Perforated Pipe Underdrain for Road Construction

Underdrain is often used to passively remove water from road drainage layers (subbase stone, permeable treated base, soil cement base course, or just common borrow). Here we see a common construction method, although there are many variants on the underdrain design and installation methods. The underdrain is usually allowed to "daylight" to a roadside swale or shoulder, but sometimes it is connected to an inlet/catch basin for a stormwater collection system. US 301 in Delaware was constructed over a 3-year period using seven contracts, in addition to advance clearing, tolling, and landscaping. It extends from the Maryland /Delaware State Line to State Route 1, and was opened to traffic on January 10, 2019. It is a 14-mile limited access highway with four interchanges, 28 bridges, and an all electronic tolling (AET) system. The Delaware T2/LTAP Center provides direct technical assistance, training, and technology transfer to Delaware local agencies relative to their transportation challenges. https://sites.udel.edu/dct/t2-center/