HomeMy WebLinkAboutELIZABETH & CITY PARK CORNER REDEVELOPMENT - PDP - PDP120008 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT (3)Design Procedure Form:. Rain Garden (RG)
2 of
Designer.
ES
Company:
Intatwest Cooaulting Group
awe:
March g, 2012
Project:
Elizabeth and City Park
Location:
5. Impermeable Geomembrane liner and Geoleiaile Separator Fabric
Choose One
O YES
A) Is an impermeable liner provided due to proximity
NO
Of structures or grountlaater contamination?
6. Inlet / Outlet Control
Choose One
O Stwet Flow- No ElwrlIy Dissipation Required
A) Inlet Control
0 Concentrated! pow Energy Dissipation I'mvded
Ctwcse One
7. Vegetation
O Satl (Pion for frequent: wasd control)
* Planfings
10
Sand Grown or Other Ho IM lmaian Sod
B. INlgalion
Choose One
O YES
A) Will the rain garden be irrigated?
ONO
UD-BMP_v3_01 Rain Garden.xls, RG 3WO12, 11:39 AM
{ Design Procedure Form: Rain Garden (RG)
Shutt of 22
Designer: ES
Company: Interivest Consulting Group
Date: March 8, 2012
project: Elisabeth and City Park
Location:
1. Basin Storage Volume -
A) Effective Imperviousness of Tributary Area, la
I,
. 100.0
%
(100 % it all paved and roofed areas upstream of rain garden)
B) Trbutary Area's Imperviousness Ratio (I . IJ100)
I
- tooft
C) Water Quality Capture Volume (WOCV) for a 12-hour Drain Time
WOCV - >%0.40.
V miershed inches
(WOCV. 0.8' (0.91' is- 1.19' P. 0.78' II
D) Contributing Watershed Area (including rain garden area)
Area. 16,096
sq fl
E) Water Quality Capture Volume (WQCV) Design Volume
Vw. - :-:'537
cu ff
Vol - (WQCV / 12)' Area
F) For Watersheds Outside of the Denier Region, Depth of
J..
In
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region,
Vwp,, c,,sa
:l'.
cu h
Water Quality Capture Volume (WQCV) Design Volume
H) User input of Water Ouallty Capture Volume (WQCV) Design Volume
Vwpm,. -
cu ff
(Only 9 a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)
DwocV •
12
in
B) Rain Garden Side Slopes (Z.4 min., hor¢. dirt per unit vertical)
Z.
0.00
ft / ft
(Use'0' If rain garden has vertical valls)
C) Mimimum Flat Surface Area
A. -
-''`3% -
sq If
of Actual Flat Surface Area
Ak. -
400
sq ff
E) Area at Design Depth (Top Surtace Area)
A,..
400
sq ft
F) Rain Garden Total Volume
Vr-
400
CO 11 TOTAL VOLUME c DESIGN VOLUME
(Vr ((Arm . AA..1) / 2)' Depth)
3. Gmvnng Media
Choose One
10 (9) w Rain Garden Groming Medla
Other(Explaln):
4. Unnerduin System
Choose One
A) Are umlerdrairs provided?
vE5�
O No
8) Underdraln system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage
y-
N/A
h
Volume to the Comer of the Odres
i
II) Volume to Drain in 12 Hours
V0112 =
NA
cu ft I
q
ill) Orifice Diameter, 3/8' Minimum
Dc
IN A
11 '
1
UD-6MP_v3_11 Rain Garderrxls. RG 3/8/2012, 11:39 AM
Intenvest Consulting Group
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 100-Yr Storm)
LOCATION: Elizabeth & City Park Comer Redevelopment
PROJECT NO: 1156-097-00
COMPUTATIONS BY: smb
DATE: 3/8/2012
100 yr storm, Cf = 1.25
DIRECT RUNOFF
CARRY OVER
TOTAL
REMARKS
Des.
Point
Area
Design.
A
(ac)
C Cf
tc
(min)
i
(in/hr)
Q (100)
(cfs)
from
Design
Point
Q (100)
(cfs)
all
(cfs)
0
Existing
0.52
1.00
5.0
9.95
5.1
5.1
0
Proposed
0.52
1.00
5.0
9.95
5.1
5.1
0
1
0.19
1.00
5.0
9.95
1.9
1.9
Roof Drainage to 12" PVC
1
1 2
0.25
1.00
5.0
1 9.95
2.5
1 2.5
On site parking lot to 12' PVC
1
3
0.12
1.00
5.0
9.95
1.2
1.2
Off -site parking to 12- PVC
0
4
0.07
0.64
5.0
9.95
0.6
0.6
On site directly to Street
Q=CiA
Q = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from City of Fort Collins OF curve (4/16/99)
A = drainage area (acres) i = 84.662 i (10+ tc)°'a's
Flow.xls
Interwest Consulting Group
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 10-Yr Storm)
LOCATION: Elizabeth & City Park Corner Redevelopment
PROJECT NO: 1156-097-00
COMPUTATIONS BY: smb
DATE: 3/8/2012
10 yr storm, Cf = 1.00
DIRECTRUNOFF
CARRYOVER
TOTAL
REMARKS
Design
Point
Tributary
Sub -basin
A
(ac)
C Cf
tc
(min)
i
-
(in/hr)
0 (10)
(cfs)
from
Design
Point
0 (10)
(cfs)
0(10)tot
(cfs)
Existing
0.52
0.92
5.0
4.87
2.3
2.3
Proposed
0.52
0.89
5.0
4.87
2.2
2.2
1
0.19
0.95
5.0
4.87
0.9
0.9
Roof Drainage to 12' PVC
- 1
1 2
0.25
0.92
5.0
4.87
1.1
1.1
On site parldng lot to 12' PVC
1
3
0.12
0.94
5.0
4.87
0.5
0.5
lOff-site parking to 12' PVC
4
0.07
0.67
5.0
4.87
0.2
0.2
On site directly to Street
Q=CfCiA
0 = peak discharge (cfs)
C = runoff coefficient
Cf = frequency adjustment factor
i = rainfall intensity (in/hr) from City of Fort Collins OF curve (4/16/99)
A = drainage area (acres) i =41.44 / (10+tc)o n7'
Flow.xls
LOCATION:
PROJECT NO:
COMPUTATIONS BY:
DATE:
I00-yr storm
Elizabeth & City Park Corner Redevelopment
1156-097-00
smb
3/8/2012
Cf = 1.25
STANDARD FORM SF-2
TIME OF CONCENTRATION - 100 YR
Interwest Consulting Group
SUB -BASIN
DATA
DESIGN SUBBASIN(s) Area
PONIT (ac)
(2)
INITIAL /OVERLAND
TIME (III
C C'Cf Length Slope it
(It) (min)
(3) (4) 1 (5)(6)
TRAVEL TIME / GUTTER OR CHANNEL FLOW
(tt)
Length Slope n 1.
(ft) Manning fV) (m) lt+it
(s
(7) (8) rough. 1 (9) (10) (11)
tc CHECK
(URBANIZED BASIN)
Tote IL tc=(I/l80)+10
(it) (min)
(12) (13)
FINAL
to
(min)t
(14)
REMARKS
Existing
0.52
0.92
1.00
1601
1.0
2.4
0
1.0
0.0161
2.0
0.001
2.4
160
10.9
5.0
Proposed
0.52
0.89
1.00
60
5.0
0.81
90
5.0
0.0161
4.5
0.331
1.21
150
10.8
5.0
1
1
1
2
3
0.19
0.25
0.12
0.95
0.92
0.94
1.00
1.00
1.00
0
60
55
2.0
5.0
3.0
0.0
0.8
1.0
125
90
0
0.5
5.0
3.0
0.0161
0.016
0.0161
1.4
4.5
3.5
1.471
0.331
0.001
1.51
1.21
1.01
125
150
55
10.7
10.8
10.3
5.0
5.0
5.0
4
0.07
0.67
0.84
14
2.0
1.4
0
2.0
0.0161
2.8
0.001
1.41
14
10.1
5.0
L
_jj
I
I -
EQUATIONS:
tc=ti+It
ti=[1.87(1.1-CCf)Lo.e)/S1/3
It = UVel.
Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual)
final tc = minimum of ti + tt and urbanized basin check
min. tc = 5 min. due to limits of IDF curves
Flow.xls
Interwest Consulting Group
STANDARD FORM SF-2
TIME OF CONCENTRATION -10 YR
LOCATION:
Elizabeth & City Park Corner Redevelopment
PROJECT NO:
1156-097-00
COMPUTATIONS BY:
snlb
DATE:
3/8/2012
10-yrstorm
Cl= 1.00
SUB -BASIN
DATA
DESIGN SUBBASIN(s) Area
PONIT (ac)
(1) (2)
INITIAL /OVERLAND
TIME (ti)
C Length Slope ti
(ft) (%) (min)
(3) (4) (5) (6)
TRAVEL TIME / GUTTER OR CHANNEL FLOW
(tt)
Length Slope n Vel. it tc =
(ft) (%) Manning (ft/s) (min) tl+It
(7) (8) rough. (9) (10) (11)
tc CHECK
(URBANRED BASIN)
Total tc-(1/780)+10
(ft) (min)
(12) (13
FINAL
tc
(min)
(14)
REMARKS
Existing
0.52
0.92
160
1.0
4.3
0
1.0
0.016
2.0
0.00
4.3
160
10.9
5.0
Proposed
0.52
0.89
60
5.0
1.8
90
5.0
0.016
. 4.5
0.33
2.1
150
10.8
5.0
1
0.19
0.95
0
2.0
0.0
125
0.5
0.016
1.4
1.47
1.5
125
5.0
1
1
2
3
0.25
0.12
0.92
0.94
60
55
5.0
3.0
1.6
1.6
90
0
5.0
3.0
0.016
0.016
4.5
3.5
0.33
0.00
1.9
1.6
150
55
.10.7
10.8
10.3
5.0
5.0
4
0.07
0.67
14
2.0
2.4
0
2.0
0-016
2.8
0.00
2.4
14
10.1
5.0
EQUATIONS:
tc=ti+tt
tl=(1.87(1.1 -cct) L0.51/S. 113
It = UVel.
Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual)
final tc = minimum of ti + tt and urbanized basin check
min. tc = 5 min. due to limits of OF curves
Flow.xls
LOCATION:
Elizabeth & City Park Corner Redevelopment
PROJECT NO:
1156-097-00
COMPUTATIONS BY:
smb
DATE:
31812012
Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria
Recommended % Impervious from Urban Storm Drainage Criteria Manual
Streets, parking lots (asphalt)
Sidewalks (concrete)
Roofs
Landscape Areas:
Runoff
%
coefficient
Impervious
C
0.95
100
0.95
96
0.95
90
0.25
0
NOTE - All impervious was lumped into this category.
Interwest Consulting Group
SUBBASIN
DESIGNATION
TOTAL
AREA
(ac.)
TOTAL
AREA
(sq.ft)
PAVED
AREA
(sq.ft)
ROOF
AREA
(sq.ft)
SIDEWALK
AREA
(sq.ft)
LANDSCAPE
AREA
(sq.ft)
RUNOFF
COEFF.
(C)
%
Impervious
REMARKS
Existing
0.52
22,500
21,512
0
0
988
0.92
96
Existing
Proposed
0.52
22,500
20,440
0
0
2,060
-0.89
91
Proposed
1
0.19
8,237
8,237
0
0
0
0.95
100
Roof Area Draining Directly to Storm Sewer
2
0.25
1 11,020
f0,470
0
0
550
0.92
95
Area Draining to LID
3
4
0.12
0.07
5,163
3,243
5,063
1,958
0
L 0
0
0
100
1,285
0.94
0.67
98
60
Off Site Area Draining to LID
Area Draining to Street
Eauations
- Calculated C coefficients & % Impervious are area weighted
C = E (Ci Ai) / At
Ci = runoff coefficient for specific area, Ai
Ai = areas of surface with runoff coefficient of Ci
n = number of different surfaces to consider
At = total area over which C is applicable; the sum of all Ai's
FIow.xls
No Text
- _. - . - -
W.ruZAS�E=
� s
—/z o
- 3 -ice% �/L� �I � ��• '.� � � ��
ELIZABETH & CITY PARK CORNER REDEVELOPMENT
EXISTING IMPERVIOUS AREA
21,512 SF = 96%
Mr. Wes Lamarque
March 14, 2011
Page 3 of 3
All possible measures have been taken to provide water quality for the site through the proposed
rain garden. The proposed redevelopment has improved upon the existing conditions by
reducing the overall impervious area as well as providing water quality. The site has been
designed with provisions for safe and efficient control of stormwater runoff in a manner that will
not adversely affect the downstream storm system and will improve water quality for a lot that
had no existing water quality system. Overall, it is evident that the proposed redevelopment will
have a positive impact on the overall stormwater management system.
We appreciate your time and consideration in reviewing this submittal. If you have any
questions or need additional information please feel free to call at any time (970) 674-3300 Ext.
101.
Sincerely,
4 "4tti
Skylar Brower, P.E.
Colorado Professional Engineer 44249
Interwest Consulting Group
Attachments
1218 W. ASH, STE. C, WINDSOR, COLORADO 80550
TEL. 970.674.3300 - FAX 970.674.3303
Mr. Wes Lamarque
March 14, 2011
Page 2 of 3
The site is required to provide water quality treatment. A pervious landscape detention system
(rain garden) is proposed to achieve water quality treatment for this site. Because of the grades
of the site, we are unable to drain all of the onsite water to the proposed rain garden. The onsite
parking lot, in addition to 3,050 sf of the offsite parking lot to the south, will be conveyed to the
rain garden. Due to site constraints, roof runoff and a portion of the sidewalks around the
building will not be conveyed to the rain garden. The rain garden will be 12-inch deep and filled
with a granular material following the guidelines in Urban Drainage. Once the rain garden is
completely saturated, water will flow into an area drain and be conveyed north to the existing
storm sewer in W. Elizabeth Street via a new 12-inch storm system. During large events water
will overtop the curb surrounding the rain garden and follow the original flow path north along
City Park Ave to W. Elizabeth Street.
The existing and proposed imperviousness of the lot was compared as a part of this study.
Exhibits are attached which show that the existing imperviousness is 96% while the proposed
improvements will lower the imperviousness to 91%. This is due to an increased offset from the
eastern property line to the building as well as a small landscape strip along the northern property
line between the building and the sidewalk on W. Elizabeth Street. Because the impervious area
will decrease with this project, detention is not required. Attached is a summary of the flows for
the existing and the proposed site. With the reduction of impervious area by 5%, the 10-year
flow off the site is reduced by 4%. However the 100-year flow off the site remains the same.
The proposed private 12-inch PVC storm system is the only hydraulic system on the project.
This system will be connected to the existing 24-inch main line in W. Elizabeth Street via a new
manhole. Our calculations show a 10-year flow to the proposed 12-inch system of 2.5 cfs and a
100-year flow of 5.6 cfs. We have verified that the system can convey the 10-year flow. 100-
year flows that cannot be conveyed underground will overtop and flow into City Park Ave where
it is conveyed north to W. Elizabeth Street. All overtopping occurs below the finished floor.
Following the Urban Drainage design procedure for sizing rain gardens, the required water
quality capture volume for the proposed site is 537 cubic feet. The proposed rain garden
provides 400 cubic feet of volume (approx. 74%). Please see the attached Urban Drainage
Design Procedure form for more information.
With the redevelopment of the site, the design team has followed the four step low impact
development process outlined in Urban Drainage. With the decrease in impervious area we have
reduced the runoff from the site during small storms and there is no increase in runoff during the
100-year event. A rain garden has been incorporated into the design to treat and slowly release
the approximately 74% of the water quality capture volume. When runoff leaves the site it is
conveyed to a public storm sewer system so there are no streams or channels associated with the
project to stabilize. An erosion control plan will be implemented during construction that will
address source control and unwanted materials (hazardous materials, sediment) from entering the
downstream storm systems. The contractor will be responsible for implementing the erosion
control plan and adequately addressing any spills or clean up on site.
1218 W. ASH, STE. C, WINDSOR, COLORADO 80550
TEL. 970.674.3300 - FAX 970.674.3303
INTERWEST = CONSULTING G R 0 U P
March 14, 2012
Mr. Wes Lamarque
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80522
Re: Elizabeth & City Park Corner Redevelopment — Storm Drainage Report
Dear Wes,
We are pleased to submit for your review and approval this drainage letter showing the drainage
impacts from the proposed redevelopment at the confer of Elizabeth Street and City Park Ave.
The project is located at 1401 West Elizabeth Street and is platted as Lot 2 of Eleventh Fairview
Subdivision. The site currently has an existing Mexican Restaurant (Consuelo's) and an asphalt
parking lot on the site. The project will demolish the existing building and parking lot. In its
place a new commercial/mixed use building and parking lot will be constructed. The proposed
improvements will reduce the impervious area by approximately 5% and will provide for
stormwater quality on site. The area of the site that will be improved is approximately 0.52
acres.
The site is just west of the Colorado State University campus and is bounded on the north h„
West Elizabeth Street and bounded on the east by City Park Avenue. There is approximately
0.12 acres of offsite area just south of the proposed lot that is tributary to the site. Today, the
entire site sheet flows to the east and northeast where it is intercepted by either City Park Ave or
W. Elizabeth Street. Flow continues east along W. Elizabeth Street until it is intercepted by a
Type R inlet where it enters the city storm sewer along W. Elizabeth Street. With the building
addition and reconfiguration, the majority of water in the parking lot will sheet flow to the east to
a pervious landscape detention area (rain garden). Water will then be piped north to the existing
city storm system in W. Elizabeth Street. All roof water will be piped directly to a new 12-inch
storm system that connects to the existing city storm system in W. Elizabeth Street.
The site is located in a City regulatory 100-year flood fringe and floodway in the Canal
Importation Floodplain. The base flood elevations based on City modeling range from 5033.7 to
5032.0. Following the guidelines of Chapter 10 in the City Code the finish floor elevation of the
proposed building will be 18 inches above the base flood elevation and is at 5035.2. A
floodplain use permit will be completed with the final plans.
1218 WEST ASH, SUITE C WINDSOR, COLORADO 80550
TEL. 970.674.3300 • FAX. 970.674,3303