We've got pipelines from the 40's thru 1980 on land we farm.  For the most part you don't see them, however,,,,,, in a wet year I can show you where they got red clay mixed in the blackland, that part will yellow out.  And I can show you where you can still see the trench in some sandy clay loam pastures, where you can see the settling that has occurred and sometimes even a better crop above the line.  The key is to MAKE them put the top soil back on TOP and not mix it with subsoil.

As to your question about heat, that is a fact.  I did some consulting on a major east-west line a few years ago.  The heat and its effects on crops had to be monitored for a period of several years.  The pumping stations had so much waste heat they were installing electrical co-generation stations at each pumping station.