METAL AND NONMETAL MINES
METAL AND NONMETAL MINES
ON ENFORCEMENT OF 30 CFR
PARTS 56/57 .... SAFETY AND HEALTH STANDARDS - SURFACE/UNDERGROUND METAL AND NONMETAL MINES
Subpart B Ground Control
56.3130 Wall, Bank, and Slope Stability
This standard requires that mining methods that will maintain wall, bank, and slope stability shall be used in places where persons work or travel in performing their assigned tasks.
Consistent with this standard, MSHA requires that a bench located immediately above the area where miners work or travel be maintained in a condition adequate to retain material that may slide, ravel, or slough onto the bench from the wall, bank, or slope. However, there may be instances in which the ground conditions at a mine present a particular hazard. In such situations, more than one bench above the area where miners work or travel must be maintained in a condition adequate to retain material that may come onto the bench from the wall, bank, or slope. It is normally expected that one bench will be so maintained, but if more than one bench above the area where miners work or travel is necessary, only the number of benches necessary to provide adequate protection will be required to be maintained.
A bench may be considered adequate even if material has accumulated on the bench. In determining whether a bench with material accumulated on it is adequate, consideration shall be given, but not limited to the following factors: (a) the method of mining; (2) the amount of material on the bench; (3) the amount and rate of material coming onto the bench; (4) the angle of the bank, wall, or slope, particularly if it is close to the angle of repose; (5) the composition of the wall, bank, or slope; and (6) the configuration of the bench.
If the bench immediately above an area where miners work or travel is no longer adequate to catch material, and sending miners and equipment onto the bench to clean it presents a greater hazard than raveling or sloughing, cleaning is not appropriate. Examples of such circumstances may be were there are concerns about the stability of the bench itself, concerns that removal of material from the bench would destabilize the slope immediately above the bench, or concerns that the equipment could overtravel the edge of the bench. Where the bench cannot be safely cleaned, other measures shall be taken to protect miners. Other measures may include placing a berm at the base of the wall, bank, or slope to prevent the overtravel of material into the area where miners work or travel or ceasing mining in the affected area.
56/57.3200 Correction of Hazardous Conditions
This standard prohibits work or travel, other than corrective work, in areas where hazardous ground conditions exist. Posting of a warning against entry is required until corrective work is completed if workers could enter the area inadvertently. In addition, barriers are required if the area is left unattended prior to the completion of the corrective work. The mode of travel in the area must be evaluated to determine what type of barrier is appropriate to "impede" unauthorized entry. Examples of barriers would be piles of muck, piles of large boulders or a timber barricade. These barriers would have openings to allow access for persons who are correcting the hazardous conditions. These posting and barrier requirements do not apply to underground face areas under development where the corrective work is performed on a continuing basis as a part of the mining cycle, and the only workers exposed are those engaged in the corrective activity.
56/57.3203 Rock Fixtures
This standard contains the requirements for installation and testing of all rock fixtures and accessories used for ground support. In all cases where rock fixtures are selected as the method used to support ground, they must meet the requirements of 56/57.3203.
All bolts tensioned by torquing must be within the torque range set out in paragraph (f)(1). Mine operators are required to test the first, tenth and last bolt installed in each work area during the shift as a check on whether or not the torquing requirements are being achieved. When the testing process reveals that a fixture is not properly torqued, steps must be taken to determine the extent of defective installation and to correct all improperly installed fixtures.
The ground conditions in many active face areas require the installation of only a few bolts during each blasting cycle. Testing of the first and last bolts in each work area will help ensure the integrity of the ground in these instances. Where large numbers of bolts are installed on a continuing basis, testing of the first, tenth and last bolt in each work area would normally provide the frequency of testing necessary to identify a bolting problem and enable the operator to take corrective action.
The mine operator must certify that all tests required by this standard have been conducted. In the case of testing of the ASTM bolts and accessories by the manufacturer of the devices, the mine operator's certification responsibility is satisfied by obtaining a copy of the manufacturer's certification and making it available to the inspector.
The correction of improperly installed fixtures will also help to ensure compliance with standard 56.3130 which requires that wall, bank and slope stability be maintained at surface mines where miners are exposed, and standard 57.3360, which requires that ground support systems at underground mines be designed, installed and maintained to control the ground where miners are exposed.
56/57.3401 Examination of Ground Conditions
Under this standard the mine operator must designate the persons experienced in ground control who will examine and test the ground. These persons may be supervisors or miners. Mine management retains the responsibility for examination and testing of ground conditions. The standard also specifies when examinations and tests must be made.
The 57.3401 requirement for examination of travelways is not applicable to escape routes from underground mines. The examination and maintenance of underground escape routes are specifically addressed in 57.11051, Escape Routes.
56/57.3430 Activity Between Machinery or Equipment and the
Highwall or Bank
This standard is applicable to surface mines and surface areas of underground mines. It addresses the hazards which exist when persons work or travel near a highwall or bank and their escape from a fall or slide of material could be hindered by the machinery and equipment in their escape path.
If escape could be hindered, no work or travel is permitted. If, however, the machinery or equipment poses no hindrance, the standard is not applicable. Consideration must be given to: the height of the wall or bank; the distance between the equipment and wall or bank; the size and positioning of the equipment; the location of the worker in relation to the escape route; and any surrounding noise levels or distractions which could prevent the detection of falling ground.
Where machinery or equipment becomes disabled near a highwall or bank, the equipment operator can often safely exit on the side away from the hazard. If this is not possible, exit on the wall side is permitted. Remounting on the wall side may also become necessary in order to reposition or move the equipment to a safe location for repairs. When the equipment is not removed for repair, it must be repositioned at the site so that workers will not be exposed to fall of ground hazards from which their escape is hindered.
57.3461 Rock Bursts
This standard requires mine operators to notify MSHA of a rock burst within twenty-four hours of occurrence. It also requires that a rock burst control plan be implemented within ninety days of the occurrence. The plan must be updated as conditions change or controls are altered. When innovations are added to an existing rock burst control program, the changes are considered an "update" in accordance with paragraph (c) of the standard and are to be included in the plan at that time.
Subpart C Fire Prevention and Control
57.4057 Underground Flame-Resistant Trailing Cables
This standard requires that underground trailing cables be flame- resistant in accordance with 30 CFR 18.64. Section 18.64(f) specifies that an acceptance marking be imprinted on the cable for identification purposes.
The attached list, "Manufacturers of Cables with MSHA Acceptance Numbers," can be used to verify accepted cables. An approval number will be accompanied by letter designations which denote the governmental division granting approval -- MSHA, MESA, BM (Bureau of Mines), P (Pennsylvania Bureau of Mines), etc. Cables which are marked with the prefix "P" for Pennsylvania approval shall be considered acceptable if the number is followed by an MSHA, MESA or BM notation.
When a trailing cable is imprinted with a series of numbers or letters which do not appear on the attached list, the Approval and Certification Center (A&CC) at Triadelphia, West Virginia shall be contacted for assistance in determining the acceptability of the cable. This includes newly manufactured cables which may be determined to be acceptable subsequent to the printing of the attached list.
Inquiries regarding the approval of underground trailing cables should be directed to the MSHA Approval and Certification Center, Triadelphia, West Virginia (304) 547-0400 or FTS 723-1451.
57.4460(b) Underground Storage of Vehicles Containing Gasoline
Gasoline-powered vehicles may be operated in underground mines under limited circumstances as defined in 30 CFR 57.4461. These vehicles and the gasoline in their tanks are considered to be "in use." The underground "storage" of gasoline is prohibited in any quantity by 30 CFR 57.4460(b).
The storage of any vehicle in an active underground mine having gasoline in its tank shall be considered a violation of 30 CFR 57.4460(b) and an appropriate citation shall be issued.
When a gasoline-powered vehicle is being operated underground as mining equipment in compliance with 30 CFR 57.4461, the vehicle and the gasoline in its tank are considered to be "in use" and are not in violation of part 57.4460(b).
56/57.4503 Conveyor Belt Slippage and Detection System
This standard requires that belt conveyors shall be equipped with a detection system capable of automatically stopping the drive pulley in the event of excessive slippage of the belt, where ignition of the belt could create a hazard to personnel. The detection systems required by this standard are available on an over-the-counter basis from several manufacturers.
For surface operations, areas that could create a hazard to
personnel in the event of a fire include the following:
- Surge tunnels.
- Conveyor belts located in areas where other combustible or flammable materials are stored within 25 feet of the belt. This is to prevent a conveyor belt fire from spreading and becoming a large and more serious fire. The policy is consistent with distances used as safeguards in the electrical and explosives standards.
- Any restricted area where a conveyor belt fire could hinder the escape of personnel who normally work in that area.
This standard requires that surface buildings or structures in which persons work shall have a sufficient number of exits to permit prompt escape in case of fire. The standard applies to buildings or structures where persons normally work.
Excluded from the requirements of this standard are those areas where persons work infrequently, e.g., change rooms, surge tunnels, toilet facilities, and cafeterias. "Exits" may be doorways, passageways, windows, or other openings that lead out of the building or structure. While the standard uses the word"exits", a single exit may be acceptable where it permits the prompt escape of persons in case of fire.
When considering what constitutes sufficient exits, the following factors should be considered: (1) the size of the exit(s); (2)the height of the exit(s) from the ground; (3) the size of the building; (4) the number of persons who normally work in the area serviced by the exit(s); (5) the nature of the operations; (6)the presence of potential fire hazards; (7) the type of materials with which the building is constructed, e.g., wood, brick, block,stone, metal, concrete; and (8) the presence of fire suppression devices or the availability of fire extinguishers.
56/57.4531 Surface Buildings or Rooms for Flammable or
Combustible Liquid Storage
57.4533 Surface Buildings or Structures in Vicinity of Mine Openings
Standard 56/57.4531 requires that certain ventilation and construction measures be included in buildings and rooms where flammable or combustible liquids are stored on the surface, if the storage is located within 100 feet of a work station.Standard 57.4533 requires that surface buildings and similar structures located within 100 feet of certain mine openings be constructed with specified fire protection characteristics.
Several compliance alternatives are permitted for achieving appropriate fire protection in both standards. If a mine operator chooses alternative (b)(1) of 30 CFR 56/57.4531 or alternative (b) of 57.4533, difficulty may be encountered in determining what types of construction meet a fire-resistance rating of at least one hour. MSHA enforcement personnel may also need assistance in recognizing one hour fire resistant construction due to the numerous combinations of techniques and materials which may be used.
Clarification in this regard is contained in the section on "Fire Safety in Building Design and Construction," pages 6-60 through 6-79 of the Fire Protection Handbook, 14th Edition, Section 6,Chapter 7 entitled Structural Integrity During Fire, published by the National Fire Protection Association (NAPA). This reference material provides fire resistance ratings for certain types of material and its related thickness for such structural components as beams, joists, trusses or girders, load-bearing walls, stud walls and partitions, various finishes over wood framing, and floor and roof construction. Additional information regarding fire resistant building materials and assemblies may be retrieved from Underwriters Laboratories Inc., The Factory Mutual System,The National Bureau of Standards, trade association publications,and various building codes.
57.4560 Fire-Retardant Timber in Mine Entrances
Standard 57.4560 provides mine operators with three alternative methods of compliance to deter the propagation of fire in certainties openings when support timber is in place. One of those alternatives is the coating of timber with a fire-retardant which provides a flame spread rating of 25 or less.
Flame spread ratings may be established by a testing agency or by MSHA at the request of the manufacturer. Flame spread ratings may be indicated by a document from the testing agency, a written statement from the manufacturer or by product labels which specify the rating according to test results. The attached list, "Mine Sealants Accepted From 1977 to 1985"(including mortar replacements), has been accepted by MSHA'S Approval and Certification Center for compliance with this requirement. This list is updated by the Center regularly, and the Engineering and Testing Division, Materials and Explosions testing Branch should be contacted on FTS 723-1451 or (304) 547-0400, when appropriate, to obtain the current list. Other products are also acceptable if evidence of a flame spread rating of 25 or less can be shown through test results.
Subpart D Air Quality, Radiation, and Physical Agents
56/57.5001(a) Nuisance Particulates
The only nuisance particulates for which a citation can be issued are those that are listed specifically as nuisance particulates in Appendix E of the 1973 TLV Booklet and exceed the 10 mg/m3TLV. At mines where the commodity produced is an unlisted nuisance particulate, and there is no silica hazard, continue to sample and analyze airborne dusts for listed toxic substances and take appropriate enforcement action.