Just hand dig around where the locate marks are. It will suck but this is the right way to do it. You won't want to pay for the fees if the utility has to come out and repair the line. At the very least do a couple potholes to locate and get a depth measurement.

It looks like you might have a plastic line (tough to see from the photo, but I think I see tracer wire at the riser). So when/if you find it, it might be yellow pipe, black with a yellow stripe, or it could be a pinkish color. Those are the most common colors for plastic pipe in the areas I've worked (engineer for a utility working on both gas and electric).