HomeMy WebLinkAboutDrainage Reports - 09/11/1990F
Final Drainage Report
for
LOT 2, THE MARKET AT HORSETOOTH COMMONS
Ft. Collins, Colorado
Prepared for:
KENT GOODMAN
145 West Swallow B-2
Ft. Collins, Colorado 80525
Prepared by:
SHEAR ENGINEERING CORPORATION
4836 South College Avenue Suite 12
Ft. Collins, Colorado 80525
Phone: (303) 226-5334
Project No: 1200-1-90
Date: September, 1990
4836 S. College, Suite 12 Fort Collins, CO 80525 (303)226-5334
>
IBM
i
FINAL DRAINAGE REPORT
LOT 2, THE MARKET AT HORSETOOTH COMMONS
PROJECT NO: 1200-1-90
I GENERAL LOCATION AND DESCRIPTION
A. Property
location
1.
Lot 2 of "The Market at Horsetooth Commons P.U.D." is
located in the Southeast Quarter of Section 27, Township 7
North, Range 79 West of the Gth P.M., Larimer County,
Colorado.
2.
More specifically, Lot 2 is located on the Southwest corner
of the intersection of Shields Street and Richmond Drive, in
the City of Fort Collins, Colorado.
B. Description
of Property
1.
The site has an area of approximately 0.78 acres.
2.
The lot is currently vacant and has native vegetation.
3.
This lot will be the first lot of the five lots to be
developed within the Market at Horsetooth Commons
development. Street curb and gutter already exists around
this lot. With the exception of the west side of the
property, all the street sidewalk is existing.
4.
There is an existing 36 inch R.C.P. storm sewer line in an
existing 20 foot wide utility and drainage easement which
runs the length of the lot, on the east side adjacent to
Shields Street. The lot has water and sanitary sewer
services stubbed into it on the west side.
S.
The development of the site will include an office/retail
building with approximately 4000 square feet and a
retail/showroom building with approximately 3100 square
feet. There will be an outdoor display area around the east
end of the retail/showroom building which is intended to be
a specialty auto retail outlet. Our understanding is that
the display area will be surfaced with a design block that
allows lawn grass to grow in the block openings. There will
be 1 driveway curb cut along the west side of the lot,,
leading into an asphalt parking lot that will be. shared by
the 2 buildings.
II DRAINAGE BASINS AND SUB -BASINS
A. Major Basin Description
1. The site is situated in Basin "G" of the Foothills Drainage
Basin as identified in the 1981 Basin Master Plan prepared
by Resource Consultants, Inc.
B. Sub -Basin Description
1. Redpeak Engineering of Windsor, Colorado prepared a drainage
study for "The Market At Horsetooth Commons P.U.D."
addressing all 5 lots. The study was prepared in May, 1987
and revised in June, 1987. Redpeak Engineering refers to
this site as Tract "D" Area II, containing 0.78 acres with a
storm runoff concentration point at Inlet RS. This inlet is
in the southwest corner of the Richmond Drive and Shields
Street intersection. Redpeak's comments about this site are
"Area II detention to be completed at a future date". A copy
of the drainage study for the Market at Horsetooth Commons
is included in Appendix 8 of this report for reference.
PAGE 2
Project No: 1200-1-90
Lot 2, The Market at Horsetooth Commons
III DRAINAGE DESIGN CRITERIA
A. Regulations
1. This report and the drainage and grading plan were prepared
in accordance with the requirements of the City of Fort
Collins storm drainage design criteria.
B. Development Criteria Reference and Constraints
1. This Lot requires its own site specific detention facility
according to the drainage study for The Market At Horsetooth
Commons. See Appendix B of this report.
2. One of the primary constraints of this site is that all
adjacent streets are in place. These generate a relief of
over 4.50 feet from the high point of 82.68 at back of walk
on the south side, to 78.10 at the back of walk in the
northeast corner, and the high point of 82.86 at back of
walk on the west side to the same point of 78.10 in the
northeast corner. In order to provide the needed detention
area, yet not create side slopes along the east and north
sides that would defy maintenance, it is necessary to keep
the site improvements at as low an elevation as possible.
The existing 36" storm adjacent to the site allows
flexibility in the design of the site and proposed detention
pond.
C. Hydrologic Criteria
1. Runoff calculations are based on the "Rational" method.
2. Detention volume requirements are based on the cumulative
runoff method.
D. Hydraulic Criteria
1. Detention pond outlet is based on the orifice equation.
IV DRAINAGE FACILITY DESIGN
A. General Concept
1. The drainage design concept for this portion of the Market
at Horsetooth Commons development as proposed by Redpeak
Engineering is still applicable. On -site detention will be
provided to meet lot specific needs. Parking lot grading
will be designed to maximize detention volumes. The
detention pond outlet will utilize the existing storm sewer
which parallels Shields Street.
B. Specific Details
1. Final site grading design considered all existing grades and
adjacent street improvements. A majority of the stormwater
generated within the limits of this site will be directed to
the detention area (parking lot). 100% of the site runoff
will not be conveyed to the detention area due to reasons
which are discussed in greater detail to follow.
2. The existing 36" storm sewer paralleling Shields Street,
allowed flexibility in grading design to acheive required
detention volumes, as well as providing a reasonable
detention pond outlet design.
3. The minimum finished floor elevation for each structure was
established to not only protect the structures from
stormwater, but to render logical and maintainable slopes
between them and the adjacent street improvements.
PAGE 3
Project No: 1200-1-90
Lot 2, The Market at Horsetooth Commons
IV DRAINAGE FACILITY DESIGN (continued)
B. Specific Details (continued)
4. A concrete drainage pan will convey a majority of the
stormwater generated on the southern portion of the
property, to the southeasterly corner of the parking lot.
The drainage pan which carries the flow for sub -basin A-2
(0.45 cfs) was sized using the manning equation. The
concrete pan has a carrying capacity of 0.42 cfs. The
landscaping berms will deflect the difference of 0.03 cfs to
the parking lot. See sub -basin A-2 data and illustration in
the appendix of this report. The concentration point for
this sub -basin is shown on the illustration, as well as the
contributing flow to that point.
5. A small amount of runoff from a portion of Lot 2 is conveyed
undetained from the site. The two (2) specific areas which
release stormwater undetained are designated as sub -basin
A-1 and sub -basin A-3 in this report. The data, as well as
the illustrations for these sub -basins, are contained in the
appendix of this report. The runoff from these sub -basins is
conveyed to the existing inlet located on the Southwest
corner of the intersection of Shields Street and Richmond
Drive. Contributing flows to the inlet are shown on the
illustrations.
V CONCLUSIONS
A. Compliance With Standards
1. The grading and drainage design meets the City of Fort
Collins storm drainage design criteria. The design remains
consistent with the drainage concept for this portion of the
Market at Horsetooth Commons as submitted by Redpeak
Engineering and approved by the City of Fort Collins.
B. Specific Details
1. Final grading of the site was keyed to the driveway on the
west side. The driveway slopes 6% from the street into the
parking lot.
2. A stormwater inlet has been located in the middle of the
parking lot to maximize the detention area and volume within
the parking lot.
3. The inlet will contain an orifice plate with a 3.00"
diameter orifice (see calculations in Appendix A). The
orifice will release 0.41 cfs (2-year historic runoff = 0.42
cfs). The orifice plate detail has been included in the
appendix of this report for reference. It has also been
included on the detail sheet for the sitework drawings for
Lot 2, the Market at Horsetooth Commons.
4. The discharge pipe leaving the inlet will be an B" P.V.C.
pipe. The size was selected for ease of maintenance.
Stormwater will travel approximately 51 feet from the inlet
to a proposed 5' manhole installed over the existing 36"
R.C.P. storm sewer main.
PAGE 4
Project No: 1200-1-90
Lot 2, The Market at Horsetooth Commons
V CONCLUSIONS (continued)
B. Specific Details (continued)
5. The detention pond high water line will be at an elevation
of 80.2, established by a minimum berm elevation along the
east side of the parking lot. Grading along the east side of
the parking lot incorporates additional berming to meet the
landscaping plan design. The minimum berm elevation of 80.20
will result in a maximum parking lot depth of 1.SV , meeting
City requirements.
6. The rim elevation of the parking lot inlet will be 78.70
feet, with an invert elevation of 75.92 feet. This will
allow for detention storage of 4,314 cubic feet, which is 86
cubic feet more than the 4,228 cubic feet required (see
Appendix A).
7. A concrete drainage pan will convey the flows for sub -basin
A-2 to the detention area. A detail of the proposed concrete
pan is included in the appendix of this report. It is also
included on the detail sheet of the sitework drawings for
Lot 2, the Market at Horsetooth Commons.
VI REFERENCES
A. City of Fort Collins storm drainage design criteria and
construction standards.
B. City of Fort Collins files for Horsetooth Commons P.U.D. and The
Market At Horsetooth Commons P.U.D.
C. Foothills Basin (Basin G) Drainage Master Plan, by Resource
Consultants, Inc.
D. Drainage Study for Horsetooth Commons Tract D (The Market At
Horsetooth Commons); Redpeak Engineering;
APPENDIX A
I
&14elt'ET_../r- TOO..Ti/ �./i�1M..O�✓S_.
WA WC5 .._'57 y - _.--------- - -- -
1 II
%5'clll9f2G_E
_I
'1
_-.--..---.--
2/.C....rPu!✓0...4=4=.__.COE,F.F/_C/_EDIT.............____....-
i
1° !
I
- --- - .... _._ .__,1 ...1 - -�
Ii
14
1J
T-o9-9or
r2or�- �-90
17
1°
00
21
23
24
Ij
r
27
!I
9.N_.G.ES7_..._T..4fl✓.-EL.1>/_.S_.T.AN_C.E___
)17.Co.__-_187_�L/_-. 50
iz-,4
i - 0 —,cA
.............. . .......
. .......... — ....... ............ .. . ..........
07- 09 -90
S
i- c c• Tn n n i- c �^ // n i i r-
/.50
01/ERFLOW5 BERM /A/ oyE. COR. OFPRA-6 LOT
80.20
14/
;60. 00
X
M
O
� N
�
Q
W tl�
0.30
79.00
d
W
78..70
0
/, 000
4?,000 3, 000 4.000 5, 000
STORAGE ��'f s�
'
CUMUL,4 MC CUMULAT/I/E
57A6E
CONTOUR AREA
VOL UME VOL UME
l/OL UME
�i'`)
�ft z)
ft 3 { f 9
ACRE -FEE
O
78.70 O
/03 /03
0.003
0.30
79.00 /026
364/ 3744' '_
0.086
1.4/
80.00 5535
.570 4514
0.0 99
/.SO
80.20 7/28
SQUAT/ON: DEPTH X AREA = 1/OL UME
j
i
L_o_r_2, Gi2MMOM5' I = '
_N1AR�E_T__A_ _T__i'iO_R_S_E_T_.D.QT_H
i
7 09-90,.
MA,S'a
OlAGRANI CAL C 'S
. .........
RUNOFF RA/ IAWLL
i
✓_OLUME_._RELER.SE_P._ONO...G.
......
...,....Q...Z6__....
_.-._._6.-O._..__.--
----O..-ZB.._...__.__9O.O__
. _.4 20/. _._
.....___.3...7.8.._...2,823__.
_...4,482._
__ .7510..._-
.3� TZG.---
r
103GZ._
__l43 ....
_.4,228__
._.-.
---._-_./.._87_.....
..... O_:-78_--
_3,
.Z6.......
_.... .___
0.78 -
.--.7_,
__3, 4Z4 ...
,3p./ZZ_....
_l80._.....
. _.._O..T6.---....._..-_
__ L•OS._--
-_O_._7.8____
__.-__._._.._._....__..__
.._-.-..._.._..__.___..._.-___.--.------.__-.-_------------_.,--------.___...__-.___..T.__.
22_
20
2_4;
2.6
27
No Text
�sTNv_,esEra�r_,y catirMovs P,_ IrEr;BY
u
U,.,
-----------
-----_._._.._-_.----__-._. �D_✓_�!_O_.__/_ZOO._ O/�.90__.._
'I
._.._..__Q=--
,°
„
----.._.............. _._-.,,siziw
13
1.7
,_._.__..__..___..._.... CRA.v..�.rf/_/TKO.N.4L__/��'e.EC.,E._C<aTl_oN.-C,•J�tJ=-�Z_/�-->-.f�GLGr+It.JB_LE
,
7.:;
_..._...__--_---.._.__._.__;____Q...—_�4�..5�
�o._a5��?C3�.Z�_�3...-.GL� �o_._G_G._2_.._.__.____o•-.¢./..,_cfs___._.___._____.._
,;
22
-----
�3
_..3...4. _Q—U/Atit4L72F 2 E10E_.P-.LiJTE.._
a_
_._.......
_..... —____..__..___.—_._.______-__.____.--
21
I
CE%G/E,c%T
------- ----- -
t
RICHMON® DRIVE
O = `C�= 0,25 = �• /4 c�'s'
/80' � j T /BM�,�Q
�c
�
I
�
III
I
80 to
III
F.F. = 80.50 �o
79 O
'
I'
(min.)
III
o
790
III
ej`s
i
81 23
POiVd UOr GIMP'
III
oar I
4(a,50 HT 3:: , .
II I
III
\
I
I
1
qq
III
I
' ' ' ' it�na•
,.
'
?At
CC
III
92
$dd4�
� ,
'
o
I
it
9li'
8!'_1
III III
III 8j9j I
II 1 30' II
, 77 a 8p
41
4 80 9
it I I I 8�65 8DV I
II ti I F.F= 80.50 I
II I (min.)
�ff-I 82
30 Z _--
�-
/�� _�� BZse 0ti
—="iT
i
I
W
to
I
I
t �=7750
MH /NY. - 73'ik
%B. D.W. - 79 �O
r
uj
uj
0
Lu
g
c
EllGOT
•--
Z_,Jh���vl�I.e�ET_/n_fb�eEo-rh� COirNtONS
!JT/L✓TY �PEO G/.CIES aF 7�/7 .FO
•
1'�.i1FU.P - \
�_— �J --
- 9
2
- v
3
4
-
6
7
- of
�i
1o.
AO✓t/s TEO .F�t/.1lOFF G'OEFF/C/Eit/ r =CSC
X Cr = O. zS
J
��
T/ME of CIJ.VCEA/TRAT/rJ.tl = T
87) ('/3 ¢Z) _ /S 2
3 MZa/
/,/7
,s
RA/.VFALG dZ7-;;6,U.6/TY = / = sEE =Ia._.6
= S.So
,
°
=CC) ) = Co. 2s) 6s sZCo. /off
_
'o
21
23
<<I
25
`6
2
81
30`
I vZoo-of-,�o
I - I
m I I
Rl;QHM®,ND DR.I!!E � I I
I I
I 1. )ff-77V
I I
------- ------ —J— MH/NY.•73
-------------------�- --� / �� ra.0.w.•790
F.F=80.50
(min.)
8173
811.3
F.F=
//"82su
/ LeZZ o -
82s$ a�
I
e01° I
Y9�a
LO
90
G0
ST
I i it
I
I I II
I I I
III �
n
I I {LLJ t
I I I GC i t
ch
I I n
I I
u
I I �
uj l
t I = II
I II
jt
I A. .1,F Ac. 1
S= 907 II
IO= 47' it
I Ca�.6Z II
T = V4. 5 MIN. II
q=i .45cfs 11
I I I
I
I
I
I
A —2
PnGE
t-7V —,,W
K) lly;-
2
3 II
6
A vc� , -,6/- ==
7
1AZO&S—E
iri
it
-Z
12
Z- Amp0. 075
1
eq-41,47 t—c7/-ldl6 &!IVIO62cs 0
pis
-3
—
a
0. 95"
is
7-on4l,: C2.113
iG
17
0,0-75X-O. (/,0. 0/ x
A17- AA C 7-0,4?
20 I
0
22
199E 010= CoAl
23
7,4 0.,00) Is. 7,�) "IAJ.
C7&-U-
1
0-97
25
654E 516, 3-1)
CO. 0 7
I.c
46' ifs
27
23
!RICHMOND DRIVE.
4= 0. 51CA
_ --
_—__—_—____—__—__—______—__--_—_—_—__—___—___—_—___—___—_—
�
III
80 !°
III
III.
�
F. F = 80.50 79 o
(min.)
,o
79
�� II
'.
III
III
es
�s
s
, :
O
'at:; ` ;:670--
'O,'�..
t:i. 4t',,•tty1?�p,:•;Yl, .y. d � ..
}
I
1 1�
30t
r--
4?
d0b
III I j N I F.F= 80.50
min:) `.
az L
/ ----
/ /$zoo ti =ae
/ G SI8_0
® 13/aa
ro I I
I I
I I
I I 7750
I I
—J— MH/NY.-73Ol
tB.0.W.-70LO
♦ \ IA=0.07Ac.
\ , \0 ,0= $00'
\ 11IIIT=/oA/IV.II
�I !QT.=0.5/cis i'i
M
Mi
No Text
1,07-7
2
311
Z71.r7-,4A1e--,:a = 12 =,600"
4 E4A=-V =SQ, SO 77,5j2 = F. (90,
.4 vG - FLo?=E = 5 = /. 00 70
A.,ee,4 OF fZ.1,e-e,461AJ 4-S = 0. 07 ACRES
0.
AVJZk57-V RZJAIO OCFF= C ^ =0
9 _S' je 00
00
12
7, .5-4) 0 AIIAII17-6-5 IeD
lcd&o
/0.0,0 "VAIZ17-eS
15
is
Cgee
eov = Cz A = rl. 0) ("7 -6) rO. 0 7)
20
21
I COMA42EA17�: PAA!� A-*A/,OL4/ 77/65" A"121-IA17- Cl= WA777��
d2 hF-C- CQR-AXfff!!?7� C26&Y /,-' 7714F 4d��>O'
2-4
77:4647-
24
25
27
r
X
° Q
lz
C�j
N
D
Al,
O
06 *49Z = AIVI A/
22'AZ = A /V/ M
.;W07,9=.*79N1Y
26 :91- = -77 -L b�-7k
CZ 'R./ ='7 9 -7- Z VeY
i
' N
.-/O >v Oo- 86 t0 0.
-
-0.9 = ! 0 dO B90.9 069L f 0,
.41 W
� odd �ld7dsio, � � N C
-109.9a9 061sSt0 �
q`
3 odd .�d�dsio . N
Os os = YO g90-q Os -se -AO,
i armed ,cd7ds/0
�i1b'/77 7/b'OH /O 1 bVl y O
Az'op
Nfwd 9NL�0 Q kx
0,9 = 1/4/ON 9749 OO tO,
0 o
ri
o
U
No Text
APPENDIX B
a
DRAINAGE STUDY
FOR
HORSETOOTH COMMONS TRACT D
(THE MARKET AT HORSETOOTH COMMONS)
Prepared by
Redpeak Engineering
May, 1987
Revised June, 1987
TABLE OF CONTENTS
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . I
II. Methodology . . . . . . . . . . . . . . . . . . . . . . . . I
III. Baseline Hydrology . . . . . . . . . . . . . . . . . . . . . 1
Offsite Flows . . . . . . . . . . . . . . . . . . . . . . . 2
Onsite Flows . . . . . . . . . . . . . . . . . . . . . . . . 2
Detention Requirements . . . . . . . . . . . . . . . . . . . 8
Shields Storm Sewer . . . . . . . . . . . . . . . . . . . . 10
APPENDIX
Figure 1 - Utility Map . . . . . . . . . . . . . . . . . . . 12
Figure 2 - Foothills Basin (Basin G) . . . . . . . . . . . . 13
Figure 3 - Drainage Basins 6 Improvements . . . . . . . . . . 14
a
Figure 4 - Fort Collins Time of Concentration Curves . . . . 15
Figure 5 - Fort Collins Intensity Curves Figure 3-1 . . . . 16
Figure 6 - Nomograph for Round Pipe Flowing Full . . . . . . 17
ii
I. Introduction
The Market at Horsetooth Commons is a proposed commercial development
located in the Southeast Quarter (1/4) of Section 27, Township 7
North, Range 69 West of the 6th Principal Meridian in Fort Collins,
Colorado. The development is located within Tract "D" of the
Horsetooth Commons Subdivision, which is located at the Northwest
corner of Horsetooth and Shields. (See Figure 1.)
The proposed site is approximately 5.47 acres and is situated in Basin
"G" of the Foothills Drainage Basin as identified in a 1981 Basin
Master Plan prepared by Resource Consultants, Inc. (See Figure 2.) .
Some drainage work has already been completed which will affect this
site. A 36" concrete storm sewer will be constructed along the East
boundary of the project adjacent to Shields as recommended by the
Foothills Basin Master Plan. Also, a temporary pond for Block I of
the Horsetooth Commons Subdivision was to be located in this
development. This drainage will need to be incorporated into the
Tract "D" improvements.
II. Methodology
a
The Rational Method of determining runoff was used to establish the
drainage information in this report. The Rational Method is
recognized as an excellent method of calculating flows from sites less
than 150 acres. This method is acceptable for the Horsetooth Commons
PUD since this area is less than twenty (20) acres.
Rainfall intensities and runoff coefficients were developed from the
Fort Collins "Storm Drainage Criteria and Construction Standards"
(FCSDCCS) and from the Denver Urban Drainage and Flood• District's
"Urban Storm Drainage Criteria Manual".
III. Baseline Hydrology — Existing Conditions
The Market at Horsetooth Commons (Tract "D") is currently vacant
land which drains from West to East at a 1% slope. The site has a
native hay ground cover. Flows now generally run from West to East on
this site.
Off -site Flows
The reconstruction of Horsetooth and Shields adjacent to the site had
some impact on drainage patterns which must now be taken into account.
Horsetooth Road abuts the southern side of the property. Flows from
Horsetooth flow to an inlet at the Northwest corner of Horsetooth and
Shields where they exit via a sidewalk chase onto Tract "D". To the
East, Shields Street takes flows northerly to a swale at the proposed
Richmond Drive intersection which eventually are contained on Tract
"A". Flows from both of these areas will be diverted to the proposed
36" storm sewer as it is constructed. The preliminary drainage study
completed for Tracts A, B, C and D of the Horsetooth Commons
Subdivision showed each tract detaining flows. This concept is still
true except Tracts B (Block I) and D will be combined and Tract "D"
will be split into six separate drainage areas.
A summary of off -site flows is as follows:
A. Approximately 2.8 cfs of water develops from Horsetooth Road
in the 100 Year Storm. This area is further defined as the
North 1/2 of Horsetooth Road from Richmond Drive to the west
about 250'. This area west of Richmond Drive drains along
Richmond Drive and is diverted into the 36" storm sewer at
the inlet at the east edge of this site. Point of
Concentration is Inlet RN.
B. A portion of the flows from the west side of Horsetooth run
to an inlet at the NW corner of Horsetooth and Shields.
This area is further defined as the North 1/2 of Horsetooth
Road from Shields to Richmond Drive. This will be connected
to the 36" storm sewer as identified in the Foothills Basin
Master Plan. This is approximately 6.0 cfs in the 100 Year
Storm. Point of Concentration is Manhole J-3.
C. Flows from the west side of Shields Street between
Horsetooth and the proposed Richmond Drive are routed
through an inlet at the east edge of the site. This is
approximately 8.0 cfs in the 100 Year Storm. Point of
Concentration is Inlet RS.
On -Site Flows
The Market at Horsetooth Commons will provide detention for Block I
and a portion of Tract "D". The temporary pond for Block I will be
incorporated into the Tract "D" improvements. Block I flows will be
collected by a storm sewer which will take the 100 Year Storm under
Richmond Drive and into the proposed parking lot detention in Area I
of Tract "D".
2
A summary of these subbasins follows. Figure III shows these
subbasins as they are proposed.
Area
Concentration
Subbasin
(Acres)
Point
Proposed Use
Comments
Block
I *
3.29
Inlet
#H-5
Multi -family
100 Year Flood
carried via 24"
pipe where it
empties into
Detention Pond A.
Tract
"D"
Area
I *
1.95
Inlet
#H-3
Retail
Parking lot
Detention Pond A.
Tract
"D"
Area
II
.78
Inlet
RS
Restaurant
Area II detention
to be completed at
a future date.
Tract
"D"
Area
III
.80
Inlet
C-1
Convenience Store
Detention Pond B
Tract
"D"
Area
IV
.53
Inlet
H-3
Retail
Area IV detention
to be completed at
a future date.
Tract
"D"
Area
V
.71
Inlet
H-4
Office
Area V.detention
to be completed
a
at a future date.
Tract
"D"
Area
VI
.70
Inlet
H-3
Restaurant & Retail
Area VI detention
to be completed at
a future date.
Total
8.76 Acres
*These areas will combine flows which will be detained in Pond "A".
The detention Pond A will be responsible for detaining water from
Block I and Tract "D", Area I. Water from Block I is routed to Pond A
initially by a 24" storm sewer under Richmond Drive. This storm sewer
will pass the 100 Year Flow of approximately 17 cfs flowing about 95%
full. Once under Richmond Drive, the storm sewer empties into a 200
foot section of grass lined channel. (Calculations for this channel
are attached.) This channel will flow about 1.5' full in the 100 year
3
event. The channel takes flows to another 24" storm sewer which runs
under the parking lot and outlets into inlet H-3. an orifice plate
jwith a 6" opening will limit flows outleting from inlet H-3. An 18"
pipe will take these flows from inlet H-3 to the Foothills Basin 36"
storm sewer along the west side of Shields.
The 6" orifice will restrict flows from Pond A to 2.2 cfs when the
pond is full. The 18" outlet pipe will carry considerably more water
than 2.2 cfs, however, is sized larger for maintenance purposes.
It should be noted that Areas IV, V and VI will detain flows on site.
These historical releases will be made through the 24" storm sewer
under the parking lot. The orifice plate may need to be modified for
these historical flows at that time.
Richmond ,Drive
The capacity of 1/2 of Richmond Drive is approximately 11.3 cfs. This
is adequate to carry any flows developed in the 100 Year Storm.
Capacity calculations are attached.
4
Undeveloped Conditions
Area including Block I 6 Area I
Basin Length = 960 feet
Basin Drop = 91.0 - 79.0 = 12 feet
Average Slope = 1.25%
Tc = 1.87 (1.1 - C Cf) D1/2 =
1.251/3
1.87 0 .1 - (0.4)(1.0)) 9601/2 =
40.56 = 37.7 min.
(1.25)1/3
1.077
Runoff Coefficient (C)
= 0.30
See page 300 Table 10-9
"Water in Environmental
Planning".
Time of Concentration (Tc)
= 37.7
Min.
Intensity (I)2
= 1.3
in./hr. Figure 5
Area (A)
= 5.24
Acres
Frequency Factor (Cf)
= 1.00
Table 3-4
Q2
= Cf CIA
Q2
= 1.00 (.30) 0.3) (5.24)
= 2.04
cfs
Q100
= (1.25)(0.30)(3.6)(5.24)
= 7.07
cfs
Area III
Basin Length = 240 feet
Basin Drop = 3.2 feet
Average Slope = 1.33%
Runoff Coefficient (C) = 0.30
Time of Concentration (Tc) = 18.6 Min. (Figure 4)
Intensity (I)2 = 1.9 in./hr. (Figure 5)
Area (A) = .80 Acres
Frequency Factor (Cf) = 1.00
Q2 = Cf CIA = (1.00) (.30) 0.9) (.80) = .46 cfs
Q100 = 0.25) (0.30) (5.4) (.80) = 1.62 cfs
5
Table I
Summary of Runoff Coefficients
Area I (Retail)
Use
Building
Parking &
Sidewalk
Landscaping
Total
Area II (Restaurant)
Use
Building
Sidewalk
Parking
Landscaping
Total
Runoff
Area
Coefficient
17,500
Sq.
Ft.
.95
50,600
Sq.
Ft.
.95
17,000
Sq.
Ft.
.20
85,100
Sq.
Ft.
.81
Runoff
Area
Coefficient
4,000
Sq.
Ft.
.95
2,150
Sq.
Ft.
.95
15,775
Sq.
Ft.
.95
12,375
Sq.
Ft.
.20
34,300
Sq.
Ft.
.68
Area III (Convenience Store)
Runoff
Use
Area
Coefficient
Building
3,000
Sq. Ft.
.95
Parking &
Sidewalk
22,225
Sq. Ft.
.95
Landscaping
9,675
Sq. Ft.
.20
Total
34,900
Sq. Ft.
.74
Area IV (Retail)
Runoff
Use
Area
Coefficient
Building
I1,000
Sq.
Ft.
.95
Parking &
Sidewalk
5,000
Sq.
Ft.
.95
Landscaping
7,000
Sq.
Ft.
..20
Total
23,000
Sq.
Ft.
.72
6
Table I (continued)
Area V (Office)
Use
Building
Sidewalk
Parking
Landscaping
Total
Area
5,000 Sq. Ft.
1,475 Sq. Ft.
12,090 Sq. Ft.
12,535 Sq. Ft.
31,100 Sq. Ft.
Area VI (Restaurant b Retail)
Use
Building
Sidewalk
Parking & Street
Landscaping
Total
Total Drainage Area
Area
11,000
Sq. Ft.
4,080
Sq. Ft.
7,540
Sq. Ft.
8,030
Sq. Ft.
30,650 Sq. Ft.
239,050 = 5.48 Acres
Impervious C = .95 = 172,435 72.0%
Grassed C = .20 = 66,615 28.0%
Total Weighted C = 0.74
Combined Area
Block I 3.29 0.56
Area I 1.95 0.81
Total 5.24 0.65
Runoff
Coefficient
.95
.95
.95
.20
ME
Runoff
Coefficient
.95
.95
.95
.20
.75
7
Developed Conditions
Area III
Basin Length = 290 feet
Time of Concentration = 10 + L = 10 + 290 = 12.4 Min.
120 120
Weighted Runoff Coefficient (C) = 0.70 (See Table I)
Time of Concentration (Tc) = 12.4 Min.
Intensity (I100) = 6.6 in./hr. (See Figure 5)
Area (A) _ .80 Acres
Frequency Factor (Cf) = 1.25
Q2 = (1.00) (.70) (2.1) (.86) = 1.18 cfs
Q100 = Cf CIA = 0.25) (:70) (6.6) (.80) = 4.62 cfs
Area III (Convenience Store) flows will be directed to the Northeast
corner of the site where they will be detained. An inlet structure
#C-I and outlet pipe will release historic flows into the 36" storm
sewer along Shields. The detention requirements for this site are as
follows:
Detention Requirements
a
TOTAL
HISTORICAL
REQUIRED
TIME
TIME
I100
(CF)(C)(A)
Q100
DISCHARGE
Q2
DISCHARGE
DETENTION
(MIN)
(SEC)
(cfs)
(Cu.Ft.)
(cfs)
(Cu. Ft.)
(Cu. Ft.)
20
1,200
5.2
.70
3.6
4,368
.46
552
3,816
25
1,500
4.6
.70
3.2
4,830
.46
690
4,140
30
1,800
4.2
.70
2.9
5,292
.46
828
4,464
35
2,100
3.8
.70
2.6
5,586
.46
966
4,620
40
2,400
3.5
.70
2.5
5,880
.46
1,104
4,416
45
2,700
3.2
.70
2.2
6,048
.46
1,242
4,806
50
3,000
3.0
.70
2.1
6,,300
.46
1,380
4,920
55
3,300
2.8
.70
2.0
6,468
.46
1,518
4,950*
60
3,600
2.6
.70
1.8
6,552
.46
1,656
4,896
65
3,900
2.45
.70
1.7
6,689
.46
1,794
4,895
70
4,200
2.3
.80
1.6
6,762
.46
1,932
4,830
* Approximately 4,950 cubic feet (.I1 Ac-Ft) of detention will be required.
This Volume is provided as shown on the grading plan.
0
Area II, IV, V and Area VI flows will be refined as site plans are
submitted for those areas. These areas flow into the storm sewer as
shown in Figure 3, Page 14.
Detention for Combined Basins is as follows:
Block I 6 Area I
Basin Length = 290 feet
Overland Flow 80' 2%
Slope
11.0
Min.
Gutter Flow 260' .8%
Slope
1.0
Min.
Pipe Flow 670' .8%
Slope
3.0
Min.
Total
15.0
Min.
Weighted Runoff Coefficient (C) = 0.65 (See Table I)
Time of Concentration (Tc) = 15.0 Min.
Intensity (I100) = 6.0 in./hr.
Area (A) = 5.24 Acres
Frequency Factor (Cf) = 1.25
Q100 = Cf CIA = (1.25) (.65) (5.24) (6.0) = 25.55 cfs
Q2 = (1.00) (.65) (5.24) (2.1) = 7.15 cfs
v]
Detention Requirements
TIME
(MIN)
TIME
(SEC)
I100
(CF)(C)(A)
Q100
(cfs)
TOTAL
DISCHARGE
(Cu.Ft.)
HISTORICAL
Q2 DISCHARGE
(cfs) (Cu. Ft.)
REQUIRED
DETENTION
(Cu. Ft.)
20
1,200
5.2
4.26
22.2
26,582
2.04
2,448
24,134
25
1,500
4.6
4.26
19.6
29,394
2.04
3,060
26,334
30
1,800
4.2
4.26
17.9
32,206
2.04
3,672
28,534
35
2,100
3.8
4.26
16.2
33,995
2.04
4,284
29,711
40
2,400
3.5
4.26
14.9
35,784
2.04
4,896
30,888
45
2,700
3.2
4.26
13.6
36,806
2.04
5,508
31,298
50
3,000
3.0
4.26
12.8
38,340
2.04
6,120
32,220
55
3,300
2.8
4.26
11.9
39,362
2.04
6,732
32,630
60
3,600
2.6
4.26
11.1
39,874
2.04
7,344
32,530*
65
3,900
2.45
4.26
10.4
40,704
2.04
7,956
32,748
70
4,200
2.3
4.26
9.8
41,152
2.04
8,568
32,584
75
4,500
2.15
4.26
9.2
41,216
2.04
9,180
32,036
80
4,800
2.05
4.26
8.7
41,760
2.04
9,792
31,968
* Approximately 32,748 cubic feet (.75 Ac-Ft) of detention will be required.
This detention will be provided in Pond "A". .78 acre-feet is available
there.
Shields Storm Sewer
b
It is proposed that a 36" storm sewer be provided along the west side
of Shields from Horsetooth - North approximately 1,300'. A portion of
this storm sewer was constructed under Horsetooth and a 42" section
was placed under Shields just South of Casa Grande. It is proposed
that this project will complete the 36" pipe between those two
sections.
A review of the Foothills Basin (Basin G) Drainage Master Plan,
indicates that, in its existing condition, approximately 180 cfs would
run along. the west side of Shields Street. (Page 14) (Table 3)
After completing an analysis of the area, Resource Consultants, Inc.
recommended a Storm Water Management Alternative for this area which
involved the construction of three detention areas 017, #18, #19) and
the storm sewer along Shields as shown in Figure 8, page 28 of the
Master Plan. With the construction of the three detention areas and
with fully developed conditions, 100 year flows of 46 cfs could be
expected along Shields (Table 5, page 30). The design of the 36" RCP
along Shields will adequately provide the conveyance for these flows.
Jul
One of the three detention areas (Pond 17) is to be located in Section
27. The Master Plan in Table 6 on page 36 identifies the need for 3.5
acre feet of detention and maximum outflow of 11 cfs. The Horsetooth
Commons PUD is providing 2.69 acre feet of detention and limiting
outflows to 3.9 cfs as discussed in the preliminary drainage
calculations submitted December 3, 1986 for the Williamsburg PUD. Any
additional detention would be provided by the vacant ground to the
west of the Horsetooth PUD.
Figure 5 shows that a 36" concrete pipe flowing full will convey 47
cfs — more than the 46 cfs called for in the Foothills Basin Master
Plan.
L
•
C
a
1
d
•.a
--Reach
Figure 2
Scale I in feet I
1000 500 0 1200
7 m=
13
Legend:
major drainageway
pipe only
= channel only
existing detention area
Proposed detention area
see Table 6 1
drainage concentration p '>
R I see Table 51
a
THE MARKET AT HORSETOOTH COMMONS P.U.D.
Ic
u
0
0
L
N
N
Y+
O
x
�1%6N'% . ��
Shields
TRACT 'D`
Drainage Basins
Drainage Improvements
w�
0
4�
ti
Q
0
Proposed 36" Storm Sewer'
— Z—'Tn!!n�
z
w
n
a•
0
0
C
a
RS
\\\\\\\N
Figure 3
No Text
iiiiGGiiGi7iiii7�7iii
1.500
2.400
0.00 4
0.5
0.4
2.000
0.3
0.005
1,000
1,500
0.6
0.006
0.2
800
0.007
600
1'000
0.000
O'T
500
Soo
0.009
0.1
0.01
0.8
0.09
400
600
500
0 g
0.06
500
0.05
400
I.0
0.04
200
300
20
0.03
0.02
200
IS
0.02
100
0.03
_
80
10
c
1.5
1 0.80%
100
9
u
0.04
0.008
36" Storm Sewer 60
96
8
along Shields 50
6O
a
0.10 0.05
0.006
84
7
O,pB
0.005
40
Q = 47 cfs
60
72
6
=
c 0.06
2
0.004
50
a
0.050.or
0.34%
30
60
S
•`
0.040.08
0.003
0
4 w
S4
V
- 0.03 °-09
20
.,
48
4
Z
o O.
0.002
n
= 24 cfs
0
42
36" Diameter
Concrete
°'02
/ o�
I
36
3
n = 0.011
°
3
v
jtOiiO Sewer
20 n
- •0
33
Q.
SV �'
c
0.010
"
0.001
c
from Block I 10
e
30
%y
o.000e
-
o
T
0006
E 8
24
0 0.006 02
o
0.0006
e
c
°
N
0.0005
0 6
10 u
21
c
0
4
e
<
0.0004
o
0 5
p
6 0 0.
16
0.3
=
-
c
c
u
o
0.0003
6 4
6 0
15
5
O
5
0.4
0.0002
0 3
v
12
V
4
0.5
10
6
2
3
o.0001
0.6
V=6.8
fps
e
0.00008
o.
2
Q9
0.00006
1.0
6
1.0
8
O.000OS
=
0.00004
0.8
g
0.00003
I.0
v
0.6
4
'
10
0.3
o.0
c
0.00002
0.4
0.6
e 2
G
0.3
O.S
0.00001
0.4
�. 3
0.000008
0.2
0.3
IS
0.000006
4
0.000005
0.000004
0.13
0.2
5
IB
Fig.6•. Nomograph
for flow in round pipe-Manning's
formula
17
a
�rch��,d �naQ 1.1
Ca iWk
�'�chmai rDnve IS a Ce! lchIr
ffa. nw ifrt Fe fbvlrk . On
-Fv//Ow'r,L Grptg4ojr
s = . 610 9
_ .0533 1a
�,y = GS6)GZ (0/07�)i.sg��
4A= C S6) CrZ) (. IO�Y)C.1SlS� Q� = G• 9 c�S
c f s
Q4 y g6(,o�b) qAY ` G 9c{s _ 2J cF, = 'f6cFs
Q T= 6?A F
idticflda Fa0h, (f)
F)gwf q-Z
AefF Of AU spree f � as
qB =
Yo =
133
- 0/6
s =
.0/09
qD (G, S0) �. A'0`I ! �. 33
e/6l
qa= q,SC6
= ly.l cfs
113 crs fill ov4yc
i
Rrcj�oOw J Qfrr;� Flows
t01P.83 - 0f41
o6k flaws f(ao, 45M lb QUA %z of
f Q%� µt fives a/{ off fe xPHa cfs
Gt�-e Q3 . , fdllou�S , Cq
_ f cfA A
Q4a 7
Irf I z 3.9 fps
ago = I•zS(7,1) Cs3) ASS
Qrac, = y 6 c f 5 950.8 __ 2-Y3 Src
3.5
T IQ l Q = 9,6 cf5 t tS c� =
s �P� ow
7'/d Jf• 3 ` gllowoif e It no*,s
It 4ew Y4 �l of 14 cuib.
56A SrdP Z-a„ y 5 : /,Iq 11(7
9 f 33. 73 — 0 41 = 972, 73
T( = y o IIS.P a,0 A4
05
ZS ( r7z. 73) , SO i%ios
N 3 SGO
7/
I�Oise flog f(e.
R"4'.I
as
�dQn II P,el q
to lkisQt)
fig
strut
1�elf
Tc =
.1 MIA, Use
1010 All .
cf--lZ�—
A
(Z5) (9Sb83SGo`
(ov
C =
9S
= Y 1 nli
7,Ycfs
)14 / all s +ftt f odes lvril
cf5
y.7 cf s 15 I'fx 4 t 3c cl�) ca�lh 14 ifo Sf&(A rl, of Ricie4i 1$00 .
i
4
� VIa��I/ Secfla,
Graz
�.)
n 040
213 5'�1 ti-
n
1,y9 (,97 ?h� (, oolf
.060
v= "IlkM/ •37,1 = a,3 Sys
Curve Rvolivts = So'
LIP = 16.50 ��eF
16 sy Faft
R I
r Z.lP � ll•So = .97
Q = lYl (.,1779)(.0i70)&)
Th loo y4ovAWOMOM fkll fro-, B jori l a?
a /olKM+a�t� t C�aKRll to kqv P,�o�•4
�� y �7 c s 7�is � ��d� porn � J
Cp�l ac/i 1-0 FossJGSP TldWS. Q¢p 4 flow w171 �P G7j�/ax��i
CONSTRUCTION HOES: CEREBRAL MOWS:
CD Existing storm slower ans rulWle ; Install 5' thruster standard ma overru 1. 1M City of fort Collins shall t be responsible for the maintenance
astie9 36- R.CAdlie A' V.V.L. Site Store sner into new 04 stars drainage facilities located on private property.
morale. See Sheet 3 of 3 for installation details.
z. Temporary @rollol control weal ill be required during
Q Standard storm setwer NO; gee storm .n or
Mmarofile on Sheet 3 of 3 for construction. Temporary yeales r be uud around the Pl coed inlet
•anlwle rimand invert information. AltoSee Standard Manhole detail or to parking lot p Refer to the Myoale placement detail
on Sheet 3 of 3. provided on sheet 3 of 3. Refep to Draft cane of City of Feet Collins
Erasion Control Reference Manual for additional erosion control
Q Proposed Storm Area Inlet; See storm sa profile on Sheet 3 of 3 n alternatives and oonendations.
rim and invert wformut Also see Sleet 3 op 3 for area Inlet
detail. 3. The ParPin9 lot limits which will be utilized for detention np mall be located within a ceeasement No drainage ea ment Ms base
Q Pr,POW Orir
vnar d each; Remoe eusting vertical curd and gutter dedicated by the Plat of Horsetail Cast P.L.D.Therefore a
Necessaryits to j,,Adl rim
dvtu
rner apprWIN. See Sheet 3 of 3 for drainage easement will be dedicated by Separate instrument to satisfy
Driveway approach detailsfor vertical Curd and Batten the w9uiTmI of the City of Fort Calltns.
IM1 EI/0 COR 9n c u r III occur
SEC E1 (7` Proposed stop si : Install according to the r shim% of the 1 4. Cal mashing .ill oo •nhio the showrogual building limits.
A TIN, R69N 'Manual of uniform Traffic Control Devices' Old the City of Fort 11 moor amain• .at be rovided whim mill be tied direcity to the
Collins Trafna Department. ! p4 sanitary Power system a [carding to local codes. wastewater is" ca
mashing operations all at be allowed within the City of Fart Collin;
%ara,�, storm sner ay,trm
— —
,
WAA RODN �_HW RICH8 ANMONDRDRIVE e �11 R=I6.00 RICHMOND DRIVE
4 = 89.44' 16'
—� EXIST .Al malt El -xYWRANT I 4 2506I J� FE EC. uLi _ 1__'IS T-15.93'
SB —+ ll—_�1STOB'- rani
.I px' f 1j. C =z2 sB' maw - _- -
ae\\ C8=S44°52'2 WE -. _ a° I-
II
Q it 1 ExBi S \\r _
or yEL C
1a
SEW SERVICE I "SExVICE VAIN i X1 BOp
is
STa p9 ma Y OEICE/RETAIL III III FF�W'S0 �v YI EMER6ENCV SPILLWAY 3 P6dCE5
11 AdA, a NAIEP MUE£E/CEEO J0.2Ill
AY la a.� -CWB ICI f METER III, P VL ES V f III V r �\`� O I TO ESCAPE
An I
PROPOSED "VIER TAG IR�— °SfINIEE I51 i III • \.m J
SIAOa2 CO 01 y ill „1
PATCH Racx PER TYPICAL 1 n
1 f
FRENCH DETAIL R p,
ill
Fall
I INo Auv PAY - `�.' X 1 or sec*iaHDz]sE v9 lilli 'o,A
ABANDON EXIST TAPS
t / -.EV'
SERVICE 4T WREPYAIH I I I
I
9 �o
— At � ;II Ina.
iII J r r, -
D o I 1^I I IY it r LU
1 0 f
Ib a sp 11�I W A 1I h Al w
It 0
'11 O e 6
Du:Do9n w 0 1 C 7l �� a�`
j ; — .,015PLAY - 1It
ED 1 `? W " Ill i No I �
I' dip J
14 0 it
Sells s... CE ; 1 �� 1 u p 1 11 1 we, T m — All
W
STA 0 fSTA 0 f 23 bF! "; 0 0 It
w1 it F IIm A=25'20'z]" lit 111 lTOS
R • 114.00 MN six D.co li III III 1 m Fe BOSO
RETAIL/ HOWROOAs II
A• 50.42 -- __ I' deal � L m 1 ,. 1 d I R �'' ' I I
T=25.63 —i I I n
0.
l/ i s L ow M ji t �I
CB-NI2°4D'14"E II I Ili A/I at i e� IF
1 �i II
Ali
1.-� �� �/ mplOs
i� H6I 3 It It
\ 1 � ��I P
3
—FAA, it
I'llUtz N89.45 30"W ]50] 1I �1t - _ - Iit
I II
/21
�H``AA LOT I R 2 m o5 5]" z` i `x `\ ; C III � O L OF 1 _. �a_��> .n•` t ll `
VL
N o
A= 06 i
T= 2 93' 11
C,4 1,67'
DETENTION POND DATA sl
CB= ]]°I2'30"W LEGEND wnaar:
5 E CUR Inlet rim elevation - 7B.40 Idemhtlon polo III Point,
sec.¢] EXISTING PROPOSED High water Is,. Prior to overflow • 30.20 at North corner of parxxng lit.
TIN, R69N' - - i..L H..imile depth in Parking area - 1.50' at initial werllw
-.. -- .. Detention Values available - 4650 cu is feet
Detention volume r...... I - 4E2B mamma rest (Cumulative runuff method)
CITY OF FORT COLLBNSACOLORADO
UTILITY PLAN APPROVAL
MASTER UTILITY PLAN GRADING &DRAINAGE PLAN
APPROVED: All, .mn,.a. sue
• .I . CHECKED 9Y: "I mA.eAurmn u.,ur. PA.s
C/dCKEO BY me 510" "A,s. mu.. DAra
CHECKED BY'.
ANA111 All 1OVEALI'll 'All
REVISIONS Date DULY 1990 Cal JM/BWS CLIENT TITLE MASTER UTILITY PLAN. GRADING A DRAINAGE PLAN MOACT No. SHEET NO. xo.OF
11o so"Plian SHEAR ENGINEERING CORPORATION
b DU ... phen FINISH Boon KING A ASSOC. CM ked BWS KENT GOODMAN FORT COLLINS, COLORADO LOT 2, THE MARKET AT HORSETOOTH COMMONS 1200-1-90
Data — g oarnlDnon BcaM 1-=30' Approved B9 PHONE: (303) 226-5334 FORT COLLINS, COLORADO 2 3