2019-07-09_REVISION - M2004044 (35)

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! t 2019 Wetland Delineation Report Tucson South Sand and Gravel Mine—Brighton, Colorado 3.1.6 Wetland Mapping A wetland delineation was conducted to identify the transitional area between wetland and upland conditions. Wetland scientists accomplished the delineation by walking the outer limit of visibly identifiable wetland vegetation between the paired wetland and upland sample plots recording the path with a Trimble Geo 7X GPS. The Trimble Geo 7X GPS unit provides an estimated 3-foot (1-meter) survey accuracy (post-processing). The field-collected data were plotted as a map layer using geographic information system (GIS) software. Representative Photos of the wetlands are provided in the photo log included as Attachment 3. 3.1.7 Assessment of Other WOTUS Non-wetland WOTUS are regulated under the CWA for the placement of dredged or fill materials. The desktop analysis and field surveys identified other WOTUS including ephemeral, intermittent, and perennial streams and ponds. 3.1.7.1 Surface Water Assessment Methods Stream and pond features were mapped along their ordinary high water marks (OHWM). The USACE regulations define "ordinary high water mark" as: ... that line on the shore 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 soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas. Once the OHWM was observed in the field by the team, the Trimble Geo 7X GPS unit was used to map this line in the Project area. Only the western OHWM boundary was mapped during the field survey because the Project does not extend beyond the OHWM and no impacts to the South Platte River are anticipated. . 3.1.8 Uplands Several upland points were established during the survey. Upland points were mapped to document that neither wetland nor other WOTUS conditions prevailed at these locations. These locations are generally flat or convex surfaces that do not hold surface water. They are non- jurisdictional and do not need to be avoided due to presence of wetlands or other potentially jurisdictional WOTUS. Uplands are shown in Figure 2 with an "UP" in their name. 3.1.8.1 Swales One swale feature was observed during field reconnaissance. Swales are linear or curvilinear depressional features that naturally collect overland flows from surrounding uplands. The swale location that was mapped was determined to lack a defined OHWM, bed, bank, and scoured channel. It did not contain wetland plants, but was instead vegetated with upland species. 6