The URL can be used to link to this page

Home My WebLink AboutWPO202000054 Calculations 2020-11-24Monticello Burial Ground for Enslaved People COUNTY OF ALBEMARLE, VIRGINIA DESIGN CALCULATIONS & NARRATIVE WP02020 NOVEMBER 23, 2020 TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Bryan Cichocki, PE Timmons Group 608 Preston Ave, Suite 200 Charlottesville, VA 22903 434.327.1688 iyan D. Cichocki 7z Uc. No.53741 1 1/2,/?cJ rm Table of Contents Section Title Project Narrative 2 Virginia Runoff Reduction Method Worksheet Summary Pre -Developed Hyrdaflow Calculations 4 Post -Developed Hydraflow Calculations Project Narrative: The purpose of this project is the beautify and enhance the screening around the burial ground. Existing pathways in the area are deteriorating and in need of maintenance or replacement. The project is providing new paths around the burial ground with new seating areas and replacing the path leading towards the visitor center for maintenance. Some area of existing parking is being removed to increase the buffer space around the burial ground and will be replanted. All existing drainage divides have been maintained and most of the area of work is a sheet flow condition. Stormwater Management: Water Quality The water quality for this project is quite simple as the reduction in impervious area with the removal of the parking area more than meets the requirement. The area of parking that is being removed and replanted is considered as forest in the proposed condition, however that is not necessary as it only subtracts another-0.02lb/yr. Also the path leading towards the visitor center that is anticipated to be replaced as maintenance by removing the asphalt surface, keeping the stone subbase and putting down a katka surface is counted in the impervious numbers to be conservative. Water Quantity The water quantity is also met by the reduction of impervious area with the removal of the parking lot area. Compliance with energy balance and flood protection has been demonstrated on sheet C6.0 of the WPO plan. VIRGINIA RUNOFF REDUCTION METHOD WORKSHEET DEQ Virginia Runoff Reduction Method Re -Development Compliance Spreadsheet - Version 3.0 0 20 11 BM Standards and Specifications 02013 Draft BM Standards and Specifications data input cells Project Name: MONTICELLO ENSLAVED RURAL GROUND Date: 11/13/2020 constant values Linear Development Project? No calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) -> D.76 Check., BMP Design Specifications List. 2013 Draft Stds & Specs Maximum reduction required. Lineorproject? No The site's net increase in impervious cover (acres) is:0 Land cover areas entered correctly? Post -Development r r • Total disturbed area entered? TP LOAD REDUCTION NOTREQUIRED Pre-ReDevelopment Land Cover (acres) A sails BSoils CSoils Dsoils Totals Forest/Open Space (acres) -- undisturbed forest/open space 0.13 0.13 Managed Tort (acres) -- disturbed, graded for yards or other turf to be mowed/managed 0.34 0.34 Impervious Cover (acres) 0.29 0.29 0.76 Post -Development Land Cover (acres) A Soils BSoils CSoils Dsoils Totals Forest/Open Space (acres) -- undisturbed, protected forest/open space or reforested land 0.16 0.16 Managed Tud (acres) -- disturbed, graded for yards ar other turf to be mowed/managed CAD CAD Impervious Cover (acres) 0.20 0.20 Area Check OK. OR. OK. OR. 0.76 • Farest/Open Space areas must be protected in accordance with the Virginia Fun HReduction Method Constants Runoff Coefficients Rv Annual Randall (inches) 43 ASoils BSoils CSoils Dsoils Target Rainfall Event (inches) 1.00 Forest/Open Space 0.02 0.03 0.04 0.05 Total Phosphorus (TP) EMC(mg/L) 0.26 Managed Turf 0.15 0.20 0.22 0.25 Total Nitrogen (TN) EMC (mg/L) 1.86 Impervious Cover 0.95 0.95 0.95 0.95 Target TP Load (lb/acre/n) 0.41 Pj(unitless correction factor) 0.90 LAND COVER SUMMARY POST DEVELOPMENT Land Cover Summary -Pre Land Cover Summary-Post(Final) Land Cover Summery -Post Land COVer Summary -Post Pre-ReDevelopment Listed Adjusted' Post Renee. & New ImperviousPOat-B•Developmen[ Pont -Development New Impervious Forest/Open Space Forest/Open Space t/ pen p (acres) Fares O Space Cover 0.13 0.13 0.16 0.16 Cover (acres) Cover (a.) Weighted Rv(farest) 0.03 0.03 Weighted Rv(forest) 0.03 Weighted Faltered) 0.03 %Forest 17% 17% %Forest 21% %Forest 21% Managed Turf Cover (acres) 0.34 0.34 Managed Turf Cover 040 Managed Tud Cover 040 (acres) (acres) Weighted Rv(turf) 0.20 0.20 Weighted Far (turf) 0.20 Weighted Far (turn 0.20 %Managed Turf 45% 45% %Managed Turf 53% %Managed Turf 53% Impervious Cover (acres) 0.29 0.29 Impervious Cover (acres) 0.20 ReDev. Impervious 020 New Impervious Cover 000 Cover(acres) (acres) Rv(impervious) 0.95 0.95 Rv(im"mious) 0.95 RaRmpervious) 0.95 Rv(impervious) - %Impervious 38% 38% %Impervious 26% %Impervious 26% Total She Area lacres) 0.76 0.76 Final Are Area (acres) 0.76 Total R ; K$he Mea 0.76 Site Be 0.46 0." Final Port D. Site Be 0.36 Renee, Site Be 0.36 Treatment Volume and Nutrient Load Treatment Volume and Post-ReDevelopment Nutrient Load Pre-ReDevelopment Treatment Volume Final Part -Development Pont -Development (acre-ft) 0.0290 0.0290 Treatment Volume (acre -it) 0.0229 Treatment Volume (acre-ft) 0.0229 Treatment Volume (acre-ft) - Pre-ReDevelopment Treatment Volume Final Part -Development Post-ReDevelopment Post -Development (cubic feet) 1,261 1,261 Treatment Volume 998 Treatment Volume 998 Treatment Volume(orbic (cubic fee) (cubitfeet) feet) Pre-ReDevelopment TP Load Final Post. Post-ReDevelopment Port -Development TP bad (lb/yrj 0.79 0.79 Development TP Load 0.63 Lead (TP) 0.63 (lb/yr) - (16/Yr) lIb/ni" Pre-Renevelopment TP Inad per acre Final P.-Development TP Post-Renevelopment TP (blarmlvr) S.oa IN bad per acre o.ez bad me acre ILK or p6/we/nl 116/sons nl Baseline TP Load (lb/yr) Max. Reduction Required (0.41 lbs/acre/yr applied to pre -redevelopment area excluding pervious 0.31 (Below Pre- ID% land propmad for new impervious cover) ReDevelopment bad) 'Adjusted Land Cover Summary: TP Load Reduction TP Load Reduction Pre ReDevelopment land rover minus pervious land coverer rest/open spare or managed Required for -0.09 Required for New 0 turf/ ocreagepcposedfornew impervious cover Redeveloped Area Impervious Area (Ib/yr) (Ib/yr) Adjusted total acreage is consistent with Post-ReDevelopment armage,munus acreage of new impervious rover). Column I shows load reduction re9unement for new impervious cover (based on new developmentloadlimiq 0.41 Ibs/acre/year). Post -Development Requirement for TP Load Reduction Required (16/yr) -0.09TP LOAD REDUCTION NOT REQUIRED Nitrogen Loads (Informational Purposes Only) Final Post -Development TN bad Pre-ReDevelopment TN Wad(lb/yr) 5.67 IPoSL-ReDevelopment&Newlmpervious) 4.48 lb/yr) Runoff Volume and Curve Number Calculations Enter design storm rainfall depths (in): 1-yearstorm 2-yearstorm 10-year storm 3.01 3.0 5.5] Utt NOAAANOs14 (MpJ/IMscnw ..maa.90 v�pfdo 'Notes (see helowl: 11]The c umbers and runoffvolumes computed in this spreadsheetfor each drainage area are limited in their applimbilityfor determinin"od demonstrating compliance with water quamit, requirements. see VRRM Users Guide and O¢umentation for additional information. 12]Runoff Volume(RV)for preand postd—lopment drainage areasre must be in volume,ric units (e.g.,a-feet or cubic&et) when using the Energy Balance Equation. Runoff measured inwatershed- inches and show in the spreadsheet as RV(watershed-inchi canonly be used in Energy Balance Equation when the pre -and dwitdeyelopment drainage areas are equal.OtherwiseRV(watershad- inch) must be multiplied by the drainage area. 13] Adjusted CNS are based on runoff reduction volumes as calculated in D.A tabs. M alternmive CN adjustment calculation for Vegetated Roods is included in BMR specification No. S. Drainage Area Curve Numbers and Runoff Depths Curve numbers (CN, [Nadi) and runoff depths (RV J are computed with and without reduction practices. j,,, Drainage Area ASolls BSolls CSolis DSolis Total Area(acres): 0.76 Forest/Open Space— undisturbed, protected bresbopen space Or reforested land Are. pdcm,) 0.00 30 0.16 55 0.00 70 0.00 ]] RuneBReduction Velume(aa): 0 CN Managed Turf— disturbed, graded for yards or other hum m be mdowebmanaged Area (acres) 0.00 39 OAO 61 0.00 74 0.00 80 CN Impervious Cover Area(aves) CN 0.00 98 0.20 98 0.00 98 0.00 98 CNlan Al 69 1-year storm 2-year storm 10-year storm RVoe-1,ddd (watershed-ki with no Runoff Reduction' O.B9 1.06 2.38 RVa...n,.d (watershed -inch) with Runoff Reduction' O.B9 106 2.38 Adfusted CN' 69 1 69 1 69 'See Notes above Site Results (Water Quality Compliance) Area Checks D.A.A D.A.B DA.0 DA.D 0.0.E ARFACHECK FOREST/OPEN SPACE (at) 0.16 O.W 0.00 i0.00 Ow OR. IMPERVIOUS COVER)a[) IMPERVOUS COVER TREATED)a[) 0.20 ON 0.W Ow 0.00 D.W�M. O.W Ow O.WOK. OK. MANAGED TURF AREA (aC) OAO O.W O.00 00.W OK. MANAGED TURF AREA TREATED (aC) O.W O.W D.W O.W OK. ARFACHECK OK OK. OK. OR. Site Treatment Volume (ft') .8 Runoff Reduction Volume and TP By Drainage Area D.A.ADA.0 00.EOTRUNOFF RFWOION VOLUME ACHIEVED (Fh) 000TP LOAD AVARABLE FU AL Pb/yr) 0.62 O.W O.W M-. OTPIDADREDUCTIED IIb/yr) O.W O.W D.W O.W D.W TP LOADNG IIb/yr) 0.62 O.W O.W Ow 0.62 NMOGEN LOAD REDUCTED Pb/yr) 0.W O.W O.W O.W Ow D.W Totphorus FINAL POST-DEVELOPMAD Pb/yrlW TP LOAD REDUCTREOIIb/yr)TPIDADREDUCTIED Pb/yr)TP WAD REMAINING (Ib/T): REMAINING TP LOAD REDUCTION REQUIRED(lb/yr): ON "TARGET TP REDUCTION EXCEEDED BY OM LB/YEAR" Total Nitrogen (For Information Purposes) POST-DEVELOPMEMLOADIIb/yr) 9.48 NMOGEN LOAD REDUCTON ACHIEVED Pb/yrl 0.00 REMAINING POST -DEVELOPMENT NITRWEN LOAOIIb/yr) 9.08 PRE -DEVELOPED HYDRAFLOW COMPUTATIONS Hydrograph Report I Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Hyd. No. 1 MONTICELLO EBG EX COND Hydrograph type = SCS Runoff Peak discharge Storm frequency = 1 yrs Time to peak Time interval = 2 min Hyd. volume Drainage area = 0.760 ac Curve number Basin Slope = 0.0 % Hydraulic length Tc method = User Time of cons. (Tc) Total precip. = 3.07 in Distribution Storm duration = 24 hrs Shape factor Q (Cfs) 2.00 1.00 0.00 0 2 4 Hyd No. 1 MONTICELLO EBG EX COND Hyd. No. 1 -- 1 Year Thursday, 11 / 12 / 2020 = 1.008 cfs = 12.03 hrs = 0.062 acft = 74 = 0 ft = 10.00 min = Type II = 484 6 8 10 12 14 16 18 20 22 24 Q (Cis) 2.00 1.00 . 0.00 26 Time (hrs) Hydrograph Report 2 Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Hyd. No. 1 MONTICELLO EBG EX COND Hydrograph type = SCS Runoff Peak discharge Storm frequency = 2 yrs Time to peak Time interval = 2 min Hyd. volume Drainage area = 0.760 ac Curve number Basin Slope = 0.0 % Hydraulic length Tc method = User Time of conc. (Tc) Total precip. = 3.71 in Distribution Storm duration = 24 hrs Shape factor Q (Cfs) 2.00 1.00 0.00 0 2 4 Hyd No. 1 MONTICELLO EBG EX COND Hyd. No. 1 -- 2 Year Thursday, 11 / 12 / 2020 = 1.497 cfs = 12.03 hrs = 0.091 acft = 74 = 0 ft = 10.00 min = Type II = 484 6 8 10 12 14 16 18 20 22 24 Q (Cis) 2.00 1.00 . 0.00 26 Time (hrs) 3 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Thursday, 11 / 12 / 2020 Hyd. No. 1 MONTICELLO EBG EX COND Hydrograph type = SCS Runoff Peak discharge = 3.110 cfs Storm frequency = 10 yrs Time to peak = 12.00 hrs Time interval = 2 min Hyd. volume = 0.185 acft Drainage area = 0.760 ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of cone. (Tc) = 10.00 min Total precip. = 5.58 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (Cfs) 4.00 3.00 2.00 1.00 0.00 0 2 4 Hyd No. 1 6 8 MONTICELLO EBG EX COND Hyd. No. 1 -- 10 Year Q (Cfs) 4.00 3.00 2.00 1.00 0.00 10 12 14 16 18 20 22 24 26 Time (hrs) POST -DEVELOPED HYDRAFLOW COMPUTATIONS 7 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Thursday, 11 / 12 / 2020 Hyd. No. 2 MONTICELLO EBG PR COND Hydrograph type = SCS Runoff Peak discharge = 0.703 cfs Storm frequency = 1 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 0.046 acft Drainage area = 0.760 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of cone. (Tc) = 10.00 min Total precip. = 3.07 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 �titititititititititi • : � �tititi tititititititi 1 .1 �fifi� I �fifififififi 1 1 �fififi I fififififififi �fififi I fififififififi �fififi I fififififififi � � �tititi t tititititititi �tititi a rititititititi 1 1 �tititi • rititititititi �tititi • �titititititi 1 1 �fififi It fififififififi �fififi I• �fifififififi .��•titititi� � 111 1 � Hydrograph Report 2 Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Hyd. No. 2 MONTICELLO EBG PR COND Hydrograph type = SCS Runoff Peak discharge Storm frequency = 2 yrs Time to peak Time interval = 2 min Hyd. volume Drainage area = 0.760 ac Curve number Basin Slope = 0.0 % Hydraulic length Tc method = User Time of conc. (Tc) Total precip. = 3.71 in Distribution Storm duration = 24 hrs Shape factor Q (Cfs) 2.00 1.00 0.00 0 2 4 Hyd No. 2 MONTICELLO EBG PR COND Hyd. No. 2 -- 2 Year Thursday, 11 / 12 / 2020 = 1.134 cfs = 12.03 hrs = 0.071 acft = 69 = 0 ft = 10.00 min = Type II = 484 6 8 10 12 14 16 18 20 22 24 Q (Cis) 2.00 1.00 . 0.00 26 Time (hrs) 3 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D®2019 by Autodesk, Inc. v2020 Thursday, 11 / 12 / 2020 Hyd. No. 2 MONTICELLO EBG PR COND Hydrograph type = SCS Runoff Peak discharge = 2.598 cfs Storm frequency = 10 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 0.156 acft Drainage area = 0.760 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of cone. (Tc) = 10.00 min Total precip. = 5.58 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (Cfs) 3.00 2.00 1.00 0.00 0 2 4 Hyd No. 2 6 8 MONTICELLO EBG PR COND Hyd. No. 2 -- 10 Year Q (cfs) 3.00 2.00 1.00 1� ' 0.00 10 12 14 16 18 20 22 24 26 Time (hrs)