Underground Facilities

DOE-HDBK-1092-98

3. Withstand a series of operation design tests while exposed to a circulating dust-air mixture to

verify that dust does not enter the enclosure and that operation of devices does not cause

ignition of surrounding atmosphere

4. Are marked with the appropriate class and groups for which they have been qualified.

5.10 UNDERGROUND FACILITIES

Underground facilities consist of electrical equipment and wiring installed in underground locations.

Working conditions underground can present to electrical workers hazards different from those

presented above ground. This section aids in dealing with such problems.

Electrical work in support of construction of mines, shafts, and underground utilities shall be

performed by qualified workers who must meet the requirements in Section 2.8, 30 CFR 75.153 and

77.103. Only those workers shall install equipment and conductors within the construction activity.

Note: DOE does not engage in "mining" as mining is the extraction of minerals for profit. However,

the codes related to mining (30 CFR 57, 75, and 77) should be followed, where applicable, along with

the OSHA regulations set forth in 29 CFR 1910 and 1926.

Once construction of the underground facilities is completed, all wiring used for construction

activities shall be removed and permanent wiring installed in accordance with 29 CFR 1910, Subpart

S, and the NEC as applicable. When the work is not covered by these codes as referenced, the

applicable paragraphs of 30 CFR 57, 75, and 77 shall prevail.

Electrical equipment and conductors must be used in a manner that prevents shocks and burns to

people. Should electrical equipment and conductors present a hazard to people because of improper

installation, maintenance, misuse, or damage, the equipment and conductors must be tagged out or

locked out as a hazard until fixed. All electrical equipment and conductors shall be chosen and

situated in environments conducive to their design and intended use or as tested by an NRTL for the

purpose intended.

The voltage of bare conductors, other than trolley conductors, that are accessible to contact by people

shall not exceed 50 V. Electrical equipment and conductors, other than trailing cables, shall be

protected against overloads and short circuits by fuses or automatic interrupting devices used in

accordance with 29 CFR 1910.304.

Adequate clearance between equipment and bare overhead conductors must be maintained in

accordance with 29 CFR 1910.303. Conductors not being used to supply power to electrical

equipment shall be deenergized and removed from their power supply or have their power supply

locked out and tagged out in accordance with 29 CFR 1910.147 and 29 CFR 1910.333. All exposed

ends shall be insulated.

Access doors and cover plates shall be closed at all times, except for installation, testing, and repair.

Visible signs warning of danger shall be posted at all substations, switch centers, and control centers

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