These pipes feed the oil into the oil burner from the tank.  Feeder lines are usually made of copper and are approximately ¼ to ½ inches in diameter.  Usually Underground Storage Tanks (UST) will have 2 lines and Aboveground Storage Tanks (AST) will have 1 line to the burner.  The feeder lines for Underground Storage Tanks are usually buried underground, so the only indications are usually as a result of removal of these lines.  The visible signs of removal that may be present are pinched off feeder lines coming out of the floor near the furnace or in the foundation wall.  Another sign that the feeder lines were removed, would be an area of replaced concrete that leads from the furnace to the foundation wall. This could indicate that someone previously dug in that area to remove the lines and re did the concrete in that area.