Question
I have a 2 year old home that was recently added a back concrete porch. Come to find out the slab was poured over 2 of the sprinkler control valves for my system. Is this going to be a problem, and if so how do I fix it?

Answer
Yes it is a problem.  Beside not being able to access the valves, leaks do happen, and you dont want a leak under your slab.  You will need to install new valves to replace the covered ones.  You need to locate the mainline, install the valves, and then connect them to the sprinkler lines that they serve.  You should be able to save the sprinkler lines unless they are covered as well.