FLOOD01452

• County: Larimer
• Community: Fort Collins
• Stream Name: Fossil Creek Drainageway Basin
• Title: Master Drainageway Planning Study
• Date: 8/1/1982
• Prepared For: Larimer County
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SIMONS, LI & ASSOCIATES, INC.

Mr. Robert Smith

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August 31, 1982

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3555 STANFORD ROAD
POST OFFICE BOX 1816
FORT COLLINS, COLORADO 80522

TELEPHONE (303) 223,4100
CABLE CODE: SIMONSLI

Railroad crossing on Fossil Creek, and protection of the downstream
embankment at Fossil Creek Drive and Fossil Creek.

August 31, 1982

We wish to thank the technical committee for their cooperation and
assistance. The technical committee included Robert Smith, City of
Fort Collins; Rex Burns, Larimer County; Larry Lang, Colorado Water
Conservation Board; and Randy Seaholm, Colorado Water Conservation
Board.

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Mr. Robert Smith
Engineering Service Department
City of Fort Collins
PO Box 580
Fort Collins, CO 80522

~C\D}g-1 ~

Dar~ Simon~
President

Sincerely yours,

f:::.~~

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Hydrologist

RE: Fossil Creek (our project CO-LC-Ol)

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Associate Principal Engineer

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Dear Mr. Smith:

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In compliance with the terms of our contract with the City of Fort
Collins dated November 19, 1981, we have completed the engineering
study for Fossil Creek and four tributaries. Hydrologic, hydraulic,
erosion and sedimentation analyses were made for Fossil Creek and the
four tributaries. An economic analysis of the proposed improvements
to alleviate potential flooding problems was made for Fossil Creek.
The results of the study are presented in the Fossil Creek Drainage
Basin Master Drainageway Planning Study. The detailed data and
methods of analysis are presented in the Technical Addendum.

JRK/jb
R156CL1/RD86

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cc: Rex Burns
Larry Lang

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Enclosures

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The recommended improvement alternative is designed for the 100-year
flood considering developed conditions. Natural storage behind road
embankments is used. Where necessary to prevent overtopping the road,
the culverts at the channel crossing are enlarged. Development would
not be allowed in ~Jhe flood plain. A veg~tated trapezoidal chann~l
between Fossil Creek Reservoir and Union Pacific Railroad is recom-
mended because of the limited storage upstream of County Road 11.
Enlarged channel crossings along Fossil Creek are required at County
Road 11, Trilby Road (County Road 34), Lemay Avenue (County Road 13)
and Shields Street. Improvements along the tributaries were sized for
Stanton Creek at County Road 32 and Lemay Avenue (County Road 13) and
Lang Gulch at Trilby Road (County Road 34) and Shields Street. These
improvements were not considered in the economic analysis.

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Additional construction requirements included riprap downstream of
channel crossings, a headwall to reduce entrance losses at the Union
Pacific Railroad crossing, bank protection along Fossil Creek near
Portner Reservoir, stabilization of the southwest wingwall at the C&S

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DENVER OFFICE: 4105 EAST FLORIDA AVENUE, SUITE 300, DENVER, COLORADO 80222 [phone]
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