HomeMy WebLinkAboutDrainage Reports - 09/06/1988RMINC
Engineering Consultants
2900 South College Avenue
Fort Collins, Colorado 60525
303/226-4955
September 6, 1988
Ms. Susan Hayes
Storm Drainage Department
City of Fort Collins
P.O. Box 570
Fort Collins, Colorado 80522
RE: FINAL DRAINAGE REPORT FOR THE ELEVENTH FILING OF THE CENTRE
FOR ADVANCED TECHNOLOGY
The Eleventh Filing to the Centre for Advanced Technology is lo-
cated south of the Sixth Filing, north of the Fourth Filing, west
of Research Boulevard and east of the New Mercer Ditch (see fol-
lowing vicinity map). More specifically this site is located
near the middle of the south half of Section 23, Township 7
North, Range 69 West of the 6th Principal Meridian.
This location is, as is most of the Center site, covered with
natural grasses. The ground slopes to the southeast at about
0.5%. The only recent change to the existing ground is that a
detention pond was constructed on the northern part of this site.
The detention pond is only temporary until the development of
this site.
Developed flows from the site will be combined with the developed
flows from the Sixth and Third Filings. These flows will accumu-
late in a permanent detention pond located in the central or main
parking lot. This pond will be facilitated by the use of nine
area inlets (see Drainage and Grading Plan) and a series of con-
crete pans. The maximum water surface for this pond will be at
elevation 5038.08 which is 1.48 feet above the flow line of the
inlets. The pond will have a maximum 100 year design storage
volume of 1.738 ac.-ft. which compares to a required volume of
1.675 ac.-ft. (see following calculations). A 5 1/4 inch orifice
plate will be placed at the invert -out of the most easterly
manhole. This will be done to restrict the developed flows from
this site, the Third Filing and the Sixth Filing to their two
year historic level. This easterly manhole will then be con-
nected to the storm drain system in Research Boulevard which was
master planned as Basin A3 from the Drainage Report for the
Other Offices: Vail, Colorado 3031476-6340 • Colorado Springs, Colorado 303/574-3504
Centre for Advanced Technology Special Improvement District, by
RBD, Inc. Engineering Consultants, Feb. 1987. Any emergency
overflow from this pond would flow east to a 5' type "R" inlet in
Research Boulevard (see Drainage and Grading Plan).
This project was designed according to the City of Fort Collins
Drainage Specifications to promote safe and positive drainage
through this site.
Sincerely,
RBD, Inc.
(��
Stan A. Myers,P.E\�
Project Manager
Brian Cole, P.E.
Project Engineer
cc: 035-069
VICINITY MAP
(�pINO C0.^EE% -
�A0.1=E0. M0. 7 C
ITE LOCATION
0
AO
NO SCALE'
PROJECT: CENTRE 6TH FILING
JOB NUMBER: 035-051
DESIGN ENGINEER: SAM
PASIN DES I SUAT I ON =- 3RD & 6TH COMBINED
DETERMINE EXISTING 0 FOR
2
YEAR STORM
HISTORIC RUNOFF COEFFICIENT
.2
WS1N SLOPE: .5
PERCENT
BASIN LENGTH 770
FEET
AREA: 3.S6 ACRES
HI.ST TC = 1.87 t1.1 c 1
*
2
))*SORROOT 770
))/
.5
-
5B.82643
MINUTES
HISTORIC RAINFALL INTF.'ENSIT'Y-
.9558186
INCHES/HOUR
HISTORIC OUTFALL: .6996592
CUBIC FEET
PER SECOND
DETERMINATIONN OF DETENTION POND VOLUME FOR DEVELOPED CONDITIONS
DEVELOPED STORM: 1G<) YEAR STORM
DEVELOPED RUNOFF COEFFICIENT .693
4
3.66 -
3.170475
DURIATION
GROSS VOL.
OUTFLOW VOL.
DETENTION VOL.
MIN
CU. FT.
CU. FT.
CU. FT
8674.42
209„8978
8464.521
it.)
13354. 04
419. 7956
129.34. 25
15
17006.43
629.6933
16.376.74
30
23512.24
1259.3B7
22252.86
45
28246.93
1889.08
26359.85
60
29789. 78
2518. 77:3
27271,01
90
.32186„66
3778.16
23408.5
120
.32871.49
5037.546
27833.94
ISO
35610.77
7556.37
28054.45
36,)
39719.71
15112.64
24607.07
REQUIRED DETENTION
VOLUME IS
28408.5
CU. FT. OR
.6521695
ACRE FEET
L�2�F�LE T�ESILity -.
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