discharge of a full 3,000-pound hydrogen chloride cylinder (tube) in 10 minutes in accordance with the definition provided in the United States Environmental Protection (EPA) guidance for RMP development. The release would be inside the hydrogen chloride room but the deluge system would not be activated to scrub the released hydrogen chloride, and the plant's Emergency Response Team and the Central Count Fire and Rescue would not respond to reduce the effect of the release. The condit
ions of the scenario such as weather and windspeed are those given in EPA's Off-Site Consequence Analysis Guidance. The area of potential impact was determined using Areal Location of Hazardous Atmospheres (ALOHA), modeling software developed by the United States National Oceanic and Atmospheric Administration and the EPA.
The result of the Off-Site Consequence Analysis, indicated that the release could travel 1.7 miles downwind from the hydrogen chloride room under the specific weather conditions before dispersing into the atmosphere to a harmless concentration. Since the winds can come from any direction around the plant, the possible effected area is a circle with a radius of 1.7 miles. According to the 1990 census there are 2,900 people living within the 1.7-mile radius circle. In the event of the worst-case release described above, only a small part of the area inside the circle would be effected by a release, the area downwind of the release. The actual area effected would
look similar to a cigar pointing downwind from the source to the edge of the circle. Anyone not located within the narrow band of the plume would not be adversely effected by the release.
This type of release would only occur if the cylinder was to fail open causing all the liquid to escape. Since the cylinder is over 1 inch thick of special steel, the likelihood of such an incident occurring is very minimal.
The government's ALOHA model was used instead of the RMP*Comp model, although the RMP*Comp model gave similar results. RMP*Comp model is a quick and easy model to use. Because of the effected population MEMC elected to use a more complex and difficult model for more accurate results. The ALOHA model is also used by the Central County Fire and Rescue, the St. Charles-Warren Counties Hazmat Team, St Charles County Local Emergency Planning Committee, St. Charles County Emergency Management Agency, and most of the emergency responders in the area.
The worst-case release scenar
io for a flammable material at MEMC - St. Peters is the complete release of the hydrogen tank when it is completely full of 11,820 pounds of hydrogen followed by an explosion of the hydrogen in accordance with EPA's Off-Site Consequence Analysis Guidance. The area of potential impact was determined using RMP*Comp, modeling software developed by the United States National Oceanic and Atmospheric Administration and the EPA.
The result of the Off-Site Consequence Analysis, indicated that the area effected by a one (1) psi over pressure could be 0.25 miles, without considering the blast walls. The hydrogen tank has blast walls on the east and south sides that would greatly reduce the effect of the explosion in those directions. Since there are no blast walls on the north or west sides, MEMC did not assume a reduction in the area effected by the explosion because of the blast walls.
Hydrogen is much lighter than air and experience is that it immediately rises, which reduces the likelih
ood of an explosion. Also the blast walls on the east and south sides protect the potentially effected off-site area.
THE ALTERNATIVE RELEASE SCENARIO
The alternative release scenario is, by definition, a more likely release scenario than the worst-case. Engineered controls, such as the hydrogen chloride detection system, alarm and automatic activation of the deluge system are considered in the analysis. The type of system failure selected for the alternative release at MEMC - St. Peters that could have an offsite effect is the leaking of a hydrogen chloride line from a hydrogen chloride cylinder (tube). The rate of leakage selected was the largest amount estimated by the supplier and the suppliers other users. The conditions of the scenario such as weather and windspeed are those given in EPA's Off-Site Consequence Analysis Guidance. The area of potential impact was determined using ALOHA modeling software.
The release would be inside a hydrogen chloride room where the deluge
system would scrub most of the released hydrogen chloride. The result of the Off-Site Consequence Analysis, indicated that, the release could travel 0.02 miles downwind. That distance is would be close to MEMC's property line, but not off MEMC's plant site.
A more likely possible scenario for a flammable material release at MEMC - St. Peters with the most significant effect is a broken liquid hydrogen line between the tank and its vaporizer. This would result in leaking liquid hydrogen. The rate of release was determined from the "Risk Management Plan Guidance Document for Bulk Liquid Hydrogen Systems" for the Compressed Gas Association Inc. If the leaked hydrogen produced a vapor cloud explosion, the area effected by a one (1) psi over pressure could be 0.06 miles, without considering the blast walls. The 0.06 miles is only outside the plant to the south side of the hydrogen tank. The blast walls on the east and south would keep the effects of a hydrogen explosion from leavin
g the plant site.
ACCIDENTAL RELEASE PREVENTION PROGRAM
MEMC - St. Peters has constantly improved its accidental release prevention program. Parts of the program are detailed, written operating instructions that are followed by trained and knowledgeable technicians. The operation instructions start with a safety section to stress "Safety First" and has safety as a main theme. MEMC - St. Peters has a detailed collection of process safety information to insure safe chemical handling and usage. Job Safety Analyses are also used. Job Safety Analyses are thorough reviews of jobs to identify the hazards and risks and to ensure that the jobs are done safely.
MEMC - St. Peters has had a tank and vessel inspection program and a safety relief valve testing program for years. They are part of the mechanical integrity program to insure that each piece of equipment is capable of fulfilling its requirements. There are procedures for opening and returning to service hazardous material proce
ss lines and equipment. Fire Prevention Plans, Hot Work Permits Procedures, sprinkler systems, and firewalls help eliminate the threat of fire.
All accidents and incidents at MEMC - St. Peters are thoroughly investigated. MEMC - St. Peters has a Safety Suggestion and Safety Work Order Programs to help ensure employees participation in safety. MEMC - St. Peters knows that safe employees are a must if the plant is to be profitable. All chemicals are registered before being brought into the plant to insure safe handling procedures and proper disposal.
MEMC - St. Peters works closely with Central County Fire and Rescue. They respond to plant emergencies in less than 3 minutes with three units. The plans for the anhydrous hydrogen chloride trailer room, hydrogen tank, and trichlorosilane tanks were reviewed with them. Central County Fire and Rescue reviewed the systems and response plans again before startup.
FIVE-YEAR ACCIDENT HISTORY
MEMC - St. Peters has never had an accident
involving any hazardous chemicals that caused deaths, injuries, property or environmental damage, evacuation, or shelterings in place in the nearly 40-year history of the facility.
EMERGENCY RESPONSE PROGRAM
In an event of an emergency involving any of the hazardous material at MEMC - St. Peters, the response will be handled by the plant's Emergency Response Team, department and plant personnel, and Central County Fire and Rescue, as needed. The plant's Emergency Response Team receives 40 hours of training when they join the team and 4 hours of training monthly. Several times a year the team reviews responses to various emergencies. The plant's alarms go to the security desk in the front lobby where security call the Emergency Response Team and/or Central County Fire and Rescue as needed.
MEMC - St. Peters and Central County Fire and Rescue review emergency responses and have joint training and exercises.
PLANNED CHANGES TO IMPROVE SAFETY
Because of the past work there are no p
lanned changes to improve safety at this time.