Thanks bimr. That's a good point.
I hadn't considered condensation but you may be on to something there. At this point its difficult to know what the design intent was since it was designed and installed in the mid 50's.
The community I work for hired a consultant several years ago to evaluate the condition of an existing aerial river crossing. The crossing itself is insulated 36" steel pipe that was found to be in excellent condition via ultrasonic thickness measurements taken along its length.
The water main...
