HomeMy WebLinkAboutSILVER OAKS PUD, THIRD FILING - FINAL - 14-88L - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT
SILVER OAKS P.U.D. THIRD FILING
PREPARED
FOR
TRI-TREND, INC.
FEBRUARY 28, 1994
STEWART & ASSOCIATES, INC.
103 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
303/482-9331
•
uI
—�J UU1I1'' 4 L. a2malgwnrl •43 OIlsnd`-
o:
�1 �1D oIsauob♦ ` ,
" o m 'U y� �t
'IS U2W�j 'I By oµroS � ,
Jul
ArM UIW AND08 a U 0
Z 'IS sdJD t o a r"4�ia o
in
a}Ue-) is u,IJo� sd, E c`' PA PO-1uowgDIH
g 0 0
C
O
b n R a u a a'" S Ci �T ��. � a
Wo46u1IION vD v� JS ooauag Volley
.bS c 3
v
pJO;poJ8 ��• ant/ .v �
QIM �� J 0',
u o J J n S _. JO a� Ja//a� iS aU0% O Q Al
/ J 1
a y e'//s aid uojsnOH LU U a �
S 24o,Qwad
uolu.D,Jl a fviuMo ID
J o Q a
rra WoLuauelJ cya o� ;� Sla\D and uag 61g DAIJQ luaosaJz)
`� Q�• anV .JDqunQ
ao o ,� _ m �a�Sviwlsa/y1
�3 a in -0 � l J. j .10
U
{S 1D p!Janp ? _ ov �l ^+06 4s�16u3 aniJO I D�to
8 '0 — 6 a
IS i3 1� �raU`.� '19 aAIJQ
DPU
IuaH a a u D
w
C /� g' t T IS a faspull U L W 3 10
J a
a
O N
o o o a c aUD1 II Poo v
= d w
2 Y Is au V� Z J v w v
a2F -,�IH i vt S in 3 3
scr
�okg > aUD"j Obi x
o y PaJ�II�j ��
m`
tj
O tti� t
y E` LJ U)0 brid e
1 J auDls aljunV p J
a
fairo� j Y �LN , . %_ �,
�y%'ij JO uollDQ ci �o 00
y� O
aUD� iJ00hJ ----� �0 IS. poaVq a
IS wopulM
EL
LZ
allDld m
t
sPuDlq !H a�
�_ . �'� .. _� • f� rO
o ��ayy `-1Lr
' o
z
v
_ C
r I]
j c U o
o ry Gam• U
Get
T.Ql� O d
` W j
FINAL DRAINAGE AND EROSION CONTROL REPORT
SILVER OAKS P.U.D. THIRD FILING
EXISTING SITE:
The proposed Silver Oaks P.U.D. Third Filing is located in the Southeast
T of Section 28, Township 7 North, Range 69 West of the Sixth P.M., City of
Fort Collins, County of Larimer, State of Colorado. The subdivision area is
12.2741 acres. For drainage calculations, this area is increased to 12.52
acres to include the east one-half of Auntie Stone Street and the south one-
half of Bronson Street, and exclude the north one-half of Horsetooth Road.
Horsetooth Road is excluded because it was included in the Horsetooth Road -Taft
Hill Road Improvement District. This site is bounded on the south by Horsetooth
Road, on the west by Auntie Stone Street, on the north by Bronson Street, and
on the east by undeveloped land. Horsetooth Road, Auntie Stone Street and
Bronson Street are constructed. The undeveloped land on the east is designated
for future commercial use. This site is in the upper reach of the Spring Creek
Drainage Basin.
The existing ground slopes northeast at a slope of 1.4%. The site is
covered with grass and weeds.
This proposed filing is the final phase of the Silver Oaks Master Plan
Storm Drainage Report approved March 4, 1993, by the City of Fort Collins.
Storm drainage facilities built with the First Filing include the curb inlets,
storm sewer system, and detention pond to serve this filing. There is an
existing 10-foot curb inlet at the southwest corner of the intersection of
Bronson Street and Silver Trails Drive. This inlet was designed to handle
all the runoff from this site lying west of the centerline of Silver Trails
Drive. An additional 4-foot inlet on the south side of Bronson Street about
200 feet east of this site is designed to handle flows from this site east
of the centerline of Silver Trails Drive.
There are no offsite flows onto this site from the north or south. There
is a 0.2 acre offsite area next to the southeast corner of this site that may
run off onto this site. Our design will be made to accommodate this flow.
Also, offsite flow from Olander School will run to the existing 10-foot curb
inlet. We will design for this runoff of 3.3 c.f.s.
DRAINAGE CRITERIA:
The overall drainage report used the Rational Method for determining the
peak runoff rates and required detention pond volume; therefore, it will be
used in this proposed Third Filing. Design factors used are in accordance
with the recommendations and criteria of the City of Fort Collins Storm Drainage
Design Criteria and Construction Standards Manual.
DEVELOPED SITE:
The site will be developed into 40 single-family lots and 16 patio -type
lots. The average single-family lot is 7850 square feet. The average patio
lot is 3900 square feet.
Silver Oaks P.U.D. Third Filing
Page 2
All storm drainage facilities for this Third Filing have been installed
with the First Filing construction except for the proposed drain Swale behind
Lots 31 through 39 and on the east side of Lot 40.
The site is divided into three sub -basins. Sub -basin IE-1 is Lots 1
through 9; Lots 55 through 56, and the north one-half of Lots 46 through 51.
The longest developed overland and channel flow route for this basin is across
Lot 9 northeast to Silverleaf Court, then north along the west side of
Silverleaf Court to Bronson Street, then east on Bronson Street to Inlet IE.
The area of this basin is 4.41 acres. All runoff from this basin is to Inlet
IE.
Sub -basin IE-2 is 5.61 acres. All runoff from this basin is to Inlet
IE. It includes all of Lots 10 through 25 and the south one-half of Lots 46
through 51. The longest developed overland and channel route for this basin
is across Lots 10 and 19 to Oak Hill Court, then north along Oak Hill Court
to Three Oaks Court, then east on Three Oaks Court to Silver Trails Drive,
then north to Inlet IE.
Sub -basin IB-1 is 2.50 acres. All runoff from this basin is to Inlet
IB 200 feet east of this filing on the south side of Bronson Street. The
longest overland and channel route for this basin is east across Lot 30 to
the proposed drainage channel, then north along the drain Swale to Bronson
Street. The.existing 4-foot curb Inlet IB has the capacity to handle the 2-
year developed flow.
Inlet IE has the capacity to handle 11.9 c.f.s. The 2-year runoff from
this site, including the designed maximum outlet rate of 3.3 c.f.s. from the
Olander School site, is 12.3 c.f.s, which exceeds the inlet capacity. We
verified the existing pond's maximum height before overtopping and measured
the size of the existing restriction plates and calculated the maximum release
rate from these as -built structures. We found the release rate to be 3.1 c.f.s.
We also calculated the discharge from these ponds at a depth of one foot and
found the release rate to be 2.15 c.f.s. This depth would be closer to the
2-year release rate than the maximum pond depth. The existing outlet structures
from these ponds produce a staged release rate, increasing as the pond's water
elevation increases to the maximum release rate of 3.3 c.f.s.; therefore, we
feel that the 2-year runoff to Inlet IE is 11 c.f.s., which is less than the
capacity of the inlet.
EROSION CONTROL:
Silver Oaks P.U.D. Third Filing is located in a high rainfall erodibility
zone and in a moderate wind erodibility zone. The site is fairly small (12.52
acres), and it will be developed in one phase. The overlot grading will be
done, the underground utilities will be installed, and the curbs, walks and
pavement will be placed in a continuous operation. At the beginning of overlot
grading, the contractor shall place gravel filters at the two existing inlets
• on Bronson Street, and shall install a gravel sediment trap over the outlet
of the existing detention pond. After overlot grading, the rear 50 feet of
Lots 1 through 29 and Lots 46 through 56, all of Tract C, and the rear 25 feet
of Lots 30 through 45 shall be seeded with a temporary crop of annual rye grass
mulched with straw.
Silver Oaks P.U.D. Third Filing
Page 3
0
The maximum barrier spacing to prevent wind erosion in a moderate zone
is 200 feet. The installation of curbs and pavement and the mulching shall
provide adequate barrier spacing to prevent wind erosion
All erosion control procedures shall comply with City of Fort Collins
Criteria.
Frankl i n D. Bl ake, P. E. & L. S.
enclosures
40
n
LJ
10
STEWART&6AOCIATES 103 S. MELDIO, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors /
By: ,o%G� Date: Client: Sheet No. of
Project:
Subject: _ �%Z/✓J��y �' L�C
10
STEWART&ASROCIATES 103 S. MELDF4, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors
By: Date: Client: Lti �G'/%O Sheet No. 2'— of
Project:
Subject:
_ �C'�LG'�L�TE T�/O- Y�i92 O/SCf{i921"G' �.G�c�iy �L.q/V�E2
17
i
R NV /�° .3 J'���7 4, 100� 4 aS cSfDi�rl GY/�i� ��� lc�U�i
��rsr/�v� �-a�r �•va v�r�r,� 2 0 f�
1
jf Z
V 4x0.76
V,r s
— 1 4,
STEWART&AAOCIATES 10 82-93 D�X aOFA89 C8OLLINS, CO 80521
PH.Consulting Engineers and Surveyors
By: Date: Client: /'i�� Sheet No. 3 of
Project:
Subject: 2r/2�p e C. a la / S
-/ Tc"" Gaw Tr
rYp c 2
I44
I
i i I i4'/.ST/�vlr f�AK �.vo L04
"P�".� .S
I
1 / , vim. 7
STEWART&ALICIATES 103 S. MELDS, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors
By: Date: Client: Sheet No. 4 of
Project:
Subject:.Z/�2
1 ., -
STEWART&ADCIATES
Consultin3 Engineers and Surveyors
By.
Project:
Subject:
Date:
Client:
103 S. MELDS, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Sheet No. of
STEWART&AMOCIATES 103 S. MELD&, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors 1'
By: LU2- Date: � `�" Client: 2� - k zclpk C1OWIL-' Sheet No. Co of
Project: V S
Subject:
�2ywAr-J.-
ct: N/ stoic
STEWART&AStOCIATES 103 S. MELDRO, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
Consulting Engineers and Surveyors
• By: FIR Date: Client: Tr-� Tr e r)J I r7 c Sheet No. 7 of
Project: - S i V e r O a ks i r-
Subject: EF05iOn Con�r0 Coss Co I/e �erca
Z00.00
� �- �-ro ►� �u�s de�e+� lon
_IZ!- r'a✓�) r (�i- N�ers' CA-i /U0.oc4,- 2-(/U100
pie arrler c" 75•GG�ak 7s •00
ac-' a Mv)c,e 4ely eI o� �'OG,0� cG 3 000. 00
7—o7-/4L_ _ 3 ¢75.00
e," 0 .s T 70 RC SEEP ToT4L- C TzJ4D F-D S 1 T E
a.<
coy ill. x SO O. 00 I -
I I
.: C0LL..'e-) 7ETz,,9 L 7F-AUIRED = 575-0.00 A
. I
I i j I I I I
( I
S`150.00
-4 8725, 00
2
10
u
O
p
_
(0
O
C
W
ZZ
n
J
0
70
O
Q
Z
L
O
ca
�.
CO
W 3 co
z
o
{ a,
Q
T
`T
I
V
LL
r^�^
CD
X
O
o.
O
•-
v E
T
Q
W
O
'0
_2`�Y~
O
L C Co
V U LD
CL
0
II
Q
cn
T
T
\
T-T
1
V1
z Q
co " �'
� �
U
U w
p
o
r
N
~
wwca
Cc
= II =
>
U
HU
Z
II
U-^
OOM}M
�L N
LljL
E
v'
� W
,-
O
O
O
W
� A
00
\
O a)
ZU >
w
a
'---coo
Oo
r
Q U
T
(J)
w
Q
(n
[C
W
-i
U
F—
Z
W O
II
(MD.
� c
O
1..1.E
U
O
O
�
U
C)
O
r
000p
�*
N
O
c
p
r
O
cc
uQ
QZ
Q
k
o
co
W
-
D
Q
U
u
00
o00
NOw
c
U
0 0It
cooU
�- CV O
U O c
ci
cc
1- II
Z Lq
uWN o
co
co p -
N
0 •
•
•
2
a 14
W
C W
O 0
cn -'aW
�4] LL Q>
MnN Cl)
cu
II
0
(D
0
O
U
CIO
T
N
CZ
p
n
U-1--+
U
��
a
II
II
C13
N
LO
L
N
N
C7
O
^O
W
F—
cz
�L
„ O
O
U
�N
t
ccv
�F
O
II
(z
>
0
o
U)
O
I
w
(n
O
Z
r
N
-r
O
CD
a)
O0-0
O
ca
G
II
II
00
N
N
co
S
7vz
m
N
N
E
LA
(0
rr
It
ti
M
tf)
O V7OrC7r"�NN
Cl?
.t�
N(D
QI j
0
0
0
0
.-
CV
Cl)
V•
(D
CO
co C
C
O
0 aL)
H
N
00
00
N
O
N
00.00
N
0
OOTM(Oh`CA.N(Da
N
\
o
o
C:)
0
o
'o
C.
(1)
Q O
J
Oo
ooOO'0000
•-
�wN(D0"ItORN(Do
NUOOrrNCVIN'Cr7M
d'
U E
` O
C �
N
00
CO
N
O
N
00
00
N
O
OOTm
mn
ON(Do
T
N
0
0
0
O
O
a
O
T
r
N
cr
o
0
0
0
_ J
O
o
0
0
0
O.
av
V
aoNCDO
V;wN(Do
O E
U
0
a
cT
C.
cc
m
V
O
C
�
.... ..... ...... ..... ......
OOr
V
Cnl�f�
NON
CO
UOOOOrN
V'(D000
T.
O
CD
U)
H
momomomoma
OrN
V
(DCAN0O
M
N
�
o
0
000
0
T
T
N
N
O
Q �
J
0000000000
Q
0
o
0
0
to
O
to
O
M
O
v EOTTNNMm
O
C
�
momomomomo
O
T
N
V
(D
M
N
W
O
to
TZ,6
CU
0
0
0
0
0
T
T
N
N
a)cr
Q N
o
O
o
0
0
0
0
0
o
O
r J
M
O
m
O
w
O
o
O
w
o
aa)0OrTC
NC
U E
' O
a)
`
C
�
0000000000
r
N
CO
a
0
0
N
O
m
O
CL
o00000000r
CD
o
3 �
O
C
•
ti
D
v
DRIVE OVER C & G AND INLET SIZING
THEORETICAL FLOW CAPACITY VS. FLOW DEPTH
Equation used is Q = .56 (Z/n) (S ^ .5) (Y ^ 8/3)
When solved for depth Y = ((Q * n) / (.56) Z (S) ^ .5) ^ 3/8
1.40 = Inlet Capacity (cfs/ft) Without Reduction factor
SDDCCS (Figure 5-2) enc& .wk3
St. Name/Inlet 0 S. Side Bronson / INLET IE I Type Of Street: Residential / Initial Storm
12.30 = Q flow in cfs 0.016 = n Mannin s 0.025 = Sx X—slope)
0.010 = S st. sloe 0.85 = Init. Red. Fact. 50.00 = Z 1 /Sx
0.37 = Depth Of Flow at Curb (feet)
14.78 = Encroachment Width (feet)
8.79 = Theoretical Inlet Length (ft)
10.3 = Min. Desian Inlet Size (feet)
0
0 I.0
I:
M
7
U-
cr
O .6
U
z
0 .5
I=
U
0
w .4
0-1
N
I
F=08
/
L
c
f
�I
III
5
F:0.5:
l
I
0. 4 %
I
I
I
I
i I
I
i
I
I
I
BELOW
ALLOWABLE
STREET
MINIMiU
GRADE
ii
II
I
I
I
I
II
it
�I
.0
0 2 3 4 5 6 7 8 10 12 14
SLOPE OF GUTTER (%)
Figure 4-2
REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY
Apply reduction factor for applicable slope to the theoretical gutter capacity to obtain
allowable gutter capacity.
(From: U.S. Dept. of Commerce, Bureau of Public Roads, 1965)
5 =
—>
1•',AY 1984
4-4
DESIGN CRITERIA
•
•
GUTTER CAPACITY TABLE FOR VAIABLE STREET SLOPES AND CROSS SLOPES
2 YR EVENT WILL BE EXAMINED
FOR: SILVER OAKS P.U.D. DEVELOPED BY: TRI-TREND, INC.
BY: STEWART AND ASSOCIATES
THEORETICAL CAPACITY Q = .56 (Z / n) (S) ^ .5 (y) ^ 8/3
VARIABLES AND DEFINITIONS: Q = THEORETICAL GUTTER CAPACITY (cfs)
0.42 = y (DEPTH OF FLOW AT FACE OF GUTTER, feet)
0.016 = n (MANNINGS ROUGHNESS COEFFICIENT)
S = SLOPE OF CHANNEL ( feet / feet)
Z = RECIPROCAL OF CROSS SLOPE, ( 1 / cross slope(ft / ft))
Reduction factors are from Storm Drainage Criteria & Construction Standards
DESIGN CONSTANTS
CHANNEL REDUCTION
SLOPE S FACTOR
1 / CROSS SLOPE (ft / ft)
50.000 =_ Z = 1 /.02
THEO.GUTTE REDUCED
CAPACITY (cfs) CAPACITY (cis
1 / CROSS SLOPE (ft / ft)
40.000 = Z = 10251
THEO.GUT-rER REDUCED
CAPACITY cfs CAPACITY (cfs
1 1 / CROSS SLOPE (ft / ft)
33.330 = Z = 1 [03
THEO.GUTTER REDUCED
CAPACITY (cfs) CAPACITY cfs
0.0045
0.50
11.580
5.79
9.264
4.63
7.719
3.86
0.0050
0.65
12.207
7.93
9.765
6.35
8.137
5.29
0.0060
0.80
13.372
10.70
10.697
8.56
8.914
7.13
0.0070
0.80
14.443
11.55
11.555
9.24
9.628
7.70
0.0080
0.80
15.440
12.35
12.352
9.88
10.293
8.23
0.0090
0.80
16.377
13.10
13.102
10.48
10.917
8.73
0.0100
0.80
17.263
13.81
13.810
11.05
11.507
12.069
12.606
9.21
0.0110
0.0120
0.80
0.80
0.80
18.105
14.48
14.484
15.128
11.59
9.66
18.911
15.13
12.10
10.08
0.0130
19.683
15.75
15.746
12.60
13.121
10.50
0.0140
0.80
20.426
16.34
16.341
13.07
13.616
10.89
0.0150
0.80
21.143
16.91
16.914
13.53
14.094
11.27
0.0160
0.80
21.836
17.47
17.469
13.98
14.556
11.64
0.0170
0.80
22.508
18.01
18.006
14.41
15.004
12.00
0.0180
0.80
23.161
18.53
18.528
14.82
15.439
12.35
0.0190
0.80
23.795
19.04
19.036
15.23
15.862
12.69
0.0200
0.80
24.413
19.53
19.531
15.62
16.274
13.02
0.0210
0.78
25.016
25.605
26.180
19.51
20.013
15.61
15.77
15.92
15.40
14.85
16.676
17.068
17.452
17.827
13.01
13.14
13.26
12.84
0.0220
0.0230
0.77
0.76
19.72
19.90
19.26
20.484
20.944
21.395
21.836
0.0240
0.72
26.744
0.0250
0.68
27.295
18.56
18.195
12.37
0.0260
0.66
27.836
18.37
22.268
14.70
18.555
12.25
0.0270
0.0280
0.64
28.366
28.886
29.398
29.900
18.15
22.693
14.52
18.909
19.256
19.596
12.10
0.61
17.62
23.109
14.10
11.751
0.0290
0.58
17.05
23.518
13_.64
12.92
11.37
0.0300
0.54
16.15
23.920
19.931
10.76
DRAINAGE CRITAA MANUAL
RUNOFF
m
50
REV
F- 20
z
w
U
W
° 10
z
w
a
O 5
W
¢ 3
O
U 2
W
F-
Q
*4
3
3 —
4v
0
—
-
—
a
Q-
lUPh�
J
P
V O Q S
Col
3
—
Jv hJ V h�
—
—
-
-
v~ Cl) e 3P
P
--
Q
Q, p 3
— C,
- -
—
yy
P
-v It -V 4, —
----
3~�
° o
low
4,y--
O
4P e
O
4r
QP
.2 .3 .5 1 1 2 1 i3 5 10 20
VELOCITY IN FEET PER SECOND
FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR
USE WITH THE RATIONAL FORMULA.
I MOST FREQUENTLY OCCURRING "UNDEVELQPED"
LAND SURFACES IN THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
Release No. 55, USDA, SCS Jan. 1975.
5 -1-84
URBAN DRAINAGE $ FLOOD CONTROL DISTRICT
1.0 12
5
.9 11 10 4
.� 8
10 6 3
.8
9 0 w 2
0 4
3
8 W z
a 1.5
-
.6 6 2'
7 Par %,- tL
_3-
ci
r I.0
pt e�i s �'
xam
5 -6 __ ple, Part o 1.0 z 9
z
5.5 a - a .8
o
w 5 = z .6 0 .7
.4 z Z .4 ►- `
Z 4.5 z o 3 .6
L w
w =
_. 4 v o
2 0 .5
z 3 3.5 z z
a w w .4
0 J
o �
.i
ILL U- w
0 .25 3 0 wo .08 -
H
~o .06 (D .3
0 z
2.5 = w 04 a .25
.2 a .03 a
� 3
a 02 0 .2
a
2 a =
U h-
a
.15 .01 0 .15
L w
0
0
Yo a
1.5 - -- -- a
a-2'h ,10
.1 1.2 Yo
Figure 5-2 "' ` 0
NOMOGRPAH FOR CAPACITY OF CURB OPENING INLETS IN SUMPS, DEPRESSION DEPTH 2"
Adapted from Bureau of Public Roads Nomograph
MAY 1984 5-10 DESIGN CRITERIA
,S1)
use
Irl
RAINFALL PERFORMANCE STANDARD EVALUATION
--------
--------------------------------IP-R-0-J--ECT-: S�1✓er Oc�bCs T�71 rc� STANDARD -FORM -A-
I
COMPLETED BY: DATE: q ¢
------------------------------------------------------------- ------
DEVELOPEDIERODIBI
SUBBASIN I ZONE
14
rF-
L6 =
LITYI
{-,
Asb
I Lsb
I Ssb
I Lb
I Sb
I PS
(ac)
I (ft)
I W.
1(feet)
I
1 (a)
4.4-I
1 i000
I / �7,
1
1
15, (; I
I boo
117
I i
2.50
(65U
17,
I
I�2,-5
I
1
I840 !
I
0
78,1
4-.4I
xi000 tl5
I
al xoo
I
t
I i
+z.Soxv
12.
j
4-t x�
1+ s
t x +I�.
i
X
I
I
I
I
I I
I
I
I
I
I
I
i
I
I
I---------------------------------------------------------------------I
HDI/SF-A:1939
•
EFFECTIVENESS CALCULATIONS
----------------------------------------------------------------------
PROJECT: Sit Vey Oaks %fri rJ .STANDARD FORM B
lCOMPLETED BY:
Erosion Control
C-Factor
P-Factor
Method
Value
Value
---------------------p
5are s o l
--o-------
------
nAU)cl ed te•^P cror
0.0c
/.06
P"'"4 j conc.
0.01
_ / 00
5ravel inI4 ;,lier-
(.uo
0.90
edLme-4 %c-P�
100
�.s0
MAJOR
BASIN
PS
W
76.1
SUB
BASIN
E-Z'
AREA
(Ac)
4.41
5.GI
DATE: 3
Comment
--------------
F1Gcec1 in
------------------------------
CALCULATIONS
--------- -----_ -------------------------
ar2 so r' - 1. �3
p '�c walls = 1. 2Z Ac
4-eMf crv,v/MLj)c1i = 1. Si� 4c
W G = 63X► O) f _zi)(o,o)> I 5'4XO.0C)
G = 0131
W�d p= ,gr-aJc! ir11Ci
6 ed l Me4�
Pl o ce d in ex) s } Jc-- ro-4 = 0.5
P = 0.67- x 0 5' 0. 9-
F FF = / - (0.37 x a.4-)x )v0 : 8 �-, 4- l`
Bare soil =
Z.g7 Ac
v � v��oll cJJJS -
1 4 7 Ac
11 c r 0 /M�c� _
r/¢I
I•GS Ac
W ►d G
S. G I
Plocc� in ex)Sl"de�"�,o�� 0.5
�- 0, 4-x O.'�--
'E1%r - I- (0.4-cx0.q-) -�( Iao = g 1, G 7
----------------------------------------------------------------------
HDI/SF-B:1989
0
EFFECTIVENESS-CALCULATIONS
------------------------------j- ------------------------------------
�PROJECT:-SijlJer- DakS T+� i r ..STANDARD FORM B
COMPLETED BY: DATE:
J
Erosion Control
C-Factor
P-Factor
Method
Value
Value Comment
--
dare
-
1------------
---- ---------------------------------
1-0
mulche�
fem� crop `
0.0G
(-00
pvr� �
cuoc.
p,oI
- 1.00
5 rG�Jci i dcC - F;Iier
(. 00
01(90
�t-0 ,ija I P ba tT* F.
sed
!- 0 U
i.vo
0.8 0
0-50
place in e-v-I r5
---------------------------
d---
MAJORI
PS
SUB
I AREA
---------------
---„------
BASINI
(%)
IBASINI
(Ac)
CALCULATIONS
-----
------
76. !
-----
16 -I
------
2.50
--------------------------------------------
bar-1e
so> )
/, 9-1 /4G
Tvlw" q'
wc-1�3 _
(). Ss A c
�e,rD croP%i1+vic� = O. 5" ¢ ,Ac
Z.50
G= O.SV
�/✓"�� � _ 1n le� -1'l l�i Qn� St!`a✓ bal(� �%. �j
S��IMCn)� 7 ("C/I� j�IGLC�I
nOnc)-�I
�- 6).�7—X0.51= 0.4-
FF-F = I- (o.s�-xo.f) u100 - 76.6 7`
76,1
----------------------------------------------------------------------
DI/SF-B:1989
•
• CONSTRUCTION SEQUENCE •
PROJECT: -Sl%yeF Oaks l ,f'%I STANDARD FORM C
SEQUENCE. FOR 19 I:t ONLY COMPLETED BY: DATE:
Indicate by use of a bar line or symbols when erosion control measures will be installed.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engineer..
YEAR
MONTH
----------------------------
OVERLOT GRADING
WIND EROSION CONTROL
Soil Roughing
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other cvMI- � wa1k5
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettinos/Mats/Blankets
Other
STRUCTURES: INSTALLED BY
9¢-
5
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
HDI/SF-C:1989
I
I,AJ ID !
I
I
I
I
I
!
I
I
i
1,
j
I
I
I
!
-
(
1
1
�
I
MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS ON
JANUAR'i 1991
8-20
DESIGN CRITERIA
• 0
FINAL DRAINAGE REPORT
FOR
POUDRE R-1 SCHOOL DISTRICT
1990 ELEMENTARY SCHOOL
MARCH, 1989
Prepared For:
Dulaney Architecture
5261 South Quebec Street
Suite 210
Englewood, Colorado 80111
Prepared By:
Engineering Professionals, Inc.
2000 Vermont Dr.
Fort Collins, CO 80525
•
LOCATION
FINAL DRAINAGE REPORT
FOR
POUDRE R-1 SCHOOL DISTRICT
1990 ELEMENTARY SCHOOL
0
The proposed school is to be situated on 10.0 acres located approximately 1500 feet
west of South Taft Hill Road and 200 feet north of West Horsetooth Road, within the Horsetooth
West Masterplanned area. More specifically, the site is located within the southeast quarter of
section 28, Township 7 north, Range 69 West, which puts it in the upper third of the Spring
Creek Basin (See vicinity map).
EXISTING CONDITIONS
The site presently drains by overland flow to the northeast. Two offsite basins (denoted
as OS1 and OS2 on the plan) with a combined area of 4.62 acres located southwest of the site
contribute overland flow to the site along the south and west property lines. The property has
moderate slopes ranging between 1 % and 2.5%, with ground cover generally being sparse
grasses. The site is not located within any designated floodplain.
The school is located within an area assumed to contribute flow to the Rossborough
Subdivision at historical rates, identified as offsite basin 2 in the Drainage Report for
Rossborough Subdivision, prepared by Stewart and Associates, dated April 13, 1979 (see
append} x). A drainage channel was constructed within the Rossborough Subdivision along the
east side of Taft Hill Road to accept runoff from this basin, route it around the subdivision, and
direct it to the Trend - Cedar outfall to Spring Creek. Currently, flow from this basin is directed
to the west side of Taft Hill Road north of West Horsetooth Road where it appears to pond
before ultimately flowing to the north and possibly overtopping South Taft Hill Road. To our
knowledge, no operable culverts under South Taft Hill Road exist in this area which direct flows
to the Rossborough channel.
PROPOSED DRAINAGE
School Site
The school site will be drained in such a manner so as to maintain the existing drainage
patterns as much as possible. The school site is divided into 3 basins (1, 2 and 3) with each
basin having its own detention pond. Flows are directed by swales, gutters and concrete pans
to the detention ponds which are generally located along the east side of the property adjacent
to the proposed collector street. The total runoff released from the 3 ponds will be the historic
2-year runoff for the site (3.3 cfs) in addition to the historic runoff from the offsite areas. The
ponds and release weir structure will be sized to handled the onsite flows with the offsite flows
spilling over the top of weir. The released flows will be directed to the west flow line of the
proposed collector street by a sidewalk chase and covered channel. The following tables
present the proposed developed school property drainage basin and detention pond data.
0 0
SCHOOL SITE DRAINAGE BASIN DATA
BASIN
AREA (acres)
C
Q10 (cfs)
Q100 (cfs)
1
1.48
0.72
4.8
9.7
2
3.27
0.39
3.6
7.0
3
5.25
0.40
4.8
9.8
OS1
3.03
0.25
1.2
3.1
OS2
1.59
0.25
0.9
1.9
POND NO
1
2
3
Collector Street
DETENTION POND DATA
VOLUME REQ'D
(cubic feet)
11,430
9,200
20,310
RELEASE RATE
(cis)
0.37
1.76
1.17
HIGH WATER ELEV.
5138.3
5133.9
5135.2
Three basins, S1, S2 and S3, in addition to the school site area (and offsite basins) will
ultimately direct runoff to the collector street: The boundaries of these basins were determined
by discpssions with the land planners for the Horsetooth West Master Plan as well as the
topography of the area adjacent to the street. Historic flows were assumed from basins S1 and
S3 while developed flows were projected for basin S2 and the street itself (basins S4 and S5).
Detention storage for basin S2 and the street will ultimately be provided for within the
Horsetooth West regional detention pond to be located adjacent to South Taft Hill Road.
It is anticipated that Horsetooth Road will be improved in the near future. The City's
design for Horsetooth Road calls for a storm sewer to be constructed with an inlet located at
the northwest corner of the collector street intersection. This inlet will intercept runoff from the
north side of Horsetooth west of the collector street and direct it to the east. This storm sewer
along with the grading at the south end of the collector street will prevent Horsetooth Road
runoff from impacting the collector street. The following table presents data for the drainage
basins directly contributory to the collector street.
COLLECTOR STREET DRAINAGE BASIN DATA
BASIN
AREA (acres)
C
Q10 (cfs)
Q100 (cfs)
S1
0.76
0.25
0.4
0.9
S2
2.34
0.70
7.5
11.9
S3
0.46
0.25
0.3
0.5
S4
0.64
0.95
2.7
4.5
S5
0.64
0.95
2.7
4.5