HomeMy WebLinkAboutSDP200500111 Calculations Minor Amendment 2006-01-03 1350 Stony Point Road Rivanna Engineering 434.984.1599
Charlottesville, VA 22911 & Surveying, PLC (F) 434.984.8863
Memorandum
To: Allan Sd uck
From: Tim Miller
CC: Tony
Date: January 2, 2006
Re: Minor Site Plan Amendment for Carriage Gate Apartments
Dear Alan;
This is in response to your comment on the Carriage Gate Apartments Minor Site
Plan Amendment.
We have added four concrete channels along the parking area as we discussed.
Attached is a drainage area map of this area.
The run-off calculations are as follows:
RECEIVED
DA-1: Area=0.05 Acres, C=0.90, 1=4.0 inches/hr.
Q=0.18*0.90*4.0= 0.18 cfs. AN 03 2006
DA-2: Area =0.07 Acres, C=0.90, 1=4.0 inches/hr. COMMUNITY DtVtLU,MENT
Q=0.07*0.90*4.0= 0.25 cfs.
As the run-off exits each channel it will spread out across the pavement. Spread
width downstream from each channel will average approximately 10-feet (20-feet
total since there are two channels per drainage area), and have a velocity of at least
2 fps. Under these conditions the depth of flow for 0.18 cfs will be 0.0045 feet, and
depth of flow for 0.25 cfs will be 0.0063-feet. These depths will not cause hazardous
conditions as it flows across the travel way.
Please contact me if you need any additional information.
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FHWA Urban Drainage Design Program, HY-22
Drainage of Highway Pavements
Inlets on Grade
Date: 01/02/2006
Project No. : 1139
Project Name. :Carriage Gate
Computed by :Rivanna Engineering
'ect Description
epth of Water on Speed Bump
to rainage nl et ST-
Inlets on Grade: Gutter Flow Parameters
Roadway and Discharge Data
Cross Slope Uniform
S Longitudinal Slope (ft/ft) 0 . 0450 -v13
Sx Pavement Cross Slope (ft/ft) 0. 0200 - - c9 B
Sw Gutter Cross Slope (ft/ft) 0 . 0200 '7_
n Manning' s Coefficient 0. 016
W Gutter Width (ft) 1. 00
a Gutter Depression (inch) 0 . 00
Q Discharge (cfs) 1. 770
T Width of Spread (ft) 6. 74
Gutter Flow
Eo Gutter Flow Ratio 0 . 349
d Depth of Flow (ft) 0. 13 = ‘,ca z,,\
✓ Average Velocity (ft/sec) 3. 90
VA = o.(a-AMS
L = 4.0 1 hr
• FHWA Urban Drainage Design Program, HY-22
Drainage of Highway Pavements
Inlets on Grade
Date: 01/02/2006
Project No. : 1139
Project Name. :Carriage Gate
Computed by :Rivanna Engineering
Project Description
Depth of Water on Speed Bump
to Drainage Inlet ST-2A
Inlets on Grade: Gutter Flow Parameters
Roadway and Discharge Data
Cross Slope Uniform
S Longitudinal Slope (ft/ft) 0. 1000
Sx Pavement Cross Slope (ft/ft) 0. 0200
Sw Gutter Cross Slope (ft/ft) 0. 0200
n Manning' s Coefficient 0. 016
W Gutter Width (ft) 1. 00
a Gutter Depression (inch) 0 . 00
Q Discharge (cfs) 0. 190
T Width of Spread (ft) 2 . 52
Gutter Flow
Eo Gutter Flow Ratio 0 . 741
d Depth of Flow (ft) 0 . 05 =
✓ Average Velocity (ft/sec) 3 . 00
= D.O(o G<<eS
C = 0,11
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MINOR SITE PLAN AMENDMENT FOR y,+j° "�"'0y� RIVANNA ENGINEERING &
z CARRIAGE GATE APARTMENTS CD DRAINAGE AREA MAP N: I_ 0 A SURVEYING, PLC.
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Rio District, Albemarle County, Virginia Drawing Scale: As Shown Drown By roe fie Nome:45-91-YA.dwg o %fR ". r'k 1350 Stony Point Rd PHONY:(494)984-1599
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Dote:. 01.03.06 Checked By 1RU Project No.: 1139 r� Charlottesville.VA 22911 FAX: (434)984-8863
1350 Stony Point Road Rivanna Engineering 434,984.1599
Charlottesville, VA 22911 & Surveying, PLC (F) 434.984.8863
Memorandum
Ta Allan Sthudc
From: Tim Miller
CC: Tony
Date: November 22, 2005
Re: Minor Site Plan Amendment For Carriage Gate Apartments
Dear Alan;
This is in response to your comments on the Carriage Gate Apartments Minor Site
Plan Amendment.
You have indicated that you would be amenable to reviewing run-off calculations for
the revised parking area at the rear of the site. Attached is a drainage area map of
this area. We have added a channel at each end of the parking area.
The run-off calculations are as follows:
DA-1: Area=0.05 Acres, C=0.90, 1=4.0 inches/hr.
0=0.18*0.90*4.0= 0.18 cfs.
DA-2: Area =0.07 Acres, C=0.90, 1=4,0 inches/hr.
Q=0.07*0.90*4.0= 0.25 cfs,
As the run-off exists the channels it will spread out across the pavement, Spread
width will average approximately 10-feet, and have a velocity of at least 2 fps. Under
these conditions the depth of flow for 0.25 cfs will be 0.012 feet, and depth of flow for
0.18 cfs will be 0.009-feet. These depths will not cause hazardous conditions as it
flows across the travelway.
Please contact me if you need any additional information.
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