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25990 PE-1570D DRAINAGE TECHNICAL REPORT ~ - - - , . ~ r--, ~ "-INLAfVD PACIFIc ENGINEER1NG, MNC. ~ c ~ eck 3 ~ ~ ~ . - ~ ~ ~ ~ OFFICI.~:. PUBLIC DDCUWt-NT SPOKANE COUNT1f ENGiNEER'S OFFICL OR&N PROJECT ~ i~p - SUBMITfAL ~ R~~~~N 1~0"G~UOY ENG4NFER ~ ~ _ ~ ~ ~ ~~OKANE COEVR DfALENL I - ~ - ~ - ~ ~ I ~ 1 ' . ~ DRAINAGE TECHNICAL REPORT - --i ~~r the . ~ ~ SPRINGFIELD AT AUr--'UMN CREST PLAT ~ -JANUARY 1998 - W.0, ~97117 Prepared for: ~ Scott Lalncireth, L,andreth Construction r-. - - 10801 E. Valleyway Avenue J Spokane, WA 99206 f_. Prepared By: Inland Pae~;~c Engineering Comparay 707 W. 7th Avenue S'ur'te 200 Yr Spokane, WA 99204 ~l (509)458-6840 i ~r- j I DRAINAGE REPORT for the Springfield at Autumn Crest --Plat - ~ Spokane County, Washington ~ January 1998 ~ he design ftmprove ents s ow in this s-t of plaw an calcu a~ ~ ons co.nform o the - app Aicabl e0moam (Cf m)e ko m e County ft~ 0s for ' oad an Od ' e er onswac ion - at~he Spo • ne County u~ de ines for So wate ana,gem~n . I~l esign e~Ya ~'.on:s ~ been arove by ~he Spo •an. Cou~nty ngi~neer. ap rove these plans -J calculations) for construction. v This report has been prepared by Susan K. Murphy, E.I.T. of Inland Pacific Engineering Company ^ under the direction of the undersigned professional engineer whose seal and signature appear hereon. • , ~ . 7~. ~ . ~ p-25462~ , s NAL ~ , EXPIRES 9/24 ~ - , Todd R. Whipple, P.E. , i I ' • i i ~ I - Springfield at Autumn Crest . ~ DYainage Narrative ~0 GENERAL The Springfield at Autumn Crest Plat is a 4.61 acre development ofosingle family residential , i lots located east and south of Progress Road and 161 Avenue in the Spokane Valley within - Spokane County, Washington. The site is currently vacant with field grass, alfalfa and fallow fields as the predominant land cover and vegetation. Single family residential development lies ~ to the south. A vicinity and location map have been included within the technical section of this ~ document. I ! pURPOSE ~The purpose of this report is to determine the extent of storm drainage facilities which will be required to dispose of the increase in stormwater runoff created by the development of the , Springfield at Autumn Crest plat. The stonn drainage facilities on this project will be designed to dispose of runoff from a ten year design storm for the onsite basins, and the fifty year storm event for basins with offsite drainage, as required by the Spokane County Guidelines for Stormwater Management. This development is within the Aquifer Sensitive Area of Spokane County and is subject to'208' requirements. For this project, the 10- and 50- year curve from the Spokane, Medical Lake, Reazdon, Cheney and Rockford intensity curves was used, as well as the SCS iso-pluvial rainfall curves. ! ; , LJ ANALYSIS METHODOLOGY . Per the Spokane County Guidelines for Stormwater Management, the Rational Method, which is - recommended for basins less than ten acres in size, will be used to determine the peak discharges and runoff volumes for all onsite basins. V PROJECT DESCRIPTION _The Springfield at Autumn Crest subdivision is located in Section 26, T. 25 N., R. 44 E.; W.M. within Spokane County, Washington. ~ ~ TOPOGRAPHY ~ The existing site naturally drains to the south and east. Within the plat the natural topography was used as much as possible to route stonn drainage. Due to the flat slopes encountered, no , concentrated pre-existing flows were observed nor were there any signs that anything other than j s sheet flow and ground absorption have occurred on this site. The general slopes within this plat , i' Inland Pacific Engineering Company D 1 Springfield at Autumn Crest Drainage Report ; ~ f . ~ J . i vary from flat to nearly flat with the maximum existing slope at 0.02 ft./ft. For development purposes as stated the natural sloping was used for design and is maintained as possible throughout the proj ect. ~ SOILS _ _As can be seen from the accompanying soils map from the Spokane County Soils Survey as performed by the SCS, the site consists of one type of soil within the Class B type. This soil type _J is described as follows. i GmB - Garrison gravelly loam, 0 to 5 percent slopes: Soils within this soil type are somewhat excessively drained, gravelly or stony soils of moderately rapid permeability, with a surface layer of gravelly loam, and a subsoil stratum of sand, loam and cobblestones. They formed under grass ; ' in glacial outwash mixed in the upper part with volcanic ash. Surface runoff is slow, and the I hazard of erosion is slight. Snokane Countv Guidelines for Stormwater Manaizement indicate this to be a Soil Group Type A and pre-approved for drywell installation. , ~J Hydrologic Soil Classification - B r DRAINAGE NARRATIVE Offsite L_1 There is an offsite flow crossing the plat area from southwest to northeast, in Basins labeled "T" and "V" on the enclosed basin map. Those basins will be analyzed using a 50 year storm event. ~ Onsite _As this plat is within the aquifer sensitive area of Spokane County all onsite drainage will be collected and treated using the "208" runoff method- as described in the Spokane County Guidelines for Stormwater Management. To facilitate this analysis the Springfield at Autumn Crest plat was divided into 6 permanent basins (T through V). Table 1 lists the basins and pond ~ combinations for easy reference. ~ ~ ,I , Inland Pacific Engineering Comparry D2 _ Springfield at Autumn Crest Drainage Report ~ . i ~ s ~ r-- i I Table No. 1 • ~ • ~ ~ ~ a ins o al Area ; ,tree m, . ' e7g te I (S~ ' / ) ea ~ ✓ ✓ ✓ . ` T1 31630/0.73 4644/0.11 0.39~ T2 3513 0.81 759 /5 0.17 0.43~ , ( T 66768/1.53 00-1 12239/0.28 0.43 .41 ~ I U 1 3 6260/0.8'5'- 4644/0.11 0.3 8~ ~ vo", ~ ~U2 27816/0.64 5908/0.14 0.43'~ _ U 64076 4< 10o520 4 0.4e ~ V 386750.89" 7031/0.16 0:41 ~ . W 2 8402/0. ~ 5 542/0 1~ 0.42 f ✓ ✓ ✓ v OFFSITE + 101108/2.32 12239/0.28 0.37✓ BASIN T j *5542 SF includes the half width of Progress Road; the widening from the sawcut at 10' off centerline to the gutter is 6 S; which is all that is required to be treated. The ~ impervious area of the widening only is 2463 SF. V "208" Calculations Within each basin the streets are divided into sub-basins by high and low roadway profiles. . ~ These facilities capture upstream stormwater runoff from the impervious street surface and direct - the runoff into grassy '208' ponds. As shown on the '208' calculation worksheets included, the '208' storage volume provided is adequate to perform '208' treatment for the runoff created by the ~ first half inch of rainfall. Curb Inlets and Catch Basin Calculations It is necessary to check the adequacy of the curb inlets, inlets or catch basins provided to divert the runoff from the gutter into the '208' ponds. The curb inlet calculation sheet included shows the required lengths of curb openings, as well as the adequacy of the inlet grates or. catch basin grates. ~ l~ ^ Inland Pacific Engineering Company _ D3 Springfield at Autumn Crest Drainage Report }J . , ~DRAINAGE CALCULATIONS SUMMARY ~Calculations have been included for Drainage Basin considerations such as Peak Flow, Time of ~ Concentration, "208" sizing, drywell requirements, inlet sizing and curb inlets, which are summarized below with the remaining calculations included in the appendix. , ~ r Within the calculation section and where it has been determined necessary for clarity, several ^ sketches, as well as details from the plans have been incorporated to demonstrate assumptions and conclusions. BASIN DESCRIPTIONS ~ Basins T through W ^i - J Within this plat, and due to the general geographic features, several basic assumptions were followed and can be used to describe each basin. First, due to the relative flatness of the plat and project vicinity, minimum road grade is lunited to 0.0080 ft./ft; second; ponds will be of the lot ~ pond configuration. All of these steps have been used in various basins throughout the drainage design of this project. . l~ ` The drainage design for the remainder of Progress Road to 161 Avenue will extend the proposed ~ 2' wide pond to the east. The pond extension will be designed to provide enough `208' treatment j for the future improvements on Progress Road to the intersection of Progress and 16`' Avenue, as well as meet bowstring requirements for the future basin. ~ ~ Table No. 2- Pond, 208 And Drywell Summary , , , din ~ . ji i i II~ I• i i I• u i i i~~,ee ~ I' ~ eq QC oV' , e ~ , , • _ , ~ T1 T1 194 ~ 200 '20 x 20' v - . v ~ T2 T2 316 ~ 436 , Irregulaz - ~ T - 510 ~ 636 - 2 - "B" ~l U 1 U 1 194~ 200 ✓ 20' x 20' ~ - U2 U2 246~ 262Irregulaz - U - 440462 - 1 "B" ~ V V 293 1/ 30020'x 30 1-"B W W 231 vi 298 ~ 2'x298' ~ 1-"B`/ * Based on (bottom area)(.5') ~ Type A is a Spokane Standard Drywell - Single Depth, Capacity 0.3 cfs Type B is a Spokane Standard Drywell - Double Depth, Capacity 1.0 cfs Inland Paci, fic Engineering Company D4 Springfield at Autumn Crest Drainage Repon I i 1 lI I l1 1II (l I 1) 1 `r` fI 1 I ~ 1 = ~ ,~tie__.11~111~~..:~,.1 i ~--.f 0 }.i ~ V Y- a `Y4~18i~~r UN E SI ~ R ~A m QRSITY; NIVERSRY I A~ Im 1 1Of1 T~ ~ d w s L-D ~ RTER VAN NA TFR yp~1W ~R1FA D ' ~ ~ Z 108 GL ~ m 2 n m > ~ GLENN CT N s OIL ~ Y~ a pN ~30 1, > o m Illl ~ r GII US ti'Ut~ 110 ~ 0 =~IEI CE ' RD m PI RC : AO m I PI CE ~ = m ERCE m RD a m~ACE RD ~ < o N°~ m m m m m~m m m m N o' YOfFITT ~M a p~ ~OMM60M m gq P W ORtt s l f 6 P w o A 7 N S K I P W OI T M i m ~ 1y~(~,NTN m ~ ~ SKIPW V V r cr Ikl 112 sKi w _ AD - u~ s Kivwo s~nvw mx s ' o~ m s m ne m m ,-w s~WOODWOAD IN m m m w 0 0 R D 2 W0,00'ARD WO 7DWAAD p x am C T 114 m 4ON Dl ~ RD 0 BOWDISH A A vt, ~ BOwo~sN ~ SUN r BAlEB BATES w BATES ~ < ~ • n n a ~ BATE9A0 °i ~~9 a x s~ m p~ m OOO.N ~ WILBUA m WILBUA ~ m m 531 116 ~ wi eu WILBUA 10 ttILBUA RD I IIA ~ N VI NI WlHUNION ll UA s~% r ~~z o m =WILBUA RD „ IIBV i U I E N F O% > o'a F O x D i 9 o i WILJUA r ~ ~ 1 0 m ? Cl ~ mUNION m > A ~ g 118 F07IoA0 aao y U: UIIIdN AEEYE83UN10N -yi =UNIOH ' OAFY j m > s P E R A{ N~ U N 1 0 N m CT m~ V,U~ I O .7 ~ ERAINE o ifABINE ~ `o ~ o uum pEpPJLE RD ROBIE e~0 a ^a' m 3 0 ~ o o'~ ^ g,;BIE ~ A081f pp Ii08t a sa ~ -'i C► m N_ N $ Otl ~I PLE ~ ~ PL IPPL WHIPPLE ~ W P lE s O 1YIp PlE N > m wHIvvLe pINES m" m- -J m PINES ROAD F► ~ • ~ PINES AOAD ~ ~ CHEA Y tNEAm o #X3 o m HOUK HOVK NOUK NOUa 2 ^ g a u; ~ ~ 0 IK U m ~ ~LUNg ~ ~ ~ NOUX ~ UI~ 9 > C UNS Ol N COLUH9 CT I wll~ R~ ~ OUK o ~s RCl4A YERCLEA E C lUN4 p YEACLER RD m ~I o YEAC ro q r~ : YERCIEA AO `~A ~ s ~onaA c~i \l ~ a w ~ $ YIRQINIA ~ = r f ~ = u ~ ~`,Dn aao'~ GO U- VIRGIt~A~ nooouwnVIR01HIA ~ < o 128 N' ooU'NN H = M O~ a ~am AO .,..r...Wi NDUwN WOODL. WN a H m~ cN m~z . N AAOW OAA MOAAOW + o m MDAAOW ~ p ow.0 130 Y OONAI m l.,o a c~ON~ID m 90 R~AD 9 a ~ CLINTO r 132 C1 o a'~ N s ~ ~~i ~ s s s> ewrtai _ k ~ ~ o m s m m m m"N' z z DM~ ~ m o ~ m ~ A ~ m p tXlIUA o~ C U I T ~ --°D1 MeCABE 61eCAAE 0 9~ m NC I ABE MC CAEF -1 = m m m m 134 ~j BLAKE RD A m m m lLA. E 1D B44K AO { B I A K E R O A D ~ ' I AVAyON RUb mj ~ N A 1 FATN ►H I An+e ~ < , r. MANEii ROAO 136 E~ e m MAYEII ~ MAMEB RD m m RD o o NA TN E I~~ ~ YA ER ~ m ~T ~n ~lAME r•••••• ~ m O~h ° DAYIS AD m ~ m i 138 DA IS r~ ~ EVERGAEEN ROAD ~ EVEAGREEN ROAD ~ g %0 60UYAR N~ BOIrvAR RD ' OIrvA = eourAA eauvAA so rvA o W= e 0 ~ 00 ' 140 vuifl x[MCT ~ BANNEN ~ BAN EN R~ lN ~ BOU xA ~ AA NEN n= S 9 G ' BrtitNE BANNEN s wNNEx s e~~ m y y 1 SU NWKh EApl1DANN BOLIVAR ~ BANNEN r o ~ 142 BUNN EAOOK ~ ~EN BEST BrILREES M m y BEST B E T ~A D ~ O 'BANNEN 0 O ~ ~ A. REE9 I BEST B E S 1 A O h EEt REE9 4 CALVIN o~ C TioC A l Y 1 N CAIYIN A L N I N cAivuN lx m CAIYIN WARREN " a o WA MAAAEN WA AEN t a Q ~ AAREN 100- 146 LN 3 ADAMS AOAD m 3= ADAM$ AOAD MAft YAII~ ~ R100 ~w ~ YARCVS C ~48 D = ~~0 ~ a, BURNS RD m T". _ A w ~ m BU N9 ~~euaxS eL 3- ~ euAM9 NAN 3- 6 pAOGAESS ROADi 150 p OGRESS ~0 ~ ~ ~ • OA IL- ~ o 8i CIiARIFS RD g 9T. ALF9 ~ y tl m 152 m !TC 1RAG- CXA LE YYEF 3»9 Gtl SOH~ MER ~N E N F A C T ~ N E R~ M E E R ~ N R N ° E ~ f ~ ON y E p FD~Q ~ AY a i o ~ N NfWEI p EtRUR'f 154 , SULLIYAN RD cExruar ~ Ar a~+ Y = cE Rr = f-~~ o SULLIVAN ROAD ~ % , ~ T PIOHEEAIs s ~ ,xn ~ °PIONEEAIN ~ PIONEEA~CT LN 9 a 156 f p~~ = e N AE lN s ~ d~0 Q ~ v ti" ~(1l1381111~ ti ERIANE 7 eL ( O pRK2NDg z 158 ° 0 m < a s 'a _ i a~d~ SO/AP °0 850o m m Mp}E oa k ls v ~ R e 9 N 16~ y'i a ~ ~NFOq r ~D , CANNERY AD ~ x . Y T O oA ~ I p~6 Q C T ~ SPOKANE C4UNTY, V11ASHdNGTON - "3HEET I R, 44 E. 1 R. 45 E. (loins sheet 87) - Y,ti ,x -ti. yj: d~" '.~:i~' E"; ~ys ~~r' _ f ' F~ ' ~4 - ~ $ - _ - - - j -~~r.~, ~ - -•d i :M ~'S~ „ ~i~ i r ~ f-~-i" ~'~'A S .~x'k3-S,~~Y ~Ss~" ' L'~,~. r = Si•+ - * - "r~ 5~ t '1 f^ ~ a,~~ ~C - ~ ° 'Y • i Ly . / ..•s W k ~ A:""9~ " _ _ ~ ~ ~ _ _ 1 1T _ ' -'f.' ~ _ - - _ - x ~ - _.._J N - - , ,r ' . ~ ~ . ~ ~ , - ' J ~Y^_ rc 1 ' •OS~S L I '~t~ , i - • V '~L.7r * ~ _ - ~ ~-rT ~ ~j~ , ~~A. { J - - ~J~.iu _ I I_ _ ~ F~ . ' ~ _ - 4 _ i ~ N' ~ ~ ' . / t ~ •~(y_~ B ~ ~~f `I ~J~ &MOMM 1* • l.~ Ln `s p ti t".y°r ~ • iy ~ w ~ - .2 • ~ T~ '°"w~~~• r ~ = • ~ ~L/• ~ - ,r _ ~ ~ ~ ~tj .9~1.i"''~.~ ' ~ r w, • ' ~ ~+y y S~ i •t k+=• V {f Y,~'f ' S 1 ' iR7 • -h`~ ~ C I F 5 _ ~ 'c`74 ~ ~ 'r _ ' _ 7~,' . ~ `~tiL ~ ~ ~_ti~' ~ y } .y~ A a~ ` ~ : = ~ ~ ~ ~ r~'~e ~°f`~' ' y . ti~~• - ~ ~F,. ~ - I~. 'v^,~ .IF ` :~~y~.~~.fe' ? '4,_~y ' - - -'f ` ' • ' ~4 1 ' ~ ' ~ ~ - - ' ~ S 1~ r , , k ~'x~ ' ~+-~~~~R'~i~~- _I _ 2.~ y~ 4-~ ~ `'d _4'• 1 D _ - ~ { ,,,"~a~• ' ' - M ~ I I - ~ il - i ~ - - - _ • ~ - ~ ~ - ;t ry _~~rz ➢1~~~ r ~ ' ' " i am,~ ' Hf'I~Y ' ~ ~ ~_.•'~1 . ' r _ Y~ ~`~3,, ~ ~r..,• ~ r# ~ r ~.L ~ ~ i ~ ti ~ .F ' ~ ~ 1 ^ ` +n'at~'+C4.TZ~ • f _,qy~ 4' 'oL~t`~ir`; ~ . B 8~ ~ t ~ .~~j t~. ~ ' ' .a: _ . n"~~,,v , r •i ~ . , s. • , ~ .r ~ i~':i'' ~ '.~~.e~ yd ' ~ ~ ''4~ ' ~ " • rt-'t, ' •'A, ~ ' E - - a~; : s~ n. ~;y~.e'%J i~n-~. - #.`,x t 1+ ~ _ ~~,~y-~'~.r~,~,Y~~~••' ~r'iY~~~` .~~~x,+.rk~ ' ~,ag • -7 IN BaLd i ' '7$ s. r a~'n t - ' ~`i R . r~~. - • r t. y : . ' ,iY` iw _ 4.. ~ , ,.•~~-~~i-i. .aL ~ rt - ^ "'E" f' ~ „a. . R`.. ' tlY , I - ~ ; ` _ 4~a4`G ~~:6~. ,y~-y S;y ~'y~ ~ t' • ~rh~r'^~ r , ) ~ ~f'!+ .`ZTt ~ °y ~~,~.,''L' i { ~ - • ~ ' ~ ~iy^, ~ ..+.c''{~ _ ~ ~3 ~E~.f _ _ : - " ' ~s r - r:tii •~•``'S` a~:;~ ~'i~ y~ ' ' • ' , , , _ '~.~L' . ~ t~;.; } 4 • ~ r-•~ ° sat7 ~ ~r ' ~ ~ ~ ~ . - ; ~sa-: ~ f~,• { c:~;:~r,•"y' - - - L~w F ■Y~~` ~ '~i~'~' Y _ ~ r ~4~ Z ~ Y.~ y~ , y~''~ ~ •ti; •a~_ „~n~;. N B h ~ (JOIf15 Shei--t 85) ~ Weighted Runoff Coefficient Calculation Project: Springfield at Autumn Crest Basin: . T1 ✓ IPE Job 97117 ~ Total Area (acres): 0.7300 Designer: S. Murphy ~ Imp. Area (acres): 0.1100% Date: 01/14 Grass Area (acres): 0.6200 ~ Imp. Area "C": 0.90 ~ ~ Grass Area "C": 0.30 , (Imp. Area)(Imp. "C")= 0.0990 (Grass Area)(Grass "C")= 0.1860 ~ ~ 0.7300 0.2850 Weig hted "C"= 0.2850 00-1 ~ ~ = 0.39 0.7300 ~ I G 9 Y Weighted Runoff Coefficient Calculation Project: Springfield at Autumn Crest Basin: T2 IPE Job 97117 ~ Total Area (acres): 0.8100 Designer: S. Murphy ~.J Imp. Area (acres): 0.1700 Date: 01/14 Grass Area (acres): 0.6400 Imp. Area "C": 0.90 Grass Area "C": 0.30 J ~ . ~ ^ (Imp. Area)(Imp. "C")= 0.1530 (Grass Area)(Grass "C")= 0.1920 ~ 0.8100 0.3450 ~ Weighted "C"= 0.3450 0.43 ~ ~ 0.8100 ~ ~ ~ . z ~ ~ 4 ~ ~ ~ - ` Weighted Runoff Coefficient Calculation _ Project: Springfield at Autumn Crest Basin: T IPE Job 97117 Total Area (acres): 1.5300 Designer: S. Murphy ~ Imp. Area (acres): 0.2800 Date: 01/14 Grass Area (acres): 1.2500 ` Imp. Area "C": 0.90 ' J Grass Area "C": 0.30 „ (Imp. Area)(Imp. "C")= 0.2520 (Grass Area)(Grass "C")= 0.3750 1.5300 0.6270 ~ I Weighted "C"= 0.6270 - , - 0.41 1.5300 ~ i~ ~ , . I ~ I 1 I ~ • I- • I ~ I l I 1Neigh#ed Runoff Coefficient Ca[culation Project: Springfield at Au#umn Crest Basin; OfiFsite + Basin T IPE Job 97117 ' Total Area {acres}: 2.3200 Designer: S. Murphy _Imp. Area (acres); 0.2800 Date: 01116 Grass Area {acres}: 2.0400 ~ lmp. Area "C": 0.90 Grass Area "C": 0.30 ~ (Imp, Area)(Irnp. ~~C")= 0,2520 I i (Grass Area)(Grass "G")= 0.6120 ~ ~--2.3200 0.8640 1111eig hted „C"- 0.8640 0.37 . 2.3200 ~ ~I . --1 ~I , , (I LJ r- ij _ ~ ~ i , Weighted Runaff Coeificient CaIculation ~ . - I Praject: Springfield at Au#umn Crest Basin: L1l IPE Job 97117 TvtaE Area (acres): 0.8300'~- Designer: S. Murphy Irnp. Area (acres): 0,1100 Date: 01114 Grass Area (acres): 0.7200 Imp. Area "C,". 0.90 ~ Grass Area "C": 0.30 - . (Imp. Area) (lmp. "e")= 0.0990 (Grass Area){Grass T")R 0.2160 0.8300 0.3150 ii . ~ Weighted T"- . 0.3150 0,38 w ~ - 0.8300 ~ I LJ I ~ fi r c ~ s, I ~ a ~ I - ~j I ,I - Weighted Runoff Coefficient Calculation Project: Springfield at Autumn Crest Basin: U2 40w IPE Job 97117 7-, Total Area (acres): 0.6400 ,o.. Designer: S. Murphy ' Imp. Area (acres): 0.1400 Date: 01/14 Grass Area (acres): 0.5000 Imp. Area "C": 0.90 Grass Area "C": 0.30 " (Imp. Area)(Imp. "C")= 0.1260 (Grass Area)(Grass "C")= 0.1500 ~ ~ 0.6400 0.2760 ~ Weighted "C"= 0.2760 v '0.43 0.6400 ~ ~ l~ , I - ~ ; ~ ~ ; . ~ - ~ - i i • i~ _i r 1 I ~ l Weighted Runoff Coefficient Calculation Project: Springfield at Autumn Crest Basin: U IPE Job 97117 ~ Total Area (acres): 1.4700 ~ Designer: S. Murphy Imp. Area (acres): 0.2400 Date: 01 /14 Grass Area (acres): 1.2300 ~ Imp. Area "C": 0.90 Grass Area "C": 0.30 - J ~ (Imp. Area)(Imp. "C")= 0.2160 (Grass Area)(Grass "C")= 0.3690 . 1.4700 0.5850 . Weighted "C"= 0.5850 I - 0.40 - 1.4700 - - 1 ~ E i . { ~ ' - j 1 ~ f i I I1 J 1 I I ~ i 1 ~ I i l . Weighted Runoff Coefficient Calculation Project: Springfield at Autumn Crest Basin: V IPE Job 97117 ^ Total Area (acres): 0.8900 ~ Designer: S. Murphy . Imp. Area (acres): 0.1600 Date: 01/14 Grass Area (acres): 0.7300 ` imp. Area "C": 0.90 Grass Area "C": 0.30 + I ~ (Imp. Area)(Imp. "C")= 0.1440 (Grass Area)(Grass "C")= 0.2190 ~ i 0.8900 0.3630 i ` ~ Weighted C = 0.3630 ~ ~ - 0.41 ~ - ~ 0.8900 ~I 1 , ~ - ( i ~ i - ~ I . , , , . i- 1 ` - ~ ~ 1 (sI l ~ - Weighted Runoff Coefficient Calculation Project: Springfieid at Autumn Crest Basin: W WI IPE Job 97117 ~ Total Area (acres): 0.6500 600* Designer: S. Murphy Imp. Area (acres): 0.1300 Date: 01 /14 Grass Area (acres): 0.5200 Imp. Area "C": 0.90 Grass Area "C": 0.30 " ll (Imp. Area)(Imp. "C")= 0.1170 ~ (Grass Area)(Grass "C")= 0.1560 ~ , 0.6500 0.2730 S j Weig hted "C"= 0.2730 v ~ 0.6500 , ~ f i ~ ~ . 7 ( 1 ~ I ~ i ~ ~ j l i r~ BOWSTRING METHOD PROJECT: Springfiled at Autumn Crest PEAK FLOW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: T1 BASIN: T1 10-Year Design Storm DESIGNER: SKM Tot. Area 0.73 Acres DATE: 01113 Imp. Area 4644 SF r C = ' 0.39 Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.15 Outfiow (cfs) 0 140 ft. Overland Flow Design Year Flow 10 Area (acres) 0.73 Ct = 0.15 ~ Impervious Area (sq ft) 4644 L= 140 ft. 'C' Factor 0.39 n= 0.40 ✓ '206' Volume Provided 200 S= 0.020 ✓ Area' C 0.285 Tc = 5.43 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 160 ft. Gutter flow ~ (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0V For Z2 7.15 429 2.66 0.76 435 0 435 Z2 = 3.5 Type B =1.0 n= 0.01 V Rolled = 3.5 5 300 3.18 0.91 364 0 364 S= 0.010✓ 10 600 2.24 0.64 476 0 476 15 900 1.77 0.50 527 0 527 d= 0.136 ft. 20 1200 1.45 0.41 556 0 556 25 1500 1.21 0.34 567 0 567 A R Q Tc Tc total I Qc 30 1800 1,04 0.30 576 0 576 35 2100 0.91 0.26 582 0 582 _ 0.49 0.07 0.76 1.73 7.15 2.66 0.76 40 2400 0.82 0.23 594 0 594 45 2700 0.74 0.21 600 0 600 Qpeak for Case 1= 0.76 cfs 50 3000 0.68 0.19 609 0 609 55 3300 0.64 0.18 628 0 628 60 3600 0.61 0.17 651 0 651 CASE 2 65 3900 0.60 0.17 691 0 691 70 4200 0.58 0.17 718 0 718 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0.16 741 0 141 peak flow =.90(3.18)(Imp. Area) = 0.31 cfs 80 4800 0.53 0.15 746 0 746 85 5100 0.52 0.15 777 0 711 90 5400 0.50 0.14 789 0 789 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.14 816 0 816 0.16 cfs 100 6000 0.48 0.14 840 0 840 208' DRAINAGE POND CALCULATIONS ~ Required'208' Storage Volume Impervious Area x.5 in ! 12 inlft 194 cu ft 208' Storage Volume Provided 200 cu ft` DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 717 cu ft Number and Type of Drywells Required 0 Single ERR Double ( 7 BOWSTRING METHOD PROJECT: Springfiled atAutumn Crest PEAK FLOW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: T2 BASIN: T2 10-Year Design Storm DESIGNER: SKM Tot. Area 0.61 Acres DATE; 01130 Imp. Area 7595 SF ' C = • 0,43 t • Tim6 Increment (min) ' 5 CASE 1 Time of Conc. (min) 9.11 Outflow (cfs) 2 300 ft. Overland Flow ✓ Design Year Flow 10 Area (acres) 0.81 Ct = 0.15 Impervious Area (sq ft) 7595 ~ L= 300 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 322 S= 0.020 Area ` C 0.348 Tc = 8.58 min., by Equation 3-2 of Guidelines ' Time Time Inc, Intens. Q Devel. Vol.ln Vol.Out Storage 125 ft. Gutter fiow ~ (min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 9.11 583 227 0.79 617 1165 -548 Z2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 1.11 445 600 -155 S= 0.015 10 600 2.24 0.78 623 1200 -577 15 900 1.77 0.62 677 1800 -1123 d= 0.130 ft. 20 1200 1.45 0.51 106 2400 -1694 25 1500 1.21 0,42 716 3000 -2284 A R Q Tc Tc total I Qc 30 1800 1.04 0,36 724 3600 -2876 35 2100 0.91 0.32 728 4200 -3472 0.43 0.06 0.79 1.14 9.71 2.27 0.79 40 2400 0.82 0.29 742 4800 -4058 ' 45 2700 0.74 0.26 747 5400 4653 Qpeak for Case 1= 0.79 cfs 50 3000 0.68 0.24 757 6000 -5243 55 3300 0.64 0.22 780 6600 -5820 60 3600 0.61 0.21 807 1200 -6393 CASE 2 65 3900 0.60 0.21 856 7800 -6944 70 4200 0.58 0.20 888 8400 -7512 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0.20 916 9000 -8084 peak flow =,90(3.18)(Imp. Area) = 0.50 cfs 80 4800 0.53 0.18 923 9600 -8617 85 5100 0.52 0.18 960 10200 -9240 90 5400 0.50 0.17 975 10800 -9825 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.17 1007 11400 -10393 0.79 cfs 100 6000 0.48 0.17 1036 12000 -10964 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in /12 inlft 316 cu • 208' Storage Volume Provided 322 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring -155 cu ft Number and Type of Drywells Required 0 Single 2 Double BOWSTRING METHOD PROJECT: Springfiled at Autumn Crest PEAK FLOW CALCUTATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN; T BASIN: T 10-Year Design Storm DESIGNER: SKM Tot. Area 1.53 Acres DATE: 02101 Imp. Area 12239 SF C = 0.43 • Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.72 Outflow (cfs) 2 140 ft. Overland Fiow Design Year Flow 10 Area (acres) 1.53 Ct = 0,15 Imperoious Area (sq ft) 12239 L= 140 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 636 S= 0.020 Area' C 0,658 Tc = 5,43 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 305 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) ' Z1 = 50.0 For Z2 7.12 463 2.56 1.68 1046 927 119 Z2= 1 TypeB=1.0 n= 0.016 Rolled = 3.5 5 300 3.18 2.09 841 600 241 S= 0.015 10 600 2,24 1.47 1116 1200 -84 15 900 1.77 1.16 1232 1800 -568 d= 0.173 ft. 20 1200 1.45 0.95 1295 2400 -1105 25 1500 1.21 0.80 1320 3000 -1680 A R Q Tc Tc total I Qc 30 1800 1.04 0.68 1339 3600 -2261 35 2100 0.91 0.60 1352 4200 -2848 0.76 0.09 1.68 2.30 7.72 2,56 1.68 40 2400 0,82 0.54 1380 4800 -3420 45 2700 0.74 0.49 1391 5400 -4009 Qpeak for Case 1= 1.68 cfs 50 3000 0.68 0.45 1413 6000 -4587 55 3300 0.64 0.42 1456 6600 -5144 60 3600 0.61 0.40 1508 7200 -5692 CASE 2 65 3900 0,60 0.39 1602 7800 -6198 70 4200 0.58 0.38 1663 8400 -6737 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0'.56 0.37 1716 9000 -7284 peak flow =.90(3.18)(Imp. Area) = 0.80 cfs 80 4800 0.53 0.35 1729 9600 -7871 85 5100 0.52 0.34 1799 10200 -8401 90 5400 0.50 0.33 1828 10800 -8972 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.32 1888 11400 -9512 1.68 cfs 100 6000 0.48 0.32 1945 12000 -10055 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ~ = Impervious Area x.5 in ! 12 inlft 510 cu ft 208' Storage Volume Provided 636 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 241 cu ft Number and Type of Drywells Required 0 Single 2 Double L_ A 50-year STORM BOWSTRING METHOD PROJECT: Springfield Parc Centre PEAK FLOW CALCULATION PROJECT Springfield Parc Centre DETENTION BASIN DESIGN BASIN: Offsite + Basin T BASIN Offsite + Basin T DESIGNER: SKM Tot. Area 2.32 Acres DATE: 02/01 Imp. Area 12239 SF C = 0.37 ' . Time Increment (min) 5 CASE 1 Time of Conc. (min) 9.42 Outflow (cfs) 2 300 ft. Overiand Flow Design Year Flow 50 Area (acres) 2.32 Ct = 0.15 Impervious Area (sq ft) 12239 L= 300 ft. 'C' Factor 0.37 n= 0.40 '208' Volume Provided 636 S= 0.020 Area' C 0.858 Tc = 8.58 min., by Equafion 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 125 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 9.42 565 3.06 2.62 1986 1130 856✓ Z2 = 1 n= 0.016 5 300 4.58 3.93 1580 600 980 S= 0.015 10 600 3.20 2.75 2176 1200 976 15 900 2.45 2.10 2297 1800 497 d= 0.204 ft. 20 1200 1.95 1.67 2330 2400 -70 25 1500 1.62 ' 1.39 2353 3000 -647 A R Q Tc Tctotal I Qc 30 1800 1,56 1.34 2668 3600 -932 35 2100 1.28 1.10 2518 4200 -1682 1.06 0.10 2.62 0.84 9.42 J 3.06 2.62 40 2400 1.19 1.02 2637 4800 _2163 45 2700 1.08 0,93 2681 5400 -2719 Qpeak for Case 1= 2.62 cfs 50 3000 0.99 0.85 2713 6000 -3287 55 3300 0.92 0.79 2758 6600 -3842 60 3600 0.87 0.75 2832 7200 -4368 CASE 2 65 3900 0.82 0.70 2880 7800 -4920 70 4200 0.80 0.69 3016 8400 -5384 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.66 3101 9000 -5899 peak flow =.90(4.58)(Imp. Area) = 1.16 cfs 80 4800 0,75 0.64 3214 9600 -6386 85 5100 0.72 0.62 3211 10200 -6929 90 5400 0.71 0.61 3408 10800 -7392 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.59 3490 11400 -7910 2,62 cfs 100 6000 0,67 0.58 3561 12000 -8439 208' DRAINAGE POND CALCULATIONS ~ Required'208' Storage Volume = Imperoious Area x.5 in 112 inlft 510 cu ftt r/ . 50 year Volume Provided 985 cu ft 6[~s' DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM -E-- CTZ~ ~ FSS ~ Maximum Storage Required by Bowstring 980 cu ft G~~s v Number and Type of Drywells Required 0 Single 2 Double INLAND PACIfIC ENGINEERING ~ _ 400 ✓F('S) 9-7-Z 5FC 9) BOWSTRING METHOD PROJECT: Springfiled atAutumn Crest PEAK FLOW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: U1 BASIN: U1 10-Year Design Storm DESIGNER: SKM Tot. Area 0.83 Acres DATE: 01114 Imp. Area 4644 SF C 0.38 • • ' Time Increment (min) 5 CASE 1 Time of Conc. (min) 5.18 Outflow (cfs) 0 80 ft. Overland Flow Design Year Flow 10 Area (acres) 0.8311, Ct = 0.15 / Impervious Area (sq ft) 4644 i L= 80 ft. we 'C' Factor 0.38 _ n= 0.40 '208' Volume Provided 200 S= 0.020 Area * C 0.315 Tc = 3.88 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 150 ft. Gutter flow ~ (min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.18 311 3.13 0.99 412 0 412 Z2 = 3.5 Type B =1.0 n= 0,016 Rolled = 3.5 5 300 3.18 1.00 403 0 403 S= 0.015 10 600 2.24 0.71 499 0 499 15 900 1.77 0.56 561 0 561 d= 0.139 ft. 20 1200 1.45 0.46 597 0 597 25 1500 1.21 0.38 613 0 613 A R Q Tc Tc total I Qc 30 1800 1.04 0.33 625 0 625 35 2100 0.91 0.29 633 0 633 0.52 0.07 0.99 1.30 5.18 3.13 0.99 40 2400 0.82 0.26 648 0 648 45 2700 0.74 0.23 655 0 655 Qpeak for Case 1= 0.99 cfs 50 3000 0.68 0.21 666 0 666 55 3300 0.64 0.20 687 0 687 ' 60 3600 0.61 0.19 713 0 713 CASE 2 65 3900 0.60 0.19 758 0 758 70 4200 0.58 0,18 788 0 788 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0,18 813 0 813 peak flow =.90(3.18)(Imp. Area) = 0.31 cfs 80 4800 0.53 0.17 820 0 820 85 5100 0,52 0.16 854 0 854 90 5400 0.50 0.16 868 0 868 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.15 897 0 897 0.99 cfs 100 6000 0.48 0.15 924 0 924 208' DRAINAGE POND CALCULATIONS ~ Required'208' Storage Volume . = Impervious Area x.5 in ! 12 inlft 194 cu ft v 208' Storage Volume Provided 200 cu ft~ DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 854 cu ft Number and Type of Drywells Required 0 Single ERR Double BOWSTRING METHOD PROJECT: Springfiled at Autumn Crest PEAK FLOW CALCUlATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: U2 BASIN: U2 10-Year Design Storm DESIGNER: SKM Tot. Area 0.64 Acres DATE: 02101 Imp. Area 5908 SF ' ' C = 0.43 • Time Increment (min) 5 CASE 1 Time of Conc. (min) 6.58 ✓ Outflow (cfs) 1 140 ft, Overiand Flow Design Year Flow 10 Area (acres) 0.64 Ct = 0.15 Impervious Area (sq ft) 5908000, L= 140 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 262 S= 0.020 Area * C 0.275 Tc = 5.43 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 125 ft. Gutter flow(min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 For Z2 ✓ 6.58 395 2.76 0.76 401 395 6 Z2 = 1 Type B =1,0 n= 0.016 Rolled = 3.5 5 300 3.18 0.88 352 300 52 S= 0.015 10 600 2.24 0.62 453 600 -147 15 900 1.77 0.49 504 900 -396 d= 0.128 ft. 20 1200 1.45 0.40 532 1200 -668 25 1500 1.21 0.33 544 1500 -956 A R Q Tc Tc total I Qc 30 1800 1.04 0.29 554 1800 -1246 35 2100 0.91 0.25 560 2100 -1540 0.42 0.06 0.76 1,15 6.58 2,76 0.76 40 2400 0.82 0.23 572 2400 -1828 45 2700 0.74 0.20 577 2700 -2123 Qpeak for Case 1= 0.76 cfs ~ 50 3000 0.68 0.19 587 3000 -2413 55 3300 0.64 0.18 605 3300 -2695 60 3600 0.61 0.17 627 3600 -2973 CASE 2 65 3900 0.60 0.17 666 3900 -3234 70 4200, 0.58 . 0.16 692 4200 -3508 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0.15 714 4500 -3786 peak flow =.90(3.18)(Imp. Area) = 0.39 cfs SO 4800 0,53 0.15 720 4800 4080 85 5100 0,52 0.14 749 5100 -4351 90 5400 0.50 0.14 762 5400 4638 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.13 787 5700 -4913 0.76 cfs 100 6000 0.48 0.13 810 6000 -5190 , 206' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ~ , = Impervious Area x.5 in I 12 inlft 246 cu ft 208' Storage Volume Provided 262 cu ft✓ DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 52 cu ft Number and Type of Drywells Required 0 Single 1 Double BOWSTRING METHOD PROJECT: Springfiled atAutumn Crest PEAK FLOW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: U BASIN; U 10-Year Design Storm DESIGNER: SKM Tot. Area 1.47 Acres DATE: 02101 Imp. Area 10552 SF , C = 0.40 . , Time Increment (min) 5 CASE 1 Time of Conc. (min) 6.22 Outflow (cfs) 1 80 ft. Overland Flow ' Design Year Flow 10 Area (acres) 1.47 Ct = 0.15 Impervious Area (sq ft) 10552 ' L= 80 ft. 'C Factor 0.4 n= 0.40 '208' Volume Provided 462 S= 0.020 Area ` C 0,568 Tc = 3.88 min,, by Equation 3-2 of Guidelines Tme Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 310 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 50.0 For Z2 6.22 373 2.84 1.67 834 373 461 Z2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 1.87 152 300 452 S= 0,015 10 600 2.24 1.32 957 600 357 15 900 1.77 1.04 1069 900 169 d= 0.172 ft. 20 1200 1.45 0.85 1131 1200 -69 25 1500 1.21 0.71 1157 1500 -343 A R Q Tc Tc total I Qc 30 1800 1.04 0.61 1178 1800 -622 35 2100 0.91 0.54 1192 2100 -908 0.75 0.09 1.67 2.34 6.22 2.84 1.67 40 2400 0,82 0.48 1218 2400 -1182 45 2700 0,74 0.44 1230 2700 -1470 Qpeak for Case 1= 1,67 cfs 50 3000 0.68 0.40 1250 3000 -1750 55 3300 0,64 0,38 1290 3300 -2010 60 3600 0,61 0,36 1337 3600 -2263 CAS E 2 ' 65 3900 0.60 0.35 1421 3900 -2479 70 4200 0.58 0.34 1476 4200 -2724 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0.33 1524 4500 -2976 peak flow =,90(3,18)(Imp, Area) = 0.69 cfs 80 4800 0.53 0.31 1535 4800 -3265 85 5100 0.52 0.31 1598 5100 -3502 90 5400 0,50 0.29 1625 5400 -3775 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.29 1679 5100 -4021 1.67 cfs 100 6000 0.48 0,28 1729 6000 -4271 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ~ = Impervious Area x.5 in / 12 inlft 440 cu ft , 208' Storage Volume Provided 462 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 461 cu ft Number and Type of Drywells Required 0 Single 1 Double BOWSTRING METHOD PROJECT: Springfiled at Autumn Crest PEAK FLQW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN; V BASIN: V 10-Year Design Storm DESIGNER: SKM Tot. Area 0.89 Acres DATE: 01114 Imp, Area 7031 SF . • C= 0.41 • ' Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.15 OutFlow (cfs) 1 140 ft. Overland Flow 40010, Design Year Flow 10 Area (acres) 0.89 Ct = 0.15 Impervious Area (sq ft) 7031 L= 140 ft. 'C' Factor 0.41 n= 0.40 '208' Volume Provided 300 S= 0.020 Area' C • • 0.365 Tc = 5.43 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 180 ft. Gutter flow 000000 (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 7,15 429 2.66 0.97 557 429 128 Z2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 1,16 466 300 166 S= 0,011 10 600 2.24 0.82 610 600 10 15 900 1.77 0.65 675 900 -225 d= 0.148 ft. 20 1200 1.45 0.53 712 1200 488 25 1500 1.21 0.44 727 1500 -773 A R Q Tc Tc total I Qc 30 1800 1.04 0.38 738 1800 -1062 35 2100 0.91 0.33 746 2100 -1354 ' 0.56 0.07 0.97 1.72 7.15 2.66 0.97 40 2400 0.82 0.30 762 2400 --1638 45 2100 0,74 0.27 168 2700 -1932 Qpeak for Case 1= 0.91 cfs✓ 50 3000 0.68 0.25 781 3000 -2219 55 3300 0.64 0.23 805 3300 -2495 60 3600 0.61 022 834 3600 -2766 CASE 2 65 3900 0.60 0.22 886 3900 -3014 70 4200 0,58 0.21 920 4200 -3280 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0,20 949 4500 -3551 peak flow =.90(3.18)(Imp. Area) = 0.46 cfs 80 4800 0.53 0,19 957 4800 -3843 ' 85 5100 0.52 0.19 995 5100 4105 90 5400 0.50 0.18 1012 5400 -4388 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.18 1045 5700 4655 0.97 cfs 100 6000 0.48 0.18 1076 6000 -4924 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ~ = Impervious Area x.5 in I 12 inlft 293 cu ft 208' Storage Volume Provided 300 cu ft r' DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 166 cu ft,~,► ~ Number and Type of Drywells Required 0 Single 1 Double BOWSTRING METHOD PROJECT: Springfiled at Autumn Crest PEAK FLOW CALCULATION PROJECT Springfiled at Autumn Crest DETENTION BASIN DESIGN BASIN: W BASIN: W 10-Year Design Storm DESIGNER: SKM Tot. Area 0.65 Acres DATE: 01116 Imp. Area 5542 SF C = 0.42 • Time Increment (min) 5 CASE 1 Time of Conc. (min) 6,22 Outflow (cfs) 1 80 ft. Overland Flow Design Year Flow 10 Area (acres) 0.65 Ct = 0.15 Imperoious Area (sq ft) 5542 L= 80 ft. 'C' Factor 0.42 n= 0.40 '208' Volume Provided 448 S= 0.020 Area' C 0.273 Tc = 3.88 min., by Equation 3-2 of Guidelines Time Time Inc. Intens, Q Devel. Vol.ln Vol.Out Storage 310 ft, Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 6,22 313 2.84 0.77 387 373 14 Z2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.81 349 300 49 S= 0.015 10 600 2.24 0,61 444 600 -156 15 900 1.77 0.48 496 900 -404 d= 0.172 ft. • 20 1200 1.45 0,40 525 1200 -675 25 1500 1.21 0.33 537 1500 -963 A R Q Tc Tc total I Qc 30 1800 1.04 0.28 547 1800 -1253 - - 35 2100 0.91 0.25 553 2100 -1547 0.75 0.09 1.67 2,34 6.22 2.84 0.77 40 2400 0.82 0.22 566 2400 -1834 45 2700 0.74 0.20 511 2700 -2129 Qpeak for Case 1= 0.77 cfs 50 3000 0.68 0.19 580 3000 -2420 55 3300 0.64 0.17 599 3300 -2701 60 .3600 0.61 0.17 621 3600 -2979 CASE 2 65 3900 0.60 0.16 660 3900 -3240 70 4200 0.58 0.16 685 4200 -3515 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0,56 0.15 707 4500 -3793 peak flow =.90(3.18)(Imp. Area) = 0.36 cfs 80 4800 0.53 0.14 713 4800 4087 85 5100 0.52 0.14 742 5100 -4358 90 5400 0.50 0.14 754 5400 -4646 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0,13 779 5700 -4921 0.77 cfs 100 6000 0.48 0.13 803 6000 -5197 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ~ = VOOOO Impervious Area x.5 in 112 inlft 231 cu ft 208' Storage Volume Provided 27ir p4ecu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 49 cu ft Number and Type of Drywells Required 0 Single 1 Double f I I ~ 1 50-year STORM BOWSTRING METHOD PROJECT; Springfield Parc Centre PEAK FLOW CALCULATION PROJECT Springfield Parc Centre DETENTION BASIN DESIGN BASIN: W .BASIN W DESIGNER: SKM Tot. Area 0.65 Acres DATE: 02101 Imp. Area 5542 SF C = 0.42 ' Time Increment (min) 5 CASE 1 Time of Conc. (min) 6.47 Outflow (cfs) 1 80 ft. Overland Flow Design Year Flow 50 Area (acres) 0.65 Ct = 0.15 ImpeNious Area (sq ft) 5542 L= 80 ft. 'C' Factor 0.42 n= 0.40 '208' Volume Provided 448 S= 0,020 Area' C 0.273 Tc = 3.88 min,, by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 310 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 6,47 386 4.07 1.11 518 388 190 Z2 = 1 n= 0.016 5 300 4.58 1.25 503 300 203 S= 0.015 10 600 3.20 0.87 639 600 39 15 900 2.45 0.67 690 900 -210 d= 0.148 ft. . 20 1200 1.95 0.53 709 1200 -491 25 1500 1.62 0.44 722 1500 -778 A R Q Tc Tc total I Qc 30 1800 1.56 0.43 823 1800 -977 35 2100 1.28 0.35 780 2100 -1320 0.55 0.07 1.11 2.59 6.41 4.07 1.11 40 2400 1.19 0.32 819 2400 -1581 45 2700 1.08 0.29 835 2700 -1865 Qpeak for Case 1= 1.11 cfs 50 3000 0.99 0.27 846 3000 -2154 55 3300 0.92 0.25 862 3300 -2438 60 3600 0.87 0.24 886 3600 -2714 CASE 2 65 3900 0.82 0.22 903 3900 -2997 70 4200 0.80 0,22 946 4200 -3254 Case 2 assumes a Time of Concentration less than 5 minutes so that the , 75 4500 0.77 021 974 4500 •3526 peak flow =.90(4.58)(Imp, Area) = 0.52 cfs 80 4800 0.75 0,20 1010 4800 -3790 85 5100 0.72 0.20 1028 5100 -4072 90 5400 0,71 0.19 1072 5400 -4328 So, the Peak flow for the Basin is the greater of the two flows, 95 5100 0.69 0.19 1099 5700 -4601 1.11 cfs 100 6000 0.67 0.18 1122 6000 -4878 208' DRAINAGE POND CALCULATIONS Required'208' StorageVolume ~ . = Impervious Area x.5 in 112 inlft 231 cu ft 50 yearVolume Provided 536 cu ftCw".= 5~~ DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 203 cu ft Number and Type of Drywells Required 0 Single INLAND PACIFIC ENGINEERING 1 Double CURB INLET CALCULATIONS - Springfield at Autumn Crest Curb Inlet Depression = 2 in. . , Standard Curb Inlet Length = 4 ft. • Upstream 10-Yr. Gutter Roughnes Reciprocal Depth Length Curb Inlet Imperoious Peak Flow Slope Coeff. Cross slope of Flow Required Sub-Basin Station R1L Area c.f.s. S n Z Zln d* Qa/La** QI(QalLa) Remarks T1 3+15 R 4644 ~ 150 0.0160 50 3125 0.09 0.059 5.17 Need 1- 5' curb drop 0• U1 3+15 L 4644 010 0.0150 0.0160 50 3125 0.09 0.059 5.17 Need 1- 5' curb drop *W 46+41 R 1057 0.07✓ 0.0047 0.0160 50 3125 0.06 0.042 1.65 Need 1 curb drop *W 47+00 R 1350 0.09ri/ 0.0048 0.0160 50 3125 0.07 0.046 1.93 Need 1 curb drop *W 48+60 R 1350 0.09 ✓ 0.0032 0.0160 50 3125 0.47 0.050 1.79 Need 1 curb drop *W 49+40 R 1620 0.110#0 0.004 0.0160 50 3125 0.07 0.051 2.09 Need 1 curb drop * See attached calculation sheet . 1 Calculated per Figure 18 of Guidelines Calculated per Figure 16 of Guidelines A 4 foot curb drop with a 6" gutter has a capacity of 4.0 cfs in sump condition. A ~ I y ~7¢) r 4 -7 47 t -75 _ (7-5)(/e I r~ . P7- LD 4-7 t 7 S I . ~ 47 -,L- -75- / 3 5D 51f ~-"zo ; I , I ~ rl r~ ~ r1L ~ I n I a n d MEMO ❑ PROJECT - . P a ci1 C CALC. ❑ JOB N0. ~`711-7 SHEET OF ~ ~ En ineerin g g MEETING ❑ BY DATE west 707 7tn, suite 200 sPokane, wasninyton 99204 OTHER ❑ CHK'D BY DATE 509 458-6840 Fax No. 509 458-6644 ~ ~ , ,