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HomeMy WebLinkAboutWPO200400093 Calculations 2004-08-26 (2) STORMWATER BMP CALCULATIONS FOR ADVANCE MILLS FARM SUBDIVISION PHASE 1 July 6, 2002 REV: August 26, 2004 LOCATION: Tax Map 20 Parcel 6A1 Whitehall District, Albemarle County, Virginia OWNER: Advance Mills Land Trust, LLC 40\- 11. ` P.O. Box 8147 o� Z Charlottesville, VA 22911 • o -L7l/ TIMO Y RAY MILLER DEVELOPER: • 0402 030542 • C. W. Hurt ' 4y 195 Riverbend Road o, ".F `÷.w o Charlottesville, VA 22906 s`SIONAI_V-1G PREPARED BY: Rivanna Engineering & Surveying, PLC P. O. Box 7603 Charlottesville, VA 22906 434.984.1599 F: 434.984.8863 RESI@CSTONE.NET The Stormwater Quality BMP's for this subdivision shall be a 200' Riparian Buffer Easement along the North Fork Rivanna River. • Sort Version BMP Computations For Worksheets 2 -6 Albemarle County Water Protection Ordinance: Modified Simple Method Plan: Advance Mills Farm-Phase II Water Resources Area: Preparer TRM Date: 25•Aug-04 - Project Drainage Area Designation Rural Subdivision L storm pollutant export in pounds, L=[P(Pj)Rv/12] [C(A)2.72] Rv mean runoff coefficient, Rv=0.05+0.009(I) P] small storm correction factor,0.9 I percent imperviousness P annual precipitation,43"in Albemarle A project area in acres in subject drainage area, A'=_ 19so0` C pollutant concentration, mg/I or ppm target phosphorus f factor applied to RR - ✓ required treatment volume in cy,0.5'over imperv.area= A(I)43560(0.5/12)/27 RR required removal, L(post)-f x L(pre) %RR removal efficiency, RR100/L(post) . Impervious Cover Computation(values in feet&square feet). :Item _.._.. _....._. ._...___ ._..___... _.. ._..._.__. ... . . ;predevelopment Area post development_ Area FRoads Length Width subtotal j Length Width subtotal 0 0 0 2600 18 46800, 1 . _ ._.{ . or a - . _ .. _0:.... .. P. 0. _ 0 .__.............._.._._....___..__......_.._.......i...----...J_._.__.__.—'___._. 0' of . - 0. 46800 Driveways g1600� ____ 10; 1 15000; Length_ Width no. subtotal Dnvewa s Length Width no. subtotal , ___ ,,,__—__ _,.___.,_^,. ...,,,___ and ,___ '..,,, r--�_ ' 200! 10 1 2000 I , 01 Oj 0 0; 0 0 0 0 ..._ I. .... ...O J 150001 ... .... .... .. 0 2000. ;Parking Lots 1 2 3 4 , 1 2 3 4: 0, ) ; 0:_ 16786 0. 16786' 'Gravel areas Area ; ;Area tx0.70= ' 0; -x0.70= OI. Structures Area no subtotal 1 Area no subtotal i ._ . I_ __B00 -... 0 0 8001 - 1 0 0 • 001 800 1 800, 0 0 80. l 1500 10 15000s i -- ..... Actively-grazed pasture& Area j Area -----�_.._._...._15800. !yards and cultivated turf a 8 609 080;x 0.08= 688726.4! 8 543 494 x(Loa= 683479.52':. {Active crop land Area Area •i Ix 0 x0.25= 0; ;Other Impervious Areas I ; 0! 0 Impervious Cover —tx a .89'°1 1 9GM l(pre) l(post) L Rv(post)' V New Development(For Development Areas,existing Impervious cover a 20%) C f I re Rv re I L re L(post) RR , %RR Area Type r "040 1 00 is *209'' 0 12 28507 76 90 3 89 ` F `'7796'� Development Area r 57 157.79 121 78 s „ 4135 f€ 1•00 0 (; 0.12 I 75. _g :5%j Drinking Water Watersheds `, i�y,n` .0.r�: ..,, 1 79 9017I 4,37( 5%' OtherRuralLand *min.values Redevelopment(For.Development Areas,existing Impervious cover>20%) i C f 1(pre)* " Rv(pre) i L(pre) L(post) ! RR /°RR Area Type 7 j0 70 "' + 0 9D , 20%1 0.23 : 279.57 157.79 I -93.82 " 59% Development Area i st 0 35 .. 0 85 , , �0%5 _0.12 I _75.07 78.90 I 15.09_ 19% Drinking Water W_a_tershed_s __ _ Lr „0 40 , oet ";: rim 0.121 85.79 90.17 i.. 17.24 j hPa`r19%: Other Rural Land -Interim Manual,Page 70 rev. 16 Feb 1998 GEB