1 Calories Burned For Walking: 3.15 mph (19 minutes per mile). 2  Calories Burned For Walking: 2.85 mph (21 minutes per mile). 3  Calories Burned For Treadmill: 5 mph (12 minutes per mile).4  Calories Burned For Treadmill: 5.45 mph (11 minutes per mile). Calories Burned For Walking: 3.15 mph (19 minutes per mile). 2  Calories Burned For Walking: 2.85 mph (21 minutes per mile). 3  Calories Burned For Treadmill: 5 mph (12 minutes per mile). 4  Calories Burned For Treadmill: 5.45 mph (11 minutes per mile).
Direct Burial of Cables or Conductors. Underground feeder cables, labeled UF, can be buried without additional protection from conduits because they have a tough jacket designed for burial. Bury UF cables 24 inches below the soil surface, and 18 inches deep when protected by 2 inches of concrete. For all other applications, the burial depth is the same as specified for conduits, except that conduits are required for UF cables in 2 inches of solid rock.
THHN is not made for direct bury. And copper, over time, will turn back to its original state or earth. The locate signal will no longer remain in the wire path. Articles as long ago as 2003 warning of the improper use of THHN as a tracer wire have been written by engineers and regulatory agencies. Look at your current specification; tighten it up to not allow THHN.