Orangeburg is the brand name for a type of bituminous fiber sewer pipe that was installed in Ann Arbor in the 1950s and 1960s. Previously used primarily for conduits for electrical or phone wiring, it became popular for sewer leads in the post-war housing boom. This popularity was based on its lower cost, lighter weight, and ease of cutting relative to the cast iron used for earlier sewer leads. Unfortunately, the pipes can deform over time if not carefully installed, allowing tree root penetration or other failure - a phenomenon more acutely problematic for home sewer leads than, say, telephone lines.
In the late 1960s, PVC (plastic) pipe came into more common usage for sewer leads, and building codes generally no longer permit Orangeburg. However, with an observed useful life of 50-60 years, many homes built in the 1950s-60s still have Orangeburg. If you live in a post-war ranch, it's worth determining whether your home had this pipe, and whether it's been replaced.
The City of Ann Arbor's Planning & Building Department maintains a list of homes where Orangeburg has been replaced, and encourages consulting this list to verify that a particular home's lead has been replaced, or as an indication that a neighboring home may still have an Orangeburg lead: City of Ann Arbor Orangeburg List.pdf .
Neighbors unite to replace Orangeburg sewer lines while city repaves street, AnnArbor.com, August 23, 2013.
Before the city sends crews to repave Mark Hannah Place — a neighborhood street on Ann Arbor's west side — residents on the street are jumping at the chance to save a few bucks. Well, more than a few bucks. A majority of the households on the street are paying a discount rate to have a contractor replace the decades-old Orangeburg sewer lines in front of their homes with new plastic piping.
There are some neighborhoods in Ann Arbor in which this pipe is found frequently, for example the "Airy" built homes in the Wuerth subdivision off Stadium, near Pioneer High School. These are lovely brick ranches, but if you are planning on buying one, make sure that the sewer pipe from the house to the street has already been replaced.