Arrived and found the main line is clogged. There are no floor cleanouts accessible inside the building.The lower terminal(external) cleanout on the south side of the building is covered in dirt unable to locate it. Ran a cable snake and cleared paper towels from the line. A camera inspection revealed heavy build up of scale and sludge in the cast iron section of the sewer. Unable to pass the camera beyond where the line transitions to the outside due to the poor condition of the pipe. Highly recommend digging up the sewer line on the exterior of the building and hydrojetting and descaling the cast iron. If not, the line will continue to clog. A proposal for hydrojetting will be submitted.