2023-07-12_PERMIT FILE - M2022048 (2)

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that surface modification in the area occurred to better site the tailwater drainage ditch for agricultural operations. Any such modification took place prior to 1999, as the current alignment for B3 is observable in those dated aerial images. B4. This feature is a surface water drainage (Figure 4.) that follows the depicted blue line on the 1978 USGS topographic map. This feature follows a natural sinuous drainageway, and is fed by irrigation tailwater from sources within the south parcel of West Farm. It flows from south to north along the west boundary of the primary alluvial terrace and terminates at feature B5, ultimately flowing into the South Platte River. B5. B5 is the northern terminus of the surface water features that originate in the south parcel of West Farm and end at the South Platte River to the north. This feature is an extension of B4 and continues within the natural drainageway to the terminus at the South Platte River channel. C1. This man-made ditch is a tailwater collection ditch with water origins at the irrigation pivot pump (173) and/or the off-site irrigation pond (D1). This feature collects irrigation tailwater from agricultural fields in the southeast quadrant of West Farm, and conveys the water to the north,crossing under Weld County Road 32'/2,onto the West Farm north parcel, discharging into the South Platte River at the north boundary of West Farm. C2. This feature is a cattail marsh (Figure 5.) located in a topographic low, possibly excavated, north of West Farm south parcel agricultural fields, and above the culvert conveying tailwater drainage under Weld County Road 32'/2. This feature has origins along CI, and was concluded to exist due to high water levels present as tailwater backs up prior to exiting through the culvert under the county road. This feature likely would not exist without the presence of tailwater accumulation. C3. This feature consists of two man-made irrigation ditches,portions of which are concrete lined, running east-west, draining fields immediately south of the county road, and conveying tailwater to the culvert under Weld County Road 32 %. C4. This tailwater collection ditch (Figure 6.) is a man-made feature, originating at the culvert under Weld County Road 32 %2 and proceeding northwest along the primary alluvial terrace toward the riparian corridor. Tailwater within the ditch has sources from the West Farm South Parcel,as well as irrigated agricultural and pastures to the west within the West Farm North Parcel. In historical imagery from 1999,this ditch appears to provide water to several of the wildfowl habitat locations within the North Parcel. C5. C5 is a continuation of the tailwater collection ditch C4, with less definition of a constructed drainage channel. Historical imagery(1999)reveals that this feature appears to originate from the fringes of upland dikes installed for wildfowl habitat, when water levels reached the upland edge of the dike. At that point, excess water flowed across the primary alluvial terrace downgradient toward the South Platte River. While not appearing as a defined constructed ditch, the overland flow resulted from the man-made wildfowl habitat improvement features. Flow likely continues at this time due to increased tailwater volumes in feature C4 that are not diverted by dikes into shallow wildfowl habitat pools. L.G.Everist West Farm Jurisdictional Determination Request Page 6 of 14