HomeMy WebLinkAboutDrainage Reports - 02/18/2016City of Fort Collins Approved Plans
Approved by: Wes Lamarque
Date: 2/18/2016
INTERWEST C O N 5 U L T I N G G R O U P
February 17, 2016
Mr. Wes Lamarque
Fort Collins Utilities — Stormwater
700 Wood Street
Fort Collins, CO 80522
Re: FCHA Villages on Redwood
Final Storm Drainage Report Amendment
Dear Wes,
Please accept the following letter on behalf of the Forf Collins Housing Authority (FCHA) as an
amendment to the "Final Drainage Report for Village on Redwood" prepared by Interwest Consulting
Group, dated December 1 l, 2015. The pu�pose of this amendment is to document the revised drainage
aspects in response to the amended Low Impact Development (LID) ordinance (Ordinance No. 007,
2016) and to demonstrate ability to comply with the City's current stormwater requirements.
INTRODUCTION
All site descriptions within the original report are consistent with this amend�ment. No site, bL�ildings,
walks, etc are proposed to be adjusted with this amendment. Under the current LiD ordinance, proposed
project sites are required to:
� Treat at least 75% of any newly developed or redeveloped area using one or a combination of
LID techniques, or
• Treat at least 50% of any newly developed or redeveloped area using one or a combination of
LID techniques when 25% of private drivable surfaces are permeable.
In response to the current LID requirements, FCHA has reqtiiested that we revise the storm drainage
design to satisfy the LID requirements by other techniques without penneable pavers. As you may recall,
we developed and presented preliminary options and calculations for LID alternatives. The eXhibits and
calculations attached have been further detailed in reference to the approach we discussed to satisfied the
current LID requirements.
LOW IMPACT DEVELOPMENT TECHNIQUES
Wit11 the removal of pei7neable pavers, tlle LID require�neilts are pi•oposed to be satisfied by t�•eating
storm runoff by two (2) rain gardens. All runoff from Basins D1, D2, and D3 will be treated through a
1,200 sq-ft rain garden located withiu site's central green area. The rain garden within the detention pond
is proposed to be expanded to 550 sq-ft to treat all of Basin D4. All LID calculations were prepared in
reference to Lot 1 only. Tract A is not proposed to have any development activity and was described by
Basin D7. A small portion of Lot 1, in the southwest coruer, is within Basin D7 and does not contain any
paved driving surfaces. it is assumed that the roof areas would be treated by the grass buffer and existing
1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 - FAX 970.674.3303
FCHA Villages on Redwood
Final Storm Drainage Report Amendment
February 17, 2016
Page 2 of 2
consh•ucted wetland west of the proposed residential units. The proposed L1D provides storinwater
tr-eatment to 75.6% of the developed site and satisfes the LID ordinance requirements.
The rain gardens are designed to directly spill into the detention areas for events beyond the capacity of
the rain garden. The rain garden are designed with full infiltration sections, without underdrains, and have
a maximum depth of 12 inches. All calculations are attached for reference.
DETENTION VOLUMES
With the i-emoval of fl�e permeable pavers, near is ai1 increase in % impervious, rec�uiring additional
detention volume. The basins drainin� to the detention pond originally estimated the site to be 46.7%
impe�viol�s (including the pavers). Removing the pavers causes an estimate increase of 3.2°/o impervious
for an overall 49.9% impervious. This increase in impervious area requires an additional 0.023 acre-ft of
detention storage. The previous design provided 0.0402 acre-ft of deYe�lYion storage and this revision
provides 0.0425 acre-ft. This was achieved by providing addition detention storage within the site's
central green area. All calculations are attached for reference.
Thank you in advance for your consideration and if you have any questions ot• comments please contact
me at (970) 347-8917. _
Sincerely,
Jason T. Claeys, P.
lnterwest Consu➢tir
Attachments
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oEFnR?M�r�T. Pavement Area Summary
Total Pa�ed Area: 49,417 sqft �
Permeable Paeer Area: 0 sqfl
BASINSUMMARY: PercentPavementAreaasPermeablePavers: 0.0/
5•yr Peak Rurwf.` t0yr Peak Runoff '100.yr Peak Runoff
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p� C1 1254 7�7 768 J.Bd 1.35 287 Q6E ' OE6 4.11 3.53 G.8'_ 1.07 8,q0 9.J'I Total Site Afea: 251,435 Sqft �
Q '[�'� JEE8 5�5 J.�S �]51 3.�1 15C� �.i� 0�1 45� 23? �.93 C6c 3�2 55� ProposetlAreaolPacers: Osqfl
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p5 es ae27 a.71 145 o.35 32a �2a c.�e o.°9 3.a3 •.52 o.ss c.ae a ia a.97 Are,9 to Ue Treatetl by Rain GerAen- 178.311 sqft �
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c.; c� s�=s s.aa �r i.aa �.e�� o.ze �.ca a.es a_aa aaa �.;c sa� �as� Area Treaied by Wetl2nd (no n2}ement): 11,644 sqft '
OF' OF' JC'5 SG� JZS �]01 3.d8 OGi L.�_` OCi 3.]1 003 0.31 G01 J.E3 o�? Total Area Treatetl by LID: 190,155 sqk
Percant Slte Area Treatetl by LIQ• 15.&%
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City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
APPROVED:
Clty Enqinenr Dale
CHECKEDBY:
Waie� h Wasiewater Ullilly Ddle
CHECKEDBY:
SturmwaterUlility Da[e
CHECKEDBY:
Traffr.Engineer Da�e
CHECKEDBY:
Pa�ks and Recreation Uale
CHECKEDBY:
Environmen�el Pianner Date
CHECKEDBY:
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PROJ. NO. 7237-112-00
5oF22
FCHA - Villages on Redwood
DEVELOPED IMPERVIOUS AREA CALCULATION
Design Engineer: T.Alva
Design Firm: Interwest Consulting Group
Project Number: 1237-112-00
Date: February 17, 2016
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
BASINS:
%Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Land Use % Runoff
Impervious Coefficient C
Paved 100% 0.95
Roof 90% 0.95
Walks 90% 0.95
Pavers 40% 0.50
Lawns (Heavy, 2-7%
Slope) 0% 0.25
Frequency
Return Adjustment
Period Factor (C�)
2-yearto
1.00
10- ear
700-year 1.25
Sub-basin Atotal Atotal Apaved Aroof Awalk Apavers Alawn Weighted "/o COMPOSITE
Designation (sq feet) (acres) (sq feet) (sq feet) (sq feet) (sq feet) (sq feet) Impervious � to C C
� ,o ,00
D1 54,800 t258 14,447 11,432 7,959 0 20,962 58.2% 0.68 0.85
D2 29,959 0.688 10,214 6,849 4,140 0 8,755 67.1% OJS 0.93
D3 45,346 1.041 0 8,831 5,683 0 30,833 28.8% 0.47 0.59
D4 48,207 1.107 19,660 7,420 5,959 0 15,167 65.8% oJ3 0.91
D5 36,006 0.827 3,656 5,478 1,714 0 25,158 28.1 % 0.46 0.58
D6 46,296 1.063 16,675 3,690 7,155 0 16,777 57.1% 0.67 o.a3
D7 174,015 3.995 0 2,185 523 0 171,307 1.4% 0.26 033
OF1 1,076 0.025 0 0 0 0 1,076 0.0% o.z5 031
Total 435,704 10.002 64,652 45,884 33,133 0 292,035 31.2% 0.48 0.60
Neadwall (D1+D2+D3) 130,104 2.987 24,661 27,112 17,782 0 60,550 50.0% 0.62 OJ8
InIet01 (D1+D2+D3+D4) 178,311 4.093 44,321 34,532 23,741 0 75,717 54.3% 0.65 0.82
To Detention Outlet (D1+....D5) 214,317 4.920 47,977 40,010 25,456 0 100,875 49.9 % a52 o.7a
To Redwood 260,614 5.983 64,652 43,699 32,610 0 119,652 51.2% 0.63 oJ9
FCHA - Villages on Redwood
DEVELOPED TIME OF CONCENTRATION
Design Engineer: T.Alva
Design Firm: Interwest Consulting Group
Project Number: 1237-112-00
Date: February 17, 2016
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
t�, = t� + t� -Equation RO-2 V= C�,.��°, 5-Equation RO-4
0.395(1.1- C_ )� L
tr = So �, ' -Equation RO-3 �' 6�V
CONSTRAINTS:
300 ft- Overland flow shall not exceed for developed condition
500 ft- Overland flow shall not exceed for undeveloped condition
Final t� = minimum of t; + tt and urbanized basin check
recommended minimum t� = 5 min for urbanized basins
t�, = 1 go + 10 -Urbanized Check Equation RO-5
BASINS:
SUB-BASIN DATA �NITIAL/OVERLAND TRAVEL TIME (t�)
TIME (t;) t� t;+t� t� urban Final t�
DESIGN AREA LENGTH SLOPE LENGTH SLOPE Table RO-2 VEL. (min) Check �m�n� REMARKS
POINT Sub-basin �5 (acres) (ft) (fUft) t; (min) (ft) (ft/ft) Type of rravel �� (ft/s) tt (min)
Surface
D1 D1 0.68 1.258 31 0.0370 2.76 521 0.0069 PavedAreas 20 1.67 5.21 7.97 13.07 7.97
D2 D2 0.75 0.688 78 0.0239 4.28 156 0.0079 Paved nreas 20 1.77 1.47 5.75 11.30 5.75
D3 D3 0.47 1.041 101 0.0297 8.02 159 0.0253 Paved Areas 20 3.18 0.84 8.85 11.45 8.85
D4 D4 0.73 1.107 42 0.0191 3.55 246 0.0109 Paved Areas 20 2.09 1.97 5.51 11.60 5.51
D5 D5 0.46 0.827 97 0.0264 8.37 37 0.0083 Paved Areas 20 1.82 0.34 8.71 10.75 8.71
D6 D6 0.67 1.063 12 0.0651 1.50 563 0.0040 Paved Areas 20 1.26 7.42 8.92 13.20 8.92
D7 D7 0.26 3.995 37 0.0513 5.44 0 0.0001 Paved Areas 20 0.20 0.00 5.44 10.21 5.44 All Overland Flow
OF1 OF1 0.25 0.025 6 0.1371 1.66 0 0.0001 PavedAreas 20 0.20 0.00 5.00 10.04 5.00 All Overland Flow
FCHA - Villages on Redwood
DEVELOPED PEAK RUNOFF
Design Engineer: T.Alva
Design Firm: Interwest Consulting Group
Project Number: 1237-112-00
Date: February 17, 2016
DESIGN CRITERIA:
City of Fort Collins - Storm Water Criteria Manual (1997)
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
Q„ = n-yr peak discharge (cfs)
C = n -yr runoff coefficient
Q�, = C„I�,A„ �nn_ n-yr rainfall intensity (in/hr)
A„ = Basin drainage area (ac)
28.SP I= rainfall intensity (in/hr) P�-5yr = 1.14 in
I- o.�s��s>> P- one-hour oint rainfall de th /in P - 1.40 in
�� Q+�� � 1- p p l � 1-10yr '
t� = time of concentration (min) P 1-100yr - Z•$s �n
BASIN SUMMARY:
5-yr Peak Runoff 10-yr Peak Runoff 100-yr Peak Runoff
Design Sub-basin Area acres t� min
Point ( 1 ( 1 Runoff Coeff. C(A) Intensity 3 Runoff Coeff. C(A) Intensity , Runoff Coeff. C(A) Intensity 3
(CS) (acres) (in/hr) 4 (ft �S� (CS) (acres) (in/hr) Q (ft �S� (C�oo) (acres) (in/hr) Q (ft /s)
D1 D1 1.258 7.97 0.68 0.86 3.35 2.87 0.68 0.86 4.11 3.53 0.85 1.07 8.40 9.01
D2 D2 0.688 5.75 0.75 0.51 3.71 1.90 0.75 0.51 4.56 2.34 0.93 0.64 9.32 5.97
D3 D3 1.041 8.85 0.47 0.49 3.22 1.59 0.47 0.49 3.96 1.95 0.59 0.62 8.09 4.99
D4 D4 1.107 5.51 0.73 0.81 3.76 3.04 0.73 0.81 4.62 3.73 0.91 1.01 9.43 9.52
D5 D5 0.827 8.71 0.46 0.38 3.24 1.24 0.46 0.38 3.98 1.52 0.58 0.48 8.14 3.87
D6 D6 1.063 8.92 0.67 0.71 3.22 2.28 0.67 0.71 3.95 2.80 0.83 0.88 8.07 7.14
D7 D7 3.995 5.44 0.26 1.04 3.77 3.93 0.26 1.04 4.63 4.83 0.33 1.30 9.47 12.33
OF1 OF1 0.025 5.00 0.25 0.01 3.86 0.02 0.25 0.01 4.74 0.03 0.31 0.01 9.68 0.07
Village on Redwood
100-yr Detention Volume - FAA Method
Design Engineer: T. Alva
Design Firm: Interwest Consulting
Project Number: 1237-112-00
Date: February 17, 2016
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Fiood Control District, June 2001 (Revised April 2008)
City of Fort Collins - Storm Water Criteria Manual
Detention Volume Calculation
Runoff Coefficient (C) 0.62
Frequency Factor (C f) 1.25
Adjusted Runoff Coefficient (CC f) 0.78
Area (A ) 4.92 acres
Ailowed Reiease Rate 6.96 cfs
Required Detention
{{3 acre-ft
18494.6 0.425
100-yr Accumulative Release Detained Detained
Time Intensity Q,00 Runoff Volume Volume Volume Volume
(min) (/, in/hr) (cts) (ft3) (ft3) (ft3) (acre-ft)
0 0.00 0.00 0.00 0.00 0.00 0.0000
5 9.95 37.94 11,381.81 2,088.00 9,293.81 0.2134
10 7.72 29.44 17,661.82 4,176.00 13,485.82 0.3096
15 6.52 24.86 22,374.68 6,264.00 16,110.68 0.3699
20 5.60 21.35 25,623.36 8,352.00 17,271.36 0.3965
25 4.98 18.99 28,483.11 1Q440.00 18,043.11 0.4142
30 4.52 17.23 31,022.57 12,528.00 18,494.57 0.4246
35 4.08 15.56 32,669.78 14,616.00 18,053.78 0.4145
40 3.74 14.26 34,225.49 16,704.00 17,521.49 0.4022
45 3.46 13.19 35,621.05 18,792.00 16,829.05 0.3863
50 323 12.32 36,947.97 20,880.00 16,067.97 0.3689
55 3.03 11.55 38,126.19 22,968.00 15,158.19 0.3480
60 2.86 10.91 39,258.65 25,056.00 14,202.65 0.3260
65 2.72 10.37 40,448.30 27,144.00 13,304.30 0.3054
70 2.59 9.88 41,477.81 29,232.00 12,245.81 0.2811
75 2.48 9.46 42,553.08 31,320.00 11,233.08 0.2579
80 2.38 9.07 43,559.71 33,408.00 10,151.71 0.2331
85 2.29 8.73 44,532.03 35,496.00 9,036.03 0.2074
90 2.21 8.43 45,504.34 37,584.00 7,920.34 0.1818
95 2.13 8.12 46,293.63 39,672.00 6,621.63 0.1520
100 2.06 7.85 47,128.68 41,760.00 5,368.68 0.1232
105 2.00 7.63 48,043.80 43,848.00 4,195.80 0.0963
110 1.94 7.40 48,821.65 45,936.00 2,885.65 0.0662
115 1.89 7.21 49,725.33 48,024.00 1,701.33 0.0391
120 1.84 7.02 50,514.62 50,112.00 402.62 0.0092
125 1.79 6.83 51,189.53 52,200.00 -1,010.48 -0.0232
130 1J5 6.67 52,047.45 54,288.00 -2,240.55 -0.0514
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
235
240
1.71
1.67
1.63
1.60
1.57
1.54
1.51
1.48
1.45
1.42
1.40
1.38
1.36
1.34
1.32
1.30
1.28
1.26
1.24
1.22
1.21
1.20
6.52
6.37
6.22
6.10
5.99
5.87
5.76
5.64
5.53
5.41
5.34
5.26
5.19
5.11
5.03
4.96
4.88
4.80
4.73
4.65
4.61
4.58
52, 813.86
53,488.76
54, 072.15
54,90720
55, 673.61
56, 371.39
57,000.54
57,561.05
58,052.93
58,476.17
59,254.02
59, 986.12
60,672.46
61,313.04
61,907.87
62,456.94
62,96026
63,417.82
63, 829.62
64,195.67
65, 053.59
65,888.64
56, 376.00
58,464.00
60, 552.00
62,640.00
64,728.00
66, 816.00
68, 904.00
70, 992.00
73,080.00
75,168.00
77,256.00
79,344.00
S 1,432.00
83,520.00
85,608.00
87,696.00
89,784.00
91, 872.00
93, 960.00
96,048.00
98,136.00
100,224.00
-3,562.14
-4,975.24
-6,479.85
-7,732.SO
-9,054.39
-10,444.61
-11, 903.46
-13, 430, 95
-15, 027.08
-16,691.83
-18,001.98
-19, 357.88
-20,759.54
-22,206.96
-23,700.13
-25,239.06
-26, 823Ja
-28,454.1 S
-30,130.38
-31, 852.33
-33, 082.41
-34, 335.36
-0.0818
-0.1142
-0.1488
-0.1775
-0.2079
-0.2398
-0.2733
-0.3083
-0.3450
-0.3832
-0.4133
-0.4444
-0.4766
-0.5098
-0.5441
-0.5794
-0.6158
-0.6532
-0.6917
-0.7312
-0.7595
-0.7882
Village on Redwood
Critical Pond Elevations
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
T.Alva
Interwest Consulting Group
1237-112-00
February 17, 2016
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
� _ �A, + Az + A, Az �Depth
3
VOLUME CUMULATIVE VOLUME
CONTOUR (FT) AREA (FTZ) AREA (ACRE) �ACRE-FT) DEPTH (FT) (ACRE-FT)
4962.33 0 0.000 0.000 0.00 0.000
4963.0 2019 0.046 0.010 0.67 0.010
4964.0 6600 0.152 0.094 1.67 0.104
4965.0 10636 0.244 0.208 2.67 0.312
4966.0 17563 0.403 0.320 3.67 0.632
Required 100-yr Detention Volume (including WQCV) _
0.425 Acre-Ft Interpolates to an Elev. of 4965.35 ft
DETENTION POND VOLUME
VERSUS ELEVATION
4966.50
4966.00
� 4965.50
="- 4965.00
p 4964.50
Q 4964.00
W 4963.50
W 4963.00
4962.50
4962.00
0.0
1237-112-00 PondCalcs.xls - Pond Stage Storage Page 1 of 1 Interwest Consulting Group
0.1 0.2 0.3 0.4 0.5 0.6 0.7
DETENTION POND VOLUME (AC-FT)
FCHA - Villages on Redwood
Low Impact Development
Design Engineer: T.Alva
Design Firm: Interwest Consulting Group
Project Number: 1237-112-00
Date: February 17, 2016
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID
techniques, or
- Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID
techniques when 25% of private driveab�e surfaces are permeable.
Low Impact Development Summary
Pavement Area Summary
Total Paved Area:
Permeable Paver Area:
Percent Pavement Area as Permeable Pavers:
49,417 sqft
0 sqft
0.0%
Developed Area Summary
Total Site Area:
Proposed Area of Pavers:
Additional Area Treated by Pavers:
Total Area Treated by Pavers:
Area to be Treated by Rain Garden:
Area Treated by Wetland (no pavement):
Total Area Treated by LID:
Percent Site Area Treated by LID:
251,435 sqft
0 sqft
0 sqft
0 sqft
178,311 sqft
11,844 sqft
190,155 sqft
75.6%
Design Procedure Form: Rain Garden (RG)
Sheet 1 of 2
Designer: J. qaeys
Company: Interwest Consulting Group
Date: February 17, 2016
Project: Villages at Redwood
Location: Basins D1-D3
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 50.0 %
(100 % if alI paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = la/100) i= 0.500
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches
(WQCV=0.8*(0.91*i3-1.19*iZ+0.78*i)
D) Contributing Watershed Area (including rain garden area) Area = 130,104 sq ft
E) Water Qualiry Capture Volume (WQCV) Design Voiume VWo�� = cu ft
VoI = (WQCV / 12)' Area
F) For Watersheds Outside of the Denver Region, Depth of ds = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWacvoTneR = 1,788.9 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQcv usEa = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin 6eometry
A) WQCV Depth (12-inch maximum) DWQ�� = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z= 4.00 ft/ ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AM;� = 1193 sq ft
D) Actual Flat Surface Area Aq�t„ai = 1202 sq ft
E) Area at Design Depth (Top Surface Area) ATo� = 1856 sq ft
F) Rain Garden Total Volume VT= 1,529 cu ft
�ur= ii/�ma + An�ma�) / 2) * Depth)
3. Growing Media Choose One
� 18" Rain Garden Growing Media �I
QQ Other(Expiain): '��,
City of Fort Collins Standard Rain Garden Section
4. Underdrain System
Choose One
A) Are underdrains provided? 0 YES
Q NO
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y= N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours VoI�Z= N/A cu ft
iii) Orifice Diameter, 3/8" Minimum Do = N/A in
1237-112-00 UD-BMP_v3.03 (Basins D1-D3).xlsm, RG 2/16/2016, 2:57 PM
Design Procedure Form: Rain Garden (RG)
sneet 2 of z
Designer: J. Claeys
Company: Interwest Consulting Group
Date: February 17,2016
Project: Viliages at Redwood
Location: Basins D1-D3
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric Choose One �,
Q YES
A) Is an impermeable liner provided due to proximity � NO
of structures or groundwater contamination?
6. Iniet / Outiet Control Choose One ,
Q Sheet Flow- No Energy DiSsipation Required
A) Inlet Control Q Co�centrated Flow- Energy Dissipation Provided �,,,
Choose One ��.
7. Vegetation Q Seed (Plan for frequent weed control) '�,,
Q Plantin95 ���.'�..
� Sand Grown or Other High Infiltration Sod '�
8. Irrigation Choose One
Q YES
A) Will the rain garden be irrigated? � NO
Notes:
1237-112-00 UD-BMP_v3.03 (Basins D1-D3).xlsm, RG 2/16/2016, 2:57 PM
Design Procedure Form: Rain Garden (RG)
Sheet 1 of 2
Designer: J. qaeys
Company: Interwest Consulting Group
Date: February 17, 2016
Project: Villages at Redwood
Location: Basin D4
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 65.8 %
(100 % if alI paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = la/100) i= 0.658
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.21 watershed inches
(WQCV=0.8*(0.91*i3-1.19*iZ+0.78*i)
D) Contributing Watershed Area (including rain garden area) Area = 48,207 sq ft
E) Water Qualiry Capture Volume (WQCV) Design Voiume VWo�� = cu ft
VoI = (WQCV / 12)' Area
F) For Watersheds Outside of the Denver Region, Depth of ds = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWacv oTneR = 826.8 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQcv usEa = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin 6eometry
A) WQCV Depth (12-inch maximum) DWQ�� = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z= 4.00 ft/ ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AM;� = 551 sq ft
D) Actual Flat Surface Area Aq�t„ai = 556 sq ft
E) Area at Design Depth (Top Surface Area) ATo� = 1063 sq ft
F) Rain Garden Total Volume VT= 810 cu ft
�ur= ii/�ma + An�ma�) / 2) * Depth)
3. Growing Media Choose One
� 18" Rain Garden Growing Media �I
QQ Other(Expiain): '��,
City of Fort Collins Standard Rain Garden Section
4. Underdrain System
Choose One
A) Are underdrains provided? 0 YES
Q NO
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y= N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours VoI�Z= N/A cu ft
iii) Orifice Diameter, 3/8" Minimum Do = N/A in
1237-112-00 UD-BMP_v3.03 (Basins D4).xlsm, RG 2/16/2016, 2:58 PM
Design Procedure Form: Rain Garden (RG)
sneet 2 of z
Designer: J. Claeys
Company: Interwest Consulting Group
Date: February 17,2016
Project: Villages at Redwood
Location: Basin D4
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric Choose One �,
Q YES
A) Is an impermeable liner provided due to proximity � NO
of structures or groundwater contamination?
6. Iniet / Outiet Control Choose One ,
Q Sheet Flow- No Energy DiSsipation Required
A) Inlet Control Q Co�centrated Flow- Energy Dissipation Provided �,,,
Choose One ��.
7. Vegetation Q Seed (Plan for frequent weed control) '�,,
Q Plantin95 ���.'�..
� Sand Grown or Other High Infiltration Sod '�
8. Irrigation Choose One
Q YES
A) Will the rain garden be irrigated? � NO
Notes:
1237-112-00 UD-BMP_v3.03 (Basins D4).xlsm, RG 2/16/2016, 2:58 PM