I have a infiltrated cast iron pipe that runs off a my kitchen sink/dishwasher/clothes washer waste line. It is below the concrete. It looks to be clogged at the 7 ftish mark, and the floor drain links past the clog/infiltration. My ground is super saturated and I am leery of having to excavate and follow the line out. I have the option of rerouting to the main line above ground, but the last (of many plumbers) spooked me by saying that rerouting and cutting into the main line could cause other problems, and he would prefer excavating. I really would prefer to just reroute and avoid the excavation and line chasing. Should I trust my gut and go with the reroute?
Infiltrated implies that something from outside the pipe got inside the pipe to clog it. If so, then when the pipe is bypassed, stuff could possibly flow back from other entry points to where the infiltration occurs and then it could become exfiltration, more commonly known as a leak. How old is the cast iron (house)? It should last decades. Is there an access point in the basement near where the kitchen drains etc tie in to the CI in the floor? If so, can somebody get a camera in there to see what the problem really is. Is it the pipe gone bad, or too much junk from the washing machine etc. down the drain?
I am a bit puzzled by some of the statements in your post. By "rerouting to the main line above ground" do you mean installing new drain line above your basement floor and connecting it to the existing line where it exits your house, or somewhere along the line between the kitchen and the exit point?
Does Mr "dig it up" plumber propose digging up just the seven or so feet to the clog and replacing that, or is he planning to dig from the kitchen etc. to where the pipe exits your house, and replace all of it, and tie in everything else (bathrooms etc,) to his new line?
Did the guys who want to run new line talk about how they would recommend managing the bypassed portion of cast iron, so that there isn't back flow to the area that is clogged (infiltrated).
Maybe you have asked all these questions and had them answered. I need to hear the answers before I venture my humble pinion about your situation. No matter which option you choose, it will probably be expensive.