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L S. <br />sediments, and an un-named estuary of the San Francisco Bay. The San Francisco Bay is a tidal <br />Traditional Navigable Water of the United States. <br />REGULATORY BACKGROUND <br />Clean Water Act Jurisdiction <br />The field investigations of potential jurisdictional wetlands were conducted using the routine <br />determination method provided in the Corps Wetlands Delineation Manual (Environmental <br />Laboratory 1987) and the revised procedures in the Regional Supplement to the Corps Wetland <br />Delineation Manual: Arid West Region (Version 2.0) (Arid West Supplement; U.S. Army Corps of <br />Engineers 2008). This methodology entails examination of specific sample points within potential <br />wetlands for hydrophytic vegetation, hydric soils, and wetland hydrology. By the federal definition, <br />all three parameters must be present for an area to be considered a wetland. <br />Hydrophytic plant species are listed by the National Wetland Plant List (Lichvar et al. 2016). The <br />National List identifies five categories of plants according to their frequency of occurrence in <br />wetlands. The categories are: <br />Obligate wetland plants (OBL) <br />Facultative wetland plants (FACW) <br />Facultative plants (FAC) <br />Facultative upland plants (FACU) <br />Obligate upland plants (UPL) <br />Plants that occur almost always in wetlands <br />Plants that usually occur in wetlands <br />Plants that are equally likely to occur in wetlands or non -wetlands <br />Plants that usually occur in uplands <br />Plants that occur almost always in non -wetlands <br />An area is generally considered to have hydrophytic vegetation when more than 50 percent of the <br />dominant species in each stratum (tree, shrub, and herb) are in the obligate wetland, facultative <br />wetland, or facultative categories. <br />Hydric soils are defined by criteria set forth by the National Technical Committee for Hydric Soils <br />(NTCHS). These criteria are given in the Wetland Delineation Manual Supplement and are based on <br />depth and duration of soil saturation. Hydric soils are commonly identified in the field by using <br />indirect indicators of saturated soil, technically known as redoximorphic features. These features are <br />caused by anaerobic, reduced soil conditions that are brought about by prolonged soil saturation. <br />The most common redoximorphic features are distinguished by soil color, which is strongly <br />influenced by the frequency and duration of soil saturation. Hydric soils tend to have dark (low <br />chroma) colors that are often accompanied by reddish mottles (iron mottles), reddish stains on root <br />channels (oxidized rhizospheres), or gray colors (gleying). The Arid West Supplement contains <br />descriptions of numerous federally recognized hydric soil indicators. <br />Under natural conditions, development of hydrophytic vegetation and hydric soils are dependent on <br />a third characteristic, wetland hydrology. This criterion is met if the area experiences inundation or <br />soil saturation to the surface for a period equal to at least 5 percent of the growing season (about 14 <br />4/7/20 (P:\TER2001\Delineation\5an Leandro Treatment Wetland 1D Revised 4-7-20.doc) <br />