2008-11-26_PERMIT FILE - M2008080 (3)

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Kersey Gravel Wetland Delineation Report Ecoloizical Resource Consultants. Inc. 4.0 Wetland Delineation Methodology The USACE and the Environmental Protection Agency (EPA) jointly define wetlands as "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions". Three general environmental parameters define a wetland. These parameters consist of the presence of hydrophytic vegetation, hydric soils, and wetland hydrology. Areas that do not meet any one of the wetland parameters (hydrophytic vegetation, hydric soils and/or wetland hydrology) were classified as a non-wetland and mapped as such. In addition, waters of the U.S. are defined as areas that "include essentially all surface waters such as rivers, streams and their tributaries, all wetlands adjacent to these waters, and all ponds, lakes and reservoirs". Waters of the U.S. are further defined by the ordinary high water mark (OHWM). The OHWM is characterized as "the line on the shores established by the fluctuations of water and indicated by physical characteristics such as: a clear natural line impressed on the bank, shelving, changes in the character of the soil, wetland vegetation, the presence of litter and debris, and other appropriate means that consider the characteristics of the surrounding areas". These definitions are the basis of this delineation. ERC conducted a wetland delineation to identify and document the presence and extent of wetlands and waters of the U.S. within the Study Area. The delineation was completed using the routine (on-site) methodology and criteria specified in the 1987 Corps of Engineers Wetlands Delineation Manual and subsequent guidance (1987 Manual) (Environmental Laboratory 1987, U.S. Army Corps of Engineers (USACE) 1991, USACE 1992). References to the 1987 Manual and to Environmental Laboratory 1987 in this report are intended to include all subsequent guidance to the Manual. These methods require that evidence of three parameters (a dominance of hydrophytic vegetation, hydric soils, and wetland hydrology) be simultaneously present for a wetland determination. Routine wetland determination forms were completed for each data plot identifying information on vegetation, soils, and hydrology (Appendix Q. Based on the field observations, a wetland determination was made, the limits of plant community types delineated, and a wetland/upland boundary field flagged. Each wetland boundary determination point was identified in the field with a pink pin flag. Upon completion of the delineation and GPS mapping, the wetland flags were removed at the request of the land owner. Each wetland determination point was recorded using a Trimble Global Positioning System (GPS) GeoXH. Where no wetlands were present, potential waters of the U.S. were delineated using either the OHWM of the channel, or the channel centerline. Post processing differential correction provided mapping accuracy (horizontal) of +/- 2.0 feet. Wetland areas were plotted using ArcMap GIS (Version 9.2) and overlain on a 2006 orthorectified aerial photograph which was obtained from the U.S. Department of Agriculture-Farm Service Agency (USDA-FSA). The enclosed wetland delineation map (Appendix B) dated July 10, 2008, represents the wetland areas and irrigation ditches identified by ERC within the Study Area. 5.0 Summary of Findings Irrigation Ditches Two active irrigation ditches are located within the Study Area: the North Branch of Plumb Ditch and the South Branch of Plumb Ditch. Plumb Ditch (formerly known as Highland Ditch), originates from the South Platte River and flows for approximately 2.3 miles prior to entering the Study Area on the west side. The Highland Ditch was decreed in the District Court of Arapahoe County on April 28, 1883 with an appropriation date of October 1, 1871 for 24.4 cubic feet per 5 111