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HomeMy WebLinkAboutSW8980701_HISTORICAL FILE_20000728 STORMWATER DIVISION CODING SHEET POST-CONSTRUCTION PERMITS PERMIT NO. SW8 °A$ -7Ol DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS ® HISTORICAL FILE ❑ COMPLIANCE EVALUATION INSPECTION DOC DATE 2000 012 S YYYYMMDD State,of North Carolina Department of Environment and Natural Resources • �/ Wilmington Regional Office 1 A9111h,9111MI'mm IL James B. Hunt, Jr., Governor NCDENR Bill Holman, Secretary Division of Water Quality NORTH CAROUNA DEPARTMENT OF ENVIRONMENT AND N, URAL RESOURCES July 28, 2000 Mr. Tim Matt, President Matt Holdings, LLC 1924 Lunar Lane Wilmington,NC 28405 Subject: Permit No. SW8 980701 Modification Triple T Parts and Equipment High Density Stormwater Project Dear Mr. Matt: New Hanover County The Wilmington Regional Office received a complete Modification to the Stormwater Management Permit for Triple T Parts and Equipment on June 26, 2000. 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. SW8 980701 Modification dated July 28, 2000, for the construction of Triple T Parts and Equipment. This permit shall be effective from the date of issuance until August 12,2009,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,P.O. Drawer 27447, Raleigh,NC 276 1 1-7447. 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 Linda Lewis, or me at (910) 395-3900. Sincerely, Rick Shiver Water Quality Regional Supervisor RSS/arl: S:\WQS\STORMWAT\PERMIT\980701.AUG cc: Phil Tripp, P.E. Tony Roberts, New Hanover County Inspections Beth Easley,New Hanover County Engineering Linda Lewis Wilmington Regional Office Central Files 127 Cardinal Dr.Ext.,Wilmington,North Carolina 28405 Telephone 910-395-3900 FAX 910-350-2004 An Equal Opportunity Affirmative Action Employer 50%recycled/10°/ post-consumer paper State Stormwater Management Systems Permit No. SW8 980701 Modification 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 ofNorth Carolina as amended,and other applicable Laws, Rules, and Regulations PERMISSION IS HEREBY GRANTED TO Matt Holdings, LLC Triple T Parts and Equipment New Hanover County FOR THE construction,operation and maintenance of a wet detention pond in compliance with the provisions of 15A NCAC 2H A000 (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. This permit shall be effective from the date of issuance until August 12, 2009 and shall be subject to the following specified conditions and limitations: L 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 3 of this permit,the Project Data Sheet.The stormwater control has been designed to handle the runoff from 248,915 square feet of impervious area.. 3. Approved plans and specifications for this project are incorporated by reference and are enforceable parts of the permit. 4. The tract will be limited to the amount of built-upon area indicated on page 3 of this permit, and per approved plans. 2 State Stormwater Management Systems Permit No. SW8 980701 Modification DIVISION OF WATER QUALITY PROJECT DESIGN DATA SHEET Project Name: Triple T Parts and Equipment Permit Number: SW8 980701 Location: New Hanover County Applicant: Mr. Tim Matt, President Mailing Address: Matt Holdings, LLC 1924 Lunar Lane Wilmington,NC 28405 Application Date: June 26, 2000 Name of Receiving Stream/Index#i NE Cape Fear River/(CFR 18-74-61) Classification of Water Body: "SC Sw" If Class SA, chloride sampling results: n/a Pond Depth, feet: 7 Permanent Pool Elevation, FMSL: 10 Total Impervious Surfaces, ftZ: 248,915 Offsite Area entering Pond, ftZ: None, per Engineer Required Surface Area, ftZ: 10,672 Provided Surface Area, ftZ: 11,700 Required Storage Volume, ft': 20,264 Provided Storage Volume, ft': 27,331 Temporary Storage Elevation, FMSL: 12 Controlling Orifice: 2.25" Diameter pipe 3 State Stormwater Management Systems Permit No. SW8 980701 Modification II. SCHEDULE OF COMPLIANCE 1. The stormwater management system shall be constructed in it's entirety, vegetated and operational for its intended use prior to the construction of any built-upon surface except roads. 2. During construction,erosion shall be kept to a minimum and any eroded areas of the system will be repaired immediately. 3. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted stormwater system functions at optimum efficiency. 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 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. g. Access to the outlet structure must be available at all times. 4. Records of maintenance activities must be kept and made available upon request to authorized personnel ofDWQ. The records will indicate the date,activity,name of person performing the work and what actions were taken. 5. Decorative spray fountains will not be allowed in the stormwater treatment system. 6. The facilities shall be constructed as shown on the approved plans.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. 7. Upon completion of construction,prior to issuance of a Certificate of Occupancy,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. Any deviations from the approved plans and specifications must be noted on the Certification. 8. 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. 9. 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. f. Filling in, altering, or piping of any vegetative conveyance shown on the approved plan. 10. The Director may determine that other revisions to the project should require a modification to the permit. 11. A copy of the approved plans and specifications shall be maintained on file by the Permittee for a minimum of ten years from the date of the completion of construction. 4 State Stormwater Management Systems Permit No. SW8 980701 Modification 12. Prior to the sale of any portion of the property,an access/maintenance easement to the stormwater facilities shall be granted in favor of the permittee if access to the stormwater facilities will be restricted by such sale. 13. The permittee is responsible for verifying that the proposed built-upon area does not exceed the allowable built-upon area. 14. The runoff from all built-upon area on the project must be directed into the permitted stormwater control system. 15. The Director may notify the permittee when the permitted site does not meet one or more of the minimum requirements ofthe 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. I11. 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 143-215.6A to 143-215.6C. 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 permittee grants DENR Staff permission to enter the property for the purpose of inspecting all components of the permitted stormwater management facility. 6. 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. Permit modification issued this the 28th day of July, 2000. NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION tl--.C.Iw — _o!�" A / A QJl Kerr. T. Stevens, Director l Division of Water Quality By Authority of the Environmental Management Commission Permit Number SW8 980701 Modification 5 State Stormwater Management Systems Permit No. SW8 980701 Modification Triple T Parts and Equipment Stormwater Permit No. SW8 980701 New Hanover County 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 ofmy 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: SEAL Signature Registration Number Date 6 State Stormwater Management Systems Permit No. SW8 980701 Modification 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. The outlet/bypass structure elevations are per the approved plan. 5. The outlet structure is located per the approved plans. 6. Trash rack is provided on the outletibypass structure. 7. All slopes are grassed with permanent vegetation. 8. Vegetated slopes are no steeper than 3:1. 9. The inlets are located per the approved plans and do not cause short-circuiting of the system. 10. The permitted amounts of surface area and/or volume have been provided. 11. Required drawdown devices are correctly sized per the approved plans. 12. All required design depths are provided. 13. All required parts of the system are provided, such as a vegetated shelf, and a forebay. 14. The overall dimensions of the system, as shown on the approved plans, are provided. cc: NCDENR-DWQ Regional Office Tony Roberts,New Hanover County Building Inspector 7 TE 00063 OFFICEaUSE ONLY Date Received Fee Paid Permit Number 3 SwB '�5b70t M State of North Carolina Department of Environment and Natural Resources Division of Water Quality STORMWATER MANAGEMENT PERMIT APPLICATION FORM This form may be photocopied for use as an original I. GENERAL INFORMATION I. Applicants name (specify the name of the corporation, individual, etc. who owns the project): Matt Holdings, LLC 2. Print Owner/Signing Official's name and title(person legally responsible for facility and compliance): Tim Matt, President&Owner 3. Mailing Address for person listed in item 2 above: 1924 Lunar Lane City: Wilmington State: NC Zip: 28405 Telephone Number: 910-256-2194 4. Project Name (subdivision, facility, or establishment name—should be consistent with project name on plans, specifications, letters, operation and maintenance agreements, etc.): Triple T Parts and Equipment 5. Location of Project(street address): 2715 US Hwy 421 North City: Wilmington County: New Hanover 6. Directions to project(from nearest major intersection): approx. 1000 If north from the intersection of US Hwy 421 and SR 1347 7. Latitude : N 340 16' 30" Longitude: W 770 57' 30" of project 8. Contact person who can answer questions about the project: Name: Phillip Tripp Telephone Number: 910-763-5100 II. PERMIT INFORMATION: 1. Specify whether project is(check one): New Renewal X Modification Form SWU-101 Version 3.99 Page I of 4 2. If this application is being submitted as the result of a renewal or modification to an existing permit, list The existing permit number SW8 980701 and its issue date (if known) 8/12/99 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 Stormwater Information on required state permits can be obtained by contacting the Customer Service Center at 1-877-623-6748. IIl. 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 detention pond 2. Stormwater runoff from this project drains to the Cape Fear River basin. 3. Total Project Area: 7.42 acres 4. Project Built Upon Area: 77.0 %. 5. How many drainage basins does the project have? 1 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 Drainage Basin I Drainage Basin 2 ; Receiving Stream Name N.E. Cape Fear River Receiving Stream Class C-S W Drainage Basin Area 323,215 sf Existing Impervious * Area 227,165 sf Proposed Impervious * Area 248,915 sf % Impervious* Area(total) 77% Impervious* Surface Area Drainage Basin P Drainage Basin2. On-site Buildings 34,636 sf On-site Streets 0 On-site Parking 7204 sf On-site Sidewalks 207,075 sf Other on-site 0 Off-site 0 Total: E=248,915 sf E= *Impervious area is defined as the built upon area including, but not limited to, buildings, roads,parking areas sidewalks, gravel areas, etc. Form SWU-101 Version 3.99 Page 2 of 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 deleted without the consent of the State. 2. No more than square feet ofany lot shall be covered by structures of impervious materials. Impervious materials include asphalt,gravel,concrete, brick stone,slate or similar material but do not include wood decking or the water surface of swimmingpools. 3. Swales shall not be filled in,piped or altered except as necessary 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 runoff from outparcels or future 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(910) 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 initialing in the space provided next to each item. Applic is Initials • Original and one copy of the Stormwater Management Permit Application Form • One copy of the applicable Supplement Form(s)for each BMP • Permit application processing fee of$420 (payable to NCDENR) • Detailed narrative description of stormwater treatment/management • Two copies of plans and specifications, including: - Development/Project name - Engineer and firm - Legend - North arrow - Scale - Revision number and 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) VII. AGENT AUTHORIZATION If you wish to designate authority to another individual or firm so that they may provide information on your behalf, please complete this section. Designated agent(individual or firm): Trion Engineering, P.C. Mailing Address: 419 Chestnut Street City: Wilmington State: NC Zip: 28401 Phone: (910) 763-5100 Fax: (910) 763-5631 VIII. APPLICANT'S CERTIFICATION I, (print or type name ofperson listed in General Information, item 2) Tim Matt 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 co rmance with the approved plans, that the required deed restrictions and protective covenants will be rec ( , and t t the proposed project complies with the requirements of 15A NCAC 211 .10 Signature: Date: C)lo 23 Form SWU-101 Version 3.99 Page 4 of + TE00063 /� Permit No. q7 '� (to be provided by DWQ) State of North Carolina Department of Environment and Natural Resources Division of Water Quality STORMWATER MANAGEMENT PERMIT APPLICATION FORM WET DETENTION BASIN SUPPLEMENT This form may be photocopied for use as an original DWO Stormwater Management Plan Review: A complete stormwater management plan submittal includes a wet detention basin supplement for each basin, design calculations, plans and specifications showing all basin and outlet structure details, and a signed and notarized operation and maintenance agreement. I. PROJECT INFORMATION (please complete the following information): Project Name: Triple T Parts and Equipment Contact Person: Phillip Tripp Phone Number: ( 910 ) 763-5100 For projects with multiple basins, specify which basin this worksheet applies to: elevations Basin Bottom Elevation 3.0 ft. (poor of the basin) Permanent Pool Elevation 10.0 ft. (elevation of the orifice) Temporary Pool Elevation 12.0 ft. (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 1�_ sq.ft. (water surface area at the orifice elevation) Drainage Area 6.92 ac. (on-site and off-site drainage to the basin) Impervious Area 5.80 ac. (on-site and off-site drainage to the basin) volumes Permanent Pool Volume 47,934 cu.ft. (combined volume of main basin and forebay) Temporary Pool Volume �7 331_cu.ft. (volume detained above the permanent pool) Forebay Volume 4,877 cu.ft. (approximately 20% of total volume) Other parameters SA/DA' 0.0360 (surface area to drainage area ratio from DWQ table) Diameter of Orifice 2.25 in. (2 to 5 day temporary pool draw-down required Design Rainfall 1 in. Design TSS Remova12 90 % (minimum 85% required Form SWU-102 Rev 3.99 Page I of 4 Footnotes: 1. When using the Division SAIDA tables,the correct SAIDA ratio for permanent pool sizing should be computed based upon the actual impervious%and permanent pool depth. Linear interpolation should be employed to determine the correct value for non- standard table entries. 2. In the 20 coastal counties,the requirement for a vegetative filter may be waived if the wet detention basin is designed to provide 90%TSS removal. The NCDENR BMP manual provides design tables for both 85%TSS removal and 90%TSS removal. II. 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 Code Section: 15 A NCAC 2H .1008. Initial in the space provided to indicate 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. If a requirement has not been met, attach justification. Appli��cjj ts Initials M�i a. The permanent pool depth is between 3 and 6 feet(required minimum of 3 feet). ML b. The forebay volume is approximately equal to 20% of the total basin volume. IIL c. The temporary pool controls runoff from the design storm event. (� d. The temporary pool draws down in 2 to 5 days. NA e. If required, a 30-foot vegetative filter is provided at the outlet (include non-erosive flow calculations). ML M f. The basin length to width ratio is greater than 3:1. ML g. The basin side slopes above the permanent pool are no steeper than 3:1. AL It. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). INL_ i. Vegetative cover above the permanent pool elevation is specified. — j. A trash rack or similar device is provided for both the overflow and orifice. AL k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. KL 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified to be performed prior to use as a wet detention basin ML in. A mechanism is specified which will drain the basin for maintenance or an emergency. III. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the vegetated filter if one is provided. This system (check one) ❑ does X does not incorporate a vegetated filter at the outlet. This system (check one) ❑ does X does not incorporate pretreatment other than a forebay. Form SWU-102 Rev 3.99 Page 2 of 4 Maintenance activities shall be performed as follows: 1. After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention system for sediment accumulation, erosion, trash accumulation, vegetated cover, and general condition. b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs within 2 to 5 days as designed. 2. Repair eroded areas immediately, re-seed as necessary to maintain good vegetative cover, mow vegetative cover to maintain a maximum height of six inches, and remove trash as needed. 3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to maintain proper functioning. 4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is reduced to 75% of the original design depth (see diagram below). 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 wet detention basin or stream, etc.). 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 permanent pool depth reads 5.25 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads - 2.25 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (fill in the blanks) Permanent Pool Elevation 10.0 Sediment R moval El. 7.75V516__-_____� L��eot�emoval Elevation 4.75 75%Bottom evasion 7.0 - ----------- - --------------- ----- Bottom Elevation 3.0 25°/ FOREBAY MAIN POND 5. Remove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These plants shall be encouraged to grow along the vegetated shelf and forebay berm. 6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through the emergency drain shall be minimized to the maximum extent possible. Form SWU-102 Rev 3.99 Page 3 of 4 7. All components of the wet detention basin system shall be maintained in good working order. I acknowledge and agree by my signature below that I am responsible for the performance of the seven 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: Tim Matt, Matt Holdings, LLC Title: President Address: 1924 Lunar Lane, Wilmington,NC 28405 Phone: 9 0-256-2194 Signature: Date: 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, Monica V. Loughlin , a Notary Public for the State of North Carolina County of New Hanover , do hereby certify that Tim Matt personally appeared before me this 22-)4 day of June 2000 and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, Qla may. AUBO SEAL My commission expires 08/07/01 Form SWU-102 Rev 3.99 Page 4 of 4 TRIPP ENGINEERING, P.C. 0 419 Chestnut Street Wilmington, North Carolina 28401 Phone: (910) 763-5100 • FAX: (910) 763-5631 RECEIVED JUN 2 4 2000 O Tune 26, 2000 BY: IUl NCDENR to Division Division of Environmental Management Water Quality Section /f 127 Cardinal Drive Wilmington, NC 28405-3845 Attn: Ms. Linda Lewis Re: Triple T Parts and Equipment New Hanover County, NC TE 00063 Dear Linda: Enclosed please find two (2) sets of plans, one (1) signed original and one (1) copy of the application form with narrative, one (1) wet detention system supplement and one check for the application fee. Please review for approval and contact us with any questions or comments. Thank you. Sincerely, Tripp Engineering, P.C. *�� C" I/Yye� Monica V. Loughlin MVL:dcb Enc. Stormwater Narrative June 21, 2000 Re: Triple T Parts and Equipment New Hanover County TE 00063 The total drainage area of this project is 7.42 acres. Existing impervious are on site totals 227,165 sf. A building of 15,950 will be constructed in addition to 5800 sf of sidewalk. A complete 248,915 sf of impervious area brings the total built upon area to 77.0% impervious. Stormwater runoff will be handled by an existing wet detention pond designed for the existing and proposed area. The pond exceeds the states requirement of the first one inch of runoff. This pond will drain to the Northeast Cape Fear River with a classification of C-SW. A vegetated filter is not required due to the 90% TSS removal used in the wet detention design. �ro3 6121/00 TRIPLE T ;_- CDC Stormwater Calculations Total Drains o Area ji sq.ft. I acres 323,215 11 7.42 Impervious Area Land Use .ft. aces %impervious= 0.770 EXISTING BUILDING 18,686 0.43 = 77.0% EXISTING CONCRETE 1,404 0.03 EXISTING GRAVEL 8 ASPHALT 207,075 4.75 PROPOSED BUILDING 15,950 0.37 PROPOSED CONCRETE 5,8W 0.13 Total 248,915 5.71 Stormwater Calculations: Time of Concentration: Hydraulic Length(L)= 4507 change in Height(H)- 15 Tc = (L3 IK.' 1 128 3.19 min. CPRE- 0.25 Cvow- (%imp.)(.95)+(1-%imp.)(.25) Flow for 10 year,6 hour Storm(010): = 0.79 QPRE= lCvaE)x Ora)z(Area) Iro= 7.23 in/hr = 13.41 cfs Iw= 8.87 inlhr Crow' (Cn r)x(Iru)x(Area) 42.33 cfs Flow for 50 year,6 hour Storm(Q�: QPRE- (`•PRE)X(6)X(Area) Soil Storage Capacity for 10 year Storm: = 16.45 cis CN= (98)(%imp.)+(60)(1-%imp.) QPosr= (CPosr)x(Iw)x(Area) = 90 51.93 cis P= 4.80 in. for 10 yr,6 hr storm S= 1000/CN-10 Soil Storage Capacav for 50 year Storm: 1.11 CN= (98)(%imp.)+(60)(1-%imp.) Depth(D)- [P-(0.2)(S)12I[P+(0.8)(S)1 = 90 3.68 in. P= 6.42 in. for 50 yr,6 hr storm S- 1000/CN-10 Time to Peak Flow: = 1.11 TP. [(43.5)(D)(Ares))/Qro.Posr Depth(D)= [P-(0.2)(S)12 I(P+(0.8)(3)1 28.09 min. - 5.26 in. Detention Pond Design: Time to Peak Flow: TP= [(43.5)(D)(Atea)]/Qw.Posr Pond Sae: 32.66 min. Elevation Surface Area rt. .ft Normal Pool 10.00 11,700 Flood Pool 12.00 15,631 State Surface Area Requirement at normalpool: Top of Bank 14.00 19,903 Pond side slopes- 3 :1 Bottom of Pool 3.00, 602 Depth below N.P.= 7 R. SA/DA- 0.0325 (Chart for 90%TSS Removal for Wet Detention Pond without Vegetative Fifter Total Provided Storage Volume: Required SA= (SAIDA)x(rotal Drainage Area) Vol.v [(Normal pool SA+Flood Pool SA)121 = 10.504 s .R. x(Flood Pool etev.-N.P.elev.) 27.331 cu.ft. State Volume Requirement for first 1'of runoff: Vd._ [(1/12)x(DA)x(%imp.)]+ �j j \�\\\\\11111111///yy//,/ ((1/12)x(DA)x(1-%imp.)x C1 RE C�I rJ ED ���� �PROI/ i,V c= o.2 \Q� Nq .� 21,981 cu.ft. =o sSI0N9, '; l't JUN 2 6 2000zz Si3�n ynwG@ Ay G1C`°�J / PROd # 5 I go7o �''0.,��!!/P GI.I.I 1 ///IIIIII 00063PONDxis 1 of 2 l O06(o-2i 6/21100 TRIPLE T CDC Stonnwater Calculations oreba Required Volume Provided Volume Vol.= 20%of state storage volume Normal Pool SA- 1,844 sq.8. 4.396 cu.R. Flood Pod SA- 3,033 sq.R. Vol._ [(N.P.SA+F.P.SA)121 x(F.P.el.-N.P.d.) 4,8T7 cu.ft. depth= 3 8. Outlet Structure Desian: Flow for 2-day drmdown: Flow for 5-day draxdown: for 1st V of stormwater, for 1 st V of stommvffier, Q= Provided Vol.1 172,800 sec.(2-days) Q- Provided Vol./432,000 sec.(Slays) 0.158 cis 0.063 cis Required Area of Pipe for 2-day drawdown: Required Area of Pipe for 5-day drawdown: A- Q I[Cd x SQRT(2 x g x h)] A= Q/(Cd x SQRT(2 x g x h)] Cd- 0.9 Cd= 0.6 g= 32.2 flJs' g= 32.2 ft.W h= (F.P.elev.-N.P.elev.)12 h- (F.P.elev.-N.P.elev.)12 A- 0.0328 sq.8. A= 0.0131 sq.ft. Diameter of Pipe for 2-day drawdown: Diameter of Pipe for 5-day drawdovm: - 7-- SQRT[(A x 4)/pi) DIA.- SQRT[(A x 4)/pi) 0.2045 ft. - 0.1293 8. 2.45 in. 1.55 in. USE:2.25 in ORIFICE Outlet Structure Check: Using a 4'x 4'Basin, Perimeter(L)= 16 R. Q- CIA C= (%lmp.)(.95)+(1-%imp.)(.25) 0.79 1= 7.23 in.for a 10 yr.Storm A- 7.42 Acres 42.33 cis Q- Cwx Lx H'.s H- [Q/(Cwx Qj' Cw= 3 0.92 ft. Peak elevaion- flood pool elevation+H 12.92 ft. 00063POND.)Is 2 of 2