We're rehabbing a 1950 house that has a septic tank. It also, many moons ago, had a water cistern next to the house which was removed even before the previous owners bought the house.The first photo shows a hole that we thought was access to that old cistern. We decided to make the backyard a little prettier and poured a new slab on top (Note: we did not, fortunately, fill the hole underneath with concrete or garbage or anything). Then we realized that the original hole provided access to the septic tank. So now we need to fix this. The question is how we can do it (i) quickly, (ii) cheaply and (iii) correctly. The house is located in Washington County, MD, and I am not sure what sort of code exists for septic access or concrete slabs over septic tanks . Our contractor proposed to cut a rectangular hole in the new slab over the old one and then install a metal plate as a lid. Questions: 1. Does this sound like a reasonable plan to you? Is there a better options in terms of (i), (ii) and (iii)? 2. What are our options for a lid? I guess one is steel. Maybe aluminum? Wood, as long it's pressure treated, or treated some other way again rot, and thick enough? 3. What sort of "surprises" should we anticipate? We definitely want to do this right the first time, to avoid having to fix the fix later.