The term aggregate drain refers to a small channel cut into the surface of the earth, typically 12” x 12” but sometimes larger, filled with porous aggregate, that conveys water from one location to another. One purpose for aggregate drains is to limit the need for longitudinal and subgrade pipe underdrain systems, particulary on rural and undeveloped roads with no curbs or storm sewer drainage systems.
Aggregate drains may be backfilled on the top few inches as they will still work to drain water this way but are completely concealed. The material typically used for aggregate is sized primarily from ¾” to 1-1/2”, but larger rock is sometimes used . The typical crew size for aggregate drains is a laborer and an operator. A backhoe, small excavator, or trencher can be used to excavate and shape the trench.