Properly draining pavement bases is important for longevity of pavements. Underdrain lateraldischarge pipes are high-volume, low-cost assets which are critical for pavement maintenance.Historically, little attention has been paid to monitoring the health and performance of lateraldischarge pipes and their ability to remove water from underdrain systems below pavements.After a few years, many underdrains can become filled, clogged, and non-functional. When thesedrains fail, the freeze/thaw cycle of moisture in the base contributes heavily to pavementdegradation. However, the literature is silent on how often underdrains should be maintained andwhat that maintenance activity should be.This paper reports on an empirical survey of an 8-mile section of new interstate andexamines the condition of 400 lateral underdrain discharge pipes two years after constructionwas completed. Surprisingly, 20% of the lateral discharge pipes were substantially filled withsediment and in poor shape two years after construction was completed. The paper concludes byrecommending underdrain maintenance, rarely performed earlier then on a 5 year cycle, may bemore effective after the first or second year as a contract item to remove the bulk of the fines thataccumulate in the underdrain systems. Further data collection and asset condition tracking isneeded to develop definitive recommendations for subsequent maintenance intervals, but it isexpected subsequent maintenance intervals would be on the order of 5 years or longer.
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