"Fred McKenzie" wrote in message
...
In article , Dave Lemper
wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Dave-

Last year there was a discussion here about sinking a ground rod using
an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian
White, GM3SEK, who proposed that method. There is also an article at
http://www.n4lcd.com/groundrod/ that proposes a slightly different
method of coupling the hammer drill to the ground rod.

The question is whether Caliche can be penetrated by such a method. Has
anyone tried it?

Another consideration is whether or not there is moisture in the soil
below the Caliche. If not, then it might not provide a low-impedance
ground even if you could penetrate it!

Fred
K4DII
-
If you don't have all the tools described above for an elegant way to drive
a ground rod, it isn't that bad by hand. The secret is to dig through the
soft dirt to expose the caliche. I used a crowbar hammered with a small
sledge. It isn't too bad for just a ground rod, and might be quicker than
looking for/borrowing more tools.

I planted a 60 foot self supporting tower in a hole 3 ft by 3ft and 6 feet
deep. I would have preferred an elegant solution for that!

Fred McKenzie wrote:
In article , Dave Lemper
wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Dave-

Last year there was a discussion here about sinking a ground rod using
an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian
White, GM3SEK, who proposed that method.

The other point was that SDS+ bits are available up to 1.0 metres long,
so by using both rotary and hammer action you can drill a pilot hole
through most kinds of rock down to that depth.

There is also an article at
http://www.n4lcd.com/groundrod/ that proposes a slightly different
method of coupling the hammer drill to the ground rod.

The question is whether Caliche can be penetrated by such a method. Has
anyone tried it?

We don't have caliche here, by that name, but from accounts on the web
I'd doubt if it could be penetrated by hammer action alone. However, it
seems more likely that an SDS+ bit could drill through it.

Another consideration is whether or not there is moisture in the soil
below the Caliche. If not, then it might not provide a low-impedance
ground even if you could penetrate it!

That is certainly the problem at this QTH, where an earth rod drilled
and hammered into the very rocky subsoil produced a resistance of
500ohms! Long horizontal electrodes are the only kind that work at this
QTH.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

While I don't have any 'caliche' on my property, I am blessed with a
lot of randomly placed rock. Driving any ground rod to about 6 feet
is a guessing game more than anything else. I've found that ground
radials are more practical. Not easy, just practical. They seem to
work as well as any ground rod I've ever used (better in some
instances).
The local power company is supposed to put down ground rods for
safety. Having seen some of their methods, I'd tend to go with the
radials (ground wire attached to water pipes... PVC water pipes, great
idea huh? And, NO, I'm not kidding.)
- 'Doc

On Aug 23, 11:58*am, Dave Lemper wrote:
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. *Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. *Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated. *
Dave *WB3DWE * * * * * * * * * * * * *

I know the stuff you are talking about, it will even jam up a
Ditch Witch

When I was in San Antonio with the USAF we made a spade
bit out of metal rod and welded the spades on the side.
We stared the hole with a post hole digger, filled it with water.
then drilled down into it. After drilling a couple of feet we were
able to pound in the ground rods
Im thinking using a real spade bit with an extension may work.

Jimmie

JIMMIE wrote:
I know the stuff you are talking about, it will even jam up a
Ditch Witch

They pave roads with caliche in West Texas. From Wikipedia:
"Caliche is also used for road construction, either as a
surfacing material or, more commonly, as a base material."
--
73, Cecil http://www.w5dxp.com

On Sat, 23 Aug 2008 10:58:19 -0500, Dave Lemper wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE

I would find out how local electricians do it. They have to meet code.
John Ferrell W8CCW

That caliche must be something else. I've never heard of it. But I must
question either your selection of ground rod, or method of insertion.
I've sunk a number of ground rods in semi-rock.... sometimes penetrating
granite too.

We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel
rods. We also used rotary impact hammers to drive the rods down.... often
right through a rock or whatever. Worked almost all the time, and did not
"mushroom" the top of the rod.

If a 3/4" pointed solid steel rod can not be driven through Caliche with
an impact hammer I can't imagine any other tool short of dynamite doing the
job.


Ed K7AAT

Ed,

"Ed" wrote in message
. 192.196...
We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel
rods. We also used rotary impact hammers to drive the rods down.... often
right through a rock or whatever.

Hammer-only mode? Or "rotate & hammer" mode?

---Joel

We used 5/8" copper clad steel, or sometimes 3/4" copper clad
steel
rods. We also used rotary impact hammers to drive the rods down....
often right through a rock or whatever.

Hammer-only mode? Or "rotate & hammer" mode?

---Joel


Hope I did not confuse ! I used a rotary impact hammer in all my years
of ground rod driving, but only used impact mode..... the rotary mode
would only turn the hammer head, not the rod . .. anyway. Most of the
time I had a sized Bosch tool, not some cheap import.

--- Ed K7AAT

Dave Lemper wrote in message
...
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE



Here's a snippet from the state of Washington's website that quotes the NEC:

NEC 250-52 (c)(3) (1999 edition) requires that ground rods "be driven to a
depth of not less than 8 feet
(2.44m) except that, where rock bottom is encountered, the electrode shall
be driven at an oblique angle
not to exceed 45 degrees from the vertical or shall be buried in a trench
that is at least 2½ ft. (762mm)
deep."

The requirement is that the rod be driven to a depth of 8 feet. If the rod
cannot be driven then there is a
choice of either driving it at a 45-degree angle or laying it in a trench
that is not less than 2½ feet deep.

http://www.lni.wa.gov/tradeslicensin...ts/elc0210.pdf.

I browsed some newer discussions and found nothing newer to be at variance
with the quoted material. The current NEC is $75 if snippets won't do ya'.

http://www.nfpa.org/itemDetail.asp?c...RL=Pub licati
ons/

You need 25 ohms maximum rersistance (three-point method) to say you have a
good ground.