The answer to your question will depend on the MOC. For buried steel pipe, important soil characteristics for determining corrosivity include soil resistivity, chloride content, sulfate content, and acidity (pH). It is common to protect steel pipe from corrosion through a combination of cathodic protection and protective coatings. There are many detailed references covering proper installation of buried steel pipe to prevent corrosion. A place to start is the NACE standard RP-0169 "Control of External Corrosion on Underground or Submerged Metallic Piping Systems."

Corrosion and corrosion prevention of ductile iron pipe is covered in the ANSI/AWWA C105/A21.5 Standard "Polyethylene Encasement for Ductile-Iron Pipe Systems." This standard contains a 10-point soil evaluation procedure that is used to determine if the soil is aggressive to ductile iron pipe. If the soil tests corrosive to ductile iron pipe, then corrosion protection is warranted. Polyethylene encasement is the corrosion protection method normally recommended by the Ductile Iron Pipe Research Association and the manufacturers of ductile iron pipe.

I am not as familiar with GRP piping but I suspect there would be few corrosion issues in soil. As is the case for steel and ductile iron piping, there are standards that cover installation of GRP piping underground. One example is ISO/TR 10465 "Underground Installation of Flexible GRP Pipes."