HomeMy WebLinkAboutPTIA_BOOM Stormwater Report_2023-01-25_Signed
STORMWATER REPORT FOR
BOOM FINAL ASSEMBLY LINE FACILITY – PHASE 1
PIEDMONT TRIAD INTERNATIONAL AIRPORT
GUILFORD COUNTY, NORTH CAROLINA
Stormwater Design Reference is the 2017 Edition of NCDEQ’s
“Stormwater Design Manual”
PREPARED FOR: PREPARED BY:
January 2023
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1/26/2023
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BOOM Supersonic – Phase 1 Page 2 of 4
BOOM SUPERSONIC FINAL ASSEMBLY LINE (FAL) –
PHASE 1
STORMWATER REPORT
Overview
Boom Supersonic (BOOM) is proposing to construct a Final Assembly Line (FAL)
and associated infrastructure at the Piedmont Triad International Airport. The site of the
proposed FAL has been mass graded to suit this development. Stormwater runoff will be
primarily treated via vegetated swales as allowed under airport development rules. The
treatment swales will flow to two (2) dry detention ponds. An existing sediment basin (SB-
P2) will be converted into a dry pond to treat and attenuate flow from the south and west area
of the development. A second existing sediment basin (SB-G) will be converted into a dry
pond to treat and attenuate flow from the north and east. Outfall from this basin is discharged
into a wetland subject to Jordan basin rules. Therefore, low flow outlet pipe will direct the
0.75” water quality design volume into a level spreader and across a vegetated filter strip
prior to entering the wetland buffer. The design of the dry ponds will accommodate change in
land use from Phase 1 of the development.
Phase 1 of the FAL development will include: an area with trailers and associated
parking to be used for administrative personnel, the southernmost Final Assembly Line
building and associated parking lot, a taxiway for aircraft to move in and out of the FAL, and
2 access roads (1 for trucks and 1 for regular traffic). Figure 01 shows the project area.
Figure 02 shows the site plan with Phase 1 development highlighted.
A summary of the pre- and post-development landuse for Phase 1 is provided below.
Drainage Area SB-G (34.3 acres):
Existing conditions = 0.0 acres of impervious area
Proposed conditions = 5.1 acres of impervious area
14.87% increase in impervious area
Drainage Area SB-P2 (34.3 acres):
Existing conditions = 0.7 acres of impervious area
Proposed conditions = 6.3 acres of impervious area
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BOOM Supersonic – Phase 1 Page 3 of 4
16.25% increase in impervious area
Pre-Post Results
The results of the pre-post analysis for Phase 1 is in Table 1 below. The two (2) analysis
points listed in the table are the outfalls of the dry ponds for Drainage Areas SB-G and SB-P2.
Figure 3 shows a drainage area map. The Q10 Pre-development flows were calculated using
the Rational Method. The Q10 Post-development flows are the peak flows leaving the outlet
structure of the 2 dry ponds and were calculated using HEC-HMS. The Q10 peak flow at
outfall SB-P2 (Basin 50) decreases from approximately 108 cfs to 8.9 cfs between pre and post
project conditions. The Q10 peak flow at outfall SB-G (Basin 51) decreases from
approximately 108 cfs to 44.0 cfs. The proposed improvements to the project will add
approximately 10.7 ac of impervious area.
Outfall
ID BOOM (FAL) – Phase 1: Table 1
Q10 PRE (cfs) Q10 POST (cfs) % Change
SB‐P2
(50) 108 8.9 ‐ 91.7%
SB‐G
(51) 108 44.0 ‐59.3%
Dry Pond Design
The outlet structure of the dry ponds are designed per the guidelines as specified in
the NCDEQ Stormwater Design Manual (Design Manual). Per section E.4 (Airports) of the
Design Manual, the design volume draw down time can be reduced to 40 hrs. rather than the
48hr minimum required for dry ponds not located at an airport. The outlet structures for both
dry ponds has a 4” WQ orifice. Each WQ orifice is located on the outlet structure with an
invert elevation equal to the lowest elevation in the dry pond.
The required design volume for both dry ponds was calculated using the Simple
Method as described in section B. (Stormwater Calculations) of the Design Manual. Design
volume requirements vs. storage volume during the 0.75” storm event are summarized in
Table 2 below.
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BOOM Supersonic – Phase 1 Page 4 of 4
Outfall
ID BOOM (FAL) – Phase 1: Table 2
Des. Vol. Req
(ac‐ft)
Des. Vol. Provided
(ac‐ft) % Difference
SB‐P2
(50) 0.45 0.45 0.00%
SB‐G
(51) 0.39 0.39 0.00%
Swale Treatment
Stormwater runoff from the site will be directed to the dry ponds via a series of
vegetated swales. The swales meet or exceed design criteria for water quality treatment. All
of the swales have a longitudinal slope less than 1.5% and most are less than 1.0%. In
addition, the flow depth in the swales during the 0.75” storm event is 6 inches or less.
Detailed output of channel analysis from the Hydraulic Toolbox software (FHWA) is
attached.
Level Spreader with Filter Strip
Discharge from pond SB-G feeds a delineated wetland. Therefore, stormwater
discharge from this pond will be further treated prior to entering the wetland. Discharge
from the 0.75” storm event will be directed to a level spreader and across a filter strip prior to
entering the wetland. Peak inflow into the basin during the 0.75” storm event is 4.78 cfs.
Peak outflow from the pond outlet structure is 0.31 cfs. In anticipation of future build out
conditions, the level spreader is 50 feet long and the filter strip is 30 feet wide (as shown on
the plans).
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS,USDA, USGS, AeroGRID, IGN, and the GIS User Community
Figure 1.Project Area Map
BOOM SupersonicFinal Assembly LinePhase 1
October 2022
Legend
Project_Area
Vicinity Map
Guilford County, NC
Project Location
City of Greensboro
400 0200 Feet
I-73 .
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS,USDA, USGS, AeroGRID, IGN, and the GIS User Community
Figure 2.Phase 1 Map
BOOM SupersonicFinal Assembly LinePhase 1
October 2022
Legend Vicinity Map
Guilford County, NC
Project Location
City of Greensboro
400 0200 Feet
I-73 .Only Yellow highlighted
areas to be constructed
in Phase 1. All other
proposed development
will be in subsequent
phases
FAL, parking, and
taxiway
Trailer city,
parking, and
entrance roads
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS,USDA, USGS, AeroGRID, IGN, and the GIS User Community
Figure 3.Drainage Area Map
BOOM SupersonicFinal Assembly LinePhase 1
October 2022
Legend
Phase1_Area
Drainage_Area
CONTOURS
Vicinity Map
Guilford County, NC
Project Location
City of Greensboro
400 0200 Feet
I-73 .
Basin SB-P2
Basin SB-G
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Appendix A
Calculations
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BOOM Supersonic Final Assembly Line
BASIN SB‐G
Runoff Coefficient
Total Area= 34.3 AC
Rv = 0.05 + 0.9 * Ia Ia = 0.148688 Impervious Area= 5.1 AC
Rv (Basin SB‐G)
Rv = 0.18
Design Volume
Dv (Basin SB‐G) Rd= 0.75 in
Dv = 16808.72 cu. Ft. Rv= 0.18
0.39 ac‐ft
BASIN SB‐P2
Runoff Coefficient
Total Area= 34.3 AC
Rv = 0.05 + 0.9 * Ia Ia = 0.182507 Impervious Area= 6.26 AC
Rv (Basin SB‐P2)
Rv = 0.21
Design Volume
Dv (Basin SB‐P2) Rd= 0.75 in
Dv = 19610.17 cu. Ft. Rv= 0.21
0.45 ac‐ft
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User Input Data
Calculated Value
Reference Data
Designed By:K. Higgins Date:
Checked By: Date:
Company:Parrish and Partners
Project Name:Boom Supersonic FAL
Project No.:
Site Location (City/Town)Greensboro
Culvert Id.Basin G & P2 (50& 51)
Total Drainage Area (acres)34.3
Rational Method for Flow
Outlet pipe diameter, Do (in.)30
Tailwater depth (in.) 20
Minimum/Maximum tailwater? Max TW (Fig. 8.06b)
Discharge (cfs) 37
Velocity (ft./s) 10
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d50, (ft.)1
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Minimum apron length, La (ft.)20
Apron width at pipe outlet (ft.) 7.5 7.5
Apron shape Trapezoid
Apron width at outlet end (ft.) 2.5 10.5
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0 1.5
Minimum TW Maximum TW
Apron Thickness(ft.) 0 2.25
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Appendix B
Ditch Calcs
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BOOM Supersonic Final Assembly Line (FAL)
Flow Depths in Swales during the 0.75in Storm Event
Swale 51
Swale 51‐2
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Swale 51‐A
Swale 51‐B
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Swale 51‐C
Swale 51‐D
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Swale 51‐D‐OUT
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Hydraulic Analysis Report
Project Data
Project Title: PTIA – BOOM (FINAL ASSEMBLY LINE)
Designer: Parrish and Partners / K. Higgins
Project Date: Thursday, August 11, 2022
Project Units: U.S. Customary Units
Notes: WQ – 0.75in Design Storm
Channel Analysis: Channel Analysis_51_WQ
Notes:
Input Parameters
Channel Type: Triangular
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Longitudinal Slope: 0.0075 ft/ft
Manning's n: 0.0350
Flow 0.4500 cfs
Result Parameters
Depth 0.3241 ft
Area of Flow 0.4202 ft^2
Wetted Perimeter 2.6726 ft
Hydraulic Radius 0.1572 ft
Average Velocity 1.0710 ft/s
Top Width 2.5928 ft
Froude Number: 0.4689
Critical Depth 0.2394 ft
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Critical Velocity 1.9632 ft/s
Critical Slope: 0.0377 ft/ft
Critical Top Width 1.92 ft
Calculated Max Shear Stress 0.1517 lb/ft^2
Calculated Avg Shear Stress 0.0736 lb/ft^2
Channel Analysis: Channel Analysis_51_A_WQ
Notes:
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 4.00 ft
Longitudinal Slope: 0.0077 ft/ft
Manning's n: 0.0350
Flow 1.9200 cfs
Result Parameters
Depth 0.2745 ft
Area of Flow 1.3993 ft^2
Wetted Perimeter 6.2634 ft
Hydraulic Radius 0.2234 ft
Average Velocity 1.3722 ft/s
Top Width 6.1958 ft
Froude Number: 0.5088
Critical Depth 0.1809 ft
Critical Velocity 2.2474 ft/s
Critical Slope: 0.0335 ft/ft
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Critical Top Width 5.45 ft
Calculated Max Shear Stress 0.1319 lb/ft^2
Calculated Avg Shear Stress 0.1073 lb/ft^2
Channel Analysis: Channel Analysis_51_B_WQ
Notes:
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 2.00 ft
Longitudinal Slope: 0.0250 ft/ft
Manning's n: 0.0350
Flow 0.3600 cfs
Result Parameters
Depth 0.1086 ft
Area of Flow 0.2644 ft^2
Wetted Perimeter 2.8956 ft
Hydraulic Radius 0.0913 ft
Average Velocity 1.3615 ft/s
Top Width 2.8689 ft
Froude Number: 0.7903
Critical Depth 0.0938 ft
Critical Velocity 1.6152 ft/s
Critical Slope: 0.0417 ft/ft
Critical Top Width 2.75 ft
Calculated Max Shear Stress 0.1694 lb/ft^2
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Calculated Avg Shear Stress 0.1424 lb/ft^2
Channel Analysis: Channel Analysis_51_2_WQ
Notes:
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 3.00 ft
Longitudinal Slope: 0.0075 ft/ft
Manning's n: 0.0350
Flow 1.7700 cfs
Result Parameters
Depth 0.3027 ft
Area of Flow 1.2747 ft^2
Wetted Perimeter 5.4963 ft
Hydraulic Radius 0.2319 ft
Average Velocity 1.3885 ft/s
Top Width 5.4218 ft
Froude Number: 0.5046
Critical Depth 0.2012 ft
Critical Velocity 2.3125 ft/s
Critical Slope: 0.0330 ft/ft
Critical Top Width 4.61 ft
Calculated Max Shear Stress 0.1417 lb/ft^2
Calculated Avg Shear Stress 0.1085 lb/ft^2
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Channel Analysis: Channel Analysis_51_C_WQ
Notes:
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 2.00 ft
Longitudinal Slope: 0.0144 ft/ft
Manning's n: 0.0350
Flow 0.1000 cfs
Result Parameters
Depth 0.0608 ft
Area of Flow 0.1365 ft^2
Wetted Perimeter 2.5018 ft
Hydraulic Radius 0.0546 ft
Average Velocity 0.7326 ft/s
Top Width 2.4868 ft
Froude Number: 0.5510
Critical Depth 0.0415 ft
Critical Velocity 1.1136 ft/s
Critical Slope: 0.0532 ft/ft
Critical Top Width 2.33 ft
Calculated Max Shear Stress 0.0547 lb/ft^2
Calculated Avg Shear Stress 0.0490 lb/ft^2
Channel Analysis: Channel Analysis_51_D_WQ
Notes:
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 2.00 ft
Longitudinal Slope: 0.0130 ft/ft
Manning's n: 0.0350
Flow 0.1000 cfs
Result Parameters
Depth 0.0626 ft
Area of Flow 0.1410 ft^2
Wetted Perimeter 2.5166 ft
Hydraulic Radius 0.0560 ft
Average Velocity 0.7093 ft/s
Top Width 2.5011 ft
Froude Number: 0.5265
Critical Depth 0.0415 ft
Critical Velocity 1.1136 ft/s
Critical Slope: 0.0532 ft/ft
Critical Top Width 2.33 ft
Calculated Max Shear Stress 0.0508 lb/ft^2
Calculated Avg Shear Stress 0.0454 lb/ft^2
Channel Analysis: Channel Analysis_51_D_OUT_WQ
Notes:
Input Parameters
Channel Type: Trapezoidal
Side Slope 1 (Z1): 4.0000 ft/ft
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Side Slope 2 (Z2): 4.0000 ft/ft
Channel Width 3.00 ft
Longitudinal Slope: 0.0075 ft/ft
Manning's n: 0.0350
Flow 3.6500 cfs
Result Parameters
Depth 0.4450 ft
Area of Flow 2.1270 ft^2
Wetted Perimeter 6.6694 ft
Hydraulic Radius 0.3189 ft
Average Velocity 1.7160 ft/s
Top Width 6.5599 ft
Froude Number: 0.5311
Critical Depth 0.3098 ft
Critical Velocity 2.7787 ft/s
Critical Slope: 0.0293 ft/ft
Critical Top Width 5.48 ft
Calculated Max Shear Stress 0.2083 lb/ft^2
Calculated Avg Shear Stress 0.1493 lb/ft^2
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Site Location
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Appendix C
O & M Forms
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-
-
-
-
Regrade the soil to create a berm that is higher than
the level lip, plant ground cover and water until it is
established. Provide lime and a one-time fertilizer
application.
The level lip is
cracked, settled,
undercut, eroded or
otherwise damaged
SCM element: Potential problem: How to remediate the problem:
Repair or replace the lip.
Level Spreader-Filter Strip Maintenance Requirements
Immediately after the filter strip is established, any newly planted vegetation will be
watered twice weekly if needed until the plants become established (commonly six
Stable groundcover will be maintained in the drainage area to reduce the sediment
load to the level spreader-filter strip.
Every two weeks during the growing season, the filter strip will be mowed. Turf grass
should not be cut shorter than 4-6 inches and may be allowed to grow as tall as 12
inches depending on aesthetic requirements (NIPC, 1993).
Once a year, the soil will be aerated if necessary and the filter strip will be reseeded
to maintain a dense growth of vegetation.
The flow splitter
device is clogged.
Remove the sediment and dispose of it off-site.
Once a year, soil pH will be tested and lime will be added if necessary.
For the fist two years after the LS-FS is established, it shall be inspected quarterly and within 24
hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County). After
two years of successful performance, it will be inspected quarterly. Records of operation and
maintenance shall be kept in a known set location and shall be available upon request.
Important operation and maintenance procedures
Trees or shrubs have
begun to grow on the
swale or just
downslope of the level
Remove the shrubs or trees.
Mow vegetation. Regrade and vegetate if the swale
has become silted in.
Trash/debris is
presentThe entire LS-FS
ection activities shall be performed as follows. Any problems that are found shall be repaired immediately.
Remove the trash/debris.
The flow splitter
device is damaged.
The flow splitter
device (if applicable)
There is erosion
around the end of the
level spreader that
show stormwater has
bypassed it.
Unclog the conveyance and dispose of any sediment
off-site.
The blind swale
The swale is clogged
with sediment.
The swale is
overgrown with
Areas of bare soil
and/or erosive gullies
have formed.
Regrade the soil if necessary to remove the gully,
plant ground cover and water until it is established.
Provide lime and a one-time fertilizer application.The bypass channel
Make any necessary repairs or replace if damage is
too large for repair.
The level spreader
Turf reinforcement is
damaged or ripap is
rolling downhill.
Study the site to see if a larger bypass channel is
needed (enlarge if necessary). After this, reestablish
the erosion control material.
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Potential problem: How to remediate the problem:
Areas of bare soil
and/or erosive gullies
have formed.
Regrade the soil if necessary to remove the gully,
plant ground cover and water until it is established.
Provide lime and a one-time fertilizer application.
Plants are dead,
diseased or dying.
SCM element:
Level Spreader-Vegetated Filter Strip Maintenance Requirements (continued)
Repair the damage and improve the flow dissipation
structure.
Determine the source of the problem: soils,
hydrology, disease, etc. Remedy the problem and
replace plants. Provide a one-time fertilizer
application to establish the ground cover if a soil test
indicates it is necessary. If sod was used, check to see
that it was not grown on clay or impermeable soils.
Remove the sediment and restabilize the soil with
vegetation if necessary. Provide lime and a one-time
Nuisance vegetation is
choking out the grass.
Remove vegetation by hand if possible. If pesticide is
used, do not allow it to get into the receiving water.
The receiving water Discharges from the
LS-FS are causing
erosion or
sedimentation in the
receiving water.
Contact the local NCDEQ Regional Office.
Erosion or other signs
of damage have
occurred at the outlet.
The filter strip
Grass is too short or
too long.
Maintain grass at a height of approximately three to
six inches.
Sediment is building
up on the filter strip.
Grass is dead,
diseased or dying.
Determine the source of the problem: soils,
hydrology, disease, etc. Remedy the problem and
replace plants. Provide a one-time fertilizer
application to establish the ground cover if necessary.
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Important operation and maintenance procedures:
-
-
Areas of bare soil
and/or erosive gullies
have formed.
The entire length of
the swale
SCM element:
Regrade the soil if necessary to remove the gully, re-
sod (or plant with other appropriate species) and water
until established. Provide lime and a one-time
fertilizer application.
How to remediate the problem:
Remove sediment and dispose in an area that will not
impact streams or SCMs. Re-sod if necessary.
Vegetation is too short
or too long.
Maintain grassed vegetation such that the swale or
vegetated area does not erode during the peak flow
from the 10-year storm
Sediment covers the
grass at the bottom of
the swale.
Trash/debris is
present Remove the trash/debris.
The outlet device is
damaged
Treatment Swale Maintenance Requirements
The drainage area of the grassed swale will be carefully managed to reduce the
sediment load to the grassed swale.
After the initial fertilization to establish the grass in the swale, fertilizer will not be
applied to the treatment swale.
The grassed swale will be inspected quarterly. Records of operation and maintenance shall be kept
in a known set location and shall be available upon request.
pection activities shall be performed as follows. Any problems that are found shall be repaired immediately.
Repair or replace the outlet device.
Potential problem:
Trees and/or other
woody vegetation are
present in the
treatment swale
Remove the trees and woody vegetation from the
treatment swale, regrade the treatment swale if
necessary and re-establish grass as shown on the
approved plans
Grass is dead,
diseased or dying.
Determine the source of the problem: soils,
hydrology, disease, etc. Remedy the problem and
replace plants. Provide a one-time fertilizer
application to establish the ground cover if necessary.
The receiving water
Erosion or other signs
of damage have
occurred at the outlet.
Repair the damage and improve the flow dissipation
structure.
Discharges from the
treatment swale are
causing erosion or
sedimentation in the
receiving water.
Contact the local NCDEQ Regional Office.
The outlet device (if
applicable)
Clogging has
occurred.
Clean out the outlet device. Dispose of the sediment
off-site.
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‐
‐
‐
‐
‐
How to remediate the problem:
Dry Pond Maintenance Requirements
Important operation and maintenance procedures:
The drainage area will be managed to reduce the sediment load to the dry pond.
Erosion is occurring in
the swale (if
applicable).
Regrade the swale if necessary and provide erosion
control devices such as reinforced turf matting or
riprap to avoid future problems with erosion.
The entire SCM Trash/debris is
present Remove the trash/debris.
Areas of bare soil
and/or erosive gullies
have formed.
The forebay
Erosion has occurred.
Provide additional erosion protection such as
reinforced turf matting or riprap if needed to prevent
future erosion problems.
Weeds are present.Remove the weeds, preferably by hand. If pesticide is
used, wipe it on the plants rather than spraying.
The inlet pipe is
clogged (if
Unclog the pipe. Dispose of the sediment in a
location where it will not cause impacts to streams or
The inlet device
The inlet pipe is
cracked or otherwise
damaged (if
Repair or replace the pipe.
Sediment has
accumulated to a
depth greater than the
original design depth
for sediment storage.
Search for the source of the sediment and remedy the
problem if possible. Remove the sediment and
dispose of it in a location where it will not cause
impacts to streams or the SCM.
Water is standing
more than 5 days after
a storm event.
Check the outlet structure for clogging. If it is a design
issue, consult an appropriate professional.
Weeds and noxious
plants are growing in
the main treatment
Sediment has
accumulated to a
depth greater than the
original design depth
for sediment storage.
Search for the source of the sediment and remedy the
problem if possible. Remove the sediment and
dispose of it in a location where it will not cause
impacts to streams or the SCM.
The main treatment
area
Remove the weeds, preferably by hand. If pesticide is
used, wipe it on the plants rather than spraying.
Immediately after the dry pond is established, the vegetation will be watered twice
weekly if needed until the plants become established (commonly six weeks).
After the initial fertilization to establish vegetation in the dry pond, fertilizer will not
be applied to the dry pond.The vegetation in and around the basin will be maintained at a height of
approximately six inchesAt least once annually, a dam safety expert will inspect the embankment. Any
problems that are found will be repaired immediately.
The perimeter of the
SCM
After the dry pond is established, it shall be inspected quarterly and within 24 hours after every
storm event greater than 1.0 inches (or 1.5 inches if in a Coastal County). Records of operation
and maintenance shall be kept in a known set location and shall be available upon request.
pection activities shall be performed as follows. Any problems that are found shall be repaired immediately.
SCM element: Potential problem:
Regrade the soil if necessary to remove the gully,
plant ground cover and water until it is established.
Provide lime and a one-time fertilizer application.
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
Consult a professional to remove muskrats or beavers
and repair any holes or erosion.
A tree has started to
grow on the Consult a dam safety specialist to remove the tree.
An annual inspection
by an appropriate
professional shows
that the embankment
needs repair.
Make all needed repairs immediately.
Dry Pond Maintenance Requirements (continued)
SCM element: Potential problem: How to remediate the problem:
Evidence of muskrat or
beaver activity is
The outlet device
Clogging has
occurred.
Clean out the outlet device. Dispose of the sediment
in a location where it will not cause impacts to
streams or the SCM.
The outlet device is
damaged Repair or replace the outlet device.
The embankment
Shrubs have started to
grow on the
embankment.
Remove shrubs immediately.
Erosion or other signs
of damage have
occurred at the outlet.
Repair the damage and improve the flow dissipation
structure.
The receiving water Discharges from the
dry pond are causing
erosion or
sedimentation in the
receiving water.
Contact the local NCDEQ Regional Office.
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
844.5
0 2.5
842
841
844
0 3
841
839
Has Veg. Filter Bottom Elevation:Bottom Elevation:
P2 Temporary Pool El:Temporary Pool El:
Clean Out Depth:Clean Out Depth:
Pretreatment Sediment Storage El:Sediment Storage El:
Has Veg. Filter Bottom Elevation:Bottom Elevation:
DRY POND ID FOREBAY MAIN POND
G Temporary Pool El:Temporary Pool El:
Clean Out Depth:Clean Out Depth:
Pretreatment Sediment Storage El:Sediment Storage El:
Dry Detention Pond Design Summary
DRY POND ID FOREBAY MAIN POND
Dry Pond Diagram
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
1 Project Name Boom Supersonic Final Assembly Line (FAL)
2 Project Area (ac)68.6
3 Coastal Wetland Area (ac)
4 Surface Water Area (ac)0
5 Is this project High or Low Density?High
6 Does this project use an off-site SCM?No
7 Width of vegetated setbacks provided (feet)
8 Will the vegetated setback remain vegetated?
9 If BUA is proposed in the setback, does it meet NCAC 02H.1003(4)(c-d)?
10 Is streambank stabilization proposed on this project?
11 Infiltration System
12 Bioretention Cell
13 Wet Pond
14 Stormwater Wetland
15 Permeable Pavement
16 Sand Filter
17 Rainwater Harvesting (RWH)
18 Green Roof
19 Level Spreader-Filter Strip (LS-FS)1
20 Disconnected Impervious Surface (DIS)
21 Treatment Swale 8
22 Dry Pond 1
23 StormFilter
24 Silva Cell
25 Bayfilter
26 Filterra
FORMS LOADED
27 Name and Title:Kevin Higgins, P.E. / Senior Hydraulics Engineer
28 Organization:Parrish and Partners, LLC
29 Street address:6701 Carmel Rd., Suite 210
30 City, State, Zip:Charlotte, NC 28226
31 Phone number(s):980-819-0439
32 Email:khiggins@parrishandpartners.com
Certification Statement:
Designer
______________________________________________
Signature of Designer
______________________________________________
Date
I certify, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision; that the
information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and that the engineering plans,
specifications, operation and maintenance agreements and other supporting information are consistent with the information provided here.
PROJECT INFORMATION
NUMBER AND TYPE OF SCMs:
DESIGNER CERTIFICATION
COMPLIANCE WITH 02H .1003(4)
Seal
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
DRAINAGE AREAS
1 Is this a high density project?Yes
2 If so, number of drainage areas/SCMs 1
3 Does this project have low density areas?No
4 If so, number of low density drainage areas 0
5
Is all/part of this project subject to previous rule
versions?No
CLICK TO LOAD FORM
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
LEVEL SPREADER - FILTER STRIP (LS-FS)
1 Drainage area number 51 (G)
2 Design flow rate of SCM (cfs).50 cfs
3 Is the SCM sized to treat the SW from all surfaces at build-out?
4 Is the SCM located away from contaminated soils?
5 What are the side slopes of the SCM (H:V)?N/A
6 Does the SCM have retaining walls, gabion walls or other engineered
side slopes? N/A
7 Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?Yes
8 Is there an overflow or bypass for inflow volume in excess of the
design volume?Yes
9 What is the method for dewatering the SCM for maintenance?N/A
10 If applicable, will the SCM be cleaned out after construction?N/A
11 Does the maintenance access comply with General MDC (8)?
12 Does the drainage easement comply with General MDC (9)?
13 If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?N/A
14 Is there an O&M Agreement that complies with General MDC (11)?
15 Is there an O&M Plan that complies with General MDC (12)?
16 Does the SCM follow the device specific MDC?Yes
17 Was the SCM designed by an NC licensed professional?Yes
18 Length of level spreader (feet)50 ft
19 Does the LS-FS receive flow from the drainage area or another
SCM?No
20 Flow rate to LS-FS during design storm (cfs)1 cfs
21 Is a bypass device provided?Yes
22 If yes, what is the bypass device?outlet pipe
23 Is this LS-FS designed to receive flow from the drainage area during
the 10-year storm?
24 Has a blind swale been provided?Yes
25 Does the blind swale provide for uniform overtopping of the level
spreader?Yes
26 What material will be used for the level spreader?Concrete
27 Will the construction tolerance be < 0.25 inch along the level
spreader length?
28 Will the level spreader be straight or convex in plan view?Yes
29 Height of the drop from the level spreader to the transition zone
(inches)
30 Width of the transition zone (inches)
31 Protection for the transition zone
32 Width of the filter strip (feet)
33 Is the filter strip free of draws and channels?
34 Has this been verified in the field?
35 Slope of the filter strip (%)
36 Is this slope uniform across the entire filter strip?
37 Will the first 12" of soil be adjusted if needed to promote plant
growth?
38 Will the filter strip and side slopes be planted with non-clumping,
deep-rooted sod?
39 Species of sod that will be used
40 Will soil be temporarily stabilized until permanent vegetation is
established?Yes
41 Please use this space to provide any additional information about the
level spreader-filter strip(s):
LS-FS MDC FROM 02H .1059
ADDITIONAL INFORMATION
GENERAL MDC FROM 02H .1050
LS-FS 3 3:50 PM 12/12/2022
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
TREATMENT SWALE
1 Drainage area number 51 51-A 51-2
2 Design flow rate of SCM (cfs).45 cfs 1.92 cfs 1.77 cfs
3 Is the SCM sized to treat the SW from all surfaces at build-out?
4 Is the SCM located away from contaminated soils?
5 What are the side slopes of the SCM (H:V)?4:1 4:1 4:1
6 Does the SCM have retaining walls, gabion walls or other engineered
side slopes? No No No
7 Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?Yes Yes Yes
8 Is there an overflow or bypass for inflow volume in excess of the
design volume?
9 What is the method for dewatering the SCM for maintenance?
10 If applicable, will the SCM be cleaned out after construction?
11 Does the maintenance access comply with General MDC (8)?
12 Does the drainage easement comply with General MDC (9)?N/A N/A N/A
13 If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?N/A N/A N/A
14 Is there an O&M Agreement that complies with General MDC (11)?
15 Is there an O&M Plan that complies with General MDC (12)?
16 Does the SCM follow the device specific MDC?Yes Yes Yes
17 Was the SCM designed by an NC licensed professional?Yes Yes Yes
18 SHWT elevation (fmsl)
19 Bottom of the treatment swale (fmsl)851.70 851.70 845.50
20 Depth of treatment swale (feet)4 cf 3 cf 5 cf
21 ls the swale trapezoidal in shape? No Yes Yes
22 Width of bottom of swale (feet)4 ft 3 ft
23 Side slopes of treatment swale (H:V)4:1 4:1 4:1
24 Length of swale (feet)800 ft 1280 ft 800 ft
25 Flow depth during the 0.75 inch/hour storm (inches)5 in 3 in 4 in
26 Flow velocity during the 0.75 inch/hour storm (feet per second)1 cfs 1 cfs 1 cfs
27 Hydraulic retention time for swale (minutes)
28 Species of grass that will be used
29 Will the grass be maintained at an average height of 6 inches?
30 Will the grass not be cut lower than 4 inches?
31 Velocity during the 10-year storm (feet per second)3 ft/s 3 ft/s 3 ft/s
32 Is the swale designed to non-erosively pass the 10-year storm?Yes Yes Yes
33 Please use this space to provide any additional information about the
treatment swale(s):
GENERAL MDC FROM 02H .1050
TREATMENT SWALE MDC FROM 02H .1061
ADDITIONAL INFORMATION
TrSwale 4 3:50 PM 12/12/2022
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
TREATMENT SWALE
1 Drainage area number
2 Design flow rate of SCM (cfs)
3 Is the SCM sized to treat the SW from all surfaces at build-out?
4 Is the SCM located away from contaminated soils?
5 What are the side slopes of the SCM (H:V)?
6 Does the SCM have retaining walls, gabion walls or other engineered
side slopes?
7 Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?
8 Is there an overflow or bypass for inflow volume in excess of the
design volume?
9 What is the method for dewatering the SCM for maintenance?
10 If applicable, will the SCM be cleaned out after construction?
11 Does the maintenance access comply with General MDC (8)?
12 Does the drainage easement comply with General MDC (9)?
13 If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?
14 Is there an O&M Agreement that complies with General MDC (11)?
15 Is there an O&M Plan that complies with General MDC (12)?
16 Does the SCM follow the device specific MDC?
17 Was the SCM designed by an NC licensed professional?
18 SHWT elevation (fmsl)
19 Bottom of the treatment swale (fmsl)
20 Depth of treatment swale (feet)
21 ls the swale trapezoidal in shape?
22 Width of bottom of swale (feet)
23 Side slopes of treatment swale (H:V)
24 Length of swale (feet)
25 Flow depth during the 0.75 inch/hour storm (inches)
26 Flow velocity during the 0.75 inch/hour storm (feet per second)
27 Hydraulic retention time for swale (minutes)
28 Species of grass that will be used
29 Will the grass be maintained at an average height of 6 inches?
30 Will the grass not be cut lower than 4 inches?
31 Velocity during the 10-year storm (feet per second)
32 Is the swale designed to non-erosively pass the 10-year storm?
33 Please use this space to provide any additional information about the
treatment swale(s):
GENERAL MDC FROM 02H .1050
TREATMENT SWALE MDC FROM 02H .1061
ADDITIONAL INFORMATION
51-B 51-C 51-D
.36 cfs .10 cfs .10 cfs
4:1 4:1 4:1
No No No
Yes Yes Yes
N/A N/A N/A
N/A N/A N/A
Yes Yes Yes
Yes Yes Yes
851.00 845.50 841.90
2 cf 2 cf 3 cf
Yes Yes Yes
2 ft 2 ft 2 ft
4:1 4:1 4:1
370 ft 270 ft 500 ft
1 in 1 in 1 in
1 cfs 1 cfs 1 cfs
3 ft/s 2 ft/s 2 ft/s
Yes Yes Yes
TrSwale 5 3:50 PM 12/12/2022
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
TREATMENT SWALE
1 Drainage area number
2 Design flow rate of SCM (cfs)
3 Is the SCM sized to treat the SW from all surfaces at build-out?
4 Is the SCM located away from contaminated soils?
5 What are the side slopes of the SCM (H:V)?
6 Does the SCM have retaining walls, gabion walls or other engineered
side slopes?
7 Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?
8 Is there an overflow or bypass for inflow volume in excess of the
design volume?
9 What is the method for dewatering the SCM for maintenance?
10 If applicable, will the SCM be cleaned out after construction?
11 Does the maintenance access comply with General MDC (8)?
12 Does the drainage easement comply with General MDC (9)?
13 If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?
14 Is there an O&M Agreement that complies with General MDC (11)?
15 Is there an O&M Plan that complies with General MDC (12)?
16 Does the SCM follow the device specific MDC?
17 Was the SCM designed by an NC licensed professional?
18 SHWT elevation (fmsl)
19 Bottom of the treatment swale (fmsl)
20 Depth of treatment swale (feet)
21 ls the swale trapezoidal in shape?
22 Width of bottom of swale (feet)
23 Side slopes of treatment swale (H:V)
24 Length of swale (feet)
25 Flow depth during the 0.75 inch/hour storm (inches)
26 Flow velocity during the 0.75 inch/hour storm (feet per second)
27 Hydraulic retention time for swale (minutes)
28 Species of grass that will be used
29 Will the grass be maintained at an average height of 6 inches?
30 Will the grass not be cut lower than 4 inches?
31 Velocity during the 10-year storm (feet per second)
32 Is the swale designed to non-erosively pass the 10-year storm?
33 Please use this space to provide any additional information about the
treatment swale(s):
GENERAL MDC FROM 02H .1050
TREATMENT SWALE MDC FROM 02H .1061
ADDITIONAL INFORMATION
50-A 50-B
N/A N/A
N/A N/A
TrSwale 6 3:50 PM 12/12/2022
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2
DRY POND
1 Drainage area number 51 (G)
2 Minimum required treatment volume (cu ft)18676 cf
3 Is the SCM sized to treat the SW from all surfaces at build-out?Yes
4 Is the SCM located away from contaminated soils?Yes
5 What are the side slopes of the SCM (H:V)?6:1
6 Does the SCM have retaining walls, gabion walls or other engineered
side slopes? No
7 Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?Yes
8 Is there an overflow or bypass for inflow volume in excess of the
design volume?Yes
9 What is the method for dewatering the SCM for maintenance?
10 If applicable, will the SCM be cleaned out after construction?Yes
11 Does the maintenance access comply with General MDC (8)?Yes
12 Does the drainage easement comply with General MDC (9)?N/A
13 If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?N/A
14 Is there an O&M Agreement that complies with General MDC (11)?Yes
15 Is there an O&M Plan that complies with General MDC (12)?Yes
16 Does the SCM follow the device specific MDC?Yes
17 Was the SCM designed by an NC licensed professional?Yes
18 SHWT elevation (fmsl)834
19 Elevation of the bottom of the dry pond (fmsl)842
20 Distance from bottom to SHWT (feet)8 ft
21 Elevation of the temporary pool during the design storm (feet)846 ft
22 Ponding depth of the design storm (feet)4 ft
23 Will the dry pond be uniformly graded to flow toward the outlet?Yes
24 Is a low flow channel being provided?No
25 Are the inlet(s) and outlet located in a manner that avoids short-
circuiting?Yes
26 Will berms or baffles be provided to increase the flow path?Yes
27 What method of pretreatment will be provided?Swales
28 Design volume of SCM (cu ft)18676
29 Diameter of drawdown orifice (in)3 in
30 Drawdown time for the temporary pool (hours)
31 Does the pond minimize impacts to the receiving channel from the 1-
yr, 24-hr storm?Yes
32 Is there a small permanent pool near the orifice to prevent clogging?Yes
33 Will the outlet be designed to prevent clogging?Yes
34 Are the dam and embankment planted in non-clumping turf grass?
35 Species of turf that will be used on the dam and embankment
36 Will trees and shrubs be prevented from growing on the dam and
embankment?Yes
37 Please use this space to provide any additional information about the
dry pond(s):
GENERAL MDC FROM 02H .1050
DRY POND MDC FROM 02H .1062
ADDITIONAL INFORMATION
SHWT elevation is estimated from the wetland delineation
Dry Pond 7 3:50 PM 12/12/2022
DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2