FS0018X Feasibility study

• Contract/PO #: FS0018X
• Contractor Name: Sterling, City of
• Contract Type: Loan
• Water District: 0
• County: Logan
• Loan Projects - Doc Type: Feasibility Study

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HWY 6 and the BNRRlUPRR embankments are major obstructions, which divert Pawnee Creek flood
flows from the main channel towards the City of Sterling. The Town of Atwood is located near the
natural floodplain of Pawnee Creek; however, the City of Sterling is not. The flood flows from
Pawnee Creek into Sterling are mainly due to the manmade embankments, which act as diversion
structures, since flood flows on Pawnee Creek are not entirely able to pass directly to the South Platte
River through the existing bridges or over the embankments. When flows are high enough, a portion
of the flow is diverted to Sterling along the northwest side of the highway and railroad embankments.
This situation is known as the "Pawnee Overflow". Reference is made to Figure 2, which presents a
vicinity map of the area. .

City of Sterling Contacts:

Mayor
City Manager
Director of Public Works

Bill Finch
Randy Gustafson
Joe Kiolbasa

City of Sterling
421 North 4th Street
Box 4000
Sterling, CO 80751
Phone: [phone]
Fax: [phone]

III PROJECT SERVICE AREA

Study Area

The project area is located in northeastern Colorado. The City of Sterling and the project area are
within Logan County, which is approximately 120 miles northeast of Denver. The watershed of
interest is the Pawnee Creek Basin, which is within the South Platte River Basin. The basin is a left
bank tributary with its confluence with the South Platte River located upstream of the City limits of
Sterling, Colorado. Major tributaries to Pawnee Creek include: Raymer Creek; South Pawnee Creek
with its tributary Wildhorse Creek; North Pawnee Creek with its tributary Igo Creek; Cottonwood
Creek; Horsetail Creek; and Spring Creek. These creeks are basically intermittent with running water
in the lower reaches.

Predominate topographic features of the basin include the Pawnee Buttes in the upper reaches of the
basin. The basin's drainage area is approximately 645 square miles. Elevations in the basin range
from approximately 5,400 feet to 3,980 feet. The watershed is mainly native grass with localized
regions of cultivated agriculture. Soils are predominately loams and clay loams, with sandstone, shale
and siltstone outcroppings. Hydrologic curve numbers are in the range of 77 to 79 with the primary
vegetation being native range with some winter wheat and a significant amount of irrigated cropland in
the lower part of the basin.

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