Sewer line embedded or below slab? (1950's house - St. Paul, MN)

Just curious what the typical building protocol was in the 1950's. I'm remodeling my basement and need to set some tapcons into the floor and I obviously don't want to hit the sewer line. Is it likely embedded in the slab or running underneath it? Or is it a crap shoot?

The sewer lines should at least be under the concrete which is 4" thick. Unless your using tap cons longer then 4" it shouldn't be a problem.

John

IF the sewer were imbedded in the concrete, it would be obvious, because there would be a crack in the concrete right above it following the sewer's route.