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Home My WebLink AboutWPO202000054 Calculations 2021-03-09Monticello Burial Ground for Enslaved People COUNTY OF ALBEMARLE, VIRGINIA DESIGN CALCULATIONS & NARRATIVE WP0202000056 NOVEMBER 239 2020 REV. MARCH 5, 2021 s 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 Ir YAN D. CICHOCKI Lic. No. 53741 P -WI- 4 Table of Contents Section Title Project Narrative 2 Virginia Runoff Reduction Method Worksheet Summary 3 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 managed turf 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 Tud (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 0.00 0.00 Managed Tud (acres) -- disturbed, graded for yards or other turf to be mowed/managed 0.56 0.56 Impervious Cover (acres) 0.20 0.20 Area Check OR. OR. OR. OR. 0.76 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/W) 0.41 Pj(unitless correction factor) 0.90 mul T717101111111111 LAND COVER SUMMARY POST DEVELOPMENT Land Cover Summary -Pre Land Cover Summary-Post(Final) Land Cover Summary -Post Land Cover Summory-Post Pre-ReDevelopment Listed Adjusted' loos Post ReDev. & New Impervious Pon-ReDevent lopme Port-Deaelopment New Impervious Forest/Open Space Formt/Open Space Forest/Open Space Cover (acres) 0.13 0.13 0 0 .00 Cover (acres) Cover(acres) Weighted Rv(farest) 0.03 0.03 Weighted Rv(formt) 0.00 Weighted Faltered) 0.00 %Forest 17% 17% %Forest 0% %Forest 0% Managed Turf Cover (acres) 0.34 0.34 Managed Turf Cover 0.56 Managed TurfCover 0.56 (acres) (acres) Weighted Rv(turf) 0.20 0.20 Weighted Far (turf) 0.20 Weighted Rv(turq 0.20 %Managed Turf 45% 45% %Managed Turf 74% %Managed Turf 74% Impervious Cover (acres) 0.29 0.29 Impervious Cover (acres) 0.20 Beaux. Impervious 020 New Impervious Cover 000 Cover (acres) (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 RaRmpervious) 0.95 Rv(impervious) - %Impervious 38% 38% %Impervious 26% %Impervious 26% Total She Area lecres) 0.76 0.76 Final Are Area (acres) 0.76 Total R l K$he Met 0.76 Site Re 0." 0." Final Port Clear Site Re 0.40 ReDev Site Re OAo Treatment Volume and Nutrient Load Treatment Volume and Post-ReDevelopment Nutrient Load Pre-ReDevelopment Treatment Volume Final Port -Development Port -Development (acre-ft) 0.0290 0.0290 Treatment Volume (acre-ft) 0.0252 Treatment Volume (acre-ft) 0.0252 Treatment Volume (aore-ft) - Pre-ReDevelopment Treatment Volume Final Part -Development Post-ReDevelopment Post -Development (cubic feet) 1,261 1,261 Treatment Volume 1,096 Treatment Volume 1,096 Treatment Volume (cubic (cubic fee) (cubicfeet) feet) Pre-ReDevelopment TP Load Post. Post-ReDevelopment Port -Development b Po -Development TP ad (Ib/yr) 0.79 0.79 ..,Final opment TP Load 0.69 Lead (TP) 0.69 (lb/yr) - (16/Yr) lib/M" Pre-0.enevelop men[ TP Load per acre Final Poo -Development TP Post-Renevelopment TP pmen,/yr) 1.04 1.04 Load per acre U.91 Load per acre a.91 116/x:e/nl 116/xre/nl Baseline TP Load (lb/yr) Max. Reduction Required (0.41 lbs/xre/yr applied to pre -redevelopment area excluding pervious 0.31 (Below Pre- 10% land proposed 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 -0.02 Required for New 0 turf/ ocreagepciumedfornew impervious cover Redeveloped Area Impervious Area (Ib/yr) (Ib/yr) Adjusted total acreage is consistent with Post-ReDevelopment armage (minav at eeW of new impervious cower). Column I shows load reduction requnement for new impervious cover (hosed on new developmentloadlimiq 0.41 Ihs/acre/year). Post -Development Requirement for TP Load Reduction Required (16/yr) -0.02TP LOAD REDUCTION NOT REQUIRED Nitrogen Loads (Informational Purposes Only) Final Pos-Demopment TN bad Pre-ReDevelopment TN Wad(lb/yr) 5.67 IPoaL-ReDevelopment&Newlmpervious) 4.93 Ib/yr) Runoff Volume and Curve Number Calculations Enter design storm rainfall depths (in(: 1-yearstorm 2-yearstorm 16year storm 3.04 Bb-I 5.57 We NOAR Atim 14 (http//Itls.nwarwm.ym/M1A/Pftlyf Notes (see below(: [1] The curve numbers and rumff volumes computed in thk spreadsheet for each tlrainage area are limited in their applicability, bar determinin, and demonstrating mmphance with water quantity requirements. See VRRM Wre, GAdo and Bocu trim ion for additic nal inbma4an. [2]Runoff Volume IR i for pre -and po4Ee elopmern drainage areas must be in volumrtnc units le.&, acry-f ct or cubic fertl when wing the Energy Balance Equation. Runoff measured in watershed inches and shown in the spreadsheet as RV(watershed-inch) an only be used in the Energy Balance Equation when the preandpost tlrrelopment drainage areas are equal. otherwise RVlwamrJ eGnchl must be multiplied N the drainage area. [3] Adjusted CNs are based on rune(( reduction volumes as calculated! in DA tabs. An alternative CN adrystment calculation for Vegetated Rooh is included in BMP spenfation No. 5. Drainage Area Curve Numbers and Runoff Depths* Curve numbers (CN, Mandl and runoff depths (RV )are computed with and without reduction practices. Drainage AreaA ASoils 9Sony CSoils DSoh radial Area (acres): 0.76 ForesVDpen Space- undisturbed, protected fixtWopen ,wee or rebrested land Area (acres) CN Rup 30 R. 55 D.OD 70 O.OD ]] Rumff Reduction Volume(R°): 0 Mmaged tuff- dlnuned, patled but yards or other tuff to be mowed managed Arta acres CN 0.00 39 0.56 61 D.OD ]4 O.OD ad Impervint; Cover Ama(acres) CN 0.00 99 0.20 98 0.00 9B 0.00 9B CNiow Al n 1-year storm 2-year storm Myear storm RVpeaugupeg (watershed -Ruth) with no Runoff Reduction" 0.]s 1.19 2.56 RVeeelmwa !watershed -Mat) with Runoff Reduction" 0.1B 119 256 Adjusted CNe 71 71 n "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) 0.00 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) 0.56 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') 1.096 Runoff Reduction Volume and TP By Drainage Area D.A.A D.A.BM DA.D 0.0.E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED (na) 0 0 0 0TP LOAD AVARABLE FU AL Pb/yr) 0.69 O.WOOTPIDADREDUCTIED IIb/yrl O.00 O.W OW O.W D.W TP LOADNG IIb/yr) 0.69 O.W 0.W Ow 0.69 NTIAOGEN LOAD REDUCTED Pb/yr) 0.W O.W O.W O.W Ow D.W Totphorus FINAL POST-DEVELOPMAD Pb/yrlW TP LOAD REDUC KREOIIb/yr)TPIDADREDUCTIED Pb/yrlTP WAD REMAINING Qb/,): REMAINING TP LOAD REDUCTION REQUIRED(lb/yr): ON "TARGET TP REDUCTION EXCEEDED BY 0.02 LB/YEAR" Total Nitrogen (For Information Purposes) POST-DEVELOPMEMLOADIIb/yr) 9.93 NTIAOGEN LOAD REDUCTON ACHIEVED Pb/yrl 0. W REMAINING POST -DEVELOPMENT NITRWEN LOAOIIb/yr) 9.93 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 Hydraflm Hydrographs Extension for Autodesk® Civil 31382019 by Autodesk, Inc. v2019.2 Wednesday, 02 / 3 / 2021 Hyd. No. 2 MONTICELLO EBG PR COND Hydrograph type = SCS Runoff Peak discharge = 0.821 cfs Storm frequency = 1 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 0.052 acft Drainage area = 0.760 ac Curve number = 71 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 Hydrograph Report 2 Hydraflm Hydrographs Extension for Autodesk® Civil 31382019 by Autodesk, Inc. v2019.2 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 Wednesday, 02 / 3 / 2021 = 1.276 cfs = 12.03 hrs = 0.078 acft = 71 = 0 ft = 10.00 min = Type II = 484 6 8 10 12 14 16 18 20 22 24 Q (Cfs) 2.00 1.00 . 0.00 26 Time (hrs) 3 Hydrograph Report Hydraflow Hydrographs Extension for AutodeskO Civil 3D9 2019 by Autodesk, Inc. v2019.2 Wednesday, 021312021 Hyd. No. 2 MONTICELLO EBG PR COND Hydrograph type = SCS Runoff Peak discharge = 2.802 cfs Storm frequency = 10 yrs Time to peak = 12.00 hrs Time interval = 2 min Hyd. volume = 0.167 acft Drainage area = 0.760 ac Curve number = 71 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 10.00 min Total precip. = 5.58 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (cfs) 3.00 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 y� ' I I I 10.00 10 12 14 16 18 20 22 24 26 Time (hrs)