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HomeMy WebLinkAboutSW8970128_HISTORICAL FILE_20050307STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW8 '�:'11 klF DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS HISTORICAL FILE ❑ COMPLIANCE EVALUATION INSPECTION DOC DATE 2Uo5 5'60 1 YYYYMMDD I �ATrF9 I ■ J1-7 Michael F. Easley, Governor William G. Ross, Jr., Secretary North Carolina Department of Environment and Natural Resources Alan W. Klimek, P.E. Director Division of Water Quality March 7. 2005 Mr. Ron Core, Vice Chancellor UNC-Wilmington 601 College Road Wilmington, NC 28403 Subject: Stormwater Permit No. SW8 970128 Modification UNC-W Honors, International & Privatized Housing High Density Project New Hanover County Dear Mr. Core The Wilmington Regional Office received a complete modified Stormwater Management Permit Application for UNC-W Honors, International & Privatized Housing on March 7, 2005. 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 21-1.1000. We are forwarding Permit No. SW8 970128 Mod., dated March 7, 2005, for the construction of the subject project. This permit supercedes all previously issued stormwater permits, and shall be effective from the date of issuance until March 7, 2015, 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 sixty (60) 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 Linda Lewis, or me at (910) 395-3900. Sincerejy, Edward Beck Acting Regional Supervisor Surface Water Protection Section ENB/arl: S:\WQS\STORMWAT\PERMIT\970128.mar05 cc: Stephen Thomas, P.E., Stewart Engineering Tony Roberts, New Hanover County Building Inspections City of Wilmington Stormwater Services Linda Lewis [W ilriiingtonReg iona]=Office? Central Files North Carolina Division of Water Quality 127 Cardinal Drive Extension Phone (910) 395-3900 Customer Servicel-877-623-6748 Wilmington Regional Office Wilmington, NO 28405-3845 FAX (919) 733-2496 Internet: h2o.ennstate.nc,us One ivOrtt1C3C011na \�� An Equal OpportunitylAffirma6ve Action Employer— SOe/ Recycledll0%Post Consumer Paper Natutalllf State Stormwater Management Systems Permit No. SW8 970128 Modification STATE OF NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF WATER QUALITY STATE STORMWATER MANAGEMENT PERMIT HIGH DENSITY DEVELOPMENT In accordance with the provisions of Article 21 of Chapter 143, General Statutes of North Carolina as amended, and other applicable Laws, Rules, and Regulations PERMISSION IS HEREBY GRANTED TO Ron Core and UNC-W UNC-W Honors, International & Privatized Housing New Hanover County FOR THE construction, operation and maintenance of a wet detention pond in compliance with the provisions of 15A NCAC 2H .1000 (hereafter referred to as the "stormwaterrules') 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 March 7, 2015, and shall be subject to the following specified conditions and limitations: 1. DESIGN STANDARDS 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 in Section 1.7 on page 3 of this permit. The stormwater control has been designed to handle the runoff from 398,807 square feet of impervious area. 3. The tract will be limited to the amount of built -upon area indicated on page 3 of this permit, and per approved plans. 4. All stormwater collection and treatment systems must be located per the approved plan. 5. The runoff from all built -upon area within the permitted drainage area of this project must be directed into the permitted stormwater control system. 6. The amount of built -upon area for this pond previously approved under the 1997 permit, has been increased to account for the Privatized Housing project. Page 2 of 7 State Stormwater Management Systems Permit No. SW8 970128 Modification 7. The following design criteria have been provided in the wet detention pond and must be maintained at design condition: a. Drainage Area, acres: 28.128 Onsite, ft : 1,202,757 Offsite, ft2: 22,498 b. Total Impervious Surfaces, ft2: 398,807 C. Design Storm, inches: 1 d. Pond Depth, feet: 6.0 e. TSS removal efficiency: 90% f. Permanent Pool Elevation, FMSL: 26.0 g. Permanent Pool Surface Area, ft2: 52,127 h. Permitted Storage Volume, ft3: 79,638 i. Temporary Storage Elevation, FMSL: 27.4 j. Controlling Orifice: 3" O pipe k. Permitted Forebay Volume, ft3: 58,631 I. Receiving Stream/River Basin: Bradley Creek / Cape Fear M. Stream Index Number: CPF24 18-87-24-4-(1) n. Classification of Water Body: "SC HQW #" II. SCHEDULE OF COMPLIANCE 1. The stormwater management system shall be constructed in its entirety, vegetated and operational for its intended use prior to the construction of any built -upon surface. 2. During construction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired immediately. 3. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted stormwater system functions at optimum efficiency. The approved Operation and Maintenance Plan must be followed in its entirety and maintenance must occur at the scheduled intervals including, but not limited to: a. Semiannual scheduled inspections (every 6 months). b. Sediment removal. C. Mowing and revegetation of slopes and the vegetated filter. d. Immediate repair of eroded areas. e. Maintenance of all slopes in accordance with approved plans and specifications. f. Debris removal and unclogging of outlet structure, orifice device, flow spreader, catch basins and piping. g. Access to the outlet structure must be available at all times. Page 3 of 7 State Stormwater Management Systems Permit No. SW8 970128 Modification 4. Records of maintenance activities must be kept and made available upon request to authorized personnel of DWQ. The records will indicate the date, activity, name of person performing the work and what actions were taken. 5. Decorative spray fountains will be allowed in the stormwater treatment system, subject to the following criteria: a. The fountain must draw its water from less than 2' below the permanent pool surface. b. Separated units, where the nozzle, pump and intake are connected by tubing, may be used only if they draw water from the surface in the deepest part of the pond. c. The falling water from the fountain must be centered in the pond, away from the shoreline. d. The maximum horsepower for a fountain in this pond is 3/4 horsepower. 6. The facilities shall be constructed as shown on the approved plans. This permit shall become voidable unless the facilities are constructed in accordance with the conditions of this permit, the approved plans and specifications, and other supporting data. 7. Upon completion of construction, prior to issuance of a Certificate of Occupancy, and prior to operation of this permitted facility, a certification must be received from an appropriate designer for the system installed certifying that the permitted facility has been installed in accordance with this permit, the approved plans and specifications, and other supporting documentation. Any deviations from the approved plans and specifications must be noted on the Certification. A modification may be required for those deviations. 8. If the stormwater system was used as an Erosion Control device, it must be restored to design condition prior to operation as a stormwater treatment device, and prior to occupancy of the facility. 9. Access to the stormwater facilities shall be maintained via appropriate easements at all times. 10. The permittee shall submit to the Director and shall have received approval for revised plans, specifications, and calculations prior to construction, for any modification to the approved plans, including, but not limited to, those listed below: a. Any revision to any item shown on the approved plans, including the stormwater management measures, built -upon area, details, etc. b. Project name change. C. Transfer of ownership. d. Redesign or addition to the approved amount of built -upon area or to the drainage area. e. Further subdivision, acquisition, lease or sale of all or part of the project area. The project area is defined as all property owned by the permittee, for which Sedimentation and Erosion Control Plan approval or a CAMA Major permit was sought. f. Filling in, altering, or piping of any vegetative conveyance shown on the approved plan. 11. The permittee shall submit final site layout and grading plans for any permitted future areas shown on the approved plans, prior to construction. 12. 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. Page 4 of 7 State Stormwater Management Systems Permit No. SW8 970128 Modification 13. 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. III. GENERAL CONDITIONS This permit is not transferable except after notice to and approval by the Director. In the event of a change of ownership, or a name change, the permittee must submit a formal permit transfer request to the Division of Water Quality, accompanied by a completed name/ownership change form, documentation from the parties involved, and other supporting materials as may be appropriate. The approval of this request will be considered on its merits and may or may not be approved. The permittee is responsible for compliance with all permit conditions until such time as the Division approves the transfer request. 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) having jurisdiction. 4. In the event that the facilities fail to perform satisfactorily, including the creation of nuisance conditions, the Permittee shall take immediate corrective action, including those as may be required by this Division, such as the construction of additional or replacement stormwater management systems. 5. The permittee grants DENR Staff permission to enter the property during normal business hours for the purpose of inspecting all components of the permitted stormwater management facility. 6. The permit may be modified, revoked and reissued or terminated for cause. The filing of a request for a permit modification, revocation and reissuance or termination does not stay any permit condition. 7. Unless specified elsewhere, permanent seeding requirements for the stormwater control must follow the guidelines established in the North Carolina Erosion and Sediment Control Planning and Design Manual. 8. Approved plans and specifications for this project are incorporated by reference and are enforceable parts of the permit. 9. The permittee shall notify the Division any name, ownership or mailing address changes within 30 days. Permit issued this the 7th day of March 2005. NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION Division of Water Quality By Authority of the Environmental Management Commission Page 5 of 7 _..„ ..: €;fir.`:.,- _ '�-"'-=ofr'OFF.ICE=L9SE`ONLYr"" .:.,.-:.: .••�-: : •-:,, �„-:„- ::--z:_-•:'- Y." ;it Date Re"..• ceived Fee Paid Number Permit Number 01. Z5` 05- #g000, vo ISw 9q-7012% /-00 mod.. 3-4- &Y)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 I. GENERAL INFORMATION 1. Applicants name (specify the name of the corporation, individual, etc. who owns the project): UNIVE/kSITY- Cl- A0AT&+ 6i4M4MA a �It�MI Ntr TON 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: q &C k t.OLI-aC'e RoAo City: State: PC Zip: A5 w 3 Telephone Number: 4. Project Name (subdivision, facility, or establishment name - should be consistent with project name on plans, specifications, letters, operation and maintenance agreements, etc.): UNCW 200[0 PAIVA-riace3 liv wz IvTCRNMT/owlAL 14owwf-t (40�V&S 4sc"JG 5. Location of Project (street address): UNC w CRnPuS t (9U1 �ou Er.G /wap City: WILn1,1VTON County: 111Et✓ �-i "oveA, 6. Directions to project (from nearest major intersection): 6I LOC47-CO 01-i CJN ( L"' C+ry 9 Sri o4-L c) C.J�aNEti :�At i 7. Latitude: 1623630 I Longitude: 3 ?,To `f 10 of project (w65 8V1A1#Da3� 8. Contact person who can answer questions about the project Name:bAtAA 4or¢r7'eI S7dgFe�*1T CNri, Telephone Number: ( C71°) ) 3b0-$7S0 e'-P IGC II. PERMIT INFORMATION: 1. Specify whether project is (check one): New Form SWU-101 Version3.99 Page l of Renewal _ Modification 2. If this application is being submitted as the result of a renewal or modification to an existing permit, list the existing permit number SW 6q 701 Z9 and its issue date (if known) 3. Specify the type of project (check one): _Low Density High Density _Redevelop General Permit Other 4. Additional Project Requirements (check applicable blanks): _CAMA Major ✓Sedimentation/Erosion Control _404/401 Permit _NPDES Stormwater Information on required state permits can be obtained by contacting the Customer Service Center at 1-877-623-6748. 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 . S7W-r%LOAT46R kMPFF AtE L^0cL LTEQ 6Y A Sf)',uES OF 6A7Cµ 84Sl VS A"4 PIPCio 7c7 'THE 41E7eu71oo7 PoN6. 2. Stormwater runoff from this project drains to the (,4PLE FGAtL River basin. 3. Total Project Area: ZS. 1 Z(3 acres 4. Project Built Upon Area: 3 Z -49- 5. How many drainage areas does the project have? I 6. Complete the following information for each drainage area. If there are more than two drainage areas in the project, attach an additional sheet with the information for each area provided in the same format as below. Basin Information, _ - Drainage Area I - - -_ Drainage Area 2 Receiving Stream Name &AOt-FIr Coe E %Rir�vTaa Receiving Stream Class SC+4 [J t,> Drainage Area 28-129 AC Existing Impervious' Area .2, 3 (e 2 AC Proposed Impervious"Area Cl. I SS .4C. % Impervious{ Area (total) ,33, S G/d Impervious` Surface Area Drainage Area 1 Drainage Area 2 On -site Buildings IOZ03& st On -site Streets 8100 64�t On -site Parking /00220 St On -site Sidewalks �Sr753 S-� Other on -site Off -site 2 2 98 s� Total: Total: fi Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas, sidewalks, gravel areas, etc. Form SWU-101 Version 3.99 Page 2 of 4 7. How was the off -site impervious area listed above derived? Aol,*A a.,ecs c.. Ev c. -a c u 6sod 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 stonnwater management permit number as issued by the Division of Water Quality. These covenants may not be changed or deleted without the consent of the State. 2. No more than I 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 Form SWU-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. 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 101n • One copy of the applicable Supplement Form(s) for each BMP 01--3 • Permit application processing fee of $420 (payable to NCDENR) d03 • Detailed narrative description of stormwater treatment/management rAol!s • Two copies of plans and specifications, including: 4z"6 - 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): Mailing Address: City: State: Zip: Phone: _ ) Fax: ( ) VITT. APPLICANT'S CERTIFICATION I, (print or type name of person listed in General Information, item 2) Ronald .1 . Core 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 cove�ss�will be recorded, and that the proposed project complies with the requirements of 15A NCAC 2H .1000. i , n ----7 Date: Form SWU-101 Version 3.99 Page 4 of 4 STEWARTbob ENGINEERING RECEIVED MAR 0 7 2005 BY: LETTER OF TRANSMITTAL TO: NCDENR-Wilmington Regional Office DATE: March 04, 2005 127 Cardinal Drive Extension ATTN: Linda Lewis Wilmington, NC 28405-3845 WE ARE SENDING YOU: _ SHOP DRAWINGS PRINTS SPECIFICATIONS X COPY OF LETTER COPIES DATE DESCRIPTION JOB #: C4021 RE: UNCW Privatized Housing— Express Review - Resubmitttal VIA: Standard Mail X PLANS SAMPLES X OTHER CHANGE ORDER DISKETTES 2 3104105 Revised Civil Plans (ones that changed from previous submittal — C7.00 2 3104105 Revised Draw Down Calculations 1 3104105 Response to comments letter THESE ARE TRANSMITTED AS INDICATED BELOW: X For Approval Approved as submitted Resubmit copies for approval For Your Use Approved as noted As Requested Returned for corrections For Review & Comment Returned after loan to us REMARKS: Ms. Lewis, Attached is our resubmittal for the above project based upon your comments from your March V email. Thank you for your assistance and please feel free to call if you have any questions. - David Boyette, El COPY TO: SIGNED: '�5a� /fl/s � David Boyette, El 260 Town Hall Dr., Suite C, Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com Stormwater & Erosion Control Calcs For the proposed UNCW 2006 Privatized Housing Durham, North Carolina Prepared for RECEIVED Clark Nexsen Prepared By Stewart Engineering, Inc. his � s ra ww It ENGINEERING January 24,2005 Revised January 28, 2005 Revised March 4, 2005 MAR 0 7 2005 PROJ # �i T70I2$ �&P i i a'd ZSLBOBEGIG uui 2uivaau12u3 quemagS dEE:SO SO LO JeW 7 Stormwater & Erosion Control Calculations For UNCW 2006 Privatized Housing Wilmington, North Carolina Prepared for: Clark Nexsen Prepared by: Stewart Engineering, Inc. 260 Town Hall Drive, Suite C Morrisville, NC 919.380.8750 SEI Project No. C4021 January 24, 2005 Revised January 28, 2005 STORMtiVATER MANAGEMENT NARRATIVE UNCW 2006 PRIVATIZED HOUSING WIUMINGTON, NORTH CAROLINA PROJECT SUMMARY The proposed UNCW 2006 Privatized Housing project is comprised of six apartment buildings, a community building and associated parking areas and walkways. The project is located on the eastern boundary of the UNCW campus in proximity to Wagner Hall and the Honors- Intemational-Comerstone quad. As part of this project we are requesting a revision to Stormwater Permit #SW8970128. The existing site is a wooded area of which the majority drains to an existing stormwater detention pond. The detention pond and the portion of the existing site that bypass the pond dram to a tributary of Bradley Creek. As part of this project the existing pond will be expanded and the runoff from the proposed site will be directed to it through a network of inlets and pipes. Although the existing pond is sized adequately to handle the additional drainage and build upon areas, the pond will be expanded in order to meet City of Wilmington quantity control standards. An improvement will be made to the emergency spillway of the existing pond as the spillway is inadequate in the existing condition and erodes regularly. Currently, the spillway elevation is below the 2-yr water surface elevation and approximately 15' wide. The spillway elevation will be raised to the elevation of the 10-yr storm and its length increased to safely pass the 100-yr rainfall event without overtopping the dam. An earthen baffle will also be added to the pond to increase the flow path and travel time through the pond to ensure that a length to width ratio of 3:1 is met. The Torbay will be expanded as well to meet the 20% of total volume requirement Please see the attached proposed drainage area map, wet detention pond sizing, and draw down time calculations. �� / f �'I j 1! ilk• � ti 1 ` 't\ l --- ��: \ �>` .��' , { o it ;{!f�!(o�i `�t\ �} ( \\ji �`1 `\ 1\.... j'-." C"-� \ zF .•. (15 PROPOSED DRAINAGE J/ f'^ I i Sao.. i• C \ \silt �..� ( ^ 7 N, L AREA = h8. f28 '��� (' it lllll Iill,lllJ 1111(I LI'illt.1111id� •I II IIIIIIifI177 i'i7 t(I III IIII,I w�/-.� — / �} .f`-�•� %"� - ifl 1 chi — f ✓ __ .O :Ilia I Jj •.,_ r a of r � '-#, i �.��� \ �a� _x�=�'- �i��i'% � C a v .- IJ�nuu I id" �) \\ �` t`/' 1 ' 'ti ' i ) = z~ \ %',{ 1 � S:.,`� v `a 1 .:it .�`� t w� /°'"" �.li\ \�• � ! G 1 t v� rI{t r ,{{ 9•, ern{ -,' 1t I) _ ter'/ � � ( �- ♦ � �, �}�,.I% , I_ �� 'f � - 1 / � � � r�i�� �. '\ I �t f/ ��. - j �,.,i��z���\4,- -, (�' r-,,~\ e _-.�1� �iii(,liilj� � � f\ �!J \, ( �lr �` � � � l�,•-�� �;,� 11101,11 03 •�` r, Z W a W Ia N i<� SOLE rr; 200GRAPHI0 200 IN FEET 1 inch = 200 ft. A S T E W A A T ENGINEERING Wet Detention Pond Sizing (for 90% TSS removal) Project UNC-W University Housing Project No. C4021 Date 28-Feb-05 STRUCTURAL TRANSPORTATION CIVIL Required Surface Area Required Storage for 1st inch of runoff Total Drainage Area = 28.128 ac Simple Method Total Impervious Area = 9.155 ac Percent Impervious = 33% Rv = 0.05 + 0.009(I) 1 = % impervious = 33% Perm. Pool Depth = 6 ft SA/DA Ratio (Table 1.1) = 1.75 Rv = 0.34 in Surface Area Required = 21442 sf Volume = 35015 cf = 0.49 ae Surface Area Provided = 1.2 ae Volume Provided = 96777 cf Calculation Methods are taken from NCDENR Stormwater Best Management Practices manual, April 1999 260 Town Hall Drive, Suite C, Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com S T E W A R T ENGINEERING Water Quality Drawdown Calculations - Wet Pond (1 st inch of rainfall) 'Simple Method' Total Drainage Area = 28.128 ac Drawdown Pipe Total Impervious Area = 9.155 ac Invert = 26 ft Percent Impervious = 33% Diameter = 4 in Rv = 0.05 + 0.009(I) b 1.07 I = % impervious = 33% Ks 56557 Rv = 0.34 in Req' Depth 0.65 ft Runoff Vol. = 35,015 cf Actual Depth 1.40 ft Pond Invert = 20.0 ft Increm. Drawdown Total Elevation Storage Storage Outflow Time Time (ft) (cf) (cf) (cfs) (hr) (days) 27.40 481465 0 0.466 0.000 0.00 27.30 474506 6952 0.447 4.424 0.18 27.20 467554 6945 0.426 4.639 0.38 27.10 460609 6938 0.405 4.890 0.58 27.00 453671 6931 0.383 5.188 0.80 26.90 446740 6924 0.359 5.550 1.03 26.80 439816 6917 0.334 6.002 1.28 26.70 432899 6910 0.306 6.590 1.55 26.60 425989 6903 0.276 7.398 1.86 26.50 419086 6895 0.242 8.611 2.22 26.40 412191 6888 0.203 8.557 2.58 26.30 405304 6880 0.245 8.606 2.94 26.20 398424 6872 0.200 11.203 3.40 26.10 391552 6864 0.141 26.929 4.52 26.00 384688 6856 0.000 0.000 4.52 Drawdown Time = 4.52 days �d STRUCTURAL TRANSPORTATION CIVIL 'Simple Method' taken from NCDWQ Stormwater - Best Management Practices Manual, November 1995 STRUCTURAL TRANSPORTATION CIVIL 5 T E WART Volume Calculations ENGINEERING Forbay Volume Contour (ft) Area (ft2) Incr Vol (ft3) Accum Vol (ft3) 20 6319 0 0 21 7355 6837 6837 22 8466 7911 14748 23 9654 9060 23808 24 1 10915 1 10285 1 34092 25 12251 11583 1 45675 26 13660 12956 58631 27 16147 14904 73534 Total Pond Volume Contour (ft) Area (ft2) Incr Vol (ft3) Accum Vol (ft3) 20 29839 0 0 21 33164 31502 31502 22 36645 34905 66406 23 40283 38464 104870 24 1 44076 1 42180 147050 25 48024 46050 193100 26 52127 50076 243175 27 61641 56884 300059 Forbay Vol ( 26.0') = 58631 cf Total Vol (26.0')= 243175 cf Forbay equals 24.1 % of total volume. MAR 0 3 1005 DWQ PROJ# f)WlT 970 received- Vi 2 ern a,' I Project C)/UCL-J r Ill� 7_ne�' EP214I 'w Page —/_ Of Project No. —C�� �C�'2—( Subject Client Designer— Date 2. TG I 1%EWR IN A * C Checker—_ Date Uii 001 "t ...... PL xl__ .1 cwa 7_ j----- I i---! 4vc rA_ �-�--t��II_c'f�= -LDu vo---i-- I-- ' __�---'--- r_ C4 re e V, C, GI a '�dC12 e LA?�C�o e__ I-- T 31 0 0 110 7 p-J-4 0 2- C,in 157 /4 1-:: +4 1-7, 10 1 EF E IVE�R_L- AR -0-7- 200 5 __1 1 7 Morrisville, NC 1 Tel 9193808750 Fax 919.380 8752 wwwstewart-eng.com r Project UNC LA-� 'Z006 Ph' ✓`z ej 110v ' Page Z Of Z Project No _C-4I021 Subject �w;��-'-+!^ —_ hn2 I'?- i !7�, Client Designer J Date STIWA.r "GINEER'NG INC Checker Date I62 Cz- ! /- ,L ,.--2=Uc. , l'7,z 0 I I r- ! _ �%. 3'�/ �{ LS I I =I12 i 3o I 1 i I - =- -' -_- i ..I _ _._ -__I •� IOr' dGG id Z'C �r :S —Gl/cc IC'U"��'W Fww I, ra:�t I — I S`f �-t/:0 £ • ! �• 3 2'o pa s I c.� /+ i OI I - i I j _ p£2 I ! '1 i�q i1IZ _I' I 2 V 1 : 3 +- IOrG t --- `--- (.✓C1 r5-- Fo r lI __._ �i J i Ca.S Ir I - I I Morrisville, NC I Tel 919 380.8750 Fax 919.380.8752 www Stewart -Ong com OPMEMM STRUCTURAL TRANSPORTATION A CIVIL S T E W A N T Volume Calculations ENGINEERING Forbay Volume Contour (ft) Area (ft2) Incr Vol (ft3) Accum Vol (fr3) 20 6319 0 0 21 7355 6837 6837 22 8466 7911 14748 23 9654 9060 23808 24 10915 10285 34092 25 12251 11583 45675 26 13660 12956 58631 27 16147 14904 73534 Total Pond Volume Contour (ft) Area (ft2) Incr Vol (ft3) Accum Vol (171:3) 20 29839 0 0 21 33164 31502 31502 22 36645 34905 66406 23 40283 38464 104870 24 44076 42180 147050 25 48024 46050 193100 26 52127 50076 243175 27 61641 56884 300059 28 64654 63148 363207 Forbay Vol ( 26.0') = 58631 cf Total Vol (26.0')= 243175 of Forbay equals 24.1% of total volume. S W 8 970128 Subject: SW8 970128 From: Linda Lewis <linda.lewis@ncmail.net> Date: Thu, 03 Mar 2005 18:22:14 -0500 To: sthomas@stewart-eng.com Steve: Now that you have provided the surface area at elevation 27, I was able to run my spreadsheet completely, and determine that the 4" orifice is too large. I know that a 4" orifice was I am unable to decipher how you came up with 4.52 days as a drawdown time. I use the standard orifice equation to determine the orifice size based on flowrates for a 2-day drawdown (35016 / 172800 = .203 cfs) and a 5 day drawdown (35016 /432000 =.081 cfs). Then using the average head between the permanent pool and the next available outlet (.62 ft), and I calculate the 2 day (7.72 sq. inches) and 5 day (3.09 sq. inches) areas for the orifices. The area of a 4" orifice is over 12.5 sq. in. As long as the area of the orifice you pick is between those two areas, it should work fine. Linda 1 of 1 3/3/2005 6:22 PM RE: UNCW Honors, International & Privatized Housing SW8 970128 Subject: RE: UNCW Honors, International & Privatized Housing SW8 970128 From: "Stephen Thomas" <sthomas@stewart-eng.com> Date: Thu, 3 Mar 2005 17:08:11 -0500 To: "Linda Lewis" <linda.lewis@ncmail.net> CC: "Shuford, Charles" <shufordc@uncw.edu>, "David Boyette" <dboyette@stewart-eng.com> Linda, Attached is a PDF of the contour areas for the pond with your requested amendments. Please review and notify us if any additional information is needed. Additionally, Mr. Ed Shuford of UNCW Facilities Planning Dept. will be delivering new applications to your office for the permit (signed by Ron Core, Vice -Chancellor) tomorrow. If this is not sufficient, please give me a phone call or otherwise contact me to let me know what we can do to complete this permitting process. Again, I appreciate your help and attention. Sincerely, Steve Thomas Steve Thomas, PE Civil Project Manager Stewart Engineering, Inc. (919) 380-8750 - office (919) 380-8752 - fax (919) 634-0056 - cell www.stewart-eng.com "Committed to Engineering Excellence, Employee Development, and Personal Client Services through Innovative Solutions." -----Original Message ----- From: Linda Lewis [mailto:linda.lewis@ncmail.net] Sent: Thursday, March 03, 2005 10:01 AM To: Stephen Thomas Subject: UNCW Honors, International a Privatized Housing SW8 970128 Steve: The volume calculations for the pond and forebay only go up to elevation 26 (permanent pool) . I need for you to add the area and volume at elevation 27 (or at 26.65) to support your claim that sufficient volume has been provided at 26.65 to hold the 1" storm. I also need a letter from the chancellor authorizing Mr. Freshwater to sign the permit application on behalf of the University. The Physical Plant may end up being charged with the responsibility of maintenance by the permittee (the University), but the application needs to be signed by a person who is authorized to subject the University to the financial burden of the maintenance responsibilities under that permit. Content -Description: Pond Contour Areas to Contour Areas to NCDENR.PDF NCDENR.PDF Content -Type: application/octet-stream l of2 3/3/2005 5:47 PM RE: UNCW Honors, International & Privatized Housing SW8 970128 I, Content -Encoding: base64 2 of 2 3/3/2005 5:47 PM A Sv\/2 q1 o IZ� STORMWATER NARRATIVE UNC Wilmington — Privatized Housing Wilmington, North Carolina EXECUTIVE SUMMARY This Stormwater Narrative contains a drainage analysis of the referenced project. Site Information The project site is located in the rear of the campus of University of North Carolina at Wilmington. The site may be accessed by entering the most northern entrance of campus via Randall Drive from College Avenue. Follow Randall Drive to the rear of campus where the road ends. Turn right onto Reynolds Drive. Turn left at the next road, Cahill Drive. Follow Cahill to the end of the road and the project site is directly in front of this dead end. At this time, the area has not been previously developed, and consists a mix of open area and wooded area. The site is relatively flat, having an overall slope to the east / southeast averaging 1.5%. In its observed condition, the majority of the stormwater runoff from the site tends to sheet flow from west to east. A clear destination for the storm drainage is not readily discernable. Proposed Improvements The project proposes to construct six to seven apartment buildings having an approximate footprint of I1,000 square feet. There will be parking surrounding the apartment buildings. A clubhouse will be constructed as well. The project will disturb approximately 20 acres. Proposed stormwater management will be facilitated by bioretention areas and the expansion of an existing stormwater detention pond. The storm drainage will either sheet flow from the parking areas into treatment swales, or will be collected in a storm drainage system which will discharge into the pond. Design Requirements Erosion and Sedimentation control measures shall be designed in accordance with 15A NCAC, chapter 4 (NC Sedimentation Pollution Control Act of 1973). Stormwater management measures shall be designed in accordance with stormwater management regulations, as detailed in 15 NCAC 02B.0216 (Section #3.b.i.B) In accordance with the requirements, the first 1 inch of rainfall shall be collected and infiltrated. The excess volume shall bypass across a reinforced spillway. Permits Required A general Stormwater Permit will be obtained through North Carolina Department of Environment and Natural Resources — Division of Water Quality. Concurrently, the City of Wilmington will issue approval of the construction plans on the basis of no net increase in site runoff in the 10-year design storm. � STEWART ENGINEERING LETTER OF TRANSMITTAL TO: NCDENR-Wilmington Regional Office DATE: February 28, 2005 127 Cardinal Drive Extension ATTN: Linda Lewis Wilmington, NC 28405-3845 WE ARE SENDING YOU: SHOP DRAWINGS SPECIFICATIONS COPIES DATE JOB #: C4021 RE: UNCW Privatized Housing— Express Review - Resubmitttal VIA: HAIL PRINTS X PLANS SAMPLES X OTHER X COPY OF LETTER ' CHANGE ORDER DISKETTES DESCRIPTION 2 2/28105 Completed Application for Stormwater Permit Partial Original and copy) 2 2/28/05 Revised Civil Plans ones that changed from previous submittal 1 2128/05 Revised Stormwater & Erosion Control Calculations 1 2128✓05 Response to comments letter THESE ARE TRANSMITTED AS INDICATED BELOW: X For Approval Approved as submitted Resubmit copies for approval For Your Use Approved as noted As Requested Returned for corrections For Review & Comment Returned after loan to us REMARKS: Ms. Lewis, Attached is our resubmittal for the above project based upon your comments on February 25, 2005. Tom Freshwater was chosen by the University to sign the financial responsibility due to his direct responsibility for the maintenance of the pond. Mr. Ed Shuford with UNCW would be glad to discuss this matter with you if it would help. His number is (910) 962-7968. Thank you for your assistance and please feel free to call if you have any questions. - Steve Thomas, PE FZECEIVF-D LMAR 0 1 2005 BY:------ COPY TO: Peter Aranyi, AIA — Clark Nexsen SIGNED: 4�9 Ed Shuford — UNCW Facilities Steve Thomas, PE — Project Manager 260 Town Hall Dr., Suite C, Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com By.MAR � 1 ?OOS LETTER OF TRANSMITTAL TO: NCDENR-Wilmington Regional Office DATE: February 25, 2005 127 Cardinal Drive Extension ATTN: Linda Lewis Wilmington, NC 28405-3845 WE ARE SENDING YOU: JOB #: C4021 RE: UNCW Privatized Housing— Express Review VIA: Hand Delivery SHOP DRAWINGS PRINTS X PLANS SAMPLES X OTHER SPECIFICATIONS X COPY OF LETTER CHANGE ORDER DISKETTES COPIES DATE DESCRIPTION 2 2/25/05 Completed Application for Stormwater Permit Original and copy 2 2/25/05 Civil Plans 1 2/25/05 Stormwater & Erosion Control Calculations 1 2/25/05 Drainage Ma 1 2/24/05 Completed Financial Responsibility Form 1 2/23/05 Check for $4,000.00 THESE ARE TRANSMITTED AS INDICATED BELOW: X For Approval For Your Use As Requested For Review & Comment REMARKS: Ms. Miller, Approved as submitted Approved as noted Returned for corrections Returned after loan to us Resubmit copies for approval Attached is our application for modification of the existing stormwater permit related to the above project (SW8 97012a). Thank you and please feel free to call if you have any questions. - Steve Thomas, PE COPY TO: Peter Aranyi, AIA — Clark Nexsen SIGNED: Ed Shuford — UNCW Facilities PE — Project Manager 260 Town Hall Dr., Suite C, Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com University of North Carolina at Wilmington 2006 Privatized Housing & Honors Housing & International Housing Stormwater Permit Number: SW8970128 MOD The following are the review comments and corrections for the above referenced plan: Add a note on the plans referencing a list of approved wetland species to be used for the pond. Response: This note has been added.. 2. Indicate on the section A -A that a 6:1 slope starts at the elevation of the permanent pool and running for at least 10'. Use a 3:1 slope minimum above the permanent pool. Add notes to this effect on the plans. Response: These notes have been added. 3. Need to use correct SADA ratio table for coastal regions of North Carolina. Response: This table was used and the calculations have been revised accordingly. 4. Need to show a table giving the contour areas for both the pond forbay and the forbay and main pond combined. Response: These tables have been added to the calculations. 5. Show more clearly that the rectangular hole in the outlet structure will be grouted in after installation of the drawdown pipe. Response: A clarifying note has been added to the detail for the outlet structure. 6. Verify Tom Freshwater's authority to sign for responsibility for pond. Response: After a discussion with Ed Shuford, Program Coordinator for the Office of Facilities, we are confident that Mr. Freshwater is the person who most logically has responsibility for the maintenance of the pond. It is his group that would be called in the event of any malfunction or maintenance request. As the Physical Plant Director, Mr. Freshwater has been given the authority to represent the University in all matters of this nature. Please call Mr. Shuford if any further clarification is needed on this matter at (910) 962-7968. 7. Add the longitude and latitude of the outlet structure to the application.. Response: This information has been added. 8. Revise calculations to estimate drawdown time using the full driving head which is acting on the drawdown pipe when the highest elevation of water (27.40') occurs. This change will affect the drawdown calculation. Response: The calculations have been revised to reflect the maximum head more accurately. RE�EI 7 ED MAR 0 1 2005 DWQ PROD # "'R�CEIVED ®F� FBB 2 ✓i 2005 NC®ENR - -- North Carolina Department of Environment -and -Natural -Resources Division of Land Resources James D. Simons, PG, PE Land Quality Section Michael F Easley, Governor Director and State Geologist William G. Ross Jr., Secretary February 25, 2005 LETTER OF RECEIPT OF EROSION CONTROL PLAN UNC-W Dr. Ronald Core, Vice Chancellor, Business Affairs 601 S. College Road Wilmington, NC 28403 RE: Project Name: UNC-W Privatized Housing Project ID Newha-2005-252 — EXPRESS OPTION County: New Hanover River Basin: Cape Fear Submitted By: Stewart Engineering Date Received by LOS: February 25, 2005 Plan Type: NEW Dear Dr. Ronald Core: This office has received a soil erosion and sediment control plan for the project listed above which was submitted as required by the North Carolina Sedimentation Pollution Control Act (G.S. 113A-57 (4)). The Act requires that all persons disturbing an area of one or more acres of land must obtain approval of a soil erosion control plan prior to the commencement of the land -disturbing activity (G.S. 113A-54(d) (4)). The Act further states that this plan must be filed a minimum of 30 days prior to the activity and the approving authority must approve or disapprove the submitted plan within 30 days of receipt. Failure of the approving authority to approve or disapprove the submitted plan within the 30-day period will be deemed approval of the plan. Commencement or continuation of a land -disturbing activity under the jurisdiction of this Act prior to the approval of an erosion and sediment control plan is a violation of the Act. The approval of an erosion and sediment control plan is conditioned on the applicant's compliance with Federal and State water quality laws, regulations and rules. If you have questions please do not hesitate to contact this office. Your cooperation in this matter is appreciated and we look forward to working with you on this project. Sincerely, Carol N. Miller Assistant Regional Engineer cc: Steve Thomas, PE, Stewart Engineering LQS-WiRO; SWS-WiRO Wilmington Regional Office 127 Cardinal Drive Ext., Wilmington, North Carolina 28405-3845 • Phone: 910-395-39001 FAX: 910-350-2004 2 - ENGINEERING'LETTER OF TRANSMITTAL TO: NCDENR-Wilmington Regional Office DATE: February25, 2005 JOB #: C4021 127 Cardinal Drive Extension ATTN: Linda Lewis Wilmington, NC 28405-3845 RE: UNCW Privatized Housing — Express Review VIA: Hand Delivery WE ARE SENDING YOU: SHOP DRAWINGS PRINTS X PLANS SAMPLES X OTHER SPECIFICATIONS X COPY OF LETTER CHANGE ORDER DISKETTES COPIES DATE DESCRIPTION 2 2/25/05 Completed Application for Stormwater Permit (Original and co 2 2125/05 Civil Plans 1 2125/05 Stormwater & Erosion Control Calculations 1 2125105 Drainage Ma A- n�ne� 1 2J23105 Check for $4,000.00 THESE ARE TRANSMITTED AS INDICATED BELOW: X For Approval For Your Use As Requested For Review & Comment REMARKS: Ms. Miller, Approved as submitted Approved as noted Returned for corrections Returned after loan to us Resubmit copies for approval Attached is our application for modification of the existing stormwater permit related to the above project (SW8 970128). Thank you and please feel free to call if you have any questions. Steve Thomas, PE RECEIVED JUJ FEB 2 5 2005 DWQ PROD # COPY TO: Peter Aranyi, AIA — Clark Nexsen SIGNED: Ed Shuford — UNCW Facilities , PE — Project Manager 260 Town Hall Dr., Suite C, Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com r STEWART ENGINEERING INC Steve Thomas, PE Civil Protect Manager 260 Town Hall Drive, Suite C I Mornsvdle, NC 27560 Tel 919 360 8750 Ext 138 1 Fax 919 380 8752 Cell 919 634 0056 sthomas®stewart-eng corn SEDIMENT & EROSION CONTROL NARRATIVE UNC Wilmington —Privatized Housing Wilmington, North Carolina EXECUTIVE SUNIN( RY This Sediment & Erosion Control Narrative contains a review of the methods designed on the above project to minimized sediment runoff from the construction site and also minimize erosion of the site. Site Information The project site is located in the rear of the campus of University of North Carolina at Wilmington. The site may be accessed by entering the most northern entrance of campus via Randall Drive from College Avenue. Follow Randall Drive to the rear of campus where the road ends. Turn right onto Reynolds Drive. Turn left at the next road, Cahill Drive. Follow Cahill to the end of the road and the project site is directly in front of what is currently a dead end. At this time, the area has not been previously developed, and consists a mix of open area and wooded area. The site is relatively flat, having an overall slope to the east / southeast averaging 1.5%. In its observed condition, the majority of the stormwater runoff from the site tends to sheet flow from west to east. A clear destination for the majority of the storm drainage is not readily discernable. Proposed Improvements The project proposes to construct six apartment buildings having an approximate footprint of 11,000 square feet. There will be parking surrounding the apartment buildings. A community building will be constructed as well. The project will disturb approximately 16.49 acres. Proposed erosion control measures include the use of a proposed dry detention pond as a temporary sediment basin (sediment basin #1), as well as utilizing an existing stormwater detention pond as a temporary sediment basin (sediment basin #2). The runoff from the site will sheet flow from the site either directly into one of the two basins, or it will be directed to the sediment basin #2 with a temporary diversion ditch. Design Requirements Erosion and Sedimentation control measures shall be designed in accordance with 15A NCAC, chapter 4 (NC Sedimentation Pollution Control Act of 1973). Stormwater management measures shall be designed in accordance with stormwater management regulations, as detailed in 15 NCAC 0213.0216 (Section #3.b.i.B) In accordance with the requirements, the first 1 inch of rainfall shall be collected and infiltrated. The excess volume shall bypass across a reinforced spillway. Permits Required A general Erosion & Sediment Control permit will be issued by NCDENR, Division of Land Quality through an express review process. Construction and Erosion Control Phasing Prior to commencement of work, the limits of disturbance will be flagged. An on -site pre - construction conference will then be scheduled with the architect, contractor, engineer, and a NCDENR representative to discuss requirements and procedures. Construction entrances, construction fence, perimeter silt fence, silt fence outlets, tree protection, and other temporary erosion control devices will be installed before inspection. `fire contractor will confirm that all applicable tree protection fencing and silt fencing is in place as specified on the construction drawings, before any clearing is initiated. By the time of the NCDENR site inspection, the contractor will provide a written summary of the implementation of the proposed erosion control elements. The summary will include milestones of device implementation and will have been reviewed by the engineer. After NCDENR site inspection approval, land -disturbing activities will commence. Prior to commencement of mass grading, all sediment basins and traps which are specified on the construction drawings shall be constructed. Likewise, all required diversion ditches called for on the plans shall be installed to carry sediment to the intended basin or trap for treatment. Complete construction of the improvements to the existing stormwater pond are not required to be completed before the pond is used as temporary sediment basin #2, as this pond has significantly more than the minimum characteristics required by sediment basins in its current state. Other Considerations Sediment basins will be located and sized as indicated on the erosion control plans. A measuring device must be installed in all basins to represent the amount of sediment accumulated and indicate when basin maintenance will be required. Sediment basins will utilize diversion ditches to capture overland and concentrated runoff flows. If the ditches become damaged, it is the contractor's responsibility to restore it by the end of each workday to ensure proper functionality. Temporary culvert pipes will be installed under any construction roads to allow water flow to continue to intended basins. Throughout the project, maintenance of all erosion control devices will be the responsibility of the contractor. The contractor will perform daily inspections of the performance of the erosion control devices. Any damaged or malfunctioning devices will be repaired immediately. The contractor will report any performance discrepancies to the Engineer for possible modification. Stormwater discharge outfalls (SDOs) will be inspected by the contractor in accordance with NC General Statues and DENR requirements. Inspections will be performed by the contractor after each storm event of one-half an inch or greater, with one weekly inspection minimum. DENR standard inspection reports will be prepared, signed and copies provided to the owner, architect, and engineer, by the contractor. Total area denuded at any time on the project site will be limited to reduce potential for erosion. Any areas left idle for 14 days will be temporarily stabilized by seeding. Any soil stockpiles will be stabilized at the end of each day. As portions of the project are completed, surfaces will be permanently stabilized. Upon completion of the remaining site work, grades will be restored and surfaces landscaped and permanently stabilized. Basins 3 & 6 on erosion control drawings will be excavated to their finished grade and will remain in service as a dry detention pond (sediment basin #1) and as a stormwater detention pond (sediment basin 42). An inspection will be scheduled with NCDENR. Upon approval, the remaining perimeter temporary erosion control devices and inlet protection will be removed. Riser Sediment Basin Design Worksheet Reference NC Erosion and Sediment Control Manual Job Name: UNCW Privatized Housing Job Number: C4021 Date: 2/24/2005 Designer: Steve Thomas, PE Description: Riser Sediment Basin PSD-1 Calculate peak inflow from 2, 10 & 25-year storms (1) Use Kirpich Equation to calculate Time of Concentration (See Bureau of Reclamation, 1974) Tc = (K/128)'(L3/H)03a5 K Value Overland flow on grassed surfaces: 2.0 Overland flow on paved surfaces: 0.4 Channel flow in natural channels- 1.0 Channel flow in mixed urban setting: 1.1 Channel flow in paved pipes or channels. 0.2 K 1.1 L. 1271 ft. H: 995 ft. Tc: 13.66 minutes Tc: 13.66 minutes (2) Compute Intensity Note. Values listed below are for the Raleigh -Durham IDF curves Return Period 9 h Intensity(in/hr) 2 171 24 4.54 10 252 30 5.77 25 300 32 6.57 (3) Calculate Rational C (4) Compute flows Description of Surface C Value Area (acres) Grassy Areas: 0.35 0.39 Wooded Areas: 0.2 0.30 Disturbed Areas: 0.5 4.71 Impervious Areas: 0.95 0 Total 5.4 acres Combined Rational C: 0.47 Return Period Flow (cfs) 2 11.59 10 1473 25 1677 1 OF 2/24/2005 Calculate the required sediment storage for the pond Disturbed Area = 4.71 acres Using 1800 CF/AC'YR (NC Erosion and Sediment Control Manual) Required Sediment Storage = 8478 CF Calculate the stage -storage function for the pond Contour feet Stage feet Rectangular Basin Dimensions Contour Area SF Average Contour Area SF Incremental Contour Volume CF Accumulated Contour Volume CF Estimated Stage feet Length ft Width ft 0 23.5 0.0 0 24.0 0.5 3069 1535 767 767 0.50 25.0 1.5 9257 6163 6163 6930 152 26.0 2.5 14573 11915 11915 18845 2.52 27.0 3 5 18081 16327 16327 35172 3.46 Ke = 3047.3 b = 1.9722 Enter Ks and b values from the graph of storage vs. stage shown on the next page Ks = Constant of power equation b = Exponent of power equation 2 OF 5 2/24/2005 Design pond maximum sediment storage and design cleanout level Sediment cleanout level is 1/2 of the design volume of the basin, referenced to the top of the riser. Design sediment volume = 8478 CF Top of riser set at stage = 1.68 feet 1.6B and EL= 25 30 feet Check Required Surface Area = 0 01'Qi (At Top of Riser) Area at Top of Riser = 9952 SF Area Required = 0.116 acres = 5047 SF Area OK? OK Therefore, sediment cleanout mark set at volume = 4239 CF and stage = 1.18 feet EL= 24.68 feet Check length to effective width ratio Check effective flow length vs effective flow width at principal spillway elevation. Length to width ratio = (Length) /( Effective width), should be greater than two (2). Effective Width (We) = A L A= Surface area at principal spillway crest A= 9952 SF L = Length of flow path from inflow to outflow L= 557 feet (Must be Interpolated) Effective Width = 20.00 feet Length to Width ratio = 27.85 Length to width OK ? YES Determine sizes required of orincioal soillwa Basin outflow during storms will be controlled by the barrel, which must flow 0.2 cfs/acre draining to the basin, at the elevation of emergency spillway. Drainage area to basin (total) = 5.4 acres (referenced from above) Principal Spillway outflow must be at least = 1.08 CFS In order to continue with analysis, the elevation of the emergency spillway as well as the ten year design stone to the basin (Q,a) must be determined and entered. Length of the emergency spillway will be determined later. It is customary to set the emergency spillway of a riser basin such as this between one and two feet above the crest of the principal spillway. Principal Spillway Elevation = 25.30 feet (referenced from above) Emergency Spillway Elevation = 26.25 feel Ten year storm, to basin (Q,o) = 14.73 cis 3 OF 5 2/24/2005 Constant TW elevation = 26.00 feet Riser Diameter= 54 inches Barrel Diameter= 12 inches Riser Crest Elevation = 2530 feet Barrel Invert In Elevation = 2400 feet Barrel Manning's n = 0 130 Barrel Length = 94 feet Basin Riser as Riser as Barrel TW Barrel HW Basin WSEL Orifice Weir Conditions Conditions Outflow feet) (cfs) Icfs cfs ifs cfs Action? 26.25 74.64 4320 0.18 500 0.18 OK Determine sizes for emergency spillway Required flow = Q,o - oe Required flow= 14.55 cis Set lop of berm elevation = 27.80 feet In order to allow for one (1) foot of freeboard between emergency spillway water level and top of berm, weir length required equals (from weir equation): Depth = 0.55 feet Length = 6 00 feet Check freeboard between emergency spillway water level and top of berm in the twenty five year storm (Ozz). Freeboard must be greater than or equal to one-half (0.5) foot. 025: 16.77 cfs Required Flow: 16.58 cfs Peak Elevation: 27.20 ft. Freeboard: 0.60 it. OK Design riser dewatering holes Dewatering hole design per NC Sediment and Erosion Control Manual. Formula used in this calculation given on page 8.07.8 of manual. Required detention time in basin = 24 hours Orifice discharge coefficient = 0.60 (for this computation only) Total hole area required = 0.062 ft2 8.93 in' if riser witt Number= 20 Size = 0.75 inch (diameter) Hole Area provided with above perforations = 8.84 in' Estimated actual drawdown time = 24 26 hours ?r section with NCDOT #57 washed stone filter. 4 OF 5 2/24/2005 Summary of important elevations Notes : 1) Anti -Flotation block must be sized outside this worksheet. 2) Design trash rack, or anti -vortex device / trash rack outside this worksheet. 3) Design velocity dissipator for barrel for design flow through principal spillway. 4) Fence and warning signs to be erected whenever necessary. 5) Constructed height of berm should be 10% greater than design height to allow for settlement of bens Design height is minimum. 6) Basin sideslopes should not be steeper than 2.5:1 5 OF 5 2/24/2005 Riser Sediment Basin Design Worksheet Reference* NC Erosion and Sediment Control Manual Job Name: UNCW Privatized Housing Job Number: C4021 Date: 2/24/2005 Designer: Steve Thomas, PE Description: Riser Sediment Basin #SD-2 Calculate peak inflow from 2, 10, & 25-year storms (1) Use Kirpich Equation to calculate Time of Concentration (See Bureau of Reclamation, 1974) To= (K/128)'(L3/H)03e5 K Value Overland flow on grassed surfaces: 2.0 Overland flow on paved surfaces 0.4 Channel flow in natural channels: 1.0 Channel flow in mixed urban setting: 1.1 Channel flow in paved pipes or channels: 0.2 K: 0.75 L: 1700 H: 18 To: 10.37 minutes Tc: 10.37 minutes (2) Compute Intensity Note: Values listed below are for the Raleigh -Durham OF curves Return Period 9 In Intensity (in/hr) 2 171 24 4.98 10 252 30 6.24 25 300 32 7.08 (3) Calculate Rational C (4) Compute flows Description of Surface C Value Area (acres) Grassy Areas: 0.35 8.18 Wooded Areas: 0.2 1.40 Disturbed Areas' 0.5 8.95 Impervious Areas: 0.95 3.54 Total 22.1 acres Combined Rational C: 0.50 Return Period Flow (cfs) 2 54.63 10 68.55 25 7775 1 OF 5 2/24/2005 Calculate the required sediment storage for the pond Disturbed Area = 8.95 acres Using 1800 CF/AC'YR (NC Erosion and Sediment Control Manual) Required Sediment Storage = 16110 CIF Calculate the stage -storage function for the pond Contour feet Stage feet Rectangular Basin Dimensions Contour Area SF Average Contour Area SF Incremental Contour Volume CF Accumulated Contour Volume CF Estimated Stage feet Len th Ift) Width(it) 20.0 0.0 29839 21.0 10 33164 31502 31502 31502 1.01 22.0 2.0 36645 34905 34905 66406 1.97 23.0 3 0 40283 38464 38464 104870 2.98 24.0 4.0 44076 42180 42180 147050 4.04 250 5.0 48026 46051 46051 193101 517 26.0 6.0 52127 50077 50077 243177 6.37 27.0 7.0 Ks= 31236 b= 1.1086 Enter Ks and b values from the graph of storage vs. stage shown on the next page Ks = Constant of power equation b = Exponent of power equation Storage vs. Stage 160000 14000p y = 31236x1 1066 120000 R2 = 0.9996 100000 Beebe 60000 40000 20000 0 0.0 05 1.0 15 20 25 30 35 40 45 2 OF 5 2/24/2005 Design pond maximum sediment storage and design cleanout level Sediment cleanout level is 1/2 of the design volume of the basin, referenced to the top of the riser. Design sediment volume = 16110 CF Top of riser set at stage = 0 55 feet 0.55 and EL = 27 00 feet r Check Required Surface Area = 0.0f *02 (At Tap of Riser) Area at Top of Poser = 32453 SF Area Required = 0 546 acres = 23799 SF Area OK? OK Therefore, sediment cleanout mark set at volume = 8055 CF and stage = 0 29 feet EL= 2029 feet Check length to effective width ratio Check effective flow length vs. effective flow width at principal spillway elevation Length to width ratio = (Length) /( Effective width), should be greater than two (2). Effective Width (We) = A / L A = Surface area at principal spillway crest A = 32453 SF L = Length of flow path from inflow to outflow L = 442 feet (Must be Interpolated) Effective Width = 100 00 feet Length to Width ratio = 4.42 Length to width OK ? YES Determine sizes reauired of orincioal soiliwa Basin outflow during storms will be controlled by the barrel, which must flow 0.2 cfs/acre draining to the basin, at the elevation of emergency spillway. Drainage area to basin (total) = 22 1 acres (referenced from above) Principal Spillway outflow must be at least = 4.41 CFS In order to continue with analysis, the elevation of the emergency spillway as well as the ten year design storm to the basin (010) must be determined and entered. Length of the emergency spillway will be determined later. It is customary to set the emergency spillway of a riser basin such as this between one and two feet above the crest of the principal spillway. Principal Spillway Elevation = 27.00 feet (referenced from above; Emergency Spillway Elevation = 28.00 feet Ten year storm, to basin (oio) = 66.55 cis 3 OF 5 2/24/2005 Constant TW elevation= 2600 feet Riser Diameter= 54 inches Barrel Diameter = 15 inches Riser Crest Elevation = 27.00 feet Barrel Invert In Elevation = 26.00 feet Barrel Mammng's n = 0.130 Barrel Length = 60 feet Basin Riser as Riser as Barrel TW Barrel HW Basin WSEL Orifice Weir Conditions Conditions Outflow feet cfs cfs cfs) cfs cfs Action ? 28.00 76.58 46.65 1.17 6.92 1.17 OK Determine sizes for emergency spillway Required flow = Quo - Op Required flow = 67.38 cfs Set top of berm elevation = 29.40 feet In order to allow for one (1) foot of freeboard between emergency spillway water level and top of berm, weir length required equals (from weir equation): Depth = 0.40 feet Length = 30.00 feet Check freeboard between emergency spillway water level and top of berm in the twenty five year storm (Qzs). Freeboard must be greater than or equal to one-half (0.5) foot. Q25: 77.75 cfs Required Flow: 76.59 cfs Peak Elevation: 2B.90 ft. Freeboard: 0.50 ft. OK Design riser dewatering holes Dewatering hole design per NC Sediment and Erosion Control Manual. Formula used in this calculation given on page 8.07.8 of manual. Required detention time in basin = 24 hours Orifice discharge coefficient = 0.60 (for this computation only) Total hole area required = 0.116 ft2 16 67 in2 To provide drawdown, perforate lower half of riser with Number= 20 Size= 1 inch (diameter) Hole Area provided with above perforations = 15.71 in' Estimated actual drawdown time = 25.47 hours Cover perforated riser section with NCDOT #57 washed stone filter. 4 OF 5 2/24/2005 Summary of important elevations Notes : 1) Anti -Flotation block must be sized outside this worksheet. 2) Design trash rack, or anti -vortex device / trash rack outside this worksheet. 3) Design velocity dissipator for barrel for design flow through principal spillway 4) Fence and warning signs to be erected whenever necessary. 5) Constructed height of berm should be 10 % greater than design height to allow for settlement of berm Design height is minimum. 6) Basin sideslopes should not be steeper than 2 5:1. 5 OF 5 2/24/2005 1A b i� e �c C(7o l2Z Ku� �vai F%S 2>ci5tliiq 6o4 fv PUn14✓ ZZ"'S •off C�S���y p cue l S p/?17 sS shel�' VS IN/Y--b//�t�G Stq/ 1 GsJ� �� 2 CG25><��2�J��i SOIL 'S i 6C, va ( 2CC, ijc)44 — 4 �. 00(25 , s�c2! z�� c�, sec ��, hie a� Ace 0 A/ 5)y On �P d1aU S(�2�y 7� %XJSrnPSS rN 12�r Gf2lQfC!—G(12hck�lc,' Sidi f 4 i alto O� SIRIOIure /-O / /6� ��1 G2/lam • 111 'I L% L'G�✓ei( W i cy,yFi U • i , j . i el � L !cam 1'171/I / " C--I &V, 11 M. /C� -SeC GPr OUti� e� Sh Uc%l�� deT z, lb (,�ce, ", 2 00 f 533 = (Z40 -E 3/zq = czq d — 1 E4/ C31- Czc( X 4 ¢ 64/ J C34 (Z C31 cza ft _ C33- C2b C34 C31-CZC1 C34 CC33_CZ�i� Cat=c2ci'_' .� \ (2G e71'o 07f h),ice > A SW8 970128 Mod. (Privatized Housing @UNCW) Subject: SW8 970128 Mod. (Privatized Housing @UNCW) From: Linda Lewis <Linda.Lewis@ncmail.net> Date: Mon, 21 Feb 2005 10:00:32 -0500 To: David Boyette <dboyette@stewart-eng.com> CC: Steve Thomas <sthomas@stewart-eng.com> David: I forgot to give you a copy of the revised application form that came in as part of the 2002 plan revision for SW8 970128. The current distribution of built -upon area is as follows: Buildings 26,100 sq. ft. Streets 8,100 sq. ft. Parking 28,277 sq. ft. Sidewalk 17,900 sq. ft. Offsite 22,498 sq. ft. (From SW8 020404 new residence hall) Regardless, the total built -upon area remains the same at 102,875 sq. ft, and the permitted drainage area was 9.5 acres. I also did a little more research into the pond. I had originally thought that a pond existed prior to the development of the Honors and International housing project, but it now appears that no pond existed. They needed fill material, so they just dug the pond 2-3 times larger than necessary to meet State requriements. You may be able to add the new Privatized Housing without adding any more surface area or volume to the pond, since it's already so oversized. Also, I checked on the newer parking lots behind the Honors building. They were part of the new residence hall permitted under SW8 020404 and are treated by infiltration areas. The rest of the new residence hall under 020404 is the 22,498 Offsite area permitted under 970128. Linda I of 1 2/21/2005 10:00 AM STRUCTURAL TRANSPORTATION CIVIL STEWART ENGINEERING Meeting Minutes University of North Carolina at Wilmington Privatized Student Apartments Clark Nexsen Project #: NC409.4 SEI Project #: C4021 Meeting: State Permits through NC Department of Environment and Natural Resources A meeting for the referenced project was held at 10:00am on Tuesday November 23, 2004 in the offices of the North Carolina Department of Environment and Natural Resources (NCDENR) located at 127 Cardinal Drive Extension in Wilmington. The purpose of the meeting was to introduce the NCDENR reviewers to the project and to inquire what permits would be required. Representatives attending the meeting included: Steve Thomas, PE Stewart Engineering 919-380-8750 sthomas@stewart-eng.com Cameron Weaver NCDENR 910-395-3900 cameron.weaver@ncmaiLcom Rhonda Hall NCDENR —DWQ 910-395-3900 rhonda.hall@ncmaiLcom • Steve introduces the project to Rhonda and Cameron. • Rhonda asks if the wetlands shown on the property have been certified by the Army Corps of Engineers. — It has since been verified that the wetlands shown have been certified. • Rhonda indicates that a campus Master Plan needs to be provided to determine future needs for stormwater treatment. She indicates that she will check with Rick Shriver or Linda Lewis on this issue and let Steve know its status. • It is determined that New Hanover County will do Sediment & Erosion Control review and permitting. • Discussion of the timing of review for stormwater: o With a regular review: 60-75 review minimum $420 o With an express review 3 weeks $4000 • Classification of blue -line stream must be determined. If this stream is classified as an SA water, the existing detention pond may not be allowed to expand. This would force the use of only underground detention, infiltration basins, or bio-retention basins. Rhonda indicated that she could find out the stream classification and then let Steve know. • The "Responsible Party" for the project should be the one to apply for the permits. If it has not already been done, this classification needs to be made. • Cameron and Rhonda agree that there will likely be the need for two stormwater permits for this project; one new off -site permit and one modification of existing pond permit. • Cameron indicates that a State non -discharge permit will likely be required. Dean Huntley will be the contact for this permit. • Submitted set of plans should have an overall sheet which shows the entire property boundary. • A geotechnical report will need to be consulted to determine the infiltration coefficient of the soil. 260 Town Hall Drive, SurteG Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-cng corn STIFWART ENGINEERING INC Steve Thomas. PE Civil Project Engineer 260 Town Hall Dc, S,n, C 1 Mornsville, NC 27560 Tel 919,380.8750 Ext 138 1 Fax 919 380 8752 sthomas®stewart-eng com The outline above is the writer's understanding of the major topics and conclusions of the meeting. If this does not correspond with the understanding of anyone in attendance, please notify the writer. Submitted by: Stewart Engineering, Inc. Steve, Thovna�- Steve Thomas, PE CC: All attendees (via e-mail) Neil Sauer (via e-mail) Peter J. Aranyi (via e-mail) 260 Town Hall Drive, Suite C Morrisville, NC 27560 Tel 919.380.8750 Fax 919.380.8752 www.stewart-eng.com