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Subchapter 20. Tunnel Safety Orders
Article 17. Transportation and Haulage

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§8470. Internal Combustion Engines.

(a) The use of fuel-burning or internal combustion engines for either mobile and/or stationary equipment underground is prohibited, except for diesel engines when and where permitted in writing by the Division and under conditions specified for each project as prescribed throughout this section and/or in accordance with the provisions of 30 CFR, Part 32, pages 229-241, revised as of July 1, 1993, which is hereby incorporated by reference and made a part hereof.

(b) Application for such a permit shall be made in duplicate to the Division. The application shall include detailed information regarding the proposed use, and the following:

(1) Complete details and specifications of the exhaust conditioning devices and diesel engine(s) including displacement, the rpm where maximum horsepower is produced and the rated brake horsepower.

(2) Location of tunnel and details of operation in which it is proposed to use the diesel equipment.

(3) Length, cross section, and layout of the tunnel.

(4) Maximum number and brake horsepower of diesels to be operated in any air course.

(5) Ventilation plan including direction of air flow, fan capacity, duct sizes, and auxiliary ventilation.

(6) Date when the proposed diesel use is to begin and dates and locations where a representative of the Division may make tests of the diesel's exhaust gases.

(7) Maximum number of employees working underground at any given time during diesel usage.

(8) The application shall also list the provisions in which the requirements of this Section will be met:

(c) The velocity of fresh air flowing through the area where diesels are operating shall be a minimum of 60 lineal feet per minute and shall amount to at least 100 cubic feet per minute per diesel brake horsepower plus 200 cubic feet per minute per person underground.

(d) Testing devices for nitrogen dioxide, carbon monoxide and carbon dioxide shall be provided and used in the tunnel at least once each shift at the peak of diesel operation and a written record kept of readings. Tests shall be conducted by a Certified Gas tester.

NOTE: 1: Nitrogen Dioxide is the most harmful of the gases discharged by diesel equipment. If it is held within the specified limits by proper air to fuel ratio in combustion along with adequate ventilation, the pollutants, (i.e. Hydrocarbons (HC), Carbon Monoxide (CO), Nitrogen Oxides (NO), Nitrogen Dioxide (NO2), Carbon (C) or smoke, Sulfur Dioxide (SO2)), produced in the diesel exhaust emission resulting from diesel operations will normally be well below harmful levels.

NOTE: 2: Carbon Monoxide: Whenever twenty parts per million (0.002 percent) of carbon monoxide has been measured in the general tunnel atmosphere under average working conditions, corrective action should be initiated immediately to lower this level.

(e) The maximum allowable amount of exposure to Nitrogen Dioxide shall not exceed the following limits throughout the general tunnel atmosphere under average working conditions:

(1) Nitrogen Dioxide. Exposure to Nitrogen Dioxide shall not exceed the PEL of 5 ppm (9 mg/M3) as prescribed in the requirements of 30 CFR, July 1, 1993, Subpart D, Section 57.5001, page 409, of the Federal Mine Safety and Health Administration, which is hereby incorporated by reference.

(f) The exhaust from the diesel engine shall be passed through an acceptable scrubber or exhaust purifying device that is at least as effective as a well-designed water-bath scrubber in reducing hazard and discomfort to workers.

(g) The diesel engine and scrubber shall be maintained in good mechanical condition and proper working order. Scrubbers shall have inspection openings so that the internal condition and/or water level can be determined.

(h) The exhaust from the diesel engine shall not be directed towards the diesel operator.

(i) The diesel fuel used shall not contain over .35 percent sulphur, by weight.

(j) The diesel fuel supply shall not be stored or taken into the tunnel in amounts greater than required for eight hours of operation.

(k) The piping of diesel fuel from the surface to an underground location is permitted under the following conditions:

(1) The surface tank is connected to the underground fueling station by an acceptable pipe or hose system that is controlled at the surface by a valve and at the bottom by an additional valve and hose nozzle.

(2) The pipe or hose is empty at all times except when transferring diesel fuel from the surface tank to a piece of equipment in use underground.

(3) Hoisting operations in the shaft are suspended during refueling operations if the supply piping or the hose in the shaft is not protected from damage.

(l) Application processing time for the Permit

(1) Within 15 business days of receipt of an application meeting all of the requirements of this section and the fee for a Permit to Operate Diesel Engines Underground, the Division shall issue the permit or inform the applicant in writing, if the application is deficient, describing what specific information and documentation is required to complete the application.

(2) Within 10 business days of receipt of the resubmittal of the complete and accurate permit application complying with the provisions of this section, the Division shall issue a permit.

(3) The Division's median, minimum and maximum times for processing a permit from the receipt of the initial application to the final permit decision, based on the Division's actual performance during the two years immediately preceding the proposal of this regulation have been as follows:

                Median time               21 days 
                Minimum time              15 days 
                Maximum time              90 days 

(m) The diesel permit shall be conspicuously posted at the jobsite.

NOTE: Permit requirements of the Division of Occupational Safety and Health are contained in Article 2, Subchapter 2, Chapter 3.2, Title 8, CCR.

NOTE: Authority cited: Sections 142.3 and 7997, Labor Code. Reference: Sections 142.3 and 7997, Labor Code.


1. Amendment of section heading and section and new Note filed 3-5-96; operative 4-4-96 (Register 96, No. 10).

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