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Natural Resources Assessment
<br />P125 Gravel Mine - Southwest of State Highway 66 and County Road 17
<br />Weld County, Colorado
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<br />ERO Project #24-180 7
<br />ERO Resources Corporation
<br />characteristics of the surrounding areas.” The Corps defines “stream bed” as “the substrate of the
<br />stream channel between the OHWMs. The substrate may be bedrock or inorganic particles that range in
<br />size from clay to boulders.”
<br />The boundaries of identified wetlands and other characteristics of potential WOTUS were mapped using
<br />a Trimble Global Positioning System (GPS) unit. Data were differentially corrected using the
<br />CompassCom base station. All differential correction was completed using Trimble Pathfinder Office 5.9
<br />software. GPS data were incorporated using ESRI® ArcGIS Desktop software. Additionally, where
<br />appropriate, wetlands were drawn on georectified aerials and then digitized.
<br />Wetland Classification
<br />Delineated wetlands were classified according to the U.S. Fish and Wildlife Service’s Cowardin
<br />classification system combined with a hydrogeomorphic (HGM) approach (Cowardin et al. 1979; Brinson
<br />1993). The HGM approach assesses the chemical, physical, and biological functions of wetlands based on
<br />their geomorphic setting, water source, and hydrodynamics. HGM classes found in Colorado are mineral
<br />soil flats, organic soil flats, riverine, lacustrine fringe, slope, and depressional. The Cowardin
<br />classification uses a hierarchical structure of systems, subsystems, and classes to classify both wetlands
<br />and deepwater habitats. Wetlands with persistent or nonpersistent vegetation are classified in the
<br />Cowardin system as palustrine, which typically includes wetlands referred to as marshes, fens, wet
<br />meadows, and sloughs. The palustrine system also includes small, shallow, permanent, or intermittent
<br />water bodies such as ponds. Palustrine wetlands may be situated shoreward of lakes and river channels,
<br />on river floodplains, in isolated catchments, or on slopes (Cowardin et al. 1979). Under the palustrine
<br />system, wetlands are classified as emergent (erect, rooted, herbaceous, and usually perennial
<br />hydrophytes that remain standing until at least the next growing season); scrub-shrub (woody
<br />vegetation less than 20 feet tall); or forested (woody vegetation 20 feet or taller). In wetlands where
<br />more than one wetland type occurs, the wetland type of the largest area is used. For example, an area
<br />that is predominantly palustrine emergent (PEM) wetlands but also contains a small amount of
<br />palustrine scrub-shrub wetlands would be categorized as PEM wetlands. Because of the limited
<br />occurrence of the smaller wetland types in the larger wetland polygons, these areas were not separated
<br />within the delineated polygons.
<br />The Cowardin riverine system includes wetlands and deepwater habitats contained within a channel,
<br />except wetlands dominated by trees, shrubs, and emergent vegetation. The riverine system usually
<br />contains flowing water and is bounded on the landward side by uplands, channel banks, or other
<br />wetlands. Within the riverine system, wetlands are divided into the tidal, lower perennial (low gradient
<br />and slow water), upper perennial (high gradient and fast water), and intermittent subsystems. Within
<br />these subsystems, riverine wetlands are further classified as unconsolidated bottom, aquatic bed,
<br />streambed, rocky shore, unconsolidated shore, and emergent wetland (nonpersistent).
<br />During the wetland delineation, ERO classified the wetlands as PEM, palustrine forested (PFO), and
<br />palustrine unconsolidated bottom (PUB).
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