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MSHA and OSHA Memorandum








The Mine Safety and Health Administration (MSHA), U.S. Department of Labor, and the Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, have entered into this agreement to delineate certain areas of authority, set forth factors regarding determinations relating to convenience of administration, provide a procedure for determining general jurisdictional questions, and provide for coordination between MSHA and OSHA in all areas of mutual interest.


1. The Federal Mine Safety and Health Act of 1977, Pub. L. 91-173 as amended by Pub. L. 95-164 (Mine Act), authorizes the Secretary of Labor to promulgate and enforce safety and health standards regarding working conditions of employees engaged in underground and surface mineral extraction (mining), related operations, and preparation and milling of the minerals extracted.

2. The Occupational Safety and Health Act of 1970 (OSHAct) gives the Secretary of Labor authority over all working conditions of employees engaged in business affecting commerce except those conditions with respect to which other Federal agencies exercise statutory authority to prescribe or enforce regulations affecting occupational safety or health. The OSHAct also provides that States may operate their own occupational safety and health programs under a plan approved by the Secretary.

3. This agreement is entered into to set forth the general principle and specific procedures which will guide MSHA and OSHA. The agreement will also serve as guidance to employers and employees in the affected industries in determining the jurisdiction of the two statutes involved. The general principle is that as to unsafe and unhealthful working conditions on mine sites and in milling operations, the Secretary will apply the provision of the Mine Act and standards promulgated thereunder to eliminate those conditions.

However, where the provisions of the Mine Act either do not cover or do not otherwise apply to occupational safety and health hazards on mine or mill sites (e.g., hospitals on mine sites) or where there is statutory coverage under the Mine Act but there exist no MSHA standards applicable to particular working conditions on such sites, then the OSHAct will be applied to those working conditions. Also, if an employer has control of the working conditions on the mine site or milling operation and such employer is neither a mine operator nor an independent contractor subject to the Mine Act, the OSHAct may be applied to such an employer where the application of the OSHAct would, in such a case, provide a more effective remedy than citing a mine operator or an independent contractor subject to the Mine Act who does not, in such circumstances, have direct control over the working conditions.


1. Section 4 of the Mine Act gives MSHA jurisdiction over each coal or other mine and each operator of such mine. Section 3(d) defines "operator" and includes in that definition independent contractors performing construction at mines.

2. Section 3(h)(1) of the Mine Act gives MSHA jurisdiction over lands, structures, facilities, equipment, and other property used in, to be used in, or resulting from mineral extraction or used in or to be used in mineral milling. This includes the authority to regulate the construction of such facilities, structures and other property. Further, Section 3(h)(1) directs the Secretary of Labor, in making a determination of what constitutes mineral milling, to give due consideration to the convenience of administration resulting from the delegation to one Assistant Secretary of all authority with respect to the health and safety of miners employed at one physical establishment.

3. Appendix A provides more detailed descriptions of the kinds of operations included in mining and milling and the kinds of ancillary operations over which OSHA has authority. Notwithstanding the clarification of authority provided by Appendix A, there will remain areas of uncertainty regarding the application of the Mine Act, especially in operations near the termination of the milling cycle and the beginning of the manufacturing cycle.

4. Under section 3(h)(1), the scope of the term milling may be expanded to apply to mineral product manufacturing processes where these processes are related, technologically or geographically, to milling. Or, the term milling may be narrowed to exclude from the scope of the term processes listed in Appendix A where such processes are unrelated, technologically, or geographically, to mineral milling. Determinations shall be made by agreements between MSHA and OSHA.

5. The following factors, among others, shall be considered in making determinations of what constitutes mineral milling under section 3(h)(1) and whether a physical establishment is subject to either authority by MSHA or OSHA: the processes conducted at the facility, the relation of all processes at the facility to each other, the number of individuals employed in each process, and the expertise and enforcement capability of each agency with respect to the safety and health hazards associated with all the processes conducted at the facility. The consideration of these factors will reflect Congress' intention that doubts be resolved in favor of inclusion of a facility within the coverage of the Mine Act.

6. Pursuant to the authority in section 3(h)(1) to determine what constitutes mineral milling considering convenience of administration, the following jurisdictional determinations are made:

a. MSHA jurisdiction includes salt processing facilities on mine property; electrolytic plants where the plants are an integral part of milling operations; stone cutting and stone sawing operations on mine property where such operations do not occur in a stone polishing or finishing plant; and alumina and cement plants.

b. OSHA jurisdiction includes the following, whether or not located on mine property: brick, clay pipe and refractory plants; ceramic plants; fertilizer product operations; concrete batch, asphalt batch, and not mix plants; smelters and refineries. OSHA jurisdiction also includes salt and cement distribution terminals not located on mine property, and milling operations associated with gypsum board plants not located on mine property.

7. "Borrow Pits" are subject to OSHA jurisdiction except those borrow pits located on mine property or related to mining. (For example, a borrow pit used to build a road or construct a surface facility on mine property is subject to MSHA jurisdiction). "Borrow pit" means an area of land where the overburden, consisting of unconsolidated rock, glacial debris, other earth material overlying bedrock is extracted from the surface. Extraction occurs on a one-time only basis or only intermittently as need occurs, for use as fill materials by the extracting party in the form in which it is extracted. No milling is involved, except for the use of a scalping screen to remove large rocks, wood and trash. The material is used by the extracting party more for its bulk than its intrinsic qualities on land which is relatively near the borrow pit.

8. When any question of jurisdiction between MSHA and OSHA arises, the appropriate MSHA District Manager and OSHA Regional Administrator or OSHA State Designee in those States with approved plans shall attempt to resolve it at the local level in accordance with this Memorandum and existing law and policy. Jurisdictional questions that can not be decided at the local level shall be promptly transmitted to the respective National Offices which will attempt to resolve the matter. If unresolved, the matter shall be referred to the Secretary of Labor for decision.


In the interest of administrative convenience and the efficient use of resources the agencies agree to the following enforcement procedures:

1. When OSHA receives information concerning unsafe or unhealthful working conditions in an area for which MSHA has authority for employee safety and health, OSHA will forward that information to MSHA.

2. When MSHA receives information regarding a possible unsafe or unhealthful condition in an area for which MSHA has authority and determines that such a condition exists but that none of the Mine Act's provisions with respect to imminent danger authority or any enforceable standards issued thereunder provide an appropriate remedy, then MSHA will refer the matter to OSHA for appropriate action under the authority of the OSHAct.

3. When MSHA receives information regarding unsafe or unhealthful working conditions in an area for which OSHA has authority for employee safety and health, MSHA will forward that information to OSHA for appropriate action.

4. Each agency agrees to notify the other of the disposition of enforcement matters forwarded to it for appropriate action.

5. OSHA will not conduct general inspections of mine or mill sites except with respect to those areas set forth in this Agreement and its Appendix A.


1. The Office of Legislative and Interagency Affairs in OSHA and the Office of the Assistant Secretary in MSHA shall serve as liaison points to facilitate communication and cooperation between the participating organizations.

2. MSHA and OSHA will endeavor to develop compatible safety and health standards, regulations, and policies with respect to the mutual goals of the two organizations including joint rulemaking, where appropriate. This interagency coordination may also include cooperative training, shared use of facilities, and technical assistance.


Subagreements to accomplish the purposes set by this agreement may be developed and modified, as deemed necessary, by OSHA and MSHA. Such subagreements will include specific provisions for detailing the coordination between the agencies.


This Interagency Agreement shall continue in effect unless terminated by mutual consent of both parties or terminated by either party upon thirty (30) days advance written notice to the other and approved by the Secretary in either case.

This agreement will become effective on the date of the last signature and it supersedes the Memorandum of Understanding between OSHA and MESA dated April 22, 1974.

Mine Safety and Health Administration
Assistant Secretary of Labor
for Mine Safety and Health
Dated: March 29, 1979

Occupational Safety and Health Administration
Assistant Secretary of Labor
for Occupational Safety and Health
Dated: March 29, 1979


Secretary of Labor
Dated: March 29, 1979





"Coal or other mine" is defined in the Mine Act as:

"(A) an area of land from which minerals are extracted in nonliquid form or, if in liquid form, are extracted with workers underground, (B) private ways and roads appurtenant to such area, and (C) lands, excavations, underground passageways, shafts, slopes, tunnels and workings, structures, facilities, equipment, machines, tools, or other property including impoundments, retention dams, and tailing ponds, on the surface or underground, used in, or to be used in, or resulting from, the work of extracting such minerals from their natural deposits in nonliquid form, or if in liquid form with workers underground, or used in, or to be used in, the milling of such minerals, or the work of preparing coal or other minerals, and includes custom coal preparation facilities."

"Miner" is defined in the Mine Act as:

"Any individual working in a coal or other mine."

"Operator" is defined in the Mine Act as:

"Any owner, lessee, or other person who operates, controls, or supervises a coal or other mine or any independent contractor performing services or construction at such mine."

"Mining and Milling":

Mining has been defined as the science, technique, and business of mineral discovery and exploitation. It entails such work as directed to the severence of minerals from the natural deposits by methods of underground excavations, opencast work, quarrying, hydraulicking and alluvial dredging. Minerals so excavated usually required upgrading processes to effect a separation of the valuable minerals from the gangue constituents of the material mined. This latter process is usually termed "milling" and is made up of numerous procedures which are accomplished with and through many types of equipment and techniques.

Milling is the art of treating the crude crust of the earth to produce therefrom the primary consumer derivatives. The essential operation in all such processes is separation of one or more valuable desired constituents of the crude from the undesired contaminants with which it is associated.

A CRUDE is any mixture of minerals in the form in which it occurs in the earth's crust. An ORE is a solid crude containing valuable constituents in such amounts as to constitute a promise of possible profit in extraction, treatment, and sale. The valuable constituents of an ore are ordinarily called valuable minerals, or often just minerals; the associated worthless material is called gangue.

In some ores the mineral is in the chemical state in which it is desired by primary consumers, e.g., graphite, sulphur, asbestos, talc, garnet. In fact, this is true of the majority of nonmetallic minerals. In metallic ores, however, the valuable minerals in their natural state are rarely the product desired by the consumer, and chemical treatment of such minerals is a necessary step in the process of beneficiation. The end products are usually the result of concentration by the methods of ore dressing (milling) followed by further concentration through metallurgical processes. The valuable produce of the oredressing treatment is called Concentrate; the discarded waste is Tailing.*

Specific Examples of MSHA Authority


Following is a list indicating mining operations and minerals for which MSHA has authority to regulate.

Mining Operations
Underground Mining
Open Pit Mining

*Preface, p.v., Handbook of Mineral Dressing, Arthur P. Taggart, Second Printing, March 1947, John Wiley and Sons, Inc.

Solution Mining (Precipitate & Leaching)

Dredging (When the primary purpose of the dredging operation is to recover metal or nonmetallic minerals for milling and/or sale or use.)


Ponds - Brine Evaporation

Auger Mining



Metals:                                         Nonmetals:
(Included but not limited to)        (Included but not limited to)

 Alumina                                        Abrasives
 Antimony                                      Aplite
 Bauxite                                         Asbestos
 Beryl                                             Barite
 Bismuth                                         Baron
 Chrome                                          Bromine
 Cobalt                                            Calcium Chloride
 Copper                                           Clay
 Gold                                               Mica
 Iron                                                Mineral Pigments
 Lead                                              Oil Shale
 Manganese                                     Peat
 Mercury                                          Perlite
 Molybdenum                                   Potash
 Nickel                                            Pumice
 Rare Earths                                    Potash Rock
 Silver                                             Diatomite
 Titanium                                         Feldspar
 Tungsten                                        Fluorspar
 Uranium                                         Gilsonite
 Vanadium                                       Graphite
 Zinc                                               Gypsum
 Zirconium                                       Kyanite
 Sodium Compounds
 Talc, Soapstone, and
Subgroups of Nonmetals  
(Sand and Gravel,and Crushed and Dimension Stone Industries) 

Sand                                            Marble
Gravel                                          Native Asphalt
Cement                                          (impregnated stone & sand)
Gabbro                                          Quartizite
Gneiss                                          Schist
Lime                                            Slate
Limestone                                       Taprock or Diabase

Milling - MSHA Authority

Following is a list with general definitions of milling processes for which MSHA has authority to regulate subject to Paragraph B6 of the Agreement. Milling consists of one or more of the following processes: crushing, grinding, pulverizing, sizing, concentrating, washing, drying, roasting, pelletizing, sintering, evaporating, calcining, kiln treatment, sawing and cutting stone, heat expansion, retorting (mercury), leaching, and briquetting.


Crushing is the process used to reduce the size of mined materials into smaller, relatively coarse particles. Crushing may be done in one or more stages, usually preparatory for the sequential stage of grinding, when concentration of ore is involved.


Grinding is the process of reducing the size of a mined product into relatively fine particles.


Pulverizing is the process whereby mined products are reduced to fine particles, such as to dust or powder size.


Sizing is the process of separating particles of mixed sizes into groups of particles of all the same size, or into groups in which particles range between maximum and minimum sizes.


Concentrating is the process of separating and accumulating economic minerals from gangue, or the upgrading of ore or minerals.


Washing is the process of cleaning mineral products by the buoyant action of flowing water.


Drying is the process of removing uncombined water from mineral products, ores, or concentrates, for example, by the application of heat, in air-actuated vacuum type filters, or by pressure type equipment.


Roasting is the process of applying heat to mineral products to change their physical or chemical qualities for the purpose of improving their amenability to other milling processes.


Pelletizing is the process in which finely divided material is rolled in a drum, cone, or an an inclined disk so that the particles cling together and roll up into small spherical pellets. This process is applicable to milling only when accomplished in relation to, and as an integral part of, other milling processes.


Sintering is the process of agglomerating small particles to form larger particles, cakes or masses, usually by bringing together constituents through the application of heat at temperatures below the melting point.

This process is applicable to milling only when accomplished in relation to, and as an integral part of, other milling processes.


Evaporating is the process of upgrading or concentrating soluble salts from naturally occurring, or other brines, by causing uncombined water to be removed by application of solar or other heat.


Calcining is the process of applying heat to mineral materials to upgrade them by driving off volatile chemically combined components and effecting physical changes.

This process is applicable to milling only when accomplished in relation to, and as an integral part of, other milling processes.

Kiln Treatment

Kiln Treatment is the process of roasting, calcining, drying, evaporating, and otherwise upgrading mineral products through the application of heat.

This process is applicable to milling only when accomplished in relation to, and as an integral part of, other milling processes.

Sawing and Cutting Stone

Sawing and cutting stone is the process of reducing quarried stone to smaller sizes at the quarry site when the sawing and cutting is not associated with polishing or finishing.

Heat Expansion

Heat expansion is a process for upgrading material by sudden heating of the substance in a rotary kiln or sinter hearth to cause the material to bloat or expand to produce a lighter material per unit of volume.


Retorting is a process usually performed at certain mine sites, and is accomplished by heating the crushed material in a closed retort to volatilize the metal, material or hydrocarbon which is then condensed and recovered as upgraded metal, material or hydrocarbon.


Leaching is the process by which a soluble metallic compound is removed from a mineral by selectively dissolving it in a suitable solvent, such as water, sulfuric acid, hydrochloric acid, cyanide, or other solvent, to make the compound amenable to further milling processes.


Briquetting is a process by which iron ore, or other pulverized mineral commodities, are bound together into briquettes, under pressure, with or without a binding agent, and thus made conveniently available for further processing.

MSHA Authority Ends - OSHA Authority Begins

Subject to Paragraph B.5. of the Agreement, the following are types of operations which may be on or contiguous to mining and/or milling operations listed above, over which MSHA does not have authority to prescribe and enforce employee safety and health standards, and over which OSHA has full authority, under the Act, to prescribe and enforce safety and health standards regarding working conditions of employees.

OSHA regulatory authority commences as indicated in the following types of operations:

Gypsum Board Plant

If the plant is located on mine property, commences at the point when milling, as defined, is completed, and the gypsum and other materials are combined to enter the sequential processes necessary to produce gypsum board. If not located on mine property, OSHA has authority over entire plant.

Brick, Clay Pipe and Refractory Plants

Commences after arrival of raw materials at the plant stockpile.

Ceramic Plant

Commences after arrival of the clay and other additives at the plant stockpile.

Fertilizer Products

Commences at the point when milling, as defined, is completed, and two or more raw materials are combined to produce another product. Note that a "kiln", as it relates to these products for roasting and drying, is considered to be within the scope of the milling definition.

Asphalt-Mixing Plant

Commences after arrival of sand and gravel or aggregate at the plant stockpile.

Concrete Ready-Mix or Batch Plants

Commences after arrival of sand and gravel or aggregate at the plant stockpile.

Custom Stone Finishing

Commences at the point when milling, as defined, is completed, and the stone is polished, engraved, or otherwise processed to obtain a finished product and includes sawing and cutting when associated with polishing and finishing.


Commences at the point when milling, as defined, is completed, and metallic ores or concentrates are blended with other materials and are thermally processed to produce metal.


Commences at the point when milling, as defined, is completed, and metals are recovered by means of electrochemical processes.

Salt and cement distribution terminals not located on mine property.


Commences at the point when milling, as defined, is completed, and material enters the sequential processes to produce a product of higher purity.