26.A.09 Electrical and lighting.
- All electrical systems used in hazardous locations must be approved for that location. > See Section 11.H.
- Lighting circuits must be installed on one side of the tunnel near the spring line and must be mounted on insulators at each point of suspension.
- Light fixtures must be nonmetallic and weatherproof and mounted in a manner that provides safe clearance for personnel and equipment.
- Only portable lighting equipment that is approved for the hazardous location must be used within:
- (1) Storage areas, or
- (2) 50 ft (15.2 m) of any underground heading during explosives handling.
26.A.10 Inspections, testing and documentation.
- A program for testing all rock bolts for tightness must be established. The frequency of testing must be determined by rock conditions and the distance from vibration sources.
- The employer must examine and test the roof, face, and walls of the work area at the start of each shift and frequently thereafter.
- Ground conditions along underground haulways and accessways must be inspected by a Competent Person (CP) as frequently as necessary to maintain safe passage.
- All drilling and associated equipment to be used during a shift must be inspected before each shift by a CP.
- Drilling areas must be inspected for hazards before drilling operations are started.
- A CP must inspect haulage equipment before each shift.
- Whenever defects affecting safety or health are identified, the defects must be corrected before activities are initiated or continued.
26.A.11 Protection from falling material.
- A CP must inspect the roof, face and walls of the work area at the start of each shift and as often as necessary to determine the stability of the tunnel. > See 29 CFR 1926.800(o)(3)(i)(A).
Reinforced ceiling give protection against falling material.
- Portal openings and access areas must be guarded by shoring, fencing, head walls, shotcreting, or other equivalent means to ensure safe access of employees and equipment. Adjacent areas must be scaled or otherwise secured to prevent loose soil or rock from endangering the portal and access areas.
- Ground stability in hazardous subsidence areas must be ensured by shoring or filling in, or by erecting barricades and posting warning signs to prevent entry.
- Loose ground in underground areas that might be hazardous to employees must be taken down, scaled, or supported.
- Rock masses separated from the main mass by faults, joints, or fractures must be secured by rock bolting or other suitable means or must be removed. The means of securing must be designed by a foundation engineer, an engineering geologist, or other qualified person.
- Anchored chain-link fabric or other method approved by the GDA must be provided on rock faces subject to spalling.
- Where tunnels are excavated through earth or shale, any excavation above or adjacent to portal areas must be sloped to the angle of repose or held in place by ground supports. When undercutting occurs on these slopes (whether due to erosion or other causes) the overhanging material must be promptly removed.
- Where the need is indicated, a protective shelter must be provided at each underground portal to protect persons and equipment from the hazards of falling rock or other material. The protective shelter must project at least 15 ft (4.5 m) out from the portal.
- Ice or snow buildup on rock faces or earth slopes that create a hazard must be promptly removed.
26.A.12 Tunneling in soil.
- Where tunnels are excavated by conventional methods, the excavation must not be extended more than 24 in (60.9 cm) ahead of ground supports; where continuous mining machines are used for tunnel excavation, the excavation must not be extended more than 48 in (121.8 cm) ahead of ground supports.
- Under no circumstances must persons be permitted to work in unsupported sections of the tunnels.
- All voids in back of ground supports must be filled, blocked, braced, or treated to prevent further cave-ins.
- Where liner plate is not used for tunnel support, 2 in (5 cm) wire mesh or chain-link fabric must be installed over the crown section, extending down to the spring line on each side of the tunnel and secured in place.
Knowledge Check Choose the best answer for the question.
26-3. Where tunnels are excavated by conventional methods, how far may the excavation be extended ahead of ground supports?
You forgot to answer the question!