FLOOD09102

• County: Logan
• Community: Sterling
• Basin: South Patte
• Title: Sterling Flood Control Interceptor Channel Project
• Date: 4/1/2002
• Prepared For: Sterling
• Prepared By: URS
• Floodplain - Doc Type: Project

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SEmI.TWO

Alternatives Considered

The President's CEQ has developed regulations for the preparation of environmental impact
documents in compliance with NEP A. The CEQ requires an investigation and evaluation of
practicable alternatives as part ofthe environmental assessment process.

2.1 ALTERNATIVES ANALYZED AND DISMISSED

2.1.1 Flood Control Levees

This alternative, identified as Alternative 2 in the applicant's Flood Hazard Mitigation Feasibility
Study (ICON 1998), would restrict the 100-year flood flows from overflowing into the overbank
floodplain near where Pawnee Creek crosses Highway 6. It would provide protection to
agricultural lands and would provide protection to Sterling (ICON 1998). This alternative
included the construction of a system of flood control levees that would follow the north bank of
Pawnee Creek, beginning upstream of County Road (CR) 29 and continuing east to Highway 6.
The conveyance capacity of the bridge for the southbound lanes of Highway 6 would be
increased by adding four 20- foot by 8- foot concrete box culverts west ofthe existing bridge.
The existing timber bridge for the northbound lanes of Highway 6 would be replaced by the
Colorado Department of Transportation (CDOT), and the span of the new bridge would have the
capacity to pass the 100-year flood flows. Fill material presently beneath the UPRR bridge
would be removed to open the entire span. A second system of levees and a floodwall would be
constructed to convey storm water from the UPRR bridge downstream to the 100-year floodplain
ofthe South Platte River. When compared to other alternatives, this alternative required the
construction of more levees on agricultural land. Additionally, if a flood of greater than the
100-year event occurred, levees constructed upstream of the Highway 6 bridges with the required
3-foot freeboard could increase the level of flooding in Atwood (ICON 1998). Due to negative
impacts associated with the large amount of agricultural lands that would be required for the
flood control facilities and the potential for greater flood damage in Atwood, this alternative was
eliminated from consideration.

2.1,2 Upstream Flood Control Reservoirs

This alternative, identified as Alternative 3 in the applicant's Flood Hazard Mitigation Feasibility
Study (ICON 1998), is a series of upstream flood control detention darns. With this alternative,
seven detention structures would be constructed in the upper watershed to temporarily store
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 (ICON 1998), would provide a floodway upstream (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

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