Run conduits Underground??

[Alwayslearningelec]

I have several 3"+ conduit runs that are shown below in a cellar parking garage. It's slab on grade.
Trying to decide if I should bid the conduits run underground. Any reasons why they would not be able to be run below slab on grade?

 

[don_resqcapt19]

Check the specs about back fill and compaction under the concrete if the do the underground run.

 

[ron]

I would check their ampacities against Annex B tables to be sure they are really size correctly. Most forget the derating associated with underground which may make the installation change.

 

[ptonsparky]

Table 300.5