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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I. EXECUTIVE SUMMARY

General

This study was authorized and funded jointly by the Colorado Water Conservation Board and the City
of Sterling, Colorado. The study was contracted through the City of Sterling in an agreement with the
Denver Office of Greenhorne and O'Mara, Inc. dated January 23, 1996. ICON Engineering, Inc
purchased the Denver Office of Greenhorne and O'Mara in February of 1997 along with the contract
for this study. This report was subsequently completed by I CON Engineering, Inc

Several studies have been completed to investigate the existing flooding conditions in the City of
Sterling and address alternatives for mitigation to the flooding problems. The purpose of this report is
to review the existing work and develop the most feasible and economical plan of improvements for
the City of Sterling. The City has a limited annual budget available for the design and construction of
flood control and drainage projects. Therefore, the objective of this report is to develop an
implementation plan which prioritizes the proposed improvements so that the City can use this study as
a guide for budgeting future drainage and flood control improvements.

Study Area

The major drainageways studied in this report include Pawnee Creek, Sand Creek, and the Pioneer
Ditch. Pawnee Creek is a left bank tributary to the South Platte River. Its confluence is located
approximately 4 miles southwest of the City of Sterling along U.S. Highway 6 (HWY 6) and the Union
Pacific Railroad (UPRR). During large storm events, stormwater overtops the banks of Pawnee Creek
and flows into the City. These overflows are estimated to be 5,000 cfs during the 100-year storm. This
study includes the reach along Pawnee Creek from its confluence with the South Platte River 100-year
floodplain upstream to County Road 29 (CR. 29), a distance of about 7.5 miles.

Sand Creek is also a left bank tributary to the South Platte River. Stormwater from Sand Creek drains
west through Pioneer Park just north of U.S. Highway 14 (HWY 14) and into the City of Sterling
where it is intercepted by the Pioneer Ditch, The 100-year peak discharge along sand creek at Pioneer
Park is estimated to be 4400 cfs. The Pioneer Ditch eventually drains to the South Platte River. This
study includes the reach of Sand Creek from its confluence with the Pioneer Ditch, upstream through
Pioneer Park to approximately the Pawnee Ditch.

The Pioneer Ditch is a principle storm water conveyance for the City of Sterling. The Ditch begins in
the southwest portion of Sterling near Westview Drive and Iris Drive. In general, the Ditch drains to
the South Platte River along the western and northern edges of the City. The Pioneer Ditch serves as a
drainage conveyance for local flows, as well as the overflows from Pawnee Creek and for Sand Creek.
This study includes the reach of Pioneer Ditch from U.S. Highway 138 (HWY 138) and the Burlington
Northern Railroad (BNRR) to its upstream limit. Figure I presents the general locations of the streams
included in this study.

The approximate limits of the existing I DO-year floodplain from all three sources of flooding are
presented on Figure 2.

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