Appendix A Natural Environment Study (Minimal Impacts)

Home Browse Search

JURISDICTIONAL DELINEATION REPORT FAIRVIEW STREET IMPROVEMENTS A N OVEMBER 2018 FROM 9TH STREET TO 16TH STREET AND BRIDGE REPLACEMENT PROJECT `J" SANTA ANA, CALIFORNIA In some cases, waters found to be isolated and not subject to CWA regulation may be regulated by the Regional Water Quality Control Board (RWQCB) under the State's Porter -Cologne Water Quality Control Act (Porter -Cologne Act), as described later in this section. WETLANDS Wetland delineations for Section 404 purposes must be conducted according to the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region (Version 2.0) (Regional Supplement) (Corps 2008) and the Corps of Engineers Wetlands Delineation Manual (1987 Manual) (Corps 1987). Where there are differences between the two documents, the Regional Supplement takes precedence over the 1987 Manual. The Corps and the United States Environmental Protection Agency (EPA) define "wetlands" as follows: Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted to life in saturated soil conditions. To be considered a jurisdictional wetland under Section 404, an area must possess three wetland characteristics (three parameters): hydrophytic vegetation, hydric soils, and wetland hydrology. Each characteristic has a specific set of mandatory wetland criteria that must be satisfied for that particular wetland characteristic to be met. Several indicators may be analyzed to determine whether the criteria are satisfied. Hydrophytic vegetation and hydric soil indicators provide evidence that episodes of inundation have lasted more than a few days or have occurred repeatedly over a period of years, but do not confirm that an episode has occurred recently. Conversely, wetland hydrology indicators provide evidence that an episode of inundation or soil saturation occurred recently, but do not provide evidence that episodes have lasted more than a few days or have occurred repeatedly over a period of years. Because of this, if an area lacks one of the three characteristics under normal conditions, the area is considered nonwetland under most circumstances. Determination of wetland limits may be complicated by a variety of natural environmental factors or human activities, collectively called "difficult wetland situations," including cyclic periods of drought and flooding or highly ephemeral stream systems. During periods of drought, for example, bank return flows are reduced and water tables are lowered. This results in a corresponding lowering of the OHWM and invasion of upland plant species into wetland areas. Conversely, extreme flooding may create physical evidence of high water well above what might be considered ordinary and may allow the temporary invasion of hydrophytic species into nonwetland areas. In the highly ephemeral systems typical of Southern California, these problems are encountered frequently. In these situations, professional judgment based on years of practical experience along with extensive knowledge of local ecological conditions comes into play in delineating wetlands. The Regional Supplement provides additional guidance for difficult wetland situations. \\vcorp12\projects\WKE1702\N ES- MI\November 2018 Sub mittal\Fairview Street I m proveme nts_Draft JD 110918.docx all/09/18»