WATER - ROADS' NUMBER ONE ENEMY By WILLIAM T. SUNLEY, Engineer of Local Roads and Streets

Whether it is concrete, asphalt or gravel, when a road fails, inadequate drainage is often the cause. Drainage cannot be overemphasized in road construction and maintenance. Water affects the entire serviceability of a road. Shoulders, side ditches, culverts and embankments that have been damaged can allow water to stand on the road or seep back into the base, saturating and weakening the base/road. Surface cracks also allow water to penetrate and weaken the base. Too much water remaining in the surface, base and subgrade combine with traffic action to cause potholes, cracks, and pavement failure.

To reduce water damage, build and maintain a good drainage system. One dollar spent on drainage will save two dollars on maintenance. A proper drainage system has four major elements-roadway, shoulders, ditches and culverts-which must be maintained.

MAINTAINING PROPER DRAINAGE. Even if a road has been constructed with all the proper drainage design elements, when maintenance is neglected, flooding, washouts, and potholes are likely to occur. To keep a road in good condition, maintain the road surface and shoulders to retain and restore, as nearly as possible, the original design. This involves smoothing and reshaping gravel roads and periodic patching, seal coating or overlaying of surfaced roads. Doing this allows the road and shoulder to properly shed water to the side ditches.

Ditches clogged with debris of sediment should be cleaned to avoid overflowing and washouts. It's very important that water flow through ditches and not stand. Standing water may saturate the subsurface preventing the road from draining during the next storm. The next storm could wash out the roadway. Vegetation in ditches is necessary to help keep the soil in place and minimize erosion. However, it is important to mow vegetation and cut the brush so it will not obstruct water flow. When erosion problems occur, proper protection methods should be used to control and eliminate the eroding soil that can fill other road ditches and culverts or pollute streams and lakes.

Culverts usually channel water from one side of the road to the other, helping to control the flow of water and slowing it down to reduce erosion. Keeping culverts free of sediment avoids roads deterioration and the flooding of adjacent property. Clogged culverts can be cleared using hand tools or mechanized equipment. Damaged culverts should be repaired or replaced.

SUMMARY. Attention to proper drainage maintenance procedures cannot be over-emphasized. A proper drainage system has four well maintained elements-roadways, shoulders, ditches and culverts-that, working together, prevent water from passing through the road surface, remove water from the driving lanes to the side ditches, and carry water away from the roadway. Even roads with all the proper drainage design elements will flood, washout, and develop cracks and potholes if maintenance is neglected. Now is the appropriate time to deal with your drainage problems. •

Credits to: Willy Scheller, Technology Transfer Program Coordinator.

May 1996 / Illinois Municipal Review / Page 23