The earliest forms of shoulder drains are called French drains and were popularized by Henry French (1813–1885) of Concord, Massachusetts. These were simple ditches that were pitched from a high area to a lower one and filled with gravel and perforations.  Today a typical shoulder drain installation used on NCDOT ROI would encompass a high production trencher to excavate earth material and then a geotextile fabric lining the trench would be installed by hand. Geotextiles prevent migration of the drainage material and also prevent soil and roots from entering and clogging the pipe. Next a HDPE or PVC pipe would be installed in the bottom of the trench and then an aggregate material would be placed around the pipe and then trench filled in. The perforated pipe provides a minor subterranean volume of storage for water, yet the prime purpose is drainage of the area along the full length of the pipe via its perforations and to discharge any surplus water at its terminus. The last step is to install a solid outlet pipe that is connected laterally to the adjacent runs and attached to drainage boxes or outlet pads.