I have built decks over septic stuff often my last house on an acreage we just made a hinged door set into the deck for access to the septic clean out . We used the concrete blocks for the posts no pounding or digging except to level the ground

Just put your walkway in, if it's concrete set expansion joints on each side of the pavers and you don't have to worry about it, if the pipe needs to be repaired, etc down the road you take that section out and replace it when done, it would be much easier and less expensive in comparison having a low-level deck there.