FLOOD05819

• County: Logan
• Community: Sterling
• Basin: South Platte
• Title: City of Sterling Drainage and Flood Control Implementation Plan
• Date: 6/1/1997
• Prepared For: Sterling
• Prepared By: ICON Engineering, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Sand Creek: A dam and reservoir was proposed to be located just west of Pioneer Park to control
Sand Creek floods. An outlet channel was proposed to convey attenuated peak discharges from the
dam about 4,500 feet downstream to the Pioneer Ditch. The storage volume in the reservoir would be
1950 acre-feet. The dam would be about 1,400 feet in length and 32 feet height at its maximum cross-
section. In 1983, the estimated cost of these improvements was $3,096,260 which is about $5,033,052
in 1996 dollars.

Pioneer Ditch: The 1983 Leafi'RCI Report recommended that all of the street crossings along the ditch
be replaced with a structure that would at a minimum convey the 10-year peak discharge. This would
include seven new hydraulic structures. In addition, the ditch would be enlarged from Franklin Street
all the way downstream to HWY 138. Within this reach, the ditch was proposed to be realigned
between HWY 14 and Division Avenue in order to increase the channel gradient. The new alignment
would more closely follow the natural Sand Creek channel and floodplain. Finally, a 150 acre-feet
detention pond was proposed on the north side of Division Avenue near Filmore Street based on
existing developed conditions at the time of the study. The pond would reduce peak discharges
downstream and reduce flooding caused be the undersized crossing at HWY 138. The estimated cost
ofthese improvements in 1983 was $4,601,835 which is estimated to be $7,067,268 in 1996 dollars.

Based on the proposed improvements and construction cost estimates in the 1983 Leafi'RCI Report, a
benefit cost ratio of 1.29 was calculated for the combined improvement to Pawnee Creek and Sand
Creek.

Sand Creek Watershed, Sterling, Colorado by the V.S.D.A. Soil Conservation Service, dated
November 1984 (Reference 2).
The purpose of this report is to study five proposed alternatives to mitigate flood damages caused by
Sand Creek. The alternatives are summarized as follows:

· Alternative I involved a dam and reservoir located about 1,500 feet upstream of the dam proposed
in the 1983 Leaf/RCI Report.

· Alternative 2 proposed to construct the same dam as in Alternative I and construct an additional
dam upstream. The second structure would be located about two thirds of the way up the basin.

· Alternative 3 was the same as Alternative 2, but a third dam was proposed between the first two
structures, located about one third of the way up the basin.

· Alternative 4 included a natural bottom channel along a similar alignment as the Pioneer Ditch to
convey the 10-year storm from Sand Creek. The proposed channel would have an 80 foot bottom
width, a 16 foot depth, 4:1 sideslopes, and a top width of 208 feet. A 20 foot wide maintenance
road was proposed on either side of the channel which would be about 15,900 feet long. New
bridges were proposed at all of road and railroad crossings,

· Alternative 5 was the same as Alternative 4 except that a concrete channel would be used instead of
a natural channel. The proposed concrete channel would have a 30 foot bottom width and I: I
sideslopes. New bridges were also proposed at all of road and railroad crossings.

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