37 Miss. Code R. § 1-7501-04001-501
Encasements will extend at least six (6) feet from the toe of fill slopes and at least six (6) feet from the ditch line in ditch sections; however, all encasements will extend at least ten (10) feet from the roadway shoulder when shallow or no ditch sections; flat slopes, etc. are encountered. (See Attachment A for details). The required encasement lengths and limits for the specific permit shall be determined by the District on a case-by-case basis. Open trenches approaching jacked, bored or tunneled crossings will not be excavated more than two (2) feet toward the highway from the end of the encasement. No open trench in cut sections or no ditch sections will encroach upon the pavement base, subbase or treated design soil. Depth of cover will be sufficient to clear any pavement base, sub-base or treated design soil by at least one (1) foot and in no instance should the top of the encasement or the carrier pipe be less than thirty-six (36) inches below any ditch bottom. Crossing approaches and parallel lines shall have thirty-six (36) inches minimum cover. Where soil conditions, depth of trench, or other factors constitute a hazard to the roadway or to the highway user, the length of encasement and open trench restrictions will be increased as necessary. Where necessary, sheeting may be required.
All fuel carrier pipes which are required to be encased or on which encasements are used will be vented. Vents will be placed on the right of way line or not more than one (1) foot inside the right of way and the top of the vent will be located three (3) feet above the ground as a minimum. In municipal or other built-up sections, there is often not enough street width to provide the required open trench clearances or sufficient space for boring, jacking or tunneling pits. These instances will be treated as special cases, each according to its merits. They should be fully documented and referred to the State Maintenance Engineer for disposition.
37 Miss. Code. R. § 1-7501-04001-501