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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III. EXISTING STUDIES AND PROPOSED IMPROVEMENTS

General

Numerous reports have been completed in the past investigating the issues related to flooding in the
City of Sterling. Several of the reports proposed drainage iInprovements to mitigate flood damages
and included construction cost estimates for the proposed improvements. As a part of the review of
existing studies, construction cost estimates were updated to account for inflation. The Inflation rates
for the Denver-Boulder Metropolitan area over the last \3 years were obtained from the Colorado
Department of Revenue and were used to update the costs. These rates are presented in Table 2.

Table 2. Denver-Boulder Inflation Rates

YEAR Inflation Rate % YEAR Inflation Rate % YEAR Inflation Rate %
1983 5.7 1988 2.6 1993 4.2
1984 3.8 1989 1.8 1994 4.4
1985 2.7 1990 4.4 1995 *4.8
1986 0.7 1991 3.9 1996 *4.0
1987 2.7 1992 3.7

* Values estimated by the Colorado Department of Revenue

Review and Discussion

Flood Plain Information and Drainage Plan for Sand Creek and the Pawnee Creek Overflow at
Sterling, Colorado by Charles F. Leaf and Resource Consultants, Inc., dated May 1983 (Reference
1).
The purpose of this study was to evaluate the potential for flooding given the existing conditions and to
propose improvements to mitigate the existing flooding problems. Pawnee Creek, Sand Creek, and the
Pioneer Ditch were all studied in this report. Detailed hydrology was completed using the u.S. Soil
Conservation Service Procedure, A hydraulics analysis was completed using the U.S. Army Corps of
Engineers' HEC-2 computer program to determine the magnitude of the existing flooding for the 5-,
10-,25-,50-, 100-, and 500-year flood events, An economic evaluation was completed to determine
the potential magnitude of the flood damage. Several improvements were proposed to mitigate the
potential flood damage and the proposed improvements are summarized as follows:

Pawnee Creek: A flood control levee ranging in height from 3 feet to 10 feet was proposed around the
Riverside Cemetery located on the west side of HWY 6 about 2 mile south of the City. The levee
would be approximately 2,500 feet in length and prevent overflows generated by Pawnee Creek from
flooding the City of Sterling. In addition to the levee, HWY 6 would have to be raised about 4 feet for
a distance of some 1,500 feet and CR. 24 would have to be raised west of the cemetery between 1 and
7 feet for a distance of about 4,200 feet. The estimated cost of these proposed improvements in 1983
was $819,000 which is estimated to be about $1,257,779 in 1996 dollars.

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