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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SECTIONTWO

Alternatives Considered

floodwaters. This alternative was eliminated from consideration due to the continued potential
for flooding in the lower portion of the basin.

2.1.3 Construction of Drainage Floodway Upstream of Atwood

The alternative, identified as Alternative 6 in the applicant's Flood Hazard Mitigation Feasibility
Study, would provide a floodway upstreanl (southwest) of Atwood that would divert Pawnee -
Creek to the south along CR 29, directly to the South Platte River. The floodway would be sized
to accommodate the peak flows associated with the 100-year flood event. The constructed
floodway would intercept the Pawnee Irrigation Ditch, Highway 6, and the UPRR tracks. The
alternative was eliminated due to the large amount of agricultural lands that would be impacted
and the cost of moving large quantities of fill material. In addition, this alternative was perceived
to have more unknowns that could potentially increase costs (ICON 1998).

2.2 ALTERNATIVES CARRIED FORWARD

The potential environmental impacts for three alternatives are evaluated in this report. These
alternatives include:

.. No Action

. Improve Routing of Pawnee Creek Flood Flows
. Pawnee Creek Overflow Cutoff

2.2.1 Alternative 1 . No Action

With the No Action Alternative, no improvements would be made to or other work performed
along Pawnee Creek. Without improvements, flooding and resultant damages would continue to
occur as they have historically.

2.2.2 Alternative 2 . Improve Routing of Pawnee Creek Flood Flows (Proposed
Action)

This alternative is identified as Alternative 5 in the applicant's Flood Hazard Mitigation
Feasibility Study QCON 1998). This alternative includes flood flow routing activities near
Atwood, near the Highway 6 and UPRR bridges over Pawnee Creek, and near Riverside
Cemetery. Exhibit 2 shows the general location of the project activities. Specific features at
each location are shown in Exhibit 3 and are described below.

Atwood Improvements

Culverts and flood channels would be sized to handle 5,000 cfs of floodwater, which represents
approximately 20 percent of the U.S. Army Corps of Engineers' predicted 100-year flood event
of24,500 cfs (URS Greiner Woodward Clyde 1999). Project components at this location
include:

2-2