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CONTROLLING MERCURY HAZARDS IN GOLD MINING: A BEST PRACTICES TOOLBOX APPENDIX A:
REPORTS ON MERCURY VAPOR CONTROL COMPLETED BY MSHA"S DENVER SAFETY AND HEALTH TECHNOLOGY CENTER, 1992-1996 Weems, G. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Newmont Gold Company, Mine ID Number: 26-00500, Carlin, NV. Field Report Number D7562T524. February, 1992.
Weems, G. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. American Barrick Company, Mine ID Number: 26-01089, Elko, NV. Field Report Number D7858T548. August, 1993. Lynham, M. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Amax Gold Company, Mine ID Number: 26-01932, Winnemucca, NV. Field Report Number D7999T579. August, 1993. Trabant, G. and M. Lynham. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Pegasus Gold Corporation, Mine ID Number: 10-01839, Burley, ID. Field Report Number D8163T606. October, 1994. Trabant, G. and S. Kneipple. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Newmont Gold Company, Mine ID Number: 26-00500, Carlin, NV. Field Report Number D8248T612. May, 1995. Trabant, G. and M. Lynham. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Castle Mountain Joint Venture, Mine ID Number: 04-04918, Searchlight, CA Field Report Number D8266T617. May, 1995. Lynham, M. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Santa Fe Pacific Gold Corporation, Mine ID Number: 26-01942, Golconda, NV. Field Report Number D8342T626. June, 1996. Lynham, M. and T. Lloyd. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Getchell Gold Corporation, Mine ID Number: 26-01801, Golconda, NV. Field Report Number D8359T631. August, 1996. Lynham, M. and T. Lloyd. Mine Safety and Health Administration, Denver Safety and Health Technology Center, Toxic Materials Division. Mercury Vapor Control Evaluation. Echo Bay Minerals Company, Mine ID Number: 26-02051, Battle Mountain, NV. Field Report Number D8366T633. August, 1996. APPENDIX B: PROCEDURES TO CLEAN-UP MERCURY CONTAMINATED EQUIPMENT AND WORK AREAS I. Introduction This section addresses the actions necessary to remove mercury contamination from equipment and work areas at gold processing facilities. General cleanup procedures are followed by step-by-step procedures suggested for effective remediation. The recommended cleanup procedures consist of the following five steps:
These steps are most applicable to sealed, painted and metal surfaces in the refining and retort rooms. A list of materials and equipment necessary for cleanup of mercury contamination is contained in Appendix "C". The following is a discussion of each of step. II. Clean-Up Procedures Protective Clothing During cleanup operations, personnel must wear protective gloves, rubber boots, coveralls and respirators. Cartridge type respirators should be worn to limit mercury vapor exposures. Proper training in respirator inspection and use is necessary to assure that the units function properly. After each day, disposable clothing is to be sealed in plastic bags and placed in the disposal drum(s) provided. Personal Hygiene At the end of each day, all persons involved in cleanup operations should shower and scrub thoroughly with soap. Any contaminated clothing or rubber boots to be reused should be vacuumed, decontaminated with a mercury complexing agent and placed in lockers used only for work clothes (street clothing should not be placed in the same locker). During actual cleanup operations, the following procedures and precautions should also be used:
III. Step-By-Step Procedure As previously stated, the cleanup is designed to eliminate or reduce mercury contamination. In some cases where porous materials are present, complete decontamination is impossible; therefore, items such as rugs and wood surfaces should be removed and disposed of in accordance with State and Federal environmental regulations. Porous concrete and cinder blocks also cannot be completely decontaminated and should be sealed with an epoxy paint to facilitate cleaning. On most metal and painted surfaces, the cleanup activities described below will eliminate or reduce the mercury levels significantly. All materials should be checked for the presence of mercury after cleanup. If mercury still exists, remedial actions (such as application of a sealant) are recommended. In other areas (e.g., where insulation has been exposed to mercury vapor), replacement or covering with a smooth, nonporous surface may be necessary. Vacuum The mercury vacuum cleaner is designed specifically to cleanup mercury and mercury contaminated materials. The vacuum is usually made up of the following components:
The vacuum is designed to collect liquid mercury, contain particulate materials and adsorb mercury vapors. The vacuum cleaner must be used to clean all exposed surfaces. Extension tubes can be used to reach all beams and lights from ladders or scaffolding. When appropriate, the crevice or other attachments are used for cracks, corners, and other hard to get places. The manufacturer's instructions should be carefully read and followed. The extension tubes should be washed (with a mercury complexing agent) after use and stored with the vacuum in an exhausted closet. If mercury remains on aluminum extension tubes it will amalgamate (combine) with the aluminum and become a potential source of mercury vapor. Typically, the carbon filter on the vacuum has a capacity for up to two years of use. However, to avoid a potential problem and to maximize this equipment's effectiveness, the exhaust from the vacuum should periodically be monitored using a mercury vapor analyzer. The centrifugal droplet collection device should be checked periodically during cleanup and its contents sealed in a plastic bag and placed in the disposal drum. The disposable dust collector bag should be periodically checked and when full should also be sealed in a plastic bag and placed in the disposal drum. All items placed in the drums should be recorded on the disposal form. After use, the vacuum should be disassembled, the bag replaced and the filters cleaned. Mercury Sponge (optional) After vacuum cleanup of all surfaces, difficult to clean locations where mercury may collect such as cracks may be scrubbed with mercury sponges. The sponge is a zinc scrubbing pad which is activated with sulfamic acid and a wetting agent. Any free mercury present will amalgamate with the zinc. After use, the sponge should be sealed in a plastic bag and placed in the designated disposal drum. Experience has shown that the sponge does not effectively adsorb mercury that has already amalgamated with other metals, therefore, the use of the sponge is probably best reserved for use with free mercury. Washing Surfaces All nonporous surfaces (metal, sealed or painted surface) should be washed and scrubbed with fresh water to remove the dirt. The surface should then be scrubbed with a sodium thiosulfate solution (3% by weight in water). The thiosulfate will complex with and remove the mercury. Finally, the surfaces should be rinsed with fresh water to remove the thiosulfate solution. Absorptive Material A carbon that has been activiated with iodine can be used to absorb material. At the end of the previous steps, the material should be spread on cracks and put in hard to reach places. The material will adsorb any mercury present as vapor or finely divided microdroplets. When applied, the material should be left overnight. Revacuuming After a sufficient period (about 12 hours), the mercury complexing agent should be vacuumed using the mercury vacuum cleaner. All waste material collected should be sealed in a plastic bag and placed in the disposal drum. IV. Evaluation of Decontamination Effectiveness An important part of the cleanup program is determining the level at which cleanup was effective. An evaluation should be performed using the following techniques:
Chemical Indicator (Optional) A chemical mercury indicator may be applied to selected surfaces during cleanup operations (preferably at the same time that the mercury complexing agent is applied). The indicator will turn pink or black (depending on the mercury concentrations) if mercury vapors are being evolved from the surfaces. Experience has shown that only large concentrations of mercury can be detected using the indicator. Scrape Samples Scrape samples of paints, concrete and metal should be obtained from various locations in the work areas and placed individually in a funnel flask. If possible, a minimum of two to three gram samples should be used. The flask should then be sealed, connected to the mercury vapor analyzer and heated to approximately 135 degrees Fahrenheit (57 degrees Celsius). If mercury vapor is evolved from the material, its presence will be detected by this procedure. Although not quantitative, this procedure will provide the necessary information to determine if the material still contains mercury. If desired, samples may be sent to a laboratory for quantitative analysis. Air Monitoring After cleanup, the mercury concentration in the ambient air should be monitored. The values obtained should be compared to dosimeter measurements before, during and after cleanup and ambient air levels before and during cleanup. This comparison is extremely important because selected surfaces or materials may still contain some mercury that contaminates small areas while the overall air concentration has been reduced to an acceptable level. As part of this procedure, a comparison should be made of the values obtained prior to and after cleanup from scrape samples and ambient air. Depending upon the values obtained, the following future actions may be required:
The actions required will depend upon sitespecific information and input from onsite personnel. Any proposed requirements may consist of a combination of all three actions listed above or may be combined with personal hygiene and monitoring programs such as limiting exposure time in the room or changing operational procedures. Records of sampling results and pertinent sampling information should be maintained. V. Disposal Waste items will require secured disposal:
When the use of the equipment or clothing is completed or when it has become contaminated, it should be placed in plastic bags and sealed, then placed in disposal drums. The drum should be lined with teflon and labeled "MERCURY CONTAMINATED WASTE". The drum should be clamped shut so that it is sealed when not in use. After a drum is full, it should be handled and disposed of according to Federal and State requirements. I. Equipment
II. Cleanup Procedures 1. Vacuum all surfaces to remove droplets of elemental mercury and mercury contaminated debris. 2. Remove porous materials that cannot be completely cleaned or sealed with an epoxy paint and dispose of the debris properly. 3. Seal porous materials, such as cinder block or concrete with an epoxy paint. 4. Clean cracks and crevices that contain elemental mercury with a zinc scrubbing pad. 5. Wash all nonporous surfaces with fresh water to remove dirt, wash with a sodium thiosulfate solution, and rinse with fresh water to remove the thiosulfate. 6. Spread mercury complexing agent or similar material on cracks and hard-to-reach places to adsorb micro-droplets of mercury and leave overnight; then remove the material using a mercury vacuum cleaner. 7. Seal all waste material in a plastic bag and place the bag in disposal a drum. 8. Use chemical indicators, scrape samples, and air monitoring to evaluate decontamination effectiveness. 9. Reclean areas that are still sources of mercury vapor, as indicated by the above step. APPENDIX C: SOURCES OF EQUIPMENT AND SUPPLIES
APPENDIX D: SELECTED MSHA STANDARDS 56/57.5001 Exposure limits for airborne contaminants. (a) Respirators approved by NIOSH under 42 CFR part 84 which are applicable and suitable for the purpose intended shall be furnished and miners shall use the protective equipment in accordance with training and instruction. (b) A respirator program consistent with the requirements of ANSI Z88.2-1969, published by the American National Standards Institute and entitled "American National Standards Practices for Respiratory Protection ANSI Z88.2-1969,” approved August 11, 1969, which is hereby incorporated by reference and made a part hereof. This publication may be obtained from the American National Standards Institute, Inc., 1430 Broadway, New York, New York 10018, or may be examined in any Metal and Nonmetal Health District Office of the Mine Safety and Health Administration. (c) When respiratory protection is used in atmosphere immediately harmful to life, the presence of at least one other person with backup equipment and rescue capability shall be required in the event of failure of the respiratory equipment. 56/57.15001 First aid materials Adequate first-aid materials, including stretchers and blankets shall be provided at places convenient to all working areas. Water or neutralizing agents shall be available where corrosive chemicals or other harmful substances are stored, handled, or used. 56/57.15006 Protective equipment and clothing for hazards and irritants. Special protective equipment and special protective clothing shall be provided, maintained in a sanitary and reliable condition and used whenever hazards or process or environment, chemical hazards, radiological hazards, or mechanical irritants are encountered in a manner capable of causing injury or impairment. 56/57.16003 Storage of hazardous materials. Materials that can create hazards if accidentally liberated from their containers shall be stored in a manner that minimizes the dangers. 56/57.16004 Containers for hazardous materials. Hazardous materials shall be stored in containers of a type approved for such use by recognized agencies; such containers shall be labeled appropriately. 56/57.16012 Storage of incompatible substances. Chemical substances, including concentrated acids and alkalies shall be stored to prevent inadvertent contact with each other or with other substances, where such contact could cause a violent reaction of the liberation of harmful fumes or gases. 56/57.18002 Examination of working places. (a) A competent person designated by the operator shall examine each working place at least once each shift for conditions which may adversely affect safety and health. The operator shall promptly initiate appropriate action to correct such conditions. (b) A record that such examinations were conducted shall be kept by the operator for a period of one year, and shall be made available for review by the Secretary or his authorized representative. (c) In addition, conditions that may present an imminent danger which are noted by the person conducting the examination shall be brought to the immediate attention of the operator who shall withdraw all persons from the area affected (except persons referred to in Section 104 (c) of the Federal Mine Safety and Health Act of 1977) until the danger is abated. 56/57.20011 Barricades and warning signs. Areas where health or safety hazards exist that are nor immediately obvious to employees shall be barricaded, or warning signs shall be posted at all approaches. Warning signs shall be readily visible, legible, and display the nature of the hazard and any protective action required. 56/57.20012 Labeling of toxic materials. Toxic materials used in conjunction with or discarded from mining or milling of a product shall be plainly marked or labeled so as to positively identify the nature of the hazard and the protective action required. 56/57.20014 Prohibited areas for food and beverages. No persons shall be allowed to consume or store food or beverages in a toilet room or in any area exposed to a toxic material. | ||||||||||||||||||||||||||||||||||||||||||||
