HomeMy WebLinkAboutDrainage Reports - 09/13/1988 (2)T:IDINC
Engineering Consultants
2900 South College Avenue
Fort Collins, Colorado 80525
303/226-4955
August 5, 1988
Susan Hayes
Storm Drainage Department
City of Fort Collins
P.O. Box 570
Fort Collins, Colorado 80522
RE: FINAL DRAINAGE REPORT FOR THE SEVENTH FILING OF THE
CENTRE FOR ADVANCED TECHNOLOGY
Dear Susan:
The Seventh Filing of the Centre for Advanced Technology is lo-
cated immediately northwest of Centre Avenue's crossing of the
New Mercer Ditch. The site is bounded on the north and east by
the New Mercer Ditch; on the south by Centre Avenue and on the
west by Worthington Circle. Historically the site was used for
experimental farming by CSU and covered with field stubble,
draining to the north and east. Recent grading connected with
the construction of Centre Avenue and Worthington Circle has
changed the site grades. The current grading leaves this area
low with essentially no surface outlet.
The eventual development of this site will include three office
buildings, two parking areas and a permanent landscape pond. 1. A
permanent detention facility will be located in the northwestAof
the site. This detention area will detain flows from basins D2
and D3 as they appear on the Amended Master Drainage Plan for the
Centre for Advanced Technology dated February 1988. A copy of
the pertinent area is attached. In addition to these flows the
flows from Worthington Circle will also be detained. The deten-
tion area will be drained by a pipe system connected to the
Centre Avenue storm drain system. Outfall will be restricted to
the two year historic rate (1.38 cfs) by an appropriately sized
orifice, see the following calculations. Emergency overflow will
be provided by an overflow structure at the outlet point. Basin
D1 from the Master Plan will now have onsite detention due to the
changes made from this filing.
Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado 303/574-3504
With the proposed drainage improvements installed onsite
stormwater should be safely conveyed through and from the site.
Sincerely,
RBD, Inc. �q
Stan A. Myers, P.E.
D:"ITE: 7�28�88
PROJ71H FILING
JOB NUMBER: 035�052
DE -SIGN ENGINEER: BC
BASIN DESIGNATION = 1'.)2 & D3
DETERMINE EXISTING Q FOR 2 YEAR STORM
HISTORIC RUNOFF COEFFICIENT
BASIN SLOPE: ` .5
BASIN LENGTH 1000
AREA: 7.81 ACRES
HIST TC = 1.87*(1.11
)>*SQRROOT 1000
^ 1/3 =
HISTORIC RAINFALL INTENSITY:
HISTORIC OUTFALL: 1.375696
.2
PERCENT
FEET
* .2
)>/ .5
67.03894 MINUTES
.8807274 INCHES/HOUR
DETERMINATION OF DETENTION POND VOLUME FOR DEVELOPED CONDITIONS
DEVELOPED STORM: 100
DEVELOPED RUNOFF COEFFICIENT
CCFAC =
7.81
.71
�
DURATION
MIN
5
10
15
30
45
61,-)
90
120
180
360
*
6.931375
GROSS VOL.
CU. FT.
18964.24
29194.95
37179.9
51403.08
61758.55
65127.19
70367.32
71864.5
77853.2
S6836.27
YEAR STORM
` .71
1.25
OUTFLOW VOL.
CU. FT.
412.7089
825.4178
1238.127
2476.253
3714^38
4952.507
7428.76
99O5.012
14857.52
29715.04
DETENTION VOL.
CU. FT
18551.53
28369.53
35941.77
48926.82
58044.17
60174.69
62938.57
61959.49
62995.68 .
57121.23
REQUIRED DETENTION VOLUME IS 62995.68 CU. FT, OR
1.446182 ACRE FEET
,
��~ ����� ~ *z�
6 � SA A �0Z6,
x� �
cr%-A ^& .�z 4zt Zt?7H
�� �
�� � \,� � ���c� �� 1 .�� �� �� 5 �UGL00ZL(D
�� - �
.���� {���� ��� �� �� �������� ���� ��k ^�'��/�'
T �A\ 1� IF- �_ c�w,q i N-\ 1P \�� \.~\- /9 T-C
\ 'D c�>'/D c'( --- uwo . ��j 0G�\C�
CLIENT JOB NO. o35-057-
INC PROJECTCALCULATIONSCALCULATIONS FOR
Engineering Consultants MADE BVw,-DATE 63 CHECKEDBVDATE -SHEET-OF
t 43.4Z i i
43
• (
!
41
LAI
41
- --.
f
4
r
1
�
lllbi.J�
T
is
a
•• 'Q
ul
1
J
)
Q
�
�
77
1p
UN
ILI
77
'2
c
F` —
1z
$
w oo.
o �+
td
8 0
az
073
_ p
�W
N � J� W
'b
•,�
.•,
.',
g'
JamJ{{
u:l 0
ZddffQ
N
`
N
o
,
OL m7Z
Ol 1� -1V
�
••h:_
claoasr=-
•
z
Na
Z c
O_
W
N
up
No Text