My yard has an in-ground sprinkler system. It also has poor soil. I'd like to rip up the lawn and bring in a lot of organic matter and rototill it in and put down a good layer of topsoil and then resod or seed. But I can't have the yard graded or the sprinkler heads will be damaged. I could dig them out and put temporary plugs in them but then how do I find them again after all the work has been done -- they will all be buried?

Any ideas? Thanks.