HomeMy WebLinkAboutSDP200500019 Calculations 2005-07-26PAVEMENT CACLULATIONS FOR
ABBINGTON PLACE AT HOLLYMEAD TOWNCENTER
July 26 2005.
LOCATION:
Tax Map 32 Parcel 46
Rivanna District, Albemarle County, Virginia
DEVELOPER
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
434.984.1599
F) 434.984.8863
JUL 2 6 2005
Cr•
Flexible Pavement Design
County: Albemarle Date: 09- Feb -04
Site: Hollymead Town Center
Street Name: Gathering Place
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 2600 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 2600.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 17.75
Course Material Depth Equivalency D(p)
Surface SM -9.5A 2 2.25 4.5
Intermediate BM -25.0 4 2.15 8.6
Base 21A 8 0.6 4.8
Total Depth 14 Total D(p)17.9
D(p) -D(r) =0.15
D(p) >D(r) Therefore: ADEQUATE
Flexible Pavement Design
County: Albemarle Date: 26-Jul-05
Site: Hollymead Town Center
Street Name: Deerwood Drive
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix!SSV 5.00 Soil Support Value
Current ADT 500 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 500.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement /stone thickness for a road.D(r)= 12.01
Course Material Depth Equivalency D(p)Surface SM -9.5A 1.5 2.25 3.375
Intermediate BM -25.0 3 2.15 6.45Base21A60.6 3.6
Total Depth 10.5 Total D(p)13.425
D(p) =1.41
D(p) >D(r) Therefore: ADEQUATE
1350 Stony Point Road Rivanna Engineering 434.984.1599
Charlottesville, VA 22911 Surveying, PLC F) 434.984.8863
Memorandum
To:Glenn Brooks
From:Justin Shimp
CC:
Date:7 -15 -2005
Re:Abington Place SWM Plan.
Dear Glenn,
Attached to this memo are two copies of the SWM plan for Abington place and the
BMP calculation sheets. Please note that level spreaders have been provided at the
outfall of the BMP facilities to take advantage of the 50' stream buffer.
The BMP sizing has been calculated as follows:
Basin #1
Total Impervious: 173,487 SF.
Required BMP area: 4,337 SF.*
Provided BMP area: 4,750 SF.
Basin #2
Total Impervious: 58,430 SF.
Required BMP area: 1,460 SF.*
Provided BMP area: 1,550 SF.
Basin sizing requirement based on the less than 50% RR requirement of 2.5 %. The
stream buffer provides the additional water quality required for basin #1.
Detention for this site has been provided by stormwater basin #2 at Hollymead.
If you have any questions or would like to meet and discuss the plan please give me
a call.
Page 1
Short Version BMP Computations ,-or Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan: Abington Place at Hollymead Water Resources Area:
Preparer JMS Date:15- Jul -05
Project Drainage Area Designation Bio- Filter #1
L storm pollutant export in pounds, L = [P(Pj)Rv /12 ] [ C(A)2.72 ]
Rv mean runoff coefficient, Rv = 0.05 + 0.0090)
Pj small storm correction factor, 0.9
I percent imperviousness
P annual precipitation, 43" in Albemarle
A
C
project area in acres in subject drainage area,A =8.40
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)
IImpervious Cover Computation (values in feet & square feet)
Item
pre - development Area post development Area
Roads Length Width subtotal Length Width subtotal
0 0 0 750 32 24000
0 0 0 770 18 13860
0 1220 14 17080
0 0 0 54940
Driveways Length Width no.subtotal Length Width no.subtotal
and walks 0 0 1 0 14 16 88 19712
0,0 0 3485 5 1 17425
0 0 0 37137
Parking Lots 1 2 3 4 1 2 3 4
0 0 0 0
Gravel areas Area Area
x0.70=0?x0.70=0
Structures Area no.subtotal Area no.subtotal
0 0 0 870 63 54810
0 0 0 350 76 26600
0 0 0 0 0 81410
Actively- grazed pasture & Area Area
yards and cultivated turf 0 x 0.08 =0 117597 x 0.08 =9407.76
Active crop land Area Area
x 0.25 =0 x 0.25 =0
Other Impervious Areas
0 0
Impervious Cover 0%50%
I(pre)post)
Rv(post) V
0.50 282.2
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type
0.70 1.00 20% 0.23 11.86 25.78 13.92 54% Development Area
0.35 1.00 0% 0.05 1.29 12.89 11.60 90% Drinking Water Watersheds
0.40 1.00 1% 0.06 1.74 14.73 12.99 88% 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 20% 0.23 11.86 25.78 15.10 59% Development Area
0.35 0.85 0% 0.05 1.29 12.89 11.79 91% Drinking Water Watersheds
0.40 0.85 1% 0.06 1.74 14.73 13.25 90% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
Short Version BMP Computations r or Worksheets 2 - 6 ir,
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan: Abington Place Water Resources Area:Development
Preparer JMS Date:15- Jul -05
Project Drainage Area Designation Bio- Filter #2
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
percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area,A =4.00Cpollutantconcentration, mg /l or ppm target phosphorusffactorappliedtoRR
required treatment volume in cy, 0.5" over imperv. area = A(I)43560(0.5/12)/27RRrequiredremoval , L(post) - f x L(pre)
RR removal efficiency , RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)Item
pre - development Area post- development AreaRoadsLengthWidthsubtotalLengthWidthsubtotal0004501463000007501813500
0 0 .0
0 0
Driveways Length Width no.subtotal Length Width no.subtotal
0 19800
and walks 0 0 1 0 5 1 550000001616358960
Parking Lots ..__..__..._ -..1 2 3
0 0
1 .2 3 ..,....._.._
14460
4
0 0 0 0GravelareasAreaArea
x070 0 x0.70=Structures Area no.subtotal Area no .subtotal000s4301981700001000161600000
m .Actively - grazed pasture & Area
0 0 0` 24170
Areayardsandcultivatedturf0x0.08 =0 30500 x 0.08 =Active crop land Area 2440
Area
x0.25=0 x025 0OtherImperviousAreas
0
0ImperviousCover
0%
l(pre)
35%
Rv(post) V post)
0.36 93.9
New Development (For Development Areas, existing impervious cover <= 20 %)C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type0.70 1.00 20% 0.23 5.65 8.95 3.30 37% Development Area0.35 1.00 0% 0.05 0.61 4.47 3.86 86% Drinking Water Watersheds0.40 1.00 1% 0.06 0.83 5.11 4.29 84% Other Rural Landmin. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type0.70 0.90 20% 0.23 5.65 8.95 3.87 43% Development Area0.35 0.85 0% 0.05 0.61 4.47 3.95 88% Drinking Water Watersheds0.40 0.85 1% 0.06 0.83 5.11 4.41 86% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
STORM SEWER CALCULATIONS
FOR
ABINGTON PLACE SITE PLAN
March 14, 2005
LOCATION:
Tax Map 32 Parcel 46
Albemarle County, Virginia
Y
e_ % J
PREPARED BY:
Rivanna Engineering & Surveying, PLC
P.O. Box 7603
Charlottesville, VA 22906
P: 434.984.1599
F: 434.984.8863
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Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan:Abington Place at Hollymead Water Resources Area:
Preparer: JDB Date: 14- Oct -05
Project Drainage Area Designation Bio Filter #1 Js
L storm pollutant export in pounds, L = [P(Pj)Rv /12 1 [ C(A)2.72 j
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 =6.40
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)
Item
pre - development Area post - development Area
Roads Length Width subtotal Length Width subtotal
0 0 0 750 32 24000
0 0 0 770 18 13860
0 1220 14 17080
O 0'0 54940
Driveways Length Width no.subtotal Length Width no.subtotal
and walks 0 0 1 0 14 ... ,.. 16 88 ._..._ 19712 ,.
0 0 0 0 3485;5 1 17425:
0 0:0 37137
Parking Lots 1 2 3 4 1 2 3 4
0 0 0
Gravel areas Area Area
x0.70=0?x0.70=0.
Structures Area no.subtotal Area no.subtotal
0 0 0 870 ........ 63 54810
0 0 0 350 .,,.,....
r
76 26600
0 0 0 0 0 81410
Actively - grazed pasture &Area Area
yards and cultivated turf 0 x 0.08 =0 105297 x 0.08 =8423.76
Active crop land Area Area
x0.25=0 x0.25=0
Other Impervious Areas
0 0
Impervious Cover 0%85 %
I(pfe)l(post)
Rv(post) V
0.64 280.7
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type .. _.._._. _ ..... ...............................
0.70 1.00 20% 0.23 9.04 25.04 16.00 64% Development Area
0.35 1.00 0% 0.05 0.98 12.52 11.54 92% Drinking Water Watersheds
0,40 1.00 1% 0.06 1.32 14.31 12.98 91% 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 20% 0.23 9.04 25.04 16.90 68% Development Area
0.35 0.85 0% 0.05 0.98 12.52 11.68 93% Drinking Water Watersheds
0.40 0.85 1% 0.06 1.32 14.31 13.18 92% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan:Abington Place Water Resources Area:Development
Preparer: JDB Date: 14- Oct -05
Project Drainage Area Designation Bio- Filter #2
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 =2.37
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
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)
Item
pre - development Area post - development Area
Roads Length Width subtotal Length Width subtotal
0 0 0 450 14 6300
0 0 0 750 18 13500
0 0 0 0
0 0 0 19800
Driveways Length Width no.subtotal Length Width no.subtotal
and walks 0 0 1 0 1100 5 1 5500
0 0 0 0 16 16 35 8960
0 0 0 14460
Parking Lots 1 2 3 4 1 2 3 4
0 0 0 0 0
Gravel areas Area Area
x0.70=0 x0.70=0
Structures Area no.subtotal Area no.subtotal
0 0 0 430 19 8170
0 0 0 1000 16 16000
0 0 0 0 0 24170
Actively - grazed pasture &Area Area
yards and cultivated turf 0 x 0.08 =0 44807 x 0.08 =3584.56
Active crop land Area Area
x0.25=0 x0.25=0
Other Impervious Areas
0 0
Impervious Cover 0%60%
l(pre)post)
Rv(post) V
0.59 95.7
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type
0.70 1.00 20% 0.23 3.35 8.59 5.25 61% Development Area
0.35 1.00 0% 0.05 0.36 4.30 3.93 92% Drinking Water Watersheds
0.40 1.00 1% 0.06 0.49 4.91 4.42 90% 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 20% 0.23 3.35 8.59 5.58 65% Development Area
0.35 0.85 0% 0.05 0.36 4.30 3.99 93% Drinking Water Watersheds
0.40 0.85 1% 0.06 0.49 4.91 4.49 92% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
ft./
FHWA Urban Drainage Design Program, HY -22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Trapezoidal, Rectangular, or Triangular X- Section
Date: 10/13/2005
Project No. 4110
Project Name.:Abington Place
Computed by Rivanna Engineering
Project Description
Concrete V -Ditch
Ditch A
INPUT PARAMETERS
1. Channel Slope ft /ft)0.0200
2. Channel Bottom Width ft)0.00
3. Left Side Slope Horizontal to 1)12.00
4. Right Side Slope Horizontal to 1)12.00
5. Manning's Coefficient 0.013
6. Discharge cfs)0.99
7. Depth of Flow ft)0.16
OUTPUT RESULTS
Cross Section Area Sqft)0.31
Average Velocity ft /sec)3.21
Top Width ft)3.84
Hydraulic Radius ft)0.08
Froude Number 16.51
FHWA Urban Drainage Design Program, HY -22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Trapezoidal, Rectangular, or Triangular X- Section
Date: 10/13/2005
Project No. 4110
Project Name.:Abington Place
Computed by Rivanna Engineering
Project Description
Concrete V -Ditch
Ditch B
INPUT PARAMETERS
1. Channel Slope ft /ft)0.0240
2. Channel Bottom Width ft)0.00
3. Left Side Slope Horizontal to 1)12.00
4. Right Side Slope Horizontal to 1)12.00
5. Manning's Coefficient 0.013
6. Discharge cfs)0.90
7. Depth of Flow ft)0.15
OUTPUT RESULTS
Cross Section Area Sqft)0.27
Average Velocity ft /sec)3.32
Top Width ft)3.60
Hydraulic Radius ft)0.07
Froude Number 17.65
awr ave
FHWA Urban Drainage Design Program, HY -22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Trapezoidal, Rectangular, or Triangular X- Section
Date: 10/13/2005
Project No. 4110
Project Name.:Abington Place
Computed by Rivanna Engineering
Project Description
Concrete V -Ditch
Ditch C
INPUT PARAMETERS
1. Channel Slope ft /ft)0.0300--
2. Channel Bottom Width ft)0.00
3. Left Side Slope Horizontal to 1)12.00
4. Right Side Slope Horizontal to 1)12.00 1'dF
5. Manning's Coefficient 0.013 r
6. Discharge cfs)1.35 9'r
7. Depth of Flow ft)0.17 Id LIT 1,6
OUTPUT RESULTS
Cross Section Area Sqft)0.35
Average Velocity ft /sec)3.89
Top Width ft)4.08
Hydraulic Radius ft)0.08
Froude Number 19.44
Nur Niue
FHWA Urban Drainage Design Program, HY -22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Trapezoidal, Rectangular, or Triangular X- Section
Date: 10/13/2005
Project No. 4110
Project Name.:Abington Place
Computed by Rivanna Engineering
Project Description
Concrete V -Ditch
Ditch D
INPUT PARAMETERS
1. Channel Slope ft /ft)0.0200
2. Channel Bottom Width ft)0.00
3. Left Side Slope Horizontal to 1)12.00
4. Right Side Slope Horizontal to 1)12.00
5. Manning's Coefficient 0.013
6. Discharge cfs)0.77
7. Depth of Flow ft)0.14
OUTPUT RESULTS
Cross Section Area Sqft)0.24
Average Velocity ft /sec)3.29
Top Width ft)3.36
Hydraulic Radius ft)0.07
Froude Number 18.11
FHWA Urban Drainage Design Program, HY -22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Trapezoidal, Rectangular, or Triangular X- Section
Date: 10/13/2005
Project No. 4110
Project Name.:Abington Place
Computed by Rivanna Engineering
Project Description
Concrete V -Ditch
Ditch E
INPUT PARAMETERS
1. Channel Slope ft /ft)0.0215
2. Channel Bottom Width ft)0.00
3. Left Side Slope Horizontal to 1)12.00
4. Right Side Slope Horizontal to 1)12.00
5. Manning's Coefficient 0.013
6. Discharge cfs)0.85
7. Depth of Flow ft)0.15
OUTPUT RESULTS
Cross Section Area Sqft)0.27
Average Velocity ft /sec)3.16
Top Width ft)3.60
Hydraulic Radius ft)0.07
Froude Number 16.80
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29-03
Checked
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3063
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Chapter 9— Storm Drains
Appendix 9C-1 Flow in Triangular Gutter Sections
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4C
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0
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z
u. ,.
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s cr
1..3 60.01
tr:1--
i.... 0.1 6
0.06 -
0.02
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0,04_ _i,'.
a04 I 2
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1.__-.0.4
1 Fcr V-S!lApe, use :he romograph ./.111
t --' -
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0.004
2i Ta de'.errn i'.e d scharge in gutter v. 111
0.2
1---- W carrposi1 ups:, s ope... MIL: 0.1- ultic,
t T, and S, Then, J se App 9C-8 to
C ____.....- ---Fild Eo The Iola, d sciaryew
S),0- and C)0-0,.
S'S
Source:HEC No. 12, FHWA
1 of 1 VDOT Drainage Manual
FLEXIBLE PAVEMENT DESIGN
FOR
ABINGTON PLACE, PHASE 1
PRIVATE ROADS
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
Flexible Pavement Design
County: Albemarle Date: 19- Apr -05
Site: Abington Place
Street Name: Abington Drive
Developer: Southern Development Phone:
Station
CBR #1 7.50 19 +00
CBR #2 7.50 22 +00
CBR #3 7.50 25 +00
CBR #4 7.50 28 +00
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 350 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 350.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 10.77
Course Material Depth Equivalency D(p)
Surface SM -9.5A 2 1.67 3.34
Intermediate BM -25.0 0 2.25 0
Base 21A 8 1 8
Total Depth 10 Total D(p)11.34
D(p) -D(r) =0.57
D(p) >D(r) Therefore: ADEQUATE
Flexible Pavement Design
County: Albemarle Date: 26-Jul-05
Site: Hollymead Town Center
Street Name: Community Street
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 300 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 300.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 10.24
Course Material Depth Equivalency D(p)
Surface SM -9.5A 1.5 2.25 3.375
Intermediate BM -25.0 3 2.15 6.45
Base 21A 6 0.6 3.6
Total Depth 10.5 Total D(p)13.425
D(p) -D(r) =3.19
D(p) >D(r) Therefore: ADEQUATE
Flexible Pavement Design
County: Albemarle Date: 26-Jul-05
Site: Hollymead Town Center
Street Name: Aldersgate Way
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 600 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 600.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 12.65
Course Material Depth Equivalency D(p)
Surface SM -9.5A 1.5 2.25 3.375
Intermediate BM -25.0 3 2.15 6.45
Base 21A 6 0.6 3.6
Total Depth 10.5 Total D(p)13.425
D(p) -D(r) =0.78
D(p) >D(r) Therefore: ADEQUATE
DI -7 PERFORMANCE CURVES
FOR
ABINGTON PLACE, PHASE 1
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
Chapter 9— Storm Drams
Appendix 9C -14 Performance Curve 01-7 in a Sump
10 • 0Iw IIIINIIIIIIIiIIIIIII IIN IIIMMIII111111111111111111111111111111111111111111110311111111111111111111 al
11.01111111.1.1111111. MEI MOM IMIIIIIIIIMII ra
IIIIIIIIIIIIIIIIIIIIMIIIIIIIIMIII MI IIIIIIIIIIIIIIIIIIIIIMIMIIIIIMIIIIIIIIM II
MIEHM.1111111111111111111111111111 IIIIIIINIIIIIIIIIMPIIIIIIIIIIIIP r
1a 1111111111111111111illi
1111 I =
111111111111111111111111 Mill
eL 1.0 1111111111111111111111111111111111111111111111111111111111111 111111111111111111111111MMIIIIIIIIMPAIIIIIIIIIIIIIIII111111111111
NIHNNN NNNI!NN•N•IIoMMEMMIMMMM• e
MP OMMI Si MU1
II r. -u IIII III
0.5 __ C 200U iiaauiu
p ,P ri_IIllI
I111 111111
D FT`
PERIMETER
PEN AREA = 1.2 . FT
0 . I
1 5 10 50 100
DISCHARGE CFS)
S O
7 A = 0 . o ck c
Q = 0. IS((,.s1(v.oi 0,3 c'
f
Source:VDOT
1 of 1 VDOT Drainage Manual
Chapter 9 - Storm Drips
Appendix 9C -14 Performance Curve DI -7 in a Sump
10 . 0 momilim .n. mi _umwoo
IN11111•1111•1111111111110 1111•11/1111111111111
5.0 1111111111111111111111111111111111111111111111111111111111111111111110111
Miliall111111 1111111M11111511111111
w . 11111111111111111111111111111111111111111111111111111111111111MINIMMINEMINIMIIIIIIIIIIIIIIIMMIM
CD MONME.111111111111111111111111111 rlNI 1111 1111.1111111111111111111111111111 Ir
0. 11111111111111111111111 2/ 11/''..d11111111 111111
iHI 111111
Min
OPEN AREA = 6.0 FTC
111111PERtMETER
1 10 50 100
DISCHARGE CFS)
A=
c
u55 50 c1vcect
0. I =
S, s
JJ
Source:VDOT
1 of 1 VDOT Drainage Manual
YARD DRAIN CALCULATIONS
FOR
ABINGTON PLACE
PHASE 1
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
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FLEXIBLE PAVEMENT DESIGN
FOR
ABINGTON PLACE, PHASE 1
PUBLIC ROADS
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
Flexible Pavement Design
County: Albemarle Date: 26- Jul -05
Site: Hollymead Town Center
Street Name: Livingston Drive
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 500 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 500.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 12.01
Course Material Depth Equivalency D(p)
Surface SM -9.5A 1.5 2.25 3.375
Intermediate BM -25.0 3 2.15 6.45
Base 21A 6 0.6 3.6
Total Depth 10.5 Total D(p)13.425
D(p) -D(r) =1.41
D(p) >D(r) Therefore: ADEQUATE
Flexible Pavement Design
County: Albemarle Date: 09- Feb -04
Site: Hollymead Town Center
Street Name: Lockwood Drive
Developer: Southern Development Phone:
Station
CBR #1 7.50 All
CBR #2
CBR #3
CBR #4
CBR #5
CBR(d)5.00 Average CBR * (2/3)
RF 1.00 Resiliency Factor from Appendix I
SSV 5.00 Soil Support Value
Current ADT 2600 Average Daily Traffic Volume
Growth 0 per year
Design Year 0 Number of years after construction
HCV 5 Heavy Commercial Vehicles
Design ADT 2600.00 Average Daily Traffic Volume
This equation solves for D(r), which is used to determine pavement/stone thickness for a road.
D(r)= 17.75
Course Material Depth Equivalency D(p)
Surface SM -9.5A 2 2.25 4.5
Intermediate BM -25.0 4 2.15 8.6
Base 21A 8 0.6 4.8
Total Depth 14 Total D(p)17.9
D(p) -D(r) =0.15
D(p) >D(r) Therefore: ADEQUATE
BMP CALCULATIONS
FOR
ABINGTON PLACE
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
arl
Short Version BMP Computations For Worksheets 2 - 6AlbemarleCountyWaterProtectionOrdinance: Modified Simple MethodPlan:Abington Place at Hollymead
Water Resources Area:Preparers JDS
Date:14- Oct -05
Project Drainage Area Designation Bio- Filter #1L
storm pollutant export inRvmeanrunoffcoefficient, R = 0.0
L . [P(Pj)Rv/12 ] [ C(A)2.72 ]Pj small storm correction factor, 0.9 5 + 0.009(1)I
percent imperviousnessperviousness
annual precipitation, 43" in AlbemarleAprojectareainacresinsubjectdrainage area,
6.40
t
A
C
pollutant conc mg /I or ppm target phosphorus Z r 7 S4-f
factor applied to RRV
required treatment volume in c ,RR required removal , L(post)
0.5" over imperv. area = A IRRPost) f x L(pre)43560 (0.5/12) /27removalefficiency , RR100 /L post)
tj 4. (0C) 4 G' ° , aa 1 Computation (values in feet & square feet)
Impervious Cover
Item
pre- development Off.
r
1 $ ( 2
Area
i Roads
Length Width subtotal Post- development
0 0 0 Length Width Area
0 0 0 750 subtotal
770
32 2400001813860Lengtho1220
and walks g Width 0 14 17080no.subtotal Length Width no.
0 0 1 0 0 54940
Driveways Len
0 0 0 14 16 subtotal
Parkin 0
3485 88 19712ParkingLots
1 0 0 5 1 17425234Gravelareas
0
1 2 0 37137Area034
Structures x 0.70 =Area p 0Areano.subtotal
0
x 0.70000Areano.subtotal
0
0 0 0 870 63 54810Actively- grazed pasture &0 0 350Area00 76 26600yardsandcultivatedturf
Active crop land 0 x 0.08 =Area 0 81410Area0
105297 x 0.08OtherImperviousAreasx0.25 =Area 8423.760
x 0.25ImperviousCover _-0
q r 0
Drinking
0.64 280.7
l(pre)
l(po
New Development c42,._C
Pment (For Development Areas, existing impervious Q
0.70
f l (Pre) Rv(pre) L(pre) L(post) RR *
9 cover <= 20 %)t ,l, + 10 . 74
1.00
pre)*
0.35 1 0Q 0%
0.23 9.04 25.04 Area Type
t i Y0% 0,05 16.00 64% Development Area 1 1 l0.40 1.00 0.98 12.52 11.54 92min. values
1 O 0.06 1.32 14.392% 12'98 91% Other Rural Land
atersheds
D
Redevelopment I''pment (For Development Areas, existing impervious
0.70
f I (pre) Rv {prej L(pre) *re Pervious cover > 20%)0.90
e) *P ) L(post) RR o0.35 0.85 0%
0.23 9.04 25.04 16.90
RR
68% Developmentoppe
S.7
C
0.40 0.85 1 % 0.06 1.32 14.31
0.05 0.98 12 52 11 68 68% Development
r Watersheds
f
93 Drinking 9
13 18 92% Other Rural Land
9 Water Watersheds92 /°
Interim Manual, Page 70 1 t
rev. 16 Feb 1998 GEB
Cid LI"
PY Au
4
Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan:Abington Place Water Resources Area:Development
Preparer: JDB Date:14- Oct -05
Project Drainage Area Designation Bio- Filter #2
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
3
2.37Cpollutantconcentration, mg /1 or ppm target phosphorus Z 2 C
f factor applied to RR y 1' rrequiredtreatmentvolumeincy, 0.5" over imperv. area = A(I)43560(0.5/12)/27RRrequiredremoval , L(post) - f x L(pre)
RR removal efficiency , RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)Item
pre - development Area post - development AreaRoadsLengthWidthsubtotalLength, Width subtotal
450 14 63000007501813500
0 0 0 0
0 0 0 19800DrivewaysLengthWidthno.subtotal Length Width no.subtotalandwalks0010110051550000001616358960
0 0 0 14460ParkingLots134123400000GravelareasAreaArea
x 0.70 =0 x 0.70 =01StructuresAreano.subtotal Area no.subtotal0004301981700001000161600000000 24170Actively - grazed pasture &Area Areayardsandcultivatedturf0x0.08 =0 44807 x 0.08 =3584.56ActivecroplandAreaArea
x0.25=0 x0.25=0OtherImperviousAreas
0
Impervious Cover 0%
I q Lif
0%Cf/' v/
Rv(post)V 2 2 r66
P )}I(Po
0 .59 95.7 127 n 5 j (0 2
New Development (For Development Areas,ng ipervious cover <= 20 %)C f I (pre) * Rv(prej L(pre) L(post) RR A c rea Type c
t
0.70 1.00 20% 0.23 3.35 8.59 5.25 675 -Development Area
O
0.35 1.00 0% 0.05 0.36 4.30 3.93 92% Drinking Water Watersheds0.40 1.00 1% 0.06 0,49 4.91 4.42 90% Other Rural Landmin. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type 2-1(60.70 0.90 20% 0.23 3.35 8.59 5.58 65% Development Area0.35 0.85 0% 0.05 0.36 4.30 3.99 93% Drinking Water Watersheds0.40 0.85 1% 0.06 0.49 4.91 4.49 92% Other Rural Land 5 105-911
Interim Manual, Page 70 rev. 16 Feb 1998 GEB i P
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LD -229 Storm Drain Design Computations
Route; Abington Place Proj: Hollymead Towncenter
County: Albemarle District: Rivanna
Description: Pipe Calculations
From To Point Catch Runoff Inc Accum Tot Tot Tot Up Dn Pipe Inv Pipe Pipe Velocity Flow time
Point A Coef AC AC Tc Int Flow Inv Inv Len S Dim Cap Inc
ac)min) in /hr) cfs)El El ft)in)cfs)ft/s)min)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
ST -28 ST -27 0.33 0.80 0.26 0.26 5.0 6.81 1.80 564.00 563.43 44.0 1.30 15 7.35 2.95 0.25
ST -27 Outfall 0.33 0.80 0.26 0.53 5.2 6.74 3.56 562.90 560.97 89.0 2.17 15 9.51 7.28 0.20
ST -226 ST -22A 3.07 0.75 2.30 2.30 9 5.83 13.42 572.47 571.66 44.0 1.84 24 30.7 9.48 0.1
ST -22A ST -22 0.44 0.80 0.35 2.65 9.1 5.81 15.41 570.00 567.50 81.6 3.07 24 51.5 14.38 0.1
ST -24 ST -23 0.31 0.80 0.25 0.25 5 6.81 1.69 569.86 566.66 160.0 2.00 15 11.9 3.2 0.8
ST -23 ST -22 0.30 0.80 0.24 0.49 5.4 6.70 3.27 566.47 566.31 8.0 2.00 15 11.9 8.23 0.0
ST -22 ST -21 0.14 0.75 0.11 3.25 9.2 5.79 18.79 560.89 559.83 105.5 1.00 24 29.5 6.86 0.3
ST -21 ST -20A 0.08 0.70 0.06 3.30 9.5 5.73 18.94 559.38 559.22 32.0 0.50 30 37.7 4.78 0.1
ST -20A ST -20 -1 0.09 0.75 0.07 3.37 9.6 5.71 19.25 559.12 558.74 76.0 0.50 30 37.8 5.81 0.2
ST -20 -2 ST -20 -1 0.40 0.68 0.27 0.27 5 6.81 1.85 560.66 560.50 32.0 0.50 15 5.9 4.33 0.1
ST -20 -1 ST -20 0.23 0.72 0.17 3.81 9.8 5.67 21.59 558.64 558.16 97.0 0.50 36 47.1 5.65 0.3
ST -20 ST -19 0.00 0.00 0.00 3.81 10.1 5.61 21.37 559.38 559.22 32.0 0.50 30 37.7 4.78 0.1
ST -19E ST -19D 1.70 0.80 1.36 1.36 5.0 6.81 9.26 581.71 580.83 44.0 2.00 18 14.9 8.97 0.1
ST -19D ST -19CC 0.21 0.90 0.19 1.55 5.1 6.79 10.51 578.83 578.01 41.0 2.00 18 14.9 9.21 0.1
ST -19CC ST -19C 0.00 0.00 0.00 1.55 5.2 6.77 10.48 574.52 572.40 105.8 2.00 18 14.9 6.80 0.3
ST -19C ST -19B 0.35 0.80 0.28 1.83 5.4 6.69 12.24 570.40 569.70 32.0 2.19 18 15.5 9.81 0.1
ST -1913 ST -19A 0.29 0.85 0.25 2.08 5.5 6.68 13.86 567.05 565.00 97.7 2.10 24 32.8 10.11 0.2
ST -19A ST -19 0.45 0.85 0.38 2.46 5.6 6.63 16.31 562.25 562.03 18.0 1.22 24 32.3 10.41 0.0
ST -19 Outfall 0.03 0.90 0.03 6.29 9.9 5.64 35.52 557.28 556.00 256.5 0.50 36 47.1 7.20 0.6
ST -14A ST -14 0.19 0.80 0.15 0.15 5.0 6.81 1.04 546.55 546.25 32.5 0.92 15 8.06 4.58 0.1
ST -14 ST -13A 0.22 0.70 0.15 0.31 5.1 6.78 2.07 544.75 538.43 61.3 10.30 15 26.95 13.23 0.1
ST -13A ST -13 0.25 0.66 0.17 0.47 5.2 6.75 3.18 535.76 534.85 19.9 4.58 15 17.96 11.12 0.0
ST -13 Outfall 0.05 0.901 0.05 0.52 5.2 6.75 3.48 534.60 534.00 15.1 3.96 15 16.71 10.81 0.0
ST -16A Outfall 0.25 0.59 0.15 0.15 5.0 6.81 1.00 540.90 540.00 27.7 3.25 15 15.14 7.1 0.1
ST -18 ST -17 0.35 0.75 0.26 0.26 5.0, 6.81 1.79 550.50 550.20, 13.7 2.19 18 26.11 7.29 0.0
ST -17 ST -16 0.19 0.6 0.11 0.38 5.0 6.80 2.56 546.20 541.65 85.6 5.31 18 31.46 10.78 0.1
ST -16B ST -16 0.42 0.61 0.26 0.26 5.0 6.81 1.74 542.75 541.98 56.0 1.37 15 7.57 3.03 0.3
ST -16 ST -15 0.07 0.81 0.06 0.69 5.3 6.72 4.63 541.55 541.30 25.0 1.00 18 10.5 4.28 0.1
ST -15 Outfall 0.12 0.9 0.11 0.80 5.4 6.70 5.34 541.10 541.00 10.2 0.98 18 10.41 5.97 0.0
ST -11 ST -10 0.60 0.70 0.42 0.42 5.0 6.81 2.86 557.68 557.32 17.9 2.01 15 11.9 8.07,0.0
ST -10 ST -9 0.29 0.69 0.20 0.62 5.0 6.80 4.22 554.49 552.60 54.0 3.50 15 15.7 4.33 0.2
ST -9A ST -9 0.11 0.80 0.09 0.09 5.0 6.81 0.60 552.68 552.50 17.9 1.01 15 6.5 4.09 0.1
ST -9 ST -8 0.04 0.76 0.03 0.74 5.2 6.74 4.98 551.85 551.61 24.1 1.00 15 8.4 5.04 0.1
ST -8 ST -7 0.13 0.81 0.11 0.84 5.3 6.72 5.67 551.26 550.94 32.0 1.00 15 8.4 7.41 0.1
ST -7B ST -7A 0.37 0.62 0.23 0.23 5.0 6.81 1.56 555.56 555.24 32.3 0.99 15 8.4 2.83 0.2
ST -7A ST -7 0.18 0.77 0.14 0.37 5.2 6.76 2.49 555.14 553.90 91.2 1.36 15 9.8 6.75 0.2
ST -7 ST -6 0.12 0.75 0.09 1.30 5.4 6.70 8.72 549.39 549.21 18.0 1.00 18 13.7 8.27 0.0
ST -6 ST -5 0.00 0.00 0.00 1.30 5.4 6.69 8.71 546.80 541.84 90.8 5.46 18 31.9 5.78 0.3
ST -5A ST -5 0.10 0.80 0.08 0.08 5.0 6.81 0.54 542.09 541.91 18.0, 1.00 15 8.4 3.91 0.1
ST -5 ST -4 0.33 0.80 0.26 1.65 5.7 6.62 10.89 539.01 536.34 61.2 4.36 18 28.5 15.20 0.1
ST -4 ST -3 0.08 0.70 0.06 1.70 5.8 6.60 11.23 532.31 531.85 49.3 0.93 24 28.3 8.57 0.1
ST -3 ST -2 0.20 0.80 0.16 1.86 5.9 6.57 12.24 531.25 531.00 25.1 0.99 24 29.4 9.02 0.0
ST -2 ST -1 0.04 0.90 0.04 1.90 5.9 6.56 12.45 526.00 521.50 260.4 1.73 30 70.1 4.19 1.0
ST -1 Outfall 3.35 0.85 2.85 4.75 6.9 6.30 29.87 520.60 520.50 15.6 0.64 30 42.7 9.45 0.0
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1992 3.14
TEMPORARY SEDIMENT BASIN DESIGN DATA SHEET
with or without an emergency spillway)
Project AAj, f,c r * ckcs2_
Basin #53 1 Location p 3a -4(p
Total area draining to basin: 0, KS acres.
Basin Volume Design
Wet Storage:
1.Minimum required volume = 67 cu. yds. x Total Drainage Area (acres).
67 cu. yds. x 10 , ‘s acres = ('O cu. yds.
2.Available basin volume = s cu. yds. at elevation -, 1/.1(6. From
storage - elevation curve)
3.Excavate C cu. yds. to obtain required volume *.
Elevation corresponding to required volume = invert of the dewatering
orifice.
4.Available volume before cleanout required.
33 cu. yds. x yp, 15 acres = 33S cu. yds.
5.Elevation corresponding to cleanout level = X11. C2 -
From Storage - Elevation Curve)
6.Distance from invert of the dewatering orifice to cleanout level = x,17 ft.
Min. 1.0 ft.) d
Dry Storage:
7.Minimum required volume = 67 cu. yds. x Total Drainage Area (acres).
67 cu. yds. x 10.1 acres = Lo /D cu. yds.
II1 - 112
1992 3.14
8.Total available basin volume at crest of riser* cu. yds. at
elevation S31.30. (From Storage - Elevation Curve)
Minimum 134 cu. yds. /acre of total drainage area.
9.Diameter of dewatering orifice =C in.
10. Diameter of flexible tubing =in. (diameter of dewatering orifice
plus 2 inches).
Preliminary Design Elevations
11. Crest of Riser = Sa\ . 50
Top of Dam =5 • OD
Design High Water =3aa .00
Upstream Toe of Dam =516).5D
Basin Shape
12. Length of Flow L gib
Effective Width We 37f
If 2, baffles are not required 3.2
If < 2, baffles are required
Runoff
13. Q cfs From Chapter 5)
14. Q I cfs From Chapter 5)
r
Principal Spillway Design
15. With emergency spillway, required spillway capacity Q = Q =cfs.
riser and barrel)
Without emergency spillway, required spillway capacity Q = Q =cfs.
riser and barrel)
III - 113
1992 3.14
16. With emergency spillway:
Assumed available head (h) 0,7 ft. (Using Q
h Crest of Emergency Spillway Elevation Crest of Riser Elevation
Without emergency spillway:
Assumed available head (h) ft. (Using Q25)
h Design High Water Elevation - Crest of Riser Elevation
17. Riser diameter (D = 3Co in. Actual head (h) = p.c\ ft.
From Plate 3.14 -8.)
Note: Avoid orifice flow conditions.
18. Barrel length (1) _ft.
Head (H) on barrel through embankment = 10 ft.
From Plate 3.14 -7).
19. Barrel diameter =34 in.
From Plate 3.14 -B [concrete pipe] or Plate 3.14 -A [corrugated pipe]).
20. Trash rack and anti- vortex device
Diameter = sy-inches.
Height =j inches.
From Table 3.14 -D).
Emergency Spillway Design
21. Required spillway capacity Q = Q - Q 11. 1 cfs.
22. Bottom width (b) a. ft.; the slope of the exit channel (s)
O.ft. /foot; and the minimum length of the exit channel (x)
40 ft.
From Table 3.14 -C).
III - 114
1992 3.14
Anti -Seep Collar Design
23. Depth of water at principal spillway crest (Y) _ 1 ft.
Slope of upstream face of embankment (Z) _1.
Slope of principal spillway barrel (S = 1. a
Length of barrel in saturated zone (L = p ft.
24. Number of collars required = g dimensions =3.S
from Plate 3.14 -12).
Final Design Elevations
25. Top of Dam = Sa3
Design High Water = aa.ab
Emergency Spillway Crest =DO
Principal Spillway Crest = Sa 1.30
Dewatering Orifice Invert = SI1./d
Cleanout Elevation
Elevation of Upstream Toe of Dam
or Excavated Bottom of "Wet Storage
Area" (if excavation was performed) 51 (,
III - 115
Y_
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SEDIMENT BASIN CALCULATIONS
FOR
ABINGTON PLACE MASS GRADING PLAN
September 23, 2005
LOCATION:
Tax Map 32 Parcel 46
Albemarle County, Virginia
PREPARED BY:
Rivanna Engineering & Surveying, PLC
P.O. Box 7603
Charlottesville, VA 22906
P: 434.984.1599
F: 434.984.8863
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 9/23/2005
LOCATION BY JMS
INPUT
DRAINAGE AREA 10.40 ac
BASIN VOLUME DESIGN
WET STORAGE
1. MINIMUM REQUIRED VOLUME 696.80 cy
2. AVAILABLE BASIN VOLUME
AVERAGE END AREA - BASIN VOLUME ESTIMATES
ELEVATIOt AREA VOLUME VOLUME TOTAL
ft sf cf cy cy
532 3,200.00
8,277.00 306.56
534 5,077.00 306.56
14,433.00 534.56
536 9,356.00 841.11
22,788.00 844.00
538 13,432.00 1,685.11
REQUIRED WET STORAGE VOLUME 696.80 cy
APPROX. ELEVATION 535.29 x,
3. EXCAVATE CUBIC YARDS
4. AVAILABLE VOLUME BEFORE CLEANOUT REQUIRED 348.40 cy
5. ELEVATION CORRESPONDING TO CLEANOUT LEVEL 534.30
1
6. DISTANCE FROM DEWATERING ORIFICE TO C/O LEVEL
INVERT DEWATERING ORIFICE R'QD 535.29
INVERT DEWATERING ORIFICE USED 535.30
APPROX. VOLUME AT INVERT USED 703.01 cy
DISTANCE FROM INVERT TO C/O LEVEL 1.00 ft
DISTANCE ACCEPTABLE
WET STORAGE VOLUME ACCEPTABLE
DRY STORAGE
7. MINIMUM REQUIRED VOLUME 696.80 cy
8. TOTAL AVAILABLE VOLUME AT CREST OF RISER
CREST OF RISER 1 537.40
APPROX. AVAILABLE TOTAL VOLUME 1426.75 cy
ADEQUATE DRY STORAGE VOLUME
f
9. DIAMETER OF DEWATERING ORIFICE
q 0.90 cfs
d(1 ST ITERATION)5.80 In
d(2nd ITERATION)6.19 In
d(3rd ITERATION)6.22 In
d(4th ITERATION)6.23 in
USE d 6 In
10. DIAMETER OF FLEXIBLE TUBING 8 In
STANDARD SIZE
Page 1 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 9/23/2005
LOCATION BY JMS
PRELIMINARY DESIGN
11. PRELIMINARY DESIGN ELEVATIONS:
CREST OF RISER 537.40 ft
TOP OF DAM 539.40 ft
DESIGN HIGH WATER 538.20 ft
UPSTREAM TOE OF DAM 529.00 ft
BASIN SHAPE
12. LENGTH OF FLOW / EFFECTIVE WIDTH:
SURFACE AREA OF NORMAL POOL 9100 sf
LENGTH OF FLOW PATH 108 it
EFFECTIVE WIDTH 84 ft
L/We 1.28 BAFFLES REQUIRED
RUNOFF
RATIONAL METHOD CALCULATION)
USE MAXIMUM C VALUE DURING CON STRUCTION AND MINIMUM Tc VALUE
13. FLOW FROM 2 -YEAR STORM
C:0.50
Tc:5.0 I:5.5 In /hr
Q=28.6 cfs
14. FLOW FROM 25 -YEAR STORM
C:0.50
Tc:5.0 I:8.1 In /hr
Q=42.1 cis
PRINCIPAL SPILLWAY DESIGN
15. REQUIRED SPILLWAY CAPACITY:
EMERGENCY SPILLWAY? (YIN)Y
REQUIRED SPILLWAY CAPACITY:28.6 CFS
16. ASSUMED AVAILABLE HEAD:
ELEV. OF CREST OF E.S. IF USED:538.00
ASSUMED AVAILABLE HEAD=0.60 ft
17. RISER DIMENSIONS: I
RISER DIAMETER:36.00 In From Plate 3.14 -8 or Calcs)
ACTUAL MAX. ELEV.:537.40 tt From Calcs if appropriate)
ACTUAL HEAD:0.00 ft From Plate 3.14 -8 or Calcs)
18. BARREL LENGTH:
BARREL LENGTH:33.00 ft
BARREL INVERT OUT:529.00 ft
HEAD H ON BARREL:8.40 it From Plate 3.14 -7)
19. BARREL DIAMETER:
BARREL DIAMETER:24 In From Plate 3.14A or 3.14B)
20. TRASH RACK AND ANTI- VORTEX DEVICE:
DIAMETER:48 In From Plate 3.14D)
HEIGHT:24 in
Page 2 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abln •ton Place PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 9/23/2005
LOCATION BY JMS
EMERGENCY SPILLWAY DESIGN
21. REQUIRED SPILLWAY CAPACITY:
Qe = 0(25 -0. =13.5 CFS
22. DIMENSIONS:
BOTTOM WIDTH kb):18.00 ft From Table 3.14-C) -
SLOPE OF EXIT CHANNEL s:0.04 ft/ft From Table 3.14-_C)
MIN. LENGTH EXIT CHANNEL x:33.00 ft From Table 3.14-C)
ANTI-SEEP COLLAR DESIGN
23. DIMENSIONS:
DEPTH WATER @ CREST OF P.S. U:8.40 ft
SLOPE UPSTREAM FACE DAM 2.00 :1
SLOPE P.S. BARREL (Sb):6.10 %
LENGTH BARREL IN SAT. ZONE (Ls 60.00 ft From Plate 3.14-11)
24. NUMBER OF COLLARS: I
NUMBER REQUIRED:2 from Plate 3.14-12)
DIMENSIONS:5.0 ft"2 jFrom Plate 3.14-12)
FINAL DESIGN ELEVATIONS
25. ELEVATIONS:
TOP OF DAM:539.40 ft
DESIGN HIGH WATER:537.40 ft
EMERGENCY SPILLWAY CREST:538.00 ft
PRINCIPAL SPILLWAY CREST:537.40 ft
DEWATERING ORIFICE INVERT:535.30 ft
CLEANOUT ELEVATION:534.30 ft
Page 3 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place, EnS PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #2 DATE 9/23/2005
LOCATION BY JMS
INPUT
DRAINAGE AREA 8.90 ac
BASIN VOLUME DESIGN
WET STORAGE
1. MINIMUM REQUIRED VOLUME 596.30 cy
2. AVAILABLE BASIN VOLUME
AVERAGE END AREA - BASIN VOLUME ESTIMATES
ELEVATIOI AREA VOLUME VOLUME TOTAL
ft sf cf cy cy
544 2,037.00
7,711.00 285.59
546 5,674.00 285.59
15,224.00 563.85
548 9,550.00 849.44
23,231.00 860.41
550 13,681.00 1,709.85
REQUIRED WET STORAGE VOLUME 596.30 cy
APPROX. ELEVATION 547.03
3. EXCAVATE CUBIC YARDS
4. AVAILABLE VOLUME BEFORE CLEANOUT REQUIRED 298.15 cy
5. ELEVATION CORRESPONDING TO CLEANOUT LEVEL 546.20
f I I 1
6. DISTANCE FROM DEWATERING ORIFICE TO C/O LEVEL
INVERT DEWATERING ORIFICE R'QD 547.03
INVERT DEWATERING ORIFICE USED 547.20
APPROX. VOLUME AT INVERT USED 663.44 cy
DISTANCE FROM INVERT TO C/O LEVEL 1.00 ft
DISTANCE NOT ACCEPTABLE -1' R'QD
WET STORAGE VOLUME ACCEPTABLE
DRY STORAGE
7. MINIMUM REQUIRED VOLUME 596.30 cy
8. TOTAL AVAILABLE VOLUME AT CREST OF RISER
CREST OF RISER 1 548
APPROX. AVAILABLE TOTAL VOLUME 1268.75 cy
ADEQUATE DRY STORAGE VOLUME
9. DIAMETER OF DEWATERING ORIFICE
Q 0.76 cfs
d(1ST ITERATION)5.59 In
d(2nd ITERATION)6.06 In
d(3rd ITERATION)6.11 In
d(4th ITERATION)6.11 In
USE d 6 in
10. DIAMETER OF FLEXIBLE TUBING 8 In
STANDARD SIZE
Page 1 Abington - SB.xis
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place, EnS PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #2 DATE 9/23/2005
LOCATION BY JMS
PRELIMINARY DESIGN
11. PRELIMINARY DESIGN ELEVATIONS:
CREST OF RISER 548.90 ft
TOP OF DAM 550.80 ft
1 DESIGN HIGH WATER 549.30 ft
UPSTREAM TOE OF DAM 541.00 ft
BASIN SHAPE
12. LENGTH OF FLOW / EFFECTIVE WIDTH:
SURFACE AREA OF NORMAL POOL 8500 sf
LENGTH OF FLOW PATH 90 ft
EFFECTIVE WIDTH 94 ft
1/We 0.95 BAFFLES REQUIRED
RUNOFF
RATIONAL METHOD CALCULATION)
USE MAXIMUM C VALUE DURING CONSTRUCTION AND MINIMUM Tc VALUE
13. FLOW FROM 2-YEAR STORM
C:0.50
Tc:5.0 5.5 In/hr
0=24.5 cfs
14. FLOW FROM 25-YEAR STORM
C:0.50
Tc:5.0 8.1 in/hr
Ct.36.0 cfs
PRINCIPAL SPILLWAY DESIGN
T
15. REQUIRED SPILLWAY CAPACITY:
EMERGENCY SPILLWAY? (Y/N)
REQUIRED SPILLWAY CAPACITY:24.5 CFS
16. ASSUMED AVAILABLE HEAD:
ELEV. OF CREST OF E.S. IF USED:549.30
ASSUMED AVAILABLE HEAD=0.40 ft
17. RISER DIMENSIONS: 1
RISER DIAMETER:36.00 In From Plate 3.14-8 or Calcs)
ACTUAL MAX. ELEV.:548.90 ft From Calcs if appropriate)
ACTUAL HEAD:0.00 ft From Plate 3.14-8 or Calcs)
18. BARREL LENGTH: 1
BARREL LENGTH:37.00 ft
BARREL INVERT OUT:540.30 ft
HEAD H ON BARREL:8.60 ft From Plate 3.14-7)
19. BARREL DIAMETER: 1
1 BARREL DIAMETER:24 In From Plate 3.14A or 3.14B)
20. TRASH RACK AND ANTI-VORTEX DEVICE:
DIAMETER:48 In From Plate 3.14D)
HEIGHT:24 In
Page 2 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place, EnS PROJ NO
BASIN #TEMPORARY SEDIMENT BASIN #2 DATE 9/23/2005
LOCATION BY JMS
EMERGENCY SPILLWAY DESIGN
21. REQUIRED SPILLWAY CAPACITY:
Qe = Q(25)-Qp =11.6 CFS
22. DIMENSIONS:
BOTTOM WIDTH (b):16.00 ft fFrom Table 3.14-C)
SLOPE OF EXIT CHANNEL (s):0.04 fVft From Table 3.14-C)
MIN. LENGTH EXIT CHANNEL (x):33.00 It From Table 3.14-C)
ANTI-SEEP COLLAR DESIGN
23. DIMENSIONS:
DEPTH WATER @ CREST OF P.S. (Y):7.90 ft
SLOPE UPSTREAM FACE DAM 174 2.00 :1
SLOPE P.S. BARREL (Sb):7.30 %
LENGTH BARREL IN SAT. ZONE (Ls):70.00 ft From Plate 3.14-11)
24. NUMBER OF COLLARS: r
NUMBER REQUIRED:2 From Plate 3.14-12)
DIMENSIONS:5.3 ft"2 From Plate 3.14-12)
FINAL DESIGN ELEVATIONS
F
25. ELEVATIONS:
TOP OF DAM:550.80 ft
DESIGN HIGH WATER:548.90 ft
EMERGENCY SPILLWAY CREST:549.30 ft
PRINCIPAL SPILLWAY CREST:548.90 ft
DEWATERING ORIFICE INVERT:547.20 ft
CLEANOUT ELEVATION:546.20 ft
Page 3 Abington - SB.xls
EROSION AND SEDIMENT CONTROL NARRATIVE
FOR
ABINGTON PLACE AT HOLLYMEAD TOWNCENTER
February 28, 2006
LOCATION:
Tax Map 32 Parcel 46
Rivanna District, Albemarle County, Virginia
DEVELOPER
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
434.984.1599
F) 434.984.8863
A. MINIMUM STANDARDS (MS):
All applicable Virginia Erosion and Sediment Control Regulations and Minimum Standards
shall be adhered to during all phases of construction. These include, but are not limited to
the following:
1. STABLIZATION OF DENUDED AREAS:
Permanent or temporary soil stabilization shall be applied to bare areas within seven days
after final grade is reached on any portion of the site. Temporary soil stabilization shall be
applied within seven days to denuded areas that may not be at final grade, but will remain
dormant or undisturbed for longer than 30 days. Permanent stabilization shall be applied
at areas that are to be left dormant for more than 1 year.
2. STABILIZATION OF SOIL STOCKPILES:
During construction of the project, soil stockpiles shall be stabilized or protected with
sediment trapping measures. The applicant is responsible for temporary protection and
permanent stabilization of all soil stockpiles on site as well as soil intentionally transported
from the project site.
3. PERMANENT VEGETATIVE COVER
A permanent vegetative cover shall be established on denuded areas not otherwise
permanently stabilized. Permanent vegetation shall not be considered established until a
ground cover is achieve that, in the opinion of the county Inspector, is uniform and mature
enough to survive to inhibit erosion.
4. TIMING & STABILIZATION OF SILT TRAPPING MEASURES:
Sediment basins and traps, perimeter dikes, sediment barriers and other measures
intended to trap sediment shall be constructed as a first step in any land disturbing activity
and shall be made functional before upslope land disturbance takes place.
5. STABILIZATION OF EARTHEN STRUCTURES:
Stabilization measures shall be applied to earthen structures such as dams, dikes and
diversions immediately after installation.
6. SEDIMENT TRAPS AND BASINS:
A sediment basin shall control surface runoff from disturbed areas that is comprised of
flow from drainage areas greater than or equal to three acres. The sediment basin shall
be designed and constructed to accommodate the anticipated sediment loading for the
land disturbing activity. The outfall device or system device shall take into account the
total drainage area flowing through the disturbed area to be served by the basin.
7. CUT AND FILL SLOPES:
Cut and fill slopes shall be designed and constructed in a manner that will minimize
erosion. Slopes that are found to be eroding excessively within one year of permanent
stabilization shall be provided with additional slope stabilizing measures until the problem
is corrected.
8. CONCENTRATED RUN -OFF DOWN CUT OR FILL SLOPES:
Concentrated runoff shall not flow down cut or fill slopes unless contained within an
adequate temporary or permanent channel, flume, or slope drain structure.
1
9. WATER SEEPS FROM A SLOPE FACE:
Whenever water seeps from a slope face, adequate drainage or other protection shall t e
provided.
10. STORM SEWER INLET PROTECTION:
All storm sewer inlets that are made operable during construction shall be protected sc
that sediment -laden water cannot enter the conveyance system without first being filter ed
or otherwise treated to remove sediment.
11. STABILIZATION OF OUTLETS:
Before newly constructed stormwater conveyance channels are made operational,
adequate outlet protection and any required temporary or permanent channel lining sh.ill
be installed in both the conveyance channel and receiving channel.
12. WORK IN LIVE WATERCOURSES:
When work in a live watercourse is performed, precautions shall be taken to minimize
encroachment, control sediment transport and stabilize the work area to the greatest
extent possible during construction. Nonerodible material shall be used for the
construction of causeways and cofferdams. Earthen fill may be used for these structur s s if
armored by nonerodible cover materials.
13. CROSSING A LIVE WATERCOURSE:
When a live watercourse must be crossed by construction vehicles more than twice in -my
six month period, a temporary stream crossing constructed of nonerodible materials shut all
be provided.
14. APPLICABLE REGULATIONS:
All applicable federal, state and local regulations pertaining to working in or crossing lip --•e
watercourses shall be met.
15. STABILIZATION OF BED AND BANKS
The bed and banks of a watercourse shall be stabilized immediately after work in the
watercourse is completed.
16. UNDERGROUND UTILITIES:
Underground utilities shall be installed in accordance with the following standards in
addition to other criteria:
a. No more than 500 linear feet of trench may be opened at one time.
b. Excavated material shall be placed on the uphill side of trenches
c. Effluent for dewatering operations shall be filtered or passed through approved
sediment trapping device, or both, and discharged in a manner that does not adver --- ely
affect flowing streams or offsite property.
d. Material used for backfilling trenches shall be properly compacted in order to minim – ate ize
erosion and promote stabilization.
e. Restabilization shall be accomplished in accordance with these regulations.
f. Applicable safety regulations shall be complied with.
2
17. CONSTRUCTION ACCESS ROUTES:
Where construction vehicle access routes intersect paved public roads, provisions shall be
made to minimize the transport of sediment by vehicular tracking onto paved surfaces.
Where sediment is transported on to a public road surface, the road shall be cleaned
thoroughly at the end of each day. Sediment shall be removed by shoveling or sweeping
and transported to a sediment control disposal area. Street washing shall be allowed only
after sediment is removed in this manner. This provision shall apply to individual lots as
well as to larger land disturbing activities.
18. TEMPORARY E &S CONTROL MEASURE REMOVAL:
All temporary erosion and sediment control measures shall be removed within 30 days
after final site stabilization or after temporary measures are no longer needed, unless
otherwise authorized by the local program authority. Trapped sediment and the disturbed
soil areas resulting from the disposition of temporary measures shall be permanently
stabilized to prevent further erosion and sediment.
19. ADEQUACY OF RECEIVING CHANNELS:
Properties and waterways downstream from the development site shall be protected from
sediment deposition, erosion and damage, due to increases in volume, velocity and peak
flow rates of stormwater runoff for the stated frequency storm of 24 -hour duration.
B1. PROJECT DESCRIPTION:
The purpose of this project is to build an 88 lot townhouse development. The total area to
be disturbed by this project will be 14.1 acres.
B2. EXISTING SITE CONDITIONS:
The site is currently grassed with mixed deciduous trees. The current vegetation is small
trees and brush. The existing topography is rolling terrain with slopes of 10 -20 %.
B3. ADJACENT AREAS:
The site is bounded to the east, west and south by the Hollymead Towncenter
development, which is mixed use. To the north is the existing Deerwood subdivision.
B4. SOIL DESCRIPTIONS:
According to the Albemarle County Soils Survey conducted by the United States
Department of Agriculture Soil Conservation Service, the primary soil types that may be
disturbed during this scope of work have been identified as the following:
1. Loisburg sandy loam (47C) — Permeability is rapid, surface runoff is rapid, and
the hazard of erosion is severe. Hydrologic group B, K factor .24
2. Wedowee sandy loam (94B) — Permeability is moderate, surface runoff is
medium, and the hazard of erosion is moderate. Hydrologic group B, K factor
28
3. Wedowee sandy loam (94C) — Permeability is moderate, surface runoff is rapid,
and the hazard of erosion is severe. Hydrologic group B, K factor .28
3
B5. CRITICAL AREAS:
The stream along the north property line with Deerwood subdivision is a critical area, and
a 50' undisturbed stream buffer must be maintained.
B6. EROSION AND SEDIMENT CONTROL MEASURES:
Unless otherwise indicated, all erosion and sediment control practices will be constructed
and maintained according to the minimum standards and specifications as set forth in the
Virginia Erosion and Sediment Control Handbook, latest edition. The minimum standards
of the Virginia Erosion and Sediment Control Regulations shall be adhered to unless
otherwise waived or approved by variance.
SAFETY FENCE (SAF) — 3.01
Safety fence will be installed to prevent access to erosion control measures. Location and details
are shown on the plans.
TEMPORARY CONSTRUCTION ENTRANCE (CE) — 3.02
An asphalt pad shall be constructed at the entrance of the project site to provide a means
of removing sediment from the tires of construction vehicles leaving the work site. The
Contractor shall remove any mud from the existing road surface by means of sweeping
and shoveling, in the event the asphalt pad is not adequate in sediment removal.
SILT FENCE (SF) — 3.05
Silt fencing will be installed as a first step in construction activities. Location and details
are shown on the plans.
STORM DRAIN INLET PROTECTION (IP) — 3.07
A sediment filter around a storm drain drop inlet or curb inlet used to prevent sediment
from entering storm drainage systems prior to permanent stabilization of the disturbed
area. Location and details of inlet protection are shown on the plans.
CULVERT INLET PROTECTION (CIP) — 3.08
Culvert inlet protection will be installed according to Virginia Erosion and Sediment Control
regulations. Location and details are shown on the plans.
TEMPORARY DIVERSION DIKE (DD) — 3.09
A temporary diversion dike will be installed before site grading begins, for the purposes of
diverting storm and sediment -laden runoff to the appropriate outlet or trapping facility.
Location and details are shown on the plans.
TEMPORARY RIGHT -OF -WAY DIVERSION (RWD) — 3.11
Temporary right -of -way diversion will be installed to shorten the flow length within a
sloping right -of -way, thereby reducing the erosion potential by diverting storm runoff to a
stabilized outlet. Location and details for the right -of -way diversion are shown on the
plans.
TEMPORARY SEDIMENT TRAP (ST) — 3.13
A temporary sediment trap will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment traps are shown on the plans.
4
TEMPORARY SEDIMENT BASIN (SB) — 3.14
A temporary sediment basin will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment basins are shown on the plans.
OUTLET PROTECTION (OP) — 3.18
Outlet protection will be installed according to Virginia Erosion and Sediment Control
regulations. Location and details are shown on the plans.
DUST CONTROL (DC) — 3.39
A variety of methods are available to prevent surface and air movement of dust from
exposed soil surfaces and reduce the presence of airborne substances which may
present health hazards, traffic safety problems or harm animal or plant life.
B7. PERMANENT AND TEMPORARY STABILIZATION:
SURFACE ROUGHENING — 3.29
Disturbed areas to be seeded and mulched shall be left in a roughened condition to help
decrease runoff velocities and aid in the establishment of vegetation.
TOPSOILING — 3.30
Topsoil may be stripped from the area to be graded and stockpiles for later use. All
stockpiles which will be left dormant for more than 30 days shall be temporarily seeded. A
topsoil stockpile may be selected onsite by the developer and shall be temporarily
protected with surrounding silt fencing.
TEMPORARY SEEDING — 3.31
Temporary soil stabilization shall be applied within 7 days to denuded areas that may not
be at final grade, but will remain dormant (undisturbed) for longer than 30 days and less
than 1 year. This includes, but is not limited to areas such as soil stockpiles. Seeded
areas shall be limed when necessary at a rate of 2 tons per acre, and fertilized at a rate of
450 lbs. per acre of 10 -20 -20 (10 lbs. per 1,000 square feet) or equivalent. A Temporary
Seeding Schedule is attached for proper seed selection.
PERMANENT SEEDING —3.32
A perennial vegetative covering shall be established on disturbed areas within 7 days of
being brought to final grade on areas not otherwise protected. Selection of the seed
mixture shall depend on the time of year it is to be applied according to the Permanent
Seed Schedule as shown on the drawing. Seeded areas shall be limed when necessary
at a rate of 2 tons per acres, and fertilized at a rate of 1,000 lbs. per acre of 10 -20 -10 (10
lbs. per 1,000 square feet) or equivalent.
MULCHING — 3.35
All seeded areas shall be mulched with straw immediately following seeding operations.
Straw mulch shall be applied at a rate of two tons per acre.
SOIL STABILIZATION BLANKETS AND MATTING — 3.36
Soil stabilization matting shall be applied in the conveyance areas of the designed
diversions to help reduce velocities and aid in the establishment of vegetation. A detail
showing the proper materials and installation is shown on the plan.
5
B8. SOIL STOCKPILES AND BORROW AREAS
Fill material for this project will be obtained from the Hollymead Towncenter -- Area A
property. An erosion plan has been approved for that property.
B9. STORM WATER MANAGEMENT:
Hollymead Towncenter Stormwater Management Facility SWM -2, which is just upstream
of the site, provides stormwater detention for this development.
B10. MAINTENANCE SCHEDULE:
A program of maintenance for the erosion and sediment controls specified in this narrative
and shown on the plans are recommended as follows:
1. The Site Superintendent or his representative shall make a visual inspection of all
erosion and sediment controls on a daily basis until the site is stabilized and especially
after a heavy rainfall to assure that all controls are in place and that none have been
damaged. Any damaged control shall be repaired prior to the end of each workday to
include re- seeding if necessary.
2. All silt trapping devices shall be cleaned out at 50 percent capacity and sediment shall
be disposed of by spreading on site or hauling away if not suitable for fill.
3. Gravel outlets shall be checked regularly for sediment buildup that may prevent
drainage. Controls shall be inspected and repaired after each rainfall and cleaned if
sediment has accumulated to half of the device's original height.
4. All earthen structures such as diversion dikes and berms shall be checked daily during
construction for breaching by equipment. Repairs shall be made immediately.
5. Silt fences shall be checked after each rainstorm to assure they have not fallen or
become clogged with silt. All repairs shall be made immediately.
6. All seeded areas shall be inspected regularly to see that good stand is maintained.
Areas will be re- fertilized and re- seeded as necessary.
7. After construction operations have ended and disturbed areas have been stabilized, all
berms and sediment - trapping devices may be removed after removal, the ground shall
be restored to its natural or proposed condition to include establishment of permanent
vegetation. Removal of any control is contingent upon approval of the County
Inspector.
6
EROSION CALCULATIONS FOR
ABINGTON PLACE AT HOLLYMEAD TOWNCENTER
March 2, 2006
LOCATION:
Tax Map 32 Parcel 46
Rivanna District, Albemarle County, Virginia
OWNER:
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC.
1350 Stony Point Rd.
Charlottesville, VA 22911
434) 984 -1599
F: (434) 984 -8863
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SEDIMENT BASIN
PROJECT Abington Place PROJ NO.
BASIN #SEDIMENT BASIN 41 DATE 2/24/2006
LOCATION BY ABB
INPUT
DRAINAGE AREA 10.15 ac
BASIN VOLUME DESIGN
WET STORAGE
1. MINIMUM REQUIRED VOLUME 680.05 cy
2. AVAILABLE BASIN VOLUME
AVERAGE END AREA - BASIN VOLUME ESTIMATES
1 1 1
516.4 0.00 0.00
346.10 12.82
516.5 6.922,00 12.82
7,239.00 268.11
517.5 7,556.00 280.93
7,876.00 291.70
518.5 8,196.00 1 572.63
17,692.00 655.26
520.5 9,496.00 1,227.89
16,530.00 612.22
522 12.544.00 1,840.11
REQUIRED WET STORAGE VOLUME 680.05 cy
APPROX. ELEVATION 518.75
3. EXCAVATE CUBIC YARDS
4. AVAILABLE VOLUME BEFORE CLEANOUT REQUIRED 340.03 cy
5. ELEVATION CORRESPONDING TO CLEANOUT LEVEL 517.62
6. DISTANCE FROM DEWATERING ORIFICE TO CIO LEVEL
INVERT DEWATERING ORIFICE R'QD 518.75
INVERT DEWATERING ORIFICE USED 519.00
APPROX. VOLUME AT INVERT USED 754.98 cy
DISTANCE FROM INVERT TO C/O LEVEL 1.38 ft
DISTANCE ACCEPTABLE
WET STORAGE VOLUME ACCEPTABLE
DRY STORAGE
7. MINIMUM REQUIRED VOLUME 680.05 cy
8. TOTAL AVAILABLE VOLUME AT CREST OF RISER
CREST OF RISER 521.50
APPROX. AVAILABLE TOTAL VOLUME 1505.25,cy
ADEQUATE DRY STORAGE VOLUME
9. DIAMETER OF DEWATERING ORIFICE
0 0.94 cfs
d(1ST ITERATION)5.65 in
d(2nd ITERATION)5.96 in
d(3rd ITERATION)5.98 in
d(4th ITERATION)5.98 in
USE d 6 in
10. DIAMETER OF FLEXIBLE TUBING 8 i
STANDARD SIZE
Page 1 ABINGTON- REV- SB1.XLS
Abington Place Subdivision
Sediment Trap Calculations
NO. A B C X W
WEIR DRAINAGE WET
D1
Al Al DRY
D2
A2 A2
LENGTH AREA VOL.Req) Prov) VOL.Req) Prov)
1 549 552 554 3 2 9 1.51 2732 3 1071 1133 2732 2 1660 1698
ABINGTON -REV SEDIMENT TRAP.XLS 3/2/2006
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STORM SEWER CALCULATIONS
FOR
ABINGTON PLACE SITE PLAN
July 29, 2005
LOCATION:
Tax Map 32 Parcel 46
Albemarle County, Virginia
PREPARED BY:
Rivanna Engineering & Surveying, PLC
P.O. Box 7603
Charlottesville, VA 22906
P: 434.984.1599
F: 434.984.8863
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A.
STORM SEWER CALCULATIONS
FOR
ABINGTON PLACE SITE PLAN
July 29, 2005
LOCATION:
Tax Map 32 Parcel 46
Albemarle County, Virginia
PREPARED BY:
Rivanna Engineering & Surveying, PLC
P.O. Box 7603
Charlottesville, VA 22906
P: 434.984.1599
F: 434.984.8863
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HYDROLOGIC/HYDRAULIC CALCULATIONS
FOR
ABINGTON PLACE AT HOLLYMEAD TOWNCENTER
BIOFILTER-1
March 2, 2006
LOCATION:
Rio District, Albemarle County, Virginia
OWNER:
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
INDEX
Summary:2
Post-Development:
DA-A Hydrographs:3-8
Pond & Outlet Structure:9-13
Routed Hydrographs:14-19
Drainage Area Maps are included attached at the end of this report.
feN vL 7
Rivanna Engineering & Surveying, PLC Page 1
434) 984-1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Summary
Two bio- filters will provide stormwater management for Abington Place at Hollymead Towncenter. Drainage
area DA -A flows into Bio - Filter -1.
Rivanna Engineering & Surveying, PLC Page 2
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
Name:DA- Abington 'A' 2 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)17.86 (cfs)
Time to Peak (Tp)12.00 (min)
Time of Base (Tb)30.00 (min)
Volume 0.37 ac -ft)
Time Step 1.00 (min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 (cfs)
Maximum Storage 0.37 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 6.47 NA 0.69
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)12.00 (min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 0.79 (in)
Return Period 2 (yr)
Storm Duration 0.20 (hr)
Rivanna Engineering & Surveying, PLC Page 3
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
DA- Abington 2 Ye
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.07 0.00 1.49
2 2.00 0.07 0.13 1.49 2.98
3 3.00 0.07 0.20 1.49 4.46
4 4.00 0.07 0.26 1.49 5.95
5 5.00 0.07 0.33 1.49 7.44
6 6.00 0.07 0.40 1.49 8.93
7 7.00 0.07 0.46 1.49 10.42
8 8.00 0.07 0.53 1.49 11.91
9 9.00 0.07 0.60 1.49 13.39
10 10.00 0.07 0.66 1.49 14.88
11 11.00 0.07 0.73 1.49k6 ^gym
12 12.00 0.07 0.79 1.4917.86,13 13.00 0.00 0.79 0.99 T
14 14.00 0.00 0.79 0.99 15.87
15 15.00 0.00 0.79 0.99 14.88
16 16.00 0.00 0.79 0.99 13.89
17 17.00 0.00 0.79 0.99 12.90
18 18.00 0.00 0.79 0.99 11.91
19 19.00 0.00 0.79 0.99 10.91
20 20.00 0.00 0.79 0.99 9.92
21 21.00 0.00 0.79 0.99 8.93
22 22.00 0.00 0.79 0.99 7.94
23 23.00 0.00 0.79 0.99 6.95
24 24.00 0.00 0.79 0.99 5.95
25 25.00 0.00 0.79 0.99 4.96
26 26.00 0.00 0.79 0.99 3.97
27 27.00 0.00 0.79 0.99 2.98
28 28.00 0.00 0.79 0.99 1.98
29 29.00 0.00 0.79 0.99 0.99
30 30.00 0.00 0.79 0.99 0.00
Rivanna Engineering & Surveying, PLC Page 4
434) 984 -1599
4
Abington Place at Hollymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
Name:DA- Abington 'A' 10 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)24.95 (cfs)
Time to Peak (Tp)12.00 (min)
Time of Base (Tb)30.00 (min)
Volume 0.52 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 cfs)
Maximum Storage 0.52 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 6.47 NA 0.69
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)12.00 min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 1.11 in)
Return Period User Defined (yr)
Storm Duration 0.20 hr)
Rivanna Engineering & Surveying, PLC Page 5
434) 984 -1599
Abington Place at Hoflymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
DA- Abington 'A' 10 Year
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.09 0.00 2.08
2 2.00 0.09 0.18 2.08 4.16
3 3.00 0.09 0.28 2.08 6.24
4 4.00 0.09 0.37 2.08 8.32
5 5.00 0.09 0.46 2.08 10.40
6 6.00 0.09 0.55 2.08 12.48
7 7.00 0.09 0.65 2.08 14.56
8 8.00 0.09 0.74 2.08 16.64
9 9.00 0.09 0.83 2.08 18.72
10 10.00 0.09 0.92 2.08 20.80
11 11.00 0.09 1.02 2.08 22.87
12 12.00 0.09 1.11 2.08 24.95
13 13.00 0.00 1.11 1.39 23.57
14 14.00 0.00 1.11 1.39 22.18
15 15.00 0.00 1.11 1.39 20.80
16 16.00 0.00 1.11 1.39 19.41
17 17.00 0.00 1.11 1.39 18.02
18 18.00 0.00 1.11 1.39 16.64
19 19.00 0.00 1.11 1.39 15.25
20 20.00 0.00 1.11 1.39 13.86
21 21.00 0.00 1.11 1.39 12.48
22 22.00 0.00 1.11 1.39 11.09
23 23.00 0.00 1.11 1.39 9.70
24 24.00 0.00 1.11 1.39 8.32
25 25.00 0.00 1.11 1.39 6.93
26 26.00 0.00 1.11 1.39 5.55
27 27.00 0.00 1.11 1.39 4.16
28 28.00 0.00 1.11 1.39 2.77
29 29.00 0.00 1.11 1.39 1.39
30 30.00 0.00 1.11 1.39 0.00
Rivanna Engineering & Surveying, PLC Page 6
434) 984-1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
Name:DA- Abington 'A' 100 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)35.84 (cfs)
Time to Peak (Tp)12.00 (min)
Time of Base (Tb)30.00 (min)
Volume 0.74 ac -ft)
Time Step 1.00 (min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 (cfs)
Maximum Storage 0.74 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 6.47 NA 0.69
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)12.00 (min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 1.59 (in)
Return Period 100 (yr)
Storm Duration 0.20 (hr)
Rivanna Engineering & Surveying, PLC Page 7
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Post - Development Hydrographs
DA- Abington 'A' 100 Year
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.13 0.00 2.99
2 2.00 0.13 0.27 2.99 5.97
3 3.00 0.13 0.40 2.99 8.96
4 4.00 0.13 0.53 2.99 11.95
5 5.00 0.13 0.66 2.99 14.93
6 6.00 0.13 0.80 2.99 17.92
7 7.00 0.13 0.93 2.99 20.91
8 8.00 0.13 1.06 2.99 23.89
9 9.00 0.13 1.19 2.99 26.88
10 10.00 0.13 1.33 2.99 29.87
11 11.00 0.13 1.46 2.99 32.85
12 12.00 0.13 1.59 2.99 35.84
13 13.00 0.00 1.59 1.99 33.85
14 14.00 0.00 1.59 1.99 31.86
15 15.00 0.00 1.59 1.99 29.87
16 16.00 0.00 1.59 1.99 27.88
17 17.00 0.00 1.59 1.99 25.89
18 18.00 0.00 1.59 1.99 23.89
19 19.00 0.00 1.59 1.99 21.90
20 20.00 0.00 1.59 1.99 19.91
21 21.00 0.00 1.59 1.99 17.92
22 22.00 0.00 1.59 1.99 15.93
23 23.00 0.00 1.59 1.99 13.94
24 24.00 0.00 1.59 1.99 11.95
25 25.00 0.00 1.59 1.99 9.96
26 26.00 0.00 1.59 1.99 7.96
27 27.00 0.00 1.59 1.99 5.97
28 28.00 0.00 1.59 1.99 3.98
29 29.00 0.00 1.59 1.99 1.99
30 30.00 0.00 1.59 1.99 0.00
Rivanna Engineering & Surveying, PLC Page 8
434) 984 -1599
I
Abington Place at Hollymead Towncenter, Bio- Filter -1
Pond Report
Name: Water Quality Pond
RATING CURVE LIMIT]
Minimum Elevation 516.50 ft)
Maximum Elevation 523.00 ft)
Elevation Increment 0.20 ft)
STAGE STORAGE INFORMATION]
Storage Method: User - Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative
Volume
ft)sq ft)sq ft)cu ft)cu ft)
1 516.50 0.00 0.00 0.00 0.00
2 520.20 0.00 0.00 0.00 0.00
3 520.30 9496.00 4748.00 474.80 474.80
4 522.50 13545.00 11520.50 25345.10 25819.90
5 523.00 14592.00 14068.50 7034.25 32854.15
DISCHARGE INFORMATION]
Structure Number: 1
Type:
Name:Stand Pipe
Structure Number: 2
Type:Trapezoidal Weir
Name:Bio - Filter #1 Weir
RESERVOIR STAGE STORAGE /DISCHARGE]
Elevation Stage Area Storage Discharge
ft)ft)sq ft)cu ft)cfs)
516.50 0.00 0.00 0.00 0.00
516.70 0.20 0.00 0.00 0.00
516.90 0.40 0.00 0.00 0.00
517.10 0.60 0.00 0.00 0.00
517.30 0.80 0.00 0.00 0.00
517.50 1.00 0.00 0.00 0.00
517.70 1.20 0.00 0.00 0.00
517.90 1.40 0.00 0.00 0.00
518.10 1.60 0.00 0.00 0.00
518.30 1.80 0.00 0.00 0.00
518.50 2.00 0.00 0.00 0.00
518.70 2.20 0.00 0.00 0.00
518.90 2.40 0.00 0.00 0.00
519.10 2.60 0.00 0.00 0.00
519.30 2.80 0.00 0.00 0.00
519.50 3.00 0.00 0.00 0.00
519.70 3.20 0.00 0.00 0.00
519.90 3.40 0.00 0.00 0.00
520.10 3.60 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 9
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Pond Report
520.30 3.80 9496.00 949.60 0.00520.50 4.00 9864.09 2885.61 0.00520.70 4.20 10232.18 4895.24520.90 4.40 0.00
10600.27 6978.48 0.00521.10 4.60 10968.36 9135.35 0.00521.30 4.80 11336.45 11365.83 0.00521.50 5.00 11704.55
521.70 13669.93 3,875.20 12072.64 16047.65 10.95521.90 5.40 12440.73 18498.98 18.62522.10 5.60 12808.82 21023.94 20.30522.30 5.80 13176.91 23622.51 26.06522.50 6.00 13545.00 26294.70 34.17522.70 6.20 13963.80 29045.58 44.09522.90 6.40 14382.60 31880.22 55.59
Maximum Storage 33328.95 cu ft)Maximum Discharge 61.87 cfs)
Type Stand Pipe
Name Stand Pipe
RATING CURVE LIMIT]
Minimum Elevation 516.50 ft)Maximum Elevation 523.00 ft)Elevation Increment 0.20 ft)
STAND PIPE INFORMATION]
ORIFICE INFORMATION]
Height 3.50 ft)Width
3.00 ft)Crest Length 13.00 ft)Effective Crest Length 13.00 ft)Orifice Coefficient 0.60
Fractional Open Area 0.60
ORIFICE EQUATION]
Q = Co *A((2gh) /k) ^0.5
DEFINITIONS]
Co Orifice Coefficient
A Wetted Area, sq ft)
WEIR INFORMATION]
Crest Elevation 521.30 ft)Weir Coefficient 3.33Exponential1.50
WEIR EQUATION]
Q = Cw * L * H ^exp
Rivanna Engineering & Surveying, PLC
Page 10434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Pond Report
DEFINITIONS]
Cw Weir Coefficient
H Headwater depth above inlet control section invert ft
L Crest length ft
CULVERT INFORMATION]
Type Circular Concrete - Square Edge with Headwall
OUTLET STRUCTURE INFORMATION]
Diameter 18.00 in)
Invert Elevation 516.50 ft)
OUTLET STRUCTURE REPORT
Pipe Length 86.00 ft)
Slope 0.03
Manning's n Value 0.01
Orifice Coefficient 0.60
Tailwater Elevation 514.50 ft)
Number of Barrels 1
UNSUBMERGED EQUATION]
H /Diam = Hc/ Diam +K *(Q /(A *Diam ^0.5)) ^M -0.5 *S
Coefficient K 0.01
Coefficient M 2.00
Q Maximum 7.58
SUBMERGED EQUATION]
H /Diam = c *(Q /(A *Diam ^0.5)) ^2 +Y -0.5 *S
Coefficient c 0.04
Coefficient Y 0.67
Q Minimum 8.66
DEFINITIONS]
H Headwater depth above inlet control section invert, ft)
Diam Interior height of culvert barrel, ft)
He Specific head at critical depth (dc +Vc ^2/2g), ft)
Q Discharge, cfs)
A Full cross sectional area of culvert barrel, sq ft)
S Culvert barrel slope, ft /ft)
STAND PIPE STAGE VS. DISCHARGE]
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.50 0.00 0.00 0.00 0.00 0.00 0.00
516.70 0.20 0.00 0.00 0.00 0.20 0.00
516.90 0.40 0.00 0.00 0.00 0.70 0.00
517.10 0.60 0.00 0.00 0.00 1.46 0.00
517.30 0.80 0.00 0.00 0.00 2.40 0.00
517.50 1.00 0.00 0.00 0.00 3.46 0.00
517.70 1.20 0.00 0.00 0.00 4.60 0.00
517.90 1.40 0.00 0.00 0.00 5.76 0.00
518.10 1.60 0.00 0.00 0.00 6.91 0.00
Rivanna Engineering & Surveying, PLC Page 11
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Pond Report
518.30 1.80 0.00 0.00 0.00 7.58 0.00
518.50 2.00 0.00 0.00 0.00 8.94 0.00
518.70 2.20 0.00 0.00 0.00 9.78 0.00
518.90 2.40 0.00 0.00 0.00 10.55 0.00
519.10 2.60 0.00 0.00 0.00 11.27 0.00
519.30 2.80 0.00 0.00 0.00 11.94 0.00
519.50 3.00 0.00 0.00 0.00 12.58 0.00
519.70 3.20 0.00 0.00 0.00 13.19 0.00
519.90 3.40 0.00 0.00 0.00 13.77 0.00
520.10 3.60 0.00 0.00 0.00 14.33 0.00
520.30 3.80 0.00 0.00 0.00 14.87 0.00
520.50 4.00 0.00 0.00 0.00 15.39 0.00
520.70 4.20 0.00 0.00 0.00 15.89 0.00
520.90 4.40 0.00 0.00 0.00 16.38 0.00
521.10 4.60 0.00 0.00 0.00 16.85 0.00
521.30 4.80 0.00 0.00 0.00 17.31 0.00
521.50 5.00 0.00 0.00 3.87 17.76 3.87
521.70 5.20 0.00 0.00 10.95 18.19 10.95
521.90 5.40 0.00 0.00 19.48 18.62 18.62
522.10 5.60 0.00 0.00 26.53 19.04 19.04
522.30 5.80 0.00 0.00 30.32 19.44 19.44
522.50 6.00 0.00 0.00 33.22 19.84 19.84
522.70 6.20 0.00 0.00 35.88 20.23 20.23
522.90 6.40 0.00 0.00 38.35 20.62 20.62
523.00 6.50 0.00 0.00 39.54 20.81 20.81
WEIR STAGE VS. DISCHARGE]
Elevation Stage Weir 1 Weir 2 Weir 3 Weir 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.50 0.00 0.00 0.00 0.00 0.00 0.00
516.70 0.20 0.00 0.00 0.00 0.00 0.00
516.90 0.40 0.00 0.00 0.00 0.00 0.00
517.10 0.60 0.00 0.00 0.00 0.00 0.00
517.30 0.80 0.00 0.00 0.00 0.00 0.00
517.50 1.00 0.00 0.00 0.00 0.00 0.00
517.70 1.20 0.00 0.00 0.00 0.00 0.00
517.90 1.40 0.00 0.00 0.00 0.00 0.00
518.10 1.60 0.00 0.00 0.00 0.00 0.00
518.30 1.80 0.00 0.00 0.00 0.00 0.00
518.50 2.00 0.00 0.00 0.00 0.00 0.00
518.70 2.20 0.00 0.00 0.00 0.00 0.00
518.90 2.40 0.00 0.00 0.00 0.00 0.00
519.10 2.60 0.00 0.00 0.00 0.00 0.00
519.30 2.80 0.00 0.00 0.00 0.00 0.00
519.50 3.00 0.00 0.00 0.00 0.00 0.00
519.70 3.20 0.00 0.00 0.00 0.00 0.00
519.90 3.40 0.00 0.00 0.00 0.00 0.00
520.10 3.60 0.00 0.00 0.00 0.00 0.00
520.30 3.80 0.00 0.00 0.00 0.00 0.00
520.50 4.00 0.00 0.00 0.00 0.00 0.00
520.70 4.20 0.00 0.00 0.00 0.00 0.00
520.90 4.40 0.00 0.00 0.00 0.00 0.00
521.10 4.60 0.00 0.00 0.00 0.00 0.00
521.30 4.80 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 12
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Pond Report
521.50 5.00 0.00 0.00 0.00 0.00 0.00
521.70 5.20 0.00 0.00 0.00 0.00 0.00
521.90 5.40 0.00 0.00 0.00 0.00 0.00
522.10 5.60 0.00 0.00 0.00 0.00 0.00
522.30 5.80 0.00 0.00 0.00 0.00 0.00
522.50 6.00 0.00 0.00 0.00 0.00 0.00
522.70 6.20 0.00 0.00 0.00 0.00 0.00
522.90 6.40 0.00 0.00 0.00 0.00 0.00
523.00 6.50 0.00 0.00 0.00 0.00 0.00
ORIFICE STAGE VS. DISCHARGE]
Elevation Stage Orifice 1 Orifice 2 Orifice 3 Orifice 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.50 0.00 0.00 0.00 0.00 0.00 0.00
516.70 0.20 0.00 0.00 0.00 0.00 0.00
516.90 0.40 0.00 0.00 0.00 0.00 0.00
517.10 0.60 0.00 0.00 0.00 0.00 0.00
517.30 0.80 0.00 0.00 0.00 0.00 0.00
517.50 1.00 0.00 0.00 0.00 0.00 0.00
517.70 1.20 0.00 0.00 0.00 0.00 0.00
517.90 1.40 0.00 0.00 0.00 0.00 0.00
518.10 1.60 0.00 0.00 0.00 0.00 0.00
518.30 1.80 0.00 0.00 0.00 0.00 0.00
518.50 2.00 0.00 0.00 0.00 0.00 0.00
518.70 2.20 0.00 0.00 0.00 0.00 0.00
518.90 2.40 0.00 0.00 0.00 0.00 0.00
519.10 2.60 0.00 0.00 0.00 0.00 0.00
519.30 2.80 0.00 0.00 0.00 0.00 0.00
519.50 3.00 0.00 0.00 0.00 0.00 0.00
519.70 3.20 0.00 0.00 0.00 0.00 0.00
519.90 3.40 0.00 0.00 0.00 0.00 0.00
520.10 3.60 0.00 0.00 0.00 0.00 0.00
520.30 3.80 0.00 0.00 0.00 0.00 0.00
520.50 4.00 0.00 0.00 0.00 0.00 0.00
520.70 4.20 0.00 0.00 0.00 0.00 0.00
520.90 4.40 0.00 0.00 0.00 0.00 0.00
521.10 4.60 0.00 0.00 0.00 0.00 0.00
521.30 4.80 0.00 0.00 0.00 0.00 0.00
521.50 5.00 0.00 0.00 0.00 0.00 0.00
521.70 5.20 0.00 0.00 0.00 0.00 0.00
521.90 5.40 0.00 0.00 0.00 0.00 0.00
522.10 5.60 0.00 0.00 0.00 0.00 0.00
522.30 5.80 0.00 0.00 0.00 0.00 0.00
522.50 6.00 0.00 0.00 0.00 0.00 0.00
522.70 6.20 0.00 0.00 0.00 0.00 0.00
522.90 6.40 0.00 0.00 0.00 0.00 0.00
523.00 6.50 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 13
434) 984-1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Name:Routed 2 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)4.71 (cfs)
Time to Peak (Tp)25.00 (min)
Time of Base (Tb)224.00 (min)
Volume 0.11 (ac -ft)
Time Step 1.00 (min)
Peak Elevation 521.52 (ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 33328.95 (cu ft)
Maximum Discharge 61.87 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 1
Name DA- Abington 'A' 2 Year
Peak Flow (Qp)17.86 (cfs)
Time to Peak (Tp)12.00 (min)
Time of Base (Tb)30.00 (min)
Volume 0.37 (ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
I1 = Previous inflow
I2 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 S1) / dt) - 01
C = (2 (S2) / dt) + 02
Rivanna Engineering & Surveying, PLC Page 14
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Routed 2 Year
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 1.49 1.49 0.00 89.30 0.00 44.65 520.11
2 2.00 2.98 4.46 89.30 357.18 0.00 178.59 520.14
3 3.00 4.46 7.44 357.18 803.66 0.00 401.83 520.18
4 4.00 5.95 10.42 803.66 1428.73 0.00 714.36 520.25
5 5.00 7.44 13.39 1428.73 2232.39 0.00 1116.19 520.32
6 6.00 8.93 16.37 2232.39 3214.64 0.00 1607.32 520.37
7 7.00 10.42 19.35 3214.64 4375.48 0.00 2187.74 520.43
8 8.00 11.91 22.32 4375.48 5714.91 0.00 2857.46 520.50
9 9.00 13.39 25.30 5714.91 7232.93 0.00 3616.47 520.57
10 10.00 14.88 28.28 7232.93 8929.55 0.00 4464.77 520.66
11 11.00 16.37 31.25 8929.55 10804.75 0.00 5402.38 520.75
12 12.00 17.86 34.23 10804.75 12858.55 0.00 6429.27 520.85
13 13.00 16.87 34.73 12858.55 14942.11 0.00 7471.06 520.95
14 14.00 15.87 32.74 14942.11 16906.61 0.00 8453.31 521.04
15 15.00 14.88 30.76 16906.61 18752.05 0.00 9376.03 521.12
16 16.00 13.89 28.77 18752.05 20478.43 0.00 10239.22 521.20
17 17.00 12.90 26.79 20478.43 22085.75 0.00 11042.87 521.27
18 18.00 11.91 24.80 22085.75 23532.91 0.67 11766.79 521.33
19 19.00 10.91 22.82 23532.91 24758.38 1.70 12380.04 521.39
20 20.00 9.92 20.84 24758.38 25752.98 2.54 12877.76 521.43
21 21.00 8.93 18.85 25752.98 26538.85 3.20 13271.02 521.47
22 22.00 7.94 16.87 26538.85 27136.03 3.70 13569.87 521.49
23 23.00 6.95 14.88 27136.03 27554.41 4.20 13779.30 521.51
24 24.00 5.95 12.90 27554.41 27802.06 7 1 3
25 25.00 4.96 10.91 27802.06 27899.9 4.7 13952.34,. 521 52
26 26.00 3.97 8.93 27899.96 27872.68 67 13938.67 52
27 27.00 2.98 6.95 27872.68 27740.73 4.48 13872.60 521.52
28 28.00 1.98 4.96 27740.73 27521.29 4.15 13762.72 521.51
29 29.00 0.99 2.98 27521.29 27224.65 3.78 13614.21 521.50
30 30.00 0.00 0.99 27224.65 26850.00 3.46 13426.73 521.48
31 31.00 0.00 0.00 26850.00 26454.68 3.13 13228.91 521.46
32 32.00 0.00 0.00 26454.68 26097.31 2.83 13050.07 521.45
33 33.00 0.00 0.00 26097.31 25774.25 2.56 12888.40 521.43
34 34.00 0.00 0.00 25774.25 25482.19 2.31 12742.25 521.42
35 35.00 0.00 0.00 25482.19 25218.17 2.09 12610.13 521.41
36 36.00 0.00 0.00 25218.17 24979.49 1.89 12490.69 521.40
37 37.00 0.00 0.00 24979.49 24763.72 1.71 12382.72 521.39
38 38.00 0.00 0.00 24763.72 24568.67 1.54 12285.11 521.38
39 39.00 0.00 0.00 24568.67 24392.33 1.40 12196.86 521.37
40 40.00 0.00 0.00 24392.33 24232.93 1.26 12117.09 521.37
41 41.00 0.00 0.00 24232.93 24088.82 1.14 12044.98 521.36
42 42.00 0.00 0.00 24088.82 23958.55 1.03 11979.79 521.35
43 43.00 0.00 0.00 23958.55 23840.78 0.93 11920.86 521.35
44 44.00 0.00 0.00 23840.78 23734.31 0.84 11867.58 521.34
45 45.00 0.00 0.00 23734.31 23638.07 0.76 11819.42 521.34
46 46.00 0.00 0.00 23638.07 23551.06 0.69 11775.88 521.34
47 47.00 0.00 0.00 23551.06 23472.41 0.62 11736.52 521.33
48 48.00 0.00 0.00 23472.41 23401.31 0.56 11700.93 521.33
Rivanna Engineering & Surveying, PLC Page 15
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Name:Routed 10 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)11.20 (cfs)
Time to Peak (Tp)22.00 (min)
Time of Base (Tb)228.00 min)
Volume 0.25 (ac -ft)
Time Step 1.00 (min)
Peak Elevation 521.71 ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 33328.95 (cu ft)
Maximum Discharge 61.87 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 2
Name DA- Abington 'A' 10 Year
Peak Flow (Qp)24.95 (cfs)
Time to Peak (Tp)12.00 (min)
Time of Base (Tb)30.00 (min)
Volume 0.52 (ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
I1 = Previous inflow
I2 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 (S1) / dt) - 01
C = (2 (S2) / dt) + 02
Rivanna Engineering & Surveying, PLC Page 16
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Routed 10 Year
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 2.08 2.08 0.00 124.77 0.00 62.39 520.11
2 2.00 4.16 6.24 124.77 499.08 0.00 249.54 520.15
3 3.00 6.24 10.40 499.08 1122.94 0.00 561.47 520.22
4 4.00 8.32 14.56 1122.94 1996.33 0.00 998.17 520.31
5 5.00 10.40 18.72 1996.33 3119.27 0.00 1559.63 520.36
6 6.00 12.48 22.87 3119.27 4491.75 0.00 2245.87 520.43
7 7.00 14.56 27.03 4491.75 6113.77 0.00 3056.88 520.52
8 8.00 16.64 31.19 6113.77 7985.33 0.00 3992.67 520.61
9 9.00 18.72 35.35 7985.33 10106.43 0.00 5053.22 520.72
10 10.00 20.80 39.51 10106.43 12477.08 0.00 6238.54 520.83
11 11.00 22.87 43.67 12477.08 15097.27 0.00 7548.63 520.95
12 12.00 24.95 47.83 15097.27 17966.99 0.00 8983.50 521.09
13 13.00 23.57 48.52 17966.99 20878.31 0.00 10439.16 521.22
14 14.00 22.18 45.75 20878.31 23579.76 0.71 11790.24 521.34
15 15.00 20.80 42.98 23579.76 25951.13 2.71 12976.92 521.44
16 16.00 19.41 40.20 25951.13 27914.80 4.73 13959.77 521.52
17 17.00 18.02 37.43 27914.80 29452.61 7.03 14729.82 521.59
18 18.00 16.64 34.66 29452.61 30585.73 8.72 15297.23 521.64
19 19.00 15.25 31.89 30585.73 31380.53 9.90 15695.22 521.67
20 20.00 13.86 29.11 31380.53 31892.49 10.67 15951.58 521.69
21 21.00 12.48 26.34 31892.49 32167.65 11..08._:.: 16089.36 521.70
22 22.00 11.09 23.57 32167.65 32244.52, 11.20 16127.86 521.71
23 23.00 9.70 20.80 32244.52 32156.35' 11.06 16083.71 521.70
24 24.00 8.32 18.02 32156.35 31930.81 10.72 15970.77 521.69
25 25.00 6.93 15.25 31930.81 31590.07 10.21 15800.14 521.68
26 26.00 5.55 12.48 31590.07 31152.71 9.56 15581.14 521.66
27 27.00 4.16 9.70 31152.71 30634.59 8.79 15321.69 521.64
28 28.00 2.77 6.93 30634.59 30048.94 7.92 15028.43 521.61
29 29.00 1.39 4.16 30048.94 29406.85 6.96 14706.91 521.59
30 30.00 0.00 1.39 29406.85 28717.58 5.93 14361.75 521.56
31 31.00 0.00 0.00 28717.58 28065.09 4.96 14035.03 521.53
32 32.00 0.00 0.00 28065.09 27519.62 4.15 13761.88 521.51
33 33.00 0.00 0.00 27519.62 27053.33 3.63 13528.48 521.49
34 34.00 0.00 0.00 27053.33 26638.49 3.29 13320.89 521.47
35 35.00 0.00 0.00 26638.49 26263.48 2.97 13133.22 521.45
36 36.00 0.00 0.00 26263.48 25924.46 2.68 12963.57 521.44
37 37.00 0.00 0.00 25924.46 25617.99 2.43 12810.21 521.43
38 38.00 0.00 0.00 25617.99 25340.93 2.19 12671.56 521.41
39 39.00 0.00 0.00 25340.93 25090.47 1.98 12546.23 521.40
40 40.00 0.00 0.00 25090.47 24864.05 1.79 12432.92 521.39
41 41.00 0.00 0.00 24864.05 24659.36 1.62 12330.49 521.38
42 42.00 0.00 0.00 24659.36 24474.32 1.47 12237.89 521.38
43 43.00 0.00 0.00 24474.32 24307.05 1.32 12154.19 521.37
44 44.00 0.00 0.00 24307.05 24155.83 1.20 12078.51 521.36
45 45.00 0.00 0.00 24155.83 24019.12 1.08 12010.10 521.36
46 46.00 0.00 0.00 24019.12 23895.54 0.98 11948.26 521.35
47 47.00 0.00 0.00 23895.54 23783.82 0.88 11892.35 521.35
48 48.00 0.00 0.00 23783.82 23682.82 0.80 11841.81 521.34
Rivanna Engineering & Surveying, PLC Page 17
434) 984 -1599
4
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Name:Routed 100 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)19.10 (cfs)
Time to Peak (Tp)20.00 min)
Time of Base (Tb)230.00 min)
Volume 0.48 ac -ft)
Time Step 1.00 (min)
Peak Elevation 521.96 (ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 33328.95 (cu ft)
Maximum Discharge 61.87 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 3
Name DA- Abington 'A' 100
Year
Peak Flow (Qp)35.84 cfs)
Time to Peak (Tp)12.00 min)
Time of Base (Tb)30.00 (min)
Volume 0.74 ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
Il = Previous inflow
I2 = Current inflow
Si = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A _ (II + 12)
B = (2 (S1) dt) - 01
C = (2 (S2) dt) + 02
Rivanna Engineering & Surveying, PLC Page 18
434) 984-1599
Abington Place at Hollymead Towncenter, Bio- Filter -1
Routed Hydrographs
Routed 100 Year
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 2.99 2.99 0.00 179.20 0.00 89.60 520.12
2 2.00 5.97 8.96 179.20 716.82 0.00 358.41 520.18
3 3.00 8.96 14.93 716.82 1612.84 0.00 806.42 520.27
4 4.00 11.95 20.91 1612.84 2867.27 0.00 1433.63 520.35
5 5.00 14.93 26.88 2867.27 4480.11 0.00 2240.05 520.43
6 6.00 17.92 32.85 4480.11 6451.35 0.00 3225.68 520.53
7 7.00 20.91 38.83 6451.35 8781.01 0.00 4390.50 520.65
8 8.00 23.89 44.80 8781.01 11469.07 0.00 5734.54 520.78
9 9.00 26.88 50.77 11469.07 14515.54 0.00 7257.77 520.93
10 10.00 29.87 56.75 14515.54 17920.42 0.00 8960.21 521.08
11 11.00 32.85 62.72 17920.42 21683.71 0.00 10841.86 521.25
12 12.00 35.84 68.69 21683.71 25655.43 2.46 12828.94 521.43
13 13.00 33.85 69.69 25655.43 29278.90 6.77 14642.83 521.58
14 14.00 31.86 65.71 29278.90 32147.91 11.05 16079.48 521.70
15 15.00 29.87 61.73 32147.91 34317.98 14.45 17166.21 521.79
16 16.00 27.88 57.74 34317.98 35897.63 16.92 17957.28 521.86
17 17.00 25.89 53.76 35897.63 36988.80 18.62 18503.71 521.90
18 18.00 23.89 49.78 36988.80 37725.88 18.87 18872.38 521.93
19 19.00 21.90 45.80 37725.88 38199.88 19.03 19109.45 521.9 5,
20 20.00 19.91 41.81 38199.88 38421.10 19.10 19220.10 521.96
21 21.00 17.92 37.83 38421.10 38399.48 19.09 19209.28 521.96
22 22.00 15.93 33.85 38399.48 38144.52 19.01 19081.76 521.95
23 23.00 13.94 29.87 38144.52 37665.40 18.85 18842.12 521.93
24 24.00 11.95 25.89 37665.40 36971.47 18.61 18495.04 521.90
25 25.00 9.96 21.90 36971.47 36132.96 17.29 18075.13 521.87
26 26.00 7.96 17.92 36132.96 35220.21 15.86 17618.04 521.83
27 27.00 5.97 13.94 35220.21 34245.96 14.34 17130.15 521.79
28 28.00 3.98 9.96 34245.96 33220.76 12.73 16616.75 521.75
29 29.00 1.99 5.97 33220.76 32153.36 11.06 16082.21 521.70
30 30.00 0.00 1.99 32153.36 31046.64 9.40 15528.02 521.66
31 31.00 0.00 0.00 31046.64 30012.19 7.86 15010.03 521.61
32 32.00 0.00 0.00 30012.19 29147.39 6.57 14576.98 521.58
33 33.00 0.00 0.00 29147.39 28424.42 5.49 14214.96 521.55
34 34.00 0.00 0.00 28424.42 27820.01 4.59 13912.30 521.52
35 35.00 0.00 0.00 27820.01 27313.93 3.85 13658.89 521.50
36 36.00 0.00 0.00 27313.93 26874.08 3.48 13438.78 521.48
37 37.00 0.00 0.00 26874.08 26476.45 3.15 13239.80 521.46
38 38.00 0.00 0.00 26476.45 26116.99 2.85 13059.92 521.45
39 39.00 0.00 0.00 26116.99 25792.04 2.57 12897.30 521.43
40 40.00 0.00 0.00 25792.04 25498.27 2.33 12750.30 521.42
41 41.00 0.00 0.00 25498.27 25232.71 2.10 12617.41 521.41
42 42.00 0.00 0.00 25232.71 24992.63 1.90 12497.27 521.40
43 43.00 0.00 0.00 24992.63 24775.60 1.72 12388.66 521.39
44 44.00 0.00 0.00 24775.60 24579.41 1.55 12290.48 521.38
45 45.00 0.00 0.00 24579.41 24402.04 1.40 12201.72 521.37
46 46.00 0.00 0.00 24402.04 24241.70 1.27 12121.49 521.37
47 47.00 0.00 0.00 24241.70 24096.76 1.15 12048.95 521.36
48 48.00 0.00 0.00 24096.76 23965.72 1.04 11983.38 521.35
I
Rivanna Engineering & Surveying, PLC Page 19
1 434) 984 -1599
BMP CALCULATIONS
FOR
ABINGTON PLACE
February 27, 2006
LOCATION:
Rio District
Albemarle County, Virginia
Tax Map 32, Parcel 46
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
CV#0444,4,k
Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan:Abington Place at Hollymead Water Resources Area:
Preparer: JDB Date:14- Oct -05
Project Drainage Area Designation Bio- Filter #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
percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area,A =6.40
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
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)
Item
pre - development Area post - development Area
Roads Length Width subtotal Length Width subtotal
0 0 0 750 32 24000
0 0 0 770 18 13860
0 1220 14 17080
0 0 0 54940
Driveways Length Width no.subtotal Length Width no.subtotal
and walks 0 0 1 0 14 16 88 19712
0 0 0 0 3485 5 1 17425
0 0 0 37137
Parking Lots 1 2 3 4 1 2 3 4
0 0 0 0
Gravel areas Area Area
x0.70=0 x0.70=0
Structures Area no.subtotal Area no.subtotal
0 0 0 870 63 54810
0 0 0 350 76 26600
0 0 0 0 0 81410
Actively - grazed pasture &Area Area
yards and cultivated turf 0 x 0.08 =0 105297 x 0.08 =8423.76
Active crop land Area Area
x0.25=0 x0.25=0
Other Impervious Areas
0 0
Impervious Cover 0%65%
l(pre)post)
Rv(post)V
0.64 280.7
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type
0.70 1.00 20% 0.23 9.04 25.04 16.00 64% Development Area
0.35 1.00 0% 0.05 0.98 12.52 11.54 92% Drinking Water Watersheds
0.40 1.00 1% 0.06 1.32 14.31 12.98 91% 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 20% 0.23 9.04 25.04 16.90 68% Development Area
0.35 0.85 0% 0.05 0.98 12.52 11.68 93% Drinking Water Watersheds
0.40 0.85 1% 0.06 1.32 14.31 13.18 92% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan:Abington Place Water Resources Area:Development
Preparer: JDB Date: 14- Oct -05
Project Drainage Area Designation Bio- Filter #2
L storm pollutant export in pounds, L = [P(Pj)Rv /12 j [ C(A)2.72 jRvmeanrunoffcoefficient, 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 =2.37Cpollutantconcentration, mg /I or ppm target phosphorusffactorappliedtoRR
required treatment volume in cy, 0.5" over imperv. area = A(I)43560(0.5/12)/27RRrequiredremoval , L(post) - f x L(pre)
RR removal efficiency , RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)Item
pre - development Area post - developmentRoadsLengthWidthsubtotal Area
Length Width subtotal0004501463000007501813500
0 0 0 0
0 0 0 19800DrivewaysLengthWidthno.subtotal Length Width no.subtotalandwalks0010110051550000001616358960
0 0 0 14460ParkingLots1234123400000GravelareasAreaArea
x 0.70 =0 x 0.70 =0StructuresAreano.subtotal Area no.subtotal0004301981700001000161600000000 24170Actively - grazed pasture &Area Areayardsandcultivatedturf0x0.08 =44807 x 0.08 =0 3584.56ActivecropandAreaArea
x0.25=0 x0.25=0OtherImperviousAreas
0
0ImperviousCover0%
l(pre)
60%
Rv(post)V post)
0.59 95.7
New Development (For Development Areas, existing impervious cover <= 20 %)C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type0.70 1.00 20% 0.23 3.35 8.59 5.25 61% Development Area0.35 1.00 0% 0.05 0.36 4.30 3.93 92% Drinking Water Watersheds0.40 1.00 1% 0.06 0.49 4.91 4.42 90% Other Rural Landmin. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)C f I (pre) * Rv(pre) L(pre) L(post) RR RR Area Type0.70 0.90 20% 0.23 3.35 8.59 5.58 65% Development Area0.35 0.85 0% 0.05 0.36 4.30 3.99 93% Drinking Water Watersheds0.40 0.85 1% 0.06 0.49 4.91 4.49 92% Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
HYDROLOGIC /HYDRAULIC CALCULATIONS
FOR
ABINGTON PLACE AT HOLLYMEAD TOWNCENTER
BIOFILTER -2
March 2, 2006
LOCATION:
Rio District, Albemarle County, Virginia
OWNER:
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
INDEX
Summary:2
Post - Development:
DA -B Hydrographs:3-8
Pond & Outlet Structure:9 -12
Routed Hydrographs:13 -18
Drainage Area Maps are included attached at the end of this report.
Rivanna Engineering & Surveying, PLC Page 1
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Summary
Two bio- filters will provide stormwater management for Abington Place at Hollymead Towncenter. Drainage
area DA -B flows into Bio - Filter -2.
Rivanna Engineering & Surveying, PLC Page 2
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
Name:DA- Abington 'B' 2 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)7.26 (cfs)
Time to Peak (Tp)8.00 min)
Time of Base (Tb)20.00 (min)
Volume 0.10 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 cfs)
Maximum Storage 0.10 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 2.30 A 0.67
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)8.00 min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 0.62 in)
Return Period 2 yr)
Storm Duration 0.13 (hr)
Rivanna Engineering & Surveying, PLC
434) 984 -1599 Page 3
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
DA- Abington 'B' 2 Year
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.08 0.00 0.91
2 2.00 0.08 0.16 0.91 1.82
3 3.00 0.08 0.23 0.91 2.72
4 4.00 0.08 0.31 0.91 3.63
5 5.00 0.08 0.39 0.91 4.54
6 6.00 0.08 0.47 0.91 5.45
7 7.00 0.08 0.55 0.91 6.35
8 8.00 0.08 0.62 0.91 7.26
9 9.00 0.00 0.62 0.60 6.66
10 10.00 0.00 0.62 0.61 6.05
11 11.00 0.00 0.62 0.61 5.45
12 12.00 0.00 0.62 0.61 4.84
13 13.00 0.00 0.62 0.61 4.24
14 14.00 0.00 0.62 0.61 3.63
15 15.00 0.00 0.62 0.61 3.03
16 16.00 0.00 0.62 0.61 2.42
17 17.00 0.00 0.62 0.61 1.82
18 18.00 0.00 0.62 0.61 1.21
19 19.00 0.00 0.62 0.61 0.61
20 20.00 0.00 0.62 0.61 0.00
Rivanna Engineering & Surveying, PLC Page 4
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
Name:DA- Abington 'B' 10 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)9.95 (cfs)
Time to Peak (Tp)8.00 (min)
Time of Base (Tb)20.00 min)
Volume 0.14 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 cfs)
Maximum Storage 0.14 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 2.30 NA 0.67
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)8.00 (min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 0.85 in)
Return Period User Defined (yr)
Storm Duration 0.13 hr)
Rivanna Engineering & Surveying, PLC Page 5
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
DA- Abington 'B' 10 Year
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.11 0.00 1.24
2 2.00 0.11 0.21 1.24 2.49
3 3.00 0.11 0.32 1.24 3.73
4 4.00 0.11 0.43 1.24 4.98
5 5.00 0.11 0.53 1.24 6.22
6 6.00 0.11 0.64 1.24 7.46
7 7.00 0.11 0.75 1.24 8.71
8 8.00 0.11 0.85 1.24 9.95
9 9.00 0.00 0.85 0.83 9.13
10 10.00 0.00 0.85 0.83 8.30
11 11.00 0.00 0.85 0.83 7.47
12 12.00 0.00 0.85 0.83 6.64
13 13.00 0.00 0.85 0.83 5.81
14 14.00 0.00 0.85 0.83 4.98
15 15.00 0.00 0.85 0.83 4.15
16 16.00 0.00 0.85 0.83 3.32
17 17.00 0.00 0.85 0.83 2.49
18 18.00 0.00 0.85 0.83 1.66
19 19.00 0.00 0.85 0.83 0.83
20 20.00 0.00 0.85 0.83 0.00
Rivanna Engineering & Surveying, PLC Page 6
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
Name:DA- Abington 'B' 100 Year
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)14.14 cfs)
Time to Peak (Tp)8.00 min)
Time of Base (Tb)20.00 min)
Volume 0.19 (ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 cfs)
Maximum Storage 0.19 (cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 2.30 NA 0.67
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)8.00 min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 1.21 in)
Return Period 100 yr)
Storm Duration 0.13 hr)
Rivanna Engineering & Surveying, PLC Page 7
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Post - Development Hydrographs
DA- Abington 'B' 100 Year
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental. Design
Irterval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.15 0.00 1.77
2 2.00 0.15 0.30 1.77 3.54
3 3.00 0.15 0.46 1.77 5.30
4 4.00 0.15 0.61 1.77 7.07
5 5.00 0.15 0.76 1.77 8.84
6 6.00 0.15 0.91 1.77 10.61
7 7.00 0.15 1.06 1.77 12.37
8 8.00 0.15 1.21 1.77 14.14
9 9.00 0.00 1.21 1.17 12.97
10 10.00 0.00 1.21 1.18 11.79
11 11.00 0.00 1.21 1.18 10.61
12 12.00 0.00 1.21 1.18 9.43
13 13.00 0.00 1.21 1.18 8.25
14 14.00 0.00 1.21 1.18 7.08
15 15.00 0.00 1.21 1.18 5.90
16 16.00 0.00 1.21 1.18 4.72
17 17.00 0.00 1.21 1.18 3.54
18 18.00 0.00 1.21 1.18 2.36
19 19.00 0.00 1.21 1.18 1.18
20 20.00 0.00 1.21 1.18 0.00
Rivanna Engineering & Surveying, PLC Page 8
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Pond Report
Name: Water Quality Pond
RATING CURVE LIMIT]
Minimum Elevation 530.00 ft)
Maximum Elevation 536.50 ft)
Elevation Increment 0.20 ft)
STAGE STORAGE INFORMATION]
Storage Method: User - Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative Volume
ft)sq ft)sq ft)cu ft)cu ft)
1 530.00 0.00 0.00 0.00 0.00
2 533.90 0.00 0.00 0.00 0.00
3 534.00 887.00 443.50 44.35 44.35
4 536.00 3613.00 2250.00 4500.00 4544.35
5 536.50 4153.00 3883.00 1941.50 6485.85
DISCHARGE INFORMATION]
Structure Number: 1
Type:
Name:Stand Pipe
Structure Number: 2
Type:Trapezoidal Weir
Name:Bio- Filter #2 Weir
RESERVOIR STAGE STORAGE /DISCHARGE]
Elevation Stage Area Storage Discharge
ft)ft)sq ft)cu ft)cfs)
530.40 0.40 0.00 0.00 0.00
530.80 0.80 0.00 0.00 0.00
531.20 1.20 0.00 0.00 0.00
531.60 1.60 0.00 0.00 0.00
532.00 2.00 0.00 0.00 0.00
532.40 2.40 0.00 0.00 0.00
532.80 2.80 0.00 0.00 0.00
533.20 3.20 0.00 0.00 0.00
533.60 3.60 0.00 0.00 0.00
534.00 4.00 887.00 88.70 0.00
534.40 4.40 1432.20 552.54 0.00
RESERVOIR REPORT
534.80 4.80 1977.40 1234.46 0.00
535.20 5.20 2522.60 2134.46 3.87
535.60 5.60 3067.80 3252.54 14.31
536.00 6.00 3613.00 4588.70 23.63
536.40 6.40 4045.00 6120.30 38.14
Maximum Storage 6530.20 cu ft)
Maximum Discharge 42.42 cfs)
Rivanna Engineering & Surveying, PLC Page 9
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Pond Report
Type Stand Pipe
Name Stand Pipe
RATING CURVE LIMIT]
Minimum Elevation 530.00 ft)
Maximum Elevation 536.50 ft)
Elevation Increment 0.20 ft)
STAND PIPE INFORMATION]
ORIFICE INFORMATION]
Height 3.50 ft)
Width 3.00 ft)
Crest Length 13.00 ft)
Effective Crest Length 13.00 ft)
Orifice Coefficient 0.60
Fractional Open Area 0.60
ORIFICE EQUATION]
Q = Co *A((2gh) /k) ^0.5
DEFINITIONS]
Co Orifice Coefficient
A Wetted Area, sq ft)
WEIR INFORMATION]
Crest Elevation 535.00 ft)
Weir Coefficient 3.33
Exponential 1.50
WEIR EQUATION]
Q = Cw * L * H ^exp
DEFINITIONS]
Cw Weir Coefficient
H Headwater depth above inlet control section invert ft
L Crest length ft
CULVERT INFORMATION]
Type Circular Concrete - Square Edge with Headwall
OUTLET STRUCTURE INFORMATION]
Diameter 15.00 in)
Invert Elevation 530.00 ft)
OUTLET STRUCTURE REPORT
Pipe Length 57.00 ft)
Slope 0.04
Manning's n Value 0.01
Orifice Coefficient 0.60
Tailwater Elevation 528.50 ft)
Number of Barrels 1
Rivanna Engineering & Surveying, PLC Page 10
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Pond Report
UNSUBMERGED EQUATION]
H /Diam = Hc/ Diam +K *(Q /(A*Diam ^0.5)) ^ M - 0.5 *S
Coefficient K 0.01
Coefficient M 2.00
Q Maximum 4.80
SUBMERGED EQUATION]
H /Diam = c'(Q /(A *Diam ^0.5)) ^2 +Y - 0.5 *S
Coefficient c 0.04
Coefficient Y 0.67
Q Minimum 5.49
DEFINITIONS]
H Headwater depth above inlet control section invert, ft)
Diam Interior height of culvert barrel, ft)
He Specific head at critical depth (dc +Vc ^2/2g), ft)
Q Discharge, cfs)
A Full cross sectional area of culvert barrel, sq ft)
S Culvert barrel slope, ft /ft)
STAND PIPE STAGE VS. DISCHARGE]
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
530.40 0.40 0.00 0.00 0.00 0.64 0.00
530.80 0.80 0.00 0.00 0.00 2.09 0.00
531.20 1.20 0.00 0.00 0.00 3.84 0.00
531.60 1.60 0.00 0.00 0.00 4.80 0.00
532.00 2.00 0.00 0.00 0.00 6.71 0.00
532.40 2.40 0.00 0.00 0.00 7.76 0.00
532.80 2.80 0.00 0.00 0.00 8.68 0.00
533.20 3.20 0.00 0.00 0.00 9.51 0.00
533.60 3.60 0.00 0.00 0.00 10.27 0.00
534.00 4.00 0.00 0.00 0.00 10.99 0.00
534.40 4.40 0.00 0.00 0.00 11.66 0.00
534.80 4.80 0.00 0.00 0.00 12.29 0.00
535.20 5.20 0.00 0.00 3.87 12.89 3.87
535.60 5.60 0.00 0.00 19.48 13.46 13.46
536.00 6.00 0.00 0.00 30.32 14.01 14.01
536.40 6.40 0.00 0.00 35.88 14.54 14.54
WEIR STAGE VS. DISCHARGE]
Elevation Stage Weir 1 Weir 2 Weir 3 Weir 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
530.40 0.40 0.00 0.00 0.00 0.00 0.00
530.80 0.80 0.00 0.00 0.00 0.00 0.00
531.20 1.20 0.00 0.00 0.00 0.00 0.00
531.60 1.60 0.00 0.00 0.00 0.00 0.00
532.00 2.00 0.00 0.00 0.00 0.00 0.00
532.40 2.40 0.00 0.00 0.00 0.00 0.00
532.80 2.80 0.00 0.00 0.00 0.00 0.00
533.20 3.20 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 11
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Pond Report
533.60 3.60 0.00 0.00 0.00 0.00 0.00
534.00 4.00 0.00 0.00 0.00 0.00 0.00
534.40 4.40 0.00 0.00 0.00 0.00 0.00
534.80 4.80 0.00 0.00 0.00 0.00 0.00
535.20 5.20 0.00 0.00 0.00 0.00 0.00
535.60 5.60 0.00 0.00 0.00 0.00 0.00
536.00 6.00 0.00 0.00 0.00 0.00 0.00
536.40 6.40 0.00 0.00 0.00 0.00 0.00
ORIFICE STAGE VS. DISCHARGE]
Elevation Stage Orifice 1 Orifice 2 Orifice 3 Orifice 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
530.40 0.40 0.00 0.00 0.00 0.00 0.00
530.80 0.80 0.00 0.00 0.00 0.00 0.00
531.20 1.20 0.00 0.00 0.00 0.00 0.00
531.60 1.60 0.00 0.00 0.00 0.00 0.00
532.00 2.00 0.00 0.00 0.00 0.00 0.00
532.40 2.40 0.00 0.00 0.00 0.00 0.00
532.80 2.80 0.00 0.00 0.00 0.00 0.00
533.20 3.20 0.00 0.00 0.00 0.00 0.00
533.60 3.60 0.00 0.00 0.00 0.00 0.00
534.00 4.00 0.00 0.00 0.00 0.00 0.00
534.40 4.40 0.00 0.00 0.00 0.00 0.00
534.80 4.80 0.00 0.00 0.00 0.00 0.00
535.20 5.20 0.00 0.00 0.00 0.00 0.00
535.60 5.60 0.00 0.00 0.00 0.00 0.00
536.00 6.00 0.00 0.00 0.00 0.00 0.00
536.40 6.40 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 12
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Name:Routed 2 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)5.25 (cfs)
Time to Peak (Tp)11.00 min)
Time of Base (Tb)57.00 min)
Volume 0.06 (ac -ft)
Time Step 1.00 min)
Peak Elevation 535.24 ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 6530.20 cu ft)
Maximum Discharge 42.42 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 4
Name DA- Abington 'B' 2 Year
Peak Flow (Qp)7.26 (cfs)
Time to Peak (Tp)8.00 (min)
Time of Base (Tb)20.00 min)
Volume 0.10 ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
I1 = Previous inflow
I2 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 S1) dt) - 01
C = (2 S2) dt) + 02
Rivanna Engineering & Surveying, PLC Page 13
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Routed 2 Year
Computation of Reservoir Ou:flow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 0.91 0.91 0.00 54.46 0.00 27.23 533.86
2 2.00 1.82 2.72 54.46 217.85 0.00 108.93 534.02
3 3.00 2.72 4.54 217.85 490.17 0.00 245.08 534.15
4 4.00 3.63 6.35 490.17 871.41 0.00 435.70 534.31
5 5.00 4.54 8.17 871.41 1361.57 0.00 680.79 534.48
6 6.00 5.45 9.98 1361.57 1960.66 0.00 980.33 534.66
7 7.00 6.35 11.80 1960.66 2668.68 0.00 1334.34 534.8588.00 7.26 13.62 2668.68 3451.55 0.56 1726.05 535.03
9 9.00 6.66 13.92 3451.55 4066.88 3.06 2034.97 535.16
10 10.00 6.05 12.71 4066.88 4369.81 4.57 2187.19 535.22
11 11.00 5.45 11.50 4369.81 4470.09 5.25 2237.67 535.24
12 12.00 4.84 10.29 4470.09 4461.59 5.19 2233.39 535.24
13 13.00 4.24 9.08 4461.59 4406.39 4.82 2205.60 535.23
14 14.00 3.63 7.87 4406.39 4331.15 4.31 2167.73 535.21
15 15.00 3.03 6.66 4331.15 4245.04 3.79 2124.41 535.20
16 16.00 2.42 5.45 4245.04 4142.68 3.37 2073.03 535.17
17 17.00 1.82 4.24 4142.68 4022.23 2.88 2012.56 535.15
18 18.00 1.21 3.03 4022.23 3890.77 2.35 1946.56 535.12
19 19.00 0.61 1.82 3890.77 3752.61 1.78 1877.19 535.09
20 20.00 0.00 0.61 3752.61 3610.37 1.21 1805.79 535.062121.00 0.00 0.00 3610.37 3494.61 0.73 1747.67 535.04
22 22.00 0.00 0.00 3494.61 3424.06 0.45 1712.25 535.02
23 23.00 0.00 0.00 3424.06 3381.13 0.27 1690.70 535.01
24 24.00 0.00 0.00 3381.13 3355.01 0.17 1677.59 535.01
25 25.00 0.00 0.00 3355.01 3339.11 0.10 1669.60 535.01
26 26.00 0.00 0.00 3339.11 3329.44 0.06 1664.75 535.00
27 27.00 0.00 0.00 3329.44 3323.55 0.04 1661.79 535.00
28 28.00 0.00 0.00 3323.55 3319.97 0.02 1660.00 535.002929.00 0.00 0.00 3319.97 3317.79 0.01 1658.90 535.00
30 30.00 0.00 0.00 3317.79 3316.46 0.01 1658.23 535.00
31 31.00 0.00 0.00 3316.46 3315.65 0.01 1657.83 535.00
32 32.00 0.00 0.00 3315.65 3315.16 0.00 1657.58 535.003333.00 0.00 0.00 3315.16 3314.86 0.00 1657.43 535.00
34 34.00 0.00 0.00 3314.86 3314.68 0.00 1657.34 535.003535.00 0.00 0.00 3314.68 3314.57 0.00 1657.29 535.00
36 36.00 0.00 0.00 3314.57 3314.50 0.00 1657.25 535.003737.00 0.00 0.00 3314.50 3314.46 0.00 1657.23 535.003838.00 0.00 0.00 3314.46 3314.44 0.00 1657.22 535.003939.00 0.00 0.00 3314.44 3314.42 0.00 1657.21 535.00
40 40.00 0.00 0.00 3314.42 3314.41 0.00 1657.21 535.00
Rivanna Engineering & Surveying, PLC
434) 984 -1599 Page 14
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Name:Routed 10 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)8.15 (cfs)
Time to Peak (Tp)10.00 min)
Time of Base (Tb)58.00 min)
Volume 0.10 ac -ft)
Time Step 1.00 min)
Peak Elevation 535.32 ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 6530.20 (cu ft)
Maximum Discharge 42.42 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 5
Name DA- Abington 'B' 10 Year
Peak Flow (Qp)9.95 cfs)
Time to Peak (Tp)8.00 min)
Time of Base (Tb)20.00 (min)
Volume 0.14 ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
I1 = Previous inflow
I2 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 (S1) dt) - 01
C = (2 (S2) dt) + 02
Rivanna Engineering & Surveying, PLC Page 15
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Routed 10 Year
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 1.24 1.24 0.00 74.65 0.00 37.32 533.88
2 2.00 2.49 3.73 74.65 298.59 0.00 149.30 534.06
3 3.00 3.73 6.22 298.59 671.84 0.00 335.92 534.23
4 4.00 4.98 8.71 671.84 1194.38 0.00 597.19 534.43
5 5.00 6.22 11.20 1194.38 1866.22 0.00 933.11 534.64
6 6.00 7.46 13.69 1866.22 2687.35 0.00 1343.67 534.85
7 7.00 8.71 16.17 2687.35 3589.45 1.12 1795.2.8 535.06
8 8.00 9.95 18.66 3589.45 4365.73 4.55 2185.14 535.22
9 9.00 9.13 19.08 4365.73 4791.08 7.40 2399.24 535.30
10 10.00 8.30 17.42 4791.08 4903.12 8.15 2455.63 535.32
11 11.00 7.47 15.77 4903.12 4880.56 8.00 2444.2.8 535.32
12 12.00 6.64 14.11 4880.56 4800.22 7.46 2403.84 535.30
13 13.00 5.81 12.45 4800.22 4695.09 6.75 2350.92 535.28
14 14.00 4.98 10.79 4695.09 4579.32 5.98 2292.65 535.26
15 15.00 4.15 9.13 4579.32 4458.98 5.17 2232.07 535.24
16 16.00 3.32 7.47 4458.98 4336.68 4.35 2170.51 535.21
17 17.00 2.49 5.81 4336.68 4206.92 3.64 2105.28 535.19
18 18.00 1.66 4.15 4206.92 4057.13 3.03 2030.08 535.16
19 19.00 0.83 2.49 4057.13 3886.27 2.33 1944.30 535.12
20 20.00 0.00 0.84 3886.27 3702.57 1.58 1852.07 535.08
21 21.00 0.00 0.00 3702.57 3550.76 0.96 1775.86 535.05
22 22.00 0.00 0.00 3550.76 3458.23 0.59 1729.41 535.03
23 23.00 0.00 0.00 3458.23 3401.92 0.36 1701.14 535.02
24 24.00 0.00 0.00 3401.92 3367.66 0.22 1683.94 535.01
25 25.00 0.00 0.00 3367.66 3346.81 0.13 1673.47 535.01
26 26.00 0.00 0.00 3346.81 3334.12 0.08 1667.10 535.00
27 27.00 0.00 0.00 3334.12 3326.40 0.05 1663.22 535.00
28 28.00 0.00 0.00 3326.40 3321.70 0.03 1660.87 535.00
29 29.00 0.00 0.00 3321.70 3318.84 0.02 1659.43 535.00
30 30.00 0.00 0.00 3318.84 3317.10 0.01 1658.56 535.00
31 31.00 0.00 0.00 3317.10 3316.05 0.01 1658.03 535.00
32 32.00 0.00 0.00 3316.05 3315.40 0.00 1657.70 535.00
33 33.00 0.00 0.00 3315.40 3315.01 0.00 1657.51 535.00
34 34.00 0.00 0.00 3315.01 3314.77 0.00 1657.39 535.00
35 35.00 0.00 0.00 3314.77 3314.63 0.00 1657.31 535.00
36 36.00 0.00 0.00 3314.63 3314.54 0.00 1657.27 535.00
37 37.00 0.00 0.00 3314.54 3314.48 0.00 1657.24 535.00
38 38.00 0.00 0.00 3314.48 3314.45 0.00 1657.2.3 535.00
39 39.00 0.00 0.00 3314.45 3314.43 0.00 1657.22 535.00
40 40.00 0.00 0.00 3314.43 3314.42 0.00 1657.21 535.00
Rivanna Engineering & Surveying, PLC Page 16
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Name:Routed 100 Year
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)11.80 (cfs)
Time to Peak (Tp)10.00 min)
Time of Base (Tb)58.00 min)
Volume 0.16 (ac -ft)
Time Step 1.00 min)
Peak Elevation 535.45 ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 6530.20 cu ft)
Maximum Discharge 42.42 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 6
Name DA- Abington 'B' 100
Year
Peak Flow (Qp)14.14 cfs)
Time to Peak (Tp)8.00 min)
Time of Base (Tb)20.00 (min)
Volume 0.19 (ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
I1 = Previous inflow
12 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 S1) / dt) - 01
C = (2 S2) / dt) + 02
Rivanna Engineering & Surveying, PLC Page 17
434) 984 -1599
Abington Place at Hollymead Towncenter, Bio- Filter -2
Routed Hydrographs
Routed 100 Year
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 1.77 1.77 0.00 106.07 0.00 53.03 533.92
2 2.00 3.54 5.30 106.07 424.27 0.00 212.14 534.12
3 3.00 5.30 8.84 424.27 954.61 0.00 477.30 534.34
4 4.00 7.07 12.37 954.61 1697.08 0.00 848.54 534.59
5 5.00 8.84 15.91 1697.08 2651.69 0.00 1325.84 534.84
6 6.00 10.61 19.45 2651.69 3718.13 1.64 1859.89 535.08
7 7.00 12.37 22.98 3718.13 4619.08 6.24 2312.66 535.27
8 8.00 14.14 26.52 4619.08 5216.54 10.25 2613.40 535.38
9 9.00 12.97 27.11 5216.54 5533.40 11.56 2772.48 535.44
10 10.00 11.79 24.76 5533.40 5617.07 11.80 2814.43 535.45
11 11.00 10.61 22.40 5617.07 5555.86 11.62 2783.74 535.44
12 12.00 9.43 20.04 5555.86 5392.25 11.15 2701.70 535.41
13 13.00 8.25 17.69 5392.25 5183.67 10.03 2596.85 535.37
14 14.00 7.08 15.33 5183.67 4982.42 8.68 2495.55 535.34
15 15.00 5.90 12.97 4982.42 4795.66 7.43 2401.54 535.30
16 16.00 4.72 10.62 4795.66 4615.11 6.22 2310.66 535.27
17 17.00 3.54 8.26 4615.11 4437.23 5.03 2221.13 535.23
18 18.00 2.36 5.90 4437.23 4259.92 3.85 2131.88 535.20
19 19.00 1.18 3.55 4259.92 4060.13 3.04 2031.58 535.16
20 20.00 0.00 1.19 4060.13 3825.27 2.08 1913.68 535.11
21 21.00 0.00 0.00 3825.27 3625.50 1.27 1813.38 535.07
22 22.00 0.00 0.00 3625.50 3503.71 0.77 1752.24 535.04
23 23.00 0.00 0.00 3503.71 3429.59 0.47 1715.03 535.02
24 24.00 0.00 0.00 3429.59 3384.50 0.29 1692.39 535.01
25 25.00 0.00 0.00 3384.50 3357.05 0.17 1678.61 535.01
26 26.00 0.00 0.00 3357.05 3340.36 0.11 1670.23 535.01
27 27.00 0.00 0.00 3340.36 3330.19 0.06 1665.13 535.00
28 28.00 0.00 0.00 3330.19 3324.01 0.04 1662.03 535.00
29 29.00 0.00 0.00 3324.01 3320.25 0.02 1660.14 535.00
30 30.00 0.00 0.00 3320.25 3317.96 0.01 1658.99 535.00
31 31.00 0.00 0.00 3317.96 3316.57 0.01 1658.29 535.00
32 32.00 0.00 0.00 3316.57 3315.72 0.01 1657.86 535.00
33 33.00 0.00 0.00 3315.72 3315.20 0.00 1657.60 535.00
34 34.00 0.00 0.00 3315.20 3314.89 0.00 1657.44 535.00
35 35.00 0.00 0.00 3314.89 3314.70 0.00 1657.35 535.00
36 36.00 0.00 0.00 3314.70 3314.58 0.00 1657.29 535.00
37 37.00 0.00 0.00 3314.58 3314.51 0.00 1657.26 535.00
38 38.00 0.00 0.00 3314.51 3314.47 0.00 1657.23 535.00
39 39.00 0.00 0.00 3314.47 3314.44 0.00 1657.22 535.00
40 40.00 0.00 0.00 3314.44 3314.42 0.00 1657.21 535.00
Rivanna Engineering & Surveying, PLC Page 18
434) 984 -1599
EROSION AND SEDIMENT CONTROL NARRATIVE
FOR MASS GRADING OF
ABBINGTON PLACE AT HOLLYMEAD TOWNCENTER
July 20 2005.
REV: September 23, 2005.
LOCATION:
Tax Map 32 Parcel 46
Rivanna District, Albemarle County, Virginia
DEVELOPER
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
434.984.1599
F) 434.984.8863
A. MINIMUM STANDARDS (MS):
All applicable Virginia Erosion and Sediment Control Regulations and Minimum Standards
shall be adhered to during all phases of construction. These include, but are not limited to
the following:
1. STABLIZATION OF DENUDED AREAS:
Permanent or temporary soil stabilization shall be applied to bare areas within seven days
after final grade is reached on any portion of the site. Temporary soil stabilization shall be
applied within seven days to denuded areas that may not be at final grade, but will remain
dormant or undisturbed for longer than 30 days. Permanent stabilization shall be applied
at areas that are to be left dormant for more than 1 year.
2. STABILIZATION OF SOIL STOCKPILES:
During construction of the project, soil stockpiles shall be stabilized or protected with
sediment trapping measures. The applicant is responsible for temporary protection and
permanent stabilization of all soil stockpiles on site as well as soil intentionally transported
from the project site.
3. PERMANENT VEGETATIVE COVER
A permanent vegetative cover shall be established on denuded areas not otherwise
permanently stabilized. Permanent vegetation shall not be considered established until a
ground cover is achieve that, in the opinion of the county Inspector, is uniform and mature
enough to survive to inhibit erosion.
4. TIMING & STABILIZATION OF SILT TRAPPING MEASURES:
Sediment basins and traps, perimeter dikes, sediment barriers and other measures
intended to trap sediment shall be constructed as a first step in any land disturbing activity
and shall be made functional before upslope land disturbance takes place.
5. STABILIZATION OF EARTHEN STRUCTURES:
Stabilization measures shall be applied to earthen structures such as dams, dikes and
diversions immediately after installation.
6. SEDIMENT TRAPS AND BASINS:
A sediment basin shall control surface runoff from disturbed areas that is comprised of
flow from drainage areas greater than or equal to three acres. The sediment basin shall
be designed and constructed to accommodate the anticipated sediment loading for the
land disturbing activity. The outfall device or system device shall take into account the
total drainage area flowing through the disturbed area to be served by the basin.
7. CUT AND FILL SLOPES:
Cut and fill slopes shall be designed and constructed in a manner that will minimize
erosion. Slopes that are found to be eroding excessively within one year of permanent
stabilization shall be provided with additional slope stabilizing measures until the problem
is corrected.
8. CONCENTRATED RUN -OFF DOWN CUT OR FILL SLOPES:
Concentrated runoff shall not flow down cut or fill slopes unless contained within an
adequate temporary or permanent channel, flume, or slope drain structure.
1
9. WATER SEEPS FROM A SLOPE FACE:
Whenever water seeps from a slope face, adequate drainage or other protection shall be
provided.
10. STORM SEWER INLET PROTECTION:
All storm sewer inlets that are made operable during construction shall be protected so
that sediment -laden water cannot enter the conveyance system without first being filtered
or otherwise treated to remove sediment.
11. STABILIZATION OF OUTLETS:
Before newly constructed stormwater conveyance channels are made operational,
adequate outlet protection and any required temporary or permanent channel lining shall
be installed in both the conveyance channel and receiving channel.
12. WORK IN LIVE WATERCOURSES:
When work in a live watercourse is performed, precautions shall be taken to minimize
encroachment, control sediment transport and stabilize the work area to the greatest
extent possible during construction. Nonerodible material shall be used for the
construction of causeways and cofferdams. Earthen fill may be used for these structures if
armored by nonerodible cover materials.
13. CROSSING A LIVE WATERCOURSE:
When a live watercourse must be crossed by construction vehicles more than twice in any
six month period, a temporary stream crossing constructed of nonerodible materials shall
be provided.
14. APPLICABLE REGULATIONS:
All applicable federal, state and local regulations pertaining to working in or crossing live
watercourses shall be met.
15. STABILIZATION OF BED AND BANKS
The bed and banks of a watercourse shall be stabilized immediately after work in the
watercourse is completed.
16. UNDERGROUND UTILITIES:
Underground utilities shall be installed in accordance with the following standards in
addition to other criteria:
a. No more than 500 linear feet of trench may be opened at one time.
b. Excavated material shall be placed on the uphill side of trenches
c. Effluent for dewatering operations shall be filtered or passed through approved
sediment trapping device, or both, and discharged in a manner that does not adversely
affect flowing streams or offsite property.
d. Material used for backfilling trenches shall be properly compacted in order to minimize
erosion and promote stabilization.
e. Restabilization shall be accomplished in accordance with these regulations.
f. Applicable safety regulations shall be complied with.
2
17. CONSTRUCTION ACCESS ROUTES:
Where construction vehicle access routes intersect paved public roads, provisions shall be
made to minimize the transport of sediment by vehicular tracking onto paved surfaces.
Where sediment is transported on to a public road surface, the road shall be cleaned
thoroughly at the end of each day. Sediment shall be removed by shoveling or sweeping
and transported to a sediment control disposal area. Street washing shall be allowed only
after sediment is removed in this manner. This provision shall apply to individual lots as
well as to larger land disturbing activities.
18. TEMPORARY E &S CONTROL MEASURE REMOVAL:
All temporary erosion and sediment control measures shall be removed within 30 days
after final site stabilization or after temporary measures are no longer needed, unless
otherwise authorized by the local program authority. Trapped sediment and the disturbed
soil areas resulting from the disposition of temporary measures shall be permanently
stabilized to prevent further erosion and sediment.
19. ADEQUACY OF RECEIVING CHANNELS:
Properties and waterways downstream from the development site shall be protected from
sediment deposition, erosion and damage, due to increases in volume, velocity and peak
flow rates of stormwater runoff for the stated frequency storm of 24 -hour duration.
B1. PROJECT DESCRIPTION:
The purpose of this project is to mass grade the property. The total area to be disturbed
by this project will be 8.8 acres.
B2. EXISTING SITE CONDITIONS:
The site is currently grassed with mixed deciduous trees. The current vegetation is small
trees and brush. The existing topography is rolling terrain with slopes of 10 -20 %.
B3. ADJACENT AREAS:
The site is bounded to the east, west and south by the Hollymead Towncenter
development, which is mixed use. To the north is the existing Deerwood subdivision.
B4. SOIL DESCRIPTIONS:
According to the Albemarle County Soils Survey conducted by the United States
Department of Agriculture Soil Conservation Service, the primary soil types that may be
disturbed during this scope of work have been identified as the following:
1. Pacolet Sandy loam (65B) — Permeability is moderate, surface runoff is rapid,
and the hazard of erosion is severe. Hydrologic group B, K factor .28
2. Mount Lucas silt loam (57C) — Permeability is slow, surface runoff is medium,
and the hazard of erosion is moderate. Hydrologic group C, K factor .28
3. Elioak Loam (27B) — Permeability is moderate, surface runoff is medium, and the
hazard of erosion is moderate. Hydrologic group C, K factor .28
3
B5. CRITICAL AREAS:
The stream along the north property line between Deerwood subdivision and parcel 46 is
a critical area, and a 50' undisturbed stream buffer must be maintained. The designated
Critical slope areas shall be protected with safety fence prior to grading.
B6. EROSION AND SEDIMENT CONTROL MEASURES:
Unless otherwise indicated, all erosion and sediment control practices will be constructed
and maintained according to the minimum standards and specifications as set forth in the
Virginia Erosion and Sediment Control Handbook, latest edition. The minimum standards
of the Virginia Erosion and Sediment Control Regulations shall be adhered to unless
otherwise waived or approved by variance.
SILT FENCE (SF) — 3.05
Silt fencing will be installed as a first step in construction activities. Location and
details are shown on the plans.
TEMPORARY DIVERSION DIKE (DD) — 3.09
A temporary diversion dike will be installed before site grading begins, for the purposes of
diverting storm and sediment -laden runoff to the appropriate outlet or trapping facility.
Location and details are shown on the plans.
TEMPORARY SEDIMENT TRAP (ST) — 3.13
A temporary sediment trap will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment traps are shown on the plans.
TEMPORARY SEDIMENT BASIN (SB) — 3.14
A temporary sediment basin will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment basins are shown on the plans.
DUST CONTROL (DC) — 3.39
A variety of methods are available to prevent surface and air movement of dust from
exposed soil surfaces and reduce the presence of airborne substances which may
present health hazards, traffic safety problems or harm animal or plant life.
B7. PERMANENT AND TEMPORARY STABILIZATION:
SURFACE ROUGHENING — 3.29
Disturbed areas to be seeded and mulched shall be left in a roughened condition to help
decrease runoff velocities and aid in the establishment of vegetation.
TOPSOILING — 3.30
Topsoil may be stripped from the area to be graded and stockpiles for later use. All
stockpiles which will be left dormant for more than 30 days shall be temporarily seeded. A
topsoil stockpile may be selected onsite by the developer and shall be temporarily
protected with surrounding silt fencing.
TEMPORARY SEEDING — 3.31
Temporary soil stabilization shall be applied within 7 days to denuded areas that may not
be at final grade, but will remain dormant (undisturbed) for longer than 30 days and less
4
than 1 year. This includes, but is not limited to areas such as soil stockpiles. Seeded
areas shall be limed when necessary at a rate of 2 tons per acre, and fertilized at a rate of
450 lbs. per acre of 10 -20 -20 (10 lbs. per 1,000 square feet) or equivalent. A Temporary
Seeding Schedule is attached for proper seed selection.
PERMANENT SEEDING — 3.32
A perennial vegetative covering shall be established on disturbed areas within 7 days of
being brought to final grade on areas not otherwise protected. Selection of the seed
mixture shall depend on the time of year it is to be applied according to the Permanent
Seed Schedule as shown on the drawing. Seeded areas shall be Timed when necessary
at a rate of 2 tons per acres, and fertilized at a rate of 1,000 lbs. per acre of 10 -20 -10 (10
lbs. per 1,000 square feet) or equivalent.
MULCHING — 3.35
All seeded areas shall be mulched with straw immediately following seeding operations.
Straw mulch shall be applied at a rate of two tons per acre.
SOIL STABILIZATION BLANKETS AND MATTING — 3.36
Soil stabilization matting shall be applied in the conveyance areas of the designed
diversions to help reduce velocities and aid in the establishment of vegetation. A detail
showing the proper materials and installation is shown on the plan.
B8. SOIL STOCKPILES AND BORROW AREAS
No offsite activities are expected for this project.
B9. STORM WATER MANAGEMENT:
Stormwater management facility #2 at Hollymead, which is just upstream of the site,
provides stormwater detention for parcel 46. Stormwater quality shall be provided by
onsite facilities to be installed after site stabilization.
5
B10. MAINTENANCE SCHEDULE:
A program of maintenance for the erosion and sediment controls specified in this narrative
and shown on the plans are recommended as follows:
1. The Site Superintendent or his representative shall make a visual inspection of all
erosion and sediment controls on a daily basis until the site is stabilized and especially
after a heavy rainfall to assure that all controls are in place and that none have been
damaged. Any damaged control shall be repaired prior to the end of each workday to
include re- seeding if necessary.
2. All silt trapping devices shall be cleaned out at 50 percent capacity and sediment shall
be disposed of by spreading on site or hauling away if not suitable for fill.
3. Gravel outlets shall be checked regularly for sediment buildup that may prevent
drainage. Controls shall be inspected and repaired after each rainfall and cleaned if
sediment has accumulated to half of the device's original height.
4. All earthen structures such as diversion dikes and berms shall be checked daily during
construction for breaching by equipment. Repairs shall be made immediately.
5. Silt fences shall be checked after each rainstorm to assure they have not fallen or
become clogged with silt. All repairs shall be made immediately.
6. All seeded areas shall be inspected regularly to see that good stand is maintained.
Areas will be re- fertilized and re- seeded as necessary.
7. After construction operations have ended and disturbed areas have been stabilized, all
berms and sediment - trapping devices may be removed after removal, the ground shall
be restored to its natural or proposed condition to include establishment of permanent
vegetation. Removal of any control is contingent upon approval of the County
Inspector.
6
EROSION AND SEDIMENT CONTROL NARRATIVE
FOR MASS GRADING OF
ABBINGTON PLACE AT HOLLYMEAD TOWNCENTER
July 20 2005.
LOCATION:
Tax Map 32 Parcel 46
Rivanna District, Albemarle County, Virginia
DEVELOPER
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
JUL 2 2005RivannaEngineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
434.984.1599
F) 434.984.8863
A. MINIMUM STANDARDS (MS):
All applicable Virginia Erosion and Sediment Control Regulations and Minimum Standards
shall be adhered to during all phases of construction. These include, but are not limited to
the following:
1. STABLIZATION OF DENUDED AREAS:
Permanent or temporary soil stabilization shall be applied to bare areas within seven days
after final grade is reached on any portion of the site. Temporary soil stabilization shall be
applied within seven days to denuded areas that may not be at final grade, but will remain
dormant or undisturbed for longer than 30 days. Permanent stabilization shall be applied
at areas that are to be left dormant for more than 1 year.
2. STABILIZATION OF SOIL STOCKPILES:
During construction of the project, soil stockpiles shall be stabilized or protected with
sediment trapping measures. The applicant is responsible for temporary protection and
permanent stabilization of all soil stockpiles on site as well as soil intentionally transported
from the project site.
3. PERMANENT VEGETATIVE COVER
A permanent vegetative cover shall be established on denuded areas not otherwise
permanently stabilized. Permanent vegetation shall not be considered established until a
ground cover is achieve that, in the opinion of the county Inspector, is uniform and mature
enough to survive to inhibit erosion.
4. TIMING & STABILIZATION OF SILT TRAPPING MEASURES:
Sediment basins and traps, perimeter dikes, sediment barriers and other measures
intended to trap sediment shall be constructed as a first step in any land disturbing activity
and shall be made functional before upslope land disturbance takes place.
5. STABILIZATION OF EARTHEN STRUCTURES:
Stabilization measures shall be applied to earthen structures such as dams, dikes and
diversions immediately after installation.
6. SEDIMENT TRAPS AND BASINS:
A sediment basin shall control surface runoff from disturbed areas that is comprised of
flow from drainage areas greater than or equal to three acres. The sediment basin shall
be designed and constructed to accommodate the anticipated sediment loading for the
land disturbing activity. The outfall device or system device shall take into account the
total drainage area flowing through the disturbed area to be served by the basin.
7. CUT AND FILL SLOPES:
Cut and fill slopes shall be designed and constructed in a manner that will minimize
erosion. Slopes that are found to be eroding excessively within one year of permanent
stabilization shall be provided with additional slope stabilizing measures until the problem
is corrected.
8. CONCENTRATED RUN -OFF DOWN CUT OR FILL SLOPES:
Concentrated runoff shall not flow down cut or fill slopes unless contained within an
adequate temporary or permanent channel, flume, or slope drain structure.
1
9. WATER SEEPS FROM A SLOPE FACE:
Whenever water seeps from a slope face, adequate drainage or other protection shall be
provided.
10. STORM SEWER INLET PROTECTION:
All storm sewer inlets that are made operable during construction shall be protected so
that sediment -laden water cannot enter the conveyance system without first being filtered
or otherwise treated to remove sediment.
11. STABILIZATION OF OUTLETS:
Before newly constructed stormwater conveyance channels are made operational,
adequate outlet protection and any required temporary or permanent channel lining shall
be installed in both the conveyance channel and receiving channel.
12. WORK IN LIVE WATERCOURSES:
When work in a live watercourse is performed, precautions shall be taken to minimize
encroachment, control sediment transport and stabilize the work area to the greatest
extent possible during construction. Nonerodible material shall be used for the
construction of causeways and cofferdams. Earthen fill may be used for these structures if
armored by nonerodible cover materials.
13. CROSSING A LIVE WATERCOURSE:
When a live watercourse must be crossed by construction vehicles more than twice in any
six month period, a temporary stream crossing constructed of nonerodible materials shall
be provided.
14. APPLICABLE REGULATIONS:
All applicable federal, state and local regulations pertaining to working in or crossing live
watercourses shall be met.
15. STABILIZATION OF BED AND BANKS
The bed and banks of a watercourse shall be stabilized immediately after work in the
watercourse is completed.
16. UNDERGROUND UTILITIES:
Underground utilities shall be installed in accordance with the following standards in
addition to other criteria:
a. No more than 500 linear feet of trench may be opened at one time.
b. Excavated material shall be placed on the uphill side of trenches
c. Effluent for dewatering operations shall be filtered or passed through approved
sediment trapping device, or both, and discharged in a manner that does not adversely
affect flowing streams or offsite property.
d. Material used for backfilling trenches shall be properly compacted in order to minimize
erosion and promote stabilization.
e. Restabilization shall be accomplished in accordance with these regulations.
f. Applicable safety regulations shall be complied with.
2
17. CONSTRUCTION ACCESS ROUTES:
Where construction vehicle access routes intersect paved public roads, provisions shall be
made to minimize the transport of sediment by vehicular tracking onto paved surfaces.
Where sediment is transported on to a public road surface, the road shall be cleaned
thoroughly at the end of each day. Sediment shall be removed by shoveling or sweeping
and transported to a sediment control disposal area. Street washing shall be allowed only
after sediment is removed in this manner. This provision shall apply to individual lots as
well as to larger land disturbing activities.
18. TEMPORARY E &S CONTROL MEASURE REMOVAL:
All temporary erosion and sediment control measures shall be removed within 30 days
after final site stabilization or after temporary measures are no longer needed, unless
otherwise authorized by the local program authority. Trapped sediment and the disturbed
soil areas resulting from the disposition of temporary measures shall be permanently
stabilized to prevent further erosion and sediment.
19. ADEQUACY OF RECEIVING CHANNELS:
Properties and waterways downstream from the development site shall be protected from
sediment deposition, erosion and damage, due to increases in volume, velocity and peak
flow rates of stormwater runoff for the stated frequency storm of 24 -hour duration.
61. PROJECT DESCRIPTION:
The purpose of this project is to mass grade the property. The total area to be disturbed
by this project will be 13.8 acres.
B2. EXISTING SITE CONDITIONS:
The site is currently grassed with mixed deciduous trees. The current vegetation is small
trees and brush. The existing topography is rolling terrain with slopes of 10 -20 %.
B3. ADJACENT AREAS:
The site is bounded to the east, west and south by the Hollymead Towncenter
development, which is mixed use. To the north is the existing Deerwood subdivision.
B4. SOIL DESCRIPTIONS:
According to the Albemarle County Soils Survey conducted by the United States
Department of Agriculture Soil Conservation Service, the primary soil types that may be
disturbed during this scope of work have been identified as the following:
1. Pacolet Sandy loam (65B) — Permeability is moderate, surface runoff is rapid,
and the hazard of erosion is severe. Hydrologic group B, K factor .28
2. Mount Lucas silt loam (57C) — Permeability is slow, surface runoff is medium,
and the hazard of erosion is moderate. Hydrologic group C, K factor .28
3. Elioak Loam (27B) — Permeability is moderate, surface runoff is medium, and the
hazard of erosion is moderate. Hydrologic group C, K factor .28
B5. CRITICAL AREAS:
The stream along the north property line between Deerwood subdivision and parcel 46 is
a critical area, and a 50' undisturbed stream buffer must be maintained.
3
B6. EROSION AND SEDIMENT CONTROL MEASURES:
Unless otherwise indicated, all erosion and sediment control practices will be constructed
and maintained according to the minimum standards and specifications as set forth in the
Virginia Erosion and Sediment Control Handbook, latest edition. The minimum standards
of the Virginia Erosion and Sediment Control Regulations shall be adhered to unless
otherwise waived or approved by variance.
SILT FENCE (SF) — 3.05
Silt fencing will be installed as a first step in construction activities. Location and
details are shown on the plans.
TEMPORARY DIVERSION DIKE (DD) — 3.09
A temporary diversion dike will be installed before site grading begins, for the purposes of
diverting storm and sediment -laden runoff to the appropriate outlet or trapping facility.
Location and details are shown on the plans.
TEMPORARY SEDIMENT TRAP (ST) — 3.13
A temporary sediment trap will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment traps are shown on the plans.
TEMPORARY SEDIMENT BASIN (SB) — 3.14
A temporary sediment basin will be installed before site grading begins, for the purpose of
detaining sediment -laden runoff from disturbed areas. Location and details of the
sediment basins are shown on the plans.
DUST CONTROL (DC) — 3.39
A variety of methods are available to prevent surface and air movement of dust from
exposed soil surfaces and reduce the presence of airborne substances which may
present health hazards, traffic safety problems or harm animal or plant life.
B7. PERMANENT AND TEMPORARY STABILIZATION:
SURFACE ROUGHENING — 3.29
Disturbed areas to be seeded and mulched shall be left in a roughened condition to help
decrease runoff velocities and aid in the establishment of vegetation.
TOPSOILING — 3.30
Topsoil may be stripped from the area to be graded and stockpiles for later use. All
stockpiles which will be left dormant for more than 30 days shall be temporarily seeded. A
topsoil stockpile may be selected onsite by the developer and shall be temporarily
protected with surrounding silt fencing.
TEMPORARY SEEDING — 3.31
Temporary soil stabilization shall be applied within 7 days to denuded areas that may not
be at final grade, but will remain dormant (undisturbed) for longer than 30 days and less
than 1 year. This includes, but is not limited to areas such as soil stockpiles. Seeded
areas shall be limed when necessary at a rate of 2 tons per acre, and fertilized at a rate of
450 lbs. per acre of 10 -20 -20 (10 lbs. per 1,000 square feet) or equivalent. A Temporary
Seeding Schedule is attached for proper seed selection.
4
PERMANENT SEEDING — 3.32
A perennial vegetative covering shall be established on disturbed areas within 7 days of
being brought to final grade on areas not otherwise protected. Selection of the seed
mixture shall depend on the time of year it is to be applied according to the Permanent
Seed Schedule as shown on the drawing. Seeded areas shall be limed when necessary
at a rate of 2 tons per acres, and fertilized at a rate of 1,000 lbs. per acre of 10 -20 -10 (10
lbs. per 1,000 square feet) or equivalent.
MULCHING — 3.35
All seeded areas shall be mulched with straw immediately following seeding operations.
Straw mulch shall be applied at a rate of two tons per acre.
SOIL STABILIZATION BLANKETS AND MATTING — 3.36
Soil stabilization matting shall be applied in the conveyance areas of the designed
diversions to help reduce velocities and aid in the establishment of vegetation. A detail
showing the proper materials and installation is shown on the plan.
B8. SOIL STOCKPILES AND BORROW AREAS
No offsite activities are expected for this project.
B9. STORM WATER MANAGEMENT:
Stormwater management facility #2 at Hollymead, which is just upstream of the site,
provides stormwater detention for parcel 46. Stormwater quality shall be provided by
onsite facilities to be installed after site stabilization.
B10. MAINTENANCE SCHEDULE:
A program of maintenance for the erosion and sediment controls specified in this narrative
and shown on the plans are recommended as follows:
1. The Site Superintendent or his representative shall make a visual inspection of all
erosion and sediment controls on a daily basis until the site is stabilized and especially
after a heavy rainfall to assure that all controls are in place and that none have been
damaged. Any damaged control shall be repaired prior to the end of each workday to
include re- seeding if necessary.
2. All silt trapping devices shall be cleaned out at 50 percent capacity and sediment shall
be disposed of by spreading on site or hauling away if not suitable for fill.
3. Gravel outlets shall be checked regularly for sediment buildup that may prevent
drainage. Controls shall be inspected and repaired after each rainfall and cleaned if
sediment has accumulated to half of the device's original height.
4. All earthen structures such as diversion dikes and berms shall be checked daily during
construction for breaching by equipment. Repairs shall be made immediately.
5. Silt fences shall be checked after each rainstorm to assure they have not fallen or
become clogged with silt. All repairs shall be made immediately.
6. All seeded areas shall be inspected regularly to see that good stand is maintained.
Areas will be re- fertilized and re- seeded as necessary.
7. After construction operations have ended and disturbed areas have been stabilized, all
berms and sediment - trapping devices may be removed after removal, the ground shall
be restored to its natural or proposed condition to include establishment of permanent
vegetation. Removal of any control is contingent upon approval of the County
Inspector.
5
HYDROLOGIC /HYDRAULIC CALCULATIONS
FOR
ABINGTON PLACE AT HOLLYMEAD TOWNCENTER
SEDIMENT BASIN -1
March 2, 2006
LOCATION:
Rio District, Albemarle County, Virginia
OWNER:
Southern Development
South Pantops Drive
Charlottesville, VA 22911
PREPARED BY:
Rivanna Engineering & Surveying, PLC
1350 Stony Point Rd.
Charlottesville, VA 22911
P: 434.984.1599
F: 434.984.8863
INDEX
Summary:2
Pre - Development:
Flood Hydrographs:3 -4
Pre - Development:
Pond & Outlet Structure:4 -8
Routed Hydrographs:9 -10
Drainage Area Maps are included attached at the end of this report.
Rivanna Engineering & Surveying, PLC Page 1
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Summary
One sediment basin will provide erosion and sediment control for Abington Place at Hollymead Towncenter.
Drainage area DA -SB1 flows into SB -1.
Rivanna Engineering & Surveying, PLC Page 2
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Pre - Development Hydrographs
Name:DA -SB1 25 Yr
Type:Modified Rational
HYDROGRAPH INFORMATION]
Peak Flow (Qp)31.94 (cfs)
Time to Peak (Tp)10.00 min)
Time of Base (Tb)25.00 min)
Volume 0.55 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier 1.00
Receding Limb Factor 1.50
APPROXIMATE STORAGE]
Maximum Outflow 0.00 cfs)
Maximum Storage 0.55 cu ft)
BASIN INFORMATION]
WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
None>
Overall Approximation 10.15 NA 0.45
TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc)10.00 min)
RAINFALL DESCRIPTION]
Distribution Type Synthetic
Total Precipitation 1.16 in)
Return Period 25 yr)
Storm Duration 0.17 hr)
Rivanna Engineering & Surveying, PLC Page 3
434) 984-1599
Abington Place at Hollymead Towncenter, SB -1
Pre - Development Hydrographs
DA -SB1 25 Yr
Hydrograph Flow Values: Time vs. Flow
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
min)in)in)cfs)cfs)
1 1.00 0.00 0.12 0.00 3.19
2 2.00 0.12 0.23 3.19 6.39
3 3.00 0.12 0.35 3.19 9.58
4 4.00 0.12 0.46 3.19 12.78
5 5.00 0.12 0.58 3.19 15.97
6 6.00 0.12 0.69 3.19 19.17
7 7.00 0.12 0.81 3.19 22.36
8 8.00 0.12 0.92 3.19 25.56
9 9.00 0.12 1.04 3.19 28.75
10 10.00 0.12 1.16 3.19 31.94
11 11.00 0.00 1.16 2.13 29.82
12 12.00 0.00 1.16 2.13 27.69
13 13.00 0.00 1.16 2.13 25.56
14 14.00 0.00 1.16 2.13 23.43
15 15.00 0.00 1.16 2.13 21.30
16 16.00 0.00 1.16 2.13 19.17
17 17.00 0.00 1.16 2.13 17.04
18 18.00 0.00 1.16 2.13 14.91
19 19.00 0.00 1.16 2.13 12.78
20 20.00 0.00 1.16 2.13 10.65
21 21.00 0.00 1.16 2.13 8.52
22 22.00 0.00 1.16 2.13 6.39
23 23.00 0.00 1.16 2.13 4.26
24 24.00 0.00 1.16 2.13 2.13
25 25.00 0.00 1.16 2.13 0.00
Rivanna Engineering & Surveying, PLC Page 4
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Pond Report
Name: Water Quality Pond
RATING CURVE LIMIT]
Minimum Elevation 516.40 ft)
Maximum Elevation 523.00 ft)
Elevation Increment 0.20 ft)
STAGE STORAGE INFORMATION]
Storage Method: User - Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative Volume
ft)sq ft)sq ft)cu ft)cu ft)
1 516.40 0.00 0.00 0.00 0.00
2 518.90 0.00 0.00 0.00 0.00
3 519.00 8519.00 4259.50 425.95 425.95
4 520.50 9496.00 9007.50 13511.25 13937.20
5 522.50 13545.00 11520.50 23041.00 36978.20
6 523.00 14592.00 14068.50 7034.25 44012.45
DISCHARGE INFORMATION]
Structure Number: 1
Type:
Name:Stand Pipe
Structure Number: 2
Type:Trapezoidal Weir
Name:Bio- Filter #1 Weir
RESERVOIR STAGE STORAGE /DISCHARGE]
Elevation Stage Area Storage Discharge
ft)ft)sq ft)cu ft)cfs)
516.80 0.40 0.00 0.00 0.00
517.20 0.80 0.00 0.00 0.00
517.60 1.20 0.00 0.00 0.00
518.00 1.60 0.00 0.00 0.00
518.40 2.00 0.00 0.00 0.00
518.80 2.40 0.00 0.00 0.00
519.20 2.80 8649.27 2568.73 C).00
519.60 3.20 8909.80 6080.54 0.00
520.00 3.60 9170.33 9696.57 0.00
520.40 4.00 9430.87 13416.81 0.00
520.80 4.40 10103.35 17309.92 0.00
521.20 4.80 10913.15 21513.22 0.00
521.60 5.20 11722.95 26040.44 7.11
522.00 5.60 12532.75 30891.58 18.83
522.40 6.00 13342.55 36066.64 29.87
522.80 6.40 14173.20 41569.09 49.65
Maximum Storage 44445.61 cu ft)
Maximum Discharge 61.87 cfs)
Rivanna Engineering & Surveying, PLC Page 5
434) 984-1599
Abington Place at Hollymead Towncenter, SB -1
Pond Report
Type Stand Pipe
Name Stand Pipe
RATING CURVE LIMIT]
Minimum Elevation 516.50 ft)
Maximum Elevation 523.00 ft)
Elevation Increment 0.20 ft)
STAND PIPE INFORMATION]
ORIFICE INFORMATION]
Height 3.50 ft)
Width 3.00 ft)
Crest Length 13.00 ft)
Effective Crest Length 13.00 ft)
Orifice Coefficient 0.60
Fractional Open Area 0.60
ORIFICE EQUATION]
Q = Co *A((2gh) /k) ^0.5
DEFINITIONS]
Co Orifice Coefficient
A Wetted Area, sq ft)
WEIR INFORMATION]
Crest Elevation 521.30 ft)
Weir Coefficient 3.33
Exponential 1.50
WEIR EQUATION]
Q = Cw * L * H ^exp
DEFINITIONS]
Cw Weir Coefficient
H Headwater depth above inlet control section invert ft
L Crest length ft
CULVERT INFORMATION]
Type Circular Concrete - Square Edge with Headwall
OUTLET STRUCTURE INFORMATION]
Diameter 18.00 in)
Invert Elevation 516.50 ft)
OUTLET STRUCTURE REPORT
Pipe Length 86.00 ft)
Slope 0.03
Manning's n Value 0.01
Orifice Coefficient 0.60
Tailwater Elevation 514.50 ft)
Number of Barrels 1
Rivanna Engineering & Surveying, PLC Page 6
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Pond Report
UNSUBMERGED EQUATION]
H /Diam = Hc/ Diam +K *(Q /(A *Diam ^0.5)) ^M -0.5 *S
Coefficient K 0.01
Coefficient M 2.00
Q Maximum 7.58
SUBMERGED EQUATION]
H /Diam = c *(Q /(A *Diam ^0.5)) ^2 +Y -0.5 *S
Coefficient c 0.04
Coefficient Y 0.67
Q Minimum 8.66
DEFINITIONS]
H Headwater depth above inlet control section invert, ft)
Diam Interior height of culvert barrel, ft)
He Specific head at critical depth (dc +Vc ^2 /2g), ft)
Q Discharge, cfs)
A Full cross sectional area of culvert barrel, sq ft)
S Culvert barrel slope, ft /ft)
STAND PIPE STAGE VS. DISCHARGE]
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.90 0.40 0.00 0.00 0.00 0.70 0.00
517.30 0.80 0.00 0.00 0.00 2.40 0.00
517.70 1.20 0.00 0.00 0.00 4.60 0.00
518.10 1.60 0.00 0.00 0.00 6.91 0.00
518.50 2.00 0.00 0.00 0.00 8.94 0.00
518.90 2.40 0.00 0.00 0.00 10.55 0.00
519.30 2.80 0.00 0.00 0.00 11.94 0.00
519.70 3.20 0.00 0.00 0.00 13.19 0.00
520.10 3.60 0.00 0.00 0.00 14.33 0.00
520.50 4.00 0.00 0.00 0.00 15.39 0.00
520.90 4.40 0.00 0.00 0.00 16.38 0.00
521.30 4.80 0.00 0.00 0.00 17.31 0.00
521.70 5.20 0.00 0.00 10.95 18.19 10.95
522.10 5.60 0.00 0.00 26.53 19.04 19.04
522.50 6.00 0.00 0.00 33.22 19.84 19.84
522.90 6.40 0.00 0.00 38.35 20.62 20.62
WEIR STAGE VS. DISCHARGE]
Elevation Stage Weir 1 Weir 2 Weir 3 Weir 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.90 0.40 0.00 0.00 0.00 0.00 0.00
517.30 0.80 0.00 0.00 0.00 0.00 0.00
517.70 1.20 0.00 0.00 0.00 0.00 0.00
518.10 1.60 0.00 0.00 0.00 0.00 0.00
518.50 2.00 0.00 0.00 0.00 0.00 0.00
518.90 2.40 0.00 0.00 0.00 0.00 0.00
519.30 2.80 0.00 0.00 0.00 0.00 0.00
519.70 3.20 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 7
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Pond Report
520.10 3.60 0.00 0.00 0.00 0.00 0.00
520.50 4.00 0.00 0.00 0.00 0.00 0.00
520.90 4.40 0.00 0.00 0.00 0.00 0.00
521.30 4.80 0.00 0.00 0.00 0.00 0.00
521.70 5.20 0.00 0.00 0.00 0.00 0.00
522.10 5.60 0.00 0.00 0.00 0.00 0.00
522.50 6.00 0.00 0.00 0.00 0.00 0.00
522.90 6.40 0.00 0.00 0.00 0.00 0.00
ORIFICE STAGE VS. DISCHARGE]
Elevation Stage Orifice 1 Orifice 2 Orifice 3 Orifice 4 Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
516.90 0.40 0.00 0.00 0.00 0.00 0.00
517.30 0.80 0.00 0.00 0.00 0.00 0.00
517.70 1.20 0.00 0.00 0.00 0.00 0.00
518.10 1.60 0.00 0.00 0.00 0.00 0.00
518.50 2.00 0.00 0.00 0.00 0.00 0.00
518.90 2.40 0.00 0.00 0.00 0.00 0.00
519.30 2.80 0.00 0.00 0.00 0.00 0.00
519.70 3.20 0.00 0.00 0.00 0.00 0.00
520.10 3.60 0.00 0.00 0.00 0.00 0.00
520.50 4.00 0.00 0.00 0.00 0.00 0.00
520.90 4.40 0.00 0.00 0.00 0.00 0.00
521.30 4.80 0.00 0.00 0.00 0.00 0.00
521.70 5.20 0.00 0.00 0.00 0.00 0.00
522.10 5.60 0.00 0.00 0.00 0.00 0.00
522.50 6.00 0.00 0.00 0.00 0.00 0.00
522.90 6.40 0.00 0.00 0.00 0.00 0.00
Rivanna Engineering & Surveying, PLC Page 8
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Routed Hydrographs
Name:DA -SB1 25 Rtd
Type:Reservoir: Modified Puls
HYDROGRAPH INFORMATION]
Peak Flow (Qp)1.31 (cfs)
Time to Peak (Tp)24.00 min)
Time of Base (Tb)530.00 min)
Volume 0.06 (ac -ft)
Time Step 1.00 min)
Peak Elevation 521.39 (ft)
Detention Time NA
RESERVOIR STRUCTURE INFORMATION]
Number 1
Name Water Quality Pond
Storage Type User - Defined Area
Maximum Storage 44445.61 cu ft)
Maximum Discharge 61.87 cfs)
INFLOW HYDROGRAPH INFORMATION]
Number 1
Name DA -SB1 25 Yr
Peak Flow (Qp)31.94 cfs)
Time to Peak (Tp)10.00 min)
Time of Base (Tb)25.00 (min)
Volume 0.55 ac -ft)
Flow Multiplier 1.00
EQUATION]
I1 +I2) + (2(S1) /dt) -01 = (2(S2) /dt) +02
Where:
Il = Previous inflow
I2 = Current inflow
S1 = Previous storage
S2 = Current storage
dt = Time increment
01 = Previous outflow
02 = Current outflow
A = (I1 + I2)
B = (2 S1) dt) - 01
C = (2 (S2) dt) + 02
Rivanna Engineering & Surveying, PLC Page 9
434) 984 -1599
Abington Place at Hollymead Towncenter, SB -1
Routed Hydrographs
DA-S81 25 Rtd
Computation of Reservoir Outflow Table of Modified Puls Method
Intv Time Inflow A B C Outflow Storage Elev
min) cfs)cfs)cfs)cfs)cfs)cu ft) ft)
1 1.00 3.19 3.19 0.00 191.66 0.00 95.83 518.82
2 2.00 6.39 9.58 191.66 766.66 0.00 383.33 518.89
3 3.00 9.58 15.97 766.66 1724.98 0.00 862.49 519.00
4 4.00 12.78 22.36 1724.98 3066.62 0.00 1533.31 519.08
5 5.00 15.97 28.75 3066.62 4791.60 0.00 2395.80 519.18
6 6.00 19.17 35.14 4791.60 6899.90 0.00 3449.95 519.30
7 7.00 22.36 41.53 6899.90 9391.54 0.00 4695.77 519.44
8 8.00 25.56 47.92 9391.54 12266.50 0.00 6133.25 519.61
9 9.00 28.75 54.30 12266.50 15524.79 0.00 7762.39 519.79
10 10.00 31.94 60.69 15524.79 19166.40 0.00 9583.20 519.99
11 11.00 29.82 61.76 19166.40 22872.16 0.00 11436.08 520.19
12 12.00 27.69 57.51 22872.16 26322.62 0.00 13161.31 520.37
13 13.00 25.56 53.25 26322.62 29517.54 0.00 14758.77 520.54
14 14.00 23.43 48.99 29517.54 32456.90 0.00 16228.45 520.69
15 15.00 21.30 44.73 32456.90 35140.70 0.00 17570.35 520.83
16 16.00 19.17 40.47 35140.70 37568.96 0.00 18784.48 520.94
17 17.00 17.04 36.21 37568.96 39741.66 0.00 19870.83 521.05
18 18.00 14.91 31.95 39741.66 41658.81 0.00 20829.41 521.14
19 19.00 12.78 27.69 41658.81 43314.99 0.09 21657.54 521.21
20 20.00 10.65 23.43 43314.99 44684.64 0.51 22342.58 521.27
21 21.00 8.52 19.17 44684.64 45753.77 0.84 22877.30 521.32
22 22.00 6.39 14.92 45753.77 46533.27 1.08 23267.17 521.36
23 23.00 4.26 10.66 46533.27 47033.65 1.23 23517.44 521.38
24 24.00 2.13 6.40 47033.65 47265.05 1.31 23633.18 521.39
25 25.00 0.00 2.14 47265.05 47237.21 1.30 23619.25 521.39
26 26.00 0.00 0.00 47237.21 47084.70 1.25 23542.98 521.38
27 27.00 0.00 0.00 47084.70 46937.48 1.20 23469.34 521.38
28 28.00 0.00 0.00 46937.48 46795.60 1.16 23398.38 521.37
29 29.00 0.00 0.00 46795.60 46658.87 1.12 23330.00 521.36
30 30.00 0.00 0.00 46658.87 46527.10 1.08 23264.09 521.36
31 31.00 0.00 0.00 46527.10 46400.11 1.04 23200.57 521.35
32 32.00 0.00 0.00 46400.11 46277.72 1.00 23139.36 521.35
33 33.00 0.00 0.00 46277.72 46159.78 0.97 23080.37 521.34
34 34.00 0.00 0.00 46159.78 46046.11 0.93 23023.52 521.34
35 35.00 0.00 0.00 46046.11 45936.57 0.90 22968.73 521.33
36 36.00 0.00 0.00 45936.57 45831.00 0.86 22915.93 521.33
37 37.00 0.00 0.00 45831.00 45729.26 0.83 22865.04 521.32
38 38.00 0.00 0.00 45729.26 45631.21 0.80 22816.01 521.32
39 39.00 0.00 0.00 45631.21 45536.72 0.77 22768.74 521.31
40 40.00 0.00 0.00 45536.72 45445.65 0.75 22723.20 521.31
Rivanna Engineering & Surveying, PLC Page 10
434) 984 -1599
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place f PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 10/25/2005
LOCATION L BY JMS
INPUT
DRAINAGE AREA 10.40 ac
BASIN VOLUME DESIGN
WET STORAGE
1. MINIMUM REQUIRED VOLUME i 696.80 cy
2. AVAILABLE BASIN VOLUME
AVERAGE END AREA - BASIN VOLUME ESTIMATES
1
ELEVATION AREA VOLUME VOLUME TOTAL
sf at cy cy
532 3,338.00
8,415.00 311.67
534 5,077.00 311.67
14,433.0 534.56
536 9,356.00 846.22
I 22,788.00 844.00
538 13,432 00 1,690.22
REQUIRED WET STORAGE VOLUME 696.80 cy
APPROX. ELEVATION i --535.28
3. EXCAVATE CUBIC YARDS
4. AVAILABLE VOLUME BEFORE CLEANOUT REQUIRED 348.40 cy
5. ELEVATION CORRESPONDING TO CLEANOUT LEVEL 534.29
6. DISTANCE FROM DEWATERING ORIFICE TO C/O LEVEL
INVERT DEWATERING ORIFICE R'QD 535.28
INVERT DEWATERING ORIFICE USED 535.30
APPROX. VOLUME AT INVERT USED 7 cy
DISTANCE FROM INVERT TO C/O LEVEL 1.01 ft
DISTANCE ACCEPTABLE
WET STORAGE VOLUME ACCEPTABLE
DRY STORAGE
7. MINIMUM REQUIRED VOLUME 696.80 cy
8. TOTAL AVAILABLE VOLUME AT CREST OF RISER
CREST OF RISER 537.40
APPROX. AVAILABLE TOTAL VOLUME 14 1.86 c_y
ADEQUATE DRY STORAGE VOLUME
9. DIAMETER OF DEWATERING ORIFICE
Q 0.90 cfs
d(1ST ITERATION)5.80 in
d(2nd ITERATION)6.19 in
d(3rd ITERATION)In
d(4th ITERATION)6.23 in
USE d 6 in
10. DIAMETER OF FLEXIBLE TUBING 8 In
STANDARD SIZE
Page 1 Abington - SB.xls
J
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place I PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 10/25/2005
LOCATION BY JMS
PRELIMINARY DESIGN
11. PRELIMINARY DESIGN ELEVATIONS:
CREST OF RISER 537.40 It
TOP OF DAM 539.40 tt
DESIGN HIGH WATER 538.20,tt
UPSTREAM TOE - - i 529.00 tt
BASIN SHAPE
12. LENGTH OF FLOW / EFFECTIVE WIDTH
SURFACE AREA OF NORMAL POOL 9100 sf
LENGTH OF FLOW PATH 108 ft
EFFECTIVE WIDTH 84 ft
L/We 1.28IBAFFLES REQUIRED
RUNOFF
RATIONAL METHOD CALCULATION)
USE MAXIMUM C VALUE DURING CONSTRUCTION AND MINIMUM Tc VALUE
13. FLOW FROM 2 -YEAR STORM
C:0.50
Tc:5.0 I:5.5 in /hr
Q=28.6 cfs
14. FLOW FROM 25 -YEAR STORM
C:0.50
Tc.5.0 I:8.1 in /hr
Q.42.1 cfs
PRINCIPAL SPILLWAY DESIGN
15. REQUIRED SPILLWAY CAPACITY:
EMERGENCY SPILLWAY ?JY /NJ;
REQUIRED SPILLWAY CAPACITY:28.6 CFS
16. ASSUMED AVAILABLE HEAD:
ELEV. OF CREST OF E.S. IF USED:538.00
ASSUMED AVAILABLE HEAD=0.60 tt
17. RISER DIMENSIONS: I
RISER DIAMETER:36.00 In From Plate 3.14 -8 or Calcs)
ACTUAL MAX. ELEV.:537.40 It From Calcs if appropriate)
ACTUAL HEAD:0.00 ft From Plate 3.14 -8 or Cal)
18. BARREL LENGTH:
BARREL LENGTH:I 33.00 ft
BARREL INVERT OUT:(529.00 ft
HEAD H ON BARREL:I 8.40 ft From Plate 3.14 -77
19. BARREL DIAMETER: 1
BARREL DIAMETER 24 in From Plate 3.14A or 3.148)
20. TRASH RACK AND ANTI - VORTEX DEVICE:
DIAMETER:48 in From Plate 3.14D)
HEIGHT:24 In
Page 2 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT lAbington Place PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #1 DATE 10/25/2005
LOCATION BY JM S
1 I
EMERGENCY SPILLWAY DESIGN
21. REQUIRED SPILLWAY CAPACITY:
I Qe = Q(25)-Qp =13.5 CFS
22. DIMENSIONS:
1 BOTTOM WIDTH (b):18.00 ft From Table 3.14 -C)
SLOPE OF EXIT CHANNEL (s):0.04 tt/tt i (From Table 3.14 -C)
MIN. LENGTH EXIT CHANNEL (x):33.00 ft From Table 3.14 -C)
I I
ANTI -SEEP COLLAR DESIGN
I
23. DIMENSIONS:
DEPTH WATER @ CREST OF P.S. 8.40 it
SLOPE UPSTREAM FACE DAM (Z):2.00 :1
SLOPE P.S. BARREL (Sb):6.10 %
LENGTH BARREL IN SAT. ZONE (Ls):60.00 It From Plate 3.14 -11)
24. NUMBER OF COLLARS:
NUMBER REQUIRED:2 From Plate 3.14 -12)
I DIMENSIONS:5.0 tt "2 From Plate 3.14-12)
FINAL DESIGN ELEVATIONS
25. ELEVATIONS:
1 TOP OF DAM 539.40 ft
DESIGN HIGH WATER:537.40 ft
EMERGENCY SPILLWAY CREST:538.00 ft
PRINCIPAL SPILLWAY CREST:537.40 ft
DEWATERING ORIFICE INVERT:535.30 ft
CLEANOUT ELEVATION:534.29 ft
Page 3 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place, EnS PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #2 DATE 10/25/2005
LOCATION BY JMS
INPUT f _
DRAINAGE AREA 1 8.90 ac
BASIN VOLUME DESIGN
WET STORAGE
1. MINIMUM REQUIRED VOLUME 596.30 cy
2. AVAILABLE BASIN VOLUME
AVERAGE END AREA - BASIN VOLUME ESTIMATES
I
ELEVAiic? AREA VOLUME VOLUME TOTAL
ft st of cV cy
544 2,037.00
7,711.00 285.59
546 5,674.00 285.59
15,224.00 563.85
548 9,550.00 849.44
23,231.00 860.41
550 13,681.00 1,709.85
REQUIRED WET STORAGE VOLUME 596.30 cy
APPROX. ELEVATION 547.03
3. EXCAVATE CUBIC YARDS
4. AVAILABLE VOLUME BEFORE CLEANOUT REQUIRED 298.15jcy
5. ELEVATION CORRESPONDING TO CLEANOUT LEVEL 546.20
6. DISTANCE FROM DEWATERING ORIFICE TO C/O LEVEL
INVERT DEWATERING ORIFICE R'QD 1 547.03
INVERT DEWATERING ORIFICE USED 547.20
APPROX. VOLUME AT INVERT USED 663.44 cy
DISTANCE FROM INVERT TO C/0 LEVEL 1.00 ft
DISTANCE NOT ACCEPTABLE- 1' R'QD
WET STORAGE VOLUME ACCEPTABLE
DRY STORAGE
7. MINIMUM REQUIRED VOLUME 596.30 cy
8. TOTAL AVAILABLE VOLUME AT CREST OF RISER
CREST OF RISER 1 548.90
APPROX. AVAILABLE TOTAL VOLUME 1268.75Icy
ADEQUATE DRY STORAGE VOLUME
9. DIAMETER OF DEWATERING ORIFICE
p 0.76 cfs
d(1ST ITERATION)5.59 in
d(2nd ITERATION)6.06 in
d(3rd ITERATION)6.11 in
d(4th ITERATION)6.11 In
USE d 7 6 in
10. DIAMETER FLEXIBLE TUBING 8 in
1STANDARD SIZE
Page 1 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT Abington Place, EnS PROJ NO.
BASIN #TEMPORARY SEDIMENT BASIN #2 DATE 10/25/2005
LOCATION BY JMS
PRELIMINARY DESIGN
11. PRELIMINARY DESIGN ELEVATIONS:
CREST OF RISERI 548.90 ft
TOP OF DAM 550.80 tt
I DESIGN HIGH WATER 549.30 tt
UPSTREAM TOE OF DAM 541.001tt
I
BASIN SHAPE
12. LENGTH OF FLOW / EFFECTIVE WIDTH:
SURFACE AREA OF NORMAL POOL 8500 sf
LENGTH OF FLOW PATH 90 tt
EFFECTIVE WIDTH 94 It
L/We 0.95 BAFFLES REQUIRED
RUNOFF
RATIONAL METHOD CALCULATION)
USE MAXIMUM C VALUE DURING CONSTRUCTION AND MINIMUM Tc VALUE
13. FLOW FROM 2 -YEAR STORM
C:,0.50
Tc:5.0 I:5.5 In /hr
0=24.5 cfs
14. FLOW FROM 25 -YEAR STORM
C:f 0.50
Tc:5.0 I:8.1 in /hr
Q=36.0 cfs
PRINCIPAL SPILLWAY DESIGN
15. REQUIRED SPILLWAY CAPACITY:
EMERGENCY SPILLWAY? (Y /N)'Y
REQUIRED SPILLWAY CAPACITY:24.5 CFS
16. ASSUMED AVAILABLE HEAD:
ELEV. OF CREST OF E.S. IF USED:549.30
ASSUMED AVAILABLE HEAD_0.40 ft
17. RISER DIMENSIONS:
RISER DIAMETER 36.00 in From Plate 3.14 -8 or Calcs)
548.90 tt From Calcs if appropriate)ACTUAL MAX. ELEV.:
A C TUAL HEAD:0.00 ft F_rom Plate 3.14 -8 or Calcs)
18. BARREL LENGTH: 1
BARREL LENGTH:37.00 tt
BARREL INVERT OUT:540.30 tt
HEAD HON BARREL:8.60 It From Plate 3.14 -71
19. BARREL DIAMETER:
BARREL DIAMETER:24 In om P_ late 3.14A or 3 14B)
20. TRASH RACK AND ANTI - VORTEX DEVICE:
DIAMETER:48 In From Plate 3.14Dj
HEIGHT:24 In
Page 2 Abington - SB.xls
TEMPORARY SEDIMENT BASIN
PROJECT lAbington Place, EnS PROJ NO.
BASIN #1TEMPORARY SEDIMENT BASIN #2 1DATE 10/25/2005
LOCATION BY JMS
1
EMERGENCY SPILLWAY DESIGN
21. REQUIRED SPILLWAY CAPACITY:
Qe = Q(25) -Qp =1 11.6 CFS
22. DIMENSIONS:
1 BOTTOM WIDTH (b) •16.00 tt j from Table 3.14-CL
SLOPE OF EXIT CHANNEL (s):'0.04 ft/ft From Table 3.14 -C)
MIN. LENGTH EXIT CHANNEL (x):33.00 ft From Table 3.14 -C)
1
ANTI -SEEP COLLAR DESIGN
23. DIMENSIONS:
DEPTH WATER @ CREST OF P.S. (Y):7.90 ft
SLOPE UPSTREAM FACE DAM (Z4:2.00 :1
SLOPE P.S. BARREL (Sb):7.30 %
LENGTH BARREL IN SAT. ZONE (Ls):70.00 ft From Plate 3 14 -11)
24. NUMBER OF COLLARS:
NUMBER REQUIRED:2 From Plate 3.14 -12)
DIMENSIONS:5.3 ft"2 From Plate 3.14 -12)
FINAL DESIGN ELEVATIONS
1
25. ELEVATIONS:
TOP OF DAM:550.80 tt
DESIGN HIGH WATER:548.90 ft
EMERGENCY SPILLWAY CREST:549.30 ft
PRINCIPAL SPILLWAY CREST:548.90 ft
DEWATERING ORIFICE INVERT:547.20 ft
CLEANOUT ELEVATION:546.20 ft
Page 3 Abington - SB.xls
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