Here are some pics which will hope explain where I'm at. The first pic is a photo of my front yard. It's a slight slope which goes downward toward the road. The yellow arrows are about where the sprinkler heads popup. The pink arrow in the middle is the sprinkler head that's leaking. It's the lowest one in the zone and is right at the curb in the middle. I Assume the pipe runs parallel to the driveways since the heads are right next to them. I wonder how the line is run to the middle head that's leaking though. Also, the piping that goes into the ground comes from the side of the house and must go under the driveway on the left to get to the area of the grass in the photo.
Next photo is the cover of the can that has a valve and piping and wiring in it. This is the only one I know about. It's pretty close to the house and inbetween where the electric and water come out of the house.
Here it is with the lid removed
And here is a photo of the side of my house. The yellow arrow on the left is where the electric from the rainbird brain comes out of the garage and into the ground. The yellow arrow on the right is where the water piping comes out the house and into the ground. (FYI, I had to replace the faulty pressure vacuum breaker a month ago). And the pink arrow in the middle is the can with the valve and electric that I referenced above.
So, now that you can see what I'm working with should I start blindly just sticking the screwdriver in the ground in that patch of grass in the front yard with the leaky head. Should I be looking for a similar can as above with the green top or could the valve be buried by itself without any protection elsewhere in the yard?