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JURISDICTIONAL DELINEATION REPORT FAIRVIEW STREET IMPROVEMENTS A <br />N OVEMBER 2018 FROM 9TH STREET TO 16TH STREET AND BRIDGE REPLACEMENT PROJECT `J" <br />SANTA ANA, CALIFORNIA <br />Hydrophytic Vegetation <br />Hydrophytic vegetation is plant life that grows and is typically adapted for life in permanently or <br />periodically saturated soils. The hydrophytic vegetation criterion is met if more than 50 percent of <br />the dominant plant species from all strata (tree, shrub, herb, and woody vine layers) are considered <br />hydrophytic. Hydrophytic species are those included on the Corps most current National Wetland <br />Plant List (Lichvar, R.W., et al. 2016). Each species on that list is rated according to a wetland <br />indicator category, as shown in Table A. To be considered hydrophytic, the species must have <br />wetland indicator status (i.e., be rated as Obligate Wetland [OBL], Facultative Wetland [FACW], or <br />Facultative [FAC]). <br />Table A: Hydrophytic Vegetation <br />Category <br />Rating <br />Probability <br />Obligate Wetland <br />OBL <br />Almost always occur in wetlands (estimated probability > 99 percent) <br />Facultative Wetland <br />FACW <br />Usually occur in wetlands (estimated probability 67-99 percent) <br />Facultative <br />FAC <br />Equally likely to occur in wetlands and nonwetlands (estimated probability <br />34-66 percent) <br />Facultative Upland <br />FACU <br />Usually occur in nonwetlands (estimated probability 67-99 percent) <br />Obligate Upland <br />UPL <br />Almost always occur in nonwetlands (estimated probability > 99 percent) <br />The delineation of hydrophytic vegetation is typically based on the most dominant species from <br />each vegetative stratum (strata are considered separately). When more than 50 percent of these <br />dominant species are hydrophytic (i.e., FAC, FACW, or OBL), the vegetation is considered <br />hydrophytic. In particular, the Corps recommends the use of the "50/20" rule (also known as the <br />dominance test) from the Regional Supplement for determining dominant species. Under this <br />method, dominant species are the most abundant species that immediately exceed 50 percent of <br />the total dominance measure for the stratum, plus any additional species composing 20 percent or <br />more of the total dominance measure for the stratum. <br />In cases where indicators of hydric soil and wetland hydrology are present but the vegetation <br />initially fails the dominance test, the prevalence index must be used. The prevalence index is a <br />weighted average of all plant species within a sampling plot. The prevalence index is particularly <br />useful when communities only have one or two dominants, where species are present at roughly <br />equal coverage, or when strata differ greatly in total plant cover. In addition, Corps guidance <br />provides that morphological adaptations may be considered when determining hydrophytic <br />vegetation when indicators of hydric soil and wetland hydrology are present (Corps 2008). If the <br />plant community passes either the dominance test or the prevalence index after reconsideration of <br />the indicator status of any plant species that exhibit morphological adaptations for life in wetlands, <br />then the vegetation is considered hydrophytic. <br />\\vcorp12\projects\WKE1702\N ES- MI\November 2018 Sub mittal\Fairview Street I m proveme nts_Draft JD 110918.docx all/09/18» 6 <br />