to meet the site requirements.
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Grounding electrodes shall be installed as shown on the drawings and as
follows:
a. Driven rod electrodes - Unless otherwise indicated, ground rods
shall be driven into the earth until the tops of the rods are
approximately 300 mm 1 foot below finished grade.
b. Ground mat - A ground mat shall be installed as shown consisting of
bare copper conductors installed [300] [450] [600] mm [12] [18] [24]
inches, plus or minus 75 mm 3 inches, below the finished top of soil
grade. Mat conductors shall be bonded to all rod electrodes,
electrolytic electrodes, and to all other intersecting mat conductors.
Mat conductors shall be sized as shown on the drawings.
c. Ground ring - A ground ring shall be installed as shown consisting
of bare copper conductors installed [300] [450] [600] mm [12] [18] [24]
inches, plus or minus 75 mm 3 inches below finished top of soil grade.
Ground ring conductors shall be [sized as shown] [No. 2 AWG, minimum].
d. Additional electrodes - When the required ground resistance is not
met, additional electrodes shall be provided [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] [3.7] m [10] [12] feet
apart] [a single extension-type rod, [15.9] [19.1] mm [5/8] [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 notified immediately.
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 and Bonding Conductors
Grounding and bonding conductors include conductors used to bond
transformer enclosures and equipment frames to the grounding electrode
system. Grounding and bonding conductors shall be sized as shown, and
located to provide maximum physical protection. Bends greater than 45
degrees in ground conductors are not permitted. Routing of ground
conductors through concrete shall be avoided. When concrete penetration is
necessary, nonmetallic conduit shall be cast flush with the points of
concrete entrance and exit so as to provide an opening for the ground
conductor, and the opening shall be sealed with a suitable compound after
installation.
3.10.4
Surge Arrester Grounding
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SECTION 16375A
Page 61
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