The benefits of tri-axial Tendrain over natural materials in wastewater treatment applications are numerous. Only a tri-axial structure is capable of meeting all of the requirements of the subsurface drainage layer. These requirements include: high flow capacity; compressive resistance over long periods of time; constant void space for capillary break; and rapid fluid movement from point of entry to collection. For a concrete liner, additional requirements include the ability to pour concrete directly on top of the geocomposite without blinding the flow voids. The bottom layer of geotextile provides filtration and renention of underlying soil.