PERMEABLE BASES PROLONG PAVEMENT, STUDIES SHOW

It is described how several states are opting to use open-graded or permeable bases to allow infiltrated moisture to rapidly drain through the base and out the bottom of the structure. A permeable base is normally characterized by an open-graded, crushed, angular aggregate with essentially no fines. A longitudinal edge drain collector system commonly is used to rapidly drain the moisture that collects in the permeable base. Typical permeable base pavement sections are illustrated. States' experience in this area are reported. The various drainage methods used are described: lognitudinal edge drain collector, excavated trench, and V-ditch. Those states using untreated permeable bases use a filter aggregate layer, which in most cases, is the state's conventional dense-graded aggregate base material. It has been found that properly designed and constructed permeable bases virtually eliminate pumping, faulting and cracking. Comments are also made on the rideability and cost factors.