It is described as "steel pipe," and I agree that the walls are way
too thick for steel or iron pipe. And the pipes are too long to
represent precast concrete pipe.

The wall thickness of precast concrete pipe varies with the load it
is specified for, but as a general rule the wall thickness (in
inches) is about one greater than the pipe diameter (in feet). So a
2-foot diameter concrete pipe would have a 3" wall thickness, and a
6-foot diameter concrete pipe would have a 7" wall thickness.
Concrete pipes are usually 8 or 12 feet long.

Steel or iron pipe would have wall thickness measured in the
fractions of an inch. Lengths would vary from 20 feet (cast iron
pipe) up to 60 feet (steel pipe).