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HomeMy WebLinkAboutSDP200400057 Calculations 2005-01-25 OW Enterprises II 4686 Garth Road♦Crozet,Va.22932 (434)823-2815 (434)823-5102(fax) nflsil6Wuno.com January 24, 2005 Mr. Glenn Brooks Department of Engineering 401 McIntire Road Charlottesville, Va. 22902-4596 Re: Snow's Offices and Storage Yards Dear Glenn: Attached you will find the routing calculations for the SWM basin for the referenced project. I've also included the cross sections showing the area at each elevation. Thanks for your assistance. t70247;eir(74---- David C. Wyant, P. E. RECEIVED JAN 25 2005 COMMUNITY DEVELOPMENT ROUTING Snow's Offices and Yards (4.70 ac.) 1. Drop inlet grate(24 inches in diameter) is weir. 2. Length of weir is 6.3 ft. 3. Length of descending leg(min) (=1.67*TC) ********************************* HYDRO ********** ********************************* VERSION 2.2 ********** Pre Development Area Number C Area(ac) CA 1 0.250 4.700 1.175 Weighted Totals: 0.250 4.700 1.175 Time of concentration = 18 min Period Intensity Peak Flow (years) (in/hr) (cfs) 2 3.07 3.61 5 3.80 4.46 10 4.25 4.99 25 5.05 5.93 50 5.57 6.54 100 6.20 7.29 Hydrograph(Pre) Time of concentration= 18.0 min Storm duration= 18.0 min Length of descending leg(min) (=1.67*TC) Time Q2 Q5 Q10 Q25 Q50 Q100 (min) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) 2.0 0.40 0.50 0.55 0.66 0.73 0.81 4.0 0.80 0.99 1.11 1.32 1.45 1.62 6.0 1.20 1.49 1.66 1.98 2.18 2.43 8.0 1.60 1.98 2.22 2.64 2.91 3.24 10.0 2.00 2.48 2.77 3.30 3.64 4.05 12.0 2.40 2.98 3.33 3.96 4.36 4.86 14.0 2.81 3.47 3.88 4.62 5.09 5.67 16.0 3.21 3.97 4.44 5.27 5.82 6.48 18.0 3.61 4.46 4.99 5.93 6.54 7.29 (Peak Discharge) 20.0 3.37 4.17 4.66 5.54 6.11 6.80 22.0 3.13 3.87 4.33 5.14 5.67 6.32 24.0 2.89 3.57 4.00 4.75 5.24 5.83 26.0 2.65 3.28 3.66 4.35 4.80 5.35 28.0 2.41 2.98 3.33 3.96 4.37 4.86 30.0 2.17 2.68 3.00 3.56 3.93 4.38 32.0 1.93 2.39 2.67 3.17 3.50 3.89 34.0 1.69 2.09 2.34 2.78 3.06 3.41 36.0 1.45 1.79 2.00 2.38 2.63 2.92 38.0 1.21 1.49 1.67 1.99 2.19 2.44 40.0 0.97 1.20 1.34 1.59 1.75 1.95 42.0 0.73 0.90 1.01 1.20 1.32 1.47 44.0 0.49 0.60 0.67 0.80 0.88 0.98 46.0 0.25 0.31 0.34 0.41 0.45 0.50 48.0 0.01 0.01 0.01 0.01 0.01 0.01 ********************************* ROUT *********** ********************************* VERSION 5.4 *********** (Types: 1:Weir;2:Pipe; 3:Riser) Structure 1 1: Type 1: Weir Weir: 2: Elevation(ft) 589.0 3: Length(ft) 6.28 4: Coefficient 3.33 Riser: 5: Elevation(ft) 0.00 6: Inlet Area(sf) 0.00 7: Inlet Perimeter(ft) 0.00 8: Orifice Elevation(ft) 0.00 9: Orifice Diameter(in) 0.00 10: Orifice Elevation(ft) 0.00 11: Orifice Diameter(in) 0.00 12: Orifice Elevation(ft) 0.00 13: Orifice Diameter(in) 0.00 Pipe: 14: Invert Elevation(ft) 0.00 15: Diameter(in) 0.00 16: Orifice Diameter(in) 0.00 17: Length(ft) 0.00 18: Manning's n 0.000 19: Slope(ft/ft) 0.000 20: Entrance Loss Coefficient 0.0 Surface: 21: Initial Elevation(ft) 585.0 Basin Geometry(Cross-sectional Areas Or Volumes At Given Elevations) Section Elevation Area (ft) (sq ft) 1 585.0 2250 2 587.0 2870 3 589.0 3490 4 591.0 4248 5 592.0 4696 2-yr. Event(Pre)for Snow's Offices/Storage Site Time Inflow Weir Total Elev Storage (min) (cfs) (cfs) (cfs) (ft) (cu ft) 0.0 0.00 0.0 0.00 585.00 0.00 2.0 0.40 0.0 0.00 585.01 22.49 4.0 0.80 0.0 0.00 585.04 90.07 6.0 1.20 0.0 0.00 585.09 202.89 8.0 1.60 0.0 0.00 585.16 361.10 10.0 2.00 0.0 0.00 585.25 564.90 12.0 2.40 0.0 0.00 585.35 814.46 14.0 2.81 0.0 0.00 585.48 1,109.97 16.0 3.21 0.0 0.00 585.62 1,451.61 18.0 3.61 0.0 0.00 585.77 1,839.56 20.0 3.37 0.0 0.00 585.93 2,237.07 22.0 3.13 0.0 0.00 586.07 2,607.28 24.0 2.89 0.0 0.00 586.20 2,950.15 26.0 2.65 0.0 0.00 586.32 3,265.67 28.0 2.41 0.0 0.00 586.43 3,553.82 30.0 2.17 0.0 0.00 586.52 3,814.60 32.0 1.93 0.0 0.00 586.61 4,047.99 34.0 1.69 0.0 0.00 586.68 4,254.00 36.0 1.45 0.0 0.00 586.75 4,432.61 38.0 1.21 0.0 0.00 586.80 4,583.84 40.0 0.97 0.0 0.00 586.84 4,707.69 42.0 0.73 0.0 0.00 586.88 4,804.18 44.0 0.49 0.0 0.00 586.90 4,873.30 46.0 0.25 0.0 0.00 586.92 4,915.09 r 10-yr.Event(Pre)for Snow's Offices/Storage Site Control: RW=Riser acting as a weir(DI acts as weir with 6.28 ft. of length) Time Inflow Weir Total Elev Storage (min) (cfs) (cfs) (cfs) (ft) (cu ft) 0.0 0.00 0.0 0.00 585.00 0.00 2.0 0.55 0.0 0.00 585.01 31.16 4.0 1.11 0.0 0.00 585.06 124.81 6.0 1.66 0.0 0.00 585.12 281.25 8.0 2.22 0.0 0.00 585.22 500.79 10.0 2.77 0.0 0.00 585.34 783.74 12.0 3.33 0.0 0.00 585.48 1,130.44 14.0 3.88 0.0 0.00 585.65 1,541.19 16.0 4.44 0.0 0.00 585.84 2,016.31 18.0 4.99 0.0 0.00 586.06 2,582.63 20.0 4.66 0.0 0.00 586.28 3,135.78 22.0 4.33 0.0 0.00 586.47 3,650.86 24.0 4.00 0.0 0.00 586.64 4,127.84 26.0 3.66 0.0 0.00 586.80 4,566.73 28.0 3.33 0.0 0.00 586.94 4,967.51 30.0 3.00 0.0 0.00 587.06 5,330.18 32.0 2.67 0.0 0.00 587.17 5,654.73 34.0 2.34 0.0 0.00 587.27 5,941.18 36.0 2.00 0.0 0.00 587.35 6,189.52 38.0 1.67 0.0 0.00 587.42 6,399.77 40.0 1.34 0.0 0.00 587.48 6,571.93 42.0 1.01 0.0 0.00 587.53 6,706.04 44.0 0.67 0.0 0.00 587.56 6,802.12 46.0 0.34 0.0 0.00 587.58 6,860.19 ********************************* HYDRO ********* ********************************* VERSION 2.2 ********* Post Development Area Number C Area(ac) CA 1 0.250 2.490 0.623 2 0.900 2.210 1.989 Weighted Totals: 0.556 4.700 2.612 Time of concentration= 5 min Period Intensity Peak Flow (years) (in/hr) (cfs) 2 5.40 14.10 5 6.35 16.58 10 7.10 18.54 25 8.00 20.89 50 8.90 23.24 100 9.60 25.07 Hydrograph(Post) Time of concentration= 5.0 min Storm duration=5.0 min Time Q2 Q5 Q10 Q25 Q50 Q100 (min) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) 0.0 0.00 0.00 0.00 0.00 0.00 0.00 1.0 2.82 3.32 3.71 4.18 4.65 5.01 2.0 5.64 6.63 7.42 8.36 9.30 10.03 3.0 8.46 9.95 11.12 12.54 13.95 15.04 4.0 11.28 13.27 14.83 16.71 18.59 20.06 5.0 14.10 16.58 18.54 20.89 23.24 25.07 (Peak Discharge) 6.0 12.41 14.60 16.32 18.39 20.46 22.07 7.0 10.72 12.61 14.10 15.89 17.68 19.07 8.0 9.04 10.63 11.88 13.39 14.89 16.06 9.0 7.35 8.64 9.66 10.88 12.11 13.06 10.0 5.66 6.65 7.44 8.38 9.32 10.06 11.0 3.97 4.67 5.22 5.88 6.54 7.06 12.0 2.28 2.68 3.00 3.38 3.76 4.05 13.0 0.59 0.70 0.78 0.88 0.97 1.05 ********************************* VERSION 5.4 ******** 2-yr. Event(Post)for Snow's Offices/Storage Site Control: RW=Riser acting as a weir Time Inflow Weir Total Elev Storage (min) (cfs) (cfs) (cfs) (ft) (cu ft) 0.0 0.00 0.0 0.00 585.00 0.00 1.0 2.82 0.0 0.00 585.04 79.30 2.0 5.64 0.0 0.00 585.14 318.42 3.0 8.46 0.0 0.00 585.31 719.10 4.0 11.28 0.0 0.00 585.56 1,311.84 5.0 14.10 0.0 0.00 585.87 2,073.99 6.0 12.41 0.0 0.00 586.17 2,870.07 7.0 10.72 0.0 0.00 586.43 3,564.65 8.0 9.04 0.0 0.00 586.64 4,131.63 9.0 7.35 0.0 0.00 586.81 4,601.12 10.0 5.66 0.0 0.00 586.94 4,973.36 11.0 3.97 0.0 0.00 587.04 5,248.56 12.0 2.28 0.0 0.00 587.10 5,426.96 ********************************* VERSION 5.4 ******** 10-yr. Event(Post)for Snow's Offices/Storage Site Control: RW=Riser acting as a weir Time Inflow Weir Total Elev Storage (min) (cfs) (cfs) (cfs) (ft) (cu ft) 0.0 0.00 0.0 0.00 585.00 0.00 1.0 3.71 0.0 0.00 585.05 104.35 2.0 7.42 0.0 0.00 585.18 419.48 3.0 11.12 0.0 0.00 585.42 976.16 4.0 14.83 0.0 0.00 585.74 1,755.59 5.0 18.54 0.0 0.00 586.13 2,757.74 6.0 16.32 0.0 0.00 586.52 3,804.47 7.0 14.10 0.0 0.00 586.85 4,717.75 8.0 11.88 0.0 0.00 587.12 5,497.61 9.0 9.66 0.0 0.00 587.33 6,117.70 10.0 7.44 0.0 0.00 587.49 6,609.17 11.0 5.22 0.0 0.00 587.61 6,972.40 12.0 3.00 0.0 0.00 587.69 7,207.80 ********************************* VERSION 5.4 ********** 100-yr. Event(Post)for Snow's Offices/Storage Site Control: RW=Riser acting as a weir Time Inflow Weir Total Elev Storage (min) (cfs) (cfs) (cfs) (ft) (cu ft) 0.0 0.00 0.0 0.00 585.00 0.00 1.0 5.01 0.0 0.00 585.06 141.25 2.0 10.03 0.0 0.00 585.26 592.83 3.0 15.04 0.0 0.00 585.57 1,345.63 4.0 20.06 0.0 0.00 585.99 2,399.59 5.0 25.07 0.0 0.00 586.50 3,754.58 6.0 22.07 0.0 0.00 587.01 5,169.84 7.0 19.07 0.0 0.00 587.43 6,404.69 8.0 16.06 0.0 0.00 587.77 7,459.16 9.0 13.06 0.0 0.00 588.03 8,302.12 10.0 10.06 0.0 0.00 588.24 8,969.92 11.0 7.06 0.0 0.00 588.39 9,463.29 12.0 4.05 0.0 0.00 588.49 9,782.92 Summary of Routing(Snow's Offices/Storage Site) Period Total (cfs) Elev. (Ft.) Storage (Cu. Ft.) 2-yr. 0 587.10 5427 10-yr. 0 587.69 7208 100-yr. 0 588.49 9783 5 Pion k Cr000 ad BloWtor $ to 00' Ito to 24 in. Sur I Slay. s80' ♦ 242o 5p' Kiev. lot k. .9180 SP Elev. 587' A - 2870 SF :1 elope (m) Eleev. 588' A - 2580 OF S1ev. 58W - - r!. 1 :1 Arr���r ll(� PVC Pips 20111 dope ion t Elev. 581.5' 4• Non-Portaeated PIC Pipe !1% dope Nate: 1. Unifordrain Gonlol end.136n.) psou.odenndralstor Lat Mulch i" Short Version BMP Computations For Worksheets 2-6 Albemarle County Water Protection Ordinance: Modified Simple Method Plan: Snow's Storage Yard and Offices Water Resources Area: Development Area Preparer: David Wyant,P.E. Date: 05-Dec-02 Project Drainage Area Designation Upper Portion of Site L storm pollutant export in pounds, L=[P(Pj)Rv/12][C(A)2.72] Rv mean runoff coefficient, Rv=0.05+0.009(1) Pj 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= 4.70 ac. C pollutant concentration,mg/I or ppm target phosphorus f factor applied to RR ✓ required treatment volume in cy,0.5"over impery 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 pre-development Area post-development Area Roads Length Width subtotal Length Width subtotal 0 0 0 0 0 0 0 0 0 0 0 0 0 Driveways Length Width no. subtotal Length Width no. subtotal and walks 0 0 0 0 0 0 0 0 0 34,103 34103 Parking Lots 1 2 3 4 1 2 3 4 0 0 __ 0 Gravel areas Area Area x 0.70= 0 33,600 x 0.70= 23520 Structures Area no. subtotal Area no. subtotal 0 0 0 0 0 0 0 0 0 0 0 0 _0 0 25,200 25,200 Actively-grazed pasture& Area_ Area yards and cultivated turf 204,750 x 0.08= 1638.0 108,647 x 0.08= 8,692 Active crop land Area Area x0.25= 0 x0.25= 0 Other Impervious Areas 3200 Impervious Cover - 8% 46% l(pre) l(post) Rv(post) V 0.46 145.3 New Development(For Development Areas,existing imperviou_s cover<=20%) C f I(pre)4' Rv(pre) L(pre) L(post) RR %RR Area Type s -0.70,',.-;,.",=1t00, .4-<`20% 0.12 3.46 13.28 9.82 74% Development Area °_0 35:<'`=- ''1 00. - 0%0 0.12 0.00 0.00 0.00 Drinking Water Watersheds ''0:40 ---"r;-',1:00`'.4 -;1% 0.12 0.00 0.00 0.00 Other Rural Land *min.values Redevelopment(For Development Areas,existing impervious cover>20%) _ C f I(pre)* Rv(pre) L(pre) L(post) RR %RR Area Type 0:70' 0 90'-,`.y:- 20% 0.23 0.00 0.00 0.00 _ Development Area `0:35 ' ,_,'0'85= ;�0% 0.12 0.00 0.00 0.00 Drinking Water Watersheds .':040 0.85 1%0 0.12 0.00 0.00 0.00 - Other Other Rural Land Interim Manual, Page 70 rev 16 Feb 1998 GEB