HomeMy WebLinkAboutSW4230101_Stormwater Narrative_20230526NARRATIVE / CALCULATIONS / MAPS/ SUPPORTING
INFORMATION FOR
STORMWATER, EROSION AND SEDIMENT CONTROL
REVIEW
for project
EM HOLT ELEMENTARY SCHOOL QUEUING
IMPROVEMENTS
TG#52013
Stormwater Permit No. SW4230101
GTON 3Cy
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kP
* �Gf July 1, 1996
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0,5780
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Site Address: 4751 NC-62, Burlington, NC 27215
Issued:
May 26, 2023
f
TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
5410 Trinity Road, Suite 102
Raleigh, North Carolina 27607
Phone:919.866.4951 Fax:919.859.5663
TABLE OF CONTENTS
Project Narrative
USGS, Soils, & FIRM Maps
Deed
Supporting Calculations:
Rip Rap Outlet Protection Design
Sediment Basin Design
Channel Design
Pre/Post Impervious Map.
(Refer to Full size plan set for additional information)
PROJECT NARRATIVE
Project Narrative
1. General Information
a. Project: EM Holt Elementary School On -Site Queuing Improvements
b. Address: 4751 NC-62, Burlington, NC 27215
c. Site Area: 30.2 Acres
d. Disturbed Area: 4.64 Acres
e. Wetlands and Jurisdictional Streams: None located within project area.
f. Ownership: Alamance-Burlington School System
g. Proposed Development: This project will be to provide an approximate 1,300 LF two-lane
on -site queuing drive at EM Holt Elementary School in Burlington, North Carolina. The site
work will include asphalt paving of the new queuing drive, concrete sidewalks, and
installation of drainage culverts to accommodate the site improvements. The project will also
repave an existing staff and visitor parking lot in front of the school. The total disturbed area
is approximately 4.64 acres. The disturbed area will flow to a temporary diversion ditch to a
temporary sediment basin to treat most of the disturbed area. The remaining disturbed area
will be protected by silt fence, silt fence stone outlets, inlet protection, and rock pipe inlet
protection.
This project meets all low -density stormwater requirements. The proposed development will
have a built upon area (BUA) below 24% and has maximized the usage of vegetated swales
and culverts only for driveway crossings. The amount of impervious area flowing to the
existing unmodified storm network has been reduced with new impervious flowing through
the proposed swales.
h. Phasing: This project will be completed in a single phase.
i. Water & Sewer Service: None
j. Historic Sites & Public Funding: This project is being funded with public monies. This site
is not an historic site.
k. NCDEQ Compliance Issues: None.
1. FEMA FIRM # 3710885200K, dated November 17, 2017 indicates there are no 100-year or
500-year flood plains that exist on the project site.
m. Soils on the site consist of predominately Cullen clay loam (CnB2), Cullen clay loam (CnD2)
and Udorthents loamy (Ud). Cn132 and CnD2 has an HSG Classifications of B.
n. River Basin: Cape Fear
o. Receiving Stream: Big Alamance Creek, Class WS-V;NSW
2. Permanent Ditch Calculations
Ditch
Slope
(ova)
Len th
g
(FT )
Bottom
Width
(FT ))
Right
Slope
(H: V)
Left
Sloe
p
(H: V)
Flow
Depth
p
(FT)
Permanent
Liner
Velocity
(FPS)
Erosive
(Y/N)
PDD1
3.2
138
0
4:1
5:1
0.35
Grass
2.73
N
PDD2
1.9
155
2
20:1
11:1
0.40
Grass
3.37
N
*PDD3
1.6
122
2
1 12:1
14:1
0.15
Grass
1.90
N
PDD4
3.7
195
0
9:1
13:1
0.35
Grass
2.98
N
PDD5
3.1
159
0
11:1
7:1
0.35
Grass
2.74
N
PDD6
1.0
357
0
4:1
6:1
1.10
Grass
3.19
N
PDD7
4.7
147
0
3:1
7:1
0.30
Grass
2.93
N
PDD8
4.1
124
2
20:1
18:1
0.30
Grass
3.71
N
PLANNED EROSION AND SEDIMENT CONTROL PRACTICES:
1. Silt Fence: Silt fence will be utilized to filter sediment laden runoff in locations where the drainage
area is less than acre per 100-ft of fence.
2. Tree Protection Fencing: Tree protection fencing will be installed to protect existing trees that are
intended to remain. In some locations, silt fence will serve as tree protection fence
3. Construction Entrance: Temporary gravel construction entrances will be utilized to minimize soil
being tracked off the site by construction traffic.
4. Outlet Protection: Riprap outlet protection aprons will be installed at outlets as they are constructed
to slow storm -water velocities and dissipate energy to protect downstream channels from erosion.
5. Sediment Skimmer Basin: Sediment skimmer basin will be installed to filter concentrated sediment
laden runoff prior to discharge from the site.
6. Channel Matting: Straw or excelsior matting will be installed in permanent channels and swales to
stabilize the seedbed and promote vegetative growth.
7. Check Dams: Rock check dams will be installed in permanent channels to reduce flow velocities and
erosion in the channel.
8. Temporary Wattles: Temporary Wattles will be installed around installed curb inlet to prevent
sediment from entering storm drainage systems.
9. Temporary Inlet Protection: Gravel block inlet protection will be installed around existing drop inlets
to prevent sediment from entering storm drainage systems.
10. Rock Pipe Inlet Protection: Rock pipe inlet protection will trap sediment at the approach to the storm
drainage systems.
Refer to drawings C-4.0-4.1 for Erosion Control Construction Sequences and Maintenance Plan.
USGS, SOILS, Et FIRM MAPS
(Sheet 13)
i.' I mile It j vvv
�__ j Scale 1:20000 t 1 1 E I
'She,,! 251
1:20000
FLOOD HAZARD INFORMATION
SEE 1-1101 I—SID LEEINI INI Mll
IER ..Al M.Ol —.1
Rh.1 ft. FI.d B.— (BFQ
Depth .—I A.
HAZARD AR Regulatory Roopwey
—RO
NO SCREEN
—ER AREAS H.ml—
GENERAL -------
"E'
F—R.
NOTES TO USERS
SCALE
NATIONAL FLOOD INSURANCE PROGRAM
FLOOD INSURANCE RATE MAP
I-- R.- 1.,
ld
0eon 8852 9920
A1:6,000
0 2.-
F-1
M—
N 0 EL 100 200 WO 400
COMMUNITY
NUMBER PANEL
NGE,
T 11.1.1:1
E
00
2m
MAP NUMBER
3710885 OOK
EFFECTIVE DATE
N.,..b., 17,2017
DEED
t 204
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SUPPORTING CALCULATIONS
RIP RAP OUTLET DESIGN
Rip Rap Calcs 5/3/2023 Page 1 of 6
Rip Rap Calcs 5/3/2023 Page 2 of 6
Rip Rap Calcs 5/3/2023 Page 3 of 6
Rip Rap Calcs 5/3/2023 Page 4 of 6
Rip Rap Calcs 5/3/2023 Page 5 of 6
Rip Rap Calcs 5/3/2023 Page 6 of 6
SEDIMENT BASIN DESIGN
Skimmer Basin A EM Holt Elementary School
TIMMONS GROUP
Anaad Sinah 52013
Time of Concentration Calculation
Modified Rational
Highest Elevation =
650
feet
Inlet Elevation =
634
feet
Difference =
16
feet
Travel Length =
556
feet
Tc =
L� 3 I H)0.385
Equation 2.3 i(irpich Equation
128
Where:
Tc =Time of Concentration (min)
H =Height of the most remote point on the watershed above
the outlet (ft)
L =Length of flow from the most remote point on the
watershed to the outlet (fl)
(Civil Engineering, Vol. 10, No. 6,June 1940,p.362.)
A graph of the Kirpich Equation also appears in Figure 2.4.
Tc =
3.98
min
Tc =
5
min
Intensity 10 year =
7.08
in/hr
C =
0.60
Disturbed Area =
4.31
acres
Additional Drainage Area =
0.00
acres
Total Drainage Area =
4.31
acres
Equation 2.1 Rational Equation Q = C I A
*RED IS USER INPUT
Where:
Q = Peak flow from the drainage area (cfs)
C = Coefficient of runoff (dimensionless)
I = Rainfall intensity for a given time to peak (in/hr)
A = Drainage area (acres)
Q10 = 18.31 cfs
LATEST REVISION: 1/2/2023 11:41 AM
Skimmer Basin A EM Holt Elementary School
TIMMONS GROUP IIIIIE3T.67TTO
Angad Singh ENGINEERING I DESIGN I TECHNOLOGY 52013
Skimmer Basin A
Disturbed Area:
4.31 ac
Additional Drainage Area:
0.00 ac
Total Drainage Area:
4.31 ac
Runoff Coeff [Cc]:
0.60
10-yr Rainfall Intensity [I]:
7.08 in/hr
10-yr Discharge [Q10]:
Sizing
18.31 cfs
7758 Required Volume ft3
(Disturbed Area x 1800 cf/ac)
5950 Required Surface Area ft2
(Q10 x 325)
54.5 Suggested Width ft
109.1 Suggested Length ft
112 Width at Surface Area (ft)
125 Length at Surface Area (ft)
3 Side Slope Ratio Z:1
2 Depth (ft)
24 Bottom Width (ft)
79 Bottom Length (ft)
4177 Bottom Area (ft2)
14854 Actual Volume (ft3) Okay
6500 Actual Surface Area (ft2) Okay
7 Emergency Spillway Width (ft)
1 Depth of Flow (ft)
21.0 Spillway Capacity (cfs) Okay
4 Skimmer Size (in)
0.333 Head on Skimmer (ft)
1.25 Orifice Size (1/4 inch increments)
3.72 Dewatering Time (days)
Suggest about 3 days
Skimmer Size
(Inches)
1.5
2
2.5
3
4
5
6
8
631.50
4177
0.00
0
0
632.50
5310
1.00
4744
4744
633.50
6500
2.00
5905
10649
634.50
7746
3.00
7123
17772
635.50
9049
4.00
8398
26169
Emergency Spillway Elevation: 634.00 ft
Top of Embankment Elevation: 635.00 ft
Bottom Elevation: 631.50 ft
Embankment Width: 5 ft
*RED IS USER INPUT
LATEST REVISION: 1/2/2023 11:41 AM
CHANNEL DESIGN
W*C6't 61 0002922MEM3
TDD Al E M HOLT
TIMMONS GROUP IN U.T97f
Angad Singh 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
2.70 (Acres)
Coef. (C) =
0.75 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qlo) =
14.3 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 183 LF
Slope =
0.005 (ft/ft) Highest Elevation = 635.5
Z Required =
3.90 Ratio Lowest Elevation = 634.5
Side Slope (M) =
3 :1
Flow Depth (Y) = 1.35 ft 16.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.46 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 5.47 SF
New P = 8.54 Wetted perimeter
New R = 0.64 Hydraulic radius
Z Actual = 4.06 Must be greater than z required=> 3.90 Okay
New V = 2.73 fps
Liner: Curled Mat
1.55 LB/SF > 0.47 LB/SF Okay
................................... ....
To.. ._
Width - 8.1 ft
Min. Ditch Depth 1.35 ft ..................:.......
3 Flow Depth (Y) = 1.35 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
1.35 0.00 1.35 8.1 371
Ditch Liner
Curled Mat *RED IS USER INPUT
LATEST REVISION: 12/8/2022 4:12 PM
TDD Al
Angad Singh
ego*
op
TIMMONS GROUP
NNNNGWE��
E M HOLT
- •
52013
Ditch Outlet Protection (NYDOT Method)
Ditch Name: DD Al
Velocity =
2.73 fps
From Fig. 8.06.c:
ZONE = 1
Top Width =
8.1 ft
Ditch Area =
5.4675 sf
Rip Rap Class =
A
Equivalent Pipe Diameter =
31.66 in
Apron Thickness =
12 in
Equivalent Pipe Diameter =
36 in
Apron Length =
12.0 ft
Apron Width = Top Width.=
8.1 ft
From Fig. 8.06.e:
LATEST REVISION: 12/8/2022 4:12 PM
W*C6't 61 0002922MEM3
TDD A2 E M HOLT
TIMMONS GROUP IN U.T97f
Angad Singh 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
0.47 (Acres)
Coef. (C) =
0.75 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qio) =
2.5 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 79.1 LF
Slope =
0.040 (ft/ft) Highest Elevation = 643.6
Z Required =
0.25 Ratio Lowest Elevation = 640.4
Side Slope (M) =
3 :1
Flow Depth (Y) = 0.50 ft 6.0 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 1.26 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.75 SF
New P = 3.16 Wetted perimeter
New R = 0.24 Hydraulic radius
Z Actual = 0.29 Must be greater than z required=> 0.25 Okay
New V = 3.83 fps
Liner: Curled Mat
Min. Ditch Depth = 0.5 ft
1.55 LB/SF > 1.27 LB/SF Okay
..........................
Top Width = 3 ft
3 Flow Depth (Y) = 0.5 ft
_j
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.50 0.00 0.50 3 3:1
Ditch Liner
Curled Mat *RED IS USER INPUT
LATEST REVISION: 12/8/2022 4:13 PM
*000 MENEGME
TDD A2 w E M HOLT
TIMMONS GROUP •
Angad Singh 52013
Ditch Outlet Protection (NYDOT Method)
Velocity =
3.83 fps
From Fig. 8.06.c:
ZONE = 1
Top Width =
3 ft
Ditch Area =
0.75 sf
Rip Rap Class =
A
Equivalent Pipe Diameter =
11.73 in
Apron Thickness =
12 in
Equivalent Pipe Diameter =
18 in
Apron Length =
6.0 ft
Apron Width = Top Width.=
3.0 ft
From Fig. 8.06.e:
LATEST REVISION: 12/8/2022 4:13 PM
W*C6't 61 0002922MEM3
TDD A3 E M HOLT
TIMMONS GROUP IN U.T97f
Angad Singh 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
0.78 (Acres)
Coef. (C) =
0.60 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qlo) =
3.3 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 293.5 LF
Slope =
0.032 (ft/ft) Highest Elevation = 640
Z Required =
0.37 Ratio Lowest Elevation = 630.5
Side Slope (M) =
3 :1
Flow Depth (Y) = 0.60 ft 7.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 1.21 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 1.08 SF
New P = 3.79 Wetted perimeter
New R = 0.28 Hydraulic radius
Z Actual = 0.47 Must be greater than z required=> 0.37 Okay
New V = 3.87 fps
Liner: Curled Mat
1.55 LB/SF > 1.22 LB/SF Okay
................................... ....
To.. ._
Width - 3.6 ft
Min. Ditch Depth 0.6 ft ..................:.......
3 Flow Depth (Y) = 0.6 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.60 0.00 0.60 3.6 371
Ditch Liner
Curled Mat *RED IS USER INPUT
LATEST REVISION: 12/8/2022 4:13 PM
PROJECT NAME
DD A3 E M HOLT
CALCULATED BY TIMMONS GROUP PROJECT NUMBER
... Singh 52013
Ditch Outlet Protection (NYDOT Method)
Velocity =
3.87 fps
From Fig. 8.06.c:
ZONE = 1
Top Width =
3.6 ft
Ditch Area =
1.08 sf
Rip Rap Class =
A
Equivalent Pipe Diameter =
14.07 in
Apron Thickness =
12 in
Equivalent Pipe Diameter =
18 in
Apron Length =
6.0 ft
Apron Width = Top Width.=
3.6 ft
From Fig. 8.06.e:
LATEST REVISION: 12/8/2022 4:13 PM
PDD1 EM Holt ES
TIMMONS GROUP '
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) = 0.31 (Acres)
Coef. (C) = 0.54 (Dimensionless)
Inte. (1) = 7.08 (in/hr)
Flow (Qlo) = 1.2 (cfs)
QuantitiesKnown
Line channel with: 6 " rip -rap (Assume 6" even if using grass)
Manning n = 0.030 (Dimensionless) Ditch Length = 138 LF
Slope = 0.032 (ft/ft) Highest Elevation = 644.7
Z Required = 0.13 Ratio Lowest Elevation = 640.25
Side Slope (M) = 4 :1
Flow Depth (Y) = 0.35 ft 4.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.70 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.49 SF
New P = 2.89 Wetted perimeter
New R = 0.17 Hydraulic radius
Z Actual = 0.15 Must be greater than z required=> 0.13 Okay
New V = 2.73 fps
Liner: Grass
3.20 LB/SF > 0.71 LB/SF Okay
................................... ....
To..Width ._- 2.8 ft
Min. Ditch Depth 0.35 ft ..................:.......
4 Flow Depth (Y) = 0.35 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.35 0.00 0.35 2.8 471
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:49 PM
PDD2 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) = 1.64 (Acres)
Coef. (C) = 0.58 (Dimensionless)
Inte. (1) = 7.08 (in/hr)
Flow (Qlo) = 6.7 (cfs)
QuantitiesKnown
Line channel with: 6 " rip -rap (Assume 6" even if using grass)
Manning n = 0.030 (Dimensionless) Ditch Length = 155 LF
Slope = 0.032 (ft/ft) Highest Elevation = 639.9
Z Required = 0.76 Ratio Lowest Elevation = 635
Side Slope (M) = 11 :1
Flow Depth (Y) = 0.40 ft 4.8 in
Bottom Width (B) = 2.00 It 24.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.79 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 2.56 SF
New P = 10.84 Wetted perimeter
New R = 0.24 Hydraulic radius
Z Actual = 0.98 Must be greater than z required=> 0.76 Okay
New V = 3.37 fps
Liner: Grass
3.20 LB/SF > 0.79 LB/SF Okay
................................... ....
Top _ Width - 10.8 ft
Min. Ditch Depth 0.4 ft ..................:.......
11 Flow Depth (Y) = 0.4 ft
Bottom Width (B) = 2 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.40 2.00 0.40 10.8 11:1
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:50 PM
PDD3 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) = 0.18 (Acres)
Coef. (C) = 0.76 (Dimensionless)
Inte. (1) = 7.08 (in/hr)
Flow (Qlo) = 1.0 (cfs)
QuantitiesKnown
Line channel with: 6 " rip -rap (Assume 6" even if using grass)
Manning n = 0.030 (Dimensionless) Ditch Length = 122 LF
Slope = 0.031 (ft/ft) Highest Elevation = 638.75
Z Required = 0.11 Ratio Lowest Elevation = 635
Side Slope (M) = 12 :1
Flow Depth (Y) = 0.15 ft 1.8 in
Bottom Width (B) = 2.00 It 24.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.29 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.57 SF
New P = 5.61 Wetted perimeter
New R = 0.10 Hydraulic radius
Z Actual = 0.12 Must be greater than z required=> 0.11 Okay
New V = 1.90 fps
Liner: Grass
3.20 LB/SF > 0.29 LB/SF Okay
................................... ....
To.. ._
Width - 5.6 ft
Min. Ditch Depth 0.15 ft
12 Flow Depth (Y) = 0.15 ft
Bottom Width (B) = 2 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.15 2.00 0.15 5.6 12:1
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:50 PM
PDD4 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) = 0.65 (Acres)
Coef. (C) = 0.63 (Dimensionless)
Inte. (1) = 7.08 (in/hr)
Flow (Qlo) = 2.9 (cfs)
QuantitiesKnown
Line channel with: 6 " rip -rap (Assume 6" even if using grass)
Manning n = 0.030 (Dimensionless) Ditch Length = 195 LF
Slope = 0.037 (ft/ft) Highest Elevation = 644.25
Z Required = 0.30 Ratio Lowest Elevation = 637
Side Slope (M) = 9 :1
Flow Depth (Y) = 0.35 ft 4.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.81 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 1.10 SF
New P = 6.34 Wetted perimeter
New R = 0.17 Hydraulic radius
Z Actual = 0.34 Must be greater than z required=> 0.30 Okay
New V = 2.98 fps
Liner: Grass
3.20 LB/SF > 0.82 LB/SF Okay
................................... ....
To.. ._
Width - 6.3 ft
Min. Ditch Depth 0.35 ft ..................:.......
9 Flow Depth (Y) = 0.35 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.35 0.00 0.35 6.3 971
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:50 PM
PDD5 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
0.49 (Acres)
Coef. (C) =
0.46 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qlo) =
1.6 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 159 LF
Slope =
0.031 (ft/ft) Highest Elevation = 641.5
Z Required =
0.18 Ratio Lowest Elevation = 636.5
Side Slope (M) =
7 :1
Flow Depth (Y) = 0.35 ft 4.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.69 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.86 SF
New P = 4.95 Wetted perimeter
New R = 0.17 Hydraulic radius
Z Actual = 0.27 Must be greater than z required=> 0.18 Okay
New V = 2.74 fps
Liner: Grass
3.20 LB/SF > 0.69 LB/SF Okay
................................... ....
To..Width ._- 4.9 ft
Min. Ditch Depth 0.35 ft ..................:.......
7 Flow Depth (Y) = 0.35 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.35 0.00 0.35 4.9 771
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:50 PM
PDD6 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
3.71 (Acres)
Coef. (C) =
0.55 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qio) =
14.4 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 357 LF
Slope =
0.010 (ft/ft) Highest Elevation = 635
Z Required =
2.98 Ratio Lowest Elevation = 631.6
Side Slope (M) =
4 :1
Flow Depth (Y) = 1.10 ft 13.2 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.65 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 4.84 SF
New P = 9.07 Wetted perimeter
New R = 0.53 Hydraulic radius
Z Actual = 3.18 Must be greater than z required=> 2.98 Okay
New V = 3.19 fps
Liner: Grass
3.20 LB/SF > 0.66 LB/SF Okay
................................... ....
To.. ._
Width - 8.8 ft
Min. Ditch Depth 1.1 ft ..................:.......
4 Flow Depth (Y) = 1.1 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
1.10 0.00 1.10 8.8 471
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:50 PM
PDD7 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
0.23 (Acres)
Coef. (C) =
0.45 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qlo) =
0.7 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 147 LF
Slope =
0.047 (ft/ft) Highest Elevation = 642.9
Z Required =
0.07 Ratio Lowest Elevation = 636
Side Slope (M) =
3 :1
Flow Depth (Y) = 0.30 ft 3.6 in
Bottom Width (B) = 0.00 It 0.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.88 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.27 SF
New P = 1.90 Wetted perimeter
New R = 0.14 Hydraulic radius
Z Actual = 0.07 Must be greater than z required=> 0.07 Okay
New V = 2.93 fps
Liner: Grass
3.20 LB/SF > 0.88 LB/SF Okay
................................... ....
To.. ._
Width - 1.8 ft
Min. Ditch Depth 0.3 ft ..................:.......
3 Flow Depth (Y) = 0.3 ft
Bottom Width (B) = 0 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.30 0.00 0.30 1.8 371
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:51 PM
PDD8 EM Holt ES
TIMMONS GROUP'
Lynsie Barnes 52013
Drainage Ditch Design (Velocity Constraint)
This worksheet is designed to determine channel lining based on flow and ditch geometry (base width, side
slope, & channel slope). This program determines depth of flow, velocity and tractive force assuming
n=0.03 for grass or rip rap (n can be varied if desired). (Vary depth until z actual equals z required; v & t will
be correct; select appropriate lining based on tractive force)
Area (A) =
0.64 (Acres)
Coef. (C) =
0.61 (Dimensionless)
Inte. (1) =
7.08 (in/hr)
Flow (Qlo) =
2.8 (cfs)
Known Quantities
Line channel with:
6 " rip -rap (Assume 6" even if using grass)
Manning n =
0.030 (Dimensionless) Ditch Length = 124 LF
Slope =
0.041 (ft/ft) Highest Elevation = 645
Z Required =
0.27 Ratio Lowest Elevation = 639.9
Side Slope (M) =
3 :1
Flow Depth (Y) = 0.30 ft 3.6 in
Bottom Width (B) = 2.00 It 24.0 in
Freeboard = 0.00 ft 0.0 in
T=YxDxS
T = 0.77 LB/SF
Y = Weight of water (62.4 LB/CUFT)
D=Depth of flow in channel (ft)
S=Slope of channel (ft/ft)
General Lining LB/SF North American
Jute Net 0.45 Green Lining LB/SF
Curled Mat 1.55 S75 1.55
Class A (4"@9"THK) 2.00 S150 1.75
Class B (8"@18"THK) 3.50 SC150 2.10
Class I (12"@22"THK) 5.00 C125 2.25
Class II (18"@30"THK) 7.50 P300 8.00
Determine
New A = 0.87 SF
New P = 3.90 Wetted perimeter
New R = 0.22 Hydraulic radius
Z Actual = 0.32 Must be greater than z required=> 0.27 Okay
New V = 3.71 fps
Liner: Grass
3.20 LB/SF > 0.77 LB/SF Okay
................................... ....
To.. ._
Width - 3.8 ft
Min. Ditch Depth 0.3 ft ..................:.......
3 Flow Depth (Y) = 0.3 ft
Bottom Width (B) = 2 ft
Min. Ditch Depth (ft) Bottom Width (ft) Flow Depth (ft) Top Width (ft) Side Slope
0.30 2.00 0.30 3.8 371
Ditch Liner
Grass *RED IS USER INPUT
LATEST REVISION: 5/24/2023 2:49 PM
PRE/POST IMPERVIOUS MAP
I
� I
I
I
I
I
I
I
I
11
EXISTING CONDITIONS
E M HOLT RENOVATION AND ADDITION BUA:
A: TOTAL PARCEL SIZE: 30.2 AC
Ind
SCALE 1 "=100'
0 160, 200'
B: 2007 GRANDFATHERED BUA: 5.46 AC (PRE -ORDINANCE)
C (A-B): NEW "PARCEL" SIZE SUBJECT TO 24% BUA: 24.74 AC
D (C X 24%): ALLOWABLE IMPERVIOUS: 5.94 AC
E (B + D): TOTAL ALLOWABLE IMPERVIOUS: 11.40 AC
F: TOTAL ONSITE IMPERVIOUS 2023: 5.77 AC
G (F - B): 2023 ADDITIONAL IMPERVIOUS: 0.31 AC
H (G/C x 100): % BUA 2023: 1.25% (UNDER 24%)
IMPERVIOUS AREA UNDER ALLOWABLE (D-G): 5.63 ± ACRES
% BUA UNDER ALLOWABLE (24% - H): 22.75% BUA
11
POST CONDITIONS
E M HOLT RENOVATION AND ADDITION BUA:
EXISTING IMPERVIOUS
PROPOSED IMPERVIOUS
PROPERTY BOUNDARY
THIS DRAWING IS FOR AGENCY REVIEW ONLY - NOT FOR CONSTRUCTION
DRAINAGE TO EXISTING PIPE NETWORK -POINT OF ANALYSIS 1
PRE -DEVELOPMENT
POST -DEVELOPMENT
DIFFERENCE
IMPERVOUS AREA
0.457 ACRES
(19,923 SQFT)
0.439 ACRES
(19,119 SQFT)
0.018 ACRES
(804 SQFT)
co
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