HomeMy WebLinkAboutDrainage Reports - 06/15/2016. _-
INTERWEST C O N S U LTI N G GROUP
June 8, 2016
City of Fort Collins Approv Plans
Mr. Shane Boyle
City of Fort Collins APproved by:
Stormwater Utility ' pate:
700 Wood Street
Fort Collins, CO 80522
Re: Lot 1, Eye Center of Northern Colorado — Amendment Storm Drainage Letter
Dear Shane,
We are pleased to submit for your review and approval this drainage letter showing the drainage
changes to Lot 1, Eye Center of Northern Colorado. Please accept the following letter on behalf
of Marasco & Associates, Inc. to demonstrate the site's compliance with the previously approved
"Final Drainage Report -Eye Center of Northern Colorado — Lot 1", as prepared by. Interwest
Consulting Group, approved May 13, 2016.
The site is required to follow the four step low impact development (LID) process outlined in
Urban Drainage and provide water quality treatment for the added impervious area; therefore,
seven bioretention pond systems (rain gardens) were proposed to achieve these requirements.
Five of these rain gardens were proposed next to the building. The changes proposed for this
amendment include removing the five rain gardens adjacent to the building and increasing the
size of the remaining two rain gardens (A and C) located in the parking lots. These changes
effect flows from Basins A-C. Basins D and E remain the same.
Rain garden A will capture flows from Basin A and the north half of Basin B. Rain garden C
will capture flows from Basin C and the south half of Basin B. The following is a summary of
each rain garden.
RAIN
RAIN
RAIN GARDEN
RAIN
RAIN
GARDEN
GARDEN
FLAT AREA
RAIN
GARDEN
BASIN
GARDEN
FLAT AREA
TOTAL
PROVIDED
GARDEN
VOLUME
REQUIRED
VOLUME
(SAND AREA)
DEPTH
PROVIDED
(SAND AREA)
REQUIRED
SF
CF
SF
INCH `
CF
A+1/26
A
869
1304.
1000
12
1370
C+1/213
C
870
1306
906
12
1310
1218 W. ASH, STE. C, WINDSOR, COLORADO 80550
TEL. 970.674.3300 - FAX 970.674.3303
Mr. Shane Boyle
June 8, 2016
Page 2 of 2
Roof drains and area inlets located on the north and south sides of the building will tie into the
12-inch storm systems that will route water to the top surface of the rain gardens.
Following the Urban Drainage design procedure for sizing rain gardens, the required water
quality capture volume for Basins A, B and C is 2,610 cubic feet. The two proposed rain
gardens provide 2,734 cubic feet of volume which exceeds volume required. Please see the
attached Urban Drainage Design Procedure form for more information.
All other design information from the previously approved report remains the same. The
proposed changes to the rain gardens have improved upon the design by moving these areas
away from the building.
Sincerely,
Michael Oberlander, P.E.
Colorado Professional Engineer 34288
Interwest Consulting Group
Attachments
1218 W. ASH, STE. C, WINDSOR, COLORADO 80550
TEL. 970.674.3300 - FAX 970.674.3303
1 '-6 to, I(P e
Design Procedure Form: Rain Garden (RG)
Sheet 1 of 2
Designer: ES
Company:
INTERWEST
Date:
March 8, 2016
Project:
EYE CENTER
Location:
RAIN GARDEN BASIN A PLUS 1/2 B
i. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, I,
I, =
76.0
%
(100 % it all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Idl00)
1 =
0.760
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time
WQCV =
0.24
watershed inches
(WQCV=0.8"(0.91'1'-1.19-i'+0.78"1)
D) Contributing Watershed Area (including rain garden area)
Area =
64,150
sq If
E) Water Quality Capture Volume (WQCV) Design Volume
VwOCV =
11304
cu ft
Vol = (WQCV / 12)' Area
F) For Watersheds Outside of the Denver Region, Depth of
ds =
in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region,
Vwocv OTHER =
cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume
Vwocv USER =
cu ft
(Only it a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)
Dwacv -
12
in
B) Rain Garden Side Slopes (Z - 4 min., hortz, dist per unit vertical)
Z =
0.00
ft / ft
(Use "0" 1 rain garden has vertical walls)
C) Mimimum Flat Surface Area
AM,,, =
869
sq ft
D) Actual Flat Surface Area
AA,,m =
sq ft
E) Area at Design Depth (Top Surface Area)
AT. =
sq ft
F) Rain Garden Total Volume
VT=
cu ft
(VT- ((AT.+ATv, ) / 2)' Depth)
3. Growing Media
Choose One
18" Rain
Garden Growing Media
Other (Explain):
4. Underdrain System
r Choaw One
0 YES
A) Are underdrains provided?
I
Q NO
8) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage
y=
3A
ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours
Vol,,.
1.306
cu ft
iii) Orifice Diameter, 3/8" Minimum
DO =
0,75
in
5-19-16 RG A add half of B.xlsm, RG 6/7/2016, 2:12 PM
Design Procedure Form: Rain Garden (RG)
Sheet 1 of 2
Designer: MPO
Company:
INTERWEST
Date:
March 8, 2016
Project:
EYE CENTER
Location:
RAIN GARDEN BASIN C PLUS 1/2 B
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, I,
I, =
60.0
(100 % d all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = I,1700)
=
0.800
C) Water Quality Capture Volume (WOCV) for a 12-hour Drain Time
WOCV =
026 watershed inches
(WOCV_ 0.8 - (0.91- i' - 1.19. iz+ 0.78 " i)
D) Contributing Watershed Area (including rain garden area)
Area =
59.650 sq It
E) Water Quality Capture Volume (WOCV) Design Volume
Vwocv =
1,306 cu h
Vol = (WOCV / 12) " Area
F) For Watersheds Outside of the Denver Region, Depth of
d, =
in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region,
Vwocv omen =
cu ff
Water Quality Capture Volume (WOCV) Design Volume
H) User Input of Water Quality Capture Volume (WOCV) Design Volume
Vwocv USER =
cu it
(Only A a different WOCV Design Volume is desired)
2. Basin Geometry
A) WOCV Depth (12-inch maximum)
Dwocv -
12 in
B) Rain Garden Side Slopes (Z = 4 min., honzdist per unit vertical)
Z .
0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area
AM,,, =
17.0 sq ft
D) Actual Flat Surface Area
Ak„ =
sq 1t
E) Area at Design Depth (Top Surface Area)
ATm =
sq ft
F) Rain Garden Total Volume
VT=
cu it
(VT= ((ATw+Aiwa) 12) * Depth)
3. Growing Media
Choose One
O 18" Rain Garden Growing Medal
Q Other (Explain);
4. Underdrain System
A) Are underdrains provided?
rn�, One
0 YES
Q NO
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage
y=
3.4 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours
Vol,,=
14306 cu If
iii) Orifice Diameter. 3/8" Minimum
Do =
0.75 in
5-19-16 RG C add half of B.xlsm, RG 6,7:2D76, 2:13 PM
RAIN GARDEN SUMMARY
Project Name:
Project Number:
Company:
Designer:
Date: 5/19/2016
Eye Center
1253-142-00
INTERWEST CONSULTING GROUP
ES
RAIN GARDEN SUMMARY
RAIN GARDEN
RAIN GARDEN
RAIN GARDEN
RAIN
RAIN GARDEN
RAIN
TOTAL
FLAT (SAND)
BASIN
FLAT (SAND)
GARDEN
VOLUME
GARDEN
VOLUME
AREA
AREA REOD
DEPTH
PROVIDED
REOD
PROVIDED
SF
CIF
SF
INCH
CIF
A+1/213
A
869
1304
1000
12
1370
C+1/213
C
870
1306
908
12
1310
TOTAL
2610
2680
Sn r
TREE RANFAG
axim
ma
R 3TAJ
YET a.m
sl a.
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BW mm
n o
m
w xim
21a
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RAN GlRIF1Y A (2Y.1J 1
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MINE
CRY OF FORT CO WNS
610RETENTTON SAND MEDIA SPECIFICATION
PWET I - ONFRAL
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A OIYOOOAERJS mNSSION, SHALL K ODHE O THE SAIWKIKXA OF THE OAANER.
PART 2 - SET. MATIDUALS
A SAID
1. BSH ENA. CONSIST W W-HOSE SAW BY V01NE YEETND ASn C-JJ.
B. SNE00F11 PAPUT
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A TEXTURAL ANAL'95 SHNA BE PEIiORWFa ONE TWA"L PRDERABIY AT HS EDURCE PMLR TO INRAICIHf LOP6FK IN TN W.
TMSUL SHAI. BE FREE OF SUBSX_ OEBMS fEIDS FOIEM MATIFA, AND MY OTER MADMk DFIEIENEXIS To PLANT
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L TIE MAYORAL SHALL K YELL RMPOST I, TREE£ 0 MABIL YEID YIDS AND CMtAN MAYBE O A OJERALY HEAAES
MAIIME WAGE OF ETSTNANO MONTH OF WE ATNN, WITH NO MX DREAS ro c TO NMIt WORN.
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PART 3 - DERTMN
A GENUAL
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B. NARSCTT MEREM
1. BS1 MAIIIAL SIAL RE SMMKI ETENIi N Wr6z0NTA IArtTS
z nEROEM OF LOOSE NATURAL N EARH uYEn SHALL "I EXCEID 91MMES.
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BACK OF WALL 3(Y
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MAX OPDSFD BALL HEIGHT N'
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TIP-19.9 (ROC)
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A-
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EYE CENTER PARKING LOT RAIN GARDENS
NTS
SOL C
CALL URUW NOTIFICATION
CENTER OF COLORADO
811
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EETME YOU DIG MACE, M EXCAVATE
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CITY OF FORT COLLINS, COLORADO
unurr PUN APPROVAL
APPROVED
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CHECKED BY: '&
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CHECKED BY: A.- f}
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PROD. NO. 12531420p
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MAT
DRAINAGE SOMMARY TABLE
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VNOJ.NO. 124}14200
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