I've come across quite a few underground pool pump & light ridgid installations that were correctely wrapped but had rusted out anyway and eventually caused the wires to either short and/or open, and the pool pump quit in residential homes. Usually takes 5 to 10 years.
"I'M SURPRISED THIS IS CODE, I THINK PVC SHOULD BE USED".
No matter how well you wrap it, I think water gets through over time. The soil here in AZ is acidic too.

We have to keep in mind that the NEC is a minimum safety code, not a design manual.

Personally I feel the only use for PVC is underground.

I am not a fan of GRC underground, but I do not feel it should be prohibited.

I think it is going to be a local call. In Md I have seen garden variety EMT hold up for a long time underground but like Aldv, here in Florida, even rigid goes pretty fast.
Vote me "plastic" too.

gfretwell, I agree..

Concrete encased pvc buried pipe gets my votiest vote of all.

I prefer PVC for underground work. We just installed 500' of 4" sched 80 in 3 parallel runs Friday. They ran from the padmount transformer to the future mechanical room location for a church addition. We put them 66" below the pad and bedded them in 24" of coarse sand before backfilling. Nobody should come near these pipes, but if they do they are going to see sand before they hit PVC, I hope. The same excavator is doing all of the digging on this job. My conduits under the slab will be done the same way only they will be 48" below the slab. Well below the plumber's drains.

Out here in Orange County, CA, I try to use nothing but PVC underground. Not only is the soil super acidic (especially near the ocean), but alot of the irrigation systems are run with reclaimed water - metal of any kind doesn't stand a chance. I've even run across rubberized-rigid that corroded right inside the rubber from a leak at one of the joints, and just disolved into oblivion.

Concrete-encased PVC is nice, as it's basically just a plastic-lined concrete conduit. I've seen this in the snack bars that are actuall ON the beach. Works great until a plumber comes along with a concrete saw... Gotta love plumbers, they keep my bills paid =)

Zapped, You're from HB!

GRC, IMC, or EMT aren't even permitted to be installed outdoors abovegroundin your town unless they are painted with a marine grade paint (that's about $65 a gallon).