ECONOMIC IMPACT OF PAVEMENT SUBSURFACE DRAINAGE

Even though road builders have recognized the role of water in pavement deterioration since the last century, with the development of the rational methods of pavement design evolved a strong reliance on the ability to build pavements stout enough to resist damage without the benefits of good drainage. Even today, most designers attempt to improve the strength and quality of the pavement and base layers used in road construction and neglect rapid drainage. Much of the water that falls on pavements penetrates the structural section through cracks, joints, and porous surfaces. Conventional slow-draining pavements are deteriorating more rapidly than is necessary because of the impacts of heavy vehicles on flooded structural sections. The most positive pavement drainage systems use an open-graded drainage layer under the full width of a roadbed with adequate collector pipes and outlet pipes. However, the California Department of Transportation has found that retrofit edge drains are greatly reducing the rate of step faulting of existing portland cement concrete pavements. The impact of positive rapid drainage features on the performance of a number of pavements is reviewed, with particular emphasis on the establishment of a cost-benefit relationship. The results of this evaluation indicate that the increased cost of effective pavement drainage is almost incidental to the savings realized through improved performance.