HomeMy WebLinkAboutSDP201900018 Calculations 2019-10-29pq14
W1
BALZER
& ASSOCIATES
PLANNERSiARCHITECT$
MINE'ERS / SURVEYORS
1561 Commerce
Road
Suite 401
Verona, VA 24482
540.248.3220
www.balzer.cc
Roanoke
Richmond
New River Valley
Staunton
Hamfsonburg
Lynchburg
It
October 29h, 2019
County of Albemarle
Department of Engineering
401 McIntire Road
Charlottesville, VA 22902
RE: Stormwater Calculations Cover Letter
Office Parking Relocation — SWM Report
Balzer Project No: 34180014.01
This letter certifies the attached channel adequacy calculations have been reviewed and approved
by a Licensed Professional. The attached calculations are in accordance to the Virginia Stormwater
Management Handbook (VSMH) 21 Edition and the Virginia Erosion & Sediment Control Handbook
(VESCH) 3w Edition.
A conveyance ditch was proposed along the western side of the property running parallel to the
shared access road. This ditch, along with the proposed driveway trench drain, conveys the runoff from the
proposed improvements to the existing swale at the rear of the property. Although the flow is minimal, outlet
protection was provided at the end of the swale in order to dissipate the channelization of the stormwater as
it enters the natural swale. The culvert and ditch have been analyzed for 2-yr velocity and 10-yr capacity.
See attached calculations for finiher analysis.
It will be the responsibility of the landowner to maintain all stormwater conveyance systems
proposed.
Please do not hesitate to call with any questions.
Respectfidly,
i-l�e 10�
D. Kent O'Donohue Jr., LA
Associate
dodonohue balzer.cc
Attachments
Culvert & SCC Drainage Map, DA-1
Culvert Calculation (1 Page)
Ditch Calculations (3 Pages)
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BAMR
& ASSOCIATES
PLANNERS 1 ARCHITECTS
ENGINEERS !SURVEYORS
Roanoke ! Richmond
New River Valley ! Staunton
Harrisonburg 1 Lynchburg
www.balzer.cc
1561 Commerce Road
Suite 401
Verona, VA 24482
540.248.3220
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DATE 10/29/2019
SCALE 1" = 20'
REVISIONS
DA-1
PROJECT NO 34180014.01
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HYDROLOGY WORKSHEET
PROJECT NAME: OFFICE PARKING RELOCATION
PROJECT #: 34180014.01
DATE: 11/11/2019
BY: DKO
06F-Seelye from VDOT Drainage manual App GD-1
CF-Kirpich from VDOT Drainage manual App 6D-6
inlet DATA
CALCULATIONS
DITCH
Area =
CA=
Tc =
I2 =
I10=
125 =
I100 =
0.38 ac
0.21
9A I
4.40 in/hr
5.71 iwk
6.39 in/hr
7.46 in&r
Q2 = 0.92
Q10= 1.20
Q25 = 1.49
Q100 = 1.96
cfs
cfs
ofs
cfs
0 Valve
0.14 ac=
0.24 ac =
ac =
ao=
ac =
36.8
63.2 %r[�
0 %@
0 %®
0 %@
0.90 C=
0.35 C =
C =
C-
C =
ADJ. C =
0.33
0.22
0.00
0.00
0.00
0.553
Tane of Concentration
100.00 ftOLFQ 4.50 %=
43.00 ft CF AH 4.00 =
ft CF AH =
Tc=
User defined
C fa or for OLF= 0.35
8.02 min
0.39 min
0.00 min
8.41 min
Worksheet
Worksheet for Triangular Channel
Projed Desafption
Worksheet
`bi 'CH�-!R
Flow Element
Triangular Char
Method
Manning's Forrr
Solve For
Channel Depth
Input Data
Mannings Coeffic
0.030
Qhanneal Slope60(300 i'•t1ft
Left Side Slope
3.00 H : V
Right Side Slope
3.00 H : V
pAlschatae
`;0.92 cfs
Results
Depth
0.30 It
Flow Area
0.3 ftz
Wetted Perimi
1.92 ft
Top Width
1.82 ft
Critical Depth
0.36 ft
Critical Slope 0.025006 fttft
Vetocrty
3 33 ttfs
Velocity Head
0.17 ft
Specific Eneq
0.48 ft
Froude Numbi
1.51
Flow Type iuperoritical
Project Engineer. BALZER
j:1... lciviKcalcslstormkditah calc.fm2 Balzer and Associates, Inc. FlowMaster v7.0 [7.0005]
11/12/19 12:09:31 PM 0 Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1
Worksheet
Worksheet for Triangular Channel
Project Deswiption
Worksheet
�i?ITCH 40-YR
Flow Element
Triangular Char
Method
Manning's FonT
Solve For
Channel Depth
Input Data
Mannings Coeffic 0.030
,Channel Slope 010000 tit
Left Side Slope 3.00 H : V
Right Side Slope 3.00 H : V
D. iso wge :1.20 tea
Results
Depth
`0:47 ff
Flow Area
0.7 ft
Wetted Perim(
2.97 ft
Top Width
2.81 ft
Critical Depth
0.40 ft
Critical Slope
0.024117 fifft
Velocity
1.82 f fs
Velocity Head
0.05 ft
Specific Enerc
0.62 ft
Froude Numb,
0.66
Flow Type
3ubcritical
Project Engineer: BALZER
j:1..%civirlcalcslstormlditch calc.fm2 Balzer and Associates, Inc. FlowMaster v7.0 [7.0005]
11/12/19 12:09:67 PM * Haestad Methods, Inc_ 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1