Actually I believe they mark pipeline crossings under the state highways. Blue would denote a water line. The gas lines are usually marked by stand pipes that act as vents for the steel casing the lines are installed within. The storm drain are marked by either the flexible vertical laths or the metal stakes. Both have a white refelctor on them. I have never noted a marker using the blue laths working with INDOT drainage.
Interesting. I've never seen anything like that around here.