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HomeMy WebLinkAboutSW8000505_HISTORICAL FILE_20000816 (2)STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW8 00 0 S 0 5 DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS HISTORICAL FILE ❑ COMPLIANCE EVALUATION INSPECTION DOC DATE Z000 09 16 YYYYMMDD State of North Carolina Department of Environment and Natural Resources Wilmington Regional Office James B. Hunt, Jr., Governor Bill Holman, Secretary Division of Water Quality Mr. Ernest D. Hackney, General Partner 1st Wilmington Properties PO Box 3442 Wilmington, NC 28406 Dear Mr. Hackney: 1� NCDENR NORTH CAROUNA DEPARTMENT OF ENVIRONMENT AND N/ uRA REsouROEs August 16, 2000 Subject: Permit No. SW8 000505 Ashcroft at The Commons High Density Subdivision Stormwater Project Onslow County The Wilmington Regional Office received a complete Stormwater Management Permit Application for Ashcroft at The Commons on July 14, 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 Pen -nit No. SW8 000505, dated August 16, 2000, for the construction of the project, Ashcroft at The Commons. This permit shall be effective from the date of issuance until August 16, 2010, 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 27611-7447. 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 Scott Vinson, or me at (910) 395-3900. Sincerely, Rick Sliver Water Quality Regional Supervisor RSS/:sav S:\WQS\STOP.MR'AT\PERMIT\000505.AUG cc: Timothy Stewart, P.E. Mitchell Parker, Onslow Count), Inspections Scott Vinson 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 000505 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 1st Wilmington Properties Ashcroft at The Commons Onslow County FOR THE construction, operation and maintenance of three wet detention ponds 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. This permit shall be effective from the date of issuance until August 16, 2010 and shall be subject to the following specified conditions and limitations: I. 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 Proj ect Data Sheet. The subdivision is permitted for 117 lots, each allowed 2,400 square feet of built -upon area. 3. Approved plans and specifications for this project are incorporated by reference and are enforceable parts of the permit. 2 State Stormwater Management Systems Permit No. SW8 000505 DIVISION OF WATER QUALITY PROJECT DATA SHEET Project Name: Ashcroft at The Commons Permit Number: SW8 000505 Location: Onslow County Applicant: Mr. Ernest D. Hackney, General Partner Mailing Address: 1st Wilmington Properties PO Box 3442 Wilmington, NC 28406 Application Date: July 14, 2000 Name of Receiving Stream / Index #: Northeast Creek / WOK02 1946-(0.5) Classification of Water Body: "SC NSW" If Class SA, chloride sampling results: n/a Design Storm: V Pond #1 Pond 42 Pond 43 Pond Depth, feet: 6.0 6.0 6.0 Permanent Pool Elevation, FMSL: 42.50 43.50 44.00 Drainage Area, acres: 9.23 7.82 8.46 Total Impervious Surfaces, ftz: 194,387 122,643 154,678 117 lots at 2,400 ftz: 103,200 81,600 96,000 Roads/Parking, ftz 91,187 41,043 58,678 Offsite Area entering Ponds, ftz: None, per Engineer Required Surface Area, ftz: 10,457 6,473 8,175 Provided Surface Area, ftz: 11,100 11,100 11,100 Required Storage Volume, ft': 16,254 10,618 13,136 Provided Storage Volume, ft': 18,563 18,510 18,458 Temporary Storage Elevation, FMSL: 44.00 45.00 45.50 Controlling Orifice: 1.50" � 1.50" � 1.50" � pipe 3 State Stormwater Management Systems Permit No. SW8 000505 ]I. SCHEDULE OF COMPLIANCE No homeowner/lot owner/developer shall fill in, alter, or pipe any drainage feature (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. 2. The permittee is responsible for verifying that the proposed built -upon area for the entire lot, including driveways and sidewalks, does not exceed the allowable built -upon area. Once the lot transfer is complete, the built -upon area may not be revised without approval from the Division of Water Quality, and responsibility for meeting the built -upon area limit is transferred to the individual property owner. If an Architectural Review Committee (ARC) is required to review plans for compliance with the BUA limit, the plans reviewed must include sidewalks and driveways. Any approvals given by the ARC do not relieve the homeowner of the responsibility to maintain compliance with the permitted BUA limit. 4. 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. C. Further subdivision, acquisition, orsale of theproject area. Theprojectarea is defined as allproperty owned by the permittee, for which Sedimentation and Erosion Control Plan approval was sought. f. Filling in, altering, or piping of any vegetative conveyance shown on the approved plan. 5. The Director may determine that other revisions to the project should require a modification to the permit. 6. 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. 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. 8. During constriction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired immediately. 9. 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. 10. Decorative spray fountains will not be allowed in the stormwater treatment system. 11. Iffthe 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. 12. Unless specified elsewhere, permanent seeding requirements for the stormwater control must follow the guidelines established in theNorth Carolina Erosion and Sediment Control Planning and Design Manual. El State Stormwater Management Systems Permit No. SW8 000505 13. Prior to transfer of the permit, the pond must be inspected by DWQ personnel, and determined to be in compliance with all permit conditions. Any items not in compliance must be repaired or replaced to design condition prior to the transfer. Records of maintenance activities performed to date will be required. 14. 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. C. 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. 15. 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. 16. Prior to the sale of any lot, deed restrictions must be recorded which limit the built -upon area per lot to the amount as shown on the Project Data Sheet, per Section I, Part 2. The recorded statements must follow the form: a. The maximum built -upon area per lot is 2,400 square feet. This allotted amount includes any built - upon area constructed within the lot property boundaries, and that portion of the right-of-way between the front lot line and the edge of the pavement. Built upon area includes, but is not limited to, structures, asphalt, concrete, gravel, brick, stone, slate, coquina and parking areas, but does not include raised, open wood decking, or the water surface of swimming pools." b. "The covenants pertaining to stormwater regulations may not be changed or deleted without concurrence of the State." C. Alteration of the drainage as shown on the approved plan may not take place without the concurrence of the State." d. "Lots within CAMA's Area of Environmental Concern may be subject to a reduction in their allowable built -upon area due to CAMA regulations." e. "All runoff on the lot must drain into the permitted system. This may be accomplished through providing roof drain gutters which drain to the street, grading the lot to drain toward the street, or grading perimeter swales and directing them into the pond or street. Lots that naturally drain into the system are not required to provide these measures." 17. A copy of the recorded deed restrictions must be submitted to the Division within 30 days of the date of recording the plat, and prior to selling lots. The recorded copy must bear the signature of the Permittee, the deed book number and page, and stamp/signature of the Register of Deeds. State Stormwater Management Systems Permit No. SW8 000505 18. 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. 19. 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. 20. Built upon area includes, but is not limited to, structures, asphalt, concrete, gravel, brick, stone, slate, coquina and parking areas, but does not include raised, open wood decking, or the water surface of swimming pools. I11. GENERAL CONDITIONS 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 "Name/Ownership Change Form" must be submitted to the Division of Water Quality accompanied by appropriate documentation from the parties involved, such as a copy of the deed of trust. Other supporting materials, such as a signed Operation and Maintenance plan in the case of engineered systems, will also be required. The project must be in good standing with DWQ. 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 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. Permittee grants permission to staff of the DWQ to access the property for the purposes of inspecting the stormwater facilities during normal business hours. The permittee shall notify the Division of any mailing address changes within 30 days. Permit issued this the 16th day of August, 2000. NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION Kerr T. Stevens, Director Division of Water Quality By Authority of the Environmental Management Commission Permit Number SW8 000505 State Stormwater Management Systems Permit No. SW8 000505 Ashcroft at The Commons Stormwater Permit No. SW8 000505 Onslow County Designer's Certification Page 1 of 2 1, , as a duly registered 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. The checklist of items on page 2 of this form are a part of this Certification. Noted deviations from approved plans and specifications: SEAL Signature Registration Number Date State Stormwater Management Systems Permit No. SW8 000505 Certification Requirements: Page 2 of 2 _I . 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 outlet1bypass structure. 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, a forebay, and the vegetated filter. 14. The overall dimensions of the system, as shown on the approved plans, are provided. cc: NCDENR-DWQ Regional Office Mitchell Parker, Onslow County Building Inspector DETENTION POND ANALYSIS FILE NAME: S:\WQS\POND\000505.WK1 PROJECT #: SW8 000505 Pond #1 PROJECT NAME: Ashcroft at the Commons REVIEWER: sav DATE: 16-Aug-2000 Receiving Stream: Northeast Creek Class: SC N$W Chlorides: _ Drainage Basin: White Oak Index No. WOK02 19-6-(0.5) Site Area 29.03 acres Drainage Area 402Q58.80' square feet needs to be verified Area in Acres 9.23 acres IMPERVIOUS AREA Rational C-list beside each item below in E15 to E20 On -Site Buildings & Drives 103200.00 square feet On -Site Streets & Sidewalks 91187.00 square feet square feet square feet square feet square feet TOTAL 194387:9 Cc= 0.10 % IMPERVIOUS 48.35% Des. Depth 6.0 TSS: 90 SURFACE AREA CALCULATION Rational ? If Rational is used put a SNDA 2.60% "1" in box E26. If not, leave it blank. Req. SA 10457 square feet Prov. SA 111'00;; square feet [From plan Contours] VOLUME CALCULATION Perm. Pool Volume= 34887 Req. Forebay Volume= 6977.4 Bottom 36.50 MSL Provided Volume= 6900 Perm. Pool 42'50' MSL Percent= F7720W Design Pool 44.00 MSL Design SA 13650 square feet inches Des. Storm Req. Volume 16254 cubic feet Rv= r13113 Prov. Volume ­18563,1 cubic feet SA @ _ Elevation= Avg. Head = 0.72 ft Flow Q2, cfs 0.094 Area, in 3.32 Flow Q5, cfs 0.038 Area, in 1.33 No. of Orifices C 1 JDiameter, in. Area = 1.767 in' Q, cfs = 0.050 Drawdown 38" days COMMENTS Surface Area , Volume and Orifice are within Design Guidelines. DETENTION POND ANALYSIS FILE NAME: S:\WQS\POND\000505.WK1 PROJECT* SW8 000505 Pond #2 PROJECT NAME: Ashcroft at the Commons REVIEWER: sav DATE: 16-Aug-2000 Receiving Stream: Northeast Creek Class: $SSW Chlorides: Drainage Basin: White Oak Index No. WOK02 19-6-(0.5) Site Area 29.03 acres Drainage Area square feet needs to be verified Area in Acres 7.82 acres IMPERVIOUS AREA Rational C-list beside each item below in E15 to E20 On -Site Buildings & Drives 81600.00 square feet On -Site Streets & Sidewalks 41043.00 square feet square feet square feet square feet square feet TOTAL 122643.00' Cc= 0.13 1:1� , % IMPERVIOUS 36.00% Des. Depth 6.0 TSS: 90 SURFACE AREA CALCULATION Rational ? OIf Rational is used put a SA/DA 1.90% "1" in box E26. If not, leave it blank. Req. SA 6473 square feet Prov. SA 77 square feet [From plan Contours] VOLUME CALCULATION Perm. Pool Volume= 34887 Req. Forebay Volume= 6977.4 Bottom 37.50 MSL Provided Volume= 6900 Perm. Pool F: 43. MSIL Percent= FFE20%i Design Pool 45.00 MSIL Design SA 13580 square feet inches IDes. Storm ij�,,!i�:,tOO Req. Volume i 106,18:icubic feet Rv= 0.37403405 Prov. Volume Fr 3.18510 cubic feet SA @ Elevation= Avg. Head = 0.72 ft Flow Q2, cfs 0.061 Area, in' 2.17 Flow Q5, cfs 0.025 Area, in 2 0.87 No. of Orifices 01 Diameter, in. 1.5Q Area 1.767 in 2 Q, cfs = 0.050 Drawdown days COMMENTS Surface Area , Volume and Orifice are within Design Guidelines. DETENTION POND ANALYSIS FILE NAME: S:\WQS\POND\000505.WK1 PROJECT* SW8 000505 Pond #3 PROJECT NAME: Ashcroft at the Commons REVIEWER: sav DATE: 16-Aug-2000 Receiving Stream: Northeast Creek Class: S_C_N,$W Chlorides: Drainage Basin: White Oak Index No. WOK02 19-6-(0.5) Site Area 29.03 acres Drainage Area square feet needs to be verified Area in Acres 8.46 acres IMPERVIOUS AREA Rational C-list beside each item below in E15 to E20 On -Site Buildings & Drives On -Site Streets & Sidewalks TOTAL % IMPERVIOUS 41.97% SURFACE AREA CALCULATION 96000.00 square feet 58678.00 square feet square feet square feet square feet square feet Cc= 0.12 Des. Depth 6.0 TSS: 90 Rational ? SA/DA 2.22% Req. SA 8175 square feet Prov. SA 111 square feet Req. Volume 131.�cubic feet Prov. Volume .,�1.8458 cubic feet Avg. Head = Flow Q2, cfs 0.076 Flow Q5, cfs 0.030 If Rational is used put a "'I" in box E26. If not, leave it blank. [From plan Contours] Forebay Volume= 6977.4 ded Volume= 6900 Des. Storm Rv= SA @ 0.72 ft Area, in' 2.68 Area, in 2 1.07 No. of Orifices Diameter, in 1.50 Area = 1.767 in 2 Q, cfs = 0.050 Drawdown days COMMENTS Surface Area , Volume and Orifice are within Design Guidelines. PARKER & ASSOCIATES, INC. Consulting Engineers - Land Surveyors - Land Planners 306 New Bridge Street ♦ P.O. Box 976 Jacksonville, NC 28541-0976 (910) 455-2414 ♦ Fax:(910) 455-3441 Scott Vinson NCDENR Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405-3845 Dear. Mr. Vinson, Jul' RE C E i V ED JUL 14 2000 DWO PAOJB RE: Ashcrofl at the Commons Stormwater Project No. SW8000505 Onslow County, North Carolina This letter is in response to comments in your letter dated June 30, 2000 concerning the above referenced project. The Application and all three (3) Supplemental Forms have now been hand initialed in the areas required. Please find enclosed the original forms that you had returned to me to initial, and one copy of the forms for your use. 2. I have recalculated the required Temporary Storage Volume and Orifice Size as you requested. I lowered the Temporary Storage height in all of the ponds to 1.5 feet instead of 3 feet as originally designed, and the Orifice Diameter changed to 1.5 inches instead of 2 inches as originally designed. These volumes and sizes are reflected in the enclosed calculations and revised forms. Also the changes are reflected on the enclosed two copies of the revised sheet 10 of 10 Stormwater Pond Detail Sheet. Along with the above enclosed revised plans and forms, please find enclosed two sets of the revised specifications. If you have any questions or need any additional information, please call. Sincerely, PARK R & AS O I TES, INC. Timothy Swart, P.E. xc: Mr. Deans Hackney w/enclosures CIF (P) LAM TMS/ees c3: %TAmshms/ashcroB.Itr ENVIRONMENTAL ENGINEERING ♦ STORM WATER MANAGEMENT ♦ WATER AND WASTEWATER SYSTEMS DEVELOPMENT CONSULTING ♦ FEASIBILITY REPORTS ♦ COMPUTER AIDED DESIGN ♦ CONSTRUCTION PLANS ASHCROFT AT THE COMMONS Stormwater Narrative Ashcroft at The Commons is being developed by I' Wilmington Properties. The subdivision consists of H 7 Lots. The asphalt roads will be constructed with curb inlet catch basins to collect stormwater and route it to the stormwater detention ponds prior to releasing the stormwater runoff to the existing ditches. Due to the flatness of the site and the shallow existing ditches, three stormwater ponds were necessary to serve this site. The ponds have been designed with a maximum impervious area for each lot to be 2,400 square feet (this includes house, driveway and sidewalk at house). As shown on the typical Lot Grading Sketches #1 and #2 shown on Sheet 2 of 10, the exterior lots shall be built up so that all of the runoff from all impervious areas shall flow to the roads and then to the stormwater ponds. The project drains into an unnamed tributary which flows into Northeast Creek which is classified as SC -NSW. For additional information, see the plans and specifications, and the rest of the permit application package. c:mydocumcnts\tm \ash.nu TECHNICAL SPECIFICATIONS FOR STORMWATER DETENTION PONDS #1, #2 AND #3 TO SERVE ASHCROFT AT THE COMMONS -New-Hanover County, North Carolina (l)nsloo OWNER: 1ST Wilmington Properties Wilmington, North Carolina April 2000 Revised July 2000 PARKER & ASSOCIATES, INC. Engineering - Surveying - Land Planning P.O. Box 976 Jacksonville, North Carolina 28541. N �n M.5 a�ECE1V'E0 JUL 14EM Dwo PROD ®-- Copyright ® 2000 by Parker & Associates, Inc. tLl rights reserved. No part of this document may bc. reproduced in any form or by any means without prioz written permission. lase of this document, except by those expressly authorized, is strictly prohibited. w PROJECT INFORMATION SHEET OWNER: 1st Wilmington Properties P.O. Box 3442 Wilmington, North Carolina 28406 Contact Person: Mr. Deans Hackney, General Partner (910) 815-8012 ENGINEER: Parker & Associates, Inc. P. 0. Box 976 Jacksonville, NC 28541-0976 Contact Person: Timothy M. Stewart, P.E. (910) 455-2414 ASHCROFT AT THE COMMONS STORMWATER DETENTION PONDS #1, #2 and #3 GENERAL REQUIREMENT ................................... GR 1 - 4 1. Summary of Work 2. Field Engineering 3. Submittals 4. Testing Lab Services 5. Inspection/Certification 6. Guarantee of Work SITE WORK ................................................. SW 1 - 5 1. Clearing and Grubbing 2. Excavation and Grading 3. Dewatering 4. Backfill 5. Piping System 6. Grassing 7. Erosion and Sediment Control Measures DWQ STORMWATER APPLICATION AND SUPPLEMENT ................1 - 10 STORMWATER NARRATIVE.........................................1 ENGINEERING CALCULATIONS...............................ENG 1 -15 C: mydocumenls\specs�ash. cov 2. GENERAL REQUIREMENTS SUMMARY OF WORK The CONTRACTOR for this.section shall furnish all materials, supplies, equipment, labor, tools and all other incidentals necessary to construct the Stormwater Detention Pond and appurtenances, complete, and ready for use, as shown on the plans and as enumerated herein. Work necessary for the construction of the Stormwater Pond includes but is not limited to clearing and grubbing, dewatering, excavation, backfill, install piping system, grassing, and erosion control as shown on the plans and as outlined hereinafter. FIELD ENGINEERING A. OWNER will establish base lines for Project and a site benchmark for use by the CONTRACTOR. OWNER will furnish boundary surveys if required. B. CONTRACTOR shall: Develop and make all detail surveys and measurements needed for construction including slope stakes, batter boards, and all other working lines, elevations and cut sheets. 2. Be solely responsible for all locations, dimensions` and levels. No data other than written orders of the ENGINEER shall justify departure from the dimensions and levels required by the Drawings. 3. Safeguard all points, stakes, grade marks, monuments and bench marks made or established on the Work, re- establish same if disturbed and rectify all Work improperly installed because of not maintaining, not protecting or removing without authorization such established points, stakes, marks and monuments. 4. When requested by ENGINEER, provide such facilities as may be necessary for ENGINEER to check line and grade points placed by CONTRACTOR. Where applicable, CONTRACTOR shall do no excavation or embankment work until cross -sectioning necessary for determining pay quantities has been completed and checked by ENGINEER. GR-2 3. SUBMITTALS The CONTRACTOR shall a minimum of three (3) copies of all submittals of the various materials and products to the ENGINEER for approval. Of these, one (1) copy will be returned to the CONTRACTOR. Each set of submittals shall include but not be limited to: 1. Drawings showing all dimensions units and locations of all other accessory equipment, including a piping layout. 2. All technical information needed by the ENGINEER to determine if the proposed equipment meets the plans and specifications. 4. TESTING LAB SERVICES A. General: Testing of materials, testing for moisture content during placement and compaction .of fill materials, and of compaction requirements for compliance with technical requirements of the specifications shall be performed by a testing laboratory. B. Testing Services: 1. Test the CONTRACTOR'S proposed materials in the laboratory and/or field for compliance with the specifications. 2. Perform field moisture content and density tests to assure that the specified compaction of backfill materials has been obtained. 3. Report all test results to the ENGINEER and the CONTRACTOR. C. Authority and Duties of Testing Agency: Technicians representing the testing laboratory shall inspect the materials in the field and perform tests, and shall report their findings to the ENGINEER and the CONTRACTOR. When the materials furnished or work performed fails to fulfill specification requirements, the technician will direct the attention of the ENGINEER and. CONTRACTOR to such failure. The technician shall not act as foreman or perform other duties for the CONTRACTOR. Work will be checked as it progresses, but failure to detect any defective work or materials shall not in any way prevent later rejection when such defect is discovered, nor shall it obligate the ENGINEER for acceptance. Technicians are not authorized to revoke, alter, relax, enlarge, or release any requirements of the specifications, nor to approve or accept any portion of the work. GR-3 5. 6. D. Responsibilities and Duties of CONTRACTOR: The use of testing services shall in no way relieve the CONTRACTOR of his responsibility to furnish materials and construction in full compliance with the drawings and specifications. To facilitate testing services, the CONTRACTOR shall: Secure and deliver to the testing agency, without cost, preliminary representative samples of the materials he proposes to use and which are required to be tested. 2. Furnish such casual labor as is necessary to obtain and handle samples at the project or at other sources of material. Advise the testing agency sufficiently in advance of operations to allow for completion of quality tests and for the assignment of personnel. INSPECTION/CERTIFICATION Inspection by an ENGINEER is required in order to issue the Certification of Construction as required by the Division of Water Quality to assure the pond is built according to the plans and specifications. Parker & Associates, Inc., as ENGINEER, if authorzed by the OWNER, will provide inspection throughout the performance of this Contract. Inspections will be made periodically or on a full time basis as the work progresses to insure compliance.. with these specifications and with the specification requirements shown on the plans. When requested by the ENGINEER, CONTRACTOR shall provide his services to insure to the ENGINEER's satisfaction that all dimensions, lines and grades are as designed. In order for the ENGINEER to adequately inspect and approve this construction, testing services shall be provided by an approved testing laboratory. GUARANTEE OF WORK A. Except as otherwise specified, all work .shall be guaranteed by the CONTRACTOR and his sureties against defects resulting from the use of faulty or inferior materials, equipment, or workmanship for 12 months from the date of final completion of the work as signified by acknowledgement of receipt of Final Payment by the CONTRACTOR. If, within any guarantee period, repairs, or changes are required in connection with guaranteed work, which, in the opinion of the ENGINEER, are rendered necessary as GR-4 the result of the use of materials, equipment, or workmanship, which are inferior, defective, or no*. in accordance with the terms of the CONTRACT, the CONTRACTOR shall, promptly upon receipt of notice from the OWNER, and without expense to the OWNER: 1. Place in satisfactory condition, in every particular, all of such guaranteed work. 2. Correct all defects therein. 3. Make good all damage •to the site, which in the opinion of the ENGINEER, is the result of the use of materials, equipment, or workmanship which are inferior, defective, or not in accordance with the terms of the CONTRACT. 4. Make good any work or material, or the equipment and contents of said building site, disturbed in fulfilling any such guarantee. C. If in fulfilling the requirements of the CONTRACT or of any guarantee embraced therein or required thereby, the CONTRACTOR disturbs any work guaranteed under another CONTRACT, he shall restore such disturbed work to condition satisfactory to the ENGINEER, and shall guarantee such restored work to the same extent as it was guaranteed under such other CONTRACT. D. If the CONTRACTOR, after notice, fails to proceed promptly to comply with the terms of the guarantee, the OWNER may have the. defects corrected and the CONTRACTOR and/or his Surety shall be liable for all expenses incurred. E. All special guarantees applicable to definite parts of the work that may be stipulated in the specifications or other papers forming a part of the CONTRACT shall be subject to the terms of this section during the first year of the life of such special guarantee. SITE WORK 1. CLEARING AND GRUBBING Clearing shall consist of the cutting, removal, and satisfactory disposal of all trees, down timber, project roots, stumps, lap wood rubbish, trash, and all other objectionable material within the construction limits as directed. Any specific trees or shrubs designated to be saved by the OWNER shall be protected from injury during construction. Grubbing shall consist of the excavation, removal, and disposal of all stumps, roots, logs, and other perishable and objectionable material within the construction limits as directed. .. All clearing and grubbing shall be accomplished in such a manner as not to injure or destroy any merchantable timber or other property on land adjacent to the project site. Before any burning of debris shall occur, contractor shall contact owner and engineer for permission and location and contractor will be required to secure ANY and ALL burning permits required. All perishable material shall be burned in such a manner as not to injure trees or shrubs outside the project site or any tree or shrub designated to be saved. Any• material that cannot be completely burned will be removed and disposed of at an off -site location at the expense of the contractor. If burning is not allowed, contractor is responsible to remove all material from the site. 2. EXCAVATION AND GRADING All grading and excavation shall be in accordance with typical dimensions and cross -sections shown on the plans and specifications contained herein. During excavation all topsoil suitable for reuse shall be stockpiled in an area designated by the OWNER. All soils suitable for reuse as backfill material shall be stockpiled. in a separate area designed by OWNER. All soils unsuitable for reuse shall be stockpiled in a separate location as designated by the OWNER. Services of the testing laboratory shall be used to determine which soils are best suitable for reuse as backfill. In areas requiring back fill to construct the pond dikes, a minimum of 12-inches of topsoil and subsoil stripping shall occur prior to the commencement of backfill. SV7-2 3. DEWATERING 1. The CONTRACTOR shall provide and maintain adequate dewatering equipment to remove and dispose of all surface and ground water entering excavations, trenches, or other parts of the work. Each excavation shall be kept dry during subgrade preparation and continually thereafter until the structure to be built,. or the pipe to be installed therein is completed to the extent that no damage from hydrostatic pressure, flotation., or other cause will result. A. The working areas on the site (exclusive of sediment entrapment devices) shall be kept free of surface water at all times. The CONTRACTOR shall install drainage ditches and dikes and shall perform all pumping and other work necessary to divert or remove rainfall and all other accumulations of surface water from the excavations and fill areas. The diversion and removal, of surface eater shall be performed in a manner that will prevent the accumulation of water behind temporary structures or at any other locations within the construction area where it may be detrimental. B. Water used for working or processing, resulting from dewatering operations, or containing oils or sediments that will reduce the quality of the water sediments that will reduce the quality of the water downstream of the point of discharge shall not be directly discharged. Such waters shall be diverted through a settling basin or filter before being discharged. C. The CONTRACTOR is responsible for the condition of any pipe, conduit or channel which he may use for drainage purposes and all such pipes, conduits or channels shall be left clean and free of sediment. 2. The CONTRACTOR shall provide, install, and operate sufficient trenches, sumps, pumps, hose, piping, wellpoints, deep wells, etc., necessary to depress and maintain the ground water level below the base of the excavations during all stages of construction operations. The ground water table shall be lowered in advance of subgrade excavation and maintained two feet below the lowest subgrade excavation made until the structure has sufficient strength and weight to withstand horizontal and vertical soil and water pressures from natural ground water. The system must be operated on a 24-hour basis and standby pumping facilities and personnel shall be provided to maintain the continued effectiveness of the system. If, in the opinion of the ENGINEER, the water levels are not being lowered or maintained as required by SW-3 these specification, the CONTRACTOR shall .install additional or alternate dewatering devices as necessary, at no additional cost to the OWNER. 4. BACKFILL After completion of stripping the area to receive embankment backfill and compaction, the CONTRACTOR shall place compacted backfill to construct the dikes for the stormwater pond in accordance with typical dimensions and cross -sections shown on the plans and requirements contained in the specifications herein. Any soft areas of subgrade containing unsuitable, wet or yielding material not readily capable of site compaction shall be removed and replaced with compacted select borrow material. Services of a testing laboratory shall be used to determine which soils are suitable as select borrow material. All fill shall be placed in horizontal loose lifts not exceeding 8-inches in thickness and shall be mixed and spread in a manner assuring uniform lift thickness after placing. Each lift shall be compacted by not less than two (2) complete coverages of the specified compactor. The compaction of the complete area of the backfill shall have i minimum compacted density of 95 percent as obtained by test procedures in ASTM D 1557 (modified proctor). Services of a testing laboratory shall be required to provide the CONTRACTOR with the required compaction density results to insure compliance with the above required compaction density. No fill material shall be placed when free water is standing on the surface of the area where the fill is to be placed. No compaction of fill will be permitted with free water on any portion of the fill to be compacted. No fill shall be placed or compacted in a frozen condition or on top of frozen material. Any fill containing organic materials or other unacceptable material previously described shall be removed and replaced with approved fill material prior to compaction. Each lift of compacted fill shall be compacted by the designated number of coverages of all portions of the surface of each lift by a smooth -drum vibratory roller for granular material having a static weight not less than 5,500 pounds, a sheepsfoot roller for cohesive material exerting a pressure of 250 psi on the surface of the feet, or equivalent equipment approved by the ENGINEER prior to commencement of the work. One coverage is defined as the condition obtained when subjected to the direct contact of the compactor. The compactor shall be operated at a forward speed not exceeding 40 feet per minute. SW-4 In some ares where soft soils are removed, it may be difficult to properly compact the first lift or two on the base of the undercut area. If the base is excessively wet, a working mat of compacted crushed stone shall be placed prior to placement and compaction of the fill. 5. PIPING SYSTEM A. GENERAL The piping system required shall be constructed and installed as shown on the plans and as further described herein. The stormwater pond piping system shall include but not be limited to one 18-inch outlet pipe, one 18- inch riser pipe, one trash rack, an anti -seep plate and all appurtenances required for a complete installation. B. PIPING The piping included shall be to the diameters and lengths shown on the plans. These pipes shall be fabricated of corrugated aluminum made from alloys of ALCAD 3004 or 5052. They shall be helically corrugated Corlix as manufactured by Kaiser Aluminum or an approved equal. All welding required shall be done in the factory. The units shall arrive to the site ready for installation. Flanges shall be welded to the pipes for easy connections in the field. The flanges shall be bolted together using 3/8-inch stainless steel bolts, nuts and washers and using 3/16-inch neoprene gaskets. A trash rack shall be provided to the dimensions shown on the plan. The trash rack shall include an aluminum grate top with %-inch opening welded to the top. An aluminum anti -seep plate shall be provided and installed per the dimensions and locations shown on the plans. 6. GRASSING A. DIKES AND EMBANKMENTS The CONTRACTOR after grading and shaping the dikes and remaining areas as shown on the plans, shall furnish labor, tools and equipment to till and seed any and all areas, as outlined hereinbefore under site work. The entire .area shall be given one application of agricultural lime at the rate of 2,000 pounds per acre; super phosphate at 500 pounds per acre; a 12-4-8 grade fertilizer at the rate of 600 pounds per acre, all harrowed to a point that it is thoroughly mixed with the SW-5 soil. The Contractor shall then furnish and sow, Rebel Fescue seed, at the rate of 100 pounds per acre mixed with 25 pounds per acre of Bermuda. A suitable cover of straw mulch shall be placed at a rate of 1.5 to 2 tons per acre on the entire area following the entire area to prevent the straw much from blowing away and to assist in earlier germination. In the case of extreme slopes, the straw mulch shall be stabilized by the application of an asphalt or other approved binding material. The Contractor shall guarantee a full stand of grass over the entire area. A stand of grass shall be considered acceptable when cover is at least 95 percent. 7. EROSION AND SEDIMENT CONTROL MEASURERS The erosion and sedimentation control measures shown on the plans and contained in the Contract Documents indicate the approximate locations of those measures on the basis of the existing topography within the area or on the basis of the predetermined need for any specific area. Upon commencement'of the operations in those areas where measures are proposed, the ENGINEER may make minor adjustments in location. CONTRACTOR shall note and observe all conditions as outlined in the Erosion and Sedimentation Control Approval Letter. It will be the CONTRACTOR'S responsibility to provide the erosion and sediment control measures as shown on the plans or as otherwise specified in the Contract Documents or as directed by the Engineer. The CONTRACTOR is cautioned that these facilities will be installed as shown on the plans and/or as directed by the ENGINEER during the construction process. Any citations, penalties, or fines issued by the N.C. Department of Environment and Natural Resources or any other agency resulting from negligence of the CONTRACTOR shall hold the ENGINEER or OWNER harmless from any resulting damages or fines. OFFICE USE ONLY - Date Received Fee Paid Permit Number State of North Carolina Department of Environment and Natural Resources Division of Water Quality STORMWATER MANAGEMENT PERMIT APPLICATION FORM This form maybe photocopied for use as an original I. GENERAL INFORMATION 1. Applicants name (specify the name of the corporation, individual, etc. who owns the project): 1st Wilmington Properties 2. Print Owner/Signing Official's name and title (person legally responsible for facility and compliance): 3. Mailing Address for person listed in item 2 above: P.O. Box 3442 City: Wilmington State: (AC Zip: 281i06 Telephone Number: ( 910 ) 7 6 3- 1 7 6 4 4. Project Name (subdivision, facility, or establishment name - should be consistent with project name on plans, specifications, letters, operation and maintenance agreements, etc.): Ashcroft at The'Commons - 5. Location of Project (street address): Commons Drive South and Fairway Road City: Jacksonville' County: Onslow- 6. Directions to project (from nearest major intersection): On Western Boulevard Extension turn onto Gateway Drive h, then turn onto Commons Drive South then turn right on West Fairway Road, across from, Northside High School 7. Latitude: N 34°47' 20" Longitude: W77023' 31" of project 8. Contact person who can answer questions about the project: Deans Hackne IL PERMIT INFORMATION: 1. Specify whether project is (check one): Telephone Number: ( 910 ) 7 6 3-17 6 4 X New Renewal Modification Donn SN't,1-101 Version 3.99 1 01-1 2. If this application is being submitted as the 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): _LAMA Major XSedimentation/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. III. 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. Subdivision will drain to three stormwater ponds 2. Stormwater runoff from this project drains to the 3. Total Project Area: 29.03 acres White Oak 5. How many drainage areas does the project have? 3 River basin. 4. Project Built Upon Area: 37.3 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. Pond 111 Pond #2 Pond #3 r .aYA(stt;"AMMRaa^...MY> #•$a ..> Nam u...« .. .... Receiving Stream Name Northeast Creek -Northeast Creek -'Northeast Creek Receiving Stream Class S Drainage Area Existing Impervious* Area 0 0 0 Proposed Imervious'Area 4.463 Acres 2.816 Acres 3.551 Acres % Impervious* Area (total) 48% 36% 42% ervious` Stiff ce Area �s Diiinage . arvl . r ge Area 3 .. On -site Buildings &drives 103,200 SF 81 600 SF 96 000 SF On -site Streetsgsidewalks On.site-P-arking- On-site Sidewalks - Other on -site Off -site Total:19 3S7 F=4.463 =2 - Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas, sidewalks, gravel areas, etc. 43 L:> s [' 31 k4k � } Form SNU-Illl Version 3.99 Page 2 of 4 s /. How was the off -site impervious area listed above derived? -V. 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 .S W S 600,Yos- 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 21400 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 of swimming pools. 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 (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 Fuxin SWt:-Illl Version 3.99 Pa@e 3 of 4 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. Initials • Original and one copy of the Stormwater Management Permit Application Form _ --J m 5 • One copy of the applicable Supplement Form(s) for each BMP _ 11VAS • Permit application processing fee of $420 (payable to NCDENR) I iti 1 • Detailed narrative description of stormwater treatment/management TtM j • Two copies of plans and specifications, including: 1M� - Development/Project name - Engineer 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) 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): Parker & Associates, Inca Mailing Address: P.O. Box 976, City: Jacksonville State: NC Zip: 28540 Phone:( 910 ) 455- 2414 Fax: ( 910 1 455-3441 VIII. APPLICANT'S CERTIFICATION I, (print or type name of person listed in General Information, item 2) Ernes Deans Hackney 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 requirements of 15A NCAC 2H I nnn Date: �Z_6 -oa Form S%v1;-101 Version I(A) Pale 4 of 4 Pennit No. G�c� O60 6 r (to be provided b7 DWQ) State of North Carolina Department of Envirorunent 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 DWQ Stormwater Management Plan Review: A. complete stormwater management plan submittal includes an application form, a wet detention basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashnrnft at The Commons Contact Person: neant Harkney Phone Number: ( 910) 763 1764 For projects with multiple basins, specify which basin this worksheet applies to: 1 elevations Basin Bottom Elevation 36.5 ft. Permanent Pool Elevation 42.5 ft. Temporary Pool Elevation 44.0, ft, areas Permanent Pool Surface Area i i I oo sq. ft. Drainage Area Impervious Area volumes Permanent Pool Volume Temporary Pool Volume Forebay Volume Other parameters SA/DAI Diameter of Orifice 9.23 ac. (floor of the basin) (elevation of the orifice) (elevation of the discharge structure overflow) (wuter surface area at the orifice elevation) (on -site and off -site drainage to the basin) (on -site and off -site drainage to the basin) 34 - 887 cu. ft. (combined volume of main basin and forebay) 18,365 cu. ft. (volume detained above the permanent pool) 6,900 cu. ft. (approximately 20% of total volume) 2 Ty (surface area to drainage area ratio from DWQ table) 1 .5 in. (2 to 5 day temporan, pool draw -down required) Design Rainfall 1 Design TSS Removal z 90 in. % (minimum 85% required) Form SWU-102 Rey V)Q Page I of 4 Footnotes: 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. 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%c 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. Applicants Initials ., IMS a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). TM4 b. The forebay volume is approximately equal to 20% of the basin volume. �Ml c. The temporary pool controls runoff from the design storm event. TMi d. The temporary pool draws down in 2 to 5 days. IIAti N / n e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) _6A f. The basin length to width ratio is greater than 3:1. (M� g. The basin side slopes above the permanent pool are no steeper than 3:1. TMS h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).' Tt^� i. Vegetative cover above the permanent pool elevation is specified. Thi j. A trash rack or similar device is provided for both the overflow and orifice. k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. �My * m. A mechanism is specified which will drain the basin for maintenance or an emergency. *k: will be recroded at a later date *m: If pond ever has to be drained, a pump will be used. 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) 0 does d does not incorporate a vegetated filter at the outlet. This system (check one) 0 does Q does not incorporate pretreatment other than a forebay. Form S1XU-]()2 kev 3.99 Pope 2 of 3 Maintenance activities shall be performed as follows: I. After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention basin 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 be handled in a manner that will not 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 4.5 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4.5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (M in the blanks) Permanent Pool Elevation 42 ti Sediment Re oval El.Q,Sj 75 Sediment Removal Elevation a a n 75'h Bottom Ele ation 3 % ------------------------ ------------- Bottom Elevation s 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 practical. Donn SWU• 102 Rev 3.99 Page 3 of 4 All components of the wet detention basin system shall be maintained in food 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. A Print name: v v Title: s- Address: l�o. -ix Date: Z/'G - 00 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. 1 C2rxwz' , , a Notary Public for the State of County of A2r / 122 ' 1' ti' do hereby certify that Ezi sI O personally appeared before me this day of ZJO ° > and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, = z i =mt ° s YgNO `✓ EP GO\\\�� SEAL My commission expires '�°` , SWU-102 Rev 3.99 Page 4 of 4 P e n n i t No. _3LJ�'' 0to ,5b7 (robe provided b.N 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 an application form, a wet detention -basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashcroft at'The Commons Contact Person: Deans Hackney Phone Number: L910 For projects with multiple basins, specify which basin this worksheet applies to: 2 763 174I elevations Basin Bottom Elevation 37.5 ft. (floor of the basin) Permanent Pool Elevation 43.5 ft. (elevation of the orifice) Temporary Pool Elevation 45.0 ft. (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11,100 sq. ft. (water surface area at the orifice elevation) Drainage Area 7.82 ac. (on -site and off -site drainage to the basin) Impervious Area 2.816 ac. (on -site and off -site drainage to the basin) volumes Permanent Pool Volume Temporary Pool Volume Forebay Volume Other parameters SA/DA t Diameter of Orifice Design Rainfall Design TSS Removal 2 34,887 cu. ft. (combined volume of main basin and forebay) 1 8, 365 cu. ft. (volume detained above the permanent pool) 6,900 cu. ft. (approximately 20% of total volume) 2.1% (surface area to drainage area ratio from Dli'Q table) 1 .5 in. (2 to 5 day ternporary pool draw -down required 1 in. 90 % (rnininuun 85r10 required) i........ III" • �. ') „.... � Dui II...,.. I ICI _I Footnotes: When using the Division SA/DA tables, the correct.SA/DA 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. '- In the 20 coastal counties, the requirement for a vegetative filter may be waived if the wet detentionbasin 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. Applicants Initials Hai a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). (r+i b. The forebay volume is approximately equal to 20% of the basin volume. TMi c. The temporary pool controls runoff from the design storm event. TMi d. The temporary pool draws down in 2 to 5 days. '(lal NLA e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) 1M1 f. The basin length to width ratio is greater than 3:1. �P^4 g. The basin side slopes above the permanent pool are no steeper than 3:1. Tf^i h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). 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. TMf k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. TM1 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. TNrti m. A mechanism is specified which will drain the basin for maintenance or an emergency. *k: Will be recorded at a later time *m: If pond ever needs to bewdra.ined, a pump will be used 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) 0 does *does not incorporate a vegetated filter at the outlet. ']'his system (check on(!) 0 does (%floes not incorporate pretreatment other than a forebay. POrin SIXI- oI key _I u() I`i,.,,. , n;'.. Maintenance activities shall be performed as follows: After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention basin 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 be handled in a manner that will not 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 4.5 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4. 5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (fill in the blanks) Permanent Pool Elevation 4 3 : 5 _. Sediment Re oval El. 3g p _____________175 _ Sediment Removal Elevation3 `_. Q_ 75% Bottom Ele •anon 37 • 5 "�--------------------------------------------- ------- Bottom Elevation 37. 5 259c FOREBAY MAIN POND 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 practical. Form SWU-102 Rev 399 Pave 3 of 4 7 All rnmponcMl 01 the wcl d-"; !Rion hasin <Iem .hall he m:oni:tinctl in L'ood workin, or r. I acknowledge and agree by my signature below that I am responsible for the performance of the seven maintenance procedures listed abo%e. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Printname: Ernest Deans Hackney General Partner P.O. Box 3442, Wilmington, NC 28406 (910) 815 8012 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. a Notary Public for the State of✓�-r/--.i., County of k ✓. ; l4 r1.r .Ln, e do hereby certify that '5L 7-)c 4 Ar' personally appeared before me this '­"?6' day of ` , ZL)O 6, and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, i O,'�CARo p✓, ...... ate;'• NOT Z' G -P m` -C rn zz NX /i/OUN'T ( ,\�0 llq ttlttttt\Ct� SEAL My commission expires Form S W 0-102 Rev i.99 Pine 4 of 4 i Pennit No. 4kJe O[iU )Us (to he provided by DIt Q) 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 DWQ Stormwater Management Plan Review: A complete stormwater management plan submittal includes an application form, a wet detention .basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashcroft at The Commons Contact Person: Deans Hackney Phone Number: (910 ) 763 1741 For projects with multiple basins, specify which basin this worksheet applies to: 3 elevations Basin Bottom Elevation 38.0 ft. (floor of the basin) Permanent Pool Elevation 44.0 ft. (elevation of the orifice) Temporary Pool Elevation 45.5 ft. (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11,100 sq. ft. (water surface area at the orifice elevation) Drainage Area 8.46 ac. (on -site and off -site drainage to the basin) Impervious Area 3,551 ae. (on -site and off -site drainage to the basin) volumes Permanent Pool Volume 34,887 cu. ft. (combined volume of main basin and foreba)) Temporary Pool Volume 18,365 cu. ft. (volume detained above the permanent pool) Forebay Volume 6,900 cu. ft. (approximately 20% of total volume) Outer parameters SA/DAI ?_4% (surface area to drainage area ratio from DWQ table) Diameter of Orifice 1 •5 in. (2 to 5 da.v temporan• pool draw -down required) Design Rainfall 1 in. Design TSS Removal 2 90 no (minimum 8517o required) Footnotes: When using the Division SA/DA tables, the correct SA/DA 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. '- 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 is 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. Applicants Initials 7MS a. 1t�.S b. fR C. %S d. TMi N/A e. �AS f The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). The forebay volume is approximately equal to 20% of the basin volume. The temporary pool controls runoff from.the design storm event. The temporary pool draws down in 2 to 5 days. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) The basin length to width ratio is greater than 3:1. The basin side slopes above the permanent pool are no steeper than 3:1. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). Vegetative cover above the permanent pool elevation is specified. A trash rack or similar device is provided for both the overflow and orifice. A recorded drainage easement is provided for each basin including access to nearest right- of-way. TM� 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. h) m. A mechanism is specified which will drain the basin for maintenance or an emergency.. *k: Will be recorded at a later time *m: If pond ever has to be drained, a pump will be used 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) 0 does 0 does not incorporate a vegetated filter at the outlet. This system (check one) 0 does 0 does not incorporatepretreatment other than a forehay. . v�m, �'.\�I �-Ili' i'•,� ,r.: Maintenance activities shall be performed as follows: I. After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention basin 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 be handled in a manner that will not 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 4. 9 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4. 5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (fill in the blanks) �rC� "'r• . Permanent Pool Elevation Sediment Re oval El. 39 _ 5 75 ' 39. 5 ,. ,: -------------- -- Sediment Removal Elevation 75% Bottom Ele ation 3 B . 0 qc--------------------------------------------- ------ Bottom Elevation 38 . 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 practical. Form SwU-10'_' Rev 3.99 Page 3 ol'4 All components of life wet detention basin systcm Shall he maintained in ,_oval w li.ina 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 General Par 'Flo ' 1 .. .. .. �. t)ate: Z-rl;z& -Ott 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, �/'�7 �e S_ %��a ��i�� a Notary Public for the State of County of firs/a 1 do hereby certify that personally appeared before me this 26 day of 7000 , and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, M:W My commission expires �" -'2 � - Z O0/ Form SNVG-102 Rev 3.99 Pa�c 4 of 4 ASHCROFT AT TIM COMMONS Stormwater Narrative Ashcroft at The Commons is being developed by 1" Wilmington Properties. The subdivision consists of 117 Lots. The asphalt roads will be constructed with curb inlet catch basins to collect stormwater and route it to the stormwater detention ponds prior to releasing the stormwater runoff to the existing ditches. Due to the flatness of the site and the shallow existing ditches, three stormwater ponds were necessary to serve this site. The ponds have been designed with a maximum impervious area for each lot to be 2,400 square feet (this includes house, driveway and sidewalk at house). As shown on the typical Lot Grading Sketches #1 and 92 shown on Sheet 2 of 10, the exterior lots shall be built up so that all of the runoff from all impervious areas shall flow to the roads and then to the stormwater ponds. The project drains into an unnamed tributary which flows into Northeast Creek which is classified as SC -NSW. For additional information, see the plans and specifications, and the rest of the permit application package. c:nrydncumentsUms�wli. nar ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #1 ENGINEERING CALCULATIONS 1. AREA Total Area Draining to Pond from Roads and Lots (including pond area)...................................................................9.23 Acres Impervious Area: Roads and Sidewalks................................................................91,187 SF = 2.093 Acres Houses, driveways and walks ..... 43 Lots x 2400 SF/Lot (Max)=103,200 SF = 2.369 Acres Total = 194,387 SF=4.463Acres Percent Impervious = Impervious = 4.463 = 48 % Total 9.23 2. PERMANENT POND SURFACE AREA From Chart 4 -Appendix E from D.E.M. Report 87-05, for 50% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.7% 9.23 acres x 2.7% = 0.2492 acres or 10,856 SF surface area required Top of permanent pond elevation is 42.5 Area at 42.5 elevation = 11.100 SF provided 11,100 SF provided > 10,856 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1" of runoff from impervious area draining to pond Total Area = 4.463 Acres Total Runoff = 4.463 AcAn. Find Temporary Storage Volume 4.463 AcAn. x 3,630 C.F. = 16,201 C.F. required AcAn. ENG-2 4. TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 42.5 elevation (permanent pond) = 11,100 SF Area at 44.0 elevation (temporary pond) = 13,386 SF Average Area = 12,243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 18,365 C.F. provided > 16,201 C.F. required 5. RELIEVE TEMPORARY STORAGE VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 16,201 C.F. = 2 days = 0.0938 CFS Q = 16,201 C.F. + 5 days = 0.0375 CFS Cd = 0.60 g = 32.2 ft/sec h = 0.75 average height For 2 Day Release Solve For A = Q = CD 2gh Solve for Orifice Diameter, D A = 0.0225 SF = n R' R = 0.085 ft. = 1.06 inch D=2.Oinch For 5 Day Release 0.0938 (0.6) 2(32.2)(0.75) = 0.0225 S.F. Solve For A = Q = 0.0375 = 0.0090 S.F. CD 2gh (0.6) 2(32.2)(0.75) ENG-3 Solve for Orifice Diameter, D A = 0.0090 SF = TT R2 R = 0.054 ft. = 0.642 inch D = 1.3 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q = CiA A = 9.23 acres C = 0.6 i = 2.88 in./hr. - 10 year, 1 hr. storm Q = 0.6 (2.88) 9.23 = 15.9 cfs 7. Outlet Weir Water height before topping spillway = 46.0 - 45.5 = 0.5 Q = Cd A 2gh(odfice equation) Cd = 0.6 (typical valve) H = 0.5 A=9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS -Will accept 10 Yr. 1 Hr. Flow a. Check Gravity Flow ENG-4 24" Pipe Installed at 0.50% Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 16.0 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE 100-YR. 1 HR. STORM THROUGH RISER, OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q = CiA Composite C = 0.6 iloo = 4.15 irtlhr for 100 year, 1 hr storm A = 9.23 Ac. Q = 0.6(4.15)(9.23) = 23.0 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Pipe As calculated previously, outlet pipe will carry 16.0 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. C. Emergency Spillway ENG-5 Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3% Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 16.0=33.5 CFS 33.5 CFS > 23.0 CFS Therefore will handle 100-yr. 1 hr. storm 10. FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CF X 20% = 6,977 CF Total Volume Provided = 6,900 CF uwpdocsVms�ashpond 1.cal ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #2 ENGINEERING CALCULATIONS Total Area Draining to Pond from Roads and lots (including pond area)...................................................................7.82 Acres Impervious Area: Roads and Sidewalks................................................................41,043 SF = 0.942 Acres Houses, driveways and walks ..... 34 Lots x 2400 SF/Lot (Max) = 81,600 SF = 1.873 Acres Total = 122,643 = 2.816 Acres Percent Impervious = Impervious = 2.816 = 36 % Total 7.82 2. PERMANENT POND SURFACE AREA From Chart4 - Appendix E from D. E.M. Report87-05, for 40% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.1 % 7.82 acres x 2.1 % = 0.1642 acres or 7,153 SF surface area required Top of permanent pond elevation is 43.5 Area at 43.5 elevation = 11,100 SF provided 11,100 SF provided > 7,153 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1" of runoff from impervious area draining to pond Total Area = 2.816 Acres Total Runoff = 2.816 Ac.-In. Find Temporary Storage Volume 2.816 Ac.-In. x 3,630 C.F. = 10,222 C.F. required Ac.-In. 4. TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 43.5 elevation (permanent pond) = 11,100 SF Area at 45.0 elevation (temporary pond) = 13,386 SF Average Area = 12,243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 18,365 C.F. provided > 10,222 C.F. required 5. RELIEVE TEMPORARY STORAGE VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 10,222 C.F. = 2 days = 0.0592 CFS Q = 10,222 C.F. = 5 days = 0.0237 CFS Cd = 0.60 g = 32.2 ft/sec In = 0.75 average height For 2 Day Release Solve For A = Q = 0.0592 = 0.0142 S.F. CD 2gh (0.6) 2(32.2)(0.75) Solve for Orifice Diameter, D A=0.0142SF=TT RI R = 0.0672 ft. = 0.81 inch D = 1.6 inch For 5 Day Release Solve For A = Q = CD 2gh 0.0237 (0.6) 2(32.2)(0.75) = 0.0057 S.F. ENG-2 ENG-3 Solve for Orifice Diameter, D A = 0.0057 SF = TT RI R = 0.043 ft. = 0.51 inch D = 1.0 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q = CiA A = 7.82 acres C = 0.6 i = 2.88 in./hr for 10 year 1 hr. storm Q = 0.6 (2.86) 7.82 = 13.5 cfs; 7. Outlet Weir Water height before topping spillway = 47.0 - 46.5 = 0.5 Q = Cd A 2gh(orifice equation) Cd = 0.6 (typical valve) H=0.5 A=9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS - Will accept 10 Yr. 1 Hr. Flow 8. Check Gravity Flow ENG-4 24" Pipe Installed at 0.35% Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 13.5 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE 100-YR. 1 HR. STORM THROUGH RISER, OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q = CiA Composite C = 0.8 i100 = 4.15 inlhr for 100 year, 1 hr storm Q = 0.6(4.15)(7.82) = 19.5 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Pipe As calculated previously, outlet pipe will carry 13.5 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. 10 ENG-5 C. Emergency Spillway Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3% Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 13.5=31.0 CFS 31.0 CFS > 19.5 CFS Therefore will handle 100-yr. 1 hr. storm FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CF X 20% = 6,977 CF Total Volume Provided = 6,900 CF c wpdocsfts�ashcroft.cal ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #3 ENGINEERING CALCULATIONS 1. AREA Total Area Draining to Pond from Roads and lots (including pond area)...................................................................8.46 Acres Impervious Area: Roads and Sidewalks................................................................58,678 SF = 1.347 Acres Houses, driveways and walks ..... 40 Lots x 2400 SF/Lot (Max) = 96,000 SF = 2.204 Acres Total=154,678 SF = 3.551 Acres Percent Impervious = Impervious = 3.551 = 42 % Total 8.46 2. PERMANENT POND SURFACE AREA From Chart 4 - Appendix E from D. E.M. Report 87-05, for 45% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.4% 8.46 acres x 2.4% = 0.2030 acres or 8,844 SF surface area required Top of permanent pond elevation is 44.0 Area at 44.0 elevation = 11,100 SF provided 11,100 SF provided > 8,844 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1" of runoff from impervious area draining to pond Total Area = 3.551 Acres Total Runoff = 3.551 Ac.-In. Find Temporary Storage Volume 3.551 Ac.-In. x 3,630 C.F. = 12,890 C.F. required Ac.-In. El ENG-2 TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 44.0 elevation (permanent pond) = 11,100 SF Area at 45.5 elevation (temporary pond) = 13,386 SF Average Area = 12.243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 18,365 C.F. provided > 12,890 C.F. required 5. RELIEVE TEMPORARY STORAGE. VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 12,890 C.F. _ 2 days = 0.0746 CFS Q = 12,890 C.F. = 5 days = 0.0298 CFS Cd = 0.60 g = 32.2 ft/sec h = 0.75 average height For 2 Day Release Solve For A = Q = 0.0746 = 0.0179 S.F. CD 2gh (0.6) 2(32.2)(0.75) Solve for Orifice Diameter, D A=0.0179SF=TTR' R = 0.076 ft. = 0.91 inch D = 1.8 inch For 5 Day Release Solve For A = Q = 0.0298 = 0.0071 S.F. CD 2gh (0.6) 2(32.2)(0.75) ENG-3 Solve for Orifice Diameter, D A=0.0071 SF=nRZ R = 0.0477 ft. = 0.572 inch D = 1.1 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q = CiA A = 8.46 acres C = 0.6 i = 2.88 inAhr. storm Q = 0.6 (2.88) 8.46 = 14.6 cfs 7. Outlet Weir Water height before topping spillway = 46.5 - 47.0 = 0.5 Q = Cd A 2gh(orifice equation) Cd = 0.6 (typical valve) H = 0.5 A =9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS - Will accept 10 Yr. 1 Hr. Flow B. Check Gravity Flow 24" Pipe Installed at 0.06% ENG-4 Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 17.5 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE 100-YR, 1 HR. STORM THROUGH RISER, OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q = CiA Composite C = 0.8 i100 = 4.15 inlhr for 100 year, 1 hr storm Q = 0.6(4.15)(8.46) = 21.1 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Pipe As calculated previously, outlet pipe will carry 17.5 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. C. Emergency Spillway ENG-5 Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3 Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 17.5=35.0 CFS 35.0 CFS > 21.1 CFS Therefore will handle 100-yr. 1 hr. storm 10. FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CIF X 20% = 6,977 CIF Total Volume Provided = 6,900 CIF c:wpdocs\t ms\a shpon d3. cal ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #2 ENGINEERING CALCULATIONS 1. AREA Total Area Draining to Pond from Roads and lots (including pond area)...................................................................7.82 Acres Impervious Area: Roads and Sidewalks................................................................41.043 SF = 0.942 Acres Houses, driveways and walks ..... 34 Lots x 2400 SF/Lot (Max) = 81,600 SF = 1.873 Acres Total = 122,643 = 2.816 Acres Percent Impervious = Impervious = 2.816 = 36 % Total 7.82 2. PERMANENT POND SURFACE AREA From Chart 4 - Appendix E from D. E.M. Report 87-05, for 40% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.1 % 7.82 acres x 2.1 % = 0.1642 acres or 7,153 SF surface area required Top of permanent pond elevation is 43.5 Area at 43.5 elevation = 11,100 SF provided 11,100 SF provided > 7,153 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1'' of runoff from impervious area draining to pond Total Area = 2.816 Acres Total Runoff = 2.816 Ac.-In. Find Temporary Storage Volume 2.816 Ac.-In. x 3,630 C.F. = 10,222 C.F. required AcAn. o�CF- 1vED jUL 14 2000 DWa PpoJ # ��� 4. TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 43.5 elevation (permanent pond) = 11,100 SF Area at 45.0 elevation (temporary pond) = 13,386 SF Average Area = 12.243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 18,365 C.F. provided > 10,222 C.F. required 5. RELIEVE TEMPORARY STORAGE VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 10,222 C.F. = 2 days = 0.0592 CFS Q = 10,222 C.F. = 5 days = 0.0237 CFS Cd = 0.60 g = 32.2 ft/sec h = 0.75 average height For 2 Day Release Solve For A = Q = CD 2gh Solve for Orifice Diameter, D A=0.0142SF=TTRI R = 0.0672 ft. = 0.81 inch D=1.6inch For 5 Day Release Solve For A = Q CDV2gh 0.0592 (0.6) 2(32.2)(0.75) 0.0237 (0.6) 2(32.2)(0.75) = 0.0142 S.F. = 0.0057 S.F. ENG-2 ENG-3 Solve for Orifice Diameter, D A = 0.0057 SF = n RI R = 0.043 ft. = 0.51 inch D = 1.0 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q =. CiA A = 7.82 acres C = 0.6 i = 2.88 in./hr for 10 year 1 hr. storm Q = 0.6 (2.88) 7.82 = 13.5 cfs 7. Outlet Weir Water height before topping spillway = 47.0 - 46.5 = 0.5 Q = Cd A 2gh(orifice equation) Cd = 0.6 (typical valve) H=0.5 A=9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS - Will accept 10 Yr. 1 Hr. Flow 8. Check Gravity Flow z1►[em 24" Pipe Installed at 0.35% Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 13.5 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE 100-YR, 1 HR. STORM THROUGH RISER OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q = CiA Composite C = 0.8 i100 = 4.15 inlhr for 100 year, 1 hr storm A = 7.82 Ac. Q = 0.6(4.15)(7.82) = 19.5 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Pipe As calculated previously, outlet pipe will carry 13.5 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. ENG-5 C. Emergency Spillway Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3% Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 13.5=31.0 CFS 31.0 CFS > 19.5 CFS Therefore will handle 100-yr. 1 hr. storm 10. FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CF X 20% = 6,977 CF Total Volume Provided = 6,900 CF c wpdocs\t msW she roft. cal ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #3 ENGINEERING CALCULATIONS 1. AREA Total Area Draining to Pond from Roads and lots (including pond area)...................................................................8.46 Acres Impervious Area: Roads and Sidewalks................................................................58,678 SF = 1.347 Acres Houses, driveways and walks ..... 40 Lots x 2400 SF/Lot (Max) = 96,000 SF = 2.204 Acres Total=154,678 SF = 3.551 Acres Percent Impervious = Impervious = 3.551 = 42 % Total 8.46 2. PERMANENT POND SURFACE AREA From Chart 4 - Appendix E from D.E.M. Report 87-05, for 45% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.4% 8.46 acres x 2.4% = 0.2030 acres or 8,844 SF surface area required Top of permanent pond elevation is 44.0 Area at 44.0 elevation = 11,100 SF provided 11,100 SF provided > 8,844 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1" of runoff from impervious area draining to pond 0 V EO Total Area = 3.551 Acres Total Runoff = 3.551 Ac.-In. �O O Find Temporary Storage Volume 001 3.551 Ac.-In. x 3,630 C.F. = 12,890 C.F. required Ac.-In. 4. TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 44.0 elevation (permanent pond) = 11,100 SF Area at 45.5 elevation (temporary pond) = 13,386 SF Average Area = 12,243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 18,365 C.F. provided > 12,890 C.F. required 5. RELIEVE TEMPORARY STORAGE. VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 12,890 C.F. _ 2 days = 0.0746 CFS Q = 12,890 C.F. _ 5 days = 0.0298 CFS Cd = 0.60 g = 32.2 ft/sec h = 0.75 average height For 2 Day Release Solve For A = Q = 0.0746 CD 2gh (0.6) 2(32.2)(0.75) Solve for Orifice Diameter. D A=0.0179SF=rrR2 R = 0.076 ft. = 0.91 inch D=1.8inch For 5 Day Release Solve For A = Q CDV2gh 0.0298 (0.6) 2(32.2)(0.75) = 0.0179 S.F. = 0.0071 S.F. ENG-2 ENG-3 Solve for Orifice Diameter, D A=0.0071 SF=nRI R = 0.0477 ft. = 0.572 inch D = 1.1 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q = CiA A = 8.46 acres C = 0.6 i = 2.88 inAhr. storm Q = 0.6 (2.88) 8.46 = 14.6 cfs 7. Outlet Weir Water height before topping spillway = 46.5 - 47.0 = 0.5 Q = Cd A 2gh(orifice equation) Cd = 0.6 (typical valve) H = 0.5 A =9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS - Will accept 10 Yr. 1 Hr. Flow 8. Check Gravity Flow 24" Pipe Installed at 0.06% ENG-4 Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 17.5 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE 100-YR, 1 HR. STORM THROUGH RISER OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q=CiA Composite C = 0.8 i100 = 4.15 inlhr for 100 year, 1 hr storm Q = 0.6(4.15)(8.46) = 21.1 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Pipe As calculated previously, outlet pipe will carry 17.5 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. C. Emergency Spillway ME ENG-5 Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3 Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 17.5=35.0 CFS 35.0 CFS > 21.1 CFS Therefore will handle 100-yr. 1 hr. storm FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CF X 20% = 6,977 CF Total Volume Provided = 6,900 CF c:wpdocsUms%shpond3. ca I ASHCROFT AT THE COMMONS ONSLOW COUNTY, NORTH CAROLINA STORMWATER DETENTION POND #1 ENGINEERING CALCULATIONS 1. AREA Total Area Draining to Pond from Roads and Lots (including pond area)...................................................................9.23 Acres Impervious Area: Roads and Sidewalks................................................................91,187 SF = 2.093 Acres Houses, driveways and walks ..... 43 Lots x 2400 SF/Lot (Max) = 103,200 SF = 2.369 Acres Total = 194,387 SF=4.463Acres Percent Impervious = Impervious = 4.463 = 48 % Total 9.23 2. PERMANENT POND SURFACE AREA From Chart4 -Appendix E from D.E.M. Report87-05, for 50% impervious,6.0 basin depth without Vegetative Filter (90% TSS Removal) Yields SA/DA = 2.7% 9.23 acres x 2.7% = 0.2492 acres or 10,856 SF surface area required Top of permanent pond elevation is 42.5 Area at 42.5 elevation = 11,100 SF provided 11,100 SF provided > 10,856 SF required 3. TEMPORARY DETENTION STORAGE VOLUME Retain 1" of runoff from impervious area draining to pond Total Area = 4.463 Acres p E C V E D Total Runoff = 4.463 Ac.-In. JUL 1 4 2000 Find Temporary Storage Volume oWo PROJ p 4.463 Ac.-In. x 3.630 C.F. = 16,201 C.F. required Ac.-In. ENG-2 4. TEMPORARY DETENTION STORAGE VOLUME Use 1.5 Ft. Temporary Pool Area at 42.5 elevation (permanent pond) = 11,100 SF Area at 44.0 elevation (temporary pond) = 13,386 SF Average Area = 12,243 SF Storage Vol.= 12,243 SF x 1.5 Height = 18,365 C.F. provided 16,365 C.F. provided > 16,201 C.F. required 5. RELIEVE TEMPORARY STORAGE VOLUME IN 2 TO 5 DAYS Q = Cd A 2gh (orifice equation) Q = 16,201 C.F. _ 2 clays— 0.0938 CFS Q = 16,201 C.F. _ 5 days = 0.0375 CFS Cd = 0.60 g = 32.2 ft/sec h = 0.75 average height For 2 Day Release Solve For A = Q = 0.0938 = 0.0225 S.F. CD 2gh (0.6) 2(32.2)(0.75) Solve for Orifice Diameter, D A = 0.0225 SF = TT R2 R = 0.085 ft. = 1,06 inch D=2.Oinch For 5 Day Release Solve For A = Q = 0.0375 = 0.0090 S.F. CD 2gh (0.6)� 2(32 ENG-3 Solve for Orifice Diameter, D A = 0.0090 SF = n RI R = 0.054 ft. = 0.642 inch D = 1.3 inch Use 1.5 inch diameter orifice 6. SIZE INLET RISER PIPE AND OUTLET PIPES TO HANDLE 10 YR. 1 HR. STORM A. Storm Flow Q = CA A = 9.23 acres C = 0.6 i = 2.88 in./hr. - 10 year, 1 hr. storm Q = 0.6 (2.88) 9.23 = 15.9 cfs 7. Outlet Weir Water height before topping spillway = 46.0 - 45.5 = 0.5 Q = Cd A 2gh(orifice equation) Cd = 0.6 (typical valve) H = 0.5 A=9SF g = 32.2 Q = 0.6(9) 2(32.2)0.5 = 30.6 C.F.S. Q = 30.6 CFS - Will accept 10 Yr. 1 Hr. Flow 8. Check Gravity Flow ENG-4 24" Pipe Installed at 0.50% Use Manning's Equation Q= 1.49 A R 2/3 S 1/2 n For 24" Pipe, Q = 16.0 CFS, which is equal to the 10 year - 1 hour flow Use 24" Pipe 9. DESIGN TO HANDLE .100-YR. 1 HR. STORM THROUGH RISER, OUTLET PIPE AND SPILLWAY PRIOR TO TOPPING POND Q = CiA Composite C = 0.6 iloo = 4.15 inlhr for 100 year, 1 hr storm Q = 0.6(4.15)(9.23) = 23.0 CFS A. Outlet Weir As Previously calculated, outlet weir can handle 30.6 CFS which is greater than 100 yr. flow B. Outlet Fipe As calculated previously, outlet pipe will carry 16.0 CFS flowing full which is less than the 100 yr. flow, therefore, emergency spillway is required. C. Emergency Spillway 10 ENG-5 Use Manning's Equation 0.50 ft. deep Trapezoidal Swale with 10 ft. wide bottom and 10:1 side slopes @ 3.3% Longitudal slope Use n=0.06 for Grassed Swale Q=17.5 CFS Total capacity of Spillway + Outlet Pipes=17.5 + 16.0=33.5 CFS 33.5 CFS > 23.0 CFS Therefore will handle 100-yr. 1 hr. storm FOREBAY VOLUME Forebay Volume shall contain approximately 20% of the total permanent pond volume. Volume of Permanent Pool 34,887 CF Forebay Volume Required 34,887 CF X 20% = 6,977 CF Total Volume Provided = 6,900 CF c:wpdocs\tms�ashpondi .cal State of North Carolina Department of Environment and Natural Resources Wilmington Regional Office .lames B. Bunt, Jr., Governor Bill Holman, Secretary Division of Water Quality Mr. Tiro Stewart, P.E. Parker $ Associates, Inc. PO Box 976 Jacksonville, NC 28540 Dear Mr. Stewart: June 30, 2000 NCDENR NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RE OURCE5 Subject: ACKNOWLEDGMENT OF RECEIPT AND REQUEST FOR ADDITIONAL INFORMATION Stormwater Project No. SW8 000505 Ashcroft at The Commons Onslow County The Wilmington Regional Office received a Stormwater Management Permit Application for Ashcroft at The Commons on May 1, 2000. A preliminary review of that information has determined that the application is not complete. The following information is needed to continue the stormwater review: 1. Please hand initial the blanks on the application and all 3 supplement forms. Typed initials cannot be accepted. 2. Please base the draw down orifices on the volume that is required and not on the volume that is provided. Resubmit the calculations and two copies of the details showing the new orifice diameters proposed. Please note that this request for additional information is in response to a preliminary review. The requested information should be received by this Office prior to July 30, 2000, or the application will be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including the application fee. If you need additional time to submit the information, please mail or fay your request for a time exteninn ,.o tllc Division at t;le ado: ---ss and fax number at the bottom of this letter. The request must indicate the date by which you expect to submit the required information. The Division is allowed 90 days from the receipt of a completed application to issue the permit. The construction of any impervious surfaces, other than a construction entrance under an approved Sedimentation Erosion Control Plan, is a violation ofNCGS 143-215.1 and is subject to enforcement action .pursuant io NCGS 143-215.6A.. ... Please reference the State assigned project number on all correspondence. Any original documents that need to be revised have been sent to the engineer or agent. All original documents must be returned or new originals must be provided. Copies are not acceptable. If you have any questions concerning this matter please feel free to call me at (910) 395-3900. - Sincerely, Cott Vinson Environmental Engineer RSS/sav: S:\WQS\STORMWAT\ADDINFO\000505.NN cc: Wilmington Regional Office Ernest D. Hackney, 1st Wilmington Properties 127 Cardinal Dr. EXL, Wilmington, North Carolina 28405 Telephone 910-395-3900 FAX 910-350-2004 An Equal Opportunity Affirmative Action Employer 50% recycled/10 post -consumer paper PARKER & ASSOCIATES, INC. Consulting Engineers - Land Surveyors - Land Planners 306 New Bridge Street - P.O. Box 976 Jacksonville, NC 28541-0976 (910) 455-2414 - Fax: (910) 455-3441 LETTER OF TRANSMITTAL TO: Ms. Linda Lewis NCDENR-Division of Water Quality 127 Cardinal Drive Extension Wi mington, NC 28405-3845 DATE: April 27, 2000 REF: Ashcroft at The Commons Onslow County, NC Stormwater Control Submittal WE ARE SENDING YOU: One (1) original and one (1) copy of the Stormwater Submittal Form, including Narrative and Calculations, Supplement Forms, two (2) sets of Plans and Specifications, one (1) Review Fee Check for $420.00, and one (1) copy of the Stormwater Submittal Plan all for the above referenced project. DELIVERY VIA: M REGULAR NAIL ❑ HAND ❑ UPS OVERNIGHT ❑ UPS GROUND THESE ARE TRANSMITTED AS CHECKED BELOW: 6 FOR APPROVAL ❑ AS REQUESTED ❑ FOR YOUR USE ❑ OTHER COMMENTS: Linda, ❑ FOR BIDS DUE ❑ FEDERAL EXPRESS ❑ OTHER ❑ FOR REVIEW AND COMMENT This package is being resubmitted per your letter dated April 19, 2000. We now have original signatures on all Wet Pond Supplement Forms. Also, the Developer name has changed from Linden Ridge Partners to 1st Wilmington ies. t, COPIES TO: Mr. Tom Anderson Mr. Beetrrs Hackney TMS/hjb CF (P) Enclosures (IF ENCLOSURES ARE NOT AS NOTED, XZNDLY NOTIFY US AT ONCE) Pennit No. JOe 6605b (to be provided by DW& 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 an application form, a wet detention .basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashcroft at The Commons Contact Person: Deans Hackney Phone Number: (910 ) 763 1741 For projects with multiple basins, specify which basin this worksheet applies to: 3 elevations Basin Bottom Elevation 38.0 ft. (floor of the basin) Permanent Pool Elevation 44.0 ft. (elevation of the orifice) Temporary Pool Elevation 45.5 ft. (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11,100 sq. ft. (water surface area at the orifice elevation) Drainage Area 8.46 ac. (on -site and off -site drainage to the basin) Impervious Area 3,551 ac. (on -site and off -site drainage to the basin) volumes Permanent Pool Volume 34,887 cu. ft. (combined volume of main basin and forebay) Temporary Pool Volume 18,365 cu. ft. (volume detained above the permanent pool) Forebay Volume 6,900 cu. ft. (approximately 20% of total volume) Other parameters SAIDA[ 7.4% (surface area to drainage area ratio from DWQ table) Diameter of Orifice 1 •5 in. (2 to 5 day temporary pool draw -down required) Design Rainfall t in. Design TSS Removal Z 9n % (minimum 85% required) Form SwU-10'_ Rev 3,90 Page 1 01' 4 Footnotes: 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. 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. Applicants Initials TS a. TSS b. Tfl5 C. _66 d. TM, N%jA ; e. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). The forebay volume is approximately equal to 20% of the basin volume. The temporary pool controls runoff from the design storm event. The temporary pool draws down in 2 to 5 days. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) f. The basin length to width ratio is greater than 3:1. g. The basin side slopes above the permanent pool are no steeper than 3:1. It. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). i. Vegetative cover above the permanent pool elevation is specified. A trash rack or similar device is provided for both the overflow and orifice. �M) ` k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. TM� 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. IM) * m. A mechanism is specified which will drain the basin for maintenance or an emergency. *k: Will be recorded at a later time *m: If pond ever has to be drained, a pump will be used 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) 0 does ® does not incorporate a vegetated filter at the outlet. This system (check one) 0 does 9 does not incorporate pretreatment other than a forebay. Form SWIJI-102 Rev 3.0`t Rigc 2 of d Maintenance activities shall be performed as follows: After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention basin 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 be handled in a manner that will not 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 4. 5 feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4. 5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (flll in the blanks) t�� r Permanent Pool Elevation 44;.0'-'•, Sediment RetEleat . ,;.; n __ Sediment Removal Elevation 39 . 5 75% Bottom38. 0 %--------------------------------------------- ---- Bottom Elevation 38 . 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. 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 practical. \ Form SWU-102 Rev 3.99 Page 3 of 4 1 All components of the �ket 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: Ernest Heanc Hackney Title: General Partner IN 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, _Cle,-2 ✓4 S 7-�� a Notary Public for the State of �✓or�� C °�:�Q County of do hereby certify that f . i/earls (lrac�ne h personally appeared before me this 26 day of 7000 , and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, '1060TAR�.'•� ,o. pUBL�G: ?s�OW co13N�y?'; .SEAL My commission expires Form SWU-102 Rev 3.99 Page 4 of 4 Permit No. cswD QQ7 s0.7 (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 DWQ Stormwater Management Plan Review: A complete stormwater management plan submittal includes an application form, a wet detention ,basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashcroft at'The Commons Contact Person: Deans Hackney Phone Number: 1 91, For projects with multiple basins, specify which basin this worksheet applies to: elevations Basin Bottom Elevation 37.5 ft. Permanent Pool Elevation 43.5 ft. Temporary Pool Elevation 45.0 ft. 763 1741 t, (floor of the basin) (elevation of the orifice) (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11,100 sq. ft. (water surface area at the orifice elevation) , Drainage Area 7.82 ac. (on -site and off -site drainage to the basin) Impervious Area 2.816 ac. (on -site and off -site drainage to the basin) volumes Permanent Pool Volume 34,887 cu. ft. (combined volume of main basin and forebay) Temporary Pool Volume 18,365 cu. ft. (volume detained above the permanent pool) Forebay Volume 6,900 cu. ft. (approximately 20% of total volume) Other parameters SA/DA( 2.1% (surface area to drainage area ratio from DWQ table) Diameter of Orifice 1.5 in. (2 to 5 day temporary pool draw -down required) Design Rainfall 1 in. Design TSS Removal 2 90 % (minimum 85% required) Form SW(J-102 Rev 3.99 Pale I of 4 Footnotes: When using the Division SA/DA tables, the correct SA/DA 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. 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. H. 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. Applicants Initials -W ; Tat TMi TMS J - (tnl NZA a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). b. The forebay volume is approximately equal to 20% of the basin volume. e. The temporary pool controls runoff from the design storm event. d. The temporary pool draws down in 2 to 5 days. e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) f. The basin length to width ratio is greater.than 3:1. g. The basin side slopes above the permanent pool are no steeper than 3:1. It. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). i. Vegetative cover above the permanent pool elevation is specified. A trash rack or similar device is provided for both the overflow and orifice. k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. TMi 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. tN�ti * m. A mechanism is specified which will drain the basin for maintenance or an emergency. *k: Will be recorded at a later time *m: If pond ever needs to bewdrained, a pump will be used 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) 0 does A does not incorporate a vegetated filter at the outlet. This system (check one) 0 does ddoes not incorporate pretreatment other than a forebay. Form Swu-lo'_ Rev 399 Paige 2 of d Maintenance activities shall be performed as follows: After every significant runoff producing rainfall event and at least monthly: a. Inspect the wet detention basin 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. 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 be handled in a manner that will not 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 4 - s feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4. 5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM ill in the blanks) Permanent Pool Elevation 43 , 5 Sediment Re oval El. 3 g p 75 b ______________ _ Sediment Removal Elevation3� ------------------------------75% Bottom Ele anon 37 .5 %---------------------- Bottom Elevation i 7 - S 25% / FOREBAY MAIN POND 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 practical. 1 Form SWU-l02 Rev 3.99 Pave 3 of 4 All ComponCM< of IhC wet dr::nlion hasin 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 abo%e. I agree to notify DWQ of any problems with the system or prior to any changes to the system or responsible party. Ptintname: Ernest Deans Hackney General Partner Address: P.O. Box 3442, Wilmgngton, NC 28406 La Le 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, — � / Ge,u S a Notary Public for the State of County of ,1 ?, l-rvvYcK , do hereby certify that C. personally appeared before me this �`� day of 4 (_ dO 6, and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, �u.Cc4.Li tT : ! �. NOT '•. Z v v •': z t CDUNT'I /ttlttttN SEAL My commission expires 2 -j -d- Form SWU-102 Rev 3.99 Page 4 of 4 ., eF ,. ,..... �".a ..• at' .`_z=.OFFICE USE ONLY Qw:...,�- Date Received Fee Paid Permit Number S-4-00 °� 08 U) D .�5 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 1. GENERAL INFORMATION 1. Applicants name (specify the name of the corporation, individual, etc. who owns the project): 1st Wilmington Properties 2. Print Owner/Signing Official's name and title (person legally responsible for facility and compliance): Ernest D. Hackney_, Ceneral Partner -- 3. Mailing Address for person listed in item 2 above: P.O. Box 3442 City: Wilmington State: Nr zip:4Ab Telephone Number: ( 910 ) 7 6 9- 1 76 4 4. Project Name (subdivision, facility, or establishment name - should be consistent with project name on plans, specifications, letters, operation and maintenance agreements, etc.): Ashcroft at The Commons 5. Location of Project (street address): Commons Drive South and Fairway Road City: Jacksonville County: 0 n % I o w 6. Directions to project (from nearest major intersection): On Western Boulevard Extent6on turn onto Gateway Drive South, Fhen turn onto Commons Drive South then turn right on West Fairway Road, arrnss from Northside High School 7. Latitude: N 34 14 7 ' 2 0 " Longitude: W 7 7 ° 2 3 ' 31 " of project 8. Contact person who can answer questions about the project: Deans Hackne IT. PERMIT INFORMATION: 1. Specify whether project is (check one): Telephone Number: ( 910 ) 7 6 3-17 6 4 x New Renewal Modification Form SWU-101 Version 3.99 Page 1 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 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): _LAMA Major XSedimentation/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. III. PROJECT INFORMATION 1. In the space provided below, summarize how stormwatei will be treated. Also attach a detailed narrative (one to two pages) describing stormwater management for the project. Subdivision will drain to three stormwater ponds 2. Stormwater runoff from this project drains to the 3. Total Project Area: 29.03 acres White Oak 5. How many drainage areas does the project have? 3 River basin. 4. Project Built Upon Area: 37.3 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. Pond #1 Pond #2 Pond #3 BasuiIIriformation 9 e�� r... "�ra f,. x�SxF+`* e ",< :, svwe.,.�.-,_. , Al p, .� Receiving Stream Name Northeast Creek Northeast Creek 14ortheast Creek Receiving Stream Class S C NSW se NSW Drainage Area Existing Impervious* Area 0 0 0 Proposed Irn ervious"Area 4.463 Acres 2.816 Acres 3.551 Acres % Im ervious Area (total) 48% 36% 42% ervtousM Surface Area, ¢ hDa , 2 On -site Buildings &drives 103,200 SF 81,600 SF 96,000 SF On -site Streettsidewalks On -site -Parking - On -site Sidewalks - Other on -site Off -site Total: 19 387 F=4463 - - " Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas, sidewalks, gravel areas, etc. 43 L k Q 34 ID-k- @ 40 l,,is e 7."I'vsr. d,10DSir A,yso sr. Form SWU-101 Version 3.99 Page 2 of 4 7. How was the off -site impervious area listed above derived? N / A 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. 5W 9' coo J 0S 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 2,400 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 of swimming pools. 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 (919) 733-5083 for the status and availability of these forms. Form SWU-102 Wet Detention Basin Supplement Form SWU-103 hifiltration 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 SW U-101 Version 3.99 Page 3 of 4 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. • Original and one copy of the Stormwater Management PermInitials it Application Form �f ffi 5 • One copy of the applicable Supplement Form(s) for each BMP - 6 • Permit application processing fee of $420 (payable to NCDENR) • Detailed narrative description of stormwater treatment/management • Two copies of plans and specifications, including: 1MS - Development/Project name - Engineer 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) 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): Parker & Associates, Inc. Mailing Address: P.O. Box 976, City: Jacksonville State: NC Zip: 28540 Phone:( 910 ) 455- 2414 Fax: ( 910 ) 455.3441 VIII. APPLICANT'S CERTIFICATION I, (print or type name of person listed in General Information, item 2) Frnest Deans Hackney 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 requirements of 15A NC'AC' 7H 1non Date: Y-6 -00 Form SWU-101 Version 3.99 Paee 4 of 4 Permit No.'So'g'966 SQ� (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 DWQ Stormwater Management Plan Review: A complete stormwater management plan submittal includes an application form, a wet detention basin supplement for each basin, design calculations, and plans and specifications showing all basin and outlet structure details. I. PROJECT INFORMATION Project Name: Ashcroft at The Commons Contact Person: Deans Hankne)4 Phone Number: ( 910) 763 1764 For projects with multiple basins, specify which basin this worksheet applies to: 1 elevations Basin Bottom Elevation 36.5 ft. Permanent Pool Elevation 42.5 ft. Temporary Pool Elevation 4.4.0, ft. (floor of the basin) (elevation of the orifice) (elevation of the discharge structure overflow) areas Permanent Pool Surface Area 11 �t oo sq. ft. (water surface area at the orifice elevation) Drainage Area Impervious Area volumes Permanent Pool Volume Temporary Pool Volume Forebay Volume Other parameters SA/DA 1 Diameter of Orifice Design Rainfall Design TSS Removal 2 9.23 ac. (on -site and off -site drainage to the basin) 4,463 ae. (on -site and off -site drainage to the basin) 34,887 cu. ft. (combined volume of main basin and forebay) 1 8t 365 cu. ft. (volume detained above the permanent pool) 6,900 cu. ft. (approximately 20% of total volume) 2 -71Y 1 .5 in. 1 in. (surface area to drainage area ratio from DWQ table) (2 to 5 day temporary pool draw -down required) 90 % (minimum 85% required) Form S W U-102 Rev 3.99 Page I of 4 Footnotes: 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. 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. Applicants Initials _W _ a. (mi b. (Ml. C. d. 7t�ti NSA " e. -frA, :L(Al lr� Tt~� _W The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet). The forebay volume is approximately equal to 20% of the basin volume. The temporary pool controls runoff from the design storm event. The temporary pool draws down in 2 to 5 days. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations) The basin length to width ratio is greater than 3:1. g. The basin side slopes above the permanent pool are no steeper than 3:1. h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail). i. Vegetative cover above the permanent pool elevation is specified. A trash rack or similar device is provided for both the overflow and orifice. k. A recorded drainage easement is provided for each basin including access to nearest right- of-way. 1. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified prior to use as a wet detention basin. "y in. A mechanism is specified which will drain the basin for maintenance or an emergency. *k: will be recroded at a later date *m: If pond ever has to be drained, a pump will be used. 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) 0 does 0 does not incorporate a vegetated filter at the outlet. This system (check one) 0 does Q 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 basin 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 be handled in a manner that will not 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 4.,5_ feet in the main pond, the sediment shall be removed. When the permanent pool depth reads 4.5 feet in the forebay, the sediment shall be removed. BASIN DIAGRAM (fill in the blanks) Permanent Pool Elevation 42 9 Sediment Re ovalEl. 38.0 75 --""""' - Sediment Removal Elevation 3a n Bottom Ele Ptio75% n 3r_5 % -------------------------- -------------- Bottom Elevation 25% FOREBAY MAIN POND 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. 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 practical. Form SWU-102 Rev 3.99 Page 3 of 4 All components of the wet detention basin system shall be maintained in good working order. 1 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. A Print name: V V Title: t- nrirlrPcc• OUgc) � Date: 'd/'G - 00 Note: The legally responsible patty 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 C22dL 61?,O,y , a Notary Public for the State of Mw-11L County of A . ' do hereby certify that personally appeared before me this GYM .day of" 412 Zoo o , and acknowledge the due execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal, LEW�S"'�ii��' zi �> m `• aue�-sG.�2 /V E� 0 SEAL My commission expires % m4W-d`� i SWU-102 Rev 3.99 Page 4 of 4