; (BB) a subterranean river; (CC) a culvert, dam, tunnel, or similar artificial feature; or (DD) a debris pile, boulder field, or similar natural feature. (cc) Relocation A ditch that relocates a tributary, is constructed in a tributary, or is constructed in an adjacent wetland is a tributary if the ditch meets the requirements of subclause (I). (xiv) Typical year The term typical year means a year within which precipitation and other climactic variables are within the normal periodic range (e.g., seasonally, annually) for the geographic area of the applicable body of water based on the most recent 30-year period. (xv) Upland The term upland means a land area that, under normal circumstances— (I) is not a wetland because it does not meet the requirements described in each of items (aa), (bb), and (cc) of clause (xvii)(I); and (II) does not lie below the ordinary high water mark or the high tide line of a body of water described in subparagraph (A). (xvi) Waste treatment system The term waste treatment system includes all components, including lagoons and treatment ponds (such as settling or cooling ponds), that are designed to either convey or retain, concentrate, settle, reduce, or remove pollutants, either actively or passively, from wastewater prior to discharge (or eliminating any such discharge). (xvii) Wetland (I) In general The term wetland means an area— (aa) that is inundated or saturated by surface water or groundwater; (bb) for which the inundation or saturation described in item (aa) is at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of vegetation