FLOOD10070

• County: Larimer
• Community: Fort Collins
• Basin: South Platte
• Title: Master Drainage Plan Update Colorado State University
• Date: 1/1/1998
• Prepared For: Fort Collins
• Prepared By: Ayres Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

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INTRODUCTION

On June 28, 1997 after several days of rainfall, the City of Fort Collins experienced
torrential rains from about five p.m. until about eleven p.m. During this time over five inches
of rain fell on Colorado State University's (CSU) main campus. In areas west and
southwest of the CSU campus over ten inches of rain fell during the six hour period, The
resulting runoff severely inundated the main campus, causing damage to 24 buildings and
costing millions of dollars in damages.

This report reviews stormwater flows on campus utilizing the SWMM hydrologic model used
in the 1996 drainage planning study for CSU. The study was presented in the June 1996
report entitled, "Drainage Master Plan for Colorado State University." The master plan
outlined improvements to prevent damage to buildings during a 100-year event. In light of
recent events, the drainage master plan was reviewed to evaluate how the proposed
improvements would have performed, and how much damage could have been avoided.

The general approach was to utilize the original hydrologic model for the campus, and
simulate runoff from the 1997 storm. The model was calibrated to match the experienced
inundation and simulate the proposed improvements. The model evaluated potential
damage assuming proposed master improvements had been implemented, Master plan
recommendations are made from the results of these analyses.

This report is divided into four major sections as follows:

. Analysis of the 1997 Storm Event: This section provides the results from simulation
of the 1997 rainfall event on the CSU Campus,

. Review of the Proposed Master Plan: Proposed drainage improvements were
analyzed and reviewed using the 1997 rainfall conditions. This section summarizes the
results of the evaluation,

. Proposed Master Plan Revisions: Based upon evaluation results, and discussions
with facility services staff, revisions to the master plan were reviewed.

. Summary and Conclusions: The final section provides a summary of the report, and
presents recommended drainage plan improvements.

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Ayres Associates