Unfortunately many of our pipelines are way past their economic life. Along with age, the cathodic protection systems that are supposed to prevent corrosion are gone, used up, or poorly maintained compounding the problems. Blame poor government oversight and pipeline companies chasing the almighty dollar and it is a recipe for disaster.
My SIL works the pipelines as a third party inspector, surveiling new installations, and testing the coating systems. Currently in WV they are installing new/larger lines in existing rightaways. He told me that existing as built drawings are often very inaccurate. Even after doing extensive locating they still encounter piping in locations that are supposed to be clear. That is why the backhoes find them. He has been on jobs where the engineers did not field check the pipe constructors rough as built before they were covered. That engineer time costs money.
Ron