propane
Unless the plastic line is yellow, it is not an approved material for any gas line, much less propane. If it is yellow, you should not be able to buy any materials to relocate it. Gas lines of any kind, but especially propane, normally cannot go under concrete slabs AT ALL. But occassionally natural gas lines are permitted under specific circumstances as long as it is inserted in a properly designed sleeve to avoid gas buildup in the event of a leak.