What: Structures are maintained, repaired or constructed to protect pavements from water from ground sources and from rain. These include ditches, culverts, interception drains (such as subsurface drains including underdrains and trench drains), free draining (permeable) bases, shoulder maintenance and erosion control. Ditches should be routinely maintained by mowing, cleaning and reshaping. They should have a gentle enough slope for easy maintenance. Culverts should be inspected periodically for cracks, corrosion or sediment buildup that might lead to failure. Culvert maintenance includes flushing, lining, cleaning debris, and extending ends. Erosion control can be addressed with vegetation, fabrics and stones with geotextile. Cross-slopes should also be maintained to allow proper drainage.
Where: Water may enter roadways through cracks and surface defects on the pavement or it can infiltrate from the side. Capillary action may draw moisture up from the water table and cause the base to become saturated. Excess water in ditches and flowing through culverts can cause damage to roads by causing washouts and failure of storm water systems, slope instability, and erosion. All of these avenues must be addressed to insure water drains away quickly from the pavement structure, including the subbase.
Why (advantages): Good drainage is absolutely critical to allow roads to last as long as possible. Poor drainage is the single most common problem that leads to premature failures on all types of pavements. It can be responsible for rutting, cracking, potholes, erosion, washouts, heaving and flooding and eventual premature roadway failure.
Why not (disadvantages): The only time a road should not have its drainage maintained is when it is to be abandoned.
When: Drainage maintenance should be an ongoing process. Drainage repair should be done as soon as a problem or any standing water is noted. Bleeding, water pumping, corner breaks, unbound aggregates, potholes and rutting can all be signs of drainage or moisture problems.
Estimated life extension: 5-20 years.