I have an old concrete septic tank. I don't know much about septic tanks and this is the first house I have owned with one. I think it was installed when the house was built in the early 1950's. When I dug it up the lid is cast iron and about 24" by 48" and the hole into the tank is about 20" by 40" or so. I don't know if I have a second tank lid or just the one. I also want to be able to have access without digging it up but I don't know if I can install a riser conversion for it. Any advice would be of great help.