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HomeMy WebLinkAboutPTIA_BOOM Stormwater Report_2023-01-25_Signed.pdf DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 STORMWATER REPORT FOR BOOM FINAL ASSEMBLY LINE FACILITY — PHASE 1 PIEDMONT TRIAD INTERNATIONAL AIRPORT GUILFORD COUNTY, NORTH CAROLINA 1 Stormwater Design Reference is the 2017 Edition of NCDEQ's "Stormwater Design Manual" PREPARED FOR: PREPARED BY: a*r NORTH CAROLINA Environmental Quality PARRI SH&PARTNERS ���klliti�111�J�ff w H A it0 r�� Sib ' - SEAL TV 035700 �= DocuSigned by: / • f1��7�� r�ftrll� I�Lti�1/26/2023 E w;s, P. H E898DBE48FC2444... January 2023 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 BOOM SUPERSONIC FINAL ASSEMBLYLINE (FAL) — PHASE I 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 BOOM Supersonic—Phase 1 Page 2 of 4 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 • 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 Q 10 Pre-development flows were calculated using the Rational Method. The Q 10 Post-development flows are the peak flows leaving the outlet structure of the 2 dry ponds and were calculated using HEC-HMS. The Q 10 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. Outfal I 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 EA (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. BOOM Supersonic—Phase 1 Page 3 of 4 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 Outfall ID BOOM (FAL)—Phase 1: Table 2 Des.Vol. Req Des.Vol. Provided (ac-ft) (ac-ft) % Difference SB-P2 (50) 0.45 0.45 0.00% SB-G (51) 0.39 1 0.39 1 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). BOOM Supersonic Phase 1 Page 4 of 4 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 uy r. ' J r i 4'* 4 ., i f 4 I Vicinity MapI N Figure 1. Legend S Cit of Greensboro w ; E Project Area Map PARRISH&iPARTNERS u Project—Area BOOM Supersonic -73 S Final Assembly Line 400 200 0 Feet Phase I Project Location Gilford County, NC October 2022 u DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 1 - rk . rt J d Trailer city, parking, and entrance roads FAL, parking, and taxiway i Vicinity Map N Figure 2. highlighted Cit of Greensboro areas to be constructed v w E Phase 1 Map PARRISH PARTNERS In Phase 1. All other BOOM Supersonic proposed development 1�73 S Final Assembly Line will be in subsequent Project Location 400 200 0 Feet Phase I phases Guilford County, NC October 2022 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 � 4 p -4F r POP- Basin 0,704 WIF 7 JI � ` 4 M� �< 2EN`�� �� ; _ , , �►�; % Basin SBlaw -P2 . I. A" I kIA N / 111 ' Or s'T Legend Vicinity Map N Figure 3. Cit of Greensboro Drainage Area Map Phase1 Area w E PARRISH&PARTNERS BOOM Supersonic Drainage \Area 1'73 S Final Assembly Line CONTOURS Pr 400 200 0 Fee Phase I oject Location Guilford County, NC October 2022 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 Appendix A Calculations DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 BOOM Supersonic Final Assembly Line BASIN SB-G Runoff Coefficient Total Area= 34.3 AC Rv=0.05 +0.9 * la la = 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 * la la = 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-DOC7BAD230A2 DESIGN OF RIP RAP' PROTECTIONOUTLET 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 Step 1. Determine the tail-water depth from channel characteristics below the pipe outlet for the design capacity of the pipe_ If the tailwater depth is less than half the outlet pipe diameter, it is classified minimum tailwater condition. If it is greater than half the pipe diameter, it is classified maximum condition_ Pipes that outlet onto wide flat areas with no defined channel are assiumed to have a minimum tailwater condition unless reliable flood stage elevations shop; otherwise. 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 Step 2. Based on the tailwater conditions determined in step 1. enter Figure 8.06a or Figure 8.06b,and determine duo riprap size and minimum apron length (Q_ The d,, size is the median stone size in a well-graded riprap apron. Step 3. Determine apron width at the pipe outlet, the apron shape_ and the apron width at the outlet end from the same figure used in Step 2. Minimum TW Maximum TW Figure 8.06a Figure 8.06b Riprap d50, (ft.) 1 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 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 Step 4. Determine the nia%inuni stone dia nneter: d�_x = 1 .5xd-,o Minimum TW Maximum TW Max Stone Diameter, dmax (ft.) 0 1.5 Step 5. Determine the apron thickness: Apron thickness = 1 .5 x dr,..,. Minimum TW Maximum TW Apron Thickness(ft.) 0 2.25 Step 6. Fit the riprap apron to the site by making it level for the minimum length, L., from Figure 8.06a or Figure 8.06b. Extend the apron farther downstream and along channel banks until stability- is assured. Keep the apron as straight as possible and align it with the$o«of the receiving stream. Make any necessary alignment bends near the pipe outlet so that the entrance into the receiving stream is straight. Some locations may require lining of the entire channel cross section to assure stability. It may be necessary to increase the size of riprap where protection of the charnel side slopes is necessary (Appendix 8.05)_ R'here overfalls exist at pipe outlets or flows are excessive, a plunge pool should be considered, see page 8.06.8. DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 Appendix B Ditch Cal cs DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 BOOM Supersonic Final Assembly Line (FAL) Flow Depths in Swales during the 0.75in Storm Event • Swale 51 Triangular Chaiuiel 0.45 0.40 0.35 0.30 0 0.25 i Q_20 w 015 0.10 0.05 0-- 0 0.5 1.0 1.5 2A 2.5 3.0 3.5 Station(ft) • Swale 51-2 Trapezoidal Chaiuiel 0.40 0.35 0.30 Z 0.25 0 0.20 7 .iJ 0.15 0.10 0.05 0 0 1 2 3 4 5 6 Station(ft) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 • Swale 51-A 1 rapezoidal Chamiel 0.35 0.30 0.25 0 0.20 m w 0.15 0.10 0.05 0 0 1 2 3 4 5 6 7 Station(ft) • Swale 51-B Trapezoidal Chaiuiel 0.14 0.12 0.1 a Y 0 0.08 co w 0.0fi 0.04 0.02 0 0 0.5 1.0 1.5 2.0 2.5 3.0 Station (ft) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 • Swale 51-C Trapezoidal Channel 0.08 0.07 0.06 0.05 c 0 0 0.04 } a� w 0.03 0.02 0.01 0 6 0.5 1.0 1.5 2.0 2.5 Station(ft) • Swale 51-D Trapezoidal Chaimel 0.0s 0.07 0.06 0.05 C O 0.04 cu w 0.03 0.02 0.01 0 0 0.5 1.0 1.5 2.0 2.5 Station(ft) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 • Swale 51-D-OUT Trapezoidal Channel 0.60 0.55 0.50 0.45 0.40 0.35 c 0.30 w 025 0.20 0.15 0.10 0.05 0 0 1 2 3 4 5 6 7 8 Station(ft) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 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-DOC7BAD23OA2 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-DOC7BAD23OA2 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-DOC7BAD23OA2 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 ft12 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-DOC7BAD23OA2 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 ft12 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-DOC7BAD230A2 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-DOC7BAD23OA2 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-DOC7BAD23OA2 NC Surface Water Classifications F r �. � �r � mq •'� Legend Layers h g la°l c `o. � yr�W:v`' °o� 3 � , Site Location Surface Surface Water Classifications: Stream Index: 16-11-4-(1) Stream Name: Brush Creek ' Gor Coura rr^Tr:Vxn k� Description: From source to a point F ro .1 0.5 mile downstream of �z„^j,r Guilford County SR 2190 Classification: WS-III;NSW Date of Class.: August 2,1992 What does this Class. View c I mean? s River Basin: Cape Fear A C' L� She G c O i � hO P\.fnnm[i hrf � r rP`F `a HMn•,—,t9 qg a R a` brumh Crux ea N Aau� Smm or Narth CifNiriA 007,E:n,HERE,Gamin.Geo7xhnakgrr irLc..lJEGS.ME711NPSA,Epq USDA NC.. Paxercd yy Esr� DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 Appendix C O & M Forms Level Snreader-Filter Strin Maintenance Requirements DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 Important operation and maintenance procedures 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. 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. ection activities shall be performed as follows. Any problems that are found shall be repaired immediately. SCM element: Potential problem: How to remediate the problem: The entire LS-FS Remove the trash/debris. The flow splitter Unclog the conveyance and dispose of any sediment The flow splitter device is clogged. off-site. device (if applicable) The flow splitter Make any necessary repairs or replace if damage is device is damaged. too large for repair. The swale is clogged Remove the sediment and dispose of it off-site. with sediment. The blind swale The swale is Mow vegetation. Regrade and vegetate if the swale overgrown with has become silted in. cracked, settled, Repair or replace the lip. undercut, eroded or There is erosion Regrade the soil to create a berm that is higher than around the end of the the level lip, plant ground cover and water until it is The level spreader level spreader that established. Provide lime and a one-time fertilizer show stormwater has application. bVpassed it. Trees or shrubs have begun to grow on the Remove the shrubs or trees. swale or just downslope of the level Areas of bare soil Regrade the soil if necessary to remove the gully, and/or erosive gullies plant ground cover and water until it is established. The bypass channel have formed. Provide lime and a one-time fertilizer application. Turf reinforcement is Study the site to see if a larger bypass channel is damaged or ripap is needed (enlarge if necessary). After this, reestablish rolling downhill. Ithe erosion control material. LPVPI %nrPacJPr_VPnPtatPrJ Filter Strin MaintPnanre Requirements (continued) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 SCM element: Potential problem: How to remediate the problem: Grass is too short or Maintain grass at a height of approximately three to too long. six inches. Areas of bare soil Regrade the soil if necessary to remove the gully, and/or erosive gullies plant ground cover and water until it is established. have formed. Provide lime and a one-time fertilizer application. Sediment is building Remove the sediment and restabilize the soil with up on the filter strip. vegetation if necessary. Provide lime and a one-time Determine the source of the problem: soils, Grass is dead, hydrology, disease, etc. Remedy the problem and The filter strip diseased or dying. replace plants. Provide a one-time fertilizer application to establish the ground cover if necessary. etermine the source of the problem: soils, hydrology, disease, etc. Remedy the problem and Plants are dead, replace plants. Provide a one-time fertilizer diseased or dying. 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. Nuisance vegetation is Remove vegetation by hand if possible. If pesticide is choking out the grass. used, do not allow it to get into the receiving water. Erosion or other signs Repair the damage and improve the flow dissipation of damage have structure. occurred at the outlet. The receiving water Discharges from the LS-FS are causing erosion or Contact the local NCDEQ Regional Office. sedimentation in the receiving water. TrPatmPnt RwalP MaintPnancP Requirements DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 Important operation and maintenance procedures: 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. section activities shall be performed as follows. Any problems that are found shall be repaired immediately. SCM element: Potential problem: How to remediate the problem: Remove the trash/debris. Areas of bare soil egra e the soil it necessary to remove the gully, re- and/or erosive gullies sod (or plant with other appropriate species)and water have formed. until established. Provide lime and a one-time fertilizer application. Sediment covers the Remove sediment and dispose in an area that will not grass at the bottom of impact streams or SCMs. Re-sod if necessary. the swale. The entire length of Vegetation is too short Maintain grassed vegetation such that the swale or the Swale or too long. vegetated area does not erode during the peak flow from the 10-year storm Determine the source of the problem: soils, Grass is dead, hydrology, disease, etc. Remedy the problem and diseased or dying. replace plants. Provide a one-time fertilizer application to establish the ground cover if necessary. woody vegetation are treatment swale, regrade the treatment swale if present in the necessary and re-establish grass as shown on the Clogging has Clean out the outlet device. Dispose of the sediment occurred. off-site. The outlet device (if applicable) The outlet device is Repair or replace the outlet device. damaged Erosion or other signs Repair the damage and improve the flow dissipation of damage have structure. occurred at the outlet. The receiving water Discharges from the treatment swale are causing erosion or Contact the local NCDEQ Regional Office. sedimentation in the receiving water. Dry Pnnd MaintPnancP RPnijirements DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 Important operation and maintenance procedures: - The drainage area will be managed to reduce the sediment load to the dry pond. - 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. I HU VCyt:!LdUUll III dnU d[UUIIU UIC Ud5111 will UC IIIdillLdII1CU dl d litil lit.UI At least once annually, a dam safety expert will inspect the embankment. Any problems that are found will be repaired immediately. 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. ,ection activities shall be performed as follows. Any problems that are found shall be repaired immediately. SCM element: Potential problem: How to remediate the problem: The entire SCM Remove the trash/debris. Areas of bare soil Regrade the soil if necessary to remove the gully, The perimeter of the SCM and/or erosive gullies plant ground cover and water until it is established. have formed. Provide lime and a one-time fertilizer application. The inlet pipe is Unclog the pipe. Dispose of the sediment in a clogged (if location where it will not cause impacts to streams or The inlet pipe is The inlet device cracked or otherwise Repair or replace the pipe. damaged (if Erosion is occurring in Regrade the swale if necessary and provide erosion the swale (if control devices such as reinforced turf matting or applicable). riprap to avoid future problems with erosion. Sediment has Search for the source of the sediment and remedy the accumulated to a problem if possible. Remove the sediment and depth greater than the dispose of it in a location where it will not cause original design depth impacts to streams or the SCM. for sediment stora e. The forebay Provide additional erosion protection such as Erosion has occurred. 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. Sediment has Search for the source of the sediment and remedy the accumulated to a problem if possible. Remove the sediment and depth greater than the dispose of it in a location where it will not cause original design depth impacts to streams or the SCM. The main treatment for sediment storage. Water is standing area more than 5 days after Check the outlet structure for clogging. If it is a design issue, consult an appropriate professional. a storm event. Weeds and noxious Remove the weeds, preferably by hand. If pesticide is plants are growing in the main treatment used, wipe it on the plants rather than spraying. Dry Pnnd MaintPnanrP RPnuirPmPntS (continued) DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 SCM element: Potential problem: How to remediate the problem: Shrubs have started to grow on the Remove shrubs immediately. embankment. Evidence of muskrat or Consult a professional to remove muskrats or beavers beaver activity is and repair any holes or erosion. The embankment A tree has started to Consult a dam safety specialist to remove the tree. grow on the An annual inspection by an appropriate professional shows Make all needed repairs immediately. that the embankment needs repair. Clogging has Clean out the outlet device. Dispose of the sediment gg g occurred. in a location where it will not cause impacts to The outlet device streams or the SCM. The outlet device is Repair or replace the outlet device. damaged Erosion or other signs Repair the damage and improve the flow dissipation of damage have structure. occurred at the outlet. The receiving water Discharges from the dry pond are causing erosion or Contact the local NCDEQ Regional Office. sedimentation in the receiving water. ^^• ^-*-^*ion Pond Design Summary DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 Dry Pond Diagram DRY POND ID FOREBAY MAIN POND G Temporary Pool El: Temporary Pool El: 844.5 Clean Out Depth: 0 Clean Out Depth: 2.5 Pretreatment Sediment Storage El: Sediment Storage El: 842 Has Veg. Filter Bottom Elevation: Bottom Elevation: 841 DRY POND ID FOREBAY MAIN POND P2 Temporary Pool El: Temporary Pool El: 844 Clean Out Depth: 0 Clean Out Depth: 3 Pretreatment Sediment Storage El: Sediment Storage El: 841 Has Veg. Filter Bottom Elevation: Bottom Elevation: 839 i DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 V V I 1 V`11F1`1\ 1 -`L V V Y `1% 1 r\V` FORMS LOADED PROJECT INFORMATION 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 1 Does this project use an off-site SCM? No COMPLIANCE WITH 02H.1003(4) 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.1 003(4)(c-d)? 10 Is streambank stabilization proposed on this project? NUMBER AND TYPE OF SCMs: 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 JStormFilter 24 Silva Ce1I 25 Bayfilter 26 Filterra FORMS LOADED DESIGNER CERTIFICATION 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: 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. Designer Signature of Designer Seal Date I DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD230A2 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 Is all/part of this project subject to previous rule 5 versions? No CLICK TO LOAD FORM LocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 S� V v VV V I I\V/"AVVI\ - I IV I VI\ V I I%II `L-%# .7 1 Drainage area number 51 (G) 2 Design flow rate of SCM cfs .50 cfs GENERAL MDC FROM 02H.1050 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 N/A side slopes? 7 Are the inlets,outlets,and receiving stream protected from erosion Yes 10- ear storm)? 8 Is there an overflow or bypass for inflow volume in excess of the Yes design volume? 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 N/A 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 1 Does the SCM follow the device specific MDC? Yes 17 lWas the SCM designed by an NC licensedprofessional? Yes LS-FS MDC FROM 02H.1059 18 Length of level spreader(feet) 50 ft Does the LS-FS receive flow from the drainage area or another 19 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 Yes spreader? 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 Height of the drop from the level spreader to the transition zone 29 (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, dee -rooted sod? 39 1 Species of sod that will be used 40 Will soil be temporarily stabilized until permanent vegetation is Yes established? ADDITIONAL INFORMATION 41 Please use this space to provide any additional information about the level spreader-filter strip(s): LS-FS 3 3:50 PM 12/12/2022 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 1 IRCM 1 IVICIV 1 0VVML.0 11 Drainage area number 51 51-A 51-2 21 Design flow rate of SCM cfs .45 cfs 1.92 cfs 1.77 cfs GENERAL MDC FROM 02H.1050 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 No No No side slopes? 7 Are the inlets,outlets,and receiving stream protected from erosion Yes Yes Yes (10-year storm)? 8 Is there an overflow or bypass for inflow volume in excess of the design volume? 9 1 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 N/A N/A N/A General MDC(10)? 14 Is there an O&M Agreement that complies with General MDC(11)? 151 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 1 Was the SCM designed by an NC licensed rofessional? Yes Yes Yes TREATMENT SWALE MDC FROM 02H.1061 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 Is the swale trapezoidal in shape? No Yes Yes 22 Width of bottom of swale(feet) 4 ft 3 ft 231 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 1 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 ADDITIONAL INFORMATION 33 Please use this space to provide any additional information about the treatment swale(s): TrSwale 4 3:50 PM 12/12/2022 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 1 IRCM 1 IVICIV 1 0VVML.0 11 Drainage area number 51-B 51-C 51-D 21 Design flow rate of SCM cfs .36 cfs .10 cfs .10 cfs GENERAL MDC FROM 02H.1050 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 No No No side slopes? 7 Are the inlets,outlets,and receiving stream protected from erosion Yes Yes Yes (10-year storm)? 8 Is there an overflow or bypass for inflow volume in excess of the design volume? 9 1 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 N/A N/A N/A General MDC(10)? 14 Is there an O&M Agreement that complies with General MDC(11)? 151 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 1 Was the SCM designed by an NC licensed rofessional? Yes Yes Yes TREATMENT SWALE MDC FROM 02H.1061 18 SHWT elevation (fmsl) 19 Bottom of the treatment swale fmsl 851.00 845.50 841.90 20 Depth of treatment swale(feet) 2 cf 2 cf 3 cf 21 Is the swale trapezoidal in shape? Yes Yes Yes 22 Width of bottom of swale(feet) 2 ft 2 ft 2 ft 23 Side slopes of treatment swale H:V 4:1 4:1 4:1 24 Length of swale(feet) 370 ft 270 ft 500 ft 25 Flow depth during the 0.75 inch/hour storm inches 1 in 1 in 1 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 2 ft/s 2 ft/s 32 Is the swale designed to non-erosively pass the 10-year storm? Yes Yes Yes ADDITIONAL INFORMATION 33 Please use this space to provide any additional information about the treatment swale(s): TrSwale 5 3:50 PM 12/12/2022 DocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 1 IRCM 1 IVICIV 1 0VVML.0 11 Drainage area number 50-A 50-B 21 Design flow rate of SCM cfs GENERAL MDC FROM 02H.1050 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)? N/A N/A 13 If the SCM is on a single family lot,does(will?)the plat comply with N/A N/A General MDC(10)? 14 Is there an O&M Agreement that complies with General MDC(11)? 151 Is there an O&M Plan that complies with General MDC 12 ? 16 Does the SCM follow the device specific MDC? 17 1 Was the SCM designed by an NC licensed rofessional? TREATMENT SWALE MDC FROM 02H.1061 18 SHWT elevation (fmsl) 19 Bottom of the treatment swale fmsl 20 Depth of treatment swale(feet) 21 Is 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 281 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? ADDITIONAL INFORMATION 33 Please use this space to provide any additional information about the treatment swale(s): TrSwale 6 3:50 PM 12/12/2022 LDocuSign Envelope ID:5DC4E730-9943-4129-85E3-DOC7BAD23OA2 F% 1 r V I Is V 1 Drainage area number 51 G 2 Minimum required treatment volume cu ft 18676 cf GENERAL MDC FROM 02H.1050 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 No side slopes? 7 Are the inlets,outlets,and receiving stream protected from erosion Yes 10- ear storm)? 8 Is there an overflow or bypass for inflow volume in excess of the Yes design volume? 9 What is the method for dewatering the SCM for maintenance? 10 If applicable,will the SCM be cleaned out after construction? Yes 111 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 N/A General MDC 10? 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 licensedprofessional? Yes DRY POND MDC FROM 02H.1062 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- Yes circuiting? 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 1 Drawdown time for the temporary pool(hours) 31 Does the pond minimize impacts to the receiving channel from the 1- Yes Yr,24-hr storm? 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 Yes embankment? ADDITIONAL INFORMATION Please use this space to provide any additional information about the 37 dry pond(s): SHWT elevation is estimated from the wetland delineation Dry Pond 7 3:50 PM 12/12/2022