HomeMy WebLinkAboutSDP200400082 Calculations Final Site Plan and Comps. 2004-11-15 GLENWOOD STATION PHASE 2
'STORMWA, ER/BMP SUMMARY
AND
CALCULATIONS
STORM WATER DETENTION:
As part of Phase 1 of Glenwood Station a bio-retention facility was designed to satisfy County
storrnwater detention requirements for both Phase 1 and Phase 2 of the project. Assumptions were
made for the Phase 2 proposed improvements and a c factor of 0.64 was calculated and used for the
pond modeling and design. With the proposed site plan for Phase 2 nearly complete,the c-factor
was re-calculated for a value of 0.65. This is a very slight increase so since none of the other pond
variables have changed,i.e.,the drainage area and time of concentration,the pond model has not
been updated. This can be done if needed. From the previous pond calculations:
Q2(pre)=22.92 ccs •
Q2 postt=22.99 cffs
Qio(pre)=31.02 offs
Qio(post)=28.10 cfs
STORM DRAINAGE SYSTEM A:
Storm Drain System A was designed to handle Qlo,=16.06 cffs from fully developed Phase 2 portion
of the property entering structure A7. With this proposed site plan for Phase 2,Q10=13.40 offs
entering structure A7 as planned.
WATER QUALITY/BMP:
31
Phase 1 consumed most of the water quality capacity in the proposed bio-retention facility, therefore,water quality control for this phase will be provided by a combination of three bio-filters constructed
between Rio Road and the proposed buildings and by porous paving block along the parking spaces
along the back of the office building parking lot. For the water quality control plan to be fully
utilized,all roof drainage from the proposed building should be routed to the bio-filters. The surface
area provided by the proposed BMP's exceeds the County requirement if full credit is given for
square footage of porous paving block.
Phase 2 Impervious Area=52,272 sf
Required BMP Surface Area=52,272 x 0.05=2,614 sf
Proposed BMP Surface Area=6,750 sf
REDEWED •
NOV 15 2004
Please see the enclosed storrnwater calculations.
COMMUNITY '_NT
GLENWO( D STATION PHASE 2
STORMWATER/BMP SUMMARY AND
CALCULATIONS
STORMVVATER MANAGEMENT/BMP CALCULATIONS:
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GLENWO( D STATION
PHASE 2
STORMWATER/BMP SUMMARY AND
CALCULATIONS
PHASE 2 INLET AND PIPE CALCULATIONS:
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STORMWATER INLET COMPUTATIONS
GLENWOOD PHASE 2
9/27/2004
Terra Partners-AGF
INLET SEE HY-22 OUTPUT
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T3 3A 2.5 - 0.14 0.61 0.09 0.09 4.0 0.34 0.00 0.34 SAG 0.035 2.39 2.0 1.00 0.34 0.00 0.26 0.62 SUMP
R2 2B 6.0 - 0.17 0.74 0.13 0.13 4.0 0.50 0.00 0.50 0.039. 0.010 1.64 2.0 1.22 0.083 8.30 0.92 0.46 0.04 OVERFLOW TO Q1
Q1 2B 6.0 - 0.30 0.76 0.23 0.23 4.0 0.91 0.04 0.96 SAG 0.010 12.35 2.0 1.00. 0.96 0.00 0.35 0.83 SUMP
P1 2B 6.0 - 0.19 0.87 0.17 0.17 4.0. 0.66 0.00 0.66 0.035 0.020 1.85 '2.0 1.08 0.083 4.15 0.88 0.58 0.08 OVERFLOW TO 01
01 2B 6.0 - 0.22 0.88 0.19 0.19 4.0 0.77 0.08 0.86 0.035 0.020 2.21 2.0 0.90 0.083 4.15 0.82 0.71 0.15 OVERFLOW TO G1
G1 3B 6.0 - 0.47 0.80 0.38 0.38 4.0 1.50 0.15 1.65 SAG 0.020 8.86 2.0 1.00 1.65 0.00 0.39 0.93 SUMP
G5 '3A 2.5 - 0.14 0.90 0.13 0.13 4.0 0.50 0.00 0.50 SAG 0.020 5.41 2.0 1.00 0.50 0.00 0.32 0.76 SUMP
G5.TXT TLij4
FHWA Urban Drainage Design Program, HY-22 V
Drainage of Highway Pavements
Inlets on Sag ,
Date: 11/15/2004
Project No. .
Project Name. :
computed by .
Inlets on Sag: Curb-opening Inlet
Roadway and Discharge Data
Cross Slope Composite/Dep
Sx Pavement Cross Slope (ft/ft) 0.0200
Sw Gutter Cross Slope (ft/ft) 0.0830
n Manning's Coefficient 0.013
W Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Inlet Interception
Inlet Type *Sag* Curb-Opening
T Width of spread (ft) 5.41
L Curb-opening Length (ft) 2.50
H Curb-Opening Height (in) 5.00
d_curb Depth at Curb (ft) 0.318
Qi Intercepted Flow (cfs) 0.500
0
Page 1
G1..TXT
FHWA urban Drainage Design Program, HY-22 ( i
Drainage of Highway Pavements
Inlets on Sag
Date: 11/15/2004
. Project No. .
Project Name. :
Computed by .
Inlets on Sag: Curb-opening Inlet
Roadway and Discharge Data
cross Slope Composite/Dep
sx Pavement Cross Slope (ft/ft) 0.0200
Sw Gutter Cross Slope (ft/ft) 0.0830
n Manning's Coefficient 0.013
W Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Inlet Interception
Inlet Type *Sag* Curb-opening
T width of spread (ft) 8.86
L Curb-Opening Length (ft) 6.00
H Curb-opening Height (in) 5.00
d_curb Depth at Curb (ft) 0.387
Qi Intercepted Flow (cfs) 1.650
0
Page 1
P1.TXT I (_
FHWA Urban Drainage Design Program, HY-22
Drainage of Highway Pavements
Inlets on Grade
Date: 11/15/2004
Project No. .
Project Name. :
Computed by .
Inlets on Grade: Curb Opening Inlet
Roadway and Discharge Data
Cross Slope Composite
S Longitudinal Slope (ft/ft) 0.0350
Sx Pavement Cross Slope (ft/ft) 0.0200
Sw Gutter cross Slope (ft/ft) 0.0830
n Manning's Coefficient 0.013
W Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Q Discharge (cfs) 0.660
T width of Spread (ft) 1.85
Gutter Flow
Eo Gutter Flow Ratio 1.000
d Depth of Flow (ft) 0.15
✓ Average Velocity (ft/sec) 3.98
Inlet Interception
Inlet Type Curb-opening
LT Length for 100% Inteception (ft) 8.70
L Curb-Opening Length (ft) 6.00
e Inlet Efficiency 0.878
Qi Intercepted Flow (cfs) 0.579
Qb By-pass Flow (cfs) 0.081
0
Page 1
Q1.TXT (e+
FHWA Urban Drainage Design Program, HY-22 Q
I
Drainage of Highway Pavements
Inlets on Sag
Date: 11/15/2004
Protect No. .
Project Name. :
Computed by .
Inlets on Sag: Curb-Opening Inlet
Roadway and Discharge Data
Cross Slope Composite/Dep
Sx Pavement Cross Slope (ft/ft) 0.0100
Sw Gutter Cross Slope `(ft/ft) 0.0830
n Manning's Coefficient 0.016
W Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Inlet Interception
Inlet Type *Sag* Curb-opening
T width of Spread (ft) 12.35
L Curb-opening Length (ft) 6.00
H curb-opening Height (in) 5.00
d_curb Depth at Curb (ft) 0.353
Qi Intercepted Flow (cfs) 0.960
0
Page 1
R2.TXT (� I e/-
CZ/
FHWA Urban Drainage Design Program, HY-22
Drainage of Highway _ Pavements
Inlets on Grade
Date: 11/15/2004
Project No. .
Project Name. :
Computed by .
Inlets on Grade: Curb opening Inlet
Roadway and Discharge Data
Cross slope Composite
S Longitudinal slope (ft/ft) 0.0390
Sx Pavement Cross slope (ft/ft) 0.0100
sw Gutter cross Slope (ft/ft) 0.0830
n Manning's Coefficient 0.013
W Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Q Discharge (cfs) 0.500
T width of Spread (ft) 1.64
Gutter Flow
Eo Gutter Flow Ratio 1.000
d Depth of Flow (ft) 0.14
✓ Average Velocity (ft/sec) 3.01. .
Inlet Interception
Inlet Type Curb-opening
LT Length for 100% Inteception (ft) 8.00
L Curb-opening Length (ft) 6.00
e Inlet Efficiency 0.917
Qi Intercepted Flow (cfs) 0.459
Qb By-pass Flow (cfs) 0.041
0
Page 1
T3.TXT
FHWA Urban Drainage Design Program, HY-22
Drainage of Highway Pavements
Inlets on Sag
Date: 11/15/2004
Protect No. .
Project Name. :
Computed by .
Inlets on sag: curb-opening Inlet
Roadway and Discharge Data
Cross Slope Composite/Dep
Sx Pavement Cross Slope (ft/ft) 0.0350
Sw Gutter Cross Slope (ft/ft) 0.0830
n Manning's Coefficient 0.013
w Gutter width (ft) 2.00
a Gutter Depression (inch) 1.00
Inlet Interception
Inlet Type *Sag* Curb-Opening
T width of Spread (ft) 2.39
curb-opening Length (ft) 2.50
H Curb-opening Height (in) 5.00
d_curb Depth at curb (ft) 0.263
Qi Intercepted Flow (cfs) 0.340
0
Page 1
& B Chapter 9-Storm Drains .: a 2,_ c__F
Appendix 9C-13 Performance Curve DI-1 in a Sump
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1 of 1 VDOT Drainage Manual
11_11.) Lc(' U7
Chapter 9—Storm Drains = 0 to 9 q 1
6
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Chapter 9—Storm Drains 00 z— Z. 0 `1,
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'1 of I ' VDOT Drainage Manual
GLENWOO 1 STATION PHASE 2
STORMWATER/BMP SUMMARY AND
CALCULATIONS
PHASE 1 CALCULATIONS:
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Short Version BMP Computations For Worksheets 2-6
Albemarle County Water Protection Ordinance:Modified Simple Method
Plan: GLENWOOD STATION Water Resources Area: Development Area
Preparer: Alan G.Franklin, PE Date: 10/29/20031
Project Drainage Area Designation DA 1
L storm pollutant export in pounds, L=[P(Pj)Rv/12][C(A)2.72]
Rv mean runoff coefficient, Rv=0:05+0.009(1)
Pj small storm correction factor,0.9 .
I percent imperviousness
P annual precipitation,43"in Albemarle •
A project area in acres in subject drainage area, A_= _ 9.47
C pollutant concentration,mg/I or ppm target phosphorus
f factor applied to RR
V required treatment volume in cy,0.5"over imperv.area= A(I)43560(0.5/12)/27 '
RR required removal, L(post)-f x L(pre)
%RR removal efficiency, RR100/L(post)
Impervious Cover Computation(values_in feet&square feet) c
Item
pre-development .Area post-development
Roads Length Width subtotal _ Area
Length Width subtotal
0: 0 0 t 0- 0 0
_0 ... . 0 _ ._0- 0' 0 0
0 -0 _ ._. 0
,
Width0 0 ;; -
Driveways Length no. , subtotal _gam 0
and walks 0 00 LenWidth no. subtotal 0
- --._. -0 .._. 0_ . _ 0 o 0: 0 0
Parking Lots 1 2 0 0 0 0
3 4 f." 3 4
•
Structures 0 _ 0- 0
Area Area_no. subtotal ' no. subtotal
0 0. 0.. - 0 0. 0
O. •- -- 0 0 _ - 0; 0 . .." _- 0
Actively-grazed pasture& Area D' 0 0 0 Area - 0• 0
yards and cultivated turf *O:x 0.08= 00 x 0.08=Active crop land Area "" .-- ,. ..d 0
Area - . .
0x0,25= 0 x0.25= 0
Other Impervious Areas
Impervious Cover 0 236625
O% 57%
RV(post)'__"- V
l(Pre)..._ I(post)
• 0.57 365.2
New Development(For Development Areas,existing impervious cover<=20%)
C f I(pre)* ` Rv(pre) L(pre) L(post) RR .. .%RR 3 Area Type .
• 0.70 -.1;00: ,.20% 0.23 ; 13.37 • 32.92 ..1 _9.55 59% Development Area
0:35 'LOP, ` _ .0%' 0.05 1.45 16.46 ; 15.01 91%1 Drinking Water Watersheds
-0.40 _ 21:00 :- JP* 0.06 1.96 18_81 " 16_85 ' .. 96%1 Other Rural Land
'min.values
Redevelopment(For Development Areas,existing impervious cover>20%)
C f I(pre).' Rv(pre). L(pre) L(post)- -RR %RR `Area Type
0 70-. 0:90. 26% 0.23 13.37 , 32.92 , 20.89 . "
.. ... 63%'s DevetopmentArea
b 85•.... 0%: 0.05 1.45 16.46 15.22 92%j Drinking Water Watersheds
0.40 0.85' _ -1% 0.06 1.96 18.81 17.15 '91%; Other Rural Land
Interim Manual,Page 70 rev.31 March 1998 GEB
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