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HomeMy WebLinkAboutWPO202100054 Calculations 2021-10-15Keswick Hall Family Pool COUNTY OF ALBEMARLE, VIRGINIA VSMP wro-2021-00054 DESIGN CALCULATIONS & NARRATIVE SEPTEMBER 10, 2021 REV. OCTOBER 15, 2021 •�0000 TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Craig Kotarski, PE Timmons Group 608 Preston Ave, Suite 200 Charlottesville, VA 22903 434.327.1688 U CRAIG W. J. KOTARSKI Lie. No. 0402048507 10/15/21 Table of Contents Section Title Project Narrative 2 Pipe and Inlet Computations Virginia Runoff Reduction Method Worksheet Summary 4 Pre -Developed HydroCAD Calculations Post -Developed HydroCAD Calculations 6 Nutrient Credit Availability Letter Project Narrative: This project includes the demolition of an existing parking spaces, pool building, and pool deck and the construction of new pool building, pool deck, parking and associated utilities. Erosion & Sediment Control Limits of Disturbance is 1.68. Water Quality Compliance: The disturbed area of 1.68 acres was used for the water quality analysis. In the proposed condition there will be 0.61 acres of managed turf, 1.07 acres of impervious cover. The required phosphorus removal is 0.80 lb/yr. Approximately 0.46 lb/yr of phosphorus shall be removed through the installation of permeable pavement. The remaining 0.34 lb/yr will be purchased from an offsite nutrient credit bank. Water Quantity Compliance: Stormwater Quantity requirements for analysis point 1 are met utilizing a reduction in area to comply with channel and flood protection requirements. Stormwater Quantity requirements for analysis point 2 are met utilizing a CMP detention system located within the parking area. Energy balance and channel projection for the analysis point are incompliance with all requirements. FORM LO 201 STORMWATER INLET COMPUTATIONS SHEEF1 OF ROUTE PROJECT Ka Al FaMl P tl DESIGNER J.DN DATE lwlI 21 CHECKED: UNITS EHGUSH mmm�mmmomom��mmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmm®mmmmm�m��®� �mm�mm�mmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomomm�mmo®ommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmmmmmmmmmmmmmmommmmmmm��m� �mm�mm�mmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomommm®mo®ommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmmmmmmmmmmmmmmommmmmmm��m� mmm�®m�mmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmo�ommmmm�m�m®mmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmmmmmmmmmmmmmm®mm�mm�m��m� ®mm�mmmmmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomommmm®m®gym®mmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmmmmmmmmmmmmmm©mmmm®m®�®®� �mm�mmmmmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomom�mmmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmmommmmmmm�m.mom ®mm�mmmmmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomom�mmmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmmommmmm�m��m �mm�mmmmmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomom�mmmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmmommmmmmm��m� mmm�mmmmmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomom�mmmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmmommmmmm®��m� ©mm�mm�mmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomom��mmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmm�mmmmmmmmmmmommmmmmm��m ®mm�mm�mmmmmmmmmmmmmmmmmmmmmmmmm��m mmm�mmmomommmmmomommmmmmmmmmmmm��m mmm�mmm0000mmmmmmmmmmmmmmmmmmmmm��m mmm�mmmmmmmmmmmmmmmmmmmmomm�mmm®�m.m INLETSOFT RY ENSOFTEC DATE: 1Ni Ul STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: Keswick Family Pool LOCATION: COUNTY: Albemarle County Designed by: J. Danko Checked by: C. Kolamki UNITS ENGLISN PIPE NO FROM POMT TO POMT DRAM. AREA "A" Acre (3) RUNOFF COEFF, "C" (4) CA TOTAL MLEL TIME Minutes (7) RAM FALL RJFIr (S) RUNOFF Q CFS (9) MVERTELEVATIONSLING UPPER LOWER of Pipe END END Ft (10) (11) (12) SLOPE Ft/Ft (13) SIZE (Dia. Or Span/Risc) In. (I4) SHAPE apaci CFS (15) Friction Slopc Ft Nt. VEL Vn Ft/Scc (16) FLOW TIME Min. (17) REMARKS (18) INCRE MT (5) ACCUM LATE (6) ADDTL CA ERENC (I) STA. ERENC (2) STA. 109 110 108 0.020 0.900 0.018 0.018 0.000 6.000 6.230 0.112 433.811 433.610 20.050 0.010 12.000 Circular 3.858 0.000 2.182 0.153 107 108 106 0.110 0.860 0.095 0.113 0.000 6.000 6.230 0.702 433.510 433.130 14.694 0.026 12.000 Circular 6.205 0.000 5.247 0.047 105 106 104 0.050 0.570 0.029 0.208 0.067 6.047 6.216 1.291 433.030 432.576 45.438 0.010 12.000 Circular 3.858 0.001 4.433 0.171 103 104 102 0.060 0.530 0.032 0.258 0.019 6.218 6.167 1.593 432.480 426.927 57.484 0.097 15.000 Circular 21.744 0.001 10.363 0.092 101 102 100 0.140 0.370 0.052 0.348 0.038 6.310 6.140 2.138 426.827 425.990 79.732 0.011 15.000 Circular 7.170 0.001 5.110 0.260 201 1 202 1 1 200 1 10.000 1 0.000 10.000 1 0.357 1 0.357 1 0.000 18.9011 3.179 1 427.250 1 418.000 1152.19410.0611 15.000 1 Circular 117.24810.002 110.745 10.236 UGD Oulfall 305 306 304 0.120 0.500 0.060 0.098 0.038 6.000 6.230 0.811 430.160 429.450 70.909 0.010 12.000 Circular 3.861 0.000 3.598 0.329 303 304 302 0.140 0.740 07. 0.202 0.000 EMS 6.135 1.237 429.3SO 428.933 41.657 0.010 12.000 Circular 3.858 0.001 4.382 0.158 307 308 302 1 0.0801 0.730 10.058 1 0.058 1 0.000 1 6.000 16.2301 0.364 1 433.460 1 431.395 190.50110.0231 12.000 1 Circular 1 5.828 0.000 4.140 10.361. 301 1 302 1 1 300 1 1 0.3101 0.870 10.270 1 0.568 1 0.038 1 8.700 15.5371 3.143 1 428.830 1 428.532 128.666 10.010 1 15.000 1 Circular 1 7.130 1 0.0021 5.640 10.085 403 404 402 1 10.780 1 0.390 1 0.3D41 0.304 1 O.000 1 8.900 15.4921 1.671 1 432.870 1 431.756 121.09510.0531 12.D00 1 Circular I 8.868 10.002 1 8.686 10.040 401 402 400 1 10.000 1 0.000 1 0.000 I 0.304 I 0.DD0 1 8.940 15.4841 1.668 1 431.681 1 428.250 188.97110.039 1 12.DD0 I Circular 7.576 10.002 1 7.756 10.191 503 1 504 1 1 502 1 10.36010.600 10.2161 0.216 1 0.000 1 6.000 16.2301 1.346 1 431.260 1 430.965 129.45310.010 1 12.000 1 Circular 13.858 10.0011 4.483 10.1091 501 1 502 1 1 500 1 10.000 1 0.000 10.0001 0.216 1 0.000 1 6.109 16.1981 1.339 1 430.870 1 430.689 118.05710.0101 12.000 1 Circular 3.858 0.001 1 4.477 10.067 PROJECT: Kesvnck Family Pool DESIGNED BY: J. Danko HYDRAULIC GRADE LINE ANALYSIS Checked: C. Kotanski INCIDENCE PROBABILITY 10 Year INLET OR JUNCTION INLET STATION OUTLET WATER 3URFACE ELEV. DIA. PIPE Do In) DESIGN DISCH. Do (CFS) -ENGTi PIPE Lo (Ff FRICTIO LOPE, Sf FT/(Ft) RICTION LOSS HF JUNCTION LOSS FINAL H Ft Inlet Water Surface Elevation Rim Elev Comments Vo Ho Ft Oi V DV Vl mg Hi Angle HA Ht 1.3 Ht 0.5 At 102 426.99 15 2.14 79.73 0.09% 0.07 5.11 0.1 1.59 10.36 16.51 1.6T 0.58 12.14 0.22 0.9 0 TRUE 0.53 427.52 429.59 OK -2.07 104 42T.93 15 1.59 5T.48 0.05% 0.03 10.36 0.42 1.29 4.43 5.T2 0.31 0.11 ]2.3 0.19 O.T1 0 TRUE 0.. 428.31 437.13 OK -8.82 106 433.38 12 1.29 45.44 0.11% 0.05 4.43 0.08 0.7 5.25 3.68 0.43 0.15 40.95 0.18 0.41 0 TRUE 0.26 433.63 436.9 OK -3.27 108 433.93 12 0.7 14.69 0.03% 0 5.25 0.11 0.11 2.18 0.24 0.07 0.03 1 75.13 0.05 0.18 0.24 1 FALSE 1 0.24 434.17 437.21 OK -3.04 110 434.41 12 0.11 20.05 0.00% 0 2.18 0.62 0 0 0 0 0 1 0 0 0.02 0.02 I FALSE I 0.02 434.43 437.65 OK -3.21 202 1 1 419 1 15 1 3.18 1152.191 0.21% 0.31 10.]5 0.45 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.45 1 0 1 TRUE 1 0.76 1 419.76 1 435.06 1 OK -15.29 302 1 1 433.15 15 1 3.14 1 28.67 1 0.20% 0.06 1 5.64 1 0.12 1.24 1 4.38 1 5.42 1 0.3 0.1 1 89.69 1 0.19 0.41 1 0.54 1 TRUE 1 0.33 433.48 1 435.76 1 OK -2.29 304 1 1 433.48 1 12 1 1.24 1 41.66 1 0.10% 1 0.04 1 4.38 1 0.07 1 0.61 1 3.6 1 2.2 1 0.2 1 0.07 1 45.64 1 0.1 1 0.25 1 0.32 1 TRUE 1 0.2 1 433.68 1 433.75 1 OK -0.07 306 1 1 433.68 1 12 1 0.61 1 70.91 1 0.03% 1 0.02 1 3.6 1 0.05 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.05 1 0.07 1 TRUE 1 0.05 1 433.73 1 433.75 1 OK -0 W 308 433.48 1 12 1 0.36 1 90.5 1 0.01% 1 0.01 1 4.14 1 0.07 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.07 1 0.09 1 TRUE 1 0.05 1 433.53 1 437.16 1OK -3.63 402 433.15 1 12 1 1.67 1 $8.97 0.19% 1 0.17 1 7.76 1 0.23 1 1.67 1 8.69 1 14.51 1 1.17 1 0.41 1 35.09 1 0.5 1 1.15 1 0 1 TRUE 1 0.74 1 433.89 1 437.64 1 OK -3.75 404 433.89 1 12 1 1.67 1 21.091 0.19% 1 0.04 1 8.69 1 0.29 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.29 1 0.38 1 TRUE 1 0.23 1 434.12 1 436.37 1 OK -2.25 502 433.15 1 12 1 1.34 1 18.06 1 0.12% 1 0.02 1 4.48 1 0.08 1 1.35 1 4.48 1 6.03 1 0.31 1 0.11 1 39.93 1 0.13 1 0.32 1 0 1 TRUE 1 0.18 1 433.33 1 434.87 1 OK -1.54 504 1 433.33 1 12 1 1.35 1 29.451 0.12% 1 0.04 1 4.48 1 0.08 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.08 1 0.1 1 TRUE 1 0.09 1 433.42 1 434.96 1 OK -1.54 Project Name: Keswick Family Pool constant values Date: 10/14/2021 Linear Development Project? NO calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) 1.68 Check: BMP Design Specifications List: 2013 Draft Stills & Specs Linear project? No Land cover areas entered correctly? t� Total disturbed area entered? Pre-ReDevelopment Land Cover (acres) ASoils BSoils CSoils 0Soils Fares[/Open Space, (acres) --undisturbed forest/open space Managed Turt (acres)--tlis[urbeQ gretletl for yam: or othertu0.81 mperviousCowr(acrez) 087 ET16 Post -Development Land Cover (acres)A Solls Bsoils CSoils DSoils Forest/Open Space (acres) -- undisturbed, 0.00 protected forest/open space or rearrested! land Managed Turt(acres)-- disturba ,gradetl for 0.61 yards or other turf to be mowe llmanaged 0.61 Impervious Cover (acres) 107 1.07 Area Check OK. OK. I OIL of. 1.68 Constants Runoff Coefficients Rv annual Rainfall(inchm) 43 ASoils BSoils CSoils DSoils argm Rainfall Event (inches) 1.00 Forest/Open Space 0.02 0.03 0.04 0.05 atil Pmsphoms(TP) EMC(mg/L) 0.26 Managetl Turt 0.15 0.20 0.22 0.25 ate( Nitrogen (TN) EMC(mg/L) 1.86 Impervious Cover 0.95 0.95 0.95 0.95 arget TP Load (lb/acre/yr) 0.41 PI(unitims correction factor) 0.90 LAND COVER SUMMARY -- PRE -REDEVELOPMENT• COVER SUMMARY POST DEVELOPMENT Lard Cover summary -Pre Lantl cover Summary-Post/Final) Land Coversummon,~ tarMcoversuprommy st Pre-ReDevelopment listed Adjusted' Port Reoor.&New Impervious Post-ReDevelopment Porest/Open space 0.00 Post -Development New Impervious Forest/Open Space Cover (acres) 0.00 0.00 Forest/Open Space 0.00 Cover (acres) Cover (acres) Weighted Rv(finest) 0.00 0.00 Weighted Rv(fimest) 0.00 Weighted Rv(forard 0.00 %Forest 0% 0% %Forest 0% %Forest 0% Managed Turf Cover (acres) 0.81 0.61 Managed Turf Cover 0.61 Managetl Turf Cover 0.61 (acres) (acres) Weighted Rv(turf) 0.25 0.25 Weighted Rv(turf) 0.25 Weighted Rv(turf) 0.25 %Managetl Turf 48% 41% %Managetl Turf 36% %Managed Tuff 41% Impervious Cover (acres) 0.87 0.87 ImperviousC r 107 ReDev. Impervious 087 New Impervious Cover 0.20 (acres) Cover (at.) (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rv(impendous) 0.95 Rv(impervious) 0.95 %Impervious 52% 59% %Impervious 64% %Impervious 59% Total Site Area (acres) 1.68 1.48 Final She A. (acres) 1.68 Total Above. Sate Arta 1A8 (acres) Site Rv 0.61 0.66 Final Port Ever She for 0.70 ReDev Site IN 0.66 Treatment Volume and Nutrient Laad Treatment Volume and Nutrient Load Post -Development Final Post- Post - Part-ReDevelopmem Pre-0.eOewlapmen[Treatment Volume 0.0858 0.0816 Development 0.0974 Treatment Valume 0.0816 TreatmentVolume 0.01S8 (acre-kl TreatmentVolume (acre-tt) (acre-k) (acre-k) Poz[-Dewlapment Final Post- Post-ReOewlapmem Pre-ReDevelopment Treabnent Volume 3,735 3,554 Development 9243 TreabnentValume 3,554 Treatment Volume (cubic 690 (cubic feet) TreatmentVolume (mbkhat) feat) (cubic feet) port -Development TP Pre-ReDevelopment TP Load Final Post- Port-ReDevelopment (lb/Yr) 2.35 2.23 Development TP Load 2.67 Laaa(Tv) 723 Load(lb/yr) OA3 (lb/Yr) Ob/nla Pre-ReDevelopment lP Wad per acre Final part Development TP PosLReDevelopmen[lP (lb/acre/yQ lap 151 La atlperacre 1.59 Toad Per arm L51 (Ib/arm/yr) (Iblane/YQ Baseline TP Wad (lb/yr) Maw Reduction Required (O.l11bs/aveMapplied mre pr Nevelopmenn area -loading pervious .elow 061 (a pre,2(% land proposed for new impervious cover) ReDevelopment Wad) 'Adjusted Land Cover summary: TP Load Reduction TP Load Reduction Pre ReDevelopment land rover minus pervious land cover (foresVopen space Or Required for 0.45 Required for New 0.35 staged Lure aneOge PcoposetlJarnewimpervious roves Redeveloped Area p Impervious Area (Ib/yr) lb/yrl Adjusted font( acreage is consistent with Post-ReDevelopment acreage (minus acreage Of new impervious cover). Column I shows load reduction reviuriement for new impervious cover (based on new development fond Omit, 0.4116s/ ne/yeorf. Post -Development TP Load Reduction Required (Ib/yr) 0.80 Nitrogen Loads (Informational Purposes Only) Final Post -Development TN Load Pre-ReDevelopment TN Wad(lb/yr) 16.79 (Post-ReDevelopment&New 19.07 Impervious) (lb/yr) WRM Rem Conplarce_spoeseEtiee1_0 08201T1 own Drainage Area A Drainage Area A Land Cover (acres) A Soils BSoils C5oils 0Soils Totals Land Cover RV Forest/Open Som,(acres) 0.00 0.00 Managed Twf(acres) 0.02 0.02 0.2S Impervious Cover(aan') 0.36 0.36 0.95 Total 0.39 Total Phosphorus Available for Removal in D.A.A(lb/yr) 0.80 Post Development Treatment Volume in DA.A(fta) 1,271 Stormwater Best Management Practices (RR = Runoff Reduction) -select From drop town III RunoH Managed Impervious Volumefrom Remaining Total BMP Phosphorus re Phosphorus Load Untreated Phosphorus Remaining Practice RetluRion Turf Credit [over Credit Runoff Upstream a Runoff Volume Treatment Removal from Upstream PhosphorusLoad Removed By Phosphorus Loatl Downstream Practice tobe Credit (%) Area (acres) Area (acres) Pramire Reduction (k) ft ( � (fta) Volume (fts) EHicienry(%) Practices (lb) to Practice (lb) Practice (lb) (lb) Employed Em to ed P Y 1. Vegetated Roof (RR) 1.e. Va erattd Rmf N1(Spec WS) 45 0 0 0 a 0.00 0.00 0.00 1.b. Vegetated Raafp2(SpeCK5) 60 0 0 0 a 0.00 0.00 0.00 2. cite,, Di,�emnrction (RR) •2.a.Simple DisommectionWA/BSoils 50 0 0 0 0 0 DID am DIDDID (Spec m) 2.b. Simple Disconnection to C/D Soils 25 0 0 0 0 0 DAO am D00 DID (Specal) 2.c. To Son Amended Filter Path as Per sa a 0 o a o D.00 am D00 DIDsceuficatme, hoisting C/D sods)(Speca4( 2,1. To Dry Well or French Dram al, 50 a a 0 0 25 D.00 am D00 DID Mi rminfibation #1(5pec a) 2.e. To Dry Well or Framer Drain K2, 90 a a 0 0 25 0.00 am 000 DID Micro -Infiltration W2 (Spec 118) 21 To Rain Garden Cl, b 0 0 0 0 25 0.00 am 000 DID Micm-Bioretention #1(Spec 89) 2, To Rain Garden K2, g0 0 0 0 0 50 0.00 am 000 0A0 MicroBioretention#2(SPec 89) 2.h. To Rainwater Hervesting(Spec 06) 0 0 0 0 0 0 0.00 am 000 0A0 2i.TOStmoommer Plards, b 0 0 0 0 25 0.00 am 000 0A0 Urban ffilmetwaimi (Spec N, Appendix A) Permeable Pavement (RR) 3.e. Permeable Pavement Cl(Spec WT) 45 --- a.36 D 559 683 1,241 25 ROD 0.28 -4. 0.32 3.1h. Permeable Pavemem W2(SPeCKT) 25 0 0 0 25 1 0.00 -- -- M 4. Grass Channel (RR) 4.a. Grass Channel A/B Soils (Spec C3) 20 0 0 0 0 15 D.00 am DID DID 4.1h. Grass Channel C/D Soils (Spec C3) 10 0 0 0 0 15 0.00 am DID DID 4.tGrass Channel with Comport Amended Seib p 0 0 0 0 15 0.00 am DID DID as per spea (see Spec RD 6.a.1iomdentian star Mvm-Bmo :)tion"or Urban me at m ISpe[l19) 40 0 0 0 0 25 DID DID DID 0.00 6.1h. Bioretention p2 or MicroBiostention 42 Sp- g0 0 0 0 0 50 0.00 0.00 0.00 0.00 2.a. Infiltration#1(Spec DB) 50 0 0 0 0 25 DID DID DID 0.00 T.b. Infiltration#2(Spec a) 50 0 0 0 0 25 DID DID DID hD0 8. Extended Detention Pond (RR) Pa. ED #1 (Spec #15) 0 0 0 0 0 15 DID DID 0.00 0.Do 8.b. ED#2(SPec#15) 15 0 0 0 0 15 0.00 0.00 0.00 O.CO 0 D.00 D00 DID DID 0 D00 D00 DID DID 15 not not 0.00 0.00 15 not not 0.00 0.00 In not not 0.00 0.00 0 not not DID 0.00 In 000 not Got 0.00 3. Permeable Pavement (RR) 4. Grass Channel (RR) 5. Dry Swale (RR) 6. Bioretention (RR) ]. Infiltration (RR) 8. Extended Detention Pond (RR) lm1Y1021 1W2 h'n. VRRM ReDev_DPnpJia�xe_$Aea]a1wH_✓J_09201 ]-1 DA A 9.a. 5heemow W ConsemHan Area, AIR Soils (Spec N2) 75 0 0 a 0 a 0.00 0.00 0.00 0.00 9.b. Sbeetfow to Conservation Area, C/D Soils 50 0 0 0 0 a 0.00 0.00 0.00 0.00 (Speca2) 9.c. SbeetOow to Vegetated Filter Stnp, A Soils or Compost Amended B/C/D Soils 50 0 0 0 0 a 0.00 0.00 0.00 0.00 (Speca2&aAl TOTAL IMPERVIOUS COVER TREATED(ac) 0.36 AREA CHECK: OK. TOTAL MANAGED TURF AREA TREATED(ac) 0.00 AREA CHECK: OK. TOTAL RUNOFF REDUCTION IN D.A. A (fta) 559 TOTAL PHOSPHORUS AVAILABLE FOR REMOVAL IN D.A. A(Ib/yr) 0.80 TOTAL PHOSPHORUS REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A(Ib/yr) 0.46 TOTAL PHOSPHORUS REMAINING AFTER APPLYING RUNOFF REDUCTION PRACTICES IN DA. A(Ib/yr) 0.34 SEE WATER QUALITY COMPLIANCE TAB FOR SITE COMPLIANCE CALCULATIONS TOTAL RUNOFF REDUCTION IN D.A. A (ft) 559 NITROGEN REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A(lb/yr) 3.27 SEE WATER QUALITY COMPLIANCE TAB FOR SITE CALCULATIONS (Information Only) Bnnort 2N2 939 AM Site Results (Water Quality Compliance) Area Checks D.A.A D.A.B DA.0 DA.D 0.0.E ARENCHECK FOREST/OPEN SPACE (at) 0.00 O.W 0.00 i0.00 OLD OR. IMPERVIOUS COVER)a[) IMPERVOUS COVER TREATED )a[) 0.36 0.36 0.W Ow 0.00 O.W�M. O.W Ow 0WOK. OK. MANAGEDTURFAREA(m) 0.02 O.W 0.00 00.W OK. MANAGED TURF AREA TREATED (a[) O.W O.W D.W O.W OK. ARFACHECK OK OK. OK. OR. Site Treatment Volume (fe) 4.243 Runoff Reduction Volume and TP By Drainage Area D.A.A D.A.BME. 0.0.E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED pIa) 559 0 0 559TP LOAD AVAILABLE FOR REMOVAL pb/yr) 0.80 0.WOW0.80TPIDAOREDUCTIONACHIEVED )Ib/yrl 0.46 O.W O.W 0.46TP LOAD REMAINING IIb/yr) 0.34 O.W 0.CO 0.34 NPROGENIDADREDUCTONACHIEVED(lb/yr) 3.27 O.W O.W O.W O.W 3.27 Total Phosphorus FINALPOST-DEVELOPMENTTP LOAD pb/yr) 2.67 TP LOAD REDUCTION REQUIRED IIb/yr) 0.80 TPIDADREDUCTIONACHIEVED pb/yrl 0.46 TP LOAD REMAINING Qb/,): 2.21 REMAINING TP LOAD REDUCTION REQUIRED pb/yr): 0.34 Total Nitrogen (For Information Purposes) POST-DEVEIOPMENT WAD jiblr)II 19.07 NnROGEN LOAD REDUCTON ACHIEVED pb/yrl 3.27 REMAINING POST -DEVELOPMENT NITRWEN LOAD IIb/yr) 15.00 Runoff Volume and Curve Number Calculations Enter design storm rainfall depths (in(: 1-Yearooden xryearsmrm 10y ar storm 2.92 L 3.. 5.35 1/ae NOM Atlm 14 (Mp//Itls.nwtrxuug. /M1LvJpfJyf "Nmes (see below): [1] The curve numbers and rumff volumes camp need in this spreadsheet for each tlrainage area are limited in their appliabdity br doterminim and demonstrating mmphance with water quantity requirements. See Mail Ilsee, GAdo and Bocurrim ion for additica ahnbrmatlnn. [2]Runoff Volume IR i for pre -and po4Ee elapmee drainage areas must be in volumemc units le.&, acry-f ct or cubic feet) when using the Energy Balanre Equation. Runoff measured in watershed - inches and shown in the spreadsheet as RV(watershN-inch) an only be used in the Energy Balance Equation when the preandpost tlrrelopment drainage areas are equal. Otherwise RVlwatersheGnch) must be mukiplied N the drainage area. [3] Adjusted CN, are based on runoff reduction volumes a, calculated! in Di tabs. An alternative CN adjustment calculation for Vegetated Rooh is included in BMp spenfation Na 5. Drainage Area Curve Numbers and Runoff Depths* Curve numbers (CN, Mandl and runoff depths (RV J are computed with and without reduction practices. Drainage AreaA ASoils BSails CSoils DSoh Teal Area (acres): 0.39 ForesVDpen Space- undisturbed, proarded fore4/open ,pare or rebrested land Area aLfe CN RuD 30 R. 55 D.DD ]B D.DD ]] Ruff Reduction m Volume(R3): 559 Mmaged Tuff -admitted, graded b, yards or other tuff to b, mowed/managed Area acre, CN Reef 39 R. 61 D.DD ]< D.o2 BB Impervious Cover Ama(acres) CN Reef 98 R. 98 D.DD 9B D.36 9B Chip, AI 9] 1-year storm 2-year storm Myear storm RVpevadvpe (watershed -Rid) with no RunaH Reduction" 2.1e 3.19 s.BD RVDerebpee!watershed-MMJ with Runoff Reduction" 218 2.8D 4.6D Adjusted Me 93 93 93 -See Notes above Drainage Area ASoils BSails CSoils DSoh Teal Arm James): 0.00 Forest/open Space- undisturbed, proarded forest open Tore or rebrested land Area (acres) CN Reef 30 Rept 55 D.DD ]B D.DD ]] Rumff Retluction Volume R': 0 Mamged Tuff-d.rt.r d.Sr.dedbry.rds.rothertuff to b, mawed/managed Area acre, CN Reef 39 R. 61 D.DD ]< D.DD BB Impervious Cover Ama(acres) CN Reef 98 R. 98 D.DD 9B D.DD 9B Chips,A 0 1-yearsWrm 2-yearsWrm 16Yearstorm RVeevdepm (watershed -Rich) with no Runoff Reduction" D.DD am 0.00 RVoerelana(warefzMd-Matt with RunaH Reduction" D.DD 0... orn, Atlj dtL CN" 0 0 0 view Notes above Drainage AreaC ASoils BSails CSoils DSoh Teal Am.(2—): 0.00 ForesVDpen Space- undaturbed, proarded brest/open Tore or rebrested land Area (acres) CN Reef 30 R. 55 D.DD ]B D.DD ]] Rurofl ReduWm Volumefl! 0 Managed Tuff- admitted, graded br yards or other tuff to be mowed/managed Area acre, CN Reef 39 R. at D.DD 74 D.DD 80 Impervious Cover Ama(acres) CN D.DB 98 R. 98 B.BD 9B B.BD 9B Chips, 0 1-vearnorm z-vearnorm lo-vearstprm 4 RVpeedugpe (wamrshed-Rid) with no Runoff Reduction" D.DO B.DO D.aD RVDerelenalwarefzhed-Matt with Runoff Reductions D.up 0.D0 D.aD Adjusted CN" 0 0 0 -See Notes above Drainage Area D ASoils BSails CSoils DSoh Teal Are. (acres): 0.00 Forest/open Space- undisturbed, proarded fixtWopen space or rebrected land Area (acres) CN 0.00 30 0.00 55 B.OD 70 B.OD ]] Ronan Reduction Volume(R'): 0 Managed Turf -admitted, graded br yards or other tuff to b, mowed/managed Area acre, CN 0.00 39 R. 61 B.BD ]4 B.BD BB Impervious Cover Area(acres) CN D.DB 98 R. 98 B.aD 9B Bm 9B CN,VA. DI 0 1-year sWrm z-year sWrm IDYea RVDevawai (watershed-Ricti d) with no Runoff Reduon" D.DO B.DD prad D.BD RVoerelarea (warefzhed-Matt with Runoff Reduction* R. O.DD Dm Adjusted CAP II 0 1 0 'S.Next. above Drainage AreaE ASoila 9Saga CSoils DSaila Toad Area (aces(: 0.00 Forest/Open Space— unElsturbed, protectedbreWopen space or rebrested land Area (acres) CN 0.. 30 0.. 55 O.W 70 0.W ]] Rumfl ReduWm Vtlume'R): 0 MmageE Turf— returned, graded for yards or oMer tuff b ennoseeNcranaged Area (acres) CN 0.. 39 0.. 61 rl0. ]< 0.00 B0 Mpemous Cancer Area (acres) CN 0.. 98 0.. 98 0.00 9B 0.00 9B CNlo.nai 0 I -year at rm 2-year storm My.. storm RVpeepa, (yeal Inch) with no Runoff Reduction" 0..0.00 0.a0 RVoe,Nelee(Ivarersb heay)vAtl Run., Reduction" 0.00 0.00 0.a0 Adjusted! CN" a a a eSee Not -above Virginia Runoff Reduction Method Worksheet DEQ Virginia Runoff Reduction Method Re -Development Compliance Spreadsheet -Version 3.0 BMP Design Specifications List: 2013 Draft Stds & Specs Site Summary Project Title: Keswick Family Pool Date: 44484 Total Rainfall (in): 43 Total Disturbed Acreage: 1.68 Site Land Cover Summary Pre-ReDevelopment Land Cover (acres) Asoils HSoils CSoils DSoils Totals %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(acres) 0.00 0.00 0.00 0.81 0.81 48 I mpervious Cover (acres) 0.00 0.00 0.00 0.87 0.87 52 1.68 100 Post-ReDevelopment Land Cover (acres) Asoils !.Soils CSoils DSoils Totals %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(acres) 0.00 0.00 0.00 0.61 0.61 36 Impervious Cover (acres) 0.00 0.00 0.00 1.07 1.07 64 1.68 100 Site Tv and Land Cover Nutrient Loads Final Port -Development Post- Port Adjusted Pre- (Post-ReDevelopment ReDevelopment Development ReDevelopment &New Impervious) (New, Impervious) Site Rv 0.70 0.66 0.95 0.66 Treatment Volume(ft') 4,243 3,554 690 3,554 TP Load(lb/yr) 2.67 2.23 0.43 2.23 Total TP Load Reduction Required (lb/yr) 0.90 0.45 0.35 Final Post-Developmem Load (Post-ReDevelopment & New Impervious) Pre. ReDevelopment TN Load (lb/yr) 19.07 16.79 Pre- ReDevelopment Final Post -Development Port-ReDevelopment TP TPLoadpe TP Load per acre Load per acre (Ib/acre/yr) (lb/acre/yr) (lb/acre/yr) 1.51 1.59 I.51 Summary Print Virginia Runoff Reduction Method Worksheet Site Compliance Summary Maximum %Reduction Required Below Pre-ReDevelopment Load 06 Total Runoff Volume Reduction (k') 559 Total TP Load Reduction Achieved (lb/yr) 0.46 Total TN Load Reduction Achieved (I b/yr) 3.27 Remaining Post Development TP Load 2.21 (lb/yr) Remaining TP Load Reduction (Ib/yr) Required 0.34 Summary Print Virginia Runoff Retlucfion Method Woftheet Drainage Area Summary D.A. A D.A. B DA. C D.A. D DA. E Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acros) 0.02 0.00 0.00 0.00 0.00 0.02 Impervious Corer(acres) 0.36 0.00 0.00 0.00 0.00 0.36 Total Area (acres) 0.39 0.00 0.00 0.00 0.00 0.39 Drainage Area Compliance Summary DA. A D.A. B DA. C DA. D D.A. E Total TP Load Reduced (lb/yr) 0.46 0.00 1 0.00 1 0.00 0.00 0.46 TN Load Reduced (lb/yr) 3.27 0.00 1 0.00 1 0.00 0.00 3.27 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary A Soils BSoils CSoils DSoils Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(acres) 0.00 0.00 0.00 0.02 1 0.02 1 6 Impervious Cover (acres) 0.00 0.00 0.00 0.36 1 0.36 1 94 0.39 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Treatment Practice Credit Area [over Credit I s volume (ft) Upstream to Practice (Ihs) (Ih/yr) (Ih/yr) to be Employed (acres) Area (acres) practices (Ihs) 3.a. Permeable Pavement#1 (Spec#7) 0.106014692 365.59 0.00 0.23 0.13 0.09 Total Impervious Cover Treated(acres) 0.36 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. 0.46 (lh/yr) Total TN Load Reduction Achieved in D.A. 3.27 (Ih/yr) Summary Print 7S 8S 10S 11S Pre Area 1 nsite Pre Area 2 ( site) Pre A a 2 (Offsite) ( ) Pre re 1 (Offsite) 9L 12L Areas Combined (Prel On+Off-site) Subcat Reach Aon Llnk Area 2 Combined (Pre On+Off-site) Keswick Hall_PreDev NOAA 24-hr D 1-Year Rainfall=2.92" Prepared by Timmons Group Printed 9/9/2021 HVdroCADO 10.10-4a s/n 06538 © 2020 HVdroCAD Software Solutions LLC Paae 2 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Pre Areal (Onsite) Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>1.91" Flow Length=280' Tc=6.2 min CN=90 Runoff=2.11 cfs 0.157 of Subcatchment 8S: Pre Areal (Offsite) Runoff Area=0.760 ac 0.00% Impervious Runoff Depth>1.31" Flow Length=435' Tc=8.9 min CN=82 Runoff=1.03 cfs 0.083 of Subcatchment 10S: Pre Area 2 (Onsite) Runoff Area=0.540 ac 0.00% Impervious Runoff Depth>1.91" Tc=6.0 min CN=90 Runoff=1.15 cfs 0.086 of Subcatchment 11S: Pre Area 2 (Offsite) Runoff Area=0.400 ac 0.00% Impervious Runoff Depth>1.38" Flow Length=454' Tc=10.5 min CN=83 Runoff=0.54 cfs 0.046 of Link 9L: Areas Combined (Prel On+Off-site) Inflow=3.10 cfs 0.241 of Primary=3.10 cfs 0.241 of Link 12L: Area 2 Combined (Pre On+Off-site) Inflow=1.64 cfs 0.132 of Primary=1.64 cfs 0.132 of Total Runoff Area = 2.690 ac Runoff Volume = 0.373 of Average Runoff Depth = 1.66" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Summary for Subcatchment 7S: Pre Area 1 (Onsite) Runoff = 2.11 cfs @ 12.13 hrs, Volume= 0.157 af, Depth> 1.91" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=2.92" Area (ac) CN 0.990 90 CN - VRRM Spreadsheet 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.4 59 0.0700 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.3 96 0.1300 5.80 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 125 0.0070 4.40 5.40 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 6.2 280 Total N V Subcatchment 7S: Pre Areal (Onsite) Hydrograph Time (hours) ■ Rurwff Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Summary for Subcatchment 8S: Pre Area 1 (Offsite) Runoff = 1.03 cfs @ 12.16 hrs, Volume= 0.083 af, Depth> 1.31" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=2.92" Area (ac) CN 0.760 82 >75% Grass cover, Good, HSG D 0.760 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.8 100 0.0800 0.21 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.5 100 0.0500 3.60 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 135 0.0500 4.54 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.1 100 0.0500 11.77 14.44 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 8.9 435 Total Subcatchment 8S: Pre Areal (Offsite) Hydrograph ■ Rurwff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Printed 9/9/2021 Summary for Subcatchment 10S: Pre Area 2 (Onsite) Runoff = 1.15 cfs @ 12.13 hrs, Volume= 0.086 af, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=2.92" Area (ac) CN Description 0.540 90 CN - VRRM Spreadsheet 0.540 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Pre Area 2 (Onsite) Hydrograph ■ Runoff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Printed 9/9/2021 Summary for Subcatchment 11S: Pre Area 2 (Offsite) Runoff = 0.54 cfs @ 12.18 hrs, Volume= 0.046 af, Depth> 1.38" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=2.92" Area (ac) CN Description 0.400 83 >75% Grass cover, Good, HSG D 0.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.7 163 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.5 165 0.1200 5.58 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 10.5 454 Total Subcatchment 11S: Pre Area 2 (Offsite) Hydrograph ❑ Runoff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Printed 9/9/2021 Summary for Link 9L: Areas Combined (Pre1 On+Off-site) Inflow Area = 1.750 ac, 0.00% Impervious, Inflow Depth > 1.65" for 1-Year event Inflow = 3.10 cfs @ 12.14 hrs, Volume= 0.241 of Primary = 3.10 cfs @ 12.14 hrs, Volume= 0.241 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 9L: Areas Combined (Pre1 On+Off-site) Hydrograph ■ InMov ■ Primary Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 1-Year Rainfall=2.92" Printed 9/9/2021 Summary for Link 12L: Area 2 Combined (Pre On+Off-site) Inflow Area = 0.940 ac, 0.00% Impervious, Inflow Depth > 1.68" for 1-Year event Inflow = 1.64 cfs @ 12.14 hrs, Volume= 0.132 of Primary = 1.64 cfs @ 12.14 hrs, Volume= 0.132 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 12L: Area 2 Combined (Pre On+Off-site) Hydrograph ■ Inflow C Primary Time (hours) Keswick Hall_PreDev NOAA 24-hr D 2-Year Rainfall=3.54" Prepared by Timmons Group Printed 9/9/2021 HVdroCADO 10.10-4a s/n 06538 © 2020 HVdroCAD Software Solutions LLC Paae 9 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Pre Areal (Onsite) Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>2.48" Flow Length=280' Tc=6.2 min CN=90 Runoff=2.71 cfs 0.205 of Subcatchment 8S: Pre Areal (Offsite) Runoff Area=0.760 ac 0.00% Impervious Runoff Depth>1.81" Flow Length=435' Tc=8.9 min CN=82 Runoff=1.43 cfs 0.115 of Subcatchment 10S: Pre Area 2 (Onsite) Runoff Area=0.540 ac 0.00% Impervious Runoff Depth>2.48" Tc=6.0 min CN=90 Runoff=1.48 cfs 0.112 of Subcatchment 11S: Pre Area 2 (Offsite) Runoff Area=0.400 ac 0.00% Impervious Runoff Depth>1.89" Flow Length=454' Tc=10.5 min CN=83 Runoff=0.74 cfs 0.063 of Link 9L: Areas Combined (Prel On+Off-site) Inflow=4.08 cfs 0.320 of Primary=4.08 cfs 0.320 of Link 12L: Area 2 Combined (Pre On+Off-site) Inflow=2.15 cfs 0.175 of Primary=2.15 cfs 0.175 of Total Runoff Area = 2.690 ac Runoff Volume = 0.494 of Average Runoff Depth = 2.20" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 7S: Pre Area 1 (Onsite) Runoff = 2.71 cfs @ 12.13 hrs, Volume= 0.205 af, Depth> 2.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.54" Area (ac) CN Description 0.990 90 CN - VRRM Spreadsheet 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.4 59 0.0700 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.3 96 0.1300 5.80 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 125 0.0070 4.40 5.40 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 6.2 280 Total Subcatchment 7S: Pre Areal (Onsite) Hydrograph ■ Rurwff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Summary for Subcatchment 8S: Pre Area 1 (Offsite) Runoff = 1.43 cfs @ 12.16 hrs, Volume= 0.115 af, Depth> 1.81" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.54" Area (ac) CN 0.760 82 >75% Grass cover, Good, HSG D 0.760 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.8 100 0.0800 0.21 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.5 100 0.0500 3.60 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 135 0.0500 4.54 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.1 100 0.0500 11.77 14.44 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 8.9 435 Total Subcatchment 8S: Pre Areal (Offsite) Hydrograph ■ Rurwff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 10S: Pre Area 2 (Onsite) Runoff = 1.48 cfs @ 12.13 hrs, Volume= 0.112 af, Depth> 2.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.54" Area (ac) CN Description 0.540 90 CN - VRRM Spreadsheet 0.540 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Pre Area 2 (Onsite) Hydrograph 0 Runoff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 11S: Pre Area 2 (Offsite) Runoff = 0.74 cfs @ 12.18 hrs, Volume= 0.063 af, Depth> 1.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.54" Area (ac) CN Description 0.400 83 >75% Grass cover, Good, HSG D 0.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.7 163 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.5 165 0.1200 5.58 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 10.5 454 Total 0,7 Subcatchment 11S: Pre Area 2 (Offsite) Hydrograph I :■ .......... .......... :::::::::: MIMEMEMEM ; 0..1..2..3.4.5..5..7..8.9.10.11 12.13.14 15.16,7.,3. 020 21 2223.2 24 Time (hours) ❑ Runoff Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Printed 9/9/2021 Summary for Link 9L: Areas Combined (Prel On+Off-site) Inflow Area = 1.750 ac, 0.00% Impervious, Inflow Depth > 2.19" for 2-Year event Inflow = 4.08 cfs @ 12.14 hrs, Volume= 0.320 of Primary = 4.08 cfs @ 12.14 hrs, Volume= 0.320 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 9L: Areas Combined (Prel On+Off-site) Hydrograph ■ hifim— ■ Primary Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 2-Year Rainfall=3.54" Printed 9/9/2021 Summary for Link 12L: Area 2 Combined (Pre On+Off-site) Inflow Area = 0.940 ac, 0.00% Impervious, Inflow Depth > 2.23" for 2-Year event Inflow = 2.15 cfs @ 12.14 hrs, Volume= 0.175 of Primary = 2.15 cfs @ 12.14 hrs, Volume= 0.175 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 12L: Area 2 Combined (Pre On+Off-site) Hydrograph ■ InMov ■ Primary Time (hours) Keswick Hall_PreDev NOAA 24-hrD 10-Year Rainfall=5.35" Prepared by Timmons Group Printed 9/9/2021 HVdroCADO 10.10-4a s/n 06538 © 2020 HVdroCAD Software Solutions LLC Paoe 16 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Pre Areal (Onsite) Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>4.21" Flow Length=280' Tc=6.2 min CN=90 Runoff=4.45 cfs 0.347 of Subcatchment 8S: Pre Areal (Offsite) Runoff Area=0.760 ac 0.00% Impervious Runoff Depth>3.39" Flow Length=435' Tc=8.9 min CN=82 Runoff=2.64 cfs 0.215 of Subcatchment 10S: Pre Area 2 (Onsite) Runoff Area=0.540 ac 0.00% Impervious Runoff Depth>4.21" Tc=6.0 min CN=90 Runoff=2.44 cfs 0.189 of Subcatchment 11S: Pre Area 2 (Offsite) Runoff Area=0.400 ac 0.00% Impervious Runoff Depth>3.49" Flow Length=454' Tc=10.5 min CN=83 Runoff=1.34 cfs 0.116 of Link 9L: Areas Combined (Prel On+Off-site) Inflow=7.01 cfs 0.562 of Primary=7.01 cfs 0.562 of Link 12L: Area 2 Combined (Pre On+Off-site) Inflow=3.68 cfs 0.306 of Primary=3.68 cfs 0.306 of Total Runoff Area = 2.690 ac Runoff Volume = 0.868 of Average Runoff Depth = 3.87" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 7S: Pre Area 1 (Onsite) Runoff = 4.45 cfs @ 12.13 hrs, Volume= 0.347 af, Depth> 4.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.35" Area (ac) CN Description 0.990 90 CN - VRRM Spreadsheet 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.4 59 0.0700 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.3 96 0.1300 5.80 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 125 0.0070 4.40 5.40 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 6.2 280 Total Subcatchment 7S: Pre Areal (Onsite) Hydrograph ■ Rurwff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Summary for Subcatchment 8S: Pre Area 1 (Offsite) Runoff = 2.64 cfs @ 12.16 hrs, Volume= 0.215 af, Depth> 3.39" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.35" Area (ac) CN 0.760 82 >75% Grass cover, Good, HSG D 0.760 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.8 100 0.0800 0.21 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.5 100 0.0500 3.60 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.5 135 0.0500 4.54 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.1 100 0.0500 11.77 14.44 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 8.9 435 Total Subcatchment 8S: Pre Areal (Offsite) Hydrograph ■ Rurwff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 10S: Pre Area 2 (Onsite) Runoff = 2.44 cfs @ 12.13 hrs, Volume= 0.189 af, Depth> 4.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.35" Area (ac) CN Description 0.540 90 CN - VRRM Spreadsheet 0.540 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Pre Area 2 (Onsite) Hydrograph ■ Runoff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 11S: Pre Area 2 (Offsite) Runoff = 1.34 cfs @ 12.18 hrs, Volume= 0.116 af, Depth> 3.49" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.35" Area (ac) CN Description 0.400 83 >75% Grass cover, Good, HSG D 0.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.7 163 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.5 165 0.1200 5.58 Shallow Concentrated Flow, Unpaved Kv= 16.1 fos 10.5 454 Total Subcatchment 11S: Pre Area 2 (Offsite) Hydrograph ■ Runoff 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Printed 9/9/2021 Summary for Link 9L: Areas Combined (Pre1 On+Off-site) Inflow Area = 1.750 ac, 0.00% Impervious, Inflow Depth > 3.85" for 10-Year event Inflow = 7.01 cfs @ 12.14 hrs, Volume= 0.562 of Primary = 7.01 cfs @ 12.14 hrs, Volume= 0.562 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs ■ 1WM— ■ Primary Keswick Hall_PreDev Prepared by Timmons G NOAA 24-hr D 10-Year Rainfall=5.35" Printed 9/9/2021 Summary for Link 12L: Area 2 Combined (Pre On+Off-site) Inflow Area = 0.940 ac, 0.00% Impervious, Inflow Depth > 3.90" for 10-Year event Inflow = 3.68 cfs @ 12.14 hrs, Volume= 0.306 of Primary = 3.68 cfs @ 12.14 hrs, Volume= 0.306 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 12L: Area 2 Combined (Pre On+Off-site) Hydrograph ■ Inflow ■ Primary Time (hours) 1S Post Area 1 Total Post Area 1 Subcat Reach Aon Llnk 3S O 5S Post Area (Onsite, P t Area 2 (Ofisite) P tArea2b(Onslte, Data ad untletainetl) 6PL UGU 8L Total Post Area 2 Keswick Hall_PostDev Type 1124-hr 1-YR Rainfall=2.92" Prepared by Timmons Group Printed 9/9/2021 HydroCADO 10.10-4a s/n 06538 © 2020 HydroCAD Software Solutions LLC Page 2 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Post Area 1 (Onsite) Runoff Area=0.810 ac 0.00% Impervious Runoff Depth>1.99" Tc=6.0 min CN=91 Runoff=2.70 cfs 0.135 of Subcatchment 3S: Post Area 2a (Onsite, Runoff Area=0.600 ac 0.00% Impervious Runoff Depth>2.27" Tc=6.0 min CN=94 Runoff=2.20 cfs 0.114 of Subcatchment 4S: Post Area 2 (Offsite) Runoff Area=1.160 ac 0.00% Impervious Runoff Depth>1.38" Flow Length=126' Tc=9.3 min CN=83 Runoff=2.50 cfs 0.133 of Subcatchment 5S: Post Area 2b (Onsite, Runoff Area=0.120 ac 0.00% Impervious Runoff Depth>1.25" Tc=6.0 min CN=81 Runoff=0.26 cfs 0.013 of Pond 6P: UGD Peak Elev=429.94' Storage=0.079 of Inflow=4.58 cfs 0.247 of Outflow=1.03 cfs 0.246 of Link 7L: Total Post Area 1 Inflow=2.70 cfs 0.135 of Primary=2.70 cfs 0.135 of Link 8L: Total Post Area 2 Inflow=1.15 cfs 0.258 of Primary=1.15 cfs 0.258 of Total Runoff Area = 2.690 ac Runoff Volume = 0.394 of Average Runoff Depth = 1.76" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PostDev Prepared by Timmons Gi Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Summary for Subcatchment 1S: Post Area 1 (Onsite) Runoff = 2.70 cfs @ 11.97 hrs, Volume= 0.135 af, Depth> 1.99" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=2.92" Area (ac) CN Description 0.810 91 CN - VRRM Spreadsheet 0.810 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Post Area 1 (Onsite) Hydrograph 3 z 70 d, Type II 24-hr 1-YR Rainfall=2.92" Runoff Area=0.810 ac 2 Runoff Volume=0.135 of Runoff Depth>1.99" Tc=6.0 min CN=91 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ❑ RunoH Keswick Hall_PostDev Prepared by Timmons Gi Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Summary for Subcatchment 3S: Post Area 2a (Onsite, Detained) Runoff = 2.20 cfs @ 11.96 hrs, Volume= 0.114 af, Depth> 2.27" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=2.92" Area (ac) CN Description 0.600 94 CN - VRRM Spreadsheet 0.600 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Post Area 2a (Onsite, Detained) Hydrograph ❑ Runoff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type 1124-hr 1-YR Rainfall=2.92" Summary for Subcatchment 4S: Post Area 2 (Offsite) Runoff = 2.50 cfs @ 12.01 hrs, Volume= 0.133 af, Depth> 1.38" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=2.92" Area (ac) CN 1.160 83 >75% Grass cover, Good, HSG D 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unoaved Kv= 16.1 fos 9.3 126 Total L° u Subcatchment 4S: Post Area 2 (Offsite) Hydrograph Time (hours) O Runoff Keswick Hall_PostDev Prepared by Timmons Gi Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Summary for Subcatchment 5S: Post Area 2b (Onsite, undetained) Runoff = 0.26 cfs @ 11.98 hrs, Volume= 0.013 af, Depth> 1.25" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=2.92" Area (ac) CN Description 0.120 81 0.120 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Post Area 2b (Onsite, undetained) Hydrograph 1 1 1 1 1 1 1 1 1 1 1 1 1 /I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Rurwff Keswick Hall_PostDev Prepared by Timmons Gi Summary for Pond 6P: UGD Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Inflow Area = 1.760 ac, 0.00% Impervious, Inflow Depth > 1.68" for 1-YR event Inflow = 4.58 cfs @ 11.99 hrs, Volume= 0.247 of Outflow = 1.03 cfs @ 12.20 hrs, Volume= 0.246 af, Atten= 77%, Lag= 12.9 min Primary = 1.03 cfs @ 12.20 hrs, Volume= 0.246 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 429.94' @ 12.20 hrs Surf.Area= 0.038 ac Storage= 0.079 of Plug -Flow detention time= 30.1 min calculated for 0.246 of (100% of inflow) Center -of -Mass det. time= 27.4 min ( 840.5 - 813.1 ) Volume Invert Avail.Storage Storage Description #1 427.25' 0.182 of 72.0" Round CMP Round 72" L= 280.0' Device Routing Invert Outlet Devices #1 Primary 427.25' 15.0" Round Culvert L= 158.3' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 427.25' / 418.00' S= 0.0584 '/' Cc= 0.900 n= 0.010, Flow Area= 1.23 sf #2 Device 1 427.25' 5.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 430.00' 7.0" W x 4.0" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads MPrimary OutFlow Max=1.03 cfs @ 12.20 hrs HW=429.94' (Free Discharge) L1=Culvert (Passes 1.03 cfs of 6.70 cfs potential flow) �2=Orifice/Grate (Orifice Controls 1.03 cfs @ 7.58 fps) 3=Orifice/Grate ( Controls 0.00 cfs) Keswick Hall_PostDev Prepared by Timmons Gr Pond 6P: UGD Hydrograph Time (hours) Type 11 24-hr 1-YR Rainfall=2.92" Printed 9/9/2021 ❑ INlow ❑ Primary Keswick Hall_PostDev Prepared by Timmons Gi Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Summary for Link 7L: Total Post Area 1 Inflow Area = 0.810 ac, 0.00% Impervious, Inflow Depth > 1.99" for 1-YR event Inflow = 2.70 cfs @ 11.97 hrs, Volume= 0.135 of Primary = 2.70 cfs @ 11.97 hrs, Volume= 0.135 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 7L: Total Post Area 1 Hydrograph ■ Inflow ■ Primary Time (hours) Keswick Hall_PostDev Prepared by Timmons GI Type 1124-hr 1-YR Rainfall=2.92" Printed 9/9/2021 Summary for Link 8L: Total Post Area 2 Inflow Area = 1.880 ac, 0.00% Impervious, Inflow Depth > 1.65" for 1-YR event Inflow = 1.15 cfs @ 12.02 hrs, Volume= 0.258 of Primary = 1.15 cfs @ 12.02 hrs, Volume= 0.258 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 8L: Total Post Area 2 Hydrograph ■ Inflow ■ Primary Time (hours) Keswick Hall_PostDev Type/1 24-hr 2-YR Rainfall=3.54" Prepared by Timmons Group Printed 9/9/2021 HydroCADO 10.10-4a s/n 06538 © 2020 HydroCAD Software Solutions LLC Page 11 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Post Area 1 (Onsite) Runoff Area=0.810 ac 0.00% Impervious Runoff Depth>2.58" Tc=6.0 min CN=91 Runoff=3.43 cfs 0.174 of Subcatchment 3S: Post Area 2a (Onsite, Runoff Area=0.600 ac 0.00% Impervious Runoff Depth>2.87" Tc=6.0 min CN=94 Runoff=2.74 cfs 0.144 of Subcatchment 4S: Post Area 2 (Offsite) Runoff Area=1.160 ac 0.00% Impervious Runoff Depth>1.89" Flow Length=126' Tc=9.3 min CN=83 Runoff=3.41 cfs 0.183 of Subcatchment 5S: Post Area 2b (Onsite, Runoff Area=0.120 ac 0.00% Impervious Runoff Depth>1.74" Tc=6.0 min CN=81 Runoff=0.36 cfs 0.017 of Pond 6P: UGD Peak Elev=430.60' Storage=0.104 of Inflow=6.00 cfs 0.326 of Outflow=1.78 cfs 0.325 of Link 7L: Total Post Area 1 Inflow=3.43 cfs 0.174 of Primary=3.43 cfs 0.174 of Link 8L: Total Post Area 2 Inflow=1.85 cfs 0.342 of Primary=1.85 cfs 0.342 of Total Runoff Area = 2.690 ac Runoff Volume = 0.517 of Average Runoff Depth = 2.31" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 1S: Post Area 1 (Onsite) Runoff = 3.43 cfs @ 11.97 hrs, Volume= 0.174 af, Depth> 2.58" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.54" Area (ac) CN Description 0.810 91 CN - VRRM Spreadsheet 0.810 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Post Area 1 (Onsite) Hydrograph ❑ RunoH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 3S: Post Area 2a (Onsite, Detained) Runoff = 2.74 cfs @ 11.96 hrs, Volume= 0.144 af, Depth> 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.54" Area (ac) CN Description 0.600 94 CN - VRRM Spreadsheet 0.600 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Post Area 2a (Onsite, Detained) Hydrograph ❑ Runoff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 4S: Post Area 2 (Offsite) Runoff = 3.41 cfs @ 12.01 hrs, Volume= 0.183 af, Depth> 1.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.54" Area (ac) CN Description ' 1.160 83 >75% Grass cover, Good, HSG D 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unoaved Kv= 16.1 fos 9.3 126 Total 31 Subcatchment 4S: Post Area 2 (Offsite) Hydrograph I ' K 9 1 2 3 4 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 29 21 22 23 24 Time (hours) p Runoff Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Subcatchment 5S: Post Area 2b (Onsite, undetained) Runoff = 0.36 cfs @ 11.97 hrs, Volume= 0.017 af, Depth> 1.74" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.54" Area (ac) CN Description 0.120 81 0.120 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Post Area 2b (Onsite, undetained) Hydrograph ■ Runoff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Summary for Pond 6P: UGD Type 1l 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Inflow Area = 1.760 ac, 0.00% Impervious, Inflow Depth > 2.22" for 2-YR event Inflow = 6.00 cfs @ 11.99 hrs, Volume= 0.326 of Outflow = 1.78 cfs @ 12.16 hrs, Volume= 0.325 af, Atten= 70%, Lag= 10.5 min Primary = 1.78 cfs @ 12.16 hrs, Volume= 0.325 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 430.60' @ 12.16 hrs Surf.Area= 0.038 ac Storage= 0.104 of Plug -Flow detention time= 31.4 min calculated for 0.324 of (99% of inflow) Center -of -Mass det. time= 29.0 min ( 835.3 - 806.2 ) Volume Invert Avail.Storage Storage Description #1 427.25' 0.182 of 72.0" Round CMP Round 72" L= 280.0' Device Routing Invert Outlet Devices #1 Primary 427.25' 15.0" Round Culvert L= 158.3' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 427.25' / 418.00' S= 0.0584 '/' Cc= 0.900 n= 0.010, Flow Area= 1.23 sf #2 Device 1 427.25' 5.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 430.00' 7.0" W x 4.0" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads MPrimary OutFlow Max=1.77 cfs @ 12.16 hrs HW=430.59' (Free Discharge) L1=Culvert (Passes 1.77 cfs of 7.69 cfs potential flow) �2=Orifice/Grate (Orifice Controls 1.16 cfs @ 8.53 fps) 3=Orifice/Grate (Orifice Controls 0.61 cfs @ 3.13 fps) Keswick Hall_PostDev Prepared by Timmons Gr Pond 6P: UGD Hydrograph Type 11 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 ■ Inflow Of Primary 111,1,111 111,1,111,1I 1'11"111111 1 11 ® 1'11„111111 �1��W111 r , Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Link 7L: Total Post Area 1 Inflow Area = 0.810 ac, 0.00% Impervious, Inflow Depth > 2.58" for 2-YR event Inflow = 3.43 cfs @ 11.97 hrs, Volume= 0.174 of Primary = 3.43 cfs @ 11.97 hrs, Volume= 0.174 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 7L: Total Post Area 1 Hydrograph ■ hifim— ■ Primary Time (hours) Keswick Hall_PostDev Prepared by Timmons GI Type/1 24-hr 2-YR Rainfall=3.54" Printed 9/9/2021 Summary for Link 8L: Total Post Area 2 Inflow Area = 1.880 ac, 0.00% Impervious, Inflow Depth > 2.19" for 2-YR event Inflow = 1.85 cfs @ 12.14 hrs, Volume= 0.342 of Primary = 1.85 cfs @ 12.14 hrs, Volume= 0.342 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 8L: Total Post Area 2 Hydrograph ■ Inflow e Primary Time (hours) Keswick Hall_PostDev Type/1 24-hr 10-YR Rainfall=5.35" Prepared by Timmons Group Printed 9/9/2021 HydroCADO 10.10-4a s/n 06538 © 2020 HydroCAD Software Solutions LLC Page 20 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Post Area 1 (Onsite) Runoff Area=0.810 ac 0.00% Impervious Runoff Depth>4.32" Tc=6.0 min CN=91 Runoff=5.57 cfs 0.292 of Subcatchment 3S: Post Area 2a (Onsite, Runoff Area=0.600 ac 0.00% Impervious Runoff Depth>4.65" Tc=6.0 min CN=94 Runoff=4.30 cfs 0.232 of Subcatchment 4S: Post Area 2 (Offsite) Runoff Area=1.160 ac 0.00% Impervious Runoff Depth>3.49" Flow Length=126' Tc=9.3 min CN=83 Runoff=6.19 cfs 0.337 of Subcatchment 5S: Post Area 2b (Onsite, Runoff Area=0.120 ac 0.00% Impervious Runoff Depth>3.29" Tc=6.0 min CN=81 Runoff=0.67 cfs 0.033 of Pond 6P: UGD Peak Elev=433.15' Storage=0.181 of Inflow=10.27 cfs 0.569 of Outflow=3.18 cfs 0.564 of Link 7L: Total Post Area 1 Inflow=5.57 cfs 0.292 of Primary=5.57 cfs 0.292 of Link 8L: Total Post Area 2 Inflow=3.37 cfs 0.597 of Primary=3.37 cfs 0.597 of Total Runoff Area = 2.690 ac Runoff Volume = 0.894 of Average Runoff Depth = 3.99" 100.00% Pervious = 2.690 ac 0.00% Impervious = 0.000 ac Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 1S: Post Area 1 (Onsite) Runoff = 5.57 cfs @ 11.96 hrs, Volume= 0.292 af, Depth> 4.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.35 Area (ac) CN Description 0.810 91 CN - VRRM Spreadsheet 0.810 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Post Area 1 (Onsite) Hydrograph ❑ RunoH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 3S: Post Area 2a (Onsite, Detained) Runoff = 4.30 cfs @ 11.96 hrs, Volume= 0.232 af, Depth> 4.65" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.35 Area (ac) CN Description 0.600 94 CN - VRRM Spreadsheet 0.600 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Post Area 2a (Onsite, Detained) Hydrograph ❑ Runoff 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Summary for Subcatchment 4S: Post Area 2 (Offsite) Runoff = 6.19 cfs @ 12.00 hrs, Volume= 0.337 af, Depth> 3.49" Printed 9/9/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.35 Area (ac) CN 1.160 83 >75% Grass cover, Good, HSG D 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.2 100 0.0530 0.18 Sheet Flow, Grass: Dense n= 0.240 P2= 3.54" 0.1 26 0.2300 7.72 Shallow Concentrated Flow, Unoaved Kv= 16.1 fos 9.3 126 Total Subcatchment 4S: Post Area 2 (Offsite) Hydrograph Time (hours) ■ Rurwff Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Printed 9/9/2021 Summary for Subcatchment 5S: Post Area 2b (Onsite, undetained) Runoff = 0.67 cfs @ 11.97 hrs, Volume= 0.033 af, Depth> 3.29" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.35 Area (ac) CN Description ' 0.120 81 0.120 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Q Subcatchment 5S: Post Area 2b (Onsite, undetained) Hydrograph ■■■■■■■ III■■ .■ • . 1 0 _ • • _ No ■■■■■■■■ "® ■■■■■■■■ , I �I, ■■■■■■■■ ■■■■■■■■ ■■■■■■■■ ■■■■■■■■ ■■■■■■■■ ■■■■■■■■■■ ■■■....■ .■■■■■■■■ ■■■.■■■■■..,,,.,,,,,,._... 0. 1. .2. 3. 4 .5. 5. .7. 8. 0 .10 .11 12 13 14 .15 .16 17 13. 1,0 20 .21 22 23. 24 Time (hours) ■ Runott Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Summary for Pond 6P: UGD Printed 9/9/2021 Inflow Area = 1.760 ac, 0.00% Impervious, Inflow Depth > 3.88" for 10-YR event Inflow = 10.27 cfs @ 11.99 hrs, Volume= 0.569 of Outflow = 3.18 cfs @ 12.14 hrs, Volume= 0.564 af, Atten= 69%, Lag= 9.0 min Primary = 3.18 cfs @ 12.14 hrs, Volume= 0.564 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 433.15' @ 12.14 hrs Surf.Area= 0.010 ac Storage= 0.181 of Plug -Flow detention time= 36.3 min calculated for 0.564 of (99% of inflow) Center -of -Mass det. time= 30.7 min ( 823.1 - 792.4 ) Volume Invert Avail.Storage Storage Description #1 427.25' 0.182 of 72.0" Round CMP Round 72" L= 280.0' Device Routing Invert Outlet Devices #1 Primary 427.25' 15.0" Round Culvert L= 158.3' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 427.25' / 418.00' S= 0.0584 '/' Cc= 0.900 n= 0.010, Flow Area= 1.23 sf #2 Device 1 427.25' 5.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 430.00' 7.0" W x 4.0" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads MPrimary OutFlow Max=3.18 cfs @ 12.14 hrs HW=433.13' (Free Discharge) L1=Culvert (Passes 3.18 cfs of 10.70 cfs potential flow) �2=Orifice/Grate (Orifice Controls 1.56 cfs @ 11.47 fps) 3=Orifice/Grate (Orifice Controls 1.61 cfs @ 8.29 fps) Keswick Hall_PostDev Prepared by Timmons Gr Pond 6P: UGD Hydrograph Time (horns) Type 1124-hr 10-YR Rainfall=5.35" Printed 9/9/2021 ■ 1-flM— ■ Primary Keswick Hall_PostDev Prepared by Timmons GI Type/1 24-hr 10-YR Rainfall=5.35" Printed 9/9/2021 Summary for Link 7L: Total Post Area 1 Inflow Area = 0.810 ac, 0.00% Impervious, Inflow Depth > 4.32" for 10-YR event Inflow = 5.57 cfs @ 11.96 hrs, Volume= 0.292 of Primary = 5.57 cfs @ 11.96 hrs, Volume= 0.292 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 7L: Total Post Area 1 Hydrograph ■ Inflow ■ Primary Time (hours) Keswick Hall_PostDev Prepared by Timmons Gi Type/1 24-hr 10-YR Rainfall=5.35" Printed 9/9/2021 Summary for Link 8L: Total Post Area 2 Inflow Area = 1.880 ac, 0.00% Impervious, Inflow Depth > 3.81" for 10-YR event Inflow = 3.37 cfs @ 12.11 hrs, Volume= 0.597 of Primary = 3.37 cfs @ 12.11 hrs, Volume= 0.597 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 8L: Total Post Area 2 Hydrograph ■ Inflow ■ Primary Time (hours) ECOSYSTEM SERVICES, LLC 1739 Allied Street, Suite A Charlottesville, VA 22903 540.578.4296 www.ecosystemservices.us ion@ecosystemservices.us October 15, 2021 Riki van Niekerk Project Engineer Timmons Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 RE: Nutrient Offset Credit — Credit Availability Letter Keswick Hall Family Pool Project Project Address: 701 Club Drive — Albemarle County, VA WPO-2021-00054 Project TMP: 0800-00-00-00820 Project HUC: 02080204 Bank HUC: 02080204 Bank Address: 1705 Lambs Road, Charlottesville, VA 22901 Dear Riki, We appreciate the opportunity to provide a credit availability letter for 0.34 pounds of phosphorus for the above referenced project. This letter is to certify that as of today, October 13, 2021, Ivy Creek Nutrient Bank has 125.85 pounds of phosphorus (TP), 193.77 pounds of nitrogen (TN), and 39,685.16 pounds of TSS available for transfer to those entities requiring offsets in accordance with the Chesapeake Bay Watershed Nutrient Credit Exchange Program (VA Code § 62.1-44.19:14 et seq.). Those offsets are also transferable in accordance with the Virginia stormwater offset program (VA Code § 62.1-44.15:35) and the Virginia Soil and Water Conservation Board's Guidance Document on Stormwater Nonpoint Nutrient Offsets approved on July 23, 2009, to those regulated entities qualifying for nutrient credits. We can certainly accommodate your needs and could offer to fulfil the order of 0.34 pounds of phosphorus. Please feel free to contact us with any questions. I hope we have the opportunity to work together on this project. Sincerely, Ecosystem Services, LLC By: 9, E bL. Jonathan R. Roller, AOSE PSS CNMP Manager —Authorized Representative