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HomeMy WebLinkAboutSW7061025_CURRENT PERMIT_20070110STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. DOC TYPE CURRENT PERMIT ❑ APPROVED PLANS ❑ HISTORICAL FILE ❑ COMPLIANCE EVALUATION INSPECTION DOC DATE�71���� YYYYMMDD v �II�o Michael F. Easley, Governor William G. Ross Jr., Secretary North Carolina Department of Environment and Natural Resources January 10, 2007 Mr. James Geraghty, Managing Member Sea Grass, LLC 4326 Shady Lane Kitty Hawk, NC 27949 Subject: Permit No. SW7061025 Villas at Kilmarlic High Density Stormwater Project Currituck County Dear Mr. Geraghty: Alan W. Klimek, P.E. Director Division of Water Quality The Washington Regional Office received a completed Stormwater Application for the subject project on October 31, 2006. Staff review of the plans and specifications has determined that the project, as proposed, will comply with the Stormwater Regulations set forth in Title 15A NCAC 2H.1000. We are forwarding Permit No. SW7061025 dated January 10, 2007 to Sea Grass, LLC for the construction and operation of two wet infiltration basin systems to serve the Villas at Kilmarlic located on Caratoke Hwy in Currituck County. This permit shall be effective from the date of issuance until January 10. 2017 and shall be subject to the conditions and limitations as specified therein. Please pay special attention to the Operation and Maintenance requirements in this permit. Failure to establish an adequate system for operation and maintenance of the stormwater management system will result in future compliance problems. If any parts, requirements, or limitations contained in this permit are unacceptable, you have the right to request an adjudicatory hearing upon written request within thirty (30) days following receipt of this permit. This request must be in the form of a written petition, conforming to Chapter 150B of the North Carolina General Statutes, and filed with the Office of Administrative Hearings, 6714 Mail Service Center, Raleigh, NC 27699-6714. Unless such demands are made this permit shall be final and binding. If you have any questions, or need additional information concerning this matter, please contact Roger Thorpe or me at (252) 946-6481. mcerely, Al Hodge, Regional Supervisor Surface Water Protection Section Washington Regional Office cc: Bissell Professional Group Currituck County Inspections ,,Washington Regional Office Central Files North Carolina Division of Water Quality Internet: ,ca,c nc,cmer calm or, One 943 Washington Square Mall Phone (232) 946-6481 NorthCarolina Washington, NC 27889 Fax 12521946-9215 Naturally State Stormwater Management Systems Permit No. SW7061025 STATE OF NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF WATER QUALITY STATE 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 Sea Grass, LLC Villas at Kilmarlic Currituck COUNTY FOR THE construction, operation and maintenance of stormwater management systems in compliance with the provisions of 15A NCAC 21-1.1000 (hereafter referred to as the "stormwater rules') and the approved stormwater management plans and specifications and other supporting data as attached and on file with and approved by the Division of Water Quality and considered a part of this permit for two wet filtration basin systems to serve the Villas at Kilmarlic located on Caratoke Hwy in Currituck County. This permit shall be effective from the date of issuance until January 10, 2017 and shall be subject to the following specified conditions and limitations: DESIGN STANDARDS 1. This permit is effective only with respect to the nature and volume of stormwater described in the application and other supporting data. 2. This stormwater system has been approved for the management of stormwater runoff as described on page 2 of this permit, the Project Data Sheet. 3. A maximum of 4.74 acres of built upon area is allowed on this 11.56 site. 4. All stormwater collection and treatment systems must be located in either dedicated common areas or recorded easements. The final plats for the project will be recorded showing all such required easements, in accordance with approved plans. 5. Approved plans and specifications for this project are incorporated by reference and are enforceable parts of the permit. DIVISION OF WATER QUALITY PROJECT DATA Project Name: Villas at Kilmadic Permit Number: SW7061025 Location: Cunituck County Applicant: Sea Grass, LLC Mailing Address: 4326 Shady Lane Kitty Hawk, NC 27949 Application Date: 10/31/2006 Receiving Stream: UT to Albemarle Sound Classification of Water Body: SB Total Site Area: 11.56 ac Basin: # 1 # 2 Drainage Area to Basin: 311,219 sf 192,613 sf Total Impervious: 125,704 sf 80,455 sf Infiltration Basin Storage Depth: 3.5 feet 3.5 ft Required Storage Volume: 10,727 cf 6,841 cf Provided Storage Volume: 59,652 cf 34,953 cf Bypass Overflow Elevation: 9.4 ft 9.5 ft 6. No homeowner/lot owner/developer shall be allowed to fill in, alter, or pipe any vegetative practices (such as swales) shown on the approved plans as part of the stormwater management system without submitting a revision to the permit and receiving approval from the Division. The following items will require a modification to the permit: a. Any revision to the approved plans, regardless of size b. Project name change C. Transfer of ownership d. Redesign or addition to the approved amount of built -upon area e. Further subdivision of the project area. In addition, the Director may determine that other revisions to the project should require a modification to the permit. 8. 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. Il. SCHEDULE OF COMPLIANCE The permittee will comply with the following schedule for construction and maintenance of the stormwater management system. a. 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 surfaces except roads. b. During construction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired immediately. 2. The facilities must be properly maintained and operated at all times. The approved Operation and Maintenance Plan must be followed in its entirety and maintenance must occur at the scheduled intervals. 3. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted stormwater system functions at optimum efficiency including, but not limited to: a. Semiannual scheduled inspections (every 6 months) b. Sediment removal C. Mowing and revegetation of side slopes d. Immediate repair of eroded areas e. Maintenance of side slopes in accordance with approved plans and specifications f. Debris removal and unclogging of outlet structure, orifice device and catch basins and piping. 4. Records of maintenance activities must be kept and made available upon request to authorized personnel of DWQ. The records will indicate the date, activity, name of person performing the work and what actions were taken. 5. This permit shall become voidable unless the facilities are constructed in accordance with the conditions of this permit, the approved plans and specifications, and other supporting data. 6. Upon completion of construction and prior to operation of this permitted facility, a certification must be received from an appropriate designer for the system installed certifying that the permitted facility has been installed in accordance with this permit, the approved plans and specifications, and other supporting documentation. Mail the Certification to the Washington Regional Office, 943 Washington Square Mall, Washington, North Carolina, 27889, attention Division of Water Quality. A copy of the approved plans and specifications shall be maintained on file by the Permittee for a minimum of five years from the date of the completion of construction. . Ill. GENERAL CONDITIONS 1. This permit is not transferable. In the event there is a desire for the facilities to change ownership, or there is a name change of the Permittee, a formal permit request must be submitted to the Division of Water Quality accompanied by an application fee, documentation from the parties involved, and other supporting materials as may be appropriate. The approval of this request will be considered on its merits and may or may not be approved. 2. Failure to abide by the conditions and limitations contained in this permit may subject the Permittee to enforcement action by the Division of Water Quality, in accordance with North Carolina General Statute 143- 215.6(a) to 143-215.6(c). 3. The issuance of this permit does not preclude the Permittee from complying with any and all statutes, rules, regulations, or ordinances which may be imposed by other government agencies (local, state, and federal) which have jurisdiction. 4. In the event that the facilities fail to perform satisfactorily, including the creation of nuisance conditions, the Permittee shall take immediate corrective action, including those as may be required by this Division, such as the construction of additional or replacement stormwater management systems. 5. The permit may be modified, revoked and reissued or terminated for cause. The filing of a request for a permit modification, revocation and reissuance or termination does not stay any permit condition. 6. The Permittee, at least six (6) months prior to the expiration of this permit, shall submit in writing a request for an extension along with appropriate application fee. Permit issued this the 10 th day of January, 2007. NORT CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION L. L Alan W. Klimek, P.E. Director Division of Water Quality By Authority of the Environmental Management Commission Permit Number SW7061026 Sea Grass, LLC — Villas at Kilmarlic Stormwater Permit No. SW7061025 Designer's Certification 1, , as a duly registered Professional Engineer in the State of North Carolina, having been authorized to observe (periodically/weekly/full time) the construction of the 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. Signature Registration Number Date 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 roof drains are located such that the runoff 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. All slopes are grassed with permanent vegetation. _8. Vegetated slopes are no steeper than 3:1. _9. The permitted amounts of surface area and/or volume have been provided. _10. All required.design depths are provided. _11. All required parts of the system are provided including any vegetated filter. _12. The required system dimensions are provided per the approved plans. us State of North Carolina OCT 3 1 2006 Department of Environment and Natural Resources Division of Water Quality T'i.�ro p. rermlt Um�)el' X7061025 sWA-cK 1o131/0& ®WQ"VSTORMWATER MANAGEMENT PERMIT APPLICATION FORM This form may be photocopied for use as an original I. GENERAL INFORMATION 1. Applicants name (specify the name of the corporation, individual, etc. who owns the project): Sea Grass L.L.C. 2. Print Owner/Signing Official's name and title (person legally responsible for facility and compliance): James Geraghty, Managing Member 3. Mailing Address for person listed in item 2 above: 4326 Shady Lane City Kitty Hawk State NC Telephone Number: 252-202-1631 Zip: 27949 4. Project Name (subdivision, facility, or establishment name -should be consistent with project name on plans. specifications, letters, operation and maintenance agreements, etc.): Villas at Kilmarlic 5. Location of Project (street address): U.S. Hiqhway 158 (Caratoke Hwy.) City Powels Point Currituck 6. Directions to project (from nearest major intersection): Approximately 3.9 miles North of the Wright Memorial Bridge on the West side of US HWY 158 . Located on both the north and south sides of North Side Lane, the entrance to Kilmarlic Subdivision. 7. Latitude: 36007'15"N Longitude: 8. Contact person who can answer questions about the project: Name: David M. Ryan. P.E. II. PERMIT INFORMATION: I. Specify whether project is (check one): X New 75°50'00"W Telephone Number: (252) 261-3266 of project Renewal Modification Fonn SWU-101 Version 3.99 Page I of 4 2. If this application is being submitted as a result of a renewal or modification to an existing permit, list the existing permit number and its issue date (if known) 3. Specify the type of project (check one): Low Density x High Density Redevelop General Permit Other 4. Additional Project Requirements (check applicable blanks): CAMA Major X Sedimentation/Erosion Control 404/401 Permit NPDES Information on required state permit can be obtained by contacting the Customer Service Center at 1-877-623-6748 I1I. PROJECT INFORMATION 1. In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative (one to two pages) describing stormwater management for the project. Stormwater runoff from all impervious surfaces will be collected and directed by curb and gutter to various drop inlets located around the permiter of the parking and drive areas. Runoff will then be directed via a pipe network to wet -infiltration basins located within the respective drainage areas. 2. Stormwater runoff from this project drains to the Pasquaotank River Basin 3. Total Project Area: 11.56 5. How many drainage areas does the project have? acres 4. Project Built Upon Area: 40.90% 6. Complete the following information for each drainage area. If there are more than two drainage areas in the project, attach an additional sheet with the information for each area provided in the same format as below. ."., Basin Information ,DramagetArea,l ;, �j , , Dramage Area�2 ; , , aDrainage Area 3' Receiving Stream Name Albemarle Sound Albemarle Sound Receiving Stream Class SB SB Drainage Area 311,219 s.f. / 7.14 ac. 192,613 s.f. / 4.42 ac. Existing Impervious* Area 0 0 Proposed Impervious* Area 125,704 s.f. / 2.89 ac. 80,455 s.f. / 1.85 ac. Impervious* Area (total) 40% 42% Ymper'vious* Surtace`4rca ,`. Drainage"Area It 11 _ rDraiiiage Area2�;"_a; r,;Dratnage Area Future On -Site Buildings 64,367 s.f. 48,002 s.f. On -Site Streets 45,389 s.f. 23,217 s.f. On -Site Parking 8,684 s.f 5,696 s.f Other On -Site 7,264 s.f. 3,540 s.f. Off -Site 0 0 Impervious* Area (total) 40% i42% *Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas, sideivalke, gravel areas, etc. FormSWU-101 Version3.99 Page 2of4 7. How was the off -site impervious area listed above derived'? IV. DEED RESTRICTIONS AND PROTECTIVE COVENANTS The following italicized deed restrictions and protective covenants are required to be recorded for all subdivisions, outparcels and future development prior to the sale of any lot. If lot sizes vary significantly, a table listing each lot number, size and the allowable built -upon area for each lot must be provided as an attachment. 1. The following covenants are intended to ensure ongoing compliance with state stormwater management permit number as issued by the Division of Water Quality. These covenants may not be changed or delted without consent of the State. 2. No more than square feet of any lot shall be covered by structures or impervious materials. Impervious materials include asphalt, gravel, concrete, brick, stone, slate or similar material but do not include wood decking or the water surface ofswimming pools. 3. Swales shall not be filled in, piped, or altered except as necessray to provide driveway crossings. 4. Built -upon area in excess of the permitted amount requires a state stormwater management permit modification prior to construction. 5. All permitted runofffrom outparcels orfuture development shall be directed into the permitted stormwater control system. These connections to the stormwater control system shall be performed in a manner that maintains the integrity and performance of the system as permitted. By your signature below, you certify that the recorded deed restrictions and protective covenants for this project shall include all the applicable items required above, that the covenants will be binding on all parties and persons claiming under them, that they will run with the land, that the required covenants cannot be changed or deleted without concurrence from the State, and that they will be recorded prior to the sale of any lot. V. SUPPLEMENT FORMS The applicable state stormwater management permit supplement form(s) listed below must be submitted for each BMP specified for this project. Contact the Stormwater and General Permits Unit at (919) 733-5083 for the status and availability of these forms. Form SWU-102 Wet Detention Basin Supplement Form SWU-103 Infiltration Basin Supplement Form SWU-104 Low Density Supplement Form SWU-105 Curb Outlet System Supplement Form SWU-106 Off -Site System Supplement Form SWU-107 Underground Infiltration Trench Supplement Form SWU-108 Neuse River Basin Supplement Form SWU-109 Innovative Best Management Practice Supplement Form SWU-101 Version 3.99 Page 3 of VI. SUBMITTAL REQUIREMENTS Only complete application packages will be accepted and reviewed by the Division of Water Quality (DWQ). A complete package includes all of the items listed below. The complete application package should be submitted to the appropriate DWQ Regional Office. 1. Please indicate that you have provided the following required information by initaling in the space provided next to each item. Initials Original and one copy of the (252) 261-1760 7M2 • One copy of the applicable Supplement Form(s) for each BMP m • Permit application processing fee of $420 (payable to NCDENR) • Detailed narrative description of stormwater treatment/management Hl • Two copies of plans and specifications, including: M - Development/Project Name - Engineering and firm - Legend - North arrow - Scale - Revision number & date - Mean high water line - Dimensioned property/project boundary - Location map with named streets or NCSR numbers - Original contours, proposed contours, spot elevations, finished floor elevations - Details of roads, drainage features, collection systems, and stormwater control measures - Wetlands delineated, or a note on plans that none exist - Existing drainage (including off -site), drainage easements, pipe sizes, runoff calculations - Drainage areas delineated - Vegetated buffers (where required) VIL AGENT AUTHORIZATION If you wish to desginate authority to another individual or firth so that they may provide information on your behalf, please complete this section. Designated agent (individual or firm): B issell Professional Group Mailing Address: P.O. Box 1068 City Kitty Hawk State: NC Zip 27949 Phone: (252)261-3266 Fax: (252)261-1760 VIII APPLICANT'S CERTIFICATION 1, (print or type name ofperson listed in General Information, item 2) certify that the information included on this permit application form is, to the best of my knowledge, correct and that the project will be constructed in conformance with the approved plans, that the required deed restrictions and protective covenants will be recorded, and that the proposed project complies with the requuirements of 15A Date: 1 T7 • D ' " D L1 Form SWU-101 Version 3.99 Page 4 of 4 Permit No. (to be provided by DIPO State of North Carolina��� Department of Environment and Natural Resources Division of Water Quality OCT 3 1 2006 STORMWATER MANAGEMENT PERMIT APPLICATION FORM INFILTRATION BASIN SUPPLEMENT This form may be photocopied for use as an original DWQ-WARD DWO Stormwater Management Plan Review: A complete stormwater management plan submittal includes a Stormwater management permit application, an infiltration basin supplement for each system, design calculations, soils report and plans and specifications showing all Stormwater conveyances and system details. I. PROJECT INFORMATION Project Name: Sea Grass, L.L.C. Contact Person: James Geraghty, Managing Member Phone Number: 1252 202-1631 This worksheet applies to: Basin No. B in Drainage Area 2 (as identified on plans) (from Form SWU-101) II. DESIGN INFORMATION Attach supporting calculations/documentation. The soils report must be based upon an actual field investigation and soil borings. County soil maps are not an acceptable source of soils information. All elevations shall be in feet mean sea level (fmsl). Soils Report Summary Soil Type Bojac/Conetoe loamy sand Infiltration Rate 6.0 + in/hr or of/hr/sf (circle appropriate units) SHWT Elevation 6.5' fmsl fmsl (Seasonal High Water Table elevation) Basin Design Parameters Design Storm inch (1.5 inch eventfor SA ivaters, I inch eventfor others) Design Volume 6,902 c.f. Drawdown Time 16.0 hrs Basin Dimensions (irregular geometry see attached plan) Basin Size ft. x Basin Volume Provided 34,953 c.f. Basin Elevations Bottom Elevation Storage Elevation Top Elevation 6.5 fmsl 7.20 fmsl 10.0 finsl 'K 1] v9 Ick) Page I of 3 Form SWU-103 Rev3.99 (irregular geometry see attached plan) ft. = sq. ft. III. REQUIRED ITEMS CHECKLIST The following checklist outlines design requirements per the Stormwater Best Management Practices Manual (N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Qor Section: 15 A NCAC 2H .1008. Initial in the space provided to indicate that the following design requirements have been met and supporting documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit Application Form, the agent may initial below. Attach justification if a requirement has not been met. Initials a. System is located 50 feet from class SA waters and 30 feet from other surface waters. 2 b. System is located at least 100 feet from water supply wells. inrvu�-ry c. Bottom of system is at least 2 feet above the seasonal high water table. �^ d. Bottom of the system is 3 feet above any bedrock or impervious soil horizon. e. System is not sited on or in fill material or DWQ approval has been obtained. �AIZ f. System is located in a recorded drainage easement for the purposes of operation and maintenance and has recorded access easements to the nearest public right-of-way. bw g. Drainage area for the device is less than 5 acres: }' �/ufL h. Soils have a minimum hydraulic conductivity of 0.52 inches per hour and soils report is attached. i. System captures and infiltrates the runoff from the first 1.0 inch of rainfall (1.5 inch event for areas draining to SA waters ). Design volume and infiltration calculations attached. DMrL j. System is sized to take into account the runoff at the ultimate built -out potential from all surfaces draining to the system, including any off -site drainage. Calculations attached. �M rL k. All side slopes stabilized with vegetated cover are no steeper than 3:1 (H: V). A pretreatment device such as a catch basin, grease trap, filter strip, grassed Swale or t�17YZA-fiori sediment trap is provided. t:;, N in. Bottom of the device is covered with a layer of clean sand to an average depth of 4 inches �To or dense vegetative cover is provided. N n. Vegetated filter is provided for overflow and detail is shown on plans (Required minimum length is 50 feet for SA waters, 30 feet for other waters). ^N/n` o. Flow distribution mechanism within the basin is provided. ^M2 p. A benchmark is provided to determine the sediment accumulation in the pretreatment (5 device. q. Runoff in excess of the design volume bypasses off-line systems (bypass detail provided). DM IZ r. System is designed to draw down the design storage volume to the proposed bottom elevation under seasonal high water conditions within five days. A soils report and all pertinent draw -down calculations are attached. L>AAiZ s. Plans ensure that the installed system will meet design specifications (constructed or restored) upon initial operation once the project is complete and the entire drainage area is stabilized. Form SWU-103 Rev 3.99 Page 2 of 3 IV. INFILTRATION BASIN OPERATION AND MAINTENANCE AGREEMENT 1. After every runoff producing rainfall event and at least monthly inspect the infiltration system for erosion, trash accumulation, vegetative cover, and general condition. 2. Repair eroded areas immediately, re -seed as necessary to maintain adequate vegetative cover, mow vegetated cover to maintain a maximum height of six inches, and remove trash as needed. 3. After every runoff producing rainfall event and at least monthly inspect the bypass, inflow and overflow structures for blockage and deterioration. Remove any blockage and repair the structure to approved design specifications. 4. Remove accumulated sediment from the pretreatment system and infiltration basin annually or when depth in the pretreatment unit is reduced to 75% of the original design depth. The system shall be restored to the original design depth without over -excavating. Over -excavating may cause the required water table separation to be reduced and may compromise the ability of the system to perform as designed. Removed sediment shall be disposed of in an appropriate manner and shall not be handled in a manner that will adversely impact water quality (i.e. stockpiling near a stormwater treatment device or stream, etc.). A benchmark shall be established in the pretreatment unit. The benchmark will document the original design depth so that accurate sediment accumulation readings can be taken. The measuring device used to determine the depth at the benchmark shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the design depth reads • 575 feet in the pretreatment unit, the sediment shall be removed from both the pretreatment unit and the infiltration basin. 5. If the Division determines that the system is failing, the system will immediately be repaired to original design specifications. If the system cannot be repaired to perform its design function, other stormwater control devices as allowed by NCAC 2H A000 must be designed, approved and constructed. I acknowledge and agree by my signature below that I am responsible for the performance of the five 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. Print Name and Title: ( ohe Zl� 3-yC Note: The %egtffly responsible party should node a homeowners association unless more than 50% of the lots have been sold and a resident of the subdivision has been named the president. a Notary Public for the State of Z�Q}I—�-�L ��t-1 � ({&.unty L__ t(�� , do hereby certify that [i �Zth JCL-r aC'n :'_ l.epersonally appeared before me this�� day ofQ0UC) twt , ) I , and acknowledge the due execution of the forgoing infiltration basin maintenance requirements. Witness my hand and official seal, OFFICIAL SEAL ° l?',y �} Notary Public, North Carolina `T'!l y�1 County of Dare 3`1 ' a Nancy W. Warren . '\;�r MvCommissionExoires4/10I2010 My commission expires Form SWU-103 Rev 3.99 Page 3 of 3 Permit No. (to be provided by DIVQ) State of North Carolina Department of Environment and Natural Resources Division of Water Quality STORMWATER MANAGEMENT PERMIT APPLICATION FORM INFILTRATION BASIN SUPPLEMENT This form may be photocopied for use as an original OCT 3 12006 ®WQ-WARO DWO Stormwater Management Plan Review: A complete stormwater management plan submittal includes a stormwater management permit application, an infiltration basin supplement for each system, design calculations, soils report and plans and specifications showing all stormwater conveyances and system details. I. PROJECT INFORMATION Project Name : Sea Grass, L.L.C. Contact Person: James Geraghty, Managing Member Phone Number: 1252 202-1631 This worksheet applies to: Basin No. A in Drainage Area 1 (as identified on plans) (from Form SWU-101) II. DESIGN INFORMATION Attach supporting calculations/documentation. The soils report must be based upon an actual field investigation and soil borings. County soil maps are not an acceptable source of soils information. All elevations shall be in feet mean sea level (fmsl). Soils Report Summary Soil Type Bojac/Conetoe loamy sand Infiltration Rate 6.0 + in/hr or ef/hr/sf (circle appropriate units) SHWT Elevation 6.5' fmsl fmsl (Seasonal High Water Table elevation) Basin Design Parameters Design Storm 1.0 inch (L5 inch eventforSA waters, I inch eventforothers) Design Volume 10,633 c.f. Drawdown Time 20.5 hrs Basin Dimensions (irregular geometry see attached plan) Basin Size ft. x Basin Volume Provided 59,652 c.f. Basin Elevations Bottom Elevation 6.5 fmsl Storage Elevation 7.12 fmsl Top Elevation 10.0 fmsl W ��Ar-EQ UF-&,j SH-W 1. Page 1 of 3 (irregular geometry see attached plan) ft. = sq. ft. Form SWU-103 Rev.3.99 III. REQUIRED ITEMS CHECKLIST The following checklist outlines design requirements per the Stormwater Best Management Practices Manual (N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Cot' Section: 15 A NCAC 2H .1008. Initial in the space provided to indicate that the following design requirements have been met and supporting documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit Application Form, the agent may initial below. Attach justification if a requirement has not been met. Applicants Initials pM�Z a. UMtc b. D� C. �^^2 d. e. A127- f. bw L)MfZ bm(Z- DM2 �)ntlZ �VJIZA. JOIJ 5,c cw; ~MiZ N/A 6�2 L>AAfZ System is located 50 feet from class SA waters and 30 feet from other surface waters. System is located at least 100 feet from water supply wells. Bottom of system is at least 2 feet above the seasonal high-water table. Bottom of the system is 3 feet above any bedrock or impervious soil horizon. System is not sited on or in fill material or DWQ approval has been obtained. System is located in a recorded drainage easement for the purposes of operation and maintenance and has recorded access easements to the nearest public right-of-way. g. Drainage area for the device is less than 5 acres+ h. Soils have a minimum hydraulic conductivity of 0.52 inches per hour and soils report is attached. - i. System captures and infiltrates the runoff from the fast 1.0 inch of rainfall (1.5 inch event for areas draining to SA water ). Design volume and infiltration calculations attached. j. System is sized to take into account the runoff at the ultimate built -out potential from all surfaces draining to the system, including any off -site drainage. Calculations attached. k. All side slopes stabilized with vegetated cover are no steeper than 3:1 (H:V). I. A pretreatment device such as a catch basin, grease trap, filter strip, grassed swale or sediment trap is provided. in. Bottom of the device is covered with a layer of clean sand to an average depth of 4 inches or dense vegetative cover is provided. n. Vegetated filter is provided for overflow and detail is shown on plans (Required minimum length is 50 feet for SA waters, 30 feet for other waters). o. Flow distribution mechanism within the basin is provided. p. A benchmark is provided to determine the sediment accumulation in the pretreatment device. q. Runoff in excess of the design volume bypasses off-line systems (bypass detail provided). r. System is designed to draw down the design storage volume to the proposed bottom elevation under seasonal high water conditions within five days. A soils report and all pertinent draw -down calculations are attached. s. Plans ensure that the installed system will meet design specifications (constructed or restored) upon initial operation once the project is complete and the entire drainage area is stabilized. Form SWU-103 Rev 3.99 Page 2 of 3 IV. INFILTRATION BASIN OPERATION AND MAINTENANCE AGREEMENT 1. After every runoff producing rainfall event and at least monthly inspect the infiltration system for erosion, trash accumulation, vegetative cover, and general condition. 2. Repair eroded areas immediately, re -seed as necessary to maintain adequate vegetative cover, mow vegetated cover to maintain A maximum height of six inches, and remove trash as needed. 3. After every runoff producing rainfall event and at least monthly inspect the bypass, inflow and overflow structures for blockage and deterioration. Remove any blockage and repair the structure to approved design specifications. 4. Remove accumulated sediment from the pretreatment system and infiltration basin annually or when depth in the pretreatment unit is reduced to 75% of the original design depth. The system shall be restored to the original design depth without over -excavating. Over -excavating may cause the required water table separation to be reduced and may compromise the ability of the system to perform as designed. Removed sediment shall be disposed of in an appropriate manner and shall not be handled in a manner that will adversely impact water quality (i.e. stockpiling near a stormwater treatment device or stream, etc.). A benchmark shall be established in the pretreatment unit. The benchmark will document the original design depth so that accurate sediment accumulation readings can be taken. The measuring device used to determine the depth at the benchmark shall be such that it will give an accurate depth reading and not readily penetrate into accumulated sediments. When the design depth reads V3115 feet in the pretreatment unit, the sediment shall be removed from both the pretreatment unit and the infiltration basin. 5. If the Division determines that the system is failing, the system will immediately be repaired to original design specifications. If the system cannot be repaired to perform its design function, other stormwater control devices as allowed by NCAC 2H A000 must be designed, approved and constructed. I acknowledge and agree by my signature below that I am responsible for the performance of the five 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. Print Name and Title: J r>- Date: Note: A41 ally 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. (�\, 1, IV R. r7 C• l v , % . t- r- a�- ' , a Notary Public (ffo�r the State of 1401? l �c. t d �yyc—ounty of"1',.'�'✓�_r>� y� do hereby, certify that JcLre,w G <� r" c 12i'� personally appeared before me this_ ok day of 1Vtl f0 bE24— � %<)G� , and acknowledge the due execution of the forgoing infiltration basin maintenance requirements. Witness my hand and official seal, S 'OFFICIAL SEAL' sRi1 $�4 Notary Public, North Carolina J31 County of Dare y $f Nancy W. Warren M Commission Expires 4/10/2010 Form SWU-103 Rev 3.99 My commission expires "'t 1 3 C7 Il. Page 3 of 3 II. Stormwater Manacpement Narrative: OCT 3 7 2006 The following developmental activities require a stormwater management permit under Rule .1003 of the NCDENR Division of Water Quality Administrative Code for Stormwater. Management, 15A NCAC 2H.1000. Developmental activities will result in the project being permitted pursuant with Rule .1005 (2) (b), High Density Projects, with proposed built -upon area of 30% or greater, with best management practices being employed via; vegetative buffers, and wet -infiltration basins. The intent of this application, to the maximum extent possible, is to employ the best management practices for all proposed developmental activities. The proposed development will consist of utility, parking, and drainage infrastructure improvements to service the (13) proposed Villas at MImarlic Mult-family, residential townhouses to be located along North Side Lane on the west side of US HWY 158, (36.12°N, 75.83OW), in the Poplar Branch Township of, Currituck County, North Carolina. The proposed developmental activities are as follows; a) Total project area: 12.20 ac. b) Construction of (13) multi -family townhouse buildings. c) Construction of associative sidewalks, asphalt ingress/egress drives and parking. d) Construction of stormwater management and utility infrastructures. An on -site visit was conducted by David Meyer, L.S.S. with Protocol Sampling Service, Inc. of Raleigh, to investigate the existing groundwater profiles through multiple soil borings to determine the soils suitability for the proposed Stormwater and Wastewater management infrastructures. Seven borings were advanced across the site and the majority of the soils encountered were found to belong to the Bojac and Conetoe loamy sand series, which match those mapped in the USDA soil survey maps for Currituck County. These soils are described as being well drained and are typically found in sandy alluvial sediments along small streams and rivers in the Coastal Plain. Subsurface permeabilities range from 0.6 to 6.0 inches per hour but can exceed 20 inches per hour in the underlying sand layers. Seasonal high water tables in these soils typically range from 4.0 to 6.0 feet below the undisturbed landscape but were found in this case to range between 30" and 55" below existing grade. Since soil borings were not advanced in the exact locations of the proposed stormwater management basins an average seasonal high water table relative to existing grade will be taken. For the purpose of this design the seasonal high water table is given as 30" bls, which is the shallowest measured across the site. The northern of the (2) proposed stormwater management basins will be excavated in an area that currently has an average existing grade of 9.0'msl and therefore the SHWT is given as 6.5'msl. The construction of the southern stormwater management basin will simply involve the expansion of an existing pond that currently has a water table measurement of approximately 6.0'msl. For the purpose of this design SHWT for this basin will also be given as 6.5'msl. (Reference the attached Soils report for more detailed it formation, ATTACHMENT B) Information referenced froni United States Department of Agriculture, Soil Conservation Service, Soil Survey of Currituck County, North Carolina The proposed developmental site, with the existing North Side Lane dividing it into two separate areas, is bounded to the south by West Side Lane and to the east by US HWY 158. Existing topography mainly slopes away from an elevation of about 13.0' msl +/-, found along the bounding roadways and a smooth ridge along the sites northern boundary, towards two existing ponds that are located near each of the (2) sub areas respective western boundary. These ponds are reclamations of two borrow pits and typical water surface elevations measured at 6.0 msl +/-. There is an existing 125' wide power easement that straddles the entire western boundary of the site that is currently clear with grass vegetation. The balance of the southern site area is currently wooded with tall pines and light under brush and no existing developments. The nor -them site area has a few woodland pockets located near its center and a tree line running along the ridge on the northern boundary. There were several existing small dwellings locate out along HWY 158 that have since been removed for the purpose of the development. All development activities are to be designed in conform ty with the requirements for application and issuance of permits for stormwater management systems in pursuant with rules .1003 and .1005 in accordance with G.S. 143-215.1 and 15A NCAC 214.0200 as set forth. These requirements are designed to control pollutants associated with stormwater runoff applicable to the development of land for residential, commercial, industrial, or institutional uses. The developmental activities as described above have been designed in compliance with the requirements set forth for stormwater management within coastal counties Rule .1005, section 3, subparagraph B: (i) Control systems must be infiltration systems, wet detention ponds, or alternative stormwater management control systems designed in accordance with Rule .1008; . (ii) Control systems must be designed to control runoff from all surface generated by one inch of rainfall. Design of the active stormwater management measures are based on the design criteria indicated in .1008(d) Infiltration System Requirements, under the NCDENR Division of Water Quality Administrative Code for Stormwater Management,15A NCAC 2H.1000. The proposed Villas at Kilmarlic Mult-family residential development is to be located along North Side Lane on the west side of US HWY 158 , (36.120N, 75.830W), in the township of Poplar Branch in, Currituck County, North Carolina. The proposed developmental activities will consist of those previously itemized in the Proposed Development Activities Section above. Rainfall runoff from all proposed impervious surfaces will primarily sheet flow overland, be collected and directed by curb and gutter to several drop inlets and ultimately discharging to one of two wet -infiltration basins. Rip - Rap outlet protection will be placed at all basin inlets for velocity dissipation, provide sediment collection and to aid in infiltration. Do to the existing nature of the site it has been considered as two independent drainage basins that will accommodate the rainfall runoff from all the developmental activities as described above. Vegetative buffers will be provided, to the maximum extent possible, for pollutant filtration. The vegetative buffer is described as a passive best management practice that provides a small degree of filtration and pollutant removal from stormwater runoff. The basin side slopes will be planted with vegetation as described in the Soil Sedimentation & Erosion Control Plan for the purpose of filtrating small particulate matter and pollutants. Each infiltration basin will be vegetated with Tifway 2 Bennudagrass, aiding in the filtration of pollutant removal in conjunction with providing soil stabilization from the basin construction. This measure is described as an active best management practice in the treatment of stormwater runoff. The intent of this design is to provide storage amounts in excess of 5 times the typical design storm storage requirement. To achieve this, in this particular application, it was necessary to calculate the proposed impervious surface coverage areas in each respective drainage basin. Measures were designed to the maximum extent possible to ensure minimal to no pollutant -ridden runoff off -site. This is done by providing wet -infiltration basins capable of completely storing the post development runoff associated with a 10 year 24 hour, 6.2", rainfall event. In light of the excessive storage and no provisions of formal outlets associated with this design, the typical infiltration and pollutant removal requirements, such as a 2' separation to the seasonal high water table, level spreaders, vegetative overflows, etc., have all been disregarded. Since the basins will be constructed with bottom elevations lower than the seasonal high water table, only the sidewall areas of the basin have been considered when determining the infiltration drawdown time. The tabulated impervious surface areas were utilized to compute the required storage volumes relative to the 1.0 in. design rainfall storm event. Drawdown computations are then done to illustrate that the design storage volumes will infiltrate away in less than the maximum 5-day requirement. Each of the two wet -infiltration basins have ultimate design storage capacity's capable of storing in excess of 5.0 times the 1.0" design rainfall event prior to infiltrating into the surrounding sandy soil. (Reference the attached Stormwater Management Calculationfor details, ATTACHMENT A) Drainage Basin#1 As mentioned previously this development has been divided into two separate drainage areas. The area north of North Side Lane has been considered as drainage basin #1 with a total post development drainage area of approximately 7.14 acres. The proposed parking, roadway, and drainage improvements will be graded to ensure positive drainage away from the buildings to various drop inlets located around the site that will direct the runoff to a wet -infiltration basin located at the center of the respective development. Runoff velocities from the design storm event will be dissipated via rip -rap outlets specifically designed for flow reduction, sediment collection, and flow dispersion into the wet -infiltration basin. The infiltration basin has been designed with an ultimate open storage capacity capable of handling runoff amounts in excess of 5 inches, without accounting for infiltration or interstitial storage. In the event of runoff amounts larger than design, an emergency overflow outlet has been designed to discharge the excess volume to the R/W swale running along the north side North Side Lane. This swale eventually drains to adjoining western wetlands and ultimately the Albemarle Sound, but not before adequately filtering pollutants via existing vegetation. (Reference the attached Drainage Basin L*vut for delineation of the drainage areas, ATTACHMENT C) Drainage Basin#2 The area south of North Side Lane has been considered as drainage basin #2 with a total post development drainage area of approximately 4.42 acres. The proposed parking, roadway, and drainage improvements will be graded to ensure positive drainage away from the buildings to various drop inlets located around the site that will direct the runoff to a wet -infiltration basin located near the western boundary of the respective development. Runoff velocities from the design storm event will be dissipated via rip -rap outlets specifically designed for flow reduction, sediment collection, and flow dispersion into the wet -infiltration basin. The infiltration basin has been designed with an ultimate open storage capacity capable of handling runoff amounts in excess of 5 inches, without accounting for infiltration or interstitial storage. In the event of runoff amounts larger than design, an emergency overflow weir has been designed to discharge that excess volume to the R/W swale running along the south side of North Side Lane. Again, this Swale eventually drains to adjoining western wetlands and ultimately the Albemarle Sound, but not before adequately filtering pollutants via existing vegetation. (Reference the atlached Drainage Basin Layout for delineation ofthe drainage areas, A7TACHMENT C) 3 Stormwater runoff from all impervious surfaces will receive a form of pollutant and sediment removal as described in best management practices. The following information is in conformance with the regulations as specified for high -density development: 1) Proposed impervious coverage of 41 % over the total development area 2) Provision of a combination of vegetative buffers and wet -infiltration basins along all proposed developmental activities to collect and transport stormwater runoff from all impervious surfaces. 3) Provision of rip -rap outlet protection for velocity dissipation, sediment collection, and to aid in infiltration. The following measures will be provided to control the stormwater runoff from the proposed high - density development: 1) Provision of excessive storage within multiple wet -infiltration basins for temporary stormwater runoff storage. 2) Provision of 5.0 times the storage volume required ensuring minimal to no polluted discharge or runoff off site. 3) Additional runoff above the basins capacity will overflow into the adjoining R/W swale along North Side Lane. An easement has been set for the stormwater management basins for the purpose of operation and maintenance. A drainage easement has been provided around the perimeter of the stormwater basins. Access is provided through the parking & drive areas. 1) Accumulated sediment within the basin shall be removed semi-annually or when depth is reduced to 75% of the original design depth. (See individual infiltration basin supplementsforproperlevels) 4