FWIW....
We just moved back to Texas to retire, and so, the tower projects have
begun.
I leased some of our land to Verizon for a self-supporting 150' monopole
cell tower.
It was very interesting to see how their subcontractors handled the
grounding, and I was able to watch every step of their process. Soil here is
very poor (read, lots of rocks close to surface etc).
They grounded everything in sight: the perimeter 10' high chain-link fence,
the monolithic "communications hut", and of course the base of the tower.
After pouring the cement in the base hole (6' dia by 16' deep), they dug a
four foot deep trench around the circumference of the tower. Then they put
in 8 each 2'X4' X.125"thick copper plates, each with its own 1/2" braided
copper lead. These 8 copper wires were then attached around the periphery of
the tower base. They poured a Bentonite slurry into the trench and covered
it with fill dirt. One of the copper leads attached to the copper wire in
another trench with more ground plates that surround the "hut"; more
Bentonite poured in that trench and then covered with fill. Another wire
from the "hut" trench went to the fence trench ground system. The last wire
went to the power transformer pad and to their electrical service about 12'
from the hut.
None of the rebar in the hole is bonded to anything; there are 8 each 2.25"
dia by 16' galvanized allthread rods that go down near, but not touching,
the bottom of the hole (dirt). The allthread anchor rods were suspended at
the top of the hole by 4X4 supports set in place until the cement set up.
They seemed to know what they were doing, so I hired the sub to do the
grounding on my 7 towers.
Hope I was right ;).
73
Dick, K5AND
Austin, TX
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