Appeal 33550

NEC 356.10 AND 300.5

The NEC and our adopted Oregon Electrical Specialty Code (OESC) allows you to reduce burial depth to 12” with a 2” layer of concrete above the conduit in a trench. It could be immediately above the conduit or anywhere above the conduit so long as the final depth remains at least 12” Keep in mind that final grade can be raised some to accomplish the final depth. You would only need a 4” slab extending 6” beyond the conduit if you wished to reduce required depth to 4” total.

I’m not certain why following the code provision of adding 2” of concrete on top of the conduit would cause any liability. It would certainly protect the conduit at a level equal to that of achieving the required 18” burial depth.

See Colum 3 in the table below for your conduit type. This article 300.5 is taken from NFPA.link National Electrical Code 2023 which is current code and not amended by the OESC.

300.5 Underground Installations.
(A) Minimum Cover Requirements.
Direct-buried cable, conduit, or other raceways shall be installed to meet the minimum cover requirements of Table 300.5(A).

In trench below 50 mm (2 in.) thick concrete or equivalent

Requiring a concrete narrow slab over the electrical conduit creates more problems than it solves.

Gravel covering an electrical conduit provides adequate protection by distributing weight, preventing soil erosion, and allowing drainage, while offering flexibility and easier access for future maintenance compared to the permanence and rigidity of concrete.

Gravel covering an electrical conduit provides adequate protection by distributing weight, preventing soil erosion, and allowing drainage, while offering flexibility and easier access for future maintenance compared to the permanence and rigidity of concrete.