6" , min. In trench below 2-in thick concrete or (((equivalent))).
Pavement is not (((equivalent)) to concrete.
CONCRETE:A hard, strong construction material consisting of sand, conglomerate gravel, pebbles, broken stone, or slag in a mortar or cement matrix.
ASPHALT: 1. A brownish-black solid or semisolid mixture of bitumens obtained from native deposits or as a petroleum byproduct, used in paving, roofing, and waterproofing. 2. Mixed asphalt and crushed stone gravel or sand, used for paving or roofing.