The pipeline is welded the full length, so a linear leak rate doesn't really make sense. Where it could leak would be at valve station flanges, which by code a

The pipeline is welded the full length, so a linear leak rate doesn't really make sense. Where it could leak would be at valve station flanges, which by code are required every X km depending on the land risks. You can test to see whether the flanges are leaking, and you can tighten accordingly in most cases. Effectively this leaking can be avoided in a transmission/industrial sense with the right amount of applied effort.