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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SEma.TWO

Alternatives Considered

. Construction of approximately 13,500 linear feet of grass-lined flood control channel with a
bottom width varying between 110 feet and 220 feet. The channel would be located north of
and parallel to CR 22.5, would start east ofCR 35, and extend east to the South Platte River.
Construction ofthe channel's discharge structure would involve approximately 450 linear
feet of the South Platte River's stream bank. The channel would have 3:1 side slopes. A
cross-section of the channel is shown in Exhibit 4. Riprap would be placed at the flood
control channel's confluence with the South Platte River. The current estimate of excess
excavated material is 450,000 cubic yards. Some ofthis material would be used to raise a
portion of State Highway 6 as a part of the Highway 6 bridge construction. The City of
Sterling has plans for approximately 75 percent to 100 percent ofthe material to be used on
City property near the project. The CDOT has made a request to use a portion of the material
on local state projects. All disposed material would be placed and protected according to the
latest version of the "CDOT Erosion Control and Stormwater Quality Guide," which outlines
the National Pollutant Discharge Elimination System (NPDES) Program requirements and
provides design guidelines for erosion and sediment systems.

. Construction of an approximately 140- foot-long by 80- foot-wide highway (4-lane) bridge at
State Highway 6. The bridge would carry both northbound and both southbound Highway 6
lanes plus the median over the channel.

. Construction of an approximately 144-foot-long railroad bridge at the UPRR tracks over the
channel.

. Construction of a twin 60-inch-diameter, concrete pipe siphon structure to carry the Sterling
No. I Ditch under the proposed channel and relocated county road. The siphon structure
would be constructed of a concrete pipe running under the channel and would utilize gravity
to move the water through the pipe. The siphon would be designed to carry 200 cfs.

. Relocation of one well owned by the Groundwater Appropriators ofthe South Platte River
Basin, Inc. (GASP) (Exhibit 5).

. Closure ofCR 39, north of the proposed channel that would be constructed, and
abandonment of portions of County Road 39 within and immediately north of the constructed
channel.

. Extension ofCR 22 to allow access to two homesteads after the closure ofCR 39. Presently,
it is planned that Logan County would extend CR 22 because it is a county road.

. Modification of irrigation works (head ditch and water turnouts) associated with two existing
irrigation wells located just south of the proposed channel.

. Construction of a 13,500-foot access road along the north side of the proposed flood control
channel. The elevation of the access road would be less than the adjacent county road at all
locations.

. Construction ofa drop structure at the outfall of the proposed flood control channel at the
South Platte River.

Photographs ofthe location of the proposed flood channel are provided in Exhibits 6 and 7.

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