Howmet Ti-Cast - Executive Summary
EXECUTIVE SUMMARY |
EPA's new rule concerning the "Chemical Accident Prevention Provisions: Risk Management Program (RMP Rule)" of the Clean Air Act Amendments of 1990, requires Howmet Corporation to document its already existing programs that protect the environment and neighborhoods that surround Howmet Corporation facilities. As such, a Risk Management Program (RMP) has been implemented for the Whitehall facilities. This effort is a summary of the RMP needed to address the issues generated by the use of hydrofluoric acid at the Whitehall facilities.
Howmet Corporation has always endeavored to be a responsible neighbor in all municipalities in which facilities are located. The Howmet Corporation "Environmental Procedures Manual" Policy EPM001 expresses that general sentiment as it commits the corporation to:
Comply with all pollution control laws.
Identify and manage environmental hazards that are not yet regulated.
Eliminate pollution to the fullest e
xtent possible through the use of the best pollution control technology economically available.
Establish emergency response programs for all Howmet facilities that use hazardous materials.
Train workers regarding hazardous materials and incident response.
Inform the public, when appropriate, regarding the company's environmental protection activities.
Review on a regular basis the adequacy of Howmet's environmental protection program, and make improvements as necessary.
This Risk Management Program submittal is another part of Howmet Corporation's responsible stewardship.
The Whitehall Operations of Howmet Corporation are located within the city of Whitehall, Michigan. These facilities are primarily involved in investment casting, coating, and heat treating of aircraft components and parts, titanium alloy production, ceramic and wax products manufacturing, and research and development activities for the aircraft industry. The majority of these operations
are in operation 5-7 days per week. On a typical day, over 2,500 people are on the various sites.
Various hazardous materials are used in the manufacturing processes. Included among them is hydrofluoric acid. This material is used to chemically mill cast titanium aircraft components. Hydrofluoric acid is regulated as a toxic substance under section 112(r) of the Clean Air Act. Howmet Corporation has therefore, developed this RMP to address those requirements.
HYDROFLUORIC ACID PROCESS DESCRIPTION
70% hydrofluoric acid is transported to the Ti-Cast facility (Plant 5) in Whitehall by tanker truck and is transferred to a single 6,500-gallon outdoor, storage tank. This tank has a limited maximum storage capacity of 5,000 gallons. This steel tank is located on a coated concrete pad and is contained within a coated concrete dike that can hold 150% of the tank's 6,500 gallon design volume (9,750-gallons) in the event of a spill from the tank.
The acid is transfered from the tank
to the adjoining building. An argon gas blanket is used to force the acid through piping to the hydrofluoric acid process tanks. There the acid is diluted to a 10% or less concentration. At this point, the acid no longer presents air emissions concern due to the low acid concentration.
Subsequently, titanium alloy castings are immersed in this 10% or less hydrofluoric acid solution to remove brittle, oxygen enriched layer found on the surface of the castings. This treatment improves the durability of these aerospace application castings.
EPA's Risk Management Program requires facilities that store greater than 1,000 pounds of hydrogen fluoride in a process, in concentration of 50% hydrofluoric acid solution or greater, to implement an RMP program to reduce the risks inherent in the use of this material. The Ti-Cast storage tank system holds a maximum of 5,000 gallons of 70% HF acid. This has an equivalent weight of 35,600 lbs. of hydrogen fluoride and therefore, exceeds RMP pla
nning threshold requirements. Since the potential exists for off-site consequences from a release of hydrogen fluoride vapors, the storage area falls under RMP Program 2 prevention requirements.
The intent of this document is to inform the public that a spill of 70% hydrofluoric acid could affect the community to some degree depending on the extent of the release of acid. At present, 70% acid can only be accidentally released from two fixtures, the 6,500-gallon storage tank and its associated piping.
Worst Case Scenario
The worst case release of 70% hydrofluoric acid is described here as the Worst Case Scenario. Such a release could occur if the entire maximum operating contents (5,000-gallons) of 70% hydrofluoric acid were released from the storage tank to the diked containment area. This dike limits the surface area of the acid pool and reduces the amount of vapors that will be emitted. Thus only 6.16 pounds per minute of hydrogen fluoride vapors will evolv
e to the air in the event of a worst case spill. This is based on computations using EPA's RMP Comp modeling software.
EPA has determined that hydrogen fluoride fumes can have a toxic effect down to a concentration as low as 0.016 mg/L. The extent of maximum toxic effect or the "toxic endpoint" for the emission of hydrogen fluoride vapors to the atmosphere, that would be released under worst case conditions, was calculated to extend in a circle to a 0.30 mile radius from the storage tank location. Again, this calculation was made using the EPA's RMP Comp dispersion modeling software.
A residential population of up to 72 people was estimated to lie within this radius as well as a part of the Shoreline Elementary School property (but not the school itself) and a part of the Whitehall Industrial Park property. No environmental receptors are located within this radius. U.S. Bureau of the Census, LandView III Software was used to calculate the affected residential population.
e of the concerns over the release of any hydrofluoric acid vapors, let alone the vapors from the unlikely Worst Case Scenario release, certain precaution have been taken by Howmet Corporation in addition to the use of a dike around the storage tank. Personnel have been trained on how to respond to spill or leak events and a maintenance program is in effect to prevent the occurrence of spills or leaks. The hydrofluoric acid tank is monitored daily by facility staff and by plant security personnel. Additionally, the tank is inspected annually for wall thickness and hardness. Tests have always shown the tank to be structurally sound.
Alternative Release Scenario
Though a Worst Case Scenario release is possible, its occurrence is highly improbable. Therefore, EPA asks all affected facilities to generate an Alternative Release Scenario that describes a more probable release occurrence that can impact areas beyond facility boundaries.
Since the 70% hydrofluoric acid storage system con
sists of only a storage tank and its associated piping, a probable alternative occurrence was determined to be a leak in the tank or piping. A review of the storage systems accident history revealed that only two incidents (September 24, 1996 and May 3, 1997) have occurred in the last five years.
During the first incident, only 2 to 5 gallons of 70% acid leaked from a pipe flange into the HF acid tank containment dike. No effects were noted on-site or off-site from this leak to individuals, property or the environment other than a reported minor "tingling of the skin" on the leg of one emergency responder. This individual was treated as a precaution. The second incident involved a squirt of acid released during a maintenance operation. A maintenance worker was burned on the arm by the HF acid and subsequently, treated.
Neither of these leak events provides what is felt to be a good alternative scenario, so management is using a hypothetical event that could have off-site impacts
. The chosen Alternative Release Scenario consists of an event in which 1 gallon per minute of 70% hydrofluoric acid is leaked from a pipe, over a one hour period before discovery, to an area outside the storage tank containment dike. EPA's modeling software, RMP Comp was used to calculate this event's toxic endpoint. This endpoint was found to extend in a circle to a 0.20 mile radius from the storage tank location.
A residential population of 32 people was estimated to lie within this radius as well as a part of the Whitehall Industrial Park property. No environmental receptors are located within this radius.
Again, due to Howmet Corporation's concerns about this 70% acid, certain precautions have been taken minimize spill impacts; personnel are incident response trained, a maintenance program is in effect, and daily area inspections are performed.
ACCIDENTAL RELEASE PREVENTION PROGRAM and CHEMICAL SPECIFIC PREVENTION STEPS
The RMP rule requires Howmet Corporation to impleme
nt a Program 2 level Risk Management Program. The following narrative briefly describes the elements of The Howmet Corporation Risk Management Program for the Ti-Cast hydrofluoric acid storage system.
Howmet Corporation maintains a variety of technical documents that are used to help ensure the safe operation of the hydrofluoric acid storage system. Included are Material Safety Data Sheets that describes the inherent hazards and recommended precautions for the management of this material. Safety information materials are supplied to appropriate personnel and area hospitals that define specialized HF acid exposure treatment procedures. Contractors are trained in HF safety procedures.
Howmet Corporation performs and periodically updates hazard reviews of the HF acid storage process to help identify and control process hazards. Checklists are used to guide the hazard process review.
Ti-Cast developed and maintains operating p
rocedures to define how tasks related to storage system operations are performed. The operating procedures are used to train employees and to serve as reference guides for appropriate actions to take during normal operation and process upsets.
Facility personnel are trained and tested in the operating procedures to help ensure safe and effective performance of their assigned tasks. A training documentation file is maintained to help ensure that refresher training is provided, as necessary.
Ti-Cast carefully maintains the acid storage system. The maintenance program includes procedures to safely guide workers in their maintenance tasks, worker training and in maintenance procedures. An inspection and testing program is used to help identify equipment deterioration and damage before the equipment fails.
Howmet Corporation performs periodic compliance audits of HF storage system to verify that it is operating in compliance with the requirements
of the RMP rule. A compliance audit report is prepared after each audit, and any deficiencies noted in the audit report are corrected in a timely manner.
Howmet Corporation investigates all incidents that could reasonably have resulted in a serious injury to personnel, the public, or the environment. Employees are trained to identify and report any incident requiring investigation. An appropriate investigation team is assembled, and the investigation is initiated shortly thereafter. The results of the investigation are documented, recommendations are resolved, and appropriate process enhancements are implemented.
HF Acid-Specific Prevention Steps
Industry standards are followed to help ensure safe handling of aqueous HF acid. The vendor supplies 70% HF acid via a Department of Transportation (DOT) approved tank truck and follows DOT standards when loading the HF acid storage tank. The storage tank design and construction are consistent with American Nat
ional Institute Standards. Workers who perform operations involving HF acid receive training emphasizing safe handling procedures for HF acid developed by AlliedSignal, Inc.
Five Year Accident History
Howmet Corporation maintains a 5-year accident history for the HF storage system that fulfills the requirements of the RMP rule. The RMP rule defines accidents to include events that result in deaths, injuries, or significant property damage on-site; or known deaths, injuries, evacuations, sheltering-in-place, property damage, or environmental damage off-site. The Ti-Cast operation HF storage system had two accidents (incidents) in the past 5 years. These accidents were previously noted in the Alternative Release Scenario portion of this report. The releases resulted in a potential injury to the skin of one spill responder and an arm burn to a maintenance worker in a separate incident. Both individuals were treated.
Emergency Response Programs
The Howmet Corporation Whitehall faci
lities have a written emergency response plan that complies with the RMP rule and with other federal contingency plan regulations. This plan has been communicated to local emergency response officials through the local police and fire departments. Regular dialogue is maintained between Howmet Corporation and the local officials, and Howmet Corporation provides appropriate information to them.