FLOOD06925

• County: Larimer
• Community: Greeley
• Stream Name: Cache La Poudre River
• Basin: South Platte
• Title: Master Floodway Planning
• Date: 3/11/1983
• Prepared For: Greeley
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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f.

To provide all technical information required for the City to
reenter the National Flood Insurance Program and to ammend the
floodplain map issued by FEMA, if necessary.

2. Study Area

The study area is located in the northeastern section of the City of

Greeley including approximately 2.5 miles of the Cache La Poudre River. The

floodplain within the study reach is heavily developed with commercial, resi-

dentia11 and industrial structures present in the floodplain and floodway.

The channel is crossed by eight bridges in the study area. The lOa-year flood

discharges range from 8,000 cfs to 10,000 cfs in the study reach. The

floodplain is wide and generally shallow through the study reach. The City

has been required to dredge the channel about every other year indicating the

stream bed undergoes aggradation because of the mild slope (0.14 percent) and

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wide cross section.

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3.

Scope of Work

We have carefully reviewed the project tasks presented in the RFP. We

have also discussed the intent of the project with Mr. Sam Sasaki of the City

and Mr. Larry Lang of CWCB. Our understanding of the scope of work for this

project includes:

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a.

Conduct a field visit to familiarize ourselves with the physi-
cal environment of the study area.

b.

Collect and review all existing information pretinent to the
proposed project.

c.

Conduct field investigation to collect all pertinent data
needed for hydraulic computation and floodplain and channel
conditions that may affect the formulation of improvement
plans.

d.

Reprogram the COE's data into the HEC-2 program and match the
HEC-2 results with the 1974 COE report and 1979 FEMA report
within acceptable range utilizing the flood discharges
developed by the COE.

e.

Perform hydraulic analysis using HEC-2 to determine a most
practical floodway plan using the FEMA one-foot rise criteria.

f.

Formulate a minimum of three alternative preliminary improve-
ment plans considering practical floodway, sedimentation, flow
blockage, channel stability, and maintenance.