Funny strip in my lawn

[jmstenz]

I need help!! I have this C shapped stripe in my lawn. Its greener and longer then the rest of my lawn. Someone told me it could be a mole so I dug it up the whole 15 feet of the c shapped area and I couldn't find any trace of a critter. Does anyone have any idea what it could be caused from? I noticed my neighbor has one in his yard too? If it is a mole how deep do they live underground? There is no sign of anything on top of the ground as in holes or dirt showing, just the long greener grass.
Any suggestions?

[Lindsaylew82]

Do you have a septic tank? The grass is always greener over our septic tank. And it's also kinda c shaped. Is the neighbors in roughly the same spot as yours?