FLOOD00961

• County: Larimer
• Community: Fort Collins
• Stream Name: Spring Creek
• Title: Hydraulic Evaluation of the Centre Avenue Bridge at Spring Creek
• Date: 11/22/2000
• Prepared For: Fort Collins
• Prepared By: Anderson Consulting Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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The scope of the current study included the following general tasks:

(a) obtaining duplicate effective hydrologic and hydraulic computer models and recreating
hydrologic and hydraulic modeling results;

(b) modifying the duplicate effective floodplain and floodway models to correct several minor
inconsistencies in the previous hydraulic models;

(c) calibration of EXTRAN, a dynamic flow routing model, to the pre-project BNRR detention
pond system using inflow hydro graphs from the duplicate effective hydrologic model;

(d) application of EXTRAN to the post-project detention pond system in order to: (i) analyze
the two hydraulically connected ponds, and (ii) determine ponded water surface elevations
at the upstream face of both the BNRR and Centre Avenue embankments, as well as
releases from the BNRR detention pond;

(e) modifying the corrected effective floodplain and floodway models to reflect the as-built
grading associated with the project, and applying stage-discharge rating curves upstream
of the BNRR and Centre Avenue embankments, based on the EXTRAN modeling results;
and

(I) conducting the requIsIte hydraulic analyses to support the definition of post-project
condition floodplain and floodway boundaries and water surface profiles,

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ANdERSON CONSUlTiNG ENGiNEERS, I.,c.