Contemplating replacing 83 year old cast iron sewer under basement floor. Even contemplating getting permits! Main 4" and secondary 2" stacks already PVC to basement floor so easy tie in to them. Sewer runs under main basement floor, under front wall of house, under front porch coal cellar floor and under front wall of porch. Wife wants to add 1/2 bath in room under front porch so toilet/sink rough in and venting will need to be added there.
Question: What would the normal procedure be where the sewer runs under front wall footer? Excavate under footer and backfill with concrete? Leave three foot section of iron in the middle of an otherwise new PVC DVW system?