underdrain(redirected from underdrainage)
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A subsurface drain with holes into which water flows when the water table reaches the drain level.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
A drain, installed in porous fill, for drawing off surface water or water from the soil, as under the slab of a structure.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.