design required to ensure that the grounding values
are obtained. For areas where the water table is
low and/or the soil resistivity is high (such as
volcanic soils, sand, or rock), delete the
additional electrode provisions and provide a design
to meet the site requirements.
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Grounding electrodes shall be installed as follows:
a.
Driven rod electrodes - Unless otherwise indicated, ground rods
shall be located approximately 900 mm 3 feet out from base of the
pole and shall be driven into the earth until the tops of the rods
are approximately 300 mm 1 foot below finished grade. Multiple
rods shall be evenly spaced at least 3 m 10 feet apart and
connected together 600 mm 2 feet below grade with a minimum No. 6
bare copper conductor.
b.
Pole butt electrodes - Pole butt electrodes shall be installed
where indicated, except that this method shall not be the sole
grounding electrode at transformer locations. The pole butt
electrode shall consist of a coil of at least 4 m 12 feet of
minimum No. 6 bare copper conductor stapled to the butt of the
pole.
c.
Plate electrodes - Plate electrodes shall be installed in
accordance with the manufacturer's instructions and IEEE C2 and
NFPA 70.
d.
Ground Resistance - The maximum resistance of a [driven ground
rod] [pole butt electrode] [plate electrode] shall not exceed 25
ohms under normally dry conditions. Whenever the required ground
resistance is not met, provide additional electrodes
[interconnected with grounding conductors] [as indicated], to
achieve the specified ground resistance. The additional
electrodes will be [up to three, [2.4] [3] m [8] [10] feet rods
spaced a minimum of 3 m 10 feet apart], [a single extension-type
rod, 15.9 mm 5/8 inch 19.1 mm 3/4 inch diameter, up to 9.1 m 30
feet long, [driven perpendicular to grade] [coupled and driven
with the first rod]]. In high ground resistance, UL listed
chemically charged ground rods may be used. If the resultant
resistance exceeds 25 ohms measured not less than 48 hours after
rainfall, the Contracting Officer shall be notifies immediately.
Connections below grade shall be fusion welded. Connections above
grade shall be fusion welded or shall use UL 467 approved
connectors.
3.10.2
Grounding and Bonding Connections
Connections above grade shall be made by the fusion-welding process or with
bolted solderless connectors in compliance with UL 467, and those below
grade shall be made by a fusion-welding process. Where grounding
conductors are connected to aluminum-composition conductors, specially
treated or lined copper-to-aluminum connectors suitable for this purpose
shall be used.
3.10.3
Grounding Electrode Conductors
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SECTION 16370A
Page 40
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