When can rigid metal conduit be installed directly in the soil for underground raceways?

Question

Quizplus · Accepted Answer

The Answer is Rigid metal conduit can be installed directly in the soil if:
-ferrous conduits (iron or steel) do not rely solely on enamel for corrosion protection;
-the conduit is made of a material judged suitable for the condition; and
-the conduit is not placed in an excavation that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive material.

When Can Rigid Metal Conduit Be Installed Directly in the Soil