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HomeMy WebLinkAboutSW8040323_HISTORICAL FILE_20041014STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW8 O`} p 323 DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS HISTORICAL FILE ❑ COMPLIANCE EVALUATION INSPECTION DOC DATE 'ZoOLAiDIy YYYYMMDD �OFWATF9Q Michael F. Easley, Governor �O G William G. Ross, Jr., Secretary 01 7 North Carolina Department of Environment and Natural Resources O Y Alan W. Klimek, P.E. Director Division of Water Quality October 14, 2004 Mr. Jon Vincent, Member/Manager Tri-Coast Properties, LLC 1508 Military Cutoff Road, Suite 302 Wilmington, NC 28403 Subject: Approved Plan Revision Shallotte Shops Stormwater Project No. SW8 040323 Brunswick County Dear Mr. Vincent On July 19, 2004, the Wilmington Regional Office received a plan revision for Stormwater Management Permit Number SW8 040323, Shallotte Shops, located at 4501 Main Street in Shallotte, NC. The revisions include the reduction in overall built - upon area due to the deletion of a building, and the reconfiguration of the parking area. The remaining built -upon area of 10,891 square feet has been set aside for future development. It has been determined that a formal permit modification is not required for the proposed changes. We are forwarding you an approved copy of the revised plans for your files. Please replace the old approved plan sheet with the new one, and replace the old page 2 of the application with the new one, enclosed. Please be aware that all terms and conditions of the permit issued on April 12, 2004, remain in full force and effect. Please also understand that the approval of this revision to the approved plans for the subject State Stormwater Permit is done on a case -by -case basis. Any other changes to this project must be approved through this Office prior to construction. If you have any questions concerning this matter, please do not hesitate to call me at (910) 395-3900. Sincerely, Linda Lewis Environmental Engineer RSS\arl: S:\WQS\STORMWAT\REVISION\040323.oct04 cc: Mike Hoffer, Tripp Engineering Town, of Shallotte Building Inspections —..�. Linda' Lewis W ilmi ngton-Regional Office Centfal Files North Carolina Division of Water Ci ity 127 Cardinal Drive Extension Phone (910) 395-3900 Customer Servicel-877£23-6748 Wilmington Regional Office :' Wilmington, NC 28405-3845 FAX (919) 733-2496 Internet: h2o.encOnestate.nc.us NorthCarolina An Equal Opportunity/Affirmative Action Employer— 50% Recycled110% Post Consumer PaperNaturally 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): CAMA Major X Sedimentation/Erosion Control 404//401 Permit NPDES Stormwater Information on required state permits can be obtained by contacting the Customer Service Center at 1-877-623-6748. 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. Stormwater will be treated with wet detention 2. Stormwater runoff from this project drains to the Cape Fear River basin. 3. Total Project Area: 2.04 acres 5. How many drainage basins does the project have? 1 4. Project Built Upon Area: 72.2 %. 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 air ;,y <. K t Dr'aina a Basm`1 ' v k. g p y , $Drainage Basin 2e ; Receiving Stream Name Shallotte River Receiving Stream Class SC HQW Drainage Basin Area 2.04 ac Existing Impervious * Area - Proposed Impervious * Area 1.47 ac % Impervious* Area (total) 72.2% Impery�ous�aSurface Area r IDrainage BastnLr�''`' Y''��*q 'kDramageBasin 2 °"y On -site Buildings 11,286 sf On -site Streets - On -site Parking 39,200 sf On -site Sidewalks 2,650 sf Other on -site (future) 10,891 sf Off site Total: E=64,027 sf E_ * Impervious area is defined as the built upon area including, birt not limited to, buildings, roads, parking areas sidewalks, gravel areas, etc. Form SWU-101 Version 3.99 Page 2 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): CAMA Major X Sedimentation/Erosion Control _ 404H401 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. Stormwater will be treated with wet detention 2. Stormwater runoff from this project drains to the Cape Fear River basin. 3. Total Project Area: 2.04 acres 5. How many drainage basins does the project have? 1 4. Project Built Upon Area: 72.2 %. 6. Complete the following information for each drainage area. If there are more than two drainage areas in the project, attach an additional sheet with the information for each area provided in the same format as below. Basin Information Drainage Basin 1 Draiiage Basin 2 Receiving Stream Name Shallotte River Receiving Stream Class SC HQW Drainage Basin Area 2.04 ac Existing Impervious * Area - Proposed Impervious * Area 1.47 ac % Impervious* Area (total) 72.2% "Ihipervious *`Surface'Area " I Drainage Basin'l '` 'Drainage Basin 2 On -site Buildings 10,032 sf On -site Streets - On -site Parking 43,480 sf On -site Sidewalks 3,016 sf Other on -site (future) 7,499 sf Off -site - Total: E=64,027 sf E= * Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas sidewalks, gravel areas, etc. Form SWU-101 Version 3.99 Page 2 of Shallotte Shops Subject: Shallotte Shops From: Linda Lewis <Linda.Lewis@ncmai1.net> Date: Thu, 30 Sep 2004 11:40:02 -0400 To: Michael Hoffer <trippeng@ec.rr.com> Mike: Forget about the permit modification. I found a condition in the original permit that requires that any future development areas be permitted prior to development, so we are covered. I still need a revised page 2 of the application, though. Thanks, Linda 1 of 1 10/4/2004 3:59 PM nShallotte Shops SW8 040323 Subject: Shallotte Shops SW8 040323 From: Linda Lewis <Linda.Lewis@ncmail.net> Date: Thu, 30 Sep 2004 11:09:44 -0400 To: Michael Hoffer <trippeng@ec.rr.com> Mike: Good news! I found the file with your plan revision (aka modification) attached. Please send in (fax is fine) a revised page 2 of the permit to reflect the changes in the distribution of the BUA. The building and parking amounts have decreased, and you have provided for a future amount that was not there before. I haven't determined yet if the permit needs to be rewritten to reflect the future BUA since none was originally accounted for. I'll,have to get back to you on that. Please go ahead and send in the revised page 2. If I need to rewrite the permit, I'll request the modification fee at a later date. Thanks, Linda C S I of 1 10/4/2004 3:59 PM „_ TRIPP ENGINEERING, P.C. 4iW Chestnut street Wilmington, North Carolina 28401 Phone: (910) 763-5100 • FAX: (910) 763-5631 July 16, 2004 NCDENR Division Water Quality 127 Cardinal Drive Wilmington, NC 28405-3845 Attn: Ms. Laurie Munn Re: Shallotte Shops Project No. SW8 040323 TE 03128 Dear Laurie: JUL 1 q 2004 I'm writing to request a modification to existing permit No. SW8 04023. Due to town zoning requests and fire marshal concerns, the rear building has been removed from the site plan, and the parking areas reconfigured accordingly. Also, the property lines have shifted. Please note that the drainage area, impervious surfaces and pond dimensions have not changed. All of your original concerns remain addressed and the outfall location is unchanged. Revised calculations and narrative are attached. Please review for approval and contact us with any questions, comments or if you need additional assistance. Thank you. Sincerely, Tripp Engineering, P.C. 01. . �, �14 Michael Hoffer MBH:dcb Enc. 07/13/04 Stormwater Narrative Shallotte Shops Brunswick County, NC TE03128 Shallotte Shops is a 2.04-acre existing vacant tract proposed for a commercial shopping center. Impervious areas include 11,286 SF of building, 2,650 SF of sidewalk and 39,200 SF of asphalt. 10,891 SF is allocated for future impervious area, creating a total lot impervious area of 64,027 SF. The total percent impervious is 72.2%. The project will be treated by wet detention. The detention pond will be designed to meet the State's P and the County's I0-year pre -post requirement. Outflow from the pond drains to the Shallotte River, classification SC HQW. RECEIVED JUL.19 2004 pit. 5004v3Z3 7/13/2004 Shallotte Shops 03128 MBH Stormwater Calculations Total Draina e Area s . ft. acres 88,652 1 2.04 Impervious Area Land Use sq. ft. acres buildings 11,286 0,26 asphalt 39,200 0.90 concrete 2,650 0.06 future 10,891 0.25 Tota I 64,027 1.47 Stormwater Calculations: Time of Concentration Hydraulic Length (L) = 630 ft. hange in Height (H) = 4 ft. TO = (L, /H).Jeo / 128 = 7.84 min. Flow for 10 year, 6 hour Storm (Qjo) QPRE _ (CPRE) x (110) x (Area) = 3.21 cfs QPosT = (CPosT) x (1i0) x (Area) 9.74 cfs Detention Pond Design: Pond Size: Elevation (ft.) Surface Area (Sq. ft.) Normal Pool 31.00 4,615 Flood Pool 32.10 51710 Top of Bank 35.00 7,988 Bottom of Pool 26.00 254 Total Provided Storage Volume: Vol. _ [(Normal pool SA + Flood Pool SA) / 2] x (F.P. elev - N.P. elev.) 5,679 cu.ft. % impervious = 0.722 = 72.2% say 73.0% CPRE = 025 CPOST= (% imp .)(.95)+(1%imp.)(.25) = 0.76 lio = 6.30 in/hr log = 7.79 in/hr Flow for 50 year, 6 hour Storm (Qso) QPRE _ (CPRE) x (110) x (Area) = 3.96 cfs QPosT= (CPOST) x (I,0) x (Area) = 12.05 cfs State Surface Area Requirement at normal pool Pond side slopes = 3 :1 Depth below N.P. = 5 ft. SA/DA = 0.0444 (Chart for 90% TSS Removal for Wet Detention Pond without Vegetative Filter) Required SA = (SA/DA) x (Total Drainage Area) 3,936 s . ft. State Volume Requirement for Storage of first 1" runoff: Rv = .05+.009(Percent Impervious) 0.7000056 in/in = 5171 cu.ft. C A R p �xxliz RECEIVED ;QO oy; JUL 112004 = a SEAL y; t»�a •'a DWQ lljF�GI NEQ �Q PROD# S��,gogo323 ��iii �REGOA o` y °j�7nnnnnnta`0� of 03128-Pond 1 of 2 7/13/2004 MBH Pond Volume: Bottom SA = 254 sq. ft Normal Pool SA = 4,615 sq. ft. Vol. _ [(N.P. SA+ Bott, = 12,173 cu.ft. Forebav: Required Volume Vol. = 20% of storage volume 2,435 cu.ft. Provided Volume Shallotte Shops Stormwater Calculations 171QNSM-! bottom SA = 300 sq, ft. Normal Pool SA = 1,430 sq. ft. Vol. _ [(N.P. SA + Bottom SA) / 2] x (N.P. el. - Bottom el.) = 2,595 cu.ft. I = 3 ft. Outlet Structure Design: Flow for 2-day drawdown: for 1st 1" of stormwater, Q = Required Vol. /172,800 sec. (2-days 0.030 cfs nequirea Area or Hipe Tor 2-dav drawdown A= Q/ [Cd x SQRT(2 x g x h)] Cd = 0.6 g = 32.2 ft./sz h = (F.P. elev.- N.P. elev.) /2 0.55 ft. A = 0.0084 sq. ft. Diameter of Pipe for 2-dav drawdown DIA. = SQRT[(A x 4) / pi] 0.1033 ft. 1.24 in. Use 1.0" orifice Outlet Structure Check: Using a 4' x 4' Basin, Perimeter (L) = 16 ft. M C = (% imp.)(95) + (1 % imp.)(25) 0.76 1 = 6.30 in. for a 10 yr. Storm A = 2.04 Acres 9.74 cfs Flow for 5-day drawdown: 7for 1st 1" of stormwater, Q = Required Vol. /432,000 sec.(5-days) = 0.012 cfs megwrea Area or Hipe Tor J-dav drawdown 03128 A= Q/[Cd xSQRT(2xgxh)] Cd = 0.6 g = 32.2 ft./sz h = (F. P. elev. - N. P. elev.) / 2 = 0.55 ft. A = 0.0034 sq. ft. Diameter of Pipe for 5-day drawdown: DIA. = SQRT[(A x 4) / pi] = 0.0653 ft. = 0.78 in. Q= CwxLxH H= [Q/(CwxL] Cw = 3 0.35 ft. Peak elevation = flood pool elevation + H = 32.45 ft. 03128-Pond 2 of 2