Loading...
HomeMy WebLinkAboutWPO202000030 Calculations WPO VSMP 2021-03-24 2415 IVY ROAD COMMERCIAL REDEVELOPMENT FINAL STORMWATER MANAGEMENT CALCULATIONS PACKET (WPO 202000030) Date of Calculations June 1, 2020 Revised on January 11, 2021 PREPARED BY: COLLINS ' NGINEERING 200 GARRETT STREET, SUITE K CHARLOTTESVILLE, VA 22902 434.293.3719 PH 434.293.2813 FX www.collins-engineering.com APPROVED by the Albemarle County Communi D v lopment Department Date 3 File L eic96 Table of Contents Section 1- DEQ Virginia Runoff Reduction Method for ReDevelopment Water Quality Calculations Section 2-SCS TR-55 Calculations Section 3-Channel and Flood Protection Compliance Section 4- Pre-Development SCS Unit Hydrographs Section 5- Post-Development SCS Unit Hydrographs Section 6- Proposed Dry Detention Basin Routing Calculations Section 1 DEQ Virginia Runoff Reduction Method for ReDevelopment Water Quality Calculations DEQ Virginia Runoff Reduction Method Re-Development Compliance Spreadsheet -Version 3.0 E 2011 BMP Standards and Specifications Ell 2013 Draft BMP Standards and Specifications Project Name: 2415 IVY ROAD COMMERCIAL REDEVELOPMENT PLAN FINAL data input cells - Date: 1st Submittal 5/11/2020,Revised 1/6/21 constant values Linear Development Project? No calculation cells Site Information final results Post-Development Project(Treatment Volume and Loads) Enter Total Disturbed Area(acres) - 2.86 1 Check: BMP Design Specifications List: 2013 Draft Stds&Specs Maximum reduction required: 20% Llnea►project? No The site's net increase in impervious cover(acres)is:_ 0 Land cover areas entered correctly? 1,/ Post-Development TP Load Reduction for Site(lb/yr): 0.86 Total disturbed area entered? l/ Pre-ReDevelopment Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space(acres)-undisturbed, protected forest/open space or reforested land 0.00 Managed Turf(acres)-disturbed,graded for yards or other turf to be mowed/managed 1.04 1.04 Impervious Cover(acres) 1.82 1.82 ............. ...... 2.86 Post-Development Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space(acres)--undisturbed, protected forest/open space or reforested land 0.00 - Managed Turf(acres)--disturbed,graded for yards or other turf to be mowed/managed 1.07 1.07 Impervious Cover(acres) 1.79 1.79 Area Check OK. OK. OK. OK. 2.86 Constants Runoff Coefficients(Rv) Annual Rainfall(inches) 43 A Soils B Soils C Soils D soils 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/yr) 0.41 _1_ Pi(unitless correction factor) 0.90 _ LAND COVER SUMMARY-- PRE-REDEVELOPMENT LAND COVER SUMMARY--POST DEVELOPMENT Land Cover Summary-Pre Land Cover Summary-Post(Final) Land Cover Summary-Post_ Land Cover Summary-Post Pre-ReDevelopment Listed Adjusted' Post ReDev.&New Impervious Post-ReDevelopment Post-Development New Impervious Forest/Open Space Cover(acres) 0.00 0.00 Forest/Open Space Cover 0 oo - Forest/Open Space I - (acres) Cover(acres) Weighted Rv(forest) 0.00 0.00 Weighted Rv(forest) 0.00 Weighted Rv(forest) 000 %Forest 0% 0% %Fost 0% %Forest 0% na re Managed Turf Cover(acres) 1.04 1 04 Managed Turf Cover 1.07 Managed Turf Cover 1.07 - _ ____._ (acres) _ _ _.(acre5l (: ., Weighted Rv(turf) 0.25 0.25 Weighted Rv(turf) 0.25 Weighted Rv(turf) 025 '` %Managed Turf 36% 36% %Managed Turf 37% %Managed Turf 37% Impervious Cover(acres) 1.82 1.82 Impervious Cover(acres) 1.79 ReDev Impervious 1.79 New Impervwus Cover 0.00 Cover(acres) ...... (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 Rv(impervious) -- %Impervious 64% 64% %Impervious 63% %Impervious 63% �� Total Site Area(acres) 2.86 2.86 Final Site Area(acres) 2.86 Total Re Ske Area 286 - Site Rv 0.70 0.70 Final Port Dev Site Rv 0.69 ReDev Site Rv 0.69 Treatment Volume and Nutrient Load Treatment Volume and Nutrient Load • Pre-ReDevelopment Treatment Volume Final Post-Development Post- Development : _2. Post-Development (acre-ft) 0.1658 0.1658 Treatment Volume 0.1640 - Treatment Volume 0.1640 Treatment Volume (acre-ft) (acre-A) = (am-R) Pre-ReDevelo t Treatment Volume Final PosbDevelopmen[ Post ReDev'1 pment Post-Development pmen 7,220 7,220 Treatment Volume 7,144 ( Treatment Volume 7,144 =Treatment Volume(cubic: - (cubic feet) (abk feet) (cubic fee[) = feet) II 7i Final Post- Fos[-ReDevelopment Pre-ReDevelopment TP Load 'Post-Development TP Load (Ib/yr) 4.54 4.54 Development TP Load 4.49 i Load(TN 4.49 (Ib/YQ - (Ib/yr) i ilb/yN' _ Pre-Relevelopmenl TP Load per acre Final Post Development Tr Past-ReDevelopment TP (lb/acre/wl 1.59 LS9 toad per acre 1.57 Load per acre 1.57 (Ib/acre/Yr) (lb/acre/Yr) Baseline TP Load(lb/yr) Mao.Reduction Required (0.41 lbs/acre/yt applied to pre-redevelopment area excluding pervious 1.17 (Below Pre- 20% land proposed for new impervious cover) ReDevelopment load) TP Load Reduction 'Adjusted Land Cover Summery TP Load Reduction Pro ReDevelopment land cover minus pervious land cover(forest/open space or managed Required for 0.86 Required for New 0 Dud)acreage proposed for new impervious cover Redeveloped Area Impervious Area(lb/ye) (lb/yr) Adjusted total acreage is consistent with Post-ReDevelopment acreage(minus acreage of c new impervious cover). Column I rhaws lead reduction requrienrent for new impervious cover(based on new development load limit,0 41 lbs/aree/yeoel Post-Development Requirement for Site Area TP Load Reduction Required(lb/yr) 0.86 • Nitrogen Loads(Informational Purposes Only) ' Final Post-Development TN Load Pre-ReDevelopment TN Load(Ib/ye) 32.45 (Post-ReDevelopment&New Impervious) 32.11 (lb/yr) VPPG,R4Der_imloArpret44EVP.Pr.5 Drainage Area B pain.Am a Land Caro,Naval =Ma •Sells ItSoll• Catras _ {MAY To. land Cara Ps ForostrOpen 5Psra MO 0.03 0.00 P- 'Pampa turt laant 0.31 0.31 0 25 antaraurn Cow Issratl 0.27 0 27 0.95 Total Phosphorus Available I or Ramovol M DA 31112/yr) 0 7P Total OM Post Development treatment VoluM•In 0.0.B(ft) ,..”a Stormwater Best Management Practices(RR=Runoff Reduction) -Select from Proprlawn lists- Phosphorus Vatter,. 3232. 3.0•111.17art Imam-Haus Velar...ram . gamete. Total 1510P Phosphorus 0905011009S 00105MMS Nitrogen Nit,ogen S. wows. wowv awoe practice ReelMPIOn owitrew owe crew woo... cowo Treatment Iter.val °' P"*.'"'" Perna.By Phosphorua '''''''''''.r.c.""'' RemPal horn Upstream Pare,laad la Nmarad Ily IOU..load revenge 000too iewo croo loom now.(ft)"d'''''''')vow..ift) Volume(11) Meier.MI..%:.; ....,,:. Praatke(115) La.,0h1 52010 (%) Pr...GM) Prxtlre(lbsl Practlar Ohs) llhsl 11 ,0 2',swifts PO.Mal .' .' 7 o 0 ono °' 11:111111= 10 Vowteel WOO 15ow WI 0 o o ,' , , 0. 0 oa 000 Z. '' =MM. II=IIIMM=MMIll la 5MMe OlsemmOtion lo AA SoP4 SO 0 0 0 0 0 OW 0 00 OW 150.411 . 2 lbs..Duo...noon to CA3,5Ms 0 0 0 0 0 OM 000 0 00 0 00 0 000 0 OD OM 0 OD 15Per 511 2 cro 5o4 AmenGed'On Gotha oer 50 o ,,-7;,. 0. OM 040 0 00 .. 0 , OM 0 CO OM GOO MedMaions MINI.Cr0 Gbh)150.4.0 2 41.M Dry weii or French or4rn s/. 50 a o o o 25 OM 000 0 00 000 15 ODD 0.00 0 CO papromMiropm.0ara Nat 10 To Drovell or rm.Want, 90 0 0 o 0 25 OM OM 0 00 15 °CO 0 00 0 00 OM , 1PlenrInfrluaba0 4215per NO . 2 I To Ram GrMn 81. PO 0 0 15 OM 0 00 OM 0 00 PAPro-Morekention Ill(SOK.5) . .. 2 g Po.n Corrlen 42, PO 0 0 0 0 50 0.00 0 CO OW o Oo so 0 c0 000 OM 000 raurreasarrentlen.2(Sass•9I 2 a Total...war marresurcspar AO 0 0 0 0 , 0.00 , 0 00 C.GO 0 00 0 00 0.00 . 0 0 0 0 0 LO 0 00 0 00 40 OM OM OW .....5meterGM0 1.4e M.GPOeMb al 0.-/;./.;1": 3 Permeable Pavement ORR) pamernent 41(Spec.) . 0(4.'Y OP, MIE 4. 512 "' " a on 0 34 024 1.1. °' '' MEESE 3 b IermeAM Prem.,.,Spec.1 n GV'" 0/// '. <;;;;;:. ' 25 :;,<,:/:r OM 0 LO 0 DO ME :'''''''''' '' .1:. '' la Oral•Chion41.50.0.4 031 M 0 0 0 0 IS 0 00 OM 000 0 00 20 000 000 OM 0 00 00 Ors0000.00I10DS0515004 MI II 0 0 I I IS 0 00 OM 0 00 000 .20 0 00 OM OM 0 00 Cc arsoCaanraltalre Campo Pa*.Sails 2o 0 a o o 15 ow o co o.00 o oo N 0 00 0 00 OM 000 0414e,elmm Om*O.) 5 Ory 525sh lar I 0 0 0 0 20 0 00 0 OD ODD 25 000 OM , OM , OM 5 e 00 same.215aer.2.1 so a a 0 3 40 ODD 35 000 OW 0 00 OM -a w000ronba isrl 6 a lboreteraran 41 or 14000MretenlIon SI or .0 urn Barcena,.istres as, 6 b Boretentron el or korroPsoretentron In . o o o a so a on 0 03 0 or. OM 50 ooa 7 InfittrabonfRill 1.Inlittlet5:01 IRO) 1 a InfiltratonS1(5per 051 50 0 0 0 0 is 00) OM OW IlEll '' ".' 11:111.1:. 712 Mbitromn 112 15.4401 M 0 0 0 0 ODD OLO 000 ME 'C''' '' MM.= S f%tended Detentl on PM,.(RR) P.Prtentled Detentmet POnd(RR/ 8 a 2041,5pec./51 0 0 0 0 0 15 OM OW OM 0 00 ME ".' '''' =MM. se ED.213..1 IS 0 0 0 0 OM 000 WM ".' °' =MM. •.5Pmet1 10m,to P,P,100en Space(RR, P 4...Mow to Cons...non Area,PA 5Ms n a o 0 a 0 0 co 0 to ow ==ETIIIIIIIMIMIMIIIIo coo 000 o oo 000 a o 0 o 0 OM 0 OD 0[0 OW 0 0 00 0 00 0 00 OM 15mr 11,21 - - SO 0 0 0 0 0 0 00 0 CO 0 00 15per.a 44, IMMO, 1 M2 4 45 MA maw +M Rood FnNAEWARuv TOTAL IMPERVIOUS COVER TREATED(x) 0.37 AREA CHECK.OIL TOTAL TURF AREA TREATED 00 000 AREA OEM.OR. TOTAL RUNOFF REDUCTION M DAEIRI A19 TOTAL PHOSPHORUS TABLE FOR REMOVAL IN O.A.B(Br/WI 0.76 T0TALPU01000RUS REMOVEDWTTNRUNOFF REDUCTION PRACTCOSIN DA.B(N/yrl 0. TOTAL RUNOFF REDUCTION IMU.A.1IN'1 A19 TOTAL PHOSPHORUS REMAINING AFTER APPLYING RUNOFF REDUCTION PRACTICES IN DA.BIIyyr) ILO NITROGEN REMOVED WIlN RUNOFF REDUCTION PRACTICES IN DA BIIb/Yrl L66 SEE WATER 0U4LITV COMP:,4NC£741i MR SITE COMPLIANCE L'05CLL41'IONS SEE WATER QUALITY CATA01JNCT TAR FCA Se1E CA(C:ILADONS 0n0+mn4,>T 00,4 10 We•S..d.e lro PP, 10.Wet Swle(Coastal Kowa lno RRl 10a.We 5.61e al/LPe,O1U 0 0 0 0 0 10 000 000 Pao OW © 0.00 0a0 10.0 WHS4.1•1121LPee E111 0 A 0 0 0 10 030 SW 000 090 a aw P00 m 11.rate B ¢rtetI.O RRI eTI fro RR) 11.or01 [ IVe NI 150.104 0 I 0 0 0 0 0.03 a.00 um 0.00 ME Om 0.0 Rom I0000enreP/L�e1IIT.r.I1l 0 0 0 I 0 01 000 QM ® I/O Mam 1E.Constructed Wed Ind l.o RN wetland Tne RAI 11.eCo..daWdW...d1„Pee01„ R 0 0 0 0 Lo 000 00 OW ®W Pw P' Rom 1T,.Ta.0matsa%ynam11�IIII P B R P 0 IS Poo 000 BIO ® 0OU Rom 13.Wet Pan.010 nRl 13...We rob dl poet nel 0 0 0 0 0 50 0.00 000 0.00 OM w m E o.00 O.Oa 0.a0 o.eo 110 Wet Pnl,Coastal elel - 0 - 0 0 0 0 es 000 0.00 OW 000 10 0.00 o.a0 OA0 O.OD -11.e.Wet Pond n...mai Pion)lSoerEul 0 0 0 0 0 M 0.m 010 OM 0.00 n O. OW 000 o.m 4,n.olatmree BwP I MO.a - 0 0 a 0 0 OW OM 0 CO ME Bm Pad Rom 1.,N. . ..ST�a. ...F.�.tD . . P 0 E 0 P m0.0010 IT OW E 003 0 IT Pad om LOT.10..wRw4 0. 001U..U._ 0 0 0 0 0 10 RW OW O000AW ME Gm OW o TREATED UU 0.E7 AREA CHECK.OC TOTAL MANAGED TURF ARLR TREATED(W) 0.00 AREA ONCC OK TOTAL PHOSPHORUS REMOVAL REQUIRED ON SITE(Ibhr)l OM 1 TOTAL PHOSPHORUS AVAIUBLE.FOR REMOVAL IN D.A.O pbMI 0.76 TOTAL PHUSnIORUS REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A.B 110/nl D.W TOTAL PHOSPHORUS REMOVED WIM RUNOFF REDUCTON PRACTICES IN D.A.a/U/Yrl 0.3E TOTAL PHOSPHORUS LOAO REDUCTION ACHIEVED IN D.A.Bub/Yrl 0.3a TOTAL PHOSPHORUS REMAINING AFTER APPLYING ow LOAD REDUCOON9 M O.A.B(10/yrl 06E SEE WATER//UAUTY COMPLIANCE TAB FOR SLTE COMPLIANCE CALCULATIONS NITROGEN REMOVED WITH RUNOFF REDUITION MACTICES IN D.A.B(1116.1 LK NITROGEN REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A B(Ib/v0 O.0) TOTAL NITROGEN REMOVED IN DA.B Ub/WI 2.46 Site Results (Water Quality Compliance) Area Checks D.A.A D.A.B D.A.C D.A.D D.A.E AREA CHECK FOREST/OPEN SPACE(ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER(ac) 0.00 0.27 0.00 0.00 0.00 OK, 7 IMPERVIOUS COVER TREATED(ac) 0.00 0.27 0.00 0.00 0.00 OK. _ MANAGED TURF AREA(ac) 0.00 0.31 0.00 0.00 0.00 OK. - MANAGED TURF AREA TREATED(ac) 0.00 0.00 0.00 0.00 0.00 OK. AREA CHECK OK. OK. OK. OK. OK. Site Treatment Volume(ft3) 7,144 Runoff Reduction Volume and TP By Drainage Area r D.A.A [ D.A.B D.A.C D.A.D D.A.E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED(ft3) 0 419 0 0 0 419 TP LOAD AVAILABLE FOR REMOVAL (Ib/yr) 0.00 0.76 0.00 0.00 0.00 0.76 TP LOAD REDUCTION ACHIEVED (ib/yr) 0.00 0.34 0.00 0.00 0.00 0.34 TP LOAD REMAINING (Ib/yr) 0.00 0.42 0.00 0.00 0.00 0.42 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr)L 0.00 2.46 0.00 0.00 0.00 2.46 Total Phosphorus FINAL POST-DEVELOPMENT TP LOAD(Ib/yr) 4.49 TP LOAD REDUCTION REQUIRED(Ib/yr) 0.86 TP LOAD REDUCTION ACHIEVED (Ib/yr) 0.34 TP LOAD REMAINING(Ib/yr): 4.15 REMAINING TP LOAD REDUCTION REQUIRED(ib/yr): U.U1 i Total Nitrogen(For Information Purposes) POST-DEVELOPMENT LOAD(Ib/yr) 32.11 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 2.46 REMAINING POST-DEVELOPMENT NITROGEN LOAD(Ib/yr) 29.65 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 Total Rainfall(in): 43 Total Disturbed Acreage: 2.86 Site Land Cover Summary Pre-ReDevelopment Land Cover (acres) A soils B Soils C Soils D Soils 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 1.04 1.04 36 Impervious Cover(acres) 0.00 0.00 0.00 1.82 1.82 64 2.86 100 Post-ReDevelopment Land Cover (acres) A soils B Soils C Soils D Soils 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 1.07 1.07 37 Impervious Cover(acres) 0.00 0.00 0.00 1.79 1.79 63 2.86 100 Site Tv and Land Cover Nutrient Loads Pre- Final Post-Development Post- Post- Adjusted Pre- ReDevelopment Final Post-Development Post-ReDevelopment TP (Post-ReDevelopment Development TP Load per acre Load per acre &New Impervious) ReDevelopment (New Impervious) ReDevelopment TP Load per acre (Ib/acre/yr) (Ib/acre/yr) Qb/acre/yr) _ Site Rv 0 69 0.69 -- 0.70 1.59 1.57 1.57 Treatment Volume(ft3) 7,144 7,144 -- 7,220 TP Load(Ib/yr) 4.49 4.49 -- 4.54 Total TP Load Reduction Required(Ib/yr) 0.86 0.86 0 Final Post-Development Load Pre- (Post-ReDevelopment&New Impervious) ReDevelopment TN Load(Ib/yr) 32.11 32.45 Summary Print Virginia Runoff Reduction Method Worksheet Site Compliance Summary Maximum%Reduction Required Below Pre-ReDevelopment Load 20/ Total Runoff Volume Reduction(ft3) 419 Total TP Load Reduction Achieved(Ib/yr) 0.34 Total TN Load Reduction Achieved(Ib/yr) 2.46 Remaining Post Development TP Load (lb/yr) 4.15 Remaining TP Load Reduction(Ib/yr) Required Summary Print Virginia Runoff Reduction Method Worksheet -------------------"-----'-----'--'------------------- Drainage Area Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total Forest/Open(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acres) 0.00 0.31 0.00 0.00 0.00 0.31 Impervious Cover(acres) 0.00 0.27 0.00 0.00 0.00 0.27 Total Area(acres) 0.00 0.58 0.00 0.00 0.00 0.58 Drainage Area Compliance Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total TP Load Reduced(Ib/yr) 0.00 0.34 0.00 0.00 0.00 0.34 TN Load Reduced(Ib/yr) 0.00 2.46 0.00 0.00 0.00 2.46 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area B Summary Land Cover Summary A Soils B Soils C Soils D Soils 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 0.31 0.31 53 Impervious Cover(acres) 0.00 0.00 0.00 0.27 0.27 47 0.58 BMP Selections Managed Turf Impervious TP Load from BMP Treatment Untreated TP Load TP Removed TP Remaining Downstream Treatment Practice Credit Area Cover Credit Upstream (acres) Area(acres) Volume(ft;) Practices(Ibs) to Practice(Ibs) (Ib/yr) (Ib/yr) to be Employed 3.a.Permeable Pavement#1(Spec#7) 0.27 931.10 0.00 0.58 0.34 0.24 Total Impervious Cover Treated(acres) 0.27 Total Turf Area Treated(acres) 0.00 Total TP Load Reduction Achieved in D.A. (Ib/yr) 0.34 Total TN Load Reduction Achieved in D.A. (Ib/yr) 2.46 Summary Print Virginia Runoff Reduction Method Worksheet Runoff Volume and CN Calculations 1-year storm 2-year storm 10-year storm Target Rainfall Event(in) 3.04 3.67 5.55 Drainage Areas RV&CN Drainage Area A Drainage Area B Drainage Area C Drainage Area D Drainage Area E CN 0 88 0 0 0 RR(ft3) 0 419 0 0 0 RV wo RR(ws-in) 0.00 1.85 0.00 0.00 0.00 1-year return period RV w RR(ws-in) 0.00 1.65 0.00 0.00 0.00 CN adjusted 0 85 0 0 0 RV wo RR(ws-in) 0.00 2.42 0.00 0.00 0.00 2-year return period RV w RR(ws-in) 0.00 2.23 0.00 0.00 0.00 CN adjusted 0 86 0 0 0 RV wo RR(ws-in) 0.00 4.19 0.00 0.00 0.00 10-year return period RV w RR(ws-in) 0.00 3.99 0.00 0.00 0.00 CN adjusted 0 86 0 0 0 Summary Print Section 2 SCS TR-55 Calculations Soils Mapping (Source: NRCS Web Soil Survey Online Database) \\ '3t a\ 'R \ \ \\ \ \\`e '\ \, �� \�� $ ` �\ � v�A v ��> v�\, A icy;; -:vim V a ca� 4rlr vv ..� vv Aa \yVw A'� vVv z � \\\\ 4., `�� e �\a \ '\\�\�\\\\ � \ e am'. b \ 4,1 . • 44114 • fj „,. \ \\\ d M • 7 m,. \pa ' •« `f ,.# .. :e \ \`\:v ° _ate�� a, mow\ -\: :. ' .� ^�::...ua g \ .a .���,. \ a .' Z`� Soils Table (Source: NRCS Web Soil Survey Online Database) Albemarle County, Virginia (VAO03) Map Unit Percent of Symbol Map Unit Name AOI 19B Minnieville 3.00`0 loam, 2 to 7 percent slopes 36C Hayesville 4,1010 loam, 7 to 15 percent slopes 91 Urban land 92.9% Totals for Area of 100.00/o Interest The NRCS web soil survey defiaerialnes this development's soils as being primarily Urban Land. The following calculations conservatively consider'Urban Land' as having a hydrologic group type of D. Precipitation Data (Source: NOAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates) Map ^J EI Terrain ca t 0 1 I Bell air 4> 6 U 109r11 33000tt POINT PRECIPITATION FREQUENCY (PF) ESTIMATES WITH 90%CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION NOAA Atlas 14,Volume 2,Version 3 PDS-based precipitation frequency estimates with 90% confidence intervals(in inches)" Average recurrence interval{years} Duration I 1 I 2 II 5 II 10 11 25 II 50 II 100 II 200 II 500 JI 1000 ,fir 3.04 3.67 4.69 5.55 6.82 7.90 9.11 10.4 12.4 14.1 ?2 73-3 40; 1331.4 11) :4.21-5.25t ;4.96-6618) (6 66-7 57) -6 97-3 751 i7 06-10 t) ,,9 02-11 St 10 6-13 7' (11_8-15 5) U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 2:Runoff Curve Number and Runoff Project: 2415 Ivy Road Commercial Redevelopment Final Designed By: FGM,PE Date: 1/11/2021 Location: 2415 Ivy Road,Charlottesville,VA Checked By: SRC,PE Date: 1/11/2021 Check One: Present X Developed X 1.Runoff curve Number(CN) Cover description CN(weighted)= Drainage Area Soil name and hydrologic Area Product of CN x Calculated'S' tion group(Appendix (Cover type,treatment,and hydrologic condition;percent CN total product/ Descrip tion A) (Acres) Area Value impervious;unconnected/connected impervious area ratio) total area Impervious Areas-Paved 98 0.72 71.0 Impervious Areas-Gravel Parking 91 0.94 85.3 Onsite DA A D Impervious Areas-Dirt Parking 89 0.03 3.1 87 1.49 (Pre-Dev.) Lawns in Good Condition 80 0.75 60.3 Woods in Good Condition 77 0.64 49.3 Impervious Areas-Paved 98 0.03 2.5 Onsite DA B D Impervious Areas-Dirt Parking 89 0.00 0.3 81 2.37 (Pre-Dev.) Lawns in Good Condition 80 0.55 44.1 Impervious Areas-Paved 98 1.47 144.2 Onsite DA A D Lawns in Good Condition 80 1.02 81.5 88 1.37 (Post-Dev.) Woods in Good Condition 77 0.60 46.2 Impervious Areas-Paved 98 0.27 26.2 Onsite DA B D Lawns in Good Condition 80 0.31 25.0 88 1.33 (Post-Dev.) Woods in Good Condition 77 0.00 0.0 2.Runoff 1-Year Storm 2-Year Storm 10-Year Storm Drainage Area Description Frequency-years 1 _ 2 10 :n/a Rainfall,P(24 hour)-inches 3.04 3.67 5.55 n/a Runoff,Q-inches 1.78 _ 2.34 4.09 Onsite DA A(Pre-Dev.) Runoff,Q-inches 1.33 1.83 3.46 Onsite DAB(Pre-Dev.) Runoff,Q-inches 1.85 2.42 4.19 Onsite DA A(Post-Dev.) Runoff,Q-inches 1.88 2.45 4.22 Onsite DA B(Post-Dev.) U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 3:Time of Concentration(Ta)or Travel Time(Ti) Project: 2415 Ivy Road Commercial Redevelopment Final Designed By: FGM,PE Date: 1/11/2021 Location: 2415 Ivy Road,Charlottesville,VA Checked By: SRC,PE Date: 1/11/2021 Check One: Present X Developed X Check One: Tc X T, Through subarea n/a Onsite DA A Onsite DA B Onsite DA A Onsite DA B Segment ID: (Pre-Dev.) (Pre-Dev.) (Post-Dev.) (Post-Dev.) Sheet Flow:(Applicable to Tc only) 1 Surface description(Table 3-1) Dense Grass Dense Grass Dense Grass Dense Grass 2 Manning's roughness coeff.,n(Table 3-1 0.24 0.24 0.24 0.24 3 Flow length,L(total L<100)(ft) 100 100 100 100 4 Two-year 24-hour rainfall,P2(in.) 3.67 3.67 3.67 3.67 5 Land slope,s(ft/ft) 0.06 0.06 0.06 0.06 6 Compute T,=[0.007(n*L)°$]/Pz.s 50.4 0.14 0.14 0.14 0.14 Shallow Concentrated Flow: 7 Surface description(paved or unpaved) Unpaved Unpaved Unpaved Unpaved 8 Flow Length,L(ft) 10 210 10 18 9 Watercourse slope,s(ft/ft) 0.100 0.057 0.100 0.33 10 Average velocity,V(Figure 3-1)(ft/s) 5.0 3.2 5.0 9.5 11 T,=L/3600*V 0.00 0.02 0.00 0.00 Channel Flow: 12 Cross sectional flow area,a(ft2) 3 3 3 o c o o2j o -, L.L 41 LT_ a-. LL v 13 Wetted perimeter,Pw(ft) Tu E v v v E 14 Hydraulic radius,r=a/Pw(ft) c > 'E E a, c > co co to v a CO n3 15 Channel Slope,s(ft/ft) a a 16 Manning's Roughness Coeff,n o 2 o 0 o 2 17 V=[1.49r2/3s115]/nb Q cr in o o Q 18 Flow length,L(ft) `» N Q N 19 Tt=L/3600*V 0.02 0.01 0.01 20 Watershed or subarea T,or T, (Add T,in steps 6,11 and 19) 0.16 0.16 0.15 0.15 Note:The shortest SCS Tc is 0.10 hrs. U.S.Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 4:Graphical Peak Discharge Method Project: 2415 Ivy Road Commercial Redevelopment Final Designed By: FGM,PE Date: 1/11/2021 Location: 2415 Ivy Road,Charlottesville,VA Checked By: SRC,PE Date: 1/11/2021 Check One: Present X Developed X Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area 1.Data Description Description Description Description Description Onsite DA A Onsite DA B Onsite DA A Onsite DA B (Pre-Dev.) (Pre-Dev.) (Post-Dev.) (Post-Dev.) Drainage Area(Am)in miles2= 0.0048 0.0009 0.0048 0.0009 Runoff curve number CN= 87 81 88 88 Time of concentration(Tc)= 0.16 0.16 0.15 0.15 Rainfall distribution type= II II II II Pond and swamp areas spread 0 0 0 0 throughout the watershed= 2.Frequency-years _ 1 2 10 1 2 10 1 2 10 1 2 10 3.Rainfall,P(24 hour)-inches 3.04 3.67 5.55 3.04 3.67 5.55 3.04 3.67 5.55 3.04 3.67 5.55 4.Initial Abstraction,la-inches _ 0.30 0.30 0.30 0.47 0.47 0.47 0.27 0.27 0.27 0.27 0.27 0.27 5.Compute Ia/P 0.10 0.08 0.05 0.16 0.13 0.09 0.09 0.07 0.05 0.09 0.07 0.05 6.Unit peak discharge,Qu-csm/in Out of Range Out of Range Out of Range Out of Range 7.Runoff,Q from Worksheet 2-inches 1.78 2.34 4.09 1.33 1.83 3.46 1.85 2.42 4.19 1.88 2.45 4.22 8.Pond and Swamp adjustment factor,Fp 1 1 1 1 1 1 1 1 1 1 1 1 9.Peak Discharge,Qp-cfs Routed Through The where Qp=Qu Am Q Fp 8.67 11.41 19.95 1.22 1.68 3.17 SWM Facility 1.72 2.24 3.87 WATERSHED SUMMARY Area, 1-year Flow, 2-year Flow, 10-year Flow, CN ac. cfs cfs cfs Onsite DA A(Pre-Dev.) 87 3.09 8.67 11.41 19.95 Onsite DA B(Pre-Dev.) 81 0.58 1.22 1.68 3.17 86 3.67 9.89 13.09 23.12 Area, 1-year Flow, 2-year Flow, 10-year Flow, CN ac. cfs cfs cfs Onsite DA A(Post-Dev.) 88 3.09 5.40 8.44 15.03 Onsite DA B(Post-Dev.) 88 0.58 1.72 2.24 3.87 88 3.67 7.12 10.68 18.90 Section 3 Channel and Flood Protection Compliance 9 VAC 25-870-66 (Onsite Subareas A& B) Section B:Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system,following the land-disturbing activity, either..." a. or b. shall be met: Section B.1.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section B.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land-disturbing activity shall be calculated either.." a. or b." Section B.3.a. In accordance with the following methodology: Q Allowed(Calcuated) I.F. „ Q * *Pre-Developed RV Pre-Developed) RV Developed 7 Q Allowed(Calcuated) < 7.25 cfs Where: Q Pre-Developed= 9.89 cfs (From Worksheet 4 Watershed Summary) CN Pre-Developed= 86 (From Worksheet 4 Watershed Summary) S Pre-Developed= 1.62 (From SCS TR-55 eq. 2-4) RV Pre-Developed= 1.70 in. (From SCS TR-55 eq. 2-3) CN Post-Developed= 88 (From Worksheet 4 Watershed Summary) S Post-Developed= 1.36 (From SCS TR-55 eq. 2-4) RV Post-Developed= 1.86 in. (From SCS TR-55 eq. 2-3) I.F. = 0.80 (Factor of Safety) Q Developed = 7.12 cfs Section B.4 Limits of Analysis The analysis terminates at the site outfalls (i.e. outfalls 'A' & 'B') since "...subsection 3 of this subsection is utilized to show compliance with the channel protection criteria..." 9 VAC 25-870-66 (Onsite Subareas A& B) Section C: Flood Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic methodologies:" Section C.2.b.: The point of discharge (i.e. outfalls 'A' & 'B'), "releases a postdevelopment peak flow rate for the 10-year 24-hour storm event that is less than the predevelopment peak flow rate from the 10-year 24-hour storm event. Downstream stormwater conveyance systems do not require any additional analysis to show compliance with flood protection criteria if this option is utilized." Pre-Development 10-yr 24-hr SCS TR-55 Design Storm Peak Total Flow= 23.12 cfs Post-Development 10-yr 24-hr SCS TR-55 Design Storm Peak Total Flow= 18.90 cfs Section C.3 Limits of Analysis The flood protection analysis terminates at the site outfall (i.e. outfalls 'A' & 'B')since subsection C.2.b is met. Section 4 Pre-Development SCS Unit Hydrographs Worksheet 5b(Modified for Clarity):Basic watershed Data 1-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA A(Pre-Dev.) 0.16 0.16 0.10 0.0086 Hydrograph Time 1-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.21 SCS TR-55 Pre-Development Unit 11.3 0.29 Hydrograph Onsite DA A) 11.6 0.45 11.9 2.87 10.00 12.0 5.55 9.00 12.1 8.67 8.00 12.2 5.35 7.00 12.3 1.86 6.00 12.4 1.26 5.00 4.0011 12.5 1.06 300 12.6 0.89 2.00 i ) 12.7 0.74 1.00 12.8 0.65 0.00 13.0 0.57 0.0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.49 13.4 0.44 13.6 0.39 13.8 0.36 14.0 0.33 14.3 0.29 14.6 0.27 15.0 0.25 15.5 0.22 16.0 0.20 16.5 0.18 17.0 0.17 17.5 0.16 18.0 0.15 19.0 0.13 20.0 0.11 22.0 0.10 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 2-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA A(Pre-Dev.) 0.16 0.16 0.08 0.0113 Hydrograph Time 2-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.27 SCS TR-55 Pre-Development Unit 11.3 0.38 Hydrograph Onsite DA A) 11.6 0.60 11.9 3.77 12.00 12.0 7.31 10.00 12.1 11.41 12.2 7.04 8.00 12.3 2.45 6.00 12.4 1.66 12.5 1.39 4.00 12.6 1.17 2.00 12.7 0.97 R 12.8 0.86 13.0 0.75 0.0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.64 13.4 0.58 13.6 0.52 13.8 0.47 14.0 0.43 14.3 0.38 14.6 0.36 15.0 0.33 15.5 0.29 16.0 0.26 16.5 0.24 17.0 0.23 17.5 0.21 18.0 0.20 19.0 0.17 20.0 0.15 22.0 0.14 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 10-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA A(Pre-Dev.) 0.16 0.16 0.05 0.0198 Hydrograph Time 10-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.47 SCS TR-55 Pre-Development Unit 11.3 0.67 Hydrograph (Onsite DA A) 11.6 1.05 11.9 6.60 25.00 12.0 12.78 12.1 19.95 20.00 12.2 12.31 12.3 4.29 15.00 12.4 2.90 io.00 12.5 2.43 12.7 2.05 5.00 4e. 12.7 1.70 12.8 1.50 13.0 1.30 0.0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 1.13 13.4 1.01 13.6 0.91 13.8 0.83 14.0 0.75 14.3 0.67 14.6 0.63 15.0 0.57 15.5 0.51 16.0 0.45 16.5 0.41 17.0 0.40 17.5 0.38 18.0 0.36 19.0 0.30 20.0 0.26 22.0 0.24 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 1-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Pre-Dev.) 0.16 0.16 0.16 0.0012 Hydrograph Time 1-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.03 SCS TR-55 Pre-Development Unit 11.3 0.04 Hydrograph (Onsite DA B) 11.6 0.06 11.9 0.40 140 12.0 0.78 1.20 12.1 1.22 12.2 0.75 1.00 12.3 0.26 0.80 12.4 0.18 0.60 12.5 0.15 0.40 12.6 0.13 12.7 0.10 0.20 12.8 0.09 o.00 13.0 0.08 0.0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.07 13.4 0.06 13.6 0.06 13.8 0.05 14.0 0.05 14.3 0.04 14.6 0.04 15.0 0.04 15.5 0.03 16.0 0.03 16.5 0.03 17.0 0.02 17.5 0.02 18.0 0.02 19.0 0.02 20.0 0.02 22.0 0.01 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 2-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Pre-Dev.) 0.16 0.16 0.13 0.0017 Hydrograph Time 2-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.04 SCS TR-55 Pre-Development Unit 11.3 0.06 Hydrograph Onsite DA B) 11.6 0.09 11.9 0.56 1.80 12.0 1.08 1.60 12.1 1.68 1.40 12.2 1.04 1.20 it 12.3 0.36 too ,I II 12.4 0.24 0.80 11 12.5 0.20 0.60 12.6 0.17 040 (( 12.7 0.14 0.20 12.8 0.13 0.00 �_ ... �.� . 13.0 0.11 0 0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.09 13.4 0.08 13.6 0.08 13.8 0.07 14.0 0.06 14.3 0.06 14.6 0.05 15.0 0.05 15.5 0.04 16.0 0.04 16.5 0.03 17.0 0.03 17.5 0.03 18.0 0.03 19.0 0.02 20.0 0.02 22.0 0.02 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 10-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Below Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Pre-Dev.) 0.16 0.16 0.09 0.0031 Hydrograph Time 10-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.08 SCS TR-55 Pre-Development Unit 113 0.11 Hydrograph (Onsite DA B) 11.6 0.17 11.9 1.05 3.50 12.0 2.03 3.00 12.1 3.17 12.2 1.95 2.50 12.3 0.68 2.00 ! ` 12.4 0.46 1.50 12.5 0.39 1.0o a 12.6 0.33 12.7 0.27 0.50 12.8 0.24 0.00 -. 13.0 0.21 0 0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.18 13.4 0.16 13.6 0.14 13.8 0.13 14.0 0.12 14.3 0.11 14.6 0.10 15.0 0.09 15.5 0.08 16.0 0.07 16.5 0.07 17.0 0.06 17.5 0.06 18.0 0.06 19.0 0.05 20.0 0.04 22.0 0.04 26.0 0.00 Section 5 Post-Development SCS Unit Hydrographs Worksheet 5b(Modified for Clarity):Basic watershed Data 1-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Belov Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Post-Dev.) 0.15 0.15 0.09 0.0017 Hydrograph Time 1-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.04 SCS TR-55 Post-Development Unit 11.3 0.06 Hydrograph (Onsite DA B) 11.6 0.09 ` 11.9 0.57 2.00 12.0 1.10 1.80 12.1 1.72 1.60 12.2 1.06 1.40 12.3 0.37 1.20 1.00II 12.4 0.25 0.80 Is 12.5 0.21 060 a 12.6 0.18 0.40 12.7 0.15 0.20 12.8 0.13 _... 13.0 0.11 0 0 5.0 10.0 150 20.0 25.0 30.0 13.2 0.10 13.4 0.09 13.6 0.08 13.8 0.07 14.0 0.06 14.3 0.06 14.6 0.05 15.0 0.05 15.5 0.04 16.0 0.04 16.5 0.04 17.0 0.03 17.5 0.03 18.0 0.03 19.0 0.03 20.0 0.02 22.0 0.02 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 2-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Belov Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Post-Dev.) 0.15 0.15 0.07 0.0022 Hydrograph Time 2-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.05 SCS TR-55 Post-Development Unit 11.3 0.08 Hydrograph (Onsite DA B) 11.6 0.12 11.9 0.74 2.50 12.0 1.44 12.1 2.24 2.00 12.2 1.38 11 12.3 0.48 1.50 1 12.4 0.33 1.00 ) 12.5 0.27 12.6 0.23 0.50 12.7 0.19 12.8 0.17 0.00 �__.. ! _ 13.0 0.15 0.0 5.0 10 0 15.0 20.0 25.0 30.0 13.2 0.13 13.4 0.11 13.6 0.10 13.8 0.09 14.0 0.08 14.3 0.08 14.6 0.07 15.0 0.06 15.5 0.06 16.0 0.05 16.5 0.05 17.0 0.04 17.5 0.04 18.0 0.04 19.0 0.03 20.0 0.03 22.0 0.03 26.0 0.00 Worksheet 5b(Modified for Clarity):Basic watershed Data 10-yr.24-hr.SCS TR-55 Method Unit Hydrograph for the la/P&Tc Listed Belov Subarea Tc(hrs.) Tt(hr.) la/P Am*Q (mi2-in) Onsite DA B(Post-Dev.) 0.15 0.15 0.05 0.0038 Hydrograph Time 10-yr Discharges (hrs.) (cfs) 0.0 0.00 11.0 0.09 SCS TR-55 Post-Development Unit 11.3 0.13 Hydrograph (Onsite DA B) 11.6 0.20 11.9 1.28 4.50 12.0 2.48 4.00 12.1 3.87 3.50 12.2 2.38 3.00 12.3 0.83 2.50 12.4 0.56 2.00 11 12.5 0.47 150 12.6 0.40 1.00 11 12.7 0.33 0.50 12.8 0.29 0 00 - 13.0 0.25 0.0 5.0 10.0 15.0 20.0 25.0 30.0 13.2 0.22 13.4 0.20 13.6 0.18 13.8 0.16 14.0 0.15 14.3 0.13 14.6 0.12 15.0 0.11 15.5 0.10 16.0 0.09 16.5 0.08 17.0 0.08 17.5 0.07 18.0 0.07 19.0 0.06 20.0 0.05 22.0 0.05 26.0 0.00 Section 6 Proposed Dry Detention Basin Routing Calculations Dry Detention Basin BasinFlow printout INPUT: Basin: Dry Detention Basin 7 Contour Areas Elevation(ft) Area(sf) Computed Vol. (cy) 557.19 272.00 0.0 558.00 549.00 12.1 559.00 1140.00 42.7 560.00 1983.00 99.8 561.00 3063.00 192.5 562.00 4517.00 332.0 562.25 3260.00 367.9 Start_Elevation(ft) 557.19 Vol. (cy) 0.00 3 Outlet Structures Outlet structure 0 Orifice name: Pipe 11- Barrel Discharging to Outfall 'A' area (sf) 3.142 diameter or depth (in) 24.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 557.190 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low-Flow Orifice in Str. 16 area (sf) 0.785 diameter or depth (in) 12.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 557.190 multiple 1 discharge into riser Page 1 Dry Detention Basin Outlet structure 2 Weir name: Str. 16- Standpipe with Trashrack diameter (in) 48.000 side angle 0.000 coefficient 3.300 invert (ft) 559.450 multiple 1 discharge into riser transition at (ft) 1.215 orifice coef. 0.500 orifice area (sf) 12.566 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS Design Storm Event Area (acres) 3.090 CN 88.000 Type 2 rainfall, P (in) 3.040 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 6.670 peak time (hrs) 11.930 volume (cy) 769.521 Hydrograph 1 SCS name: 2-yr 24-hr SCS Design Storm Event Area (acres) 3.090 CN 88.000 Type 2 rainfall, P (in) 3.670 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 8.722 peak time (hrs) 11.930 volume (cy) 1006.327 Page 2 Dry Detention Basin Hydrograph 2 SCS name: 10-yr 24-hr SCS Design Storm Event Area (acres) 3.090 CN 88.000 Type 2 rainfall, P (in) 5.550 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 15.089 peak time (hrs) 11.930 volume (cy) 1740.833 Hydrograph 3 SCS name: 100-yr 24-hr SCS Design Storm Event Area (acres) 3.090 CN 88.000 Type 2 rainfall, P (in) 9.110 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 27.546 peak time (hrs) 11.930 volume (cy) 3178.084 Page 3 Dry Detention Basin OUTPUT: Routing Method: storage-indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr SCS Design Storm Event inflow (cfs) 6.664 at 11.94 (hrs) discharge (cfs) 5.404 at 12.02 (hrs) water level (ft) 559.540 at 12.02 (hrs) storage (cy) 69.643 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr SCS Design Storm Event inflow (cfs) 8.714 at 11.94 (hrs) discharge (cfs) 8.443 at 11.96 (hrs) water level (ft) 559.661 at 11.96 (hrs) storage (cy) 76.901 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr SCS Design Storm Event inflow (cfs) 15.075 at 11.94 (hrs) discharge (cfs) 15.025 at 11.96 (hrs) water level (ft) 559.848 at 11.96 (hrs) storage (cy) 89.026 Hydrograph 3 Routing Summary of Peaks: 100-yr 24-hr SCS Design Storm Event inflow (cfs) 27.520 at 11.94 (hrs) discharge (cfs) 22.044 at 12.04 (hrs) water level (ft) 561.251 at 12.04 (hrs) storage (cy) 222.515 Mon Jan 11 10:34:49 EST 2021 Page 4