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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PROPOSED MASTER PLAN REVISIONS

The dominant flow that effected facilities on campus was the flow of water from the west of
campus, Therefore, improvements that would minimize the effects of inundation in the
lagoon/library parking lot area were focused on, Secondarily, minimizing the inundation in
the oval area was also studied. One consideration was to enlarge the storage capacity of
the athletic field detention ponds. Protection for the library, the student center, health
center, Eddy and Education Buildings was also considered.

The proposed ponding area for the athletic field was modified to increase storage volume.
The volume was increased from 44 ac-ft to 90 ac-ft, Also, the allowable storage elevation in
the lagoon/library parking lot area was assumed to be at an elevation of 5005 feet which
provides an additional 65 ac-ft of storage.

As a result the improvements were simulated by the model and summarized in Tables 5
and 6. The results indicate that even with additional storage, the elevation of water in the
oval would be 4991,8 ft. which is about 6 ft. above the elevation of the heating plant.
Therefore the increased storage from the athletic field detention pond would make little
difference in the need for major protection of the oval area.

Table 5. Summary Elevation Results for the Simulation of the July 28-29, 1997
Rainfall Event with Revised Master Plan Improvements.
Master Revised
SWMM Plan Master Differ.
HWM Model Location Conditions Plan From
Element (Elevation) (Elevation) Existing
#15&16 14 College Gym 4986,1 4986.1 -0.0
#17-20 15 Heating Plant and Oval 4992,2 4991.8 -0.4
#21-2 224 Engineering Parking Lot 4993.4 4993,2 -0,2
#22 53 Lagoon NW of Student Center 5004,7 5004.6 -0.1
#31 259 Athletic Fields - Football Practice 5024.5 5024,5 0.0

Table 6. Summary Discharge Results for the Simulation of the July 28-29, 1997
Rainfall Event with Revised Master Plan Improvements.
%
SWMM Master Plan Revised Differ. Reduction
Model Location Conditions Master from from
Element (cfs) Plan Existing Master
(cfs) (cfs) Plan
14 College Gym 267 246 -21 8
15 Heating Plant and Oval 251 231 -20 8
224 Engineering Parking Lot 674 596 -78 12
53 Lagoon NW of Student Center 1204 1069 -135 11
259 Athletic Fields - Football Practice 1886 1886 0 0
45 Prospect & RR 435 393 -42 10
299 Lake Street 435 393 -42 10

14

Ayres Associates