FLOOD09522

• County: Logan
• Community: Sterling, Atwood
• Basin: South Platte
• Title: Pawnee Creek Flood Mitigation, City of Sterling, Town of Atwood and Logan County
• Date: 7/1/1999
• Prepared For: Logan County
• Prepared By: URS Greiner Woodward Clyde
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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SECTIONTHREE Anected Environments and Environmental Consequences

The U.S. Fish and Wildlife Service (USFWS) National Wetland Inventory (NWI) map and the
Soil Survey map for Logan County were examined to determine the presence of known wetlands
in the project area. Within the project area, the NWI map noted the presence of two small
wetlands on Pawnee Creek and one wetland area on the South Platte River. On Pawnee Creek,
one wetland area was noted immediately upstream of the Highway 6 bridges and the second was
between the UPRR bridge and the South Platte River. The wetland on the South Platte River
was near the location where the drop structure would be constructed with Alternatives 2 and 3
downstream from Riverside Cemetery. The two wetlands on Pawnee Creek were classified as
riverine, intermittent, located in the streambed, and artificially created (USFWS 1977). The
wetland on the South Platte River was classified as palustrine and forested with open water
(USFWS 1997). All three would be considered riparian wetlands. In addition to examining
maps, a site reconnaissance of the project area was conducted on August 26, 1998, and no other
wetland vegetation was identified along Pawnee Creek within the project area.

3.10.1.1 Alternative 1- No Action

Since the No Action Alternative does not include any construction activities, it would have no
impact on wetlands.

3.10.1.2 Alternative 2 -Improve Routing of Pawnee Creek Flood Flows (Proposed
Action)

With Alternative 2, waters of the United States, including wetlands, would not be affected by
construction activities near Atwood. Construction of the drop structure downstream from the
Riverside Cemetery would approach, but not encroach on the wetland area on the South Platte
River. However, on Pawnee Creek both small wetland areas would be affected by channel
deepening or construction of the new low-flow channel. Approximately 0.1 acres of wetland
would be affected at these two locations. Both of the affected wetlands are classified as artificial,
indicating that previous road or stream alignment activities resulted in the formation of the
wetland area. Impacts to these two wetland areas would be offset by the development of similar
wetland areas adjacent to the bridges and along the constructed low-flow channel on Pawnee
Creek.

Since construction activities would affect more than 500 feet of stream, an individual 404 Permit
would be required by this alternative. The USACE, in consultation with the Colorado
Department of Health, would also be responsible for 401 Certification prior to issuing the 404
Permit.

3.10.1.3 Alternative 3 - Pawnee Creek Overflow Cutoff

With Alternative 3, no wetlands are present within the construction area. Therefore, a 404
Permit would not be required from the USACE.

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