Ground rod in disturbed back-fill

[Wire-Smith]

code says driven 8'.

does this mean the rod has to be 8' in undisturbed soil?


is it not code compliant to hydro-vac a hole 6' deep then drive the rod the last 4', then back-fill the hole?


what is the best back-fill for this application?



thanks

 

[petersonra]

code says driven 8'.

yes it does (mostly anyhow).

does this mean the rod has to be 8' in undisturbed soil?

it does not say that.


is it not code compliant to hydro-vac a hole 6' deep then drive the rod the last 4', then back-fill the hole?

it uses the word 'driven". IMO you can dig a hole and then fill it back in and drive the rod into the now filled hole.


what is the best back-fill for this application?

code does not specify and it really does not matter much anyway.

thanks

you're welcome.

 

[Wire-Smith]

you're welcome.

what do you think about installing the rod before back-fill?

 

[infinity]

what do you think about installing the rod before back-fill?

Well then it's not driven but really who would know?

 

[Wire-Smith]

do you think crushed limestone would be good back-fill, or slightly corrosive?

 

[petersonra]

do you think crushed limestone would be good back-fill, or slightly corrosive?

i think there is no "best" backfill. it just does not matter all that much. put the dirt back in and pound the rods. you will probably need two of them 6 feet apart.

 

[infinity]

I tend to agree with Bob, people seem to get all warm and fuzzy over ground rods even though they're not that great to begin with. I did have an inspector tell me that he pulls on the rod to see if it moves which could happen in very loose fill or if it's only 2' long.

 

[Tony S]

You could add Bentonite clay to the backfill. It retains moisture and so improves the effectiveness of the electrode.

 

[Dennis Alwon]

You could add Bentonite clay to the backfill. It retains moisture and so improves the effectiveness of the electrode.

I agree, bentonite is used with chemical ground rods.

 

[kwired]

I tend to agree with Bob, people seem to get all warm and fuzzy over ground rods even though they're not that great to begin with. I did have an inspector tell me that he pulls on the rod to see if it moves which could happen in very loose fill or if it's only 2' long.

I can recall many places where soil is sandy and you can nearly push a rod all the way in with bare hands.

 

[K8MHZ]

I can recall many places where soil is sandy and you can nearly push a rod all the way in with bare hands.

I live in such an area. The dirt near Lake Michigan is white sand. I can usually push a ground rod down 6-8 feet by hand in some areas.

 

[kwired]

I live in such an area. The dirt near Lake Michigan is white sand. I can usually push a ground rod down 6-8 feet by hand in some areas.

I live practically right on the border of where the "Nebraska sandhills region" begins. Have both heavy soils and sandy soils all around me. In fact where my house sits is all sand, go just a few hundred feet to the rear and there is clay soil back there. Kind of a mix at the surface but dig down and it is all clay.

Many of sandy areas you only push the rod in 5 or 6 feet and it gets too hard to push any further by hand. Go to a high water table area and you may push it all the way in pretty easily though.

 

[K8MHZ]

I live practically right on the border of where the "Nebraska sandhills region" begins. Have both heavy soils and sandy soils all around me. In fact where my house sits is all sand, go just a few hundred feet to the rear and there is clay soil back there. Kind of a mix at the surface but dig down and it is all clay.

Many of sandy areas you only push the rod in 5 or 6 feet and it gets too hard to push any further by hand. Go to a high water table area and you may push it all the way in pretty easily though.

Years ago we did a job where we had to put the rods in new sandy back fill. We would push them down to about a foot tall until we needed a hammer, but if you used too big of a hammer, the rod would disappear and you would have to dig down and pull some of it back up.

 

[Tony S]

do you think crushed limestone would be good back-fill, or slightly corrosive?

Get limestone washings (quarry sand). It’s fine, it holds water well and mixed with 25% Bentonite clay will be as good as you’ll get.

 

[Wire-Smith]

thanks for the great responses everyone, does anyone have any published data or a suggestion on where to maybe find something published that says this is a good idea? thank you very much for the suggestions already

 

[petersonra]

thanks for the great responses everyone, does anyone have any published data or a suggestion on where to maybe find something published that says this is a good idea? thank you very much for the suggestions already

the problem with your question is it assumes somehow that a "better" ground is somehow desirable. Most cases it just does not matter.

 

[Wire-Smith]

i will look into the chemical ground rods using bentonite should get me some published information for reasoning, thanks dennis

 

[Wire-Smith]

http://www.ground1.com/ground_rod_installation.htm

 

[kwired]

If you put same soil back in the hole but don't compact it to same consistency it was before removing it- you likely have more resistance to ground then you would have had if it were driven. Over time it may eventaully work itself to about where it would have been if driven though.

 

[jeremysterling]

After reading post #2, I looked at my 2008 NEC. Rings are "buried", rods are "driven", and plates are "installed". Only the NEC could come up with three ways to say "covered in dirt."