Open trench to the lamp post
This circuit feeds the lantern and the 120 V receptacle on the post. What's wrong here?
- The UF cable is buried with far too little cover for a 120 V circuit
- UF cable is not rated for direct burial and must be run in conduit
- In Minnesota the cable must go below the frost line, about 42 in down
- A warning ribbon is required 12 in above any buried branch circuit
Show the answer and the code reference
The answer
The direct-buried UF branch-circuit cable has only about 6 in of cover, less than Table 300.5(A) allows for any 120 V circuit.
Correct choice: 1. The UF cable is buried with far too little cover for a 120 V circuit
Table 300.5(A) requires 24 in of cover for direct-buried cable (column 1). The only reductions that fit a 120 V lamp post are 12 in for a residential branch circuit of 120 V or less that is GFCI protected and on a 20 A or smaller breaker (column 4), or 18 in in a trench below 2 in of concrete or equivalent. The 6 in column is only for irrigation and landscape-lighting circuits limited to 30 V, and this 12-2 UF feeds a 120 V receptacle and lantern. The tape reads about 6 in to the top of the sod, close enough that one pass with an edger, aerator, or fence-post auger can cut into a live cable.
How to fix it
Deepen the trench to 24 in of cover, or to 12 in if the circuit is a 20 A or smaller GFCI-protected 120 V residential branch circuit (GFCI at the source, so the buried cable is protected). Have the trench inspected before backfill and keep rocks out of the backfill per 300.5(F).
Code references
NEC 2023 Table 300.5(A) — Minimum Cover Requirements, 0 to 1000 Volts, Nominal, Burial in Millimeters (Inches)
Direct-burial cables or conductors need 24 in of cover in general (column 1). Residential branch circuits rated 120 V or less with GFCI protection and maximum overcurrent protection of 20 A need 12 in (column 4). Irrigation and landscape-lighting control circuits limited to 30 V need 6 in (column 5).
Drills citing Table 300.5(A)NEC 2023 300.5(A) — Underground Installations: Minimum Cover Requirements
Direct-buried cable, conduit, or other raceways shall be installed to meet the minimum cover requirements of Table 300.5(A).
Drills citing 300.5(A)NEC 2023 340.10(1) — Uses Permitted (Type UF)
Type UF cable is permitted for use underground, including direct burial in the earth, with cover as required by 300.5.
Drills citing 340.10(1)
2026 NEC:same rule and number. 2026 summaries report that the Table 300.5(A) cover depths are unchanged (24 in direct burial, 12 in for 120 V, 20 A max, GFCI-protected residential branch circuits, 6 in for 30 V landscape circuits). Some secondary summaries describe an added finished-grade clarification, which does not change this drill's answer, since cover was already measured to finished grade. Confidence: medium
Minnesota
Minnesota enforces the 2023 NEC, adopted by reference without amendments in Minn. Rules 1315.0200 (Minn. Stat. 326B.35), effective July 1, 2023. No Minnesota amendment to 300.5 or Table 300.5(A) exists, and Minnesota does not tie cable burial depth to frost depth. Inspectors in Minnesota commonly ask to see an open trench before backfill. The Board of Electricity adopted the 2026 NEC, also without amendment, for permits filed on or after Aug. 17, 2026 (exams moved to the 2026 NEC on Sept. 8, 2026); see the 2026 NEC note on this drill.
How Minnesota adopts the NECWhy the other choices are wrong
- UF cable is not rated for direct burial and must be run in conduit. Type UF is listed for direct burial; 340.10(1) permits it underground, with cover per 300.5.
- In Minnesota the cable must go below the frost line, about 42 in down. Neither the NEC nor Minnesota ties burial depth to frost depth. Frost depth is a building-code footing rule; Table 300.5(A) sets the cover for cables.
- A warning ribbon is required 12 in above any buried branch circuit. The 300.5(D)(3) warning ribbon applies to underground service conductors buried 18 in or more that are not encased in concrete, not to a lamp-post branch circuit.