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HomeMy WebLinkAboutWPO201700051 Calculations 2017-08-28 SHIMPROJECT MANAGEMENT p ' CIVIL ENGINEERING LAND PLANNING ENGINEERING . August 23, 2017 County of Albemarle Department of Community Development 401 McIntire Road Charlottesville, VA 22902 • Regarding: Malloy Ford Stormwater Management Plan Dear Reviewer, The purpose of construction at Malloy Ford is to add a small building to the site and remove pavement to insert landscape islands as required by the ARB. The stormwater management for this site will be addressed through replacing asphalt with the landscape islands to decrease the peak flow of concentrated runoff. The Energy Balance Equation is satisfied and is shown in the table below. Malloy Ford Energy Balance Equation 24 Hr 1 year Storm: Qdeveloped:5 I.E. *(Qpre-developed*RVPre-Developed)/Redeveloped Qdeveloped— (Qforested*RVforestedWRVdeveloped Drainage Area : (2,((6 G 0'7)(2 )( 2.46)j 2.24 0.77 ac G 3, D (� Qpre-developed = 3.12 RVpre-Developed = 0.158 MaxQdeveloped = 3.06 cfs RVDeveloped = 0. 145 Qdeveloped = 2.96 cfs PreDevelopment PostDevelopment 10 yr 5.97 5.84 According to the VRRM spreadsheet included in this packet, there is no remaining phosphorus load reduction required. Contents: Pre-Development Stormwater Management Calculations: Pre-Development Landuse Map Pre-Development HydroCAD Analysis Post-Development Stormwater Management Calculations: Post-Development Landuse Map Post-Development HydroCAD Analysis Storm Structure Drainage Map Stormwater Quality Calculations: VRRM Re-Development Spreadsheet Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre-Development Stormwater Management Calculations Pre-Development Landuse Map Pre-Development HydroCAD Analysis PreDevelopment I TMP 45-68C Landuse Nap for 1 MALL YF FORD __ _ ' �� � rCarr' �/.� - ET- 1■■■/.////■■■///■■��` t ow r ,`II ,• ► 1 1111�C11111111111% INN r I4 ‘►1 I 1///%///////Irl///// / ■1/ 1 �1 •� �v ■/I//////////////1 / •//11////////Y////// / / 111/r . . I , ILA111 11111111111111 I ■/// I� II ���� �. /////////////////� I / 11, r : '\ I. Limits of Disturbance ''� 111111111111111 / .. ow^ ,� I ■n//111///.//////// I , r , I ► ,�,. *�" �, ♦000 ' I 111:1111IM1111111C ' I III '► 00 ■////////n//////// �� ® ♦ .////////�//////// D I I : ► //11/////I/////////► i/ , I` t I,I ► . �♦ I iiiihi1Ii1iuJi!i / t■• ,, / 1// i • r I ►� 1///////N. . / / I 1///////./11111' ► ---_-/ Soil Divide ' k k \k\4‘Wal ■1/11 11N1111�- I/ / -Ii r /N////////////////////IG//// - 11111111111111111111111111111111011111111111111111111I / ri — I so IIIIIIIIIIIIIN ,� ► • 1 1 Nu■I////t//././1, ni / . ► ///////N/////111 I ' • ' /////////////11111 ► 93D 88 .. ' } ■///munnu//■//// / // / III : �11 ► • m//////%/////.� HSG B HSG D . ■■■■■///■■//// / // III I° I rl ,� �� N c ' 1 ^ ------------a.. Q '�Ii'IIIIIIIIIIIII' • •. * / 9 .-3D__ _. ____ 111111111111111111111 , , , ■// TMP 45-68C1 • . . ///////////rJ////// I r rl ���� MANAGED TURF / — — —— — 111111'I'%////////I . v. Total 0.11 acres _ /■■//■■■■//Iru.■ // /// I \�\��♦�� 7.1•■■■///■■■■■■/N//// i' 1/1•///////////►////// ■IIt!/////%//1��11%1S�%�- ■■/I '11111111111:111111111 ,/ IMPERVIOUS . /E�//MM/■■■■■■///.■■■/ MiNdEM■■ 7•/// �� Total 0.66 acres ---- ///////■//■/■/I!i///////1li�///////// - - -- ■EIf// 1 ////111111 ��-----7/■//■n o / , . - 0 - 1 / t 30 0 30 60 90 TMP 45-68A ' iiiii MMI m I SCALE. 1" = 30' I 0 PreDev Type 1124-hr 1-yr Rainfall-9.01" Prepared by Shimp Engineering Printed 8/24/2017 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 1 Summary for Subcatchment 1S: PreDev Limits of Disturbance Runoff = 3.12 cfs @ 11.95 hrs, Volume= 0.158 af, Depth> 2.46" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-yr Rainfall=3.01" Area (ac) CN Description 0.180 98 Paved parking, HSG B 0.480 98 Paved parking, HSG D 0.110 80 >75% Grass cover, Good, HSG D 0.770 95 Weighted Average 0.110 14.29% Pervious Area 0.660 85.71% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, PreDev Type 1124-hr 10-yr Rainfall=5.50" Prepared by Shimp Engineering Printed 8/24/2017 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: PreDev Limits of Disturbance Runoff = 5.97 cfs @ 11.95 hrs, Volume= 0.315 af, Depth> 4.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-yr Rainfall=5.50" Area (ac) CN Description 0.180 98 Paved parking, HSG B 0.480 98 Paved parking, HSG D 0.110 80 >75% Grass cover, Good, HSG D 0.770 95 Weighted Average 0.110 14.29% Pervious Area 0.660 85.71% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Development Stormwater Management Calculations Post-Development Landuse Map Post-Development HydroCAD Analysis Storm Structure Drainage Map PostDevelopment TMP 45-68C I Landuse Map for MALLOYFORD 4 t 71- - — / r r , a 1 I I==uIii Nam �Ir.r,a c r J n=n=====m= : i Inn//1/nnnnnnnn�� ' / Inf//nnn=n=nn== / j. nt11nnnnnn11�1nnn I I ► =nln=nnn==11=nn=nn • ' kr 4 0MN11==nnn=Nln==nnI / : : � 4♦ ■ �=n/IUnnnnnn/Innnnnnl In111111n===n=1 =n==n■ I I ad � Limits of Disturbance=nn�lnnn= /IInn=nn= '♦ ■n=annnnnn1l=nn==ninniinnnrnn I / I i , � •''' iiniuinnnnnn ; !I , L \ ,4 log ♦ nnnnlnnn=non=n==nnI � , ,00 /n==11=1111MInn ==nn / I � ♦*0 n=!nn/nnnl/IInnnnnnn ., / 1iiiniuniini/�=nnnnnnl♦ l 1 ' , / ` ♦O. nnnnnn�nntiiiiiiiiy , 4I , I 0 ♦I=n=nCl7nn/nIIlnnP" . -- /. , J r \iL , ♦ /I 7==naII=nin1l=n1 so ' 1===nlin=nn/=n . / / / I 1 ■ I=Nnnllnnnnnnn I / /a 1111111111111111111111111111111 / ! ' k " \ \ V drill 70--- e t Soil Divide ' Inlln=Ilnnnnnnn . I I ` � I� I IA ►♦♦ I ■n11nn11UUNnnnn I I I I �♦ ■=11nn11==Nn==nl_ I - r, / r I` r1 ♦♦1 Innnnllnnnn=n=nn r k/ r ' r ' . I I • •mmanammon annim F 1�. / �� .II ♦♦ c I nn=h►==nn/Inn==1 I / h 1 1 �♦♦♦ cn nun/lnnnnnllnnnn/ / n==I/nnnnn1Jnnn/11 J / / I // • .♦♦�■ o =nRI/unarm,/nnn/I1 / / I I i '\ 1� �� es 93D 88 r�- ' nnnl1nnnu=/=n=11/nn / I -+ ���>nnn//,=n=n11� / / / I I ♦♦� m HSG B HSG D ��� ' Rana ' k /, manna / / // II 1 01 �♦♦ ■ nun== /n11=n�1 g g / / ■ I \IA �♦ , OPEN SPACE �� \ Inn=//nnnnGlInnnnnelln / / ;♦♦♦ Total 0.00 acres • nnnian=nswannnnnnn■ / / ' y WOO --- / nnn,CC�/n//nnnnnr/nn■ rv,� -- - - --- 1Girnnnnn%=nnnn=nnnl �'/•� :�11�����/:::�:::::: TMP 45-68C1 / I •� ♦ MANAGED TURF 1, - - _ - _-- -- man=munon%nnnnnn , I / ♦♦ /='/nnn//mmmum=nn==/i II I iR♦♦ Total 0.21 acres NN I - .=»CGii>r=n/nnn�n=aura=� / / // , I V� /,��♦� :--,/_7_=__:_ �iI _ �_� °� ' allat Ai- an in j `� • i I i =nnnnnnn ■ mono i 1� re �j►`� IMPERVIOUS - �==nn=nl �� "� - ,-r4�rr \ Total 0.56 acres -::-- ■nnnnnnn - unman=/ 9- �. r r /k '�._, 0��♦ \ mmannann-- - ' ' '68 i /-- 30 0 30 60 90 TMP 45-68A ■■■■■■■■■■I -�� I SCALE. t" = 30' I 0 PostDev Type 1124-hr 1-yr rainfall=3.01" Prepared by Shimp Engineering Printed 8/23/2017 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 1 Summary for Subcatchment 1 S: PostDev Limits of Disturbance Runoff = 2.96 cfs @ 11.95 hrs, Volume= 9.145 af, Depth> 2.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1-yr Rainfall=3.01" Area (ac) CN Description 0.020 61 >75% Grass cover, Good, HSG B 0.160 98 Paved parking, HSG B 0.410 98 Paved parking, HSG D 0.180 80 >75% Grass cover, Good, HSG D 0.770 93 Weighted Average 0.200 25.97% Pervious Area 0.570 74.03% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, PostDev Type 1124-hr 10-yr fiainfall=5.50" Prepared by Shimp Engineering Printed 8/23/2017 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1 S: PostDev Limits of Disturbance Runoff = 5.84 cfs @ 11.95 hrs, Volume= 0.301 af, Depth> 4.69" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10-yr Rainfall=5.50" Area (ac) CN Description 0.020 61 >75% Grass cover, Good, HSG B 0.160 98 Paved parking, HSG B 0.410 98 Paved parking, HSG D 0.180 80 >75% Grass cover, Good, HSG D 0.770 93 Weighted Average 0.200 25.97% Pervious Area 0.570 74.03% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, "i. r / �4 Storm Structure , . /',/ / ! 1i Drainace vlap ,./ 1 1 MALLOY FORD Existing Service Building Existing Sales Building 1.. rt. I I :I : I ST-5 I 1 +��`. Dr inage Area I I 1 .28 acres i I i 1 �'I 1.:III . . �' I l - I l I 4I / 7 I ''. .I ' In 0 / 1 . I / I1 `;l'• Itl I /1 / I >•r .+: / / 1 ;.:_A-7 ----- ---- -_, /, 1 L ____ ____ .4,1 ,.. ,,,,.,_ z, . ,1 1 1 1:../ , . 1 i ,•1„. / / / / .1 :„„:„. 1 Drairfage Area ! •i ' / 1 j:: 0.57 acres / / I\i/ 1 . .` / II LI l // / Ihti/ -- --- -----\---- - '• I / .\/ ' l� / -w / , / /1 /� / / i1 - --' Buildinc Addition _ _- -- - - / / ,,I I / / / / I \. 1 I nlI I J // / I 68 _ i _ ._._ - - -7 it I / / ..../F---------------- --- - . L n ! n ! 3 :0 i LD-204 Stormwater Inlet Computations Inlets on Grade Only a) E as as m m Q E' Z a) Q. o d >, (1) a z c N N 47 o_ o U N c o E o m U c Q v) a n a) U _c o rn `� X m m ' H O E w �' _ X C� 3 c> i a U V O c I6 as .6 C � 0 4) (6 .c w N >-. ? a� i6 Q N U 0 coo co is W c V) U U Q' U c a a a g 5 a- 0 H U) 0 o m C7 0 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 (ft) (ac) (in/hr) (cfs) (cfs) (cfs) (ft/ft) (ft/ft) (ft/ft) (ft) (ft) (cfs) (cfs) ST-3 DI-2B 12 0.57 0.98 0.56 7.1 3.97 - 3 966 0.012 0.0667 0.021 - 7.38 0.15 • 83 0% • 3 30 0.67 3: ■0 33060 90 12 0 98 0.56 5.5 3.07 - 3.072 0.012 0.0667 0.021 - 6.70 0.14 88.0% 2.7 0.37 • • • • s uNomii ST-5 DI-2B 6 0.28 0.98 0.27 7.1 1.95 - 1.948 0 012 0.04 0.010 - 0.10 SCALE = 30' 6 0.98 0 27 5 5 1.51 - 1.509 0.012 0 04 0 010 - 0.09 Stormwater Quality Calculations VRRM Re-development Spreadsheet Virginia Runoff Reduction Method ReDevelopment Worksheet-v2.8-June 2014 To be used w/2011 BMP Standards and Specifications Site Data Project Name:Malloy Ford Date:7/5/17 data input cells 11111111111111111.11111111 calculation cells constant values Post-ReDevelopment Project&Land Cover information Total Disturbed Acreage Constants Annual Rainfall(inches) Target Rainfall Event(inches) Phosphorus EMC(mgIL) 0.26 Nitrogen EMC(mg/L)_ 1 88 Target Phosphorus Target Load(Ib/acre/yr) Pj -Pre-ReDevelopment Land Cover(acres) A soils B Sella -C Sells 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 IITM 0 00 0 00 0 11 0.11 Im.ervious Cover(acres) ''..__ . - _ Total Post-ReDevelopment Land Cover(acres) Avila BSoils CSolh D Soils totals Forest/Open Space(acres) undisturbed, protected foresVopen space or reforested land 0 00 0.00 Managed Turf(acres)--disturbed,graded for yards or other tud to be mowed/managed 0 02 0 00 la 0.20 Impervious Cover(acres) - 0 16 0 00 0.57 Al .Total 077 Area Check Okay Okay Okay Okay _ Rv Coefficients A soils BSoils CSoils DSolis Forest/Open Space 0 02 0 03 0.04 0.05 Managed Tud 0 15 0.20 0.22 025 ` Impervious Cover 0 95 0.95 0.95 0.95 Land Cover Summary Listed Adjusted' Land Cover Summary Land Cover Summery Pre-ReDevelopment Poet-ReDevelopment Post-ReDevelopment New Impervious ForesVOpen Space CoverForesVOpen Space - 0.00 0.00 Cover(acres) 0.00 Composite Com mite Rv forest 0.00 0.00 Ro(forest 0.00 %Forest 0% 0% %Forest 0% Managed Turf Managed Tad Cover(acres) 0.11 0 11 Cover(acres) 0.20 Composite Rv(turf) 0.25 0.25' Composite Rv(tudl 0.25 %Managed Turf 14% 14% %MMaa aged Turf 26% ReDev Impervious Impervious Cover(acres) 0.66 4PM 0.66_ Cover(acres) 0.57 _ New Impervious Cover(acres) 1E 0.00 Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rvlimpervbusl 0.95 %Impervious 66% 86% %Impervious 74% %Impervious Check Area Total ReDev Site Total Site Area(acres) 0 77 0.77 Area(acres) 0 77 __ Total New Den Site Area(acres) Site Rv 0.85 0.85 ReDev.Site Rv 0 77 New Den.Site Rv Post- ReDevelopment Treatment Volume Post-Development Treatment Pre-Development Treatment Volume(acre-a) 0.0548 0.0548 (acre-ft) 0.0492 Volume(acre-ft.. it 0.0000 Post- ReDevelopment Treatment Volume Post-Development Treatment Pre-Development Treatment Volume(cubic feet) 2.386 2,386 (cubic feeI) 2,144 _ Volume(cubic feet) 0 Post- �.aa� ReDevelopmenl Pre-Development Load(TP)(lb/yr) 150 �® Load(TP)(Ib/yr) 1 35 Post-Development Load(TP)(Ibyr) A.00 'Adjusted Land Cover Summary reflects the pre redevelopment land Masmum%Redactor Required Below cover minus the pervious land cover(forest/open space or managed Pre-ReDevelopment Load l 10% turf)acreage proposed for new impervious cover The adjusted total acreage a consistent with the Post Redevelopment acreage(minus TP Load Reduction Rsquired for the acreage of new impervious cover) The load reduction squired for TP Load Reduction R requnemenl for Me new impervious cover to meal the new Redeveloped Area(Ib:yr) 0.00 New Impervious Area(Ib/yr) 1111111000 development load lima is computed in Column I. Total Load Reduction Required(10/yr) 0.00 Pre-Development Load(TN)(Ib/yr) Post-Development Load(TN.(lb y-I 9.61 Site Results — D.A.A D.A.B D.A.C D.A.D D.A.E AREA CHECK IMPERVIOUS COVER 0.00 0.00 lip. 0.00 mow 0.00 iiip, 0.00 OK. IMPERVIOUS COVER TREATED 0.00 0.00 0.00 - "- 0.00 0.00 OK. TURF AREA 0 00 0.00 0.00 0.00 0.00 OK. TURF AREA TREATED : 0.00 0.00 0.00....... ., 0.00 0.00 OK. AREA CHECK OK. tali OK. OK. Phosphorous TOTAL PHOSPHOROUS LOAD REDUCTION REOUIRED(LB/YEAR)7 0.001 RUNOFF REDUCTION(cf) 0 _ PHOSPHOROUS LOAD REDUCTION ACHIEVED(LB/YR) j, 0.00 _ ADJUSTED POST-DEVELOPMENT PHOSPHOROUS LOAD(TP)(Ib/yr) 'IMM 1.35 _ _ REMAINING PHOSPHOROUS LOAD REDUCTION(LB/YR)NEEDED CONGRATULATIONS!!YOU EXCEEDED THE TARGET REDUCTION BY 0 LB/YEAR!! Nitrogen(for information purposes) RUNOFF REDUCTION(et) fMlir NITROGEN LOAD REDUCTION ACHIEVED(LB/YR) 0. ADJUSTED POST-DEVELOPMENT NITROGEN LOAD(TP)(Ib/yr)I 9. Virginia Runoff Reduction Method Worksheet Site Data Summary Total Rainfall= 43 inches Site Land Cover Summary A Soils B Soils C Soils D Soils Total %of Total Forest(acres) 0.00 0.00 0 00 0 00 0 00 0 00 Turf(acres) 0 00 0 02 0 00 0 18 0 20 25 97 Impervious(acres) 0 00 0 16 0.00 0.41 0 57 74 03 0 77 100 00 Site Rv 0.77 Post Development Treatment Volume(ft3) 2144 Post Development TP Load(Ib/yr) 1 35 Post Development TN load(Ib/yr) 9 63 Total TP Load Reduction Required(Ib/yr) 0 00 Total Runoff Volume Reduction(ft3) 0 Total TP Load Reduction Achieved(Ib/yr) 0 Total TN Load Reduction Achieved(Ib/yr) 0 00 Adjusted Post Development TP Load(Ib/yr) 1.35 Remaining Phosphorous Load Reduction(Lb/yr)Required 0 00 Summary Print Independent Reports Excerpt from NRCS Soils Report NOAA Precipitation Report Soil Map 721780 721800 721840 721880 Custom Soil Resource Report 721920 721930 7L&U.) 722040 722080 722120 722180 38°5'43"N I 0 7 r pa , ! 38°S 43"N 0:0, 0.. .• ' i. 1,0 .* ,No° Z. C► ''fit` • fir, �. ". ,. 1 a u 4 / V yyY��� y R* 71T • ' '1_ Je . ° /�/ % At ''' N i if it•, .1,H..1 Ci.j.ti'l'At*. 414!I it.-' :• ‘ k.40 <1- ,' ' .... • 11 t, tom; * ,+ �' J� N/1. , 5; a l F' / eoa0Hap maw�ot�ID®nta d,te 14. / /, / r / , 3SN"ti'ia"N 8°5 34"N 721760 721800 721840 721880 721920 721983 722000 722090 1Z8383 722120 722160 Map Scale.1:1,950 if printed on A landscape(11"x 8.5")sheet Meters N 0 25 50 100 150 A Feet 0 50 10D 200 300 Map projection'Web Meroto► Corner 000rdinats'WGS84 Edge bcs.UTM Zone 17N WGS84 6 Custom Soil Resource Report MAP LEGEND MAP INFORMATION Area of Interest(A01) Spoil Area The soil surveys that comprise your AOI were mapped at n Area of Interest(AOI) Stony Spot 1 15,800 Soils Very Stony Spot Soil Map Unit Polygons Warning Soil Map may not be valid at this scale Wet Spot ry Soil Map Unit Lines Enlargement of maps beyond the scale of mapping can cause Other misunderstandingof the detail of mapping and accuracyof soil • Soil Map Unit Points PP 9 Special Line Features line placement The maps do not show the small areas of Special Point Features contrasting soils that could have been shown at a more detailed Blowout Water Features scale. Streams and Canals El Borrow Pit Transportation Please rely on the bar scale on each map sheet for map Clay Spot 4.44 Rails measurements 0 Closed Depression ti Interstate Highways Source of Map: Natural Resources Conservation Service Gravel Pit US Routes Web Soil Survey URL Gravelly Spot Major Roads Coordinate System Web Mercator(EPSG:3857) • Landfill Local Roads Maps from the Web Soil Survey are based on the Web Mercator Al Lava Flow Background projection,which preserves direction and shape but distorts distance and area.A projection that preserves area,such as the • Marsh or swamp . Aerial Photography Albers equal-area conic projection,should be used if more Mine or Quarry accurate calculations of distance or area are required. ift0 Miscellaneous Water This product is generated from the USDA-NRCS certified data as O Perennial Water of the version date(s)listed below Rock Outcrop Soil Survey Area: Albemarle County,Virginia + Saline Spot Survey Area Data Version 10,Dec 11,2013 Sandy Spot Soil map units are labeled(as space allows)for map scales g Severely Eroded Spot 1 50,000 or larger. • Sinkhole Date(s)aerial images were photographed: May 9,2011—Jun 4, 3:y Slide or Slip 2011 • Sodic Spot The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps.As a result,some minor shifting of map unit boundaries may be evident. 7 Custom Soil Resource Report Map Unit Legend Albemarle County,Virginia(VA003) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 27C Elioak loam,7 to 15 percent 1.7 23.8% slopes 39D Hazel loam, 15 to 25 percent 2 1 29 5% slopes 88 Udorthents,loamy 1.3 19 2% 93D Watt channery silt loam, 15 to 1.9 27 5% 25 percent slopes [Totals for Area of Interest 7.0 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas.A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each.A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate 8 7/5/2017 Precipitation Frequency Data Server NOAA Atlas 14,Volume 2,Version 3 „'`�'- N. Location name:Charlottesville,Virginia,USA* € noeo„ a a Latitude:38.0942°, Longitude:-78.4688° i Elevation:477.16 ft** z •source ESRI Maps " ti \,. f- g� Y 'source USGS POINT PRECIPITATION FREQUENCY ESTIMATES G M Bonnin,D Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley NOAA,National Weather Service,Silver Spnng,Maryland PF tabular I PF ciraohical I Maps &_aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval(years) Duration 1 2 5 10 25 50 100 200 500 1 1000 5-min 0.351 0.419 i 0.492 0.553 0.623 0.678 0.729 0.778 0.837 0.885 (0 317-0 390) (0 378-0.465)!(0.443-0.545) (0.497-0.612) (0.557-0.687) (0.604-0.747) (0.646-0 803) (0 684-0.857) (0.728-0.925) (0 763-0.982) 10-min 0.561 0.670 0.788 0.884 ( 0.993 1.08 1.16 1.23 1.32 1.39 (0.506-0 622) (0 605-0 744)i(0.710-0.872) (0.795-0.978)1 (0.888-1.10) (0 961-1 19) (1 03-1 28) (1.08-1.36) (1.15-1.46) (1.20-1.55) 15-min 0.701 0.842 0.996 1.12 1.26 1.37 1.46 1.56 1.67 1.75 (0.632-0.778) (0 760-0 935) (0.898-1.10) (1.00-1.24) (1.13-1.39) (1.22-1 51) (1 30-1 61) (1.37-1.72) (1.45-1.84) (1.51-1.94) 30-mln 0.962 1.16 i 1.42 1.62 1.87 2.06 2.24 2.42 2.65 2.83 (0.867-1.07) (1.05-1.29) (1 27-1 57) (1 46-1 79) (1.67-2.06) (1.83-2.27) (1.99-2.47) (2 13-2 67) (2 31-2 93) (2.44-3.14) 60-min 1.20 1.46 1.82 2.11 2.48 2.79 3.09 3.40 3.81 4.14 (1 08-1 33) (1 32-1 62) L (1 64-2 01) (1 90-2 34) (2.22-2.74) (2.48-3.07) (2 74-3.40) (2.99-3.74) (3.31-4 21) (3.57-4 59) i 1.44 1.75 2.19 2.57 3.07 3.48 3.91 4.36 4.98 5.50 2-hr (1 27-1 64) (1.54-1 99) (1.93-2.49) (2.27-2.91) (2.68-3.47) (3.03-3.93) (3.38-4 41) i (3.74-4.91) (4 22-5 62) (4 62-6 23) 1.58 1.91 2.39 2.81 3.35 3.81 4.28 4.77 5.46 6.05 3-hr (1.39-1 81) (168-219) (210-275) (245-3.21) (2 91-3.82) (3.29-4.33) (3.67-4.87) 4.06-5.44( ) (4.59-6.23) (5.03-6.90) 6-hr 2.01 2.43 3.02 3.55 4.27 4.90 5.56 6.27 7.29 8.19 (1 78-2.28) (2.15-2.75) (2.66-3.42) (3.11-4.02) (3.72-4.82) (4 24-5 52) (4 76-6 26) (5 32-7 07) (6 09-8 23) (6 75-9 26) 12-hr 2.52 3.04 3.80 4.49 5.47 6.33 7.27 8.31 9.84 11.2 (2.23-2.89) (2.69-3.48) (3.34-4.34) (3 94-5 12) (4 75-6 21) (5 45-7 19) (6 18-8 25) (6 97-9 41) (8 10.11 2) (9 08-12 8) 24-hr • 3.01 3.64 4.65 i 5.50 6.75 7.83 9.02 10.3 12.3 14.0 (2.70-3.38) (3.27-4.09) (4.16-5.22) (4.91-6.15) (5 99-7 54) (6 89.8 72) (7 87-10 0) (8.91-11 5) (10.4-13 6) (11 7-15.5) 3.55 4.30 5.47 6.43 7.82 8.99 10.3 11.6 13.6 15.3 2-day (3.19-3.97) (3.87-4 81) (4 90-6 10) (5 74-7 16) (6 94-8 69) (7 92-9 97) [(8 96-11 4) (10 1-12 9) (11.7-15 2) (13.0-17.1) 3.78 4.58 5.81 6.83 8.31 9.54 10.9 12.3 14.4 16.2 3-day (3.43-4.19) (4.15-5.07) (5.27-6.44) (6.17-7.56) (7.46-9.17) (8.51-10 5) (9 63-12 0) (10 8-13 6) (12.5-16.0) (13.9-18.0) 4.01 4.86 6.16 7.24 8.80 10.1 I 11.5 13.0 15.2 17.1 4-day (3.67-4.42) (4.44-5.34) (5.63-6.78) (6.60-7.95) (7.98-9.65) (9.11-11.1) i (10.3-12.6) (11 6-14 3) (13.4-16.8) (14.9-18.9) 4.66 5.61 7.01 8.16 9.81 11.2 12.7 14.2 16.5 18.4 7-day (4.27-5.09) (5 15-6 13) (6 42-7.66) (7.46-8.91) (8.92-10.7) (10.1-12.2) (11.4-13.8) (12.7-15 6) (14 5-18.1) (16.0-20.2) 10-day 5.29 6.34 i 7.83 9.04 10.7 12.1 13.6 15.1 17.3 19.1 (4.87-5 73) (5 85-6 87) (7 21-8.48) (8.31-9.78) (9 83-11.6) (11.0-13.1) (12.3-14.7) (13 6-16 4) (15 4-18.9) (16.9-20.9) 6.94 8.28 10.00 11.3 13.2 14.6 16.1 17.6 19.6 21.2 20-day (6.49-7 44) (7 75-8 87) (9 34-10.7) (10.6-12.2) (12 3-14.1) (13.5-15.7) (14.9-17.3) (16 2-18 9) (17 9-21.2) (19.2-22.9) 30-da 8.51 10.1 11.9 13.3 15.2 I 16.6 17.9 19.2 21.0 22.3 y (8.01-9.08) (9 50-10 8) (11 2-12.7) (12.5-14.2) (14 2-16.2) I (15 5-17 6) (16 7-19 1) (17 9-20 5) (19 4-22.5) (20.5-23.9) 10.6 12.6 14.7 16.3 18.3 19.8 21.2 22.6 24.4 25.8 45-day (10.0-11 3) (11 8-13 3) (13 8-15 5) (15.3-17.2) (17.2-19.4) (18.6-21 0) (19 9-22 5) (21 1-24 0) (22 7-26 0) (23 8-27.5) 60-day 12.5 14.7 16.9 18.6 20.8 224 23.9 25.3 27.1 28.4 (11 8-13 2) (13 9-15.5) (16 0-17.9) (17.6-19.7) (19 6-21 9) (21.1-23.6) (22.4-25 2) (23 7-26 8) (25 3-28 7) (26 5-30.2) 1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS) Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval The probability that precipitation frequency estimates(for a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5% Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values Please refer to NOAA Atlas 14 document for more information Back to Top https//hdsc.nws.noaa.gov/hdsc/pfds/pfds_pnntpage.html?lat=38.0942&Ion=-78.4688&data=depth&units=english&series=pds 1/4