49 CFR §195.248

1. (a)Unless specifically exempted in this subpart, all pipe must be buried so that it is below the level of cultivation. Except as provided in paragraph (b) of this section, the pipe must be installed so that the cover between the top of the pipe and the ground level, road bed, river bottom, or underwater natural bottom (as determined by recognized and generally accepted practices), as applicable, complies with the following table:
2. (b)Except for the Gulf of America and its inlets in waters less than 15 feet (4.6 meters) deep, less cover than the minimum required by paragraph (a) of this section and § 195.210 may be used if—
   1. (1)It is impracticable to comply with the minimum cover requirements; and
   2. (2)Additional protection is provided that is equivalent to the minimum required cover.