Abstract: A substantially cylindrical drainage unit for use when buried in soil as part of a wastewater leach field comprises a first plastic aggregate mass that is contained within netting, with an optional central perforated pipe. A segmented quilt comprises the exterior surface of the drainage unit which is in contact with soil. Pebble aggregate that is smaller in particle size than the first aggregate is contained with the cavities of the quilt segments. Quilts having different segment shapes and sizes are manufactured by specialized apparatus which creates rectilinear or serpentine seams.