Question
How do you find valves that are under the sod

Answer
There are two ways I use most often.  The easiest is to use a metal detector and probe.  Another way is to locate the main water line by "witching" it, and start probing all the way along the line until you come up with something.  For witching, I use 2 brass welding rods, about 24", with a 4" bend to use as a handle.  It takes a little practice, but it usually works.