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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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 1/26/2023 ___________________________________________________________________________________ _ 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 ___________________________________________________________________________________ _ 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. DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 ___________________________________________________________________________________ _ 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2   Appendix A Calculations DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2   Appendix B Ditch Calcs DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 BOOM Supersonic Final Assembly Line (FAL)  Flow Depths in Swales during the 0.75in Storm Event   Swale 51     Swale 51‐2    DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2  Swale 51‐A     Swale 51‐B    DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2  Swale 51‐C     Swale 51‐D    DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2  Swale 51‐D‐OUT      DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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 DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2   Site Location DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2   Appendix C O & M Forms DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 - - - - - 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. DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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. DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2 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. DocuSign Envelope ID: 5DC4E730-9943-4129-85E3-D0C7BAD230A2  ‐   ‐   ‐   ‐   ‐  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