2025-03-14_PERMIT FILE - M2025016 (26)

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Natural Resources Assessment P125 Gravel Mine - Southwest of State Highway 66 and County Road 17 Weld County, Colorado ERO Project #24-180 8 ERO Resources Corporation Jurisdictional Assessment To assist the Corps in making a preliminary jurisdictional determination, ERO reviewed the proximity and potential surface water connection of wetlands to known jurisdictional WOTUS using aerial photo interpretation and information from the wetland delineation. This information is accurate as of the date of this report and may change if further guidance documentation is issued. The project area is adjacent to St. Vrain Creek, an unnamed tributary to St. Vrain Creek, and the Last Chance Ditch. The Last Chance Ditch is an agricultural ditch that appears to have been excavated in uplands and would revert to uplands if irrigation flows were removed and, therefore, is an exempt feature. The Last Chance Ditch is likely nonjurisdictional. St. Vrain Creek is a known jurisdictional WOTUS. Description of Wetlands and Other Waters ERO conducted a wetland delineation of the project area during the 2024 site visit. Data were collected from various locations in the project area to document the characteristics of uplands, wetlands, and the transition areas between them. Each data point (DP) was given a label that corresponds to a location shown on Figure 2 and routine wetland determination data forms in Appendix B. ERO mapped approximately 2.7437 acres of wetlands in the project area during the 2024 site visit. Table 1 provides a summary of the mapped areas, including the Cowardin classification and HGM class for each wetland in the project area. No open waters or streams were identified in the project area during the 2024 site visit. Table 1. Wetland area, Cowardin classification, and HGM. Wetland ID1 Latitude Longitude Feature Size (acre) Cowardin Classification2 HGM W1 40.1994° -104.911° 0.0769 PEM Depressional W2 40.1987° -104.911° 0.0134 PEM Depressional W3 40.1971° -104.916° 0.1033 PEM Riverine W4 40.1973° -104.917° 0.3982 PFO/PUB Riverine W5 40.19547° -104.912° 2.1519 PEM Slope Wetland Total 2.7437 1W = Wetland. 2PEM = palustrine emergent, PFO = palustrine forested, PUB = palustrine unconsolidated bottom. Depressional Wetlands (W1 and W2) W1 and W2 are in the northeastern portion of the project area in depressional swales (Figure 2; Photo 4 and Photo 5). W1 and W2 are not identified in the NHD or on the NWI (USGS 2024; Service, n.d.). W1 and W2 have direct hydrological connections to the unnamed tributary to St. Vrain Creek. ERO believes these features would be considered jurisdictional. At DP1 and DP3, vegetation was dominated by Pennsylvania smartweed (Persicaria pensylvanica), common threesquare (Schoenoplectus pungens), and foxtail barley (Hordeum jubatum). Vegetation at DP1 and DP3met the rapid test for hydrophytic vegetation. At DP1 and DP3, the soils contained matrix colors of 10YR 3/1 and 10YR 2/1 with redoximorphic concentrations of 7.5YR3/3 and 5YR 3/4. The hydric