Relief Drains (Tile Drains)

Relief drains are installed similarly to interceptor drains except in a designed pattern arranged to artificially lower the groundwater elevation in the slope soils to a specific elevation. They can also be constructed to intercept surface water drainage if placed at the surface. Figure 13 shows a number of grid patterns. Typically, they are shallower trenches sloped to drain to a collection tightline pipe. Groundwater continues to flow below the drains because these drains are not typically excavated into the impermeable soil.

Figure 13. Relief drain and example grid patterns.


System requires complete coverage of the project area to be effective. May not be feasible in areas where there is vehicle traffic loading on pipes. Previous property development may limit extent of system.


Flexible design layout. Can be used to keep groundwater from daylighting on slope face. Can be used in conjunction with geotextile wrap (sock) around pipe instead of gravel in different areas.


Trenches open at surface can accumulate fine grained soil reducing the system capacity for surface water capture. Requires some maintenance.