This configuration tied two neighbor's sewers together. The neighbor had replaced his sewer 20 years ago, but the tie-in was still on my customer's line, as was the main sewer.
We had to dig it up, put in a clean out to access the 80' that runs under slab and a clean out to do the sewer to the street. Confusing, yes. And dirty.
After we did the repairs, we still had to clean the sewer.