In any of these cases, a cross drain interceptor should be provided. Details of cross drain interceptors at various locations are shown in Figure 606.3 . The cross drain outlets should be tied into the longitudinal edge drain collector and outlet system with provision of maintenance access for cleaning. The lack of adequate structural section drainage for concrete pavement has become increasingly evident. This combination creates the potential for severe pavement damage, especially in heavily traveled truck lanes.
Heavy trucks depress the edges of curled slabs at the transverse joints.
In addition, the pumping action along the outer edge of the pavement has resulted in the erosion and movement of fine materials from the existing aggregate base under the adjoining shoulders. The fine materials from both sources are transported by pumping action and deposited under the trailing edge of the pavement slabs, resulting in step faulting, uneven slab support, and slab rocking and cracking. Failure of the inner edge of the shoulder also results from loss of aggregate base support. In an effort to provide positive drainage and minimize base erosion and resultant slab faulting, edge drains and lean concrete base were adopted as standards for new construction in 1980. Because of their excellent drainage characteristics, the treated permeable bases must be given first consideration in the design of structural sections for concrete pavements.