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Safety Department::.. lw Fier Coaaaty EnVmwmg W Regal Off cs Staanawater File Nw* QwQ&M Dqwfteat of Quafty I Dirf wn ofFtmw MIRaM and Land Res"m Of e l M7 Car&W Dnw Eamdm l W&wVtm North C Post -Construction Stormwater Management Permit No. SW8 050547 STATE OF NORTH CAROLINA DEPARTMENT OF ENVIRONMENTAL QUALITY DIVISION OF ENERGY, MINERAL AND LAND RESOURCES POST -CONSTRUCTION STORMWATER MANAGEMENT PERMIT HIGH DENSITY DEVELOPMENT In accordance with the provisions of Article 21 of Chapter 143, General Statutes of North Carolina as amended, and other applicable Laws, Rules, and Regulations PERMISSION IS HEREBY GRANTED TO New Hanover County Airport Authority Wilmington International Airport Extended Dry Detention Basins (EDDB) 1740 Airport Boulevard, Wilmington, New Hanover County FOR THE construction, operation and maintenance of three (3) extended dry detention basin ("stormwater control measures" or "SCM") in compliance with the provisions of 15A NCAC 2H .1000 (1995 Rules) as amended on January 1, 2017 (2017 Rules) (collectively, the "stol7nwaterruiesl and as outlined in the application, approved stormwater management plans, supplement, calculations, operation and maintenance agreement, recorded documents, specifications, and other supporting data (the "approved plans and specifications") as attached and/or on file with and approved by the Division of Energy, Mineral and Land Resources (the "Division" or "DEMLR"). The project shall be constructed, operated and maintained in accordance with these approved plans and specifications. The approved plans and specifications are incorporated by reference and are enforceable part of this permit. This permit shall be effective from the date of issuance until June 15, 2027 and shall be subject to the following specified conditions and limitations. The permit issued shall continue in force and effect until the permittee files a request with the Division for a permit modification, transfer, renewal, or rescission; however, these actions do not stay any condition. The issuance of this permit does not prohibit the Director from reopening and modifying the permit, revoking and reissuing the permit, or terminating the permit for cause as allowed by the laws, rules, and regulations contained in Title 15A NCAC 2H.1000 and NCGS 143-215.1 et.al. I. DESIGN STANDARDS 1. The drainage area identified as Phase I&II is subject to the 1995 Rules and as clarified in the 1995 specific conditions listed herein. The drainage areas identified as Phase IIIA, Phase 11113 and Phase IIIC are subject to the 1995 Rules and the 2017 Rules and as clarified in the 2017 Rules specific conditions listed herein. 2. This project and SCMs have been approved based on the "Wilmington International Airport Stormwater Master Plan" document approved on November 24, 2004 as a variation to the stormwater rules and in accordance with G.S. 143-214.7(c3). All future major modifications to this permit must either meet the 2004 "Wilmington International Airport Stormwater Master Plan" in its entirety, meet the most current set of stormwater rules, or provide technical justification that the proposed modification is providing equal or better control and equal or better protection of water of the State as a variation under the current set of stormwater rules. Approval of such variations that do not meet all of the requirements is done on a case -by -case basis. 3. FAA requirements prohibit standing water (i.e., permanent pools) and stipulate that the design storm must be fully drained within 48 hours. This is supported by G.S. 143-214.7(c3) where the Division does not require the use of an SCM with standing water. The approved SCM design for the 3 extended dry detention basins includes a low flow device but does not include a permanent pool at the low flow outlet or sediment storage. Page 1 of 6 Post -Construction Stormwater Management Permit No. SW8 050547 4. The approved "Wilmington International Airport Stormwater Master Plan" document is not intended to limit or restrict the airport or its current or prospective tenants from pursuing alternative or modified stormwater management solutions in various locations than those listed in the document itself. Since the approval of the "Wilmington International Airport Stormwater Master Plan" document, other stormwater control measure (SCM) options that do not contain areas of standing water have been developed and should be evaluated for future projects. 5. This permit is effective only with respect to the nature and volume of stormwater described in the application and other supporting data. The maximum amount of built -upon area (BUA) allowed for the entire project is 9,304,059 square feet. 6. The three (3) SCMs identified as "Phase I and 11" Extended Dry Detention Basin, Phase IIIA Extended Dry Detention Basin and Phase IIIB Extended Dry Detention Basin have been designed to handle the runoff from 8,520,835 square feet, 116,598 square feet, and 367,596 square feet of BUA, respectively, within the delineated drainage areas. The BUA for future development within the drainage areas to the SCMs identifies as "Phase I and 11" Extended Dry Detention Basin, Phase IIIA Extended Dry Detention Basin and Phase IIIB Extended Dry Detention Basin is limited to 2,057,505 square feet, 48,788 square feet, and 264,031 square feet, respectively. 7. Where an individual project within the drainage area is being leased or sold, the stormwater collection system for that project must be located in either dedicated common areas or easements and the final plats will be recorded showing all such required easements. 8. The drainage areas for the on -site stormwater systems will be limited to the amounts of built - upon area indicated in this permit and the approved plans and specifications. The runoff from all built -upon area within the permitted drainage areas of this project must be directed into the permitted stormwater control measures. 9. (2017 Rules) The peak flow from the 10-year storm event shall not cause erosion downslope of the discharge point. 10. (2017 Rules) A 50-foot wide vegetative setback must be provided and maintained in grass or other vegetation adjacent to all surface waters as shown on the approved plans. The setback is measured horizontally from the normal pool elevation of impounded structures, from the top of bank of each side of streams or rivers, and from the mean high waterline of tidal waters, perpendicular to the shoreline. 11. The portion of the existing airport previously included in the drainage area of the permitted dry detention basin that is being removed, must be submitted in a future permit application as a modification or under G.S. 143-214.7(c4). 12. (1995 Rules) The following design criteria have been provided and must be maintained in the "Phase I and II" Extended Dry Detention Basin. Phase I & II a. Drainage Area, acres: 287.63 Onsite, ft2: 12,529,107 Offsite, ft2: 0 b. Total Impervious Surfaces, ft2: 8,520,835 C. Design Storm, inches: 4,552,087 @1" 3,968,748 @1.5- d. Basin Bottom Elevation, feet: 7.0 e. TSS removal efficiency: 50% f. Storage Elevation, FMSL: 13.0 g. Storage Surface Area, ft2: 506,082 h. Permitted Detention Volume, ft3: 1,058,112 i. Seasonal High Water Table, FMSL: 6.0 j. Controlling Orifice: 12.0" 0 k. Drawdown Time for 12.0" fd orifice, hours: 57 I. Receiving Stream/River Basin: Smith Creek / Cape Fear M. Stream Index Number: 18-74-63 n. Classification of Water Body: C;Sw Page 2 of 6 Post -Construction Stormwater Management Permit No. SW8 050547 13. (2017 Rules) The SCMs identified as Phase IIIA Extended Dry Detention Basin and Phase IIIB Extended Dry Detention are permitted based on the design criteria presented in the sealed, signed and dated supplements, the sealed and signed "Technical Justification" document dated April 13, 2021 justifying the variations from the Wilmington International Airport Stormwater Master Plans well as the 2017 minimum design criteria, and as shown in the approved plans and specifications. These SCMs must be provided and maintained at the design condition. The approved supplements are incorporated by reference into this permit. 14. (2017 Rules) If the SCMs identified as Phase IIIA Extended Dry Detention Basin and Phase IIIB Extended Dry Detention are found to not meet the approved design criteria, a modification must be submitted to either meet the requirements or propose another variation from the rules. This is based on a case -by -case decision and should not be used as a precedent for future permitting actions. 15_ Tributary projects outside of the drainage area of the previously approved "for -credit" grassed swales, but inside the drainage area of the approved SCMs, must provide an additional BMP with a sufficient TSS removal efficiency such that the total TSS removal, including the extended dry detention basin, is at least 85%. II. SCHEDULE OF COMPLIANCE 1. The stormwater management system shall be constructed in its entirety, vegetated and operational for its intended use prior to the construction of any built -upon surface. 2. During construction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired immediately. If the stormwater system was used as an Erosion Control device, it must be restored to design condition prior to operation as a stormwater treatment device, and prior to occupancy of the facility. 3. The facilities shall be constructed, operated, and maintained in accordance with the provisions of this permit, the approved plans and specifications, and the supporting documents attached to this permit and on file with the Division. 4. The permittee is responsible for verifying that the proposed built -upon area for the entire project does not exceed the maximum allowed by this permit. 5_ Upon completion of the project, the permittee shall determine if the project is in compliance with the approved plans and take the necessary following actions: a. If the permittee determines that the project is in compliance with the approved plans, then within 45 days of completion, the permittee shall submit to the Division one hard copy and one electronic copy of the following: i. The completed and signed Designer's Certification provided in Attachment A noting any deviations from the approved plans and specifications. Deviations may require approval from the Division; ii. A copy of the recorded operation and maintenance agreement; iii. Unless already provided, a copy of the recorded deed restrictions and protective covenants; and iv. A copy of the recorded plat delineating the public rights -of -way, dedicated common areas and/or permanent recorded easements, when applicable. b. If the permittee determines that the project is not in compliance with the approved plans, the permittee shall submit an application to modify the permit within 30 days of completion of the project or provide a plan of action, with a timeline, to bring the site into compliance. Page 3 of 6 Post -Construction Stormwater Management Permit No. SW8 050547 6. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted stormwater system functions at the design condition. The approved Operation and Maintenance Plan must be followed in its entirety and maintenance must occur at the scheduled intervals including, but not limited to: a. Semiannual scheduled inspections (every 6 months). b. Sediment removal. C. Mowing and revegetation of slopes and the vegetated filter. d. Immediate repair of eroded areas. e. Maintenance of all slopes in accordance with approved plans and specifications. f. Debris removal and unclogging of outlet structure, orifice device, flow spreader, catch basins and piping. g. Access to the outlet structure must be available at all times. 7. Records of maintenance activities must be kept and made available upon request to authorized personnel of DEMLR. The records will indicate the date, activity, name of person performing the work and what actions were taken. 8. (2017 Rules) The operation and maintenance agreement must be recorded with the Office of the Register of Deeds. 9. (2017 Rules) The final plats for the project must be recorded with the Office of the Register of Deeds. The recorded plat must reference the Operation and Maintenance Agreement and must also show all public rights -of -way, dedicated common areas, and/or permanent drainage easements, in accordance with the approved plans. 10. Access to the permitted stormwater facilities shall be maintained via appropriate easements (as required) at all times. 11. No person or entity, including the permittee, shall alter any component shown in the approved plans and specifications. Prior to the construction of any modification to the approved plans, the permittee shall submit to the Director, and shall have received approval for modified plans, specifications, and calculations including, but not limited to, those listed below. For changes to the project or SCM that impact the certifications, a new or updated certification(s), as applicable, will be required and a copy must be submitted to the appropriate DEQ regional office upon completion of the modification. a. Any modification to the approved plans and specifications, regardless of size including the SCM(s), BUA, details, etc. b. Redesign or addition to the approved amount of BUA or to the drainage area. C. Further development, subdivision, acquisition, lease or sale of any, all or part of the project and/or property area as reported in the approved plans and specifications. d. Altering, modifying, removing, relocating, redirecting, regrading, or resizing of any component of the approved SCM(s), the stormwater collection system and/or vegetative conveyance shown on the approved plan. e. The construction of any allocated future BUA. f. The construction of any permeable pavement, #57 stone area, public trails, or landscaping material to be considered a permeable surface that were not included in the approved plans and specifications. g. Other modifications as determined by the Director. 12. The Director may notify the permittee when the permitted site does not meet one or more of the minimum requirements of the permit. Within the time frame specified in the notice, the permittee shall submit a written time schedule to the Director for modifying the site to meet minimum requirements. The permittee shall provide copies of revised plans and certification in writing to the Director that the changes have been made. Ili. GENERAL CONDITIONS CORRECTIVE ACTIONS REQUIRED. If the facilities fail to perform satisfactorily, the permittee shall take immediate corrective actions. This includes actions required by this Division and the stormwater rules such as the construction of additional or replacement on -site stormwater systems. These additional or replacement measures shall receive a permit from the Division prior to construction. Page 4of6 Post -Construction Stormwater Management Permit No. SW8 050547 2. PERMIT RENEWAL. A permit renewal request must be submitted at least 180 days prior to the expiration date of this permit. The renewal request must include the appropriate application, documentation and the processing fee as outlined in Title 15A NCAC 02H.1045(3). 3. CHANGES TO THE PROJECT NAME, PERMITTEE NAME OR CONTACT INFORMATION. The permittee shall submit a completed Permit Information Update Application Form to the Division within 30 days to making any one of these changes. 4. TRANSFER. This permit is not transferable to any person or entity except after notice to and approval by the Director. Neither the sale of the project and/or property, in whole or in part, nor the conveyance of common area to a third party constitutes an approved transfer of the permit. a. TRANSFER REQUEST. The transfer request must include the appropriate application, documentation and the processing fee as outlined in 15A NCAC 02H.1045(2). This request must be submitted within 90 days of the permit holder meeting one or more of the following: i. A natural person who is deceased; ii. A partnership, limited liability corporation, corporation, or any other business association that has been dissolved; iii. A person or entity who has been lawfully and finally divested of title to the property on which the permitted activity is occurring or will occur through foreclosure, bankruptcy, or other legal proceeding. iv. A person or entity who has sold the property, in whole or in part, on which the permitted activity is occurring or will occur. b. TRANSFER INSPECTION. Prior to transfer of the permit, a file review and site inspection will be conducted by Division personnel to ensure the permit conditions have been met and that the project and the on -site stormwater system complies with the permit conditions. Records of maintenance activities performed to date may be requested. Projects not in compliance with the permit will not be transferred until all permit and/or general statute conditions are met. 5. COMPLIANCE. The permittee is responsible for compliance with the terms and conditions of this permit until the Division approves the transfer request. a. APPROVED PLANS AND SPECIFICATIONS. A copy of this permit, approved plans, application, supplement, operation and maintenance agreement, all applicable recorded documents, and specifications shall be maintained on file by the permittee at all times. b. DIVISION ACCESS. The permittee grants Division Staff permission to enter the property during normal business hours to inspect all components of the permitted project. c. ENFORCEMENT. Any individual or entity found to be in noncompliance with the provisions of a stormwater management permit or the requirements of the stormwater rules is subject to enforcement procedures as set forth in NCGS 143 Article 21. d. ANNUAL CERTIFICATION. The permittee shall electronically submit to the Division an annual certification completed by either the permittee or their designee confirming the projects conformance with permit conditions e. OBTAINING COMPLIANCE. The Director may notify the permittee when the permitted site does not meet one or more of the minimum requirements of the permit. Within the time frame specified in the notice, the permittee shall submit a written time schedule to the Director for modifying the site to meet minimum requirements. The permittee shall provide copies of modified plans and certification in writing to the Director that the changes have been made. Page 5 of 6 Post -Construction Stormwater Management Permit No. SW8 050547 OTHER PERMITS. The issuance of this permit does not preclude the permittee from complying with and obtaining any other permits or approvals that are required for this development to take place, as required by any statutes, rules, regulations, or ordinances, which may be imposed by any other Local, State or Federal government agency having jurisdiction. Any activities undertaken at this site that cause a water quality violation or undertaken prior to receipt of the necessary permits or approvals to do so are considered violations of NCGS 143-215.1, and subject to enforcement procedures pursuant to NCGS 143-215.6. Permit modified, updated and reissued this the 6th day of April 2022. NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION rAZL'-_0 u Brian Wrenrl,irec r Division of Energy, Mineral and Land Resources By Authority of the Environmental Management Commission Permit No. SW8 050547 Page 6 of 6 Post -Construction Stormwater Management Permit No. SW8 050547 Wilmington International Airport Stormwater Permit No. SW8 050547 New Hanover County Attachment A Designer's Certification I, , as a duly registered in the State of North Carolina, having been authorized to observe (periodically/ weekly/ full time) the construction of the project, (Project) for (Project Owner) hereby state that, to the best of my abilities, due care and diligence was used in the observation of the project construction such that the construction was observed to be built within substantial compliance and intent of the approved plans and specifications. The checklist of items on page 2 of this form is included in the Certification. Noted deviations from approved plans and specification: Signature Registration Number Date SEAL Page 1 of 2 Post -Construction Stormwater Management Permit No. SW8 050547 Certification Requirements: 1. The drainage area to the system contains approximately the permitted acreage. 2. The drainage area to the system contains no more than the permitted amount of built - upon area. 3. All the built -upon area associated with the project is graded such that the runoff drains to the system. 4. All drainage within the permitted contributing drainage area is directed into the system. 5. The outlet/bypass structure elevations are per the approved plan. 6. The outlet structure is located per the approved plans. 7. A trash rack is provided on the outlet/bypass structure. 8. All slopes are grassed with permanent vegetation. 9. Vegetated slopes are no steeper than 3:1. 10. The inlets are located per the approved plans and do not cause short-circuiting of the system. 11. The permitted amounts of surface area and/or volume have been provided. 12. Required drawdown device is correctly located and sized per the approved plans. 13. All required design depths are provided. 14. All required parts of the system are provided, such as pretreatment devices, outlet structure and/or forebay. 15. The required system dimensions are provided per the approved plans. 16. The maximum drainage area and/or built -upon area have not been exceeded for the "Phase I & II" condition. cc: NCDEQ-DEMLR Regional Office New Hanover County Building Inspections Page 2 of 2 Post -Construction Stormwater Management Permit No. SW8 050547 Attachment C - Permitting History Wilmington International Airport EDDB Permit No. SW8 050547 Approval PermittBBIMS I I__ Description of the Changes- T- E Date Action Version This original issuance approved the 150 acre area pocket of high density Phase I, in accordance with 6/15/2005 Original 1.0 SW8 040836, to be treated in an extended dry Approval detention basin (EDDB) #1 designed to handle the runoff from 4,247,100 square feet of impervious area. Approved the modification of the permit to include Phase II, which brought the total project area to 10/28/2009 Modification 1.1 264 acres and increased the size of the EDDB # 1 to handle a total of 8,468,064 square feet of impervious area. Approved the modification to include Phase III, which brought the total project area to 321.35 acres and increased the size of the EDDB # 1 to handle a 10/26/2011 Modification 1.2 total of 8,468,064 square feet of impervious area. This permit also took into account the impervious area for SW8 060326 and SW8 060515, which both drain to EDDB #1 and were permitted as Offsite permits to SW8 050547. Approved the modification to the overall drainage area to 3 22.3 8 acres and the increased size of EDDB # 1 to handle a total of 9,751,185 square feet 11/29/2012 Modification 1.3 of impervious area. This modification included the addition of two grassed pre-treatment swales. This issuance left 3,177,214 square feet of Future allocation for the Phase I & II area. Approved the reallocation of 205,202 square feet of Plan Future allocation for the development of the Rental 2/8/2013 Revision 1.4 Car Facility within the Phase I & II drainage area. This issuance left 2,972,012 square feet of Future allocation. Approved the reallocation of 32,453 square feet of Plan Future allocation for the expansion of the North 8/4/2015 Revision 1.5 General Aviation Apron draining to EDDB #1. This issuance left 2,939,559 square feet of Future allocation for the Phase I & II area. Page 1 of 3 Post -Construction Stormwater Management Permit No. SW8 050547 Approved the reallocation of a total of 129,082 square feet of future allocation, 62,570 square feet Plan for the Business Park access road and 66,512 9/9/2015 Revision 1.6 square feet for Lot 9 of the Business Park, both draining to EDDB #1. This issuance left 2,810,477 square feet of Future allocation for the Phase I & Il area. Approved the reallocation of 122,922 square feet of future allocation for the North General Aviation Hangar Taxiline and Corporate Hanger Complex. 6/29/2016 Plan 1 This also took into account the 24,190 square feet Revision '7 of impervious area allocated to SW8 150723, which drains to EDDB # 1 and is permitted as an Offsite permit to SW8 050547. This issuance left 2,663,295 square feet of Future allocation. Approved the reallocation of 75,596 square feet of 8/22/2017 Plan 1'8 future allocation for the Avis Car Rental Facility Revision draining to EDDB #1. This issuance left 2,587,699 square feet of Future allocation. Approved the reallocation of 29,337 square feet of 4/18/2018 Minor 1.9 future allocation for the Social Bark Kennel Modification draining to EDDB #1. This issuance left 2,558,362 square feet of Future allocation. Approved the reallocation of 110,358 square feet of 10/5/2018 Minor 2.0 future allocation for the FBO #2 project draining to Modification EDDB #1. "Ibis issuance left 2,448,004 square feet of Future allocation. 10/3/2019 Renewal 3.0 This issuance renewed Permit No. SW8 050547 until June 15, 2027. Approved the reallocation of 224,194 square feet of future allocation for the Air Carrier Apron Expansion draining to EDDB #1. This modification Major also adds Pre-treatment Swale #3 as pretreatment 10/6/2020 Modification 3.1 for EDDB #1. The submittal also included 9,268 square feet of impervious area that meets NCGS 143-214.7(c4) that does not drain to EDDB #l. This issuance left 2,223,812 square feet of Future allocation for the Phase I & U area. Page 2 of 3 Post -Construction Stormwater Management Permit No. SW8 050547 This issuance replaces the originally approved Phase III expansion (and "Overall" condition) of Extended Dry Detention Basin (EDDB) #1 with two new EDDB's. EDDB # 1 remains unmodified at the Phase I&II condition. The two new EDDB's, identified as Phase IIIA and Phase IHB on the plans, are permitted as a variation to the rules based 4/20/2021 Major 3.2 on the 2004 "Wilmington International Airport Modification Stormwater Master Plan" document, signed and sealed "Technical Justification " document dated April 13, 2021, and supplements as shown in the approved plans and specifications. The Phase IIIA EDDB has been designed to handle the runoff from 116,598 square feet of BUA and he Phase IIIB EDDB has been designed to handle the runoff from 367,596 square feet of BUA. This issuance approved the reallocation of 48,658 Minor square feet of future BUA within the EDDB # 1 6/10/2021 3.3 drainage area for the construction of the Aero Modification Center Wilmington project. This issuance left a total of 2,175,154 square feet of future allocation. This issuance approved the reallocation of 117,649 square feet of future BUA within the EDDB # 1 4/6/2022 Minor 3.4 drainage area for the Air Carrier Apron Expansion. Modification This issuance left a total of 2,057,505 square feet of future allocation within the EDDB # 1 drainage area. Page 3 of 3 Permit Number: S WB (37tpS-i ( -4 (to be provided by DWQ) Drainage Area Number: rr-41 wsC M:A Dry Extended Detention Basin Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BUT elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BUT. The dry extended detention basin system is defined as the dry detention basin, outlet structure, pretreatment including forebays and the vegetated filter if one is provided. This system (check one): ® does ❑ does not incorporate a vegetated filter at the outlet. This system (check one): ® does ❑ does not incorporate pretreatment other than a forebay. Important maintenance procedures: - The drainage area will be managed to reduce the sediment load to the dry extended detention basin. - Immediately after the dry extended detention basin is established, the vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - No portion of the dry extended detention pond will be fertilized after the first initial fertilization that is required to establish the vegetation- - I will maintain the vegetation in and around the basin at a height of approximately six inches. - Once a year, a dam safety expert will inspect the embankment. After the dry extended detention basin is established, it will be inspected once a quarter 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 will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potentialproblem: How I will remediate theproblem: The entire BMP Trash/debris is present. Remove the trash/debris. The perimeter of the dry Areas of bare soil and/or Regrade the soil if necessary to extended detention erosive gullies have formed. remove the gully, and then plant a basin ground cover and water until it is established. Provide lime and a one-time fertilizer application Form SW401-Dry Detention O&M-Rev.3 Page 1 of 4 BMP element: Potentialproblem: How I will remediate theproblem: The inlet device: pipe or The pipe is clogged (if Unclog the pipe. Dispose of the swale applicable). sediment off -site. The pipe is cracked or Replace the pipe. otherwise damaged (if applicable). Erosion is occurring in the Regrade the swale if necessary to swale (if applicable). smooth it over and provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. The forebay Sediment has accumulated Search for the source of the and reduced the depth to 75 % sediment and remedy the problem if of the original design depth possible. Remove the sediment and (see diagram below). dispose of it in a location where it will not cause impacts to streams or the BMP. Erosion has occurred or Provide additional erosion riprap is displaced. 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 pesticides are used, wipe them on the plants rather than spraying. The main treatment area Sediment has accumulated Search for the source of the and reduced the depth to 75% sediment and remedy the problem if of the original design depth possible. Remove the sediment and (see diagram below). dispose of it in a location where it will not cause impacts to streams or the BMP. Revegetate disturbed areas immediately with sod (preferred) or seed protected with securely staked erosion mat. Water is standing more than Check outlet structure for clogging. 5 days after a storm event. If it is a design issue, consult an appropriate rofessional. Weeds and noxious plants are Remove the plants by hand or by growing in the main wiping them with pesticide (do not treatment area. spray). Form SW401-Dry Detention O&M-Rev.3 Page 2 of 4 BMP element: Potentialproblem: How I will remediate theproblem: The embankment Shrubs or trees have started Remove shrubs or trees to grow on the embankment. immediately. Grass cover is unhealthy or Restore the health of the grass cover eroding, - consult a professional if necessary. Signs of seepage on the Consult a professional. downstream face. Evidence of muskrat or Use traps to remove muskrats and beaver activity is present. consult a professional to remove beavers. An annual inspection by an Make all needed repairs. appropriate professional shows that the embankment needs repair. The outlet device Clogging has occurred. Clean out the outlet device. Dispose of the sediment off -site. The outlet device is damaged Repair or replace the outlet device. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality 401 Oversight Unit at 919- outlet. 733-1786. The measuring device used to determine the sediment elevation shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the basin depth reads 15.50 feet in the main pond, the sediment shall be removed. When the basin depth reads NA feet in the forebay, the sediment shall be removed. Sediment Removal Bottom BASIN DIAGRAM (fill in the blanks) NA----------- T porar� olume NA 25% Sediment Storage FOREBAY Temporary Pool.Flevation 17.7..6' Pool emporar \------Sediment Removal Elevation 15.50---- .;- Volume tom Elevation 14.50•z, 1 25% MAIN POND Form SW401-Dry Detention O&M-Rev.3 Page 3 of 4 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name:CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 BMP drainage area numberTHASE 3A Print name:GRANSEUR DICK Title:FACILITIES DIRECTOR - NEW HANOVER COUNTY AIRPORT AUTHORITY Address:1740 AIRPORT BLVD, WILMINGTON, NC 28405 Signature: Date: 9�9 jz® 2- Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, �()R 01. 1)&V6 , a Notary Public for the State of N& fk CCtrp 1 let& , County of NeL4) 4AhoU(,r , do hereby certify that l lYaMe.t .r1),ck, personally appeared before me this q day of / , 2020 , and acknowledge the due execution of the forgoing dry detention basin maintenance requirements. Witness my hand and official seal, M Q-°sE M oq s NOTARY z PUBLIC 2 VER C09 SEAL My commission expiresI y Form SW401-Dry Detention O&M-Rev.3 Page 4 of 4 Permit Number: 6tsOrzFq-T (to be provided by DWQ) Drainage Area Number: Dry Extended Detention Basin Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BUT elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BUT. The dry extended detention basin system is defined as the dry detention basin, outlet structure, pretreatment including forebays and the vegetated filter if one is provided. This system (check one): ® does ❑ does not incorporate a vegetated filter at the outlet. This system (check one): ® does ❑ does not incorporate pretreatment other than a forebay. Important maintenance procedures: - The drainage area will be managed to reduce the sediment load to the dry extended detention basin. - Immediately after the dry extended detention basin is established, the vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - No portion of the dry extended detention pond will be fertilized after the first initial fertilization that is required to establish the vegetation. - I will maintain the vegetation in and around the basin at a height of approximately six inches. -- Once a year, a dam safety expert will inspect the embankment. After the dry extended detention basin is established, it will be inspected once a quarter 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 will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potentialproblem: How I will remediate theproblem: The entire BMP Trash/debris is present. Remove the trash/debris. The perimeter of the dry Areas of bare soil and/or Regrade the soil if necessary to extended detention erosive gullies have formed. remove the gully, and then plant a basin ground cover and water until it is established. Provide lime and a one-time fertilizer application Form SW401-Dry Detention O&M-Rev.3 Page 1 of 4 BMP element: Potentialproblem: How I will remediate theproblem: The inlet device: pipe or The pipe is clogged (if Unclog the pipe. Dispose of the Swale applicable). sediment off -site. The pipe is cracked or Replace the pipe. otherwise damaged (if applicable). Erosion is occurring in the Regrade the swale if necessary to swale (if applicable). smooth it over and provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. The forebay Sediment has accumulated Search for the source of the and reduced the depth to 75% sediment and remedy the problem if of the original design depth possible. Remove the sediment and (see diagram below). dispose of it in a location where it will not cause impacts to streams or the BMP. Erosion has occurred or Provide additional erosion riprap is displaced. 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 pesticides are used, wipe them on the plants rather than spraying. The main treatment area Sediment has accumulated Search for the source of the and reduced the depth to 75% sediment and remedy the problem if of the original design depth possible. Remove the sediment and (see diagram below). dispose of it in a location where it will not cause impacts to streams or the BMP. Revegetate disturbed areas immediately with sod (preferred) or seed protected with securely staked erosion mat. Water is standing more than Check outlet structure for clogging. 5 days after a storm event. If it is a design issue, consult an appropriate rofessional. Weeds and noxious plants are Remove the plants by hand or by growing in the main wiping them with pesticide (do not treatment area. I spray) - Form SW401-Dry Detention O&M-Rev.3 Page 2 of 4 BMP element: Potentialproblem: How I will remediate the problem: The embankment Shrubs or trees have started Remove shrubs or trees to ow on the embankment. immediately. Grass cover is unhealthy or Restore the health of the grass cover eroding. - consult a professional if necessary. Signs of seepage on the Consult a professional. downstream face. Evidence of muskrat or Use traps to remove muskrats and beaver activity is present. consult a professional to remove beavers. An annual inspection by an Make all needed repairs. appropriate professional shows that the embankment needs repair. The outlet device Clogging has occurred. Clean out the outlet device. Dispose of the sediment off -site. The outlet device is damaged Repair or replace the outlet device. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality 401 Oversight Unit at 919- outlet. 733-1786. The measuring device used to determine the sediment elevation shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the basin depth reads 15.00 feet in the main pond, the sediment shall be removed. When the basin depth reads NA feet in the forebay, the sediment shall be removed. Sediment Removal Bottom BASIN DIAGRAM ill in the hlanks) Q Temporary Pool Elevation.16,90 NA T por Pool -------------- -- olume Sediment Removal Elevation 15.00', NA25%--------------.-------------------=..---------= Sediment Bottom Elevation 13.25 Storage FOREBAY MAINYOND Form SW401-Dry Detention O&M-Rev.3 Page 3 of 4 Volum 25% Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name:CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 BMP drainage area number:PHASE 3B Print name:GRANSEUR DICK Title:FACILITIES DIRECTOR - NEW HANOVER COUNTY AIRPORT AUTHORITY Address:1740 AIRPORT BLVD WILMINGTON, NC 28405 Signature: C. CL-0 01 Date: VOL 0 2 O Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, ?105e- Iy , • 1JQ �/�^S , a Notary Public for the State of N &-M "I I n.- , County of 1kx,3 F r�o r , do hereby certify that �4 6Lr152u.r D1Gk.� personally appeared before me this -7 day of Se64fAJQeC r a20 , and acknowledge the due execution of the forgoing dry detention basin maintenance requirements. Witness my hand and official seal, P49+ M . I s NOTARY m PUBLIC z co��� DER .V SEAL My commission expires Zy Form SW401-Dry Detention O&M-Rev.3 Page 4 Of 4 Permit Name: SL01 1 ors n (to be provided by DWQ) Drainage Area Number' �[T A Grassed Swale Operation and Maintenance Agreement I will keep a maintenance record on this BNT. This maintenance record will be kept in a log in a known set location. Any deficient BMP elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BW. Important maintenance procedures: - The drainage area of the grassed swale will be carefully managed to reduce the sediment load to the grassed Swale. - After the first-time fertilization to establish the grass in the swale, fertilizer will not be applied to the grassed swale. The grassed swale will be inspected once a quarter. Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potentialproblem: How I will remediate theproblem: The entire length of the swale Trash/debris is present. Remove the trash/debris. Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then re -sod (or plant with other appropriate species) and water until established. Provide lime and a one-time fertilizer application. Sediment covers the grass at the bottom of the swale. Remove sediment and dispose in an area that will not impact streams or BMPs. ;Re -sod ii necessary. Vegetation is too short or too Maintain vegetation at a height of long approximatelyapproxirnately six inches. , The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality 401 Oversight Unit -at 919- outlet. 733-1786. Form SW401-Grassed Swale O&M-Rev.3 Page 1 of 2 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name:CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 BMP drainage area numberTHASE 3A Print name:GRANSEUR DICK Title:FACILITIES DIRECTOR - NEW HANOVER COUNTY AIRPORT AUTHORITY Address:1740 AIRPORT BLVD WILMINGTON, NC 28405 Signature: Date: V 91Zd Z Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. I, PDV_ M ,16ciu'O , a Notary Public for the State of t_ tN+J, "I I VW,�. , County of WtZ 44&A,o" ! , do hereby certify that %•wnr _D I cle— personally appeared before me this day of 5 , c)COO, and acknowledge the due execution of the forgoing grassed Swale maintenance requirements. Witness my hand nd official seal, rA* M. 1.aAn�� z NOTARY PUBLIC 2 CLIER CC119 SEAL My commission expires Form SW401-Grassed Swale O&M-Rev.3 Page 2 of 2 Permit Name: $Wg p�m —fir, (to be provided by DWQ) Drainage Area Number: fljwN, 11r3 Grassed Swale Operation and Maintenance Agreement I will keep a maintenance record on this BMP. This maintenance record will be kept in a log in a known set location. Any deficient BUT elements noted in the inspection will be corrected, repaired or replaced immediately. These deficiencies can affect the integrity of structures, safety of the public, and the removal efficiency of the BMP. Important maintenance procedures: — The drainage area of the grassed swale will be carefully managed to reduce the sediment load to the grassed swale. — After the first-time fertilization to establish the grass in the swale, fertilizer will not be applied to the grassed swale. The grassed swale will be inspected once a quarter. Records of operation and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. BMP element: Potential problenc How I will remediate theproblem: The entire length of the Trash/debris is present. Remove the trash/debris. swale Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then re -sod (or plant with other appropriate species) and water until established. Provide lime and a one-time fertilizer application. Sediment covers the grass at the bottom of the swale. Remove sediment and dispose in an area that will not impact streams or BMPs.. Re=sod.if necessary. Vegetation is too short or too Maintain vegetation at a height of long. approximately six inches. - The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the outlet. Quality 401 Oversight Unit at 919- 733-1786. Form SW401-Grassed Swale O&M-Rev.3 Page 1 of 2 Permit Number: (to be provided by DWQ) I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Project name:CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 BMP drainage area number:PHASE 3B Print name:GRANSEUR DICK Title:FACILITIES DIRECTOR - NEW HANOVER COUNTY AIRPORT AUTHORITY Address:1740 AIRPORT BLVD WILMINGTON, NC 28405 Phone: 910-341-4333 Signature Date: IX Zd20 Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. 4, a Notary Public for the State of kly% ,C&-rol 1y-.k , County of kk!4) J-e-- , do hereby certify that CWrLN_f4ttA, f- —b1ek, personally appeared before me this day of �--' -207,0 ' and acknowledge the due execution of the forgoing grassed swale maintenance requirements. Witness my hand and official seal, K&k m .^', "�* s NOTARY Z PUBLIC = y*OVER 0,0J0 SEAL My commission expires `7 I Zff Pq Form SW401-Grassed Swale O&M-Rev.3 Page 2 of 2 DEMLR USE ONLY Date Received Fee Paid Permit Number STORMWATER PERMITTING FORM 7: MINOR MODIFICATION Standard Permitting Program — No Fee for Minor Modification Express Permitting Program — See Express Fee Schedule Only complete applications packages will be accepted and reviewed. This form and the required items (with original signatures) must be sent to the appropriate DEMLR Regional Office, which can be determined by locating the project on the interactive online map at. http://deg.nc.gov/contacUregional-offices. This form is to only to be used by the current permittee to notify the Division of a minor modification. Pursuant to Rule 15A NCAC 02H .1002. a minor modification is a change to the project that. 1) does not increase the net built -upon area; and/or 2) does not change the size or design of the SCM(s). A. GENERAL INFORMATION 1. State Stormwater Permit Number: SW8 050547 2. Current Permit Holder's Company Name/Organization: New Hanover County Airport Authority 3. Signing Official's Name: Granseur Dick 4. Signing Official's Title: Facilities Director 5. Mailing Address: 1740 Airport Boulevard, Suite 12 City: Wilmington State: NC ZIP: 28405 6. Street Address (if different): City: State: ZiP: 7. Phone: (910) 341-4333 Email: gdick(aflyilm.com 8. Describe the minor modifications that you are requesting, including any revised BUA allocations (attach additional pages or supporting tables similar to Section IV.10 of the original application, if needed): The proposed project will be requesting an additional BUA reallocation of 117,649 sf of future allocation for the Air Carrier Apron Expansion draining to EDDB #1 (under permit SW8-050547) See additional pages. B. SUBMITTAL REQUIREMENTS Please mark "Y" to confirm the items are included with this form. Please mark `V if previously provided. if not applicable or not available, please mark N/A.: Y 1. Two hard copies (with original signatures) and one electronic copy of this completed form. Y 2. Two hard copies and one electronic copy of the revised plan sheets (must be a revision of the originally approved plan sheets). X 3. If there is reallocation of lot BUA, a copy of the revised recorded deed restrictions and protective revenants OR. the proposed recorded deed restrictions and protective covenants documenting the changes and a signed agreement to provide the finai recorded document. NA 4. If applicable, the appropriate Express review fee. Stormwater Permit Form 7: Minor Modification Page 1 of 2 July 14, 2017 C. CONTACT INFORMATION 1. The Design Professional who is authorized to provide information on the Applicant's behalf: Design Professional's Name: JD Lannou. PE Consulting Firm: Talbert & Bright, Inc. Mailing Address:4810 Shelley Drive City:Wilmington State: NC Zip:28405 Phone: (910) 763-5350 Fax: (910) 762-6281 Email::ilannou(a)-tlbiilfiserx; �i�;;1nn , c*M 2. [OPTIONAL] If you would like to designate another person to answer questions about the project: Name & Title: Organization: Mailing Address: City:_ Phone: Email: D. CERTIFICATION OF PERMITTEE State: Zip: ax: ( I, Granseur Dick , the current permittee, certify that I have authorized the minor modifications listed in Section A and shown in the attached revised plan sheets. I further attest that this information is accurate and complete to the best of my kUpwledge. Signature: /z/l1zozl I, 9.0V M - a Notary Public for th State of 611, cc-q-, (i A" - County of �f �� , do hereby certify that �GlhSf,L�r Dkc � personally appeared before me this the S�- day of �Qr - yob e - , 20 a l , and acknowledge the due execution of the forgoing instrument. Witness my hand and official seal, �SSM Seal) b��/cS� Z NOTARY a PUBLIC 2 Ne&ry Signature �.� . "'� 0 "VE GGW l My pires L er 2021 Storri r:xtir Permit Form is ,.tinor k1odi'iication Papj • 2 of 2 C.;,L 15, 201 Table in Form SWU-101, Section IV. 10. SW8 050547 Basin Information Overall Drainage Area Phase I & If Drainage Area Pretreatment Swale #3 . Drainage Area Receiving Stream Name Smith Cree Smith Creek Smith Creek Stream Class C, S C, Sw C, Sw Stream Index Number 1 7 -63 18-74-63 18-74-63 Total Drainage Area (sf) 14 075 12,529,107 696,960 On -site Drainage Area (sf) ,041, 5 12,529,107 696,960 Off -site Drainage Area (sf) 0 0 0 Proposed Impervious Area (sf) 9,751,185 8,520,835 522,720 % Impervious Area (total) 69.4% 68.0% 75.0% Impervious Surface Area Overall % Drainage Area 1 r Phase l & II Drainage Area, Pretreatment Swale #3 Drainage Area On -site Buildings/Lots (sf) 0 0 0 On -site Streets (sf) 1,994 1,994 1,994 On -site Parking (sf) �89,9X 289,918 241,260 On -site Sidewalks (sf) V0 0 Other on -site (sf) A0 0 Future (sf) ,287, 5 2,057,505 180,879 Off -site (sf) 0 0 0 Existing BUA (sf) 6,171,418 6,171,418 98,587 Total (sf): 9,751,185 8,520,835 522,720 %0"",\\ 1 04""6 n V%V UN a gall cam' IMP, eU� aM3 1c a�G 'C6►� �� Permit Number:�� (to be provided by DWQ) A "A O� m A. *I- ��F W pTF,QOG 9 MIEHR Ei STORMWATER MANAGEMENT PERMIT APPLICATION FORM 401 CERTIFICATION APPLICATION FORM GRASSED SWALE SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part I//) must also be filled out, printed and submitted along with all of the required information. Project name CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 Contact name RICK BAKER, PE Phone number 919-8664939 Date January 14,2021 Drainage area number PHASE 3A Site Characteristics Drainage area 189,922.00 ftz Impervious area 113,256.00 ftz Percent impervious 59.6% % Design rainfall depth 0.75 inch Peak Flow Calculations 10-yrstorm runoff depth 10-yr storm intensity Post -development 10-yr storm peak flow Velocity Maximum non -erosive velocity (peak 10-year storm) Soil characteristics (enter "x" below) Sand/silt (easily erodible) Clay mix (erosion resistant) Grass Type (enter 'Y' below) Bermuda Tall fescue Bahiagrass Kentucky bluegrass Grass -legume mixture Swale type: Fill out one of the options below: Option 1: Curb Outlet Swale: Maximum velocity Side slopes Swale length Option 2: Swale Seeking Pollutant Credit ("For -Credit" Swale): Maximum velocity for 10-yr storm Side slopes Swale length NIA in 0.75 inlhr 2.50 ft3/sec 5.00 ft/sec x x N Y 0.61 6.00 1 r%n nn Itillil k CA I - f (Y or N) 2 {{ "WinW ��11111 t 110N (Y or N) 011140.1 ft/sec OK :1 OK ft OK Form SW401-Grassed Swale-Rev.4 Parts I and II. Project Design Summary, Page 1 of 3 Permit Number: (to be provided by DWQ) Swale Characteristics Swale Shape: Enter an'Y' in the appropriate cell below: Trapezoidal x Parabolic V-shaped Width of the bottom of the swale 6.00 ft Width of the top of the swale 18.00 ft Additional information Is the swale sized for all runoff from ultimate build -out? Y (Y or N) OK Is the BMP located in a proposed drainage easement with a recorded access easement to a public Right of Way (ROW)? Y (Y or N) OK What is the distance from the bottom of the swale to the SHWf? -4.65 ft Insufficient distance to SHWT, unless conveyance swale only. What is the ground level elevation? 21.67 fmsl What is the elevation of the bottom of the swale? 16.35 fmsl What is the SHWT elevation? 21.00 fmsl What is the lonqitudinal slope of the swale? 0.10 % OK What is the depth of freeboard? 1.50 ft OK Form SW401-Grassed Swale-Rev.4 Parts I and II. Projeci Design Summary, Page 2 of 3 Permit No: (to be assigned by DWQ) Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Initials Page/ Plan Sheet No. RB 1. Plans 0" = 50' or larger) of the entire site showing: - Design at ultimate build -out, - Off -site drainage (if applicable), Delineated drainage basins (include Rational C coefficient per basin), Swale dimensions (width, length, depth), - Maintenance access, - Proposed drainage easement and public right of way (ROW), Grass species, and Boundaries of drainage easement. _RB 2. Plan details (V = 50' or larger) for the grassed swale showing: - Swale dimensions (width, length, depth), - Maintenance access, - Proposed drainage easement and public right of way (ROM, Design at ultimate build -out, - Grass species, - Off -site drainage (if applicable),and - Boundaries of drainage easement. _RB 3. Section view of the grassed swale (1" = 20' or larger) showing: - Side slopes, - Longitudinal slope, - Freeboard - Swale dimensions, and - SHWT level(s) _RB 4. Supporting calculations (including maximum velocity calculations for applicable storms) _RB 5. A copy of the signed and notarized operation and maintenance (0&M) agreement. 6. A copy of the deed restrictions (if required). SW401-Grassed Swale-Rev.3 Part III, Page 3 of 3 Permit Number: 5LA j OMS- (to be provided by DWQ) OF W ATF9 H=HR STORMWATER MANAGEMENT PERMIT APPLICATION FORM 401 CERTIFICATION APPLICATION FORM GRASSED SWALE SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part 111) must also be filled out, printed and submitted along with all of the required information. Project name CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NC.115 Contact name RICK BAKER, PE Phone number 919-866-4939 Date January 14, 2021 Drainage area number Phase 3B Site Characteristics Drainage area 680,076.00 ftz Impervious area 367,596.00 ftz Percent impervious 54.1 % % Design rainfall depth 0.75 inch Peak Flow Calculations 10-yr storm runoff depth 10-yr storm intensity Post -development 10-yr storm peak flow Velocity Maximum non -erosive velocity (peak 10-year storm) Soil characteristics (enter "x" below) Sand/silt (easily erodible) Clay mix (erosion resistant) Grass Type (enter "x" below) Bermuda - Tall fescue Bahiagrass Kentucky bluegrass Grass -legume mixture Swale type: Fill out one of the options below: Option 1: Curb Outlet Swale: Maximum velocity NIA In 0.75 in/hr 8.80 ft3/sec 5.00 ftlsec x x N (Y or N) Side slopes :1 Swale length ft Option 2: Swale Seekino Pollutant Credit ("For -Credit" Swale): Y (Y or N) Maximum velocity for 10-yr storm 0.60 ft/sec OK Side slopes 5.00 :1 OK Swale length 150.00 ft OK Form SW401-Grassed Swale-Rev.4 Parts I and 11. Project Design Summary, Page 1 of 3 Permit Number. (to be provided by DWQ) Swale Characteristics Swale Shape: Enter an 'Y' in the appropriate cell below: Trapezoidal x Parabolic V-shaped Width of the bottom of the swale 27.00 ft Width of the top of the swale 34.50 ft Additional Information Is the Swale sized for all runoff from ultimate build -out? Y (Y or N) OK Is the BMP located in a proposed drainage easement with a recorded access easement to a public Right of Way (ROW)? Y (Y or N) OK What is the distance from the bottom of the Swale to the SHWT? -5.45 ft Insufficient distance to SHWT, unless conveyance Swale only. What is the ground level elevation? 20.67 fmsl What is the elevation of the bottom of the Swale? 14.55 fmsl What is the SHWT elevation? 20.00 fmsl What is the longitudinal slope of the swale? 0.20 % OK What is the depth of freeboard? 0.25 ft OK Form SW401-Grassed Swale-Rev.4 Parts I and II. Project Design Summary, Page 2 of 3 Permit No: (to be assigned by DWQ) ID Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Initials Pagel Plan Sheet No. RB 1 Plans 0 = 50' or larger) of the entire site showing: - Design at ultimate build -out, - Off -site drainage (if applicable), - Delineated drainage basins (include Rational C coefficient per basin), - Swale dimensions (width, length, depth), - Maintenance access, - Proposed drainage easement and public right of way (ROW), Grass species, and - Boundaries of drainage easement. RB 2. Plan details (1" = 50' or larger) for the grassed swale showing: Swale dimensions (width, length, depth), Maintenance access, Proposed drainage easement and public right of way (ROW), Design at ultimate build -out, Grass species, Off -site drainage (if applicable),and Boundaries of drainage easement. _RB 3. Section view of the grassed swale (1" = 20' or larger) showing: Side slopes, - Longitudinal slope, Freeboard - Swale dimensions, and - SHWT level(s) _RB 4. Supporting calculations (including maximum velocity calculations for applicable storms) _RB 5. A copy of the signed and notarized operation and maintenance (0&M) agreement. _RB _ 6. A copy of the deed restrictions (if required). SW401-Grassed Swale-Rev.3 Part lll, Page 3 of 3 11 Permit No. 5&J8 oaos"1 (to be provided by DWL) OF WATT OG -AWA STORMWATER MANAGEMENT PERMIT APPLICATION FORM WDENR 401 CERTIFICATION APPLICATION FORM DRY EXTENDED DETENTION BASIN SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part I//) must be printed, filled out and submitted along with all the required information. Project name CIRCLE K - NTI AIRPORT BLVD WILMMTON - NC.115 Contact person RICK BAKER, PE Phone number 919-866-4939 Date 3/8/2021 Drainage area number PHASE 3A Site Characteristics Drainage area 213,213.00 fe Impervious area 116,598.00 ft� % Impervious 0.55 Design rainfall depth 1.50 in Peak Flow Calculations 1-yr, 24-hr rainfall depth 3.83 in Rational C, pre -development 50.00 (unitless) Rational C, post -development 76.00 (unitless) Rainfall intensity: 1-yr, 24-hr storm 0.16 in/hr eak 1.38 fe/sec C'4•RO`/elr`�. Post -development l-yr, 24hhrppea flow 1.34 ft/sec •pO L'(H Pre/Post 1-yr, 24-hr peak control -0.04 fe/sec Storage Volume: Non -SA Waters SEAL r Minimum required volume 14,416.00 fe Provided volume 20,107.00 fe OK Sediment storage volume provided Storage Volume: SA Waters 5,691.00 ft3 OK •�'' •G;N.:•,i� y�. Q W. Bp Iq1�/NN 1.5" runoff volume ft3 D 3 `� 9f 2 / Pre -development 1-yr, 24-hr runoff volume ft, Post -development 1-yr, 24-hr runoff volume if Minimum required volume ft Provided volume ft3 Sediment storage volume provided fe Basin Design Parameters Drawdown time 3.90 days SHWT elevation 19.00 fmsl Basin bottom elevation 14.50 fmsl Storage elevation 17.70 fmsl Basin side slopes 3.0 :1 Top elevation 2075 fmsl Freeboard provided 1.50 It Basin Bottom Dimensions Basin length 220.00 It Basin width 27.00 ft Length to width ratio 8.00 :1 OK Raise basin bottom, Must be at least 2-ft above SHWT OK OK OK OK Form SW401-Dry Extended Detention Basin-Rev.3 Parts I. & II. Design Summary, Page 1 of 3 Additional Information Total runoff volume captured by basin Forebay provided Is basin in a recorded drainage easement? Does basin capture all runoff at ultimate build -out? Is a sediment depth indicator included? Does the basin include a drain? 12.55 ac-in Forebay is required N (Y or N) Y (Y or N) OK Y (Y or N) OK Y (Y or N) OK Y (Y or N) OK Permit (to be provided by DWQ) Form SW401-Dry Extended Detention Basin-Rev.3 Parts I. & II. Design Summary, Page 2 of 3 Permit ;4 94OLID RM C!*;"T (to be provided by DWQ) Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Pagel Plan Initials Sheet No. _RB_ 1. Plans (1" - 50' or larger) of the entire site showing: - Design at ultimate build -out, - Off -site drainage (if applicable), - Delineated drainage basins (include Rational C coefficient per basin), - Basin dimensions, - Pretreatment system, - Maintenance access, Proposed drainage easement and public right of way (ROW), - Overflow device, and - Boundaries of drainage easement. _RB_ 2. Plan details (1" = 30' or larger) for the bioretention cell showing: - Basin dimensions Pretreatment system, Maintenance access, Outlet structure, Overflow device, Flow distribution detail for basin inflow, and - Vegetation specifications. 3. Section view of the basin (1" 20' or larger) showing: - Side slopes, 3:1 or lower, - Pretreatment and treatment areas, and - Inlet and outlet structures. RB 6. A construction sequence that shows how the dry detention basin will be protected from sediment until the entire drainage area is stabilized. _RB 7. The supporting calculations. _RB 8. A copy of the signed and notarized operation and maintenance (O&M) agreement. _RB 9. A copy of the deed restrictions (if required). _RB 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County soil maps are not an acceptable source of soils information. Form SW401-Dry Extended Detention Basin-Rev.3 Part III. Required Items Checklist, Page 3 of 3 Permit No. 5wf45 bS�Si-1� (to be provided by DWQ) of WA'r RA STORMWATER MANAGEMENT PERMIT APPLICATION FORM WDEI+lR 401 CERTIFICATION APPLICATION FORM c DRY EXTENDED DETENTION E This form must be filled out, printed and submitted. The Required Items Checklist (Part //I) must be printed, filled out and submitted along with all the required information. Project name CIRCLE K - NTI AIRPORT BLVD WILMINGTON - NCA 15 Contact person RICK BAKER, PE Phone number 919-866-4939 Date 3/8/2021 Drainage area number PHASE 3B Site Characteristics Drainage area 756,099.00 ftz Impervious area 367,596.00 ft' % Impervious 0.49 Design rainfall depth 1.50 in Peak Flow Calculations 1-yr, 24-hr rainfall depth 3.83 in Rational C, pre -development 50.00 (unitless) Rational C, post -development 77.00 (unitless) Rainfall intensity: 1-yr, 24-hr storm 0.16 inthr Pre -development 1 yr, 24•hr pcak flow, 8.69 fOlsec Post -development l-yr,24-hrpeak flow 1.37 ft3/sec Pre/Post 1-yr, 24-hr peak control -7.32 1'0/sec ZN CAt� Storage Volume: Non -SA Waters -s�0¢0 60861 ski Minimum required volume 46,037.00 ft3 � 9 Provided volume 61,848.00 fe OK Sediment storage volume provided 15,811.00 ft' OK �I Storage Volume: SA Waters 1.5" runoff volume ft3 Pre -development 1-yr. 24-hr runoff.volume { Post -development 1-yr, 24-hr runoff volume fta Minimum required volume ft" Provided volume ft3 Sediment storage volume provided ft3 Basin Design Parameters Drawdown time 3.00 days SHWT elevation 20.00 fmsl Basin bottom elevation 13.25 fmsl Storage elevation 16.50 fmsl Basin side slopes 3.0 :1 Top elevation 20.00 fmsl Freeboard provided 1.50 ft Basin Bottom Dimensions Basin length 700.00 ft Basin width 51.00 ft Length to width ratio 13.00 :1 a3/d 8/ -% OK Raise basin bottom, Must be at least 2-ft above SHWT OK OK OK OK Form SW401-Dry Extended Detention Basin-Rev.3 Parts I. & II. Design Summary, Page 1 of 2 Permit No. Additional Information (to be provided by DWQ) Total runoff volume captured by basin 44.83 ac-in Forebay is required Forebay provided N (Y or N) Is basin in a recorded drainage easement? Y (Y or N) OK Does basin capture all runoff at ultimate build -out? Y (Y or N) OK Is a sediment depth indicator included? Y (Y or N) OK Does the basin include a drain? Y (Y or N) OK Form SW401-Dry Extended Detention Basin-Rev.3 Parts I. & II. Design Summary, Page 2 of 2 Permit *, REQU'0*D ITEMFS CHECKLIST (to be provided by DWQ) Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach justification. Pagel Plan Initials Sheet No. RB 1. Plans (1" - 50' or larger) of the entire site showing: - Design at ultimate build -out, - Off -site drainage (if applicable), Delineated drainage basins (include Rational C coefficient per basin), Basin dimensions, - Pretreatment system, Maintenance access, Proposed drainage easement and public right of way (ROW), Overflow device, and Boundaries of drainage easement. _RB_ _ 2. Plan details (1" = 30' or larger) for the bioretention cell showing: - Basin dimensions - Pretreatment system, Maintenance access, Outlet structure, Overflow device, Flow distribution detail for basin inflow, and Vegetation specifications. _rots_ 3. Section view of the basin 0" = 20' or larger) showing: - Side slopes, 3:1 or lower, - Pretreatment and treatment areas, and - Inlet and outlet structures. _RB 6. A construction sequence that shows how the dry detention basin will be protected from sediment until the entire drainage area is stabilized. _RB 7. The supporting calculations. _RB 8. A copy of the signed and notarized operation and maintenance (O&M) agreement. _RB 9. A copy of the deed restrictions (if required). _RB 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County soil maps are not an acceptable source of soils information. Form SW401-Dry Extended Detention Basin-Rev.3 Part III. Required Items Checklist, Page 3 of 3