37 Miss. Code R. § 1-7501-04001-803
Gas pipelines carrying gases with a pressure in excess of forty-five (45) pounds per square inch crossing under roads, streets, frontage roads, ramps, conventional highways, partially controlled and fully controlled access highways shall be encased unless such pipelines have regularly inspected and adequately maintained cathodic protection in accordance with the utility company's safety program and extra strength pipe is used for the length required to be encased in SECTION 500. Pipe will be considered extra strength when either the wall thickness is increased a minimum of ten (10) percent above that used for the design pressure of the subject line or the extra strength is achieved by use of pipe having ten (10) percent higher minimum yield strength. Pipe will also be considered extra strength when the combination of diameter, wall thickness and tensile properties is such that the internal pressure required to produce a hoop stress in the crossing pipe equal to its minimum yield strength is at least ten (10) percent higher than the internal pressure required to produce a hoop stress in the pipe on either side of the crossing equal to its minimum yield strength. If encasements are used, they shall be in accordance with SECTIONS 501 - 503.
37 Miss. Code. R. § 1-7501-04001-803