300.5

[Aselectric]

My question is in table 300.5 if I have a ridged metal conduit running under a roadway the table says 24” depth trench, but what if the roadway has 2” of concrete and then the roadway can I go 12” deep on my trench? Based on the 2nd location listed in table 300.5

 

[augie47]

No. You have to meet the most stringent condition. The "under a roadway" trumps the "covered" situation.

 

[SSDriver]

Also, the 24" is not the trench depth. Its is the cover (dirt) over the conduit. Your trench will be deeper than 24", depth will depend on the size of the conduit.

 

[infinity]

I agree you need a minimum of 24" to the top of the RMC if it's under a roadway.

 

[reast]

Agreed with the above. Table 300.15 for "Rigid metal conduit" says that you can reduce the depth if under concrete slabs of various thicknesses, but none of those situations apply if there is vehicular traffic, which you have. Therefore, the "below 2" concrete" doesn't apply because you have vehicular traffic, and the "Below a 4" concrete slab" doesn't apply because you have vehicular traffic and only a 2" slab. So go with the "under streets, roads...etc" section, which puts you at 24" of dirt, from the top of the dirt to the top of the conduit.