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Re: [TowerTalk] Ground Rods in rocky soil

Subject: Re: [TowerTalk] Ground Rods in rocky soil
From: Jim Lux <>
Date: Thu, 18 Jan 2007 10:41:30 -0800
List-post: <>
At 09:50 AM 1/18/2007, wrote:
>After being spoiled by Florida's sugar sand in which you could dig  a hole
>for a base for holes and anchors by hand and drive a ground rod down  by
>"jetting" it, I now live on one of the biggest rock piles in the world.
>Most of the Big Island of Hawaii has solid lava rock.   Fortunately, my area
>is a little bit better...a mix of clay, small rocks  and rocks up to a foot
>across, certainly not the kind of stuff easy to 
>get  into.  Sometimes the layer
>of pure clay is just a few inches thick, in  other places it can be ten feet
>deep.  Ground rods and copper are  pretty expensive out here and I don't want
>to experiment losing rods just a  couple of feet into the ground and getting
>stuck at that depth.
>I know I can use a backhoe to dig the holes and will have one on the
>property to dig the cesspool, but what is the best way to go getting 
>ground rods  in?
>  I asked the locals at one of the radio club meetings and they weren't  much
>help.  Responses were.....most guys just drive it in a foot or so and  use
>radials.  Since the station will sit on a hill, I really don't feel 
>too  secure
>putting the rod in only a foot, however I do plan on running the radials,
>since I know it will help.
Why not bury the electrodes horizontally?  Nothing special about 
driving them vertically, it just happens to be simple (in some kinds 
of soil); that is, pounding a rod into soft loam is a heck of a lot 
easier than digging a 10 ft long trench 18" deep.  The key is contact 
area with the soil, which is why the Ufer (Concrete Encased Grounding 
Electrode) is popular... 20 ft of wire in a big conductive concrete 
block is a pretty good connection to the surrounding soil. It's kind 
of expensive, though, if you aren't putting concrete in for something 
else (you're looking at a yard or so of concrete, if you figure the 
concrete is going to be 1x1x22 ft or something, and that's a lot more 
than just buying a few extra rods and hammering them in.)  OTOH, if 
you're already pouring a building foundation, laying the wire into 
the footing is easy, and the cost is MUCH lower (just the wretchedly 
expensive copper wire.. but hey the price of that is coming down, too)

Just have your backhoe operator zap some trenches in to bury your 
rods at whatever depth is convenient..  18" is probably a good 
minimum depth, but it's not all that critical.



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