SW6240106_Design Calculations_20240516 (4)

Project Name Riprap Dissipator#1 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC nni814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 ,ILH
[phone] Checked By
.1LH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o = 18 in. Pipe diameter in inches
D-o = 1.50 ft. Pipe diameter in feet
0-25 = 1.20 cfs Pipe outlet (from drainage calculations)
d-50 = 0.3 ft. from Figure 8.06 a
L-a = 9 ft. from Figure 8.06 a
Step 3. 3*D-o= 4.50 ft. 3 times the outlet pipe diameter
W= 10.50 ft. Pipe diameter+Apron length
Step 4. d-max 0.45 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 5 in. Maximum Stone Diameter(1.5"d-50) in feet
Step 5. Thickness= 0.68 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness= 8 in. Min. Apron Thickness With Filter Fabric(1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
9 11 5 18in. B
TERMINOLOGY: Q10= 10-Year Design Storm. Peak Discharge, (cfs)
D-o= Pipe Diameter, (in. &ft.)
d-50 = Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o= Width of Rip-Rap Apron @ Pipe Outlet, (ft.)
W= Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness= Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#2 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 JLH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o = 18 in. Pipe diameter in inches
D-o = 1.50 ft. Pipe diameter in feet
Q-25 = 1.70 cfs Pipe outlet (from drainage calculations)
d-50 = 0.3 ft. from Figure 8.06 a
L-a = 9 ft. from Figure 8.06 a
Step 3. 3*D-o = 4.50 ft. 3 times the outlet pipe diameter
W = 10.50 ft. Pipe diameter+Apron length
Step 4. d-max 0.45 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 5 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness = 0.68 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness = 8 in. Min. Apron Thickness With Filter Fabric (1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3"D-o Thick Class
9 11 5 18in. B
TERMINOLOGY: Q10 = 10-Year Design Storm, Peak Discharge, (cfs)
D-o = Pipe Diameter, (in. &ft.)
d-50 = Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron @ Pipe Outlet, (ft.)
W = Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max = Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness= Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#3 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 JLH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning& Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Taiiwater Condition
Step 2. D-o = 24 in. Pipe diameter in inches
D-o = 2.00 ft. Pipe diameter in feet
Q-25 = 19.71 cfs Pipe outlet (from drainage calculations)
d-50 = 0.4 ft. from Figure 8.06 a
L-a = 12 ft. from Figure 8.06 a
Step 3. 3*D-o = 6.00 ft. 3 times the outlet pipe diameter
W= 14.00 ft. Pipe diameter+Apron length
Step 4. d-max 0.60 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 7 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness = 0.90 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness= 11 in. Min. Apron Thickness With Filter Fabric(1.5`d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
12 14 6 24in. 1
TERMINOLOGY: Q10= 10-Year Design Storm, Peak Discharge, (cfs)
D-o = Pipe Diameter, (in. &ft.)
d-50= Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron @ Pipe Outlet. (ft.)
W= Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. &in.)
Thickness= Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#4 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 JLH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o= 42 in. Pipe diameter in inches
D-o= 3.50 ft. Pipe diameter in feet
Q-25 = 46.88 cfs Pipe outlet (from drainage calculations)
d-50 = 0.7 ft. from Figure 8.06 a
L-a = 22 ft. from Figure 8.06 a
Step 3. 3*D-o = 10.50 ft. 3 times the outlet pipe diameter
W = 25.50 ft. Pipe diameter+Apron length
Step 4. d-max 1.05 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 13 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness = 1.58 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness = 19 in. Min. Apron Thickness With Filter Fabric(1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3"D-o Thick Class
22 26 11 36in. 2
TERMINOLOGY: Q10= 10-Year Design Storm, Peak Discharge, (cfs)
D-o= Pipe Diameter, (in. & ft.)
d-50= Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron © Pipe Outlet, (ft.)
W= Width of Rip-Rap Apron © End of Apron. (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness= Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#5 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 JLH
[phone] Checked By
.1LH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o= 24 in. Pipe diameter in inches
D-o= 2.00 ft. Pipe diameter in feet
Q-25= 6.90 cfs Pipe outlet(from drainage calculations)
d-50 = 0.4 ft. from Figure 8.06 a
L-a = 12 ft. from Figure 8.06 a
Step 3. 3*D-o = 6.00 ft. 3 times the outlet pipe diameter
W= 14.00 ft. Pipe diameter+Apron length
Step 4. d-max 0.60 ft. Maximum Stone Diameter(1.5"d-50) in inches
d-max 7 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness = 0.90 ft. Min. Apron Thickness With Filter Fabric (1.5*d-max) in feet
Thickness = 11 in. Min. Apron Thickness With Filter Fabric (1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
12 14 6 24in. 1
TERMINOLOGY: Q10 = 10-Year Design Storm, Peak Discharge, (cfs)
D-o = Pipe Diameter, (in. &ft.)
d-50 = Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron @ Pipe Outlet, (ft.)
W = Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness = Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#6 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 JLH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o = 18 in. Pipe diameter in inches
D-o = 1.50 ft. Pipe diameter in feet
Q-25 = 15.32 cfs Pipe outlet (from drainage calculations)
d-50 = 0.4 ft. from Figure 8.06 a
L-a = 14 ft. from Figure 8.06 a
Step 3. 3*D-o = 4.50 ft. 3 times the outlet pipe diameter
W= 15.50 ft. Pipe diameter+Apron length
Step 4. d-max 0.60 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 7 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness= 0.90 ft. Min.Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness= 11 in. Min. Apron Thickness With Filter Fabric(1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
14 16 5 24in. 1
TERMINOLOGY: 010= 10-Year Design Storm, Peak Discharge, (cfs)
D-o= Pipe Diameter. (in. & ft.)
d-50 = Mean Stone Diameter of Rip-Rap, (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3"D-o= Width of Rip-Rap Apron @ Pipe Outlet, (ft.)
W= Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness= Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipator#7 Date
WindFall Lakes Phase 1 Apr,2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines, NC 28387 .ILH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR: 1993)
Step 1. Minimum Taiiwater Condition
Step 2. D-o= 24 in. Pipe diameter in inches
D-o= 2.00 ft. Pipe diameter in feet
Q-25 = 30.14 cfs Pipe outlet(from drainage calculations)
d-50= 1.2 ft. from Figure 8.06 a
L-a = 18 ft. from Figure 8.06 a
Step 3. 3*D-o = 6.00 ft. 3 times the outlet pipe diameter
W= 20.00 ft. Pipe diameter+Apron length
Step 4. d-max 1.80 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 22 in. Maximum Stone Diameter(1.5`d-50) in feet
Step 5. Thickness = 2.70 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness = 32 in. Min. Apron Thickness With Filter Fabric(1.5*d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
18 20 6 36in. 2
TERMINOLOGY: Q10= 10-Year Design Storm, Peak Discharge, (cfs)
D-o= Pipe Diameter. (in. &ft.)
d-50= Mean Stone Diameter of Rip-Rap. (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron @ Pipe Outlet, (ft.)
W= Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max = Maximum Stone Diameter of Rip-Rap, (ft. & in.)
Thickness = Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)

Project Name Riprap Dissipater#8 Date
WindFall Lakes Phase 1 Apr, 2021
DD Project No.
Location Double D Engineering, PLLC DD1814
Moore County, North Carolina 150 S. Page Street Calculated By
Southern Pines. NC 28387 JLH
[phone] Checked By
JLH
STORM DESIGN: 25 Year
BACKGROUND: Use the E&S Control Planning & Design Manual, Section 8.06.
REFERENCE: (NCDEHNR, 1993)
Step 1. Minimum Tailwater Condition
Step 2. D-o= 24 in. Pipe diameter in inches
D-o= 3.00 ft. Pipe diameter in feet
Q-25= 52.75 cfs Pipe outlet(from drainage calculations)
d-50= 0.7 ft. from Figure 8.06 a
L-a = 20 ft. from Figure 8.06 a
Step 3. 3*D-o= 9.00 ft. 3 times the outlet pipe diameter
W= 23.00 ft. Pipe diameter+Apron length
Step 4. d-max 1.05 ft. Maximum Stone Diameter(1.5*d-50) in inches
d-max 13 in. Maximum Stone Diameter(1.5*d-50) in feet
Step 5. Thickness= 1.58 ft. Min. Apron Thickness With Filter Fabric(1.5*d-max) in feet
Thickness= 19 in. Min. Apron Thickness With Filter Fabric(1.5`d-max) in inches
DESIGN DIMENSIONS: Apron Dimensions Riprap
Length Width 3*D-o Thick Class
20 23 9 36in. 2
TERMINOLOGY: 010= 10-Year Design Storm, Peak Discharge, (cfs)
D-o= Pipe Diameter, (in. &ft.)
d-50 = Mean Stone Diameter of Rip-Rap. (ft.)
L-a = Length of Rip-Rap Apron, (ft.)
3*D-o = Width of Rip-Rap Apron © Pipe Outlet, (ft.)
W= Width of Rip-Rap Apron @ End of Apron, (ft.)
d-max= Maximum Stone Diameter of Rip-Rap, (ft. &in.)
Thickness = Thickness of Rip-Rap Apron With Filter Fabric, (ft. &in.)