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Cross Section for Overflow Swale
Project Description
Flow Element: Irregular Section
Friction Method: Manning Formula
Solve For: Normal Depth
Section Data
Roughness Coefficient:
0.030
Channel Slope:
0.80000 ft/ft
Normal Depth:
0.52 ft
Elevation Range:
0.00 to 1.24 ft
Discharge:
31.00 ft%s
TOP OF
FOUNDATION
N
Ch
0.52 rt
Workshop! for Overflow Swale
0+07 012
Worksheet for Overflow Swale
Project Description
Flow Element: Irregular Section
Friction Method: Manning Formula
Solve For: Normal Depth
Channel Slope: 0.80000 ft/ft
Discharge: 31.00 ft3/s
Current Roughness Weighted Methc ImprovedLotters
Open Channel Weighted Roughness ImprovedLotters
Closed Channel Weighted Roughne Hortons
Roughness Coefficient:
0.030
Water Surface Elevation:
0.52
It
Elevation Range:
0.00 to 1.24 ft
Flow Area:
1.73
ft'
Wetted Perimeter:
6.71
ft
Top Width:
6.62
ft
Normal Depth:
0.52
ft
Critical Depth:
1.07
ft
Critical Slope:
0.01623
ft/ft
Velocity:
17.95
Ws
Velocity Head:
5.01
ft
Specific Energy:
5.53
ft
Froude Number:
6.19
Flow Type:
Supercritical
Segment Roughness
Start Station End Station Roughness
Coefficient
(-0+06. 1 24) (0+07, 0.82) 1.030
Section Geometry
Station Elevation
-0+00 124
0+00 0.00
SUMMARY
DRAINAGE SUMMARY TABLE
Design
Point
Tributary
Sub -basin
Area
(ac)
c (10)
c (100)
tc (10)
(min)
tc (100)
(min)
0(2)tot
(cfs)
O(10not
(cfs)
0(100)tOt
(cfs)
REMARKS
a
A
0.14
0.40
0.50
7.1
6.3
0.1
0.2
0.6
0
Page 11
Interwest Consulting Group
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins, 100-Yr Storm)
LOCATION: Habitat for Humanity - Skyline House
PROJECC NO: 1291-02540
COMPUTATIONS BY: sb
DATE: 8/15/2016
100 yr storm. C1= 1.25
DIRECT RUNOFF
CARRY OVER
AL
REMARKS
Des.
Poini
Area
Design.
A
(ac)
C Cf
IC
(min)
i
(inthr)
O (100)
(CIS)
from
Design
Point
O (100)
(Cts)
O(1 D0)tot
(cfs)
a
A
0.14
0.50
62
9.15
0.6
0.6
0
O=CiA
FLOW(08-15-16).xin
O = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from City of Fort Collins IDF curve (4/16/99)
A = drainage area (acres) i = 84.682 / (10. tcf°1
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins. 10-Yr Storm)
LOCATION: Habitat for Humanity - Skyline House
PROJECT NO: 1291-025-00
COMPUTATIONS BY: sb
DATE: 8/152016
10 yr storm. Cf = 1.00
DIRECT RUNOFF
ICARRY OVER[TOTAL
IREIIIIAMS
Design
Point
Trbulary A
SUDnasin
(ac)
C CI
Ic
(min)
I
(inRa1
O (10)
(d6)
tram
Design
Paint
O (10)
(CIS)
0(10)tot
(CIS)
a
A 0.14
0.40
7.1
4.30
02
0.2
0
Q=CICiA
FLOW(Oa-15-16).xis
Q = peak discharge (cis)
C = runoff coefficient
Cr = frequency adjustment factor
i - rainfall intensity (in/hr) from City of Fort Collins IDF curve (4/16/99)
A = drainage area (acres) i = An." 1(10, 1cff'
Inter est Consulting Group
RATIONAL METHOD PEAK RUNOFF
(City of Fort Collins. 2-Yr Storm)
LOCATION: Habitat for Humanity - Skyline House
PROJECT NO: 1291-025-(1l1
COMPUTATIONS BY: sb
DATE: 8115/1016
2 yr storm. Cf = 1.00
DIRECT RUNOFF
CARRY OVER
ITOTAL
IREMARKS
Design
Point
Tributary
Su"asin
A
(ant
C Cf
tc
(min)
i
(inihn
O (2)
(cts)
from
Design
Point
O (2)
(cis)
0(2)101
(CIS)
a
A
L 4
0.40
7.1
2S2
0.1
0.1
O=CICiA
FLOW(09-15-16)..xls
O = peak discharge (cfs)
C = runoff coefficient
C, = frequency adjustment factor
i - rainfall intensity (inthr) from City of Fort Collins IDF curve (4/16/99)
A = drainage area (acres) 1- 24.221 t n 0. lc)''
Interwest Consulting Group
Interwest Consulting Group
STANDARD FORM SF-2
TIME OF CONCENTRATION -100 YR
LOCATION:
Habitat for Humanity - Skyline House
PROJECT NO:
1291-025-(K)
COMPUTATIONS BY:
sb
DATE:
8/15/2016
100-yr storm Cf = 1.25 from Table RO-12 of City of Fort Collins Stormwater Code, Volume I
SUB -BASIN
DATA
INITIAL /OVERLAND
TIME (1t)
TRAVEL TIME / GUTTER OR CHANNEL FLOW
(n)
tc CHECK
(URBANIZED BASIN)
FINAL
tc
REMARKS
DESIGN
PONIT
SUBBASIN(s)
(1)
Area
(ac)
(2)
C
(3)
C'Cf
Length
(ft)
(4)
Slope
M)
(5)
ti
(min)
(6)
Length
(ft)
(7)
Slope
(%)
(8)
n
Manning
rough.
Vel.
(f/s)
(9)
R
(min)
(10)
tc =
ti+n
(11)
Total L
M
(12)
tc=(V180)+10
(min)
(13)
(min)
(14)
a
A
0.14
0.40
0.50
32
2.0
5.0
86
0.6
0.022
1.1
1.3
6.3
118
10.7
6.3
EQUATIONS:
tc=ti+It
ti=(1.87(1.1-CC,)0.1]/S113
tt = L/Vel.
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 + it and urbanized basin check
min. tc = 5 min. due to limits of IDF curves
FLOW (08-15-16).xls
Interwest Consulting Group
STANDARD FORM SF-2
TIME OF CONCENTRATION - 2 and 10 YR
LOCATION:
Habitat for Humanity - Skyline House
PROJECT NO:
1291-0251K)
COMPUTATIONS BY:
sb
DATE:
8/15/2016
2 and 10-yr Storm Cf = 1.00 Irom Table RO-12 of City of Fort Collins Stormwater Code. Volume I
SUB -BASIN
DATA
INITIAL/OVERLAND
TIME (ti)
TRAVEL TIME / GUTTER OR CHANNEL FLOW
(tt)
to CHECK
(URBANIZED BASIN)
FINAL
to
REMARKS
DESIGN
PONIT
SUBBASIN(s)
(1)
Area
(ac)
(2)
C
(3)
Length
(ft)
(4)
Slope
N)
(5)
li
(min)
(6)
Length
(ft)
(7)
Slope
(%)
M
n
Manning
rough.
Vol.
(ft/s)
(9)
tt
(min)
(10)
is =
ti. ft
(11)
Total L
(ft)
(12)
Ic=(U78o)+10
(min)
(13)
(min)
(14)
a
A
0.14
0.40
32
2.0
5.9
86
0.6
0.022
1.1
1.3
7.1
118
10.7
7.1
EQUATIONS:
tc=ti+tt
ti = [1.87 (1.1 - CC, ) Lo.s ] / S. 1/3
If = L/VeL
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(08-15-16).zis
Interwest Consulting Group
RUNOFF COEFFICIENTS & %IMPERVIOUS
LOCATION: Hublrat fir Humanin, - S'kplinc House
PROJECT NO: 1291-025-00
COMPUTATIONS BY: sb
DATE: 811"n16
Recommended Runoff Coefficients from Table RO.11 of City of Fort Collins Stormwater Code, Volume I
Recommended % Impervious from Table RO-3 Urban Storm Drainage Criteria Manual, Volume I
Type B Soils
Streets, parking lots (asphalt)
Sidewalks (concrete)
Roofs
Gravel or Pavers
Lawns, sandy soil (Flat <2%)
Runoff
%
coefficient
Impervious
C
0.95
100
0.95
96
0.95
90
0.50
40
0.10
0
SUBBASIN
DESIGNATION
TOTAL
AREA
(W.)
TOTAL
AREA
(50)
ROOF
AREA
(e0.11)
PAVED
AREA
(30)
SIDEWALK
AREA
(s0.fl)
LANDSCAPE
AREA
(sO.B)
RUNOFF
COEFF,
(C)
%
Impsrvlous REMARKS
A
0.14
61003
1,540
600
0
3.863
0.00
33
Calculated C coefficients & % Impervious are area weighted
C=£(CiAi) /At
Cl . 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
FLOW(OB-16-16).sls
Interest Consulting Group
RUNOFF COEFFICIENTS & % IMPERVIOUS
LOCATION: Habitat far Hronanhy - Sk-Wine House
PROJECT NO: 1291-025-M
COMPUTATIONS BY: ab
DATE: 8/15/1016
Recommended Runoff Coefficients from Table RO-11 of City or Fort Collins Slormwater Code, Volume I
Recommended % Impervious from Table R0-3 Urban Storm Drainage Criteria Manual, Volume I
Type B Soils
Streets, parking lots (asphalt)
Sidewalks (concrete)
Roofs
Pavers
Lawns, sandy loll (Flat <2%)
Runoff
coefficient
Impervious
C
0.95
100
0.95
96
0.95
90
0.50
40
0.10
0
SUBBASIN
DESIGNATION
TOTAL
AREA
(ae.)
TOTAL
AREA
( .11)
ROOF
AREA
I .II
PAVED
AREA
niqlff
PAVERS
AREA
• .Ip
SIDEWALK
AREA
fa .ill
LANDSCAPE
AREA
la .II
RUNOFF
COEFF.
IC)
%
IMPBNIOue
REMARKS
Exlalln
Lot
0.14
61003
0
0
0
0
6,003
0,10
0
Pro bed
Lot
0,14
6.003
1.540
600
0
0
3.663
0.40
33
Eouations
- Calculated C coefficients & % Impervious are area weighted
C = E (CI Ai)I At
Ci = runoff coefficient for specific area, Al
Al - areas of surface with runoff coefficient of Cl
n - number of different surfaces to consider
At = total area over which C is applicable; the sum of all At's
FLOW(06-15-16).aIS
No Text
Ms. Heather McDowell
August 15, 2016
Page 2 of 2
SWMM Master Plan that City Stormwater is modeling and it was confirmed that the output
change was minimal and within the margin of error.
As shown on the attached SWMM printout from the Master Plan there is 31 cfs of off -site runoff
coming through the lot during the 100-year event. This flow will be routed on the south side of
the property through a swale that will drain any overtopping stormwater from the street curb and
gutter east through the church property to the ultimate outfall which is the canal that runs along
the east side of the church property. During the 100-year event there is approximately 15" of
free board from the top of foundation to the water surface of the Swale. Please see the attached
channel calculation that shows the proposed grading can accommodate this overflow without
impacting the house.
Thank you for reviewing the proposed stormwater improvements for the proposed single family
home. If you have any questions or comments please contact meat (970) 460-1091.
Sincerely,
Skylar Brower, P.E.
Colorado Professional
Engineer No. 44248
Reviewed By:
Robert Almirall, P.E.
Colorado Professional
Engineer No. 33441
l
INTl RRIetT CONSULTING GROUP
August 15, 2016
Ms. Heather McDowell
City of Fort Collins
Storm Water Utility
700 Wood Street
Fort Collins, CO 80522
Re: Drainage Memorandum — Habitat for Humanity Skyline House
Dear Heather,
Please accept the following letter on behalf of Habitat for Humanity to demonstrate that the
proposed single family home on Skyline Drive is in compliance with current City Code. Please
note that a separate erosion control / stormwater management report has been prepared for this
project and erosion control is not addressed in this letter.
INTRODUCTION
The proposed project includes the subdivision of the existing Westminster Presbyterian Church
property located in the southeast comer of W Elizabeth Street and Skyline Drive. The
subdivision will consist of 0.14 acres. Habitat for Humanity will be placing one single family
home on this new lot which will front Skyline Drive and is adjacent to existing single family
homes in the area.
EXISTING CONDITIONS
The 0.14 acres of land that will be subdivided from the church is located in the southwest corner
of the church property. This space is currently open space covered with natural grasses and is
100% pervious. This property is in the Canal Importation Basin Master Plan.
PROPOSED DEVELOPMENT
As previously mentioned, the proposed project will consist of constructing one single family
home on the subdivided property. The proposed impervious area associated with the
improvements is 2,140 square feet.
The proposed property is located in Basin 549 of the Canal Importation Basin Master Plan which
is assumed to be 45% imperviousness. The additional 2,140 sf of impervious area that will be
added to this basin and the additional 0.6 cfs of runoff that it will produce will have a negligible
impact to the overall drainage of the area. The additional impervious area was input into the