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4/7/20 (P:\TER2001\Delineation\San Leandro Treatment Wetland JD Revised 4‐7‐20.doc) 3 sediments, and an un‐named estuary of the San Francisco Bay. The San Francisco Bay is a tidal Traditional Navigable Water of the United States. REGULATORY BACKGROUND Clean Water Act Jurisdiction The field investigations of potential jurisdictional wetlands were conducted using the routine determination method provided in the Corps Wetlands Delineation Manual (Environmental Laboratory 1987) and the revised procedures in the Regional Supplement to the Corps Wetland Delineation Manual: Arid West Region (Version 2.0) (Arid West Supplement; U.S. Army Corps of Engineers 2008). This methodology entails examination of specific sample points within potential wetlands for hydrophytic vegetation, hydric soils, and wetland hydrology. By the federal definition, all three parameters must be present for an area to be considered a wetland. Hydrophytic plant species are listed by the National Wetland Plant List (Lichvar et al. 2016). The National List identifies five categories of plants according to their frequency of occurrence in wetlands. The categories are: Obligate wetland plants (OBL) Plants that occur almost always in wetlands Facultative wetland plants (FACW) Plants that usually occur in wetlands Facultative plants (FAC) Plants that are equally likely to occur in wetlands or non‐wetlands Facultative upland plants (FACU) Plants that usually occur in uplands Obligate upland plants (UPL) Plants that occur almost always in non‐wetlands An area is generally considered to have hydrophytic vegetation when more than 50 percent of the dominant species in each stratum (tree, shrub, and herb) are in the obligate wetland, facultative wetland, or facultative categories. Hydric soils are defined by criteria set forth by the National Technical Committee for Hydric Soils (NTCHS). These criteria are given in the Wetland Delineation Manual Supplement and are based on depth and duration of soil saturation. Hydric soils are commonly identified in the field by using indirect indicators of saturated soil, technically known as redoximorphic features. These features are caused by anaerobic, reduced soil conditions that are brought about by prolonged soil saturation. The most common redoximorphic features are distinguished by soil color, which is strongly influenced by the frequency and duration of soil saturation. Hydric soils tend to have dark (low chroma) colors that are often accompanied by reddish mottles (iron mottles), reddish stains on root channels (oxidized rhizospheres), or gray colors (gleying). The Arid West Supplement contains descriptions of numerous federally recognized hydric soil indicators. Under natural conditions, development of hydrophytic vegetation and hydric soils are dependent on a third characteristic, wetland hydrology. This criterion is met if the area experiences inundation or soil saturation to the surface for a period equal to at least 5 percent of the growing season (about 14