The side slope of a table drain should be 6 to 1 where possible, but can be as steep as 4 to 1.
The function of a table drain is to collect water that has fallen on the carriageway or the batters of a cutting and flowed to the edge of the formation. Table drains are essential wherever the road is in cutting and often desirable along the shoulders of embankments. Table drains require frequent maintenance, such as grading of unlined drains to remove silt and other debris that may easily block the flow, and to restore the original shape. Scours in table drains need prompt attention to prevent serious damage that may lead to undermining of the drain lining, the carriageway, or the cutting batters.
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