Types of Subsurface Drainage

Deep Open Drains

• Shallow open drains are open ditches used to remove standing water from the surface. Deep open drains provide subsurface drainage and differ only in their depth. They need to be deep enough to lower the water table level to the desired level. They are dug at strategic locations and not only drain excess water from the soil, but also drain away surface water directly. Deep open drains are the least expensive subsurface drains to install, but they use up land, interfere with machinery and require a significant amount of maintenance.

Pipe Drains

• Pipe drains are perforated or slotted pipes buried underground at the desired water table level and covered with permeable landfill. In the past they were usually made of clay or concrete, but modern systems are more likely to be made of polyvinylchloride (PVC) or corrugated plastic. Although more expensive to install than deep open ditches, pipe drains do not take up surface space and require less maintenance.

Mole Drains

• Mole drains work like pipe drains but without the pipe. They are useful in certain types of soil where pipe drainage is impractical. They are unlined cylindrical channels formed in the soil by a mole plow. The plow consists of a cylinder sharpened at the front called a foot and a slightly larger cylinder attached behind it called an expander. The foot is connected to the surface by a leg which cuts a channel above the mole cylinder. The action of the leg and the expander also create fissures along the sides of the leg channel. The leg channel and the fissures provide a conduit to the mole cylinder for both surface and subsurface drainage.

Interceptor Drains

• Interceptor drains are named more for their function than their form. They are drains placed at the intersection of sloped and flat land to intercept the runoff from the slope. They may be open, pipe or mole drains.

Groundwater Pumps

• In some cases, groundwater pumps may be used to pump water from an aquifer--an underground water supply--in order to lower the water table level. Groundwater pumping is expensive, effective only under very specific conditions and usually requires a government permit.