Section 75.1903 - Underground diesel fuel storage facilities and areas; construction and safety precautions(a) Permanent underground diesel fuel storage facilities must be- (1) Constructed of noncombustible materials, including floors, roofs, roof supports, doors, and door frames. Exposed coal within fuel storage areas must be covered with noncombustible materials. If bulkheads are used they must be tightly sealed and must be built of or covered with noncombustible materials;(2) Provided with either self-closing doors or a means for automatic enclosure;(3) Provided with a means for personnel to enter and exit the facility after closure;(4) Ventilated with intake air that is coursed into a return air course or to the surface and that is not used to ventilate working places, using ventilation controls meeting the requirements of § 75.333(e) ;(5) Equipped with an automatic fire suppression system that meets the requirements of § 75.1912 . Actuation of the automatic fire suppression system shall initiate the means for automatic enclosure;(6) Provided with a means of containment capable of holding 150 percent of the maximum capacity of the fuel storage system; and(7) Provided with a competent concrete floor or equivalent to prevent fuel spills from saturating the mine floor.(b) Permanent underground diesel fuel storage facilities and temporary underground diesel fuel storage areas must be- (1) Equipped with at least 240 pounds of rock dust and provided with two portable multipurpose dry chemical type (ABC) fire extinguishers that are listed or approved by a nationally recognized independent testing laboratory and have a 10A:60B:C or higher rating. Both fire extinguishers must be easily accessible to personnel, and at least one fire extinguisher must be located outside of the storage facility or area upwind of the facility, in intake air; or(2) Provided with three portable multipurpose dry chemical type (ABC) fire extinguishers that are listed or approved by a nationally recognized independent testing laboratory and have a 10A:60B:C or higher rating. All fire extinguishers must be easily accessible to personnel, and at least one fire extinguisher must be located outside of the storage facility or area upwind of the facility, in intake air.(3) Identified with conspicuous markings designating diesel fuel storage; and(4) Maintained to prevent the accumulation of water.(c) Welding or cutting other than that performed in accordance with paragraph (d) of this section shall not be performed within 50 feet of a permanent underground diesel fuel storage facility or a temporary underground diesel fuel storage area.(d) When it is necessary to weld, cut, or solder pipelines, tanks, or other containers that may have contained diesel fuel, these practices shall be followed: (1) Cutting or welding shall not be performed on or within pipelines, tanks, or other containers that have contained diesel fuel until they have been thoroughly purged and cleaned or inerted and a vent or opening is provided to allow for sufficient release of any buildup pressure before heat is applied.(2) Diesel fuel shall not be allowed to enter pipelines, tanks, or containers that have been welded, soldered, brazed, or cut until the metal has cooled to ambient temperature.