If EMT was ever legal to use for underground of any kind, it shouldn't have been. I used to have a 1975 NEC. I think I'll try to find that old code book, and look it up.
Here in Houston you will see PVC, and RMC if Houston Lighting & Power standards are to be met. We've done jobs where the engineer required PVC coated RMC (Plastabond), concrete encased PVC, or coated RMC. I've been on jobs where stainless was required for all exposed conduit runs.
IMHO PVC is the best for underground, then convert to RMC where subject ot damage. If you see coated RMC in the spec's for a job, it is usually an older engineer who won't give up the "old methods". Heck, the NEC even allows PVC for undergroung in gas stations. Have a nice day......
HMEL #688
