So we are putting a 4" concrete slab in the entire backyard, the electrician put the PVC conduit raceways for gfi 110v in a 4-5" deep trench which will be covered by 4" of concrete. Inspector failed us stating it needs to be in a 6" trench? Nec 300.5 allows for 4" deep if under 4" of concrete. They cited NEC 680 something about being near a pool, which there is a pool in the yard also but the pool is more than 5ft from the conduit? Who is right?