HomeMy WebLinkAboutDrainage Reports - 04/17/1984STORM WATER DRAINAGE REPORT
I&OW
WILLOW GROVE VILLAGE
AT CUNNINGHAM CORNER
A PLANNED UNIT DEVELOPMENT
IN THE
CITY OF FORT COLLINS, COLORADO
qUW ,. 4117114
FEBRUARY 1984
m
TARANTO. STANTON & TAGGE
CONSUL•CING ENGINEERS
FORT COLLINS, COLORADO
+:+or
ccn
March 2, 1984
Re: Willow Grove P.U.D. at Cunningham
Corner Drainage Study
Job No. 280-063
CONSULTING ENGINEERS
City of Fort Collins
Department of Engineering
Drainage Division
P.O. Box 580
Fort Collins, CO 80522
Attn: Mr. Phil Waite
Dear Phil:
We are pleased to present this Final Drainage Study for Willow Grove
Village P.U.D. at Cunningham Corner. This study includes Final Drainage
Calculations for Parcels B, C, D, F and G, so a complete comprehensive
study can be presented. Please refer to the "Preliminary Report for
Cunningham Corner P.U.D. - January 1983" - for documentation of approved
developed design drainage criteria which applies to this study.
If you have any questions regarding this study, please contact our
office.
Respec$fULlj ed,
4bier�te
?i1schewmerling,
TARANTO, STANTON & TM9
CONSULTING ENGINEERS
11
112 W. 11TH AVE. 6412 S. COLLEGE AVE. P.O. BOX 703
HOLDREGE, NE 68949 FORT COLLINS, C080525 HAYDEN, C081639
(308) 995-6677 (303) 226-0557 (303) 276-3834
DRAINAGE STUDY
FOR
WIIIM GROVE VILLAGE P.U.D.
AT CUNNINGHAM CORNET.
FEBRUARY 24, 1984
F-1 - Gip M k
Cum:irigham Corner P.U.D. comprises approximately 39 acres in the southwest
quarter of Section 26, Township 7 North, Range 69 West of the Sixth
Principal Meridian. It is bounded on the north by Woodwest Subdivision, on
the east by Sundisk Village P.U.D., or. the south by Horsetooth Road, and on
the west by .Shields Street (Figure A). This study evaluates developed
drainage for Parcel B and F, Willow Grove Village P.U.D. Also, developed
drainage for Parcels C, D, and G is evaluated 'because of their affects on
the stonm drainage system and overall construction proposed.
UYNTEILLOPED COIvTITICNS
This report is issued in conjunction with our Preliminary Drainage Study
dated January 27, 1983. Existing dra.irage flows are still derived from two
on -site areas (Figure A) and site flows are excerpted fror, the preliminary
drainage report as follcxas:
Area 1
Q2 5.24 cfs
Q100 17.94 cfs
Area 2
4.07 cfs
3.4.63 cfs
-1-
Totals
9.31 cfs
32.57 cfs
22
Drakes •
7 Darn[ ( �ao�n it I�G:;•. yv,. l_ s I -pf� DRAKE
506 Al
cp
27
TRY-POfNTFOR
ROM SHIELDS STREET
wl Omegas - I
65? HaRSET00 — RD. _ ....
SOSL T
zi
CUNNINGRAM _
' _ p CORN`R P.:U.D
33OS-
FF-SITE AREA
�'- LOMc ellands�•
CONTRIBUTING TO ;I
' DRAINAGE OF
FOOTHILLS BASIN — — — ---
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DEVELOPED CCNDITIONS
Willow Grove Village P.U.D. is in Undeveloped Basin II as defined in the
Preliminary Drainage -Study for Cunningham Corner. Because the remainder of
Windmill Drive, Richmond Drive, and Cunningham Drive will be constructed
during this phase of construction, a storm drain system will have to be
constructed. This storm drain system will also have to transfer future
developed flows from Parcels C, D, and G in addition to Parcel B and F.
Therefore, the developed conditions outlined in this report will encompass
developed flows from these Parcels and only clarification reports will be
required in the future.
Developed flows from Parcel B have been calculated as follows:
Q2 = 1.4 cfs
Q100 = 23.0 cfS
These. ,`.lows include all drainage on Cunningham Drive and the north half of
Pichmond Drive. The 2-pear flocs drain off of Parcel B and enter a
stornxlrai.ii inlet at the northeast irtersectior of Cunningham Drive and
Richmond Drive, (Sheet 16 of 17, Consi niction Drawings). 1n addition,
calculated 2-year flows of 2.5 cfs off of the sCuth half of PiChAMnd Drive,
east half of Shields Street, and Parcel F parking area drain into a storm
drain inlet at the southeast collier of Cunnincham and Richmond Drive. The
100 year flaws including 10.4 cfs from the south half of Richmond Drive,
east half of Shields Street and the Parcel F parkinq esea, will be carried
in Richmond Drive's curb and gutter section. All flows are carried in
Ricl=nd Drive or the storm drain system to the retention area in Parcel H.
-2-
Parcel B undeveloped flows for the 2- and 100-year storms are 1.2 cfs and
4.4 cfs, respectively. Subtracting these flows from Basin II undeveloped
flows, and adding developed flows from Parcel B gives a developed flaw into
Parcel H for Basin II of 8.3 cfs and 33.2 cfs for the 2- and 100-year .
floods. Adding these flows to those generated for Basin I including
developed Parcel E, the overall flows expected in Parcel H are:
Basin I
Basin
II
Total
in H
Q2
9.10 cfs
8.30
cfs
17.4
cfs
Q100
36.10 cfs
33.20
cfs
69.3
cfs
Based on these flows and a prorated C value of .3 for the entire Cunningham
Corner Area w-ith Parcels P.. and E fully developed., 122148 cu.ft. of
retention will be rcrn:iied in Parcel. H. This is equal to 2.8 Ac-ft. of
retention, which is 1.4 Ac-ft. areater than the retention required for
Parcel E development alone. This volume was generated teased on the mass
flow diagram procedure. This volume is still less than the 3.5 Ac-ft. of
retention currently available from construction completed Chestnut Village
P.U.D. and therefore, no improvements will be required to the Foothills
basin under this submittal.
The proposed storm drain system must be designed to carry minor flood
storms from Parcels C and D in the future. For this reason the developed
flows from these parcels have been calculated and are:
Parcel C Parcel D
Q10 - 23.9 cfs
Q100 - 54 cfs
-3-
Q10 - 4.3 cfs
Q100 - 8.2 cfs
Thus, the current storm drain system in Richmond Drive will have to carry
the 23.9 and 4.3 cfs flows in addition to 5.4 cfs and 2.5 cfs from Parcels
B and the parking area of Parcel F. The 100-year flows from Parcels C and
D will flow in a future open grass lined channel which will discharge into
Richmoond Drive. The proposed future location of this storm drain extension
and open channel will be in a 20-foot utility easement along the west line
of Parcel F.
The current storm drainage required is thus sunnarized as follows:
- Discharge at Parcel B inlet to the Parcel H 36" R.C.P.
Inlet - 36.6 cfs at 0.30%
- Parcel F Inlet to Parcel B Inlet - 30" R.C.P. /
31.2 cfs at 0.58%
The future storm drainage required is estimated as follows:
Inlet at S.E. Car. Richmond and Cunninghar.Dr. 30" R.C.P. /
to Parcels C and D. /
Property Line - 28.2 cfs at 0.46%
Other on -site storm drainage ro2. Parcels C and D may be required, but their
cunilative capacities should not be greater than the 28.2 cfs allowed
above. All future 100-year flaws -in these_ parcels must be channelized
within these parcels as required.
An additional storm drain is proposed under the low point of Windmill Drive
from Parcel G to Parcel H. This drain will handle future minor developed
flows from Parcel G. These flows have been calculated and are:
Q2 = 4.5 cfs
Q100 = 20.0 cfs
-4-
4-'�
' This storm drain has thus been designed as a 14" x 23" R.C.P. capable of
carrying 11.0 cfs at 1.008 slope. This storm drain may also be extended
' into Parcel G in the future, if required.
'
Inlets for the required minor flows
have been based on City of Fort Collins
'
drainage
criteria and sizing is shown
on the calculation
sheets. A summary
of Inlet
sizes are as follows:
'
N.E.
Corner Richmond and Cunningham Drives 15'
Throat
S.E.
Corner Richmond and Cunningham Drives 4'
Throat
'
No.
Side Windmill Dr. @ Parcel
G 4'
Throat
So.
Side Windmill Dr. @ Parcel
G 10'
Throat
' Future inlets for Parcels C, D, and G will have to be sized at the time
they are developed.
1
All 100-year flows from, upstream parcels that flow into Ricl-crond and
Windmill Drives will be diverted at the long -point of Win&Lill Drive into
Parcel H. Curb and gutter capacities for the drive over curb acid gutter in
V:.-chnill and Richmond Drives are sufficient as can be seer. by the enclosed?
curb and gutter capacity table.
In conclusion, the inevitable constriction of the Foothills Basin
drainageway has been avoided for Parcel B and F development, but additional
development will require the construction of this floodway and we recoarmend
completion at the earliest possible date.
-5-
Shields street flows from the center line east to R.O.W. and north fran
Richmond Drive will flow north into a future inlet, low point, north of
Cunningham Drive. This will be designed with the design of Shields Street.
PAR( F7 B UNDE 7FMOP= FLOV S
PAQ CEL ..A..
o `
Qz 5.2 c=
\XF'
G,"
UNDEVELOPED AREA II
Q2 = 4.1 cfs Q1CQ = 14.6 cfs
S(Avg) = .72%
UNOEVF,LOPED FL hS FOR PAKM B
TC2 = 1.87 (1.1 - (.2) i=.0) Sd"= 42 min.
0.721/3
TC100 = 1.17 (1.1 -(.2) (1.25)) 500 = 40 min.
0.721/3
L2 = 1.2 min. Q2 = (.2)(1)(1.2)(5) = 1.2 cfs
L100 = 3.5 min. Q100 = (.2)(1.25)(3.5)(5) = 4.4 cfs
APPENDIX A
No Text
ItgICE'
C = 0.60 Developed
DEVELOPED FLOWS
PARCEL B - CUNNINGHAM CORNER
C = 0.20 Undeveloped
Cf2 = 1.0 Cf100 = 1.25 A = 6.0 Acres
Includes Outlot
Q2 Developed = C Cf i A
T = 1.87 (1.1 - C C ) D2
c S1/3 €
D = 900' Developed
EL. High = 76 Elev. = 10' SAvg = 10 = .9%
EL. Law = 66 900
Tc2 = 1.87 (1.1 - (.6)(1.00)) 900'
9 1 3
Tc2 = 29 min.
i2 = 1.5 in%hr. Q, _ (.6) (1.0) (1.5) (6.0) = 5.4 cfs
__ 1.87 (1.1 - 1.6) (1.25) ) 900'-
Tc100 9 1 3
rc'_ o = 20.3 Miry.
i100 - 5.1. in/rs, Q100 = (•6) (1_25) (5.1) (6.0) = 23 cfs
Extra A-rea
A = 1.4 Acres D = 1200'
S Avg. _ .80
T = 1.87 (1.1 - (.85) (1.0) ) 1200 `k
= 15 min.
c� .8 1/3
11c100 = 1.87 (1.1 - (.85)(1.25)) 1200 = 5 min.
8 1 3
C') = 2.1 inihr. 02 = (.85) (1) (2.1) (1.4) = 2.5 cfs
C100 _ 7.0 im/hr' Q100 = (.85) (1.25) (7.0) (1.4) = 10.4 cfs
BASIN II WITH DEVELOPED PARCEL E AND PARCEL B REQUIRED RETENTION
Tc i cc A Tc Volurne
(cu. ft.)
10
7.0
.30
39
600
20
5.2
.30
39
1200
30
4.2
.30
39
1800
40
3.5
.30
39
2400
50
3.0
.30
39
3000
60
2.6
.30
39
3600
70
2.3
.30
39
4200
80
2.05
.30
39
4800
90
1.85
.30
39
5400
100
1.70
.30
39
6000
110
1.55
.30
39
6600
120
1.45
.30
39
7200
130
1.30
.30
39
7800
Max. Volune = 122,148 cu.ft. = 2.8 Ac=ft.
Have 3.5 Ac-It.
Farce] r A = .73 Acres
S Ava. = 1.0%
C Developed = .35
D = 2G0'
116,883
119,340
119,691
122,148 = Max Volturve
118,638
Tc2 = 1.67 (1.1 - (.c5)(i)) 2002 = 20 min.
1 1 3
Tc100 = 1.67 (1.1 - (.35)(1.25)) 200;' = 17.5 min.
1 1/3
i2 = 1.8 in/hr. Q2 = (.35) (1.0) (1.8) (.73) = .5 cfs
i, = 5.6 it/hr. Q100 = (•35)(1.25)(5.6)(.73) = 1.8 cfs
II
II
II
CUMMIGHAM CORNEP. - PARM S C & D
C = .85 Cf = 1.0 C'100 = 1.25
A = 7.3 Acres i8ffice Park)`
A = 1.1 Acres (Cc mtiercial Area)
AT = 8.4 Acres
D = 400' Ccmnercial
D = 900' Office Park
Office Park - Parcel C
Tc10 = 1.87 (1.1 - (.85) (1.0)) 900;i
2
1 1/3
Tc100 = 1.87 (1.1 - .85 (1.25)) 900
1 1/3
i10 = 3.65 in/hr.
i100 = 7.0 in/hr.
Q10 = (•85)(1)(3.85)(7.3) = 23.9 cfs
Q100 = (.85) (1.25) (7.0) (7.3) = 54 cfs
Conmercial Area - Parcel D
S Avg. = 1.0%
= 14 min.
= 5.6 min.
Tc10 = 1.67 (1.1 - (.C5)(1)) 400� = 9 rd.r.
Zia
3'c100 - 1.87 (1.1 - .85(1.251) 400min.
1 1/�
i10 = 4.6 in/hx.
1100 = 7.0 in/hr.
Q10=_(•85)(1)(4.6)(1.1) = 4.3 cfs
Q100 - (•85)(1.25)(7.0)(1.1) = 8.2 cis
PITPCF,I. G
C Developed = .6 Area = 5.0 Acres
D = 700' S Avg. = 0.75%
Tc2 = 1.87 (1.1 - (.6)(1.0)) 700 = 17 min.
0.751
Tc1C10 = 1.87 (1.1 - (.011.25)) 700 = 19 min.
0.751/3
i = 1.5 in/hr. Q = (.6)(1.0)(1..5)(5) = 4.5 cfs
i100 = 5.3 in/hr. Q100 = (.6)(1.25)(5.3)(5) = 20.0 cfs
1
' Windmill Drive
L = STA. (8 + 07.88) - (14 + 50) = 642.12' use 650'
' Savg. = 0.88%
' A = 54' R.O.W. x 650' = 0.40 Acres
2
' C = 0.90, Cf2 = 1.0
Tc2 = 1.87 (1.1 - (.90) (1)) 650� = 10.0 min.
.88 1/3
' i2 = 2.5 in/hr
' 42 = (.90) (1.0) (2.5) (0.4) = 090 Use 0.90 cfs for both sides of CL
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