Adding ground wire to existing URD

[csp]

I have an existing building that had 4/0, 4/0, 2/0 wire running from the power pole to the building in a trench when I bought the place in 2000. It had never been electrified, however. The wire is way overkill as the distance is only about 60'.

I'm finally to the point of powering this building and would like to use the existing URD and just add a ground wire. Can I do this? I was told once that the ground had to be twisted with the other three wires to be up to code. I"d really like to avoid replacing the existing URD as it's up to the task.

It's easy digging to open the trench again as I've done it once already. I can set my trencher a few inches above the cable and just pull the cable upwards through the remaining depth.

#2 related question: My power pole contains the meter and a feed through panel that powers my house underground via the feed through lugs. I will be powering the building from a breaker in the feed through panel. To avoid wrestling the 4/0 conductors into a breaker I had planned on cutting them short underground a few feet from the panel and reducing to 1/0 with an underground splice. Which type of splice do people recommed, the ones in a plastic, gel filled enclosure or the ones with the glue heat shrink? Or is it six of one, half-dozen of the other?

 

[wyliesdiesels]

Lots of potential issues here

URD is not permitted inside structures regardless if its ran in conduit.

The 4/0 sounds like its way oversized (you didnt list the breaker size you will be using) which means you will have to oversize the ground wire

in terms of twisting the ground wire with the existing cable, there is no such requirement in the code.

Splicing wire underground is asking for trouble. why not splice it in a junction box or use pin connectors?

 

[sberry]

I have added a wire, dug it up found it then dug beside and kind of caved it away taped the wire a few places so it stayed with it while covering.

 

[csp]

URD is not permitted inside structures regardless if its ran in conduit.

The URD is not in a structure. It's in a trench that will supply the sub-panel for the building.

The 4/0 sounds like its way oversized (you didnt list the breaker size you will be using) which means you will have to oversize the ground wire

Yes it is, as I said it's overkill. The breaker at the source panel will be 100 amp. I don't mind oversizing the ground wire. That's better than re-running all new cable.

in terms of twisting the ground wire with the existing cable, there is no such requirement in the code.

That's the answer I was looking for.

Splicing wire underground is asking for trouble. why not splice it in a junction box or use pin connectors?

Thanks for those suggestions. I considered a junction box but thought the underground would be easier. I certainly don't want to create future issues, and I don't want to wrestle that large wire into the source panel.

Thanks for the help!